Showing papers by "Ben-Gurion University of the Negev published in 2002"

Choice is good, but relevance is excellent: autonomy-enhancing and suppressing teacher behaviours predicting students' engagement in schoolwork.

Abstract: Background and aims: This article examines two questions concerning teacher-behaviours that are characterised in Self-Determination Theory (Ryan & Deci, 2000) as autonomy-supportive or suppressive: (1) Can children differentiate among various types of autonomy-enhancing and suppressing teacher behaviours? (2) Which of those types of behaviour are particularly important in predicting feelings toward and engagement in schoolwork? It was hypothesised that teacher behaviours that help students to understand the relevance of schoolwork for their personal interests and goals are particularly important predictors of engagement in schoolwork. Samples and methods: Israeli students in grades 3-5 (N = 498) and in grades 6-8 (N = 364) completed questionnaires assessing the variables of interest. Results: Smallest Space Analyses indicated that both children and early adolescents can differentiate among three types of autonomy enhancing teacher behaviours — fostering relevance, allowing criticism, and providing choice — and three types of autonomy suppressing teacher behaviours — suppressing criticism, intruding, and forcing unmeaningful acts. Regression analyses supported the hypothesis concerning the importance of teacher behaviours that clarify the personal relevance of schoolwork. Among the autonomy-suppressing behaviours, ‘Criticism-suppression’ was the best predictor of feelings and engagement. Conclusions: The findings underscore the active and empathic nature of teachers' role in supporting students' autonomy, and suggest that autonomy-support is important not only for early adolescents but also for children. Discussion of potential determinants of the relative importance of various autonomy-affecting teacher actions suggests that provision of choice should not always be viewed as a major indicator of autonomy support.

Fluorescence correlation spectroscopy: the technique and its applications

Abstract: Fluorescence correlation spectroscopy (FCS) is an experimental technique using statistical analysis of the fluctuations of fluorescence in a system in order to decipher dynamic molecular events, such as diffusion or conformational fluctuations of biomolecules. First introduced by Magde et al to measure the diffusion and binding of ethidium bromide onto double-stranded DNA, the technique has been undergoing a renaissance since 1993 with the implementation of confocal microscopy FCS. Since then, a flurry of experiments has implemented FCS to characterize the photochemistry of dyes, the translational and rotational mobilities of fluorescent molecules, as well as to monitor conformational fluctuations of green fluorescent proteins and DNA molecules. In this review, we present the analytical formalism of an FCS measurement, as well as practical considerations for the design of an FCS setup and experiment. We then review the recent applications of FCS in analytical chemistry, biophysics and cell biology, specifically emphasizing the advantages and pitfalls of the technique compared to alternative spectroscopic tools. We also discuss recent extensions of FCS in single-molecule spectroscopy, offering alternative data processing of fluorescence signals to glean more information on the kinetic processes.

Stabilization of Individual Carbon Nanotubes in Aqueous Solutions

Abstract: Single-wall carbon nanotubes pack into crystalline ropes that aggregate into tangled networks due to strong van der Waals attraction. Aggregation acts as an obstacle to most applications, and diminishes the special properties of the individual tubes. We describe a simple procedure for dispersing as-produced nanotubes powder in aqueous solutions of Gum Arabic. In a single step, a stable dispersion of full-length, well separated, individual tubes is formed, apparently due to physical adsorption of the polymer.

A Highly Significant Association between a COMT Haplotype and Schizophrenia

Abstract: Several lines of evidence have placed the catechol-O-methyltransferase (COMT) gene in the limelight as a candidate gene for schizophrenia. One of these is its biochemical function in metabolism of catecholamine neurotransmitters; another is the microdeletion, on chromosome 22q11, that includes the COMT gene and causes velocardiofacial syndrome, a syndrome associated with a high rate of psychosis, particularly schizophrenia. The interest in the COMT gene as a candidate risk factor for schizophrenia has led to numerous linkage and association analyses. These, however, have failed to produce any conclusive result. Here we report an efficient approach to gene discovery. The approach consists of ( i ) a large sample size—to our knowledge, the present study is the largest case-control study performed to date in schizophrenia; ( ii ) the use of Ashkenazi Jews, a well defined homogeneous population; and ( iii ) a stepwise procedure in which several single nucleotide polymorphisms (SNPs) are scanned in DNA pools, followed by individual genotyping and haplotype analysis of the relevant SNPs. We found a highly significant association between schizophrenia and a COMT haplotype ( P =9.5×10 −8 ). The approach presented can be widely implemented for the genetic dissection of other common diseases.

Assessing carotenoid content in plant leaves with reflectance spectroscopy

Abstract: Spectral reflectance of maple, chestnut and beech leaves in a wide range of pigment content and composition was investigated to devise a nondestructive technique for total carotenoid (Car) content estimation in higher plant leaves. Reciprocal reflectance in the range 510 to 550 nm was found to be closely related to the total pigment content in leaves. The sensitivity of reciprocal reflectance to Car content was maximal in a spectral range around 510 nm; however, chlorophylls (Chl) also affect reflectance in this spectral range. To remove the Chl effect on the reciprocal reflectance at 510 nm, a reciprocal reflectance at either 550 or 700 nm was used, which was linearly proportional to the Chl content. Indices for nondestructive estimation of Car content in leaves were devised and validated. Reflectances in three spectral bands, 510+/-5 nm, either 550+/-15 nm or 700+/-7.5 nm and the near infrared range above 750 nm are sufficient to estimate total Car content in plant leaves nondestructively with a root mean square error of less than 1.75 nmol/cm2.

Addition of omega-3 fatty acid to maintenance medication treatment for recurrent unipolar depressive disorder

Abstract: OBJECTIVE: Studies have reported that countries with high rates of fish oil consumption have low rates of depressive disorder. The authors studied a specific omega-3 fatty acid, the ethyl ester of eicosapentaenoic acid (E-EPA), as an adjunct to treatment for depressive episodes occurring in patients with recurrent unipolar depressive disorder who were receiving maintenance antidepressant therapy. METHOD: Twenty patients with a current diagnosis of major depressive disorder participated in a 4-week, parallel-group, double-blind addition of either placebo or E-EPA to ongoing antidepressant therapy. Seventeen of the patients were women, and three were men. RESULTS: Highly significant benefits of the addition of the omega-3 fatty acid compared with placebo were found by week 3 of treatment. CONCLUSIONS: It is not possible to distinguish whether E-EPA augments antidepressant action in the manner of lithium or has independent antidepressant properties of its own.

Mechanisms of long-distance dispersal of seeds by wind

Abstract: Long-distance dispersal (LDD) is central to species expansion following climate change, re-colonization of disturbed areas and control of pests1,2,3,4,5,6,7,8. The current paradigm is that the frequency and spatial extent of LDD events are extremely difficult to predict9,10,11,12. Here we show that mechanistic models coupling seed release and aerodynamics with turbulent transport processes provide accurate probabilistic descriptions of LDD of seeds by wind. The proposed model reliably predicts the vertical distribution of dispersed seeds of five tree species observed along a 45-m high tower in an eastern US deciduous forest. Simulations show that uplifting above the forest canopy is necessary and sufficient for LDD, hence, they provide the means to define LDD quantitatively rather than arbitrarily. Seed uplifting probability thus sets an upper bound on the probability of long-distance colonization. Uplifted yellow poplar seeds are on average lighter than seeds at the forest floor, but also include the heaviest seeds. Because uplifting probabilities are appreciable (as much as 1–5%), and tree seed crops are commonly massive, some LDD events will establish individuals that can critically affect plant dynamics on large scales.

Mutation of TRPM6 causes familial hypomagnesemia with secondary hypocalcemia.

Abstract: Familial hypomagnesemia with secondary hypocalcemia (OMIM 602014) is an autosomal recessive disease that results in electrolyte abnormalities shortly after birth. Affected individuals show severe hypomagnesemia and hypocalcemia, which lead to seizures and tetany. The disorder has been thought to be caused by a defect in the intestinal absorption of magnesium, rather than by abnormal renal loss of magnesium. Restoring the concentrations of serum magnesium to normal values by high-dose magnesium supplementation can overcome the apparent defect in magnesium absorption and in serum concentrations of calcium. Life-long magnesium supplementation is required to overcome the defect in magnesium handling by these individuals. We previously mapped the gene locus to chromosome 9q in three large inbred kindreds from Israel. Here we report that mutation of TRPM6 causes hypomagnesemia with secondary hypocalcemia and show that individuals carrying mutations in this gene have abnormal renal magnesium excretion.

Optimization of cardiac cell seeding and distribution in 3D porous alginate scaffolds.

Abstract: Cardiac tissue engineering has evolved as a potential therapeutic approach to assist in cardiac regeneration. We have recently shown that tissue-engineered cardiac graft, constructed from cardiomyocytes seeded within an alginate scaffold, is capable of preventing the deterioration in cardiac function after myocardial infarction in rats. The present article addresses cell seeding within porous alginate scaffolds in an attempt to achieve 3D high-density cardiac constructs with a uniform cell distribution. Due to the hydrophilic nature of the alginate scaffold, its >90% porosity and interconnected pore structure, cell seeding onto the scaffold was efficient and short, up to 30 min. Application of a moderate centrifugal force during cell seeding resulted in a uniform cell distribution throughout the alginate scaffolds, consequently enabling the loading of a large number of cells onto the 3D scaffolds. The percent cell yield in the alginate scaffolds ranged between 60-90%, depending on cell density at seeding; it was 90% at seeding densities of up to 1 x 10(8) cells/cm(3) scaffold and decreased to 60% at higher densities. The highly dense cardiac constructs maintained high metabolic activity in culture. Scanning electron microscopy revealed that the cells aggregated within the scaffold pores. Some of the aggregates were contracting spontaneously within the matrix pores. Throughout the culture there was no indication of cardiomyocyte proliferation within the scaffolds, nor was it found in 3D cultures of cardiofibroblasts. This may enable the development of cardiac cocultures, without domination of cardiofibroblasts with time.

Reduction of nasopharyngeal carriage of Streptococcus pneumoniae after administration of a 9-valent pneumococcal conjugate vaccine to toddlers attending day care centers.

Abstract: A double-blind, randomized study involving 264 toddlers attending day care centers was conducted to document the effect of a 9-valent pneumococcal conjugate vaccine on the carriage rate of pneumococci. Of 3750 cultures done on nasopharyngeal samples obtained from subjects during a 2-year follow-up period after vaccination, 65% were positive for Streptococcus pneumoniae. In all age windows, the rate of carriage of vaccine-type pneumococci was lower among subjects who received the pneumococcal vaccine than among control subjects, because the acquisition rate was lower in the former group. The effect was most pronounced among subjects aged < or =36 months. The sample size enabled us to study protection against carriage of S. pneumoniae serotypes 6B, 9V, 14, 19F, and 23F; significant protection against all serotypes except 19F was seen in the pneumococcal-vaccine group. The rate of carriage of serotype 6A (not included in the vaccine) was also reduced significantly, but the rate of carriage of serotype 19A (not included in the vaccine) was not. The rate of carriage of non-vaccine-type pneumococci (excluding serotype 6A) was higher in the pneumococcal-vaccine group than in the control group.

Classroom goal structure and student disruptive behaviour.

Abstract: Background: Achievement goal theory suggests that the emphasis on mastery and performance goals in the classroom (the classroom goal structure) is related to students' patterns of learning and behaviour. This theory can offer a preventative holistic approach for dealing with students' disruptive behaviour. Aims: The present study investigates whether the goal structure in the classroom is related to the incidence of disruptive behaviour. Sample and Methods: A total of 388 ninth-grade students from 60 classrooms in five ethnically diverse high schools responded to surveys asking about the perceived goal structures, their personal achievement goals, and their involvement in disruptive behaviour in their maths classroom. Their maths teachers responded to surveys asking about their goal-related approaches to instruction. Results: Using hierarchical linear modelling (HLM), at the student level, being male and having lower achievement was related to reports of disruptive behaviour. In addition, personal mastery goals were related to lower reports of disruptive behaviour and personal performance-approach and performance-avoidance goals were related to higher reports of disruptive behaviour. Disruptive behaviour also varied significantly between classrooms. Aggregated student perceptions of a mastery goal structure were related to a lower incidence, and aggregated student perceptions of a performance-approach goal structure were related to a higher incidence of disruptive behaviour. Conclusion: The implications of the findings to approaches for dealing with disruptive behaviour are discussed.

Identification of the gene (BBS1) most commonly involved in Bardet-Biedl syndrome, a complex human obesity syndrome.

Abstract: Bardet-Biedl syndrome (BBS, OMIM 209900) is a genetic disorder with the primary features of obesity, pigmentary retinopathy, polydactyly, renal malformations, mental retardation and hypogenitalism. Individuals with BBS are also at increased risk for diabetes mellitus, hypertension and congenital heart disease. What was once thought to be a homogeneous autosomal recessive disorder is now known to map to at least six loci: 11q13 (BBS1), 16q21 (BBS2), 3p13 p12 (BBS3), 15q22.3 q23 (BBS4), 2q31 (BBS5) and 20p12 (BBS6). There has been considerable interest in identifying the genes that underlie BBS, because some components of the phenotype are common. Cases of BBS mapping ro BBS6 are caused by mutations in MKKS; mutations in this gene also cause McKusick-Kaufman syndrome (hydrometrocolpos, post-axial polydactyly and congenital heart defects). In addition, we recently used positional cloning to identify the genes underlying BBS2 (ref. 16) and BBS4 (ref. 17). The BBS6 protein has similarity to a Thermoplasma acidophilum chaperonin, whereas BBS2 and BBS4 have no significant similarity to chaperonins. It has recently been suggested that three mutated alleles (two at one locus, and a third at a second locus) may be required for manifestation of BBS (triallelic inheritance). Here we report the identification of the gene BBS1 and show that a missense mutation of this gene is a frequent cause of BBS. In addition, we provide data showing that this common mutation is not involved in triallelic inheritance.

Protein kinase C(theta) in T cell activation.

Abstract: The novel protein kinase C (PKC) isoform, PKC theta, is selectively expressed in T lymphocytes and is a sine qua non for T cell antigen receptor (TCR)-triggered activation of mature T cells. Productive engagement of T cells by antigen-presenting cells (APCs) results in recruitment of PKC theta to the T cell-APC contact area--the immunological synapse--where it interacts with several signaling molecules to induce activation signals essential for productive T cell activation and IL-2 production. The transcription factors NF-kappa B and AP-1 are the primary physiological targets of PKC theta, and efficient activation of these transcription factors by PKC theta requires integration of TCR and CD28 costimulatory signals. PKC theta cooperates with the protein Ser/Thr phosphatase, calcineurin, in transducing signals leading to activation of JNK, NFAT, and the IL-2 gene. PKC theta also promotes T cell cycle progression and regulates programmed T cell death. The exact mode of regulation and immediate downstream substrates of PKC theta are still largely unknown. Identification of these molecules and determination of their mode of operation with respect to the function of PKC theta will provide essential information on the mechanism of T cell activation. The selective expression of PKC theta in T cells and its essential role in mature T cell activation establish it as an attractive drug target for immunosuppression in transplantation and autoimmune diseases.

Spectroscopic Studies of Photoexcitations in Regioregular and Regiorandom Polythiophene Films

Abstract: Using a variety of optical probe techniques we studied the steady state and transient dynamics of charged and neutral photoexcitations in thin films of poly-3-alkyl thiophene with regioregular order, which forms self-assembled lamellae structures with increased interchain interaction, as well as regiorandom order that keeps a chain-like morphology. In regiorandom polythiophene films we found that intrachain excitons with correlated photoinduced absorption and stimulated emission bands are the primary photoexcitations; they give rise to a moderately strong photoluminescence band, and long-lived triplet excitons and intrachain charged polarons. In regioregular polythiophene films, on the contrary we found that the primary photoexcitations are excitons with much larger interchain component; this results in lack of stimulated emission, vanishing intersystem crossing, and a very weak photoluminescence band. The long-lived photoexcitations in regioregular polythiophene films are interchain excitons and delocalized polarons (DP) within the lamellae, with very small relaxation energy. The characteristic properties of the DP species are thoroughly investigated as a function of the alkyl side group of the polymer backbone, film deposition conditions and solvents used, as well as at high hydrostatic pressure. The quantum interference between the low energy absorption band of the DP species and a series of photoinduced infrared active vibrations, which give rise to antiresonances that are superimposed on the electronic absorption band is studied and explained by a Fano-type interference mechanism, using the amplitude mode model.

Refining the Search for Project Success Factors: A Multivariate, Typological Approach

Abstract: Although the causes for project success and failure have been the subject of many studies, no conclusive evidence or common agreement has been achieved so far. One criticism involves the universalistic approach used often in project management studies, according to which all projects are assumed to be similar. A second problem is the issue of subjectiveness, and sometimes weakly defined success measures; yet another concern is the limited number of managerial variables examined by previous research. In the present study we use a project-specific typological approach, a multidimensional criteria for assessing project success, and a multivariate statistical analysis method. According to our typology projects were classified according to their technological uncertainty at project initiation and their system scope which is their location on a hierarchical ladder of systems and subsystems. For each of the 127 projects in our study that were executed in Israel, we recorded 360 managerial variables and 13 success measures. The use of a very detailed data and multivariate methods such as canonical correlation and eigenvector analysis enables us to account for all the interactions between managerial and success variables and to address a handful of perspectives, often left unanalyzed by previous research. Assessing the variants of managerial variables and their impact on project success for various types of projects, serves also a step toward the establishment of a typological theory of projects. Although some success factors are common to all projects, our study identified project-specific lists of factors, indicating for example, that high-uncertainty projects must be managed differently than low-uncertainty projects, and high-scope projects differently than low-scope projects.

Risk Management, Project Success, and Technological Uncertainty

Abstract: In times of increased competition and globalization, project success becomes even more critical to business performance, and yet many projects still suffer delays, overruns, and even failure. Ironically, however, risk management tools and techniques, which have been developed to improve project success, are used too little, and many still wonder how helpful they are. In this paper we present the results of an empirical study devoted to this question. Based on data collected on over 100 projects performed in Israel in a variety of industries, we examine the extent of usage of some risk management practices, such as risk identification, probabilistic risk analysis, planning for uncertainty and trade-off analysis, the difference in application across different types of projects, and their impact on various project success dimensions. Our findings suggest that risk management practices are still not widely used. Only a limited number of projects in our study have used any kind of risk management practices and many have only used some, but not all the available tools. When used, risk management practices seem to be working, and appear to be related to project success. We also found that risk management practices were more applicable to higher risk projects. The impact of risk management is mainly on better meeting time and budget goals and less on product performance and specification. In this case, we also found some differences according levels of technological uncertainty. Our conclusion is that risk management is still at its infancy and that at this time, more awareness to the application, training, tool development, and research on risk management is needed.

Complete sequence and organization of pBtoxis, the toxin-coding plasmid of Bacillus thuringiensis subsp. israelensis.

Abstract: The entire 127,923-bp sequence of the toxin-encoding plasmid pBtoxis from Bacillus thuringiensis subsp. israelensis is presented and analyzed. In addition to the four known Cry and two known Cyt toxins, a third Cyt-type sequence was found with an additional C-terminal domain previously unseen in such proteins. Many plasmid-encoded genes could be involved in several functions other than toxin production. The most striking of these are several genes potentially affecting host sporulation and germination and a set of genes for the production and export of a peptide antibiotic.

Origin-Based Algorithm for the Traffic Assignment Problem

Abstract: We present an origin-based algorithm for the traffic assignment problem, which is similar conceptually to the algorithm proposed by Gallager and Bertsekas for routing in telecommunication networks. Apart from being origin-based, the algorithm is different from other algorithms used so far for the traffic assignment problem by its restriction to acyclic solutions and by the use of approach proportions as solution variables. Projected quasi-Newton search directions are used to shift flows effectively and to eliminate residual flows. Experimental results comparing the proposed algorithm with the state-of-the-practice algorithm of Frankand Wolfe demonstrate the algorithm's excellent convergence performance, especially when highly accurate solutions are needed. Reasonable memory requirements make this algorithm applicable to large-scale networks. The resulting solution has an immediate route flow interpretation, thus providing equivalent detail to route-based solutions.

Exploiting local similarity for indexing paths in graph-structured data

Abstract: XML and other semi-structured data may have partially specified or missing schema information, motivating the use of a structural summary which can be automatically computed from the data. These summaries also serve as indices for evaluating the complex path expressions common to XML and semi-structured query languages. However, to answer all path queries accurately, summaries must encode information about long, seldom-queried paths, leading to increased size and complexity with little added value. We introduce the A(k)-indices, a family of approximate structural summaries. They are based on the concept of k-bisimilarity, in which nodes are grouped based on local structure, i.e., the incoming paths of length up to k. The parameter k thus smoothly varies the level of detail (and accuracy) of the A(k)-index. For small values of k, the size of the index is substantially reduced. While smaller, the A(k) index is approximate, and we describe techniques for efficiently extracting exact answers to regular path queries. Our experiments show that, for moderate values of k, path evaluation using the A(k)-index ranges from being very efficient for simple queries to competitive for most complex queries, while using significantly less space than comparable structures.

Risk management, project success, and technological uncertainty

Abstract: In times of increased competition and globalization, project success becomes even more critical to business performance, and yet many projects still suffer delays, overruns, and even failure. Ironically, however, risk management tools and techniques, which have been developed to improve project success, are used too little, and many still wonder how helpful they are. In this paper we present the results of an empirical study devoted to this question. Based on data collected on over 100 projects performed in Israel in a variety of industries, we examine the extent of usage of some risk management practices, such as risk identification, probabilistic risk analysis, planning for uncertainty and trade-off analysis, the difference in application across different types of projects, and their impact on various project success dimensions. Our findings suggest that risk management practices are still not widely used. Only a limited number of projects in our study have used any kind of risk management practices and many have only used some, but not all the available tools. When used, risk management practices seem to be working, and appear to be related to project success. We also found that risk management practices were more applicable to higher risk projects. The impact of risk management is mainly on better meeting time and budget goals and less on product performance and specification. In this case, we also found some differences according levels of technological uncertainty. Our conclusion is that risk management is still at its infancy and that at this time, more awareness to the application, training, tool development, and research on risk management is needed.

The Measurement of Intellectual Influence

Abstract: We examine the problem of measuring influence based on the information contained in the data on the communications between scholarly publications, judicial decisions, patents, web pages, and other entities. The measurement of influence is useful to address several empirical questions such as reputation, prestige, aspects of the diffusion of knowledge, the markets for scientists and scientific publications, the dynamics of innovation, ranking algorithms of search engines in the World Wide Web, and others. In this paper we ask why any given methodology is reasonable and informative applying the axiomatic method. We find that a unique ranking method can be characterized by means of five axioms: Anonymity, invariance to citation intensity, weak homogeneity, weak consistency, and invariance to splitting of journals. This method is easily implementable and turns out to be different from those regularly used in social and natural sciences, arts and humanities, and computer science.

Refining the search for project success factors: a multivariate, typological approach

Abstract: Although the causes for project success and failure have been the subject of many studies, no conclusive evidence or common agreement has been achieved so far. One criticism involves the universalistic approach used often in project management studies, according to which all projects are assumed to be similar. A second problem is the issue of subjectiveness, and sometimes weakly defined success measures; yet another concern is the limited number of managerial variables examined by previous research. In the present study we use a project-specific typological approach, a multidimensional criteria for assessing project success, and a multivariate statistical analysis method. According to our typology projects were classified according to their technological uncertainty at project initiation and their system scope which is their location on a hierarchical ladder of systems and subsystems. For each of the 127 projects in our study that were executed in Israel, we recorded 360 managerial variables and 13 success measures. The use of a very detailed data and multivariate methods such as canonical correlation and eigenvector analysis enables us to account for all the interactions between managerial and success variables and to address a handful of perspectives, often left unanalyzed by previous research. Assessing the variants of managerial variables and their impact on project success for various types of projects, serves also a step toward the establishment of a typological theory of projects. Although some success factors are common to all projects, our study identified project-specific lists of factors, indicating for example, that high-uncertainty projects must be managed differently than low-uncertainty projects, and high-scope projects differently than low-scope projects.