bluuebunny/crossref_metadata_2025 huggingface dataset:
Observations of day-to-day variability in precursor signatures to equatorial F-region plasma depletions
Authors: Fagundes P. R. , Sahai Y. , Batista I. S. , Abdu M. A. , Bittencourt J. A. , Takahashi H.
Published: June 2005

Abstract. In December 1995, a campaign was carried out to study the day-to-day variability in precursor signatures to large-scale ionospheric F-region plasma irregularities, using optical diagnostic techniques, near the magnetic equator in the Brazilian sector. Three instruments were operated simultaneously: (a) an all-sky (180° field of view) imaging system for observing the OI 630 nm nightglow emission at Alcântara (2.5°S, 44.4°W); (b) a digisonde (256-Lowell) at São Luis (2.6°S, 44.2°W); and (c) a multi-channel tilting filter-type zenith photometer for observing the OI 630 nm and mesospheric nightglow emissions at Fortaleza (3.9°S, 38.4°W). During the period December 14-18, 1995 (summer in the southern hemisphere), a good sequence of the OI 630 nm imaging observations on five consecutive nights were obtained, which are presented and discussed in this study. The observing period was geomagnetically quiet to moderate  (Kp = 0+ to 5+; Dst = 18 nT to -37 nT). On four nights, out of the five observation nights, the OI 630 nm imaging pictures showed formations of transequatorial north-south aligned intensity depletions, which are the optical signatures of large-scale ionospheric F-region plasma bubbles. However, considerable day-to-day variability in the onset and development of the plasma depleted bands was observed. On one of the nights it appears that the rapid uplifting of the F-layer in the post-sunset period, in conjunction with gravity wave activity at mesospheric heights, resulted in generation of very strong plasma bubble irregularities. One of the nights showed an unusual formation of north-south depleted band in the western sector of the imaging system field of view, but the structure did not show any eastward movement, which is a normal characteristic of plasma bubbles. This type of irregularity structure, which probably can be observed only by wide-angle imaging system, needs more investigations for a better understanding of its behaviour.Key words. Atmospheric composition and structure (airglow and aurora) · Ionosphere (equatorial ionosphere; ionospheric irregularities)
Letter to the Editor: Complete maps of the aspect sensitivity of VHF atmospheric radar echoes
Authors: Worthington R. M. , Palmer R. D. , Fukao S.
Published: June 2005

Abstract. Using the MU radar at Shigaraki, Japan (34.85°N, 136.10°E), we measure the power distribution pattern of VHF radar echoes from the mid-troposphere. The large number of radar beam-pointing directions (320) allows the mapping of echo power from 0° to 40° from zenith, and also the dependence on azimuth, which has not been achieved before at VHF wavelengths. The results show how vertical shear of the horizontal wind is associated with a definite skewing of the VHF echo power distribution, for beam angles as far as 30° or more from zenith, so that aspect sensitivity cannot be assumed negligible at any beam-pointing angle that most existing VHF radars are able to use. Consequently, the use of VHF echo power to calculate intensity of atmospheric turbulence, which assumes only isotropic backscatter at large beam zenith angles, will sometimes not be valid.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; turbulence; instruments and techniques)
On the dispersion of two coexisting nongyrotropic ion species
Authors: Brinca A. L. , Motschmann U. , Romeiras F. J.
Published: June 2005

Abstract. Space observations in the solar wind and simulations of high Mach number bow-shocks have detected particle populations with two coexisting nongyrotropic ion species. We investigate the influence of these two sources of free energy on the stability of parallel (with respect to the ambient magnetic field) and perpendicular propagation. For parallel modes, we derive their dispersion equation in a magnetoplasma with protons and alpha particles that may exhibit stationary nongyrotropy (SNG) and discuss the characteristics of its solutions. Kinetic simulations study the behaviour of perpendicular electrostatic (Bernstein-like) waves in a plasma whose ion populations (positrons and fictitious singly-charged particles with twice the electron mass, for the sake of simulation feasability) can be time-varying nongyrotropic (TNG). The results show that the coexistence of two gyrophase bunched species does not significantly enhance the parallel SNG instability already found for media with only one nongyrotropic species, whereas it strongly intensifies the growth of Bernstein-like modes in TNG plasmas. Key words. Magnetospheric physics (plasma waves and instabilities) · Space plasma physics (numerical simulation studies; waves and instabilities)
The dynamic cusp aurora on 30 November 1997: response to southward turning of the IMF
Authors: Sandholt P. E. , Farrugia C. J. , Lybekk B.
Published: June 2005

Abstract. We document the detailed dynamics of the dayside aurora in the \\sim1200-1600 MLT sector in response to a sharp southward turning of the interplanetary magnetic field (IMF) under negative IMF By conditions. Features not documented in previous work are elucidated by using two meridan scanning photometers (separated by 2 h) and an all-sky auroral imager in Ny Ålesund, Svalbard (75.5°MLAT) in combination with magnetograms from stations on Svalbard, covering the latitude range 71°75°MLAT. The initial auroral response may be divided into three phases consisting of: (1) intensification of both the red (630.0 nm) and green (557.7 nm) line emissions in the cusp aurora near 1200 MLT and ~100 km equatorward shift of its equatorward boundary, at ~75°MLAT, (2) eastward and poleward expansions of the cusp aurora, reaching the 1430 MLT meridian after 5-6 min, and (3) east-west expansion of the higher-latitude aurora (at ~77°78°MLAT) in the postnoon sector. The associated magnetic disturbance is characterized by an initial positive deflection of the X-component at stations located 100-400 km south of the aurora, corresponding to enhanced Sunward return flow associated with the merging convection cell in the post-noon sector. The sequence of partly overlapping poleward moving auroral forms (PMAFs) during the first 15 min, accompanied by corresponding pulsations in the convection current, was followed by a strong westward contraction of the cusp aurora when the ground magnetograms indicated a temporary return to the pre-onset level. These observations are discussed in relation to the Cowley-Lockwood model of ionospheric response to pulsed magnetopause reconnection.Key words. Mangetospheric physics (magnetopause · cusp and boundary layers; solar wind-magnetosphere interactions; auroral phenomena)
How does the U-shaped potential close above the acceleration region? A study using Polar data
Authors: Janhunen P. , Olsson A. , Mozer F. S. , Laakso H.
Published: June 2005

Abstract. We present a statistical study of Polar electric field observations using auroral oval passes over Scandinavia above the acceleration region. We are especially interested in seeing whether we can find large perpendicular electric fields associated with an upward extended classical U-shaped potential drop for these passes, during which Polar is in the northern hemisphere usually at about 4 RE altitude. We also use Polar magnetic field data to infer the existence of a field-aligned current (FAC) and conjugate ground-based magnetometers (the IMAGE magnetometer network) to check whether the event is substorm-related or not. We find several events with a FAC but only weak perpendicular electric fields at Polar. In those rare cases where the Polar electric field was large, its direction was mostly found to be incompatible with the U-shaped potential model, or it was associated with disturbed conditions (substorms), where one cannot easily distinguish between inductive and static perpendicular electric fields. We found only two cases which are compatible with the upward extended U-shaped potential picture, and even in those cases the potential value is quite small (1-2 kV). To check the validity of the analysis method we also estimate the perpendicular electric field on the southern hemisphere, where Polar flies within or below the acceleration region, and we found a large number of inverted-V-type signatures as expected from previous studies. To explain the lack of perpendicular electric fields at high altitudes we suggest an O-shaped potential model instead of the U-shaped one.Key words. Ionosphere (particle acceleration) · Magnetospheric physics (auroral phenomena; magnetosphere · ionosphere interactions)
A multipoint study of a substorm occurring on 7 December, 1992, and its theoretical implications
Authors: Fox N. J. , Cowley S. W. H. , Davda V. N. , Enno G. , Friis-Christensen E. , Greenwald R. A. , Hairston M. R. , Lester M. , Lockwood M. , Lühr H. , Milling D. K. , Murphree J. S. , Pinnock M. , Reeves G. D.
Published: June 2005

Abstract. On 7 December 1992, a moderate substorm was observed by a variety of satellites and ground-based instruments. Ionospheric flows were monitored near dusk by the Goose Bay HF radar and near midnight by the EISCAT radar. The observed flows are compared here with magnetometer observations by the IMAGE array in Scandinavia and the two Greenland chains, the auroral distribution observed by Freja and the substorm cycle observations by the SABRE radar, the SAMNET magnetometer array and LANL geosynchronous satellites. Data from Galileo Earth-encounter II are used to estimate the IMF Bz component. The data presented show that the substorm onset electrojet at midnight was confined to closed field lines equatorward of the pre-existing convection reversal boundaries observed in the dusk and midnight regions. No evidence of substantial closure of open flux was detected following this substorm onset. Indeed the convection reversal boundary on the duskside continued to expand equatorward after onset due to the continued presence of strong southward IMF, such that growth and expansion phase features were simultaneously present. Clear indications of closure of open flux were not observed until a subsequent substorm intensification 25 min after the initial onset. After this time, the substorm auroral bulge in the nightside hours propagated well poleward of the pre-existing convection reversal boundary, and strong flow perturbations were observed by the Goose Bay radar, indicative of flows driven by reconnection in the tail.Key words. Ionosphere (auroral ionosphere; plasma convection) · Magnetospheric physics (storms and substorms)
Identification of magnetosheath mirror modes in Equator-S magnetic field data
Authors: Lucek E. A. , Dunlop M. W. , Balogh A. , Cargill P. , Baumjohann W. , Georgescu E. , Haerendel G. , Fornacon G.-H.
Published: June 2005

Abstract. Between December 1997 and March 1998 Equator-S made a number of excursions into the dawn-side magnetosheath, over a range of local times between 6:00 and 10:40 LT. Clear mirror-like structures, characterised by compressive fluctuations in |B| on occasion lasting for up to 5 h, were observed during a significant fraction of these orbits. During most of these passes the satellite appeared to remain close to the magnetopause (within 1–2 Re), during sustained compressions of the magnetosphere, and so the characteristics of the mirror structures are used as a diagnostic of magnetosheath structure close to the magnetopause during these orbits. It is found that in the majority of cases mirror-like activity persists, undamped, to within a few minutes of the magnetopause, with no observable ramp in |B|, irrespective of the magnetic shear across the boundary. This suggests that any plasma depletion layer is typically of narrow extent or absent at the location of the satellite, at least during the subset of orbits containing strong magnetosheath mirror-mode signatures. Power spectra for the mirror signatures show predominately field aligned power, a well defined shoulder at around 3–10 x 10 –2 Hz and decreasing power at higher frequencies. On occasions the fluctuations are more sinusoidal, leading to peaked spectra instead of a shoulder. In all cases mirror structures are found to lie approximately parallel to the observed magnetopause boundary. There is some indication that the amplitude of the compressional fluctuations tends to be greater closer to the magnetopause. This has not been previously reported in the Earth's magnetosphere, but has been suggested in the case of other planets.Key words. Magnetospheric physics (magnetosheath; plasma waves and instabilities; magnetopause, cusp and boundary layers)
Magnetopause boundary structure deduced from the high-time resolution particle experiment on the Equator-S spacecraft
Authors: Parks G. K. , Datta S. , McCarthy M. , Lin R. P. , Reme H. , Sauvaud J. A. , Sanderson T. , Baumjohann W. , Haerendel G. , Torkar K.
Published: June 2005

Abstract. An electrostatic analyser (ESA) onboard the Equator-S spacecraft operating in coordination with a potential control device (PCD) has obtained the first accurate electron energy spectrum with energies ≈7 eV–100 eV in the vicinity of the magnetopause. On 8 January, 1998, a solar wind pressure increase pushed the magnetopause inward, leaving the Equator-S spacecraft in the magnetosheath. On the return into the magnetosphere approximately 80 min later, the magnetopause was observed by the ESA and the solid state telescopes (the SSTs detected electrons and ions with energies ≈20–300 keV). The high time resolution (3 s) data from ESA and SST show the boundary region contains of multiple plasma sources that appear to evolve in space and time. We show that electrons with energies ≈7 eV–100 eV permeate the outer regions of the magnetosphere, from the magnetopause to ≈6Re. Pitch-angle distributions of ≈20–300 keV electrons show the electrons travel in both directions along the magnetic field with a peak at 90° indicating a trapped configuration. The IMF during this interval was dominated by Bx and By components with a small Bz.Key words. Magnetospheric physics (magnetopause · cusp · and boundary layers; magnetospheric configuration and dynamics; solar wind · magnetosphere interactions)
Effects of violence exposure and daily stressors on psychological outcomes in urban adolescents
Authors: Self‐Brown Shannon , LeBlanc Monique , Kelley Mary Lou
Published: June 2005

Relations between adolescent violence exposure, daily stress, and psychological outcome were examined. Parent/adolescent dyads (N = 80) completed questionnaires, which included parent ratings of adolescent externalizing and internalizing problems and adolescent self‐ratings of emotional adjustment. Severity of daily stress moderated the relation between levels of violence exposure and extent of adolescent externalizing and internalizing problems. The relation was significant at higher levels of daily stress, but nonsignificant at lower levels of stress. In contrast, daily stress did not emerge as a moderator in the relation between violence exposure and adolescent emotional adjustment. Results suggest that adolescents experiencing high levels of violence exposure and daily stress should be considered at great risk for poor psychological outcome.
Is it an accident? Recurrent traumatic life events in level I trauma center patients compared to the general population
Authors: Ramstad Sarah M. , Russo Joan , Zatzick Douglas F.
Published: June 2005

The trauma history screen developed for the National Comorbidity Survey (NCS) was used to assess prior trauma in a representative sample of injured acute care inpatients (n = 251). Adjusted logistic regressions compared the trauma histories of intentionally (n = 66) and unintentionally (n = 185) injured patients with NCS participants (n = 5873). Whereas only 11% of NCS respondents reported 4 or more lifetime traumas, 61% of intentionally injured patients (Adjusted OR = 7.97, 95% CI = 4.33. 14.68) and 40%, of unintentionally injured patients (Adjusted OR = 4.26, 95% CI = 2.94, 6.16) reported 4 or more lifetime traumas. In adjusted analyses, inpatients were at increased risk for reporting all types of trauma except combat. Screening and intervention procedures that address the unique characteristics of this high‐risk patient population are needed in the acute care setting.
In vitro developmental expression of dystroglycan and laminin‐α2 in human skeletal muscle
Authors: Chen Lie , Burgunder Jean‐Marc
Published: June 2005

The α‐subunit of dystroglycan, a member of the dystrophin associated protein complex, binds to extracellular laminin‐α2, while its β‐subunit interacts with cytoskeletal dystrophin. The exact biological role of dystroglycan, especially during human skeletal muscle development, has not been fully explored. Here, we analysed the distribution and expression characteristics of both dystroglycan subunits and laminin‐α2 in primary human skeletal muscle cells. During development, expression levels of all three proteins increased with differentiation. The proteins were relocated from the sarcoplasm to the sarcolemma. The size of α‐dystroglycan decreased from 150–220 kDa at the proliferation stage to 100–120 kDa at the late developmental stage. Both α‐ and β‐dystroglycan were involved in forming a complex with their respective partners laminin‐α2 and dystrophin/utrophin. Our data show that, during development, cells may employ tightly regulated post‐translational species‐specific modification to produce different isoforms of α‐dystroglycan to participate in appropriate functions.
Ubiquitination‐resistant p53 protein transduction therapy facilitates anti‐cancer effect on the growth of human malignant glioma cells
Authors: Michiue Hiroyuki , Tomizawa Kazuhito , Matsushita Masayuki , Tamiya Takashi , Lu Yun-Fei , Ichikawa Tomotsugu , Date Isao , Matsui Hideki
Published: June 2005

Protein transduction therapy using poly‐arginine can deliver the bioactive p53 protein into cancer cells and inhibits the proliferation of the cells. However, one disadvantage of such therapy is the short intracellular half‐life of the delivered protein. Here, we generated mutant proteins in which multiple lysine residues in the C‐terminal were substituted by arginines. The mutant proteins were effectively delivered in glioma cells and were resistant to Mdm2‐mediated ubiquitination. Moreover, the mutant proteins displayed higher transcription regulatory activity and powerful inhibition of the proliferation of glioma cells. These results suggest that ubiquitination‐resistant p53 protein therapy may become a new effective cancer therapy.
Light‐dependent dimerisation in the N‐terminal sensory module of cyanobacterial phytochrome 1
Authors: Strauss Holger M. , Schmieder Peter , Hughes Jon
Published: June 2005

Phytochromes, photoreceptors controlling important physiological processes in plants and many prokaryotes, are photochromic biliproteins. The red‐absorbing Pr ground state is converted by light into the farred‐absorbing Pfr which can be photoconverted back to Pr. In plants at least Pfr is the physiologically active signalling state. Here, we show that the N‐terminal photochromic module of Cph1 homodimerises reversibly and independently in Pr and Pfr, Pfr‐dimers being significantly more stable. Implications for the mechanism of signal transduction are discussed.
Sense and non-sense of polypharmacy: increasing efficacy, decreasing compliance?
Authors: Boyer Patrice
Published: June 2005

The objective in managing patients with schizophrenia is to provide effective control of symptoms and enable the patient to reintegrate into society. Pharmacotherapy should, therefore, aim to provide optimum symptom control with minimal side effects using a simple dosage regimen. Ideally, this would be achieved through the use of a single agent. Some patients are successfully managed with a single antipsychotic drug, but it is often necessary or thought to be necessary to use a combination of agents to provide effective treatment. One European survey reported that most patients receive two to three psychotropic agents on average, but at least 5-22% receive five or more agents [53]. Unfortunately, the addition of more agents increases the risk of drug interactions, adverse events and non-compliance. This is amplified by the paucity of evidence-based medicine currently available to guide physicians in the use of combinations of agents, and the tendency of polypharmaceutical practice to be mostly driven by personal preference, clinical experience and marketing. This article therefore briefly looks at the feasibility of using various drug classes as adjunctive therapy in patients with schizophrenia.
Genetic control of intermediate erucic acid content in the seed oil of the mutant Ethiopian mustard line L-935
Authors: RÍO-CELESTINO M. DEL , FONT R. , FERNÁNDEZ-MARTÍNEZ J. M. , DE HARO-BAILÓN A.
Published: June 2005

Chemical-mutagen treatment of Ethiopian mustard (Brassica carinata A. Braun) line C-101 seeds (which contained about 441 g/kg C22[ratio ]1) led to isolation of a mutant, L-935, which contained about 190 g/kg erucic acid (intermediate C22[ratio ]1) in the seed oil. The objective was to determine the inheritance of the intermediate C22[ratio ]1 level in this mutant. The mutant L-935 was reciprocally crossed to C-101 and to the mutant line L-2890 (which contained 112 g/kg C22[ratio ]1; low). The F1, F2 and BC1F1 generations were obtained. Cytoplasmic effects were not observed in any of the crosses. The analysis of the fatty acid composition in the F2 populations from the crosses of L-935 with C-101 revealed a segregation pattern fitting a ratio 1[ratio ]2[ratio ]1 for intermediate, high and very high C22[ratio ]1 content. The segregation patterns fitted a one-locus (designated M2) model with two alleles (M2 and mi) and with partial dominance of high over intermediate C22[ratio ]1 content. The segregating generations of the crosses L-935×L-2890 showed a strong transgressive segregation with C22[ratio ]1 values ranged from 1·3–406·5 g/kg. The analyses of the F2, BC1F1 and F3 generations indicated that the combination of alleles at two loci, M1 and M2 controlled the transgressive segregation for C22[ratio ]1 content. The proposed genotypes (C22[ratio ]1 content) for each parent were as follows: L-935 (190 g/kg 22[ratio ]1)=MMmimiEEEE; L-2890 (112 g/kg C22[ratio ]1)=mmmmEEEE; and C-101 (441 g/kg C22[ratio ]1)=MMMMEEEE.
Robyn Carston on semantics, pragmatics and ‘encoding’
Authors: BURTON-ROBERTS NOEL
Published: June 2005

Robyn Carston,Thoughts and utterances: the pragmatics of explicit communication. Oxford: Blackwell Publishers, 2002. Pp. x+408.

Robyn Carston's Thoughts and utterances is, in every sense, a big book. The result of years of thinking about communication from a relevance-theoretic perspective, it is long, wide-ranging, rich, intricate, demanding and radical. And it is (or should be) controversial. Essential reading therefore for anyone with any interest in language and communication, philosophy of language, semantics and pragmatics.
Transmission dynamics ofEchinococcus multilocularis; its reproduction number, persistence in an area of low rodent prevalence, and effectiveness of control
Authors: TAKUMI K. , VAN DER GIESSEN J.
Published: June 2005

On the basis of high prevalences ofEchinococcus multilocularisin the growing fox populations in Central Europe, its total biomass may have increased significantly in the past 20 years.E. multilocularisis now also found in areas outside the known endemic area in Central Europe. Therefore,E. multilocularis, the causative agent of a serious parasitic zoonosis, might be of major concern for public health and a challenge to control. Some experimental field trials to controlE. multilocularisusing an anti-worm drug reduced parasite burden in a contaminated region during the control campaign, but failed to eradicate the parasite completely. It was our aim to develop a mathematical model describing the biomass of egg, larval, and adult worm stages of theE. multilocularislife-cycle, and simulate a hypothetical control campaign. Additionally, we derived the reproduction number of this parasite and explored conditions for the persistence of the parasite's life-cycle. Our model shows that while control campaigns rapidly reduce the worm burden in the definitive host, and consequently eggs in the environment, the pool of larvae in the intermediate host remains large. The parasite's life-cycle persists in a region where prevalence in the intermediate host is low (∼1%). Therefore, we conclude that the parasite is likely to re-emerge if control is discontinued on the basis of reduced worm population. Continued treatment of the definitive host is required to eradicate the larval stage of the parasite from the intermediate host population.
Brine micro‐droplets and solid inclusions in accreted ice from Lake Vostok (East Antarctica)
Authors: de Angelis Martine , Morel‐Fourcade Marie‐Christine , Barnola Jean‐Marc , Susini Jean , Duval Paul
Published: June 2005

Lake Vostok, the largest Antarctic sub‐glacial lake (14,000 km2), lies beneath nearly 4 km of ice. Sub‐glacial geophysical observations and studies of ice accreting at the lake‐glacier interface are the only means available to obtain information on the environment and dynamics of this huge water body formed several million years ago. Accretion ice has been studied using high‐resolution synchrotron X‐Ray micro‐fluorescence. For the first time, liquid brine micro‐droplets (3–10 μm) are observed, coexisting with large irregular sulfur‐rich aggregates (10–800 μm) containing gases and a mixture of very fine particles. Most of these objects are sequestered inside large crystals that grew slowly after ice formation. Their structure and composition support the existence of hydrothermal activity at the lake bottom and the occurrence of haline water pulses carrying fine solid debris and eventually biota from a deeper evaporitic reservoir into the lake.
Exciton trapping at heterojunctions in polymer blends
Authors: Morteani Arne C. , Friend Richard H. , Silva Carlos
Published: June 2005

Optoelectronic devices made from semiconductor polymers often employ partially phase-separated binary polymer blends with “distributed heterojunctions” in the polymer film, and the migration of bulk excitons towards these heterojunctions crucially influences the device performance. Here, we investigate exciton migration in blend films of two polyfluorene derivatives. Localized exciplex states form in electron-hole capture at the heterojunction between the two polymers and these can be thermally excited to transfer to bulk excitons. Rapid radiative emission from these excitons can then allow efficient light-emitting diode operation. We show here that when these excitons migrate to another heterojunction site within their lifetime they are re-trapped at the interface and again form exciplex states or dissociate completely. We demonstrate that in polymer blend light-emitting diodes this can reduce the exciton population by more than 54% and can strongly influence the emission spectrum. We then analyze exciton re-trapping in detail using time-resolved photoluminescence spectroscopy on blends with different morphologies and find that for nanometer-scale phases exciton emission is completely suppressed. We show that the data agree well with a simple kinetic model which confirms the importance of the blend morphology for the exciton trapping efficiency.
Decomposition of nitramine energetic materials in excited electronic states: RDX and HMX
Authors: Guo Y. Q. , Greenfield M. , Bernstein E. R.
Published: June 2005

Ultraviolet excitation (8-ns duration) is employed to study the decomposition of RDX (1,3,5-trinitro-1,3,5-triazacyclohexane) and HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane) from their first excited electronic states. Isolated RDX and HMX are generated in the gas phase utilizing a combination of matrix-assisted laser desorption and supersonic jet expansion techniques. The NO molecule is observed as one of the initial dissociation products by both time-of-flight mass spectroscopy and laser-induced fluorescence spectroscopy. Four different vibronic transitions of NO are observed: AΣ2(v′=0)←XΠ2(v″=0,1,2,3). Simulations of the NO rovibronic intensities for the A←X transitions show that dissociated NO from RDX and HMX is rotationally cold (∼20K) and vibrationally hot (∼1800K). Another potential initial product of RDX and HMX excited state dissociation could be OH, generated along with NO, perhaps from a HONO intermediate species. The OH radical is not observed in fluorescence even though its transition intensity is calculated to be 1.5 times that found for NO per radical generated. The HONO intermediate is thereby found not to be an important pathway for the excited electronic state decomposition of these cyclic nitramines.
Novel Monte Carlo scheme for systems with short-ranged interactions
Authors: Boulougouris Georgios C. , Frenkel Daan
Published: June 2005

We propose a Monte Carlo (MC) sampling algorithm to simulate systems of particles interacting via very short-ranged discontinuous potentials. Such models are often used to describe protein solutions or colloidal suspensions. Most normal MC algorithms fail for such systems because, at low temperatures, they tend to get trapped in local potential-energy local minima due to the short range of the pair potential. To circumvent this problem, we have devised a scheme that changes the construction of trial moves in such a way that the potential-energy difference between initial and final states drops out of the acceptance rule for the Monte Carlo trial moves. This approach allows us to simulate systems with short-ranged attraction under conditions that were unreachable up to now.
A heuristic approach to determine the modifications of electronic and optical properties of “intrinsic” GaAs under free-carrier injection. Part II
Authors: Reinhart F. K.
Published: June 2005

We develop a heuristic approach to determine the electronic density of states from the measured absorption function of high-quality and high-purity (“intrinsic”) GaAs, from which we derive the intrinsic carrier concentration. This intrinsic concentration is considerably larger than the one obtained from elementary parabolic theory. As a major consequence, the calculated radiative recombination factor at zero injection agrees much better with experimental determinations. We extend this heuristic theory in a simple self-consisting manner to include modifications of the electronic and optical properties under free-carrier injection. Under free-carrier injection, the radiative recombination factor becomes a function of the injection density and decreases by more than 20% from the zero-injection case for carrier densities exceeding 3×1017cm−3. We calculate the carrier density, the gain maximum and its associated photon energy under high injection as a function of the quasi-Fermi level separation with the temperature as a parameter. For easy applications, we provide approximate analytical representations. The refractive index and the group refractive index also change in important ways due to the modifications of the absorption function under injection. We show that the changes associated with the absorption function dominate the contributions by the gain and free-carrier plasma. The group refractive-index dispersion under injection is shown to be considerably smaller than that at zero injection in agreement with experimental observations.
Fluorescence-dip infrared spectroscopy and predissociation dynamics of OH AΣ+2 (v=4) radicals
Authors: Derro Erika L. , Pollack Ilana B. , Dempsey Logan P. , Greenslade Margaret E. , Lei Yuxiu , Radenović Dragana Č. , Lester Marsha I.
Published: June 2005

Fluorescence-dip infrared spectroscopy, an UV-IR double-resonance technique, is employed to characterize the line positions, linewidths, and corresponding lifetimes of highly predissociative rovibrational levels of the excited AΣ+2 electronic state of the OH radical. Various lines of the 4←2 overtone transition in the excited AΣ+2 state are observed, from which the rotational, centrifugal distortion, and spin-rotation constants for the AΣ+2 (v=4) state are determined, along with the vibrational frequency for the overtone transition. Homogeneous linewidths of 0.23–0.31cm−1 full width at half maximum are extracted from the line profiles, demonstrating that the N=0to7 rotational levels of the OH AΣ+2 (v=4) state undergo rapid predissociation with lifetimes of ⩽23ps. The experimental linewidths are in near quantitative agreement with first-principles theoretical predictions.
A new ultrafast technique for measuring the terahertz dynamics of chiral molecules: The theory of optical heterodyne-detected Raman-induced Kerr optical activity
Authors: Wynne Klaas
Published: June 2005

Optical heterodyne-detected Raman-induced Kerr optical activity (OHD-RIKOA) is a nonresonant ultrafast chiroptical technique for measuring the terahertz-frequency Raman spectrum of chirally active modes in liquids, solutions, and glasses of chiral molecules. OHD-RIKOA has the potential to provide much more information on the structure of molecules and the symmetries of librational and vibrational modes than the well-known nonchirally sensitive technique optical heterodyne-detected Raman-induced Kerr-effect spectroscopy (OHD-RIKES). The theory of OHD-RIKOA is presented and possible practical ways of performing the experiments are analyzed.
Particle-in-cell Monte Carlo modeling of Langmuir probes in an Ar plasma
Authors: Cenian A. , Chernukho A. , Bogaerts A. , Gijbels R. , Leys C.
Published: June 2005

The Langmuir-probe diagnostic of a plasma is studied using a particle-in-cell Monte Carlo model. The electron-density, temperature, and potential profiles are determined for a probe immersed in an Ar plasma. The model is verified using the low-pressure results of Sternovsky et al. [J. Appl. Phys. 94, 1374 (2003)]. It was proved that the ion to electron temperature ratio may not be constant in the sheath–presheath region.
Flow unit for measuring heats of mixing at subambient conditions
Authors: Poledníček Miloš , Majer Vladimír , Hynek Vladimír , Jose Jacques
Published: June 2005

A type of mixing flow unit for BT 2.15D SETARAM calorimeter was designed for measuring heats of mixing of two liquids or a gas and a liquid. A cooling system using a cryostat circulating a cooling agent (ethanol) through the instrument was proposed and tested for temperatures down to −50°C. In addition, a special heat exchanger was constructed for cooling down fluids entering the calorimeter when experiments are performed at subambient temperatures. In comparison with cooling by liquid nitrogen, the operation is less expensive and no tedious manipulations with liquid nitrogen are needed. A procedure for measuring with the mixing unit was developed and the assembly was successfully tested in the temperature range from −30to75°C and at pressures up to 14MPa using several binary systems (liquid-liquid) where reliable literature data were available. The proposed flow arrangement is much more efficient and convenient to use at subambient temperatures compared to conducting experiment in a batch mode, which is the approach still prevailing at these conditions.
Determination of the baric coefficient using a double ac method
Authors: Morchshakov V. , Annaorazov M. , Medvedeva I. V. , Baerner K.
Published: June 2005

An apparatus has been designed which measures the baric coefficient γ, defined as the relative change of a resistance under pressure: R=R0(1+γp), using a double ac method, the pressure modulation of the resistance being obtained via compressional sound waves. First results on manganites RE1−xAxMnO3 are obtained and compared with the pressure derivatives of R(p,T) as obtained with static methods. Good agreement was obtained at larger superimposed static pressure Pst, however, extra results are obtained in the limit Pst→0 and in the case of a percolation of phase separated volumes.
Dynamics of fluids near the consolute critical point: A molecular-dynamics study of the Widom–Rowlinson mixture
Authors: Jagannathan Kamakshi , Yethiraj Arun
Published: June 2005

Molecular-dynamics simulations are presented for the dynamic behavior of the Widom–Rowlinson mixture [B. Widom, and J. S. Rowlinson, J. Chem. Phys. 52, 1670 (1970)] at its critical point. This model consists of two components where like species do not interact and unlike species interact via a hard-core potential. Critical exponents are obtained from a finite-size scaling analysis. The self-diffusion coefficient shows no anomalous behavior near the critical point. The shear viscosity and thermal conductivity show no divergent behavior for the system sizes considered, although there is a significant critical enhancement. The mutual diffusion coefficient, DAB, vanishes as DAB∼ξ−1.26±0.08, where ξ is the correlation length. This is different from the renormalization-group (DAB∼ξ−1.065) mode coupling theory (DAB∼ξ−1) predictions. The theories and simulations can be reconciled if we assume that logarithmic corrections to scaling are important.
The “Blow up” problem for a quasilinear Schrödinger equation
Authors: Guo Boling , Chen Jianqing , Su Fengqiu
Published: June 2005

Consider the blow up results for W2,2(RN) solutions of a quasilinear Schrödinger equation iut+Δu+β∣u∣p−2u+θ(Δ∣u∣2)u=0, u∣t=0=u0(x),x∊RN. When ∣x∣u0∊L2(RN), we show that the W2,2(RN) solutions must blow up for any β⩾0, θ∊R and some restriction on p. We also show that the radial symmetric solutions in W2,2(RN) must blow up at finite time without assuming ∣x∣u0∊L2(RN).
Reynolds-number dependence of turbulence structures in a drag-reducing surfactant solution channel flow investigated by particle image velocimetry
Authors: Li F.-C. , Kawaguchi Y. , Segawa T. , Hishida K.
Published: June 2005

The Reynolds-number dependence of turbulence structures in a drag-reducing surfactant solution flow is attributed to the Reynolds-number effect on rheology of the solution flowing in the passage and the rheological properties are associated with the shear-induced structure (SIS) formed in a sheared surfactant solution. Through analysis of turbulence statistics of the two-dimensional velocity field, measured by particle image velocimetry, for a drag-reducing flow with addition of cetyltrimethyl ammonium chloride (CTAC) in different flow regimes characterized by the drag-reducing effectiveness dependent on the Reynolds number, we studied the characteristics of turbulence structures for different Reynolds-number-dependent flow states and indirectly revealed the dynamic processes of SIS across the flow passage. A 25ppm (ppm—parts per million) CTAC solution at 30°C was tested. Based on the relationship between the Reynolds number and the drag-reduction levels, the CTAC solution flow was categorized into four regimes: Regime I is laminar and transitional flow without drag-reducing ability; in regime II drag-reduction level increased with the Reynolds number; in regime III drag-reduction level decreased with the Reynolds number; and in regime IV drag-reducing ability disappeared. Five cases of CTAC solution flow—two in regime II, two in regime III, and one in regime IV—were measured. Five cases of water flow at similar Reynolds numbers corresponding to those of CTAC solution flows were also measured for comparison. It was found that the flows in regimes II and III behave differently in turbulence statistics, including mean streamwise velocity, turbulence intensities of both streamwise and wall-normal velocity components, Reynolds shear stress and contour map of spectral density functions of velocity fluctuations in a coordinate plane of wave number and wall-normal position, regardless of similar drag-reduction levels. In regimes III and IV, multilayer structures associated with different flow states were obtained from the analysis of profiles of the Reynolds shear stress and the viscoelastic shear stress, which characterize the dynamic processes of SIS in the solution across the flow passage at different Reynolds numbers.
Computing resonance energies, widths, and wave functions using a Lanczos method in real arithmetic
Authors: Tremblay Jean Christophe , Carrington Tucker
Published: June 2005

We introduce new ideas for calculating resonance energies and widths. It is shown that a non-Hermitian–Lanczos approach can be used to compute eigenvalues of H+W, where H is the Hamiltonian and W is a complex absorbing potential (CAP), without evaluating complex matrix-vector products. This is done by exploiting the link between a CAP-modified Hamiltonian matrix and a real but nonsymmetric matrix U suggested by Mandelshtam and Neumaier [J. Theor. Comput. Chem. 1, 1 (2002)] and using a coupled-two-term Lanczos procedure. We use approximate resonance eigenvectors obtained from the non-Hermitian–Lanczos algorithm and a very good CAP to obtain very accurate energies and widths without solving eigenvalue problems for many values of the CAP strength parameter and searching for cusps. The method is applied to the resonances of HCO. We compare properties of the method with those of established approaches.
Effects of heat generation during electron-beam-induced deposition of nanostructures
Authors: Randolph S. J. , Fowlkes J. D. , Rack P. D.
Published: June 2005

To elucidate the effects of beam heating in electron-beam-induced deposition (EBID), a Monte Carlo electron-solid interaction model has been employed to calculate the energy deposition profiles in bulk and nanostructured SiO2. Using these profiles, a finite element model was used to predict the nanostructure tip temperatures for standard experimental EBID conditions. Depending on the beam energy, beam current, and nanostructure geometry, the heat generated can be substantial. This heat source can subsequently limit the EBID growth by thermally reducing the mean stay time of the precursor gas. Temperature-dependent EBID growth experiments qualitatively verified the results of the electron-beam-heating model. Additionally, experimental trends for the growth rate as a function of deposition time supported the conclusion that electron-beam-induced heating can play a major role in limiting the EBID growth rate of SiO2 nanostructures.
Effect of current processing on the transport property of the La0.67Ca0.33MnO3 film
Authors: Sun J. R. , Liu G. J. , Zhang S. Y. , Zhang H. W. , Han X. F. , Shen B. G.
Published: June 2005

Current effect on the transport property of the La0.67Ca0.33MnO3 film has been studied as a function of temperature and magnetic field. The two-lead resistance of the sample shows a strongly asymmetric behavior with respect to current direction after a treatment under a current of the density of ∼1.6×105A∕cm2, and the resistance is much lower in forward direction, the direction of the processing current, than in backward direction. A definite change in current–voltage slope at small but finite forward voltages is observed when alternating the electric field from backward to forward, which is indicative of the presence of two different resistive states corresponding to the two current directions and an energy barrier between these states. The magnetoresistance effect of the two resistive states is significantly different, and it is much stronger for the backward current than for the forward one. This has been proved a combined effect of the inclining of the current–voltage slope and the depression of intermediate energy barrier under magnetic field. The present work suggests a possibility to get a different magnetoresistance via interfacial engineering.
Growing evanescent waves in a cutoff rectangular waveguide loaded with an inductive iris and a capacitive post
Authors: Stickel Micah , Eleftheriades George V.
Published: June 2005

There has been much interest recently in the area of engineered materials with unusual electromagnetic properties known as metamaterials. Of particular interest are those metamaterials that are characterized by a negative refractive index (NRI). The existence of growing evanescent waves is one of the very interesting phenomena that has been observed within such NRI materials. It is the purpose of this paper to investigate the presence of growing evanescent waves within a cutoff rectangular waveguide. It will be shown through theoretical analysis, full-wave simulations, and experimental results that the development of such a wave is not unique to NRI materials. Indeed, it is possible to generate such growing evanescent waves through the simple loading of a cutoff rectangular waveguide with a shunt capacitive post. The further loading of the waveguide with a shunt inductive iris can impedance match the growing evanescent wave to a standard decaying evanescent field, thus producing an evanescent field pattern similar to that observed in a NRI slab in air.
The 1856 lemma of Cayley revisited. I. Infinitesimal generators
Authors: Yue Jin
Published: June 2005

The result of classical invariant theory commonly referred to as Cayley’s lemma is reviewed. Its analog in the invariant theory of Killing tensors defined in pseudo-Riemannian spaces of constant curvature is formulated and proven. Illustrative examples are provided.
Effect of well number on the performance of quantum-well solar cells
Authors: Bushnell D. B. , Tibbits T. N. D. , Barnham K. W. J. , Connolly J. P. , Mazzer M. , Ekins-Daukes N. J. , Roberts J. S. , Hill G. , Airey R.
Published: June 2005

The effect of increasing the number of quantum wells in a strain-compensated, multiquantum-well solar cell is investigated. It is found that as the well number is increased, dark current level close to the operating point rises linearly. Short-circuit current in the AM0 spectrum also rises linearly with the inclusion of more quantum wells. This allows the cell to maintain a constant open-circuit voltage irrespective of the number of wells grown. This is anticipated to have advantages when the cell is used as a replacement for the GaAs junction in the existing generation of tandem and triple-junction cells since current levels can be matched to the upper junction without detriment to the voltage performance. This result allows us to predict a tandem cell AM0 efficiency of 23.8% based on the 50-well cell.
NaCl particle interaction with 193-nm light: Ultraviolet photofragmentation and nanoparticle production
Authors: Choi Jong Hyun , Stipe Christopher B. , Koshland Catherine P. , Sawyer Robert F. , Lucas Donald
Published: June 2005

The interaction of nanoscale NaCl particles with 193-nm photons is studied to better understand particle disintegration and production by ultraviolet photofragmentation. The particles are irradiated in a constrained air stream with laser fluences from 0.08to0.23J∕cm2 with single and multiple pulses striking the particles. The resulting particle size distributions are measured with a scanning mobility particle sizer and the morphology is analyzed qualitatively by scanning electron microscopy (SEM). Photofragmentation of NaCl particles at 193nm produces gas-phase species as well as small solid-phase fragments without significantly heating the particles or creating a plasma. The irradiated particles have a mean diameter from 20to55nm (depending on the photon energy) and a number concentration an order of magnitude higher than the 118-nm mean diameter nonirradiated particles. The SEM images before and after 193-nm irradiation reveal that the irradiated particles are less fractal and more spherical.
Pneumatic capillary gun for ballistic delivery of microparticles
Authors: Rinberg Dmitry , Simonnet Claire , Groisman Alex
Published: June 2005

A pneumatic gun for ballistic delivery of microparticles to soft targets is proposed and demonstrated. The particles are accelerated by a high-speed flow of helium in a capillary tube. Vacuum suction applied to a concentric larger diameter tube is used to divert substantially all of the flow of helium from the gun nozzle, thereby preventing the gas from hitting and damaging the target. Speed of ejection of micron-sized gold particles from the gun nozzle, and their depth of penetration into agarose gels are reported.