Showing papers by "Ben-Gurion University of the Negev published in 1984"

Thermally Optimum Spacing of Vertical, Natural Convection Cooled, Parallel Plates

Abstract: While component dissipation patterns and system operating modes vary widely, many electronic packaging configurations can be modeled by symmetrically or asymmetrically isothermal or isoflux plates. The idealized configurations are amenable to analytic optimization based on maximizing total heat transfer per unit volume or unit primary area. To achieve this anlaytic optimization, however, it is necessary to develop composite relations for the variation of the heat transfer coefficient along the plate surfaces. The mathematical development and verification of such composite relations as well as the formulation and solution of the optimizing equations for the various boundary conditions of interest constitute the core of this presentation.

Coping with a threat to life: A longitudinal study of self-concept, social support, and psychological distress

Abstract: The relationship of self-concept (self-esteem and mastery) and social support to psychological distress was studied among 68 Israeli women immediately prior to undergoing biopsy for suspected cancer (acute stress) and 3 months later for the noncancer group (everyday stress). It was predicted that women with stronger self-concepts and more social support would experience less state depression and state anxiety during the acute crisis than women with weaker self-concepts and less social support. It was further predicted that self-concept would be more critical than social support due to the acute nature of the event. Finally, self-concept was predicted to be related to psychological distress both during the acute and everyday stress situations (a direct effect), while social support was predicted to be related to psychological distress only during the acute stress situation (a buffering effect). The hypotheses were generally confirmed. However, self-concept and social support were seen as complexly related to psychological distress during the acute phase, one not necessarily being more critical than the other. The selective employment of available resistance resources to fit the situation and implications for preventive intervention were discussed.

Tilman's predicted productivity–diversity relationship shown by desert rodents

Abstract: Tilman has developed a model to predict the number of plant species that can coexist competitively on a limited resource base. Species diversity first increases over low resource supplies, then declines as the environment becomes richer. Although Tilman 's model was developed to describe interspecific interactions between plant species, it may also apply to animal species. Tilman questions whether animals specialize on particular proportions of nutrients. However, we believe animals probably specialize on relatively subtle microhabitat differences, especially in a multispecies competitive regime. Thus, microhabitats may act like nutrients. We hypothesize that animal species, too, show a peaked curve of diversity over productivity. The present data provide a confirmation of the hypothesis using rodent species. We have investigated the number of rodent species along a geographical gradient of increasing rainfall. The gradient extends from extremely poor desert habitats to those with annual rainfall over 300 mm. Because of the aridity , precipitation reflects productivity. The diversity pattern in desert rodents agrees with that predicted by Tilman for plants. It even possesses similar asymmetry, rising steeply then falling slowly. The pattern is duplicated in rocky and sandy habitats, each of which has a distinct and almost nonoverlapping assemblage of species. As mean precipitation is closely correlated with the variability of precipitation, the diversity pattern might also be caused by a decline in the frequency of disturbances, models for which have been proposed by several investigators.

The differential expression of H-2K versus H-2D antigens, distinguishing high-metastatic from low-metastatic clones, is correlated with the immunogenic properties of the tumor cells.

Abstract: Two clones of the 3LL Lewis lung carcinoma, a low-metastatic clone A9 and a high-metastatic clone D122, were studied for MHC expression and immunogenic properties. Using monoclonal antibodies, we demonstrated that the A9 clone expresses both the H-2Kb and the H-2Db, whereas the D122 expresses only the H-2Db, and lacks the expression of the H-2Kb encoded molecules. Cells of the low-metastatic clone A9 grew progressively in syngeneic (C57BL/6J) or in F1 mice, but were rejected in allogeneic recipients. The high-metastatic D122 grew progressively in all mouse strains tested, yet metastases were formed only in syngeneic recipients. When H-2 recombinant mice were used, the A9 again manifested a significantly greater immunogenic potency than the metastatic D122, which grew in all 4 recombinants tested. Metastases, however, were formed in B10HTG and to a lesser extent in B10A(4R), thus indicating that metastasis formation is restricted by both C57BL background and H-2Db sub region. We subsequently tested whether the higher immunogenicity of the H-2Kb-positive A9 cells is expressed also in syngeneic mice, to examine whether this could account for its low metastatic phenotype. We found that immunization by A9 cells significantly inhibited the growth of a subsequent A9 graft and even of D122, yet D122 did not retard the growth of secondary D122 or A9 cells. The increased immunogenic effect was expressed also in the generation of syngeneic cytotoxic lymphocytes by A9 but not by D122 cells. We suggest that expression of H-2K molecules on the 3LL clones, immunogenicity and the metastatic phenotype are causally related in this system.

Warehouse design with storage policy considerations

Abstract: A search procedure for finding a global optimal solution for a, specific formulation of the warehouse design problem is presented. In this formulation three types of costs are considered: costs associated with the initial investment (construction and handling facilities), a shortage cost and costs associated with the storage policy. The search procedure for finding the optimal storage design is developed, comprising analytical optimization and simulation techniques.

Entropy content and information flow in systems with limited energy

Abstract: Physical systems of finite size and limited total energy $E$ have limited entropy content $S$ (alternatively, limited information-storing capacity). We demonstrate the validity of our previously conjectured bound on the specific entropy $\frac{S}{E}$ in numerous examples taken from quantum mechanics (number of energy levels upto given energy), free-field systems (entropy of miscellaneous radiations for given energy), and strongly interacting particles (number of many-hadron states up to given energy). In the quantum-mechanical examples we have compared the bound directly with the logarithm of the number of levels for the harmonic oscillator, the rigid rotator, and a particle in an arbitrary potential well. For many-particle systems such as radiations, there is no closed formula for the number of configurations associated with a specified one-particle spectrum. To overcome this barrier we use an efficient numerical algorithm to calculate the number of configurations up to given energy from the spectrum. In all our examples of systems of scalar, electromagnetic, and neutrino quanta contained in spaces of various shapes, the numerical results are in harmony with the bound on $\frac{S}{E}$. This conclusion is buttressed by an approximate analytical estimate of the peak $\frac{S}{E}$ which leaves little doubt as to the general applicability of the bound for systems of free quanta. We consider a gas of hadrons confined to a cavity as an example of a system of strongly interacting particles. Our numerical algorithm applied to the Hagedorn mass spectrum for hadrons confirms that the number of many-hadron states up to a given energy is consistent with the bound. Finally, we show that a rather general one-channel communication system has an information-carrying capacity which cannot exceed a bound akin to that on $\frac{S}{E}$. It is argued that a complete many-channel system is similarly limited.

Genetic resources of wild cereals in Israel and vicinity. I. Phenotypic variation within and between populations of wild wheat, Triticum dicoccoides

Abstract: Populations of wild emmer wheat, Triticum dicoccoides, in Israel, originating from diverse habitats, and tested earlier for allozyme (Nevo et al., 1982) and disease resistance polymorphisms (Moseman et al., 1983a, 1983b; Nevo et al., 1984a, 1984b), were compared and contrasted for performance in agronomically important phenotypic traits. The traits compared involved 10 variables comparing germination, earliness, biomass and yield variables. The field experiments were conducted in 1980, 1981 and 1982 in two relatively standardized and contrasting environments: mesic (Mount Carmel, Haifa) and xeric (Acedat Farm, and Sede Boqer, in the northern Negev desert). The experimental design involved 12 population quadrangles at Avedat Farm in 1980, and rows of randomized genotypes of five populations in both Haifa and Sede Boqer in 1981 and 1982. The results indicate that the characters studied are partly genetically determined. Striking genetic variation was found between and, at least in some characters, also within populations in each site, whereas remarkable environmental variation including genetic-environmental interaction was found between the mesic and the xeric sites. We conclude that natural populations of wild emmer wheat in Israel vary not only in genetic polymorphisms of allozymes and disease resistance, but also in quantitative traits of agronomic importance. These traits are economically significant and should be conserved and utilized in wheat crop improvement.

Analysis and Automatic Classification of Breath Sounds

Abstract: Analysis of breath sounds (auscultation) is an important part of the diagnosis of pulmonary diseases. An automatic breathsounds classification scheme is suggested. Types of normal and abnormal breath sounds are classified, with the goal of providing the physician with a diagnostic assist device. The classification is performed in two levels. The first level is based on the linear prediction coefflcients, and the second level on energy envelope features. Seven types of breath sounds were classified. Out of 105 trials, the system exhibited only five errors The system can be implemented on a microprocessor and thus can be offered as a low-cost clinical instrument.

Actual versus estimated night-time pedestrian visibility

Abstract: The effects of headlight beams (high and low), glare and the use of a retroreflective tag by a pedestrian were studied simultaneously on the actual pedestrian night-time visibility distance and the pedestrian's estimate of his or her visibility distance. It was found that with a dark-clothed pedestrian for each of the visibility conditions studied (high beams, low beams and low beams + glare) the use of a retroreflective tag approximately doubled the pedestrian visibility distance. Furthermore, the tag invariably made the pedestrian visible at a distance greater than the stopping distance for a car travelling at 90 km/h. Most important, the pedestrian's estimate of his or her visibility distance also varied as a function of the same variables but in the case of high beams it was twice as far as the actual visibility and when the approaching car had its low beams on it was 1·4 times as far. Only in the presence of glare was the pedestrian's estimate of the visibility distance on average less than ...

Genetic resources of wild cereals in Israel and vicinity. II. Phenotypic variation within and between populations of wild barley, Hordeum spontaneum

Abstract: Populations of wild barley, Hordeum spontaneum, in Israel, originating from diverse habitats, and tested earlier for allozyme (Nevo et al., 1979a) and disease resistance polymorphisms (Moseman et al., 1984; Nevo et al., 1984a), were compared and contrasted for performance in agronomically important phenotypic traits. The traits compared involved 10 variables comparing germination, earliness, numerical and weight variables of biomass and yield. The field experiments were conducted in 1980, 1981 and 1982 in two relatively standardized and contrasting environments: mesic (Mount Carmel, Haifa) and xeric Avedat farm, and Sede Boqer (both in the northen Negev desert). The experimental design involved 26 population quadrangles at Avedat farm (1980), and rows of randomized plants of 11 populations in both Haifa and Sede Boqer (1981 and 1982).

Numerical simulation of singular solutions to the two-dimensional cubic schrödinger equation

Abstract: Numerical simulations of the cubic nonlinear Schrodinger equation are presented in dimension N = 2. The emphasis is on a detailed mechanism of blow up. The numerical results indicate that the blow up is not restricted to the case where the problem is posed in the entire R2-space but also occurs with periodic boundary conditions. The structure of the solution as the singular time t* is approached has been investigated using examples with and without radial symmetry and/or periodicity. In most cases we observe that the amplitude develops something like the peaked self-similar profile predicted by Zakharov and Synakh [38] which has a (t*-t)-2/3 maximum amplitude and a (t*-t)2/3 width.

The initial kinetics of uranium hydride formation studied by a hot-stage microscope technique

Abstract: The initial stages of the formation of uranium trihydride on the surface of uranium samples reacted with gaseous hydrogen (about 1.5 atm) were studied utilizing a hot-stage microscope. The nucleation and growth processes of the product hydride were continuously monitored with a television camera and were recorded on a videotape. The formation kinetics and the morphological characteristics of the developing hydride phase are discussed. A comparison with the kinetic results obtained in the more advanced bulk hydriding stage is made.

Experimental measurements and general conclusions on the effective thermal conductivity of powdered metal hydrides

Abstract: The effective thermal conductivity K e of Mg 2 NiH 4 and MmNi 4 FeH 5.2 (Mm ≡; misch metal) was measured under steady state conditions as a function of the hydrogen pressure and the temperature. The effective thermal conductivity of the two hydrides increases significantly as a function of the hydrogen pressure up to approximately 40 atm and then remains almost constant. The K e values for Mg 2 NiH 4 and MmNi 4 FeH 5.2 are 0.83 W m −1 K −1 and 1.05 W m −1 K −1 at 373 K and 273 K respectively and a hydrogen pressure of 40 atm. The results were analysed using the Yagi-Kunii model for the effective thermal conductivity in powder-fluid beds. The solid thermal conductivity K s of the above two hydrides was then estimated. The most important and significant result of the present work is the conclusion that K e “saturates” at relatively low values of K s . For example, the maximum K e values (above the hydrogen breakaway pressure) at 300 K and a typical hydride void fraction (ϵ = 0.5) change from about 0.4 to about 1.5 W m −1 K −1 for a corresponding K s change between 1 and 500 W m −1 K −1 . A survey of the existing data in the literature for the effective thermal conductivities of powdered metal hydrides supports the above conclusion. The practical meaning of this result is that, in engineering applications of hydrides in which a knowledge of K e is necessary, it can safely be assumed that K e ≈ 1–2 Wm −1 K −1 .

Thalamocortical and other synapses involving nonspiny multipolar cells of mouse SmI cortex.

Abstract: Golgi-impregnated and -deimpregnated neurons having somata in layer IV of mouse posteromedial barrel subfield (PMBSF) cortex were identified with the light microscope and then extensive portions of them were examined with the electron microscope. Dendrites of nine nonspiny multipolar cells and eight of their cell bodies were reconstructed from serial thin sections to determine the numbers and types of symmetrical, asymmetrical, and thalamocortical synapses they formed. Results of this analysis show that cells of the same general morphological class may form widely different patterns of synaptic connections: some nonspiny multipolar cells had dendrites that formed a high proportion of their synapses with thalamocortical axon terminals, whereas dendrites belonging to other cells formed only very small proportions of thalamocortical synapses. A similar diversity characterized the synaptic connections of cell bodies: some formed more symmetrical than asymmetrical synapses, others the reverse. Some formed high proportions of thalamocortical synapses, others much less. Comparisons of thalamocortical synaptic input to cell bodies and dendrites showed that one cell formed about the same proportions of thalamocortical synapses with its cell body as with its dendrites. For two other cells the proportions of thalamocortical synapses formed with their somata was about double that formed with their dendrites. The remaining five cell bodies examined formed far higher proportions of thalamocortical synapses than did their dendrites. That different nonspiny multipolar cells form such contrasting synaptic patterns suggests that included within this morphological classification are cells which are likely to have very different functional roles.

Polyamine Biosynthetic Enzymes in the Cell Cycle of Chlorella Correlation between Ornithine Decarboxylase and DNA Synthesis at Different Light Intensities

Abstract: During the life cycle of Chlorella vulgaris Beijerinck var vulgaris fa. vulgaris growing synchronously, the specific activity of ornithine decarboxylase peaked at the 2nd hour of the cycle, whereas that of arginine decarboxylase changed only slightly, increasing towards the end of the cycle. The endogenous level of putrescine and spermidine on a per cell basis increased gradually up to the 8th hour of the cycle, and declined thereafter. Thus, the peak of ornithine decarboxylase activity and the polyamine increase preceded both DNA replication (which took place between the 6th and 8th hours of the cycle) and autospore release (which started at the 8th hour). A 2-fold increase in the light intensity caused doubling of the DNA content, resulting in doubling of the number of autospores per mother cell. It also brought about a 2-fold increase in the specific activity of ornithine decarboxylase and polyamine content, the peaks being at the same hour of the cycle under high and low light intensities. The increase in cell number and polyamine content in a Chlorella culture grown under high light intensity was inhibited by α-difluoromethyl ornithine, a specific inhibitor of ornithine decarboxylase, this inhibition being partially reversed by putrescine. It is suggested that in C. vulgaris the sequence of events which relates polyamine biosynthesis to cell division is as follows: increased ornithine decarboxylase activity, accumulation of polyamines, DNA replication, and autospore release.

Reproductive outcomes in families of DBCP-exposed men.

Abstract: The families of 30 workers employed in a plant which, until 1977, had produced 1,2-dibromo-3-chloropropane (DBCP), have been monitored for 5 yr. Thirteen men who were azoospermic in 1977 had more than 100 hr of estimated exposure in production; of these, 4 have recovered spermatogenesis and 2 have fathered 4 female children. Eight men who were oligospermic in 1977 had been exposed for 34-95 hr; of 8 children subsequently born to their wives, 6 were female. Five men with exposure times estimated to be between 10 and 60 hr were normospermic in 1977, and of 5 children subsequently born to them, 4 were male and 1 was female. The outcome of the pregnancies among families of 4 non-exposed men and of exposed men prior to exposure resulted in 27 male and 24 female children. No increase in spontaneous abortion occurred in pregnancies fathered by exposed men. Four infant deaths and 5 congenital anomalies occurred among the babies born of unexposed pregnancies. No infant or fetal deaths and no congenital abnormalities occurred among children born to wives of men after the men were exposed. The birth of at least 10 females of 12 babies born to wives of exposed men with evidence of testicular toxicity would be expected according to binomial probabilities with a P = .015. The children born to families of exposed workers are in good health. A possible explanation for the observed female sex predominance might be Y chromosome non-disjunction, which was reported to be more frequent in sperm of DBCP workers by Kapp et al.