Showing papers by "Bar-Ilan University published in 1995"
09 Jul 1995
TL;DR: A general method for efficiently training probabilistic classifiers, by selecting for training only the more informative examples in a stream of unlabeled examples, which is particularly attractive because it evaluates the expected information gain from a training example implicitly.
Abstract: In many real-world learning tasks, it is expensive to acquire a sufficient number of labeled examples for training. This paper proposes a general method for efficiently training probabilistic classifiers, by selecting for training only the more informative examples in a stream of unlabeled examples. The method, committee-based sampling , evaluates the informativeness of an example by measuring the degree of disagreement between several model variants. These variants (the committee) are drawn randomly from a probability distribution conditioned by the training set selected so far (Monte-Carlo sampling). The method is particularly attractive because it evaluates the expected information gain from a training example implicitly, making the model both easy to implement and generally applicable. We further show how to apply committee-based sampling for training Hidden Markov Model classifiers, which are commonly used for complex classification tasks. The method was implemented and tested for the task of tagging words in natural language sentences with parts-of-speech. Experimental evaluation of committee-based sampling versus standard sequential training showed a substantial improvement in training efficiency.
544 citations
Proceedings Article•
20 Aug 1995TL;DR: This research combines the KDD and text categorization paradigms and suggests advances to the state of the art in both areas.
Abstract: The information age is characterized by a rapid growth in the amount of information available in electronic media. Traditional data handling methods are not adequate to cope with this information flood. Knowledge Discovery in Databases (KDD) is a new paradigm that focuses on computerized exploration of large amounts of data and on discovery of relevant and interesting patterns within them. While most work on KDD is concerned with structured databases, it is clear that this paradigm is required for handling the huge amount of information that is available only in unstructured textual form. To apply traditional KDD on texts it is necessary to impose some structure on the data that would be rich enough to allow for interesting KDD operations. On the other hand, we have to consider the severe limitations of current text processing technology and define rather simple structures that can be extracted from texts fairly automatically and in a reasonable cost. We propose using a text categorization paradigm to annotate text articles with meaningful concepts that are organized in hierarchical structure. We suggest that this relatively simple annotation is rich enough to provide the basis for a KDD framework, enabling data summarization, exploration of interesting patterns, and trend analysis. This research combines the KDD and text categorization paradigms and suggests advances to the state of the art in both areas.
493 citations
TL;DR: In this article, the authors assess the impact of attachment style on the ways young adults react to the stress of 4-month combat training and find that ambivalent persons reported more emotion-focused coping, appraised the training in more threatening terms, assessed themselves as less capable of coping with the training, and were evaluated by their peers as less fitting for military leadership.
Abstract: The current study assesses the impact of attachment style on the ways young adults react to the stress of 4-month combat training. Ninety-two Israeli recruits completed an attachment scale at the beginning of the training. Their appraisal of the training their ways of coping with it, and peer evaluations of their leadership ability were assessed 4 months later. Compared with secure persons, ambivalent persons reported more emotion-focused coping, appraised the training in more threatening terms, appraised themselves as less capable of coping with the training, and were evaluated by their peers as less fitting for military leadership. Avoidant persons reported more distancing coping and less support seeking and appraised the training in more threatening terms. They did not differ from secure persons in the appraisal of their ability to cope with the training or in the nominations they received for leadership positions. Results are discussed in the framework of attachment theory.
439 citations
TL;DR: One hundred and twenty Israeli students were classified into secure, avoidant, and anxious-ambivalent attachment groups as discussed by the authors, and they completed scales that tap the construct of repressive defensiveness and recalled early personal experiences of anger, anxiety, sadness, and happiness.
Abstract: One hundred and twenty Israeli students were classified into secure, avoidant, and anxious-ambivalent attachment groups. They completed scales that tap the construct of repressive defensiveness and recalled early personal experiences of anger, anxiety, sadness, and happiness. Secure people reported moderate defensiveness and low anxiety and had easy access to negative memories without being overwhelmed by the spreading of the dominant emotional tone to nondominant emotions. Anxious-ambivalent people were unable to repress negative affects, reported high anxiety, had easy access to negative memories, and could not inhibit emotional spreading. Avoidant people reported high levels of defensiveness and anxiety and showed low accessibility to negative memories. The discussion emphasizes the parallel between a person's interaction with the social world and the makeup of his or her inner world.
421 citations
TL;DR: The data suggest that TNF induces serine phosphorylation of IRS-1 through inhibition of Ser/Thr phosphatases or activation of serine kinases other than protein kinase C, which interferes with insulin-induced tyrosine phosphORYlation of IRS-1 and impairs insulin action.
414 citations
TL;DR: Hazan and Shaver as discussed by the authors found that adults who defined themselves as secure in their close relationships reported more secure interactions with their parents than adults who described themselves as insecure, either avoidant or anxious-ambivalent.
Abstract: Six studies examined the association between attachment style and several aspects of the mental representation of the self in adolescents. Studies 1 and 2 focused on the hedonic tone of the selfstructure, Studies 3 and 4 focused on its complexity, and Studies 5 and 6 focused on discrepancies between domains and standpoints of the self. Results indicated that secure and avoidant persons had a more positive view of themselves than anxious-ambivalent persons. In addition, secure persons were found to have a more balanced, complex, and coherent self-structure than insecure persons, either avoidant or anxious-ambivalent. The discussion emphasizes the connection between the internalization of attachment experiences and the construction of the self. Research on adult attachment uses Bowlby's (1973) construct of working models—mental representations of attachment figures and the self—to explain how past interactions with significant others influence social and emotional development. Initial studies of adult attachment focused on the way people think about and behave in their relationships (e.g., Hazan & Shaver, 1987). The present series of studies focuses on a neglected aspect of attachment working models: the mental representation of the self. Attachment Theory and Research Attachment theory (Bowlby, 1969, 1973, 1980) proposes that the quality of infant-caregiver interactions results in mental working models that organize cognitions, affects, and behavior in later relationships; guide affect regulation; and shape selfimage. Following these ideas, Hazan and Shaver (1987) examined attachment working models in adults, using the tripartite classification of infant attachment style (Ainsworth, Blehar, Waters, & Wall, 1978). The secure style is defined by confidence in the availability of attachment figures in times of need, comfort with closeness, interdependence, and trust. The avoidant style is characterized by insecurity in others' intentions and preference for emotional distance. The anxious-ambivalent style portrays a strong desire for intimacy together with insecurity about others' responses to this desire and high fear of rejection. Hazan and Shaver (1987) found that self-reports of adult attachment style were related to reports of parent-child attachment. Adults who defined themselves as secure in their close relationships reported more secure interactions with their parents than adults who described themselves as insecure, either avoidant or anxious-ambivalent. Building on Hazan and Shaver's (1987) work, a wealth of studies have assessed several correlates of adult attachment
412 citations
TL;DR: Application of fractal scaling analysis and related techniques provides new approaches to assessing cardiac risk and forecasting sudden cardiac death, as well as motivating development of novel physiologic models of systems that appear to be heterodynamic rather than homeostatic.
348 citations
TL;DR: A strategic model of negotiation is proposed that takes the passage of time during the negotiation process itself into account, and a distributed negotiation mechanism is introduced that is simple, efficient, stable, and flexible in various situations.
330 citations
TL;DR: This article used a Zipf plot to demonstrate that the upper tail of the size distribution of firms is too thin relative to the log normal rather than too fat, as had previously been believed.
315 citations
TL;DR: In this article, the authors found that two components of hardiness -commitment and control measured at the beginning of training--predicted mental health at the end of the training through mediation of appraisal and coping variables.
Abstract: Israeli recruits (N = 276) completed questionnaires on hardiness, mental health, cognitive appraisal, and ways of coping at the beginning and end of a demanding, 4-month combat training period. Path analysis revealed that 2 components of hardiness--commitment and control measured at the beginning of the training--predicted mental health at the end of the training through the mediation of appraisal and coping variables. Commitment improved mental health by reducing the appraisal of threat and the use of emotion-focused strategies and by increasing secondary appraisal. Control improved mental health by reducing the appraisal of threat and by increasing secondary appraisal and the use of problem-solving and support-seeking strategies.
315 citations
TL;DR: The surface normal structure of the mercury liquid-vapor interface has been investigated by measuring the x-ray reflectivity out to a momentum transfer of {ital q}{sub {ital z}}=2.5 A, providing direct experimental proof of surface layering in liquid metals.
Abstract: The surface normal structure of the mercury liquid-vapor interface has been investigated by measuring the x-ray reflectivity out to a momentum transfer of ${q}_{z}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2.5$ ${\mathrm{\AA{}}}^{--1}$. The results provide direct experimental proof of surface layering in liquid metals. The layer spacing is given by the atomic dimensions of the Hg atoms. The minimum layer width agrees well with the predictions of capillary wave theory; the layering amplitude decays into the bulk with a characteristic length of 3--3.5 \AA{}, which is close to the decay length of the bulk pair correlation function.
TL;DR: Findings showed that secure persons perceived higher levels of emotional and instrumental support from the assessed figures and reported seeking more emotional and Instrumental support than avoidant and ambivalent persons did.
Abstract: Effects of adult attachment style on the perception of and search for social support were examined. One hundred and fifty undergraduate students completed self-report scales tapping their attachment styles, the extent to which they perceive the availability of emotional and instrumental support from significant figures (father, mother, same-sex friend, opposite-sex friend, romantic partner), and the extent to which they look for instrumental and emotional assistance in times of need. Findings showed that secure persons perceived higher levels of emotional and instrumental support from the assessed figures and reported seeking more emotional and instrumental support than avoidant and ambivalent persons did. Results are discussed in the context of an attachment perspective of social support.
05 Dec 1995
TL;DR: It is shown that making optimal use of skips is NP-hard, and two algorithms called Skip-Over Algorithms (one a variant of earliest deadline first and one of rate monotonic scheduling) that exploit skips are looked at.
Abstract: In applications ranging from video reception to telecommunications and packet communication to aircraft control, tasks enter periodically and have fixed response time constraints, but missing a deadline is acceptable, provided most deadlines are met. We call such tasks "occasionally skippable". We look at the problem of uniprocessor scheduling of occasionally skippable periodic tasks in an environment having periodic tasks. We show that making optimal use of skips is NP-hard. We then look at two algorithms called Skip-Over Algorithms (one a variant of earliest deadline first and one of rate monotonic scheduling) that exploit skips. We give schedulability bounds for both.
Proceedings Article•
20 Aug 1995TL;DR: This paper gives an efficient solution to the problem of task allocation among autonomous agents, and suggests that the agents will form coalitions in order to perform tasks or improve the efficiency.
Abstract: Autonomous agents working in multi-agent environments may need to cooperate in order to fulfill tasks. Given a set of agents and a set of tasks which they have to satisfy, we consider situations where each task should be attached to a group of agents which will perform the task. The allocation of tasks to groups of agents is necessary when tasks cannot be performed by a single agent. It may also be useful to assign groups of agents to tasks when the group's performance is more efficient than the performance of single agents. In this paper we give an efficient solution to the problem of task allocation among autonomous agents, and suggest that the agents will form coalitions in order to perform tasks or improve the efficiency. We present a distributed algorithm with a low ratio bound and with a low computational complexity. Our algorithm is an any-time algorithm, it is simple, efficient and easy to implement.
TL;DR: The amplitude of the electron density oscillations decays with a characteristic length of 6 A, which is unexpectedly twice that of recent results for Hg, and the difference may be related to covalent bonding or supercooling.
Abstract: Surface-induced atomic layering in liquid gallium has been observed using x-ray reflectivity, ultrahigh vacuum conditions, and sputtered clean surfaces. Reflectivity data, collected on a supercooled liquid sample to momentum transfers as large as {ital q}{sub {ital z}}=3.0 A{sup {minus}1}, exhibit a strong maximum near 2.4 A{sup {minus}1} indicating a layer spacing that is comparable to its atomic dimensions. The amplitude of the electron density oscillations decays with a characteristic length of 6 A. This is unexpectedly twice that of recent results for Hg, and the difference may be related to covalent bonding or supercooling.
TL;DR: In this article, the correlation between Li-cycling efficiency, morphology, interfacial properties and surface chemistry in a variety of Li battery electrolyte solutions is reviewed, and the principal points are: (i) the surface chemistry of Li is determined by a delicate balance between reduction processes of the solvents, salts and common contaminants; (ii) surface films initially formed are subjected to ageing processes which gradually change their structure and properties; (iii) the heterogeneous chemical structure of the Li electrode's surface films induces non-uniform Li deposition; (iv) the cycling
TL;DR: This paper presents an optimal on-line scheduling algorithm for overloaded uniprocessor systems that is optimal in the sense that it gives the best competitive ratio possible relative to an off-line scheduler.
Abstract: Consider a real-time system in which every task has a value that it obtains only if it completes by its deadline. The problem is to design an on-line scheduling algorithm (i.e., the scheduler has no knowledge of a task until it is released) that maximizes the guaranteed value obtained by the system.
When such a system is underloaded (i.e., there exists a schedule for which all tasks meet their deadlines), Dertouzos [Proceedings IFIF Congress, 1974, pp.\ 807--813] showed that the earliest deadline first algorithm will achieve 100% of the possible value. Locke [Ph. D. thesis, Computer Science Dept., Carnegie-Mellon Univ., Pittsburgh, PA] showed that earliest deadline first performs very badly, however, when the system is overloaded, and he proposed heuristics to deal with overload.
This paper presents an optimal on-line scheduling algorithm for overloaded uniprocessor systems. It is optimal in the sense that it gives the best competitive ratio possible relative to an off-line scheduler.
TL;DR: In this paper, the behavior of graphite electrodes in various electrolyte solutions was explored using in situ x-ray diffraction in conjunction with chronopotentiometry, and the results revealed that graphite anodes behave reversibly in these solutions and are stable on Li intercalation−deintercalation cycling.
Abstract: The behavior of graphite electrodes in various electrolyte solutions was explored using in situ x‐ray diffraction in conjunction with chronopotentiometry The solvent systems studied included ethylene and diethyl carbonate mixtures (EC‐DEC), propylene carbonate (PC), tetrahydrofuran (THF), and dimethyl carbonate (DMC) These studies revealed that the above systems can be divided into three classes EC‐DEC and water contaminated DMC are solvent systems in which highly passivating and protective surface films are precipitated on the carbon at potentials much higher than the intercalation potentials Therefore, graphite electrodes behave reversibly in these solutions and are stable on Li intercalation‐deintercalation cycling An opposite case occurs with PC and THF, where the carbon is destroyed before or during the intercalation processes, and therefore graphite anodes behave totally irreversibly in these systems In an intermediate case (dry DMC is a good example), a passivating layer is formed on the carbon at a potential higher than where Li intercalation occurs, but it is not sufficient to protect the carbon totally and therefore the electrode is slowly destroyed by cycling
TL;DR: In this article, the authors examined the stages preceding and following the intention to withdraw from an organization and found that a nurse first decides to leave the ward, then the hospital, and finally the profession.
Abstract: The stages preceding and following the intention to withdraw from an organization have not been adequately examined. Data were collected at two time periods from a sample of 146 nurses working in a general hospital located in a large metropolitan area in Israel. Essentially, intention to withdraw from three levels — ward, hospital and profession — were examined. LISREL was used to test alternative longitudinal models for the best fitting set of linkages among variables. The findings supported a progression model of withdrawal intention. According to this conceptualization, a nurse first decides to leave the ward, then the hospital, and, finally, the profession. Theoretical and practical implications of the results were presented.
TL;DR: Sports activities account for a large number and substantial proportion of all injuries to children and youth and cause and nature of injury are strongly related to age.
Abstract: OBJECTIVES: To estimate and describe morbidity from sports and recreation injuries in children and adolescents. DESIGN: Survey conducted by the National Center for Health Statistics--the Child Health Supplement to the 1988 National Health Interview Survey. SETTING: The general community. PARTICIPANTS: Representative sample of the noninstitutionalized civilian US population. Five percent of the eligible households did not participate. The subject of this report is 11,840 children and adolescents aged 5 to 17 years. MAIN OUTCOME MEASURES: Medically attended nonfatal injuries resulting from sports and recreation, and serious sports injuries, defined as injuries resulting in hospitalization, surgical treatment, missed school, or half a day or more in bed. Sports and recreation injuries were defined as those occurring in a place of recreation or sports, or receiving any of the following International Classification of Diseases, Ninth Revision (ICD-9) E-codes: struck in sports, fall in sports, bicycle-related injury, riding an animal, water sports, overexertion, fall from playground equipment or other vehicles, primarily skates and skateboards. RESULTS: The estimated annual number of all injuries from sports and recreation in US children and adolescents is 4,379,000 (95% confidence interval = 3,147,000 to 5,611,000); from serious sport injuries, 1,363,000 (95% confidence interval = 632,000 to 2,095,000). Sports account for 36% of injuries from all causes. Cause and nature of injury are strongly related to age. Sports do not account for a disproportionate number of serious or repeated injuries compared with other causes of injuries. CONCLUSION: Sports activities account for a large number and substantial proportion of all injuries to children and youth.
TL;DR: Results indicate substantial stressor specificity of PVN catecholaminergic and of HPA responses to different stressors and are inconsistent with a founding tenet of Selye's stress theory, the doctrine of nonspecificity.
Abstract: The hypothalamic-pituitary adrenocortical (HPA) system and sympathoneural and adrenomedullary systems are major effector systems that serve to maintain homeostasis during stress. Corticotropin-releasing hormone (CRH) in the paraventricular nucleus (PVN) of the hypothalamus, a determinant of both HPA and autonomic responses to stress, is under the control of many neurotransmitters and neuropeptides. Norepinephrine (NE) potently stimulates CRH neurons in the PVN; however, the physiologic role of NE in stress-induced activation of the HPA is unknown. In the present study we exposed animals to various stressors (immobilization (IMMO), cold (COLD), hemorrhage (HEM), hypoglycemia elicited by insulin administration (INS), pain and tissue damage caused by formalin injection (FORM) and sc injection of physiological saline (SAL), all of which are known to activate the HPA axis. Injection of physiological saline iv was used as a control. In vivo microdialysis was used to assess stressor- and intensity-specific activation of the PVN noradrenergic system, based on measurements of NE, its intraneuronal metabolite dihydroxyphenylglycol (DHPG), and the dopamine metabolite, dihydroxyphenylacetic acid (DOPAC). Simultaneously with microdialysate collections, blood samples were obtained via catheters in the femoral artery to measure plasma ACTH and corticosterone (CORT) levels as dependent measures, to assess stress-induced activation of the HPA axis. At their highest intensities, all the stressors significantly increased levels of PVN microdialysate NE, DHPG, and DOPAC, and plasma ACTH and CORT. PVN NE levels varied across stressors, with IMMO and FORM more potent than INS, COLD, or HEM. INS and HEM evoked proportionately larger plasma ACTH responses than did IMMO, FORM, and COLD. Plasma CORT responses were largest during IMMO, FORM, and HEM. Except for COLD and HEM, there was a strong correlation of plasma ACTH levels with levels of NE, DHPG, and DOPAC in PVN microdialysate. The data suggest that, except for COLD or HEM, there is a strong positive correlation of PVN noradrenergic activation and activity of the HPA axis. With stressors such as IMMO and FORM, NE synthesis, reflected by DOPAC changes, is strongly positively correlated with activity of the HPA axis. Furthermore, the results indicate substantial stressor specificity of PVN catecholaminergic and of HPA responses to different stressors and are inconsistent with a founding tenet of Selye's stress theory, the doctrine of nonspecificity, which defines stress as the nonspecific response of the body to any demand.
TL;DR: In this paper, a distinction is made between human capital depreciation related to a worker's aging and depreciation due to the obsolescence of the worker's education, which is incorporated in the Mincerian model of earnings.
TL;DR: Topical 5-aminolevulinic acid application in three different creams was carried out on mice bearing subcutaneously transplanted C26 colon carcinoma to study protoporphyrin IX production in the skin and in the tumour by laser-induced fluorescence (LIF) and chemical extraction.
Abstract: Topical 5-aminolevulinic acid (ALA) application in three different creams was carried out on mice bearing subcutaneously transplanted C26 colon carcinoma. The creams contained (a) 20% ALA alone, (b) ALA with 2% dimethylsulphoxide (DMSO) and (c) ALA, DMSO and 2% edetic acid disodium salt (EDTA). Protoporphyrin IX (PP) production in the tumour and in the skin overlying the tumour was studied by two methods: laser-induced fluorescence (LIF) and chemical extraction. The kinetics of PP production in the skin and in the tumour, as studied by the LIF method, was similar for all three cream preparations. The PP fluorescence intensity in the tissues reached its maximum 4-6 h after application of the creams. Quantitative analysis showed that the PP concentration after treatment was more pronounced in the skin than in the tumour. The efficiency of porphyrin production in the skin by the creams used was in the following order: ALA-DMSO-EDTA > ALA-DMSO > ALA. In the tumour the enhancing effect of DMSO and EDTA on PP accumulation induced by ALA was observed mainly in the upper 2 mm section. However, the concentration of PP in the tumour was found to be approximately the same for ALA-DMSO and ALA-DMSO-EDTA cream combinations. The possible mechanisms of the effect of DMSO and EDTA are discussed.
TL;DR: The evaluation suggests that this method performs better than existing, frequency-based, smoothing methods, and may provide an alternative to class-based models.
TL;DR: The purpose is to describe some recent progress in applying fractal concepts to systems of relevance to biology and medicine, with a particular focus on the long-range power-law correlations found recently in DNA sequences containing noncoding material.
Abstract: Our purpose is to describe some recent progress in applying fractal concepts to systems of relevance to biology and medicine. We review several biological systems characterized by fractal geometry, with a particular focus on the long-range power-law correlations found recently in DNA sequences containing noncoding material. Furthermore, we discuss the finding that the exponent alpha quantifying these long-range correlations ("fractal complexity") is smaller for coding than for noncoding sequences. We also discuss the application of fractal scaling analysis to the dynamics of heartbeat regulation, and report the recent finding that the normal heart is characterized by long-range "anticorrelations" which are absent in the diseased heart.
TL;DR: In this paper, the authors investigated the impact of temporary-help work arrangement on salarids by comparing a sample of 90 temporary help employees with a larger sample of 134 permanent employees with respect to work involvement, work satisfaction, and stress measures.
Abstract: On souhaite, avec cette recherche, completer les travaux empiriques encore rares concernant l'impact du travail interimaire sur les salarids concerned. On a compare un echantillon de 90 interimaires a un autre echantillon compose de 134 titulaires pour ce qui est de l'implication dans le travail, de la satisfaction professionnelle et du stress. Conformement au schema theorique et aux hypotheses operatoires issus de leurs propres declarations, les interimaires ont ete separes en deux sous-groupes sur la base du (non) volontariat pour cette forme de travail. Une analyse de variance multivariee (MANOVA) et une analyse de covariance multivariee (MANCOVA) ont mis en evidence des differences significatives au niveau de la satisfaction, mais pas de la motivation, ni du stress lie au role.
The current research is an attempt to extend the scant empirical literature addressing the impact of the temporary-help work arrangement on the temporary-help employees (THEs) employed under that arrangement. A sample of 90 THEs was compared to a sample of 134 permanent employees with respect to work involvement, work satisfaction, and stress measures. In accordance with the conceptual framework and the operational hypotheses that were derived and based on their own statements, THEs were divided into those who work on that arrangement voluntarily as opposed to those who worked as THEs involuntarily. Multivariate analysis of variance (MANOVA) and multivariate analysis of covariance (MANCOVA) revealed significant differences only with regard to satisfaction measures and not for work involvement or role stress measures.
TL;DR: Results indicated that both the humor and repulsive groups showed a significant increase in pain tolerance as compared to the other groups, and Discussion focused on the type of distraction that would be meaningful for increasing pain tolerance and on the place of humor in pain control.
Abstract: Substantial research has demonstrated that cognitive psychological techniques including distraction can increase pain tolerance. In recent years, there also have been claims that humor and laughter possess unique characteristics for coping with pain and stress. Theoretically, explanations include the release of endorphins, the lowering of tension, as well as the distraction that results from humor. The question is whether humor is more effective than simple distraction. For this purpose humor was contrasted with a repulsive stimulus and a neutral stimulus controlled for interest level, that would also have distraction capabilities but not the unique aspects of humor. Pain tolerance was tested using cold pressor stimulation. Four groups (20 subjects in each) were tested. Three groups were shown a film: (1) a humorous film, (2) a repulsive film, (3) a neutral film. Group 4 was not shown any film. Results indicated that both the humor and repulsive groups showed a significant increase in pain tolerance as compared to the other groups. The repulsive group yielded the largest increase in pain tolerance although not different from the humor group. Except for sex differences, pain ratings did not show any group effects. Discussion focused on the type of distraction that would be meaningful for increasing pain tolerance and on the place of humor in pain control.
TL;DR: This work addresses the claim of Voss that there is no difference in the statistical properties of coding and non-coding regions of DNA by systematically applying the DFA algorithm, as well as standard FFT analysis, to every DNA sequence in the entire GenBank database.
Abstract: We review evidence supporting the idea that the DNA sequence in genes containing non-coding regions is correlated, and that the correlation is remarkably long range--indeed, nucleotides thousands of base pairs distant are correlated. We do not find such a long-range correlation in the coding regions of the gene. We resolve the problem of the "non-stationarity" feature of the sequence of base pairs by applying a new algorithm called detrended fluctuation analysis (DFA). We address the claim of Voss that there is no difference in the statistical properties of coding and non-coding regions of DNA by systematically applying the DFA algorithm, as well as standard FFT analysis, to every DNA sequence (33301 coding and 29453 non-coding) in the entire GenBank database. Finally, we describe briefly some recent work showing that the non-coding sequences have certain statistical features in common with natural and artificial languages. Specifically, we adapt to DNA the Zipf approach to analyzing linguistic texts. These statistical properties of non-coding sequences support the possibility that non-coding regions of DNA may carry biological information.
TL;DR: It is suggested that under certain circumstances, dopamine and/or its metabolites, may induce a process of apoptotic cell death of the dopamine-producing cells in the substantia nigra, which may cause the progressive nigral degeneration in Parkinson's disease.
TL;DR: The results show that cortical F-actin has two roles in regulating sperm exocytosis, one is to form a scaffolding to hold phospholipase C at the membrane, and it also functions as a physical barrier to membrane fusion which is removed by the increases in intracellular calcium and pH which precede fusion.
Abstract: We used a cell-free system to study membrane fusion during sperm exocytosis (acrosome reaction). Extracted bovine sperm plasma and outer acrosomal membranes were labeled with chlorophyll a or DCY, respectively. The occurrence of membrane fusion is indicated by the ability of the probes to diffuse from one membrane species to another which is revealed by resonance energy transfer between the two probes. We have previously shown using this system that the requirement of capacitation for sperm exocytosis is retained in cell-free membrane fusion, and that the pH and calcium dependence of the cell-free fusion mimics those of exocytosis in intact cells. In the present report we further characterize the fusion of sperm membranes which we observe in our assay. Phosphoproteins and phospholipases were found to be involved in the membrane fusion step of sperm exocytosis. Protein kinases, phosphatases, and Gi-like proteins, while involved in exocytosis in intact cells, are not involved specifically in the membrane fusion step of exocytosis. The role of membrane bound F-actin in regulating membrane fusion was also studied using fluorescently labeled phalloidin. The results show that cortical F-actin has two roles in regulating sperm exocytosis. One is to form a scaffolding to hold phospholipase C at the membrane. It also functions as a physical barrier to membrane fusion which is removed by the increases in intracellular calcium and pH which precede fusion.