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Articles 2551 - 2580 of 3136

Full-Text Articles in Physical Sciences and Mathematics

Wave Profile For Antiforce Class Ii Waves, Rory Roberts, Mostafa Hemmati Jan 2000

Wave Profile For Antiforce Class Ii Waves, Rory Roberts, Mostafa Hemmati

Journal of the Arkansas Academy of Science

Breakdown waves propagating in the opposite direction of the applied electric field force are referred to as antiforce waves. Breakdown waves moving into a pre-ionized medium are referred to as Class II waves. Using a one-dimensional, steady state, three-fluid, hydrodynamical model and considering the electrons as the main element in propagation of ionizing waves, we have derived the proper boundary conditions for antiforce waves moving into a preionized medium. Using the new boundary conditions and for several current values ahead of the wave, the set of electron fluid dynamical equations (equations of conservation of mass, momentum, and energy coupled with …

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Hammett Correlations Of The Sulfonamide Proton Chemical Shift In A Series Of N-(Substituted Aryl)-P-Toluenesulfonamides, Frank L. Setliff, Tyson K. Spradlin Jan 2000

Hammett Correlations Of The Sulfonamide Proton Chemical Shift In A Series Of N-(Substituted Aryl)-P-Toluenesulfonamides, Frank L. Setliff, Tyson K. Spradlin

Journal of the Arkansas Academy of Science

No abstract provided.

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Versatile Apparatus For Measuring Kinetics Of Gaseous Reactions By A Relative Method, Edmond W. Wilson Jr., Holly A. Sawyer, Amber A. Sawyer Jan 2000

Versatile Apparatus For Measuring Kinetics Of Gaseous Reactions By A Relative Method, Edmond W. Wilson Jr., Holly A. Sawyer, Amber A. Sawyer

Journal of the Arkansas Academy of Science

It is important that accurate, reproducible values for the rates of chemical reactions occurring in the atmosphere be obtained. The value of accurate kinetics measurements is to improve the accuracy of mathematical models used to forecast the state of the atmosphere. We describe a versatile, robust apparatus for obtaining atmospheric reaction rate values and their temperature dependencies by a relative method. This relative method has the advantage over absolute methods in that errors due to impurities and adsorption on walls of the reaction apparatus are minimized. In addition, relative values serve as an important verification for absolute values. The apparatus …

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Hypothetical Origins Of Paleozoic Fossils From The Gulf Coastal Plain Of Arkansas, Karen Arbuckle Jan 2000

Hypothetical Origins Of Paleozoic Fossils From The Gulf Coastal Plain Of Arkansas, Karen Arbuckle

Journal of the Arkansas Academy of Science

A fauna of reworked Paleozoic fossils has been found in chert pebbles from the Gulf Coastal Plain in eastern Columbia County, Arkansas, although the nearest mapped exposure of Mississippian and Pennsylvanian rocks are fifty-five miles northward in the southern edge of the Ouachita Mountains. The surficial rocks at the collection site have been referred to the Claiborne Group of Eocene age by the authors of the geological map of Arkansas. Additional outcrops containing similar Paleozoic fossils have been found within a 15-mile radius. The fauna includes both lacy and twig-like bryozoans, articulate brachiopods, tabulate and rugose corals, stalked echinoderms, gastropods, …

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Reaction Of Alpine-Borane With Aldehydes: Reactivity Rate Assessment By Observation Of The Disappearance Of The Carbonyl N - Pi* Peak By Uv-Visible Spectroscopy, Layla Bland, Michael J. Panigot Jan 2000

Reaction Of Alpine-Borane With Aldehydes: Reactivity Rate Assessment By Observation Of The Disappearance Of The Carbonyl N - Pi* Peak By Uv-Visible Spectroscopy, Layla Bland, Michael J. Panigot

Journal of the Arkansas Academy of Science

Due to an unexpectedly difficult reduction of indole-3-carbaldehyde and of isobutyraldehyde using the chiral reducing agent Alpine-Borane, the reactivity of several aliphatic, aromatic, and unsaturated aldehydes was investigated. This was done in order to determine whether there was a relationship between aldehyde structure and reduction rate. It was found that aliphatic aldehydes and aromatic aldehydes with no strongly electron-donating groups on the arene ring reduced faster than unsaturated aldehydes.

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Physicochemical Characteristics And Macroinvertebrate Assemblages Of Riffles Upstream And Downstream Of A Streambank Impacted By Unrestricted Cattle Access, Ronald L. Johnson, Daniel D. Ward, Richard S. Grippo Jan 2000

Physicochemical Characteristics And Macroinvertebrate Assemblages Of Riffles Upstream And Downstream Of A Streambank Impacted By Unrestricted Cattle Access, Ronald L. Johnson, Daniel D. Ward, Richard S. Grippo

Journal of the Arkansas Academy of Science

Riparian zones are important contributors to stream ecosystem health. Alteration of such areas can change stream structure and function, resulting in modified productivity and hydrologic patterns. We studied two riffle sites on the South Fork of the Spring River in Fulton County, AR upstream and downstream of a streambank ostensibly degraded by unrestricted cattle access. The two sites were measured for differences in physical habitat (including bank width, stream velocity, depth, substrate composition, and embeddedness), chemical characteristics (including dissolved oxygen, pH, conductivity, turbidity and total suspended solids) and biological characteristics (including benthic macroinvertebrate community composition, similarity, and standing crop). Measurements …

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Study Of The Amplitude Of Pressure And Thrust Oscillations In A Lab-Scale Hybrid Rocket, Ann Wright, Lawrence Dunn, Brian Alford, Justin Patton, M. Keith Hudson Jan 2000

Study Of The Amplitude Of Pressure And Thrust Oscillations In A Lab-Scale Hybrid Rocket, Ann Wright, Lawrence Dunn, Brian Alford, Justin Patton, M. Keith Hudson

Journal of the Arkansas Academy of Science

Hybrid rockets are being studied as a potential replacement for the solid rocket boosters on the NASA space shuttle. One physical characteristic of hybrid rockets that must be understood and overcome is potentially severe pressure oscillations during combustion. Pressure oscillations inside the rocket combustion chamber lead to oscillations in the thrust of the rocket. These oscillations are damaging to potential human passengers and cargo and must be minimized. Current theories surmise that the oscillations are caused by combustion chamber geometry, oxygen feed line parameters, and/or fuel combustion characteristics. This study focuses on the role of the fuel characteristics in pressure …

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Large Pleistocene Box Turtle From Southwest Arkansas, Leo Carson Davis, John G. Scoggins, J. Alan Holman Jan 2000

Large Pleistocene Box Turtle From Southwest Arkansas, Leo Carson Davis, John G. Scoggins, J. Alan Holman

Journal of the Arkansas Academy of Science

No abstract provided.

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Illinois River 1998 Nutrient And Suspended Sediment Loads At Arkansas Highway 59 Bridge, Marc A. Nelson, Thomas S. Soerens Sep 1999

Illinois River 1998 Nutrient And Suspended Sediment Loads At Arkansas Highway 59 Bridge, Marc A. Nelson, Thomas S. Soerens

Arkansas Water Resources Center Technical Reports

Automatic water samplers and a U.S. Geological Survey (USGS) gauging station were established in 1995 on the main stem of the Illinois River at the Arkansas Highway 59 Bridge. Since that time, continuous stage and discharge measurements and water quality sampling have been used to determine pollutant concentrations and loads in the Arkansas portion of the Illinois River. This report represents the results from the measurement and sampling for January 1, 1998 to December 31, 1998.

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Cavefish Population Status And Environmental Quality In Cave Springs Cave, Arkansas - Final Report Submitted To Arkansas Natural Heritage Commission, G. O. Graening, Arthur V. Brown Aug 1999

Cavefish Population Status And Environmental Quality In Cave Springs Cave, Arkansas - Final Report Submitted To Arkansas Natural Heritage Commission, G. O. Graening, Arthur V. Brown

Arkansas Water Resources Center Technical Reports

This report summarizes the continuing effort to monitor environmental quality in the Cave Springs Cave Natural Area and to implement the Ozark Cavefish Recovery Plan. Last year’s report (Brown et al., 1998) identified certain environmental stressors, including a trend over 15 years of increasing nutrient pollution, a low cavefish population count of only 106, and the presence of heavy metals in the cave water and one semi-volatile organic compound (the phthalate DEHP at 500 ppb) in resident crayfish tissue. This year’s monitoring effort demonstrates that fecal coliforms continue to exceed Arkansas State Water Quality Standards (Regulation 2), sometimes by a …

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Influence Of Nitrogen Rate And Sampling Date On Soil Analysis Values Of Highbush Blueberries, John R. Clark, Ronald W. Mcnew, Richard C. Maples Jun 1999

Influence Of Nitrogen Rate And Sampling Date On Soil Analysis Values Of Highbush Blueberries, John R. Clark, Ronald W. Mcnew, Richard C. Maples

AAES Research Reports and Research Bulletins

Three studies were conducted on nitrogen (N) fertilization effects on soil of highbush blueberries in Arkansas. Objectives included: 1) determination of varying N rate effects on the standard soil analysis variables, 2) determination of date of soil sampling effects on soil analyses, 3) evaluation of the interactions of N rate and time of sampling, and 4) determination of changes in soil content over years. This research was done in two of the more important highbush blueberry production areas in Arkansas: the Arkansas River Valley where blueberries are grown on sandy loam soils, and northwest Arkansas where production is more common …

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Arkansas Soil Fertility Studies 1998, Wayne Sabbe Mar 1999

Arkansas Soil Fertility Studies 1998, Wayne Sabbe

Arkansas Agricultural Experiment Station Research Series

Rapid technological changes in crop management and production require that the research efforts also be presented in an expeditious manner. The contributions of soil fertility and fertilizers are major production factors in all Arkansas crops. The studies contained within will allow producers to compare their practices with the university’s research efforts. Additionally, soil test data and fertilizer sales are presented to allow comparisons among years, crops, and other areas within Arkansas.

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Speed Range For Breakdown Waves, Mostafa Hemmati, Eric L. George, Frances Terry Jan 1999

Speed Range For Breakdown Waves, Mostafa Hemmati, Eric L. George, Frances Terry

Journal of the Arkansas Academy of Science

Considering the electrons as the main element in breakdown wave propagation and using a one-dimensional, steady-state, three-fluid, hydrodynamical model, previous investigations have resulted in the completion of a set of equations for conservation of mass, momentum, and energy. We will use the terms proforce and antiforce waves, depending on whether the applied electric field force on electrons is with or against the direction of wave propagation. In the case of antiforce waves, the electron gas temperature and therefore the electron fluid pressure is assumed to be large enough to sustain the wave propagation down the discharge tube. For strong discontinuity …

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Statistical Analysis Of Climatic Variables In The Arkansas-Red River Basin, Felix Tendeku Jan 1999

Statistical Analysis Of Climatic Variables In The Arkansas-Red River Basin, Felix Tendeku

Journal of the Arkansas Academy of Science

Surface meteorological data for the Arkansas-Red River basin are analyzed in order to provide statistical data for modeling and simulation of climatic trends within the basin. The variables studied are the ambient temperature, temperature range and precipitation. Daily and monthly mean values, spatial and seasonal variations, and frequency distributions are determined.

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Changes In Soil Chemistry Beneath Exposed Poultry House Pads And Manure Storage Areas, Stanley L. Chapman, William R. Teague Jan 1999

Changes In Soil Chemistry Beneath Exposed Poultry House Pads And Manure Storage Areas, Stanley L. Chapman, William R. Teague

Journal of the Arkansas Academy of Science

Concerns about nitrates in private drinking water supplies in the older poultry growing areas of Arkansas prompted soil and water testing in the early 1990's. Exposed poultry house pads were recognized as a potential source of nitrates in the groundwater. Soils beneath nine different poultry house pads in five counties were sampled in 10-30 cm increments to bedrock or to a maximum sampling depth of 90 cm. The nine sites had been exposed to natural weathering conditions ranging from never to for more than 20 years. Routine soil tests were conducted by the University of Arkansas Soil Testing Lab at …

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Effects Of Predation On Two Species Of Stream-Dwelling Crayfish (Orconectes Marchandi And Cambarus Hubbsi) In Pool And Riffle Microhabitats, Heidi Dukat, Daniel D. Magoulick Jan 1999

Effects Of Predation On Two Species Of Stream-Dwelling Crayfish (Orconectes Marchandi And Cambarus Hubbsi) In Pool And Riffle Microhabitats, Heidi Dukat, Daniel D. Magoulick

Journal of the Arkansas Academy of Science

Community structure may be governed by many abiotic and biotic factors. Of the biotic factors, predation is often considered to be critical in structuring freshwater stream communities. In the Warm Fork of the Spring River, the crayfish Cambarus hubbsi is found mainly in riffles, whereas the crayfish Orconectes marchandi is found in high numbers in pools. We hypothesized that predation, mainly by fish, is a factor causing this segregation. Higher predation rates for C. hubbsi than 0. marchandi in the pools and higher predation rates for 0. marchandi than C. hubbsi in the riffles were expected. A transplant tethering experiment …

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Locating Napls In Ground Water Using Partitioning Fluorescent Dyes, A. Ghanem, J. Smith, M. Elzey, T. S. Soerens, M. A. Miah, G. Thoma Jan 1999

Locating Napls In Ground Water Using Partitioning Fluorescent Dyes, A. Ghanem, J. Smith, M. Elzey, T. S. Soerens, M. A. Miah, G. Thoma

Journal of the Arkansas Academy of Science

A major challenge in ground water remediation is locating nonaqueous phase liquids (NAPLs). Partitioning tracers can be used to identify NAPL sources between injection and extraction wells. NAPLs are only slightly soluble in water, pose a long-term source of groundwater contamination, and can be difficult to remove. The complexity of recovery processes requires the development of new technologies that guarantee cost effective methods for locating and quantifying NAPLs. Traditional methods like soil coring have been inefficient since they underestimate the quantity of NAPLs and are expensive. Partitioning tracer tests are some of the most recent methods developed for locating these …

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Analysis Of Phytoestrogens By High Performance Liquid Chromatography, Anne A. Grippo, Yan Xie, Benjamin L. Rougeau, William V. Wyatt Jan 1999

Analysis Of Phytoestrogens By High Performance Liquid Chromatography, Anne A. Grippo, Yan Xie, Benjamin L. Rougeau, William V. Wyatt

Journal of the Arkansas Academy of Science

Phytoestrogens are biochemicals synthesized in plants which mimic steroidal estrogen activity in mammals. Analysis of these compounds in the legumes which produce them and in body fluids is important to the study of their physiological effects. High pressure liquid chromatography (HPLC) has been found to be an efficient and sensitive method of identification and quantitation of isoflavonoids, one class of phytoestrogen. Here we report the separation of three isoflavonoids, biochanin A, genistein and daidzein using an HPLC system with a Cg reverse phase column and a linear gradient mobile phase containing acetonitrile and acetic acid/water (10/90, v/v) over 60 minutes. …

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Comparison Of Environmental Assessments Of Two Proposed Harbor Expansions On The Mississippi River, Richard S. Grippo, Bobby Bennett, Randel T. Cox Jan 1999

Comparison Of Environmental Assessments Of Two Proposed Harbor Expansions On The Mississippi River, Richard S. Grippo, Bobby Bennett, Randel T. Cox

Journal of the Arkansas Academy of Science

The National Environmental Policy Act of 1969 requires federally funded projects to be evaluated for environmental impact to determine if a complete environmental impact statement must be prepared. Such an environmental assessment must also be included in any feasibility study for harbor enlargement and bank stabilization measures under the Water Resources Development Act. Population increases, coupled with economic growth from increased agricultural and industrial productivity, have resulted in increased Mississippi River barge transportation needs for Arkansas and Missouri. We report here two such environmental assessments of planned harbor expansions of the New Madrid County and Pemiscot County ports in the …

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Microlevel Climate Change Due To Changes In Surface Features In The Ganges Delta, M. M. Adel Jan 1999

Microlevel Climate Change Due To Changes In Surface Features In The Ganges Delta, M. M. Adel

Journal of the Arkansas Academy of Science

The Ganges had been the world's 8th largest river in terms of the volume of water discharge of 490 km3/yr to the ocean 4 prior to 1975. Since that time, over a period of two decades, India has reduced the Ganges discharge through Bangladesh to 40% from its original annual average discharge of 1,932+7-223 m3 /s by diverting water for irrigation in her upper states. The , resulting consequences have been disastrous due to the depletion of the surface water resources. One of the devastating consequences has been the generation of extreme climate. The summertime maximum temperature has risen to …

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Morphometry And Limnology Of Ferguson Lake, Saline County, Arkansas, John D. Rickett, E. P. (Perk) Floyd Jan 1999

Morphometry And Limnology Of Ferguson Lake, Saline County, Arkansas, John D. Rickett, E. P. (Perk) Floyd

Journal of the Arkansas Academy of Science

To more fully understand Ferguson Lake as an ecosystem and eventually relate its water quality and production potential to fisheries management, several limnological variables were sampled monthly from April 1997 through March 1999. Vertical profiles of temperature and dissolved oxygen were recorded, and water samples from 0.5 m. depth were tested for turbidity, pH, total alkalinity, total hardness, ortho-phosphate, nitrate-nitrogen, sulfate, iron and specific conductance. Evaporation rate experiments, spillway discharge and rainfall records were used to estimate lake hydrology. Depth transects on the lake and USGS topographic maps were used to measure and calculate morphometric and watershed features. The lake …

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Synthesis And Molecular Structure Of [Cpru(Pph3)(Pms)2]Otf1.3/4 C2>H4C12, Paul M. Nave, Mark Draganjac, A. W. Cordes, Tosha M. Barclay Jan 1999

Synthesis And Molecular Structure Of [Cpru(Pph3)(Pms)2]Otf1.3/4 C2>H4C12, Paul M. Nave, Mark Draganjac, A. W. Cordes, Tosha M. Barclay

Journal of the Arkansas Academy of Science

No abstract provided.

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Completion Report: Arkansas State Plant Board Pesticide Ground Water Monitoring Project - Phase Vi, T. Nichols, P. Vendrell, K. Steele, H. D. Scott, C. Armstrong Nov 1998

Completion Report: Arkansas State Plant Board Pesticide Ground Water Monitoring Project - Phase Vi, T. Nichols, P. Vendrell, K. Steele, H. D. Scott, C. Armstrong

Arkansas Water Resources Center Technical Reports

No abstract provided.

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Field Trip Guide: Illinois River Summary, National Poultry Water Management Symposium, Kenneth F. Steele Oct 1998

Field Trip Guide: Illinois River Summary, National Poultry Water Management Symposium, Kenneth F. Steele

Arkansas Water Resources Center Technical Reports

No abstract provided.

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Storm And Base Flow Water Quality For Bear, Calf And Tomahawk Creeks, Kenneth F. Steele, David N. Mott Oct 1998

Storm And Base Flow Water Quality For Bear, Calf And Tomahawk Creeks, Kenneth F. Steele, David N. Mott

Arkansas Water Resources Center Technical Reports

Appendices for MSC 255

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Storm And Base Flow Water Quality For Bear, Calf, And Tomahawk Creeks, Kenneth F. Steele, David N. Mott Oct 1998

Storm And Base Flow Water Quality For Bear, Calf, And Tomahawk Creeks, Kenneth F. Steele, David N. Mott

Arkansas Water Resources Center Technical Reports

Because of the conversion of 92,780 acres of forest to pasture land in the Buffalo River watershed over a 27 year period, there is concern about the affect of agricultural activities on the water quality of the river. Three tributaries (Bear, Calf and Tomahawk creeks) located about mid-length of the Buffalo River were chosen to investigate the affect of agricultural activity on water quality because these streams provide the greatest amounts of fecal bacteria, nitrate+nitrite and phosphorus to the river, despite comprising only 13% of the watershed.

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Quality Of Surface And Ground Water And Best Management Practices, Kenneth F. Steele Sep 1998

Quality Of Surface And Ground Water And Best Management Practices, Kenneth F. Steele

Arkansas Water Resources Center Technical Reports

Arkansas is fortunate to have outstanding water resources, especially in terms of water quality. However, this is not to say that there are no problems. The Arkansas Water Resources Center (AWRC) in cooperation with other state and federal agencies is characterizing our water resources and providing data important to the wise use of these resources. One wise use of our water resources is to mitigate the impact of non-point sources of pollution on water quality through the use of best management practices. These proceedings address not only the characterization of the quality of ground and surface water but also address …

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Vulnerability And Use Of Ground And Surface Waters In The Southern Mississippi Valley Region, H. Don Scott Sep 1998

Vulnerability And Use Of Ground And Surface Waters In The Southern Mississippi Valley Region, H. Don Scott

Arkansas Water Resources Center Technical Reports

There is a concern in the Southern Mississippi River Valley of the United States over non-point source pollution of ground and surface waters resulting from activities associated with agricultural production. This agriculturally intensive region consists of two major land resource areas (MLRAs): Southern Mississippi Valley Silty Uplands (MLRA 134) and the Southern Mississippi Valley Alluvium (MLRA 131). Both MLRAs have level to undulating and rolling topography, relatively fertile soils and a climate particularly conducive for row crop production.

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Llinois River 1997 Pollutant Loads At Arkansas Highway 59 Bridge, Marc A. Nelson, Thomas S. Soerens Sep 1998

Llinois River 1997 Pollutant Loads At Arkansas Highway 59 Bridge, Marc A. Nelson, Thomas S. Soerens

Arkansas Water Resources Center Technical Reports

Automatic water samplers and a USGS gauging station were established in 1995 on the main stem of the Illinois River at the Arkansas Highway 59 Bridge. Since that time, continuous stage and discharge measurements and water quality sampling have been used to determine pollutant concentrations and loads in the Arkansas portion of the Illinois River. This report represents the results from the measurement and sampling for January 1, 1997 to December 31, 1997.

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Directory Of Water Related Courses Offered At Colleges And Universities In Arkansas As Of November 1998, Kenneth F. Steele Sep 1998

Directory Of Water Related Courses Offered At Colleges And Universities In Arkansas As Of November 1998, Kenneth F. Steele

Arkansas Water Resources Center Technical Reports

This publication lists the water and water-related courses at several universities and colleges in Arkansas as reported during the Fall of 1 998. It is anticipated that users of this directory will extend beyond college students, and will include professionals seeking continuing education, and professors desiring to exchange Information on courses. This directory is not an "absolute" source of water and water-related courses because all of the higher learning Institutions In Arkansas are not listed, and, secondly, because the definition of "water and water-related" varies from institution to institution. None-the-less this directory provides a very valuable and impressive reference on …

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