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2003

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Articles 3601 - 3630 of 3876

Full-Text Articles in Physical Sciences and Mathematics

Application Of A Three-Stage Sequential Extraction Procedure For The Determination Of Extractable Metal Contents In Highway Soils, Şeri̇fe Tokalioğlu, Şenol Kartal, Gökhan Bi̇rol Jan 2003

Application Of A Three-Stage Sequential Extraction Procedure For The Determination Of Extractable Metal Contents In Highway Soils, Şeri̇fe Tokalioğlu, Şenol Kartal, Gökhan Bi̇rol

Turkish Journal of Chemistry

A sequential extraction procedure, a three-step protocol proposed by the Standards, Measurements and Testing programme (SM & T--formerly BCR) of the European Union, was applied to soil samples for the determination of metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn). This procedure provides measurements of extractable metals from media such as acetic acid (0.11 mol L^{-1}), hydroxylammonium chloride (0.1 mol L^{-1}) and hydrogen peroxide (8.8 mol L^{-1}) plus ammonium acetate (1 mol L^{ - 1}), which are exchangeable, reducible and oxidisable metals, respectively. Analyses were carried out using flame atomic absorption spectrometry (FAAS). The results obtained from …

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Aluminum Fractionation In The Water Of Karakaya Dam Lake (Malatya, Turkey), F. Zehra Küçükbay, Mustafa Demi̇r Jan 2003

Aluminum Fractionation In The Water Of Karakaya Dam Lake (Malatya, Turkey), F. Zehra Küçükbay, Mustafa Demi̇r

Turkish Journal of Chemistry

A method was developed for the determination of trace amounts of Al species in water samples using the amberlite type XAD-4 resin. For this purpose, total dissolved Al, organically bonded Al and particulate Al in water samples taken from Karakaya dam lake (Malatya, Turkey) were determined by flame atomic absorption spectroscopy (FAAS) or graphite furnace atomic absorption spectroscopy (GFAAS) after an enrichment procedure. The total dissolved Al in the water samples was determined using 8-hydroxyquinoline as complexing reagent at pH 8 and amberlite type XAD-4 resins for the enrichment. The organically bonded Al species in the water samples were destroyed …

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Purification And Characterization Of Glucose 6-Phosphate Dehydrogenase From Sheep Liver, Vedat Türkoğlu, Si̇nan Aldemi̇r, Mehmet Çi̇ftçi̇ Jan 2003

Purification And Characterization Of Glucose 6-Phosphate Dehydrogenase From Sheep Liver, Vedat Türkoğlu, Si̇nan Aldemi̇r, Mehmet Çi̇ftçi̇

Turkish Journal of Chemistry

Glucose 6-phosphate dehydrogenase (D-glucose 6-phosphate: NADP^{+} oxidoreductase, EC 1.1.1.49; G6PD) was purified from sheep liver by a simple and rapid method. The purification process consisted of two steps: preparation of the homogenate, and 2', 5'-adenosine diphosphate (ADP) Sepharose 4B affinity chromatography. Through the use of these two consecutive steps, the enzyme was purified with a yield of 35.6% and 1,920 fold, having the specific activity of 11.2 enzyme units (EU/mg protein). A K_{M} of 0.176 mM and a V_{\max} of 0.0179 EU/ml were obtained for G6-P, and 0.0194 mM and 0.0223 EU/ml for NADP^{+}. Enzymatic activity was measured spectrophotometrically according …

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Preparation And Characterization Of Conducting Polybutadiene/ Polythiophene Composites, Senem Kiralp, Zuhal Küçükyavuz, Atef F. Qasrawi Jan 2003

Preparation And Characterization Of Conducting Polybutadiene/ Polythiophene Composites, Senem Kiralp, Zuhal Küçükyavuz, Atef F. Qasrawi

Turkish Journal of Chemistry

Conductive composite films of cis-1,4-polybutadiene (PBD) with polythiophene (PTh) were prepared electrochemically. Thiophene was polymerized on PBD-coated platinium electrodes. The composites with different PTh percentages showed conductivity in the order of 10^{-3} (\Omega cm)^{-1}. The characterization of the films was performed using FTIR, scanning electron microscope and differential scanning calorimetry techniques. In order to understand the dominant transport mechanism, the temperature dependence of conductivity was investigated.

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Some Polyamidoxime Derivatives And Their Metal Complexes, Fatma Kari̇pci̇n, İbrahi̇m Karataş, Hali̇l İsmet Uçan Jan 2003

Some Polyamidoxime Derivatives And Their Metal Complexes, Fatma Kari̇pci̇n, İbrahi̇m Karataş, Hali̇l İsmet Uçan

Turkish Journal of Chemistry

In this paper the synthesis of six polyamidoximes from their corresponding diamines with 4,4'-methylenebis (phenylglyoxylohydroximoyl chloride) and 4,4'-methylenebis(chlorophenylgly-oxime) is presented. The average molecular weights of these organic polymers were determined. In addition, the complexes of 4,4'-methylenebis (phenylglyoxylohydroximoyl chloride) with Ni(II), Co(II) and Cu(II) salts were prepared. The structures of these compounds were identified by IR or ^{1}H NMR spectral data, elemental analyses, magnetic measurements and thermal analysis.

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Synthesis Of New 4-(5-Chloro-2-Oxo-3h-Benzoxazol-3-Yl)Butanamide Derivatives And Their Analgesic And Anti-Inflammatory Properties, H. Ozan Gülcan, Serdar Ünlü, Erden Banoğlu, M. Fethi̇ Şahi̇n, Esra Küpeli̇, Erdem Yeşi̇lada Jan 2003

Synthesis Of New 4-(5-Chloro-2-Oxo-3h-Benzoxazol-3-Yl)Butanamide Derivatives And Their Analgesic And Anti-Inflammatory Properties, H. Ozan Gülcan, Serdar Ünlü, Erden Banoğlu, M. Fethi̇ Şahi̇n, Esra Küpeli̇, Erdem Yeşi̇lada

Turkish Journal of Chemistry

In this preliminary screening study for developing potent analgesic and anti-inflammatory compounds, eight new 4-(5-chloro-2-oxo-3H-benzoxazol-3-yl)butanamide derivatives were synthesized and screened for their analgesic and anti-inflammatory activities as well as gastric ulceration potential in tested animals. Their structures were elucidated by their IR, ^{1}H-NMR and elemental analysis. All of the compounds exhibited high analgesic and anti-inflammatory activities. None of the compounds except compound 2g caused gastric lesions or bleeding in tested animals.

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Isolation And Structure Elucidation Of Novel Natural Products From Turkish Lichens, Süheyla Kirmizigül, Ömer Koz, Hüseyi̇n Anil, Siddik İçli̇, Ulvi̇ Zeybek Jan 2003

Isolation And Structure Elucidation Of Novel Natural Products From Turkish Lichens, Süheyla Kirmizigül, Ömer Koz, Hüseyi̇n Anil, Siddik İçli̇, Ulvi̇ Zeybek

Turkish Journal of Chemistry

Three natural products were isolated from three different Turkish lichens. Microbiological investigations were also examined of these lichens. Compound 1 is known as 2-hydroxy-4-methoxy-3,6-dimethyl benzoic acid, and is isolated from Pseudevernia furfuracea for the first time. Compounds 2 and 3 are detected as new compounds and called, 3-acetyl-4-amino-2-chloro-1- (4-hydroxy-2-methoxy- 6-methylphenyl carbonyloxy) benzene and 2-(4-methoxyphenyl)-2-(5-oxo-4-phenyl-2,5- dihydro-2-furaniliden) acetic acid; they were isolated from Evernia prunastri and Letharia vulpina, respectively. All these compounds had different skeletons. Their structures were established by chemical methods and spectroscopic techniques using IR, UV, 1D and 2D NMR and EI and (+) FAB-Mass methods.

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Catalytic Spectrophotometric Determination Of Manganese In Some Medicinal Plants And Their Infusions, Kostantin L. Mutaftchiev Jan 2003

Catalytic Spectrophotometric Determination Of Manganese In Some Medicinal Plants And Their Infusions, Kostantin L. Mutaftchiev

Turkish Journal of Chemistry

The catalytic effect of manganese (II) on the oxidation of the dye 1,3-Dimethyl- 2 [4-N (N,N-dimethylamino) phenylazo] imidazolium perchlorate (BR) with potassium periodate in the presence of 1,10-phenanthroline was investigated. The reaction was followed spectrophotometrically by measuring the decrease in the absorbance of the dye at 540 nm. Under optimum conditions (5 \times 10^{-5} mol dm^{-3} BR, 2 \times 10^{-4} mol dm^{-3} potassium periodate, 1 \times 10^{-4} mol dm^{-3} 1,10-phenanthroline, 0.1 mol dm^{-3} buffer -- pH 3.0, 70 °C, 5 min) manganese (II) in the range 0.1--4.5 ng cm^{-3} can be determined by the fixed-time method with a detection limit …

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Study On Papain Immobilization On A Macroporous Polymer Carrier, Liang Ding, Zihua Yao, Tong Li, Qiang Yue, Jia Chai Jan 2003

Study On Papain Immobilization On A Macroporous Polymer Carrier, Liang Ding, Zihua Yao, Tong Li, Qiang Yue, Jia Chai

Turkish Journal of Chemistry

Macroporous resin microbeads of methyl methacrylate-divinyl benzene copolymer were synthesized by radical suspension polymerization of acrolein with divinylbenzene in the presence of a pore-creating agent, petroleum ether. The microbeads had a large specific surface area and large pores covered the entire surface of the resin. This macroporous polymer carrier was aminated by hydrazine hydrate that produced a large number of amino groups on the carrier. Papain was immobilized on the porous polymer carrier by glutaraldehyde cross-linking or diazo-coupling. The factors involved in the activity recovery of the immobilized papain and the enzymic properties of the resulting immobilized papain were studied …

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Phenolic, Megastigmane, Nucleotide, Acetophenon And Monoterpene Glycosides From Phlomis Samia And P. Carica, Funda Nuray Yalçin, Tayfun Ersöz, Pinar Akbay, İhsan Çaliş, Ali̇ Arslan Dönmez, Otto Sticher Jan 2003

Phenolic, Megastigmane, Nucleotide, Acetophenon And Monoterpene Glycosides From Phlomis Samia And P. Carica, Funda Nuray Yalçin, Tayfun Ersöz, Pinar Akbay, İhsan Çaliş, Ali̇ Arslan Dönmez, Otto Sticher

Turkish Journal of Chemistry

Phytochemical investigations on the aerial parts of Phlomis samia resulted in the isolation of a simple phenolic glucoside, 2,6-dimethoxy-4-hydroxyphenol-1-O-\beta -D-glucopyranoside (1); a megastigmane glucoside, phlomuroside (=3-hydroxy-5,6-epoxy-\beta -ionol-9-O-\beta -D-glucopyranoside) (2); and a nucleotide glycoside, uridine (3). From the aerial parts of P. carica, the same phenolic glucoside, 2,6-dimethoxy-4-hydroxyphenol-1-O-\beta -D-glucopyranoside (1); as well as an acetophenon glucoside, picein (4); and 2 monoterpenoid glucosides, - betulalbuside A (5) and 1-hydroxylinaloyl-6-O-\beta -D-glucopyranoside (6) - were isolated and identified. The structure elucidation of the isolates was based on spectroscopic evidence.

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Application Of Ibx Method For The Synthesis Of Ketones From Carboxylic Acids, H. R. Ferhat Karabulut, Mesut Kaçan, Hasan Özyildirim Jan 2003

Application Of Ibx Method For The Synthesis Of Ketones From Carboxylic Acids, H. R. Ferhat Karabulut, Mesut Kaçan, Hasan Özyildirim

Turkish Journal of Chemistry

Methoxy phenyl propionic acid and some derivatives are converted to ketones using a new method. All classical methods to obtain ketones from carboxylic acids via acid halide consistently gave very low yields and regularly generated intermolecular cyclisation products or polymeric materials. However, high ketones yields are obtained by using the new IBX method.

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Neolignan, Flavonoid, Phenylethanoid And Iridoid Glycosides From Phlomis Integrifolia, İclal Saracoğlu, Mehtap Varel, İhsan Çaliş, Ali̇ Arslan Dönmez Jan 2003

Neolignan, Flavonoid, Phenylethanoid And Iridoid Glycosides From Phlomis Integrifolia, İclal Saracoğlu, Mehtap Varel, İhsan Çaliş, Ali̇ Arslan Dönmez

Turkish Journal of Chemistry

From the aerial parts of Phlomis integrifolia Hub.-Mor. (Lamiaceae) were isolated a neolignan glucoside, dehyrodiconiferyl alcohol-4-O-\beta -D-glucopyranoside (1), an ester flavone glycoside, chrysoeriol 7-O-(3''-O-trans-p-coumaroyl)-\beta -D-glucopyranoside (2), four phenylethanoid glycosides, forsythoside B (3), verbascoside (=acteoside) (4), leucosceptoside A (5) and martynoside (6) along with an iridoid glucoside, lamiide (7). The structure elucidation of the isolated compounds was carried out by spectroscopic (UV, IR, 1D- and 2D-NMR) methods. The isolation of neolignan glucoside dehyrodiconiferyl alcohol-4-O-\beta -D-glucopyranoside (1) is reported for the first time from a Phlomis species as well as for the family Lamiaceae.

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Solar And Wind Energy Development In Maine: 1973-1997, Evan Rallis Jan 2003

Solar And Wind Energy Development In Maine: 1973-1997, Evan Rallis

Electronic Theses and Dissertations

Focusing on how Maine reflected, as well as stood out from national trends in the development of wind and solar energy, this study concentrates particularly on how Maine state government and environmental groups contributed to this development, as well as on the technological progress of these energy sources. It draws primarily on state government documents, newspapers, and periodicals for evidence. The 1973-74 energy crisis, combined with the rise of the environmental movement, led to an increased exploration of alternative energy sources, in particular those that were relatively friendly to the environment like solar and wind energy. Attempts to utilize these …

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Design, Synthesis, And Applications Of Bio-Derived Crosslinking Monomers For Molecular Imprinting, Martha Sibrian-Vazquez Jan 2003

Design, Synthesis, And Applications Of Bio-Derived Crosslinking Monomers For Molecular Imprinting, Martha Sibrian-Vazquez

LSU Doctoral Dissertations

Most of the research in the field of molecular imprinting has been focused on the development of new functional monomers, in order to improve the molecular recognition properties afforded by these materials. The role of the crosslinking monomer has often been overlooked, since it is considered an inert component that only provides a scaffold to support the binding sites. However, the crosslinking monomer represents a high percent (80-90%) of the composition of molecularly imprinted polymers (MIPs), which can have a large influence on the MIPs properties. This research addresses the design, synthesis, and applications of new crosslinking monomers for molecular …

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Synthesis, Characterization, And Application Of Water-Soluble Chiral Calix[4]Arene Derivatives In Spectroscopy And Capillary Electrokinetic Chromatography, Kim Hamilton Jan 2003

Synthesis, Characterization, And Application Of Water-Soluble Chiral Calix[4]Arene Derivatives In Spectroscopy And Capillary Electrokinetic Chromatography, Kim Hamilton

LSU Doctoral Dissertations

This dissertation is an account of the synthesis, characterization, and application of novel water-soluble chiral calixarenes in spectroscopy and capillary electrophoresis. It is divided into four sections. The first part describes the synthesis and nuclear magnetic resonance (NMR) characterization of four p-t-butylcalix[4]arenes bearing L-amino acid moieties on their lower rims (CX4-AA). The structure and conformation of the derivatives have been determined using one- and two-dimensional NMR techniques. Proton and carbon-13 spectra show that the derivatives are tetra-substituted and adopt a cone conformation. The preparation and characterization of silica-bonded calixarene stationary phases for capillary electrochromatography is also reported in Chapter 2. …

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Negotiating High Stakes Water Conflicts: Lessons Learned From Experienced Practitioners, Stephen E. Snyder, University Of Colorado Boulder. Natural Resources Law Center Jan 2003

Negotiating High Stakes Water Conflicts: Lessons Learned From Experienced Practitioners, Stephen E. Snyder, University Of Colorado Boulder. Natural Resources Law Center

Books, Reports, and Studies

36 p. ; 28 cm

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Design And Synthesis Of Handles For Solid-Phase Peptide Synthesis And Convergent Peptide Synthesis, Jose Giraldes Jan 2003

Design And Synthesis Of Handles For Solid-Phase Peptide Synthesis And Convergent Peptide Synthesis, Jose Giraldes

LSU Doctoral Dissertations

The recent popularity of methods for solid-phase peptide synthesis that use the 9-fluorenylmethyloxycarbonyl (Fmoc) group for Nα-amino protection has created a need for compatible anchoring linkages and handles. In an effort to develop mild new methods for use in solid-phase peptide synthesis (SPPS), a new ferrocene containing linker or “handle”, the 1’1-ferrocenyl carboxaldehyde handle was designed, synthesized, characterized and tested. This linker is analogous to those commercially available and developed by Barany. The ferrocenyl amine linker(FAL) releases C-terminal peptide amides upon acidolysis. Since the FAL handle is acid labile it is compatible with Fmoc and Nα-dithiasuccinoyl …

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On The Geometry And Topology Of Moduli Spaces Of Multi-Polygonal Linkages, Michael Edward Holcomb Jan 2003

On The Geometry And Topology Of Moduli Spaces Of Multi-Polygonal Linkages, Michael Edward Holcomb

LSU Doctoral Dissertations

The geometric, topological, and symplectic properties of moduli spaces (spaces of configurations modulo rotations and translations) of polygonal linkages have been studied by Kapovich, Millson, and Kamiyama, et. al. One can form a polygonal linkage by taking two free linkages and identifying initial and terminal vertices. This can be generalized so that one takes three free linkages and identifies initial and terminal vertices. Then one obtains a linkage which contains multiple polygons, any two of which have shared edges. The geometric and topological properties of moduli spaces of these multi-polygonal linkages are studied. These spaces turn out to be compact …

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Mode-Cleaning And Injection Optics Of The Gravitational-Wave Detector Geo600, S. Goßler, M. M. Casey, A. Grant, H. Grote, Volker Quetschke Jan 2003

Mode-Cleaning And Injection Optics Of The Gravitational-Wave Detector Geo600, S. Goßler, M. M. Casey, A. Grant, H. Grote, Volker Quetschke

Physics and Astronomy Faculty Publications and Presentations

The British–German interferometric gravitational-wave detector GEO600 uses two high-finesse triangular ring cavities of 8 m optical pathlength each, as an optical mode-cleaning system. The modecleaner system is housed in an ultrahigh-vacuum environment to avoid contamination of the optics and to minimize both the influence of refractive index variations of the air and acoustic coupling to the optics. To isolate the cavities from seismic noise, all optical components are suspended as double pendulums. These pendulums are damped at their resonance frequencies at the upper pendulum stage with magnet-coil actuators. A suspended reaction mass supports three coils matching magnets bonded onto the …

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Black Willow (Salix Nigra) Use In Phytoremediation Techniques To Remove The Herbicide Bentazon From Shallow Groundwater, Robert Mark Conger Jan 2003

Black Willow (Salix Nigra) Use In Phytoremediation Techniques To Remove The Herbicide Bentazon From Shallow Groundwater, Robert Mark Conger

LSU Doctoral Dissertations

Wetland environments have been impacted by the activities of man over the past several hundred years in North America. Industrialization into wetland areas has brought with it anthropogenic compounds that have been released into soils and groundwater. The use of phytoremediation to detoxify soil and groundwater began in the mid 1990's and has become a popular remediation technology. In 1994, a feasibility study for using phytoremediation in such an industrialized wetland area was conducted at a petrochemical facility at BASF Corporation, located about 20 kilometers south of Baton Rouge, Louisiana in Ascension Parish. The test site consisted of low level …

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Influences On State-Level Policies For Wildfire Risk Reduction, Marios Anastasis Valiantis Jan 2003

Influences On State-Level Policies For Wildfire Risk Reduction, Marios Anastasis Valiantis

LSU Master's Theses

Wildland fires are part of the United State’s history and culture. The human dimension of State wildland fire management, - the relationship of people and wildland fire in America- is an important and driving force in how federal and state agencies respond to wildland fire, now and in the future. In many ways, the critical element for the management of wildland fire is the management of people, communities, and organizations. Explosive growth in the wildland-urban interface puts entire communities, their associated infrastructure and the socioeconomic fabric that holds communities together at a high risk from wildland fire. Year after year …

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Measurement Of The Stochasticity Of Low-Latitude Geomagnetic Temporal Variations, Mark Anthony Reynolds, James A. Wanliss Jan 2003

Measurement Of The Stochasticity Of Low-Latitude Geomagnetic Temporal Variations, Mark Anthony Reynolds, James A. Wanliss

Publications

Ground magnetometer measurements of total magnetic field strength from 6 stations at low latitudes were analyzed using power spectrum and Hurst range scaling techniques. The Hurst exponents for most of these time-series were near 0.5, which indicates stochasticity, with the highest latitude stations exhibiting some persistence with Hurst exponents greater than 0.6. Although no definite correlations are evident, the relative increase of the Hurst exponent with latitude suggests the possibility that the underlying dynamics of the magnetosphere change with latitude. This result may help quantify the dynamics of the inner magnetosphere itself without the direct presence of the solar wind …

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The Local-Time Variation Of The Quiet Plasmasphere: Geosynchronous Observations And Kinetic Theory, Mark Anthony Reynolds, G. Ganguli, Y-J Su, M.F. Thomsen Jan 2003

The Local-Time Variation Of The Quiet Plasmasphere: Geosynchronous Observations And Kinetic Theory, Mark Anthony Reynolds, G. Ganguli, Y-J Su, M.F. Thomsen

Publications

The quiet-time structure of the plasmaspheric density was investigated using observations of the Los Alamos geosynchronous satellites, and these observations were compared with theoretical predictions of the quasi-static localtime variation by a kinetic model. It was found that the coupling to the ionosphere (via the local-time variation of the exobase) played a key role in determining the density structure at 6.6 RE. The kinetic model predicts that most of the local-time variation at geosynchronous orbit is due to the variation of the exobase parameters. During quiet times, when the convection electric field is dominated by the corotation field, the effects …

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A Multilevel Discontinuous Galerkin Method, Jay Gopalakrishnan, Guido Kanschat Jan 2003

A Multilevel Discontinuous Galerkin Method, Jay Gopalakrishnan, Guido Kanschat

Mathematics and Statistics Faculty Publications and Presentations

A variable V-cycle preconditioner for an interior penalty finite element discretization for elliptic problems is presented. An analysis under a mild regularity assumption shows that the preconditioner is uniform. The interior penalty method is then combined with a discontinuous Galerkin scheme to arrive at a discretization scheme for an advection-diffusion problem, for which an error estimate is proved. A multigrid algorithm for this method is presented, and numerical experiments indicating its robustness with respect to diffusion coefficient are reported.

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A Schwarz Preconditioner For A Hybridized Mixed Method, Jay Gopalakrishnan Jan 2003

A Schwarz Preconditioner For A Hybridized Mixed Method, Jay Gopalakrishnan

Mathematics and Statistics Faculty Publications and Presentations

In this paper, we provide a Schwarz preconditioner for the hybridized versions of the Raviart-Thomas and Brezzi-Douglas-Marini mixed methods. The preconditioner is for the linear equation for Lagrange multipliers arrived at by eliminating the ux as well as the primal variable. We also prove a condition number estimate for this equation when no preconditioner is used. Although preconditioners for the lowest order case of the Raviart-Thomas method have been constructed previously by exploiting its connection with a nonconforming method, our approach is different, in that we use a new variational characterization of the Lagrange multiplier equation. This allows us to …

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Multiply Charged Ions Produced After Deexcitation Processes For Important Elements In Astrophysics, Adel M. El-Shime, Adel A. Ghoneim, Yehia A. Lotfy Jan 2003

Multiply Charged Ions Produced After Deexcitation Processes For Important Elements In Astrophysics, Adel M. El-Shime, Adel A. Ghoneim, Yehia A. Lotfy

Turkish Journal of Physics

Selection random number method (Monte Carlo technique) is used to calculate the ion charge state distributions (CSD) and mean ion charge \bar{q} after K-, L_{I}, L_{III}- and M_{I}- shell ionization in neutral atoms and their q-fold ground state ions (q = 0 to 10) from C to Fe elements. Atomic data for radiative and non-radiative transitions and electron shake off process, which is used in the modeling vacancy cascade program, are computed with relativistic wave functions. Use of atomic data is important to accurately model vacancy cascades. To enhance the agreement between calculated and experimental values, the electron shake-off processes …

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Semi-Infinite Polarized Nuclear Matter With A Seyler-Blanchard Interaction, H. M. M. Mansour, Kh. A. Ramadan Jan 2003

Semi-Infinite Polarized Nuclear Matter With A Seyler-Blanchard Interaction, H. M. M. Mansour, Kh. A. Ramadan

Turkish Journal of Physics

The surface and curvature properties of semi-infinite polarized nuclear matter (SPNM) are calculated using a modified form of the Seyler-Blanchard potential. The level density parameter is extracted from the free energy using T^{2}-approximation. Good agreement is obtained between our calculations for the level density and other parameters which characterize the surface and curvature properties of SPNM and previous theoretical estimates. PACS number(s): 21.65.+f, 21.30.Fe

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Electron Transport Mechanism In Gan/Algan Hemt Structures, Si̇bel Gökden Jan 2003

Electron Transport Mechanism In Gan/Algan Hemt Structures, Si̇bel Gökden

Turkish Journal of Physics

The electron transport mechanism in GaN/AlGaN HEMT (High Electron Mobility Transistors) structures grown with MBE on sapphire substrate was investigated by using the temperature dependence of the Hall coefficient, resistivity, carrier density and Hall mobility. Hall measurements were carried out using Van der Pauw geometry. From the LO-phonon-scattering-limited component of the mobility, we obtain LO phonon energy \hbar \omega \approx 90 meV and the momentum relaxation time of \tau_{m} \approx 4 fs. Also, from the temperature dependence of the 2D carrier density, we obtain the donor activation energy E_{a} \approx 29 meV.

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Null Membranes In Dyonic Black Hole Background, Alexandr Lelyakov, Sergey Nikolaevich Roshchupkin Jan 2003

Null Membranes In Dyonic Black Hole Background, Alexandr Lelyakov, Sergey Nikolaevich Roshchupkin

Turkish Journal of Physics

We consider null bosonic p-branes in curved spacetimes. The general solutions of the classical equations of motions and constraints for the null-membrane in four-dimensional dyonic black hole background are found.

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Mesoscopic D-Wave Qubits: Can High-T_C Cuprates Play A Role In Quantum Computing?, Alexandre M. Zagoskin Jan 2003

Mesoscopic D-Wave Qubits: Can High-T_C Cuprates Play A Role In Quantum Computing?, Alexandre M. Zagoskin

Turkish Journal of Physics

Due to nontrivial orbital pairing symmetry, surfaces and interfaces of high-T_c superconductors support states which violate time-reversal (T-) symmetry. Such naturally degenerate states, useful as working states of a qubit, are standard for atomic or molecular-size qubit prototypes (e.g. based on nuclear spins), but exceptional for mesoscopic qubits. (In particular, they hold promise of a better scalability.) In these lectures I review the physics of T-breaking on surfaces and interfaces of high-T_c superconductors; then describe existing proposals for high-T_c based qubits and the current state of experiments; finally, I discuss the decoherence sources in the system, open questions, and future …

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