Functional state of various physiological systems of the human body during respiration of neon-oxygen mixture at depth up to 400 meters]

Hyperbaric neon-oxygen mixture has been studied for the effect of its high density under pressure of 41 ata on basic physiological functions of human organism. Typical changes of the cardiorespiratory system and tissue respiration parameters are revealed. Changes in physical working capacity are shown. Exposure to gaseous medium of high pressure and density is accompanied by the development of some compensatory-adaptive reactions. The possibility to perform mid-hard physical work is attained with overstrain of respiration and circulation function.     

Simulation of the Plasma Density Evolution during Electron Cyclotron Resonance Heating at the T-10 Tokamak

In ohmically heated (OH) plasma with low recycling, an improved particle confinement (IPC) mode is established during gas puffing. However, after gas puffing is switched off, this mode is retained only for about 100 ms, after which an abrupt phase transition into the low particle confinement (LPC) mode occurs in the entire plasma cross section. During such a transition, energy transport due to heat conduction does not change. The phase transition in OH plasma is similar to the effect of density pump-out from the plasma core, which occurs after electron cyclotron heating (ECH) is switched on. Analysis of the measured plasma pressure profiles in the T-10 tokamak shows that, after gas puffing in the OH mode is switched off, the plasma pressure profile in the IPC stage becomes more peaked and, after the peakedness exceeds a certain critical value, the IPC-LPC transition occurs. Similar processes are also observed during ECH. If the pressure profile is insufficiently peaked during ECH, then the density pump-out effect comes into play only after the critical peakedness of the pressure profile is reached. In the plasma core, the density and pressure profiles are close to the corresponding canonical profiles. This allows one to derive an expression for the particle flux within the canonical profile model and formulate a criterion for the IPC-LPC transition. The time evolution of the plasma density profile during phase transitions was simulated for a number of T-10 shots with ECH and high recycling. The particle transport coefficients in the IPC and LPC phases, as well as the dependences of these coefficients on the ECH power, are determined.     

Population census of the chimpanzees in the Kalinzu Forest,Uganda: Comparison between methods with nest counts

The population of chimpanzees in the Kalinzu Forest, Uganda was censused with nest counts using the line-transect method. Four methods were examined to estimate density. The estimated densities, ranging from 2.0 to 4.7 chimpanzees per km², all indicated a high population density, in comparison with other chimpanzee habitats. Moreover, the density in the logged area of the Kalinzu Forest was higher than that in the unlogged area. Several factors are thought to contribute to the high density in the Kalinzu Forest. Notable are the mosaic forest structure dominated by mature forest with patches of logged areas, selective logging of non-food tree species of chimpanzees, and low hunting pressure. These results suggest that selective logging may be a practical means of primate conservation in places where timbers are exploited.     

Theoretical studies on the structures and detonation properties of nitramine explosives containing benzene ring

The nitramine compounds containing benzene ring were optimized to obtain their molecular geometries and electronic structures at DFT-B3LYP/6-31+G(d) level. The theoretical molecular density (ρ), heat of formation (HOF), energy gap (ΔE(LUMO-HOMO)), charge on the nitro group (-Q(NO2)), detonation velocity (D) and detonation pressure (P), estimated using Kamlet-Jacobs equations, showed that the detonation properties of these compounds were excellent. It is found that there are good linear relationships between density, heat of formation, detonation velocity, detonation pressure and the number of nitro group. The simulation results reveal that molecule G performs similarly to famous explosive HMX, and molecule H outperforms HMX. According to the quantitative standard of energetics as an HEDC (high energy density compound), molecule H essentially satisfies this requirement. These results provide basic information for molecular design of novel high energetic density compounds.     

The effects of structural parameters of zeolite on the adsorption of hydrogen: a molecular simulation study

The adsorption isotherm of hydrogen in zeolites FAU, LTA, KFI, RWY, RHO and TSC has been simulated employing grand canonical Monte Carlo procedure for a temperature range of 77 to 95 K and different pressures. The effects of structural composition, unit cell volume, framework density and specific surface area of zeolite on hydrogen adsorption in zeolites were investigated. The results clearly show that the adsorption of hydrogen in zeolites with the same silica density is a function of oxygen density at low pressures, and it is approximately the same at intermediate pressures. Nevertheless, at high pressures, the adsorption of hydrogen is a function of pore diameter for zeolites with same silica density. The effect of specific surface area on the adsorption isotherm of hydrogen on zeolites with approximately the same specific surface area is significant at low and high pressures. The results clearly indicate that the adsorption of hydrogen in RWY zeolite has maximum value at 77 K and at high pressures. The optimum condition of pressure for hydrogen adsorption isotherm in RWY zeolite is determined to be 600 bar. At a temperature of 77 K and a pressure of 600 bar, the adsorption of hydrogen in RWY zeolite is 6.93 wt %.     

Boundary nature induces greater group size and group density in habitat edges: an agent-based model revealed

Apart from the amount and distribution of food resources and predation pressure, we sought to clarify habitat spatial features that affect group size and group density. To simulate animal groups interacting with one another, we made an agent-based model in a computational space. Assuming no predation pressure, we change the resource conditions between the habitat (comprising ‘interior’ and ‘edges’) and the ‘exterior’. The results are as follows: when the group density is high throughout the habitat, large groups tend to frequent the edges (i.e., the boundaries between the interior and exterior) even if food resources are scarce in the exterior. Additionally, when the group density is high and the group size variation is small, both group size and group density increase at the edges. These findings are discussed with reference to primates, particularly the Japanese macaque (Macaca fuscata) as an example of group-living animal.     

Density functional study on the derivatives of purine

The derivatives of purine are designed through substituting the hydrogen atoms on it for nitro and amino functional groups. Geometries and frequency are analyzed at the B3LYP/6-31 G** level of density functional theory(DFT). Heats of formation (HOF), bond dissociation energy(BDE) and detonation parameters (detonation velocity and detonation pressure) are obtained in detail at the same level. It is found that the BDE values of all derivatives are over 120KJ·mol(-1), and have high positive heats of formation. These derivatives possess excellent detonation properties, for B1, B2, and C, the detonation velocity are 9.58, 9.57,and 9.90 km·s(-1), and the detonation pressure are 43.40,46.05, and 46.37 Gpa, respectively, the detonation performances are better than cyclotrimethylenetrinitramine (RDX)and cyclotetramethylenetetranitramine (HMX). Hence, the derivations of purine may be promising well-behaved high energy density materials.     

Probing the structure of cometary ice

Computer simulations of bulk and vapor deposited amorphous ices are presented. The structure of the bulk low density amorphous ice is in good agreement with experiments on pressure disordered amorphous ice. Both the low density bulk ice and the vapor deposited ices exhibit strong ordering. Vapor deposition of hot (300 K) water molecules onto a cold (77 K) substrate yields less porous ices than deposition of cold (77 K) water molecules onto a cold subtrate. Both vapor deposited ices are more porous than the bulk amorphous ice. The structure of bulk high density amorphous ice is only in fair agreement with experimental results. Attempts to simulate high density amorphous icevia vapor deposition were not successful. Electron diffraction results on vapor deposited amorphous ice indicate that the temperature of the nucleation of the cubic phase depends upon the amount of time between the deposition and the onset of crystallization, suggesting that freshly deposited ice layers reconstruct on times of the order of hours. The temperature dependence of the microporosity of the vapor deposited amorphous ices might affect laboratory experiments that are aimed at simulating astrophysical ices in the context of the origin of prebiotic organic material and its transport to the Earth.     

Characterizing fishing effort and spatial extent of coastal fisheries

Biodiverse coastal zones are often areas of intense fishing pressure due to the high relative density of fishing capacity in these nearshore regions. Although overcapacity is one of the central challenges to fisheries sustainability in coastal zones, accurate estimates of fishing pressure in coastal zones are limited, hampering the assessment of the direct and collateral impacts (e.g., habitat degradation, bycatch) of fishing. We compiled a comprehensive database of fishing effort metrics and the corresponding spatial limits of fisheries and used a spatial analysis program (FEET) to map fishing effort density (measured as boat-meters per km2) in the coastal zones of six ocean regions. We also considered the utility of a number of socioeconomic variables as indicators of fishing pressure at the national level; fishing density increased as a function of population size and decreased as a function of coastline length. Our mapping exercise points to intra and interregional 'hotspots' of coastal fishing pressure. The significant and intuitive relationships we found between fishing density and population size and coastline length may help with coarse regional characterizations of fishing pressure. However, spatially-delimited fishing effort data are needed to accurately map fishing hotspots, i.e., areas of intense fishing activity. We suggest that estimates of fishing effort, not just target catch or yield, serve as a necessary measure of fishing activity, which is a key link to evaluating sustainability and environmental impacts of coastal fisheries.     

Influence of plasma pedestal profiles on access to ELM-free regimes in ITER

The influence of current density and pressure gradient profiles in the pedestal on the access to the regimes free from edge localized modes (ELMs) like quiescent H-mode in ITER is investigated. Using the simulator of MHD modes localized near plasma boundary based on the KINX code, calculations of the ELM stability were performed for the ITER plasma in scenarios 2 and 4 under variations of density and temperature profiles with the self-consistent bootstrap current in the pedestal. Low pressure gradient values at the separatrix, the same position of the density and temperature pedestals and high poloidal beta values facilitate reaching high current density in the pedestal and a potential transition into the regime with saturated large scale kink modes. New version of the localized MHD mode simulator allows one to compute the growth rates of ideal peeling-ballooning modes with different toroidal mode numbers and to determine the stability region taking into account diamagnetic stabilization. The edge stability diagrams computations and sensitivity studies of the stability limits to the value of diamagnetic frequency show that diamagnetic stabilization of the modes with high toroidal mode numbers can help to access the quiescent H-mode even with high plasma density but only with low pressure gradient values at the separatrix. The limiting pressure at the top of the pedestal increases for higher plasma density. With flat density profile the access to the quiescent H-mode is closed even with diamagnetic stabilization taken into account, while toroidal mode numbers of the most unstable peeling-ballooning mode decrease from n = 10?40 to n = 3?20.     

Spatial distribution of dispersing animals

Summary A mathematical model for the dispersal of an animal population is presented for a system in which animals are initially released in the central region of a uniform field and migrate randomly, exerting mutually repulsive influences (population pressure) until they eventually become sedentary. The effect of the population pressure, which acts to enhance the dispersal of animals as their density becomes high, is modeled in terms of a nonlinear-diffusion equation. From this model, the density distribution of animals is obtained as a function of time and the initial number of released animals. The analysis of this function shows that the population ultimately reaches a nonzero stationary distribution which is confined to a finite region if both the sedentary effect and the population pressure are present. Our results are in good agreement with the experimental data on ant lions reported by Morisita, and we can also interpret some general features known for the spatial distribution of dispersing insects.     

Population parameters of indigenous populations ofMyocastor coypus: the effect of hunting pressure

The coypu or nutriaMyocastor coypus Molina, 1782 is a semiaquatic rodent intensively harvested for fur in its native region. We studied population parameters at four sites differing in hunting pressure and characterised hunting activity in north-eastern Buenos Aires province, Argentina. Our interviews with hunters, local inhabitants and wildlife managers revealed that hunting is a cultural tradition in the countryside with the coypu being used as meat and, fur and the young occasionally used as pets. Quarterly live trapping captured a high proportion of all coypus present at each site. In sites with higher hunting pressure, low density of coypus was associated with high population losses and immigration. I n these sites the proportion of juveniles and pregnant females was similar to that obtained at sites with no hunting pressure. No foraging deficiencies were evident from diet quality analysis. Our results suggest that harvesting determines the dynamics of coypu populations in, this region where hunting pressure can be assessed by accessibility of hunting sites, their distance to urban or rural settlements, effective control of hunting, and human population density of the area.     

Effects of physiologically relevant pressures of helium on the structure of cholesterol-containing lipid bilayers. A neutron diffraction study.

We have used neutron diffraction to study the effects of helium gas (1-210 atm) on the structure of a lipid bilayer model of neuronal plasma membranes. We have recorded diffraction patterns from hydrated multilayers of dimyristoyl lecithin and 40% (molar) cholesterol to a resolution of approximately 6.5 A and have calculated scattering amplitude density distributions as a function of pressure. We find that there are no significant changes in the scattering density profiles at 95% confidence over the range of pressures investigated, suggesting that the physiological effects of high helium pressure are unlikely to be a consequence of changes in the structures of the lipid bilayer portions of membranes.     

Factors affecting the spatial distribution of natural populations of Octopus joubini robson

Observations were made on the density and distribution of Octopus joubini in its natural environment. The average density of octopuses was 1/33 m² but their distribution was clumped. This distribution correlated significantly with the distribution of molluscan shells in which they hid. In addition, octopuses were attracted to sites that had been enriched with extra empty gastropod shells. Since site stability was not observed and they were not repelled from one another when placed at a high density, octopuses were probably not spaced by social pressure. Small crab species, the normal prey of O. joubini, were at a very high density of 30/m², and food abundance probably did not limit octopus number. The main factor affecting distribution of this population of octopuses may be predator pressure acting through the availability of places to hide.     

High and low density intracellular water.

The proposal that liquid water consists of microdomains of rapidly-exchanging polymorphs of high and low density is examined for its impact upon roles of water in biology. It is assumed that the two polymorphs persist in solution and adjacent to surfaces and that solutes partition asymmetrically between them. It transpires that chaotropes are solutes which partition preferentially into low density water and displace the water equilibrium toward the high density polymorph. Kosmotropes. both ionic and non-polar, partition into high density water and induce low density water. Displacement of the water equilibrium at constant temperature and pressure has a thermodynamic cost which can be high. This appears to be a dominant factor in folding of proteins and DNA, aggregation of biopolymers and insolubility of non-polar kosmotropes. Cells control both the concentration of proteins and the selection of small solutes to produce an intracellular environment most conducive to co-ordinated enzyme function. Intracellular water has similar microdomains to bulk water, but surfaces and solutes redistribute them. Average properties, as measured by NMR are similar, but local properties on a nm scale may differ widely. Enzymes apparently use these local differences to activate cations for transport, induce movement and for synthesis.     

Density-dependent sexual selection in the monogamous fish Archocentrus nigrofasciatus

To date, density-dependent effects on sexual selection have been studied only scantly. In this study we experimentally assessed the effect of breeding site density on the size distribution of mating convict cichlids Archocentrus nigrofasciatus in the field. We found that females were larger under low than high nest density. These results are better explained by density-dependent mate choice and mating competition than competing hypotheses of resource competition and predation pressure. We did not find differences in brood survival between the two nest density regimes. Nevertheless, convict cichlids avoided breeding in each other's close proximity, indicating that a high density of breeding pairs entails some other costs, such as energy loss through increased territorial aggression. Our results stress the importance of considering evolutionary effects of mate choice and mate competition in the context of availability of resources that determine the density of individuals that succeed to mate.     

Applicability of a Bayesian state-space model for evaluating the effects of localized culling on subsequent density changes: sika deer as a case study

At the landscape scale, localised culling is often conducted to achieve various deer management aims. However, few studies have assessed the effects of localised culling on deer population dynamics, owing to the spatially and temporally insufficient datasets of deer abundance that are derived from limited survey efforts. In this study, we estimated the population dynamics of a sika deer (Cervus nippon) population in the Tanzawa Mountains, central Japan, by Bayesian state-space modelling using spatiotemporally insufficient abundance indices and evaluated the effects of unit-specific culls on subsequent density changes in 56 units. The responses of deer density to unit-specific culls differed greatly among units, and a very weak correlation was observed between the intensities of unit-specific culls and the reduction in density. Deer populations in some units tended to resist density decreases despite high culling pressure, whereas those in other units were susceptible to density decreases with little to no culling pressure. Because the spatial scales of each unit were relatively small, annual density changes in each unit were largely influenced by deer movement in this estimation. The obscured effects of unit-specific culls, which were probably derived from deer movement among units in this case study, re-emphasized that deer migration should be incorporated into the planning of localised culling and that deer management should be coordinated over a wide area beyond landscape components and landownerships. Thus, we conclude that Bayesian state-space modelling is valuable for practical deer management programs at a large spatial scale even if different abundance indices are used.     

Arteriovenous difference of the blood density in the coronary circulation

The mechanical oscillator technique permits determining blood density continuously with high accuracy. Using this technique arteriovenous density gradients were recorded in the coronary vascular bed of anesthetized dogs. It was found that the coronary sinus blood has a higher density than arterial blood due to the loss of filtered fluid in the microcirculation. The amount of fluid loss corresponds to the lymph flow in the myocardium. Increase of venous pressure leads to an increase of the density gradient. Intermittent coronary sinus occlusion (ICSO) surprisingly leads to a reduction of the density gradient. Injection of osmotically hypertensive fluids influences the arteriovenous gradient by shifting extravascular fluid into the blood. The method permits the determination of filtration coefficients and to estimate the tissue volume available for fluid exchange.     

Mountain hare populations on islands: effects of predation by red fox

Summary On islands off the west coast of Sweden the density of mountain hares (Lepus timidus L.) is very high. One of the main predators on hares, the red fox (Vulpes vulpes L.), is only present during short periods. Data on hare density and predation by red fox and eagle owl (Bubo bubo (L.)) has been analyzed from five islands over several years. Winter mortality in years with low predation pressure was independent of hare density. But when red fox or eagle owl were present on islands (i.e., high predation pressure) winter mortality became density dependent. Thus, at low density, winter mortality did not increase through red fox predation. But at densities up to two hares/ha, predation pressure was increasing and could be limiting for these populations. At still higher hare density predation pressure became less intensive. The functional response for foxes preying on hares showed a type II or a sigmoid type III response pattern. In normal summers, the population increase due to reproduction was at least two-fold. When a fox was present there was instead a sharp decrease in hare numbers. Fox predation had a stronger effect in summer than in winter. By switching between islands and mainland areas from winter to summer, a fox can stabilize fluctuations in hare numbers on the islands. This is dependent on how often the ice permits a fox to reach an island and the lack of numerical response by predators.     

Molecular dynamics simulation of tensile strain-altered hydrogen behaviour and its effects on local plasticity

Using molecular dynamics simulation, local plasticity of bcc Fe (0 0 1) is studied at different density of Fe–H cluster. H-induced softening and hardening of Fe substrate are observed along with the tensile elongation at low and high density, respectively. The two contradictory phenomena are ascribed to H behaviours-related plastic deformation. At high H partial pressure, initial H aggregation would lead to the formation of many H-enriched clusters similar to hydride. Tensile strain-induced dislocations (TSID) prefer to be generated and grow at the weakening interface of clusters and iron substrate. At low H partial pressure, TSIDs are uniformly distributed in the whole substrate. Owing to the affinity between H and dislocations, the diffusion of H appears to be distinct under different spatial distribution of TSIDs. H aggregation and dispersion can be enhanced and produce nonuniform and uniform plastic deformation during the continuous tensile process at high and low Fe–H cluster density, respectively. The former can stimulate local failures and accelerate the degradation of mechanical property. The results are helpful for better understanding of Fe–H cluster-related hardening and softening considering external strain-altered H behaviours except for the mechanism of H-dislocation interaction.