The northwestern Indian Ocean hosts globally crucial marine biodiversity, which is relatively understudied. There has, however, been significant research and conservation effort focused on marine ...turtles across the region in recent decades. We undertook an exhaustive review of 251 relevant publications to extract and collate the current information concerning marine turtles. To ensure completeness, we received input on a preliminary draft from a large group of experts who have worked extensively in the region. Data presented here are from all 13 countries with significant coastlines in the region (Bahrain, Djibouti, Egypt, Eritrea, Iran, Kuwait, Oman, Qatar, Saudi Arabia, Somalia, Sudan, United Arab Emirates, and Yemen) on occurrence, nesting biology, morphology, foraging areas, population status, threats, and relevant national legislation and international conservation strategies. The experts independently provided details on what they felt were the (1) most significant threats to marine turtles, (2) most critical knowledge gaps for marine turtle ecology, (3) impediments to practical conservation, and (4) essential strengths and opportunities in the region.
The United Arab Emirates (UAE) host valuable coastal and marine biodiversity that is subjected to multiple pressures under extreme conditions. To mitigate impacts on marine ecosystems, the UAE ...protects almost 12% of its Exclusive Economic Zone. This study mapped and validated the distribution of key coastal and marine habitats, species and critical areas for their life cycle in the Gulf area of the UAE. We identified gaps in the current protection of these ecological features and assessed the quality of the data used. The overall dataset showed good data quality, but deficiencies in information for the coastline of the north-western emirates. The existing protected areas are inadequate to safeguard key ecological features such as mangroves and coastal lagoons. This study offers a solid basis to understand the spatial distribution and protection of marine biodiversity in the UAE. This information should be considered for implementing effective conservation planning and ecosystem-based management.
•Mapping species and habitats is necessary for effective ecosystem-based management.•We compiled data to map marine and coastal biodiversity distribution in the UAE.•Data quality assessment showed that data are sufficient to guide management.•Current MPA extension is insufficient to safeguard some habitats such as mangroves.•The information provided should be used in future conservation plans and management.
Many workers 1–9 studied the kinetics of dolomite decomposition to study the effects of different parameters like, gas (CO₂, N₂ etc.) pressures, water vapor, presence of other impurities, particle ...size and grain size of the dolomite samples, crystallinity etc. on the decomposition kinetics of dolomite using different tools like, thermal analysis, thermo-gravimetric analyses, XRD technique etc. and different values of the activation energies for the decomposition reaction, order of reactions have been reported. It has been observed that pure dolomite decomposed in only two steps. The first stage of the thermal decomposition of dolomite resulted in the formation of Mg-calcite (CaMg)CO₃ and periclase (MgO), with the liberation of CO₂. It was further observed that under CO₂, dolomite decomposed directly to CaCO₃, accompanied by the formation of MgO between 550 and 765∘C. Calcite decomposed to CaO between 900 and 960∘C and under air, simultaneous formation of CaCO₃, CaO and MgO accompanied dolomite decomposition between 700 and 740–750∘C. At the latter temperature, the calcite began to decompose even though a significant amount of dolomite was still present and simultaneous decomposition of the two carbonates was terminated at 780∘C. Also, changes in decomposition rates of the various phases correlated with changes in the rate of weight loss determined by derivative thermo-gravimetric analysis.
We present a numerical model of flow and bed morphology in meandering submarine channels. The conservation equations of fluid mass and momentum, suspended sediment concentration, and turbulent ...kinetic energy are expressed in depth‐averaged form and an intrinsic coordinate system. These equations, along with the Exner equation of bed sediment continuity, are solved using a predictor‐corrector explicit finite difference scheme. The numerical model is validated against laboratory experiments conducted in a straight flume. The model is generalized to any sinuous planform geometry, but this study focuses on sine‐generated sinuous channels. A series of numerical experiments have been performed with various inflow conditions and channel shapes to characterize the nature of in‐channel flow, deposition, and erosion, as well to investigate the tendency for meander migration. The model predicts an overall decrease in depth‐averaged current velocity and suspended sediment concentration in the down‐channel direction. Variations of current thickness, streamwise velocity, concentration, and bed level across the channel have been found to increase with an increase in channel curvature. Model runs made with erosional currents display significant change in bed level in the lateral direction because of erosion near the out side and deposition near the inside of a bend. The lateral bed slope generated by the flow of a depositional current is found to be relatively small. Model results are compared with the sedimentation pattern of a seismically interpreted buried submarine channel.
After the last apparition of comet Halley in 1985–86, a number of other comets were observed in polarimetry with IHW-continuum filters. From the in situ dust measurements of Halley, dust size ...distribution functions were obtained (Lamy et al. CITE, A&A, 187, 767; Mazets et al. CITE, Nature, 321, 276), which were later used by several authors to interpret polarisation data of Halley. In the present work, polarimetric data of various comets have been analyzed, using Mie theory and assuming that the composition of dust particles does not differ from comet to comet (Delsemme CITE, ESA SP-278, 19). The individual grain size distribution functions so obtained for various comets suggest different values for the relative abundance of coarser grains. Introducing a “relative abundance of coarser grains” index g, we study any possible dependence of g on the dynamical age of a comet, where the dynamical age can be defined in terms of some of the orbital parameters of the comet. For the four non-periodic comets available for our analysis, we find a clear empirical relation $g=-2.5.q ^{2/3}$ emerging from our work. This relation strengthens the concept that comets whose grains are processed more by the solar radiation (these comets may be dynamically older) contain a relatively smaller number of finer grains. The case for other periodic comets is also discussed here. Since the work has been carried out using Mie scattering theory meant for perfect compact spheres, it is also suggested to repeat the calculations with more realistic porous grains in a follow-up paper.
The polarization observed for stars behind dark clouds (Bok globules) is often used as a diagnostic to study the ongoing star formation processes in these clouds. Such polarization maps in the ...optical have been reported for eight nearby clouds, CB3, CB25, CB39, CB52, CB54, CB58, CB62 and CB246, in our previous work. With a view to understanding the origin of this polarization, in the present work attempts are made to look for any possible relation between this observed polarization and other physical parameters in the cloud (like temperature, turbulence, etc.). The observed polarization does not seem to be clearly related to the dust and gas temperatures (Td and Tg) in the cloud as expected from the Davis-Greenstein grain alignment mechanism. However, the average observed polarization (pav) appears to be related to the turbulence ΔV (measured by the 12CO linewidth) by the mathematical relation pav= 2.95 exp(−0.24ΔV). The possible relation between the direction of the polarization vector and other physical parameters is also discussed. For this analysis, in addition to the data on the above eight dark clouds, the data on CB4 are also included for comparison. In order to study the spatial distribution of the degree of polarization and position angles across the different parts of the cloud a simple model is proposed, where the cloud has been assumed to be a simple dichroic polarizing sphere and the light from the background star first passes through the interstellar medium and then through the cloud, before reaching the observer. One finds this simple model can explain to a reasonable extent the observed spatial (radial) dependence of the value of p for two of the clouds (CB25, CB39), but for the rest of the clouds the model fails. However, through this model one can explain why the polarization (p) need not always increase with total extinction Av as one moves into the deeper interior of the cloud.
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