bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dielectric Studies on Liquid Crystals under High Pressure: VI. Low Frequency Relaxation Process in the Nematic and Smectic A Phase of 4-n-Octyl-4'-Cyanobiphenyl (8 CB)
Authors: Urban S. , Brückert T. , Würflinger A. 
Published: February 2015

Abstract
Dielectric relaxation studies of 4-n-octyl-4'-cyanobiphenyl (8 CB) were performed in the pressure range 0.1 -120 MPa, the frequency range 1 kHz -13 MHz and the temperature range 295-331 K. The dielectric behaviour of 8C B in the nematic phase is similar to that of 5 CB, 6 CB and 7 CB. In particular, the activation enthalpy decreases with increasing pressure and the activation volume decreases with increasing temperature in the nematic phase. In the smectic A phase of 8 CB both these parameters are markedly lower and show opposite pressure and temperature dependencies. We tentatively interpret these effects as a result of breaking of the dipole-dipole correlations which manifests itself differently in these liquid crystalline phases.
Orientational Order-Disorder and Phase Transition in Solid Trichloromethane Sulfonic Acid Chloride, Cl3CSO2Cl
Authors: Dou Shi-qi , Fuess Hartmut , Schmahl Wolfgang , Strauss Roman , Weiss Alarich 
Published: February 2015

Abstract
By DTA DSC a phase transition of Cl3CSO2Cl was observed, TII,I = 227.4 K, ΔHII,I = 7.10 kJ · Mol-1; ΔSII,I/R = 3.63; Tm = 418.5 K, ΔHm = 7.46 kJ · Mol-1, ΔSm/R = 2.14. By X-ray'powder diffraction, the orientationally disordered solid phase I (plastic phase) was found to be body centered cubic, Im3m, Z = 2, a = 721.7 (5) pm at room temperature. The 35CL NQR quartet fades out at the transition temperature TII,I = Tf, and the fade out temperature Tf is identical for the four 35Cl NQR lines. The NQR spectrum shows a hysteresis in TI,II - TII,I.
Magnetic Order in Li-Mn Spinels
Authors: Azzoni C. B. , Mozzati M. C. , Paleari A. , Massarottib V. , Capsonib D. , Binib M. 
Published: February 2015

Abstract
Magnetic measurements were carried out on different samples of Lithium-Manganese spinel LiMn2O4 , great care having been taken to avoid the presence of spurious magnetic phases, such as Mn3O4 . Susceptibility data, showing deviations from paramagnetic behaviour at about 40 K, were analyzed in terms of local magnetic interactions, taking into account the structural and transport properties of these com-pounds. The magnetic response of pure and stoichiometric samples suggests that the onset of a longrange magnetic ordering is hindered by the topological frustration of the antiferromagnetic octahedral sublattice of the spinel.
Topological Properties of Circumcoronenes
Authors: Gutman Ivan , Cyvina Sven J. , Ivanov-Petrović Vesna 
Published: February 2015

Abstract
The regular-hexagon-shaped benzenoid hydrocarbons: B1 = benzene (C6H6), B2 = coronene (C24H12), B3 = circumcoronene (C54H18), B4 = circumcircumcoronene (C150H30), etc. possess unique topological properties. General expressions for the most important of such properties (number of fun-damental structural invariants, number of Kekule and Clar structures, number of aromatic sextets, Wiener and Szeged indices, spectral moments) are given, including a number of results that are communicated here for the first time. Cyclic conjugation in circumcoronenes is analyzed by means of its energy-effect, and found to agree with the predictions of Clar's aromatic sextet theory only in the case of B1 and B2.
Relations between Nematic Potential and Order Parameters (P2) and (P4)
Authors: Würflinger A. , Urban S. 
Published: February 2015

Abstract
The Maier-Saupe theory is employed in order to calculate order parameters (P2) , (P4) from the nematic potential q. The relation between σ=q/(RT) and S = (P2) corresponds well with a recently established formula by Kalmykov. The relation between the order parameters is in accordance with the analytic expression (P4)=5/7 (P2)2 proposed by Zanonni, but deviates significantly from the Faber model, according to which log (P4)=(10/3) log (P2). Experimental results for 5 CB obtained from Raman measurements, however, are in better agreement with the Faber model.
Determination of the Absolute Configuration of 1,5-Diaza-cis-decalin by Comparison of Measured and Calculated CD-Spectra
Authors: Fleischhauer Jörg , Raabe Gerhard , Santos A. G. , Schiffer Jan , Wollmer Axel 
Published: February 2015

Abstract
The absolute configurations of both 1,5-diaza-c/s-decalin enantiomers were determined by com-parison of measured and calculated CD spectra.
CD spectra for both enantiomers were recorded. Theoretical CD spectra for one of the isomers were calculated by means of the semiempirical CNDO/2S method. Eight local minima on the energy hypersurface of the title compound were used to describe the conformer equilibrium mixture. The geometries of these conformers were calculated employing one-determinant ab initio calculations using the split valence 6-31G* basis set. Boltzmann factors were then obtained using relative energies calculated with three different basis sets and including correlation(MP2)-and zero point vibrational energy.
Comparing the sign of the observed and calculated longest wavelength Cotton effect, we assign an absolute configuration to the compound. This assignment was verified by means of X-ray structure determination of one of the enantiomers’ α-methoxy-α-trifluoromethylphenyl aceticacid (MTPA, Mosher’s reagent) derivative.
Elastic Constants of Binary Liquid Crystalline Mixtures
Authors: Kapanowski A. , Sokalski K. 
Published: February 2015

Abstract
Microscopic expressions for the elastic constants of binary liquid crystalline mixtures composed of short rigid uniaxial molecules are derived in the thermodynamic limit at small distorsions and a small density. Uniaxial and biaxial nematic phases are considered. The expressions involve the one-particle distribution functions and the potential energy of two-body short-range interactions. The theory is used to calculate the phase diagram of a mixture of rigid prolate and oblate molecules. The concentration dependence of the order parameters and the elastic constants are obtained. The possibility of phase separation is not investigated.
On the Experimental Proofs of Relativistic Length Contraction and Time Dilation
Authors: Jefimenko Oleg D. 
Published: February 2015

Abstract
Recent advances in the theory of electromagnetic retardation have made it possible to derive the basic equations of the special relativity theory and to duplicate the most important practical results of this theory without using the concepts of relativistic length contraction and time dilation. Thus the reality of these concepts appears to be questionable. It is imperative therefore to reexamine the experimental evidence supporting these concepts. The calculations presented in this paper show that some of the experiments allegedly proving the reality of length contraction and time dilation can be unambiguously interpreted as manifestations of velocity-dependent dynamical interactions taking place within the systems involved in the experiments rather than as manifestations of length contraction or time dilation.
Dielectric Relaxation Study of Zn(NO3) 2, Cu(NO3)2 , Ni(NO3)2 , and Mg(NO3)2 Solutions in Water/DMSO Mixtures
Authors: Galstian A. , Stockhausen M. 
Published: February 2015

Abstract
Dielectric spectra have been measured for the title systems up to 72 GHz at 20 °C with salt concentrations ≤1 mol/1 and DMSO mole fractions of the mixed solvent in the 0.3 to 0.6 range. Results can be described by a superposition of two Debye terms (at lower frequencies) plus one Cole-Davidson term (at higher frequencies). The discussion is particularly focused on the lowest frequency term, which is related to ionic species. These are likely to consist in nonsymmetrically solvated cations rather than ion pair complexes. While Cu, Ni and Mg nitrates behave similarly, the Zn salt shows some differences which possibly are due to a change of the coordination number with increasing salt content.
63Cu Nuclear Magnetic Resonance and Viscosity Studies of Copper (I) Perchlorate in Mixed Solvents Containing Acetonitrile
Authors: Gill Dip Singh , Byrne Lindsay , Quiekenden Terry I. 
Published: February 2015

Abstract

63Cu nuclear magnetic resonance and viscosity studies of 0.064 M copper (I) Perchlorate solutions have been made at 298 K in binary mixtures of acetonitrile (AN) with dimethylsulphoxide (DMSO), hexamethylphosphotriamide (HMPA), N,N-dimethylacetamide (DMA), nitromethane (NM), propylene carbonate (PC) and 3-hydroxypropionitrile (3 HPN) at several compositions of the mixtures using a 500 MHz NMR Spectrometer and Ubbelohde viscometer, respectively. The chemical shift (δ), linewidth (Δ) and line intensity (I) of the 63Cu NMR signal in these mixed solvents have been measured relative to the 63Cu signal in 0.064 M copper (I) Perchlorate (CuClO4) solution in pure AN. The quadrupolar re-laxation rates (1/T2)Q, reorientational correlation times (τR) and quadrupolar coupling constants (QCC) of the copper (I) solvates have also been estimated from the data. The QCC values show a big variation in all solvent systems with the change of solvent composition, indicating the formation of mixed com-plexes. The variation of all NMR parameters with solvent composition shows strong effects of DMSO, HMPA, and DMA on the solvation behaviour of Cu + in the first three mixtures, and relatively much weaker effects of PC, NM and 3HPN in the other three mixtures.
Statistical Invariances in Artificial, Natural, and Urban Images
Authors: Ziegaus Christian , Lang Elmar W. 
Published: February 2015

Abstract
To answer the question about the way our visual system processes images it has to work with every day, it is necessary to investigate the statistical structure of these pictures. For this purpose we investigated several ensembles of artificial and real-world greyscale images to find different invariance properties: translation invariance by determining an average pair-correlation function, scale invariance by investigating the power spectrum and the coarse graining of the images, and a new hierarchical invariance recently proposed [D. L. Ruderman, Network 5, 517 (1994)]. The results of our work indicated that the assumption of translational invariance can be taken for granted. Our results concerning the scale invariance are qualitatively the same as those found by Ruderman and others. The deviations of the distributions of the logarithmically transformed images from a Gaussian distribution cannot be seen as clearly as stated by Ruderman. This results from the fact that for a correct determination of the deviations the non-linear transformation must be considered. Depending on the preprocessing of the images the results concerning the hierarchical invariance differed widely. It seems that this new invariance can be confirmed only for logarithmically transformed images.
NMR and NQR Studies of Borate Glasses
Authors: Bray Philip J. , Petersen Gary L. 
Published: February 2015

Abstract
Nuclear magnetic resonance (NMR) has been used for some 40 years to study atomic arrangements, chemical bonding, and structural groupings in borate glasses and crystalline compounds, and nuclear quadrupole resonance (NQR) has more recently increased the resolution and accuracy of the measurements. Examples are presented of the use of first-order and second-order quadrupolar effects in 11B NMR spectra to obtain structural information, and 11B and 10B NQR spectra to obtain the quadrupolar parameters Qcc (the coupling constant) and ƞ (the asymmetry parameter) with accuracies of 5 or 6 significant figures, and 3 figures, respectively. Qcc and ƞ are extremely sensitive to changes in atomic rearrangements and chemical bonds, so they are excellent monitors and provide identification of bonding configurations and structural groupings in borates: Examples are also presented in which combinations of NMR and NQR data are used to extract the desired information. NQR detection of resonances at frequencies as low as 276 kHz is discussed.
Electric Quadrupole Interactions of the Short-Lived β-Emitter 12N in Insulator Crystals (12N Implanted in Single Crystal TiO2)
Authors: Minamisono T. , Sato K. , Akai H. , Takeda S. , Maruyama Y. , Matsuta K. , Fukuda M. , Miyake T. , Morishita A. , Izumikawa T. , Nojir Y. 
Published: February 2015

Abstract
The electronic structure of nitrogen atoms as impurities in an ionic TiO2 crystal has been investigated by analyzing electric field gradients (EFGs) measured by use of short-lived β-emitting 12N implant-ed following nuclear reactions. Conventional β-NMR and its modification, suitable for the detection of quadrupole effects in the NMR spectra, were used for the investigation of hyperfine interactions of 12N located in substitutional sites of O atoms and interstitial sites in the crystal. In order to deduce absolute values of the EFGs from the obtained eqQ/h, the quadrupole moment of 12N has been determined from the NMR detection of 12N implanted in BN(hexagonal) crystal. Here the EFG at the N atom in BN was measured by detecting the FT-NMR of 14N in the crystal. The EFGs in TiO2 are compared with the theoretical predictions based on the ab initio band-structure calculation in the framework of the KKR method.
NMR Detection of Oxygen Isotopes in TiO2 Single Crystal
Authors: Tanigaki M. , Takeda S. , Matsuta K. , Matsumoto Y. , Minamisono T. , Akai H. , Sato K. , Miyake T. , Maruyama Y. , Morishita A. , Fukuda M. , Nojiri Y. 
Published: February 2015

Abstract
We studied the electric quadrupole interactions of Oxygen isotopes in a TiO2 single crystal. For 13O and 19O nuclei, quadrupole coupling constants were measured by the β-NMR technique, and for the 17O nucleus the FT-NMR technique was utilized. We synthesized a TiO2 single crystal which was enriched in 17O up to 5 atom % to observe NMR signals without any perturbations from impurities. Using the known quadrupole moment of 17O, EFGs at an O site in TiO2 and the quadrupole moments of 13O and 19O were determined.
Electric Field Gradients at the In Site in Au-In Compounds
Authors: Wodniecki P. , Kulińska A. , Wodniecka B. , Hrynkiewicz A. Z. 
Published: February 2015

Abstract
The quadrupole interaction in Au-In compounds of different stoichiometrics was studied with the perturbed angular correlation technique. The electric field gradients at 111Cd probes were measured and the temperature dependences of the quadrupole frequencies were determined. A new high temperature phase of Auln above 630 K and a new metastable modification of Au7In3 were found.
Halogen Nuclear Quadrupole Coupling Constants in Non-axially symmetric Molecules; Ab initio Calculations, which Include Correlation, Compared with Experiment
Authors: Palmer Michael H. , Blair-Fish John A. 
Published: February 2015

Abstract
Ab initio determination of the electric field gradient (EFG) tensors at halogen and other centres ena-bled determination of the nuclear quadrupole coupling constants (NQCC) for a diverse set of C2v , C3v and other symmetry molecules of general formula MH2X2 and MHX3 , where the halogen atoms (X) are Cl, Br and I, and the heavy central atoms (M) are C and Si. The study presents results at a standardised level of calculation, triple-zeta in the valence space plus polarisation functions (TZVP) for the equilib-rium geometry stage; all-electron MP2 correlation is included in all these studies. For the bromo and iodo compounds, especially the latter, it is essential to allow core polarisation, by decontraction of the p,d-functions. This is conveniently done by initial optimization of the structure with a partly contract-ed basis, followed by reestablishment of the equilibrium structure with the decontracted basis.
The NQCCs, derived from the EFGs, using the 'best' values for the atomic quadruple moments Cl, Br and I, lead to good agreement with the inertial axis (IA) data obtained from microwave spectroscopy. When the data from the present study is plotted against the values derived from the IA data, obtained by whatever approximations chosen by the MW authors, we obtain a linear regression for the data (85 points) with the slope 1.0365 and intercept -0.1737, with standard errors of 0.0042 and 0.2042, respectively; these are statistically identical results irrespective of whether the data is restricted to IA or EFG principal axis (PA) data.
Since as in the C3v MH3X compounds studied previously, a close correlation of the microwave spectral data with the calculations was observed using the 'best' current values for Qz , there seems no need to postulate that the values of QBr for both 79Br and 81Br are seriously in error. A scaling downwards of Qz by about 5% for Br and I increases the agreement with experiment, but the contributions of relativistic effects are unknown, and could lead to further reassessment.
Of the two common assumptions used in MW spectroscopy, to convert from IA to EFG-PA data, either (a) cylindrical symmetry of the NQCC along the bond direction, or (b) coincidence of the tensor principal element with the bond axis, the latter is found to be a much more realistic approximation.
NQR Relaxation Studies on Halogenomethyl Groups in Halogenoacetates
Authors: Zdanowska-Fnjczek Maria 
Published: February 2015

Abstract
The effect of temperature on the chlorine NQR spin-lattice relaxation times in CsH(ClH2-CCOO)2 , KH(Cl3 CCOO) 2 and N(CH3)4 H(ClF2CCOO)2 has been studied in the temperature range 77 K to room temperature. The results were discussed on the basis of NQR relaxation theory.
Spin Gap, Electronic Crossover, and Charge Density Waves in Y-Ba-Cu-O Superconductors
Authors: Brinkmann Detlef 
Published: February 2015

Abstract
This paper discusses recent NQR/NMR studies performed on Y-Ba-Cu-0 superconductors at the University of Zürich. The work is concerned with normal state properties which are still controversial, for instance the spin-gap effect, i.e. the opening of a pseudo gap in the electron spin excitation spectrum at a temperature T*, which lies above Tc . We will report on the detection of “anomalies” which are dis-played in the temperature dependence of several NMR and NQR quantities measured in the normal state of YBa2Cu4O8 . These anomalies are interpreted as an electronic crossover which involves a charge re-distribution in the CuO2 planes and an enhancement of the charge fluctuations. As a possible mechanism of the crossover, a charge density wave instability is proposed.
Chlorine-35 NQR Study of a Structural Phase Transition in (ND4)2PdCl6
Authors: Kume Yoshio , Asaji Tetsuo 
Published: February 2015

Abstract
Temperature dependences of 35Cl NQR frequencies and spin-lattice relaxation times were measured at 4.2 to 400 K for natural and deuterated ammonium hexachloropalladate. It was confirmed that only the deuterated salt undergoes a first order phase transition at 30 K. The crystal structure of the low-temperature phase is predicted to be the same as that of the deuterated ammonium hexachloroplatinate and hexachloroplumbate. The mechanism of the deuteration-induced phase transition is discussed.
Phase Transitions and Crystal Structure of Dimethylammonium Tribromomercurate(II), (CH3)2NH2HgBr3 , as Studied by 81Br NQR and Single Crystal X-ray Diffraction
Authors: Terao Hiromitsu , Hashimoto Masao , Okuda Tsutomu , Weiss Alarich 
Published: February 2015

Abstract
The temperature dependence of the 81Br NQR frequencies of the title compound has revealed the presence of three phases (I, II and III, in the order of decreasing temperature): Tcl (II -1) = (318 ± 10) K and Tc2 (III -II) = (202 ± 1) K. The transitions were confirmed by thermal analysis (DTA). Both of the II-I and I-II transitions exhibited strong hysteresis (i. e., superheating and supercooling, respectively). The crystal data, determined by single crystal X-ray diffraction, are: monoclinic, space group P2/a, a = 1384.8(3), b = 934.7(4), c = 1452.0(2) pm, β = 104.10(1)°, Z= 8, R = 0.076. The crystal has two crystallographically independent cations (CH3)2NH2+ and an infinite chain of anions almost in the c-direction. The anion chain is considered to consist of a HgBr2 molecule and two different HgBr4
2- anions which are interconnected via weak intermolecular Hg···Br bonds. The splitting patterns of the 81Br NQR spectra indicate that rearrangements of the Hg-Br bonds are slight at the III-II transition but serious at the II-I transition. Some of the 81Br NQR lines show anomalous temperature coefficients, attributable probably to thermal motions of cations.
Stability of in 111In-ligand Complexes Studied by TDPAC
Authors: Shpinkova L. G. , Kulakov V. N. , Sorokin A. A. , Ryasny G. K. , Komissarova B. A. , Nikitin S. M. 
Published: February 2015

Abstract
The TDPAC technique has been applied to study the stability of 111In complexes with NTA and DTPA in solutions with different concentrations of stable In at pH = 7. A sample of In-DTPA complexes attached to microspheres of albumin (MSA) has been measured at temperatures of 293 and 130 K. The results show that the products formed after 111ln → 111Cd decay and following Auger-effect are determined by the stability of In (Cd)-complexes with organic ligands. The daughter Cd behaviour depends on the In: ligand mole ratio, from 1: ∞ to 1:1. The possibility of Cd-ligand complex destruction and following Cd rechelating is discussed. The results indicate that the rechelating probability correlates with the stability of the parent and daughter complexes.
Pre- and Post-Activity Stretching Practices of Collegiate Athletic Trainers in the United States
Authors: Popp Jennifer K. , Bellar David M. , Hoover Donald L. , Craig Bruce W. , Leitzelar Brianna N. , Wanless Elizabeth A. , Judge Lawrence W. 
Published: February 2015

Abstract
Popp, JK, Bellar, DM, Hoover, DL, Craig, BW, Leitzelar, BN, Wanless, EA, and Judge, LW. Pre- and post-activity stretching practices of collegiate athletic trainers in the United States. J Strength Cond Res 31(9): 2347–2354, 2017—The aim of the study was to investigate the knowledge and practices of collegiate-certified athletic trainers (ATs) in the United States. Participants (n = 521) were provided an overview of the study and a hyperlink to a web-based survey. The “pre- and post-activity practices in athletic training questionnaire” consisted of demographic items and elements to measure knowledge and practices related to pre- and post-activity stretching routines. In previous studies, the survey demonstrated construct validity, α = 0.722. Pearson chi-square test was used to evaluate goodness of fit, and kappa was calculated to measure agreement between items. Only 32.2% of ATs recommended dynamic stretching (DS) to be performed pre-activity, whereas a larger percentage (42.2%) recommended a combination of static stretching (SS) and DS. Athletic trainers reported that only 28.0% of athletes are performing DS before activity. Conversely, 60.6% of collegiate ATs recommended SS postexercise, and 61.0% of athletes agree and perform after workout SS (κ = 0.761, p < 0.001). Collegiate ATs seem to underuse the current research evidence, which indicates that DS is more beneficial than SS when used pre-activity, and ATs continue to regularly incorporate SS in their pre-activity routines. However, there is evidence that collegiate ATs in the United States emphasize SS postactivity in a manner consistent with current research.
Rediscovery of Passiflora danielii Killip, 1960 (subgenus Passiflora): a threatened narrow endemic species of Colombia
Authors: Ocampo John , Restrepo Jorge Julián , Giraldo Wilmer 
Published: February 2015

Passiflora danielii, an endemic species to Colombia, which is threatened, was rediscovered in the Department of Antioquia, where it has not been reported since 1938. The species was only known from the type locality (Municipality of Cocorná). Now, four new locations are added near it. The current study further presents a revised morphological description of P. danielii based on fresh material, along with an updated distribution map. Finally, following the IUCN Red List Criteria, P. danielii was classified as Critically Endangered (CR) species.