Dispersion features of two-dimensional phononic crystal with rotating square rods

Bu çalışmada, bir kare örgülü hava matrisinde yer alan kare şekilli saçılardan oluşan iki boyutlu fononik kristallerin bant yapısı çalışıldı. Bant yapısı hesaplamaları için, bir hava matrisindeki kare LiNbO3 çubuklarından oluşan iki boyutlu bir fononik kristal dikkate alındı. Kare çubukların yönelimlerinin akustik bant aralıkları üzerindeki etkisi, iletim kaybı spektrumları, basınç alanı haritası ve dağılım ilişkileri sonlu elemanlar yöntemi ve Bloch teoremi kullanılarak hesaplandı. Bu yapı için maksimum bant aralığı 45° dönme açısında bulundu. Sayısal sonuçlar, bant aralıklarının kare çubukların dönüş açısını değiştirerek ayarlanabileceğini göstermektedir.In the present work, band structures of two-dimensional phononic crystals (PC) composed of squareshaped scaters in an air matrix with a square lattice are investigated. A two-dimensional phononiccrystal consisting of square LiNbO3 rods in an air matrix is considered for band structure calculations. Effects of orientations of square rods on the acoustic band gaps, transmission loss spectra, pressure field map and dispersion relations are calculated using the finite element method and Bloch theorem. The maximum acoustic band gaps for this structure is found at the rotation angle of 45°. The numerical results show that the band gaps can be tuned by changing the rotation angle of the square rods

Visible spectroscopy of 5CB/8CB liquid crystals

WOS: 000368610600004Electro-optical properties of nematic liquid crystals (LCs) have attracted a great deal of research interest and have resulted in a number of practical applications in many areas. In the present study, wavelength dependence of electro-optical properties of two different types of nematic LCs and their binary mixtures are investigated. LCs used in this study are 5CB and 8CB and their mixtures in different proportions. The optical transmittance of the structures has been studied by means of visible spectroscopy by measuring the transmitted light intensity as a function of the wavelength under various driving AC electric field values. Experiments were carried out at the wavelength interval 380-780 nm at a constant temperature of 25 degrees C in order to see the effect of the applied field alone

Comparative QSTR Study Using Semi-Empirical and First Principle Methods Based Descriptors for Acute Toxicity of Diverse Organic Compounds to the Fathead Minnow

Abstract: Several quantum-mechanics-based descriptors were derived for a diverse set of 48 organic compounds using AM1, PM3, HF/6-31+G, and DFT-B3LYP/6-31+G (d) level of the theory. LC50 values of acute toxicity of the compounds were correlated to the fathead minnow and predicted using calculated descriptors by employing Comprehensive Descriptors for Structural and Statistical Analysis (CODESSA) program. The heuristic method, implemented in the CODESSA program for selecting the ‘best ’ regression model, was applied to a pre-selection of the most-representative descriptors by sequentially eliminating descriptors that did not satisfy a certain level of statistical criterion. First model, statistically, the most significant one has been drawn up with the help of DFT calculations in which the squared correlation coefficient R 2 is 0.85, and the squared cross-validation 2 correlation coefficient R CV is 0.79. Second model, which has been drawn up with the help of HF calculations, has its statistical quality very close to the DFT-based one and in this model value of R 2 2 is 0.84 and that of R CV is 0.78. Third and fourth models have been drawn up with the help of AM1 and PM3 calculations, respectively. The values of R 2 and 2 RCV in the third case are correspondingly 0.79 and 0.66, whereas in the fourth case they are 0.78 and 0.65 respectively. Results of this study clearly demonstrate that for the calculations o

Imaging Method Based on Attenuation, Refraction and Ultra-Small-Angle-Scattering of X-Rays

A method for detecting an image of an object by measuring the intensity at a plurality of positions of a transmitted beam of x-ray radiation emitted from the object as a function of angle within the transmitted beam. The intensity measurements of the transmitted beam are obtained by a crystal analyzer positioned at a plurality of angular positions. The plurality of intensity measurements are used to determine the angular intensity spectrum of the transmitted beam. One or more parameters, such as an attenuation property, a refraction property and a scatter property, can be obtained from the angular intensity spectrum and used to display an image of the object.Sponsorship: Illinois Institute of TechnologyUnited States Paten

A DFT-Based QSARs study of Acetazolamide/Sulfanilamide derivatives with carbonic anhydrase (CA-II) isozyme inhibitory activity

Abstract: This study presents Quantitative Structure Activity Relationships (QSAR) study on a pool of 18 bio-active sulfonamide compounds which includes five acetazolamide derivatives, eight sulfanilamide derivatives and five clinically used sulfonamides molecules as drugs namely acetazolamide, methazolamide, dichlorophenamide, ethoxolamide and dorzolamide. For all the compounds, initial geometry optimizations were carried out with a molecular mechanics (MM) method using the MM+ force fields. The lowest energy conformations of the compounds obtained by the MM method were further optimized by the Density Functional Theory (DFT) method by employing Becke’s three-parameter hybrid functional (B3LYP) and 6-31G (d) basis set. Molecular descriptors, dipole moment, electronegativity, total energy at 0 K, entropy at 298 K, HOMO and LUMO energies obtained from DFT calculations provide valuable information and have a significant role in the assessment of carbonic anhydrase (CA-II) inhibitory activity of the compounds. By using the multiple linear regression technique several QSAR models have been drown up with the help these calculated descriptors and carbonic anhydrase (CA-II) inhibitory data of the molecules. Among the obtained QSAR models presented in the study, statistically the mos

A DFT-Based QSARs Study of Acetazolamide/Sulfanilamide Derivatives with Carbonic Anhydrase (CA-II) Isozyme Inhibitory Activity

This study presents Quantitative Structure Activity Relationships (QSAR) studyon a pool of 18 bio-active sulfonamide compounds which includes five acetazolamidederivatives, eight sulfanilamide derivatives and five clinically used sulfonamides moleculesas drugs namely acetazolamide, methazolamide, dichlorophenamide, ethoxolamide anddorzolamide. For all the compounds, initial geometry optimizations were carried out with amolecular mechanics (MM) method using the MM force fields. The lowest energyconformations of the compounds obtained by the MM method were further optimized by theDensity Functional Theory (DFT) method by employing Becke’s three-parameter hybridfunctional (B3LYP) and 6-31G (d) basis set. Molecular descriptors, dipole moment,electronegativity, total energy at 0 K, entropy at 298 K, HOMO and LUMO energiesobtained from DFT calculations provide valuable information and have a significant role inthe assessment of carbonic anhydrase (CA-II) inhibitory activity of the compounds. By usingthe multiple linear regression technique several QSAR models have been drown up with thehelp these calculated descriptors and carbonic anhydrase (CA-II) inhibitory data of themolecules. Among the obtained QSAR models presented in the study, statistically the mostsignificant one is a five parameters linear equation with the squared correlation coefficient R2 values of ca. 0.94 and the squared cross-validated correlation coefficient R2CV values of ca. 0.85. The results were discussed in the light of the main factors that influence theinhibitory activity of the carbonic anhydrase (CA-II) isozyme

Ferroelectrics, 483 (2015) 1-17.

The nonlinear optical properties and electro-optic effects of some oxygen-octahedra ferroelectrics are studied by the density functional theory (DFT) in the local density approximation (LDA) expressions based on first principle calculations without the scissor approximation. We present calculations of the frequency- dependent complex dielectric function ? ? v and the second harmonic generation response coefficient x? ?2 ? ? ¡ 2v; v; v over a large frequency range in tetragonal and rhombohedral phases. The electronic linear electro-optic susceptibility x? ?2 ? ? ¡ v; v; 0 is also evaluated below the band gap. These results are based on a series of the LDA calculation using DFT. The results for x? ?2 ? ? ¡ v; v; 0 are in agreement with the experiment below the band gap and those for x? ?2 ? ? ¡ 2v; v; v are compared with the experimental data where available

Preliminary investigation of a multiple-image radiography method

Conventional radiography seeks to produce, at each location in the image plane, a measure of the x-ray absorption of the object. In this paper, we present a method of determining a much more complete object description at each point, namely the intensity distribution (as a function of angle) of the emerging x-ray beam. From this distribution one can compute many different images, depicting the refraction, absorption, and scattering characteristics of the object. The method is based on acquisition of multiple x-ray images using monochromator and analyzer crystals, followed by a deconvolution operation (over angle) at each pixel. Parameters of the deconvolved angular intensity function are measured to obtain the various images of interest. We present experimental results obtained using x-rays produced by a synchrotron, along with simulated images showing the effect of noise in a hypothetical photonlimited imaging situation. 1