bluuebunny/crossref_metadata_2025 huggingface dataset:
Second-order superintegrable systems in conformally flat spaces. V. Two- and three-dimensional quantum systems
Authors: Kalnins E. G. , Kress J. M. , Miller W.
Published: September 2006

This paper is the conclusion of a series that lays the groundwork for a structure and classification theory of second-order superintegrable systems, both classical and quantum, in conformally flat spaces. For two-dimensional and for conformally flat three-dimensional spaces with nondegenerate potentials we have worked out the structure of the classical systems and shown that the quadratic algebra always closes at order 6. Here we describe the quantum analogs of these results. We show that, for nondegenerate potentials, each classical system has a unique quantum extension. We also correct an error in an earlier paper in the series (that does not alter the structure results) and we elucidate the distinction between superintegrable systems with bases of functionally linearly independent and functionally linearly dependent symmetries.
InN nanoflowers grown by metal organic chemical vapor deposition
Authors: Kang Ting-Ting , Liu Xianglin , Zhang Ri Q. , Hu Wei G. , Cong Guangwei , Zhao Feng-Ai , Zhu Qinsheng
Published: September 2006

Hexangular indium nitride nanoflower pattern is observed from scanning electron microscopy and atomic force microscopy. The sample is grown on c-plane (0001) sapphire by metal organic chemical vapor deposition with intentional introduction of hydrogen gas. With the aid of hydrogen, a stable existence of metallic indium is achieved. This will induce the growth of InN nanoflowers via self-catalysis vapor-liquid-solid (VLS) process. It is found that the VLS process is modulated by the interface kinetics and thermodynamics among the sapphire substrate, indium, and InN, which leads to the special morphology of the authors’ InN nanoflower pattern.
Observation of secondary relaxation in a fragile Pd40Ni10Cu30P20 bulk metallic glass
Authors: Zhao Zuo Feng , Wen Ping , Wang Wei Hua , Shek C. H.
Published: September 2006

The dynamic elastic moduli in the temperature domain of a Pd40Ni10Cu30P20 bulk metallic glass were measured with dynamic mechanical spectroscopy at frequencies less than 100Hz. The primary relaxation is characterized by a single loss modulus peak and a rapid drop of storage modulus in the metallic supercooled liquid region. Below the conventional glass transition temperature, a pronounced shoulder in the loss modulus curves appears and the corresponding storage modulus decreases with increasing temperature. The phenomenon is common to glass formers of all types. The observations present the evidence of the existence of the slow β relaxation and affirm the universality of the separation of the primary and secondary relaxations in the supercooled liquid.
Study of coupling effect in double-layer quantum dots by admittance spectroscopy
Authors: Yuan Fengying , Jiang Zuimin , Lu Fang
Published: September 2006

The influence of the coupling effect on quantum confinement energy levels and on the Coulomb charging effect in double-layer GeSi quantum dots (QDs) is investigated by admittance spectroscopy. The coupling effect depends on the thickness of the space layer between QD layers. The increasing Coulomb charging energy observed in QD samples with different thickness (4.5, 6, and 7.5nm) indicates that the coupling effect can weaken the quantum confinement effect and Coulomb charging interaction. When the space layer is thicker than 7.5nm, the influence of the coupling effect can be neglected.
Current-induced magnetization switching under magnetic field applied along the hard axis in MgO-based magnetic tunnel junctions
Authors: Inokuchi T. , Sugiyama H. , Saito Y. , Inomata K.
Published: September 2006

The authors have investigated the dependence of the critical current density (Jc) for the current-induced magnetization switching (CIMS) on external magnetic fields applied along the hard axis of a free layer (Hhard) and on the duration of pulse current in MgO-based magnetic tunnel junctions. The Jc and the intrinsic current density (Jc0), derived from the dependence of the Jc on the pulse duration, decreased as ∣Hhard∣ increased. These reductions of Jc and Jc0 would be attributed to the decrease of energy barrier for CIMS and the increase of the spin transfer efficiency.
Observation of optical bistability in a ZnO powder random medium
Authors: Fujiwara Hideki , Sasaki Keiji
Published: September 2006

Optical bistability has been observed in photoluminescence from a ZnO powder random medium. The emission spectra and the excitation intensity dependence of 420nm emission clearly exhibit the existence of bistable steady states with changing excitation intensity.
Mechanical strain effect of n-channel polycrystalline silicon thin-film transistors
Authors: Huang C.-F. , Yang Y.-J. , Peng C.-Y. , Yuan F. , Liu C. W.
Published: September 2006

The current change of n-channel polycrystalline silicon thin-film transistors is analyzed experimentally and theoretically under different strain conditions. Under the uniaxial strain parallel to the channel, the +6.7% and +5.3% drain current enhancements are achieved in linear and saturation regions, respectively. There are −4.4% (linear) and −4.6% (saturation) drain current degradations when the uniaxial strain is applied perpendicular to the channel. The polycrystalline silicon is mainly composed of (111)-oriented grains, measured by electron diffraction pattern. Phonon-limited mobility is theoretically calculated. There is a qualitative agreement between experiments and theoretical analysis.
Long-pulse operation of a megawatt-class plasma-assisted slow-wave oscillator
Authors: Shkvarunets A. G. , Rodgers J. , Carmel Y. , Nusinovich G. S.
Published: September 2006

Demonstration of a plasma-assisted, helix-based slow-wave 1.2GHz oscillator (pasotron) operating at megawatt power levels with pulse durations of approximately 0.6ms and generating about 0.6kJ of microwave energy per pulse without pulse shortening is presented. This result was achieved in spite of significant voltage and current drop as well as the temporal evolution of the gas pressure in the interaction space during the rf pulse. The conditions for stable operation or mode hopping were studied and experimentally observed. The physical interpretation for this effect, which was caused by drop in the accelerating voltage due to limited energy storage in the power supply, is given. The results indicate that stable, high-efficiency, single mode operation of the pasotron with output energy of 1kJ/pulse and beyond can be realized.
Current density dependence of electromigration-induced flip-chip Cu pad consumption
Authors: Lin C. T. , Chuang Y. C. , Wang S. J. , Liu C. Y.
Published: September 2006

Current density dependence on the mechanism of the electromigration-induced flip-chip Cu pad consumption was observed. A critical current density was determined, which defines the consumption mechanism of Cu pad. Below this critical current density, a constant interfacial compound layer would be established. The mechanism whereby the Cu pad is consumed is the dissolution of the interfacial Cu–Sn compound. Above the critical current density, the interfacial compound layer continues to grow over time. The consumption of the Cu pad was then primary controlled by the total Cu flux in the interfacial Cu–Sn compound layer.
Evidence of metallic clustering in annealed Ga1−xMnxAs from atypical scaling behavior of the anomalous Hall coefficient
Authors: Choi H. K. , Kim Y. S. , Seo S. S. A. , Jeong I. T. , Lee W. O. , Oh Y. S. , Kim K. H. , Woo J. C. , Noh T. W. , Khim Z. G. , Park Y. D. , Chun S. H.
Published: September 2006

The anomalous Hall coefficient (Rs) and longitudinal resistivity (ρxx) scaling relationship (RS=cρxxn) for a series of annealed Ga1−xMnxAs epilayers (x≈0.055) are investigated. As-grown samples exhibit a scaling parameter n∼1 and samples annealing near the optimal annealing temperature, n∼2. For annealing temperatures far above the optimum they observe scaling with n>3, which is similar to the behavior of certain inhomogeneous systems. Optical spectroscopy measurements also reveal an enhancement of the absorption coefficient in these samples for photons of energy around 1eV. These atypical behaviors are characteristic of spherical resonance from metallic inclusions.
Electronic transportation through asymmetrically substituted oligo(phenylene ethynylene)s: Studied by first principles nonequilibrium Green’s function formalism
Authors: Yin Xing , Liu Hongmei , Zhao Jianwei
Published: September 2006

Theoretical investigations of a series of asymmetrically substituted conducting molecular wires [oligo(phenylene ethynylene)s] have been carried out using density functional theory and nonequilibrium Green’s function formalism. To get the molecular rectification, the electron-donating group (–NH2) and the electron-withdrawing group (–NO2) are placed on the different positions of the molecular wire. The dependences of spatial distribution and lowest unoccupied molecular orbital (LUMO) energy level on the applied voltage have been found playing dominating but opposite roles in controlling the rectification behavior. In the tested bias range, since the shift LUMO energy level is more important, the electrons transfer more easily from donor to acceptor through the molecular junction in general.
Polarizable contributions to the surface tension of liquid water
Authors: Rivera Jose L. , Starr Francis W. , Paricaud Patrice , Cummings Peter T.
Published: September 2006

Surface tension, γ, strongly affects interfacial properties in fluids. The degree to which polarizability affects γ in water is thus far not well established. To address this situation, we carry out molecular dynamics simulations to study the interfacial forces acting on a slab of liquid water surrounded by vacuum using the Gaussian charge polarizable (GCP) model at 298.15K. The GCP model incorporates both a fixed dipole due to Gaussian distributed charges and a polarizable dipole. We find a well-defined bulklike region forms with a width of ≈31Å. The average density of the bulklike region agrees with the experimental value of 0.997g∕cm3. However, we find that the orientation of the molecules in the bulklike region is strongly influenced by the interfaces, even at a distance five molecular diameters from the interface. Specifically, the orientations of both the permanent and induced dipoles show a preferred orientation parallel to the interface. Near the interface, the preferred orientation of the dipoles becomes more pronounced and the average magnitude of the induced dipoles decreases monotonically. To quantify the degree to which molecular orientation affects γ, we calculate the contributions to γ from permanent dipolar interactions, induced dipolar interactions, and dispersion forces. We find that the induced dipole interactions and the permanent dipole interactions, as well as the cross interactions, have positive contributions to γ, and therefore contribute stability to the interface. The repulsive core interactions result in a negative contribution to γ, which nearly cancels the positive contributions from the dipoles. The large negative core contributions to γ are the result of small oxygen-oxygen separation between molecules. These small separations occur due to the strong attractions between hydrogen and oxygen atoms. The final predicted value for γ (68.65mN∕m) shows a deviation of ≈4% of the experimental value of 71.972mN∕m. The inclusion of polarization is critical for this model to produce an accurate value.
Role of strain in the blistering of hydrogen-implanted silicon
Authors: Lee Jung-Kun , Lin Yuan , Jia Q. X. , Höchbauer Tobias , Jung Hyun Suk , Shao Lin , Misra Amit , Nastasi Michael
Published: September 2006

The authors investigated the physical mechanisms underlying blistering in hydrogen-implanted silicon by examining the correlation between implantation induced damage, strain distribution, and vacancy diffusion. Using Rutherford backscattering, scanning electron microscopy, and atomic force microscopy, they found that the depth of blisters coincided with that of maximum implantation damage. A model based on experimental results is presented showing the effect of tensile strain on the local diffusion of vacancies toward the depth of maximum damage, which promotes the nucleation and growth of platelets and ultimately blisters.
Influence of the positive ion temperature in cold plasma diagnosis
Authors: Ballesteros J. , Fernández Palop J. I. , Hernández M. A. , Morales Crespo R.
Published: September 2006

The influence of the positive ion temperature in cold plasma diagnosis by using Langmuir probes is analyzed. The positive ion zone of the I-V characteristic is used. This zone is distinguished because the charge drained from the plasma is small, diminishing the perturbation due to the measurement process. Nevertheless, it is much affected by the positive ion temperature, thus the traditional methods give inaccurate values for the electron density. Moreover, for an accurate measurement of that current, a good calibration of the instrument used must be ensured. The authors propose the floating potential as the proper parameter to control that calibration.
Controlled preparation and electron emission properties of three-dimensional micropatterned aligned carbon nanotubes
Authors: Patil Ajeeta , Ohashi Toshiyuki , Buldum Alper , Dai Liming
Published: September 2006

The authors have developed a simple, but very effective and versatile, dry contact transfer technique for controlled preparation of three-dimensional (3D) perpendicularly aligned carbon nanotube micropatterns with region-specific tube lengths. The 3D micropatterned aligned carbon nanotubes were demonstrated to show a stepwise electron emission behavior, providing an effective means for developing multifunctional electron emitters with tailor-made field emission characteristics.
Rubberlike entropy elasticity of a glassy alloy
Authors: Fukuhara M. , Inoue A. , Nishiyama N.
Published: September 2006

The authors report observations of thermal-induced entropy elasticity and the Gough-Joule effect for a glassy alloy, Pd40Cu30Ni10P20, in terms of acoustoelasticity. Seven kinds of elastic parameters of the glassy alloy have been simultaneously measured as a function of temperature ranging from 298to673K. The decrease in elastic moduli and Poisson’s ratio and the increase in tension below the second-order-like phase transition temperature suggest rubberlike thermal dynamic micro-Brownian stretching, described as F(Pa)=0.282T+562, which may be associated with the rotational and vibrational motions of polyhedron clusters.
Coupled-cavity two-dimensional photonic crystal waveguide ring laser
Authors: Alija A. R. , Martínez L. J. , Postigo P. A. , Seassal C. , Viktorovitch P.
Published: September 2006

Coupled-cavity hexagonal ringlike photonic crystal lasers are fabricated as a class of single mode photonic crystal laser light sources. The structures are formed by placing one missing hole nanocavity (H1 type) between each two segments at 60° that form the hexagonal ringlike photonic crystal laser. The H1 cavities act as a mode filter, clamping the frequency of emission of the laser device. The emission frequency in these rings with cavities varies as the filling factor is changed, allowing the tuning of the laser emission. Stable single mode lasing occurs with side mode suppression greater than 20dB. This kind of devices may be used as an efficient selective filter of modes and may have important applications in future photonic devices for optical communications and optical sensing.
Monte Carlo simulation of phonon confinement in silicon nanostructures: Application to the determination of the thermal conductivity of silicon nanowires
Authors: Lacroix David , Joulain Karl , Terris Damian , Lemonnier Denis
Published: September 2006

The authors study the thermal conductivity of silicon nanowires by simulation of phonon motion and interactions through a dedicated Monte Carlo model. This model solves the Boltzmann transport equation, taking into account silicon acoustic mode dispersion curves and three phonon interactions (the normal and umklapp processes). The confinement, which limits the thermal conductivity in such structures, is described by diffuse reflection at lateral boundaries of the nanowire without any adjustment by a boundary collision time, which depends on a specularity factor. They compare simulation results to experimental measurements on similar nanostructures. A good agreement is achieved for almost all the considered diameters.
Formation of p-type MgZnO by nitrogen doping
Authors: Wei Z. P. , Yao B. , Zhang Z. Z. , Lu Y. M. , Shen D. Z. , Li B. H. , Wang X. H. , Zhang J. Y. , Zhao D. X. , Fan X. W. , Tang Z. K.
Published: September 2006

A wurtzite N-doped MgZnO film with 20at.% Mg (MgZnO:N) was grown by plasma-assisted molecular beam epitaxy on c-plane sapphire using radical NO as oxygen source and nitrogen dopant. The as-grown MgZnO:N film behaves n-type conduction at room temperature, but transforms into p-type conduction after annealed for 1h at 600°C in an O2 flow. The p-type MgZnO:N has a hole concentration of 6.1×1017cm−3 and a mobility of 6.42cm2∕Vs. X-ray photoelectron spectroscopy measurement indicates that substitution of N for O site is in forms of N atom (N)O and N molecule (N2)O for the as-grown MgZnO:N, but almost only in a form of (N)O for the annealed MgZnO:N. The mechanism of the conduction-type transition induced by annealing is discussed in the present work.
Growth, structure, and properties of epitaxial thin films of first-principles predicted multiferroic Bi2FeCrO6
Authors: Nechache Riad , Harnagea Catalin , Pignolet Alain , Normandin François , Veres Teodor , Carignan Louis-Philippe , Ménard David
Published: September 2006

The authors report the structural and physical properties of epitaxial Bi2FeCrO6 thin films on epitaxial SrRuO3 grown on (100)-oriented SrTiO3 substrates by pulsed laser ablation. The 300nm thick films exhibit both ferroelectricity and magnetism at room temperature with a maximum dielectric polarization of 2.8μC∕cm2 at Emax=82kV∕cm and a saturated magnetization of 20emu∕cm3 (corresponding to ∼0.26μB per rhombohedral unit cell), with coercive fields below 100Oe. The results confirm the predictions made using ab initio calculations about the existence of multiferroic properties in Bi2FeCrO6.
Electronic spectroscopy of the ÃA″1↔X̃A′1 system of CDBr
Authors: Tao Chong , Deselnicu Mihaela , Mukarakate Calvin , Reid Scott A.
Published: September 2006

We report fluorescence excitation and single vibronic level emission spectra of jet-cooled CDBr in the 450–750nm region. A total of 32 cold bands involving the pure bending levels 20n with n=3–10 and combination bands 20n301 (n=2–10), 20n302 (n=2–9), 10120n (n=7–10), and 10120n301 (n=6,8–9) in the ÃA″1←X̃A′1 system of this carbene were observed; most of these are reported and/or rotationally analyzed here for the first time. Rotational analysis yielded band origins and effective (B¯) rotational constants for both bromine isotopomers (CD79Br and CD81Br). The derived ÃA″1 vibrational intervals are combined with results of Yu et al. [J. Chem. Phys. 115, 5433 (2001)] to derive barriers to linearity for the 2n, 2n31, and 2n32 progressions. The ÃA″1 state C–D stretching frequency (2350cm−1) is determined for the first time, in excellent agreement with theory, as are the Br79–Br81 isotope splittings in the excited state. Our emission spectra probe the vibrational structure of the X̃A′1 and ãA″3 states up to ∼9000cm−1 above the vibrationless level of the X̃A′1 state; the total number of levels observed is around twice that previously reported. Unlike CHBr, where even the lowest bending levels are perturbed by spin-orbit interaction with the triplet origin, the term energy of every level save one below 3000cm−1 in CDBr is reproduced by a Dunham expansion to within a standard deviation of 1cm−1, and a spin-orbit coupling matrix element of ∼330cm−1 is derived from a deperturbation analysis of the triplet origin. The multireference configuration interaction (MRCI) calculations of Yu et al. [J. Chem. Phys. 115, 5433 (2001)] well reproduce triplet perturbations in the pure bending manifold, and globally, the vibrational frequencies of X̃A′1, ãA″3, and ÃA″1 are in excellent agreement with theoretical predictions.
Some Studies in Inorganic Complexes. X. Cadmium and Indium with 2-Picolylamine
Authors: Sutton GJ
Published: September 2006

Colourless or very pale yellow complexes
of the type Cdpic2X2, Cdpic3(ClO4)2,
Inpic3X3, and Inpic2X3 have been
prepared and studied, pic being the ligand 2-picolylamine and X halogen. The
cadmium complexes are stable in water, in which they may be prepared and in
which they react as bi-univalent electrolytes, whereas the iodide Cdpic2I2,
having a very low conductance in nitromethane, has a 6-coordinate octahedral
structure. The indium complexes Inpic3X3 may be prepared
in ethanol, whilst the Inpic2X3 complexes are obtained by
pyrolysis of the latter. Conductance measurements of the iodides Inpic3I3
and Inpic2I3, as well as those of ethylenediamine Inen3I3
and Inen2I3, in nitromethane show that in all cases a
6-coordinate structure is maintained. All the indium picolylamine complexes
hydrolyse in water.
Methylsteroids. VII. Factors Affecting the Hydrolysis of 7α- and 11β-Acetoxylanostanes
Authors: Barnes CS , Beilby BD
Published: September 2006

Doubly bonded methylene groups have been
introduced into 7α- and 11β-acetoxylanostanes and the rate of
hydrolysis compared with compounds having a hydroxy or carbonyl group at the
same position as the methylene group. It was found that methylene groups
facilitate hydrolysis of the hindered acetoxy groups in the same way, but not
to the same extent, as carbonyl groups. It is concluded that the facilitation
in each case results from a conformational disturbance, but that there is some
other factor involved in carbonyl facilitation. It was not possible to
demonstrate a similar effect resulting from steric crowding of substituents.
Unimolecular Films from Certain Anthracene Derivatives
Authors: Stewart FHC
Published: September 2006

Monolayers of varying stability are formed
by a series of alcohols, carboxylic acids, and other derivatives containing an
anthracene nucleus. Surface pressure-area curves have been obtained for the
more stable films. The limiting areas and other properties of the films are
discussed with reference to the molecular configurations of the compounds.
The Proton Magnetic Resonance Spectrum and Structure of Himgravine
Authors: Abraham RJ , Bernstein HJ
Published: September 2006

The high resolution proton magnetic
resonance spectra of himgravine and himbacine have been obtained in CHCl3 solution at 60 Mc/s. The spectra are
consistent with only one of the two possible structures proposed. Other
information with regard to relative orientation of groups within the molecule
has also been obtained.
The reaction of protein thiol and disulphide groups with cupric sulphite solutions
Authors: Swan JM
Published: September 2006

Thiol and disulphide groups in proteins
react with neutral and alkaline cupric sulphite solutions and are thereby
converted into thiolsulphate (-SSO3H) groups. Solutions of
cuprammonium sulphite at pH 9-10.6 can dissolve large amounts of keratins ; under
other conditions the disulphide bonds can be broken without the proteins
entering solution. The reactions are highly specific, proceed to completion,
and large excesses of reagent are not required. The " S-sulphokerateines
" so obtained constitute a new class of water-soluble protein derivative.
The thiolsulphate group can be readily labelled with radioactive sulphur and
may be converted into a thiocyanate (" S-cyano-kerateine ") by
reaction with cyanide, and into a mixed disulphide by reaction with a thiol.
S-Cyanokerateines, containing the ?CH2SCN side chain, react with
cysteine to give thiocyanate ion and a protein containing lanthionine residues,
presumably by nucleophilic displacement of SCN- from the CH2
group.
The magnetic properties of rhenium halides. II. Rhenium trichloride
Authors: Brown D , Colton R
Published: September 2006

Magnetic susceptibility measurements have
been made on anhydrous rhenium trichloride and the dihydrate, ReCl3,2H2O. Infrared spectra and
X-ray powder diffraction studies are reported for anhydrous rhenium trichloride
and the possible existence of a low temperature modification of the trichloride
is discussed.
The hyperfine E.S.R. spectrum of copper(II) N-(n-Alkyl)salicylideneimine chelate in solution
Authors: Marriage AJ
Published: September 2006

Measurements have been made of the e.s.r.
spectrum of copper(II) N-(n-alkyl)-salicylideneimine
chelate when dissolved in various solvents. The line widths of the hyperfine
spectrum have been obtained by curve fitting using an iterative procedure. The
line width broadening has been shown to depend on the product of aliphatic
chain length and solvent viscosity.
Nuclear magnetic resonance spectra and structures of some C-glycosyl flavonoids
Authors: Hillis WE , Horn DHS
Published: September 2006

From an examination of the nuclear
magnetic resonance spectra, optical rotations, and other properties of a number
of flavonoid C-glycosides, their acetates, and related model compounds, it is
concluded that vitexin, bayin, puerarin, and isohemiphloin are C-β-D-glucosides
with the sugar substituent in the 8-position of the flavonoid nucleus.
Hemiphloin and saponaretin are two of the corresponding 6-substituted
compounds. In hemiphloin and isohemiphloin the phenyl B ring has the equatorial
configuration.
Structure of α-hydroxysantonin and some aspects of the stereochemistry of related eudesmanolides and guaianolides
Authors: Pinhey JT , Sternhell S
Published: September 2006

Chemical and spectroscopic evidence shows
that the principal metabolite of a-santonin isolated from the urine of dog, α-hydroxysantonin,
has structure (Ic; R = H, R' = OH).

P.m.r. evidence shows that artemisin has
the same configuration at C6, C7, and C11 as α-santonin and that
6-epiartemisin has the same configuration at C6, C7, and C11 as 6-epi-α-santonin.
β-Santonin is the C11 epimer of a-santonin and the configuration at C6 and
C7 in 1-desmotroposantonin is analogous to that in 6-epi-a-santonin. The p.m.r.
spectra of ψ-santonin, lumisantonin, isophoto-α-santonic lactone, and
6-epi-isophoto-α-santonic lactone are discussed.
The chemical constituents of Galbulimima species. V. The isolation of further alkaloids
Authors: Binns SV , Dunstan PJ , Guise GB , Holder GM , Hollis AF , McCredie RS , Pinhey JT , Prager RH , Rasmussen M , Ritchie E , Taylor WC
Published: September 2006

The isolation and characterization of 19
new alkaloids from the bark of Galbulimima species is described. After some
corrections to previous work, the number of alkaloids from this source now
stands at 28.
Studies on Xanthorrhoea resins. III. Xanthorrhoeol
Authors: Duewell H
Published: September 2006

Xanthorrhoeol, C15H14O3,
has been isolated from Xanthorrhoea resinosa Pers., and its structure is shown
to be that of 4-acetyl-5-hydroxy-2-methyl-2H,3H- naphtho[l,8-b,c]pyran.
The effect of nitrate on the autooxidation of tin(II) in citric acid solutions
Authors: Smith TD
Published: September 2006

Autooxidation of tin(II) in
citric acid-sodium citrate solutions has been studied and the rate of oxidation
was described by a rate law first order in tin(II) concentration. The oxidation
is inhibited by relatively small concentrations of nitrate ion though nitrate
is not consumed in the reaction. It has been found that during the oxidation of
tin(II) to tin(IV) keto-acid breakdown products of citric acid are formed and
that their presence is critical in overcoming the inhibiting effect of the
nitrate ion.
Octahedral cobalt complexes in dipolar aprotic solvents. VIII. The proton magnetic resonance spectra of some octahedral cis- and trans-Bisethylenediaminecobalt(III) isomers in NN-dimethylformamide, NN-dimethyl-acetamide, and dimethyl sulphoxide
Authors: Lantzke IR , Watts DW
Published: September 2006

The proton magnetic
resonance spectra of a series of octahedral bisethylene-diaminecobalt(III)
complexes in the dipolar aprotic solvents NN-dimethylformamide,
NN-dimethylacetamide, and dimethyl sulphoxide have been examined. Resonances
due to the protons attached to the nitrogen atoms of the ethylenediamine
ligands are easily observed in these solvents, and their chemical shifts are
reported, together with some similar data determined in deuterium oxide, and
95% sulphuric acid.

The pattern of the nitrogen proton
resonances is dependent on the stereo- chemistry of the complex. Using these
differences in resonance, the cis configuration of some recently synthesized
solvent complexes has been confirmed.

The observed resonances are assigned to
the particular protons in most cases.
Multidentate chelating agents derived from Quinoline-8-aldehyde. II. Stereochemistry of complexes of a tridentate and a sexadentate ligand
Authors: Dekkers J , Goodwin HA
Published: September 2006

Complexes of the sexadentate
chelating agent, 1,8-bis(8- quinolylmethyleneimino)-3,6-diazaoctane
with iron(II), cobalt(III), and nickel(II) are described. The mode of
coordination of this base is such that its complexes must be very closely
related structurally to octahedral complexes of 1-amino-2-(8-quinolylmethyleneimino)ethane, and the similarities in the
properties of corresponding complexes of both bases reflect this relationship. The
resolution of the cobalt(III) complexes of both bases into their stable enantiomorphous forms is described.
Transition metal complexes of substituted alkynes. I. 3,3,3-Trifluoropropyne complexes of iron and cobalt
Authors: Dickson RS , Yawney DBW
Published: September 2006

Treatment of pentacarbonyliron with 3,3,3-trifluoropropyne, CF3C≡CH,
has given the stable complex tricarbonylbis(trifluoromethyl)cyclopentadi-
enoneiron. Although a disubstituted cyclopentadienone
can exist as three structural isomers, only one metal complex has been
isolated.

The interaction of octacarbonyldicobalt
and 3,3,3-trifluoropropyne has given two metal complexes, one of which is a
bridging alkyne complex of molecular stoicheiometry Co2(CO)6(CF3CCH);
the other, of formula Co2(CO)4(CF3CCH)3,
is shown to have a metal-metal bridging unit which is formed by condensation of
three alkyne groups.

Infrared, nuclear magnetic resonance, and
mass spectra of these complexes are given, and the structures of the compounds
described.
The distribution of interstitial zinc in zinc oxide
Authors: Norman VJ
Published: September 2006

A method is described which
enables the position of interstitial zinc within the crystals of zinc oxide
powders to be determined. The crystals are etched to various depths with acid,
and the excess zinc content of each fraction is estimated. It is shown that the
distribution of the interstitial zinc is dependent upon the species of
chemisorbed oxygen prevalent, and that a marked concentration of excess zinc in
the surface fraction of the crystals is apparent only in those samples of zinc
oxide on which the oxygen chemisorbed is predominantly of the reactive variety.

The method provides a convenient means of
following the diffusion of interstitial zinc on heating. The changes in the
distribution of interstitial zinc in both types of zinc oxide that occur on
heating in air are shown and discussed.
Solvent effects on the infrared spectra of anilines. IV. Secondary aromatic amines and amides with trifluoromethyl or phenyl as ortho substituents
Authors: Dyall LK
Published: September 2006

The N-H stretching
frequencies of five N-substituted anilines with trifluoro- methyl or phenyl as
ortho substituent have been measured in a variety of solvents. Elevation of
v(NH) by steric compression is observed. The frequency shifts observed for
N-methyl-2-phenylaniline fit none of the three classes of solvent shift
behaviour recognized for other ortho-substituted secondary amines. The results
confirm that solvent shifts of v(NH) cannot be used to distinguish between the
steric and hydrogen bonding properties of the ortho substituent.
The structure of the alkali fusion product derived from maesopsin. The evidence based on mass spectrometry and N.M.R. spectroscopy
Authors: Bowie JH , Morgan JWW
Published: September 2006

Maesopsin, C15H12O6,
(obtained from the heartwood of Maesopsis eminii, Rhamnaceae) on fusion
with alkali forms a yellow product, C15H10O5,
which on methylation forms two methyl ethers. Structures for these products are
suggested from a consideration of their N.M.R. and mass spectra, which afford
confirmation of the original work.
The valence isomerization of 9,10-Diphenyl-1,2,3,4-tetrahydro-2,1,4-ethanylylidenenaphthalene
Authors: Sasse WHF , Collin PJ
Published: September 2006

9,10-Diphenyl-1,2,3,4-tctrahydro-2,1,4-othanylylidenenaphthalalie
(II) isomerizes at 160-250� to give 1-(cis-1,2-diphenylethenyl)-1,2- dihydronaphthalene
(IV). The structure of (IV) is supported by its p.m.r.,
u.v., and mass spectra, as well as by its conversion into 1- (1,2-diphenylethyl)naphthalene (V) and into 1-(cis-1,2- diphenylethenyl)naphthalene
(VII) by palladium and palladium- nitrobenzene, respectively. Compounds (V) and
(VII) have been synthesized independently from 1-(1-naphthyl)-1,2-diphenylethanol
(VI).
The pyrolysis of polycarbonyl compounds. II. Synthesis of biphenylenes from phthalic anhydrides and other carbonyl compounds
Authors: Bowie RFC , Gardner DV , McOmie JFW , Solly RK
Published: September 2006

Pyrolysis of phthalic
anhydride or o-sulphobenzoic anhydride at 700- 1100� and 0.1-10 mm produces
benzyne, as shown by the formation of biphenylene and triphenylene. Biphenylene
and several polychloro and polymethyl derivatives have been conveniently synthesized
by pyrolysis of the corresponding phthalic anhydrides in yields ranging from 3
to 26%. These reactions afford further examples of the parallel between the
pyrolytic and mass spectral fragmentations of certain aromatic carbonyl
compounds. The yield of biphenylene obtained by pyrolysis of compounds
structurally related to phthalic anhydride can be correlated with the
instability of the corresponding molecular ions in the mass spectrometer.
Diterpenoids. XI. Manool trihydrochloride
Authors: Carman RM , Dennis N
Published: September 2006

The crystalline trichloro
compound obtained from sclareol (I), manool (VI), and the manoyl oxides (IX, X)
by addition of hydrogen chloride has the 8R,13,16-trichlorolabdane structure
(XII). The compound is a 1 : 1 mixture of C13 epimers which are inseparable by
normal means. However, addition of the trichloride to an equal amount of the
antipodal mixture obtained from the enantiomeric manoyl oxide [(-)X] readily
gave two separable racemates.
Metal complexes of 1,10-phenanthroline derivatives. I. Bis complexes of 2-Carboxy-1,10-phenanthroline with first row transition metal ions
Authors: Goodwin HA , Sylva RN
Published: September 2006

2-Carboxy-1,10-phenanthroline
has been prepared by brominating 2- methyl-phenanthroline and then hydrolysing
in acidic solution the resultant 2-tribromomethyl derivative. The acid acts as
a tridentate chelating agent and six-coordinate inner complexes of manganese(II),
iron(II), cobalt(II), nickel(II),
copper(II), and zinc(II) as well as a complex of iron(III) are
described. The formulation of the complexes as six-coordinate is supported by
their magnetic and spectral properties. The temperature dependence of the magnetism
of the iron(II) complex indicates that the complex is a simple paramagnetic.
Sulphur-nitrogen chelating agents. III. Metal complexes of 2-methylthiomethylpyridine
Authors: Chia PSK , Livingstone SE , Lockyer TN
Published: September 2006

Complexes of 2-methylthiomethylpyridine (mmp) have
been obtained with cobalt(II), nickel(II), copper(II), copper(I), palladium(II), platinum(II), silver(I), and mercury(II). The compounds MX2
mmp2 (M = Co, Ni; X = Cl,
Br, SCN) and NiI2 mmp2
are high-spin and their reflectance spectra indicate that the complexes are
octahedral in the solid state. The visible absorption spectrum of CoCl2 mmp2
in nitrobenzene indicates that the complex is tetrahedral in solution with the
ligand probably coordinated through the pyridine nitrogen only. The
tris-chelated complexes [M mmp3](ClO4)2 were also characterized. Spectral
data indicate that the complexes CuX2 mmp (X = Cl, Br) possess a
tetragonal polymeric structure in the solid state. Conductimetric titration of
the perchlorate [Cu mmp2](ClO4)2 with chloride ion in
nitromethane demonstrated the formation of [CuCl mmp2]+ in solution. This was confirmed
by the isolation of [CuCl mmp2]ClO4 and [CuBr mmp2]ClO4.
The bis-chelated complex CuCl2 mmp2 gives a solution in nitrobenzene which is
virtually non-conducting.

The complexes PdX2
mmp (X = Cl, Br, I, SCN),
Pt(SCN)2 mmp, [M mmp2]-
(ClO4)2 (M = Pd, Pt, Hg), [Pt mmp2][PtCl4],
and [Cu mmp2]ClO4
were also isolated. The silver(I) complex Ag mmp ClO4 probably contains the dimeric cation [Ag2 mmp2]2+.
Conformations, configurations, and proton reactions of colbalt(III) complexes
Authors: Buckingham DA , Durham L , Sargeson AM
Published: September 2006

Proton magnetic resonance
spectroscopy allows the cis and trans isomers of [CoX2
en2] complexes to be distinguished. Some
information has been obtained concerning the rate of chelate conformational
interchange for cobalt-ethylenediamine, propylenediamine,
N-methylethylenediamine, and malonate rings. For
[Co(amino acid)en2]2+ complexes
the diastereoisomeric pairs can be differentiated and the relative rates of CH
and NH proton exchange have been observed for a variety of chelate rings
including cobalt-amino acid, acetylacetonato, ethylenediamine, and malonato.
Nickel-catalysed hydrogen exchange of aniline, phenol, and their alkylated derivatives with deuterium oxide
Authors: Macdonald CG , Shannon JS
Published: September 2006

Selective exchange of
hydrogen atoms ortho to amino or hydroxyl groups, together with benzylic
hydrogen atoms in aniline, phenol, and their C- alkylated derivatives, was
achieved by allowing these compounds to react with deuterium oxide over nickel
on kieselguhr at 99�. In addition to the benzylic hydrogen atoms, alkyl
hydrogen atoms farther from the aromatic ring underwent slower exchange.
Hydrogen atoms ortho to methoxyl did not exchange. Mechanisms of the catalytic
exchange reactions are discussed in the light of the results of deuterium
distribution measurements and poisoning experiments with electron donors.
The base-catalysed skeletal rearrangement of a thianaphthofluorene derivative
Authors: Cherry WH , Davies W , Ennis BC , Porter QN
Published: September 2006

The Diels-Alder adduct of
3-vinylbenzo[b]thiophen and 1,4- naphthaquinone has been shown to undergo a
novel base-catalysed rearrangement, in which its partly hydrogenated
12-thianaphtho[2,3- a]fluorene structure is replaced by a 5-thianaphtho[2,3-b]fluorene
structure.
Cyclic nitrones. I. Reactions of α-keto nitrones at nitrone carbon
Authors: Brown RFC , Subrahmanyan L , Whittle CP
Published: September 2006

The chemistry of
3,4,5,6-tetrahydro-3-oxopyridine 1-oxides has been studied with respect to:

reaction with
hydrazine-the 6,6-dimethyl compound (IV) gave a hydrazone (VII) by ring
contraction following initial attack at C 2;

(ii)(ii) 2-arylation with diazonium salts, e.g.
conversion of (III) into (XIII);

(iii) acid- and base-catalysed
deuterium exchange at C 2, C 4, and C 6;

(iv)(iv) oxidation of the
5,5-dimethyl compound (III) by chromate ion to a 2,2?-linked dimer (XV).
The adsorption of ethylene on silver(I) oxide. I. Rates of adsorption
Authors: Allen JA , Scaife PH
Published: September 2006

The rates of adsorption of
ethylene on silver(I) oxide, Ag2O, have
been measured in the temperature range 273-313�K. The kinetic data are analysed
in terms of the generalized Elovich equation by
methods developed and described in a previous paper.1
The activation energy derived from the rates at zero coverage is 15.6 kcal mole-1.
The presence of isothermal anomalies is noted and the extent of each kinetic
stage defined. A qualitative explanation of the existence of these stages is
suggested.
Anomalous magnetic properties in the solid state of salts of the Bis[2-(2-pyridylamino)-4-(2-pyridyl)thiazole]iron(II) ion
Authors: Sylva RN , Goodwin HA
Published: September 2006

The magnetism of nine salts
containing the bis[2-(2-pyridylamino)-4-(2-
pyridyl)thiazole]iron(II) ion has been investigated over the temperature range
c. 100-350�K. All salts were obtained hydrated and in some instances the
magnetism of the anhydrous salts was also investigated. The magnetism was found
to be markedly dependent on the anion of the salt. Two distinct classes of
compounds were recognized- those obeying a simple Curie-Weiss law and having
magnetic moments corresponding to the expected value for spin-free iron(II);
and those whose temperature dependence of magnetism was found to be anomalous.
For these compounds the magnetic moments varied from almost spin-paired to
almost spin-free values. The anomalous behaviour has been qualitatively
interpreted in terms of a thermal equilibrium between the nearly equi-energetic
spin-paired and spin-free states of the iron atom. The differences in the
behaviour of different salts have been ascribed to differences in crystal
lattice forces. The presence of hydrate water in the crystal lattice has been
shown in some instances to have a marked influence on the magnetism.

Two magnetically isomeric forms of the
anhydrous chloride salt have been obtained.

It has been shown that there is an
association between the magnetism and colour of the compounds.
The reaction of pyridine with iron(II) acetylacetonate in benzene solutions
Authors: Buckingham DA , Gorges RC , Henry JT
Published: September 2006

The titration of monomeric
Fe acac2 in dilute benzene solutions has
been shown to result in the formation of [Fe acac2]2py, [Fe acac2
py]2, and Fe acac2
py2 species with stability constants of
> 104, 1.8 � 1 x 102, and 25 � 10 respectively. Only
Fe acac2 py2
was isolated in the solid state. These species are compared to the similar CoII and KiII
systems and structural possibilities are discussed.
Pigments of marine animals. IV. The anthraquinoid pigments of the crinoids, Comatula pectinata L. and C. cratera A. H. Clark
Authors: Sutherland MD , Wells JW
Published: September 2006

A review of the literature
describing the pigments of the crinoids (phylum Echinodermata)
reveals a prevalence of indicator-type pigments which are of unknown nature,
except for certain polyhydroxy-meso- naphthodianthrones isolated from a fossilized Jurassic
stalked crinoid. The
highly coloured free-swimming crinoids, Comatula
pectinata L. and C. cratera A. H. Clark, contain
mixtures of indicator-type pigments which have been separated by adsorption
chromatography on magnesium carbonate to yield three principal constituents,
the 6-methyl and the 6,8-dimethyl ethers of rhodocomatulin, and a monomethyl
ether of rubrocomatulin. The structure of the rhodocomatulin skeleton is shown
to be 4-butyryl-1,3,6,8-tetrahydroxyanthraquinone
rather than 2- butyryl-1,3,6,8-tetrahydroxyanthraquinone
as previously suggested.1
Pigments of marine animals. V. Rubrocomatulin monomethyl ether, an anthraquinoid pigment of the Comatula genus of crinoids
Authors: Powell VH , Sutherland MD , Wells JW
Published: September 2006

The chemistry of
rubrocomatulin monomethyl ether, the third major quinone pigment of the
crinoids Comatula pectinata Linnaeus and C. cratera A. H. Clark, and supporting spectral data determine
the structure as 8-butyryl-1,4,5,7-tetra-hydroxy-2-methoxyanthraquinone. The
paper chromatography of hydroxyanthraquinones and the utility of various
adsorbents in their column chromatography are discussed.
Pigments of marine animals. VI. Anthraquinoid pigments of the crinoids Ptilometra australis Wilton and Tropiometra afra Hartlaub
Authors: Powell VH , Sutherland MD
Published: September 2006

The crinoid Ptilometra australis Wilton
yields to organic solvents a complex mixture of pigments from which the three
principal components have been separated by chromatography on magnesium
carbonate. These substances have been shown by spectral and chemical
examination to be 1,6,8-trihydroxy-3-(1-hydroxypropyl). anthraquinone,
1,6,8-trihydroxy- 3-(2-hydroxypropyl)anthraquinone, and 1,6,8-trihydroxy-3- propylanthraquinone-2-carboxylic acid. The distinct types
of crinoidal pigments isolated from Comatula species1 and from Ptilometra
australis both conform to the acetate rule and are
probably endogenous in origin. Both
yellow and black specimens of the crinoid Tropiometra
afra Hartlaub also contain the anthraquinonecarboxylic
acid isolated from P. australis.
(+)-9-Aza-1-methylbicyclo[3,3 ,1]nonan-3-one, a new alkaloid from Euphorbia atoto Forst
Authors: Hart NK , Johns SR , Lamberton JA
Published: September 2006

A new alkaloid isolated
from Euphorbia atoto Forst. has been shown to be
(+)-9-aza-1-methylbicyclo[3,3,1]nonan-3-one.
The magnetic properties of some complexes of higher-valent manganese
Authors: Goodwin HA , Sylva RN
Published: September 2006

The magnetic
susceptibilities of the compounds [bipy-H2][MnCl5],
[phen- H2]-[MnCl5],
[MnCl3(H2O)bipy], [MnCl3(H2O)phen],
[MnF3(H2O)phen],
[MnCl3 trpy], [MnCl4 bipy], [MnCl3
bipy], [MnCl3 phen],
and [MnO phen2](ClO4)2,0.5H2O have been
determined over the temperature range c. 100-300�K. All compounds appeared to
follow a Curie-Weiss law. The Curie-Weiss θ values indicate that the first
seven compounds are simple paramagnetics, while the last three are
antiferromagnetics. The antiferromagnetic behaviour of these compounds
indicates that they have bridged structures.
The mass spectra of phenyl methyl ethers. II. Polycyclic compounds
Authors: Barnes CS , Collins DJ , Hobbs JJ , Mortimer PI , Sasse WHF
Published: September 2006

The fragmentation of the
aryl methyl ether grouping on electron impact has been studied in a number of
naphthalene, phenanthrene, stilbene, and tolane derivatives. In addition to the
known aryl-oxygen fission with migration of one hydrogen atom (loss of formaldehyde),
and alkyl- oxygen fission (loss of a methyl radical), an examination of
metastable ions has indicated two new pathways which may occur in special
circumstances. The first was found unequivocally only in the single example of
9-methoxyphenanthrene and may be related to the stability of the resultant fluorenyl
ion. The second was simple aryl-oxygen fission without rearrangement and
occurred in those cases where the corresponding hydrocarbon showed a strong P -
1 ion on electron impact. However, this feature in the hydrocarbon does not
always ensure loss of a methoxy radical from the methoxy derivative, because
the possibility of forming a stable quinonoid ion may make loss of a methyl
radical the preferred course.
Azepinones. II. Syntheses of substituted pyridazines
Authors: Evans NA , Johns RB , Markham KR
Published: September 2006

Two attempted synthetic
routes to diphenyldiazatropones are described. Cyclization with hydrazine of 2-oximino-1,5-diphenylpentane-1,5-dione (IV) yielded
substituted pyridazines rather than perhydrodiazepines. Oximination of the
diphenyldihydrodiazepine (II) was successful, but attempts to dehydrogenate the
ring proved only promising. A new and fully conjugated 10 π-electron
system, the pyridazotriazole (VII), is described, as well as some unexpected
rearrangements of the oxime (V).
Azepinones. III. N-Oxidation and subsequent nitration of dibenzodiazepinone
Authors: Amiet RG , Johns RB
Published: September 2006

Dibenzo[c,f]-[1,2]-diazepin-11-one
(I) is converted under conditions favour- able for nitration into the N-oxide
(IV), and this in turn nitrates readily to form 2-nitro- and 2,4-dinitrodibenzo[c,f]-[1,2]-
diazepin-11-one-6-oxide the structures of which are proposed largely on
spectroscopic evidence. The experimental results suggest that the heterocyclic
ring in compound (I) has little tropone-like character.