Showing papers by "Louisiana State University published in 1998"
Book•
01 Jan 1998TL;DR: This chapter discusses research design issues for Mixed Method and Mixed Model Studies, as well as applications, applications, and future directions of mixed model research.
Abstract: PART ONE: PARADIGMS AND POLITICS OF RESEARCH Introduction to Mixed Methods and Mixed Model Studies in the Social and Behavioral Sciences Pragmatism and the Choice of Research Strategy Research Design Issues for Mixed Method and Mixed Model Studies PART TWO: METHODS AND STRATEGIES OF RESEARCH Sampling, Measurement, and Quality of Inferences Data Collection Strategies and Research Procedures Alternatives to Traditional Data Analytic Strategies PART THREE: APPLICATIONS, EXAMPLES AND FUTURE DIRECTION OF MIXED MODEL RESEARCH Examples of Mixed Model Designs Extended Examples of Mixed Model Designs Conclusions and Future Directions
6,052 citations
University of Tokyo1, Boston University2, Brookhaven National Laboratory3, University of California, Irvine4, California State University5, George Mason University6, Gifu University7, University of Hawaii at Manoa8, Kobe University9, Los Alamos National Laboratory10, Louisiana State University11, University of Maryland, College Park12, University of Chicago13, Stony Brook University14, Niigata University15, Osaka University16, Seoul National University17, Tohoku University18, Tokai University19, Tokyo Institute of Technology20, University of Warsaw21, University of Washington22, Stanford University23
Abstract: We present an analysis of atmospheric neutrino data from a 33.0 kton yr (535-day) exposure of the Super-Kamiokande detector. The data exhibit a zenith angle dependent deficit of muon neutrinos which is inconsistent with expectations based on calculations of the atmospheric neutrino flux. Experimental biases and uncertainties in the prediction of neutrino fluxes and cross sections are unable to explain our observation. The data are consistent, however, with two-flavor ${\ensuremath{
u}}_{\ensuremath{\mu}}\ensuremath{\leftrightarrow}{\ensuremath{
u}}_{\ensuremath{\tau}}$ oscillations with ${sin}^{2}2\ensuremath{\theta}g0.82$ and $5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}l\ensuremath{\Delta}{m}^{2}l6\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}3}\mathrm{eV}{}^{2}$ at 90% confidence level.
3,784 citations
Book•
20 Aug 1998TL;DR: In this paper, the authors explore the roots of andraggy and explore the world of learning theory Theories of learning A theory of adult learning: Andragogy Theory of teaching Part 2: Advancements in Adult Learning New perspectives on andragogy Adult learning within human resource development Beyond andraggery Part 3: Selected Readings
Abstract: Introduction Part 1: The Roots of Andragogy Exploring the world of learning theory Theories of learning A theory of adult learning: Andragogy Theories of teaching Part 2: Advancements in Adult Learning New perspectives on andragogy Adult learning within human resource development Beyond andragogy Part 3: Selected Readings.
2,373 citations
Book•
01 Jan 1998TL;DR: Proximal Calculus in Hilbert Space and Generalized Gradients in Banach Space are studied in this article for a short course in control theory in the context of control theory.
Abstract: Proximal Calculus in Hilbert Space.- Generalized Gradients in Banach Space.- Special Topics.- A Short Course in Control Theory.
1,918 citations
TL;DR: It is concluded that dietary fat plays a role in the development of obesity and to reduce the prevalence of obesity, there must be an increase in energy expenditure, a reduction in total energy intake, or both.
1,147 citations
Book•
05 Aug 1998TL;DR: Algorithms for Parallel Computing: Algebraic Equations and Matrices, Differentiation and Integration, and Tree Algorithms.
Abstract: FOUNDATIONS OF PARALLEL COMPUTING. Elements of Parallel Computing. Data Structures for Parallel Computing. Paradigms for Parallel Algorithm. Simple Algorithms. ALGORITHMS FOR GRAPH MODELS. Tree Algorithms. Graph Algorithms. NC Algorithms for Chordal Graphs. ARRAY MANIPULATION ALGORITHMS. Searching and Merging. Sorting Algorithms. NUMERICAL ALGORITHMS. Algebraic Equations and Matrices. Differentiation and Integration. Differential Equations. Answers to Selected Exercises. Index.
816 citations
TL;DR: Because it is difficult to directly scavenge peroxynitrite because of its fast reaction with CO2, scavenging of intermediates from the peroxysitrite/CO2 reaction would provide an additional way of preventing peroxlynitrite-mediated cellular effects.
810 citations
TL;DR: There appears to be a complex interrelationship between Zn and both Type 1 and Type 2 diabetes, and the role of Zn in the clinical management of diabetes, its complications, or in its prevention is, at best, unclear.
Abstract: The relationship between diabetes, insulin and zinc (Zn) is complex with no clear cause and effect relationships. In Type 1 diabetes there is a lack of insulin production, in Type 2 diabetes resistance to the effects of insulin are predominant. Both Type 1 and Type 2 have the same long-term complications. Diabetes effects zinc homeostasis in many ways, although it is most probably the hyperglycemia, rather than any primary lesion related to diabetes, which is responsible for the increased urinary loss and decreases in total body zinc. The role of Zn deficiency, which could, at least potentially, exacerbate the cytokine-induced damage in the autoimmune attack which destroys the islet cell in Type 1 diabetes, is unclear. Since Zn plays a clear role in the synthesis, storage and secretion of insulin as well as conformational integrity of insulin in the hexameric form, the decreased Zn, which affects the ability of the islet cell to produce and secrete insulin, might then compound the problem, particularly in Type 2 diabetes. Several of the complications of diabetes may be related to increased intracellular oxidants and free radicals associated with decreases in intracellular Zn and in Zn dependent antioxidant enzymes. There appears to be a complex interrelationship between Zn and both Type 1 and Type 2 diabetes. The role of Zn in the clinical management of diabetes, its complications, or in its prevention is, at best, unclear.
691 citations
University of Tokyo1, Boston University2, Seoul National University3, Brookhaven National Laboratory4, University of California, Irvine5, California State University6, George Mason University7, Gifu University8, University of Hawaii at Manoa9, Kobe University10, Los Alamos National Laboratory11, Louisiana State University12, University of Maryland, College Park13, University of Chicago14, Miyagi University of Education15, Stony Brook University16, Niigata University17, Shizuoka University18, Osaka University19, Tohoku University20, Tokai University21, Tokyo Institute of Technology22, University of Warsaw23, University of Washington24
TL;DR: The first results of the solar neutrino flux measurement from Super-Kamiokande are presented in this article, where the results are obtained from data taken between 31 May 1996, and 23 June 1997.
Abstract: The first results of the solar neutrino flux measurement from Super-Kamiokande are presented. The results shown here are obtained from data taken between 31 May 1996, and 23 June 1997. Using our measurement of recoil electrons with energies above 6.5 MeV, we infer the total flux of ${}^{8}\mathrm{B}$ solar neutrinos to be $2.42\ifmmode\pm\else\textpm\fi{}0.06(\mathrm{stat}{)}_{\ensuremath{-}0.07}^{+0.10}(\mathrm{syst})\ifmmode\times\else\texttimes\fi{}{10}^{6}\mathrm{cm}{}^{\ensuremath{-}2}{\mathrm{s}}^{\ensuremath{-}1}$. This result is consistent with the Kamiokande measurement and is 36% of the flux predicted by the BP95 solar model. The flux is also measured in 1.5 month subsets and shown to be consistent with a constant rate.
677 citations
TL;DR: The results suggest that overexpression of COX may not be unique to colon cancer and may be a feature common to other epithelial tumors.
Abstract: Background: Numerous studies have demonstrated that the levels of prostaglandins are greater in various cancers, including breast cancer and colon cancer, than in normal tissues. In particular, the inducible form of cyclooxygenase (COX), the rate-limiting enzyme in prostaglandin biosynthesis, is overexpressed in colon tumors. Epidemiologic studies have demonstrated that the use of aspirin or other nonsteroidal antiinflammatory drugs (NSAIDs) can reduce the risk of colon cancer and, to a lesser extent, the risk of breast cancer. NSAIDs are known to inhibit COX, suggesting that the beneficial effect of NSAIDs in colon cancer may be related to COX overexpression in this disease. This possibility led us to ask whether COX is also overexpressed in breast cancers. Methods: Surgical specimens from 44 patients with breast cancer who had undergone lumpectomy or mastectomy were analyzed by immunoblot analysis and immunohistochemical analysis to determine the expression profile of the constitutively expressed form of cyclooxygenase (COX-1) and the inducible form (COX-2); the specimens from 14 patients included normal breast tissue. Results: Expression of COX-1 protein was substantially higher in 30 of 44 tumor samples than in any of the 14 normal tissue specimens. Immunoblot analysis revealed extremely high levels of COX-2 protein in two tumor samples. Immunohistochemical staining of specimens that expressed COX-1 and/or COX-2 revealed that COX-1 was localized in stromal cells adjacent to the tumor but not in tumor cells. In contrast, COX-2 was localized primarily in tumor cells but also appeared in stromal cells. Conclusion : Our results suggest that overexpression of COX may not be unique to colon cancer and may be a feature common to other epithelial tumors.
665 citations
TL;DR: In contrast to other phosphopantetheinyl transferases (PPTases) previously examined, Sfp will modify the apo forms of heterologous recombinant proteins, including the PCP domain of Saccharomyces cerevisiae Lys2, the aryl carrier protein (ArCP) domain of Escherichia coli EntB, and the E. coli acyl carrierprotein (ACP) subunit, suggesting Sfp as a good candidate forheterologous coexpression
Abstract: The Bacillus subtilis enzyme Sfp, required for production of the lipoheptapeptide antibiotic surfactin, posttranslationally phosphopantetheinylates a serine residue in each of the seven peptidyl carrier protein domains of the first three subunits (SrfABC) of surfactin synthetase to yield docking sites for amino acid loading and peptide bond formation. With recombinant Sfp and 16−17-kDa peptidyl carrier protein (PCP) domains excised from the SrfB1 and SrfB2 modules as apo substrates, kcat values of 56−104 min-1 and Km values of 1.3−1.8 μM were determined, indicating equivalent recognition of the adjacent PCP domains by Sfp. In contrast to other phosphopantetheinyl transferases (PPTases) previously examined, Sfp will modify the apo forms of heterologous recombinant proteins, including the PCP domain of Saccharomyces cerevisiae Lys2 (involved in lysine biosynthesis), the aryl carrier protein (ArCP) domain of Escherichia coli EntB (involved in enterobactin biosynthesis), and the E. coli acyl carrier protein (...
TL;DR: It is concluded that biological membranes and other tissue hydrophobic compartments are important sites for disappearance of NO and for formation of NO-derived reactive species and that attenuation of these potentially damaging reactions is an important protective action of lipid-soluble antioxidants such as vitamin E.
Abstract: We demonstrate herein dramatic acceleration of aqueous nitric oxide (NO) reaction with O2 within the hydrophobic region of either phospholipid or biological membranes or detergent micelles and demonstrate that the presence of a distinct hydrophobic phase is required. Per unit volume, at low amounts of hydrophobic phase, the reaction of NO with O2 within the membranes is approximately 300 times more rapid than in the surrounding aqueous medium. In tissue, even though the membrane represents only 3% of the total volume, we calculate that 90% of NO reaction with O2 will occur there. We conclude that biological membranes and other tissue hydrophobic compartments are important sites for disappearance of NO and for formation of NO-derived reactive species and that attenuation of these potentially damaging reactions is an important protective action of lipid-soluble antioxidants such as vitamin E.
University of Washington1, Michigan State University2, University of Wisconsin-Madison3, University of Paris-Sud4, TRIUMF5, Colorado School of Mines6, University of North Carolina at Chapel Hill7, Duke University8, University of California, Berkeley9, University of Connecticut10, Weizmann Institute of Science11, North Carolina State University12, Louisiana State University13, Columbia University14, California Institute of Technology15, University of South Carolina16, Aarhus University17, Rikkyo University18, University of Illinois at Urbana–Champaign19, Yale University20, Ruhr University Bochum21, University of California, Santa Barbara22, Texas A&M University23
TL;DR: In this paper, the available information on the nuclear-fusion cross sections that are most important for solar energy generation and solar neutrino production is reviewed and analyzed, and best values for the low-energy cross-section factors and, wherever possible, estimates of the uncertainties are provided.
Abstract: We review and analyze the available information on the nuclear-fusion cross sections that are most important for solar energy generation and solar neutrino production. We provide best values for the low-energy cross-section factors and, wherever possible, estimates of the uncertainties. We also describe the most important experiments and calculations that are required in order to improve our knowledge of solar fusion rates.
TL;DR: Nonlinear Model Predictive Control (NMPC) as discussed by the authors is the industry standard for controlling constrained multivariable nonlinear processes with a large operating regime, and it is well suited for controlling nonlinear process with constraints.
TL;DR: In this paper, a measure of consumers' attitude toward private label brands is developed, and its psychometric properties are assessed, and predictions are then tested regarding relationships between private label attitude and latent perceptual and sales promotion constructs, and purchase behaviors measured in a field setting.
Abstract: A measure of consumers’ attitude toward private label brands is developed, and its psychometric properties are assessed. Predictions are then tested regarding relationships between private label attitude and (1) latent perceptual and sales promotion constructs, and (2) purchase behaviors measured in a field setting. The measure is positively related to value consciousness, deal proneness, and smart-shopper self-perceptions, and negatively related to the propensity to be brand loyal and hold price-quality perceptions. Predictive validity of the private label measure is supported by a positive relationship with private label purchases from a grocery store shopping trip. Despite a positive relationship between the latent constructs of private label attitude and deal proneness, the consumer segment that allocated a high percentage of total purchases to private label products made fewer purchases on sale or with a coupon. These findings suggest that consumers may choose between price-related deals and private label purchases.
TL;DR: Direct assessment of movement remains the most valid approach to many key issues in population biology, and studies of paternity, kinship and phylogeography generate the most reliable results.
Abstract: Indirect methods using genetic markers are the primary measure of gene flow levels among interbreeding populations. Results from studies employing these methods are often ambiguous and open to multiple interpretation. This is primarily due to low resolution of molecular markers and low precision of model-based estimates. Studies of paternity, kinship and phylogeography generate the most reliable results. Future studies should employ more powerful analytical methods, analyse loci independently, and attempt to distinguish confounding contributions of vicariance to isolation-by-distance studies. Moreover, direct assessment of movement remains the most valid approach to many key issues in population biology.
TL;DR: The data indicate that the reaction of NO with oxyhemoglobin within RBCs is limited by the diffusion of NO into the cell, which has also been shown previously for the Reaction of O2 with deoxyhemoglobin.
University of California, Riverside1, Linfield College2, Embry–Riddle Aeronautical University3, Louisiana Tech University4, University of New Mexico5, Louisiana State University6, University of California, San Diego7, Los Alamos National Laboratory8, Temple University9, University of California, Santa Barbara10
TL;DR: In this paper, a beam-on high-energy (60-200 MeV) electron event was observed consistent with the observed oscillation probability of $(2.6\ifmmode\pm\else\textpm\fi{}1.0
Abstract: A search for ${\ensuremath{
u}}_{\ensuremath{\mu}}\ensuremath{\rightarrow}{\ensuremath{
u}}_{e}$ oscillations has been conducted with the LSND apparatus using ${\ensuremath{
u}}_{\ensuremath{\mu}}$ from ${\ensuremath{\pi}}^{+}$ decay in flight. Two analyses observe a total of 40 beam-on high-energy (60--200 MeV) electron events consistent with the ${\ensuremath{
u}}_{e}\mathrm{C}\ensuremath{\rightarrow}{e}^{\ensuremath{-}}X$ inclusive reaction. This number is significantly above the $21.9\ifmmode\pm\else\textpm\fi{}2.1$ events expected from the ${\ensuremath{
u}}_{e}$ contamination in the beam and the beam-off background. If interpreted as an oscillation signal, the observed oscillation probability of $(2.6\ifmmode\pm\else\textpm\fi{}1.0\ifmmode\pm\else\textpm\fi{}0.5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ is consistent with the previously reported ${\overline{\ensuremath{
u}}}_{\ensuremath{\mu}}\ensuremath{\rightarrow}{\overline{\ensuremath{
u}}}_{e}$ oscillation evidence from LSND.
TL;DR: These findings demonstrate that CLA reduces body fat by several mechanisms, including a reduced energy intake, increased metabolic rate, and a shift in the nocturnal fuel mix.
Abstract: Conjugated linoleic acid (CLA) is a naturally occurring group of dienoic derivatives of linoleic acid found in the fat of beef and other ruminants. CLA is reported to have effects on both tumor development and body fat in animal models. To further characterize the metabolic effects of CLA, male AKR/J mice were fed a high-fat (45 kcal%) or low-fat (15 kcal%) diet with or without CLA (2.46 mg/kcal; 1.2 and 1.0% by weight in high- and low-fat diets, respectively) for 6 wk. CLA significantly reduced energy intake, growth rate, adipose depot weight, and carcass lipid and protein content independent of diet composition. Overall, the reduction of adipose depot weight ranged from 43 to 88%, with the retroperitoneal depot most sensitive to CLA. CLA significantly increased metabolic rate and decreased the nighttime respiratory quotient. These findings demonstrate that CLA reduces body fat by several mechanisms, including a reduced energy intake, increased metabolic rate, and a shift in the nocturnal fuel mix.
TL;DR: Results suggest that preventive health care behaviors are strongly influenced by the value consumers perceive in engaging in such actions, which is greatly affected by response efficacy, or the person’s belief that a specific action will mitigate the health threat.
Abstract: A conceptual model of preventive health care behavior is proposed and tested. Results suggest that preventive health care behaviors are strongly influenced by the value consumers perceive in engaging in such actions. This value is greatly affected by response efficacy, or the person’s belief that a specific action will mitigate the health threat. A separate consideration affecting adherence to a prescribed preventive health care behavior is self-efficacy, or the person’s belief that the target behaviors can be enacted. Additionally, health motivation and health consciousness are also shown to influence preventive health care behaviors. Future research directions and managerial implications of the findings are outlined.
TL;DR: In this article, degradation models and data are used to make inferences and predictions about a failure-time distribution, and the connection between degradation reliability models and failure time reliability models is explained.
Abstract: High reliability systems generally require individual system components having extremely high reliability over long periods of time. Short product development times require reliability tests to be conducted with severe time constraints. Frequently few or no failures occur during such tests, even with acceleration. Thus, it is difficult to assess reliability with traditional life tests that record only failure times. For some components, degradation measures can be taken over time. A relationship between component failure and amount of degradation makes it possible to use degradation models and data to make inferences and predictions about a failure-time distribution. This article describes degradation reliability models that correspond to physical-failure mechanisms. We explain the connection between degradation reliability models and failure-time reliability models. Acceleration is modeled by having an acceleration model that describes the effect that temperature (or another accelerating variable) has on...
TL;DR: In this paper, acute muscle stretching inhibits maximal strength performance, and it is shown that stretching in conjunction with hypertrophy reduces the maximal strength of the human body's muscle.
Abstract: (1998). Acute Muscle Stretching Inhibits Maximal Strength Performance. Research Quarterly for Exercise and Sport: Vol. 69, No. 4, pp. 411-415.
01 Jan 1998
TL;DR: This paper provides a comprehensive survey of some methods for eliciting data for MCDM problems and also for processing such data.
Abstract: The core of operations research is the development of approaches for optimal decision making. A prominent class of such problems is multi-criteria decision making (MCDM). The typical MCDM problem deals with the evaluation of a set of alternatives in terms of a set of decision criteria. This paper provides a comprehensive survey of some methods for eliciting data for MCDM problems and also for processing such data.
TL;DR: Results demonstrated that the brief preference assessment identified stimuli that functioned as reinforcers for a simple operant response, identified preferred stimuli that were differentially effective as rein forcers compared to nonpreferred stimuli, was associated with fewer problem behaviors, and required less time to complete than a commonly used paired-stimulus preference assessment.
Abstract: We evaluated the utility of a brief (5-min) stimulus preference assessment for individuals with developmental disabilities. Participants had noncontingent (free) access to an array of stimuli and could interact with any of the stimuli at any time. Stimuli were never withdrawn or withheld from the participants during a 5-min session. In Experiment 1, the brief preference assessment was conducted for 10 participants to identify differentially preferred stimuli, and reinforcer assessments were conducted to test the reinforcing efficacy of those stimuli identified as highly preferred. In Experiment 2, a comparison was conducted between the brief preference assessment and a commonly used paired-stimulus preference assessment. Collectively, results demonstrated that the brief preference assessment identified stimuli that functioned as reinforcers for a simple operant response, identified preferred stimuli that were differentially effective as reinforcers compared to nonpreferred stimuli, was associated with fewer problem behaviors, and required less time to complete than a commonly used paired-stimulus preference assessment.
Book•
01 Jan 1998TL;DR: In this paper, the authors discuss the origins and evolution of Biogeochemical Cycles and Thermodynamics, and the role of Symbiosis in the Biosphere. But they do not discuss the relationship between the two processes.
Abstract: Preface. Introduction. General Considerations: Bacterial Metabolism. Bioenergetics of Microbial Metabolism. Transport Mechanisms and Structure of Microbial Communities. Mineral Cycles: Hydrolysis of Organic Polymers. Comparison of Element Cycles. The Water Column: Prokaryotic Primary Producers. Water Column Bacteria and Mineralisation. Biogeochemical Cycling in Soils: Soil Water as a Master Variable. Responses to Plant Organic Matter. Responses of Soil Biogeochemistry to Disturbance and Change. Aquatic Sediments: Comparison of Freshwater and Marine Sediments. The Carbon Cycle. The Nitrogen Cycle. The Phosphorus Cycle. Manganese and Iron. Microbial Mats and Stratified Water Columns: Mats Based on Colourless Sulfur Bacteria. Cyanobacterial Mats. Other Types of Mats. Stratified Water Columns. Symbiotic Systems: The Role of Symbiosis in the Biosphere. Symbiotic Polymer Degradation. Symbiotic Nitrogen Fixation. Autotrophic Bacteria as Symbionts. Biogeochemistry and Extreme Environments. Microbial Biogeochemical Cycling and the Atmosphere: The Atmosphere as an Elemental Reservoir. Atmospheric Structure and Evolution. Synopsis of Trace Gas Biogeochemistry and Linkages to Climate Change. Trace Gas Dynamics and Climate Change: An Analysis of Methane Production and Consumption. Summary and Conclusion. Origins and Evolution of Biogeochemical Cycles: Biogeochemical Cycles and Thermodynamics. Pre-Biotic Earth and Mineral Cycles. Theoretical Perspectives on the Origin of Life. Evolution of Biogeochemical Cycles. Appendix: Thermodynamics and Calculation of Energy Yields of Metabolic Processes.
TL;DR: To the extent that breaking points provide an index of reinforcing efficacy, these studies demonstrate that a wide range of variables can influence the reinforcing efficacy of self-administered drugs.
Abstract: Drugs, like other reinforcers, can vary in their relative abilities to support operant responding. Considerable research has been designed to obtain useful measures of a given drug’s or dose’s ”reinforcing efficacy” and to identify the ways in which a variety of behavioral and pharmacological variables impact these measures. Progressive-ratio schedules of drug delivery generate an index of a drug’s or dose’s reinforcing efficacy (the breaking point) and are being used increasingly as tools in the analysis of drug self-administration. Progressive-ratio schedules of drug delivery have been used to characterize the effects of pretreatment drugs, lesions, drug deprivation, physical dependence, and repeated non-contingent drug exposure on breaking points. Behavioral factors, including food restriction and electric shock, and organismic factors, including gender and strain, have also been investigated using progressive-ratio schedules of drug delivery. To the extent that breaking points provide an index of reinforcing efficacy, these studies demonstrate that a wide range of variables can influence the reinforcing efficacy of self-administered drugs. The objectives of this review are to critique existing research themes, outline potential limitations of progressive-ratio procedures, and to suggest potentially fruitful uses of these procedures in future research.
TL;DR: In this paper, the authors considered relationships between bases of social power and subordinates' adverse work reactions, hypothesizing that procedural justice would mediate such relationships, and tested a mediational model rejlecting this hypothesis.
TL;DR: In this article, the authors measured the lithium concentrations and isotopic compositions of major world rivers draining representative geological terrains to constrain the river endmember and to understand the behavior of lithium isotopes in the continental weathering environment.
TL;DR: In this article, the authors examined the responses of tree species to soil type, topographic position and slope angle in an upland old-growth tropical rain forest landscape in Costa Rica, Central America.
Abstract: 1 Do local edaphic factors over short environmental gradients affect the distribution and abundance of tree species in tropical rain forests? We addressed this question by examining the responses of tree species to soil type, topographic position and slope angle in an upland old-growth tropical rain forest landscape in Costa Rica, Central America.
2 The study area covered 216 ha of non-swamp old growth and included replicated landscape units such as ridgetop to swale catenas, small watersheds, and alluvial terraces. An existing soils map was refined using additional sampling along a regularly spaced grid. Three soil units were defined: residual soils derived from in-place weathering of basaltic parent material; old alluvial terrace soils formed by precontemporary flooding; and soils of stream valleys. A Geographic Information System was used to assign soil type to 2190 post-establishment individuals of nine tree species in a long-term demographic study. Topographic position and slope angle were measured in the field.
3 Data from 433 regularly spaced sample points were used to generate an expected distribution of edaphic variables, which was compared with the number of individuals of each species in each edaphic category.
4 Non-random distributions among soil types were found for seven of the nine species, with topographic positions for six species, and with slope angle classes for four species.
5 The issue of what constitutes an independent sample of establishment was analysed by considering the old-growth character of the landscape and evidence for frequent dispersal among edaphic units. A re-analysis of species’ distributions using only individuals > 4 cm diameter showed that results from the original analyses were robust.
6 Soil type (residual vs. old alluvial) was not significantly related to diameter growth. Three species showed significant differences in size class distributions between soil types with increasing diameter.
7 Tree species in tropical rain forests are frequently non-randomly distributed along relatively short edaphic gradients on upland soils. Future studies should increase the number of species and spatial scale analysed, incorporate better analyses of edaphic variables, and include experiments to identify the ecological processes that generate these non-random distributions.
Journal Article•
TL;DR: Early recognition and expeditious initial wide excision and debridement along with appropriate antibiotic coverage and support of systemic effects of necrotizing fasciitis serve to decrease morbidity and mortality.
Abstract: Necrotizing fasciitis is an aggressive soft-tissue infection that in the past has carried a significant mortality rate. One of the most important determinants of outcome is recognition of the disease process. This is followed by aggressive resuscitation measures and radical debridement at the initial operation to control the infectious spread at the outset. The objective of this study is to help reveal the benefits of aggressive early surgical debridement in the treatment of necrotizing fasciitis. A retrospective review of the medical records of 68 patients between the years 1980 and 1996 with the diagnosis of necrotizing fasciitis was performed. The patients were assigned to two groups, Group A (21; 31%), who had delay in therapy or inadequate preliminary therapy and Group B (47; 69%), who underwent aggressive surgical debridement from the outset. Concomitant disease processes were noted. The medical records of 68 patients were studied. Age ranged from 13 to 67 (mean, 52) years of age. There were 38 (56%) females, 21 (64%) of the patients were African-American, 24 (73%) of the patients had concomitant disease processes, 29 (42%) of the patients had a history of tobacco use, 11 (16%) of the patients had a history of alcohol consumption, and 11 (16%) of the patients were obese. Mortality in Group A was 8 of 21 patients (38%). Mortality in Group B was 2 of 47 patients (4.2%). The difference in mortality was found to be statistically significant (P = 0.0007). Early recognition and expeditious initial wide excision and debridement along with appropriate antibiotic coverage and support of systemic effects of necrotizing fasciitis serve to decrease morbidity and mortality. We believe the above is an absolute necessity followed by frequent washing and minor debridement of the wound until granulating tissue is observed. This can then be followed by procedures to close/cover the surgical defect (i.e., split-thickness skin grafts or various coverage flaps).