bluuebunny/crossref_metadata_2025 huggingface dataset:
A molecular epidemiological analysis of the incursion of the raccoon strain of rabies virus into Canada
Authors: NADIN-DAVIS S. A. , MULDOON F. , WANDELER A. I.
Published: October 2005

Three physically separate incursions of the raccoon strain of rabies have entered Canada, two into eastern Ontario in 1999 and one into New Brunswick in 2000. The course of these epizootics is described. Phylogenetic analysis of the index cases from these two provinces with raccoon rabies viruses representative of this strain in the United States supported the independence of these incursions into Canada via cross-border transmission from the United States. Genetic characterization of 190 isolates from these two Canadian provinces over a 550-bp region of the variable central portion of the viral P gene distinguished 14 variants in Ontario and five in New Brunswick although in both regions the variant represented by the initial case was most commonly encountered. The quasi-species nature of the Ontario virus was analysed using isolates taken at different times during the main outbreak to examine whether viral variation was increasing with time as well as changing in nature. These data provide a framework for study of future incursions of this rabies strain into Canada.
Association of Mycobacterium tuberculosis Beijing genotype with tuberculosis relapse in Singapore
Authors: SUN Y.-J. , LEE A. S. G. , WONG S.-Y. , PATON N. I.
Published: October 2005

The relationship of Mycobacterium tuberculosis Beijing genotype with tuberculosis relapse was examined. Beijing strains were detected from 32 out of 45 (71%) relapsed cases and 148 out of 290 (51%) non-relapsed cases. Multivariate logistic regression analysis revealed that Beijing genotype was significantly associated with tuberculosis relapse (OR 2·64, 95% CI 1·30–5·34, P=0·005).
Verstehen verstehen
Authors: Dörner Dietrich
Published: October 2005

Zusammenfassung. In der kognitiven Psychologie ist eine Auffassung des Verstehens weit verbreitet, die annimmt, dass die zu verstehenden Inputs (z.B. Sätze) in einen propositionalen Code transformiert werden, der dann in das Langzeitgedächtnis, dessen Struktur gleichfalls als propositional angenommen wird, integriert wird. Diese Auffassung wird kritisiert, weil sie die Annahme beinhaltet, dass Denken “amodal“ geschieht, die Bedeutungen der Begriffe nicht berücksichtigt und ausschließlich mit begrifflichen Relationen operiert. Außerdem lässt der propositionale Code keinen Raum für Metaphorik und Ironie, da er von der Eindeutigkeit der Begriffe ausgeht, und schließlich zerstört die Propositionalisierung die Bedeutungen, die in einer differenzierten grammatischen Struktur stecken.
Intracerebral Error-Related Negativity in a Simple Go/NoGo Task
Authors: Brázdil Milan , Roman Robert , Daniel Pavel , Rektor Ivan
Published: October 2005

Abstract: Performance monitoring represents a critical executive function of the human brain. In an effort to identify its anatomical and physiological aspects, a negative component of event-related potentials (ERPs), which occurs only on incorrect trials, has been used in the extensive investigation of error processing. This component has been termed “error-negativity” (Ne) or error-related negativity (ERN) and has been interpreted as a correlate of error detection. The aim of the present intracerebral ERP study was to contribute knowledge of the sources of the Ne/ERN, with a particular focus on the involvement of a frontomedian wall (FMW) in the genesis of this negativity. Seven patients with intractable epilepsy participated in the study. Depth electrodes were implanted to localize the seizure origin prior to surgical treatment. A total of 574 sites in the frontal, temporal, and parietal lobes were investigated. A simple Go/NoGo task was performed and EEG epochs with correct and erroneous motor responses were averaged independently using the response as the trigger. Ne/ERN was generated in multiple cortical structures, with the most consistent involvement being that of the FMW structures. Ne/ERN generators were revealed there in both the rostral and caudal anterior cingulate cortex (ACC), but also in the pre-SMA and in the parts of the medial frontal gyrus adjacent to the ACC. Different timing of activations between the rostral and caudal anterior cingulate Ne/ERN sources was observed in this study. Other neural sources of the Ne/ERN were found in the dorsolateral prefrontal cortex, in the orbitofrontal cortex, in the lateral temporal neocortex, and in one isolated case in the supramarginal gyrus. Our findings support the key role of the FMW in the genesis of Ne/ERN. At the same time, our findings suggest a different functional significance for the rostral and caudal ACC involvement in error processing. In addition to the FMW, the other prefrontal cortical sites, the lateral temporal neocortex, and the supramarginal gyrus seem to represent integral components of the brain's error monitoring system.
Error-Related Brain Activity in Patients with Obsessive- Compulsive Disorder and in Healthy Controls
Authors: Ruchsow Martin , Grön Georg , Reuter Kathleen , Spitzer Manfred , Hermle Leopold , Kiefer Markus
Published: October 2005

Abstract: Obsessive-compulsive disorder (OCD) has been related to a hyperactive frontal-striatal-thalamic circuit and associated with altered mechanisms of action and error monitoring. In the present study, we examined whether these results only hold for errors in choice reaction time experiments and Stroop tasks or extend to errors of commission in a Go/NoGo task, as well. We investigated the electrophysiological correlates of error monitoring in 11 patients with OCD and 11 age-, sex-, and education-matched healthy controls using event-related potentials (ERPs). Participants performed a Go/NoGo task while a 64-channel EEG was recorded. Our study focused on three ERP components: the error-related negativity (ERN)/error negativity (Ne), the “early” error positivity (“early” Pe) reflecting automatic error processing, and the “late” error positivity (“late” Pe), which is thought to mirror the awareness of erroneous responses. Artifact-free EEG-segments were used to compute ERPs on correct Go trials and incorrect NoGo trials (i.e., errors of commission), separately. Patients with OCD showed enhanced (more negative) ERN/Ne amplitudes compared to control subjects. Groups did not differ with regard to the early Pe component and the late Pe component. Our results support the view that compulsivity in OCD patients is related to hyper-functioning error monitoring processes.
Error Processing in Parkinson's Disease
Authors: Falkenstein Michael , Willemssen Rita , Hohnsbein Joachim , Hielscher Horst
Published: October 2005

Abstract: The present study investigates differences in error processing between Parkinson's disease patients (PD) and controls. More specifically, we wanted to know whether patients with PD showed similar differences in the late error-specific ERP component, the error positivity (Pe), as we recently found for the error negativity (Ne/ERN) - a component most probably mediated by the dopaminergic (DA) system. When using the same tasks as in the preceding study we consistently found no Pe differences for patients compared to controls, which is in sharp contrast to the reduced Ne for the patients in all tasks, as reported earlier. This demonstrates again the differential variation of Ne and Pe and suggests that the Pe is not dependent on the DA system.
Dissociable Components of Error Processing
Authors: Overbeek Thérèse J.M. , Nieuwenhuis Sander , Ridderinkhof K. Richard
Published: October 2005

Abstract: We conducted a literature review to examine the functional significance of the error positivity (Pe), an error-related electrophysiological brain potential often observed in combination with the error negativity (Ne). The review revealed many dissociations between documented effects on the Ne and Pe, suggesting that these components reflect different aspects of error processing. We found little support for the proposed hypotheses that the Pe is associated with the affective processing of errors or with posterror behavioral adaptation. Some support was found for the hypothesis that the Pe reflects conscious recognition of an error. Finally, we discuss the notion that the Pe may reflect a P3b associated with the motivational significance of the error. We conclude that more research is needed to test predictions of the various Pe hypotheses, and that more rigorous investigation of the neural generators of the Pe may contribute to a better understanding of the neurocognitive processes involved in error monitoring.
Attitudes to Farm Animal Welfare
Authors: Austin Elizabeth J. , Deary Ian J. , Edwards-Jones Gareth , Arey Dale
Published: October 2005

Abstract. Although the there is considerable public interest in farm animal welfare, relatively little work has been done on the welfare attitudes of farmers. We describe the development of a welfare attitude scale, the EFAWS. The factor structure and correlates of this scale were examined in Scottish pig and sheep farmers, and in agriculture students. The EFAWS was found to have a hierarchical structure, with two superordinate dimensions corresponding to welfare and business orientations being present in both groups. Five narrower facets were extracted for farmers and six for students, with the two factor structures being similar. Factor scores were found to be correlated significantly with personality traits, knowledge about welfare, and farm welfare scores in interpretable ways.
Resting Brain Asymmetry and Affective Reactivity
Authors: Hagemann Dirk , Hewig Johannes , Naumann Ewald , Seifert Jan , Bartussek Dieter
Published: October 2005

Abstract. Neuropsychological evidence has given rise to alternative models on brain asymmetry in emotion, each with different implications concerning the biological basis of individual differences in affective responses. The present study tested these implications. Resting EEG and self-reported emotions after the presentation of film clips were collected on four occasions of measurement. Subjects with greater right-sided and smaller left-sided cortical activity reported greater intensities of felt emotions after the presentation of films irrespective of valence. This finding is in line with a recent formulation of the right-hemisphere hypothesis, which proposes that the right hemisphere may play an important role in the automatic generation of emotional responses, whereas the left hemisphere may be involved in the control and modulation of emotional reactions.
Simulation of entry of shock‐drift‐accelerated solar energetic protons into the magnetosphere
Authors: Shimazu Hironori , Tanaka Takashi
Published: October 2005

The entry of solar energetic protons in the energy range from 100 keV to 10 MeV into the Earth's magnetosphere is simulated to examine the effect of shock drift acceleration at the quasi‐perpendicular bow shock. The proton trajectories are traced from the upstream side of the solar wind in time‐dependent electric and magnetic fields obtained from global MHD simulation data. To investigate the efficiency of the shock drift acceleration, the dynamic pressure (density) of the solar wind is increased. We find that when the dynamic pressure is increased, the proton flux entering the magnetosphere is increased and the cutoff latitude becomes lower. We show that protons having energies on the orders of 100 keV and 1 MeV and reaching the inner magnetosphere can experience shock drift acceleration at the quasi‐perpendicular bow shock when the dynamic pressure is increased. We further show that the shock drift acceleration of solar protons up to energies on the order of 1 MeV is possible at the Earth's bow shock, which is consistent with the observation.
The 7 May 2001 induced seismic event in the Ekofisk oil field, North Sea
Authors: Ottemöller L. , Nielsen H. H. , Atakan K. , Braunmiller J. , Havskov J.
Published: October 2005

A moderate size seismic event on 7 May 2001 was strongly felt on platforms in the Ekofisk oil field, in the southern North Sea, but did not cause damage to platforms or wells. We combined near‐ and far‐field observations to develop a consistent source model and to determine whether the event was induced. Seismic data placed the epicenter inside the Ekofisk field and suggested a shallow source depth based on spectral and moment tensor analysis. GPS data from the Ekofisk platforms displayed permanent vertical and horizontal movement due to the event. A topographic bulge in the sea bottom, revealed by differential bathymetry data, and overpressure in the overburden in the northeastern part of the field, detected only after the event, had been caused by unintentional water injection that started in 1999. The injection pressure and rate were sufficient to raise the overburden. Pressure gauge and compaction data ruled out that the event occurred at reservoir level, which was further supported by unaffected production rates and absence of well failure. We therefore conclude that the event occurred in the overburden, at less than 3 km depth. Initially, this appeared unlikely on account of very low shear strength of the overburden clay‐rich shale and mud rocks. The seismic event was induced owing to stress changes caused by water injection. The event possibly initiated on the northern flank of the field near the water injector and may have involved flexure of the overburden into the depression bowl in the rest of the field. Moment tensor analysis is consistent with a pure double‐couple source. We suggest that slip occurred on the near‐horizontal rather than along the near‐vertical nodal plane. Stress drop was low, and owing to the low overburden shear strength, the event released less energy than a typical stress drop event with similar source dimensions.
Freshwater and brine behaviors in the Arctic Ocean deduced from historical data of δ18O and alkalinity (1929–2002 A.D.)
Authors: Yamamoto‐Kawai Michiyo , Tanaka Noriyuki , Pivovarov Sergey
Published: October 2005

The long‐term data sets of total alkalinity (TA) (1929–2002 A.D.) and δ18O (1966–2002 A.D.) are used to investigate freshwater and brine distributions in the Arctic Ocean. Fractions of sea ice meltwater and other freshwaters (OF) (precipitation, river runoff, and freshwater carried by Pacific water implied as salinity deficit) are calculated on the basis of salinity‐TA and salinity‐δ18O relationships. Rejected brine during sea ice growth resides in surface water in the central Arctic Ocean, while net melting is found along the surface flow of water from the Pacific and Atlantic oceans. Distribution of OF at 10 m water depth suggests that Russian runoff leaves the shelf mainly west of the Mendeleyev Ridge, enters into the deep basin, and exits from the ocean through the western part of Fram Strait. The influence of Mackenzie River water is limited in the region and in depth. Accumulation of freshwater in the Canadian Basin is caused by deep penetration of OF with brine, indicating the transport of freshwater by shelf‐derived water. The major origin of shelf‐derived water entering into the upper halocline layer in the Canadian Basin should be the Chukchi and East Siberian Sea shelves, and the main freshwater sources are the salinity deficit of Pacific water and/or Russian runoff. An increase in OF inventory accompanied by an increase in brine content may suggest an increase of the shelf‐derived water supply into the western Canadian Basin in anticyclonic years.
Projection of future sea level and its variability in a high‐resolution climate model: Ocean processes and Greenland and Antarctic ice‐melt contributions
Authors: Suzuki Tatsuo , Hasumi Hiroyasu , Sakamoto Takashi T. , Nishimura Teruyuki , Abe‐Ouchi Ayako , Segawa Tomonori , Okada Naosuke , Oka Akira , Emori Seita
Published: October 2005

Using a high‐resolution climate model, we projected future sea level and its variability based on two scenarios for 21st century greenhouse gas emission. The globally averaged sea level rise attributable to the steric contribution was 23 and 30 cm for the two scenarios. The results of the high‐resolution model and a medium‐resolution version of the same model for global and local sea level change agreed well. However, the high‐resolution model represented more detailed ocean structure changes under global warming. The changes affected not only the spatial distribution of sea level rise, but also the changes in local sea level variability associated with ocean eddies. The enhanced eddy activity was responsible for extreme sea level events.
Global neutral polar wind model
Authors: Gardner Larry C. , Schunk Robert W.
Published: October 2005

The neutral polar wind shows a highly dynamic structure that depends on the characteristics of convection and precipitation. The ions in the polar wind are highly dependent on convection electric fields at high latitudes, and their outflow dynamics are modified by the heat input of precipitating electrons in the auroral zone. A new three‐dimensional model of the neutral polar wind has been developed which takes into account the convecting ion polar wind and heating due to precipitating electrons in the auroral zone, along with charge exchange between the ion polar wind and the background thermal and geocoronal neutral atoms. The results show that over the polar caps the neutral polar wind particles exhibit extremely large fluxes in both the horizontal and vertical directions, and to a fixed observer it would appear that the neutral polar wind particles are moving in all directions. The results also show that the heating that occurs during geomagnetic storms leads to a significant coupling between the ionosphere and magnetosphere via both ion and neutral particles.
Dynamical mechanisms for African monsoon changes during the mid‐Holocene
Authors: Su Hui , Neelin J. David
Published: October 2005

During the mid‐Holocene, about 6 ka BP, the African monsoon was stronger and extended farther north than in present‐day climate associated with differences in orbital parameters affecting insolation. Earlier research suggests that land surface vegetation interaction and atmosphere‐ocean coupling may be important to the northward extension of the Holocene monsoon rainfall, but different climate models produce different results in terms of rainfall distribution. This study examines the dynamical mechanisms that modulate the orbital forcing effect on the African monsoon convection. A series of simulations with 6 ka BP orbital parameters, modified land surface albedo that mimics grassland extending over North Africa, and alterations of the model dynamics are used. It is found that the “ventilation mechanism” (inflow of low moist static energy air from oceanic or poleward regions) is a key process in setting the northern rainfall boundary for the African monsoon. In particular, advection and diffusion of less moist air oppose the increase of moisture that would be required to meet the increased convective instability criteria set by the warmer tropospheric air above the continent. While changes in heat fluxes into the atmospheric column favor convection in principle, the ventilation mechanism limits the poleward extent of the region that can actually convect.
Volume sensitivity of Vatnajökull Ice Cap, Iceland, to perturbations in equilibrium line altitude
Authors: Aðalgeirsdóttir G. , Gudmundsson G. H. , Björnsson H.
Published: October 2005

The sensitivity of Vatnajökull ice cap, Iceland, to perturbations in equilibrium line altitude (ELA) is analyzed by performing a series of model experiments using a shallow ice approximation (SIA) flow model. For this purpose a simple but realistic parameterization for the mass balance is used that accurately simulates the observed variability in surface mass balance over a period of nine years. We find that because of feedback between mass balance and altitude the ice cap either grows without bounds or settles to steady states depending on whether ELA is larger or smaller than a critical value ELAcrit. The largest modeled steady state is 60% of the current volume of the ice cap. The ice cap, as modeled, is therefore currently not close to a possible stable steady state. Past climate history and spatial and temporal variations in basal condition, such as surges, can be expected to have an influence on the ice cap and have to be taken into account when modeling the response of the ice cap to future climate change scenarios. For the neighboring ice cap, Hofsjökull, the relationship between ELA and volume is, in contrast, found to be simple, and Hofsjökull is close to a stable steady state with respect to the current climatic conditions. Introducing surges, which is not done here, will likely change the details of the ELA‐volume relationship of Vatnajökull, presumably by making the relationship between volume and ELA more complex, and possibly less sensitive, as a further nonlinear feature is added to the model.
Influence of Carl Jung and William James on the Origin of Alcoholics Anonymous
Authors: Finlay Steven W.
Published: October 2005

Alcoholics Anonymous is probably the most influential self-help organization in the world, with a current worldwide membership approaching 2 million. The origin of the organization has ties to Carl Gustav Jung and William James, 2 very prominent figures in the history of psychology. A brief history of the events that led to the formation of Alcoholics Anonymous is presented, with particular emphasis on the influence of Jung and James. An account of relevant life events of both Jung and James is provided, in addition to a summary of their views on alcoholism and its treatment. Speculation is offered on how the 2 men might view their unsolicited association with the organization.
Cognitive Regularities in Creative Activity
Authors: Bink Martin L. , Marsh Richard L.
Published: October 2005

Theories of creativity have not traditionally considered whether novel ideas or inventive behaviors can result from regularities in the cognitive processes responsible for such activities. Most of these traditional theories are based on the evaluation of products as meeting (or not) some abstract metric of creative output. However, cognitive theories of creativity can be proposed in which creative activity is a function of more traditional cognitive processes that are not unique to inventive behaviors. The purpose of this article is to review the cognitive regularities of creative activity and organize the research on this topic into a framework that might be useful in understanding and extending investigations directed at studying creativity. To these ends, cognitive processes underlying generation, synthesis, and selection of information in creative activities are delineated.
Adult Romantic Attachments: A Developmental Perspective on Individual Differences
Authors: Cassidy Jude
Published: October 2005

Attachment theory has, since its inception, contained the proposition that long-term adult romantic relationships (i.e., relationships described by ethologists as “pair bonds”) are generally attachments. In this article, the possibility that individual differences in adult romantic attachments may emerge, in part, from individual differences in childhood attachments is discussed. The article begins with an examination of the developmental precursors of individual differences in two of the behavioral systems prominent in adult romantic relationships: the attachment system and the caregiving system. For each of these behavioral systems, theory is discussed and the empirical literature is reviewed. The remainder of the article addresses the mechanisms of both continuity across development (i.e., factors that may account for the influences of early attachments on later romantic relationships) and discontinuity (i.e., factors that may account for change in the quality of attachments from childhood to adulthood).
Adult Romantic Attachment: Theoretical Developments, Emerging Controversies, and Unanswered Questions
Authors: Fraley R. Chris , Shaver Phillip R.
Published: October 2005

The authors review the theory of romantic, or pair-bond, attachment as it was originally formulated by C. Hazan and P. R. Shaver in 1987 and describe how it has evolved over more than a decade. In addition, they discuss 5 issues related to the theory that need further clarification: (a) the nature of attachment relationships, (b) the evolution and function of attachment in adulthood, (c) models of individual differences in attachment, (d) continuity and change in attachment security, and (e) the integration of attachment, sex, and caregiving. In discussing these issues, they provide leads for future research and outline a more complete theory of romantic attachment.
Effect of Spatial Smoothing on t-Maps: Arguments for Going Back from t-Maps to Masked Contrast Images
Authors: Reimold Matthias , Slifstein Mark , Heinz Andreas , Mueller-Schauenburg Wolfgang , Bares Roland
Published: October 2005

Voxelwise statistical analysis has become popular in explorative functional brain mapping with fMRI or PET. Usually, results are presented as voxelwise levels of significance ( t-maps), and for clusters that survive correction for multiple testing the coordinates of the maximum t-value are reported. Before calculating a voxelwise statistical test, spatial smoothing is required to achieve a reasonable statistical power. Little attention is being given to the fact that smoothing has a nonlinear effect on the voxel variances and thus the local characteristics of a t-map, which becomes most evident after smoothing over different types of tissue. We investigated the related artifacts, for example, white matter peaks whose position depend on the relative variance (variance over contrast) of the surrounding regions, and suggest improving spatial precision with ‘masked contrast images’: color-codes are attributed to the voxelwise contrast, and significant clusters (e.g., detected with statistical parametric mapping, SPM) are enlarged by including contiguous pixels with a contrast above the mean contrast in the original cluster, provided they satisfy P < 0.05. The potential benefit is demonstrated with simulations and data from a [11C]Carfentanil PET study. We conclude that spatial smoothing may lead to critical, sometimes-counterintuitive artifacts in t-maps, especially in subcortical brain regions. If significant clusters are detected, for example, with SPM, the suggested method is one way to improve spatial precision and may give the investigator a more direct sense of the underlying data. Its simplicity and the fact that no further assumptions are needed make it a useful complement for standard methods of statistical mapping.
15d-Prostaglandin J2 Activates Peroxisome Proliferator-Activated Receptor-γ, Promotes Expression of Catalase, and Reduces Inflammation, Behavioral Dysfunction, and Neuronal Loss after Intracerebral Hemorrhage in Rats
Authors: Zhao Xiurong , Zhang Yujian , Strong Roger , Grotta James C , Aronowski Jaroslaw
Published: October 2005

Peroxisome proliferator-activated receptor-γ (PPARγ) is a transcription factor that regulates the expression of various gene products that are essential in lipid and glucose metabolism, as well as that of the peroxisome-enriched antioxidant enzyme, catalase. Activation of PPARγ is linked to anti-inflammatory activities and is beneficial for cardiovascular diseases. However, little is known about its role in intracerebral hemorrhage (ICH). 15-Deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) acts as a physiologic agonist for PPARγ. In this study, we found that injection of 15d-PGJ2 into the locus of striatal hematoma increased PPARγ-deoxyribonucleic acid (DNA) binding activity and the expression of catalase messenger ribonucleic acid (mRNA) and protein in the perihemorrhagic area. Additionally, 15d-PGJ2 significantly reduced nuclear factor-κB (NF-κB) activation and prevented neutrophil infiltration measured by myeloperoxidase (MPO) immunoassay, and also reduced cell apoptosis measured by terminal deoxynucleotide transferase dUTP nick-end labeling (TUNEL). In addition, 15d-PGJ2 reduced behavioral dysfunction produced by the ICH. Altogether, our findings indicate that injection of 15d-PGJ2 at the onset of ICH is associated with activation of PPARγ and elevation of catalase expression, suppression of NF-κB activity, and restricted neutrophil infiltration. All these events predicted reduced behavioral deficit and neuronal damage.
A vacuum ultraviolet pulsed field ionization-photoelectron study of cyanogen cation in the energy range of 13.2–15.9 eV
Authors: Hochlaf M. , Baer Tomas , Qian X.-M. , Ng C. Y.
Published: October 2005

The vacuum ultraviolet pulsed field ionization-photoelectron and photoionization efficiency spectra of NCCN have been measured in the energy region of 13.25–17.75 eV. The analyses of these spectra have provided accurate ionization energy (IE) values of 13.371±0.001, 14.529±0.001, 14.770±0.001, and 15.516±0.001eV for the formation of NCCN+ in the X̃Πg2, ÃΣg+2, B̃Σu+2, and C̃Πu2 states, respectively. The ionization energy [NCCN+(B̃Σu+2)] value determined here indicates that the origin of the NCCN+(B̃Σu+2) state lies lower in energy by 25 meV than previously reported. A set of spectroscopic parameters for NCCN+(X̃Πg2) has been calculated using high level ab initio calculations. The experimental spectra are found to consist of ionizing transitions populating the vibronic levels of NCCN+, which consist of pure vibronic progressions, combination modes involving the symmetric CN stretch, the CC stretch, and even quanta of the antisymmetric CN stretch, and bending vibrations. These bands are identified with the guidance of the present ab initio calculations.
The ideal glass transition of hard spheres
Authors: Parisi Giorgio , Zamponi Francesco
Published: October 2005

We use the replica method to study the ideal glass transition of a liquid of identical hard spheres. We obtain estimates of the configurational entropy in the liquid phase, of the Kauzmann packing fraction φK, in the range of 0.58–0.62, and of the random close packing density φc, in the range of 0.64–0.67, depending on the approximation we use for the equation of state of the liquid. We also compute the pair-correlation function in the glassy states (i.e., dense amorphous packings) and we find that the mean coordination number at φc is equal to 6. All these results compare well with numerical simulations and with other existing theories.
Simulation and theory of self-assembly and network formation in reversibly cross-linked equilibrium polymers
Authors: Kindt James T.
Published: October 2005

A simulation model of hard spheres capable of reversible assembly into chains, which then may reversibly cross-link into networks, has been studied through grand canonical Monte Carlo simulation. Effects of varying intra- and interchain bond strengths, chain flexibilities, and restrictions on cross-linking angle were investigated. Observations including chain-length distributions and phase separation could be captured in most cases using a simple model theory. The coupling of chain growth to cross-linking was shown to be highly sensitive to the treatment of cross-linking by chain ends. In some systems, ladderlike domains of several cross-links joining two chains were common, resulting from cooperativity in the cross-linking. Extended to account for this phenomenon, the model theory predicts that such cooperativity will suppress phase separation in weakly polymerizing chains and at high cross-link concentration. In the present model, cross-linking stabilizes the isotropic phase with respect to the nematic phase, causing a shift in the isotropic-nematic transition to higher monomer concentration than in simple equilibrium polymers.
Surface migration of branched molecules: Analysis of energetic and entropic factors
Authors: Minnikanti Venkatachala S. , Archer Lynden A.
Published: October 2005

We have introduced energetic factors into the response theory developed by Wu and Fredrickson [Macromolecules 29, 7919 (1996)] to predict the enrichment of branched molecules due to architectural effects at surfaces. This development simultaneously increases the utility of the theory for guiding experimental investigations, and makes possible a rigorous assessment of theoretical predictions in careful studies of isotopically labeled linear/branched species binary blends at surfaces. For example, the introduction of energetic factors allows us to predict the existence of a crossover molecular weight, below which an energetically unfavorable species at a surface can be enriched entirely due to architecture. For binary blends of linear chains, the degree of polymerization (Kuhn) of the energetically unfavorable species at the crossover point is rc≅2Ue∕ΔUs. Here, Ue is the attraction of chain ends towards the surface and ΔUs is the difference in the interaction potential of main chain segments to the surface due to chemical differences and/or isotopic labeling. We also show that surface segregation of an additive in a host polymer due to architectural effects alone is significantly enhanced as the spinodal temperature of a branched/linear blend is approached. Detailed comparisons of the modified response theory with lattice simulations are used to evaluate the theory and to determine the limits of its applicability.
Bridging the gap between thermodynamic integration and umbrella sampling provides a novel analysis method: “Umbrella integration”
Authors: Kästner Johannes , Thiel Walter
Published: October 2005

We present a method to analyze biased molecular-dynamics and Monte Carlo simulations, also known as umbrella sampling. In the limiting case of a strong bias, this method is equivalent to thermodynamic integration. It employs only quantities with easily controllable equilibration and greatly reduces the statistical errors compared to the standard weighted histogram analysis method. We show the success of our approach for two examples, one analytic function, and one biological system.
Density functional theory calculations for endohedral complexes of non-πC60H60 cage with small guest molecules
Authors: Hu Yun Hang , Ruckenstein Eli
Published: October 2005

Hybrid density-functional theory (B3LYP) calculations were carried out to determine the structures and energies of endohedral complexes of non-πC60H60 with H2, CO, and LiH. It was demonstrated that the endohedral complexes of C60H60 with the above three guest molecules are more stable than the corresponding complexes with C60. Furthermore, the interaction between C60H60 and the inside H2 or CO is negligible, but the formation of the LiH-C60H60 complex is exothermic with a stabilization energy of −6.0kcal∕mol. While the bond lengths of H2 and CO changed a little when placed inside the cages, that of the LiH molecule increased and decreased inside C60H60 and C60, respectively.
Home-built magnetic resonance imaging system (0.3 T) with a complete digital spectrometer
Authors: Jie Shen , Qin Xu , Ying Liu , Gengying Li
Published: October 2005

A home-built magnetic resonance imaging (MRI) system with a complete digital spectrometer has been designed for investigation of plants and animals. With the application of the latest digital integrated circuit technology, the digital spectrometer is greatly simplified without the loss of flexibility and performance. A powerful pulse sequence compiler with a graphical editor can allow the user to edit the pulse sequence more easily and more conveniently than ever before. Moreover, a permanent magnet capable of producing a 180 mm diam spherical homogeneous region is employed in our MRI system to ensure a comparatively large image size. Compared with previous work, our MRI system has the features of flexibility, relatively large imaging size, and low cost. Experimental results obtained with the proposed system are presented in this article.
Circulating pump for high-pressure and high-temperature applications
Authors: Peleties Fotos , Martin Trusler J. P. , Goodwin Anthony R. H. , Maitland Geoffrey C.
Published: October 2005

A high-pressure high-temperature magnetic circulating pump is described. The design is based on the concept of contactless bidirectional pumping action. This pump can deliver a continuous flow at temperatures up to 175°C and pressures up to 2000bars. Wetted parts are fabricated from stainless steels, there are no elastomeric seals or lubricants required, and the pump can be physically mobile during operation. Tests with toluene at ambient temperature and pressure showed that volumetric flow rates of up to 320cm3min−1 and pressure heads of up to 2.2bars could be achieved.
Inflow and shock formation in supersonic, rarefied plasma expansions
Authors: Vankan P. , Mazouffre S. , Engeln R. , Schram D. C.
Published: October 2005

In this paper the physics of plasma expansion in the rarefied regime is reviewed. Densities, temperatures, and velocity distributions in argon, hydrogen, and nitrogen expansions that have been measured using laser scattering and fluorescence techniques are compared. The velocity distributions in the region of the expansion where the density is below the background density show a bimodal character. It is interpreted in terms of a component expanding from the source and a component flowing into the plasma expansion from the periphery. Also in the shock of the expansion, bimodal velocity distributions are encountered. These distributions show the gradual change in the flow from supersonic to subsonic—the formation of the shock. From a comparison of the three expansions, a general view of the shock formation is derived. This new insight leads to a better understanding of how the chemical reactivity of the usually impenetrable, supersonic plasma can be used most efficiently.
Isothermal and nonisothermal crystallization of polymers: Analysis with a shear differential thermal analyzer
Authors: Martins J. A. , Zhang Wd. , Brito A. M. , Infante U. , Romero M. , Soares F. O.
Published: October 2005

The working principle of an instrument developed for studying the effects of controlled shear pulses on the isothermal and nonisothermal solidification of polymers is presented. The device combines a capillary rheometer and a differential thermal analyzer (DTA). The capillary rheometer part of the system allows the production of shear pulses with controlled duration and intensity at any prescribed temperature up to 300°C, and the DTA records the thermal effects resulting from the solidification. Results obtained for quiescent isothermal and nonisothermal crystallizations compare well with those obtained from power compensation differential scanning calorimetry. The effect of controlled shear pulses on the overall isothermal crystallization kinetics enables the evaluation of a critical strain responsible for the saturation of crystallization in sheared polymer melts. Additional shear (increase of the shear rate or of the shearing time) does not accelerate the crystallization kinetics. The shear-induced nonisothermal crystallization of polyethylene filled with talc shows the acceleration of the crystallization kinetics with the shear rate increase, thus confirming this device as a valuable experimental tool for studying the effect of shear on the solidification of fast crystallizing materials.
An apparatus to grain refine metals and alloys with mold vibrations
Authors: Maltais Alexandre , Fiset Michel , Dubé Dominique
Published: October 2005

An apparatus has been built to study the grain refining effect of mechanical vibrations applied during the solidification of magnesium alloys. The experimental setup consists of a pneumatic vibrator attached to a vertical beam onto which a permanent mold is clamped. This mold experiences peak accelerations up to 120m∕s2 at a frequency of 160Hz and an amplitude of 0.12mm. This method of transferring the vibrational energy to the molten metal is surprisingly efficient as less than 55W are needed to maintain the resonant oscillatory motion. It is shown that vibrations are severe enough to induce grain refinement in high-purity magnesium and in a commercial purity AZ91 magnesium alloy.
Stability analysis of a coaxial-waveguide gyrotron traveling-wave amplifier
Authors: Hung C. L. , Yeh Y. S.
Published: October 2005

The gyrotron traveling-wave tube (gyro-TWT) amplifier is known to be highly susceptible to spurious oscillations. This study develops a simulation approach to analyze the stability of a coaxial-waveguide gyro-TWT with distributed wall losses. The interplay among the absolute instabilities, the gyrotron backward-wave oscillations, and the circuit parameters is analyzed. Simulation results reveal that the distributed wall losses effectively stabilize spurious oscillations in the coaxial gyro-TWT. Furthermore, the wall resistivity of the center conductor is shown to be an additional effective mechanism for suppressing oscillations. Under stable operation conditions, the coaxial gyro-TWT with distributed losses is predicted to generate 435kW in the Ka band with 31% efficiency, a saturated gain of 45dB, and a bandwidth of 1.86GHz (≈5.8%) for a 70kV, 20A electron beam with an α(=ν⊥∕νz)=1.0 and an axial velocity spread of Δνz∕νz=5%.
Far-infrared absorption due to electronic transitions of N–O complexes in Czochralski-grown silicon crystals: Influence of nitrogen and oxygen concentration
Authors: Alt H. Ch. , Gomeniuk Y. V. , Bittersberger F. , Kempf A. , Zemke D.
Published: October 2005

Fourier-transform infrared absorption measurements have been carried out on nitrogen-doped Czochralski-grown silicon crystals after thermal annealing at 600°C. The strength of the electronic transitions due to N–O related shallow donors shows a square root dependence on the nitrogen concentration and donor-specific power dependences on the interstitial oxygen concentration. Based on mass action laws, chemical compositions are discussed. It is found that the N–O complexes investigated all involve one nitrogen atom but three different numbers of oxygen atoms.
Vanadium pentoxide modified polycrystalline silicon anode for active-matrix organic light-emitting diodes
Authors: Zhu X. L. , Sun J. X. , Peng H. J. , Meng Z. G. , Wong M. , Kwok H. S.
Published: October 2005

Recently, polycrystalline silicon (p-Si) has been demonstrated to be an efficient anode for organic light-emitting diode (OLED) [X. L. Zhu, J. X. Sun, H. J. Peng, Z. G. Meng, M. Wong, and H. S. Kwok, Appl. Phys. Lett. 87, 083504 (2005)]. In this letter, we show that, by depositing an ultrathin vanadium pentoxide (V2O5) layer on the p-Si anode, the performance of the OLED can be greatly improved. Detailed x-ray photoelectron spectroscopy study shows that strong band bending occurs at the p-Si∕V2O5 interface, leading to much stronger hole injection. This modified p-Si anode can be integrated with the active p-Si layer of thin-film transistors in active-matrix OLED displays.
Photoluminescence from 8-hydroxy quinoline aluminum embedded in porous anodic alumina membrane
Authors: Huang G. S. , Wu X. L. , Xie Y. , Kong F. , Zhang Z. Y. , Siu G. G. , Chu Paul K.
Published: October 2005

By immersing porous alumina membranes in 8-hydroxy quinoline aluminum (Alq3) solutions, we embed Alq3 molecules into the nanovoids of the membranes. Photoluminescence (PL) spectral examinations show that the Alq3 molecules embedded in the alumina membrane show a blueshifted luminescent spectrum compared to that of Alq3 solid film. Since the blueshift of ∼18nm does not change with nanopore diameter, we consider it to be due to the confinement of nanovoids in the nanopore walls, which prevents Alq3 molecules from aggregation and thus weakens the interaction between them. Further spectral analyses suggest that the photogeneration of carriers takes place in oxygen vacancies at the surfaces of nanopore walls, whereas the radiative recombination occurs in the embedded Alq3 molecules. Förster energy transfer from oxygen vacancies to the embedded Alq3 molecules is proposed to be responsible for the enhancement of the PL intensity.
Electrically induced surface instability of a conductive thin film on a dielectric substrate
Authors: Huang Rui
Published: October 2005

The stability of a conductive thin film on a dielectric substrate subjected to a transverse electric field and a residual strain is analyzed. Under a uniform electric field, an equilibrium state exists with a constant thickness reduction of the substrate. The equilibrium state, however, can be unstable, depending on the intensity of the electric field, the stiffness, and Poisson’s ratio of the substrate, and on the residual strain in the film. Based on a linear perturbation analysis, the critical condition is determined, beyond which wrinkling of the film is expected.
High-efficiency inverted top-emitting polymer light-emitting diodes
Authors: Hou Lintao , Huang Fei , Zeng Wenjin , Peng Junbiao , Cao Yong
Published: October 2005

A major challenge to inverted top-emitting polymer light-emitting diodes (ITEPLEDs) is to prepare a reflective bottom cathode capable of effectively injecting electrons. Reported in this letter is the creation of an efficient electron injection layer (EIL) by using environment-friendly alcohol-/water-soluble aminoalkyl-substituted conjugated quanternized polyfluorene copolymers containing 0.5%mol of benzothiadiazole to reduce the electron injection barrier between the high-work-function Al reflective bottom cathode and the light-emitting layer. The inverted top-emitting devices exhibit superior electrical characteristics with maximal quantum and luminance efficiencies of 2.71% and 1.6cd∕A respectively, at an operating voltage of 13.3V by employing poly[2-methoxy,5-(2-ethylhexyloxy)-1,4-phenylenevinylene] as a light-emitting polymer. The utilization of water/alcohol soluble conjugated polyelectrolyte/Al bilayer bottom cathode offers an important advantage for avoiding intermixing between the emitting layer and the EIL for solution-processable ITEPLEDs.
Control of threshold voltage in pentacene thin-film transistors using carrier doping at the charge-transfer interface with organic acceptors
Authors: Abe Y. , Hasegawa T. , Takahashi Y. , Yamada T. , Tokura Y.
Published: October 2005

Well-controlled carrier doping was performed in pentacene thin-film transistors (TFTs) by depositing additional organic acceptor (F4TCNQ) layers on top of existing channels. The doping concentration could be predefined by changing the area covered with the acceptor layer, which provides control of the threshold gate voltage, while keeping both the field-effect mobility (∼1.0cm2∕Vs) and the current on/off ratio (>105). The transport properties of these devices are discussed in terms of the trap and release model for the doped organic TFTs.
Hopping charge transport mechanisms in conducting polypyrrole: Studying the thermal degradation of the dielectric relaxation
Authors: Papathanassiou A. N. , Grammatikakis J. , Sakellis I. , Sakkopoulos S. , Vitoratos E. , Dalas E.
Published: October 2005

Isotherms of the imaginary part of the permittivity from 10−2to2×106Hz from liquid nitrogen to room temperature for fresh and thermally aged specimens of conducting polypyrrole reveal a dielectric loss peak, which is affected by the reduction of conducting grains with aging. Charge trapping at the interfaces separating the conductive islands seems invalid. Thermal aging indicates that macroscopic conductivity and short range one have different aging evolution. The first (dc conductivity) is dominated by the tunneling of the carriers between neighboring grains through the intermediate insulating barriers, though the second (ac conductivity) is due to a backward-forward movement of the carriers and is controlled by the intrachain transport of them and their hopping between the chains.