检索结果-南通市图书馆

LINEAR WAVES THAT EXPRESS THE SIMPLEST POSSIBLE PERIODIC STRUCTURE OF THE COMPRESSIBLE EULER EQUATIONS

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Scientia 2009年第6期29卷 1749-1766页

作者： Blake Temple Robin Young Department of Mathematics University of California Davis CA 95616 USA Department of Mathematics and Statistics University of Massachusetts Amherst MA 01003 USA

In this paper we show how the simplest wave structure that balances compression and rarefaction in the nonlinear compressible Euler equations can be represented in a solution of the linearized compressible Euler equations. Such waves are exact solutions of the equations obtained by linearizing the compressible Euler equations about the periodic extension of two constant states separated by entropy jumps. Conditions on the states and the periods are derived which allow for the existence of solutions in the Fourier 1-mode. In [3, 4, 5] it is shown that these are the simplest linearized waves such that, for almost every period, they are isolated in the kernel of the linearized operator that imposes periodicity, and such that they perturb to nearby nonlinear solutions of the compressible Euler equations that balance compression and rarefaction along characteristics in the formal sense described in [3]. Their fundamental nature thus makes them of interest in their own right.

关键词： compressible Euler periodic solutions conservation laws

Predictors of the placebo response in a nutraceutical randomized controlled trial for depression

在线全文

学校读者我要写书评

暂无评论

Journal of Integrative Medicine 2024年第1期22卷 46-53页

作者： Rosemary Arnold Jenifer Murphy-Smith Chee H.Ng David Mischoulon Gerard J.Byrne Chad A.Bousman Con Stough Michael Berk Jerome Sarris Professorial Unit the Melbourne ClinicDepartment of PsychiatryUniversity of MelbourneRichmond 3121Australia Depression Clinical and Research Program Department of PsychiatryMassachusetts General HospitalHarvard Medical SchoolBostonMA 02115USA Faculty of Medicine Discipline of PsychiatryCentre for Clinical ResearchRoyal Brisbane&Women’s HospitalHerstonthe University of QueenslandBrisbane 4006Australia Departments of Medical Genetics PsychiatryPhysiology&Pharmacology and Community Health SciencesUniversity of CalgaryCalgaryAB T2N 1N4Canada Department of Psychiatry the University of MelbourneMelbourne 3052Australia Centre for Human Psychopharmacology Swinburne UniversityMelbourne 3122Australia The Institute for Mental and Physical Health and Clinical Translation School of MedicineBarwon HealthDeakin UniversityGeelong 3220Australia The Centre of Excellence in Youth Mental Health the University of MelbourneParkville 3052Australia Florey Institute of Neuroscience and Mental Health the University of MelbourneParkville 3052Australia NICM Health Research Institute Western Sydney UniversityWestmeadNSW 2145Australia

Objective The placebo response in depression studies is the change in symptoms amongst those who receive an inactive *** well-designed randomized controlled trials(RCTs)of depression have a high proportion of placebo responders,with little understanding as to *** present study assesses characteristics associated with the placebo response in a nutraceutical trial with a large proportion of placebo *** This is a secondary analysis of a nutraceutical depression RCT which identified no overall treatment benefit relative to placebo(n=69 in placebo group).We investigated participant characteristics such as socio-demographics,clinical features,and recruitment methods,and their association with the placebo *** genetic polymorphisms were also *** response was measured based on change in Montgomery-Asberg Depression Rating Scale *** association of these hypothesis-driven variables of interest and the placebo response was examined using linear mixed effects *** Greater levels of education,particularly pursuing post-high school education,better self-reported general health,marriage/de facto,greater improvement in the first trial week,and more failed antidepressant therapies in the current depressive episode were associated with greater placebo *** increased placebo response was not found in those recruited via social media nor in those with concomitant antidepressant *** nucleotide polymorphisms from the tryptophan hydroxylase 1(TPH1)gene(A779C and A218C)were weakly associated with greater placebo response,although the evidence was attenuated after accounting for multiple *** This is,to our knowledge,the first study within nutraceutical research for depression to assess the association between participant characteristics and variation in the placebo *** variables appeared to predict the placebo *** findings may encourage future trial design

关键词： Randomized controlled trial Placebo Depression Nutraceutical Psychiatry

Salient object detection: A survey

在线全文

学校读者我要写书评

暂无评论

Computational Visual Media 2019年第2期5卷 117-150页

作者： Ali Borji Ming-Ming Cheng Qibin Hou Huaizu Jiang Jia Li MarkableAI New YorkUSA TKLNDST College of Computer ScienceNankai UniversityTianjinChina university of massachusetts amherst AmherstMAUSA State Key Laboratory of Virtual Reality Technology and Systems School of Computer Science and EngineeringBeihang UniversityBeijingChina

Detecting and segmenting salient objects from natural scenes, often referred to as salient object detection, has attracted great interest in computer vision. While many models have been proposed and several applications have emerged, a deep understanding of achievements and issues remains lacking. We aim to provide a comprehensive review of recent progress in salient object detection and situate this field among other closely related areas such as generic scene segmentation, object proposal generation, and saliency for fixation prediction. Covering 228 publications, we survey i) roots, key concepts, and tasks, ii) core techniques and main modeling trends, and iii) datasets and evaluation metrics for salient object detection. We also discuss open problems such as evaluation metrics and dataset bias in model performance, and suggest future research directions.

关键词： salient object detection saliency visual attention regions of interest

POLY (β-HYDROXYALKANOATES): NATURAL BIOCOMPATIBLE AND BIODEGRADABLE POLYESTERS PRODUCED BY BACTERIA

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 1989年第4期7卷 289-298页

作者： ROBERT W. LENZ RICHARD A. GROSS HELMUT BRANDL R. CLINTON FULLER Department of Polymer Science and Engineering University of MassachusettsAmherstMA 01003USADepartment of ChemistryUniversity of Lowell1 University Ave.LowellMA 01854USAInstitute for Plant BiologyZollikerstrasse 1078008 ZurichSwitzerlandDepartment of BiochemistryUniversity of MassachusettsAmherstMA 01003USA

A wide variety of different types of microorganisms are known to produce intracellular energy and carbon storage products, which have been generally described as being poly (β-hydroxybutyrate), PHB, but which are, more often than not, copolymers containing different alkyl groups at the β-position. Hence, PHB belongs to the family ofpoly (β-hydroxyalkanoastes), PHA, all of which are usually formed as intracellular inclusions in bacteria under unbalanced growth conditions. Recently, it became of industrial interest to evaluate these PHA polyesters as natural biodegradable and biocompatible plastics for a wide range of possible applications, such as surgical sutures or packaging containers. For industrial applications, the controlled incorporation of repeating units with different chain lengths into a series of copolymers is desirable in order to produce polyesters with a range of material properties because physical and chemical characteristics depend strongly on the polymer composition. Such 'tailor-made' copolymers can be produced under controlled growth conditions in that, if a defined mixture of substrates for a certain type of microorganisms is supplied, a well defined and reproducible copolymer is formed.

关键词： PHB POLY HYDROXYALKANOATES NATURAL BIOCOMPATIBLE AND BIODEGRADABLE POLYESTERS PRODUCED BY BACTERIA

Prenatal and postnatal factors associated with sudden infant death syndrome:an umbrella review of meta-analyses

在线全文

学校读者我要写书评

暂无评论

World Journal of Pediatrics 2024年第5期20卷 451-460页

作者： Tae Hyeon Kim Hyeri Lee Selin Woo Hayeon Lee Jaeyu Park Guillaume Fond Laurent Boyer Jong Woo Hahn Jiseung Kang Dong Keon Yon Department of Medicine Kyung Hee University College of MedicineSeoulSouth Korea Center for Digital Health Medical Science Research InstituteKyung Hee University College of MedicineSeoulSouth Korea Department of Regulatory Science Kyung Hee UniversitySeoulSouth Korea Department of Biomedical Engineering Kyung Hee UniversityYonginSouth Korea CEReSS-Health Service Research and Quality of Life Center Assistance Publique des Hôpitaux de MarseilleAix-Marseille UniversityMarseilleFrance Department of Pediatrics Seoul National University College of MedicineSeoulSouth Korea Department of Pediatrics Seoul National University Bundang HospitalSeongnamSouth Korea Department of Anesthesia Critical Care and Pain MedicineMassachusetts General Hospital14913th StreetRoom 4140CharlestownBostonMAUSA Division of Sleep Medicine Harvard Medical SchoolBostonMAUSA Department of Pediatrics Kyung Hee University Medical CenterKyung Hee University College of Medicine23 Kyungheedae-roDongdaemun-guSeoul02447South Korea Department of Precision Medicine Kyung Hee University College of MedicineSeoulSouth Korea

Background Comprehensive quantitative evidence on the risk and protective factors for sudden infant death syndrome(SIDS)effects is *** investigated the risk and protective factors related to *** We conducted an umbrella review of meta-analyses of observational and interventional studies assessing SIDS-related ***/MEDLINE,Embase,EBSCO,and Google Scholar were searched from inception until January 18,*** extraction,quality assessment,and certainty of evidence were assessed by using A Measurement Tool Assessment Systematic Reviews 2 following PRISMA *** to observational evidence,credibility was graded and classified by class and quality of evidence(CE;convincing,highly suggestive,suggestive,weak,or not significant).Our study protocol was registered with PROSPERO(CRD42023458696).The risk and protective factors related to SIDS are presented as equivalent odds ratios(eORs).Results We identified eight original meta-analyses,including 152 original articles,covering 12 unique risk and protective factors for SIDS across 21 countries/regions and five *** risk factors,including prenatal drug exposure[eOR=7.84(95%CI=4.81–12.79),CE=highly suggestive],prenatal opioid exposure[9.55(95%CI=4.87–18.72),CE=suggestive],prenatal methadone exposure[9.52(95%CI=3.34–27.10),CE=weak],prenatal cocaine exposure[4.38(95%CI=1.95–9.86),CE=weak],prenatal maternal smoking[2.25(95%CI=1.95–2.60),CE=highly suggestive],postnatal maternal smoking[1.97(95%CI=1.75–2.22),CE=weak],bed sharing[2.89(95%CI=1.81–4.60),CE=weak],and infants found with heads covered by bedclothes after last sleep[11.01(95%CI=5.40–22.45),CE=suggestive],were *** the other hand,three protective factors,namely,breastfeeding[0.57(95%CI=0.39–0.83),CE=non-significant],supine sleeping position[0.48(95%CI=0.37–0.63),CE=suggestive],and pacifier use[0.44(95%CI=0.30–0.65),CE=weak],were also *** Based on the evidence,we propose several risk and protecti

关键词： Infant Protective factor Risk factor Sudden infant death syndrome Umbrella review

The frontier of microplastics and nanoplastics: Soil health and carbon neutrality

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Pedosphere 2023年第1期33卷 11-13页

作者： Zhuanxi LUO Aoze LI Haiming WANG Baoshan XING College of Chemical Engineering Huaqiao UniversityXiamen 361021China Stockbridge School of Agriculture University of MassachusettsAmherst MA 01003USA

Microplastics and nanoplastics(MNPs)in soil have drawn increasing concerns about their potential threats to soil ecosystems due to their ubiquitous occurrence and *** interactions of MNPs with soil components,microbial community,plants,and fauna determine their impacts on soil biogeochemical processes and food ***,they are not largely *** research is also needed to develop reliable and standardized techniques and methods to characterize the relevant MNPs interacting with different types of soil ecosystems and to deeply examine their impacts on soil health,food security,and climate *** addition,mitigation protocols and regulation guidelines need to be *** findings will provide scientific and technological support for the understanding and management of soil health and carbon neutrality as influenced by MNPs.

关键词： soil neutral frontier

A general analysis of Wtb anomalous couplings

在线全文

学校读者我要写书评

暂无评论

Chinese Physics C 2017年第6期41卷 11-32页

作者：曹庆宏岩斌于江浩张宸 Department of Physics and State Key Laboratory of Nuclear Physics and Technology Peking University Collaborative Innovation Center of Quantum Matter Center for High Energy Physics Peking University amherst Center for Fundamental Interactions Department of Physics University of Massachusetts-Amherst

We investigate new physics effects on the Wtb effective couplings in a model-independent framework. The new physics effects can be parametrized by four independent couplings, f1^L, f1^R, f2^L and f2^R. We further introduce a set of parameters x0, xm, xp and x5 which exhibit a linear relation to the single top production cross sections. Using recent data for the t-channel single top production cross section at, tW associated production cross section crtw, s-channel single top production cross section δs, and W-helicity fractions F0, FL and FR collected at the 8 TeV LHC and Tevatron, we perform a global fit to impose constraints on the top quark effective couplings. Our globM fitting results show that the top quark effective couplings are strongly correlated. We show that （i） improving the measurements of δt and δtw is important in constraining the correlation of （f1^R, f2^R） and （f2^L,f2^R）; （ii） f1^L and f2^R are anti-correlated, and are sensitive to all the four experiments; （iii） f1^R and f2^L are also anti-correlated, and are sensitive to the F0 and FL measurements; （iv） the correlation between f2^L and f2^R is sensitive to the precision of the δt, δtw and F0 measurements. The effective Wtb couplings are studied in three kinds of new physics models： the G（221） = SU（2）1 SU（2）2 U（1）x models, the vector-like quark models and the Littlest Higgs model with and without T-parity. We show that the Wtb couplings in the left-right model and the un-unified model are sensitive to the ratio of gauge couplings when the new heavy gauge boson＇s mass （Mw,） is less than several hundred GeV, but the constraint is loose if Mw^t 〉 1 TeV. Fhrthermore, the Wtb couplings in vector-like quark models and the Littlest Higgs models are sensitive to the mixing angles of new heavy particles and SM particles.

关键词： top quark TeV physics anomalous coupling

Effects of Added Mass on Muscle Activity and Joint Movement During Walking

在线全文

学校读者我要写书评

暂无评论

Journal of Bionic Engineering 2023年第6期20卷 2703-2715页

作者： Yali Han Frank C.Sup IV Ziyang Han Zhangzhang Mi Department of Mechanical Engineering Nanjing Institute of TechnologyNanjing211167China Department of Mechanical and Industrial Engineering University of MassachusettsAmherstMA01003USA

Added mass provided irregular interference towards human movement and shifted the force generated by lower limb ***,the association between mass and muscle activities is not well *** study aims at investigating the influence of added mass on lower *** our study,five young,healthy walkers performed walking trials under three load conditions(unload;C1:0.25 pounds on feet,1 pound on calves,and 2 pounds on thighs;C2:1 pound on feet,2 pounds on calves,and 4 pounds on thighs).During walking,three-dimensional kinematics,sEMG signals,and oxygen consumption were collected which allowed us to understand the effects of added mass on *** also generated OpenSim simulation,designed to comprehend the relationship between added mass and *** the increase of added mass,maximum sEMG signal and peak joint torque increased;whereas,the horizontal stride time reduced(unload:1.697±0.02 s,C1:1.651±0.02 s,C2:1.622±0.02 s).Energy expenditure raised correspondingly(C1:6.53%,C2:24.85%).Moreover,joint moment increased,while same change occurred in muscle ***,our results show that participants responded positively to additional mass by adjusting muscle activities,joint movement,and stride frequency,which demonstrates the relationship between energy consumption and added mass.

关键词： Biomechanics Load carriage Gait Muscle force

Computing the Smallest Eigenvalue of Large Ill-Conditioned Hankel Matrices

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Communications in Computational Physics 2015年第6期18卷 104-124页

作者： Niall Emmart Yang Chen Charles C.Weems College of Information and Computer Science University of MassachusettsAmherstMA 01002USA Department of Mathematics University of MacaoMacaoChina

This paper presents a parallel algorithm for finding the smallest eigenvalue of a family of Hankel matrices that are *** matrices arise in random matrix theory and require the use of extremely high precision ***,we find that a group of commonly-used approaches that are designed for high efficiency are actually less efficient than a direct approach for this class of *** then develop a parallel implementation of the algorithm that takes into account the unusually high cost of individual arithmetic *** approach combines message passing and shared memory,achieving near-perfect scalability and high tolerance for network *** are thus able to find solutions for much larger matrices than previously possible,with the potential for extending this work to systems with greater levels of *** contributions of this work are in three areas:determination that a direct algorithm based on the secant method is more effective when extreme fixed-point precision is required than are the algorithms more typically used in parallel floating-point computations;the particular mix of optimizations required for extreme precision large matrix operations on a modern multi-core cluster,and the numerical results themselves.

关键词： Parallel eigensolver Hankel matrices extremely ill-conditioned matrices