bluuebunny/crossref_metadata_2025 huggingface dataset:
Review of recent research (2000–2008) on applied linguistics and language teaching with specific reference to L2 Italian
Authors: Macaro Ernesto
Published: March 2010

L'apprendimento della lingua italiana come lingua straniera (L2), probabilmente per motivazioni storico-culturali, è di carattere specialistico. Di conseguenza, l'impronta globale della lingua italiana, rispetto ad altre lingue straniere come l'inglese, lo spagnolo ed il francese, risulta essere abbastanza limitata. Sorprende quindi il fatto che in diversi progetti di ricerca, nel campo della linguistica applicata e dell'apprendimento delle L2, l'italiano sia la lingua studiata dai partecipanti oggetto di studio. Questa rassegna di studi verte ad identificare gli approfondimenti della ricerca nel campo dell'apprendimento della lingua italiana come seconda lingua piuttosto che il contributo dell'italiano alla teoria della SLA in genere. Inoltre, ha l'obbiettivo di valutare lo stato attuale della lingua italiana nell'ambito dell'istruzione formale. L'autore suggerisce la presenza di un rapporto tra la comprensione del processo di apprendimento della lingua italiana e la richiesta dell'italiano come L2. Questa rassegna riassume e categorizza quasi settanta studi condotti in una varietà di contesti educativi e offre proposte e stimoli per futuri progetti di ricerca.

Italian has for many years been considered somewhat of a specialist language when studied as a second language (L2) and this is perhaps due to historical and cultural factors. Its footprint worldwide compared to such languages as English, Spanish and French is therefore somewhat limited. Surprisingly, however, there is a considerable body of research in applied linguistics and second language acquisition (SLA) in which Italian features as the language being studied. This review sought to identify the extent to which the research provided specific insights into how Italian as a second or foreign language (L2 Italian) is learnt as opposed to the ways in which it has contributed to SLA theory-building more generally. In addition, it sought to assess how well Italian is holding up as a language being learnt in formal instructed contexts. The author suggests that insights into the learning of Italian and uptake by Italian students may be inter-related. The present review summarises and categorises nearly seventy empirical studies conducted in a variety of educational contexts and offers suggestions for future avenues of research.
Foreign and second language anxiety
Authors: Horwitz Elaine K.
Published: March 2010

The possibility that anxiety interferes with language learning has long interested scholars, language teachers, and language learners themselves. It is intuitive that anxiety would inhibit the learning and/or production of a second language (L2). The important term in the last sentence is ‘anxiety’. The concept of anxiety is itself multi-faceted, and psychologists have differentiated a number of types of anxiety including trait anxiety, state anxiety, achievement anxiety, and facilitative-debilitative anxiety. With such a wide variety of anxiety-types, it is not surprising that early studies on the relationship between ‘anxiety’ and achievement provided mixed and confusing results, and Scovel (1978 – this timeline) rightly noted that anxiety is ‘not a simple, unitary construct that can be comfortably quantified into ‘high’ or ‘low’ amounts’ (p. 137). Scovel did not, however, anticipate the identification in the mid-1980s of a unique form of anxiety that some people experience in response to learning and/or using an L2. Typically referred to as language anxiety or foreign language anxiety (FLA), this anxiety is categorized as a situation-specific anxiety, similar in type to other familiar manifestations of anxiety such as stage fright or test anxiety.
BAAL/CUP seminars 2009
Authors: Cutting Joan , Murphy Bróna
Published: March 2010

The Moray House School of Education, The University of Edinburgh, UK; 7–8 May 2009

The seminar, organised by Joan Cutting and Bróna Murphy, aimed

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to bring together researchers involved in both emergent and established academic corpora (written and spoken) as well as linguists, lecturers and teachers researching in education, be it language teaching, language-teacher training or continuing professional development in language awareness, all of whom may be new to corpora and its applications;

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to explore the possibilities of working together with researchers in speech recognition and synthesis, and other specialists in technological innovation;

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to provide an opportunity to disseminate the latest developments in academic language corpora.

The seminar strengthened links between institutions and created networks for researchers to explore ways that corpora can help to study general classroom practice and be used as part of language classroom teaching. It attracted 30 participants from universities in the Czech Republic, the Republic of Ireland, Italy, Japan, Switzerland and the UK; there were two plenary papers and 14 individual papers.
CONFIDENCE BANDS IN QUANTILE REGRESSION
Authors: Härdle Wolfgang K. , Song Song
Published: March 2010

Let (X1, Y1), …, (Xn, Yn) be independent and identically distributed random variables and let l(x) be the unknown p-quantile regression curve of Y conditional on X. A quantile smoother ln(x) is a localized, nonlinear estimator of l(x). The strong uniform consistency rate is established under general conditions. In many applications it is necessary to know the stochastic fluctuation of the process {ln(x) – l(x)}. Using strong approximations of the empirical process and extreme value theory, we consider the asymptotic maximal deviation sup0≤x≤1 |ln(x) − l(x)|. The derived result helps in the construction of a uniform confidence band for the quantile curve l(x). This confidence band can be applied as a econometric model check. An economic application considers the relation between age and earnings in the labor market by means of parametric model specification tests, which presents a new framework to describe trends in the entire wage distribution in a parsimonious way.
Prevalence and characteristics of asymptomatic norovirus infection in the community in England
Authors: PHILLIPS G. , TAM C. C. , RODRIGUES L. C. , LOPMAN B.
Published: March 2010

Norovirus is a major cause of infectious intestinal disease, and a substantial prevalence of asymptomatic infection has been reported. We describe the prevalence, seasonality and characteristics of asymptomatic norovirus infection in England. Healthy individuals were recruited at random from the general population during the Study of Infectious Intestinal Disease (1993–1996). Norovirus was identified using real-time RT–PCR. The age-adjusted prevalence of asymptomatic norovirus infection was 12%; prevalence was highest in children aged <5 years and showed wintertime seasonality. More work is needed to understand whether asymptomatic infections are important for norovirus transmission leading to sporadic illness and outbreaks.
Psychopathy-, Temperaments- und Charakterdimensionen bei inhaftierten Mädchen
Authors: Sevecke Kathrin , Lehmkuhl Gerd , Krischer Maya K.
Published: March 2010

Fragestellung: Die Studie widmet sich der Frage, inwiefern sich Temperaments- und Charakterunterschiede zwischen antisozialen Mädchen mit und ohne Psychopathy finden lassen und ob sich anhand derer eine Differenzierung von Gruppen mit verschiedenen Psychopathy-Symptomen vornehmen lässt. Methodik: Es wurden 170 inhaftierte Mädchen (Alter 14–19) mit dem Junior Temperament and Character Inventory und der Psychopathy-Checkliste Youth Version untersucht. Anhand ihrer PCL:YV-Werte wurden die Mädchen in drei Gruppen mit hoch ausgeprägten Psychopathy-Dimensionen eingeteilt und mit der Gruppe ohne Psychopathy verglichen. Ergebnisse: Bei 3/4 der untersuchten jugendlichen Straftäterinnen lag keine Psychopathy vor, der Anteil derjenigen mit Psychopathy-Kerndimensionen betrug nur 7 %. Mit Hilfe des Persönlichkeitsmodells von Cloninger konnten Unterschiede in den Dimensionen Neugierverhalten, Belohnungsabhängigkeit, Kooperativität und Selbsttranszendenz zwischen den Psychopathy-Gruppen und der Gruppe ohne Psychopathy nachgewiesen werden. Allerdings gelang es nicht, spezifische Zusammenhänge zwischen den einzelnen Psychopathy-Dimensionen und den JTCI-Faktoren zu eruieren. Schlussfolgerungen: Anhand der Ergebnisse gelingt es, das Psychopathy-Konstrukt für Straftäterinnen zu bestätigen, wenngleich der Anteil derjenigen mit Psychopathy-Kerndimensionen sehr gering ist. Die in der Untersuchung gefundenen differenziellen Temperamentsfaktoren bei Mädchen mit hoch ausgeprägten Psychopathy-Dimensionen im Vergleich zu Mädchen ohne Psychopathy stärken die Annahme, dass es sich um ein valides Konzept handelt, das eine spezifische Untergruppe mit Psychopathy-Kernsymptomen von anderen antisozialen Mädchen unterscheidet.
Intelligenzdiagnostik mit den Wechsler-Skalen bei sechsjährigen Kindern
Authors: Daseking Monika , Petermann Franz , Waldmann Hans-Christian
Published: March 2010

Fragestellung: Es soll die praktische Vergleichbarkeit von Testergebnissen aus HAWIVA-III und HAWIK-IV geprüft werden. Methodik: N = 45 sechsjährigen Kindern wurden beide Tests in ausbalancierter Reihenfolge vorgegeben. Es werden Stichprobenkennwerte (Mittelwert, Standardabweichung) und Zusammenhangsmaße (unkorrigierte und korrigierte Korrelationen, Standarddifferenz) bestimmt sowie Regressionsanalysen durchgeführt. Ergebnisse: Mit Korrelationskoeffizienten von r = .81 (VT/SV), r = .86 (HT/WLD)und r = .77 (VG/VG) korrelieren die Indizes sehr hoch miteinander, für den Gesamt-IQ beträgt der Zusammenhangswert r = .91. Es werden für die HAWIK-IV-Indizes die aus HAWIVA-III vorhergesagten Werte berichtet. Schlussfolgerungen: Aus den Korrelationskoeffizienten lässt sich ein hoher Zusammenhang zwischen beiden Tests ableiten. Damit kann ein sinnvoller Vergleich von HAWIK-IV-Ergebnissen mit Vorbefunden aus HAWIVA-III vorgenommen werden.
Evidenzbasierte Einzelpsychotherapie bei schizophrenen Psychosen 1Diese Arbeit wurde vom Bundesministerium für Bildung und Forschung gefördert (Förderkennzeichen 01GV0618).
Authors: Klingberg Stefan
Published: March 2010

Psychotherapie ist ein wirksamer Bestandteil der Gesamtbehandlung von Patienten mit schizophrenen Störungen. Dies wird durch evidenzbasierte Leitlinien und systematische Reviews klar belegt. In besonderer Weise haben Familieninterventionen für das Behandlungsziel der Rückfallverhütung und die Kognitive Verhaltenstherapie (KVT) als Einzelpsychotherapieverfahren für das Ziel der Symptomreduktion bei persistierenden psychotischen Symptomen ihre Wirksamkeit nachgewiesen. In diesem Beitrag werden die Wirksamkeitsnachweise von KVT für die Behandlung der Positiv-Symptomatik, der Negativ-Symptomatik sowie der Rückfallprophylaxe zusammengefasst. Die jeweiligen psychotherapeutischen Ansatzpunkte werden herausgearbeitet und die abgeleiteten Therapieziele vorgestellt. Die wesentlichen Therapiestrategien für die genannten drei Zielbereiche werden dargelegt und die Vorgehensweise bei der Durchführung erläutert.
Hallucinations, Pseudohallucinations, and Severity of Suicidal Ideation Among Emergency Psychiatry Patients
Authors: Penagaluri Praveen , Walker Kristin L. , El-Mallakh Rif S.
Published: March 2010

Aims: This study investigated relative relationships between auditory hallucinations and nonpsychotic hallucinations (pseudohallucinations), and suicidal risk. Methods: A sample of 206 consecutive patients seen in an emergency psychiatric service was evaluated for the presence and intensity of hallucinatory experiences (the hallucination item of the Positive and Negative Symptoms Scale), suicidal intensity (the suicide item of the Montgomery Asberg Depression Rating Scale), and cumulative suicide risk (the total number of risk factors). Results: Individuals with nonpsychotic hallucinations experienced greater intensity of suicidal ideation versus subjects with no hallucinations or subjects with psychotic hallucinations (p = .0001). Conclusions: Pseudohallucinosis is associated with higher intensity of suicidal ideation compared with psychotic hallucinations or no hallucinations.
Pi2 band activity at low latitudes during non‐substorm intervals
Authors: Sutcliffe P. R.
Published: March 2010

Pi2 pulsations are impulsive, damped oscillations associated with magnetospheric substorm onsets and intensifications. We show that Pi2 activity, with different characteristics, occurs during non‐substorm intervals. Examples showing the nature of the association between low‐latitude Pi2s and “tail reconnection during IMF‐northward, non‐substorm intervals” or TRINNIs are presented. These events are thought to be related to reconnection at a more distant neutral line than that associated with substorms and that maps to the poleward auroral oval boundary. In particular, using a new method of Pi2 identification, we for the first time show that modulated quasi continuous activity in the Pi2 band occurs regularly (∼40% of the time) at low latitudes during IMF‐northward, non‐substorm intervals.
Scintillation‐producing Fresnel‐scale irregularities associated with the regions of steepest TEC gradients adjacent to the equatorial ionization anomaly
Authors: Muella M. T. A. H. , Kherani E. A. , de Paula E. R. , Cerruti A. P. , Kintner P. M. , Kantor I. J. , Mitchell C. N. , Batista I. S. , Abdu M. A.
Published: March 2010

Using ground‐based GPS and digital ionosonde instruments, we have built up at latitudes of the equatorial ionization anomaly (EIA), in the Brazilian sector, a time‐evolving picture of total electron content (TEC), L‐band amplitude scintillations, andFregion heights, and we have investigated likely reasons for the occurrence or suppression of equatorial scintillations during the disturbed period of 18–23 November 2003. During the prestorm quiet nights, scintillations are occurring postsunset, as expected; however, during the storm time period, their spatial‐temporal characteristics and intensity modify significantly owing to the dramatic changes in the ionospheric plasma density distribution and in the temporal evolution of TEC. The two‐dimensional maps showing both TEC and amplitude scintillations revealed strong evidence of turbulences at the Fresnel length (causing scintillations) concurrent with those regions of steepest TEC gradients adjacent to the crests of the EIA. The largest density gradients have been found to occur in an environment of increased background electron density, and their spatial distribution and location during the disturbed period may differ significantly from the magnetic quiet night pattern. However, in terms of magnitude the gradients at equatorial and low latitudes appear to not change during both magnetic quiet and disturbed conditions. The scenarios for the formation or suppression of scintillation‐producing Fresnel‐scale irregularities during the prestorm quiet nights and disturbed nights are discussed in view of different competing effects computed from numerical simulation techniques.
Tectonothermal processes and mechanical strength in a recent orogenic belt: Northern Apennines
Authors: Pasquale V. , Chiozzi P. , Verdoya M.
Published: March 2010

This paper investigates the seismic cutoff temperature at the maximum depth of seismicity across a young orogenic belt, the northern Apennines, by attempting to take account of the different tectonothermal processes which have occurred in the region since the last 20 Myr. The analysis of seismicity over a period of 20 years (1981–2002) in combination with the thermal regime shows that the western part of the northern Apennines (peri‐Tyrrhenian zone) is characterized by extensional tectonics, few earthquakes, generally shallow and of low magnitude, and high surface heat flux. The entire crust of the eastern part of the orogenic belt (external zone) is affected by seismic activity of moderate magnitude and low heat flux. Earthquakes increase both in number and energy released in the inner portion of the belt (internal zone), where events with larger focal depth indicate subduction. The cutoff potential temperature at the largest depth of seismicity is 550°C for the internal zone. In the external zone of the orogen, the temperature at the maximum depth of seismicity is about 550°C. This result agrees with recent work on the thermal structure and seismicity of several continental areas. The limiting temperature in the peri‐Tyrrhenian zone can, instead, exceed 750°C. A possible explanation is that the deepest earthquakes might be associated to magma movement. The overall earthquake spatial distribution across the orogen appears related to the long‐term rheology, which varies roughly in the same direction of tectonic transport of the chain. This consistency appears also from the b value of the frequency‐magnitude relation, which can be interpreted in relation to the rheological properties of the medium. The b value seems to be inversely correlated to the expected mechanical strength of the crust and increases eastward in the direction of tectonic transport. The largest number of shocks and magnitude of the internal zone happen where a sharp lateral change of strength should occur.
The GCM‐Oriented CALIPSO Cloud Product (CALIPSO‐GOCCP)
Authors: Chepfer H. , Bony S. , Winker D. , Cesana G. , Dufresne J. L. , Minnis P. , Stubenrauch C. J. , Zeng S.
Published: March 2010

This article presents the GCM‐Oriented Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) Cloud Product (GOCCP) designed to evaluate the cloudiness simulated by general circulation models (GCMs). For this purpose, Cloud‐Aerosol Lidar with Orthogonal Polarization L1 data are processed following the same steps as in a lidar simulator used to diagnose the model cloud cover that CALIPSO would observe from space if the satellite was flying above an atmosphere similar to that predicted by the GCM. Instantaneous profiles of the lidar scattering ratio (SR) are first computed at the highest horizontal resolution of the data but at the vertical resolution typical of current GCMs, and then cloud diagnostics are inferred from these profiles: vertical distribution of cloud fraction, horizontal distribution of low, middle, high, and total cloud fractions, instantaneous SR profiles, and SR histograms as a function of height. Results are presented for different seasons (January–March 2007–2008 and June–August 2006–2008), and their sensitivity to parameters of the lidar simulator is investigated. It is shown that the choice of the vertical resolution and of the SR threshold value used for cloud detection can modify the cloud fraction by up to 0.20, particularly in the shallow cumulus regions. The tropical marine low‐level cloud fraction is larger during nighttime (by up to 0.15) than during daytime. The histograms of SR characterize the cloud types encountered in different regions. The GOCCP high‐level cloud amount is similar to that from the TIROS Operational Vertical Sounder (TOVS) and the Atmospheric Infrared Sounder (AIRS). The low‐level and middle‐level cloud fractions are larger than those derived from passive remote sensing (International Satellite Cloud Climatology Project, Moderate‐Resolution Imaging Spectroradiometer–Cloud and Earth Radiant Energy System Polarization and Directionality of Earth Reflectances, TOVS Path B, AIRS–Laboratoire de Météorologie Dynamique) because the latter only provide information on the uppermost cloud layer.
Estimation of UV‐B irradiation from total global solar meteorological data in central Spain
Authors: Bilbao Julia , de Miguel Argimiro
Published: March 2010

Measurements of solar ultraviolet‐B (UV‐B) in the range (280–315 nm) and total global solar irradiation (G) for the period 2002–2006 in a continental Mediterranean environment have been analyzed. UV‐B and G data have been recorded at the Low Atmosphere Research Laboratory, Valladolid, Spain, using a YES UVB‐1 pyranometer and a Kipp&Zonen CM‐6 radiometer, respectively. According to the cloud conditions, the time data series shows that the highest UV‐B values are obtained in June and the lowest ones are obtained in December. A comparison of monthly UV‐B values reveals that some summer months show more dispersion than winter ones. An empirical relationship between UV‐B and G was established to estimate the daily UV‐B irradiation from commonly measured daily total global solar irradiation. The annual cycle effects of the solar zenith angle and the ozone total column have been taken into account. A correction factor that depends on the daily total ozone column has been included in the relationship between UV‐B and total global solar irradiation. The performance of this relationship has been evaluated comparing estimated and measured UV‐B values in three different stations. Scatterplot, root‐mean‐square error (RMSE), mean bias error (MBE), and linear regression correlation coefficient have been used to compare measured and estimated values. The results of this comparison show that the correlation coefficients were similar to 1 while the RMSE ranges between 2.10 kJ m−2 and 1.94 k Jm−2 and, in percentage, 9.18% and 7.64%, respectively. According to these results, it can be concluded that total global solar irradiation is an appropriate variable to obtain UV‐B daily values in places where ultraviolet radiation is not measured or to extend the existing data set back in time.
Similarity normalization method for thermal conductivity depth profile reconstructions from inhomogeneous cylindrical and flat solids using thermal waves
Authors: Liu Liwang , Wang Chinhua , Yuan Xiao , Mandelis Andreas
Published: March 2010

A similarity normalization method for thermal-wave depth profiling of layered and radial continuously varying inhomogeneous thermophysical properties in cylindrical solids is investigated and related to that developed for inhomogeneous flat solids both theoretically and experimentally using photothermal radiometry. The deconvolution of the curvature effect out of the overall thermal-wave field of inhomogeneous cylindrical solids allows conventional rectilinear thermal-wave inverse-problem techniques to be applied to thermal conductivity depth profile reconstructions in layered and inhomogeneous depth-varying cylindrical solids and opens new possibilities for depth profilometry of such solids using existing flat-surface inverse techniques.
Effect of local surface potential distribution on its relaxation in polycrystalline ferroelectric films
Authors: Kim Yunseok , Park Moonkyu , Bühlmann Simon , Hong Seungbum , Kim Yong Kwan , Ko Hyoungsoo , Kim Jiyoon , No Kwangsoo
Published: March 2010

We have studied the effect of local surface potential distribution on its relaxation in the polycrystalline ferroelectric thin films. A lower surface potential region, i.e., potential pit, is generated near a grain boundary. The deep potential pit has a faster relaxation than the area far away from the potential pit due to the acceleration of the screen charge draining near the grain boundary and the domains formed by applying higher voltage have a faster relaxation due to the larger gradient of screen charge distribution. In addition, the surface potential and its relaxation depend on the sign of applying voltage. The result shows that the surface potential distribution may influence significantly to the reliability of bit signal on the memory devices.
Dissociation of dicarboxylate and disulfonate dianions
Authors: Ard Shaun , Mirsaleh-Kohan Nasrin , Steill Jeffrey D. , Oomens Jos , Nielsen Steen Brøndsted , Compton R. N.
Published: March 2010

Collision-induced dissociation (CID), along with infrared multiple photon dissociation/detachment (IRMPD) techniques, is utilized to study a series of doubly substituted aromatic dianions containing sulfonate and carboxylate functionalities (1,2- and 1,3-benzenedisulfonate, 1,5-naphthalenedisulfonate, 2,6-naphthalenedisulfonate, 4-sulfobenzoate, 2,6-naphthalenedicarboxylate, and terephthalate dianions). The molecules were chosen because of the electronegativity of the CO2 and SO3 moieties along with their varied spatial separation in order to investigate the effect of the repulsive Coulomb barrier (RCB) on the dianions’ respective dissociation pathways. Density functional theory calculations of the structures, electron detachment and dissociation energies, as well as vibrational frequencies are performed. Calculated infrared active vibrational frequencies are largely in agreement with the IRMPD spectra which provide support for interpretations based upon computed energies. Calculated and experimental results show that fragmentation dominates over electron detachment as the lowest energy dissociation pathway for these systems and the nature of this dissociation is dictated by properties of the substituent group. CID and IRMPD of dianions with two sulfonate groups (SO3−) resulted in a single dissociation channel leading to observation of SO3− and its anion conjugate pair, whereas the carboxylate (CO2−) containing dianions dissociated via loss of one or both CO2 molecules and an electron. The SO3− collisional dissociation exhibited a clear energetic threshold toward ionic fragmentation with an isomeric dependence that is in reasonable agreement with a simple electrostatic model of the RCB, as well as with published reports on electron photodetachment. The loss of one or both CO2 units and an electron from CID of the carboxylate dianions appeared with no threshold (dissociation occurs with no collision gas), implying these dianions to be metastable toward the dissociation pathway. However, calculations show these ions to be energetically stable toward dissociation as well as electron detachment. More importantly, in the case of the 2,6-naphthalenedicarboxylate dianion, experiments performed at the FELIX Fourier-transform ion cyclotron resonance facility and the ELISA electrostatic storage ring, where ions are collisionally cooled prior to analysis, showed this ion to be stable (τ>1.5 s). We conclude that the carboxylate (CO2−) containing dianions formed in the present CID experiment are electronically stable but vibrationally metastable due to internal energy imparted in the harsh electrospray conditions. The delocalized nature of the excess electrons associated with the carboxylate containing dianions may lead to circumvention of the RCB by dissociating via neutral fragmentation followed by (or accompanied by) electron detachment.
Hysteresis jumps of the surface reactance of a layered superconductor as the incident wave amplitude varies
Authors: Apostolov S. S. , Kadygrob D. V. , Mayselis Z. A. , Slipchenko T. M. , Savel’ev S. E. , Yampol’skii V. A.
Published: March 2010

The nonlinear response of a layered superconductor to symmetric (in magnetic field) electromagnetic excitation has been theoretically investigated. An ambiguous dependence of the phase of the reflected signal on the amplitude H0 of the irradiating wave is predicted. This causes hysteresis jumps in the dependence of the surface reactance of the superconductor on H0. If the frequency of the irradiating field is close to the Josephson plasma frequency, this unusual nonlinear effect can be observed when the amplitudes of the ac field are not very strong. The conditions for the appearance of hysteresis are obtained. Expressions for the phase shift of the reflected wave are derived, using the coupled sine-Gordon equations. Moreover, a class of solutions of these equations that are discontinuous in the coordinate are studied that correspond to a continuous spatial distribution of the magnetic field in the superconductor. Such solutions result in the appearance of additional branches in the dependence of the phase shift of the reflected wave on the incident wave amplitude.
On momentum conservation and thermionic emission cooling
Authors: Kim Raseong , Jeong Changwook , Lundstrom Mark S.
Published: March 2010

The possibility of increasing the performance of thermionic cooling devices by relaxing lateral momentum conservation is examined. Upper limits for the ballistic emission current are established. It is then shown that for most cases, nonconserved lateral momentum model produces a current that exceeds this upper limit. For the case of heterojunctions with a much heavier effective mass in the barrier and with a low barrier height, however, relaxing lateral momentum may increase the current. These results can be simply understood from the general principle that the current is limited by the location, well or barrier, with the smallest number of conducting channels. They also show that within a thermionic emission framework, relaxing lateral momentum conservation does not increase the upper limit performance in most cases, and when it does, the increase is modest. More generally, however, especially when the connection to the carrier reservoir is poor and performance is well below the upper limit, relaxing lateral momentum conservation could prove beneficial.
Microwave responses and general model of nanotetraneedle ZnO: Integration of interface scattering, microcurrent, dielectric relaxation, and microantenna
Authors: Fang Xiao-Yong , Cao Mao-Sheng , Shi Xiao-Ling , Hou Zhi-Ling , Song Wei-Li , Yuan Jie
Published: March 2010

Based on the unique geometrical structure of nanotetra-ZnO needle (T-ZnON), we investigate the microwave responses of T-ZnON, including interface scattering, microcurrent attenuation, microantenna radiation, and dielectric relaxation, and build an energy attenuation model. The associated quantitative formula is deduced for calculating the microwave absorption properties of T-ZnON/SiO2 nanocomposite (T-ZnON/SiO2) in the range 8–14 GHz according to the present energy attenuation model. Very good agreement between the calculated and experimental results is obtained in a wide frequency range. The maximum deviation less than 0.5 dB in the range 8–14 GHz is obtained. Using the aforementioned model, we analyze the contribution of microwave responses to the energy attenuation in the frequency range 2–18 GHz, and the results reveal that interface scattering and microcurrent attenuation make the contribution most important. In addition, we calculate the effects of the volume fraction, conductivity, permittivity, needle length of T-ZnON, and thickness of T-ZnON/SiO2 on the reflectivity. The results show that the microwave absorption is evidently dependent on these effect factors, and the optimal microwave absorption band and the strongest microwave absorption peak of T-ZnON/SiO2 would appear when these physical parameters are changed.
Influence of inhomogeneous magnetic field on the characteristics of very high frequency capacitively coupled plasmas
Authors: Bera Kallol , Rauf Shahid , Kenney Jason , Dorf Leonid , Collins Ken
Published: March 2010

The effect of inhomogeneous magnetic field on the spatial structure of very high frequency (VHF) plasmas is investigated for different coil configurations, gas pressures, high frequency bias powers, and degrees of electronegativity. The simulation results show that the electron density peaks in the center of the chamber for VHF plasmas due to the standing electromagnetic wave effect. On application of a magnetic field, the density increases near the wafer edge and decreases at the chamber center. The radial magnetic field component is found to limit electron loss to the electrodes and locally enhance the electron density. The axial magnetic field component limits plasma diffusion in the radial direction helping preserve the effect of improved electron confinement by the radial magnetic field. The peak electron density decreases with increasing magnetic field as the plasma moves toward the electrode edge occupying a larger volume. The effect of magnetic field becomes weaker at higher pressure due to the increased electron-neutral collisions which reduce the effectiveness of electron confinement around the magnetic field lines. The impact of magnetic field on plasma profile is somewhat weaker in an electronegative Ar/CF4 plasma because of the presence of less mobile and unmagnetized negative ions.
Oxygen migration in TiO2-based higher-k gate stacks
Authors: Kim SangBum , Brown Stephen L. , Rossnagel Stephen M. , Bruley John , Copel Matthew , Hopstaken Marco J. P. , Narayanan Vijay , Frank Martin M.
Published: March 2010

We report on the stability of high-permittivity (high-k) TiO2 films incorporated in metal-oxide-silicon capacitor structures with a TiN metal gate electrode, focusing on oxygen migration. Titanium oxide films are deposited by either Ti sputtering [physical vapor deposition (PVD)] followed by radical shower oxidation or by plasma-enhanced atomic layer deposition (PEALD) from titanium isopropoxide (Ti{OCH(CH3)2}4) and O2 plasma. Both PVD and PEALD films result in near-stoichiometric TiO2 prior to high-temperature annealing. We find that dopant activation anneals of TiO2-containing gate stacks at 1000 °C cause 5 Å or more of additional SiO2 to be formed at the gate-dielectric/Si-channel interface. Furthermore, we demonstrate for the first time that oxygen released from TiO2 diffuses through the TiN gate electrode and oxidizes the poly-Si contact. The thickness of this upper SiO2 layer continues to increase with increasing TiO2 thickness, while the thickness of the regrown SiO2 at the gate-dielectric/Si interface saturates. The upper SiO2 layer degrades gate stack capacitance, and simultaneously the oxygen-deficient TiOx becomes a poor insulator. In an attempt to mitigate O loss from the TiO2, top and bottom Al2O3 layers are added to the TiO2 gate dielectric as oxygen barriers. However, they are found to be ineffective, due to Al2O3-TiO2 interdiffusion during activation annealing. Bottom HfO2/Si3N4 interlayers are found to serve as more effective oxygen barriers, reducing, though not preventing, oxygen downdiffusion.
The parameters of electron cyclotron resonance/radio-frequency hybrid hydrogen plasma adjusted by substrate arrangements
Authors: Zhou H. Y. , Wang L. , Zhu X. D. , Ke B. , Ding F. , Wen X. H. , Wang Y. N.
Published: March 2010

Hybrid hydrogen plasma was formed by biasing 13.56 MHz radio-frequency (rf) power on a substrate immersed in 2.45 GHz microwave electron cyclotron resonance (ECR) plasma. The influences of the substrate configuration on plasma characteristics were investigated. With increasing rf self-bias voltage, electron temperature, Te, increases obviously in the case of the single-electrode substrate, whereas a slight change in Te was observed with the double-electrode substrate condition. Electron density rises almost with a same magnitude under both two substrate conditions. It exhibited that electron energy and density in ECR-rf hybrid mode could be adjusted independently by controlling rf discharge with favorable substrate configurations.
Note: Measurement of saturable absorption by intense vacuum ultraviolet free electron laser using fluorescent material
Authors: Inubushi Y. , Yoneda H. , Higashiya A. , Ishikawa T. , Kimura H. , Kumagai T. , Morimoto S. , Nagasono M. , Ohashi H. , Sato F. , Tanaka T. , Togashi T. , Tono K. , Yabashi M. , Yamaguchi Y. , Kodama R.
Published: March 2010

Advances in free electron lasers (FELs) which generate high energy photons are expected to open novel nonlinear optics in the x-ray and vacuum ultraviolet (VUV) regions. In this paper, we report a new method for performing VUV-FEL focusing experiments. A VUV-FEL was focused with Kirkpatrick−Baez optics on a multilayer target, which contains fused silica as a fluorescent material. By measuring the fluorescence, a 5.6×4.9 μm2 focal spot was observed in situ. Fluorescence was used to measure the saturable absorption of VUV pulses in the tin layer. The transmission increases nonlinearly higher with increasing laser intensity.
Energy and charge transfers between (Bu4N)2(Ru)(dcbpyH)2(NCS)2 (N719) and ZnO thin films
Authors: Ni Manman , Cheng Qiang , Zhang W. F.
Published: March 2010

ZnO thin films and (Bu4N)2(Ru)(dcbpyH)2(NCS)2 (called N719) sensitized ZnO thin films are grown on fluorine-doped tin oxide (FTO) conducting glass substrates using laser molecular beam epitaxy. Ultraviolet-visible absorption, photoluminescence (PL), surface photovoltage spectroscopy, and Raman scattering are employed to probe into the transition process of photogenerated charges and the interaction between ZnO and N719. The experimental results indicate that there is a significant electronic interaction between N719 and ZnO through chemiadsorption. The interaction greatly enhances the photogenerated charge separation and thus the photovoltaic response of the ZnO film but remarkedly weakens its radiative recombination, i.e., PL, implying strong energy and charge transfer occurring between N719 and ZnO. In addition, a new PL peak observed at about 720 nm in N719 sensitized ZnO/FTO is attributed to the electron-hole recombination of N719.
Shallow-donor impurity in zinc-blende InGaN/GaN asymmetric coupled quantum dots: Effect of electric field
Authors: Xia Congxin , Zeng Zaiping , Wei Shuyi
Published: March 2010

We have performed a theoretical calculation of the shallow-donor impurity states in cylindrical zinc-blende (ZB) InGaN/GaN asymmetric coupled quantum dots (QDs), considering the effect of the electric field applied to the left (opposite to the growth direction). Numerical results show that the donor binding energy in ZB InGaN/GaN asymmetric coupled QDs is highly dependent on the impurity positions, asymmetric coupled QD structure parameters, and the electric field. In the presence of the electric field, if the left dot height is increased from zero, the donor binding energy of the impurity localized inside the middle barrier layer has a maximum value; if the right dot is increased from zero, the donor binding energy of impurity localized inside the right dot has a maximum value. It is also found that for the impurity located at the center of the right dot, the donor binding energy is insensible to the electric field when the electric field is large; however, the critical electric field is smaller if the right dot is wide. In particular, numerical results show that if the right dot is wide, the asymmetric coupled QDs are much easier to be decoupled under the influence of the electric field.
There is no Hartman effect in graphene structures
Authors: Dragoman D. , Dragoman M.
Published: March 2010

The paper shows that there is no Hartman effect due to Klein paradox for electrons traversing electrostatic barriers in graphene. In addition, the quantum dwell time in such single- and double-barrier structures can be modulated by an applied gate voltage.
Polarization conversion of electromagnetic waves by Faraday chiral media
Authors: Meng Fan-Yi , Zhang Kuang , Wu Qun , Li Le-Wei
Published: March 2010

The reflection of a normally incident plane wave due to the interface between vacuum and a Faraday chiral medium (FCM) supported by a perfect electric conductor was rigorously derived. Numerical results strongly indicated that arbitrary polarization conversions are realizable from the incident plane wave to the reflected plane wave by properly choosing the constitutive parameters of the FCM.
Finite amplitude solitary excitations in rotating magnetized nonthermal complex (dusty) plasmas
Authors: El-Taibany W. F. , Mushtaq A. , Moslem W. M. , Wadati Miki
Published: March 2010

The nonlinear dynamics of finite amplitude dust acoustic solitary waves in rotating magnetized nonthermal plasma are investigated. For this purpose, the hydrodynamic equations for the dust grains, nonthermal ion density, and Boltzmann electron distributions together with the Poisson equation are used to derive the energy integral equation with a new Sagdeev potential. It is found that the solitary excitations strongly depend on the nonthermal ion parameters, rotational frequency, as well as dust gyrofrequency. The present investigations may be applicable to the dusty plasma situation near to the moon.
Diagram for vortex formation in quasi-two-dimensional magnetic dots
Authors: Rocha J. C. S. , Coura P. Z. , Leonel S. A. , Dias R. A. , Costa B. V.
Published: March 2010

The existence of nonlinear objects of the vortex type in two-dimensional magnetic systems presents itself as one of the most promising candidates for the construction of nanodevices, useful for storing data, and for the construction of reading and writing magnetic heads. The vortex appears as the ground state of a magnetic nanodisk whose magnetic moments interact via the dipole-dipole potential {D∑[S⃗i⋅S⃗j−3(S⃗i⋅r̂ij)×(S⃗j⋅r̂ij)]/rij3} and the exchange interaction (−J∑S⃗i⋅S⃗j). In this work it is investigated the conditions for the formation of vortices in nanodisks in triangular, square, and hexagonal lattices as a function of the size of the lattice and of the strength of the dipole interaction D. Our results show that there is a “transition” line separating the vortex state from a capacitorlike state. This line has a finite size scaling form depending on the size, L, of the system as Dc=D0+1/A(1+BL2). This behavior is obeyed by the three types of lattices. Inside the vortex phase it is possible to identify two types of vortices separated by a constant, D=Dc, line: An in-plane and an out-of-plane vortex. We observed that the out-of-plane phase does not appear for the triangular lattice. In a two layer system the extra layer of dipoles works as an effective out-of-plane anisotropy inducing a large Sz component at the center of the vortex. Also, we analyzed the mechanism for switching the out-of-plane vortex component. Contrary to some reported results, we found evidences that the mechanism is not a creation-annihilation vortex anti-vortex process.
Spin dependent behavior in a Rashba film
Authors: Caliskan S.
Published: March 2010

Two-dimensional system with Rashba spin-orbit interaction, named as Rashba film with transverse confinement is considered. Spin dependent behavior of the Rashba film is investigated through two possible, even and odd, solutions. The spin dependent eigenfunctions, eigenvalues, and quantization conditions are derived, and energy dispersion relations are determined. Even and odd solutions are characterized and a mapping between them is demonstrated.
Growth, structure, and cathodeluminescence of Eu-doped ZnO nanowires prepared by high-temperature and high-pressure pulsed-laser deposition
Authors: Yang Y. H. , Feng Y. , Zhu H. G. , Yang G. W.
Published: March 2010

Eu-doped ZnO nanowires have been prepared by the high-temperature and high-pressure pulsed-laser deposition, and the structure and cathodeluminescence (CL) of the as-prepared nanostructures were characterized. It was found that the alloying catalyst droplets are located at the top of the as-prepared Eu-doped ZnO nanowires, meaning that the Eu-doped ZnO nanowires growth is a typical vapor-liquid-solid process. X-ray photoelectron spectra of samples provided the experimental evidence of the Eu-doping in ZnO nanowires. Two peaks near 611 and 755 nm, respectively, are identified to be from the doped Eu in the CL spectra of samples.
Development of loading system for liquid hydrogen into diamond-anvil cells under low temperature
Authors: Machida Shin-ichi , Hirai Hisako , Gotou Hirotada , Sakakibara Toshiro , Yagi Takehiko
Published: March 2010

A loading system for hydrogen gas into the diamond-anvil cell has been developed. The loading of hydrogen gas is performed under low temperature by using liquid helium as a cooling medium. Also, a compression apparatus has been developed to load gaseous materials into various diamond-anvil cells. The present loading system and compression apparatus have been used successfully to form hydrogen hydrate. The present loading system can also be used to load other gaseous materials as a pressure medium.
Oxygen vacancy migration in ceria and Pr-doped ceria: A DFT+U study
Authors: Dholabhai Pratik P. , Adams James B. , Crozier Peter , Sharma Renu
Published: March 2010

Oxygen vacancy formation and migration in ceria (CeO2) is central to its performance as an ionic conductor. It has been observed that ceria doped with suitable aliovalent cationic dopants improves its ionic conductivity. To investigate this phenomenon, we present total energy calculations within the framework of density functional theory to study oxygen vacancy migration in ceria and Pr-doped ceria (PDC). We report activation energies for oxygen vacancy formation and migration in undoped ceria and for different migration pathways in PDC. The activation energy value for oxygen vacancy migration in undoped ceria was found to be in reasonable agreement with the available experimental and theoretical results. Conductivity values for reduced undoped ceria calculated using theoretical activation energy and attempt frequency were found in reasonably good agreement with the experimental data. For PDC, oxygen vacancy formation and migration were investigated at first, second, and third nearest neighbor positions to a Pr ion. The second nearest neighbor site is found to be the most favorable vacancy formation site. Vacancy migration between first, second, and third nearest neighbors was calculated (nine possible jumps), with activation energies ranging from 0.41 to 0.78 eV for first-nearest-neighbor jumps. Overall, the presence of Pr significantly affects vacancy formation and migration, in a complex manner requiring the investigation of many different migration events. We propose a relationship illuminating the role of additional dopants toward lowering the activation energy for vacancy migration in PDC.
A compact, transportable, microchip-based system for high repetition rate production of Bose–Einstein condensates
Authors: Farkas Daniel M. , Hudek Kai M. , Salim Evan A. , Segal Stephen R. , Squires Matthew B. , Anderson Dana Z.
Published: March 2010

We present a compact, transportable system that produces Bose–Einstein condensates near the surface of an integrated atom microchip. The system occupies a volume of 0.4 m3, operates at a repetition rate as high as 0.3 Hz, and consumes an average power of 525 W. Evaporative cooling in a chip trap with trap frequencies of several kilohertz leads to nearly pure condensates containing 1.9×104 R87b atoms. Partial condensates are observed at a temperature of 1.58(8) μK, close to the theoretical transition temperature of 1.1 μK.
Frequency analysis of nanotubes with consideration of surface effects
Authors: Farshi Behrooz , Assadi Abbas , Alinia-ziazi Ali
Published: March 2010

Consideration of surface effects in microscaled and nanoscaled materials is important for accurate prediction of their dynamic behavior. In this study, the Timoshenko beam model is modified to include the surface effects and used to analyze the vibration of nanotubes as well as calculate their natural frequencies. The thin surface layers have been taken into account for rotary inertia computation. Through an example it is shown that dynamic behavior of nanoscaled tubes with consideration of surface effects considerably deviates from the results obtained by classical theories. Plots illustrating such deviations are given to support the conclusions.
Hard x-ray nanobeam characterization by coherent diffraction microscopy
Authors: Schropp A. , Boye P. , Feldkamp J. M. , Hoppe R. , Patommel J. , Samberg D. , Stephan S. , Giewekemeyer K. , Wilke R. N. , Salditt T. , Gulden J. , Mancuso A. P. , Vartanyants I. A. , Weckert E. , Schöder S. , Burghammer M. , Schroer C. G.
Published: March 2010

We have carried out a ptychographic scanning coherent diffraction imaging experiment on a test object in order to characterize the hard x-ray nanobeam in a scanning x-ray microscope. In addition to a high resolution image of the test object, a detailed quantitative picture of the complex wave field in the nanofocus is obtained with high spatial resolution and dynamic range. Both are the result of high statistics due to the large number of diffraction patterns. The method yields a complete description of the focus, is robust against inaccuracies in sample positioning, and requires no particular shape or prior knowledge of the test object.