Showing papers by "University of Rochester published in 1986"

The role of mononuclear phagocytes in HTLV-III/LAV infection

Abstract: Cells with properties characteristic of mononuclear phagocytes were evaluated for infectivity with five different isolates of the AIDS virus, HTLV-III/LAV. Mononuclear phagocytes cultured from brain and lung tissues of AIDS patients harbored the virus. In vitro-infected macrophages from the peripheral blood, bone marrow, or cord blood of healthy donors produced large quantities of virus. Virus production persisted for at least 40 days and was not dependent on host cell proliferation. Giant multinucleated cells were frequently observed in the macrophage cultures and numerous virus particles, often located within vacuole-like structures, were present in infected cells. The different virus isolates were compared for their ability to infect macrophages and T cells. Isolates from lung- and brain-derived macrophages had a significantly higher ability to infect macrophages than T cells. In contrast, the prototype HTLV-III beta showed a 10,000-fold lower ability to infect macrophages than T cells and virus production was one-tenth that in macrophage cultures infected with other isolates, indicating that a particular variant of HTLV-III/LAV may have a preferential tropism for macrophages or T cells. These results suggest that mononuclear phagocytes may serve as primary targets for infection and agents for virus dissemination and that these virus-infected cells may play a role in the pathogenesis of the disease.

Methods of multilocus enzyme electrophoresis for bacterial population genetics and systematics

Abstract: Methodes d'extraction d'enzymes, d'electrophorese en gel et de coloration specifique des enzymes utilisees pour etudier la variation genetique chez Escherichia coli et d'autres bacteries. Les procedures decrites peuvent s'appliquer, avec quelques modifications mineures, a toute espece de bacterie

Complex Cobordism and Stable Homotopy Groups of Spheres

Abstract: An introduction to the homotopy groups of spheres Setting up the Adams spectral sequence The classical Adams spectral sequence $BP$-theory and the Adams-Novikov spectral sequence The chromatic spectral sequence Morava stabilizer algebras Computing stable homotopy groups with the Adams-Novikov spectral sequence Hopf algebras and Hopf algebroids Formal group laws Tables of homotopy groups of spheres Bibliography Index

Origins and pawns in the classroom: Self-report and projective assessments of individual differences in children's perceptions.

Abstract: Two studies examined the significance of children's perceptions of their classroom environment along autonomy versus external control dimensions. Study 1 related a self-report measure of the perceived classroom climate to other self-related constructs. In a sample of 140 elementary children, it was found that the more "origin" the children perceived in their classroom, the higher their perceived self worth, cognitive competence, internal control, and mastery motivation, and the lower their perceived control by unknown sources or powerful others. These relationships were primarily due to individual differences within classrooms rather than average classroom differences. Children also wrote projective stories about an ambiguous classroom scene. Ratings of these stories indicated that, within children's fantasy, origin-like behavior of students was associated with autonomy-oriented teachers and low aggression. Self-report and projective methods converged, particularly for children whose self-reported perceptions were extreme. In a second study (N = 578), relative contributions of classroom and individual difference effects were further examined. Results are discussed in terms of the importance of perceived autonomy and issues in assessment strategies.

American Voter Turnout in Comparative Perspective

Abstract: Despite relatively favorable citizen attitudes, voter turnout in American national elections is far below the average of 80% of the eligible electorate that votes in other industrialized democracies. The American institutional setting—particularly the party system and the registration laws—severely inhibits voter turnout, and probably also accounts for the unusual degree to which education and other socioeconomic resources are directly linked to voting participation in the United States.Using a combination of aggregate and comparative survey data, the present analysis suggests that in comparative perspective, turnout in the United States is advantaged about 5% by political attitudes, but disadvantaged 13% by the party system and institutional factors, and up to 14% by the registration laws. The experience of other democracies suggests that encouraging voter participation would contribute to channeling discontent through the electoral process. Even a significantly expanded American electorate would be more interested and involved in political activity than are present voters in most other democracies.

Constraint propagation algorithms for temporal reasoning

Abstract: This paper considers computational aspects of several temporal representation languages. It investigates an interval-based representation, and a point-based one. Computing the consequences of temporal assertions is shown to be computationally intractable in the interval-based representation, but not in the point-based one. However, a fragment of the interval language can be expressed using the point language and benefits from the tractability of the latter.

Change in View

Abstract: Change in view : , Change in view : , کتابخانه دیجیتال و فن آوری اطلاعات دانشگاه امام صادق(ع)

Experimental realization of a localized one-photon state.

Abstract: In the process of spontaneous parametric down-conversion a signal and an idler photon are created simultaneously. By use of the photoelectric detection of the signal photon as a gate, a good approximation to the ideal localized one-photon state can be achieved. This has been confirmed by direct photon-counting measurements.

The Teacher–Child Rating Scale: A brief objective measure of elementary children's school problem behaviors and competencies.

Abstract: This paper presents two related studies describing the development and validation of the Teacher-Child Rating Scale (T-CRS), a brief objective socioemotional measure. More than 200 teachers rated 1...

Generalized plan recognition

Abstract: This paper outlines a new theory of plan recognition that is significantly more powerful than previous approaches. Concurrent actions, shared steps between actions, and disjunctive information are all handled. The theory allows one to draw conclusions based on the class of possible plans being performed, rather than having to prematurely commit to a single interpretation. The theory employs circumscription to transform a first-order theory of action into an action taxonomy, which can be used to logically deduce the complex action(s) an agent is performing.

Athletic injuries: Comparison by age, sport, and gender

Abstract: Injuries treated at the University of Rochester Section of Sports Medicine over a 7 year period were surveyed. Patients were drawn from professional, intercollegiate (Division III), high school, intramural, and unorganized athletics at the University and the surrounding community. Data on injury diagnosis was available for 4,551 cases, with data on age, gender, and sport of injury available for 3,431 of the cases. The average patient age was 21.6 years, with a peak in the 16 to 19 age group. Patients with fractures had an average age below the overall mean, while those with internal derangement of the knee, patellofemoral pain syndrome, and inflammatory injuries were significantly older than average. Males accounted for 80.3% of all injuries. For both sexes the most common areas injured were the knee and ankle, with sprains/strains the most common injuries. Injuries involving the patellofemoral articulation were significantly more frequent among females. The most common sport of injury was football, with greater than 12 times the number of injuries seen in the next most common sport.

A study of classification criteria for a diagnosis of juvenile rheumatoid arthritis.

Abstract: Criteria for the classification of juvenile rheumatoid arthritis were analyzed in a detailed database of 250 children in order to assess the accuracy of diagnosis and validity of onset types and course subtypes. A number of conclusions have been derived from this study: All definitions of the 1973 criteria for classification of juvenile rheumatoid arthritis should be retained. The addition of onset types to the 1976 revision of the criteria has been validated. The course of the disease after the onset period of 6 months is as important to the outcome of a group of children as is the onset type. The current classification should be broadened to include the course subtypes.

Subpicosecond electrooptic sampling: Principles and applications

Abstract: This paper reviews the principles and applications of electrooptic sampling for the characterization of repetitive ultrafast electrical transients. Electrooptic sampling is an electric field sensitive technique that utilizes ultrashort optical pulses as "sampling gates" via the Pockels effect in electrooptic media and has demonstrated subpicosecond temporal resolution and microvolt sensitivity. The technique can be adapted to characterize a wide variety of picosecond electronic devices such as field-effect transistors and photodetectors as well as probe complete integrated circuits with high temporal and spatial resolution.

Mechanisms of color constancy.

Abstract: We develop a model of how the visual system finds the colors of objects that have unknown shapes and positions. The model relies on mechanisms of light adaptation, coupled with eye movements, to recover three descriptors of surface reflectance that are represented in the signals of an achromatic mechanism and two color-opponent mechanisms. These descriptors are transformed to yield estimates of hue, the dimension of surface color that is independent of object shape and viewing geometry.

Theory of a microscopic maser

Abstract: We present the theory of a truly microscopic maser consisting of a single-mode high-Q resonator in which a monoenergetic beam of excited two-level atoms is injected at such a low flux that at most one atom at a time is present inside the cavity. Both a microscopic theory and a heuristic Fokker-Planck approach are presented. We show that the micromaser exhibits a number of novel features that are averaged out in usual masers and lasers. First, the field is in general sub-Poissonian, which reflects the quantization of both the field and its sources. Second, the onset of maser oscillations may be followed by a succession of abrupt transitions in the state of the field. Finally, as the atomic flux through the resonator is increased, the maser threshold acquires characteristics of a continuous phase transition, whereas the subsequent changes in the field distribution become analogous to first-order phase transitions.

Cortical connections and parallel processing: structure and function

Abstract: The cerebral cortex is a rich and diverse structure that is the basis of intelligent behavior. One of the deepest mysteries of the function of cortex is that neural processing times are only about one hundred times as fast as the fastest response times for complex behavior. At the very least, this would seem to indicate that the cortex does massive amounts of parallel computation.This paper explores the hypothesis that an important part of the cortex can be modeled as a connectionist computer that is especially suited for parallel problem solving. The connectionist computer uses a special representation, termed value unit encoding, that represents small subsets of parameters in a way that allows parallel access to many different parameter values. This computer can be thought of as computing hierarchies of sensorimotor invariants. The neural substrate can be interpreted as a commitment to data structures and algorithms that compute invariants fast enough to explain the behavioral response times. A detailed consideration of this model has several implications for the underlying anatomy and physiology.

Invariance of the spectrum of light on propagation.

Abstract: The question is raised as to whether the normalized spectrum of light remains unchanged on propagation through free space. It is shown that for sources of a certain class that includes the usual thermal sources, the normalized spectrum will, in general, depend on the location of the observation point unless the degree of spectral coherence of the light across the source obeys a certain scaling law. Possible implications of the analysis for astrophysics are mentioned.

Virus isolation from and identification of HTLV-III/LAV-producing cells in brain tissue from a patient with AIDS.

Abstract: Primary cultures from a brain biopsy specimen of a human T-cell lymphotropic virus type III/lymphadenopathy-associated virus (HTLV-III/LAV) seropositive patient with progressive dementia contained small numbers of monocytoid cells and showed reverse transcriptase activity that persisted for as long as 100 days. Electron microscopy of these cells revealed the presence of HTLV-III/LAV virions. Subcultured cells removed from primary cultures by trypsinization were nonspecific esterase negative and did not express virus or show evidence of HTLV-III/LAV proviral sequences, while those remaining in the original flasks were nonspecific esterase positive and continued to produce virus. Virus from primary cultures was transmitted to peripheral blood-derived monocytemacrophages and T cells. Virus production in T-cell cultures was transient while the monocyte-macrophages, like the primary cultures, produced virus for at least 120 days. Infection of several brain-derived cells with this and another HTLV-III/LAV isolate failed to demonstrate virus replication. These results indicate that the HTLV-III/LAV-infected cells recovered from the brain of this patient are cells of the mononuclear phagocyte series. ( JAMA 1986;256:2365-2371)

Models for analysis of packet voice communications systems

Abstract: In a packet voice communication system, packets are fed to a common queue by a number of independent voice sources and are removed from this queue on a first-come-first-serve basis for transmission over a communication link of finite capacity. Each voice source alternates between active periods, during which packets are generated at regular intervals, and inactive periods, during which no packets are generated. In this paper, we discuss three models, a semi-Markov process model, a continuous-time Markov chain model, and a uniform arrival and service model, to assess the queueing behavior of such systems. Numerical results obtained from each of the three models are compared to each other, to results obtained from a discrete event simulation program, and to results obtained from an M/D/1 analysis. Parameters of the model are the average duration of active and inactive periods, the packet generation rate, the communication link capacity, and the total number of voice sources. Conclusions are drawn regarding which models appear to be most appropriate in the parameter ranges investigated.

Genetic relationships of serologically nontypable and serotype b strains of Haemophilus influenzae.

Abstract: A collection of 242 strains of Haemophilus influenzae, including 65 nontypable (unencapsulated) isolates and 177 encapsulated serotype b isolates recovered largely from children with invasive and noninvasive diseases in the United States, was characterized by the electrophoretic mobilities of 15 metabolic enzymes presumably encoded by chromosomal genes. All enzymes were polymorphic for three to seven electromorphs, and 94 distinctive multilocus genotypes (electrophoretic types [ETs]) were distinguished, among which mean genetic (allelic) diversity was 0.500. Isolates recovered from cases of invasive or noninvasive diseases did not differ significantly in level of genetic variation. The observation that 29 ETs were represented exclusively by serotype b isolates and that each of the 65 nontypable isolates was of a unique ET strongly confirmed the hypothesis that unencapsulated clinical isolates are not merely phenotypic variants of the common serotype b cell lines. Rather, the two types of isolates are distinctive subsets of the multilocus chromosomal genotypes of the species as a whole. Serotype b capsule occurred in three groups of isolates that are distantly related in multilocus enzyme genotype. Isolates of four closely related nontypable biotype IV ETs associated with obstetrical infections or neonatal bacteremia were highly divergent from all others examined and may be specifically distinct. A phylogenetic scenario was proposed in which the ancestor of H. influenzae was encapsulated and the nontypable clones arose by convergent evolutionary loss of the ability to synthesize or extracellularly express a polysaccharide capsule.