bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flexibel, leicht und durchsichtig
Authors: Ecker Bernhard 
Published: March 2013

AbstractOrganische Solarzellen basieren auf organischen Halbleitern. Sie eröffnen der Photovoltaik völlig neue Anwendungsgebiete, denn sie lassen sich auf flexible Folien gedruckt in Kleidung integrieren oder semitransparent strukturiert in Fenster einbetten. Inzwischen erreichen die besten organischen Solarzellen Wirkungsgrade über 10 % und befinden sich auf dem Weg zur Kommerzialisierung. Allerdings ist noch Grundlagenforschung erforderlich. Eine Herausforderung ist das effiziente Trennen und Einsammeln der vom Licht erzeugten elektrischen Ladungsträger im Material. Das erfordert eine gezielte Nanostrukturierung der organischen Halbleiterschichten. Weitere Herausforderungen sind die Verbesserung der Lebensdauer sowie die Entwicklung von Herstellungsmethoden, die wenig Energie verbrauchen und die Produktionskosten senken.
Markgräfler Scheibenfeuer
Authors: Nachtigall Werner 
Published: March 2013

AbstractDas Markgräfler Brauchtum des Scheibenschlagens zur Fasnachtszeit ist nicht nur ein traditionelles Spektakel; es lässt sich auch physikalisch untermauern. Wie hoch sind Startgeschwindigkeit und Startimpuls der Scheibe? Wie wirkt sie als Flugkörper und wie stabilisiert sie ihren Flug? Strömungsmechanische Messungen an Originalscheiben geben darüber Auskunft.
Der Sound der Nanowelt
Authors: Euler Manfred 
Published: March 2013

AbstractDer Beitrag stellt akustische Modelle der Rastertunnelmikroskopie vor. Diese nutzen Schallwellen und computergenerierte Visualisierungen zur Abbildung akustischer Systeme. Quantenanalogien veranschaulichen abstrakte Konzepte wie den Tunneleffekt und die Zustandsdichten von Elektronen. Die Experimente vermitteln einen praktischen, an Alltagserfahrungen orientierten Zugang zu Konzepten sowie Mess‐ und Visualisierungsmethoden der Nanowissenschaft. Sie demonstrieren auch, wie Nahfeldabbildungen die Beugungsgrenze der konventionellen Mikroskopie überwinden können.
Negative absolute Temperaturen
Authors: Schneider Ulrich 
Published: March 2013

AbstractAm absoluten Nullpunkt kommt jede klassische, thermische Bewegung zum Erliegen, und nichts kann kälter sein als T = 0 K. Dennoch ist es unserer Gruppe vom Max‐Planck‐Institut für Quantenoptik und der Ludwig‐Maximilians‐Universität München gelungen, negative absolute Temperaturen zu erzeugen. Wie passt das zusammen?
Physikalische Konstanten in Raum und Zeit
Authors: Henkel Christian , Menten Karl 
Published: March 2013

AbstractSeit einigen Jahrzehnten können durch Messung optischer Spektrallinien in astronomischen Objekten die Größen physikalischer Fundamentalkonstanten bestimmt werden. Bei dem Versuch, immer genauere Daten zu erhalten, erweisen sich seit kurzem Linien interstellarer Moleküle im Radiobereich als besonders geeignet. So konnten wir kürzlich das Proton‐zu‐Elektron‐Massenverhältnis mit bislang unerreichter Präzision im jungen Universum messen und mit dem heutigen Wert vergleichen.
Verräterische Lichtmuster in der Teetasse
Authors: Schlichting H. Joachim 
Published: March 2013

AbstractEin senkrecht durch eine dünne Wasserschicht dringender Laserstrahl zeichnet auf dem Boden eines Gefäßes ein strukturiertes Ringsystem. Ursache ist die diffuse Reflexion am Tassenboden.
pH‐sensitive residues in the p19 RNA silencing suppressor protein from carnation Italian ringspot virus affect siRNA binding stability
Authors: Law Sean M. , Zhang Bin W. , Brooks Charles L. 
Published: March 2013

AbstractTombusviruses, such as Carnation Italian ringspot virus (CIRV), encode a protein homodimer called p19 that is capable of suppressing RNA silencing in their infected hosts by binding to and sequestering short‐interfering RNA (siRNA) away from the RNA silencing pathway. P19 binding stability has been shown to be sensitive to changes in pH but the specific amino acid residues involved have remained unclear. Using constant pH molecular dynamics simulations, we have identified key pH‐dependent residues that affect CIRV p19–siRNA binding stability at various pH ranges based on calculated changes in the free energy contribution from each titratable residue. At high pH, the deprotonation of Lys60, Lys67, Lys71, and Cys134 has the largest effect on the binding stability. Similarly, deprotonation of several acidic residues (Asp9, Glu12, Asp20, Glu35, and/or Glu41) at low pH results in a decrease in binding stability. At neutral pH, residues Glu17 and His132 provide a small increase in the binding stability and we find that the optimal pH range for siRNA binding is between 7.0 and 10.0. Overall, our findings further inform recent experiments and are in excellent agreement with data on the pH‐dependent binding profile.
Plasma‐assisted molecular beam epitaxy of AlGaN heterostructures for deep‐ultraviolet optically pumped lasers
Authors: Jmerik V. N. , Lutsenko E. V. , Ivanov S. V. 
Published: March 2013

AbstractThe paper reports on elaboration of plasma‐assisted molecular beam epitaxy (MBE) of AlxGa1 − xN‐based quantum‐well (QW) structures with high Al content (up to 50% in the QW) grown directly on c‐sapphire. Different elements of the structure design are considered consecutively in detail along with the advanced growth approaches developed for each element. Special attention is paid to the growth conditions of (i) AlN nucleation layers with suppressed generation of threading dislocations (TDs), (ii) 2‐µm thick AlN buffer layers with atomically smooth droplet‐free morphology (rms = 0.46 nm) grown under the strongly metal‐rich conditions, (iii) cladding and waveguide AlGaN layers also possessing the atomically smooth droplet‐free morphology that is ensured by the accurately established phase diagram of metal(Ga)‐rich growth conditions within the temperature range 660–780 °C. Employing several 3‐nm thick strained GaN insertions in the AlN buffer layer and a AlGaN/AlN superlattice (SL) on top of it is shown to result in a significant decrease of TD's density down to 108–109 cm−2 in the top QW region fabricated by a submonolayer digital alloying (SDA) technique. Finally, advanced AlGaN‐based QW structures are presented, which demonstrate optically pumped lasing within the deep‐ultraviolet (UV) wavelength range with the threshold power density below 600 kW cm−2 (at 289 nm).
Field‐induced quantum criticality – application to magnetic cooling
Authors: Lang Michael , Wolf Bernd , Honecker Andreas , Balents Leon , Tutsch Ulrich , Cong Pham Than , Hofmann Georg , Krüger Natalia , Ritter Franz , Assmus Wolf , Prokofiev Andrey 
Published: March 2013

AbstractMaterials close to a quantum‐critical point – a zero‐temperature phase transition – exhibit anomalous thermodynamic properties also at finite temperatures. Close to a magnetic field‐induced quantum‐critical point, for example, the finite‐temperature entropy ST shows strong variations upon varying the magnetic field. Here we discuss the possibility to use this accumulation of entropy around a field‐induced quantum‐critical point for realizing an efficient magnetic cooling. Our proof‐of‐principle demonstration is based on measurements and theoretical calculations of the magnetocaloric properties of low‐dimensional spin‐1/2 antiferromagnets close to their field‐induced quantum‐critical points. We present results of the magnetocaloric effect ΓB = T−1(∂T/∂B)S ≈ const as a function of both field and temperature in the vicinity of the quantum‐critical point and discuss various performance characteristics, such as range of operation, efficiency and hold time. These figures are compared with those of a state‐of‐the‐art paramagnetic coolant.
Defect‐related visible luminescence of silica nanoparticles
Authors: Vaccaro L. , Spallino L. , Agnello S. , Buscarino G. , Cannas M. 
Published: March 2013

AbstractWe have investigated the visible emission of silica nanoparticles by time‐resolved luminescence spectra. We have characterized the spectroscopic properties of the blue band, centered around 2.8 eV, peculiar of as received samples and we have evidenced the effects induced by high power UV laser irradiation on the emitting defects.Moreover, the comparison with the luminescence of samples thermochemically treated in controlled atmosphere allows us to critically discuss the structural model proposed in the current literature. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phonon modes and Raman scattering in SixGe1‐x nanocrystals: microscopic modelling
Authors: Vasin A. S. , Vikhrova O. V. , Vasilevskiy M. I. 
Published: March 2013

AbstractSi1‐xGex nanocrystals (NCs) of different composition and size were generated using the Molecular Dynamics (MD) method by minimizing NC's total energy calculated using Tersoff's empirical potential and applying rigid boundary conditions. The dynamical matrix of the relaxed NC was constructed and the NC phonon modes were calculated. The localisation of the principal (Si‐Si, Si‐Ge and Ge‐Ge) modes is investigated by analysing their inverse participation ratio. The dependence of the corresponding Raman spectra, obtained by employing the bond polarisability model, upon x and the NC size is presented and compared to previous calculated results and available experimental data. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Control of condensation and evaporation of electron–hole liquid in diamond by femtosecond laser pulses
Authors: Kozák Martin , Trojánek František , Popelárˇ Tomáš , Malý Petr 
Published: March 2013

AbstractWe demonstrate the ultrafast control of condensation and evaporation of an electron–hole liquid in diamond prepared by chemical vapor deposition. The electron–hole liquid dynamics was measured using a three‐pulse pump and probe experiment. The transient transmission changes in the presence of electron–hole drops were assigned to the increase in the Drude scattering rate in the model of free carrier absorption due to a high carrier density. The fast (∼1 ps) liquid evaporation was induced by infrared femtosecond pulses and its dynamics was investigated under different photon energies and fluences. The value of the electron–hole liquid binding energy per electron–hole pair 80 ± 40 meV determined from the measured transient transmission signal agrees well with previously published values. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A study of IP prefix hijacking in cloud computing networks
Authors: Liu Yujing , Peng Wei , Su Jinshu 
Published: March 2013

ABSTRACTIP prefix hijacking remains a serious security threat to the traditional services in the Internet. It also harms the confidentiality and integrity of user data in Internet‐enabled cloud services because of its great dependence on Internet routing infrastructure. In addition, collaborations between networks in the cloud environment, especially in cross‐domain deployment, bring about new types of prefix hijacking attack, which may cause greater impact due to side‐effect of the cooperation of victim and infected autonomous systems. It is important to understand what impact a prefix hijacking attack can cause and how the number and locations of participants can affect the attacking results. In this paper, we model this problem as an attack planning task and solve it by applying a genetic algorithm. By analyzing the best solution to the problem, we find that the type of victims plays a more important role in IP prefix hijacking than that of attackers. Attackers can gain great impact even when the prefixes of a small number of victims are hijacked. For attack planning, the degree of an autonomous system is a major criterion to be considered. These findings are useful for securing cloud computing networks by preventing and eliminating IP prefix hijacking attacks. Copyright © 2013 John Wiley & Sons, Ltd.
Verifying cloud service‐level agreement by a third‐party auditor
Authors: Zhang Hongli , Ye Lin , Shi Jiantao , Du Xiaojiang , Guizani Mohsen 
Published: March 2013

ABSTRACTIn this paper, we study the important issue of verifying service‐level agreement (SLA) with an untrusted cloud and present an SLA verification framework that utilizes a third‐party auditor (TPA). A cloud provides users with elastic computing and storage resources in a pay‐as‐you‐go way. An SLA between the cloud and a user is a contract that specifies the computing resources and performances that the cloud should provide to the user. A cloud service provider (CSP) has incentives to cheat on the SLA, for example, providing a user with less central processing unit and memory resources than specified in the SLA, which allows the CSP to support more users and make more profits. A malicious CSP can easily disrupt the existing SLA monitoring/verification techniques by interfering with the monitoring/measurement process. A TPA resolves the trust dilemma between a CSP and its users. Under the TPA framework and the untrusted‐cloud threat model, we design two effective testing algorithms that can detect an SLA violation of the virtual machine memory size. Using real experiments, we demonstrate that our algorithms can detect cloud cheating on a virtual machine's memory size (i.e., SLA violations). Furthermore, we show that our testing algorithms can defend various attacks from a malicious CSP, which tries to hide an SLA violation. Copyright © 2013 John Wiley & Sons, Ltd.
Toward a Lived Science Curriculum in Intersecting Figured Worlds: An Exploration of Individual Meanings in Science Education
Authors: Price Jeremy F. , McNeill Katherine L. 
Published: March 2013

AbstractAs knowledge of and familiarity with science becomes an increasingly important aspect of contemporary life and citizenship, efforts have been made to make the science curriculum a “lived” curriculum (Hurd, 2000), one that reaches out to the lives, communities, and experiences of students. In this research around a high school urban ecology curriculum, we advance the idea that a focus on meaning, as the keystone for identity development, can help reach the goal of a lived science curriculum. Drawing upon social practice theory (Holland & Lave, 2001, 2009) and figured worlds (Holland, Lachicotte, Skinner, & Cain, 1998; Urietta, 2007), we present a way to conceptualize the meanings which emerge. We find through interviews with the adult participants (two curriculum developers and a classroom teacher) and students that meaning is described using three layers: meaning in person, meaning in intent, and meaning in practice. There are points of continuity and discontinuity of these meanings attributed to the curriculum by the adult participants. We further present data through the analysis of classroom video and artifacts created by students during an activity designed to elicit the meanings that students attribute to the curriculum. We discuss these findings and the possibilities for curriculum to provide opportunities for intersecting figured worlds which provide a focus on meaning and opportunities for agency in and with science. © 2013 Wiley Periodicals, Inc. J Res Sci Teach 50: 501–529, 2013.
Mapping extreme snowfalls in the French Alps using max‐stable processes
Authors: Gaume J. , Eckert N. , Chambon G. , Naaim M. , Bel L. 
Published: March 2013

Key Points
Analysis of extreme snowfall data using spatial extreme statistics
Mapping of extreme snowfall water equivalent using max‐stable processes
Obtaining return level maps, operational tool for avalanche risk management
Yellowstone grizzly delisting rhetoric: An analysis of the online debate
Authors: Parker Israel D. , Feldpausch‐Parker Andrea M. 
Published: March 2013

AbstractThe Yellowstone ecosystem is a hotbed of environmental issues and conflicts such as endangered species management. The Yellowstone grizzly bear (Ursus arctos horribilis) delisting debate illustrates how rhetoric can contribute to fragmentation and polarization among stakeholders engaged in endangered species conflicts. The partisan view of the grizzly ideograph, and what it represented, created impediments to conflict management (e.g., mistrust and development of and/or belief in stereotypes). The debate coalesced as the U.S. Fish and Wildlife Service began proceedings to delist the Yellowstone population from the endangered species list in 2005. Our objective was to use a rhetorical analysis of the Internet‐based debate to identify strategies used by disputants in conflicts over the Endangered Species Act. By analyzing web‐based stakeholder texts from 1998 through 2009, we found that rhetoric about grizzly bears fell into three main categories of rhetorical appeal: authority, ethics, and identity. Arguments relying on these appeals contributed to destructive communication amongst stakeholders. Rhetorical strategies served to clearly define stakeholder belief systems and clarify exclusionary practices. We found as an emerging theme that perspectives toward climate change influenced perception of grizzly delisting (e.g., climate change influences grizzly bear food availability). The Endangered Species Act's lack of directives regarding anthropogenic climate change further complicated the debate. We demonstrated how rhetorical analyses can reveal disputants' preferred social control frameworks. This provides important information to managers seeking to promote common ground between otherwise conflicted stakeholders that leads to legitimate and lasting policy decisions. © 2013 The Wildlife Society.
Cryptographic protocols with everyday objects
Authors: Heather James , Schneider Steve , Teague Vanessa 
Published: March 2013

Abstract
Most security protocols appearing in the literature make use of cryptographic primitives that assume that the participants have access to some sort of computational device. However, there are times when there is need for a security mechanism to evaluate some result without leaking sensitive information, but computational devices are unavailable. We discuss here various protocols for solving cryptographic problems using everyday objects: coins, dice, cards, and envelopes.
Robotically Assisted Revision of Bariatric Surgeries Is Safe and Effective to Achieve Further Weight Loss
Authors: Snyder Brad , Wilson Todd , Woodruff Vicky , Wilson Erik 
Published: March 2013

AbstractBackgroundAs more bariatric operations are being performed in the USA every year, the number of revisions has increased. These operations are challenging and have a higher morbidity than the initial operation. We have reviewed our series of robotically assisted revisions.MethodsAt the University of Texas Medical School at Houston, we reviewed robotic revision cases from 2004 through 2011 and found 99 bariatric revisions using robotic assistance. Selected endpoints included body mass index (BMI) at follow‐up, percent excess weight loss (%EWL), complications, intubation time, operative time, and length of hospital stay.ResultsThe average BMI at the time of revision was 44.8 kg/m2 and fell to 29 kg/m2 after 3 years. BMI was significantly lower at all time intervals (3, 12, 24, and 36 months) compared to initial BMI (p < 0.001). The %EWL was also significant at 1, 3, 12, 24, and 36 months post‐revision (p < 0.001). There was a 24 % (13/55) 90‐day readmission rate. The overall complication rate was 17 %, with each individual complication rate between 2 and 4 %. There were no deaths. The average operative time was 204 min, and the average length of hospital stay was 2.3 days.ConclusionsRevising previous bariatric operations to gastric bypass is difficult and time consuming. Although robotically assisted revision can be done safely and can result in effective further weight loss, the high postoperative complication rate is an issue that warrants further attention.
Responses of soil microbial biomass and enzymatic activities to different forms of organic nitrogen deposition in the subtropical forests in East China
Authors: Lü Yanna , Wang Congyan , Jia Yanyan , Du Jingjing , Ma Xu , Wang Wenwen , Pu Gaozhong , Tian Xingjun 
Published: March 2013

AbstractNumerous studies reported that inorganic nitrogen (N) deposition strongly affected forest ecosystems. However, organic N is also an important component of atmospheric N deposition. The influence of organic N deposition on soil microbial biomass and extracellular enzymatic activities (EEA) in subtropical forests remains unclear. Coniferous forest (CF) and broad‐leaved forest (BF) were chosen from the Zijin Mountain in China. Five forms of organic N (urea, glycine, serine, nonylamine, and a mixture of all four) were used to fertilize the soils in CF and BF every month for 1 year. Soil samples were collected every 2 months. Subsequently, soil microbial biomass and EEA were assayed. Results showed that the microbial biomass and EEA of soils fertilized with urea and amino acids increased significantly, whereas those fertilized with nonylamine and mixed N decreased significantly. Urea and amino acid fertilizations had a more positive influence on EEA of BF than on those of CF. Nonylamine fertilization had a more negative influence on EEA of CF than on those of BF. Organic N fertilization shifted soil microbial biomass away from the excretion of N‐degrading enzymes and toward the excretion of C‐degrading enzymes. These results suggest that organic N type is an important factor that affects soil microbial biomass, EEA, and their relationship. Organic N deposition may seriously affect soil C and N cycling, as well as carbon dioxide releasing from the soils by influencing microbial activities and biomass. This study thereby provides evidence that soil microorganisms have strong feedback to different forms of organic N deposition.
Amaranth Oil Increased Fecal Excretion of Bile Acid but Had No Effect in Reducing Plasma Cholesterol in Hamsters
Authors: de Castro Luíla Ívini Andrade , Soares Rosana Aparecida Manólio , Saldiva Paulo H. N. , Ferrari Roseli A. , Miguel Ana M. R. O. , Almeida Claudia A. S. , Arêas José Alfredo Gomes 
Published: March 2013

AbstractHamsters were fed for 4 weeks on four different diets: control (C) (balanced diet containing 20 % corn oil as the lipid source), hypercholesterolemic (H) (identical to C but containing 12 % coconut oil, 8 % corn oil and 0.1 % cholesterol as the lipid source), amaranth oil (A) (identical to H without corn oil but with amaranth oil), and squalene (S) (identical to H but admixed with squalene in the ratio found in amaranth oil). There were no significant differences in lipid profile, and in the cholesterol excreted in the animals' feces from amaranth oil (A) and squalene (S) groups. Fecal excretion of bile acids was greater in the amaranth oil (A) and squalene groups (S) as compared to the other groups. The scores of steatosis and parenchymal inflammation observed in the amaranth oil (A) and squalene groups (S) were superior to the ones observed in the other groups. Our findings demonstrated that amaranth oil, and its component squalene, increased the excretion of bile acids but did not have a hypocholesterolemic effect in hamsters fed on a diet containing high amounts of saturated fat and cholesterol.