Showing papers by "Bar-Ilan University published in 1994"

Rock fragments in top soils: significance and processes

Abstract: This introductory paper reviews various aspects of rock fragments in top soils. Such information is required for various reasons and in particular for predicting the impact of climatic or landuse changes on the response of these soils. Particular attention is paid to the definition and measurement of rock fragment content in top soils, the density of soils containing rock fragments, the spatial distribution and movement of rock fragments in top soils, the effects of rock fragments on some key hydrological processes, thermal properties of top soils, physical soil degradation, soil erosion and soil productivity.

The effects of recall on estimating annual nonfatal injury rates for children and adolescents.

Abstract: OBJECTIVES. This study used a recent national population survey on childhood and adolescent non-fatal injuries to investigate the effects of recall bias on estimating annual injury rates. Strategies to adjust for recall bias are recommended. METHODS. The 1988 Child Health Supplement to the National Health Interview Survey collected 12-month recall information on injuries that occurred to a national sample of 17,110 children aged 0 through 17 years. Using information on timing of interviews and reported injuries, estimated annual injury rates were calculated for 12 accumulative recall periods (from 1 to 12 months). RESULTS. The data show significantly declining rates, from 24.4 per 100 for a 1-month recall period to 14.7 per 100 for a 12-month recall period. The largest declines were found for the 0- through 4-year-old age group and for minor injuries. Rates of injuries that caused a school loss day, a bed day, surgery, or hospitalization showed higher stability throughout recall periods. CONCLUSIONS. Varying recall periods have profound effects on the patterns of childhood injury epidemiology that emerge from the data. Recall periods of between 1 and 3 months are recommended for use in similar survey settings.

The Surface Chemistry of Lithium Electrodes in Alkyl Carbonate Solutions

Abstract: The chemical composition of the surface films formed on lithium in alkyl carbonate solutions was explored using surface sensitive Fourier transform infrared spectroscopy (external reflectance mode). The solvents included propylene carbonate, ethylene carbonate, and dimethyl carbonate. The salts included LiAsF{sub 6}, LiClO{sub 4}, LiBF{sub 4}, and LiPF{sub 6}. The advantages of this work over previous studies are that highly reflective Li surfaces were prepared fresh in solution and that the aging processes of the surface films initially formed could be rigorously investigated. Furthermore these three important solvents were investigated in a single study. This work further proves that the films initially formed on Li surfaces in these solvents consist of ROCO{sub 2}Li as the major constituents. Upon storage, the films initially formed react with trace water to form Li{sub 2}CO{sub 3}, which gradually also becomes a major surface species. It was found that these aging processes also depend on the salts used (for example ROCO{sub 2}Li or Li{sub 2}CO{sub 3} films are not stable in LiPF{sub 6} or LiBF{sub 4} solutions).

Wave-field phase singularities: The sign principle

Abstract: Phase singularities (topological charges, dislocations, defects, vortices, etc.), which may be either positive or negative in sign, are found in many different types of wave fields. We show that on every zero crossing of the real or imaginary part of the wave field, adjacent singularities must be of opposite sign. We also show that this ``sign principle,'' which is unaffected by boundaries, leads to the surprising result that for a given set of zero crossings, fixing the sign of any given singularity automatically fixes the signs of all other singularities in the wave field. We show further how the sign of the first singularity created during the evolution of a wave field determines the sign of all subsequent singularities and that this first singularity places additional constraints on the future development of the wave function. We show also that the sign principle constrains how contours of equal phase may thread through the wave field from one singularity to another. We illustrate these various principles using a computer simulation that generates a random Gaussian wave field.

Individual and Contextual Correlates of Marital Change across the Transition to Parenthood.

Abstract: To explore multiple prenatal antecedents and postnatal correlates of change in marital adjustment and satisfaction in men and women across the transition to parenthood, 102 couples from diverse sociocultural backgrounds were studied longitudinally from pregnancy to the 9th postpartum month. Guided by an ecological model, the pre- and postnatal assessments included questionnaires of marital adjustment, personality traits, attitudes toward parenthood, work role centrality, social support, as well as observations and ratings of infant behaviors, maternal and paternal behaviors, and marital communication

[beta]-Aminobutyric Acid Induces the Accumulation of Pathogenesis-Related Proteins in Tomato (Lycopersicon esculentum L.) Plants and Resistance to Late Blight Infection Caused by Phytophthora infestans.

Abstract: Tomato (Lycopersicon esculentum L.) plants were sprayed with aqueous solutions of isomers of aminobutyric acid and were either analyzed for the accumulation of pathogenesis-related (PR) proteins or challenged with the late blight fungal agent Phytophthora infestans. The [beta] isomer of aminobutyric acid induced the accumulation of high levels of three proteins: P14a, [beta]-1,3 glucanase, and chitinase. These proteins either did not accumulate or accumulated to a much lower level in [alpha]- or [gamma]-aminobutyric acid-treated plants. Plants pretreated with [alpha]-, [beta]-, and [gamma]-aminobutyric acid were protected up to 11 d to an extent of 35, 92, and 6%, respectively, against a challenge infection with P. infestans. Protection by [beta]-aminobutyric acid was afforded against the blight even when the chemical was applied 1 d postinoculation. Examination of ethylene evolution showed that [alpha]-aminobutyric acid induced the production of 3-fold higher levels of ethylene compared with [beta]-aminobutyric acid, whereas [gamma]-aminobutyric acid induced no ethylene production. In addition, silver thiosulfate, a potent inhibitor of ethylene action, did not abolish the resistance induced by [beta]-aminobutyric acid. The results are consistent with the possibility that [beta]-aminobutyric acid protects tomato foliage against the late blight disease by a mechanism that is not mediated by ethylene and that PR proteins can be involved in induced resistance.

Statistical mechanics in biology: how ubiquitous are long-range correlations?

Abstract: The purpose of this opening talk is to describe examples of recent progress in applying statistical mechanics to biological systems. We first briefly review several biological systems, and then focus on the fractal features characterized by the long-range correlations found recently in DNA sequences containing non-coding material. We discuss the evidence supporting the finding that for sequences containing only coding regions, there are no long-range correlations. We also discuss the recent finding that the exponent alpha characterizing the long-range correlations increases with evolution, and we discuss two related models, the insertion model and the insertion-deletion model, that may account for the presence of long-range correlations. Finally, we summarize the analysis of long-term data on human heartbeats (up to 10(4) heart beats) that supports the possibility that the successive increments in the cardiac beat-to-beat intervals of healthy subjects display scale-invariant, long-range "anti-correlations" (a tendency to beat faster is balanced by a tendency to beat slower later on). In contrast, for a group of subjects with severe heart disease, long-range correlations vanish. This finding suggests that the classical theory of homeostasis, according to which stable physiological processes seek to maintain "constancy," should be extended to account for this type of dynamical, far from equilibrium, behavior.

Apertured cell carrier

Abstract: An apertured cell carrier defines first and second outer surfaces and comprises an ordered array of holes therethrough, the holes being in identifiable positions on the carrier and sized to contain individual living cells, the cross sections of the holes at the first outer surface and at a level spaced from the first outer surface, as well as the height between the first outer surface and the level of the second cross section, being defined. Preferably, the ordered array comprises at least one sub-group of uniformly shaped holes sized to accommodate individual living cells of the same size. The carrier may contain entire living cells or substantially entire living cells, held within individual holes. The carrier may be supported on a holder, in which case the carrier is preferably constructed to include a device for aligning it with a complementary device on the holder, whereby the individual addresses of holes in the carrier are identifiable by a set of x and y coordinates. The carrier may be integral with the holder.

Peak effect and scaling of irreversible properties in untwinned Y-Ba-Cu-O crystals.

Abstract: We measured the peak effect in the magnetic hysteresis loop of an untwinned ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ crystal in the vicinity of the critical temperature and studied its temperature, time, and angular dependence. The location of the peak is determined by the component of the field along the c direction. The pinning force density ${\mathit{F}}_{\mathit{p}}$(B) is scaled into a single curve for all measured isotherms (75--87 K) and time scales (4--1500 sec), and its functional form reflects the observed peak effect. The scaling field is related to the irreversibility field of oxygen-deficient regimes. The results indicate that pinning in this system is due to inhomogeneity of the oxygen deficiency and that the peak is related to the formation of a percolationlike network of reversible regimes.

Measuring Workers′ Burnout and Intention to Leave

Abstract: Identifies workers′ burnout as an important factor influencing productivity, commitment, and intentions to leave a job, which disrupt organizational operation and costs. Examines the relationship between the burnout of female school teachers and its effect on their intentions to leave their jobs. Based on a comparative analysis of three measures of burnout, shows two major findings. First, the best burnout predictor of intention to leave a job was obtained when 21 items measuring burnout level were factorily analysed and consolidated into three factors, which were then employed as independent variables in a regression analysis. This was superior to the utilization of the mean score of the 21 items or to a single direct measure. Explained variances were 66.5 per cent, 55.7 per cent, and 44.5 per cent, respectively. Second, a more detailed identification of types of burnout obtained by the first method showed that physical and mental burnout components are significant in explaining workers′ intention to lea...

Cohesive discourse in pervasive developmental disorders.

Abstract: Investigated the use of cohesive links to create a reciprocal conversation in individuals with autism, Asperger syndrome, and a control group of children and adolescents with nonspecific social problems. All subjects engaged in a 10-minute conversation with an examiner that touched on various topics. The conversation was audiotaped, transcribed, and coded blindly for several types of cohesive links. Compared to controls, the higher functioning autistic group referred less to a previous stretch of the conversation and more to an aspect of the physical environment. The Asperger group, on the other hand, was very similar to the controls except they made more unclear references that were difficult to interpret. Implications of these findings for understanding the communicative failure of subjects with pervasive developmental disorder are discussed.

Human Learned Helplessness: A Coping Perspective

Abstract: The Empirical and Theoretical Basis of Human Learned Helplessness. Proximal Mediators of LH Effects: 1. Coping Strategies. Proximal Mediators of LH Effects: 2. Mental Rumination. Distal Mediators of LH Effects: 1. The Expectancy of Control. Distal Mediators of LH Effects: 2. Emotional Arousal. Moderators of LH Effects: 1. Perceived Task Value. Moderators of LH Effects: 2. Self-focused Attention. A Coping Perspective of Human Learned Helplessness. Index.

Talking, Relating, and Achieving: Effects of Cooperative Learning and Whole-Class Instruction

Abstract: The effects of cooperative learning with the Group Investigation method on eighthgrade students in ethnically heterogeneous classrooms in a junior high school in Israel were compared with effects of the traditional Presentation-Recitation method ordinarily employed in most schools. Our study involved 351 Jewish students from Western and Middle Eastern backgrounds, with 197 in five classes taught for 6 months with the Group Investigation method and 154 in four classes taught with the Whole-Class method. Dependent variables included students' academic achievement in geography and history as assessed by tests composed collectively by all of the teachers, their verbal behavior during 30-min videotaped discussions in 27 six-person groups (three heterogeneous groups from each classroom), and the nature of their social interaction during the group discussions. All students from the Group Investigation method expressed themselves more frequently and used more words per turn of speech than their peers from classrooms taught with the traditional Whole-Class method. In groups from the Whole-Class method, Western students dominated the discussion in regard to the number of turns of speech, whereas in groups from classes taught with the Group Investigation method, turn-taking was almost symmetrical among students from the two ethnic groups. Students from both ethnic groups addressed more cooperative statements to Middle Eastern students after studying in Group Investigation classes than did students from the Whole-Class method. Finally, students' achievement scores were higher in classes taught with the Group Investigation method than in those taught with the Whole-Class method, using both aggregated classroom and individual scores. This finding was true for students of both ethnic groups.

Stages of Friendship Growth in Preadolescence as Related to Attachment History

Abstract: A process model of friendship formation in preadolescence is proposed in this article, and the continuity of early parent-child relationships (quality of attachment) with later friendship processes and peer competence is explored. Thirty-two preadolescents, subjects in a longitudinal study of attachment and subsequent social development, were observed in 4-week summer day camps. Those who had been securely attached with their caregivers as infants revealed a higher level of peer competence than did those with anxious attachment histories. However, preadolescents of both types of attachment reported and were observed to form friendships. In-depth case studies of four friendship pairs of preadolescents with different attachment histories suggested that there are corresponding differences in the quality and growth processes of those pairs of friendships. A three-stage model of preadolescent friendship growth is proposed, based on relationship dimensions and reflective of earlier relational patterns.

Organizational attitudes and behaviors as a function of participation in strategic and tactical change decisions: An application of path–goal theory†

Abstract: Based upon path–goal theory of leadership, decision type (strategic versus tactical) was suggested as a moderator variable between employee participation in decision making (PDM) and work outcomes. A total of 249 respondents in five Israeli organizations undergoing planned changes, participated in the study. Results from four out of the five organizations revealed that participation in tactical rather than strategic decisions was a better predictor of an increase in change acceptance, work satisfaction, effectiveness, and time allotted to work. The stronger effects associated with tactics rather than strategy were found even if PDM expectations were included. Theoretical and practical implications of the results were discussed.

Biological and Environmental Correlates of Developmental Outcome of Prematurely Born Infants in Early Adolescence

Abstract: Examined the role of biological factors (birth weight and perinatal medical complications) and psychosocial factors (maternal attitudes, paternal involvement, mother's personal state, marital adjustment, family relations, and socioeconomic status) in predicting long-term outcome of 90 Israeli adolescents born prematurely at very low birth weight (VLBW). As compared with 90 adolescents born full-term at normal birth weight (NBW), the VLBW children scored lower on all measures except reading comprehension. IQ, visual-motor coordination, and hyperactive behavior were predicted by both biological and psychosocial variables, visual memory by biological variables, and reading comprehension by psychosocial variables. The findings support chiefly the main effects model of developmental psychopathology (i.e., biological and psychosocial variables are additive in predicting outcomes), but also the interactional model (e.g., SES was influential in predicting visual-motor coordination and hyperactive behavior in the VLBW group but not in the NBW group).

Giant flux creep through surface barriers and the irreversibility line in high-temperature superconductors.

Abstract: Magnetic and transport phenomena in high-temperature superconductors due to magnetic flux relaxation and transport over the surface barrier are investigated. Vortex dynamics controlled by the penetration both of pancake vortices and vortex lines is discussed. The penetration field ${\mathit{H}}_{\mathit{p}}$ for pancakes decays exponentially with temperature. The size of the magnetization loop is determined by the decay of ${\mathit{H}}_{\mathit{p}}$ during the process of relaxation, but its shape remains unchanged. The irreversibility line associated with the pancake penetration is given by ${\mathit{H}}_{\mathrm{irr}}$ \ensuremath{\propto}exp(-2T/${\mathit{T}}_{0}$) and may lie both above and below the melting line.

Vortices in random wave fields: Nearest neighbor anticorrelations

Abstract: In a random Gaussian wave field there is on average one vortex (phase singularity) for every two coherence areas. These vortices exhibit an unexpected, highly surprising correlation--nearest neighbors are 90% anticorrelated in sign. We show that on the zero crossings of the real or imaginary parts of the field adjacent vortices must be of opposite sign. This principle, which is unaffected by boundaries, accounts for the observed sign anticorrelations. We also show how the sign of any single vortex in a random wave field determines the sign of all other vortices in the wave field.

Bioactive conjugates of cellulose with amino compounds

Abstract: Polymers containing a plurality of free hydroxy groups, such as cellulose, agarose or polyvinyl alcohol, are contacted in absence of reactants for hydroxy groups, with at least one N-heterocyclic compound, e.g. pyridine, pyrrole, pyridazine, their partially or fully hydrogenated analogs and any of these which may be substituted, in a pre-activation step prior to reaction with reactant for free hydroxy groups in the polymer, the polymer-bound residue of which reactant may be thereafter reacted in turn with amino compounds containing at least one unsubstituted N-attached hydrogen atom, e.g. proteins, thereby to form amine-polymer conjugates. The invention further relates to a powder, bandage, patch or like cover for application to wounds which has been manufactured from polymer containing a plurality of hydroxy groups by a process which includes the step of providing an amine conjugated to the polymer; the amine may be, e.g., trypsin, chymotrypsin, lysozyme, collagenase, albumin and hyaluronidase.

Dynamic characteristics of the anomalous second peak in the magnetization curves of Bi-Sr-Ca-Cu-O.

Abstract: We present magnetization curves for Bi-Sr-Ca-Cu-O crystals which exhibit an anomalous second peak. Between 20 and 40 K the peak disappears gradually with time. At lower temperatures (18 K) the peak is absent in the short-time limit and it is gradually built up with time. A smooth universal function relates the magnetization at the peak (400 Oe) with that at the minimum (200 Oe) for all isotherms and at any given time, thus demonstrating the absence of the anomalous peak in the short-time limit at all isotherms.

Optical vortices in gaussian random wave fields : statistical probability densities

Abstract: Simple, closed-form analytical expressions are given for the statistical probability densities of the six parameters that define an optical vortex (phase singularity) in a Gaussian random wave field. Good agreement is found between calculation and a computer simulation that generates these vortices.