bluuebunny/crossref_metadata_2025 huggingface dataset:
Mini-Mental-State
Authors: Kaiser Andreas , Gusner-Pfeiffer Renate , Griessenberger Hermann , Iglseder Bernhard
Published: May 2009

Im folgenden Artikel werden fünf verschiedene Versionen der Mini-Mental-State-Examination dargestellt, die alle auf der Grundlage des Originals von Folstein erstellt wurden, sich jedoch deutlich voneinander unterscheiden und zu unterschiedlichen Ergebnissen kommen, unabhängig davon, ob das Screening von erfahrenen Untersuchern durchgeführt wird oder nicht. Besonders auffällig ist, dass Frauen die Aufgaben «Wort rückwärts» hoch signifikant besser lösten als das «Reihenrechnen». An Hand von Beispielen werden Punkteunterschiede aufgezeigt.
Was lernen Medizinstudenten im Wahlfach Kinder- und Jugendpsychiatrie?
Authors: Frank Reiner , Gegenfurtner Gisela , Steininger Christine , Kopecky-Wenzel Marie , Noterdaeme Michele
Published: May 2009

Fragestellung: Im Rahmen des medizinischen Curriculums der Ludwig-Maximilians-Universität (MeCuMLMU) wird ein Kurs «Wahlfach Kinder- und Jugendpsychiatrie und Psychotherapie» durchgeführt. Ziele und Schwerpunkte sind der Einblick in den klinischen Alltag und der Erwerb von Grundfertigkeiten in psychopathologischer Befunderhebung und in Gesprächsführung.

Methodik: Die 23 Unterrichtseinheiten erstrecken sich innerhalb einer Woche über vier Tage. Der Kurs wird zweimal im Semester für jeweils 12 Studierende angeboten. Der Einblick ins Fachgebiet wird durch Fallbeispiele von Kindern unterschiedlichen Alters mit je einer externalisierenden, internalisierenden Störung und einer Entwicklungsverzögerung und durch eine klinische Visite mit individueller Betreuung der Studierenden im Lehrkrankenhaus vermittelt. Das Erstellen eines psychischen Befundes wird anhand von Videoaufnahmen von Patienten in Gruppenarbeit unter Anleitung eingeübt. Rollenspiel mit Videofeedback bietet die Möglichkeit, Gesprächsfertigkeiten zu entwickeln.

Ergebnisse: Die Evaluation erfolgt durch eine schriftliche Prüfung am Ende des Kurses, in der eigenständig ein Befund aufgeschrieben werden muss. Der Kurs wird von Studierenden und Dozenten in strukturierter Form beurteilt. Videoaufnahmen werden im Anschluss an den Kurs ausgewertet. Bei einer Teilgruppe konnte nach sechs Monaten eine Nachbefragung durchgeführt werden.

Schlussfolgerungen: Der Kurs bietet eine hervorragende Möglichkeit, Studierende für das Fach Kinder- und Jugendpsychotherapie zu begeistern und als Nachwuchs zu gewinnen.
Die Bedeutung der Lehre im Spannungsfeld zwischen «Evidence-based Medicine» und «Experience-based Medicine»
Authors: Resch Franz , Fegert J.M.
Published: May 2009

Als medizinisches Fachgebiet hat die Kinder- und Jugendpsychiatrie und -psychotherapie eine besondere gesellschaftliche Bedeutung erlangt, da sie angesichts der epidemiologischen Bedeutung psychischer Störungen im Kindes- und Jugendalter die Entwicklungschancen von Kindern unter verschiedenen Risikobedingungen nachweislich vergrößert. Kinder- und Jugendpsychiatrie und -psychotherapie sollte daher eine Verankerung in der Pflichtlehre für Medizinstudenten nach der Approbationsordnung erfahren. Im Rahmen des Bio-psycho-sozialen Modells, das die integrale Erklärungsfigur für psychische Störungen darstellt, muss das Problem des hermeneutischen Verstehens beachtet werden. Evidence-based Medicine und das Erfahrungslernen am einzelnen Patienten (Experience-based Learning) müssen in einem ausgewogenen Verhältnis das Medizinstudium bestimmen und sollten nicht gegeneinander ausgespielt werden. Ethische Dilemmata des therapeutischen Handelns gilt es zu beachten.
Als Panikattacken imponierende Occipitallappenanfälle
Authors: Stolle Martin , Sieben Claudia , Püst Burkhard
Published: May 2009

Die elfjährige Stephanie wurde mit der Verdachtsdiagnose auf eine Angst- und Panikstörung mit assoziierten Zwangshandlungen und selbstverletzendem Verhalten in einer kinder- und jugendpsychiatrischen Tagesklinik aufgenommen. Detailliert beschrieb Stephanie äußerst real wirkende hoch bedrohliche szenische Sequenzen, die sie in Panik versetzten. Im Zuge der Diagnostik konnten die Symptome der Angst- und Panikstörung einer Epilepsie mit visuell dominierten komplex-partialen Anfällen des Occipitallappens zugeordnet werden. Neben der medikamentösen Anfallsbehandlung mit Oxcarbazepin halfen umfangreiche multimodale Interventionen im Rahmen der kinder- und jugendpsychiatrischen tagesklinischen Behandlung, das Anfallsgeschehen für die Familie versteh- und handlebar zu machen. Acht Wochen nach Behandlungsbeginn war Stephanie dauerhaft anfallsfrei. Komplexe Partialepilepsien mit affektiver Symptomatik können als primär kinderpsychiatrische Störung fehl gedeutet werden.
Umsetzung der ESH/ESC-Hypertonie-Richtlinien mithilfe verschiedener Blutdruckmessmethoden
Authors: Schulz  , Battegay  , Neumann  , Schmidt-Weitmann  , Brockes
Published: May 2009

Das bessere Verständnis der Epidemiologie und Pathophysiologie der arteriellen Hypertonie hat zu einer neuen Blutdruckkategorisierung und Definitionen neuer Behandlungsziele geführt. Der Hauptgrund für die weltweit mässigen Behandlungserfolge besteht ausser Malcompliance und Medikamenten-Nebenwirkungen in einer suboptimalen Medikamentenbehandlung mit unvollständiger Dosistitration und einer unangemessenen kleinen Anzahl miteinander kombinierter Antihypertensiva. Neue Techniken wie die Fernübermittlung der Blutdruckmessungen zu Hause in Kombination mit der ambulanten 24-Stunden-Blutdruckmessung könnten Ärzte unterstützen, eine adäquatere antihypertensive Therapie zu ermöglichen, die Medikamentencompliance zu verbessern und die Dauer bis zum Erreichen des optimalen Blutdrucks zu reduzieren.
Numerical modeling of two‐phase flow in the NaCl‐H2O system: Introduction of a numerical method and benchmarking
Authors: Lewis K. C. , Lowell R. P.
Published: May 2009

In order to facilitate modeling of fluid flow processes in seafloor hydrothermal systems, we introduce a numerical scheme called FISHES that is capable of simulating two‐phase fluid flow in the NaCl‐H2O system. We discuss the equations governing fluid flow, the thermodynamic relations between various quantities employed, and the coupling of these elements together in a time marching scheme. The thermodynamic relations are expressed in terms of equations of state compiled from lookup tables. These are based on previously published formulations for the density and enthalpy of NaCl‐H2O fluid in regions of phase space that are relevant to the study of seafloor hydrothermal systems. We show that the thermodynamic quantities vary both smoothly and physically in P‐T‐X space. In particular, vapor salinity values near the vapor‐liquid‐halite coexistence surface are in agreement with recently measured values. We compare code output from an approximately one‐dimensional scenario to the analytic solution of the classical one‐dimensional thermal advection‐diffusion equation and find that the numerical output and analytic solution are in agreement. The numerical code is also benchmarked against previously published results for the Elder problem and for the problem of fluid extraction from a one‐dimensional, two‐phase horizontal pipe. We find that the results using FISHES are in agreement with previously published results. Finally, we show that results from a one‐dimensional vertical salt pipe simulation agree with an analytic solution.
Central South Pacific thermocline water circulation from a high‐resolution ocean model validated against satellite data: Seasonal variability and El Niño 1997–1998 influence
Authors: Martinez Elodie , Ganachaud Alexandre , Lefevre Jerome , Maamaatuaiahutapu Keitapu
Published: May 2009

The oceanic circulation in French Polynesia, central South Pacific, is investigated based on a high‐resolution model validated with satellite data. We focus on the upper 500 m, where ocean current variability has been barely documented due to a lack of in situ measurements. Seasonal and El Niño–Southern Oscillation 1997–1999 variability of surface and subsurface currents are characterized. In the north, the South Equatorial Current (SEC) follows a seasonal cycle with winter enhancement corresponding to trade wind strengthening. During summer, the SEC slows and the eastward South Equatorial Countercurrent (SECC) appears across the domain north of an upward Ekman pumping region related to the South Pacific Convergence Zone development in the area. Around the Marquesas Islands, a wind curl dipole is suspected to create westward and eastward (Marquesas Countercurrent, MCC) jets. The eastward Subtropical Countercurrent (STCC) is found south of 20°S. It is disturbed by eddies and broken into westward and eastward branches. During El Niño 1997–1998, due to the reversed winds in the equatorial band, the SEC weakened, while eastward countercurrents appeared. The SECC reinforced and moved northeastward in summer 1998. During La Niña 1998–1999, following the trade wind enhancement, the SEC strengthened. The countercurrents weakened or disappeared and the SECC moved southwestward in summer 1999. During both El Niño and La Niña events, the STCC eddy activity strengthened, while the MCC and associated westward jet were absent. These variations and their dynamical origins are discussed, and a coherent picture of the French Polynesian current system and its variations is proposed.
Comparison of mineral dust layers vertical structures modeled with CHIMERE‐DUST and observed with the CALIOP lidar
Authors: Vuolo Maria Raffaella , Chepfer Hélène , Menut Laurent , Cesana Grégory
Published: May 2009

The final budget of dust remaining in the atmosphere or deposited on the surface depends directly on the emissions, boundary layer turbulence, stability in the troposphere, and clouds properties. The modeling of these processes remains uncertain and mineral dust long‐range transport constitutes a major unknown. To improve this transport, it is crucial to improve modeling of altitudes and thicknesses of mineral dust layers. The spaceborne lidar Cloud‐Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) collects new information about the aerosol vertical distribution. Here we diagnose the lidar profile from the outputs of the transport model CHIMERE‐DUST and we compare those with their observed counterparts. During the periods June to September 2006 and January to March 2007, the occurrences and structures of dust layers are estimated from the observed and modeled lidar signals. Accounting for the daytime and nighttime periods, the seasonal variability, and CALIPSO flight tracks, it is shown that the presence/absence of dust is correctly reproduced by the model in 70% of the 170,000 vertical profiles studied. The mineral dust horizontal distribution is quite correctly reproduced by the model, while the vertical one shows a vertical overspread which is more pronounced during winter (+100% compared to observations) than summer (+50%). The maximum value of the modeled lidar signal is underestimated with respect to the measured one by typically 30%. Multilayered dust situations are more frequent in the observations (30% of the total data set) than in the model (10%). Despite these errors, the model is able to catch the seasonal variations of the dust layers: the increases of the dust load and of the dust altitudes during summer and the northward shift of the maximum dust occurrence.
Inventories and mobilization of unsaturated zone sulfate, fluoride, and chloride related to land use change in semiarid regions, southwestern United States and Australia
Authors: Scanlon Bridget R. , Stonestrom David A. , Reedy Robert C. , Leaney Fred W. , Gates John , Cresswell Richard G.
Published: May 2009

Unsaturated zone salt reservoirs are potentially mobilized by increased groundwater recharge as semiarid lands are cultivated. This study explores the amounts of pore water sulfate and fluoride relative to chloride in unsaturated zone profiles, evaluates their sources, estimates mobilization due to past land use change, and assesses the impacts on groundwater quality. Inventories of water‐extractable chloride, sulfate, and fluoride were determined from borehole samples of soils and sediments collected beneath natural ecosystems (N= 4), nonirrigated (“rain‐fed”) croplands (N= 18), and irrigated croplands (N= 6) in the southwestern United States and in the Murray Basin, Australia. Natural ecosystems contain generally large sulfate inventories (7800–120,000 kg/ha) and lower fluoride inventories (630–3900 kg/ha) relative to chloride inventories (6600–41,000 kg/ha). Order‐of‐magnitude higher chloride concentrations in precipitation and generally longer accumulation times result in much larger chloride inventories in the Murray Basin than in the southwestern United States. Atmospheric deposition during the current dry interglacial climatic regime accounts for most of the measured sulfate in both U.S. and Australian regions. Fluoride inventories are greater than can be accounted for by atmospheric deposition in most cases, suggesting that fluoride may accumulate across glacial/interglacial climatic cycles. Chemical modeling indicates that fluorite controls fluoride mobility and suggests that water‐extractable fluoride may include some fluoride from mineral dissolution. Increased groundwater drainage/recharge following land use change readily mobilized chloride. Sulfate displacement fronts matched or lagged chloride fronts by up to 4 m. In contrast, fluoride mobilization was minimal in all regions. Understanding linkages between salt inventories, increased recharge, and groundwater quality is important for quantifying impacts of anthropogenic activities on groundwater quality and is required for remediating salinity problems.
Unexpected peak near −15°C in CloudSat echo top climatology
Authors: Riley Emily M. , Mapes Brian E.
Published: May 2009

We examine a radar‐derived climatology of Earth's cloudiness, focusing on the vertical distribution echo tops. Between the two main peaks at ∼2 km and ∼14 km associated with low and high clouds, respectively, lie two distinct midlevel peaks in the tropics. One is in the 5–6 km layer, the other between 7 and 8 km. Both are seen day and night, over land and sea, over each tropical ocean basin, and in published ground radar climatology. In the extratropics, the vertical echo top distribution by temperature reveals a strikingly sharp peak in the −15 to −20°C layer (corresponding to the 7–8 km peak in the tropics). Again the signal is robust (night‐day, land‐sea, summer‐winter). We consider interpretations of the −15°C peak ranging from data artifacts (unlikely), to mere radar brightening, to possible true microphysical or dynamical cloudiness enhancement mechanisms.
Twenty‐five years of Atlantic basin seasonal hurricane forecasts (1984–2008)
Authors: Klotzbach Philip J. , Gray William M.
Published: May 2009

The Tropical Meteorology Project at Colorado State University, led by Dr. William Gray, has been issuing Atlantic basin seasonal hurricane forecasts in early June and early August since 1984. This paper examines the skill of these forecasts over the past twenty‐five years (1984–2008) compared with climatology and a previous 3‐year, 5‐year and 10‐year mean. Seasonal forecasts are shown to have smaller mean‐squared errors than any of these metrics for most parameters, although improvements have been modest. The forecast models used by the Tropical Meteorology Project have changed over time, and the current early June and early August model's skill at hindcasting the past twenty‐five years are investigated using cross‐validation. Preliminary research indicates that using these new models may result in more significant skill improvements in future years.
The Antarctic ozone hole and the Northern Annular Mode: A stratospheric interhemispheric connection
Authors: Rind D. , Jonas J. , Stammerjohn S. , Lonergan P.
Published: May 2009

The S.H. ozone hole deepened into the mid‐1990s, while the Northern Annular Mode (NAM) became more positive. Both effects have since stabilized. We investigate a possible connection with modeling experiments of a S. H. spring ozone hole, and also year‐round ozone loss in both polar regions. The S.H. ozone hole results in a more positive NAM‐like phase extending down to the surface. Reduced vertical stability increases S.H. tropospheric wave energy flux into the stratosphere which drives a residual circulation with relative subsidence over the Southern pole and upwelling and reduced planetary wave energy flux at Northern high latitudes. The results suggest that similar trends in the Southern Ozone hole and the NAM over the last 20 years may be more than just a coincidence, although other factors undoubtedly influence the Northern high latitude circulation.
Moving candidate vaccines into development from research: lessons from HIV
Authors: Sullivan Mark
Published: May 2009

There is a logarithmic increase in the cost and complexity of the research and development process when transitioning a promising candidate vaccine from the laboratory into the clinic. Managing complex development programs involving people from diverse technical, cultural and geographical backgrounds is a specialised skill. It is essential that the group is clear on their objectives and how their activities affect others, that communication is open, inclusive and effective, and that the most rigorous, scientific approach based on statistical principles in compliance with regulatory requirements is used. Applying these standards to all vaccine development programs will filter out inappropriate candidates more readily and enhance the efficiency of vaccine development. The challenges of developing a new vaccine are illustrated in human immunodeficiency virus (HIV) vaccinology. Selecting vaccine candidates for HIV requires the ability to evaluate the large number of potential antigens in imperfect and non‐standardised animal models. Further, using these models to evaluate questions such as dose scaling to humans, optimal route of administration, the use of adjuvants and potential formulation improvements adds variable to variable, making the interpretation of results particularly challenging. This may lead to the promotion of a poor candidate or the elimination of a good one. The absence of precise immunological correlates of protection and the prohibitive cost of confirmatory clinical trials are further significant barriers. However, there are practical steps that can be taken to standardise early vaccine evaluation, which would result in more efficient development of new vaccines for HIV and other disease areas with similarly challenging development issues (such as hepatitis C virus, influenza, Mycobacterium tuberculosis and malaria).
Human NK cell lines migrate differentially in vitro related to matrix interaction and MMP expression
Authors: Edsparr Karin , Johansson Bengt R , Goldfarb Ronald H , Basse Per H , Nannmark Ulf , Speetjens Frank M , Kuppen Peter JK , Lennernäs Bo , Albertsson Per
Published: May 2009

Matrix metalloproteinases (MMPs) are thought to be of importance for the migratory ability of natural killer (NK) cells. Their expression and production may influence the amount of tumour‐infiltrating NK cells and thereby any therapeutic capability. In this study, we sought to investigate the importance of MMPs for human NK cells’ ability to degrade and migrate through the extracellular matrix (ECM). The two human NK cell lines, NK‐92 and YT, migratory ability, MMP expression and production as well as their morphological appearance when cultured in the ECM equivalent Matrigel were analysed and compared. The quantitatively more migratory NK‐92 cells were found to express invadopodia/podosomes at a significantly higher degree when cultured in Matrigel and gave rise to a general disintegration of the Matrigel. The NK‐92 cells had a higher mRNA expression of MMP‐2, ‐9, ‐13, MT1‐, MT3‐ and MT6‐MMP and a significantly higher production of MMP‐9 compared to YT cells. These differences could explain the substantial functional difference observed between the two cell lines with respect to migratory capacity. In addition, the number of Matrigel invading NK‐92 cells decreased significantly in the presence of the MMP inhibitor GM6001, demonstrating that MMPs have a critical function in their migration.
Childhood Obesity Prevention: An Intervention Targeting Primary Caregivers of School Children
Authors: Bruss Mozhdeh B. , Michael Timothy J. , Morris Joseph R. , Applegate Brooks , Dannison Linda , Quitugua Jackie A. , Palacios Rosa T. , Klein David J.
Published: May 2009

Community‐based participatory research (CBPR) was used to design and evaluate the effectiveness of a culturally relevant, science‐based intervention for the prevention of childhood obesity in the Commonwealth of the Northern Mariana Islands (CNMI), a US Commonwealth in the western Pacific. This cognitive behavioral lifestyle intervention, Project Familia Giya Marianas (PFGM), was offered during the 2005–2007 school years in all CNMI public elementary schools over eight sessions to primary caregivers of 3rd grade children (N = 407). A crossover design was utilized with half of the schools offering the intervention in the Fall term, while the other half delivered the sessions in the Spring term. The primary outcome measure was change in BMI z‐score. There was an intervention‐dependent effect on BMI z‐score, with program impact being a function of baseline BMI and the number of lessons attended. This effect was most apparent in students whose baseline BMI z‐score was in healthy range (≥5 to <85 percentile). In both Asian and Pacific Island groups, children whose caregivers completed 5–8 lessons experienced a significant change in BMI z‐score as compared to those with 0 lessons (P < 0.05). Research that integrates multidisciplinary and multimethod approaches is effective in identifying and/or devising solutions to address a complex condition such as childhood obesity. PFGM demonstrated that community participation can be successfully utilized in the development and implementation of childhood obesity prevention programs.
Distribution, pharmacological characterization and function of the 18 kDa translocator protein in rat small intestine
Authors: Ostuni Mariano Anibal , Péranzi Gabriel , Ducroc Robert A. , Fasseu Magali , Vidic Branislav , Dumont Janice , Papadopoulos Vassilios , Lacapere Jean‐Jacques
Published: May 2009

Background information. The TSPO (18 kDa translocator protein) is a mitochondrial transmembrane protein involved in cholesterol transport in organs that synthesize steroids and bile salts. Different natural and synthetic high‐affinity TSPO ligands have been characterized through their ability to stimulate cholesterol transport, but also to stimulate other physiological functions including cell proliferation, apoptosis and calcium‐dependent transepithelial ion secretion. Here, we investigate the localization and functions of TSPO in the small intestine.

Results. TSPO was present in enterocyte mitochondria but not in rat intestinal goblet cells. Enterocyte cytoplasm also contained the endogenous TSPO ligand, polypeptide DBI (diazepam‐binding inhibitor). Whereas intestinal TSPO had high affinity for the synthetic ligand PK 11195, the pharmacological profile of TSPO in the duodenum was distinct from the jejunum and ileum. Specifically, benzodiazepine Ro5‐4864 and protoporphyrin IX showed 5–13‐fold lower affinity for duodenal TSPO. The mRNA and protein ratios of TSPO to other mitochondrial membrane proteins VDAC (voltage‐dependent anion channel) and ANT (adenine nucleotide transporter) were significantly different. PK 11195 stimulated calcium‐dependent chloride secretion in the duodenum and calcium‐dependent chloride absorption in the ileum, but did not affect jejunum ion transport.

Conclusions. The functional differences in subpopulations of TSPO in different regions of the intestine could be related to structural organization of mitochondrial protein complexes that mediate the ability of TSPO to modulate either chloride secretion or absorption in the duodenum and ileum respectively.
NAD(P)H oxidase-mediated reactive oxygen species production alters astrocyte membrane molecular order via phospholipase A2
Authors: Zhu Donghui , Hu Chunhua , Sheng Wenwen , Tan Kevin S. , Haidekker Mark A. , Sun Albert Y. , Sun Grace Y. , Lee James C.-M.
Published: May 2009

ROS (reactive oxygen species) overproduction is an important underlying factor for the activation of astrocytes in various neuropathological conditions. In the present study, we examined ROS production in astrocytes and downstream effects leading to changes in the signalling cascade, morphology and membrane dynamics using menadione, a redox-active compound capable of inducing intracellular ROS. NAD(P)H oxidase-mediated menadione-induced ROS production, which then stimulated phosphorylation of p38 MAPK (mitogen-activated protein kinase) and ERK1/2 (extracellular-signal-regulated kinase 1/2), and increased actin polymerization and cytoskeletal protrusions. We also showed that astrocyte plasma membranes became more molecularly ordered under oxidative stress, which was abrogated by down-regulating cPLA2 (cytosolic phospholipase A2) either with a pharmacological inhibitor or by RNA interference. In addition, mild disruption of F-actin with cytochalasin D suppressed menadione-enhanced phosphorylation of cPLA2 and membrane alterations. Taken together, these results suggest an important role for ROS derived from NAD(P)H oxidase in activation of astrocytes to elicit biochemical, morphological and biophysical changes reminiscent of reactive astrocytes in pathological conditions.
Multiple matching scheme for broadband 0.72Pb(Mg1/3Nb2/3)O3−0.28PbTiO3 single crystal phased-array transducer
Authors: Lau S. T. , Li H. , Wong K. S. , Zhou Q. F. , Zhou D. , Li Y. C. , Luo H. S. , Shung K. K. , Dai J. Y.
Published: May 2009

Lead magnesium niobate–lead titanate single crystal 0.72Pb(Mg1/3Nb2/3)O3−0.28PbTiO3 (abbreviated as PMN-PT) was used to fabricate high performance ultrasonic phased-array transducer as it exhibited excellent piezoelectric properties. In this paper, we focus on the design and fabrication of a low-loss and wide-band transducer for medical imaging applications. A KLM model based simulation software PiezoCAD was used for acoustic design of the transducer including the front-face matching and backing. The calculated results show that the −6 dB transducer bandwidth can be improved significantly by using double λ/8 matching layers and hard backing. A 4.0 MHz PMN-PT transducer array (with 16 elements) was fabricated and tested in a pulse-echo arrangement. A −6 dB bandwidth of 110% and two-way insertion loss of −46.5 dB were achieved.
Picosecond time scale dynamics of short pulse laser-driven shocks in tin
Authors: Grigsby W. , Bowes B. T. , Dalton D. A. , Bernstein A. C. , Bless S. , Downer M. C. , Taleff E. , Colvin J. , Ditmire T.
Published: May 2009

The dynamics of high strain rate shock waves driven by a subnanosecond laser pulse in thin tin slabs have been investigated. These shocks, with pressure up to 1 Mbar, have been diagnosed with an 800 nm wavelength ultrafast laser pulse in a pump-probe configuration, which measured reflectivity and two-dimensional interferometry of the expanding rear surface. Time-resolved rear surface expansion data suggest that we reached pressures necessary to shock melt tin upon compression. Reflectivity measurements, however, show an anomalously high drop in the tin reflectivity for free standing foils, which can be attributed to microparticle formation at the back surface when the laser-driven shock releases.
The role of amorphous silicon and tunneling in heterojunction with intrinsic thin layer (HIT) solar cells
Authors: Kanevce Ana , Metzger Wyatt K.
Published: May 2009

This work analyzes heterojunction with intrinsic thin layer (HIT) solar cells using numerical simulations. The differences between the device physics of cells with p- and n-type crystalline silicon (c-Si) wafers are substantial. HIT solar cells with n-type wafers essentially form a n/p/n structure, where tunneling across the junction heterointerfaces is a critical transport mechanism required to attain performance exceeding 20%. For HIT cells with p-type wafers, only tunneling at the back-contact barrier may be important. For p-wafer cells, the hydrogenated amorphous silicon (a-Si:H) between the indium tin oxide (ITO) and crystalline silicon may act as a passivating buffer layer but, otherwise, does not significantly contribute to device performance. For n-wafer cells, the carrier concentration and band alignment of this a-Si:H layer are critical to device performance.
Holonomy and parallel transport in the differential geometry of loop spaces and generalized gauge transformations
Authors: Rossi Carlo A.
Published: May 2009

The motivation of this paper stems from the need to construct explicit isomorphisms of (possibly nontrivial) principal G-bundles on the space of loops or, more generally, of paths in some manifold M, over which we consider a fixed principal bundle P; the aforementioned bundles are then pull backs of P with respect to evaluation maps at different points. The explicit construction of these isomorphisms between pulled-back bundles relies on the notion of parallel transport. We introduce and discuss extensively at this point the notion of generalized gauge transformation between (a priori) different principal G-bundles over the same base M, and we see immediately that the parallel transport is a generalized gauge transformation for two special kinds of bundles on the space of loops or paths; at this point, we may try and generalize the previous arguments for more general pulled-back bundles. Finally, we discuss how flatness of the reference connection, with respect to which we consider parallel transport, is related to horizontality of the associated generalized gauge transformation.
Optimization of device geometry in single-plate digital microfluidics
Authors: Abdelgawad Mohamed , Park Philip , Wheeler Aaron R.
Published: May 2009

Digital microfluidics is a popular tool for lab-on-a-chip applications and is typically implemented in one of two formats: single-plate (“open”) devices or two-plate (“closed”) devices. Single-plate devices have some advantages relative to the more common two-plate format such as faster mixing, the capacity to move larger volumes on a given footprint, and easier access to droplets for handling or optical detection. In contrast with the two-plate format, in which ground potential is generally supplied via a top electrode, in the single-plate format, many different geometries of ground wires/electrodes have been used. Until the present study, there has been no metric to determine which of these geometries is best suited for droplet actuation. Here, we present a combination of numerical simulations and experimental tests to compare six different single-plate designs. We applied finite element analysis, using the commercially available COMSOL software package to calculate the electrodynamic actuation forces in each of the different designs and used the results to optimize device design. Forces predicted by the electrodynamic model were in agreement with forces predicted using electromechanical models. More importantly, results were verified experimentally using a unique technique that permits indirect estimation of actuation forces on digital microfluidic devices. This work illustrates the promise of using numerical modeling to enhance the design and performance of digital microfluidic devices.
Electromechanical properties of A-site (LiCe)-modified sodium bismuth titanate (Na0.5Bi4.5Ti4O15) piezoelectric ceramics at elevated temperature
Authors: Wang Chun-Ming , Wang Jin-Feng , Zhang Shujun , Shrout Thomas R.
Published: May 2009

The Aurivillius-type bismuth layer-structured (NaBi)0.46(LiCe)0.04Bi4Ti4O15 (NBT-LiCe) piezoelectric ceramics were synthesized using conventional solid-state processing. Phase analysis was performed by x-ray diffraction and microstructural morphology was assessed by scanning electron microscopy. The dielectric, piezoelectric, ferroelectric, and electromechanical properties of NBT-LiCe ceramics were investigated. The piezoelectric activities were found to be significantly enhanced compared to NBT ceramics, which can be attributed to the lattice distortion and the presence of bismuth vacancies. The dielectric and electromechanical properties of NBT-LiCe ceramics at elevated temperature were investigated in detail. The excellent piezoelectric, dielectric, and electromechanical properties, coupled with high Curie temperature (Tc=660 °C), demonstrated that the NBT-LiCe ceramics are the promising candidates for high temperature applications.
Agglomeration process in thin silicon-, strained silicon-, and silicon germanium-on-insulator substrates
Authors: Capellini G. , Ciasca G. , De Seta M. , Notargiacomo A. , Evangelisti F. , Nardone M.
Published: May 2009

In this paper we present a comparative study of the agglomeration process in silicon-on-insulator (SOI), silicon germanium-om-insulator (SGOI), and strained SOI (SSOI) thin layers under thermal annealing in ultrahigh vacuum. In particular, we provide the first evidence and characterization of agglomeration in SGOI and SSOI substrates. A common agglomeration dynamics is observed in all the substrates investigated, with the semiconductor-on-insulator layer thickness being the main parameter governing it. These findings provide a better understanding of the surface-energy-driven dewetting phenomenon in semiconductor layers and allow us to single out the influence of the surface and stress energies on the void formation and evolution, as well as on the size and density of the agglomerated islands.
Competition between structural distortion and magnetic moment formation in fullerene C20
Authors: Han Myung Joon , Kim Gunn , Lee Jae Il , Yu Jaejun
Published: May 2009

We investigate the effect of on-site Coulomb interactions on the structural and magnetic ground state of C20 fullerene based on density-functional-theory calculations within the local density approximation (LDA) plus on-site Coulomb corrections (LDA+U). The total energies of the high symmetry (Ih) and the distorted (D3d) structures of C20 are calculated for different spin configurations. The ground state configurations are found to depend on the forms of exchange-correlation potentials and the on-site Coulomb interaction parameter U, reflecting the subtle nature of the competition between Jahn–Teller distortion and magnetic instability in the C20 fullerene. While the nonmagnetic state of the distorted D3d structure is robust for small U, a magnetic ground state of the undistorted Ih structure emerges for U larger than 4 eV when the LDA exchange-correlation potential is employed.
The impact of barrier height distributions in tunnel junctions
Authors: Miller Casey W. , Belyea Dustin D.
Published: May 2009

We demonstrate that including continuous and discrete tunnel barrier height distributions in otherwise traditional tunneling formalisms enables straightforward modeling of several phenomena important to tunneling. Random barrier height inhomogeneities significantly impact the tunneling conductance, as evidenced by ideal tunneling models extracting faulty barrier parameters, with the incurred errors strongly dependent on the variance. Thermal smearing is addressed by transferring the energy distribution from the electrons to the barrier potential energy, thereby enabling zero-temperature tunneling models to model temperature dependent tunneling. For discrete tunneling channels, a secondary, impuritylike channel is shown to dominate the net conductance at surprisingly low impurity levels, implying that the observation of intrinsically large barrier heights is highly unlikely with transport measurements. Finally, spin-filter tunneling is modeled with independent tunneling channels whose barrier heights are linked to a temperature-dependent exchange splitting.
Nonlinear laser energy depletion in laser-plasma accelerators
Authors: Shadwick B. A. , Schroeder C. B. , Esarey E.
Published: May 2009

Energy depletion of intense, short-pulse lasers via excitation of plasma waves is investigated numerically and analytically. The evolution of a resonant laser pulse proceeds in two phases. In the first phase, the pulse steepens, compresses, and frequency redshifts as energy is deposited in the plasma. The second phase of evolution occurs after the pulse reaches a minimum length at which point the pulse rapidly lengthens, losing resonance with the plasma. Expressions for the rate of laser energy loss and rate of laser redshifting are derived and are found to be in excellent agreement with the direct numerical solution of the laser field evolution coupled to the plasma response. Both processes are shown to have the same characteristic length scale. In the high intensity limit, for nearly resonant Gaussian laser pulses, this scale length is shown to be independent of laser intensity.
Generation of highly spin-polarized currents in cascaded InAs spin filters
Authors: Jacob Jan , Meier Guido , Peters Sebastian , Matsuyama Toru , Merkt Ulrich , Cummings Aron W. , Akis Richard , Ferry David K.
Published: May 2009

We report the generation of highly spin-polarized currents and their detection in cascaded InAs spin filters via transport measurements below 300 mK. The intrinsic spin-Hall effect is used in the first filter to generate two oppositely spin-polarized currents. From the conductance asymmetry at the outputs of the second filter high spin polarizations are determined in all-electrical measurements. The experiments are in good agreement with ballistic quantum transport simulations, which mimic the double-Y-shaped structure constricted by quantum-point contacts.
Microstructure and texture developments in multiple pulses excimer laser crystallization of GaAs thin films
Authors: Pirzada Daniel , Cheng Gary J.
Published: May 2009

In this paper, we observed and characterized changes in the microstructure and texture during recrystallization and grain growth in polycrystalline GaAs thin films using multiple pulses crystallization by a KrF excimer laser. Films of various thicknesses were studied to assess film thickness and laser energy density effects. In the low temperature domain corresponding to the partial melting regime, normal grain growth was observed. In the superlateral grain growth regime the increase in grain size was notable with grain sizes much greater than the film thickness. A bimodal grain size distribution emerged implying the onset of secondary grain growth. The change in grain size distribution, texture, and grain boundary texture were analyzed using scanning electron microscopy and electron backscatter diffraction. It was found that grain growth is accompanied by a strengthening in {001} texture, indicating that the grain growth phenomenon is strain energy driven. The experimental results are explained with theory of secondary grain growth in thin films.
Shock compression behavior of a S2-glass fiber reinforced polymer composite
Authors: Tsai Liren , Yuan Fuping , Prakash Vikas , Dandekar Dattatraya P.
Published: May 2009

Synthetic heterogeneous material systems, e.g., layered composite materials with organic matrices reinforced by glass fibers (GRP), are attractive materials for a variety of lightweight armor applications. However, while the dynamic response of homogeneous materials, such as, metals and ceramics, has been well documented, the ballistic response of heterogeneous material systems is poorly understood. In the present study, in an attempt to better understand the shock-induced compression response of GRPs, a series of plate impact experiments were conducted on a S2-glas fiber reinforced polymer composite comprising S2-glass woven roving in a Cycom 4102 polyester resin matrix. The plate-impact experiments were conducted using an 82.5 mm bore single-stage gas-gun at the Case Western Reserve University. The history of the shock-induced free-surface particle velocity at the rear surface of the target plate was monitored using the multibeam VALYN™ VISAR system. The results of the experiments indicate the absence of an elastic front in the shock-induced free-surface particle velocity profile in the GRP. Moreover, in the low impact velocity range, relatively weak late-time oscillations are observed in the particle velocity profiles. Increasing the amplitude of the shock-induced compression resulted in a decrease in the rise-time of the shock wave front. The critical shock stress amplitude at which a clear shock-front is seen to develop during the shock loading was determined to be between 1.5 and 2.0 GPa. The results of the experiments are used to obtain the equation of state of the GRP in the stress range 0.04–20 GPa. Moreover, the Hugoniot curve (Hugoniot stress versus Hugoniot strain) was calculated using the Rankine–Hugoniot relationships; the departure of the Hugoniot stress versus the particle velocity curve from linearity allowed the estimation of the Hugoniot elastic limit of the GRP to be about 1.6 GPa.
A microcontroller-based microwave free-space measurement system for permittivity determination of lossy liquid materials
Authors: Hasar U. C.
Published: May 2009

A microcontroller-based noncontact and nondestructive microwave free-space measurement system for real-time and dynamic determination of complex permittivity of lossy liquid materials has been proposed. The system is comprised of two main sections—microwave and electronic. While the microwave section provides for measuring only the amplitudes of reflection coefficients, the electronic section processes these data and determines the complex permittivity using a general purpose microcontroller. The proposed method eliminates elaborate liquid sample holder preparation and only requires microwave components to perform reflection measurements from one side of the holder. In addition, it explicitly determines the permittivity of lossy liquid samples from reflection measurements at different frequencies without any knowledge on sample thickness. In order to reduce systematic errors in the system, we propose a simple calibration technique, which employs simple and readily available standards. The measurement system can be a good candidate for industrial-based applications.
Development of generalized potential-energy surfaces using many-body expansions, neural networks, and moiety energy approximations
Authors: Malshe M. , Narulkar R. , Raff L. M. , Hagan M. , Bukkapatnam S. , Agrawal P. M. , Komanduri R.
Published: May 2009

A general method for the development of potential-energy hypersurfaces is presented. The method combines a many-body expansion to represent the potential-energy surface with two-layer neural networks (NN) for each M-body term in the summations. The total number of NNs required is significantly reduced by employing a moiety energy approximation. An algorithm is presented that efficiently adjusts all the coupled NN parameters to the database for the surface. Application of the method to four different systems of increasing complexity shows that the fitting accuracy of the method is good to excellent. For some cases, it exceeds that available by other methods currently in literature. The method is illustrated by fitting large databases of ab initio energies for Sin(n=3,4,…,7) clusters obtained from density functional theory calculations and for vinyl bromide (C2H3Br) and all products for dissociation into six open reaction channels (12 if the reverse reactions are counted as separate open channels) that include C–H and C–Br bond scissions, three-center HBr dissociation, and three-center H2 dissociation. The vinyl bromide database comprises the ab initio energies of 71 969 configurations computed at MP4(SDQ) level with a 6-31G(d,p) basis set for the carbon and hydrogen atoms and Huzinaga’s (4333/433/4) basis set augmented with split outer s and p orbitals (43321/4321/4) and a polarization f orbital with an exponent of 0.5 for the bromine atom. It is found that an expansion truncated after the three-body terms is sufficient to fit the Si5 system with a mean absolute testing set error of 5.693×10−4 eV. Expansions truncated after the four-body terms for Sin(n=3,4,5) and Sin(n=3,4,…,7) provide fits whose mean absolute testing set errors are 0.0056 and 0.0212 eV, respectively. For vinyl bromide, a many-body expansion truncated after the four-body terms provides fitting accuracy with mean absolute testing set errors that range between 0.0782 and 0.0808 eV. These errors correspond to mean percent errors that fall in the range 0.98%–1.01%. Our best result using the present method truncated after the four-body summation with 16 NNs yields a testing set error that is 20.3% higher than that obtained using a 15-dimensional (15-140-1) NN to fit the vinyl bromide database. This appears to be the price of the added simplicity of the many-body expansion procedure.
Energetics, relative stabilities, and size-dependent properties of nanosized carbon clusters of different families: Fullerenes, bucky-diamond, icosahedral, and bulk-truncated structures
Authors: Yu M. , Chaudhuri I. , Leahy C. , Wu S. Y. , Jayanthi C. S.
Published: May 2009

Structures and relative stabilities of carbon clusters belonging to different families have been investigated for diameters d≤5 nm based on an efficient semiempirical molecular dynamics (MD) scheme as well as a density functional theory based simulation. Carbon clusters studied include fullerenes and fullerene-derived structures (e.g., cages and onions), icosahedral structures, bucky-diamond structures, and clusters cut from the bulk diamond with spherical and facetted truncations. The reason for using a semiempirical MD is partly due to the large number of different cases (or carbon allotropes) investigated and partly due to the size of the clusters investigated in this work. The particular flavor of the semiempirical MD scheme is based on a self-consistent and environment-dependent Hamiltonian developed in the framework of linear combination of atomic orbitals. We find that (i) among the families of carbon clusters investigated, fullerene structures have the lowest energy with the relative energy ordering being Efullerene<Eonion<Eicosahedral<Ebucky-diamond<Ebulk-truncated, (ii) a crossover between bucky-diamond and icosahedral structures is likely at d∼8 nm, (iii) the highest occupied molecular orbital-lowest unoccupied molecular orbital gap as a function of the diameter for the case of fullerenes shows an oscillatory behavior with the gap ranging from 2 eV to 6 meV, and the gap approaching that of gapless graphite for d>3.5 nm, and (iv) there can be three types of phase transformations depending on the manner of heating and cooling in our simulated annealing studies: (a) a bucky-diamond structure→an onionlike structure, (b) an onionlike→a cage structure, and (c) a bucky-diamond→a cage structure.
Influence of interparticle interaction on melting of gold nanoparticles in Au/polytetrafluoroethylene nanocomposites
Authors: Yeshchenko Oleg A. , Dmitruk Igor M. , Grytsenko Konstantin P. , Prokopets Vadym M. , Kotko Andriy V. , Schrader Sigurd
Published: May 2009

The temperature dependence of the surface plasmon resonance energy and width in 5 nm spherical gold nanoparticles embedded in a polymer polytetrafluoroethylene matrix has been studied using absorption spectroscopy. The jumplike features have been observed in these dependences indicating the melting of gold nanoparticles at temperatures considerably lower than the bulk melting point. The interaction between gold nanoparticles sufficiently affects the melting of nanoparticles. The increase in the filling factor of the particles leads to a decrease in the melting temperature of gold nanoparticles.