bluuebunny/crossref_metadata_2025 huggingface dataset:
Co-infection withOnchocerca volvulusandLoa loamicrofilariae in central Cameroon: are these two species interacting?
Authors: PION S. D. S. , CLARKE P. , FILIPE J. A. N. , KAMGNO J. , GARDON J. , BASÁÑEZ M.-G. , BOUSSINESQ M.
Published: February 2006

Ivermectin treatment may induce severe adverse reactions in some individuals heavily infected withLoa loa. This hampers the implementation of mass ivermectin treatment against onchocerciasis in areas whereOnchocerca volvulusandL. loaare co-endemic. In order to identify factors, including co-infections, which may explain the presence of highL. loamicrofilaraemia in some individuals, we analysed data collected in 19 villages of central Cameroon. Two standardized skin snips and 30 μl of blood were obtained from each of 3190 participants and the microfilarial (mf) loads of bothO. volvulusandL. loawere quantified. The data were analysed using multivariate hierarchical models. Individual-level variables were: age, sex, mf presence, and mf load; village-related variables included the endemicity levels for each infection. The two species show a certain degree of ecological separation in the study area. However, for a given individual host, the presence of microfilariae of one species was positively associated with the presence of microfilariae of the other (OR=1·79, 95% CI [1·43–2·24]). Among individuals harbouringLoamicrofilariae, there was a slight positive relationship between theL. loaandO. volvulusmf loads which corresponded to an 11% increase inL. loamf load per 100O. volvulusmicrofilariae. Co-infection withO. volvulusis not sufficient to explain the very highL. loamf loads harboured by some individuals.
Predestination and freedom in Milton's Paradise Lost
Authors: Myers Benjamin
Published: February 2006

John Milton's epic poem Paradise Lost (1667) offers a highly creative seventeenth-century reconstruction of the doctrine of predestination, a reconstruction which both anticipates modern theological developments and sheds important light on the history of predestinarian thought. Moving beyond the framework of post-Reformation controversies, the poem emphasises both the freedom and the universality of electing grace, and the eternally decisive role of human freedom in salvation. The poem erases the distinction between an eternal election of some human beings and an eternal rejection of others, portraying reprobation instead as the temporal self-condemnation of those who wilfully reject their own election and so exclude themselves from salvation. While election is grounded in the gracious will of God, reprobation is thus grounded in the fluid sphere of human decision. Highlighting this sphere of human decision, the poem depicts the freedom of human beings to actualise the future as itself the object of divine predestination. While presenting its own unique vision of predestination, Paradise Lost thus moves towards the influential and distinctively modern formulations of later thinkers like Schleiermacher and Barth.
God's trinitarian substance in Athanasian theology
Authors: Meyer John R.
Published: February 2006

The attraction of what Richard Cross describes as a generic view of God's trinitarian substance is undeniable. Even before the Arians professed belief in the Son of God as being of secondary divine rank vis-à-vis the Father, Origen demonstrated a tendency to envisage a derivation view of God's substance in which the Son was somewhat less divine than the Father. However, Cross's contention that Athanasius promoted this same concept is not as clear-cut as he suggests, although there are texts in the Athanasian corpus of writings lending credence to such an interpretation. While Athanasius did accept the monarchical view of the Trinity, with God the Father as the origin or source of intra-trinitarian life, he also stressed the consubstantial nature of the Son and the Father.
Image of God as both fount and destiny of humanity: how Herderian is Pannenberg?
Authors: Wong Kam Ming
Published: February 2006

This paper demonstrates that, despite the much discussed Hegelian influence on Pannenberg, Herder's thought plays a pivotal role in forming and shaping Pannenberg's theological work in the important areas of the image of God and human destiny. However, Pannenberg differentiates himself from Herder in a crucial respect in that Pannenberg grounds Herder's anthropology on a christological foundation in order to present a salvific rather than a providential account of the renewal of the imago Dei. This paper also offers a reflection upon other significant similarities and differences between these two major thinkers.
Samuel Rutherford's supralapsarianism revealed: a key to the lapsarian position of the Westminster Confession of Faith?
Authors: Richard Guy M.
Published: February 2006

Samuel Rutherford (1600–61) has long been assumed to be an advocate of a harsh supralapsarian predestinarianism. Such an assumption, however, cannot be substantiated by the claims that he makes in his writings. New evidence from his writings suggests that while Rutherford was supralapsarian, he expressed his supralapsarianism only in the most moderate of terms. In fact, he consistently employed infralapsarian language to express his thinking in regard to predestination. This essay will seek to demonstrate this in Rutherford and then to explore whether such an expression of supralapsarian predestinarianism can help us in determining the lapsarian position of the Westminster Confession of Faith. While some scholars have claimed that the Confession is an infralapsarian document, this essay will show that, by using Rutherford's supralapsarianism as a hermeneutic, it is perhaps better understood as a supralapsarian document that is phrased in such a way so as to facilitate consensus on the lapsarian issue.
An Australian Idol of Modernist Consumerism: Minnie Tittell Brune and the Gallery Girls
Authors: KELLY VERONICA
Published: February 2006

The Australian career of the young American actor Minnie Tittell Brune exemplifies the complex cultural and economic forces operating on the institution of live theatre at the beginning of the twentieth century. Brune focalizes the contemporary processes which reconstituted the international institution of mass entertainment out of the traditional cultural practices of theatre. The theatrical star is seen as both engaging with and resisting the commodification of her labour power, image and talent resulting from her ambiguous industrial role as magnetic ‘star’ and as managerial commodity. However, the iconic and affective power of the actor evokes strong attachment from significant sections of the newly heterosocial popular audience, in particular from the gallery girls, the young female audience who idolized Brune as a performative personality enacting social self-realization and glamorous transformation. Through reading Brune's repertoire, her social persona as ‘star’ and her ‘emotional’ performative style, it is demonstrated how artistic retro-glamour, religious evangelicalism and discourses of sexuality and femininity serve to manage theatre's move into the mass-entertainment age.
Rasa, ‘Rasaesthetics’ and Dramatic Theory as Performance Packaging
Authors: MASON DAVID
Published: February 2006

In an attempt to distinguish themselves from the increasing proliferation of like projects, some theories, training programmes, productions, sub-disciplines and the like project a kinship with already authoritative voices. This artificial association characterizes the inevitably ‘intercultural’ product not simply as another element in the postmodern mix, but as a truth validated by tradition and transcending the limits of cultural fads. Richard Schechner's self-styled ‘rasaesthetics’ seeks to associate itself with the rasa concept of classical Sanskrit theory. But rasa and ‘rasaesthetics’ have little in common, and Schechner's attempt to project their kinship requires misunderstandings of theatre in India and in the West. Ultimately, ‘rasaesthetics’ is an example of a tendency in dramatic theory not to try to explain phenomena but to try to legitimize practices.
Analyse und Förderung der Organspendebereitschaft bei Studierenden
Authors: Krampen Günter , Junk Herbert
Published: February 2006

Zusammenfassung. Empirische Untersuchungsbefunde zu differentialpsychologischen Korrelaten und zur Verstärkung der Organspendebereitschaft werden vorgestellt. Auf der Basis des Handlungstheoretischen Partialmodells der Persönlichkeit (HPP) wurden in einer Stichprobe von 190 Universitätsstudierenden auf den Handlungsbereich der Organspende bezogene Persönlichkeitsvariablen der Informiertheit, des subjektiven Konzeptualisierungsniveaus und des Vertrauens (in Ärzte und Medizin) erfasst. Unter Bezug auf vorliegende Befunde zu Korrelaten der Organspendebereitschaft wurden ergänzend soziodemographische Variablen, Vorbehalte gegenüber der Organspende (Antidonation), religions- und todesbezogene Einstellungen sowie Altruismus erhoben. Als abhängige Variablen dienten neben der Einstellung gegenüber der Organspende und der Absicht, einen Organspendeausweis auszufüllen und bei sich zu tragen, der bei der Ersterhebung und der bei der eine bis sechs Wochen später durchgeführten Nacherhebung behavioral geprüfte Besitz eines Organspendeausweises. Die Befunde zeigen, (1) dass von der Erst- zur Nacherhebung der Anteil der Organspendeausweis-Inhaber von 18% auf 39% gesteigert werden konnte, (2) dass soziodemographische Variablen bei Studierenden keine Bedeutung für die Organspendebereitschaft haben, (3) dass neben den allgemeinen Vorbehalten gegenüber der Organspende die handlungstheoretischen Persönlichkeitsvariablen (Informiertheit, Vertrauen, Konzeptualisierungsniveau) den höchsten Prädiktorwert für die Organspendebereitschaft und für den Besitz eines Spendeausweises aufweisen. Ergänzend wird auf die Gründe, die von denen angegeben wurden, die bei der Nacherhebung keinen Organspendeausweis hatten, sowie die Interkorrelationen und differentialpsychologischen Korrelate dieser Begründungen eingegangen. Die Befunde werden im Hinblick auf den Nutzen des HPP für psychologische Analysen der Organspendebereitschaft und Möglichkeiten ihrer Verstärkung sowie darauf bezogene Anschlussfragestellungen diskutiert.
Bewältigung allgemeiner Problemsituationen bei Kindern mit chronischen Kopfschmerzen
Authors: Saile Helmut , Hülsebusch Tanja
Published: February 2006

Zusammenfassung. Auf dem Hintergrund transaktionaler Stresskonzepte führen fehlende Passung zwischen situativen Anforderungen und Bewältigungshandeln zu Anpassungsproblemen. Diese Studie untersucht, ob Kinder mit chronischen Kopfschmerzen ihr Bewältigungshandeln an der Kontrollierbarkeit von Situationen orientieren und ob diese Passung mit der Schmerzverarbeitung zusammenhängt. Untersucht wurden 71 Kinder mit chronischen Kopfschmerzen. Die Anwendung verschiedener Bewältigungsstrategien wurde beurteilt für kurze Beschreibungen von kontrollierbaren und unkontrollierbaren Situationen. Die Ergebnisse zeigen, dass Kinder in ihrem Bewältigungsverhalten nach der Kontrollierbarkeit der Situation differenzieren: Problemlösen wird in kontrollierbaren Situationen häufiger verwendet, Problemausweichen in unkontrollierbaren. Konstruktive Emotionsbewältigung und Suche nach sozialer Unterstützung sind dominant in unkontrollierbaren Situationen. Ein hohes Ausmaß ungünstiger Schmerzverarbeitung liegt vor, wenn Problemlösen und -ausweichen nicht den situativen Anforderungen angepasst werden. Die Ergebnisse zeigen, dass Bewältigung kontextabhängig ist. Dabei spielt die Kontrollierbarkeit von Situationen eine Rolle und steht mit ungünstiger Schmerzverarbeitung in Zusammenhang.
Effect of electrojet irregularities on DC current flow
Authors: Buchert S. C. , Hagfors T. , McKenzie J. F.
Published: February 2006

A study is presented of the effect of plasma density irregularities in the auroral and equatorial electrojets on the DC currents giving rise to these irregularities. It is shown that the theory predicts extra dissipation and deviation in the direction of the mean current flow from that of E0 × B0/B2, in general agreement with observations. The average power input to the turbulent plasma, equal to the product of the externally applied electric field and the mean current, can be equated to the power input with that resulting in a plasma devoid of irregularities but with an increased collision frequency. Similarly one can compute the deviation in direction of the current flow due to the irregularities and compare this with the deviation caused in a plasma without irregularities, but with an increased collision frequency, and from this comparison assign an anomalous dissipation in the plasma caused by the irregularities. Our study applies elementary principles and deals with the mean current driven by an external field, including effects of the mean values of second order terms in the perturbed quantities. We do not discuss the elementary processes giving rise to the irregularities in the plasma; only their effect on the mean current flow. The anomalous dissipation or the increased apparent collision frequency, is related directly to the angular power spectrum of plasma density fluctuations. It is shown that the power dissipated by the DC current in these anomalous collisions is exactly the same as the power dissipated through normal collisions by the wave modes making up the power spectrum leading to the anomalous DC current dissipation. The study also suggests that the saturation of the instabilities, giving rise to the electrojet turbulence, is likely to be caused by the control of the current by the anomalous resistivity rather than by local nonlinear effects.
Near‐surface ocean temperature
Authors: Ward B.
Published: February 2006

The first open ocean deployment of the Skin Depth Experimental Profiler (SkinDeEP) was from the R/V Melville in the Gulf of California during the Marine Optical Characterization Experiment (MOCE‐5). SkinDeEP is an autonomous, vertical profiler for the upper few meters of the ocean. During MOCE‐5, SkinDeEP was deployed on ten separate occasions, and profiles were made at intervals of approximately 1 min each. A total of 976 profiles was acquired during the cruise. The ocean skin temperatures were measured by the Marine Atmosphere Emitted Radiance Interferometer (M‐AERI), an infrared spectroradiometer. Typical meteorological conditions were of low winds and high insolation. The data set provided captures the near‐surface temperature structure that decouples the skin layer from the conventional in situ bulk sea surface temperature (SST) measurements made at a depth of a few meters. Data from SkinDeEP showed strong diurnal warming within the upper few meters, with one extreme case of 4.6 K. There were large discrepancies when computing the skin‐bulk temperature difference with bulk temperatures at different depths. Results also show the strong dependency of the SST on air‐sea heat flux estimates, with warm‐layer errors of almost 60 Wm−2 associated with intense stratification. This indicates the importance of the inclusion of the skin temperature for accurate calculation of latent, sensible, and net longwave heat fluxes.
Fluvial response to horizontal shortening and glaciations: A study in the Southern Alps of New Zealand
Authors: Herman Frédéric , Braun Jean
Published: February 2006

It has been postulated that a steady state between erosional and tectonic processes may develop in continental collision. However, it is not clear whether steady state conditions can be reached for all components of the landscape. Here we show, using landscape evolution models and field evidence, that a true geomorphic steady state may never be reached in the Southern Alps of New Zealand. The strong asymmetries in tectonic uplift and tectonic advection and the onset of glaciations constantly interact to prevent the landscape from reaching a topographic steady state. Evidence suggests that the first‐order geomorphology on the western side of the Southern Alps is controlled by orographic precipitation combined with extreme rates of tectonic uplift, whereas the development of deep glacial valleys on the eastern side is initiated by differential uplift along large faults. We also develop a first‐order equation, governing the dynamics of the Main Divide, to show that both tectonic advection and fluvial erosion efficiency control the position and the height of the main drainage divide. Using a two‐dimensional landscape evolution model, we demonstrate that the transition from glacial to fluvial conditions at the end of the last glaciation led to substantial modifications of the landscape: While the main trunk channels get slowly uplifted, ridges are leveled down, causing the relief to decrease. Hillslopes appear to be affected by fluvial processes which seem to be driven by incision of river tributaries. This reduction of relief will probably never reach a steady state since warmer interglacial periods are substantially shorter than glacial periods.
Ammonia emissions from a Cape fur seal colony, Cape Cross, Namibia
Authors: Theobald M. R. , Crittenden P. D. , Hunt A. P. , Tang Y. S. , Dragosits U. , Sutton M. A.
Published: February 2006

Large animal colonies are significant sources of atmospheric NH3 that can potentially increase the nitrogen status of nearby ecosystems. Atmospheric NH3 concentrations were measured at different distances from a Cape fur seal colony at Cape Cross, northwest coast of Namibia, and an atmospheric dispersion model was applied inversely to estimate the total NH3 emission. Mean concentrations ranged from 354 to 0.01 μg NH3 m−3 at 0.01 and 26 km from the source, respectively. The model simulations suggest that the colony emits 25–70 tonnes of NH3‐N yr−1, c. 3% of the total N excreted by the seals.
High resolution atmospheric monitoring of urban carbon dioxide sources
Authors: Pataki D. E. , Bowling D. R. , Ehleringer J. R. , Zobitz J. M.
Published: February 2006

Estimates of fossil fuel emissions on local to regional spatial scales and hourly to weekly temporal scales are increasingly useful in studies of the carbon cycle and mass and energy flow in cities. We used a tunable diode laser absorption spectrometer (TDL) to measure CO2 mixing ratios and carbon isotope composition of CO2 in order to estimate the contribution of gasoline versus natural gas combustion to atmospheric CO2 in Salt Lake City. The results showed a pronounced diurnal pattern: the proportional contribution of natural gas combustion varied from 30–40% of total anthropogenic CO2 during evening rush hour to 60–70% at pre‐dawn. In addition, over a warming period of several days, the proportional contribution of natural gas combustion decreased with air temperature, likely related to decreased residential heating. These results show for the first time that atmospheric measurements may be used to infer patterns of energy and fuel usage on hourly to daily time scales.
Impact of global warming on the East Asian winter monsoon as revealed by nine coupled atmosphere‐ocean GCMs
Authors: Hori Masatake E. , Ueda Hiroaki
Published: February 2006

Impact of global warming on the East Asian Winter Monsoon (EAWM) is studied using nine coupled atmosphere‐ocean general circulation models (AOGCMs). Models are mostly successful in simulating the basic features of the EAWM with varied location of monsoon northwesterlies (NW). Under the global warming scenario, most models show a weakening of the EAWM accompanied by a strong anticyclonic anomaly over the North Pacific corresponding to a weakened and/or the northern shift of the Aleutian Low (AL). Response in Sea Level Pressure (SLP) also shows the weakening of both the AL and the Siberian High (SH), which gives rise to a weakened pressure gradient along the eastern coast of the Eurasian continent. Among other factors, weakening of the tropical local Hadley circulation was found to substantially weaken the East Asian Jet (EAJ) and the resultant EAWM.
Trends in precipitation and streamflow in the eastern U.S.: Paradox or perception?
Authors: Small David , Islam Shafiqul , Vogel Richard M.
Published: February 2006

Many studies have reported that total precipitation is increasing across the United States with most of the increase resulting from a positive trend in the upper tail of the daily precipitation distribution. Other studies have found that low and moderate, but not high flows are also increasing across much of the United States. How can precipitation, especially that produced by intense events, increase without a corresponding increase in high flows? We analyzed trends in annual 7‐day low, average and high flows along with seasonal precipitation that is averaged over individual basins. Our findings suggest that statistically significant trends in both fall precipitation and 7‐day low flow are found in a large percentage of the basins in the upper Mississippi and Great Lakes regions of the country. A large fraction of the trends in annual precipitation can be explained by an increase in fall precipitation. By estimating trends in precipitation at the spatial scale of individual basins, we offer a simple explanation for the apparent paradox of lack of trends in high flows. At the spatial scale of individual basins, precipitation is increasing during the fall but not during the spring, the season when high flows are generally observed. The increase in fall precipitation appears to result in an increase in the low flows while the lack of trends in precipitation in spring explains the lack of widespread trends in the high flows.
Slow slip below Port Blair, Andaman, during the great Sumatra‐Andaman earthquake of 26 December 2004
Authors: Singh S. K. , Ortiz M. , Gupta H. K. , Ramadass D. G. A.
Published: February 2006

Although several studies suggest that a slow slip followed the seismic slip on the northern half of the 1300‐km long plate interface that ruptured during the great Sumatra‐Andaman earthquake, the onset and duration of the slow slip remain unresolved. In this paper we analyze a tide gauge record at Port Blair, situated about 1000 km north of the epicenter. Our preferred model, which fits the observed data well, consists of a mixed mode of slip: ∼half of the total slip occurring seismically in less than 5 min after the rupture arrival and the rest developing in the next 30 min. A scenario of slow slip on the northern half of the rupture area, that is consistent with seismic data, and GPS data, consists of slip on the time scale of <35 min over some parts of the fault, such as below Port Blair, and > 1 hour over the rest.
Impact of atmospheric submonthly oscillations on sea surface temperature of the tropical Indian Ocean
Authors: Han Weiqing , Liu W. Timothy , Lin Jialin
Published: February 2006

Impacts of atmospheric intraseasonal oscillations (ISOs) at submonthly periods (10–30 days) on Indian Ocean sea surface temperature (SST) are studied using satellite observed outgoing long wave radiation, QuikSCAT winds, SST and an ocean general circulation model for the period of 1999–2004. The results suggest that submonthly ISOs can cause significant 10–30 day SST changes throughout the equatorial basin and northern Bay of Bengal, with an amplitude of as large as 0.5°C and standard deviation of exceeding 0.2°C for a 4‐year record. Impact of the submonthly ISO associated with the Indian summer monsoon is separately examined. It is associated with basin‐scale SST evolution with distinct spatial structures. The SST variation results mainly from submonthly wind forcing, which causes changes in oceanic processes and surface turbulent heat fluxes. Radiative fluxes can also have large influences in some regions for some ISO events.
Enhanced transport in the polar mesosphere of Jupiter: Evidence from Cassini UVIS helium 584 Å airglow
Authors: Parkinson C. D. , Stewart A. I. F. , Wong A. S. , Yung Y. L. , Ajello J. M.
Published: February 2006

The eddy diffusion profile (K) in the auroral regions of Jupiter is not well determined. However, because of the intense auroral energy input, eddy mixing is expected to be much more effective and may be responsible for the enhancement of heavy hydrocarbon production in the polar region. In this paper, we estimate the increased eddy mixing in the Jovian auroral regions by comparing the Cassini Ultraviolet Imaging Spectrograph (UVIS) observations during the 2000 Jupiter flyby with radiative transfer calculations of the He 584 Å airglow intensity. We derive a range for the eddy diffusion coefficients at the homopause (Kh) in the auroral regions to be at least 8 × 106 cm2 s−1 and possibly greater than 4 × 107 cm2 s−1. By comparison, equatorial Kh is on the order of 2 × 106 cm2 s−1.
Magic numbers, excitation levels, and other properties of small neutral He4 clusters (N⩽50)
Authors: Guardiola Rafael , Kornilov Oleg , Navarro Jesús , Peter Toennies J.
Published: February 2006

The ground-state energies and the radial and pair distribution functions of neutral He4 clusters are systematically calculated by the diffusion Monte Carlo method in steps of one He4 atom from 3 to 50 atoms. In addition the chemical potential and the low-lying excitation levels of each cluster are determined with high precision. These calculations reveal that the “magic numbers” observed in experimental He4 cluster size distributions, measured for free jet gas expansions by nondestructive matter-wave diffraction, are not caused by enhanced stabilities. Instead they are explained in terms of an enhanced growth due to sharp peaks in the equilibrium concentrations in the early part of the expansion. These peaks appear at cluster sizes which can just accommodate one more additional stable excitation. The good agreement with experiment provides not only experimental confirmation of the energy level and the chemical potential calculations, but also evidence for a new mechanism which can lead to magic numbers in cluster size distributions. By accounting for the falloff of the radial density distributions at the surface and a size-dependent surface tension, the energy levels are demonstrated to be consistent with a modified Rayleigh model of surface excitations. The compressibility coefficient of these small clusters is found to be one order of magnitude smaller than the bulk compressibility.
Optical upconverter with integrated heterojunction phototransistor and light-emitting diode
Authors: Luo H. , Ban D. , Liu H. C. , Wasilewski Z. R. , Buchanan M.
Published: February 2006

We report an optical upconversion device that converts input 1.5μm light to output 0.87μm light with a built-in gain mechanism. The device consists of an InGaAs∕InP heterojunction phototransistor (HPT) integrated with a GaAs∕AlGaAs light-emitting diode (LED) by wafer fusion process. Incoming 1.5μm optical radiation is absorbed by the HPT, generating an amplified photocurrent. The resultant photocurrent drives the LED that emits at 0.87μm, which could be detected by a conventional silicon charge-coupled device. Upconversion is demonstrated at room temperature with a gain of 20 from the HPT and an overall external upconversion efficiency of 0.07W∕W.
Diabatic free energy curves and coordination fluctuations for the aqueous Ag+∕Ag2+ redox couple: A biased Born-Oppenheimer molecular dynamics investigation
Authors: Blumberger Jochen , Tavernelli Ivano , Klein Michael L. , Sprik Michiel
Published: February 2006

Biased Born-Oppenheimer molecular dynamics simulations are performed to compute redox potential and free energy curves for the redox half reaction Ag+→Ag2++e− in aqueous solution. The potential energy surfaces of reactant and product state are linearly coupled and the system transferred from the reduced state to the oxidized state by variation of the coupling parameter from 0 to 1. The redox potential is obtained by thermodynamic integration of the average ionization energy of Ag+. Diabatic free energy curves of reduced (R) and oxidized (O) states are obtained to good statistical accuracy by reweighting and combining the set of biased distributions of the ionization energy. The diabatic free energy curves of Ag+ and Ag2+ are parabolic over a wide range of the reaction coordinate in agreement with the linear response assumption that underlies Marcus theory. However, we observe deviations from parabolic behavior in the equilibrium region of Ag+ and find different values for the reorganization free energy of R (1.4 eV) and O (0.9 eV). The computed reorganization free energy of Ag2+ is in good agreement with the experimental estimate of 0.9–1.2 eV obtained from photoelectron spectroscopy. As suggested by our calculations, the moderate deviation from linear response behavior found for Ag+ is likely related to the highly fluxional solvation shell of this ion, which exhibits water exchange reactions on the picosecond time scale of the present molecular dynamics simulation.
The hydration of Cu2+: Can the Jahn-Teller effect be detected in liquid solution?
Authors: Chaboy Jesús , Muñoz-Páez Adela , Merkling Patrick J. , Sánchez Marcos Enrique
Published: February 2006

The long elusive structure of Cu(II) hydrate in aqueous solutions, classically described as a Jahn-Teller distorted octahedron and recently proposed to be a fivefold coordination structure [Pasquarello et al., Science 291, 856 (2001)], has been probed with x-ray-absorption spectroscopy by performing a combined theoretical and experimental analysis. Two absorption channels were needed to obtain a proper reproduction of the x-ray-absorption near-edge structure (XANES) region spectrum, as already observed in other Cu(II) complexes [Chaboy et al., Phys. Rev. B 71, 134208 (2005)]. The extended x-ray-absorption fine-structure (EXAFS) spectrum was analyzed as well within this approach. Quite good reproductions of both XANES and EXAFS spectra were attained for several distorted and undistorted structures previously proposed. Nevertheless, there is not a clearly preferred structure among those including four-, five-, and sixfold coordinated Cu(II) ions. Taking into account our results, as well as many more from several other authors using different techniques, the picture of a distorted octahedron for the Cu(II) hexahydrate in aqueous solution, paradigm of the Jahn-Teller effect, is no longer supported. In solution a dynamical view where the different structures exchange among themselves is the picture that better suits the results presented here.
Hyperbolic geometrical optics: Hyperbolic glass
Authors: De Micheli Enrico , Scorza Irene , Viano Giovanni Alberto
Published: February 2006

We study the geometrical optics generated by a refractive index of the form n(x,y)=1∕y (y>0), where y is the coordinate of the vertical axis in an orthogonal reference frame in R2. We thus obtain what we call “hyperbolic geometrical optics” since the ray trajectories are geodesics in the Poincaré-Lobachevsky half-plane H2. Then we prove that the constant phase surface are horocycles and obtain the horocyclic waves, which are closely related to the classical Poisson kernel and are the analogs of the Euclidean plane waves. By studying the transport equation in the Beltrami pseudosphere, we prove (i) the conservation of the flow in the entire strip 0<y⩽1 in H2, which is the limited region of physical interest where the ray trajectories lie; (ii) the nonuniform distribution of the density of trajectories: the rays are indeed focused toward the horizontal x axis, which is the boundary of H2. Finally the process of ray focusing and defocusing is analyzed in detail by means of the sine-Gordon equation.
Generalized nonholonomic mechanics, servomechanisms and related brackets
Authors: Cendra H. , Grillo S.
Published: February 2006

It is well known that nonholonomic systems obeying D’Alembert’s principle are described on the Hamiltonian side, after using the Legendre transformation, by the so-called almost-Poisson brackets. In this paper we define the Lagrangian and Hamiltonian sides of a class of generalized nonholonomic systems (GNHS), obeying a generalized version of D’Alembert’s principle, such as rubber wheels (like some simplified models of pneumatic tires) and certain servomechanisms (like the controlled inverted pendulum), and show that corresponding equations of motion can also be described in terms of a bracket. We present essentially all possible brackets in terms of which the mentioned equations can be written down, which include the brackets that appear in the literature, and point out those (if any) that are naturally related to each system. In particular, we show there always exists a Leibniz bracket related to a GNHS, and conversely, that every Leibniz system is a GNHS. The control of the inverted pendulum on a cart is studied as an illustrative example.
Use of a single trajectory to study product energy partitioning in unimolecular dissociation: Mass effects for halogenated alkanes
Authors: Sun Lipeng , Park Kyoyeon , Song Kihyung , Setser Donald W. , Hase William L.
Published: February 2006

A single trajectory (ST) direct dynamics approach is compared with quasiclassical trajectory (QCT) direct dynamics calculations for determining product energy partitioning in unimolecular dissociation. Three comparisons are made by simulating C2H5F→HF+C2H4 product energy partitioning for the MP2∕6-31G* and MP2∕6-311++G** potential energy surfaces (PESs) and using the MP2∕6-31G* PES for C2H5F dissociation as a model to simulate CHCl2CCl3→HCl+C2Cl4 dissociation and its product energy partitioning. The trajectories are initiated at the transition state with fixed energy in reaction-coordinate translation Et‡. The QCT simulations have zero-point energy (ZPE) in the vibrational modes orthogonal to the reaction coordinate, while there is no ZPE for the STs. A semiquantitative agreement is obtained between the ST and QCT average percent product energy partitionings. The ST approach is used to study mass effects for product energy partitioning in HX(X=ForCl) elimination from halogenated alkanes by using the MP2∕6-31G* PES for C2H5F dissociation and varying the masses of the C, H, and F atoms. There is, at most, only a small mass effect for partitioning of energy to HX vibration and rotation. In contrast, there are substantial mass effects for partitioning to relative translation and the polyatomic product’s vibration and rotation. If the center of mass of the polyatomic product is located away from the C atom from which HX recoils, the polyatomic has substantial rotation energy. Polyatomic products, with heavy atoms such as Cl atoms replacing the H atoms, receive substantial vibration energy that is primarily transferred to the wag-bend motions. For Et‡ of 1.0kcal∕mol, the ST calculations give average percent partitionings to relative translation, polyatomic vibration, polyatomic rotation, HX vibration, and HX rotation of 74.9%, 6.8%, 1.5%, 14.4%, and 2.4% for C2H5F dissociation and 39.7%, 38.1%, 0.2%, 16.1%, and 5.9% for a model of CHCl2CCl3 dissociation.
Novel chemical-vapor deposition technique for the synthesis of high-quality single-crystal nanowires and nanotubes
Authors: He Maoqi , Mohammad S. Noor
Published: February 2006

The strength and versatility of a chemical-vapor deposition technique for thin, long, uniform, single-crystal, good-quality nanowire growth, without the use of template, have been described. Remarkably, while the full width at half maximum of a high-quality GaN thin film is 4 meV, that of a GaN whisker is 9 meV, which confirms high quality of the grown whiskers and nanowires. The versatility of the method is reflected by its ability to produce II-VI and III-V binary, ternary, and even, for the first time, quaternary nanowires in a controlled manner. The same versatility enables the realization of both cubic and hexagonal phases of nanowires and nanotubes. Chemical-vapor deposition technique generally makes use of highly poisonous arsine and phosphine for the synthesis of As- and P-based films. The present one is free from this shortcoming; it can produce As- and P-based nanowires without the use of these poisonous gases. A notable feature of the method is that properties of nanowires thus synthesized depend strongly on their shape, size, and geometry, and that certain growth conditions can only lead to such shapes and sizes.
Multiscale spatial Monte Carlo simulations: Multigriding, computational singular perturbation, and hierarchical stochastic closures
Authors: Chatterjee Abhijit , Vlachos Dionisios G.
Published: February 2006

Monte Carlo (MC) simulation of most spatially distributed systems is plagued by several problems, namely, execution of one process at a time, large separation of time scales of various processes, and large length scales. Recently, a coarse-grained Monte Carlo (CGMC) method was introduced that can capture large length scales at reasonable computational times. An inherent assumption in this CGMC method revolves around a mean-field closure invoked in each coarse cell that is inaccurate for short-ranged interactions. Two new approaches are explored to improve upon this closure. The first employs the local quasichemical approximation, which is applicable to first nearest-neighbor interactions. The second, termed multiscale CGMC method, employs singular perturbation ideas on multiple grids to capture the entire cluster probability distribution function via short microscopic MC simulations on small, fine-grid lattices by taking advantage of the time scale separation of multiple processes. Computational strategies for coupling the fast process at small length scales (fine grid) with the slow processes at large length scales (coarse grid) are discussed. Finally, the binomial τ-leap method is combined with the multiscale CGMC method to execute multiple processes over the entire lattice and provide additional computational acceleration. Numerical simulations demonstrate that in the presence of fast diffusion and slow adsorption and desorption processes the two new approaches provide more accurate solutions in comparison to the previously introduced CGMC method.
Orbital susceptibilities of PbSe quantum dots
Authors: Jian W. B. , Lu Weigang , Fang Jiye , Chiang S. J. , Lan M. D. , Wu C. Y. , Wu Z. Y. , Chen F. R. , Kai J. J.
Published: February 2006

Different sizes of three-dimensional PbSe quantum dots have been synthesized for the study of orbital magnetic susceptibilities. Two types of orbital susceptibilities have been found, including the Curie susceptibility and finite-size corrections to the Landau susceptibility. The Curie term of a quantum dot manifests itself in the temperature dependence of magnetic susceptibility at low temperatures, while the field dependence of differential susceptibility at high temperatures shows finite-size corrections to the Landau susceptibility. Both of the two kinds of orbital susceptibility, estimated per quantum dot, show linear dependence on the size.
Chemical reaction equilibrium in nanoporous materials: NO dimerization reaction in carbon slit nanopores
Authors: Lísal Martin , Brennan John K. , Smith William R.
Published: February 2006

We present a molecular-level simulation study of the effects of confinement on chemical reaction equilibrium in nanoporous materials. We use the reaction ensemble Monte Carlo (RxMC) method to investigate the effects of temperature, nanopore size, bulk pressure, and capillary condensation on the nitric oxide dimerization reaction in a model carbon slit nanopore in equilibrium with a bulk reservoir. In addition to the RxMC simulations, we also utilize the molecular-dynamics method to determine self-diffusion coefficients for confined nonreactive mixtures of nitric oxide monomers and dimers at compositions obtained from the RxMC simulations. We analyze the effects of the temperature, nanopore width, bulk pressure, and capillary condensation on the reaction equilibrium with respect to the reaction conversion, fluid structure, and self-diffusion coefficients. We show that the influence of the temperature, nanopore size, and capillary condensation on the confined reaction equilibrium is quite dramatic while the effect of the bulk pressure on the reaction equilibrium in the carbon slit nanopore is only moderate. This work is an extension of previous work by Turner et al. [J. Chem. Phys. 114, 1851 (2001)] on the confined reactive nitric oxide system.
On NO3−–H2O interactions in aqueous solutions and at interfaces
Authors: Dang Liem X. , Chang Tsun-Mei , Roeselova Martina , Garrett Bruce C. , Tobias Douglas J.
Published: February 2006

The constrained molecular-dynamics technique was employed to investigate the transport of a nitrate ion across the water liquid/vapor interface. We developed a nitrate-ion–water polarizable potential that accurately reproduces the solvation properties of the hydrated nitrate ion. The computed free-energy profile for the transfer of the nitrate ion across the air/water interface increases monotonically as the nitrate ion approaches the Gibbs dividing surface from the bulk liquid side. The computed density profiles of 1M KNO3 salt solution indicate that the nitrate and potassium ions are both found below the aqueous interface. Upon analyzing the results, we conclude that the probability of finding the nitrate anion at the aqueous interface is quite small.
Study on in-plane optical anisotropy of Si0.75Ge0.25∕Si∕Si0.5Ge0.5 asymmetric superlattice by reflectance difference spectroscopy
Authors: Zhao L. , Zuo Y. H. , Shi W. H. , Wang Q. M. , Chen Y. H. , Wang H. N.
Published: February 2006

Si 0.75 Ge 0.25 ∕ Si ∕ Si 0.5 Ge 0.5 trilayer asymmetric superlattices were prepared on Si (001) substrate by ultrahigh vacuum chemical vapor deposition at 500 °C. The nonlinear optical response caused by inherent asymmetric interfaces in this structure predicted by theories was verified by in-plane optical anisotropy in (001) plane measured via reflectance difference spectroscopy. The results show Si0.75Ge0.25∕Si∕Si0.5Ge0.5 asymmetric superlattice is optically biaxial and the two optical eigen axes in (001) plane are along the directions [110] and [−110], respectively. Reflectance difference response between the above two eigen axes can be influenced by the width of the trilayers and reaches as large as ∼10−4–10−3 in 15-period 2.7nm-Si0.75Ge0.25∕8nm-Si∕1.3nm-Si0.5Ge0.5 superlattice when the normal incident light wavelength is in the range of 500–1100 nm, which is quite remarkable because the optical anisotropy does not exist in bulk Si.
Statistical parameters for gloss evaluation
Authors: Peiponen Kai-Erik , Juuti Mikko
Published: February 2006

The measurement of minute changes in local gloss has not been presented in international standards due to a lack of suitable glossmeters. The development of a diffractive-element-based glossmeter (DOG) made it possible to detect local variation of gloss from planar and complex-shaped surfaces. Hence, a demand for proper statistical gloss parameters for classifying surface quality by gloss, similar to the standardized surface roughness classification, has become necessary. In this letter, we define statistical gloss parameters and utilize them as an example in the characterization of gloss from metal surface roughness standards by the DOG.
Optimization scheme for the quantum efficiency of GaInN-based green-light-emitting diodes
Authors: Fuhrmann D. , Netzel C. , Rossow U. , Hangleiter A. , Ade G. , Hinze P.
Published: February 2006

We have optimized the internal quantum efficiency (IQE) of GaInN∕GaN quantum-well (QW) structures. For an emission wavelength of 460nm, a high IQE of 73% was achieved. For a longer emission wavelength, calculations predict higher oscillator strength for thinner QWs but higher In content. We observe an improvement in IQE of almost 50% when reducing the QW width from 2.7nmto1.8nm, and increasing the In content for the whole blue to green spectral region with IQE=40% at 525nm. The typical saturation of the output power with increasing current that occurs, particularly for green-light-emitting diodes, is extremely weak in our structures.
Luminescence properties of highly Si-doped AlN
Authors: Monroy E. , Zenneck J. , Cherkashinin G. , Ambacher O. , Hermann M. , Stutzmann M. , Eickhoff M.
Published: February 2006

We report on the optical characterization of highly Si-doped AlN layers grown by plasma-assisted molecular-beam epitaxy. Cathodoluminescence spectra reveal a sharp band-edge line and two broadbands around 4.4eV and 3.6eV. Near-band-edge luminescence remains intense at room temperature, and shows a systematic redshift with increasing Si concentration. Regarding the low-energy bands, we observe a redshift of the emission around 3.6eV with increasing Si concentration accompanied by an increase in relative intensity compared to the 4.4eV band.
Low-voltage and high-field-effect mobility organic transistors with a polymer insulator
Authors: Jang Yunseok , Kim Do Hwan , Park Yeong Don , Cho Jeong Ho , Hwang Minkyu , Cho Kilwon
Published: February 2006

A key issue in research into organic thin-film transistors (OTFTs) is low-voltage operation. In this study, we fabricated a pentacene thin-film transistor with an ultrathin layer of polyvinyl alcohol (9nm) as a gate insulator, and obtained a device with excellent electrical characteristics at low operating voltages (below 2V). This device was found to have a field-effect mobility of 1.1cm2∕Vs, a threshold voltage of −0.98V, an exceptionally low subthreshold slope of 180mV/decade, and an on/off current ratio of 106. This favorable combination of properties means that such OTFTs can be operated successfully at voltages below 2V.
Significantly enhanced critical current densities in MgB2 tapes made by a scaleable nanocarbon addition route
Authors: Ma Yanwei , Zhang Xianping , Nishijima G. , Watanabe K. , Awaji S. , Bai Xuedong
Published: February 2006

Nanocarbon-doped Fe-sheathed MgB2 tapes with different doping levels were prepared by the in situ powder-in-tube method. Compared to the undoped tapes, Jc for all the C-doped samples was enhanced by more than an order of magnitude in magnetic fields above 9T. At 4.2K, the transport Jc for the 5at.% doped tapes reached 1.85×104A∕cm2 at 10T and 2.8×103A∕cm2 at 14T, respectively. Moreover, the critical temperature for the doped tapes decreased slightly. Transmission electron microscopy showed a number of intragranular dislocations and the dispersed nanoparticles embedded within MgB2 grains induced by the C doping. The mechanism for the enhancement of flux pinning is also discussed. These results indicate that powder-in-tube-processed MgB2 tape is very promising for high-field applications.
Photoleakage currents in organic thin-film transistors
Authors: Cho Sang Mi , Han Seung Hoon , Kim Jun Hee , Jang Jin , Oh Myung Hwan
Published: February 2006

We studied the light illumination effect on the performance of pentacene organic thin-film transistors (TFTs) exhibiting a field-effect mobility of 0.7cm2∕Vs, threshold voltage of −7V and on/off current ratio of 108. The transfer characteristics of the orgnaic TFT change remarkably by illumination in the subthreshold and off-state regions because of the photogenerated carriers in the TFT channel. The minimum off current increases by 105 under the illumination of 1350lux. The drain current increases linearly with light intensity in the region where holes are majority carriers. On the other hand, the off-state currents increase superlinearly with light intensity when electrons are majority carriers. The photoleakage current increases with illumination time at the constant temperature. The results can be explained on the basis of the trapping of carriers at the grain boundaries and significant recombination of electrons and holes when electrons are majority carrier. The holes can be trapped at the grain boundaries during illumination, reducing the potential barriers at the boundaries.