CALCULATION OF THE STRUCTURE OF THE S1(0) AND S1(0)+S1(0) LINES IN THE INFRARED SPECTRUM OF SOLID HYDROGEN

1962 ◽  
Vol 40 (10) ◽  
pp. 1461-1479 ◽  
Author(s):  
H. P. Gush ◽  
J. Van Kranendonk
Keyword(s):  
Lattice Structure ◽  
Hexagonal Lattice ◽  
Solid Hydrogen ◽  
Absorption Feature ◽  
Lattice Vibrations ◽  
Doublet Structure ◽  
Rotational Motions ◽  
Experimental Values ◽  
Best Fit ◽  
Para Molecule

At low ortho concentrations, the satellites appearing in the S1(0) infrared absorption feature of solid hydrogen arise from transitions in para molecules possessing one nearest-neighboring ortho molecule. The 15-fold degeneracy of the combination of the v = 1, J = 2 excited state of the para molecule and the v = 0, J = 1 ground state of the ortho molecule is partially lifted by the quadrupole–quadrupole interaction between the two molecules. The calculated structure of the S1(0) line is in good over-all agreement with the observed profile. The agreement is improved by taking into account the quadrupole–hexadecapole interaction. The best fit is obtained for a positive value of the hexadecapole moment of about 1.2 atomic units. The fine structure of the S1(0)+S1(0) line in the overtone region of pure parahydrogen, resulting from the splitting of the 25-fold degeneracy of the upper state by the combined quadrupole–quadrupole and quadrupole–hexadecapole interaction, is also calculated. The splitting and relative intensity of the two components of the resulting doublet structure are in close agreement with the experimental values. All the calculations are performed assuming a rigid close-packed hexagonal lattice structure. The discrepancy of about 20% between the theoretical values of the quadrupole moment of a hydrogen molecule in the v = 0 and v = 1 states and the empirical values deduced from the analysis of the S1(0) and S1(0)+S1(0) lines may be due to the neglect of the splittings arising from the coupling between the rotational motions of the molecules and the lattice vibrations.

Structural analysis of the photosynthetic membrane from Ectothiorhodospira halochloris

1983 ◽  
Vol 41 ◽  
pp. 740-741
Author(s):  
H. Engelhardt ◽  
R. Guckenberger ◽  
W. Baumeister
Keyword(s):  
Lattice Structure ◽  
Bacterial Species ◽  
Hexagonal Lattice ◽  
Reaction Centre ◽  
Photosynthetic Membrane ◽  
Rhodopseudomonas Viridis ◽  
Photosynthetic Membranes ◽  
Ectothiorhodospira Halochloris ◽  
Main Components

Bacterial photosynthetic membranes contain, apart from lipids and electron transport components, reaction centre (RC) and light harvesting (LH) polypeptides as the main components. The RC-LH complexes in Rhodopseudomonas viridis membranes are known since quite seme time to form a hexagonal lattice structure in vivo; hence this membrane attracted the particular attention of electron microscopists. Contrary to previous claims in the literature we found, however, that 2-D periodically organized photosynthetic membranes are not a unique feature of Rhodopseudomonas viridis. At least five bacterial species, all bacteriophyll b - containing, possess membranes with the RC-LH complexes regularly arrayed. All these membranes appear to have a similar lattice structure and fine-morphology. The lattice spacings of the Ectothiorhodospira haloohloris, Ectothiorhodospira abdelmalekii and Rhodopseudomonas viridis membranes are close to 13 nm, those of Thiocapsa pfennigii and Rhodopseudomonas sulfoviridis are slightly smaller (∼12.5 nm).

THEORY OF THE INTERACTION BETWEEN THE LATTICE VIBRATIONS AND THE ROTATIONAL MOTION IN SOLID HYDROGEN

1966 ◽  
Vol 44 (2) ◽  
pp. 313-335 ◽  
Author(s):  
J. Van Kranendonk ◽  
V. F. Sears
Keyword(s):  
Rotational Motion ◽  
Zero Point ◽  
Solid Hydrogen ◽  
The Self ◽  
Intermolecular Potential ◽  
Lattice Vibrations ◽  
Energy Effect ◽  
Self Energy ◽  
Blowing Up ◽  
Point Lattice

The effects of the interaction between the rotational motion of the molecules in solid hydrogen and the lattice vibrations, resulting from the anisotropic van der Waals forces, have been investigated theoretically. For the radial part of the anisotropic intermolecular potential an exp–6 model has been adopted. First, the effect of the lattice vibrations, and of the anistropic blowing up of the crystal by the zero-point lattice vibrations, is discussed. The effective anisotropic interaction resulting from averaging the instantaneous interaction over the lattice vibrations is calculated by assuming a Gaussian distribution for the modulation of the relative intermolecular separations by the lattice vibrations. Secondly, the displacement of the rotational levels due to the self-energy of the molecules in the lattice is calculated both classically and quantum mechanically, and the resulting shifts in the frequencies of the rotational transitions in solid hydrogen are given. Finally, the splitting of the rotational levels due to the anisotropy of the self-energy effect is calculated. The theory is applied to the calculation of the asymmetry of the S0(0) triplet in the rotational Raman spectrum of solid parahydrogen, and of the specific heat anomaly in solid hydrogen at low ortho-concentrations.

NUMERICAL ANALYSIS OF GUTs PREDICTIONS IN THE LIGHT OF RECENT RESULTS FROM LEP

1992 ◽  
Vol 07 (35) ◽  
pp. 3319-3330
Author(s):  
DARIUSZ GRECH
Keyword(s):  
Z Boson ◽  
Electromagnetic Coupling ◽  
Boson Mass ◽  
Threshold Effects ◽  
Coupling Constant ◽  
Central Values ◽  
Unified Theories ◽  
Proton Lifetime ◽  
Experimental Values ◽  
Best Fit

We find numerical best fit for sin 2 Θw(MZ), unifying mass MX and the proton lifetime τp as the outcome of analysis where experimental values of Z boson mass MZ, strong coupling constant αs(MZ) and electromagnetic coupling α0(MZ) are taken as the only input parameters. It is found that simple nonsupersymmetric models are unlikely to be realistic ones. On the other hand, we find the best numerical fit: sin 2Θw(MZ = 0.2330 ± 0.0007 (theor.) ± 0.0027 (exp.) , [Formula: see text] yr for supersymmetric unified theories with three generations. The central values require, however, that the supersymmetric mass Λs≲300 GeV . Possibilities of increasing this limit as well as cases with four generations and threshold effects are also discussed. Compact formulas for theoretical and experimental uncertainties involved in the analysis are also produced.

scholarly journals STUDIES ON AMPHIBIAN YOLK

1963 ◽  
Vol 18 (1) ◽  
pp. 135-151 ◽  
Author(s):  
Shuichi Karasaki
Keyword(s):  
Fine Particles ◽  
Lattice Structure ◽  
Hexagonal Lattice ◽  
Superficial Layer ◽  
Crystalline Lattice ◽  
Main Body ◽  
Embryonic Cells ◽  
Amphibian Species ◽  
Ca 50 ◽  
Band Spacing

The yolk platelets of mature eggs and young embryonic cells of all amphibian species studied (Rana pipiens, Triturus pyrrhogaster, Diemictylus viridescens, Rana nigromaculata, and Bufo vulgaris) have a superficial layer of fine particles or fibrils (ca. 50 A in diameter), a central main body with a crystalline lattice structure, and an enclosing membrane approximately 70 A in thickness. Electron micrographs of the main body reveal hexagonal net (spacing ca. 70 A), square net (spacing ca. 80 A), and parallel band (spacing from 35 to 100 A but most frequent at ca. 70 A) patterns. The crystalline structure is believed to be a simple hexagonal lattice made of closely packed cylindrical rods. Each rod is estimated to be about 80 A in diameter and 160 A in length.

scholarly journals Near- to mid-infrared spectroscopy of the heavily obscured AGN LEDA 1712304 with AKARI/IRC

2019 ◽  
Vol 626 ◽  
pp. A130
Author(s):  
T. Tsuchikawa ◽  
H. Kaneda ◽  
S. Oyabu ◽  
T. Kokusho ◽  
K. Morihana ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Spectral Properties ◽  
Spectral Energy Distribution ◽  
Galactic Nuclei ◽  
Spectral Energy ◽  
Absorption Feature ◽  
Distribution Fitting ◽  
Submillimeter Range ◽  
Spectral Fitting ◽  
Best Fit

Context. Although heavily obscured active galactic nuclei (AGNs) have been found by many observational studies, the properties of the surrounding dust are poorly understood. Using AKARI/IRC spectroscopy, we discovered a new heavily obscured AGN in LEDA 1712304 which shows a deep spectral absorption feature due to silicate dust. Aims. We study the infrared (IR) spectral properties of circumnuclear silicate dust in LEDA 1712304. Methods. We performed IR spectral fitting, considering silicate dust properties such as composition, porosity, size, and crystallinity. Spectral energy distribution fitting was also performed on the flux densities in the UV to submillimeter range to investigate the global spectral properties. Results. The best-fit model indicates 0.1 μm-sized porous amorphous olivine (Mg2xFe2−2xSiO4; x = 0.4) with 4% crystalline pyroxene. The optical depth is τsil ∼ 2.3, while the total IR luminosity and stellar mass are estimated to be LIR = (5 ± 1)×1010 L⊙ and Mstar = (2.7 ± 0.8)×109 M⊙, respectively. In such low LIR and Mstar ranges, there are few galaxies that show such a large τsil. Conclusion. The silicate dust in the AGN torus of LEDA 1712304 has properties that are notably similar to those in other AGNs overall, but slightly different in the wing shape of the absorption profile. The porosity of the silicate dust suggests dust coagulation or processing in the circumnuclear environments, while the crystallinity suggests that the silicate dust is relatively fresh.

Modification of kaolinite by controlled hydrothermal deuteration – a DRIFT spectroscopic study

Clay Minerals ◽  
2004 ◽  
Vol 39 (3) ◽  
pp. 349-362 ◽  
Author(s):  
Hui Ming
Keyword(s):  
Diffuse Reflectance ◽  
Near Infrared ◽  
Vibration Mode ◽  
Lattice Structure ◽  
Structural Defects ◽  
Hydroxyl Group ◽  
Isomorphous Substitution ◽  
Lattice Vibrations ◽  
Diffuse Reflectance Infrared ◽  
Hydroxyl Band

AbstractKaolinites were modified by controlled hydrothermal deuteration. Both infrared and near infrared vibration spectra of deuterated kaolinite were investigated by Diffuse Reflectance Infrared Fourier Transform spectroscopy. The stretching vibrations (v) of deuteroxyl groups of the kaolinite were observed at 2726, 2709, 2697 and 2667 cm-1, respectively. The overtone bands (2n) of the deuteroxyl groups were visible in NIR regions at 5454, 5419, 5388 and 5342 cm-1, respectively. The lattice vibrations of the kaolinite taking part in deuteration included 937, 915, 792, 751 and 690 cm-1 which are assigned to hydroxyl group-related deformation or translation-vibration mode. The hydroxyl band at 3435 cm-1 with its deuteroxyl band at 2542 cm-1 resulted from unevenly distributed structural defects, either due to the isomorphous substitution of foreign cations or the imperfections of the kaolinite lattice structure.

scholarly journals Structure of archaerhodopsin-2 at 1.8 Å resolution

2014 ◽  
Vol 70 (10) ◽  
pp. 2692-2701 ◽  
Author(s):  
Tsutomu Kouyama ◽  
Ryudo Fujii ◽  
Soun Kanada ◽  
Taichi Nakanishi ◽  
Siu Kit Chan ◽  
...  
Keyword(s):  
Structural Information ◽  
Lattice Structure ◽  
Hexagonal Lattice ◽  
Structural Features ◽  
Proton Pumping ◽  
Tryptophan Residue ◽  
Order Structure ◽  
Proton Release ◽  
Decay Kinetics ◽  
Release Channel

Archaerhodopsin-2 (aR2), the sole protein found in the claret membrane ofHalorubrumsp. Aus-2, functions as a light-driven proton pump. In this study, structural analysis of aR2 was performed using a novel three-dimensional crystal prepared by the successive fusion of claret membranes. The crystal is made up of stacked membranes, in each of which aR2 trimers are arranged on a hexagonal lattice. This lattice structure resembles that found in the purple membrane ofH. salinarum, except that lipid molecules trapped within the trimeric structure are not distributed with perfect threefold symmetry. Nonetheless, diffraction data at 1.8 Å resolution provide accurate structural information about functionally important residues. It is shown that two glutamates in the proton-release channel form a paired structure that is maintained by a low-barrier hydrogen bond. Although the structure of the proton-release pathway is highly conserved among proton-pumping archaeal rhodopsins, aR2 possesses the following peculiar structural features: (i) the motional freedom of the tryptophan residue that makes contact with the C13 methyl group of retinal is restricted, affecting the formation/decay kinetics of the L state, and (ii) the N-terminal polypeptide folds into an Ω-loop, which may play a role in organizing the higher-order structure.

Atomic and Electronic Structure of LaAlO3 and LaAlO3:Mg from First-Principles Calculations

2009 ◽  
Vol 79-82 ◽  
pp. 1257-1260
Author(s):  
Li Guan ◽  
Li Tao Jin ◽  
Wei Zhang ◽  
Qiang Li ◽  
Jian Xin Guo ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Band Structure ◽  
Band Gap ◽  
Density Functional ◽  
Lattice Structure ◽  
Cell Structure ◽  
Functional Theory ◽  
Super Cell ◽  
Direct Band ◽  
Experimental Values

In the present paper, the lattice structure, band structure and density of state of LaAlO3 and LaAlO3:Mg are calculated by first-principle method based on density functional theory. Firstly, we select the different cutoff energy and k-point grid in the calculations, and obtain the most stable geometry structure of single crystal LaAlO3. The calculated lattice parameters are a=b=5.441 Å, c=13.266 Å, which matches with experimental values. To deeply understand the electronic structure of LaAlO3, a 2×1×1 super-cell structure is established and the doping concentration of Mg at Al sites is 25%. From the band structure and density of states, it can be seen that LaAlO3 has a direct band gap Eg=3.6 eV. However, LaAlO3:Mg has a larger band gap Eg=3.89 eV and the Fermi level enters into the valence band, which indicates the holes are introduced. The calculated results show that the conductivity of LaAlO3:Mg is better than pure LaAlO3, which is in good agreement with experimental results.

Specific lipid–protein interactions in a novel honeycomb lattice structure of bacteriorhodopsin

1999 ◽  
Vol 55 (7) ◽  
pp. 1251-1256 ◽  
Author(s):  
Hidenori Sato ◽  
Kazuki Takeda ◽  
Koji Tani ◽  
Tomoya Hino ◽  
Tetsuji Okada ◽  
...  
Keyword(s):  
Protein Interactions ◽  
Lattice Structure ◽  
Hexagonal Lattice ◽  
Crystallographic Analysis ◽  
Purple Membrane ◽  
Honeycomb Lattice ◽  
Vesicular Structure ◽  
Lipid Protein Interactions ◽  
Planar Membranes ◽  
Inside Out

In the purple membrane of Halobacterium salinarium, bacteriorhodopsin trimers are arranged in a hexagonal lattice. When purple membrane sheets are incubated at high temperature with neutral detergent, membrane vesicularization takes place, yielding inside-out vesicles with a diameter of 50 nm. The vesicular structure becomes unstable at low temperature, where successive fusion of the vesicles yields a crystal which is composed of stacked planar membranes. X-ray crystallographic analysis reveals that the bacteriorhodopsin trimers are arranged in a honeycomb lattice in each membrane layer and that neighbouring membranes orient in opposite directions. The native structure of the trimeric unit is preserved in the honeycomb lattice, irrespective of alterations in the in-plane orientation of the trimer. One phospholipid tightly bound to a crevice between monomers in the trimeric unit is suggested to act as a glue in the formation of the trimer.

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