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Showing papers by "Ben-Gurion University of the Negev published in 2001"


Journal ArticleDOI
TL;DR: In this paper, the AERONET program of spectral aerosol optical depth, precipitable water, and derived Angstrom exponent were analyzed and compiled into a spectral optical properties climatology.
Abstract: Long-term measurements by the AERONET program of spectral aerosol optical depth, precipitable water, and derived Angstrom exponent were analyzed and compiled into an aerosol optical properties climatology. Quality assured monthly means are presented and described for 9 primary sites and 21 additional multiyear sites with distinct aerosol regimes representing tropical biomass burning, boreal forests, midlatitude humid climates, midlatitude dry climates, oceanic sites, desert sites, and background sites. Seasonal trends for each of these nine sites are discussed and climatic averages presented.

1,891 citations


Journal ArticleDOI
TL;DR: Based on thermal radiance transfer equation, an attempt has been made in this paper to develop a mono-window algorithm for retrieving land surface temperature (LST) from Landsat TM6 data.
Abstract: Remote sensing of land surface temperature (LST) from the thermal band data of Landsat Thematic Mapper (TM) still remains unused in comparison with the extensive studies of its visible and near-infrared (NIR) bands for various applications. The brightness temperature can be computed from the digital number (DN) of TM6 data using the equation provided by the National Aeronautics and Space Administration (NASA). However, a proper algorithm for retrieving LST from the only one thermal band of the sensor still remains unavailable due to many difficulties in the atmospheric correction. Based on thermal radiance transfer equation, an attempt has been made in the paper to develop a mono-window algorithm for retrieving LST from Landsat TM6 data. Three parameters are required for the algorithm: emissivity, transmittance and effective mean atmospheric temperature. Method about determination of atmospheric transmittance is given in the paper through the simulation of atmospheric conditions with LOWTRAN 7 program. A ...

1,134 citations


Journal ArticleDOI
22 Feb 2001-Nature
TL;DR: Findings indicate how NKp46-expressing NK cells may recognize target cells infected by influenza or parainfluenza without the decreased expression of target-cell MHC class I protein.
Abstract: Natural killer (NK) cells destroy virus-infected and tumour cells, apparently without the need for previous antigen stimulation. In part, target cells are recognized by their diminished expression of major histocompatibility complex (MHC) class I molecules, which normally interact with inhibitory receptors on the NK cell surface. NK cells also express triggering receptors that are specific for non-MHC ligands; but the nature of the ligands recognized on target cells is undefined. NKp46 is thought to be the main activating receptor for human NK cells. Here we show that a soluble NKp46-immunoglobulin fusion protein binds to both the haemagglutinin of influenza virus and the haemagglutinin-neuraminidase of parainfluenza virus. In a substantial subset of NK cells, recognition by NKp46 is required to lyse cells expressing the corresponding viral glycoproteins. The binding requires the sialylation of NKp46 oligosaccharides, which is consistent with the known sialic binding capacity of the viral glycoproteins. These findings indicate how NKp46-expressing NK cells may recognize target cells infected by influenza or parainfluenza without the decreased expression of target-cell MHC class I protein.

1,005 citations


Proceedings Article
04 Aug 2001
TL;DR: R-MAX as mentioned in this paper is a model-based reinforcement learning algorithm which can attain near-optimal average reward in polynomial time, where the agent always maintains a complete, but possibly inaccurate model of its environment and acts based on the optimal policy derived from this model.
Abstract: R-MAX is a simple model-based reinforcement learning algorithm which can attain near-optimal average reward in polynomial time. In R-MAX, the agent always maintains a complete, but possibly inaccurate model of its environment and acts based on the optimal policy derived from this model. The model is initialized in an optimistic fashion: all actions in all states return the maximal possible reward (hence the name). During execution, the model is updated based on the agent's observations. R-MAX improves upon several previous algorithms: (1) It is simpler and more general than Kearns and Singh's E3 algorithm, covering zerosum stochastic games. (2) It has a built-in mechanism for resolving the exploration vs. exploitation dilemma. (3) It formally justifies the "optimism under uncertainty" bias used in many RL algorithms. (4) It is much simpler and more general than Brafman and Tennenholtz's LSG algorithmfor learning in single controller stochastic games. (5) It generalizes the algorithm by Monderer and Tennenholtz for learning in repeated games. (6) It is the only algorithm for near-optimal learning in repeated games known to be polynomial, providing a much simpler and more efficient alternative to previous algorithms by Banos and by Megiddo.

923 citations


Journal ArticleDOI
TL;DR: There seems to be a subgroup with characteristic clinical features and a typical course which is mostly caused by drugs for which the term acute generalized exanthematous pustulosis (AGEP) has been established.
Abstract: Background: A wide range of diseases or reactions can cause pustular eruptions of the skin. In this spectrum there seems to be a subgroup with characteristic clinical features and a typical course which is mostly caused by drugs for which the term acute generalized exanthematous pustulosis (AGEP) has been established. Objective: To describe the clinical features of AGEP. Methods: The authors’ experience from a multinational epidemiological study on severe cutaneous adverse reactions and a comprehensive review of the literature were used to provide an overview of the disease and it’s possible causes. An algorithm for validating cases which was established for this study is also presented. Results: AGEP typically presents with at least dozens of non follicular sterile pustules occurring on a diffuse, edematous erythema predominalty in the folds and/or on the face. Fever and elevated blood neutrophils are common. Histopathology typically shows spongiform subcorneal and/or intraepidermal pustules, a marked edema of the papillary dermis, and eventually vasculitis, eosinophils and/or focal necrosis of keratinocytes. Onset is acute, most often following drug intake, but viral infections can also trigger the disease. Pustules resolve spontaneously in less than 15 days. Conclusion: The diagnosis AGEP should be considered in cases of acute pustular rashes and detection of the causative drug should be strived for. Knowledge of the clinical features and usual course of this disease can often prevent unnecessary therapeutical measures.

687 citations


Journal ArticleDOI
TL;DR: A new model for vegetation patterns is introduced that predicts transitions from bare soil at low precipitation to homogeneous vegetation at high precipitation, through intermediate states of spot, stripe, and hole patterns and predicts wide precipitation ranges where different stable states coexist.
Abstract: A new model for vegetation patterns is introduced. The model reproduces a wide range of patterns observed in water-limited regions, including drifting bands, spots, and labyrinths. It predicts transitions from bare soil at low precipitation to homogeneous vegetation at high precipitation, through intermediate states of spot, stripe, and hole patterns. It also predicts wide precipitation ranges where different stable states coexist. Using these predictions we propose a novel explanation of desertification phenomena and a new approach to classifying aridity.

565 citations


Journal ArticleDOI
TL;DR: It seems that the better protection of Lpa roots from salt-induced oxidative damage results, at least partially, from the increased activity of their antioxidative system.
Abstract: The response of the antioxidant system to salt stress was studied in the roots of the cultivated tomato Lycopersicon esculentum Mill. cv. M82 (Lem) and its wild salt-tolerant relative L. pennellii (Corr.) D'Arcy accession Atico (Lpa). Roots of control and salt (100 mM NaCl)-stressed plants were sampled at various times after commencement of salinization. A gradual increase in the membrane lipid peroxidation in salt-stressed root of Lem was accompanied with decreased activities of the antioxidant enzymes: superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6), ascorbate peroxidase (APX; EC 1.11.1.11) and decreased contents of the antioxidants ascorbate and glutathione and their redox states. In contrast, increased activities of the SOD, CAT, APX, monodehydroascorbate reductase (MDHAR; EC 1.6.5.4), and increased contents of the reduced forms of ascorbate and glutathione and their redox states were found in salt-stressed roots of Lpa, in which the level of membrane lipid peroxidation remained unchanged. It seems that the better protection of Lpa roots from salt-induced oxidative damage results, at least partially, from the increased activity of their antioxidative system.

457 citations


Journal ArticleDOI
TL;DR: A game-theoretic model for considering the effects of intra- and interplant competition on root proliferation and reproductive yield predicts that if space and resources per individual are held constant, plants should produce more roots per individual and less reproductive yield per individual as the number of plants sharing the combined space increases.
Abstract: Summary 1 We develop and test a game-theoretic model for considering the effects of intra- and interplant competition on root proliferation and reproductive yield. 2 We predict that if space and resources per individual are held constant, plants should produce more roots per individual and less reproductive yield per individual as the number of plants sharing the combined space increases. 3 We tested the predictions using soybean plants ( Glycine max ) cultivated in the glasshouse either as owners or as two individuals sharing twice the space and nutrients. 4 Sharing individuals produced 85% more root mass than owners. Owners, however, produced 30% more reproductive yield per plant (dry mass of seeds), as a result of significantly more seed pods (8.70 vs. 7.66), more seeds per pod (1.87 vs. 1.72) and larger seeds (0.205 vs. 0.195 g seed ‐1 ), than did sharing individuals. 5 Total plant biomass did not differ between owners and sharing individuals, but owners had significantly higher shoot to root ratios, produced significantly more seeds per unit root mass, and allocated a significantly higher percentage of total biomass production to seeds. 6 Possession of an evolutionarily stable strategy (ESS) of root competition suggests that different roots and parts of a plant assess and respond to opportunities in a manner that maximizes the good of the whole plant. Thus, plants may be more sophisticated and share more in common with animals in their non-cognitive behaviours than previously thought. A plant operating as a co-ordinated whole should, all else being equal, first proliferate roots in unoccupied soil, then in soil occupied by a conspecific competitor, and lastly in soil already occupied by its own roots.

453 citations


Journal ArticleDOI
TL;DR: It is shown that NKp44, but not NKp30, can also recognize the HA of both IV and SV and that the recognition of IV HA requires the sialylation of theNKp44 receptor in a similar way to that of NKp46.
Abstract: Natural killer (NK) cells destroy virus-infected and tumor cells without prior antigen stimulation. The NK cell cytotoxicity is regulated in large part by the expression of NK cell receptors that are able to bind major histocompatibility complex (MHC) class I glycoproteins. NK cells also express lysis triggering receptors specific for non-MHC ligands, including NKp30, NKp44, NKp46 and CD16. However, the nature of their ligands, recognized on target cells, is undefined. We have recently shown that the NKp46 protein, but not the CD16 protein, recognizes the hemagglutinin (HA) of influenza virus (IV) and the hemagglutinin-neuraminidase (HN) of Sendai virus (SV), and that the recognition of HA from IV requires the sialylation of NKp46 oligosaccharides. We have also demonstrated that binding of NKp46 to HA of IV is required for lysis of cells expressing the corresponding glycoproteins by a substantial subset of NK clones. Here we show that NKp44, but not NKp30, can also recognize the HA of both IV and SV and that the recognition of IV HA requires the sialylation of the NKp44 receptor in a similar way to that of NKp46. SV infection of 721.221 cells expressing MHC class I proteinsresulted in the abrogation of the inhibition by NK clones expressing high levels of NKp44. In addition, the binding of NKp44 to HA improves the ability of some NK clones to lyse IV infected cells.

449 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that the wind accelerates significantly in the course of reconnection, which dilates the timescale over which the reconnection process operates, and requires a much larger distance than was previously thought to convert the Poynting flux to particle flux.
Abstract: It is generally thought that most of the spin-down power of a pulsar is carried away in an MHD wind dominated by Poynting flux. In the case of an oblique rotator, a significant part of this energy can be considered to be in a low-frequency wave, consisting of stripes of a toroidal magnetic field of alternating polarity propagating in a region around the equatorial plane. Magnetic reconnection in such a structure has been proposed as a mechanism for transforming the Poynting flux into particle energy in the pulsar wind. We have reexamined this process and conclude that the wind accelerates significantly in the course of reconnection. This dilates the timescale over which the reconnection process operates so that the wind requires a much larger distance than was previously thought in order to convert the Poynting flux to particle flux. In the case of the Crab pulsar, the wind is still Poynting-dominated at the radius at which a standing shock is inferred from observation. An estimate of the radius of the termination shock for other pulsars implies that all except the millisecond pulsars have Poynting flux-dominated winds all the way out to the shock front.

433 citations


Journal ArticleDOI
TL;DR: Research issues in the Information Filtering research arena are presented, such as user modeling, evaluation standardization and integration with digital libraries and Web repositories, and the framework to classify IF systems according to several parameters is defined.
Abstract: An abundant amount of information is created and delivered over electronic media Users risk becoming overwhelmed by the flow of information, and they lack adequate tools to help them manage the situation Information filtering (IF) is one of the methods that is rapidly evolving to manage large information flows The aim of IF is to expose users to only information that is relevant to them Many IF systems have been developed in recent years for various application domains Some examples of filtering applications are: filters for search results on the internet that are employed in the Internet software, personal e-mail filters based on personal profiles, listservers or newsgroups filters for groups or individuals, browser filters that block non-valuable information, filters designed to give children access them only to suitable pages, filters for e-commerce applications that address products and promotions to potential customers only, and many more The different systems use various methods, concepts, and techniques from diverse research areas like: Information Retrieval, Artificial Intelligence, or Behavioral Science Various systems cover different scope, have divergent functionality, and various platforms There are many systems of widely varying philosophies, but all share the goal of automatically directing the most valuable information to users in accordance with their User Model, and of helping them use their limited reading time most optimally This paper clarifies the difference between IF systems and related systems, such as information retrieval (IR) systems, or Extraction systems The paper defines a framework to classify IF systems according to several parameters, and illustrates the approach with commercial and academic systems The paper describes the underlying concepts of IF systems and the techniques that are used to implement them It discusses methods and measurements that are used for evaluation of IF systems and limitations of the current systems In the conclusion we present research issues in the Information Filtering research arena, such as user modeling, evaluation standardization and integration with digital libraries and Web repositories

Journal ArticleDOI
TL;DR: In this paper, a review and evaluation of magnesium use and applications in the transportation industry that can significantly contribute to the environmental conservation is presented, which relates to the basic characteristics of magnesium being 35% lighter than aluminum and is used as structural material for vehicles and aerospace applications.

Journal ArticleDOI
TL;DR: It is reported that purified voltage-dependent anion channel (VDAC) reconstituted into lipid bilayers or liposomes is highly permeable to Ca(2+), and that the inhibition ofCa(2+) uptake by RuR and La(3+) may result from their interaction with VDAC Ca( 2+)-binding sites.
Abstract: Mitochondria play a central role in energy metabolism, Ca(2+) signalling, aging and cell death. To control cytosolic or mitochondrial Ca(2+) concentration, mitochondria possess several Ca(2+)-transport systems across the inner membrane. However, the pathway for Ca(2+) crossing the outer membrane has not been directly addressed. We report that purified voltage-dependent anion channel (VDAC) reconstituted into lipid bilayers or liposomes is highly permeable to Ca(2+). VDAC contains Ca(2+)-binding sites that bind Ruthenium Red (RuR), La(3+) and that RuR completely closed VDACs in single or multichannel experiments. Energized, freshly prepared mitochondria accumulate Ca(2+) (500-700 nmol/mg of protein), and subsequently released it. The release of Ca(2+) is accompanied by cyclosporin A-inhibited swelling, suggesting activation of permeability transition pore (PTP). RuR and ruthenium amine binuclear complex, when added to mitochondria after Ca(2+) accumulation has reached a maximal level and before PTP is activated, prevented the release of Ca(2+) and the accompanied mitochondrial swelling. RuR also prevented PTP opening promoted by atractyloside, an adenine nucleotide translocase inhibitor. These results suggest that VDAC, located in the mitochondrial outer membrane, controls Ca(2+) transport into and from the mitochondria, and that the inhibition of Ca(2+) uptake by RuR and La(3+) may result from their interaction with VDAC Ca(2+)-binding sites. Inhibition of PTP opening or assembly by RuR and ruthenium amine binuclear complex suggest the involvement of VDAC in PTP activity and/or regulation. The permeability of VDAC to Ca(2+) and its binding of Ca(2+), suggest that VDAC has a role in regulation of the mitochondrial Ca(2+) homoeostasis.

Journal ArticleDOI
TL;DR: NC measurement is a simple and time-saving screening measure that can be used to identify overweight and obese patients and requires additional evaluation of overweight or obesity status.
Abstract: Objective: There are numerous methods of assessing overweight and obesity. We undertook an observational study to test a method of identifying overweight or obese patients solely by measuring the circumference of the neck. Research Methods and Procedures: A test sample and a second validation sample included 979 subjects (460 men and 519 women), who visited a family medicine clinic in a southern Israeli urban district for any reason between the randomly chosen months of January and September 1998. Main outcome included neck, waist, and hip circumferences; body mass index (BMI); and waist:hip ratio measures. Results: Pearson's correlation coefficients indicated a significant association between neck circumference (NC) and: BMI (men, r = 0.83; women, r = 0.71; each, p < 0.0001), age (men, r = 0.33; women, r = 0.36; each, p < 0.0001), weight (men, r = 0.7; women, r = 0.81; each, p < 0.0001), waist circumference (men, r = 0.86; women, r = 0.85; each, p < 0.0001), hip circumference (men, r = 0.62; women, r = 0.56; each, p < 0.0001), and waist:hip ratio (men, r = 0.66; women, r = 0.87; each, p < 0.0001). NC ≥37 cm for men and ≥34 cm for women were the best cutoff levels for determining the subjects with BMI ≥25.0 kg/m2 using the receiver output curve analysis. In the validation unrelated group, the test characteristics were excellent with 98% sensitivity, 89% specificity, and 94% accuracy for men, and 100% sensitivity, 98% specificity, and 99% accuracy for women. NC ≥39.5 cm for men and ≥36.5 cm for women were the best cutoff levels for determining the subjects with BMI ≥30 kg/m2 using the receiver output curve analysis. In the validation unrelated group, the test characteristics were excellent with 93% sensitivity, 90% specificity, and 91% accuracy for men, and 93% sensitivity, 98% specificity, and 97% accuracy for women. Discussion: NC measurement is a simple and time-saving screening measure that can be used to identify overweight and obese patients. Men with NC <37 cm and women with NC <34 cm are not to be considered overweight. Patients with NC ≥37 cm for men and ≥34 cm for women require additional evaluation of overweight or obesity status.

Journal ArticleDOI
TL;DR: In this paper, the authors used satellite spectral measurements and ground-based sky measurements to demonstrate that Saharan dust absorption of solar radiation is several times smaller than the current international standards.
Abstract: Dust absorption of solar radiation is not well known due to limitations in the accuracy of in situ measurements. Here we report two new independent remote sensing techniques that provide sensitive measurements of dust absorption. One uses satellite spectral measurements, the second ground based sky measurements. Both techniques demonstrate that Saharan dust absorption of solar radiation is several times smaller than the current international standards. For example, at wavelength of 0.64 µm the dust single scattering albedo is reported here as 0.97±0.02 rather than 0.87±0.04 in recent review.

Journal ArticleDOI
TL;DR: The incidence of HIV remained high among IDUs in Baltimore over the past decade and risk factors for HIV seroconversion differed markedly by sex.
Abstract: Background Injection drug use directly or indirectly accounts for nearly half the annual human immunodeficiency virus (HIV) infections in the United States. Prospective studies that investigate both sexual and parenteral HIV risks among injection drug users (IDUs) are needed. We studied factors for HIV seroconversion among male and female IDUs in Baltimore, Md. Methods The HIV-negative IDUs (1447 male and 427 female) were recruited into a prospective study from 1988 to 1989 or in 1994. Participants underwent semiannual HIV tests and surveys through December 1998. Poisson regression was used to identify risk factors for HIV seroconversion, stratified by sex. Behaviors were treated as time-dependent covariates that varied at each semiannual period. Results Subjects were primarily African American (91%), and median age at enrollment was 35 years. Incidence of HIV was 3.14 per 100 person years (95% confidence interval, 2.78-3.53) and did not significantly differ by sex. Younger age independently predicted HIV seroconversion for both men and women. Among men, factors that independently predicted HIV seroconversion were the following: less than a high school education, recent needle sharing with multiple partners, daily injection, and shooting-gallery attendance. The incidence of HIV was double for men recently engaging in homosexual activity and cocaine injection. Among women, the incidence of HIV was more than double for those recently reporting sexually transmitted diseases. Conclusions The incidence of HIV remained high among IDUs in Baltimore over the past decade. Risk factors for HIV seroconversion differed markedly by sex. Predominant risks among men included needle sharing and homosexual activity; among women, factors consistent with high-risk heterosexual activity were more significant than drug-related risks. Human immunodeficiency virus interventions aimed at IDUs should be sex-specific and incorporate sexual risks.

Journal ArticleDOI
TL;DR: The results of the study demonstrate that postural adjustments require cognitive processing; young and old subjects showed similar interference effects on postural steadiness (postural sway) caused by the concurrent attention-demanding task.
Abstract: Background: Postural control and falls in the elderly constitute a major health problem. The interest in balance deficits is growing, as concern about the rising costs of health car

Journal ArticleDOI
TL;DR: Mutation screening of a novel gene (BBS2) with a wide pattern of tissue expression revealed homozygous mutations in two inbred pedigrees, including the large Bedouin kindred used to initially identify the BBS2 locus.
Abstract: Bardet-Biedl syndrome (BBS) is a genetically heterogeneous autosomal recessive disorder with the primary clinical features of obesity, pigmented retinopathy, polydactyly, hypogenitalism, mental retardation and renal anomalies. Associated features of the disorder include diabetes mellitus, hypertension and congenital heart disease. There are six known BBS loci, mapping to chromosomes 2, 3, 11, 15, 16 and 20. The BBS2 locus was initially mapped to an 18 cM interval on chromosome 16q21 with a large inbred Bedouin kindred. Further analysis of the Bedouin population allowed for the fine mapping of this locus to a 2 cM region distal to marker D16S408. Physical mapping and sequence analysis of this region resulted in the identification of a number of known genes and expressed sequence tag clusters. Mutation screening of a novel gene (BBS2) with a wide pattern of tissue expression revealed homozygous mutations in two inbred pedigrees, including the large Bedouin kindred used to initially identify the BBS2 locus. In addition, mutations were found in three of 18 unrelated BBS probands from small nuclear families.

Journal ArticleDOI
TL;DR: The positional cloning and identification of mutations in BBS patients in a novel gene designated BBS4 is reported, which has no significant similarity to other chaperonins or known proteins.
Abstract: Bardet–Biedl syndrome (BBS, MIM 209900) is a heterogeneous autosomal recessive disorder characterized by obesity, pigmentary retinopathy, polydactyly, renal malformations, mental retardation, and hypogenitalism1,2,3,4. The disorder is also associated with diabetes mellitus, hypertension, and congenital heart disease4,5,6. Six distinct BBS loci map to 11q13 (BBS1), 16q21 (BBS2), 3p13–p12 (BBS3), 15q22.3–q23 (BBS4), 2q31 (BBS5), and 20p12 (BBS6)7,8,9,10,11,12,13. Although BBS is rare in the general population (<1/100,000), there is considerable interest in identifying the genes causing BBS because components of the phenotype, such as obesity and diabetes, are common. We and others have demonstrated that BBS6 is caused by mutations in the gene MKKS (refs. 12,13), mutation of which also causes McKusick–Kaufman syndrome (hydrometrocolpos, post-axial polydactyly, and congenital heart defects)14,15. MKKS has sequence homology to the alpha subunit of a prokaryotic chaperonin in the thermosome Thermoplasma acidophilum15. We recently identified a novel gene that causes BBS216. The BBS2 protein has no significant similarity to other chaperonins or known proteins. Here we report the positional cloning and identification of mutations in BBS patients in a novel gene designated BBS4.

Journal ArticleDOI
TL;DR: In this article, the authors examined the performance factors of small Israeli tourism ventures using an integrated model that combines four theoretical approaches, each focusing on a different central facet: environmental milieu, institutional support, entrepreneurial human capital, and the venture's bundle of services.

01 Jan 2001
TL;DR: In this article, a universal controller is constructed, formulated in input-output terms only, which causes the output of any uncertain smooth SISO minimum-phase dynamic system with known relative degree to vanish in finite time.
Abstract: An universal controller is constructed, formulated in input-output terms only, which causes the output of any uncertain smooth SISO minimum-phase dynamic system with known relative degree to vanish in finite time. That allows exact tracking of arbitrary real-time smooth signals. Only one parameter is to be adjusted. The approach being based on higher-order finite-time-convergence sliding modes, the control can be made arbitrarily smooth, providing for the arbitrarily-high tracking- accuracy order with respect to the sampling step.

Posted Content
TL;DR: For example, this article showed that when different cultural groups separately determine the social content of their school curricula excessive polarization can result, with less than optimal growth, in a political context in which all agents are identified with one group or another.
Abstract: Analysis of the contribution of education to growth through its role in promoting a common culture indicates that when different cultural groups separately determine the social content of their school curricula excessive polarization can result, with less than optimal growth. The optimal trajectory involves a gradual, reciprocal convergence of school curricula towards the middle ground. However, this may be difficult to implement in a political context in which all agents are identified with one group or another. When curricula are determined by legislative bargaining, centralization of schooling may result in overly rapid homogenization in some cases, and - perhaps surprisingly - excessive polarization in others.

Journal ArticleDOI
TL;DR: It is shown that the final outcome of any subgame perfect equilibrium of this mechanism always coincides with the vector of the Shapley value payoffs.

Journal ArticleDOI
TL;DR: There is no single high-risk group that is most likely to violate all three safe driving behaviors, and, contrary to some stereotypes, the only consistent effect was that of sex: women reported higher observance rates of all three behaviors.

Journal ArticleDOI
TL;DR: Recombinant PhtA, PhtB, and PhtD elicited protection against certain pneumococcal capsular types in a mouse model of systemic disease and may serve as effective vaccines against the most prevalent pneumococCal serotypes.
Abstract: Four pneumococcal genes (phtA, phtB, phtD, and phtE) encoding a novel family of homologous proteins (32 to 87% identity) were identified from the Streptococcus pneumoniae genomic sequence. These open reading frames were selected as potential vaccine candidates based upon their possession of hydrophobic leader sequences which presumably target these proteins to the bacterial cell surface. Analysis of the deduced amino acid sequences of these gene products revealed the presence of a histidine triad motif (HxxHxH), termed Pht (pneumococcal histidine triad) that is conserved and repeated several times in each of the four proteins. The four pht genes (phtA, phtB, phtD, and a truncated version of phtE) were expressed in Escherichia coli. A flow cytometry-based assay confirmed that PhtA, PhtB, PhtD and, to a lesser extent, PhtE were detectable on the surface of intact bacteria. Recombinant PhtA, PhtB, and PhtD elicited protection against certain pneumococcal capsular types in a mouse model of systemic disease. These novel pneumococcal antigens may serve as effective vaccines against the most prevalent pneumococcal serotypes.

Journal ArticleDOI
TL;DR: A novel ligand-binding domain, named the 'ACT domain', was recently identified by a PSI-BLAST search and is proposed to be a conserved regulatory ligand binding fold.

Journal ArticleDOI
TL;DR: It is shown that a micromolar concentration of extracellular zinc triggers a massive release of calcium from thapsigargin-sensitive intracellular pools in the colonocytic cell line HT29, indicating that a previously uncharacterizedextracellular, G protein-coupled, Zn2+-sensing receptor is functional in colonocytes.
Abstract: Changes in extracellular zinc concentration participate in modulating fundamental cellular processes such as proliferation, secretion, and ion transport in a mechanism that is not well understood. Here, we show that a micromolar concentration of extracellular zinc triggers a massive release of calcium from thapsigargin-sensitive intracellular pools in the colonocytic cell line HT29. Calcium release was blocked by a phospholipase-C inhibitor, indicating that formation of inositol 1,4,5-triphosphate is required for zinc-dependent calcium release. Zinc influx was not observed, indicating that extracellular zinc triggered the release. The Ca(i)2+ release was zinc specific and could not be triggered by other heavy metals. Furthermore, zinc failed to activate the Ca(2+)-sensing receptor heterologously expressed in HEK293 cells. The zinc-induced Ca(i)2+ rise stimulated the activity of the Na(+)/H(+) exchanger in HT29 cells. Our results indicate that a previously uncharacterized extracellular, G protein-coupled, Zn(2+)-sensing receptor is functional in colonocytes. Because Ca(i)2+ rise is known to regulate key cellular and signal-transduction processes, the zinc-sensing receptor may provide the missing link between extracellular zinc concentration changes and the regulation of cellular processes.

Journal ArticleDOI
TL;DR: There was evidence for nonoptimal use of the information from the warning system, whether it was valid or not valid, and a possible distinction between two dimensions of users' trust in warning systems: compliance and reliance is indicated.
Abstract: The effects of a warning's validity and display characteristics on the responses to binary warnings were studied in a categorization task that resembled the control of a simulated production environment. Students performed a visual signal detection task and were aided by a binary warning indicator. Experimental conditions differed in the validity of the warning and its proximity to the judged stimulus. Participants' performance improved over the course of the experiment, and they partly adjusted their responses to the validity of the warnings but continued to respond to nonvalid warnings throughout the experiment. It was particularly difficult to ignore the nonvalid information when it was integrated with the continuous information. There was evidence for nonoptimal use of the information from the warning system, whether it was valid or not valid. The results indicate a possible distinction between two dimensions of users' trust in warning systems: compliance and reliance. Actual or potential implications of this research include improved warning design based on analysis of system and operator characteristics.

Journal ArticleDOI
TL;DR: The paper shows that, by an appropriate choice of a rich assertional language, it is possible to extend the utility of symbolic model checking beyond the realm of BDD-represented finite-state systems into the domain of infinite- state systems, leading to a powerful technique for uniform verification of unbounded (parameterized) process networks.

Journal ArticleDOI
07 Jun 2001-Oncogene
TL;DR: It is suggested that lycopene inhibits cell cycle progression via reduction of the cyclin D level and retention of p27 in cyclin E–cdk2, thus leading to inhibition of G1 CDK activities.
Abstract: Numerous studies have demonstrated the anticancer activity of the tomato carotenoid, lycopene. However, the molecular mechanism of this action remains unknown. Lycopene inhibition of human breast and endometrial cancer cell growth is associated with inhibition of cell cycle progression at the G(1) phase. In this study we determined the lycopene-mediated changes in the cell cycle machinery. Cells synchronized in the G(1) phase by serum deprivation were treated with lycopene or vehicle and restimulated with 5% serum. Lycopene treatment decreased serum-induced phosphorylation of the retinoblastoma protein and related pocket proteins. This effect was associated with reduced cyclin-dependent kinase (cdk4 and cdk2) activities with no alterations in CDK protein levels. Lycopene caused a decrease in cyclin D1 and D3 levels whereas cyclin E levels did not change. The CDK inhibitor p21(Cip1/Waf1) abundance was reduced while p27(Kip1) levels were unaltered in comparison to control cells. Serum stimulation of control cells resulted in reduction in the p27 content in the cyclin E--cdk2 complex and its accumulation in the cyclin D1--cdk4 complex. This change in distribution was largely prevented by lycopene treatment. These results suggest that lycopene inhibits cell cycle progression via reduction of the cyclin D level and retention of p27 in cyclin E--cdk2, thus leading to inhibition of G(1) CDK activities.