160 research outputs found
Optimal execution for portfolio transactions
Thesis (S.M.)--Massachusetts Institute of Technology, System Design and Management Program, February 2007.Includes bibliographical references.In my thesis I explore the problem of optimizing trading strategies for complex portfolio transitions. Institutional investors run into this issue during periodic portfolio rebalancing or transition between asset managers. The costs of rebalancing can be broadly broken into trading costs (both the transaction cost and the market impact) and the opportunity costs of delaying the execution and bearing the risk of current-to-target portfolio divergence. This thesis proposes a methodology for measuring the opportunity cost as well as a strategy that minimizes the proposed measure through optimal portfolio transition execution. The benefits from the proposed trading strategy are benchmarked against the industry standard portfolio trading practices.by Alexander Fadeev.S.M
Capillary-Wave Model for the Solidification of Dilute Binary Alloys
Starting from a phase-field description of the isothermal solidification of a
dilute binary alloy, we establish a model where capillary waves of the
solidification front interact with the diffusive concentration field of the
solute. The model does not rely on the sharp-interface assumption, and includes
non-equilibrium effects, relevant in the rapid-growth regime. In many
applications it can be evaluated analytically, culminating in the appearance of
an instability which, interfering with the Mullins-Sekerka instability, is
similar to that, found by Cahn in grain-boundary motion.Comment: 17 pages, 12 figure
In vitro synthesis of uniform poly(dG)âpoly(dC) by Klenow exo(â) fragment of polymerase I
In this paper, we describe a production procedure of the one-to-one double helical complex of poly(dG)âpoly(dC), characterized by a well-defined length (up to 10 kb) and narrow size distribution of molecules. Direct evidence of strands slippage during poly(dG)âpoly(dC) synthesis by Klenow exo(â) fragment of polymerase I is obtained by fluorescence resonance energy transfer (FRET). We show that the polymer extension results in an increase in the separation distance between fluorescent dyes attached to 5âČ ends of the strands in time and, as a result, losing communication between the dyes via FRET. Analysis of the products of the early steps of the synthesis by high-performance liquid chromatography and mass spectroscopy suggest that only one nucleotide is added to each of the strand composing poly(dG)âpoly(dC) in the elementary step of the polymer extension. We show that proper pairing of a base at the 3âČ end of the primer strand with a base in sequence of the template strand is required for initiation of the synthesis. If the 3âČ end nucleotide in either poly(dG) or poly(dC) strand is substituted for A, the polymer does not grow. Introduction of the T-nucleotide into the complementary strand to permit pairing with A-nucleotide results in the restoration of the synthesis. The data reported here correspond with a slippage model of replication, which includes the formation of loops on the 3âČ ends of both strands composing poly(dG)âpoly(dC) and their migration over long-molecular distances (ÎŒm) to 5âČ ends of the strands
Strategies for Large Oil and Gas Companies Operating to Support Sustainable Development and Environmental Safety in the Russian Arctic
IAs conventional oil and gas sources become less productive, unconventional hydrocarbon sources become more attractive due to new technologies and become the target of expanded exploration. Oil and gas development in the Arctic is challenging but promising, the largest reserves of Oil and Gas in the Arctic are on the Arctic Shelf in Russia. Most Arctic communities, especially indigenous communities, depend on fishing, hunting, and gathering, this requires the preservation of environmental health. In this article we tried to delineate a strategy for large oil and gas companies to diversify risk by proposing a form of social entrepreneurship that works for environmentally vulnerable regions with low infrastructure or skilled labor. With this framework, large oil and gas companies could effectively and reliably support smaller-scale enterprises preserving environmental health and creating an innovative business ecosystem that promotes a Arctic. Our model could also lead to local and indigenous entrepreneurship and a more equitable distribution of wealth in the Arctic
assessment of blood capillaries and structural proteins localization
The papillary dermis of human skin is responsible for its biomechanical
properties and for supply of epidermis with chemicals. Dermis is mainly
composed of structural protein molecules, including collagen and elastin, and
contains blood capillaries. Connective tissue diseases, as well as
cardiovascular complications have manifestations on the molecular level in the
papillary dermis (e.g. alteration of collagen I and III content) and in the
capillary structure. In this paper we assessed the molecular structure of
internal and external regions of skin capillaries using two-photon
fluorescence lifetime imaging (FLIM) of endogenous compounds. It was shown
that the capillaries are characterized by a fast fluorescence decay, which is
originated from red blood cells and blood plasma. Using the second harmonic
generation signal, FLIM segmentation was performed, which provided for spatial
localization and fluorescence decay parameters distribution of collagen I and
elastin in the dermal papillae. It was demonstrated that the lifetime
distribution was different for the inner area of dermal papillae around the
capillary loop that was suggested to be due to collagen III. Hence, we propose
a generalized approach to two-photon imaging of the papillary dermis
components, which extends the capabilities of this technique in skin
diagnosis
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Label-free characterization of white blood cells using fluorescence lifetime imaging and flow-cytometry: molecular heterogeneity and erythrophagocytosis [Invited]
Article reporting the results of blood cell characterization using label-free fluorescence imaging techniques and flow-cytometry. Autofluorescence parameters of different cell types â white blood cells, red blood cells, erythrophagocytic cells â are assessed and analyzed in terms of molecular heterogeneity and possibilities of differentiation between different cell types in vitro and in vivo
Geographical and temporal distribution of SARS-CoV-2 clades in the WHO European Region, January to June 2020
We show the distribution of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) genetic clades over time and between countries and outline potential genomic surveillance objectives. We applied three genomic nomenclature systems to all sequence data from the World Health Organization European Region available until 10 July 2020. We highlight the importance of real-time sequencing and data dissemination in a pandemic situation, compare the nomenclatures and lay a foundation for future European genomic surveillance of SARS-CoV-2
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