Showing papers by "University of Alabama published in 1988"

Genetic Algorithms and Machine Learning

Abstract: There is no a priori reason why machine learning must borrow from nature. A field could exist, complete with well-defined algorithms, data structures, and theories of learning, without once referring to organisms, cognitive or genetic structures, and psychological or evolutionary theories. Yet at the end of the day, with the position papers written, the computers plugged in, and the programs debugged, a learning edifice devoid of natural metaphor would lack something. It would ignore the fact that all these creations have become possible only after three billion years of evolution on this planet. It would miss the point that the very ideas of adaptation and learning are concepts invented by the most recent representatives of the species Homo sapiens from the careful observation of themselves and life around them. It would miss the point that natural examples of learning and adaptation are treasure troves of robust procedures and structures. Fortunately, the field of machine learning does rely upon nature's bounty for both inspiration and mechanism. Many machine learning systems now borrow heavily from current thinking in cognitive science, and rekindled interest in neural networks and connectionism is evidence of serious mechanistic and philosophical currents running through the field. Another area where natural example has been tapped is in work on genetic algorithms (GAs) and genetics-based machine learning. Rooted in the early cybernetics movement (Holland, 1962), progress has been made in both theory (Holland, 1975; Holland, Holyoak, Nisbett, & Thagard, 1986) and application (Goldberg, 1989; Grefenstette, 1985, 1987) to the point where genetics-based systems are finding their way into everyday commercial use (Davis & Coombs, 1987; Fourman, 1985).

The Physics of Solar Flares

Abstract: Solar flare phenomena are examined in an introduction for advanced undergraduate and graduate physics students. Chapters are devoted to the history of observations, flare spectroscopy, flare magnetohydrodynamics, flare plasma physics, radiative processes in the solar plasma, preflare conditions, the impulsive phase, the gradual phase, and coronal mass ejections. Diagrams, graphs, and photographs are provided.

OJ 287 - Binary pair of supermassive black holes

Abstract: A historical light curve of the BL Lacertae object OJ 287 is constructed in the optical V band using observations between 1890 and the present The curve exhibits periodic outbursts at intervals of 116 yr or 9 yr The individual outbursts show an initial maximum with decaying submaxima at intervals of about 1 month It is proposed that these characteristics are caused by a binary in the nucleus of OJ 287, with the binary members having an accretion disk around them The outbursts at 9-yr intervals would be caused by the tidal action of the companion on the disk of the larger black hole A computer simulation is used to demonstrate that the inflow into the center of such a disk during the repeated periastron passages of a companion will produce an outburst similar to the ones observed Based on indirect evidence, probable masses of 5 billion solar and 20 million solar are determined for the two objects 38 references

Azole antifungal agents: emphasis on new triazoles.

Abstract: Many advances have been made in antifungal therapy over the last three decades. Itraconazole and fluconazole, two investigational triazole agents, are the most recent additions to the list of antifungal drugs. This review has focused primarily on their mechanisms of action, favorable pharmacologic properties, and spectra of activity against a broad range of systemic pathogens. Itraconazole and fluconazole show much promise as orally active agents, with less potential for toxicity than the currently available azoles. Fluconazole and, to a lesser degree, itraconazole are especially promising therapies for cryptococcal meningitis. In addition, fluconazole may prove to be highly effective in urinary tract infections caused by Candida species and other fungi. Ongoing and future clinical trials will more clearly define the specific roles of itraconazole and fluconazole in the treatment of systemic mycoses.

Mean Reversion in Stock Prices? A Reappraisal of the Empirical Evidence

Abstract: Recent research based on variance ratios and multiperiod-return autocorrelations concludes that the stock market exhibits mean reversion in the sense that a return in excess of the average tends to be followed by partially offsetting returns in the opposite direction Dividing history into pre-1926, 1926-46, and post-1946 subperiods, we find that the mean-reversion phenomenon is a feature of the 1926-46 period, but not of the post-1946 period which instead exhibits persistence of returns Evidence for pre-1926 data is mixed The statistical significance of test statistics is assessed by estimating their distribution using stratified randomization Autocorrelations of multiperiod returns imply a forecast of future returns, which is presented for post-war three-year returns using 1926-46, full sample, and sequentially updated coefficient estimates The correlation between actual and forecasted returns is negative in each case We conclude that evidence of mean reversion in US stock returns is substantially weaker than reported in the recent literature If mean-reversion continues to be a feature of the stock market, then the experience of the past forty years has been an aberration

Cryptococcal Meningitis in Patients with AIDS

Abstract: The Cryptococcus has become a major cause of meningitis in patients infected with the human immunodeficiency virus (HIV), and the expression of cryptococcal infection in this population of patients is quite unique. Often the infection is devoid of inflammatory response and is associated with very high antigen and fungal titers. Response to amphotericin therapy is erratic, and relapse is common. We have asked Dr. William E. Dismukes, principal investigator of the NIAID Mycoses Study Group, to discuss the following clinical questions: When and how does cryptococcal infection in HIV-infected patients present? How does it differ in HIV-infected and non-HIV-infected individuals? How is the diagnosis established? What is the sensitivity of the CSF cryptococcal antigen test? Is the serum antigen test of any value? What is the best way to treat patients--the recommended drugs, dosages, and duration of therapy? Is maintenance therapy necessary, and finally, what drugs are available for it? [Please note that an AIDS training program is now available for members of the Infectious Diseases Society of America and that details of this program appear in the Notices section of this Journal issue (pages 859-60).]

Alternative Hierarchies of the Attitude-Behavior Relationship: The Impact of Brand Commitment and Habit

Abstract: The theory of reasoned action and the low-involvement hierarchy model were tested using cross-lagged panel correlation. It was proposed that the low-involvement hierarchy model would more accurately reflect the behavior of low-brand-committed individuals and that the theory of reasoned action would more accurately reflect the behavior of high-brand-committed individuals. Although the findings did not completely support these hypotheses, the general thrusts of the hypotheses appear to be supported. Additionally, behavior was hypothesized and shown to influence habit for all individuals.

Low-temperature deformation mechanisms and their interpretation

Abstract: Low-temperature deformation is characterized by heterogeneous strain in which the bulk of the material clearly retains its primary texture. Deformation is by grain-scale crystal plasticity, rotation, fracture, and pressure solution, and by transgranular mechanisms that crosscut numerous grains. The important low-temperature crystal-plastic features are twin lamellae, deformation bands, and undulatory extinction. Subgrain formation by recrystallization or crystal-plastic strain of more than 15% marks the upper limit of the low-temperature regime. Grain rotation may produce foliations in soft sediments or rocks. Microscopic to mesoscopic kinks and crenulations of bedding occur in soft clay and shale. Transgranular features include Luders' bands, cooling and desiccation cracks, joints, extension-fracture cleavage, clastic dikes, mineral-filled veins of several types, recrystallization/replacement veins, vein arrays, boudins, faults, stylolites, slickolites, solution cleavages that range from widely spaced to slaty and pencil cleavage. Pressure fringes form adjacent to relatively rigid grains and have fabrics analogous to those in veins. Faults include conjugate fault pairs (Andersonian faults) multiple simultaneous conjugates (Oertel faults), and Riedel shear-zone configurations. The sense of fault displacement is determined from bends, steps, trails, tails, and feather fractures. Superplasticity, especially if aided by diffusion in grain-boundary water, might be important at low temperatures. Fault textures are diagnostic of the environment of deformation but have yet to be uniquely correlated with the presence or absence of earthquakes. Riedel shears and pseudotachylite may form in earthquake source regions, although pseudotachylite is evidently rare in brittle fault zones. The best indicators of stress magnitudes are the critical' resolved shear stress for deformation twinning and the presence of tensile fractures. Strain magnitudes and stress and strain tensor orientations can be determined with a variety of methods that are based on mechanical twins, platy grain orientation, grain center distribution, and fault geometry and slip directions. Different deformation mechanism associations, expressed by the partitioning of the total strain into different mechanisms, are related to the ductility and environment of deformation. Deformation fronts separating different mechanism associations are defined on the basis of changes in the crystal-plastic component of strain.

Pulmonary vascular resistance and the risk of heart transplantation.

Abstract: Elevated pulmonary vascular resistance was an incremental risk factor for premature death after heart transplantation (p = 0.0002). Its effect was continuously variable and not dichotomous (yes or no). The rate of rise in risk of death corresponded quite evenly to the progressive increase in pulmonary vascular resistance from low to high values, rather than abruptly increasing at a certain point. This effect was incremental to the risk imposed by congenital heart disease (in contrast to idiopathic or ischemic cardiomyopathy). Expression of the pulmonary vascular resistance in units times square meters provides more accurate predictions than expression in Wood units (p for difference = 0.03).

Avian T cells expressing gamma delta receptors localize in the splenic sinusoids and the intestinal epithelium.

Abstract: A panel of murine mAb specific for the chicken homologues of the CD3, CD4, CD8, TCR gamma delta, and TCR alpha beta has been used to study the distribution of T cells expressing these markers in sections of chicken lymphoid tissues. These studies have revealed that the T cells possessing the two classes of TCR occupy distinct histologic microenvironments. The TCR1+ cells (gamma delta TCR homologue) are localized preferentially in the splenic sinusoids and the intestinal epithelium, where most of them express the CD8 homologue. The TCR2+ cells (alpha beta TCR homologue), a majority of which express the CD4 homologue, are found primarily in the splenic periarteriolar sheath and the lamina propria of the intestine. The frequency and distribution of the two classes of T cells in the thymus is also unique. The different tissue homing patterns of the TCR1 and TCR2 cells suggest that they represent separate lineages of T cells with distinctive physiologic roles.

Behavior of ceramic particles at the solid- liquid metal interface in metal matrix composites

Abstract: Directional solidification results were obtained in order to investigate particle behavior at the solid-liquid interface in Al-2 pct Mg (cellular interface) and Al-6.1 pct Ni (eutectic interface) alloys. It is found that particles can be entrapped in the solid if adequate solidification rates and temperature gradients are used. Model results showed critical velocity values slightly higher than those obtained experimentally.

Beyond Fear Appeals: Negative and Positive Persuasive Appeals to Health and Self‐Esteem

Abstract: The present research was designed to extend our knowledge of fear appeals and attitude change in two directions. The first purpose was to compare a traditional negative, or fear, appeal to its counterpart, an appeal emphasizing the positive consequences of accepting a communicator's recommendation. The second purpose was to test the assumption of the theory of protection motivation that people are motivated to protect themselves from psychological and social, as well as physical, threats. The results disclosed that, compared to a no-message control condition, the traditional negative appeal to health was more persuasive than the positive appeal. A positive appeal to self-esteem, however, was superior to a negative appeal to self-esteem. Several implications for health psychology were discussed. First, the traditional negative appeals to health may be more persuasive than positive appeals. Second, people may be persuaded to adopt healthy lifestyles for reasons other than health per se (i.e., to enhance self-esteem). The following tentative conclusions were based on unexpected findings and should be interpreted with caution. The decision to use a positive or negative appeal should consider the number of available adaptive responses. Finally, the data suggested that mass media health campaigns should use both negative and positive appeals.

Tumor Formation Dependent on Proteoglycan Biosynthesis

Abstract: The role proteoglycans play in tumor formation was examined by measuring the tumorigenicity of proteoglycan-deficient Chinese hamster ovary cell mutants in nude mice. When 10(7) cells were injected subcutaneously, mutants with less than about 15% of the wild-type level of proteoglycan synthesis did not produce tumors. Mutants defective in the synthesis of heparan sulfate proteoglycans also did not form tumors, whereas mutants with altered chondroitin sulfate proteoglycans were tumorigenic. Tumors arose from mixtures of wild-type and nontumorigenic mutant cells and contained both cell types, suggesting that wild-type cell proteoglycans enabled mutant cells to survive. The failure of heparan sulfate-deficient mutants to form tumors depended on the ability of the host to mount a B cell-mediated immune reaction.

Sex, race, residence, region, and education differences on the 11 WAIS-R subtests.

Abstract: The relationship of test performance on the 11 WAIS-R subtests to five background variables was examined by MANOVAs and univariate ANOVAs on standardization data. For all four broad age groups (16-19, 20-34, 35-54, 55-74), significant differences were found for sex, race, and education main effects. Geographic region produced significant main effects for three of the age groups, but residence yielded significant results only for the oldest group. The pattern of the relationships of subtest scores to each background variable was analyzed, interpreted, and integrated with previous research.

Phase I trial of multiple large doses of murine monoclonal antibody CO17-1A. II: Pharmacokinetics and immune response

Abstract: Twenty-five patients with metastatic gastrointestinal adenocarcinoma received one to four infusions of large doses (400 mg) of murine monoclonal antibody CO17-1A (17-1A). The pharmacokinetics of 17-1A at the time of first, second, third, or fourth infusion were not statistically different; plasma half-lives were 15.0 +/- 1.7 hours (n = 5), 15.1 +/- 1.8 (n = 10), 25.3 +/- 6.2 (n = 3), and 14.4 +/- 1.8 (n = 5), respectively. Most patients had an antibody response to 17-1A, with peak levels occurring 15-22 days after infusion. The presence of serum antibody to 17-1A at the time of the second or third infusion did not significantly alter the pharmacokinetics of this large dose of antibody. Four of 25 patients failed to develop an antibody response, but this did not correlate with the amount of 17-1A administered. The administration of four doses of 400 mg over 1 week provided continuously circulating 17-1A for 10 days.

Symmetrical erosive peripheral polyarthritis in the Late Archaic Period of Alabama

Abstract: Rheumatoid arthritis was first described unambiguously in 1800, but its etiology and historical origins are still obscure. Definite rheumatoid arthritis has not been demonstrated in pre-19th century Old World skeletal remains. Six individuals who lived 3000 to 5000 years ago in northwestern Alabama and present erosive polyarthritis characteristic of rheumatoid arthritis are described. The diagnosis raises the possibility that rheumatoid arthritis can be associated with a New World pathogen or allergen.

Pathologic features of allergic bronchopulmonary aspergillosis.

Abstract: We describe the pathologic features in surgically excised lung tissue specimens from 18 cases of allergic bronchopulmonary aspergillosis (ABPA). The main abnormalities involved bronchi and bronchioles. All cases showed bronchocentric granulomatosis (BCG), mucoid impaction of bronchi (MIB), or both. The impacted mucin of MIB contained large numbers of eosinophils and Charcot-Leyden crystals. A distinctive exudative bronchiolitis was present distal to areas of BCG in 13 cases. This lesion was characterized by filling of bronchiolar lumens with necrotic neutrophils and eosinophils in a basophilic mucinous exudate. A peribronchiolar chronic inflammatory infiltrate was seen in 15 cases; eosinophils were prominent in 10 of these cases. Foci of eosinophilic pneumonia were seen in 13 cases, and noninvasive fungal hyphae were identified in 14. We conclude that the finding of BCG or MIB, or a combination of both, especially in conjunction with tissue eosinophilia, should suggest the diagnosis of ABPA. When noninvasive fungal hyphae are also present, the changes are diagnostic of ABPA or a related allergic fungal reaction.

Ratios of photoelectron to EUV ionization rates for aeronomic studies

Abstract: This paper presents calculations performed on the photoelectron impact to EUV photoionization rate ratios for atmospheric O, O2, and N2, and also for the production of N(+) by photodissociative ionization of N2. It was found that the ratios vary greatly with altitude. At high altitudes in the absence of photoelectron transport, the O(+) and N2(+) ionization rate ratios are about 0.35, but they increase with increasing optical depth; in the vicinity of the ionization peak, the photoelectron rate can exceed the EUV ionization rate for O(+) and N2(+). At high altitudes, the O2(+) ionization rate ratio is about half that of O(+); this ratio increases with increasing optical depth to reach a peak of about 0.4. There are also seasonal variations in the ratios at high altitudes depending on the magnitude of the conjugate photoelectron flux.

Mouse/Human Chimeric Antibodies to a Tumor-Associated Antigen: Biologic Activity of the Four Human IgG Subclasses

Abstract: Variable region genes from mouse monoclonal antibody 17-1A (gamma 2a kappa) with specificity for human gastrointestinal malignancies have been paired with human immunoglobulin constant region genes (for heavy and light chains) to produce mouse/human chimeric immunoglobulin molecules (chIgG) for each of the four human IgG subclasses. Mouse 17-1A and the four chIgG bound similarly to two human colon cancer cell lines and had comparable binding affinities. The chIgG1 and chIgG3 molecules mediated lymphocyte and monocyte antibody-dependent cell-mediated cytotoxicity (ADCC) to colon cancer tumor cell lines comparable to that of the parent murine 17-1A. The chIgG2 and chIgG4 molecules were able to mediate ADCC to colon cancer cell lines but were clearly inferior to the chIgG1 and chIgG3 reagents. None of the chIgG antibodies or the murine 17-1A was able to mediate complement lysis of colon cancer cell lines. These studies demonstrate the ability to produce all four human IgG subclass chimeric molecules which retain biologic activity. We have confirmed the subclass preferences of human lymphocyte and monocyte Fc receptors for human IgG subclasses previously determined by studies with monomeric or aggregated IgG. These data may aid in the selection of chimeric antibodies for in vivo trials.

Effect of coefficient of thermal expansion on microleakage

Abstract: This study examines the relationship between thermal coefficient of expansion and microleakage. Six restorative materials with varying coefficients of thermal expansion were thermocycled in basic fuschin dye and compared for relative microleakage. The use of dental restorative materials with low coefficients of thermal expansion such as glass ionomer can control microleakage.