2,344 research outputs found

    Portfolio optimisation models and properties of return distributions

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    Mean-risk models have been widely used in portfolio optimisation. However, such models may produce portfolios that are dominated with respect to second order stochastic dominance and therefore not optimal for rational and risk-averse investors. This paper considers the problem of constructing a portfolio which is nondominated with respect to second order stochastic dominance and whose return distribution has specified desirable properties. The problem is multi-objective and is transformed into a single objective problem by using the reference point method, in which target levels, known as aspiration points, are specified for the objective function values. A model is proposed in which the aspiration points relate to ordered return outcomes of the portfolio return. The model is extended by additionally specifying reservation points, which act pre-emptively in the optimisation. The theoretical properties of the models are studied. The performance of the models on real data drawn from the Hang Seng index is also investigated

    A Revision of the Ordovician Trilobite Asaphus platycephalus Stokes

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    63-73http://deepblue.lib.umich.edu/bitstream/2027.42/48398/2/ID244.pd

    Epidemiological data of falciparum malaria in Ado-Odo/Ota, Southwest Ogun State, Nigeria

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    In this data article, Blood and corresponding saliva samples from subjects presenting with fever and parasetaemia Z2000 were obtained from selected hospitals in Ado-Odo/Ota, Ogun State over a period of two years and analyzed using Polymerase chain reaction-Restriction fragment Length Polymorphism (PCR/Nested PCR-RFLP) to detect genetic mutations of Plasmodium falciparum chloroquine resistance transporter (Pfcrt), Plasmodium falciparum multidrugs resistance (Pfmdr1) and non-synonymous Pkelch (pk13) mutated genes. The study confirmed the presence of resistance genes in the blood and saliva samples collected from the study sit

    In-gas-cell laser ionization spectroscopy in the vicinity of 100Sn: Magnetic moments and mean-square charge radii of N=50-54 Ag

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    In-gas-cell laser ionization spectroscopy studies on the neutron deficient 97-101Ag isotopes have been performed with the LISOL setup. Magnetic dipole moments and mean-square charge radii have been determined for the first time with the exception of 101Ag, which was found in good agreement with previous experimental values. The reported results allow tentatively assigning the spin of 97,99Ag to 9/2 and confirming the presence of an isomeric state in these two isotopes, whose collapsed hyperfine structure suggests a spin of 1/2 . The effect of the N=50 shell closure is not only manifested in the magnetic moments but also in the evolution of the mean-square charge radii of the isotopes investigated, in accordance with the spherical droplet model predictions

    Four Reports of Ostracod Investigations Conducted Under National Science Foundation Project GB-26

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    1-79http://deepblue.lib.umich.edu/bitstream/2027.42/48586/2/ID447.pd

    Lewisian quidditism, humility, and diffidence

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    In ‘Ramseyan Humility’ Lewis presents the Permutation Argument for quidditism. As he presents it the argument is simple enough, but once one digs beneath its surface, and attempts to understand it in strictly Lewisian terms, difficulties arise. The fundamental difficulty is that, as he presents it, the argument only seems to be sound if one rejects views that Lewis explicitly holds. One aim of this paper is to clarify the argument to show that one can make sense of it in strictly Lewisian terms. In so doing I clarify Lewis’s view, clearly lay out the commitments that Lewis has, and define quidditism in strictly Lewisian terms. However, I also have a secondary aim. Lewis accepts that quidditism entails a form of scepticism, that he calls ‘Humility’. However, by an extension of the permutation argument I show that quidditism entails a form of scepticism, that I call ‘Diffidence’, that is far more wide-reaching than Humility

    Properties of purified enzymes induced by pathogenic drug-resistant mutants of herpes simplex virus. Evidence for virus variants expressing normal DNA polymerase and altered thymidine kinase

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    The DNA polymerases and thymidine kinases induced by three drug-resistant mutants of herpes simplex virus type 1 (S1, Tr7, and B3) and their common parent strain, SC16, have been purified and their properties compared. No significant differences were seen in the affinities of the polymerases for TTP and dGTP, or for the triphosphates of 9-(2-hydroxyethyloxymethyl)guanine (acyclovir) or (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVdU) (drugs used in their isolation). In contrast all three mutants induced abnormal thymidine kinases. Those induced by the acyclovir-resistant mutants, S1 and Tr7, showed reduced affinities for thymidine, acyclovir, and also BVdU. Thymidine kinase induced by the BVdU-resistant mutant B3 showed reduced affinity for BVdU, but its affinities for thymidine and acyclovir were similar to those of the wild type enzyme. Thus, it appears that these variants of herpes simplex virus express altered thymidine kinases with impaired ability to phosphorylate particular nucleoside analogue drugs and these characteristics probably account for the drug resistance of the viruses. This strategy for resistance is important as it may result in variants with undiminished pathogenicity

    Orbital dependent nucleonic pairing in the lightest known isotopes of tin

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    By studying the 109Xe-->105Te-->101Sn superallowed alpha-decay chain, we observe low-lying states in 101Sn, the one-neutron system outside doubly magic 100Sn. We find that the spins of the ground state (J = 7=2) and first excited state (J = 5=2) in 101Sn are reversed with respect to the traditional level ordering postulated for 103Sn and the heavier tin isotopes. Through simple arguments and state-of-the-art shell model calculations we explain this unexpected switch in terms of a transition from the single-particle regime to the collective mode in which orbital-dependent pairing correlations, dominate.Comment: 5 pages 3 figure

    Genome-Wide Gene Expression in relation to Age in Large Laboratory Cohorts of \u3ci\u3eDrosophila melanogaster\u3c/i\u3e

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    Aging is a complex process characterized by a steady decline in an organism’s ability to perform life-sustaining tasks. In the present study, two cages of approximately 12,000 mated Drosophila melanogaster females were used as a source of RNA from individuals sampled frequently as a function of age. A linear model for micro array data method was used for the micro array analysis to adjust for the box effect; it identified 1,581 candidate aging genes.Cluster analyses using a self-organizing map algorithm on the 1,581 significant genes identified gene expression patterns across different ages. Genes involved in immune system function and regulation, chorion assembly and function, and metabolism were all significantly differentially expressed as a function of age. The temporal pattern of data indicated that gene expression related to aging is affected relatively early in life span. In addition, the temporal variance in gene expression in immune function genes was compared to a random set of genes. There was an increase in the variance of gene expression within each cohort, which was not observed in the set of random genes.This observation is compatible with the hypothesis that D. melanogaster immune function genes lose control of gene expression as flies age
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