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Volume 5 Issue 1

March 2007

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Open Access October 24, 2006

Pre-low-mass X-ray binaries containing a black hole: investigating a detection mechanism

James Bleach

Page range: 1-10

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Abstract

This work investigates the feasibility of detecting close, detached, black hole-red dwarf binaries, which are expected to be evolutionary precursors of low-mass X-ray binaries (LMXBs). Although this pre-low-mass X-ray binary (pre-LMXB) phase of evolution is predicted theoretically, as yet no such systems have been identified observationally. The calculations presented here suggest that the X-ray luminosity of black hole wind accretion in a pre-LMXB system could exceed the intrinsic X-ray luminosity of the red dwarf secondary star, thereby providing a detection mechanism. However, there is significant uncertainty regarding the efficiency of the conversion of gravitational potential energy to X-ray luminosity resulting from accretion onto a black hole, for example energy may be lost via advection across the event horizon. Still, sources with X-ray luminosities greater than that expected for a red dwarf star, but whose positions coincide with that of a red dwarf would represent candidate pre-LMXB systems. These candidates should be surveyed for the radial velocity shifts that would occur as a result of the orbital motion of a red dwarf star within a close binary system containing a black hole.

Open Access March 1, 2007

Coupling in Fe(2 ML)/V(y ML) and Fe(2 ML)/V(y ML)/Fe(3 ML)/V(y ML) (y ≥ 4) superlattices

Karen Paul

Page range: 11-24

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Abstract

Fe(2 ML)/V(y ML) and interleaved Fe(2 ML)/V(y ML)/Fe(3 ML)/V(y ML) superlattice systems with spacer thicknesses, y, (4 ≤ y ≤ 17) were investigated macro-magnetically to estimate the coupling strength and the magnetoresistance in these materials, and particularly in the antiferromagnetically coupled monolayers. The results from the magnetic and magnetoresistive measurements indicate that adding one monolayer of Fe increases the antiferromagnetic coupling and the magnetoresistivity ratio from 0.0075 mJ/m2 at 20 K and 2 % at 10 K for Fe(2 ML)/V(y ML), to 0.05 mJ/m2 and 2.5 % for Fe(2 ML)/V(y ML)/Fe(3 ML)/V(y ML) at the same temperatures. Both systems exhibit in-plane magnetic and magnetoresistive isotropy, therefore the increase of the conferred physical parameters is attributed mainly to the stresses at the interface as governing mechanisms over the magnetoelastic forces.

Open Access November 11, 2006

Ab-initio calculation of band structure and linear optical properties of SbSI in para- and ferroelectric phases

Harun Akkus, Amirullah Mamedov

Page range: 25-34

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Abstract

An ab-initio pseudopotential calculation has been performed by using density functional methods within the local density approximation (LDA) to investigate the band structure and optical properties of the ferroelectric-semiconductor SbSI in the para- and ferroelectric phases. It has been shown that SbSI has an indirect gap in both phases (1.45 eV and 1.49 eV in the para- and ferroelectric phases respectively) and that the smallest direct gap is at the S point of the Brillouin zone (1.56 eV and 1.58 eV in the para- and ferroelectric phases respectively). Furthermore, it is shown that first-order phase transition, from the paraelectric phase to the ferroelectric phase (the transiton temperature is about 22 °C), does not change the nature of the band gap. Moreover, the linear frequency dependent dielectric function, including self-energy effects, has been calculated along the c-polar axis in the para- and ferroelectric phases.

Open Access March 1, 2007

Non-linear dynamics of spinodal decomposition in multi-component polymer systems. I. General approach

Ekaterina Prostomolotova

Page range: 35-48

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Abstract

Spinodal decomposition of multi-component systems is analyzed within the framework of a new approach focusing on the description of this dynamic process in terms of the Langevin equation for the one-time structure factor S(q, t) treated as an independent dynamic object. We apply this approach, in particular, to multi-component incompressible polymer systems (binary polymer solutions, ternary polymer blends etc.). The dynamic equation describing the simultaneous relaxation of both the order parameters (component concentrations) and the matrix of the component-component dynamic correlation functions ∥S ij(q, t)∥, including the explicit expression for the corresponding effective kinetic coefficients, is derived.

Open Access March 1, 2007

Structural analysis of base mispairing in DNA containing oxidative guanine lesion

Hirofumi Fujimoto, Miroslav Pinak, Toshiyuki Nemoto, Juraj Bunta

Page range: 49-61

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Abstract

Classical molecular dynamics methods were used to analyze the importance of 8-oxoguanine (8-oxoG) pairing with other DNA bases in order to determine the impact of oxidative guanine lesions on DNA structure. Six lesioned molecules, each containing 8-oxoG mispaired with one of the four normal bases on the the opposite strand at the center of 40-mer DNA, and one non-damaged DNA molecule, were simulated for 2 nanoseconds of real time. The 8-oxoG lesioned bases were found to incorporate opposite all normal bases. There are observed conformational and energetical differences among these parings. 8-oxoG in anti-form creates firm hydrogen bonds with cytosine and this bonding has a strong attractive electrostatic interaction energy similar to that of a native base pair-guanine to cytosine. Meanwhile, it does not form a stable base pair with purine bases (adenine and guanine) nor with the pyrimidine base thymine. On the other hand, the 8-oxoG in syn-form was found to pair with adenine.

Open Access November 24, 2006

Amplification of solitary optical waves in fibers with positive group velocity dispersion

Todor Arabadzhiev, Ivan Uzunov

Page range: 62-69

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Abstract

Solitary optical waves with characteristic red frequency shift have been numerically identified in fibers with positive group velocity dispersion in the presence of amplification by semiconductor amplifiers. Influence of the Henry factor, the net gain, gain saturation characteristics, and frequency modulation on the frequency shift of the observed solitary optical waves has been examined. Normalized pulse energy as a function of the gain saturation characteristics has been studied.

Open Access December 5, 2006

The inhomogeneous quantum invariance group of commuting fermions

Azmi Altintas, Metin Arik

Page range: 70-82

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Abstract

We consider a model of d fermions where creation and annihilation operators of different fermions commute. We show that this particle algebra is invariant under an inhomogeneous quantum group.

Open Access November 24, 2006

Electronic transport mechanism in polydiacetylene crystals — variable range hopping or phonon-assisted tunnelling

Povilas Pipinys, Antanas Kiveris

Page range: 83-90

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Abstract

Experimental results on the current-voltage characteristics of polydiacetylene (PDA) single crystals reported by Aleshin et al [Phys. Rev. Vol. B 69, (2004) art. 214203] are reinterpreted in terms of the phonon-assisted electron tunnelling model. It is shown that the experimental results, measured in the temperature range from 1.8 K to 300 K are consistent with the tunnelling rate dependence on field strength, computed for the same range of temperatures. An advantage of this model over that of Aleshin et al, using the variable range hopping (VRH) model, is the possibility of describing the behaviour of I — V data measured at both high and low temperatures with the same set of parameters characterizing this material. This assertion is confirmed by comparison of the temperature-dependent current-voltage data extracted from Aleshin et al’s work with tunnelling rate dependence on temperature, computed using two different expressions of the phonon-assisted tunnelling theory. The temperature dependence of the conductivity of an ion implanted PDA crystals [B. S. Elman et al, Appl. Phys. Lett., Vol. 46, (1985) p. 100] and polypyrrole [P. Dutta et al, Synth. Met., Vol. 139 (2003) p. 201] are also explained on the basis of this model.

Open Access November 24, 2006

The oscillatory galvanomagnetic size-effect in multilayered structures

Leonid Dekhtyaruk

Page range: 91-102

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Abstract

Within the framework of the modified semi-classical Fuchs-Sondheimer model, we investigated theoretically the electrical resistivity of multilayered structures (MLS) consisting of alternating metallic layers (of different purity and different thicknesses) in a transverse magnetic field as functions of the ratio of the adjacent layer thicknesses and the magnetic field value. We have derived both a general formula (valid at arbitrary values of layer thicknesses) and asymptotic expressions that are valid when metallic layers are thick or thin compared with the electron mean free path. We found a non-monotonic behavior in the resistivity vs. the value of an applied magnetic field. As we demonstrated, this behavior is sensitive to the characteristics of the electron scattering in the interlayer interfaces in low magnetic fields. Moreover, the MLS resistivity oscillates in high magnetic fields with the field value (or with the layer thicknesses). The oscillation includes the harmonics that correspond both to the each layer thicknesses and the total thickness. The intensity of the oscillation is determined by the diffusive electron scattering in the interfaces, and the oscillation amplitude is proportional to the coefficient of the electron transmission through the interlayer interfaces. We have calculated numerically the resistivity in a wide range of fields and layer thicknesses at various values of the parameters of the interface and bulk electron scattering.

Open Access November 24, 2006

The effect of doping by IV-family elements on the electronic structure and electrical characteristics of Sb2O5

Juan Du, Zhenguo Ji, Chao Wang

Page range: 103-109

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Abstract

The electronic structures of doped Sb2O5 by IV-family elements (Si, Ge and Sn) were examined using the density function theory (DFT). Density of states (DOSs) results showed that the substituted IV-family elements act as acceptors in Sb2O5. Partial DOSs indicates that by substituting Ge(GeSb) or Sn(SnSb), there may be a larger contribution to the total DOSs near EF than by substituting Si, which suggests that doping Ge or Sn in Sb2O5 produces better ptype doping compared to doping Si. Formation energy results show that IV-family elements are more likely to exist in the substituted position rather than in the interstitial position in Sb2O5, decreasing any self-compensation effect and making it easier for IV-family elements to realize ptype doping in Sb2O5. Ionization energy results show that GeSb or SnSb, two among the three impurities considered, act as shallow acceptors in Sb2O5, thus producing a higher concentration of holes.

Open Access March 1, 2007

NIR photoresponse in the mixed phthalocyanine films

Geogrij Pakhomov, Evgenij Kuzin, Arkadij Murel

Page range: 110-110

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Abstract

The original version of the article was published in Cent. Eur. J. Phys., Vol. 4(4), (2006), pp. 494-502. It can be also found online at: http://dx.doi.org/10.2478/s11534-006-0027-9. Unfortunately, the original version of this article contains mistakes in the numbering of its references. The reference numbers should be changed according to the following table: PageLineThere isThere should be19[2, 5, 7, 13-15][2, 5, 7, 13-16]25[2, 3, 7-10, 12, 17][2, 3, 7-10, 12, 18]27[2, 4, 5, 7, 14, 17][2, 4, 5, 7, 14, 18]29[11, 17][11, 18]213[18][19]2Footnote[16][17]321[4, 5, 7, 14, 19][4, 5, 7, 14, 20]510[20][21]717[21][22]723[14, 15][15, 16]

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Open Physics is a peer-reviewed, open access, electronic journal devoted to the publication of fundamental research results in all fields of physics. The journal provides the readers with free, instant, and permanent access to all content worldwide; and the authors with extensive promotion of published articles, long-time preservation, language-correction services, no space constraints and immediate publication.
Open Physics is listed inter alia by Clarivate Analytics (formerly Thomson Reuters) - Current Contents/Physical, Chemical and Earth Sciences, JCR and SCIE. Our standard policy requires each paper to be reviewed by at least two Referees and the peer-review process is single-blind.

Special / Topical Issues:

Special Issue on Predicting Patern Alterations in Nature
Guest Editors:
Prof. Abdon Atangana, University of the Free State, South (Lead Guest Editor)
Prof. Dr. Emile Franc Goufo, University of South Africa
Prof. Dr Seda İğret Araz, Siirt University, Turkey

The journal publishes research and review articles, rapid and short communications, comments and replies that cover the following areas of physical sciences:

Acoustics
Astrophysics,
Atomic and Molecular Physics,
Biological and Medical Physics,
Complex Networks, Socio- and Econophysics,
Computational Physics,
Condensed Matter Physics,
Cosmology and Gravitation,
Fluid Mechanics,
Geophysics,
Nanophysics,
Optics and Lasers,
Particle and Nuclear Physics,
Plasma Physics,
Statistical and Nonlinear Physics,
Surface Physics,
Theoretical and Mathematical Physics.

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