bluuebunny/crossref_metadata_2025 huggingface dataset:
Solitonen im Bose‐Einstein‐Kondensat: Nichtlineare Materiewellenoptik
Authors: Eiermann Bernd , Oberthaler Markus
Published: June 2006

Bose‐Einstein‐Kondensate sind perfekte Quantensysteme für das Studium der Dynamik von Wellenpaketen. Ein mächtiges Werkzeug sind dabei periodische optische Potentiale aus Laserlicht. Ein solches optisches Gitter wirkt auf das Wellenpaket aus ultrakalten Atomen wie ein atomares Kristallgitter auf freie Elektronen. Dadurch entstehen Energiebänder. Weil die Potentialtiefe des optischen Gitters frei einstellbar ist, wird so die effektive Masse der Wellenpakete elegant steuerbar. Sogar eine negative effektive Masse ist im optischen Gitter realisierbar. Mit ihr lässt sich das Zerfließen eines Wellenpakets zeitlich umkehren. Das System ermöglicht auch die Erzeugung heller Solitonen, also nichtzerfließender Wellenpakete, obwohl sich die Atome untereinander abstoßen. Bislang wurden diese aus Wolken mit etwa 350 Rubidium‐Atomen erzeugt.
Möglichst keine Wellen schlagen. Physik des Schwimmens
Authors: Thaller Sigrid , Mathelitsch Leopold
Published: June 2006

Die durchschnittliche Dichte des menschlichen Körpers weicht kaum von der des Wassers ab. Deshalb kann der Mensch schwimmen und auch tauchen. Wettkampfschwimmer nutzen den Auftrieb und den Wasserwiderstand optimal aus, um möglichst hohe Geschwindigkeiten zu erreichen. Die Energiebereitstellung im Körper spielt dabei eine wesentliche Rolle.
Tanz supermassereicher Schwarzer Löcher
Authors: Reiprich Thomas , Hudson Daniel
Published: June 2006

Vermutlich befindet sich im Zentrum fast jeder Galaxie ein supermassereiches Schwarzes Loch. Wenn Galaxien miteinander verschmelzen, sollten dies deshalb auch die Schwarzen Löcher tun. Mit Beobachtungen des Röntgen‐Weltraumteleskops Chandra ist es einem deutsch‐amerikanischen Astronomenteam nun gelungen, zwei supermassereiche Schwarze Löcher als gebundenes Paar zu identifizieren. Dieses steht am Beginn eines langsamen Verschmelzungsprozesses.
Licht im Rückwärtsgang
Authors: Dolling Gunnar , Linden Stefan , Wegener Martin
Published: June 2006

Metamaterialien können qualitativ neuartige optische Eigenschaften besitzen, zum Beispiel eine negative optische Brechzahl. Die resultierende negative Phasengeschwindigkeit des Lichts ist sicher gewöhnungsbedürftig. Kürzlich konnte dieses Phänomen aber ein internationales Team mit Wissenschaftlern aus Karlsruhe und Heraklion direkt nachweisen.
Auf dem Weg zum International Linear Collider
Authors: Elsen Eckhard
Published: June 2006

Führende Beschleuniger‐ und Teilchenphysiker in Amerika, Asien und Europa arbeiten gemeinsam an der Planung des International Linear Collider (ILC). In dieser etwa 30 Kilometer langen Maschine werden Elektronen und Positronen beschleunigt und mit bisher unerreicht hohen Energien aufeinander prallen. Die Wissenschaftler erwarten davon Einblicke in die Welt jenseits des Standardmodells.
Das dunkle, kalte Ende
Authors: Hasinger Günther
Published: June 2006

Sterne verlöschen, Protonen zerfallen, das Universum expandiert unablässig weiter. Die Welt endet als kalter, schwarzer und fast leerer Raum. Einziger Trost: Menschen werden diese Ära nicht mehr erleben.
Visualisierung mit der Schlierenmethode
Authors: Heering Peter
Published: June 2006

Der Name des österreichischen Forschers Ernst Mach ist heute noch mit der Schallgeschwindigkeit verbunden. Diese Auszeichnung resultiert aus Machs Untersuchungen, wie sich Projektile mit Überschallgeschwindigkeit durch die Luft bewegen. Gerade in jüngster Zeit hat die Anwendung derartiger Methoden durch technische Modifikationen wieder einen Aufschwung erfahren.
Phæno Wolfsburg – die Welt entdecken
Authors: Rösner Peter
Published: June 2006

In Deutschlands jüngstem Science Center, dem phæno in Wolfsburg, öffnet sich die faszinierende und spannende Welt von Naturwissenschaft und Technik. Die Besonderheit und Schönheit verblüffender, grundlegender und auch rätselhafter naturwissenschaftlicher Phänomene am eigenen Leib zu erleben, dies ist das Thema von phæno.
Pervaporation properties of crosslinked poly(dimethylsiloxane) membranes for the removal of hydrocarbons from water
Authors: Ohshima Tadahiro , Kogami Yoshihisa , Minakuchi Masashi , Miyata Takashi , Uragami Tadashi
Published: June 2006

The pervaporation (PV) performance of crosslinked poly(dimethylsiloxane) dimethylmethacrylate (PDMSDMMA) membranes for an aqueous solution of various hydrocarbons was studied using sorption–diffusion theory. Three chlorinated hydrocarbons (chloroform, trichloroethylene, and tetrachloromethane) and three aromatic hydrocarbons (benzene, chlorobenzene, and toluene) were used as the permeants. When aqueous solutions of 0.05 wt % hydrocarbon were permeated through the crosslinked PDMSDMMA membranes, they showed high hydrocarbon/water selectivity and permeability during PV. The hydrocarbon/water selectivity of the crosslinked PDMSDMMA membranes was significantly dependent upon the permeants; in particular, chloroform removed the hydrocarbons most efficiently in this study. The results of the temperature dependence of the PV performance and hydrocarbon absorption into the membrane revealed that the difference in hydrocarbon/water selectivity for various aqueous solutions of hydrocarbons during PV depended significantly on the molar volume and diameter of the hydrocarbons. The permeation and removal mechanism of hydrocarbons from water through crosslinked PDMSDMMA membranes can be explained by a qualitative model based on the diffusion jump model. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2079–2090, 2006
Microstructure and protonic conductivity of H3PO4‐doped polyethylenimine–siloxane chemically covalently organic–inorganic hybrids
Authors: Liang Wuu‐Jyh , Hsieh Shang‐Ju , Hsu Chang‐Yu , Chen Wei‐Fu , Kuo Ping‐Lin
Published: June 2006

The chemically covalent polyethylenimine–siloxane hybrids doped with various amounts of ortho‐phosphoric acid (H3PO4) were prepared and characterized by FTIR, DSC, TGA, and solid‐state NMR spectra. The protonic conduction behavior of these materials was also investigated by means of impedance measurements. These observations indicate that the hydrogen bonding and protonic interactions exist between the dopant H3PO4 and the hybrid host, resulting in an increase in T
g of polyethylenimine segments. These hybrids are thermally stable up to 200 °C from TGA analysis. Conductivity studies show an Arrhenius behavior characteristic and the Grotthus‐like proton conduction, and a high conductivity of 10−2–10−3 S cm−1 at 110 °C in dry atmosphere for the hybrid membrane with H3PO4/EI of 0.5. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2135–2144, 2006
Statistical potential‐based amino acid similarity matrices for aligning distantly related protein sequences
Authors: Tan Yen Hock , Huang He , Kihara Daisuke
Published: June 2006

Aligning distantly related protein sequences is a long‐standing problem in bioinformatics, and a key for successful protein structure prediction. Its importance is increasing recently in the context of structural genomics projects because more and more experimentally solved structures are available as templates for protein structure modeling. Toward this end, recent structure prediction methods employ profile–profile alignments, and various ways of aligning two profiles have been developed. More fundamentally, a better amino acid similarity matrix can improve a profile itself; thereby resulting in more accurate profile–profile alignments. Here we have developed novel amino acid similarity matrices from knowledge‐based amino acid contact potentials. Contact potentials are used because the contact propensity to the other amino acids would be one of the most conserved features of each position of a protein structure. The derived amino acid similarity matrices are tested on benchmark alignments at three different levels, namely, the family, the superfamily, and the fold level. Compared to BLOSUM45 and the other existing matrices, the contact potential‐based matrices perform comparably in the family level alignments, but clearly outperform in the fold level alignments. The contact potential‐based matrices perform even better when suboptimal alignments are considered. Comparing the matrices themselves with each other revealed that the contact potential‐based matrices are very different from BLOSUM45 and the other matrices, indicating that they are located in a different basin in the amino acid similarity matrix space. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Structural characterization of the Acetobacter xylinum endo‐β‐1,4‐glucanase CMCax required for cellulose biosynthesis
Authors: Yasutake Yoshiaki , Kawano Shin , Tajima Kenji , Yao Min , Satoh Yasuharu , Munekata Masanobu , Tanaka Isao
Published: June 2006

Previous studies have demonstrated that endoglucanase is required for cellulose biosynthesis both in bacteria and plants. However, it has yet to be elucidated how the endoglucanases function in the mechanism of cellulose biosynthesis. Here we describe the crystal structure of the cellulose biosynthesis‐related endo‐β‐1,47‐glucanase (CMCax; EC 3.2.1.4) from the cellulose‐producing Gramnegative bacterium, Acetobacter xylinum (= Gluconacetobacter xylinus), determined at 1.65‐Å resolution. CMCax falls into the glycoside hydrolase family 8 (GH‐8), and the structure showed that the overall fold of the CMCax is similar to those of other glycoside hydrolases belonging to GH‐8. Structure comparison with Clostridium thermocellum CelA, the best characterized GH‐8 endoglucanase, revealed that sugar recognition subsite +3 is completely missing in CMCax. The absence of the subsite +3 leads to significant broadness of the cleft at the cellooligosaccharide reducing‐end side. CMCax is known to be a secreted enzyme and is present in the culture medium. However, electron microscopic analysis using immunostaining clearly demonstrated that a portion of CMCax is localized to the cell surface, suggesting a link with other known membrane‐anchored endoglucanases that are required for cellulose biosynthesis. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Inference methods for saturated models in longitudinal clinical trials with incomplete binary data
Authors: Song James X.
Published: June 2006

In the longitudinal studies with binary response, it is often of interest to estimate the percentage of positive responses at each time point and the percentage of having at least one positive response by each time point. When missing data exist, the conventional method based on observed percentages could result in erroneous estimates. This study demonstrates two methods of using expectation‐maximization (EM) and data augmentation (DA) algorithms in the estimation of the marginal and cumulative probabilities for incomplete longitudinal binary response data. Both methods provide unbiased estimates when the missingness mechanism is missing at random (MAR) assumption. Sensitivity analyses have been performed for cases when the MAR assumption is in question. Copyright © 2006 John Wiley & Sons, Ltd.
GSA algorithm applied to electronic structure II: UHF‐GSA method
Authors: Dias De Andrade Micael , Nascimento Marco , Mundim Kleber , Malbouisson Luiz
Published: June 2006

In this paper we propose a stochastic algorithm to investigate the real unrestricted Hartree–Fock problem. The approach is based on a global optimization method, the Generalized Simulated Annealing. The main characteristic of this method is that it enables the mapping of the electronic hyper‐surface in such a way as to guarantee that the absolute minimum of the functional in focus will be achieved. We tested this methodology by determining the Hartree–Fock ground‐state of the H2, LiH, BH, CH+, OH−, FH, CO, N2, BeH2, H2O, NH3, HCHO, CH4, CH, NH, CH2, NH2, OH and O2 molecules using minimal, double‐zeta, triple‐zeta and with polarization basis sets. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
X‐ray Structural Characterization of Diethyl Ether Solvated Lithium Iodide Derived from a Metathesis Reaction
Authors: Brym Markus , Jones Cameron , Junk Peter C. , Kloth Marc
Published: June 2006

[LiI(Et2O)]4 was isolated from the reaction mixture following the reaction of [Li(FIso)(Et2O)n] (HFIso = N,N′‐di(2,6‐diisopropylphenyl)formamidine) with GaI. [LiI(Et2O)]4 was characterized by X‐ray crystallography and was shown to be a centrosymmetric tetranuclear species with a pseudo‐cubane core, and isostructural to its chloride and bromide counterparts.
Ag2Te2O7, ein neues Silbertellurat mit Weberit‐Struktur
Authors: Klein Wilhelm , Curda Jan , Peters Eva‐Maria , Jansen Martin
Published: June 2006

Ag2Te2O7, a Novel Silver Tellurate of Weberite Structure Type

Ag2Te2O7 has been synthesized by solid state reaction of Ag2O and TeO2 under elevated oxygen pressure. The compound is diamagnetic and insulating, and decomposes at 560 °C in an Ar atmosphere into oxygen, Ag2TeO3 and TeO2. Ag2Te2O7 crystallizes orthorhombic in space group Imma with a = 7.266(2), b = 10.1430(9), c = 7.6021(17) Å, V = 560.3(2) Å3, Z = 4, 410 independent reflections, R1 = 4.65 %, wR2 = 11.13 %. The crystal structure consists of a three‐dimensional framework of TeO6 octahedra which are linked by common vertices. Voids of the framework accommodate silver atoms which are coordinated by eight oxygen atoms. The structure derives from that one of naturally occurring Weberite, Na2MgAlF7. The relationship to the pyrochlore structure type is discussed.
New Saccharinato/Ammonia Complexes of Nickel(II) and Zinc(II). A Structural and Spectroscopic Study
Authors: Williams Patricia A. M. , Ferrer Evelina G. , Baeza Natalia , Piro Oscar E. , Baran Enrique J.
Published: June 2006

Part of the unit cell parameters reported in Table 1 for [Zn(sac)2(NH3)2] are incorrect. The correct values are as follows:

a/Å : 7.004(1); b/Å : 11.639(2); c/Å : 12.571(2) and the unit cell volume/Å3 : 917.1(3)
Coming Out, Visibility, and Creating Change: Empowering Lesbian, Gay, and Bisexual People in a Rural University Community
Authors: D'Augelli Anthony R.
Published: June 2006

Personal and professional challenges faced in encouraging the development of a gay community in a rural university setting are described. Community psychologists who are lesbian, gay, or bisexual (LGB) must assess their willingness to be open and the roles they can play in developing helping resources. These issues concern how to encourage the empowerment of others while maintaining a collaborative role in a situation of major personal investment. Two specific challenges–developing informal helping resources for local LGB people and fostering institutional and policy changes to make the university a safer place for LGB faculty, staff, and students–are described. Community psychologists must consider personal risk when they become involved in empowerment efforts with this population.
Entwicklungslinien der Aggressionsforschung im letzten Viertel des 20. Jahrhunderts
Authors: Krampen Günter , Schui Gabriel
Published: June 2006

Zusammenfassung: Nachgezeichnet und reflektiert wird die Entwicklung der psychologischen Aggressionsforschung anhand des einschlägigen Fachliteraturaufkommens in den Literaturdatenbanken PsycINFO (mit dem Schwerpunkt auf angloamerikanischen Publikationen) und PSYNDEX (Publikationen von Autoren/innen aus dem deutschsprachigen Bereich) in der Zeit von 1977 bis 2003. Die bibliometrischen Befunde beziehen sich sowohl auf Entwicklungstrends im Gesamt der Aggressionsforschung als auch auf Trends in sozialpsychologischen (aggressives, antisoziales Verhalten) und persönlichkeitspsychologischen (Aggressivität) Forschungsbereichen sowie in den Bereichen der Aggression und Gewalt in Mikro-/Meso-/Makrosystemen, bei Straftaten, bei der Viktimisierung und im klinischen Kontext. Ebenso werden die Schwerpunkte der Aggressionsforschung global und differenziert nach den unterschiedlichen Grundlagendisziplinen und Anwendungsdisziplinen der Psychologie aufgefächert beschrieben. Alle Analysen folgen einem komparativen und zeitvergleichenden Zugang, wobei neben essenziellen Gemeinsamkeiten auch einige Unterschiede in der Entwicklung der Aggressionsforschung im angloamerikanischen und deutschsprachigen Bereich deutlich werden.
Personal Need for Structure als differenzialpsychologisches Konstrukt in der Sozialpsychologie
Authors: Machunsky Maya , Meiser Thorsten
Published: June 2006

Zusammenfassung: Eine reliable und valide deutschsprachige Version der Personal Need for Structure (PNS)-Skala wird vorgestellt. Hierzu wurde eine Übersetzung der englischsprachigen Originalskala erstellt, welche einer Skalenanalyse unterzogen sowie anhand persönlichkeits- und sozialpsychologischer Variablen validiert wurde. Studie 1 (N = 702), in der die psychometrische Qualität der deutschsprachigen Übersetzung überprüft wurde, zeigte, dass die deutsche PNS-Skala hinsichtlich Reliabilität und Faktorenstruktur mit der englischen Originalskala vergleichbar ist. Die Prüfung der konvergenten wie divergenten Validität der PNS-Skala anhand der Persönlichkeitsvariablen des Fünf-Faktoren Inventar (Big Five) und Need for Cognition sowie Konservatismus erfolgt in Studie 2 (N = 86). In Studie 3 (N = 66) wird die deutsche PNS-Skala im Inhaltsbereich der Intergruppenforschung an den Variablen Identifikation mit der Eigengruppe, “diversity beliefs”, Wahrnehmung der Homogenität von Eigen- und Fremdgruppe und Eigengruppenfavorisierung validiert.
Kodierung transaktiver Wissensprozesse (TRAWIS)
Authors: Brauner Elisabeth
Published: June 2006

Zusammenfassung: Das zunehmende Interesse an Prozessen der Interaktion und Kommunikation in der Gruppenforschung erfordert die Entwicklung von Verfahren, die eine für die jeweilige Fragestellung adäquate Datenanalyse ermöglichen. Um Prozesse des Wissenstransfers in Gruppen und insbesondere des Aufbaus und der Nutzung von transaktiven Wissenssystemen untersuchen zu können, wurde das hier beschriebene Verfahren zur Kodierung transaktiver Wissensprozesse (TRAWIS) entwickelt. Mittels TRAWIS werden Prozesse des Exponierens von Wissen, des Wissenserwerbs, der Wissenssuche und der Wissenszuweisung erfasst. Zwei Hauptdimensionen, die Ebene des angesprochenen Wissens und der Fokus der sprechenden Person, werden unterschieden. TRAWIS weist hohe Reliabilität auf und hat sich für die Forschung bereits als nützlich erwiesen. Da bisher vorwiegend kumulative Output-Maße transaktiven Wissens verwendet wurden, wird mit TRAWIS eine Lücke in der Forschungsmethodik geschlossen.
Simulation of CO2 concentrations, temperature, and stratification in Lake Nyos for different degassing scenarios
Authors: Schmid Martin , Halbwachs Michel , Wüest Alfred
Published: June 2006

A large gas cloud erupted unexpectedly in 1986 from Lake Nyos, the larger of the two Cameroonian “Killer Lakes,” with devastating consequences. Regular monitoring subsequently revealed that the deep water of the lake was gradually recharged with CO2. To preclude a similar event in the future, a degassing pipe was installed in the lake in 2001. In the present study a one‐dimensional model is used to predict the effects of this pipe and other degassing options on the CO2 concentrations and the stratification within the lake for the next 50 years. The results of the simulations show that without degassing, total CO2 content would reach the preeruption value within a few decades. The presently installed pipe is sufficient to reduce CO2 pressures in the entire water column above the pipe inlet to <5 bar within 10 years, and a steady state is reached within 50 years. Depending on the assessment of the risk due to the gas currently remaining in the lake and the costs involved, the installation of additional pipes could be considered (1) to remove the gas more quickly and (2) as a backup for long‐term failures and maintenance. Once the steady state is reached, degassing with one pipe is a practicable long‐term solution which can also be used for monitoring the approximate deep water CO2 concentrations by nonprofessionals. Assuming a doubled deep water input in the future as an upper limit of the expected source strength, the pipe is still able to prevent a CO2 accumulation. As a side effect, the degassing operation strongly changes the stratification in the lake. It transforms the lake from a meromictic to an oligomictic system and gradually removes the dissolved salts from the lake.
Modeling events of sea‐surface variability using spectral nudging in an eddy permitting model of the northeast Pacific Ocean
Authors: Stacey Michael W. , Shore Jennifer , Wright Daniel G. , Thompson Keith R.
Published: June 2006

Eddies are an important part of the current system that hugs the coasts of British Columbia and Alaska. The ability of “spectral nudging” to improve the eddy statistics determined from model simulations of this current system is investigated. Spectral nudging differs from standard nudging in that only specified frequency and wave number bands of the simulated potential temperature and salinity fields are nudged toward the observed climatology. Therefore the simulated eddy field can develop and evolve with time while the model is prevented from drifting far from the observed climatology. The Parallel Ocean Program (POP) is used to do the simulations, with 0.25° horizontal resolution and 23 vertical levels. The simulated standard deviation and skewness fields for the sea surface height are compared with those estimated from ten years of TOPEX/Poseidon altimetry observations. This comparison shows that spectral nudging allows the model to simulate the eddy statistics of the current system with significantly more accuracy than when the nudging is not used.
An assessment of buoy‐derived and numerical weather prediction surface heat fluxes in the tropical Pacific
Authors: Cronin Meghan F. , Fairall Christopher W. , McPhaden Michael J.
Published: June 2006

As part of the Eastern Pacific Investigation of Climate Processes program, from 2000 through 2003, the easternmost 95°W Tropical Atmosphere Ocean (TAO) moorings were enhanced to provide time series of net surface heat flux, and the National Oceanic and Atmospheric Administration ship maintaining the 95°W and 110°W TAO lines was enhanced to monitor surface heat fluxes and atmospheric boundary layer structure. In this study we compare the ship‐based and buoy‐based radiative, bulk latent, and sensible heat fluxes, as well as the meteorological state variables used to compute the turbulent heat fluxes. The buoy net surface heat flux measurements appear to have an overall uncertainty near the target 10 W m−2, when careful attention is paid to the state variables. When hourly averaged data were unavailable, the telemetered daily averaged data were used in combination with an estimate of the mesoscale gustiness. In the eastern tropical Pacific a warm layer correction to account for stratification above 1‐m depth was important only during the warm season (January–May) near the equator. These high‐quality, cross‐validated buoy heat flux time series are then used to assess the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR), NCEP/Department of Energy, and 40‐year European Centre for Medium‐Range Weather Forecasts reanalyses' surface heat fluxes. All reanalyses show that over warm water where deep convection is prominent, latent heat loss is too large and net solar radiation is too weak; conversely, in regions of stratocumulus over cool water, net solar radiation is too strong, and for NCEP/NCAR, latent heat loss is too weak.
Dust model intercomparison (DMIP) study over Asia: Overview
Authors: Uno I. , Wang Z. , Chiba M. , Chun Y. S. , Gong S. L. , Hara Y. , Jung E. , Lee S.‐S. , Liu M. , Mikami M. , Music S. , Nickovic S. , Satake S. , Shao Y. , Song Z. , Sugimoto N. , Tanaka T. , Westphal D. L.
Published: June 2006

An intercomparison study involving eight dust emission/transport models over Asia (DMIP) has been completed. Participating dust models utilize a variety of dust emission schemes, horizontal and vertical resolutions, numerical methods, and different meteorological models. Two huge dust episodes occurred in spring 2002 and were used for the DMIP study. Meteorological parameters, dust emission flux and dust concentration (diameter < 20 μm) are compared within the same domain on the basis of PM and NIES lidar measurements. We found that modeled dust concentrations between the 25% and 75% percentiles generally agreed with the PM observations. The model results correctly captured the major dust onset and cessation timing at each observation site. However, the maximum concentration of each model was 2–4 times different. Dust emission fluxes from the Taklimakan Desert and Mongolia differ immensely among the models, indicating that the dust source allocation scheme over these regions differs greatly among the various modeling groups. This suggests the measurements of dust flux and accurate updated land use information are important to improve the models over these regions. The dust vertical concentration profile at Beijing, China, and Nagasaki, Japan, has a large scatter (more than two times different) among the models. For Beijing, the scaled dust profile has a quite similar vertical profile and shows relatively good agreement with the lidar extinction profile. However, for Nagasaki, the scaled dust profiles do not agree. These results indicate that modeling of dust transport and removal processes between China and Japan is another important issue in improving dust modeling.
Do river profiles record along‐stream variations of low uplift rate?
Authors: Carretier S. , Nivière B. , Giamboni M. , Winter T.
Published: June 2006

Spatial variations of gradients in landscapes may be used to identify and quantify recent deformation. The problem with doing this is to determine whether tectonic or climatic forcing is responsible for these variations, especially for low uplift rate environments (≪1 mm yr−1) where climate changes may have erased tectonic features. We evaluate the respective contribution of low uplift rate (∼0.1 mm yr−1) and Pleistocene climate oscillations on gradient variations of two comparable river profiles crossing different uplift zones in the southern Upper Rhine Graben. We compare the observed points of discontinuity in river profile (knickpoints) and convex portions (knickzones) with those predicted by a detachment‐limited model that includes stochastic short‐term and cyclic long‐term variations in climate, a bedrock detachment threshold and rock uplift. The detachment‐limited model is chosen as it predicts the development of persistent knickpoints. Differing values of the shear stress exponent, erosion threshold, climate variability and uplift pattern have been checked. Our modeling suggests that climate changes had no significant effects on profiles and that anomalies are more likely due to anticline growth. This surprising result arises from the combination of a very low regional uplift rate and the detachment‐limited assumption. The detachment‐limited model implies an upstream propagation of knickpoints and knickzones generated by uplift at the outlet during dry climate periods of low erosion. The greater the uplift rate, the larger the variations in river bed elevation. Thus, for high uplift rate, knickpoints and knickzones generated by climate oscillations are more likely to hide tectonic features. This result seems counterintuitive because it suggests that tectonic knickzones will be better preserved in low uplift rate environments, provided that the lithology is homogeneous.
Forest leaf area index determination: A multiyear satellite‐independent method based on within‐stand normalized difference vegetation index spatial variability
Authors: le Maire G. , François C. , Soudani K. , Davi H. , Le Dantec V. , Saugier B. , Dufrêne E.
Published: June 2006

The Leaf Area Index (LAI) and its spatial distribution are key features to describe the forest ecophysiological processes. A stable and reproducible relationship is obtained between the LAI and the standard deviation σNDVI of the pixel‐based satellite‐derived normalized difference vegetation indices (NDVI) of forest stands. In situ measurements of LAI have been performed with the LAI‐2000 Plant Canopy Analyser over 8 years in the managed Fontainebleau forest (France) on about 31 stands each year, including oak, beech, and mixed oak‐beech stands. Simultaneous satellite images have been acquired, atmospherically and geometrically corrected, and included into a geographic information system to get the mean NDVI and the σNDVI for each stand. A total of six different satellites with a 20‐ to 30‐m spatial resolution have been considered over the eight studied years: SPOT1, SPOT2, SPOT4, LANDSAT ETM+, IKONOS, and HYPERION. The mean LAI of a stand is linked to the σNDVI with a unique relationship that appears to be mostly year‐ and satellite‐independent, because the σNDVI is nearly insensitive to additive or proportional shifts on NDVI. The theoretical bases of the σNDVI‐LAI relationship are investigated. The results show the combined importance of the shape of the within‐stand LAI distribution (following a Weibull probability density function) and the shape of the within‐stand LAI‐NDVI curves (showing a saturation). The root mean square error of the predicted LAI over the 259 samples is 1.14 m2/m2 when all years and satellites are considered, using the following equation: LAI = −2.45 ln(σNDVI) − 5.58 (r2 = 0.63).
Extreme solar EUV flares and ICMEs and resultant extreme ionospheric effects: Comparison of the Halloween 2003 and the Bastille Day events
Authors: Tsurutani B. T. , Guarnieri F. L. , Fuller‐Rowell T. , Mannucci A. J. , Iijima B. , Gonzalez W. D. , Judge D. L. , Gangopadhyay P. , Saito A. , Tsuda T. , Verkhoglyadova O. P. , Zambon G. A.
Published: June 2006

Extreme solar flares can cause extreme ionospheric effects. The 28 October 2003 flare caused a ∼25 total electron content units (TECU = 1016 el/m2 column density), or a ∼30%, increase in the local noon equatorial ionospheric column density. The rise in the TEC enhancement occurred in ∼5 min. This TEC increase was ∼5 times the TEC increases detected for the 29 October and the 4 November 2003 flares and the 14 July 2000 (Bastille Day) flare. In the 260–340 Å EUV wavelength range, the 28 October flare peak count rate was more than twice as large as for the other three flares. Another strong ionospheric effect is the delayed influence of the interplanetary coronal mass ejection (ICME) electric fields on the ionosphere. For the 28 and 29 October flares, the associated ICMEs propagated from the Sun to the Earth at particularly high speeds. The prompt penetration of the interplanetary electric fields (IEFs) caused the dayside near‐equatorial ionosphere to be strongly uplifted by E × B convection. Consequential diffusion of the uplifted plasma down the Earth's magnetic field lines to higher magnetic latitudes is a major plasma transport process during these IEF (superstorm) events. Such diffusion should lead to inverted midlatitude ionospheres (oxygen ions at higher altitudes than protons). The energy input into the midlatitude ionospheres by this superfountain phenomenon could lead to local dayside midlatitude disturbance dynamos, features which cannot propagate from the nightside auroral zones.
Paleoseismology of the southeastern Reelfoot Rift in western Tennessee and implications for intraplate fault zone evolution
Authors: Cox Randel Tom , Cherryhomes Jenny , Harris James B. , Larsen Dan , Van Arsdale Roy B. , Forman Steve L.
Published: June 2006

The southeastern Reelfoot Rift margin is expressed as a series of collinear scarps across western Tennessee, and shallow S wave reflection profiles, coring, and trenches show late Quaternary faulting along this lineament. At the north end, our seismic profile and coring suggest ≥1.5 m of Wisconsin down‐to‐the‐NW faulting. Coring and trenches across the central lineament show ≥3 m of up‐to‐the‐NW and 8–15 m of right‐lateral Late Wisconsin/Holocene faulting. Averaged late Quaternary right‐lateral slip has been 0.85–0.37 mm/yr on one fault plane at this locality, suggesting that total slip across all southeast rift margin fault planes may accommodate much of the regional strain. Our seismic profile at this site shows up‐to‐the‐west faulting of Eocene strata folded down‐to‐the‐west, indicating structural inversion. Seismic profiles, electrical surveys, coring, and a trench across the southern lineament segment show Holocene faulting. Trenching exposed a vertical fault with ∼0.5 m of late Holocene down‐to‐the‐NW displacement. Nearby, coring and electrical surveys show ∼0.5 m of late Holocene up‐to‐the‐NW faulting. We conclude the southeastern Reelfoot Rift margin is a right‐lateral system with high‐angle faults showing both up‐to‐the‐NW and down‐to‐the‐NW separations. Age constraints permit an earthquake circa 2500 to 2000 years B.P. on the southwestern/central segment of this fault system that ruptured ≥80 km. We suggest the northeastern segment of the southeastern rift margin turned off in Holocene when the Reelfoot step over thrust turned on.
Early Cretaceous extensional exhumation of the lower crust of a magmatic arc: Evidence from the Mount Irene Shear Zone, Fiordland, New Zealand
Authors: Scott J. M. , Cooper A. F.
Published: June 2006

The Mount Irene Shear Zone (MISZ) in Fiordland, New Zealand, is a low‐angle extensional mylonitic structure that has contributed to exhumation of a deep section of a Cretaceous magmatic arc. The dominantly metasedimentary hanging wall last equilibrated at ∼5.9 kbar, 603°C, whereas the metadioritic footwall, correlated with the Western Fiordland Orthogneiss (WFO), equilibrated at ∼8.5 kbar, 722°C, during retrogression associated with the MISZ. Displacement across the MISZ is also implied from differences in deformational episodes, metamorphic fabrics, and the presence/absence of partial melt products. A late stage synkinematic granitoid dike swarm intrudes the MISZ, but the dikes are invariably truncated and sheared within the basal calc‐silicate mylonites of the hanging wall. U/Pb dates from one such dike demonstrate that juxtaposition of the footwall against the hanging wall was effectively complete by ∼108 Ma. This date makes the MISZ the earliest Cretaceous extensional shear zone yet established in Fiordland and indicates that the switch from a convergent to an extensional tectonic regime on the paleo‐Pacific arc margin of Gondwana occurred between 111 and 108 Ma. Therefore there was only 8 Myr between final intrusion and high‐pressure metamorphism of the WFO and the initiation of extensional exhumation of the lower crust of this magmatic arc.
Upper‐air temperatures around Greenland: 1964–2005
Authors: Box Jason E. , Cohen Ariel E.
Published: June 2006

A 42‐year collection of 12h balloon soundings from six sites surrounding Greenland reveal distinct patterns of tropospheric and stratospheric temperature variability. Seasonal mean upper‐air temperatures exhibit statistically significant correlations with surface air temperature records. Over the full 1964–2005 record, patterns of statistically significant tropospheric warming and stratospheric cooling are evident. Overall, the magnitude of warming decreases with height, becoming cooling in the mid‐stratosphere. During the recent 12‐year period (1994–2005) lacking major volcanic forcing, statistically significant warming (+2.5 K to +5 K) is evident throughout the troposphere at all sites, with seasonal changes in the +3 K to +9 K range near the surface at 1000 hPa. The recent (1994–2005) tropospheric warming has dominated the 1964–2005 lower troposphere temperature change, despite 1964–1982 upper‐tropospheric cooling.
Monitoring the atmospheric boundary layer by GPS radio occultation signals recorded in the open‐loop mode
Authors: Sokolovskiy S. , Kuo Y.‐H. , Rocken C. , Schreiner W. S. , Hunt D. , Anthes R. A.
Published: June 2006

A new type of radio occultation (RO) data, recorded in open‐loop (OL) mode from the SAC‐C satellite, has been tested for monitoring refractivity in the Atmospheric Boundary Layer (ABL). Previously available RO signals, recorded in phase‐locked loop mode were often unusable for sensing the lower troposphere (LT) or resulted in significant inversion errors, especially in the tropics. The OL RO signals allow sensing of the LT and accurate monitoring of the ABL and, especially, its depth. Comparison of RO‐inverted refractivity profiles to ECMWF analysis and available radiosondes generally shows good agreement in the depth of the ABL. However, in a number of cases, ECMWF fails to reproduce the top of ABL. Future OL RO signals will provide information about the ABL depth which is an important parameter for weather prediction and climate monitoring.
On inverse scattering for the multidimensional relativistic Newton equation at high energies
Authors: Jollivet Alexandre
Published: June 2006

Consider the Newton equation in the relativistic case (that is the Newton-Einstein equation) ṗ=F(x), F(x)=−∇V(x), p=ẋ∕1−(∣ẋ∣2∕c2), p=dp∕dt, ẋ=dx∕dt, x∊C1(R,Rd), where V∊C2(Rd,R), ∣∂xjV(x)∣⩽β∣j∣(1+∣x∣)−(α+∣j∣) for ∣j∣⩽2 and some α>1. We give estimates and asymptotics for scattering solutions and scattering data for the equation for the case of small angle scattering. We show that at high energies the velocity valued component of the scattering operator uniquely determines the x-ray transform PF. Applying results on inversion of the x-ray transform P we obtain that for d⩾2 the velocity valued component of the scattering operator at high energies uniquely determines F. In addition we show that our high energy asymptotics found for the configuration valued component of the scattering operator does not uniquely determine F. The results of the present work were obtained in the process of generalizing some results of Novikov to the relativistic case.
Laser-produced annular plasmas
Authors: Veloso F. , Chuaqui H. , Aliaga-Rossel R. , Favre M. , Mitchell I. H. , Wyndham E.
Published: June 2006

A new technique is presented for the formation of annular plasmas on a metal surface with a high-power laser using a combination of axicon and converging lenses. The annular plasma formed on a titanium target in a chamber of hydrogen gas was investigated using schlieren imaging and Mach Zehnder interferometry. Expansion of the plasma was shown to be anisotropic with velocities of ∼103–104m∕s. Electron densities of 1018cm−3 were measured with radial profiles that confirm the presence of a hollow structure. The interferometric observations also show the presence of an inward shock wave traveling to the center of the annular plasma, which compresses the background neutrals, reaching a density around 18 times initial gas density, at 95ns after the initial annular plasma is produced.
Evidence for adiabatic heating during fracture of W-reinforced metallic glass composites
Authors: Lee Min Ha , Sordelet Daniel J.
Published: June 2006

At appropriate strain rates below their glass transition temperature, amorphous alloys deform inhomogeneously by strain localization within narrow shear planes. In the current study, we present experimental evidence of viscous flow by adiabatic heating at the fracture surface of W-reinforced Hf-based metallic glass composites under quasistatic uniaxial compressive deformation. Also, based on microstructural analysis, estimation of the temperature rise in a shear band shows that when fracture occurs, it releases a high level of strain energy, which when converted to heat, reaches temperatures sufficiently high enough to induce melting or softening of the W in the composite, producing vein patterns.
Periodic Hartree-Fock and density functional theory calculations for Li-doped polyacetylene chains
Authors: Ramírez-Solís A. , Zicovich-Wilson C. M. , Kirtman B.
Published: June 2006

We have performed periodic restricted Hartree-Fock/6-31G** and B3LYP∕6-31G** density functional theory calculations on Li-doped trans-polyacetylene at various dopant concentrations, using C2mH2mLi2 unit cells (m=7–14). Except for maintaining P1¯ rod symmetry the geometry was completely optimized for both uniform and nonuniform doping structures. In addition to geometry we obtain atomic charges, along with soliton formation and dopant binding energies, as well as band structures and densities of states. A thorough analysis of the band structure and density of states, as a function of dopant concentration, is presented. We also characterize the complex nature of the binding interaction between Li and the polyacetylene chain.
Coherent spectroscopy in dissipative media: Time-domain studies of channel phase and signal interferometry
Authors: Ramakrishna S. , Seideman Tamar
Published: June 2006

We extend a recently formulated coherence spectroscopy of dissipative media [J. Chem. Phys. 122, 084502 (2005)] from the stationary excitation limit to the time domain. Our results are based on analytical and numerical solutions of the quantum Liouville equation within the Bloch framework. It is shown that the short pulse introduces a new, controllable time scale that allows better insight into the relation between the coherence signal and the phase properties of the material system. We point to the relation between the time-domain coherence spectroscopy and the method of interferometric two-photon photoemission spectroscopy, and propose a variant of the latter method, where the two time-delayed excitation pathways are distinguishable, rather than identical. In particular, we show that distinguishability of the two excitation pathways introduces the new possibility of disentangling decoherence from population relaxation.
More anomaly free models of six-dimensional gauged supergravity
Authors: Suzuki Ryo , Tachikawa Yuji
Published: June 2006

We construct a huge number of anomaly free models of six-dimensional N=(1,0) gauged supergravity. The gauge groups are products of U(1) and SU(2), and every hyperino is charged under some of the gauge groups. It is also found that the potential may have flat directions when the R-symmetry is diagonally gauged together with another gauge group. In an Appendix, we determine the contribution to the global SU(2) anomaly from symplectic Majorana Weyl fermions in six dimensions.
In situ neutron diffraction measurement of transient temperature and stress fields in a thin plate
Authors: Woo Wanchuck , Feng Zhili , Wang Xun-Li , An Ke , Hubbard Camden R. , David Stan A. , Choo Hahn
Published: June 2006

Separating the elastic and thermal strains has been a long standing problem for in situ neutron diffraction measurement of transient temperature and stress fields. Using the plane stress condition, we demonstrate a method to decompose the thermal and elastic strains from the measured lattice spacing changes. The method was validated using a thin plate subjected to a local moving heat source. The methodology developed herein has practical applications for a variety of materials processing technologies such as welding, forming, and heat treatment.
Hyperfine spectrum of RbCl
Authors: Cederberg J. , Fortman S. , Porter B. , Etten M. , Feig M. , Bongard M. , Langer L.
Published: June 2006

The molecular beam electric resonance technique has been used to conduct a high precision examination of the hyperfine spectrum of the four isotopomers of RbCl. Coupling constants for the nuclear electric quadrupole interactions, the spin-rotation interactions, the tensor and scalar spin-spin interactions, and a rubidium nuclear octupole interaction, and their dependence on vibrational and rotational states have been determined. The dominant interaction, the rubidium nuclear electric quadrupole interaction, shows a small shift with substitution of the chlorine isotope.
Rescaling of equilibrium magnetically insulated flow theory based on results from particle-in-cell simulations
Authors: Ottinger P. F. , Schumer J. W.
Published: June 2006

By relaxing an assumption on the electron density in the flow layer used in magnetically insulated transmission line (MITL) theory, the theory is rescaled to match particle-in-cell (PIC) simulation results, providing a more accurate determination of the line voltage from the measurement of anode and cathode currents over a broad range of parameters. Results from the PIC simulations also show that self-limited flow is not determined by either a minimum-current or a minimum-energy condition, but rather is closer to saturated flow. In addition, analytic expressions are obtained for the first time for the self-limited flow impedance ZfSL(V)∕Z0 and the self-limited anode and cathode currents Z0IaSL(V) and Z0IcSL(V), where Z0 is the vacuum impedance of the line and V is the voltage. Similar expressions for both minimum-current flow and minimum-energy flow are also obtained. Results are compared with other models for MITL flow and show that this rescaled MITL flow model is most consistent with the PIC simulation results. Finally, it is shown that a matched load condition can never be satisfied for self-limited (or line-limited) flow.
New approach for measuring the microwave Hall mobility of semiconductors
Authors: Murthy D. V. B. , Subramanian V. , Murthy V. R. K.
Published: June 2006

Measurement of Hall mobility in semiconductor samples using bimodal cavity method gives distinct advantages due to noncontact nature as well as the provision to measure anisotropic mobility. But the measurement approaches followed till now have a disadvantage of having high error values primarily due to the problem in evaluating the calibration constant of the whole experimental arrangement. This article brings out a new approach that removes such disadvantage and presents the calibration constant with 1% accuracy. The overall error in the carrier mobility values is within 5%.
Optical scanning instrument for ultrafast pump-probe spectroscopy of biomolecules at cryogenic temperatures
Authors: Ionascu Dan , Rosca Florin , Gruia Florin , Yu Anchi , Champion Paul M.
Published: June 2006

We demonstrate novel optical scanning and detection instrumentation that is particularly useful for the interrogation of stationary cryogenic samples in pump-probe spectroscopy. The technique uses a spinning lens to scan multiple laser beams over a stationary sample while maintaining the focal properties of the beams. This significantly lengthens the time window for the sample reset to equilibrium and improves the photostability of stationary samples. In addition, we describe a signal processing methodology that discriminates against the strong background signal that can arise from leakage of the pump laser pulse train into the detector. These techniques are particularly useful in pump-probe studies of ultrafast processes in biological systems where sample deterioration, pump induced thermal lensing, and light scattering into the detection channel (e.g., induced by light scattering from a cryogenic matrix) are problematic. Generally, the optical scanning and detection instrumentation described here enable the study of a variety of biological systems, without the need for intricate spinning or flowing sample containers, making it possible to perform ultrafast pump-probe experiments on stationary samples such as a cryogenic matrix.
Study of two-dimensional Debye clusters using Brownian motion
Authors: Sheridan T. E. , Theisen W. L.
Published: June 2006

A two-dimensional Debye cluster is a system of n identical particles confined in a parabolic well and interacting through a screened Coulomb (i.e., a Debye-Hückel or Yukawa) potential with a Debye length λ. Experiments were performed for 27 clusters with n=3–63 particles (9μmdiam) in a capacitively coupled 9 W rf discharge at a neutral argon pressure of 13.6mTorr. In the strong-coupling regime each particle exhibits small amplitude Brownian motion about its equilibrium position. These motions were projected onto the center-of-mass and breathing modes and Fourier analyzed to give resonance curves from which the mode frequencies, amplitudes, and damping rates were determined. The ratio of the breathing frequency to the center-of-mass frequency was compared with theory to self-consistently determine the Debye shielding parameter κ, Debye length λ, particle charge q, and mode temperatures. It is found that 1≲κ≲2, and κ decreases weakly with n. The particle charge averaged over all measurements is −14200±200e, and q decreases slightly with n. The two center-of-mass modes and the breathing mode are found to have the same temperature, indicating that the clusters are in thermal equilibrium with the neutral gas. The average cluster temperature is 399±5K.