Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99


Any time

2019 ( 58 )

2018 ( 648 )

2017 ( 676 )

2016 ( 776 )

Custom range...

Search Results: 1 - 10 of 231603 matches for " D. Xu "
All listed articles are free for downloading (OA Articles)
Page 1 /231603
Display every page Item
Biomass Converting Enzymes as Industrial Biocatalysts for Fuels and Chemicals: Recent Developments
Matt D. Sweeney,Feng Xu
Catalysts , 2012, DOI: 10.3390/catal2020244
Abstract: The economic utilization of abundant lignocellulosic biomass as a feedstock for the production of fuel and chemicals would represent a profound shift in industrial carbon utilization, allowing sustainable resources to substitute for, and compete with, petroleum based products. In order to exploit biomass as a source material for production of renewable compounds, it must first be broken down into constituent compounds, such as sugars, that can be more easily converted in chemical and biological processes. Lignocellulose is, unfortunately, a heterogeneous and recalcitrant material which is highly resistant to depolymerization. Many microorganisms have evolved repertoires of enzyme activities which act in tandem to decompose the various components of lignocellulosic biomass. In this review, we discuss recent advances in the understanding of these enzymes, with particular regard to those activities deemed likely to be applicable in commercialized biomass utilization processes.
Concentration of endogenous estrogens and estrogen metabolites in the NCI-60 human tumor cell lines
Xia Xu, Timothy D Veenstra
Genome Medicine , 2012, DOI: 10.1186/gm330
Abstract: In this study we systemically surveyed endogenous estrogen and estrogen metabolite levels in each of the NCI-60 human tumor cell lines, which include human breast, central nerve system, colon, ovarian, prostate, kidney and non-small cell lung cancers, as well as melanomas and leukemia. The absolute abundances of these metabolites were measured using a liquid chromatography-tandem mass spectrometry method that has been previously utilized for biological fluids such as serum and urine.Endogenous estrogens and estrogen metabolites were found in all NCI-60 human tumor cell lines and some were substantially elevated and exceeded the levels found in well known estrogen-dependent and estrogen receptor-positive tumor cells such as MCF-7 and T-47D. While estrogens were expected to be present at high levels in cell lines representing the female reproductive system (that is, breast and ovarian), other cell lines, such as leukemia and colon, also contained very high levels of these steroid hormones. The leukemia cell line RMPI-8226 contained the highest levels of estrone (182.06 pg/106 cells) and 17β-estradiol (753.45 pg/106 cells). In comparison, the ovarian cancer cell line with the highest levels of these estrogens contained only 19.79 and 139.32 pg/106 cells of estrone and 17β-estradiol, respectively. The highest levels of estrone and 17β-estradiol in breast cancer cell lines were only 8.45 and 87.37 pg/106 cells in BT-549 and T-47D cells, respectively.The data provided evidence for the presence of significant amounts of endogenous estrogens and estrogen metabolites in cell lines not commonly associated with these steroid hormones. This broad discovery of endogenous estrogens and estrogen metabolites in these cell lines suggest that several human tumors may be beneficially treated using endocrine therapy aimed at estrogen biosynthesis and estrogen-related signaling pathways.Endogenous estrogens and estrogen metabolites (EMs) have long been associated with carcinogenesis and
A novel EB-1/AIDA-1 isoform, AIDA-1c, interacts with the Cajal body protein coilin
Hongzhi Xu, Michael D Hebert
BMC Cell Biology , 2005, DOI: 10.1186/1471-2121-6-23
Abstract: In this report, we identify a novel protein isoform of EB-1/AIDA-1, termed AIDA-1c, that interacts with the CB marker protein, coilin. Northern and nested PCR experiments reveal that the AIDA-1c isoform is expressed in brain and several cancer cell lines. Competition binding experiments demonstrate that AIDA-1c competes with SmB' for coilin binding sites, but does not bind SMN. When ectopically expressed, AIDA-1c is predominantly nuclear with no obvious accumulations in CBs. Interestingly, another EB-1/AIDA-1 nuclear isoform, AIDA-1a, does not bind coilin in vivo as efficiently as AIDA-1c. Knockdown of EB-1/AIDA-1 isoforms by siRNA altered Cajal body organization and reduced cell viability.These data suggest that specific EB-1/AIDA-1 isoforms, such as AIDA-1c, may participate in the regulation of nucleoplasmic coilin protein interactions in neuronal and transformed cells.Studies conducted to understand nuclear organization and function have revealed that the nucleus contains a myriad of dynamic, highly organized domains, territories and bodies [1-3]. The Cajal body (CB) is one such structure and contains the highest concentration of small nuclear ribonucleoproteins (snRNPs) in the nucleus [4,5]. SnRNPs are a vital part of the pre-mRNA processing machinery, necessary for both splice site recognition and the splicing reaction. More precisely, the catalyst for the splicing reaction is probably the small nuclear ribonucleic acid (snRNA) component of the snRNP [6]. The human U1, U2, U4, U5 and U6 snRNAs share the intriguing characteristic in that they contain numerous post-transcriptionally modified nucleotides, namely pseudouridines and 2'-O-methyl groups [7]. These modifications appear to be important for efficient splicing of RNA and, in the case of U2, are essential for spliceosomal assembly [8]. In addition to base modification, U1, U2, U4 and U5 snRNAs undergo an elaborate maturation pathway in which they are exported to the cytoplasm. In the cytoplasm, these snRNA
New classes of generalized invex monotonicity
B. Xu,D. L. Zhu
Journal of Inequalities and Applications , 2006,
Abstract: This paper introduces new classes of generalized invex monotone mappings and invex cocoercive mappings. Their differential property and role to analyze and solve variational-like inequality problem are presented.
On the zero-dispersion limit of the Benjamin-Ono Cauchy problem for positive initial data
Peter D. Miller,Zhengjie Xu
Physics , 2010,
Abstract: We study the Cauchy initial-value problem for the Benjamin-Ono equation in the zero-disperion limit, and we establish the existence of this limit in a certain weak sense by developing an appropriate analogue of the method invented by Lax and Levermore to analyze the corresponding limit for the Korteweg-de Vries equation.
Identifying AGN's Balmer-Absorptions and stratified NLR kinematics in SDSSJ112611.63+425246.4
J. Wang,D. W. Xu
Physics , 2014, DOI: 10.1051/0004-6361/201424848
Abstract: Balmer absorption is a rare phenomenon in active galactic nuclei (AGNs). So far, only seven Balmer-absorption AGNs have been reported in literature. We here report the identification of SDSS\,J112611.63+425246 as a new Balmer-absorption AGN through our spectral analysis, and study the kinematics of its narrow emission-line region (NLR). We model the continuum by a linear combination of a starlight component, a powerlaw from the central AGN and the emission from the FeII complex. After the subtraction of the modeled continuum, each emission/absorption line is profiled by a sum of multi Gaussian functions. All the line shifts are determined with respect to the modeled starlight component. By using the host starlight as a reference for the local system, both H$\alpha$ and H$\beta$ show AGN's absorptions with a blueshift of $\sim300\mathrm{km\ s^{-1}}$. We identify a strong anti-correlation between the inferred velocity shifts and ionization potential for various narrow emission lines, which suggests a stratified NLR kinematics. A de-accelerated outflow is implied for the inner NLR gas, while an accelerated inflow for the outer NLR gas. This complicated NLR kinematics additionally implies that AGN's narrow emission lines, even for the low-ionized lines, might not be a reliable surrogate for the velocity of the local system.
The radiation properties of an accretion disk with a non-zero torque on its inner edge
Xinwu Cao,Y. D. Xu
Physics , 2002, DOI: 10.1093/pasj/55.1.149
Abstract: The structure of the inner edge of the accretion disk around a black hole can be altered, if the matter inside the marginally stable orbit is magnetically connected to the disk. In this case, a non-zero torque is exerted on its inner edge, and the accretion efficiency $\epsilon$ can be much higher than that in the standard accretion disk model. We explore the radiation properties of an accretion disk at its sonic point around a black hole with a time-steady torque exerted on the inner edge of the disk. The local structure of the accretion flow at the sonic point is investigated in the frame of general relativity. It is found that the accretion flow will be optically thin at its sonic point for most cases, if the additional accretion efficiency $\delta\epsilon$ caused by the torque is as high as $\sim$10 %. The results imply that the variable torque may trigger transitions of the flow between different accretion types.
The Benjamin-Ono Hierarchy with Asymptotically Reflectionless Initial Data in the Zero-Dispersion Limit
Peter D. Miller,Zhengjie Xu
Physics , 2011,
Abstract: We study the Benjamin-Ono hierarchy with positive initial data of a general type, in the limit when the dispersion parameter tends to zero. We establish simple formulae for the limits (in appropriate weak or distributional senses) of an infinite family of simultaneously conserved densities in terms of alternating sums of branches of solutions of the inviscid Burgers hierarchy.
A model for the compositions of non-stoichiometric intermediate phases formed by diffusion reactions, and its application to Nb3Sn superconductors
Xingchen Xu,Mike D. Sumption
Physics , 2015,
Abstract: In this work we explore the compositions of non-stoichiometric intermediate phases formed by diffusion reactions: a mathematical framework is developed and tested against the specific case of Nb3Sn superconductors. In the first part, the governing equations for the bulk diffusion and inter-phase interface reactions during the growth of a compound are derived, numerical solutions to which give both the composition profile and growth rate of the compound layer. The analytic solutions are obtained with certain approximations made. In the second part, we explain an effect that the composition characteristics of compounds can be quite different depending on whether it is the bulk diffusion or grain boundary diffusion that dominates in the compounds, and that frozen bulk diffusion leads to unique composition characteristics quite distinct from equilibrium expectations; then the model is modified for the case of grain boundary diffusion. Finally, we apply this model to the Nb3Sn superconductors and propose the approaches to control their compositions.
The Collins-Roscoe mechanism and D-spaces
Yuming Xu,Dániel Soukup
Mathematics , 2010, DOI: 10.1007/s10474-011-0083-5
Abstract: We prove that if a space X is well ordered $(\alpha A)$, or linearly semi-stratifiable, or elastic then X is a D-space.
Page 1 /231603
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.