bluuebunny/crossref_metadata_2025_split huggingface dataset:
One-Dimensional Inviscid Flow through a Rocket Nozzle
Authors: Rastogi R. P. , Pandya T. P. 
Published: January 2005

A thermodynamic theory of one-dimensional nonisentropic flow through a rocket nozzle is developed by using a parameter called ``extent of reaction'' introduced by de Donder. The formalism makes it possible to compute the exhaust velocity and cooling rate when there are significant departures from chemical as well as internal equilibrium.
It is shown that the cooling rate at the throat is likely to increase when the departures from equilibrium become significant.
Mass Spectrometric Study of Phase Changes in Aluminum, Praseodymium, and Neodymium
Authors: Johnson Robert G. , Hudson Donald E. , Caldwell Wallace C. , Spedding Frank H. , Savage William R. 
Published: January 2005

A sensitive method has been developed for measuring rapidly the latent heat of vaporization or sublimation of metals of low volatility. Atoms from the saturated vapor emerge from a small Knudsen-type effusion cell and impinge upon a hot filament. A fraction of the incident atoms re-evaporate from the filament as ions and are detected by a mass spectrometer. The Clausius-Clapeyron equation is used to obtain the latent heat from the dependence of ion current upon cell temperature. Application has been made to aluminum, praseodymium, and neodymium. The work on aluminum yielded an enthalpy of sublimation at 298°K of 78.0±0.4 kcal/M. Some anomalous behavior was observed in the rare earths. Preliminary molar enthalpy values are: Pr, 79.3±2.0 kcal (vaporization at 1380°K); Nd, 70.6±2.0 kcal (vaporization at 1348°K) and 74.1±2.0 kcal (sublimation at 1236°K). An estimate of the heat of fusion of Nd yielded 3.5±1.0 kcal/M.
The method also provided a convenient measurement of first-order phase transition temperatures. The melting points of Pr and Nd were found to be 1192±2°K and 1292±2°K respectively. In addition, a solid-to-solid phase transition was found in Nd at 1142±2°K.
Delta-Potential Function Model. II. Aromatic Hydrocarbons
Authors: Frost Arthur A. , Leland Frances E. 
Published: January 2005

The pi electrons are considered as following a one-dimensional network through the molecule as in the free electron model. The potential energy is taken as zero everywhere except at each pi-carbon nucleus where it goes to minus infinity as a negative delta function. By a procedure of linear combination of atomic orbitals, suitably defined, exact solutions of the Schrödinger equation are easily obtained. Negative one-electron energy levels, of which there may be as many as there are pi-carbon nuclei, are interpreted as bound states, with energy zero or positive as ionized states.
This model stands between the free electron model on the one hand and the LCAO molecular orbital model on the other. It goes beyond the former in that it can predict not only excitation energies and resonance energies, but also ionization potentials. It surpasses the latter in that exact solutions are obtainable. Numerical results are qualitatively of the right order of magnitude after adjustment of the strength of the delta function which is the one and only variable parameter.
Isothermal Calorimeter and the Heat of Mixing of Iso-Octane-Perfluoroheptane Solutions
Authors: Mueller Charles R. , Lewis James E. 
Published: January 2005

An isothermal calorimeter for measuring heats of mixing of binary solutions has been designed. The instrument utilizes twin calorimeters to eliminate troublesome corrections and a pair of differential thermistors for controlling the electrical circuit. There is no vapor space and the rate of mixing is controlled so that the heat absorbed is automatically compensated and the maximum temperature change is of the order of 0.001° to 0.002°C. This is accomplished by a differential bridge.
The heats of mixing of perfluoroheptane and isooctane were measured and the results compared with the values calculated from vapor pressure measurements.
Hindered Rotation in Molecules with Relatively High Potential Barriers
Authors: Hecht Karl T. , Dennison David M. 
Published: January 2005

The theory of hindered rotation has been applied to the type of asymmetric molecule in which the hindering barrier is high enough so that the hindered rotation splittings of the energy levels are small compared with the rotational energies but yet large enough to be observable in the microwave spectrum. The specific type of molecule considered consists of a rigid asymmetric component which may undergo a hindered rotation about the symmetry axis of a rigid symmetric component where the symmetric component is in addition assumed to have threefold symmetry and the asymmetric component at least a plane of symmetry containing the symmetry axis of the symmetric component. An example might be the acetaldehyde molecule, CH3CHO.
In principle, the theory developed by Burkhard and Dennison can be used directly but in practice the method is difficult to apply to such a molecule since the matrix elements of the Hamiltonian used previously do not degenerate naturally or easily to those for the rigid asymmetric rotator in the infinite barrier limit. In the present treatment a transformation is made on the Hamiltonian whereby this complication is avoided and the resulting calculations are greatly simplified.
It is found that the spectrum is essentially that of the rigid rotator with the important exception that all the strong lines are split into two components. For the low J transitions specific formulas have been derived for these splittings which are relatively simple functions of the barrier height, the principal moments of inertia, and two additional parameters involving the molecular dimensions and the masses. The barrier height can thus be deduced from the observed splittings without the use of the somewhat cumbersome machinery needed in the general case.
Concerning the Electron-Withdrawing Power and the Electronegativity of Groups
Authors: Taft Robert W. 
Published: January 2005

The polar substituent constants, σ*, obtained recently by Taft from reactivity considerations are discussed. Several qualitative relationships of σ* values to substituent constitution are established. These relationships relate quantitative correlations of the effect of structure on reactivity to concepts of bonding and electronegativity. The Mulliken concept of electronegativity is supported.
The relatively large electron-withdrawing powers of Cl, Br, and I in bonds to carbon suggest the participation of the d orbitals of the valence shell. A discrepancy is noted between σ* values (and Mulliken's electronegativities) and the group electronegativities proposed by Dailey and Shoolery on the basis of proton nuclear magnetic resonance shifts in ethyl and methyl derivatives.
On the Second-Order Decay of the Thermoluminescence of Polycrystalline Materials
Authors: Weyl Peter K. 
Published: January 2005

The results of an isothermal decay and glow-curve experiment for a thermoluminescent material having second-order kinetics have been investigated. In contrast to the first-order case, the location of the peak of the glow curve depends on the initial trap density. The effect of a distribution of trap densities for a polycrystalline material is investigated. It is found that for a narrow distribution function, a plot of the reciprocal of the square root of the light intensity versus the time in the isothermal decay experiment will give a straight line whose slope and intercept will depend on the distribution function. The location of the peak of the glow curve is not materially affected by the distribution function, and from its location and the energy of the trap depth, a parameter proportional to the initial trap density and independent of the optical efficiency can be determined.
Plots of first- and second-order generalized glow curves are presented from which the parameters of an experimental curve can be determined.
Alpha-Induced Decomposition of Ammonia. II. Effects of Variations in Intensity and Pressure
Authors: Burtt Benjamin P. , Zahlan Antoine B. 
Published: January 2005

The alpha-induced decomposition of ammonia was studied as a function of pressure (70–740 mm) and intensity. The ion yield was found to increase both with increasing intensity and decreasing pressure. The variation with intensity was more pronounced below 200 mm than at higher pressures.
Several models were examined to account for the experimental results. The decrease in the yield with increasing pressure was due to the deactivation of NH3* generated by the reaction NH2+H→NH3*.
At all intensities used in this work, gas phase ion recombination was negligible. The positive ions were assumed to react with NH3 to form NH4+ which was neutralized at the wall.
At sufficiently high pressure and intensity, the NH2 radicals reacted homogeneously in the gas phase, but at low pressure and intensity, wall reactions became important.
This ``intensity'' effect was caused by the ions and does not appear in photolysis. The ion-molecule reactions generate the NH4+, the pressure controls the diffusion process, and the intensity determines the relative importance of the gas phase and the wall reactions. The intensity effect is a function of all four variables.
On the basis of the reaction scheme and the present knowledge of the mass spectrum, it was possible to calculate a lower limit for the ion yield.
Nuclear Magnetic Relaxation in 1,2-Dichloroethane
Authors: Linder Solomon 
Published: January 2005

Analysis of thermal relaxation times in solid and liquid 1,2-dichloroethane suggests the following:
(1) The mechanism causing thermal relaxation in the solid is a partial rotation of the molecule about the molecular axis (which is approximately the C–C axis) against a potential barrier of about 1.5 kcal per mole.
(2) It is likely that the narrowing of the resonance line is a result of the completion of this partial motion.
(3) At the melting point, a drop in the thermal relaxation time of about an order of magnitude occurs.
(4) In the liquid, a new motion has set in, characterized by a lower activation energy (roughly 0.6 kcal/mole). This motion may be end-over-end tumbling.
The spin-lattice relaxation time (``thermal'' relaxation time) in the solid ranges between 1 and 20 sec, and its length permits its measurement by a method which is slightly different from the conventional technique. This technique utilizes the fact that, immediately upon application of the radio-frequency field, the magnetization of the sample decays with a time which can be related to the thermal relaxation time and to the strength of the radio-frequency field. The measurement is a direct measurement of a characteristic time of the sample, and is therefore more reliable than the conventional indirect measurement.
The technique also enables one to calibrate the radio-frequency field more easily.
Interaction between Sulfur Dioxide and Polar Molecules. I. Systems Containing Aliphatic Alcohols, Ethers, or Benzene in Carbon Tetrachloride
Authors: de Maine P. A. D. 
Published: January 2005

The absorption band of sulfur dioxide near 2800 A in mixed solvents of benzene, aliphatic alcohols, or ethers with carbon tetrachloride is probably in part the result of a donor-acceptor complex with sulfur dioxide as acceptor.
The characteristic constants for the MeOH, EtOH, n-PrOH, n-BuOH, and benzene complexes with sulfur dioxide, and the heats of formation of the benzene and ethanol complexes with sulfur dioxide in carbon tetrachloride have been estimated. The effect of atmospheric water vapor on these systems is also discussed.
Interaction between Sulfur Dioxide and Polar Molecules. III. Water-Ethanol-Sulfur Dioxide and Water-Sulfur Dioxide Systems
Authors: de Maine P. A. D. 
Published: January 2005

It is shown that the temperature dependence of the ultraviolet absorption spectra for water-sulfur dioxide solutions cannot be explained by the theories of Ley and Konig or Boyd-Campbell and Maass. Qualitative arguments show that the mechanism, (SO2)gas⇀lhdSO2+H2O⇀lhdcomplex⇀lhdH2SO3⇀lhdH++-HSO3⇀lhd2H++-2SO3, does explain the spectroscopic behavior of dilute sulfur dioxide solutions.
A linear relation is reported between the heat of solution, calculated from vapor pressure data, and the smallest effective molecular diameter of several gases.
Attempts to analyse the absorption spectra of the water-ethanol-sulfur dioxide solutions in terms of the separate systems, EtOH+SO2⇀lhdcomplex1 and (SO2)gas⇀lhdSO2+H2O⇀lhdcomplex2⇀lhdH2SO3⇀lhdH++-HSO3 are reported. These results are explained by the new liquid lattice theory.
Zinc Oxide Photoconduction, an Oxygen Adsorption Process
Authors: Melnick Donald A. 
Published: January 2005

Photoconductive rise and decay curves of porous sintered zinc oxide are studied as a function of time (0.3 to 107 sec), ambient oxygen pressure (5×10—5 to 760 mm), temperature (110° to 373°K), incident light intensity (factor of 103), and various cycling procedures in regard to illumination. The photoconductivity is shown to be entirely due to the desorption of chemically adsorbed oxygen atoms from the surfaces of the porous sample. Light of wavelength near the fundamental absorption edge forms electron-hole pairs of which the hole is captured by the oxygen, converting the oxygen to physically adsorbed. The physically adsorbed oxygen easily desorbs and the electron remains to increase the conductivity. The kinetics of the adsorption process when the light is removed are found to obey the Elovich equation, dq/dt=a exp(—bq), where q is the density of adsorbate, and a and b are constants. It is believed that the limiting process is electron transfer through the Schottky barrier, since it results in an equation equivalent to the empirical one above.
Experimentally a continuous spectrum of time constants is found. A technique has been developed for analyzing experimental curves into component time constant processes. The Elovich equation results in time constants depending upon the intensity of illumination. The continuous spectrum of time constants can therefore be attributed to this variation of intensity with depth in the sample.
Electrical Conductivity Measurements on Cuprous Halides
Authors: Wagner J. Bruce , Wagner Carl 
Published: January 2005

The total electrical conductivity and the electron hole conductivity in solid CuCl, CuBr, and CuI between 250 and 450°C have been determined with help of ac measurements on samples between copper electrodes and dc polarization measurements on the cell
Cu|cuprous halide|graphite.
Thermal Conductivity of Gas Mixtures in Chemical Equilibrium
Authors: Butler James N. , Brokaw Richard S. 
Published: January 2005

A general expression applying to the steady state has been derived which permits calculation of the increase in thermal conductivity due to chemical reaction in mixtures of gases in chemical equilibrium. In addition to the gas composition, heats of reaction and binary diffusion coefficients among the component gases are required.
In the case of a simple dissociation, the thermal conductivity may be related to the equilibrium heat capacity. This suggests a possible method for estimating heat transfer in various practical systems with dissociating gases.
Approximate calculations for dissociation of diatomic molecules at equilibrium show that the thermal conductivity may be an order of magnitude greater than in nonreacting mixtures. Calculations for the systems 2NO2⇆N2O4 and 6HF⇆(HF)6 are in satisfactory agreement with experiment.
Decomposition of Carbon Dioxide by Ionizing Radiation. Part II
Authors: Harteck P. , Dondes S. 
Published: January 2005

An extension of the research on carbon dioxide described in Part I was conducted at pressures from one atmosphere to fifty atmospheres, and on liquid carbon dioxide at 10°C, near the critical temperature. Also a novel method was developed in using the direct impact of the fission fragments on the gases (uranium-235 in contact with the gases on bombardment with thermal neutrons). The action of inhibitors other than nitrogen dioxide to stop the back reaction of the decomposed carbon dioxide was also investigated. Since the decomposition of nitrous oxide by ionizing radiation was determined as a dosimeter, parallel decomposition experiments were conducted with the nitrous oxide and carbon dioxide under identical conditions. The G values of the carbon dioxide decomposition were determined with and without inhibitors at high pressures and the liquid state by pile radiation and by the impact of fission fragments. The G values ranged from 0.005 to 8.5±0.5 depending upon conditions. The basic mechanism described in Part I was confirmed. No difference in behavior was noticed in the gas phase when irradiated with pile radiation or fission fragments.
In the liquid state, it could be shown that the ``hot spots'' or ``hot needles'' along the ionization track of the fission fragments are not ``hot'' enough to initiate the thermal decomposition, which in the case of nitrous oxide requires a heat of activation of 53 kcal and for carbon dioxide 128 kcal. However, two markedly different behaviors between the gaseous and liquid states were noted. First, the inhibitors became inefficient in the liquid carbon dioxide phase, and second, the G value for the decomposition of liquid carbon dioxide was found to be 4 to 5. These behaviors are not altered if the liquid carbon dioxide is irradiated with normal pile radiation or with fission fragments.
Nuclear Magnetic Relaxation in Polytetrafluoroethylene and Polyethylene
Authors: Wilson C. W. , Pake G. E. 
Published: January 2005

Nuclear magnetic resonance studies of the linear chain polymer polytetrafluoroethylene (Teflon) indicate the coexistence of two phases, each characterized by its own pair of relaxation times T1 and T2. Decomposition of the complex resonance lines and complex saturation curves into normal curves permits determination of the fraction of nuclei in each phase. It is suggested that the phases are the crystalline and amorphous regions of these polymers, and some additional evidence to support this suggestion is presented.
The phase thought to be crystalline shows a marked line-narrowing at the first-order thermodynamic-transition point near 293°K.
The less complete data presented for polyethylene suggest the analogous presence of two phases, and the line-shape analysis yields reasonable values for the degree of crystallinity.
Structure of the Methylamine Molecule. I. Microwave Spectrum of CD3ND2
Authors: Lide David R. 
Published: January 2005

The spectrum of CD3ND2 has been investigated in the 24 000–36 000 Mc region and about thirty lines have been assigned. The rotational spectrum exhibits a fine structure as a result of internal rotation and inversion. An approximate treatment of these internal motions is formulated and shown to give an excellent fit of the observed spectrum. A treatment of Stark effects and nuclear quadrupole interactions is developed and applied to the CD3ND2 spectrum. The relation to the CH3NH2 spectrum is discussed.
Molecular constants of CD3ND2 determined from the spectral analysis are: torsional barrier height H=684.7±2 cm-1; dipole moment components μa=0.265 D, μc=1.299 D, total μ=1.326±0.015 D; N14 quadrupole coupling constants χaa=2.35 Mc, χbb=2.12 Mc, χcc=—4.47 Mc. Structural parameters calculated from data on CD3ND2 and CH3NH2 are: rCH=1.093 A (assumed), ∠HCH=109°28′ (assumed), rCN=1.474 A, rNH=1.011 A, ∠HNH=105°52′, ∠CNH=112°3′; the nitrogen atom is located 0.091 A from the CH3 symmetry axis.
Hydrogen Bonding in Radical Reactions. Some Remarks on CF3 Radicals
Authors: Szwarc M. , Smid J. 
Published: January 2005

Studies of the decomposition of acetyl or propionyl peroxide on the one hand and benzoyl peroxide on the other seem to demonstrate that Ph·COO radicals form hydrogen bonds with carboxylic acids, while the nonpolar alkyl radicals do not form such bonds.
The formation of hydrogen bonds facilitates the hydrogen transfer between the carboxylic acid and the polar radicals.
Magnetic Relaxation Spectroscopy with Ionic Solutions
Authors: Broersma S. 
Published: January 2005

When the protons in a liquid are subjected to varying magnetic interactions, and a rapid averaging is prevented, it is possible to distinguish liquid elements, chemically similar, but differing in the amount of relaxation ∫0tdt′/T. The customary ac modulation of the magnetic field produces the required transient conditions. The phenomena of line broadening, line shift, and reversal of magnetization with time help to recognize the phases. The signal of the weak relaxation phase can easily be diminished by inducing eddy currents in the magnet iron.
Additional non-uniformities can be made in water by introducing dia- or para-magnetic ions. An analysis of the processes of relaxation and adsorption shows that these water molecules or protons prevail in the observation for which the time of adsorption is close to the local relaxation time. The transient rate of relaxation of the entire sample is approximately equal to this rate of adsorption, and to the sweep frequency at which the magnetizations of the phases balance.
The life time found for the protons in the inner layer of water surrounding trivalent ions, by studying concentrated diamagnetic solutions, is about 10 msec. For dilute paramagnetic solutions the values range from three hundred to one micro second, decreasing with the distance to the ion, increasing its magnetic moment. The activation energy involved times the power of its dependence upon the distance to the center ion, is 20 kcal/mole. The effective size of the atmosphere changes from one or two layers for dilute to two or three layers for concentrated solutions. Ice crystals with four layers radius and five milliseconds life time show up.
Nonstoichiometry and Lattice Defects in Uranium Hydride
Authors: Libowitz George G. 
Published: January 2005

Expressions were derived for the hydrogen pressure over nonstoichiometric metallic hydrides from statistical mechanical considerations. Two separate relations were obtained depending on whether lattice vacancies or interstitial atoms were taken to be the cause of hydrogen deficiency in hydrides. For the case of one-to-one binary hydrides, the two equations become identical.
By comparing the pressure-temperature-composition data for uranium hydride with the derived equations, it was established that the nonstoichiometry of this compound was due to hydrogen vacancies in the lattice rather than interstitial uranium atoms. The energy necessary to form a hydrogen vacancy in uranium hydride was found to be 68.2 kcal/mole, while a value of 6.5 kcal/mole was determined for the interaction energy between vacancies.
Decomposition of Nitric Oxide and Nitrogen Dioxide by the Impact of Fission Fragments of Uranium-235
Authors: Harteck P. , Dondes S. 
Published: January 2005

A study was made of the decomposition of nitric oxide and nitrogen dioxide using the fission recoil energy of 5 mg of uranium-235 oxide powder. The irradiations were conducted in a 23-cc quartz vessel, at a flux of 3×1012 neutrons | cm2 second, and at a temperature of 70°C in the Brookhaven National Laboratory Reactor. With a dose of 2×109 r, the over-all GNO is 9.5±1.0, using a radiation intensity of 1.0×107 r | min, a filling pressure of 500 mm at 21°C. With a dose of 108 r, the GNO is 13.8±1.4. Since three additional nitric oxide molecules are consumed for each nitric oxide molecule decomposed at 108 r, the GNO value calculated for the primary decomposition (including the dissociation due to ion-recombination) is 3.45±0.35.
The GNO2 value is 1.2 for a dose of 3×109 r and 0.5 for 5×107 r, conducted under a radiation intensity of 1.2×107 r | min and a filling pressure of 550 mm of the 2 NO2⇄N2O4 equilibrium at 21°C. For the principal reactions in the nitric oxide and nitrogen dioxide systems, when irradiated with ionizing radiation, a reaction mechanism is proposed which seems to explain the characteristic features of the system.