bluuebunny/crossref_metadata_2025 huggingface dataset:
Observational evidence for the mechanism of the poleward propagation of zonal wind anomalies over the North Atlantic
Authors: Yuan Jiacan , Lee Sukyoung , Tan Benkui
Published: September 2012

This study examines the physical mechanisms that drive the poleward propagation of zonal‐mean flow anomalies over the North Atlantic during the boreal winter with ECMWF ERA40 reanalysis data that spans the years 1958–2001. An empirical orthogonal function (EOF) analysis is performed on the zonal wind anomalies for the North Atlantic domain. Based on time‐lag correlations between the first two EOFs, 14 poleward propagation events are identified.

A series of lagged composite calculations of the poleward propagation events reveals the following processes: midlatitude synoptic‐scale Rossby waves propagate equatorward and break when they encounter their critical latitudes in the Tropics and Subtropics; a new critical latitude is generated slightly poleward of the previous critical latitude, and the subsequent wave breaking occurs at this new critical latitude. This interaction between the wave breaking and the critical latitude drives the poleward propagation of zonal‐mean zonal wind anomaly. A comparison between the poleward propagation events and zonal index events indicates that the poleward propagation is associated with a relatively weak potential vorticity gradient over the Subtropics. These North Atlantic poleward propagation events are found to be preceded by anomalously strong transient eddy activity over the subtropical North Pacific, and by anomalously weak tropical convection over the tropical Atlantic Ocean and the Amazon. Copyright © 2012 Royal Meteorological Society
The Intersection of Service‐Learning and Moral Growth
Authors: Scott Joel H.
Published: September 2012

This chapter highlights emerging research and implications for service‐learning and moral development. Sections explore questions and considerations, including a reflective planning tool for increasing moral growth opportunities within postsecondary service‐learning environments.
Promoting Civic Engagement to Educate Institutionally for Personal and Social Responsibility
Authors: Boyd Karen D. , Brackmann Sarah
Published: September 2012

This chapter explores the components of civic engagement with the ultimate goal of increasing personal and social responsibility.
Promoting Moral Growth Through Pluralism and Social Justice Education
Authors: Stewart Dafina Lazarus
Published: September 2012

This chapter considers the role of pluralism and social justice education in promoting moral growth among college students using Rest's Four Component Model. Implications of these issues and recommendations for the promotion of moral maturity for social justice action are offered.
The Role of the Campus Professional as a Moral Mentor
Authors: Healy Margaret A. , Lancaster James M. , Liddell Debora L. , Stewart Dafina Lazarus
Published: September 2012

How can we help students and mentees aspire to be their best? Doing so does not require perfection, but it does call on us to help students engage with their imperfections while owning our own.
Providing Evidence in the Moral Domain
Authors: Cooper Diane L. , Liddell Debora L. , Davis Tiffany J. , Pasquesi Kira
Published: September 2012

In this era of increased accountability, it is important to consider how student affairs researches and assesses the outcomes of our efforts to increase moral competence. This chapter examines both qualitative and quantitative inquiry methods for measuring moral development.
Speed-Accuracy Response Models: Scoring Rules based on Response Time and Accuracy
Authors: Maris Gunter , van der Maas Han
Published: September 2012

Starting from an explicit scoring rule for time limit tasks incorporating both response time and accuracy, and a definite trade-off between speed and accuracy, a response model is derived. Since the scoring rule is interpreted as a sufficient statistic, the model belongs to the exponential family. The various marginal and conditional distributions for response accuracy and response time are derived, and it is shown how the model parameters can be estimated. The model for response accuracy is found to be the two-parameter logistic model. It is found that the time limit determines the item discrimination, and this effect is illustrated with the Amsterdam Chess Test II.
Opportunities for the CTEI: disentangling frequency and quality in evaluating
teaching behaviours
Authors: Scho¨nrock-Adema Johanna , Boendermaker Peter M. , Remmelts Pine
Published: September 2012

Students’ perceptions of teaching quality are vital for quality assurance
purposes. An increasingly used, department-independent instrument is the (Cleveland)
clinical teaching effectiveness instrument (CTEI). Although the CTEI was developed
carefully and its validity and reliability confirmed, we noted an opportunity for
improvement given an intermingling in its rating scales: the labels of the answering
scales refer to both frequency and quality of teaching behaviours. Our aim was to
investigate whether frequency and quality scores on the CTEI items differed. A sample of
112 residents anonymously completed the CTEI with separate 5-point rating scales for
frequency and quality. Differences between frequency and quality scores were analyzed
using paired t tests. Quality was, on average, rated higher than frequency, with
significant differences for ten out of 15 items. The mean scores differed significantly
in favour of quality. As the effect size was large, the difference in mean scores was
substantial. Since quality was generally rated higher than frequency, the authors
recommend distinguishing frequency from quality. This distinction helps to obtain
unambiguous outcomes, which may be conducive to providing concrete and accurate
feedback, improving faculty development and making fair decisions concerning promotion,
tenure or salary.
Disaster Curricula in Medical Education: Pilot Survey
Authors: Smith Jared , Levy Matthew J. , Hsu Edbert B. , Lee Levy J.
Published: September 2012

Introduction

An understanding of disaster medicine and the health care system during mass-casualty events is vital to a successful disaster response, and has been recommended as an integral part of the medical curriculum by the Association of American Medical Colleges (AAMC). It has been documented that medical students do not believe that they have received adequate training for responding to disasters. The purpose of this pilot study was to determine the inclusion of disaster medicine in the required course work of medical students at AAMC schools in the United States, and to identify the content areas addressed.

Methods

An electronic on-line survey was developed based upon published core competencies for health care workers, and distributed via e-mail to the education liaison for each medical school in the United States that was accredited by the AAMC. The survey included questions regarding the inclusion of disaster medicine in the medical school curricula, the type of instruction, and the content of instruction.

Results

Of the 29 (25.2%) medical schools that completed the survey, 31% incorporated disaster medicine into their medical school curricula. Of those schools that included disaster medicine in their curricula, 20.7% offered disaster material as required course work, and 17.2% offered it as elective course work. Disaster medicine topics provided at the highest frequency included pandemic influenza/severe acute respiratory syndrome (SARS, 27.5%), and principles of triage (10.3%). The disaster health competency included most frequently was the ability to recognize a potential critical event and implement actions at eight (27.5%) of the responding schools.

Conclusions

Only a small percentage of US medical schools currently include disaster medicine in their core curriculum, and even fewer medical schools have incorporated or adopted competency-based training within their disaster medicine lecture topics and curricula.

>SmithJ, LevyMJ, HsuEB, LevyJL. Disaster curricula in medical education: pilot survey. Prehosp Disaster Med.2012;27(5):1-3.
Phenological changes of oceanic phytoplankton in the 1980s and 2000s as revealed by remotely sensed ocean‐color observations
Authors: D'Ortenzio Fabrizio , Antoine David , Martinez Elodie , Ribera d'Alcalà Maurizio
Published: September 2012

We investigated the phenology of oceanic phytoplankton at large scales over two 5‐year time periods: 1979–1983 and 1998–2002. Two ocean‐color satellite data archives (Coastal Zone Color Scanner (CZCS) and Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS)) were used to investigate changes in seasonal patterns of concentration‐normalized chlorophyll. The geographic coverage was constrained by the CZCS data distribution. It was best for the Northern Hemisphere and also encompassed large areas of the Indian, South Pacific, and Equatorial Atlantic regions. For each 2° pixel, monthly climatologies were developed for satellite‐derived chlorophyll, and the resulting seasonal cycles were statistically grouped using cluster analysis. Five distinct groups of mean seasonal cycles were identified for each half‐decade period. Four types were common to both time periods and correspond to previously identified phytoplankton regimes: Bloom, Tropical, Subtropical North, and Subtropical South. Two other mean seasonal cycles, one in each of the two compared 5‐year periods, were related to transitional or intermediate states (Transitional Tropical and Transitional Bloom). Five mean seasonal cycles (Bloom, Tropical, Subtropical North, and Subtropical South, Transitional Bloom) were further confirmed when the whole SeaWiFS data set (1998–2010) was analyzed. For ∼35% of the pixels analyzed, characteristic seasonal cycles of the 1979–1983 years differed little from those of the 1998–2002 period. For ∼65% of the pixels, however, phytoplankton seasonality patterns changed markedly, especially in the Northern Hemisphere. Subtropical regions of the North Pacific and Atlantic experienced a widespread expansion of the Transitional Bloom regime, which appeared further enhanced in the climatology based on the full SeaWiFS record (1998–2010), and, as showed by a more detailed analysis, is associated to La Niña years. This spatial pattern of Transitional Bloom regime reflects a general smoothing of seasonality at macroscale, coming into an apparent greater temporal synchrony of the Northern Hemisphere. The Transitional Bloom regime is also the result of a higher variability, both in space and time. The observed change in phytoplankton dynamics may be related not only to biological interactions but also to large‐scale changes in the coupled atmosphere–ocean system. Some connections are indeed found with climate indices. Changes were observed among years belonging to opposite phases of ENSO, though discernible from the change among the two periods and within the SeaWiFS era (1998–2010). These linkages are considered preliminary at present and are worthy of further investigation.
Volume and area changes of the Milne Ice Shelf, Ellesmere Island, Nunavut, Canada, since 1950
Authors: Mortimer Colleen A. , Copland Luke , Mueller Derek R.
Published: September 2012

Ground penetrating radar (GPR) surveys of the 205 km2Milne Ice Shelf conducted in 2008 and 2009 are compared with radio echo sounding (RES) data from 1981 to provide the first direct measurements of thinning for any northern Ellesmere Island ice shelf. Our results show an average thinning for the ice shelf as a whole of 8.1 ± 2.8 m, with a maximum of >30 m, over this 28‐year period. Direct‐line comparisons along a 7.5 km transect near the front of ice shelf indicate a mean thinning of 2.63 ± 2.47 m over the same period. Reductions in areal extent (29%, 82 ± 8.4 km2: 1950–2009) and volume (13%, 1.5 ± 0.73 km3 water equivalent (w.e.): 1981–2008/2009) indicate that the Milne Ice Shelf has been in a state of negative mass balance for at least the last 59 years. A comparison of mean annual specific mass balance measurements with the nearby Ward Hunt Ice Shelf (WHIS) suggests that basal melt is a key contributor to Milne Ice Shelf thinning. Glacier inflow to the ice shelf has also reduced markedly over the past 28 years. The transition of ice shelf ice to lake ice was the most important source of mass loss. A 28.5 km2 epishelf lake now exists on the landward side of the ice shelf. Given these recent changes, disintegration of the Milne Ice Shelf will almost certainly continue in the future.
U.S. and Russia sign agreements to cooperate in Antarctica and Beringia
Authors: Showstack Randy
Published: September 2012

U.S. secretary of state Hillary Rodham Clinton and Russian foreign minister Sergey Lavrov signed a Memorandum of Understanding (MOU) for Cooperation in Antarctica and issued a Joint Statement on Pursuing a Transboundary Area of Shared Beringian Heritage, which is related to a segment of the Bering Strait, at an 8 September ceremony in Vladivostok, Russia. The Antarctica MOU strengthens cooperation and improves coordination of bilateral policies, science, logistics, search and rescue, training, and public outreach in Antarctica. “We are formally deepening our scientific cooperation in Antarctica, a continent with vast opportunities for research,” Clinton said. “Scientists from both our countries will work together to explore Antarctica's terrain, study the effects of climate change, and cooperate on a range of issues to better understand and protect our shared environment.” She added that U.S. and Russian officials and scientists will work together to enforce the 1959 Antarctic Treaty, including inspecting foreign facilities and looking for violations of the treaty and environmental commitments.
List identifies threatened ecosystems
Authors: Showstack Randy
Published: September 2012

The International Union for Conservation of Nature (IUCN) announced on 9 September that it will develop a new Red List of Ecosystems that will identify which ecosystems are vulnerable or endangered. The list, which is modeled on the group's Red List of Threatened Species™, could help to guide conservation activities and influence policy processes such as the Convention on Biological Diversity, according to the group. “We will assess the status of marine, terrestrial, freshwater, and subterranean ecosystems at local, regional, and global levels,” stated Jon Paul Rodriguez, leader of IUCN's Ecosystems Red List Thematic Group. “The assessment can then form the basis for concerted implementation action so that we can manage them sustainably if their risk of collapse is low or restore them if they are threatened and then monitor their recovery.”
“Flooding” versus “inundation”
Authors: Flick Reinhard E. , Chadwick D. Bart , Briscoe John , Harper Kristine C.
Published: September 2012

As mean sea level rise (MSLR) accelerates, it will become increasingly necessary and useful to distinguish coastal “flooding” from “inundation.” The growing number of coastal MSLR vulnerability assessments makes it clear that confused usage is abundant. We propose that the term “flooding” be used when dry areas become wet temporarily—either periodically or episodically—and that “inundation” be used to denote the process of a dry area being permanently drowned or submerged. According to these proposed defnitions, flooding is always higher than inundation, but they are fundamentally different. Flooding, including tidal flooding, is and has been dominant along open coasts. However, inundation is likely to become ever more important in the coming decades and centuries and may itself eventually become a dominant physical coastal process. Differentiating between the two will clarify and emphasize the differences between these processes.
Monsoons intensify with peak sunspot activity
Authors: Bhattacharya Atreyee
Published: September 2012

Scientists are increasingly pointing toward a strong connection between sunspots and climate, driven by what appears to be a coupled response of the atmosphere all the way from Earth's surface through the stratosphere. Sunspots are dark areas that develop temporarily on the photosphere of the Sun, and when they appear in large numbers, the surface of the Sun cools. The number of sunspots waxes and wanes approximately every 11 years. During the years with the maximum numbers of sunspots, the southeast trade winds over the equatorial region of the Pacific Ocean appear to grow stronger, and the associated major atmospheric systems, like the Hadley and Walker circulations, intensify. These changes in the tropics also influence atmospheric circulation over the northern and southern Pacific as shown in a new study by van Loon and Meehl. There is no observed connection between weather and years with low or average sunspot activity.
Mechanical behavior and localized failure modes in a porous basalt from the Azores
Authors: Loaiza S. , Fortin J. , Schubnel A. , Gueguen Y. , Vinciguerra S. , Moreira M.
Published: September 2012

Basaltic rocks are the main component of the oceanic upper crust, thus of potential interest for water and geothermal resources, storage of CO2and volcanic edifice stability. In this work, we investigated experimentally the mechanical behavior and the failure modes of a porous basalt, with an initial connected porosity of 18%. Results were acquired under triaxial compression experiments at confining pressure in the range of 25–200 MPa on water saturated samples. In addition, a purely hydrostatic test was also performed to reach the pore collapse critical pressure P*. During hydrostatic loading, our results show that the permeability is highly pressure dependent, which suggests that the permeability is mainly controlled by pre‐existing cracks. When the sample is deformed at pressure higher than the pore collapse pressure P*, some very small dilatancy develops due to microcracking, and an increase in permeability is observed. Under triaxial loading, two modes of deformation can be highlighted. At low confining pressure (Pc < 50 MPa), the samples are brittle and shear localization occurs. For confining pressure > 50 MPa, the stress‐strain curves are characterized by strain hardening and volumetric compaction. Stress drops are also observed, suggesting that compaction may be localized. The presence of compaction bands is confirmed by our microstructure analysis. In addition, the mechanical data allows us to plot the full yield surface for this porous basalt, which follows an elliptic cap as previously observed in high porosity sandstones and limestones.
Tidal variability in the mesosphere and lower thermosphere due to the El Niño–Southern Oscillation
Authors: Pedatella N. M. , Liu H.‐L.
Published: September 2012

Whole Atmosphere Community Climate Model (WACCM) simulations are used to investigate the migrating and nonmigrating tidal variability in the mesosphere and lower thermosphere (MLT) due to the El Niño–Southern Oscillation (ENSO). The most notable changes occur in the equatorial region during Northern Hemisphere winter in the diurnal migrating tide (DW1), diurnal eastward propagating nonmigrating tides with zonal wavenumbers 2 and 3 (DE2 and DE3), and the semidiurnal westward propagating nonmigrating tide with zonal wavenumber 4 (SW4). The WACCM simulations indicate that the ENSO represents a source of interannual tidal variability of ∼10–30% in the MLT. The tidal changes are attributed to changes in tropical precipitation, altered tidal propagation due to changing zonal mean zonal winds, and changes in planetary wave activity associated with the ENSO. During the El Niño phase of the ENSO the DE2 and DE3 are decreased, and the DW1 and SW4 are enhanced. The opposite response occurs during the La Niña phase of the ENSO; however, the magnitude of the tidal changes due to El Niño and La Niña are different. This is especially notable for the DE2 and DE3 which are enhanced by ∼2 K during La Niña time periods, and only reduced by ∼1 K during El Niño time periods. The results demonstrate that changing sea surface temperatures associated with the ENSO significantly impact the overall dynamics of the MLT. Our results further suggest that the ENSO is a source of significant interannual variability in the low‐latitude ionosphere and thermosphere.
Correlations among leaf traits provide a significant constraint on the estimate of global gross primary production
Authors: Wang Y. P. , Lu X. J. , Wright I. J. , Dai Y. J. , Rayner P. J. , Reich P. B.
Published: September 2012

Current estimates of gross primary productivity (GPP) of the terrestrial biosphere vary widely, from 100 to 175 Gt C year−1. Ecosystem GPP cannot be measured directly, and is commonly estimated using models. Among the many parameters in those models, three leaf parameters have strong influences on the modelled GPP: leaf mass per area, leaf lifespan and leaf nitrogen concentration. The first two parameters affect the modelled canopy leaf area and the last two determine the maximal leaf photosynthetic rate. Ecological studies have firmly established that these three parameters are significantly correlated at regional to global scales, but this knowledge is yet to be used in predicting global GPP. We hypothesize that incorporating multi‐trait covariance can reduce uncertainties of model predictions in a way likely to provide improved realism. Using the Australian community land surface model (CABLE), we find that correlations among these three parameters reduce the variance among GPP estimates by CABLE by over 20% for shrub, C4 grassland and tundra, and by between 5% and 20% for most other PFTs, as compared with the simulated GPP without considering the correlations. Globally the correlations do not alter the mean but reduce the variance of modeled GPP by CABLE by 28% and result in fewer extremely high or extremely low (and unlikely) global GPP predictions. Therefore correlations among the three leaf parameters, and possibly other parameters, can be used as a significant constraint on the estimates of model parameters or predictions by those models.
Improved prediction of quasi‐global vegetation conditions using remotely‐sensed surface soil moisture
Authors: Bolten J. D. , Crow W. T.
Published: September 2012

The added value of satellite‐based surface soil moisture retrievals for agricultural drought monitoring is assessed by calculating the lagged rank correlation between remotely‐sensed vegetation indices (VI) and soil moisture estimates obtained both before and after the assimilation of surface soil moisture retrievals derived from the Advanced Microwave Scanning Radiometer‐EOS (AMSR‐E) into a soil water balance model. Higher soil moisture/VI lag correlations imply an enhanced ability to predict future vegetation conditions using estimates of current soil moisture. Results demonstrate that the assimilation of AMSR‐E surface soil moisture retrievals substantially improve the performance of a global drought monitoring system ‐ particularly in sparsely‐instrumented areas of the world where high‐quality rainfall observations are unavailable.
Remote influences on freshwater flux variability in the Atlantic warm pool region
Authors: Zhang Liping , Wang Chunzai
Published: September 2012

The understanding of freshwater flux variability is both scientifically and socially important. Local freshwater flux response to a large Atlantic warm pool (AWP) is excessive freshwater or negative Evaporation minus Precipitation (EmP) anomalies, whereas the response is deficient to a small AWP. However, the EmP anomalies in the AWP region are also influenced by the SST anomalies in the tropical eastern Pacific and in the tropical South Atlantic. These remote influences operate through the inter‐basin mode represented by the SST gradient between the tropical North Atlantic and eastern Pacific and the Atlantic meridional mode (AMM) defined as the SST gradient between the tropical North and South Atlantic. When either of these two modes is in the negative phase, the EmP and sea surface salinity anomalies in the AWP region can be positive although the AWP is large. This indicates that the remote influences of the inter‐basin mode and/or the AMM can overwhelm the local effect and induce an opposite freshwater response. Additionally, although ENSO and the AMM sometimes coincide with AWP variability, an El Niño in the preceding winter or a positive AMM in the spring does not necessarily follow a large AWP in the summer.
VHF lightning mapping observations of a triggered lightning flash
Authors: Edens H. E. , Eack K. B. , Eastvedt E. M. , Trueblood J. J. , Winn W. P. , Krehbiel P. R. , Aulich G. D. , Hunyady S. J. , Murray W. C. , Rison W. , Behnke S. A. , Thomas R. J.
Published: September 2012

On 3 August 2010 an extensive lightning flash was triggered over Langmuir Laboratory in New Mexico. The upward positive leader propagated into the storm's midlevel negative charge region, extending over a horizontal area of 13 × 13 km and 7.5 km altitude. The storm had a normal‐polarity tripolar charge structure with upper positive charge over midlevel negative charge. Lightning Mapping Array (LMA) observations were used to estimate positive leader velocities along various branches, which were in the range of 1–3 × 104 m s−1, slower than in other studies. The upward positive leader initiated at 3.4 km altitude, but was mapped only above 4.0 km altitude after the onset of retrograde negative breakdown, indicating a change in leader propagation and VHF emissions. The observations suggest that both positive and negative breakdown produce VHF emissions that can be located by time‐of‐arrival systems, and that not all VHF emissions occurring along positive leader channels are associated with retrograde negative breakdown.
Energetics, equation of state, and elasticity of NAL phase: Potential host for alkali and aluminum in the lower mantle
Authors: Mookherjee Mainak , Karki Bijay B. , Stixrude Lars , Lithgow‐Bertelloni Carolina
Published: September 2012

The new aluminous (NAL) phase and aluminous phase with calcium ferrite (CF) structure constitutes more than 25 volume % of the deeply subducted crust at lower mantle depths. Using first principle simulations, we calculate the energetics, equation of state, and elasticity of NAL phase with a widely varying composition including CaMg2Al6O12, NaNa2Al3Si3O12 and KNa2Al3Si3O12. Our calculations indicate the relative stability of NAL and CF phases is a sensitive function of pressure, temperature, and composition, with increasing pressure tending to favor the CF phase, and increasing temperature, Mg‐content and alkali‐content tending to favor the NAL phase. The sound wave velocities of the NAL phase is significantly lower than CF phases and other major lower mantle phases. In deeply subducted MORB and CC, the faster sound velocity of silica (SiO2) and its high‐pressure polymorphic phase is likely to be compensated with the slower sound wave velocities of NAL phase.
Short large‐amplitude magnetic structures (SLAMS) at Venus
Authors: Collinson G. A. , Wilson L. B. , Sibeck D. G. , Shane N. , Zhang T. L. , Moore T. E. , Coates A. J. , Barabash S.
Published: September 2012

We present the first observation of magnetic fluctuations consistent with short large‐amplitude magnetic structures (SLAMS) in the foreshock of the planet Venus. Three monolithic magnetic field spikes were observed by theVenus Expresson 11 April 2009. The structures were ∼1.5–11 s in duration, had magnetic compression ratios between ∼3 and 6, and exhibited elliptical polarization. These characteristics are consistent with the SLAMS observed at Earth, Jupiter, and Comet Giacobini‐Zinner, and thus we hypothesize that it is possible SLAMS may be found at any celestial body with a foreshock.
Long‐term variability of mean winds in the mesosphere and lower thermosphere at low latitudes
Authors: Venkateswara Rao N. , Tsuda T. , Riggin D. M. , Gurubaran S. , Reid I. M. , Vincent R. A.
Published: September 2012

Long‐term variations of monthly mean zonal and meridional winds in the Mesosphere and Lower Thermosphere (MLT) at low‐latitudes are analyzed using four medium frequency (MF) radars and three meteor radars located in the Asia‐Oceania region. Radar data taken at close‐by latitudes are appended to construct long‐term data sets. With this, we have long‐term data from five distinct latitudes within ±22° (viz., 22°N, ∼9°N, 0–2°N, 6–7°S and 21°S). The data length varies at different latitudes and spans a maximum of two decades during 1990–2010. The zonal winds show semiannual oscillation (SAO) at all locations with westward (eastward) winds during equinoxes (solstices). The month height pattern of SAO is similar within ±9° and is different at ±22°. The westward winds in the March equinox were enhanced every two or three years during 1990–2002. We define this phenomenon as Mesospheric Quasi‐Biennial Enhancement (MQBE). Such signature is not clear after 2002. The meridional winds show annual oscillation (AO), with northward and southward winds during the December and June solstices, respectively. However, the timing at which the wind direction changes does not coincide at all latitudes. The amplitude of the AO is enhanced after 2004 and 2008 at ∼9°N and ∼7°S, respectively. Orthogonal components of SAO and AO are detected with persistent phase relation, which suggests that the zonal and meridional winds are coupled. The meridional winds show long‐term trends at latitudes of ∼9°N and ∼6–7°S, but not at other latitudes . The zonal winds do not show significant long‐term trends.
Motion of high‐latitude nighttime medium‐scale traveling ionospheric disturbances associated with auroral brightening
Authors: Shiokawa K. , Mori M. , Otsuka Y. , Oyama S. , Nozawa S.
Published: September 2012

We report for the first time the rapid oscillating motion of nighttime medium‐scale traveling ionospheric disturbances (MSTIDs) based on airglow imaging observations at Tromsø (magnetic latitude: 67.1°N), Norway on 8 December, 2009. The MSTIDs appeared in 630‐nm airglow images at 1530 UT as wave‐like structures south of Tromsø with a horizontal wavelength of ∼200 km and a phase surface of north to south. They moved eastward with velocities of 30–60 m/s. The velocity was faster in the poleward‐side of the MSTIDs, forming a northeast–southwest phase surface at later times. This phase surface direction is opposite to that of midlatitude MSTIDs. The MSTIDs show sudden oscillations and phase jump in the east–west direction with a timescale of ∼10 min at 1730 UT. The oscillations were associated with an auroral brightening observed at the poleward edge of the images and small magnetic field perturbations observed by ground magnetometers. The Doppler measurement of the 630‐nm airglow by a Fabry‐Perot interferometer at Tromsø showed a stable southeastward thermospheric wind with a velocity of ∼150 m/s. These observations indicate that the MSTID oscillations were linked to auroral electric field in the ionosphere, implying that the observed MSTIDs are ionospheric plasma structures. We suggest that the observed MSTIDs were created by atmospheric gravity waves at the beginning, left as fossil plasma structures even after the gravity wave packet dissipated in the thermosphere, moved eastward according to the background electric field driven by the F‐region dynamo, and oscillated associated with the auroral electric field.
Reconstructing the 20th century high‐resolution climate of the southeastern United States
Authors: DiNapoli Steven M. , Misra Vasubandhu
Published: September 2012

We dynamically downscale the 20th Century Reanalysis (20CR) to a 10‐km grid resolution from 1901 to 2008 over the southeastern United States and the Gulf of Mexico using the Regional Spectral Model. The downscaled data set, which we call theFlorida Climate Institute‐Florida State University Land‐Atmosphere Reanalysis for theSoutheastern United States at 10‐km resolution (FLAReS1.0), will facilitate the study of the effects of low‐frequency climate variability and major historical climate events on local hydrology and agriculture. To determine the suitability of the FLAReS1.0 downscaled data set for any subsequent applied climate studies, we compare the annual, seasonal, and diurnal variability of temperature and precipitation in the model to various observation data sets. In addition, we examine the model's depiction of several meteorological phenomena that affect the climate of the region, including extreme cold waves, summer sea breezes and associated convective activity, tropical cyclone landfalls, and midlatitude frontal systems. Our results show that temperature and precipitation variability are well‐represented by FLAReS1.0 on most time scales, although systematic biases do exist in the data. FLAReS1.0 accurately portrays some of the major weather phenomena in the region, but the severity of extreme weather events is generally underestimated. The high resolution of FLAReS1.0 makes it more suitable for local climate studies than the coarser 20CR.
Factors influencing ice formation and growth in simulations of a mixed‐phase wave cloud
Authors: Dearden C. , Connolly P. J. , Choularton T. , Field P. R. , Heymsfield A. J.
Published: September 2012

In this paper, numerical simulations of an orographically induced wave cloud sampled in‐situ during the ICE‐L (Ice in Clouds Experiment ‐ Layer clouds) field campaign are performed and compared directly against the available observations along various straight and level flight paths. The simulations are based on a detailed mixed‐phase bin microphysics model embedded within a 1‐D column framework with the latest parameterizations for heterogeneous ice nucleation and an adaptive treatment of ice crystal growth based on the evolution of crystal habit. The study focuses on the second of two clouds sampled on 16th November 2007, the in‐situ data from which exhibits some interesting and more complex microphysics than other flights from the campaign. The model is used to demonstrate the importance of both heterogeneous and homogeneous nucleation in explaining the in‐situ observations of ice crystal concentration and habit, and how the ability to isolate the influence of both nucleation mechanisms helps when quantifying active IN concentrations. The aspect ratio and density of the simulated ice crystals is shown to evolve in a manner consistent with the in‐situ observations along the flight track, particularly during the transition from the mixed‐phase region of the cloud to the ice tail dominated by homogeneous nucleation. Some additional model runs are also performed to explore how changes in IN concentration and the value of the deposition coefficient for ice affect the competition between heterogeneous and homogeneous ice formation in the wave cloud, where the Factorial Method is used to isolate and quantify the effect of such non‐linear interactions. The findings from this analysis show that the effect on homogeneous freezing rates is small, suggesting that any competition between the microphysical variables is largely overshadowed by the strong dynamical forcing of the cloud in the early stages of ice formation.
Understanding the multistate SET process in Ge-Sb-Te-based phase-change memory
Authors: Skelton J. M. , Loke D. , Lee T. H. , Elliott S. R.
Published: September 2012

Multilevel operation is a topic of much current research in the field of phase-change memory materials, representing the most feasible method for increasing memory density beyond the ultimate scaling limits of the cell size. In this work, we present a combined experimental and ab initio molecular dynamics study of the formation of intermediate states during the crystallisation of Ge2Sb2Te5 (GST). A single intermediate resistance level is formed within a narrow voltage window, and simulations suggest this consists of microscopic crystallites embedded in a bulk amorphous phase. These findings are interpreted within the framework of classical nucleation theory, and a mechanism is proposed to explain the formation of the intermediate state. Our findings suggest that it may be difficult to obtain multiple intermediate states reliably during the crystallisation of Ge2Sb2Te5 and shed light on the fundamental limitations of using this method for multilevel programming.
Unipolar behavior of asymmetrically doped strained Si0.5Ge0.5 tunneling field-effect transistors
Authors: Schmidt M. , Minamisawa R. A. , Richter S. , Schäfer A. , Buca D. , Hartmann J. M. , Zhao Q.-T. , Mantl S.
Published: September 2012

We investigate here the impact of the dopant concentration in the source and drain regions on the ambipolar behavior of band-to-band tunneling field-effect transistors with compressively strained Si0.5Ge0.5 channels grown on Si on insulator. Source and drain areas were formed by BF2+ and As+ ion implantation to doses of 1 × 1013, 1 × 1014, and 1 × 1015 cm−2. We show that the dopant concentration impacts the energy band alignment of source/drain and the channel region, and thus influences the tunneling current. The ambipolar device behavior is strongly reduced toward unipolar for source-to-drain implantation dose ratio of 100, but at the expense of the on-current, as compared to symmetric implanted devices. Moreover, our results indicate that for SiGe devices, the change of the B doping concentration has a greater impact on the tunneling currents than the variation of the As concentration.
Interference rings formation inside cellulose from a back-reflected femtosecond laser pulse
Authors: Meunier Trevor , Weck Arnaud
Published: September 2012

We report on the formation of concentric rings within the bulk of cellulose films after laser machining with high energy femtosecond laser pulses. The rings originate from an interference effect, where the front of the pulse is reflected from the back surface of the sample and interferes with its tail. Ray tracing simulations confirmed the interference and rings formation. Modification at the back surface of materials may go unnoticed and lead to undesired properties. These findings are therefore important for the ultrafast laser community interested in machining of transparent materials.
A mathematical model for void evolution in silicon by helium implantation and subsequent annealing process
Authors: Hasanuzzaman Mohammad , Haddara Yaser M. , Knights Andrew P.
Published: September 2012

We propose a physically based model that describes the diameter and the density of voids in silicon introduced via high dose helium ion implantation and subsequent annealing. The model takes into account interactions between vacancies, interstitials, small vacancy clusters, and voids. Void evolution in silicon occurs mainly by a migration and coalescence process. Various factors such as implantation energy and dose, anneal temperature, atmospheric pressure, and impurity level in silicon can influence the migration and coalescence mechanism and thus play a role in the void evolution process. Values for model parameters are consistent with known values for point defect parameters and assumed diffusion limited reaction rates. A single “fitting parameter” represents the rate of cavity migration and coalescence and is, therefore, related to surface diffusion of adatoms. Results obtained from simulations based upon the model were compared to our experimental results and to previously reported experimental results obtained over a wide range of conditions. Data from the literature included experiments with helium ion implantation energies in the range 30–300 keV, doses of 1 × 1016−1 × 1017 cm−2, subsequent annealing temperatures in the range 700–1200 °C, and annealing duration in the range 15 min–2 h. Excellent agreement is found between the simulated results and those from reported experiments. The extracted migration and coalescence rate parameter show an activation energy consistent with surface diffusivity of silicon. It shows a linear dependence on helium dose, and increases with decreased implantation energy, decreased ambient pressure, decreased substrate impurities, increased temperature ramp rate, or increased Ge fraction in cavity layer, all consistent with the proposed physical mechanism.
A fusion of the closed-shell coupled cluster singles and doubles method and valence-bond theory for bond breaking
Authors: Small David W. , Head-Gordon Martin
Published: September 2012

Closed-shell coupled cluster singles and doubles (CCSD) is among the most important of electronic-structure methods. However, it fails qualitatively when applied to molecular systems with more than two strongly correlated electrons, such as those with stretched or broken covalent bonds. We show that it is possible to modify the doubles amplitudes to obtain a closed-shell CCSD method that retains the computational cost and desirable features of standard closed-shell CCSD, e.g., correct spin symmetry, size extensivity, orbital invariance, etc., but produces greatly improved energies upon bond dissociation of multiple electron pairs; indeed, under certain conditions the dissociation energies are exact.
Alfvén's critical ionization velocity observed in high power impulse magnetron sputtering discharges
Authors: Brenning N. , Lundin D.
Published: September 2012

Azimuthally rotating dense plasma structures, spokes, have recently been detected in several high power impulse magnetron sputtering (HiPIMS) devices used for thin film deposition and surface treatment, and are thought to be important for plasma buildup, energizing of electrons, as well as cross-B transport of charged particles. In this work, the drift velocities of these spokes are shown to be strongly correlated with the critical ionization velocity, CIV, proposed by Alfvén. It is proposed as the most promising approach in combining the CIV and HiPIMS research fields is to focus on the role of spokes in the process of electron energization.
Photochemical deterioration of the organic/metal contacts in organic optoelectronic devices
Authors: Wang Qi , Williams Graeme , Tsui Ting , Aziz Hany
Published: September 2012

We study the effect of exposure to light on a wide range of organic/metal contacts that are commonly used in organic optoelectronic devices and found that irradiation by light in the visible and UV range results in a gradual deterioration in their electrical properties. This photo-induced contact degradation reduces both charge injection (i.e., from the metal to the organic layer) and charge extraction (i.e., from the organic layer to the metal). X-ray photoelectron spectroscopy (XPS) measurements reveal detectable changes in the interface characteristics after irradiation, indicating that the photo-degradation is chemical in nature. Changes in XPS characteristics after irradiation suggests a possible reduction in bonds associated with organic-metal complexes. Measurements of interfacial adhesion strength using the four-point flexure technique reveal a decrease in organic/metal adhesion in irradiated samples, consistent with a decrease in metal-organic bond density. The results shed the light on a new material degradation mechanism that appears to have a wide presence in organic/metal interfaces in general, and which likely plays a key role in limiting the stability of various organic optoelectronic devices such as organic light emitting devices, organic solar cells, and organic photo-detectors.
Nanopores in GaN by electrochemical anodization in hydrofluoric acid: Formation and mechanism
Authors: Chen Danti , Xiao Hongdi , Han Jung
Published: September 2012

We report the use of hydrofluoric acid (HF) as an electrolyte in etching and porosifying GaN. HF is found to be effective in rendering a wide range of nanoporous morphology, from curved branches to highly parallel straight pores. Under suitable conditions, the porosification proceeds at a rate greater than 100 μm/min. To elucidate the etching mechanism, cyclic voltammetry is performed, together with a parametric mapping of electrolysis variables such as the doping of GaN, the concentration of HF electrolyte, and the anodization voltage. We demonstrate that the formation of nanoporous structures is largely due to the local breakdown of the reverse-biased semiconductor junction. A quantitative agreement between the estimated width of space-charge region and the observed variation in morphology lends support to a depletion layer model developed previously in the etching of porous-Si.
Mn doping-induced structural and magnetic transformations in the antiferroelectric phase of the Bi1−xNdxFeO3 perovskites
Authors: Khomchenko V. A. , Troyanchuk I. O. , Maria T. M. R. , Karpinsky D. V. , Das S. , Amaral V. S. , Paixão J. A.
Published: September 2012

X-ray diffraction, differential scanning calorimetry, and magnetization measurements of the Bi0.825Nd0.175Fe1−yMnyO3 (y ≤ 0.3) compounds were carried out to follow the effect of Mn doping on the crystal structure and magnetic properties of the intermediate antiferroelectric and weak ferromagnetic phase of the Bi1−xNdxFeO3 perovskites. Suppression of the antipolar displacements typical of the parent B-site undoped compound followed by stabilization of the GdFeO3-type structure as well as decrease of the antipolar-to-nonpolar transition temperature were found in this series with increasing Mn content. Compositional variation of the spontaneous magnetization in the Bi0.825Nd0.175Fe1−yMnyO3 (y ≤ 0.3) system was shown to have a temperature-dependent character. At room temperature, a close to linear decrease of the spontaneous magnetization takes place with increase of the Mn content. At low temperatures, enhancement of the magnetization is observed with increasing the dopant concentration.
Vibrational effects on valence electron momentum distributions of ethylene
Authors: Watanabe Noboru , Yamazaki Masakazu , Takahashi Masahiko
Published: September 2012

We report an electron momentum spectroscopy study of vibrational effects on the electron momentum distributions for the outer valence orbitals of ethylene (C2H4). The symmetric noncoplanar (e,2e) experiment has been conducted at an impact energy of 1.2 keV. Furthermore, a theoretical method of calculating electron momentum distributions for polyatomic molecules has been developed with vibrational effects being involved. It is shown from comparisons between experiment and theory that taking into account effects of the CH2 asymmetric stretching and CH2 rocking vibrational modes of C2H4 is essential for a proper understanding of the electron momentum distribution of the 1b3g molecular orbital.
Depolarization effect in optical absorption measurements of one- and two-dimensional nanostructures
Authors: Herman Lihong H. , Kim Cheol-Joo , Wang Zenghui , Jo Moon-Ho , Park Jiwoong
Published: September 2012

We measure absolute optical absorption cross-sections of one- (1D) and two-dimensional (2D) nanostructures using a focused laser beam while varying the numerical aperture (NA) of the focusing lens. We find the optical absorption deviates at higher NA. In the high NA regime, absorption by graphene decreases from 2.2% to below 1.8%; for Ge nanowires, it decreases from an expected value by a factor of 1.2. We explain this using the depolarization effect at the focal spot and conclude that these corrections allow for accurate quantitative measurements of optical and optoelectronic processes in 1D or 2D nanostructures.
Elucidating the mechanism for indentation size-effect in dielectrics
Authors: Robinson C. R. , White K. W. , Sharma P.
Published: September 2012

Recent work presented experimental evidence of a strong elastic indentation size-effect in ferroelectric BaTiO3. The apparent elastic modulus was shown to exhibit significant stiffening with decreasing contact size and this was attributed to the phenomenon of flexoelectricity. There is however room for debate whether domain wall movement, nucleation, and related phenomena are responsible for the size-effect in BaTiO3. In this work, we present a nanoindentation study of paraelectric SrTiO3 and argue that indeed flexoelectricity rather than ferroelectric-specific effects cause the observed size dependent behavior.