bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of insemination technique, semen quality and oocyte cryopreservation on pronuclear morphology of zygotes derived from sibling oocytes
Authors: Nicoli Alessia , Capodanno Francesco , Valli Barbara , Di Girolamo Roberta , Villani Maria Teresa , Nucera Andrea , Focarelli Riccardo , La Sala Giovanni B.
Published: June 2009

Pronuclear morphology seems to be an important predictive value of zygote development and integrity. In this study we want to evaluate the effect of insemination technique, male factor and oocyte cryopreservation on pronuclear morphology of zygotes derived from sibling oocytes in our Centre of Reproductive Medicine, Department of Obstetrics and Gynecology, Arcispedale S. Maria Nuova, Reggio Emilia, Italy. Subjects (n = 190) were submitted to IVF cycles with non-frozen and frozen sibling oocytes. Morphological evaluations were assessed using zygote pronuclear morphology (pronuclei, nucleoli and axis) in four groups: Group 1: 144 zygotes from 85 conventional IVF cycles with non-frozen oocytes; Group 2: 164 zygotes from 85 intracytoplasmic sperm injection (ICSI) cycles with Group 1 patients' sibling frozen oocytes; Group 3: 221 zygotes from 123 ICSI cycles with non-frozen oocytes; Group 4: 197 zygotes from 123 ICSI cycles with Group 3 patients' sibling frozen oocytes. No differences between Group 1 and Group 2 were seen. Group 3 was statistically different from Group 4 in relation to the nucleolar morphology. Oocyte cryopreservation procedure modified the nucleolar morphology of zygotes only in the presence of poor semen quality.
A theory for formation of large empires
Authors: Turchin Peter
Published: June 2009

Between 3000 BCE and 1800 CE there were more than sixty ‘mega-empires’ that, at the peak, controlled an area of at least one million square kilometres. What were the forces that kept together such huge pre-industrial states? I propose a model for one route to mega-empire, motivated by imperial dynamics in eastern Asia, the world region with the highest concentration of mega-empires. This ‘mirror-empires’ model proposes that antagonistic interactions between nomadic pastoralists and settled agriculturalists result in an autocatalytic process, which pressures both nomadic and farming polities to scale up polity size, and thus military power. The model suggests that location near a steppe frontier should correlate with the frequency of imperiogenesis. A worldwide survey supports this prediction: over 90% of mega-empires arose within or next to the Old World’s arid belt, running from the Sahara desert to the Gobi desert. Specific case studies are also plausibly explained by this model. There are, however, other possible mechanisms for generating empires, of which a few are discussed at the end of the article.
The Eurasian silver century, 1276–1359: commensurability and multiplicity
Authors: Kuroda Akinobu
Published: June 2009

Across the Eurasian continent, from England to Korea, silver suddenly became abundant in the late thirteenth century, only to become scarce again in the 1360s. The annual silver output from the London mint and the yearly silver rupee issued in Bengal moved virtually in tandem, arguably as a result of the Mongol empire lifting silver out of the lower tiers of the market and maintaining its flow along the highways of long-distance trade. In this first silver century, monetary usages formed multiple strata, and the circulation of silver remained in a high-level circuit in the hierarchy of monies. Units of account, denominated in terms of silver by weight, worked to give value to silver coinage in the western parts of the commercial highways and kept a link with paper monies in the eastern parts under the Mongol Yuan dynasty. Throughout the silver century, the Mongol empire lowered commercial barriers, to allow the ready flow of silver along trade routes, and consequently created a horizontal unity that, on the surface, was continent-wide. This contrasted with the second silver century, beginning in the 1570s, which ushered in a system of competition between territorial states, some of which vertically cemented the tiers of their domestic markets with credit, and created a space for compatible monies.
Gruppentherapeutische Behandlung bei beginnender dementieller Erkrankung
Authors: Scheurich Armin , Fellgiebel Andreas
Published: June 2009

Es liegen nur wenige Studien zur Wirksamkeit von Gruppenpsychotherapie bei beginnenden dementiellen Erkrankungen vor. Deshalb wurde die Arbeit in den größeren Rahmen der empirischen Evidenz von Psychotherapie bei Demenz gestellt. Zusätzlich wurden die Wirkfaktoren der Gruppentherapie (Yalom, 2007) theoretisch auf die Symptome und Probleme der Patienten mit beginnender Demenz bezogen und die therapeutischen Ansatzpunkte wurden abgeleitet. Dieses theoretische Potential der Gruppentherapie wurde mit den Ergebnissen der vorliegenden Studien zu Gruppentherapie bei Demenz und beginnender dementieller Erkrankung abgeglichen. Aus den Gemeinsamkeiten und Unterschieden wurden erste Hinweise auf die Wirksamkeit abgeleitet. Für die Gruppentherapie dementer Patienten zeichnete sich keine durchgängige empirische Unterstützung ab. Wie für die Psychotherapie der Demenz allgemein scheinen spezifische Interventionen wie die Einbeziehung und Psychoedukation der pflegenden Angehörigen und potentiell der Aufbau positiver Aktivitäten auch im Gruppenformat erfolgreich zu sein. Demgegenüber wurden bei beginnender Demenz auch für unterschiedliche inhaltliche Interventionen im Gruppenformat Erfolge beschrieben. Obwohl die wenigen Daten in erster Linie als Ansatzpunkte für die Ableitung klinischer Studien zu werten sind, könnte diese Beobachtung darauf hinweisen, dass die unspezifischen Gruppenwirkfaktoren wie die Ermöglichung sozialer Interaktion und die Relativierung des eigenen Leidens bei Patienten mit beginnender dementieller Erkrankung einen eigenständigen Beitrag zur Überwindung der Einsamkeit und Not leisten können.
Depressionstherapie bei früher Alzheimerdemenz: Modifikation kognitiv-verhaltenstherapeutischer Techniken
Authors: Werheid Katja , Baron Stefanie
Published: June 2009

Depressionen treten bei etwa einem Drittel der Patienten mit leichtgradiger Demenz auf und beeinträchtigen Lebensqualität und Alltagsbewältigung der Betroffenen und ihrer Angehörigen. Epidemiologische und neurobiologische Befunde sprechen für eine Interdependenz von Depression und Demenz, die weit über das Konzept einer „reaktiven“ affektiven Störung bei chronisch-organischer Erkrankung hinausgeht. Depressionstherapie kann als eine progressionsverzögernde Form der Demenztherapie betrachtet werden, analog zu anderen symptomatischen Behandlungsoptionen. Erste Wirksamkeitsnachweise für kognitive Verhaltenstherapie bei leichtgradiger Alzheimerdemenz mit Depression liegen vor. Das vorhandene Methodeninventar, insbesondere kognitive Therapietechniken, muss jedoch unter Berücksichtigung der kognitiven Kapazitäten, des spezifischen Symptomprofils bei Alzheimerdemenz und der Lebenssituation dieser Patienten modifiziert werden. Im vorliegenden Artikel stellen wir Praxisbeispiele für Modifikationen zentraler verhaltenstherapeutischer Techniken wie Verhaltensanalyse, ABC-Technik und sokratischer Dialog zur Diskussion.
Memory Networks Supporting Retrieval Effort and Retrieval Success Under Conditions of Full and Divided Attention
Authors: Skinner Erin I. , Fernandes Myra A. , Grady Cheryl L.
Published: June 2009

We used a multivariate analysis technique, partial least squares (PLS), to identify distributed patterns of brain activity associated with retrieval effort and retrieval success. Participants performed a recognition memory task under full attention (FA) or two different divided attention (DA) conditions during retrieval. Behaviorally, recognition was disrupted when a word, but not digit-based distracting task, was performed concurrently with retrieval. PLS was used to identify patterns of brain activation that together covaried with the three memory conditions and which were functionally connected with activity in the right hippocampus to produce successful memory performance. Results indicate that activity in the right dorsolateral frontal cortex increases during conditions of DA at retrieval, and that successful memory performance in the DA-digit condition is associated with activation of the same network of brain regions functionally connected to the right hippocampus, as under FA, which increases with increasing memory performance. Finally, DA conditions that disrupt successful memory performance (DA-word) interfere with recruitment of both retrieval-effort and retrieval-success networks.
Substorm expansion triggered by a sudden impulse front propagating from the dayside magnetopause
Authors: Keika K. , Nakamura R. , Baumjohann W. , Angelopoulos V. , Chi P. J. , Glassmeier K. H. , Fillingim M. , Magnes W. , Auster H. U. , Fornaçon K. H. , Reeves G. D. , Yumoto K. , Lucek E. A. , Carr C. M. , Dandouras I.
Published: June 2009

We examine a substorm expansion on 21 June 2007, which occurred <2 min after a solar wind discontinuity accompanied by a dynamic pressure (Pd) increase impinged on the magnetopause. To investigate how the perturbation due to such Pd increase propagates in the magnetosphere and what the timing analysis may imply about how this type of substorms is triggered, we utilize a large number of in situ magnetic field and plasma observations, a remote sensing of auroral brightening, and ground‐based magnetic field observations. The timing analysis shows that the front of a compression‐associated sudden impulse can reach the substorm expansion onset site (dawnside near‐Earth plasma sheet) at the substorm onset time. The onset site and time are determined from aurora images displaying aurora expansion, energetic electron data at geosynchronous orbit showing dispersed injection, and geomagnetic field data at high latitudes showing negative bays in the H component. Our 2‐D calculations of the fast‐mode propagation also demonstrate the arrival of the wavefront at the onset site and time. We suggest that for the class of substorms triggered by solar wind Pd increases, the triggering could occur within as short as 2 min after a Pd increase impinges on the magnetopause, consistent with the time needed for the sudden impulse wavefront to propagate inside the magnetosphere from the dayside magnetopause to the magnetotail.
Geographical distribution of long‐term changes in the height of the maximum electron density of the F region: A nonmigrating‐tide effect?
Authors: Bencze P.
Published: June 2009

The geographical distribution of trends in the height of the maximum electron density of the F2 region (hmF2) seemed to indicate that ionospheric stations showing decreasing (i.e., negative) hmF2 trends are mostly located on or in the vicinity of seashores. In contrast, ionospheric stations in continental areas exhibit generally increasing (i.e., positive) hmF2 trends. On the basis of the present study, it is shown that considering the whole world, the geographical distribution of hmF2 trends is affected essentially by the nonmigrating tidal wind. Moreover, besides the field‐aligned drift, the elecrodynamical drift must also be considered in the development of hmF2 trends. Taking into account both the field‐aligned and the electrodynamical drift, northward (eastward) tidal winds and southward (westward) tidal winds would create downward and upward drifts, respectively, in the Northern Hemisphere but southward (eastward) and northward (westward) tidal winds in the Southern Hemisphere. An upward drift is accompanied by an increase and a downward drift is accompanied by a decrease of hmF2. It has been suggested that because of the thermal driven origin of the nonmigrating tides, the distribution may also be connected with ocean currents warming or cooling the neighborhood of the coastline. The effect of ocean currents would create downward drift due to cooling at the western coastlines of the continents but upward drift at the eastern coastlines as a result of the warming. This has been shown by comparing the distribution of hmF2 trends with the map of ocean currents. The corresponding hmF2 trends may develop because of changes in the land/sea‐warming ratio, where the land‐surface air temperature increases faster than the sea‐surface air temperature.
Projected future changes in surface marine winds off the west coast of Canada
Authors: Merryfield W. J. , Pal B. , Foreman M. G. G.
Published: June 2009

Projected future changes in the seasonal climatology of surface marine winds at locations off the west coast of Canada having long records of buoy wind observations are evaluated, drawing on output from 18 climate models. The ensemble mean modeled wind climatology for a late 20th century control period 1976–1995 is found to reproduce that of the buoy observations reasonably well, except where local orographic influences not resolved by the models are strong. Over the 21st century, ensemble mean summertime upwelling favorable winds increase in speed by 5–10% and rotate clockwise by ≈5°, statistically significant changes. By contrast, 21st century changes in ensemble mean wintertime downwelling favorable winds are not statistically significant. These trends are too weak to be detectable in the 20th century buoy observations.
Subsurface equatorial zonal current in the eastern Indian Ocean
Authors: Iskandar Iskhaq , Masumoto Yukio , Mizuno Keisuke
Published: June 2009

Variations of subsurface zonal current in the eastern equatorial Indian Ocean are investigated by examining 6‐year data (December 2000–November 2006) from acoustic Doppler current profiler (ADCP) mooring at 0°S, 90°E. The analysis indicates the presence of an eastward equatorial subsurface current between 90 and 170 m depths during both boreal winter and summer. During boreal winter, the generation of eastward pressure gradient, which drives an eastward flow in the thermocline, is caused primarily by upwelling equatorial Kelvin waves excited by prevailing easterly winds. On the other hand, the downwelling Rossby waves generated by the reflection of the spring downwelling Kelvin waves in the eastern boundary, as well as the upwelling equatorial Kelvin waves triggered by easterlies, create an oceanic state that favors the generation of the eastward pressure gradient during boreal summer. The subsurface current reveals a distinct seasonal asymmetry. The maximum eastward speed of 63 cm s−1 is observed in April, and secondary maximum of 49 cm s−1 is seen in October. The zonal transport per unit width within depth of the subsurface current exhibits similar variations: reaching maximum eastward transport of 35 m2 s−1 in April and secondary maximum of 29 m2 s−1 in October. Moreover, the subsurface current during boreal summer undergoes significant interannual variations; it was absent in 2003, but it was anomalously strong during 2006.
Laboratory study of vortex dipoles interacting with step topography
Authors: Hinds A. K. , Eames I. , Johnson E. R. , McDonald N. R.
Published: June 2009

Laboratory experiments are performed which study the behavior of two‐dimensional vortex dipoles propagating toward a rectilinear step change in depth. The dipoles are formed in a homogeneous shallow water layer by an impulsive jet and approach the step from either relatively deep or shallow water at normal or oblique incidence. Qualitative observations agree well with previous theoretical predictions: At normal incidence the separation of the two vortices forming the dipole increases for a dipole crossing from deep water and decreases for a dipole crossing from shallow water. Dipoles with oblique angles of incidence refract toward the normal when passing into shallower water, and dipoles that cross the step into deep water refract away from the normal. Dipoles approaching from shallow water at sufficiently large angles of incidence reflect off the step.
Tropical Pacific–high latitude south Atlantic teleconnections as seen in δ18O variability in Antarctic coastal ice cores
Authors: Divine D. V. , Isaksson E. , Kaczmarska M. , Godtliebsen F. , Oerter H. , Schlosser E. , Johnsen S. J. , van den Broeke M. , van de Wal R. S. W.
Published: June 2009

We use a network of eight ice cores from coastal Dronning Maud Land (DML), Antarctica, to examine the role of the tropical ENSO (El Niño‐Southern Oscillation) in the temporal variability of δ18O in annual accumulation. The longest record from the S100 ice core covering the period 1737–1999 is used to analyze the teleconnections between the tropical Pacific and coastal DML on decadal scales and longer. A shorter stacked coastal DML δ18O series spanning 1955–1999 is constructed to assess the variability of ENSO teleconnection on interannual scales. Results suggest that, on typical ENSO timescales of 2–6 years, the strength of the teleconnection varies in time, being stronger for years with generally negative phase of the Southern Annular Mode (SAM). On the timescales of approximately two decades (bidecadal), positive isotope anomalies are associated with oceanic warming and a westward sea surface temperature (SST) gradient in the equatorial Pacific. Bidecadal variability in SAM, forced by the tropical Pacific, is proposed as a critical element in the teleconnection. Our analysis suggests that a multidecadal positive trend in the annual mean δ18O values from the analyzed cores can be indicative of the atmospheric warming that begun in this part of the DML already in the 1910s. The trend in δ18O, quantified in terms of long‐term surface air temperature (SAT) changes, is consistent with the instrumental data. Yet, we speculate that the accurate estimation of SAT trends requires an assessment of the potential role of secular SAM and sea ice extent changes in shaping the isotopic signal.
A study of the NOAA‐15 AMSU‐A brightness temperatures from 1998 through 2007
Authors: Mo Tsan
Published: June 2009

Global mean brightness temperatures from the NOAA‐15 Advanced Microwave Sounding Unit‐A (AMSU‐A) over the period from May 1998 through December 2007 are studied. A time series of global daily mean brightness temperatures are constructed. These time series show a clear pattern of annual variation of the measurements which can be modeled with a Fourier series. After the annual variation as represented by the Fourier series is removed from the time series, extraannual variations of the measurements are obtained for examination of information about climate trends. Linear regressions of the extraannual variations at individual channels are performed, and the results demonstrate that the slopes for channels below the tropopause are positive whereas those above it are negative. This is strong evidence that the troposphere is warming and that the stratosphere is cooling. It is interesting to note that channel 5 has a slope of 0.0092 Kelvin per annum (K/a; or 0.092 K/decade) which agrees well with some of currently known climate trends of the middle troposphere. Diurnal variations of the monthly mean brightness temperatures measured over the globe with three AMSU‐A radiometers onboard NOAA‐15, ‐16, and ‐17, respectively, are also studied to provide a simple approach for correction of the effect of drifts of local equator crossing time on the data. A sensitivity test of the climate trend detection demonstrates that the method developed in this study can accurately detect an arbitrary climate trend which is introduced into the time series.
Polar mesospheric summer echoes at 78°N, 16°E, 2008: First results of the refurbished sounding system (SOUSY) Svalbard radar
Authors: Hall C. M. , Röttger J. , Kuyeng K. , Tsutsumi M. , Dyrland M. , Chau J. L.
Published: June 2009

The second‐generation sounding system (SOUSY) 53.5‐MHz mesosphere‐stratosphere‐troposphere (MST) radar at 78°N, 16°E on Svalbard has recently completed its inaugural summer, 2008, of polar mesospheric summer echoes (PMSE) observations. Here PMSE observations have been assembled in order to identify dates of the earliest and latest occurrences and how the frequency of PMSE occurrence correlates with dynamics and temperature, which are available from the collocated Nippon/Norway Svalbard Meteor 31‐MHz Radar (NSMR). We find strong correlations between preferred PMSE altitude and low temperature, and between equatorward flow and occurrence rate. Temperature drops cause increases in PMSE occurrence: for the height interval 82–92 km, a drop of around 7 K increases the occurrence, typically by 1–2% d−1 and similarly for a 1 m s−1 increase in equatorward wind. A temperature drop of 5 K at 90 km altitude results in a lowering of the underlying preferred PMSE altitude by 1 km. This study therefore qualifies, at least for 78°N, 16°E and 2008, the dependence of PMSE occurrence rates and preferred heights on 90 km temperature and dynamics.
Size of suspended sediment over dunes
Authors: Kuhnle R. A. , Wren D. G.
Published: June 2009

Samples of suspended sediment were collected at four elevations simultaneously over two‐dimensional mobile dunes in two mixtures of 0.5 mm sand in a laboratory flume channel. A constant sampling position relative to the dunes was maintained by adjusting the translation rate of the sampling carriage to be the same as the migration rate of the dunes. The rate of change of concentration of the suspended sediment with distance from the bed for individual grain sizes was found to be related to the part of the dune over which the samples were collected. The suspended sediment concentration over the lowest third of the flow depth was nearly constant over the trough of the bed forms, while concentration varied rapidly with depth over the brink point, with intermediate rates of change, similar to measurements over a flat bed, over the rest of the dune. The concentration of coarser grains was reasonably explained by assuming they were in intermittent suspension from the brink point of one dune to that of the next. Differences between the vertical changes in grain size were reduced when the sizes were plotted relative to the mean crest elevation of the dunes rather than the local bed elevation. The Rouse equation was found to yield accurate predictions of median grain sizes above the crest level using a reference sample, while median grain size was found to be nearly constant below the level of the crest.
Measurements and simulation of ionospheric scattering on VHF and UHF radar signals: Channel scattering function
Authors: Rogers Neil C. , Cannon Paul S. , Groves Keith M.
Published: June 2009

The design and operation of transionospheric VHF and UHF radars requires knowledge of amplitude and phase scintillation due to ionospheric scattering. Phase coherence is of particular importance where long coherent integration periods and large bandwidths are required. A thin phase screen, parabolic equation based, Trans‐Ionospheric Radio Propagation Simulator (TIRPS) is described. Modeled channel scattering functions (CSFs) are compared to experimental VHF and UHF data derived from the Advanced Research Projects Agency Long‐range Tracking and Instrumentation Radar on Kwajalein Island (9.4°N, 166.8°E). TIRPS quantitatively reproduces the experimental results, including the quasi‐parabolic profile observed in the measured CSFs under strong turbulence conditions. Variations in the simulated CSF with ionospheric phase screen parameters are also presented. Under conditions of high integrated strength of turbulence (CkL), a low phase spectral index (p = 1), indicating relatively dense small‐scale irregularities, produces pronounced range spreading. Conversely, when the spectral index is high (p = 4), indicative of strong focusing/defocusing by large‐scale irregularities, there is increased Doppler spreading and, when the outer scale of irregularities is large, a greater likelihood of asymmetry of the CSF about the zero Doppler axis.
Recent unprecedented skewness towards positive Indian Ocean Dipole occurrences and its impact on Australian rainfall
Authors: Cai W. , Cowan T. , Sullivan A.
Published: June 2009

Is the recent high frequency of positive Indian Ocean Dipole (pIOD) events a consequence of global warming? Using available observations and reanalyses, we show that the pIOD occurrences increase from about four per 30 years early in the 20th century to about 10 over the last 30 years; by contrast, the number of negative Indian Ocean Dipole (nIOD) events decreases from about 10 to two over the same periods, respectively. A skewness measure, defined as the difference in occurrences of pIODs and nIODs, illustrates a systematic trend in this parameter commencing early in the 20th century. After 1950, there are more pIODs than nIODs, with consistent mean circulation changes in the pIOD‐prevalent seasons. Over southeastern Australia (SEA), these changes potentially account for much of the observed austral winter and spring rainfall reduction since 1950. These features are consistent with projected future climate change and hence with what is expected from global warming.
Tsallis distribution of the interplanetary magnetic field at 0.72 AU: Venus Express observation
Authors: Li X. Y. , Wang C. , Zhang T. L.
Published: June 2009

Previous work shows that Probability Distribution Functions (PDFs) of the interplanetary magnetic field strength differences can be described by a single function ‐ Tsallis distribution at Earth and beyond. Launch of Venus Express enables us to extend the application of Tsallis distribution to the inner heliosphere at 0.72 AU. This paper analyzes the distributions of increments of interplanetary magnetic field magnitude on scales from 1 hour to 211 hours (∼85.3 days), and fit all these PDFs to Tsallis distribution. The entropy index q value of all the PDFs on these scales at 0.72 AU are in the range of 1.5 to 1.7, which implies the non‐Gaussianality of the PDFs. The variation of the statistical parameters such as cumulants, variance and kurtosis with scales is also discussed.
Missing salts on early Mars
Authors: Milliken R. E. , Fischer W. W. , Hurowitz J. A.
Published: June 2009

Our understanding of the role of water on Mars has been profoundly influenced over the past several years by the detection of widespread aqueous alteration minerals. Clay minerals are found throughout ancient Noachian terrains and sulfate salts are abundant in younger Hesperian terrains, but these phases are rarely found together in the early Martian rock record. Full alteration assemblages are generally not recognized at local scales, hindering our ability to close mass balance in the ancient crust. Here we demonstrate the dissolution of basalt and subsequent formation of smectite results in an excess of cations that should reside with anions such as OH−, Cl−, SO32−, SO42−, or CO32−in a significant reservoir of complementary salts. Such salts are largely absent from Noachian terrains, yet the composition and/or fate of these ‘missing salts’ is critical to understanding the oxidation state and primary atmospheric volatile involved in crustal weathering on early Mars.
Congener specific organic carbon normalized soil and sediment-water partitioning coefficients for the C~1~ through C~8~ perfluoroalkyl carboxylic and sulfonic acids
Authors: Rayne Sierra , Forest Kaya
Published: June 2009

Organic carbon normalized soil and sediment-water partitioning coefficients (K~oc~) were estimated for all C~1~ through C~8~ perfluoroalkyl carboxylic (PFCA) and sulfonic (PFSA) acid congeners. The limited experimental K~oc~ dataset for the straight chain C~7~ through C~10~ PFCAs and C~8~ and C~10~ PFSAs was correlated to SPARC and ALOGPS computationally estimated octanol-water partitioning / distribution constants and used to predict K~oc~ values for both branched and linear C~1~ through C~8~ isomers. Branched and linear congeners in this homologue range are generally expected to have K~oc~ values >1, leading to their accumulation in organic matter on sediments and soils, retardation during ground and pore water flow, and the preferential association with dissolved organic matter in aquatic systems. Both increasing perfluoroalkyl chain length and linearity increase K~oc~ values with substantial intra- and inter-homologue variation and interhomologue mixing. Variability in K~oc~ values among the PFCA and PFSA congeners will likely lead to an enrichment of more linear and longer chain isomers in organic matter fractions, resulting in aqueous phases fractionated towards shorter chain branched congeners. The expected magnitude of fractionation will require inclusion in source apportionment models and risk assessments. A comparison of representative established quantitative structure property relationships for estimating K~oc~ values from octanol-water partitioning constants suggests that these equilibrium partitioning frameworks may be applicable towards modeling PFCA and PFSA environmental fate processes.
Simulation of asymmetric solar wind electron distributions
Authors: Ryu Chang-Mo , Ahn Hee-Chul , Rhee Tongnyeol , Yoon P. H. , Ziebell L. F. , Gaelzer R. , Viñas A. F.
Published: June 2009

The electron distributions detected in the solar wind feature varying degrees of anisotropic high-energy tail. In a recent work the present authors numerically solved the one-dimensional electrostatic weak turbulence equations by assuming that the solar wind electrons are initially composed of thermal core plus field-aligned counterstreaming beams, and demonstrated that a wide variety of asymmetric energetic tail distribution may result. In the present paper, the essential findings in this work are tested by means of full particle-in-cell simulation technique. It is found that the previous results are largely confirmed, thus providing evidence that the paradigm of local electron acceleration to high-energy tail by self-consistently excited Langmuir turbulence may be relevant to the solar wind environment under certain circumstances. However, some discrepancies are found such that the nearly one-sided energetic tail reported in the numerical solution of the weak turbulence kinetic equation is not shown.
Development of measurement technique for carbon atoms employing vacuum ultraviolet absorption spectroscopy with a microdischarge hollow-cathode lamp and its application to diagnostics of nanographene sheet material formation plasmas
Authors: Takeuchi Wakana , Sasaki Hajime , Kato Satoru , Takashima Seigo , Hiramatsu Mineo , Hori Masaru
Published: June 2009

This study describes the development of a compact measurement technique for absolute carbon (C) atom density in processing plasmas, using vacuum ultraviolet absorption spectroscopy (VUVAS) employing a high-pressure CO2 microdischarge hollow-cathode lamp (C-MHCL) as the light source. The characteristics of the C-MHCL as a resonance line source of C atoms at 165.7 nm for VUVAS measurements of the absolute C atom density are reported. The emission line profile of the C-MHCL under typical operating conditions was estimated to be the Voigt profile with a ΔνL/ΔνD value of 2.5, where ΔνL is the Lorentz width and ΔνD is the Doppler width. In order to investigate the behavior of C and H atoms in the processing plasma used for the fabrication of two-dimensional nanographene sheet material, measurements of the atom densities were carried out using the VUVAS technique. The H atom density increased with increasing pressure, while the C atom density was almost constant at 5×1012 cm−3. The density ratio of C to H atoms in the plasma was found to influence the morphology of carbon nanowalls (CNWs). With increasing H/C density ratio, the growth rate decreased and the space between the walls of the CNWs became wider.
Characterizing the light guiding of fluorescent concentrators
Authors: Goldschmidt Jan Christoph , Peters Marius , Hermle Martin , Glunz Stefan W.
Published: June 2009

Fluorescent concentrators have gained new research interest recently. The development of new material systems for this type of solar concentrator requires the testing of a wide range of materials. The most important characteristic to be tested is the ability of the concentrators to guide light to their edges where the solar cells are mounted. This ability depends on a large set of parameters and cannot be determined with one simple measurement. We present a method to determine this light guiding efficiency spectrally resolved with transmission, reflection, and centermount measurements using a photospectrometer and an integrating sphere. This method represents considerable progress in comparison to external quantum efficiency (EQE) measurements on systems with attached solar cells. The method is fast and flexible. Because no optical coupling and no solar cells with varying properties are involved, accuracy and reproducibility are higher. The method gives an area average of the light guiding efficiency, rather than the value for the point of excitation as does the EQE measurement. Reasonably similar samples can be compared without requiring corrections. For fully quantitative results on an absolute scale, for samples with large Stokes shifts and/or very different properties, additional corrections must be applied. These corrections use data from samples without luminescent material incorporated, which are measured as references. The information obtained for this correction can be also used to derive additional relevant data, such as the absorption of the dyes used and the fraction of light lost into the escape cone. For the tested materials, the measured spectral collection efficiency reached up to 60% at certain wavelengths.
Optical properties of antimony-doped p-type ZnO films fabricated by pulsed laser deposition
Authors: Pan X. H. , Guo W. , Ye Z. Z. , Liu B. , Che Y. , He H. P. , Pan X. Q.
Published: June 2009

We investigated optical properties of Sb-doped p-type ZnO films grown on n-Si (100) substrates by oxygen plasma-assisted pulsed laser deposition. Two acceptor states, with the acceptor levels of 161 and 336 meV, are identified by well-resolved photoluminescence spectra. Under oxygen-rich conditions, the deep acceptor in Sb-doped ZnO film is Zn vacancy. The shallow acceptor is SbZn-2VZn complex induced by Sb doping. The origin of p-type behavior in Sb-doped ZnO has been ascribed to the formation of SbZn-2VZn complex.
Microscopic design of GaInNAs quantum well laser diodes on ternary substrates for high-speed and high-temperature operations
Authors: Fujisawa Takeshi , Arai Masakazu , Yamanaka Takayuki , Kondo Yasuhiro , Kano Fumiyoshi
Published: June 2009

Material properties of highly strained GaInNAs quantum wells grown on GaInAs or quasi-GaInAs substrates are investigated by using microscopic theory together with a band structure calculation based on ten-band k⋅p theory specially formulated for highly strained materials. It is shown that the material gain of GaInNAs quantum wells is reduced by incorporating N into a well layer although the strain in the well layer becomes small. The reduction can be compensated by properly choosing barrier materials. The performance of laser diodes, such as characteristic temperatures T0 and differential gains, is also investigated, and the present results show that very high T0(≃140K) and differential gain with moderate strain (≃1.6%) can be achieved by carefully designing quantum well structures, indicating the applicability of these lasers for high-temperature and high-speed operation.
Interference color modulation, tunable refractive index, and chiroptical electrochromism in a π-conjugated polymer with cholesteric liquid crystal order
Authors: Goto Hiromasa
Published: June 2009

A π-conjugated polymer film prepared by electrolytic polymerization using a cholesteric liquid crystal (CLC) is demonstrated to have a tunable interference function under electrochemical doping and dedoping. The polymer exhibits a CLC-like periodic structure with a potential-dependent refractive index and optical absorption properties. The interference color of the polymer film can thus be modulated dynamically by appropriate application of a voltage in the ±1 V range. This research involves structural chirality and tunable chiroptical properties, doping-dedoping driven tunable refractive index, electrochromism, and interference color modulation for the present polymer. The phenomena demonstrate the possibility of electrochemical photonics.
Proposal for a standard problem for micromagnetic simulations including spin-transfer torque
Authors: Najafi Massoud , Krüger Benjamin , Bohlens Stellan , Franchin Matteo , Fangohr Hans , Vanhaverbeke Antoine , Allenspach Rolf , Bolte Markus , Merkt Ulrich , Pfannkuche Daniela , Möller Dietmar P. F. , Meier Guido
Published: June 2009

The spin-transfer torque between itinerant electrons and the magnetization in a ferromagnet is of fundamental interest for the applied physics community. To investigate the spin-transfer torque, powerful simulation tools are mandatory. We propose a micromagnetic standard problem including the spin-transfer torque that can be used for the validation and falsification of micromagnetic simulation tools. The work is based on the micromagnetic model extended by the spin-transfer torque in continuously varying magnetizations as proposed by Zhang and Li. The standard problem geometry is a permalloy cuboid of 100 nm edge length and 10 nm thickness, which contains a Landau pattern with a vortex in the center of the structure. A spin-polarized dc current density of 1012 A/m2 flows laterally through the cuboid and moves the vortex core to a new steady-state position. We show that the new vortex-core position is a sensitive measure for the correctness of micromagnetic simulators that include the spin-transfer torque. The suitability of the proposed problem as a standard problem is tested by numerical results from four different finite-difference and finite-element-based simulation tools.
Spatially resolved determination of the dark saturation current of silicon solar cells from electroluminescence images
Authors: Glatthaar Markus , Giesecke Johannes , Kasemann Martin , Haunschild Jonas , The Manuel , Warta Wilhem , Rein Stefan
Published: June 2009

We present a novel method to determine spatially resolved the dark saturation current of standard silicon solar cells. For this two electroluminescence images are taken at two different voltages. From these two images, first the spatial voltage distribution can be calculated. Second by applying the Laplacian to the voltage image from Ohm’s law and the continuity equation, the current through the device at a certain position can be determined. Knowing the local current through the device, the local voltage, and the emitter sheet resistance allows to determine the local dark saturation current. The clue of this method is to cope with the noise by using an appropriate noise reduction algorithm. By simulating electroluminescence images with realistic noise and known dark saturation current we demonstrate the applicability of the method with our noise reduction algorithm. Experimentally we compare our method with spectral response light beam induced current on multicrystalline solar cell.
Cubic Sc1−xAlxN solid solution thin films deposited by reactive magnetron sputter epitaxy onto ScN(111)
Authors: Höglund Carina , Bareño Javier , Birch Jens , Alling Björn , Czigány Zsolt , Hultman Lars
Published: June 2009

Reactive magnetron sputter epitaxy was used to deposit thin solid films of Sc1−xAlxN (0≤x≤1) onto MgO(111) substrates with ScN(111) seed layers. Stoichiometric films were deposited from elemental Sc and Al targets at substrate temperatures of 600 °C. The films were analyzed by Rutherford backscattering spectroscopy, elastic recoil detection analysis, x-ray diffraction, and transmission electron microscopy. Results show that rocksalt structure (c)-Sc1−xAlxN solid solutions with AlN molar fractions up to ∼60% can be synthesized. For higher AlN contents, the system phase separates into c- and wurtzite structure (w)-Sc1−xAlxN domains. The w-domains are present in three different orientations relative to the seed layer, namely, Sc1−xAlxN(0001)∥ScN(111) with Sc1−xAlxN[1¯21¯0]∥ScN[11¯0], Sc1−xAlxN(101¯1)∥ScN(111) with Sc1−xAlxN[1¯21¯0]∥ScN[11¯0], and Sc1−xAlxN(101¯1)‖ScN(113). The results are compared to first-principles density functional theory calculations for the mixing enthalpies of c-, w-, and zinc blende Sc0.50Al0.50N solid solutions, yielding metastability with respect to phase separation for all temperatures below the melting points of AlN and ScN.
Refraction-enhanced x-ray radiography for inertial confinement fusion and laser-produced plasma applications
Authors: Koch Jeffrey A. , Landen Otto L. , Kozioziemski Bernard J. , Izumi Nobuhiko , Dewald Eduard L. , Salmonson Jay D. , Hammel Bruce A.
Published: June 2009

We explore various laser-produced plasma and inertial confinement fusion applications of phase-contrast x-ray radiography, and we show how the main features of these enhancements can be considered from a geometrical optics perspective as refraction enhancements. This perspective simplifies the analysis and often permits simple analytical formulas to be derived that predict the enhancements. We explore a raytrace approach to various material interface applications, and we explore a more general example of refractive bending of x rays by an implosion plasma. We find that refraction-enhanced x-ray radiography of implosions may provide a means to quantify density differences across shock fronts as well as density variations caused by local heating due to high-Z dopants. We also point out that refractive bending by implosions plasmas can blur fine radiograph features and can also provide misleading contrast information on area-backlit pinhole imaging experiments unless its effects are taken into consideration.
Effect of spin-polarized electrons on terahertz emission from photoexcited GaAs
Authors: Schleicher James M. , Harrel Shayne M. , Schmuttenmaer Charles A.
Published: June 2009

The influence of elliptically and circularly polarized excitation on terahertz emission from unbiased bulk GaAs at normal incidence and room temperature is reported. Illumination of GaAs above the bandgap produces both spin-polarized electrons and shift currents. The induced currents are monitored via terahertz emission spectroscopy. The terahertz emission amplitude is compared to theoretical calculations as a function of excitation beam ellipticity. Exciting slightly above the bandgap (800 nm at room temperature) with elliptical polarization generates shift currents that deviate substantially from theoretical predictions. On the other hand, exciting either below the bandgap (835 nm at 77 K) to produce optical rectification or far above the bandgap (400 nm at room temperature) to produce shift currents generates emission in agreement with theoretical calculations. Spin-polarized electrons created by elliptically polarized excitation are the source of the observed discrepancy.
Vapor-phase silanization of oxidized porous silicon for stabilizing composition and photoluminescence
Authors: Li Hong-Liang , Zhu Yingchun , Xu Dongsheng , Wan Yong , Xia Linhua , Zhao Xiu-song
Published: June 2009

A vapor-phase deposition approach to the silanization modification of the oxidized porous silicon (PSi) surface using (CH3O)3Si(CH2)3NH2 has been exploited. Standard clean (SC)-1 (NH3H2O/H2O2/H2O, 1:1:5,v/v) and SC-2 [HCl/H2O2/H2O (1:1:6,v/v)] solutions are utilized for the first time to obtain oxidized PSi and have been proved to be a very efficient combination for creating Si–OH species on the PSi surface. After the modification, an amine group terminated surface was successfully created as demonstrated by the contact angle with water, the x-ray photoelectron spectroscopy, and the Fourier transform infrared (FTIR) spectra. The influences of the surface derivatives on the composition stability of the PSi layer and on its photoluminescence properties were investigated by means of FTIR spectra, photoluminescence spectra, and time-resolved photoluminescence measurements.
Thickness scalability of large volume cadmium zinc telluride high resolution radiation detectors
Authors: Awadalla S. A. , Chen H. , Mackenzie J. , Lu P. , Iniewski K. , Marthandam P. , Redden R. , Bindley G. , He Z. , Zhang F.
Published: June 2009

This work focuses on the thickness scalability of traveling heater method (THM) grown CdZnTe crystals to produce large volume detectors with optimized spectroscopic performance. To meet this challenge, we have tuned both our THM growth process, to grow 75 mm diameter ingots, and our postgrowth annealing process. We have increased the thickness of our sliced wafers from 6 to 12 and 18 mm allowing the production of 10 and 15 mm thick detectors. As the detectors’ thickness is scaled up, the energy resolution of both types, as pseudo-Frisch grid and pixelated monolithic detectors showed no degradation indicating improved materials uniformity and transport properties.
Experiments with an 834 m2 ring laser interferometer
Authors: Hurst R. B. , Stedman G. E. , Schreiber K. U. , Thirkettle R. J. , Graham R. D. , Rabeendran N. , Wells J.-P. R.
Published: June 2009

An ultralarge ring He–Ne ring laser gyroscope, UG-2, with area 834 m2 and dimensions 39.7×21 m2, has been built underground at Cashmere Cavern, Christchurch, New Zealand (latitude −43.575°). Earth rotation is sufficient to unlock it, giving a Sagnac frequency of 2.18 kHz. Supermirrors are used with transmission ∼0.18 parts per million (ppm) and optical loss unexpectedly high at ∼200 ppm per reflection. The cavity Q is 1.5×1012. Residual Sagnac frequency error caused by backscatter coupling is measured as <2 parts in 108. Its best stability is achieved for an averaging time of ∼2000 s, for which the Allan Deviation of the Sagnac frequency is 0.08 mHz, or four parts in 108 of Earth rotation rate. The dominant processes generating the residual rotational noise are, for times <10 s, microseismic ground movements, and for times >1000 s, mechanical movement of the mirror assemblies, which act to change the geometrical dimensions and tilt. At all averaging times the residual rotational noise is well above the limit imposed by quantum phase fluctuations. It is concluded from comparisons among many large ring lasers that the excess mirror losses arise from high order aberrations, and UG-2 may be larger than the optimum size.
Carbon nanotube and conducting polymer dual-layered films fabricated by microcontact printing
Authors: Huh Jin Woo , Jeong Jin Wook , Lee Jin Woo , Shin Sang-Il , Kwon Jae-Hong , Choi Jinnil , Yoon Ho Gyu , Cho Gyeong-Ik , You In-Kyu , Kang Seung-Youl , Ju Byeong Kwon
Published: June 2009

We report carbon nanotube/conducting polymer dual-layered film (CPDF) electrodes fabricated by microcontact printing for flexible transparent electrodes of organic thin film transistors (OTFTs). The CPDFs show ∼1000 Ω/sq surface resistivity and ∼93% transmittance at an extremely low loading of single-walled carbon nanotubes, and can be self-aligned with a precision of 20 μm. The CPDFs are applied as the source and drain electrodes in OTFTs without any supplementary alignment process, which leads to a mobility and a current on/off ratio of approximately 0.02 cm2 V−1 s−1 and ∼104, respectively.