Showing papers by "Louisiana State University published in 1990"

Persistence in Variance, Structural Change, and the GARCH Model

Abstract: This article examines the persistence of the variance, as measured by the generalized autoregressive conditional heteroskedasticity (GARCH) model, in stock-return data. In particular, we investigate the extent to which persistence in variance may be overstated because of the existence of, and failure to take account of, deterministic structural shifts in the model. Both an analysis of daily stock-return data and a Monte Carlo simulation experiment confirm the hypothesis that GARCH measures of persistence in variance are sensitive to this type of model misspecification.

Distinguishing coupon proneness from value consciousness: An acquisition-transaction utility theory perspective.

Abstract: Previous research on coupon proneness has measured the construct only in behavioral terms (i.e., consumers who are more responsive to coupon promotions are coupon prone). On the basis of the study ...

Analysis of role conflict and role ambiguity in a structural equations framework

Abstract: In this study a confirmatory methodology was implemented to analyze a model that uses the Rizzo, House, and Lirtzman (1970) scales of role conflict (RC) and role ambiguity (RA; i.e., the Bedeian and Armenakis, 1981, model). The validity of the RC and RA scales were examined through structural equations analysis, and a nested models approach was used to compare the Bedeian and Armenakis model with a model suggesting a more parsimonious representation of the data. Furthermore, path estimates from models incorporating random measurement error were compared with estimates from a model not incorporating the effects of random measurement error

Determination of the Wavelength Dependence of Refractive Indices of Flame Soot

Abstract: The spectral variation of the optical properties of soot particles is determined by combining classical and dynamic light scattering measurements with the Kramers-Kronig relations. Particle size and number densities are determined from scattering/extinction and autocorrelation measurements at the wavelength of 0.488 μm. This information is then combined with the spectral extinction measurements in the wavelength range 0.2 to 6.4 μm to determine the spectral variation of the refractive indices of flame soot. Results are presented for a premixed propane-oxygen flame with a fuel equivalence ratio ϕ = 1.8. The sensitivity of the technique and its advantage over the previous methods are discussed.

A Longitudinal Assessment of the Impact of Selected Organizational Influences on Salespeople's Organizational Commitment during Early Employment:

Abstract: To examine the antecedents and consequences of the development of salespeople's organizational commitment during early employment, the authors conducted a longitudinal study. The study focused on h...

The fuelling of active galactic nuclei

Abstract: We review accretion mechanisms for powering the central engines of active galactic nuclei (AGN) and possible sources of fuel. Local sources, such as dense star clusters, require extreme set of parameters. Instead we argue that the interstellar matter in the main body of the host galaxy is channelled towards the centre and address the problem of angular momentum transport. Thin accretion disks are not a viable means of delivering fuel to luminous AGN on scales much larger than a parsec because of the long inflow time and effects of self-gravity. There are also serious obstacles to maintaining and regulating geometrically thick, hot accretion flows. We emphasize the role of non-axisymmetric perturbations of the gravitational potential on galactic scales and their triggers: galaxy interactions and internal self-gravitational instabilities. We outline a unified model for fuelling AGN, in which the inflow on large scales is driven by gravitational torques, and on small scales forms a mildly self-gravitating disk of clouds with inflow driven by magnetic torques or cloud–cloud collisions.

The Role of Intestinal Barrier Failure and Bacterial Translocation in the Development of Systemic Infection and Multiple Organ Failure

Abstract: Traditionally, evaluation of intestinal function has been limited largely to monitoring gastric pH and intestinal motility. This clinical approach has led clinicians to equate normal intestinal motility with normal intestinal function and to assume that if stress-induced gastric bleeding can be prevented, all will be well. However, it is becoming increasingly clear that the gastrointestinal tract is not a passive organ and that intestinal dysfunction is not limited to ileus and upper gastrointestinal bleeding. Instead, the gastrointestinal tract is recognized as having important endocrine, metabolic, immunologic, and barrier functions, as well as its traditional role in nutrient absorption. Over the last 5 years, there has been a resurgence of interest in the role of intestinal barrier failure in the development of systemic infection and multiple organ failure in the critically ill or injured patient.

The sequence of cell and matrix changes in atherosclerotic lesions of coronary arteries in the first forty years of life

Abstract: We have studied the cell and matrix composition of normal intima and of atherosclerotic lesions in the coronary arteries of 691 subjects less than 40 years old. These arteries were obtained at autopsy and fixed by perfusion with glutaraldehyde under physiological pressure. A defined segment of the left coronary artery, known for its susceptibility to develop advanced lesions, was studied by light and electron microscopy. The initial intimal lesion occurred in infants and consisted in an increase in intimal macrophages and presence of isolated lipid-laden macrophages (foam cells). At puberty, more substantial accumulations of foam cells, accompanied now by lipid droplets in smooth muscle cells and by thinly scattered extracellular lipid (fatty streaks), were present. After puberty, an increasing number of subjects had intermediate lesions and atheroma. Intermediate lesions, characterized by greatly increased extracellular lipid, were the link between fatty streaks and atheroma. Atheroma was characterized by a massive core of extracellular lipid that damaged arterial structure by displacing normal intimal cells and matrix. In the third and more often in the fourth decade, some atheroma contained greatly increased collagen and smooth muscle cells above the lipid core (fibroatheroma). Collagenization and thickening were more marked when evidence of thrombotic deposits was present on the surface or within lesions. Smooth muscle cells were present in the intima of all subjects from birth. In early lesions, lipid in the intima was not associated with an increase in the number of smooth muscle cells. Smooth muscle cells were increased in lesions containing massive extracellular lipid, more so in those having, in addition, a thrombotic component; smooth muscle cells with massive basement membranes occurred in advanced lesions. Macrophages and macrophage foam cells were the cells that increased intimal cellularity at the onset of lesions. Other cell types associated with lesions were lymphocytes, mast cells, and plasma cells, but all of these were less numerous than either smooth muscle cells or macrophages. From birth, intima was always thicker opposite the flow divider wall of a bifurcation (eccentric thickening). When atherosclerotic lesions of any type were present in coronary arteries, the amount of lipid and accompanying cell reactions were greatest in eccentric thickening; intermediate lesions and atheroma were present only in eccentric thickening while fibroatheroma often extended beyond eccentric thickening.

Transfer of Drugs and Other Chemicals into Human Milk

Abstract: To the Editor.— I read with interest the Committee on Drugs second report about transfer of drugs and other chemicals into human milk.1 Although the objective to categorize those drugs with reported harmful, or not, effects on children has been achieved with admirable brevity, the report fails to cite two useful areas of information. The WHO Task Force on Drugs in Human Milk reviewed the world literature and compiled a recently published book entitled Drugs and Human Lactation.2

The gap between patient reading comprehension and the readability of patient education materials.

Abstract: Patient education materials and hospital forms are given to patients with little regard for their ability to read them. Nationwide sampling and data from the 1980 census suggest that a high proportion of patients cared for in public hospitals are functionally illiterate. In this study, 151 adult primary care patients in five different ambulatory care settings were tested for reading comprehension. Patient education materials and forms from each clinic were analyzed for readability using a standard computer program. A large discrepancy was found between the average patient reading comprehension and the ability levels needed to read patient education materials. The average reading comprehension of public clinic patients was 6th grade 5th month. Most tested patient education materials required a reading level of 11th to 14th grade, and standard institutional consent forms required a college-level reading comprehension. In the public clinics there was a gap of more than 5 years between patient reading levels and the comprehension levels required by written patient materials.

Helicobacter pylori and gastric carcinoma. Serum antibody prevalence in populations with contrasting cancer risks.

Abstract: This investigation examined the correlation between Helicobacter pylori (HP) infection, as reflected in immunoglobulin G serum antibodies, and the risk of gastric cancer. Serum samples were obtained from populations with contrasting gastric cancer risks. The highest prevalence of HP infection, 93%, was observed in the adult population at highest gastric cancer risk, the residents of Pasto, Colombia. In the lower risk Colombian city of Cali, a 63% overall prevalence rate was found. Both children and adults were sampled in New Orleans, Louisiana, where gastric cancer rates are high for blacks but not for whites. The prevalence of HP infection was significantly higher in black than in white adults, 70% versus 43%, P = 0.0001. A higher prevalence was also detected in black compared with white children, 49% versus 32%, P = 0.01; however, an even greater disparity was noted when comparing children from two hospitals, regardless of race, which serve different socioeconomic groups. A prevalence rate of 54% was found at Charity Hospital compared with 24% (P = 0.0001) at Children's Hospital. Our findings indicate that socioeconomic conditions, known to influence gastric cancer risk, are also important determinants of HP infection.

Physics of white dwarf stars

Abstract: White dwarf stars, compact objects with extremely high interior densities, are the most common end product in the evolution of stars. The authors review the history of their discovery, and of the realisation that their structure is determined by the physics of the degenerate electron gas. Spectral types and surface chemical composition show a complicated pattern dominated by diffusion processes and their interaction with accretion, convection and mass loss. While this interaction is not completely understood in all its detail at present, the study may ultimately lead to important constraints on the theory of stellar evolution in general. Variability, caused by nonradial oscillations of the star, is a common phenomenon and is shown to be a powerful probe of the structure of deeper layers that are not directly accessible to observation. Very strong magnetic fields detected in a small fraction of white dwarfs offer a unique opportunity to study the behaviour of atoms under conditions that cannot be simulated in terrestrial laboratories.

Valve cutter for arterial by-pass surgery

Abstract: A valve cutter for arterial bypass surgery is provided and includes a blade assembly for cutting the venous valves, a shaft for guiding the blade assembly through the bypass vein, an expansion means for preventing the blade assembly from contacting the walls of the bypass vein and for helping to propagate the incisions made in the valve leaflets by the blade assembly, and a control means for controlling the expansion and contraction of the expansion means in order to allow for use of the invention in a variety of bypass vein diameter sizes.

Mechanism for the hydrogen sulfide-induced growth limitation in wetland macrophytes

Abstract: Hydrogen sulfide, a phytotoxin that often accumulates in anoxic marine and freshwater marsh soils, suppressed the activity of alcohol dehydrogenase (ADH), the enzyme that catalyzes the terminal step in alcoholic fermentation, in the roots of two wetland macrophytes. This inhibition of root ADH activity with increasing sulfide concentration was associated with decreases in root total adenine nucleotide pool (ATP + ADP + AMP), the adenylate energy charge ratio (AEC), nitrogen uptake (percent recovery of rSNH,+-N) and growth (leaf elongation). These responses were species-specific with a greater negative impact in the freshwater marsh species that naturally inhabits low-sulfide environments. These findings lend support to the hypotheses that ADH activity, as a mcasurc of fermcntative metabolism, is important in maintaining the root energy status of wetland plants under hypoxic-anoxic conditions, that there is a significant negative effect of H,S on the anoxic production of energy in these roots, and that an important negative effect of H,S on plant growth is an inhibition of the energy-dependent process of N uptake.

Obstructive jaundice promotes bacterial translocation from the gut

Abstract: Experiments were performed to determine if obstructive jaundice promotes the translocation of bacteria from the gastrointestinal tract to visceral organs. Three groups of mice were studied: control (n=20), sham ligated (n=28), and bile duct ligated (n=33). The sham-ligated group underwent laparotomy and manipulation of the portal region, whereas the ligated group had their common bile ducts ligated. Seven days later, the mice were killed, their organs cultured, and the gastrointestinal tract examined histologically. The bilirubin levels of the ligated group (18.7 mg/dL) were elevated compared with the other groups (0.5 mg/dL) (p

Persistence of avian influenza viruses in water.

Abstract: Persistence of five avian influenza viruses (AIVs) derived from four waterfowl species in Louisiana and representing five hemagglutinin and neuraminidase subtypes was determined in distilled water at 17 C and 28 C. Infectivity was determined over 60 days by microtiter endpoint titration. One AIV was tested over 91 days at 4 C. Linear regression models for these viruses predicted that an initial concentration of 1 x 10(6) TCID50/ml water could remain infective for up to 207 days at 17 C and up to 102 days at 28 C. Significant differences in slopes for AIV persistence models were detected between treatment temperatures and among viruses. Results suggest that these viruses are adapted to transmission on waterfowl wintering habitats. Results also suggest a potential risk associated with waterfowl and domestic poultry sharing a common water source.

School-based cardiovascular health promotion: the child and adolescent trial for cardiovascular health (CATCH).

Abstract: The Child and Adolescent Trial for Cardiovascular Health (CATCH) is a multisite intervention research study that builds on significant progress made in school health education research in the 1980s. The study has three phases: Phase I deals with study design, intervention, and measurement development, Phase II involves the main trial in 96 school'; in four states, and Phase III focuses on analysis. The intervention program targets third-fifth grade students and focuses on multiple cardiovascular health behaviors, including eating habits, physical activity, and cigarette smoking. Classroom curricula, school environmental change, and family involvement programs are developed for each grade level and behavioral focus. This paper describes Phase II of CATCH with a rationale for cardiovascular health promotion with youth. The process of change that appears to be necessary for school-based health promotion and that will be tested in CATCH are presented as a framework to guide these efforts.

Role of the Eastern California Shear Zone in accommodating Pacific-North American Plate motion

Abstract: The newly recognized Eastern California shear zone (ECSZ) of the Mojave Desert-Death Valley region has played a major, but previously underappreciated role in accommodating the dextral shear between the Pacific and North American plates in late Cenozoic time. Comparison of integrated net slip along the shear zone with motion values across the entire transform boundary indicates that between 9% and 23% of the total relative plate motion has occurred along the ECSZ since its probably inception {approximately}10-6 Ma. Long-term integrated shear along the ECSZ (6-12 mm yr{sup {minus}1}) is similar to historic measurements (6.7 {plus minus} 1.3 mm yr{sup {minus}1}). Time-space patterns of faulting suggest that shear was concentrated in the eastern part of the Mojave Desert block and Death Valley during late Miocene and early Pleistocene time, but that the locus of faulting in the south-central Mojave jumped westward between 1.5 and 0.7 Ma.

Evidence for mendelian inheritance in the pathogenesis of lung cancer.

Abstract: Segregation analyses that allowed for variable age of onset of lung cancer and smoking history were performed on 337 families, each ascertained through a lung cancer proband. Results indicated compatibility of the data with mendelian codominant inheritance of a rare major autosomal gene that produces earlier age of onset of the cancer. Segregation at this putative locus could account for 69% and 47% of the cumulative incidence of lung cancer in individuals up to ages 50 and 60, respectively. The gene was involved in only 22% of all lung cancers in persons up to age 70, a reflection of an increasing proportion of noncarriers succumbing to the effects of long-term exposure to tobacco.

A Comparison of the Efficacy and Safety of a β-Blocker, a Calcium Channel Blocker, and a Converting Enzyme Inhibitor in Hypertensive Blacks

Abstract: A double-blind, positively controlled, forced dose titration study comparing the efficacy and safety of atenolol, captopril, and verapamil sustained release as single agents in the treatment of black patients with mild to moderate hypertension (diastolic blood pressure, 95 to 114 mm Hg) was conducted. A total of 394 patients were randomized to one of the three therapies. Mean blood pressures during a 2- to 4-week placebo treatment period (baseline) ranged from 100.4 to 100.7 mm Hg diastolic and 151.7 to 152.5 mm Hg systolic for the three groups. Of the patients, 355 (of whom 345 had assessable data) completed the first treatment period, which consisted of therapy with either 50 mg/d of atenolol, 25 mg every 12 hours of captopril, or 240 mg/d of verapamil sustained release. During the second 4-week treatment period, which 319 patients completed (307 assessable), half of the patients had their antihypertensive medication increased and the other half continued the same dose. Goal blood pressure was defined as a supine diastolic pressure of less than 90 mm Hg or a 10—mm Hg or greater drop in supine diastolic blood pressure from pretreatment levels. Atenolol, captopril, and verapamil sustained release therapy was associated with goal blood pressure achievement during the first treatment period 55.1%, 43.8%, and 65.2% of the time, respectively, and during the second treatment period 59.6%, 57.1%, and 73.0% of the time. Side effects were minimal and comparable for all three drugs. (Arch Intern Med.1990;150:1707-1713)

Effects of pH, temperature, and salinity on persistence of avian influenza viruses in water.

Abstract: The combined effects of water temperature, salinity, and pH on persistence of avian influenza virus (AIV) were evaluated in a model distilled-water system using three isolates from ducks sampled in Cameron Parish, Louisiana. Variables were tested within the ranges normally associated with surface water. Differences were detected between temperature (17 C and 28 C), pH (6.2, 7.2, 8.2), and salinity (0 ppt and 20 ppt), with a strong interactive effect observed between pH and salinity. Estimated persistence of infectivity for 1 x 10(6) mean tissue-culture infective dose of A/mottled duck/LA/38M/87 (H6N2) was longest at 17 C/0 ppt/pH 8.2 (100 days) and shortest at 28 C/20 ppt/pH 8.2 (9 days). Differences in the response to these variables were apparent between viruses. The ability of AIV to persist in surface water was also evaluated using samples collected from varied waterfowl habitats in coastal Louisiana. Observations were consistent with the model system, with duration of infectivity decreasing with increased salinity and pH. This suggests that experimental results may have application to field conditions.

Wetland soil formation in the rapidly subsiding Mississippi River Deltaic Plain: mineral and organic matter relationships.

Abstract: The elevation of submerging coastal marshes is maintained by vertical accretion of mineral and organic matter. Submergence rates currently exceed 1·0 cm year −1 in the Mississippi Deltaic Plain and are expected to increase. Mineral matter-organic matter relationships were examined in surface profiles of Mississippi Deltaic Plain soil from both Active Delta Zone marsh (which receives freshwater and mineral sediment from the Atchafalaya or Mississippi Rivers) and Inactive Delta Zone marsh (which relies on rainfall for freshwater and on reworked sediments for mineral matter) to gain insights into marsh soil structure and formation. Mineral and organic matter accounted for 4–14% of soil volume. The remainder was pore space and was occupied by water and entrapped gases. Organic matter occupied more volume than mineral matter in all but saline marsh soil. The regular influx of mineral matter to active fresh marsh resulted in active fresh marsh soil containing twice as much mineral and organic matter as inactive fresh marsh soil. Within the Inactive Delta Zone, the volume of mineral and organic matter increased from fresh (inland) to saline (seaward) marshes. Saline marsh soil required 1·7 times as much mineral matter as brackish marsh soil to vertically accrete at similar rates, possibly as a result of soil bulk density requirements of the dominant saline marsh plant, Spartina alterniflora . Vertical accretion rates were highest in the Active Delta Zone, probably as a result of increased mineral matter availability and delivery. Current, best estimates of the combination of mineral and organic matter required (g m −2 year −1 ) to maintain marsh surface-water level relationship are fresh marsh: organic matter = 1700 + 269 x , mineral matter = 424 x ; brackish marsh: organic matter = 553 + 583 x , mineral matter = 1052 x ; saline marsh: organic matter = 923 + 601 x , mineral matter = 1798 x , where x = the rate of submergence (cm year −1 ).

Immunohistochemical demonstration of a novel hypothalamic peptide, pituitary adenylate cyclase-activating polypeptide, in the ovine hypothalamus.

Abstract: We recently reported isolation, characterization and synthesis of a novel ovine hypothalamic peptide with 38 residues which stimulates accumulation of cAMP in rat anterior pituitary cell cultures. The peptide was named PACAP38 (pituitary adenylate cyclase-activating polypeptide with 38 residues). The presence of another peptide corresponding to the N-terminal 1-27 residues (PACAP27) was also demonstrated. Both PACAP38 and PACAP27 have an amidated C-terminus. Antisera against synthetic PACAP27 were generated in rabbits. These antisera were tested for titer and specificity in enzyme-linked immunosorbent assay. One of the antisera (no. 88121-3) exhibited a high titer of antibody, which was specific to PACAP27 and PACAP38 with exception of slight cross-reactivity with ovine CRF (oCRF). Therefore, the antibodies against oCRF were removed from the antiserum using a solid phase method. Removal of oCRF antibodies was confirmed by enzyme-linked immunosorbent assay. A dense immunoreactive fiber network was found in both external and internal zones of the median eminence and pituitary stalk. The fibers were demonstrated to be in close contact with the hypophysial portal capillaries. The preabsorption of antiserum with vasoactive intestinal polypeptide or with the mixture containing TRH, LHRH, oCRF, ovine GH-releasing factor, somatostatin, and bovine thyroglobulin did not affect the immunostaining. On the other hand, the preabsorption of antiserum with an excess of PACAP27 or PACAP38 abolished the immunostaining. Therefore, the staining is considered specific for PACAP27 and PACAP38. Stained fibers were also present in the posterior pituitary. A dense fiber network was observed and the lateral hypothalamus the fibers appeared to cling to unstained neuronal cell bodies and their dendrites. In the lateral septum the fibers surrounded some blood vessels. Immunolabeled cell bodies were found in the paraventricular and supraoptic nuclei. These findings support the view that PACAP may play a multifunctional role, including that of a hypophysiotropic hormone, neurotransmitter, neuromodulator, and vasoregulator.