Showing papers by "University of Houston published in 1981"

Postnatal development: coordination of feeding, digestion, and metabolism.

Abstract: The rat is immature at birth and undergoes major developmental changes at the end of the suckling period. This review deals with the maturation of ingestive behavior, gastrointestinal digestive and absorptive functions, liver metabolism, and brain structure and function. Each aspect of development is physiologically correlated with the dietary transition of weaning. However, it is unlikely that the process of weaning acts as a cue for the ontogenic changes. In contrast, there is strong evidence for an important role of both thyroxine and corticosterone as coordinators of maturational events in various organ systems.

The internal dynamics of globular proteins.

Abstract: (1981). The Internal Dynamics of Globular Protein. Critical Reviews in Biochemistry: Vol. 9, No. 4, pp. 293-349.

Vascular endothelial morphology as an indicator of the pattern of blood flow.

Abstract: A quantitative study of the en face size and shape of endothelial cells from aortic intercostal ostia has been carried out in rabbits. Photomicrographs were taken from vascular casts of the rabbit aorta and the endothelial cell outlines were analyzed quantitatively using a digitizer and digital computer. The morphology of the endothelial cells was described using 8 calculated parameters (area, perimeter, length, width, angle of orientation, width: length ratio, axis-intersection ratio and shape index). Marked changes in cell morphology were found in the regions proximal and distal to ostia as well as around flow dividers. Cells on the aorta are aligned with the flow direction, and the endothelial cells within the ostia have an angle of orientation of approximately 45 deg to the axis of the vessel. The results obtained to date suggest that endothelial cell morphology and orientation around a branch vessel may be a natural marker or indicator of the detailed features of blood flow.

The ‘preferred mode’ of the axisymmetric jet

Abstract: Detailed distributions of different time-average and phase-average flow properties for an axisymmetric free jet under controlled perturbation at the jet preferred mode are explored. The data are compared with the corresponding unexcited jet data. It is found that the effect of the perturbation is to increase jet spread and mean velocity decay, as well as to increase the peak values of the time-average fluctuation intensities and Reynolds stress in the axisymmetric mixing layer.

Institutional Context and Leadership Style: The House from Cannon to Rayburn

Abstract: This article deals with the transition in House leadership from Cannon to Rayburn. The transition involved moving from a hierarchical pattern of leadership to a bargaining pattern. In accounting for this transition, we argue that it is the institutional context of the House that determines leadership power and style. Moreover, we argue that there is no straightforward relationship between leadership style and effectiveness; rather, style and effectiveness are contingent or situational. We conclude that the impact of institutional context on leadership behavior is itself primarily determined by party strength. When party strength is high, power is concentrated and leaders are task- or goal-oriented, whereas when party strength is low, power is dispersed and leaders will be oriented to bargaining and maintaining relationships.

Turbulence suppression in free shear flows by controlled excitation.

Abstract: Turbulence suppression in the near field of a free shear flow under controlled excitation is investigated in four circular jets, a plane jet, and a plane mixing layer The suppression is a consequence of an excitation-induced modification of the shear layer structure and occurs at the excitation frequency corresponding to the maximally unstable disturbance frequency of the initial free shear layer The most pronounced suppression occurs when the shear layer is excited at a frequency 40% higher than the natural roll-up frequency Excitation at a Strouhal number of about 0017 produces a rapid roll-up and early breakdown of the shear layer, and thus inhibits the formation of the energetic large-scale vortices which otherwise survive farther downstream, grow to larger sizes, and undergo successive pairings in the corresponding unexcited flow

An Evolutionary Strategy for Implementing a Decision Support System

Abstract: This paper investigates two alternative strategies for implementing Decision Support Systems DSS: evolutionary and traditional. The evolutionary approach utilizes judgement modeling boot strapping as a means to create felt need, to provide insight into the decision process and the implied weighting of decision variables, and to establish a learning-based, participatory implementation strategy. In contrast, the traditional approach is characterized by a problem solving orientation wherein the DSS is portrayed as providing a valuable "product" that can be theoretically justified. Decision making in a simulated production environment is used to test the alternative strategies. Decision style is also included in the experimental design. Results indicate significantly higher utilization of the DSS with the evolutionary approach. Decision style findings are consistent with reported research.

Retrolental Fibroplasia: Efficacy of Vitamin E in a Double-Blind Clinical Study of Preterm Infants

Abstract: We performed a double-blind study in 101 preterm infants who weighed less than or equal to 1500 g at birth, who had respiratory distress, and who survived for at least four weeks, to evaluate the efficacy of oral vitamin E in preventing the development of retrolental fibroplasia. Weekly indirect ophthalmologic examinations begun when the infants were three weeks old revealed a significant decrease in the incidence of retrolental fibroplasia greater than or equal to Grade III (P less than 0.03) and greater than or equal to Grade II (P less than 0.05) (McCormick classification) in the 50 infants given 100 mg of vitamin E per kilogram of body weight per day as compared with 51 given 5 mg per kilogram per day (controls). When multivariate analysis was applied to the controls, five risk factors were identified: gestational age, level and duration of administration oxygen, intraventricular hemorrhage, sepsis, and birth weight. When multivariate analysis was applied to both control and treatment groups, the severity of retrolental fibroplasia was found to be significantly reduced in infants given 100 mg of vitamin E (P = 0.012).

Taylor hypothesis and large-scale coherent structures

Abstract: The applicability of the Taylor hypothesis to large-scale coherent structures in turbulent shear flows has been evaluated by comparing the actual spatial distributions of the structure properties with those deduced through the use of the hypothesis. This study has been carried out in the near field of a 7[sdot ]62 cm circular air jet at a jet Reynolds number of 3[sdot ]2 x 104, where the coherent structures and their interactions have been organized through controlled excitation. Actual distributions of the structure properties have been obtained through phase-average hot-wire data, the measurements having been repeated at different spatial points over the extents of the structure crosssections at a fixed phase. The corresponding ‘spatial’ distributions of these properties obtained (by using the Taylor hypothesis) from the temporal data at appropriate phases and locations, show that the hypothesis works quite well for an isolated coherent structure if a constant convection velocity, equal to the structure centre velocity, is used in the hypothesis everywhere across the shear flow. The popular use of the local time-average or even the instantaneous streamwise velocity produces unacceptably large distortions. When structure interactions like pairing are involved, no convection velocity can be found with which the hypothesis works. Distributions of the terms in the Navier–Stokes equation contributing to the phase-average vorticity, but neglected by the hypothesis, have been quantitatively determined. These show that the terms associated with the background turbulence field, but not those associated with the coherent motion field, can be neglected. In particular, the pressure term due to the coherent motion field is large and cannot be neglected.

The Effects of Reference Prices in Retail Advertisements

Abstract: This article considers the effects of reference prices in retail advertisements, that is, comparison prices cited as evidence of the savings represented by advertised prices. Reference prices are f...

2,3,7,8-Tetrachlorodibenzo-p-Dioxin

Abstract: This teratogen is so toxic that the U.S. Environmental Protection Agency recommends that analytical laboratories do not acquire the authentic material for use as a standard. It is present as an impurity in chlorinated phenols and related compounds. It is a particular hazard in waste materials produced as byproducts in the manufacture of such compounds.

On the coherent structure of the axisymmetric mixing layer: A flow-visualization study

Abstract: In an effort to resolve some controversies regarding the turbulent mixing-layer structure, the near field of a large (18 cm diameter) air jet has been investigated for the jet exit speed of 30 m s−1. The smoke-laden axisymmetric mixing layer has been illuminated by a thin sheet of laser light in an azimuthal plane passing through the jet axis. High-speed visualization films of the mixing layer in the region of its self-preservation (of which a few picture sequences depicting space-time evolutions of the structure of the layer are presented) reveal that most of the time the mixing layer is in a state of disorganization, consisting of relatively smaller scale, random and diffuse turbulent motions; only occasionally are organized distinct large-scale coherent structures formed. The survival distances of the large-scale structures are found to be comparable to their average sizes. The survival time of these structures is about one ‘turnover’ time, each being roughly about five times the local characteristic time scale of the mixing layer. It is seen that tearing is as dominant a mode of large-scale interaction as pairing is; large-scale structures are continually sheared and typically fragmented due to a segment on the high-speed side being torn and swept away from the slower-moving outer portion. Evolution of the large structures occur not primarily through complete pairing as widely believed but quite frequently through ‘fractional pairing’ between segments which have been torn from different upstream large-scale coherent structures or through ‘partial pairing’ when one structure captures only a part of another. The movies show that along with entrainment of non-vortical ambient fluid, radially outward ejection of vortical fluid into the ambient is an important aspect of jet mixing. From aligned displays of cine film frame sequences, space-time trajectories of identifiable vortical fluid elements have been traced. The convection velocity variation across the shear layer and even the overall structure convection velocity measured from these trajectories agree with those determined from the wave-number-celerity spectra, obtained from double-Fourier transformation of longitudinal velocity space-time correlation measurements with hot-wires.The visualization films do not bear out the two-street vortex ring model recently propounded by Lau. Based on our observations, we propose that tearing, ‘slippage’ and fractional and partial pairings are responsible for the observed radial variation of structure passage frequency, and the causes of the different coherent structures educed by Bruun on the high- and low-speed sides of the mixing layer and for Yule's failure in educing a coherent structure on the low-speed side of the layer.

Intermediary metabolism during low temperature acclimation in the overwintering gall fly larva, Eurosta solidaginis

Abstract: 1. The levels of glycogen, lipid, protein, polyols (glycerol and sorbitol), sugars, amino acids, adenylates, and other intermediary metabolites were measured in the overwintering, third instar larvae of the gall fly,Eurosta solidaginis, sampled at specified temperatures during a controlled (1°C per day decrease) low temperature acclimation of the larvae from 15° to − 30°C. 2. Glycogen reserves were depleted as temperature was decreased, the decrease in glycogen fully accounting for the observed increases in glycerol, sorbitol, glucose, and trehalose in the larvae at low temperatures. Protein and total glyceride reserves of the larvae, however, were not altered during low temperature acclimation. 3. Temperature specific patterns of glycerol and sorbitol accumulation were found. Glycerol concentrations, which were 65% of maximum at 15°C, reached a plateau in concentration of 235 μmol/g wet wt. between 5 and 0°C. Sorbitol first appeared in larvae at 5° C and then increased in concentration rapidly as temperature decreased further to reach a plateau level of 145 μmol/g wet wt. by −10°C. 4. The free amino acid pool increased in size by 50% during acclimation from 15 to −5°C, this increase due largely to a 24 μmol/g wet wt. increase in proline concentration and a smaller 4.4 μmol/g wet wt. increase in alanine. 5. Arginine phosphate and ATP levels, as well as energy charge and the ratio [ATP]/[ADP]·[Pi], remained high and constant in larvae acclimated to temperatures as low as −5°C but in larvae acclimated to −30°C phosphagen and ATP levels had declined by 54 and 29% respectively and energy charge had decreased from 0.92 to 0.82. 6. The data suggest that aerobic metabolism with continued polyol synthesis is fully active in these larvae at temperatures as low as −10°C. However, below −10°C, the temperature at which hemolymph freezing takes place, mitochondria appear to be metabolically inactive. Evidence for this includes the cessation of polyol, sugar, and amino acid accumulation by this temperature and the drop in arginine phosphate, ATP, and energy charge and build-up of lactate at −30°C. 7. The regulation of metabolism inE. solidaginis larvae during low temperature acclimation is discussed with particular emphasis on the possible metabolic ‘switches’ regulating the flow of carbon to glycerol versus sorbitol synthesis.

Gated binding of ligands to proteins

Abstract: The binding of ligands to proteins often occurs at rates that approach the diffusion-controlled limit1. For spherical molecules with negligible interactions apart from isotropic reactivity on contact, the diffusion-controlled rate constant is KD≡ 4πRD, where R is the distance between molecular centres at contact and D is the relative translational diffusion constant1–3. Deviations from this limiting rate due to interaction potentials4,5, hydrodynamic interactions6,7 and static geometric features of the binding sites8–13 have previously received much attention. Here, we point out another possible cause of such deviations, the dynamic modulation of binding site accessibility due to internal motions of the protein. Such motions may occur, for example, in proteins such as lysozyme, in which the active site cleft opens and closes in a stochastic manner14,15.

On the One-Dimensional Space Allocation Problem

Abstract: The One-Dimensional Space Allocation Problem ODSAP arises when locating rooms along a corridor, when setting books on a shelf, when allocating information items among the "cylinders" of a magnetic disk, or when storing products in certain warehouses The rooms objects to be located have a known length or width and, for each pair of rooms, there is a given number of "trips" between them; the problem is to find a sequencing of the rooms which minimizes the total traveled distance This paper deals first with two particular cases In the rooted tree case, previous results obtained by Adolphson and T C Hu for the Linear Ordering Problem are extended and provide efficient solution methods In addition, it is shown that most of the assumptions made by Adolphson and Hu are necessary, since relaxing any of them leads to an NP-complete problem In the case of independent destinations solved by Bergmans and Pratt when all lengths are equal, a unimodality property is shown for an optimum solution, but this is not sufficient to lead to a "good" algorithm and the problem is shown to be NP-complete For the general problem, an exact algorithm using dynamic programming is described and computationally tested

Bed Allocation in a Public Health Care Delivery System

Abstract: Due to changing patient loads and demand patterns over time, assigning bed complements for various medical services in a hospital is a recurring problem facing the administrators. For a large public health care delivery system, we present an approach for periodically reallocating beds to services to minimize the expected overflows. Using a queueing model to approximate the patient population dynamics for each service-with admission rates provided by forecasts-the expected overflows under each configuration are computed via a Normal loss integral. Bed allocation is done in two stages. First, we establish a base line requirement for each service so that it can handle a prescribed amount of patient load based on a yearly projection of demand. We then use marginal analysis to distribute the remaining beds to minimize the expected total average overflows while taking month-to-month demand fluctuations into account. The proposed model requires only a modest amount of computation, because of several simplifying assumptions, which were tested for reasonableness. For the two largest services, we used empirical data to evaluate the nonhomogeneous Poisson representation of admissions, and we performed simulation experiments to assess the extent of discrepancy in performance characteristics caused by the ignorance of day-of-week effect on admission rates. In view of the intrinsic complexity of the underlying system, the results obtained from the validation studies suggest that the model is relatively "robust" with respect to the case under consideration. It is hoped that the simplicity of the model and the usefulness of the results will induce practitioners to use this type of formal analysis for bed allocation in an institutional setting on a routine basis.

Why Do People Vote? Because They Are Registered

Abstract: This article separately investigates who registers to vote and who votes among the registered. Standard predictors of participation are much better predictors of registration than of voting among the registered. It is speculated that voting is stimulated by the act of registration.

The elliptical microstrip antenna with circular polarization

Abstract: A theoretical analysis of an elliptical microstrip antenna is presented. It is shown that radiation from this antenna is left-hand or right-hand circularly polarized in a narrow frequency band when the eccentricity of the ellipse is small. The theoretical result agrees with the experimental data.

Incidence of Plasmids in Marine Vibrio spp. Isolated from an Oil Field in the Northwestern Gulf of Mexico

Abstract: Presumptive marine Vibrio spp. were collected from an operational oil field and control site located in the northwestern Gulf of Mexico. Of 440 isolates analyzed for the presence of extrachromosomal deoxyribonucleic acid elements or plasmids by using the cleared lysate and agarose gel techniques, 31% showed distinct plasmid bands on agarose gels. A majority of the plasmids detected were estimated to have molecular masses of 10 x 10 or less. Multiple plasmids were observed in approximately half of the plasmid-containing strains. A number of isolates contained plasmids with similar banding and mobility patterns. The oil field area had noticeably more plasmid-containing strains (35 versus 23% in the control site) and a greater number of plasmids per plasmid-containing strain (an average of 2.5 plasmids, versus 1.5 in the control site). Oil field discharges might have resulted in increased plasmid incidence and diversity.

Revision of kynch sedimentation theory

Abstract: Much of the theory of gravity sedimentation has been based on the work of Coe and Clevenger (1916) and Kynch (1952). They provided methods for obtaining rates of sedimentation in batch, static tests which are presently used for design of continuous thickeners. Kynch assumed that a first order partial differential equation controlled the entire sedimentation process. His equation was based on: (1) continuity balance; and (2) sedimentation velocity being a unique function of solid particulate concentration. A general solution was presented in the form of volume fraction of solids ϕs = f(x − vt). During the constant rate fall of the upper interface, the boundary condition of uniform initial concentration combines with the Kynch equations to adequately describe the sedimentation phenomena. Kynch ignored the sediment rising from the bottom of the settling chamber, and assumed that the characteristics y = x − vt originated at the origin of coordinates (height, time) during the first falling rate period. The characteristics actually originate at the surface of the rising sediment where the upward liquid velocity affects the rate of fall of the particulates. New equations have been derived based upon the assumption that the characteristics emanate from the rising sediment.

Homogeneous Nucleation and the Spinodal Line

Abstract: The limit of homogeneous nucleation in a liquid is shown to lie very close to its liquid spinodal line. It is also argued that the homogeneous nucleation prediction should be based on a comparison of the critical work of nucleation with the “potential well” energy instead of the kinetic molecular energy. The result is a new prediction of the liquid spinodal line for water that is valid to large negative pressures. This prediction compares well with spinodal points obtained by extrapolating liquid and vapor water data with the Himpan equation.

Influence of Subject Response Style Effects on Retrospective Measures

Abstract: Recent attempts to reduce internal invalidity in studies employing pretest/posttest self-report in dices of improvement have included the refinement of methodologies employing retrospective reports of pre-treatment states. The present study investigated the operation of social desirability and impression management response bias on such retrospective measures. The results do not support the hypothesis of greater bias on retrospective measurement and, in fact, are in a direction that might suggest an in terpretation of reduced bias on such measures. The results also continue to support superior validity of retrospective over traditional pretest/posttest in dices of improvement following treatment.