Phototoxic effects of Hypericum extract in cultures of human keratinocytes compared with those of psoralen

Extracts of Hypericum perforatum (St. John's wort) are used in the treatment of depression. They contain the plant pigment hypericin and hypericin derivates. These compounds have light-dependent activities. In order to estimate the potential risk of phototoxic skin damage during antidepressive therapy, we investigated the phototoxic activity of hypericin extract using cultures of human keratinocytes and compared it with the effect of the well-known phototoxic agent psoralen. The absorbance spectrum of our Hypericum extract revealed maxima in the whole UV range and in parts of the visible range. We cultivated human keratinocytes in the presence of different Hypericum concentrations and irradiated the cells with 150 mJ/cm2 UVB, 1 J/cm2 UVA or 3 h with a white light of photon flux density 2.6 mumol m-2 s-1. The determination of the bromodeoxyuridine incorporation rate showed a concentration- and light-dependent decrease in DNA synthesis with high hypericin concentrations (> or = 50 micrograms/mL) combined with UVA or visible light radiation. In the case of UVB irradiation a clear phototoxic cell reaction was not detected. We found phototoxic effects even with 10 ng/mL psoralen using UVA with the same study design as in the case of the Hypericum extract. These results confirm the phototoxic activity of Hypericum extract on human keratinocytes. However, the blood levels that are to be expected during antidepressive therapy are presumably too low to induce phototoxic skin reactions.     

The general nucleolus and the reduced game property

The nucleolus of a TU game is a solution concept whose main attraction is that it always resides in any nonempty -core. In this paper we generalize the nucleolus to an arbitrary pair (,F), where is a topological space andF is a finite set of real continuous functions whose domain is . For such pairs we also introduce the least core concept. We then characterize the nucleolus forclasses of such pairs by means of a set of axioms, one of which requires that it resides in the least core. It turns out that different classes require different axiomatic characterizations.One of the classes consists of TU-games in which several coalitions may be nonpermissible and, moreover, the space of imputations is required to be a certain generalized core. We call these gamestruncated games. For the class of truncated games, one of the axioms is a new kind ofreduced game property, in which consistency is achieved even if some coalitions leave the game, being promised the nucleolus payoffs. Finally, we extend Kohlberg's characterization of the nucleolus to the class of truncated games.     

On locally optimal nonparametric tests

Summary There is an abundancy of problems in which no parametric model realistically describes the situation and in which, accordingly, we have to resort to nonparametric methods. As the numerical problems connected with nonparametric tests are becoming less and less important, rank tests, permutation tests and the like are becoming more and more part of the standard armatory of applied statisticians. The lack of tabulated critical values, for instance, should no longer be a serious objection against the use of permutation tests in practice; cf. Edgington (1987).The rationale underlying permutation and rank tests has been outlined in quite a number of text books and papers; cf. Fraser (1957), Lehmann (1959), Hájek-Sidák (1967) or Witting (1970). Roughly speaking, permutation tests are constructibel if the data can be condensed by means of a sufficient and complete statistic allowing for the proper kind of conditioning. Rank tests arise if the underlying problem is invariant with respect to (w.r.t.) a large group of transformations which leads to a maximal invariant statistic consisting of (signed) ranks.Most practical nonparametric problems, however, are too complex to be tractable by just one of those approaches. Many of them, however, can be handled by a combination of both techniques. In this paper we outline the logic underlying that combined reduction method and apply it to construct locally most powerful tests. Moreover, we discuss what we label Hoeffding's transfer problem, i.e. the uniformity aspect of locally most powerful tests with respect to the starting point at the boundary. We are concentrating on the discussion of the nonparametric two-sample location and scale problem. Further important problems are mentioned in Section III.This is a written account of an invited lecture delivered by the third author on occasion of the 14th Symposium über Operations Research, Ulm, September 6–8, 1989.     

L.P.-games with sufficiently many players

L.P.-games aren-person cooperative games arising from a linear program as studied by Owen and Billera/Raanan. Employing a version of nondegeneracy of games developed by Weidner and the author, we show that methods from the Geometry of Numbers are the suitable tool in order to obtain lower bounds for the number of players of each type that ensure that the core and the competitive equilibrium coincide.     

Professor Sivaramakrishna Chandrasekhar,FRS

Abstract

Optical microscopy in mixtures of di-octylazoxybenzene (8AB) and di-nonylazoxybenzene (9AB) reveals that a smectic A-nematic-isotropic triple point occurs at 71·5±0·5°C and 38±2wt% 8AB. Although this concentration induced triple point is different from the pressure induced triple point known to exist in pure 9AB at elevated pressure, analysis of the data from both the mixing and pressure experiments reveals that the phase transition surfaces in temperature-pressure-concentration space for this system are nearly planar.     

AN IMPROVED ARC-LENGTH METHOD AND APPLICATION IN THE POST-BUCKLING ANALYSIS FOR COMPOSITE STRUCTURES

Based on the conventional arc- length method, an improved arc- length method with high-efficiency is proposed. The weighted modifications with respect to the variation of structural stiffness and extra-interpolation modification by using the information of known equilibrium points are introduced to improve the incremental arc- length . An approximate expansion method for the accumulated and expected arc-length is used to ensure the convergence at given load levels in large range of applications. Numerical results show that the improved arc-length method has well adaptability and higher efficiency in the post-buckling analysis of plates and sheik structures for tracing whole load-deflection path and obtaining the convergence values at any specified load levels.     

ON THE ASYMPTOTIC BEHAVIOR OF HOPFIELD NEURAL NETWORK WITH PERIODIC INPUTS

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