bluuebunny/crossref_metadata_2025 huggingface dataset:
Charging of mirror surfaces in space
Authors: Lai Shu T.
Published: January 2005

Spacecraft often charge to negative potentials of several kilovolts in eclipse at geosynchronous altitudes. We suggest that optical mirrors at geosynchronous altitudes will charge in sunlight as if in eclipse. Modern mirrors can attain very high reflectance, the reflected light being nearly as intense as the incoming light. With high reflectance, the sunlight photon energy imparted to mirror surfaces is greatly reduced, resulting in little or no photoemission. As a result, mirrors will charge as if they would in eclipse, the equilibrium potential being governed by the balance of currents without photoelectrons. When the plasma electron temperature is high, the equilibrium potential may reach several kilovolts negative, despite sunlight. This occurs often in the morning hours and in severe space weather. We stress that in general, the finite reflectance and Sun angle should be included in calculations of spacecraft charging in sunlight. As an important application for mirror charging, we bring to attention recent news, the Boeing 702 model geosynchronous satellite fleet, featuring two long solar panels on each side. Each solar panel is equipped with two mirrors flanking both sides for sunlight enhancement on the solar cells. The entire satellite fleet has suffered a similar fate, namely, gradual, permanent, and sometimes stepwise degradation. While the true cause of the Boeing solar panels deterioration may never be known, we suggest that sudden development of differential charging between the solar panels and the mirrors on their sides could be the culprit. Differential charging of mirrored solar panels may develop rapidly when the satellite is coming out of eclipse. Indeed, the sudden 25% degradation of PanAmSat PAS‐7, a Boeing 702 model satellite, did occur shortly after eclipse exit in the morning of 6 September 2001. Finally, we suggest a simple mitigation method for solving the problem.
Fault location and source process of the Boumerdes, Algeria, earthquake inferred from geodetic and strong motion data
Authors: Semmane Fethi , Campillo Michel , Cotton Fabrice
Published: January 2005

The Boumerdes earthquake occurred on a fault whose precise location, offshore the Algerian coast, was unknown. Geodetic data are used to determine the absolute position of the fault. The fault might emerge at about 15 km offshore. Accelerograms are used to infer the space‐time history of the rupture using a two‐step inversion in the spectral domain. The observed strong motion records agree with the synthetics for the fault location inferred from geodetic data. The fault plane ruptured for about 18 seconds. The slip distribution on the fault indicates one asperity northwest of the hypocenter with maximum slip amplitude about 3 m. This asperity is probably responsible for most of the damage. Another asperity with slightly smaller slip amplitude is located southeast of the hypocenter. The rupture stops its westward propagation close to the Thenia fault, a structure almost perpendicular to the main fault.
The shapes of very small cirrus particles derived from in situ measurements
Authors: Baumgardner D. , Chepfer H. , Raga G. B. , Kok G. L.
Published: January 2005

The shapes of ice crystals have been derived from measurements in cirrus during the CRYSTAL/FACE experiment in July, 2002. The measurements were made in the size range from 5–45 μm with an optical particle spectrometer that measures forward (4–12°) and backscattered (168–176°) light from individual particles. The phase functions for ensembles of ideal crystal shapes were integrated over these collection angles to compare with the measured ratios of forward to backward scattered light from nine research flights. Approximately 90% of the crystals agreed with the theoretical model for a mixture of bullet rosettes, plates and hollow columns. Approximately 10% of the crystals were characterized as ice spheres. There was no significant dependency of shape on wind direction, temperature or relative humidity with respect to ice.
In‐situ elasticity measurement for the unquenchable high‐pressure clinopyroxene phase: Implication for the upper mantle
Authors: Kung Jennifer , Li Baosheng , Uchida Takeyuki , Wang Yanbin
Published: January 2005

Polycrystal elasticity of the unquenchable MgSiO3high‐pressure clinoenstatite has been measured using ultrasonic interferometry in conjunction with in‐situ X‐ray diffraction and imaging techniques within its stability field in a large volume multi‐anvil apparatus for the first time. At 6.5 GPa, we obtained ∂KS/∂P = 5.6(3), ∂G/∂P = 1.5(1), ∂KS/∂T = −0.017(1) GPa K−1and (∂G/∂T) = −0.015(1) GPa K−1. Our results show that the elastic velocities of HP‐CEN are not only higher than those of OEN but also higher than olivine at upper mantle conditions. According to these new data, the elastic velocities for the “depleted” mantle composition, with ∼20 vol% of HP‐CEN, would result in ∼0.8% and ∼1.6% in difference for P and S waves, respectively, when OEN data were used in previous calculations. Newly measured results also suggest that it is possible to distinguish “undepleted” and “depleted” composition models in the upper mantle.
ROCSAT observation of the field line resonance effect in a plasma pulsation at topside ionosphere
Authors: Su S.‐Y. , Chen K. Y. , Wu J. M. , Yeh H. C. , Chao C. K.
Published: January 2005

During the recovery phase of the 29–31 October 2003 storm, a plasma pulsation event of large flow oscillation perpendicular to the field line was observed by ROCSAT‐1 in a circular orbit at 600 km topside ionosphere. The flow undulation amplitude grows large as ROCSAT moves around the southernmost latitudes of the orbital coverage around the dusk region from dip latitude −50° to −53° to reach the largest observed oscillation amplitude of 380 m/s that is equivalent to an electric field of 18 mV/m. The undulation amplitude then decreases as ROCSAT moves back toward low latitudes in the northbound leg. A reversal of polarization and changes in polarization ellipticity are also observed as ROCSAT traverses across −50° dip latitude. The variation in wave amplitude together with the change in polarization suggests that a field line resonance (FLR) effect in the plasma pulsation has been observed along the ROCSAT orbit traversing different dip latitudes of magnetic shells. This event is different from past spacecraft observations of the Pi2 pulsation events manifested in the magnetospheric or plasmaspheric cavity resonance. The ROCSAT observation of the FLR effect will be for the first time to observe the plasma pulsation directly in space at a location just above the ionosphere where the induced ionospheric currents (or flows) have been manifesting the FLR effect observed on the ground. Our observation also indicates that a strong coupling exists between the global compressional eigenmodes and the excited transverse modes, as proposed in a model by Kivelson and Southwood [1986].
Variations of polar cap index in response to solar wind changes and magnetospheric substorms
Authors: Huang Chao‐Song
Published: January 2005

The polar cap (PC) index is used to measure the geomagnetic activity over the polar caps. Changes in the solar wind are able to cause disturbances in the magnetospheric‐ionospheric currents, which in turn cause variations in the PC index. In order to understand how different processes in the solar wind and magnetosphere influence the PC index, it is necessary to separate the effects of solar wind pressure impulses, interplanetary magnetic field (IMF) reorientations, and magnetospheric substorms. We study the variations of the PC index under different solar wind conditions and during substorms and present case analyses and statistical results. The main conclusions are as follows. A solar wind pressure impulse alone, without IMF southward turning or substorm, is to cause a negative spike of ∼1 in the PC index within a time interval of 2–6 min and a subsequent increase to a positive value of ∼1 within 30 min. The PC index enhances significantly after the IMF turns southward, and the increase of the PC index is 3–5 in most cases and can be as large as 8–9. When a solar wind pressure impulse occurs with a simultaneous southward turning of the IMF, the large increase of the PC index is mainly a response to the southward IMF but not to the solar wind pressure impulse. Magnetospheric substorms have significant effects on the PC index. The response of the PC index to substorms is an increase of 2–4 in most cases and can reach 6 or larger. The effects of IMF southward turnings and substorms on the PC index are much stronger than that of solar wind pressure impulses. On average, the increases of the PC index caused by solar wind pressure impulses, substorm onsets, and IMF southward turnings are 0.8, 3.2, and 3.6, respectively.
Understanding electron heat flux signatures in the solar wind
Authors: Pagel C. , Crooker N. U. , Larson D. E. , Kahler S. W. , Owens M. J.
Published: January 2005

Suprathermal electrons (E > 80 eV) carry heat flux away from the Sun. Processes controlling the heat flux are not well understood. To gain insight into these processes, we model heat flux as a linear dependence on two independent parameters: electron number flux and electron pitch angle anisotropy. Pitch angle anisotropy is further modeled as a linear dependence on two solar wind components: magnetic field strength and plasma density. These components show no correlation with number flux, reinforcing its independence from pitch angle anisotropy. Multiple linear regression applied to 2 years of Wind data shows good correspondence between modeled and observed heat flux and anisotropy. The results suggest that the interplay of solar wind parameters and electron number flux results in distinctive heat flux dropouts at heliospheric features like plasma sheets but that these parameters continuously modify heat flux. This is inconsistent with magnetic disconnection as the primary cause of heat flux dropouts. Analysis of fast and slow solar wind regimes separately shows that electron number flux and pitch angle anisotropy are equally correlated with heat flux in slow wind but that number flux is the dominant correlative in fast wind. Also, magnetic field strength correlates better with pitch angle anisotropy in slow wind than in fast wind. The energy dependence of the model fits suggests different scattering processes in fast and slow wind.
MODIS bidirectional reflectance distribution function and albedo Climate Modeling Grid products and the variability of albedo for major global vegetation types
Authors: Gao Feng , Schaaf Crystal B. , Strahler Alan H. , Roesch Andreas , Lucht Wolfgang , Dickinson Robert
Published: January 2005

Global land surface albedo data sets derived from the Terra Moderate‐Resolution Imaging Spectroradiometer (MODIS) from March 2000 to present have been completed for ready use by the global modeling community. This paper describes these albedo and bidirectional reflectance distribution function Climate Modeling Grid products and their variability within major global vegetation types. Preliminary results based on collection 4 data reveal that these coarse resolution (0.05°), geographic (latitude/longitude), global albedos have spatial and temporal patterns appropriate for the underlying land cover classes, further encouraging modelers to introduce albedos as functions of ground cover, geographic location, temporal season, and spatial resolution in the various climate‐modeling schemes.
Mitochondrial DNA Diversity in Indigenous Populations of the Southern Extent of Siberia, and the Origins of Native American Haplogroups
Authors: Starikovskaya Elena B. , Sukernik Rem I. , Derbeneva Olga A. , Volodko Natalia V. , Ruiz‐Pesini Eduardo , Torroni Antonio , Brown Michael D. , Lott Marie T. , Hosseini Seyed H. , Huoponen Kirsi , Wallace Douglas C.
Published: January 2005

In search of the ancestors of Native American mitochondrial DNA (mtDNA) haplogroups, we analyzed the mtDNA of 531 individuals from nine indigenous populations in Siberia. All mtDNAs were subjected to high‐resolution RFLP analysis, sequencing of the control‐region hypervariable segment I (HVS‐I), and surveyed for additional polymorphic markers in the coding region. Furthermore, the mtDNAs selected according to haplogroup/subhaplogroup status were completely sequenced. Phylogenetic analyses of the resulting data, combined with those from previously published Siberian arctic and sub‐arctic populations, revealed that remnants of the ancient Siberian gene pool are still evident in Siberian populations, suggesting that the founding haplotypes of the Native American A‐D branches originated in different parts of Siberia. Thus, lineage A complete sequences revealed in the Mansi of the Lower Ob and the Ket of the Lower Yenisei belong to A1, suggesting that A1 mtDNAs occasionally found in the remnants of hunting‐gathering populations of northwestern and northern Siberia belonged to a common gene pool of the Siberian progenitors of Paleoindians. Moreover, lineage B1, which is the most closely related to the American B2, occurred in the Tubalar and Tuvan inhabiting the territory between the upper reaches of the Ob River in the west, to the Upper Yenisei region in the east. Finally, the sequence variants of haplogroups C and D, which are most similar to Native American C1 and D1, were detected in the Ulchi of the Lower Amur. Overall, our data suggest that the immediate ancestors of the Siberian/Beringian migrants who gave rise to ancient (pre‐Clovis) Paleoindians have a common origin with aboriginal people of the area now designated the Altai‐Sayan Upland, as well as the Lower Amur/Sea of Okhotsk region.
The Contribution of Genetic and Environmental Factors to Quantitative Variability of Erythrocyte Membrane Proteins in Primary Hypotension
Authors: Ivanov V. P. , Polonikov A. V. , Solodilova M. A.
Published: January 2005

Our previous studies have shown that, compared with healthy individuals, patients with primary arterial hypotension (PAH) have significant quantitative changes in erythrocyte membrane proteins. The purpose of the present study was to evaluate the contribution made by genetic and environmental factors to quantitative variation of erythrocyte membrane proteins in PAH. We studied 109 hypotensive patients, 124 normotensive subjects, 222 of their first‐degree relatives and 24 twin pairs by sodium dodecyl sulphate (SDS) polyacrylamide gel electrophoresis. The decomposition of total phenotypic variance of erythrocyte membrane proteins to genetic and environmental components was performed on the basis of correlations among first‐degree relatives by the least squares method. The genetic dominance and shared environmental factors were found to influence the variability of cytoskeletal membrane proteins whose contents were changed in PAH. Furthermore, variations in α‐spectrin, actin and anion exchanger in hypotensives were substantially influenced by major gene and maternal effects. Ankyrin 2.1 and actin content was under the control of common underlying genes. Variations in membrane‐associated glutathione‐S‐transferase and tropomyosin were predominantly affected by polygenes. These findings suggest that the putative major genes with pleiotropic effects appear to be involved in the control of quantitative disorders of erythrocyte membrane proteins in primary hypotension.
Comprehensive Cystic Fibrosis Mutation Epidemiology and Haplotype Characterization in a Southern Italian Population
Authors: Castaldo G. , Polizzi A. , Tomaiuolo R. , Cazeneuve C. , Girodon E. , Santostasi T. , Salvatore D. , Raia V. , Rigillo N. , Goossens M. , Salvatore F.
Published: January 2005

We screened the whole coding region of the cystic fibrosis transmembrane regulator (CFTR) gene in 371 unrelated cystic fibrosis (CF) patients from three regions of southern Italy. Forty‐three mutations detected 91.5% of CF mutated chromosomes by denaturing gradient gel electrophoresis analysis, and three intragenic CFTR polymorphisms predicted a myriad of rare mutations in uncharacterized CF chromosomes. Twelve mutations are peculiar to CF chromosomes from southern Italy: R1158X, 4016insT, L1065P and 711+1G>T are present in 6.3% of CF chromosomes in Campania; G1244E and 852del22 are present in 9.6% of CF chromosomes in Basilicata and 4382delA, 1259insA, I502T, 852del22, 4016insT, D579G, R1158X, L1077P and G1349D are frequent in Puglia (19.6% of CF alleles). Several mutations frequently found in northern Italy (e.g., R1162X, 711+5G>T) and northern Europe (e.g., G551D, I507del and 621+1G>T) are absent from the studied population. The I148T‐3195del6 complex allele was present in two CF chromosomes, whereas I148T was present in both alleles (as a single mutation) in another CF patient and in five CF carriers; this could result from crossover events. The haplotype analysis of three intragenic polymorphisms (IVS8CA, IVS17bTA and IVS17bCA) compared with data from other studies revealed that several mutations (3849+10kbC>T, 1717‐1G>A, E585X, 3272‐26G>A, L558S, 2184insA and R347P) originated from multiple events, whereas others (R1158X and S549R) could be associated with one or more intragenic recombinant events. Given the large population migration from southern Italy, knowledge of the CF molecular epidemiology in this area is an important contribution to diagnosis, counselling and interlaboratory quality control for molecular laboratories worldwide.
Linkage Analysis of Chromosome 1 with Essential Hypertension and Blood Pressure Quantitative Traits in Chinese Families
Authors: Ge D. , Huang J. , Yang W. , Zhao J. , Shen Y. , Qiang B. , Gu D.
Published: January 2005

Several recent studies have linked human chromosome 1p to essential hypertension (EH) or blood pressure (BP) levels. In an independent population of 148 hypertensive families from China we tested these findings. Thirty highly informative microsatellite markers spanning about 284 cM were genotyped. Qualitative linkage analysis was conducted using non‐parametric linkage analysis implemented within the GENEHUNTER 2.0 software, whereas quantitative analysis was performed with the variance‐component method integrated in the S.O.L.A.R. 1.7.4. software with an additional Haseman‐Elston method using the SAGE/SIBPAL2 program. We observed suggestive linkage between D1S2890 (1p31, 80.9 cM) and hypertension using the multipoint non‐parametric linkage analysis (NPL = 2.19, P = 0.01). In the quantitative analysis we didn't observe a significant excess of identity‐by‐descent allele sharing between the systolic blood pressure levels and the markers. However, the D1S207 microsatellite marker (1p21) which is located about 107 cM from the telomere of 1p showed weak linkage evidence with the diastolic blood pressure levels (LOD = 1.42). These findings suggest linkage of 1p31 with essential hypertension in the ethnic Chinese, and provide a potential clue for future studies involving candidate genes for hypertension.
Genetic Heterogeneity of Beta Thalassemia in Lebanon Reflects Historic and Recent Population Migration
Authors: Makhoul N. J. , Wells R. S. , Kaspar H. , Shbaklo H. , Taher A. , Chakar N. , Zalloua P. A.
Published: January 2005

Beta thalassemia is an autosomal recessive disorder characterized by reduced (β+) or absent (β0) beta‐globin chain synthesis. In Lebanon it is the most predominant genetic defect. In this study we investigated the religious and geographic distribution of the β‐thalassemia mutations identified in Lebanon, and traced their precise origins. A total of 520 β‐globin chromosomes from patients of different religious and regional backgrounds was studied. Beta thalassemia mutations were identified using Amplification Refractory Mutation System (ARMS) PCR or direct gene sequencing.

Six (IVS‐I‐110, IVS‐I‐1, IVS‐I‐6, IVS‐II‐1, cd 5 and the C>T substitution at cd 29) out of 20 β‐globin defects identified accounted for more than 86% of the total β‐thalassemia chromosomes. Sunni Muslims had the highest β‐thalassemia carrier rate and presented the greatest heterogeneity, with 16 different mutations. Shiite Muslims followed closely with 13 mutations, whereas Maronites represented 11.9% of all β‐thalassemic subjects and carried 7 different mutations. RFLP haplotype analysis showed that the observed genetic diversity originated from both new mutational events and gene flow from population migration. This study provides information about the types and distribution of β‐thalassemia mutations within each religious group and geographic region, which is essential for the implementation of screening and prevention programs.
Linkage Analysis of Affected Sib Pairs Allowing for Parent‐of‐Origin Effects
Authors: Wu Chih‐Chieh , Shete Sanjay , Amos Christopher I.
Published: January 2005

Parent‐of‐origin effects, also known as genomic imprinting, exist for many mammalian genes. For imprinted genes the expression of an allele depends upon the sex of the transmitting parent. Here we have developed a method based on alleles that are shared identical by descent by affected sib pairs, that allows for parent‐of‐origin effects. Our method allows for sex‐specific recombination rates, an important consideration in studying imprinted genes. We have also derived a tetrahedron for the true identical‐by‐descent frequencies accounting for parent‐of‐origin effects. Using this tetrahedron, we propose a robust generalized minmax test for linkage and discuss its properties in the presence of genomic imprinting. We have also performed power comparisons of various allele sharing tests and provide regions of the tetrahedron in which the different tests are optimal. We also provide useful strategies to determine the optimal tests to use while performing a genome scan.
Electron Spin Resonance of Vanadyl Phthalocyanine
Authors: Assour J. M. , Goldmacher J. , Harrison S. E.
Published: January 2005

An electron spin resonance study of vanadyl phthalocyanine magnetically diluted in metal-free and zinc phthalocyanine salts, and in sulfuric acid solution, confirms the placement of the 3d unpaired electron in the dxy singlet orbital of the vanadium ion. An improved method of synthesis for vanadyl phthalocyanine which increased the yield to 64% is described. The infrared spectrum of vanadyl phthalocyanine indicates that this complex exists in only one polymorphic modification.
Microwave Spectrum, Quadrupole Coupling Constants, and Heavy-Atom Geometry of 2-Bromopropane
Authors: Schwendeman R. H. , Tobiason F. L.
Published: January 2005

The microwave spectra of (CH3)2CH79Br, (CH3)2CH81Br, (CH3)213CH79Br, and 13CH3CH79BrCH3 have been examined, and the coordinates of the Br and C atoms have been obtained by the substitution method. The resulting bond distances and bond angles are as follows: r(CBr) = 1.957 Å, r(CC) = 1.508 Å, ∠CCBr = 110.0°, and ∠CCC = 114.2°.

The quadrupole coupling constants of (CH3)2CH79Br have been determined to be χaa = 479.5 Mc/sec, χbb = −264.9 Mc/sec, and χcc = −214.6 Mc/sec. Second-order perturbation corrections were included in the analysis of the hyperfine splittings. The quadrupole coupling constants are consistent with χzz = 529.8 Mc/sec, assuming a cylindrical charge distribution, and with χzz = 514.2 Mc/sec, ηbond = 0.0303, assuming that the z axis and the CBr internuclear line coincide.
Systematic Perturbations of the EPR Spectra of Anthracene and Azulene Anions in Solution
Authors: Reddoch A. H.
Published: January 2005

Experimental measurements of the hyperfine coupling constants of anthracene and azulene anions with various solvents and cations are presented. It is shown that the proton coupling constants depend on solvent, cation, concentration, and temperature and that variations of these constants of about 10% can occur. The variation of the proton coupling constants is shown to be systematic and is ascribed to the electrostatic perturbation of the cation. Calculations are presented to support this view. Most of the systems studied are classified as ion pairs, free anions, or equilibrium mixtures on the basis of qualitative features of their EPR spectra. The absence of hyperfine coupling from the counterion does not necessarily indicate that the anion is unassociated.
Molecular Motion and Relaxation in Free-Radical Solutions of Benzene, Toluene, and Some Ethers as Studied by Dynamic Nuclear Polarization
Authors: Kramer K. D. , Müller-Warmuth W. , Schindler J.
Published: January 2005

Magnetic double-resonance methods have been used to investigate the spectrum of motion, the proton and electron spin relaxation in organic solutions of free radicals. Studies of both frequency and temperature dependences of the dynamic nuclear polarization and the relaxation times yield information on the solvent-nucleus—free-radical interactions and on the molecular motion. Measurements in very weak magnetic fields (15 G) realize the conditions of ``extreme narrowing,'' data at 1070 and 3230 G fall into the main region of decay of the Overhauser effect. The results in radical solutions of benzene, toluene, dimethoxymethane, dimethoxyethane, and diethoxymethane can be explained by a pure dipole—dipole interaction governed by translational random motions of the spin-carrying molecules. Correlation times, activation energies, and other parameters are evaluated. An influence of different free radicals (molecules and ions) could obviously not be observed. Toluene at low temperatures displays an exceptional behavior. Some consequences for the phenomena of Overhauser polarization, proton, and electron spin—lattice relaxation in general are discussed. This especially includes the high-frequency limit of the dynamic nuclear polarization and the dependences of both leakage and saturation parameters important for all applications.
Vibrational Structuring in Optical Activity. I. Vibronic Coupling in the Circular Dichroism of Dimers
Authors: Weigang Oscar E.
Published: January 2005

The characteristics of circular dichroism arising from near-degenerate electronic states under the influence of vibration are considered and compared to the ordinary absorption. A ``pseudo-Jahn—Teller effect'' operates between limits of strong and weak coupling, the influence of which on ordinary absorption has been considered earlier. An exciton or coupled-oscillator model is used which seems especially appropriate to optically active biaryls. For intermediate coupling, overlapping band systems of equal net rotatory strength but opposite sign will give a resultant dichroism altogether different in appearance from the ordinary absorption.
Microwave and Infrared Spectra of Sulfur Dicyanide: Molecular Structure, Dipole Moment, Quadrupole Coupling Constants, Centrifugal Distortion Constants, and Vibrational Assignment
Authors: Pierce Louis , Nelson Richard , Thomas Clarence
Published: January 2005

The microwave spectra of S(CN)2, SC13CN2, SC2N15N, and 34S(CN)2 were studied in the frequency region 8 to 30 Gc/sec. Isotope shifts yield the following structural parameters: CS=1.701 Å, ∠CSC=98°22′, CN=1.156 Å, 2φ=108°24′, where 2φ is the angle between the two C–N internuclear lines. Thus the SCN angle deviates from linearity by 5°. From Stark-effect measurements the dipole moment was determined to be 3.04±0.03 D. Quadrupole hyperfine structure partially resolved in several transitions of S(CN)2 and SC2N15N yields the following coupling constants (Mc/sec): S(CN)2 (χAA=−1.51, χBB=0.30, χCC=1.21) SC2N15N (χAA=−1.51, χBB=0.24, χCC=1.27). Centrifugal distortion constants and the inertial defect for a low-lying vibrationally excited state (v4=1) of S(CN)2 were of great value in making the following assignment of normal frequencies: ω1(A1) 2190 cm−1 (CN stretch),ω5(B1) 2180 cm−1 (CN stretch),ω2(A1)  672 cm−1 (CS stretch),ω6(B1)  690 cm−1 (CS stretch),ω3(A1)  378 cm−1 (SCN def.),ω7(B1)  328 cm−1 (SCN def.),ω4(A1)  135 cm−1 (CSC def.),ω8(B2)  372 cm−1 (SCN def.),ω9(A2) (376) cm−1 (SCN def.).Measurements of the infrared spectrum extended to 50 cm−1; ω9(A2) which is infrared inactive, is estimated from an approximate potential function. Vibration—rotation interaction parameters determined from a normal coordinate analysis give inertial defects of 0.4503, 0.4499, 0.4548, and 0.4564 amu Å2 for S(CN)2, SC13CN2, SC2N15N, and 34S(CN)2, respectively. The corresponding observed values are 0.4869, 0.4864, 0.4927, and 0.4920. For the excited state v4=1, the calculated and observed values of the inertial defect are 1.2726 and 1.3837 amu Å2, respectively.
NMR Studies of Some Liquid Crystal Systems
Authors: Rowell J. C. , Phillips W. D. , Melby L. R. , Panar M.
Published: January 2005

Alignment by electric or magnetic fields of molecules comprising the liquid crystalline phase of a nematogenic material is manifested in proton magnetic resonance spectroscopy by the appearance of nuclear dipole-dipole fine structure. Additionally, much larger splittings ranging up to 300 G are observed in the deuterium magnetic resonance spectrum of deuterium substituted nematogens. These latter splittings arise from perturbation of the Zeeman levels by the quadrupole coupling constant of deuterium and have been of value in elucidating structure and organization in nematic phases. Results of NMR studies on nematogens based on azoxy and carboxylic compounds are presented. Use of nematic phases as ordering matrices for molecules such as benzene, toluene, naphthalene, and stilbene are discussed. Some preliminary results on effects of electric fields and dissolved cholesteryl acetate on orientation and organization of nematogens also are presented. In addition, quadrupole coupling constants for deuterium bound to sp2 and sp3 carbon and for deuterium bound to oxygen in a carboxylic acid dimer were determined for a few selected compounds.
Phase Diagram of Argon—Carbon Monoxide
Authors: Barrett C. S. , Meyer Lothar
Published: January 2005

The phase diagram Ar–CO has been determined by cooling curves and x-ray diffraction. Like the Ar–N2 system, a solid solution of hcp structure extends over essentially the entire range of concentration at temperatures just under the solidus, but unlike the Ar–N2 system, the hcp phase decomposes (eutectoidally) into a fcc Ar-rich phase and a primitive cubic CO-rich phase at 53°K; the eutectoid point is at 66% CO. The miscibility gap at 53°K extends from 5% to 85% CO and is probably complete at 0°K. There are quite extensive two-phase regions between the phases in the solid state, which were not found in the Ar–N2 system. There is again an indication that Ar would have the hcp structure just a few degrees above the melting point if melting did not intervene. Liquidus and solidus temperatures for Ar–CO reach a minimum (65°K) near 60%—70% CO. Lattice constants for the different phases are presented.
Photolysis of Low-Temperature Glasses. I. Ethanol and Ether at 77°K
Authors: Judeikis Henry S. , Siegel Seymour
Published: January 2005

The sensitized photolytic decomposition of ethanol and diethyl ether glasses at 77°K has been investigated utilizing electron paramagnetic resonance (EPR) spectroscopy. Support is given to a proposed mechanism of sensitized solvent decomposition by a two-step biphotonic absorption by an aromatic impurity molecule followed by a solute—solvent energy-transfer process. Subsequent dissociation processes from the excited solvent molecule are considered.

It is demonstrated that the results obtained upon prolonged photolysis of ethanol or ether can be attributed to a steady-state competition between the abstraction reactions of the type CH3CH2 (or CH3) +CH3CH2OR→CH3CH3 (or CH4) +CH3CHOR and the photoreaction CH3CHOR+hv→CH3+CH3CH2+ other products. The predicted dependence of the direction of the steady-state competition with respect to the relative radical concentrations on the incident light intensity is verified experimentally. Extinction of the excitation source results in a cessation of the steady-state condition, leading to the decay of the ethyl and methyl radical concentrations via the abstraction reactions. The latter abstraction process is discussed, and a significant isotope effect in the decay of the hydrocarbon radicals in CH3CD2OH is indicated.

The products of the dark abstraction reactions are the ethanol (CH3CHOH) or etheral (CH3CHOC2H5) radicals. In some cases, an EPR spectrum tentatively assigned to the acetyl radical (CH3CO) is also obtained. The latter species are photolyzable, and the wavelengths responsible for the photolyses are indicated. The EPR and electronic absorption spectral characteristics of the acetyl radical are compared to somewhat similar results obtained in the γ radiolysis of ethanol glasses. It is demonstrated that the similarity of the results is coincidental and that the results in the present study are not attributable to the solvated electron as they are in the case of γ radiolysis.

A series of reactions is proposed to qualitatively account for the spectral observations and gaseous product yields. This scheme is in satisfactory agreement with the experimental results.
Vacuum-Ultraviolet Studies of Sulfides. I. Spectral Correlations and Assignment of the NV Transitions
Authors: Clark Leigh B. , Simpson William T.
Published: January 2005

The electronic spectra of a number of divalent sulfur compounds in the vacuum ultraviolet are presented. A working criterion for the separation of non-Rydberg from Rydberg transitions is applied. The non-Rydberg transitions are then considered in the framework of NV theory, and assignments of the observed bands are made.
Absorption and Emission Measurements of C2 and CH Electronic Bands in Low-Pressure Oxyacetylene Flames
Authors: Bleekrode R. , Nieuwpoort W. C.
Published: January 2005

Absorption and emission spectra pertaining to electronic transitions of the short-lived molecules C2 and CH as present in the reaction zone of low-pressure oxyacetylene flames are studied. Steady flame absorption in the 4315-Å band of CH (2Δ—2Π) is reported for the first time. The concentration of CH in the 2Π(v=0) state is estimated to be [CH]≈1012 cm−3. The absorption measurements of the 0–0 C2 Swan band (3Πg—3Πu) extend existing measurements in that the rotational structure of the P and R branches is now well resolved. The rotational intensity distributions in emission and absorption are compared and the concentration in the 3Πu state is derived: [C2]≈1013 cm−3. Furthermore it is concluded that the C2 exitatation is nonthermal. This conclusion is supported by the observation of an interesting nonequilibrium rotational intensity distribution in the C2 emission spectrum.
Reaction of Oxygen Atoms with Acetaldehyde
Authors: Avery H. E. , Cvetanović R. J.
Published: January 2005

The reaction of the ground-state triplet oxygen atoms with acetaldehyde at room temperature has been reinvestigated. Two different sources of oxygen atoms have been used: mercury photosensitized decomposition of nitrous oxide and photolysis of nitrogen dioxide at 3660 Å. The results confirm the earlier conclusion from this Laboratory that the primary attack involves the abstraction of the aldehydic H atoms and not an insertion into the CH bonds of the aldehyde nor other primary steps suggested recently in the literature.
Matrix-Isolation Infrared Spectrum of the Free Radical CCO
Authors: Jacox Marilyn E. , Milligan Dolphus E. , Moll Norman G. , Thompson Warren E.
Published: January 2005

The photolysis of matrix-isolated cyanogen azide in the presence of carbon monoxide at wavelengths shorter than 2800 Å has been found to lead to the appearance of the free radical CCO in concentration sufficient for direct spectroscopic observation. This species has also been produced by the vacuum ultraviolet photolysis of matrix-isolated carbon suboxide. The three vibrational fundamentals of CCO have been observed in an argon matrix at 381, 1074, and 1978 cm−1, and CCO has been found to have a continuum near 5000 Å. Isotopic studies are consistent with a linear structure for CCO. Estimates of the force constants and thermodynamic properties are given. CCO has been observed to react with CO with little or no activation energy to form carbon suboxide. Other reactions occurring in the matrix are also discussed.
Magnetic Characteristics of Lanthanide Elements Combined with Tin, Lead, and Indium
Authors: Tsuchida T. , Wallace W. E.
Published: January 2005

The magnetic behavior of CeIn3, CePb3, and the series of compounds represented by the formula LnSn3 with Ln=Ce, Pr, Nd, Sm, and Gd has been investigated over the temperature range 2° to 300°K. Curie—Weiss behavior was observed in the upper portion of the temperature range for all compounds except SmSn3, and effective moments were in close agreement with those expected for the free tripositive ions. The behavior for SmSn3 is attributed to contribution of the first excited multiplet (J=7/2). Néel points were observed for CeIn3, PrSn3, NdSn3, and SmSn3. Deviations from Curie—Weiss behavior at low temperatures were observed in all cases and were ascribed to antiferromagnetic ordering, crystal-field effects, and ionization of Ce in the Ce compounds into the quadripositive state. GdSn3 is complex in that it shows deviation from Curie—Weiss below 40°K but it has no susceptibility peak.
Surface Tension and Molecular Correlations near the Critical Point
Authors: Widom B.
Published: January 2005

The van der Waals, Cahn—Hilliard theory of interfacial tension is reformulated for a fluid in the neighborhood of its critical point. The reformulated theory becomes equivalent to the Ornstein—Zernike, Debye theory of molecular correlations when the interface thickness is identified with the correlation length. When account is taken of the nonclassical behavior of the compressibility and coexistence curve, the theory is found to be in good agreement with independently known facts in three-dimensional systems, yet slightly but unambiguously wrong in two dimensions. When one of the hypotheses of the original theory is replaced by an alternative hypothesis, the resulting theory is found to be correct in both two and three dimensions.
Equation of State in the Neighborhood of the Critical Point
Authors: Widom B.
Published: January 2005

A specific form is proposed for the equation of state of a fluid near its critical point. A function Φ(x, y) is introduced, with x a measure of the temperature and y of the density. Fluids obeying an equation of state of van der Waals type (``classical'' fluids) are characterized by Φ being a constant. It is suggested that in a real fluid Φ(x, y) is a homogeneous function of x and y, with a positive degree of homogeneity (Sec. 2). This leads to a nonclassical compressibility, the behavior of which is determined by the degree of homogeneity of Φ (Sec. 3). A previously derived relation connecting the degree of the critical isotherm, the degree of the coexistence curve, and the compressibility index, again follows, this time without the restrictive assumption of effective isochore linearity (Sec. 4). The locus in the temperature—density plane of the points of inflection in the pressure—density isotherms, as determined experimentally by Habgood and Schneider, is accounted for (Sec. 5). It is shown that if a certain combination of the compressibility and coexistence curve indices is an integer, then the constant-volume specific heat on the critical isochore has a logarithmic singularity at the critical temperature with, in general, a superimposed finite discontinuity (Sec. 6).
Cluster Theory of Polyelectrolyte Solutions. II. Additivity Rules, Osmotic Pressure, and Donnan Equilibrium
Authors: Manning Gerald S.
Published: January 2005

We apply the results of the previous paper describing the free energy of a polyelectrolyte-added salt solution to the derivation of a relation between the osmotic coefficient and the activity coefficients of the mobile ions. From this relation, observed to be in excellent agreement with experiment, we obtain expressions resembling the empirical additivity rules. We conclude that the concept of ion binding may not be the appropriate way to interpret these rules. We also obtain an expression for the Donnan distribution of mobile ions and discuss the difficulties involved in the calculation of the Donnan osmotic pressure.
Absolute Intensities of the Discrete and Continuous Absorption Bands of Oxygen Gas at 1.26 and 1.065 μ and the Radiative Lifetime of the 1Δg State of Oxygen
Authors: Badger Richard M. , Wright Alan C. , Whitlock Rodger F.
Published: January 2005

Laboratory measurements have been made of the absolute intensities of the discrete-line absorption band at 1.26 μ, and of the continuous bands at 1.26 and 1.065 μ in oxygen gas at pressures up to 4.3 atm. It has been shown that discrete and continuous absorptions are quite independent features, the one being a measure of the intrinsic transition probability in isolated molecules, the other of its enhancement in collision complexes. In the former the lines show significant pressure broadening, but the integral molecular absorption coefficients are constant; in the latter they are proportional to pressure and continuous absorption dominates in the 1.26-μ region at about ½ atm oxygen pressure.

The radiative half-life of isolated 1Δg oxygen molecules is estimated to be 45 min, and the effect of gas pressure on the rate of decay has been predicted.
Valence Excited States of N2, CO, and BF
Authors: Nesbet R. K.
Published: January 2005

Excitation energies and other spectroscopic constants (re, ωe, ωexe, Be) are computed for excited electronic valence states of N2, CO, and BF and their singly positive ions. The states considered are the lowest states of symmetry 1Σ−, 1Δ, 1Π, 3Π, 3Σ+, 3Δ, 3Σ− for the molecules and 2Σ+, 2Π for the ions. Approximate ground-state Hartree—Fock molecular orbitals and the first unoccupied π orbital obtained by diagonalizing the ground-state one-electron Hamiltonian in a limited orbital basis set are used to construct electronic wavefunctions of the correct symmetry for each excited state. Electric dipole moments and dipole-moment derivatives are computed. The computed Σ and Δ states of BF lie above the first ionization limit and are not expected to represent observable physical states. Computed spectroscopic constants for the other states considered are compared with observed data.
Studies of Hydrogen-Bonded Systems. III. Potential-Energy Surface, Tunneling, and Tautomeric Equilibria in the N–H···N and O···H–N Bonds of the Guanine—Cytosine Base Pair
Authors: Rein Robert , Harris Frank E.
Published: January 2005

An earlier study of the authors on hydrogen bonding in the guanine—cytosine complex is extended so that the σ electrons of all three connecting hydrogen bonds are considered explicitly. This extension permits a discussion of possible simultaneous tautomeric rearrangements involving more than one proton. Calculations are presented for 74 protonic configurations characterizing the simultaneous rearrangement of the N–H···N and one of the N–H···O bonds. The results indicate four relative minima corresponding to different metastable tautomeric forms. The equilibrium distribution and tunneling between tautomers is examined, and leads to a predicted mechanism for the rearrangement. Equilibration among the tautomers is estimated to have a time constant of 3.8×10−5 sec.
Repulsion Center of a Bonded Hydrogen Atom
Authors: Williams Donald E.
Published: January 2005

The center of repulsion of a bonded hydrogen atom in a hydrogen molecule was found to be appreciably shifted from the proton into the bond. The magnitude of the shift was found to be 0.07–0.10 Å based on quantum-mechanical calculations of the energy of the He–H2 and H2–H2 systems. The shift of the repulsion center is in good agreement with the shift of the center of spherical electron density found by Stewart, Davidson, and Simpson.
Matrix-Isolation Infrared Spectrum of the Free Radical NH2
Authors: Milligan Dolphus E. , Jacox Marilyn E.
Published: January 2005

The free radical NH2 has been produced in concentration sufficient for direct infrared detection by photolysis of ammonia isolated in argon, nitrogen, and carbon monoxide matrices at 14°K with microwave-powered hydrogen and xenon discharges. Ultraviolet absorptions characteristic of both NH and NH2 are observed in photolyzed argon and nitrogen matrix samples. In the CO matrix, infrared observations show a high concentration of HCO after photolysis, further demonstrating the production of H atoms by the photolysis of ammonia. Two of the infrared fundamentals of 14NH2, at 1499 and 3220 cm−1, and of 15NH2, at 1495.5 and 3215 cm−1, one of NHD, at 1321 cm−1, and one of ND2, at 1110 cm−1, have been observed. Spectra observed in an argon matrix are relatively complex, suggesting that rotation of NH2 may be possible in this matrix. The force constants and thermodynamic properties of NH2 are estimated. The photolysis of matrix-isolated ammonia has been found to be relatively inefficient, in contrast to an earlier prediction.
Phase Changes and Electrical Conductivity of Concentrated Lithium—Ammonia Solutions and the Solid Eutectic
Authors: Morgan J. A. , Schroeder R. L. , Thompson J. C.
Published: January 2005

The electrical conductivities of concentrated solutions of lithium in ammonia have been measured over the temperature range 65° to 300°K by both conventional dc techniques and electrodeless techniques. In the liquid phase, conductivities ranged from 400 to 15 000 Ω−1·cm−1 at 240°K; the temperature coefficient of conductivity varied from +1.0% deg−1 to zero. Phase changes were indicated by discontinuities in either the conductivity or the temperature derivative of conductivity. No sign of a maximum in the melting-point-vs-concentration curve near the tetra-amine lithium [Li(NH3)4] concentration was found. The eutectic was found to be 89.6°±0.3°K. The conductivity of the solid was 6.7 times as large as that of the liquid at the melting point. In addition to phase changes in the liquid, two solid-phase changes were observed; one at 82°K and the other at 69°K. Conductivities in the solid were decreasing functions of the temperature in each solid phase, yet were higher in the high-temperature solid phases. The highest conductivity observed was 90 000 Ω−1·cm−1 (at 83°K). The solid does not behave as do the eutectics of sodium—ammonia or potassium—ammonia solutions. A comparison with other metal—ammonia solutions is made.
Gaussian-Transform Method for Molecular Integrals. I. Formulation for Energy Integrals
Authors: Shavitt I. , Karplus M.
Published: January 2005

The Gaussian-transform method for the evaluation of multicenter nuclear-attraction and electron-repulsion integrals over one-electron exponential orbitals is described. The basic formulas for 1s orbitals are developed, and machine methods for their extension to higher orbitals are outlined. Computational techniques for the implementation of the Gaussian-transform method are given with emphasis on the requirements for accuracy and speed in the calculations. Possible improvements and extensions of the method are discussed.
Electronic Structure of CO and BF
Authors: Huo Winifred M.
Published: January 2005

Single-determinantal self-consistent-field wavefunctions calculated by the expansion method are reported for the ground state of CO and BF. These calculations were performed at four different internuclear distances, including the experimental equilibrium internuclear distance. Exponents are optimized at all four distances. Potential curves and dipole-moment curves are obtained. From the potential curve, spectroscopic constants are calculated via the Dunham analysis. An SCF calculation was then performed at the calculated Re. Exponents are also optimized. Expectation values of a number of one-electron operators, including the electric dipole moment, the gradient of the electric field at the nucleus, and the Hellmann—Feynman force, are presented and compared with experimental data available. Contour diagrams for the total charge densities and orbital charge densities are included.