bluuebunny/crossref_metadata_2025 huggingface dataset:
Classification of potassium and chlorine ionic currents in retinal ganglion cell line (RGC-5) by whole-cell patch clamp
Authors: WANG SHU-JIE , XIE LAI-HUA , HENG BIN , LIU YAN-QIANG
Published: October 2012

Retinal ganglion cell line (RGC-5) has been widely used as a valuable model for studying pathophysiology and physiology of retinal ganglion cellsin vitro.However, the electrophysiological characteristics, especially a thorough classification of ionic currents in the cell line, remain to be elucidated in details. In the present study, we determined the resting membrane potential (RMP) in RGC-5 cell line and then identified different types of ionic currents by using the whole-cell patch-clamp technique. The RMP recorded in the cell line was between −30 and −6 mV (−17.6 ± 2.6 mV,n= 10). We observed the following voltage-gated ion channel currents: (1) inwardly rectifying Cl−current (ICl,ir), which could be blocked by Zn2+; (2) Ca2+-activated Cl−current (ICl,Ca), which was sensitive to extracellular Ca2+and could be inhibited by disodium 4,4’-diisothiocyanatostilbene-2,2’-disulfonate; (3) inwardly rectifying K+currents (IK1), which could be blocked by Ba2+; (4) a small amount of delayed rectifier K+current (IK). On the other hand, the voltage-gated sodium channels current (INa) and transient outward potassium channels current (IA) were not observed in this cell line. These results further characterize the ionic currents in the RGC-5 cell line and are beneficial for future studies especially on ion channel (patho)physiology and pharmacology in the RGC-5 cell line.
Altered Wnt signalling in the teenage suicide brain: focus on glycogen synthase kinase-3β and β-catenin
Authors: Ren Xinguo , Rizavi Hooriyah S. , Khan Mansoor A. , Dwivedi Yogesh , Pandey Ghanshyam N.
Published: October 2012

Glycogen synthase kinase (GSK)-3β and β-catenin are important components of the Wnt signalling pathway, which is involved in numerous physiological functions such as cognition, brain development and cell survival. Their abnormalities have been implicated in mood disorders and schizophrenia. Teenage suicide is a major public health concern; however, very little is known about its neurobiology. In order to examine if abnormalities of GSK-3β and β-catenin are associated with teenage suicide, we determined the gene and protein expression of GSK-3β and β-catenin in the prefrontal cortex (PFC) and hippocampus obtained from 24 teenage suicide victims and 24 normal control subjects. Protein expression was determined using Western blot with specific antibodies and gene expression (mRNA levels) was determined using the real-time polymerase chain reaction method. No significant change was observed in the GSK-3β protein levels either in the PFC or hippocampus of suicide victims compared to controls. However, protein levels of pGSK-3β-ser9 were significantly decreased in the PFC and hippocampus of suicide victims compared to normal controls. We also found that GSK-3β mRNA levels were significantly decreased in the PFC but not in the hippocampus of teenage suicide victims compared to controls. Mean protein and mRNA levels of β-catenin were significantly decreased in both the PFC and hippocampus of teenage suicide group compared to controls. The observation that there is a decrease in β-catenin and pGSK-3β-ser9 in the PFC and hippocampus of teenage suicide victims does indicate a disturbance in the Wnt signalling pathway in teenage suicide.
Transforming floundering into success
Authors: NAISH LEE
Published: October 2012

We show how logic programs with “delays” can be transformed to programs without delays in a way that preserves information concerning floundering (also known as deadlock). This allows a declarative (model-theoretic), bottom-up or goal-independent approach to be used for analysis and debugging of properties related to floundering. We rely on some previously introduced restrictions on delay primitives and a key observation which allows properties such as groundness to be analysed by approximating the (ground) success set.
Redundant Sudoku rules
Authors: DEMOEN BART , GARCIA DE LA BANDA MARIA
Published: October 2012

The rules of Sudoku are often specified using 27 all_different constraints, referred to as the big constraints. Using graphical proofs and exploratory logic programming, the following main and new result is obtained: Many subsets of six of these big constraints are redundant (i.e., they are entailed by the remaining 21 constraints), and six is maximal (i.e., removing more than six constraints is not possible while maintaining equivalence). The corresponding result for binary inequality constraints, referred to as the small constraints, is stated as a conjecture.
Rewriting and narrowing for constructor systems with call-time choice semantics
Authors: LÓPEZ-FRAGUAS FRANCISCO J. , MARTIN-MARTIN ENRIQUE , RODRÍGUEZ-HORTALÁ JUAN , SÁNCHEZ-HERNÁNDEZ JAIME
Published: October 2012

Non-confluent and non-terminating {constructor-based term rewriting systems are useful for the purpose of specification and programming. In particular, existing functional logic languages use such kinds of rewrite systems to define possibly non-strict non-deterministic functions. The semantics adopted for non-determinism iscall-time choice, whose combination with non-strictness is a non-trivial issue, addressed years ago from a semantic point of view with the Constructor-based Rewriting Logic (CRWL), a well-known semantic framework commonly accepted as suitable semantic basis of modern functional logic languages. A drawback of CRWL is that it does not come with a proper notion of one-step reduction, which would be very useful to understand and reason about how computations proceed. In this paper, we develop thoroughly the theory for the first-order version of let-rewriting, a simple reduction notion close to that of classical term rewriting, but extended with a let-binding construction to adequately express the combination of call-time choice with non-strict semantics. Let-rewriting can be seen as a particular textual presentation of term graph rewriting. We investigate the properties of let-rewriting, most remarkably their equivalence with respect to a conservative extension of the CRWL-semantics coping with let-bindings, and we show by some case studies that having two interchangeable formal views (reduction/semantics) of the same language is a powerful reasoning tool. After that, we provide a notion of let-narrowing, which is adequate for call-time choice as proved by soundness and completeness results of let-narrowing with respect to let-rewriting. Moreover, we relate those let-rewriting and let-narrowing relations (and hence CRWL) with ordinary term rewriting and narrowing, providing in particular soundness and completeness of let-rewriting with respect to term rewriting for a class of programs which are deterministic in a semantic sense.
China's role in WTO dispute settlement
Authors: KENNEDY MATTHEW
Published: October 2012

This study describes and analyzes trends in China's participation in the WTO dispute settlement system during the first ten years of its membership. China has used the system to challenge differentiated treatment of its exports by its two largest trading partners, a theme related to sensitive aspects of its accession negotiations. The study reviews the record of China's conformity to WTO dispute settlement practices, and its contribution to their development, and finds that China is playing the role of a ‘system-maintainer’. The study concludes by considering a future challenge that the emergence of this large new player may pose for the system.
Assessing genetic diversity, allelic richness and genetic relationship among races in ICRISAT foxtail millet core collection
Authors: Vetriventhan M. , Upadhyaya H. D. , Anandakumar C. R. , Senthilvel S. , Parzies H. K. , Bharathi A. , Varshney R. K. , Gowda C. L. L.
Published: October 2012

Foxtail millet (Setaria italica(L.) P. Beauv.) is an ideal crop for changing climate and food habits of peoples due to its short duration, high photosynthetic efficiency, nutritional richness and fair resistance to pest and diseases. However, foxtail millet yields are low mainly due to the lack of effort for its improvement and the lack of proper utilization of existing genetic variability. To enhance the use of diverse germplasm in breeding programmes, a core collection in foxtail millet consisting of 155 accessions was established. Core collection accessions were fingerprinted using 84 markers (81 simple sequence repeats (SSRs) and three Expressed Sequence Tag (EST)-SSRs). Our results showed the presence of greater molecular diversity in the foxtail millet core collection. The 84 markers detected a total of 1356 alleles with an average of 16.14 alleles (4–35) per locus. Of these, 368 were rare alleles, 906 common alleles and 82 the most frequent alleles. Sixty-one unique alleles that were specific to a particular accession and useful for germplasm identification were also detected. In this study, the genetic diversity of foxtail millet was fairly correlated well with racial classification, and the race Indica showed a greater genetic distance from the races Maxima and Moharia. The pairwise estimate of dissimilarity was >0.50 except in 123 out of 11,935 pairs which indicated a greater genetic variability. Two hundred and fifty pairs of genetically most diverse accessions were identified. This large molecular variation observed in the core collection could be utilized effectively by breeders or researchers for the selection of diverse parents for breeding cultivars and the development of mapping populations.
A scaling model for severity of operational losses using generalized additive models for location scale and shape (GAMLSS)
Authors: Ganegoda Amandha , Evans John
Published: October 2012

In this paper, we investigate the problem of how to combine operational losses collected from various banks of different sizes and loss reporting thresholds in order to estimate the distribution of operational loss severities for a bank of a given size. We model the severity of operational losses by using the extreme value theory to account for the reporting bias of the external data, and a regression analysis based on the GAMLSS framework to model the scaling properties of operational losses. In contrast to previous studies on the scaling problem, our analysis gives particular emphasis to the scaling properties of the tail of the loss distribution. Contrary to existing knowledge, we find that the size of a bank is an important determinant of the severity of operational losses and that the tail index of the distribution is negatively correlated with the size of the bank. The results indicate that for very large banks, distribution of the operational loss severity can be extremely heavy tailed (i.e. tail index less than 1), a finding which have significant implications for capital calculation as well as for risk management. Furthermore, we also demonstrate that the capital estimates provided by our model is consistent with the industry standards and the model can be used by individual banks to simulate data to complement their internal data.
Malaysian Twin Registry
Authors: Jahanfar Shayesteh , Jaffar Sharifah Halimah
Published: October 2012

The National Malaysian Twin Registry was established in Royal College of Medicine, Perak, University Kuala Lumpur (UniKL) in June 2008 through a grant provided by UniKL. The general objective is to facilitate scientific research involving participation of twins and their family members in order to answer questions of health and wellbeing relevant to Malaysians. Recruitment is done via mass media, poster, and pamphlets. We now have 266 adult and 204 children twins registered. Several research projects including reproductive health study of twins and the role of co-bedding on growth and development of children are carried out. Registry holds annual activities for twins and seeks to provide health-related information for twins. We seek international collaboration.
Twins Early Development Study (TEDS): A Genetically Sensitive Investigation of Cognitive and Behavioral Development From Childhood to Young Adulthood
Authors: Haworth Claire M. A. , Davis Oliver S. P. , Plomin Robert
Published: October 2012

The Twins Early Development Study (TEDS) is a large longitudinal sample of twins born in England and Wales between 1994 and 1996. The focus of TEDS has been on cognitive and behavioral development, including difficulties in the context of normal development. TEDS began when multiple births were identified from birth records and the families were invited to take part in the study; 16,810 pairs of twins were originally enrolled in TEDS. More than 10,000 of these twin pairs remain enrolled in the study to date. DNA has been collected for more than 7,000 pairs, and genome-wide genotyping data for two million DNA markers are available for 3,500 individuals. The TEDS families have taken part in studies when the twins were aged 2, 3, 4, 7, 8, 9, 10, 12, 14, and 16 years of age. Data collection is currently underway to assess the adult destinations of the twins as they move from school to university and the workplace. Between January 2012 and December 2014, all of the TEDS twins will turn 18, and the study will transition to an adult sample. TEDS represents an outstanding resource for investigating the developmental effects of genes and environments on complex quantitative traits from childhood to young adulthood and beyond.
The Texas Twin Project
Authors: Harden K. Paige , Tucker-Drob Elliot M. , Tackett Jennifer L.
Published: October 2012

Socioeconomic position, racial/ethnic minority status, and other characteristics of the macro-environment may be important moderators of genetic influence on a wide array of psychosocial outcomes. Designed to maximize representation of low socioeconomic status families and racial/ethnic minorities, the Texas Twin Project is an ongoing study of school-age twins (preschool through 12th grade) enrolled in public schools in the Austin, Texas and Houston, Texas metropolitan areas. School rosters are used to identify twin families from a target population with sizable populations of African American (18%), Hispanic/Latino (48%), and non-Hispanic White (27%) children and adolescents, over half of whom meet US guidelines for classification as economically disadvantaged. Initial efforts have focused on a large-scale, family-based survey study involving both parent and child reports of personality, psychopathology, physical health, academic interests, parent–child relationships, and aspects of the home environment. In addition, the Texas Twin Project is the basis for an in-laboratory study of adolescent decision-making, delinquency, and substance use. Future directions include geographic expansion of the sample to the entire state of Texas (with a population of over 25 million) and genotyping of participating twins.
Psychopharmakologische Behandlung von Depressionen im Kindes- und Jugendalter
Authors: Plener Paul L. , Fegert Jörg M. , Kölch Michael G.
Published: October 2012

Die psychopharmakologische Behandlung kann – je nach Schweregrad- eine wichtige Option in der Therapie depressiver Erkrankungen bei Kindern und Jugendlichen darstellen. Diese Überblicksarbeit gibt klinische Behandlungsempfehlungen mit einem Fokus auf den Umgang mit Suizidalität und therapieresistenten Patienten. Die Studienlage zur medikamentösen Therapie der depressiven Erkrankung im Kindes- und Jugendalter hat sich seit den Warnungen der amerikanischen Zulassungsbehörde zum Auftreten von Suizidalität unter Therapie mit Selektiven Serotonin Wiederaufnahmehemmern (SSRIs) deutlich verbessert. In der Versorgung von depressiven Kindern und Jugendlichen ist in den letzten Jahren in Deutschland ein Trend hin zu einer evidenzbasierten psychopharmakologischen Therapie zu erkennen.
Wirksamkeit universeller und selektiver Prävention von Depression im Kindes- und Jugendalter
Authors: Schulte-Körne Gerd , Schiller Yvonne
Published: October 2012

Fragestellung: Depressive Störungen beginnen häufig im Kindesalter, sodass bereits frühzeitig präventive Maßnahmen einsetzten sollten. Ziel der vorliegenden Arbeit ist es, auf der Basis bereits publizierter systematischer Reviews und Metaanalysen die Evidenz der selektiven, indizierten und universellen Prävention für das Kindes- und Jugendalter zusammenfassend darzustellen und Empfehlungen für die Praxis abzuleiten. Methodik: Zwischen 1990 und 2012 wurde in wissenschaftlichen Datenbanken nach deutsch und englischsprachigen Arbeiten zur Prävention von Depression im Kindes- und Jugendalter recherchiert. 10 systematische Reviews und Metaanalysen wurden eingeschlossen. Diese untersuchten insgesamt 121 ausschließlich kontrollierte Studien zu 52 universellen, 46 selektiven und 19 indizierten Präventionsprogrammen. Vier Studien kombinierten selektive und indizierte Prävention. Ergebnisse: Im Vergleich zu unbehandelten Kontrollgruppen gibt es sowohl für selektive und indizierte als auch universelle Prävention Evidenz für deren Wirksamkeit in der Reduktion depressiver Symptome. Dies gilt kurzfristig und bis zu einem Follow-up- Zeitraum von 9 Monaten. Selektive Ansätze zeigen Wirksamkeitsnachweise bis 12 Monate. Die Effektstärken sind meist niedrig. Wenn die Vergleiche mit Placebo- Kontrollgruppen durchgeführt werden, ist die Evidenz deutlich geringer oder nicht nachweisbar. Schlussfolgerungen: Die Ergebnisse der einzelnen Reviews sind sehr heterogen. Wichtig erscheint zukünftig zu klären, welche Faktoren für wirksame Prävention verantwortlich sind und wie die Präventionsprogramme erfolgreich in die Praxis integriert werden können.
Role of snow and glacier melt in controlling river hydrology in Liddar watershed (western Himalaya) under current and future climate
Authors: Jeelani G. , Feddema Johannes J. , van der Veen Cornelis J. , Stearns Leigh
Published: October 2012

Snowmelt and icemelt are believed to be important regulators of seasonal discharge of Himalayan rivers. To analyze the long term contribution of snowmelt and glacier/icemelt to river hydrology we apply a water budget model to simulate hydrology of the Liddar watershed in the western Himalaya, India for the 20th century (1901–2010) and future IPCC A1B climate change scenario. Long term (1901–2010) temperature and precipitation data in this region show a warming trend (0.08°C yr−1) and an increase in precipitation (0.28 mm yr−1), with a significant variability in seasonal trends. In particular, winter months have undergone the most warming, along with a decrease in precipitation rates; precipitation has increased throughout the spring. These trends have accelerated the melting and rapid disappearance of snow, causing a seasonal redistribution in the availability of water. Our model results show that about 60% of the annual runoff of the Liddar watershed is contributed from the snowmelt, while only 2% is contributed from glacier ice. The climate trend observed from the 1901 to 2010 time period and its impact on the availability of water will become significantly worse under the IPCC climate change scenarios. Our results suggest that there is a significant shift in the timing and quantity of water runoff in this region of the Himalayas due to snow distribution and melt. With greatly increased spring runoff and its reductions in summer potentially leading to reduced water availability for irrigation agriculture in summer.
Statistical maps of small‐scale electric field variability in the high‐latitude ionosphere
Authors: Cousins E. D. P. , Shepherd S. G.
Published: October 2012

Statistical maps of small‐scale electric field variability in the high‐latitude ionosphere are derived for the Northern and Southern Hemispheres using 48 months of data from the Super Dual Auroral Radar Network (SuperDARN). Maps of variability magnitude (from scales of 45–450 km and 2–20 min) are derived for a range of interplanetary magnetic field (IMF) orientations and dipole tilt angles (the angle between the best fit dipole axis and the plane perpendicular to the Sun‐Earth line). It is found that the observed spatial distribution of average variability is significantly modified as the IMF and dipole tilt conditions change. Under negative (winter‐like) and neutral (equinox‐like) dipole tilt angles, variability is concentrated in the auroral and dayside cusp regions, and the spatial distributions of variability appear to be correlated to those of large‐ and small‐scale field‐aligned currents (FACs). Additionally, variability on the nightside is found to be more enhanced in the downward FAC region than it is in the upward FAC region. Under positive (summer‐like) dipole tilt angles, the average variability magnitudes across the high‐latitude regions are smaller than those observed under negative dipole tilt angles, and the spatial distributions are more uniform. These dipole tilt effects suggest that scale‐size‐ and conductivity‐dependent field‐aligned potential drops and conductivity‐dependent changes in the processes that generate variability are possible factors that impact the observed small‐scale electric field variability. In general, Southern Hemisphere maps appear very similar to Northern Hemisphere maps, although some minor differences are observed that may result from interhemispheric asymmetries in the geomagnetic field.
Excitation of the third harmonic mode in meridian planes for Pi2 in the auroral zone
Authors: Saka O. , Hayashi K. , Koga D.
Published: October 2012

Polarizations of Pi2 pulsations in the magnetosphere and on the ground in the auroral zone are inconsistent when field line motions in the meridian and transverse planes are both in the fundamental harmonic. To resolve these inconsistencies, we propose a third harmonic mode in the meridian planes. The excitation of the third harmonic is explained by dusk‐to‐dawn currents at the equatorial plane, which are driven by diamagnetic currents during substorm injections. We propose diamagnetic currents in the equatorial plane and compressional input at the outer boundary as the source of Pi2 pulsations in the magnetosphere.
P‐wave tomography of eastern North America: Evidence for mantle evolution from Archean to Phanerozoic, and modification during subsequent hot spot tectonism
Authors: Villemaire M. , Darbyshire F. A. , Bastow I. D.
Published: October 2012

The unique physical and chemical properties of cratonic lithosphere are thought to be key to its long‐term survival and its resistance to pervasive modification by tectonic processes. Study of mantle structure in southeast Canada and the northeast US offers an excellent opportunity to address this issue because the region spans 3 billion years of Earth history, including Archean formation of the Superior craton and younger accretion of terranes to eastern Laurentia during the Proterozoic Grenville and Phanerozoic Appalachian orogenies. Trending NW–SE through each of these terranes is the track of the Great Meteor hot spot, which affected the region during the Mesozoic. Here we study mantle seismic velocity structure beneath this region of eastern North America using tomographic inversion of teleseismic P‐wave relative arrival‐times recorded by a large‐aperture seismograph network. There are no large‐scale systematic differences between Superior and Grenville mantle wave speed structure, which may suggest that tectonic stabilization of cratons occurred in a similar fashion during the Archean and Proterozoic. Cratonic lithosphere is largely thought to be resistant to modification by hot spot processes, in contrast to younger terranes where lithospheric erosion and significant magmatism are expected. Low velocities beneath the regions affected by the Great Meteor hot spot are broadest beneath the Paleozoic Appalachian terranes, indicating pervasive modification of the lithosphere during magmatism. The zone of modification narrows considerably into the Proterozoic Grenville province before disappearing completely in the Archean Superior craton, where the surface signature of Mesozoic magmatism is limited to kimberlite eruptions.
Distribution characteristics of transparent exopolymer particles in the Pearl River estuary, China
Authors: Sun Cui‐Ci , Wang You‐Shao , Li Qian P. , Yue Wei‐Zhong , Wang Yu‐Tu , Sun Fu‐Lin , Peng Ya‐Lan
Published: October 2012

Distribution of Transparent Exopolymer Particles (TEP) in the Pearl River estuary, China, was investigated during two cruises in August 2009 and January 2010. TEPcolor concentrations were 521.5–1727.4 μg Xeq.L−1 (μg Gum Xanthan equivalent liter−1) in August 2009 and 88.7–1586.9 μg Xeq.L−1 in January 2010, respectively. The size of TEP generally increased in the seaward along the longitudinal section with the dominant size of 2–40 μm during the cruises. Experimental work suggested that both concentration and size of TEP increased with Ca2+ concentration (from 0.8 mmol L−1 to 10 mmol L−1). In the field study, Ca2+ concentration had a positive correlation with TEPcolor concentration in the surface layer with salinity <16. Decrease of TEP concentration seaward from intermediary salinity was partly due to dilution of seawater as well as enhanced aggregation and sedimentation of TEP via increasing divalent cation concentration. TEP concentration and turbidity maximum coexisted at the tip of salt wedge in the bottom layer during the wet season, and positive correlation between TEP and turbidity was observed in the winter. Relationships between TEP and turbidity suggested the important contribution of TEP aggregation to flocculation and sedimentation of particles in estuaries. Different pattern of TEP during two cruises can be attributed to physical process (i.e., mixing type) in estuaries. These findings indicated that formation and distribution of TEP were largely influenced by interaction between physical and biogeochemical processes in the Pearl River estuary. A conceptual model for TEP formation and distribution in the Pearl River estuary was developed.
Abundance and patterns of transparent exopolymer particles (TEP) in Arctic floodplain lakes of the Mackenzie River Delta
Authors: Chateauvert C. Adam , Lesack Lance F. W. , Bothwell Max L.
Published: October 2012

The Mackenzie River Delta is a lake‐rich arctic floodplain that receives high inputs of dissolved organic matter (DOM) and suspended particulates from allochthonous and autochthonous sources, and may transfer carbon from dissolved to particulate phase via in situ formation of transparent exopolymer particles (TEP). TEP provides food for grazers, surfaces for bacteria, and increased potential for aggregation and sedimentation of organic matter. During open water 2006, we tracked TEP abundances in three Delta lakes representing gradients that include declining river‐to‐lake connection times, increasing levels of dissolved organic carbon (DOC), and declining chromophoric‐DOM (CDOM). Unexpectedly, TEP abundances were highest immediately after the flood, when autochthonous autotrophic production was at a seasonal low and CDOM a seasonal high. Moreover, the lake with the strongest riverine influence and lowest levels of autochthonous autotrophic production had the highest mean TEP‐carbon (TEP‐C) concentrations among the lakes. The mean proportion of particulate organic carbon (POC) represented by TEP‐C increased with increasing river connection time, and appears to represent a substantial proportion of POC in Mackenzie Delta Lakes. Unexpectedly, the TEP gradient was most strongly related to CDOM (river water source) rather than overall DOC. Variations in CDOM accounted for 53% of TEP‐C variation among the lakes, indicating allochthonous matter was the most important source of TEP. DOC release from in situ macrophytes during periods of high photosynthesis may contribute to TEP formation in the lake with lowest riverine influence, but pH levels >9.5 driven by the high photosynthetic rates complicate the interpretation of results from this lake.
Equatorial range spread F echoes from coherent backscatter, and irregularity growth processes, from conjugate point digital ionograms
Authors: Abdu M. A. , Batista I. S. , Reinisch B. W. , MacDougall J. W. , Kherani E. A. , Sobral J. H. A.
Published: October 2012

Radio wave returns from spread F plasma structures as received by ionosondes can originate from total/specular reflection, partial reflection or coherent backscattering. The dominant mechanism to account for the spread F traces in equatorial ionograms is still an open question. Depending upon the precise mechanism, ionosondes are sensitive to irregularity scale sizes of tens of meters to several tens/hundreds of kilometers. In this paper we analyze signatures of range spreading F layer traces in Digisonde ionograms, taken at Fortaleza (3.9°S, 38.45°W, dip: −9°) and Sao Luis (2.33 S, 44.2W, dip angle: −0.5°), and at a dip equatorial site Cachimbo (9.5°S, 54.8°W, dip: −4.2°) and at its two conjugate sites Bova Vista (02.8°N, 60.7°W, dip: 22.0°) and Campo Grande (20.5 S, 54.7 W, dip −22.3°) in Brazil, to determine the dominant process/mechanism of echo returns from the irregularity structures. A significant component of the ESF trace structures is found to be consistent with the echoes originating from coherent backscattering at field line perpendicular directions. The degree of range spreading of the echoes is found to increase linearly with the top frequency of the echo trace, which is shown to be a more precise indicator of the irregularity strength. Further, the irregularity strength exhibits a significant increase from the equator toward the EIA crests, as well as a strong asymmetry between the conjugate sites.
Impact of tidal density variability on orbital and reentry predictions
Authors: Leonard J. M. , Forbes J. M. , Born G. H.
Published: October 2012

Since the first satellites entered Earth orbit in the late 1950's and early 1960's, the influences of solar and geomagnetic variability on the satellite drag environment have been studied, and parameterized in empirical density models with increasing sophistication. However, only within the past 5 years has the realization emerged that “troposphere weather” contributes significantly to the “space weather” of the thermosphere, especially during solar minimum conditions. Much of the attendant variability is attributable to upward‐propagating solar tides excited by latent heating due to deep tropical convection, and solar radiation absorption primarily by water vapor and ozone in the stratosphere and mesosphere, respectively. We know that this tidal spectrum significantly modifies the orbital (>200 km) and reentry (60–150 km) drag environments, and that these tidal components induce longitude variability not yet emulated in empirical density models. Yet, current requirements for improvements in orbital prediction make clear that further refinements to density models are needed. In this paper, the operational consequences of longitude‐dependent tides are quantitatively assessed through a series of orbital and reentry predictions. We find that in‐track prediction differences incurred by tidal effects are typically of order 200 ± 100 m for satellites in 400‐km circular orbits and 15 ± 10 km for satellites in 200‐km circular orbits for a 24‐hour prediction. For an initial 200‐km circular orbit, surface impact differences of order 15° ± 15° latitude are incurred. For operational problems with similar accuracy needs, a density model that includes a climatological representation of longitude‐dependent tides should significantly reduce errors due to this source.
Temporal moments revisited: Why there is no better way for physically based model reduction in time
Authors: Leube P. C. , Nowak W. , Schneider G.
Published: October 2012

Many hydro(geo)logical problems are highly complex in space and time, coupled with scale issues, variability, and uncertainty. Especially time‐dependent models often consume enormous computational resources, but model reduction techniques can alleviate this problem. Temporal moments (TM) offer an approach to reduce the time demands of transient hydro(geo)logical simulations. TM reduce transient governing equations to steady state and directly simulate the temporal characteristics of the system, if the equations are linear and coefficients are time independent. This is achieved by an integral transform, projecting the dynamic system response onto monomials in time. In comparison to classical approaches of model reduction that involve orthogonal base functions, however, the monomials for TM are nonorthogonal, which might impair the quality and efficiency of model reduction. Thus, we raise the question of whether there are more suitable temporal base functions than the monomials that lead to TM. In this work, we will derive theoretically that there is only a limited class of temporal base functions that can reduce hydro(geo)logical models. By comparing those to TM we conclude that, in terms of gained efficiency versus maintained accuracy, TM are the best possible choice. While our theoretical results hold for all systems of linear partial or ordinary differential equations (PDEs, ODEs) with any order of space and time derivatives, we illustrate our study with an example of pumping tests in a confined aquifer. For that case, we demonstrate that two (four) TM are sufficient to represent more than 80% (90%) of the dynamic behavior, and that the information content strictly increases with increasing TM order.
Simple microwave field imaging technique using hot atomic vapor cells
Authors: Böhi Pascal , Treutlein Philipp
Published: October 2012

We demonstrate a simple technique for microwave field imaging using alkali atoms in a vapor cell. The microwave field to be measured drives Rabi oscillations on atomic hyperfine transitions, which are detected in a spatially resolved way using a laser beam and a camera. Our vapor cell geometry enables single-shot recording of two-dimensional microwave field images with 350 μm spatial resolution. Using microfabricated vapor cell arrays, a resolution of a few micrometers seems feasible. All vector components of the microwave magnetic field can be imaged. Our apparatus is simple and compact and does not require cryogenics or ultra-high vacuum.
Direct visualization of Ni-Nb bulk metallic glasses surface: From initial nucleation to full crystallization
Authors: Oreshkin A. I. , Mantsevich V. N. , Savinov S. V. , Oreshkin S. I. , Panov V. I. , Maslova N. S. , Louzguine-Luzgin D. V.
Published: October 2012

This article is devoted to in situ investigation of the Ni-based bulk metallic glass structural evolution and crystallization behavior by scanning tunneling microscopy/spectroscopy. The possibility of different surface nanostructures formation is shown by annealing of an original bulk glassy alloy in ultra high vacuum. Atomic locations in these surface nanostructures are completely different from those formed according to Ni-Nb binary phase diagram in the bulk area of the sample. The validity of the results is also verified by transmission electron microscopy and nano-beam diffraction measurements.
Vibrational mode frequencies of H4SiO4, D4SiO4, H6Si2O7, and H6Si3O9 in aqueous environment, obtained from ab initio molecular dynamics
Authors: Spiekermann Georg , Steele-MacInnis Matthew , Kowalski Piotr M. , Schmidt Christian , Jahn Sandro
Published: October 2012

We report the vibrational properties of H4SiO4, D4SiO4, H6Si2O7, and H6Si3O9 in aqueous solution at 300 K and 1000 K, obtained from the combination of ab initio molecular dynamics (MD) and a mode-decomposition approach. This combination yields vibrational subspectra for selected vibrational modes at finite temperatures. We also performed normal-mode analysis (NMA) on numerous configurations from the same MD run to sample the effect of the variable molecular environment. We found good agreement between both approaches. The strongest effect of temperature is on the SiOH bending mode δSiOH, which is at about 1145 cm−1 in solution at 300 K, opposed to about 930 cm−1 in solution at 1000 K. The frequency of the δSiOH vibration also depends on environment, shifting from 1145 cm−1 in solution to about 845 cm−1 in the gas-phase. We found both in the mode-decomposition approach and in multiple-configuration NMA that the H6Si2O7 dimer shows a vibrational mode at about 790 cm−1, which we consider to be responsible for a hitherto unexplained shoulder of the monomer Raman band at 770 cm−1 in dilute silica solutions. Our results demonstrate the importance of temperature and solvation environment in calculations that aim to support the interpretation of experimental Raman spectra of dissolved silica.
Propagation of gamma rays and production of free electrons in air
Authors: Dimant Y. S. , Nusinovich G. S. , Sprangle P. , Penano J. , Romero-Talamas C. A. , Granatstein V. L.
Published: October 2012

This paper is devoted to the analysis of production of free electrons in air by gamma-rays leaking from radioactive materials. A model based on the Klein-Nishina scattering theory is used to calculate scattering cross sections and approximate the electron production rate. The model includes the effects of primary gamma-quanta radiated by the source as well as that scattered in air. Comparison of the model with the mcnpx kinetic code (http://mcnpx.lanl.gov/) in a sample problem shows excellent agreement. The motivation for this research comes from the recently proposed concept of remote detection of concealed radioactive materials [V. L. Granatstein and G. S. Nusinovich, J. Appl. Phys. 108, 063304 (2010)]. The concept is based on the breakdown in air at the focal point of a high-power beam of electromagnetic waves produced by a THz gyrotron with a 10-20 μs pulse. The presence of a radioactive material can greatly exceed the production rate of free electrons over the natural background rate. Additional electrons act as seeds to initiate the breakdown and create sufficiently dense plasma at the focal region. The dense plasma can then be remotely detected as an unambiguous effect of the concealed radioactive material.
Current pulse induced toggle switching of dual-vortex magnetization in Ni80Fe20/Cu/Co nanopillar element
Authors: Kolthammer J. , Gardner R. , Speliotis Th. , Hong Y. K. , Abo G. , Liu Q. , Choi B. C.
Published: October 2012

The combined effect of the spin-transfer torque and circular Amperian field to the switching of the chiralities of the dual-vortex magnetization in multilayered Ni80Fe20/Cu/Co nanopillar elements (ø = 100 nm) is investigated numerically. It is demonstrated that, by passing a current pulse through the nanopillar, the chirality of the Ni80Fe20 layer can be controllably switched while that of the fixed Co layer persists. Consequently, reliable toggle switching between bistable low- and high-MR states can be achieved by applying current pulses with appropriate amplitude, polarity, and duration. It is found that the magnetization dynamics after the onset of a current pulse includes the excitation of spin-wave eigenmodes and that the predominant process throughout is the precessional motion of the free-layer magnetization. A shift of the eigenfrequency is observed when the chirality of the free-layer vortex magnetization switches from parallel to antiparallel relative to that of the fixed layer. This frequency shift is attributed to dynamic magnetostatic coupling between the vortices.
Investigation on structural instability induced relaxation and crystallization in ZrCuAlNi bulk metallic glass
Authors: Wu Xuebang , Shui Jiapeng , Wang Zhi-Zhi , Zu Fang-Qiu
Published: October 2012

The nature of internal friction peak associated with the first-order phase transformation remains an unsolved fundamental problem in many fields of science and technology. Here, the internal friction behaviors of crystallization process of Zr55Al10Ni5Cu30 bulk metallic glass were investigated. With increasing temperature, the internal friction spectra exhibit a peak, which shows a crossover from a relaxation behavior to a phase transformation behavior. The combined differential scanning calorimetry results show that the phase transformation behavior at higher temperature is related to the crystallization process of amorphous alloy, while the relaxation behavior at lower temperature is composed of two processes: One originates from the glass transition and the other from the relaxation due to the structural instability before phase transformation. According to the coupling model and the compensation effect, the primitive activation energies for the glass transition and the structural instability before crystallization are about 1.0 eV and 1.4 eV, respectively. Therefore, it is suggested that the mechanism of internal friction peak associated with the first-order phase transformation is due to the structural instability before phase transformation and the sudden change of the relaxation parameters when phase transformation happens.
Polarization spectroscopy of N-polar AlGaN/GaN multi quantum wells grown on vicinal (0001¯) GaN
Authors: Keller S. , Pfaff N. , DenBaars S. P. , Mishra U. K.
Published: October 2012

Pronounced polarized light emission was observed from N-polar AlGaN/GaN multi quantum wells grown on (0001¯) GaN with a misorientation of 4° toward the m-direction grown by metal organic chemical vapor deposition. The misoriented (Al,Ga,In)N layers exhibited a high density of surface steps parallel to the 〈112¯0〉 direction with step heights between 1 and 2 nm. The corrugated surfaces led to the formation of self organized quantum wire arrays in samples with 2.5 and 3.5 nm thick wells, revealed by a degree of polarization of 0.19 and 0.14, respectively, for light emission at 10 K.
Shock-induced intermediate-range structural change of SiO2 glass in the nonlinear elastic region
Authors: Ichiyanagi K. , Kawai N. , Nozawa S. , Sato T. , Tomita A. , Hoshino M. , Nakamura K. G. , Adachi S. , Sasaki Y. C.
Published: October 2012

We study shock compressed fused quartz in the nonlinear elastic region using single-shot time-resolved x-ray scattering measurements. The first sharp diffraction peak (FSDP) of fused quartz shifts to the high Q region under shock compression. In contrast, the short-range order structure does not change around 3.5 GPa. The nanosecond FSDP shift provides clear evidence of intermediate-range order structural changes in the nonlinear elastic region. Because the intermediate-order structure is too short to produce the final structural state in the nonlinear elastic region, the FSDP shift is lower compared with hydrostatic experiments.
Three-dimensionally isotropic negative refractive index assisted by two-photon resonance via quantum coherence
Authors: Qi Shen Jian
Published: October 2012

An experimentally feasible and promising scheme for realizing simultaneously negative permittivity and permeability in a single-photon off-resonant atomic vapor is suggested by taking full advantage of the mechanism of two-photon resonance that is assisted by atomic phase coherence. The present quantum-coherent atomic vapor can exhibit three-dimensionally isotropic negative refractive index (NRI) at visible and near-infrared wavelengths, and would find potential applications in design of NRI-based quantum optical and photonic devices.
High performance radial p-n junction solar cell based on silicon nanopillar array with enhanced decoupling mechanism
Authors: Dou Bingfei , Jia Rui , Li Haofeng , Chen Chen , Ding Wuchang , Meng Yanlong , Xing Zhao , Liu Xinyu , Ye Tianchun
Published: October 2012

High performance radial p-n junction solar cells based on silicon nanopillar array were synthesized from p-type silicon substrates and compared with planar cell. These radial p-n junction cells exhibited considerable higher short-circuit current, due to their unique carriers' decoupling mechanism. After the electrode enhancement via light induced plating, a best efficiency of near 12% was achieved for radial p-n junction solar cell, which is better than the planar control cell.
A 2 nm low temperature GaN spacer to improve the transport properties of two-dimensional electron gas in AlGaN/InAlN/AlN/GaN heterostructures
Authors: Ding Jieqin , Wang Xiaoliang , Xiao Hongling , Wang Cuimei , Chen Hong , Bi Yang , Deng Qinwen , Zhang Jingwen , Hou Xun
Published: October 2012

AlGaN layers were grown on InAlN/AlN/GaN heterostructure with various temperatures. The two-dimensional electron gas density and mobility in heterostructure with high temperature AlGaN were deteriorated which is attributed to the reverse polarization field of AlGaN and the degradation of InAlN structural quality and surface morphology. A 2 nm low temperature GaN spacer was inserted to reduce the risk of InAlN degradation. The improved structures demonstrated an increase of two-dimensional electron gas density and mobility compared to the heterostructures without the GaN spacer, which results in the reduction of sheet resistance. Particularly, at 855 °C, an enhancement of mobility in the improved structure indicates that the heterostructure is relatively stable at this temperature. At higher temperature of 920 °C, significant increase of sheet resistance indicates a sharp degradation of InAlN quality.
Defeating the trade-off between process complexity and electrical performance with vertical zinc oxide transistors
Authors: Nelson S. F. , Levy D. H. , Tutt L. W.
Published: October 2012

Short-channel devices can show high performance, but typically have difficult processing and alignment steps. We show here a simple low-temperature process to produce sub-micrometer-channel zinc-oxide thin-film transistors. The thickness of the gate metal defines the channel length, while a combination of conformal and non-conformal depositions create the channel and electrodes. Layer-to-layer alignment is noncritical. With mobility values ten times greater than amorphous silicon, high on/off current ratios at low voltage, good yield, and good thermal sinking in operation, these vertical transistors unite the performance of metal oxide semiconductors with the advantages of short-channel devices.