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2.
Joel D. Gunn 《Human ecology: an interdisciplinary journal》1994,22(1):1-22
The articles in this special issue range across such influences on climate as solar emissions, orbital precession, atmosphere, oceans, and precipitation, and generally approach, each in some context, human implications of these phenomena. The common underlying theme of all of the papers is the effect the phenomena have on radiation balance as measured by global average temperature. This introductory paper undertakes a formulation of radiation balance theory that makes it serviceable to students of regional science. The objective is to go beyond inference of cause and effect by correlation to causal accounts of cause and effect through regional climatic and cultural processes. This is accomplished primarily by revisualization of the energy system with regions as dependent spatiotemporal entities, and temporally through a protocol for regional episode definition.This special issue ofHuman Ecology consists of the American Anthropological Association Invited Symposium on Global Climate Change. 相似文献
3.
《Saudi Journal of Biological Sciences》2020,27(11):2936-2941
In this research, a proto-type study we have conducted, where we have synthesized tungsten based composite materials which are tungsten along with combined oxides of other elements like calcium, scandium, barium, and aluminium in the form of powder with bones powder of mice devised by high energy ball mill and later on fabricating high dense pellets by sintering by spark plasma. The particle sizes of the composite materials are found to be 1–2 µm, as evidenced by the electron microscope, suggesting synthesized materials are of micron size. The quantitative and qualitative analysis of sintered pellets are well confirmed by electron probe micro analyzer (EPMA) and energy dispersive X-ray spectrometer (EDS) which illustrate the greater percentage of tungsten presents in the profound scan areas with other elements of the composite. The absence of pores across the 3D geometry suggesting dense sample, which is quite revealed by the X-ray tomography inspection. The prepared sintered pellets from the tungsten based composites are found to be ≈ 99.5% density with the observation of tungsten to be accumulated uniformly across the scan regions along with focussed hot spots as implied by EPMA. This study paves the way, to examine how the tungsten accumulation and the distribution with the other elements for future understanding in bone tissue engineering application and the in vivo specification of tungsten. 相似文献
4.
Dietary sodium intake for freshwater salmonids feeding in the wild (invertebrate diet) or in captivity (pellet diet) was calculated and compared with published branchial sodium influx values. Dietary sodium intake (mmol kg−1 per month) increases from winter minimum values of 5 and 30-40 to reach maximum values in summer of 175 and 240 for invertebrate and pellet diet, respectively. In summer, dietary sodium intake for fish feeding in the wild was of the same magnitude as branchial sodium influx. The implications of dietary sodium intake for sodium balance in freshwater fish are discussed. 相似文献
5.
Computer modeling of substrate binding to lipases from Rhizomucor miehei, Humicola lanuginosa, and Candida rugosa. 总被引:3,自引:3,他引:0 下载免费PDF全文
M. Norin F. Haeffner A. Achour T. Norin K. Hult 《Protein science : a publication of the Protein Society》1994,3(9):1493-1503
The substrate-binding sites of the triacyl glyceride lipases from Rhizomucor miehei, Humicola lanuginosa, and Candida rugosa were studied by means of computer modeling methods. The space around the active site was mapped by different probes. These calculations suggested 2 separate regions within the binding site. One region showed high affinity for aliphatic groups, whereas the other region was hydrophilic. The aliphatic site should be a binding cavity for fatty acid chains. Water molecules are required for the hydrolysis of the acyl enzyme, but are probably not readily accessible in the hydrophobic interface, in which lipases are acting. Therefore, the hydrophilic site should be important for the hydrolytic activity of the enzyme. Lipases from R. miehei and H. lanuginosa are excellent catalysts for enantioselective resolutions of many secondary alcohols. We used molecular mechanics and dynamics calculations of enzyme-substrate transition-state complexes, which provided information about molecular interactions important for the enantioselectivities of these reactions. 相似文献
6.
PurposeTo evaluate the use of pseudo-monoenergetic reconstructions (PMR) from dual-energy computed tomography, combined with the iterative metal artefact reduction (iMAR) method.MethodsPseudo-monoenergetic CT images were obtained using the dual-energy mode on the Siemens Somatom Definition AS scanner. A range of PMR combinations (70–130 keV) were used with and without iMAR. A Virtual Water™ phantom was used for quantitative assessment of error in the presence of high density materials: titanium, alloys 330 and 600. The absolute values of CT number differences (AD) and normalised standard deviations (NSD) were calculated for different phantom positions. Image quality was assessed using an anthropomorphic pelvic phantom with an embedded hip prosthesis. Image quality was scored blindly by five observers.ResultsAD and NSD values revealed differences in CT number errors between tested sets. AD and NSD were reduced in the vicinity of metal for images with iMAR (p < 0.001 for AD/NSD). For ROIs away from metal, with and without iMAR, 70 keV PMR and pCT AD values were lower than for the other reconstructions (p = 0.039). Similarly, iMAR NSD values measured away from metal were lower for 130 keV and 70 keV PMR (p = 0.002). Image quality scores were higher for 70 keV and 130 keV PMR with iMAR (p = 0.034).ConclusionThe use of 70 keV PMR with iMAR allows for significant metal artefact reduction and low CT number errors observed in the vicinity of dense materials. It is therefore an attractive alternative to high keV imaging when imaging patients with metallic implants, especially in the context of radiotherapy planning. 相似文献
7.
N. D. De With 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1996,166(5):337-343
InLymnaea stagnalis, oral uptake of ambient medium was studied using51Cr-ethylenediaminetetra-acetic acid. In normal snails Cr-ethylenediaminetetra-acetic acid uptake showed two components: a
high uptake rate within the first hour followed by moderate uptake proportional with time. The tracer accumulated mainly in
the digestive system. All animals showed initial, transient uptake. Moderate uptake proportional with time did not occur in
snails in which the buccal ganglia had been extirpated, in which both the buccal ganglia had been extirpated and the oesophagus
was sectioned, or in snails provided with an oesophageal fistula. These snails did not accumulate tracer in the intestinal
system. This type of tracer accumulation clearly represented oral ingestion of surrounding water. The oral water ingestion
rate ranged from 8 to 12 μl·h−1·g−1. Assuming complete absorption, this accounts for 20–30% of the urine production rate. At low external concentrations the
contribution of oral water ingestion to Na+ balance is negligible. However, its importance will grow with increasing external concentrations and becomes a major factor
at higher concentrations. The ingestion rate increased almost sixfold when starving snails were allowed to feed. It is suggested
that oral water ingestion is a consequence of making bite cycles and swallowing. 相似文献
8.
E. Golomer P. Dupui H. Monod 《European journal of applied physiology and occupational physiology》1997,76(2):140-144
We investigated the effects of maturation on the dynamic body sways of healthy girls. Prepubertal and postpubertal girls
practising professional physical activities requiring a good ability to maintain equilibrium (acrobats and dancers) were asked
to stand on a free seesaw platform and the results compared to those for untrained age-matched girls. This platform (stabilometer)
allows self-induced body sways. Stabilograms were obtained by a double integration of the angular acceleration from the recordings
of the platform sways made with an accelerometer. Fast Fourier transform processing of stabilograms allowed spectral frequency
analysis. The total spectrum energy and the energies of three frequency bands (0–0.5 Hz, 0.5–2 Hz, 2–20 Hz) were determined.
ANOVA showed that, for all groups of different equilibrium activity and independent of visual input, prepubertal girls had
higher energy values than postpubertal girls in the 0- to 0.5-Hz band whereas the opposite was true for 0.5- to 2-Hz band.
Ballet dancers were more dependent than acrobats on visual inputs for the regulation of their postural control but were less
dependent than untrained girls at both ages. Maturation seemed to shift body sways towards higher frequencies and the utilization
of the cues of postural control was different according to the type of equilibrium activity practised by the subjects.
Accepted: 7 February 1997 相似文献
9.
Rechargeable graphite dual‐ion batteries (GDIBs) have attracted the attention of electrochemists and material scientists in recent years due to their low cost and high‐performance metrics, such as high power density (≈3–175 kW kg?1), energy efficiency (≈80–90%), long cycling life, and high energy density (up to 200 Wh kg?1), suited for grid‐level stationary storage of electricity. The key feature of GDIBs is the exploitation of the reversible oxidation of the graphite network with concomitant and highly efficient intercalation/deintercalation of bulky anionic species between graphene layers. In this review, historical and current research aspects of GDIBs are discussed, along with key challenges in their development and practical deployment. Specific emphasis is given to the operational mechanism of GDIBs and to unbiased and correct reporting of theoretical cell‐level energy densities. 相似文献
10.
Hassina Tabassum Chenxu Zhi Tanveer Hussain Tianjie Qiu Waseem Aftab Ruqiang Zou 《Liver Transplantation》2019,9(39)
Trogtalite CoSe2 nanobuds encapsulated into boron and nitrogen codoped graphene (BCN) nanotubes (CoSe2@BCN‐750) are synthesized via a concurrent thermal decomposition and selenization processes. The CoSe2@BCN‐750 nanotubes deliver an excellent storage capacity of 580 mA h g?1 at current density of 100 mA g?1 at 100th cycle, as the anode of a sodium ion battery. The CoSe2@BCN‐750 nanotubes exhibit a significant rate capability (100–2000 mA g?1 current density) and high stability (almost 98% storage retention after 4000 cycles at large current density of 8000 mA g?1). The reasons for these excellent storage properties are illuminated by theoretical calculations of the relevant models, and various possible Na+ ion storage sites are identified through first‐principles calculations. These results demonstrate that the insertion of heteroatoms, B–C, N–C as well as CoSe2, into BCN tubes, enables the observed excellent adsorption energy of Na+ ions in high energy storage devices, which supports the experimental results. 相似文献