bluuebunny/crossref_metadata_2025 huggingface dataset:
Fourier Transform EPR Measurement of Homogeneous Electron Transfer Rates
Authors: Angerhofer A. , Massoth R.J. , Bowman M.K.
Published: November 2013

Fourier‐Transform Electron Paramagnetic Resonance has measured the rates of homogeneous electron transfer reactions involving duroquinone radical anions. The radicals are generated by laser photolysis of duroquinone in methanol solution containing 10% triethylamine. The duroquinone concentration was varied over a factor of 1000. The rate constant for electron transfer between the radical anion and the neutral duroquinone is 1.5×108M−1s−1 and the intrinsic spin relaxation rates, T−11 and T−12 are 0.32 MHz and 0.44 MHz, respectively. Two‐Dimensional magnetization transfer spectra show that the reaction is a homogeneous electron transfer reaction. The electron transfer rates are measured by two novel pulse sequences designed for more efficient data acquisition in samples with no unresolved inhomogeneous broadening. These two sequences result in a more rapid, accurate determination of the second‐order chemical rate constant since the second‐order rate constant is obtained directly and is not derived from a single measurement of a pseudo‐first‐order rate. The transient duroquinone radical anions studied here appear to have the same T1, T2 and electron transfer rates as stable duroquinone radical anions in alkaline solutions.
Using Magnetic Resonance of Protons to Image Flowing Blood
Authors: Thomas Dixon W.
Published: November 2013

Physicians often request angiograms or images of arteries. Conventional angiography requires catheterizing a patient, injecting an iodine compound into an artery, and X‐ray photography. All 3 steps have hazards and, compared to clinical nuclear magnetic resonance (NMR) examinations, the procedure is painful, time consuming, and expensive. Iodine distinguishes blood from other tissues in conventional angiography; blood motion serves the same purpose in several recent NMR experiments reviewed here. Blood spins can be inverted upstream of a region of interest. After they flow downstream, blood will be labeled in the region of interest. Comparing NMR images made with and without labeling identifies blood. Alternatively, equal and opposite magnetic field gradient pulses can mark moving blood by changing the phase of its magnetization. The second gradient cancels the phase effect of the first for spins which are still in the same place, thus only blood is affected. Two images with different blood phases are compared. The blood phases may differ because gradients used to produce the images differ or because blood velocities differ owing to different synchronization with the heart. Results of several NMR experiments are presented. All have much lower quality and higher convenience than the conventional X‐ray method.
Geometry‐Directed Generation and Synthetic Application of α‐Lithio Oxime Ethers
Authors: Shatzmiller Shimon , Lidor Rami , Shalom Eytan , Bahar Naim Menashe Eliezer
Published: November 2013

Several mono‐ and di‐O‐alkyloximes have been regioselectively transformed to the syn α‐lithio derivatives by treatment with n‐butyllithium. The control of oxime ether geometry served to control regioselectivity in α‐lithiation and subsequent carbon‐carbon (alkylation, oxidative coupling) and carbon‐halogen bond formation reactions. The geometry‐directed α‐lithiation‐dimerization sequence was used for the synthesis of large ring compounds.
Synthesis and Enzymic Conversion of Isobutanoyl‐carba(dethia)‐Coenzyme A
Authors: Brendelberger Günter , Rétey János
Published: November 2013

Acyl coenzyme A analogues in which the sulphur is replaced by methylene are stable to hydrolysis and can be used to investigate enzymatic reaction mechanisms. With this idea in mind we synthesized isobutanoyl‐carba(dethia)‐coenzyme A (isobutanoyl‐CH2CoA) and monitored its reaction in enzymatic systems. A cell‐free extract of Pseudomonas putida (ATCC 21244) complemented with FAD, phenazine methosulphate, and DCIP catalyzed the conversion of isobutanoyl‐CH2CoA into methacryloyl‐CH2CoA and β‐hydroxyisobutanoyl‐CH2CoA. The latter could not be further oxidized to the aldehyde and carboxyl level, indicating that these oxidations normally occur after hydrolysis of the CoA ester.
Mechanistic Studies on the [2 + 2] Photocycloaddition of Deuterium‐Labeled Olefins
Authors: Becker Dan , Haddad Nizar
Published: November 2013

The mechanism of intramolecular [2 + 2] photocycloaddition of 1b has been investigated. Structure determination of deuterium‐labeled photoadducts was accomplished by 2H NMR.
Dynamics, Spectra, and Relaxation Phenomena of Excess Electrons in Clusters
Authors: Barnett Robert N. , Landman Uzi , Rajagopal Gunaretnam , Nitzan Abraham
Published: November 2013

In this paper, we review quantum simulation methods for studies of coupled quantum‐classical systems and their applications in investigations of dynamics, spectra, and relaxation phenomena of excess electrons in polar molecular and ionic clusters.
Resonances, Cross Sections, and Partial Widths by the Complex Coordinate Method
Authors: Moiseyev Nimrod
Published: November 2013

The Complex Coordinate Method (CCM) is reviewed, emphasizing the theoretical aspects and properties of the complex‐scaled Hamiltonian. It is shown that the CCM not only enables the calculation of resonance positions and widths by computational techniques that had originally been developed for bound states, but also can be used as a powerful tool in the calculation of scattering cross sections and partial widths.
Aspects of the Softness and Hardness Concepts of Density‐Functional Theory
Authors: Harbola Manoj K. , Chattaraj Pratim K. , Parr Robert G.
Published: November 2013

In the density‐functional theory of the ground state of an electronic system there arise the concepts of softness, hardness, local softness, and local hardness. Definitions of these quantities are reviewed, and then local softness and local hardness are discussed in some detail. The local softness of a species, the derivative magnified image, is a measure of the chemical reactivity of a site in the molecule. From it can be obtained the total global absolute softness in the sense of Pearson and a normalized chemical reactivity index of frontier type. Several formulas for s(r) are obtained, including new fluctuation formulas, and its determinative role in chemisorption, catalysis, and frontier‐controlled charge‐transfer processes is briefly discussed. Local hardness is a corresponding appropriately defined functional derivative η(r) = [δμ/δp(r)]v(r). Difficulties associated with ambiguities in this definition are discussed and resolved. It is concluded that for most purposes the best working formula for local hardness is magnified image, where η(r, r′) is the hardness kernel; magnified image, where F[p] is the usual Hohenberg‐Kohn functional and f(r) is the Fukui function. With this definition, η(r) = η, a constant which is the global hardness. Just as the chemical potential equalizes in the ground state, so does the hardness. It is demonstrated that hardness can be taken to be an average of orbital contributions.
Interaction of Carbohydrates with Phosphatidylcholine Inverse Micelles
Authors: Wachtel Ellen , Federman Silvina , Greenspoon Noam
Published: November 2013

Small angle X‐ray scattering experiments indicate that egg phosphatidylcholine dissolved in benzene at a concentration of 12–50 mM organizes into approximately isometric inverse micelles with a size that depends upon the amount of water present. These inverse micelles can serve as self‐assembled hosts for monosaccharide derivatives. For a given amount of water, addition of carbohydrates causes an increase in the micelle size. In contrast, cyclohexane solutions of egg phosphatidylcholine contain highly anisotropic structures, possibly elongated rods. Monosaccharide derivatives can be extracted into these structures and are bound, at low water content, to the polar head groups. Upon addition of water the sugar is probably displaced from the polar head groups and gains some motional freedom in the water pool which is formed. This fact indicates that the polar head group of phosphatidylcholine interacts, probably by means of hydrogen bond formation, with monosaccharides and brings about their solubilization in nonpolar solvents.
Optical Nuclear Polarization of Deuterium Spins: Mechanisms and Applications in Solid State NMR
Authors: Allgeier Jürgen , Buntkowsky Gerd , Hentrich Sven , Hoffmann Werner , Vieth Hans‐Martin
Published: November 2013

A gain in detection sensitivity of more than three orders of magnitude has been achieved in high resolution solid state 2H NMR of monocrystalline systems by applying optical nuclear polarization (ONP) via excited triplet states. The method is demonstrated for crystals of fluorene doped with optically active guest molecules which have localized triplet states and for the 1: 1 mixed crystal of anthracene/tetracyanobenzene with excitonic states. The factors determining the efficiency of ONP are discussed and compared to the case of proton spin systems.
Single and Multiple Quantum NMR Relaxation Times of Sodium and Potassium in Red Blood Cells
Authors: Shinar Hadassah , Eliav Uzi , Navon Gil
Published: November 2013

The two components T2f and T2s of the transverse magnetization decay curve of 23Na in dog erythrocytes were measured using the triple quantum filtered spectra. It was shown that this technique, in spite of its inferior sensitivity, may be used for systems where T2f and T2s are not very different. Thus it was possible to measure the effect of 2, 3‐diphosphoglycerate (2, 3 DPG) depletion on the intracellular 23Na relaxation rates. The effect found indicates some contribution of hemoglobin‐2, 3‐DPG complexes to the 23Na relaxation in intact erythrocytes. 39K relaxation times were measured in human and chicken erythrocytes. The results indicate binding similar to that of 23Na. Finally, a decrease of the cellular volume of erythrocytes was found to shorten 23Na relaxation times. The result was interpreted as due to an increase in intracellular concentration of proteins.
Kinetic Basicities of Aqueous Binary Mixtures: A Surprisingly Good Linear Correlation with the Gas Phase Basicity of the Organic Cosolvent
Authors: Pines Ehud , Fleming Graham R.
Published: November 2013

A remarkably good correlation between the rate of proton transfer from excited protonated 1‐aminopyrene and the gas phase basicities of the organic component in water: organic solvent binary mixtures has been found. We suggest that use of anilinium acids minimizes the effect of anion solvation and Coulomb interactions and enables the influence of the organic cosolvent on the proton transfer to be clearly observed. The model proposed is one in which the proton is always transferred to a water molecule and a concerted proton transfer to a water molecule solvated by the organic cosolvent also occurs. The cosolvent influence is then on this latter species via hydrogen bond interactions. The correlation holds in pure water but not in pure organic solvents where, clearly, the proton must be transferred to the organic molecule.
Transition Structures of the Electrocyclic Reactions of cis,cis,cis‐1,3,5‐Cyclooctatriene
Authors: Thomas Bert E. , Evanseck Jeffrey D. , Houk Kendall N.
Published: November 2013

The electrocyclic reactions of cis,cis,cis‐1,3,5‐cyclooctatriene have been studied using ab initio molecular orbital theory. cis,cis,cis‐1,3,5‐cyclooctatriene can undergo an electrocyclic ring opening in a conrotatory fashion to form cis,cis‐1,3,5,7‐octatetraene and a disrotatory electrocyclization to form bicyclo[4.2.0]octa‐2,4‐diene. The transition structures for these electrocyclic reactions have been located. Geometry optimizations employed restricted Hartree‐Fock calculations and the 3–21G and 6–31G* basis sets. Electron correlation energies were calculated using second‐order, and in some cases fourth‐order, Møller‐Plesset theory. Scaled RHF/6–31G* force constants were employed in the prediction of secondary deuterium isotope effects for the conrotatory ring opening. The ground state of cis,cis,cis‐1,3,5‐cyclooctatriene exists in a twist‐boat conformation with staggering at the saturated linkage. The transition structure for the conrotatory electrocyclic ring opening to form cis,cis‐1,3,5,7‐octatetraene has a helical structure, which has implications for the stereoselectivities of ring closure of 1‐substituted‐cis,cis‐1,3,5,7‐octatetraenes. The disrotatory transition structure for the electrocyclization to form bicyclo[4.2.0]octa‐2,4‐diene is strongly distorted from Cs symmetry, in contrast to the transition structure for the disrotatory electrocyclization of cis‐1,3,5‐hexatriene. This distortion is caused by staggering about the saturated linkage.
Ab Initio Molecular Orbital Study of Electronic and Geometrical Structures of MCH2+ Complex and its Reactivity with H2, Where M = Co, Rh, and Ir
Authors: Musaev Djamaladdin G. , Morokuma Keiji
Published: November 2013

By using CASSCF (for optimization of geometries) and MR‐SDGI‐CASSCF (for energies) methods we have studied and compared the mechanism of reaction MCH2+ + H2, as well as the electronic and geometrical structure of the MCH2+ complex, where M = Co, Rh, and Ir. It has been found that the mechanisms of reaction MCH2+ + H2 → M+ + CH4 (1) for M = Co and Rh are similar and follow the path: MCH2++H2 → (H2)MCH2+ → [TS1, H2‐activation] → MCH4+ → M+ + CH4. The key step is activation of the H‐H bond, which has a barrier about twice as high for M = Co as for M = Rh; reaction (1) occurs more easily for M = Rh than M = Co. M = Ir completely changes the mechanism of reaction (1), which now follows the path: IrCH2+(3A2) + H2 → (H2) IrCH2+(3A2) → [TS1, H2‐activation] → (H)2 IrCH2+(1A') → [TS2, H‐migration] → HIrCH3+(3A) → [TS3, CH4‐elimination] → IrCH4+(3A2) → Ir+(5F, s1d7) + CH4. The reaction (1) is exothermic for M = Co and Rh, but endothermic for M = Ir. For M = Co and Rh, the reverse reaction M+ + CH4 can give only one product MCH4+ and does not proceed further easily; for M = Co, at elevated temperature CoCH4+may give CoH+ and CoCH3+. However, for M = Ir the reverse reaction can proceed further to give hydridomethyl HIrCH3+ and bishydrido (H)2CH2+ complexes, as well as IrCH4+.
Atmospheric Chemistry of 2‐Ethyl Acrolein
Authors: Grosjean Daniel , Grosjean Eric , Williams Edwin L.
Published: November 2013

The atmospheric oxidation of the unsaturated aldehyde 2‐ethyl acrolein, CH2=C(C2H5)CHO, has been studied in laboratory experiments involving the reaction of ozone with 2‐ethyl acrolein in the dark (with cyclohexane added to scavenge the hydroxyl radical), and the sunlight irradiation of 2‐ethyl acrolein with NO in air. The major carbonyl products of the 2‐ethyl acrolein reaction with ozone are formaldehyde, acetaldehyde, and the dicarbonyl ethylglyoxal, CH3CH2COCHO. Sunlight irradiation of 2‐ethyl acrolein and NO led to the formation of three carbonyls (formaldehyde, acetaldehyde, and ethylglyoxal) and three peroxyacyl nitrates, (RC(O)OONO2), including PAN (R = CH3), PPN (R = C2H5), and the unsaturated compound EPAN (R = CH2=C(C2H5)). Mechanisms are outlined for the reactions of ozone and of the hydroxyl radical with 2‐ethyl acrolein. These mechanisms are consistent with the observed carbonyl and peroxyacyl nitrate products. Thermal decomposition, a major atmospheric removal process for peroxyacyl nitrates, has been studied for EPAN. The decomposition rate of EPAN relative to that of PAN is 0.59–0.73 at 292–294 K and 1 atm of air. Atmospheric implications of these results are discussed.
A Preliminary Apportionment of the Sources of Fine Particulates Impacting on the Israeli Coast
Authors: Gertler Alan W.
Published: November 2013

The Chemical Mass Balance (CMB) receptor model was used to apportion the sources of PM2.5 aerosol (particulate matter with aerodynamic diameter <2.5 μm) sampled during a limited period at Caesarea, a site located in northern Israel along the Mediterranean coast, from late May to early June, 1993, a period corresponding to the time of year when air mass transport from Europe is frequent. Observed PM2.5 concentrations averaged 25.5 μg/m3 during the sampling period, with sulfate accounting for the majority (>50%) of the total observed mass. Source contribution estimates predicted by the CMB receptor model were similar for all periods, with predicted ammonium sulfate, mobile source, coal‐fired power plants, marine aerosol, and residual oil combustion contributions of 74, 14, 9, 3, and 0.3%, respectively. Transport (coupled with transformation) sources accounted for almost 97% of the ambient particulate loadings observed in this preliminary study.
Glass Transition Behavior in Ultra‐Thin Polystyrene Films
Authors: Keddie J.L. , Jones R.A.L.
Published: November 2013

We have used ellipsometry to measure the glass transition temperature (Tg) of ultra‐thin films of polystyrene (PS) (less than 20 nm thick) obtained by spin‐casting from solution onto silicon substrates. We find that Tg in these ultra‐thin films is depressed from the bulk value in qualitative accord with our earlier results on thicker films of PS. In films as thin as 8 nm, the depression from the bulk value of Tg is 35 K. We have also prepared ultra‐thins by grafting PS‐COOH on the native oxide of Si and by spin‐casting PS‐COOH onto Si. Here we have been able to measure the Tg of 5‐nm films in which we find a Tg depression of 10 K. We tentatively ascribe the smaller value of Tg depression for these grafted chains to the constraining effect of the anchor.
Role of Surface‐Anchored Polymer Chains in Adhesion and Slippage
Authors: Léger L. , Hervet H. , Marciano Y. , Deruelle M. , Massey G.
Published: November 2013

When in contact with an attractive wall, polymer chains tend to form thick, surface‐anchored layers with an internal structure which can be controlled. We present and analyze experiments conducted on model systems aimed at understanding how such surface‐anchored polymer layers can act as adhesion promoters or can induce wall slip. For both situations, the key parameter is the degree of interdigitation between the surface layer and the bulk polymer system, either an elastomer or a melt. We analyze how this degree of interdigitation governs the optimum enhancement in the adhesion energy between the solid wall and an elastomer, and how it is at the origin of the very different wall slip regimes observed experimentally.
Reactions on Single‐Crystal Metal Surfaces Studied with Scanning Tunneling Microscopy
Authors: Murray P.W. , Besenbacher F. , Stensgaard I.
Published: November 2013

A review is given of scanning tunneling microscopy (STM) studies of reactions between different chemical species on metal surfaces. Results presented for a variety of systems show that STM can give unique insight at the atomic level into the mechanistic details of surface reactions and decomposition of molecules. This is illustated with a number of examples of reactions occuring on single‐crystal metal surfaces, such as Ni(110), Cu(110), Ag (110), Rh (110), and Pt(111). The ability of the local STM probe to study the influence of defect sites on reactivity is highlighted, and similarities and differences in reactivity of different systems are discussed. Finally, the application of STM to enhance reactivity via tip interactions is addressed.
Sequence Similarity and Cross‐Reactivity of a Diels–Alder Catalyst and an Anti‐Progesterone Antibody
Authors: Haynes Matthew R. , Lenz Martin , Taussig Michael J. , Wilson Ian A. , Hilvert Donald
Published: November 2013

Antibody 1E9 catalyzes the bimolecular Diels–Alder reaction between tetrachlorothiophene dioxide and N‐ethylmaleimide with high catalytic efficiency. The genes encoding the heavy and light chains were cloned, sequenced, and expressed as a mouse/human chimera in a murine hybridoma. Comparison with the closely related and structurally characterized anti‐progesterone antibody DB3 has permitted identification of the residues that are likely to line the binding cavity. In addition to confirming the expectation of a highly hydrophobic active site, modeling results suggest that shape complementarity, achieved mainly through van der Waals rather than hydrogen bonding or electrostatic interactions, is likely to be the dominant factor in achieving effective preorganization of the substrates for catalysis. These conclusions can now be investigated through targeted mutagenesis of the putative active site residues exploiting the mammalian expression system.
Electric Field Measurements inside Self‐Assembled Multilayer Films at Electrode Surfaces by Electrochemically Modulated Surface Plasmon Resonance Experiments
Authors: Hanken Dennis G. , Corn Robert M.
Published: November 2013

The new in situ optical technique of electrochemically modulated surface plasmon resonance (EM‐SPR) is described and applied to the measurement of the electrostatic fields inside noncentrosymmetric zirconium phosphonate (ZP) films formed from the asymmetric nonlinear optical material [1‐[4‐[4‐[(N‐(2‐hydroxyethyl)‐N‐methyl)amino]phenyl]azo](5‐phosphonopentyl)] pyridinium bromide (PY‐AZO). In situ EM‐SPR measurements on PY‐AZO films yield a value for the change in electric field strength (ΔE) of 4 × 103 V/cm for a change in electrode potential (Δϕm) at 0.0 V vs. SCE of ±25 mV (8 × 104 V/cm for Δϕm = 1 V). This electric field strength value indicates that there is substantial ion penetration into the film in the electrochemical environment. Both the phase and magnitude of the surface optical response in the EM‐SPR measurements are used to distinguish the molecular and metal electrode contributions to the overall optical signal. These two EM‐SPR contributions are identified and separated in a quantitative fashion through a series of theoretical Fresnel calculations.
Adsorption of Some Atmospherically Important Molecules onto Large Water Clusters: SO2, SO3, HCl, and ClONO2
Authors: Apps C.J. , Watt N.E. , Whitehead J.C.
Published: November 2013

The adsorption of a range of atmospherically important molecules (SO2, SO3, HCl, and ClONO2) on large water clusters have been studied using a supersonic molecular beam expansion to generate water clusters containing 50–450 water molecules. SO2 and HCl were found to stick with low efficiency to the water cluster, retaining their chemical identity. In contrast, both SO3 and ClONO2 undergo heterogeneous reactions on the surface of the water cluster forming, respectively, H2SO4 and HOCl with HNO3. For SO3, calculations show that the large barrier that exists in the gas‐phase to the reaction of SO3 with water is removed for water clusters of a sufficient size because of stabilization of the transition state by solvation. For ClONO2, the barrier to reaction is much larger and cannot be removed by solvation for any size cluster. In this case, it is likely that reaction takes place on the water cluster by the ionic dissociation of ClONO2 in a similar manner to that observed for ClONO2 on ice films.
CVD Diamond Wafers Fabricated by DC Arc Jet
Authors: Windischmann Henry , Simpson Matthew A.
Published: November 2013

As the clock speed and chip power density continue to increase, heat management is becoming an ever‐increasing challenge for package designers. In addition, the demand for a narrow profile in consumer products and compact footprint may disqualify traditional heat dissipation materials as viable solutions. Diamond is a premier candidate for this application because of its unmatched thermal conductivity and low density. However, the outstanding issue is cost and availability. This paper discusses dc arc jet deposition technology and the stress issues that must be addressed to develop a reliable fabrication process. By adopting tight process control and matching the substrate's thermal properties to the film, a crack‐free 175‐mm‐diameter diamond wafer fabrication process has been developed with uniform properties and wafer yields that exceed 90% for thicknesses greater than 200 μm.
Growth and Adhesion Enhancement of Diamond Films Deposited on Steel Substrates by a Cr–N Interlayer
Authors: Glozman Olga , Hoffman Alon
Published: November 2013

Diamond film deposition onto iron‐based substrates by chemical vapor deposition methods is complicated by the formation of black carbon or graphitic soot on the substrate surface prior to diamond nucleation and growth, by fast diffusion of carbon into the iron substrate, and by poor adhesion of the deposited film. These complications suggested the use of a buffer layer between the deposited diamond film and the iron‐based substrate. We review different methods used to improve the adhesion of diamond film to steel substrates. In particular we describe in detail our own studies which involve the use of a Cr‐N interlayer. The use of a chromium nitride interlayer has been found to improve significantly the adhesion of diamond films deposited on ferrous substrates. This is achieved by hindering diffusion processes of carbon and iron, very stable mechanical and chemical bonding between the interlayer and the diamond film, and good adhesion of the interlayer to the steel substrate. We also report on our studies related to residual stress present in the films, as well as a correlation between the interlayer properties and adhesion strength of deposited films.
Diamond‐Coated WC–Co Cutting Tools
Authors: Inspector Aaron , Bauer C. Erik , Gates Alfred S. , Oles Edward J.
Published: November 2013

The unique combination of high hardness, high thermal conductivity, and low friction coefficient makes diamond an excellent cutting tool material for the machining of abrasive, non‐ferrous workpieces. This paper reviews basic and applied aspects of the technology as applied to the preparation of diamond coated cutting tools.
Homoepitaxial Diamond Devices
Authors: Fox Bradley A. , Dreifus David L.
Published: November 2013

Diamond has been proposed as an excellent material for high‐temperature, high‐power, and high‐frequency applications. The interest in diamond electronics is due to its large electric breakdown field, high‐saturated current velocity and high‐thermal conductivity. As silicon and gallium arsenide devices begin to reach their performance limits, there is a need to develop new, better performing materials such as diamond. Significant progress in the development of diamond as a semiconducting material has been made and diamond has been implemented into numerous conventional and novel device designs. In this work homoepitaxial diamond material properties and device performance are reviewed. In summary, the large activation energy of boron‐doped p‐type diamond and phosphorus‐doped n‐type diamond severely limits diamond's use in conventional semiconductor device designs. The large activation energy reduces the number of charge carriers, which limits the current handling capability and produces temperature‐dependent device performance. To overcome diamond's limitations, novel devices, such as enhancement mode field effect transistors (FETs) that use a hydrogenated surface conducting layer or pulsed doped devices with almost complete ionization, have been investigated. These devices require further development. The initial results show promise for high‐temperature, high‐frequency, and high‐power applications.
Devices at High Temperatures—Status and Prospects
Authors: Kohn Erhard , Ebert Wolfgang , Vescan Andrei
Published: November 2013

The temperature‐handling capability of diamond diode and field effect transistor structures is discussed and compared with recent results on GaN. The main parameters limiting the high‐temperature performance are identified and evaluated. A diamond high‐temperature technology is presented which has allowed 1000°C operation of a diamond Schottky diode, the highest temperature of operation of any semiconductor diode yet.
Laser Studies of Small Radicals in Rich Methane Flames: OH, HCO, and 1CH2
Authors: McIlroy Andrew
Published: November 2013

Chemical mechanisms for combustion processes are often developed for nearly stoichiometric flames, a perfect balance of fuel and oxidizer. As the fuel content is increased and flames become richer, these models will eventually break down because they lack reactions leading to the formation of larger hydrocarbons and ultimately soot. In this contribution, we investigate the behavior of two methane combustion models, the GRI 2.11 and Prada–Miller mechanisms, in a series of rich flames of stoichiometry 1.0, 1.2, 1.4, and 1.6. Using non‐intrusive laser diagnostics, laser‐induced fluorescence, and cavity ring‐down spectroscopy, the concentration profiles as a function of height above burner for OH, HCO, and 1CH2 have been measured in these rich low‐pressure methane flames. The experimental results are compared to the calculated profiles. In general, good agreement is found for all species over the range of stoichiometries investigated. The agreement of the OH and HCO profiles with the models is particularly striking. For 1CH2, the width, position, and relative height of the profiles match the model predictions for flames of stoichiometry 1.0 and 1.2. Discrepancies are noted for the richer flames investigated, those with stoichiometrics of 1.4 and 1.6. An analysis of the models suggests that additional pathways for 1CH2 formation and removal should be considered. Even under fairly rich conditions, stoichiometry of 1.6, both models perform well for the radicals investigated here. There is no indication of the requirement for >C2 chemistry to reproduce the present data.
Experimental and Numerical Study of the Effect of an Electric Field on a Bunsen‐type Flame
Authors: Hu Jing , Rivin Boris , Sher Eran
Published: November 2013

The effect of an electric field on the behavior of premixed methane‐air flames has been studied. A candle‐type flame has been observed experimentally and analyzed for its geometrical proportions under an electric field. A numerical model has been developed to explain some of the experimental observations. The model employs a two‐dimensional cylindrical coordinate system and assumes axial symmetry. The mass, momentum, species, and energy conservation equations are solved by an integrated version of the PHOENICS and CHEMKIN computer codes. It is concluded that the effect of the electric field on the flame behavior is mainly due to ionic wind effects.
Temperature Dependence of Excited‐State Proton Transfer and Geminate Recombination Processes in Water and in Glycerol‐Doped Ice
Authors: Poles Ehud , Cohen Boiko , Huppert Dan
Published: November 2013

The reversible proton dissociation and geminate recombination of photoacids was studied as a function of temperature in neat water, binary water mixture containing 0.6 mol% glycerol, and doped ice containing 0.6 mol% glycerol. The deuterium isotope effect on both condensed phases was also studied. 8‐hydroxypyrene‐1,3,6 trisulfonate trisodium salt was used as the electronically‐excited‐state proton emitter. The experimental data are analyzed by the Debye–Smoluchowski equation solved numerically with boundary conditions to account for the reversibility of the reaction. We propose a qualitative model to describe the unusual temperature dependence of the proton transfer rate in the liquid phase. We also propose a model for proton transfer in solid ice based on L‐defects transport as proton acceptors. While in the liquid phase at t > 10°C the proton dissociation rate constant is almost temperature independent, in glycerol‐doped ice we find a large temperature dependence.
Ground‐ and Excited‐State Proton Transfer in Some o‐Hydroxy Aromatic Compounds and Solvent Effect
Authors: Guha Dipanwita , Mandal Abhijit , Das Ranjan , Mitra Sivaprasad , Mukherjee Samaresh
Published: November 2013

Proton transfer reaction in the ground and excited state of 4‐methyl‐2,6‐diformyl phenol (MFOH) and some of its derivatives in different nonpolar and polar solvents has been studied using steady‐state and nanosecond transient emission spectroscopy at room temperature and 77 K. The stable molecular structure in the ground state is an intramolecularly hydrogen‐bonded closed conformer from which the intramolecular proton transfer (ESIPT) takes place in the first excited singlet state in nonpolar solvents. An emission band originates from the proton‐transferred enol tautomer of the closed conformer. From a detailed study of the absorption, emission, and excitation spectra in highly polar protic and aprotic solvents, two other conformers have been identified. At 77 K in nonpolar solvents, emission spectra show phosphorescence only in the case of MFOH and 4‐methyl‐2,6‐diamidophenol (MDOH). In the case of other derivatives, such as 4‐methyl‐2,6‐diacetylphenol (MAOH) and 4‐methyl‐2,6‐dicarbomethoxyphenol (MOOH), phosphorescence is observed only in the presence of a strong base, such as trimethylamine. This conversion of fluorescence into phosphorescence is markedly slow in the case of MDOH, MAOH, and MOOH compared to that of MFOH. The relatively larger values of fluorescence lifetimes at 77 K are consistent with our observation. It is proposed that the occurrence of phosphorescence is from an open conformer and is caused by the rotation of the formyl group. From nanosecond measurements and quantum yields of fluorescence, we have estimated the decay rate constants. The fluorescence decay rates are slower in polar than in nonpolar solvents; nonradiative decay rates are always found to be dominant over the radiative ones.
Proton Solvation and Proton Mobility
Authors: Agmon Noam
Published: November 2013

Experimental evidence for proton solvation and proton mobility is analyzed and the results are compared with recent simulations. Three factors contribute to differences in proton solvation energies: hydrogen‐bond cleavage, changes in hydrogen‐bond lengths, and proton derealization. These factors are estimated from experimental attributes. In dilute acidic aqueous solutions H3O+ is more stable than H5O2+ by about 0.6 kcal/mol. This estimate, together with the activation energy for proton mobility, supports the 121 mechanism for proton mobility in which a protonated water monomer is transformed, by second‐shell hydrogen‐bond cleavage, to a protonated dimer and back to another protonated monomer.
Electronic properties of anodized TiO2 electrodes and the effect on in vitro response
Authors: Löberg Johanna , Gretzer Christina , Mattisson Ingela , Ahlberg Elisabet
Published: November 2013

For dental implants, improved osseointegration is obtained by modifying the surface roughness as well as oxide morphology and composition. A combination of different effects contributes to enhanced performance, but with surface roughness as the dominant factor. To single out the effect of oxide conductivity on biological response, oxide films with similar thickness and surface roughness but different electronic properties were formed using galvanostatic anodization. Three different current densities were used, 2.4, 4.8, and 11.9 mA cm−2, which resulted in growth rates ranging from 0.2 to 2.5 V s−1. The electronic properties were evaluated using cyclic voltammetry and impedance spectroscopy, while the biological response was studied by cell activity and apatite formation. The number of charge carrier in the oxide film close to the oxide/solution interface decreased from 5.8 × 10−19 to 3.2 × 10−19 cm−2 with increasing growth rate, that is, the conductivity decreased correspondingly. Cell response of the different surfaces was tested in vitro using human osteoblast‐like cells (MG‐63). The results clearly show decreased osteoblast proliferation and adhesion but higher mineralization activity for the oxide with lower conductivity at the oxide/solution interface. The apatite‐forming ability was examined by immersion in simulated body fluid. At short times the apatite coverage was ∼26% for the anodized surfaces, significantly larger than for the reference with only 3% coverage. After 1 week of immersion the apatite coverage ranged from 73 to 56% and a slight differentiation between the anodized surfaces was obtained with less apatite formation on the surface with lower conductivity, in line with the cell culture results. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 826–839, 2014.
Effects of sterilization methods on the physical, chemical, and biological properties of silk fibroin membranes
Authors: de Moraes Mariana Agostini , Weska Raquel Farias , Beppu Marisa Masumi
Published: November 2013

Silk fibroin has been widely explored for many biomedical applications, due to its biocompatibility and biodegradability. Sterilization is a fundamental step in biomaterials processing and it must not jeopardize the functionality of medical devices. The aim of this study was to analyze the influence of different sterilization methods in the physical, chemical, and biological characteristics of dense and porous silk fibroin membranes. Silk fibroin membranes were treated by several procedures: immersion in 70% ethanol solution, ultraviolet radiation, autoclave, ethylene oxide, and gamma radiation, and were analyzed by scanning electron microscopy, Fourier‐transformed infrared spectroscopy (FTIR), X‐ray diffraction, tensile strength and in vitro cytotoxicity to Chinese hamster ovary cells. The results indicated that the sterilization methods did not cause perceivable morphological changes in the membranes and the membranes were not toxic to cells. The sterilization methods that used organic solvent or an increased humidity and/or temperature (70% ethanol, autoclave, and ethylene oxide) increased the silk II content in the membranes: the dense membranes became more brittle, while the porous membranes showed increased strength at break. Membranes that underwent sterilization by UV and gamma radiation presented properties similar to the nonsterilized membranes, mainly for tensile strength and FTIR results. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 869–876, 2014.
6‐Methoxy‐2‐oxo‐1,2‐dihydroquinoline‐3,4‐dicarbonitriles, A Red Compound Class with Solvent and pH Independent Green Fluorescence Maxima
Authors: Enoua G. C. , Lahm G. , Uray G. , Stadlbauer W.
Published: November 2013

The sodium p‐toluenesulfinate mediated reaction of potassium cyanide with 4‐chlorocarbostyrils 8, 16, 18, and 23 gave in all cases the highly fluorescent and stable 6‐methoxy‐2‐oxoquinoline‐3,4‐dicarbonitrile 9 (λexc 460 nm and λem 545 nm). This is remarkable, because starting carbostyrils 8, 16, 18, and 23 had a chloro substituent, a nitro substituent, an acetylamino substituent, or a piperidinyl substituent in position 3. Hence, we observed not only a substitution of the 4‐chloro and expected 3‐chloro substituents by the cyanide nucleophile but also an exchange of a nitro substituent, an acetylamino substituent, and a piperidinyl substituent in position 3. The multistep insertion of substituents leading to 8, 16, 18, and 23 started from 4‐hydroxy‐6‐methoxyquinolone 4, easily obtained from p‐anisidine and malonic acid. Substitutions in position 3 gave 4‐hydroxy‐3‐nitro and 3‐chloro intermediates, which were converted to 3,4‐dichlorocarbostyril 8 and 4‐chloro‐3‐nitrocarbostyril 16. Reduction of the 3‐nitro intermediate led to the 3‐acetylamino analog and subsequent chlorination led to 3‐acetylamino‐4‐chlorocarbostyril 18. 4‐Chloro‐3‐piperidinylcarbostyril 23 was obtained from intermediate 3,3‐dichloroquinolinedione by subsequent amination, reduction and chlorination. Further, 3‐acetylamino‐4‐chlorocarbostyril 18 gave with lithium p‐toluenesulfinate highly fluorescent 3‐amino‐6‐methoxy‐4‐p‐tolylsulfonylquinolone 19.
Kinetics of Fading of Some Triphenylmethane Dyes: Effects of Electric Charge, Substituent, and Aqueous Binary Mixtures of Dimethyl Sulfoxide and 2‐Propanol
Authors: Samiey B. , Dalvand Z.
Published: November 2013

The rate constants of alkaline fading of a number of triphenylmethane (TPM) dyes including methyl green (ME2+), brilliant green (BG+), fuchsin acid (FA2−), and bromophenol blue (BPB2−) were obtained in aqueous binary mixtures of 2‐propanol (protic solvent) and dimethyl sulfoxide (DMSO) (aprotic solvent) at different temperatures. It was observed that the reaction rate constants of BG+ and ME2+ increased and those of FA2− and BPB2− decreased with an increase in weight percentages of aqueous 2‐propanol and DMSO binary mixtures. 2‐Propanol and DMSO interact with the used TPM molecules through hydrogen bonding and ion–dipole interaction, respectively, in addition to their hydrophobic interaction with TPM dyes. The fundamental rate constants of a fading reaction in these solutions were obtained by the SESMORTAC model. Also, the effect of electric charge and substituent groups of a number of TPM dyes on their alkaline fading rate was studied.
Improved voluntary cough immediately following office‐based vocal fold medialization injections
Authors: Ruddy Bari H. , Pitts Teresa E. , Lehman Jeff , Spector Brian , Lewis Vicki , Sapienza Christine M.
Published: November 2013

Objectives/Hypothesis

This study examined changes in voluntary cough airflow measures immediately following in‐office injection of Radiesse in patients diagnosed with glottic insufficiency. Due to significant comorbidities, these patients were poor candidates for medialization under general anesthesia. Each patient presented with dysphonia and dysphagia and ineffective voluntary cough, resulting in a poor clearing of secretions and a presence of ingested fluids on examination.

Study Design

Prospective cohort and case series study.

Methods

Three patients with a diagnosis of glottic insufficiency were included for study based on flexible endoscopy and laryngostroboscopic examination. Voluntary cough airflow measures were obtained approximately 30 minutes before and after the Radiesse injections. The airflow measures were: compression phase duration (CPD), expiratory rise time (EPRT), expiratory phase peak airflow (EPPF), and cough volume acceleration (CVA).

Results

Injection of Radiesse was found to improve voluntary cough airflow measures.

Conclusion

The immediate increase in the objective airflow measures obtained from voluntary cough production after Radiesse injections can be used to document airway protection improvements. Cough airflow is a straightforward measure to obtain and is considered an objective measure of cough function.

Level of Evidence

4. Laryngoscope, 124:1645–1647, 2014
Tagging & Tracking und Kollisionsprävention im Untertagebergbau
Authors: Becker Franz
Published: November 2013

Bei der Anwendung von Tagging & Tracking (T&T) im Untertagebergbau werden alle Bergleute, Fahrzeuge, Transportbehälter und Betriebsmittel mit einem codierten RFID‐Baustein, dem sogenannten Tag, ausgerüstet. Sein Code kann von im Bergwerk verteilten Lesegeräten empfangen werden, die in das bergwerksweite Datenübertragungsnetz eingebunden sind. Neben der Disposition von Personen, Fahrzeugen und Material liegen die Hauptaufgaben aktueller T&T‐Systeme bei sicherheitlichen Funktionen wie der Ortung von Personen nach Unfällen. Die Komponenten eines weltweit eingesetzten T&T‐Systems werden vorgestellt.

Ferner befasst sich der Beitrag mit Aufbau und Funktionsweise eines neuentwickelten Systems zur Vermeidung von Kollisionen zwischen Fahrzeugen und Bergleuten sowie von Fahrzeugen untereinander. Für diesen Zweck wurde die UHF‐Technologie, die für das T&T‐System genutzt wird, um zwei weitere elektromagnetische Verfahren zur Verbesserung der Umfelderkennung erweitert. Über den Aufbau des Kollisionsschutzsystems und erste Erfahrungen im Bergbau wird berichtet.

Tagging & Tracking and collision avoidance in underground mining.

When Tagging & Tracking (T&T) is used in underground mining, all miners, vehicles and transport containers or equipment be tracked in the mine workings are provided with a coded RFID module, the so‐called tag. Its code can be received by readers distributed in the mine which are integrated in a mine wide communication network. Alongside vehicle, personnel and material scheduling, the main tasks for current T&T systems in underground mining are safety functions such as locating persons after accidents and risk warnings. The components of a T&T system used globally and applications in international mining shall be introduced in this presentation.

It also deals with the design and functions of a newly developed concept to avoid collisions between vehicles and miners and to prevent vehicles colliding. For this purpose the UHF technology which is used for the T&T‐system has been supplemented with two additional electromagnetic processes to improve environment detection. The design of the collision protection system and its technologies are explained and initial experiences with use in mining are reported.
Applications of Kalman filtering and inertial navigation in future autonomous mining methods
Authors: Zingsheim Moritz , Möllemann Gerhard , Shute Dean , Nienhaus Karl
Published: November 2013

A Kalman filtering algorithm, when applied to inertial navigation data gathered during mining operations, can provide a clear and accurate analysis of the velocity and position of the mining machinery used during cutting and standard operation. The Kalman filter algorithm can be used both to determine the velocity and position of the mining machinery from a combination of accelerometer and gyroscope data, and to eliminate a reasonable amount of sensor noise and drift obtained during the mining operations.

Anwendung des Kalman‐Filters bei inertialen Navigationssystemen für zukünftige mannlose Gewinnungsprozesse

Mineralische Rohstoffe tragen in entscheidendem Maße zur Zukunftsfähigkeit moderner Gesellschaften bei. Der Zugang zu Bodenschätzen ist von hoher Bedeutung für die europäische Wirtschaft. Die Bergbauindustrie sieht sich mit vielen Herausforderungen konfrontiert. Bodenschätze müssen in immer größeren Tiefen abgebaut werden, gleichzeitig muss die Sicherheit der Mitarbeiter genauso gewährleistet werden wie die Umweltverträglichkeit.

Das Streben nach erhöhten Automatisierungsgraden ist in dieser rauen und Effizienz fordernden Umgebung die Motivation für die Anpassung modernster Sensorik an das bergbauliche Umfeld. Für einen autonomen, mannlosen Gewinnungsprozesses ist es erforderlich, die räumliche Position des Gewinnungsgerätes exakt und kontaktlos zu bestimmen und zu verfolgen. Eine Kernkomponente für diesen Automatisierungsprozess ist die Positions‐ und Richtungsbestimmung (=Navigation). Inertiale Navigationssysteme (INS) auf der Basis von orthogonal angeordneten Beschleunigungs‐ und Drehratensensoren ermöglichen das Bestimmen von Positionen und Orientierungen eines bewegten Objektes im Raum.
Asymptomatic lambert–eaton syndrome
Authors: Denys Eric H. , Lennon Vanda A.
Published: November 2013

Introduction

All descriptions of the Lambert–Eaton syndrome are based on symptomatic patients. We incidentally encountered electromyographic evidence of this syndrome in a patient being studied for another reason. The patient had controlled hypothyroidism and smoked for 9 pack‐years but never had symptoms of weakness or had evidence of cancer. Methods: Detailed electrophysiological and serological evaluations were undertaken in this study. Results: Neuromuscular transmission tests were consistent with a presynaptic disorder. Autoantibodies specific for P/Q‐type voltage‐gated calcium channels (VGCC) were detected in the serum and persisted throughout 7 years of follow‐up. Multiple IgG markers of thyrogastric autoimmunity also were detected. Conclusions: This demonstration of asymptomatic Lambert–Eaton syndrome persisting for 8 years provided novel insight into the natural history of the disorder. It is plausible that patients with a subclinical syndrome would have abrupt neuromuscular decompensation when challenged with medications that compromise the safety factor for synaptic transmission. Muscle Nerve 49: 764–767, 2014