bluuebunny/crossref_metadata_2025 huggingface dataset:
Scaling exponents of the velocity structure functions in the interplanetary medium
Authors: Carbone V.
Published: April 2005

Abstract. We analyze the scaling exponents of the velocity structure functions, obtained from the velocity fluctuations measured in the interplanetary space plasma. Using the expression for the energy transfer rate which seems the most relevant in describing the evolution of the pseudo-energy densities in the interplanetary medium, we introduce an energy cascade model derived from a simple fragmentation process, which takes into account the intermittency effect. In the absence and in the presence of the large-scale magnetic field decorrelation effect the model reduces to the fluid and the hydromagnetic p-model, respectively. We show that the scaling exponents of the q-th power of the velocity structure functions, as obtained by the model in the absence of the decorrelation effect, furnishes the best-fit to the data analyzed from the Voyager 2 velocity field measurements at 8.5 AU. Our results allow us to hypothesize a new kind of scale-similarity for magnetohydrodynamic turbulence when the decorrelation effect is at work, related to the fourth-order velocity structure function.
Instability of the magnetosphere-ionosphere convection and formation of auroral arcs
Authors: Kozlovsky A. E. , Lyatsky W. B.
Published: April 2005

Abstract. In this paper we study an instability of the plasma moving towards the Earth near the inner plasma sheet boundary. We include both the interchange instability of the plasma sheet and the magnetosphere-ionosphere interaction instability caused by an effect of field-aligned currents (connected with electron precipitation) on ionospheric conductivity. The instability leads to the separation of steady-state magnetospheric convection into parallel layers. This instability may be responsible for the appearance of quiet auroral arcs inside region 2 of field-aligned currents flowing out of the ionosphere. This instability allows us to explain also the existence of crossing auroral arcs.
Precambrian glaciations and the evolution of the atmosphere
Authors: Carver J. H. , Vardavas I. M.
Published: April 2005

Abstract. Precambrian glaciations appear to be confined to two periods, one in the early Proterozoic between 2.5 and 2 Gyears BP (Before Present) and the other in the late Proterozoic between 1 and 0.57 Gyear BP. Possible reasons for these broad features of the Precambrian climate have been investigated using a simple model for the mean surface temperature of the Earth that partially compensates for the evolution of the Sun by variations in the atmospheric CO2 content caused by outgassing, the formation of continents and the weathering of the Earth's land surface. It is shown that the model can explain the main changes in the Precambrian climate if the early Proterozoic glaciations were caused by a major episode of continental land building commencing about 3 Gyears BP while the late Proterozoic glaciations resulted from biologicallyenhanced weathering of the land surface due to the proliferation of life forms in the transition from the Proterozoic to the Phanerozoic that began about 1 Gyear BP.
Dynamics of aircraft exhaust plumes in the jet-regime
Authors: Kärcher B. , Fabian P.
Published: April 2005

Abstract. A computational model describing the two-dimensional, turbulent mixing of a single jet of exhaust gas from aircraft engines with the ambient atmosphere is presented. The underlying assumptions and governing equations are examined and supplemented by a discussion of analytical solutions. As an application, the jet dynamics of a B747-400 aircraft engine in cruise and its dependence on key parameters is investigated in detail. The computer code for this dynamical model is computationally fast and can easily be coupled to complex chemical and microphysical models in order to perform comprehensive studies of atmospheric effects from aircraft exhaust emissions in the jet regime.
Modeling of aircraft exhaust emissions and infrared spectra for remote measurement of nitrogen oxides
Authors: Beier K. , Schreier F.
Published: April 2005

Abstract. Infrared (IR) molecular spectroscopy is proposed to perform remote measurements of NOx concentrations in the exhaust plume and wake of aircraft. The computer model NIRATAM is applied to simulate the physical and chemical properties of the exhaust plume and to generate low resolution IR spectra and synthetical thermal images of the aircraft in its natural surroundings. High-resolution IR spectra of the plume, including atmospheric absorption and emission, are simulated using the molecular line-by-line radiation model FASCODE2. Simulated IR spectra of a Boeing 747-400 at cruising altitude for different axial and radial positions in the jet region of the exhaust plume are presented. A number of spectral lines of NO can be identified that can be discriminated from lines of other exhaust gases and the natural atmospheric background in the region around 5.2 µm. These lines can be used to determine NO concentration profiles in the plume. The possibility of measuring nitrogen dioxide NO2 is also discussed briefly, although measurements turn out to be substantially less likely than those of NO. This feasibility study compiles fundamental data for the optical and radiometric design of an airborne Fourier transform spectrometer and the preparation of in-flight measurements for monitoring of aircraft pollutants.
Chemical composition and photochemical reactivity of exhaust from aircraft turbine engines
Authors: Spicer C. W. , Holdren M. W. , Riggin R. M. , Lyon T. F.
Published: April 2005

Abstract. Assessment of the environmental impact of aircraft emissions is required by planners and policy makers. Seveal areas of concern are: 1. exposure of airport workers and urban residents to toxic chemicals emitted when the engines operate at low power (idle and taxi) on the ground; 2. contributions to urban photochemical air pollution of aircraft volatile organic and nitrogen oxides emissions from operations around airports; and 3. emissions of nitrogen oxides and particles during high-altitude operation. The environmental impact of chemicals emitted from jet aircraft turbine engines has not been firmly established due to lack of data regarding emission rates and identities of the compounds emitted. This paper describes an experimental study of two different aircraft turbine engines designed to determine detailed organic emissions, as well as emissions of inorganic gases. Emissions were measured at several engine power settings. Measurements were made of detailed organic composition from C1 through C17, CO, CO2, NO, NOx, and polycyclic aromatic hydrocarbons. Measurements were made using a multi-port sampling pro be positioned directly behind the engine in the exhaust exit plane. The emission measurements have been used to determine the organic distribution by carbon number and the distribution by compound class at each engine power level. The sum of the organic species was compared with an independent measurement of total organic carbon to assess the carbon mass balance. A portion of the exhaust was captured and irradiated in outdoor smog chambers to assess the photochemical reactivity of the emissions with respect to ozone formation. The reactivity of emissions from the two engines was apportioned by chemical compound class.
Electron transport and energy degradation in the ionosphere: evaluation of the numerical solution, comparison with laboratory experiments and auroral observations
Authors: Lummerzheim D. , Lilensten J.
Published: April 2005

Abstract. Auroral electron transport calculations are a critical part of auroral models. We evaluate a numerical solution to the transport and energy degradation problem. The numerical solution is verified by reproducing simplified problems to which analytic solutions exist, internal self-consistency tests, comparison with laboratory experiments of electron beams penetrating a collision chamber, and by comparison with auroral observations, particularly the emission ratio of the N2 second positive to N+2 first negative emissions. Our numerical solutions agree with range measurements in collision chambers. The calculated N22P to N+21N emission ratio is independent of the spectral characteristics of the incident electrons, and agrees with the value observed in aurora. Using different sets of energy loss cross sections and different functions to describe the energy distribution of secondary electrons that emerge from ionization collisions, we discuss the uncertainties of the solutions to the electron transport equation resulting from the uncertainties of these input parameters.
Doppler-shifted auroral H β emission: a comparison between observations and calculations
Authors: Søraas F. , Måseide K. , Torheim P. , Aarsnes K.
Published: April 2005

Abstract. Two sounding rockets equipped with photometers and particle detectors have been flown into proton auroras. The measured altitude dependence of the proton flux is compared with calculations based upon known energy-range relations for protons in air. Expressions suitable for numerical calculations of Doppler profiles at arbitrary angles to the geomagnetic field and at different heights within an aurora are developed. Profiles due to some typical proton spectra have been calculated and it is shown that altitude profiles at some wavelengths are more sensitive to the shape of the proton spectrum than are profiles at other wavelengths. Variations in the Hβ Doppler profile versus height for several angles with the magnetic field is studied. Profiles, as generated by the actually measured protons in the energy range 1 keV to 1 MeV, have been calculated and are compared with direct optical measurements made by ground and rocket photometers. The rocket photometers took measurements at different wavelengths within the Doppler profile. The correspondence between calculations and measurements is generally good. The total Hβ is calculated and fair agreement with the measured intensity is found.
Ionospheric convection during the magnetic storm of 20-21 March 1990
Authors: Taylor J. R. , Yeoman T. K. , Lester M. , Buonsanto M. J. , Scali J. L. , Ruohoniemi J. M. , Kelly J. D.
Published: April 2005

Abstract. We report on the response of high-latitude ionospheric convection during the magnetic storm of March 20-21 1990. IMP-8 measurements of solar wind plasma and interplanetary magnetic field (IMF), ionospheric convection flow measurements from the Wick and Goose Bay coherent radars, EISCAT, Millstone Hill and Sondrestrom incoherent radars and three digisondes at Millstone Hill, Goose Bay and Qaanaaq are presented. Two intervals of particular interest have been identified. The first starts with a storm sudden commencement at 2243 UT on March 20 and includes the ionospheric activity in the following 7 h. The response time of the ionospheric convection to the southward turning of the IMF in the dusk to midnight local times is found to be approximately half that measured in a similar study at comparable local times during more normal solar wind conditions. Furthermore, this response time is the same as those previously measured on the dayside. An investigation of the expansion of the polar cap during a substorm growth phase based on Faraday's law suggests that the expansion of the polar cap was nonuniform. A subsequent reconfiguration of the nightside convection pattern was also observed, although it was not possible to distinguish between effects due to possible changes in By and effects due to substorm activity. The second interval, 1200-2100 UT 21 March 1990, included a southward turning of the IMF which resulted in the Bz component becoming -10 nT. The response time on the dayside to this change in the IMF at the magnetopause was approximately 15 min to 30 min which is a factor of ~2 greater than those previously measured at higher latitudes. A movement of the nightside flow reversal, possibly driven by current systems associated with the substorm expansion phases, was observed, implying that the nightside convection pattern can be dominated by substorm activity.
High resolution crystal structures of human Rab4a in its active and inactive conformations
Authors: Huber Silke K. , Scheidig Axel J.
Published: April 2005

The Ras‐related human GTPase Rab4a is involved in the regulation of endocytosis through the sorting and recycling of early endosomes. Towards further insight, we have determined the three‐dimensional crystal structure of human Rab4a in its GppNHp‐bound state to 1.6 Å resolution and in its GDP‐bound state to 1.8 Å resolution, respectively. Despite the similarity of the overall structure with other Rab proteins, Rab4a displays significant differences. The structures are discussed with respect to the recently determined structure of human Rab5a and its complex with the Rab5‐binding domain of the bivalent effector Rabaptin‐5. The Rab4 specific residue His39 modulates the nucleotide binding pocket giving rise to a reduced rate for nucleotide hydrolysis and exchange. In comparison to Rab5, Rab4a has a different GDP‐bound conformation within switch 1 region and displays shifts in position and orientation of the hydrophobic triad. The observed differences at the S2–L3–S3 region represent a new example of structural plasticity among Rab proteins and may provide a structural basis to understand the differential binding of similar effector proteins.
Internal drive vs external directive: the delivery of conservation through zoo-based research – a response to Rees
Authors: Thomas Rob
Published: April 2005

In the title of his paper Rees (2005) asked a perfectly valid question with regard to one specific element: the effectiveness of European legislation in enhancing the impact of zoo research in conservation. However, the question was not fully addressed, and the answer may be difficult to determine, due in part to the increasing importance placed on research by zoos independently, and in many cases ahead of, legislation. He discusses at some length the way in which the proportion of zoo based research has shifted in recent years to accommodate and address many of the more technically challenging issues of nutrition, reproduction and population dynamics but without losing sight of the valuable behavioural elements of research on captive animals. Rees manages during the
course of his argument to answer many of his own questions, with some clear examples of where and how the practical link can be made between many zoo activities, not just research, and the ultimate delivery of conservation benefits to species. It is worth noting, however, that in many cases the truly measurable and sustainable effect of conservation action on populations, species and habitats requires a timescale that spans generations and therefore may not yet be apparent.
Towards a research-based conservation identity for zoos – a reply to Wehnelt and Wilkinson, and Thomas
Authors: Rees Paul A.
Published: April 2005

Wehnelt & Wilkinson (2005) suggest that I am confused about the aim of the Zoos Directive, stating that it is ‘… to further the conservation role of zoos rather than increasing research activities.’ On the contrary, they have confused the aim with the means of compliance. Participating in research is but one means by which a zoo may demonstrate a conservation role. I have not suggested that research activity should be increased, or that poorly resourced zoos should develop research programmes, or indeed that research is a compulsory activity. I have merely suggested that much of the research undertaken
in zoos is not directly relevant to conservation and, as such, does not fulfil the requirements of the Directive. Wehnelt & Wilkinson have produced no evidence to the contrary.
PETER MAXWELL DAVIES'S ‘NAXOS’ QUARTETS
Authors: Lister Rodney
Published: April 2005

The path of a composer's career may include a number of unexpected twists and turns. Some of them may immediately seem to be quite radical, leaving many observers always in a state of thinking that the very last thing that the composer was doing was so much better than this new thing. Then, after time, in retrospect, the way is seen to have been straight and plain, rather than crooked and rough, and the development to have proceeded quietly with a consistent, internally logical progress, producing works whose commonality of artistic vision and structural procedure is more apparent than their more minor surface stylistic differences.
ABOVE AND BEYOND THE BASS: HARMONY AND TEXTURE IN GEORGE BENJAMIN'S ‘VIOLA, VIOLA’
Authors: Rupprecht Philip
Published: April 2005

George Benjamin's rich harmonic imagination was apparent from his earliest published works. A distinctive chordal sensibility is already evident in the 1978 Piano Sonata, with its glittering streams of five- or six-pitch clusters; in the hollow bell-chords punctuating the 1979 orchestral score, Ringed by the Flat Horizon; and in the supreme stasis of the A-minor pedal chord (a six-three triad) unveiled by the icy glissandi lines opening A Mind of Winter (1981). All three pieces share a fascination with degrees of chordal resonance – the interplay of upper partials above a fundamental – and a sensitivity to chords as sound objects. True, Benjamin's style, beginning at least with Antara (1987), has shown signs of a more linear-contrapuntal orientation, and less reliance on what one critic terms ‘purely coloristic phenomena’. Yet one could equally claim some continuity between the refined harmonic world of the early scores and the surprising richness of chordal sonority to be heard in a far more recent arrival, the 1997 duo Viola, Viola.
Piano Music by Gurney and Ferguson
Authors: McBurney Gerard
Published: April 2005

IVOR GURNEY: Despair; Sehnsucht; Song of the Summer Woods; The Sea; Nocturnes in B and A flat; Preludes Nos.1–9. HOWARD FERGUSON: Piano Sonata in F minor; Five Bagatelles. Mark Bebbington (pno). Somm New Horizons SOMMCD 038.
Natural and anthropogenic modes of surface temperature variations in the last thousand years
Authors: Zorita E. , González‐Rouco J. F. , von Storch H. , Montávez J. P. , Valero F.
Published: April 2005

The spatial patterns of surface air‐temperature variations in the period 1000 to 2100, simulated with the ECHO‐G atmosphere‐ocean coupled model, are analyzed. The model was driven by solar, volcanic and greenhouse gas forcing. The leading mode of temperature variability in the preindustrial period represents an almost global coherent variation of temperatures, with larger amplitudes over the continents and Northern Hemisphere. This mode also describes a large part of the spatial structure of the warming simulated in the 21st century. However, in the 21st century, regional departures from this spatial structure are also present and can be ascribed to atmospheric circulation responses to anthropogenic forcing in the last decades of the 21st century.
Midlatitude TEC enhancements during the October 2003 superstorm
Authors: Foster J. C. , Rideout W.
Published: April 2005

We use observations from the array of North American GPS receivers to examine the formation and severity of midlatitude enhancements and steep gradients in total electron content (TEC) during the October 30–31, 2003 superstorm. A large (∼10x) enhancement in dayside TEC was observed over the US mainland during these events as Dst decreased sharply and strong SAPS electric fields eroded the outer reaches of the post‐noon plasmasphere boundary layer (PBL) forming poleward‐streaming plumes of storm enhanced density. TEC increased to >250 TECu equatorward of the PBL. TEC gradients across the PBL over the central US exceeded 60 TECu per deg latitude. While intense, these features are qualitatively similar to those seen in lesser storms.
Teleseismic P‐wave tomogram of the Yellowstone plume
Authors: Yuan Huaiyu , Dueker Ken
Published: April 2005

Inversion of a new data set of teleseismic P‐wave travel‐times from three PASSCAL seismic deployments around the Yellowstone hotspot reveals a 100 km diameter upper mantle plume that extends from the Yellowstone volcanic caldera to 500 km depth and dips 20° to the northwest. A monotonic decrease in the velocity perturbation of the plume from −3.2% at 100 km to −0.9% at 450 km is consistent with a uniform thermal anomaly of 180°C. Where the plume crosses the 410 km discontinuity, previous research shows a depression in the 410 km discontinuity consistent with a warm plume (Fee and Dueker, 2004). Additionally, a region of high velocities extends to 250 km beneath the Wind River basin in NW Wyoming that may represent a convective downwelling of the lithosphere.
El Niño–driven landsliding and postgrazing vegetative recovery, Santa Cruz Island, California
Authors: Pinter Nicholas , Vestal W. Dean
Published: April 2005

El Niño–driven storms triggered widespread slope failures on Santa Cruz Island (SCI), California, during the 1997–1998 winter. After 120 years of intensive grazing, sheep had been removed from the western 90% of SCI in the 1980s. The contrast between sheep‐free western SCI and heavily grazed eastern SCI created a natural laboratory for studying the effects of grazing and postgrazing recovery. Logistic regression was used to identify factors that exerted significant control upon slope failure and to test the hypothesis that land use and vegetation were the dominant controls on failure occurrence in 1997–1998. High‐resolution air photos were shot immediately before and after the storm season and were precisely orthorectified using a custom‐generated 10 m digital elevation model. The before and after orthoimages were used to map 1922 discrete slope failures across the island, of which 720 were measured in the field and 202 were precisely surveyed. Although sheep‐grazed land comprised just 10% of the island, 80% of all slope failures occurred in those areas. Additional controls on soil slip occurrence included bedrock lithology, slope aspect, slope curvature, and elevation. The predominate influence of land use on the 1997–1998 slope failures reflects the dramatic vegetative change on SCI in the ∼25 years since sheep removal on western SCI. On the basis of the best‐fit logistic regression model, slope failures were 67 times less likely with each unit increase in Normalized Difference Vegetation Index. Increases in vegetation density and variety appear to have added significant strength to the soil, reinforcing the surface against widespread slope failures during precipitation events with return times as high as 100 years. Heavy rainfall also occurred in the study area during the 2004–2005 winter, 4 years after removal of the last sheep from all areas of the island in 2001. Field reconnaissance showed that vegetation density had increased markedly, and soil slippage was virtually absent in 2005 in areas heavily impacted in 1997–1998.
Sp3 is involved in the regulation of SOCS3 gene expression
Authors: EHLTING Christian , HÄUSSINGER Dieter , BODE Johannes G.
Published: April 2005

Cytokine-induced expression of SOCS (suppressor of cytokine signalling) molecules is important for the negative regulatory control of STAT (signal transduction and activators of transcription)-dependent cytokine signalling, e.g. for the signal transduction of IL-6 (interleukin-6)-type cytokines through the JAK (Janus kinase)/STAT cascade. STAT activation itself represents an important step in the transcriptional activation of SOCS3 gene expression. However, downstream of the STAT-responsive element, the SOCS3 gene contains a GC-rich element in its 5′-upstream region. The aim of the present study was to investigate the implications of this GC-rich element in the transcriptional control of SOCS3 gene expression. In the present study, we show that mutation of this GC-rich element abolishes IL-6-dependent transcriptional activation of the SOCS3 promoter and that Sp3 (specificity protein 3), a ubiquitously expressed transcription factor, but not Sp1 binds to this GC-rich motif, suggesting that Sp3 is involved in the regulation of SOCS3 expression. The results suggest that Sp3 is important for IL-6-induced transcriptional activation of the SOCS3 (gene) promoter and acts as an enhancer of basal as well as induced transcriptional activity, resulting in enhanced SOCS3 mRNA and protein expression. Mutation of Lys-483, a potential target for Sp3 acetylation, inhibited Sp3-mediated enhancement of SOCS3 mRNA expression and SOCS3 promoter activation, indicating that the acetylation of this lysine residue of Sp3 is important for the enhancing effect of Sp3 on SOCS3 expression.
The plastid division proteins, FtsZ1 and FtsZ2, differ in their biochemical properties and sub-plastidial localization
Authors: EL-KAFAFI El-Sayed , MUKHERJEE Sunil , EL-SHAMI Mahmoud , PUTAUX Jean-Luc , BLOCK Maryse A. , PIGNOT-PAINTRAND Isabelle , LERBS-MACHE Silva , FALCONET Denis
Published: April 2005

Plastid division in higher plants is morphologically similar to bacterial cell division, with a process termed binary fission involving constriction of the envelope membranes. FtsZ proteins involved in bacterial division are also present in higher plants, in which the ftsZ genes belong to two distinct families: ftsZ1 and ftsZ2. However, the roles of the corresponding proteins FtsZ1 and FtsZ2 in plastid division have not been determined. Here we show that the expression of plant FtsZ1 and FtsZ2 in bacteria has different effects on cell division, and that distinct protein domains are involved in the process. We have studied the assembly of purified FtsZ1 and FtsZ2 using a chemical cross-linking approach followed by PAGE and electron microscopy analyses of the resulting polymers. This has revealed that FtsZ1 is capable of forming long rod-shaped polymers and rings similar to the bacterial FtsZ structures, whereas FtsZ2 does not form any organized polymer. Moreover, using purified sub-plastidial fractions, we show that both proteins are present in the stroma, and that a subset of FtsZ2 is tightly bound to the purified envelope membranes. These results indicate that FtsZ2 has a localization pattern distinct from that of FtsZ1, which can be related to distinct properties of the proteins. From the results presented here, we propose a model for the sequential topological localization and functions of green plant FtsZ1 and FtsZ2 in chloroplast division.
Pregnenolone-16α-carbonitrile inhibits rodent liver fibrogenesis via PXR (pregnane X receptor)-dependent and PXR-independent mechanisms
Authors: MAREK Carylyn J. , TUCKER Steven J. , KONSTANTINOU Dimitrios K. , ELRICK Lucy J. , HAEFNER Dee , SIGALAS Charalambos , MURRAY Graeme I. , GOODWIN Bryan , WRIGHT Matthew C.
Published: April 2005

The effect of liver growth stimulation [using the rodent PXR (pregnane X receptor) activator PCN (pregnenolone-16α-carbonitrile)] in rats chronically treated with carbon tetrachloride to cause repeated hepatocyte necrosis and liver fibrogenesis was examined. PCN did not inhibit the hepatotoxicity of carbon tetrachloride. However, transdifferentiation of hepatic stellate cells and the extent of fibrosis caused by carbon tetrachloride treatment was significantly inhibited by PCN in vivo. In vitro, PCN directly inhibited hepatic stellate cell transdifferentiation to a profibrogenic phenotype, although the cells did not express the PXR (in contrast with hepatocytes), suggesting that PCN acts independently of the PXR. Mice with a functionally disrupted PXR gene (PXR−/−) did not respond to the antifibrogenic effects of PCN, in contrast with wild-type (PXR+/+) mice, demonstrating an antifibrogenic role for the PXR in vivo. However, PCN inhibited the transdifferentiation of PXR−/−-derived mouse hepatic stellate cells in vitro, confirming that there is also a PXR-independent antifibrogenic effect of PCN through a direct interaction with hepatic stellate cells. These data suggest that the PXR is antifibrogenic in rodents in vivo and that a PXR-independent target for PXR activators exists in hepatic stellate cells that also functions to inhibit fibrosis.
Exploring the functions of RNA interference pathway proteins: some functions are more RISCy than others?
Authors: JARONCZYK Katarzyna , CARMICHAEL Jon B. , HOBMAN Tom C.
Published: April 2005

PPD (PAZ Piwi domain) proteins and the Dicer family have been the subjects of intense study over the last 6 years. These proteins have well-established roles in RNAi (RNA interference), a process that relies on siRNAs (small interfering RNAs) or miRNAs (microRNAs) to mediate specificity. The development of techniques for applying RNAi as a laboratory tool and a molecular therapeutic technique has rapidly outpaced our understanding of the biology of this process. However, over the last 2 years, great strides have been made towards elucidating how PPD proteins and Dicer regulate gene-silencing at the pre- and post-transcriptional levels. In addition, evidence is beginning to emerge that suggests that these proteins have additional siRNA-independent roles as cell-cycle regulators. In the present review, we summarize the well-known roles of these two classes of proteins in gene-silencing pathways, as well as explore the evidence for novel roles of PPD and Dicer proteins.
Symmetry Classification of the Energy Levels of Some Triarylmethyl Free Radicals and Their Cations
Authors: Li Chu Ting , Weissman S. I.
Published: April 2005

The absorption and luminescence spectra of triphenylmethyl, tri-p-xenylmethyl, phenyl-di-p-xenylmethyl, diphenyl-p-xenylmethyl, and their cations have been determined. Polarization of the luminescence of each substance under excitation by plane polarized light has been examined. Assignment of symmetry classifications to the energy levels of these substances has been attempted.
The Infrared Spectrum and Molecular Constants of C14O2
Authors: Nielsen Alvin H. , Lagemann Robert T.
Published: April 2005

A detailed account of the appearance of and the constants derivable from the infrared absorption spectra of the active fundamentals v2 and v3 of C14O2 is given. The following constants have been determined: v2 = 632.20 cm—1, v3 = 2225.85 cm—1, B000 = 0.39078 cm—1, α3 = 0.00293 cm—1. The harmonic frequencies ωi and the anharmonic constants xij for the three isotopic species have been determined. Excellent agreement is obtained between observed and calculated band centers.
Temperature Gradients in Reacting Systems
Authors: Benson Sidney W.
Published: April 2005

A study of the heat conduction equation for reactions going on in a spherical flask leads to a calculation of three parameters, τ the mean lifetime for the establishment of stationary states, ΔTm the maximum temperature difference between the walls of the vessel and the reacting gas, and the average temperature difference 〈ΔTm〉Av. These are given by τ=ρcvr02π2K,  ΔTm=RHr026K,  〈ΔTm〉Av=RHr0215K in which ρ is the density, cv the specific heat at constant volume, r0 the radius of the vessel, K the coefficient of thermal conductivity, R the specific rate of reaction, and H the heat of reaction.

In liquid systems under usual conditions τ is of the order of r02 minutes (r0 in cm) while 〈ΔTm〉Av is about ±0.2°C (for H = ±10 kcal, half-life = 1 hour, r0 = 5 cm) so that such effects are usually negligible. In gases on the other hand 〈ΔTm〉Av can be of the order of magnitude of 2°C or higher depending on the various conditions, resulting in significant errors in observed rate constants and activation energies. The effects of added inert gases, pressure, vessel packing, and other parameters are discussed. A very crude treatment of convection shows that it is not expected to alter appreciably the magnitude of 〈ΔTm〉Av.
The Effect of Nonrigidity on the Line Strengths of Vibrational-Rotational Transitions
Authors: Allen Harry C.
Published: April 2005

The effect of the difference in asymmetry of the ground and excited states of a vibrttional band on the line strengths of the vibrational-rotational transitions has been investigated. It is found that for sufficiently large Δk (∼0.1—0.2) in A- and C-type bands there is an enhancement of the line strengths of either the R or P branch, depending on whether or not k of the ground state is greater or less than k of the excited state. In B-type bands certain sub-bands are enhanced, but in general no branch of the band is enhanced as a whole.
Microwave Spectra and Structures of Methyl Mercury Chloride and Bromide
Authors: Gordy Walter , Sheridan John
Published: April 2005

From the pure rotational spectra of several different isotopic species of CH3HgCl it is shown that dCHg=2.061±0.02A, dHgCl=2.282±0.005A, and ∠CHgCl=180°. Similarly, for CH3HgBr it is shown that dCHg=2.074±0.015A, dHgBr=2.406±0.005A, and ∠CHgBr=180°. Nuclear quadrupole couplings evaluated are Cl35=—42 Mc, Cl37=—33 Mc in CH3HgCl, and Br79=350 Mc, Br81=290 Mc in CH3HgBr. These indicate ionic character of 62 percent for the HgCl and 55 percent for the HgBr bond in these molecules, and lead to a value of 1.7 to 1.8 for the electronegativity of divalent mercury.
Electronic Structure of Disordered One-Dimensional Chains
Authors: Landauer Rolf , Helland Joseph C.
Published: April 2005

The positions of the electronic levels in a variety of finite one-dimensional models of disordered alloys and of liquids have been evaluated numerically over a wide range of energies. The disordered alloys consist of two types of potential wells thrown together in a random sequence, but in equal proportions. In the disordered case the tightly bound states give rise to narrow bands in which the distribution of states cannot be described by a smooth function. The distribution of states can be interpreted in terms of an approximation in which each electron is confined to its own group of adjacent identical atoms. At high energy levels the disordered alloys obey perturbation theory, at least in a qualitative fashion, and the ordered alloy differs from the disordered one because of the effect of Bragg reflections from the superlattice. At high energies the distribution of states can be described by a reasonably smooth density function. Between the high energy range and the tightly bound levels, in some of the cases a transition region occurs, in which the levels are distributed irregularly, but without well-defined gaps and without being susceptible to the simple explanation of localized states. The total number of states (not counting the two spin possibilities as separate states) up to a well-pronounced energy gap is always an integral multiple of one-half the total number of atoms in the chain.

The liquids consist of a series of identical wells separated by a variable well-to-well space. In a liquid the forbidden energy ranges are either smaller than in the strictly periodic crystal, or else nonexistent. The extent to which an energy gap in the strictly periodic crystal will be affected by the introduction of dispersion in the spacing depends on the original gap width as well as on the sensitivity of the gap position, in the strictly periodic case, to uniform dilations. In both the liquid cases and the disordered alloy models a distinction must be made between energy ranges in which the density of states is very low and ranges in which it is strictly zero.
Vacuum Ultraviolet Photochemistry, Part I. Nitrous Oxide at 1470 A
Authors: Zelikoff Murray , Aschenbrand Leonard M.
Published: April 2005

The photolysis of nitrous oxide at 1470 A has been studied and the quantum yields measured for N2O disappearance and NO, O2, and N2 appearance. The average of 38 measurements gives φN2O=1.70, φO2=0.50, and φN2=1.44 with φNO being pressure dependent. The data obtained here can be explained by a mechanism involving initial dissociation of nitrous oxide into nitrogen molecules and oxygen atoms. The source of NO can be in the reaction O+N2O→2NO. These results are discussed in the light of previous work.
Application of the Hertz Theory of Impact to Explosion Phenomena
Authors: Murgai M. P.
Published: April 2005

Pressure and time of impact have been calculated by Hertz theory of impact, taking data from some experiments on explosion. The calculated temperature rise, by adiabatic compression of an entrapped gas bubble, is within a reasonable range of that obtained experimentally. The calculated times have been compared with experimental observations on impact explosion delays. The adiabatic compression of solids has been referred to.
Dielectric Polarization in Polar Substances. Remark on a Paper by F. E. Harris and B. J. Alder
Authors: Fröhlich H.
Published: April 2005

A correction of a formula for the static dielectric constant derived by Harris and Alder is given in this paper.
Derivations of Onsager's Reciprocal Relations
Authors: Wigner Eugene P.
Published: April 2005

Two derivations of Onsager's reciprocal relations are presented in simplified form, and the range of their validity is discussed.
Infrared Spectrum and Molecular Constants of C2D2
Authors: Talley Robert M. , Nielsen Alvin H.
Published: April 2005

The infrared spectrum of C2D2 has been reinvestigated in the region 500 to 8000 K with a prism-grating spectrometer. Thirty-nine absorption bands were observed, of which twenty-six are new, and ten have been resolved into rotational fine structure. This brings the present total of observed bands to fifty one. Figures of the bands are shown, wave numbers of all observed lines are given in kaysers reduced to vacuum, and the absorption regions are described. All the bands observed have been given vibrational assignments, and a vibrational analysis has been made which yields the wave numbers of the harmonic frequencies and the values of the anharmonic constants. Rotational analyses of all the resolved bands have been made, and from these the rotational constants which agree with those obtained by Saksena have been determined.
Ionization of Strong Electrolytes. III. Proton Magnetic Resonance in Nitric, Perchloric, and Hydrochloric Acids
Authors: Hood G. C. , Redlich O. , Reilly C. A.
Published: April 2005

Since the proton magnetic resonance shift in an acid is a colligative property, the derivation of degrees of dissociation requires assumptions which cannot be tested directly. Results derived from measurements of this resonance shift in nitric acid and in perchloric acids are in sufficient agreement with earlier results obtained from a specific property (intensity of Raman lines) to confirm the interpretation of the shift. The value 22 has been found for the thermodynamic dissociation constant of nitric acid, the value 38 for perchloric acid.

The association of nitric acid in aqueous solutions containing more than 50 mole percent of acid is reflected in the shift. Differences in the limiting slopes of the resonance shift of the proton in various acids at high dilution are interpreted as due to different influences of the anions on the association of water.
The Infrared Spectra and Structure of LiOH, LiOH·H2O and the Deuterium Species. Remark on Fundamental Frequency of OH-
Authors: Jones Llewellyn H.
Published: April 2005

The infrared spectrum of a thin path of solid LiOH and LiOH·H2O (undeuterated, partially deuterated, and completely deuterated) has been observed. The spectra indicate that both hydrogens from each water molecule are used to form strong hydrogen bonds in the hydrate. The results serve to substantiate the crystal structures previously determined by x-ray diffraction. For LiOH the absorption maximum occurs at 3678±1 cm-1; the fundamental frequency of OH- in LiOH is 3839±10 cm-1. The spectrum of LiOH·HDO exhibits an anomaly in the bending frequency of HDO.
The Relation between Energy Levels of Substituent Groups and Electron Migration Effects in Some Monosubstituted Benzenes
Authors: Nagakura Saburo , Tanaka Jiro
Published: April 2005

Determinations of the highest occupied (HB, HS) and the lowest vacant levels (VB, VS) were made with benzene and some substituent groups using experimental knowledge of their ionization potentials and their near ultraviolet absorption spectra. On the basis of the relative height of these levels, monosubstituted benzenes can be classified into following three groups: (1) | VS–HB | < | VB–HS | for meta-directing molecules: (2) | VS–HB | > | VB–HS | for ortho-, para-directing molecules: (3) | VS–HB | ≈ | VB–HS | for styrene. By the aid of a simple quantum-mechanical treatment, it becomes sure that in the case of (1) the interaction between levels VS and HB is predominant and the migrating electron flows out of benzene into the substituent: on the other hand in the case of (2) the interaction between levels VB and HS is the stronger and the migrating electron moves in the reverse direction: and finally, in the case of (3), both interactions referred to in the foregoing should be taken into account with almost equal importance.

Furthermore, it was shown that the difference in the ionization potential between the meta- and the ortho-, para-directing monosubstituted benzenes can be interpreted by taking into consideration the interaction of HB with HS or VS, and that the absorption bands in the wavelength region 2300∼2600A, observed with meta-directing molecules, may be regarded as due to the transition between two levels which occur by the interaction between levels VS and HB.
The Lattice Constants of the Alkali Borohydrides and the Low-Temperature Phase of Sodium Borohydride
Authors: Abrahams S. C. , Kalnajs J.
Published: April 2005

The lattice constants of sodium, potassium, rubidium, and cesium borohydrides have been measured at 25.0°C as 6.1635±0.0005, 6.7272±0.0005, 7.029±0.001, and 7.419±0.001A, respectively. All four crystals are face-centered cubic and have the sodium chloride structure. Below the transition point (—83°C) sodium borohydride becomes tetragonal with lattice constants of a=4.354±0.005 and c=5.907±0.005A at —195°C.
The Intermolecular Potentials of Helium and Hydrogen
Authors: Mason Edward A. , Rice William E.
Published: April 2005

The parameters for helium and hydrogen of the ``exp-six'' potential, [open phi](r)=ε1−6/α[6αeα(1−r/rm)−(rmr)6],have been calculated by use of experimental values of the second virial coefficients and viscosity coefficients. Because of the uncertainty of the quantum corrections, no low temperature data were used in determining the parameters. The exp-six potential is able to reproduce both the second virial and the viscosity coefficients within experimental error, and is thus an improvement over the simpler Lennard-Jones (12-6) potential. In addition, other transport properties are accurately predicted. A combination rule is suggested for calculation of the exp-six potential between two unlike molecules from the potentials between two pairs of like molecules, and is used to calculate a number of properties of helium-hydrogen mixtures with satisfactory results.
Equilibrium Theory of Unimolecular Reactions
Authors: Giddings J. Calvin , Eyring Henry
Published: April 2005

This paper develops an equilibrium theory of unimolecular reactions, and shows how this theory is related to other theories, such as the Rice-Ramsperger-Kassel treatment. Unimolecular decomposition reactions and isomerization reactions are described in terms of statistical mechanics and quantum mechanics (potential energy surfaces). The nature of the transmission coefficient is discussed in detail.
l-Type Doubling in C2H2 and HCN
Authors: Wiggins T. A. , Shearer J. N. , Shull E. R. , Rank D. H.
Published: April 2005

A high-resolution infrared grating spectrometer has been used to investigate l-type doubling of energy levels of the linear molecules C2H2 and HCN. Resolving power of 145 000 was obtained at 4100 cm—1 which permitted the resolution of the Q branch of ν1+ν51(Σg+→πu) of C2H2 to J″ = 6. The difference between the B′—B″ value determined from the Q branch and the same quantity obtained from the P and R branches of this band yields a value of q = 4.72×10—3 cm—1. The doublet structure in the difference band 0110→0112(π→π) of HCN has been resolved for J″≥6 in the R branch and J″≥10 in the P branch. This π→π band is treated as two bands with slightly different molecular constants. Evaluation of rotational constants shows that different α values are obtained for the + and — components of these π states. The difference in frequency between lines of equal J″ in the 000→002 and 0110→0112 bands is shown to be a quadratic function of J″. The value obtained for q′ was 7.68×10—3 cm—1.
Magnetic Susceptibilities of K3MoCl6 and RuCl3
Authors: Epstein Charles , Elliott Norman
Published: April 2005

Magnetic susceptibilities of K3MoCl6 and RuCl3 were measured in the temperature range 76°—297°K. Curie's law is obeyed by both salts. The magnetic moments 3.83β and 2.07β are calculated for the ions Mo3+ and Ru3+, respectively.
An Investigation of the Microwave Spectrum of Pyridine
Authors: McCulloh K. E. , Pollnow Gilbert F.
Published: April 2005

The microwave spectrum of pyridine has been observed in the region from 22 140 to 27 300 mc. One hundred twenty-four lines have been found, while measured frequencies have been assigned to thirty-one Q transitions and three R branch transitions. From these data the molecular constants, including those pertaining to an approximate treatment of centrifugal distortion, have been evaluated.
The Intermolecular Potentials for Some Simple Nonpolar Molecules
Authors: Mason Edward A. , Rice William E.
Published: April 2005

Experimental data on the crystal properties, second virial coefficients, and viscosity coefficients of Ne, A, Kr, Xe, CH4, N2, CO, O2, and CO2 were analyzed for the purpose of obtaining values of the parameters in the exp-six intermolecular potential, [open phi](r)=ε1−6/α[6αeα(1−r/rm)−(rmr)6]. For gases whose molecules are spherical, it was possible to reproduce, with a single set of potential parameters, not only the crystal, second virial, and viscosity data, but also data on other transport properties with fair accuracy. For gases whose molecules deviate appreciably from spherical symmetry it was necessary to choose at least two different sets of potential parameters in order to reproduce different types of properties. Such behavior was taken to indicate the inadequacy of the assumptions, made in the fundamental gas theories, that intermolecular forces are central and that intermolecular collisions are elastic.
Infrared Spectrum of Hydrogen Sulfide. II. The 5100 cm-1 Region
Authors: Allen Harry C. , Plyler Earle K.
Published: April 2005

The absorption of hydrogen sulfide in the region near 2μ has been measured under high resolution. The rotational fine structure has been analyzed with the use of published energy tables for the rigid rotor. A classical centrifugal distortion correction was applied to the rigid rotor energy levels. The absorption can be accounted for by three bands plus overlapping water-vapor absorption. The three bands are the (n1,n2,n3) = (1,0,1) at 5147.36 cm-1, the (0,2,1) at 4939.23 cm-1, and the lower component of the resonating pair (2,0,0) and (0,0,2) at 5145.12 cm-1. The excited-state inertial parameters in cm-1 giving the best fits are A*B*C*(1,0,1)10.0768.7094.608(2,0,0)10.0598.7194.612(0,2,1)10.8719.3324.562.With the location of the (0,2,1) band it is possible to place the (0,0,1) band at 2628 cm-1.