Showing papers by "University at Buffalo published in 1990"

Methodological Guidelines for Impedance Cardiography

Abstract: Impedance cardiography was introduced over 20 years ago as a noninvasive and unobtrusive technique for measuring systolic time intervals and cardiac output. Although our understanding of the physiological events reflected in the impedance cardiogram has become more refined, the technique's theoretical basis remains somewhat controversial and acceptance of its validity has relied heavily upon empirical validation. Largely as a consequence of this status, there have been inadequate grounds on which to develop sound methodological standardization. Currently, the methodological approaches that have been most frequently adopted may be viewed as representing the standard. The various aspects of impedance methodology are discussed, and alternative approaches described, with the objective of providing an informed basis for choosing among these methodological alternatives. It is recommended that studies utilizing impedance cardiography should be reported with clear and detailed methodological description. This should help clarify the extent to which methodological differences may underlie any discrepant research observations, as well as facilitate the emergence of improved methodological standards.

Coalescence and separation in binary collisions of liquid drops

Abstract: An extensive experimental investigation of the binary collision dynamics of water drops for size ratios of 1 075, and 05, for the Weber-number range of 1 to 100, and for all impact parameters is reported Two different types of separating collisions, namely reflexive and stretching separations, are identified Reflexive separation is found to occur for near head-on collisions, while stretching separation occurs for large-impact-parameter collisions The boundaries between both of the separating collisions and coalescence collision are found experimentally Theoretical models for predictions of the reflexive and stretching separation are also given

Seismic Isolation: History, Application, and Performance—A World View

Abstract: The concept of seismic or base isolation as a means of earthquake protection seems to be more than 100 years old. However, until very recently, few structures were built using this principle. Today the concept has matured into a practical reality and is taking its place as a viable alternate to conventional (fixed base) seismic resistant construction. This paper reviews some of the history of isolation and restates the basic elements of a modern isolation system. It then proceeds to review current activity, worldwide. Progress in the United States is discussed first followed by that in China, France, Greece, Italy, Japan, New Zealand and the Soviet Union. Directories of isolated structures in the United States, New Zealand and Japan are also included. Finally the performance of a selection of these structures during actual earthquakes is given.

Type 2 Diabetes Mellitus and Periodontal Disease

Abstract: The relationship between type 2 diabetes mellitus and periodontal disease was evaluated in 2,878 Pima Indians of the southwestern United States. Two independent measures of periodontal disease, probing attachment loss and radiographic bone loss, were used to compare prevalence and severity of periodontal disease in diabetic and nondiabetic subjects. In all age groups studied, subjects with diabetes had a higher prevalence of periodontal disease, indicating that diabetes may be a risk factor for periodontal disease.

Friction at a Lubricated Line Contact Operating at Oscillating Sliding Velocities

Abstract: Although many contacts operate under unsteady loading and sliding conditions, friction behavior under such conditions is still not well understood. In this paper we report on a series of experiments that were run to examine friction-velocity characteristics of line contacts operating under unsteady sliding velocities in the mixed, elastohydrodynamic and hydrodynamic lubrication regimes. A periodic, time-varying velocity component was superimposed on a steady sliding speed in such a way that all three lubrication regimes could be covered in a cycle. It was found that as the frequency of oscillation was increased, a multi-valued friction coefficient appeared as a loop about the average (steady state) friction-velocity relation. It is shown that this behavior can be modeled by a characteristic time lag between a changing velocity and the corresponding steady state friction. The latter is described by a single equation that was matched to measured average friction data. In the mixed lubrication regime, which is where this lag most significantly affects friction behavior, the lag time increases with normal load and lubricant viscosity. It is shown that the time shift is not associated with a fixed characteristic distance. The observed delay arises due to entrainment and normal approach, which includes squeeze-films combined with rough surface contact deformations.

Similarity neighbourhoods of words in young children's lexicons.

Abstract: Similarity neighbourhoods for words in young children's lexicons were investigated using three computerized databases. These databases were representative of three groups of native English speakers: 5-year-olds, 7-year-olds, and adults. Computations relating to the similarity neighbourhoods of words in the children's and adult's lexicon revealed that words in the 5- and 7-year-olds' lexicons have many fewer similar neighbours than the same words analyzed in the adult lexicon. Thus, young children may employ more global recognition strategies because words are more discriminable in memory. The neighbourhood analyses provide a number of insights into the processes of auditory word recognition in children and the possible structural organization of words in the young child's mental lexicon.

Estimation of the polar surface-tension parameters of glycerol and formamide, for use in contact-angle measurements on polar solids

Abstract: By measuring contact angles with water, glycerol and formamide on a number of polar surfaces, an estimate could be made of the electron-acceptor (γ+ ) and the electron-donor (γ− ) parameters of glycerol (G) and formamide (F), relative to the parameters of. water (W), for which a reference value of γ+ W = γ− W = 25.5 mJ/m2 has been assumed. The values thus found are: γ+ G ≈ 3.92 mJ/m2 (which yields γ− G ≈ 57.4 mJ/m2) and γ+ F ≈2.28 mJ/m2 (which yields γ− F ≈ 39.6 mJ/m2).

Children's Use of Anatomically Detailed Dolls to Recount an Event

Abstract: The use of anatomically detailed dolls in child sexual abuse investigations has raised several controversial issues related to important theoretical questions in developmental psychology. The present study was designed to examine some of these issues in a methodologically sound experiment. 80 3- and 5-year-old children experienced a social interaction with a male confederate and were later tested under 1 of 4 recall conditions: reenactment with anatomically detailed dolls, reenactment with regular dolls, free recall with visual cues, or free recall without visual cues. The children were also asked a variety of specific and misleading questions, some of them dealing with acts associated with abuse ("He took your clothes off, didn't he?"). Both anatomically detailed and regular dolls along with other props aided 5-year-olds more than 3-year-olds in recounting the event. To use increased rather than decreased age differences. Anatomically detailed dolls did not foster false reports of abuse. Overall, 3-year-olds were more suggestible than 5-year-olds. The findings have implications for children's testimony in child abuse cases and for psychological theories concerning the effects of stimulus support on children's memory.

Pneumonia: incidence, risk factors, and outcome in injured patients.

Abstract: One hundred thirty (44.2%) of 294 patients hospitalized for trauma and admitted to the Surgical Intensive Care Unit for mechanical ventilation developed hospital-acquired bacterial pneumonia. The predominant pathogens isolated were gram-negative enteric bacilli (72%), but there was not an increase in mortality associated with gram-negative pneumonia compared with similar patients without pneumonia. Of the seven admission risk factors univariately associated with the development of acquired bacterial pneumonia, only emergent intubation (p less than 0.001), head injury (p less than 0.001), hypotension on admission (p less than 0.001), blunt trauma as the mechanism of injury (p less than 0.001), and Injury Severity Score (p less than 0.001) remained significant after stepwise logistic regression. Not surprisingly, as mechanical ventilation is continued, the probability of pneumonia emerging increases. The consequences of hospital-acquired bacterial pneumonia are a significant seven-, five-, and two-fold increase in mechanically ventilated days, intensive care, and hospital stay, respectively. We conclude that the incidence of hospital-acquired pneumonia in injured patients admitted to the ICU for mechanical ventilation occurs in nearly half the patients, is associated with specific risk factors, and significantly increases morbidity but does not increase mortality.

Inositol metabolism in plants

Abstract: When detached flowers or isolated pistils of Lilium longiflorum are given myoinositol-U-14C or -2-3H as dilute solution through the severed pedicel, label is quickly distributed by the vascular system. In the case of pistils, a pattern of labeling in ovary, style, and stigma is obtained which indicates that products of myoinositol metabolism are utilized in the biosynthesis of exudate (secretion product) of the stigma and style as well as for components of pistil cell walls. Pollination had no discernible effect on labeling pattern.

An Evaluation of the Ensemble Averaged Impedance Cardiogram

Abstract: The ensemble averaged impedance cardiogram was evaluated during rest and during vocal mental arithmetic stress in samples of female (n=17) and male (n=40) undergraduates. Measures of myocardial performance determined from ensemble averaged signals were compared to those determined by simple beat-to-beat averaging over 60-s and 20-s sampling intervals. In addition, the influence of cardiac interval variability on dZ/dt amplitude measures was assessed. As expected, measures derived by the two averaging techniques corresponded closely, with correlations ranging from r=0.882 to r=1.000 for the 60-s sampling intervals, and from r=0.726 to r=1.000 for the 20-s sampling intervals. Inverse relationships of comparable magnitude were found between cardiac interval variability and dZ/dt amplitude measures determined by both averaging techniques, suggesting that these relationships did not result simply from artifacts introduced by the ensemble averaging technique. The results support the validity of ensemble averaging as a method for deriving impedance cardiographic measures of myocardial performance.

Mammographic changes associated with postmenopausal hormone replacement therapy: a longitudinal study.

Abstract: A retrospective study of radiologic findings from 50 postmenopausal women who underwent hormone replacement therapy was performed to determine the frequency and distribution of changes in the screen-film mammographic appearance of breast tissue between pretreatment and posttreatment mammography. Twelve (24%) of the women developed increased parenchymal density during a median follow-up of 18 months (range, 6-39 months). Mammographic changes included diffuse increase in density in seven (14%) of the women; increased multifocal, asymmetric densities in two (4%); and cyst formation in three (6%). A greater percentage of women who received estrogen-progesterone replacement (26%, 10 of 38) demonstrated changes than those who received estrogen alone (17%, two of 12), but the difference was not statistically significant. The authors conclude that benign increases in mammographic density associated with postmenopausal hormone replacement therapy are not uncommon, and they suggest that the serial changes observed in some women may diminish the sensitivity of mammography for the earlier detection of breast cancer.

Comparative Evaluation of Immunization with Live Attenuated and Enhanced-Potency Inactivated Trivalent Poliovirus Vaccines in Childhood: Systemic and Local Immune Responses

Abstract: Serum neutralizing, nasopharyngeal neutralizing, and IgA antibodies were determined in 123 infants immunized with one of four schedules containing live oral vaccine (OPV), inactivated vaccine (IPV), or combinations of the two trivalent poliovirus vaccines: OPV-OPV-OPV, IPV-IPV-IPV, IPV-OPV-OPV, or IPV-IPV-OPV. Nearly 100% of individuals formed serum neutralizing antibodies. The highest geometric mean titer (GMT) of antibody to polioviruses 1, 2, and 3 occurred in groups IPV-IPV-OPV, IPV-OPV-OPV, and IPV-IPV-IPV, respectively. Local neutralizing and IgA antibody responses were detected in 41%-88% and 75%-100%, respectively. Peak GMT of nasopharyngeal antibodies differed minimally between immunization groups. The data suggest that incorporation of at least one dose of IPV at the start of the immunization schedule tends to increase systemic as well as local antibody production.

X-ray analysis of the incommensurate modulation in the 2:2:1:2 Bi-Sr-Ca-Cu-O superconductor including the oxygen atoms

Abstract: Single-crystal x-ray diffraction data on the 2:2:1:2 Bi-Sr-Ca-Cu-O superconducting phase have been used in a four-dimensional refinement of the modulations of both the metal and oxygen atoms. An expression for an analytical temperature-factor modulation function has been derived and applied to the bismuth atoms. The large value of the temperature factor of Bi in some of the unit cells indicates a contribution from static disorder. The modulation of the oxygen atoms in the bismuth layer is best described by a function that allows the displacement to vary linearly with unit-cell position and incorporates the possibility of excess oxygen near the end of a modulation period. The results on oxygen occupancy and the behavior of the Bi temperature factor are compatible with models that attribute the origin of the modulation to the existence of extra oxygen atoms in the Bi-O layers. Refinement in the noncentrosymmetric super space group M:A2aa:1\ifmmode\bar\else\textasciimacron\fi{}11 leads to significantly better results than the centrosymmetric treatment.

Diet in the epidemiology of gastric cancer.

Abstract: We examined the nutritional epidemiology of gastric cancer in 293 cases and neighborhood-, age-, and sex-matched controls in communities throughout the counties of Niagara, Monroe, and Erie in western New York. The interview was highly detailed, requiring two and one-half hours to complete; it attempted to provide an estimate of total calories ingested as well as of macro- and micronutrients and behaviors that could affect alimentary exposures, such as the use of refrigeration. We found that risk was enhanced by sodium, fat, and retinol. Substantial reductions in risk were associated with ingestion of carotene, especially raw vegetables (including celery, cucumbers, carrots, green peppers, tomatoes, and onions), as well as with increased use of low-temperature food storage. Both refrigeration and carotene could inhibit oxidation products that could act as carcinogens in the stomach.

Long-term potentiation of electrotonic coupling at mixed synapses

Abstract: Long-term potentiation of chemical synapses is closely related to memory and learning. Studies of this process have concentrated on chemically mediated excitatory synapses. By contrast, activity-dependent modification of gap junctions, which also widely exist in higher structures such as hippocampus and neocortex, has not been described. Here we report that at mixed synapses between sensory afferents and an identified reticulospinal neuron, the electrotonic coupling potential can be potentiated, as well as the chemically mediated excitatory postsynaptic potential, for a prolonged time period using a stimulation paradigm like that which produces long-term potentiation in hippocampus. The effect on coupling is due to an increase in gap-junctional conductance. Our data indicate that the potentiation of both synaptic components requires an increase in intracellular calcium, involves activation of NMDA (N-methyl-D-aspartate) receptors, and is specific to the tetanized pathway.

A pattern identification approach to cartographic visualization

Abstract: Mental visualization and tools that foster it have recently been acknowledged as significant factors in scientific creativity. Cartography occupies a critical position in the growing array of scientific visualization tools, particularly for geographers, earth scientists and atmospheric scientists. Treating the map as a visualization tool leads to a different perspective on cartography than that generally taken when the map is viewed as a communication device. The goal of cartography and cartographic research shifts from a search for the optimal map to a search for spatial data abstraction methods that prompt pattern identification and lead to insight. A model is proposed for cartographic visualization that stresses the role of maps in data exploration. Emphasis is on the potential for maps to stimulate scientific insight by facilitating the discovery of patterns and relationships in spatial data. Following from this pattern identification model for cartographic visualization some perspectives are offered ...

Modification by Sialic Acid of Neisseria gonorrhoeae Lipooligosaccharide Epitope Expression in Human Urethral Exudates: An Immunoelectron Microscopic Analysis

Abstract: Expression of lipooligosaccharide (LOS) antigenic determinants during human gonococcal infection was studied in secretions from seven men with gonococcal urethritis. Five monoclonal antibodies with distinct gonococcal LOS specificities and an H.8 lipoprotein monoclonal antibody were used in combination with immunogold electron microscopic analysis. The LOS epitope defined by antibody 6B7 was present on all seven strains in secretions and after in vitro growth. Gonococci from six of seven patients, when grown in vitro, expressed the 6B4 LOS epitope. The 6B4 epitope is a Gal beta 1-4-GlcNAc residue, which is immunochemically similar to the precursor of the human erythrocyte i antigen. This epitope was found unmodified on gonococcal LOS in urethral secretions from two patients. The unmodified epitope could not be demonstrated on organisms in five secretions. Neuraminidase digestion exposed the 6B4 epitope on organisms in these secretions and increased the 6B4 epitope density in the two secretions, which contained the unmodified epitope. These studies indicate that in vivo modification by sialylation of gonococcal LOS Gal beta 1-4-GlcNAc residue occurs during human infection.

Aluminum Coagulation of Natural Organic Matter

Abstract: The concentration and nature of natural organic matter (NOM) influence the processes selected for water treatment plants. Water supplies containing NOM dominated by humic substances require careful design and operation of the chemical pre-treatment step of coagulation. Humic substances in untreated waters exert a greater demand for chemical coagulants compared to particulate matter, and their removal is important for health reasons because they are precursors to trihalomethanes and other disinfection by-products. Furthermore, coagulation affects the performance of downstream particle separation processes of clarification (sedimentation or flotation) and filtration.

The Reproductive Consequences Associated with Inducible Alkaloidal Responses in Wild Tobacco

Abstract: We experimentally examined the phenotypic cost (as measured by the effect on seed set) associated with an inducible alkaloidal response in Nicotiana sylvestris (Solanaceae). Alkaloid concentrations were partially uncoupled from leaf damage in two experiments with the use of two techniques: (1) applying auxins to damaged leaf edges, and (2) minimizing the damage to veins of the leaf. Both of these techniques inhibited the induced response. In both experiments with flowering—stage plants, damaged plants with elevated alkaloids contents had lower reproductive output than similarly damaged plants with low alkaloid contents. Plants were able to compensate for damage inflicted during the rosette stage; reproductive output of damage plants did not differ from that of control plants. In addition, we found a significant negative correlation between seed number and leaf alkaloid content in undamaged full—sib plants. While these results are consistent with the hypothesis that the alkaloidal response to damage is associated with diminished reproductive output, and decrement in reproductive output cannot be directly attributed to alkaloid production because other unmeasured responses to damage may accompany the alkaloidal response to damage and thereby confound these measures of phenotypic cost. Last, we examined the consequences of altering leaf alkaloid concentrations, within the range found during the induced response, on rates of carbon gain and found no effect in tobacco.