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2003

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Articles 19981 - 20010 of 20591

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Cover And Contents Jan 2003

Cover And Contents

Turkish Journal of Physics

No abstract provided.

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Extragalactic Objects In Basle Fields, Selçuk Bi̇li̇r, Yüksel Karataş, Serap Ak Jan 2003

Extragalactic Objects In Basle Fields, Selçuk Bi̇li̇r, Yüksel Karataş, Serap Ak

Turkish Journal of Physics

We discriminated between the extragalactic objects (galaxies and quasars) and stars for Basle star fields, Plaut I, SA 54, and SA 82 by comparing Basle fields and APS POSS I finder charts. Their numbers are 187, 70, and 93 for Plaut I, SA 54, and SA 82, respectively. Most of these objects are apparently faint in V, and they cause an overestimated local luminosity function for absolutely faint magnitudes, M(V) > 5. This effect is more conspicious for the field Plaut I.

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Microwave Rotational Components Of The \Nu_9= 1 And \Nu _{10} = 2 Vibrational Modes Of ^{13}Ch_{3}Cch Molecule In The Range 16 -- 50 Ghz, Mohammad Al-Share, J. A. Roberts Jan 2003

Microwave Rotational Components Of The \Nu_9= 1 And \Nu _{10} = 2 Vibrational Modes Of ^{13}Ch_{3}Cch Molecule In The Range 16 -- 50 Ghz, Mohammad Al-Share, J. A. Roberts

Turkish Journal of Physics

Some rotational components have been measured in the ground, the \nu _9 = 1 and the \nu _{10} = 2 vibrational states for ^{13}CH_3CCH isotopic species in the frequency range 16--50 GHz. A set of rotational constants has been determined, which gives the best fit between the observed and the calculated frequencies, for each vibrational state. A Fermi resonance was found between these two states.

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Studies On Some Lithium-Borate Glasses Containing Iron And Copper, G. A. Yahya Jan 2003

Studies On Some Lithium-Borate Glasses Containing Iron And Copper, G. A. Yahya

Turkish Journal of Physics

A lithium-borate-glass system containing iron and copper cations has been thoroughly investigated, in order to obtain information about the structural role of both the iron and copper in such glass hosts. The amorphous phase of the prepared glass samples was confirmed from their X-ray diffraction. From the infrared spectra it was concluded that the glass networks are highly deformed and boron appeared in both tri- and tetra-hedral coordination states as well as in some ring structure. As copper was introduced, replacing lithium, it acts as a network modifier only while the iron acts as network former (FeO_4). The molar magnetic …

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Esr Studies Of A Quartz Single Crystal From The Menderes Massif-Turkey, Ülkü Ulusoy Jan 2003

Esr Studies Of A Quartz Single Crystal From The Menderes Massif-Turkey, Ülkü Ulusoy

Turkish Journal of Physics

In a recent work, quartz single crystal extracted from the pegmatitic vein in the Menderes Massif (Western Turkey) was investigated and the most recent geological events of the sample was dated using Al centers by ESR (electron spin resonance) techniques. The estimated age of 1.8 \pm 0.5 My agree with neither the previous age evaluated to be 12 My by using isotopic dating techniques nor the lifetimes of these centers in the sample. It was suggested that the thermal or geothermal stressing history of the metamorphic region must have changed the apparent ESR age several cycles in this period. The …

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Photoelectrochemical Properties Of Cdse:Sb Thin Film Based Solar Cells: Influence Of Electrode Thickness, Elahipasha U. Masumdar, L. P. Deshmukh Jan 2003

Photoelectrochemical Properties Of Cdse:Sb Thin Film Based Solar Cells: Influence Of Electrode Thickness, Elahipasha U. Masumdar, L. P. Deshmukh

Turkish Journal of Physics

CdSe:Sb (0.1 mol%) thin films of varying thicknesses (423--1838 nm) have been deposited onto the glass and stainless steel substrates in an alkaline medium (pH = 10) using a solution growth technique. The photoelectrochemical activities of these films have been examined using CdSe:Sb (0.1 mol%)/0.25 M NaOH - 0.25M Na_2S- 0.25M S/graphite cell configuration. The films were characterized under illumination of 20 mW/cm^2} intensity to evaluate various cell parameters such as \eta, ff, R_s, R_{sh} etc. It is found that the efficiency \eta and fill factor ff increased from 0.24% to 0.45%, and 51% to 52.9%, respectively, with increase in …

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Electrical, Optical, Structural And Morphological Properties Of Nis Films, Ferhunde Atay, Sali̇h Köse, Vi̇ldan Bi̇lgi̇n, İdri̇s Akyüz Jan 2003

Electrical, Optical, Structural And Morphological Properties Of Nis Films, Ferhunde Atay, Sali̇h Köse, Vi̇ldan Bi̇lgi̇n, İdri̇s Akyüz

Turkish Journal of Physics

The electrical, optical, structural and morphological properties of NiS films are less studied than other materials such as CdS, CdTe, ZnS, ZnO, CdO etc. Our aim in this work is to deposit NiS films, examine some of their physical properties and investigate their suitability for photovoltaic devices. NiS films were deposited onto glass substrates at a substrate temperature of 300 \pm 5 °C using the ultrasonic spray pyrolysis (USP) technique. The variations of temperature-dependent conductivity under the conditions of light and dark were investigated and it was seen that illumination reduces conductivity. The activation energy for the doped region and …

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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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Phase Measurements In Aharonov-Bohm Interferometers, Amnon Aharony, Ora Entin-Wohlman, Yoseph Imry Jan 2003

Phase Measurements In Aharonov-Bohm Interferometers, Amnon Aharony, Ora Entin-Wohlman, Yoseph Imry

Turkish Journal of Physics

In this paper we address measurements of the resonant quantum transmission amplitude t_{QD} = -i t_{QD} e^{i\alpha_{QD}} through a quantum dot (QD), as function of the plunger gate voltage V. Mesoscopic solid state Aharonov-Bohm interferometers (ABI) have been used to measure the ``intrinsic" phase, \alpha_{QD}, when the QD is placed on one of the paths. In a ``closed" interferometer, connected to two terminals, the electron current is conserved, and Onsager's relations require that the conductance G through the ABI is an even function of the magnetic flux \Phi = \hbar c\phi/e threading the ABI ring. Therefore, if one fits G …

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Dephasing Of Entangled Electron-Hole Pairs In A Degenerate Electron Gas, J. L. Van Velsen, M. Kindermann, C. W. J. Beenakker Jan 2003

Dephasing Of Entangled Electron-Hole Pairs In A Degenerate Electron Gas, J. L. Van Velsen, M. Kindermann, C. W. J. Beenakker

Turkish Journal of Physics

A tunnel barrier in a degenerate electron gas was recently discovered as a source of entangled electron-hole pairs. Here, we investigate the loss of entanglement by dephasing. We calculate both the maximal violation E_{max} of the Bell inequality and the degree of entanglement (concurrence) C. If the initially maximally entangled electron-hole pair is in a Bell state, then the Bell inequality is violated for arbitrary strong dephasing. The same relation E_{max} = 2 \sqrt{1 + C^2} then holds as in the absence of dephasing. More generally, for a maximally entangled superposition of Bell states, the Bell inequality is satisfied for …

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Adiabatic Quantum Pumping Of Coherent Electrons, Ora Entin-Wohlman, Amnon Aharony, Vyacheslavs Kashcheyevs Jan 2003

Adiabatic Quantum Pumping Of Coherent Electrons, Ora Entin-Wohlman, Amnon Aharony, Vyacheslavs Kashcheyevs

Turkish Journal of Physics

We review recent theoretical calculations of charge transfer through mesoscopic devices in response to slowly-oscillating, spatially-confined, potentials. The discussion is restricted to non-interacting electrons, and emphasizes the role of quantum interference and resonant transmission in producing almost integer values (in units of the electronic charge e) of the charge transmitted per cycle, Q. The expression for the pumped charge is derived from a systematic expansion of the system scattering states in terms of the temporal derivatives of the instantaneous solutions. This yields the effect of the modulating potential on the Landauer formula for the conductance in response to a constant …

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Quantum Computing With Electrons On Liquid Helium, İsmai̇l Karakurt Jan 2003

Quantum Computing With Electrons On Liquid Helium, İsmai̇l Karakurt

Turkish Journal of Physics

A quantum computer based on electrons floating over liquid helium is described. Each qubit is made of combinations of ground and first excited states of an electron trapped over micro-electrodes just below the helium surface. We describe mechanisms for preparing the initial state of the qubit, operations with the qubits, and a proposed readout. This system is, in principle, capable of \sim 10^4 operations in a decoherence time, the time in which the wave function collapses.

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Persistent Currents In Mesoscopic Loops And Networks, Igor O. Kulik Jan 2003

Persistent Currents In Mesoscopic Loops And Networks, Igor O. Kulik

Turkish Journal of Physics

The paper describes persistent (also termed ``permanent", or ``non-decaying") currents in mesoscopic metallic and macromolecular rings, cylinders and networks. The current arises as a response of system to Aharonov-Bohm flux threading the conducting loop and does not require external voltage to support the current. Magnitude of the current is periodic function of magnetic flux with a period of normal-metal flux quantum \Phi_0 = hc/e. Spontaneous persistent currents arise in regular macromolecular structure without the Aharonov-Bohm flux provided the azimuthal periodicity of the ring is insured by strong coupling to periodic background (a ``substrate"), otherwise the system will undergo the Peierls …

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Au Nanoparticle Clusters: A New System To Model Hopping Conduction, Ç. Kurdak, J. Kim, L. A. Farina, K. M. Lewis, X. Bai, M. P. Rowe, A. J. Matzger Jan 2003

Au Nanoparticle Clusters: A New System To Model Hopping Conduction, Ç. Kurdak, J. Kim, L. A. Farina, K. M. Lewis, X. Bai, M. P. Rowe, A. J. Matzger

Turkish Journal of Physics

We study electrical transport through self-assembled Au nanoparticle clusters which can be viewed as a new model system to study hopping transport. The physics of such systems is governed by two parameters: the charging energy and tunnel coupling between the particles. The charging energy is determined by the size of the nanoparticles. When the diameter of the nanoparticles is less than 4-5 nm the charging energy is large enough that Coulomb blockade effects were observed in electrical transport even at room temperature. The magnitude of the tunnel coupling between the particles was determined by the thiol coating used. To study …

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Towards Quantum Communication With Electron Spins, D. S. Saraga, G. Burkard, J. C. Egues, H. A. Engel, P. Recher, Daniel Loss Jan 2003

Towards Quantum Communication With Electron Spins, D. S. Saraga, G. Burkard, J. C. Egues, H. A. Engel, P. Recher, Daniel Loss

Turkish Journal of Physics

We review our recent work towards quantum communication in a solid-state environment with qubits carried by electron spins. We propose three schemes to produce spin-entangled electrons, where the required separation of the partner electrons is achieved via Coulomb interaction. The non-product spin-states originate either from the Cooper pairs found in a superconductor, or in the ground state of a quantum dot with an even number of electrons. In a second stage, we show how spin-entanglement carried by a singlet can be detected in a beam-splitter geometry by an increased (bunching) or decreased (antibunching) noise signal. We also discuss how a …

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First Principles Modeling Of Nanostructures, Serdar Öğüt Jan 2003

First Principles Modeling Of Nanostructures, Serdar Öğüt

Turkish Journal of Physics

Among the various theoretical tools for investigating microscopic material properties, ab initio (first principles) methods based on density functional theory and pseudopotentials have had a very good track record over the last two decades in terms of accuracy, reliability, and efficiency. The application of these methods to nanostructures to investigate their structural, electronic, and optical properties has, however, not been quite straightforward due to the large computational demand and new physics inherent in the nanometer and sub-nanometer size region. One particularly useful extension to overcome the computational demand imposed by localized nanostructures has been the introduction of methods based on …

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Quantum State Generation And Entanglement Manipulation Using Linear Optics, Şahi̇n Kaya Özdemi̇r, Takashi Yamamoto, Masato Koashi, Nobuyuki Imoto Jan 2003

Quantum State Generation And Entanglement Manipulation Using Linear Optics, Şahi̇n Kaya Özdemi̇r, Takashi Yamamoto, Masato Koashi, Nobuyuki Imoto

Turkish Journal of Physics

Quantum information processing (QIP) requires unitary operations, measurements and synthesis, manipulation and characterization of arbitrary quantum states. Linear optics provides efficient tools for these purposes. In this review paper, we introduce the elements of linear optics toolbox, and briefly discuss some experimental and theoretical investigations using this toolbox. Our main focus will be the qubit state generation and entanglement extraction using linear optics toolbox.

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Orbital Entanglement And Violation Of Bell Inequalities In The Presence Of Dephasing, P. Samuelsson, Eugene Sukhorukov, Markus Büttiker Jan 2003

Orbital Entanglement And Violation Of Bell Inequalities In The Presence Of Dephasing, P. Samuelsson, Eugene Sukhorukov, Markus Büttiker

Turkish Journal of Physics

We discuss orbital entanglement in mesoscopic conductors, focusing on the effect of dephasing. The entanglement is detected via violation of a Bell Inequality formulated in terms of zero-frequency current correlations. Following closely the recent work by Samuelsson, Sukhorukov and Büttiker [1], we investigate how the dephasing affects the possibility to violate the Bell Inequality and how system parameters can be adjusted for optimal violation.

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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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Cover And Contents Jan 2003

Cover And Contents

Turkish Journal of Physics

No abstract provided.

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Mean Multiplicity Of Quark And Gluon Jets As A Function Of Opening Angle In E^{+}E^{-} \Rightarrow B\Overline{B} G Events, Ayda Beddall Jan 2003

Mean Multiplicity Of Quark And Gluon Jets As A Function Of Opening Angle In E^{+}E^{-} \Rightarrow B\Overline{B} G Events, Ayda Beddall

Turkish Journal of Physics

A comparison of the properties of quark and gluon jets has been madeby Monte Carlo simulation of the reaction Z \rightarrow b \overline{b} g. The jet energy is held fixed for every 5 GeV between 15--30 GeV energies and the mean multiplicity of b-quark and gluon jets are obtained as function of the angle between them. It is seen that the jet properties not only depend on the jet energies but also on the angle between the jets.

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Preparation And Optimization Of High Quality Tin Films, Özlem Duyar, Cengi̇z Koçum, H. Zafer Durusoy Jan 2003

Preparation And Optimization Of High Quality Tin Films, Özlem Duyar, Cengi̇z Koçum, H. Zafer Durusoy

Turkish Journal of Physics

TiN thin films have been deposited by DC reactive magnetron sputtering method on glass substrates. The effects of the substrate temperature and the substrate bias voltage on the structural, optical and electrical properties of the films were studied by using XRD, STM, optical transmission and resistivity measurements. The bias voltage was varied in the 0 to 200 V range for two substrate temperatures, 100 °C and 300 °C. The results showed that the substrate bias voltage influenced the stoichiometry and structure of the films. The smoothest and least porous TiN films were prepared at about 160 V substrate bias voltage …

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Physical Properties Of Spray Pyrolysed Cds Thin Films, A. Ashour Jan 2003

Physical Properties Of Spray Pyrolysed Cds Thin Films, A. Ashour

Turkish Journal of Physics

Cadmium sulphide (CdS) thin films were prepared by chemical spray-pyrolysis technique. Cleaned glass substrates were used. The substrate temperature was varied in the range 200 -- 400 °C and seems to be one of the more important parameters affecting the physical properties of the semiconductor. The films were characterized by X-ray diffraction (XRD). XRD patterns indicated the presence of single-phase hexagonal CdS. The resistivity of the as-deposited films was found to vary in the range 10^3 - 10^5 \Omega. Cm, depending on the substrate temperature. Direct band gap values of 2.39--2.42 eV were obtained from optical absorption measurements.

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Cover And Contents Jan 2003

Cover And Contents

Turkish Journal of Physics

No abstract provided.

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Qce: A Simulator For Quantum Computer Hardware, Kristel Michielsen, Hans De Raedt Jan 2003

Qce: A Simulator For Quantum Computer Hardware, Kristel Michielsen, Hans De Raedt

Turkish Journal of Physics

The Quantum Computer Emulator (QCE) described in this paper consists of a simulator of a generic, general purpose quantum computer and a graphical user interface. The latter is used to control the simulator, to define the hardware of the quantum computer and to debug and execute quantum algorithms. QCE runs in a Windows 98/NT/2000/ME/XP environment. It can be used to validate designs of physically realizable quantum processors and as an interactive educational tool to learn about quantum computers and quantum algorithms. A detailed exposition is given of the implementation of the CNOT and the Toffoli gate, the quantum Fourier transform, …

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Cover And Contents Jan 2003

Cover And Contents

Turkish Journal of Physics

No abstract provided.

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High-Pressure Phase Transition In Some Alkali Halides Using Interatomic Potential Model, Harun Reşi̇t Yazar Jan 2003

High-Pressure Phase Transition In Some Alkali Halides Using Interatomic Potential Model, Harun Reşi̇t Yazar

Turkish Journal of Physics

We have predicted the phase transition pressure in some alkali halides NaCl and KCl using an interatomic potential approach based on a rigid ion model. We have obtained phase transition pressures 28.69 and 2.4 GPa, respectively, and are in close agreement with their corresponding experimental transition pressures 29.0 and 2.0 GPa. This approach is promising with respect to the prediction of the phase transition pressures of other alkali halides.

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Ventilator-Associated Pneumonia In A Multi-Hospital System: Differences In Microbiology By Location, Hilary M. Babcock, Jeanne E. Zack, Teresa Garrison, Ellen Trovillion, Marin H. Kollef, Victoria J. Fraser Jan 2003

Ventilator-Associated Pneumonia In A Multi-Hospital System: Differences In Microbiology By Location, Hilary M. Babcock, Jeanne E. Zack, Teresa Garrison, Ellen Trovillion, Marin H. Kollef, Victoria J. Fraser

Open Access Publications

No abstract provided.

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Sensitivity To Changes In Disability After Stroke: A Comparison Of Four Scales Useful In Clinical Trials, Alexander W. Dromerick, Dorothy F. Edwards, Michael N. Diringer Jan 2003

Sensitivity To Changes In Disability After Stroke: A Comparison Of Four Scales Useful In Clinical Trials, Alexander W. Dromerick, Dorothy F. Edwards, Michael N. Diringer

Open Access Publications

No abstract provided.

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Structural, Electrical And Spectral Studies On Double Rare-Earth Orthoferrites La_{1-X}Nd_Xfeo_3, O.M. Hemeda, Mohsen Mohamed Barakat, D. M. Hemeda Jan 2003

Structural, Electrical And Spectral Studies On Double Rare-Earth Orthoferrites La_{1-X}Nd_Xfeo_3, O.M. Hemeda, Mohsen Mohamed Barakat, D. M. Hemeda

Turkish Journal of Physics

Samples of double rare-earth ferrite La_{1-x}Nd_xFeO_3 are synthesized by a high-temperature double sintering ceramic technique. X-ray diffraction shows that all compounds have an orthorhombic structure. The values of lattice parameter and the volume of the unit cell, changes with increasing Nd^{3+} content. The Goldschmidt tolerance factor decreases and goes far from unity with increasing Nd content. The samples containing Nd ions with x = 0.1, 0.2 and 0.3 have higher resistivity than that of LaFeO_{3}, but for x \ge 0.4 the resistivity decreases. The results indicate the presence of extrinsic semiconducting properties up to 100 °C above which the hopping …

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