bluuebunny/crossref_metadata_2025 huggingface dataset:
An evaluation of vitamin D status in individuals with systemic lupus erythematosus
Authors: Breslin Leanne C. , Magee Pamela J. , Wallace Julie M. W. , McSorley Emeir M.
Published: August 2011

Systemic lupus erythematosus (SLE) is a multi-system inflammatory disease where genetic susceptibility coupled with largely undefined environmental factors is reported to underlie the aetiology of the disease. One such factor is low vitamin D status. The primary source of vitamin D is endogenous synthesis following exposure of the skin to UVB light. Photosensitivity, sunlight avoidance and the use of sun protection factor in combination with medications prescribed to treat the symptoms of the disease, puts SLE patients at increased risk of vitamin D deficiency. Decreased conversion of 25-hydroxyvitamin D to the metabolically active form, 1,25-dihydroxyvitamin D3, is possible, due to renal impairment common in SLE putting additional stress on vitamin D metabolism. The majority of studies have identified low 25-hydroxyvitamin D in SLE patients, albeit using varying cut-offs (<25 to <80 nmol/l). Of these studies, fifteen have investigated a link between status and disease activity with conflicting results. Variation with disease activity index measures used alongside methodological limitations within the study design may partially explain these findings. This review discusses the importance of optimal vitamin D status in SLE, critically evaluates research carried out to date that has investigated vitamin D in SLE, and highlights the need for a well-designed observational study that controls for diet, medication use, dietary supplements, UV exposure and seasonality, that uses sensitive methods for measuring vitamin D status and disease activity in SLE to conclusively establish the role of vitamin D in SLE.
Does vitamin D during pregnancy impact offspring growth and
bone?
Authors: Specker Bonny L.
Published: August 2011

During pregnancy, maternal and fetal Ca demands are met through increased
intestinal Ca absorption. Increased Ca absorption may be more dependent on
oestrogen's up-regulation of Ca transport genes than on vitamin D
status. Numerous studies, however, have found that severe vitamin D deficiency
with secondary hyperparathyroidism during pregnancy leads to abnormal Ca
homoeostasis in the neonate. Some, but not all, studies of maternal vitamin D
supplementation during pregnancy find a greater birth weight among infants of
mothers with adequate vitamin D status. Observational studies find a higher
incidence of small-for-gestational age (SGA) infants among
mothers who are vitamin D deficient, but this effect may be modified by
genetics. In addition, the effect of vitamin D status on SGA may not be linear,
with increased occurrence of SGA at high maternal 25-hydroxyvitamin D
(25-OHD) concentrations. Some studies, but not all, also
have found that maternal vitamin D status is associated with growth trajectory
during the first year of life, although the findings are contradictory. There
are recent studies that suggest maternal 25-OHD, or surrogates of vitamin D
status, are associated with growth and bone mass later in childhood. These
results are not consistent, and blinded randomised trials of vitamin D
supplementation during pregnancy with long-term follow-up are needed to
determine the benefits, and possible risks, of maternal vitamin D status on
offspring growth and bone development. The possibility of adverse outcomes with
higher maternal 25-OHD concentrations should be considered and investigated in
all ongoing and future studies.
Closing the praziquantel treatment gap: new steps in epidemiological monitoring and control of schistosomiasis in African infants and preschool-aged children
Authors: STOTHARD J. RUSSELL , SOUSA-FIGUEIREDO JOSÉ C. , BETSON MARTHA , GREEN HELEN K. , SETO EDMUND Y. W. , GARBA AMADOU , SACKO MOUSSA , MUTAPI FRANCISCA , VAZ NERY SUSANA , AMIN MUTAMAD A. , MUTUMBA-NAKALEMBE MARGARET , NAVARATNAM ANNALAN , FENWICK ALAN , KABATEREINE NARCIS B. , GABRIELLI ALBIS F. , MONTRESOR ANTONIO
Published: August 2011

Where very young children come into contact with water containing schistosome cercariae, infections occur and schistosomiasis can be found. In high transmission environments, where mothers daily bathe their children with environmentally drawn water, many infants and preschool-aged children have schistosomiasis. This ‘new’ burden, inclusive of co-infections with Schistosoma haematobium and Schistosoma mansoni, is being formally explored as infected children are not presently targeted to receive praziquantel (PZQ) within current preventive chemotherapy campaigns. Thus an important PZQ treatment gap exists whereby infected children might wait up to 4–5 years before receiving first treatment in school. International treatment guidelines, set within national treatment platforms, are presently being modified to provide earlier access to medication(s). Although detailed pharmacokinetic studies are needed, to facilitate pragmatic dosing in the field, an extended ‘dose pole’ has been devised and epidemiological monitoring has shown that administration of PZQ (40 mg/kg), in either crushed tablet or liquid suspension, is both safe and effective in this younger age-class; drug efficacy, however, against S. mansoni appears to diminish after repeated rounds of treatment. Thus use of PZQ should be combined with appropriate health education/water hygiene improvements for both child and mother to bring forth a more enduring solution.
Detection of Dicrocoelium dendriticum larval stages in mollusc and ant intermediate hosts by PCR, using mitochondrial and ribosomal internal transcribed spacer (ITS-2) sequences
Authors: MARTÍNEZ-IBEAS A. M. , MARTÍNEZ-VALLADARES M. , GONZÁLEZ-LANZA C. , MIÑAMBRES B. , MANGA-GONZÁLEZ M. Y.
Published: August 2011

The aim of this study was to develop, perfect and validate the PCR (polymerase chain reaction) technique using mitochondrial (mt) and ribosomal (ITS-2) DNA for the accurate identification of Dicrocoelium dendriticum in molluscs and ants, the first and second intermediate hosts, and their early detection. The first primers that were designed amplified a 169 pb mtDNA fragment of D. dendriticum permitted the detection of a single D. dendriticum metacercaria from the Formica rufibarbis and Formica pratensis abdomen, as well as the detection of the brainworm in the head of the ants collected in tetania. Although these primers did not amplify Dicrocoelium chinensis DNA and permitted detected D. dendriticum in the molluscs, they did not discriminate Brachylaimidae metacercariae found in the same mollusc. The PCR that was designed to amplify a 93 bp fragment of the ITS-2 is D. dendriticum specific as it did not amplify D. chinensis, Brachylaimidae and other trematodes. This technique is very sensitive since it permitted the detection of D. dendriticum in the molluscs from the first day post-infection, the brainworm in the head of the ants and only 1 D. dendriticum metacercaria from the abdomen of the ants. Both techniques are important, mainly the latter.
Simultaneous evaluation of the harms and benefits of treatments in randomized clinical trials: demonstration of a new approach
Authors: Frank E. , Kupfer D. J. , Rucci P. , Lotz-Wallace M. , Levenson J. , Fournier J. , Kraemer H. C.
Published: August 2011

Background

One aim of personalized medicine is to determine which treatment is to be preferred for an individual patient, given all patient information available. Particularly in mental health, however, there is a lack of a single objective, reliable measure of outcome that is sensitive to crucial individual differences among patients.

Method

We examined the feasibility of quantifying the total clinical value provided by a treatment (measured by both harms and benefits) in a single metric. An expert panel was asked to compare 100 pairs of patients, one from each treatment group, who had participated in a randomized clinical trial (RCT) involving interpersonal psychotherapy (IPT) and escitalopram, selecting the patient with the preferred outcome considering both benefits and harms.

Results

From these results, an integrated preference score (IPS) was derived, such that the differences between any two patients' IPSs would predict the clinicians' preferences. This IPS was then computed for all patients in the RCT. A second set of 100 pairs was rated by the panel. Their preferences were highly correlated with the IPS differences (r=0.84). Finally, the IPS was used as the outcome measure comparing IPT and escitalopram. The 95% confidence interval (CI) for the effect size comparing treatments indicated clinical equivalence of the treatments.

Conclusions

A metric that combines benefits and harms of treatments could increase the value of RCTs by making clearer which treatments are preferable and, ultimately, for whom. Such methods result in more precise estimation of effect sizes, without increasing the required sample size.
Partial volume characteristics of ionization chambers in kilovoltage x-ray exposure measurements
Authors: Akber Syed F. , Kehwar Than S.
Published: August 2011

The partial volume (spatial) response of four ionization chambers (Keithley) in kilovoltage X-ray beams, generated by the Philips Super 80CP X-ray unit, was assessed. The volume of the ionization chambers were of 10 cm3, 15 cm3, 150 cm3, and 600 cm3 used with Keithley electrometer Model 35040. The beam output was measured using a monitor chamber (Radcal 6.0 cm3) placed close to the collimator. The source to chamber distance was kept constant at 1 m. For the measurement of the response of ionization chambers of 15 cm3, 150 cm3, and 600 cm3, a slit of 2.0 mm width was made in a lead sheet of 3.2 mm thick and size of 30 × 30 cm2 and was placed on the ionization chamber. The measurements were made for 81 kVp, 400 mA, and 0.25 s and the slit was moved at an increment of 2.0 mm over the entire length of the chamber. For the measurements of the ionization chamber of 10 cm3 (CT chamber), the beams of 120 kVp, 200 mA and 0.2 s were generated, and a slit of 5 mm width was made in a similar lead sheet that was moved at an increment of 5.0 mm. From the result it appears that the sensitive volumes of the ionization chambers affect the response of the ionization chamber to incident radiation.
Universelle Prävention des Substanzkonsums: Effekte des Grundschulprogramms Klasse2000
Authors: Maruska Karin , Isensee Barbara , Hanewinkel Reiner
Published: August 2011

Fragestellung: Wie wirkt sich das Grundschulprogramm Klasse2000 auf den Einstieg in den Zigaretten- und/oder heimlichen Alkoholkonsum aus? Methodik: Aufgeteilt auf die beiden Bedingungen „Teilnahme an Klasse2000“ vs. „Keine Teilnahme an Klasse2000“ wurden Schüler (MAlter = 9,0, SD = 0,5), die am Ende der dritten Klasse als Nie-Raucher (N = 1.027), als Nie-Trinker (N = 1.072) bzw. sowohl als Nie-Raucher und -Trinker (N = 979) identifiziert wurden, zum Ende der vierten Klasse hinsichtlich der Inzidenz des Substanzkonsums verglichen. Multiple hierarchische Poisson-Regressionen unter Kontrolle soziodemgraphischer Charakteristika sowie sozialer Einflussfaktoren wurden berechnet. Ergebnisse: Es konnte ein signifikanter Effekt von Klasse2000 auf den Einstieg in den Zigarettenkonsum sowie den Konsum mindestens einer der beiden Substanzen gefunden werden (p = 0,031 bzw. p = 0,010). Die Number needed to treat betrug für den Einstieg in den Zigarettenkonsum 28, für den Einstieg in den Substanzkonsum allgemein 19. Bezüglich des Einstiegs in den heimlichen Alkoholkonsum konnten keine Programmeffekte gefunden werden. Schlussfolgerungen: Es deutet sich ein primärpräventiver Effekt von Klasse2000 auf den Konsum psychotroper Substanzen an.
Gambling Among Adults in Germany: Prevalence, Disorder and Risk Factors
Authors: Sassen Monika , Kraus Ludwig , Bühringer Gerhard , Pabst Alexander , Piontek Daniela , Taqi Zainab
Published: August 2011

Aims: The present study aimed at analyzing prevalence of participation in gambling activities, gambling disorder as well as associated risk factors in the German adult population. Methods: Data came from the 2009 Epidemiological Survey of Substance Abuse (ESA) using a mixed-mode design including questionnaires, telephone and Internet interviews. The cross-sectional random sample consisted of 8,006 subjects aged 18 to 64 years. The response rate was 50.1 %. Results: With a 12-month prevalence of 48.0 %, gambling was a common activity differing by gender (males: 53.9 %, females: 42.0 %). Prevalence of pathological gambling (PG; past 12 months) was estimated at 0.3 % and at 1.1 % for subthreshold pathological gambling (SPG). Various socioeconomic characteristics were related to SPG and/or PG. Male gender and non-German nationality have shown the greatest risk factors for PG. Moreover, gambling frequency and multiple gambling participation were positive associated with SPG and PG. A strong association was found for preference for Internet gambling with SPG and for preference for gaming machines and sports events with PG. Conclusions: The results indicate that SPG was genuinely different from gambling without endorsing any DSM-IV criteria calling for more research on the clinical relevance and classification of this subgroup. Furthermore, findings highlight the need for prevention and intervention measures that target subjects with specific socioeconomic and gambling-related risk factors.
Therapie der Computerspiel- und Internetsucht
Authors: Wölfling Klaus , Leménager Tagrid
Published: August 2011

Einleitung: Die Problematik exzessiver Computerspiel- und Internetnutzung wurde insbesondere in den letzten Jahren durch die erhöhte Verfügbarkeit des Internets zu einem Focus des Interesses in der psychiatrischen und psychologischen Forschung. Besonders der enorm facettenreiche Spielesektor bildet hierbei eine neue Interaktionsform. Zur Behandlung von Computerspiel- und Internetabhängigkeit gibt es bisher nur wenig empirisch fundierte wissenschaftliche Forschung und dem entsprechend auch wenig evaluierte spezifische psychotherapeutische Konzepte. Methodik: Der folgende Artikel soll einen Überblick über bisherige allgemeine und therapiespezifische Forschungsbefunde zur Computerspiel- und Internetabhängigkeit geben. Dabei werden diagnostische Verfahren, Erklärungsansätze sowie aus den Studienergebnissen abgeleitete verhaltenstherapeutische Ansätze vorgestellt und diskutiert. Ergebnisse: Aufgrund der hohen Komorbidität von Angst- und depressiven Störungen, die besonders mit sozialen Kompetenz Defiziten und schlechten Stressbewältigungsstrategien assoziiert sind, stehen verhaltenstherapeutische Interventionen in Gruppen, die auf die Analyse des Problemverhaltens und seiner aufrechterhaltenden Bedingungen abzielen, in der Behandlung von Patienten mit exzessivem Computerspiel- und Internetgebrauch im Vordergrund. Daneben deuten neurobiologische Befunde als auch Ergebnisse aus der Persönlichkeitsforschung auf ähnliche Mechanismen hin, die zu der Entstehung und Aufrechterhaltung von substanzbezogenen Abhängigkeiten beitragen. Hieraus lassen sich Elemente aus der suchtspezifischen Therapie, wie cue-exposure Training mit dem Avatar als auch Situationsanalysen, die mit dem exzessiven Verhalten gekoppelt sind, auf die Behandlung die von Computerspiel und Internetabhängigen sehr gut transferieren. Schlussfolgerungen: Aus bisherigen Forschungsbefunden lassen sich zwar therapeutische Konzepte für die Behandlung von computerspiel- und internetabhängigen Patienten ableiten, es bedarf jedoch an empirischen Studien die den Transfer dieser Interventionen etablieren. Die zu beobachtende Psychopathologie unterstützt die Annahme Computerspiel- und Internetabhängigkeit als eigenes Störungsbild in die klinischen Manuale des DSM V unter die Kategorie Sucht und verwandte Störungen einzuordnen.
Die Wirksamkeit psychologischer und psychopharmakologischer Interventionen bei pathologischem Glückspiel – eine Metaanalyse
Authors: Leibetseder Max , Laireiter Anton-Rupert , Vierhauser Miriam , Hittenberger Bernhard
Published: August 2011

Fragestellung: Die vorliegende Studie berichtet über eine Meta-Analyse zur Wirksamkeit psychologischer und psycho-pharmakologischer Behandlungsmethoden des pathologischen Spiels. Methode: Dazu wurde eine systematische Literaturanalyse bis einschließlich Juli 2006 der Datenbanken PsycInfo, PsyndexPlus, Pascal, Biomed, Medline und Scopus durchgeführt. Von den daraus resultierenden 144 Studien erfüllten 56 mit einem N = 3.551 die Einschlusskriterien. Inkludiert wurden sowohl Studien mit einem Prä-Post-Katamnese-Design wie auch solche mit einer Vergleichs- oder Kontrollgruppe. Effektstärken wurden nach Cohen’s d berechnet. Bei Studien mit mehr als einem Outcome-Kriterium wurden diese gemittelt. Ergebnisse: Psychopharmakologische Behandlungen (d = .83; p ≤ .01; CI(95 %) = .72 – .95) erwiesen sich zum Therapieende als effektiver als psychologische (d = .63; p ≤ .01; CI(95 %) = .54 – .72). Deren Effekte waren zum Follow-up (M = 17 Monate) jedoch hoch (d = 1.26; p ≤ .01; CI(95 %) = 1.15 – 1.37): Wegen fehlender Studien konnten keine entsprechenden Effekte für pharmakologische Behandlungen berechnet werden. Im Hinblick auf die spezifischen Behandlungen erwiesen sich Psycho-Stimulantien und Stimmungsstabilisierer als am effektivsten; bei den psychologischen Methoden waren es multimodale Programme, die aus einer Kombination von Selbsthilfe, Kompetenztrainings und Familieninterventionen bestanden. Allerdings wurden diese primär über Prä-Postvergleiche evaluiert. In diesem Design erwiesen sich jedoch in einer Reanalyse verhaltenstherapeutische Interventionen den multimodalen Programmen überlegen. In den Moderatoranalysen zeigte sich das Studiendesign als einzige bedeutsame Variable. Diskussion: Die Ergebnisse müssen als vorläufig gewertet werden, denn das Feld weist noch viele Mängel auf. So fehlen vor allem kontrollierte randomisierte Studien mit langfristigen Katamnesen. Auch wurden Kombinationstherapien noch nicht untersucht.
Stable carbon isotope patterns of marine biomarker lipids in the Arctic Ocean during Eocene Thermal Maximum 2
Authors: Schoon Petra L. , Sluijs Appy , Sinninghe Damsté Jaap S. , Schouten Stefan
Published: August 2011

The middle Paleocene through early Eocene long‐term gradual warming was superimposed by several transient warming events, such as the Paleocene‐Eocene Thermal Maximum (PETM) and Eocene Thermal Maximum 2 (ETM2). Both events show evidence for extreme global warming associated with a major injection of carbon into the ocean‐atmosphere system, but the mechanisms of carbon injection and many aspects of the environmental response are still poorly understood. In this study, we analyzed the concentration and stable carbon isotopic (δ13C) composition of several sulfur‐bound biomarkers derived from marine photoautotrophs, deposited in the Arctic Ocean at ∼85°N, during ETM2. The presence of sulfur‐bound biomarkers across this event points toward high primary productivity and anoxic bottom water conditions. The previously reported presence of isorenieratene derivatives indicates euxinic conditions in the photic zone, likely caused by a combination of enhanced primary productivity and salinity stratification. The negative carbon isotope excursion measured at the onset of ETM2 for several biomarkers, ranges between 3‰ and 4.5‰, much larger than the ∼1.4‰ recorded in marine carbonates elsewhere, suggesting substantial enhanced isotopic fractionation by the primary producers likely due to a significant rise in pCO2. In the absence of biogenic carbonates in the ETM2 section of our core we use coeval planktonic δ13C from elsewhere to estimate surface water δ13C in the Arctic Ocean and then apply the relation between isotopic fractionation and pCO2, originally calibrated for haptophyte alkenones, to three selected organic biomarkers (i.e., S‐bound phytane, C35 hopane, and a C25 highly branched isoprenoid). This yields pCO2 values potentially in the range of four times preindustrial levels. However, these estimates are uncertain because of a lack of knowledge on the importance of pCO2 on photosynthetic isotopic fractionation.
Toward understanding the post‐collisional evolution of an orogen influenced by convergence at adjacent plate margins: Late Cretaceous–Tertiary thermotectonic history of the Apuseni Mountains
Authors: Merten S. , Matenco L. , Foeken J. P. T. , Andriessen P. A. M.
Published: August 2011

The relationship between syn‐ to post‐collisional orogenic shortening and stresses transmitted from other neighboring plate boundaries is important for understanding the kinematics of mountain belts, but has received little attention so far. The Apuseni Mountains are an example of an orogen in the interference zone between two other subduction systems located in the external Carpathians and Dinarides. This interference is demonstrated by the results of a combined thermochronological and structural field study that quantifies the post‐collisional latest Cretaceous–Tertiary evolution. The exhumation history derived from apatite fission track and (U‐Th)/He thermochronology indicates that the present‐day topography of the Apuseni Mountains originates mainly from latest Cretaceous times, modified by two tectonic pulses during the Paleogene. The latter are suggested by cooling ages clustering around ∼45 Ma and ∼30 Ma and the associated shortening recorded along deep‐seated fault systems. Paleogene exhumation pulses are similar in magnitude (∼3.5 km) and are coeval with the final collisional phases recorded in the Dinarides and with part of the Carpathian rotation around the Moesian promontory. These newly quantified Paleogene exhumation and shortening pulses contradict the general view of tectonic quiescence, subsidence and overall sedimentation for this time interval. The Miocene collapse of the Pannonian Basin did not induce significant regional exhumation along the western Apuseni flank, nor did the subsequent Carpathian collision. This is surprising in the overall context of Pannonian Basin formation and its subsequent inversion, in which the Apuseni Mountains were previously interpreted as being significantly uplifted in both deformation stages.
Auditory Spectral Integration in the Perception of Static Vowels
Authors: Fox Robert Allen , Jacewicz Ewa , Chang Chiung-Yun
Published: August 2011

Purpose

To evaluate potential contributions of broadband spectral integration in the perception of static vowels. Specifically, can the auditory system infer formant frequency information from changes in the intensity weighting across harmonics when the formant itself is missing? Does this type of integration produce the same results in the lower (first formant [F1]) and higher (second formant [F2]) regions? Does the spacing between the spectral components affect a listener’s ability to integrate the acoustic cues?

Method

Twenty young listeners with normal hearing identified synthesized vowel-like stimuli created for adjustments in the F1 region (/ʌ/–/ɑ/, /
i
/–/ε/) and in the F2 region (/ʌ/–/æ/). There were 2 types of stimuli: (a) 2-formant tokens and (b) tokens in which 1 formant was removed and 2 pairs of sine waves were inserted below and above the missing formant; the intensities of these harmonics were modified to cause variations in their spectral center of gravity (COG). The COG effects were tested over a wide range of frequencies.

Results

Obtained patterns were consistent with calculated changes to the spectral COG, in both the F1 and F2 regions. The spacing of the sine waves did not affect listeners' responses.

Conclusion

The auditory system may perform broadband integration as a type of auditory wideband spectral analysis.
Preliminary Investigation of Visual Attention to Human Figures in Photographs: Potential Considerations for the Design of Aided AAC Visual Scene Displays
Authors: Wilkinson Krista M. , Light Janice
Published: August 2011

Purpose

Many individuals with complex communication needs may benefit from visual aided augmentative and alternative communication systems. In visual scene displays (VSDs), language concepts are embedded into a photograph of a naturalistic event. Humans play a central role in communication development and might be important elements in VSDs. However, many VSDs omit human figures. In this study, the authors sought to describe the distribution of visual attention to humans in naturalistic scenes as compared with other elements.

Method

Nineteen college students observed 8 photographs in which a human figure appeared near 1 or more items that might be expected to compete for visual attention (such as a Christmas tree or a table loaded with food). Eye-tracking technology allowed precise recording of participants' gaze. The fixation duration over a 7-s viewing period and latency to view elements in the photograph were measured.

Results

Participants fixated on the human figures more rapidly and for longer than expected based on the size of these figures, regardless of the other elements in the scene.

Conclusions

Human figures attract attention in a photograph even when presented alongside other attractive distracters. Results suggest that humans may be a powerful means to attract visual attention to key elements in VSDs.
The MOC Reflex During Active Listening to Speech
Authors: Garinis Angela C. , Glattke Theodore , Cone Barbara K.
Published: August 2011

Purpose

The purpose of this study was to test the hypothesis that active listening to speech would increase medial olivocochlear (MOC) efferent activity for the right vs. the left ear.

Method

Click-evoked otoacoustic emissions (CEOAEs) were evoked by 60-dB p.e. SPL clicks in 13 normally hearing adults in 4 test conditions for each ear: (a) in quiet; (b) with 60-dB SPL contralateral broadband noise; (c) with words embedded (at −3-dB signal-to-noise ratio [SNR]) in 60-dB SPL contralateral noise during which listeners directed attention to the words; and (d) for the same SNR as in the 3rd condition, with words played backwards.

Results

There was greater suppression during active listening compared with passive listening that was apparent in the latency range of 6- to 18-ms poststimulus onset. Ear differences in CEOAE amplitude were observed in all conditions, with right-ear amplitudes larger than those for the left. The absolute difference between CEOAE amplitude in quiet and with contralateral noise, a metric of suppression, was equivalent for right and left ears. When the amplitude differences were normalized, suppression was greater for noise presented to the right and the effect measured for a probe in the left ear.

Conclusion

The findings support the theory that cortical mechanisms involved in listening to speech affect cochlear function through the MOC efferent system.
Time dependent quantum generators for the Galilei group
Authors: Filippelli G.
Published: August 2011

In 1995, Doebner and Mann introduced an approach to the ray representations of the Galilei group in (1 + 1)-dimensions, giving rise to quantum generators with an explicit dependence on time. Recently (2004), Wawrzycki proposed a generalization of Bargmann's theory: in his paper, he introduce phase exponents that are explicitely dependent by 4-space point. In order to find applications of such generalization, we extend the approach of Doebner and Mann to higher dimensions: as a result, we determine the generators of the ray representation in (2 + 1) and (3 + 1) dimensions. The differences of the outcoming formal apparatus with respect to the smaller dimension case are established.
A general and precise method to evaluate the series resistance of photovoltaic cells from I-V characteristics
Authors: Chibbaro C. , Zimbone M. , Litrico G. , Baeri P. , Lo Trovato M. L. , Aleo F.
Published: August 2011

This paper presents a general method for extracting solar cell parameters from current- voltage characteristics obtained under illumination. In particular, it focuses on the problem of measuring very low values of series resistance with sufficient precision. The method makes use of two different sets of experimental data: a cell current-voltage characteristic measured at a fixed sun irradiance level and a set of short circuit current and open circuit voltage value pairs measured at various sun irradiance levels. The method involves an interplay of different fitting procedures iteratively performed to these two data sets. The method is tested on two single junction silicon cells with the same very low series resistance however, having two very different values of shunt resistance. It is shown that in both cases this method is much more precise and reproducible than other conventional methods.
Multi-time multi-scale correlation functions in hydrodynamic turbulence
Authors: Biferale Luca , Calzavarini Enrico , Toschi Federico
Published: August 2011

High Reynolds numbers Navier-Stokes equations are believed to break self-similarity concerning both spatial and temporal properties: correlation functions of different orders exhibit distinct decorrelation times and anomalous spatial scaling properties. Here, we present a systematic attempt to measure multi-time and multi-scale correlations functions, by using high Reynolds numbers numerical simulations of fully homogeneous and isotropic turbulent flow. The main idea is to set-up an ensemble of probing stations riding the flow, i.e., measuring correlations in a reference frame centered on the trajectory of distinct fluid particles (the quasi-Lagrangian reference frame introduced by Belinicher and L’vov [Sov. Phys. JETP 66, 303 (1987)]). In this way, we reduce the large-scale sweeping and measure the non-trivial temporal dynamics governing the turbulent energy transfer from large to small scales. We present evidences of the existence of the dynamic multiscaling properties of turbulence - first proposed by L’vov et al. [Phys. Rev. E 55, 7030 (1997)] - in which multi-time correlation functions are characterized by an infinite set of characteristic times.
Dust particle charge in plasma with ion flow and electron depletion near plasma boundaries
Authors: Douglass Angela , Land Victor , Matthews Lorin , Hyde Truell
Published: August 2011

The charge on micrometer-sized dust particles suspended in plasma above the powered electrode of radio-frequency discharges is studied. Using a self-consistent fluid model, the plasma profiles above the electrode are calculated and the electron depletion towards the electrode, as well as the increasing flow speed of ions toward the electrode are considered in the calculation of the dust particle floating potential. The results are compared with those reported in literature and the importance of the spatial dust charge variation is investigated.
Elastic properties of porous low-k dielectric nano-films
Authors: Zhou W. , Bailey S. , Sooryakumar R. , King S. , Xu G. , Mays E. , Ege C. , Bielefeld J.
Published: August 2011

Low-k dielectrics have predominantly replaced silicon dioxide as the interlayer dielectric for interconnects in state of the art integrated circuits. In order to further reduce interconnect RC delays, additional reductions in k for these low-k materials are being pursued via the introduction of controlled levels of porosity. The main challenge for such dielectrics is the substantial reduction in elastic properties that accompanies the increased pore volume. We report on Brillouin light scattering measurements used to determine the elastic properties of these films at thicknesses well below 200 nm, which are pertinent to their introduction into present ultralarge scale integrated technology. The observation of longitudinal and transverse standing wave acoustic resonances and their transformation into traveling waves with finite in-plane wave vectors provides for a direct non-destructive measure of the principal elastic constants that characterize the elastic properties of these porous nano-scale films. The mode dispersion further confirms that for porosity levels of up to 25%, the reduction in the dielectric constant does not result in severe degradation in the Young’s modulus and Poisson’s ratio of the films.
Effective channels of breaking the phonon bottleneck: A lattice relaxation approach
Authors: Wang Zi-Wu , Li Shu-Shen
Published: August 2011

We theoretically study the relaxation of electron orbital states of a quantum dot due to two-phonon processes by applying a lattice relaxation approach based on a multimode description for the electron-phonon interaction. The fast relaxation time is obtained in a large energy detuning around the longitudinal optical phonon energy. This model offers an effective channel to break the phonon bottleneck. We calculate the lattice temperature and energy separation dependence of the relaxation time for different two-phonon scattering channels and obtain a good agreement with the available experimental measurement for the phonon bottleneck in quantum dots.
Ab initio studies of the para- and antiferroelectric structures and local polarized configurations in NH4H2PO4
Authors: Lasave J. , Koval S. , Migoni R. L. , Dalal N. S.
Published: August 2011

A study of differently polarized structures relevant to the H-bonded antiferroelectric (AFE) compound NH4H2PO4 (ADP) is performed by first-principles calculations in the framework of the density functional theory. The calculated structures for the AFE and paraelectric (PE) phases are found in general good agreement with the available experimental data. We study the energetics and relative stability of different polarized clusters embedded in a PE matrix of ADP. We find that local ferroelectric and AFE clusters are stable and may coexist in the PE phase, which explains the coexistence of both type of microregions determined by electron spin probe measurements above the AFE-PE transition temperature. The dependency with the O–H⋅⋅⋅O bridge length of the energy barrier heights for proton transfer is studied for coordinated proton displacements along the bridges within clusters of different sizes. This dependency may have implications for the geometric isotopic effects on Tc. We analyze Mulliken orbital and bond populations which confirm the existence of a charge flow within the ${\rm NH}_4^+$ NH 4+ ion, an essential fact for the stabilization of the AFE phase over other possible polarized structures. This charge transfer is correlated with the optimization of the N–H⋅⋅⋅O bridges and with distortions of the ${\rm NH}_4^+$ NH 4+ group.
Ruby and Sm:YAG fluorescence pressure gauges up to 120 GPa and 700 K
Authors: Wei Qingguo , Dubrovinskaia Natalia , Dubrovinsky Leonid
Published: August 2011

Diamond anvil cell (DAC) technique relies on pressure determination based on use of pressure gauges. Fluorescence-based gauges, such as ruby and Sm doped yttrium aluminum garnet (Sm:YAG), are frequently used in the high pressure research. Here we present the results of DAC experiments which allowed extending calibration curves of the fluorescence frequency versus pressure up to 120 GPa at high temperatures up to 700 K for both for ruby and Sm:YAG. Cubic boron nitride was used as the reference gauge.
Computational study of dielectric composites with core-shell filler particles
Authors: Wang Yu U. , Tan Daniel Q. , Krahn John
Published: August 2011

Phase field modeling and computer simulation is employed to study dielectric composites with core-shell filler particles for high-energy-density applications. The model solves electrostatic equations in terms of polarization vector field in reciprocal space using fast Fourier transform technique and parallel computing algorithm. Composites composed of linear constituent phases (matrix, core, and shell materials) of different dielectric constants are considered. Inter-phase boundary conditions are automatically taken into account without explicitly tracking inter-phase interfaces in the composites. The core-shell structures of filler particles are systematically investigated in terms of shell thickness and dielectric constant with respect to core size and matrix dielectric constant, respectively. The effects of filler particle size, shape, and orientation are considered. It is found that core-shell structures of filler particles provide effective means to mitigate local electric field concentration in dielectric composites, improving dielectric breakdown strength and energy density of the composites. Optimal design of core-shell filler particles requires low shell dielectric constant and thick shell coating as compared to core material and core size, respectively.
Depolarization effect on optical control of exciton states confined in GaAs thin films
Authors: Yamashita Takae , Kojima Osamu , Kita Takashi , Isu Toshiro
Published: August 2011

We report the effects of depolarization on the excitonic Rabi oscillation in GaAs thin films measured in the 2k1-k2 direction of a degenerate four-wave-mixing signal. The Rabi frequency, measured by changing the k2 pulse intensity, varies with the k1 pulse intensity; the Rabi frequency decreases with an increase in the k1 power. This decrease originates from the reduction in the field intensity of the k2 pulse, which consists of the local field and depolarization terms. Cancellation of the k2 field due to depolarization leads to the decrease in the Rabi frequency.
Magnetoelectricity of lateral 1-3 type composites with CoFe2O4 ferromagnetic microstrips embedded in (K,Na)NbO3-based piezoceramic substrate
Authors: Xu Ying , Li Jing-Feng , Ma Jing , Nan Ce-Wen
Published: August 2011

Microscale 1-3-type-like magnetoelectric (ME) composites with ferromagnetic microstrips laterally embedded in a piezoelectric ceramic substrate were fabricated by a dice-and-insert method. Mechanically sliced microstrips of Li/Ta-modified (K,Na)NbO3 lead-free ceramics and CoFe2O4 ceramics were used as the piezoelectric and piezomagnetic phases, respectively, which were inserted into each other and bonded together by epoxy. The ME properties of such 1-3-type-like composites with piezoelectric substrates were verified. The maximum ME coefficient was found to vary with the strip size, substrate thickness, and thickness of epoxy bonding layers. A maximum value of 48 mV/(cm·Oe) was achieved. In addition, a special anisotropy was obtained in the present lateral 1-3 type ceramic composites and made it have potential applications in detecting magnetic field directions.
Grain boundary grooving induced by the anisotropic surface drift diffusion driven by the capillary and electromigration forces: Simulations
Authors: Akyildiz Oncu , Omer Ogurtani Tarik
Published: August 2011

The morphological evolution kinetics of a bicrystal thin film induced by anisotropic surface drift diffusion and driven by the applied electrostatic field is investigated via self consistent dynamical computer simulations. The physico-mathematical model, which is based upon the irreversible thermodynamic treatment of surfaces and interfaces with singularities [T. O. Ogurtani, J. Chem. Phys. 124, 144706 (2006)], provided us with auto-control on the otherwise free-motion of the triple junction at the intersection of the grooving surface and the grain boundary, without having any a priori assumption on the equilibrium dihedral angles. The destruction of the symmetry of the freshly formed grain boundary grooves under the anisotropic surface diffusion driven by the concurrent action of the capillarity and electromigration is observed. After prolonged exposure times the applied electric field above the well defined threshold level modifies Mullins’ familiar stationary state time law as, t¯1/4, and causes the premature termination of the groove penetration because of the current crowding at the tips of counteracting grain boundary-grooves initiated on both sides of the test modulus. That finding indicates that the electromigration plays the same role as a healing agent [T. O. Ogurtani, J. Appl. Phys. 106, 053503 (2009)] in arresting the thermal grooving, thereby avoiding the premature interconnect failure as in the case of surface roughening and crack initiation caused by compressive stress gradients. The role of the electromigration and wetting parameter on the ridge/slit formations are thoroughly investigated in this study and the prerequisite conditions are also identified.
Exchange bias in magnetic nanoparticle capped with amorphous magnetic shell
Authors: Nguyen Ha M. , Lee Chih-Hao , Hsiao Pai-Yi , Phan Manh-Huong
Published: August 2011

An extensive Monte Carlo (MC) simulation is performed to investigate exchange bias in a novel model of a nanoparticle consisting of a ferromagnetic (FM) core and an amorphous magnetic (AM) shell. The magnetic glassy ordering of the AM shell governed by random magnetic anisotropy (RMA) is shown to be responsible for the unidirectional anisotropy to the FM core. Our MC results show that, while the bias field and coercivity exhibit a strong dependence on RMA strength, which looks like that on the antiferromagnetic (AFM) thickness in traditional FM/AFM bilayers, they are independent of AM thickness. However, the bias field and coercivity abruptly change with increasing small core size and get saturated for a large enough core size. The cooling field and temperature dependencies show the peculiar sign inversion of the bias field. Our study supports the argument that the exchange bias observed in some magnetic nanoparticles or nanocrystallined alloys is not necessarily due to the presence of an AFM phase.
Investigation of lower hybrid wave coupling and current drive experiments at different configurations in experimental advanced superconducting tokamak
Authors: Ding B. J. , Qin Y. L. , Li W. K. , Li M. H. , Kong E. H. , Zhang L. , Ekedahl A. , Peysson Y. , Decker J. , Wang M. , Xu H. D. , Hu H. C. , Xu G. S. , Shan J. F. , Liu F. K. , Zhao Y. P. , Wan B. N. , Li J. G. , Group EAST
Published: August 2011

Using a 2 MW 2.45 GHz lower hybrid wave (LHW) system installed in experimental advanced superconducting tokamak, we have systematically carried out LHW-plasma coupling and lower hybrid current drive experiments in both divertor (double null and lower single null) and limiter plasma configuration with plasma current (Ip) ∼ 250 kA and central line averaged density (ne) ∼ 1.0–1.3 × 1019 m−3 recently. Results show that the reflection coefficient (RC) first is flat up to some distance between plasma and LHW grill, and then increases with the distance. Studies indicate that with the same plasma parameters, the best coupling is obtained in the limiter case (with plasma leaning on the inner wall), followed by the lower single null, and the one with the worst coupling is the double null configuration, explained by different magnetic connection length. The RCs in the different poloidal rows show that they have different coupling characteristics, possibly due to local magnetic connection length. Current drive efficiency has been investigated by a least squares fit with N//peak=2.1, where N//peak is the peak value of parallel refractive index of the launched wave. Results show that there is no obvious difference in the current drive efficiency between double null and lower single null cases, whereas the efficiency is somewhat small in the limiter configuration. This is in agreement with the ray tracing/Fokker-Planck code simulation by LUKE/C3PO and can be interpreted by the power spectrum up-shift factor in different plasma configurations. A transformer recharge is realized with ∼0.8 MW LHW power and the energy conversion efficiency from LHW to poloidal field energy is about 2%.
Extensibility enables locomotion under isotropic drag
Authors: Pak On Shun , Lauga Eric
Published: August 2011

Anisotropic viscous drag is usually believed to be a requirement for the low Reynolds number locomotion of slender bodies such as flagella and cilia. Here, we show that locomotion under isotropic drag is possible for extensible slender bodies. After general considerations, a two-ring swimmer and a model dinoflagellate flagellum are studied analytically to illustrate how extensibility can be exploited for self-propulsion without drag anisotropy. This new degree of freedom could be useful for some complex swimmer geometries and locomotion in complex fluid environments where drag anisotropy is weak or even absent.
Extension of the invariant environment refinement technique + reverse Monte Carlo method of structural modelling for interpreting experimental structure factors: The cases of amorphous silicon, phosphorus, and liquid argon
Authors: Gereben Orsolya , Pusztai László
Published: August 2011

The invariant environment refinement technique, as applied to reverse Monte Carlo modelling [invariant environment refinement technique + reverse Monte Carlo (INVERT + RMC); M. J. Cliffe, M. T. Dove, D. A. Drabold, and A. L. Goodwin, Phys. Rev. Lett. 104, 125501 (2010)10.1103/PhysRevLett.104.125501], is extended so that it is now applicable for interpreting the structure factor (instead of the pair distribution function). The new algorithm, called the local invariance calculation, is presented by the examples of amorphous silicon, phosphorus, and liquid argon. As a measure of the effectiveness of the new algorithm, the ratio of exactly fourfold coordinated Si atoms was larger than obtained previously by the INVERT-RMC scheme.
Special features of the relation between Fisher information and Schrödinger eigenvalue equation
Authors: Flego S. P. , Plastino A. , Plastino A. R.
Published: August 2011

It is well known that a suggestive relation exists that links Schrödinger's equation (SE) to the information-optimizing principle based on Fisher's information measure. The connection entails the existence of a Legendre transform structure underlying the SE. Here, we show that appeal to this structure leads to a first order differential equation for the SE's eigenvalues that, in certain cases, can be used to obtain the eigenvalues without explicitly solving the SE. Complying with the above mentioned equation constitutes a necessary condition to be satisfied by an energy eigenvalue. We show that the general solution is unique.
Experimental observation of the steady-oscillatory transition in a cubic lid-driven cavity
Authors: Liberzon A. , Feldman Yu. , Gelfgat A. Yu.
Published: August 2011

Particle image velocimetry is applied to the lid-driven flow in a cube to validate the numerical prediction of steady-oscillatory transition at lower than ever observed Reynolds number. Experimental results agree with the numerical simulation demonstrating large amplitude oscillatory motion overlaying the base quasi-two-dimensional flow in the mid-plane. A good agreement in the values of critical Reynolds number and frequency of the appearing oscillations as well as similar spatial distributions of the oscillations amplitude are obtained.