Showing papers by "Tel Aviv University published in 1989"

Statistical Modelling in GLIM

Abstract: Part 1 Introducing GLIM 3: getting started in GLIM 3. Part 2 Statistical modelling and statistical inference: the Bernoulli distribution for binary data types of variables definition of a statistical model model criticism likelihood-based confidence intervals. Part 3 Normal regression and analysis of variance: the normal distribution and the Box-Cox transformation family link functions and transformations regression models for prediction the use of regression models for calibration fatorial designs midding data. Part 4 Binomial response data: binary responses transformations and link functions contingency table construction from binary data multidimensional contingency tables with a binary response. Part 5: multinomial and Poisson response data. Part 6 Survival data: probability plotting with censored data - the Kaplan-Meier estimator the Weibull distribution the Cox proportional hazards model and the piecewise exponential distribution the logistic and log logistic distributions time-dependent explanatory variables. Appendices: discussion GLIM directives system defined structures in GLIM datasets and macros.

Seigniorage and Political Instability

Abstract: The importance of seigniorage relative to other sources of government revenue differs markedly across countries. This paper tries to explain this regularity by studying a political model of tax reform. The model implies that countries with a more unstable and polarized political system will have more inefficient tax structures and, thus, will rely more heavily on seigniorage. This prediction of the model is tested on cross-sectional data for 79 countries. We find that, after controlling for other variables, political instability is positively associated with seigniorage. (JEL E52, E62, F41)

Quality Ladders and Product Cycles

Abstract: We develop a two-country model of endogenous innovation and imitation in order to study the interactions between these two processes. Firms in the North race to bring out the next generation of a set of technology-intensive products. Each product potentially can be improved a countably infinite number of times, but quality improvements require the investment of resources and entail uncertain prospects of success. In the South, entrepreneurs invest resources in order to learn the production processes that have been developed in the North. All R&D investment decisions are made by forward looking, profit maximizing entrepreneurs. The steady-state equilibrium is characterized by constant aggregate rates of innovation and imitation. We study how these rates respond to changes in the sizes of the two regions and to policies in each region to promote learning.(This abstract was borrowed from another version of this item.)

The multitone channel

Abstract: The maximum bit rate of multitone QAM (quadrature amplitude modulation) over a general linear channel is found. First, the overall bit rate for an AWGN channel with a two-level transfer function is maximized, using a multitone QAM system. The power distribution between the tones and the number of bits/symbol per tone is optimized for a given symbol error rate. Extending these results to the general channel, it is shown that the optimum power division for multitone signals is similar to the water-pouring solution of information theory. Furthermore, multitone QAM performance is about 9 dB worse than the channel capacity, independent of the channel characteristics. The multitone results throughout are compared to those of an equivalent single-tone linearly equalized system. The comparison shows that the multitone system is useful for some channels, e.g. those with deep nulls in the transfer function. The maximum bit error rate over a twisted-pair channel which is performance dominated by near-end crosstalk (NEXT) is also found. >

Maxmin Expected Utility with Non-Unique Prior

Abstract: Acts are functions from states of nature into finite-support distributions over a set of 'deterministic outcomes'. We characterize preference relations over acts which have a numerical representation by the functional J(f) = min > {∫ uo f dP / P∈C } where f is an act, u is a von Neumann-Morgenstern utility over outcomes, and C is a closed and convex set of finitely additive probability measures on the states of nature. In addition to the usual assumptions on the preference relation as transitivity, completeness, continuity and monotonicity, we assume uncertainty aversion and certainty-independence. The last condition is a new one and is a weakening of the classical independence axiom: It requires that an act f is preferred to an act g if and only if the mixture of f and any constant act h is preferred to the same mixture of g and h. If non-degeneracy of the preference relation is also assumed, the convex set of priors C is uniquely determined. Finally, a concept of independence in case of a non-unique prior is introduced.

Latrunculins--novel marine macrolides that disrupt microfilament organization and affect cell growth: I. Comparison with cytochalasin D.

Abstract: The latrunculins are architecturally novel marine compounds isolated from the Red Sea sponge Latrunculia magnifica. In vivo, they alter cell shape, disrupt microfilament organization, and inhibit the microfilament-mediated processes of fertilization and early development. In vitro, latrunculin A was recently found to affect the polymerization of pure actin in a manner consistent with the formation of a 1:1 molar complex with G-actin. These in vitro effects as well as previous indications that the latrunculins are more potent than the cytochalasins suggest differences in the in vivo mode of action of the two clases of drugs. To elucidate these differences we have compared the short- and long-term effects of latrunculins on cell shape and actin organization to those of cytochalasin D. Exposure of hamster fibroblast NIL8 cells for 1–3 hr to latrunculin A, latrunculin B, and cytochalasin D causes concentration-dependent changes in cell shape and actin organization. However, the latrunculin-induced changes were strikingly different from those induced by cytochalasin D. Furthermore, while initial effects were manifest with both latrunculin A and cytochalasin D already at concentrations of about 0.03 μg/ml, latrunculin A caused complete rounding up of all cells at 0.2 μg/ml, whereas with cytochalasin D maximum contraction was reached at concentrations 10–20 times higher. The short-term effects of latrunculin B were similar to those of latrunculin A although latrunculin B was slightly less potent. All three drugs inhibited cytokinesis in synchronized cells, but their long-term effects were markedly different. NIL8 cells treated with latrunculin A maintained their altered state for extended periods. In contrast, the effects of cytochalasin D progressed with time in culture, and the latrunculin B-induced changes were transient in the continued presence of the drug. These transient effects were found to be due to a gradual inactivation of latrunculin B by serum and were used to compare recovery patterns of cell shape and actin organization in two different cell lines. This comparison showed that the transient effects of latrunculin B were fully reversible for the NIL8 cells and not for the mouse neuroblastoma N1E-115 cells.

Isotropic position and inertia ellipsoids and zonoids of the unit ball of a normed n-dimensional space

Abstract: It is a special pleasure and honor for the first named author to dedicate this paper to the 60th birthdays of two of his outstanding friends — Israel Gohberg and Ilya Piatetski-Shapiro.

Convergence of spectral methods for nonlinear conservation laws

Abstract: The convergence of the Fourier method for scalar nonlinear conservation laws which exhibit spontaneous shock discontinuities is discussed. Numerical tests indicate that the convergence may (and in fact in some cases must) fail, with or without post-processing of the numerical solution. Instead, a new kind of spectrally accurate vanishing viscosity is introduced to augment the Fourier approximation of such nonlinear conservation laws. Using compensated compactness arguments, it is shown that this spectral viscosity prevents oscillations, and convergence to the unique entropy solution follows.

Inhibitory activity of cranberry juice on adherence of type 1 and type P fimbriated Escherichia coli to eucaryotic cells.

Abstract: Inhibition of bacterial adherence to bladder cells has been assumed to account for the beneficial action ascribed to cranberry juice and cranberry juice cocktail in the prevention of urinary tract infections (A. E. Sobota, J. Urol. 131:1013-1016, 1984). We have examined the effect of the cocktail and juice on the adherence of Escherichia coli expressing surface lectins of defined sugar specificity to yeasts, tissue culture cells, erythrocytes, and mouse peritoneal macrophages. Cranberry juice cocktail inhibited the adherence of urinary isolates expressing type 1 fimbriae (mannose specific) and P fimbriae [specific for alpha-D-Gal(1----4)-beta-D-Gal] but had no effect on a diarrheal isolate expressing a CFA/I adhesin. The cocktail also inhibited yeast agglutination by purified type 1 fimbriae. The inhibitory activity for type 1 fimbriated E. coli was dialyzable and could be ascribed to the fructose present in the cocktail; this sugar was about 1/10 as active as methyl alpha-D-mannoside in inhibiting the adherence of type 1 fimbriated bacteria. The inhibitory activity for the P fimbriated bacteria was nondialyzable and was detected only after preincubation of the bacteria with the cocktail. Cranberry juice, orange juice, and pineapple juice also inhibited adherence of type 1 fimbriated E. coli, most likely because of their fructose content. However, the two latter juices did not inhibit the P fimbriated bacteria. We conclude that cranberry juice contains at least two inhibitors of lectin-mediated adherence of uropathogens to eucaryotic cells. Further studies are required to establish whether these inhibitors play a role in vivo.

The unseen companion of HD114762: a probable brown dwarf

Abstract: BROWN dwarfs are substellar objects with too little mass to ignite hydrogen in their cores. Despite considerable effort to detect brown dwarfs astrometrically1–4, photometrically4–9, and spectroscopi-cally10–12, only a few good candidates have been discovered. Here we present spectroscopic evidence for a probable brown-dwarf companion to the solar-type star HD114762. This star undergoes periodic variations in radial velocity which we attribute to orbital motion resulting from the presence of an unseen companion. The rather short period of 84 days places the companion in an orbit similar to that of Mercury around the Sun, whereas the rather low velocity amplitude of about 0.6 km s-1 implies that the mass of the companion may be as low as 0.011 solar masses, or 11 Jupiter masses. This leads to the suggestion that the companion is probably a brown dwarf, and may even be a giant planet. However, because the inclination of the orbit to the line of sight is unknown, the mass of the companion may be considerably larger than this lower limit.

Constant depth circuits, Fourier transform, and learnability

Abstract: Boolean functions in AC/sup O/ are studied using the harmonic analysis of the cube. The main result is that an AC/sup O/ Boolean function has almost all of its power spectrum on the low-order coefficients. This result implies the following properties of functions in AC/sup O/: functions in AC/sup O/ have low average sensitivity; they can be approximated well be a real polynomial of low degree; they cannot be pseudorandom function generators and their correlation with any polylog-wide independent probability distribution is small. An O(n/sup polylog(/ /sup sup)/ /sup (n)/)-time algorithm for learning functions in AC/sup O/ is obtained. The algorithm observed the behavior of an AC/sup O/ function on O(n/sup polylog/ /sup (n)/) randomly chosen inputs and derives a good approximation for the Fourier transform of the function. This allows it to predict with high probability the value of the function on other randomly chosen inputs. >

Dynamic Labour Force Participation of Married Women and Endogenous Work Experience

Abstract: This paper presents and estimates a dynamic model of married women's labour force participation and fertility in which the effect of work experience on wages is explicitly taken into account. Because current participation alters future potential earnings, the investment return to work will be an important factor in the current work decision in any forward-looking behavioural model. The model is estimated using the National Longitudinal Surveys mature women's cohort. We use the estimates of our model to predict changes in the lifecycle patterns of employment due to changes in schooling, fertility, husband's income, and the magnitude of the experience effect on wages. We find that although work experience increases the disutility of further work, the effect is overwhelmed by the positive effect of experience on wages, leading to persistence in the employment patterns of these women. In addition we find that an increase in young children and in husband's income substantially reduces participation while increased schooling has a powerful positive impact on participation. This paper presents an estimable structural dynamic model of married women's labour force participation and fertility in which wages are stochastic and work experience or cumulative participation is endogeneous. The model is structural in the sense that the parameters which are estimated are contained in the fundamental relationships governing behaviour, namely the utility function and the constraints. The model is contained in the class of models which describe the life-cycle capital accumulation process with endogeneous labour supply such as Weiss (1972) and Heckman (1976). It is closest in spirit to that of Weiss and Gronau (1981).1 The basic feature of their model and ours is that labour market participation affects future wages, which then affects future participation. The investment return to current work will necessarily be taken into account in any forward-looking optimizing model. As Weiss and Gronau note, estimates of labour supply models have ignored the inherent behavioural dynamics associated with a positive wageexperience profile. There is no adequate empirical treatment of the human capital investment dimension of the labour force participation decision in the literature. Heckman and Willis (1977) have studied a sequential discrete choice model of the labour force participation of married women in a reduced-form framework. Their work

Lithium‐Sulfur Battery: Evaluation of Dioxolane‐Based Electrolytes

Abstract: The lithium‐sulfur battery recently developed in our laboratory shows 95%+ sulfur utilization but low rate capability due to its poorly conducting electrolyte, which is based on a THF:toluene solvent mixture. In order to increase the rate capability of this cell, dioxolane‐based electrolytes have been evaluated. The conductivity of electrolytes consisting of mixtures of THF, toluene, and dioxolane were measured in the temperature range −30° to +60°C. The compatibility of lithium with these electrolytes was also studied. It was found that dioxolane‐rich electrolytes are compatible with lithium and have one order of magnitude higher conductivity than do THF:toluene‐rich electrolytes. However, sulfur utilization in dioxolane‐rich electrolytes is only 50%, even at a very low discharge rate. This is due to a different discharge product, namely, .

Are the polarization colors of picrosirius red-stained collagen determined only by the diameter of the fibers?

Abstract: Polarization colors of various purified collagens were studied in fibers of similar thickness. Three different soluble collagens of type I, insoluble collagen type I, lathyritic collagen type I, two p-N-collagens type I, pepsin extract collagen type II, two soluble collagens type III, p-N-collagen type III, and soluble collagen type V were submitted to a routine histopathologic procedure of fixation, preparation of 5-microns-thick sections, staining with Picrosirius red and examination under crossed polars. Polarization colors were determined for thin fibers (0.8 micron or less) an thick fibers, (1.6-2.4 microns). Most thin fibers of collagens and p-N-collagens showed green to yellowish-green polarization colors with no marked differences between the various samples. Thick fibers of all p-N-collagens, lathyritic and normal 0.15 M NaCl-soluble collagens showed green to greenish-yellow polarization colors, while in all other collagens, polarization colors of longer wavelengths (from yellowish-orange to red) were observed. These data suggested that fiber thickness was not the only factor involved in determining the polarization colors of Picrosirius red-stained collagens. Tightly packed and presumably, better aligned collagen molecules showed polarization colors of longer wavelengths. Thus, packing of collagen molecules and not only fiber thickness plays a role in the pattern of polarization colors of Picrosirius red-stained collagens.

A systematic comparative analysis and synthesis of two business-level strategic typologies

Abstract: Two important business-level strategic typologies were systematically evaluated, analyzed and compared in this study: Porter'S Overall Cost Leadership, Differentiation, Focus, and ‘Stuck in the Middle’ generic competitive strategies, and Miles and Snow'S Defender, Prospector, Analyzer, and Reactor types of organizational adaptation. On the basis of strategic theory, and following a pilot study, 31 strategic variables were evaluated by judges on a seven-point maximum-minimum scale, for each strategy, within its typology. Analysis of variances and concordance among judges regarding the ranking of the strategies on each variable were examined, and a strategic profile was built for each strategy. Proximities between strategies of the two typologies were analyzed using monotonic multidimensional scaling. The analysis indicated similarities and differences between the two typologies. A synthesis of the two typologies is suggested along two dimensions: internal consistency of the strategy, and level of proactiveness.

Massive thin accretion discs – I. Calculated spectra

Abstract: Les calculs detailles de la structure et du spectre de disques d'accretion massifs et geometriquement minces sont presentes, les calculs etant realises pour un disque α avec differentes hypotheses sur la viscosite et les corrections relativistes. Les equations du transfert radiatif sont resolues avec l'approximation d'Eddington pour une atmosphere possedant un gradient vertical de temperature. Toutes les sources significatives d'opacite, pour T>10 4 K, sont inclues et tous les modeles s'averent partout optiquement epais

Mortality from neuroleptic malignant syndrome.

Abstract: The authors assess the mortality from the neuroleptic malignant syndrome (NMS) based on an exhaustive review of 202 published case reports, including a differential assessment of risk factors and protective factors. The results indicate a significant (p less than .05) decrease in mortality since 1984 (11.6% vs. 25% before 1984), which occurs independently of the therapeutic use of dopamine agonists and dantrolene. A significantly (p less than .001) lower rate of mortality from haloperidol-induced NMS (7%) and a high rate of mortality (38.5%) among patients with organic brain syndrome were also found. Myoglobinemia and renal failure are strong predictors of mortality, representing a mortality risk of approximately 50%. The authors discuss the implications of these findings.

Systemic effects of low-power laser irradiation on the peripheral and central nervous system, cutaneous wounds, and burns

Abstract: In this paper, we direct attention to the systemic effect of low-power helium-neon (HeNe) laser irradiation on the recovery of the injured peripheral and central nervous system, as well as healing of cutaneous wounds and burns. Laser irradiation on only the right side in bilaterally inflicted cutaneous wounds enhanced recovery in both sides compared to the nonirradiated control group (P less than .01). Similar results were obtained in bilateral burns: irradiating one of the burned sites also caused accelerated healing in the nonirradiated site (P less than .01). However, in the nonirradiated control group, all rats suffered advanced necrosis of the feet and bilateral gangrene. Low-power HeNe laser irradiation applied to a crushed injured sciatic nerve in the right leg in a bilaterally inflicted crush injury, significantly increased the compound action potential in the left nonirradiated leg as well. The statistical analysis shows a highly significant difference between the laser-treated group and the control nonirradiated group (P less than .001). Finally, the systemic effect was found in the spinal cord segments corresponding to the crushed sciatic nerves. The bilateral retrograde degeneration of the motor neurons of the spinal cord expected after the bilateral crush injury of the peripheral nerves was greatly reduced in the laser treated group. The systemic effects reported here are relevant in terms of the clinical application of low-power laser irradiation as well as for basic research into the possible mechanisms involved.

Effect of Gender and Computer Experience on Attitudes toward Computers.

Abstract: The purpose of this study was to determine the extent to which gender and prior computer exposure (has a computer at home; participated in a computer course; knows how to work with computers) affect students' attitudes toward computers prior to computer instruction in school. An attitude questionnaire including cognitive and affective attitude scales was administered to 222 Israeli pupils in grades 8 through 10 who study in schools where computers have not yet been introduced. The results showed that prior computer exposure (in particular, having a computer at home), had a stronger effect on attitudes toward computers than sex. Pupils owning computers were more motivated to become familiar with computers; felt a stronger need for computers in their lives and had more positive affective attitudes toward computers than pupils who don't have computers at home. Sex differences in affective and cognitive attitudes were also observed where boys had significantly more positive affective attitudes toward computer...

Approximation of zonoids by zonotopes

Abstract: On etudie une propriete d'approximation des corps convexes de R n qui sont des limites de sommes de segments

International Tax Competition and Gains from Tax Harmonization

Abstract: In a world economy there are two types of distortions which can be caused by capital income taxation in addition to the standard closed-economy wedge between the consumer-saver marginal intertemporal rate of substitution and the producer-investor marginal productivity of capital: (i)international differences in intertemporal marginal rates of substitution, implying an inefficient allocation of world savings across countries; and (ii) international differences in the marginal productivity of capital, implying an inefficient allocation of world investment across countries. The paper focuses on the structure of taxation for countries which are engaged in tax competition and on potential gains from s tax harmonization. We show that if the competing countries are sufficiently coordinated with the rest of the world then tax competition leads each country to apply the residence principle of taxation and there are no gains from tax harmonization. If, however there is not sufficient coordination,tax competition leads to low capital income taxes and the tax burden falls on the internationally immobile factors. The outcome is nevertheless still efficient relative to the available constrained set of tax instruments.

Weakly interacting massive particles and neutron stars.

Abstract: Neutron stars are used to set constraints on the characteristics of weakly interacting massive particles (WIMP's) suggested as dark-matter candidates. Some special classes of WIMP's are ruled out because they would be trapped in neutron stars, concentrate towards the star center, and become self-gravitating. This results in the formation of a mini black hole that consumes the neutron star, transforming it into a black hole, on a time scale shorter than observed ages of neutron stars in various astrophysical systems.

A Middle Palaeolithic human hyoid bone

Abstract: The origin of human language, and in particular the question of whether or not Neanderthal man was capable of language/speech, is of major interest to anthropologists but remains an area of great controversy. Despite palaeoneurological evidence to the contrary, many researchers hold to the view that Neanderthals were incapable of language/speech, basing their arguments largely on studies of laryngeal/basicranial morphology. Studies, however, have been hampered by the absence of unambiguous fossil evidence. We now report the discovery of a well-preserved human hyoid bone from Middle Palaeolithic layers of Kebara Cave, Mount Carmel, Israel, dating from about 60,000 years BP. The bone is almost identical in size and shape to the hyoid of present-day populations, suggesting that there has been little or no change in the visceral skeleton (including the hyoid, middle ear ossicles, and inferentially the larynx) during the past 60,000 years of human evolution. We conclude that the morphological basis for human speech capability appears to have been fully developed during the Middle Palaeolithic.

Existence of correlated equilibria

Abstract: An elementary proof, based on linear duality, is provided for the existence of correlated equilibria in finite games. The existence result is then extended to infinite games, including some that possess no Nash equilibria.