The biosynthetic products of Chinese insect medicine, Aspongopus chinensis     

Luo XH  Wang XZ  Jiang HL  Yang JL  Crews P  Valeriote FA  Wu QX 《Fitoterapia》2012,83(4):754-758

A new oxazole (1) was obtained from Chinese insect medicine Aspongopus chinensis, along with three known N-acetyldopamine derivatives (2-4). Their structures were determined on the basis of NMR and ESI-MS analyses. The possible biosynthetic pathways of the isolated compounds are discussed. Cytotoxicities of those compounds against 10 selected cancer cells were measured in vitro.  相似文献   

Implications of growth uncertainties associated with climate change for stand management     

Ljusk Ola Eriksson  Sofia Backéus  Frederick Garcia 《European Journal of Forest Research》2012,131(4):1199-1209

Climate change is expected to have substantial effects on many aspects of forest ecosystems, including timber production. Temperatures in northern Europe are expected to increase considerably, although there is substantial uncertainty about both the seasonal and average changes that will occur. In Scandinavia, production is predicted to increase across most of the area covered by boreal forest, since the growth of trees in the region is currently limited by temperature. Therefore, we have analyzed the importance of adapting management practices to future climate changes and considered possible ways to address associated stand management problems. For this purpose, we simulated climate scenarios with temperature increases ranging from 2.5 to 6.0°C over a 100-year period, and effects on typical Swedish stands with several species, then optimized their management with simulated annealing. The results indicate that the maximum considered temperature trend would raise the economic value of the stands by almost 5% more than the minimum trend. However, the importance of optimizing management plans in accordance with the correct temperature scenario appears to be limited. The plan optimized for the minimum temperature trend was only marginally inferior to the plan optimized for the maximum temperature trend in the maximum trend scenario, and vice versa. It also seemed adequate to use a deterministic formulation of the problem, and in cases where a stochastic climate change model generated more robust plans, the advantage could be attributed to model artifacts rather than climate change per se.  相似文献   

Hydrothermal Assessment of Temporal Variability in Seedbed Microclimate     

Stuart P. Hardegree  Corey A. Moffet  Gerald N. Flerchinger  Jaepil Cho  Bruce A. Roundy  Thomas A. Jones  Jeremy J. James  Patrick E. Clark  Frederick B. Pierson 《Strength and Conditioning Journal》2013,66(2):127-135

The microclimatic requirements for successful seedling establishment are much more restrictive than those required for adult plant survival. The purpose of the current study was to use hydrothermal germination models and a soil energy and water flux model to evaluate intra- and interannual variability in seedbed microclimate relative to potential germination response of six perennial grasses and cheatgrass. We used a 44-yr weather record to parameterize a seedbed microclimate model for estimation of hourly temperature and moisture at seeding depth for a sandy loam soil type at the Orchard Field Test Site in southwestern Ada County, Idaho. Hydrothermal germination response was measured in the laboratory for two seed lots of cheatgrass (Bromus tectorum L.), four seed lots of bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] Löve), three seed lots of bottlebrush squirreltail (Elymus elymoides [Raf] Swezey), and one seed lot each of Sandberg bluegrass (Poa secunda J. Presl.), big squirreltail (Elymus multisetus [J.G. Smith] M.E. Jones), thickspike wheatgrass (Elymus lanceolatus [Scribn. And J.G. Smith] Gould) and Idaho fescue (Festuca idahoensis Elmer). Germination response models were developed to estimate potential germination rate for 13 subpopulations of each seed lot for every hour of the 44-yr simulation. Seedbed microclimate was assessed seasonally and for each day, month, and year, and germination rate-sum estimates integrated for a numerical index of relative site favorability for germination for each time period. The rate-sum favorability index showed a consistent pattern among seed lots for different years, and provides a relatively sensitive indicator of annual and seasonal variability in seedbed microclimate. This index could be used with field data to define minimum weather thresholds for successful establishment of alternative plant materials, in conjunction with weather forecast models for making restoration and fire-rehabilitation management decisions in the fall season, for evaluation of potential climate-change impacts on plant community trajectories, and in optimization schemes for selecting among alternative restoration/rehabilitation management scenarios.  相似文献   

Seedling Recruitment and Sapling Retention Following Thinning,Chipping, and Prescribed Fire in Mixed Sierra Nevada Conifer     

Roger F. Walker  Robert M. Fecko  Wesley B. Frederick  Dale W. Johnson  Watkins W. Miller 《Journal of Sustainable Forestry》2013,32(8):747-776

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Rheological Properties of Vital Wheat Gluten Suspensions     

Jingyuan Xu  Jerold A. Bietz  Frederick C. Felker  Craig J. Carriere  Denis Wirtz 《Cereal Chemistry》2001,78(2):181-185

Flour and doughs represent rheologically complex materials whose properties are dependent on many factors including processing conditions. To avoid some of the problems associated with the rheological characterization of dough, we have initiated a study focused on the rheological properties of one of the major components of dough, vital wheat gluten. Suspensions of vital wheat gluten were prepared with concentrations of 225–325 mg/mL.The moduli of the gluten suspensions was 0.2 Pa at 225 mg/mL to 37 Pa at 325 mg/mL. At <250 mg/mL, the gluten suspensions exhibited fluidlike behavior. The crossover frequency, (G′[ω] = G″[ω]) shifted slightly from 0.5 rad/sec at 225 mg/mL to 0.9 rad/sec at 250 mg/mL. At >300 mg/mL, the gluten suspensions exhibited solidlike behavior. The crossover frequencies were independent of concentration and equal to 100 rad/sec. At <250 mg/mL, the high‐frequency behavior of moduli were proportional to ω^3/4, as expected for a semiflexible coil. At >300 mg/mL, the high‐frequency behavior of moduli were proportional to ω^1/2, indicating a flexible coil. These results suggest vital wheat gluten suspensions undergo a structural change between 250 and 300 mg/mL.  相似文献   

Dissolved oxygen controls summer habitat of Clear Lake Hitch (Lavinia exilicauda chi), an imperilled potamodromous cyprinid     

Frederick Feyrer  Matthew Young  Oliver Patton  David Ayers 《Ecology of Freshwater Fish》2020,29(2):188-196

Clear Lake Hitch is an imperilled minnow endemic to Clear Lake, Lake County, California, United States listed as threatened under the California Endangered Species Act (ESA) and a candidate for listing under the United States ESA. It exhibits a potamodromous life cycle whereby adults, which reach up to 6 + years in age and over 350 mm in length, migrate into Clear Lake's ephemeral tributaries briefly during spring to spawn. Conservation and management of Clear Lake Hitch is inhibited, in part, by a lack of information on the lacustrine habitat of nonbreeding individuals within Clear Lake. To address this problem, we sampled Clear Lake Hitch with gill nets in a stratified random sampling design to determine the distribution and habitat associations in early summer 2017 and 2018. We identified abundance-habitat relationships for juveniles and adults using Bayesian zero-inflated negative binomial generalised linear mixed modelling. Results indicated that dissolved oxygen concentration was the most important habitat feature measured; juveniles and adults were substantially more abundant in normoxic (≥2 mg/l) than in hypoxic (<2 mg/l) habitat. Both also exhibited weak positive relationships with chlorophyll fluorescence, suggesting relatively productive habitats may support higher numbers of Clear Lake Hitch. Spatially, juveniles were most abundant in nearshore habitats while adults were ubiquitous, indicating an ontogenetic habitat expansion that may be associated with a resource availability-predation risk trade-off. Management actions undertaken to improve hypoxia problems in Clear Lake would also improve Clear Lake Hitch habitat.  相似文献   

The Low Potential of Teff (<Emphasis Type="Italic">Eragrostis tef</Emphasis>) as an Inoculum Source for <Emphasis Type="Italic">Verticillium dahliae</Emphasis>     

Z. A. Frederick  D. A. Johnson 《American Journal of Potato Research》2018,95(2):164-169

Teff (Eragrostis tef) is a fine stemmed annual grass and gluten free small grain that is of interest as a forage, cover, or a rotation crop. Little is known about the susceptibility of teff to many diseases. Teff could be grown in rotation with potato in the northwestern United States provided teff cultivation is economical and does not increase soil populations for pathogens affecting rotation crops such as Verticillium dahliae. Verticillium dahliae infects a wide range of dicotyledonous plants, making it one of the most important fungal pathogens of crop plants in North America, including potato. The objective of this study was to quantify the susceptibility of teff to eight V. dahliae isolates and compare the susceptibility of teff to eggplant. Teff was confirmed as a host for V. dahliae, as indicated by the presence of microsclerotia in teff stems and roots after artificial inoculation in two years of greenhouse studies. The number of microsclerotia produced in teff did not differ between mint and potato pathotypes of V. dahliae. No V. dahliae isolate produced significantly greater numbers of microsclerotia than any of the seven other isolates tested in a two-year study. Microsclerotia production of V. dahliae in teff was consistently less than in susceptible eggplant cv. Night shadow in both greenhouse experiments (P?<?0.02). It is unlikely that teff infected by V. dahliae will proliferate microsclerotia of mint or potato-aggressive pathotypes, especially when compared to susceptible eggplant cultivars.  相似文献   

Impact of Spodoptera frugiperda neonate pretreatment conditions on Vip3Aa19 insecticidal protein activity and laboratory bioassay variation          下载免费PDF全文

Karen F Da Silva  Terence A Spencer  Carolina Camargo Gil  Blair D Siegfried  Frederick S Walters 《Pest management science》2016,72(4):837-844

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Updating our knowledge of mycobacterial infection of fish     

Creevy KE  Quinn FD 《Veterinary journal (London, England : 1997)》2009,180(1):5-6

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The environmental fate of diuron under a conventional production regime in a sugarcane farm during the plant cane phase     

Stork PR  Bennett FR  Bell MJ 《Pest management science》2008,64(9):954-963

BACKGROUND: Field studies of diuron and its metabolites 3-(3,4-dichlorophenyl)-1-methylurea (DCPMU), 3,4-dichlorophenylurea (DCPU) and 3,4-dichloroaniline (DCA) were conducted in a farm soil and in stream sediments in coastal Queensland, Australia. RESULTS: During a 38 week period after a 1.6 kg ha(-1) diuron application, 70-100% of detected compounds were within 0-15 cm of the farm soil, and 3-10% reached the 30-45 cm depth. First-order t(1/2) degradation averaged 49+/-0.9 days for the 0-15, 0-30 and 0-45 cm soil depths. Farm runoff was collected in the first 13-50 min of episodes lasting 55-90 min. Average concentrations of diuron, DCPU and DCPMU in runoff were 93, 30 and 83-825 microg L(-1) respectively. Their total loading in all runoff was >0.6% of applied diuron. Diuron and DCPMU concentrations in stream sediments were between 3-22 and 4-31 microg kg(-1) soil respectively. The DCPMU/diuron sediment ratio was >1. CONCLUSION: Retention of diuron and its metabolites in farm topsoil indicated their negligible potential for groundwater contamination. Minimal amounts of diuron and DCMPU escaped in farm runoff. This may entail a significant loading into the wider environment at annual amounts of application. The concentrations and ratio of diuron and DCPMU in stream sediments indicated that they had prolonged residence times and potential for accumulation in sediments. The higher ecotoxicity of DCPMU compared with diuron and the combined presence of both compounds in stream sediments suggest that together they would have a greater impact on sensitive aquatic species than as currently apportioned by assessments that are based upon diuron alone.  相似文献