bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Resolution Spectroscopy of N3 by Laser Induced Fluorescence
Authors: Haas Tobias , Gericke Karl‐Heinz 
Published: July 2012

AbstractThe azide radical was generated in the gas‐phase photolysis of HN3 and detected by the high resolution laser induced fluorescence (LIF) technique. Rotationally resolved spectra of the Ã2Σu000 ← X̃2Πg000 and Ã2Σu010 → X̃2Πg010 transitions were obtained. Analysing single rotational lines, the spin splitting constant of the Ã2Σu000 state was derived to be γ = (1.35 ± 0.05) · 10−3 cm−1. Evidence was obtained for a lifetime τ of the Ã2Σu000 state of 0.37 ≤ τ ≤ 20 ns. The observed narrow linewidths are important in other experiments where the determination of scalar and vector properties allows an elucidation of reaction and photodissociation dynamics.
Fluorescent Dyes as Probes of Voltage Transients in Neuron Membranes Progress Report
Authors: Fromherz P. , Dambacher K. H. , Ephardt H. , Lambacher A. , Müller C. O. , Neigl R. , Schaden H. , Schenk O. , Vetter T. 
Published: July 2012

AbstractFluorescent dyes derived from anilino‐pyridinium are studied with respect to their application as probes of voltage‐transients in neuron membranes. Their photophysical properties are characterized in bulk solvents. The spectral features of their voltage‐sensitivity in membranes are determined. A mechanistic scheme of voltage‐sensitivity is proposed. The dyes are applied for optical recording in neurites of cultivated neurons of the leech. The relative sensitivity is evaluated from the fluorescence transients induced by hyperpolarization on the basis of the cable equation. The pervasion of a neuritic tree by action potentials is observed.
Laser Induced Reactions in and at Thin Semiconductor Films Progress Report
Authors: Schultze J. W. , Bade K. , Michaelis A. 
Published: July 2012

AbstractFocussed laser light can be used to induce chemical or electrochemical reactions in the μm scale. The attainable high power densities allow to achieve fast reaction rates. At metals and insulators thermal heating dominates. On semiconductors short pulses or low energy densities cause mainly electronic processes under isothermal conditions. These will be emphasized in this paper for thin semiconductor films in electrolyte solutions. The induced reactions measured under potentiostatic or potentiodynamic conditions include electron (ETR) and ion transfer (ITR) as well.—Examples are discussed for n‐type semiconducting passive films on some base metals with thicknesses in the range from nm to μm. The ETR depend mainly on the potential showing the tendency to saturation while the ITR depend on the field strength. Doping by ion implantation reduces ETR and ITR as well. Amorphous films show a smaller tendency to inner reactions like breakdown. Bubble formation can be detected in a microscopic scale. Substrate effects are due to epitaxy on various grains, changes of the structure and crystallinity (suboxide and TiN) and electronic processes at the substrate surface (Al/Al2O3).
Plasma Polymerization
Authors: Kay E. 
Published: July 2012

AbstractPlasma polymerization leads to polymer film formation at low temperatures, e.g. at room temperature, on any substrate. It is one of relatively few processes which permits the formation of very thin uniform polymer films which conform to a substrate of any shape. In general, such films are amorphous throughout, using electron diffraction as a criterion. By appropriate control of the rate limiting plasma processes the structure of the polymer can be modified at will. So, for example, the degree of cross‐linking and resultant chemical and physical properties can be manipulated over a wide range. Work in this laboratory has specialized in a unique process which permits uniform matrix isolation of a variety of materials, such as for example zero valent metal clusters, throughout the polymer matrix. The volume fraction and size of such clusters within the matrix can be readily controlled. Clearly, a variety of properties of such a composite system can be changed in a systematic way. Emission spectroscopy as well as mass spectrometry provide convenient means of monitoring some of the key processes occurring in the plasma. Solid state N.M.R., E.S.C.A., I.R., T.G.A., and D.T.A. and electron microscopy and diffraction serve to characterize the structure of the films.
The Adsorption of Ordered Polyimide Monolayers
Authors: Schedel‐Niedrig Th. , Keil M. , Sotobayashi H. , Schilling T. , Tesche B. , Bradshaw A. M. 
Published: July 2012

AbstractOrdered polyimide monolayers can be prepared on solid surfaces using the Langmuir‐Blodgett technique of Kakimoto and co‐workers. In the present study we have investigated the adsorption of two different monolayers (PMDA‐ODA and PMDA‐PDA) on both graphite and oxidised silicon surfaces. Scanning tunneling microscopy indicates that on graphite both the rod‐like PMDA‐PDA and the zig‐zag PMDA‐ODA are characterized by a high degree of two‐dimensional order. X‐ray absorption near edge spectroscopy (XANES) at the carbon, nitrogen and oxygen K‐edges has been used to obtain information on the orientation of the different moieties in the polymer chain. These XANES data are compared to the corresponding spectra of pyromellitic diimide and diphenyl ether, which may be regarded as the building blocks of PMDA‐ODA polyimide, in order to obtain more insight into the origin of the resonances.
Diamond Thin Films: Preparation, Characterization and Selected Applications Progress Report
Authors: Bachmann Peter K. , Leers Dieter , Wiechert Detlef U. 
Published: July 2012

AbstractPreparation and characterization of vapor‐deposited diamond coatings and free‐standing diamond membranes are reviewed. General trends and implications of a C/H/O‐phase diagram, which provides a common basis for all diamond chemical vapor deposition methods are discussed. The status of selected mechanical, optical and electronical applications is summarized.
Grain Growth and Reaction in Nickel‐Silicon Thin‐Films
Authors: Knauth P. , Charaï A. , Bergman C. , Gas P. 
Published: July 2012

AbstractThin‐film reactions in nickel‐silicon bilayers were studied by differential scanning calorimetry and transmission electron microscopy. Interesting particularities of thin‐film reactions were observed: a small exothermic effect before the main peak of reaction is due to grain growth of polycrystalline nickel. The activation energy of the process ((220 ± 50) kJ/mol) is in the same order of magnitude as the activation energy of grain boundary self diffusion of nickel. A mean grain boundary enthalpy of nickel ((0.7 ± 0.3) J/m2) is calculated. The main exothermic peak is due to the formation of di‐nickel silicide; its molar enthalpy of formation (‐(155 ± 20) kJ/mol)) and the energy of activation of the reaction ((150 ± 30) kJ/mol) are in good agreement with literature values. The activation energy is comparable to the activation energy of grain boundary diffusion of nickel in δ‐Ni2Si.
LaF3 Thin Films as Chemically Sensitive Material for Semiconductor Sensors
Authors: Szeponik Jan , Moritz Werner , Sellam Farid 
Published: July 2012

AbstractA new kind of semiconductor based fluoride sensor was prepared by growing thin polycrystalline LaF3 films directly on silicon substrates using vacuum vapour deposition technique. The EICS (Electrolyte Ion Conductor Semiconductor) structure was investigated by means of impedance spectroscopy, CV measurements and exchange measurements with labeled ions (18F). Whereas charge and potential conditions at the LaF3/ electrolyte interface are governed by the fast fluoride exchange the LaF3 bulk and the blocked Si/LaF3 interface determine the electrical behavior. Although the Si/LaF3 contact is not reversible the potential stability of the EICS structure is surprisingly high. Additional results at epitaxial LaF3 layers, prepared by MBE, were taken into account for comparision with those at polycrystalline layers.
Electrochemical Observation of Phase Transitions in Thin Films of Nickel/Phosphorus Alloys
Authors: Hofmann Udo , Weil Konrad G. 
Published: July 2012

AbstractThin films of Ni100‐xPx alloys with x = 26, 20, and 16 were prepared by electrodeposition onto one face of a gold plated quartz crystal which at the same time was part of a microbalance. Initially the films consisted of a mixture of an amorphous alloy and fcc nickel crystals, supersaturated with phosphorus. The compositions of the two phases as well as their relative amounts are determined by simultaneous measurement of charge and mass change during anodic oxidation of the film. Films that were annealed at different temperatures prior to their oxidation consist of other phases, known from the nickel phosphorus phase diagram. Hence, electrochemical measurements on annealed samples provide a simple access to the reaction pattern leading from a mixture of metastable phases to the final equilibrium state.
Resistance Changes of Thin Film Electrodes of Silver
Authors: Körwer D. , Schumacher D. , Otto A. 
Published: July 2012

AbstractResistance measurements of thin film electrodes allow to monitor different kinds of surface processes. We examined the resistance change of silver electrodes in KCl and KClO4 electrolytes due to anion adsorption and desorption, corrosion from Cl−, and surface roughness from oxidation reduction cycles or silver deposition from solution. Surface roughness is known to be important for surface enhanced Raman scattering (SERS). The influence of pyridine was investigated in some cases and in‐situ SER‐spectra were recorded during silver deposition.
Schichtsynthese von Übergangsmetallnitriden mit ionenstrahlunterstütztem Aufdampfen
Authors: Ensinger W. 
Published: July 2012

AbstractNitrides of titanium, chromium, molybdenum and tantalum were prepared by evaporation of the metal in an atmosphere of reduced nitrogen pressure under simultaneous irradiation with highly energetic nitrogen ions.—Chemical analysis showed that the elemental composition of the nitrides is strongly correlated with ion irradiation intensity and with chemical reactivity of the metal. Under identical process conditions titanium formed TiN, but chromium Cr2N. In case of molybdenum and tantalum X‐ray diffractometry revealed that by deposition under ion irradiation with high energy and beam intensity metastable nitrides with cubic structure could be formed.
Structural Relationships between Floating and Deposited Monolayers of Docosanoic Acid
Authors: Engel M. , Merle H. J. , Peterson I. R. , Riegler H. , Steitz R. 
Published: July 2012

AbstractFloating docosanoic acid (behenic acid) monolayers in the SmI and SmH phase were deposited with the Langmuir‐Blodgett technique onto thin polymethylmethacrylate (PMMA) and Formvar substrates and investigated by electron diffraction. The molecular packing of the monolayers on the substrates vary from those on the water surface and are different for different substrates. On PMMA four phases (H, SmB, SmI, SmL) have been identified, depending on the deposition conditions. While SmB and SmI are known for docosanoic acid on the water surface, H and SmL have only been unequivocally observed in other substances or on other subphases. The monolayer structure on Formvar was identical under all deposition conditions and identified as the H‐phase. The monolayer/substrate interaction was directly addressed by measurements of the work of adhesion. The work of adhesion between the monolayer and PMMA depends strongly on the surface pressure, indicative of interactions that vary with the molecular arrangement in the monolayer.
Preparation and Thermal Behavior of Freely‐Suspended and Transferred Films Composed of a Single Compound, the Liquid Crystal 707PP
Authors: Decher G. , Maclennan J. , Reibel J. 
Published: July 2012

AbstractWe have recently introduced a new method for the preparation of ultrathin smectic films on solid supports by transferring freely‐suspended liquid‐crystalline films [1, 2]. Here we report on the preparation, structural properties and thermal behavior of freely‐suspended and transferred films of 2‐(4'‐Heptyloxyphenyl)‐5‐heptylpyridine (707PP). Freely‐suspended and transferred films were investigated using optical microscopy and X‐ray diffraction. Both types of films exhibit reversible phase transitions comparable to bulk values.
Photoelectrochemical Investigations of Molecular Semiconductors: Characterization of the Conduction Type of Various Substituted Porphyrins
Authors: Schlettwein D. , Jaeger N. I. , Wöhrle D. 
Published: July 2012

AbstractThe charge transfer from thin film electrodes (thickness ≈ 130 nm) of the zinc(II) complexes of phthalocyanine (1), 2,3,9,10,16,17,23,24‐octacyanophthalocyanine (2), tetrapyrido[2,3‐b; 2′,3′‐g; 2″,3″‐1; 2′″,3′″‐q]‐5,10,15,20‐tetraazaporphyrin (3) and tetrapyrazino[b;g;l;q]‐5,10,15,20.tetraazaporphyrin (4) to oxygen or EDTA dissolved in an aqueous electrolyte was investigated. Illumination with visible light results in photocurrents which are characteristic for each of the studied compounds. The observations are discussed in terms of the band model suitable for molecular organic semiconductors. From the observed predominant direction of the photocurrent a trend in the band positions and the conduction type of the materials 1, 2, 3 and 4 is established. The transformation of a p‐type into a n‐type porphyrin solid can be achieved by appropriate chemical substitution in the ligand system.
Anodic Dissolution of Metallophthalocyanine Layers and Their Intrinsic Oxidation
Authors: Jansen Rolf , Beck Fritz 
Published: July 2012

AbstractVoltammetric measurements at a PtRRDE, where vacuumdeposited MePc‐layers (70–700 nm) are present at the disc, were performed in 0.1 M LiClO4 in acetonitrile. Any dissolved MePcz+‐species can be rereduced at the ring. Anodic dissolution was found to be the only process in the case of FePc and CoPc at relatively negative potentials. The cations dissolve layer by layer. For NiPc and CuPc, three different anodic processes can be distinguished: I) Anodic insertion of anions into the solid without any dissolution of cationic species. II) A further insertion of anions at more positive potentials, which is accompanied by a slow dissolution of the material. This is indicated by a relatively weak cathodic ring current. Lattice dynamics in the course of the anodic insertion of anions leads to a destabilization of the solid. III) A strong ring current shows the anodic dissolution of the whole MePc‐layer at even more positive potentials. It is accompanied by a chemical dissolution to release the anions, which were inserted in the course of steps I and II. The consequences with respect to the long term stability of MePc are discussed.
Photophysical Properties of Heterogeneous AgBr Layers
Authors: Böttcher Horst , Räbisch Mathias , Schreiber Kerstin , Siegel Jörg 
Published: July 2012

AbstractBy Multi Source Physical Vapour Deposition (MS‐PVD) the preparation of mixed thin layers consisting of different inorganic or organic substances is possible. By this method it was investigated which effect admixture of different metal halides (NaX, PbX2) had on structure and photosensitivity of evaporated AgBr layers. Unexpectedly the mixed layers revealed a considerable increase in photosensitivity in the range between 20 and 60 vol‐% metal halide admixture as compared to pure AgBr.—The results of photo‐EMF and microwave photoconductivity measurements are indicative of an effective charge carrier separation at the segregated crystallite phase boundaries.
On Coulombic and Solvophobic Liquid‐Liquid Phase‐Separation in Electrolyte Solutions
Authors: Weingärtner Hermann , Merkel Thomas , Maurer Ulrich , Conzen Jörg‐Peter , Glasbrenner Heike , Käshammer Stefan 
Published: July 2012

AbstractWe have performed a systematic study of liquid‐liquid phase equilibria in aqueous and non‐aqueous solutions of tetraalkylammonium salts up to about 500 K, covering a large number of hydrogen‐bonding, dipolar aprotic and non‐polar solvents. There appear to be two different types of liquid‐liquid phase equilibria resulting from long‐range Coulombic and from short‐range specific forces, respectively. These may be denoted as Coulombic and solvophobic unmixing. Coulombic unmixing is observed in solutions of 1:1‐electrolytes in solvents of low dielectric constant, as is exemplified for solutions in hydrocarbons and long‐chain alcohols. It appears to be closely related to a general instability of ionic fluids at low reduced temperatures. Increase of the dielectric constant results in complete miscibility, as is demonstrated for salts dissolved in short‐chain alcohols and some common dipolar aprotic solvents. Solvophobic unmixing occurs if salts with large cations and anions are dissolved in water. A phenomenological analysis shows that this phase separation results from those thermodynamic pecularities which are usually attributed to the hydrophobic nature of the cations. Some cation‐anion association appears also to play a role. Similar immiscibilities have been observed with other hydrogen‐bonding solvents of high cohesive energy density, namely glycerol, ethylene glycol, 1,3‐propanediol, formamide and monoethanolamine, suggesting the existence of a more general solvophobic unmixing effect.
Internal Solid State Reactions of the Type A + B = AB: Diffusion‐Controlled Formation of AB from A and B Dissolved in a Crystalline Host Matrix
Authors: Backhaus‐Ricoult M. , Schmalzried H. , Tarento R. J. 
Published: July 2012

AbstractA and B diffuse from opposite sides into a finite slice of solid C. After a certain diffusion time the solubility product of a product phase, AB, may be reached and AB precipitates. The location of the first nuclei formation is calculated as a function of the solubilities and the diffusion coefficients of A and B in the matrix C, and of the solubility product. Chemical diffusion coefficients of A and B, which are either constant or proportional to their own concentration, or proportional to the concentration of the other diffusing species are considered. For some sets of typical system parameters the diffusion profiles are calculated and the time and coordinate for first precipitation are shown.—Further growth of small nuclei is given by further diffusion of A and B into the matrix C and to the precipitate, which constitutes a sink for A and B. The precipitate grows in the diffusion field with a preference for certain directions. These directions and the initial growth rate of the precipitate depend on the transport properties of both the matrix and the precipitate, as well as on the thermodynamic conditions of phase coexistence of precipitate and matrix. Limiting cases of an infinitely fast or negligible material transport inside the precipitated phase are considered and the initial growth of a single precipitate in the diffusion field and its shape evolution during growth are calculated.—The global morphology of the assembly of AB precipitates for long diffusion times is discussed by considering the morphological evolution of an intermediate AB layer.
Electroreduction of 1‐and 2‐naphthylhydrazonodimedones in DMSO
Authors: Vasudevan D. , Venkatachalam C. S. , Kalidas C. 
Published: July 2012

AbstractA detailed investigation on the reduction of 2‐(1‐naphthylhydrazono)dimedone (1‐NHD) and 2‐(2‐naphthylhydrazone)dimedone (2‐NHD) in 0.1 M TEAI‐DMSO was made using various electroanalytical techniques. Each of the two compounds gave two well‐defined polarographic waves/cyclic voltammetric (CV) peaks. The first one‐electron diffusion‐limited wave/peak arises out of the formation of the corresponding anion radical and has been characterised to be of oxy type from in‐situ EPR studies. However, the second wave/peak is attributed to an EC reaction involving a fast reverse disproportionation reaction by which the anion radical is regenerated, as confirmed from CV studies and also from the non‐integral n value obtained for the second wave from microcoulometry. Macroscale CPE experiments carried out at the limiting regions of the first and second polarographic waves of 1‐NHD and 2‐NHD afforded the corresponding naphthylamines as the major product. Based on these results, a plausible mechanism for the electroreduction of 1‐NHD and 2‐NHD in DMSO has been proposed.
Concentration Dependent far Infrared Absorption Spectra of the Mixtures FURAN/CS2, FURAN/CCl4, FURAN/C6H6
Authors: Haritopoulou M. , Samios J. , Zoidis E. , Dorfmüller Th. 
Published: July 2012

AbstractThe far infrared absorption spectra of furan in liquid solutions with carbon disulphide, carbon tetrachloride and benzene, are to the first time presented, along with the absorption spectra of neat furan at three different temperatures. The spectral behaviour of the absorption curves is studied for each solvent at three mole fractions of furan. The results are qualitatively discussed in terms of the intermolecular geometry in the solution, as determined by the structure characteristics of the non‐polar solvents, and also in terms of the interaction between solvent and solute, producing under certain circumstances an interaction induced contribution to the permanent dipole moment of the furan molecule.
Surface Ionization of Dipalmitoylphosphatidylcholine as Detected by the pH Dependence of the Phase Transition Temperature of Liposomes
Authors: Fernández Marta S. , Calderón Estela 
Published: July 2012

AbstractThe surface ionization of lecithin phosphodiester has been studied following the effect of bulk pH on the increment in the gel to liquid‐crystal phase transition temperature (tm) of dipalmitoylphosphatidylcholine (DPPC) liposomes, induced by incorporation of protonated stearylamine. At constant pHb, the increment (Δtm is a monotone increasing function of stearylamine concentration which deviates from linearity, toward lower Δtm values, at high proportions of additive. From plots of Δtm as function of the stearylamine proportion in DPPC liposomes at different pHb values, the initial slopes, as stearylamine concentration approaches zero, is obtained and interpreted as a potentiality for tm elevation of DPPC bilayers. The slope value, seems to be related to the ionization degree of the phosphate group since it increases with bulk pH and levels off above pHb 4 i.e., for zwitterionic lecithin. If the titration curve resulting from normalization of those slope values, is attributed to ionization of lecithin phosphate, an apparent pK of 1.3 is obtained. The consistency of the data analysis is supported by the good fitting found between the experimental results and a theoretical curve based on Henderson‐Hasselbach, Boltzmann, and Gouy‐Chapman equations. Best fit is obtained when the intrinsic interfacial pK, which is the pK in the absence of surface electrostatic effects, is set equal to 4. Such a high intrinsic pK value is explained in terms of the effect of the reduced dielectric constant of the lipid‐water interface, on the ionization of the phosphate group which is a molecular acid and, as such, will be stabilized in a low polarity region.
Multiprocessed Simulation of Competing Folding Pathways in RNA: The Shaping of the Catalytic Site for Splicing
Authors: Fernández Ariel 
Published: July 2012

AbstractThe open problem in RNA catalysis we focus on is how to predict which mitochondrial mRNA introns belonging to group I will splice exclusively in vivo. We have simulated competing folding pathways by a parallel distributed process in order to prove that early base‐pair disruptions ultimately cause the internal guiding sequence (IGS) to function as intramolecular adaptor in an otherwise‐inert structure. In this way, the participation of the IGS‐3′exon pairing in promoting splicing in vivo is elucidated. The case of the YC4 intron is chosen as an illustration. Our approach requires implementing parallel‐processed Monte‐Carlo simulations to monitor the effect of base‐pair disruptions, leading to competing folding pathways. The search for active structures is subject to time constraints characteristic of the assembling of pre‐mRNA's.