327 research outputs found
Temporal changes of the fish community in a seagrass bed after disappearance of vegetation caused by disturbance of the sea bottom and sediment deposition
To investigate the response of the fish community structure to a natural disturbance in their habitat, fish abundance, biomass and species composition were analysed in relation to temporal variability of environmental conditions in a seagrass Zostera marina bed. A total of 3024 fishes belonging to 46 taxa (22 families) were collected by quantitative sampling for 10 years from 2007 to 2016 in the Seto Inland Sea, south-western Japan. Seagrass shoot density decreased to less than 1/20 of its original density after disappearance of vegetation caused by heavy rain in the autumn of 2011 and the area did not recover for the next five years. In order to analyse temporal changes of fish community, the fishes were divided into three groups depending on their habitats or lifestyles: pelagic or migratory species (PM), sand or mud bottom-associated species (SM) and seagrass (Z. marina) – or substrate (rocky bottom including macrophytes) – associated species (ZS). Multiple regression analysis showed seagrass shoot density had the most significant effect on biomass of ZS among the three groups, with higher fish biomass under higher seagrass shoot density. Fish community composition changed after the disappearance of the seagrass vegetation coverage with an increase in abundance of SM during the five years of the post-disturbance period. Seagrass vegetation was concluded to affect temporal change of fish community structure through a stronger influence on fish species that are more dependent on seagrass beds as habitat.This study was partially supported by the Global Environment Research Fund (J.S., grant number RF-0907and RF-1102) of the Ministry of the Environment, and Grant-in-Aid for Scientific Research (B) (J.S., grant number 24380107)
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Glaucomatous vertical vessel density asymmetry of the temporal raphe detected with optical coherence tomography angiography.
Changes in retinal vasculature and ocular circulation may play an important role in the glaucoma development and progression. We evaluated the vertical asymmetry across the temporal raphe of the deep retinal layer vessel density, using swept-source optical coherence tomography angiography (SS-OCTA), and its relationship with the central visual field (VF) loss. Thirty-four eyes of 27 patients with open-angle glaucoma were included. SS-OCTA macular scanning was performed within a 3 × 3 mm (300 × 300 pixels) volume, centred on the fovea. The relationships between the vertical asymmetrical deep retinal vessel density reduction (ADRVD) across the temporal raphe and various ocular parameters were analysed. Twenty-two glaucomatous eyes with ADRVDs had central VF loss. Contrarily, ADRVDs were not found in any of the 12 eyes without central VF loss. Thirteen eyes (59.1%) with central VF loss had ADRVDs topographically corresponding to the central VF loss and macular ganglion cell complex thinning. The glaucomatous eyes with ADRVDs exhibited inferior rather than superior central VF loss (P = 0.032). Thus, ADRVD specifically indicates the glaucomatous central visual loss. Further analysis of ADRVD may improve our understanding on glaucoma pathogenesis, offering new treatment insights
Satellite Constellation Pattern Optimization for Complex Regional Coverage
The use of regional coverage satellite constellations is on the rise, urging
the need for an optimal constellation design method for complex regional
coverage. Traditional constellations are often designed for continuous global
coverage, and the few existing regional constellation design methods lead to
suboptimal solutions for periodically time-varying or spatially-varying
regional coverage requirements. This paper introduces a new general approach to
design an optimal constellation pattern that satisfies such complex regional
coverage requirements. To this end, the circular convolution nature of the
repeating ground track orbit and common ground track constellation is
formalized. This formulation enables a scalable constellation pattern analysis
for multiple target areas and with multiple sub-constellations. The formalized
circular convolution relationship is first used to derive a baseline
constellation pattern design method with the conventional assumption of
symmetry. Next, a novel method based on binary integer linear programming is
developed, which aims to optimally design a constellation pattern with the
minimum number of satellites. This binary integer linear programming method is
shown to achieve optimal constellation patterns for general problem settings
that the baseline method cannot achieve. Five illustrative examples are
analyzed to demonstrate the value of the proposed new approach.Comment: 47 pages, 23 figures, Journal of Spacecraft and Rockets (Published
Electronic structure and electrical properties of amorphous OsO2
The valence-band spectrum of an amorphous OsO2 film deposited by glow discharge of OsO4 vapor can be
predicted well with calculated electronic band structure of crystalline OsO2 from first principles using the
liner-muffin-tin-orbital method with the local-density approximation. Resistivity of the amorphous OsO2 was
less than 631023 V cm at 80 K, and it was almost temperature independent, but the temperature coefficient of
resistivity was negative. The Hall coefficient of the amorphous OsO2 increased with temperature, and was
saturated at around 220 K. Temperature dependence of the Hall mobility was proportional to T3/2, and it
implies that the scattering of charged carriers by ionized atoms is dominant below 220 K
Characterization of the lasing properties of a 5%Yb doped Lu_2SiO_5 crystal along its three principal dielectric axes
The laser performance of a 5% Yb doped Lu2SiO5 (Yb:LSO) has been investigated in quasi continuous-wave pumping regime along the three principal dielectric axes of the crystal, to obtain a complete characterization of its laser properties. The comparison among the obtained results for differently polarized lasers, in term of relative slope efficiency and absolute efficiency, allows the exploitability of different orientations of the material in order to be determined to obtain efficient laser sources. The laser slope efficiency and the energy conversion efficiency were similar for emission polarized along the three indicatrix axes, with noticeable maximum values of slope efficiency around 90% for polarization along the Y and Z axes. Tunable laser action has been obtained in the range 990 nm - 1084 nm, with sizeable differences in the shape of the tuning curve for polarization along the X, Y and Z axes. In particular, the tuning for polarization along the Z axis is relatively flat and uniform in the range 1023 nm - 1083 nm
Measurements of neutron total and capture cross sections of La and evaluation of resonance parameters
Neutron total and capture cross sections of Lanthanum(La)-139 were measured
at the Accurate Ne-utron-Nucleus Reaction measurement Instrument (ANNRI) of the
Materials and Life Science Experimental Facility (MLF) in the Japan Proton
Accelerator Research Complex (J-PARC). The total cross section was largely
different from that in evaluated libraries, such as JENDL-5, in the energy
range from 80 to 900~eV. Resonance parameters for four resonances including one
negative resonance were obtained using a resonance analysis code, REFIT. The
resonance analysis revealed discrepancies in several resonance parameters with
the evaluated libraries. Furthermore, the information about the scattering
radius was also extracted from the results of the total cross section. The
obtained scattering radius was larger than that recorded in the evaluated
libraries.Comment: 12 pages, 16 figure
Analysis of Edge Plasma Turbulence and Neutral Particle Transport in Open Magnetic Field Configuration Plasmas
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