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Articles 1 - 17 of 17

Full-Text Articles in Life Sciences

Denitrification, Nutrient Regeneration And Carbon Mineralization In Sediments Of Galveston Bay, Texas, Usa, Andrew R. Zimmerman, Ronald Benner Nov 1994

Denitrification, Nutrient Regeneration And Carbon Mineralization In Sediments Of Galveston Bay, Texas, Usa, Andrew R. Zimmerman, Ronald Benner

Faculty Publications

Rates of benthic denitrification, oxygen consumption and nutrient regeneration were measured during winter, spring and summer in Galveston Bay (Texas, USA) sediments. Denitrification ranged from 0 to 47 µmol N2 m-2 h-1 with maximal rates generally occurring in the summer and the upper estuary. Oxygen consumption rates ranged from 38 µmol O2 m-2 h-1 in the winter to 353 µmol O2 m-2 h-1 in the summer and were correlated with denitrification rates. Variations in bay water temperature accounted for 52 % of the variability associated with denitrification rates whereas only 28% of ...


Semiclassical Quantization Of A Nonintegrable System: Pushing The Fourier Method Into The Chaotic Regime, Karl Sohlberg, Randall B. Shirts Nov 1994

Semiclassical Quantization Of A Nonintegrable System: Pushing The Fourier Method Into The Chaotic Regime, Karl Sohlberg, Randall B. Shirts

Faculty Publications

Semiclassical Einstein–Brillouin–Keller (EBK) quantization of the nonintegrable Hénon–Heiles Hamiltonian succeeds using the Fourier transform method of Martens and Ezra. Two innovations are required for this success: (1) the use of tunneling corrected quantizing actions obtained from an approximate, one-dimensional Hamiltonian and (2) exploitation of intermediate-time approximate quasiperiodicity or "vague tori'' wherein the Fourier transform of chaotic motion over 10–100 vibrational periods allows the determination of frequencies and amplitudes which approximate motion during the time interval. Approximate tori, actions, and EBK energy levels are then straightforward. We use an interpolation method to smooth over small resonance zones ...


Biochemical And Histological Changes During Ovarian Development Of Cobia, Rachycentron Canadum, From The Northern Gulf Of Mexico, Patricia M. Biesiot, Robert E. Caylor, James S. Franks Oct 1994

Biochemical And Histological Changes During Ovarian Development Of Cobia, Rachycentron Canadum, From The Northern Gulf Of Mexico, Patricia M. Biesiot, Robert E. Caylor, James S. Franks

Faculty Publications

Female cobia, Rachycentron canadum, were sampled on their spawning grounds in the Northern Gulf of Mexico to study changes in proximate analysis (protein, lipid, carbohydrate, and ash) of the ovaries during gonadal maturation. Four major stages of oocyte development were studied: stage 1, previtellogenesis; stage 2, vitellogenesis; stage 3, final maturation; and stage 4, postovulation. Cobia are multiple spawning fish; therefore, ovaries engaged in a sequential round of oogenesis were distinguished as stages 1' and 2'. Protein was the major constituent of cobia ovaries and its contribution of cobia ovaries and its contribution remained fairly constant (49-55% fo the dry ...


Contextual Interference Effects In The Acquisition And Retention Of Motor Tasks By Individuals With Mild Mental Handicaps, William J. Vincent, Mary A. Painter, Kathleen B. Inman Oct 1994

Contextual Interference Effects In The Acquisition And Retention Of Motor Tasks By Individuals With Mild Mental Handicaps, William J. Vincent, Mary A. Painter, Kathleen B. Inman

Faculty Publications

The effects of contextual interference on motor skill acquisition and retention were examined in 24 subjects (mean age 13.9 years) with mild mental retardation and 24 chronologically age-matched subjects (mean age 13.11 years) with no disabilities. Subjects from each group were assigned randomly to either a blocked or a random practice schedule. All subjects performed 15 practice trials for each of three different beanbag throwing tasks, 45 trials total. Following a 10-min filled retention interval, 2 trials of each throw (6 total) were performed in a random order by all subjects. Accuracy scores were measured as absolute error ...


The Structure And Dynamics Of The Cs2 Molecular Ion, Karl Sohlberg, Chan Yibai Sep 1994

The Structure And Dynamics Of The Cs2 Molecular Ion, Karl Sohlberg, Chan Yibai

Faculty Publications

Several common elementary methods of computing molecular properties, prerequisite to molecular dynamics studies, are tested for their validity for CS+2. Judged sufficiently accurate, these methods are then used to aid in investigating the collisionally activated dissociation of CS+2 upon impact with xenon. Rice–Ramsperger–Kassel–Marcus (RRKM) unimolecular decay rate calculations are presented and compared to experimental studies employing collisional activation. RRKM theory is shown to reproduce the experimental results for collision energies near threshold. When corrected for vibrational anharmonicity, the RRKM calculation shows agreement with the experimental results over a slightly wider range of energies. A discussion ...


Activity And Distribution Of Attached Bacteria In Chesapeake Bay, Peter Griffith, Fuh-Kwo Shiah, Kathryn Gloersen, Hugh W. Ducklow, Madilyn Fletcher May 1994

Activity And Distribution Of Attached Bacteria In Chesapeake Bay, Peter Griffith, Fuh-Kwo Shiah, Kathryn Gloersen, Hugh W. Ducklow, Madilyn Fletcher

Faculty Publications

The purpose of this study was to further our understanding of the role of particle-associated bacteria in phytoplankton degradation in the Chesapeake Bay, USA, and to identify environmental parameters that control production by free and particle-associated bacteria. Surface and bottom waters at 10 stations along the length of the Bay were sampled over a 2 yr period. Samples were analyzed for temperature, salinity, chlorophyll, phaeophytin, particulate protein, thymidine incorporation (an estimate of bacterial growth rate), and bacterial total direct counts. Results demonstrated that freeliving bacteria were responsible for most of the total bacterial production, which was correlated with temperature and ...


Predicting Evolutionary Consequences Of Greater Reproductive Effort In Tripsacum Dactyloides, A Perennial Grass, Laura L. Jackson, Chester L. Dewald Apr 1994

Predicting Evolutionary Consequences Of Greater Reproductive Effort In Tripsacum Dactyloides, A Perennial Grass, Laura L. Jackson, Chester L. Dewald

Faculty Publications

To test the prediction that a mutation causing greater reproductive effort will result in reduced vegetative vigor, we compared the seed production, growth, and carbohydrate status of normal and pistillate genotypes of the grass Tripsacum dactyloides differing in seed production by up to fourfold. We evaluated the costs of reproduction by two methods: experimental manipulation of reproductive effort and comparison of highand low-yielding genotypes. Despite the large difference in seed production, normal and pistillate (high-yielding) genotypes did not differ in growth rate over a 1-yr period. Contrary to predictions, carbohydrate reserves in the high-yielding genotype were significantly higher at the ...


The Herpes Simplex Virus Thymidine Kinase Gene As A Conditional Negative-Selection Marker Gene In Arabidopsis Thaliana, Mihály Czakó, László Márton Mar 1994

The Herpes Simplex Virus Thymidine Kinase Gene As A Conditional Negative-Selection Marker Gene In Arabidopsis Thaliana, Mihály Czakó, László Márton

Faculty Publications

The human herpes simplex virus thymidine kinase type 1 gene (HSVtk) acts as a conditional lethal marker in mammalian cells. The HSVtk-encoded enzyme is able to phosphorylate certain nucleoside analogs (e.g. ganciclovir, an antiherpetic drug), thus converting them to toxic DNA replication inhibitors. The utility of HSVtk as a conditional negative-selection marker was explored in Arabidopsis thaliana (L.) Heynh. HSVtk was introduced into Arabidopsis by Agrobaderium-mediated transformation. Transgenic plants were morphologically indistinguishable from wild type and exhibited normal fertility. Canciclovir at lO-5to 10-4 M drastically reduced shoot regeneration on transgenic, HSVtk* root explants or ...


The Processing Pathway Of Prelamin A, Michael Sinensky, K. Fantle, M. Trujillo, T. Mclain, A. Kupfer, M. Dalton Jan 1994

The Processing Pathway Of Prelamin A, Michael Sinensky, K. Fantle, M. Trujillo, T. Mclain, A. Kupfer, M. Dalton

Faculty Publications

The conversion of mammalian prelamin A to mature lamin A proceeds through the removal of 18 amino acids from the carboxyl terminus. The initial step in this processing is the isoprenylation of a CAAX box cysteine. This proteolytic event is distinctive for prelamin A among the known prenylated mammalian proteins. Since the carboxyl terminus of prelamin A is removed during maturation, it is not obvious that this protein would undergo the two reactions subsequent to prenylation observed in other CAAX box proteins-the endoproteolytic removal of the carboxyl-terminal 3 amino acids and the subsequent methylation of the now carboxyl-terminal cysteine. To ...


Expression Of Prelamin A Confers Sensitivity Of Dna Biosynthesis To Lovastatin On F9 Teratocarcinoma Cells, Michael Sinensky, T. Mclain, K. Fantle Jan 1994

Expression Of Prelamin A Confers Sensitivity Of Dna Biosynthesis To Lovastatin On F9 Teratocarcinoma Cells, Michael Sinensky, T. Mclain, K. Fantle

Faculty Publications

No abstract provided.


Characterization Of An Old-Growth Bottomland Hardwood Wetland Forest In Northeast Texas: Harrison Bayou, Laurence C. Walker, Thomas Brantley, Virginia Burkett Jan 1994

Characterization Of An Old-Growth Bottomland Hardwood Wetland Forest In Northeast Texas: Harrison Bayou, Laurence C. Walker, Thomas Brantley, Virginia Burkett

Faculty Publications

Most wetland losses in the southern region over the past 200 years have occurred in bottomland hardwood forests. By 1980 the original extent of palustrine bottomland in Texas had been reduced by 63%, from roughly 16 to 6 million acres. Additional losses have occurred during more recent years as a result of conversion to agriculture and timber harvests; these factors and the need to supply new hardwood chip mills in the region pose a potential threat to the remaining hardwood resource. The Harrison Bayou watershed in northeast Texas contains one of the few relatively undisturbed bottomland hardwood wetland forests in ...


Growth Models Of Loblolly And Shortleaf Pine Red-Cockaded Woodpeckers Nesting Trees, W. D. Hacker, W. G. Ross, David Kulhavy Jan 1994

Growth Models Of Loblolly And Shortleaf Pine Red-Cockaded Woodpeckers Nesting Trees, W. D. Hacker, W. G. Ross, David Kulhavy

Faculty Publications

No abstract provided.


Forval A Software Package For Forestry And Natural Resources Project Valuation, Thomas J. Straka, Steven H. Bullard Jan 1994

Forval A Software Package For Forestry And Natural Resources Project Valuation, Thomas J. Straka, Steven H. Bullard

Faculty Publications

FORV(AFLO ResVt ALuationis) an interactive, user-friendly computeprr ogramfo r discountedc ash flow analysis of forestry andn atural resource investments.M anyfo rest economics applicationsa re includeda nde mphasiiss on the nonindustrial privatef orest sector; howeveri,n dustrya ndp ublics ector applications are easily performewdi th the programC. alculations includen et presentv alue, equivalenta nnuali ncome,b enefit/ cost ratio, internal rate of return, future value, sinking funds, installmentp aymentsa, ndl and expectationv alue. Thep rogram also allows the user to accountf or amortizationo f reforestation costs andd epletiona llowancesI. t includess elf-contained instructionsa ndw ill generatet he details of ...


Characterizing Fusiform Rust Incidence And Distribution In East Texas, J. David Lenhart, Gary D. Kronrad, A. Gordon Holley, T.G. Gregoire Jan 1994

Characterizing Fusiform Rust Incidence And Distribution In East Texas, J. David Lenhart, Gary D. Kronrad, A. Gordon Holley, T.G. Gregoire

Faculty Publications

Three measurement cycles were completed on an extensive network of loblolly( Pinus taeda L.) pine and slash (Pinus elliottii Engelm.) pine plots in industrial plantations throughout East Texas in 1984, 1987, and 1990.Because the incidence of fusiform rust caused by Cronartium quercuum [Berk.] Miyabe ex Shirai f. sp. fusiforme had been recorded at each measurement, it is possible to characterize the temporal and geographic distribution of fusiform rust among these industrial pine plantations in East Texas. Average rust incidence for each species by two year age classes is presented. For loblolly pine, there is no apparent change in overall ...


Basic Concepts In Computer Analysis Of Forestry Investments, Steven H. Bullard, Thomas J. Straka Jan 1994

Basic Concepts In Computer Analysis Of Forestry Investments, Steven H. Bullard, Thomas J. Straka

Faculty Publications

In the last 20 years alone, computer hardware and software developments have dramatically increased our ability to calculate financial criteria quickly and accurately. While these advances have dramatically increased our ability to calculate, they have not replaced the need to understand what is being calculated, or how the results should be interpreted and applied. Our objective in the present article is to provide background information for understandingthe "what" and "how" of computer applications for forestry investment analysis. We briefly discuss the most important financial criteria that are calculated by investment analysis computer programs; we also describe their recommended uses and ...


A Performance Evaluation Of Edging And Trimming Operations In U.S. Hardwood Sawmills, Tony El-Radi, Steven H. Bullard, Philip Steele Jan 1994

A Performance Evaluation Of Edging And Trimming Operations In U.S. Hardwood Sawmills, Tony El-Radi, Steven H. Bullard, Philip Steele

Faculty Publications

Edger and trimmer operators must make constant decisions in short time periods on the amount of materials to remove from boards produced in the sawmill. Their decisions directly affect the total volume, grade, and value of the boards, and they therefore directly affect the total value of lumber produced. In recent years, many softwood sawmills have installed computer controlled edgers and trimmers with scanners and optimizers to achieve higher recovery rates. Before similar, relatively expensive, technologies can be seriously evaluated for the hardwood industry, however, the current performance of edging and ·trimming operations must be known. Using a sample of ...


Comparison Of Dietary Overlap Between Allopatric And Sympatric Geckos, Paul D. Klawinski, R. Kathryn Vaughan, Daniel Saenz, William Godwin Jan 1994

Comparison Of Dietary Overlap Between Allopatric And Sympatric Geckos, Paul D. Klawinski, R. Kathryn Vaughan, Daniel Saenz, William Godwin

Faculty Publications

Two gecko species, Hemidactylus turcicus and Cyrtopodion scabrum, have been introduced into the Port of Galveston, Texas. While H. turcicus has been established for a longer period of time, the relatively recent introduction of C. scabrum near the entrance of the Port has apparently led to the displacement of H. turcicus in that area. This has resulted in a distribution in which the two populations’ are largely allopatric except for a narrow band of sympatry at the periphery of each of their ranges. We examined stomach contents of both species in allopatry and sympatry in order to determine if dietary ...