Short sales in Log-robust portfolio management

This paper extends the Log-robust portfolio management approach to the case with short sales, i.e., the case where the manager can sell shares he does not yet own. We model the continuously compounded rates of return, which have been established in the literature as the true drivers of uncertainty, as uncertain parameters belonging to polyhedral uncertainty sets, and maximize the worst-case portfolio wealth over that set in a one-period setting. The degree of the manager’s aversion to ambiguity is incorporated through a single, intuitive parameter, which determines the size of the uncertainty set. The presence of short-selling requires the development of problem-specific techniques, because the optimization problem is not convex. In the case where assets are independent, we show that the robust optimization problem can be solved exactly as a series of linear programming problems; as a result, the approach remains tractable for large numbers of assets. We also provide insights into the structure of the optimal solution. In the case of correlated assets, we develop and test a heuristic where correlation is maintained only between assets invested in. In computational experiments, the proposed approach exhibits superior performance to that of the traditional robust approach.     

Quantification of surface functional groups on polymer microspheres by supramolecular host-guest interactions

We introduce a method to determine the number of accessible functional groups on a polymer microsphere surface based on the interaction between the macrocyclic host cucurbit[7]uril (CB7) and a guest reacted to the microsphere surface. After centrifugation, CB7 in the supernatant is quantified by addition of a fluorescent dye. The difference between added and detected CB7 affords the number of accessible surface functional groups.     

In-situ X-ray investigation of a PbMg1/3Nb2/3O3-28%PbTiO3 single-crystal plate in an external electric field

A (001) single-crystal plate PbMg_1/3Nb_2/3O₃28 mol %PbTiO₃ was investigated by wide-angle X-ray scattering at room temperature in situ under the influence of an external static electric field E, applied along the [001] direction of the specimen. Excluding an initial stage of the electric field processing, the induced strain s calculated from the change of interplanar spacing, exhibited a symmetrical increase with |E|, and an anhysteretic character of the s(E) dependence, during unidirectional loops of the applied electric field. Reasons for the observed s(E) behaviour are discussed.Dedicated to Professor Hartmut Fuess (TU Darmstadt, Germany) on the ocassion of his 65th birthdayPACS 61.10.NZ; 61.50.-f; 83.60.Np; 84.37.+q     

Kapillarstrukturen in ionotropen Gelen

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Darstellung und Charakterisierung von Iodoplatinaten MexNH4–xPtI4 (x = 2 − 4), gemischtvalenten Octaiododiplatinaten(II,IV) mit Pt2I8-Baugruppen

Preparation and Characterization of Iodoplatinates Me_xNH_4–xPtI₄ (x = 2–4), Mixed Valence Octaiododiplatinates(II,IV) with Pt₂I₈ Groups Iodoplatinates APtI₄ (A = Me_xNH_4–x with x = 2–4) have been prepared by partial oxidation of the correspondent hexaiododiplatinates(II) A₂Pt₂I₆ with I₂ in methanolic solutions. X-ray structure analyses of the bronze-coloured needle-shaped crystals of the compounds showed rows of dinuclear anions Pt₂I₈^2?, built up by edgesharing planar PtI₄ groups with Pt^II und octahedral PtI₆ groups with Pt^IV. The different space requirement of the cations leads to the formation of three different structures. Within the anion stacks weak intermolecular Pt^IV? I …? Pt^II interactions are detectable by Raman spectroscopy.     

Aluminiumalkyle mit Heteroatomen. III. Über Reaktionen von Titan(IV)-chlorid mit Tris(trimethylsilylalkyl)-aluminium-Verbindungen

Aluminium Alkyls with Heteroatoms. III. On Reactions of Titanium(IV) Chloride with Trimethylsilylmethyl Aluminium Compounds Trimethylsilylmethyl titanium trichloride can be obtained by reaction of titanium(IV) chloride with tris(trimethylsilylmethyl)aluminium diethyl ether (1:1). Its catalytic activity for polymerisation of butadiene has been investigated.     

Über die Spinnbarkeit kolloider Systeme

Ohne Zusammenfassung