Physics Research International The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Linear Sigma Model at Finite Temperature and Baryonic Chemical Potential Using the -Midpoint Technique Thu, 06 Mar 2014 00:00:00 +0000 A baryonic chemical potential () is included in the linear sigma model at finite temperature. The effective mesonic potential is numerically calculated using the -midpoint rule. The meson masses are investigated as functions of the temperature () at fi…xed value of baryonic chemical potential. The pressure and energy density are investigated as functions of temperature at fixed value of . The obtained results are in good agreement in comparison with other techniques. We conclude that the calculated effective potential successfully predicts the meson properties and thermodynamic properties at finite baryonic chemical potential. M. Abu-Shady Copyright © 2014 M. Abu-Shady. All rights reserved. Estimating the Cation Distributions in Ferrites Using X-Ray, FT-IR, and Magnetization Measurements Tue, 04 Mar 2014 13:04:56 +0000 The fundamental requirements for the shift of critical frequency to microwave frequencies are smaller grains with single domain, high resistivity, high saturation magnetization, moderate permeability, moderate magnetic anisotropy, and low spin relaxation time. With these guidelines an attempt to produce high performance ferrite for high frequency applications the present work aimed to synthesize cobalt substituted Ni-Zn ferrites using sol-gel method. Investigation of effects of cobalt on crystallite size, saturation magnetization, initial permeability, magnetic anisotropy, and spin relaxation time reveals the suitability of these materials for high frequency applications. Further in this paper cat ion distribution was proposed from the basis of variations in these properties. The results of this paper are thus useful to tailor the properties apt for high frequency applications. M. Chaitanya Varma, GSVRK Choudary, A. Mahesh Kumar, and K. H. Rao Copyright © 2014 M. Chaitanya Varma et al. All rights reserved. Structural and Optical Properties of Germanium Thin Films Prepared by the Vacuum Evaporation Technique Mon, 17 Feb 2014 08:55:44 +0000 Germanium (Ge) thin films have been deposited onto the glass substrates by the vacuum evaporation technique. The effect of annealing temperature on the structural and optical properties of the germanium thin films was investigated. The structural and optical properties of thin films were characterized by XRD, SEM, and UV-Vis techniques. XRD results showed that the structure of the deposited thin films changed from amorphous phase for the films, which deposited at room temperature, to crystalline phase for the films, which deposited at high temperature. Optimum temperature to obtain a good crystalline structure was 525°C. The SEM image also showed that the crystallization of the thin films is increased with increasing of annealing temperature. Transmittance and reflectance spectral were used to calculate the absorption coefficient. Two absorption edges in two spectral regions were distinguished according to direct and indirect electron transitions. Energy band gap was calculated by using the Tauc relationship for both direct and indirect electron transitions. The average value of was equal to 0.79 eV and 0.61 eV for direct and indirect transitions, respectively. Z. Al-Sharafi, S. Mohyeddine, Samir Osman Mohammed, and R. M. Kershi Copyright © 2014 Z. Al-Sharafi et al. All rights reserved. Magnetohydrodynamic Boundary Layer Flow of Nanofluid over an Exponentially Stretching Permeable Sheet Wed, 08 Jan 2014 07:51:52 +0000 A mathematical model of the steady boundary layer flow of nanofluid due to an exponentially permeable stretching sheet with external magnetic field is presented. In the model, the effects of Brownian motion and thermophoresis on heat transfer and nanoparticle volume friction are considered. Using shooting technique with fourth-order Runge-Kutta method the transformed equations are solved. The study reveals that the governing parameters, namely, the magnetic parameter, the wall mass transfer parameter, the Prandtl number, the Lewis number, Brownian motion parameter, and thermophoresis parameter, have major effects on the flow field, the heat transfer, and the nanoparticle volume fraction. The magnetic field makes enhancement in temperature and nanoparticle volume fraction, whereas the wall mass transfer through the porous sheet causes reduction of both. For the Brownian motion, the temperature increases and the nanoparticle volume fraction decreases. Heat transfer rate becomes low with increase of Lewis number. For thermophoresis effect, the thermal boundary layer thickness becomes larger. Krishnendu Bhattacharyya and G. C. Layek Copyright © 2014 Krishnendu Bhattacharyya and G. C. Layek. All rights reserved. Preparation, Characterization, and Luminescence Properties of Orthorhombic Sodium Sulphate Tue, 24 Dec 2013 11:15:39 +0000 A highly efficient thermoluminescence Na2SO4 phosphor with thenardite polymorphic structure was prepared by simple slow evaporation technique followed by subsequent calcination at 200°C, 400°C, and 600°C for 4 h and the resultant crystals were characterized by various analytical techniques. All the samples exhibited thermodynamically stable thenardite phase and the grain growth was increased for the calcined samples. SEM analysis indicated the fine distribution of twinned orthogonal prism and pyramidal structure without any agglomeration. The electron spin resonance spectroscopy showed the existence of radicals as trap centre. The thermoluminescence behavior suggested the charge carrier recombination dynamics in the thenardite sample followed second-order kinetics. The trapping parameters such as activation energy (), order of kinetics (), and frequency factor () have been determined using Chen’s peak shape method. Further fading of the TL intensity of Na2SO4 showed that thenardite is quite suitable for radiation dosimetry even up to 15 days. The photoluminescence band of Na2SO4 reduced in its intensity after γ-irradiation, suggesting that defects are unstable and decay rapidly. Y. S. Vidya and B. N. Lakshminarasappa Copyright © 2013 Y. S. Vidya and B. N. Lakshminarasappa. All rights reserved. Molecular Tomography of the Quantum State by Time-Resolved Electron Diffraction Mon, 23 Dec 2013 09:40:53 +0000 A procedure is described that can be used to reconstruct the quantum state of a molecular ensemble from time-dependent internuclear probability density functions determined by time-resolved electron diffraction. The procedure makes use of established techniques for evaluating the density matrix and the phase-space joint probability density, that is, the Wigner function. A novel expression for describing electron diffraction intensities in terms of the Wigner function is presented. An approximate variant of the method, neglecting the off-diagonal elements of the density matrix, was tested by analyzing gas electron diffraction data for N2 in a Boltzmann distribution and TRED data obtained from the 193 nm photodissociation of CS2 to carbon monosulfide, CS, at 20, 40, and 120 ns after irradiation. The coherent changes in the nuclear subsystem by time-resolved electron diffraction method determine the fundamental transition from the standard kinetics to the dynamics of the phase trajectory of the molecule and the tomography of molecular quantum state. A. A. Ischenko Copyright © 2013 A. A. Ischenko. All rights reserved. Reconciliating the Vertical and Horizontal Gradients of the Sunspot Magnetic Field Mon, 23 Dec 2013 08:26:43 +0000 In the literature, we found 15 references showing that the sunspot photospheric magnetic field vertical gradient is on the order of 3-4 G/km, with field strength decreasing with height, whereas the horizontal gradient is nine times weaker on the order of 0.4-0.5 G/km. This is confirmed by our recent THEMIS observations. As a consequence, the vanishing of is not realized. In other words, a loss of magnetic flux is observed with increasing height, which is not compensated for by an increase of the horizontal flux. We show that the lack of spatial resolution, vertical as well as horizontal, cannot be held responsible for the nonvanishing observed . The present paper is devoted to the investigation of this problem. We investigate how the magnetic field is influenced by the plasma anisotropy due to the stratification, which is responsible for an “aspect ratio” between horizontal and vertical typical lengths. On the example of our THEMIS observations, made of two spectral lines formed at two different depths, which enables the retrieval of the three components entering , it is shown that once this aspect ratio is applied, the rescaled vanishes, which suggests a new methodology for MHD modeling in the photosphere. Véronique Bommier Copyright © 2013 Véronique Bommier. All rights reserved. Analytical Approach to Model and Diagnostic Distribution of Dopant in an Implanted-Heterojunction Rectifier Accounting for Mechanical Stress Thu, 05 Sep 2013 08:10:04 +0000 We calculate spatiotemporal distributions of dopant in an implanted-heterojunction rectifier. We analyzed the influence of inhomogeneity of heterostructure on dopant distribution. The influence of radiation processing of materials of the heterostructure, which has been done during ion implantation, on properties of the heterostructure has been also analyzed. It has been shown that radiation processing of materials of heterostructure leads to a decrease in mechanical stress in heterostructure. Our calculations have been done by using analytical approach, which gives us the possibility to obtain all results without joining solutions on all interfaces of heterostructure. E. L. Pankratov and E. A. Bulaeva Copyright © 2013 E. L. Pankratov and E. A. Bulaeva. All rights reserved. A Sturm-Liouville Problem with a Discontinuous Coefficient and Containing an Eigenparameter in the Boundary Condition Sun, 01 Sep 2013 11:12:20 +0000 We study a Sturm-Liouville operator with eigenparameter-dependent boundary conditions and transmission conditions at two interior points. We give an operator-theoretic formulation, construct fundamental solutions, investigate some properties of the eigenvalues and corresponding eigenfunctions of the discontinuous Sturm-Liouville problem and then obtain asymptotic formulas for the eigenvalues and eigenfunctions and find Green function of the discontinuous Sturm-Liouville problem. Erdoğan Şen Copyright © 2013 Erdoğan Şen. All rights reserved. Luminescence Studies of Eu3+ Doped Calcium Bromofluoride Phosphor Tue, 20 Aug 2013 08:12:12 +0000 The present paper reports photoluminescence (PL) and thermoluminescence (TL) properties of rare earth-doped calcium bromo-fluoride phosphor. The europium (Eu3+) was used as rare earth dopant. The phosphor was prepared by Solid state reaction method (conventional method). The PL emission spectrum of the prepared phosphor shows intense peaks in the red region at 611 nm for 5D0→7F2 transitions, and the PL excitation spectra show a broad band located around 220–400 nm for the emission wavelength fixed at 470 nm. The TL studies were carried out after irradiating the phosphor by UV rays with different exposure time. The glow peak shows second-order kinetics. The present phosphor can act as host for red light emission in display devices. Jagjeet Kaur, Yogita Parganiha, and Vikas Dubey Copyright © 2013 Jagjeet Kaur et al. All rights reserved. Self-Consistent Green Function Method in Nuclear Matter Tue, 16 Jul 2013 15:27:08 +0000 Symmetric nuclear matter is studied within the Brueckner-Hartree-Fock (BHF) approach and is extending to the self-consistent Green’s function (SCGF) approach. Both approximations are based on realistic nucleon-nucleon interaction; that is, CD-Bonn potential is chosen. The single-particle energy and the equation of state (EOS) are studied. The Fermi energy at the saturation point fulfills the Hugenholtz-Van Hove theorem. In comparison to the BHF approach, the binding energy is reduced and the EOS is stiffer. Both the SCGF and BHF approaches do not reproduce the correct saturation point. A simple contact interaction should be added to SCGF and BHF approaches to reproduce the empirical saturation point. Khaled S. A. Hassaneen Copyright © 2013 Khaled S. A. Hassaneen. All rights reserved. Effect of Electrohydraulic Discharge on Viscosity of Human Blood Sun, 07 Jul 2013 08:43:21 +0000 Electrohydraulic plasma discharge is a novel technology with high efficiency and high speed and can generate chemically active species like free radicals, ions, atoms, and metastables, accompanied by ultraviolet light emission and shock pressure waves. The aim of this work is to examine the effect of electrohydraulic discharge (EHD) system on viscosity of the human blood after different exposure time. The voltage pulsation introduces electric field and temperature jump and at the same time leads to haemolysis of the blood cells. The ratio of blood viscosity under the influence of magnetic field to the viscosity in the absence of magnetic field is directly proportional to the applied magnetic field . G. M. El-Aragi Copyright © 2013 G. M. El-Aragi. All rights reserved. Applicability of Different Isothermal EOS at Nanomaterials Mon, 17 Jun 2013 15:46:04 +0000 The present study explains the behaviour of nanomaterials such as AlN, CdSe, Ge, WC, and Ni- and Fe-filled-MWCNTs under high pressure. Among the number of isothermal EOSs available, we prefer only two parameter-based isothermal equations (i.e., Murnaghan equation, usual Tait's equation, Suzuki equation and Shanker equation). The present work shows the theoretical study of thermo-elastic properties especially relative compression (), isothermal bulk modulus (), and compressibility () of nanomaterials. After comparing all formulations with available experimental data, we conclude that pressure dependence of relative compression () for the nanomaterials, are in good agreement for all the equations at lower pressure range. At higher pressure range, Suzuki and Shanker formulations show some deviation from experimental values. Deepika P. Joshi and Anjali Senger Copyright © 2013 Deepika P. Joshi and Anjali Senger. All rights reserved. Renormalisation Group Analysis of Turbulent Hydrodynamics Wed, 12 Jun 2013 13:50:54 +0000 Turbulent hydrodynamics is characterised by universal scaling properties of its structure functions. The basic framework for investigations of these functions has been set by Kolmogorov in 1941. His predictions for the scaling exponents, however, deviate from the numbers found in experiments and numerical simulations. It is a challenge for theoretical physics to derive these deviations on the basis of the Navier-Stokes equations. The renormalization group is believed to be a very promising tool for the analysis of turbulent systems, but a derivation of the scaling properties of the structure functions has so far not been achieved. In this work, we recall the problems involved, present an approach in the framework of the exact renormalisation group to overcome them, and present first numerical results. Dirk Barbi and Gernot Münster Copyright © 2013 Dirk Barbi and Gernot Münster. All rights reserved. Scale-Free Networks with the Same Degree Distribution: Different Structural Properties Wed, 29 May 2013 08:34:17 +0000 We have analysed some structural properties of scale-free networks with the same degree distribution. Departing from a degree distribution obtained from the Barabási-Albert (BA) algorithm, networks were generated using four additional different algorithms (Molloy-Reed, Kalisky, and two new models named A and B) besides the BA algorithm itself. For each network, we have calculated the following structural measures: average degree of the nearest neighbours, central point dominance, clustering coefficient, the Pearson correlation coefficient, and global efficiency. We found that different networks with the same degree distribution may have distinct structural properties. In particular, model B generates decentralized networks with a larger number of components, a smaller giant component size, and a low global efficiency when compared to the other algorithms, especially compared to the centralized BA networks that have all vertices in a single component, with a medium to high global efficiency. The other three models generate networks with intermediate characteristics between B and BA models. A consequence of this finding is that the dynamics of different phenomena on these networks may differ considerably. José H. H. Grisi-Filho, Raul Ossada, Fernando Ferreira, and Marcos Amaku Copyright © 2013 José H. H. Grisi-Filho et al. All rights reserved. Semiclassical Modeling of Isotropic Non-Heisenberg Magnets for Spin and Linear Quadrupole Excitation Dynamics Wed, 27 Mar 2013 17:13:23 +0000 Equations describing one-dimensional non-Heisenberg model are studied by use of generalized coherent states in real parameterization, and then dissipative spin wave equation for dipole and quadrupole branches is obtained if there is a small linear excitation from the ground state. Finally, it is shown that for such exchange-isotropy Hamiltonians, optical branch of spin wave is nondissipative. Yousef Yousefi and Khikmat Kh. Muminov Copyright © 2013 Yousef Yousefi and Khikmat Kh. Muminov. All rights reserved. Advances in Novel Optical Materials and Devices Thu, 14 Mar 2013 11:54:00 +0000 Michael R. Gleeson, Yasuo Tomita, Sergi Gallego, and Robert McLeod Copyright © 2013 Michael R. Gleeson et al. All rights reserved. On the Divergenceless Property of the Magnetic Induction Field Mon, 25 Feb 2013 07:46:44 +0000 Maxwell's equations beautifully describe the electromagnetic fields properties. In what follows we will be interested in giving a new perspective to divergence-free Maxwell’s equations regarding the magnetic induction field: . To this end we will consider some physical aspects of a system consisting of massive nonrelativistic charged particles, as sources of an electromagnetic field (e.m.) propagating in free space. In particular the link between conservation of total momentum and divergence-free condition for the magnetic induction field will be deeply investigated. This study presents a new context in which the necessary condition for the divergence-free property of the magnetic induction field in the whole space, known as solenoidality condition, directly comes from the conservation of total momentum for the system, that is, sources and field. This work, in general, leads to results that leave some open questions on the existence, or at least the observability, of magnetic monopoles, theoretically plausible only under suitable symmetry assumptions as we will show. Sergio Severini and Alessandro Settimi Copyright © 2013 Sergio Severini and Alessandro Settimi. All rights reserved. A Minireview of the Natures of Radiation-Induced Point Defects in Pure and Doped Silica Glasses and Their Visible/Near-IR Absorption Bands, with Emphasis on Self-Trapped Holes and How They Can Be Controlled Wed, 13 Feb 2013 10:15:50 +0000 The natures of most radiation-induced point defects in amorphous silicon dioxide (a-SiO2) are well known on the basis of 56 years of electron spin resonance (ESR) and optical studies of pure and doped silica glass in bulk, thin-film, and fiber-optic forms. Many of the radiation-induced defects intrinsic to pure and B-, Al-, Ge-, and P-doped silicas are at least briefly described here and references are provided to allow the reader to learn still more about these, as well as some of those defects not mentioned. The metastable self-trapped holes (STHs), intrinsic to both doped and undoped silicas, are argued here to be responsible for most transient red/near-IR optical absorption bands induced in low-OH silica-based optical fibers by ionizing radiations at ambient temperatures. However, accelerated testing of a-SiO2-based optical devices slated for space applications must take into account the highly supralinear dependence on ionizing-dose-rate of the initial STH creation rate, which if not recognized would lead to false negatives. Fortunately, however, it is possible to permanently reduce the numbers of environmentally or operationally created STHs by long-term preirradiation at relatively low dose rates. Finally, emphasis is placed on the importance and utility of rigorously derived fractal-kinetic formalisms that facilitate reliable extrapolation of radiation-induced optical attenuations in silica-based photonics recorded as functions of dose rate backward into time domains unreachable in practical laboratory times and forward into dose-rate regimes for which there are no present-day laboratory sources. David L. Griscom Copyright © 2013 David L. Griscom. All rights reserved. A New Technology for Fast Two-Dimensional Detection of Proton Therapy Beams Sun, 30 Dec 2012 12:45:40 +0000 The Micromesh Gaseous Structure, or Micromegas, is a technology developed for high count-rate applications in high-energy physics experiments. Tests using a Micromegas chamber and specially designed amplifiers and readout electronics adapted to the requirements of the proton therapy environment and providing both excellent time and high spatial resolution are presented here. The device was irradiated at the Roberts Proton Therapy Center at the University of Pennsylvania. The system was operated with ionization gains between 10 and 200 and in low and intermediate dose-rate beams, and the digitized signal is found to be reproducible to 0.8%. Spatial resolution is determined to be 1.1 mm (1σ) with a 1 ms time resolution. We resolve the range modulator wheel rotational frequency and the thicknesses of its segments and show that this information can be quickly measured owing to the high time resolution of the system. Systems of this type will be extremely useful in future treatment methods involving beams that change rapidly in time and spatial position. The Micromegas design resolves the high dose rate within a proton Bragg peak, and measurements agree with Geant4 simulations to within 5%. Robert Hollebeek, Mitch Newcomer, Godwin Mayers, Brian Delgado, Gaurav Shukla, Richard Maughan, and Derek Dolney Copyright © 2012 Robert Hollebeek et al. All rights reserved. Nonlinear Optics of Nanostructures Sun, 09 Dec 2012 14:27:16 +0000 Vladimir I. Gavrilenko, Tatiana V. Murzina, and Goro Mizutani Copyright © 2012 Vladimir I. Gavrilenko et al. All rights reserved. Modeling of Optical Nanoantennas Thu, 08 Nov 2012 09:40:16 +0000 The optical properties of plasmonic nanoantennas are investigated in detail using the finite integration technique (FIT). The validity of this technique is verified by comparison to the exact solution generalized Mie method (GMM). The influence of the geometrical parameters (antenna length, gap dimension, and shapes) on the antenna field enhancement and spectral response is discussed. Localized surface plasmon resonances of Au (gold) dimers nanospheres, bowtie, and aperture bowtie nanoantennas are modeled. The enhanced field is equivalent to a strong light spot which can lead to the resolution improvement of the microscopy and optical lithography, thus increasing the optical data storage capacity. Furthermore, the sensitivity of the antennas to index changes of the environment and substrate is investigated in detail for biosensing applications. We confirm that our approach yields an exact correspondence with GMM theory for Au dimers nanospheres at gap dimensions 5 nm and 10 nm but gives an approximation error of less than 1.37% for gap dimensions 1 nm and 2 nm with diameters approaching 80 nm. In addition, the far-field characteristics of the aperture bowtie nanoantenna such as directivity and gain are studied. The promising results of this study may have useful potential applications in near-field sample detection, optical microscopy, and so forth. Bedir B. Yousif and Ahmed S. Samra Copyright © 2012 Bedir B. Yousif and Ahmed S. Samra. All rights reserved. Quantitative Comparison of Five Different Photosensitizers for Use in a Photopolymer Wed, 12 Sep 2012 11:18:07 +0000 Several studies of the time varying photon absorption effects, which occur during the photoinitiation process involving in photopolymer materials, have been presented. Three primary mechanisms have been identified: (i) the dye absorption, (ii) recovery, and (iii) bleaching. Based on an analysis of these mechanisms, the production of primary radicals can be physically described and modelled. In free radical photopolymerization systems, the excited dye molecules induce the production of the primary radicals, 𝑅•, which are key in determining how many monomers are polymerized. This, in turn, is closely related to the refractive index modulation formed during holographic recording. In this paper, to avoid the complexities involved in estimating the rate constant of intersystem crossing, 𝑘𝑠𝑡, in going from the excited singlet state dye to the excited triplet state dye, we introduce two rates, 𝑘𝑎𝑆 and 𝑘𝑎𝑇 these are the proposed rate constants of photon absorption in going from the ground state to the singlet and triplet states, respectively. Using the resulting model, four kinds of Xanthene dyes: Erythrosin B; Eosin Y; Phloxine B, Rose Bengal, and one Thiazine dye: Methylene Blue, are experimentally characterised for use in an AA/PVA photopolymer. Yue Qi, Michael R. Gleeson, Jinxin Guo, Sergi Gallego, and John T. Sheridan Copyright © 2012 Yue Qi et al. All rights reserved. Coaxial Self-Trapping of White and Gray Regions of an Incandescent Field: A Bright Core with a Dark Cladding Sun, 09 Sep 2012 16:06:36 +0000 We report the generation of a self-trapped incoherent hybrid beam comprising a dark-sheathed bright core. The hybrid beam originates from refractive index changes in a photocrosslinkable organosiloxane, which allow simultaneous and cooperative self-trapping of a gray ring with a white core embedded in a broad incandescent beam. The core narrowed and increased in intensity while the encircling gray ring decreased in intensity until rendered very dark. This dark sheath improves light confinement in the bright core and protects it from interactions with nearby self-trapped filaments. This is the first example of a self-trapped hybrid beam, which is moreover spatially and temporally incoherent. Kailash Kasala and Kalaichelvi Saravanamuttu Copyright © 2012 Kailash Kasala and Kalaichelvi Saravanamuttu. All rights reserved. Development of Laser-Produced Tin Plasma-Based EUV Light Source Technology for HVM EUV Lithography Wed, 05 Sep 2012 15:49:54 +0000 Since 2002, we have been developing a carbon dioxide (CO2) laser-produced tin (Sn) plasma (LPP) extreme ultraviolet (EUV) light source, which is the most promising solution because of the 13.5 nm wavelength high power (>200 W) light source for high volume manufacturing. EUV lithography is used for its high efficiency, power scalability, and spatial freedom around plasma. We believe that the LPP scheme is the most feasible candidate for the EUV light source for industrial use. We have several engineering data from our test tools, which include 93% Sn ionization rate, 98% Sn debris mitigation by a magnetic field, and 68% CO2 laser energy absorption rate. The way of dispersion of Sn by prepulse laser is key to improve conversion efficiency (CE). We focus on prepulsed laser pulsed duration. When we have optimized pulse duration from nanosecond to picosecond, we have obtained maximum 4.7% CE (CO2 laser to EUV; our previous data was 3.8%) at 2 mJ EUV pulse energy. Based on these data we are developing our first light source as our product: “GL200E.” The latest data and the overview of EUV light source for the industrial EUV lithography are reviewed in this paper. Junichi Fujimoto, Tsukasa Hori, Tatsuya Yanagida, and Hakaru Mizoguchi Copyright © 2012 Junichi Fujimoto et al. All rights reserved. Length Bidisperse Carbon Nanotubes Dispersions in Thermotropic Liquid Crystals Wed, 29 Aug 2012 13:53:57 +0000 We study nematic liquid crystal driven alignment of carbon nanotubes dispersed in them. We extend the mesoscopic model presented in (P. Van der Schoot et al. 2008, V. Popa-Nita, and S. Kralj 2010) including the effect of length bidispersity of carbon nanotubes. The free energy of the mixture is written as the sum of the Doi free energy for lyotropic nematic ordering of the two carbon nanotubes types, the Landau-de Gennes free energy for the thermotropic ordering of liquid crystal, and the coupling term between liquid crystal molecules and carbon nanotubes. The phase ordering of the mixtures is analyzed as a function of volume fraction, the strength of coupling, and the temperature. V. Popa-Nita and S. Buček Copyright © 2012 V. Popa-Nita and S. Buček. All rights reserved. Design and Analysis of a THz Metamaterial Structure with High Refractive Index at Two Frequencies Thu, 23 Aug 2012 17:42:17 +0000 The concept of a single frequency band, single high-refractive-index metamaterial has been extended and applied in the design of dual frequency band, dual high-refractive-index metamaterials in the THz regime. The structure design consists of twenty five unit cells with a surface area of 250 um by 250 um and a thickness of 5 um. Each cell has metallic structures embedded in a polyimide substrate. The return loss (S-parameter) analysis shows two strong electric responses at two frequency ranges, and the extracted constitutive parameters suggested high values of simultaneous dielectric constant and permeability at these frequencies. Results retrieved from the S-parameters also show high refractive index values. A first peak refractive index of 61.83 was observed at a resonant frequency of 0.384 THz, and another peak refractive index of 19.2 was observed at the resonant frequency 1.416 THz. Analysis show that higher refractive index at the second resonance frequency band is achievable through redesign of the structures, and modifications could lead to a single structure with multiple frequency, multiple high-refractive-index metamaterials that can be put to practical use. Zan Lu, Bruno Camps-Raga, and N. E. Islam Copyright © 2012 Zan Lu et al. All rights reserved. Closed-Aperture Z-Scan Analysis for Nonlinear Media with Saturable Absorption and Simultaneous Third- and Fifth-Order Nonlinear Refraction Tue, 07 Aug 2012 09:06:21 +0000 We present a theory of open- and closed-aperture Gaussian beam Z-scan for nonlinear optical materials with saturable absorption and high-order nonlinear refraction. We show that an approximate expression for a transmitted intensity through the nonlinear optical material is possible by means of the Adomian’s decomposition method and the thin film approximation. The theory is applied to semiconductor CdSe quantum dot-polymer nanocomposite films. It is shown that the theory well explains measured results of open- and closed-aperture transmittances in the Z-scan setup. It is also shown that the nanocomposite film possesses simultaneous third- and fifth-order nonlinear refraction as well as saturable absorption of a homogeneously broadened type. Xiangming Liu and Yasuo Tomita Copyright © 2012 Xiangming Liu and Yasuo Tomita. All rights reserved. Zero Spatial Frequency Limit: Method to Characterize Photopolymers as Optical Recording Material Thu, 19 Jul 2012 09:43:54 +0000 Photopolymers are useful for different holographic applications such as holographic data storage or diffractive optical elements. However, due to the presence of two different phenomena, polymer formation and monomer diffusion, it is difficult to characterize each parameter independently. We propose a direct method based on zero spatial frequency recording, to eliminate the diffusion influence, and on interferometric techniques, both in transmission and in reflection, to obtain quantitative values of shrinkage, polymerization rate, polymer refractive index and relation between intensity and polymerization, and so forth, This method has been implemented in the Holography and Optical Processing Group from the University of Alicante to characterize different photopolymers. In this paper, we present a compilation of the results obtained with this method for different photopolymers and we compare their characteristics. Sergi Gallego, Andrés Márquez, Manuel Ortuño, Cristian Neipp, Inmaculada Pascual, and Augusto Beléndez Copyright © 2012 Sergi Gallego et al. All rights reserved. Advanced Magnetic Materials Mon, 09 Jul 2012 14:59:32 +0000 Arcady Zhukov, Mitsuteru Inoue, Manh-Huong Phan, and Vladimir Shavrov Copyright © 2012 Arcady Zhukov et al. All rights reserved.