bluuebunny/crossref_metadata_2025 huggingface dataset:
CHILDREN'S VOICES: SINGING AND LITERACY IN SIXTEENTH-CENTURY FRANCE
Authors: van Orden Kate
Published: August 2006

Around 1600, students in France learnt to read with printed primers. They began with the letters of the alphabet, learning them by playing with little wooden or cardboard tablets or picking them out of books, and then moved on to syllables, which were learnt from syllabaries printed in large letters and containing the Pater noster, Ave Maria, Credo, Confiteor and the Benedicite. When they began to spell out whole words, children moved on to another syllabary containing the Magnificat, the Nunc Dimittis, Salve Regina, the Seven Penitential Psalms and the litanies of the Saints, all of them common prayers. Two pages from Jacques Cossard's Methodes pour apprendre a lire, a escripre, chanter le plain chant, et compter (Paris, 1633) can give us some idea of what these early modern primers looked like (see Figures 1–2). In the first lesson the text of the Pater noster is broken into syllables, whereas in the second lesson the students must discern the syllables of the Ave Maria themselves, a task aided by the small numbers Cossard has placed beneath the text to show how many letters should be read together as a syllable.
Ein auf Evidenz basierendes Praxisprogramm zur pflegerischen Betreuung HIV-infizierter Menschen mit Fatigue
Authors: Unger Miriam , Spirig Rebecca
Published: August 2006

In der Schweiz leben zwischen 15000 und 16000 Menschen mit HIV/AIDS. Diese Population leidet unter einer Vielzahl von Symptomen und Beschwerden. Besonders schwerwiegend und häufig ist die Fatigue, welche gemäß aktueller Studien bei 20 bis 74% der HIV-infizierten Menschen auftritt. Das Symptom beeinträchtigt alle Aktivitäten des täglichen Lebens, das Empfinden körperlicher und mentaler Gesundheit sowie die Lebensqualität der Betroffenen stark. An der HIV-Sprechstunde des Universitätsspitals Basel, Schweiz, äußern viele Patienten und Patientinnen Beschwerden, die auf das Bestehen von Fatigue hinweisen, oder sprechen direkt über ihre starke Erschöpfung. Eine systematische Literatursuche wurde durchgeführt und ein evidenzbasiertes Praxisprogramm erarbeitet, um den Betroffenen eine angepasste Betreuung bieten zu können. Das Programm enthält die Elemente: Screening, systematisches Assessment, Interventionen und Beratung. Für das Assessment werden der adaptierte Global Fatigue Index und eine visuelle Analogskala eingesetzt. Die Patientinnen werden durch systematische Interventionen bei der Verbesserung ihres Selbstmanagements unterstützt. Ziel der vorliegenden Arbeit ist es, Pflegenden, die HIV-infizierte Menschen betreuen, eine Zusammenfassung der aktuellen Literatur bezüglich HIV-induzierter Fatigue zu präsentieren und die Elemente, den Ablauf sowie des Praxisprogramms darzustellen. Es kann davon ausgegangen werden, dass mit Hilfe des Praxisprogramms Menschen, die mit HIV/AIDS leben und unter Fatigue leiden, positiv beim Management dieses Symptoms ihrer chronischen Erkrankung unterstützt werden können.
Beratungsempfehlung für HIV/AIDS-infizierte Menschen, deren Alkoholkonsum ein gesundheitliches Problem darstellt
Authors: Voggensperger Jacqueline , Fierz Katharina , Spirig Rebecca
Published: August 2006

In der Schweiz leben etwa 300 000 Alkoholkranke. Aufgrund der Praxiserfahrung wissen wir, dass auch Menschen mit einer HIV/AIDS-Infektion davon betroffen sind, genaue Zahlen gibt es bis jetzt allerdings nicht. Da wir an der HIV-Sprechstunde am Universitätsspital Basel, Schweiz, in den pflegerischen Erst- und Verlaufsgesprächen viele Patienten und Patientinnen sehen, deren Alkoholkonsum ein gesundheitliches Problem darstellt, erarbeiteten wir aufgrund einer systematischen Literaturarbeit eine Beratungsempfehlung zu Assessment und Intervention. Das Assessment des Alkoholkonsums wird mittels AUDIT und CAGE durchgeführt, da diese Instrumente für die ambulante Pflege die höchste Sensitivität und Spezifität aufweisen. Die Veränderungsbereitschaft der Betroffenen wird in Zusammenarbeit mit Patienten und Patientinnen eingeschätzt. Die Intervention erfolgt mittels einer Kurzintervention. Ziel dieses Artikels ist es, Pflegefachpersonen und anderen Professionellen eine Zusammenfassung der Evidenz zu präsentieren und ihnen mit der Beratungsempfehlung eine Möglichkeit zur Intervention bei HIV/AIDS-infizierten Menschen anzubieten, deren Alkoholkonsum ein gesundheitliches Problem darstellt.
Familiengesundheitspflege in Deutschland: Konsensfindung als Grundlage
Authors: Eberl Inge , Schnepp Wilfried
Published: August 2006

Die «Projektdesign- und Konsensphase zur Implementierung der Family Health Nurse in Deutschland» wurde vom Institut für Pflegewissenschaft der Universität Witten/Herdecke im Auftrag des DBfK-Bundesverbands durchgeführt. In dieser Studie sollte vor dem Beginn des «Pilotprojekts zur Machbarkeit der Family Health Nurse in Deutschland» zur Stärkung der Prävention und Gesundheitsförderung, entsprechend dem Strategiekonzept «Gesundheit 21» der WHO, in einer Konsensfindung von elf als Experten benannten Vertretern zehn entscheidungstragender Einrichtungen, Verbände und Organisationen der deutschen Versorgungsstruktur der generelle Bedarf und Umfang der neuen Rolle für Pflegende und Hebammen ermittelt werden. Ziel war es zudem, die Machbarkeit der Family Health Nurse im deutschen Gesundheitssystem vorab virtuell abzubilden. Für das methodische Vorgehen wurde ein mehrstufiges Verfahren gewählt. Die Expertenaussagen wurden in leitfadengestützten Interviews ermittelt, qualitativen Inhaltsanalysen unterzogen, deren zentrale Aussagen identifiziert und hieraus einzelfallbezogene Einstiegsszenarien zu möglichen Aufgabenfeldern der Family Health Nurse in Deutschland entwickelt. Aus den Resultaten der anschließend zu diesen Szenarien geführten Gruppendiskussionen entstanden letztendlich fünf, von den Experten konsentierte Ergebnisszenarien. Diese wurden weiter fallübergreifend generalisiert, nach den Variablen Zielgruppen, Anlass, Bedarf, Zugang, Handlungskompetenz, Ansiedlung und Finanzierung strukturiert und so die zielgruppenspezifischen Merkmale des neuen Handlungsfeldes definiert. Auf der Basis der Resultate dieser Vorstudie wurde abschließend von den Experten der Konsens zur Durchführung des Pilotprojekts ausgesprochen. Für den Begriff «Family Health Nurse» wurden für Deutschland vorläufig die Bezeichnungen Familiengesundheitspflegerin und Familiengesundheitshebamme festgelegt. Das Projekt wurde zwischenzeitlich im Frühjahr 2005 gestartet und wird entsprechend den Forderungen der WHO wissenschaftlich begleitet und evaluiert.
Resultate der qualitativen Evaluation von allfit – einem Schulungs- und Bewegungsprogramm für chronischkranke ältere Menschen: Die Wirkungsweise aus der Sicht von Teilnehmenden an Diabetes- oder Rheumakursen
Authors: Bonsack Stefania , Spirig Rebecca , Baldegger Esther , Wettstein Albert
Published: August 2006

Gruppenprogramme, welche ältere Menschen mit chronischen Krankheiten befähigen, ihr Selbstmanagement zu verbessern, können einen wichtigen Beitrag zur Gesundheitsförderung leisten. Deren Wirksamkeit wurde mit kontrollierten Studien im angloamerikanischen Raum belegt. Mit allfit wird ein solches Programm erstmals auch in der Schweiz angeboten. Allfit kombiniert Gruppenschulung, Gymnastik und Einzelberatung und wird von Fachpersonen unterschiedlicher Disziplinen unter Leitung der Pflege geleitet. Anhand von offenen Interviews mit 16 Teilnehmenden aus Diabetes- und Rheumakursen und qualitativer Inhaltsanalyse wurde der Frage nach der Wirkungsweise von allfit nachgegangen. Gefunden wurden pro Teilnehmende mehrere Auswirkungen sowie der Weg, wie die Auswirkungen zustande kamen: 1. Verschiedene Anstöße im Kurs, u.a. eindrückliche Erlebnisse, Austausch in der Gruppe und Vorbilder setzen eine Veränderung in Gang. 2. Nur mit bestimmten Zwischenschritten, wie der Revision von Überzeugungen, gehen die Pfade weiter. 3. Die resultierenden Veränderungen können zwei Bereichen zugeordnet werden: Verhaltensänderung im Selbstmanagement und Erleichterung in der Krankheitsverarbeitung. 4. Tragende Faktoren wie Erinnerungen gereichen wahrscheinlich zur Nachhaltigkeit. Mit der vorliegenden Studie wird gezeigt, dass in allfit in hohem Maße soziales und praktisches Lernen stattfindet und ein großer Teil der Wirksamkeit dem Gruppensetting zuzuordnen ist.
Effekt einer Schulung in Aggressionsmanagement bei Schülerinnen und Schülern in der Pflegeausbildung
Authors: Zeller Adelheid , Needham Ian , Halfens Ruud
Published: August 2006

Das Ziel dieser Studie war die Überprüfung des Effekts einer Schulung in Aggressionsmanagement bei Schülerinnen und Schülern in der Pflegeausbildung. Folgende Frage bildete die Ausgangslage dieser Untersuchung: Fühlen sich Schülerinnen und Schüler einer vierjährigen Pflegegrundausbildung nach einer Schulung in Aggressionsmanagement kompetenter und sicherer im Umgang mit aggressivem Verhalten von Patientinnen und Patienten als vor der Schulung? Mit einem quasi-experimentellen Design wurde der Effekt der Schulung bezüglich Kompetenzerwartung und Sicherheitsgefühl der Schülerinnen und Schüler überprüft. Die Experimentalgruppe (n = 57) absolvierte eine viertägige Schulung in Aggressionsmanagement. Die Kontrollgruppe (n = 60), welche in diesem Zeitraum keinen vergleichbaren Unterricht erhielt, wurde in den gleichen Zeitabständen wie die Experimentalgruppe befragt. Die Auswertung der Daten mit univariater Varianzanalyse mit Messwiederholung zeigte, dass im Vergleich mit der Kontrollgruppe die Schülerinnen und Schüler der Experimentalgruppe sich nach der Schulung bezüglich ihren Kompetenzerwartungen signifikant höher (p ≤ 0.001) einschätzen als vor der Schulung. In der Einschätzung des Sicherheitsgefühls ist ebenfalls eine Verbesserung ersichtlich, wobei hier nicht in allen Bereichen eine statistische Signifikanz nachgewiesen werden konnte. Trotzdem lassen die Einschätzungen der Schulungsteilnehmerinnen und -teilnehmer darauf schließen, dass sie sich nach dem Besuch der Schulung im Umgang mit aggressivem Verhalten von Patientinnen und Patienten sicherer fühlen. Die Ergebnisse zeigen, dass durch die Schulung eine Verbesserung bezüglich der Kompetenzerwartungen und des Sicherheitsgefühls bei Schülerinnen und Schülern in der Pflegeausbildung erreicht werden kann.
Extremely long baseline interplanetary scintillation measurements of solar wind velocity
Authors: Breen A. R. , Fallows R. A. , Bisi M. M. , Thomasson P. , Jordan C. A. , Wannberg G. , Jones R. A.
Published: August 2006

We present results of observations of interplanetary scintillation (IPS) made using the telescopes of the MERLIN and EISCAT networks in which the beam separation approached 2000 km, much larger than in any previous IPS experiments. Significant correlation between the scintillation patterns was observed at time lags of up to 8 s and fast and slow streams of solar wind were very clearly resolved. One observation showed clear evidence of two discrete modes of fast solar wind, which we interpret as originating in the crown of the northern polar coronal hole and in an equatorward extension of the polar hole. We suggest that experiments of this type will provide a new and important source of information on the temporal and spatial variation of small‐scale turbulence in the solar wind. The improved velocity resolution available from extremely long baseline measurements also provides new information on the development of the large‐scale velocity structure of the solar wind in interplanetary space.
Saharan dust intrusions in the Mediterranean area: Three years of Raman lidar measurements
Authors: Mona Lucia , Amodeo Aldo , Pandolfi Marco , Pappalardo Gelsomina
Published: August 2006

A multiyear climatological study of Saharan dust intrusions in the central Mediterranean in terms of aerosol optical parameters vertical profiles is carried out for the first time. Observations are performed at Istituto di Metodologie per l'Analisi Ambientale (IMAA) Raman/elastic lidar station located in Tito Scalo, Potenza (40°36′N, 15°44′E), from May 2000 to April 2003, in the framework of European Aerosol Research Lidar Network (EARLINET). Desert dust aerosols are observed between 1.8 and 9 km in 112 days. Mean values within the desert dust layer of 76 Mm−1, 1.0 Mm−1 sr−1 and 0.54 Mm−1 sr−1 are observed for aerosol extinction at 355 nm and aerosol backscatter at 355 and 532 nm. Desert dust layer optical depth at 355 nm ranges between 0.001 and 0.68, with a mean of 0.13. The source origin is the central Sahara in about 65% of the cases, the western Sahara in about 31%, and only in four cases the eastern Sahara. The most extended database of Saharan dust lidar ratio data was collected: Values range between 6 and 126 sr following a 3‐modal Gaussian distribution centered at 22, 37 and 57 sr. A mean value of 37 sr is found around the center of the Saharan dust layer. At its extremes, where dust particles are mixed to PBL and free troposphere background aerosols, a mean value of 57 sr is found. Finally, low lidar ratio values of about 22 sr are observed when large amount of dust is transported at low altitudes over the Mediterranean Sea.
Climate variability in a simple model of warm climate land‐atmosphere interaction
Authors: Wei Jiangfeng , Dickinson Robert E. , Zeng Ning
Published: August 2006

A simple model is developed to describe the significant land‐atmosphere interaction processes in the warm climate. It includes bulk soil hydrology, dynamic vegetation, and simple land‐atmosphere interaction processes. The model can simulate the basic features of land surface control on evapotranspiration (ET) and exhibits a multiequilibrium behavior similar to that of some more complex models. In order to study the role of land surface processes in climate variability on monthly to seasonal timescales, a series of experiments are performed with the model over different land covers and at different external forcings. The major findings are: (1) The maximum soil wetness memory and precipitation predictability tend to occur at a sparser (denser) vegetation cover with the weakening (strengthening) of external forcing. (2) For vegetated region, the soil moisture memory and precipitation persistence will be underestimated if vegetation is not interactive, and the percentage of underestimation is larger over denser vegetation covers. (3) Interactive vegetation can enhance the low‐frequency coherency between soil wetness and precipitation, but its influence on high‐frequency coherency is small. (4) Large coherencies between soil wetness and precipitation in the time‐frequency domain correspond to strong wavelet power of external forcing in the same domain. These findings provide guidance for the development of and study with more complex models.
Ocean warming and freshening in the northern Gulf of Alaska
Authors: Royer Thomas C. , Grosch Chester E.
Published: August 2006

Water column temperatures on the shelf in the northern Gulf of Alaska have increased more than 0.8°C and vertical density stratification has increased since 1970 near Seward, Alaska throughout the 250 m depth. This high latitude marine system has low water temperatures, high rates of precipitation, glacial melting, high wind speeds and high rates of biological productivity. A more than 300 km alongshore shift (locally westward) of isotherms is suggested. The observations are consistent with a conceptual ocean‐atmosphere circulation model that employs coastal freshwater discharge, glacial ablation and wind forcing. Positive regional feedback mechanisms accelerate the discharge and poleward heat flux, leading to even higher temperatures, increased ocean stratification and increased storminess. This warming and ocean freshening will have significant impacts on the atmosphere and marine ecosystems of the Northeast Pacific, Bering Sea, Arctic Ocean and quite possibly global ocean circulation.
Exchange of sea ice between the Arctic Ocean and the Canadian Arctic Archipelago
Authors: Kwok Ron
Published: August 2006

First estimates of sea ice exchange between the Arctic Ocean and the Canadian Arctic Archipelago (CAA) are obtained using six years (1997–2002) of RADARSAT ice motion. Over the period, the mean annual flux of sea ice area from the Amundsen Gulf (AG), M'Clure Strait (MS), and Queen Elizabeth Islands (QEI) are −85 ± 26 × 103, −20 ± 24 × 103, and 8 ± 6 × 103 km2. Positive/negative sign indicates Arctic outflow/inflow. Overall, net sea ice area is exported from the CAA; rough estimates suggest a mean annual volume flux of ∼102 km3 into the Canada Basin. Ice types are largely seasonal near the AG flux gate, mixed seasonal and multiyear at the MS gate, and primarily multiyear at the QEI gates. Sea ice at the QEI flux gates remains land fast for most of the year. Cross‐strait gradient in sea level pressure explains more than 50% of the variance in the area flux at these passages. The role of ice exchange during the anomalous decrease in multiyear ice coverage in the Sverdrup Basin during September 1998 is examined.
Southern Hemisphere carbon monoxide interannual variability observed by Terra/Measurement of Pollution in the Troposphere (MOPITT)
Authors: Edwards D. P. , Pétron G. , Novelli P. C. , Emmons L. K. , Gille J. C. , Drummond J. R.
Published: August 2006

Biomass burning is an annual occurrence in the tropical Southern Hemisphere (SH) and represents a major source of regional pollution. Vegetation fires emit carbon monoxide (CO), which because of its medium lifetime is an excellent tracer of tropospheric transport. CO is also one of the few tropospheric trace gases currently observed from satellite, and this provides long‐term global measurements. In this paper, we use the 5‐year CO data record from the Measurement of Pollution in the Troposphere (MOPITT) instrument to examine the interannual variability of the SH CO loading and show how this relates to climate conditions which determine the intensity of fire sources. The MOPITT observations show an annual austral springtime peak in the SH zonal CO loading each year with dry season biomass burning emissions in South America, southern Africa, the maritime continent, and northwestern Australia. Although fires in southern Africa and South America typically produce the greatest amount of CO, the most significant interannual variation is due to varying fire activity and emissions from the maritime continent and northern Australia. We find that this variation in turn correlates well with the El Niño–Southern Oscillation precipitation index. Between 2000 and 2005, emissions were greatest in late 2002, and an inverse modeling of the MOPITT data using the Model of Ozone Research in the Troposphere (MOZART) chemical transport model estimates the Southeast Asia regional fire source for the year August 2002 to September 2003 to be 52 Tg CO. Comparison of the MOPITT retrievals and NOAA surface network measurements indicate that the latter do not fully capture the interannual variability or the seasonal range of the CO zonal average concentration because of biases associated with atmospheric and geographic sampling.
Comparison and validation of the aerosol optical depth obtained with the Langley plot method in the UV‐B from Brewer Ozone Spectrophotometer measurements
Authors: Cheymol Anne , De Backer Hugo , Josefsson Weine , Stübi René
Published: August 2006

The Aerosol Optical Depths (AODs) retrieved from Brewer Ozone Spectrophotometer measurements with a method previously developed (Cheymol and De Backer, 2003) are now validated by comparisons between AODs from six Brewer spectrophotometers and two CSEM SPM2000 sunphotometers: two Brewer spectrophotometers 016 and 178 at Uccle in Belgium; one Brewer spectrophotometer 128 and one sunphotometer CSEM SPM2000 at Norrköping in Sweden; and three Brewer instruments 040, 072, 156 at Arosa and one CSEM SPM2000 sunphotometer at Davos in Switzerland. The comparison between AODs from Brewer spectrophotometer 128 at 320.1 nm and sunphotometer SPM2000 at 368 nm at Norrköping shows that the AODs obtained from the Brewer measurements with the Langley Plot Method (LPM) are very accurate if the neutral density filter spectral transmittances are well known: with the measured values of these filters, the correlation coefficient, the slope, and the intercept of the regression line are 0.98, 0.85 ± 0.004, and 0.02 ± 0.0014, respectively. The bias observed is mainly owing to the wavelength difference between the two instruments. The comparison between AODs from different Brewer spectrophotometers confirm that AODs will be in very good agreement if they are measured with several Brewer instruments at the same place: At Uccle, the correlation coefficient, slope, and intercept of the regression line are 0.98, 1.02 ± 0.003, and 0.06 ± 0.001, respectively; at Arosa, the comparisons between the AODs from three Brewer spectrophotometers 040, 072, and 156 give a correlation coefficient, a slope, and an intercept of the regression line above 0.94, 0.98 and below 0.04, respectively.
Direct and indirect effects of atmospheric conditions and soil moisture on surface energy partitioning revealed by a prolonged drought at a temperate forest site
Authors: Gu Lianhong , Meyers Tilden , Pallardy Stephen G. , Hanson Paul J. , Yang Bai , Heuer Mark , Hosman Kevin P. , Riggs Jeffery S. , Sluss Dan , Wullschleger Stan D.
Published: August 2006

The purpose of this paper is to examine the mechanism that controls the variation of surface energy partitioning between latent and sensible heat fluxes at a temperate deciduous forest site in central Missouri, USA. Taking advantage of multiple micrometeorological and ecophysiological measurements and a prolonged drought in the middle of the 2005 growing season at this site, we studied how soil moisture, atmospheric vapor pressure deficit (VPD), and net radiation affected surface energy partitioning. We stratified these factors to minimize potential confounding effects of correlation among them. We found that all three factors had direct effects on surface energy partitioning, but more important, all three factors also had crucial indirect effects. The direct effect of soil moisture was characterized by a rapid decrease in Bowen ratio with increasing soil moisture when the soil was dry and by insensitivity of Bowen ratio to variations in soil moisture when the soil was wet. However, the rate of decrease in Bowen ratio when the soil was dry and the level of soil moisture above which Bowen ratio became insensitive to changes in soil moisture depended on atmospheric conditions. The direct effect of increased net radiation was to increase Bowen ratio. The direct effect of VPD was very nonlinear: Increased VPD decreased Bowen ratio at low VPD but increased Bowen ratio at high VPD. The indirect effects were much more complicated. Reduced soil moisture weakened the influence of VPD but enhanced the influence of net radiation on surface energy partitioning. Soil moisture also controlled how net radiation influenced the relationship between surface energy partitioning and VPD and how VPD affected the relationship between surface energy partitioning and net radiation. Furthermore, both increased VPD and increased net radiation enhanced the sensitivity of Bowen ratio to changes in soil moisture and the effect of drought on surface energy partitioning. The direct and indirect effects of atmospheric conditions and soil moisture on surface energy partitioning identified in this paper provide a target for testing atmospheric general circulation models in their representation of land‐atmosphere coupling.
CAESURA: Measurement of slow molecular dynamics by solid-state nuclear magnetic resonance chemical shift anisotropy modulation amplification
Authors: Shao Limin , Titman Jeremy J.
Published: August 2006

An alternative magic angle spinning (MAS) exchange NMR experiment based on chemical shift anisotropy (CSA) amplification is described. The CSA amplification experiment correlates a standard MAS spectrum in the ω2 dimension with a sideband pattern in ω1 in which the intensities are identical to those expected for a sample spinning at some fraction 1∕N of the actual rate ωr. In common with 2D-PASS, the isotropic shift appears only in the ω2 dimension, and long acquisition times can be avoided without loss of resolution of different chemical sites. The new CSA amplification exchange experiment provides information about the time scale and geometry of molecular motions via their effect on the sideband intensities in a one-dimensional pattern. The one-dimensional patterns from different chemical sites are separated across two frequency dimensions according to the isotropic shifts.
Dynamics of X+CH4 (X=H,O,Cl) reactions: How reliable is transition state theory for fine-tuning potential energy surfaces?
Authors: Varandas A. J. C. , Caridade P. J. S. B. , Zhang J. Z. H. , Cui Q. , Han K. L.
Published: August 2006

Trajectory calculations run on global potential energy surfaces have shown that the topology of the entrance channel has strong implications on the dynamics of the title reactions. This may explain why huge differences are observed between the rate constants calculated from global dynamical methods and those obtained from local methods that employ the same potential energy surfaces but ignore such topological details. Local dynamics approaches such as transition state-based theories should then be used with caution for fine-tuning potential energy surfaces, especially for fast reactions with polyatomic species since the key statistical assumptions of the theory may not be valid for all degrees of freedom.
Constrained dynamics and extraction of normal modes from ab initio molecular dynamics: Application to ammonia
Authors: Siddick M. M. , Ackland G. J. , Morrison C. A.
Published: August 2006

We present a methodology for extracting phonon data from ab initio Born-Oppenheimer molecular dynamics calculations of molecular crystals. Conventional ab initio phonon methods based on perturbations are difficult to apply to lattice modes because the perturbation energy is dominated by intramolecular modes. We use constrained molecular dynamics to eliminate the effect of bond bends and stretches and then show how trajectories can be used to isolate and define in particular, the eigenvalues and eigenvectors of modes irrespective of their symmetry or wave vector. This is done by k-point and frequency filtering and projection onto plane wave states. The method is applied to crystalline ammonia: the constrained molecular dynamics allows a significant speedup without affecting structural or vibrational modes. All Γ point lattice modes are isolated: the frequencies are in agreement with previous studies; however, the mode assignments are different.
Mode-selective O–H stretching relaxation in a hydrogen bond studied by ultrafast vibrational spectroscopy
Authors: Kozich Valeri , Dreyer Jens , Ashihara Satoshi , Werncke Wolfgang , Elsaesser Thomas
Published: August 2006

The ultrafast relaxation of the excited O–H stretching vibration is studied by ultrafast infrared-pump/infrared-probe and infrared-pump/Raman-probe spectroscopy. We demonstrate a 200fs lifetime of the hydrogen-bonded O–H stretching mode in 2-(2′-hydroxy-5′-methyl-phenyl)benzotriazole (TINUVIN P). O–H stretching relaxation occurs through a few major channels that all involve combination and overtone bands of modes with considerable in-plane O–H bending character. In particular, the mode, which contains the largest O–H bending contribution, plays a prominent role for primary processes of intramolecular vibrational energy redistribution. Theoretical calculations of vibrational energy transfer rates based on a Fermi golden rule approach account for the experimental findings.
Automerization reaction of cyclobutadiene and its barrier height: An ab initio benchmark multireference average-quadratic coupled cluster study
Authors: Eckert-Maksić Mirjana , Vazdar Mario , Barbatti Mario , Lischka Hans , Maksić Zvonimir B.
Published: August 2006

The problem of the double bond flipping interconversion of the two equivalent ground state structures of cyclobutadiene (CBD) is addressed at the multireference average-quadratic coupled cluster level of theory, which is capable of optimizing the structural parameters of the ground, transition, and excited states on an equal footing. The barrier height involving both the electronic and zero-point vibrational energy contributions is 6.3kcalmol−1, which is higher than the best earlier theoretical estimate of 4.0kcalmol−1. This result is confirmed by including into the reference space the orbitals of the CC σ bonds beyond the standard π orbital space. It places the present value into the middle of the range of the measured data (1.6–10kcalmol−1). An adiabatic singlet-triplet energy gap of 7.4kcalmol−1 between the transition state Btg1 and the first triplet A2g3 state is obtained. A low barrier height for the CBD automerization and a small ΔE(A2g3,B1g1) gap bear some relevance on the highly pronounced reactivity of CBD, which is briefly discussed.
Renner-Teller quantum dynamics of the N(D2)+H2→NH+H reaction
Authors: Defazio Paolo , Petrongolo Carlo
Published: August 2006

We present the Born-Oppenheimer (BO) and Renner-Teller (RT) quantum dynamics of the reaction N14(D2)+H21(X̃Σg+1)→NH(X̃Σ−3)+H(S2), considering the NH2 electronic states X̃B12 and ÃA12. These states correlate to the same Πu2 linear species, are coupled by RT nonadiabatic effects, and give NH(X̃Σ−3)+H and NH(ãΔ1)+H, respectively. We develop the Hamiltonian matrix elements in the R embedding of the Jacobi coordinates and in the adiabatic electronic representation, using the permutation-inversion symmetry, and taking into account the nuclear-spin statistics. Collision observables are calculated via the real wave-packet (WP) and flux methods, using the potential-energy surfaces of Santoro et al. [J. Phys. Chem. A 106, 8276 (2002)]. WP snapshots show that the reaction proceeds via an insertion mechanism, and that the RT-WP avoids the ÃA12 potential barrier, jumping from the excited to the ground surface and giving mainly the NH(X̃Σ−3) products. X̃B12 BO probabilities and cross sections show large tunnel effects and are approximately four to ten times larger than the ÃA12 ones. This implies a BO rate-constant ratio k(X̃B12)∕k(ÃA12)≈105 at 300K, i.e., a negligible BO formation of NH(ãΔ1). When H2 is rotationally excited, RT couplings reduce slightly the X̃B12 reaction observables, but enhance strongly the ÃA12 reactivity. These couplings are important at all collision energies, reduce the collision threshold, and increase remarkably reaction probabilities and cross sections. The RT k(ÃA12) is thus ∼3.3 order of magnitude larger than the BO value, and degeneracy-averaged, initial-state-resolved rate constants increase by ∼13% and by ∼47% at 300 and 500K, respectively. Owing to an overestimation of the X̃B12 potential barrier, the calculated thermal rate is too low with respect to that observed, but we obtain a good agreement by shifting down the calculated cross section.
Nonlinear stability of boundary layers of the Boltzmann equation for cutoff hard potentials
Authors: Wang Weike , Yang Tong , Yang Xiongfeng
Published: August 2006

Many physical models have boundaries. For the Boltzmann equation, the study on the boundary layer in the region of the width in the order of the Kundsen number along the boundary is important both in mathematics and physics. In this paper, we consider the nonlinear stability of boundary layer solutions to the Boltzmann equation for hard potentials with angular cut-off. The boundary condition is imposed on incoming particles of the Dirichlet type and the solution tends to a global Maxwellian in the far field. For the existence of the boundary layer solutions, it is proved by Chen et al. [Anal. Appl. 2, 337–363 (2004)] by introducing a weight function which is a function of both position and velocity to overcome the difficulty from the sublinear growth in the collision frequency. Unlike the hard sphere model, even for stability in the case when the Mach number of the far field is less than −1, exponential decay in time cannot be expected for the cutoff hard potentials. Instead, an algebraic decay in time to the boundary layer solution is proved in this paper by using some recursive weighted energy estimates and the bootstrap argument.
Separation of unistochastic matrices from the double stochastic ones: Recovery of a 3×3 unitary matrix from experimental data
Authors: Diţă Petre
Published: August 2006

The aim of the paper is to provide a constructive method for recovering a unitary matrix from experimental data. Since there is a natural immersion of unitary matrices within the set of double stochastic ones, the problem to solve is to find necessary and sufficient criteria that separate the two sets. A complete solution is provided for the three-dimensional case, accompanied by a χ2 test necessary for the reconstruction of a unitary matrix from error affected data.
Structure formation and fractionation in systems of polydisperse attractive rods
Authors: Richter Andreas , Gruhn Thomas
Published: August 2006

Fractionation effects and the formation of structured domains are investigated in polydisperse systems of attractive spherocylinders with the help of Monte Carlo simulations. For sufficiently high attractive interaction strength and pressure, the large rods in the system aggregate and form a highly ordered hexatic monolayer that coexists with an isotropic fluid of smaller rods. Fractionation diminishes with decreasing interaction strength but is still observed for hard rod systems, in which the large rods form a nematic droplet rather than a monolayer. Results for polydisperse systems are accompanied by phase diagrams for monodisperse systems of attractive spherocylinders. Here, the phase behavior is shown as a function of rod length and pressure.
Nonlinear electromagnetic plasma eigenmodes and their stability to stimulated Raman scattering
Authors: Pathak Vishwa Bandhu , Tripathi V. K.
Published: August 2006

Transverse mode structure of nonlinear laser eigenmodes in underdense and overdense plasmas has been obtained by numerically solving the wave equation under relativistic and ponderomotive nonlinearities. The mode structure closely resembles a Lorentzian with half width scaling inversely as the axial intensity of the laser. The threshold condition for laser penetration in an overdense plasma turns out to be γ0≡(1+a02∕2)1∕2⩾2n0∕ncr−1, where n0 is the equilibrium electron density, ncr is the critical density at laser frequency, and γ0 is the electron Lorentz factor due to the laser of normalized axial intensity a02. The nonlinear laser eigenmode, in a low density plasma, is unstable to stimulated Raman backscattering off a copropagating space charge reactive quasimode. The growth rate increases with laser intensity as a0 rises up to a0∼1. Beyond this value, growth rate decreases with a0, due to the enhancement of electron mass and depletion of electrons from the axial region. Geometrical effects also reduce the growth rate.
Fragility and thermodynamics in nonpolymeric glass-forming liquids
Authors: Wang Li-Min , Angell C. Austen , Richert Ranko
Published: August 2006

For nonpolymeric supercooled liquids, the empirical correlation m=56TgΔCp(Tg)∕ΔHm provides a reliable means of correlating dynamic and thermodynamic variables. The dynamics are characterized by the fragility or steepness index m and the glass transition temperature Tg, while thermodynamics enter in terms of the heat capacity step ΔCp at Tg and the melting enthalpy ΔHm. The combination of the above correlation with the 2∕3 rule for the Tg∕Tm ratio yields an expression, m=40ΔCp(Tg)∕ΔSm, which was rationalized as the correlation of the thermodynamic and kinetic fragilities. Defining a thermodynamic fragility via ΔCp(Tg)∕ΔSm also reveals that the slopes in Kauzmann’s original ΔS(T)∕ΔSm versus T∕Tm plot reflect the fragility concept [Chem. Rev. 43, 219 (1948)], so long as Tm∕Tg=1.5. For the many liquids whose excess heat capacity is a hyperbolic function of temperature, we deduce that the fragility cannot exceed m=170, unless the Tg∕Tm=2∕3 rule breaks down.
Origin invariant approaches to the calculation of two-photon circular dichroism
Authors: Rizzo Antonio , Jansík Branislav , Pedersen Thomas Bondo , Ågren Hans
Published: August 2006

The origin dependence of the expression of two-photon circular dichroism in the length formulation employed by the authors in a recent computational study [B. Jansík et al., Chem. Phys. Lett. 414, 461 (2005)] is discussed in detail, and some inherently origin invariant alternative formulations are introduced. Extensive computational tests on a small reference chiral system, namely, a chiral form of H2O2, are performed at the density functional theory (DFT)/B3LYP level of theory with large diffuse correlation consistent basis sets. The results indicate that the velocity formulation originally proposed by Tinoco, Jr. [J. Chem. Phys. 62, 1006 (1975)] provides the most convenient approach for an origin invariant calculation of two-photon circular dichroism.
Non-Born-Oppenheimer variational calculation of the ground-state vibrational spectrum of LiH+
Authors: Bubin Sergiy , Adamowicz Ludwik
Published: August 2006

Very accurate, rigorous, variational, non-Born-Oppenheimer (non-BO) calculations have been performed for the fully symmetric, bound states of the LiH+ ion. These states correspond to the ground and excited vibrational states of LiH+ in the ground Σ+2 electronic state. The non-BO wave functions of the states have been expanded in terms of spherical N-particle explicitly correlated Gaussian functions multiplied by even powers of the internuclear distance and 5600 Gaussians were used for each state. The calculations that, to our knowledge, are the most accurate ever performed for a diatomic system with three electrons have yielded six bound states. Average interparticle distances and nucleus-nucleus correlation function plots are presented.
Simulation of high-energy particle production through sausage and kink instabilities in pinched plasma discharges
Authors: Haruki Takayuki , Yousefi Hamid Reza , Masugata Katsumi , Sakai Jun-Ichi , Mizuguchi Yusuke , Makino Nao , Ito Hiroaki
Published: August 2006

In an experimental plasma, high-energy particles were observed by using a plasma focus device, to obtain energies of a few hundred keV for electrons, up to MeV for ions. In order to study the mechanism of high-energy particle production in pinched plasma discharges, a numerical simulation was introduced. By use of a three-dimensional relativistic and fully electromagnetic particle-in-cell code, the dynamics of a Z-pinch plasma, thought to be unstable against sausage and kink instabilities, are investigated. In this work, the development of sausage and kink instabilities and subsequent high-energy particle production are shown. In the model used here, cylindrically distributed electrons and ions are driven by an external electric field. The driven particles spontaneously produce a current, which begins to pinch by the Lorentz force. Initially the pinched current is unstable against a sausage instability, and then becomes unstable against a kink instability. As a result high-energy particles are observed.
Low-energy electron scattering by deoxyribose and related molecules
Authors: Winstead Carl , McKoy Vincent
Published: August 2006

We apply first-principles computational methods to study elastic scattering of low-energy electrons by 2-deoxyribose and 2-deoxyribose monophosphate, which are of interest as components of the DNA backbone, and to tetrahydrofuran (THF), which has been studied as a deoxyribose analog. To investigate the dependence of the scattering process on the molecular conformation, we examine Cs and C2 conformers of THF as well as the planar C2v geometry imposed in earlier calculations. There is little difference between the elastic cross sections determined at the nonplanar geometries, but there are noticeable differences between those results and the cross sections computed using the planar ring. By comparing results for tetrahydrofuran obtained with and without inclusion of polarization effects, we obtain energy shifts that are applied to the computed resonance positions for deoxyribose and deoxyribose monophosphate.
Nitride-based high electron mobility transistors with a GaN spacer
Authors: Palacios T. , Shen L. , Keller S. , Chakraborty A. , Heikman S. , DenBaars S. P. , Mishra U. K. , Liberis J. , Kiprijanovic O. , Matulionis A.
Published: August 2006

A GaN/ultrathin AlN∕GaN heterojunction has been used to introduce a GaN spacer between the GaN channel and the AlGaN barrier in AlGaN∕GaN high electron mobility transistors (HEMTs). In conventional AlGaN∕GaN devices, the alloy scattering of the electrons with the AlGaN barrier degrades the electron velocity at high electric fields. This effect is significantly reduced in GaN-spacer transistors, which therefore have much better high field transport properties. While the dc performance of these transistors is similar to conventional AlGaN∕GaN HEMTs, a 20% increase in the electron velocity has been measured by two different techniques.
Synthesis of large-scale GaN nanobelts by chemical vapor deposition
Authors: Xu Bingshe , Yang Dong , Wang Fei , Liang Jian , Ma Shufang , Liu Xuguang
Published: August 2006

GaN nanobelts were synthesized in mass by direct reaction of metallic gallium with flowing ammonia using nickel as a catalyst. X-ray diffraction, field emission scanning electron microscope equipped with an energy dispersive spectroscopy, and high resolution transmission electron microscopy were used to characterize the products. The results showed that the products are of hexagonal wurtzite structure. The widths of nanobelts were in the range of 50–200nm with the thickness ranging from 3to10nm and their lengths up to several tens of microns. The catalytic growth mechanism of the GaN nanobelts was also discussed.
Electrical-stress-induced conductivity increase in SrTiO3 films
Authors: Karg S. , Meijer G. I. , Widmer D. , Bednorz J. G.
Published: August 2006

The charge transport of polycrystalline SrTiO3 films doped with Cr is investigated by means of temperature- and electric-field-dependent current measurements. In particular, the effect of electrical stress on the conduction mechanism is analyzed to understand the forming process of samples exhibiting resistance-switching phenomena. The temperature dependence of the conductivity can be described with the variable-range hopping model. The electrical-stress-induced conductivity increase of SrTiO3:Cr films is accompanied by a change of the temperature dependence corresponding to a significant increase of the density of localized states.
Quantifying the elastic deformation behavior of bridged nanobelts
Authors: Mai Wenjie , Wang Zhong Lin
Published: August 2006

A new approach for quantifying the elastic deformation behavior of one-dimensional nanostructures is presented by fitting the image profile measured using atomic force microscopy in contact mode along the entire length of a bridged/suspended nanobelt/nanowire/nanotube under different load forces. Consistently fitting the measured deformation profiles can uniquely determine if the measured data are best explained by either the clamped-clamped beam model or the free-free beam model without preassumption, and it eliminates the uncertainty in defining the central point of the suspended beam, thus, greatly increasing the precision and reliability of the measurements.
Room temperature gas sensitivity of ultrathin SnO2 films prepared from Langmuir-Blodgett film precursors
Authors: Choudhury Sipra , Betty C. A. , Girija K. G. , Kulshreshtha S. K.
Published: August 2006

The authors report the room temperature gas sensitivity of ultrathin SnO2 films prepared by thermal decomposition of multilayer Langmuir-Blodgett (LB) films. The SnO2 films, which are characterized by various spectroscopic techniques and electrical measurements, have been shown to sense ammonia gas at room temperature with fast response and recovery. The presence of a large number of surface states in the ultrathin SnO2 film is responsible for the room temperature gas sensitivity. Present results demonstrate the potential of LB technique to fabricate high quality ultrathin oxide films useful for sensor applications.
Magnetization depth dependence in exchange biased thin films
Authors: Morales R. , Li Zhi-Pan , Petracic O. , Batlle X. , Schuller Ivan K. , Olamit Justin , Liu Kai
Published: August 2006

The depth dependence of the magnetization has been studied in antiferromagnet/ferromagnet (AF/FM) exchange coupled systems. Results from vector magnetometry and magneto-optical Kerr effect probing both the AF/FM and FM/air interfaces demonstrate the existence of a magnetization depth profile in FeF2∕FM (FM=Fe, Ni, and Py) bilayers, contrary to the assumptions of most exchange bias models. The appearance of asymmetrical hysteresis loops below the AF Néel temperature (TN) is explained by the creation of spring-like walls parallel to the AF/FM interface and the existence of incomplete domain walls. Changes in the reversal mechanism above TN have also been discussed.
Suppression of interfacial reaction for HfO2 on silicon by pre-CF4 plasma treatment
Authors: Lai Chao Sung , Wu Woei Cherng , Chao Tien Sheng , Chen Jian Hao , Wang Jer Chyi , Tay Li-Lin , Rowell Nelson
Published: August 2006

In this letter, the effects of pre-CF4 plasma treatment on Si for sputtered HfO2 gate dielectrics are investigated. The significant fluorine was incorporated at the HfO2∕Si substrate interface for a sample with the CF4 plasma pretreatment. The Hf silicide was suppressed and Hf–F bonding was observed for the CF4 plasma pretreated sample. Compared with the as-deposited sample, the effective oxide thickness was much reduced for the pre-CF4 plasma treated sample due to the elimination of the interfacial layer between HfO2 and Si substrate. These improved characteristics of the HfO2 gate dielectrics can be explained in terms of the fluorine atoms blocking oxygen diffusion through the HfO2 film into the Si substrate.
Transport properties of the thermoelectric layered cobalt oxide Pb–Sr–Co–O single crystals
Authors: Kobayashi W. , Terasaki I.
Published: August 2006

The authors have synthesized single-crystal samples of the layered cobalt oxide Pb–Sr–Co–O and measured resistivity, thermopower, and Hall coefficient from 4.2to300K. The resistivity, the thermopower, and the Hall coefficient are 13mΩcm, 150μV∕K, and 1.6×10−2cm3∕C at 300K, respectively, which are typical values for a misfit-layered cobalt oxide. The thermopower and resistivity are associated with spin density wave, and a close relationship between the pseudogap temperature and the thermopower is suggested for all the misfit-layered cobalt oxides.
Migration and redistribution of oxygen vacancy in barium titanate ceramics
Authors: Chen L. , Xiong X. M. , Meng H. , Lv P. , Zhang J. X.
Published: August 2006

Degradation of barium titanate based multilayer capacitor mainly results from migration and redistribution of oxygen vacancy. For barium titanate ceramics, the authors observe an internal friction relaxation peak around 70°C due to oxygen vacancy, and its relaxation strength differs greatly for specimen aged at 85°C for 120h and at 150°C for 5h. Two possible explanations are proposed, one based on symmetry-conforming short-range order while the other on the interaction between oxygen vacancy and domain wall during aging process. In any case, relaxation thermodynamics is a powerful tool to investigate the migration and redistribution of oxygen vacancy in barium titanate ceramics.
Remanent electrical spin injection from Fe into AlGaAs∕GaAs light emitting diodes
Authors: van ’t Erve O. M. J. , Kioseoglou G. , Hanbicki A. T. , Li C. H. , Jonker B. T.
Published: August 2006

We compare surface and edge emission electroluminescence of spin-polarized light emitting diodes with Fe contacts. The edge emission geometry permits transduction of the spin state variable between the electron spin and optical polarization utilizing the in-plane remanent magnetization and low coercive fields of the metal contacts. The spin injection efficiencies are similar for electron spins oriented normal to the surface plane and in plane. The lower circular polarization consistently observed in edge emission at low magnetic fields is attributed to a partial out-of-plane orientation of the heavy hole angular momentum which persists even in wide quantum wells.