bluuebunny/crossref_metadata_2025 huggingface dataset:
Shear stress alters the expression of myelin‐associated glycoprotein (MAG) and myelin basic protein (MBP) in Schwann cells
Authors: Gupta Ranjan , Truong Linh , Bear David , Chafik Dara , Modafferi Edward , Hung Clark T.
Published: April 2005

Schwann cells within a peripheral nerve respond robustly after an axonal injury. Recent results have revealed that Schwann cells undergo concurrent proliferation and apoptosis after a chronic nerve injury that is independent of axonal pathology. Although the exact nature of the stimulus that produces this Schwann cell response remains unknown, we postulated that this response may be triggered directly by mechanical stimuli. Thus, we sought to determine how pure Schwann cells responded to a sustained shear stress in the form of laminar fluid flow by evaluating for proliferation, expression of S‐100, myelin‐associated glycoprotein (MAG), and myelin basic protein (MBP). Immunohistochemistry demonstrated that the Schwann cells were positive for S‐100, MAG, and MBP in greater than 99% of the experimental cells. Stimulated cells also revealed an increased rate of proliferation by as much as 100% (p <.001). The mRNA expression of MAG and MBP was down‐regulated by 21% (p <.035) and 18% (p <.015), respectively, in experimental cells from RT‐PCR assays. Furthermore, Western blot showed a down‐regulation in MAG and MBP protein expression by 29% (p <.035) and 35% (p <.02), respectively. This study provides novel information regarding Schwann cell direct response to this physical stimulus that is not secondary to an axonal injury. © 2005 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.
Will the EC Zoos Directive increase the conservation value of zoo research?
Authors: Rees Paul A.
Published: April 2005

Article 9 of the Convention on Biological Diversity 1992 requires parties to adopt measures for the ex situ conservation of biodiversity. Within the European Union this has been implemented by the Zoos Directive. The Directive requires zoos and aquariums to adopt a conservation role. Zoos may comply with the Directive by undertaking research from which conservation benefits accrue. However, most current zoo research is concerned with behaviour, environmental enrichment, nutrition and reproduction, and is therefore largely irrelevant to ex situ conservation. It is unlikely that zoos will increase their output of conservation relevant research because most do not have appropriate resources. Furthermore, as an alternative to undertaking research, a zoo may comply with the Directive by engaging in training, information exchange or captive breeding. Most, if not all, zoos already engage in at least one of these activities and therefore may comply with the Directive by doing nothing.
Some of them came home: the Cayman Turtle Farm headstarting project for the green turtle Chelonia mydas
Authors: Bell Catherine D.L. , Parsons Joe , Austin Timothy J. , Broderick Annette C. , Ebanks-Petrie Gina , Godley Brendan J.
Published: April 2005

Headstarting is a management technique employed to enhance recruitment of turtles into diminished or extirpated marine turtle populations. Although there have been numerous projects worldwide, there has been a paucity of detailed investigations into its efficacy. Between 1980 and 2001, 16,422 captive-raised hatchlings and 14,347 yearling green marine turtles Chelonia mydas were released from the Cayman Turtle Farm. Approximately 80% of all turtles released were subject to some form of tagging, including living tags. A total of 392 tagged animals have been recaptured at intervals of up to 19 years. Of this total, 160 individuals were captured in the Cayman Islands and 232 were recorded from other locations within the wider Caribbean and southeastern USA. There was significant variation in the release-recapture intervals at the three countries with most returns (Cayman, Cuba and Nicaragua). A positive relationship exists between time at large and size at recapture and data suggest growth rates comparable to those of wild green turtles in the region. There have been at least six living tag returns, four involving turtles released as yearlings and two involving turtles released as hatchlings. This demonstrates an age at maturity that may be as short as 15–19 years, depending on stage of release. Results show that some headstarted turtles are moving around the Caribbean, surviving for long periods of time, contributing to the local breeding population, and are possibly displaying shifts in habitat utilization with age similar to those recorded by wild individuals.
Hunting in northern French Guiana and its impact on primate communities
Authors: de Thoisy Benoit , Renoux François , Julliot Catherine
Published: April 2005

The Guianas contain one of the largest single remaining tracts of undisturbed tropical rainforest in the world, but this forest and its fauna are facing increased threats. In the north of French Guiana both anthropogenic pressures and conflicts between settlements related to the use of natural resources are growing. Based on surveys in 17 forest sites we show that hunting pressure was the main factor determining current primate species richness, masking the effects of logging or forest type. Three of the larger species, the red howler monkey Alouatta seniculus, black spider monkey Ateles paniscus and tufted capuchin Cebus apella, were less abundant in hunted areas. In the areas around four settlements the harvested biomass of primates was low compared to other game species, but the harvests were close to or beyond the maximal sustainable thresholds for the red howler monkey and tufted capuchin. In French Guiana primates are either fully protected by law (the spider monkey and white-faced saki Pithecia pithecia), or their hunting is restricted to subsistence use (howler monkey, tufted capuchin and wedge-capped capuchin Cebus olivaceus). Most hunted meat is, however, destined for sale. Current conservation policy in French Guiana is limited to legal protection for some species and areas, and laws are poorly enforced. Although large areas of forest and its wildlife are protected simply by their remoteness, there is an increasingly urgent need for the legal protection of all primate species, and the establishment of large protected areas and efficient forest management schemes to minimize the impacts of logging and hunting.
The Tongan flying fox Pteropus tonganus: status, public attitudes and conservation in the Cook Islands
Authors: Cousins Jenny A. , Compton Steve G.
Published: April 2005

In the Cook Islands the population of Pteropus tonganus tonganus is thought to be declining, but a lack of knowledge of its status, feeding and roosting requirements has precluded effective conservation plans. We surveyed P. t. tonganus on the Cook Islands through observations, counts and interviews with local residents. We estimated the population to be c. 1,730 on Rarotonga and 78 on Mangaia. A lack of suitable habitat on Mangaia was the most important factor affecting abundance. Overhunting appears to have reduced the populations on both islands. All roost sites were found in undisturbed forest on steep slopes and ridges in the inner and most inaccessible parts of the islands, with roost preference determined by the relative safety from humans rather than food availability. The residents of the Cook Islands seem generally unaware of the serious threat the bats face, with little thought for sustainable hunting. For successful conservation it will be important to alter people's negative perception of these mammals, promoting the value of the bats both ecologically and as a potential source of income from tourists. Habitat protection and enhancement, particularly on Mangaia, will be essential.
The state of lemur conservation in south-eastern Madagascar: population and habitat assessments for diurnal and cathemeral lemurs using surveys, satellite imagery and GIS
Authors: Irwin Mitchell T. , Johnson Steig E. , Wright Patricia C.
Published: April 2005

The unique primates of south-eastern Madagascar face threats from growing human populations. The country's extant primates already represent only a subset of the taxonomic and ecological diversity existing a few thousand years ago. To prevent further losses remaining taxa must be subjected to effective monitoring programmes that directly inform conservation efforts. We offer a necessary first step: revision of geographic ranges and quantification of habitat area and population size for diurnal and cathemeral (active during both day and night) lemurs. Recent satellite images are used to develop a forest cover geographical information system, and censuses are used to establish range boundaries and develop estimates of population density and size. These assessments are used to identify regions and taxa at risk, and will be a useful baseline for future monitoring of habitat and populations. Precise estimates are impossible for patchily-distributed taxa (especially Hapalemur aureus, H. simus and Varecia variegata variegata); these taxa require more sophisticated modelling.
Decline of the endemic Hose's langur Presbytis hosei in Kayan Mentarang National Park, East Borneo
Authors: Nijman Vincent
Published: April 2005

I present data on the decline of Hose's langur Presbytis hosei over a 7-year period in the Kayan Mentarang National Park in the remote northern part of East Kalimantan, Indonesia. In 1996 Hose's langurs were among the most common primates in the Nggeng Bio valley, occurring at densities of over two groups km−2, and could be observed almost daily. A repeat census of the same area in 2003 indicated that these densities had dropped by 50–80%, and observation of the species in the valley had become a rare occurrence. During the 7-year period the forest remained in a relatively pristine condition but, despite being part of a National Park, active protection of the valley was lacking and hunting was common. From interviews with local hunters and Park staff it appeared that hunting for bezoar stones (visceral excretions found in langurs and used in traditional medicine) was the primary reason for the observed decline in Hose's langur. In 1998 a merchant calling at a nearby village had expressed an interest in the stones and guaranteed to purchase them, and this sparked excessive hunting of Hose's langur in the area, to such an extent that 3 years later this hunting was no longer economically viable. This study demonstrates that, with increasing access to markets, hunting large vertebrates for medicinal purposes, even for short periods only, can have a dramatic impact on population numbers. In such cases, habitat protection alone does not guarantee preservation, and more active protection of wildlife is required.
Absolute photon cross sections for Balmer lines from proton‐SO2 collisions
Authors: Ammirati Thomas F. , Monce Michael N. , Tadesse Desta , Luthy Peter M. , Alvarado Naja
Published: April 2005

Observations of atomic emissions from the Io plasma torus and previously published laboratory work suggest that proton collisions with SO2 may be a source of some of the spectral lines. We present an analysis of Balmer series lines seen in the spectra of collisions of protons with SO2 over the range of 50 to 250 keV. Absolute emission cross sections for these lines are measured to be on the order of 10−19 cm2 and are in rough agreement with a parametric model for electron capture which supports charge‐transfer ionization of the SO2 target.
Storm‐time convection electric field in the near‐Earth plasma sheet
Authors: Hori T. , Lui A. T. Y. , Ohtani S. , C:son Brandt P. , Mauk B. H. , McEntire R. W. , Maezawa K. , Mukai T. , Kasaba Y. , Hayakawa H.
Published: April 2005

We have examined the electric field observations made by the Geotail spacecraft in the near‐Earth magnetotail during magnetic storms to study enhanced convection and the associated electric field that is thought to be key to causing the injection of particles into the ring current. Several recent modeling studies of the storm‐time ring current suggest that an enhanced convection electric field in the magnetosphere, which is induced by a continuous southward interplanetary magnetic field (IMF), is responsible for steady particle transport into the inner magnetosphere during the storm main phase. The enhanced convection is envisioned to weaken, or cease after the main phase in response to the decrease of southward IMF, leading to the formation of a relatively symmetric ring current around the Earth during the recovery phase. However, surprisingly, our present study has not found clear evidence for the existence of such a large, steady earthward convection during either the storm main phase or the recovery phase. The observed electric field properties in the near‐Earth plasma sheet are basically classified into two categories: One is characterized by intermittent bursts of fluctuating duskward electric fields associated with substorm expansions, and the other is dominated by a relatively steady, weak duskward electric field. The weak strength of the convection electric field in the latter category is seen even during storm main phase. The statistical study on this relatively steady, weak field shows that it has a weak duskward component of ∼0.3 mV/m on average during both the main and recovery phases, which is almost comparable to that observed during quiet times. Their comparison with the solar wind parameters and the polar cap potential drop calculated using the Boyle model and Weimer model reveals that the weak duskward electric field tends to show poor correlation with these parameters, suggesting that storm‐time convection electric field in the plasma sheet is not directly driven by either of them. These results imply that in the near‐Earth plasma sheet beyond geosynchronous distance, particle injection for the storm‐time ring current is not governed by enhanced convection induced by the solar wind, contrary to conclusions based on simulation studies of the storm‐time ring current. The present study suggests the importance of re‐examining the contribution to the ring current from the near‐Earth plasma sheet for both substorm and nonsubstorm time intervals on the basis of observations made in the magnetosphere.
Model simulations of the Gulf of Maine response to storm forcing
Authors: Fan Y. , Brown W. S. , Yu Z.
Published: April 2005

The storm response of the Gulf of Maine/Georges Bank region was investigated using the Dartmouth three‐dimensional, nonlinear, finite element coastal ocean circulation model called QUODDY, with uniform density and quadratic bottom stress. A suite of model hindcast experiments were conducted for the 4–8 February 1987 period that featured a strong nor'easter. The model was forced at the open ocean boundaries by the M2 semidiurnal tidal sea level and in the interior by realistic surface wind stresses and, in some cases, atmospheric pressure. The reference model run, with just tidal and wind stress forcing and a time‐space constant bottom drag coefficient Cd of 0.005, captured 65% of the observed detided, low‐pass filtered or “subtidal” sea level variance of a representative array of coastal and bottom pressure stations in the Gulf. However, there remained large unexplained model/observed sea level differences, particularly during the storm. Model sensitivity testing to a realistic range of constant Cd values did not improve model results significantly. However, results of a model run in which atmospheric pressure forcing, derived through linear interpolations of regional measurements, was added to wind stress forcing captured 82% of the observed subtidal sea level variance.
Observations of divergence and upwelling around Point Loma, California
Authors: Roughan Moninya , Terrill Eric J. , Largier John L. , Otero Mark P.
Published: April 2005

Historical records of near‐surface water temperatures in the Southern Californian Bight often show a preferential cooling in the lee of headlands such as Point Dume, Palos Verdes, and Point Loma. At times, this cooler water is associated with an increase in chlorophyll‐a as is evident in satellite images of ocean color from the region. Here we combine hydrographic data from a 1 day cruise aboard the RV Roger Revelle (a precursor to the 0304 California Cooperative Oceanic Fisheries Investigations (CalCOFI) cruise) with high‐frequency (HF) radar (CODAR) measurements, satellite images, and long‐term thermistor records of near‐surface temperature to identify a small‐scale, isolated upwelling in the lee of Point Loma (32.5°N). Associated with the more saline water downstream of the headland are higher nutrient concentrations, an increase in chlorophyll‐a concentration, and a bloom of chain‐forming diatoms, indicative of a mature upwelling system. It is suggested that this upwelling is not primarily due to local or remote wind forcing but rather to the divergence of the prevailing southerly flow as it passes the Point Loma headland. Time series of surface vorticity calculated from HF radar measurements of sea surface velocity show that as the flow separates from the headland, relative vorticity increases offshore of the cape. Inshore, the time series of divergence/convergence shows a tendency toward divergence at the surface, indicating a preferential upwelling which appears to raise the thermocline, thus resulting in a flux of cold nutrient‐rich water to the surface. In the presence of high nutrients and light, photosynthetic organisms bloom in these upwelled waters as they are advected away from the headland and offshore by the prevailing surface currents.
Estimating soil hydraulic parameters from transient flow experiments in a centrifuge using parameter optimization technique
Authors: Šimůnek Jirka , Nimmo John R.
Published: April 2005

A modified version of the Hydrus software package that can directly or inversely simulate water flow in a transient centrifugal field is presented. The inverse solver for parameter estimation of the soil hydraulic parameters is then applied to multirotation transient flow experiments in a centrifuge. Using time‐variable water contents measured at a sequence of several rotation speeds, soil hydraulic properties were successfully estimated by numerical inversion of transient experiments. The inverse method was then evaluated by comparing estimated soil hydraulic properties with those determined independently using an equilibrium analysis. The optimized soil hydraulic properties compared well with those determined using equilibrium analysis and steady state experiment. Multirotation experiments in a centrifuge not only offer significant time savings by accelerating time but also provide significantly more information for the parameter estimation procedure compared to multistep outflow experiments in a gravitational field.
Effects of Temperature Gradients, Self-Absorption, and Line Shape on Apparent Rotational Temperatures of OH
Authors: Elliott B. H. , Penner S. S.
Published: April 2005

The effect on apparent rotational temperatures (of OH) of adjacent radiating and absorbing regions at different temperatures and of spectral line shape, coupled with varying degrees of self-absorption, has been studied. The calculations emphasize the fact that definitive conclusions regarding interpretation of flame spectra are difficult to obtain by use of conventional low-resolution spectroscopic studies of flames. Multiple path experiments, or absorption studies with a discrete line source, appear promising provided they are restricted to conditions under which the spectral line shape is known.
The Quenching of Mercury Resonance Radiation. III. The Total Effective Cross Sections of Some Saturated Compounds
Authors: Darwent B. deB. , Phibbs M. K.
Published: April 2005

Total effective cross sections have been measured for 22 compounds in the processes 3P1 ← 3P0 and 3P1 ← 1S0, by which mercury resonance radiation is quenched. The compounds include the methylamines, methyl halides, methyl alcohol, dimethyl ether, H2S, ethyl mercaptan, dimethyl sulfide, ethylene oxide, cyclo-paraffins, and dimethyl mercury. The cross sections varied from less than 0.01A2 (fluoroform) to 46A2 (dimethyl mercury). In general σQ2 is increased when a carbon atom is replaced by oxygen and even larger increases occur when the substituting atom or group is, or contains, nitrogen, sulfur, or mercury. The presence of halogens, except fluorine, increases σQ2; the introduction of fluorine reduces the cross section.
Evaluation of Some Electron Repulsion Integrals Needed in Molecular Quantum Mechanics. II. Use of the Neumann Expansion in Evaluation of Two Electron Three-Center Repulsion Integrals
Authors: Barker Roland S. , Eyring Henry
Published: April 2005

Formulation of two types of three-center electron interaction integrals in convergent series is explicitly considered. These expressions place no restrictions on the effective nuclear charges of the composite atomic orbitals. The basic expansions are made in elliptical coordinates. The auxiliary functions used are discussed in detail and when of known form, references to the original literature are cited. Examples arising in the triatomic hydrogen molecular complex are given. Possibilities of extension of the method to complex molecules are pointed out.
Unified Orbital Treatment of Ethylene
Authors: Mueller C. R.
Published: April 2005

Quantum-mechanical calculations of the properties of pi and sigma bonds in ethylene were carried out using atomic, molecular, and semilocalized orbital methods. Theoretical values were obtained for binding, and singlet-triplet separation energies. The polarizabilities of these bonds were also calculated, as were the charge distributions.

The electronic structure of the π bond was found to be largely localized contrary to the assumptions of molecular orbital theory, but the sigma bond was found to have molecular orbital structure.

On the basis of calculations of bond polarizability it was concluded that π bond accounts for about 90 percent of total bond polarizability. This result is due to the sp2 hybridization of the sigma bond.

The results of extended orbital treatments of π-electron systems are also discussed.
Mass Spectrometric Study of the Molecular Sublimation of Graphite
Authors: Honig Richard E.
Published: April 2005

The emission of neutral and charged carbon molecules from spectroscopically pure graphite has been studied by rate of vaporization experiments in a 180° mass spectrometer. Small filaments (diameter: 0.015 in.), heated by ac up to 2600°K, yielded neutral particles which were converted into positive ions by bombardment with low-energy electrons. C3+, C2+, and C1+ ions were found. Although the effects of fragmentation and of differences in ionization cross sections may not be negligible, it is believed that carbon vapor consists largely of C3 molecules. Graphite was found to emit negative ions containing from one to eight carbon atoms. C2—, C4—, and C3— were the most abundant species, in that order. A search was made for carbon particles emitted as positive ions, but none were found.

Heats of activation were obtained for the neutrals and the more abundant negative ions from the slopes of logp vs 1/T plots. Identical heats measured for C1 and C3 (178±10 kcal/mole at 2400°K) suggest that these two species may sublime at rates that are interdependent. Thus, this value may not be representative of the true heat of sublimation of C1. For C2, a heat of 199±20 kcal/mole was measured at 2400°K. Electron affinities have been computed for C1, C2, and C3, and estimated bond energies deduced for C2 and C3. Some of the earlier measurements of the heat of sublimation of graphite, obtained from rates of vaporization and equilibrium effusion, but without mass analysis, have been reinterpreted, taking into account the complex character of the sublimation processes.
A Note on the Fluorine Resonance Shifts
Authors: Saika A. , Slichter C. P.
Published: April 2005

A theoretical analysis is given of the fluorine magnetic resonance shifts in molecules. It is shown that the large range of shifts among different fluorine compounds arises from the effects of binding on the magnetic fields at the nucleus produced by the orbital motion of the electrons in the unfilled valence shell. The simple dependence on ionic character of the bond is also explained. The chemical shift between F2 and HF is calculated to be 14×10—4 compared to the experimentally observed value 6.3×10—4.
On the Scavenger Effect in the n, γ Reaction in Carbon Tetrachloride
Authors: Hamill William H. , Williams Russell R.
Published: April 2005

Neutron bombardment of liquid carbon tetrachloride yields 38.5 min Cl38, and approximately 40 percent of the induced activity is retained in organic form. Dissolved chlorine reduces this retention in a regular fashion to approximately 25 percent at a concentration of 6 mole percent. Allyl chloride increases retention to 53 percent in equivalent concentrations. Neither of these ``scavenger effects'' is significantly dependent on the intensity of total dose of concomitant nonactivating pile radiation. This rules out the radiation-decomposition theory of scavenger action and supports an atom-radical diffusion-recombination mechanism.
The Theory of Radioactive Ion Exchange
Authors: Pitts E.
Published: April 2005

Experiments reported by other workers have shown that when a precipitate of silver bromide is shaken with a solution containing either silver or bromide ions, some of which are radioactive, the radioactive strength of the solution decreases. The final value reached corresponds to a uniform distribution of the active material throughout both solid and solution. No agreement on the interpretation of these results has up until now been reached. Two possible mechanisms for this exchange are described, and their consequences are examined. A new theoretical treatment is given which includes a consideration of the effect of the spread in crystal sizes, which was neglected in previous discussions of the problem. From those results, a new method of comparison between theory and experiment is suggested. This shows unambiguously that the exchange of silver ions is in agreement with predictions based on the hypothesis that the ions diffuse through the solid. It is shown that the exchange of bromide ions cannot be explained in this way. Values obtained for the diffusion constant of silver are in fair agreement with those from other sources. The relation of these results to the various suggestions put forward by other workers is discussed.
Radiation-Induced Reaction between Iodine and Heptane
Authors: Forsyth Paul F. , Weber Edward N. , Schuler Robert H.
Published: April 2005

The radiation-induced reaction between iodine and n-heptane has been studied with a view to its use in the quantitative determination of free radical production in the radiolysis of liquid hydrocarbons. The yield of this reaction has been found to be nearly independent of iodine concentration and of temperature of the sample. The reaction is inhibited by the presence of dissolved oxygen. For each mole of hydrogen produced, 0.6 mole of iodine is absorbed which indicates that free radical production is a major component of the over-all process. The primary decomposition yield is of the order of 10 bonds broken per 100 ev of absorbed energy.
Ion-Exchange and Adsorption Column Kinetics with Uniform Partial Presaturation
Authors: Vermeulen Theodore , Hiester Nevin K.
Published: April 2005

The available mathematical solutions for fixed-bed concentration histories apply primarily to one-component systems in adsorption and to two-component systems in ion exchange. Thomas has developed explicit general relations for the saturation of an adsorbent bed initially free of saturating component by a fluid phase containing only this component; as well as for the converse elution situation.

These results are extended here to cases of mixed binary feeds (in ion exchange), and cases of columns that are uniformly partially saturated prior to the run under study. New definitions of the dimensionless parameters that characterize the sorption processes render the existing numerical framework applicable for evaluating this broadened range of operating conditions. From the theoretical standpoint, these new parameters clarify the mathematical interrelationships between adsorption and ion exchange, between saturation and elution, and between sorption of trace components and sorption of gross or bulk components. A method is suggested for calculating physical-adsorption operations which do not conform to Langmuir isotherms.

Calculation procedures based upon this approach are illustrated by an idealized but representative example.
Thermodynamics of Adsorption
Authors: Tykodi Ralph J.
Published: April 2005

The thermodynamics of the adsorption of gases on solids is developed in terms of a two-component system. It is shown that all solids swell during the adsorption process, and that spontaneous first-order phase changes in the adsorbed layer are unlikely. The ideal process: i(gas) → i(adsorbed)—constant environment—is introduced and discussed; thermodynamic functions appropriate to the process are defined. Two types of heat capacity of the adsorbed layer are defined and discussed. The chemical potential of a solid is treated at some length.
Neutron Diffraction Study of Liquid Mercury
Authors: Vineyard George H.
Published: April 2005

The neutron diffraction pattern of liquid mercury at 23°C has been measured. The pattern has general resemblance to the x-ray patterns obtained by Debye and Menke and by Jennings, although the angular resolution is not quite as good. The inner peak which has been reported by several investigators is not seen. The radial density function has been calculated from the data.
Excited States of the Naphthalene Molecule. I. Symmetry Properties of the First Two Excited Singlet States
Authors: McClure Donald S.
Published: April 2005

The detailed polarization properties of the bands in absorption and fluorescence spectra of the naphthalene molecule have been determined by a method which makes use of a substitutional solid solution of naphthalene in durene. A single crystal of about 0.1 percent naphthalene in durene was cut so that the short axes of the naphthalenes lie strictly parallel to the surface and in one direction. The spectra were then determined in polarized light at 20°K under moderately high dispersion. The results clearly indicate that the first state is 1B3u (the transition from the ground state is long-axis polarized) and the second 1B2u. Vibrational-electronic interaction involving b1g vibrations apparently couples the first state with the second, and this results in a large short-axis polarized transition moment. This fact has been at the root of most of the previous difficulties with analysis of the spectra.
Vacuum Ultraviolet Photochemistry, Part II. Nitrous Oxide at 1849 A
Authors: Zelikoff Murray , Aschenbrand Leonard M.
Published: April 2005

The photolysis of nitrous oxide at 1849 A has been studied and the quantum yield ratios φN2O/φN2, φN2O/φO2, and φN2O/φNO measured. The former two ratios compare well with the same ratios at 1470 A and the latter ratio is pressure dependent. It appears that the photolysis mechanism at 1849 A is similar to that at 1470 A. The absorption coefficient of N2O is calculated from the photolysis data and found to compare well with previous work.
Thermodynamics of Alcohol-Hydrocarbon Mixtures
Authors: Kretschmer Carl B. , Wiebe Richard
Published: April 2005

The thermodynamic properties of alcohol-hydrocarbon mixtures are explained on the basis of association of the alcohol to form polymers of all orders from two to infinity. Our treatment differs from that of Redlich and Kister in using the Flory-Huggins expression for free energy, and an equilibrium constant in terms of concentrations rather than mole fractions. The equations derived are in satisfactory agreement with vapor-pressure data for several systems. They also agree with the experimental energy of mixing and excess entropy for ethanol-methylcyclohexane solutions. For mixtures of alcohols with aromatic hydrocarbons, it is necessary to assume that each alcohol monomer or polymer can combine with one molecule of hydrocarbon.
Oxidation Ions in Hydrocarbons on Ultraviolet Irradiation
Authors: Gemant Andrew
Published: April 2005

Ultraviolet irradiation, mostly in the presence of a peroxide, increases the electrical conductivity, thus produces oxidation ions in solutions of aromatic diols, to a lesser extent in those of monohydroxyl compounds, and to a still lesser, but measurable, extent in a hydrocarbon itself, namely o-xylene. Ultraviolet spectroscopy permits identification of the chief oxidation products: o-phthalic aldehyde in the case of o-xylene. The ions are probably oxidation intermediates of relative stability. Whereas the anion can be derived from the acids, the cations are probably oxonium-type ions, derivable from the o-aldehydes formed.
Magnetic Dipolar Interactions in MnO and in Ferrites
Authors: Kaplan Jerome I.
Published: April 2005

The magnetic dipole energies of MnO and of the normal and inverse spinel structures are calculated. It is found that with this interaction alone MnO would have its direction of spin alignment in a (111) plane, in contrast to the experimentally found [100]. The addition of a nearest neighbor quadrupole interaction is suggested as a means of making the [100] direction preferred. The normal and the inverse spinel structures are found to have zero magnetic dipole energies.
N-Particle Distribution Functions
Authors: Frisch H. L.
Published: April 2005

An investigation of a certain class of approximate solutions of the Yvon-Born-Green recurrence relations for the lower-dimensional molecular distribution functions has been presented, based on a particular mechanism of exclusion of interactions among ``clusters'' composed of successively larger number of molecules. This mechanism leads to a chain of equations for the approximate distribution functions which (a) converge to the exact molecular distribution function after a finite number of approximations, (b) are linear in the dependent variable just like the Yvon-Born-Green recurrence relations, and (c) are time reversible. The connection between these equations and certain natural generalizations of Boltzmann's equation to other than binary collisions is obtained. Finally the application of this hierarchy to certain problems of fluids at equilibrium has been indicated.
Approximate Treatment of the Viscosity of Idealized Liquids. I. The Collisional Contribution
Authors: Collins F. C. , Raffel H.
Published: April 2005

The instantaneous transport of momentum across the bodies of molecules occurs upon molecular collision in a rigid sphere liquid undergoing viscous flow. The contribution of this effect to the viscosity is calculated on a quasi-equilibrium basis for a liquid consisting of hard spherical molecules. The calculation makes use of the free volume theory, a correction being introduced to take account of the blocking effect of third neighbors. The equation so obtained may be expressed in terms of the adiabatic compressibility of the liquid and its heat of vaporization. The calculated viscosity contributions are of the order of a quarter to a half of the experimental viscosities for various low molecular weight liquids investigated. The temperature coefficients of the viscosity contributions are also lower than those of the experimental viscosities.
Partial Molal Volumes of Hydrocarbons in Water Solution
Authors: Masterton W. L.
Published: April 2005

The partial molal volumes of benzene, methane, ethane and propane in water solution have been determined at temperatures ranging from 10—40°C. All the volumes measured were less than those of the same hydrocarbons in nonpolar solvents. This decrease in volume is explained in terms of the abnormally high internal pressure of water, which decreases the free volume available to the hydrocarbon molecules. The temperature dependence of the partial molal volumes of the aliphatic hydrocarbons differs sharply from that of benzene. It is suggested that this is caused by a difference in solution structure in the two cases.
An Infrared Band of a Molecular Complex Between Hydrogen Fluoride and Chlorine Trifluoride
Authors: Pemsler J. Paul , Smith D. F.
Published: April 2005

A band at 2.57μ wavelength has an absorbance which depends upon the product of the partial pressures of hydrogen fluoride and chlorine trifluoride and is hence attributable to a molecular complex HF·ClF3. This complex is present only in low concentration. The temperature variation per unit product of the pressures indicates a heat of reaction of 3.9 kcal per mole for the reaction HF+ClF3⇄HF·ClF3. The band is a hydrogen-fluorine stretching vibration. The complex probably does not contain a hydrogen bond.
Electron Impact Studies of Some Aromatic Hydrocarbons. Implications Regarding Certain Aromatic Reactions
Authors: Field F. H. , Franklin J. L.
Published: April 2005

The ionization potential of several alkyl-substituted aromatics have been measured by an electron impact method, and the results are found to agree with values predicted by equivalent orbital calculations. The appearance potential of several alkyl-substituted benzyl ions have been measured, and the results show that the energies of these ions are independent of ring substitution. The appearance potential of several alkyl-substituted phenyl ions were measured, and the results appear to be anomalous. The results can be understood if it is assumed that the ions rearrange during decomposition to the isomeric benzyl ions. The implications of these results in terms of several chemical reactions are discussed. The heat of formation of the phenyl and ethyl phenyl radicals were found to be approximately 66 and 49 kcal/mole, respectively.
Mechanism of Formation of the Quinonoid Hydrocarbon CH2:C6H4:CH2
Authors: Levy M. , Szwarc M. , Throssell J.
Published: April 2005

Para-xylyl radicals were generated by pyrolysing para-xylyl bromide in the presence of toluene or of para-xylene. Investigation of their behavior led to the conclusion that the quinonoid hydrocarbon CH2:C6H4:CH2 is formed by the disproportionation process. Further information about this reaction was secured by studying the pyrolysis of ω, ω′ dibromo para-xylene (Br·CH2·C6H4·CH2·Br). Semiquantitative treatment of the data indicates that the activation energy of the dissociation process CH2·C6H4·CH3→CH2:C̀6H6:CH2+His of the order 70 kcal/mole. Consequently, the dissociation process is too slow to account for the formation of the quinonoid hydrocarbon, at temperatures below 1100°K. We therefore attribute the formation of the quinonoid hydrocarbon to the disproportionation reaction.

Reinvestigation of the pyrolysis of benzyl bromide confirmed the past results and particularly the value for D(C6H5·CH2–Br). It was shown that the rate constant for the decomposition of para-xylyl bromide is essentially equal to the rate constant for the decomposition of benzyl bromide, and it appears that the rate constant for the decomposition of ω, ω′ dibromo para-xylene is higher by statistical factor of 2 from the rate constant of the decomposition of para-xylyl bromide.
Structure of a Steady-State Plane Detonation Wave with Finite Reaction Rate
Authors: Kirkwood John G. , Wood William W.
Published: April 2005

An analytical elaboration of von Neumann's model of the detonation wave is presented. A hydrodynamic argument for the well-known Chapman-Jouguet condition is advanced, and the sound speed to be used therein is identified as that obtained with frozen chemical equilibrium, in agreement with a recent result of Brinkley and Richardson. Possible situations in which the classical Chapman-Jouguet hypothesis might be incorrect are very briefly discussed.
Photolysis of Methyl Bromide in the Presence of Mercury
Authors: Boynton Charles F. , Taylor H. Austin
Published: April 2005

A study has been made of the photolysis of methyl bromide in the presence of liquid mercury over a pressure range of the bromide from 25 to 100 mm and at temperatures from 35° to 200°C. The removal of the bromine atoms formed in the initial split as mercurous bromide reduces the back reaction. Unlike the corresponding reaction with silver, ethane is formed in considerable amounts. The rate of methane formation decreases while that of ethane formation increases with duration of photolysis. The rate of methane formation increases and that of ethane decreases with increase in pressure of methyl bromide. The energy of activation of methane production in the absence of mercury is 2.1 kcal. In the presence of mercury the energy of activation for methane is approximately zero while that for ethane is less than 2 kcal. The results are interpreted as indicating the formation of mercury methyl radicals or mercury dimethyl.
Sedimentation Potential and Velocity of Solid Spherical Particles
Authors: Booth F.
Published: April 2005

The electrical effects accompanying the steady fall of solid charged spherical particles under gravity in an electrolyte are examined theoretically. For a single particle falling in an infinite electrolyte, it is shown that, owing to fluid flow round the particle, the double layer field is modified. The effect in the double layer region is complicated, but outside this region a field is set up of the same form as that which would arise from a dipole fixed at the center of the particle with its axis vertical. A general expression is given for this dipole field in the case of nonconducting particles. The calculations extend previous work in that no restriction on the relative dimensions of the particle size and the double-layer thickness is imposed.

It is shown that the interaction between the charge on the particle and the modified field alters the sedimentation velocity of the particle. The calculations show that in practical cases the effect might, in favorable circumstances, reduce the velocity by a few percent.

The analysis is extended to suspensions containing a large number of particles uniformly distributed.
Studies on a Group of Silicon Carbide Structures
Authors: Mitchell Richard S.
Published: April 2005

Morphological and structural details of silicon carbide type 141R are given. This polymorph, having a structure represented by the zigzag sequence 3333333333333332, is a member of the `3...2' rhombohedral series proposed by Ramsdell [Am. Mineralogist 32, 64 (1947)].

A detailed study of the `3...2' series is undertaken, resulting in an empirical mechanism which can be used for the direct determination of the structure of any member of this series. Using this means the structure of the new polymorph 393R is suggested.
Microwave Determination of the Structure of Pyridine
Authors: Bak Børge , Hansen Lise , Rastrup-Andersen John
Published: April 2005

2-, 3-, and 4-mono-deutero-pyridine have been prepared and the microwave spectra recorded. For each of the isotopic species 11—12 transitions (Q- and R-branch lines) were localized, a number of which could be identified by their Stark effect. For all three species rotational constants of high precision were calculated. The material so provided in connection with known rotational constants for ordinary pyridine is insufficient for a complete determination of the ten geometrical parameters of the molecule. Seven models with a choice of C – H distances close to the correct value (1.075-1.085 A) were considered one of which was shown to be consistent with electron-diffraction work and current valence theory. In this model d(N – C(2)) = 1.340±0.005; d(C(2) – C(3)) = 1.390±0.005; d(C(3) – C(4)) = 1.400±0.005 A. The valence angles in the aromatic ring (starting with the C(6) – N – C(2) angle) are: 116° 42′; 124° 00′; 118° 36′; 118° 06′.
Chemical Effects of (d,p), (n,2n), and (γ,n) Activation of Iodine
Authors: Schuler Robert H.
Published: April 2005

The organic retentions for (d,p), (n,2n), and (γ,n) activation of iodine in liquid methyl and ethyl iodide, containing added iodine, have been found to be equal to the retentions observed in radiative neutron capture. This demonstrates that the chemical effects are independent of the recoil energy of the activated nucleus, of the mode of nuclear formation, and of variation of fragmentation effects within the recoil track. In the absence of scavenger iodine, the increase in retention due to radiation damage is less than 10 percent in all cases studied.
Study of Carbon Monoxide, Nitrogen, Propylene, and Benzene Ionization Probability Curves near Threshold
Authors: Fox R. E. , Hickam W. M.
Published: April 2005

Ionization probability curves for the formation of CO+, N2+, C3H6+, and C6H6+ have been obtained for some six volts above threshold. The technique employed provided both ionization by essentially monoenergetic electrons and a m/ε separation of the ions. In the case of the diatomic ions, the structure in the curves can be interpreted in terms of spectroscopically identified energy levels. The curves for propylene and benzene exhibit considerable structure which, when analyzed in a similar manner to that used for the diatomic molecules, results in the location of a number of unidentified energy levels. The presence of these levels explains the discrepancies in ionization potential measurements obtained by various electron impact methods.
Magnetic Moments of Some Octahedral Complexes of Iridium
Authors: Sloth Eric N. , Garner Clifford S.
Published: April 2005

Magnetic susceptibilities of Na2IrCl6, Na3IrCl6·2H2O, and (NH4)2Ir(H2O)Cl5 were determined for these solids and for aqueous solutions 0.6f in the complex compound and 1f in HCl by the Gouy method. Na2IrCl6 is paramagnetic in the solid state and in solution, with a magnetic moment corresponding to one unpaired 5d electron and to d2sp3 covalent Ir–Cl bonds. The two iridium (III) complexes are diamagnetic, corresponding likewise to d2sp3 bond formation.
Double-Bond Character of Conjugated Carbon-Chlorine Bonds
Authors: Bersohn R.
Published: April 2005

The π electron loss of a chlorine atom conjugated with a resonating system can be obtained at least approximately from experimental measurements of the asymmetry of the chlorine nuclear electric quadrupole interaction. Using molecular orbital theory the π electron loss ρ can be simply expressed in terms of the chlorine Coulomb integral, the carbon-chlorine resonance integral, and the energies and wave functions of the system with which the chlorine atom is conjugated. Comparison of theoretical and experimental values of ρ show that the carbon-chlorine resonance integral is about one-third of the carbon-carbon resonance integral. The basic conclusion is that chlorine atoms in general resonate only weakly with attached aromatic systems. Most of the effects previously ascribed to double bond character can alternatively be explained by an increased electronegativity of the carbon sp2 orbital.
Modified Transition State Theory of Reaction Rates
Authors: Matsen F. A.
Published: April 2005

The specific reaction rate for chemical reactions is formulated in terms of the total transmission coefficient in the reaction coordinate and a modified transition state, which differs from the original transition state only in the treatment of the reaction coordinate. If the total transmission coefficient is factored into two partial transmission coefficients, the modified theory gives the transition state theory in both the classical and the quantum-mechanical-particle-in-a-box treatments. It is then shown that the momentum density in the virtual state over a symmetrical square barrier is that of a quantum-mechanical-particle-in-a-box at low momentum and that of a classical system at high momentum. Finally, the reaction rate transmission coefficient is calculated from the modified theory for an unsymmetric square barrier and shown to depend on the temperature, the activation energy, and the thermicity of the reaction.