检索结果-南通市图书馆

Broadband 1-GHz mid-infrared frequency comb

在线全文

学校读者我要写书评

暂无评论

Light(Science & Applications) 2022年第10期11卷 2358-2364页

作者： Nazanin Hoghooghi Sida Xing Peter Chang Daniel Lesko Alexander Lind Greg Rieker scott Diddams Precision Laser Diagnostics Laboratory University of ColoradoBoulderCO 80309USA Time and Frequency Division National Institute of Standards and TechnologyBoulderCO 80305USA Department of Physics University of ColoradoBoulderCO 80309USA Department of Chemistry University of ColoradoBoulderCO 80309USA Electrical Computer and Energy Engineering University of ColoradoBoulderCO 80309USA

mid-infrared(mIR)spectrometers are invaluable tools for molecular fingerprinting and hyper-spectral *** the available spectroscopic approaches,GHz mIR dual-comb absorption spectrometers have the potential to simultaneously combine the high-speed,high spectral resolution,and broad optical bandwidth needed to accurately study complex,transient events in chemistry,combustion,and ***,such a spectrometer has not yet been demonstrated due to the lack of GHz mIR frequency combs with broad and full spectral ***,we introduce the first broadband mIR frequency comb laser platform at 1 GHz repetition rate that achieves spectral coverage from 3 to 13 μ*** frequency comb is based on a commercially available 1.56 μm mode-locked laser,robust all-fiber Er amplifiers and intra-pulse difference frequency generation(IP-DFG)of few-cycle pulses in x(2)nonlinear *** used in a dual comb spectroscopy(DCS)configuration,this source will simultaneously enable measurements with μs time resolution,1 GHz(0.03 cm-1)spectral point spacing and a full bandwidth of>5 THz(>166 cm-1)anywhere within the mIR atmospheric *** represents a unique spectroscopic resource for characterizing fast and non-repetitive events that are currently inaccessible with other sources.

关键词： repetition spacing transient

The importance of pre-and postcopulatory sexual selection promoting adaptation to increasing temperatures

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Current Zoology 2021年第3期67卷 321-327页

作者： miguel Gomez-Llano Eve scott Erik I.Svensson Department of Biological Sciences University of ArkansasFayettevilleAR72701USA Faculty of Biology Medicine and HealthThe University of ManchesterOxford RoadManchesterM139PLUK Department of Animal and Plant Sciences The University of SheffieldSheffieldS102TNUK Biology Department Lund UniversityEvolutionary Ecology UnitLund22362Sweden

Global temperatures are increasing rapidly affecting species *** if and how different species can adapt fast enough to keep up with increasing temperatures is of vital *** mechanism that can accelerate adaptation and promote evolutionary rescue is sexual *** different mechanisms by which sexual selection can facilitate adaptation are pre-and postcopulatory sexual ***,the relative effects of these different forms of sexual selection in promoting adaptation are ***,we present the results from an experimental study in which we exposed fruit flies Drosophila melanogaster to either no mate choice or 1 of 2 different sexual selection regimes(pre-and postcopulatory sexual selection)for 6 generations,under different thermal *** showed evidence of thermal adaptation under preco-pulatory sexual selection,but this effect was not detected in the postcopulatory sexual selection and the no choice mating *** further demonstrate that sexual dimorphism decreased when flies evolved under increasing temperatures,consistent with recent theory predicting more sexually concordant selection under environmental *** results suggest an important role for precopulatory sexual selection in promoting thermal adaptation and evolutionary rescue.

关键词： evolutionary rescue local adaptation climate change Drosophila sexual selection

Ion source perturbation and control in intense laser plasma interaction

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

matter and Radiation at Extremes 2020年第4期5卷 47-52页

作者： B.Ramakrishna S.Krishnamurthy m.Tayyab S.Bagchi K.makur Raoul Trines Robbie scott Alex Robinson J.A.Chakera Department of Physics Indian Institute of Technology HyderabadKandiSangareddy 502285India Laser Plasma Division Raja Ramanna Centre for Advanced TechnologyIndore 452013India Homi Bhabha National Institute Training School ComplexAnushakti NagarMumbai 400094India Central Laser Facility STFC Rutherford-Appleton LaboratoryDidcot OX110QXUnited Kingdom

We present here experimental results on the optimization of the mega-electronvolt ion source from the target front surface by using relativistic(10^(18)W/cm^(2))interactions with ultra-short laser pulses(50 fs).The source perturbation in the accelerated proton/ion beam was primarily controlled by the addition of a pre-pulse to main pulse contrast *** 2D particle-in-cell simulations agreed well with the observed experimental results for the ion source perturbation and *** work provides insights into ion source perturbations(temporal and spatial)and the need to control them in intense laser–plasma *** results may assist in the efficient guiding of proton/ion beams to the core of fusion fuel or of ions in cancer therapy.

关键词： intense source primarily

Effects of N on Plant Response to Heat-wave:A Field Study with Prairie Vegetation

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Integrative Plant Biology 2008年第11期50卷 1416-1425页

作者： Dan Wang scott A. Heckathorn Kumar mainali E. William Hamilton Department of Environmental Sciences University of Toledo Toledo Ohio 43606 USA Department of Biology Washington and Lee University Lexington Virginia 24450 USA

more intense, more frequent, and longer heat-waves are expected in the future due to global warming, which could have dramatic ecological impacts. Increasing nitrogen （N） availability and its dynamics will likely impact plant responses to heat stress and carbon （C） sequestration in terrestrial ecosystems. This field study examined the effects of N availability on plant response to heat-stress （HS） treatment in naturally-occurring vegetation. HS （5 d at ambient or 40.5 ℃） and N treatments （±N） were applied to 16 1 m^2 plots in restored prairie vegetation dominated by Andropogon gerardii （warm-season C4 grass） and Solidago canadensis （warm-season C3 forb）. Before, during, and after HS, air, canopy, and soil temperature were monitored; net CO2 assimilation （Pn）, quantum yield of photosystem Ⅱ （ФpsⅡ）, stomatal conductance （gs）, and leaf water potential （ψw） of the dominant species and soil respiration （Rsoll） of each plot were measured daily during HS. One week after HS, plots were harvested, and C% and N% were determined for rhizosphere and bulk soil, and above-ground tissue （green/senescent leaf, stem, and flower）. Photosynthetic N-use efficiency （PNUE） and N resorption rate （NRR） were calculated. HS decreased Pn, gs, ψw, and PNUE for both species, and ＋N treatment generally increased these variables （±HS）, but often slowed their post-HS recovery. Aboveground biomass tended to decrease with HS in both species （and for green leaf mass in S. canadensis）, but decrease with ＋N for A. gerardii and increase with ＋N for S. canadensis. For A. gerardii, HS tended to decrease N% in green tissues with ＋N, whereas in S. canadensis, HS increased N% in green leaves. Added N decreased NRR for A. gerardii and HS increased NRR for S. canadensis. These results suggest that heat waves, though transient, could have significant effects on plants, communities, and ecosystem N cycling, and N can influence the effect of heat waves.

关键词： global climate change heat stress N resorption rate photosynthesis photosynthetic N-use efficiency.

Influence of towing speed on effectiveness of rolling dynamic compaction

在线全文

学校读者我要写书评

暂无评论

Journal of Rock mechanics and Geotechnical Engineering 2020年第1期12卷 126-134页

作者： Brendan T.scott mark B.Jaksa Peter W.mitchell School of Civil Environmental and Mining EngineeringThe University of AdelaideSouth Australia5005Australia Aurecon AdelaideSouth Australia5000Australia

The influence of towing speed on the effectiveness of the 4-sided impact roller using earth pressure cells(EPCs)is *** field trials were undertaken;the first trial used three EPCs placed at varying depths between 0.5 m and 1.5 m with towing speeds of 9-12 km/*** second used three EPCs placed at a uniform depth of 0.8 m,with towing speeds of 5-15 km/*** findings from the two trials confirmed that towing speed influences the pressure imparted to the ground and hence compactive *** paper proposes that the energy imparted to the ground is best described in terms of work done,which is the sum of the change in both potential and kinetic *** practice of using either kinetic energy or gravitational potential energy should be avoided as neither can accurately quantify rolling dynamic compaction(RDC)when towing speed is varied.

关键词： Rolling dynamic compaction(RDC) Optimum towing speed Ground improvement

Biochar improves diary pasture yields by alleviating P and K constraints with no influence on soil respiration or N2O emissions

在线全文

学校读者我要写书评

暂无评论

Biochar 2019年第1期1卷 115-126页

作者： Lukas van Zwieten Stephen Kimber Stephen morris Lynne m.macdonald Josh Rust scott Petty Stephen Joseph Terry Rose NSW Department of Primary Industries 1243 Bruxner HighwayWollongbar 2477NSWAustralia CSIRO Land and Water Agriculture and Food/Sustainable Agricultural Flagship UrrbraeSA 5064Australia School of materials Science and Engineering University of New South WalesKensington 2033NSWAustralia Southern Cross Plant Science Southern Cross UniversityLismore 2480NSWAustralia Centre for Organics Research Southern Cross UniversityLismore 2480NSWAustralia

Dairy pastures can be a major source of soil nitrous oxide(N_(2)O)emissions due to the combination of intensive nitrogen(N)fertiliser use and high soil water content,from either rainfall and/or *** application is a promising approach to lower soil greenhouse gas emissions,particularly under high soil moisture conditions where denitrification is the primary N-transformation *** a replicated field trial,we evaluated the effects of two contrasting biochars derived from poul-try litter and from hardwood on soil N_(2)O emissions,soil ammonium(NH4^(+))and nitrate(NO3^(−))status,pasture productivity and herbage nutrient content.A liming treatment to mimic the liming equivalence of the poultry litter biochar was used to separate any effects observed from changes in soil *** further separate the effects of biochars on soil N status,N_(2)O emissions and pasture N uptake,high and low N fertiliser doses(annual application of 672 kg N ha^(−1),336 kg N ha^(−1))were superimposed across all of the *** N fertiliser dose had no significant impact on pasture *** of poultry litter biochar resulted in significant increases in pasture productivity under both high and low N *** was achieved by alleviating soil P,and possibly K nutritional constraints that are typical in Australian *** the high N fertiliser dose,emissions of N_(2)O from the treatments and control were not significantly different(p>0.05)and ranged between 1.14 and 1.78 kg N_(2)O-N ha^(−1)across the 11-month *** low N dose resulted in significantly lower emissions of N_(2)O of between 0.80 and 0.84 kg N_(2)O-N ha^(−1),but biochar had no significant effect on net emissions across the *** lack of impact of biochar on N_(2)O emissions was attributed to the relatively dry conditions over the trial period resulting in nitrification being the most likely N-transformation *** brief episodes of high soil moisture,peak emissions from the bio

关键词： Ferralsol Autochamber methodology Nitrification Urea Lime Poultry litter biochar Hardwood biochar Emission intensity

Exercise attenuates bone mineral density loss during diet-induced weight loss in adults with overweight and obesity:A systematic review and meta-analysis

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Sport and Health Science 2021年第5期10卷 550-559页

作者： Jakub mesinovic Paul Jansons Ayse Zengin Barbora de Courten Alexander J.Rodriguez Robin m.Daly Peter R.Ebeling David scott Department of medicine School of Clinical Sciences at Monash HealthMonash UniversityClaytonVIA 3168Australia Institute for Physical Activity and Nutrition(IPAN) School of Exercise and Nutrition SciencesDeakin UniversityBurwoodVIA 2134Australia School of medical and Health Sciences Edith Cowan UniversityPerthWA 6027Australia Department of medicine and Australian Institute of musculoskeletal Science Melbourne Medical SchoolWestern CampusUniversity of MelbourneSt AlbansVIA 3021Australia

Background:Weight-loss-induced fat loss improves cardiometabolic health in individuals with overweight and obesity;however,weight loss can also result in bone loss and increased fracture ***-loss-induced bone loss may be attenuated with *** aim was to compare changes in bone mineral density(BmD)in adults with overweight and obesity who undertook diet-induced weight loss alone or in combination with ***:We included randomized controlled trials(RCTs)in adults with overweight or obesity(aged-18 years;body mass index-25 kg/m^(2))that prescribed diet-induced weight loss alone or in combination with supervised exercise,and measured any bone structural *** of bias was assessed using the Cochrane Risk of Bias ***-effects meta-analyses determined mean changes and net mean differences(95%confidence intervals(95%CIs))in the percentage of areal BmD(aBmD)change between ***:We included 9 ***-induced weight loss led to significant losses in femoral neck aBmD(mean change:-1.73%(95%CI:-2.39%to-1.07%),pmD(-2.19%(95%CI:-3.84%to-0.54%),p=0.009).Femoral neck aBmD losses were significantly greater in the diet-induced weight loss group compared to the exercise plus diet-induced weight loss group(net difference:-0.88%(95%CI:-1.73%to-0.03%));however,there were no differences in aBmD changes at any other skeletal site:total hip(-1.96%(95%CI:-4.59%to 0.68%))and lumbar spine(-0.48%(95%CI:-1.81%to 0.86%)).aBmD changes did not differ significantly according to exercise modality(resistance exercise,aerobic exercise,or a combination of the two)during diet-induced weight ***:Diet-induced weight loss led to greater femoral neck bone loss compared to diet-induced weight loss plus *** loss at the total hip and lumbar spine was not attenuated by exercise during diet-induced weight *** lack of consistent skeletal benefits may be due to the insufficient duration and/or training intensities

关键词： Bone mass Exercise Obesity Overweight Weight loss

Validation of a discrete element model using magnetic resonance measurements

在线全文

学校读者我要写书评

暂无评论

Particuology 2009年第4期7卷 297-306页

作者： Christoph R.müller Stuart A.scott Daniel J.Holland Belinda C.Clarke Andrew J.Sederman John S.Dennis Lynn F.Gladden Department of Chemical Engineering and Biotechnology University of CambridgePembroke StreetCambridge CB2 3RAUnited Kingdom

The discrete element model （DEm） is a very promising modelling strategy for two-phase granular systems. However, owing to a lack of experimental measurements, validation of numerical simulations of two-phase granular systems is still an important issue. In this study, a small two-dimensional gas- fluidized bed was simulated using a discrete element model. The dimensions of the simulated bed were 44mm × 10mm × 120 mm and the fluidized particles had a diameter dp = 1.2 mm and density ρp = 1000 kg/m^3. The comparison between DEm simulations and experiments are performed on the basis of time-averaged voidage maps. The drag-law of Beetstra et al. [Beetstra, R., van der Hoef, m.A., ＆ Kuipers,J. A. m. （2007b）. Drag force of intermediate Reynolds number flow past mono- and bidispersed arrays of spheres. AIChE Journal, 53,489-501 ] seems to give the best results. The simulations are fairly insensitive to the coefficient of restitution and the coefficient of friction as long as some route of energy dissipation during particle-particle and particle-wall contact is provided. Changing the boundary condition of the gas phase at the side-walls from zero-slip to full-slip does not affect the simulation results. Care is to be taken that the cell sizes are chosen so that a reasonable number of particles can be found in a fluid cell.

关键词： Discrete element modelling magnetic resonance imaging Voidage Gas-fluidized beds

Assessing vulnerability to panic:a systematic review of psychological and physiological responses to biological challenges as prospective predictors of panic attacks and panic disorder

在线全文

学校读者我要写书评

暂无评论

General Psychiatry 2019年第6期32卷 297-303页

作者： Donald J Robinaugh meredith J Ward Emma R Toner mackenzie L Brown Olivia m Losiewicz Eric Bui scott P Orr Department of Psychiatry Massachusetts General HospitalBostonMassachusettsUSA Department of Psychiatry Harvard Medical SchoolBostonMassachusettsUSA

Background Cognitive-behavioural theories of panic disorder posit that panic attacks arise from a positive feedback loop between arousal-related bodily sensations and perceived *** a recently develope computational model formalising these theories of pani attacks,it was observed that the response to a simulate perturbation to arousal provided a strong indicator of vulnerability to panic attacks and panic *** this/review,we evaluate whether this observation is borne o in the empirical literature that has examined responses biological challenge(eg,C02 inhalation)and their relatio to subsequent panic attacks and panic *** We searched Pubmed,Web of Science and PsycINFO using keywords denoting provocation agents(eg,sodium lactate)and procedures(eg,infusion)combined with keywords relevant to panic disorder(eg,panic).Articles were eligible if they used response to a biologic challenge paradigm to prospectively predict panic attac or panic *** We identified four eligible *** effect sizes suggest that there is biological challenge response a moderate prospective association with subsequent pani attacks,but no prospective relationship with panic disorde Conclusions These findings provide support for the prediction derived from cognitive-behavioural theories an some preliminary evidence that response to a biological challenge may have clinical utility as a marker of vulnerab to panic attacks pending further research and developme Trial registration number 135908.

关键词： behaviour subsequent sizes