2,791 research outputs found

    Continuous-time Mean-Variance Portfolio Selection with Stochastic Parameters

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    This paper studies a continuous-time market {under stochastic environment} where an agent, having specified an investment horizon and a target terminal mean return, seeks to minimize the variance of the return with multiple stocks and a bond. In the considered model firstly proposed by [3], the mean returns of individual assets are explicitly affected by underlying Gaussian economic factors. Using past and present information of the asset prices, a partial-information stochastic optimal control problem with random coefficients is formulated. Here, the partial information is due to the fact that the economic factors can not be directly observed. Via dynamic programming theory, the optimal portfolio strategy can be constructed by solving a deterministic forward Riccati-type ordinary differential equation and two linear deterministic backward ordinary differential equations

    3D printing of continuous carbon fibre reinforced powder-based epoxy composites

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    This paper presents an experimental study on 3D printing of continuous carbon fibre reinforced thermoset epoxy composites. Powder-based solid epoxy was electrostatically flocked on the 1K continuous carbon fibre tow and then melted to fabricate composite filaments. The produced filament was printed using a modified extrusion-based printer which melted and deposited the filament following designed printing paths, to form multilayer preforms with complex geometries. After vacuum bagging and oven curing, high tensile strength (1372.4 MPa) and modulus (98.2 GPa) were obtained in the fibre direction due to the good wettability of epoxy and the consequent high fibre volume fraction (56%). The tensile tests of open-hole composites were also conducted, in which the sample with designed stress-lines fibre paths was seen to improve the ultimate strength by 95% compared with the mechanically-drilled sample. Other case studies, such as a spanner and a lattice structure, further demonstrated the design freedom of produced filaments for complex geometries

    Parental use of the term "Hot Qi" to describe symptoms in their children in Hong Kong: a cross sectional survey "Hot Qi" in children

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    BACKGROUND: The Chinese term "Hot Qi" is often used by parents to describe symptoms in their children. The current study was carried out to estimate the prevalence of using the Chinese term "Hot Qi" to describe symptoms in children by their parents and the symptomatology of "Hot Qi". METHOD: A cross sectional survey by face-to-face interview with a semi-structured questionnaire was carried out in a public hospital and a private clinic in Hong Kong. The parental use of the term "Hot Qi", the symptoms of "Hot Qi" and the remedies used for "Hot Qi" were asked. RESULTS: 1060 pairs of children and parents were interviewed. 903 (85.1%) of parents claimed that they had employed the term "Hot Qi" to describe their children's symptoms. Age of children and place of birth of parents were the predictors of parents using the term "Hot Qi". Eye discharge (37.2%), sore throat (33.9%), halitosis(32.8%), constipation(31.0%), and irritable (21.2%) were the top five symptoms of "Hot Qi" in children. The top five remedies for "Hot Qi" were the increased consumption of water (86.8%), fruit (72.5%), soup (70.5%), and the use of herbal beverages "five-flower- tea" (a combination of several flowers such as Chrysanthemum morifolii, Lonicera japonica, Bombax malabaricum, Sophora japonica, and Plumeria rubra) (57.6%) or selfheal fruit spike (Prunella vulgaris) (42.4%). CONCLUSION: "Hot Qi" is often used by Chinese parents to describe symptoms in their children in Hong Kong. Place of birth of parents and age of the children are main factors for parents to apply the term "Hot Qi" to describe symptoms of their children. The common symptoms of "Hot Qi" suggest infections or allergy

    Structure of GrlR and the Implication of Its EDED Motif in Mediating the Regulation of Type III Secretion System in EHEC

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    Enterohemorrhagic Escherichia coli (EHEC) is a common cause of severe hemorrhagic colitis. EHEC's virulence is dependent upon a type III secretion system (TTSS) encoded by 41 genes. These genes are organized in several operons clustered in the locus of enterocyte effacement. Most of the locus of enterocyte effacement genes, including grlA and grlR, are positively regulated by Ler, and Ler expression is positively and negatively modulated by GrlA and GrlR, respectively. However, the molecular basis for the GrlA and GrlR activity is still elusive. We have determined the crystal structure of GrlR at 1.9 Å resolution. It consists of a typical β-barrel fold with eight β-strands containing an internal hydrophobic cavity and a plug-like loop on one side of the barrel. Strong hydrophobic interactions between the two β-barrels maintain the dimeric architecture of GrlR. Furthermore, a unique surface-exposed EDED (Glu-Asp-Glu-Asp) motif is identified to be critical for GrlA–GrlR interaction and for the repressive activity of GrlR. This study contributes a novel molecular insight into the mechanism of GrlR function

    Proteomics of synapse

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    Large-scale phosphoproteome analysis on synaptosome and preparation of post-synaptic density (PSD) were investigated. It was found that protein phosphor is a common event in the synapse, which is consistent with the presence of diverse classes of kinases and phosphatases in the synapse. Synaptic proteomics analysis required the purification of subcellular organelles from the brain regions of interest. Multiple steps of discontinuous density gradient ultra-centrifugation were employed to enrich the distinct organelles. Two-dimensional gel electrophoresis was used to separate and quantify proteins, including post-translational modified forms, from synaptic structures. It was observed that proteomic analysis of the synaptic vesicle identified 36 proteins, including seven integral membrane proteins and vesicle regulatory proteins

    Group 1 metabotropic glutamate receptors 1 and 5 form a protein complex in mouse hippocampus and cortex

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    The group 1 metabotropic glutamate receptors 1 and 5 (mGluR1/5) have been implicated in mechanisms of synaptic plasticity and may serve as potential therapeutic targets in autism spectrum disorders. The interactome of group 1 mGluRs has remained largely unresolved. Using a knockout-controlled interaction proteomics strategy we examined the mGluR5 protein complex in two brain regions, hippocampus and cortex, and identified mGluR1 as its major interactor in addition to the well described Homer proteins. We confirmed the presence of mGluR1/5 complex by (i) reverse immunoprecipitation using an mGluR1 antibody to pulldown mGluR5 from hippocampal tissue, (ii) coexpression in HEK293 cells followed by coimmunoprecipitation to reveal the direct interaction of mGluR1 and 5, and (iii) superresolution microscopy imaging of hippocampal primary neurons to show colocalization of the mGluR1/5 in the synapse

    Excess ribosomal protein production unbalances translation in a model of Fragile X Syndrome

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    Dysregulated protein synthesis is a core pathogenic mechanism in Fragile X Syndrome (FX). The mGluR Theory of FX predicts that pathological synaptic changes arise from the excessive translation of mRNAs downstream of mGlu1/5 activation. Here, we use a combination of CA1 pyramidal neuron-specific TRAP-seq and proteomics to identify the overtranslating mRNAs supporting exaggerated mGlu1/5 -induced long-term synaptic depression (mGluR-LTD) in the FX mouse model (Fmr1−/y). Our results identify a significant increase in the translation of ribosomal proteins (RPs) upon mGlu1/5 stimulation that coincides with a reduced translation of long mRNAs encoding synaptic proteins. These changes are mimicked and occluded in Fmr1−/y neurons. Inhibiting RP translation significantly impairs mGluR-LTD and prevents the length-dependent shift in the translating population. Together, these results suggest that pathological changes in FX result from a length-dependent alteration in the translating population that is supported by excessive RP translation
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