bluuebunny/crossref_metadata_2025 huggingface dataset:
2H NMR Studies of Liquid Crystal Main Chain Polymers
Authors: Müller Klaus , Kothe Gerd
Published: July 2012

Semiflexible thermotropic polyesters, specifically deuterated at different positions of the polymer chain, are studied by multipulse dynamic NMR techniques. Analysis of the various 2H NMR experiments is achieved, employing a comprehensive theory, based on the stochastic Liouville equation. Computer simulations provide the orientational distributions and conformations of the polymer chains and the correlation times of the various motions. In the anisotropic melt the correlation times for chain rotation and chain fluctuation are of the order of 10−8s, while trans‐gauche isomerization occurs even faster. Below the melting point two components are observed in the NMR experiments. The dynamics of the liquid crystalline component (40%) continues into the biphasic region. In contrast, the crystalline component (60%) shows a drastic motional decrease at the melting point. The chain order parameters Szz increase with decreasing temperature to limiting values, which depend upon the number n of flexible spacer segments. Polymers with n = even exhibit limiting order parameters of Szz = 0.9, a value considerably higher than those observed in low molecular weight nematogens. In addition, the chains adopt highly extended conformations, evidenced by trans populations of nt= 0.76, exhibited throughout the spacer. The liquid crystalline order is quantitatively retained, when the polymers are cooled below the melting point and glass transition, respectively.
Dielectric Measurements at High Pressures and Low Temperatures VIII: Dielectric and Thermodynamic Properties of Cycloheptanol
Authors: Poser U. , Schulte L. , Würflinger A.
Published: July 2012

The thermodynamic and dielectric behaviours of liquid and solid cycloheptanol have been investigated using differential thermal analysis and capacitance measurements up to 10 MHz. The phase behaviour has been studied between 80 and 340 K and pressures up to 300 MPa. The well‐known phase transformations at 1 atm have also been observed at elevated pressures that enables to calculate the associated volume changes. The static and complex permittivities have been determined in the temperature range 240–310 K and pressures up to 300 MPa. Activation parameters derived from the dielectric relaxation occurring in the two plastic phases are similar to previously reported data for cyclopentanol and cyclohexanol.
The Influence of Surface Oxygen on the Auger Signal Intensities of Ti, Mn, Ni, Zr, La and Fe
Authors: Sicking G. , Eisenhuth A.
Published: July 2012

The Auger electron intensities of some metals are measured as a function of the oxygen content of the metallic surface. A strong correlation between the Auger signal strength of the metal and that of oxygen is discovered. Thus correlation is discussed as a weakening process of Auger electrons by surface oxygen. The relationships allow to calculate elemental sensitivity factors for the metal Auger signals from oxygen containing surfaces. It is also possible to determine relative weakening coefficients by oxygen for different elements or for the same element but different Auger energies. It is found that the weakening coefficient of low energy Auger electrons is about twice that of high energy Auger electrons. The 92 eV Auger electrons of Zr show up an anomaly since they are roughly not weakened by oxygen. —It is pointed out that the different contributions responsible for a weakening of the peak‐to‐peak amplitudes of differentiated Auger spectra sum up and can be described by a single weakening coefficient.
Temperature Dependence of the Inhibition and Enhancement of Positronium Formation by Pyridine in Decane and Toluene Solutions
Authors: Alfassi Zeev B. , Ache Hans J.
Published: July 2012

The effect of temperature (‐20°C‐+25°C) on positronium formation in decane and toluene solutions of pyridine was studied. At low concentration of pyridine an enhancement was found in decane solution at ‐20°C and toluene solution at +25°C. Decane solutions at 25°C and toluene solutions at ‐20°C show constant yield of o‐Ps, independent of pyridine concentration, at low concentration. At high pyridine concentration there is an inhibition in all cases. The rate constants for inhibition decreases with temperature for both toluene and decane solutions.
Oxide Formation during the Reaction of Carbon Monoxide and Oxygen on Polycrystalline Platinum
Authors: Häfele E. , Lintz H.‐G.
Published: July 2012

The oxidation of carbon monoxide by air is studied on polycrystalline platinum at normal pressure in the temperature range 350 < ϑ/°C < 600. Simultaneously the oxygen activity on the surface is measured under reaction conditions by solid electrolyte potentiometry. The results show that the formation of PtO2 is thermodynamically possible in a certain temperature range but oxide formation is only observed in the case of preoxidized samples.
Catalytic Activity of Colored Sodium Chloride for the Dehydrochlorination of t‐Butyl Chloride
Authors: Ueda W. , Hiraiwa J. , Yoshida N. , Kishimoto S.
Published: July 2012

When NaCl was colored with Na vapor, X‐rays and Cl2 vapor, respectively, the surface became highly active catalytically. Almost without exception, the decrease in the enhanced activity upon heating occurs in the range of the annihilation temperature of the color centers. This result indicates that both F‐ and V‐centers in NaCl may contribute to the reaction as active sites.
A Further 1H NMR Study on Cubic HxWO3: Reasons for the Apparent “Prefactor Anomaly”
Authors: Ritter Cl. , Müller‐Warmuth W. , Schöllhorn R.
Published: July 2012

NMR studies of the cubic hydrogen bronze Hx WO3 have confirmed the hydrogen location proposed by Dickens et al. The diffusion of protons is limited by the availability of a framework of suitable oxygen sites and was found to contain elements of reduced dimensionality. The activation energy is of the order of magnitude of 40–50 kJ/mol, and the preexponential factor amounts to about 10‐13 s as usual. A “prefactor anomaly” observed in several other studies may arise if the dimensionality of the motion is not considered. Comparison with hydrogen bronzes HxMoO3 is discussed.
Self‐Diffusion, Overall Rotation of Molecules, and Ring Motions in the Three Solid Phases of Formylferrocene, Fe(C5H5) (C5H4CHO), as Studied by 1H NMR and Differential Thermal Analysis
Authors: Kubo Atsushi , Ikeda Ryuichi , Nakamura Daiyu
Published: July 2012

The temperature dependences of static and rotating frame 1H spin‐lattice relaxation times, T1 and T1ϱ, respectively, and also of 1H spin‐spin relaxation time, T*2 were studied for formylferrocene Fe(C5H5)(C5H4CHO). Broadline 1H NMR was investigated over a wide range of temperature. Differential thermal analysis revealed a new second‐order phase transition at 294 K. At 77 K, formylferrocene was found to form a rigid lattice. Above 130 K, the onset of the Cs reorientation of the cyclopentadienyl ring in the molecule about its C5 axis was observed to take place with the average activation energy of 14.5 kJ mol−1. In the plastic phase above 317 K, the uniaxial as well as overall rotations and self‐diffusion of the molecule as a whole were detected to occur. Other motional parameters of the unsubstituted cyclopentadienyl rings and the molecules in each phase were evaluated.
Study of Dipolar Interaction in Liquid Pyridine by X‐Ray and Neutron Diffraction
Authors: Bertagnolli H. , Engelhardt T. , Chieux P.
Published: July 2012

X‐ray and neutron diffraction experiments on liquid pyridine are reported. After data reduction and evaluation the intramolecular contribution was separated from the total intensity and the intramolecular geometry in the liquid phase was determined. The combination of X‐ray and neutron intermolecular differential cross sections permits an assignment of intermolecular distances to specific atom pairs. Based on these identifications a two‐dimensional model of the local order existing in liquid pyridine is deduced. A quantitative calculation leads to a refined model, reproducing simultaneously the X‐ray and neutron data. Most probable is an antiparallel “side‐side” for the nearest and a “head‐on‐tail” configuration for the next molecule respectively. This means, that the dipolar interaction is the structure determining factor.
Optical Absorbance and Photoelectrochemical Quantum Efficiency of Titanium Oxide Modified by Ion Implantation and Reductive/Oxidative Annealing
Authors: Teschner D. M. , Schumacher R. , Stritzker B.
Published: July 2012

We report on the optical absorbance A and the photoelectrochemical quantum efficiency η of Titanium oxide samples modified by ion implantation and reductive/oxidative annealing. Rutherford‐Backscattering spectra were taken to probe the depth profile of implanted Kr+. It is shown that A varies drastically upon modification. Generally, with increasing Ti/O ratios the absorbance decreases. The observed decrease in A upon implantation of stoichiometric TiO2 is attributed to an increase of the Ti/O ratio. The suggested explanation takes into account the formation of Ti3+ ‐ O vacancy complexes which influence the electronic structure of TiO2. Furthermore it is shown that changes of A give rise to conductivity changes. This reflects changes in ND, the doping density, εr, the relative dielectric constant, and lp, the mean free diffusion length of minority carriers. The observed photoelectrochemical quantum efficiency η of modified samples is discussed in terms of model calculations which take into account changes of ND, εr, lp and the absorption coefficient α. Recombination losses of photo‐produced electron‐hole‐pairs via band gap states introduced by the implanted ions are also discussed.
Bulk Counterion Diffusion in Rod‐Like Polyelectrolyte Solutions
Authors: Cametti C. , Biasio A. Di
Published: July 2012

The bulk counterion diffusion along a charged rod‐like polyion is considered in the light of the linearized Poisson‐Boltzmann equation of the Gouy‐Chapman double layer theory to estimate the contribution of this process on the high‐frequency dielectric dispersions of dilute polyelectrolyte solutions. This model, which has been previously applied to colloidal suspensions of charged spherical particles, allows to predict the functional form of the dependence of the dielectric and conductometric parameters on the bulk counterion concentration and on the dielectric constants of the polyion domain and electrolyte solution, in the limit of very small polyion content. The derived expressions for the dielectric and conductivity increments show that the influence of the bulk counterion diffusion is generally very small and in particular conditions negligible. Nevertheless these effects may be important correcting factors to take into account in the accurate interpretation of dielectric measurements.
Interstitial Site Occupancy of Hydrogen Atoms in Laves Phases and Structurally Related Compounds
Authors: Hauck J.
Published: July 2012

The Laves phases with MgCu2 or MgZn2 structure and structurally related phases with CeNi3, PuNi3, Ce2Ni7, or CaCu5 structure were compared for site preference of hydrogen atoms in different octahedral and tetrahedral sites. The site preference energies of different transition metals are similar to crystal field stabilization energies of transition metal atoms in oxides. The structural data and some thermodynamic properties as solubility of hydrogen in alloys and instability of ternary phases are correlated to the site preference energies.
An Experiment for Determining the Kinetics of Heterogeneously Catalysed Gas Reactions
Authors: Schneider U. , Alavi M. , Duschner H.
Published: July 2012

An experiment for determining the kinetics of heterogeneously catalysed gas reactions is presented. In a closed glas tube system, a gas flow is induced by a temperature gradient between the heated catalyst and a jacket cooler. Partial pressures of all gaseous components are monitored by a quadrupole mass‐spectrometer, directly connected to the reaction chamber via a special mica filter. Using this apparatus, the catalytic hydrogen reduction of sulfur dioxide over 0.5% Ru/Al2O3 was investigated.
A X‐Ray Study of Specific Bromine Interaction in Liquid Ethylbromine and its Interpretation by Geometrical and Potential Models
Authors: Bertagnolli H. , Schulz G.
Published: July 2012

A X‐ray experiment on liquid ethylbromine at 25°C is reported. After the usually applied data reduction and evaluation the intramolecular contribution was separated and the intra‐ and intermolecular geometry in the liquid phase was determined. A well defined Br ‐ Br distance of 3.9 Å exists indicating a strongly attractive interaction between the highly polarizable Br‐atoms. Quantitative calculations based on geometrical models lead to a more antiparallel orientation of the ethylbromine molecules with close Br‐contact. Comparison with potential calculations without and with electrostatic interactions confirms that dispersion forces outweigh the dipole effect on the orientation of neighbouring molecules.
Melt Grown Layered Crystals: Comparison of Optoelectronic Properties
Authors: Hofmann W. K. , Könenkamp R. , Schwarzlose Th. , Kunst M. , Tributsch H. , Lewerenz H. J.
Published: July 2012

Single crystals of the layer type compounds MoSe2 and WSe2 have been grown from various high temperature solutions. The fluxes used for crystal growth were either metals (Sb, Bi, Te), semiconductors (Se) or saltlike melts (PbCl2). The photoactivity of these materials was investigated by photoelectrochemical methods, time resolved microwave conductivity (TRMC) and temperature dependent DC conductivity. The comparison of crystals grown from different melts and from chemical vapor transport (CVT) indicates that foreign phase melts are deleterious for the optoelectronic properties. Melt grown crystals are less photoactive than selected CVT material. Possible origins of the observed differences are discussed.
On Some Aspects of the Modelling of the Crystal Growth
Authors: Beckmann Wolfgang , Lacmann Rolf
Published: July 2012

The growth of crystals is a complex process where several steps can be rate determining. For the deduction of growth mechanisms from experimental data, it is essential, that the models yield realistic parameters. For the growth of stearic acid from solutions, the sensitivity of parameters of the growth models was analyzed by simulating rate data and evaluating then by different techniques. The influence of different growth limiting steps and errors in the measurements was analyzed. For the electrochemical deposition of an alloy, the influence of several parameters on the composition of the alloy was studied.
Infrared Laser Induced Ignition of Gas Mixtures
Authors: Raffel B. , Wolfrum J.
Published: July 2012

O2/O3 mixtures are ignited by absorption of laser pulses of a TEA CO2 laser along the axis of a cylindrical vessel. For mixtures of 0.35 bar total pressure and 20% O3 the laser excitation as well as the molecular relaxation of O3 and the flame propagation is observed by UV‐light absorption of O3 perpendicular to the cell axis. Temperatures reached in the irradiated volume by absorption of the laser pulses are deduced from the alteration of the UV intensity and from absorbed laser energy below and above the ignition limit. The results are compared with corresponding numerical simulations. Minor differences can be attributed to the simplifications of the simulations being performed in one spatial dimension with the uniform pressure assumption and a solely thermal source term.
Parameter Optimization in Detailed Chemical Kinetics Modeling
Authors: Gardiner William
Published: July 2012

Computer models describing complex chemical kinetics are often based on the assumption that each reaction included is a true elementary process in the physical‐chemical sense. If the elementary reaction rate coefficients are to be determined as part of the modeling study, then one has to solve a parameter optimization problem that differs in two respects from a textbook response‐function analysis: use of numerical integration of kinetic equations for computing parameter sensitivities and dominance of systematic over random errors in the data base. While modern computing technology offers efficient solutions to the sensitivity computation problem, dealing with systematic errors requires reformulation and simplification of the mathematical structure so that it interacts efficiently with chemical understanding derived from experimental investigations. A systematic procedure for extending a proposed mathematical structure to the entire literature data base of hydrocarbon combustion is presented and discussed.
Ein diskretes mathematisches Modell für die Dynamik der Methanoloxidation an einem Palladium‐Trägerkatalysator
Authors: Gerhardt M. , Schuster H. , Plath P. J.
Published: July 2012

The dynamics of the methanol oxidation on a Pd‐supported catalyst is described by a discrete mathematical model including a phase transition of the catalytic system. A possible synchronisation of the not uniformly acting catalyst by an heat transfer between neighboured Pd‐crystallites is studied by coupling several dynamical systems.
Transport Properties of Liquids VI. Viscosity, Excess Volumes, and Self‐Diffusion of Nearly Athermal Mixtures
Authors: Fischer Jens , Weiss Alarich
Published: July 2012

Self‐diffusion D, dynamic viscosity ζ, mass density η, and excess volume VE were measured for twelve binary liquid systems CCl4‐compound 2 in the temperature range 285 ≤ T/K. ≤ 345 at p = 1 bar. In average for each system, seven different compositions were studied within the range 0 < x2 ≤ 1. Compounds 2 were: cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclodecane, cyclo‐dodecane, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, cis‐decaline, trans‐decaline, and bicyclohexane.—The self‐diffusion coefficients found are discussed within the frame of the extended free volume model of liquids. η=f(x2, T) can be explained by the Arrhenius relation for the viscosity of liquids, including a modified Grunberg‐Nissan parameter. The excess viscosities and the molar excess volumes observed are rather small, in correspondence with the fact that the twelve systems investigated are nearly athermal. This fact reproduces itself in the excess activation energies of the viscous flow and mass transport.
The Volume of Liquid HgIn and HgSn Alloys
Authors: Morikawa Y. , Itami T. , Shimoji M.
Published: July 2012

Precise measurements were made to determine the concentration dependence of the volume and the thermal expansion coefficient of liquid HgIn and HgSn alloys. The molar volume of both systems shows slightly negative deviations from the linear law. For liquid HgIn alloys, a small hump was found in the curve of the thermal expansion coefficient in the dilute In range, but not for liquid HgSn.—The molar volumes of these alloys have been calculated by modifying a simple pseudopotential approach, and results obtained in this way are found to be in qualitative agreement with experimental values.
Scheibe‐Aggregate Monolayers of Cyanine Dyes without Long Alkyl Chains
Authors: Yonezawa Y. , Möbius D. , Kuhn H.
Published: July 2012

Scheibe‐aggregates of three cyanine dyes with methyl or ethyl groups instead of long alkyl substituents have been prepared at the air‐water interface by spreading a mixture of the cyanine dye and arachidic acid on a water surface and compressing the monolayer. The general features of the reflection spectra of the dye‐arachidic acid monolayers at the air‐water interface, in particular the presence of a distinct J‐band, are in accordance with absorption spectra of monolayers deposited on glass plates by the Langmuir‐Blodgett technique. The dichroism observed in polarized absorption spectra of the dye‐arachidic acid films indicates that the Scheibe‐aggregates of the dyes with a meso phenyl group have a preferential orientation of the long axis of the molecules in the layer plane parallel to the direction of motion in depositing the layer. The brick‐stone model of Scheibe‐aggregates is adequate for chromophore organization in these monolayers.
A Comment on the β‐Factor and Enthalpy of Activation for Oxygen Reduction at Pt and Au Electrodes
Authors: Damjanovic A. , Sepa D. B. , Vracar Lj. M. , Vojnovic M. V.
Published: July 2012

Temperature dependence of the symmetry factor, β, for oxygen reduction at Au electrodes is found to be different than that at Pt electrodes under similar experimental conditions. At Au electrodes, β is proportional to absolute temperature, i.e., β = β'T, while at Pt electrodes β is independent of T. The significance of apparent enthalpies of activation at these electrodes, ΔH*ap, determined at a constant potential E, is reassessed in view of the different dependences of β on T. At Au, Δ*ap is equal to Δ*0, the enthalpy of activation at the zero Galvani potential difference at the electrode. It is therefore independent of the potential at which the change of current density with T has been determined. At Pt, ΔH*ap is the enthalpy corresponding to the potential at which the change of current density with T has been determined. It increases linearly with electrode potential.
Röntgenstrukturuntersuchung des flüssigen Silicium‐, Germanium‐ und Zinntetrachlorids. Ein Beitrag zur Frage einer gemeinsamen Flüssigkeitsstruktur. II. Bestimmung der individuellen partiellen Paarkorrelationsfunktionen. Vorschlag eines einheitlichen Strukturmodells
Authors: Jöllenbeck K. M. , Weidner J. U.
Published: July 2012

The determination of partial atomic pair correlation functions for liquid tetrachlorides following the method of isomorphic chemical substitution in X‐ray scattering, is reported. From the properties of the intensity distributions of radiation scattered by silicon‐, germanium‐, and tin tetrachloride and binary liquid mixtures, which were investigated recently, there is evidence for the individual partial functions to differ gradually when changing the components or the mole fraction of the mixtures. For separating the partials from the intermolecular reduced intensities, a procedure of successive refinement was employed, therefore, that accounts for such differences, and allows for the realization of well‐known restrictions reflecting, for example, the limiting behaviour of the pair correlation functions with respect to small and large intermolecular atomic distances, and the preservation of particle numbers. Using functions that are parametrized adequately, the procedure enables the individual partial pair correlation functions of pure compounds SiCl4, GeCL4, SnCl4, to be deduced.—By analysis of the partial correlation functions and partial particle numbers conclusions are drawn concerning the structure of short range order that amount to a definite suggestion for a structural model. Accordingly, short range order is represented by a space filling configuration common to the tetrachloride liquids under consideration, but exposing gradually different features, which is derived from a structural model for liquid CCl4 proposed by Narten.
Extraction of nickel with dihexyl phosphinic acid and study of Ni(II)‐saccharate complexes
Authors: Beneitez P. , Millan A.
Published: July 2012

The equilibrium extraction behavior for nickel(II) using a kerosene (Shellsol‐T) solution containing dihexyl‐phosphinic acid is studied. From experimental data, treated by a graphical method, monomeric Ni(DHP)2(HDHP)2 and dimeric (Ni(DHP)2(HDHP)2)2 species are found responsible for the extraction. Constants for the extraction equilibrium have been determined as: log K12 = −11.45 and log K22 = −18.81. Constant for monomer‐dimer equilibrium of nickel species is given as: log K = 4.10. —In presence of ligand, saccharate, is concluded to exist in the aqueous phase a nickel(II)‐saccharate complex (1:1) with a stability constant of 3.46 · 103 and general formula C6H8O8Ni · 3H2O.
The use of high UV photon densities for physicochemical studies in the life sciences
Authors: Greulich K. O. , Wolfrum J.
Published: July 2012

High UV photon densities can be used in a wide range of applications in life sciences. Below the threshold for photodamage, time resolved fluorescence spectroscopy and UV resonance Raman Spectroscopy with proteins and nucleic acids can be performed. 1 GW/cm2 is significantly above the ablation threshold of tissue and can now be transported conveniently through tapered quartz fibres. 100 GW/cm2 in the tunable wavelength region 265 to 685 nm are generated by coupling nearly diffraction limited dye laser pulses into a microscope. This allows a detailed wavelength study on the interaction of high photon densities with human red blood cells, which may serve as a model for biological tissue. Using the same equipment, biological cells can be fused with each other in a very selective way. Furthermore, human chromosomes can be microdissected into fine slices and DNA for diagnosis of human disease can be isolated from these localized regions of the human genome.
Search of “chlorophyll forms” in vivo by non‐linear laser spectroscopy
Authors: Leupold D. , Stiel H. , Klose E. , Hoffmann P.
Published: July 2012

Induction of a non‐linearity in the long‐wavelength part of the S0 —S1 absorption band of chlorophyll in vivo by a monochromatic pulse results in a simultaneous band shape change in the whole range of investigation (645 – 680 nm). Such homogeneous broadening behaviour at least for time periods ⩾0.5 ns (pulse duration) does not support the hypothesis of many small sub‐bands representing “chlorophyll forms”. The band shape changes at different excitation intensities indicate two excited state absorptions of antenna chlorophyll.
Laser induced dynamic nuclear polarization
Authors: Hausser K. H.
Published: July 2012

A large nuclear spin polarization pn is desirable for most NMR investigations since NMR is basically an insensitive method and since the signal‐to‐noise ratio is proportional to pn. The classical method to polarize nuclear spins is the “solid effect” in which the much higher Boltzmann polarization of unpaired electrons in doublet ground states is transferred to the nuclear spins by inducing forbidden transitions with the selection rules Δms = ±1, Δm1 = ±1. However, a drawback of this method is the presence of unpaired electrons within the sample which produce unwanted effects in most experiments to be performed with polarized nuclear spins. Using the unpaired electronic spins of optically excited triplet states instead of doublet ground states has the important advantage that after switching off the exciting light it renders a diamagnetic crystal with polarized nuclear spins due to the short lifetime of the triplet states. —The population differences of the electronic sublevels of the excited triplet states to be transferred to the nuclear spins originate in this case from the very selective population rates si and depopulation rates ki due to the selection rules of spin orbit coupling. Since the transfer occurs by inducing forbidden transitions by microwaves, the method was termed Microwave Induced Optical Nuclear Polarization (MI —ONP). The different CW‐ and pulse‐techniques are discussed. Furthermore, a more recently developed technique will be described where the polarization is obtained with special cross‐relaxation transitions which satisfy the “Hartmann‐Hahn condition” for electronic spins spin‐locked in the rotating frame to the radio frequency B1‐field and nuclear spins in the static magnetic field B0 in the laboratory frame. —The highest nuclear polarization obtained so far is pn = 33% which corresponds to an amplification factor of more than 2000 as compared to the Boltzmann polarization in the same magnetic field, but we expect to reach even higher polarizations of more than 50% with improved techniques, in particular with higher B1‐fields.
Application of confocal laser scanning microscopy in plant biology
Authors: Knebel W. , Quader H. , Wijnaendts‐van‐Resandt R. , Engelhardt H.
Published: July 2012

Fluorescence confocal laser scanning microscopy (CLSM) is increasingly acknowledged as a suitable technique to study the 3‐dimensional structure of animal and plant cells. The imaging process involves the collection of the emitted fluorescent light of a defined volume in the object. A powerful processing system is, however, required to store the single data and reconstruct the image of the object. A 3‐D‐image of an object can be achieved either by the extended focus, the stereo image, or the shadowing mode1). —These procedures were applied to elaborate on the spatial arrangement of structural components and organells in fixed or living plant cells. Microtubule arrays in dividing onion root cells and in caulonema tip cells of moss protonemata are visualized by the indirect immunofluorescence technique. In addition, the endoplasmic reticulum is visualized through vital staining with the fluorochrome 3,3'‐dihexyloxacarbocyanine‐iodide (DiOC). For example in adaxial onion bulb scale epidermis cells and root hair cells. Also, several examples are shown which demonstrate the possibilities the CLSM offers with respect to magnification, image, and motility measurements of single organelles. Some of the measurements have been performed with a compact inverted confocal system which also includes a classical fluorescence microscope. Fluorescence confocal laser scanning microscopy turned out to be of great advantage for studying the 3‐D‐arrangement of plant cell constituents due to the property of the focal scanner which discriminates fluorescent light outside of the depth of focus.
Far Infrared Absorption and Rotational Motion of CH3F and of CH3F‐Argon Mixtures at High Pressures to 1000 bar
Authors: Frost M. , Bohn M. A. , Franck E. U.
Published: July 2012

FIR‐absorption spectra of methyl fluoride (CH3F) as a pure fluid and as a one mole percent component in mixtures with dense argon and CF4 have been measured. A frequency range between 10 cm‐1 and 200 cm‐1 was covered. Temperatures of —10, 69 and 125°C were used. Total sample pressures extended to 1000 bar. PVT‐data permit the discussion of the spectra as functions of density. Measurements were made with a modified Fourier‐transform IR‐spectrometer. An optical absorption cell for use to 1000 bar and 200°C is described. The molar absorptivity at 69°C has a pronounced maximum at 40 cm‐1 at all temperatures and densities which indicates hindered rotation. This absorption decreases with growing density and an increasing absorption develops above 70 cm‐1, caused by in termolecular libration. The suppression of the CH3F‐rotation in the dense argon is much weaker than in the pure polar fluid. The intermolecular mean squared torque increases linearly with density with the pure fluids CH3F and CHFl2F and about four times as strongly as with the compounds diluted in argon. Spectral fourth moments of the power spectra and time correlation functions for pure fluids and mixtures are compared to show the influence of dipole interaction on rotation and libration. Spectra obtained with CH3F in high pressure CF4 are analogous to those with argon as solvent.
Effects of oxygen‐glucose deprivation on microglial mobility and viability in developing mouse hippocampal tissues
Authors: Eyo Ukpong , Dailey Michael E.
Published: July 2012

As brain‐resident immune cells, microglia (MG) survey the brain parenchyma to maintain homeostasis during development and following injury. Research in perinatal stroke, a leading cause of lifelong disability, has implicated MG as targets for therapeutic intervention during stroke. Although MG responses are complex, work in developing rodents suggests that MG limit brain damage after stroke. However, little is known about how energy‐limiting conditions affect MG survival and mobility (motility and migration) in developing brain tissues. Here, we used confocal time‐lapse imaging to monitor MG viability and mobility during hypoxia or oxygen‐glucose deprivation (OGD) in hippocampal tissue slices derived from neonatal GFP‐reporter mice (CX3CR1GFP/+). We found that MG remain viable for at least 6 h of hypoxia but begin to die after 2 h of OGD, while both hypoxia and OGD reduce MG motility. Unexpectedly, some MG retain or recover motility during OGD and can engulf dead cells. Additionally, MG from younger neonates (P2–P3) are more resistant to OGD than those from older ones (P6–P7), indicating increasing vulnerability with developmental age. Finally, transient (2 h) OGD also increases MG death, and although motility is rapidly restored after transient OGD, it remains below control levels for many hours. Together, these results show that MG in neonatal mouse brain tissues are vulnerable to both transient and sustained OGD, and many MG die within hours after onset of OGD. Preventing MG death may, therefore, provide a strategy for promoting tissue restoration after stroke. © 2012 Wiley Periodicals, Inc.
Intercurrent infection predicts mortality in patients with late hepatic artery thrombosis listed for liver retransplantation
Authors: Leithead Joanna Agnes , Smith Matthew R. , Materacki Luke B. , Sagar Vandana M. , Gunson Bridget K. , Bramhall Simon R. , Mutimer David J. , Shah Tahir
Published: July 2012

Liver retransplantation for late hepatic artery thrombosis (HAT) is considered the treatment of choice for select patients. Nevertheless, there is a paucity of data to aid decision making in this setting. The aims of this single-center study of patients listed for late HAT were (1) to determine variables associated with wait-list mortality, (2) to describe survival after retransplantation, and (3) to determine variables associated with mortality after retransplantation. Seventy-eight patients were diagnosed with late HAT (incidence = 3.9%). Of the 49 patients listed for retransplantation, 9 died on the waiting list and 36 were retransplanted. The estimated 1-year survival after listing for retransplantation was 53.7%. Only multidrug-resistant (MDR) bacteria–positive cultures were predictive of wait-list mortality (P = 0.01). After retransplantation, the estimated 1- and 5-year patient survival was 71.9% and 62.5%, respectively. Increasing Model for End-Stage Liver Disease score (overall P = 0.007), MDR bacteria–positive cultures (P = 0.047), and continued antibiotic therapy (P = 0.001) at the time of retransplantation were risk factors for post retransplant death. In conclusion, patients who undergo liver retransplantation for late HAT have satisfactory outcomes. However, the presence of active infection and MDR bacteria–positive cultures should be taken into account when risk stratifying such patients. Liver Transpl, 2012. © 2012 AASLD.
Roles of cytokines and progesterone in the regulation of the nitric oxide generating system in bovine luteal endothelial cells
Authors: Yoshioka Shin , Acosta Tomas J. , Okuda Kiyoshi
Published: July 2012

Nitric oxide (NO) produced by luteal endothelial cells (LECs) plays important roles in regulating corpus luteum (CL) function, yet the local mechanism regulating NO generation in bovine CL remains unclear. The purpose of the present study was to elucidate if tumor necrosis factor‐α (TNF), interferon γ (IFNG), and/or progesterone (P4) play roles in regulating NO generating system in LECs. Cultured bovine LECs obtained from the CL at the mid‐luteal stage (Days 8–12 of the cycle) were treated for 24 hr with TNF (2.9 nM), IFNG (2.5 nM), or P4 (0.032–32 µM). NO production was increased by TNF and IFNG, but decreased by P4 (P < 0.05). TNF and IFNG stimulated the relative steady‐state amounts of inducible nitric oxide synthase (iNOS) mRNA and iNOS protein expression (P < 0.05), whereas P4 inhibited relative steady‐state amounts of iNOS mRNA and iNOS protein expression (P < 0.05). In contrast, endothelial nitric oxide synthase (eNOS) expression was not affected by any treatment. TNF and IFNG stimulated NOS activity (P < 0.05) and 1400W, a specific inhibitor of iNOS, reduced NO production stimulated by TNF and IFNG in LECs (P < 0.05). Onapristone, a specific P4 receptor antagonist, blocked the inhibitory effect of P4 on NO production in LECs (P < 0.05). The overall findings suggest that TNF and IFNG accelerate luteolysis by increasing NO production via stimulation of iNOS expression and NOS activity in bovine LECs. P4, on the other hand, may act in maintaining CL function by suppressing iNOS expression in bovine LECs. Mol. Reprod. Dev. 79: 689–696, 2012. © 2012 Wiley Periodicals, Inc.
All‐electron scalar relativistic calculations of atomic hydrogen adsorption on cubo‐octahedron Pt55 nanoparticles
Authors: Shin Jungho , Choi Jung‐Hae , Lee Seung‐Cheol
Published: July 2012

Adsorption energies of hydrogen atoms on Pt were investigated by all‐electron density functional calculations using numeric atom‐centered orbital basis sets. The all‐electron calculations gave lower predicted adsorption energies for hydrogen atoms than pseudopotential calculations. Size effects were considered by comparing adsorption on bulk surfaces and nanoparticles. How size affects catalytic activity is presented on volcano curves, which can give insights into the catalytic activities of practical nanocatalysts.
A Novel Technique for Conduction Studies of the Infrapatellar Nerve
Authors: Tsenter Jeanna , Schwartz Isabella , Katz‐Leurer Michal , Meiner Zeev , Goldin Diana , Vatine Jean‐Jacques
Published: July 2012

Objective

To introduce a noninvasive method for electrodiagnostic evaluation of the infrapatellar nerve (IPN).

Design

A prospective cohort study.

Setting

Electrodiagnostic laboratory, rehabilitation department, Hadassah University Hospital.

Participants

A total of 38 healthy adults; 57 asymptomatic limbs were studied.

Methods

Sensory nerve action potential of the IPN was recorded with surface electrodes placed 2.5 cm below the distal pole of the patella and 2 cm medially from the medial border of the patellar tendon. Transcutaneous antidromic electrical stimulation of IPN was applied above the medial femoral condyle and 8‐10 cm proximally from the active surface electrode.

Results

The sensory nerve action potential mean (n = 38) onset latency was 1.69 ± 0.32 ms. Peak latency was 2.36 ± 0.47 ms, and amplitude was 6.96 ± 3.68 μV.

Conclusions

This article describes a novel and simple technique for IPN conduction electrodiagnostic examination. The method used provides a new tool to evaluate IPN injury in reference to anterior or inferior knee pain with associated sensory deficit.
Late-Quaternary vegetational history of the Inner Hebrides
Authors: Birks H. J. B. , Williams W.
Published: July 2012

Synopsis

The Inner Hebrides support a diverse flora and a wide range of vegetation types today. Native woodland is rare, even on the larger islands of Skye and Mull. The present-day floristic and vegetational diversity and the scarcity of native woodland raise important ecological questions, answers to which can be provided by pollen analysis of loch or bog sediments.

Pollen analysis of sediments deposited during the last glacial stage on Skye and on Lewis suggest that some plants may have survived the last glaciation within the Hebrides. Pollen analysis of late-glacial (13500–10000 years ago) sediments on Skye indicate that even at the close of the last glaciation there was considerable floristic and vegetational diversity related to geology, altitude, and climate.

Post-glacial (10000–0 year ago) vegetational histories are available from Skye, Soay, Canna, Tiree, and Jura. Forest was rare or absent on Canna and Tiree as well as on the Outer Hebrides throughout the postglacial. In contrast Soay and southern and eastern Skye were well forested, with birch, alder, hazel, and small amounts of elm and oak. Pine was confined to eastern Skye. Since 5,000 years ago there has been extensive forest destruction by man, especially on the better soils, and the spread of bog and heath on the poorer soils. Northern Skye supported birch, hazel, and willow scrub during the post-glacial. This has largely been removed by man since about 5,000 years ago. The present-day vegetation of the Inner Hebrides is predominantly anthropogenic.
Lichens of Colonsay
Authors: Rose Francis , Coppins Brian J.
Published: July 2012

Synopsis

The results of eight days' recording and collecting of lichens on the island of Colonsay are presented. A wide range of habitats were studied but particular attention was paid to the two relict oak-woodlands and some areas of calcareous machair. An impressive total of 342 lichen taxa was recorded, and two species were added to the British flora.
Shellfish resources in the Inner Hebrides
Authors: Mason James , Shelton R. G. J. , Drinkwater J. , Howard F. G.
Published: July 2012

Synopsis

Shellfish fishing, traditionally associated with crofting areas, has expanded greatly in Scotland generally, and particularly in the Inner Hebrides, during the past 30 years. Landings from Inner Hebrides waters in 1979 were valued at about £11 millions. Processing factories and storage installations have facilitated marketing.

The seas around the Inner Hebrides provide a wide variety of habitats, from the fine mud necessary for Norway lobsters, through the sandy gravel on which scallops live, to the rocky sea bed inhabited by lobsters.

The most valuable fisheries, those for Norway lobsters and scallops, are post-war developments. In both, the stocks appear to be in a healthy state. Landings in the traditional lobster fishery have declined recently and the stocks are giving some cause for concern. Periwinkles and queens make useful contributions to the economy. Pink shrimps and squat lobsters, though not sufficiently abundant to support a directed fishery, form a useful, occasional by-catch. Squids are caught sporadically, but their availability is very variable. The crab stocks could stand much greater exploitation.
Evaluation of an unsteady flamelet progress variable model for autoignition and flame development in compositionally stratified mixtures
Authors: Mukhopadhyay Saumyadip , Abraham John
Published: July 2012

The unsteady flamelet progress variable (UFPV) model has been proposed by Pitsch and Ihme [“An unsteady/flamelet progress variable method for LES of nonpremixed turbulent combustion,” AIAA Paper No. 2005-557, 2005] for modeling the averaged/filtered chemistry source terms in Reynolds averaged simulations and large eddy simulations of reacting non-premixed combustion. In the UFPV model, a look-up table of source terms is generated as a function of mixture fraction Z, scalar dissipation rate χ, and progress variable C by solving the unsteady flamelet equations. The assumption is that the unsteady flamelet represents the evolution of the reacting mixing layer in the non-premixed flame. We assess the accuracy of the model in predicting autoignition and flame development in compositionally stratified n-heptane/air mixtures using direct numerical simulations (DNS). The focus in this work is primarily on the assessment of accuracy of the probability density functions (PDFs) employed for obtaining averaged source terms. The performance of commonly employed presumed functions, such as the dirac-delta distribution function, the β distribution function, and statistically most likely distribution (SMLD) approach in approximating the shapes of the PDFs of the reactive and the conserved scalars is evaluated. For unimodal distributions, it is observed that functions that need two-moment information, e.g., the β distribution function and the SMLD approach with two-moment closure, are able to reasonably approximate the actual PDF. As the distribution becomes multimodal, higher moment information is required. Differences are observed between the ignition trends obtained from DNS and those predicted by the look-up table, especially for smaller gradients where the flamelet assumption becomes less applicable. The formulation assumes that the shape of the χ(Z) profile can be modeled by an error function which remains unchanged in the presence of heat release. We show that this assumption is not accurate.
Comparisons of Precision and Bias with Two Age Interpretation Techniques for Opercular Bones of Longnose Sucker, a Long-Lived Northern Fish
Authors: Perry Robert C. , Casselman John M.
Published: July 2012

Two preparations of opercular bones for estimating age of longnose suckers Catastomus catastomus revealed that annuli were obscured by dense bone and undetected when the whole operculum technique was used. By thin-sectioning the opercula, we removed the dense bone, revealing previously obscured annuli. Using opercula collected from older fish in Labrador, Canada, we found that the dense bone overgrowth led to an overall age bias of 1 year. When samples were broken into groups based on sectioned ages, however, there were minimal differences in age between the two techniques for fish age 6 and younger and a 2-year age difference for fish estimated to be age 10 and older. To compare precision in locating annuli between the two techniques, we calculated coefficient of variation values among independent determinations. Both techniques demonstrated low variance, however, age determinations had greater variation with thin-sectioning than with whole opercula interpretations. Therefore, we conclude that care must be taken when making annulus determinations from thin-sectioning. Due to the presence of dense bone overgrowth, associated with the whole operculum technique, we conclude a combination of both techniques would provide the most thorough procedure for interpreting opercular age for such long-lived fish (30–50 years).

Received November 23, 2011; accepted April 5, 2012
Oxford Handbook of Geriatric Medicine
Authors: Bowker Lesley , Price James , Smith Sarah
Published: July 2012

The Oxford Handbook of Geriatric Medicine provides user-friendly advice in a field that has limited evidence, yet makes up a substantial proportion of the work of most clinicians.
Renal pathology
Authors: Carton James
Published: July 2012

Chronic kidney disease 142

Acute renal failure 144

Hypertensive nephropathy 145

Diabetic nephropathy 146

Minimal change disease 147

Focal segmental glomerulosclerosis 148

Membranous nephropathy 149

IgA nephropathy 150

Acute tubular injury 151

Acute drug-induced interstitial nephritis 152

Anti-glomerular basement membrane disease 153

Reflux nephropathy 154...
Skin pathology
Authors: Carton James
Published: July 2012

Eczemas 286

Psoriasis 287

Lichen planus 288

Erythema multiforme 289

Granuloma annulare 290

Pemphigus vulgaris 291

Bullous pemphigoid 292

Dermatitis herpetiformis 293

Erythema nodosum 294

Pyoderma gangrenosum 295

Skin infections 296

Benign cutaneous lumps 298

Basal cell carcinoma 300

Squamous cell carcinoma 301

Malignant melanoma ...
Osteoarticular pathology
Authors: Carton James
Published: July 2012

Osteoarticular malformations 306

Osteoporosis 307

Paget's disease 308

Osteomalacia 309

Osteomyelitis 310

Benign bone tumours 311

Malignant bone tumours 312

Osteoarthritis 313

Rheumatoid arthritis 314

Spondyloarthropathies 315

Crystal arthropathies 316

Septic arthritis 317

Soft tissue tumours 318

• An imperfect development of the hip joint, which
predisposes the joint to dislocation....
Mayo Clinic Challenging Images for Pulmonary Board Review
Authors: Rosenow, III Edward C.
Published: July 2012

This resource features a collection of more than 150 very unusual intrathoracic conditions that every pulmonologist, thoracic surgeon, and chest radiologist should know and understand. Featuring a broad array of chest images and corresponding pearls of wisdom on how to best interpret the chest radiograph and other images that are reviewed primarily by pulmonologists, thoracic surgeons, radiologists, and pathologists, the conditions are presented in a didactic, user-friendly, and interactive tutorial format to help practitioners recognize these conditions when encountered in practice.
Aminoglycoside Adult Dosing and Monitoring
Authors: Wilson John W. , Estes Lynn L.
Published: July 2012

Several protocols exist, but this is the one used at Mayo Clinic. (See also guidelines that follow for pulse [extended-interval or once-daily] dosing.)

Creatinine clearance (ClCr) calculation:

Males:

(140−age[y])×(weight[kg])...
Pediatric Aminoglycoside Dosing
Authors: Wilson John W. , Estes Lynn L.
Published: July 2012

The following tables do NOT apply to the dosing of antimicrobials in neonates.