Showing papers by "Louisiana State University published in 2000"

Functional and chemical anatomy of the afferent vagal system.

Abstract: The results of neural tracing studies suggest that vagal afferent fibers in cervical and thoracic branches innervate the esophagus, lower airways, heart, aorta, and possibly the thymus, and via abdominal branches the entire gastrointestinal tract, liver, portal vein, billiary system, pancreas, but not the spleen. In addition, vagal afferents innervate numerous thoracic and abdominal paraganglia associated with the vagus nerves. Specific terminal structures such as flower basket terminals, intraganglionic laminar endings and intramuscular arrays have been identified in the various organs and organ compartments, suggesting functional specializations. Electrophysiological recording studies have identified mechano- and chemo-receptors, as well as temperature- and osmo-sensors. In the rat and several other species, mostly polymodal units, while in the cat more specialized units have been reported. Few details of the peripheral transduction cascades and the transmitters for signal propagation in the CNS are known. Glutamate and its various receptors are likely to play an important role at the level of primary afferent signaling to the solitary nucleus. The vagal afferent system is thus in an excellent position to detect immune-related events in the periphery and generate appropriate autonomic, endocrine, and behavioral responses via central reflex pathways. There is also good evidence for a role of vagal afferents in nociception, as manifested by affective-emotional responses such as increased blood pressure and tachycardia, typically associated with the perception of pain, and mediated via central reflex pathways involving the amygdala and other parts of the limbic system. The massive central projections are likely to be responsible for the antiepileptic properties of afferent vagal stimulation in humans. Furthermore, these functions are in line with a general defensive character ascribed to the vagal afferent, paraventricular system in lower vertebrates.

Indications for Computed Tomography in Patients with Minor Head Injury

Abstract: Background Computed tomography (CT) is widely used as a screening test in patients with minor head injury, although the results are often normal. We performed a study to develop and validate a set of clinical criteria that could be used to identify patients with minor head injury who do not need to undergo CT. Methods In the first phase of the study, we recorded clinical findings in 520 consecutive patients with minor head injury who had a normal score on the Glasgow Coma Scale and normal findings on a brief neurologic examination; the patients then underwent CT. Using recursive partitioning, we derived a set of criteria to identify all patients who had abnormalities on CT scanning. In the second phase, the sensitivity and specificity of the criteria for predicting a positive scan were evaluated in a group of 909 patients. Results Of the 520 patients in the first phase, 36 (6.9 percent) had positive scans. All patients with positive CT scans had one or more of seven findings: headache, vomiting, an age ov...

Development of a generalized learning transfer system inventory

Abstract: This study expands on the concept of the learning transfer system and reports on the validation of an instrument to measure factors in the system affecting transfer of learning. The Learning Transfer System Inventory (LTSI) was developed and administered to 1,616 training participants from a wide range of organizations. Exploratory common factor analysis revealed a clean interpretable factor structure of sixteen transfer system constructs. Second-order factor analysis suggested a three-factor higher order structure of climate, job utility, and rewards. The instrument development process, factor structure, and use of the LTSI as a diagnostic tool in organizations are discussed.© 2000 Jossey-Bass, A Publishing Unit of John Wiley & Sons, Inc.

Multiple-Locus Variable-Number Tandem Repeat Analysis Reveals Genetic Relationships within Bacillus anthracis

Abstract: Bacillus anthracis is one of the most genetically homogeneous pathogens described, making strain discrimination particularly difficult. In this paper, we present a novel molecular typing system based on rapidly evolving variable-number tandem repeat (VNTR) loci. Multiple-locus VNTR analysis (MLVA) uses the combined power of multiple alleles at several marker loci. In our system, fluorescently labeled PCR primers are used to produce PCR amplification products from eight VNTR regions in the B. anthracis genome. These are detected and their sizes are determined using an ABI377 automated DNA sequencer. Five of these eight loci were discovered by sequence characterization of molecular markers (vrrC1, vrrC2, vrrB1, vrrB2, and CG3), two were discovered by searching complete plasmid nucleotide sequences (pXO1-aat and pXO2-at), and one was known previously (vrrA). MLVA characterization of 426 B. anthracis isolates identified 89 distinct genotypes. VNTR markers frequently identified multiple alleles (from two to nine), with Nei's diversity values between 0.3 and 0.8. Unweighted pair-group method arithmetic average cluster analysis identified six genetically distinct groups that appear to be derived from clones. Some of these clones show worldwide distribution, while others are restricted to particular geographic regions. Human commerce doubtlessly has contributed to the dispersal of particular clones in ancient and modern times.

Dendritic integration of excitatory synaptic input.

Abstract: A fundamental function of nerve cells is the transformation of incoming synaptic information into specific patterns of action potential output. An important component of this transformation is synaptic integration--the combination of voltage deflections produced by a myriad of synaptic inputs into a singular change in membrane potential. There are three basic elements involved in integration: the amplitude of the unitary postsynaptic potential; the manner in which non-simultaneous unitary events add in time (temporal summation), and the addition of unitary events occurring simultaneously in separate regions of the dendritic arbor (spatial summation). This review discusses how passive and active dendritic properties, and the functional characteristics of the synapse, shape these three elements of synaptic integration.

Tau neutrinos favored over sterile neutrinos in atmospheric muon neutrino oscillations.

Abstract: The previously published atmospheric neutrino data did not distinguish whether muon neutrinos were oscillating into tau neutrinos or sterile neutrinos, as both hypotheses fit the data. Using data recorded in 1100 live days of the Super-Kamiokande detector, we use three complementary data samples to study the difference in zenith angle distribution due to neutral currents and matter effects. We find no evidence favoring sterile neutrinos, and reject the hypothesis at the $99%$ confidence level. On the other hand, we find that oscillation between muon and tau neutrinos suffices to explain all the results in hand.

Mitochondrial dna phylogeography of the polytypic north american rat snake (elaphe obsoleta): a critique of the subspecies concept

Abstract: Subspecies have been considered artificial subdivisions of species, pattern classes, or incipient species. However, with more data and modern phylogenetic techniques, some subspecies may be found to represent true species. Mitochondrial DNA analysis of the polytypic snake, Elaphe obsoleta, yields well-supported clades that do not conform to any of the currently accepted subspecies. Complete nucleotide sequences of the cytochrome b gene and the mitochondrial control region produced robust maximum-parsimony and maximum-likelihood trees that do not differ statistically. Both trees were significantly shorter than a most parsimonious tree in which each subspecies was constrained to be monophyletic. Thus, the subspecies of E. obsoleta do not represent distinct genetic lineages. Instead, the evidence points to three well-supported mitochondrial DNA clades confined to particular geographic areas in the eastern United States. This research underscores the potential problems of recognizing subspecies based on one or a few characters.

A Cross-Country Empirical Investigation of the Aggregate Production Function Specification

Abstract: Many growth models assume that aggregate output is generated by a Cobb-Douglas production function. In this article we question the empirical relevance of this specification. We use a panel of 82 countries over a 28-year period to estimate a general constant-elasticity-of-substitution (CES) production function specification. We find that for the entire sample of countries we can reject the Cobb-Douglas specification. When we divide our sample of countries up into several subsamples, we find that physical capital and human capital adjusted labor are more substitutable in the richest group of countries and are less substitutable in the poorest group of countries than would be implied by a Cobb-Douglas specification.

Pattern and Process of Land Loss in the Mississippi Delta: A Spatial and Temporal Analysis of Wetland Habitat Change

Abstract: An earlier investigation (Turner 1997) concluded that most of the coastal wetland loss in Louisiana was caused by the effects of canal dredging, that loss was near zero in the absence of canals, and that land loss had decreased to near zero by the late 1990s. This analysis was based on a 15-min quadrangle (approximately 68,000 ha) scale that is too large to isolate processes responsible for small-scale wetland loss and too small to capture those responsible for large-scale loss. We conducted a further evaluation of the relationship between direct loss due to canal dredging and all other loss from 1933–1990 using a spatial scale of 4,100 ha that accurately captures local land-loss processes. Regressions of other wetland loss on canal area (i.e., direct loss) for the Birdfoot, Terrebonne, and Calcasieu basins were not significant. Positive relationships were found for the Breton (r2=0.675), Barataria (r2=0.47), and Mermentau (r2=0.35) basins, indicating that the extent of canals is significantly related to wetland loss in these basins. A significant negative relationship (r2=0.36) was found for the Atchafalaya coastal basin which had statistically lower loss rates than the other basins as a whole. The Atchafalaya area receives direct inflow of about one third of the Mississippi discharge. When the data were combined for all basins, 9.2% of the variation in other wetland loss was attributable to canals. All significant regressions intercepted the y-axis at positive loss values indicating that some loss occurred in the absence of canals. Wetland loss did not differ significantly from the coast inland or between marsh type. We agree with Turner that canals are an important agent in causing wetland loss in coastal Louisiana, but strongly disagree that they are responsible for the vast majority of this loss. We conclude that wetland loss in the Mississippi delta is an ongoing complex process involving several interacting factors and that efforts to create and restore Louisiana’s coastal wetlands must emphasize riverine inputs of freshwater and sediments.

Multi-Criteria Decision Making Methods

Abstract: With the continuing proliferation of decision methods and their variants, it is important to have an understanding of their comparative value. Each of the methods uses numeric techniques to help decision makers choose among a discrete set of alternative decisions. This is achieved on the basis of the impact of the alternatives on certain criteria and thereby on the overall utility of the decision maker(s). The difficulty that always occurs when trying to compare decision methods and choose the best one is that a paradox is reached, i.e., What decision-making method should be used to choose the best decision-making method? This problem is examined in Chapter 9.

The falling stage systems tract: recognition and importance in sequence stratigraphic analysis

Abstract: Until recently, sequence stratigraphic models have attributed systems tracts to periods of relative sea-level rise, highstand and lowstand. Recognition of a discrete phase of deposition during relative sea-level fall has been limited to a few studies, both in clastic and carbonate systems. Our work in siliciclastic ramp settings suggests that deposition during relative sea-level fall produces a distinctive falling stage systems tract (FSST), and that this is the logical counterpart to the transgressive systems tract. The FSST lies above and basinward of the highstand systems tract, and is overlain by the lowstand systems tract. The FSST is characterized by stratal offlap, although this is likely to be difficult or imposs- ible to recognize because of subsequent subaerial or transgressive ravinement erosion. The most practical diagnostic criteria of the FSST is the presence of erosive-based shoreface sandbodies in nearshore areas. The erosion results from wave scouring during relative sea- level fall, and the stratigraphically lowest surface defines the base of the FSST. Further off- shore, shoaling-upward successions may be abruptly capped by gutter casts filled with HCS sandstone, reflecting increased wave scour on the shelf during both FSST and LST time. The top of the FSST is defined by a subaerial surface of erosion which corresponds to the sequence boundary. This surface becomes a correlative submarine conformity seaward of the shoreline, where it forms the base of the lowstand systems tract. Differentiation of the FSST and LST may be difficult, but the LST is expected to contain gradationally-based shoreface successions because it was deposited when relative sea level was rising. Intern- ally, the FSST may be an undifferentiated body of sediment or it may be punctuated by internal regressive surfaces of marine erosion and ravinement surfaces which record higher- frequency sea-level falls and rises superimposed on a lower-frequency sea-level fall. The corresponding higher-order sequences are the building blocks of lower-order sequences. The addition of a falling stage systems tract results in a significant reduction in the pro- portion of strata within a sequence that are assigned to the classical highstand and lowstand systems tracts. Many outcrop and subsurface cross-sections use an overlying ravinement, or maximum flooding surface as datum. Those surfaces might be flat, but they are not horizontal. Both dip seaward at slopes that generally are steeper than the fluvial system responsible for cre- ating the sequence boundary. When a section is restored to such a datum, the falling stage systems tract will appear to record stratigraphic climb, whereas in fact it does not.

Energy dissipation and radical scavenging by the plant phenylpropanoid pathway.

Abstract: Environmental stresses such as high light, low temperatures, pathogen infection and nutrient deficiency can lead to increased production of free radicals and other oxidative species in plants. A growing body of evidence suggests that plants respond to these biotic and abiotic stress factors by increasing their capacity to scavenge reactive oxygen species. Efforts to understand this acclimatory process have focused on the components of the 'classical' antioxidant system, i.e. superoxide dismutase, ascorbate peroxidase, catalase, monodehydroascorbate reductase, glutathione reductase and the low molecular weight antioxidants ascorbate and glutathione. However, relatively few studies have explored the role of secondary metabolic pathways in plant response to oxidative stress. A case in point is the phenylpropanoid pathway which is responsible for the synthesis of a diverse array of phenolic metabolites such as flavonoids, tannins, hydroxycinnamate esters and the structural polymer lignin. These compounds are often induced by stress and serve specific roles in plant protection, i.e. pathogen defence, ultraviolet screening, antiherbivory, or structural components of the cell wall. This review will highlight a novel antioxidant function for the taxonomically widespread phenylpropanoid metabolite chlorogenic acid (CGA; 5-O-caffeoylquinic acid) and assess its possible role in abiotic stress tolerance. The relationship between CGA biosynthesis and photosynthetic carbon metabolism will also be discussed. Based on the properties of this model phenolic metabolite, we propose that under stress conditions phenylpropanoid biosynthesis may represent an alternative pathway for photochemical energy dissipation that has the added benefit of enhancing the antioxidant capacity of the cell.

Associations of Coronary Heart Disease Risk Factors With the Intermediate Lesion of Atherosclerosis in Youth

Abstract: The raised fatty streak (fatty plaque) is the gross term for the lesion intermediate between the juvenile (flat) fatty streak and the raised lesion of atherosclerosis. We measured the percentage of intimal surface involved with flat fatty streaks, raised fatty streaks, and raised lesions in the aortas and right coronary arteries of 2876 autopsied persons aged 15 through 34 years who died of external causes. Raised fatty streaks were present in the abdominal aortas of approximately 20% of 15- to 19-year-old subjects, and this percentage increased to approximately 40% for 30- to 34-year-old subjects. Raised fatty streaks were present in the right coronary arteries of approximately 10% of 15- to 19-year-old subjects, and this percentage increased to approximately 30% for 30- to 34-year-old subjects. The percent intimal surface involved with raised fatty streaks increased with age in both arteries and was associated with high non-high density lipoprotein (HDL) and low HDL cholesterol concentrations in the abdominal aorta and right coronary artery, with hypertension in the abdominal aorta, with obesity in the right coronary artery of men, and with impaired glucose tolerance in the right coronary artery. Associations of risk factors with raised fatty streaks became evident in subjects in their late teens, whereas associations of risk factors with raised lesions became evident in subjects aged >25 years. These results are consistent with the putative transitional role of raised fatty streaks and show that coronary heart disease risk factors accelerate atherogenesis in the second decade of life. Thus, long-range prevention of atherosclerosis should begin in childhood or adolescence.

Systemic determinants of international news coverage: a comparison of 38 countries

Abstract: This study investigates the influence of systemic determinants on international news coverage in 38 countries. Systemic factors include traits of nations, magnitude of interaction and relatedness between nations, and logistics of news gathering. Multiple regression is implemented to assess 9 systemic determinants in each individual country. Findings indicate that the U.S. was the most covered country in the world. In spite of some variation, trade volume and presence of international news agencies were found to be the 2 primary predictors of the amount of news coverage. The study concludes that the prediction framework of international news coverage has probably altered in the post-Cold War epoch and, therefore, that the relevant problems need to be revisited.

Practice parameters for the evaluation of chronic insomnia

Abstract: Chronic insomnia is the most common sleep complaint which health care practitioners must confront. Most insomnia patients are not, however, seen by sleep physicians but rather by a variety of primary care physicians. There is little agreement concerning methods for effective assessment and subsequent differential diagnosis of this pervasive problem. The most common basis for diagnosis and subsequent treatment has been the practitioner's clinical impression from an unstructured interview. No systematic, evidence-based guidelines for diagnosis exist for chronic insomnia. This practice parameter paper presents recommendations for the evaluation of chronic insomnia based on the evidence in the accompanying review paper. We recommend use of these parameters by the sleep community, but even more importantly, hope the large number of primary care physicians providing this care can benefit from their use. Conclusions reached in these practice parameters include the following recommendations for the evaluation of chronic insomnia. Since the complaint of insomnia is so widespread and since patients may overlook the impact of poor sleep quality on daily functioning, the health care practitioner should screen for a history of sleep difficulty. This evaluation should include a sleep history focused on common sleep disorders to identify primary and secondary insomnias. Polysomnography, and the Multiple Sleep Latency Test (MSLT) should not be routinely used to screen or diagnose patients with insomnia complaints. However, the complaint of insomnia does not preclude the appropriate use of these tests for diagnosis of specific sleep disorders such as obstructive sleep apnea, periodic limb movement disorder, and narcolepsy that may be present in patients with insomnia. There is insufficient evidence to suggest whether portable sleep studies, actigraphy, or other alternative assessment measures including static charge beds are effective in the evaluation of insomnia complaints. Instruments such as sleep logs, self-administered questionnaires, symptom checklist, or psychological screening tests may be of benefit to discriminate insomnia patients from normals, but these instruments have not been shown to differentiate subtypes of insomnia complaints.

Core networks and tie activation: what kinds of routine networks allocate resources in nonroutine situations?

Abstract: Social resources research has linked activated ties to outcomes-but not to the core networks from which the ties came. This study shifts the focus to the question of how networks allocate resources. The activation of core network ties is analyzed in a nonroutine situation-a hurricane-to determine how core network structure affects the degree to which individuals activate core network ties to gain one type of social resource-informal support. Results show that the structures of individuals' core networks affect the degree to which individuals activate ties from those networks to gain informal support. Individuals embedded in higher-density core networks (i.e., alters are connected to one another), core networks with more gender diversity (i.e., a mix of men and women), and networks that contain higher proportions of men, kin, and younger individuals, activated core network ties for informal support to a greater degree than did individuals embedded in core networks lacking these characteristics. The conclusions consider the study's implications for understanding resource activation in the contexts of social support and job searches.

Multiple Scattering in Clumpy Media. II. Galactic Environments

Abstract: We present and discuss the results of new multiple-scattering radiative transfer calculations for three representative types of galactic environments, filled with either homogeneous or two-phase clumpy dust distributions. Extinction and scattering properties for two types of interstellar dust, similar to those found in the average diffuse medium of the Milky Way (MW) and the Bar of the Small Magellanic Cloud (SMC), are considered. The wavelength coverage extends from 1000 to 30000 A, with particular emphasis on the rest-frame UV. This makes these models especially applicable to starburst galaxies and Lyman-break galaxy samples. The examination of the models concentrates on the study of UV/visual/near-IR reddening effects, the wavelength dependence of attenuation, and on the changes that arise from the transition from homogeneous to clumpy dust distributions in different star/dust geometries. Embedded dust, especially when clumpy, leads to saturation at fairly low reddening values with correspondingly gray attenuation functions. This makes the assessment of the attenuation of the far-UV flux from starburst galaxies difficult, if only UV/visual/near-IR data are available. Existing data for UV-selected starburst galaxies indicate a range of UV attenuation factors of 0-150. Our models reproduce the "Calzetti Attenuation Law," provided one adopts SMC-type dust and a clumpy shell-type dust distribution surrounding the starbursts. The average far-UV attenuation factor for the Calzetti sample is found to be 7.4. The only relatively reliable measure for the UV attenuation factor for single galaxies was found in the ratio of the integrated far-IR flux to the far-UV flux, measured near 1600 A, requiring the measurement of the entire spectral energy distribution of galaxies.

Palaeovegetation of China: a pollen data‐based synthesis for the mid‐Holocene and last glacial maximum

Abstract: Pollen data from China for 6000 and 18,000 C-14 yr BP Were compiled and used to reconstruct palaeovegetation patterns, using complete taxon lists where possible and a biomization procedure that entailed the assignment of 645 pollen taxa to plant functional types. A set of 658 modern pollen samples spanning all biomes and regions provided a comprehensive test for this procedure and showed convincing agreement between reconstructed biomes and present natural vegetation types, both geographically and in terms of the elevation gradients in mountain regions of north-eastern and south-western China. The 6000 C-14 yr BP map confirms earlier studies in showing that the forest biomes in eastern China were systematically shifted northwards and extended westwards during the mid-Holocene. Tropical rain forest occurred on mainland China at sites characterized today by either tropical seasonal or broadleaved evergreen/warm mixed forest. Broadleaved evergreen/warm mixed forest occurred further north than today, and at higher elevation sites within the modern latitudinal range of this biome. The northern limit of temperate deciduous forest was shifted c. 800 km north relative to today. The 18,000 C-14 yr BP map shows that steppe and even desert vegetation extended to the modem coast of eastern China at the last glacial maximum, replacing today's temperate deciduous forest. Tropical forests were excluded from China and broadleaved evergreen/warm mixed forest had retreated to tropical latitudes, while taiga extended southwards to c. 43 degreesN.

Density and diversity of lianas along a chronosequence in a central Panamanian lowland forest.

Abstract: The abundance and diversity of lianas were examined along a tropical forest chronosequence at the Barro Colorado Nature Monument, Panama. Lianas M 0.5 cm diameter were sampled along transects in two replicated stands in second- ary (20, 40, 70 and 100 y after abandonment) and old-growth (>500 y) forests. Ordination of stands based on relative abundance, but not presence-absence, showed a significant separation of stands by age. Lianas were significantly more abundant and diverse (Fisher's α) in younger forests (20 and 40 y) than in older forests (70 and 100 y, and old-growth). The decline in liana abundance with stand age was offset by increased mean basal area per individual, resulting in a relatively constant total basal area and estimated biomass across stand age. The proportions of tendril climbers decreased and stem twiners increased over stand age. Decline in liana abundance and changes in liana composition may be related to changes in support and light availability. Although lianas are recognized as playing an important role in the early secondary succession of many tropical forests, these results have shown that their important contribution to total basal area and biomass can continue as the forest matures, even as the number of established lianas declines.

Differences in Spending Habits and Credit Use of College Students

Abstract: In a study of college students, affective credit attitude (feeling about using credit cards) and gender influenced college students' credit purchasing. Affective credit attitude predicted the purchase of clothing, electronics, entertainment, travel, gasoline, and food away from home. Females purchased clothing; males purchased electronics, entertainment, and food away from home. Gender was more influential in predicting financial management practices than was affective credit attitude, with female students employing a greater number of financial practices. A path analysis model showed gender differences in the relationship between financial practices, financial stress, affective credit attitude, and the number of credit cards with a balance.