פרסומים

For fixed i let X(i)=(X1(i),...,Xd(i) be a d-dimensional random vector with some known joint distribution. Here i should be considered a time variable. Let X(i)=1,...,n be a sequence of n independent vectors, where n is the total horizon. In many examples Xj(i) can be thought of as the return to partner j, when there are d2 partners, and one stops with the i-th observation. If the j-th partner alone could decide on a (random) stopping rule t, his goal would be to maximize EXj(t) over all possible stopping rules tn. In the present "multivariate" setup the d partners must however cooperate and stop at the same stopping time t, so as to maximize some agreed upon function h( ) of the individual expected returns. The goal is thus to find a stopping rule t* for which h(EX1(t),...,EXd(t)=h(EX(t) is maximized. For continuous and monotone h we describe the class of optimal stopping rules t*. With some additional symmetry assumptions we show that the optimal rule is one which (also) maximizes EZt where Zi= Xj(i), and hence has a particularly simple structure. Examples are included, and the results are extended both to the infinite horizon case and to the case when X(1),..., X(n) are dependent. Asymptotic comparisons between the present problem of finding sup h(E X(t)) and the "classical" problem of finding sup Eh( X(t)) are given. Comparisons between the optimal return to the statistician and to a "prophet" are also included. In the present context a "prophet" is someone who can base his (random)choice g on the full sequence X(1),..., X(n), with corresponding return sup h(E X(g)).

Large unilamellar vesicles (120-160 nm) composed of egg phosphatidylcholine (egg PC) containing approximately 22 wt% of polyunsaturated fatty acids (PUFA) and various mol% (0, 10, 22, or 45) of cholesterol were exposed to oxidative stress. The hydrophilic azo compound 2,2'-azobis-(2-amidinopropane)2HCl (AAPH) which was thermally decomposed to produce a constant flux of peroxy radicals was the source of the oxidative stress (< or = 48 h incubation at 37 degrees C). Cholesterol loss following the oxidation was up to 33%, while PUFA were more extensively damaged; loss was up to 52, 88, and 100% for C-18:2, C-20:4, and C-22:6, respectively. (ii) Oxidizability of cholesterol when quantified in absolute amount was three-fold higher when its level was 45 mol%. The interrelationship between bilayer structure, especially its lateral organization and free volume, and lipid peroxidation are discussed. Differential scanning calorimetry of oxidized multilamellar vesicles lacking cholesterol revealed that a high level of oxidative damage to egg phosphatidylcholine PUFA resulted in the loss of the gel to liquid-crystalline phase transition of egg PC (broad peak at around -8 degrees C).

Valproyl glycinamide (TV 1901-VPGD) is a new antiepileptic drug, which is currently undergoing clinical trials. The present study explored the pharmacokinetics and pharmacodynamics (anticonvulsant activity and neurotoxicity) of two new isomers of valproyl glycinamide: valnoctyl glycinamide (VCGD) and diisopropylacetyl (DIGD). Both VCGD and DIGD showed anticonvulsant activity and a safety margin in mice similar to those of VPGD. Following i.v. administration (556 mg) to six dogs, VCGD had a clearance (Cl) value of 3.8 +/- 1.1 Lh-1 (mean +/- SD), a volume of distribution (Vss) of 15 +/- 2 L, and a half-life (t1/2) of 1.9 +/- 0.3 h. DIGD had Cl, Vss, and t1/2 values of 10 +/- 0.8 Lh-1, 19 +/- 3 L, and 1.6 +/- 0.2 h, respectively. Neither VCGD nor DIGD operated as chemical drug delivery systems (CDDSs) of glycine, valnoctic acid, or diisopropyl acetic acid and both showed antiepileptic profiles different from that of valproic acid (VPA). Both glycinamides were biotransformed to their glycine analogues with similar fractions metabolized (fm): 59 +/- 5% (VCGD) and 62 +/- 15% (DIGD). The two glycine metabolites, valnoctyl glycine (VCGA) and diisopropylacetyl glycine (DIGA), were also administered to the same dogs in order to calculate the above fm values. Both VCGA and DIGA had higher Cl and lower Vss values than VCGD and DIGD and therefore their mean t1/2 values were 0.43 +/- 0.02 and 0.30 +/- 0.07 h, respectively. VCGA and DIGA were excreted mainly intact in the urine, with fractions excreted unchanged (fe) of 60 +/- 9 and 55 +/- 7%, respectively. The improved pharmacokinetic profile of VCGD and DIGD relative to their glycine analogues may explain the similarity of their anticonvulsant activity to that of valproyl glycinamide. The current study demonstrates the benefit of the structure-pharmacokinetic-pharmacodynamic relationship (SPPR) approach in developing and selecting a potent antiepileptic compound in intact animals based not only on its intrinsic pharmacodynamic activity but also on its improved pharmacokinetic profile.

The photodissociation of HCl in solid Ar is studied by non-adiabatic Molecular Dynamics simulations, based on a surface-hopping treatment of transitions between different electronic slates. The relevant 12 potential energy surfaces and the non-adiabatic interactions between them were generated by a Diatomics-in-Molecules (DIM) approach, which incorporated also spin-orbit coupling. The focus of the study is on the non-adiabatic transitions, and on their role both in the cage-exit of the H atom, and in the recombination process. It is found that non-adiabatic transitions occur very frequently. In some of the trajectories, all the 12 electronic states are visited during the timescale studied. At least one non-adiabatic transition was found to occur even in the fastest cage-exit events. The other main results are: (1) The total yields for photofragment separation (by cage exit of the H atom) and for H+Cl recombination onto the ground state are roughly equal in the conditions used. (2) The cage exit events take place in the time-window between similar to 70 fs and similar to 550 fs after the excitation pulse, and are thus all ar least somewhat delayed. The recombination events span a much broader time-window, from almost immediately after excitation, and up to similar to 1100 fs and beyond. (3) The electronic energy relaxation events during the process depend significantly on symmetry and interactions of the states involved, and not only on the energy gaps between them. (4) Different electronic stales reached in the course of the process exhibit; different propensities with regard to the recombination versus cage exit outcome. (5) Spin-orbit interactions, and spin-forbidden transitions play an important role in the process, especially for recombination events. (C) 1997 American Institute of Physics.

The photodissociation of HCl embedded in argon clusters is studied by semiclassical molecular dynamics, based on a surface-hopping approach for the non-adiabatic transitions. The diatomics-in-molecules (DIM) method is used to construct the 12 electronic potential energy surfaces that are involved, and the non-adiabatic couplings. Caging effects, including recombination and electronic relaxation are investigated for Ar-12(HCl) and Ar-54(HCl), corresponding respectively to one and two complete solvation layers. The effects of the process on the cluster, e.g. fragmentation and structural deformation, are also studied. The main findings are: (1) non-adiabatic transitions play a major role in the dynamics for both clusters; (2) some recombination occurs in Ar-12(HCl), and it is much greater, about 7%, in Ar-54(HCl); (3) all 12 electronic states are visited, at least to some extent, in the process, but the distributions remain non-statistical throughout in both systems; (4) rates of spin-forbidden transitions are roughly of similar magnitudes to these of spin-allowed transitions between electronic states; (5) the energy gap law of radiationless relaxation theory does not work well for these systems. Symmetry and shape of the electronic states greatly affect the relaxation rates; (6) the clusters undergo melting and extensive evaporation in the processes.

Memory impairment associated with the loss of cortical cholinergic neurons in AD has stimulated the development of animal models based on blockade or destruction of these systems. Strategies include mechanical lesions, local injection of excitotoxic amino acids or ethylcholine aziridinium (AF 64A), which disrupt reference and working memory in rats, but lack specificity for cholinergic systems. Other models involving, reduction in cerebral blood flow and interference with oxidative metabolism of glucose, mimic those found in AD, and also interfere with working and long-term memory in the rat. Memory impairments can be reversed by acetylcholinesterase inhibitors and cholinergic agonists but beneficial effects of these agents in AD patients are small and inconsistent. This may be partly due to unfavorable pharmacokinetics and dose-limiting side effects of existing drugs. Newer, brain specific acetylcholinesterase inhibitors and M1 muscarinic agonists with a lower incidence of unwanted effects are currently being evaluated.

Whereas probabilistic calibration has been a central normative concept of accuracy in previous research on interval estimates, we suggest here that normative approaches for the evaluation of judgmental estimates should consider the communicative interaction between the individuals who produce the judgements and those who receive or use them for making decisions. We analyze precision and error in judgement and consider the role of accuracy-informativeness trade-off (Yaniv & Foster, 1995) in the communication of estimates. The results shed light on puzzling findings reported earlier in the literature concerning the calibration accuracy of subjective confidence intervals.

This article presents one of the first studies dealing with beliefs about wife beating in Arab societies. The data were collected from a random sample of 434 engaged Arab men from Israel, in an attempt to explain their different beliefs about wife beating, based on variables representing three frameworks: (a) male dominance; (b) intergenerational learning; and (c) interpersonal skills deficit. The results revealed that a combination of predictors from disparate frameworks best explained the variance in the different criterion variables of the study. The study finds that different beliefs about wife beating among engaged Arab men are explained by the following variables: Patriarchal and nonegalitarian expectations of marriage; inability to establish positive communication; negative attitudes toward women; sex role stereotypes; and witnessing or experiences with violence in their families of origin. The implications of the results are discussed.

No abstract is available for this item.