bluuebunny/crossref_metadata_2025 huggingface dataset:
Maligne Tumoren des Uterus
Authors: Mundhenke  , Bauerschlag  , Fischer  , Friedrich  , Maass
Published: June 2007

Maligne Tumoren des Uterus sind für fast 9% aller Krebsneuerkrankungen und für etwa 4,5% aller tumorbedingten Todesfälle bei Frauen verantwortlich. Die drei wichtigen Malignome des Uterus sind das Endometriumkarzinom, das Uterussarkom, die beide den Uteruskörper betreffen, sowie das Zervixkarzinom, welches vom Gebärmutterhals ausgeht. Das Endometriumkarzinom kommt gehäuft im höheren Lebensalter vor und ist zu > 70% hormonsensibel (Typ I) Der Karzinomtyp II ist häufig entdifferenziert und nicht hormonsensibel. Die Diagnose wird besonders durch die Vaginalsonographie und histologisch nach Hysteroskopie und fraktionierter Abrasio gesichert. Als Therapie der Wahl ist die stadiengerechte Operation (gegebenenfalls inklusive Lymphonodektomie) anzustreben, da nur diese ein exaktes Staging erlaubt. Postoperativ oder auch in fortgeschrittener Erkrankungssituation können der Einsatz endokriner Therapien, sowie der perkutanen bzw. Afterloading Strahlentherapie sinnvolle Therapiebestandteile sein. Chemotherapien kommen nur bei nicht hormonsensiblen oder fortgeschrittenen Tumoren zum Einsatz. Die uterinen Sarkome sind eine heterogene Gruppe seltener Tumoren. Daher gibt es keine umfassende Leitlinie zur Diagnostik und Therapie der Sarkome. Da diese häufig aggressiven Tumoren wenig auf medikamentöse Therapien und Strahlentherapien ansprechen, kommt der primären Operation eine zentrale Rolle zu. Das Zervixkarzinom entsteht maßgeblich auf dem Boden einer persistierenden Infektion mit onkogenen HPV-Typen. Als onkogene Co-Faktoren werden häufig der Nikotinabusus, eine Immundefizienz und zusätzliche chronische Genitalinfektionen genannt. Das Zervixkarzinom (80% plattenepitheliale Typen und 20% Adenokarzinome) und seine Vorstufen sind einer Vorsorgeuntersuchung sehr gut zugänglich. Viele Tumoren werden in frühen Stadien diagnostiziert. Präoperativ steht die lokale und distante Ausbreitungsdiagnostik im Vordergrund. Die stadiengerechte Therapie in frühen Stadien besteht in der radikalen Hysterektomie (inkl. Lymphonodektomie) und seltener in organerhaltenden Operationen (bei Kinderwunsch). Alternativ kann eine primäre Radiochemotherapie durchgeführt werden. Tumorstadien ≥ FIGO IIb werden mit einer primären kombinierten Strahlenchemotherapie behandelt.
Reading Aloud
Authors: Blais Chris , Besner Derek
Published: June 2007

Abstract. A central feature of many formal accounts of reading aloud, and of Coltheart and colleagues dual-route cascaded model in particular, is that activation across various modules is cascaded. Evidence is reviewed that this assumption is problematic in a particular context, along with a solution that involves thresholding the output of the letter level to the nonlexical routine. Consideration of the known effects of repetition leads to the prediction of a three-way interaction between stimulus quality, repetition, and lexicality in which repetition and stimulus quality interact when reading aloud exception words, but produce additive effects when reading aloud nonwords. The result of such an experiment confirms this prediction, and appears consistent with the localized dual-route model. Implications for other accounts are briefly noted.
Evolution of ring current and radiation belt particles under the influence of storm‐time electric fields
Authors: Nishimura Y. , Shinbori A. , Ono T. , Iizima M. , Kumamoto A.
Published: June 2007

Electric field and potential distributions in the inner magnetosphere during geomagnetic storms have been investigated using the Akebono/EFD data. Using this electric field, we study injection of ring current particles and acceleration of radiation belt electrons by single‐particle calculations. During the main phase, the dawn‐dusk electric field is intensified especially in a range of 2 < L < 5 with a maximum amplitude of 6 mV/m on the duskside, and a two‐cell convection pattern with a potential difference of 180 kV is identified. The convection pattern on the equatorial plane is significantly distorted with a large potential drop of 70 kV on the dawn and dusk sectors, indicating an intrinsic source of large‐scale electric field in the inner magnetosphere. The plasma sheet ions are gathered into the dusk to premidnight sector in the inner magnetosphere in the region of enhanced electric field due to the strong E × B drift. The ions are transported into around 4 RE with an acceleration of more than 1 order of magnitude within 40 min, conserving the first adiabatic invariants. Relativistic electrons with initial energy of some hundreds of kiloelectron volts at 5 RE are energized to more than 100 keV for 3 hours. The energy spectrum during the recovery phase of 9 October 1990 geomagnetic storm observed by the CRRES satellite is reproduced without the radial diffusion or nonadiabatic acceleration by plasma waves. It is possible that this acceleration process is the inhomogeneity of the large‐scale electric field, which corresponds to the ∇ × E term along orbits of electrons around the Earth.
Continental thermal isostasy: 2. Application to North America
Authors: Hasterok Derrick , Chapman David S.
Published: June 2007

Continental elevations can be partitioned into contributions from thermal and compositional buoyancy and geodynamic forces. In order to isolate the thermal component, elevations of 36 North American tectonic provinces are adjusted for the effects of compositional thickness and density variations by computing an isostatic adjustment relative to a standard crustal section (2850 kg m−3 density and 39 km thickness). Crustal densities are estimated using an empirical velocity‐density relationship. Compositional elevation adjustments applied to North American provinces range from ∼−1100 m in the southern Rocky Mountains to 2300 m in the Gulf of California, with uncertainties ranging from ∼200 m to >600 m. Theoretical thermal buoyancy is estimated by integrating the difference between a geotherm derived from observed values of heat flow and a reference geotherm. The best fitting continental heat flow–elevation model has a reference heat flow of 46.6 mW m−2 at 0 km and a 60:40 partitioning of surface heat flow between reduced and upper crustal radiogenic heat flow. Raw elevations of continental provinces show little correlation with heat flow, while compositionally adjusted elevations show a clear trend with ∼3 km difference between hot and cold provinces. A continental heat flow–elevation plot is used to identify outliers in adjusted province elevations. Anomalous elevations may reflect a nonsteady state thermal regime, dynamically supported elevation, anomalous mantle, or some combination of these states. Discriminating between these elevation sources provides insight into the geodynamics of North America, demonstrating the usefulness of this approach in continental geodynamic studies.
Origin of orogenic remagnetizations in Mississippian carbonates, Sawtooth Range, Montana
Authors: O'Brien V. J. , Moreland K. M. , Elmore R. D. , Engel M. H. , Evans M. A.
Published: June 2007

Paleomagnetic results are presented from Mississippian Madison Group carbonates in the Sawtooth Range, northwestern Montana. Samples were collected from sites along two east‐west trending transects perpendicular to the thrust faults in the Sun River Canyon and in the North and South Forks of the Teton River and from three folds. The Madison Group contains a widespread characteristic remanent magnetization (ChRM) that resides in magnetite with southerly declinations and moderately steep up inclinations. Tilt test results suggest that the ChRM is pretilting in the thrust sheets and Teton anticline but syntilting in the Clary Coulee and Swift Dam folds. The ChRMs all have the same characteristics and were probably caused by the same remagnetization event, yet the tilt test results are different. One explanation involves the difference in fold types between the Teton anticline (fault bend fold geometry) and the Clary Coulee and Swift Dam folds (fault propagation fold geometries). The deformation that produced the two geometries could have caused variations in strain/stress, which may have altered an original pretilting into a syntilting ChRM. A mean paleopole for the three pretilting tilt test results (67.2°N, 177.9°E; A95 = 13.1°) suggests remanence acquisition in the late Jurassic–early Tertiary. The ChRM is interpreted as a chemical remanent magnetization (CRM). Geochemical studies indicate that the Mississippian carbonates were altered by evolved fluids with radiogenic 87Sr/86Sr values, and petrographic analysis indicates that hydrocarbons migrated through the carbonates. The CRM is interpreted to be related to alteration by one of these fluids.
A ray‐tracing technique for improving Satellite Laser Ranging atmospheric delay corrections, including the effects of horizontal refractivity gradients
Authors: Hulley G. C. , Pavlis E. C.
Published: June 2007

In this paper we study the effects of horizontal refractivity gradients on the propagation of optical signals for a globally distributed set of Satellite Laser Ranging (SLR) stations. Using two‐dimensional ray tracing and globally distributed satellite data from NASA’s Atmospheric Infrared Sounder (AIRS), as well atmospheric fields from the National Center for Environmental Prediction (NCEP), we calculate the effects of horizontal gradients on a global set of SLR stations using 2 years of data during 2004 and 2005. We investigate in detail how seasonal and diurnal changes, latitudinal dependence, topography, and oceans affect the gradients at specific locations, as well as the application of these gradients on a set of SLR data from the LAGEOS 1 and 2 geodetic satellites. For the year 2004, AIRS ray‐tracing results showed maximum north‐south (NS) gradient delays of 50 mm at 10° elevation angle at Herstmonceux, UK and east‐west (EW) gradient delays of 35 mm at Yarragadee, Australia. Mean NS and EW gradients had delays not exceeding 5 mm for both AIRS and NCEP analysis at all stations. The standard deviations of AIRS gradients ranged from 6 to 12 mm, while NCEP gradients ranged from 3 to 9 mm, depending on location and time of year. The effects of applying AIRS and NCEP total ray‐tracing results, including horizontal gradient contributions, to a set of global SLR geodetic data resulted in reduction of the solution residuals by up to 43% in variance percent difference. This is a highly significant contribution for the SLR technique’s effort to reach an accuracy at the 1‐mm level this decade.
Experimental determination of salinity, temperature, growth, and metabolic effects on shell isotope chemistry ofMytilus eduliscollected from Maine and Greenland
Authors: Wanamaker Alan D. , Kreutz Karl J. , Borns Harold W. , Introne Douglas S. , Feindel Scott , Funder Svend , Rawson Paul D. , Barber Bruce J.
Published: June 2007

To study the effects of temperature, salinity, and life processes (growth rates, size, metabolic effects, and physiological/genetic effects) on newly precipitated bivalve carbonate, we quantified shell isotopic chemistry of adult and juvenile animals of the intertidal bivalveMytilus edulis(Blue mussel) collected alive from western Greenland and the central Gulf of Maine and cultured them under controlled conditions. Data for juvenile and adultM. edulisbivalves cultured in this study, and previously by Wanamaker et al. (2006), yielded statistically identical paleotemperature relationships. On the basis of these experiments we have developed a species‐specific paleotemperature equation for the bivalveM. edulis[T °C = 16.28 (±0.10) − 4.57 (±0.15) {δ18OcVPBD −δ18OwVSMOW} + 0.06 (±0.06) {δ18OcVPBD −δ18OwVSMOW}2; r2= 0.99; N = 323; p < 0.0001]. Compared to the Kim and O'Neil (1997) inorganic calcite equation,M. edulisdeposits its shell in isotope equilibrium (δ18Ocalcite) with ambient water. Carbon isotopes (δ13Ccalcite) from sampled shells were substantially more negative than predicted values, indicating an uptake of metabolic carbon into shell carbonate, andδ13Ccalcitedisequilibrium increased with increasing salinity. Sampled shells ofM. edulisshowed no significant trends inδ18Ocalcitebased on size, cultured growth rates, or geographic collection location, suggesting that vital effects do not affectδ18OcalciteinM. edulis. The broad modern and paleogeographic distribution of this bivalve, its abundance during the Holocene, and the lack of an intraspecies physiologic isotope effect demonstrated here make it an ideal nearshore paleoceanographic proxy throughout much of the North Atlantic Ocean.
New constraints on Northern Hemisphere growing season net flux
Authors: Yang Z. , Washenfelder R. A. , Keppel‐Aleks G. , Krakauer N. Y. , Randerson J. T. , Tans P. P. , Sweeney C. , Wennberg P. O.
Published: June 2007

Observations of the column‐averaged dry molar mixing ratio of CO2 above both Park Falls, Wisconsin and Kitt Peak, Arizona, together with partial columns derived from aircraft profiles over Eurasia and North America are used to estimate the seasonal integral of net ecosystem exchange (NEE) between the atmosphere and the terrestrial biosphere in the Northern Hemisphere. We find that NEE is ∼25% larger than predicted by the Carnegie Ames Stanford Approach (CASA) model. We show that the estimates of NEE may have been biased low by too weak vertical mixing in the transport models used to infer seasonal changes in Northern Hemisphere CO2 mass from the surface measurements of CO2 mixing ratio.
Two-way coupling of finitely extensible nonlinear elastic dumbbells with a turbulent shear flow
Authors: Peters Thomas , Schumacher Jörg
Published: June 2007

We present numerical studies for finitely extensible nonlinear elastic dumbbells which are dispersed in a turbulent plane shear flow at moderate Reynolds number. The polymer ensemble is described on the mesoscopic level by a set of stochastic ordinary differential equations with Brownian noise. The dynamics of the Newtonian solvent is determined by the Navier-Stokes equations. Momentum transfer of the dumbbells with the solvent is implemented by an additional volume forcing term in the Navier-Stokes equations, such that both components of the resulting viscoelastic fluid are connected by a two-way coupling. The dynamics of the dumbbells is given then by Newton’s second law of motion including small inertia effects. We investigate the dynamics of the flow for different degrees of dumbbell elasticity and inertia, as given by Weissenberg and Stokes numbers, respectively. For the parameters accessible in our study, the magnitude of the feedback of the polymers on the macroscopic properties of turbulence remains small as quantified by the global energy budget and the Reynolds stresses. A reduction of the turbulent drag by up to 20% is observed for the larger particle inertia. The angular statistics of the dumbbells shows an increasing alignment with the mean flow direction for both, increasing elasticity and inertia. This goes in line with a growing asymmetry of the probability density function of the transverse derivative of the streamwise turbulent velocity component. We find that dumbbells get stretched preferentially in regions where vortex stretching or biaxial strain dominate the local dynamics and topology of the velocity gradient tensor.
Spatially periodic reversing core in a twisted-fin generated swirling pipe flow
Authors: Aidun Cyrus K. , Parsheh Mehran
Published: June 2007

Experimental results for swirling turbulent flow in a pipe, generated by a 180° twisted fin inside the pipe, are presented. The results show that the core region undergoes a spatially periodic change in direction of rotation from counter-rotating to co-rotating and back to counter-rotating flow relative to the main swirling flow. Up to four transitions in direction of rotation have been recorded with a two-component laser-Doppler velocimeter downstream of the swirl generating fin. The Reynolds number is varied from 25 000 to 85 000 and the average swirl number varies from 0.5 to 0.25 downstream of the fin. The underlying cause of the periodicity in the direction of rotation of flow in the core region is conjectured to be based on the secondary flows generated by a pair of co-rotating helical vortices forming upstream at the spiral-shaped swirl generating fin.
Monte Carlo simulations of single crystals from polymer solutions
Authors: Zhang Jianing , Muthukumar M.
Published: June 2007

A novel “anisotropic aggregation” model is proposed to simulate nucleation and growth of polymer single crystals as functions of temperature and polymer concentration in dilute solutions. Prefolded chains in a dilute solution are assumed to aggregate at a seed nucleus with an anisotropic interaction by a reversible adsorption/desorption mechanism, with temperature, concentration, and seed size being the control variables. The Monte Carlo results of this model resolve the long-standing dilemma regarding the kinetic and thermal roughenings, by producing a rough-flat-rough transition in the crystal morphology with increasing temperature. It is found that the crystal growth rate varies nonlinearly with temperature and concentration without any marked transitions among any regimes of polymer crystallization kinetics. The induction time increases with decreasing the seed nucleus size, increasing temperature, or decreasing concentration. The apparent critical nucleus size is found to increase exponentially with increasing temperature or decreasing concentration, leading to a critical nucleus diagram composed in the temperature-concentration plane with three regions of different nucleation barriers: no growth, nucleation and growth, and spontaneous growth. Melting temperatures as functions of the crystal size, heating rate, and concentration are also reported. The present model, falling in the same category of small molecular crystallization with anisotropic interactions, captures most of the phenomenology of polymer crystallization in dilute solutions.
High density Ru nanocrystal deposition for nonvolatile memory applications
Authors: Farmer Damon B. , Gordon Roy G.
Published: June 2007

Arrays of Ru nanocrystals 1–4nm in diameter are deposited via a hybrid chemical vapor deposition/atomic layer deposition reaction. The nanocrystal density is found to depend sensitively on the nucleating surface. A maximum density of (7–8)×1012cm−2 is achieved on Al2O3. Incorporation of these nanocrystals in floating-gate memory cells results in C-V curves that exhibit large, counterclockwise hysteresis. Leakage current analysis reveals Coulomb blockade phenomena, Frenkel-Poole emission, and space-charge-limited conduction. This analysis allows for the determination of nanocrystal size and connectivity. Charge storage converges to approximately 50% of the maximum value after two days. The corresponding loss mechanisms are discussed.
Exact functional derivative of the nonadditive kinetic-energy bifunctional in the long-distance limit
Authors: Jacob Christoph R. , Beyhan S. Maya , Visscher Lucas
Published: June 2007

We have investigated the functional derivative of the nonadditive kinetic-energy bifunctional, which appears in the embedding potential that is used in the frozen-density embedding formalism, in the limit that the separation of the subsystems is large. We have derived an exact expression for this kinetic-energy component of the embedding potential and have applied this expression to deduce its exact form in this limit. Comparing to the approximations currently in use, we find that while these approximations are correct at the nonfrozen subsystem, they fail completely at the frozen subsystem. Using test calculations on two model systems, a H2O⋯Li+ complex and a cluster of aminocoumarin C151 surrounded by 30 water molecules, we show that this failure leads to a wrong description of unoccupied orbitals, which can lead to convergence problems caused by too low-lying unoccupied orbitals and which can further have serious consequences for the calculation of response properties. Based on our results, a simple correction is proposed, and we show that this correction is able to fix the observed problems for the model systems studied.
Complementary neutron and x-ray reflectivity studies of “near-frictionless” carbon films
Authors: Johnson Jacqueline A. , Park Sungkyun , Roy Sujoy , Sinha Sunil K. , Erdemir Ali , Eryilmaz Osman L. , Woodford John B.
Published: June 2007

“Near-frictionless carbon,” a form of amorphous hydrogenated diamondlike carbon developed at Argonne National Laboratory, has been investigated by neutron and x-ray reflectivity under ambient conditions, in vacuum, and at elevated temperature. A series of films was made with different ratios of hydrogen to carbon in the plasma; the deuterated counterparts were also synthesized. The details of scattering length density profiles, thickness, and surface and interfacial roughness of the films were obtained from neutron and x-ray reflectivity profiles. This allowed us to calculate the mass density and hydrogen composition of the bulk carbon film, leading to insight into the frictional properties. From the analysis we found that the magnitude of the scattering length density of the top surface layer was greatly affected by the experimental atmosphere in which the films were contained although the trend with hydrogen in the plasma remained the same. All samples were fitted with a three-layer model in addition to the substrate.
Time-dependent density-functional theory/localized density matrix method for dynamic hyperpolarizability
Authors: Wang Fan , Yam Chi Yung , Chen GuanHua
Published: June 2007

Time-dependent density-functional theory/localized density matrix method (TDDFT/LDM) was developed to calculate the excited state energy, absorption spectrum and dynamic polarizability. In the present work we generalize it to calculate the dynamic hyperpolarizabilities in both time and frequency domains. We show that in the frequency domain the 2n+1 rule can be derived readily and the dynamic hyperpolarizabilities are thus calculated efficiently. Although the time-domain TDDFT/LDM is time consuming, its implementation is straightforward because the evaluation of the derivatives of exchange-correlation potential with respect to electron density is avoided. Moreover, the time-domain method can be used to simulate higher order response which is very difficult to be calculated with the frequency-domain method.
On high explosive launching of projectiles for shock physics experiments
Authors: Swift Damian C. , Forest Charles A. , Clark David A. , Buttler William T. , Marr-Lyon Mark , Rightley Paul
Published: June 2007

The hydrodynamic operation of the “Forest Flyer” type of explosive launching system for shock physics projectiles was investigated in detail using one and two dimensional continuum dynamics simulations. The simulations were numerically converged and insensitive to uncertainties in the material properties; they reproduced the speed of the projectile and the shape of its rear surface. The most commonly used variant, with an Al alloy case, was predicted to produce a slightly curved projectile, subjected to some shock heating and likely exhibiting some porosity from tensile damage. The curvature is caused by a shock reflected from the case; tensile damage is caused by the interaction of the Taylor wave pressure profile from the detonation wave with the free surface of the projectile. The simulations gave only an indication of tensile damage in the projectile, as damage is not understood well enough for predictions in this loading regime. The flatness can be improved by using a case of lower shock impedance, such as polymethyl methacrylate. High-impedance cases, including Al alloys but with denser materials improving the launching efficiency, can be used if designed according to the physics of oblique shock reflection, which indicates an appropriate case taper for any combination of explosive and case material. The tensile stress induced in the projectile depends on the relative thickness of the explosive, expansion gap, and projectile. The thinner the projectile with respect to the explosive, the smaller the tensile stress. Thus if the explosive is initiated with a plane wave lens, the tensile stress is lower than that for initiation with multiple detonators over a plane. The previous plane wave lens designs did, however, induce a tensile stress close to the spall strength of the projectile. The tensile stress can be reduced by changes in the component thicknesses. Experiments verifying the operation of explosively launched projectiles should attempt to measure porosity induced in the projectile: arrival time measurements are likely to be insensitive to porous regions caused by damaged or recollected material.
First-principles theoretical analysis of sequential hydride dissociation on surfaces of silicon thin films
Authors: Singh Tejinder , Valipa Mayur S. , Mountziaris T. J. , Maroudas Dimitrios
Published: June 2007

We report results from first-principles density functional theory calculations for the mechanism and activation barrier of sequential hydride dissociation on crystalline silicon surfaces and discuss their implications for the surface chemical composition of hydrogenated amorphous silicon (a-Si:H) thin films. We find that, in the presence of fivefold coordinated surface Si atoms, surface trihydride species dissociate sequentially to form surface dihydrides and surface monohydrides via thermally activated pathways with reaction barriers of 0.15–0.55eV. The results are consistent with our molecular-dynamics simulations on a-Si:H film growth surfaces and with experimental measurements of a-Si:H film surface composition.
Steric effect: A quantitative description from density functional theory
Authors: Liu Shubin
Published: June 2007

The concepts of steric energy, steric potential, and steric charge are introduced within the density functional theory framework. The steric energy, representing a hypothetical state with all electrons packed into the lowest orbital and other effects entirely excluded, is a measure of the intrinsic space occupied by an electronic system. It is exclusive, repulsive, and extensive, and it vanishes for homogeneous electron gas. When Bader’s zero-flux boundary condition is adopted, atoms in molecules are found to achieve balanced steric repulsion among one another with vanished steric energy density interfaces. A few molecular systems involving conformation changes and chemical reactions have been investigated to examine the relative contribution of the steric and other effects, providing insights for a few controversial topics from a different perspective.
Modeling the adiabatic connection in H2
Authors: Peach Michael J. G. , Teale Andrew M. , Tozer David J.
Published: June 2007

Full configuration interaction (FCI) data are used to quantify the accuracy of approximate adiabatic connection (AC) forms in describing the ground state potential energy curve of H2, within spin-restricted density functional theory (DFT). For each internuclear separation R, accurate properties of the AC are determined from large basis set FCI calculations. The parameters in the approximate AC form are then determined so as to reproduce these FCI values exactly, yielding an exchange-correlation energy expressed entirely in terms of FCI-derived quantities. This is combined with other FCI-derived energy components to give the total electronic energy; comparison with the FCI energy quantifies the accuracy of the AC form. Initial calculations focus on a [1∕1]-Padé-based form. The potential energy curve determined using the procedure is a notable improvement over those from existing DFT functionals. The accuracy near equilibrium is quantified by calculating the bond length and vibrational wave numbers; errors in the latter are below 0.5%. The molecule dissociates correctly, which can be traced to the use of virtual orbital eigenvalues in the slope in the noninteracting limit, capturing static correlation. At intermediate R, the potential energy curve exhibits an unphysical barrier, similar to that noted previously using the random phase approximation. Alternative forms of the AC are also considered, paying attention to size extensivity and the behavior in the strong-interaction limit; none provide an accurate potential energy curve for all R, although good accuracy can be achieved near equilibrium. The study demonstrates how data from correlated ab initio calculations can provide valuable information about AC forms and highlight areas where further theoretical progress is required.
Deep-level emissions in GaAsN∕GaAs structures grown by metal organic chemical vapor deposition
Authors: Chen J. F. , Ke C. T. , Hsieh P. C. , Chiang C. H. , Lee W. I. , Lee S. C.
Published: June 2007

This work presents the deep-level photoluminescence of coherently strained GaAsN∕GaAs quantum-well (QW) structures with various GaAsN thicknesses and N contents. A broad deep-level emission at ∼1.1eV is observed, whose wavelength is redshifted as the GaAsN thickness increases. Based on its energy separation from the QW emission, this emission is attributed to a transition between the QW electron ground state and a deep level at ∼0.2eV above the GaAsN valence-band (VB) edge. This level is shown to be tied to the GaAs band edge. A transition between this level and the GaAs conduction band allows the GaAsN–GaAs band alignment to be evaluated. A type II band lineup is obtained with VB offsets of 0.03 and 0.002eV for N=0.6% and 1.8%, respectively. The decreased VB offset suggests a transition from type II to type I with increasing N content. Thermal annealing effectively removes this level and improves the QW emission. The concentration of this level is not clearly correlated with N content, suggesting that this level is induced by a low-temperature growth of the GaAsN layer to suppress the composition fluctuation. Given its energy, this level is tentatively assigned to VGa.
Formation and atomic configuration of binary metallic glasses studied by ion beam mixing and molecular dynamics simulation
Authors: Tai K. P. , Gao N. , Dai X. D. , Li J. H. , Liu B. X.
Published: June 2007

Metallic glasses are obtained in an immiscible Ag–Nb system with overall composition ranging from 25to90at.% of Nb by ion beam mixing. Interestingly, the diffraction analysis shows that the formed Nb-rich metallic glass features are two distinct atomic configurations. In atomistic modeling, an n-body Ag–Nb potential is derived, under the assistance of ab initio calculation, and then applied in molecular dynamics simulations. An atomic configuration is discovered, i.e., an icositetrahedral ordering, and as well as an icosahedral ordering observed in the Ag–Nb metallic glasses and in some previously reported systems. Simulations confirm that the two dominate local atomic packing units are formed through a structural phase transition from the Nb-based bcc and fcc solid solutions, respectively, suggesting a concept of structural heredity that the crystalline structure of the constituent metals play a decisive role in determining the atomic structure of the resultant metallic glasses.
Destruction and enhancement of photonic band gap and coherent localization of optical fields in functional photonic crystals
Authors: Sadeghi S. M. , Li X. , Huang W.-P. , Li W.
Published: June 2007

We use electromagnetically induced transparency combined with coherent enhancement of refractive index in the conduction intersubband transitions of a n-doped quantum well structure to study one-dimensional functional (active) photonic band gap structures. In the absence of a control laser field, such structures act as conventional photonic band gaps created by off-resonant (background) refractive index perturbations. In the presence of the control field, they are transformed into resonant structures with transitions around the Bragg wavelength. We show that this process can be used to (i) destroy the band gap, making the structure fully transparent around the Bragg wavelength, or (ii) coherently tune the band gap while enhancing its width by nearly a factor of 2. Using these phenomena we then study coherent localization of electromagnetic modes in photonic band gap structures without having any structural defects. Such a localization process here happens via partial illumination of such structures by the control field, generating electromagnetically induced optical defects. We show that the phase associated with such defects can be adjusted by the control field, allowing us to generate tunable electromagnetically induced transmission resonances (or photonic electromagnetically induced transparency) within the band gap.
Towards three-dimensional and multilayer rod-split-ring metamaterial structures by means of deep x-ray lithography
Authors: Casse B. D. F. , Moser H. O. , Lee J. W. , Bahou M. , Inglis S. , Jian L. K.
Published: June 2007

Presently existing THz electromagnetic metamaterials were mostly produced as planar single layer structures, either deposited on a substrate or embedded in a polymer matrix, and patterned by a primary pattern generator such as an electron beam writer or a laser writer. Some attempts to produce more voluminous structures were made using ultraviolet photolithography and a stacking process. We explore deep x-ray lithography and subsequent stacking of chips to fabricate, with good yield, substantial quantities of rod-split-ring structures that come closer to three dimensions than before. Samples were characterized layer-by-layer using Fourier transform interferometry in the far infrared.
Exploring magnetic plasmon polaritons in optical transmission through hole arrays perforated in trilayer structures
Authors: Li Tao , Li Jia-Qi , Wang Fu-Ming , Wang Qian-Jin , Liu Hui , Zhu Shi-Ning , Zhu Yong-Yuan
Published: June 2007

Optical transmission properties through hole arrays in metal/dielectric/metal trilayer structures were demonstrated. Besides the surface plasmon induced strong transmission and well-recognized negative refraction band, a higher mode was observed and elaborately investigated. Detailed results showed that this mode belongs to a higher magnetic excitation related to the reciprocal vector G1,1 of the lattice, and a “magnetic plasmon polariton (MPP)” model was proposed to describe such magnetic excitations in periodically modulated structure. By adjusting the structural parameters, the authors can conveniently control the MPPs’ properties, which provide us another way to tailor the light propagation properties in subwavelength structures.
Texture formation of GeSbTe thin films prepared by multilayer deposition of modulating constituent elements
Authors: Ie Sang Yub , Bea Byung Tack , Ahn Young-kun , Chang M. Y. , You D. G. , Cho M. H. , Jeong K. , Oh Jae-Hee , Koh Gwan-Hyeob , Jeong Hongsik
Published: June 2007

The preferred oriented texture Ge2Sb2Te5 (GST) thin film was prepared on SiO2∕Si(001) and TiN(60nm)∕Si(001) substrates. With the modulated layers of each constituent materials, the stoichiometry of thin film was controlled. Through cross section transmission electron microscope analysis and the x-ray diffraction (XRD) measurement at different temperatures, the evolutions of as-grown multilayer from amorphous to textured crystalline state were studied. Highly preferred orientation to ⟨00l⟩ direction of GST film was verified by XRD pole figure measurements to deduce the orientation distribution function. From these results, the authors could suggest the effective synthetic method to make the texture GST film with high crystalline quality.
High-performance reflection gratings in photorefractive polymers
Authors: Gallego-Gomez Francisco , Salvador Michael , Köber Sebastian , Meerholz Klaus
Published: June 2007

To date highest external diffraction efficiency and two-beam coupling gain at moderate applied fields (about 30% and 260cm−1, respectively, at 60V∕μm) are obtained in photorefractive reflection gratings with grating periods of about 0.2μm using a standard low-glass-temperature polyvinylcarbazole based composite. Reflection gratings exhibit five times faster growth/erasure rates than conventional transmission gratings. Further, their performance is very sensitive to changes in the saturation field. This allows a reliable calculation of the photorefractive trap density, which shows a significant enhancement with the field. Finally, the theoretical analysis reveals the geometry-dependent competition between the birefringence and electro-optic contributions.
Magnetization of Re-based double perovskites: Noninteger saturation magnetization disclosed
Authors: De Teresa J. M. , Michalik J. M. , Blasco J. , Algarabel P. A. , Ibarra M. R. , Kapusta C. , Zeitler U.
Published: June 2007

Using static magnetic fields up to 30T, the authors have measured the high-field magnetization in high-quality samples made from Re-based double perovskites: A2FeReO6 (A2=Ca2, Sr2, BaSr) and Sr2CrReO6, with Curie temperatures ranging from 360 up to 610K. The results indicate that the saturation magnetization in these compounds is higher than the assumed spin-only ionic values, 3μB∕f.u. for A2FeReO6 and 1μB∕f.u. for Sr2CrReO6, which is explained by the large orbital contribution to the magnetization. Indirectly, these results show that Re-based double perovskites cannot be described as half-metals.
Generation and detection of coherent longitudinal acoustic phonons in the La0.67Sr0.33MnO3 thin films by femtosecond light pulses
Authors: Ren Y. H. , Trigo M. , Merlin R. , Adyam Venimadhav , Li Qi
Published: June 2007

The authors report on an anomalous first-to-zero sound crossover in the colossal magnetoresistance compound La0.67Sr0.33MnO3 (LSMO) using ultrafast time-resolved optical techniques. Two-color pump-probe setup was employed to record the photoinduced reflectance oscillations due to excitations of longitudinal acoustic phonons. By changing the sample thickness and probe wavelength, they determine the longitudinal sound velocities of both the thin film and substrate . The values of the sound velocity in LSMO at gigahertz frequencies are more than 20% larger than those from ultrasound experiments in the megahertz regime near TC. The results show the possible existence of dynamic polaron correlations in LSMO.
Hygroscopic and volatile properties of marine aerosol observed at Cape Grim during the P2P campaign
Authors: Fletcher Catherine A. , Johnson Graham R. , Ristovski Zoran D. , Harvey Mike
Published: June 2007

Environmental context. The marine environment covers 71% of the Earth’s surface, and accounts for most of the planet’s cloud cover. Water droplets in these clouds all form on pre-existing marine aerosol particles. The number, size and composition of these particles determine the cloud droplet size and consequently, the cloud’s light scattering and precipitation behaviour. Marine aerosols, therefore, have a major influence on the planet’s radiation balance and climate. The origin of marine aerosols is still not completely resolved. The newly developed VH-TDMA technique has been applied to marine aerosols that come from the Southern Ocean. The technique enabled new insights into the composition and structure of these aerosols. It has been found that organic matter constitutes 20–40% of these particles, which suppresses their hygroscopic growth.
Abstract. Simultaneous measurement of particle hygroscopic and volatile properties was performed using a VH-TDMA on both Aitken and accumulation mode particles. In addition, deliquescence measurements at different thermodenuder temperatures were also performed. The measurements were part of the P2P campaign which took place in February 2006 at the Cape Grim monitoring station in Tasmania, Australia. During baseline conditions, there was often a volatilisation step that occurred below 125°C in the volatility scans, where up to 25% of the volume is lost. Analysis of the changes in growth as this took place indicates that different substances are responsible for this volatilisation on different days – ammonium nitrate, sulfuric acid, or a volatile non-hygroscopic organic. The major volatilisation in all cases occurred in the temperature range ~140–200°C, which is taken to indicate the presence of ammonium sulfate or ammonium bisulfate. A degree of growth suppression is generally evident before this volatilisation, which indicates that a non-hygroscopic material with a similar volatility to ammonium sulfate/bisulfate may be present, which cannot be distinguished in the volatility scans. Organic matter was typically present at around ~20–40% for these particles. When Aitken and accumulation mode particles were measured on the same day, it was found that the organic content of the smaller particles tended to be higher than the larger particles by roughly 20 percentage points.
Volatile organic compounds in marine air at Cape Grim, Australia
Authors: Galbally Ian E. , Lawson Sarah J. , Weeks Ian A. , Bentley Simon T. , Gillett Rob W. , Meyer Mick , Goldstein Allen H.
Published: June 2007

Environmental context. Gaseous organic compounds fuel the production of ozone in the background lower atmosphere. There have been no measurements of many of these compounds in the temperate and polar latitudes of the Southern Hemisphere. Here some first results are presented that show in general much lower concentrations than the Northern Hemisphere, due in part to the lower land surfaces and biomass burning in the Southern Hemisphere.
Abstract. Measurements were made of volatile organic compounds (VOCs) at Cape Grim using proton transfer reaction mass spectrometry (PTR-MS) during the Precursors to Particles (P2P) Campaign from 10 February to 1 March 2006. Approximately 14 days of clean air data were obtained along with 4 days of data from when polluted air, first from a smoke plume from a fire on Robbins Island adjacent to the station and then air from Victoria, was present. This paper deals with the results obtained in clean air, the focus of the P2P campaign. The protonated masses and probable VOCs measured in the clean marine air were: methanol, 33; acetonitrile, 42; acetaldehyde, 45; acetone, 59; isoprene, 69; methylvinyl ketone/methacrolein (MVK/MACR), 71; methylethyl ketone, 73; and benzene, 79. The measurements at Cape Grim were in some cases near the detection limit and an analytical challenge. The range of concentrations detected in clean maritime air, the relationship to the limited range of previous measurements in marine air in the Northern Hemisphere tropics, and the physical, chemical and biological processes controlling these compounds in the marine air are discussed. The methanol concentrations observed at Cape Grim are consistent with global modelling, incorporating sources that are mainly of vegetation origin. Isoprene has recently been implicated as a precursor to cloud condensation nuclei over the Southern Ocean. In this snapshot of observations at Cape Grim, Tasmania, isoprene and the isoprene oxidation products MVK and MACR appeared to be absent in air from the Southern Ocean. However, isoprene has a very short atmospheric lifetime and the spatial distribution of its emissions may be very heterogeneous. The concentrations of the other VOCs in marine air at Cape Grim, acetonitrile, acetaldehyde, acetone, methylethyl ketone and benzene, were typically a factor of four lower than that observed over the remote tropical ocean in the Northern Hemisphere. The lower concentrations of carbonyls and their precursor hydrocarbons may indicate a limitation on ozone production potential in the Southern Hemisphere compared with the Northern Hemisphere troposphere.
Additional keywords: atmospheric composition, oxygenated volatile organic compounds, proton transfer reaction mass spectrometry, Southern Ocean, volatile organic compounds.
An LIL for cover times of disks by planar random walk and Wiener sausage
Authors: Hough J. , Peres Yuval
Published: June 2007

Let

R
n

R_n

be the radius of the largest disk covered after

n
n

steps of a simple random walk. We prove that almost surely
\[

lim sup

n
→
∞

(
log
⁡

R
n

)
2

/

(
log
⁡
n

log
3

⁡
n
)
=
1

/

4
,

\limsup _{n \rightarrow \infty }(\log R_n)^2/(\log n \log _3 n) = 1/4,

\]
where

log
3

\log _3

denotes 3 iterations of the

log
\log

function. This is motivated by a question of Erdős and Taylor. We also obtain the analogous result for the Wiener sausage, refining a result of Meyre and Werner.
Phantom depth and stable phantom exactness
Authors: Epstein Neil
Published: June 2007

Phantom depth, phantom nonzerodivisors, and phantom exact sequences are analogues of the non-“phantom” notions which have been useful in tackling the (very difficult) localization problem in tight closure theory. In the present paper, these notions are developed further and partially reworked. For instance, although no analogue of a long exact sequence arises from a short stably phantom exact sequence of complexes, we provide a method for recovering the kind of information obtainable from such a long sequence. Also, we give alternate characterizations of the notion of phantom depth, including one based on Koszul homology, which we use to show that with very mild conditions on a finitely generated module

M
M

, any two maximal phantom

M
M

-regular sequences in an ideal

I
I

have the same length. In order to do so, we prove a “Nakayama lemma for tight closure”, which is of independent interest. We strengthen the connection of phantom depth with minheight, we explore several analogues of “associated prime” in tight closure theory, and we discuss a connection with the problem of when tight closure commutes with localization.
Homological integral of Hopf algebras
Authors: Lu D.-M. , Wu Q.-S. , Zhang J.
Published: June 2007

The left and right homological integrals are introduced for a large class of infinite dimensional Hopf algebras. Using the homological integrals we prove a version of Maschke’s theorem for infinite dimensional Hopf algebras. The generalization of Maschke’s theorem and homological integrals are the keys to studying noetherian regular Hopf algebras of Gelfand-Kirillov dimension one.
On a singular perturbation problem involving a “circular-well” potential
Authors: André Nelly , Shafrir Itai
Published: June 2007

We study the asymptotic behavior, as a small parameter

ε
\varepsilon

goes to

0
0

, of the minimizers for a variational problem which involves a “circular-well” potential, i.e., a potential vanishing on a closed smooth curve in

R

2

\mathbb {R}^2

. We thus generalize previous results obtained for the special case of the Ginzburg-Landau potential.