Showing papers by "University of Connecticut published in 1989"

Conduction in Non-Crystalline Materials

Abstract: Abstract If the distance between atoms in a crystalline lattice is increased, an energy gap appears, which in a divalent material will separate occupied from unoccupied states of an electron. In a non-crystalline substance, a minimum is expected in the density of states (a ‘pseudogap’). An approximate theoretical estimate is given of the depth of the minimum at which the one-electron states become localized so that 〈σE(0)〉 vanishes; this turns out to be such that N(E F)/N(E F)free is about ⅓. The result depends rather sensitively on the parameters used; the value deduced from the experiments of Hensel and Franck (1966, 1968) on the resistivity of mercury at high temperatures gives for this ratio a value of ⅕. It is shown also that the localized states at the extremities of a valence or conduction band are of negligible importance if the wave functions are s-like on the atoms or ions, but may be of importance if they are not. A discussion is given of the electrical behaviour of chalcogenide glasses, amorph...

Standardization of International Marketing Strategy: Some Research Hypotheses:

Abstract: Two aspects of international marketing strategy standardization are process and program standardization. A framework for determining marketing program standardization is introduced. Factors affecti...

Development and Validation of the Computer Self-Efficacy Scale

Abstract: A 32-item Computer Self-Efficacy Scale (CSE) was developed to measure perceptions of capability regarding specific computer-related knowledge and skills Data from 414 individuals engaged in learning to use computers in three settings were used to conduct analyses for assessing the reliability and construct validity of the instrument A principal factor analysis with oblique rotation produced a conceptually meaningful 3-factor solution with high alpha reliabilities An additional analysis suggested that the males and females in this study differed in judgments of their computer capability

Nonlinear joint power spectrum based optical correlation.

Abstract: A nonlinear joint transform image correlator is investigated. The Fourier transform interference intensity is thresholded to provide higher correlation peak intensity and a better defined correlation spot. Analytical expressions for the thresholded joint power spectrum are provided. The effects of nonlinearity at the Fourier plane on the correlation signals at the output plane are investigated. The correlation signals are determined in terms of nonlinear characteristics of the spatial light modulator (SLM) at the Fourier plane. We show that thresholding the interference intensity results in a sum of infinite harmonic terms. Each harmonic term is envelope modulated due to the nonlinear characteristics of the device and phase modulated by m times the phase modulation of the nonthresholded joint power spectrum. The correct phase information about the correlation signal is recovered from the first-order harmonic of the thresholded interference intensity. We show that various types of autocorrelation signal can be produced simply by varying the severity of the nonlinearity and without the need to synthesize the specific matched filter. For example, the autocorrelation signal produced by a phase-only matched filter can be obtained by selecting the appropriate nonlinearity.

Fractal feature analysis and classification in medical imaging

Abstract: Following B.B. Mandelbrot's fractal theory (1982), it was found that the fractal dimension could be obtained in medical images by the concept of fractional Brownian motion. An estimation concept for determination of the fractal dimension based upon the concept of fractional Brownian motion is discussed. Two applications are found: (1) classification; (2) edge enhancement and detection. For the purpose of classification, a normalized fractional Brownian motion feature vector is defined from this estimation concept. It represented the normalized average absolute intensity difference of pixel pairs on a surface of different scales. The feature vector uses relatively few data items to represent the statistical characteristics of the medial image surface and is invariant to linear intensity transformation. For edge enhancement and detection application, a transformed image is obtained by calculating the fractal dimension of each pixel over the whole medical image. The fractal dimension value of each pixel is obtained by calculating the fractal dimension of 7*7 pixel block centered on this pixel. >

Somatic symptom index (SSI): a new and abridged somatization construct. Prevalence and epidemiological correlates in two large community samples.

Abstract: An abridged somatization construct (the Somatic Symptom Index) derived from the Diagnostic Interview Schedule's somatization disorder items was tested on community epidemiological samples to examine its prevalence, risk factors, and predictive value. The construct had a high prevalence (range, 4.4%

Selective release from cultured mammalian cells of heat-shock (stress) proteins that resemble glia-axon transfer proteins

Abstract: Cultured rat embryo cells were stimulated to rapidly release a small group of proteins that included several heat-shock proteins (hsp110, hsp71, hscp73) and nonmuscle actin. The extracellular proteins were analyzed by two-dimensional polyacrylamide gel electrophoresis. Heat-shocked cells released the same set of proteins as control cells with the addition of the stress-inducible hsp110 and hsp71. Release of these proteins was not blocked by either monensin or colchicine, inhibitors of the common secretory pathway. A small amount of the glucose-regulated protein grp78 was externalized by this pathway. The extracellular accumulation of these proteins was inhibited after they were synthesized in the presence of the lysine analogue aminoethyl cysteine. It is likely that the analogue-substituted proteins were misfolded and could not be released from cells, supporting our conclusion that a selective release mechanism is involved. Remarkably, actin and the squid heat-shock proteins homologous to rat hsp71 and hsp110 are also among a select group of proteins transferred from glial cells to the squid giant axon, where they have been implicated in neuronal stress responses (Tytell et al.: Brain Res., 363:161-164, 1986). Based in part on the similarities between these two sets of proteins, we hypothesized that these proteins were released from labile cortical regions of animal cells in response to perturbations of homeostasis in cells as evolutionarily distinct as cultured rat embryo cells and squid glial cells.

Average daily blood pressure, not office blood pressure, determines cardiac function in patients with hypertension.

Abstract: To determine the presence of cardiac disease in hypertensive patients with disparities between physician and out-of-office blood pressures, we prospectively studied three groups of age-matched patients identified by both casual (office) and ambulatory blood pressures: (1) office blood pressure greater than 140/90 mm Hg and awake ambulatory blood pressure of 130/80 mm Hg or less ("office" hypertensives); (2) office blood pressure less than 135/85 mm Hg and awake ambulatory blood pressure of 130/80 mm Hg or less (normotensives); and (3) office blood pressure greater than 140/90 mm Hg and awake ambulatory blood pressure of 140/90 mm Hg or greater ("daytime" hypertensives). In the patients with office hypertension, both the left atrial index and left ventricular mass index were significantly less than in patients with daytime hypertension and not statistically different from those of the normotensive subjects. Left ventricular filling rate at rest and ejection fraction at peak exercise were significantly greater in the office hypertensive group than in the daytime hypertensive group but were no different from those of the normotensive subjects. These findings demonstrate that patients with blood pressure elevation only in the physician's office have cardiac size and function similar to those of normotensive individuals. Thus, the average daily blood pressure best predicts cardiac end-organ damage. (JAMA1989;261:873-877)

The Influence of Particle Size on the Catalytic Properties of Supported Metals

Abstract: Publisher Summary Metals constitute a wide class of catalysts, and because catalysis occurs on the surface, there is an economic incentive, especially for precious metals, to obtain catalysts in the form of small metal particles. This, however, raises two main problems. One is fundamental in nature and addresses the question as to below which particle size the metallic properties are lost. The other is more practical and concerns the preparation and characterization of very small particles and their catalytic activity. The other problem concerns the practical ways of producing metals with particle sizes around the critical value calculated above. The easiest and most practical way to achieve this goal is to deposit the metal in low concentration on a high-surface-area support. The main purpose of using a carrier is, of course, to achieve a high dispersion of the metal and to stabilize it against sintering. In a number of reactions, however, the metal support is not inert and the overall process is actually a combination of two functions: that of the metal and that of the catalytically active support.

Banach spaces related to integrable group representations and their atomic decompositions. Part II

Abstract: We continue the investigation of coorbit spaces which can be attached to every integrable, irreducible, unitary representation of a locally compact groupG and every reasonable function space onG. Whereas Part I was devoted to atomic decompositions of such spaces, Part II deals with general properties of these spaces as Banach spaces. Among other things we show that inclusions, the quality of embeddings, reflexivity and minimality and maximality of coorbit spaces can be completely characterized by the same properties of the corresponding sequence spaces. In concrete examples (cf. Part III) one recovers several and often difficult theorems with ease.

Tracking a maneuvering target using input estimation versus the interacting multiple model algorithm

Abstract: Two maneuvering-target tracking techniques are compared. The first, called input estimation, models the maneuver as constant unknown input, estimates its magnitude and onset time, and then corrects the state estimate accordingly. The second models the maneuver as a switching of the target state model, where the various state models can be of different dimension and driven by process noises of different intensities, and estimates the state according to the interacting multiple model (IMM) algorithm. While the first requires around twenty parallel filters, it is shown that the latter, implemented in the form of the IMM, performs equally well or better with two or three filters. >

Health transition in middle-income countries: new challenges for health care

Abstract: The health transition occurring in middle-income countries such as Mexico is characterized by competition for scarce health resources between people with "leftover" ills such as infectious diseases and malnutrition and emerging threats such as chronic diseases mental illness and AIDS. This epidemiologic transition can not be expected to occur in the same way as it did in the industrialized countries. Their model was a series of 3 eras: pestilence and famine with high mortality no population growth and life expectancy of 20-40; receding pandemias and falling mortality with population growth; degenerative and man-made diseases with life expectancy over 50. In middle-income countries however the 3 eras are not necessarily sequential but may be protracted with reverses for some diseases. The co-existence of pre- and post-transitional diseases leads to polarization of different populations in the country. Data from Mexican mortality statistics indeed show decreased overall mortality from malaria childhood diarrhea and whooping cough but increased mortality from heart disease cancer diabetes and motor vehicle accidents. Data from Mexico City reveal falling postneonatal deaths due to diarrhea and respiratory infections but rising neonatal deaths (1st month of age) due to low birth weight and prematurity. Another aspect of the epidemiologic transition model is that the decline in mortality from infectious diseases in industrialized countries was due to lower incidence. In Mexico the incidence of infections remains high but mortality is lower because of antibiotics vaccines and vector control all reversible measures. Examples are diarrhea treated by ORT malaria considered "refractory" dengue fever considered "re-emerging" and AIDS considered "emerging." Resources to handle this continuing mixture of old and emerging diseases will be stressed to the limit with the coincident population growth due to momentum of the young population already born. 6 principles are presented to make primary health services equitable: population-based service delivery quality assurance community participation anticipatory care operation integrated with other social services and innovative models of health care.

Weed macaques: The evolutionary implications of macaque feeding ecology

Abstract: Patterns of feeding ecology among the living macaques conform poorly with recognized phyletic distinctions within the genus because there is an important ecological division which cross-cuts phyletic groupings. This division, between weed species and non-weed species, is based on the differing abilities of macaques to tolerate and even prosper in close association with human settlements. Based on available information about their ecology in the wild, we tentatively assign macaque species to these two categories. Finally, we consider the implications of our argument for scenarios of the initial spread of the macaques.

Mammalian pineal melatonin: A clock for all seasons

Abstract: The central role of the pineal gland and its hormone melatonin (MEL) in mammalian photoperiodic responses is discussed in terms of: 1) evidence for the involvement of MEL in photoperiodism, 2) which feature of the MEL secretion profile might be most important for regulating photoperiodic responses, 3) evidence for the modulation of responses to changes in daylength based on previous photoperiod exposure (i.e., photoperiodic history) and 4) how the MEL signal might be processed at its target sites to elicit physiological responses.

Impact of dental conditions on patients'quality of life

Abstract: – Quality of life measures have rarely been used in dentistry to assess oral health status. The purpose of this paper is to assess the utility of using standard indicators to measure the impacts of dental conditions on patients’ quality of life. Quality of life was conceptualized as a multidimensional construct including three major aspects: social functioning, measured by the Sickness Impact Profile; well-being, measured by the Gill Well-Being Scale, Spielberger State/Trait Anxiety Scale, and the Corah Dental Anxiety Scale; and symptoms, measured by the Kiyak Oral Functioning Scale, the McGill Pain Questionnaire, and the West Haven Multidimensional Pain Inventory. 152 patients were recruited from private dental practices consisting of 48 TMJ, 33 periodontal, 23 denture, and 48 recall patients. Patients in the first three groups reported numerous impacts on quality of life and the impacts were particularly severe for the TMI patients. The indicators used were sensitive to differences among the four groups and hold promise for further development of quality of life indicators for use in epidemiologic surveys and clinical dental trials.

Functional dioecy and andromonoecy in solanum.

Abstract: Field and laboratory studies of 19 diclinous species endemic to Australia help to clarify the nature and evolution of andromonoecy, androdioecy, and dioecy in the genus Solanum. Ten species are andromonoecious; typically these species bear inflorescences with a single, large basal hermaphroditic flower and 12-60 distal, smaller staminate flowers. We suggest that the andromonoecious condition was derived from hermaphroditic-flowered ancestors in part by hemisterilization of flowers but largely by addition of staminate flowers. The resultant larger inflorescences are hypothesized to serve both to attract and to entrain pollinators, yielding more or higher-quality seed set in hermaphroditic flowers and/or greater dispersion of pollen from staminate flowers. We suggest that andromonoecy may also serve to reduce selling. Nine other species are morphologically androdioecious but functionally dioecious. In these species, staminate flowers, like those of the andromonoecious species, bear anthers with copious tricolporate pollen and a highly reduced gynoecium. The morphologically hermaphroditic flowers are functionally pistillate and borne singly in inflorescences, and they bear anthers with inaperturate pollen. The inaperturate pollen, although viable, never germinates and is hypothesized to be retained in pistillate flowers as a reward to pollinators in the nectarless Solanum flowers. All other species of Solanum studied with pollen dimorphism in which one pollen morph is inaperturate are also best treated as functionally dioecious. We conclude that there is no evidence for androdioecy in Solanum. A review of other families suggests that there is little support for this unusual breeding system in any other angiosperm group either. Preliminary analyses suggest that andromonoecy and dioecy are polyphyletic in Solanum. Furthermore, dioecy is as likely to have arisen from hermaphroditic as from andromonoecious ancestors.

Efferent neurons and suspected interneurons in S-1 vibrissa cortex of the awake rabbit : receptive fields and axonal properties

Abstract: 1. The behavioral tractability of the rabbit was exploited and enabled, in the fully awake state, receptive-field analysis of antidromically identified efferent neurons within the vibrissa represen...

Explaining Vertical Integration: Lessons from the American Automobile Industry

Abstract: The early history of the American automobile industry provides fertile hunting grounds for theorists seeking corroboration of various, conflicting theories of vertical integration. An examination of the whole history suggests that no single theory always fits the facts perfectly. A complete explanation must combine specific theories in a way that is attentive to such factors as industry life-cycle, demand, economies of scale, and appropriability. If there is any “general” theory, it lies in the set of “dynamic” transaction-cost approaches rather than in the asset-specificity approach now dominant.

Affect comprehension in children with pervasive developmental disorders.

Abstract: Affect comprehension was studied in children with pervasive developmental disorders (PDD) and normal children matched for mental age. Three matching tasks were used: matching objects (a nonsocial control task), matching faces, and matching affects. The three tasks were developed to be of equal difficulty for normal children. Children were also tested for comprehension and expression of affect terms. The PDD children were impaired on affect matching relative to the normal controls. The PDD children were impaired on face and affect matching relative to their own performance on object matching, whereas the normal children were not. Within the PDD sample, object matching was correlated with mental age measures but not with measures of social behavior and play, but face and affect matching were significantly correlated with mental age as well as social behavior and play. Individual PDD children who showed relative deficits on face or affect matching tended to be more socially impaired than PDD children whose face and affect matching was consonant with their mental age. Results are discussed in terms of possible etiologies of the social deficit in PDD children, and the importance of subtypes within this population.

Multisensor tracking of a maneuvering target in clutter

Abstract: An algorithm is presented for tracking a highly maneuvering target using two different sensors, a radar and an infrared sensor, assumed to operate in a cluttered environment. The nonparametric probabilist data association filter (PDAF) has been adapted for the multisensor (MS) case, yielding the MSPDAF. To accommodate the fact that the target can be highly maneuvering, the interacting multiple model (IMM) approach is used. The results of single-model-based filters and of the IMM/MSPDAF algorithm with two and three models are presented and compared. The IMM has been shown to be able to adapt itself to the type of motion exhibited by the target in the presence of heavy clutter. It yielded high accuracy in the absence of acceleration and kept the target in track during the high acceleration periods. >

Risk of enamel fluorosis associated with fluoride supplementation, infant formula, and fluoride dentifrice use

Abstract: Eight hundred fifty 11- to 14-year-old residents of nonfluoridated communities in Massachusetts and Connecticut, who were born between 1972 and 1975, were investigated in a case-control study of the possible association between enamel fluorosis and exposure to fluoride supplements, infant formula, and/or fluoride dentifrice. The effect of median household income, an indicator of socioeconomic status, was also examined. Clinical examination, using the Fluorosis Risk Index, a fluorosis index developed for this project, allowed cases and controls to be identified based upon the specific time period of exposure to the various sources of ingested fluoride. Risk factor exposure was assessed via a mailed questionnaire with a response rate of 80%. Mild-to-moderate enamel fluorosis was strongly associated with fluoride supplementation during the first six years of life (odds ratio = 4.0) and with median household income (odds ratio = 6.6). Subjects in the middle median household income group who had used fluoride supplements through the first six years of life had a 28-fold increase in the risk of fluorosis compared with unexposed subjects in the lower median household income group. An odds ratio of 1.7 associated with infant formula use was suggestive of an increased risk of enamel fluorosis as was an odds ratio of 2.9 associated with fluoride dentifrice use.

Schedule generation and reconfiguration for parallel machines

Abstract: A methodology for scheduling independent jobs with due dates on identical, parallel machines is presented. The jobs have different levels of importance and various processing times on the machines, and the objective is to minimize the total weighted job tardiness of the schedule. Since the problem is NP hard, the goal is not to obtain the optimal schedule. Rather, an efficient near-optimal algorithm based on Lagrangian relaxation is presented. This approach provides a lower bound on the cost, which can be used as a measure of suboptimality. According to an implementation for a work center at Pratt and Whitney, most schedules generated are within 1% of the optima with reasonable CPU times. Furthermore, the method provides valuable job interaction information, which shop floor management uses to answer 'what if' questions, to reconfigure the schedule to accommodate dynamic changes, and to schedule new jobs. >

Terrestrial helium degassing fluxes and the atmospheric helium budget: Implications with respect to the degassing processes of continental crust

Abstract: The terrestrial degassing fluxes of He from continental crust, oceanic crust, mid-ocean ridges, subduction volcanism and hot-spot volcanism are estimated and/or reviewed. The only significant terrestrial sources of 3He are mid-ocean ridge (MOR) and subduction volcanism. The degassing of the continental crust (approximately equivalent to whole crustal production) represents ∼60% of the total terrestrial 4He degassing flux with MOR volcanism supplying an additional ∼22%. These terrestrial flux estimates are evaluated with regard to an atmospheric He budget, and the results strongly suggest a steady-state He atmosphere. To achieve a continental crustal degassing flux approximately equivalent to the whole crustal production, 4He must be released from the solid phase and transported from ∼40 km of crust to the atmosphere. A discussion of the mechanisms involved in this degassing process suggests the release of 4He by both small-scale and tectonic forcing functions. A much simplified model of pore-fluid transport in the crust suggests that this degassing flux can only be achieved by enhanced fluid/gas transport (advection/convection ). Fluid transport in the upper brittle crust is likely to be discontinuous, while in the lower ductile crust rapid transport by grain boundary diffusion is possible and consistent with theory. These results are in agreement with recent observations and theories on the magnitude of crustal fluid transport and strongly suggest that crustal fluid transport is ubiquitous, rapid and large-scale.