Showing papers by "Louisiana State University published in 1981"

Relative tension and potential excursion of muscles in the forearm and hand.

Abstract: Muscle strength varies enormously from person to person and even from time to time, but the ratio of strength from muscle to muscle within the same limb varies much less. The mass or volume of a muscle is proportional to its work capacity, and the fiber length of a muscle is proportional to its potential excursion. By dividing the fiber length into the volume of each muscle, the cross-sectional area of the muscle was determined, and a list of relative tension capacities offorearm and hand muscles was prepared. Although based on a small number of specimens, this list has the first data on forearm and hand muscles which should be of practical use in planning the operation of tendon transfer.

Oxygen Deficiency in Spartina alterniflora Roots: Metabolic Adaptation to Anoxia

Abstract: The aerenchyma (air-space) tissue in the wetland macrophyte Spartina alterniflora conveys sufficient oxygen to roots for predominately aerobic respiration in moderately, but not highly, reduced substrates. Continuously flooded plants survive by respiring anaerobically, although growth is decreased. Two metabolic adaptations to flooding are displayed in this species, depending on the degree of soil reduction.

Plate reconstructions, aseismic ridges, and low-angle subduction beneath the Andes

Abstract: Low-angle—subduction segments beneath Peru and Chile are believed to represent interaction of the subduction zone with the aseismic Nazca and Juan Fernandez Ridges. On the basis of symmetric sea-floor–spreading models and plate-hotspot reconstructions, predicted continuations of the relatively buoyant ridges correspond well with the limits of the low-angle–subduction segments. Further, the history of interaction of the aseismic ridges with the subduction zone, as predicted by plate reconstructions, is not inconsistent with available information on volcanic episodes of the Andes, if the contemporary correlation of volcanic gaps and low-angle subduction is also applicable to the rest of the late Cenozoic. The occurrence of deep seismicity beneath the eastern flanks of the Andes is also believed to reflect the effects of low-angle subduction. The deep-seismic segments are adjacent to segments which are presently, or were recently, experiencing low-angle subduction. Thus, the deep seismicity is interpreted as representative of remnants of “normal” oceanic lithosphere subducted before interaction of aseismic ridges with the subduction zone. Other geologic phenomena are associated with low-angle subduction beneath South America, including landward shift in loci of tectonism, surficial subsidence, and Laramide-style deformation. The aseismic-ridge—buoyancy hypothesis appears to be a valuable predictive tool for the interpretation of such geologic effects.

Dynamic changes of serum lipoproteins in children during adolescence and sexual maturation

Abstract: A cross-sectional study of 4074 children, ages 5--17 years, in Bogalusa, Louisiana indicated significant changes of serum lipids and lipoproteins occurring during puberty. These changes could be related to both age and maturation and likely reflect the influence of sex hormones on serum lipoprotein metabolism. Considerable differences were observed in the race/sex groups, with boys showing a more marked decrease of serum total cholesterol, reflecting decreases of beta- and alpha- lipoproteins. While the ratio of mean beta-lipoprotein cholesterol/mean alpha-lipoprotein cholesterol for the white girls and black children remained relatively constant over the age span, the ratio beginning around age 11 years rose dramatically in white boys, reflecting an inordinate decrease of alpha-lipoprotein and an earlier beginning rise of beta-lipoprotein. The observations have important implications for earlier coronary artery disease in white men.

Mechanisms of nitrogen dioxide reactions: initiation of lipid peroxidation and the production of nitrous Acid.

Abstract: The reactions of nitrogen dioxide with cyclohexene have been studied as a model for the reactions that occur between nitrogen dioxide in smoggy air and unsaturated fatty acids in pulmonary lipids. As predicted from earlier studies at high nitrogen dioxide concentrations, this gas reacts with cyclohexene predominantly by addition to the double bond at nitrogen dioxide concentrations of 1 percent (10,000 parts per million) to 40 percent in nitrogen; in the presence of air or oxygen, this reaction initiates the autoxidation of the alkene. However, at concentrations below 100 parts per million in nitrogen, nitrogen dioxide reacts with cyclohexene almost exclusively by abstraction of allylic hydrogen; this unexpected reaction also initiates the autoxidation of the alkene in the presence of oxygen or air, but it leads to the production of nitrous acid rather than of a product containing a nitro group attached to a carbon atom. The nitrous acid can react with amines to produce nitrosamines. Moreover, the nitrite ion produced by the hydrogen abstraction mechanism would be expected to diffuse throughout the body, unlike nitrated lipids that would be confined to the pulmonary cavity. These findings have been confirmed with methyl oleate, linoleate, and linolenate; some of the kinetic features of the nitrogen dioxide—initiated autoxidation of these unsaturated fatty acids have been studied.

Effects of smoking different doses of nicotine on human aggressive behavior.

Abstract: A new methodology was employed to study the effects of drugs on human aggressive behavior in a laboratory situation. The effects of not smoking, smoking a low nicotine dose (0.42 mg/cigarette), and smoking a high nicotine dose (2.19 mg/cigarette) on human nonaggressive and aggressive responding was determined. A nonaggressive response, which resulted in the accumulation of money, was continuously available to the subject. Two different aggressive responses were also available: the ostensible subtraction of money from, and the ostensible presentation of a 1-s blast of white noise to a (fictitious) person. Aggressive responding was elicited by subtracting money from the research subjects, which was attributed to a fictitious person paired with the research subject randomly each day. Nicotine, administered with experimental cigarettes, produced dose-dependent decrease in both types of aggressive responding elicited by low or high frequency subtractions of money attributed to another person. Generally, the more aggressive response option, i.e., subtraction of money from another person, decreased more following nicotine administration. Smoking the same doses of nicotine increased nonaggressive monetary reinforced responding. This indicates that the suppressant effects of nicotine on aggressive responding was not due to a non-specific depressant action.

Comparison of the vegetation of three louisiana swamp sites with different flooding regimes

Abstract: Net primary productivity and community structure were studied at three adjacent swamp sites that were all once subject to seasonal flooding. Because of man-related activities one is now permanently flooded, and a second is managed on a summer-fall dry period and a winterspring flooded period. In the permanently flooded area such flood-intolerant trees as green ash are dying while shrubs and aquatic plants are increasing. Competition among overstory trees is reduced, enhancing growth of existing baldcypress and water tupelo trees. Total areal production, however, is low (887 gIm2/yr) because of fewer trees. Productivity in the managed area is high (1,780 gIm2/yr). The baldcypress-water tupelo community is being replaced by a swamp maple-ash community typical of bottomlands. In the natural swamp forest, baldcypress and water tupelo have remained dominant. Canopy closure has limited understory and aquatic growth but has also increased competition among overstory trees, resulting in a slow increase in basal area. Productivity is about 1,166 gIm2/yr. It is suggested that the flooding regime is an important controlling factor in each of the areas. SWAMP FORESTS are recognized as integral parts of wetland ecosystems, serving as habitats, spawning and nursery grounds, and sources of food for many organisms (Brown, Brinson and Lugo, 1979; Wharton and Brinson, 1979). Seasonal flooding and draining of swamps are vital to the maintenance of these functions. Recent studies have illustrated the high productivity of seasonally flooded swamp forests (Conner and Day, 1976; Mitsch and Ewel, 1979; Carter et al., 1973) and the export of large amounts of organic and inorganic nutrients from the swamp to downstream lake and marsh environments (Day, Butler and Conner, 1977; Kemp, 1978; Wharton and Brinson, 1979). In many wetlands the construction of canals, spoil deposits, embankments and impoundments associated with mining, timber, highway activities, and, in Louisiana, crawfish culture, has altered the flow of water. The purpose of this study was to compare plant community structure and productivity of three swamp areas with different flooding re1 Received for publication 20 February 1980; revision accepted 11 September 1980. Contribution No. LSU-CEL-79-17 of the Coastal Ecology Laboratory, LSU Center for Wetland Resources, Baton Rouge, La. This research was supported by the LSU Sea Grant College Program, a part of the National Sea Grant College Program maintained by the National Oceanic and Atmospheric Administration, U.S. Department of Commerce. We would like to thank Ron Paille, Lynne Bowers, Paul Kemp, Steve Whipple, and John Day whose assistance and comments helped make this paper possible. gimes. Three major tree species, baldcypress (Taxodium distichum), water tupelo (Nyssa aquatica), and ash (Fraxinus sp.) are emphasized. MATERIALS AND METHODS-Study sitesThe Lac des Allemands swamp is located at the upper end of the Barataria Bay estuary, between the Mississippi River and Bayou Lafourche, La. (Fig. 1). During a routine examination of 1972 infrared false color imagery of this swamp, we noticed a 970-ha area that appeared white in comparison to the red and bluegreen of the other forested areas. Earlier imagery (December 1940 and March 1952) showed that extensive logging operations had occurred throughout the swamp, but the distinctive pattern of the 1972 imagery was not evident. Natural water flows through this swamp forest are northeast to southeast. However, the 970-ha site was found to be impounded and permanently flooded by water up to 1 m deep. Impoundment began when Louisiana Highway 20 was completed in 1930 along the western boundary, blocking overland flows from upstream. A natural ridge runs along the southeastern side of the area. The Vacherie Canal was dredged in 1955 along the northern boundary, and Bayou Chevreuil along the southern boundary in 1959, impounding the area with spoil deposits so that natural water flow has been altered for at least 20 yr. North of the permanently flooded area is a dense, healthy forest (320 ha). This area was isolated by construction of a board road in the

Trust and Symbolic Exchange

Abstract: This paper analyzes some of the ways that actors try to establish their trustworthiness in interaction. It is argued that they do so through a type of social exchange in which the principal importance of the goods exchanged lies not in their utilitarian value to those who receive them but in their significance as gestures that communicate the intentions of the actors making them. This type of social exchange is called symbolic exchange. A vocabulary of symbolic exchange in American society is described, and the influence of various dimensions of social structure on the 'character of symbolic exchange is discussed. Social structural dimensions discussed include status hierarchy vs. status equality, formality vs. informality, and specificity vs. diffuseness. Finally, it is suggested that symbolic exchange acts as a link between communicative behavior and social exchange as such.

Rotation in solar-type stars. I. Evolutionary models for the spin-down of the sun

Abstract: Models of rotating, 1 solar mass stars through the pre-main sequence and main sequence stages have been calculated. The calculations begin on the Hayashi track with rapid, rigid-body rotation, with angular momentum removed from the convective envelope to simulate the effect of the solar wind as the models evolve. Interior angular momentum redistribution by circulation flows and rotational instabilities is computed by a diffusion technique. It is found that at the present age of solar evolution, the models employed have internal rotation rates significantly larger than those allowed by measured solar oblateness, suggesting that the effects of circulation currents near the outer boundary of the radiative interior have been underestimated. An important result of this study is the implication that circulation currents produce deep mixing of such minor constituents as He-3 and C-13, perhaps also explaining the observed steady depletion of lithium during the main-sequence stage.

Projections from visual areas of the middle suprasylvian sulcus onto the lateral posterior complex and adjacent thalamic nuclei in cat.

Abstract: The distribution of corticothalamic projections from lateral suprasylvian areas AMLS, PMLS, ALLS, and PLLS was investigated with the autoradiographic method. Areas AMLS and PMLS were both found to project retinotopically upon the medial interlaminar nucleus and the lateral and pulvinar zones of the lateral posterior complex, as well as to the ventral lateral geniculate nucleus, intralaminar nuclei, and thalamic reticular complex. Retinotopic projections to the dorsal lateral geniculate nucleus were demonstrated from PMLS but not AMLS, and projections to zona incerta were demonstrated from AMLS but not PMLS. Areas PLLS and ALLS were both found to project retinotopically upon the interjacent zone of the lateral posterior complex, as well as to the intermediate and suprageniculate divisions of the posterior nuclear group, the magnocellular division of the medial geniculate complex, the thalamic reticular complex, and central lateral nucleus. Area ALLS was also found to project onto the dorsal division of the medial geniculate complex and lateral division of the posterior nuclear group. Differences between the four cortical areas in the pattern and density of their thalamic projections supports the parcellation of these areas as proposed by Palmer et al. ('78). The projection patterns of areas PMLS, AMLS, PLLS, and ALLS were found to respect the boundaries of the zones of the lateral posterior complex, which had been identified and defined previously (Updyke, ′77), and the results thus support the hypothesis that these zones are the functional units of organization for visual traffic between the cat's extrastriate visual areas.

Accumulation of plant nutrients and heavy metals through sedimentation processes and accretion in a Louisiana salt marsh

Abstract: The accumulation of selected plant nutrients and heavy metals in a rapidly accreting Louisiana salt marsh was examined. Sedimentation processes were shown to be supplying large amounts of plant nutrients to the marsh. Accumulation of heavy metals was low and appeared to be associated with the natural heavy metal content of incoming sediment rather than from a pollution source. A large portion of organic carbon from primary production remained in the marsh, contributing to the aggradation process of vertical marsh accretion. Nitrogen accumulated in the marsh at rates as great as 21 g per m2 per yr.

Evaluation of Durapatite Ceramic as an Alloplastic Implant in Periodontal Osseous Defects: I. Initial Six‐Month Results

Abstract: Eight patients received a new polycrystalline ceramic form of pure hydroxylapatite (Durapatite) as a bone implant material in various types of infrabony defects following internally beveled full thickness flaps, root planing, and defect debridement. All osseous margins and defects were measured from the CEJ using a standardized periodontal probe. Similarly debrided defects that were not implanted served as controls. Defect selection as either experimental or control site was based on either split-mouth or alternating defects design. Periodontal dressing and systemic tetracycline were used for 10 days. Recalls for documentation and plaque control were at 10, 20, and 30 days, and 3 and 6 months. Measurements relating to defect changes were made at the 6-month surgical re-entry. For evaluation purposes original defect depths were divided into three groups. In Group I (<3 mm) defect fill was 1.2 mm (60%) for the implanted defects and 0.6 mm (40.5%) for the control sites (significantly different at P < 0.05). ...

Satisfaction in Communication: An Examination of the Downs-Hazen Measure

Abstract: First-line supervisors from five textile mills located in the southeast completed the eight-scale Downs-Hazen measure of satisfaction in communication. These data were examined to determine the dimensional stability and the intrascale internal consistency of the measure. The results indicate that, although an eight-factor solution is reasonable, only in a few instances is the generated subscale structure as originally hypothesized. Further, the subscales do not appear orthogonal.

Submarine chutes on the slopes of fjord deltas

Abstract: The first side-scan sonograph images of submarine landslide chutes from arctic fjords presented here indicate that submarine slopes of fjord head deltas are subject to instability. The chutes transport sediment from the upper delta slopes into deeper water parts of the fjords. Previously, sediment distribution and budgets in the bottom of deepwater fjords were ascribed to settling of suspended sediment supplied by streams and rivers during the short summer melt period. Previous descriptions of submarine mass movements from some subarctic fjords have been limited to isolated major catastrophic events. The sonographs from an arctic fjord suggest that delta-front instability occurs as multiple small-scale events that recur at frequent intervals and are intrinsic to the fjord sedimentation system.

A model for a weighted retrieval system

Abstract: There has been a good deal of work on information retrieval systems that have continuous weights assigned to the index terms that describe the records in the database, and/or to the query terms that describe the user queries. Recent articles have analyzed retrieval systems with continuous weights of either type and/or with a Boolean structure for the queries. They have also suggested criteria which such systems ought to satisfy and record evaluation mechanisms which partially satisfy these criteria. We offer a more careful analysis, based on a generalization of the discrete weights. We also look at the weights from an entirely different approach involving thresholds, and we generate an improved evaluation mechanism which seems to fulfill a larger subset of the desired criteria than previous mechanisms. This new mechanism allows the user to attach a “threshold” to the query term.

Threshold values and Boolean retrieval systems

Abstract: Several papers have appeared that have analyzed recent developments in the problem of processing, in a document retrieval system, queries expressed as Boolean expressions. The purpose of this paper is to continue that analysis. We shall show that the concept of threshold values resolves the problems inherent with relevance weights. Moreover, we shall explore possible evaluation mechanisms for retrieval of documents, based on fuzzy-set-theoretic considerations.

Nitrate reduction to ammonium and organic nitrogen in an estuarine sediment

Abstract: Nitrate reduction to NH 4 + and incorporation into organic matter was investigated in sediment-water systems composed of a 2.4-cm layer of estuarine sediment covered by 2 cm of water. Between 15 and 28% of the 15 N-labelled NO 3 − added to the sediment or floodwater of the systems was recovered as NH 4 + and organic N. The results indicated that NO 3 − was reduced to NH 4 + by a dissimilatory mechanism. A separate experiment examined the influence of redox potential (+300, 0 and −200 mV) on NO 3 − reduction in sediment suspensions maintained at pH 7.5. Conversion of NO 3 − to NH 4 + and organic N increased markedly with decreasing redox potential. The results suggested that although the reaction accounted for 35–42% of the NO 3 − reduced under intensely-reduced conditions (−200 mV), the significance of the reaction in nature was dependent upon NO 3 − movement into zones sufficiently reduced for reduction of NO 3 − to NH 4 + instead of denitrification. Under conditions in which NO 3 − moved downward through a sediment-water column into a reduced sediment zone approximately 15% of the NO 3 − was reduced to NH 4 + and recycled in the sediment.