Showing papers by "University of Maryland, Baltimore County published in 1994"
29 Nov 1994
TL;DR: The Knowledge Query and Manipulation Language (KQML) as mentioned in this paper is a new language and protocol for exchanging information and knowledge, which is used in the ARPA Knowledge Sharing Effort.
Abstract: This paper describes the design of and experimentation with the Knowledge Query and Manipulation Language (KQML), a new language and protocol for exchanging information and knowledge. This work is part of a larger effort, the ARPA Knowledge Sharing Effort which is aimed at developing techniques and methodology for building large-scale knowledge bases which are sharable and reusable. KQML is both a message format and a message-handling protocol to support run-time knowledge sharing among agents. KQML focuses on an extensible set of performatives, which defines the permissible “speech acts” agents may use and comprise a substrate on which to develop higher-level models of interagent interaction such as contract nets and negotiation. In addition, KQML provides a basic architecture for knowledge sharing through a special class of agent called communication facilitors which coordinate the interactions of other agents. The ideas which underlie the evolving design of KQML are currently being explored through experimental prototype systems which are being used to support several testbeds in such areas as concurrent engineering, intelligent design and intelligent planning and scheduling.
1,446 citations
TL;DR: This paper presents a decomposition method for solving convex minimization problems that preserves the good features of the proximal method of multipliers, with the additional advantage that it leads to a decoupling of the constraints, and is thus suitable for parallel implementation.
Abstract: This paper presents a decomposition method for solving convex minimization problems. At each iteration, the algorithm computes two proximal steps in the dual variables and one proximal step in the primal variables. We derive this algorithm from Rockafellar's proximal method of multipliers, which involves an augmented Lagrangian with an additional quadratic proximal term. The algorithm preserves the good features of the proximal method of multipliers, with the additional advantage that it leads to a decoupling of the constraints, and is thus suitable for parallel implementation. We allow for computing approximately the proximal minimization steps and we prove that under mild assumptions on the problem's data, the method is globally convergent and at a linear rate. The method is compared with alternating direction type methods and applied to the particular case of minimizing a convex function over a finite intersection of closed convex sets.
420 citations
TL;DR: In this article, the theory of the two-photon state generated by type-II optical parametric down-conversion is studied with emphasis on the space-time and polarization entanglement of the photons.
Abstract: The theory of the two-photon state generated by type-II optical parametric down-conversion is studied with emphasis on the space-time and polarization entanglement of the photons. Several experiments are reviewed that demonstrate various aspects of the quantum nature of this state. The theory of a different type of two-photon interferometer is presented.
408 citations
TL;DR: The three-dimensional structure of recombinant HIV-1 matrix protein, determined at high resolution by nuclear magnetic resonance (NMR) methods, suggests that both membrane binding and nuclear localization may be mediated by complex tertiary structures rather than simple linear determinants.
279 citations
29 Nov 1994
TL;DR: It is suggested that KQML can offer an all purpose communication language for software agents that requires no limiting pre-commitments on the agents' structure and implementation and a semantic framework for the language is proposed.
Abstract: We investigate the semantics for Knowledge Query Manipulation Language (KQML) and we propose a semantic framework for the language. KQML is a language and a protocol to support communication between software agents. Based on ideas from speech act theory, we propose a semantic description for KQML that associates descriptions of the cognitive states of agents with the use of the language's primitives (performatives). We use this approach to describe the semantics for the basic set of KQML performatives. We also investigate implementation issues related to our semantic approach. We suggest that KQML can offer an all purpose communication language for software agents that requires no limiting pre-commitments on the agents' structure and implementation. KQML can provide the Distributed AI, Cooperative Distributed Problem Solving and Software Agents communities with an all purpose language and environment for intelligent inter-agent communication.
239 citations
TL;DR: The study summarized in this paper represents the first comprehensive assessment of the physical and mental health and educational status of children in kinship care and the anticipated high risk status of these children was supported by study findings.
201 citations
TL;DR: It can be argued that theUnderstanding of eukaryotic rRNA processing is no less important than the understanding of mRNA maturation, since the capacity of a cell to carry out protein synthesis is controlled, in part, by the abundance of ribosomes.
Abstract: In summary, it can be argued that the understanding of eukaryotic rRNA processing is no less important than the understanding of mRNA maturation, since the capacity of a cell to carry out protein synthesis is controlled, in part, by the abundance of ribosomes. Processing of pre-rRNA is highly regulated, involving many cellular components acting either alone or as part of a complex. Some of these components are directly involved in the modification and cleavage of the precursor rRNA, while others direct the packaging of the rRNA into ribosome subunits. As is the case for pre-mRNA processing, snoRNPs are clearly involved in eukaryotic rRNA processing, and have been proposed to assemble with other proteins into at least one complex called a "processosome" (17), which carries out the ordered processing of the pre-rRNA and its assembly into ribosomes. The formation of a processing complex clearly makes possible the regulation required to coordinate the abundance of ribosomes with the physiological and developmental changes of a cell. It may be that eukaryotic rRNA processing is even more complex than pre-mRNA maturation, since pre-rRNA undergoes extensive nucleotide modification and is assembled into a complex structure called the ribosome. Undoubtedly, features of the eukaryotic rRNA-processing pathway have been conserved evolutionarily, and the genetic approach available in yeast research (6) should provide considerable knowledge that will be useful for other investigators working with higher eukaryotic systems. Interestingly, it was originally hoped that the extensive work and understanding of bacterial ribosome formation would provide a useful paradigm for the process in eukaryotes. However, although general features of ribosome structure and function are highly conserved between bacterial and eukaryotic systems, the basic strategy in ribosome biogenesis seems to be, for the most part, distinctly different. Thus, the detailed molecular mechanisms for rRNA processing in each kingdom will have to be independently deciphered in order to elucidate the features and regulation of this important process for cell survival.
196 citations
TL;DR: The three dimensional solution structure of the carboxy terminal LIM domain of the avian Cysteine Rich Protein (CRP) has been determined by nuclear magnetic resonance spectroscopy, raising the possibility that the LIM motif may have a DNA binding function.
Abstract: The three dimensional solution structure of the carboxy terminal LIM domain of the avian Cysteine Rich Protein (CRP) has been determined by nuclear magnetic resonance spectroscopy. The domain contains two zinc atoms bound independently in CCHC (C=Cys, H=His) and CCCC modules. Both modules contain two orthogonally-arranged antiparallel β-sheets, and the CCCC module contains an α-helix at its C terminus. The modules pack due to hydrophobic interactions forming a novel global fold. The structure of the C-terminal CCCC module is essentially identical to that observed for the DNA-interactive CCCC modules of the GATA-1 and steroid hormone receptor DNA binding domains, raising the possibility that the LIM motif may have a DNA binding function.
178 citations
TL;DR: A new image thresholding technique is presented which uses the relative entropy (also known as the Kullback-Leiber discrimination distance function) as a criterion of thresholding an image and provides the least computational complexity.
155 citations
154 citations
TL;DR: Men who had physically assaulted female partners (PA group; N = 24) were compared with maritally discordant nonviolent men (DNV group; n = 24), and happily married non-violent men (HNV group, n =24) on measures of dependency and related constructs.
Abstract: Men who had physically assaulted female partners (PA group; N = 24) were compared with maritally discordant nonviolent men (DNV group; N = 24) and happily married nonviolent men (HNV group; N = 24) on measures of dependency and related constructs. PA men reported higher interpersonal dependency, higher spouse-specific dependency, and lower self-esteem than both contrast groups, but did not differ significantly on a measure of jealously. Data reduction indicated two constructs underlying these measures: perceived personal inadequacy and emotional investment in the primary relationship. PA men were high on both, while DNV men had moderate perceived inadequacy and low emotional investment and HNV men had low perceived inadequacy and high emotional investment. The findings support the clinical observation that interpersonal dependency is an important factor in the motivational dynamics of relationship violence.
TL;DR: For example, this article investigated to what extent students at a highly selective university on the East coast changed their political and social attitudes during college and found that the influences of religious background, gender, membership in a fraternity or sorority, and time in college on attitudes were examined.
Abstract: In the last two decades a considerable volume of research has focused on how the college experience affects students. The purpose of the research reported here was to investigate to what extent students (predominantly Caucasian) at a highly selective university on the East coast changed their political and social attitudes during college. In particular, the influences of religious background, gender, membership in a fraternity or sorority, and time in college on attitudes were examined. Results indicated that students as seniors scored higher on measures of liberalism, social conscience, homosexuality tolerance and feminist attitudes and lower on male-dominant attitudes than they did as first year students. Given the lack of previous studies of change in attitudes toward homosexuality in college and the current political debate about issues relating to sexual orientation, an important finding was the substantial increase in tolerance of homosexuality by all subgroups. Results are discussed with respect to the special characteristics and potential influence of Ivy League students.
TL;DR: The structural findings provide a rationalization for the general conservation of these hydrophobic and basic residues in CCHC zinc fingers, and are consistent with site‐directed mutagenesis results that implicate these residues as direct participants in viral genome recognition.
Abstract: The nucleic acid interactive properties of a synthetic peptide with sequence of the N-terminal CCHC zinc finger (CCHC = Cys-X2-Cys-X4-His-X4-Cys; X = variable amino acid) of the human immunodeficiency virus (HIV) nucleocapsid protein, Zn(HIV1-F1), have been studied by 1H NMR spectroscopy. Titration of Zn(HIV1-F1) with oligodeoxyribonucleic acids containing different nucleotide sequences reveals, for the first time, sequence-dependent binding that requires the presence of at least one guanosine residue for tight complex formation. The dynamics of complex formation are sensitive to the nature of the residues adjacent to guanosine, with residues on the 3' side of guanosine having the largest influence. An oligodeoxyribonucleotide with sequence corresponding to a portion of the HIV-1 psi-packaging signal, d(ACGCC), forms a relatively tight complex with Zn(HIV1-F1) (Kd = 5 x 10(-6) M). Two-dimensional nuclear Overhauser effect (NOESY) data indicate that the bound nucleic acid exists predominantly in a single-stranded, A-helical conformation, and the presence of more than a dozen intermolecular NOE cross peaks enabled three-dimensional modeling of the complex. The nucleic acid binds within a hydrophobic cleft on the peptide surface. This hydrophobic cleft is defined by the side chains of residues Val1, Phe4, Ile12, and Ala13. Backbone amide protons of Phe4 and Ala13 and the backbone carbonyl oxygen of Lys2 that lie within this cleft appear to form hydrogen bonds with the guanosine O6 and N1H atoms, respectively. In addition, the positively charged side chain of Arg14 is ideally positioned for electrostatic interactions with the phosphodiester backbone of the nucleic acid. The structural findings provide a rationalization for the general conservation of these hydrophobic and basic residues in CCHC zinc fingers, and are consistent with site-directed mutagenesis results that implicate these residues as direct participants in viral genome recognition.
TL;DR: In this article, the impact of roads on the degradation of tropical forests is discussed for the forested, humid montane zone, where roads often augment slope instability and fragment ranges of specialized species, and studies and mitigation efforts are needed to reduce their effects on the specialized biota of montane forests.
Abstract: Roads are often a causal agent in the degradation of tropical forests; in this paper their impact is discussed for the forested, humid montane zone. Because of their steep slopes and high elevations, these forests have disturbance regimes associated with slope instability, limited resilience, and numerous species that are elevational specialists, restricted to narrow altitudinal belts. Roads often augment slope instability and fragment ranges of specialized species. Roads can allow uncontrolled extraction of natural products and landscape conversion. Improvements are needed in the design, construction, and maintenance of these roads. Also needed are studies and mitigation efforts to reduce their effects on the specialized biota of montane forests.
Las carreteras son frecuentemente agentes causales en la degradacion de los bosques tropicales. En este trabajo discutimos el impacto que ellas tienen sobre la zona del bosque tropical montanoso humedo. Debido a pronuciadas pendientes y altas elevaciones, estos bosques presentan regimenes de perturbacion asociados con inestabilidad de laderas, una limitada capacidad de la vegetacion para recuperarse (resiliencia limitada) y numerosas especies que son especialistas altitudinales, restringidas a angostos cinturones altitudinales. Las carreteras aumentan frecuentemente la inestabilidad de las pendientes y fragmentan las areas de distribucion de las especies especializadas. Las carreteras a menudo permiten la extraccion incontrolada de productos naturales y la conversion del paisaje. Mejoras en el diseno, construccion y mantenimiento de estas carreteras son necesarias. Asi mismo, se requieren estudios y esfuerzos de mitigacion para reducir sus efectos en la biota especializada de los bosques montanosos.
TL;DR: A low‐cost, optical oxygen sensor is reported here on as an attractive alternative to the widely used amperometric Clark‐type oxygen electrode for measuring dissolved oxygen tensions in cell cultures and bioreactor.
Abstract: We report here on a low-cost, optical oxygen sensor as an attractive alternative to the widely used amperometric Clark-type oxygen electrode for measuring dissolved oxygen tensions in cell cultures and bioreactor. Our sensor is based on the defferential quenching of the fluorescence lifetime of chromophore in response to the partial pressure of oxygen. This is measured as a phase shift in fluorescence emission from the chromophore due to oxygen quenching when excited by an intensity modulated beam of light. In this article we demonstrate the advantages of lifetime-based optical methods over both intensity based optical methods and amperometric electrodes. Our sensor is particularly suitable for measuring dissolved oxygen in bioreactors. It is autoclavable, is free of maintenance requirements, and solvents the problems of long-term stability, calibration drifts, and reliable measurement of low oxygen tensions in dense microbial cultures that limit the utility of Clark-type elcectordes. (c) 1994 John Wiley & Sons, Inc.
TL;DR: A comparison of structural characteristics between the fish GHs and hGH was executed using the Wisconsin GCG program package and suggests that the GH-family ancestral gene may have been involved in the osmoregulation response of the deuterostome-invertebrate ancestors of chordates.
Abstract: Publisher Summary This chapter examines the structure and evolution of fish growth hormone and insulin-like growth factor genes. Growth hormone (GH), prolactin (PRL), placental lactogen (PL), and somatolactin (SL) form a family of polypeptide hormones with common structural and overlapping biological characteristics. The chapter presents a study in which amino acid sequence comparisons were carried out for GHs by aligning the conserved half-cystine residues and by introducing several deletions to maximize the homology. A comparison of structural characteristics between the fish GHs and hGH was executed using the Wisconsin GCG program package. The somatolactin precursor is a single-chain polypeptide of approximately 231 amino acid residues. Although the amino acid homology among SL, GH, and PRL is low, they are structurally related to one another because four of the six cysteine residues are present in positions similar to those in GH and PRL polypeptides. GH, PRL, and SL are all known to be actively involved in the osmoregulatory responses of teleosts. This suggests thatthat the GH-family ancestral gene may have been involved in the osmoregulation response of the deuterostome-invertebrate ancestors of chordates.
TL;DR: In this paper, a generalized p value is applied for testing hypotheses in two situations, testing the significance of a variance component in a general balanced mixed model when an exact F test does not exist and comparing randomeffects variance components in two independent balanced mixed models.
Abstract: The concept of a generalized p value, introduced by Tsui and Weerahandi, is applied for testing hypotheses in two situations, testing the significance of a variance component in a general balanced mixed model when an exact F test does not exist and comparing randomeffects variance components in two independent balanced mixed models. Extensions to the unbalanced cases are also indicated. The proposed test is compared with the test based on the Satterthwaite approximation through their simulated Type I error probabilities. The simulations indicate that the test based on the generalized p value hasType I error probabilities less than the chosen significance level most of the time, whereas the Type I error probabilities of the Satterthwaite approximate test can be much larger than the significance level. The results are illustrated using two examples.
TL;DR: In this paper, a nonlinear loop mirror can be used as a solid state saturable loss element, and the implications for its use in a laser cavity are discussed, as well as its transmission characteristics when used in the soliton-forming wavelength range.
Abstract: A nonlinear loop mirror can be used as a solid state saturable loss element. The transmission characteristics of the different embodiments of this mirror are shown to change significantly when it is used in the soliton-forming wavelength range. The implications for its use in a laser cavity are discussed. >
TL;DR: Trends in medication use for hyperactive/inattentive (HA/I) secondary school students from 1975 through 1993 are described and differences in the treatment of HA/I relative to school grade are presented.
Abstract: Objective To describe trends in medication use for hyperactive/inattentive (HA/I) secondary school students from 1975 through 1993 and to present differences in the treatment of HA/I relative to school grade. Design A comprehensive survey of the HA/I treatment of public elementary and secondary school students has been conducted biennially by school nurses in Baltimore County, MD since 1975. Results Although only 11% of all public school students on medication for HA/I were in secondary schools in 1975, the proportion gradually rose such that in the 1990s, 30% of all medicated students were attending secondary schools. Also in secondary schools, the gender ratio for students on medication for HA/I narrowed from a 1:12 female/male ratio in 1981 to a 1:6 female/male ratio in 1993. Conclusions Many more elementary school students are now remaining on stimulant medication for HA/I into their teens. Compared with a decade ago, relatively more girls are on stimulant treatment for HA/I during their secondary school years.
TL;DR: In this article, the authors further explore the concept of RSS when the population is partially known and the parameter of interest is not necessarily the mean, and address the problem of estimation of the parameters of a two-parameter exponential distribution.
Abstract: In situations where the experimental or sampling units in a study can be easily ranked than quantified, McIntyre (1952,Aust. J. Agric. Res.,3, 385–390) proposed that the mean ofn units based on aranked set sample (RSS) be used to estimate the population mean, and observed that it provides an unbiased estimator with a smaller variance compared to a simple random sample (SRS) of the same sizen. McIntyre's concept ofRSS is essentially nonparametric in nature in that the underlying population distribution is assumed to be completely unknown. In this paper we further explore the concept ofRSS when the population is partially known and the parameter of interest is not necessarily the mean. To be specific, we address the problem of estimation of the parameters of a two-parameter exponential distribution. It turns out that the use ofRSS and its suitable modifications results in much improved estimators compared to the use of aSRS.
TL;DR: An experimental study of the entangled two-photon polarization states in type-II optical parametric down-conversion shows that the polarization entanglement depends on the detection spectral bandwidth, i.e., the bandwidth of the spectral filters placed in front of the detectors.
Abstract: We present an experimental study of the entangled two-photon polarization states in type-II optical parametric down-conversion. It is interesting to see that the polarization entanglement depends on the detection spectral bandwidth, i.e., the bandwidth of the spectral filters placed in front of the detectors. The entanglement is also dependent on the length of the down-conversion crystal. A simple quantum model is provided to explain these phenomena.
TL;DR: DNA base damage in mammalian cells exposed to tert.-butyl hydroperoxide is investigated and the nature of the identified DNA base lesions suggests the involvement of the hydroxyl radical in their formation.
Abstract: tert.-Butyl hydroperoxide has been utilized to study the effect of oxidative stress on living cells; however, its effect on DNA bases in cells has not been characterized. In the present work, we have investigated DNA base damage in mammalian cells exposed to this organic hydroperoxide. SP2/0 derived murine hybridoma cells were treated with 4 concentrations of tert.-butyl hydroperoxide for varying periods of time. Chromatin was isolated from treated and control cells and subsequently analyzed by gas chromatography-mass spectrometry with selected-ion monitoring for DNA base damage. Quantification of damaged DNA bases was achieved by isotope-dilution mass spectrometry. The amounts of 8 products were significantly higher than control levels in cells treated with tert.-butyl hydroperoxide at a concentration range of 0.01-0.1 mM. At concentrations from 1.0 to 10 mM, product formation was inhibited and the amounts of products were similar to those in control cells. The bimodal nature of the dose-response may be qualitatively analogous to previous reports of bimodal killing of E. coli bacteria by hydrogen peroxide. The nature of the identified DNA base lesions suggests the involvement of the hydroxyl radical in their formation. tert.-Butyl hydroperoxide is known to produce the tert.-butoxyl radical in reactions with metal ions. However, it is unlikely that the tert.-butoxyl radical produces these DNA lesions. It is suggested that DNA base damage arises from tert.-butyl hydroperoxide-mediated oxidative stress in cells, resulting in formation of hydroxyl radicals in close proximity to DNA. The inhibition of product formation at high concentrations of tert.-butyl hydroperoxide may be explained by the scavenging of tert.-butoxyl radical by tert.-butyl hydroperoxide resulting in inhibition of oxidative stress. The plausibility of the scavenging mechanism was evaluated with a mathematical simulation of the dose-response for DNA damage in solutions containing hydrogen peroxide. The simulation model predicted a bimodal dose-response which agreed qualitatively with the results in this study and with other in vivo and in vitro studies reported in the literature.
TL;DR: The authors examined how parental and peer sexual socialization influences are related to gender, ethnicity, religious background, and college membership in a fraternities or sorority, and found that men continue to experience a more permissive sexual socialisation from both parents and peers compared to women.
Abstract: Socialization theories have included parents and peers as important determinants of the initial sexual standards and sexual behavior of teenagers and young adults. The purpose of the research reported here was to examine how parental and peer sexual socialization influences are related to gender, ethnicity, religious background, and college membership in a fraternity or sorority. A sample that included a majority of Caucasian university students and about 13% Asian and 7% Black students completed questionnaires both as entering first-year students and as seniors. Results indicated that compared to women, men continue to experience a more permissive sexual socialization from both parents and peers. Greek membership was associated with a more permissive socialization from peers but not parents. Asian students reported a more restrictive socialization than Blacks or Caucasians. Findings are discussed with respect to concerns of social scientists regarding the influence of fraternities and differential gender...
TL;DR: A fusion of soxS to MalE, which encodes maltose‐binding protein, is constructed and it is demonstrated that the in vivo expression of the MaIE‐SoxS fusion protein can provide SoxS function to a soxRS deletion mutant.
Abstract: In Escherichia coli, the soxRS genes effect the cell's defence against superoxide by activating the transcription of more than 14 genes, including zwf, sodA, nfo, micF and fumC. Previous work from other laboratories has indicated that SoxR is the sensor of oxidative stress and induces synthesis of SoxS, which in turn activates transcription of the regulon's target genes. Although SoxS appears to be a DNA-binding protein, its ability to bind to the promoter regions of target genes has not been demonstrated. To facilitate purification and characterization of SoxS, we constructed a fusion of soxS to malE, which encodes maltose-binding protein, and demonstrated that the in vivo expression of the MalE-SoxS fusion protein can provide SoxS function to a soxRS deletion mutant. We purified the fusion protein by affinity chromatography on an amylose column. The purified fusion protein stimulated in vitro expression of zwf in a coupled transcription-translation system and formed specific complexes with DNA fragments carrying target gene promoters. Moreover, MalE-SoxS protected from DNase I attack 22-27 bp segments immediately adjacent to or overlapping the -35 hexamers of the zwf, sodA, nfo, micF, and fumC promoters. The protected regions revealed a consensus 'soxbox' sequence.
TL;DR: An UV-sensitive class of photoreceptors exists in all regions of the retinas of mantis shrimps and may be useful for enhancing the visual contrast of midwater predators or prey.
TL;DR: S-(N-Aryl-N-hydroxycarbamoyl)glutathione derivatives are powerful competitive inhibitors of the anticancer target enzyme glyoxalase I and the N-p-bromophenyl derivative is the strongest inhibitor of the enzyme from human erythrocytes yet reported.
Abstract: S-(N-Aryl-N-hydroxycarbamoyl)glutathione derivatives are powerful competitive inhibitors of the anticancer target enzyme glyoxalase I. Indeed, the N-p-bromophenyl derivative is the strongest inhibitor of the enzyme from human erythrocytes yet reported (Ki = 1.4 x 10(-8) M). Structure-activity correlations indicate that the high affinities of the derivatives for both human and yeast glyoxalase I are due to the fact that the derivatives are hydrophobic analogs of the enediol(ate) intermediate associated with the glyoxalase I reaction. The derivatives also proved to be slow substrates for the thioester hydrolase glyoxalase II (bovine liver). Compounds of this type are of interest as potential tumor-selective anticancer agents, based on the abnormally low levels of glyoxalase II activity in some types of cancer cells.
TL;DR: In this article, a parameterization of first-order line-mixing in CO2 Q-branches is presented for use in atmospheric radiative transfer codes, and regression coefficients for the temperature dependence of the firstorder linemixing parameters for each J in 11 of the strongest q-branch between 600 and 3000/cm are given.
Abstract: A parameterization of first-order line-mixing in CO2 Q-branches is presented for use in atmospheric radiative transfer codes. Regression coefficients for the temperature dependence of the first-order line-mixing parameters for each J in 11 of the strongest Q-branches between 600 and 3000/cm are given. These coefficients may only be used with the line strengths and widths reported in the HITRAN92 line compilation; otherwise large errors will be introduced into the calculated line shape. Other potential problems in the implementation of first-order line-mixing in radiative transfer codes are also discussed.