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1999

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Articles 1951 - 1980 of 2348

Full-Text Articles in Physical Sciences and Mathematics

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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Reply To Comment On ‘Nondipole Resonant X-Ray-Raman Spectroscopy: Polarized Inelastic Scattering At The K Edge Of Cl2,’, J. D. Mills, J. A. Sheehy, T. A. Ferrett, S. H. Southworth, R. Mayer, Dennis W. Lindle, P. W. Langhoff Jan 1999

Reply To Comment On ‘Nondipole Resonant X-Ray-Raman Spectroscopy: Polarized Inelastic Scattering At The K Edge Of Cl2,’, J. D. Mills, J. A. Sheehy, T. A. Ferrett, S. H. Southworth, R. Mayer, Dennis W. Lindle, P. W. Langhoff

Chemistry and Biochemistry Faculty Research

Mills et al. Reply: In their Comment on our Letter [1], Gel’mukhanov and Ågren [2] reiterate recent assertions [3] based on their earlier theoretical studies [4]. The primary purpose of their Comment is apparently to refute our stated conclusion that core-excited-state localization/ delocalization mechanisms are irrelevant to interpretations of reported Raman scattering experiments on homonuclear diatomic molecules.

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A Spatial And Temporal Analysis Of Riparian Vegetation Along Satus Creek On The Yakama Indian Reservation, Kathryn Gellenbeck Jan 1999

A Spatial And Temporal Analysis Of Riparian Vegetation Along Satus Creek On The Yakama Indian Reservation, Kathryn Gellenbeck

All Master's Theses

Satus Creek provides critical habitat for the Yakima River Basin steelhead. A diverse community of riparian vegetation is important for healthy fish habitat; vegetation changes can affect shade, cover, channel structure, water quality, and food availability. The purpose of this thesis is to analyze and illustrate riparian vegetation change, both temporally and spatially, along three separate reaches of Satus Creek. A Geographic Information Systems approach was applied to assess the vegetation change by comparing plant species composition and density on 1949 and 1995 aerial photographs. The GIS approach allowed patterns and trends in the vegetation to be identified. In less …

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Soft X-Ray Photochemistry At The L₂,₃-Edges In K₃[Fe(Cn)₆], [Co(Acac)₃] And [Cp₂Fe][Bf₄], David Collison, Catherine David Garner, Catherine M. Mcgrath, J. Fred Willem Mosselmans, Mark D. Roper, Jon M. W Seddon, Ekkehard Sinn, Nigel A. Young Jan 1999

Soft X-Ray Photochemistry At The L₂,₃-Edges In K₃[Fe(Cn)₆], [Co(Acac)₃] And [Cp₂Fe][Bf₄], David Collison, Catherine David Garner, Catherine M. Mcgrath, J. Fred Willem Mosselmans, Mark D. Roper, Jon M. W Seddon, Ekkehard Sinn, Nigel A. Young

Chemistry Faculty Research & Creative Works

Soft X-ray photoreduction has been observed in K3[Fe(CN)6], [Co(acac)3] and [Cp2Fe][BF4].

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Thermal Characterization Of Pmma Thin Films On Silica Using Modulated Differential Scanning Calorimetry, Crystal E. Porter, Frank D. Blum Jan 1999

Thermal Characterization Of Pmma Thin Films On Silica Using Modulated Differential Scanning Calorimetry, Crystal E. Porter, Frank D. Blum

Chemistry Faculty Research & Creative Works

The number of studies of thin polymer films has increased over recent years as technological processes incorporate the use of nanomaterials. An enhanced understanding of these films would enable us to predict bound-polymer behavior and thus improve the efficiency of processes and the quality of products. This is especially true as the thickness of the films approach molecular dimensions. The glass transition temperature of a polymer is one of the most important properties for characterization because it indicates how the polymer might perform macroscopically. when a polymer is confined, such as one the surface of a substrate, its behavior is …

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Dynamics Of Acrylic Coupling Agents At Interfaces Of Composites, Hyoryoon Jo, Frank D. Blum Jan 1999

Dynamics Of Acrylic Coupling Agents At Interfaces Of Composites, Hyoryoon Jo, Frank D. Blum

Chemistry Faculty Research & Creative Works

Most applications of polymers involve composites, wherein a polymer is used in conjunction with another material, typically a solid fiber or filler. A coupling agent can enhance the adhesion between a polymer matrix and an inorganic filler. Organofunctional silanes, RSiX are often used as coupling agents. The methoxy or ethoxy group, X, can typically be hydrolyzed with water and an acid or a base catalyst in a protic solvent. The silanol groups of a hydrolyzed coupling agent can condense with other silanol groups from a glass surface, while the alkyl group, R, blends physically or bonds chemically to the polymer …

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Cost-Benefit Analysis Of Web Bag In A Web Warehouse, Sanjay Kumar Madria, Wee Keong Ng, Ee-Peng Lim, Sourav S. Bhowmick Jan 1999

Cost-Benefit Analysis Of Web Bag In A Web Warehouse, Sanjay Kumar Madria, Wee Keong Ng, Ee-Peng Lim, Sourav S. Bhowmick

Computer Science Faculty Research & Creative Works

Sets and bags are closely related structures and have been studied in relational databases. A bag is different from a set in that it is sensitive to the number of times an element occurs, while a set is not. In this paper, we introduce the concept of a Web bag in the context of a World Wide Web warehouse called WHOWEDA (WareHouse Of WEb DAta) which we are currently building. Informally, a Web bag is a Web table which allows multiple occurrences of identical Web types. A Web bag helps one to discover useful knowledge from a Web table, such …

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Pi-Web Join In A Web Warehouse, Sanjay Kumar Madria, Wee Keong Ng, Ee-Peng Lim, Sourav S. Bhowmick Jan 1999

Pi-Web Join In A Web Warehouse, Sanjay Kumar Madria, Wee Keong Ng, Ee-Peng Lim, Sourav S. Bhowmick

Computer Science Faculty Research & Creative Works

With the enormous amount of data stored in the World Wide Web, it is increasingly important to design and develop powerful web warehousing tools. The key objective of our web warehousing project, called WHOWEDA (Warehouse of Web Data), is to design and implement a web warehouse that materializes and manages useful information from the web. We introduce the concept of Π-web join in the context of WHOWEDA. Pi-web join operator is a web information manipulation operator to combine relevant web information residing in two web tables. Informally, it is the combination of web join and web project operators which filter …

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One-Prong Τ Decays With Kaons, R. Barate, M. Thulasidas Jan 1999

One-Prong Τ Decays With Kaons, R. Barate, M. Thulasidas

Research Collection School Of Computing and Information Systems

One-prong ττ decays into final states involving kaons are studied with about 161 000 τ+τ−τ+τ− events collected by the ALEPH detector from 1991 to 1995. Charged kaons are identified by dE/dx measurement, while K0LKL0's are detected through their interaction in calorimeters. Branching ratios are measured for the inclusive mode, B(τ−→K−Xντ)=(1.52±0.04±0.04)%B(τ−→K−Xντ)=(1.52±0.04±0.04)%, where X can be any system of neutral particles, and for the exclusive modesB(τ−→K−ντ)=(6.96±0.25±0.14)×10−3,B(τ−→K−π0ντ)=(4.44±0.26±0.24)×10−3,B(τ−→K−π0π0ντ)=(0.56±0.20±0.15)×10−3,B(τ−→K−π0π0π0ντ)=(0.37±0.21±0.11)×10−3,B(τ−→K−K0ντ)=(1.62±0.21±0.11)×10−3,B(τ−→K−K0π0ντ)=(1.43±0.25±0.15)×10−3,B(τ−→K0¯¯¯¯¯¯¯π−ντ)=(9.28±0.45±0.34)×10−3,B(τ−→K0¯¯¯¯¯¯¯π−π0ντ)=(3.47±0.53±0.37)×10−3,B(τ−→K−ντ)=(6.96±0.25±0.14)×10−3,B(τ−→K−π0ντ)=(4.44±0.26±0.24)×10−3,B(τ−→K−π0π0ντ)=(0.56±0.20±0.15)×10−3,B(τ−→K−π0π0π0ντ)=(0.37±0.21±0.11)×10−3,B(τ−→K−K0ντ)=(1.62±0.21±0.11)×10−3,B(τ−→K−K0π0ντ)=(1.43±0.25±0.15)×10−3,B(τ−→K0¯π−ντ)=(9.28±0.45±0.34)×10−3,B(τ−→K0¯π−π0ντ)=(3.47±0.53±0.37)×10−3,where the first error is statistical and the second is systematical. Upper limits for B(τ−→K0¯¯¯¯¯¯¯π−π0π0ντ)B(τ−→K0¯π−π0π0ντ) and B(τ−→K−K0π0π0ντ)B(τ−→K−K0π0π0ντ) are also obtained. Mass spectra in the final states are investigated in order to study the relevant dynamics.

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Search For Bs0 Oscillations Using Inclusive Lepton Events, R. Barate, M. Thulasidas Jan 1999

Search For Bs0 Oscillations Using Inclusive Lepton Events, R. Barate, M. Thulasidas

Research Collection School Of Computing and Information Systems

A search for B0sBs0 oscillations is performed using a sample of semileptonic b-hadron decays collected by the ALEPH experiment during 1991–95. Compared to previous inclusive lepton analyses, the proper time resolution and b-flavour mistag rate are significantly improved. Additional sensitivity to B0sBs0 mixing is obtained by identifying subsamples of events having a B0sBs0 purity which is higher than the average for the whole data sample. Unbinned maximum likelihood amplitude fits are performed to derive a lower limit of Δms>9.5ps−1Δms>9.5ps−1 at the 95% confidence limit (95% CL). Combining with the ALEPH D−sDs−-based analyses yields Δms>9.6ps−1Δms>9.6ps−1 at 95% …

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Neural Classifiers For Learning Higher-Order Correlations, Marifi Güler Jan 1999

Neural Classifiers For Learning Higher-Order Correlations, Marifi Güler

Turkish Journal of Physics

Studies by various authors suggest that higher-order networks can be more powerful and are biologically more plausible with respect to the more traditional multilayer networks. These architectures make explicit use of nonlinear interactions between input variables in the form of higher-order units or product units. If it is known a priori that the problem to be implemented possesses a given set of invariances like in the translation, rotation, and scale invariant pattern recognition problems, those invariances can be encoded, thus eliminating all higher-order terms which are incompatible with the invariances. In general, however, it is a serious set-back that the …

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Ordering Due To Disorder In Frustrated Quantum Magnetic Systems, Taner Yildirim Jan 1999

Ordering Due To Disorder In Frustrated Quantum Magnetic Systems, Taner Yildirim

Turkish Journal of Physics

The phenomenon of order by disorder in frustrated magnetic systems is reviewed. Disorder (thermal or quantum fluctuations) may sometimes give rise to long range ordering in systems with frustration, where one must often consider the selection among classically degenerate ground states which are not equivalent by any symmetry. The lowest order effects of quantum fluctuations in such frustrated systems usually resolves the continues degeneracy of the ground state manifold into discrete Ising--type degeneracy. A unique ground state selection out of this Ising degenerate manifold then occurs due to higher order effects of quantum fluctuations. For systems such as face-centered cubic …

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Diverging Strains Near Threshold: Breakdown Of The Elastic Description Of A Charge Density Wave Model, Muhittin Mungan, Susan N. Coppersmith, Valeri M. Vinokur Jan 1999

Diverging Strains Near Threshold: Breakdown Of The Elastic Description Of A Charge Density Wave Model, Muhittin Mungan, Susan N. Coppersmith, Valeri M. Vinokur

Turkish Journal of Physics

We analyze the strains near threshold in 1-d charge density wave models at zero temperature and strong pinning. We show that in these models local strains diverge near the depinning threshold and characterize the scaling behavior of the phenomenon. This helps quantify when the underlying elastic description breaks down and plastic effects have to be included.

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Photon Counting In Astrophotometry. Fundamentals And Some Advices For Beginners, Romualdas Kalytis Jan 1999

Photon Counting In Astrophotometry. Fundamentals And Some Advices For Beginners, Romualdas Kalytis

Turkish Journal of Physics

The beginners in astrophotometry are reminded of fundamentals of photon counting. Several advices for new users of electrophotometric technics are given.

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Kinematics Of Rs Cvn And W Uma Binaries In The Hipparcos Catalogue, Zeki̇ Aslan, Tuncay Özdemi̇r, Cahi̇t Yeşi̇lyaprak, Ahmet İskender Jan 1999

Kinematics Of Rs Cvn And W Uma Binaries In The Hipparcos Catalogue, Zeki̇ Aslan, Tuncay Özdemi̇r, Cahi̇t Yeşi̇lyaprak, Ahmet İskender

Turkish Journal of Physics

Space motions of RS CVn and W UMa binaries have been calculated using parallaxes and proper motions from Hipparcos catalogue and radial velocities from the literature. We have calculating the mean motions and velocity dispersions. We have excluded those binaries with relative parallax errors \geq 0.5. The comparison of the asymmetric drift, velocity ellipsoids and vertex deviation with those of main sequence stars given by Dehnen and Binney indicates that both RS CVn and W UMa binaries have kinematics similar to main sequence stars slightly bluer than the Parenago's discontinuity and B-V \simeq 0.62. Implication of this has been discussed.

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Heat Pulse Studies Of The Emission And Absorption Of Acoustic Phonons In Gaas Quantum Wells And Wires, A. J. Kent Jan 1999

Heat Pulse Studies Of The Emission And Absorption Of Acoustic Phonons In Gaas Quantum Wells And Wires, A. J. Kent

Turkish Journal of Physics

This paper reviews some recent experiments in which heat pulse techniques have been used to study the interaction of acoustic phonons with electrons in semiconductor quantum wells and wires. Heat pulse experiments provide temporal and spatial resolution of the phonons that are emitted or absorbed by the electrons and so give more detailed information about the electron-phonon interaction than can be obtained by other methods (e.g. transport measurements). Phonon experiments demonstrate clearly the effect of the electron confinement on the carrier-phonon interaction and the overall energy loss rate due to acoustic phonon emission. A qualitative explanation of the results is …

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Modelling Of Devices For Optoelectronic Applications: The Quantum Confined Stark Effect And Self-Electrooptic Effect Devices, Eckehard Scholl Jan 1999

Modelling Of Devices For Optoelectronic Applications: The Quantum Confined Stark Effect And Self-Electrooptic Effect Devices, Eckehard Scholl

Turkish Journal of Physics

Electro-optical effects, such as the Franz-Keldysh effect in bulk materials or the quantum confined Stark effect in quantum well structures, lead to strong optoelectronic nonlinearities which form the basis for optical modulators and optically bistable devices. They result from a modification of the optical absorption properties by an applied electric field and are particularly pronounced in the case of low dimensional semiconductors. We review theoretical modelling and computer simulations of such optoelectronic devices in particular for ZnSe based quantum well structures, where excitonic features dominate even at room temperature. The field dependent absorption spectra are calculated by a many-body theory …

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Stability Of Quasi-Two-Dimensional Bipolarons, R. Tuğrul Senger, Ati̇lla Erçelebi̇ Jan 1999

Stability Of Quasi-Two-Dimensional Bipolarons, R. Tuğrul Senger, Ati̇lla Erçelebi̇

Turkish Journal of Physics

The stability criteria of quasi-two-dimensional dimensional bipolarons have been studied within the framework of strong coupling and path-integral theories. It is shown that the critical values of the electron-phonon coupling constant (\alpha), and the ratio of dielectric constants (\eta = \epsilon_{\infty}/\epsilon_{0}) exhibit some non-trivial features as the effective dimensionality is tuned from three to two.

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Band-Gap Renormalization In Quantum Wires, K. Güven, C. R. Bennett, B. Tanatar Jan 1999

Band-Gap Renormalization In Quantum Wires, K. Güven, C. R. Bennett, B. Tanatar

Turkish Journal of Physics

Improved techniques in semiconductor fabrication increased the interest in quantum wire structures, because of their opto-electronic device application possibilities. Many-body interactions among the electrons and holes in the wire lead to the band-gap renormalization (BGR), which in turn affect the optical properties of the system. We study the BGR within the random-phase approximation incorporating the dynamical effects, and investigate the density dependence.

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Light Emission From Travelling Space Charge Domains, M. Hostut, N. Balkan Jan 1999

Light Emission From Travelling Space Charge Domains, M. Hostut, N. Balkan

Turkish Journal of Physics

We report light emission from n-doped GaAs epilayers associated with impact ionization when the device is biased in the negative difference resistance (NDR) regime (F > 3.5 kV cm^{-1}). Spectral distribution of the emitted light (electroluminescence) has been measured to identify the energy distribution of the recombining electron-hole pairs. Electron temperatures, calculated from the high energy tail of the electroluminescence spectra, show that the light emission is due to the recombination of the impact ionized holes with the background, channel, and the travelling space charge electrons. The range of the electron temperatures obtained indicate that the contribution to the light emission …

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The Orbit Center Dependence Of The Energy Levels In A Multiple Quantum Wells Under External Tilted Magnetic And Electric Fields, R. Amca, Y. Ergün, H. Sari, S. Elagöz, İ. Sökmen Jan 1999

The Orbit Center Dependence Of The Energy Levels In A Multiple Quantum Wells Under External Tilted Magnetic And Electric Fields, R. Amca, Y. Ergün, H. Sari, S. Elagöz, İ. Sökmen

Turkish Journal of Physics

An analytical solution to the Schrödinger equation for a multiple quantum well system subjected to an externally applied electric field the growth direction and an externally applied tilted magnetic field are obtained and the results are discussed. The energy dependence energy spectrum of the system as a function of the external electric field and the orbit center is also discussed.

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Feasibility Of Fabrication Of Heteroepitaxial Ge_X Si_{1-X}/Si(111) Structure By Pulsed Nd: Yag Laser, R. N. Al-Rawi, R. A. Ismail, R. N. Mousis Jan 1999

Feasibility Of Fabrication Of Heteroepitaxial Ge_X Si_{1-X}/Si(111) Structure By Pulsed Nd: Yag Laser, R. N. Al-Rawi, R. A. Ismail, R. N. Mousis

Turkish Journal of Physics

Heteroepitaxial Ge_x Si_{1-x} alloy layers have been formed by 10 ms and 300 \mu s laser pulse induced mixing of pure germanium films and Si(111) substrates where Ge films of thickness (500-1250) Å are thermally evaporated onto Si(111) under vacuum pressure \sim 10^{-5} Torr. The near surface of the sample then undergoes rapid melting and regrowth processes during each pulse from a free running Nd; YAG laser. The alloy layers are (4.6-6.5) \mum thick and have a Ge fraction of x = 6-8.2%.

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Electronic And Lattice Thermal Conductivity Of Bi_{1-X} Sb_X And Ag-Sb-Te Systems, Sabi̇r Ali̇yev, Agami̇rza Movsum-Zadeh, Sadiyar Ragimov, Eldar Zulfigarov Jan 1999

Electronic And Lattice Thermal Conductivity Of Bi_{1-X} Sb_X And Ag-Sb-Te Systems, Sabi̇r Ali̇yev, Agami̇rza Movsum-Zadeh, Sadiyar Ragimov, Eldar Zulfigarov

Turkish Journal of Physics

An investigation of the electronic (\aleph_e) and lattice (\aleph_L) parts of the thermal conductivity for samples of Bi_{1-x} Sb_x (0,02 < X < 0,12) and system of Ag-Sb-Te was carried out in the temperature interval 6-300K. Separation of \aleph_L and \aleph_e has been made by suppressing \aleph_e in magnetic field. The experimental data of \aleph_L and \aleph_e have been compared, respectively, with Gallaway's theory and with a theory which takes into account the inelastic character of scattering. It is observed that the Lorentz number L calculated by using the experimental values of \aleph_e and thermomagnetic coefficients is smaller than its Zommerfeld's value L_0 in high doping Bi_{0.88}Sb_{0.12}. A satisfactory agreement between the theory and the experiment allows to conclude that besides the normal and U-processes in Bi_{1-x}Sb_x the defects of mass also plays a considerable role in scattering. It is observed that \aleph_L of single phase samples Ag_{0.82}Sb_{1.18}Te_{2.18} is smaller than AgSbTe_2 samples. It is shown that this is due to the presence of p-Ag_2 Te in AgSbTe_2. It is established that the high concentration of intrinsic defects plays a considerable role in scattering for Ag-Sb-Te as well.

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