bluuebunny/crossref_metadata_2025 huggingface dataset:
Outreach and support in south London (OASIS): implementation of a clinical service for prodromal psychosis and the at risk mental state
Authors: Broome Matthew R. , Woolley James B. , Johns Louise C. , Valmaggia Lucia R. , Tabraham Paul , Gafoor Rafael , Bramon Elvira , McGuire Philip K.
Published: April 2005

Background

While recent research points to the potential benefits of clinical intervention before the first episode of psychosis, the logistical feasibility of this is unclear.

Aims

To assess the feasibility of providing a clinical service for people with prodromal symptoms in an inner city area where engagement with mental health services is generally poor.

Methods

Following a period of liaison with local agencies to promote the service, referrals were assessed and managed in a primary care setting. Activity of the service was audited over 30 months.

Results

People with prodromal symptoms were referred by a range of community agencies and seen at their local primary care physician practice. Over 30 months, 180 clients were referred; 58 (32.2%) met criteria for an at risk mental state, most of whom (67.2%) had attenuated psychotic symptoms. Almost 30% were excluded due to current or previous psychotic illness, of which two-thirds were in the first episode of psychosis. The socio-demographic composition of the 'at risk' group reflected that of the local population, with an over-representation of clients from an ethnic minority. Over 90% of suitable clients remained engaged with the service after 1 year.

Conclusion

It is feasible to provide a clinical service for people with prodromal symptoms in a deprived inner city area with a large ethnic minority population.
A targeted antioxidant reveals the importance of mitochondrial reactive oxygen species in the hypoxic signaling of HIF‐1α
Authors: Sanjuán-Pla Alejandra , Cervera Ana M. , Apostolova Nadezda , Garcia-Bou Remedios , Víctor Víctor M. , Murphy Michael P. , McCreath Kenneth J.
Published: April 2005

Exposure to limiting oxygen in cells and tissues induce the stabilization and transcriptional activation of the hypoxia‐inducible factor 1 alpha (HIF‐1α) protein, a key regulator of the hypoxic response. Reactive oxygen species (ROS) generation has been implicated in the stabilization of HIF‐1α during this response, but this is still a matter of some debate. In this study we utilize a mitochondria‐targeted antioxidant, mitoubiquinone (MitoQ), and examine its effects on the hypoxic stabilization of HIF‐1α. Our results show that under conditions of reduced oxygen (3% O2), MitoQ ablated the hypoxic induction of ROS generation and destabilized HIF‐1α protein. This in turn led to an abrogation of HIF‐1 transcriptional activity. Normoxic stabilization of HIF‐1α, on the other hand, was unchanged in the presence of MitoQ suggesting that ROS were not involved. This study strongly suggests that mitochondrial ROS contribute to the hypoxic stabilization of HIF‐1α.
Compartmentalisation of phosphodiesterases and protein kinase A: opposites attract
Authors: Baillie George S. , Scott John D. , Houslay Miles D.
Published: April 2005

Understanding the molecular organisation of intracellular signalling pathways is a topic of considerable research interest. Since many signalling enzymes are widely distributed and have several substrates, a critical component in signal transduction is the control of specificity. This is achieved, in part by the assembly of multiprotein complexes where clusters of signalling enzymes create focal points to disseminate the intracellular action of many hormones. This is particularly true for the cAMP dependent protein kinase (PKA) that is localised throughout the cell via its association with A‐kinase anchoring proteins (AKAPs). Recent data suggest that some AKAPs also interact with phosphodiesterases (PDEs). Compartmentalisation of PDEs not only provides an elegant means to control PKA activation by monitoring the local cAMP flux, but also serves to concentrate and segregate the action of these important regulatory enzymes.
A 5′ intronic splice site polymorphism leads to a null allele of the P2X7 gene in 1–2% of the Caucasian population
Authors: Skarratt Kristen K. , Fuller Stephen J. , Sluyter Ronald , Dao-Ung Lan-Phuong , Gu Ben J. , Wiley James S.
Published: April 2005

The P2X7 gene is important for the innate immune response but known polymorphisms do not explain all subjects with loss of P2X7 function. A splice site mutation (g → t) was found at position +1 of the first intron of the P2X7 gene in 7 of 336 Caucasians and 1 of 39 subjects of Indian ethnicity. All eight subjects were heterozygous for the uncommon 1513A → C polymorphism of the P2X7 gene. RT‐PCR and sequencing showed the splice site mutation was on the 1513C allele in the Caucasians and on the 1513A allele in the Indian subject. The splice site mutation is an inherited polymorphism and gives rise to a P2X7 null allele in 1–2% of the Caucasian population.
Oligomerization and assembly of the matrix protein of Borna disease virus
Authors: Kraus Ina , Bogner Elke , Lilie Hauke , Eickmann Markus , Garten Wolfgang
Published: April 2005

The matrix protein M of Borna disease virus (BDV) is a constituent of the viral envelope covering the inner leaflet of the lipid bilayer. BDV‐M was expressed as recombinant protein in Escherichia coli, purified to homogeneity and structurally analyzed. Recombinant M (i) forms non‐covalently bound multimers with a Stoke's radius of 35 Å estimated by size exclusion chromatography, (ii) consists of tetramers detected by analytical ultracentrifugation, and (iii) appears by electron microscopy studies as tetramers with the tendency to assemble into high molecular mass lattice‐like complexes. The structural features suggest that BDV‐M possesses a dominant driving force for virus particle formation.
Growth factors and fibrochondrocytes in scaffolds
Authors: Pangborn Christine A. , Athanasiou Kyriacos A.
Published: April 2005

Four growth factors, transforming growth factor‐β1 (TGF‐β1), platelet‐derived growth factor‐AB (PDGF‐AB), insulin‐like growth factor I (IGF‐I), and basic fibroblastic growth factor (bFGF), were tested at different concentrations for their effects on extracellular matrix (ECM) production in three‐dimensional cultures of meniscal fibrochondrocytes. Cells from New Zealand white rabbits were seeded on poly‐glycolic acid (PGA) scaffolds and were stimulated with growth factors for three weeks. 3H‐proline and 35S‐sulfate labels were used to measure uptake of collagen and glycosaminoglycan (GAG) components, respectively. Biochemical assays were performed to measure the total collagen, GAG, and DNA present in the scaffolds at the end of the study. TGF‐β1 (10 and 100 ng/ml) stimulated both 3H‐proline and 35S‐sulfate uptake, showing a dose‐dependent response for both and a temporal response for 35S‐sulfate uptake. IGF‐I (5 ng/ml) and bFGF (25 and 100 ng/ml) showed increases in 3H‐proline uptake by the third week of growth factor addition. PDGF‐AB did not show notable increases in uptake. Because TGF‐β1 (10 and 100 ng/ml) had visibly denser scaffolds, as evidenced by gross microscopy, at 100x, and the strongest uptake responses to both 35S‐sulfate and 3H‐proline, it appears to be the most effective growth factor for use in scaffold‐based approaches to tissue engineer the knee meniscus. © 2005 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.
Targeting the molecular basis for tumour hypoxia
Authors: Carroll Veronica A. , Ashcroft Margaret
Published: April 2005

Tumour hypoxia stems from impaired oxygen delivery as a result of a disorganised tumour vasculature and inadequate blood supply. Hypoxic tumours are highly resistant to chemotherapy and radiation therapy and correlate with a poor patient prognosis. Hypoxia is a powerful stimulus for the expression of genes involved in cell survival and angiogenesis. A key factor in this process is hypoxia-inducible factor (HIF), which regulates transcription of hypoxia-activated genes. Efforts are currently under way to develop targeted cancer therapeutics to hypoxia-activated pathways, and in particular to the transcription factor HIF.
On the role of atmospheric chemistry in the global CO2budget
Authors: Folberth G. , Hauglustaine D. A. , Ciais P. , Lathière J.
Published: April 2005

A global 3D‐chemistry‐transport model is applied to study the magnitude and geographical distribution of the in situ photochemical CO2production in the atmosphere. In the model 1823 TgC/y of reactive carbon compounds (RCC) are emitted at the surface on global and annual average. 46% of the RCC source is released by the vegetation, 27% from biomass burning, and 27% from fossil fuel incomplete combustion. Of these, 1213 TgC/y are oxidized to produce CO2. Physical removal of the emitted species represents a loss of 154 TgC/y; wet and dry deposition of intermediate oxidation products account for approximately 360 TgC/y. The relative importance of different reaction pathways is assessed. Sensitivity experiments indicate that only 30% to 45% of the RCC emitted are oxidized to CO2. Interhemispheric gradients of CO2at the Earth's surface produced from RCC, including photochemistry and physical removal, are compared to CO2gradients from RCC assuming that 100% of the RCC are released as CO2, common in CO2inverse models. A maximum difference of 0.3 ppmv in the CO2gradients is revealed, a result of potential significance for carbon cycle studies.
Identification of multiple reflected phases from migration receiver function profile: An example for the INDEPTH‐III passive teleseismic P waveform data
Authors: Tian Xiaobo , Wu Qingju , Zhang Zhongjie , Teng Jiwen , Zeng Rongsheng
Published: April 2005

The crustal multiple reflected phases usually interfere with those converted phases from the topmost mantle discontinuities, which make them difficult to be identified and should be carefully interpreted in a migration receiver functions profile. We propose a simple scheme to identify the crustal multiples in a migration receiver functions profile. The scheme is based on the differences in both geometric and dynamic features resolved using AVP (amplitude variation verse ray parameter) and DVP (discontinuity depth variation verse ray parameter). Synthetic data shows that the crustal multiples can be distinguished from those converted phases in the receiver function migration profile, especially when the receiver functions are migrated using velocities lower than the actual velocities. As an example, we apply our procedure to the INDEPTH‐III passive teleseismic P waveform data. Our results indicate that a possible converted phase from the “220‐km” discontinuity is a crustal multiple reflected phase.
Vertical ion motion observed with incoherent scatter radars in the polar lower ionosphere
Authors: Oyama S. , Watkins B. J. , Nozawa S. , Maeda S. , Conde M.
Published: April 2005

Vertical ion velocities in excess of a few tens m s−1 have been found in the lower ionosphere (95–105 km) at high latitudes. Statistics using data from the European Incoherent Scatter (EISCAT) Tromsø UHF radar are performed to understand general character of vertical motions in the lower ionosphere for geomagnetically quiet conditions. We estimate the probability distribution function for the real vertical ion velocity, taking into account the measurement uncertainty. This calculation suggests that while most vertical ion velocities have amplitudes smaller than 20 m s−1 at 100 km level, the magnitudes larger than 20 m s−1 are observed as statistical exception. To understand if these large vertical motions in the lower ionosphere are associated with thermospheric motions, differences between ion and neutral wind velocities are calculated using data from experiments with the Sondrestrom incoherent scatter radar on 5 and 12 September 2003. The vertical ion velocities show magnitudes larger than 20 m s−1 below 103 km where the ion velocity is considered to be equal to the neutral wind velocity during the experiments according to calculations of the velocity difference.
Implications of lightning charge moment changes for sprite initiation
Authors: Cummer Steven A. , Lyons Walter A.
Published: April 2005

We report impulse lightning charge moment changes (defined as occurring in the first 2 ms after return stroke onset) in all cloud‐to‐ground lightning strokes detected by the National Lightning Detection Network in three storms during which above‐thunderstorm sprite video was recorded. After analyzing strokes that both did and did not produce sprites and carefully accounting for lightning‐sprite delay times, we found that sprite initiation on all three nights is consistent with a sharp charge moment threshold; essentially, all charge moment changes above and none below this threshold produced sprites with short delays (<5 ms) from the source lightning. On two nights this threshold was approximately 600 C km and on the other it was approximately 350 C km. This internight variability is probably due to expected variability in the nighttime mesospheric conductivity, and the thresholds themselves are consistent with predictions of conventional breakdown theory. Additionally, we found only one negative polarity lightning stroke from all three storms that exceeded this threshold, indicating that the rarity of documented sprites produced by negative strokes may be largely explained by the lack of sufficiently big negative strokes in the U.S. High Plains.
Aerosol black carbon radiative forcing at an industrial city in northern India
Authors: Tripathi S. N. , Dey Sagnik , Tare V. , Satheesh S. K.
Published: April 2005

During a comprehensive aerosol field campaign as part of ISRO‐GBP, extensive measurements of aerosol black carbon were made during December 2004, for the first time, at Kanpur, an urban continental location in northern India. BC diurnal variation is associated with changes in boundary layer mixing and anthropogenic activities. BC concentration in Kanpur is comparable to those measured in other mega cities of India but much higher than in similar locations of Europe, USA and Asia. High BC concentration is found both in absolute terms (6–20 μg m−3) and mass fraction (∼10%) yielding very low single scattering albedo (0.76). The estimated surface forcing is as high as −62 ± 23 W m−2 and top of the atmosphere (TOA) forcing is +9 ± 3 W m−2, which means the atmospheric absorption is +71 W m−2. The short wave atmospheric absorption translates to a lower atmospheric heating of ∼1.8°K/day. Large surface cooling and lower atmospheric heating may have impacts to regional climate.
Seasonal variation in velocity before retreat of Jakobshavn Isbræ, Greenland
Authors: Luckman Adrian , Murray Tavi
Published: April 2005

Using repeat‐pass satellite feature tracking, the dynamic behaviour of Jakobshavn Isbræ, which drains around 7% of the Greenland ice sheet, is investigated in improved detail through its recent period of thinning, acceleration and retreat. The departure in 1995 from the normal seasonal invariance in velocity near the grounding line suggests a possible change in dynamics well before the subsequent thinning phase. The initiation of the acceleration and retreat is pinpointed to spring 1998 and may have been prompted by the same mechanism that gave rise to the spring 1995 flow increase.
Electronic structure of 1,3,5-triaminobenzene trication and related triradicals: Doublet versus quartet ground state
Authors: Nguyen Hue Minh Thi , Dutta Antara , Morokuma Keiji , Nguyen Minh Tho
Published: April 2005

Quantum chemical calculations have been carried out to determine the electronic ground state of the parent 1,3,5-triaminobenzene trication triradical (TAB3+,C6H9N33+) containing a six-membered benzene ring coupled with three exocyclic amino NH2∙+ groups, each containing an unpaired electron, as the simplest model for high-spin polyarylamine polycations. Related triradicals, including the 1,3,5-trimethylenebenzene (TMB, C9H9) and its nitrogen derivatives such as the monocation C8H9N+, the dication C7H9N22+, and the neutral C8H8N, C7H7N2, and C6H6N3 systems containing NH groups, have also been considered. Results obtained using the CASSCF [multiconfigurational complete active space (SCF—self-consistent field)] method, with active spaces ranging from (9e∕9o) to (15e∕12o), followed by second-order perturbation theory [CASPT2 and MS-CASPT2 (MS—multistate)] with polarized 6-311G(d,p) and natural orbital (ANO-L) basis sets reveal the following: (i) both TAB3+ and TMB (D3h) have a quartet A1″4 ground state with doublet-quartet B12-A1″4 energy gaps of 8.0±2.0 and 12.4±2.0kcal∕mol, respectively; (ii) in the neutral N series, the quartet state remains the electronic ground state, irrespective of the number of N atoms, but each with slightly reduced gap, 11kcal∕mol for C8H8N (A″4), 10kcal∕mol for C7H7N2 (A24), and 9kcal∕mol for C6H6N3 (A24); and (iii) the ground state of monoamino cation and diamino dication is a low-spin doublet state (B12 for C8H9N+ and A22 for C7H9N22+) and lying well below the corresponding quartet state by 10 and 12kcal∕mol, respectively. In the monocationic and dicationic amino systems, a slight preference is found for the low-spin state, apparently violating Hund’s rule. This effect is due to the splitting of the orbital energies and the presence of the positive charge whose delocalization strongly modifies the electronic distribution and some structural features. In the latter cations, the positive charge basically pushes unpaired electrons onto the ring forming a kind of distonic radical cations and thus gives a preference for a low-spin state.
Thermodynamics and equilibrium structure of Ne38 cluster: Quantum mechanics versus classical
Authors: Predescu Cristian , Frantsuzov Pavel A. , Mandelshtam Vladimir A.
Published: April 2005

The equilibrium properties of classical Lennard-Jones (LJ38) versus quantum Ne38 Lennard-Jones clusters are investigated. The quantum simulations use both the path-integral Monte Carlo (PIMC) and the recently developed variational-Gaussian wave packet Monte Carlo (VGW-MC) methods. The PIMC and the classical MC simulations are implemented in the parallel tempering framework. The classical heat capacity Cv(T) curve agrees well with that of Neirotti et al. [J. Chem. Phys. 112, 10340 (2000)], although a much larger confining sphere is used in the present work. The classical Cv(T) shows a peak at about 6 K, interpreted as a solid-liquid transition, and a shoulder at ∼4K, attributed to a solid-solid transition involving structures from the global octahedral (Oh) minimum and the main icosahedral (C5v) minimum. The VGW method is used to locate and characterize the low energy states of Ne38, which are then further refined by PIMC calculations. Unlike the classical case, the ground state of Ne38 is a liquidlike structure. Among the several liquidlike states with energies below the two symmetric states (Oh and C5v), the lowest two exhibit strong delocalization over basins associated with at least two classical local minima. Because the symmetric structures do not play an essential role in the thermodynamics of Ne38, the quantum heat capacity is a featureless curve indicative of the absence of any structural transformations. Good agreement between the two methods, VGW and PIMC, is obtained. The present results are also consistent with the predictions by Calvo et al. [J. Chem. Phys. 114, 7312 (2001)] based on the quantum superposition method within the harmonic approximation. However, because of its approximate nature, the latter method leads to an incorrect assignment of the Ne38 ground state as well as to a significant underestimation of the heat capacity.
Excited states of boron isoelectronic series from explicitly correlated wave functions
Authors: Gálvez F. J. , Buendía E. , Sarsa A.
Published: April 2005

The ground state and some low-lying excited states arising from the 1s22s2p2 configuration of the boron isoelectronic series are studied starting from explicitly correlated multideterminant wave functions. One- and two-body densities in position space have been calculated and different expectation values such as ⟨δ(r⃗)⟩, ⟨rn⟩, ⟨δ(r⃗12)⟩, ⟨r12n⟩, ⟨δ(R⃗)⟩, and ⟨Rn⟩, where r⃗, r⃗12, and R⃗ stand for the electron-nucleus, interelectronic, and two electron center of mass coordinates, respectively, have been obtained. The energetic ordering of the excited states and the fulfillment of the Hund’s rules is analyzed systematically along the isoelectronic series in terms of the electron-electron and electron-nucleus potential energies. The effects of electronic correlations have been systematically studied by comparing the correlated results with the corresponding noncorrelated ones. All the calculations have been done by using the variational Monte Carlo method
Rate constants and branching ratios for the dissociative recombination of C3D7+ and C4D9+
Authors: Larsson M. , Ehlerding A. , Geppert W. D. , Hellberg F. , Kalhori S. , Thomas R. D. , Djuric N. , Österdahl F. , Angelova G. , Semaniak J. , Novotny O. , Arnold S. T. , Viggiano A. A.
Published: April 2005

Product branching ratios and thermal rate coefficients for the dissociative recombination of C3D7+ and C4D9+ have been measured in the ion storage ring CRYRING. The results for C3D7+ are believed to be slightly more accurate than those obtained earlier for C3H7+. Only the C–C bond breaking channels could be measured for C4D9+ and were found to be in excellent agreement with earlier data.
Model study of coherent quantum dynamics of hole states in functionalized semiconductor nanostructures
Authors: Rego Luis G. C. , Abuabara Sabas G. , Batista Victor S.
Published: April 2005

Functionalization of semiconductor nanocrystals can be achieved by anchoring organic ligands to the surface dangling bonds. The resulting surface complexes often introduce electronic states in the semiconductor band gap. These interband states sensitize the host material for photoabsorption at frequencies characteristic of the molecular adsorbates, leading to the well-known process of photoexcitation and subsequent femtosecond interfacial electron transfer. This paper investigates the relaxation dynamics of hole states, energetically localized deep in the semiconductor band gap, after the ultrafast electron-hole pair separation due to interfacial electron transfer. Mixed quantum-classical methods, based on mean-field nuclear dynamics approximated by ab initio density functional theory molecular dynamics simulations, reveal superexchange hole tunneling between adjacent adsorbate molecules in a model study of functionalized TiO2-anatase nanostructures. It is shown that electronic coherences can persist for hundreds of picoseconds under cryogenic and vacuum conditions, despite the partial intrinsic decoherence induced by thermal ionic motion, providing results of broad theoretical and experimental interest.
Polar direct drive: Proof-of-principle experiments on OMEGA and prospects for ignition on the National Ignition Facility
Authors: Craxton R. S. , Marshall F. J. , Bonino M. J. , Epstein R. , McKenty P. W. , Skupsky S. , Delettrez J. A. , Igumenshchev I. V. , Jacobs-Perkins D. W. , Knauer J. P. , Marozas J. A. , Radha P. B. , Seka W.
Published: April 2005

Polar direct drive (PDD) [S. Skupsky et al., Phys. Plasmas 11 2763 (2004)] shows promise for achieving direct-drive ignition while the National Ignition Facility (NIF) [E. M. Campbell and W. J. Hogan, Plasma Phys. Control. Fusion 41 B39 (1999)] is initially configured for indirect drive. Experiments have been carried out using 40 repointed beams of the 60-beam OMEGA laser system [T. R. Boehly et al., Rev. Sci. Instrum. 66 508 (1995)] to approximate the NIF PDD configuration. Backlit x-ray framing-camera images of D2-filled spherical CH capsules show a characteristic nonuniformity pattern that is in close agreement with predictions. Saturn targets (similar capsules surrounded by a plastic ring) increase the drive on the equator, suggesting that highly symmetric PDD implosions may be possible with appropriate tuning. Two-dimensional (2D) simulations reproduced the approximately threefold reduction in yield found for the non-Saturn PDD capsules. Preliminary simulations for a NIF Saturn design predict a high gain close to the 1D prediction. These results increase the prospects of obtaining direct-drive ignition with the initial NIF configuration.
Transport-driven scrape-off layer flows and the x-point dependence of the L-H power threshold in Alcator C-Mod
Authors: LaBombard B. , Rice J. E. , Hubbard A. E. , Hughes J. W. , Greenwald M. , Granetz R. S. , Irby J. H. , Lin Y. , Lipschultz B. , Marmar E. S. , Marr K. , Mossessian D. , Parker R. , Rowan W. , Smick N. , Snipes J. A. , Terry J. L. , Wolfe S. M. , Wukitch S. J. ,   the Alcator C-Mod Team
Published: April 2005

Factor of ∼2 higher power thresholds for low- to high-confinement mode transitions (L-H) with unfavorable x-point topologies in Alcator C-Mod [Phys. Plasmas 1, 1511 (1994)] are linked to flow boundary conditions imposed by the scrape-off layer (SOL). Ballooning-like transport drives flow along magnetic field lines from low- to high-field regions with toroidal direction dependent on upper/lower x-point balance; the toroidal rotation of the confined plasma responds, exhibiting a strong counter-current rotation when B×∇B points away from the x point. Increased auxiliary heating power (rf, no momentum input) leads to an L-H transition at approximately twice the edge electron pressure gradient when B×∇B points away. As gradients rise prior to the transition, toroidal rotation ramps toward the co-current direction; the H mode is seen when the counter-current rotation imposed by the SOL flow becomes compensated. Remarkably, L-H thresholds in lower-limited discharges are identical to lower x-point discharges; SOL flows are also found similar, suggesting a connection.
Q-S (lag or anticipated) synchronization backstepping scheme in a class of continuous-time hyperchaotic systems—A symbolic-numeric computation approach
Authors: Yan Zhenya
Published: April 2005

First, a Q-S (lag or anticipated) synchronization of continuous-time dynamical systems is defined. Second, based on a backstepping design with one controller, a systematic, concrete, and automatic scheme is developed to investigate the Q-S (lag or anticipated) synchronization between the drive system and response system with a strict-feedback form. Two identical hyperchaotic Tamasevicius-Namajunas-Cenys(TNC) systems as well as the hyperchaotic TNC system and hyperchaotic Rössler system are chosen to illustrate the proposed scheme. Numerical simulations are used to verify the effectiveness of the proposed scheme. The scheme can also be extended to study Q-S (lag or anticipated) synchronization between other dynamical systems with strict-feedback forms. With the aid of symbolic-numeric computation, the scheme can be performed to yield automatically the scalar controller in computer.
Analysis of one-dimensional pure-exchange NMR experiments for studying dynamics with broad distributions of correlation times
Authors: deAzevedo E. R. , Tozoni J. R. , Schmidt-Rohr K. , Bonagamba T. J.
Published: April 2005

One-dimensional (1D) exchange NMR experiments can elucidate the geometry, time scale, memory, and heterogeneity of slow molecular motions (1 ms–1 s) in solids. The one-dimensional version of pure-exchange (PUREX) solid-state exchange NMR, which is applied to static samples and uses the chemical shift anisotropy as a probe for molecular motion, is particularly promising and convenient in applications where site resolution is not a problem, i.e., in systems with few chemical sites. In this work, some important aspects of the 1D PUREX experiment applied to systems with complex molecular motions are analyzed. The influence of intermediate-regime (10 μs–1 ms) motions and of the distribution of reorientation angles on the pure-exchange intensity are discussed, together with a simple method for estimating the activation energy of motions occurring with a single correlation time. In addition, it is demonstrated that detailed information on the motional geometry can be obtained from 1D PUREX spectral line shapes. Experiments on a molecular crystal, dimethyl sulfone, confirm the analysis quantitatively. In two amorphous polymers, atactic polypropylene (aPP) and polyisobutylene (PIB), which differ only by one methyl group in the repeat unit, the height of the normalized exchange intensity clearly reveals a striking difference in the width of the distribution of correlation times slightly above the glass transition. The aPP shows the broad distribution and Williams–Landel–Ferry temperature dependence of correlation times typical of polymers and other “fragile” glass formers. In contrast, the dynamics in PIB occur essentially with a single correlation time and exhibits Arrhenius behavior, which is more typical of “strong” glass formers; this is somewhat surprising given the weak intermolecular forces in PIB.
Temperature dependence of the ambipolar carrier migration in a structure with InAs quantum dots grown in a strained GaInAs quantum well
Authors: Popescu Dan P. , Eliseev Peter G. , Malloy Kevin J.
Published: April 2005

The lateral carrier migration in a structure with InAs quantum dots (QDs) imbedded in a Ga0.85In0.15As quantum well grown on a GaAs substrate is investigated by confocal microscopy in a temperature range from 80 to 300K. Carrier spreading is measured by recording the ground and the first excited QD state emission. Carrier migration seems to be dominated by the diffusion in the GaAs barrier. The characteristic length of this transport phenomenon is 1.5μm at 80K. The characteristic migration length shows a linear increase with temperature up to a value of 1.7μm at 150K and then it remains constant up to 300K. The excited-state emission is spread in a spot with a smaller radius (1.0–1.2μm) and it has the same temperature dependence of the spreading distance as the characteristic migration length of carriers that recombine in the ground state.
Hysteresis trace in cylindrical magnetic nanoparticles with individual defects
Authors: Pereira Afranio R.
Published: April 2005

Lithographically defined detects can be intentionally incorporated in nanodots, changing the hysteresis loop. This change is associated with the mechanism of vortex pinning by the defect. We analytically calculate the magnetization of a nanodisk with an individual defect in the presence and in the absence of an applied magnetic field. The calculations are used to describe the hysteresis trace, which is compared to experimental results. There is a good qualitative agreement between our simple model and the experiments reported in the literature.
Crystal structure and atomic arrangement of the metastable Ge2Sb2Te5 thin films deposited on SiO2∕Si substrates by sputtering method
Authors: Park Y. J. , Lee J. Y. , Youm M. S. , Kim Y. T. , Lee H. S.
Published: April 2005

The Ge2Sb2Te5 thin films deposited by a sputtering method on SiO2∕Si substrates were annealed through a rapid thermal annealing process and performed a high-resolution transmission electron microscopy study in order to investigate the atomic arrangement of the metastable Ge2Sb2Te5. The metastable rocksalt structure having face-centered-cubic lattice was confirmed by high-resolution transmission electron microscopy images and simulated images on the directions of ⟨100⟩, ⟨110⟩, and ⟨211⟩ zone axes. According to the position of Ge and Sb in the metastable rocksalt structure, the atomic distribution alters when observed in different direction and this causes change in the charge-density distribution, resulting in different images in a high-resolution transmission electron microscopy. It is expected that as the crystallization proceeds, the Ge and Sb atoms tend to position themselves on a specific plane. From this aspect, the ordered structure model of the metastable Ge2Sb2Te5 was proposed by varying the position of the Ge and Sb atoms.
The effects of confinement on the behavior of water molecules between parallel Au plates of (001) planes
Authors: Ju Shin-Pon , Chang Jee-Gong , Lin Jenn-Sen , Lin Yong-Sheng
Published: April 2005

Molecular dynamics simulation is utilized to investigate the behavior of water molecules confined between two Au plates of (001) planes separated by gaps of 24.48, 16.32, 12.24, 11.22, and 10.20 Å. The simulation results indicate that the arrangements of the water molecules are dependent on the gap size. For the largest gap size, adsorption of the Au surface creates two permanent water layers in the vicinity of each Au plate. Furthermore, in this case, the gap size is sufficiently large to permit the formation of a central region within which the water molecules are randomly oriented in a similar manner to bulk water molecules. The results indicate that the orientation of the first water layer directly absorbed by the plate surface does not change as the gap size between the two Au plates is reduced. However, the orientations of the O–H bonds in the second water layer parallel to the surface rearrange to form hydrogen bonds between the water layers as the separation between the plates is decreased. Finally, an inspection of the variation of the self-diffusion coefficients with the gap size suggests that the difference between the dynamic properties of the water molecules in the z direction and the x-y plane decreases as the distance between the two Au plates increases.
Approximate density functionals applied to molecular quantum dots
Authors: Zhuang Min , Rocheleau Philippe , Ernzerhof Matthias
Published: April 2005

Recently, molecular quantum dots (MQDs) have been investigated experimentally and found to exhibit the Kondo effect. The Kondo effect leads to an enhancement of the zero-voltage conductance. Here, we study a finite cluster model of a MQD by means of Kohn–Sham density functional theory. Furthermore, employing an implementation of Landauer’s formula, we calculate the conductance of the dot. We find that the electronic structure and the molecular conductance depend strongly on the exchange-correlation functional employed. While the local spin density approximation and the Perdew–Burke–Ernzerhof (PBE) generalized gradient approximation qualitatively reproduce certain features of the Kondo effect, PBE hybrid does not. Based on the MQD, we discuss the limitations of using density functional theory to model molecular electronic devices.
Epitaxial growth of highly coercive Sm–Co thin films using pulsed laser deposition
Authors: Singh A. , Tamm R. , Neu V. , Fähler S. , Oertel C.-G. , Skrotzki W. , Schultz L. , Holzapfel B.
Published: April 2005

Hard magnetic materials with a uniaxial magnetocrystalline anisotropy can be most efficiently used if the easy axis is well aligned along one crystallographic direction in the entire sample volume. Epitaxial growth is one suitable method to achieve this aim and therefore Sm–Co thin films on Cr-buffered single-crystal MgO (100) substrates were deposited. Pulsed laser deposition from elemental Sm and Co targets was used to prepare films of nominal Sm2Co7 stoichiometry. Pole figure measurements and magnetization measurements reveal an epitaxial growth of Cr on MgO onto which the c axis of the Sm–Co layer is aligned in plane, viz., MgO(001)[100]‖Cr(001)[110]‖Sm–Co(110)[001]. At higher deposition temperatures an additional Sm–Co (1 1 16) texture was observed. This corresponds to an additional epitaxial orientation relation, where the c axis is tilted 60° out of the substrate plane. However, at low deposition temperatures and with smaller pulse repetition rates a reduction in the amount of this unwanted component can be achieved. This leads to the orientation of the c axis, which is the easy magnetization axis, only along two equivalent MgO [100] directions in the substrate plane. The resulting magnetic anisotropy has been confirmed by hysteresis measurements along three nonequivalent directions where high remanences and a high coercivity of up to 2.4T along MgO [110] can be achieved.
The hydrogen bond in ice probed by soft x-ray spectroscopy and density functional theory
Authors: Nilsson A. , Ogasawara H. , Cavalleri M. , Nordlund D. , Nyberg M. , Wernet Ph. , Pettersson L. G. M.
Published: April 2005

We combine photoelectron and x-ray absorption spectroscopy with density functional theory to derive a molecular orbital picture of the hydrogen bond in ice. We find that the hydrogen bond involves donation and back-donation of charge between the oxygen lone pair and the O–H antibonding orbitals on neighboring molecules. Together with internal s-p rehybridization this minimizes the repulsive charge overlap of the connecting oxygen and hydrogen atoms, which is essential for a strong attractive electrostatic interaction. Our joint experimental and theoretical results demonstrate that an electrostatic model based on only charge induction from the surrounding medium fails to properly describe the internal charge redistributions upon hydrogen bonding.
Fusion materials science: Overview of challenges and recent progress
Authors: Zinkle Steven J.
Published: April 2005

A brief review is given of fundamental materials science concepts important for development of structural materials for fusion energy systems. Particular attention is placed on displacement damage effects associated with the unique deuterium-tritium fusion environment. Recent examples of multiscale materials modeling results (closely coupled with experimental studies) are summarized. Fundamental differences in the behavior of body centered cubic versus face centered cubic crystal structures are highlighted. Finally, a brief overview is given of the high-performance reduced-activation materials being developed by fusion.
Molecular dynamics studies of melting and some liquid-state properties of 1-ethyl-3-methylimidazolium hexafluorophosphate [emim][PF6]
Authors: Alavi Saman , Thompson Donald L.
Published: April 2005

Molecular dynamics simulations are used to study the liquid-state properties and melting of 1-ethyl-3-methylimidazolium hexafluorosphosphate [emim][PF6] using the force field of Canongia Lopes et al. [J. Phys. Chem. B 108, 2038 (2004)] and geometric constants from crystallographic data. The structures of the solid and liquid states are characterized by carbon-carbon, carbon-phosphorous, and phosphorous-phosphorous radial distribution functions. Spatial correlations among the ions are strong in the liquid state. The cohesive energy density and the temperature dependences of the molar volume and density of the liquid have been computed. The melting point is determined by equilibrating the solid-state supercells in which void defects have been introduced to eliminate the free-energy barrier for the formation of a solid-liquid interface. The computed melting point is 375±10K, which is approximately 10% higher than the experimental value of 333 K.
Polarized near-edge x-ray-absorption fine structure spectroscopy of C60-functionalized 11-amino-1-undecane thiol self-assembled monolayer: Molecular orientation and Evidence for C60 aggregation
Authors: Patnaik Archita , Okudaira Koji K. , Kera Satoshi , Setoyama Hiroyuki , Mase Kazuhiko , Ueno Nobuo
Published: April 2005

Near-edge x-ray-absorption fine structure (NEXAFS) spectroscopy was adopted to probe the unoccupied electronic states of C60 anchored onto an organized assembly of 11-amino-1-undecane thiol on Au(111). The polarization dependence of the intensity of π* resonance associated with C60 π network revealed the self-assembled monolayer (SAM) system to be oriented with an average molecular tilt angle of 57° with respect to the surface normal. Invoking the absence of solid-state band dispersion effects and in comparison to solid C60 and /or 1-ML C60/Au(111), the electronic structure of the resulting assembly was found dominated by spectral position shift and linewidth and intensity changes of the lowest unoccupied molecular orbital (LUMO), LUMO+1, and LUMO+2 orbitals. The latter implied hybridization between N Pz of −NH2 group of thiolate SAM and π levels of C60, resulting in a nucleophilic addition with a change in the symmetry of C60 from Ih to C1 in the SAM. Occurrence of a new feature at 285.3 eV in the NEXAFS spectrum, assigned previously to π* graphitic LUMO, signified the formation of aggregated clusters, (C60)n of C60 monomer. Low tunneling current scanning tunneling microscopy confirmed them to be spherical and stable aggregates with n∼5.
Magnetic and electrical properties of single-phase multiferroic BiFeO3
Authors: Pradhan A. K. , Zhang Kai , Hunter D. , Dadson J. B. , Loiutts G. B. , Bhattacharya P. , Katiyar R. , Zhang Jun , Sellmyer D. J. , Roy U. N. , Cui Y. , Burger A.
Published: April 2005

We have reported the structural, thermal, microscopic, magnetization, polarization, and dielectric properties of BiFeO3 ceramics synthesized by a rapid liquid-phase sintering technique. Optimum conditions for the synthesis of single-phase BiFeO3 ceramics were obtained. Temperature-dependent magnetization and hysteresis loops indicate antiferromagnetic behavior in BiFeO3 at room temperature. Although saturated ferroelectric hysteresis loops were observed in single-phase BiFeO3 ceramic synthesized at 880 °C, the reduced polarization is found to be due to the high loss and low dielectric permittivity of the ceramic, which is caused by higher leakage current.
Swelling of polyelectrolyte networks
Authors: Mann Bernward A. , Holm Christian , Kremer Kurt
Published: April 2005

Employing molecular dynamics simulations of a coarse-grained model, the equilibrium swelling behavior of a cross-linked polyelectrolyte gel has been investigated with a bead-spring defect-free network with diamond-like topology under good solvent conditions and close to the θ-point, the counterions were treated explicitly. To examine the validity range of simple scaling arguments we varied the amount of charges in the system, the length of the network chains, the strength of the electrostatic interactions for both solvent qualities over a wide range of parameters. We find that classical theories only apply in the limit of weak electrostatics and suggest corrections based on the microscopic interplay of the systems’ components accessible in a simulation, which model successfully our measured data.
Multidimensional analysis of direct-drive, plastic-shell implosions on OMEGA
Authors: Radha P. B. , Collins T. J. B. , Delettrez J. A. , Elbaz Y. , Epstein R. , Glebov V. Yu. , Goncharov V. N. , Keck R. L. , Knauer J. P. , Marozas J. A. , Marshall F. J. , McCrory R. L. , McKenty P. W. , Meyerhofer D. D. , Regan S. P. , Sangster T. C. , Seka W. , Shvarts D. , Skupsky S. , Srebro Y. , Stoeckl C.
Published: April 2005

Direct-drive, plastic shells imploded on the OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] with a 1ns square pulse are simulated using the multidimensional hydrodynamic code DRACO in yield degradation in “thin” shells is primarily caused by shell breakup during the acceleration phase due to short-wavelength (ℓ>50, where ℓ is the Legendre mode number) perturbation growth, whereas “thick” shell performance is influenced primarily by long and intermediate modes (ℓ⩽50). Simulation yields, temporal history of neutron production, areal densities, and x-ray images of the core compare well with experimental observations. In particular, the thin-shell neutron production history falls off less steeply than one-dimensional predictions due to shell-breakup-induced undercompression and delayed stagnation. Thicker, more-stable shells show burn truncation due to instability-induced mass flow into the colder bubbles. Estimates of small-scale mix indicate that turbulent mixing does not influence primary neutron yields.
Anomalous features of the kinetics of subdiffusion-assisted bimolecular reactions
Authors: Shushin A. I.
Published: April 2005

Some specific features of the kinetics of subdiffusion-assisted bimolecular reactions are analyzed in detail with the use of the non-Markovian stochastic Liouville equation (SLE) recently derived within the continuous time random walk approach. The SLE allows for describing important peculiarities of the reactions: Slow long time behavior of the kinetics, nonanalytical dependence of the reaction rate on the reactivity of particles, the onset of quasistatic regime independently of particle mobility in the case long-range reactivity, strong manifestation of fluctuation kinetics showing itself in very slow reaction kinetics at long times, etc.
Optimal dynamic discrimination of similar quantum systems with time series data
Authors: Li Baiqing , Rabitz Herschel , Wolf J. P.
Published: April 2005

Optimal dynamic discrimination (ODD) was proposed [Li et al., J. Phys. Chem. B 106, 8125 (2002)] as a paradigm for discriminating noninteracting similar quantum systems in a mixture. This paper extends the ODD concept to optimize a laser control pulse for guiding similar quantum systems such that each exhibits a distinct time series signal for maximum discrimination. The use of temporal data addresses various experimental difficulties, including noise in the laser pulse, signal detection errors, and finite time resolution in the signal. Simulations of ODD with time series data are presented to explore these effects. It is found that the use of an optimally chosen control pulse can significantly enhance the discrimination quality. The ODD technique is also adapted to the case where the sample contains an unknown background species.
Investigation of the excited-state absorption of a Ru dioxolene complex by the Z-scan technique
Authors: Cassano Tiziana , Tommasi Raffaele , Meacham Andrew P. , Ward Michael D.
Published: April 2005

We investigated nonlinear absorption of picosecond laser pulses in a Ru complex [{Ru(bipy)2}2L][PF6] using the open-aperture Z-scan technique. Experiments were performed in a spectral region of moderate linear absorption (λ=532nm, σg=0.65×10−16cm−2). We observed a transition from reverse saturable absorption to saturable absorption when the excitation intensity was higher than 50GW∕cm2. To determine the population level kinetics, a model based on three- and four-level systems was considered, and the rate equations solved taking into account the propagation equation of the laser pulse inside the sample. Fitting of the experimental data allows extraction of the excited-states absorption cross sections and lifetimes.
Effects of deposition parameters on residual stresses, hardness and electrical resistivity of nanoscale twinned 330 stainless steel thin films
Authors: Zhang X. , Misra A. , Wang H. , Lima A. L. , Hundley M. F. , Hoagland R. G.
Published: April 2005

We have explored the influence of sputtering parameters on the structural, mechanical, and electrical properties of nanoscale twinned 330 stainless steel thin films. As the residual stress in the film is changed from tensile to compressive by varying the growth conditions, the nanoscale twinned structure, the average columnar grain size and texture of the film show little or no change. Hardness of the film in compression reaches 7GPa, compared to about 5.5GPa in films with high residual tension, and an order of magnitude higher than that of bulk 330 stainless steel. Molecular dynamics simulations indicate that twin boundaries pose a strong barrier to glide dislocation transmission under applied in-plane biaxial loading, consistent with the GPa level strengths measured in these films. The increase in the room temperature electrical resistivity of these films, compared to bulk 330 stainless steel, is found to be small, indicating that nanoscale twinned structures may provide the best combination of high mechanical strengths and high electrical conductivity.