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Showing papers by "University of Massachusetts Amherst published in 1994"


Journal ArticleDOI
TL;DR: The treatment of gravity is described as a quantum effective field theory that allows a natural separation of the low energy quantum effects from the high energy contributions, and the leading quantum corrections to the gravitational interaction of two heavy masses are calculated.
Abstract: I describe the treatment of gravity as a quantum effective field theory. This allows a natural separation of the (known) low energy quantum effects from the (unknown) high energy contributions. Within this framework, gravity is a well-behaved quantum field theory at ordinary energies. In studying the class of quantum corrections at low energy, the dominant effects at large distance can be isolated, as these are due to the propagation of the massless particles ( including gravitons) of the theory and are manifested in the nonlocal and/or nonanalytic contributions to vertex functions and propagators. These leading quantum corrections are parameter-free and represent necessary consequences of quantum gravity. The methodology is illustrated by a calculation of the leading quantum corrections to the gravitational interaction of two heavy masses.

1,150 citations


01 Jun 1994
TL;DR: In this article, the S = 1 interaction was introduced and the Kaon mixing and CP violation was investigated in the context of the large N expansion of the standard QCD model.
Abstract: Preface Inputs to the standard model Interactions of the standard model Symmetries and anomalies Introduction to effective Lagrangians Leptons Very low energy QCD - Pions and photons Introducing kaons and etas Kaons and the S=1 interaction Kaon mixing and CP violation The large N expansion Phenomenological models Baryon properties Hadron spectroscopy Weak interactions of heavy quarks The Higgs boson The electroweak gauge bosons Appendices References Index.

969 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that there is a universal group for every effect algebra, as well as a universal vector space over an arbitrary field, which is the prototypical example of the effect algebras discussed in this paper.
Abstract: The effects in a quantum-mechanical system form a partial algebra and a partially ordered set which is the prototypical example of the effect algebras discussed in this paper. The relationships among effect algebras and such structures as orthoalgebras and orthomodular posets are investigated, as are morphisms and group- valued measures (or charges) on effect algebras. It is proved that there is a universal group for every effect algebra, as well as a universal vector space over an arbitrary field.

911 citations


Journal ArticleDOI
01 Jul 1994-Science
TL;DR: It is shown that the purified SWI/SNF complex is composed of 10 subunits and includes the SWI1, SWI2/ SNF2, SWi3, SNF5, and SNF6 gene products, and suggests that a primary role of the SWi/SNf complex is to promote activator binding to nucleosomal DNA.
Abstract: The SWI/SNF protein complex is required for the enhancement of transcription by many transcriptional activators in yeast. Here it is shown that the purified SWI/SNF complex is composed of 10 subunits and includes the SWI1, SWI2/SNF2, SWI3, SNF5, and SNF6 gene products. The complex exhibited DNA-stimulated adenosine triphosphatase (ATPase) activity, but lacked helicase activity. The SWI/SNF complex caused a 10- to 30-fold stimulation in the binding of GAL4 derivatives to nucleosomal DNA in a reaction that required adenosine triphosphate (ATP) hydrolysis but was activation domain-independent. Stimulation of GAL4 binding by the complex was abolished by a mutant SWI2 subunit, and was increased by the presence of a histone-binding protein, nucleoplasmin. A direct ATP-dependent interaction between the SWI/SNF complex and nucleosomal DNA was detected. These observations suggest that a primary role of the SWI/SNF complex is to promote activator binding to nucleosomal DNA.

898 citations


Journal ArticleDOI
TL;DR: This short review ends with a list of series of myths and realities concerning the relationship between plant protein and human nutrition and some nutritional issues of concern to the health professional and informed consumer.

595 citations


Journal ArticleDOI
20 Jan 1994-Nature
TL;DR: Nur77, a zinc-finger transcription factor, is expressed in response to TCR engagement in immature T cells and T-cell hybrids andAntisense inhibition of nur77 expression prevents apoptosis in TCR-stimulated cells, and data support a role for nur 77 in cell death that may be distinct from that of activation.
Abstract: Engagement of the T-cell antigen receptor (TCR) on immature thymic T cells induces death by apoptosis. Although several lines of evidence indicate that apoptosis requires de novo gene expression, little is known about the molecular pathways that mediate this response. Here we show that nur77 (refs 4-7), a zinc-finger transcription factor, is expressed in response to TCR engagement in immature T cells and T-cell hybrids. Antisense inhibition of nur77 expression prevents apoptosis in TCR-stimulated cells. nur77 is also expressed in response to mitogens, but in this case transcription is regulated by 5' upstream elements that are distinct from those used for induction of apoptosis. In addition, polyadenylation is only observed on nur77 transcripts found in condemned cells. These data support a role for nur77 in cell death that may be distinct from that of activation.

549 citations


Proceedings ArticleDOI
01 Aug 1994
TL;DR: The increasing lengths of documents in full-text collections encourages renewed interest in the ranking and retrieval of document passages, but questions about how passages are defined, how they can be ranked efficiently, and what is their proper role in long, structured documents are raised.
Abstract: The increasing lengths of documents in full-text collections encourages renewed interest in the ranking and retrieval of document passages. Past research showed that evidence from passages can improve retrieval results, but it also raised questions about how passages are defined, how they can be ranked efficiently, and what is their proper role in long, structured documents.

544 citations


Journal ArticleDOI
TL;DR: The extent of environmentally degrading economic activity is a function of the balance of power between the winners, who derive net benefits from the activity, and the losers, who bear net costs as mentioned in this paper.

544 citations


Journal ArticleDOI
TL;DR: It is argued that the leading quantum corrections, in powers of the energy or inverse power of the distance, may be computed in quantum gravity through knowledge of only the low-energy structure of the theory.
Abstract: I argue that the leading quantum corrections, in powers of the energy or inverse powers of the distance, may be computed in quantum gravity through knowledge of only the low-energy structure of the theory. As an example, I calculate the leading quantum corrections to the Newtonian gravitational potential.

537 citations


Journal ArticleDOI
TL;DR: Dramatic change in lamellipodia structure, and actin stress fiber organization was observed using the same antizipcode oligonucleotides which delocalized the mRNA, suggesting discrete 3'UTR sequences direct beta-actin isoform synthesis to the leading lamellae and affect cell morphology, presumably through the actin cytoskeleton.
Abstract: We have characterized the structure and function of RNA sequences that direct beta-cytoplasmic actin mRNA to the cell periphery were mapped to two segments of 3'-untranslated region by expression of LacZ/beta-actin chimeric mRNAs in chicken embryo fibroblasts (CEFs). A 54-nt segment, the "RNA zipcode," and a homologous but less active 43-nt segment each localized beta-galactosidase activity to the leading lamellae. This zipcode contains the full activity, and mutations or deletions within it reduce, but do not eliminate, its activity, indicating that several motifs contribute to the activity. Two of these motifs, when multimerized, can regenerate almost full activity. These sequences are highly conserved in evolution, since the human beta-actin zipcode, positioned identically in the 3'UTR localizes equally well in chicken cells. Complementary phosphorothioate oligonucleotides against the zipcode delocalized endogenous beta-actin mRNA, whereas those complementary to the region just outside the zipcode, or sense oligonucleotides, did not. Actin mRNA or protein levels were unaffected by the antisense treatments, but a dramatic change in lamellipodia structure, and actin stress fiber organization was observed using the same antizipcode oligonucleotides which delocalized the mRNA. Hence, discrete 3'UTR sequences direct beta-actin isoform synthesis to the leading lamellae and affect cell morphology, presumably through the actin cytoskeleton.

520 citations


Book ChapterDOI
10 Jul 1994
TL;DR: On four datasets, it is shown that only three or four prototypes sufficed to give predictive accuracy equal or superior to a basic nearest neighbor algorithm whose run-time storage costs were approximately 10 to 200 times greater.
Abstract: With the goal of reducing computational costs without sacrificing accuracy, we describe two algorithms to find sets of prototypes for nearest neighbor classification. Here, the term “prototypes” refers to the reference instances used in a nearest neighbor computation — the instances with respect to which similarity is assessed in order to assign a class to a new data item. Both algorithms rely on stochastic techniques to search the space of sets of prototypes and are simple to implement. The first is a Monte Carlo sampling algorithm; the second applies random mutation hill climbing. On four datasets we show that only three or four prototypes sufficed to give predictive accuracy equal or superior to a basic nearest neighbor algorithm whose run-time storage costs were approximately 10 to 200 times greater. We briefly investigate how random mutation hill climbing may be applied to select features and prototypes simultaneously. Finally, we explain the performance of the sampling algorithm on these datasets in terms of a statistical measure of the extent of clustering displayed by the target classes.

Journal ArticleDOI
TL;DR: Monotherapy with ciprofloxacin is at least equivalent to monotherapy with imipenem in terms of bacteriological eradication and clinical response, and for both treatment groups, the presence of P. aeruginosa had a negative impact on treatment success.
Abstract: Intravenously administered ciprofloxacin was compared with imipenem for the treatment of severe pneumonia. In this prospective, randomized, double-blind, multicenter trial, which included an intent-to-treat analysis, a total of 405 patients with severe pneumonia were enrolled. The mean APACHE II score was 17.6, 79% of the patients required mechanical ventilation, and 78% had nosocomial pneumonia. A subgroup of 205 patients (98 ciprofloxacin-treated patients and 107 imipenem-treated patients) were evaluable for the major efficacy endpoints. Patients were randomized to receive intravenous treatment with either ciprofloxacin (400 mg every 8 h) or imipenem (1,000 mg every 8 h), and doses were adjusted for renal function. The primary and secondary efficacy endpoints were bacteriological and clinical responses at 3 to 7 days after completion of therapy. Ciprofloxacin-treated patients had a higher bacteriological eradication rate than did imipenem-treated patients (69 versus 59%; 95% confidence interval of -0.6%, 26.2%; P = 0.069) and also a significantly higher clinical response rate (69 versus 56%; 95% confidence interval of 3.5%, 28.5%; P = 0.021). The greatest difference between ciprofloxacin and imipenem was in eradication of members of the family Enterobacteriaceae (93 versus 65%; P = 0.009). Stepwise logistic regression analysis demonstrated the following factors to be associated with bacteriological eradication: absence of Pseudomonas aeruginosa (P < 0.01), higher weight (P < 0.01), a low APACHE II score (P = 0.03), and treatment with ciprofloxacin (P = 0.04). When P. aeruginosa was recovered from initial respiratory tract cultures, failure to achieve bacteriological eradication and development of resistance during therapy were common in both treatment groups (67 and 33% for ciprofloxacin and 59 and 53% for imipenem, respectively). Seizures were observed more frequently with imipenem than with ciprofloxacin (6 versus 1%; P = 0.028). These results demonstrate that in patients with severe pneumonia, monotherapy with ciprofloxacin is at least equivalent to monotherapy with imipenem in terms of bacteriological eradication and clinical response. For both treatment groups, the presence of P. aeruginosa had a negative impact on treatment success. Seizures were more common with imipenem than with ciprofloxacin. Monotherapy for severe pneumonia is a safe and effective initial strategy but may need to be modified if P. aeruginosa is suspected or recovered from patients.

Journal ArticleDOI
TL;DR: Although a "glass ceiling" is said to keep women from the top management levels of organizations, no research has investigated actual decisions about promotions to such positions as mentioned in this paper, and no study examin...
Abstract: Although a “glass ceiling” is said to keep women from the top management levels of organizations, no research has investigated actual decisions about promotions to such positions. This study examin...

Proceedings Article
11 Oct 1994
TL;DR: An approach, called PhraseFinder, is proposed to construct collection-dependent association thesauri automatically using large full-text document collections, and can be accessed through natural language queries in INQUERY, an information retrieval system based on the probabilistic inference network.
Abstract: Although commonly used in both commercial and experimental information retrieval systems, thesauri have not demonstrated consistent benefits for retrieval performance, and it is difficult to construct a thesaurus automatically for large text databases. In this paper, an approach, called PhraseFinder, is proposed to construct collection-dependent association thesauri automatically using large full-text document collections. The association thesaurus can be accessed through natural language queries in INQUERY, an information retrieval system based on the probabilistic inference network. Experiments are conducted in INQUERY to evaluate different types of association thesauri, and thesauri constructed for a variety of collections.

Journal ArticleDOI
TL;DR: The oxidative stability of skeletal muscle is also influenced by the histidine-containing dipeptides, carnosine and anserine, which are thought to inhibit lipid oxidation by a combination of free radical scavenging and metal chelation.
Abstract: Skeletal muscle is susceptible to oxidative deterioration due to a combination of lipid oxidation catalysts and membrane lipid systems that are high in unsaturated fatty acids. To prevent or delay oxidation reactions, several endogenous antioxidant systems are found in muscle tissue. These include alpha-tocopherol, histidine-containing dipeptides, and antioxidant enzymes such as glutathione peroxidase, superoxide dismutase, and catalase. The contribution of alpha-tocopherol to the oxidative stability of skeletal muscle is largely influenced by diet. Dietary supplementation of tocopherol has been shown to increase muscle alpha-tocopherol concentrations and inhibit both lipid oxidation and color deterioration. Dietary selenium supplementation has also been shown to increase the oxidative stability of muscle presumably by increasing the activity of glutathione peroxidase. The oxidative stability of skeletal muscle is also influenced by the histidine-containing dipeptides, carnosine and anserine. Whereas carnosine and anserine are affected by diet less than alpha-tocopherol and glutathione peroxidase, their concentrations vary widely with species and muscle type. In pigs, beef, and turkey muscle, carnosine concentrations are greater than anserine, while the opposite is true in rabbit, salmon, and chicken muscle. Anserine and carnosine are found in greater concentrations in muscle high in white fibers, with chicken white muscle containing over fivefold more anserine and carnosine than red muscle. Anserine and carnosine are thought to inhibit lipid oxidation by a combination of free radical scavenging and metal chelation.

Journal ArticleDOI
TL;DR: In the first comprehensive study of TSDFs to use census tract-level data, there are no nationally consistent and statistically significant differences between the racial or ethnic composition of tracts which contain commercial TSDFS and those which do not.
Abstract: Research addressing “environmental equity” and “environmental racism” claims that facilities for treatment, storage, and disposal of hazardous wastes (TSDFs) are located disproportionately in minority areas. In the first comprehensive study of TSDFs to use census tract-level data, we find no nationally consistent and statistically significant differences between the racial or ethnic composition of tracts which contain commercial TSDFs and those which do not. TSDFs are more likely to be found in tracts with Hispanic groups, primarily in regions with the greatest percentage of Hispanics. Different geographic units of analysis elaborate on, but are consistent with, these results.

Journal ArticleDOI
01 May 1994-Nature
TL;DR: In this paper, the authors used Cadra cautella, the almond moth, to show how the structure of an odour plume can greatly modify the flight track shape of C. cautella males.
Abstract: IN studies of moths flying upwind to a pheromone source, attention has focused on the influence on flight orientation of the composition1,2 and concentration3,4 of the chemical message, and of changes in the visual environment5,6 and in wind speeds7–9. The chemical signal must be intermittent for moths to fly upwind10–12, when they usually follow a zigzag track, the evident expression of a self-steered counterturning programme13,14. The integration of counterturning and optomotor anemotaxis allows insects to polarize the zigzags upwind in odour plumes10,15. Not all moths, however, zigzag along a plume16,17. It has been suggested that the propensity to zigzag or to fly straight upwind is related to the frequency at which males encounter pheromone filaments that comprise the plume, as well as the male's latency of response, characteristic for each moth species, to both the onset and loss of contact with filaments18. Here we present evidence that flight manoeuvres are dictated by the interactions of the male with individual odour pulses. We use Cadra cautella, the almond moth, to show how the structure of an odour plume19,20 can greatly modify the flight track. Males following either turbulent or mechanically pulsed plumes fly faster and straighter upwind, and locate sources more frequently than males following continuous narrow plumes. Males also fly straighter upwind to fast-pulsed plumes than to slow-pulsed plumes. The temporally modulated interplay between counterturning and optomotor anemotaxis that is induced by the plume's structure therefore seems to explain the manoeuvres and resultant flight track shapes made by C. cautella males when flying upwind towards a pheromone source.

Journal ArticleDOI
TL;DR: The authors used interviews to develop case studies of young people from a wide variety of ethnic, racial, linguistics, and social-class backgrounds who at the time interviewed were attending and successfully completing junior or senior high school.
Abstract: For the most part, discussions about developing strategies to solve educational problems lack the perspectives of one of the very groups they most affect — students, especially those students who are categorized as "problems" and are most oppressed by traditional educational structures and procedures. In this article, Sonia Nieto uses interviews to develop case studies of young people from a wide variety of ethnic, racial, linguistics, and social-class backgrounds who at the time interviewed were attending and successfully completing junior or senior high school. By focusing on students' thoughts about a number of school policies and practices and on the effects of racism and other forms of discrimination on their education, Nieto explores what characteristics of these students' specific experiences helped them remain and succeed in school, despite the obstacles. In essence, these are lessons from students, and Nieto believes that in order to reflect critically on school reform, students need to be includ...

Journal ArticleDOI
TL;DR: The strong, significant correlation observed between the Caltrac data and the 7-d recall suggests adequate validity for the 7.d recall, and would be quicker, easier, and less expensive to use in a large population study than theCaltrac.
Abstract: The purpose of this study was to compare the physical activity levels of physical therapists using five activity questionnaires and one electronic motion sensor (Caltrac). Thirty-three physical therapists (26 female, seven male) were monitored for seven consecutive days. The Caltrac data were compared with five questionnaires, including the Baecke (Baecke); Godin and Shephard (Godin); Ross and Jackson (NASA); 3-d record (3-d); and 7-d recall (7-d). A significant (P < 0.01) Spearman rank order correlation coefficient was observed between the Caltrac reading and the 7-d recall (r = 0.79). A significant correlation was also observed between the Caltrac and the Godin (r = 0.45, P < 0.01). Three of the questionnaires were also significantly (P < 0.01) correlated with each other, including the NASA with the Baecke (r = 0.52), the NASA with the Godin (r = 0.54), and the Godin with the Baecke (r = 0.61). The 3-d record was not significantly correlated with any of the other measures. The strong, significant correlation observed between the Caltrac data and the 7-d recall suggests adequate validity for the 7-d recall. The 7-d recall questionnaire would be quicker, easier, and less expensive to use in a large population study than the Caltrac.

Journal ArticleDOI
TL;DR: The findings provide evidence that growing pollen tubes have open Ca2+ channels in their tip and that these channels become inactivated in nongrowing tubes and the studies with elevated sucrose support the view that stretching of the apical plasma membrane contributes to the maintenance of the Ca2 + signal.
Abstract: Lily pollen tubes possess a steep, tip-focused intracellular Ca2+ gradient and a tip-directed extracellular Ca2+ influx. Ratiometric ion imaging revealed that the gradient extends from above 3.0 microM at the apex to approximately 0.2 microM within 20 microns from the tip, while application of the Ca(2+)-specific vibrating electrode indicated that the extracellular influx measured between 1.4 and 14 pmol cm-2 sec-1. We examined the relationship between these phenomena and their role in tube growth by using different 1,2-bis(o-aminophenoxy)ethane N,N,N',N'-tetraacetic acid (BAPTA)-type buffers and hypertonic media. Injection of active BAPTA-type buffers or application of elevated levels of sucrose reversibly inhibited growth, destroyed tip zonation of organelles, and modified normal patterns of cytoplasmic streaming. Simultaneously, these treatments dissipated both the intracellular tip-focused gradient and the extracellular Ca2+ flux. Of the BAPTA-type buffers, 5,5'-dibromo-BAPTA (dissociation constant [Kd] is 1.5 microM) and 4,4'-difluoro-BAPTA (Kd of 1.7 microM) exhibited greater activity than those buffers with either a higher affinity (5,5'-dimethyl-BAPTA, Kd of 0.15 microM; BAPTA, Kd of 0.21 microM; 5,5'-difluoro-BAPTA, Kd of 0.25 microM) or lower affinity (5-methyl, 5'-nitro-BAPTA, Kd of 22 microM) for Ca2+. Our findings provide evidence that growing pollen tubes have open Ca2+ channels in their tip and that these channels become inactivated in nongrowing tubes. The studies with elevated sucrose support the view that stretching of the apical plasma membrane contributes to the maintenance of the Ca2+ signal.

Journal ArticleDOI
TL;DR: The results of this study indicate the rapid same-day bacterial identification and susceptibility testing in the microbiology laboratory can have a major impact on the care and outcome of hospitalized patients with infection.
Abstract: During the past decade, a variety of instrument-assisted bacterial identification and antimicrobial susceptibility test systems have been developed which permit provision of test results in a matter of hours rather than days, as has been the case with traditional overnight procedures. These newer rapid techniques are much more expensive than older methods. It has been presumed but not proven that the clinical benefits of rapid testing to patients with infection offset the added cost. The intent of this study was to objectively define the clinical impact of rapid bacterial identification and antimicrobial susceptibility testing. A 1-year study was performed in which infected, hospitalized patients in a tertiary-care, teaching, medical center were randomly assigned to one of two groups: patients for whom identification and susceptibility testing was performed by using a semi-automated, rapid, same-day procedure and those for whom testing was accomplished by using traditional overnight techniques. The two groups were compared with respect to numerous demographic descriptors, and then patients were monitored prospectively through the end of their hospitalization with the aim of determining whether there existed objectively defineable differences in management and outcome between the two groups. The mean lengths of time to provision of susceptibility and identification test results in the rapid test group were 11.3 and 9.6 h, respectively. In the overnight test group, these values were 19.6 and 25.9 h, respectively (P 100 demographic descriptors. With regard to measures of outcome, the mean lengths of hospitalization were also the same in both groups. Mortality rates were however, lower in the rapid test group (i.e., 8.8% versus 15.3%). Similarly, statistically significantly fewer laboratory studies, imaging procedures, days of intubation, and days in an intensive or intermediate-care area were observed with patients in the rapid test group. Rapid testing was also associated with significantly shortened lengths of elapsed time prior to alterations in antimicrobial therapy. Lastly, patient costs for hospitalization were significantly lower in the rapid test group. The results of this study indicate the rapid same-day bacterial identification and susceptibility testing in the microbiology laboratory can have a major impact on the care and outcome of hospitalized patients with infection.

Journal ArticleDOI
05 Oct 1994-JAMA
TL;DR: All models were based on rigorous research and reported performance is good and can be used to assist in assessing prognosis, to compare ICU performance, and to stratify patients for clinical trials.
Abstract: Objective. —To review recent revisions of systems for estimating the probability of hospital mortality of adult intensive care unit (ICU) patients. Emphasis on comparison of components of systems and potential uses. Data Sources. —Published articles in which the systems were presented. Study Selection. —Acute Physiology and Chronic Health Evaluation (APACHE III), Simplified Acute Physiology Score (SAPS II), and Mortality Probability Models (MPM II) are the major severity systems for ICU patients. Data Extraction. —Information on variables collected in the systems, characteristics of databases from which they were developed, and reported performance of models were evaluated from published articles. Data Synthesis. —APACHE III and SAPS II produce a score and probability of hospital mortality based on worst values of several variables during the first 24 hours in ICU. The MPM II system has four models, one at ICU admission and one at 24, 48, and 72 hours into the ICU stay. The SAPS II and MPM II models can be implemented from published information. The APACHE III score can be calculated from published information; weights to convert score to probability are proprietary. All reported good areas under receiver operating characteristic curve. Goodness of fit was good for SAPS II and MPM II models and was not reported for APACHE III models. Conclusions. —All models were based on rigorous research and reported performance is good. All can be used to assist in assessing prognosis, to compare ICU performance, and to stratify patients for clinical trials. Direct comparison on a common cohort is needed. ( JAMA . 1994;272:1049-1055)

Journal ArticleDOI
TL;DR: In this paper, the effect of soft-segment length and soft segment concentration on the activation energy of polyurethane degradation was investigated and three methods of calculation gave activation energies at different stages of very complex weight loss process.
Abstract: Thermal degradation of polyurethane samples was studied by a thermogravimetric method. The effect of soft-segment length and soft-segment concentration on activation energy of the degradation process was measured. Three methods of calculation gave activation energies at different stages of the very complex weight loss process. It was shown that at initial stages of the weight loss the process was dominated by hard-segment degradation. Activation energy of the whole process calculated by the Ozawa–Flynn method did not offer clear insight into the structure–stability relationship of polyurethanes. The second method showed that activation energy of the initial stage of degradation increased with decrease in hard-segment length. The Flynn method of calculating activation energy produced fairly constant activation energy of the first 40% degradation, at around 150 kJ/mol, for polymers in the C series. Generally, calculation of kinetic parameters of a complex degradation process as in polyurethanes gives results that are not easy to interpret. It has been shown qualitatively that polymers with higher soft-segment concentration display lower initial weight loss and higher onset temperatures of degradation. © 1994 John Wiley & Sons, Inc.

Proceedings Article
01 Jan 1994
TL;DR: This work proposes algorithms similar to those named above, adapted to the solution of semi-Markov Decision Problems, and demonstrates these algorithms by applying them to the problem of determining the optimal control for a simple queueing system.
Abstract: Semi-Markov Decision Problems are continuous time generalizations of discrete time Markov Decision Problems. A number of reinforcement learning algorithms have been developed recently for the solution of Markov Decision Problems, based on the ideas of asynchronous dynamic programming and stochastic approximation. Among these are TD(λ), Q-learning, and Real-time Dynamic Programming. After reviewing semi-Markov Decision Problems and Bellman's optimality equation in that context, we propose algorithms similar to those named above, adapted to the solution of semi-Markov Decision Problems. We demonstrate these algorithms by applying them to the problem of determining the optimal control for a simple queueing system. We conclude with a discussion of circumstances under which these algorithms may be usefully applied.

Journal ArticleDOI
TL;DR: Septal AVP enhances paternal responsiveness by a V1a receptor-mediated mechanism and is associated with major changes in male prairie voles' social behaviors.
Abstract: After being paired with females, male prairie voles show major changes in their social behaviors among which is an increase in paternal responsiveness. These changes are accompanied by fluctuations in the density of the [Arg8]vasopressin-immunoreactive (AVP-ir) fibers in the lateral septum, suggesting that septal AVP might be involved in these changes. To explore a possible involvement of septal AVP in paternal responsiveness, we tested whether injections of saline, AVP, or the V1a receptor antagonist [1-(beta-mercapto-beta, beta-cyclopentamethylenepropionic acid),2-(O-methyltyrosine]AVP [d(CH2)5Tyr(Me)AVP] into the lateral septum influenced the four most prominent paternal activities displayed by male prairie voles; grooming, crouching over, contacting, and retrieving pups. In a first experiment, sexually inexperienced males received a single injection of AVP, saline, or d(CH2)5Tyr(Me)AVP in the lateral septum, after which their paternal responsiveness was recorded during a 10-min period. AVP-injected animals spent more time contacting and crouching over pups, while d(CH2)5Tyr(Me)AVP-injected animals spent less time grooming pups than saline-injected animals. In a follow-up study, one group of animals received an injection of AVP preceded by an injection of saline or d(CH2)5Tyr(Me)-AVP into the lateral septum. A second group of animals received an injection of saline preceded by an injection of saline or d(CH2)5Tyr(Me)AVP into the lateral septum. In both groups, animals spent less time grooming, crouching over, and contacting pups if they had first been injected with d(CH2)5Tyr(Me)AVP. Control experiments suggested that the effects of AVP on paternal responsiveness were dose- and site-specific. These data suggest that septal AVP enhances paternal responsiveness by a V1a receptor-mediated mechanism.

Journal ArticleDOI
TL;DR: Experiments indicated that prior immunity to one virus could modulate future primary immune responses to a second virus and that the cross-reactivity in killing was not due to evolutionarily conserved equivalent sequences.
Abstract: Analyses of the relationships between different viruses and viral proteins have focused on homologies between linear amino acid sequences, but cross-reactivities at the level of T cell recognition may not be dependent on a conserved linear sequence of several amino acids. The CTL response to Pichinde virus (PV) and vaccinia virus (VV) in C57BL/6 mice previously immunized with lymphocytic choriomeningitis virus (LCMV) included the reactivation of memory cytotoxic T lymphocyte (CTL) specific to LCMV. Limiting dilution assays (LDA) demonstrated that at least part of this reactivation of memory cells in LCMV-immune mice related to cross-reactivity at the clonal level, even though acute infections with these viruses in nonimmune mice elicited CTL responses that did not cross-react in conventional bulk CTL assays. Precursor CTL (pCTL) to LCMV were generated in splenic leukocytes from LCMV-immune mice acutely infected with PV or VV when stimulated in vitro with only the second virus but not with uninfected peritoneal exudate cells (PECs). Cytotoxicity mediated by LCMV-specific CTL clones activated by PV infection was greatly inhibited by anti-CD8 antibody, suggesting that these memory CTL clones recognizing LCMV-infected targets were of low affinity. LCMV-immune splenocytes stimulated in vitro with PV or VV demonstrated a low but significant precursor frequency (p/f) to the heterologous viruses, and splenocytes from PV- or VV-immune mice when stimulated in vitro against LCMV generated a low but significant p/f to LCMV. Short-term CTL clones cross-reactive between LCMV and PV were derived from splenic leukocytes from LCMV-immune mice acutely infected with PV. To distinguish whether the cross-reactivity was directed against a viral peptide or a virus-induced endogenous cellular neoantigen, we demonstrated that a pCTL frequency to PV about 1/4-1/7 that of the frequency to LCMV could be generated from LCMV-immune splenic leukocytes stimulated with the immunodominant LCMV NP peptide. A partially homologous PV peptide generated from the equivalent site to the LCMV NP peptide did not sensitize targets to lysis by either LCMV- or PV-specific CTLs, suggesting that the cross-reactivity in killing was not due to evolutionarily conserved equivalent sequences. Experiments also indicated that prior immunity to one virus could modulate future primary immune responses to a second virus. Elevated pCTL frequencies to PV were seen after acute PV infection of LCMV-immune mice, and elevated pCTL frequencies to LCMV were seen after acute LCMV infection of PV- and VV-immune mice.(ABSTRACT TRUNCATED AT 400 WORDS)

Proceedings ArticleDOI
01 Nov 1994
TL;DR: This paper presents compiler optimizations to improve data locality based on a simple yet accurate cost model and demonstrates that these program transformations are useful for optimizing many programs.
Abstract: In the past decade, processor speed has become significantly faster than memory speed. Small, fast cache memories are designed to overcome this discrepancy, but they are only effective when programs exhibit data locality. In this paper, we present compiler optimizations to improve data locality based on a simple yet accurate cost model. The model computes both temporal and spatial reuse of cache lines to find desirable loop organizations. The cost model drives the application of compound transformations consisting of loop permutation, loop fusion, loop distribution, and loop reversal. We demonstrate that these program transformations are useful for optimizing many programs.To validate our optimization strategy, we implemented our algorithms and ran experiments on a large collection of scientific programs and kernels. Experiments with kernels illustrate that our model and algorithm can select and achieve the best performance. For over thirty complete applications, we executed the original and transformed versions and simulated cache hit rates. We collected statistics about the inherent characteristics of these programs and our ability to improve their data locality. To our knowledge, these studies are the first of such breadth and depth. We found performance improvements were difficult to achieve because benchmark programs typically have high hit rates even for small data caches; however, our optimizations significantly improved several programs.

Journal ArticleDOI
TL;DR: In this article, the authors used SERVQUAL-traditionally an instrument for measuring service quality-to assess customer perceptions of service quality in restaurants and found that it is an effective tool in assessing customer perceptions.
Abstract: Can SERVQUAL-traditionally an instrument for measuring service quality- be proven as an effective tool in assessing customer perceptions of service quality in restaurants? The research presented in...

Journal ArticleDOI
01 Oct 1994-Neuron
TL;DR: It is shown that dlg immunoreactivity is expressed at one type of glutamatergic synapse and is associated with both presynaptic and postsynaptic membranes, indicating that d lg is required for normal synaptic structure and offers insights regarding the role of dlG homologs at vertebrate synapses.

Proceedings ArticleDOI
01 May 1994
TL;DR: It is shown that the receiver-initiated error control protocols provide substantially higher throughputs than their sender- initiated counterparts, and the introduction of random delays prior to generating NAKs coupled with the multicasting of Naks to all receivers has the potential for an additional substantial increase in the throughput of receiver-Initiatederror control protocols over sender-in Initiated protocols.
Abstract: Sender-initiated reliable multicast protocols, based on the use of positive acknowledgments (ACKs), lead to an ACK implosion problem at the sender as the number of receivers increases. Briefly, the ACK implosion problem refers to the significant overhead incurred by the sending host due to the processing of ACKs from each receiver. A potential solution to this problem is to shift the burden of providing reliable data transfer to the receivers—thus resulting in a receiver-initiated multicast error control protocol based on the use of negative acknowledgments (NAKs). In this paper we determine the maximum throughputs of the sending and receiving hosts for generic sender-initiated and receiver-initiated protocols. We show that the receiver-initiated error control protocols provide substantially higher throughputs than their sender-initiated counterparts. We further demonstrate that the introduction of random delays prior to generating NAKs coupled with the multicasting of NAKs to all receivers has the potential for an additional substantial increase in the throughput of receiver-initiated error control protocols over sender-initiated protocols.