检索结果-南通市图书馆

Closed-Form Formulae for European Options Under Three-Factor Models

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 Mathematics and Statistics 2020年第4期8卷 379-408页

作者： joanna Goard University of Wollongong WollongongNSWAustrali

In this paper,we derive new closed-form valuations to European options under three-factor hybrid models that include stochastic interest rates and stochastic volatility and incorporate a nonzero covariance structure between *** make novel use of the empirically proven 3/2 stochastic volatility model with a time-dependent drift inwhich we are free to choose the moving reversion *** has been shown bymany authors to empirically outperform other volatility models in maximising model *** also improve the valuation of European options under the Heston volatility and Cox,Ingersoll,Ross interest rate model,recently published in the literature,by replacing open-form infinite series with closed-form analytic *** completeness,we also add a fuller covariance structure in this setting and detail closed-form valuations for *** inclusion of nonzero covariances amongst the factors can significantly improve option pricing by allowing for a wider variety of market *** solutions are derived by firstly formulating the price of a European call option in terms of the corresponding characteristic function of the underlying price and then determining a partial differential equation for the characteristic *** including empirically proven models into our analysis,the options formulae could provide more realistic prices for investors and practitioners.

关键词： European optionvaluation Stochastic volatility Stochastic interest rates Heston model 3/2 model

Carbon Xerogel-supported Iron as a Catalyst in Combustion Synthesis of Carbon Fibrous Nanostructures

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 Materials Science & Technology 2012年第4期28卷 294-302页

作者： Wojciech Kiciński joanna Lasota Institute of Chemistry Military University of Technology Kaliskiego 2 00-908 Warsaw Poland

The catalytically assisted self-propagating high-temperature synthesis of carbon fibrous nanostructures, where the iron-doped colloidal carbon xerogel is proposed as a catalyst system, was examined. The carbon xerogel was prepared through carbonization of an iron doped organic xerogel at temperatures ranging from 600 to 1050℃. The reaction between calcium carbide and hexachloroethane in the presence of sodium azide is exothermic enough to proceed at a high temperature, self-sustaining regime. The combustion reactions of those mixtures enriched with iron-doped carbon xerogels were conducted in a stainless steel reactor---calorimetric bomb under an initial pressure of 1 MPa of argon. Scanning electron microscopy analysis of the combustion products revealed low yield of various type of carbon fibers （presumably nanotubes）, which grew via the tip-growth mechanism. The fibrous nanostructures were found in the vicinity of the spot of ignition, while in the outer and cooler area of the reactor, dusty products with soot-like morphology dominated. No significant correlation between the pyrolysis temperature of the carbon xerogel and the morphology of the obtained carbon fibrous nanostructures was observed.

关键词： Combustion synthesis Carbon xerogel Carbon fibrous nanostructures Carbonnanotubes Scanning electron microscopy

维普期刊数据库

Feeding More People on an Increasingly Fragile Planet: China's Food and Nutrition Security in a National and Global Context

在线全文

学校读者我要写书评

暂无评论

Journal of Integrative Agriculture 2014年第6期13卷 1193-1205页

作者： Shenggen Fan joanna Brzeska International Food Policy Research Institute

Developing and developed countries alike are increasingly facing the dififcult question of how to feed more people amidst a host of emerging demographic, environmental, and health challenges. At the same time, in addition to food quantity, increased attention is being given to food quality attributes, in particular nutrition and safety. This is especially evident in China, where concerns are on the rise regarding the ability of China’s food production systems to deliver nutritious and safe food to a growing, urbanizing and more aflfuent population. These food and nutrition concerns come at a time when China is an increasingly inlfuential actor within the global food security network through activities such as production, consumption and trade. We argue that China has the opportunity to increase food and nutrition security both nationally and globally through a comprehensive policy agenda that focuses on institutional reforms, investments for and in agriculture, productive social safety nets, mutually beneifcial trade, and the exchange of know-how and technologies among developing countries and donors. This agenda will help China adapt its food production systems to the changing face of agriculture and to play a vital role in addressing the emerging challenges facing food and nutrition security within and beyond China in the coming decades.

关键词： food security nutrition China agricultural development

维普期刊数据库

Hydroxyapatites enriched in silicon-Bioceramic materials for biomedical and pharmaceutical applications

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2017年第4期27卷 401-409页

作者： Katarzyna Szurkowska joanna Kolmas Medical University of Warsaw Faculty of Pharmacy with Laboratory Medicine Division Department of Inorganic and Analytical Chemistry

Hydroxyapatite ((Ca10（PO4）)6（OH）2, abbreviated as HA) plays a crucial role in implantology, dentistry and bone surgery. Due to its considerable similarity to the inorganic fraction of the mineralized tissues（bones, enamel and dentin）, it is used as component in many bone substitutes, coatings of metallic implants and dental materials. Biomaterial engineering often takes advantage of HA capacity for partial ion substitution because the incorporation of different ions in the HA structure leads to materials with improved biological or physicochemical properties. The objective of the work is to provide an overview of current knowledge about apatite materials substituted with silicon ions. Although the exact mechanism of action of silicon in the bone formation process has not been fully elucidated, research has shown beneficial effects of this element on bone matrix mineralization as well as on collagen type I synthesis and stabilization. The paper gives an account of the functions of silicon in bone tissue and outlines the present state of research on synthetic HA containing silicate ions（Si-HA）. Finally, methods of HA production as well as potential and actual applications of HA materials modified with silicon ions are discussed.

关键词： Hydroxyapatite Silicon Biomaterials Ionic substitution Bioceramics

Effect of number of granulometric fractions on structure and micromechanics of compressed granular packings

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Particuology 2018年第4期16卷 88-95页

作者： joanna Wicacke Marek Molenda Mateusz Stasiak Institute of Agrophysics Polish Academy of Sciences Doswiadczalna 4 20-290 Lublin 27 Poland

The role of number of grain size fractions on structural and mechanical properties of uniaxially com- pressed granular packings with a uniform particle size distribution in terms of number of particles and with various particle size dispersities was studied using the discrete element method. The study addressed packing density, coordination number, contact forces, global stress, and energy dissipation in assemblies composed of frictional spheres. Packing density was found to change with increasing num- ber of granulometric fractions in mixtures with a small ratio of the diameters of the largest to smallest particles. Results indicated a certain value of particle size ratio below which the number of particle size fractions strongly affected packing density. The average coordination number decreased with increasing number of fractions. Detailed analysis of the effect of particle size dispersity on mechanical coordination number, including particles with no less than four contacts, revealed that, contrary to the average coordi- nation number, the mechanical coordination number increased with increasing ratio of the diameters of the largest to smallest particles in the sample. The composition of polydisperse samples strongly affected stress distribution and energy dissipation in granular packings.

关键词： Granular packings Granulometric fractions Structure MicromechanicsDiscrete element method

Transcription tipping points for T follicular helper cell and T-helper 1 cell fate commitment

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Cellular & Molecular Immunology 2021年第3期18卷 528-538页

作者： Amania A.Sheikh joanna R.Groom Divisions of Immunology and Molecular Immunology Walter and Eliza Hall Institute of Medical ResearchParkvilleVIC 3052Australia Department of Medical Biology University of MelbourneParkvilleVIC 3010Australia

During viral infection,immune cells coordinate the induction of inflammatory responses that clear infection and humoral responses that promote ***4^(+)T-cell differentiation sits at the center of this *** toward T-helper 1(Th1)cells mediates inflammation and pathogen clearance,while T follicular helper(Tfh)cells facilitate germinal center(GC)reactions for the generation of high-affinity antibodies and immune *** Th1 and Tfh differentiation occurs in parallel,these CD4^(+)T-cell identities are mutually exclusive,and progression toward these ends is determined via the upregulation of T-bet and Bcl6,*** lineage-defining transcription factors act in concert with multiple networks of transcriptional regulators that tip the T-bet and Bd6 axis in CD4^(+)T-cell progenitors to either a Th1 or Tfh *** is now clear that these transcriptional networks are guided by cytokine cues that are not only varied between distinct viral infections but also dynamically altered throughout the duration of ***,multiple intrinsic and extrinsic factors combine to specify the fate,plasticity,and function of Th1 and Tfh cells during ***,we review the current information on the mode of action of the lineage-defining transcription factors Bcl6 and T-bet and how they act individually and in complex to govern CD4^(+)T-cell ***,we outline the multifaceted transcriptional regulatory networks that act upstream and downstream of Bcl6 and T-bet to tip the differentiation equilibrium toward either a Tfh or Th1 fate and how these are impacted by dynamic inflammatory cues.

关键词： Cytokines Infection T follicular helper cells T-helper 1 cells Transcription factors

The influence of mining factors on seismic activity during longwall mining of a coal seam

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Mining Science and Technology 2021年第3期31卷 429-437页

作者： Łukasz Wojtecki joanna Kurzeja Małgorzata Knopik Department of Geology and Geophysics Central Mining Institute40-166 KatowicePoland Polish Mining Group 40-039 KatowicePoland

In this article an attempt to determine the influence of mining factors on the seismic activity during the longwall mining of the upper layer of coal seam no.405/2 in one of the Polish hard coal mines in the Upper Silesian Coal Basin was *** longwall panels were mined in analogous geological conditions and based on the same mining system and ***,there was significant difference with regards to the mining factors,which was reflected in the observed seismic *** tools used in mining seismology were applied to illustrate the aforementioned influence of mining factors,*** frequency-energy distribution,the frequency-magnitude distribution,the 2 D distribution of released seismic energy,the relationship between released seismic energy and the volume of mined coal,the Benioff strain release,and the Gutenberg-Richter(GR)b coefficient distribution(b is the proportion between high and low energy tremors).Concerning the Benioff strain release,a new solution,based on the slope of a fitted line in a moving time window,is proposed.

关键词： Underground coal mining Induced seismicity Seismic statistics Benioff strain release

维普期刊数据库

Nonalcoholic fatty liver disease and HFE gene mutations:A Polish study

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2010年第20期16卷 2531-2536页

作者： joanna Raszeja-Wyszomirska Grzegorz Kurzawski Malgorzata Lawniczak joanna Miezynska-Kurtycz Jan Lubinski Liver Unit Pomeranian Medical University70-111 SzczecinPoland Department of Genetics and Pathology International Hereditary Cancer CentrePomeranian Medical University70-111 SzczecinPoland Department of Gastroenterology Pomeranian Medical University71-252 SzczecinPoland

AIM:To describe a Polish population with nonalcoholic fatty liver disease(NAFLD)with regard to HFE gene mutations,as well as analyzing demographic and clinical ***:Sixty-two consecutive patients with biopsy-proven NAFLD were included in the ***,clinical,and laboratory data were summarized in a database.C282Y and H63D mutations of the HFE gene were analyzed using polymerase chain reactionrestriction fragment lenght ***:The analyzed cohort consisted of 62 homo-geneic Caucasian participants,66.1%men and 33.9% women,with a median age of 48 *** median body mass index was 29.05 kg/m 2 .Hypercholesterolemia was observed in 74.2%of patients and hypertriglyceridemia in 32.2%;16.1%had type 2 diabetes mellitus(DMt2).On liver biopsy,22.6%of NAFLD patients were found to have severe *** were no differences between frequencies of HFE gene mutations in subgroups of NAFLD patients with less and more severe liver ***,older age,female gender and DMt2 were associated with more advanced fibrosis in this Polish cohort,as well as higher glucose level,serum iron and transaminase aspartate aminotransferase/alanine aminotransferase ***:HFE mutations conferred no additional hepatic fibrosis risk in NAFLD,but higher serum iron was a risk factor for severe liver damage in NAFLD,regardless of HFE mutations.

关键词： Nonalcoholic fatty liver disease HFE gene mutations Liver fibrosis

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

营养素跷跷板

环球科学 2024年第16期 38-41页

作者：乔安娜·埃尔菲克不详

想要保持健康不是一件简单的事,其中一点就是注意饮食,摄入适量的营养物质。均衡的微量营养素可以通过强化身体的物理屏障(如黏液层和皮肤),增强身体的自然防御能力。微量营养素是人体正常运作所必需的各种维生素和矿物质的总称。维生... 详细信息

想要保持健康不是一件简单的事,其中一点就是注意饮食,摄入适量的营养物质。均衡的微量营养素可以通过强化身体的物理屏障(如黏液层和皮肤),增强身体的自然防御能力。微量营养素是人体正常运作所必需的各种维生素和矿物质的总称。维生素是有机物质,由植物或其他动物生产,可分为两类:脂溶性维生素和水溶性维生素。

关键词：微量营养素脂溶性维生素水溶性维生素物理屏障跷跷板营养物质黏液层防御能力