bluuebunny/crossref_metadata_2025_split huggingface dataset:
Excited-state Reactions of 4-methylumbelliferone Studied by Nanosecond Fluorometry
Authors: Baiter Aleksander , Roliński Olaf 
Published: February 2015

Excited-state protolytic reactions of 4-methylumbelliferone were studied using pulse and phase fluorometry.
A concept of internal convolution which simplifies the data analysis was applied. The fluorescence decay of the excited neutral species was found to be monoexponential, while the decay of the long-wavelength emitting species (most probably a zwitterion) is biexponential.
An excited-state reactions model is proposed, in which the rapidly dissociating cation is an intermediate between the neutral and zwitterionic species.
Molecular Electric Quadrupole Moment, Magnetic Susceptibility Tensor and Deuterium Quadrupole Coupling Constant in Cyanoacetylene
Authors: Stolze W. H. , Sutter D. H. 
Published: February 2015

The rotational Zeeman effect in the J → J′ = 0 → 1 and 1 → 2 rotational transitions has been observed for H-C≡C-C≡14N, D-C≡C-C≡14N, D-C≡C-C=15N, and H-C≡C-C=I5N using a microwave bridge superheterodyne spectrometer. From the experimental g⊥-values, susceptibility anisotropies and rotational constants, the molecular electric quadrunole moment, which plays an important role for collisional excitation and relaxation, follows as Q∥=2.14(9) x 10-26esu cm2 (referred to the center of mass of the H-C≡C-C≡14N species).
Since the Deuterium quadrupole hyperfine splittings in the Zeeman spectra could be resolved, it was also possible to Fit the Deuterium quadrupole coupling constant. Our value, eqQ (2H) = 198.2(46) kHz is about 10% smaller than the value derived from a recent high resolution microwave Fourier transform study. The reasons for this discrepancy are discussed.
All experimental molecular parameters are compared to the results of ab initio quantum chemical calculations and it is argued that the 14N nuclear electric quadrupole moment is possibly about 30% larger than presently assumed.
Nuclear Quadrupolar Relaxation m Liquid Alloys and Nearest Neighbour Dynamics
Authors: Maxim P. , Brinkmann R. , Paulick C. A. , Elwenspoek M. , Hartrott M. v. , Kiehl M. , Quitmann D. 
Published: February 2015

A theory of the quadrupolar relaxation rate,
RQ , for ideal liquid binary metallic mixtures is
presented. The theory predicts cancellation after a few tenths of a picosecond of the two and
three particle correlation terms in the fluctuation of the electric field gradient (EFG) for pure
metals, and prevailing of the three particle term for binary mixtures. This is due to the high
symmetry in the arrangement of the atoms around a probe nucleus. The prevailing of the three
particle term in binary systems leads to a longer correlation time (a few picoseconds) of the
fluctuating EFG and explains the experimentally observed higher values of RQ and their
quadratic concentration dependence. The validity of the theory has been confirmed by experimental
data. Deviations for some real systems are discussed.
Enumeration of Kekulé Structures for Multiple Zigzag Chains and Related Benzenoid Hydrocarbons
Authors: Cyvin S. J. , Cyvin B. N. 
Published: February 2015

The benzenoid classes of multiple zigzag chains, A (n, m ), and incomplete multiple zigzag chains. A (n, m, l), are considered. Numerical numbers of Kekulé structures (K ) are given for n up to 5 and m up to 10. A recurrence relation is developed for the K numbers of A(n, m) with fixed values of n; a general formulation for arbitrary m values was achieved.
Six new benzenoid classes are studied in connection with the application of the John-Sachs theorem to double zigzag chains. A new approach to the K enumeration is introduced by nonlinearly dependent recurrence relations.
Finally a new type of combinatorial K formulas in terms of determinants and based on the John-Sachs theorem , is introduced. The new enumeration techniques are applied to multiple zigzag chains.
Experimental Investigation of Spatial Pattern Formation in Physical Systems of Activator Inhibitor Type
Authors: Purwins Hans-Georg , Radehaus Christian , Berkemeier Jürgen 
Published: February 2015

Abstract
We investigate experimentally stationary stable states of activator (w) inhibitor (υ) type systems corresponding to the reaction diffusion equation
δ · υ̇ = Δυ + w - υ; ẇ = σ Δw + f(w) - υ; δ, σ = const > 0
with f(w) monotonically increasing for small and decreasing for large |w|. We first describe some general mathematical properties and present qualitative results obtained from numerical calculations. We then investigate experimentally electrical networks described by the spatially discretized version of the above equation. Calculation and experiment are in good agreement. We also interprete a two dimensional-network as an equivalent circuit for a composite material consisting of a linear and a nonlinear layer with an s-shaped current density electric field characteristic. This model is used for a phenomenological description of spatial structures and global current voltage characteristics observed experimentally in pin-diode like and gas discharge devices. The model accounts very well for the experimental results obtained so far. It is concluded that the above equation and the corresponding experimental setup are of great interest for fundamental investigations of self con­trolled processes in nature.
Molecular Polarity and the Structure of Liquid Methanol
Authors: Pálinkás G. , Tamura Y. , Spohr E. , Heinzinger K. 
Published: February 2015

Abstract
The structure of liquid methanol as a function of the molecular polarity has been studied by MD simulations. The results obtained by scaling the partial Coulombic charges located at the molecular interaction sites show that the polar forces leading to the hydrogen bonding phenomena also influence the relative orientation of nearest neighbor molecules and thus their local packing. It is shown that hydrogen bonding in liquid methanol contributes considerably to the X-ray structure function. The changes with polarity of the pair interaction energy distributions, the intramolecular geometry, and the vibrational frequencies are reported. The results are compared with those obtai­ned from RISM calculations.
Rotational Tunnelling of CD3Groups in Molecular Crystals as Studied by NMR Spectra
Authors: Lalowicz Z. T. , Werner Ulrike , Müller-Warmuth W. 
Published: February 2015

Abstract
Tunnelling frequencies of rotating CD3 groups in solids between about 20 kHz and 2 MHz may be obtained from the 2H NMR spectra. The theory of the spectral response is developed where quadrupole and dipole-dipole interactions as well as rotational tunnelling are taken into account. Features characteristic of tunnelling, which distinguish the spectra from those of rapidly reorienting deuterated methyl groups, are found from analytically calculated spectra even for the case of very large tunnel splittings. Numerical calculations have been performed for various conditions to deter­ mine the tunnel frequency. Experimental spectra measured at 45 MHz and low temperatures have revealed the appearance of rotational tunnelling in CD3I, CD3COONa, and (CD3COO)2Cu • H2O. In the latter case, a tunnelling frequency of 608 kHz has been extracted from the spectrum at 27 K.
The Viscosity Coefficients of Oriented Nematic and Nematic Discotic Liquid Crystals; Affine Transformation Model
Authors: Baalss D. , Hess S. 
Published: February 2015

Abstract
General expressions are derived for the anisotropy of the viscosity and for the Leslie coefficients governing the flow alignment subject to the assumption that the equipotential surfaces for the interaction of oriented nonspherical molecules in the nematic or nematic discotic phase of a liquid crystal are related to a spherical interaction potential by an affine transformation. In particular, for uniaxial particles, the seven independent viscosity coefficients of a nematic are given in terms of the two viscosity coefficients of a reference fluid of spherical particles and the axes ratio of the nonsphe­rical molecules. The theory is compared with results from nonequilibrium molecular dynamics computer simulations and with experimental data.
Ramanujan and the Julia Set of the Iterated Exponential Map
Authors: Lakhtakia Akhlesh , Lakhtakia Mercedes N. 
Published: February 2015

Abstract
The Julia set of Ramanujan's iterated exponential map, Fr+1(z) = exp {Fr(z)} -1, is investigated for positive integral r. Connection with Devaney's work on the map zr+1 = λ exp[zr] is also made.
79Br, 127I NQR of Diammoniumalkyl Halides and Piperazinium Halides. Crystal Structure of Piperazinium Dibromide Monohydrate and Piperazinium Monoiodide
Authors: Hartmann Jutta , Dou Shi-Qi , Weiss Alarich 
Published: February 2015

Abstract
The 79Br and 127I NQR spectra were investigated for 1,2-diammoniumethane dibromide, -diiodide, 1,3-diammoniumpropane dibromide, -diiodide, piperazinium dibromide monohydrate, and piperazinium monoiodide in the temperature range 77 ≦ T/K ≦ 420. Phase transitions could be observed for the three iodides. The temperatures for the phase transitions are: 400 K and 404 K for 1,2-diammoniumethane diiodide, 366 K for 1,3-diammoniumpropane diiodide, and 196 K for piperazinium monoiodide.
The crystal structures were determined for the piperazinium compounds. Piperazinium dibromide monohydrate crystallizes monoclinic, space group C2/c, with a= 1148.7 pm, 0 = 590.5 pm, c= 1501.6pm, β = 118.18°, and Z = 4. For piperazinium monoiodide the orthorhombic space group Pmn 21 was found with a = 958.1 pm, b = 776.9 pm, c = 989.3 pm, Z = 4. Hydrogen bonds N - H ... X with X = Br, I were compared with literature data.
Line Spectrum Emission of Eu-Activated ZnS
Authors: Kynev K. , Kuk V. 
Published: February 2015

Abstract
It is shown that a ZnS:Eu phosphor with line emission spectrum can be prepared without coactivator introduction, contrary to previous results. The broad-band emission established in ZnS: Eu, Li is ascribed to the formation of Eu2+ centres due to the removal of lattice stress by lithium incorporation.
Structural Phase Transitions and Ionic Motions in Pyridinium Hexachlorotellurate(IV),Hexachlorostannate(IV), and Hexabromostannate(IV) Crystals as Studied by 1H NMR
Authors: Tai Yutaka , Asaji Tetsuo , Ikeda Ryuichi , Nakamura Daiyu 
Published: February 2015

Abstract
The 1H NMR second moment M2 and the spin-lattice relaxation time T1 are determined for pyridinium hexachlorotellurate(IV), hexachlorostannate(IV), and hexabromostannate(IV) at various temperatures above ca. 140 K. The phase transition temperatures already reported from halogen NQR experiments are determined as 272, 331, and 285 K, respectively, by differential thermal analysis (DTA). The DTA as well as differential scanning calorimetry measurements show that the above phase transitions are of second-order. For pyridinium hexachlorotellurate(IV) and hexa-bromostannate(I V), a sharp 1H T1 dip was observed at the transition temperature. This is interpreted in terms of a phenomenon related to the critical fluctuation of an order parameter. From the measurements of 1H M2, 60° two-site jumps (60° flips) around the pseudo C6 axis of the cation are suggested to occur in the high temperature phases of the complexes. Modulation of X...1H (X = CI, Br) magnetic dipolar interactions due to the reorientational motion of the complex anions is considered as a possible relaxation mechanism in the high temperature phases.
14N Nuclear Quadrupole Hyperfine Structure in the Microwave Spectrum of Methyl Azide, CH3N3
Authors: Heineking N. , Gerry M.C.L. 
Published: February 2015

Abstract
The 14N nuclear quadrupole hyperfine structure in the rotational spectra of three isotopic species of methyl azide, CH3
14N3, CH3
15N14N2, and CH3
14N2
15N, has been resolved using microwave Fourier transform spectroscopy. The quadrupole coupling constants of 14N at all three positions have been evaluated and are compared with those from an ab initio calculation in the literature.
Since the spectra of the substituted species have been obtained for the first time, they have provided new structural information: the rotational constants are consistent with a structure in which the NNN chain is slightly bent.
The Ground State Microwave Spectrum and Dipole Moment of 2-Isocyano-Propane
Authors: Krüger Michael , Dreizler Helmut 
Published: February 2015

Abstract
The ground state rotational spectrum of 2-isocyano-propane is assigned. The rotational constants and the quartic centrifugal distortion constants are determined by Microwave Fourier Transform (MWFT) Spectroscopy. The analysis of the Stark effect leads to a total dipole moment of 4.055(1) D.
EPR of VO2+ in KTiOPO4 Single Crystals
Authors: Vassilikou-Dova A. B. , Jansen S. , Wallrafen F. , Lehmann G. 
Published: February 2015

Abstract
KTiOPO4 single crystals doped with V2O4 were grown from fluxes between 1323 and 1123 K with dimensions up to (10x5x5) mm3. Two crystallographically inequivalent centers of VO2+ in the occupation ratio of 10:1 were detected by EPR at room temperature. Their z axes of largest hyperfine splitting are oriented close to the directions of the very short Ti-O bonds of the two Ti in the structure. An energy difference for incorporation of VO2+ into these two sites of -9.4+ 1.7 kJ/mol per pm difference in bond lengths was obtained from the occupation ratio, the large limits of error being mainly due to uncertainties in the bond lengths. Additional hyperfine splitting caused by 31P nuclei as next-nearest neighbors was also resolved in most orientations.
Mößbauer-Untersuchung der Modifikationen von Li2FeCl4
Authors: Lutz H. D. , Pfitzner A. , Schmidt W. , Riedel E. , Prick D. 
Published: February 2015

Abstract
The room temperature Mössbauer spectrum of the high-temperature polymorph of Li2FeCl4 is in agreement with an inverse spinel structure and a disordered distribution of the cations on the octahedral sites. Mössbauer spectra of the orthorhombic room-temperature modification of Li2FeCl4 correspond to a 1:1 ordering of Li+ -and Fe2+ -ions on the octahedral sites.
A Formula Periodic Table for Benzenoid Hydrocarbons and the Aufbau and Excised Internal Structure Concepts in Benzenoid Enumerations
Authors: Dias Jerry Ray 
Published: February 2015

Abstract
The genesis of two concepts of recent importance to isomeric polyhex enumeration is traced. As it will become evident from this review, the philosophy of our approach stresses the enumeration of select benzenoid groups of practical interest to chemists. These concepts were pivotal to the first published enumerations of the strictly peri-condensed, non-Kekulean, and essentially strain-free total resonant sextet benzenoid groups.
Allende Xenolith AF: Undisturbed Record of Condensation and Aggregation of Matter in the Solar Nebula
Authors: Kurat G. , Palme H. , Brandstätter F. , Huth J. 
Published: February 2015

Abstract
Allende-AF (All-AF) is chemically similar to bulk Allende, its texture is. however, completely different. It consists mainly of highly porous silicate-rich aggregates embedded in a largely opaque matrix. Occasionally olivine-sulfide-metal aggregates and large sulfide-andradite objects are found. Chondrules are absent and grain size in matrix and aggregates is the same, quite different from normal Allende.
The main mineral in All-AF is olivine (22-41 wt% FeO). low Ca-pyroxene is absent, but a variety of clinopyroxenes were encountered. Rare phases found throughout All-AF are refractory metal nuggets (Ir, Os, Ru etc.), HgS, and Ca-phosphate. Associated with sulfide-andradite objects are native-Cu, Ti-magnetite, perovskite, barite, and calcite.
Morphology, crystalline state and minor element contents of olivine strongly suggest an origin by condensation from a gas. Al20 3-contents, for example, range from 0.5 to 3% and Cr2O3-contents reach 2.5%.
Texture of All-AF indicates that condensation of olivine continued during formation of aggregates. Relictic low-Fe aluminous diopsides suggest that olivine was initially FeO-poor. Before final accretion into a solid rock exchange reactions between condensed phases and an (increasingly oxidized) vapor established the high FeO-content of olivine. A similar process led to sulfurization of most of the original metal. The exotic sulfide-andradite objects are probably alteration products of unusual, metal-rich calcium-aluminium-rich inclusions.
It appears that All-AF has preserved a unique record of condensation, hierarchical aggregation, and metasomatic exchange reactions in the solar nebula.
Allende Whole Rock and CAI Studies: Thermal Equilibration History and Noble Metal (Re)distributions in Mineral Phases*
Authors: Jovanovic S. , Reed G. W. 
Published: February 2015

Abstract
Ru, Os, and Ir in Allende whole rock and coarse grained CAIs are present in amounts up to 80% in phases other than inert Pt-metal alloys. Selective chemical dissolution was used to dissolve sulfides by ascorbic acid-H2O2 and metal (NiFe)-silicate-oxides by HF/HCl. Carbon-rich, spinel-chromite residues were left from the demineralization procedures and scavenged inert material such as Pt-metal alloy particles. The Pt-metal contents in sulfide phases from the Allende whole rock sample and the total Pt-metal contents of the CAI samples give near-cosmic to cosmic interelement ratios. Pt-metal ratios in all the other separated phases are fractionated. The Fe/Co ratio in the carbon-rich residue from the CAI and in the sulfide fractions from Allende whole rock and CAI-bulk samples is 230, the same as is reported for sulfides in the Zelda fremdlinge. A scheme for mixing aggregates from different regions of “Allende-space” in the solar nebula is proposed to account for the Pt-metal and Fe-Co distributions observed here.
Chemical alteration processes in condensed material may have required moderate to high temperatures in the nebula to have caused the interelement relationships observed. We determined the final equilibration temperatures to which components of Allende were subjected. Temperatures are based on the distribution of Hg between labile (low T) and retentive (high T) sites in silicate rocks. Compositionally and texturally different CAI clasts and the matrix associated with one of the clasts were equilibrated at 778-975 °C. The averaged thermal equilibration temperature for seven bulk (matrix) Allende samples reported previously was 670 °C. The final thermal equilibrations of the clasts probably occurred before Allende was assembled.
High Resolution Microwave Spectra of Pyridine-N-oxideanda-Picoline-N-oxide
Authors: Heineking N. , Dreizler H. , Endo K. , Kamura Y. 
Published: February 2015

Abstract
The rotational spectra of pyridine-N-oxide and x-picoline-N-oxide ( = 2-methvlpyridine-N-oxide) have been observed by means of pulsed microwave spectroscopy. For both molecules, the 14N quadrupole coupling constants have been obtained. For α-picoline-N-oxide. in addition the parameters of the internal rotation motion and the centrifugal distortion constants have been determined.
Metal Tetrahydroborates and Tetrahydroboratometalates, 18 [1] Studies on the Formation of Cadmium(II)-tetrahydroborates with Tetrahydroborate and Iodide
Authors: Nöth Heinrich , Thomann Martina 
Published: February 2015

Abstract
The structure of cadmium tetrahydroborate in THF solution is fluxional on the NMR time scale and best described as Cd[(µ-H)2BH2]2•nTHF as indicated by IR data. Reactions of LiBH4 with Cd(BH4)2 in THF yield the monoanion [Cd(BH4)3]- exclusively, while a dilithium salt Li2[Cd(BH4)4] • 4 diglyme precipitates from diglyme solutions. Equilibria involving ICd(BH4), Cdl2, Cdl3
-, [Cd(BH4)3]-and/or [ICd(BH4)2]- result from Cd(BH4)2 and LiI in THF or diglyme. The solvent as well as the cation of the iodide (Cd2+ or Li+) influence the equilibria. This can be explained in terms of the different polarity and chelating ability of the solvents.
The New Laves Phase Na2Ba
Authors: Snyder G. Jeffrey , Simon Arndt 
Published: February 2015

Abstract
The crystal structure of Na2Ba was determined from single crystal X-ray diffraction data. It is isostructural with the hexagonal Laves phase Zn2Mg; P63/mmc, a = 739.3(4) pm, c = 1199.9(9) pm. The compound Na4Ba reported in the phase diagram literature is actually Na2Ba. Comparisons are made with other Laves phases using a strain parameter diagram.
Synthese und Kristallstruktur eines Alkali-Erdalkali-Kupfer-Halogeno-Oxovanadats: KBaCuV2O7Cl / Synthesis and Crystal Structure of an Alkaline Alkaline-Earth Halide Oxide of Copper and Vanadium: KBaCuV2O7Cl
Authors: Martin F.-D. , Müller-Buschbaum H. 
Published: February 2015

Abstract
Single crystals of KBaCuV2O7Cl have been prepared by a flux technique and investigated by X-ray analysis. The compound crystallizes with tetragonal symmetry, space group C2
4v-P4 bm, a = 8.8581, c = 5.4711 Å, Z = 2. The crystal structure shows Cu2+ within a one sided strongly distorted CuO4Cl2 octahedron. The copper ion is shifted towards the nearer Cl- neighbour to form a CuO4Cl square pyramid. Two VO4 tetrahedra are connected to give stretched V2O7 double tetrahedra, and linked in planes via the oxygen corners of the CuO4Cl pyramids. The crystal structure and the structure of the complex BaO8Cl2 polyhedron are discussed.
New Dimeric Tetrapeptide Enkephalin AnaloguesHydrophilic Spacer Length and Configuration Affects Potency and Receptor Selectivity
Authors: Stępiński Janusz , Tam S. William 
Published: February 2015

Abstract
Three new bivalent opioid peptide analogues, 1,3-di-(tyrosyl-D-alanyl-glycyl-phenylalanylamido)-2-propanol, 1,4-di-(tyrosyl-D-alanyl-glycyl-phenylalanylamido)-(2R, 3S)-butanediol and 1,4-di-(tyrosyl-D-alanyl-glycyl-phenylalanylamido)-(2R,3R)-butanediol, were synthesized and tested in vitro for μ, δ and ϰ receptor affinities. They were found to have potent opioid receptor binding activity. The (2S,3S)-butanediol bridge configuration yielded selectivity and high potency for μ and ϰ receptors, while the (2R,3R)-butanediol bridge configuration yielded high potency and selectivity for δ receptors. It thus appears that changes in the length and configuration of the polyhydroxyl bridge in dimeric enkephalin analogues can produce a shift in receptor selectivity profiles and therefore suggest the possibility of developing more selective drugs.
The Direct Synthesis of Secondary Amides from Aldehydes; A Novel General Redox Procedure Mediated by Iodotrichlorosilane (ITCS)
Authors: Elmorsy Saad S. , Badawy Doria S. , Nour Mohamed A. , Kandeel Ezzat M. 
Published: February 2015

Abstract
A unique, general redox process for the preparation of secondary amides by the interaction, of aldehydes with nitriles in the presence of two equivalents of iodotrichlorosilane (ITCS) is described and possible pathways are discussed.
Synthese und Kristallstruktur von [Na(12-Crown-4)2]2[Fe4Se4Cl4] / Synthesis and Crystal Structure of [Na(12-Crown-4)2]2[Fe4Se4Cl4]
Authors: Ahle Andreas , Dehnicke Kurt , Maichle-Mössmer Cäcilia , Strähle Joachim 
Published: February 2015

Abstract
[Na(12-crown-4)2]2[Fe4Se4Cl4] has been prepared by the reaction of FeCl2 with Na2Se4 in dimethylformamide solution in the presence of 12-crown-4 as dark red crystals, which were characterized by a crystal structure determination. Space group P1̄, Z = 2, 6295 observed unique reflections, R = 0.085. Lattice dimensions at 20 °C: a = 1397.3(3), b = 1501.8(4), c = 1570.1(4) pm, α = 85.86(2)°, β = 64.06(2)°, γ = 65.01(2)°. The structure consists of [Na(12-crown-4)2]+ cations and cuban-like anions [Fe4Se4Cl4]2+ with Fe ··· Fe contacts o f 282.8(3) pm.