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A numerical model to simulate the transient frictional viscoelastic sliding contact

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friction 2024年第2期12卷 319-339页

作者： Dongze WANG gregory de BOER Anne NEVILLE Ali GHANBARZAdeH School of Mechanical Engineering University of LeedsLeeds LS29JTUK

Sliding motion has always been one of the major concerns when it comes to the analysis of viscoelastic contact problems.A new model simulating the transient sliding contact of smooth viscoelastic surfaces is developed in this *** taking the dry contact friction and the coupling between shear tractions and normal pressure into account,the effect of the early partial slip period,which is often neglected in the study of viscoelastic sliding contact problems,is investigated *** with solutions based on the frictionless assumption,the steady-state pressure profile is found to be slightly different under the effect of the partial slip regime,including a lower peak pressure and the shift of the contacting region in the direction opposite to the sliding ***,the time required for the viscoelastic contact to reach its steady state is delayed owing to the partial slip period preceding the global sliding motion.

关键词： contact mechanics frictional sliding viscoelasticity viscoelastic friction

Proteasome inhibition-induces endoplasmic reticulum dysfunction and cell death of human cholangiocarcinoma cells

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World Journal of Gastroenterology 2007年第6期13卷 851-857页

作者： Yucel Ustundag Steven f Bronk gregory J Gores Mayo Clinic College of Medicine Rochester MN 55905 United States

AIM: To determine if proteasome inhibition induces apoptosis in human cholangiocarcinoma cells, and if so, to elucidate the cellular mechanisms. METHODS: Studies were performed in the human KMCH, KMBC, and Mz-ChA-1 cholangiocarcinoma, and normal rat cell lines. MG132, a peptide aldehyde, which inhibits the chymotrypsin-like activity of the proteaosome was employed for this study. Apoptosis was assessed morphologically by 4'-6-Diamidino-2-phenylindole (DAPI) nuclear staining and fluorescence microscopy. Mitochondrial membrane potential was examined using a fluorescent unquenching assay. Ultrastructural changes during cell death were examined using transmission electron microscopy (TEM). Caspase 3/7 activity was assessed using an enzymatic-based fluorescent assay. Cytosolic-free calcium concentrations were measured using fura-2 and digitized fluorescent microscopy. RESULTS: MG132, a proteasome inhibitor, induced apoptosis in all the cholangiocarcinoma cell lines examined. In contrast, minimal cytotoxicity was observed in normal rat cholangiocytes. Apoptosis was time-and -concentration-dependent. There was no change in the mitochondrial membrane potential between treated and untreated cells. Ultrastructural examination by transmission electron microscopy displayed the classic features of apoptosis, but in addition, there was also dramatic vacuolization of the endoplasmic reticulum (ER). Unexpectedly, no increase in caspase 3/7 activity was observed in MG132 treated cells, nor did the pancaspase inhibitor, Q-VD-OPh prevent cell death. The protein synthesis inhibitor, cycloheximide, blocked apoptosis induced by proteosome inhibitor indicating that ER dysfunction was dependent upon the formation of new proteins. CONCLUSION: Proteosome inhibition induces ERdysfunction and caspase-independent cell death selectively in human cholangiocarcinoma cells. Proteasome inhibitors warrant evaluation as anticancer agents for the treatment of human cholangiocarcinoma.

关键词： MG132 Cholangiocarcinoma Proteosome Apoptosis Calcium

Discrete modeling of a longwall coal mine gob for CfD simulation

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International Journal of Mining Science and Technology 2020年第4期30卷 463-469页

作者： Aditya Juganda Claire Strebinger Jurgen f.Brune gregory E.Bogin Colorado School of Mines GoldenCO 80401USA

One area of concern in longwall coal mines is the active gob directly behind the longwall face,where high concentrations of methane are likely to accumulate and active roof caving *** computational fluid dynamics(CfD)to simulate gas flows in and through the gob,most researchers have represented the entire gob as a porous medium governed by Darcy’s ***,Darcy-type porous flow may not be applicable for the highly porous and unconsolidated fringes of the *** addition,porous medium models do not allow for representative combustion modeling to simulate in-gob ignition and flame *** study presents a hybrid approach to modeling the gob using CfD:the outer part of the gob is modeled as discrete objects that simulate coarse rock rubble,while the gob center is modeled as a porous medium.

关键词： Longwall Coal Computational fluid dynamic Modeling Ventilation

Context dependency of insect and mammalian herbivore effects on tall thistle (Cirsium altissimum) populations

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Journal of Plant Ecology 2019年第3期12卷 531-541页

作者： f.Leland Russell gregory R.Houseman department of Biological Sciences Wichita State UniversityWichitaKS 67260-0026USA

Aims Identifying factors that drive variation in herbivore effects on plant populations can provide insight for explaining plant distributions and for limiting *** resource availability to plants is a key explanation for variation in herbivore effects on individual plants,but the role of resources in determining herbivore effects on plant populations is largely *** tested the hypothesis that soil nutrient availability drives variation in insect and mam-mal herbivore effects on tall thistle(Cirsium altissimum)population *** In a Kansas USA restored tallgrass grassland that experienced prescribed fires,we manipulated soil nutrients,through fertil-izer addition,and presence of insect and mammal herbivores,using combinations of insecticide and fencing,in experimental *** 7 years,we quantified herbivore damage to repro-ductive tall thistles,tall thistle seed production and population growth *** findings Seed production was reduced by insect herbivores and increased by fertilizer addition,but treatment effects were *** effects on tall thistle population growth depended upon soil nutrients in only one of seven annual *** reduced thistle population growth in two of three annual transi-tions that included prescribed fire,whereas they reduced popula-tion growth in only one of four transitions without *** nutrient availability does not provide a general explanation for variation in herbivore effects on tall thistle population growth *** regime may be a more important aspect of ecological context for influencing herbivore effects on tall thistle populations in mesic grasslands.

关键词： fire herbivory population growth seed limitation soil nutrients

Genetic targeting of astrocytes to combat neurodegenerative disease

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Neural Regeneration Research 2020年第2期15卷 199-211页

作者： Rachel Kéry Allen P. f. Chen gregory W. Kirschen Medical Scientist Training Program MSTP)Stony Brook MedicineStony BrookNYUSA department of Neurobiology & Behavior Stony Brook UniversityStony BrookNYUSA

Astrocytes, glial cells that interact extensively with neurons and other support cells throughout the central nervous system, have recently come under the spotlight for their potential contribution to, or potential regenerative role in a host of neurodegenerative disorders. It is becoming increasingly clear that astrocytes, in concert with microglial cells, activate intrinsic immunological pathways in the setting of neurodegenerative injury, although the direct and indirect consequences of such activation are still largely unknown. We review the current literature on the astrocyte’s role in several neurodegenerative diseases, as well as highlighting recent advances in genetic manipulation of astrocytes that may prove critical to modulating their response to neurological injury, potentially combatting neurodegenerative damage.

关键词： Alzheimer's disease amyotrophic lateral sclerosis glia immune system inflammation Parkinson's disease reactive astrocyte regeneration

Synthesis and Ex Situ Doping of ZnTe and ZnSe Nanostructures with Extreme Aspect Ratios

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Nano Research 2009年第12期2卷 931-937页

作者： Joanne W.L.Yim deirdre Chen gregory f.Brown Junqiao Wu department of Materials Science and Engineering University of CaliforniaBerkeleyCA 94720USA Materials Sciences Division Lawrence Berkeley National LaboratoryBerkeleyCA 94720USA

We report synthesis windows for growth of millimeter-long ZnTe nanoribbons and ZnSe nanowires using vapor *** tuning the local conditions at the growth substrate,high aspect ratio nanostructures can be synthesized.A Cu-ion immersion doping method was applied,producing strongly p-type conduction in ZnTe and ionic conduction in *** extreme aspect ratio wide-bandgap semiconductors have great potential for high density nanostructured optoelectronic circuits.

关键词： Aspect ratio doping nanowires zinc selenide zinc telluride

Constitutive androstane receptor agonist, TCPOBOP,attenuates steatohepatitis in the methionine choline-deficientdiet-fed mouse

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World Journal of Gastroenterology 2007年第42期13卷 5635-5641页

作者： Edwina S Baskin-Bey Akira Anan Hajime Isomoto Steven f Bronk gregory J Gores department of Medicine Division of Gastroenterology and Hepatology Miles and Shirely Fitterman Center for Digestive Diseases Mayo Clinic College of Medicine Rochester MN 55905 United States

AIM： To ascertain whether constitutive androstane receptor （CAR） activation by 1,4-bis-[2-（3,5,- dichloropyridyloxy）] benzene （TCPOBOP） modulates steatohepatitis in the methionine choline-deficient （MCD） diet-fed ***： C57/BL6 wild-type mice were fed the MCD or standard diet for 2 wk and were treated with either the CAR agonist, TCPOBOP, or the CAR inverse agonist, ***： Expression of CYP2B10 and CYP3A11, known CAR target genes, increased 30-fold and 45-fold, respectively, in TCPOBOP-treated mice fed the MCD diet. TCPOBOP treatment reduced hepatic steatosis （44.6 ＋ 5.4% vs 30.4 ＋ 4.5%, P 〈 0.05） and serum triglyceride levels （48 ＋ 8 vs 20 ＋ 1 mg/dL, P 〈 0.05） in MCD diet- fed mice as compared with the standard diet-fed mice. This reduction in hepatic steatosis was accompanied by an increase in enzymes involved in fatty acid microsomal co-oxidation and peroxisomal p-oxidation, namely CYP4A10, LPBE, and 3-ketoacyI-CoA thiolase. The reduction in steatosis was also accompanied by a reduction in liver cell apoptosis and inflammation. In contrast, androstanol was without effect on any of the above ***： CAR activation stimulates induction of genes involved in fatty acid oxidation, and ameliorates hepatic steatosis, apoptosis and inflammation.

关键词： Apoptosis CYP4A fatty acid oxidation,Inflammation

Efficient visual learning by bumble bees in virtual-reality conditions:Size does not matter

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Insect Science 2023年第6期30卷 1734-1748页

作者： gregory Lafon Marco Paoli Benjamin HPaffhausen Gabriela de Brito Sanchez Mathieu Lihoreau Aurore Avarguès-Weber Martin Giurfa Centre de Recherches sur la Cognition Animale Centre de Biologie Intégrative(CBI)University of ToulouseCNRSUPSToulouseFrance french Academy of Sciences for University Professors Institut Universitaire de France(IUF)ParisFrance

Recent developments allowed establishing virtual-reality (VR) setups to study multiple aspects of visual learning in honey bees under controlled experimental conditions. Here, we adopted a VR environment to investigate the visual learning in the buff-tailed bumble bee Bombus terrestris. Based on responses to appetitive and aversive reinforcements used for conditioning, we show that bumble bees had the proper appetitive motivation to engage in the VR experiments and that they learned efficiently elemental color discriminations. In doing so, they reduced the latency to make a choice, increased the proportion of direct paths toward the virtual stimuli and walked faster toward them. Performance in a short-term retention test showed that bumble bees chose and fixated longer on the correct stimulus in the absence of reinforcement. Body size and weight, although variable across individuals, did not affect cognitive performances and had a mild impact on motor performances. Overall, we show that bumble bees are suitable experimental subjects for experiments on visual learning under VR conditions, which opens important perspectives for invasive studies on the neural and molecular bases of such learning given the robustness of these insects and the accessibility of their brain.

关键词： Bombus terrestris bumble bees interindividual size/weight differences reinforcement responses visual learning virtual reality

Effects of temperature and solvent concentration on the solvent crystallization of palm-based dihydroxystearic acid with isopropyl alcohol

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Particuology 2012年第1期10卷 127-131页

作者： gregory f.L. Koay Teong-Guan Chuah Sumaiya Zainal-Abidin Salmiah Ahmad Thomas S.Y. Choong department of Chemical and Environmental Engineering Universiti Putra Malaysia Advanced Oleochemical Technology Division Malaysian Palm Oil Board Institute of Tropical forestry and forest Products Universiti Putra Malaysia faculty of Chemical and Natural Resources Engineering Universiti Malaysia Pahang Director General's Office Malaysian Rubber Board

Palm-based dihydroxystearic acid of 69.55% purity was produced in a 500-kg-per-batch operation pilot plant and purified through solvent crystallization in a custom fabricated simultaneous batch crystallizer unit. The effects of temperature and solvent concentration on yield, particle size distribution and purity were studied. The purity was higher, while the yield and particle size were lower and smaller, respectively, at higher temperature and solvent concentration. The solvent crystallization process efficiency was rated at 66-69% when carried out with 70-80% isopropyl alcohol at 20℃.

关键词： Dihydroxystearic acidPilot plant operationSolvent crystallizationSimultaneous batch crystallizerProcess efficiency