bluuebunny/crossref_metadata_2025 huggingface dataset:
Tissue Culture and Explant Approaches to Studying and VisualizingNeospora caninumand Its Interactions with the Host Cell
Authors: Hemphill Andrew , Vonlaufen Nathalie , Naguleswaran Arunasalam , Keller Nadine , Riesen Michele , Guetg Nicole , Srinivasan Sangeetha , Alaeddine Ferial
Published: November 2004

Neospora caninumis an apicomplexan parasite first mentioned in 1984 as a causative agent of neuromuscular disease in dogs. It is closely related toToxoplasma gondiiandHammondia heydorni, and its subsequent description in 1988 has been, and still is, accompanied by discussions on the true phylogenetical status of the genusNeospora.N. caninumexhibits features that clearly distinguish this parasite from other members of the Apicomplexa, including distinct ultrastructural properties, genetic background, antigenic composition, host cell interactions, and the definition of the dog as a final host. Most importantly,N. caninumhas a particular significance as a cause of abortion in cattle.In vitroculture has been indispensable for the isolation of this parasite and for investigations on the ultrastructural, cellular, and molecular characteristics of the different stages ofN. caninum. Tissue culture systems include maintenance ofN. caninumtachyzoites, which represent the rapidly proliferating stage in a large number of mammalian host cells, culture of parasites in organotypic brain slice cultures as a tool to investigate cerebral infection byN. caninum, and the use of techniques to induce the stage conversion from the tachyzoite stage to the slowly proliferating and tissue cyst-forming bradyzoite stage. This review will focus on the use of these tissue culture models as well as light- and electron-microscopical techniques for studies onN. caninumtachyzoites and bradyzoites, and on the physical interactions between parasites and host cells.
Contribution of Microscopy to a Better Knowledge of the Biology ofGiardia lamblia
Authors: de Souza Wanderley , Lanfredi-Rangel Adriana , Campanati Loraine
Published: November 2004

Giardia lambliais a flagellated protozoan of great medical and biological importance. It is the causative agent of giardiasis, one of the most prevalent diarrheal disease both in developed and third-world countries. Morphological studies have shown thatG. lambliadoes not present structures such as peroxisomes, mitochondria, and a well-elaborated Golgi complex. In this review, special emphasis is given to the contribution made by various microscopic techniques to a better knowledge of the biology of the protozoan. The application of video microscopy, immunofluorescence confocal laser scanning microscopy, and several techniques associated with transmission electron microscopy (thin section, enzyme cytochemistry, freeze-fracture, deep-etching, fracture-flip) to the study of the cell surface, peripheral vesicles, endoplasmic reticulum–Golgi complex system, and of the encystation vesicles found in trophozoites and during the process of trophozoite-cyst transformation are discussed.
Introduction: A Special Issue on Cellular Biology of Protozoan
Parasites
Authors: Docampo Roberto
Published: November 2004

It is estimated that more than half of the human population, plus a
much greater number of domestic and wild animals, suffer from parasitic
infections. The magnitude of the problem can be illustrated by
estimates of more than 100 million cases and 1 million deaths each year
from malaria alone.
Hyporheic exchange with heterogeneous streambeds: Laboratory experiments and modeling
Authors: Salehin Mashfiqus , Packman Aaron I. , Paradis Matthew
Published: November 2004

Hyporheic exchange is generally analyzed with the assumption of a homogeneous hyporheic zone. In reality, streambed sediments have a heterogeneous structure, and this natural heterogeneity produces spatially variable interfacial fluxes and complex hyporheic exchange patterns. To assess the basic effects of sediment structure on hyporheic exchange, we performed salt and dye injection experiments in a recirculating laboratory flume with two heterogeneous sediment beds characterized by negative‐exponential correlated random hydraulic conductivity fields. Dye injections showed that the hyporheic flow structure was controlled by the spatial relationship of bed forms to high‐ and low‐permeability regions of the streambed. As no existing model could represent these effects, we developed a new finite element model to calculate the pore water flow field resulting from the interaction of the bed form‐induced boundary head distribution and the heterogeneous sediment structure. A numerical particle‐tracking approach was then used to assess the resulting hyporheic exchange. The combined flow‐transport model did an excellent job of predicting the complex hyporheic flow pathways in the heterogeneous bed and the net hyporheic exchange up to t ≈ 30 hours. The heterogeneous hydraulic conductivity field caused both greater spatial variability in the water flux through the bed surface and a greater average interfacial flux than would have occurred with a homogeneous bed. The layered correlation structure of the streambed produced an effective anisotropy that favored longitudinal pore water flow and caused a relatively rapid decrease of the mean pore water velocity with depth. As a result, solute penetration into the bed was confined to a more shallow region than would have occurred with a homogeneous bed. The combination of faster near‐surface transport and shallower solute penetration produced a shorter mean hyporheic residence time. On the basis of the combination of experimental results and model simulations we conclude that the structural heterogeneity of streambed sediments produces more spatially limited hyporheic exchange that occurs with greater spatial variability and at a higher overall rate.
Energetic plumes over the western Ross Sea continental slope
Authors: Gordon Arnold L. , Zambianchi Enrico , Orsi Alejandro , Visbeck Martin , Giulivi Claudia F. , Whitworth Thomas , Spezie Giancarlo
Published: November 2004

Rapid descent of dense Drygalski Trough (western Ross Sea, Antarctica) shelf water over the continental slope, within 100 to 250 m thick benthic plumes, is described. Speeds of up to 1.0 m/s are recorded flowing at an average angle of 35° to the isobaths, entraining ambient Lower Circumpolar Deep Water en route. This process is predominant in determining the concentration and placement of the shelf water injected into the deep sea as a precursor Antarctic Bottom Water. Nonetheless, a 4‐hour duration pulse of undiluted shelf water was observed at depth (1407 m) directly north of the Drygalski Trough, moving at around 90 degrees to isobaths, and at a speed of 1.4 m/s. Thus the export of Ross Sea shelf water to the deep sea is accomplished within plumes descending at moderate angle to isobaths, punctuated by rapid downhill cascades.
A stochastic model for the formation of channel networks in tidal marshes
Authors: Fagherazzi Sergio , Sun Tao
Published: November 2004

Salt marshes are often dissected by a network of channels formed by tidal oscillations and related water fluxes. In this note we present a stochastic model able to simulate the formation and evolution of tidal networks in salt marshes. The model is based on a simplification of the shallow water equations that enables the determination of the water surface gradients on the marsh platform and related bottom shear stresses. The governing equations are then solved with a random walk algorithm in an enclosed domain representing the marsh platform and its physical boundaries. Model results show how the development of the network depends on the tidal forcing, the critical shear stress for erosion, as well as the local heterogeneities in vegetation and sediment substrate.
Lattice Boltzmann model for crystal growth from supersaturated solution
Authors: Kang Qinjun , Zhang Dongxiao , Lichtner Peter C. , Tsimpanogiannis Ioannis N.
Published: November 2004

We develop a new, lattice effects‐free lattice Boltzmann model for simulating crystal growth from supersaturated solution. Simulations of crystal growth from a single or multiple nuclei in a domain initially filled with supersaturated solution are presented, such as in the case of gas hydrate formation. We find that as the process changes from diffusion‐controlled to surface reaction‐controlled, the crystal transforms from open cluster‐type structure, via compact coral‐type structure, to compact circular structure, and correspondingly, the fractal dimension of the crystal structure increases from a value close to that of a diffusion‐limited aggregation (DLA) structure to the Euclidian value for a circle. At a high Damkohler number, crystal formed from a single nucleus becomes more compact as the saturation increases. At a low Damkohler number, the crystal has a fairly round shape for different saturation values and the effect of saturation is insignificant.
Air bubble to clathrate hydrate transformation in polar ice sheets: A reconsideration based on the new data from Dome Fuji ice core
Authors: Ohno Hiroshi , Lipenkov Vladimir Y. , Hondoh Takeo
Published: November 2004

Mapping the spatial distribution of air bubbles and clathrate hydrates in thick sections of Antarctic ice from Dome Fuji station reveals a considerable redistribution of the inclusions in terms of number and volume in the bubble‐to‐hydrate transition zone. Analysis of the data indicated that more than 10% of the hydrates nucleated outside the preceding bubbles and more than 30% of the bubbles completely expired due to the gas outflow toward the coexisting hydrates. These features of the gas‐hydrate‐ice nonequilibrium system are of major importance for modeling the global bubble‐to‐hydrate transformation in polar ice sheets and thus the results may help improve our ability to extract paleoclimatic information from air inclusions in ice cores.
Characterization of individual airborne particles by using aerosol time‐of‐flight mass spectrometry at Mace Head, Ireland
Authors: Dall'Osto Manuel , Beddows David C. S. , Kinnersley Robert P. , Harrison Roy M. , Donovan Robert J. , Heal Mathew R.
Published: November 2004

An aerosol time‐of‐flight mass spectrometer was deployed at Mace Head (Ireland) during August 2002. The measurements provide qualitative chemical composition and size distribution (0.3–3 μm) information for single particles. Three broad categories of particles: sea salt, dust, and carbon‐containing particles were identified and apportioned, and their temporal evolution (1 hour resolution) is described. Aerosol sources were correlated with meteorological factors and with air mass trajectories, demonstrating long‐range transport of different continental air masses from Europe, Africa, and America. The major class of particles was derived from sea salt and was subdivided into pure, mixed, and aged sea salt according to the extent of displacement of chloride by nitrate. Two types of dust particles were found mainly in the coarse mode (>1 μm); the former, thought to originate from the Sahara, presented an aluminium/silicon signature, while the latter, of more local origin, had a calcium‐rich composition. Carbon‐containing particles were mainly distributed in the fine mode (<1 μm) and associated with different chemical species in different size modes, suggesting different mechanisms of formation.
The Heat of Expansion of a Gas of Varying Mass
Authors: Gillespie L. J. , Coe J. R.
Published: November 2004

In this paper equations are given for the direct treatment of experiments in which not only heat, but also masses, pass the boundary of the container of the system during the experiment. The theoretical development is correlated with the treatment of Gibbs, and certain difficulties, mentioned by others, in the physical interpretation of his equations, are incidentally removed. It was found possible, within a reasonable time, to cause a gas to expand slowly enough from a calorimeter to simulate a reversible expansion, and the special equation developed for the heat of expansion with the aid of the Beattie-Bridgeman equation of state was verified by the results for the slow expansion of carbon dioxide and ammonia. In the case of carbon dioxide the effect of the deviations from the ideal gas law was to make the heat effect in excess of that calculated for an ideal gas by a sufficient amount so that the excess itself could be calculated within about 7 percent. A series of expansions of carbon dioxide was carried out at varying rates of flow, some as fast as permissible. The results, correlated by means of an empirical relation, serve to show that the results of the slow expansions correspond practically to an infinitely slow expansion. They also indicate that the heat effect for an infinitely rapid expansion is not zero for a real gas, but possibly vanishes with the pressure. In the absence of a perfectly sound method of calculating the heat effect for an infinitely fast expansion, a method is suggested which has at least the merit of agreement with the present experiments.

The bearing of the results on variable-pressure calorimetry, as practiced in experiments on the heat of adsorption, is briefly discussed.
The Dispersion of Sound in Nitrogen Tetroxide and Its Interpretation in Terms of Dissociation Rate
Authors: Richards William T. , Reid James A.
Published: November 2004

Several types of dispersion of sound which may be manifest in a dissociating gas are discussed. Of these only the heat-capacity dispersion and the dissociation dispersion need be considered under suitable experimental conditions. The expression derived by Einstein for the velocity of sound in a dissociating gas has been modified to include heat-capacity dispersion. The experimental procedure indicated by this for obtaining significant dissociation rate constants is outlined. Measurements on the velocity of sound in nitrogen tetroxide which have been made with apparatus of special design, are reported. The range of temperature studied is 0°C to 30°C, the range of pressure 132 mm to 670 mm, and the range of frequency 9 kc to 451 kc. The velocity of sound has been thus defined with an estimated error of ±0.1 m·sec.—1. The maximum dispersion which has been observed is about 5 m·sec.—1. From these measurements it appears that the rate constant of the dissociation reaction is 4.8×104±0.5×104 at 25°C and 260 mm. The activation energy obtained for the dissociation reaction is 13.9±0.9 kg·cal. The rate constant appears to diminish slightly as the pressure is reduced. Since an upper limit for the heat capacity of nitrogen tetroxide is fixed by experiment, it is necessary to suppose that the effective molecular diameters for the activation process are at least three times those for ordinary kinetic collisions.
The Normal State of the Helium Molecule-Ions He2+ and He2++
Authors: Pauling Linus
Published: November 2004

With the use of wave functions constructed from hydrogen-like single-electron functions with an effective nuclear charge Z, the application of the variation method of treating the wave equation for the normal state of He2+, involving a three-electron bond, leads to the values Z = 1.833, r0 = 1.085A, De = 2.47 v.e., and ω0 = approximately 1950 cm—1. The experimentally determined values (from the He2 spectrum) are r0 = 1.090A, De = 2.5 v.e., and ω½ = 1628 cm—1. A similar discussion of He2++, with a covalent-plus-ionic wave function, shows that the energy curve has a minimum at r0 = 0.75A, ω0 = approximately 3200 cm—1, with a maximum 1.4 v.e. higher at about 1.1A. This configuration could act as the core for excited states of He2+ and doubly-excited states of He2, some of which would be capable of existence with either one of two moments of inertia, one corresponding to r0 = 0.75A and the other to about the same values of r0 as for the analogous states in excited H2+ or doubly-excited H2.
The Dipole Moment of Nitric Oxide
Authors: Smyth C. P. , McAlpine K. B.
Published: November 2004

The dielectric constant of nitric oxide is measured over a wide range of temperature and used to calculate the dipole moment of the molecule, which is found to be less than 0.1×10—18, and so small as to be indistinguishable from zero.
Binding Energies in the Growth of Crystal Nuclei from Metallic Atoms
Authors: Taylor Hugh S. , Eyring Henry , Sherman Albert
Published: November 2004

First order perturbation theory has been employed to compute the binding energies of various geometrical configurations of three to eight atoms of sodium. It has been assumed that in the metal lattice the binding is essentially homopolar. It has been shown that the growth of a unit cell probably proceeds via the diatomic molecule to a square, a fifth atom adding along a cube edge, a sixth at the body center and the cell completed by location of atoms at the remaining cube corners. The unit cell is still a very unstable unit, a result in agreement with high vapor pressures and solubility of finely divided particles, and with the concept of active centers on reaction surfaces. The fifth order secular equation employed to determine the energies of configurations of five and six atoms has been made more amenable to use in calculations. A fourteenth order secular equation, with similar characteristics, has been employed for the cases of seven and eight atoms. Approximate calculations with copper atoms instead of sodium give similar results but indicate that higher activation energies of nuclei formation may obtain in this case. The percentage of the total binding assigned to interchange is shown to be an important factor. The calculations indicate that the net effect of interchange forces in homopolar crystals is to increase the potential energy. The crystal structure is stable only because of the coulombic and van der Waals' forces. When applied to hydrogen (90 percent interchange) it is shown that a metallic lattice is utterly unstable.
Binary Systems in Two Phases. I. HCl–Kr. II. HCl–C3H8
Authors: Glockler George , Fuller Donald L. , Roe Charles P.
Published: November 2004

The P—T—X relations of the binary mixtures HCl–Kr and HCl–C3H8 have been determined. Retrograde condensation was observed with all mixtures studied. Not more than one liquid phase was found for any of the mixtures.
The Atomic Weights of Radioactive Substances
Authors: Western Forrest , Ruark Arthur E.
Published: November 2004

(1) The isotopic weights of Pb206, Pb207, and Pb208, on the chemical scale O = 16.0000, are obtained by three distinct methods, using in each case the assumption that they differ by an amount very close to unity. The results for Pb206 are these: (1) from packing fraction of lead, 205.965; (2) from study of the packing fraction curve, 205.992; from relative abundance of isotopes in leads of known atomic weight, 206.003. Mean, 205.987±0.03. By taking into account a recent atomic weight determination on lead from Bedford cyrtolite, reasonable rounded values for the three isotopes are 205.98, 206.98 and 207.98±0.03. (2) From these values the isotopic weights of the radioactive substances are obtained by adding the mass (and the mass-equivalent of the energy) lost in disintegration. The calculated values for radium and thorium, 226.02±0.03 and 232.03±0.03, do not agree with the International values 225.97±0.01 and 232.12±0.01. The calculated weights for U238 and U234 are 238.04±0.03 and 234.04±0.03, respectively, while the heretofore accepted atomic weight of U is 238.14±0.01. In view of Aston's conclusion that U does not contain more than 3 percent of U239 or any higher isotope, it appears probable that the accepted value for uranium is somewhat too high. (3) W — N is plotted as a function of N, for the three radioactive series, W being the isotopic weight and N the nearest integer. The graphs obtained are almost linear, and their slopes are nearly identical. In an average way they conform to the equation W — N = — 0.02+0.00214 (N — 206).
Further Observations Concerning the Propagation of Sound in Nitrogen Tetroxide
Authors: Richards William T. , Reid James A.
Published: November 2004

The absorption of sound in nitrogen tetroxide is discussed, and it is pointed out that absorption measurements should be capable of distinguishing whether a given absorptive region is due to failure of the dissociation reaction or of the heat capacity to follow the adiabatic cycle of the sound wave. Appropriate expressions for the absorption are derived from Einstein's theory, and are briefly discussed. An experimental method of determining the absorption maximum is described in which the temperature is varied at constant pressure and frequency. Under these conditions the acoustical variables are maintained very nearly constant. An attempt to detect the absorption maximum at 450.1 kc and 260 mm in nitrogen tetroxide was unsuccessful because of the inaccuracy of the absorption measurements. It is concluded that dispersion measurements provide at present an easier and more accurate method of investigating the acoustical properties of rapidly dissociating gases than measurements of the absorption coefficient. Occasion is taken to discuss the tube corrections applied to the previous dispersion measurements at greater length than was before considered necessary. Several corrections to the previous work are also appended.
An X-Ray Study of the Binary Alloys of Silicon with Ag, Au, Pb, Sn, Zn, Cd, Sb and Bi
Authors: Jette Eric R. , Gebert Emery B.
Published: November 2004

The lattice constants of the binary alloys of silicon with silver, gold, lead, tin, zinc, cadmium, antimony and bismuth have been measured. It is shown that the lattice constants of the elements in these alloys are practically identical with those of the pure elements. This fact leads to the interpretation that mutual solubility of the elements in these alloys occurs to only a very slight extent. It is further observed that silicon forms no compounds with any of these elements.
Thermodynamic Considerations on a New Kind of Transition Points
Authors: Halpern Otto
Published: November 2004

According to previous experiments liquid helium shows a ``transition point'' with discontinuity in the values of its specific heat and expansion coefficient. It has not been possible, however, to observe the coexistence of the two ``phases.'' This fact is here explained on a thermodynamic basis. Coexistence of two phases at a transition point can only be anticipated if the two phases exhibit a discontinuity in energy. An analogy is made with similar cases like that of the ``transition point of superconductivity.''
The Dielectric Constant of Liquid Sulphur
Authors: Curtis Howard J.
Published: November 2004

The dielectric constant and power factor of liquid sulphur were measured by a bridge method at four different audio-frequencies and over the temperature range 118°C to 350°C. The dielectric constant was found to be independent of frequency and equal to 3.520±0.010 at 118°C. A study of the polarization curve shows that liquid sulphur is nonpolar. A method was developed for differentiating between that part of the power factor which is due to conductivity and that which is due to molecular friction. The former was found to be large at high temperatures and the latter small at all temperatures. The infrared spectrum of liquid sulphur contains definite absorption bands, which fact shows that its molecules are polar. It is difficult to understand this contradiction, since both measurements seem to give conclusive results.
The Thermal Decomposition of Ethylene Iodide
Authors: Arnold L. B. , Kistiakowsky G. B.
Published: November 2004

The homogeneous gaseous decomposition of ethylene iodide has been studied in the temperature interval 205°—230°C. It is found that two simultaneous reactions occur to give the same final products, ethylene and iodine. One is a reaction catalyzed by iodine atoms, similar to that found to occur in solutions. The other is a unimolecular decomposition. The activation energies of the two reactions are 30,200 cal. and 36,600 cal., respectively. It is shown that the results for the iodine catalyzed reaction in solution and in the gas phase are in agreement indicating that the solvent has only a slight effect, if any, on the reaction rate.
Vapor Viscosities and the Sutherland Equation
Authors: Arnold J. Howard
Published: November 2004

Reversing the usual procedure of calculating molecular diameters from the kinetic-theory viscosity equation, it is suggested that the Sutherland constant be found, to serve as a criterion for the accuracy of this constant as obtained from viscosity-temperature data. The molecular diameter is taken proportional to the cube root of the molar volume of the liquid at the boiling point, as indicated by the theory of corresponding states; the error is small. Review of the available values of C indicates that many of them are erroneous, because of experimental error, magnified by extrapolation, or possible failure of the Sutherland equation. The Vogel rule, C = 1.47 Tb, is found valid to within 10 percent. The recent data of Braune and Linke, Melaven and Mack, and Lowry and Nasini are criticized.
The Electric Moment as a Measure of the Ionic Nature of Covalent Bonds
Authors: Malone J. Gilbert
Published: November 2004

The two-electron bond with hydrogen is found to have the following values of μ×1018: H–As 0.10; H–P 0.36; H–I 0.38; H–S 0.63; H–Br 0.78; H–Cl 1.03; H–N 1.04; H–O 1.32. These values are believed to give the positions of the elements on an electronegativity scale which is shown to be similar to that prepared by Pauling. The reported moments for inorganic halides as well as the unpublished measurements of A. L. Ferguson and M. G. Malone, giving μ=3.1×10—18 for SbCl3 and μ=2.4×10—18 for SbBr3, give fair agreement in most cases with those calculated from the above scale. On the basis of calculated values appreciable moments are predicted for all trihalides of the fifth-group elements except PI3 and NCl3 which should give close to a zero moment.
On the Theory of the Structure of CH4 and Related Molecules: Part II
Authors: Van Vleck J. H.
Published: November 2004

Explicit calculations are made to examine whether the tetrahedral model of CH4 is really the most stable in the Hund-Mulliken and Slater-Pauling theories. The secular determinant involved in the H-M procedure is too complicated (degree 8) to solve generally, but three methods of approximation are given applicable in three different limiting cases, in all of which the tetrahedral model proves to be that of least energy quite irrespective of repulsions between the H atoms. The fact that two of the methods do not assume the carbon s-p separation to be small shows that s-p hybridization is not a necessary condition for tetrahedral valence bonds. Calculations are also given which show that in the Heitler-London-Pauling-Slater method the regular tetrahedron is superior to other models of somewhat lower symmetry. It is further calculated according to both the H-M and H-L-P-S schemes that in compounds of the form CH2X2, CHX3, and CH3X, the most stable models are tetrahedra of less symmetry than the regular tetrahedron; i.e., models with the valence angles somewhat distorted from 109.5° unless the C – H and C — X bonds are of equal intensity. The predicted directions of the deviations from 109.5° are in agreement with x-ray diffraction data for CH2Cl2 and CHCl3. The conclusion is rather prevalent in the literature that with s-p hybridization and electron pairing two bond axes tend to set themselves at 109.5°. This is shown incorrect; instead the angle can be anything between 90° and 180° depending on the relative intensities of the s and p bonds. If the s bonding power is not negligible, the angle between an NH axis and the pyramidal axis in NH3 should be somewhat greater than the value 54.7° which is obtained if the three NH axes are orthogonal and which is characteristic of pure p-bonding. Actually Dennison and Uhlenbeck find 68°, and Lueg and Hedfeld 73°, from band spectra. It is shown that CH4+ should be a flattened rather than regular tetrahedron, conceivably even being plane. Also CH3 should be a flatter pyramid than NH3.
The Calculation of Matrix Elements for Lewis Electronic Structures of Molecules
Authors: Pauling Linus
Published: November 2004

Starting from the discovery by Rumer that the eigen-functions corresponding to different distributions of valence bonds in a molecule can be represented by plane diagrams which provide information regarding their mutual linear independence, a very simple graphical method is developed for calculating the coefficients of the integrals occurring in the matrix elements involved in Slater's treatment of the electronic structure of molecules.
The Normal State of the Hydrogen Molecule-Ion
Authors: Dickinson B. N.
Published: November 2004

A variation function somewhat similar to that applied by Rosen to H2 is used in the discussion of the normal state of H2+.
Concentration of H2 Isotope
Authors: Lewis Gilbert N. , Macdonald Ronald T.
Published: November 2004

A method is described of producing any desired concentration of the isotope of hydrogen, H2, by electrolysis. Starting with twenty liters of water from an old commercial electrolytic cell and electrolyzing in four stages until only one-half of a cubic centimeter of water remained, this water had the specific gravity 1.073. Having shown that no large accumulation of the heavy isotopes of oxygen occurs and assuming that the density varies linearly with the fraction of H2, 2/3 of the hydrogen in this water is H2. It is shown that a further reduction of volume to one-quarter will give 99 percent H2. In our electrolyses the percentage loss of H1 is to the percentage loss of H2 in the ratio of five to one. By two methods we have found 1 in 6500, as a provisional value for the concentration of H2 in ordinary water.
Molecular Vibrations of Three Particle Systems with Special Applications to the Ethyl Halides and Ethyl Alcohol
Authors: Cross Paul C. , Van Vleck J. H.
Published: November 2004

The vibrational potential of polyatomic molecules is discussed in the light of the theory of directed valence. Andrews' assumptions of ``valence forces'' are seen to be rather special, but at the same time are fairly good approximations under certain conditions. The normal vibrations of three body systems are calculated for the potential function V=12[k1(Δr1)2+k2(Δr2)2+k3(r102+r202)(Δγ)2]with r1, r2 radial coordinates and γ an angular one. The potential terms proportional to Δr1Δr2, etc., are treated as perturbations. These calculations are applied to the ethyl halide and ethyl alcohol molecules by considering the CH3, CH2 and OH groups as dynamic units. Force constants were determined which gave approximately the experimental frequencies. The calculation of the normal modes of vibration illustrate the approximate validity of the designation of the modes of vibration of unsymmetrical three body systems as two independent radial motions and an angular motion.
A Calculation of the Vibration Frequencies and Other Constants of the H2O Molecule
Authors: Van Vleck J. H. , Cross Paul C.
Published: November 2004

The calculation is based on the Slater-Pauling theory of directed valence, but supplemented by data from the band spectrum of the diatomic OH molecule. The heat of dissociation and valence angle, obtained incidentally, are in good agreement with experiment. The ``cross-terms'' in the vibrational potential prove to be of subordinate importance. It is found that two of the fundamentals should fall near 2.8μ, and that they should almost coincide. This designation of the observed wide absorption band at 2.6–2.8μ as the superposition of two fundamentals agrees with Mecke's interpretation of the H2O spectrum, but contradicts Johnston and Walker's. The computed value 1660 cm—1 of the third fundamental frequency ω3 differs from experimental determinations by only 4 percent, but any closer agreement than 15 percent is accidental in view of the approximate nature of the theory. Since ω3 represents a primarily angular vibration, its calculation is a particular test of the concepts of directed valence.
The Nature of the Chemical Bond. V. The Quantum-Mechanical Calculation of the Resonance Energy of Benzene and Naphthalene and the Hydrocarbon Free Radicals
Authors: Pauling Linus , Wheland G. W.
Published: November 2004

The secular equations corresponding to the five canonical structures for benzene and the forty-two for naphthalene, considered as six and ten-electron systems, respectively, are set up and solved with certain simplifying assumptions, leading to energy values differing by 1.1055α and 2.0153α, respectively, from those corresponding to unexcited (Kekulé-type) structures, α being a single exchange integral involving neighboring carbon atoms. Equating these values to the empirical values of the resonance energy, α is found to be about — 1.5 v.e.

It is pointed out that the dissociation of certain substituted ethanes into free radicals is due not to weakness of the carbon-carbon bond in the ethane but to the stabilization of the free radicals resulting from resonance among the structures in which the unpaired electron is located on the methyl carbon and those in which it is on other atoms (ortho, para, etc., to the methyl carbon). The secular equations for a number of such radicals have been solved, neglecting excited structures. The experimentally determined heat of formation of hexaphenylethane from triphenylmethyl, 0.5 v.e., when equated to the calculated value C–C+2.2156α, with C–C = 3.65 v.e., leads to α = — 1.4 v.e. The calculated tendencies towards dissociation are in satisfactory agreement with observation, such features as the smaller dissociating power of β-naphthyl than of α-naphthyl and of biphenylene than of diphenyl being accounted for, so that resonance among the structures considered may be accepted as the principal effect causing the stability of the hydrocarbon free radicals.
Activation Energies for Reactions of Atoms in Different States
Authors: Rollefson G. K. , Potts J. C.
Published: November 2004

A slight modification of Eyring's method enables the activation energy for the reaction of iodine monochloride with normal or with excited chlorine atoms to be calculated. The calculations indicate that normal chlorine atoms are much more reactive with respect to iodine chloride than are chlorine atoms excited to the 2P½ state. Experimental evidence supporting these calculations is obtained from the results of Rollefson and Lindquist with mixtures of hydrogen, chlorine and iodine monochloride.

In the modified method, the atomic interactions—which give rise to the activation energy—are obtained from the potential energies of those molecular states which may be adiabatically formed from atoms in the particular electronic states to be considered.
The Mechanism of Substitution Reactions
Authors: Olson A. R.
Published: November 2004

For many substitution reactions of the type AB+C→AC+B, the strength of the bond between A and B is too great to account for the rate of the reaction. For such reactions addition or simultaneous addition and dissociations must occur. From the quantum mechanical conception of bonds, it is shown that a spatial inversion of A occurs for every such substitution. This theory is applied in detail to some experiments on the Walden inversion, and a definite correlation between rotational and configurational changes is obtained. Its use is studying molecular rearrangements and cis-trans isomerization is sketched.
The Thermal Dissociation of Cyanogen into Cyanide Radicals
Authors: Kistiakowsky G. B. , Gershinowitz H.
Published: November 2004

The thermal dissociation of cyanogen into cyanide radicals around 1200°C has been studied. Determining the variation of CN concentration with temperature by the intensity of absorption bands, the heat of dissociation 77±4 kg cal. has been obtained. With this quantity the heat of dissociation of hydrogen cyanide into hydrogen atoms and cyanide radicals is calculated as 94.5±4 kg cal. By the use of existing thermochemical data these quantities are shown to be the most probable values for the energies of the C–C and C–H bonds, respectively. The heat of sublimation of carbon is calculated as 154±3 kg cal.
Electron Diffraction and Molecular Structure
Authors: Dornte Ralph W.
Published: November 2004

The molecular structures of cis- and trans- dibromoethylene, tribromoethylene, vinyl bromide, tetrachloroethylene and trichloroethylene have been determined by the method of electron diffraction in gases. It has been found that the diffraction pictures of these substances can be satisfactorily represented by plane structures having the following interatomic distances: C=C 1.3, C–Br 2.0 and C–Cl 1.8A. The diffraction in carbon tetrachloride has been investigated with several widely differing electron velocities.
Mathematical Methods for Computing Thermodynamic Functions from Spectroscopic Data
Authors: Kassel Louis S.
Published: November 2004

Methods of summation are given for the Q-sum, and the related sums which are needed in calculating free energies, entropies and heat capacities from spectroscopic data. All necessary formulas are presented for the treatment of a linear molecule with arbitrary orbital angular momentum, spin multiplicity and nuclear symmetry. The nonlinear molecule is much more difficult; necessary formulas are given for the special case of a 1Σ molecule with two equal principal moments of inertia. The application of these methods is illustrated by the calculation of the entropy, heat content and heat capacity of carbon monoxide from 50 to 5000°K.
The Normal State of the Hydrogen Molecule
Authors: Weinbaum Sidney
Published: November 2004

A simple wave function for the normal state of the hydrogen molecule, in which both the atomic and ionic configurations are taken into account, was set up and treated by a variational method. The dissociation energy was found to be 4.00 v.e. as compared to the experimental value of 4.68 v.e. and Rosen's value of 4.02 v.e. obtained by use of a function involving complicated integrals. It was found that the atomic function occurs with a coefficient 3.9 times that of the ionic function. A similar function with different screening constants for the atomic and ionic parts was also tried. It was found that the best results are obtained when these screening constants are equal. The addition of Rosen's term to the atomic-ionic function resulted in a value of 4.10 v.e. for the dissociation energy.
The Determination of the Structures of Methane Derivatives by the Electron Diffraction Method
Authors: Dornte Ralph W.
Published: November 2004

The molecular structures of several bromine and iodine derivatives of methane have been determined by the electron diffraction method. For tertiary butyl bromide it has been found that the tertiary carbon atom has the tetrahedral angles between the valence bonds, and the interatomic distances are: tertiary C— methyl C 1.55A and tertiary C–Br 2.06A. In methyl bromide and iodide the C—X distances are 2.06 and 2.28A, respectively. In methylene bromide and iodide it has been found that the angle between the C—X bonds is 125° and the interatomic distances are: C–Br 2.03, Br–Br 3.61, C–I 2.28 and I–I 4.06A. In bromoform the angles formed by the C–Br bonds are 115°, and the interatomic distances are: C–Br 2.05 and Br–Br 3.46A.
On the Symmetric States of Atomic Configurations
Authors: Seitz F. , Sherman Albert
Published: November 2004

In the secular equations used by Eyring and his school the equations are of high order in general. When cognizance is taken of the symmetry of the configuration considered the secular equation may factor considerably. It is to be expected that the wave function for the lowest state will be invariant under the group which expresses the symmetry of the atomic configuration. This expectation is fulfilled in all cases considered. A general method is set forth upon which a derivation of such symmetric states may be carried out, and the reduced secular equation obtained. Several interesting applications of this method are carried through, including the case of eight identical orbits, centered at the corners of a cube, and eight orbits possessing tetrahedral symmetry, as in methane. The vector model is discussed and applied to the cases considered.
Near Infrared Absorption of Solutions of Hydroxides and Hydrolyzing Salts
Authors: Gordy Walter
Published: November 2004

Absorption bands have been observed at 2.60μ, 2.30μ, 1.81μ, 1.30μ, 1.22μ, 1.04μ, 0.87μ, 0.79μ, 0.75μ and 0.67μ in aqueous solutions of hydroxides and hydrolyzing salts. From the behavior of the salt solutions the bands at 2.60μ and 1.81μ were found to be characteristic of the hydroxide molecule, while the band at 2.30μ was found to be characteristic of the OH ion. It was found that if the 2.30μ band, and the 3.65μ and 5.20μ bands previously observed were considered as fundamentals, the remaining bands observed could be classified as harmonics.
Absorption of Light in Organic Compounds
Authors: Chako Nicholas Q.
Published: November 2004

In this paper a first attempt is made to evaluate from published measurements the total strength and width of absorption bands of organic compounds, and to correlate that with the nature of the solvent and the constitution of the substance. It turns out that none of the quantities that one could consider from the theoretical standpoint remains constant.
Photochemical Studies. XVIII The Fluorescence of Acetone Vapor
Authors: Fisk Charles F. , Noyes W. Albert
Published: November 2004

A thorough understanding of the photochemical decomposition of acetone vapor must be accompanied by a study of the fluorescence of this substance. Previous work had indicated that the fluorescence is relatively weak, is affected by oxygen and (at least over part of the spectral range involved) possessed a fine structure. In the present work it is shown that the intensity of the fluorescence follows the customary behavior observed in such phenomena in that it is quenched by the acetone vapor itself. A discussion is given as to the relationship of the fluorescence to the possible modes of photochemical decomposition.
On the Question of ``Afterburning'' in Gas Explosions
Authors: Lewis Bernard , von Elbe Guenther
Published: November 2004

The works of David, Brown and El Din, Ellis and Morgan, and Ellis and Wheeler on ``afterburning'' have been reviewed critically and found to contain no conclusive evidence for ``afterburning.'' Experiments have been performed on explosions of hydrogen-oxygen mixtures with different inert gas in spherical vessels of different sizes which show, on the contrary, the absence of this phenomenon. The explosion method for determining heat capacities of gases may not be criticized on this account.
The Entropy of Polyatomic Molecules
Authors: Halford J. O.
Published: November 2004

A general expression for the entropy of the polyatomic molecule, rigid in the sense that only one form with a given set of moments of inertia is possible, is tested by comparison of calculated and experimental values. The results are satisfactory for molecules with as many as seven rotational degrees of freedom.
Photochemical Studies. XIX The Ultraviolet Absorption Spectrum of Acetone Vapor
Authors: Noyes W. Albert , Duncan A. B. F. , Manning Winston M.
Published: November 2004

The ultraviolet absorption spectrum of acetone vapor has been photographed. The well-known absorption region in the neighborhood of 3000A, common to all ketones, is found to have on its long wave end a series of discrete absorption bands. The wave-lengths of many of these bands have been measured and a vibrational analysis is given. A second absorption region beginning about 1960A and extending toward shorter wave-lengths is found to consist of several groups of bands, the bands within each group being separated by relatively small frequency differences. The analysis of this band system may be accomplished by assuming several energy levels close together in the upper state together with four fundamental frequencies in the upper state and two in the lower. Evidence for further absorption regions extending to below 1200A has been found and the approximate positions of these regions are given. These bands evidently belong to different electron transitions from the others.
The Disappearance of Hydrogen in the Presence of Potassium and Lithium Ion Sources
Authors: Kunsman C. H. , Nelson R. A.
Published: November 2004

The disappearance of hydrogen in the presence of iron-alkali catalysts, sources of K+ ions and a synthetic spodumene mixture, a source of Li+ ions, was investigated. In these experiments, like those previously reported by the authors, no gas phase reaction was detected which could be attributed to the bombardment of hydrogen by positive ions with speeds up to 565 volts. It was concluded that all cleanup effects could be accounted for by reactions on or within the materials used as ion sources.
On the Theory of Strong Electrolyte Solutions
Authors: Kirkwood John G.
Published: November 2004

The nature of the approximations involved in the derivation of the Poisson-Boltzmann equation of the Debye-Hückel theory is investigated in detail from the standpoint of classical statistical mechanics. The validity of the initial Debye approximation, under the restrictions originally imposed upon it, is confirmed. Deviations arising from fluctuation terms and van der Waals forces are roughly estimated. An alternative to the Bjerrum method for the treatment of ions of small size and high valence is outlined.
A New Electroaffinity Scale; Together with Data on Valence States and on Valence Ionization Potentials and Electron Affinities
Authors: Mulliken Robert S.
Published: November 2004

A new approximate ``absolute'' scale of electronegativity, or electroaffinity, is set up. The absolute electroaffinity on this scale is equal to the average of ionization potential and electron affinity. These quantities must, however, in general, be calculated not in the ordinary way, but for suitable ``valence states'' of the positive and negative ion. Also, the electroaffinity of an atom has different values for different values of its valence; in general the electroaffinity as here calculated (in agreement with chemical facts) is larger for higher valences. Electroaffinity values have been calculated here for H, Li, B, C, N, O, F, Cl, Br, I. They show good agreement in known cases with Pauling's electronegativity scale based on thermal data, and with the dipole moment scale. The present electronegativity scale (like the others) is rather largely empirical, especially as to its quantitative validity; and it remains to be seen whether or not the latter will be more than very rough when tested for a wider range of cases. Nevertheless the new scale has a degree of theoretical background and foundation which throws some new light on the physical meaning of the concept of electronegativity (or electro-affinity). The basis of the present scale, it should be mentioned, is simpler and more certain for univalent than for polyvalent atoms.—The nature of valence states of atoms is briefly discussed. It is hoped that the tabulations of atomic valence state energies and valence state ionization potentials and electron affinities given at the end of this paper may be useful in problems of molecular structure.