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A PERISHAbLE INVENTORY SYSTEM WITH SERVICE FACILITIES, MAP ARRIVALS AND PH- SERVICE TIMES

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Journal of Systems Science and Systems Engineering 2007年第1期16卷 62-73页

作者： paul MANUEL b. SIVAKUMAR G. ARIVARIGNAN Department of Information Science Kuwait University Kuwait. Department of Applied Mathematics and Statistics School of Mathematics Madurai Kamaraj University Madurai Tamilnadu India

We consider a continuous review perishable （s,S） inventory system with a service facility consisting of a waiting hall of finite capacity and a single server. We assume two types of customers, ordinary and negative, arrive according to a Markovian Arrival Process （MAP）. An ordinary customer joins the queue and a negative customer instead of joining the queue removes one ordinary customer from the queue. The removal rule adopted in this paper is RCE （removal of a customer from the end）. The individual customer＇s unit demand is satisfied after a random time of service which is assumed to have a phase-type distribution. The life time of each item and the lead time of the reorders have been assumed to be independent exponential distributions. The joint probability distribution of the number of customers in the system and the inventory level is obtained for the steady state case. Various stationary system performance measures are computed and the total expected cost rate is calculated. The results are illustrated numerically.

关键词： Stochastic inventory Markovian demands service facility positive lead time negative customers

The great catastrophe: causes of the Permo-Triassic marine mass extinction

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National Science Review 2024年第1期11卷 37-50页

作者： paul b.Wignall David P.G.bond School of Earth & Environment University of Leeds School of Environmental Sciences University of Hull

The marine losses during the Permo-Triassic mass extinction were the worst ever experienced. All groups were badly affected, especially amongst the benthos(e.g. brachiopods, corals, bryozoans, foraminifers,ostracods). Planktonic populations underwent a fundamental change with eukaryotic algae being replaced by nitrogen-fixing bacteria, green-sulphur bacteria, sulphate-reducing bacteria and prasinophytes. Detailed studies of boundary sections, especially those in South China, have resolved the crisis to a ～55 kyr interval straddling the Permo-Triassic boundary. Many of the losses occur at the beginning and end of this interval painting a picture of a two-phase extinction. Improved knowledge of the extinction has been supported by numerous geochemical studies that allow diverse proposed extinction mechanisms to be studied. A transition from oxygenated to anoxic-euxinic conditions is seen in most sections globally, although the intensity and timing shows regional variability. Decreased ocean ventilation coincides with rapidly rising temperatures and many extinction scenarios attribute the losses to both anoxia and high *** kill mechanisms include ocean acidification for which there is conflicting support from geochemical proxies and, even less likely, siltation(burial under a massive influx of terrigenous sediment) which lacks substantive sedimentological evidence. The ultimate driver of the catastrophic changes at the end of the Permian was likely Siberian Trap eruptions and their associated carbon dioxide emissions with consequences such as warming, ocean stagnation and acidification. Volcanic winter episodes stemming from Siberian volcanism have also been linked to the crisis, but the short-term nature of these episodes(boreal latitudes

关键词： ocean anoxia ocean acidification siltation productivity collapse volcanic winter

Metabolic effects of intestinal absorption and enterohepatic cycling of bile acids

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Acta Pharmaceutica Sinica b 2015年第2期5卷 129-134页

作者： Courtney b.Ferrebee paul A.Dawson Department of Pediatrics Division of Gastroenterology Hepatology and Nutrition Emory University Molecular Medicine Graduate Program Wake Forest School of Medicine

The classical functions of bile acids include acting as detergents to facilitate the digestion and absorption of nutrients in the gut. In addition, bile acids also act as signaling molecules to regulate glucose homeostasis, lipid metabolism and energy expenditure. The signaling potential of bile acids in compartments such as the systemic circulation is regulated in part by an efficient enterohepatic circulation that functions to conserve and channel the pool of bile acids within the intestinal and hepatobiliary compartments. Changes in hepatobiliary and intestinal bile acid transport can alter the composition, size,and distribution of the bile acid pool. These alterations in turn can have significant effects on bile acid signaling and their downstream metabolic targets. This review discusses recent advances in our understanding of the inter-relationship between the enterohepatic cycling of bile acids and the metabolic consequences of signaling via bile acid-activated receptors, such as farnesoid X nuclear receptor(FXR)and the G-protein-coupled bile acid receptor(TGR5).

关键词： bile acids Liver Intestine Transporters Lipid metabolism Energy homeostasis

Continued surprises in the cytochrome c biogenesis story

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Protein & Cell 2012年第6期3卷 405-409页

作者： Elizabeth b.Sawyer paul D.barker National Laboratory of biomacromolecules Institute of BiophysicsChinese Academy of SciencesBeijing 100101China University Chemical Laboratory University of CambridgeCambridgeCB21EWUnited Kingdom

Cytochromes c covalently bind their heme prosthetic groups through thioether bonds between the vinyl groups of the heme and the thiols of a CXXCH motif within the *** Gramnegative bacteria,this process is catalyzed by the Ccm(cytochrome c maturation)proteins,also called System *** Ccm proteins are found in the bacterial inner membrane,but some(CcmE,CcmG,CcmH,and CcmI)also have soluble functional domains on the periplasmic face of the *** of the mechanisms involved in the transport and relay of heme and the apo-cytochrome from the bacterial cytosol into the periplasm,and their subsequent reaction,has proved challenging due to the fact that most of the proteins involved are membrane-associated,but recent progress in understanding some key components has thrown up some *** this Review,we discuss advances in our understanding of this process arising from a substrate’s point of view and from recent structural information about individual components.

关键词： cytochrome c heme Ccm post-transla-tional modification cytochrome b562 heme binding

Geochemical characteristics and origin of the Neoproterozoic high-K calc-alkaline granitoids in the northern part of Mandara hills,northeastern Nigeria

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Acta Geochimica 2020年第3期39卷 337-354页

作者： Musa b.Girei Tavershima Najime paul O.Ogunleye State Key Laboratory of Geological Processes and Mineral Resources Faculty of Earth ResourcesChina University of GeosciencesWuhan 430074China Department of Geology Faculty of Earth and Environmental Sciences.Bayero UniversityKanoNigeria Department of Geology Ahmadu Bello UniversityZariaNigeria Centre for Energy Research and Training Ahmadu Bello UniversityP.M.B.1014ZariaNigeria

The high-K calc-alkaline granitoids in the northern part of the Mandara Hills are part of the wellexposed post-collisional plutons in northeastern *** calc-alkaline rock association consists of quartz monzodiorite,hornblende biotite granite,biotite granites and aplite which intruded the older basement consisting mainly of low-lying migmatitic gneisses and amphibolites during the Neoproterozoic Pan-African *** and geochemical studies have revealed the presence of hornblende,iron oxide,and metaluminous to slightly peraluminous characteristics in the granitoids which is typical of I-type *** granitoids are also depleted in some high field strength elements(*** and Ta) as well as *** of Mg#versus SiO2 indicate that the granite was derived from partial melting of crustal *** delamination at the waning stage of the PanAfrican Orogeny possibly triggered upwelling of hot mafic magma from the mantle which underplated the lower ***,in turn,caused partial melting and magma generation at the lower to middle-crustal ***,the peculiar geochemical characteristics of the quartz monzodiorite especially the enrichment in compatible elements such as MgO,Cr,and Ni,as well as LILE element(e.g.K,Ce,Cs,ba,and Sr),signify that the rock formed from an enriched upper mantle *** emplacement of high-K granites in the Madara Hill,therefore,marked an important episode of crustal reworking during the ***,further isotopic work is needed to confirm this model.

关键词： Calc-alkaline I-type granitoids Pan-African Mandara hills Nigeria

Discrete element simulation of cylindrical particles using super-ellipsoids

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Particuology 2019年第5期17卷 55-66页

作者： Yongzhi Zhao Lei Xu paul b. Umbanhowar Richard M. Lueptow Institute of Process Equipment College of Energy Engineering Zhejiang University Hangzhou 310027 China Department of Mechanical Engineering Northwestern University Evanston Illinois 60208 USA Department of Chemical and biological Engineering Northwestern University Evanston. Illinois 60208 USA The Northwestern Institute on Complex Systems (NICO) Northwestern University Evanston Illinois 60208 USA

A discrete element model based on super-ellipsoids was used to simulate cylindrical particle flow. The model can describe a cylindrical particle accurately provided the shape indices of the super-ellipsoids are set to appropriate values. To achieve more rapid calculations, we implemented an "oriented bounding box algorithm"(ObbA) for the initial contact detection of cylindrical particles. Several types of Simulations were performed to validate the super-ellipsoid model and the contact-detection algorithm. First, the effect of shape index of the super-ellipsoids on model accuracy was investigated through three simulations: impact of a cylindrical particle on a flat wall, flow of cylindrical particles in a rotating tumbler, and segregation of cylindrical particles of different length flowing down a bounded heap. The simulation results show that the super-ellipsoids describe cylindrical particles accurately when the shape index that specifies the sharpness of the cylinder edges is sufficiently large. The efficiency of the ObbA is measured by simulations in which a box is filled with cylindrical particles and a tumbler that contains cylindrical particles is rotated. The simulation results show that the ObbA can accelerate the calculations significantly. The effect of particle shape (such as aspect ratio and shape index) on the calculation speed was obtained. The simulation of rod-like particles tended to take more calculation time than that of disk-like particles, and the simulation time increased with an increasing particle-shape index.

关键词： Discrete element method Super-ellipsoid Super-quadric Cylindrical particle Non-spherical particle Granular material

Optical Measurement of Photorecombination Time Delays

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Ultrafast Science 2023年第6期3卷 17-24页

作者： Chunmei Zhang Graham brown Dong Hyuk Ko P.b.corkum Joint Attosecond Science Laboratory University of Ottawa and National Research Council of Canada25 Templeton StOttawaON K1N 6N5Canada beijing Institute of Technology No.5South StreetZhongguancunHaidian DistrictBeijingChina Max born Institute Max Born Str.2a12489 BerlinGermany

Recollision physics and attosecond pulse generation meld the precision of optics with collision *** a follow-up to our previous work,we reveal a new direction for the study of electronic structure and multielectron dynamics by exploiting the collision-physics nature of *** show experimentally that,by perturbing recollision trajectories with an infrared field,photorecombination time delays can be measured entirely optically using the Cooper minimum in argon as an *** doing so,we demonstrate the relationship between recollision trajectories and the transition moment coupling the ground and continuum *** particular,we show that recollision trajectories are influenced by their parent ion,while it is commonly assumed they are *** work paves the way for the entirely optical measurement of ultrafast electron dynamics and photorecombination delays due to electronic structure,multielectron interaction,and strong-field-driven dynamics in complex molecular systems and correlated solid-state systems.

关键词： collision entirely dynamics

Targeting inflammation to reduce brain injury in growth restricted newborns:a potential treatment?

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Neural Regeneration Research 2017年第11期12卷 1804-1806页

作者： Julie A Wixey paul b Colditz Stella Tracey bjorkman Centre for Clinical Research Faculty of MedicineThe University of QueenslandHerstonQueenslandAustralia

Introduction： Intrauterine growth restriction （IUGR） is commonly caused by placental insufficiency, resulting in a chronic hypoxic environment and subsequent abnormal fetal development. The developing brain is particularly vulnerable to IUGR conditions. Multiple causal factors associated with brain injury in fetal growth restriction include the timing of placental insufficiency, onset and subsequent severity of fetal compromise, fetal cerebrovascular response and the redistribution of brain blood flow. Although a significant proportion of IUGR infants exhibit adverse long-term neu- rological outcomes, relatively few studies have focused on the mechanisms of brain injury in the IUGR neonate. Clini- cal imaging studies of IUGR infants demonstrate alterations in grey matter and white matter volume and structure （Tolsa et al., 2004; Esteban et al., 2010; Padilla et al., 2015）. Cortical grey matter volume is reduced by up to 28% compared with control infants （Tolsa et al., 2004） and both white and grey matter show structural changes （Esteban et al., 2010）. These structural changes persist at 1 year of age and are associated with significant developmental disabilities （Tolsa et al., 2004;

关键词： Targeting inflammation brain injury

Wash water in waterworks:contaminants and process options for reclamation

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Journal of Environmental Sciences 2008年第11期20卷 1300-1305页

作者： C b Chidambara Raj Tan Ee Kwong Soh Hoo Tiong paul Stefan Klose Centre for Advanced Water Technology Singapore Utilities International Pte Ltd.82 Toh Guan Road East # C4-03Singapore 608575 Public Utilities board Water Supply (Plants) Department40 Scotts Road #14-00Singapore 228231

Reclamation of clean water from filter backwash water was studied through pilot-scale *** pilot plant consisted of clarification,sand-filtration,and ultrafiltration modules in sequence,with a provision to bypass the sand *** water that conformed to World Health Organization (WHO) guidelines on Potable Quality was ***,aluminum and iron were found to be critical contaminants in process selection and ***,followed by sand filtration,was found to be the minim...

关键词： filter backwash clarification water treatment aluminium Giardia