Showing papers by "Tel Aviv University published in 1980"
3,622 citations
2,195 citations
TL;DR: In this paper, the authors developed models for predicting flow pattern transitions during steady gas-liquid flow in vertical tubes based on physical mechanisms suggested for each transition, incorporating the effect of fluid properties and pipe size.
Abstract: Models for predicting flow pattern transitions during steady gas-liquid flow in vertical tubes are developed, based on physical mechanisms suggested for each transition. These models incorporate the effect of fluid properties and pipe size and thus are largely free of the limitations of empirically based transition maps or correlations.
1,277 citations
TL;DR: The ability of a number of agents to induce H2O2 release by guinea pig peritoneal macrophages was demonstrated and a linear relationship between absorbance at 610 nm and concentration of H2 O2 was found in the 1--60 microM range.
1,101 citations
TL;DR: In this paper, the authors consider the problem of a price-setting monopolistic marketmaker in a dealership market where the stochastic demand and supply are depicted by price-dependent Poisson processes.
1,070 citations
TL;DR: In this article, a sequence of radiating boundary conditions is constructed for wave-like equations, and it is proved that as the artificial boundary is moved to infinity the solution approaches the solution of the infinite domain as O(r exp -m-1/2) for the m-th boundary condition.
Abstract: In the numerical computation of hyperbolic equations it is not practical to use infinite domains; instead, the domain is truncated with an artificial boundary. In the present study, a sequence of radiating boundary conditions is constructed for wave-like equations. It is proved that as the artificial boundary is moved to infinity the solution approaches the solution of the infinite domain as O(r exp -m-1/2) for the m-th boundary condition. Numerical experiments with problems in jet acoustics verify the practical nature of the boundary conditions.
999 citations
TL;DR: Photosynthetic pigments from etiolated cucumber cotyledons were extracted by direct immersion of the intact cotYledons into the solvent N,N-dimethylformamide (DMF), which is especially efficient when pigment concentration is low.
Abstract: Photosynthetic pigments from etiolated cucumber (Cucumis sativus var. Beit Alpha improved, Hazera Co., Gedera) cotyledons were extracted by direct immersion of the intact cotyledons into the solvent N,N-dimethylformamide (DMF). The solvent is especially efficient when pigment concentration is low; time and tools are saved and the loss of pigment that usually occurs in more complicated extraction procedures is prevented. The specific absorption coefficient of chlorophyll a in DMF was also determined.
771 citations
28 Jan 1980
TL;DR: It is shown that with the addition of the 'until' operator -U the temporal language becomes expressively complete and two deductive systems DX and DUX are proved to be complete for the languages without and with the new operator respectively.
Abstract: The use of the temporal logic formalism for program reasoning is reviewed. Several aspects of responsiveness and fairness are analyzed, leading to the need for an additional temporal operator: the 'until' operator -U. Some general questions involving the 'until' operator are then discussed. It is shown that with the addition of this operator the temporal language becomes expressively complete. Then, two deductive systems DX and DUX are proved to be complete for the languages without and with the new operator respectively.
757 citations
TL;DR: The behavior of the chiral order parameter in the confining phase of the Dirac equation has been analyzed in this paper, where it is shown that chiral symmetry is spontaneously broken.
701 citations
TL;DR: In this paper, the authors evaluate the quality of analysts' forecasts as surrogates for the market expectation of earnings and compare it with that of prediction models commonly used in research and find that prediction errors of analysts are more closely associated with security price movements, suggesting that analyst's forecasts provide a better surrogate for market expectations than forecasts generated by time-series models.
651 citations
TL;DR: A Lagrangian relaxation algorithm is developed for the problem of finding a shortest path between two nodes in a network, subject to a knapsack-type constraint, which indicates orders of magnitude savings when the approach is applied to large networks.
Abstract: In this paper we develop a Lagrangian relaxation algorithm for the problem of finding a shortest path between two nodes in a network, subject to a knapsack-type constraint. For example, we may wish to find a minimum cost route subject to a total time constraint in a multimode transportation network. Furthermore, the problem, which is shown to be at least as hard as NP-complete problems, is generic to a class of problems that arise in the solution of integer linear programs and discrete state/stage deterministic dynamic programs. One approach to solving the problem is to utilize a kth shortest path algorithm, terminating with the first path that satisfies the constraint. This approach is impractical when the terminal value of k is large. Using Lagrangian relaxation we propose a method that is designed to reduce this value of k. Computational results indicate orders of magnitude savings when the approach is applied to large networks.
TL;DR: The incidence of intraspecific nest parasitism in birds is reviewed and this phenomenon has been reported for at least 53 species, mostly among precocial birds.
Abstract: Summary
(1) The incidence of intraspecific nest parasitism in birds is reviewed. This phenomenon can be identified by various methods, ranging from biochemical examination of protein and enzyme polymorphisms to observations on the sequence of appearance of eggs in the nest as well as on the shape and colour of the eggs. The phenomenon has been reported for at least 53 species (Table I), mostly among precocial birds.
(2) The evidence suggests that the parasites are (a) young, unmated birds, (b) females which have lost their nests and (c) mated females which also lay in the nests of other females. High proportions of such females, and scarcity of suitable nest sites increase the rate of parasitism.
(3) Breeding success in parasitized nests is reduced by factors such as egg loss, desertion, inefficient incubation, reduced clutch size and late layings. The upper limit of the rate of intraspecific parasitism is discussed. It is argued that its incidence will be higher in the tropics than in extreme zones, for example, high latitudes and deserts, because there is higher synchronization of breeding in the latter, and increased predation in the former zones. Also, it will be more common in species which lay large clutches, such as precocial species.
TL;DR: A stimulus receptor mechanism for physical forces which, like hormonal effectors, are mediated by prostaglandins and stimulate cyclic AMP and DNA synthesis is suggested and it is believed that physical forces stimulate bone remodelling through such a stimulus receptor system, mediated by Prostaglandin E2.
TL;DR: Renormalization-group techniques are applied to Ising-model spins placed on the sites of several self-similar fractal lattices in this paper, and the resulting critical properties are shown to vary with the (noninteger) fractal dimensionality $D$, but also with several topological factors: ramification, connectivity, lacunarity, etc.
Abstract: Renormalization-group techniques are applied to Ising-model spins placed on the sites of several self-similar fractal lattices. The resulting critical properties are shown to vary with the (noninteger) fractal dimensionality $D$, but also with several topological factors: ramification, connectivity, lacunarity, etc. For any $Dg~1$, there exist systems with both ${T}_{c}=0$, and ${T}_{c}g0$; hence a lower critical dimensionality is not defined. The nonvanishing values of ${T}_{c}$ and the critical exponents depend on all these factors.
TL;DR: Water loss during incubation is mandatory if the relative water content of an egg at the end of incubation was to remain essentially the same as at the beginning, and the 11% difference between the altricial and precocial categories is statistically significant.
Abstract: Synopsis. The loss of mass in eggs during incubation was examined and evidence is presented to show that this is essentially due to loss of water. The mean fraction of water lost by diffusion throughout incubation is 0.150 ? 0.025 S.D. per gram of egg and 0.162 ? 0.026 S.D. per gram of egg content for 81 species. The water fraction of fresh eggs and of hatching eggs was examined in 32 species divided according to maturity at hatching, and found to be very similar, within each category (83% in altricial; 83% in semi-altricial; 78% in semi-precocial; 72% in precocial eggs). The 11% difference between the altricial and precocial categories is statistically significant. During incubation, dry matter is metabolized, in? creasing the water fraction which is further increased by metabolic water production. Hence, water loss during incubation is mandatory if the relative water content of an egg at the end of incubation is to remain essentially the same as at the beginning. Equations are de? veloped which allow one to estimate the difference between diffusive water loss and the total water loss in altricial and precocial eggs, caused by additional water loss during pipping and hatching.
TL;DR: In this article, exact bounds for the complex, bulk, effective dielectric constant of a two-component macroscopic composite are presented and discussed, and some of these bounds are readily ascribable to special, exactly solvable, microscopic geometries.
Abstract: Exact bounds for the complex, bulk, effective dielectric constant ${\ensuremath{\epsilon}}_{e}$ of a two-component macroscopic composite that depend on the available information about the composite are presented and discussed. Some of these bounds are readily ascribable to special, exactly solvable, microscopic geometries. As a consequence, it is shown that there can exist composites where the real part of ${\ensuremath{\epsilon}}_{e}$ diverges as $\ensuremath{\omega}\ensuremath{\rightarrow}0$ while the dc conductivity ${\ensuremath{\sigma}}_{e}\ensuremath{
e}0$.
TL;DR: In this paper, the authors describe convenient and sensitive radioimmune (RI) and radiobinding (RB) assays for core and 2-5A, which can also be detected using the RB assay, were not found in significant amounts.
Abstract: The enzyme (2-5A synthetase) which synthesizes ppp(A2'p)nA where n=2 to 4 (collectively referred to as 2-5A) is widely distributed in a variety of cells and tissues in amounts which increase response to interferon and vary with growth and hormone status. 2-5A activates a nuclease which inhibits protein synthesis. The non-phosphorylated 'core' of 2-5A ((A2'p)nA, n=2 to 4) can inhibit DNA synthesis and cell growth. Here we describe convenient and sensitive radioimmune (RI) and radiobinding (RB) assays for core and 2-5A. In combination with more satisfactory high performance liquid chromatography (HPCL) methods using reverse-phase C18 columns, these assays have been used to detect core and 2-5A in crude extracts from interferon-treated cells. The novel 2-5A synthetase products NAD2'p5' A2'p5'A and A5'p45'A2'p5'A2'p5'A (ref. 13), which can also be detected using the RB assay, were not found in significant amounts. The natural occurrence of core has not been described previously.
TL;DR: In this paper, experimental measurements of flow patterns for gas-liquid flow in inclined pipes are reported, and the results compare well with a recently published theory for the prediction of flow pattern in horizontal and inclined pipes.
TL;DR: Pyogenic granuloma and peripheral fibroma with calcification occur in younger patients more often than fibroushyperplasia, and thus may represent a stage in the development of fibrous hyperplasia.
Abstract: A series of 741 consecutive cases of localized hyperplastic lesions of the gingiva were studied. The lesions were reclassified into four groups: pyogenic granuloma, peripheral giant cell granuloma, fibrous hyperplasia and peripheral fibroma with calcification. This study indicates that there are some differences between these groups in age and sex distribution as well as in location and size of the lesion. Fibrous hyperplasia was the most common type, followed in descending order by pyogenic granuloma, peripheral fibroma with calcification and peripheral giant cell granuloma. The peripheral giant cell granuloma showed no sex predilection while fibrous hyperplasia, pyogenic granuloma and peripheral fibroma with calcification were more common in females. Pyogenic granuloma and peripheral fibroma with calcification occur in younger patients more often than fibrous hyperplasia, and thus may represent a stage in the development of fibrous hyperplasia.
TL;DR: In this paper, the authors considered the problem of minimum entropy production in a heat engine subject only to thermal-resistance losses and derived an expression for the minimum total entropy production and used this to give a bound on the maximum work which can be produced by such engines.
Abstract: We consider the problem of minimum entropy production in a heat engine subject only to thermal-resistance losses. For such engines, minimizing the total entropy production is equivalent to minimizing the loss of availability. We show for any engine operating with a given cycle time that minimum total entropy production is achieved in a heat engine by operating it so as to keep the entropy production rate constant along each branch. For the limit of slow engine operation, the entropy production rate should be the same constant for all branches of the cycle. We obtain an expression for the minimum total entropy production and use this to give a bound on the maximum work which can be produced by such engines. This bound is significantly more realistic than the reversible one. Analogous results are derived for a working fluid which carries arbitrary flows from one potential to another.
TL;DR: The results indicate that α‐tubulin is an integral vesicle membrane protein, whereas most of the β sub‐unit is peripherally attached and can be easily dissociated from the vesicles membrane with EGTA.
Abstract: The major protein in isolated synaptic vesicles from bovine cerebral cortex has been compared to tubulin by sodium dodecyl sulphate-urea polyacrylamide gel electrophoresis, by two-dimensional gel electrophoresis, and by peptide mapping following limited proteolysis of the protein by Staphylococcus aureus protease. The results establish in purified synaptic vesicles the presence of tubulin, which is composed of the alpha and beta subunits. In the presence of ethyleneglycolbis)aminoethyl ether)-N,N'-tetraacetic acid (EGTA) or magnesium in the isolation buffers, the synaptic vesicles contained mainly the alpha-tubulin whereas the beta subunit was less abundant. Similarly, synaptosomal plasma membranes that were prepared in the presence of EGTA also contained more of alpha-tubulin than of the beta subunit. Non-ionic detergents such as Triton X-100 or Nonidet P-40 failed to solubilize the tubulin from the synaptic vesicles. Ionic detergents such as deoxycholate and sodium dodecyl sulphate solubilized all the vesicle proteins, including tubulin. The results indicate that alpha-tubulin is an integral vesicle membrane protein, whereas most of the beta subunit is peripherally attached and can be easily dissociated from the vesicle membrane with EGTA.
TL;DR: This article used a simple stochastic structure that incorporates temporary and permanent changes in an augmented IS-LM model to show that stagflation is likely to follow a large permanent reduction in productivity.
TL;DR: In this article, the authors applied the techniques of laser fluorescence excitation spectroscopy for the experimental study of the rotational-vibrational cooling of iodine (I2) and of several large molecules, i.e., anthracene (C14H10), tetracene, pentacene, and ovalene, in seeded supersonic beams of rare gases, and found that the mass of the rare gas expanded at stagnation pressures of p = 20-8300 Torr and through a nozzle of diameter D = 50-200 μ exhibits a marked
TL;DR: Evidence is presented indicating that, in common wheat, the gene system that determines the specific pattern of chromosomal arrangement in the nucleus is operating via the microtubular elements of the spindle system.
Abstract: Chromosomal arrangement in the interphase nucleus has two main aspects: (1) arrangement of chromosomes with respect to nuclear polarity and to other nuclear components, and (2) arrangement of chromosomes with respect to one another The latter aspect consists of two main types of spatial relationships; (a) relationships between different members of one chromosomal set, (b) relationships between different chromosomal sets Data concerning various aspects of chromosomal arrangement in the interphase nucleus are presented and discussed and the genetic control as well as subcellular mechanisms which are involvled in nuclear organization, are elucidated Evidence is presented indicating that, in common wheat, the gene system that determines the specific pattern of chromosomal arrangement in the nucleus is operating via the microtubular elements of the spindle system The significance of ordered arrangement of chromosomes in the nucleus for the regularity of genetic activity and chromosomal behavior, is pointed out
TL;DR: In this paper, three new toxins were isolated from the Red Sea sponge Latrunculia magnifica and a full structure determination of these toxins, by spectroscopic methods, was aided by an X-ray diffraction analysis of a crystalline derivative of latrunculin-A.
TL;DR: It was found that development of the phloem commenced before that of the xylem, and it was proposed thatphloem is formed in response to auxin, whilexylem is formedIn response to Auxin together with some added factor which reaches it from the Phloem.
Abstract: The differentiation of sieve and tracheary elements was studied in callus culture of Daucus carota L., Syringa vulgaris L., Glycine max (L.) Merr., Helianthus annuus L., Hibiscus cannabinus L. and Pisum sativum L. By the lacmoid clearing technique it was found that development of the phloem commenced before that of the xylem. In not one of the calluses was differentiation of tracheary elements observed in the absence of sieve elements. The influence of indole-3-acetic acid (IAA) and sucrose was evaluated quantitatively in callus of Syringa, Daucus and Glycine. Low IAA levels resulted in the differentiation of sieve elements with no tracheary cells. High levels resulted in that of both phloem and xylem. IAA thus controlled the number of sieve and tracheary elements, increase in auxin concentration boosting the number of both cell types. Changes in sucrose concentration, while the IAA concentration was kept constant, did not have a specific effect on either sieve element differentiation, or on the ratio between phloem and xylem. Sucrose did, however, affect the quantity of callose deposited on the sieve plates, because increase in the sucrose concentration resulted in an increase in the amount of callose. It is proposed that phloem is formed in response to auxin, while xylem is formed in response to auxin together with some added factor which reaches it from the phloem.
TL;DR: This paper suggests approximations for smoothing out the kinks caused by the presence of “max” or “min” operators in many non-smooth optimization problems, particularly the continuous-discrete min—max optimization problem.
Abstract: In this paper, we suggest approximations for smoothing out the kinks caused by the presence of “max” or “min” operators in many non-smooth optimization problems. We concentrate on the continuous-discrete min—max optimization problem. The new approximations replace the original problem in some neighborhoods of the kink points. These neighborhoods can be made arbitrarily small, thus leaving the original objective function unchanged at almost every point ofR
n
. Furthermore, the maximal possible difference between the optimal values of the approximate problem and the original one, is determined a priori by fixing the value of a single parameter. The approximations introduced preserve properties such as convexity and continuous differentiability provided that each function composing the original problem has the same properties. This enables the use of efficient gradient techniques in the solution process. Some numerical examples are presented.