Extreme Low Density Research Articles

A preliminary study on the distribution of spiny lobster (Panulirus spp.) in Labuan Island, Malaysia

Limited info regarding on the global distribution and fisheries data on the spiny lobster Panulirus spp. had placed the IUCN redlist in a dilemmatic position in determining the concrete status for proper conservation. The present survey was carried out in the western region of the main island which consists of seven random stations along the west coast of Labuan during day dive. An extreme low density of the spiny lobsters from the genus Panulirus was determined throughout the present study. Only four individuals of two spiny lobsters species were recorded. Two individuals of P. versicolor were observed in station 2 while the other two (P. ornatus) were spotted in station 4. Low numbers of the Panulirus spp. were spotted during the present preliminary survey was probably due to day dive sampling. Spiny lobster from the genus Panulirus tend to have a wide range of depth preference. Two adults P. versicolor were spotted in least turbid environment. In the previous studies, Panulirus spp. such as P. homarus, P. ornatus, and P. polyphagus tend to prefer slightly turbid environment. The results of the present preliminary daytime survey indicated only two species of Panulirus spp. recorded with two individual numbers per species in Labuan coastal waters. However, due to the little numbers of catchment during the preliminary survey, further studies need to be carried out to provide more concrete evidences on the depth preference of Panulirus spp. in Malaysian waters.

Fabrication of ultralow-density quantum dots by droplet etching epitaxy

Abstract

グラフェン強化 Al 基ナノ複合材料の機械的特性

Basic science of graphene with various superior characteristics has been made clear rapidly on the frontier technology. Nevertheless, various surprising mechanical properties of graphene have been not attracted great attention, such as extreme low density, tensile strength with 100 times stronger than steel by weight, Young's modulus with 1 TPa and more flexible than rubber. We focused on graphene/Al nano composite materials. Since our original successful isolation techniques of creating single layer nanographene sheets from nanographene with a several sheet and uniforming dispersion of nanographene within based materials, we have been challenging in fabrication innovative graphene reinforced Al composite sintered materials with high specific strength and established the fabrication method. It has already been demonstrated that Vickers hardness of graphene/Al composite pellet-formed sintered materials showed the maximum value of 323 Hv, and the density decreased down to 2.45 g/cm3. In this study, we investigated possibility that industrial applications of our graphene/Al nano composite materials. Standard flat-plate type specimens consisted of our graphene/Al nano composite materials were fabricated under the same sintered condition. Bending, tensile mode tests were performed. Elastic and fracture properties were analyzed using four-point bending test apparatus. The results revealed that Young's modulus increased from 40 GPa of sintered Al up to 45 GPa of composite materials. Fracture characteristics showed that the breaking stress of the composite material showed improvement up to 75 %, and the breaking strain of the composite material also increased up to 70 %. These great improvements of mechanical properties can be attributed to reinforcement effect of nanographene. Therefore, graphene/Al nano composite materials give us excellent possibility of the innovative industrial use materials with a promising future.

X Ray Phase Contrast Imaging for the Extreme Low Density or Weak Absorption Materials

In order to get better images from the extreme low density or weak absorption materials, a new modulation transfer function model is established for the X ray phase contrast imaging. Then the parameter effects of ray source size are elaborated on the basis of the partially coherent optical theory. From the simulation and calculation, the proposal and parameter optimization are revealed according to the actual materials experiment conditions.

Numerical investigations of Z-pinch plasma instabilities

A twodimensional,radiation magnetohydrodynamics model is applied to the simu lation of Zpinch plasma sausage instability.Different implosion mechanisms in the cases of the existence and the nonexistence of instability are analyzed,an d the effects of various initial density perturbation levels on the x-ray power and energy are investigated.Numerical results show that x-ray energy output is not susceptive to sausage instabilities in a certain extent but x-ray power ve rsus time is evidently dependent on the instabilities.In addition,this paper als o studies the effects of numerical treatment of extreme low density in Zpinch simulations on numerical results.

Cellular distribution of secretin receptor expression in rat pancreas.

Secretin is an important regulator of pancreatic function, but the molecular basis of its actions is not well understood. We have, therefore, used in situ autoradiography, photoaffinity labeling, and RNase protection assays with healthy rat pancreas, dispersed acinar cells, and pancreas depleted of acinar cells to explore the cellular distribution and molecular identity of high-affinity secretin receptors in this complex organ. The autoradiographic examination of 125I-labeled [Tyr10]rat secretin-27 binding to normal pancreas demonstrated saturable and specific high-affinity binding sites on both acinar and duct cells, with a uniform lobular distribution, but with no binding above background over islets or vascular structures. Photoaffinity labeling demonstrated that the ductular binding site in acinar cell-depleted copper-deficient rat pancreas represented the same glycoprotein with a molecular weight of 50,000-62,000 that was present on acinar cells. RNase protection assays confirmed the molecular identity of the secretin receptors expressed on these distinct cells. The apparent absence or extreme low density of similar secretin receptors on islets and pancreatic vascular structures suggests that the pharmacological effects of secretin on those cells may either be indirect or mediated by another secretin family receptor that recognizes this hormone with lower affinity.

Approximating Collisional Freestream Attenuation at Transitional Knudsen Numbers

When a body such as an instrument package is immersed within a rarefied flowfield, the inevitable result is distorsion of the freestream. This perturbation is a formidable stumbling block for code developers seeking reliable experimental data for comparison with flowfield predictors. Current codes produce a spatial map of dynamic pressure. Validation of the codes must rely on an accurate means of determining the undisturbed freestream dynamic pressure from experimental data for comparison. Althrough this problem is closed for a continuum case via Rayleigh-Pitot formula, the extreme low density inherent to an exoatmospheric plume renders this treatment invalid because the thickness of the shock layer may be many times larger than the body immersed in the flow. The basic approach taken to solve this problem was to analyze the interaction between two separate streams of molecules.

Tree‐ring evidence of the widespread effects of explosive volcanic eruptions

Tree‐ring evidence from 97 sites over North America and Europe are used to develop a chronology of widespread cool summers since 1600. Averaging annual maximum‐density information from the chronologies provides an index that correlates with Northern Hemisphere summer temperatures to 0.44 over 1851–1975. A number of the extreme low density years occur in both North America and Europe, suggesting a common response to high‐frequency forcing. The analysis was repeated with ring‐width information but the results are markedly less coherent. Of the five common extreme low‐density years (1601, 1641, 1669, 1699 and 1912) four are known to be coincident with the year or year following major volcanic eruptions. Other extreme low density indices in the continental series are also clearly coincident with known volcanoes. The density indices clearly demonstrate great potential for quantifying the climate effectiveness and perhaps establishing precise calendar dates of large explosive volcanoes.

Viscosity of a suspension of deformable bodies beyond the low density regime

The viscosity of a suspension of deformable bodies in a fluid is considered beyond the extreme low density regime. The range of applicability of the result is discussed.

Melting Curve of Wigner Electron Crystal

Abstract The shape of the melting line of the Wigner crystal is discussed in the temperature-density plane. It is argued that near the critical density ρ∗ for the Wigner transition at T = 0 the melting curve has the form For extreme low densities, on the other hand, the melting curve has as its asymptote the classical plasma melting line It seems that there should be a single maximum in the melting curve. The classical plasma line should provide an upper bound for the melting temperature, but is a poor bound away from the low density limit.

Band Narrowing and theT-Matrix Pole

The strongly correlated Hubbard model is shown to be significantly affected by a highlying pole of the $t$ matrix. There are important renormalization effects on the single-particle propagator due to the poles, which are of significance even for low densities. Extreme low densities are treated here.