检索结果-南通市图书馆

Diporphyrin tweezer for multichannel spectroscopic analysis of enantiomeric excess

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of Chemical Science and Engineering 2020年第1期14卷 28-40页

作者： daniel t.Payne Mandeep KChahal Vaclav Brezina Whitney A.Webre Katsuhiko Ariga Francis D’Souza Jan Labuta Jonathan P.Hill WPI Center for Materials Nanoarchitectonics National Institute for Materials ScienceIbaraki 305-0044Japan Department of Macromolecular Physics Faculty of Mathematics and PhysicsCharles University18000 PragueCzech Republic Department of Chemistry University of North TexasDentonTX 76203USA Department of Advanced Materials Science Graduate School of Frontier SciencesThe University of TokyoChiba 277-8561Japan

Chiral 1,1’-binaphthyl-linked diporphyrin‘tweezers’(R)-1/(S)-1 and the corresponding zinc(II)complexes(R)-2/(S)-2 were prepared as chiral host molecules,and their utility for chiral analyses(especially enantiomeric excess(ee)determinations)were ***(1-n-dodecyl)porphyrins were used for the first time as the interacting *** capabilities of the diporphyrin tweezers were investigated by titrations with(R,R)-and(S,S)-cyclohexane-1,2-diamine(CHDA).the host molecules could be used as multichannel probes of ee by using UVvis,circular dichroism(CD),fluorescence emission and 1H nuclear magnetic resonance(1 H-NMR)*** configurations could also be differentiated using CD or 1HNMR *** three optical techniques give good resolution of ee with reasonable sensitivity considering the low concentrations used(ca.10^-6 mol·L^-1).the ee determination of CHDA enantiomers using NMR spectroscopy is also possible because of the reasonably well separated resonances in the case of(R,R)-and(S,S)-***-metallated(R)-1/(S)-1 hosts could not be used to detect chiral information in a strongly acidic chiral *** work demonstrates the utility of 1,1’-binapthyllinked chiral hosts for chiral analysis of ditopically interacting enantiomers.

关键词： porphyrin dimer chirality enantiomeric excess CD fluorescence

A Multivariate Student’s t-Distribution

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Open Journal of Statistics 2016年第3期6卷 443-450页

作者： daniel t. Cassidy Department of Engineering Physics McMaster University Hamilton ON Canada

A multivariate Student’s t-distribution is derived by analogy to the derivation of a multivariate normal (Gaussian) probability density function. this multivariate Student’s t-distribution can have different shape parameters for the marginal probability density functions of the multivariate distribution. Expressions for the probability density function, for the variances, and for the covariances of the multivariate t-distribution with arbitrary shape parameters for the marginals are given.

关键词： Multivariate Student’s t Variance Covariance Arbitrary Shape Parameters

Relating environmental variables with aquatic community structure in an agricultural/urban coldwater stream

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Ecological Processes 2021年第1期10卷 481-499页

作者： daniel t.L.Myers Richard R.Rediske James N.McNair Aaron D.Parker E.Wendy Ogilvie Annis Water Resources Institute Grand Valley State University740 W Shoreline DriveMuskegonMI 49401USA. Michigan Department of Environment Great Lakesand Energy525 W Allegan StreetLansingMI 48909USA. Grand Valley Metropolitan Council 678 Front Avenue NWSuite 200Grand RapidsMI 49504USA.

Background:Urban areas are often built along large rivers and surrounded by agricultural *** may lead to small tributary streams that have agricultural headwaters and urbanized lower *** study objectives assessed are as follows:(1)landscape,geomorphic,and water quality variables that best explained variation in aquatic communities and their integrity in a stream system following this agricultural-to-urban land use gradient;(2)ways this land use gradient caused aquatic communities to differ from what would be expected for an idealized natural stream or other longitudinal gradients;and(3)whether the impacts of this land use gradient on aquatic communities would grow larger in a downstream direction through the agricultural and urban *** study area was an impaired coldwater stream in Michigan,***:Many factors structured the biological communities along the agricultural-to-urban land use *** woody debris had the strongest relationship with EPt(Ephemeroptera,Plecoptera,and trichoptera)abundance and richness and were most common in the lower,urbanized *** streambed substrate had the strongest relationship with Diptera taxa and surface air breather macroinvertebrates and was dominant in agricultural *** community assemblage was influenced largely by stream flow and temperature regimes,while poor fish community integrity in lower urban reaches could be impacted by geomorphology and episodic urban pollution *** macroinvertebrates were most abundant in deforested,first-order agricultural headwaters,while EPt macroinvertebrate richness was the highest downstream of agricultural areas within the urban zone that had extensive forest ***:Environmental variables and aquatic communities would often not conform with what we would expect from an idealized natural *** richness improved downstream of agricultural *** shows promise for the recovery of aquatic systems using we

关键词： Land use Habitat Stream Fish Macroinvertebrate Gradient

the effect of wilderness and medical training on injury and altitude preparedness among backcountry hikers in Rocky Mountain National Park

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

World Journal of Emergency Medicine 2018年第3期9卷 172-177页

作者： Michael D.t.Yue David W.Spivey daniel B.Gingold Douglas G.Sward University of Maryland School of Medicine BaltimoreMarylandUSA Department of Emergency Medicine University of Maryland School of MedicineBaltimoreMarylandUSA Division of Hyperbaric Medicine Program in TraumaUniversity of Maryland Medical CenterBaltimoreMarylandUSA

BACKGROUND:the purpose of this study was to document the correlation between medical and wilderness training with levels of preparedness for acute mountain sickness(AMS),illness,and injury among backcountry ***:We conducted a cross-sectional,convenience survey in Rocky Mountain National Park in July and August *** study group consisted of 380 hikers who completed a written survey that collected information about demographics,wilderness experience,altitude experience,hiking equipment,communications devices,and trip ***:Factors such as wilderness training(wilderness first aid[WFA],wilderness first responder[WFR],or wilderness emergency medical technician[WEMt]),wilderness experience,and altitude experience all affected hikers’emergency *** with medical training were more prepared to avoid or respond to AMS(62.3%vs.34.3%[Pthey were also more prepared to avoid or manage injury/illness than hikers without medical training(37.7%vs.20.7%[P=0.003]).Participants with wilderness training were more likely to be prepared to avoid or respond to AMS(52.3%vs.36.8%[P=0.025])but not significantly more likely to be prepared to manage illness/injury(31.8%vs.22.0%[Pting for experience,wilderness training,age,and gender,we found that medical training was associated with increased preparedness for AMS(OR2.72;95%CI 1.51–4.91)and injury/illness(OR 2.71;95%CI 1.5–4.89).CONCLUSION:Medically trained hikers were more likely to be prepared to avoid or manage AMS,medical emergencies,and injuries than their non-medically trained *** training increased hikers’preparedness for AMS but did not significantly alter preparedness for illness/injury.

关键词： Hiking wilderness Acute mountain illness Injury training

Potential impact of combined inhibition of 3a-oxidoreductases and 5a-reductases on prostate cancer

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Asian Journal of Urology 2019年第1期6卷 50-56页

作者： Michael V.Fiandalo daniel t.Gewirth James L.Mohler Department of Urology Roswell Park Comprehensive Cancer CenterBuffaloNYUSA Hauptman-Woodward Medical Research Institute BuffaloNYUSA

Prostate cancer(PCa)growth and progression rely on the interaction between the androgen receptor(AR)and the testicular ligands,testosterone and dihydrotestosterone(DHt).Almost all men with advanced PCa receive androgen deprivation therapy(ADt).ADt lowers circulating testosterone levels,which impairs AR activation and leads to PCa ***,ADt is palliative and PCa recurs as castration-recurrent/resistant PCa(CRPC).One mechanism for PCa recurrence relies on intratumoral synthesis of DHt,which can be synthesized using the frontdoor or primary or secondary backdoor *** metabolism inhibitors,such as those targeting 5a-reductase,aldo-keto-reductase family member 3(AKR1C3),or cytochrome P45017A1(CYP17A1)have either failed or produced only modest clinical *** goal of this review is to describe the therapeutic potential of combined inhibition of 5a-reductase and 3a-oxidoreductase enzymes that facilitate the terminal steps of the frontdoor and primary and secondary backdoor pathways for DHt *** of the terminal steps of the androgen metabolism pathways may be a way to overcome the shortcomings of existing androgen metabolism inhibitors and thereby delay PCa recurrence during ADt or enhance the response of CRPC to androgen axis manipulation.

关键词： Androstanediol Dihydrotestosterone Dutasteride 3a-oxidoreductases Androgen deprivation therapy Abiraterone

targeted Gene Knockouts Reveal Overlapping Functions of the Five Physcomitrella patens FtsZ Isoforms in Chloroplast Division, Chloroplast Shaping, Cell Patterning, Plant Development, and Gravity Sensing

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Molecular Plant 2009年第6期2卷 1359-1372页

作者： Anja Martin daniel Lang Sebastian t. Hanke Stefanie J.X. Mueller Eric Sarnighausen Marco Vervliet-Scheebaum Ralf Reski Plant Biotechnology Faculty of Biology University of Freiburg Schaenzlestr. 1 79104 Freiburg Germany Centre for Biological Signalling Studies (bioss) University of Freiburg Alberststr. 19 79104 Freiburg Germany Spemann Graduate School of Biology and Medicine (SGBM) University of Freiburg Alberststr. 19A 79104 Freiburg Germany

Chloroplasts and bacterial cells divide by binary fission. the key protein in this constriction division is FtsZ, a self-assembling GtPase similar to eukaryotic tubulin. In prokaryotes, FtsZ is almost always encoded by a single gene, whereas plants harbor several nuclear-encoded FtsZ homologs. In seed plants, these proteins group in two families and all are exclusively imported into plastids. In contrast, the basal land plant Physcomitrella patens, a moss, encodes a third FtsZ family with one member. this protein is dually targeted to the plastids and to the cytosol. Here, we report on the targeted gene disruption of all ftsZ genes in R patens. Subsequent analysis of single and double knockout mutants revealed a complex interaction of the different FtsZ isoforms not only in plastid division, but also in chloroplast shaping, cell patterning, plant development, and gravity sensing. these results support the concept of a plastoskeleton and its functional integration into the cytoskeleton, at least in the moss R patens.

关键词： Bryophyte cell wall gravitropism GtPase chloroplast plastoskeleton P patens moss.

A Fully Coupled thermomechanical Model of Friction Stir Welding(FSW) and Numerical Studies on Process Parameters of Lightweight Aluminum Alloy Joints

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2018年第1期31卷 1-18页

作者： Saad B.Aziz Mohammad W.Dewan daniel J.Huggett Muhammad A.Wahab Ayman M.Okeil t.Warren Liao Department of Mechanical and Industrial Engineering Louisiana State University Department of Civil and Environmental Engineering Louisiana State University

this paper presents a new thermomechanical model of friction stir welding which is capable of simulating the three major steps of friction stir welding （FSW） process, i.e., plunge, dwell, and travel stages. A rate-dependent Johnson- Cook constitutive model is chosen to capture elasto-plastic work deformations during FSW. two different weld schedules （i.e., plunge rate, rotational speed, and weld speed） are validated by comparing simulated temperature profiles with experimental results. Based on this model, the influences of various welding parameters on temperatures and energy generation during the welding process are investigated. Numerical results show that maximum temperature in FSW process increases with the decrease in plunge rate, and the frictional energy increases almost linearly with respect to time for different rotational speeds. Furthermore, low rotational speeds cause inadequate temperature distribution due to low frictional and plastic dissipation energy which eventually results in weld defects. When both the weld speed and rotational speed are increased, the contribution of plastic dissipation energy increases significantly and improved weld quality can be expected.

关键词： Aluminum alloy Friction stir welding temperature distribution Plastic energy Frictional energy Rate-dependent model Friction modeling

Impact of Friction Stir Welding (FSW) Process Parameters on thermal Modeling and Heat Generation of Aluminum Alloy Joints

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2016年第9期29卷 869-883页

Friction stir welding （FSW） is a solid-state joining process, where joint properties largely depend on the amount of heat generation during the welding process. the objective of this paper was to develop a numerical thermomechanical model for FSW of aluminum--copper alloy AA2219 and analyze heat generation during the welding process. the thermomechanical model has been developed utilizing ANSYS APDL. the model was verified by comparing simulated temperature profile of three different weld schedules （i.e., different combinations of weld parameters in real weld situations） from simulation with experimental results. Furthermore, the verified model was used to analyze the effect of different weld parameters on heat generation. Among all the weld parameters, the effect of rotational speed on heat generation is the highest.

关键词： Friction stir welding Frictional dissipation energy temperature distribution Friction modeling Aluminum alloy

Effective truncation of a Student’s <i>t</i>-Distribution by truncation of the Chi Distribution in a Chi-Normal Mixture

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Open Journal of Statistics 2012年第5期2卷 519-525页

作者： daniel t. Cassidy Department of Engineering Physics McMaster University Hamilton Canada

A Student’s t-distribution is obtained from a weighted average over the standard deviation of a normal distribution, σ, when 1/σ is distributed as chi. Left truncation at q of the chi distribution in the mixing integral leads to an effectively truncated Student’s t-distribution with tails that decay as exp (-q2t2). the effect of truncation of the chi distribution in a chi-normal mixture is investigated and expressions for the pdf, the variance, and the kurtosis of the t-like distribution that arises from the mixture of a left-truncated chi and a normal distribution are given for selected degrees of freedom 5. this work has value in pricing financial assets, in understanding the Student’s t--distribution, in statistical inference, and in analysis of data.

关键词： Asset Pricing Student’s t-Distribution Cauchy truncation Moments Kurtosis