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481.
介绍了开滦煤矿马家沟矿新型建材分公司使用台式振动小型砌块成型机全自动生产线中的煤矸石的主要指标及特性,及利用煤矸石生产砌块的可行性,并分析了其产品性能。 相似文献
482.
483.
This paper considers the optimal investment strategy for an insurer under the criterion of mean-variance. The risk process
is a compound Poisson process and the insurer can invest in a risk-free asset and multiple risky assets. This paper obtains
the optimal investment policy using the stochastic linear quadratic (LQ) control theory with no-shorting constraint. Then
the efficient strategy (optimal investment strategy) and efficient frontier are derived explicitly by a verification theorem
with the viscosity solution of Hamilton-Jacobi-Bellman (HJB) equation. 相似文献
484.
This paper considers a class of stochastic variational inequality problems. As proposed by Jiang and Xu (2008), by using the
so-called regularized gap function, the authors formulate the problems as constrained optimization problems and then propose
a sample average approximation method for solving the problems. Under some moderate conditions, the authors investigate the
limiting behavior of the optimal values and the optimal solutions of the approximation problems. Finally, some numerical results
are reported to show efficiency of the proposed method. 相似文献
485.
In this paper, the dynamic behaviors of a discrete epidemic model with a nonlinear incidence rate obtained by Euler method
are discussed, which can exhibit the periodic motions and chaotic behaviors under the suitable system parameter conditions.
Codimension-two bifurcations of the discrete epidemic model, associated with 1:1 strong resonance, 1:2 strong resonance, 1:3
strong resonance and 1:4 strong resonance, are analyzed by using the bifurcation theorem and the normal form method of maps.
Moreover, in order to eliminate the chaotic behavior of the discrete epidemic model, a tracking controller is designed such
that the disease disappears gradually. Finally, numerical simulations are obtained by the phase portraits, the maximum Lyapunov
exponents diagrams for two different varying parameters in 3-dimension space, the bifurcation diagrams, the computations of
Lyapunov exponents and the dynamic response. They not only illustrate the validity of the proposed results, but also display
the interesting and complex dynamical behaviors. 相似文献
486.
J. D. R. de Raadt 《Systemic Practice and Action Research》2011,24(6):509-521
Starting from the crisis in our communities—research has indicated it to be widely spread—the author explores the scientific
tradition preceding the rise of modernism in order to draw out a more humane way of thinking that may help our contemporary
societies. He discerns between two types of Renaissance humanism, one characterised by its cleverness, the other by its compassion
and desire to restore dignity to the lives of people struggling to escape the clutches of medievalism. The father of the latter
is Erasmus of Rotterdam and we follow the development of his conception of a social humanism as it branches out, through the
work of his successors, into every scientific discipline, both natural and human. These disciplines are united by an embracing
systemic idea of philosophy that unites the mind with the heart and which Erasmus called “Philosophia Christi”. We examine
the two main pillars upon which this philosophy is built, love for our neighbour and education as the only legitimate instrument
to change society, and the extraordinary impact it had on science and on communities living in the seventeenth century. We
contrast this with the idea of power, the chosen instrument of modernity to transform society, and trace some of its tragic
outcomes. We conclude by discussing the incorporation of an Erasmian type of social humanism into systems education and the
future development of such programmes. 相似文献
487.
A dispersion-strengthened copper alloy with 1 wt% TiC for commercial electrical-contact wires was prepared by in-situ reaction casting, grain-ultrafining by equal-channel angular pressing (ECAP) and subsequent annealing with aim to obtain excellent comprehensive performance. The results showed that fine TiC particles were in-situ synthesized in the as-cast Cu matrix and aggregated in clusters, and thus mechanical properties of the as-cast alloy deemed insufficient. Continued ECAP at 473 K significantly refined the grains of the as-cast alloy and improved the distribution of TiC particles. Due to multiple strengthening mechanisms, the ECAP-processed alloys maintained good conductivity with obviously enhanced tensile strength and hardness values. After post-ECAP annealing, the elongation and conductivity of the fine-grained copper alloy increased with the adequate tensile strength. The novel combined process endows the alloy appropriate performance to serve current high-frequency electrification railway systems. 相似文献
488.
BAI1 is an engulfment receptor for apoptotic cells upstream of the ELMO/Dock180/Rac module 总被引:1,自引:0,他引:1
Park D Tosello-Trampont AC Elliott MR Lu M Haney LB Ma Z Klibanov AL Mandell JW Ravichandran KS 《Nature》2007,450(7168):430-434
Engulfment and subsequent degradation of apoptotic cells is an essential step that occurs throughout life in all multicellular organisms. ELMO/Dock180/Rac proteins are a conserved signalling module for promoting the internalization of apoptotic cell corpses; ELMO and Dock180 function together as a guanine nucleotide exchange factor (GEF) for the small GTPase Rac, and thereby regulate the phagocyte actin cytoskeleton during engulfment. However, the receptor(s) upstream of the ELMO/Dock180/Rac module are still unknown. Here we identify brain-specific angiogenesis inhibitor 1 (BAI1) as a receptor upstream of ELMO and as a receptor that can bind phosphatidylserine on apoptotic cells. BAI1 is a seven-transmembrane protein belonging to the adhesion-type G-protein-coupled receptor family, with an extended extracellular region and no known ligands. We show that BAI1 functions as an engulfment receptor in both the recognition and subsequent internalization of apoptotic cells. Through multiple lines of investigation, we identify phosphatidylserine, a key 'eat-me' signal exposed on apoptotic cells, as a ligand for BAI1. The thrombospondin type 1 repeats within the extracellular region of BAI1 mediate direct binding to phosphatidylserine. As with intracellular signalling, BAI1 forms a trimeric complex with ELMO and Dock180, and functional studies suggest that BAI1 cooperates with ELMO/Dock180/Rac to promote maximal engulfment of apoptotic cells. Last, decreased BAI1 expression or interference with BAI1 function inhibits the engulfment of apoptotic targets ex vivo and in vivo. Thus, BAI1 is a phosphatidylserine recognition receptor that can directly recruit a Rac-GEF complex to mediate the uptake of apoptotic cells. 相似文献
489.
Mullighan CG Goorha S Radtke I Miller CB Coustan-Smith E Dalton JD Girtman K Mathew S Ma J Pounds SB Su X Pui CH Relling MV Evans WE Shurtleff SA Downing JR 《Nature》2007,446(7137):758-764
Chromosomal aberrations are a hallmark of acute lymphoblastic leukaemia (ALL) but alone fail to induce leukaemia. To identify cooperating oncogenic lesions, we performed a genome-wide analysis of leukaemic cells from 242 paediatric ALL patients using high-resolution, single-nucleotide polymorphism arrays and genomic DNA sequencing. Our analyses revealed deletion, amplification, point mutation and structural rearrangement in genes encoding principal regulators of B lymphocyte development and differentiation in 40% of B-progenitor ALL cases. The PAX5 gene was the most frequent target of somatic mutation, being altered in 31.7% of cases. The identified PAX5 mutations resulted in reduced levels of PAX5 protein or the generation of hypomorphic alleles. Deletions were also detected in TCF3 (also known as E2A), EBF1, LEF1, IKZF1 (IKAROS) and IKZF3 (AIOLOS). These findings suggest that direct disruption of pathways controlling B-cell development and differentiation contributes to B-progenitor ALL pathogenesis. Moreover, these data demonstrate the power of high-resolution, genome-wide approaches to identify new molecular lesions in cancer. 相似文献
490.
Telomere dysfunction may result in chromosomal abnormalities, DNA damage responses, and even cancer. Early studies in lower organisms have helped to establish the crucial role of telomerase and telomeric proteins in maintaining telomere length and protecting telomere ends. In Oxytricha nova, telomere G-overhangs are protected by the TEBP-alpha/beta heterodimer. Human telomeres contain duplex telomeric repeats with 3' single-stranded G-overhangs, and may fold into a t-loop structure that helps to shield them from being recognized as DNA breaks. Additionally, the TEBP-alpha homologue, POT1, which binds telomeric single-stranded DNA (ssDNA), associates with multiple telomeric proteins (for example, TPP1, TIN2, TRF1, TRF2 and RAP1) to form the six-protein telosome/shelterin and other subcomplexes. These telomeric protein complexes in turn interact with diverse pathways to form the telomere interactome for telomere maintenance. However, the mechanisms by which the POT1-containing telosome communicates with telomerase to regulate telomeres remain to be elucidated. Here we demonstrate that TPP1 is a putative mammalian homologue of TEBP-beta and contains a predicted amino-terminal oligonucleotide/oligosaccharide binding (OB) fold. TPP1-POT1 association enhanced POT1 affinity for telomeric ssDNA. In addition, the TPP1 OB fold, as well as POT1-TPP1 binding, seemed critical for POT1-mediated telomere-length control and telomere-end protection in human cells. Disruption of POT1-TPP1 interaction by dominant negative TPP1 expression or RNA interference (RNAi) resulted in telomere-length alteration and DNA damage responses. Furthermore, we offer evidence that TPP1 associates with the telomerase in a TPP1-OB-fold-dependent manner, providing a physical link between telomerase and the telosome/shelterin complex. Our findings highlight the critical role of TPP1 in telomere maintenance, and support a yin-yang model in which TPP1 and POT1 function as a unit to protect human telomeres, by both positively and negatively regulating telomerase access to telomere DNA. 相似文献