bluuebunny/crossref_metadata_2025 huggingface dataset:
Regionally specific alterations in functional connectivity of the anterior cingulate cortex in major depressive disorder
Authors: Davey C. G. , Harrison B. J. , Yücel M. , Allen N. B.
Published: March 2012

Background

Depression has been associated with functional alterations in several areas of the cingulate cortex. In this study we have taken a systematic approach to examining how alterations in functional connectivity vary across the functionally diverse subregions of the rostral cingulate cortex.

Method

Eighteen patients with major depressive disorder, aged 15 to 24 years, were matched with 20 healthy control participants. Using resting-state functional connectivity magnetic resonance imaging (fcMRI), we systematically investigated the functional connectivity of four subregions of the rostral cingulate cortex. Voxelwise statistical maps of each subregion's connectivity with other brain areas were compared between the patient and control groups.

Results

The depressed participants showed altered patterns of connectivity with ventral cingulate subregions. They showed increased connectivity between subgenual anterior cingulate cortex (ACC) and dorsomedial frontal cortex, with connectivity strength showing positive correlation with illness severity. Depressed participants also showed increased connectivity between pregenual ACC and left dorsolateral frontal cortex, and decreased connectivity between pregenual ACC and the caudate nucleus bilaterally.

Conclusions

The results reinforce the importance of subgenual ACC for depression, and show a close link between brain regions that support self-related processes and affective visceromotor function. The pregenual ACC also has an important role, with its increased connectivity with dorsolateral frontal cortex suggesting heightened cognitive regulation of affect; and reduced connectivity with the caudate nucleus potentially underlying symptoms such as anhedonia, reduced motivation and psychomotor dysfunction.
Childhood bullying and the association with psychosis in non-clinical and clinical samples: a review and meta-analysis
Authors: van Dam D. S. , van der Ven E. , Velthorst E. , Selten J. P. , Morgan C. , de Haan L.
Published: March 2012

Background

Approximately 11% of schoolchildren are bullied on a regular basis. It has been argued that continuous exposure to stress is related to the development of psychotic symptoms. The current study sought to investigate whether being bullied in childhood is related to the development of psychotic symptoms.

Method

A search of PubMed, PsycINFO and EMBASE was conducted. The reference lists of included papers were searched to identify other eligible papers. A meta-analysis was performed on a subgroup of studies.

Results

We found four clinical and 10 general population studies that met inclusion criteria. The results of the clinical studies were mixed. However, the results of the non-clinical studies provided more consistent evidence that school bullying is related to the development of non-clinical psychotic symptoms. Stronger associations were found with increased frequency and severity and longer duration of being bullied. We performed a meta-analysis on seven population-based studies, yielding unadjusted and adjusted odds ratios (ORs) of 2.7 [95% confidence interval (CI) 2.1–3.6] and 2.3 (95% CI 1.5–3.4) respectively.

Conclusions

Although there is some evidence of an association between bullying and psychosis in clinical samples, the research is too sparse to draw any firm conclusions. However, population-based non-clinical studies support the role of bullying in the development of psychotic symptoms later in life. These findings are consistent with findings of an increased risk of psychotic symptoms among those exposed to other types of abuse.
Fundamental difference between picosecond and nanosecond laser interaction with plasmas: Ultrahigh plasma block acceleration links with electron collective ion acceleration of ultra-thin foils
Authors: Hora Heinrich
Published: March 2012

Arguments are discussed on how ion energy measurements from ultra-thin diamond irradiation with 45 fs laser pulses of 26 terawatt power may be related to the ultra-high acceleration of plasma blocks where the significance of the highly efficient direct conversion of laser radiation into mechanical motion of ions or plasma blocks is dominated by nonlinear (ponderomotive) forces in fundamental contrast to thermo-kinetic dominated interaction with ns laser pulses.
A new threat for the globally Endangered Hooded GrebePodiceps gallardoi: the American minkNeovison vison.
Authors: ROESLER IGNACIO , IMBERTI SANTIAGO , CASAÑAS HERNÁN , VOLPE NOELIA
Published: March 2012

The Hooded GrebePodiceps gallardoihas been uplisted to globally ‘Endangered’ recently mainly because of the rapid population decline suffered within the last 20 years due to factors such as nest depredation by Kelp GullLarus dominicanusas well as destruction of colonies by wind and lake desiccation. During a census of Hooded Grebes during the 2010/2011 breeding season we found a new predator that has not previously been mentioned, the American minkNeovison vison. One individual mink killed 33 Hooded Grebes and consequently destroyed one of the five colonies found in that breeding season. Due to the characteristics of the waterbird assemblage in the area, the impact of mink could be catastrophic.
Seabird conservation status, threats and priority actions: a global assessment
Authors: CROXALL JOHN P. , BUTCHART STUART H. M. , LASCELLES BEN , STATTERSFIELD ALISON J. , SULLIVAN BEN , SYMES ANDY , TAYLOR PHIL
Published: March 2012

We review the conservation status of, and threats to, all 346 species of seabirds, based on BirdLife International’s data and assessments for the 2010 IUCN Red List. We show that overall, seabirds are more threatened than other comparable groups of birds and that their status has deteriorated faster over recent decades. The principal current threats at sea are posed by commercial fisheries (through competition and mortality on fishing gear) and pollution, whereas on land, alien invasive predators, habitat degradation and human disturbance are the main threats. Direct exploitation remains a problem for some species both at sea and ashore. The priority actions needed involve: a) formal and effective site protection, especially for Important Bird Area (IBA) breeding sites and for marine IBA feeding and aggregation sites, as part of national, regional and global networks of Marine Protected Areas; b) removal of invasive, especially predatory, alien species (a list of priority sites is provided), as part of habitat and species recovery initiatives; and c) reduction of bycatch to negligible levels, as part of comprehensive implementation of ecosystem approaches to fisheries. The main knowledge gaps and research priorities relate to the three topics above but new work is needed on impacts of aquaculture, energy generation operations and climate change (especially effects on the distribution of prey species and rise in sea level). We summarise the relevant national and international jurisdictional responsibilities, especially in relation to endemic and globally threatened species.
ACTIVE Cognitive Training and Rates of Incident Dementia
Authors: Unverzagt Frederick W. , Guey Lin T. , Jones Richard N. , Marsiske Michael , King Jonathan W. , Wadley Virginia G. , Crowe Michael , Rebok George W. , Tennstedt Sharon L.
Published: March 2012

Systematic cognitive training produces long-term improvement in cognitive function and less difficulty in performing activities of daily living. We examined whether cognitive training was associated with reduced rate of incident dementia. Participants were from the Advanced Cognitive Training for Independent and Vital Elderly (ACTIVE) study (n = 2,802). Incident dementia was defined using a combination of interview- and performance-based methods. Survival analysis was used to determine if ACTIVE treatment affected the rate of incident dementia during 5 years of follow-up. A total of 189 participants met criteria for incident dementia. Baseline factors predictive of incident dementia were older age, male gender, African American race, fewer years of education, relationship other than married, no alcohol use, worse MMSE, worse SF-36 physical functioning, higher depressive symptomatology, diabetes, and stroke (all p < .05). A multivariable model with significant predictors of incident dementia and training group revealed that cognitive training was not associated with a lower rate of incident dementia. Cognitive training did not affect rates of incident dementia after 5 years of follow-up. Longer follow-up or enhanced training may be needed to fully explore the preventive capacity of cognitive training in forestalling onset of dementia. (JINS, 2012, 18, 1–9)
Emission taxes when pollution depends on location
Authors: Marrouch Walid , Sinclair-Desgagné Bernard
Published: March 2012

It is well known that an efficient pollution taxation scheme should charge each source according to its specific marginal contribution to social damages. Despite significant advances in environmental assessment, geographic information systems and data analysis, this requirement would impose technical, informational and administrative expenses that most regulators – notably in developing countries – seem unable to afford. This paper shows that it can actually be less demanding than it seems. If polluters are price-takers, for instance, in a context where the affected population concentrates at a given location, then the optimal emission tax will disregard a source's location. Otherwise, the adjustment of the optimal tax to location will depend on the extent of a polluter's market power.
Buddhist Responses to Brāhmaṇa Challenges in Medieval India: Bodhgayā and Gayā
Authors: AMAR ABHISHEK S.
Published: March 2012

The sixth to twelfth centuries of the common era were marked by intense religious activity in all parts of India. In the Paramāra kingdom – the main focus of the articles in this special issue – the dominant religious forces were Jainism and the Śaiva traditions of Hinduism. While Buddhism was certainly present in central India, archaeological remains, inscriptions and post-medieval narratives suggest its role was much diminished compared to the early historic period. In substantial contrast, Buddhism remained a vibrant force in eastern India. Bodhgayā, as the site of the Buddha's enlightenment, had emerged as a sacred place by the time of Aśoka in the third century BCE and it evolved subsequently into one of the key centres of the Buddhist world. This importance is attested by existing remains at the site, including the Mahābodhi temple, monastic ruins and innumerable sculptures from medieval times.
Raṇasiṃha Revisited: A New Copper-plate Inscription of the Candrāvatī Paramāra Dynasty
Authors: BALOGH DÁNIEL
Published: March 2012

This copperplate charter of Raṇasiṃha came to my attention in the spring of 2008 when I was asked to study and translate the inscription. The plates are presently in a private collection and the direct study of the inscription has not been possible. Nonetheless, good quality digital photographs of the plates were made available to me and these form the basis of the present article.
Introduction: Medieval India and the Paramāra Dynasty
Authors: WILLIS MICHAEL , HARDY ADAM
Published: March 2012

This collection of essays focuses on the history, literary culture and legacy of the Paramāra dynasty. Ruling from central India, with collateral branches of the family at Candrāvatī, Vāgaḍa, Bhinmāl and Jālor, the Paramāras constituted an important force in the Indian medieval world. They flourished between the tenth and twelfth centuries and throughout their history entertained high political ambitions. In particular Vākpati Muñja (circa 973–95) and Bhoja (circa 1000–55) undertook military campaigns that sought to establish the Paramāras as a paramount power in India. Although frustrated in these aims, they are remembered nonetheless as a great dynasty, representative if not paradigmatic of the vibrant civilisation of the late medieval age.
Interpreting the History of the Paramāras
Authors: SINGH ARVIND K.
Published: March 2012

The opening essay in this special issue by Daud Ali surveys the historiography of the medieval and touches on some of the key problems of interpretation and periodisation in Indian history. However, Ali's paper does not address the Paramāras of central India and their part in building a strong kingdom in the heart of the country for several centuries. Because an introduction to the dynasty's history is essential for situating the articles that follow, this paper will survey the leading role played by the Paramāras in the history of India over the four hundred years of their political existence. This paper also provides an opportunity to contextualise the three Royal Asiatic Society copper-plates of the Paramāra dynasty now kept in the British Museum; they are illustrated in the pages that follow (Figs 1–3).
Dhār, Bhoja and Sarasvatī: from Indology to Political Mythology and Back
Authors: WILLIS MICHAEL
Published: March 2012

The Bhojśālā or ‘Hall of Bhoja’ is a term used to describe the centre for Sanskrit studies associated with King Bhoja, the most celebrated ruler of the Paramāra dynasty. The Bhojśālā is also linked to Sarasvatī – the goddess of learning – whose shrine is said to have stood in the hall's precinct. Since the early years of the twentieth century, the mosque adjacent to the tomb of Kamāl al-Dīn Chishtī in the town of Dhār has been identified as the Bhojśālā. This has turned the building into a focal point of religious, social and political tension. Access to the site, currently under the protection of the Archaeological Survey of India, has been marked by communal friction and disputes in the press and in the courts. My aim in this paper is not to chart this sorry tale of events; I only need note that the legal and political wrangles, not to mention a steady flow of inflammatory assertions, have formed a toxic backdrop to the scholarly publications cited in the pages that follow. A second issue beyond the scope of this paper is how the medieval history of Dhār has played its part in the wider ‘invention of tradition’ and formation of modern Hindu identity. Stepping back from these concerns, my ambition here is rather modest: I seek only to explore how the mosque at Dhār has come to be described as the Bhojśālā and, on this basis, to undertake an assessment of that identification. Along the way, I will touch on a number of problems concerning the history, architecture and literary culture of central India.
Foreword
Authors: Krech Volkhard
Published: March 2012

Since the time of Edward Said and Talal Asad, if not before, we have known that the Western view of ‘the Orient’ – from the Near East to Japan – is an intellectual and cultural construct. In addition, the ‘Christian occident’ has been used, and is still used, as a politically charged term. Analogous to ‘Orientalism’, ‘Occidentalism’ has become the focus of considerable debate. The geopolitical consequences of this confrontation seem obvious and culminate in Samuel Huntington's thesis of a ‘Clash of Civilisations’ based on essentialised religious differences. But the concepts of ‘Orient’ and ‘Occident’ are not, and have never been, homogenous. Nor have they been formed, nor do they continue to evolve, without mutual interaction. The global interdependence we witness today – often labelled ‘globalisation’ – is nothing new and in actual fact has its origin in the formative phases of the major cultural and religious traditions.
Zumthor's hairy paradise
Authors: Mallinson Helen
Published: March 2012

Every year since the beginning of the new century, the Serpentine Gallery in London has commissioned a summer pavilion from a famous architect. This summer, a new book Ten Years Serpentine Gallery Pavilions was published by Taschen Verlag to coincide with the opening of the eleventh annual pavilion, designed by Peter Zumthor. Helen Mallinson reviews Zumthor's pavilion here, in the context of the decade-old pavilion programme.
Modern church architect as ritual anthropologist: architecture and liturgy at Clifton Cathedral
Authors: Proctor Robert
Published: March 2012

For the modern architect, the programme for the church was fraught with the dangers of excessive individualism of style or, alternatively, a merely superficial updating of tradition. To escape from both, the architect was, by the early 1960s, being exhorted to study the church's functions. Aware of the difficulties of placing ancient rituals in the same category as the sociology of education or the productivity of offices, architects and like-minded clergy saw the church as a building not only to house certain actions and communications, but also capable of lending these a relevant meaning. The church architect had to discard his preconceptions about the building type, and begin with a new analysis of ritual, and had also, therefore, to find out what the ritual meant by questioning the client and developing a brief. In this research the architect would therefore act as a ritual anthropologist; like the anthropologist, he would encounter some significant methodological problems.
Accommodating Travelling Showpeople in England
Authors: Scullion Lisa , Brown Philip , Niner Pat
Published: March 2012

Historically, Travelling Showpeople have sought to distance themselves from the wider Gypsy and Traveller population, on the basis of their unique occupation and travelling patterns, but also based on a discourse around self sufficiency. This article explores how this distinction has been influenced by, and has influenced, policy developments relating to accommodation. It focuses on how this distinction has created a degree of exclusion in terms of accommodation needs, and how this impacts on the position of contemporary Travelling Showpeople, particularly in a time of changing travelling and employment patterns.
Choice and Information in the Public Sector: A Higher Education Case Study
Authors: Harding Jamie
Published: March 2012

Successive governments have encouraged the view of users of public services as consumers, choosing between different providers on the basis of information about the quality of service. As part of this approach, prospective students are expected to make their decisions about which universities to apply to with reference to the consumer evaluations provided by the National Student Survey. However, a case study of a post-1992 university showed that not all students made genuine choices and those who did tended to be in stronger social and economic positions. Where choices were made, they were infrequently based on external evaluations of quality.
Single Parents' Subjective Wellbeing over the Welfare to Work Transition
Authors: Cook Kay E.
Published: March 2012

The Australian government purports that employment will improve welfare recipients' wellbeing. However, longitudinal analysis of the subjective wellbeing (SWB) of 135 single parents who were compelled to make the transition from welfare to work revealed that as work hours increased, subjective wellbeing did not improve, and in some cases worsened. Participants who were employed at baseline increased their work hours by an average of 4.75 hours per week; however no change was detected in their SWB. Conversely, participants who moved from not working at baseline to working at follow-up increased their work hours by an average of 15.84 hours per week. For these participants, the change in work hours negatively predicted 20–34 per cent of the variance in SWB. From these data, it is concluded that those parents who were already working were those who faced fewer barriers to employment compared to those who were compelled to work. Those who were previously unemployed may not have the material, social and psychological resources to make a successful work transition.
Supporting User Participation in Local Policy Development: The Fife Dementia Strategy
Authors: McCabe Louise , Bradley Brittany Ellis
Published: March 2012

This article reviews the consultation process during the development of a local dementia strategy. The processes of involvement by the range of stakeholders involved and how their different views shaped the strategy are considered. Particular attention is paid to the involvement of people with dementia as they are the recipients of the services to be shaped by the strategy and also form the group most difficult to reach. This article demonstrates the value of including a wide range of stakeholders in the development of local policy and the importance of involving people with dementia in policy development.
Adolescent to Parent Violence and Youth Justice in England and Wales
Authors: Condry Rachel , Miles Caroline
Published: March 2012

Adolescent to parent violence is a problem which remains largely unarticulated within youth justice policy literature and academic discourse in England and Wales. This article presents research evidence suggesting that adolescent to parent violence is a significant problem which needs to be clearly addressed in the youth justice policy agenda. Although it is widely recognised by practitioners and regularly encountered in their work, there is a ‘silence’ at the policy level and a lack of appropriate support services or responses. The article considers reasons for the absence of adolescent to parent violence in youth justice policy and argues for the importance of recognising and defining the problem and for the development of appropriate responses.
Is Parent Abuse a Form of Domestic Violence?
Authors: Wilcox Paula
Published: March 2012

There is a lack of research on parent abuse in the UK and a lack of research on the overlap between domestic violence and parent abuse internationally. This article explores why this is the case. Findings suggest that conceptual conflicts in defining both concepts, in framing children's safety as subsumed under mothers’ safety and the desire to challenge deterministic ‘cycle of violence’ models may unwittingly have contributed to the failure to address parent abuse in the domestic violence field. The author argues that only by integrating parent abuse into the domestic violence framework will this issue be appropriately addressed.
Parent Abuse: Can Law Be the Answer?
Authors: Hunter Caroline , Piper Christine
Published: March 2012

This article reviews the different forms of legal interventions which may be available to address parent abuse. It seeks to examine the evidence as to which are actually used currently and the problems which are inherent in them. We do this both by examining the statutory basis of the existing potential legal remedies and reported cases relating to those provisions, and by drawing on evidence from a small-scale study of relevant professional workers in one city. We conclude that while recourse to the police, and hence potentially the criminal justice system, is most frequent in practice, the criminal justice system is not suited to tackling the issue. Other interventions, such as anti-social behaviour orders and injunctions, also reveal problems. Law struggles to find an effective response to such a complex problem. Notwithstanding the acknowledged limits of law in changing behaviour, we argue that law could be used more effectively to reduce the incidence and impact of parent abuse.
Low-power 8-bit 5-GS/s digital-to-analog converter for multi-gigabit wireless transceivers
Authors: Sedighi Behnam , Khafaji Mahdi , Scheytt Johann Christoph
Published: March 2012

We present a method to realize a low-power and high-speed digital-to-analog converter (DAC) for system-on-chip applications. The new method is a combination of binary-weighted current cells and R-2R ladder and is specially suited for modern BiCMOS technologies. A prototype 5 GS/s DAC is implemented in 0.13 μm SiGe BiCMOS technology. The DAC dissipates 26 mW and provides an SFDR higher than 48 dB for output frequencies up to 1 GHz.
Multipoint study of magnetosheath magnetic field fluctuations and their relation to the foreshock
Authors: Gutynska O. , Šimůnek J. , Šafránková J. , Němeček Z. , Přech L.
Published: March 2012

The magnetosheath is occupied with a variety of low‐frequency fluctuations from different sources. Among them, the bow shock and dominantly foreshock processes are often considered as their major contributors. We use distant (Wind) and close (Geotail) interplanetary magnetic field monitors and compare their measurements with simultaneous magnetic field observations within the dawn (Time History of Events and Macroscale Interactions During Substorms (THEMIS)) and dusk (Cluster) magnetosheath. We have found that coherent low‐frequency (10−4–10−3 Hz) variations can be registered in all locations; thus, their source is in the solar wind. On the other hand, no correlation was found for fluctuations of higher frequencies (up to 10−1 Hz); therefore, these fluctuations should be generated by local sources. We suggest that one of these sources is connected with magnetopause processes because the fluctuation amplitude grows toward the magnetopause.
Driving Saturn's magnetospheric periodicities from the upper atmosphere/ionosphere
Authors: Jia Xianzhe , Kivelson Margaret G. , Gombosi Tamas I.
Published: March 2012

Saturn's magnetospheric structure and the intensity of radio frequency emissions from its immediate surroundings are modulated at close to the planet's rotation period. Analogous rotation‐modulated variations at Jupiter are readily interpreted as effects of the non‐axisymmetric intrinsic magnetic field. At Saturn, to the contrary, the high level of axial symmetry in the intrinsic field suggests that the periodicity is not internally imposed. A number of mechanisms have been proposed to account for the observations. Each model explains a subset of the observations in a qualitative manner, but no quantitative models yet exist. Here, using a magnetohydrodynamic simulation, we investigate the magnetospheric perturbations that arise from a localized vortical flow structure in the ionosphere near 70° S‐latitude that rotates at roughly the rate of planetary rotation. The model reproduces nearly quantitatively a host of observed magnetospheric periodicities associated with the period of the dominant (southern) radio frequency emissions during the Cassini epoch including rotating, quasi‐uniform magnetic perturbations in the equatorial plane, rotating mass density perturbations, periodic plasmoid releases that we associate with observed bursts of energetic neutral atoms (ENAs), periodic oscillations of magnetospheric boundaries, current sheet flapping, and periodic modulation of the field‐aligned currents linked to Saturn's kilometric radiation (SKR). The model is not unique but is representative of a class of models in which asymmetric flows in the (as yet unmeasured) upper atmosphere couple to the ionosphere and generate currents that flow into the magnetosphere. It can be extended to include the second periodicity that has been associated with SKR emissions in the northern hemisphere.
Reactive silica transport in fractured porous media: Analytical solutions for a system of parallel fractures
Authors: Yang Jianwen
Published: March 2012

A general analytical solution is derived by using the Laplace transformation to describe transient reactive silica transport in a conceptualized 2‐D system involving a set of parallel fractures embedded in an impermeable host rock matrix, taking into account of hydrodynamic dispersion and advection of silica transport along the fractures, molecular diffusion from each fracture to the intervening rock matrix, and dissolution of quartz. A special analytical solution is also developed by ignoring the longitudinal hydrodynamic dispersion term but remaining other conditions the same. The general and special solutions are in the form of a double infinite integral and a single infinite integral, respectively, and can be evaluated using Gauss‐Legendre quadrature technique. A simple criterion is developed to determine under what conditions the general analytical solution can be approximated by the special analytical solution. It is proved analytically that the general solution always lags behind the special solution, unless a dimensionless parameter is less than a critical value. Several illustrative calculations are undertaken to demonstrate the effect of fracture spacing, fracture aperture and fluid flow rate on silica transport. The analytical solutions developed here can serve as a benchmark to validate numerical models that simulate reactive mass transport in fractured porous media.
Ash3d: A finite‐volume, conservative numerical model for ash transport and tephra deposition
Authors: Schwaiger Hans F. , Denlinger Roger P. , Mastin Larry G.
Published: March 2012

We develop a transient, 3‐D Eulerian model (Ash3d) to predict airborne volcanic ash concentration and tephra deposition during volcanic eruptions. This model simulates downwind advection, turbulent diffusion, and settling of ash injected into the atmosphere by a volcanic eruption column. Ash advection is calculated using time‐varying pre‐existing wind data and a robust, high‐order, finite‐volume method. Our routine is mass‐conservative and uses the coordinate system of the wind data, either a Cartesian system local to the volcano or a global spherical system for the Earth. Volcanic ash is specified with an arbitrary number of grain sizes, which affects the fall velocity, distribution and duration of transport. Above the source volcano, the vertical mass distribution with elevation is calculated using a Suzuki distribution for a given plume height, eruptive volume, and eruption duration. Multiple eruptions separated in time may be included in a single simulation. We test the model using analytical solutions for transport. Comparisons of the predicted and observed ash distributions for the 18 August 1992 eruption of Mt. Spurr in Alaska demonstrate to the efficacy and efficiency of the routine.
Equatorially forced intraseasonal propagations along the Peru‐Chile coast and their relation with the nearshore eddy activity in 1992–2000: A modeling study
Authors: Belmadani Ali , Echevin Vincent , Dewitte Boris , Colas François
Published: March 2012

A regional eddy‐resolving oceanic model spanning the 1992–2000 period is used to study the influence of 50 to 80 day intraseasonal equatorial Kelvin waves (IEKW) on mesoscale eddy activity off the west coast of Peru and northern and central Chile. The model is shown to realistically simulate nearshore intraseasonal sea level variability, poleward propagation of equatorially forced coastal trapped waves along the coastal waveguide, and offshore variability related to mesoscale eddies and Rossby waves (RW). In agreement with linear theory, RW are confined equatorward of ∼12°S in the 50–80 days period range. South of that critical latitude, westward propagation is dominated by energetic mesoscale signals resulting mainly from coastal flow instability. Sensitivity experiments to the open boundary conditions are then used to estimate to what extent eddy activity is impacted by the remote equatorial forcing. A coastal increase in eddy kinetic energy related to the energetic 60 day IEKW activity present in the open boundary forcing is evidenced and is largest off northern Peru, whereas no major changes are observed offshore. Additional regional simulations with different open boundary conditions corroborate our findings and suggest that this limited effect of IEKW on the offshore eddy kinetic energy may be a robust feature.
Isotopic measurements of atmospheric methane in Los Angeles, California, USA: Influence of “fugitive” fossil fuel emissions
Authors: Townsend‐Small Amy , Tyler Stanley C. , Pataki Diane E. , Xu Xiaomei , Christensen Lance E.
Published: March 2012

Recent studies have suggested that CH4 emissions in Los Angeles and other large cities may be underestimated. We utilized stable isotopes (13C and D) and radiocarbon (14C) to investigate sources of CH4 in Los Angeles, California. First, we made measurements of δ13C and δD of various CH4 sources in urban areas. Fossil fuel CH4 sources (oil refineries, power plants, traffic, and oil drilling fields) had δ13C values between −45 and −30‰ and dD values between −275 and −100‰, whereas biological CH4 (cows, biofuels, landfills, sewage treatment plants, and cattle feedlots) had δ13C values between −65 and −45‰ and δD values between −350 and −275‰. We made high‐altitude observations of CH4 concentration using continuous tunable laser spectroscopy measurements combined with isotope analyses (13C, 14C, and D) of discrete samples to constrain urban CH4 sources. Our data indicate that the dominant source of CH4 in Los Angeles has a δ13C value of approximately −41.5‰ and a δD value between −229 and −208‰. Δ14C of CH4 in urban air samples ranged from +262 to +344‰ (127.1 to 134.9 pMC), depleted with respect to average global background CH4. We conclude that the major source of CH4 in Los Angeles is leakage of fossil fuels, such as from geologic formations, natural gas pipelines, oil refining, and/or power plants. More research is needed to constrain fluxes of CH4 from natural gas distribution and refining, as this flux may increase with greater reliance on natural gas and biogas for energy needs.
Strato‐mesospheric ozone measurements using ground‐based millimeter‐wave spectroscopy at Thule, Greenland
Authors: Muscari Giovanni , Cesaroni Claudio , Fiorucci Irene , Smith Anne K. , Froidevaux Lucien , Mlynczak Martin G.
Published: March 2012

On January 2009 a ground‐based millimeter‐wave spectrometer (GBMS) was installed at Thule Air Base (76.5°N, 68.8°W), Greenland, for long‐term winter monitoring of several stratospheric and mesospheric trace gases in the framework of the Network for the Detection of Atmospheric Composition Change. This work is aimed at characterizing the GBMS O3 vertical profiles between 35 and 80 km altitude obtained by applying the optimal estimation method to O3pressure‐broadened spectral line measurements carried out during three winters. In this altitude range, GBMS O3 retrievals are highly sensitive to variations of the atmospheric state, and their accuracy is estimated to be the larger of 11% or 0.2 ppmv. Comparisons of GBMS O3profiles with colocated satellite‐based measurements from Aura Microwave Limb Sounder (MLS) and Thermosphere Ionosphere Mesosphere Energetics and Dynamics Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) show a good agreement below 65 km altitude once the known 10%–20% high bias of SABER O3profiles is considered, with the GBMS displaying an averaged low bias of ∼9% and 17% with respect to MLS and SABER. In the nighttime mesosphere, the GBMS detects the ozone tertiary maximum within 0.1 ppmv (6%) on average with respect to the convolved MLS, SABER, and global 3‐D ROSE model profiles but shifts its position to lower altitudes by 4–5 km compared to the height obtained by the other three data sets. In the 50–80 km altitude range, estimates of mesospheric O3 diurnal variation obtained from the GBMS and the convolved satellite measurements agree well within the ±1 standard deviation (∼0.6 ppmv) of the GBMS mean profile.
Measurements of 35S in the marine boundary layer at La Jolla, California: A new technique for tracing air mass mixing during Santa Ana events
Authors: Priyadarshi Antra , Hill‐Falkenthal Jason , Coupal Elena , Dominguez Gerardo , Thiemens Mark H.
Published: March 2012

35S (t1/2 = ∼87 days) is a radioactive isotope that is naturally produced in the upper atmosphere by the interaction of cosmic rays with 40Ar. In the atmosphere, 35S oxidizes to 35SO2, which further oxidizes to 35SO42− depending on the oxidative rates. Here, we report measurements of 35S activity in both 35SO2 (gas) and 35SO42− (aerosol) (coarse, >1.5 μm; and fine, <1.5 μm size fraction) collected during 2009–2010 at La Jolla, California, and we demonstrate that 35S is a unique tracer for understanding air mass mixing and boundary layer dynamics. The annual mean 35SO2 concentration is 71 ± 61 (mean ± 1σ) atoms/m3. The annual mean 35SO42− abundance in the fine fraction (455 ± 157 atoms/m3) is higher than in the coarse fraction (136 ± 59 atoms/m3). This is most probably a consequence of the fine sulfate aerosol fraction being produced by gas phase oxidation of 35SO2, whereas the coarse fraction is mainly derived from oceanic sea salt sulfate. 35S activity in coarse sulfate is mainly due to uptake of 35SO2 and subsequent oxidation on sea salt aerosols. 35SO2 and 35SO42−activities were observed to be higher during stratospheric‐tropospheric mixing and Santa Ana wind events that provide high‐altitude air mass mixing into the marine boundary layer. A model calculation shows that a maximum of 41% of total air sampled in the marine boundary layer recently originated from the free troposphere and mixed into the marine boundary layer during Santa Ana wind events. This work is the first to quantify and explain air mass mixing during Santa Ana events using35S activity.
Springtime boundary layer ozone depletion at Barrow, Alaska: Meteorological influence, year‐to‐year variation, and long‐term change
Authors: Oltmans Samuel J. , Johnson Bryan J. , Harris Joyce M.
Published: March 2012

In April 2008 and March–April 2009 near daily ozonesonde measurements were made over a several week period to study springtime Arctic boundary layer ozone loss in the vicinity of Barrow, Alaska. A detailed picture of the vertical structure of the depletion events from the soundings was obtained showing that the depletion was confined to approximately the lowest 1000 m with an average height of the top of the layer at ∼500 m. The two years were strongly contrasting in the frequency of ozone depletion events providing an opportunity for investigating the differing conditions under which these events develop. Short‐term variability of the ozone depletion events is closely tied to the frequency of airflow that is primarily Arctic Ocean in origin (more depletion) or originates at lower latitudes (less depletion). The ubiquitous depletion events are interrupted by periodic mixing of ozone rich air into the boundary layer with the onset of synoptic scale weather changes that interrupt flow from off the Arctic Ocean. A 38‐year record of surface ozone measurements at Barrow provides a unique time series that reveals the strong year‐to‐year variability of ozone depletion event occurrence. During March, but not April or May, there has been a significant increase in the frequency of ozone depletion events. This long‐term increase in March depletion events appears to follow the decline in multiyear sea ice in the Arctic Ocean and its replacement by first‐year ice. This significant change in the occurrence of boundary layer ozone events in March may signal a change in the oxidative chemistry in the Arctic that is related to climate change in this sensitive region.
Tree ring based precipitation reconstruction in the south slope of the middle Qilian Mountains, northeastern Tibetan Plateau, over the last millennium
Authors: Sun Junyan , Liu Yu
Published: March 2012

A tree ring (Sabina przewalskiiKom.) based millennial precipitation reconstruction on the south slope of the middle Qilian Mountains in the northeastern margin of Tibetan Plateau, China, was completed, which explains 48.5% of the variance in the instrumental precipitation from 1958 to 2004. The long‐term precipitation variation patterns were confirmed on the basis of the duration, magnitude, and intensify of the multidecadal dry (wet) events. There are several stronger multidecadal dry periods, 1092–1172, 1441–1517, and 1564–1730, whereas there is only one outstanding severe wet event of 1352–1440. The variations of the precipitation reconstruction are accordant with the glacier accumulation and dust contents of Dunde ice core and also with the variations of the precipitation, runoff, Palmer Drought Severity Index, and tree ring width series in the northeastern Tibetan Plateau. The spatial extent of the great drought in the latter half of the 15th century also concentrated on the northeastern Tibetan Plateau. The moisture variations in the northeastern Tibetan Plateau are synchronous over a large spatial and temporal range in multidecadal scale for the last millennium, especially during dry periods. Wavelet analyses and comparisons with the minimal solar activity show that the precipitation variations for the last millennium may have some association with the solar activity on multidecadal to centennial scales.
Assimilation of GIRO data into a real‐time IRI
Authors: Galkin I. A. , Reinisch B. W. , Huang X. , Bilitza D.
Published: March 2012

Increasingly accurate and detailed global 3‐D specification of the Earth's space plasma environment is required to further understand its intricate organization and behavior. For a long time space physics and aeronomy research has been data starved due to the great variety of natural time scales involved in the plasma phenomenology. We have started developing a new approach to the global ionospheric specification called Real‐Time Assimilative Mapping (RTAM). The IRI‐RTAM will use data from the Global Ionospheric Radio Observatory (GIRO) to smoothly transform IRI's background empirical maps of the ionospheric characteristics to match the observations. Such empirical assimilative modeling will provide a high‐resolution, global picture of the ionospheric response to various short‐term events observed during periods of storm activity or the impact of gravity waves coupling the ionosphere to the lower atmosphere, including timelines of the vertical restructuring of the plasma distribution. It will also contribute to the challenging task of providing a rapid insight into the temporal and spatial space weather development using the real‐time GIRO data streams. The new assimilation technique “updates” the IRI electron density distribution while preserving the overall integrity of IRI's typical ionospheric feature representations. The technique adjusts the coefficients of the spherical/diurnal expansions used by the CCIR and URSI‐88 model to obtain the global subpeak electron density distribution. The set of global corrected coefficients can be generated as frequently as every 15 min and easily disseminated using a single real‐time RTAM server operated by GIRO.
Natural conditions for more limited osmotic abnormal fluid pressures in sedimentary basins
Authors: Tremosa Joachim , Gonçalvès Julio , Matray Jean‐Michel
Published: March 2012

Chemical osmosis is considered a plausible cause of abnormal pressures in shale formations of sedimentary basins. A set of experimental data on chemical osmosis was recently obtained for different shales, mainly in the framework of studies on radioactive waste repositories in deep argillaceous formations. Based on these data, large, osmotically induced overpressures up to tens of MPa were predicted by Neuzil and Provost [2009] under appropriate conditions. However, such large overpressures have not been found in sedimentary basins such that the reasons for this disparity between predictions and observations need to be clarified. Accordingly, two natural causes for lower than expected osmotic pressure were investigated: the effect of the complex composition of natural waters, including both monovalent and divalent cations, on the osmotic efficiency and the resulting abnormal pressures, and the presence of steady state rather than transient‐state salinity distributions. For this purpose, an electrical triple‐layer model accounting for multi‐ionic solutions was developed and used to calculate the osmotic efficiency at different proportions of monovalent and divalent cations. The calculated decrease of the osmotic efficiency when Ca2+ is introduced in a Na+‐clay system yields a noticeable decrease in the ability of the shale to generate overpressures. A discussion addresses the generation of abnormal pressures at steady state conditions found in sedimentary basins, i.e., with a linear distribution of the concentration across the formation. The persistence of moderate overpressures was predicted because of the nonlinearity associated with the dependence of the chemo‐osmotic efficiency on the concentration and the porosity. Finally, a case study of the moderate excess hydraulic head measured in the Toarcian/Domerian argillaceous formation of Tournemire (SE of France) was investigated. The analysis indicated an osmotic origin for the excess head and illustrated the influence of the pore water composition.
Hydrologic and geomorphic controls on hyporheic exchange during base flow recession in a headwater mountain stream
Authors: Ward Adam S. , Fitzgerald Michael , Gooseff Michael N. , Voltz Thomas J. , Binley Andrew M. , Singha Kamini
Published: March 2012

Hyporheic hydrodynamics are a control on stream ecosystems, yet we lack a thorough understanding of catchment controls on these flow paths, including valley constraint and hydraulic gradients in the valley bottom. We performed four whole‐stream solute tracer injections under steady state flow conditions at the H. J. Andrews Experimental Forest (Oregon, United States) and collected electrical resistivity (ER) imaging to directly quantify the 2‐D spatial extent of hyporheic exchange through seasonal base flow recession. ER images provide spatially distributed information that is unavailable for stream solute transport modeling studies from monitoring wells alone. The lateral and vertical extent of the hyporheic zone was quantified using both ER images and spatial moment analysis. Results oppose the common conceptual model of hyporheic “compression” by increased lateral hydraulic gradients toward the stream. We found that the extent of the hyporheic zone increased with decreasing vertical gradients away from the stream, in contrast to expectations from conceptual models. Increasing hyporheic extent was observed with both increasing and decreasing down‐valley (i.e., parallel to the valley gradient) and cross‐valley (i.e., from the hillslope to the stream, perpendicular to the valley gradient) hydraulic gradients. We conclude that neither cross‐valley nor down‐valley hydraulic gradients are sufficient predictors of hyporheic exchange flux nor flow path network extent. Increased knowledge of the controls on hyporheic exchange, the temporal dynamics of exchange flow paths, and their the spatial distribution is the first step toward predicting hyporheic exchange at the scale of individual flow paths. Future studies need to more carefully consider interactions between spatiotemporally dynamic hydraulic gradients and subsurface architecture as controls on hyporheic exchange.
Gross ecosystem photosynthesis causes a diurnal pattern in methane emission from rice
Authors: Hatala Jaclyn A. , Detto Matteo , Baldocchi Dennis D.
Published: March 2012

Understanding the relative contribution of environmental and substrate controls on rice paddy methanogenesis is critical for developing mechanistic models of landscape‐scale methane (CH4) flux. A diurnal pattern in observed rice paddy CH4 flux has been attributed to fluctuations in soil temperature physically driving diffusive CH4transport from the soil to atmosphere. Here we make direct landscape‐scale measurements of carbon dioxide and CH4 fluxes and show that gross ecosystem photosynthesis (GEP) is the dominant cause of the diurnal pattern in CH4 flux, even after accounting for the effects of soil temperature. The time series of GEP and CH4 flux show strong spectral coherency throughout the rice growing season at the diurnal timescale, where the peak in GEP leads that of CH4 flux by 1.3 ± 0.08 hours. By applying the method of conditional Granger causality in the spectral domain, we demonstrated that the diurnal pattern in CH4 flux is primarily caused by GEP.