bluuebunny/crossref_metadata_2025 huggingface dataset:
Statistische Physik: Die Physik des Autoreifens: Kooperation zwischen Industrie und Theoretischer Physik – eine Illusion?
Authors: Vilgis Thomas A. , Heinrich Gert
Published: February 2013

Kautschuk ist ein Material, mit dem auch Physiker seit ihrer frühsten Kindheit unausweichlich in Berührung kommen – in Form von Gummireifen, zuerst an Kinderwagen oder Dreirad, später an Fahrrad, Auto oder gar Formel‐1‐Boliden. Was an Physik im Reifen steckt, bedenken wir kaum. Beim Anblick eines Autoreifens denken wir eher an schmutzige Hände vom Reifenwechsel als an theoretische Physik oder gar h. Doch die (statistische) Physik des Reifens zu verstehen ist eine wichtige Voraussetzung für Reifenhersteller, um die spezifischen Eigenschaften für unterschiedliche Anwendungen gezielt einstellen zu können.
Neutrinomasse, zum Dritten
Authors: Kirsten Till
Published: February 2013

Der kanadische Schwerwasser‐Sonnenneutrinodetektor SNO liefert erste Evidenz für ein aktives Signal von Sonnenneutrinos, die auf dem Weg von der Sonne zur Erde ihre Identität gewechselt haben.
Welt und Wissen: Sokal's hoax, die Postmoderne und der Wahrheitsanspruch der Physik
Authors: Carrier Martin
Published: February 2013

Der Streit um die realistische Deutung der Grundsätze wissenschaftlicher Theorien durchzieht die Wissenschafts‐ und Philosophiegeschichte seit der Spätantike. In den vergangenen drei Jahrzehnten hat sich dieser Streit durch die Betonung gesellschaftlicher Einflüsse auf die Wissenschaft von Seiten der Soziologie weiter verschärft und ist durch Alan Sokals kürzliche Attacke auf Postmodernismus und Relativismus in einen offenen Wissenschaftskrieg umgeschlagen. Die vom 18. bis 20. Juni am Zentrum für interdisziplinäre Forschung der Universität Bielefeld veranstaltete Tagung „Welt und Wissen”︁ diente dem Zweck, die Kriegsparteien um einen runden Tisch zu versammeln und die Beziehung der Wissenschaft zur Wirklichkeit auszuloten.
Hochtemperatur‐Supraleiter: Stand der Anwendungen
Authors: Sicking Frank , Fröhlingsdorf Joachim
Published: February 2013

Rund 15 Jahre liegt die Entdeckung der Hochtemperatur‐Supraleiter (HTSL) zurück. Nach der anfänglichen Forschungseuphorie stellte sich auf Grund der Komplexität des Materials und der damit verbundenen Schwierigkeiten eine deutliche Ernüchterung hinsichtlich schnell erzielbarer Anwendungen und Marktpotenziale ein. Bei einer realistischen Betrachtung erscheint die bisherige Entwicklungszeit von 15 Jahren jedoch eher als kurz, insbesondere da bereits heute klare Anwendungsoptionen der HTSL benannt werden können. Dieser Artikel dokumentiert an beispielhaft ausgewählten Bereichen den aktuellen Stand der Anwendung und mögliche Perspektiven.
Energie: Strom von der Sonne Erfolge und Perspektiven der Photovoltaik
Authors: Lux‐Steiner Martha Christina , Willeke Gerhard
Published: February 2013

Drei Kilowattstunden liefert die Sonne durchschnittlich pro Tag auf einen Quadratmeter Deutschlands. Die Sonnenenergie, die in einer halben Stunde auf den gesamten Erdball einfällt, würde theoretisch genügen, um den jährlichen thermischen und elektrischen Weltenergiebedarf zu decken. Wie lässt sich die Energie möglichst effizient und kostengünstig in elektrischen Strom umwandeln?
„… der Menschheit den größten Nutzen geleistet …”︁!?: 100 Jahre Nobelpreis, eine kritische Würdigung aus historischer Perspektive
Authors: Kant Horst
Published: February 2013

Die Nobelpreise sind sowohl auf den Gebieten, für die sie verliehen werden, als auch im weiteren Sinne die international begehrtesten und renommiertesten Preise. Das liegt sicher nicht nur an den beträchtlichen Preisgeldern, sondern vor allem am gesellschaftlichen Ansehen, das die Laureaten erlangen. Trotzdem werden immer wieder berechtigte Fragen laut: Ist die getroffene Auswahl gerecht bzw. gerechtfertigt? Hätte den Preis nicht so mancher verdient gehabt, der ihn nicht bekam? Ist der Nobelpreis überhaupt noch zeitgemäß? Muss man heutzutage nicht eher ganze Gruppen auszeichnen, da es sich immer weniger um Einzelleistungen handelt?
Auf Einsteins Spuren zum Nobelpreis: Physik‐Nobelpreis für Experimente zur Bose‐Einstein‐Kondensation
Authors: Görlitz Axel , Pfau Tilman
Published: February 2013

Mit dem diesjährigen Nobelpreis für Physik werden die beiden Amerikaner Eric A. Cornell und Carl E. Wieman sowie der Deutsche Wolfgang Ketterle für ihre Experimente zur Bose‐Einstein‐Kondensation ausgezeichnet [1]. Der Preis wird für die erstmalige Realisierung von Bose‐Einstein‐Kondensaten und erste grundlegende Studien dieses neuen Materiezustandes vergeben. Nur vier Jahre nach dem Nobelpreis für die Entwicklung der Laserkühlung von Atomen [2] ist dies eine weitere Auszeichnung für ein relativ junges Forschungsgebiet, das über die Atomphysik hinaus zunehmend in andere Gebiete der Physik ausstrahlt.
Gamma‐Ray Bursts: Kurzzeitig am Himmel aufleuchtende intensive Gammastrahlungsquellen sind ein aktueller Forschungsschwerpunkt der relativistischen Astrophysik
Authors: Klose Sylvio , Greiner Jochen , Hartmann Dieter H.
Published: February 2013

Kaum ein anderes Forschungsgebiet der Astrophysik hat in den letzten Jahren einen so gewaltigen Fortschritt erlebt, wie das Studium der kosmischen Gamma‐Ray Bursts — der kurzzeitig am Himmel aufleuchtenden sehr intensiven Gammastrahlungsquellen. Heute weiß man, dass es sich hierbei um die leuchtkräftigsten Erscheinungen im Universum handelt. Verbunden mit ultra‐relativistischen Materieausflüssen und womöglich der Entstehung stellarer Schwarzer Löcher hat sich hier ein kosmisches Laboratorium der relativistischen Astrophysik eröffnet, dessen Einfluss auf andere Forschungszweige der Astronomie noch gar nicht abzusehen ist.
The impact of the AMO on the West African monsoon annual cycle
Authors: Martin Elinor R. , Thorncroft Chris D.
Published: February 2013

A combination of observations and re‐analysis was used to investigate the mechanisms of the connection between the Atlantic Multidecadal Oscillation (AMO) and Sahel rainfall. A composite technique based on the AMO index was used to identify differences between warm and cold phases of the AMO. A significant summer rainfall increase over the Sahel during warm phases of the AMO was observed, with large increases during the typical monsoon onset period in June. In spring of warm phases of the AMO prior to monsoon onset, strengthening of the Saharan heat‐low and its associated shallow meridional overturning circulation is observed. The intensified shallow meridional overturning circulation increases moisture flux into the Sahel from the south during spring while increased westerly winds from the Atlantic increase westerly moisture flux into the Sahel during spring and summer. The strengthening of the heat‐low is accompanied by increases in Mediterranean sea‐surface temperatures during warm phases of the AMO that lead to increases in moisture flux convergence in the northeast Sahel. During warm phases of the AMO the African easterly jet is farther north than in cold phases, and increased African easterly wave (AEW) activity across West Africa and into the Atlantic is observed. This increased AEW activity particularly in the early hurricane season, as measured by eddy kinetic energy, may be contributing to the increased number of Atlantic tropical storms during warm phases of the AMO.
Wideband generalized admittance matrix representation for the analysis and design of waveguide filters with coaxial excitation
Authors: Mira Fermín , San Blas Ángel A. , Boria Vicente E. , Roglá Luis J. , Gimeno Benito
Published: February 2013

A very efficient technique for the full‐wave analysis and design of complex passive waveguide filters, including rectangular cavities with metallic cylindrical posts and coaxial excitation, is presented. This novel technique provides the wideband generalized admittance matrix representation of the whole structure in the form of pole expansions, thus extracting the most expensive computations from the frequency loop. For this purpose, the structure is properly segmented into its key building blocks, all of them characterized in terms of wideband admittance matrices. Then, an efficient iterative algorithm for combining these matrices, and finally providing the wideband generalized admittance matrix of the complete structure, is followed. In order to validate the accuracy and efficiency of this full‐wave modal technique, four different waveguide filters have been considered. In particular, the design of a compact four‐pole in‐line filter with tuning screws and of an evanescent‐mode filter, both operating in the X‐band and including a standard (vertical) coaxial excitation, are first presented. Finally, two C‐band six‐resonator comb‐line filters, one of them with a cross‐coupling configuration, and both excited with a collinear end‐launcher transition based on a disc‐ended coaxial, are also designed. Numerical data from a commercial software, as well as measurements of a manufactured prototype, are included for verification purposes.
Multiphoton microscopic imaging of esophagus during the early phase of tumor progression
Authors: Xu Jian , Kang Deyong , Xu Meifang , Zhuo Shuangmu , Zhu Xiaoqin , Chen Jianxin
Published: February 2013

Esophageal cancer is one of the most common cancer and leading cause of cancer death worldwide. Multiphoton microscopy (MPM) has become a novel optical tool of choice for imaging tissue architecture and cellular morphology based on two‐photon excited fluorescence and second harmonic generation. In this study, we used MPM to image microstructure of human normal esophagus, carcinoma in situ, and early invasive carcinoma in order to investigate the morphological change of tissue structure during the early phase of tumor progression. The diagnostic features such as the appearance of cancerous cells, the absence of the basement membrane were extracted to distinguish between normal and cancerous esophagus tissue. The infiltration depth during tumor progression was determined by the appearance of cancerous cells. The significant change of layer structure between cancerous tissue and normal esophagus was described. We also quantitatively described the differences of morphology between normal and cancerous cells. These results correlated well with the corresponding histological findings. With the advancement of clinically miniaturized MPM and the multi‐photon probe, combining MPM with standard endoscopy will therefore allow us to make a real‐time in vivo diagnosis of early esophageal cancer at the cellular level. SCANNING 35:387–391, 2013. © Wiley Periodicals, Inc.
Cross‐correlation analysis and information content of observed heads during pumping in unconfined aquifers
Authors: Mao Deqiang , Yeh Tian‐Chyi J. , Wan Li , Lee Cheng‐Haw , Hsu Kuo‐Chin , Wen Jet‐Chau , Lu Wenxi
Published: February 2013

Key Points

cross‐correlation for pumping tests analysis in unconfined aquifers

geological structure and variability are both considered during analysis

cross‐correlation results are not axisymmetric
Automatic parameterization of a flow routing scheme driven by radar altimetry data: Evaluation in the Amazon basin
Authors: Getirana Augusto C. V. , Boone Aaron , Yamazaki Dai , Mognard Nelly
Published: February 2013

Key Points

calibration of a flow routing scheme with radar altimetry data

sensitivity of the calibration to data availability

reliability of parameters found
Full laparoscopic total pancreatectomy with and without spleen and pylorus preservation: a feasibility report
Authors: Dallemagne Bernard , de Oliveira AntonioTalvaneTorres , Lacerda Croider Franco , D'Agostino Jacopo , Mercoli Henry , Marescaux Jacques
Published: February 2013

Background/purpose

Laparoscopic pancreatic surgery is gaining acceptance and clear advantages have been demonstrated in distal resection. Total pancreaticoduodenectomy (TPD) combines the operative steps of distal pancreatectomy and pancreaticoduodenectomy, but facilitates reconstruction and lowers the risk of common complications by avoiding the need for a pancreatic anastomosis. The aim of this report is to analyse the feasibility of laparoscopic total pancreaticoduodenectomy, with and without spleen and pylorus preservation.

Methods

Two patients underwent laparoscopic TPD for pancreatic intraductal mucinous neoplasm and endocrine tumors. Total splenopancreaticoduodenectomy (TSP) and pylorus‐ and spleen‐preserving total pancreaticoduodenectomy (PSPTP) were performed.

Results

The two procedures were successfully completed laparoscopically. PSPTP was more time‐consuming (420 vs. 360 min) and had an increased risk of hemorrhage (600 vs. 200 ml) compared with TSP. After both procedures, the postoperative outcome was uneventful and the postoperative length of hospital stay was 8 days.

Conclusions

This report confirms the feasibility of full laparoscopic TPD, and presents the first full laparoscopic pylorus‐ and spleen‐preservation technique with conservation of the splenic vessels, without robotic assistance. No conclusions can be drawn from this report, but it shows that the laparoscopic approach provides visual magnification, improved exposure, and delicate manipulation of tissues, which may reproduce the clear advantages of laparoscopic distal pancreatectomy.
Relationship between cardiolipin metabolism and oxygen availability in Bacillus subtilis
Authors: Lobasso Simona , Palese Luigi L. , Angelini Roberto , Corcelli Angela
Published: February 2013

We report changes of the content of anionic phospholipids in Bacillus subtilis in response to hypoxic conditions and inhibition of terminal respiration. Cardiolipin accumulates rapidly when bacteria are suspended in non‐growth medium under reduced aeration or exposed to the inhibitor cyanide; the increase of cardiolipin occurs at the expense of its precursor phosphatidylglycerol and is temperature‐dependent. Depending on the extent of hypoxic stress, membranes containing different levels of cardiolipin can be isolated from B. subtilis cells. The NADH oxidase activity in cardiolipin‐enriched membranes is cyanide‐resistant; furthermore O2 consumption measurements indicated that cardiolipin‐enriched cells are resistant to cyanide. Results point out a possible interdependence between the effect of cyanide on cardiolipin metabolism and the effect of cardiolipin on the effectiveness of cyanide inhibition.
Small molecule antagonism of oxysterol‐induced Epstein–Barr virus induced gene 2 (EBI2) activation
Authors: Benned-Jensen Tau , Madsen Christian M. , Arfelt Kristine N. , Smethurst Christian , Blanchard Andy , Jepras Robert , Rosenkilde Mette M.
Published: February 2013

The Epstein–Barr virus induced gene 2 (EBI2) was recently identified as the first oxysterol‐activated 7TM receptor. EBI2 is essential for B cell trafficking within lymphoid tissues and thus the humoral immune response in general. Here we characterize the antagonism of the non‐peptide molecule GSK682753A, which blocks oxysterol‐induced G‐protein activation, β‐arrestin recruitment and B‐cell chemotaxis. We furthermore demonstrate that activation triggers pertussis toxin‐sensitive MAP kinase phosphorylation, which is also inhibited by GSK682753A. Thus, EBI2 signalling in B cells mediates key phenotypic functions via signalling pathways amenable to manipulation providing additional therapeutic options for inhibiting EBI2 activity.
Climate and vegetation change during the late-glacial/early-Holocene transition inferred from multiple proxy records from Blacktail Pond, Yellowstone National Park, USA
Authors: Krause Teresa R. , Whitlock Cathy
Published: February 2013

A series of environmental changes from late-glacial ice recession through the early Holocene are revealed in a 7000-yr-long record of pollen, charcoal, geochemistry, and stable isotopes from Blacktail Pond, a closed-basin lake in Yellowstone National Park. Prior to 11,500 cal yr BP, cool conditions dominated, fire activity was low, and alpine tundra and Picea parkland grew on the landscape. A step-like climate change to warm summer conditions occurred at 11,500 cal yr BP. In response, fire activity increased facilitating a transition from Picea parkland to closed Pinus forest. From 11,500 to 8280 cal yr BP, warm summers and abundant moisture mostly likely from high winter snowfall supported closed Pinus contorta forests. Cooler drier summer conditions prevailed beginning 8280 cal yr BP due to decreased summer insolation and winter snowpack, and lower parkland developed. The timing of vegetation change in the Blacktail Pond record is similar to other low- and middle-elevation sites in the northern Rocky Mountains during the late-glacial period, suggesting local plant communities responded to regional-scale climate change; however, the timing of vegetation changes was spatially variable during the early and middle Holocene due to the varying influences of strengthened summer monsoons and subtropical high on regional precipitation patterns.
Falling styles of disks
Authors: Auguste Franck , Magnaudet Jacques , Fabre David
Published: February 2013

We numerically investigate the dynamics of thin disks falling under gravity in a viscous fluid medium at rest at infinity. Varying independently the density and thickness of the disk reveals the influence of the disk aspect ratio which, contrary to previous belief, is found to be highly significant as it may completely change the route to non-vertical paths as well as the boundaries between the various path regimes. The transition from the straight vertical path to the planar fluttering regime is found to exhibit complex dynamics: a bistable behaviour of the system is detected within some parameter range and several intermediate regimes are observed in which, although the wake is unstable, the path barely deviates from vertical. By varying independently the body-to-fluid inertia ratio and the relative magnitude of inertial and viscous effects over a significant range, we set up a comprehensive map of the corresponding styles of path followed by an infinitely thin disk. We observe the four types of planar regimes already reported in experiments but also identify two additional fully three-dimensional regimes in which the body experiences a slow horizontal precession superimposed onto zigzagging or tumbling motions.
Classical logic, conditionals and “nonmonotonic” reasoning
Authors: Allott Nicholas , Uchida Hiroyuki
Published: February 2013

Reasoning with conditionals is often thought to be non-monotonic, but there is no incompatibility with classical logic, and no need to formalise inference itself as probabilistic. When the addition of a new premise leads to abandonment of a previously compelling conclusion reached by modus ponens, for example, this is generally because it is hard to think of a model in which the conditional and the new premise are true.
Interactive Effects of Age-of-Acquisition and Repetition Priming in the Lexical Decision Task
Authors: Spataro Pietro , Longobardi Emiddia , Saraulli Daniele , Rossi-Arnaud Clelia
Published: February 2013

The analysis of the interaction between repetition priming and age of acquisition may be used to shed further light on the question of which stages of elaboration are affected by this psycholinguistic variable. In the present study we applied this method in the context of two versions of a lexical decision task that differed in the type of non-words employed at test. When the non-words were illegal and unpronounceable, repetition priming was primarily based on the analysis of orthographic information, while phonological processes were additionally recruited only when using legal pronounceable non-words. The results showed a significant interaction between repetition priming and age of acquisition in both conditions, with priming being greater for late- than for early-acquired words. These findings support a multiple-loci account, indicating that age of acquisition influences implicit memory by facilitating the retrieval of both the orthographic and the phonological representations of studied words.
Cognitive Rehabilitation Reduces Cognitive Impairment and Normalizes Hippocampal CA1 Architecture in a Rat Model of Vascular Dementia
Authors: Langdon Kristopher D , Granter-Button Shirley , Harley Carolyn W , Moody-Corbett Frances , Peeling James , Corbett Dale
Published: February 2013

Dementia is a major cause of morbidity in the western society. Pharmacological therapies to delay the progression of cognitive impairments are modestly successful. Consequently, new therapies are urgently required to improve cognitive deficits associated with dementia. We evaluated the effects of physical and cognitive activity on learning and memory in a rat model of vascular dementia (VasD). Male Sprague-Dawley rats (6 months old) were exposed to either regular chow or a diet rich in saturated fats and sucrose and chronic bilateral common carotid artery occlusion or sham surgery. First, this model of VasD was validated using a 2 × 2 experimental design (surgery × diet) and standard cognitive outcomes. Next, using identical surgical procedures, we exposed animals to a paradigm of cognitive rehabilitation or a sedentary condition. At 16 weeks post surgery, VasD animals demonstrated significant learning and memory deficits in the Morris water maze, independent of diet. Rehabilitation significantly attenuated these cognitive deficits at this time point as well as at 24 weeks. Further, rehabilitation normalized hippocampal CA1 soma size (area and volume) to that of control animals, independent of cell number. Importantly, these findings demonstrate beneficial neuroplasticity in early middle-aged rats that promoted cognitive recovery, an area rarely explored in preclinical studies.
Reference Region Approaches in PET: a Comparative Study on Multiple Radioligands
Authors: Zanderigo Francesca , Ogden R Todd , Parsey Ramin V
Published: February 2013

Reference region (RR) approaches (RRAs) for positron emission tomography (PET) brain studies aim to obtain full quantification without arterial input function (IF) sampling, an invasive and costly procedure. Although they need a reliable RR and are only able to estimate the nondisplaceable binding potential (BPND), RRAs are widely used. If quantitatively reliable, then RRAs can greatly benefit PET investigations, but their suitability can vary widely from radioligand to radioligand. This study compares estimates of BPND both using IF data and several common RRAs on an extensive data set for each of several radioligands. In addition, two new methods, likelihood estimation in graphical analysis with RR and a bootstrapping algorithm for estimating precision, are presented here for the first time. Although many factors contribute to the performance of each RRA, our results suggest that the kinetics in the RR have a role. In particular, RRAs tend to be good when (1) the RR distribution volume is high; (2) the transfer rate constant from plasma to free compartment in the RR is high; and (3) the transfer rate constant from free to plasma compartment in the RR is low.
Effects of the interaction range on structural phases of flexible polymers
Authors: Gross J. , Neuhaus T. , Vogel T. , Bachmann M.
Published: February 2013

We systematically investigate how the range of interaction between non-bonded monomers influences the formation of structural phases of elastic, flexible polymers. Massively parallel replica-exchange simulations of a generic, coarse-grained model, performed partly on graphics processing units and in multiple-Gaussian modified ensembles, pave the way for the construction of the structural phase diagram, parametrized by interaction range and temperature. Conformational transitions between gas-like, liquid, and diverse solid (pseudo) phases are identified by microcanonical statistical inflection-point analysis. We find evidence for finite-size effects that cause the crossover of “collapse” and “freezing” transitions for very short interaction ranges.
New porous medium Poisson-Nernst-Planck equations for strongly oscillating electric potentials
Authors: Schmuck M.
Published: February 2013

We consider the Poisson-Nernst-Planck system which is well-accepted for describing dilute electrolytes as well as transport of charged species in homogeneous environments. Here, we study these equations in porous media whose electric permittivities show a strong contrast compared with the electric permittivity of the electrolyte phase. Our main result is the derivation of convenient low-dimensional equations, that is, of effective macroscopic porous media Poisson-Nernst-Planck equations, which reliably describe ionic transport. The contrast in the electric permittivities between liquid and solid phase and the heterogeneity of the porous medium induce strongly oscillating electric potentials (fields). In order to account for this specific physical scenario, we introduce a modified asymptotic multiple-scale expansion which takes advantage of the nonlinearly coupled structure of the ionic transport equations. This allows for a systematic upscaling resulting in a new effective porous medium formulation which shows a new transport term on the macroscale. Solvability of all arising equations is rigorously verified. The emergence of a new transport term indicates promising physical insights into the influence of the microscale material properties on the macroscale. Hence, systematic upscaling strategies provide a source and a prospective tool to capitalize intrinsic scale effects for scientific, engineering, and industrial applications.
SuperADAM: Upgraded polarized neutron reflectometer at the Institut Laue-Langevin
Authors: Devishvili A. , Zhernenkov K. , Dennison A. J. C. , Toperverg B. P. , Wolff M. , Hjörvarsson B. , Zabel H.
Published: February 2013

A new neutron reflectometer SuperADAM has recently been built and commissioned at the Institut Laue-Langevin, Grenoble, France. It replaces the previous neutron reflectometer ADAM. The new instrument uses a solid state polarizer/wavelength filter providing a highly polarized (up to 98.6%) monochromatic neutron flux of 8 × 104 n cm−2 s−1 with monochromatization Δλ/λ = 0.7% and angular divergence Δα = 0.2 mrad. The instrument includes both single and position sensitive detectors. The position sensitive detector allows simultaneous measurement of specular reflection and off-specular scattering. Polarization analysis for both specular reflection and off-specular scattering is achieved using either mirror analyzers or a 3He spin filter cell. High efficiency detectors, low background, and high flux provides a dynamic range of up to seven decades in reflectivity. Detailed specifications and the instrument capabilities are illustrated with examples of recently collected data in the fields of thin film magnetism and thin polymer films.
Benchmark oxygen-oxygen pair-distribution function of ambient water from x-ray diffraction measurements with a wide Q-range
Authors: Skinner Lawrie B. , Huang Congcong , Schlesinger Daniel , Pettersson Lars G. M. , Nilsson Anders , Benmore Chris J.
Published: February 2013

Four recent x-ray diffraction measurements of ambient liquid water are reviewed here. Each of these measurements represents a significant development of the x-ray diffraction technique applied to the study of liquid water. Sources of uncertainty from statistical noise, Q-range, Compton scattering, and self-scattering are discussed. The oxygen-hydrogen contribution to the measured x-ray scattering pattern was subtracted using literature data to yield an experimental determination, with error bars, of the oxygen-oxygen pair-distribution function, gOO(r), which essentially describes the distribution of molecular centers. The extended Q-range and low statistical noise of these measurements has significantly reduced truncation effects and related errors in the gOO(r) functions obtained. From these measurements and error analysis, the position and height of the nearest neighbor maximum in gOO(r) were found to be 2.80(1) Å and 2.57(5) respectively. Numerical data for the coherent differential x-ray scattering cross-section IX(Q), the oxygen-oxygen structure factor SOO(Q), and the derived gOO(r) are provided as benchmarks for calibrating force-fields for water.
Invariant classification of vacuum pp-waves
Authors: Milson R. , McNutt D. , Coley A.
Published: February 2013

We solve the equivalence problem for vacuum pp-wave spacetimes by employing the Karlhede algorithm. Our main result is a suite of Cartan invariants that allows for the complete invariant classification of the vacuum pp-waves. In particular, we derive the invariant characterization of the G2 and G3 sub-classes in terms of these invariants. It is known [J. M. Collins, “The Karlhede classification of type N vacuum spacetimes,” Class. Quantum Grav. 8, 1859–1869 (1991)10.1088/0264-9381/8/10/011] that the invariant classification of vacuum pp-waves requires at most the fourth order covariant derivative of the curvature tensor, but no specific examples requiring the fourth order were known. Using our comprehensive classification, we prove that the q ⩽ 4 bound is sharp and explicitly describe all such maximal order solutions.
Time-of-flight electron spectrometer for a broad range of kinetic energies
Authors: Kothe Alexander , Metje Jan , Wilke Martin , Moguilevski Alexandre , Engel Nicholas , Al-Obaidi Ruba , Richter Clemens , Golnak Ronny , Kiyan Igor Yu. , Aziz Emad F.
Published: February 2013

A newly constructed time-of-flight electron spectrometer of the magnetic bottle type is characterized for electron detection in a broad range of kinetic energies. The instrument is designed to measure the energy spectra of electrons generated from liquids excited by strong laser fields and photons in the range of extreme ultra violet and soft X-rays. Argon inner shell electrons were recorded to calibrate the spectrometer and investigate its characteristics, such as energy resolution and collection efficiency. Its energy resolution ΔE/E of 1.6% allows resolving the Ar 2p spin orbit structure at kinetic energies higher than 100 eV. The collection efficiency is determined and compared to that of the spectrometer in its field-free configuration.
Ferroelectric and dielectric properties of ferrite-ferroelectric ceramic composites
Authors: Elena Ciomaga Cristina , Maria Neagu Alexandra , Valentin Pop Mihai , Airimioaei Mirela , Tascu Sorin , Schileo Giorgio , Galassi Carmen , Mitoseriu Liliana
Published: February 2013

Particulate composites of ferrite and ferroelectric phases with xNiFe2O4 (NF) and (1 − x)Pb0.988(Zr0.52Ti0.48)0.976Nb0.024O3 (where x = 2, 10, 20, 30, 50, 70, and 100 wt. %) were prepared in situ by sol-gel method. The presence of a diphase composition was confirmed by X-ray diffraction while the microstructure of the composites was studied by scanning electron microscopy revealing a good mixing of the two phases and a good densification of the bulk ceramics. The dielectric permittivity shows usual dielectric dispersion behavior with increasing frequency due to Maxwell-Wagner interfacial polarization. AC conductivity measurements made in frequency range 1 Hz-1 MHz suggest that the conduction process is due to mixed polaron hopping. The effect of NF phase concentration on the P-E and M-H hysteresis behavior and dielectric properties of the composites was investigated. At low NF concentration a sharp ferro-paraelectric transition peak can be observed at around 360 °C while for higher NF concentrations a trend to a diffuse phase transition occurs. All the composite samples exhibit typical ferromagnetic hysteresis loops, indicating the presence of ordered magnetic structure.
High-pressure study of the structural and elastic properties of defect-chalcopyrite HgGa2Se4
Authors: Gomis O. , Vilaplana R. , Manjón F. J. , Santamaría-Pérez D. , Errandonea D. , Pérez-González E. , López-Solano J. , Rodríguez-Hernández P. , Muñoz A. , Tiginyanu I. M. , Ursaki V. V.
Published: February 2013

In this work, we focus on the study of the structural and elastic properties of mercury digallium selenide (HgGa2Se4) which belongs to the family of AB2X4 ordered-vacancy compounds with tetragonal defect chalcopyrite structure. We have carried out high-pressure x-ray diffraction measurements up to 13.2 GPa. Our measurements have been complemented and compared with total-energy ab initio calculations. The equation of state and the axial compressibilities for the low-pressure phase of HgGa2Se4 have been experimentally and theoretically determined and compared to other related ordered-vacancy compounds. The theoretical cation-anion and vacancy-anion distances in HgGa2Se4 have been determined. The internal distance compressibility in HgGa2Se4 has been compared with those that occur in binary HgSe and ε−GaSe compounds. It has been found that the Hg-Se and Ga-Se bonds behave in a similar way in the three compounds. It has also been found that bulk compressibility of the compounds decreases following the sequence “ε-GaSe > HgGa2Se4 > HgSe.” Finally, we have studied the pressure dependence of the theoretical elastic constants and elastic moduli of HgGa2Se4. Our calculations report that the low-pressure phase of HgGa2Se4 becomes mechanically unstable above 13.3 GPa.
The competing spin orders and fractional magnetization plateaus of the classical Heisenberg model on Shastry-Sutherland lattice: Consequence of long-range interactions
Authors: Huo L. , Huang W. C. , Yan Z. B. , Jia X. T. , Gao X. S. , Qin M. H. , Liu J.-M.
Published: February 2013

The competing spin orders and fractional magnetization plateaus of the classical Heisenberg model with long-range interactions on a Shastry-Sutherland lattice are investigated using Monte Carlo simulations, in order to understand the fascinating spin ordering sequence observed in TmB4 and other rare-earth tetraborides. The simulation reproduces the experimental 1/2 magnetization plateau at low temperature by considering multifold long range interactions. It is found that more local long range interactions can be satisfied in the 1/2 plateau state than those in the 1/3 plateau state, leading to the stabilization of the extended 1/2 plateau. The phase boundaries in the magnetic field at zero temperature are determined, demonstrating the simulation results. When the energies of the Neel state and the collinear state are degenerated, the former state is more likely to be stabilized due to the competitions among the local collinear spin orders. The present work provides a comprehensive proof of the phase transitions to the Neel state at nonzero temperature, in complimentary to the earlier predictions for the Fe-based superconductors.
Hot-spot detection and calibration of a scanning thermal probe with a noise thermometry gold wire sample
Authors: Gaitas Angelo , Wolgast Steven , Covington Elizabeth , Kurdak Cagliyan
Published: February 2013

Measuring the temperature profile of a nanoscale sample using scanning thermal microscopy is challenging due to a scanning probe's non-uniform heating. In order to address this challenge, we have developed a calibration sample consisting of a 1-μm wide gold wire, which can be heated electrically by a small bias current. The Joule heating in the calibration sample wire is characterized using noise thermometry. A thermal probe was scanned in contact over the gold wire and measured temperature changes as small as 0.4 K, corresponding to 17 ppm changes in probe resistance. The non-uniformity of the probe's temperature profile during a typical scan necessitated the introduction of a temperature conversion factor, η, which is defined as the ratio of the average temperature change of the probe with respect to the temperature change of the substrate. The conversion factor was calculated to be 0.035 ± 0.007. Finite element analysis simulations indicate a strong correlation between thermal probe sensitivity and probe tip curvature, suggesting that the sensitivity of the thermal probe can be improved by increasing the probe tip curvature, though at the expense of the spatial resolution provided by sharper tips. Simulations also indicate that a bow-tie metallization design could yield an additional 5- to 7-fold increase in sensitivity.
The electrostatics of Ta2O5 in Si-based metal oxide semiconductor devices
Authors: Kornblum Lior , Meyler Boris , Salzman Joseph , Eizenberg Moshe
Published: February 2013

Thin dielectric layers are a prominent route to control the band alignments and effective work function of metal oxide semiconductor (MOS) devices. In this work, the electrostatic effects of thin Ta2O5 layers on the band alignments of MOS devices are examined. A detailed analysis of the physical properties of a thick (∼6 nm) Ta2O5 layer is reported. No significant dipoles at Ta2O5-Al2O3 and Ta2O5-SiO2 interfaces are found, as well as any significant charges inside Ta2O5 layers. When positioned at the interface, Ta2O5 is shown to prevent the formation of band offsets between Al2O3-SiO2, resulting in a shift of 1 ± 0.2 eV versus samples without interfacial Ta2O5. The relatively large magnitude of this shift in the current experimental configuration compared to previous works may indicate the participation of interface charges in the band offset. The possible use for these effects in devices is discussed.
Wavelength selective p-GaN/ZnO colloidal nanoparticle heterojunction photodiode
Authors: Qin Liqiao , Shao Dali , Shing Christopher , Sawyer Shayla
Published: February 2013

An ultraviolet heterojunction photodiode consisting of epitaxially grown p-GaN layers and polyvinyl alcohol coated ZnO colloidal nanoparticles exhibits a lowpass and bandpass alternative property depending on the illumination direction. At 0 V bias, a time response on the order of 10 s of milliseconds was demonstrated with a responsivity on the order of mA/W with about 100 nW of ultraviolet illumination. The rectification ratio at ±5 V was 1000 under dark environment. Deposition of colloidal ZnO nanoparticles on an independent p-GaN substrate introduces a technique to create a heterostructure pn junction photodiode with wavelength selection by back illumination.
Light-driven three-dimensional rotational motion of dandelion-shaped microparticles
Authors: Shpaisman Hagay , Ruffner David B. , Grier David G.
Published: February 2013

Chemically synthesized colloidal particles featuring large-scale surface asperities can be trapped and manipulated in fluid media through holographic optical trapping. Light scattering by these particles' surface features provides a mechanism for holographic optical traps also to exert torques on them, thereby setting them in steady rotation about arbitrary axes in three dimensions. When pairs of rotating particles are brought close enough that their surface features mesh, they form microscopic gear trains. These micro-opto-mechanical systems can be arranged in any desired three-dimensional configuration.
Microwave and mechanical properties of quartz/graphene-based polymer nanocomposites
Authors: Adohi B. J. P. , Bychanok D. , Haidar B. , Brosseau C.
Published: February 2013

We report microwave spectroscopy studies of graphene-based polymer-matrix composite materials subject to uniaxial elongation. The samples were prepared via shear mixing under the same thermal processing conditions of amorphous styrene butadiene rubber (SBR) with quartz grains on the order of micrometers in size and/or graphene sheets with thickness 10–20 nm and average lateral size 200 μm. An important result is the observation of a significant increase (up to 25%) in the effective microwave permittivity of hybridized nanocomposites comprising both quartz and graphene compared to the nanocomposites with quartz only. We suggest that the coating of quartz grains by graphene sheets is the most likely origin of this synergetic effect. In all cases, we also observe that the permittivity spectrum is unaffected by strain up to 8%. By examining the mechanical response, it is shown that the elasticity network of SBR polymer chains is significantly affected in the rubbery state by filling SBR with graphene and quartz particles.
Magnetic influence on the martensitic transformation entropy in Ni-Mn-In metamagnetic alloy
Authors: Barandiaran J. M. , Chernenko V. A. , Cesari E. , Salas D. , Lazpita P. , Gutierrez J. , Orue I.
Published: February 2013

We study the martensitic transformation (MT) of metamagnetic shape memory alloy Ni50Mn34.5In15.5 in the magnetic fields up to 12 T. The observed dependence of the MT temperature, Tm, on the field is highly nonlinear. As far as magnetization change, ΔM, remains field-independent, a depart from linearity of Tm(H) function is attributed to a decrease of the transformation entropy, ΔS. This decrease correlates with the parameter (TC-Tm), controlled by magnetic field, where TC is the Curie temperature of austenite, and with the dependence of ΔS on the width of the MT temperature interval deduced from a ferroelastic model of MT.
Improved Kerr constant and response time of polymer-stabilized blue phase liquid crystal with a reactive diluent
Authors: Zhu Ji-Liang , Ni Shui-Bin , Song Yue , Zhong En-Wei , Wang Yi-Jun , Ping Chen Chao , Ye Zhicheng , He Gufeng , Wu Dong-Qing , Song Xiao-Long , Lu Jian-Gang , Su Yikai
Published: February 2013

A polymer-stabilized (PS) blue phase liquid crystal (BPLC) with fast response time and large Kerr constant is investigated by doping a low molecular weight monomer (N-vinylpyrrollidone) into a conventional PS-BPLC consisting of BPLC, RM257, and 1,1,1-trimethylolpropane triacrylate. With this polymer network system, Kerr constant and the response can be improved simultaneously. Compared to the conventional PS-BPLC, Kerr constant of the proposed PS-BPLC can increase by 54% and the response time can decrease by 23% at the same time. The contrast ratio can be kept at a high level, over 1000:1 at λ = 633 nm.
Monitoring the Early Stage Self-Assembly of Enzyme-Assisted Peptide Hydrogels
Authors: Williams Richard J. , Gardiner James , Sorensen Anders B. , Marchesan Silvia , Mulder Roger J. , McLean Keith M. , Hartley Patrick G.
Published: February 2013

The early stages of the self-assembly of peptide hydrogels largely determine their final material properties. Here we discuss experimental methodologies for monitoring the self-assembly kinetics which underpin peptide hydrogel formation. The early stage assembly of an enzyme-catalysed Fmoc-trileucine based self-assembled hydrogel was examined using spectroscopic techniques (circular dichroism, CD, and solution NMR) as well as chromatographic (HPLC) and mechanical (rheology) techniques. Optimal conditions for enzyme-assisted hydrogel formation were identified and the kinetics examined. A lag time associated with the formation and accumulation of the self-assembling peptide monomer was observed and a minimum hydrogelator concentration required for gelation was identified. Subsequent formation of well defined nano- and microscale structures lead to self-supporting hydrogels at a range of substrate and enzyme concentrations. 1H NMR monitoring of the early self-assembly process revealed trends that were well in agreement with those identified using traditional methods (i.e. HPLC, CD, rheology) demonstrating 1H NMR spectroscopy can be used to non-invasively monitor the self-assembly of peptide hydrogels without damaging or perturbing the system.
Modeling shows that the NS5A inhibitor daclatasvir has two modes of action and yields a shorter estimate of the hepatitis C virus half-life
Authors: Guedj Jeremie , Dahari Harel , Rong Libin , Sansone Natasha D. , Nettles Richard E. , Cotler Scott J. , Layden Thomas J. , Uprichard Susan L. , Perelson Alan S.
Published: February 2013

The nonstructural 5A (NS5A) protein is a target for drug development against hepatitis C virus (HCV). Interestingly, the NS5A inhibitor daclatasvir (BMS-790052) caused a decrease in serum HCV RNA levels by about two orders of magnitude within 6 h of administration. However, NS5A has no known enzymatic functions, making it difficult to understand daclatasvir’s mode of action (MOA) and to estimate its antiviral effectiveness. Modeling viral kinetics during therapy has provided important insights into the MOA and effectiveness of a variety of anti-HCV agents. Here, we show that understanding the effects of daclatasvir in vivo requires a multiscale model that incorporates drug effects on the HCV intracellular lifecycle, and we validated this approach with in vitro HCV infection experiments. The model predicts that daclatasvir efficiently blocks two distinct stages of the viral lifecycle, namely viral RNA synthesis and virion assembly/secretion with mean effectiveness of 99% and 99.8%, respectively, and yields a more precise estimate of the serum HCV half-life, 45 min, i.e., around four times shorter than previous estimates. Intracellular HCV RNA in HCV-infected cells treated with daclatasvir and the HCV polymerase inhibitor NM107 showed a similar pattern of decline. However, daclatasvir treatment led to an immediate and rapid decline of extracellular HCV titers compared to a delayed (6–9 h) and slower decline with NM107, confirming an effect of daclatasvir on both viral replication and assembly/secretion. The multiscale modeling approach, validated with in vitro kinetic experiments, brings a unique conceptual framework for understanding the mechanism of action of a variety of agents in development for the treatment of HCV.
DLK initiates a transcriptional program that couples apoptotic and regenerative responses to axonal injury
Authors: Watkins Trent A. , Wang Bei , Huntwork-Rodriguez Sarah , Yang Jing , Jiang Zhiyu , Eastham-Anderson Jeffrey , Modrusan Zora , Kaminker Joshua S. , Tessier-Lavigne Marc , Lewcock Joseph W.
Published: February 2013

The cell intrinsic factors that determine whether a neuron regenerates or undergoes apoptosis in response to axonal injury are not well defined. Here we show that the mixed-lineage dual leucine zipper kinase (DLK) is an essential upstream mediator of both of these divergent outcomes in the same cell type. Optic nerve crush injury leads to rapid elevation of DLK protein, first in the axons of retinal ganglion cells (RGCs) and then in their cell bodies. DLK is required for the majority of gene expression changes in RGCs initiated by injury, including induction of both proapoptotic and regeneration-associated genes. Deletion of DLK in retina results in robust and sustained protection of RGCs from degeneration after optic nerve injury. Despite this improved survival, the number of axons that regrow beyond the injury site is substantially reduced, even when the tumor suppressor phosphatase and tensin homolog (PTEN) is deleted to enhance intrinsic growth potential. These findings demonstrate that these seemingly contradictory responses to injury are mechanistically coupled through a DLK-based damage detection mechanism.
Sulfur isotopic fractionation in vacuum UV photodissociation of hydrogen sulfide and its potential relevance to meteorite analysis
Authors: Chakraborty Subrata , Jackson Teresa L. , Ahmed Musahid , Thiemens Mark H.
Published: February 2013

Select meteoritic classes possess mass-independent sulfur isotopic compositions in sulfide and organic phases. Photochemistry in the solar nebula has been attributed as a source of these anomalies. Hydrogen sulfide (H
2
S) is the most abundant gas-phase species in the solar nebula, and hence, photodissociation of H
2
S by solar vacuum UV (VUV) photons (especially by Lyman-α radiation) is a relevant process. Because of experimental difficulties associated with accessing VUV radiation, there is a paucity of data and a lack of theoretical basis to test the hypothesis of a photochemical origin of mass-independent sulfur. Here, we present multiisotopic measurements of elemental sulfur produced during the VUV photolysis of H
2
S. Mass-independent sulfur isotopic compositions are observed. The observed isotopic fractionation patterns are wavelength-dependent. VUV photodissociation of H
2
S takes place through several predissociative channels, and the measured mass-independent fractionation is most likely a manifestation of these processes. Meteorite sulfur data are discussed in light of the present experiments, and suggestions are made to guide future experiments and models.