检索结果-南通市图书馆

ANALYSIS OF A NUMERICAL METHOD FOR RADIATIVE TRANSFER EQUATION BASED BIOLUMINESCENCE TOMOGRAPHY

在线全文

学校读者我要写书评

暂无评论

Journal of Computational Mathematics 2016年第6期34卷 648-670页

作者： Rongfang Gong joseph Eichholz Xiaoliang Cheng Weimin Han Department of Mathematics Nanjing University of Aeronautics and Astronautics Nanjing China Department of Mathematics Rose-Hulman Institute of Technology Terre Haute IN USA Department of Mathematics Zhejiang University Hangzhou China Department of Mathematics University of Iowa Iowa City IA USASchool of Mathematics and Statistics Xi'an Jiaotong University Xi'an China

In the bioluminescence tomography （BLT） problem, one constructs quantitatively the bioluminescence source distribution inside a small animal from optical signals detected on the animal＇s body surface. The BLT problem is ill-posed and often the Tikhonov regularization is used to obtain stable approximate solutions. In conventional Tikhonov regularization, it is crucial to choose a proper regularization parameter to balance the accuracy and stability of approximate solutions. In this paper, a parameter-dependent coupled complex boundary method （CCBM） based Tikhonov regularization is applied to the BLT problem governed by the radiative transfer equation （RTE）. By properly adjusting the parameter in the Robin boundary condition, we achieve one important property： the regularized solutions are uniformly stable with respect to the regularization parameter so that the regularization parameter can be chosen based solely on the consideration of the solution accuracy. The discrete-ordinate finite-element method is used to compute numerical solutions. Numerical results are provided to illustrate the performance of the proposed method.

关键词： Bioluminescence tomography radiative transfer equation Tikhonov regular-ization coupled complex boundary method convergence.

Geomorphologic Characteristics of Polygonal Features on Chloride-Bearing Deposits on Mars: Implications for Martian Hydrology and Astrobiology

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 Earth Science 2019年第5期30卷 1049-1058页

作者： Binlong Ye Jun Huang joseph Michalski Long Xiao Planetary Science Institute School of Earth Sciences China University of Geosciences Wuhan 430074 China Department of Earth Sciences and Laboratory for Space Research University of Hong Kong Hong Kong 999077 China

Over 600 chloride-bearing deposits(chlorides) have been identified on the southern highlands of Mars. These chlorides have critical implications for hydrology and astrobiology: they are indicators of an evaporating super saturated solution, and they could have provided habitat environments for halophilic microorganisms and preserved organic matter. One of the prominent geomorphology characteristics of these chloridebearing regions is the polygonal features within them. The origin of these polygonal features is still in debate. In this study, we have surveyed 153 locations of chlorides using 441 high resolution imaging science experiment(Hi RISE) images to characterize the geomorphology of polygonal features. We identified 3 types of polygonal features of distinct geomorphologic characteristics: fractures, raised ridges, and transitional polygons between fractures and raised ridges. We evaluate previously proposed hypotheses of the formation of the polygonal features, and suggest that the 3 types of polygonal features are indicators of different stages of salt crust formation. Salt crust is usually formed through multiple groundwater activities, and it often occurs in playa environment on Earth. The unique hydrological and astrobiological implications of the chlorides with polygonal features make these deposits of high priority for future landed on and/or sample return exploration missions of Mars.

关键词： chlorides polygonal feature playa hydrology astrobiology Mars

A statistical procedure to assess the significance level of barriers to gene flow

在线全文

学校读者我要写书评

暂无评论

Journal of Genetics and Genomics 2009年第11期36卷 685-693页

作者： Sébastien Rioux Paquette Franois-joseph Lapointe Allan Wilson Centre for Molecular Ecology & School of Biological Sciences Victoria University of Wellington Département de Sciences Biologiques Université de Montréal

Although several methods are available to study the extent of isolation by distance （IBD） among natural populations, comparatively few exist to detect the presence of sharp genetic breaks in genetic distance datasets. In recent years, Monmonier＇s maximum-difference algorithm has been increasingly used by population geneticists. However, this method does not provide means to measure the statistical significance of such barriers, nor to determine their relative contribution to population differentiation with respect to IBD. Here, we propose an approach to assess the significance of genetic boundaries. The method is based on the calculation of a multiple regression from distance matrices, where binary matrices represent putative genetic barriers to test, in addition to geographic and genetic distances. Simulation results suggest that this method reliably detects the presence of genetic barriers, even in situations where IBD is also significant. We also illustrate the methodology by analyzing previously published datasets. Conclusions about the importance of genetic barriers can be misleading if one does not take into consideration their relative contribution to the overall genetic structure of species.

关键词： genetic barriers genetic distances isolation by distance multiple regression on distance matrices partial regression coefficients

Genomic insights into hybridization in a localized region of sympatry between pewee sister species(Contopus sordidulus × C. virens) and their chromosomal patterns of differentiation

在线全文

学校读者我要写书评

暂无评论

Chinese Birds 2016年第1期7卷 48-55页

作者： joseph D.Manthey Mark B.Robbins Biodiversity Institute University of Kansas Department of Ecology and Evolutionary Biology University of Kansas

Background: The Great Plains of the United States includes a large number of hybrid and contact zones between bird species. The amount of gene flow between sister species in these zones ranges from very rare hybridization events to widespread and prevalent introgression. Some of these avian systems have been studied extensively, while others have been indeterminate of whether hybridization exists in areas of sympatry. Using genomic-level approaches allows investigation of genomic patterns of hybridization and gene flow between species—or lack ***: We investigated a narrow zone of sympatry in Nebraska, USA between pewee species(Contopus sordidulus and C. virens), for which no hybridization has been confirmed. We used thousands of single nucleotide polymorphisms to identify potential hybridization and investigate genomic patterns of differentiation between these two ***: We found evidence of multiple hybrid individuals in the contact zone. Little genomic variation was fixed between species, but a large proportion had differentiated allele frequencies between species. There was a positive relationship between genetic differentiation and chromosome ***: We provided the first conclusive evidence of hybridization between C. sordidulus and C. virens, in a region where secondary contact likely occurred due to human disturbance and habitat modification. The genomic patterns of differentiation affirm that these species split in the relatively recent past. Finally, the relationship of chromosome size and genetic differentiation may have resulted from differential rates of chromosomal recombination in songbirds and genetic differentiation between species largely due to genetic drift(possibly in concert with selection).

关键词： Contact zone Hybrid zone Hybridization Chromosomal patterns Next-generation sequencing Contopus North America

Micromechanical resonator with dielectric nonlinearity

在线全文

学校读者我要写书评

暂无评论

Microsystems & Nanoengineering 2018年第1期4卷 263-269页

作者： Farrukh Mateen joseph Boales Shyamsunder Erramilli Pritiraj Mohanty Department of Mechanical and Aerospace Engineering Boston University110 Cummington StreetBostonMA 02215USA Department of Physics Boston University590 Commonwealth AvenueBostonMA 02215USA

Nonlinear response of dielectric polarization to electric field in certain media is the foundation of nonlinear ***,such nonlinearities are observed at high light intensities,achievable by laser,where atomic-scale field strengths exceeding 10^(6)–10^(8) V/m can be *** optics includes a host of fascinating phenomena such as higher harmonic frequency generation,sum and difference frequency generation,four-wave mixing,self-focusing,optical phase conjugation,and optical *** though nonlinear optics has been studied for more than five decades,such studies in analogous acoustic or microwave frequency ranges are yet to be ***,we demonstrate a nonlinear dielectric resonator composed of a silicon micromechanical resonator with an aluminum nitride piezoelectric layer,a material known to have a nonlinear optical *** a novel multiport approach,we demonstrate second and third-harmonic generation,sum and difference frequency generation,and four-wave *** demonstration of a nonlinear dielectric resonator opens up unprecedented possibilities for exploring nonlinear dielectric effects in engineered structures with an equally broad range of effects such as those observed in nonlinear ***,integration of a nonlinear dielectric layer on a chip-scale silicon micromechanical resonator offers tantalizing prospects for novel applications,such as ultra high harmonic generation,frequency multipliers,microwave frequency-comb generators,and nonlinear microwave signal processing.

关键词： dielectric optics nonlinear

A retrospective review of single-institution outcomes with robotic-assisted microsurgical varicocelectomy

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Asian Journal of Andrology 2018年第2期20卷 189-194页

作者： Andrew McCullough Leon Elebyjian joseph Ellen Clay Mechlin Institute of Urology Lahey Hospital and Medical Center Burlington MA 01805 USA Division of Urology Albany Medical College Albany NY 12208 USA Virginia Urology Richmond VA 23230 USA Urology Associates of Central Missouri Columbia MO 65201 USA

We report the largest single-center experience with robotic-assisted microscopic varicocelectomy （RAMV） in male infertility. From August 2012 to February 2015, men with infertility of at least a year and varicoceles underwent RAMV by a single surgeon. Varicocele was diagnosed on physical examination and confirmed by ultrasound by a single ultrasonographer. Preoperative hormone panel, semen analyses, and testicular Doppler ultrasound were obtained from all men and repeated at 3 months. One hundred and forty consecutive men （258 varicocelectomies） were included. Mean age and duration of infertility was 36.4 and 2.8 years, respectively. Median total and free testosterone increased by 145 ng dl^-1 and 4.3 pcg ml^-1 （44.3%）, respectively （P 〈 0.0001）. Median sperm concentration increased by 37.3% （P 〈 0.03）. Median sperm motility and morphology did not significantly change. Median left and right testicular volume increased by 22.3% （P 〈 0.0001） and 12.6% （P 〈 0.0006）, respectively. Hydroceles occurred 0.8% of procedures. We had no testicular artery injuries. Persistence of varicocele by Doppler ultrasound was 9.6%. Only 37.3% of patients required pain medications postoperatively. We concluded that RAMV is a safe and effective alternative for varicocele repair with outcomes comparable to historical traditional microsurgical approach.

关键词： male infertility reproductive technology robot-assisted microsurgery varicocele varicocelectomy

Multigear Bubble Propulsion of Transient Micromotors

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Research 2020年第1期2020卷 1384-1392页

作者： Amir Nourhani Emil Karshalev Fernando Soto joseph Wang Department of Nanoengineering University of California San DiegoLa JollaCA 92093USA Department of Mechanical Engineering Department of BiologyBiomimicry Research and Innovation CenterUniversity of AkronAkronOH 44325USA

Transient,chemically powered micromotors are promising biocompatible engines for *** propose a framework to investigate in detail the dynamics and the underlying mechanisms of bubble propulsion for transient chemically powered *** observations on the variations of the micromotor active material and geometry over its lifetime,from initial activation to the final inactive state,indicate different bubble growth and ejection mechanisms that occur stochastically,resulting in time-varying micromotor *** identify three processes of bubble growth and ejection,and in analogy with macroscopic multigear machines,we call each process a *** 1 refers to bubbles that grow on the micromotor surface before detachment while in Gear 2 bubbles hop out of the *** 3 is similar in nature to Gear 2,but the bubbles are too small to contribute to micromotor *** study the characteristics of these gears in terms of bubble size and ejection time,and how they contribute to micromotor *** ability to tailor the shell polarity and hence the bubble growth and ejection and the surrounding fluid flow is *** understanding of the complex multigear bubble propulsion of transient chemical micromotors should guide their future design principles and serve for fine tuning the performance of these micromotors.

关键词： bubble transient chemically

Assessment of soil erosion in a tropical mountain river basin of the southern Western Ghats,India using RUSLE and GIS

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Geoscience Frontiers 2018年第3期9卷 893-906页

作者： Jobin Thomas Sabu joseph K.P.Thrivikramji EWRE Department of Civil EngineeringIndian Institute of Technology MadrasChennai600036Tamil NaduIndia Department of Environmental Sciences University of KeralaThiruvananthapuram695581KeralaIndia Center for Environment and Development Thiruvananthapuram695013KeralaIndia

Revised Universal Soil Loss Equation(RUSLE) model coupled with transport limited sediment delivery(TLSD) function was used to predict the longtime average annual soil loss, and to identify the critical erosion-/deposition-prone areas in a tropical mountain river basin, viz., Muthirapuzha River Basin(MRB; area=271.75 km^2), in the southern Western Ghats, India. Mean gross soil erosion in MRB is 14.36 t ha^(-1) yr^(-1), whereas mean net soil erosion(i.e., gross erosion-deposition) is only 3.60 t ha^(-1) yr^(-1)(i.e., roughly 25% of the gross erosion). Majority of the basin area(~86%) experiences only slight erosion(<5 t ha^(-1) yr^(-1)), and nearly 3% of the area functions as depositional environment for the eroded sediments(e.g., the terraces of stream reaches, the gentle plains as well as the foot slopes of the plateau scarps and the terrain with concordant summits). Although mean gross soil erosion rates in the natural vegetation belts are relatively higher, compared to agriculture, settlement/built-up areas and tea plantation, the sediment transport efficiency in agricultural areas and tea plantation is significantly high,reflecting the role of human activities on accelerated soil erosion. In MRB, on a mean basis, 0.42 t of soil organic carbon(SOC) content is being eroded per hectare annually, and SOC loss from the 4th order subbasins shows considerable differences, mainly due to the spatial variability in the gross soil erosion rates among the sub-basins. The quantitative results, on soil erosion and deposition, modelled using RUSLE and TLSD, are expected to be beneficial while formulating comprehensive land management strategies for reducing the extent of soil degradation in tropical mountain river basins.

关键词： Soil erosion RUSLE Transport limited sediment delivery Muthirapuzha river basin Western Ghats Kerala

FITC labeling of human insulin and transport of FITC-insulin conjugates through MDCK cell monolayer

在线全文

学校读者我要写书评

暂无评论

Journal of Pharmaceutical Analysis 2019年第6期9卷 400-405页

作者： Darshana Shah Yuxing Guo joseph Ocando Jun Shao Avion Pharmaceuticals 1880 McFarland ParkwaySuite 110-2Alpharett1G130005USA Department of Pharmaceutical Sciences College of Pharmacy and Health SciencesSt.John's University8000 Utopia ParkwayQueensNY11439USA

Fluorescein isothiocyanate-labeled insulin(FITC-insulin)has been widely used for bioanalytical *** to the high cost of commercial FITC-insulin and tedious labeling procedures described in the literature,there is still a need to develop a cost effective,reliable and quick labeling method for *** purpose of the present work was to develop a quick and affordable method for FITC labeling of human insulin and to determine the effect of different conjugations of FITC to human insulin on its permeability through the MDCK cell *** labeling of insulin gives mono-,di-or tri-conjugates depending on the reaction time and the molar ratio of FITC:***-conjugate with unlabeled insulin,mixture of di-and tri-conjugate,and tri-conjugate with very little amount of di-conjugate were synthesized in less than 4 *** of conjugation had an effect on the permeability of insulin through the MDCK cell ***-conjugate had higher permeability than the unlabeled insulin due to increase in partition ***,tri-conjugate showed lower permeability than the unlabeled insulin due to the increase in molecular weight.

关键词： Insulin FITC labeling Conjugates MDCK cells Mono-conjugate Tri-conjugate