bluuebunny/crossref_metadata_2025 huggingface dataset:
Is the psychopathology of acute and transient psychotic disorder different from schizophrenic and schizoaffective disorders?
Authors: Marneros Andreas , Pillmann Frank , Haring Annette , Balzuweit Sabine , Blöink Raffaela
Published: April 2005

Objective

This study explores psychopathological aspects of acute and transient psychotic disorders (ATPD), a diagnostic category introduced with ICD-10, to elucidate its relationship with schizophrenia and schizoaffective psychoses.

Methods

We recruited all consecutive inpatients fulfilling the ICD-10 criteria of ATPD (F23) during a 5-year period as well as control groups with “positive” schizophrenia (PS) and bipolar schizoaffective disorder (BSAD) matched for gender and age at index episode. For the evaluation of psychopathological parameters during index episode a standardized symptom list was used. Prepsychotic (prodromal) symptoms were also assessed.

Results

During the prepsychotic period few differences between the groups were detected. The most important difference between ATPD and the other two other psychotic disorders regarding phenomenology of the full-blown episodes was a higher frequency of “rapidly changing delusional topics”, “rapidly changing mood” and anxiety in ATPD.

Conclusion

ATPD show a characteristic psychopathological picture consistent with earlier concepts such as cycloid psychoses and bouffée délirante. Nevertheless, psychopathology alone is not enough to establish ATPD as an independent nosological entity.
Professional team's choices of intervention towards problems and needs of patients suffering from schizophrenia across six European countries
Authors: Kovess Vivianne , Caldas de Almeida José Miguel , Carta Mauro , Dubuis Jacques , Lacalmontie Elisabeth , Pellet Jacques , Roelandt Jean-Luc , Moreno Kustner Berta , Walsh Dermot , Wiersma Durk
Published: April 2005

Objectives

This article compares in a systematic way the team's intervention choices of professionals across seven European countries: France, Ireland, Italy, the Netherlands, Portugal and Spain towards problems and needs of patients with schizophrenia and relates this to the diversity of psychiatric systems.

Methods

The clinical and social status of 433 patients was assessed by means of the Schedules for Clinical Assessment in Neuropsychiatry (SCAN) and the Needs for Care Assessment instrument (NFCAS) which was used to determine teams' intervention choices toward the NFCAS problems.

Results

There is no, or little, consensus across Europe on teams' intervention choices towards either the clinical or the social problems and needs of patients suffering from schizophrenic disorders. These comparisons outlined the cultural differences concerning the interventions that were proposed and should be taken into account when interpreting the number of needs and the need status since the need status relies heavily on the interventions proposed. The differences were not connected with the availability of resources; most of the comparisons show differences between centers as well as differences between groups of relatively similar resource countries.
Molecular basis of the allosteric mechanism of cAMP in the regulatory PKA subunit
Authors: Pantano Sergio , Zaccolo Manuela , Carloni Paolo
Published: April 2005

The second messenger cyclic Adenosine MonoPosphate (cAMP) mediates many biological process by interacting with structurally conserved nucleotide binding domains (cNBD's). Here, we use molecular dynamics simulations on RIIβ‐PKA, one of the best characterized members of the cNBD family, in presence and absence of cAMP. The results of our calculations are fully consistent with the available experimental data and suggest that the key factor of the cAMP allosteric mechanism in cNBDS's is the increased flexibility of the protein upon ligand release along with a mechanical coupling between helical segments. In addition, our calculations provide a rationale for the experimentally observed cAMP selective binding to PKA.
Why females live longer than males? Importance of the upregulation of longevity‐associated genes by oestrogenic compounds
Authors: Viña Jose , Borrás Consuelo , Gambini Juan , Sastre Juan , Pallardó Federico V.
Published: April 2005

Females live longer than males in many mammalian species, including humans. Mitochondria from females produce approximately half the amount of H2O2 than males. We have found that females behave as double transgenics overexpressing both superoxide dismutase and glutathione peroxidase. This is due to oestrogens that act by binding to the estrogen receptors and subsequently activating the mitogen activated protein (MAP) kinase and nuclear factor kappa B (NF‐κB) signalling pathways. Phytoestrogens mimic the protective effect of oestradiol using the same signalling pathway. The critical importance of upregulating antioxidant genes, by hormonal and dietary manipulations, in order to increase longevity is discussed.
Survival of sardine larvae off the Atlantic Portuguese coast: a preliminary numerical study
Authors: Santos Aires J.P. , Nogueira João , Martins Helder
Published: April 2005

A bio-physical model of sardine larvae off the Atlantic Portuguese coast, incorporating a three-dimensional circulation model, was used to estimate changing biomass during winter upwelling and downwelling events. The growth rate of larvae was modelled as a function of age, temperature, and prey concentration and the mortality rate as a function of age and temperature. Numerical results indicate that upwelling events during the spawning season may have a negative impact on larval survival. Total larval biomass seems to be mainly controlled by larval prey relative to temperature. This preliminary study does not account for the dynamics of the food chain and therefore the intense biological activity associated with an upwelling event, as well as the influence of river plumes in retention mechanisms.
Reconstruction of the long-term fire history of an old-growth deciduous forest in Southern Québec, Canada, from charred wood in mineral soils
Authors: Talon Brigitte , Payette Serge , Filion Louise , Delwaide Ann
Published: April 2005

Charcoal particles are widespread in terrestrial and lake environments of the northern temperate and boreal biomes where they are used to reconstruct past fire events and regimes. In this study, we used botanically identified and radiocarbon-dated charcoal macrofossils in mineral soils as a paleoecological tool to reconstruct past fire activity at the stand scale. Charcoal macrofossils buried in podzolic soils by tree uprooting were analyzed to reconstruct the long-term fire history of an old-growth deciduous forest in southern Québec. Charcoal fragments were sampled from the uppermost mineral soil horizons and identified based on anatomical characters. Spruce (Picea spp.) fragments dominated the charcoal assemblage, along with relatively abundant wood fragments of sugar maple (Acer saccharum) and birch (Betula spp.), and rare fragments of pine (Pinus cf. strobus) and white cedar (Thuja canadensis). AMS radiocarbon dates from 16 charcoal fragments indicated that forest fires were widespread during the early Holocene, whereas no fires were recorded from the mid-Holocene to present. The paucity of charcoal data during this period, however, does not preclude that a fire event of lower severity may have occurred. At least eight forest fires occurred at the study site between 10,400 and 6300 cal yr B.P., with a dominance of burned conifer trees between 10,400 and 9000 cal yr B.P. and burned conifer and deciduous trees between 9000 and 6300 cal yr B.P. Based on the charcoal record, the climate at the study site was relatively dry during the early Holocene, and more humid from 6300 cal yr B.P. to present. However, it is also possible that the predominance of conifer trees in the charcoal record between 10,400 and 6300 cal yr B.P. created propitious conditions for fire spreading. The charcoal record supports inferences based on pollen influx data (Labelle, C., Richard, P.J.H. 1981. Végétation tardiglaciaire et postglaciaire au sud-est du Parc des Laurentides, Québec. Géographie Physique et Quaternaire 35, 345-359) of the early arrival of spruce and sugar maple in the study area shortly after deglaciation. We conclude that macroscopic charcoal analysis of mineral soils subjected to disturbance by tree uprooting may be a useful paleoecological tool to reconstruct long-term forest fire history at the stand scale.
Validation of Map Matching Algorithms using High Precision Positioning with GPS
Authors: Quddus Mohammed A. , Noland Robert B. , Ochieng Washington Y.
Published: April 2005

Map Matching (MM) algorithms are usually employed for a range of transport telematics applications to correctly identify the physical location of a vehicle travelling on a road network. Two essential components for MM algorithms are (1) navigation sensors such as the Global Positioning System (GPS) and dead reckoning (DR), among others, to estimate the position of the vehicle, and (2) a digital base map for spatial referencing of the vehicle location. Previous research by the authors (Quddus et al., 2003; Ochieng et al., 2003) has developed improved MM algorithms that take account of the vehicle speed and the error sources associated with the navigation sensors and the digital map data previously ignored in conventional MM approaches. However, no validation study assessing the performance of MM algorithms has been presented in the literature. This paper describes a generic validation strategy and results for the MM algorithm previously developed in Ochieng et al. (2003). The validation technique is based on a higher accuracy reference (truth) of the vehicle trajectory as determined by high precision positioning achieved by the carrier-phase observable from GPS. The results show that the vehicle positions determined from the MM results are within 6 m of the true positions. The results also demonstrate the importance of the quality of the digital map data to the map matching process.
A Comment on Navigation Instruction
Authors: Earle Michael A.
Published: April 2005

Use of a sphere to represent the Earth in the teaching of navigation has the advantage that the mathematics is relatively simple and has sufficient accuracy for most practical purposes. It also allows relatively simple instructional material to be developed for plane and Mercator sailing. Unfortunately, and as remarked by Williams [1], bad practice based on an error of principle has pervaded some navigation texts for some time. This error has passed into various instructional settings where it has gone un-noticed or un-remarked. The error lies in the un-rigorous use of meridional parts for the spheroidal earth together with latitude differences for the spherical earth in the teaching of plane and Mercator sailing. This is exemplified in [2, example1, p 585]. It is often argued that the resulting error in calculated distance or mid-latitude caused by this un-rigorous treatment is small and within what practical course keeping allows. However, permitting the discrepancy to remain unexplained is a disservice to students of navigation. Students should be given a clear explanation of the differences between the fictitious though useful spherical model of the earth and the spheroidal earth as presently described by WGS84. Teaching of plane and Mercator sailings should be based upon either the spherical model or upon the spheroidal model but not on parts taken from both.
Clinical profile of acute rheumatic fever in Pakistan
Authors: Chagani Hasina Suleman , Aziz Kalimuddin
Published: April 2005

We designed a multi-hospital prospective study of children less than 12 years to determine the comparative clinical profile, severity of carditis, and outcome on follow up of patients suffering an initial and recurrent episodes of acute rheumatic fever. The study extended over a period of 3 years, with diagnosis based on the Jones criteria. We included 161 children in the study, 57 having only one episode and 104 with recurrent episodes. Those seen in the first episode were differentiated from those with recurrent episodes on the basis of the history. The severity of carditis was graded by clinical and echocardiographic means. In those suffering their first episode, carditis was significantly less frequent (61.4%) compared to those having recurrent episodes (96.2%). Arthritis was more marked in the first episode (61.4%) compared to recurrent episodes (36.5%). Chorea was also significantly higher in the first episode (15.8%) compared to recurrent episodes (3.8%). Sub-cutaneous nodules were more-or-less the same in those suffering the first (7%) as opposed to recurrent episodes (5.8%), but Erythema marginatum was more marked during the first episode (3.5%), being rare in recurrent episodes at 0.9%. Fever was recorded in approximately the same numbers in first (45.6%) and recurrent episodes (48.1%). Arthralgia, in contrast, was less frequent in first (21.1%) compared to recurrent episodes (32.7%). A history of sore throat was significantly increased amongst those suffering the first episode (54.4%) compared to recurrent episodes (21.2%). When we compared the severity of carditis in the first versus recurrent episodes, at the start of study mild carditis was found in 29.8% versus 10.6%, moderate carditis in 26.3% versus 53.8%, and severe carditis in 5.3% versus 31.8% of cases, respectively. At the end of study, 30.3% of patients suffering their first episode were completely cured of carditis, and all others showed significant improvement compared to those with recurrent episodes, where only 6.8% were cured, little improvement or deterioration being noted in the remainder of the patients. We conclude that the clinical profile of acute rheumatic fever, especially that of carditis, is milder in those suffering their first attack compared to those with recurrent episodes.
Sensitivity of the quasi‐biennial oscillation to CO2 doubling
Authors: Giorgetta Marco A. , Doege Martin C.
Published: April 2005

The quasi‐biennial oscillation (QBO) is a major oscillation with a characteristic period of 28 months that influences substantially the stratospheric circulation and chemistry. This exploratory study investigates its possible change by direct simulation of the QBO in a doubled CO2 climate for a range of gravity wave sources. It is found that a QBO spin‐up is likely. In the most extreme case the period is nearly halved. Important accelerating factors are the decreased tropical upwelling and increased gravity wave drag, while increased filtering of eastward gravity waves in the upper tropical troposphere acts as a decelerating factor.
Evidence for ascending upper mantle‐derived melt beneath the Cheb basin, central Europe
Authors: Bräuer Karin , Kämpf Horst , Niedermann Samuel , Strauch Gerhard
Published: April 2005

We present new 3He/4He data of CO2‐rich gas exhalations of three presently nonvolcanic areas in Europe. The 3He/4He ratios from the Cheb basin (Czech Republic) are clearly higher than data obtained ten years ago, whereas the 3He/4He ratios from the other areas (Laacher See/Germany and Mariánské Lázně/CR) have remained nearly constant. No other locality showing such high 3He/4He ratios in free gases supplied by continental mantle degassing is known in the European Cenozoic rift system. At the northeastern edge of the Cheb basin swarm earthquakes repeatedly occur. In the context of contemporaneous periods of seismicity the increased 3He/4He ratios are interpreted as the first geochemical evidence for ascending mantle‐derived melt beneath the Cheb basin, which is related to the triggering of earthquake swarms.
Spatial variability in biogenic gas accumulations in peat soils is revealed by ground penetrating radar (GPR)
Authors: Comas Xavier , Slater Lee , Reeve Andrew
Published: April 2005

We performed surface and borehole ground penetrating radar (GPR) tests, together with moisture probe measurements and direct gas sampling to detect areas of biogenic gas accumulation in a northern peatland. The main findings are: (1) shadow zones (signal scattering) observed in surface GPR correlate with areas of elevated CH4 and CO2 concentration; (2) high velocities in zero offset profiles and lower water content inferred from moisture probes correlate with surface GPR shadow zones; (3) zero offset profiles depict depth variable gas accumulation from 0–10% by volume; (4) strong reflectors may represent confining layers restricting upward gas migration. Our results have implications for defining the spatial distribution, volume and movement of biogenic gas in peatlands at multiple scales.
An improved expected temperature formula for identifying interplanetary coronal mass ejections
Authors: Elliott H. A. , McComas D. J. , Schwadron N. A. , Gosling J. T. , Skoug R. M. , Gloeckler G. , Zurbuchen T. H.
Published: April 2005

In this study we compare nearly 5 years of solar wind proton speed and temperature measurements from the Solar Wind Electron Proton Alpha Monitor (SWEPAM) on the Advanced Composition Explorer (ACE) to derive an improved expected temperature formula to identify interplanetary coronal mass ejections (ICMEs). Anomalously low proton temperatures have long been associated with ICMEs. When transient ICMEs are not present, the solar wind speed and temperature are highly correlated, and previous studies have derived fits to these measurements. Using these fits, an expected temperature is determined from the solar wind speed. Anomalously low temperatures have been identified as times when the ratio of the measured to expected temperature is below 0.5. In this study we remove ICMEs before fitting the remaining data. Fast and slow parcels in the solar wind interact and cause compressions and rarefactions as the solar wind moves away from the Sun. Since such interaction causes the speed and temperature of these parcels to change, we separately fit compression and rarefactions. We find that the expected temperature formula derived in this way provides a better way of identifying ICMEs than previous formulas, particularly in compression regions.
Observed tidal variation in the lower thermosphere through the 20th century and the possible implication of ozone depletion
Authors: Jarvis Martin J.
Published: April 2005

Climatological change in the tides in the lower thermosphere has been estimated at five different latitudes using wavelet analysis of geomagnetic data series extending back to the beginning of the 20th century. The tidal signature present in the geomagnetic data is a consequence of atmospheric tides in the dynamo region between approximately 120 and 140 km altitude. The diurnal and semidiurnal spectral power have been accumulated through each year. The effect of solar and geomagnetic drivers has been minimized through use of proxy indices (aa index, sunspot number, F10.7 solar flux) to leave a residual which shows ∼20% reduction in both diurnal and semidiurnal amplitudes at midlatitudes since the middle of the century. This midlatitude reduction is qualitatively similar to the decrease observed using wind data from 1964 onward at approximately 90 km altitude over a range of latitudes by Bremer et al. (1997), but quantitatively it is about half the magnitude. At high latitude a similar decrease would be a statistically insignificant measurement because the estimation becomes sensitive to errors in the aa index. At low latitude there is no significant change throughout the century. The observed decrease at midlatitudes appears consistent with that predicted by Ross and Walterscheid (1991) for the dynamo region current as a consequence of global ozone depletion. Reduced tidal heating of the stratosphere during the latter half of the 20th century and the consequent reduction in tidal power propagating up to the lower thermosphere is implicated.
Adiabatic behavior of strongly nonlinear internal solitary waves in slope‐shelf areas
Authors: Vlasenko V. , Ostrovsky L. , Hutter K.
Published: April 2005

Transformation of large‐amplitude internal solitary waves (ISW) propagating over slope‐shelf topography is studied theoretically and with the use of the experimental data collected during the Coastal Ocean Probing Experiment (COPE). Taking into account a very strong nonlinearity of observed waves (the ratio of isotherm displacement to their initial depth reached a value of 5), two different approaches were employed for the theoretical investigations of the wave evolution: numerical simulations in the framework of a fully nonlinear nonhydrostatic system of equations and estimations based on a long‐wave equation derived for a two‐layer fluid without any restrictions on the wave amplitude. Special attention is paid to the adiabatic stage of the wave evolution over a gently sloping bottom when the ISW conserves its energy in the course of propagation and preserves the parameters close to a steady solitary wave corresponding to each local depth. Strong ISWs vary adiabatically along the path of propagation until their vertical scale (amplitude) becomes comparable with the total water depth. This adiabatic process typically ends when a soliton reaches its limiting amplitude, after which the breaking process occurs that leads to the generation of turbulence. For a sharp pycnocline, simplified two‐layer models are applicable for the study of the shoaling process roughly within the same limits as for steady solitons over a flat bottom. Even for a relatively smooth stratification, some soliton parameters, such as its velocity and the peak particle velocity, can be satisfactorily evaluated from two‐layer models.
Genomic and nongenomic effects of aldosterone in the rat heart: why is spironolactone cardioprotective?
Authors: Chai Wenxia , Garrelds Ingrid M , Arulmani Udayasankar , Schoemaker Regien G , Lamers Jos M J , Danser A H Jan
Published: April 2005

Mineralocorticoid receptor (MR) antagonism with spironolactone reduces mortality in heart failure on top of ACE inhibition. To investigate the underlying mechanism, we compared the actions of both aldosterone and spironolactone to those of angiotensin (Ang) II in the rat heart.

Hearts of male Wistar rats were perfused according to Langendorff. Ang II and aldosterone increased left ventricular pressure (LVP) by maximally 11±4 and 9±2%, and decreased coronary flow (CF) by maximally 36±7 and 20±4%, respectively. Spironolactone did not significantly affect LVP or CF.

In hearts that were exposed to a 45‐min coronary artery occlusion and 3 h of reperfusion, a 15‐min exposure to spironolactone prior to occlusion reduced infarct size (% of risk area) from 68±2 to 45±3%, similar to the reduction (34±2%) observed following ‘preconditioning’ (15 min occlusion followed by 10 min reperfusion) prior to the 45‐min occlusion. Aldosterone exposure did not affect infarct size (71±5%).

In cardiomyocytes, aldosterone decreased [3H]thymidine incorporation maximally by 73±3%, whereas in cardiac fibroblasts it decreased [3H]proline incorporation by 33±7%. Spironolactone inhibited both effects. Ang II increased DNA and collagen synthesis, and these effects were reversed by aldosterone.

In conclusion, aldosterone induces positive inotropic and vasoconstrictor effects in a nongenomic manner, and these effects are comparable to those of Ang II. Aldosterone reduces DNA and collagen synthesis via MR activation, and counteracts the Ang II‐induced increases in these parameters. MR blockade reduces infarct size and increases LVP recovery following coronary artery occlusion. The MR‐related phenomena may underlie, at least in part, the beneficial actions of spironolactone in heart failure.

British Journal of Pharmacology (2005) 145, 664–671. doi:10.1038/sj.bjp.0706220
Two mechanisms of action of the adamantane derivative IEM‐1460 at human AMPA‐type glutamate receptors
Authors: Schlesinger Friedrich , Tammena Derk , Krampfl Klaus , Bufler Johannes
Published: April 2005

Antagonizing glutamatergic neurotransmission by blockade of AMPA‐type glutamate receptors (GluR) is a promising pharmacological strategy for neuroprotection in neurodegenerative diseases and acute treatment of stroke.

We investigated the interaction of the adamantane derivative IEM‐1460 with human wild‐type and mutant AMPA‐type GluR channels. Different recombinant homooligomeric human AMPA‐type GluR channels and a rat nondesensitizing mutant GluR (GluR2 L504Y) channel were expressed in HEK293 cells and investigated using the patch‐clamp technique in combination with ultrafast agonist application.

When IEM‐1460 was coapplied with glutamate, an open channel block mechanism was observed at slow desensitizing GluR2 flip (0.1 mM IEM‐1460) and nondesensitizing GluR2 L504Y channels (1 μM IEM‐1460).

A competitive block of AMPA‐type channels was observed with IC50 values for the dose block curves of 0.1 mM IEM‐1460 at human unmutated and 10 μM IEM‐1460 at mutant GluR channels.

Nondesensitizing GluR2 L504Y channels were used to further characterize the block mechanism. After equilibration with the agonist, a current decay upon coapplication of glutamate and IEM‐1460 was observed. The recovery from block was independent of the glutamate and IEM‐1460 concentration. The extent of current inhibition as well as the time constant of current decay upon addition of the blocker to the test solution were dependent on agonist concentration; this strongly points to an additional competitive‐like block mechanism of IEM‐1460 at human AMPA‐type GluR channels.

The data were interpreted in the frame of a molecular scheme with two binding sites of IEM‐1460 at the receptor, one at the unliganded resting and the other at the fully liganded open state of the channels.

British Journal of Pharmacology (2005) 145, 656–663. doi:10.1038/sj.bjp.0706233
Neural mechanism for binaural pitch perception via ghost stochastic resonance
Authors: Balenzuela Pablo , García-Ojalvo Jordi
Published: April 2005

We present a physiologically plausible binaural mechanism for the perception of the pitch of complex sounds via ghost stochastic resonance. In this scheme, two neurons are driven by noise and a different periodic signal each (with frequencies f1=kf0 and f2=(k+1)f0, where k>1), and their outputs (plus noise) are applied synaptically to a third neuron. Our numerical results, using the Morris–Lecar neuron model with chemical synapses explicitly considered, show that intermediate noise levels enhance the response of the third neuron at frequencies close to f0, as in the cases previously described of ghost resonance. For the case of an inharmonic combination of inputs (f1=kf0+Δf and f2=(k+1)f0+Δf) noise is also seen to enhance the rates of most probable spiking for the third neuron at a frequency fr=f0+[Δf∕(k+1∕2)]. In addition, we show that similar resonances can be observed as a function of the synaptic time constant. The suggested ghost-resonance-based stochastic mechanism can thus arise either at the peripheral level or at a higher level of neural processing in the perception of pitch.
Dynamic response of materials on subnanosecond time scales, and beryllium properties for inertial confinement fusion
Authors: Swift Damian C. , Tierney Thomas E. , Luo Sheng-Nian , Paisley Dennis L. , Kyrala George A. , Hauer Allan , Greenfield Scott R. , Koskelo Aaron C. , McClellan Kenneth J. , Lorenzana Hector E. , Kalantar Daniel , Remington Bruce A. , Peralta Pedro , Loomis Eric
Published: April 2005

During the past few years, substantial progress has been made in developing experimental techniques capable of investigating the response of materials to dynamic loading on nanosecond time scales and shorter, with multiple diagnostics probing different aspects of the behavior. These relatively short time scales are scientifically interesting because plastic flow and phase changes in common materials with simple crystal structures—such as iron—may be suppressed, allowing unusual states to be induced and the dynamics of plasticity and polymorphism to be explored. Loading by laser-induced ablation can be particularly convenient: this technique has been used to impart shocks and isentropic compression waves from ∼1to200GPa in a range of elements and alloys, with diagnostics including line imaging surface velocimetry, surface displacement (framed area imaging), x-ray diffraction (single crystal and polycrystal), ellipsometry, and Raman spectroscopy. A major motivation has been the study of the properties of beryllium under conditions relevant to the fuel capsule in inertial confinement fusion: magnetically driven shock and isentropic compression shots at Z were used to investigate the equation of state and shock melting characteristics, complemented by laser ablation experiments to investigate plasticity and heterogeneous response from the polycrystalline microstructure. These results will help to constrain acceptable tolerances on manufacturing, and possible loading paths, for inertial fusion ignition experiments at the National Ignition Facility. Laser-based techniques are being developed further for future material dynamics experiments, where it should be possible to obtain high quality data on strength and phase changes up to at least 1TPa.
Electrostatically actuated thin-film amorphous silicon microbridge resonators
Authors: Gaspar J. , Chu V. , Conde J. P.
Published: April 2005

Doped hydrogenated amorphous silicon microbridge resonators are fabricated at temperatures below 110°C on glass substrates using thin-film technology and surface micromachining. The microelectromechanical structures are electrostatically actuated by using a superposition of dc and ac voltage components. The resulting deflection is optically detected. The effects of the measurement pressure, actuation voltage, and geometrical dimensions of the structures on the resonance frequency and quality factor are studied and the results are interpreted using electromechanical models. Resonance frequencies between 600kHz and 31MHz are observed for the micron-sized structures, corresponding to effective elastic spring constants in the range from 10 to 4000N∕m, for both the fundamental flexural mode and the symmetry-allowed harmonics. Young’s moduli of 146 and 80GPa are extracted for hydrogenated amorphous silicon and aluminum, respectively. At a measurement pressure of 10−6Torr, these resonators present quality factors as high as 5000 in the small-deflection limit. The value of the quality factor is very sensitive to both the measurement pressure and excitation voltage amplitude.
Photophysics of an electrophosphorescent platinum (II) porphyrin in solid films
Authors: Kalinowski J. , Stampor W. , Szmytkowski J. , Cocchi M. , Virgili D. , Fattori V. , Di Marco P.
Published: April 2005

We examine electronic processes in platinum (II) octaethyl porphyrin (PtOEP) embedded in an organic solid state matrix and in the form of vacuum-evaporated neat films in conjunction with potential applications of this compound to organic photovoltaic and electrophosphorescent devices. Absorption, photoexcitation, and luminescence spectra indicate the excitonic dimers to be dominant excited states, and their dissociation underlies the charge photogeneration process. Different charge separation distance (1.5nm and 2.6nm) in opposite charge carrier pairs preceding dissociation can be distinguished based on the fit of the three-dimensional Onsager theory of geminate recombination to electromodulated luminescence and photoconduction measurements. The near-positive electrode concentrated triplet dimer excitons, produced by strongly 370nm absorbed light in neat PtOEP films, are efficiently quenched by electron transfer to the metal (Al), generating the positive charge with an efficiency η+ exceeding 0.15 at high electric fields and dominating the measured photocurrent. Their dissociation efficiency in the bulk, η− (negatively biased illuminated electrode), is more than one order of magnitude lower than η+. The dissociation of singlet dimer states dominates the bulk photogeneration process induced by the weakly-absorbed light at 450nm, with comparable η+ and η−. The “hot excited state” underlying the temperature-increasing emission at 540nm has been attributed to the upper excitonic component Q+ of the first absorption band Q consistent with the exciton concept applied successfully to the interpretation of all dimer-underlain spectroscopic features of PtOEP samples studied.
Quantitative analysis of damage in an octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazonic-based composite explosive subjected to a linear thermal gradient
Authors: Peterson Paul D. , Mang Joseph T. , Asay Blaine W.
Published: April 2005

The microstructure within a slowly heated, consolidated explosive will be influenced by both physical changes and chemical reactions prior to thermal ignition. Thermal expansion, exothermic decomposition, endothermic phase change, and increased binder viscosity play significant roles in the cook-off to detonation. To further explore the details of this intricate cook-off process, we have conducted a series of experiments in which a carefully controlled temperature gradient has been applied along a cylinder of PBX 9501 [94.9/2.5/2.5/0.1-wt % octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)/Estane 5703/a eutectic mixture of bis(2,2 dinitropropyl) acetal and bis(2,2-dinitropropyl) formal [abbreviated BDNPA-F]/Irganox] and maintained for a specified amount of time. After heating and subsequent cooling of the PBX 9501, the sample morphology has been probed with polarized light microscopy and small-angle x-ray scattering. Using these techniques we have quantitatively characterized the particle morphology, porosity, and chemical state of the explosive as a function of position, and therefore thermal treatment. Results of the analyses clearly show that thermal damage in PBX 9501 can be classified into two separate temperature regimes—an initial low-temperature regime (155–174°C) dominated by the endothermic β-δ crystalline phase change, thermal expansion, and Ostwald ripening, and a high-temperature regime (175–210°C) dominated by exothermic chemical decomposition. The results further show the complex interplay between the evolving sample morphology and the chemical reactions leading to a potential thermal self-ignition in the explosive.
Laser coupling to reduced-scale hohlraum targets at the Early Light Program of the National Ignition Facility
Authors: Hinkel D. E. , Schneider M. B. , Baldis H. A. , Bonanno G. , Bower D. E. , Campbell K. M. , Celeste J. R. , Compton S. , Costa R. , Dewald E. L. , Dixit S. N. , Eckart M. J. , Eder D. C. , Edwards M. J. , Ellis A. , Emig J. A. , Froula D. H. , Glenzer S. H. , Hargrove D. , Haynam C. A. , Heeter R. F. , Henesian M. A. , Holder J. P. , Holtmeier G. , James L. , Jancaitis K. S. , Kalantar D. H. , Kamperschroer J. H. , Kauffman R. L. , Kimbrough J. , Kirkwood R. K. , Koniges A. E. , Landen O. L. , Landon M. , Langdon A. B. , Lee F. D. , MacGowan B. J. , Mackinnon A. J. , Manes K. R. , Marshall C. , May M. J. , McDonald J. W. , Menapace J. , Moses E. I. , Munro D. H. , Murray J. R. , Niemann C. , Pellinen D. , Rekow V. , Ruppe J. A. , Schein J. , Shepherd R. , Singh M. S. , Springer P. T. , Still C. H. , Suter L. J. , Tietbohl G. L. , Turner R. E. , Van Wonterghem B. M. , Wallace R. J. , Warrick A. , Watts P. , Weber F. , Wegner P. J. , Williams E. A. , Young B. K. , Young P. E.
Published: April 2005

A platform for analysis of material properties under extreme conditions, where a sample is bathed in radiation with a high temperature, is under development. Depositing maximum laser energy into a small, high-Z enclosure produces this hot environment. Such targets were recently included in an experimental campaign using the first four of the 192 beams of the National Ignition Facility [J. A. Paisner, E. M. Campbell, and W. J. Hogan, Fusion Technol. 26, 755 (1994)], under construction at the University of California Lawrence Livermore National Laboratory. These targets demonstrate good laser coupling, reaching a radiation temperature of 340 eV. In addition, there is a unique wavelength dependence of the Raman backscattered light that is consistent with Brillouin backscatter of Raman forward scatter [A. B. Langdon and D. E. Hinkel, Phys. Rev. Lett. 89, 015003 (2002)]. Finally, novel diagnostic capabilities indicate that 20% of the direct backscatter from these reduced-scale targets is in the polarization orthogonal to that of the incident light.
Ordering mechanism of asymmetric diblock copolymers confined between polymer-grafted surfaces
Authors: Ren Chun-lai , Chen Kang , Ma Yu-qiang
Published: April 2005

Using self-consistent-field calculation, we study the equilibrium morphology of asymmetric block copolymer melts between two brush-covered surfaces. We discuss systematically the morphologies formed as a function of the grafting density of brushes and show a series of reentrant structural transformations between the lamellar and hexagonal phases. Such a selection of ordered microdomains has been attributed to the interplay among entropy effects of stretched brushes, the preferential interaction of the blocks with the grafted substrate, and the bulk microphase-separated behavior of asymmetric copolymers. Interestingly for the affinitive brush-copolymer interfaces, the bulk hexagonal phase may still be remained due to entropy elasticity of brushes, and the frustration can be relieved by deforming the shape of “soft” polymer-brush surface, in contrast to the hard-wall cases. The result demonstrates a simple way to realize molecular self-assembly for confined copolymer films with well-controlled thickness and interfacial environment.
Potential industrial applications of the one atmosphere uniform glow discharge plasma operating in ambient air
Authors: Roth J. Reece
Published: April 2005

The majority of industrial plasma processing is conducted with glow discharges at pressures below 10 Torr. This tends to limit such applications to high value workpieces, as a result of the high capital cost of vacuum systems and the production constraints of batch processing. It has long been recognized that glow discharges would play a much larger industrial role if they could be generated at 1 atm and in air. The one atmosphere uniform glow discharge plasma (OAUGDP®) has these capabilities. As a normal glow discharge, the OAUGDP® can operate with maximum electrical efficiency at the Stoletow point, where the energy input per ion-electron pair is a minimum. This paper will survey exploratory investigations at the University of Tennessee’s Plasma Sciences Laboratory of seven potential industrial applications of the OAUGDP® which can be conducted at 1 atm and at room temperature with air as the working gas.
Production of high-quality electron bunches by dephasing and beam loading in channeled and unchanneled laser plasma accelerators
Authors: Geddes C. G. R. , Tóth Cs. , van Tilborg J. , Esarey E. , Schroeder C. B. , Bruhwiler D. , Nieter C. , Cary J. , Leemans W. P.
Published: April 2005

High-quality electron beams, with a few 109 electrons within a few percent of the same energy above 80 MeV, were produced in a laser wakefield accelerator by matching the acceleration length to the length over which electrons were accelerated and outran (dephased from) the wake. A plasma channel guided the drive laser over long distances, resulting in production of the high-energy, high-quality beams. Unchanneled experiments varying the length of the target plasma indicated that the high-quality bunches are produced near the dephasing length and demonstrated that channel guiding was more stable and efficient than relativistic self-guiding. Consistent with these data, particle-in-cell simulations indicate production of high-quality electron beams when trapping of an initial bunch of electrons suppresses further injection by loading the wake. The injected electron bunch is then compressed in energy by dephasing, when the front of the bunch begins to decelerate while the tail is still accelerated.
X-ray induced absorption in fused silica containing various amounts of OH
Authors: Kuzuu Nobu , Horikoshi Hideharu
Published: April 2005

Characteristics of x-ray-induced absorption spectra in various types of synthetic fused silica (SFS) containing 0.1–77×1018cm−3 of OH were studied up to an irradiation time of 6 h. Induced absorption in the SFS spectra of irradiation with x ray from a Rh target with a dosage of 2×104Ckg−1h−1 was reproduced by six Gaussian absorption bands, at 3.8, 4.8, 5.0, 5.4, 5.8, and 6.5 eV, respectively. Intensities of these absorption bands increased with power of irradiation time. The intensities of the 5.8, 5.4, and 5.0 eV bands decreased with increasing OH content at an irradiation time shorter than 2 h. At an irradiation time longer than 2 h, on the other hand, the intensities of each absorption band had a minimum at an OH content of ≈5×1018cm−3, and increased with increasing OH content at higher OH content. The power of the time dependence had a minimum at an OH content of ≈5×1017cm−3, and increased with increasing OH content for higher OH-containing samples.
High temperature thermoelectric properties of B12 icosahedral cluster-containing rare earth boride crystals
Authors: Mori Takao
Published: April 2005

B 12 icosahedral cluster-containing rare earth boride TbB44Si2, ErB44Si2, YbB44Si2 crystals were grown by the floating zone method and their high temperature thermoelectric properties (Seebeck coefficient, resistivity) measured. REB44Si2 is isostructural to the magnetic TbB50 compound. These compounds are attractive as high temperature materials due to their stability. An ErB66 crystal was also measured for comparison. Seebeck coefficients exceeding 200μV∕K are observed at temperatures above 1000K for the REB44Si2 compounds and the conductivity increases rapidly as temperature is increased through the variable range hopping mechanism. REB44Si2 compounds were found to have a larger power factor compared to ErB66. The thermal conductivity of ErB44Si2 was also measured and determined to take the low value of 0.027W∕cm∕K at room temperature.
Ion-induced surface activation, chemical sputtering, and hydrogen release during plasma-assisted hydrocarbon film growth
Authors: Hopf C. , Jacob W. , von Keudell A.
Published: April 2005

Synergisms between different species emerging from hydrocarbon plasmas can enhance the chemisorption of radicals at the surface of a growing film. It has been shown that the rate of CH3 chemisorption can be increased by a simultaneously incident flux of ions or H atoms; the latter species cause the formation of surface dangling bonds, which serve as preferred adsorption sites for incoming CH3. These synergisms can, however, be counteracted by erosion processes due to the same species. The interplay between the enhancement of film growth by ion/H atom assisted chemisorption and simultaneous erosion processes is investigated in a particle-beam experiment. An a-C:H film is exposed to three individually controllable quantified particle beams—ions, CH3, and atomic hydrogen. The data can be consistently explained if we include two effects counteracting ion- or H-induced chemisorption: (i) recombination of neighboring dangling bonds and (ii) the occurrence of chemical sputtering in case of an intense H flux. Finally, the balance between H incorporation and ion-induced hydrogen release is investigated. The latter process can be compensated by incident thermal hydrogen atoms as long as the ion range inside the film does not exceed the range of the hydrogen atoms.
Spiking dynamics of interacting oscillatory neurons
Authors: Kazantsev V. B. , Nekorkin V. I. , Binczak S. , Jacquir S. , Bilbault J. M.
Published: April 2005

Spiking sequences emerging from dynamical interaction in a pair of oscillatory neurons are investigated theoretically and experimentally. The model comprises two unidirectionally coupled FitzHugh–Nagumo units with modified excitability (MFHN). The first (master) unit exhibits a periodic spike sequence with a certain frequency. The second (slave) unit is in its excitable mode and responds on the input signal with a complex (chaotic) spike trains. We analyze the dynamic mechanisms underlying different response behavior depending on interaction strength. Spiking phase maps describing the response dynamics are obtained. Complex phase locking and chaotic sequences are investigated. We show how the response spike trains can be effectively controlled by the interaction parameter and discuss the problem of neuronal information encoding.
High-resolution room-temperature sample scanning superconducting quantum interference device microscope configurable for geological and biomagnetic applications
Authors: Fong L. E. , Holzer J. R. , McBride K. K. , Lima E. A. , Baudenbacher F. , Radparvar M.
Published: April 2005

We have developed a scanning superconducting quantum interference device (SQUID) microscope system with interchangeable sensor configurations for imaging magnetic fields of room-temperature (RT) samples with submillimeter resolution. The low-critical-temperature (Tc) niobium-based monolithic SQUID sensors are mounted on the tip of a sapphire and thermally anchored to the helium reservoir. A 25μm sapphire window separates the vacuum space from the RT sample. A positioning mechanism allows us to adjust the sample-to-sensor spacing from the top of the Dewar. We achieved a sensor-to-sample spacing of 100μm, which could be maintained for periods of up to four weeks. Different SQUID sensor designs are necessary to achieve the best combination of spatial resolution and field sensitivity for a given source configuration. For imaging thin sections of geological samples, we used a custom-designed monolithic low-Tc niobium bare SQUID sensor, with an effective diameter of 80μm, and achieved a field sensitivity of 1.5pT∕Hz1∕2 and a magnetic moment sensitivity of 5.4×10−18Am2∕Hz1∕2 at a sensor-to-sample spacing of 100μm in the white noise region for frequencies above 100Hz. Imaging action currents in cardiac tissue requires a higher field sensitivity, which can only be achieved by compromising spatial resolution. We developed a monolithic low-Tc niobium multiloop SQUID sensor, with sensor sizes ranging from 250μm to 1mm, and achieved sensitivities of 480–180fT∕Hz1∕2 in the white noise region for frequencies above 100Hz, respectively. For all sensor configurations, the spatial resolution was comparable to the effective diameter and limited by the sensor-to-sample spacing. Spatial registration allowed us to compare high-resolution images of magnetic fields associated with action currents and optical recordings of transmembrane potentials to study the bidomain nature of cardiac tissue or to match petrography to magnetic field maps in thin sections of geological samples.