Showing papers by "University of Houston published in 1988"

Solitons in conducting polymers

Abstract: Self-localized nonlinear excitations (solitons, polarons, and bipolarons) are fundamental and inherent features of quasi-one-dimensional conducting polymers. Their signatures are evident in many aspects of the physical and chemical properties of this growing class of novel materials. As a result, these polymers represent an opportunity for exploring the novel phenomena associated with topological solitons and their linear confinement which results from weakly lifting the ground-state degeneracy. The authors review the theoretical models that have been developed to describe the physics of polyacetylene and related conducting polymers and summarize the relevant experimental results obtained for these materials. An attempt is made to assess the validity of the soliton model of polyacetylene and its generalization to related systems in which the ground-state degeneracy has been lifted.

Option Valuation of Claims on Real Assets: The Case of Offshore Petroleum Leases

Abstract: This paper extends financial option theory by developing a methodology for the valuation of claims on a real asset: an offshore petroleum lease. Several theoretical and practical problems, not present in applying option pricing theory to financial assets, are addressed. Most importantly, we show the necessity of combining option pricing techniques with a model of equilibrium in the market for the underlying asset (petroleum reserves). The advantages of this approach over conventional discounted cash flow techniques are emphasized. The methodological development provides important insights for both company behavior and government policy. Promising empirical results are reported.

Superconductivity in the high-Tc Bi-Ca-Sr-Cu-O system - Phase identification

Abstract: Four phases are observed in superconducting Bi-Ca-Sr-Cu-O samples. The superconducting phase, with onset temperature near 120 K, is a 15.4-A-layered compound with composition near Bi2Ca1Sr2Cu2O9 and an A-centered orthorhombic unit subcell 5.41 x 5.44 x 30.78 A. X-ray diffraction and electron microscopy data are consistent with a structure of alternating perovskite and Bi2O2 layers. High-resolution transmission electron microscopy images reveal a b-axis superstructure of 27.2 A, numerous (001) stacking faults, and other defects.

Becoming an ex: The process of role exit

Abstract: The experience of becoming an ex is common to most people in modern society. Unlike individuals in earlier cultures who usually spent their entire lives in one marriage, one career, one religion, one geographic locality, people living in today's world tend to move in and out of many roles in the course of a lifetime. During the past decade there has been persistent interest in these "passages" or "turning points," but very little research has dealt with what it means to leave behind a major role or incorporate it into a new identity. Helen Rose Fuchs Ebaugh's pathbreaking inquiry into the phenomenon of becoming an ex reveals the profundity of this basic aspect of establishing an identity in contemporary life. Ebaugh is herself an ex, having left the life of a Catholic nun to become a wife, mother, and professor of sociology. Drawing on interviews with 185 people, Ebaugh explores a wide range of role changes, including ex-convicts, ex-alcoholics, divorced people, mothers without custody of their children, ex-doctors, ex-cops, retirees, ex-nuns, and-perhaps most dramatically-transsexuals. As this diverse sample reveals, Ebaugh focuses on voluntary exits from significant roles. What emerges are common stages of the role exit process-from disillusionment with a particular identity, to searching for alternative roles, to turning points that trigger a final decision to exit, and finally to the creation of an identify as an ex. "Becoming an Ex" is a challenging and influential study that will be of great interest to sociologists, mental health counselors, members of self-help groups such as Alcoholics Anonymous and Parents Without Partners, those in corporate settings where turnover has widespread implications for the organization, and for anyone struggling through a role exit who is trying to establish a new sense of self.

Chemistry of hot springs on the Mid-Atlantic Ridge

Abstract: The first hydrothermal fluid samples collected along the slow-spreading Mid-Atlantic Ridge (MAR) are remarkably similar in composition and temperature to fluids collected along the shallower, faster-spreading East Pacific Rise (EPR). The MAR fluids, like those from the EPR, appear to be in equilibrium with a greenschist-facies mineral assemblage. In contrast to the EPR, the more fractured nature of the MAR apparently allows fluids at one of the MAR sites to interact with weathered basalt.

The application of a homogeneous half-space model in the analysis of endothelial cell micropipette measurements.

Abstract: Experimental studies have shown that endothelial cells which have been exposed to shear stress maintain a flattened and elongated shape after detachment. Their mechanical properties, which are studied using the micropipette experiments, are influenced by the level as well as the duration of the shear stress. In the present paper, we analyze these mechanical properties with the aid of two mathematical models suggested by the micropipette technique and by the geometry peculiar to these cells in their detached post-exposure state. The two models differ in their treatment of the contact zone between the cell and the micropipette. The main results are expressions for an effective Young's modulus for the cells, which are used in conjunction with the micropipette data to determine an effective Young's modulus for bovine endothelial cells, and to discuss the dependence of this modulus upon exposure to shear stress.

A leaky-wave analysis of the high-gain printed antenna configuration

Abstract: A leaky-wave analysis is used to explain the narrow-beam resonance-gain phenomenon in which narrow beams may be produced from a printed antenna element in a substrate-superstrate geometry. It is demonstrated that the phenomenon is attributable to the presence of both transverse electric and transverse magnetic-mode leaky waves, that are excited on the structure. Asymptotic formulas for the leaky wave are compared with the exact patterns to demonstrate the dominant role of the leaky waves in determining the pattern. Results are presented as a function of frequency, the scan angle, and the permittivity of the superstrate. >

Principals, bureaucrats, and responsiveness in clean air enforcements.

Abstract: A principal-agent perspective has been employed in recent studies to rediscover the importance of democratic hierarchies in shaping public bureaucratic outputs. I test the robustness of the hierarchy model for explaining outputs from an agency that has often been cast in the image of bureaucratic independence, the Environmental Protection Agency. Examining the effect of the Reagan presidency on EPA outputs for clean air, Box-Tiao models are constructed to explain shifts in the vigor of air pollution enforcements between 1977 and 1985. The analysis shows that the influence of elected institutions is limited when an agency has substantial bureaucratic resources and a zeal for their use. Moreover, under these conditions, bureaucracy can even move outputs in directions completely opposite from what a model of hierarchy would predict. The implication is that for some agencies it is necessary to give greater consideration to the agent in explaining implementation outcomes through time.

An introduction to structural equation models

Abstract: This paper provides an overview of structural equation models, and their potential for advancing neuropsychological theory and practice. Four topics are covered: (1) an overview of the various classes of models, and an introduction to the terminology and diagrams used to describe them, (2) an outline of the steps involved in applying structural equation modeling to any research problem, (3) an overview of the information used in assessing model fit, and a discussion of the role of significance tests in structural models, and (4) an outline of the advantages and disadvantages of structural equation models, and their potential contribution to neuropsychology. The paper is intended to help researchers (1) assess the relevance of these advanced statistical techniques to their own research, and (2) begin the process of successful application.

Reliability and validity of bioelectrical impedance in determining body composition.

Abstract: This study was designed to examine the reliability and validity of the bioelectrical impedance method (BIA) of measuring body composition and compare its accuracy with the results obtained by stand...

Influence of formalization on the organizational commitment and work alienation of salespeople and industrial buyers.

Abstract: A model is investigated in which organizational formalization influences work alienation through role ambiguity, role conflict, and organizational commitment. Interrelationships are tested with dat...

Scaleup of Insect Cell Cultures: Protective Effects of Pluronic F-68

Abstract: We demonstrate that insect cells can be grown in an agitated, sparged bioreactor and an airlift bioreactor with a growth rate and maximum cell density comparable to those obtained in spinner flasks oxygenated by surface diffusion. Recombinant protein synthesis by cells infected with a genetically-modified baculovirus in the sparged bioreactor is also demonstrated. The nonionic surfactant Pluronic® F-68 was responsible for the protection of insect cells from the adverse effects of sparging. The mechanism of Pluronic® F-68 protection in a sparged environment is discussed.

Microstrip transmission line excitation of dielectric resonator antennas

Abstract: A systematic investigation of the excitation of a cylindrical dielectric resonator antenna was undertaken to illustrate the possibility of such a feed structure and to characterise the coupling behaviour and radiation patterns of the system.

Mechanism for high-temperature superconductivity.

Abstract: An explanation of the mechanism for high-temperature superconductivity is given, based upon a strong-coupling analysis of the extended Hubbard model previously introduced by one of us. The basic carriers are oxygen-hole quasiparticles in p\ensuremath{\sigma} orbitals, whose spin is strongly correlated with that of adjacent copper holes. These quasiparticles interact through the enhanced superexchange of the associated spins on the Cu sites, and an enhanced zero-point motion of the surrounding Cu holes. These are nonretarded attractive interactions whose strength increases as the oxygen-copper Coulomb repulsion increases and can be strong enough, for realistic parameters, to overcome the direct oxygen-oxygen Coulomb repulsion. The superconducting transition temperature that results is proportional to the Fermi energy of the oxygen holes.

The Puzzle of Midterm Loss

Abstract: This paper examines midterm election results since 1902, in order to account for the regularity with which the party controlling the presidency suffers an electoral decline at midterm. Standard interpretations account for midterm loss in terms of withdrawn presidential coattails (or regression-to-the-mean), surge-and-decline, or a negative referendum on presidential performance. None of these explanations is compatable with the historical data. A "presidential penalty" explanation, however, fits the data nicely. By this explanation, the midterm electorate penalized the president's party for being the party in power: holding constant the presidential year House vote, the president's party does much worse at midterm than it would if it did not control the presidency. Some implications of this finding are examined.

Electron Transfer and Charge Transfer: Twin Themes in Unifying the Mechanisms of Organic and Organometallic Reactions

Abstract: The broad varieties of organic and organometallic reactions merge into a common unifying mechanism by considering all nucleophiles and electrophiles as electron donors (D) and electron acceptors (A), respectively. Comparison of outer-sphere and inner-sphere electron transfers with the aid of Marcus theory provides the thermochemical basis for the generalized free energy relationship for electron transfer (FERET) in Equation (37) and its corollaries in Equations (43) and (44) that have wide predictive applicability to electrophilic aromatic substitutions, olefin additions, organometallic cleavages, etc. The FERET is based on the conversion of the weak nucleophile–electrophile interactions extant in the ubiquitous electron donor—acceptor (EDA) precursor complex [D, A] to the radical ion pair [D⊕, A⊖], for which the free energy change can be evaluated from the charge-transfer absorption spectra according to Mulliken theory. FERET analysis thus indicates that the charge-transfer ion pairs [D⊕, A⊖] are energetically equivalent to the transition states for nucleophile/electrophile transformations. The behavior of such ion pairs can be directly observed immediately following the irradiation of the charge-transfer bands of various EDA complexes with a 25-ps laser pulse. Such studies confirm the radical ion pair [Arene⊕, NO2] as a viable intermediate in electrophilic aromatic nitration, as presented in the electron-transfer mechanism between arenes and the nitryl cation (NO) electrophile.

Neurobehavioral effects of central nervous system prophylactic treatment of cancer in children.

Abstract: This article reviews 41 studies of the effects of prophylactic CNS treatment on the neurobehavioral development of children with cancer. This research is classified according to studies of (a) children in treatment; (b) long-term survivors; and (c) longitudinal follow-ups of children from the time of diagnosis. Studies vary considerably in design, sample, and outcome variables, so firm conclusions regarding the morbidity of CNS prophylaxis are not currently possible. However, the studies do suggest that CNS prophylaxis does impair cognitive development, particularly when cranial radiation therapy is part of the treatment. There is also evidence of greater impairment in younger children and some suggestion of more frequent impairment of non-language skills relative to language skills. The possible relationships among age, radiation, and non-language cognitive skills may be linked to disruption of white matter CNS structures apparent on autopsy and cerebral tomography following treatment.

Pornography's Impact on Sexual Satisfaction1

Abstract: Male and female students and nonstudents were exposed to videotapes featuring common, nonviolent pornography or innocuous content. Exposure was in hourly sessions in six consecutive weeks. In the seventh week, subjects participated in an ostensibly unrelated study on societal institutions and personal gratifications. On an especially constructed questionnaire, subjects rated their personal happiness regarding various domains of experience; additionally, they indicated the relative importance of gratifying experiences. Exposure to pornography was without influence on the self-assessment of happiness and satisfaction outside the sexual realm (e.g., satisfaction deriving from professional accomplishments). In contrast, it strongly impacted self-assessment of sexual experience. After consumption of pornography, subjects reported less satisfaction with their intimate partners—specifically, with these partners' affection, physical appearance, sexual curiosity, and sexual performance proper. In addition, subjects assigned increased importance to sex without emotional involvement. These effects were uniform across gender and populations.

Properties of chondrules

Abstract: Chondrules contain a record of many essential characteristics of the primordial solar nebula, whose high-temperature chondrule-generating events have spanned nearly 10 million years As chondrules cooled, they became magnetized by nebular fields; chondrule rims show that dust was present in the vicinity of chondrule formation, and that multiple melting events were possible The chondrule precursors included many large grains, showed variable degrees of Fe-oxidation, and encompassed many isotopic reservoirs The properties of these nebular materials systematically changed from the enstatite, to ordinary, and finally to carbonaceous chondrite formation regions

Agonist and antagonist characterization of a putative adrenoceptor with distinct pharmacological properties from the α- and β-subtypes

Abstract: 1. Experiments were done to characterize a putative adrenoceptor which functions to inhibit longitudinal muscle tension development in the guinea-pig ileum. Several phenylethylamine based agonists were investigated: BRL 37344, (-)-isoprenaline, (+)-isoprenaline, noradrenaline, adrenaline, and fenoterol. Propranolol and nadolol were tested as antagonists. Agonist-induced inhibition of the contractile response to histamine was measured under equilibrium conditions with alpha-adrenoceptors and muscarinic cholinoceptors inhibited. 2. Inhibitory responses were obtained to (-)-isoprenaline and BRL 37344 that were resistant to beta-adrenoceptor blockage with propranolol (5 microM) and nadolol (10 microM). These resistant responses were antagonized by much higher concentrations of nadolol (30 to 1000 microM) yielding apparent pA2 values for nadolol of 4.31 with (-)-isoprenaline as the agonist, and 4.68 with BRL 37344 as the agonist. Similar apparent pA2 values for nadolol at the putative adrenoceptor were obtained with noradrenaline (4.79), adrenaline (4.68), and fenoterol (4.38). 3. The order and relative potency of agonists at the putative adrenoceptor was: BRL 37344 (20) greater than (-)-isoprenaline (8) greater than noradrenaline (1) greater than adrenaline (0.5) greater than fenoterol (0.35) greater than (+)-isoprenaline (0.27). 4. The resistance to blockade by propranolol (5 microM), the low affinity of nadolol, and the order and relative potency of agonists, suggest the presence of an adrenoceptor with distinct pharmacological characteristics from currently defined alpha- and beta-adrenoceptors.

The Gender Division of Labor and the Reproduction of Female Disadvantage Toward an Integrated Theory

Abstract: A theory of the major mechanisms that sustain and reproduce systems of gender stratification is presented. The central support mechanism is the gender division of labor, within both the family and the wider society. Because of it, men gain superior resource and definitional power, which enable them to maintain the gender status quo regardless of women's wishes. Elite men create dominant social definitions that, together with the gender division of labor, contribute to gender differentiation. This results in women usually choosing that which they would otherwise be constrained to do, thereby legitimating the system and allowing men to refrain from exercising their coercive potential.

Marital conflict, parenting, and toddler conduct problems.

Abstract: The present research examined relationships involving marital conflict, parenting, and toddler conduct problems. Sixty mother-toddler dyads (30 boys and 30 girls) participated as subjects. Mothers completed measures of general marital satisfaction, overt marital conflict, and toddler conduct problems. Maternal parenting and toddler deviance were assessed during a laboratory observation. Marital conflict was positively correlated with observations of toddler deviance and maternal reports of conduct problems. Marital conflict also correlated positively with the frequency of maternal disapproval statements directed toward sons' misbehaviors and was correlated negatively with the ratio of disapproval statements to daughters' misbehaviors. The present results indicate that marital conflict is associated with toddler conduct problems. The results also suggest the importance of examining parenting practices and child characteristics that may mediate the relationship between marital conflict and child behavior problems.

Political Intolerance and Political Repression During the McCarthy Red Scare

Abstract: I test several hypotheses concerning the origins of political repression in the states of the United States. The hypotheses are drawn from the elitist theory of democracy, which asserts that repression of unpopular political minorities stems from the intolerance of the mass public, the generally more tolerant elites not supporting such repression. Focusing on the repressive legislation adopted by the states during the McCarthy era, I examine the relationships between elite and mass opinion and repressive public policy. Generally it seems that elites, not masses, were responsible for the repression of the era. These findings suggest that the elitist theory of democracy is in need of substantial theoretical reconsideration, as well as further empirical investigation.

Attributional style and self-control behavior in depressed and nondepressed children and their parents.

Abstract: Do the reformulated model of learned helplessness and the self-control model apply to clinically depressed children? Are the related cognitive patterns specific to depression? Are the cognitive deficits associated with depression learned from one's parents? To address these questions this investigation examined three groups of children (ages 8–12) and their parents: nonclinic (n =25),nondepressed clinic (n=22),and depressed clinic (n=15).Children were diagnosed depressed on the basis of Kiddie-SADS interview data. Depressed clinic children self-reported more depression, had a more depressive attributional style, and had more self-control problems. There were more depressed mothers in the clinic than in the nonclinic sample. Depressed clinic children had more depressed mothers than did nondepressed clinic children. There were no differences among the three groups of parents in their cognitive patterns. No relationship was found between the attributional style and self-control behavior of children and their parents.