Showing papers by "Ben-Gurion University of the Negev published in 1985"

Abrogation of metastatic properties of tumour cells by de novo expression of H-2K antigens following H-2 gene transfection

Abstract: H–2 gene transfection was used to restore expression of H–2K antigens in metastatic and non-metastatic subclones of a murine fibrosarcoma that lack their major histocompatibility complex-encoded H–2K antigens. De novo expression of H–2K reduced tumorigenicity and abolished the formation of metastasis in syngeneic mice. Expression of H–2K may lead to effective recognition of the disseminating tumour cells by the host immune system.

Non-Euclidian metrics and the robust stabilization of systems with parameter uncertainty

Abstract: This paper considers, from a complex function theoretic point of view, certain kinds of robust synthesis problems. In particular, we use a certain kind of metric on the disk (the "hyperbolic" metric) which allows us to reduce the problem of robust stabilization of systems with many types of real and complex parameter variations to an easily solvable problem in non-Euclidian geometry. It is shown that several apparently different problems can be treated in a unified general framework. A new result on the gain margin problem for multivariable plants is also given. Finally, we apply our methods to systems with real zero or pole variations.

A computational comparison of algorithms for the inventory routing problem

Abstract: The inventory routing problem is a distribution problem in which each customer maintains a local inventory of a product such as heating oil and consumes a certain amount of that product each day. Each day a fleet of trucks is dispatched over a set of routes to resupply a subset of the customers. In this paper, we describe and compare algorithms for this problem defined over a short planning period, e.g. one week. These algorithms define the set of customers to be serviced each day and produce routes for a fleet of vehicles to service those customers. Two algorithms are compared in detail, one which first allocates deliveries to days and then solves a vehicle routing problem and a second which treats the multi-day problem as a modified vehicle routing problem. The comparison is based on a set of real data obtained from a propane distribution firm in Pennsylvania. The solutions obtained by both procedures compare quite favorably with those in use by the firm.

The canine transmissible venereal tumor: a unique result of tumor progression.

Abstract: Publisher Summary The canine transmissible venereal tumor (TVT) is the only tumor known to be transmitted in nature by the transplantation of cells. Under natural conditions, the TVT is transmitted by coitus and experimentally, the tumor can be induced by the inoculation of living tumor cells to immunocompetent allogeneic dogs. Evidence that the tumor is transmitted by cells is derived from cytogenetic and immunological studies. Cytogenetic studies show that TVT from different geographical origins is characterized by extensive and characteristic chromosomal aberrations. With the characterization of the banding patterns of normal dog chromosomes, the background information for comparative banding pattern analysis of TVT chromosomes is now available. These studies may enable investigators to determine whether this unique tumor has a common origin or it arose repeatedly in the domestic dog. The results of immunological studies also suggest that the TVT is transmitted by the transplantation of cells. Investigations of the immune response against the TVT have clearly demonstrated that the tumor is antigenic in the dog and that immunological mechanisms are involved in the induction of the spontaneous regressions of this neoplasm.

Interobserver Variability in the Assessment of Neurologic History and Examination in the Stroke Data Bank

Abstract: • Interobserver reliability in obtaining neurologic histories and examinations was investigated among neurologists collaborating in the Stroke Data Bank (SDB). Seventeen in-hospital stroke patients were examined by six neurologists experienced in stroke over the course of three days. Patients were examined twice a day for two successive days, with each patient seen by four different neurologists. Data were recorded on SDB forms, according to definitions and procedures established for the SDB. Percent agreement and κ coefficients were calculated to assess the levels of agreement for each item. Important differences in levels of agreement were found among items on both neurologic history and examination. Agreement among neurologists was higher for neurologic examination than for history. Patterns of agreement for items with low prevalence or with numerous unknown ratings are discussed. Improvement in interobserver agreement due to data editing for intra-observer consistency was shown.

A General Approach to Organic Reactivity: The Configuration Mixing Model

Abstract: Publisher Summary The aim of this chapter is to present in some detail a simple, qualitative framework for understanding the factors which go into the creation of a reaction profile. Because the question raised is so fundamental —“What determines the barrier in any chemical reaction?”—the model encompasses within its single structure reactions as different as electron-transfer reactions. It brings under one roof both thermal and photochemical processes. The theory termed as the “configuration mixing (CM) model,” or when valence-bond configurations are solely utilized, the “valence-bond configuration mixing (VBCM) model” has been applied over recent years to many of these mentioned reaction types. In view of the fundamental role played by quantum theory in modern chemistry, it is not surprising that the theoretical basis of the CM model goes back to the earliest days of quantum chemistry. In fact, the basic concept of CM theory may be considered a theoretical precursor of resonance theory. The chapter concludes that the notion that a molecule “hesitates” between different structures, borrows its characteristics, and finally adopts a structure that is somewhat intermediate between them, is central to understanding “electronic behavior.” It is from this single yet powerful principle that CM theory borrows its utility and generality.

Stabilization of time-delay systems using finite-dimensional compensators

Abstract: For linear time-invariant systems with one or more noncommensurate time delays, necessary and sufficient conditions are given for the existence of a finite-dimensional stabilizing feedback compensator. In particular, it is shown that a stabilizable time-delay system can always be stabilized using a finite-dimensional compensator. The problem of explicitly constructing finite-dimensional stabilizing compensators is also considered.

Isotopic branching ratio for the reaction A+HD→AD(H)+H(D)

Abstract: Several reactions of the form A+HD→AD(H)+H(D) have been studied by a two laser experiment. One laser dissociates a molecule to form a reactive atom A and the second laser monitors the hydrogen atom products by laser induced fluorescence. When A is F(2P), O(1D), and S(1D), the H/D ratios are 0.66±0.10, 1.13±0.08, and 1.91±0.10, respectively. Muckerman and co‐workers have given qualitative arguments that abstraction reactions should have an H/D ratio less than one whereas insertion reactions should have H/D greater than one. Inasmuch as extensive previous experimental and theoretical work has shown that F(2P)+H2 procedes by abstraction whereas O(1D)+H2 and S(1D)+H2 proceed largely by insertion, the present results are consistent with the general qualitative conjecture.

Psoriasis treatment at the Dead Sea: A natural selective ultraviolet phototherapy

Abstract: A naturally filtered ultraviolet spectrum of sunlight along with other natural factors are utilized in the management of psoriasis at the Dead Sea area in Israel. In 110 patients with psoriasis, 85.5% achieved complete clearing or excellent improvement. These results compare favorably with other therapeutic regimens used today in the treatment of psoriasis. Since systemic medications are avoided, the potential risks may be considerably lessened. Therefore, this therapeutic modality may be considered in the management spectrum of psoriasis.

Geographical ecology of gerbilline rodents in sand dune habitats of Israel

Abstract: In Israel, sand dune habitats of varying sizes occur along a rainfall gradient ranging from 30 to 650 m. In these sand dunes, nine species of granivorous rodents are found, eight of which belong to the family Gerbillidae. Rodent species were sampled during the four main seasons in eleven different locations covering the major sand dune habitats. Both species and their equivalent biomass were highly and significantly correlated with the mean annual rainfall. As the amount of rainfall increased, so did the number of species and their equivalent biomass. However, once a certain amount of rainfall was reached, an additional increase in rainfall was followed by a decrease in species number and biomass. Mean annual rainfall was similarly correlated with % annual cover, an index of the size of the seed crop on which the rodents feed. Number of rodent species was also significantly correlated with the area of the sand dune habitats. Analysis suggests that both rainfall and area are important in determining species number. Most of the patterns of community structure found in Israel are similar to those reported for the rodents that occur in the sand dunes of the desert of the western U.S.A.

Genetics of salt tolerance in higher plants: theoretical and practical considerations

Abstract: An interdisciplinary approach to breeding for stress tolerance in plants has gained considerable recognition in the past few years. Accordingly, this article presents a synthesis of the genetic, physiological, and ecological aspects of salt tolerance in plants. An understanding of these aspects and the interrelationships between them is essential for an efficient breeding program.

Effects of rest and secondary task on simulated truck-driving task performance.

Abstract: The study was designed to examine the effects of extra task stimulation and extra rest on performance and fatigue of haul truck drivers engaged in a simulated driving task. Sixty male subjects, randomly selected from the population of truck drivers in a large mining company, operated a driving simulator for a period of 7 h. A 2 x 3 experimental design was employed including two levels of rest conditions and three levels of secondary-task manipulations. The results show that performance and perceived fatigue were significantly higher when a secondary task involving voice communication was added to the basic driving task, but an added vigilance task had less effect. An extra 30-minute rest period in the middle of the experimental session significantly alleviated the reported experience of fatigue but did not affect performance. The results are discussed in terms of their relevance to actual industrial driving tasks.

The Effects of Expectancy, Clothing Reflectance, and Detection Criterion on Nighttime Pedestrian Visibility

Abstract: Nighttime pedestrian visibility was studied under various combinations of driver expectancy (to see a pedestrian on the road), pedestrian clothing characteristics (dark clothing, light clothing, an...

Isomorphism types of Aronszajn trees

Abstract: We study the isomorphism types of Aronszajn trees of height ω1 and give diverse results on this question (mainly consistency results).

The Effects of Enforcement and Public Information on Compliance

Abstract: A review of enforcement strategies with and without public information campaigns was conducted. The studies dealing with these issues are evaluated in terms of basic psychological concepts such as reinforcement theory and perceived risk. It was concluded that the effectiveness of enforcement is dependent on the perceived risk, and perceived risk requires a minimal level of objective risk. They can both be enhanced by the appearance of threat, the degree of uncertainty, and extensive, continuous publicity, preferably in the form of news coverage. Specific recommendations for combining reinforcement and information as well as for a further study are made.

Principles, procedures and rules in an expert system for information retrieval

Abstract: An expert system was developed in the area of information retrieval, with the objective of performing the job of an information specialist, who assists users in selecting the right vocabulary terms for a database search. The system is composed of two components: One is the knowledge base, represented as a semantic network, in which the nodes are words, concepts, phrases, comprising a vocabulary of the application area and the links express semantic relationships between those nodes. The second component is the rules, or procedures, which operate upon the knowledge-base, analogous to the decision rules or work patterns of the information specialist. Two major stages comprise the consulting process of the system: During the “search” stage relevant knowledge in the semantic network is activated, and search and evaluation rules are applied in order to find appropriate vocabulary terms to represent the user's problem. During the “suggest” stage those terms are further evaluated, dynamically rank-ordered according to relevancy, and suggested to the user. Explanations to the findings can be provided by the system and backtracking is possible in order to find alternatives in case some suggested term is rejected by the user. This article presents the principle, procedures and rules which are utilized in the expert system.

The potential of production of sulfated polysaccharides from Porphyridium

Abstract: The environmental conditions prevailing in Israel make marine algae an attractive crop for the production of valuable chemicals. A marine species of Porphyridium seems to fit this purpose.