bluuebunny/crossref_metadata_2025 huggingface dataset:
Theory of Polymer-Chain Folding
Authors: Lindenmeyer P. H.
Published: January 2005

A molecular theory is proposed to account for the regular folding of polymer chains during crystallization. It predicts that an isolated polymer chain greater than some critical length can lower its energy by crystallizing into a regular folded-chain conformation. Similarly, a single molecular chain crystallizing upon an infinitely large substrate will also lower its free energy by regular folding. In a crystal composed of polymer molecules all having the same length the lowest free energy occurs when all chains are completely extended, however, there also exists a whole series of metastable states corresponding to one, two, three, etc., folds per molecule. When the crystal is composed of a distribution of molecular lengths, the lowest free energy corresponds to a folded-chain crystal whose thickness is a sensitive function of the distribution. If the low end of the molecular-length distribution is assumed to be truncated at the observed length of extended-chain crystals, the theory satisfactorily predicts the observed thicknesses of folded-chain crystals obtained by melt crystallization of both fractions and whole polymer.
Crystal Structure of the Transition-Metal Molybdates and Tungstates. III. Diamagnetic α-ZnMoO4
Authors: Abrahams S. C.
Published: January 2005

Diamagnetic α-ZnMoO4, the stable phase at STP, is triclinic with lattice constants a=9.625±0.015 Å, b=6.965±0.010 Å, c=8.373±0.015 Å, α=103.28°±0.15°, β=96.30°±0.15°, and γ=106.72±0.15° at 298°K, with six formula weights in the unit cell. The integrated intensities of 6489 reflections in a reciprocal hemisphere with (sinθ)/λ≤1.02 Å−1 were measured with PEXRAD; 3269 independent Fmeas were significantly above background. The structure was solved in Space Group P1; the subsequent atomic arrangement, obtained using a minimum interatomic contact requirement together with three-dimensional Fourier series and least-squares model fitting, closely approximated a centrosymmetric distribution. Refinement by the method of least squares in Space Group P1̄ gave a final agreement factor between measured and calculated structure factors of 0.0726. Each of the three crystallographically independent Mo atoms is surrounded by distorted tetrahedra of oxygen atoms; the Mo–O distances vary between 1.707±0.009 and 1.842±0.009 Å, the average being 1.764 Å. Two of the independent zinc atoms occupy distorted octahedra of oxygen atoms; the octahedral Zn–O distances range from 1.977±0.011 to 2.243±0.010 Å, with an average of 2.078 Å. The remaining zinc atom is in a distorted ``square'' pyramidal arrangement of oxygen atoms with Zn–O distances that vary from 1.954±0.012 to 2.106±0.007 Å, the average being 2.025 Å. The thermal vibration of the metal atoms is significantly anisotropic.
ESR Spectra of the Anion Radicals of 2,5-Dimethyl−2,4-hexadiene and Glyoxal
Authors: Tolles W. M. , Moore D. W.
Published: January 2005

Electrolysis of tetrahydrofuran solutions at low temperatures yields a short-lived paramagnetic species at the cathode which has a single ESR absorption line. Electrolysis in tetrahydrofuran reduces 2,5-dimethyl−2,4-hexadiene, whereas this is not observed under similar conditions in liquid ammonia. The radical anion of this molecule in tetrahydrofuran has the following coupling constants (in gauss): aH(6 protons)=9.91±0.05, aH(6 protons)=8.75±0.05, and aH(2 protons)=1.16±0.21. The glyoxal anion shows an intense 1:2:1 triplet with a splitting constant of 7.63±0.01 G in tetrahydrofuran. Effects of substitution and solvation on spectra of radicals with this isoelectronic pi-orbital structure are discussed.
Proton Spin Relaxation and the Acid Dissociation of the Cr(H2O)63+ Complex Ion
Authors: Manley C. E. , Pollak V. L.
Published: January 2005

Experimental data are presented on proton spin relaxation in aqueous Cr(III) solutions of varying acidity, at 0°C. A theoretical analysis is given on the assumption that the dominant proton-exchange mechanism for the hexaquo complex is the reaction Cr(H2O)63++H2O⇌Cr(H2O)5OH2++H3O+.
Paramagnetic Resonance of Mn2+ in Single Crystals of CuCl
Authors: Powell Harry D. , Reed C. A.
Published: January 2005

Paramagnetic resonance absorption by Mn2+ ion in single crystals of CuCl has been investigated at room temperature. High-purity CuCl was obtained by distillation of reagent-grade powder in vacuum. Crystals were grown from the vapor. The Mn2+ impurity ion was introduced by diffusion of MnCl2 into the CuCl crystals. The resonance spectra consisted of the six hyperfine lines which result from the interaction of the 3d5 electrons with the Mn nucleus. The linewidths were 15, 12, and 10 G (±0.3 G) between the first-derivative extrema for the transitions corresponding to m=±52,32,12, respectively. No fine structure was observed. These results are described by the spin Hamiltonian H=gβH·S+AI·S in which S=52, I=52, and g and A are both isotropic with g=2.0015±0.0010, | A |=(73.3±0.3)×10−4 cm−1. A comparison of this value of | A | with values of | A | for Mn2+ impurity in a representative series of crystals with diamond and zincblende structures and with some crystals which have nearly ideal ionic bonds indicates a degree of covalency which could account for the tetrahedral coordination of the CuCl bond.
One-Center Study of the Rare-Gas Hydride Ions NeH+ and ArH+
Authors: Banyard K. E. , Sutton A.
Published: January 2005

The ground states of the rare-gas hydride ions NeH+ and ArH+ have been studied by means of the united-atom (UA) treatment. Values are reported for the energy, theoretical bond length, force constant, and the diamagnetic part of the molar magnetic susceptibility. However, the present work is primarily intended as a test of the UA approach and, as such, it was useful to compare the results with those obtained by the same treatment for HF and HCl. Also, it proved to be most instructive to analyze the forces which act on the protons within each molecular ion.

As anticipated, the UA treatment of NeH+ and ArH+ met with meager success. Nevertheless, the analysis provided considerable understanding as to why a similar study, applied to neon- and argonlike molecules, yields fairly reasonable values for the above molecular properties when compared with experiment.
Phase Diagrams of Silver Sulfate, Silver Selenate, and Silver Chromate to 40 kbar
Authors: Pistorius Carl W. F. T.
Published: January 2005

The Ag2SO4 I/II transition line initially rises with pressure, but has a broad maximum at ∼16.2 kbar, after which it falls with pressure. The melting curve of Ag2SO4 I was followed to 20 kbar. The phase diagram of Ag2SeO4 was studied to 40 kbar. At atmospheric pressure transitions occur at 425° and ∼537°C (by extrapolation). These two transition lines meet at a triple point at 8 kbar, 478°C. The Ag2SeO4 I/III transition line then rises gently with increasing pressure. Ag2CrO4 has a transition at 479°C, 1 bar. The transition line is very similar to the Ag2SeO4 I/III transition line. The melting curve of Ag2CrO4 I was followed to 40 kbar. The possible polymorphic behavior of these three substances at higher pressures is discussed and some similarities between the present phase diagrams and those of Na2SO4, Na2SeO4, and Na2CrO4 are pointed out.
Approximation Method for Equilibrium Distributions in Second-Order Chemical Reaction Kinetics
Authors: Staff P. J.
Published: January 2005

The method introduced allows the classical deterministic value to be used to produce approximations to a high order of accuracy for the mean and the fluctuations in reversible second-order chemical reactions. The reaction A+B⇄C+D is examined and the results are encouraging for the use of this approach in other problems of a similar nature.
Cold-Neutron Study of Hindered Rotations in Solid and Liquid Methylchloroform, Neopentane, and Ethane
Authors: Rush J. J.
Published: January 2005

The low-frequency modes of methylchloroform (1,1,1-trichloroethane), neopentane, and ethane in their solid and liquid phases have been investigated by the scattering of cold neutrons. The energy-gain spectra for these compounds in their low-temperature solid phases exhibit broad bands peaked at about 52, 50, and 82 cm−1 for CH3CCl3, C(CH3)4, and C2H6, respectively, which are attributed to whole-molecule librations and translations in the lattice. In the high-temperature phases of the ``globular'' compounds CH3CCl3 and C(CH3)4, these spectral bands are no longer peaked, but are quite diffuse and blend into a considerably broadened elastic peak. These results show that the phase transitions below the melting points are associated with a change from strongly hindered to quasifree rotation, in agreement with the results of previous experiments. The barrier to molecular reorientation is estimated to be ≲1 kcal/mole in the high-temperature phase of each compound.

Bands are also observed in the CH3CCl3 and C(CH3)4 spectra peaked at about 300 and 286 cm−1, respectively, which are assigned primarily to the torsional oscillations of the methyl groups. These peak positions show no significant change in proceeding from the liquid to the solid phases, indicating little intermolecular contribution to the forces hindering methyl-group reorientation. One of the liquid-ethane spectra exhibits a shoulder around 260 cm−1, which is possibly due to torsional vibrations. Assuming threefold cosine potentials with no interaction between methyl groups, ``average'' barriers to rotation of 5.8 and 5.2 kcal/mole are calculated from the torsional peaks for CH3CCl3 and C(CH3)4. The CH3CCl3 barrier is considerably higher than the value derived from thermodynamic results for CH3CCl3 (and ethane) gas.
Forbidden Transitions in Molecular Crystals: The Cameron System of Solid α-CO
Authors: Hexter R. M.
Published: January 2005

A crystal splitting has been observed in the (0, 0) band of the Cameron system (a 3Π←X 1Σ+) of solid α-CO at 20°K, using a well-annealed sample. We believe that this is the first reported example of a triplet exciton splitting in a nonaromatic, the only previously reported examples having been in naphthalene and p-di-iodobenzene. A spin—orbit calculation has been carried out which demonstrates that the spectroscopic activity of this transition is primarily due to spin—orbit mixing of the 3Π1 and 1Π1 levels of the a 3Π and A 1Π states, respectively. The same calculation shows that the mixing of the ground and first triplet states can give intensity to this transition, but such intensity will be many times less than that induced via the first mechanism.

The electric-dipole character gained by the transition is insufficient to account for the observed splitting, i.e., as a Davydov splitting. Instead, it is concluded that molecules undergoing this transition are coupled via an intermolecular-exchange interaction. An estimate of the magnitudes of the exchange integrals in solid CO, relative to those in aromatic crystals, results in a prediction of a triplet exciton splitting for CO which is of the order of magnitude of the observed splitting. A vibronic interaction mechanism within the CO crystal may also account for the splitting. Experiments are discussed which can distinguish between the two coupling mechanisms and which can confirm one or the other as that responsible for the observed splitting.
ESR Studies of Electron Transfer: trans-Stilbene—Stilbene− System
Authors: Chang Raymond , Johnson Charles S.
Published: January 2005

The rate of electron transfer between the stilbene anion radical and trans-stilbene has been measured in dimethoxyethane and tetrahydrofuran. The second-order rate constants are approximately 109 liters mole−1·sec−1, and the activation energies fall between 2 and 3 kcal mole−1. In all cases the rates were measured from the ESR linewidths at the fast-exchange limit. Also, it is shown that the required second moment of the unbroadened spectrum can be determined with sufficient accuracy directly from the unresolved experimental spectra.
Nonconvective Ionic Flow in Fixed-Charge Systems
Authors: Manning Gerald S.
Published: January 2005

We have considered the movement of an ion under the influence of Brownian motion, an externally applied constant electric field, and the spatially inhomogeneous potential set up by an assemblage of fixed charges. The resulting equation of motion is solved when the lattice of fixed charges is periodic, and when the fixed-charge potential is small. Expressions are obtained for the macroscopic friction constant of the mobile ions as a function of the fixed-charge potential, and, equivalently, for the relaxation field exerted by the fixed charges. The Einstein relation is used to obtain the macroscopic diffusion constant. The fixed-charge potential is approximated by a periodic solution of the Poisson—Boltzmann equation in linearized form. The results are markedly dependent on the geometry of the fixed-charge lattice. By varying the lattice parameters we present models for both polyelectrolyte solutions and simple ion-exchange membranes, which give, in spite of the approximation of small fixed-charge potential, semiquantitative agreement with data from self-diffusion experiments on these systems.
Overlapping Dielectric Dispersions in Toluene
Authors: Santarelli Vincent A. , MacDonald John A. , Pine Charles
Published: January 2005

Evidence is presented for the existence of two overlapping dispersions at 20°C in toluene. Resolution of the two dispersions was in terms of separate Debye relaxation processes, with dispersion parameters ε01=2.384, ε∞1=2.269, and τ1=5.80×10−12 sec for the low-frequency process and ε02=2.269, ε∞2=2.222, and τ2=2.0×10−13 sec for the high-frequency process. It is pointed out that it is not precluded that the high-frequency process may in actuality be a resonance absorption. The dielectric constant and loss values were obtained by a free-space method and the results for toluene at 20°C are given for a wavelength range between 9.2 and 2.5 mm. In addition, dielectric constant and loss values for toluene at temperatures of 30°, 40°, and 50°C are reported for wavelengths between 9.2 and 4.0 mm.
Heat Capacity, Entropy, and Magnetic Moment of Single-Crystal CuSO4·5 H2O with Fields to 90 kG ‖ to the α Magnetic Axis
Authors: Anderson R. J. , Giauque W. F.
Published: January 2005

The heat capacity and magnetic moment of CuSO4·5 H2O have been measured over the range 0.4°—4 2°K in stabilized magnetic fields of 0, 5, 10, 20, 30, 50, 70, and 90 kG. The field was directed along the α magnetic axis of the 3.70-cm-diam, spherical, single crystal. A sensitive carbon thermometer was used to measure the variation of temperature with magnetic field in a calorimetric apparatus at nearly constant entropy. Very small corrections for the entropy change of the empty calorimeter and for entropy leakage enabled accurate tabulation of entropy changes in CuSO4·5 H2O ove the experimental range. Magnetic saturation was used as a zero reference for the electronic entropy and the total electronic entropy above zero was found to be R ln2 when the ``tail'' above 4°K was considered. The data add further support to the suggestion of Geballe and Giauque that the two types of Cu++ per unit cell act as essentially independent magnetic systems. Magnetic-moment values during representative adiabatic demagnetizations to zero field are given. Values for several low-entropy adiabatics fall on a straight line between 4 and 13 kG. An extrapolation of this line intersects the M axis at a point appreciably above one-half the total saturation value. This fact can be explained if the g value of the ferromagnetic system is 2.101 and that of the antiferromagnetic system is 2.051 at low temperatures. In any case, the over-all g value is 2.076. At the higher fields and lower temperatures it was necessary to consider a small amount of entropy removed by nuclear polarization. All of the observations apply to the spherical sample uncorrected for the demagnetizing effect.
Measurement of the Glass-Transition Temperature of Simple Liquids
Authors: Carpenter M. R. , Davies D. B. , Matheson A. J.
Published: January 2005

The glass-transition temperatures of 34 liquids have been measured by differential thermal analysis, and the results compared with the values predicted from viscosity measurements by the equation lnη = A″+B″/(T—T0). In those liquids which have two non-Arrhenius viscosity regions, there is good agreement between observed Tg values and those predicted from the lower-temperature form of this equation. In those liquids which have only one observable non-Arrhenius region, measured Tg values are usually lower than those predicted from viscosity measurements. It is suggested that this is caused by a change in non-Arrhenius viscosity behavior at higher viscosities which are unattainable experimentally.
Microwave Linewidths of Symmetric-Top Molecules
Authors: Birnbaum George
Published: January 2005

The Anderson—Tsao and Curnutte impact theory of pressure broadening is applied to microwave rotational lines of symmetric-top molecules. The effect of elastic and inelastic collisions on the optical cross section is examined. Simple but accurate expressions are obtained for microwave linewidths due to a variety of intermolecular interactions. The theory is applied to existing microwave linewidths, which happen to involve interactions between polar molecules. The theoretical width of the J = 1→2 line of PF3 is in good agreement with experiment, although the agreement is less satisfactory for the J = 0→1 line of CH3F and CHF3, and poor for the J = 1→2 line of CHF3. However, the theory satisfactorily accounts for widths of the NH3 3–3 inversion line broadened by CHF3 as well as other symmetric-top molecules.
Pulse Radiolysis Studies. X. Electron Transfer Reactions of Aromatic Molecules in Solution
Authors: Arai Shigeyoshi , Grev D. A. , Dorfman Leon M.
Published: January 2005

Absolute rate constants have been determined by the pulse radiolysis method for the electron transfer reaction from a series of aromatic anion radicals in isopropanol solution to a variety of different aromatic molecules: arenea−+areneb=arenea+areneb−.Nine donor—acceptor pairs were investigated in which the donor anion was diphenylide, p-terphenylide, m-terphenylide, and o-terphenylide, and the acceptor molecule was naphthalene, phenanthrene, p-terphenyl, pyrene, and anthracene. Several, but not all, of the reactions appear to be diffusion controlled with electron transfer rate constants ranging from 2.6×108 to 6.4×109 M−1·sec−1 at 25°C.
Zeros of the Grand Partition Function of a Hard-Core Lattice Gas
Authors: Nilsen T. S. , Hemmer P. C.
Published: January 2005

A lattice gas on an M×∞ square lattice with nearest-neighbor exclusion is studied in a ``grand pressure ensemble.'' It is shown how to calculate the distribution of the zeros of the grand partition function. Explicit results for M<5 are given. The nearest singularity to the origin in the complex fugacity plane is on the negative real axis, and extrapolation of its position to an ∞×∞ lattice yields the estimate R≃0.1190 for the radius of convergence of the fugacity series. This value agrees well with Gaunt and Fisher's estimate which they obtained by analyzing the first 13 terms of the fugacity series.
Compression of Mercury at High Pressure
Authors: Davis Lance A. , Gordon Robert B.
Published: January 2005

An exact method of computing volume changes under high pressure from acoustic-wave-velocity measurements is developed. It is applicable to large as well as small compressions. To illustrate the application of the method, precision ultrasonic-velocity measurements made in mercury at pressures up to 13 kbar for three temperatures have been used to compute V as a function of T and P. The volume is determined to an accuracy of better than 0.01% at each pressure and temperature. An analytical expression for the pressure dependence of the volume in which all coefficients are expressed in terms of the bulk modulus and its derivatives is developed and shown to give a better representation of the P—V data than many of the equations now in use.
Far-Infrared Spectra of Crystalline Benzene at 138°K and Intermolecular Forces
Authors: Harada Issei , Shimanouchi Takehiko
Published: January 2005

Far-infrared spectra of crystalline benzene have been measured at low temperatures. The three bands assigned to the translational lattice vibrations have been found. The frequencies of these lattice vibrations, those of the Raman-active lattice vibrations and the frequency splittings of the infrared bands at 138°K have been consistently explained from the hydrogen—hydrogen and hydrogen—carbon interactions.

The values obtained for these atom—atom interactions are correlated with the values of other intramolecular and intermolecular force constants and with the energy of internal rotation for n-butane.
Ethylene Molecule in a Gaussian Basis. II. Contracted Bases
Authors: Schulman J. M. , Moskowitz J. W. , Hollister C.
Published: January 2005

A self-consistent-field calculation on ground-state ethylene was performed using a large (sp) Gaussian basis. An upper bound to the Hartree—Fock energy and a lower bound to the correlation energy were obtained.

A SCF study was made using sets of ``contracted functions''—functions defined as linear combinations of Gaussians. It was found that orbital and total energies quite close to those of the large, straight Gaussian calculation can be obtained with contracted sets at a saving of computation time. These studies also furnished information about atomic-orbital input to be used in a LCAO orbital calculation.
Limitations of the Thermal-Wave Technique for Determining Molecular-Attachment Kinetics
Authors: O'Hara S. , Tarshis L. A. , Tiller W. A.
Published: January 2005

Consideration of the particular mechanisms of molecular attachment is shown to impose serious limitations on the thermal-wave technique for quantitatively determining molecular-attachment kinetics at least as presently applied. For a layer-edge-attachment mechanism, the variation of layer-edge density as a function of position relative to layer sources on the surface leads to a nonuniform departure from equilibrium over the surface and possibly to capillarity effects. Thus, the plane-wave analysis of Sekerka and Tiller cannot be considered to be exact. The technique is further shown to be incapable of distinguishing between layer-edge motion and uniform interface advance. The discrepancies between available experimental results and theory are considered.
Thermal Decomposition of 4,4-Dimethylpentene−1 in a Single-Pulse Shock Tube
Authors: Tsang Wing
Published: January 2005

4,4-Dimethylpentene−1 has been pyrolyzed in a single-pulse shock tube. The initial process is apparently the breaking of the allylic carbon—carbon bond. The rate expressions for the reaction C4H9−C3H5→ lim kt−C4H9·+C3H5·has been found to be k=1015.8 exp(−65 500/RT) sec−1.Assuming no activation energy for the recombination process this leads to a value of 12 kcal for the allylic resonance energy.
Nitrogen-Isotope Effects in the Reduction of Nitrate, Nitrite, and Hydroxylamine to Ammonia. I. In Sodium Hydroxide Solution with Fe (II)
Authors: Brown L. L. , Drury J. S.
Published: January 2005

Studies were made of the nitrogen-isotope effects occurring during the alkaline reduction of NO3−, NO2−, and NH2OH with Fe(II). The pertinent reduction reactions were shown to be irreversible and the yields of NH3 quantitative. The reduction of NO3− to NH3 produced a k14/k15 value of 1.075±0.004 at 25°C. A k14/k15 ratio of 1.034±0.002 at 25°C was obtained for the reduction of NO2−, or NH2OH to NH3. The rate constant, kNO3−, was shown to be slow compared to kNO2− and kNH2OH which had values of 4.09×10−2 and 9.53×10−3 sec−1, respectively.

The experimental data agreed well with results computed for a two-atom model in which the significant step in the reduction of each species was the breaking of an N–O bond. Reactions consistent with the experimental data were proposed to account for the reduction mechanism.
Intrinsic Photoconduction in Anthracene
Authors: Sharma Ramesh D.
Published: January 2005

The cross section for the photoionization of the anthracene molecule has been calculated. It is shown that the main contribution to the cross section at the threshold arises from the orthogonalized part of the orthogonal plane wave used as a wavefunction for the free electrons. The emission of electrons is shown to be highly anisotropic. Combined with further experimental work on intrinsic photoconduction, the calculations have the potential of determining the conduction band edge.
NMR Relaxation in Adsorbed Molecules. V. SF6 on Faujasite: Dipolar Coupling of Fluorine Nuclei to Ferric-Ion Impurities
Authors: Resing H. A. , Thompson J. K.
Published: January 2005

The spin—lattice and spin—spin relaxation times for fluorine nuclei of SF6 adsorbed to maximum capacity on dehydrated synthetic faujasite have been measured as functions of temperature from 77° to 300°K. These have been interpreted according to the theory of Torrey as arising from diffusion of SF6 molecules in the magnetic field of paramagnetic iron impurities in the faujasite. The mean time between diffusional jumps is well represented as τ=1.14×10−12 exp(4000/RT) sec.
EPR Spectra of Gd3+-Doped NdCl3·6H2O and PrCl3·7H2O
Authors: Singh G. B. , Upreti G. C. , Venkateswarlu Putcha
Published: January 2005

The paramagnetic resonance spectra of Gd3+-doped NdCl3·6 H2O and PrCl3·7 H2O single crystals are studied at room temperature. A six-line spectrum for H ‖ Z and a seven-line spectrum for H ‖ X corresponding to ΔM=±1 transitions, are observed in the case of Gd3+-doped NdCl3·6 H2O, whereas Gd3+-doped PrCl3·7 H2O shows a seven-line spectrum for H ‖ Z as well as for H ‖ X. The absence of the seventh line in the case of Gd3+-doped NdCl3·6 H2O for H ‖ Z spectrum is explained as due to large zero-field splitting between ±52 and ±72 levels. The angular variation of the observed spectra in ZX plane from θ=0° to θ=90° is studied and the spin-Hamiltonian analysis is presented. A number of lines have been observed in the low-field region in the case of Gd3+-doped PrCl3·7 H2O and they have been analyzed as due to transitions with ΔM>1.
Infrared Spectrum, Structure, and Thermodynamic Properties of Trifluoramine Oxide, NF3O
Authors: Curtis E. C. , Pilipovich D. , Moberly W. H.
Published: January 2005

The infrared spectrum of NF3O is reported. The general appearance of the spectrum establishes that the molecules has C3v symmetry. The bands at 1691, 743, 528, 883, 558, and 400 cm−1 are assigned as the fundamental frequencies. The rotational spacing of ν2 was used to determine the rotational constant, B=0.19 cm−1. Assuming tetrahedral angles and r(NO) = 1.15 Å with this rotational constant gives an estimate of r(NF) = 1.48 Å.
Generalized Oscillator Strengths and Absolute-Zero-Angle Cross Sections for Inelastic Electron—Helium Collisions
Authors: Heideman H. G. M. , Vriens L.
Published: January 2005

Absolute-zero-angle cross sections for excitation of helium to the 21P level have been calculated with the Bethe theory, using Lassettre's generalized oscillator strengths (for 11S→21P) normalized to the optical oscillator strength of Schiff and Pekeris. Absolute-zero-angle cross sections (in the 25–1000 eV energy region) for transitions to several other helium states were obtained, using (a) the calculated cross section for excitation to the 21P level and (b) already measured cross-section ratios (obtained from energy-loss spectra) or known optical oscillator strengths. These cross sections, which are not very accurate for small incident electron energies due to application of the Bethe theory, have been used to determine generalized oscillator strengths for the transitions 11S→31P, 41P, 51P, 61P, 21S, and 31S. It is pointed out that in the calculation of generalized oscillator strengths possible errors in the zero-angle cross sections used may cancel out, which is illustrated for the transition 11S→31P. ``Quadrupole'' matrix elements have been derived for the 11S→21S, 31S transitions. In most cases the agreement with both experimental and theoretical results of other investigations is very good.
Selection of Molecular Matrix Elements from Atomic Data. III. 3d, 4s, and 4p Orbitals for Na, Mg, Al, Si, P, S, and Cl
Authors: Cusachs Louis Chopin , Linn Joseph Ralph
Published: January 2005

A modification of the method of Cusachs and Reynolds has been used to derive valence-state ionization potentials for the 3d, 4s, and 4p orbitals of third-row elements. For a fixed ionic charge, these VSIP are found to vary linearly with atomic number.
Thermal Conductivity of Carbon Tetrafluoride in the Dense Gaseous Region
Authors: Oshen Steven , Rosenbaum B. M. , Thodos George
Published: January 2005

Using a coaxial cylindrical cell, thermal conductivities for carbon tetrafluoride have been measured for pressures up to 9610 psia and temperatures of 6.7°, 23.8°, and 41.7°C. Residual thermal conductivities, k—k*, resulting from these measurements were correlated with corresponding reduced densities, ρR, to produce for the three temperatures the unique relationship k—k*=1.72×10−5 [exp(ρR) −1]. This residual quantity, when related to the reduced thermal pressure—temperature ratio gave rise to the single relationship, k−k*=0.56×10−5(∂PR/∂TR)ρR0.845. These measured thermal conductivities were compared with values predicted from the Enskog theory, k/k*=bρ[(1/bρχ)+6/5+0.7574bρχ], where the Enskog modulus, bρχ, was obtained from existing PVT data for carbon tetrafluoride.
Ultraviolet Optical Constants of Anthracene
Authors: Wright W. H.
Published: January 2005

The real and imaginary parts n and k of the refractive index of anthracene in both the a and b crystallographic axis directions are obtained in the wavelength region 220 to 400 mμ. These optical constants are derived from the reflectivity by the Price—Robinson method. The conditions under which this technique can be validly applied to anthracene are discussed. The results are compared with absorption and refractive index data obtained by others in the vicinity of 400 mμ, and found to be in agreement.
γ-Radiolysis of Liquids at High Pressures. I. Aqueous Solutions of Ferrous Sulfate
Authors: Hentz Robert R. , Farhataziz  , Milner David J. , Burton Milton
Published: January 2005

The γ radiolysis of aerated and deaerated, acid solutions of ferrous sulfate has been studied at 20° and applied pressures in the range 0 to 6.34 kbar. Over the entire pressure range, G(Fe+++)=8.1±0.1 and G(H2)=4.1±0.1 in deaerated solutions containing 0.8N H2SO4, 1 mM NaCl and 2 mM Fe++. Radiolysis of deaerated, 0.8N H2SO4 solutions of dichromate gives G(O2)=0.78±0.02 over the whole pressure range. It is concluded from such results, and observation of a similar pressure independence of G(Ce+++) in the ceric sulfate dosimeter, that primary yields in water radiolysis are invariant as pressure varies from 0 to 6.34 kbar. In aerated ferrous solutions, G(H2), G(Fe+++), and G(—O2) vary with pressure, ferrous concentration, and acid concentration in such a manner as to indicate an effect of pressure on the competition between Reactions [1] and [2]: H+O2→HO2,H+H++Fe++→Fe++++H2.Analysis of the results, for aerated ferrous solutions containing 0.8N H2SO4 and 1 mM NaCl, gives k1/k2≈1000 at atmospheric pressure and k1/k2=80 at 6.34 kbar. The difference in activation volumes of Reactions [1] and [2] is obtained as ΔV1‡—ΔV2‡ = 11 ml mole−1. Estimation of ΔV1‡≈2 ml mole−1, from the pressure dependence of water viscosity, gives ΔV2‡≈−9 ml mole−1. Such a value is not inconsistent with H+Fe++→FeH++ as the rate-determining step in the over-all reaction [2] in 0.8N H2SO4.
Experimental and Theoretical Investigations of the Performance of a Trennschaukel: Results on Ar–He System
Authors: Joshi R. K. , Mathur B. P. , Saxena S. C.
Published: January 2005

An all-glass, eight-tube trennschaukel has been operated with the two ends maintained at 0° and 100°C. The thermal separation is measured as a function of the period of gas pumped and its amplitude. Four different mixtures of the Ar–He system, covering the entire composition range, have been tried. The details of the experimental setup together with the observed thermal-diffusion separations are given. The relevant theory and the earlier experimental efforts to understand the trennschaukel operation are briefly discussed. The calculated and the observed mixture separations are in good qualitative agreement with each other.
Magnetic and Optical Spectra of Two Dimeric Copper Chloride Pyridine-N-Oxide Complexes
Authors: Kokoszka Gerald F. , Allen Harry C. , Gordon Gilbert
Published: January 2005

The electron paramagnetic resonance spectra and the optical absorption spectra of dichlorobispyridine-N-oxide copper(II) [(C5H5NO)2CuCl3] and dichloromonoaquopyridine-N-oxide copper(II) [C5H5NOCuCl·H2O] have been observed at room temperature. The magnetic resonance studies were carried out at both X-band and K-band frequencies. The observed spectra could be fit to an S=1 spin Hamiltonian. The direction of the maximum zero-field splitting did not correspond to the principal z axis of the g tensor. For (C5H5NO)2CuCl2 the angle between these two directions was about 23° and for C5H5NOCuCl·H2O the angle was about 27°. A study of the intensity of the EPR signal as a function of temperature indicated that the triplet state was about 550 cm−1 above the single ground state for (C5H5NO)2CuCl2 and about 885 cm−1 above the singlet state for the other complex. The optical spectra of both examples revealed two bands in the 8000-to−15 000-cm−1 region and a higher energy transition at about 22 000 cm−1.
Vibrational Spectrum of Crystalline HF and DF
Authors: Kittelberger J. S. , Hornig D. F.
Published: January 2005

Infrared spectra of pure crystalline HF and DF have been obtained over the region 30–4000 cm−1, and the spectra of the dilute isotopic mixed crystals have been studied in the intramolecular region 2000–4000 cm−1. Unlike previous workers, we find four bands in the stretching region of pure DF crystals, as well as the previously-reported four in the corresponding region of the HF spectrum. Direct observation of a lattice band near 200 cm−1 in both HF and DF, together with the line spacing in the stretching region permits an unambiguous assignment of the extra pair of lines in the intramolecular region as combination bands. The Raman spectra of crystalline HF and DF reveal four lines in the stretching region and one lattice transition. With the aid of simple intensity rules and correlations with the other hydrogen halides, a complete assignment of the vibrational bands is made except for the librational region, where the multiplicity of lines and the peculiar behavior of one of them under different deposition conditions make a firm interpretation impossible. The assignment is discussed with reference to results obtained by inelastic neutron scattering. Within experimental error each Raman line is coincident with an infrared line, and the structural implications of this fact are discussed.
Fundamental Equations of Electrochemical Kinetics at Porous Gas-Diffusion Electrodes
Authors: Srinivasan S. , Hurwitz H. D. , Bockris J. O'M.
Published: January 2005

The kinetics of a charge-transfer reaction at a porous gas-diffusion electrode are presented using the simple pore model. The rate of diffusion of the reactant gas through the electrolyte-free part of the pore is sufficiently fast for pore radii of 10−4 cm or higher. The dissolution of gas at the gas—electrolyte interface causes no limitations. For the processes occurring in the electrolyte occupied part of the pore, all forms of polarization are taken into account and expressions are derived for the current distribution and overpotential—current-density relations. By using numerical values of the various parameters (diffusion coefficient, solubility of reactant gas in electrolyte, specific conductance of electrolyte), it is shown that the case of all forms of polarization reduces to one of activation and concentration overpotential. A one-dimensional treatment is valid up to about 25% of the limiting current for this case. The dependence of current-distribution and overpotential—current-density relations on the various kinetic parameters is shown graphically for these cases. It is shown that most of the current (over 90%) is generated over a small fraction of the pore length (10−2−10−4) in the practical overpotential range (i.e., for reasonable current densities) when all forms of polarization are taken into account. The case of activation and ohmic overpotential shows the interesting result that current densities can be increased by a factor of up to 103 times if concentration overpotential is eliminated, as for example by using very soluble fuels or by circulating the electrolyte saturated with reactant through the porous electrode.
Molecular Distributions at Equilibrium. VI. Some Relationships, Latent in Stochastic Graph Theory, Suitable for Simplified Data Treatment of Polymer Systems
Authors: Matula David W. , Van Wazer John R.
Published: January 2005

Nonrandom behavior in the exchange of parts between variously sized, unbranched-chain molecules is shown to be calculable from the concentrations of the two smallest chains and the over-all stoichiometry of the equilibrated system. Furthermore, in equilibrated systems the over-all compositions at which various molecules and submolecular structures maximize are treated in terms of the equilibrium constants describing the system, and it is shown that observed values of the maximal abundance of certain of these molecules and submolecular structures can be used to estimate the equilibrium constants describing the system.
Hard-Sphere Lattice Gases. II. Plane-Triangular and Three-Dimensional Lattices
Authors: Gaunt David S.
Published: January 2005

Exact low-density and high-density series are derived for the plane-triangular (pt) lattice gas, and in three dimensions, for the simple cubic (sc) and body-centered cubic (bcc) lattice gases, with first-neighbor exclusions. The series are studied by the ratio and Padé approximant extrapolation techniques. In all cases we find a continuous transition to an ordered state at the activities zt=11.05±15 (pt), 1.09±7 (sc) and 0.77±5 (bcc), and the densities ρt/ρ0=0.832±8 (pt), 0.427±20 (sc) and 0.355±20 (bcc). The grand potentials at these points are (pv0/kBT) = Γt=0.839±5 (pt), 0.380±10 (sc) and 0.290±15 (bcc). In all cases the uncertainties refer to the last decimal places.

The ordered state is characterized by a long-range order parameter which vanishes continuously and rapidly at the transition point. The transition is signed from above and below by the rapid divergence (faster than a simple pole) of the ``staggered compressibility.'' Apparently, the isothermal compressiibility also diverges to infinity from either side but with considerably less rapidity.
Evaluation of Scattering Cross Sections in the Optical Model by the Method of Stationary Phase
Authors: Sun H. Y. , Ross J.
Published: January 2005

The elastic scattering cross section is evaluated by the method of stationary phase for two assumed forms of complex phase shifts. The results are applied to the interpretation of measurements on the scattering of K by SiCl4 to yield a value for the total reaction cross section.
Mössbauer Effect in SnI4
Authors: Bukshpan S. , Herber R. H.
Published: January 2005

The Mössbauer effect of the 23.8 keV 119Sn and 26.8 keV 129I transitions has been studied in SnI4 crystals. From the temperature dependence of the recoilless fraction in tin and iodine experiments, two significantly different characteristic temperatures have been found, namely 166°K for the Sn resonance and 85°K for the I resonance. From the intensities of the peaks in the iodine spectrum, the Gol'danskii effect has been calculated. From the quadrupole-coupling and isomer-shift measurements in the iodine experiments the bond structure of the Sn–I bond is derived.
Probability of Initial Ring Closure for Self-Avoiding Walks on the Face-Centered Cubic and Triangular Lattices
Authors: Martin J. L. , Sykes M. F. , Hioe F. T.
Published: January 2005

The probability of initial ring closure in the self-avoiding walk model of a polymer is investigated. Numerical data on the exact number of self-avoiding walks and polygons on the triangular and face-centered-cubic lattices are presented. It is concluded that the initial ring closure probability for large ring size k varies inversely as kθ with θ≃1 (5/6) in two dimensions and θ=1 (11/12) in three dimensions. It is found empirically that cn, the number of self-avoiding walks of n steps, approximates for large n to A |(jn)| μnwith for the triangular lattice j=−4/3, μ=4.1515, A=1.10, and for the face-centered-cubic lattice j=−7/6, μ=10.035, A=1.04.
Schumann—Runge Bands of Oxygen Heated to 900°K
Authors: Oppenheim U. P. , Goldman A.
Published: January 2005

Absorption measurements in the 1900–2100-Å region were carried out for oxygen heated to 900°K. Beer's law was not obeyed in general and was replaced by Goody's statistical band model, which was applied to small spectral intervals in the studied region. The spectral absorption coefficient and other band-model parameters were derived for this region.
Anharmonicity in the Symmetric and Asymmetric CH Vibrations of Ethylene
Authors: Machida Katsunosuke , Overend John
Published: January 2005

The vibrational anharmonicity in the CH stretching vibrations of ethylene has been calculated from a simple anharmonic potential function. xs, the difference between the harmonic frequency ωs and the observed frequency νs, in those vibrations which are asymmetric in a CH2 group appears to be systematically about 35 cm−1 greater than in the symmetric vibrations. A similar, though smaller (∼20 cm−1) effect appears in the deformation vibrations.
Theory of Gel—Dose Curves for Polymers Undergoing Simultaneous Crosslinking and Scission
Authors: Saito O. , Kang H. Y. , Dole M.
Published: January 2005

Computer calculations of the fraction of gel as a function of radiation dose have enabled tables to be constructed of the relation between gel fraction and number of crosslinks for various initial weight to number average molecular weight ratios and for a number of different ratios of chain scissions to crosslinks. The theory is based on the Wesslau molecular-weight distribution function and the results are in much better agreement in the case of many polymers than are the theoretical calculations of Inokuti based on a normalized Poisson distribution equation or the theory of Charlesby—Pinner based on a random molecular-weight distribution. It is shown that the initial slope of the (s+s1/2)-vs-(rg/r) curve is more helpful in many cases in determining the ratio of scissions to crosslinks than is the intercept at infinite dose. Indications of the breadth of the initial molecular weight distribution can also be obtained from the initial slope.
Infrared Spectrum of LiF, Li2F2, and Li3F3 by Matrix Isolation
Authors: Snelson Alan
Published: January 2005

The infrared spectrum of the vapor species above lithium fluoride has been examined in the frequency range 4000–200 cm−1 using the matrix isolation technique. The spectrum is interpreted in terms of monomer, dimer, and trimer molecules. Isotope shifts are consistent with a planar cyclic configuration for the dimer. The 7Li dimer has the following infrared-active fundamentals: v(B3u)=655 cm−1, v(B2u)=570 cm−1, and v(B1u)=300 cm−1. The remaining infrared-inactive frequencies of the dimer are estimated at v(Ag)=560 cm−1, v(Ag′)=280 cm−1, and v(B1g)=490 cm−1. The following frequencies are tentatively assigned to the infrared active fundamentals of the 7Li trimer, 230, 267, 509, and 736 cm−1.
Kinetics of the Difluoromethylene—Nitric Oxide Reaction. I
Authors: Modica A. P.
Published: January 2005

Evidence from mass spectra and ultraviolet-light absorption behind shock waves indicates a reversible reaction CF2+NO⇌ lim k1′k1CF2NObetween difluoromethylene and nitric oxide. Above 2500°K the reaction proceeds further to equilibrium by 2CF2NO→2CF2O+N2and CF2NO+NO→CF2O+N2O.In the temperature interval 1600°—2500°K, oscillogram records of CF2 uv absorption are reduced in terms of [1,1′] by the rate law −d[CF2]/dt=k1[CF2][NO]−k1′[CF2NO] with k1=1013.951±0.338 exp(−29200±3300/RT) cc/mole·secand k1′=106.497±0.393 exp(−20600±3600/RT) sec−1.From the ratio k1/k1′, the heat of reaction [1] is found to be 4.6 kcal/mole, yielding a heat of formation of the CF2NO radical equal to −15.7 kcal/mole.
Modulation of Epithelial Morphology, Monolayer Permeability, and Cell Migration by Growth Arrest Specific 3/Peripheral Myelin Protein 22
Authors: Roux Kyle J. , Amici Stephanie A. , Fletcher Bradley S. , Notterpek Lucia
Published: January 2005

Peripheral myelin protein 22 (PMP22) is associated with a subset of hereditary peripheral neuropathies. Although predominantly recognized as a transmembrane constituent of peripheral nerve myelin, PMP22 is localized to epithelial and endothelial cell-cell junctions, where its function remains unknown. In this report, we investigated the role of PMP22 in epithelial biology. Expression of human PMP22 (hPMP22) slows cell growth and induces a flattened morphology in Madin-Darby canine kidney (MDCK) cells. The transepithelial electrical resistance (TER) and paracellular flux of MDCK monolayers are elevated by hPMP22 expression. After calcium switch, peptides corresponding to the second, but not the first, extracellular loop of PMP22 perturb the recovery of TER and paracellular flux. Finally, subsequent to wounding, epithelial monolayers expressing hPMP22 fail to migrate normally. These results indicate that PMP22 is capable of modulating several aspects of epithelial cell biology, including junctional permeability and wound closure.
A Plasma Membrane Pool of Phosphatidylinositol 4-Phosphate Is Generated by Phosphatidylinositol 4-Kinase Type-III Alpha: Studies with the PH Domains of the Oxysterol Binding Protein and FAPP1
Authors: Balla Andras , Tuymetova Galina , Tsiomenko Arnold , Várnai Péter , Balla Tamas
Published: January 2005

The PH domains of OSBP and FAPP1 fused to GFP were used to monitor PI(4)P distribution in COS-7 cells during manipulations of PI 4-kinase (PI4K) activities. Both domains were associated with the Golgi and small cytoplasmic vesicles, and a small fraction of OSBP-PH was found at the plasma membrane (PM). Inhibition of type-III PI4Ks with 10 μM wortmannin (Wm) significantly reduced but did not abolish Golgi localization of either PH domains. Downregulation of PI4KIIα or PI4KIIIβ by siRNA reduced the localization of the PH domains to the Golgi and in the former case any remaining Golgi localization was eliminated by Wm treatment. PLC activation by Ca2+ionophores dissociated the domains from all membranes, but after Ca2+chelation, they rapidly reassociated with the Golgi, the intracellular vesicles and with the PM. PM association of the domains was significantly higher after the Ca2+transient and was abolished by Wm pretreatment. PM relocalization was not affected by down-regulation of PI4KIIIβ or -IIα, but was inhibited by down-regulation of PI4KIIIα, or by 10 μM PAO, which also inhibits PI4KIIIα. Our data suggest that these PH domains detect PI(4)P formation in extra-Golgi compartments under dynamic conditions and that various PI4Ks regulate PI(4)P synthesis in distinct cellular compartments.