bluuebunny/crossref_metadata_2025 huggingface dataset:
Polypharmazie ist ein Indikator für kurze Überlebensdauer im Pflegeheim - Daran ändert das Absetzen von Medikamenten nichts
Authors: Schönenberger  , Rauber  , Hauser  , Roth  , Wettstein  , Schönenberger
Published: May 2011

Ziel: Untersuchung des Einflusses der von der zuweisenden Stelle beim Pflegeheimeintritt verordneten Anzahl Medikamente und des vom Heimarzt vorgenommenen situationsgerechten Absetzens von Medikamenten auf die Überlebenszeit. Methoden: Retrospektive Analyse der Krankengeschichten von 1249 Patienten, davon 611 in einem Pflegeheim mit und 638 in zwei Pflegeheimen ohne Praxis des Absetzens von Medikamenten. Resultate: 70% der Patienten mit exzessiver Polypharmazie (>9 Medikamente), 57% derjenigen mit Polypharmazie (6 bis 9 Medikamente) und 43% der übrigen (<6 Medikamente) starben innert 286 Tagen nach Pflegeheimeintritt (Chi-Quadrat-Wert 2 DF = 43.72; p <0.001). Das Absetzen von Medikamenten bei Pflegeheimeintritt hatte keinen Einfluss auf die Überlebenszeit. Schlussfolgerung: Polypharmazie ist nicht die Ursache einer verkürzten Lebensdauer im Pflegeheim, sondern ein Indikator für eine schlechte Prognose, an der das Absetzen von Medikamenten nichts ändert.
«The Lazy Eye» - Aktuelle Strategien der Amblyopiebehandlung
Authors: Sturm
Published: May 2011

Unter Amblyopie wird eine ein- oder beidseitige Sehschärfeminderung durch Deprivation des Mustersehens oder gestörte binokulare Interaktion verstanden. Sie ist mit einer Prävalenz von ca. 2 bis 5% die häufigste Ursache einer Sehbehinderung im Kindesalter. Die in der letzten Dekade durchgeführten prospektiven, randomisierten Studien haben den klinischen Alltag in der pädiatrischen Ophthalmologie nachhaltig beeinflusst. So wird im Ergebnis heute eine erste Therapiephase mit einer refraktiven Adaptation allein favorisiert. Die sich zumeist anschliessende Okklusionsbehandlung gilt jedoch weiterhin als Goldstandard. Die Tendenz geht allerdings hin zu kürzeren Okklusionszeiten. Die Penalisation mit Atropin hat sich der Okklusion bei mittlerer Amblyopie als gleichwertig erwiesen. Neuere Behandlungsansätze wie das «Perceptual Learning», die Pharmakotherapie mit Levodopa und Citicholin oder aber die transkranielle Magnetstimulation haben sich bislang nicht allgemein durchgesetzt.
Mononeuritis multiplex unter dem TNF-alpha-Hemmer Infliximab
Authors: Bandelow  , Wiederkehr  , Hasler
Published: May 2011

Ein 21-jähriger Patient mit einer Spondylitis ankylosans entwickelte unter der Behandlung mit Infliximab eine multifokale, axonale und demyelinisierende, simultan mehrere Nerven betreffende Neuropathie (Mononeuritis multiplex). Hierbei handelt es sich um eine weitere seltene Nebenwirkung einer Infliximab-Therapie am peripheren Nervensystem.
Gravity and seismic study of crustal structure along the Juan de Fuca Ridge axis and across pseudofaults on the ridge flanks
Authors: Marjanović Milena , Carbotte Suzanne M. , Nedimović Mladen R. , Canales Juan Pablo
Published: May 2011

Variations in topography and seismic structure are observed along the Juan de Fuca (JdF) Ridge axis and in the vicinity of pseudofaults on the ridge flanks left by former episodes of ridge propagation. Here we analyze gravity data coregistered with multichannel seismic data from the JdF Ridge and flanks in order to better understand the origin of crustal structure variations in this area. The data were collected along the ridge axis and along three ridge‐perpendicular transects at the Endeavor, Northern Symmetric, and Cleft segments. Negative Mantle Bouguer anomalies of −21 to −28 mGal are observed at the axis of the three segments. Thicker crust at the Endeavor and Cleft segments is inferred from seismic data and can account for the small differences in axial gravity anomalies (3–7 mGal). Additional low densities/elevated temperatures within and/or below the axial crust are required to explain the remaining axial MBA low at all segments. Gravity models indicate that the region of low densities is wider beneath the Cleft segment. Gravity models for pseudofaults crossed along the three transects support the presence of thinner and denser crust within the pseudofault zones that we attribute to iron‐enriched crust. On the young crust side of the pseudofaults, a 10–20 km wide zone of thicker crust is found. Reflection events interpreted as subcrustal sills underlie the zones of thicker crust and are the presumed source for the iron enrichment.
Evolution of seismic layer 2B across the Juan de Fuca Ridge from hydrophone streamer 2‐D traveltime tomography
Authors: Newman Kori R. , Nedimović Mladen R. , Canales J. Pablo , Carbotte Suzanne M.
Published: May 2011

How oceanic crust evolves has important implications for understanding both subduction earthquake hazards and energy and mass exchange between the Earth's interior and the oceans. Although considerable work has been done characterizing the evolution of seismic layer 2A, there has been little analysis of the processes that affect layer 2B after formation. Here we present high‐resolution 2‐D tomographic models of seismic layer 2B along ∼300 km long multichannel seismic transects crossing the Endeavour, Northern Symmetric, and Cleft segments of the Juan de Fuca Ridge. These models show that seismic layer 2B evolves rapidly following a different course than layer 2A. The upper layer 2B velocities increase on average by 0.8 km/s and reach a generally constant velocity of 5.2 ± 0.3 km/s within the first 0.5 Myr after crustal formation. This suggests that the strongest impact on layer 2B evolution may be that of mineral precipitation due to “active” hydrothermal circulation centered about the ridge crest and driven by the heat from the axial magma chamber. Variations in upper layer 2B velocity with age at time scales ≥0.5 Ma show correlation about the ridge axis indicating that in the long term, crustal accretion processes affect both sides of the ridge axis in a similar way. Below the 0.5 Ma threshold, differences in 2B velocity are likely imprinted during crustal formation or early crustal evolution. Layer 2B velocities at propagator wakes (5.0 ± 0.2 km/s), where enhanced faulting and cracking are expected, and at areas that coincide with extensional or transtensional faulting are on average slightly slower than in normal mature upper layer 2B. Analysis of the layer 2B velocities from areas where the hydrothermal patterns are known shows that the locations of current and paleohydrothermal discharge and recharge zones are marked by reduced and increased upper layer 2B velocities, respectively. Additionally, the distance between present up‐flow and down‐flow zones is related to the amount of sediment cover because, as sediment cover increases and basement outcrops become covered, direct pathways from the igneous basement through the seafloor are cut off, forcing convective cells to find alternate paths.
Potential causes for the non‐Newtonian rheology of crystal‐bearing magmas
Authors: Deubelbeiss Yolanda , Kaus Boris J. P. , Connolly James A. D. , Caricchi Luca
Published: May 2011

Experimental studies indicate that crystal‐bearing magma exhibits non‐Newtonian behavior at high strain rates and solid fractions. We use a zero‐dimensional (0‐D) inversion model to reevaluate rheological parameters and shear heating effects from laboratory data on crystal‐bearing magma. The results indicate non‐Newtonian behavior with power law coefficients of up to n = 13.5. It has been speculated that finite strain effects, shear heating, power law melt rheology, or plasticity are responsible for this non‐Newtonian behavior. We use 2‐D direct numerical crystal‐scale simulations to study the relative importance of these mechanisms. These simulations demonstrate that shear heating has little effect on aggregate (bulk) rheologies. Finite strain effects result in both strain weakening and hardening, but the resulting power law coefficient is modest (maximum n = 1.3). For simulations with spherical crystals the strain weakening and hardening behavior is related to rearrangement of crystals rather than strain rate related weakening. Finite strain effects were insignificant in a numerical simulation with naturally shaped crystals. Strain partitioning into the melt phase may induce microscopic stresses that are adequate to provoke a nonlinear viscous response in the melt. Large differential stresses and low effective stresses revealed by the simulations are sufficient to cause crystals to fail plastically. Numerical experiments that account for plastic failure show large power law coefficients (n ≈ 50 in some simulations). We conclude that this effect is the dominant cause of the strong nonlinear viscous response of crystal‐bearing magmas observed in laboratory experiments.
The southernmost margin of the Tethys realm during the Mesozoic and Cenozoic: Initial geometry and timing of the inversion processes
Authors: Frizon de Lamotte Dominique , Raulin Camille , Mouchot Nicolas , Wrobel‐Daveau Jean‐Christophe , Blanpied Christian , Ringenbach Jean‐Claude
Published: May 2011

Along the northern border of Africa, Pangea breakup has been diachronic. During the Jurassic, the Alpine Tethys propagated northeastward from the Atlantic to the Alps. During the Permian, the Neo‐Tethys propagated westward from Oman to northwestern Arabia. Then a secondary and late branch of Neo‐Tethys gave birth to the East Mediterranean basin. Finally the two oceans connected at end of Jurassic times, achieving the development of Africa northern plate boundary. By the Late Cretaceous, convergence between Africa and Eurasia led to the progressive closure of the Tethys realm. The continental collision is not completely achieved, and the different segments of the confrontation zone (Maghreb, central and East Mediterranean, Zagros, and Oman) expose different stages of the process. However, we emphasize the existence of synchronous geodynamic events from one end of the system to the other, although they do not have the same meaning. Two of them are particularly important. The Campanian‐Santonian (C‐S) event corresponds to (1) obduction and exhumation of high‐pressure–low‐temperature metamorphic rocks around the Arabian promontory, (2) inversion along the margins of the East Mediterranean basins, and (3) lithosphere buckling in the Atlas system (Maghreb) and adjacent Sahara platform. The middle‐late Eocene (MLE) event corresponds to (1) the onset of collision at the northern corner of Arabia, (2) the onset of slab retreat in the Mediterranean, and (3) inversion along the margin of the East Mediterranean as well as in the Atlas. The C‐S event coincides with a change in plate kinematics resulting in an abrupt increase of convergence velocity. The MLE event coincides with a period of strong coupling between the Africa and Eurasia plates and an abrupt decrease of convergence velocity. In the middle of the system, the central Mediterranean seems to escape to the effects of convergence and is the site of quite permanent extensional movements since the Triassic.
Water for food: The global virtual water trade network
Authors: Konar M. , Dalin C. , Suweis S. , Hanasaki N. , Rinaldo A. , Rodriguez‐Iturbe I.
Published: May 2011

We present a novel conceptual framework and methodology for studying virtual water trade. We utilize complex network theory to analyze the structure of the global virtual water trade associated with the international food trade. In the global virtual water trade network, the nations that participate in the international food trade correspond to the nodes, and the links represent the flows of virtual water associated with the trade of food from the country of export to the country of import. We find that the number of trade connections follows an exponential distribution, except for the case of import trade relationships, while the volume of water that each nation trades compares well with a stretched exponential distribution, indicating high heterogeneity of flows between nations. There is a power law relationship between the volume of virtual water traded and the number of trade connections of each nation. Highly connected nations are preferentially linked to poorly connected nations and exhibit low levels of clustering. However, when the volume of virtual water traded is taken into account, this structure breaks down. This indicates a global hierarchy, in which nations that trade large volumes of water are more likely to link to and cluster with other nations that trade large volumes of water, particularly when the direction of trade is considered. Nations that play a critical role in maintaining the global network architecture are highlighted. Our analysis provides the necessary framework for the development of a model of global virtual water trade aimed at applications ranging from network optimization to climate change impact evaluations.
The Relationships between Motivations of Intergroup Differentiation as a Function of Different Dimensions of Social Identity
Authors: Taşdemir Nagihan
Published: May 2011

This article aims to classify social identity-based theories of intergroup differentiation in terms of different dimensions of social identity to understand further the motivational bases of intergroup differentiation. For this purpose, I attempt to incorporate three lines of research in social psychology: (a) theories examining intergroup differentiation as a function of social identity, namely social identity theory and SCT; (b) studies suggesting social identity as a multidimensional construct; and (c) motivational theories of intergroup differentiation, namely subjective uncertainty reduction theory, optimal distinctiveness theory, and self-esteem hypothesis. It is suggested that subjective uncertainty reduction theory explains motivational basis of cognitive dimension, that optimal distinctiveness theory explains motivational basis of emotional dimension, and that self-esteem hypothesis explains motivational basis of evaluative dimension of social identity. Finally, the relationships between motivations of intergroup differentiation as a function of different dimensions of social identity are considered.
Self-Centeredness and Selflessness: A Theory of Self-Based Psychological Functioning and Its Consequences for Happiness
Authors: Dambrun Michaël , Ricard Matthieu
Published: May 2011

The theoretical model presented in this paper emerged from several different disciplines. This model proposes that the attainment of happiness is linked to the self, and more particularly to the structure of the self. We support the idea that the perception of a structured self, which takes the form of a permanent, independent and solid entity leads to self-centered psychological functioning, and this seems to be a significant source of both affliction and fluctuating happiness. Contrary to this, a selfless psychological functioning emerges when perception of the self is flexible (i.e., a dynamic network of transitory relations), and this seems to be a source of authentic-durable happiness. In this paper, these two aspects of psychological functioning and their underlying processes will be presented. We will also explore the potential mechanisms that shape them. We will conclude with an examination of possible applications of our theory.
Characteristics and Antecedents of People who Hoard Animals: An Exploratory Comparative Interview Study
Authors: Steketee Gail , Gibson Amanda , Frost Randy O. , Alabiso Janelle , Arluke Arnold , Patronek Gary
Published: May 2011

Currently, case studies and media reports provide the only descriptive information available to understand what distinguishes hoarding of animals from nonhoarding animal ownership. This poorly understood problem appears to be associated with substantial mental health difficulties. The present study investigated characteristics and antecedents that might explain hoarding behaviors. Sixteen people who fit criteria for hoarding of animals and 11 nonhoarding controls who owned large numbers of animals participated in semistructured interviews that were analyzed using somewhat atypical qualitative and quantitative methods. The interviews focused on demographic information, history of animal contact, social history, insight into physical and mental health issues, collecting behaviors, and beliefs and emotions associated with animals. Descriptive statistics and qualitative analyses were used to examine differences between hoarding and nonhoarding groups and to capture distinguishing themes and patterns. Both groups were well matched in demographic variables and were mainly White women of middle age; the average number of animals owned was 31. Thematic content common to both groups was stressful life events (both childhood and adult), strong emotional reactions to animal death, strong caretaking roles and attitudes toward animals, a tendency to rescue animals, and intense feelings of closeness or attachment to animals. Themes found significantly more often among animal hoarding participants than controls included problems with early attachment, chaotic childhood environments, significant mental health concerns, attribution of human characteristics to animals, and the presence of more dysfunctional current relationships. These themes are elaborated and discussed with regard to potential models for understanding hoarding of animals.
Constructing ABC summary statistics: semi-automatic ABC
Authors: Fearnhead Paul , Prangle Dennis
Published: May 2011

To analyze complex datasets efficiently, ABC algorithms require well-chosen low dimensional summary statistics of the data. We present a method to construct appropriate summary statistics for ABC in a semi-automatic manner. Previous attempts at this have been based around constructing statistics that are sufficient (or approximately sufficient). However, in most real applications it is difficult to know if low-dimensional sufficient statistics exist, or how to approximate them if they do. We take an alternative approach of aiming for summary statistics which will enable inference about certain parameters of interest to be as accurate as possible.  This talk describes our method, the underpinning theory, and promising empirical results on a range of applications.
Using ABC for model design and inference across biological scales
Authors: Ratmann Oliver
Published: May 2011

Using ABC for model design and inference across biological scales.
Efficient learning in Approximate Bayesian Computation
Authors: Sedki Mohammed , Pudlo Pierre
Published: May 2011

Efficient learning in Approximate Bayesian Computation
ABC for ancestral inference
Authors: Wilkinson Richard , Tavare Simon
Published: May 2011

ABC for ancestral inference
ABC SMC for parameter estimation and model selection with applications in systems biology
Authors: Toni Tina
Published: May 2011

Approximate Bayesian Computation (ABC) methods can be used in situations where the evaluation of the likelihood is computationally prohibitive. They are thus ideally suited for analyzing the complex dynamical models encountered in systems biology, where knowledge of the full (approximate) posterior is often essential.This talk gives an overview of an ABC algorithm based on Sequential Monte Carlo (ABC SMC). Different uses of the algorithm will be presented, depending on the application question of interest. The first is the general parameter estimation framework, where the interest lies in estimating the posterior parameter distribution from available experimental data. In the second context we ask whether the model can reproduce a desired qualitative or semi-quantitative behavior, and what dynamic behaviors the system can achieve. The third context discussed here for use of the ABC SMC algorithm is that of model selection. Here we ask which of the models (i.e. model topologies) from a pool of proposed candidate models represents the most suitable hypothesis about the biological system of interest.The focus of the presentation is applications of ABC SMC to questions from systems biology. ABC SMC is applied to a variety of biological models, including stochastic and deterministic descriptions of eukaryotic signaling pathways and prokaryotic stress response pathways. In particular, the algorithm is employed to understand understand the qualitative behavior of the phage shock protein response in bacteria Escherichia coli, and the model selection algorithm is applied to distinguish between differential equation models of MAP kinase phosphorylation dynamics and the JAK-STAT signaling pathway.
Precise Atomic Structures of two Important Molecules in Biochemistry:
Authors: Heyrovska Raji , Narayan Saraswathi , Atchison Lakshmi
Published: May 2011

This work celebrates the “International Year of Chemistry – 2011”, by providing “for the first time”, the structures at the atomic level of two important molecules, namely, ascorbic acid and aspirin. Ascorbic acid, also known as vitamin C, was discovered as a cure for scurvy which claimed many human lives and hence got its name. It is also supposed to be an antioxidant and to prevent flu. Aspirin is synthesized from salicylic acid and is widely used as a remedy for flu and has other medical uses such as saving the lives of cardiac patients as an anticoagulant of blood. The biochemistry and chemistry of both these compounds have been evolving for nearly a century ever since their discoveries. Here, the atomic structures of these compounds have been presented where the known lengths of the various chemical bonds are exact sums of the appropriate radii of the adjacent atoms.
Management of Jaw Injuries in the American Civil War: The Diuturnity of Bean in the South, Gunning in the North
Authors: Pollock Richard A.
Published: May 2011

James Baxter Bean published a series of articles in the Southern Dental Examiner in 1862 describing his work with “plaster and its manipulations.” This early experience included a new way of managing jaw fractures, with customized splints uniquely based on pretraumatic occlusion. Bean's oral splints and their method of construction, using an articulator, became the standard of care in the Atlanta region during the American Civil War and, by 1864, throughout The Confederacy. In short course, Bean's approach also swept The Union, following in large part the efforts of a colleague in the North, T.B. Gunning. Thus, what began in the early 1860s in a dental laboratory in the southeast swept the continental United States and revolutionized management of jaw-fractures during, and immediately after, the American Civil War.
Avulsion of the Auricle in an Anticoagulated Patient: Is Leeching Contraindicated? A Review and a Case
Authors: Mommsen Jens , Rodríguez-Fernández Javier , Mateos-Micas Mario , Vázquez-Bouso Olga , Gumbao-Grau Victor , Forteza-Gonzalez Gabriel
Published: May 2011

Amputation of the auricle is a periodic occurrence leading to disfigurement if not treated properly. Venous stasis is a common complication in reattachments and requires decongestant and anticoagulant treatment. Today, leech therapy is the treatment of choice. Common problems are that it is not available everywhere and that it is usually contraindicated in anticoagulated patients. The peculiarities of leech therapy and the various aspects of surgical management are reviewed. A case of a partial amputation of the auricle in a patient under concomitant anticoagulation therapy with warfarin is presented. The amputated part was reattached in another hospital without microvascular anastomosis. The patient presented to our department with early signs of venous congestion. Leech therapy was started 35 hours after trauma, and the patient continued his anticoagulation therapy. With this treatment, 90% of the amputated part was rescued. The anticoagulation therapy of the patient may have played an important role in the first hours after reattachment, preventing capillary thrombosis and in consequence facilitating the minimal oxygenation necessary. The claim that anticoagulation therapy is a contraindication to leeching should be questioned in cases of reattachments in well-controllable locations without arterial anastomosis.
Intraoral Approach for Treatment of Displaced Condylar Fractures: Case Report
Authors: Pereira-Filho Valfrido , Welsh Bärbel , Schübel Florian , Landes Constantin , Sader Robert , Gabrielli Mario , Monnazzi Marcelo
Published: May 2011

Dislocated subcondylar fractures often require open reduction and internal fixation. This treatment modality results in better anatomy, early function, and facilitated physical therapy. Ideal stable fixation is obtained by use of two miniplates to control the tension zone in the sigmoid notch area and stabilize the posterior border region or, if there is not enough space, one stronger plate. That is most frequently achieved through extraoral approaches. Recently new instruments have facilitated the use of an intraoral approach, which is used usually with the aid of an endoscope. However, it is possible to perform the procedure without the endoscope if proper instruments and clinical mirrors for checking the posterior border reduction and fixation are used. A case of reduction and fixation of a medially dislocated condylar fracture is presented and discussed.
Atypical Case of Congenital Maxillomandibular Fusion with Duplication of the Craniofacial Midline
Authors: Martín Lorena Pingarrón , Pérez Mercedes Martín , García Elena Gómez , Martín-Moro Javier González , González Jose Ignacio Rodríguez , García Miguel Burgueño
Published: May 2011

We report the first case of syngnathia with hypophyseal duplication and describe the central nervous system (CNS) and craniofacial anomalies associated with hypophyseal duplication in the reported autopsy case. We studied clinical reports, scanner images, and autopsy results of a 2-months-old female baby. The propositus had frontonasal dysmorphism, retrognathia, and bifid tongue. She also presented maxillomandibular bony fusion (syngnathia) and an intraoral hairy polyp. In the cranium, the sella turcica was broadened, with two complete hypophyses and two infundibulums. The CNS had both olfactory bulbs and corpus callosum agenesis. There are 27 previous cases of maxillomandibular fusion and seven previous autopsy cases of hypophyseal duplication associated with other frontonasal malformations. As far as the authors know, this is the first case reported in the literature that associates syngnathia with duplication of the craniofacial midline including hypophyseal duplication.
Piezoelectric properties of 0.5(Ba0.7Ca0.3TiO3) – 0.5[Ba(Zr0.2Ti0.8)O3] ferroelectric lead-free laser deposited thin films
Authors: Piorra A. , Petraru A. , Kohlstedt H. , Wuttig M. , Quandt E.
Published: May 2011

Ferroelectric lead-free thin films of 0.5(Ba0.7Ca0.3TiO3) – 0.5[Ba(Zr0.2Ti0.8)O3] (BCZT) were successfully deposited by pulsed laser deposition on Pt/TiO2/SiO2/Si substrates using a ceramic BCZT target prepared by conventional solid state reaction. The in (111) direction orientated 600 nm thick films shows a clamped piezoelectric response of approximately d33,f = 80 pm/V and a dielectric coefficient of about ɛr = 1010; these are close to values obtained for lead zirconate titanate (PZT) films.
Anomalous strain profiles and electronic structures of a GaAs-capped InAs/In0.53Ga0.47As quantum ring
Authors: Moon Pilkyung , Jun Won , Park Kwangmin , Yoon Euijoon , Lee JaeDong
Published: May 2011

We investigate the strain profiles and electronic structures of a novel quantum ring capped by a material different from the substrate. By comparing the novel quantum ring with an ordinary quantum dot and quantum ring, which are capped by the same material as the substrate, we find that the novel quantum ring exhibits noticeably different properties, such as an anomalous strain relaxation, band alignments, and blueshift of the emission energy. We investigate the novel properties of our quantum ring by separating the ring evolution process into (i) the step of geometric change from a dot to ring and (ii) the step of GaAs capping. The GaAs embedded in the In0.53Ga0.47As matrix provides sufficient space for the relaxation of InAs and, thus, individual strain and biaxial strain of the InAs ring are considerably reduced by the GaAs layer. We show that the blueshift in the emission energies due to ring formation is mainly caused by (i) the geometric change from a dot to ring and (ii) the weakened heavy hole–light hole splitting, and not by the enhanced compressive strain. The relaxation of the ring along the radial direction also considerably enhances the shear strain and piezoelectric potential, and the piezoelectric potential partially compensates for the blueshift resulting from the ring evolution and GaAs capping. We also show that the tensile–strained GaAs selectively acts as a potential well for light holes and as potential barriers for both the electrons and heavy holes. As a consequence, the GaAs layer considerably enhances the light-hole character of the hole states in our quantum ring.
Photoinduced Ag deposition on periodically poled lithium niobate: Wavelength and polarization screening dependence
Authors: Sun Yang , Nemanich Robert J.
Published: May 2011

This research addresses the wavelength dependence of the fabrication of Ag nanostructures through photoinduced deposition using single crystal ferroelectric lithium niobate as a template. The photoinduced deposition involves ultraviolent light illumination of polarity patterned lithium niobate while immersed in a AgNO3 solution. The results focus on the differences of the Ag nanostructure formation process on the positive and negative domains and domain boundaries. The results indicate that for below-band-gap excitation, a very low density of nanostructures is observed. However, for all above-gap-excitation wavelengths, deposition occurs on both polarity surfaces and at the domain boundaries. The density is greatest at the domain boundaries and reduced densities of smaller nanostructures are observed to form on both the positive and negative domains. The deposition on the domain surfaces is greatest for the shortest wavelengths, whereas the domain selectivity is increased for wavelengths just above the band gap. The external screening and weak band bending of single crystal lithium niobate introduces an enhanced electric field at the domain boundary. The enhanced electric field leads to migration of electrons to the domain boundary and consequently enhanced formation of Ag nanoparticles along the boundary. The variation in the reduction rate versus illumination wavelength is attributed to the light absorption depth and the competition between the photochemical and photoelectric deposition processes. To explore the transition from surface to bulk screening of the polarization charge, oxygen implanted PPLN surfaces were prepared and used for the Ag photoinduced deposition. Consistent with the transition to internal (bulk) screening, the Ag nanoparticle formation on the oxygen implanted PPLN surfaces showed suppressed boundary nanowire formation.
Zero-field magnetization reversal of two-body Stoner particles with dipolar interaction
Authors: Sun Z. Z. , López A. , Schliemann J.
Published: May 2011

We investigate magnetization reversal in a system of two Stoner particles with uniaxial anisotropies both subject to a static and antiparallel magnetic field, and taking into account their mutual dipolar interaction. We identify an interesting regime of stable synchronized magnetic dynamics where the two particles are implementing a single information bit. Here a modified Stoner-Wohlfarth limit occurs which results in a dramatically lower critical switching field Hc (including Hc=0) and also a substantially shorter reversal time. Our analytical results are verified by numerical simulations and offer new technological perspectives regarding devices for information storage and/or fast magnetic response.
Physical modeling and implementation scheme of native defect diffusion and interdiffusion in SiGe heterostructures for atomistic process simulation
Authors: Castrillo P. , Pinacho R. , Jaraiz M. , Rubio J. E.
Published: May 2011

In order to simulate the diffusion kinetics during thermal treatments in SiGe heterostructures, a physically-based atomistic model including chemical and strain effects has been developed and implemented into a nonlattice atomistic kinetic monte carlo (KMC) framework. This model is based on the description of transport capacities of native point defects (interstitials and vacancies) with different charge states in SiGe alloys in the whole composition range. Lattice atom diffusivities have been formulated in terms of point defect transport, taking into account the different probability to move Si and Ge atoms. Strain effects have been assessed for biaxial geometries including strain-induced anisotropic diffusion, as well as charge effects due to strain-induced modifications of the electronic properties. Si-Ge interdiffusion in heterostructures has been analyzed from an atomistic perspective. A limited set of physical parameters have been defined, being consistent with previously reported ab initio calculations and experiments. The model has been implemented into a nonlattice KMC simulator and the relevant implementation details and algorithms are described. In particular, an efficient point defect mediated Si-Ge exchange algorithm for interdiffusion is reported. A representative set of simulated interdiffusion profiles are shown, exhibiting good agreement with experiments.
Accurate six-band nearest-neighbor tight-binding model for the π-bands of bulk graphene and graphene nanoribbons
Authors: Boykin Timothy B. , Luisier Mathieu , Klimeck Gerhard , Jiang Xueping , Kharche Neerav , Zhou Yu , Nayak Saroj K.
Published: May 2011

Accurate modeling of the π-bands of armchair graphene nanoribbons (AGNRs) requires correctly reproducing asymmetries in the bulk graphene bands, as well as providing a realistic model for hydrogen passivation of the edge atoms. The commonly used single-pz orbital approach fails on both these counts. To overcome these failures we introduce a nearest-neighbor, three orbital per atom p/d tight-binding model for graphene. The parameters of the model are fit to first-principles density-functional theory –based calculations as well as to those based on the many-body Green’s function and screened-exchange formalism, giving excellent agreement with the ab initio AGNR bands. We employ this model to calculate the current-voltage characteristics of an AGNR MOSFET and the conductance of rough-edge AGNRs, finding significant differences versus the single-pz model. These results show that an accurate band structure model is essential for predicting the performance of graphene-based nanodevices.
Model for reflection and transmission matrices of nanowire end facets
Authors: Svendsen Guro K. , Weman Helge , Skaar Johannes
Published: May 2011

Nanowires show a large potential for various electro-optical devices, such as light emitting diodes, solar cells, and nanowire lasers. We present a method developed to calculate the modal reflection and transmission matrix at the end facets of a waveguide of arbitrary cross-section, resulting in a generalized version of the Fresnel equations. The reflection can be conveniently computed using fast Fourier transforms once the waveguide modes are known. We demonstrate that the reflection coefficient is qualitatively described by two main parameters: the modal field confinement and the average Fresnel reflection of the plane waves constituting the waveguide mode.
Effective magnetoelectric effect in multicoated circular fibrous multiferroic composites
Authors: Kuo Hsin-Yi , Pan Ernian
Published: May 2011

Rayleigh’s formalism is generalized for the evaluation of the effective material properties in multicoated circular fibrous multiferroic composites. The derived solution is applied to the special three-phase composite in which coated fibers are embedded in a matrix. For composites made of piezoelectric (BaTiO3) and piezomagnetic (CoFe2O4 or Terfenol-D) phases, we find that the magnetoelectric effect in the composite made of CoFe2O4 coated BaTiO3 in matrix Terfenol-D is five times larger than that in the composite made of BaTiO3 coated Terfenol-D in matrix CoFe2O4. Furthermore, in each case, with appropriate coating to the circular fiber, the magnetoelectric effect in the coated composites can be enhanced by more than one order of magnitude as compared to the corresponding noncoating composite.
Taylor’s hypothesis convection velocities from mass conservation equation
Authors: Davoust S. , Jacquin L.
Published: May 2011

We propose to use the continuity equation to calculate convection velocities provided by the Taylor hypothesis for flow structures crossing a measurement plane. This is carried out in Fourier space to identify a velocity associated to each frequency. High-speed PIV experimental data of an axisymmetric mixing layer is used to implement the method. We show that as expected the Taylor hypothesis fails for the lowest frequencies and predicts the convection velocity to be close to the mean velocity for the higher ones. The method is compared to one of the definitions proposed by Del Álamo and Jiménez [J. Fluid Mech. 640, 5 (2009)].
Reducing recombination losses in planar organic photovoltaic cells using multiple step charge separation
Authors: Heidel T. D. , Hochbaum D. , Sussman J. M. , Singh V. , Bahlke M. E. , Hiromi I. , Lee J. , Baldo M. A.
Published: May 2011

We enhance the efficiency of heterojunction organic solar cells by introducing a thin interfacial layer between the acceptor and donor layers. The interfacial layer energy levels are chosen to provide a gradient for charges crossing the interface, approximating a conventional p-n junction with three organic semiconductors. Devices with interfacial layers exhibit increased open circuit voltage (VOC) and increased short circuit current (JSC). The increase in VOC is due to a reduction in dark current and charge recombination. The increase in JSC is correlated with an increase in the conversion efficiency of excitons originating in the donor or acceptor layers. The interfacial layer destabilizes charge transfer states at the donor-acceptor interface, yielding reduced exciton recombination. The introduction of thin interfacial layers may prove to be an important probe of the physics of exciton separation in organic photovoltaic cells.
Full characterization of laser-accelerated ion beams using Faraday cup, silicon carbide, and single-crystal diamond detectors
Authors: Margarone D. , Krása J. , Giuffrida L. , Picciotto A. , Torrisi L. , Nowak T. , Musumeci P. , Velyhan A. , Prokůpek J. , Láska L. , Mocek T. , Ullschmied J. , Rus B.
Published: May 2011

Multi-MeV beams of light ions have been produced using the 300 picosecond, kJ-class iodine laser, operating at the Prague Asterix Laser System facility in Prague. Real-time ion diagnostics have been performed by the use of various time-of-flight (TOF) detectors: ion collectors (ICs) with and without absorber thin films, new prototypes of single-crystal diamond and silicon carbide detectors, and an electrostatic ion mass spectrometer (IEA). In order to suppress the long photopeak induced by soft X-rays and to avoid the overlap with the signal from ultrafast particles, the ICs have been shielded with Al foil filters. The application of large-bandgap semiconductor detectors (>3 eV) ensured cutting of the plasma-emitted visible and soft-UV radiation and enhancing the sensitivity to the very fast proton/ion beams. Employing the IEA spectrometer, various ion species and charge states in the expanding laser-plasma have been determined. Processing of the experimental data based on the TOF technique, including estimation of the plasma fast proton maximum and peak energy, ion beam currents and total charge, total number of fast protons, as well as deconvolution processes, ion stopping power, and ion/photon transmission calculations for the different metallic filters used, are reported.
The mechanical response of lithographically defined break junctions
Authors: Huisman E. H. , Trouwborst M. L. , Bakker F. L. , van Wees B. J. , van der Molen S. J.
Published: May 2011

We present an experimental study on the mechanical response of lithographically defined break junctions by measuring atomic chain formation, tunneling traces and Gundlach oscillations. The calibration factor, i.e., the ratio between the electrode movement and the bending of the substrate, is found to be 2.5 times larger than expected from a simple mechanical model. This result is consistent with previous finite-element calculations. Comparing different samples, the mechanical response is found to be similar for electrode separations >4 Å. However, for smaller electrode separations significant sample-to-sample variations appear. These variations are ascribed to differences in the shape of the two electrodes on the atomic scale which cannot be controlled by the fabrication process.
Effect of valence electron concentration on stability of fcc or bcc phase in high entropy alloys
Authors: Guo Sheng , Ng Chun , Lu Jian , Liu C. T.
Published: May 2011

Phase stability is an important topic for high entropy alloys (HEAs), but the understanding to it is very limited. The capability to predict phase stability from fundamental properties of constituent elements would benefit the alloy design greatly. The relationship between phase stability and physicochemical/thermodynamic properties of alloying components in HEAs was studied systematically. The mixing enthalpy is found to be the key factor controlling the formation of solid solutions or compounds. The stability of fcc and bcc solid solutions is well delineated by the valance electron concentration (VEC). The revealing of the effect of the VEC on the phase stability is vitally important for alloy design and for controlling the mechanical behavior of HEAs.
Theoretical and experimental investigation of all-optical switching based on cascaded LPFGs separated by an erbium-doped fiber
Authors: Zang Zhi-Gang , Yang Wen-xuan
Published: May 2011

A new all-optical switching device, which is constructed by connecting an erbium-doped fiber with two symmetrical long-period fiber gratings (EDF-LPFGs), is demonstrated. The performance of EDF-LPFGs switching has been investigated based on cross-phase modulation under different parameters. The theoretical analysis shows that the threshold switching power is inverse proportional to the nonlinear coefficient of the erbium-doped fiber, and is proportional to the effective area of the erbium-doped fiber and absorption coefficient. Moreover, the switching power as low as 36 mW and high extinction ratio of 18 dB are obtained in our experiment. Good agreement between the theoretical and experimental results indicate that EDF-LPFGs switching is a new design in support of switching power reduction.
Dual-resonance converse magnetoelectric and voltage step-up effects in laminated composite of long-type 0.71Pb(Mg1/3Nb2/3)O3–0.29PbTiO3 piezoelectric single-crystal transformer and Tb0.3Dy0.7Fe1.92 magnetostrictive alloy bars
Authors: Ming Leung Chung , Wing Or Siu , Wang Feifei , Ho S. L.
Published: May 2011

We report a dual-resonance converse magnetoelectric effect and a dual-resonance voltage step-up effect in a laminated composite made by sandwiching the output (or secondary) section of a long-type 0.71Pb(Mg1/3Nb2/3)O3–0.29PbTiO3 (PMN–PT) piezoelectric single-crystal transformer having a longitudinal-longitudinal polarization between two Tb0.3Dy0.7Fe1.92 (Terfenol-D) magnetostrictive alloy bars having a longitudinal magnetization. The reported converse magnetoelectric effect originates from the mechanically mediated resonance converse piezoelectric effect in the PMN–PT transformer and resonance converse magnetostrictive effect in the Terfenol-D bars. The additional voltage step-up effect results from the mechanically mediated resonance converse and direct piezoelectric effects in the PMN–PT transformer. The composite shows two sharp resonance peaks of 0.39 and 0.54 G/V in converse magnetoelectric coefficient (αB = dB/dVin) and of 1.4 and 2.1 in voltage step-up ratio (Vout/Vin) at about 54 and 120 kHz, corresponding to the half- and full-wavelength longitudinal mode resonances, respectively. The measured magnetic induction (B) exhibits good linear relationships to the applied ac voltage (Vin) with amplitude varying from 10 to 100 V in both resonance and nonresonance conditions. These dual-resonance effects make the composite great promise for coil-free electromagnetic device applications.
Investigation of C60F36 as low-volatility p-dopant in organic optoelectronic devices
Authors: Meerheim Rico , Olthof Selina , Hermenau Martin , Scholz Sebastian , Petrich Annette , Tessler Nir , Solomeshch Olga , Lüssem Björn , Riede Moritz , Leo Karl
Published: May 2011

We demonstrate highly efficient small molecule organic light emitting diodes and organic solar cells based on the p-i-n-type structure using the fluorinated fullerene molecule C60F36 as p-dopant in the hole transport layer. We present synthesis, chemical analysis, and energy level investigation of the dopant as well as the conductivity of organic layers consisting of a matrix of N,N,N′,N′-tetrakis 4-methoxyphenyl-benzidine(MeO-TPD) or N,N′-[(Diphenyl-N,N′-bis)9,?>9,-dimethyl-fluoren-2-yl]-benzidine(BF-DPB) doped by the fullerene compound. State of the art organic p-i-n devices containing C60F36 show efficiencies comparable to devices with the commonly used p-dopant2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ). The advantages of the fullerene based dopant are the low volatility and high thermal stability, which is beneficial for device operation under elevated temperature. These properties make C60F36 highly attractive for the usage as p-dopant in a broad spectrum of organic p-i-n devices like organic light emitting diodes, solar cells, memories, or transistors.
Internal quantum efficiency of III-nitride quantum dot superlattices grown by plasma-assisted molecular-beam epitaxy
Authors: Gačević Ž. , Das A. , Teubert J. , Kotsar Y. , Kandaswamy P. K. , Kehagias Th. , Koukoula T. , Komninou Ph. , Monroy E.
Published: May 2011

We present a study of the optical properties of GaN/AlN and InGaN/GaN quantum dot (QD) superlattices grown via plasma-assisted molecular-beam epitaxy, as compared to their quantum well (QW) counterparts. The three-dimensional/two-dimensional nature of the structures has been verified using atomic force microscopy and transmission electron microscopy. The QD superlattices present higher internal quantum efficiency as compared to the respective QWs as a result of the three-dimensional carrier localization in the islands. In the QW samples, photoluminescence (PL) measurements point out a certain degree of carrier localization due to structural defects or thickness fluctuations, which is more pronounced in InGaN/GaN QWs due to alloy inhomogeneity. In the case of the QD stacks, carrier localization on potential fluctuations with a spatial extension smaller than the QD size is observed only for the InGaN QD-sample with the highest In content (peak emission around 2.76 eV). These results confirm the efficiency of the QD three-dimensional confinement in circumventing the potential fluctuations related to structural defects or alloy inhomogeneity. PL excitation measurements demonstrate efficient carrier transfer from the wetting layer to the QDs in the GaN/AlN system, even for low QD densities (∼1010 cm−3). In the case of InGaN/GaN QDs, transport losses in the GaN barriers cannot be discarded, but an upper limit to these losses of 15% is deduced from PL measurements as a function of the excitation wavelength.