检索结果-南通市图书馆

Journal of materials Science & Technology 2015年第3期31卷 252-256页

作者： m.l.Huang F.Yang Electronic Packaging materials laboratory School of Materials Science & Engineering Dalian University of Technology

Solder size effect on early stage interfacial intermetallic compound(ImC) evolution in wetting reaction between Sne3.0Age0.5Cu solder balls and electroless nickel electroless palladium immersion gold(ENEPIG) pads at 250 C was investigated. The interfacial ImCs transformed from initial needle- and rodtype(Cu,Ni)6Sn5to dodecahedron-type(Cu,Ni)6Sn5and then to needle-type(Ni,Cu)3Sn4at the early interfacial reaction stage. moreover, these ImC transformations occurred earlier in the smaller solder joints, where the decreasing rate of Cu concentration was faster due to the Cu consumption by the formation of interfacial(Cu,Ni)6Sn5. On thermodynamics, the decrease of Cu concentration in liquid solder changed the phase equilibrium at the interface and thus resulted in the evolution of interfacial ImCs; on kinetics, larger solder joints had sufficient Cu flux toward the interface to feed the(Cu,Ni)6Sn5growth in contrast to smaller solder joints, thus resulted in the delayed ImC transformation and the formation of larger dodecahedron-type(Cu,Ni)6Sn5grains. In smaller solders, no spalling but the consumption of(Cu,Ni)6Sn5grains by the formation of(Ni,Cu)3Sn4grains occurred where smaller discrete(Cu,Ni)6Sn5grains formed at the interface.

关键词： Size effect lead-free solder Interfacial reaction

magnesium Uptake and Palygorskite Transformation Abilities of Wheat and Oat

在线全文

学校读者我要写书评

暂无评论

Pedosphere 2012年第6期22卷 834-841页

作者： m.H.SAlEHI l.TAHAmTANI Department of Soil Science College of AgricultureShahrekord UniversityShahrekord(Iran)

Weathering of clay minerals is a source of nutrients to plants. Palygorskite is a mg-rich fibrous clay mineral that commonly occurs in the soils and sediments of arid regions. Although many studies have examined the environmental conditions required for the formation and stability of palygorskite, information on the transformation of this mineral in the root zone （or rhizosphere） of agricultural crops is l.mited. This study explored the possibility of palygorskite transformation in the rhizosphere of wheat and oat and compared the ability of these crops to extract structural.mg from palygorskite. The crops were cultivated in pots consisting of a mixture of sand from Hamadan region, Iran and Florida palygorskite, irrigated with distilled water, and treated with either complete or mg-free nutrient solutions. After 100 d, mg uptake by the crops was measured. Clay-sized particles in each pot were also separated from the sand and were analyzed through X-ray diffraction （XRD）. The X-ray pattern of the particles was compared with that of the pure palygorskite particles （before cultivation）. The results showed that palygorskite could provide sufficient mg for the growth of wheat in the pots supplied with mg-free nutrient solution. In spite of the magnesium uptake by both plants from the palygorskite structure, no detectable peaks indicating the transformation of pmygorskite were recognized by XRD. A decrease of 1.05 nm in peak intensity was more obvious for the pots containing palygorskite and irrigated with mg-free nutrient solution than for the pots irrigated with complete nutrient solution. Although the decrease in peak intensity was greater for oat than wheat, indicating greater palygorskite weathering by oat, mg uptake by oat was low, as evidenced by the deficiency symptoms observed.

关键词： clay minerals nutrient solution rhizosphere weathering X-ray diffraction

Evaluation of clinical relevance of examining K-ras, p16 and p53 mutations along with allelic losses at 9p and 18q in EUS-guided fine needle aspiration samples of patients with chronic pancreatitis and pancreatic cancer

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2007年第27期13卷 3714-3720页

作者： C Salek l Benesova m Zavoral V Nosek l Kasperova m Ryska R Strnad E Traboulsi m minarik Department of Gastroenterology Central Military Hospital and 1~(st) Medical Faculty of Charles University Prague Czech Republic Laboratory for Molecular Genetics and Oncology Genomac International Ltd. Prague Czech Republic Department of Gastroenterology Institute for Postgraduate Medical Education Prague Czech Republic laboratory for molecular Genetics and Oncology Genomac International Ltd. Prague Czech Republic Department of Gastroenterology Central Military Hospital and 1~(st) Medical Faculty of Charles University Prague Czech Republic Department of Gastroenterology Institute for Postgraduate Medical Education Prague Czech Republic Department of Gastroenterology Central Military Hospital and 1~(st) Medical Faculty of Charles University Prague Czech Republic Department of Surgery Central Military Hospital and 2nd Medical Faculty of Charles University Prague Czech Republic Department of Pathology Central Military Hospital Prague Czech Republic

AIm： To establish an optimum combination of molecular markers resulting in best overall diagnostic sensitivity and specificity for evaluation of suspicious pancreatic mass. mETHODS： Endoscopic ultrasound （EUS）-guided fine needle aspiration cytology （FNA） was performed on 101 consecutive patients （63 males, 38 females, 60 ± 12 years; 81 with subsequently diagnosed pancreatic cancer, 20 with chronic pancreatitis） with focal pancreatic mass. Samples were evaluated on-site by an experienced cytopathologist. DNA was extracted from Giemsa stained cells selected by laser microdissection and the presence of K-ras, p53 and p16 somatic mutations was tested by cycling-gradient capillary electrophoresis （CGCE） and single-strand conformation pol.morphism （SSCP） techniques. In addition, allelic losses of tumor suppressor genes p16 （INK4, CDKN2A） and DPC4 （mADH4, SmAD4） were detected by monitoring the loss of heterozygosity （lOH） at 9p and 18q, respectively. RESUlTS： Sensitivity and specificity of EUS-guided FNA were 75% and 85%, positive and negative predictive value reached 100%. The remaining 26% samples were assigned as inconclusive. Testing of molecular markers revealed sensitivity and specificity of 70% and 100% for K-ras mutations （P 〈 0.001）, 24% and 90% for p53 mutations （NS）, 13% and 100% for p16 mutations （NS）, 85% and 64% for aUelic losses at 9p （P 〈 0.001） and 78% and 57% for allelic losses at 18q （P 〈 0.05）. When tests for different molecular markers were combined, the best results were obtained with K-ras ＋ lOH at 9p （92% and 64%, P 〈 0.001）, K-ras ＋ lOH at 18q （92% and 57%, P 〈 0.001）, and K-ras ＋ lOH 9q ＋ lOH 18q （96% and 43%, P 〈 0.001）. When the molecular markers were used as compl.ments to FNA cytology to evaluate inconclusive samples only, the overall sensitivity of cancer detection was 100% in all patients enrolled in the study. CONClUSION： EUS-guided FNA cytology combined with screening of K-ras mutations and allelic losses of tumor suppressors p16 and

关键词： Pancreatic cancer Chronic pancreatitis Endoscopic ultrasound-guided fine-needle aspiration molecular markers loss of heterozygosity

Repeatability of decision-making behaviour in male threespine stickleback Gasterosteus aculeatus： Effects of dummy vs. live stimuli

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 2011年第1期57卷 101-108页

作者： Teresa l. DZIEWECZYNSKI lindsay m. FORRETTE Department of Psychology University of New England 11 Hills Beach Rd Biddeford ME 04005 USA

Individuals select from a number of behaviours when responding to various situations and the decisions they make may affect their fitness. The costs and benefits of these responses vary among individuals causing them to differ even in identical situations. One example of this type of situation is when territorial.males encounter both a male and female simultaneously, gene- rating a trade-off that likely leads to individual differences due to differing costs of various actions among males. This situation commonly occurs in threespine stickleback, Gasterosteus aculeatus. However, for selection to act effectively, individuals must behave in a consistent manner and measuring repeatability can aid in understanding how selection may shape such trade-offs. males of this species exhibit consistent individual differences in their response to dummy males and females but it is unknown ff patterns are similar when feedback from the stimuli is present. To assess this, male threespine stickleback were tested with dummy and live male and female conspecifics, presented separately and simultaneously. While the same trends were found re- gardless of stimulus type, males were more aggressive towards the live conspecifics than to the dummies. Repeatability values were similar within a treatment regardless of whether live or dummy conspecifics were used, suggesting that individuals show the same level of consistency. This study adds to our understanding of consistent individual differences by demonstrating that feed- back may not affect responses to conflicting stimuli and that male threespine stickleback respond in a consistent manner to both dummy and live stimuli

关键词： Decision-making Stimulus efficacy Behavioural consistency Repeatability Threespine stickleback

Viscoelastic analysis of single-component and composite PEG and alginate hydrogels

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 mechanica Sinica 2014年第1期30卷 7-14页

作者： Jenna m.Shapiro michelle l.Oyen Cambridge University Engineering Department CambridgeUK Eunice Kennedy Shriver National Institute of Child Health and Human Development National Institutes of Health

Hydrogels, three-dimensional hydrophilic pol.mer networks, are appealing candidate materials for study- ing the cellular microenvironment as their substantial water content helps to better mimic soft tissue. However, hydrogels can lack mechanical stiffness, strength, and tough- ness. Composite hydrogel systems have been shown to improve upon mechanical properties compared to their single- component counterparts. Poly （ethylene glycol） dimethacrylate （PEGDmA） and alginate are pol.mers that have been used to form hydrogels for biological applications. Single- component and composite PEGDmA and alginate systems were fabricated with a range of total pol.mer concentrations. Bulk gels were mechanically characterized using spherical indentation testing and a viscoelastic analysis framework. An increase in shear modulus with increasing pol.mer con- centration was demonstrated for all systems. Alginate hydro- gels were shown to have a smaller viscoelastic ratio than the PEGDmA gels, indicating more extensive relaxation over time. Composite alginate and PEGDmA hydrogels exhib- ited a combination of the mechanical properties of the con- stituents, as well as a qualitative increase in toughness. Additionally, multiple hydrogel systems were produced that had similar shear moduli, but different viscoelastic behaviors. Accurate measurement of the mechanical properties of hydrogels is necessary in order to determine what parameters are key in modeling the cellular microenvironment.

关键词： Hydrogel Viscoelastic Indentation Nanoin-dentation Composite

Ractopamine up take by alfalfa (medicago sativa) and wheat (Triticum aestivum) from soil

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2015年第8期27卷 86-92页

作者： Weilin l.Shelver Thomas m.DeSutter USDA-ARS Biosciences Research laboratory Department of Soil Science North Dakota State University

Ractopamine is a beta adrenergic agonist used as a growth promoter in swine, cattle and turkeys. To test whether ractopamine has the potential to accumulate in plants grown in contaminated soil, a greenhouse study was conducted with alfalfa（medicago sativa） and wheat（Triticum aestivum） grown in two soils having different concentrations of organic matter（1.3% and 2.1%）, amended with 0, 0.5, and 10 μg/g of ractopamine. Plant growth ranged from 2.7 to 8.8 g dry weight（dw） for alfalfa, and 8.7 to 40 g dw for wheat and was generally greater in the higher organic matter content soil. The uptake of ractopamine in plant tissues ranged from non-detectable to 897 ng/g and was strongly dependent on soil ractopamine concentration across soil and plant tissue. When adjusted to the total fortified quantities, the amount of ractopamine taken up by the plant tissue was low, 〈 0.01% for either soil.

关键词： Ractopamine Plant uptake Environment Foodsafety

Experimental Investigation of micro Heat Pipes of Different Cross-Sections Having Same Hydraulic Diameter

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2008年第3期17卷 247-252页

作者： S.l.mahmood m.A.R.Akhanda Department of mechanical and Chemical Engineering Islamic University of Technology

Effects of micro heat pipe （mHP） cross-sections and orientations on its thermal performance are experimentally investigated in this study. Tests are conducted using five different cross-sections （circular, semicircular, elliptical, semi-elliptical and rectangular） of micro heat pipes having same hydraulic diameter of 3 rnm placed at three different inclination angles （0°, 45°, 90°）, where water is used as the working fluid. Evaporator section of the mHP is heated by an electric heater and the condenser section is cooled by circulation of water in an annular space between condenser section and the water jacket. Temperatures at different locations of the mHP are measured using five calibrated K type thermocouples. Heat supply is varied using a voltage regulator which is measured by a precision ammeter and a vol.meter. It is found that thermal performance tends to deteriorate as the mHP is flattened. Thus among all cross-sections of mHP, circular one exhibits the best thermal performance in terms of heat flux dissipation followed by semi-elliptical, semi-circular, elliptical and rectangular cross-sections. moreover, its heat transfer capability also decreases with decreasing of its inclination angle. Finally, a correlation is developed which covers all the experimental data within ＋7%.

关键词： micro heat pipe cross-section hydraulic diameter inclination.

Do concentrations in eggs and liver tissue tell the same story of temporal trends of mercury in high Arctic seabirds?

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2018年第6期30卷 65-72页

作者： mark l.mallory Birgit m.Braune Biology Department Acadia University Environment and Cl.mate Change Canada National Wildlife Research Centre Carleton University

mercury（Hg） remains a key contaminant of concern in Arctic biota, and monitoring of Hg concentrations in seabird tissues will be an effective approach to track the effects of impl.menting the minamata Convention. We examined trends in total Hg（THg） in liver and egg tissues of two Arctic seabirds, thick-billed murres（Uria l.mvia） and northern fulmars（Fulmarus glacialis）, between 1976 and 2013 to assess whether both tissues showed similar patterns of Hg change. Hepatic THg was consistently higher than egg THg, and both species had similar egg THg concentrations, but fulmars had higher hepatic THg than *** THg concentrations showed more relative variation through time than *** suggest that egg THg better reflects exposure of birds to THg in local, Arctic prey,whereas liver THg may incorporate longer term, year-round THg exposure. Additional analysis of THg distribution in Arctic seabirds post-laying would help inform interpretation of long-term trends.

关键词： Canada Fulmarus glacialis Northern fulmar Thick-billed murre Uria l.mvia

Spent coffee grounds as a renewable source of energy: An analysis of bulk powder flowability

在线全文

学校读者我要写书评

暂无评论

Particuology 2019年第2期17卷 92-100页

作者： l. massaro Sousa m.C. Ferreira Drying Center for Pastes Suspensions and Seeds. Chemical Engineering Department Federal University of Sao Carlos. P.O. Box 676 13565-905 Sao Carlos Brazil

The main use for spent coffee grounds (SCG) produced in the soluble coffee industry is thermal energy generation in the industry itself. The SCG are processed using operations that are strongly dependent on powder flow behavior. In this study, we evaluated two classical flowability in dices of non-consolidated SCG powders: the angle of repose (AoR), and the Hausner ratio (HR). The influences of the mean particle diameter, particle size distribution (PSD), and water content on the AoR and HR values of SCG were analyzed for powders with a mean particle size range of 225-550 μm. For powders with a mean particle size close to 350 μm and for mixtures containing more than 40% fine particles, the HR (>1.35) and AoR (>45 °) values were characteristic of poor flowability. The AoR was sensitive to the powder PSD, and powders with similar mean particle sizes had higher AoR values when the PSD was larger. For powders w让h water contents up to 50%, the flowability indices were not greatly affected by the water content. A modified linear-mixture packing model was used to predict the packed bed void fractions for binary and ternary mixtures of the three base powders. The model was used to construct a ternary diagram to estimate the HR values of the mixtures. An equation was fitted to correlate HR and AoR. The proposed diagram and the equation provide insight into flow behavior and could be used for process design of industrial plants that handle SCG.

关键词： Spent coffee ground Biomass Flowability Hausner ratio Angle of repose

DNS in evolution of vorticity and sign relationship in wake transition of a circular cylinder:(pure)mode A

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 mechanica Sinica 2019年第6期35卷 1131-1149页

作者： l.m.lin Z.R.Tan Key laboratory for mechanics in Fluid Solid Coupling Systems Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Navigation Wuhan University of TechnologyWuhan 430063China Hubei Key laboratory of Inland Shipping Technology Wuhan University of TechnologyWuhan 430063China

In the present paper,the spatio-temporal evolution of vorticity in the first wake instability,i.e.,(pure)mode A,is investigated in order to understand the wake vortex dynamics and sign relationships among vorticity *** numerical simulation(DNS)for the flow past a circular cylinder is performed,typically at a Reynolds number of 200,in the three-dimensional(3-D)wake *** to characteristics of time histories of fluid forces,three different stages are identified as the computational transition,the initial stage and fully developed *** the second initial stage,the original two-dimensional spanwise vortices become obviously three-dimensional associated with the streamwise or vertical vorticity intensified up to about *** a matter of fact,these additional vorticities,caused by the intrinsic 3-D instability,are already generated firstly on cylinder surfaces early in the computational transition,indicating that the three-dimensionality appeared early near the *** evolution of additional components of vorticity with features the same as mode A shows that(pure)mode A can be already formed in the late computational *** careful analysis of the vorticity field on the front surface,in the shear layers and near wake at typical times,two sign laws are *** illustrate intrinsic relationships among three vorticity components,irrelevant to the wavelength or Fourier mode and Reynolds number in(pure)mode *** importantly,the origin of streamwise vortices is found and explained by a new physical.mechanism based on the theory of vortex-induced *** a result,the whole process of formation and shedding vortices with these vorticities is firstly and completely *** characteristics are presented in detail.

关键词： Wake transition Circular cylinder Vorticity mode A Sign law