bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of the Reaction of Solvated Electrons with Water in Liquid Ammonia
Authors: Telser Th. , Schindewolf U. 
Published: July 2012

AbstractSolvated electrons (< 10−6 M) produced by flash photolysis in ammonia react with water according to the rate law d[e−]/dt = k · [e−] · [H2O] with the rate constant k = 0.16 ± 0.03 M−1 sec−1 at – 40°C. The rate law is compatible with the reaction e− + H2O → H + OH−, but the activation energy Ea (e−) = 6 ± 1 kJ/mol is too small for this endothermic process with ΔH0 = 52 kJ/mol. Therefore we conclude that in the rate determining step an unknown intermediate is formed which in turn recombines to molecular hydrogen. Evidence for this intermediate was given already 15 years ago in the pure aqueous system in which solvated electrons a few msec after their reaction could be regenerated by a photo flash too soft to photo‐generate them directly. – The reaction of very low concentrated metal ammonia solutions with water follows the same kinetics. But at higher concentrations (0.1 M) the relative reaction rate is very low. With sodium the reaction is slower than with cesium, in deutero‐ammonia it is slower than in normal ammonia. It is almost of zero order with respect to the metal and of one ha1f order with respect to water and has an activation energy Ea (Na) = 32 ± 3 kJ/mol (normal sodium‐ammonia solution). The observed kinetics suggest that the solvated electrons are still the only reactive species in these solutions; but their concentration is lower than the metal concentration by many orders of magnitude due to the well known spin pairing equilibrium, which must include a metal cation and a solvent molecule. The stability of the spin paired species increases with decreasing cation size and with increasing tendency of the solvent to form hydrogen bridges. The high experimental activation energy is partly due to the temperature dependence of the spin pairing equilibrium.
Calorimetric Investigations of Lipid Phase Transitions. II. The Heat of Transition
Authors: Knoll Wolfgang , Höhne Günther W. H. 
Published: July 2012

AbstractMultilamellar liposomes of dimyristoylphosphatidylcholine in excess water have been investigated by differential temperature scanning calorimetry. The heat, ΔQ, that is exchanged between the environment and the sample at its main phase transition (fluid ↔ ordered) has been determined as a function of the sample volume, lipid concentration, and scanning rate. No variation of the transition heat is found for sample volumes ranging from 35 μl to 785 μl and for lipid concentrations ranging from 3 mM to 300 mM. For low scanning rates α(α ≤ 0.02 K · min−1) a constant transition heat of ΔQ = 23.4 kJ · mol−1 is found that increases around α = 0.1 K · min−1 to ΔQ = 27.2 kJ · mol−1 which remains constant for higher α. We interpret this finding as being evidence for non‐equilibrium transitions at high scanning rates due to relaxation process in the lipid‐water‐system that need minutes to be completed.
Phase Equilibria in Liquid Crystalline Systems Part II. Theory and Interpretation of Experimental Results
Authors: Ballauff M. , Flory P. J. 
Published: July 2012

AbstractCharacteristic temperatures T* have been evaluated for the oligomeric p‐oxybenzoates, C6H5CO(‐OC6H4CO)n‐2‐OC6H5 from the transition temperatures TNI presented in the preceding paper. For n = 3, 4 and 5 they are, respectively, 343, 316 and 306 K. These parameters that measure the intensities of the orientation‐dependent intermolecular interactions are correlated with the optical anisotropy Δα and the average intermolecular cohesive energy expressed by the characteristic pressure p*. The characteristic temperature T* decreases slightly with chain length. The lattice theory of nematic fluids is extended to include mixtures of rodlike molecules having different characteristic temperatures T* in order to treat binary and ternary mixtures of the p‐oxybenzoate oligomers. The wide biphasic gaps predicted for the several binary systems and the concomitant pronounced partitioning of the components between the nematic and isotropic phases are not confirmed by experiments. Compositions of the coexisting phases in ternary systems were found to be identical within limits of experimental determinations. These marked departures from theory are explicable on the premise that facile rotational diffusion of the nematogens here considered, which are of comparatively low chain length, leads to rapid generation of ordered domains of large dimensions. Subsequent diffusional transport over the required distances consequently is very slow. The transition temperatures observed in binary systems are in excellent agreement with calculations carried out in the “single component” approximation using mean values of the axial ratio and of T* for the mixture, these being taken to be the same in the two phases at equal concentrations.
Composition Dependent Electronic Conductivity and Hall Coefficient of β‐Ag2 + ΔS
Authors: Sohège J. , Funke K. 
Published: July 2012

AbstractThe electronic conductivity, σe, and the Hall coefficient, RH, of β‐Ag2 + δS are experimentally determined at temperatures T between 190°C and 320°C and at values of δ covering the entire stability range. The change of composition is achieved by in situ coulometric titration. At δ > 5 · 10−4, where β‐Ag2 + δS shows a metallic behaviour, the data are consistent with a parabolic conduction band and an electronic relaxation time which is proportional to T−3/2, but does not depend on the electronic energy. The same concept, plus number densities of defect electrons taken from the titration curves, is also used for an interpretation of σe and RH at smaller δ, where the metal‐semiconductor transition is observed.
ArF Laser (193 nm) Photolysis of HNO3. Formation of Excited Fragments
Authors: Papenbrock Th. , Haak K. K. , Stuhl F. 
Published: July 2012

AbstractHNO3 was photolysed using an ArF (193 nm) excimer laser. Besides strong emission from OH(A2Σ+), weaker fluorescence from excited NO was observed in the investigated wavelength range 130‐−900 nm. The OH(A) emission is generated by absorption of two laser photons while the NO emission is produced by a one‐photon process. The rotational and vibrational populations of the OH fragments can be explained by a simplified impulsive model with additional contributions from the change of the OH bond length and by a slight bending motion of the parent molecule. Monitoring the strong OH emission appears to be a sensitive method to detect gaseous nitric acid in air in the ppb range.
A Generalized van der Waals Equation of State IV. Corrections for Medium and Low Densities for the Example of Methane
Authors: Móritz P. , Kohler Friedrich 
Published: July 2012

AbstractAn equation of state, recently developed for high densities, is extended to the whole density range and is compared to tabulated values of the thermodynamic data of methane. The agreement is very satisfactory. At subcritical temperatures, the parameters can be derived from second virial coefficient, vapour pressure, orthobaric liquid volume, and isothermal compressibility. At supercritical temperatures, the number of necessary p‐ν‐T measurements can be considerably reduced in comparison to conventional equations of state.
The Kinetic Behaviour of Polycrystalline Alloy Electrodes (σ‐(Fe, Zn))
Authors: Lang J. , Schwitzgebel G. 
Published: July 2012

AbstractThe equation for the impedance of alloy electrodes was developed on the basis of a model for diffusion in polycrystalline alloys by using Fourier transformation and was included in the total cell impedance. In order to obtain experimental confirmation, the magnitude and the phase displacement of the impedance of cells containing electrodes made of Γ(Fe,Zn) were measured with the aid of a special impedance spectrometer. The experimental results were very well represented by the theoretical equation in the frequency range from 0.3 Hz up to 7 kHz. The evaluation yielded the electrochemical parameters of the alloy electrode. Thus, the coefficients D(25 °C) = 2 · 10−16 cm2 s−1 of bulk and D' (25 °C = 5 · 10−8 cm2 s−1 of grain boundary diffusion, as well as their activation energies were determined.
Supercritical‐Fluid Extraction Calculations for High‐Boiling Petroleum Fractions Using Propane. Application of Continuous Thermodynamics
Authors: Cotterman Ronald L. , Dimitrelis Dimitrios , Prausnitz John M. 
Published: July 2012

AbstractSupercritical‐fluid extraction is a useful process for upgrading heavy multicomponent mixtures such as high‐boiling petroleum fractions. Design‐oriented calculations are reported for an extraction process using propane to extract intermediate components from a petroleum fraction with molecular weights in the range 150‐−500. The composition of the heavy‐hydrocarbon mixture is described by two continuous distribution functions of molecular weight, one for paraffinic and one for aromatic components. Process calculations are based on a recently developed thermodynamic framework for mixtures with very many components, coupled with an equation of state of the van der Waals form. Particular attention is given to multicomponent phase equilibria in the retrograde region where solvent recovery is favorable. Quantitative results are given for solvent capacity and selectivity as a function of operating conditions.
Physicochemical Properties of Supercritical Solvents (Invited Lecture)
Authors: Franck E. U. 
Published: July 2012

AbstractA survey is given of selected thermophysical properties of supercritical solvents which have been determined more recently and which may have technical interest. The static dielectric permittivity of water and of supercritical water‐benzene mixtures to 400°C and several 1000 bar is shown. The transport properties viscosity and thermal conductivity of water at high pressures and extending into the supercritical region are discussed. Of binary systems anthracene as a model solute in ten different highly compressed sub‐ and supercritical fluids is discussed and results presented as “enhancement” factors and virial coefficients B12. Critical curves of binary aqueous systems are shown and methods for calculations indicated. The binary systems water‐nitrogen and water‐oxygen were determined to 2000 bar and excess volumes of water‐methane and water‐benzene measured and calculated.
Chromatography with Mobile Phases in the Liquid and the Supercritical State
Authors: Schmitz Franz P. , Leyendecker Dietger , Klesper Ernst 
Published: July 2012

AbstractA comparative study on the chromatographic properties of the alkanes n‐pentane, n‐butane, iso‐butane, and propane in the liquid and the supercritical state has been performed using silica gel as the stationary phase and four condensed aromatic compounds as the substrates. At supercritical conditions, chromatographic parameters can be influenced by temperature and pressure to a greater extent than at liquid conditions. Both the capacity ratios and overall resolutions reach maximum values at supercritical state. The maxima become more pronounced with decreasing critical temperature of the mobile phase. The possibilities for optimizing a chromatographic analysis with supercritical eluents are considerable.
Experimental and Theoretical Investigations of the Second‐Order Zero Field Splitting Parameters of Mn(II) with Cl− as Ligand
Authors: Heming M. , Remme S. , Lehmann G. 
Published: July 2012

AbstractZero field splitting (ZFS) parameters for [MnCl6]4‐ in three Cd compounds were determined and the validity of the superposition model was demonstrated by the consistent values of the intrinsic ZFS parameter b̄2 in all three cases as well as by a detailed comparison of the experimental ZFS pattern for one compound with that calculated from the crystal structure data. Additional ZFS data for [MnCl6]4‐ from the literature are also shown to lead to only slightly variable values of b̄2. – The change of the intrinsic ZFS parameter b̄2 from a negative value for F− to a larger positive value for Cl− as ligand is shown by detailed calculations for the various mechanisms to be due to the superponable overlap and covalency contributions as a result of increased charge transfer and ligand spin‐orbit coupling constant. The reliability of such calculations is still limited by the lack of experimental data for the transferred spin densities.
The Structure of the Formic Acid Molecule in the Liquid State from Neutron Diffraction Measurements Involving Five Isotopically Different Species
Authors: Bertagnolli H. , Chieux P. , Hertz H. G. 
Published: July 2012

AbstractNeutron diffraction experiments on liquid formic acid of the five isotopically different forms DCOOD, DCOOH, HCOOD, 0.36 DCOOD + 0.64 DCOOH, and 0.36 DCOOD + 0.64 HCOOD were performed. Inelastic scattering corrections had to be performed in a particularly careful way considering that H is a strongly incoherent scatterer. From the five corrected coherent cross sections and the corresponding weighted sums of pair correlation functions a first set of intramolecular structure data is derived. A suitable decomposition of the primary experimental material in selected groups of pair correlation functions served to work out further structural details which showed that formic acid in the liquid state is a molecule for which the OH group is rotated by about 50° out of the molecular plane.
Excess Molar Enthalpies, Excess Molar Heat Capacities and Excess Molar Volumes of (Fluorobenzene + an n‐Alkane)
Authors: Roux A. H. , Grolier J.‐P. E. , Inglese A. , Wilhelm Emmerich 
Published: July 2012

AbstractA flow microcalorimeter of the Picker design was used to measure excess molar enthalpies HE at 298.15 K of {x1C6H5F + x2n‐ClH2/+2} for l = 6, 7, 8, 10, 12, 14 and 16. The calorimeter was used in the discontinuous mode. The actual mole fractions x1 were determined with the aid of a vibrating‐tube densimeter connected to the outlet of the mixing cell in conjunction with density data measured separately. The imprecision of the measurements is characterized by s(HE)/H < 0.005, where s(HE) denotes the standard deviation from a Redlich‐Kister type smoothing equation, and the subscript max indicates the maximum of HE with respect to composition. At the same temperature and for the same mixture, excess molar volumes VE were determined with a vibrating‐tube densimeter (flow conditions). With one exception (i.e. l = 6), s(VE)/V < 0.007. Another type of flow calorimeter was used to measure excess molar heat capacities C at constant pressure of mixtures belonging to the same series with l = 7, 8, 10, 12 and 14. In all cases s(C)/CP,minE < 0.013, where min indicates the minimum of C. A preliminary discussion of the results is presented in terms of the simplest version of the Guggenheim‐Barker‐Kehiaian group‐contribution theory.
Bone morphogenetic proteins regulate hinge point formation during neural tube closure by dynamic modulation of apicobasal polarity
Authors: Eom Dae Seok , Amarnath Smita , Fogel Jennifer L. , Agarwala Seema 
Published: August 2012

AbstractBACKGROUNDA critical event in neural tube closure is the formation of median hinge points (MHPs) and dorsolateral hinge points (DLHPs). Together, they buckle the ventral midline and elevate and juxtapose the neural folds for proper neural tube closure. Dynamic cell behaviors occur at hinge points (HPs), but their molecular regulation is largely unexplored. Bone morphogenetic proteins (BMPs) have been implicated in a variety of neural tube closure defects, although the underlying mechanisms are poorly understood.METHODSIn this study, we used in vivo electroporations, high‐resolution microscopy, and biochemical analyses to explore the role of BMP signaling in chick midbrain neural tube closure.RESULTSWe identified a cell‐cycle–dependent BMP gradient in the midbrain neural plate, which results in low‐level BMP activity at the MHP. We show that although BMP signaling does not have a role in midbrain cell‐fate specification, its attenuation is necessary and sufficient for MHP formation and midbrain closure. BMP blockade induces MHP formation by regulating apical constriction and basal nuclear migration. Furthermore, BMP signaling is critically important for maintaining epithelial organization by biochemically interacting with apicobasal polarity proteins (e.g., PAR3). As a result, prolonged BMP blockade disrupts apical junctions, desegregating the apical (PAR3+, ZO1+) and basolateral (LGL+) compartments. Direct apical LGL‐GFP misexpression in turn is sufficient to induce ectopic HPs.CONCLUSIONSBMPs have a critical role in maintaining epithelial organization, a role that is conserved across species and tissue types. Its cell‐cycle–dependent modulation in the neural plate dynamically regulates apicobasal polarity and helps to bend, shape, and close the neural tube. Birth Defects Research (Part A) 2012. © 2012 Wiley Periodicals, Inc.
Size‐modulated synergy of cellulase clustering for enhanced cellulose hydrolysis
Authors: Tsai Shen‐Long , Park Miso , Chen Wilfred 
Published: July 2012

AbstractImmobilization of enzymes onto nanoparticles for enhanced biocatalytic activity via enzyme clustering is a growing field. In this paper, the effect of nanoparticle size on the hydrolytic activity of artificial cellulosomes was investigated. A simple method based on metal affinity coordination was employed to directly conjugate two enzymes, an endoglucanase CelA and an exoglucanase CelE, onto CdSe–ZnS core–shell quantum dots (QDs) without the use of any chemical modification or linker molecules such as streptavidin. Artificial cellulosomes were created by clustering the enzymes onto two different QDs (5 and 10 nm) to systematically study the influence of particle size and QD to enzyme ratio on the enhancement in cellulose hydrolysis. Our results indicate that enzyme proximity is the most important factor for activity enhancement while the influence of particle size is relatively modest. This detailed understanding will provide insights for the design of other artificial cellulosomes based on nanoclustering of multiple catalytic domains with significantly enhanced activities, and may be applicable for designing improved nanobiocatalysts for biofuel production, bioremediation, and drug design.
Können Tiere zählen?
Authors: Gross Hans Joachim 
Published: August 2012

AbstractSeit über 140 Jahren wissen wir bereits, dass der Mensch die angeborene Fähigkeit besitzt, nur bis zu vier Objekte korrekt zu erkennen, wenn das Zählen strikt verhindert wird. Auch viele Wirbeltiere sowie die Arbeiterinnen der Honigbiene, die wie alle Tiere natürlich unfähig sind zu zählen, können sich bis zu vier Objekte merken. Diese angeborene, Menschen und Tieren gemeinsame numerische Kompetenz regt zu interessanten Fragen zum Nutzen und zur Evolution dieser Fähigkeit an. Die “magische” Zahl Vier ist offensichtlich ein neurologisches, historisches und mythologisches Rätsel.
Mikroskopie jenseits der Auflösungsgrenze
Authors: Manck Raphael , Fischer Reinhard 
Published: August 2012

AbstractDie Auflösung konventioneller lichtoptischer Mikroskope ist aufgrund physikalischer Gesetze durch die Wellenlänge des eingesetzten Lichts begrenzt. Die Größe vieler essenzieller intrazellulärer Komponenten wie Cytoskelett oder sekretorische Vesikel liegt jedoch weit unter dieser Auflösungsgrenze. Super Resolution‐Mikroskopietechniken wie Photoactivated Localization Microscopy ermöglichen es, diese Grenze zu durchbrechen. Durch kontrolliertes Aktivieren einer Subpopulation von photoaktivierbaren Fluorophoren in einer Probe kann die Position eines jeden Moleküls auf wenige Nanometer genau bestimmt werden.
Mimikry als Strategie von Jungfischen
Authors: Reininger Miriam 
Published: August 2012

AbstractDie hohe Räuber‐ und Konkurrentendichte im Korallenriff zwingt vor allem Jungfische dazu, neue Überlebensstrategien zu entwickeln. Mimikry, d. h. die Nachahmung eines anderen Lebewesens zum Erzielen eines biologischen Vorteils, ist nur eine mögliche Strategie. Juvenile Lippfische der Gattung Coris zeigen eine auffallende äußerliche Ähnlichkeit zu Anemonenfischen. Diese sind durch ihr enges Zusammenleben mit nesselnden Wirtsanemonen großteils vor Fressfeinden geschützt. Durch die Ähnlichkeit zu ihren Vorbildern täuschen die ansonsten wehrlosen Lippfische ihre Räuber und erhöhen so ihre Überlebenschancen.
Kraken im Eismeer reagieren schneller durch RNA‐Editing
Authors: Brennicke Axel 
Published: August 2012

AbstractOktopoden leben in Meeren mit sehr unterschiedlichen Temperaturen. Damit die Nervenreaktion in kaltem und warmem Wasser ähnlich schnell verläuft, müssen die Kaliumkanäle in den Nervenzellen unterschiedlich aufgebaut sein. Diese Unterschiede in den Proteinen beruhen aber nicht auf Mutationen, also Veränderungen in den Genen, sondern werden durch RNA‐Editing erst bei der Reifung der RNA festgelegt.
Jagdszenen in Haus und Garten: Wespen als Räuber und Beute
Authors: Petrischak Hannes 
Published: August 2012

AbstractNicht immer muss man für interessante Tierbeobachtungen Exkursionen in spektakuläre Naturräume unternehmen. Zahlreiche Arten sind dem Menschen in den Siedlungsbereich gefolgt und profitieren dort – verglichen mit intensiv genutztem Agrarland – unter anderem von Strukturreichtum und geringen Nährstoffeinträgen. In einer kleinen Serie soll an dieser Stelle der Blick darauf gerichtet werden, was sich insbesondere in der Welt der Insekten rund ums Haus und im Garten im Laufe eines Jahres entdecken lässt.
Effect of specialist decision-making on treatment strategies for colorectal liver metastases
Authors: Jones R P , Vauthey J-N , Adam R , Rees M , Berry D , Jackson R , Grimes N , Fenwick S W , Poston G J , Malik H Z 
Published: August 2012

Abstract

Background
One hundred and ten patients were treated with palliative chemotherapy, of whom 53 had liver-only disease and had not been reviewed by a specialist liver surgeon. One scan was excluded as all reviewers felt it to be of insufficient quality to assess. Improved surgical technique and better chemotherapeutic manipulation of metastatic disease has increased the number of patients eligible for potentially curative resection of colorectal liver metastases. The rapid evolution in this field suggests that non-specialist decision-making may lead to inappropriate management. This study aimed to assess the management of colorectal liver metastases by non-liver surgeons.

Methods
All patients who underwent chemotherapy with palliative intent for metastatic colorectal cancer at a regional oncology centre between 1 January and 31 December 2009 were identified from a prospectively maintained local database. Six resectional liver surgeons blinded to patient management and outcome reviewed pretreatment imaging and assigned each scan a score based on their own management choice. A consensus decision was reached on the appropriateness of palliative chemotherapy.

Results
Tumours in 33 patients (63 per cent) were considered potentially resectable, with a high level of interobserver agreement (κ = 0·577). When individual approach to management was considered, interobserver agreement was less marked (κ = 0·378).

Conclusion
Management of patients with colorectal liver metastases without the involvement of a specialist liver multidisciplinary team can lead to patients being denied potentially curative treatments. Management of these patients must involve a specialist liver surgeon to ensure appropriate management.