bluuebunny/crossref_metadata_2025 huggingface dataset:
Onset of global instability in the flow past a circular cylinder cascade
Authors: BOPPANA V. B. L. , GAJJAR J. S. B.
Published: December 2010

The effect of blockage on the onset of instability in the two-dimensional uniform flow past a cascade of cylinders is investigated. The same techniques as those described in Gajjar & Azzam (J. Fluid Mech., vol. 520, 2004, p. 51) are used to tackle the generalized eigenvalue problem arising from a global stability analysis of the linearized disturbance equations. Results have been obtained for the various mode classes, and our results show that for the odd–even modes, which correspond to anti-phase oscillatory motion about the midplane between the cylinders and are the modes most extensively studied in the literature, the effect of blockage has a marginal influence on the critical Reynolds numbers for instability. This is in sharp contrast to results cited in many studies with a fully developed inlet flow past a cylinder placed between confining walls. We are also able to find other unstable modes and in particular for low blockage ratios, the odd–odd modes which correspond to the in-phase oscillatory motion about the midplane between the cylinders are the first to become unstable as compared with the odd–even modes, and with much lower frequencies.
Prevalence of arytenoid asymmetry in relation to vocal symptoms
Authors: Hamdan A-L , Nassar J , Ashkar J , Sibai A
Published: December 2010

Objectives:

(1) To assess the prevalence of arytenoid asymmetry during adduction, and (2) to correlate arytenoid asymmetry with vocal symptoms.

Materials and method:

The medical records and video recordings of 116 patients who presented to the voice clinic were reviewed for the presence of arytenoid asymmetry, as regards sharpening of the aryepiglottic fold angle and altered positioning of the cuneiform and corniculate cartilages.

Results:

There were 61 males and 55 females, with a mean age of 39 years and a standard deviation of 15 years. Almost one-third had a history of reflux, 25 per cent had a history of smoking and 9.6 per cent had a history of allergy. Hoarseness was the most common symptom, occurring in 42.2 per cent of patients, followed by vocal fatigue (25 per cent) and inability to project the voice. The most common type of asymmetry was corniculate asymmetry, present in 27.6 per cent of the cases and accounting for 74.39 per cent of cases. This was followed by cuneiform cartilage asymmetry, present in 15.5 per cent of cases. There was no correlation between arytenoid asymmetry and vocal symptoms, except for vocal fatigue (p = 0.038).

Conclusion:

The prevalence of arytenoid asymmetry during adduction is common. The presence of vocal symptoms such as hoarseness, breathiness, inability to project the voice and straining does not generally seem to correlate with the prevalence of arytenoid asymmetry. However, subjects with vocal fatigue are more likely to have cuneiform asymmetry.
Applying the Competition Model to bilingualism
Authors: Macwhinney Brian
Published: December 2010

This special issue brings together a set of four papers devoted to the experimental study of sentence processing by bilinguals in their second language. The basic finding reported in this research is that, in many cases, learners transfer their LI sentence processing strategies onto sentence processing in L2. Moreover, the influence of this transfer can be detected in weakened form even in fluent bilinguals who have spoken L2 for many years. In effect, these studies report on a kind of comprehension analog to “foreign accent” that first came to light during work on sentence comprehension within the framework of the Competition Model of Bates and MacWhinney (1982).
The resolution of conflicts among competing systems: A bidirectional perspective
Authors: Gass Susan M.
Published: December 2010

The present study investigates the interaction of syntax, semantics, and pragmatics from the perspective of functional constraints on sentence processing. The functionalist model of Bates and Mac-Whinney (1981a, 1987) is taken as a basis for investigating subjects' reactions to sentences in which word order, topic, and animacy are varied. Subjects were native speakers of Italian, a language which is sensitive to semantics for interpretation and English, a language which is sensitive to syntax for interpretation (Bates, McNew, MacWhinney, Devescovi, & Smith, 1982). The two native speaker groups were further subdivided in terms of second versus foreign language learners. This study focusses on the question of how learners move from one organizational system to another. It is argued that the ways in which L2 learners are able to determine the strength of dominant factors provides insights not only into the processes involved in L2 acquisition but also into the relative strength of components crosslinguistically and the strength of boundaries between linguistic and extra-linguistic information. The results suggest that in moving from a semantic-dominant language to a syntactic-dominant one, learners first become aware of the importance of the concept of word order in a second language before being able to determine the specifics of word order in that language. On the other hand, moving in the other direction (from syntactic to semantic dominance) seems to come about with greater ease. To account for these results, a prototype model of acquisition is introduced. Finally, differences between second language and foreign language-learning environments are discussed.
Processing transfer: Language-specific processing strategies as a source of interlanguage variation
Authors: Harrington Michael
Published: December 2010

A sentence interpretation experiment based on the functionalist Competition Model of speech processing (Bates & MacWhinney, 1982) was administered to three groups of university-age English L1, Japanese ESL, and Japanese L1 subjects (n = 12 per group) in an attempt to elicit evidence for (1) processing strategies characteristic of the Japanese and English L1 groups and, (2) transfer/influence of Japanese L1 strategies on the English sentence interpretations of the Japanese ESL group. Subjects selected the subject/actor of simple sentences incorporating word order, animacy, and stress cues in random converging and competing orders. The English L1 and ESL groups were tested on English sentences and the Japanese L1 group tested on Japanese sentences. The Japanese L1 interpretations were most heavily influenced by animacy cues, while the English L1 group showed a higher overall sensitivity to word order manipulations. The ESL group resembled the Japanese L1 group in reliance on animacy cues, with the exception of allowing inanimate nouns to act as subjects. While the ESL group showed greater sensitivity to word order effects than the Japanese L1 group, no “second-noun” strategy (i.e., systematically interpreting the NNV and VNN orders as left- and right-dislocated SOV and VOS orders) was evident.

Although the findings were generally consistent with previous research, the presence of contrasting response patterns in the English L1 group suggests caution in attempting to typify languages on the basis of processing strategies drawn from probablistic tendencies evident in grouped data, and leaves open the role of such processing strategy typologies as a potential source of variation in inter-language.
A critical review of the literature on social and leisure activity and wellbeing in later life
Authors: ADAMS KATHRYN BETTS , LEIBBRANDT SYLVIA , MOON HEEHYUL
Published: December 2010

An engaged lifestyle is seen as an important component of successful ageing. Many older adults with high participation in social and leisure activities report positive wellbeing, a fact that fuelled the original activity theory and that continues to influence researchers, theorists and practitioners. This study's purpose is to review the conceptualisation and measurement of activity among older adults and the associations reported in the gerontological literature between specific dimensions of activity and wellbeing. We searched published studies that focused on social and leisure activity and wellbeing, and found 42 studies in 44 articles published between 1995 and 2009. They reported from one to 13 activity domains, the majority reporting two or three, such as informal, formal and solitary, or productive versus leisure. Domains associated with subjective wellbeing, health or survival included social, leisure, productive, physical, intellectual, service and solitary activities. Informal social activity has accumulated the most evidence of an influence on wellbeing. Individual descriptors such as gender or physical functioning sometimes moderate these associations, while contextual variables such as choice, meaning or perceived quality play intervening roles. Differences in definitions and measurement make it difficult to draw inferences about this body of evidence on the associations between activity and wellbeing. Activity theory serves as shorthand for these associations, but gerontology must better integrate developmental and psychological constructs into a refined, comprehensive activity theory.
A critical review of age-related research on L2 ultimate attainment
Authors: Muñoz Carmen , Singleton David
Published: December 2010

This article addresses age-related attainment effects in second language acquisition, posing the question of whether such effects are to be explained in terms of a Critical Period with a predictable and abrupt offset point or in terms of the impact of a wider range of factors. It attempts to explore this question by focusing on four discussion points in the current debate: (i) the wide use of native-speaker behaviour as the key L2 attainment yardstick; (ii) the degree of compatibility of prevailing views regarding the notion of a critical period for L2 acquisition; (iii) the relative narrowness of much research in this area, where age of L2 onset is often regarded as the crucial if not the only critical variable; and (iv) insights relative to maturational constraints on language acquisition offered by recent brain research. The article concludes that a loosening of the association between ultimate L2 attainment research and Critical Period Hypothesis (CPH) issues would shed more light on L2 attainment in terms both of the comprehensiveness and of the acuity of the insights which would result.
Pituitary tumor-transforming gene and its binding factor in endocrine cancer
Authors: Smith Vicki E. , Franklyn Jayne A. , McCabe Christopher J.
Published: December 2010

The pituitary tumor-transforming gene (PTTG1) encodes a multifunctional protein (PTTG) that is overexpressed in numerous tumours, including pituitary, thyroid, breast and ovarian carcinomas. PTTG induces cellular transformation in vitro and tumourigenesis in vivo, and several mechanisms by which PTTG contributes to tumourigenesis have been investigated. Also known as the human securin, PTTG is involved in cell cycle regulation, controlling the segregation of sister chromatids during mitosis. This review outlines current information regarding PTTG structure, expression, regulation and function in the pathogenesis of neoplasia. Recent progress concerning the use of PTTG as a prognostic marker or therapeutic target will be considered. In addition, the PTTG binding factor (PBF), identified through its interaction with PTTG, has also been established as a proto-oncogene that is upregulated in several cancers. Current knowledge regarding PBF is outlined and its role both independently and alongside PTTG in endocrine and related cancers is discussed.
Law-making at the intersection of international environmental, humanitarian and criminal law: the issue of damage to the environment in international armed conflict
Authors: Wyatt Julian
Published: December 2010

The relationship between international environmental law and international humanitarian law, like relationships between many other subsystems of contemporary international law, has not yet been articulated. The problem of environmental damage in international armed conflict lies at the intersection of these two branches and thus provides an ideal opportunity to investigate this relationship. Rather than simply evaluating the applicable international law rules in their context, we break them into elements that we separately assess from both (international) environmental law and international humanitarian/international criminal law perspectives. By doing so, we identify how international law rules for cross-sectoral problems may appropriately combine the existing expertise and institutional strengths of simultaneously applicable branches of international law, and also discover how an evaluation of the ultimate appropriateness of the cross-sectoral rules adopted may be substantially affected by the different frames of reference that are used by those working within the different fields.
Autonomie, Fürsorge und Gerechtigkeit 1Prof. Dr. A. Rothenberger zum 65. Geburtstag gewidmet.
Authors: Höger Christoph
Published: December 2010

Was ist richtiges und gutes Handeln im Umgang mit jungen Patienten in der Kinder- und Jugendpsychiatrie? Zur Beantwortung dienen fachliche Standards, rechtliche Bestimmungen und ethische Überlegungen. Als Raster für das Erkennen und Bearbeiten ethischer Probleme und Konflikte ist der 4-Prinzipien-Ansatz von Beauchamp und Childress weit verbreitet. An Hand dieses Rasters sowie rechtlicher Bestimmungen werden die Themen Selbstbestimmung von Jugendlichen über ihre psychiatrische Behandlung, Konflikte zwischen Autonomie und Fürsorge, die bei freiheitsentziehenden Maßnahmen besonders augenscheinlich werden, und die Aufnahme von Jugendlichen auf Stationen der Erwachsenenpsychiatrie diskutiert. Der 4-Prinzipien-Ansatz liefert dafür keine allgemeingültig ableitbaren Handlungsanweisungen, sondern ermöglicht einen nachvollziehbaren Entscheidungsprozess für den Einzelfall. Die Grundsätze guten Handelns sind im Kontext der Verteilungsgerechtigkeit anzuwenden. Es lassen sich Belege finden, dass im Bereich der Kinder- und Jugendpsychiatrie dafür Priorisierungsentscheidungen bereits Realität sind.
Adolescent Suicide Attempts in Bærum, Norway, 1984–2006
Authors: Dieserud Gudrun , Gerhardsen Ragnhild M. , Van den Weghe Hanne , Corbett Karina
Published: December 2010

Background: There are presently few international studies that examine adolescents’ own experience of both triggering and the underlying reasons behind their suicide attempts. Aims: To present the rates, triggering factors, and underlying reasons for such behavior. Methods: The 23-year (1984–2006) surveillance study reported includes all general hospital-treated suicide attempters aged between 13 and 19 years (n = 254) living in the municipality of Bærum, a suburb on the outskirts of Oslo, Norway. Results: Suicide attempt rates for both sexes decreased during the period of study. The female suicide attempt rate was on average 3.5 times higher than the male rate. An average of 8.2% of the suicide attempters made a repeat attempt within the following year. Overall, the most commonly reported trigger was a relational conflict (50.2%), and the most commonly reported underlying reason was a dysfunctional family situation (43.6%), followed by mental health problems (22.8%). The main gender difference for both triggers and underlying reasons was that relational conflicts were reported significantly more often by girls than by boys as triggers (55.0% versus 32.7%), and dysfunctional family issues were reported significantly more often by girls than by boys (47.1% versus 30.8%) as underlying reasons for the attempt. Mental health problems were reported less frequently as an underlying reason by girls than boys (21.2% versus 28.8%). Conclusions: A family-oriented intervention embracing the extended family system seems warranted in a majority of the cases in our study.
Characteristics of Police Officer Suicides in the Federal Austrian Police Corps
Authors: Kapusta N. D. , Voracek M. , Etzersdorfer E. , Niederkrotenthaler T. , Dervic K. , Plener P. L. , Schneider E. , Stein C. , Sonneck G.
Published: December 2010

Background: Suicide rates among police officers may be high because of strong occupational stressors. Aims: This study examined the suicide rate and suicide characteristics among police officers in the Federal Austrian Police Force. Methods: All suicides among policemen during the period 1996–2006 were analyzed retrospectively on the basis of personalized police record files from all Austrian police departments. Information on sex, age, marital status, children, region, method and place of suicide, suicide notes, position, and length of service was extracted from these files. The general Austrian population, adjusted for sex and age composition, served as the comparison group. Results: The suicide rate among male police officers was 30.2/100,000 (SD 11.0), which was comparable to the suicide rate in the adjusted general population (30.5/100,000; SD 2.9). The female police officer suicide rate was 1.8/100,000, while the corresponding suicide rate of the adjusted female general population was 12.5/100,000 (SD 1.7). Firearms were the most frequent suicide method (77.8%), and the incidence of suicide notes was 30.8%. Conclusions: Suicide rates among police officers seem comparable to those of the age-adjusted general population. Given the healthy-worker effect, these results still suggest an increased risk of suicide among police officers. These findings should stimulate further research on stressors and risk factors for suicide among officers and should also encourage departments to increase awareness regarding suicidal signs among officers.
Intervention Studies in Suicide Prevention Research
Authors: Huisman Annemiek , Pirkis Jane , Robinson Jo
Published: December 2010

Background: Despite the growing strength of the field of suicidology, various commentators have recently noted that insufficient effort is being put into intervention research, and that this is limiting our knowledge of which suicide prevention strategies might be the most effective. Aims: To profile the types of studies currently being undertaken by suicide prevention researchers from around the world, in order to examine the relative balance between intervention studies and other types of research. Methods: We searched the abstract books from the 22nd, 23rd, and 24th Congresses of the International Association for Suicide Prevention and the 10th, 11th, and 12th European Symposia on Suicide and Suicidal Behavior (held between 2003 and 2008), and classified the abstracts in them according to a modified version of an existing taxonomy. Results: We screened 1209 abstracts and found that only 12% described intervention studies. Conclusions: We need to redouble our efforts and make intervention studies our priority if we are to combat the global problem of suicide.
Whistler propagation and modulation in the presence of nonlinear Alfvén waves
Authors: Sharma R. P. , Goldstein M. L. , Dwivedi Navin Kumar , Chauhan Prashant K.
Published: December 2010

This paper presents the modulation of whistler waves due to linear interactions between a weak whistler signal and a pump kinetic Alfvén wave (KAW) in intermediate‐β(me/mi ≪ β ≪ 1) plasmas (where β is the ratio of the ion sound speed to the Alfvén speed). As a consequence of ponderomotive nonlinearity, the pump KAW becomes filamented when its power exceeds the threshold for the filamentation instability. The periodic enhancements of the whistler amplitude occur in the locations where the beam width is narrower and are thus produced by the focusing of the whistler beam. Our results reveal that KAW has a (magnetic) power spectrum with an approximate scaling of k−5/3 (where k is ∣k∣). The amplified whistler has electric field power spectra that are steeper than k−8/3 (where k is ∣k∣). These results are consistent with recent observations by the Cluster spacecraft in the magnetotail region of the Earth's magnetosphere.
Satellite altimeter‐derived monthly discharge of the Ganga‐Brahmaputra River and its seasonal to interannual variations from 1993 to 2008
Authors: Papa Fabrice , Durand Fabien , Rossow William B. , Rahman Atiqur , Bala Sujit K.
Published: December 2010

The Ganga‐Brahmaputra accounts for ∼25% of the total amount of freshwater received by the Bay of Bengal. Using daily in situ river discharge data along with altimetry‐derived river heights, the present study aims to produce a monthly data set of altimetry‐derived Ganga‐Brahmaputra River discharge at the river mouths for 1993–2008. First, we estimate the standard error of ENVISAT‐derived water levels over the Ganga to be 0.26 m, much smaller than the range of variability of ∼7 m, and consistent with the accuracy of altimeter measurements over large rivers. We then establish rating curves between altimetry‐derived water levels and in situ river discharges and show that TOPEX‐Poseidon, ERS‐2, and ENVISAT data can successfully be used to infer Ganga and Brahmaputra discharge. The mean error on the estimated daily discharge derived from altimetry ranges from ∼15% (∼4700 m3/s) using TOPEX‐Poseidon over the Brahmaputra to ∼36% (∼9000 m3/s) using ERS‐2 over the Ganga. Combined Ganga‐Brahmaputra monthly discharges for 1993–2008 are presented, showing a mean error of ∼17% (∼2700 m3/s), within the range (15%–20%) of acceptable accuracy for discharge measurements. During 2004–2008, we assess the variability of the estimate against precipitation and river heights records. Finally, we present a basic approach to infer Ganga‐Brahmaputra monthly discharge at the river mouths. The upscaled discharge exhibits a marked interannual variability with a standard deviation in excess of ∼12,500 m3/s, much larger than the data set uncertainty. This new data set represents an unprecedented source of information to quantify continental freshwater forcing flux into Indian Ocean circulation models.
On the impacts of climate change and the upper ocean on midlatitude northwest Atlantic landfalling cyclones
Authors: Perrie William , Yao Yonghong , Zhang Weiqing
Published: December 2010

The influence of climate change on midlatitude North Atlantic landfalling autumn storms is investigated using a relatively high‐resolution mesoscale atmosphere‐ocean coupled model system. Atmospheric boundary conditions for autumn storm simulations by this coupled model system are given by the Canadian second‐generation Coupled Global Climate Model (CGCM2), following the Intergovernmental Panel on Climate Change IS92a scenario. The control and high‐CO2 boundary conditions are obtained from CGCM2 simulations representing the present climate (1975–1994), and a future climate change scenario (2040–2059), corresponding to a doubling of greenhouse gases. An understanding of the possible influences of climate change on the storm climate is achieved through our simulations. The impact of climate change is seen in slightly decreased intensities in landfalling cyclones (about 5 hPa) resulting from the competition between warming provided by the climate change scenario and modest cooling around the storm center induced mainly by dynamic cooling. An additional impact is that cyclone tracks tend to shift poleward.
Dissolved noble gas and isotopic tracers reveal vulnerability of groundwater in a small, high‐elevation catchment to predicted climate changes
Authors: Singleton Michael J. , Moran Jean E.
Published: December 2010

Noble gas concentrations and multiple isotopic tracers in groundwater and stream water at a small, high‐elevation catchment of the Sierra Nevada Mountains constrain recharge conditions and subsurface residence times of different groundwater components. We identify three sources that contribute to groundwater flow: (1) seasonal groundwater recharge with short travel times, (2) water with elevated radiogenic 4He that has experienced longer flow paths, and (3) upwelling of deep fluids that have “magmatic” helium and carbon isotope signatures. Results from our study illuminate two important aspects of the hydrological system that will have a direct impact on how this system responds to climate change: (1) recharge to the alluvial aquifer occurs primarily on the lower slopes of the catchment and is therefore sensitive to changes in snowline elevation and (2) deep groundwater in the western part of the aquifer is very young and provides very little buffering capacity. Although apparent groundwater ages indicate residence times range from less than a year to several decades, the water that recharges seasonally dominates the alluvial aquifer. Noble gas recharge temperatures are close to mean annual air temperature, and are 5°–11° higher than would be expected for direct influx of snowmelt. Excess air concentrations, indicating entrapment of air bubbles during recharge, are lower than would be expected for recharge through bedrock fractures. Instead, recharge likely occurs over vegetated areas on the lower slopes, as indicated by δ13C‐dissolved inorganic carbon values that are consistent with incorporation of CO2 from soil respiration.
Observations of the lunar impact plume from the LCROSS event
Authors: Killen R. M. , Potter A. E. , Hurley D. M. , Plymate C. , Naidu S.
Published: December 2010

We observed emission from sodium (Na) ejected from the Lunar Crater Observing and Sensing Satellite (LCROSS) impact into Cabeus Crater on October 9, 2009, using the McMath‐Pierce telescope. In our 88 km2 field of view, we saw on the order of 2 g of Na in the first 9 minutes after the LCROSS impact. A comparison of our observed Na above the limb with simulations that assume a gas temperature of 1000 K indicates that 0.5 − 2.6 (1.5 ± 1) kg of Na were released during the LCROSS impact. Lower temperatures would result in a lower total sodium release. The model of an isotropic expanding cloud best reproduces the observations.
Influence of eddy‐driven jet latitude on North Atlantic jet persistence and blocking frequency in CMIP3 integrations
Authors: Barnes Elizabeth A. , Hartmann Dennis L.
Published: December 2010

The distribution of daily North Atlantic jet latitude is analyzed in 45 CMIP3 integrations. It is demonstrated that models that place the jet equatorward of its observed position have more positively skewed jet latitude distributions, while models that correctly place the jet have symmetric distributions like that of the observations. The jet is shown to be more persistent at equatorward latitudes compared to poleward latitudes, consistent with previous findings in the Southern Hemisphere. There is a robust decrease in annual blocking frequency as the jet shifts poleward with global warming, with larger decreases seen for models with larger jet shifts, consistent with the effect of latitude on jet persistence. These results imply that model biases of jet latitude of 1°–2° could result in large differences in jet variability and frequency of extreme events predicted for the future.
Wave properties in the magnetic reconnection diffusion region with high β: Application of the k‐filtering method to Cluster multispacecraft data
Authors: Huang S. Y. , Zhou M. , Sahraoui F. , Deng X. H. , Pang Y. , Yuan Z. G. , Wei Q. , Wang J. F. , Zhou X. M.
Published: December 2010

Magnetic reconnection is a crucial physical process in laboratory and astrophysical plasmas. Plasma waves are believed to provide the dissipation mechanism in magnetic reconnection. In this paper we analyze the properties of low‐frequency waves in a magnetotail reconnection diffusion region with a small guide field and high β. Using the k‐filtering method on the magnetic field data measured by Cluster spacecraft, we found that low‐frequency waves in the diffusion region were highly oblique propagating mode. We compared the measured dispersion relation with theoretical ones calculated using the linear (hot) two‐fluid and Vlasov‐Maxwell theory. It is found that the observed waves in the diffusion region (with high plasma β) follow the dispersion relation of the Alfvén‐Whistler wave mode. Comparisons with previous simulations and observational results are also discussed.
On equatorial spread F: Establishing a seeding hypothesis
Authors: Tsunoda Roland T.
Published: December 2010

A comprehensive explanation for the complex climatology of the so‐called equatorial spread F (ESF) has eluded researchers for more than 70 years. Recently, however, a seeding hypothesis has been proposed, which appears to provide the final major piece of this puzzle. The hypothesis is based on the discovery that a direct link exists between regions of deep convective activity in the troposphere, where atmospheric gravity waves (GWs) are spawned, and the occurrence frequency of ESF during solstices. The objective here is to answer two questions that may impede the general acceptance of this hypothesis. We first show why seed plasma perturbations should develop from GW‐driven neutral‐wind perturbations, but only when the GW source region is located very close to the magnetic dip equator. We then reexamine this relationship using a data set on GW source regions that is better matched (in time and longitudinal coverage), than that used previously, to the data set on ESF activity used by Tsunoda (2010a). We conclude that seeding is indeed playing an important role in the development of ESF.
Ground‐based estimates of outer radiation belt energetic electron precipitation fluxes into the atmosphere
Authors: Clilverd Mark A. , Rodger Craig J. , Gamble Rory J. , Ulich Thomas , Raita Tero , Seppälä Annika , Green Janet C. , Thomson Neil R. , Sauvaud Jean‐André , Parrot Michel
Published: December 2010

AARDDVARK data from a radio wave receiver in Sodankylä, Finland have been used to monitor transmissions across the auroral oval and just into the polar cap from the very low frequency communications transmitter, call sign NAA (24.0 kHz, 44°N, 67°W, L = 2.9), in Maine, USA, since 2004. The transmissions are influenced by outer radiation belt (L = 3–7) energetic electron precipitation. In this study, we have been able to show that the observed transmission amplitude variations can be used to determine routinely the flux of energetic electrons entering the upper atmosphere along the total path and between 30 and 90 km. Our analysis of the NAA observations shows that electron precipitation fluxes can vary by 3 orders of magnitude during geomagnetic storms. Typically when averaging over L = 3–7 we find that the >100 keV POES “trapped” fluxes peak at about 106 el. cm−2 s−1 sr−1 during geomagnetic storms, with the DEMETER >100 keV drift loss cone showing peak fluxes of 105 el. cm−2 s−1 sr−1, and both the POES >100 keV “loss” fluxes and the NAA ground‐based >100 keV precipitation fluxes showing peaks of ∼104 el. cm−2 s−1 sr−1. During a geomagnetic storm in July 2005, there were systematic MLT variations in the fluxes observed: electron precipitation flux in the midnight sector (22–06 MLT) exceeded the fluxes from the morning side (0330–1130 MLT) and also from the afternoon sector (1130–1930 MLT). The analysis of NAA amplitude variability has the potential of providing a detailed, near real‐time, picture of energetic electron precipitation fluxes from the outer radiation belts.
Acceleration of suprathermal particles by compressional plasma wave trains in the solar wind
Authors: Zhang Ming
Published: December 2010

This paper presents a calculation of particle acceleration by an idealized compressional plasma wave train. In this model, suprathermal particles, such as pickup ions, are continuously injected into a wave train consisting of a series of compression or rarefaction regions. The momentum distribution of particles will become broader and broader as they go through the wave train, which is very similar to diffusion in momentum space. The acceleration process is very fast: it does not take too many wave cycles even with a small compression amplitude to reach an asymptotic steady state momentum distribution. In the absence of large‐scale adiabatic cooling, the asymptotic distribution is flat below the initial injection momentum, and above the injection momentum, it is proportional to a power law distribution with the slope of −3. This distribution appears to be independent of any model parameters in this acceleration mechanism. If there is a prevailing large‐scale adiabatic cooling by the expanding solar wind, the asymptotic steady state distribution remains to be flat below the injection momentum and it is a power law distribution but with a steeper slope above the injection momentum. The acceleration process alone does not automatically guarantee a p−5 power law. However, since the process can quickly build up pressure from the accelerated particles, it is expected that the amplitude of compressional plasma wave will be reduced. In the final state after nonlinear wave‐particle interactions, the distribution of accelerated particles and plasma wave must achieve a balance between large‐scale adiabatic cooling and the acceleration by compressional plasma waves. The particle distribution at the equilibrium will settle with a p−5 distribution given that the initial solar wind pressure is much larger than the initial pressure of newly injected particles.
Effects of nightside O+ outflow on magnetospheric dynamics: Results of multifluid MHD modeling
Authors: Garcia K. S. , Merkin V. G. , Hughes W. J.
Published: December 2010

Through spacecraft observations and numerical modeling, it is becoming increasingly well established that ionospheric oxygen is present in the magnetosphere in amounts that can have an effect on magnetospheric dynamics, affecting pressure balance, currents, convection flows, and cross polar cap potential (CPCP). However, an understanding of the various processes through which oxygen may bring about changes in magnetospheric structure and dynamics is still lacking. In this paper, we focus on the role that ionospheric oxygen outflow from the nightside auroral zone plays in determining plasma sheet density, size, and pressure and relate the changes in plasma sheet parameters to changes in CPCP, tail geometry, and magnetospheric convection. We use the Multifluid Lyon‐Fedder‐Mobarry model as a virtual laboratory to analyze the effects of ionospheric oxygen on magnetospheric parameters. Our simulations use idealized solar wind conditions, constant and uniform ionospheric conductance, and constant nightside oxygen outflow in order to isolate the effects of a change in outflow flux. We concentrate the ionospheric outflow in the nightside auroral region, so as to avoid the possibility of directly loading the distant tail X line with oxygen and hence to avoid a direct modification of the reconnection rate in order to focus on effects within the magnetosphere. We show that the presence of O+ outflowing from an isolated patch in the nightside auroral zone increases plasma sheet density and thermal pressure, slows convection, decreases the polar cap potential, and increases the length and width of the nightside magnetosphere. We determine that ionospheric O+ mass loading can play a significant role but that strong effects on magnetospheric dynamics require a nightside flux that significantly exceeds statistical observed levels. A more realistic outflow would include both dayside and nightside sources whose total combined flux would be similar to the total fluxes used here.
Contrasting the efficiency of radiation belt losses caused by ducted and nonducted whistler‐mode waves from ground‐based transmitters
Authors: Rodger Craig J. , Carson Bonar R. , Cummer Steven A. , Gamble Rory J. , Clilverd Mark A. , Green Janet C. , Sauvaud Jean‐André , Parrot Michel , Berthelier Jean‐Jacques
Published: December 2010

It has long been recognized that whistler‐mode waves can be trapped in plasmaspheric whistler ducts which guide the waves. For nonguided cases these waves are said to be “nonducted”, which is dominant for L < 1.6. Wave‐particle interactions are affected by the wave being ducted or nonducted. In the field‐aligned ducted case, first‐order cyclotron resonance is dominant, whereas nonducted interactions open up a much wider range of energies through equatorial and off‐equatorial resonance. There is conflicting information as to whether the most significant particle loss processes are driven by ducted or nonducted waves. In this study we use loss cone observations from the DEMETER and POES low‐altitude satellites to focus on electron losses driven by powerful VLF communications transmitters. Both satellites confirm that there are well‐defined enhancements in the flux of electrons in the drift loss cone due to ducted transmissions from the powerful transmitter with call sign NWC. Typically, ∼80% of DEMETER nighttime orbits to the east of NWC show electron flux enhancements in the drift loss cone, spanning a L range consistent with first‐order cyclotron theory, and inconsistent with nonducted resonances. In contrast, ∼1% or less of nonducted transmissions originate from NPM‐generated electron flux enhancements. While the waves originating from these two transmitters have been predicted to lead to similar levels of pitch angle scattering, we find that the enhancements from NPM are at least 50 times smaller than those from NWC. This suggests that lower‐latitude, nonducted VLF waves are much less effective in driving radiation belt pitch angle scattering.
Characteristics of Jovian ionospheric Alfvén resonator observed by using wave modulations of L‐burst emissions
Authors: Koshida T. , Shibata T. F. , Taguchi S. , Misawa H.
Published: December 2010

On 4 June 2008 UT, the position of the satellite Io with respect to Jupiter was the so‐called Io‐A, we observed Jovian decametric (DAM) radio emissions using a waveform receiver (WFR) and detected wave modulations (WMs) in the DAM emissions. WMs appeared four times at intervals of approximately 7 min for durations of 3–10 s each. We found that the WMs had fundamental frequencies of 2.5–5 Hz, and the 1st and 2nd harmonics of these frequencies were odd resonances at the fundamental frequencies. Simulations confirmed that strong Alfvén waves arrive at the polar regions of Jupiter at 5–7 min intervals when Io is located at the center of the Io plasma torus, and Io was located at that location when WMs were detected. The 7 min intervals of WMs are consistent with the characteristic periods of Alfvén waves, suggesting the existence of the ionospheric Alfvén resonator (IAR) expected in the system of Jupiter. Thus far, few observations have suggested the existence of IAR in Jupiter. In this research, we suggest the existence of IAR in Jupiter by using a WFR and the millisecond modulations of Jovian L‐burst emissions.
Silicon self‐diffusion of MgSiO3 perovskite by molecular dynamics and its implication for lower mantle rheology
Authors: Ito Yosuke , Toriumi Mitsuhiro
Published: December 2010

The pressure effect of silicon self‐diffusion of MgSiO3 perovskite was investigated by molecular dynamics (MD). The viscosity variation of MgSiO3 perovskite in the lower mantle was derived by the Nabarro‐Herring (Herring‐Nabarro) model. For the MD calculation, the spontaneous jumping of atoms by self‐diffusion was reproduced without using artificial forces, and the consistency of migration enthalpy (Hm*) with experimental data was improved. The results showed that migration enthalpy increases monotonically with increasing pressure. The viscosity of MgSiO3 perovskite in the lower mantle increases monotonically with increasing depth. The obtained depth profile is distinguishable from that of MgO periclase and can be utilized to determine which mineral dominates the lower mantle rheology. Depending upon the assumed shape of the depth profile for lower mantle viscosity, we considered the dominant mineral as (1) MgSiO3 perovskite for the monotonic shape case or (2) MgO periclase for the hill shape case that has the highest‐viscosity zone in the middle of the lower mantle.
Rotationally acceptable ocean tide models for determining the response of the oceans to atmospheric pressure fluctuations
Authors: Dickman S. R.
Published: December 2010

Suitably generalized, ocean tide models can be used to determine the oceans' response to atmospheric pressure forcing; but the huge range of spatial and temporal scales of that forcing limits the relevance of state‐of‐the‐art tide modeling techniques, like data assimilation, for such determinations. With an interest in its effects on Earth's rotation, in 1998 I employed a generalized but non‐assimilating spherical harmonic tide model to determine the oceanic response to pressure forcing, however restricting its application to time scales exceeding a few days. This article revisits that spherical harmonic model in an attempt to improve its rotational predictions of short‐period tides. We find that increasing the resolution of the model ocean does not by itself affect the tidal solution much, but varying the model's frictional parameters can produce diurnal tides whose effects on Earth's polar motion are similar to those of a variety of other ocean tide models. Such an improved model will allow our calculations of the oceans' dynamic response to pressure forcing, and the effects of that response on Earth's rotation, to be extended down to diurnal time scales.
Backscattering ratio variation and its implications for studying particle composition: A case study in Yellow and East China seas
Authors: Zhang Minwei , Tang Junwu , Song Qingjun , Dong Qing
Published: December 2010

Using in situ optical measurements collected during the 2003 spring cruise over the Yellow and East China seas, the particle backscattering ratio is calculated and spectral variability is analyzed by means of geometric mean regression. The analysis shows that the particle backscattering ratio can be regarded as wavelength‐independent in the range of 442–676 nm, given the measurement uncertainties associated with the backscattering and scattering data. The backscattering ratio and attenuation measurements are used to calculate the particle refractive index, which is related to the particle composition. The distributions of the particle refractive index and the water component concentration along two transects suggest the feasibility for studying the particle composition.
Impact on quantitative precipitation forecasts of 4D‐Var rainfall data assimilation with a modified digital filter in favor of mesoscale gravity waves: A case study
Authors: Peng Shiqiu , Zou Xiaolei
Published: December 2010

A modified digital filter in favor of mesoscale gravity waves was developed and applied to a real case study of rainfall assimilation using the four‐dimensional variation data assimilation (4D‐Var) approach. The results show that the rainfall assimilation experiment with the modified digital filter produced further improvements in quantitative precipitation forecasts compared with the rainfall assimilation experiment with a regular digital filter. Spectral analysis confirms that the mesoscale gravity waves were intensified not only within the rainfall assimilation window during which the modified digital filter was applied but also beyond the assimilation window. The gravity wave–induced vertical motions along the direction of wave propagation were also intensified, resulting in a more realistic time evolution of the precipitation pattern. It is also found that the assimilation of 6 h accumulated rainfall outperformed the assimilation of hourly rainfall within the same 6 h window.
Orographic signature on multiscale statistics of extreme rainfall: A storm‐scale study
Authors: Ebtehaj Mohammad , Foufoula‐Georgiou Efi
Published: December 2010

Rainfall intensity and spatiotemporal patterns often show a strong dependence on the underlying terrain. The main objective of this work is to study the statistical signature imprinted by orography on the spatial structure of rainfall and its temporal evolution at multiple scales, with the aim of developing a consistent theoretical basis for conditional downscaling of precipitation given the topographic information of the underlying terrain. The results of an extensive analysis of the high‐resolution stage II Doppler radar data of the Rapidan storm, June 1995, over the Appalachian Mountains is reported in this study. The orographic signature on the elementary statistical structure of the precipitation fields is studied via a variable‐intensity thresholding scheme. This signature is further explored at multiple scales via analysis of the dependence of precipitation fields on the underlying terrain both in Fourier and wavelet domains. The generalized normal distribution is found to be a suitable probability model to explain the variability of the rainfall wavelet coefficients and its dependence on the underlying elevations. These results provide a new perspective for more accurate statistical downscaling of orographic precipitation over complex terrain with emphasis on preservation of extremes.
Diurnal cycle of the Intertropical Convergence Zone in the east Pacific
Authors: Bain C. L. , Magnusdottir G. , Smyth P. , Stern H.
Published: December 2010

A data set of Intertropical Convergence Zone (ITCZ) extent and location in the eastern Pacific, 90°W–180°W, 0°N–25°N, is used to examine the diurnal cycle of cloudiness over the ocean. The data set was generated using a statistical model which utilizes 30 year, 3‐hourly infrared (IR) satellite data from 1980 to 2009. The ITCZ envelope of convection has a significant diurnal cycle across the whole domain, and the area of cloudiness “pulses” in extent, peaking in the afternoon. The diurnal cycle of brightness temperatures within the ITCZ changes from east to west, but generally there are two minima in mean IR, implying cold cloud is at a peak: one in the morning, 0600–0900 LST, and another in the afternoon, 1300–1600 LST. Decomposition of cloud top temperatures show that high cloud is at a maximum in the early morning and midlevel cloud peaks in the afternoon. Low cloud is at a maximum in the late evening (2200–0000 LST) and is immediately followed by increases in high cloud, suggesting that the deepest convective systems grow rapidly, within a few hours overnight. There are seasonal changes in the diurnal cycle of cloud top temperature, and it is suggested that colder mean temperatures are more likely in the afternoon when the ITCZ is more extensive. This is shown via seasonal changes and also by comparing El Niño years, when ITCZ is more present, to La Niña years.
Elastic response of floating glacier ice to impact of long‐period ocean waves
Authors: Sergienko O. V.
Published: December 2010

Disintegration of ice shelves along the Antarctic Peninsula over the past two decades has clearly demonstrated their high sensitivity to recent changes in the local thermal regime of the atmosphere and ocean and has given rise to the question of whether mechanical coupling with waves in the ocean may provide the triggering mechanism that starts collapse events. Motivated by these events, this study considers a more general question: how ocean waves affect the stress regime of floating ice, and in particular, how ocean waves can influence the creation of fractures and its fatiguing that may lead to breakup and collapse. A new treatment of ice shelf/ocean wave interaction in which the typical “thin plate” approximation is relaxed is presented here, and exact, analytic solutions describing ice shelf stresses induced by long (>60 s period) ocean waves in various idealized ice/ocean geometries are derived. The numerical calculations demonstrate that the amplitudes of the wave‐induced stresses are sufficiently large to initiate top to bottom crevasse penetration through the depth of the ice shelf. The cyclic nature of the wave‐induced stresses contributes to ice fatigue and damage that is also a precursor to ice shelf disintegration. Although primarily theoretical, the results of the present analysis suggest that ocean waves could be a potential trigger of ice shelf collapse as well as less dramatic, but equally important, episodic calving.