A second calculation, analytic, non-perturbative and gauge-invariant. Gauge-invariant formulation of high-field transport in semiconductors. In this paper we revisit the conventional description of carrier-phonon scattering in the presence of high electric fields by means of a gauge-invariant density-matrix approach. This is recognized to be the origin of the apparent discrepancy between scalar- and vector-potential treatments of the problem; indeed, a proper account of such contributions leads, in general, to an ill-defined Markov limit in the carrier-phonon interaction process, assigning to the scalar-potential or Wannier-Stark picture a privileged role.
The neglect of such Zener-like contributions in the transport equation leads to a wrong estimation of the high-field voltage-current characteristics, and may partially account for the surprisingly good agreement between semiclassical and rigorous quantum-transport calculations previously reported.
This is confirmed by fully three-dimensional simulations of charge transport in state-of-the-art semiconductor superlattices, which show a significant current overestimation. Gauge-invariant expectation values of the energy of a molecule in an electromagnetic field. In this paper, we show that the full Hamiltonian for a molecule in an electromagnetic field can be separated into a molecular Hamiltonian and a field Hamiltonian, both with gauge-invariant expectation values.
The expectation value of the molecular Hamiltonian gives physically meaningful results for the energy of a molecule in a time-dependent applied field. In contrast, the usual partitioning of the full Hamiltonian into molecular and field terms introduces an arbitrary gauge-dependent potential into the molecular Hamiltonian and leaves a gauge-dependent form of the Hamiltonian for the field.
We resolve this problem and also remove the gauge dependence from the Hamiltonian for a molecule in a non-zero applied field and from the field Hamiltonian, by repartitioning the full Hamiltonian. It is possible to remove the gauge dependence because the interaction of the molecular charges with the gauge potential cancels identically with a gauge-dependent term in the usual form of the field Hamiltonian. We treat the electromagnetic field classically and treat the molecule quantum mechanically, but nonrelativistically.
Our derivation starts from the Lagrangian for a set of charged particles and an electromagnetic field, with the particle coordinates, the vector potential, the scalar potential, and their time derivatives treated as the variables in the Lagrangian. Any gauge may be chosen. We discuss the extension of gauge-invariant electric and magnetic screening masses in the quark-gluon plasma to the case of a finite baryon density, defining them in terms of a matrix of Polyakov loop correlators.
We confirm that there is no extra graviton modes and general relativity is recovered in IR, which achieves the consistency of the model. New physics effects in B decays are routinely modeled through operators invariant under the strong and electromagnetic gauge symmetries. Assuming the scale for new physics is well above the electroweak scale, we further require invariance under the full standard model gauge symmetry group.
Retaining up to dimension-six operators, we unveil new constraints between different new physics operators that are assumed to be independent in the standard phenomenological analyses. We illustrate this approach by analyzing the constraints on new physics from rare B q semi- leptonic decays. The innermost stable circular orbit ISCO delimits the transition from circular orbits to those that plunge into a black hole. Barack and N. Sago, Phys. The generalization of this ISCO condition to spinning binaries has the property that it also exactly reproduces the Kerr ISCO in the test-mass limit up to the order at which PN spin corrections are currently known.
The shift in the ISCO due to the spin of the test-particle is also calculated. It is surprising that an analysis of the stability of the standard PN equations of motion is able without any form of 'resummation' to accurately describe strong-field effects of the Kerr spacetime. D 81, ]. These results serve as a useful point of comparison for future gravitational self-force calculations in the Kerr spacetime. Phase difference of arrival geolocation.
Geolocation is performed by receiving, at a plurality of non-earthbound platforms each moving in a known manner within a spatial coordinate system, a radio frequency RF signal transmitted from a transmitter at an unknown location on earth within the spatial coordinate system. For each of the platforms, a phase change of the received frequency carrier is measured over the same duration of time. The measured phase changes are combined to determine the transmitter location. Comparison of different phase retrieval algorithms.
X-ray phase contrast imaging is attracting more and more interest. Since the phase cannot be measured directly an indirect method using e. This contribution compares three different approaches to calculate the phase from Talbot-Lau interferometer measurements using a phase -stepping approach. Besides the usually applied Fourier coefficient method also a linear fitting technique and Taylor series expansion method are applied and compared. Gauge Invariance and the Goldstone Theorem. This paper was originally created for and printed in the "Proceedings of seminar on unified theories of elementary particles" held in Feldafing, Germany from July 5 to 16, under the auspices of the Max-Planck-Institute for Physics and Astrophysics in Munich.
It details and expands upon the Guralnik, Hagen, and Kibble paper demonstrating that the Goldstone theorem does not require physical zero mass particles in gauge theories. Quantum phases with differing computational power. The observation that concepts from quantum information has generated many alternative indicators of quantum phase transitions hints that quantum phase transitions possess operational significance with respect to the processing of quantum information. Yet, studies on whether such transitions lead to quantum phases that differ in their capacity to process information remain limited.
Here we show that there exist quantum phase transitions that cause a distinct qualitative change in our ability to simulate certain quantum systems under perturbation of an external field by local operations and classical communication. In particular, we show that in certain quantum phases of the XY model, adiabatic perturbations of the external magnetic field can be simulated by local spin operations, whereas the resulting effect within other phases results in coherent non-local interactions.
We discuss the potential implications to adiabatic quantum computation, where a computational advantage exists only when adiabatic perturbation results in coherent multi-body interactions. The polarization phase difference of orchard trees. The PPD of orchard trees was found to be distinctly different from that of bare fields or fields covered with other crops. Thus the PPD signatures obtained from a polarimeter may be useful in the understanding of the radar remote sensing of the earth's surface. Evaluating Web accessibility at different processing phases.
Modern Web sites use several techniques e.chlorlidnionewscon.gq/koh-un-hombre-solo.php
DOM manipulation that allow for the injection of new content into their Web pages e. This has the consequence that the Web pages that are presented to users i. This poses a series of challenges for Web accessibility evaluation, especially on automated evaluation software. This article details an experimental study designed to understand the differences posed by accessibility evaluation after Web browser processing. Our study shows that, in fact, there are considerable differences between the HTML DOM trees in both phases , which have the consequence of having distinct evaluation results. We discuss the impact of these results in the light of the potential problems that these differences can pose to designers and developers that use accessibility evaluators that function before browser processing.
Geometric approach to nuclear pasta phases. By use of the variational methods and differential geometry in the framework of the liquid drop model we formulate appropriate equilibrium equations for pasta phases with imposed periodicity. The extension of the Young-Laplace equation in the case of charged fluid is obtained. All equations are shown in gauge invariant form. For the first time, the pasta shape stability analysis is carried out. The proper stability condition in the form of the generalized Jacobi equation is derived.
The presented formalism is tested on some particular cases. Yang-Mills correlators across the deconfinement phase transition. We compute the finite temperature ghost and gluon propagators of Yang-Mills theory in the Landau-DeWitt gauge. The background field that enters the definition of the latter is intimately related with the gauge-invariant Polyakov loop and serves as an equivalent order parameter for the deconfinement transition. We use an effective gauge-fixed description where the nonperturbative infrared dynamics of the theory is parametrized by a gluon mass which, as argued elsewhere, may originate from the Gribov ambiguity.
In this scheme, one can perform consistent perturbative calculations down to infrared momenta, which have been shown to correctly describe the phase diagram of Yang-Mills theories in four dimensions as well as the zero-temperature correlators computed in lattice simulations. In this article, we provide the one-loop expressions of the finite temperature Landau-DeWitt ghost and gluon propagators for a large class of gauge groups and present explicit results for the SU 2 case.
These are substantially different from those previously obtained in the Landau gauge, which corresponds to a vanishing background field. The nonanalyticity of the order parameter across the transition is directly imprinted onto the propagators in the various color modes. In the SU 2 case, this leads, for instance, to a cusp in the electric and magnetic gluon susceptibilities as well as similar signatures in the ghost sector.
We mention the possibility that such distinctive features of the transition could be measured in lattice simulations in the background field gauge studied here. Nonverbal communication is an important factor in human communication, and body movement synchronization in particular is an important part of nonverbal communication. Some researchers have analyzed body movement synchronization by focusing on changes in the amplitude of body movements.
However, the definition of "body movement synchronization" is still unclear. From a theoretical viewpoint, phase difference is the most important factor in synchronization analysis. Therefore, there is a need to measure the synchronization of body movements using phase difference.
The purpose of this study was to provide a quantitative definition of the phase difference distribution for detecting body movement synchronization in human communication. The phase difference distribution was characterized using four statistical measurements: density, mean phase difference , standard deviation SD and kurtosis. To confirm the effectiveness of our definition, we applied it to human communication in which the roles of speaker and listener were defined. Specifically, we examined the difference in the phase difference distribution between two different communication situations: face-to-face communication with visual interaction and remote communication with unidirectional visual perception.
Participant pairs performed a task supposing lecture in the face-to-face communication condition and in the remote communication condition via television. Throughout the lecture task, we extracted a set of phase differences from the time-series data of the acceleration norm of head nodding motions between two participants. Statistical analyses of the phase difference distribution revealed the characteristics of head nodding synchronization.
Although the mean phase differences in synchronized head nods did not differ significantly between the conditions, there were significant differences in the densities, the SDs and the kurtoses of the phase difference distributions of synchronized head nods. Different structures of monoclinic martensitic phases in titanium nickelide. The detailed theoretical and experimental analysis has been undertaken to bring to light the true structure of the monoclinic phase in titanium nickelide NiTi. Theoretical models for such a phase have been proposed to describe the experimental data.
Diffraction patterns have been obtained from different NiTi samples by using the neutron diffractometer IVV2 at different temperatures. From the refinement by DBWS program all these neutron patterns have been decoded successfully. Gauge invariance and infrared divergences in spinor quantum electrodynamics. This method expresses QED in terms of a manifestly gauge-independent theory. Moreover, exponentiation of the infrared divergences arises naturally. Objective: To evaluate the influence of menstrual cycle on auditory and visual reaction times.
Method: This study was conducted on thirty, healthy, regularly menstruating female subjects who were in the age group of years. Conclusion: Changes in ART and VRT during different phases of menstrual cycle could be due to changes in the levels of female sex hormones, which in turn may lead to salt and water retention. In the mutual transform between the number- difference state and the phase state corresponding to the operational phase operator we find that there exists an end-point ambiguousness.
This problem can be avoided by Lighthill's method. The project supported by the Ph. Geometrical modeling of optical phase difference for analyzing atmospheric turbulence. Ways of calculating phase shifts between laser beams propagating through atmospheric turbulence can give us insight towards the understanding of spatial diversity in Free-Space Optical FSO links.
We propose a new geometrical model to estimate phase shifts between rays as the laser beam propagates through a simulated turbulent media. Turbulence is simulated by filling the propagation path with spherical bubbles of varying sizes and refractive index discontinuities statistically distributed according to various models. For each statistical representation of the atmosphere, the trajectories of two parallel rays separated by a particular distance are analyzed and computed simultaneously using geometrical optics.
The three-dimensional geometry of the spheres is taken into account in the propagation of the rays. The bubble model is used to calculate the correlation between the two rays as their separation distance changes. The total distance traveled by each ray as both rays travel to the target is computed.
The difference in the path length traveled will yield the phase difference between the rays. The mean square phase difference is taken to be the phase structure function which in the literature, for a pair of collimated parallel pencil thin rays, obeys a five-third law assuming weak turbulence. All simulation results will be compared with the predictions of wave theory. The composition of secondary amorphous phases under different environmental conditions. The nature of these phases is not well understood and could be any combination of primary e.
Secondary amorphous phases are frequently found as weathering products in soils on Earth, but these materials remain poorly characterized. Here we study a diverse suite of terrestrial samples including: sediments from recently de-glaciated volcanoes Oregon , modern volcanic soils Hawaii , and volcanic paleosols Oregon in order to determine how formation environment, climate, and diagenesis affect the abundance and composition of amorphous phases. We combine bulk XRD mineralogy with bulk chemical compositions XRF to calculate the abundance and bulk composition of the amorphous materials in our samples.
We then utilize scanning transmission electron microscopy STEM and energy dispersive x-ray spectroscopy EDS to study the composition of individual amorphous phases at the micrometer scale. Compared to their respective crystalline counterparts, calculations indicate bulk amorphous components enriched in SiO2 for the glacial sample, and depleted in SiO2 for the modern soil and paleosol samples.
STEM analyses reveal that the amorphous components consist of a number of different phases. Enhancement effects in polarimetric radar returns: Phase difference statistics. The probability density functions pdfs of the co- and cross-polarized phase differences are derived for backscatter from vegetation using the coherent and incoherent scattering theories. Unlike previous derivations, no assumptions or observations other than the applicability of the Central Limit Theorem CLT , the low fractional volume of the medium, the reciprocity of the scatterers, and the azimuthal symmetry of the scatterer's orientation statistics are employed.
Everything else follows logically via the mathematics. The difference between the coherent theory and the incoherent theory is referred to as the backscatter enhancement effect. The influence of this enhancement effect on the phase difference pdfs is examined and found to be important under combined conditions of scatterer anisotropy and appropriate reflection coefficient values.
Phase difference statistics related to sensor and forest parameters. The information content of ordinary synthetic aperture radar SAR data is principally contained in the radiometric polarization channels, i. In the case of clutter, polarimetric information is given by the four complex degrees of coherence, from which the mean polarization phase differences PPD , correlation coefficients or degrees of polarization can be deduced. For radiometric features, the polarimetric parameters are corrupted by multiplicative speckle noise and by some sensor effects. The PPD distribution is related to the sensor, speckle and terrain properties.
Method and apparatus for measuring frequency and phase difference. Inventor ; Cunningham, Allen R. The present invention is a system for deriving direct digital indications of frequency and phase difference between two incoming pulse trains adaptable for collision avoidance systems or the like. A pair of radar beams are directed toward a target and corresponding beams returning therefrom are detected.
A digital difference circuit forms a pulse train from the Doppler shift frequencies of each beam pair having a repetition rate functionally related to the difference in magnitude of the shift frequencies. Pulses from the pulse train are counted as a function of time. Visual indications thereof on display are correlative to target position relative to beams. Relating polarization phase difference of SAR signals to scene properties. This paper examines the statistical behavior of the phase difference Delta-phi between the HH-polarized and VV-polarized backscattered signals recorded by an L-band SAR over an agricultural test site in Illinois.
Polarization- phase difference distributions were generated for about agricultural fields for which ground information had been acquired in conjunction with the SAR mission. For the overwhelming majority of cases, the Delta-phi distribution is symmetric and has a single major lobe centered at the mean value of the distribution Delta-phi. The explanation proposed for this variation is that the corn canopy, most of whose mass is contained in its vertical stalks, acts like a uniaxial crystal characterized by different velocities of propagation for waves with horizontal and vertical polarization.
Thus, it is hypothesized that the observed backscatter is contributed by a combination of propagation delay, forward scatter by the soil surface, and specular bistatic reflection by the stalks. Model calculations based on this assumption were found to be in general agreement with the phase observations. The information content of Synthetic Aperture Radar SAR data significantly included in the radiometric polarization channels, hence polarimetric SAR data should be analyzed in relation with target structure.
The importance of the phase difference between two co-polarized scattered signals due to the possible association between the biophysical parameters and the measured Polarization Phase Difference PPD statistics of the backscattered signal recorded components has been recognized in geophysical remote sensing. This paper examines two Radarsat-2 images statistics of the phase difference to describe the feasibility of relationship with the physical properties of scattering targets and tries to understand relevance of PPD statistics with various types of forest fields.
As well as variation of incidence angle due to affecting on PPD statistics is investigated. The experimental forest pieces that are used in this research are characterized white pine Pinus strobus L. The experimental results show that despite of biophysical parameters have a wide diversity, PPD statistics are almost the same. Forest fields distributions as distributed targets have close to zero means regardless of the incidence angle. Also, The PPD distribution are function of both target and sensor parameters, but for more appropriate examination related to PPD statistics the observations should made in the leaf-off season or in bands with lower frequencies.
Radiosensitivity of different tissues from carrot root at different phases of growth in culture. The present work compares the effect of.. However, nuclear volume could not account for the differences in radiosensitivity between either the tissues or irradiation times in culture. Dynamic phase differences based on quantitative phase imaging for the objective evaluation of cell behavior. Quantitative phase imaging QPI brought innovation to noninvasive observation of live cell dynamics seen as cell behavior. Unlike the Zernike phase contrast or differential interference contrast, QPI provides quantitative information about cell dry mass distribution.
We used such data for objective evaluation of live cell behavioral dynamics by the advanced method of dynamic phase differences DPDs. By subtracting the antecedent from the subsequent image in a time-lapse series, only the changes in mass distribution in the cell are detected.
The result is either visualized as a two dimensional color-coded projection of these two states of the cell or as a time dependence of changes quantified in picograms. Then in a series of time-lapse recordings, the chain of cell mass distribution changes that would otherwise escape attention is revealed. Consequently, new salient features of live cell behavior should emerge. Construction of the DPDs method and results exhibiting the approach are presented.
Advantage of the DPDs application is demonstrated on cells exposed to an osmotic challenge. For time-lapse acquisition of quantitative phase images, the recently developed coherence-controlled holographic microscope was employed. The result is either visualized as a two-dimensional color-coded projection of these two states of the cell or as a time dependence of changes quantified in picograms. Introduction Previous work by Bell et. This has been used in the Dee Estuary to give a good representation of the bathymetry in the area. However, there are some sources of inaccuracy in the method, as a uniform spatial tidal signal is assumed over the entire domain.
Motivation The method used by Bell et. This fails to account for fine-scale variations in water level and tidal phase. While methods are being developed to account for small-scale water level variations using high resolution modelling, a method to determine tidal phase variations directly from the radar intensity images could be advantageous operationally. Methods The tidal phase has been computed using two different methods, with hourly averaged images from In the first method, the cross-correlation between each raw pixel time series and a tidal signal at a number of lags is calculated, and the lag with the highest correlation to the pixel series is recorded.
For the second method, the same method of correlation is used on signals generated by tracking movement of buoys, which show up strongly in the radar image as they move on their moorings with the tidal currents. There is a broad agreement between the two methods, but validation is needed to determine the relative accuracy. The phase has also been calculated using a Fourier decomposition, and agrees broadly with the above methods.
Filtering out signal variations due to wind strength and attenuation of the radar signal will also be applied. Differences in respirogram phase between taekwondo poomsae athletes and nonathletes. The purpose of this study was to analyze the differences in the respirograms between taekwondo poomsae athletes and nonathletes according to the respirogram phase. Respiratory function was measured using spirometry while the participant was seated. The slopes of the forced vital capacity for athletes at slopes 1, 2, and 3 of the A area were significantly higher than those for the nonathletes.
In correlation analysis, chest circumference was significantly correlated with slope 1 of the A area of the forced vital capacity. Geometric phase of neutrinos: Differences between Dirac and Majorana neutrinos. We analyze the non-cyclic geometric phase for neutrinos. We find that the geometric phase and the total phase associated to the mixing phenomenon provide a theoretical tool to distinguish between Dirac and Majorana neutrinos. Our results hold for neutrinos propagating in vacuum and through the matter.
We feed the values of the experimental parameters in our formulas in order to make contact with experiments. Although it remains an open question how the geometric phase of neutrinos could be detected, our theoretical results may open new scenarios in the investigation of the neutrino nature. Analog circuit for the measurement of phase difference between two noisy sine-wave signals. A simple circuit was designed to measure the phase difference between two noisy sine waves. It locks over a wide range of frequencies and produces an output proportional to the phase difference of rapidly varying signals.
A square wave locked in frequency and phase to the first signal is produced by a phase -locked loop and is amplified by an operational amplifier. Protein phosphorylation differs significantly among ontogenetic phases in Malus seedlings. Background Although protein phosphorylation is an important post-translational modification affecting protein function and metabolism, dynamic changes in this process during ontogenesis remain unexplored in woody angiosperms.
Methods Phosphorylated proteins from leaves of three apple seedlings at juvenile, adult vegetative and reproductive stages were extracted and subjected to alkaline phosphatase pre-treatment. Abundances of the 27 spots corresponding to Rubisco activase declined between juvenile and reproductive phases. Conclusions Protein phosphorylation varied significantly during vegetative phase change and floral transition in apple seedlings.
Most of the observed changes were consistent among seedlings and between hybrid populations. Analysis and comparison of different phase shifters for Stirling pulse tube cryocooler. Investigations of phase shifters and power recovery mechanisms are of sustainable interest for developing Stirling pulse tube cryocoolers SPTC with higher power density, more compact design and higher efficiency. This paper investigates the phase shifting capacity and the applications of four different phase shifters, including conventional inertance tube, gas-liquid and spring-oscillator phase shifters, as well as a power recovery displacer.
Distributed models based on the electro-acoustic analogy are developed to estimate the phase shifting capacity and the acoustic power dissipation of the three phase shifters without power recovery. The results show that both gas-liquid and spring-oscillator phase shifters have the distinctive capacity of phase shifting with a significant reduction in the inertial component length.
- Table of contents.
- The Road to Average.
Furthermore, full distributed models of SPTCs connected with different phase shifters are developed. The cooling performance of SPTCs using all four phase shifters are presented and typical phase relations are analyzed. The comparison reveals that the power recovery displacer with a more complicated configuration provides the highest efficiency. The gas-liquid and spring-oscillator phase shifters show equivalent efficiency compared with the inertance tube phase shifter.
A merit analysis is also done by presenting the pros and cons of different phase shifters. Growth phase -dependent induction of stationary- phase promoters of Escherichia coli in different gram-negative bacteria. RSFderived plasmids carrying a fusion of a promoterless lacZ gene with the sigma s-dependent growth phase -regulated promoters of Escherichia coli, bolAp1 and fic, were constructed.
The plasmids were mobilized into the gram-negative bacterial species Acetobacter methanolicus, Xanthomonas campestris, Pseudomonas putida, and Rhizobium meliloti. The beta-galactosidase activities of bacterial cultures were determined during exponential and stationary growth phases. Transcriptional activation of the fic promoter in the different bacteria was growth phase dependent as in E. The induction of the bolA promoter was also growth phase dependent in the bacteria tested. While the expression in E.
The results show that in different gram-negative bacteria, stationary- phase -specific sigma factors which are structurally and functionally homologous to sigma s and are able to recognize the promoter sequences of both bolA and fic exist. Note: Dynamic analysis of a robotic fish motion with a caudal fin with vertical phase differences. In this paper, a robotic fish with a caudal fin with vertical phase differences is studied, especially focusing on the energy consumption.
Energies for thrusting a conventional robotic fish and one with caudal fin with vertical phase differences are obtained and compared each other. It is shown that a robotic fish with a caudal fin with vertical phase differences can save more energy, which implies the efficient thrusting via a vertically waving caudal fin. Sebum may contribute to the composition of the tear film lipid layer naturally or as a contaminant artifact from collection. The aims of this study were to determine: if sebum changes the rheology of meibum surface films; if the resonance near 5.
Human meibum was collected from the lid margin with a platinum spatula. Human sebum was collected using lipid absorbent tape. Langmuir trough technology was used to measure the rheology of surface films. Infrared spectroscopy was used to measure lipid conformation and phase transitions. The NMR resonance near 5. Both sebum and SQ lowered the lipid order of meibum. Sebum expanded meibum films at lower concentrations and condensed meibum films at higher concentrations. Sebum caused meibum to be more stable at higher pressures greater maximum surface pressure.
Physiological levels of sebum would be expected to expand or fluidize meibum making it spread better and be more surface active qualities beneficial for tear film stability. Sebum would also be expected to stabilize the tear film lipid layer, which may allow it to withstand the high shear pressure of a blink. Purpose Sebum may contribute to the composition of the tear film lipid layer naturally or as a contaminant artifact from collection.
Methods Human meibum was collected from the lid margin with a platinum spatula. Results The NMR resonance near 5. Conclusions Physiological levels of sebum would be expected to expand or fluidize meibum making it spread better and be more surface active qualities beneficial for tear film stability. The goal of the paper is to present possible use of EPE videos in different phases of a learning and teaching process.
The paper is based on an evaluation of EPE easy production educational videos. The evaluation framework used in this study, divides the teaching and learning process into four main phases : 1 The preparation phase , 2 The…. The phase function and polarized phase function are important optical parameters, which describe scattering properties of atmospheric aerosol particles. Polarization of skylight induced by the scattering processes is sensitive to the scattering properties of aerosols.
Two different observation geometries i. Polarization of skylight depends on the illumination and observation geometries. For the same solar zenith angle, retrievals of the phase function and the polarized phase function are still affected by the observation geometry.
The performance of the retrieval algorithm for the principal plane and almucantar observation geometries was assessed by the numerical experiments at two typical high and low sun's positions i. Comparing the results for the principal plane and almucantar geometries, it is recommended to utilize the principal plane observations to retrieve the phase function when the solar zenith angle is small.
The Stokes parameter U and the polarized radiance Lp from the almucantar observations are suggested to retrieve the polarized phase function, especially for short wavelength channels e. How to process the carrier phase error properly is important to improve the GNSS compass accuracy. In this work, we propose a dual frequency carrier phase error difference checking algorithm for the GNSS compass. The algorithm aims at eliminating large carrier phase error in dual frequency double differenced carrier phase measurement according to the error difference between two frequencies.
The advantage of the proposed algorithm is that it does not need additional environment information and has a good performance on multiple large errors compared with previous research. The core of the proposed algorithm is removing the geographical distance from the dual frequency carrier phase measurement, then the carrier phase error is separated and detectable.
We generate the Double Differenced Geometry-Free DDGF measurement according to the characteristic that the different frequency carrier phase measurements contain the same geometrical distance. Then, we propose the DDGF detection to detect the large carrier phase error difference between two frequencies. The theoretical performance of the proposed DDGF detection is analyzed. An open sky test, a manmade multipath test and an urban vehicle test were carried out to evaluate the performance of the proposed algorithm.
The result shows that the proposed DDGF detection is able to detect large error in dual frequency carrier phase measurement by checking the error difference between two frequencies. Comparison of different numerical treatments for x-ray phase tomography of soft tissue from differential phase projections. X-ray imaging of soft tissue is made difficult by their low absorbance. The use of x-ray phase imaging and tomography can significantly enhance the detection of these tissues and several approaches have been proposed to this end.
Methods such as analyzer-based imaging or grating interferometry produce differential phase projections that can be used to reconstruct the 3D distribution of the sample refractive index. We report on the quantitative comparison of three different methods to obtain x-ray phase tomography with filtered back-projection from differential phase projections in the presence of noise. It is found that obtaining individual phase projections and subsequently applying a conventional filtered back-projection algorithm produces the best results for noisy experimental data, when compared with other procedures based on the Hilbert transform.
The algorithms are tested on simulated phantom data with added noise and the predictions are confirmed by experimental data acquired using a grating interferometer. The experiment is performed on unstained adult zebrafish, an important model organism for biomedical studies. The method optimization described here allows resolution of weak soft tissue features, such as muscle fibers.
Journeys: Stories by Deborah Teramis Christian | Indiegogo
On precise phase difference measurement approach using border stability of detection resolution. For the precise phase difference measurement, this paper develops an improved dual phase coincidence detection method. The measurement resolution of the digital phase coincidence detection circuits is always limited, for example, only at the nanosecond level.
This paper reveals a new way to improve the phase difference measurement precision by using the border stability of the circuit detection fuzzy areas. When a common oscillator signal is used to detect the phase coincidence with the two comparison signals, there will be two detection fuzzy areas for the reason of finite detection resolution surrounding the strict phase coincidence.
Border stability of fuzzy areas and the fluctuation difference of the two fuzzy areas can be even finer than the picoseconds level. It is shown that the system resolution obtained only depends on the stability of the circuit measurement resolution which is much better than the measurement device resolution itself. Spatial-frequency spectrum of patterns changes the visibility of spatial- phase differences. It is shown that spatial-frequency components over a 4-octave range affected the visibility of spatial- phase differences.
The background could contain one or several sinusoidal components, all in 0-deg phase. Phase differences between the test and the background were visible at lower contrasts when test and background frequencies were harmonically related than when they were not, when test and background frequencies were within 1 octave than when they were farther apart, when the fundamental frequency of the background was low than when it was high, and for some discriminations more than for others, after practice.
The visibility of phase differences was not affected by additional components in the background if the fundamental and difference frequencies of the background remained unchanged. Observers' reports of their strategies gave information about the types of attentive processing that were used to discriminate phase differences.
Attentive processing facilitated phase discrimination for multifrequency gratings spanning a much wider range of spatial frequencies than would be possible by using only local preattentive processing. These results were consistent with the visibility of phase differences being processed by some combination of even- and odd-symmetric simple cells tuned to a wide range of different spatial frequencies. A new method of time difference measurement: The time difference method by dual phase coincidence points detection. In the high accurate measurement of periodic signals, the greatest common factor frequency and its characteristics have special functions.
A method of time difference measurement - the time difference method by dual ' phase coincidence points' detection is described. This method utilizes the characteristics of the greatest common factor frequency to measure time or phase difference between periodic signals.
It can suit a very wide frequency range. Measurement precision and potential accuracy of several picoseconds were demonstrated with this new method. The instrument based on this method is very simple, and the demand for the common oscillator is low. This method and instrument can be used widely. Measurement of phase function of aerosol at different altitudes by CCD Lidar. The aerosols near the ground are closely related to human health and climate change, the study on which has important significance. As we all know, the aerosol is inhomogeneous at different altitudes, of which the phase function is also different.
In order to simplify the retrieval algorithm, it is usually assumed that the aerosol is uniform at different altitudes, which will bring measurement error. In this work, an experimental approach is demonstrated to measure the scattering phase function of atmospheric aerosol particles at different heights by CCD lidar system, which could solve the problem of the traditional CCD lidar system in assumption of phase function.
The phase functions obtained by the new experimental approach are used to retrieve the aerosol extinction coefficient profiles. By comparison of the aerosol extinction coefficient retrieved by Mie-scattering aerosol lidar and CCD lidar at night, the reliability of new experimental approach is verified. Proton resonance frequency shift-based MR thermometry is a promising temperature monitoring approach for thermotherapy but its accuracy is vulnerable to inter-scan motion.
Model-based referenceless thermometry has been proposed to address this problem but phase unwrapping is usually needed before the model fitting process. In this paper, a referenceless MR thermometry method using phase finite difference that avoids the time consuming phase unwrapping procedure is proposed. Unlike the previously proposed phase gradient technique, the use of finite difference in the new method reduces the fitting error resulting from the ringing artifacts associated with phase discontinuity in the calculation of the phase gradient image.
The new method takes into account the values at the perimeter of the region of interest because of their direct relevance to the extrapolated baseline phase of the region of interest where temperature increase takes place. In simulation study, in vivo and ex vivo experiments, the new method has a root-mean-square temperature error of 0. The method also demonstrated a slightly higher, albeit small, temperature accuracy than the original referenceless MR thermometry method. Three-dimensional surface contouring of macroscopic objects by means of phase-difference images.
We report a technique to determine the 3D contour of objects with dimensions of at least 4 orders of magnitude larger than the illumination optical wavelength. Our proposal is based on the numerical reconstruction of the optical wave field of digitally recorded holograms. The required modulo 2pi phase map in any contouring process is obtained by means of the direct subtraction of two phase -contrast images under different illumination angles to create a phase-difference image of a still object.
Obtaining the phase-difference images is only possible by using the capability of numerical reconstruction of the complex optical field provided by digital holography. This unique characteristic leads us to a robust, reliable, and fast procedure that requires only two images. A theoretical analysis of the contouring system is shown, with verification by means of numerical and experimental results. Heart Rate Variability HRV , which is a measure of the cardiac autonomic tone, displays physiological changes throughout the menstrual cycle.
The functions of the ANS in various phases of the menstrual cycle were examined in some studies. The aim of our study was to observe the effect of menstrual cycle on cardiac autonomic function parameters in healthy females. A cross-sectional observational study was conducted on 50 healthy females, in the age group of years. The data consisted of Time Domain Analysis and Frequency Domain Analysis in menstrual, proliferative and secretory phase of menstrual cycle.
Data collected was analysed statistically using student's pair t-test. From the study it can be concluded that sympathetic nervous activity in secretory phase is greater than in the proliferative phase , whereas parasympathetic nervous activity is predominant in proliferative phase. Background Heart Rate Variability HRV , which is a measure of the cardiac autonomic tone, displays physiological changes throughout the menstrual cycle. Aims and Objectives The aim of our study was to observe the effect of menstrual cycle on cardiac autonomic function parameters in healthy females.
Materials and Methods A cross-sectional observational study was conducted on 50 healthy females, in the age group of years. Conclusion From the study it can be concluded that sympathetic nervous activity in secretory phase is greater than in the proliferative phase , whereas parasympathetic nervous activity is predominant in proliferative phase. Selectivity differences of water-soluble vitamins separated on hydrophilic interaction stationary phases.
In this study, the retention behavior and selectivity differences of water-soluble vitamins were evaluated with three types of polar stationary phases i. The effects of mobile phase composition, including buffer pH and concentration, on the retention and selectivity of the vitamins were investigated. In all stationary phases , the neutral or weakly charged vitamins exhibited very weak retention under each of the pH conditions, while the acidic and more basic vitamins showed diverse retention behaviors.
With the underivatized silica phase , increasing the salt concentration of the mobile phase resulted in enhanced retention of the acidic vitamins, but decreased retention of the basic vitamins. These observations thus signify the involvement of secondary mechanisms, such as electrostatic interaction in the retention of these analytes. Under optimized conditions, a baseline separation of all vitamins was achieved with excellent peak efficiency. In addition, the effects of water content in the sample on retention and peak efficiency were examined, with sample stacking effects observed when the injected sample contained a high amount of water.
KGaA, Weinheim. Gyrator transform of Gaussian beams with phase difference and generation of hollow beam. The optical expression of Gaussian beams with phase difference , which is caused by gyrator transform GT , has been obtained. The intensity and phase distribution of transform Gaussian beams are analyzed. The effect of parameters on the intensity and phase distributions of the hollow vortex beam are discussed.
Compared with previously reported results, the work shows that the hollow vortex beam can be obtained without any model conversion of the light source. Different phases of a system of hard rods on three dimensional cubic lattice. We study the different phases of a system of monodispersed hard rods of length k on a cubic lattice, using an efficient cluster algorithm able to simulate densities close to the fully-packed limit.
Within a layer, the system is disordered. In the layered-nematic phase , the system breaks up into layers, with nematic order in each layer, but very weak correlation between the ordering directions of different layers. We argue that the layered-nematic phase is a finite-size effect, and in the thermodynamic limit, the nematic phase will have higher entropy per site. We expect the systems of rods in four and higher dimensions will have a qualitatively similar phase diagram. Two different mechanisms support selective attention at different phases of training.
Selective attention supports the prioritized processing of relevant sensory information to facilitate goal-directed behavior. Studies in human subjects demonstrate that attentional gain of cortical responses can sufficiently account for attention-related improvements in behavior. On the other hand, studies using highly trained nonhuman primates suggest that reductions in neural noise can better explain attentional facilitation of behavior. Given the importance of selective information processing in nearly all domains of cognition, we sought to reconcile these competing accounts by testing the hypothesis that extensive behavioral training alters the neural mechanisms that support selective attention.
Early in training, spatial attention led to an increase in the gain of stimulus-evoked visual responses. However, after extensive training, this early attentional gain was eliminated even though there were still substantial attention-related improvements in behavior. Accordingly, the SDT-based model required noise reduction to account for the link between the stimulus-evoked visual responses and attentional modulations of behavior.
These findings suggest that training can lead to fundamental changes in the way attention alters the early cortical responses that support selective information processing. Moreover, these data facilitate the translation of results across different species and across experimental procedures that employ different behavioral training regimes. The Their increase can have a variety of only areas close to industrialized and populated negative consequences for the reef areas where mats were less abundant were those exposed to high wave energy where and the benefits that people derive nutrients are diluted faster and organic matter from reefs.
These go well beyond the settles less on the seafloor. Cyanobacterial mats can Sediments are known to be a sink of organic grow quickly over the reef. They can matter. Researchers found that organic matter prevent coral larvae from settling on Diver checking added to sediments can fuel the growth cyanobacteria.
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Furthermore, they can produce chemicals which deter the grazing of fishes and urchins and have been linked to mass reef fish die-offs. Most cyanobacteria contain poisons. Blooms of cyanobacterial mats have been associated with mass mortalities of fishes. Direct contact may cause skin, eye and respiratory problems for humans Does anything feed on cyanobacteria?
Cyanobacteria produce chemicals that fishes and urchins do not like to eat. There seems to be minimal grazing on cyanobacteria. A handful of small invertebrates are thought to feed on cyanobacterial mats. Is there any economic value to be gained from cyanobacterial mats? None has been found so far. Occasional mats are natural but an increase in their cover and frequency of occurrence management implications could indicate a problem.
High coverage of cyanobacterial mats on a reef indicates an increase in nutrients and organic matter which principally come from land- based run-off and pollution. Septic tanks, landfills and waste dumping areas leak nutrients into groundwater which can subsequently flow out onto reefs. Efforts could be made to reduce or stop untreated waste water and run-off from agricultural land reaching the reef.
Bays and other partially enclosed coastal areas have narrow or shallow openings towards the sea, naturally preventing nutrients from reaching the reefs. Dredging and other activities that change water flow and increase flushing effects can lead to higher nutrient levels and, potentially, more cyanobacteria. Reducing nutrient inputs will not only reduce the abundance of cyanobacterial mats, it can also decrease the growth of macroalgae and bioeroders and slow down the spread of coral diseases.
Organic matter degradation drives benthic Massive discharge of sediment loads by a river entering the Caribbean Sea cyanobacterial mat abundance on Caribbean coral reefs in off the Meso-American coast. Using this technique, the most organisms such as corals, algae abundant — and most damaging to coral - and cyanobacteria. Macroalgae macroalgal species Lobophora variegata was found to be limited by the availability of nitrogen are seaweeds that can overgrow and phosphorus.
Turf algae are diminutive mixed algal communities To examine which benthic organisms profit most from higher levels of nitrogen and phosphorus, composed of small macroalgae and coral, macroalgae, cyanobacteria and turf algae cyanobacteria. It has been shown were exposed to nutrient pulses raised levels of that turf algae reduce the recruitment nutrients.
Nutrients were delivered in the form of ammonium NH4 and phosphate PO4 , both of new corals and can also overgrow of which can be found in fertilizer and sewage. Cyanobacterial Macroalgae, cyanobacteria and turf algae were mats can overgrow both macroalgae all able to take up nutrients much faster than corals. Turf algae took up nutrients faster than and corals. Recent human activities e. However, increases in external sources of both nitrogen such as nitrogen and phosphorus and phosphorus can increase their growth rate onto many reefs.
It is hypothesized as these nutrients often limit their growth under that this causes macroalgae, turf Close-up of turfalgae. If nutrient influxes persist, coral reefs could turn into ecosystems dominated by algae and cyanobacteria, which decreases their ecological, economic and aesthetic value. Nutrient levels can vary both in time e. However, if you continously measure increased nutrient levels, efforts 0 0 could be made to find and eliminate the Corals Macroalgae Turfalgae Cyanobacteria source of the nutrients.
Corals do need nutrients, but they are management implications naturally adapted to very low nutrient conditions oligotrophic water. The growth of algae is limited by nutrients, so increases Reduce nutrient input to reefs, with a focus on sources of phosphate. Reducing the phosphate inflow will specifically decrease the growth of turf algae and What are the major human sources of nutrients cyanobacteria since they are less dependent on external nitrogen as that flow onto reefs?
In particular, sources Sewage, fertilizers and untreated of phosphate, such as raw sewage outfalls, should be reduced. These can come from many sources including, leaks from septic tanks, Reducing nutrient flow onto reefs will ultimately benefit corals as they run-off from agricultural land and direct compete for space with algae and cyanobacteria. Available free online: www. Corals are adapted to only of seagrasses but also of calcareous and non-calcareous fleshy algae, as well as survive in such conditions, therefore other organisms.
The composition of seagrass large inputs of nutrients into the communities varies depending upon a number waters surrounding a reef can have of factors including nutrients, light and the amount of disturbance at a site e. It is normally algae that benefit from this nutrient The reef lagoon of Puerto Morelos in Mexico enrichment, as relative to corals, they has been strongly affected by development in the surrounding tourist areas of Cancun and have higher growth rates and greater the Mexican Riviera Maya. Increases in nutrient ability to take-up nutrients. This allows levels, most likely coming from sewage output algae to overgrow parts of coral colonies into the lagoon and increased land-based run- off, are visible as changes in the coastal seagrass and reduce the space available for the meadows.
In , the seagrass meadow sites recruitment of new corals. Biological indicators bioindicators are used to assess the health of the environment and detect changes early, before damage to a habitat becomes irreversible. Seagrass meadows respond faster than corals to nutrient enrichment, and when they are located close to the reef, they act as a biological sink for nutrients, buffering the coral reef. Nutrient enrichment of seagrass meadows is visible as changes in the extent of the meadow and in community composition. These changes can be useful bioindicators, providing an early warning of nutrient enrichment in the water that may eventually impact the health of nearby reefs.
Sites closest Calcareous green algae at sites at the coast 3 , in the lagoon 4 and in the back- to the town 6,7,8,9 show either greater biomass of Halodule wrightii reef meadows 5 and 8. Calcareous green algae show the seagrass Thalassia testudinum 6,7 or of non- strong increases at all sites as they are heavier than the Syringodium filiforme calcareous algae 8,9; principally Lobophora variegata , other parts of the seagrass community.
Thalassia testudinum in part due to greater nutrient availability. Since calcareous algae are much denser than There are three possible bioindicators in seagrass meadows both seagrass and macroalgae, they increased of trophic changes in the coral reef habitat due to nutrient more as percentage weight of the community enrichment: composition. Changes should be significant and sustained, but will vary depending on the magnitude of the environmental disturbance, i.
Although large scale changes in the seagrass community can be seen on satellite or aerial photos, local monitoring of the seagrass meadow through measurement of shoot density, shoot size and leaf biomass of the dominant seagrass, provides a more sensitive method of detecting changes. Importantly these bioindicators are helpful for detecting changes in the reef environment before serious impacts are observed in the coral community. However, some care needs to be taken in interpreting environmental Calcareous algae: Halimeda.
Monitoring programs should further information therefore compare the same sites at the same times of the year Resilience Brief 2 p. Form-function variability in conditions present in the area, but it is useful to include analysis of the effect of canopy morphology on leaf self-shading in sites with low changes in sediment accretion and movement which the seagrass Thalassia testudinum. Oecologia , As seagrass meadow sites closest to the coast are the most disturbed van Tussenbroek BI.
Dynamics of seagrasses and ones, preferable sites for monitoring are closer to the reef community associated algae in coral reef lagoons. The cages excluded becoming the dominant species as herbivorous fish and urchins from the reef area so that changes in algae could be investigated the cover of hard corals declines. Abundance of Macroalgae compete with corals for algae was compared between caged areas and space and reduce the space available non-caged areas over 13 months.
Herbivores and nutrients are Macroalgae grew to be twice as abundant in known to play an important role in areas where herbivores were excluded caged areas compared to those where they were not. In most reef environments a higher abundance of algae in the summer months with higher temperature and light levels. The abundance of i. Month Lobophora variegata and halimeda. Lobophora variegata - and algal turf Overall, herbivores were found to play a strong abundances were reduced by herbivory but role in reducing the abundance of algae, but with no herbivores present, seasonal variations changes in seasons light and temperature controlled abundance.
Even on healthy reefs there are changes in the cover of macroalgae and the abundance of macroalgae species throughout the year. If reef surveys are conducted on the same reefs at more than one time during the year, managers should expect to see some variation in macroalgae, even if there are no disturbances e.
To avoid the complicating factor of seasonal changes in macroalgae, it is best to compare data that was collected at the same time month each year. Without herbivores present, macroalgae can dominate the reef, squeezing out corals and reducing the chances of reefs recovering from disturbances such as hurricanes and bleaching events. Parrotfish are the main herbivore on most Caribbean reefs, though the Diadema sea urchin can be a very important herbivore if present in sufficient numbers typically 1 or more per square metre.
It is advisable to protect both parrotfish and Diadema from overharvesting. Shallow reef underwater surveys in eight countries around the Caribbean revealed fish structure created by organisms e. Fish and coral and animals. Structurally complex species richness the number of different types of fish or coral were high even on medium habitats support a greater diversity and complexity reefs, but were dramatically reduced abundance of life, resulting in healthier on low complexity reefs.
The major decline ecosystems which are typically more in fish species appears to occur when reefs transition from medium to low complexity. Parrotfish, snapper and grouper biomass also Coral reef habitat complexity is declined as reef structure is lost. Reef complexity especially important for fishes, thus is clearly an important component of coral reefs: with higher complexity supporting greater directly supporting valuable reef diversity, abundance and biomass of fishes, fisheries, diving and tourism.
Grunts and a squirrelfish including fisheries target species snappers, under Elkhorn coral groupers and ecologically important species Acropora palmata. Historically, complex physical structure has been provided on Caribbean reefs by large, branching staghorn and elkhorn corals Acropora cervicornis and A. In their absence, reef structure has been maintained, to a large degree, by the boulder corals Orbicella, previously Montastraea spp. However, these corals are also under threat from disease outbreaks, bleaching events, sedimentation and the increasing intensity of storms and hurricanes.
The loss of structurally important corals and the complexity they provide reduces the habitat available for reef fishes and hence their populations.
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Management efforts could focus on biologically eroded. In the absence of coral human impacts such as sediment and nutrient run-off, overfishing recovery, a dead reef will lose its structural and physical damage to the reef from anchoring and tourist complexity and its function as a habitat for fish. It is hard to create the naturally-occurring complex reef structure Artificial structures will never be as good using artificial means so it is more cost-effective to prevent in a comprehensive ecosystem sense as decline of existing habitat structure than attempt to restore it.
The natural reef structure. They are expensive prevention of decline is achieved by managing the processes that and difficult to introduce on a large scale. However, at Where artificial structures are to be used, it small scales, reefs that have lost complexity may benefit from the is important to consider that just as different addition of artificial structures to provide habitat and shelter for corals provide different complexity and fish and help accelerate recovery. These reefs will need protection habitat e. Conditions for the If I increase complexity on my reef, will fish development of corals are unlikely to be favourable e.
Visual assessment of reefs using a simple 3 or However, this increased abundance may 5 point qualitative scale can also be useful for categorising reefs for simply be fish drawn from the surrounding prioritisation in spatial management. A no-take marine reserve was established and actively enforced in the Bahamas. If corals that are used to target snapper and grouper. Researchers monitored the recovery of corals remain in this degraded state for at 10 sites, 4 of which were in the reserve, over long periods of time then the benefits a 2. They found that the amount that people derive from reefs will be of algae was set by the number of parrotfish so that there was far less algae in the reserve threatened.
It is the corals that build where parrotfishes were large and plentiful. Corals showed positive recovery at sites with little algal for beaches, and protect coastal areas cover but further degradation was found where from wave erosion. In short, the protection of Stoplight parrotfish parrotfish reversed the trend in corals from one Sparisoma viride. There are many causes of this decline which include mass coral bleaching events, outbreaks of coral disease, hurricanes, mass regional decline of long-spined sea urchins, overfishing, and eutrophication.
The precise causes will vary from place to place. It has recently been shown that coral recovery can be helped by taking practical steps to manage parrotfishes. Parrotfishes are the main grazers of algae and high levels of parrotfishes are able to reduce the amount of algae on reefs.
Algae can interfere with coral recovery in two ways. Firstly, by taking up space, algae prevent larval corals finding a place to settle on the reef and this effectively cuts off the supply of new corals. Secondly, algae smother established corals, which either stunts their growth or reduces their size. Experience has shown that coral cover Draft legislation to outlaw the catch or selling of parrotfish as has can suddenly decline if the reef is struck been done in Belize.
This policy may help sustain the long-term by a hurricane, bleaching event, or disease livelihoods of fishermen by helping to preserve the reef habitat outbreak. These events are unpredictable needed by their target species. Educate fishers to retrieve the traps regularly, haul them to the surface slowly, and return surviving parrotfishes. Educate fishers to reduce their impact on parrotfishes and try to Yes.
Urchin recovery has occurred in several reduce fishing effort. The most important parrotfishes are the parts of the Caribbean but it is usually limited larger-bodied individuals. The most important species are the to the shallowest few metres. Parrotfish stoplight Sparisoma viride , rainbow Scarus guacamaia , queen remain the main grazer below this depth so Scarus vetula , and princess Scarus taeniopterus.
However, protecting while popular resistance is low. Typically, parrotfishes is a concrete step that will help recovery and help stem parrotfish become targeted once more the loss of reef services such as fisheries productivity. In Belize, for example, parrotfish harvest went from virtually unheard of to the most heavily- targeted species within a period of 10 years.
Are parrotfishes really good for reefs if they eat coral? It is true that some species of parrotfish take bites from live coral. However, all the evidence to date has shown that this impact Queen parrotfish Scarus vetula. Princess parrotfish Scarus taeniopterus. Corals suffer much more from algae than they do from parrotfishes. Marine reserves enhance the recovery of corals on Caribbean reefs. PLOS One 5: e Available free at www. Rainbow parrotfish Scarus guacamaia.
On coral reefs bioerosion in the vicinity of sewage outlets and along plays a major role in the balance eutrophication gradients. It is hypothesized between constructive calcification and that filter-feeding bioeroders such as molluscs and sponges benefit from an increase in the cementation and destructive forces availability of new substrate due to coral physical erosion, chemical dissolution declines and from surplus food in the water and bioerosion. Bioeroders create provided by sewage outflows. Bioerosion is crucial for maintenance of coral reefs as long as it is in balance with Cross-section view of sponge calcification.
Bioeroders create suitable excavation and infiltration of surfaces for corals to settle, increase limestone rock. Bioerosion is crucial for maintenance of coral reefs as long as it is in balance with calcification. This balance is now at stake. Coral reefs are declining worldwide and their calcification rates are being reduced due to factors such as eutrophication, coastal run-off and the effects of global warming and acidification. Worryingly, many bioeroders are less sensitive to these stressors than corals and are therefore colonizing newly available space on reefs.
Bioeroders might even benefit from local and global anthropogenic disturbances. Consequently the balance is tipping in favour of bioerosion leading to a flattening of reefs and the loss of fisheries, biodiversity, and aesthetic beauty of coral reefs. Bioeroders can be categorized in two different groups: i external bioeroders such as parrotfish, sea urchins and turtles that graze algae, sponges or coral tissue and as a by-product scrape off the surface of the limestone framework; ii internal bioeroders which actively penetrate into the limestone substrate where they live permanently.
The coral excavating sponges Cliona delitrix and Siphonodictyon coralliphagum can grow to become significant eroders of corals, management implications destroying entire colonies. How much limestone is removed by bioeroders? Reducing waste water and land based run-off will help to reduce Some extremely destructive excavating the supply of nutrients to the filter-feeding bioeroders. Several methods can be used to the dominant bioeroding organisms in this monitor bioerosion: region. The cover of Should we remove parrotfish and sea urchins bioeroding organisms e.
Despite the fact that sea urchins and corals giving an indication of the balance between calcifying and parrotfish scrape off limestone when grazing bioeroding organisms on the reef. The full methodology, including for food, their negative impact as bioeroders Excel data entry spreadsheets is available free online: is vastly outweighed by their positive impact www. However, anthropogenic disturbances such as eutrophication, overfishing and the effects of climate change directly or indirectly hamper coral growth and promote bioerosion, thus potentially leading to net loss of reef structure.
How is ocean acidification going to affect bioerosion? A lower pH due to ocean acidification is likely to increase bioerosion by facilitating the dissolution of limestone. At the same time these conditions hinder the calcification of framework-building corals. Both effects suggest a net loss of reef structure and stability due to ocean acidification in the Measuring coral excavating sponge cover on a transect.
Elkhorn coral Acropora palmata and staghorn coral Acropora cervicornis become a popular management tool. Although both species still the right circumstances, it may support release their gametes eggs and sperm during annual mass spawning events, no significant the natural reef recovery process. Restoration is only useful if the stressors Sexual reproduction represents a bottleneck causing degradation are significantly in the life history of corals which needs specific attention in reef management efforts. Therefore, by land-based aquaria are used to grow the increasing the number of settlers per tile, initial corals before being transplanted to the reef.
Rather than using land-based aquaria, cheaper be more easily controlled. After months, methods are to transfer recently settled corals: when settlers are large enough to be more 1 directly onto the reef, or 2 into coral resistant to algal overgrowth and other impacts, nurseries located on the sea floor, where the they can be outplanted to the reef. Whether Method 1 or how is it done?
In the case study in Curacao, needs to be initiated on shore. Gametes of tiles with elkhorn coral settlers were multiple colonies are put together in a highly outplanted on the reef within 2 weeks of concentrated suspension which turns slightly settlement. Although survival rates of settlers milky approx. Generally, is discarded. Depending on the quality of the the number of larvae is not the limiting factor gametes and the water conditions, fertilization a b c d e f from gametes to recruits A Plankton nets are put above a spawning elkhorn coral to collect egg-sperm bundles in the plastic cups at top.
A plastic-foam float keeps the nets in position. B Here, a regular cooler is used for batch fertilization. C The developing larvae are cultured for several days in flow-through devices to maintain high water quality. D Once settlement competent, larvae are transferred to bins with fresh seawater and pre-conditioned settlement tiles. The ceramic tiles have a diameter of approx. F When outplanted on the reef directly after larvae settlement, settlement tiles may be fixed to rods which are fixed to the reef substrate using u-shaped stainless steel nails; Elkhorn coral, age: 12 months. When the majority quality, therefore high fertilization rates means of larvae have settled, disappearing from better water quality and higher culture success.
However, if regular water changes are the reef. After days, when larvae start Curacao and elsewhere to determine the long actively crawling and swimming, settlement term survival of outplanted recruits as well as to may be initiated by adding pre-conditioned optimize the developed techniques in terms of settlement tiles, which have been exposed to costs which are currently relatively high. They may vary between different geographical regions. Avoid sampling of neighbors. As a result of asexual fragmentation they might be identical genotypes.
Do not use genetic material gametes, larvae, settlers from other regions i. Ideal model species are the Edwards, A. Make it a public event and invite locals to visit management program: St you at the culture facilities not while working on the reef! This helps raise awareness of reef Lucia, Australia. Download at: www. Using x-ray technology we look at the growth rings of reef-building corals to calculate the rates of expansion, Coral reefs are very important because density.
We evaluate how the rate they offer tourist services which involve of calcification has changed in these many actors. Mainly what we can see, reef builders and how these rates vary along the Caribbean, studying the for example, the white sand is produced aragonite saturation gradient. A large number of species is found there. Ultimately all fisheries depend on the reef.
For the past fourteen years I have had the opportunity to know the reef which is opposite to where I live and I have seen a big difference during this time. Before we could take a dive from the pier and there were corals from the reef lagoon, typical corals that are associated with the lagoon. We would swim out to the reef where there were a variety of breathtaking coral especially acroporas which are no longer there now.
There are other areas of the reef to the South, which are in a little better condition. However I also have already seen a dead reef in front of the coast of Yes, there swim up to the has been a change, overall I would say, a lethal impact. Before there was reef where there nothing in the south now it is full of so were a variety many hotels that are not concerned about environmental standards. The oceans are changing too; not only are their temperatures rising, but ocean chemistry is changing due to increased amounts of carbon dioxide dissolving into the water resulting in ocean acidification.
Both of these changes have important consequences for coral reefs. Higher ocean temperatures are linked to increased frequency of coral bleaching and increased prevalence of coral diseases. Ocean acidification will combine with elevated temperature to reduce the ability of corals to produce their calcium carbonate skeletons, which may lead to reefs that erode faster than they can accrete. Additionally, continued increases in the intensity of hurricanes in the Caribbean, linked to ocean warming, could hinder recovery of corals.
Although the causes of climate change need to be tackled at a global level, this does not mean that local reef management is futile. Mitigating local stressors to reefs, such as overfishing of herbivores and sediment and nutrient run-off onto reefs, can greatly improve coral reef resilience in the face of climate change. A new method for factoring coral bleaching vulnerability into the design of MPA networks offers managers a further tool for planning for a changing climate.
Freighter enters Willemstad, Curacao. In the Northern Hemisphere, to considerable stressors from anthropogenic it is likely2 that the period — was impacts such as overfishing, pollution and the warmest year period for the last land-based run-off from coastal development years. Climate change has a big impact on Mora This has led to a warming model the future impacts of climate change of the seas and an acidification of the oceans, on coral reefs and probabilistic maps of corresponding to a decrease in pH Graphs below.
Climate change is a concern for reef managers coralreefwatch. The oceans have warmed fastest series data and near-real-time maps of sea near the surface where coral reefs are located surface temperature, ocean acidification, and continued warming is expected to result with other products such as coral disease risk in an increased frequency of coral bleaching prediction tools in development.
Additionally, more acidic ocean conditions The Caribbean Community Climate Change will reduce the ability of corals to produce their Centre www. Included in the Guldberg et al.
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The impacts of precipitation, humidity and wind speed for climate change may be particularly negative the whole Caribbean region up until RCP 2. RCP 4. Vertical line at shows the end of the historical simulation and start of climate change scenario models. Shading indicates one inter-modal standard deviation.
Changes in salinity and light intensity can cause coral bleaching, but large scale bleaching events have only occurred due to anomalously high water temperatures Eakin et al. Bleached porites coral. Non-bleached porites. Ocean acidification As the concentration of CO2 in the atmosphere has increased, the amount of dissolved CO2 in the oceans has similarly increased. The absorption of carbon dioxide by the ocean triggers a series of chemical reactions which makes the oceans more acidic lower pH and decreases the concentration of carbonate in the water Doney et al.
Carbonate is vital to calcifying organisms, such as corals, which build their skeletons with calcium carbonate. The effects of extreme ocean acidification on a coral. In approximately 8. Negative effects of ocean acidification on other calcifying organisms, such as sea urchins, coralline algae and molluscs, are also expected, resulting in thinner shells and slower growth rates Doney et al. The 0. However, some corals may Caribbean Honduras Sea be able to adapt and acclimate to increasing 0 temperatures Pandolfi et al.
Longitude W Decadal warming trend for Increasing sea-surface temperature Increases in ocean temperatures are linked to the wider Caribbean. The Caribbean Sea has warmed on average outbreaks and increases in prevalence of coral by 0. This is a higher rate than This is of particular concern for the Caribbean the 0. There are considerable and wide geographic spread of coral diseases differences in the temperature trends across the in the region Harvell et al.
Disease outbreaks Caribbean region, with northern areas around and increased spread of diseases following Florida and the Bahamas actually showing some warmer ocean temperatures may be due to cooling, though the majority of the region has corals being less able to fight diseases when been warming with the greatest temperature already stressed by high temperatures, or increases in the south of the basin Map above. Poor water quality has also been linked temperatures, which is likely to push organisms to increases in the severity of coral diseases outside their ranges of thermal tolerance.
Bruno et al. A further mass bleaching event in has yet to be well documented but is known to have caused coral mortality in some areas of the southern Caribbean, such as reefs in Colombia and Venezuela, which had escaped significant damage from previous bleaching events Gaskill ; Bastidas et al. The stress experienced by corals due to bleaching White plague disease. Aragonite is the mineral 4. In the Caribbean, decreases in the pH 3. Storms and for the Caribbean region. Gledhill et al.
Stronger the Mesoamerican Barrier Reef finding no hurricanes cause more coral loss and within the widespread effects Carricart-Ganivet et al. Caribbean there is no evidence that reefs recover However, as oceans continue to acidify with a for at least 8 years post-impact Gardner et al. However, hurricanes within the Caribbean end of century Graphs p.
Tropical storms and Gardner et al. Reef sites have different exposure to bleaching risk. Using satellite data on the temperatures reef areas are used to and how intensively they are impacted during extreme heating events, reef sites that are less likely to bleach or where corals are better prepared to cope with bleaching can be identified. This information can be used to aid in the design of marine reserve networks to maximize the probability of persistence of the entire network under a changing climate Mumby, Elliott, et al.
Management actions such as decreasing land-based sources of nutrients and reducing herbivore overfishing can help improve reef health and increase reef resilience Edwards et al. This will improve the ability of reefs to recover after bleaching events and hurricanes.
The goal is the construction of a global model that will predict how the ability of corals to form reefs will change in the future. Coral reef ecosystems are not only the most iconic of the ecosystems but the services they provide to a community form a vital economic part of every one of the countries that make up the Caribbean. As food, as a main form of coastal protection and as a basis for tourism, people in the Caribbean are dependent on the services that the reefs provide. Diversity is very important for food security. In my lifetime, I have witnessed really dramatic change on reefs.
Sometimes it seems incredible considering that coral reef ecosystems have dominated as one of the most enduring of the tropical marine ecosystems. It is very alarming to think that in my short professional life I have witnessed dramatic changes on coral reefs: within the reefs right in front of my laboratory not only throughout the Caribbean. This is something that makes you think about what these ecosystems were like before the changes caused by human actions, People in the not just global change but change in local land use and cultural change Caribbean are associated with tourism. The change dependent on has been quite dramatic.
Maps showing vulnerability to bleaching can help manage reefs for climate change. When bleached, corals starve, extreme heating events acute stress. Using weaken and become more vulnerable this information, reefs can be classified into to diseases and death. In the long term it is clear that decreasing greenhouse gas emissions Coral bleaching in La Bocana, Puerto Morelos, is the appropriate course of action Mexico to reduce the impacts of warming temperatures in corals. But what can we do at local levels? When looking across reefs within a single country, there is large variability in where bleaching occurs.
Reefs differ in their preparedness acclimation to bleaching and how intensively they Aerial view of cays in Los Roques, Venezuela. This variability can be harnessed by local managers by protecting reefs that are more prepared and have been less impacted by sea warming. If your area is that differences in bleaching vulnerability do not included there, thermal regimes can be exist. While the bleaching response has been identified using data freely available on sea related to the intensity of a warming event surface temperature www.
A full description of the methods chronic stress also influence the response of is available in the manuscript referenced in the corals to elevated temperature. For example, further information section. A measure of chronic stress temperature regimes A and C are better suited is the average monthly summer temperature to a climate change scenario. When chronic and 10 acute temperature stress have been quantified for each location within the area of interest, 5 the measures are divided independently into A C B D Temperature regime three groups and locations at the extremes of each stress measure i.
This method is based on historical data, therefore assumes management that future incidence of bleaching events will be similar than past incidence. We currently are not implications able to predict future bleaching events at a fine, local scale relevant for management, but this approach provides a viable option to manage To maximize chances of success, we reefs for climate change. If feasible, further information Bilko lesson on how to calculate thermal stress from satellite data: also including areas that offer the greatest www.
Reserve design for uncertain responses of coral reefs e. Ecology Letters A modelling study of Caribbean coral reefs examined the effects of different scenarios such as coastal protection, fisheries of climate change and local management on and tourism that are vital to the the net growth of reefs.
Two climate change livelihoods of millions of people. Corals generate skeletons greenhouse gas emissions. Local management scenarios involved protecting herbivores and of calcium carbonate limestone as reducing nutrient run-off onto the reef. Results they grow which provide a natural showed that only a combination of local breakwater and the complex three management action and aggressive greenhouse gas reductions resulted in reefs continuing to dimensional habitat that is essential grow in the future.
In all other scenarios, reef to support the high biodiversity of growth began to decline before the end of the coral reefs. Other processes e. Rising ocean temperatures are projected to disrupt growth rates Local Action ONLY at for many corals and increase the Management a local scale frequency of coral bleaching. In the face of such impacts, local efforts to improve reef health might seem hopeless. However, recent research has shown that local management of reefs is vital to maintain the continued net production of reef structure, and therefore the provision of the important Both local management of reefs and global action to lower greenhouse gas emissions are ecosystem services that reefs provide.
However, the point at which reefs stopped growing dark blue line was delayed when reefs were locally managed to protect herbivorous fish and improve water quality. Where action was taken to limit GHG emissions bottom panels , only managed reefs were able to maintain their growth rates until Although global action to reduce greenhouse gas emissions is essential to ease the effects of climate change on reefs, such efforts are not sufficient on their own to ensure reefs continue to exhibit net production of three dimensional structure. Although improved local management measures alone may not be sufficient to ensure continued growth of reef structure, such measures are vital for buying time for reefs while global action on climate change is negotiated.
Local management efforts that protect herbivores and reduce nutrient run-off onto reefs will maximise the chances that healthy reefs and Time boughtbyby Time bought management management the services they provide are maintained in the future. Threshold atatwhich Threshold whicherosion exceeds erosion growthgrowth exceeds in mostin reefs most reefs further information Resilience Brief 5 p.
Current Biology 23 10 : — Dredging and landfill activities can increase sediment loads and nutrient levels on reefs. Reef fisheries also provide an important social safety-net for people when other sources of employment are unavailable. Populations of reef fishes and other important fishery species such as queen conch Strombus gigas and spiny lobster Panulirus argus have been severely reduced across the region due to a combination of overfishing and habitat degradation. Resources available for the monitoring and control of coral reef fisheries are often limited, but good management is vital for ensuring the long-term viability of the fisheries.
Ecosystem-based fisheries management EBFM is suggested as a better alternative to conventional fisheries management practices and is particularly appropriate for coral reef fisheries. The focus is on maintaining the health of the coral reef to ensure sustainable fishery yields and other critical ecosystem services of reefs. Existing fisheries management tools, such as no-take areas and catch quotas, will continue to be used alongside new and improved tools, such as habitat protection zones and vessel monitoring systems VMS , which will expand the range of fisheries management measures available.
Only by understanding and managing the effects of fishing as well as other impacts on the ecosystem can managers ensure sustainable use of coral reef fisheries. Parrotfish catch. It may involve al. While revenues from reef fishing make up only a small proportion of the GDP of most countries within the region, Reef fish catch being sorted at a dock in Honduras.
Nevis as well as Honduras depended heavily on coral reef fisheries after losing their jobs in Although there is considerable variability in other economic areas such as construction work Caribbean reef fishery data, landings of most Livelihoods Brief 2 p. This safety-net function of species have been stable or declining since the the reef-fishery may be particularly important in s Graph below left. This is despite increased Caribbean nations, many of which have limited fishing effort in terms of both improved gear social security schemes and are highly dependent and more fishers.
High demand for many reef on the seasonal and volatile tourism sector. The a matter of serious concern. Overfishing is a ease of access to the reef and the life history pervasive problem in Caribbean reef fisheries traits of many reef fishery species make them which are typically open-access i.
Archaeological As a result, some of the most vulnerable evidence suggests reef fish stocks were heavily and desirable reef-fishery species are now Queen conch. Catch value of main Caribbean reef fishery species. Queen conch Newman et al. Queen conch is also listed in Appendix Understanding these complexities is important III of the SPAW Specially Protected Areas and to ensuring effective management and hence Nassau grouper Wildlife protocol of the Cartagena convention in the long-term sustainability Epinephelus striatus.
Throughout the Caribbean, market value and leading to trophic cascades Nassau grouper Epinephelus striatus spawning aggregations have been and reefs dominated by macroalgae Fisheries, decimated by fishing and the species is now listed as endangered by the Brief 1 p. Support for protection of aggregation sites was gained by involving a wide range of stakeholders in the work, including local fishers, NGOs and The reasons for declines in reef fishery species government departments. Fishers were involved in research activities, may be complex but it is clear that an ongoing being paid for their work, and training in alternative livelihoods such as SCUBA dive guiding, kayaking and fly fishing was provided.
Following confirmation of broad support from fishers, the Minister of Fisheries signed legislation in November that created a closed season for Nassau grouper from December to March, and fully protected 11 spawning aggregation sites in new marine reserves. Belize now has four of the last few known Nassau grouper spawning aggregations of over individuals Sadovy De Mitcheson et al. Some reef-associated pelagic species may also be considered as part of the reef fishery grouping, such as barracuda Sphyraenidae , various jacks Carangidae and small tunas and mackerels Scombridae.
However, many reef fishing gears are non-selective and reef fish harvest is generally multispecies, with almost all species caught having some commercial value in local markets. Reef fisher emptying his multispecies catch from a fish trap. Vulnerable to multiple gear types including lines, spears, nets and traps. Caught on deep lines or in deep set traps. Nearshore pelagics Nearshore and coastal pelagic species that can be found in close proximity to or on reefs during some stage of their life history, e. Usually caught while trolling or with a net.
Lobster Lobster mainly Panulirus argus gathered from coral reefs and associated habitats by free-diving and SCUBA-diving, by hand or using snares, spears, or nets deployed around casitas or harvested by traps set in both shallow reef and deep slope environments. Although well suited to fishing in coral reef environments, most of the gears are non-selective which complicates the Multi-purpose inshore implementation of species-specific management pirogues in Bequia, measures.
Furthermore, some gears may cause St Vincent. Moses used for pot Since most reef areas are relatively shallow and fishing in Barbados. Caribbean reef fishing vessels are typically small, open boats, generally powered by outboard motors or oars, and can be easily hauled ashore by hand. As such, entry into the reef fishery requires relatively low capital investment. Furthermore, the reef fishery can operate effectively with little or no shore infrastructure meaning that reef fishers may land and sell their catches along almost any stretch of shoreline. The dispersed nature of the reef fishery and typical lack of centralized landing areas means that monitoring the fishery Dugouts in southern is very difficult and therefore costly.
Harvesting may take place by hand for species such as conch, whelks and urchins or with the use of a handheld prying device, spear or sling, or a speargun for species such as reef fishes, lobsters, crabs and octopus. Diving Compressed air diving includes SCUBA-diving with tanks as well as the use of compressed air supplied from the compressed surface through a tube Hookah diving.
As with free diving, harvesting may take place by hand for species such as air conch, whelks and urchins or with the use of a handheld prying device, spear or sling, or a speargun for species such as reef fish, lobster, crabs and octopus. Line fishing Line fishing, also known as bottom-fishing, refers to fishing usually whilst stationary with the use of a weighted line and one or more baited hooks to target demersal reef and deep slope species near the seafloor. Trolling Trolling refers to fishing with a baited hook and line towed behind a moving boat so that the line remains close to the surface and targets epipelagic reef-associated species.
Netting Netting refers to a variety of fishing activities that employ the use of a fishing net such as a hand thrown cast net or seine net that is activity fished, or a gill net or some type of tangle net that is left to fish passively. Nets may be deployed from a boat or from the shore and usually target nearshore pelagic schooling species or schooling reef fishes.
Trapping Trapping refers to the method of fishing with some form of cage structure. They are used baited or unbaited to target reef fishes and lobsters. Lobster-specific traps, made of slatted wood with a specialised entrance funnel are also used, as are open, lobster-attracting artificial habitats, commonly known as casitas. These may comprise a variety of materials such as wooden pallets, a collection of short pipe lengths, shelves of galvanised sheeting, or piles of cement blocks, placed on the bottom near reef habitat to aggregate lobsters for easy harvesting by hand or net.
It is Services Brief 1 p. Large reef fisheries are found in the near a desirable reference point - the maximum Bahamas, the Florida Keys and throughout the sustainable yield MSY Pikitch et al. Whilst Mesoamerican barrier reef system Mexico, there are a few examples of this single species Belize, Guatemala and Honduras. The southern MSY approach being used in the Caribbean, such and eastern Caribbean has a much smaller as in the management of the industrial queen continental shelf area, with most coral reefs conch fishery of Pedro Bank, Jamaica Aiken et forming a narrow fringe around the islands al.
In these areas, extensive fisheries data that are not available in pelagic species, such as flyingfish principally most Caribbean nations. Currently all fisheries Reef fishers A further challenge to managing reef fisheries in the Caribbean is the diverse nature of reef fishers themselves and their varying dependence on the reef resources for livelihood support.
Reef fishers often remain unregistered and may have multiple, dynamic sources of income besides reef fishing, including income from alternative fisheries as well as from agricultural, construction or tourism sectors. As such, reef fishers may be able to maximize their income and minimize livelihood risk by switching between full and part- time reef fishing, depending upon personal circumstances, changes in the seasonal availability of other fishery species, and the availability of work in other sectors. The movement of fishers in and out of the reef fishery and seasonal changes in availability of fish can complicate any efforts to manage fisheries.
Some fishers are becoming involved in the lionfish fishery. Code of Conduct, which stresses the need for territorial waters, are considered data limited improved governance to ensure the success Salas et al. Even in the U.
This includes Gulf of Mexico where there is considerable transparency, stakeholder involvement and investment in fisheries management and cooperation of all states involved in harvesting research, only one reef fishery species, the red fish stocks. This structural complexity is vital estimated as 4. Using data from coral reefs in the Thompson However, these values are based Exuma Cays Land and Sea park in the Bahamas, researchers created a on coral reef fisheries yield data that are more food web model to understand the effects of reduced structural complexity than two decades old see Dalzell for a review of on fisheries productivity.
Initial results from the model suggest that a principle sources and current MSY values for the complete loss of structural complexity may reduce fisheries productivity Caribbean are likely to be significantly lower 3-fold, i. When this complexity is lost however, the dynamics of the reef community change. Of particular concern is the fact that Increased mortality results in fewer small and medium-bodied fish, and in conventional single species assessment and turn results in fewer fish overall. There is an associated decline in the rate management invariably fails to take account of that energy is transferred up the food web meaning less food is available the complex nature of coral reef communities.
Coral reef fishery species are dependent on the reef habitat, hence changes in that habitat Maintaining a structurally complex reef is therefore important for the will affect the species, e. Fishing can also have unpredictable effects on the biomass of species on reefs as the balance between predators and prey is changed Fisheries e distri Brief 1 p. Consideration of the entire ecosystem Siz bu is therefore required for effective management Loss of structural complexity tio of coral reef fisheries.
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