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21.
The epaulette shark (Hemiscyllium ocellatum) and the grey carpet shark (Chiloscyllium punctatum) are commonly found in periodically hypoxic environments. The ecophysiological time available for these animals to safely
exploit these niches during different seasonal temperatures was examined. The time to loss of righting reflex (T
LRR) was examined in response to an open ended anoxic challenge at three seasonal temperatures (23, 25 and 27°C). Ventilation
rates were measured in an open ended anoxic challenge at 23°C and during 1.5 h of anoxia followed by 2 h of re-oxygenation
at 23 and 25°C. The mean T
LRR of epaulette and grey carpet sharks was inversely proportional to temperature. The T
LRR was similar between species at 23°C; however, grey carpet sharks had significantly reduced T
LRR at higher temperatures. During the standardised anoxic challenge, epaulette sharks entered into ventilatory depression significantly
earlier at 25°C. During re-oxygenation, epaulette sharks exposed to anoxia at 23°C had no significant increase in ventilation
rates. However, after anoxic challenge and re-oxygenation at 25°C, epaulette sharks showed a significant increase in ventilation
rates during re-oxygenation. Grey carpet sharks displayed no evidence of ventilatory depression during anoxia. However, during
re-oxygenation, grey carpet sharks had significantly elevated ventilation rates above pre-experimental levels and control
animals. These data demonstrate that the anoxia tolerance times of both species were temperature dependent, with a significant
reduction in the T
LRR occurring at higher temperatures. Epaulette sharks had a significantly greater T
LRR at higher temperatures than grey carpet sharks, which did not enter into a ventilatory depression. 相似文献
22.
23.
Kevin Lombard Mick O’Neill Robert Heyduck Blake Onken April Ulery John Mexal Adrian Unc 《Agroforestry Systems》2011,81(1):45-56
Composted sewage sludge (biosolids) supply plant available Fe and may represent a sustainable alternative to more costly chelated
Fe fertilizers currently used to supplement nutrition in hybrid poplar test plots of elevated soil pH. To test the response
of poplars, field plots were amended with composted biosolids at two agricultural rates: 22.75 and 44.5 Mg ha−1. Iron EDDHA served as a fertilizer check and control plots received no amendment. The hybrid poplar OP-367 (Populus deltoides × P. nigra) was planted on a 3.6 m grid spacing. Significant amounts of P and Fe originating from the sewage treatment process were
detected in soils 13 months after amending. Chlorosis evaluated with a SPAD-502 meter, showed that poplars amended with biosolids
remained the least chlorotic and had greater tree growth when compared to Fe EDDHA and control plots during two growing seasons.
Biosolids show promise as a cost effective alternative for the remediation of Fe chlorosis in hybrid poplar agroforestry plantations
and present new opportunities in northwestern New Mexico for municipalities seeking solid waste land disposal options. 相似文献
24.
David Parsons Charles F. NicholsonRobert W. Blake Quirine M. KetteringsLuis Ramírez-Aviles Jerome H. CherneyDanny G. Fox 《Agricultural Systems》2011,104(1):13-19
Simulation models are effective tools to examine interactions between livestock, cropping systems, households, and natural resources. Our study objective was to use an integrated livestock and crop model to assess the outcomes from selected suites of management decisions observed in smallholder sheep-cropping systems of Yucatán, Mexico. The scenarios contrasted specialized systems versus mixed farming, and evaluated the outcomes of increased crop-livestock integration. Mixed enterprise scenarios involving sheep provided more income than specialized enterprises, and capitalized on a lower price of on-farm maize grain, efficient utilization of surplus labor, and availability of common land. Labor and management income was greatest for the unintegrated and partially integrated crop and livestock scenarios. It was more profitable for producers to sell excess grain and maize stover, and use common land to feed the livestock, suggesting that increased integration does not always result in improved outcomes. The results are consistent with a system not yet pushed to the point where integration is inevitable. For all sets of scenarios, the model structure was able to accommodate subtle management differences to produce appropriate biophysical, labor, and economic outcomes. We conclude there is potential to use similar model development methods to describe other crop-livestock systems, thus providing tools for learning, scenario analysis, and impact assessment. 相似文献
25.
Fine structure constant defines visual transparency of graphene 总被引:1,自引:0,他引:1
Nair RR Blake P Grigorenko AN Novoselov KS Booth TJ Stauber T Peres NM Geim AK 《Science (New York, N.Y.)》2008,320(5881):1308
There are few phenomena in condensed matter physics that are defined only by the fundamental constants and do not depend on material parameters. Examples are the resistivity quantum, h/e2 (h is Planck's constant and e the electron charge), that appears in a variety of transport experiments and the magnetic flux quantum, h/e, playing an important role in the physics of superconductivity. By and large, sophisticated facilities and special measurement conditions are required to observe any of these phenomena. We show that the opacity of suspended graphene is defined solely by the fine structure constant, a = e2/hc feminine 1/137 (where c is the speed of light), the parameter that describes coupling between light and relativistic electrons and that is traditionally associated with quantum electrodynamics rather than materials science. Despite being only one atom thick, graphene is found to absorb a significant (pa = 2.3%) fraction of incident white light, a consequence of graphene's unique electronic structure. 相似文献
26.
Elucidation of the small RNA component of the transcriptome 总被引:3,自引:0,他引:3
Lu C Tej SS Luo S Haudenschild CD Meyers BC Green PJ 《Science (New York, N.Y.)》2005,309(5740):1567-1569
Small RNAs play important regulatory roles in most eukaryotes, but only a small proportion of these molecules have been identified. We sequenced more than two million small RNAs from seedlings and the inflorescence of the model plant Arabidopsis thaliana. Known and new microRNAs (miRNAs) were among the most abundant of the nonredundant set of more than 75,000 sequences, whereas more than half represented lower abundance small interfering RNAs (siRNAs) that match repetitive sequences, intergenic regions, and genes. Individual or clusters of highly regulated small RNAs were readily observed. Targets of antisense RNA or miRNA did not appear to be preferentially associated with siRNAs. Many genomic regions previously considered featureless were found to be sites of numerous small RNAs. 相似文献
27.
Ram RJ Verberkmoes NC Thelen MP Tyson GW Baker BJ Blake RC Shah M Hettich RL Banfield JF 《Science (New York, N.Y.)》2005,308(5730):1915-1920
Using genomic and mass spectrometry-based proteomic methods, we evaluated gene expression, identified key activities, and examined partitioning of metabolic functions in a natural acid mine drainage (AMD) microbial biofilm community. We detected 2033 proteins from the five most abundant species in the biofilm, including 48% of the predicted proteins from the dominant biofilm organism, Leptospirillum group II. Proteins involved in protein refolding and response to oxidative stress appeared to be highly expressed, which suggests that damage to biomolecules is a key challenge for survival. We validated and estimated the relative abundance and cellular localization of 357 unique and 215 conserved novel proteins and determined that one abundant novel protein is a cytochrome central to iron oxidation and AMD formation. 相似文献
28.
29.
Phosphorite concretions have been detected in the kidneys of two widespread species of mollusks, Mercenaria mercenaria and Argopecten irradians, which have relatively high population densities. These concretions are the first documentation of the direct biogenic formation of phosphorite grains. The concretions are principally amorphous calcium phosphate, which upon being heated yields an x-ray diffraction pattern which is essentially that of chlorapatite. These concretions appear to be a normal formation of the excretory process of mollusks under reproductive, environmental, or pollutant-induced stress. Biogenic production of phosphorite concretions over long periods of time and diagenetic change from amorphous to crystalline structure, coupled with secondary enrichment, may account for the formation of some marine phosphorite desposits which are not easily explained by the chemical precipitation-replacement hypothesis. 相似文献
30.
Gunning YM Parker R Ring SG Rigby NM Wegg B Blake A 《Journal of agricultural and food chemistry》2000,48(2):395-399
The compositions at which amorphous ethanol-maltose-water mixtures exhibit liquid-liquid separation have been determined in the temperature range from 20 to 80 degrees C. At water contents below approximately 20% w/w two phases were observed, with the maltose-rich phase slightly richer in water. Partition coefficients of organic nonelectrolytes ranging in hydrophobicity from 1, 2-ethanediol and 1,2-propanediol to benzyl alcohol and propyl acetate have been measured for octanol/sorbitol, benzyl alcohol/sorbitol, and 1-butanol/sorbitol mixtures. Linear correlations were found between the log partition coefficients in the various solvent systems. Replacing water with sorbitol results in more organic partitioning into the octanol. Replacing octanol with benzyl alcohol or 1-butanol also results in more organic partitioning into the hydrophobic phase. The results establish a relationship with partition coefficients for octanol/water mixtures, which are well studied experimentally and for which predictive approaches exist. The implications of these results for flavor retention and encapsulation are discussed. 相似文献