bluuebunny/crossref_metadata_2025 huggingface dataset:
Anticonvulsant drugs for pediatric migraine prevention: An evidence‐based review
Authors: Bakola Eleni , Skapinakis Petros , Tzoufi Meropi , Damigos Dimitris , Mavreas Venetsanos
Published: December 2008

Background: The use of anticonvulsant drugs for the prevention of migraine in children and adolescents has been supported in the past.

Aims: To evaluate the available evidence for the efficacy and safety of anticonvulsants drugs in the prevention of migraine attacks in children and adolescents.

Methods: Studies were selected through a comprehensive literature search. We included all types of study designs (controlled and uncontrolled) due to the limited evidence. Monthly migraine frequency was used as the primary outcome measure in most of the studies. Studies were classified into levels of evidence according to their design.

Results: Fourteen studies were included with a total of 939 patients. Topiramate (4 randomized controlled trials [RCT], two uncontrolled trials), sodium valproate/divalproex sodium (two RCTs, one uncontrolled trial, two retrospective chart reviews) levetiracetam and zonisamide (both only uncontrolled studies) are the anticonvulsants that have been reported in the literature. The findings show that valproate is not different from placebo and topiramate may not be different but further randomized trials are needed. All drugs were well tolerated in this age group with no serious events reported.

Conclusions: The use of anticonvulsants in the prevention of migraine in children and adolescents is not adequately supported by methodologically sound RCTs. More research is needed in the future to establish the efficacy and safety of specific agents.
Reductive dioxygen scavenging by flavo‐diiron proteins of Clostridium acetobutylicum
Authors: Hillmann Falk , Riebe Oliver , Fischer Ralf-Jörg , Mot Augustin , Caranto Jonathan D. , Kurtz Donald M. , Bahl Hubert
Published: December 2008

Two flavo‐diiron proteins (FDPs), FprA1 and FprA2, are up‐regulated when the strictly anaerobic solvent producer, Clostridium acetobutylicum, is exposed to dioxygen. These two FDPs were purified following heterologous overexpression in Escherichia coli as N‐terminal Strep‐tag fusion proteins. The recombinant FprA1 and FprA2 were found to be homodimeric and homotetrameric, respectively, and both FDPs functioned as terminal components of NADH oxidases (NADH:O2 oxidoreductases) when using C. acetobutylicum NADH:rubredoxin oxidoreductase (NROR) and rubredoxin (Rd) as electron transport intermediaries. Both FDPs catalyzed the four‐electron reduction of molecular oxygen to water with similar specific activities. The results are consistent with these FDPs functioning as efficient scavengers of intracellular dioxygen under aerobic or microoxic growth conditions.
Cerebral expression of DNA repair protein, Ku70, and its association with cell proliferation following cerebral hypoxia–ischemia in neonatal rats
Authors: Meng Shuzhen , Lin Lily , Lama Sanju , Qiao Min , Tuor Ursula I.
Published: December 2008

We hypothesized that increased Ku70 expression could be involved in recovery following cerebral hypoxia–ischemia. We investigated the progression of cerebral alterations in Ku70 expression at different time points (24 h, 72 h, 1 week, 4 weeks and 8 weeks) after hypoxia–ischemia (right carotid artery occlusion plus 1.5 h of hypoxia) in neonatal rats. To determine whether in addition to its known role of DNA repair, Ku70 was associated with cell death or cell proliferation we performed double staining for Ku70 and DNA fragmentation or bromodeoxyuridine, respectively. The results show that Ku70 expression was increased in the infarct core and peri‐infarct regions at 24 h following hypoxia–ischemia. The increased Ku70 expression was transient in the infarct core with a loss of Ku70 positive cells over days. In contrast, in the peri‐infarct region the expression of Ku70 remained increased at chronic times 8 weeks following the insult. Cells positive for DNA fragmentation were not co‐localized with cells positive for Ku70 after an insult. However, most of the cells positive for bromodeoxyuridine indicative of cell proliferation were positive for Ku70 in the peri‐infarct region at 8 weeks after the insult. Considering the roles of Ku70 in DNA repair or inhibiting apoptosis and its co‐localization within cells that had undergone proliferation, Ku70 may be considered a potential novel target to enhance recovery following hypoxia–ischemia.
Targeted proteomic strategy for clinical biomarker discovery
Authors: Schiess Ralph , Wollscheid Bernd , Aebersold Ruedi
Published: December 2008

The high complexity and large dynamic range of blood plasma proteins currently prohibit the sensitive and high‐throughput profiling of disease and control plasma proteome sample sets large enough to reliably detect disease indicating differences. To circumvent these technological limitations we describe here a new two‐stage strategy for the mass spectrometry (MS) assisted discovery, verification and validation of disease biomarkers. In an initial discovery phase N‐linked glycoproteins with distinguishable expression patterns in primary normal and diseased tissue are detected and identified. In the second step the proteins identified in the initial phase are subjected to targeted MS analysis in plasma samples, using the highly sensitive and specific selected reaction monitoring (SRM) technology. Since glycosylated proteins, such as those secreted or shed from the cell surface are likely to reside and persist in blood, the two‐stage strategy is focused on the quantification of tissue derived glycoproteins in plasma. The focus on the N‐glycoproteome not only reduces the complexity of the analytes, but also targets an information‐rich subproteome which is relevant for remote sensing of diseases in the plasma. The N‐glycoprotein based biomarker discovery and validation workflow reviewed here allows for the robust identification of protein candidate panels that can finally be selectively monitored in the blood plasma at high sensitivity in a reliable, non‐invasive and quantitative fashion.
Judicial Behavior under Political Constraints: Evidence from the European Court of Justice
Authors: CARRUBBA CLIFFORD J. , GABEL MATTHEW , HANKLA CHARLES
Published: December 2008

The actual impact of judicial decisions often depends on the behavior of executive and legislative bodies that implement the rulings. Consequently, when a court hears a case involving the interests of those controlling the executive and legislative institutions, those interests can threaten to obstruct the court's intended outcome. In this paper, we evaluate whether and to what extent such constraints shape judicial rulings. Specifically, we examine how threats of noncompliance and legislative override influence decisions by the European Court of Justice (ECJ). Based on a statistical analysis of a novel dataset of ECJ rulings, we find that the preferences of member-state governments—whose interests are central to threats of noncompliance and override—have a systematic and substantively important impact on ECJ decisions.
The Role of Parties' Past Behavior in Coalition Formation
Authors: TAVITS MARGIT
Published: December 2008

This study considers whether and to what extent defections from a government coalition are punished. The study employs data on coalitions in eastern and western Europe from 1950 through 2006. The results show that if a coalition breaks due to conflict between partners or if one party withdraws from it, subsequent inclusion of the conflicting parties in the same coalition becomes less likely. Additional tests demonstrate that this effect occurs because defectors are punished by their former coalition partners. Another extension of the main analysis shows that rather than becoming pariah parties, defectors lose credibility only in the eyes of their former coalition partners.
Governmental Centralization and Party Affiliation: Legislator Strategies in Brazil and Japan
Authors: DESPOSATO SCOTT , SCHEINER ETHAN
Published: December 2008

What shapes politicians' strategies in political systems where pork, rather than programmatic platforms, wins elections? We argue that resource control provides much of the answer, as politics in pork-centric systems will in large part be organized around actors who control access to pork. We use new national and subnational data from Brazil and Japan to show how the degree of centralization of resources can affect party affiliation patterns. We find that in decentralized Brazil, both national and subnational politicians join parties that control their subnational government. In contrast, in our analysis of centralized Japan, politicians at both national and subnational levels base their party affiliation decisions on national-level partisan considerations.
What Is a “Right to Have Rights”? Three Images of the Politics of Human Rights
Authors: INGRAM JAMES D.
Published: December 2008

This article seeks to elucidate some of the difficulties and reversals that afflict human rights by exploring three interpretations of Hannah Arendt's idea of a “right to have rights,” and in particular the images of politics these interpretations presuppose. The first, most conventional interpretation considers this right in terms of the use of power to implement rights; a second, broadly Kantian interpretation understands it in terms of laws and institutions; a third, which I develop through an original reading of Arendt, bases it on the activity of the rights-claimants or -holders themselves. Although each of these conceptions corresponds to different circumstances and speaks to different concerns, the third is especially valuable in helping us understand the problems that plague efforts on behalf of human rights and showing how human rights can best be realized and secured. If it is the most demanding, it alone fully honors human rights' emphasis on autonomy.
The Impartiality of International Judges: Evidence from the European Court of Human Rights
Authors: VOETEN ERIK
Published: December 2008

Can international judges be relied upon to resolve disputes impartially? If not, what are the sources of their biases? Answers to these questions are critically important for the functioning of an emerging international judiciary, yet we know remarkably little about international judicial behavior. An analysis of a new dataset of dissents in the European Court of Human Rights (ECtHR) yields a mixed set of answers. On the bright side, there is no evidence that judges systematically employ cultural or geopolitical biases in their rulings. There is some evidence that career insecurities make judges more likely to favor their national government when it is a party to a dispute. Most strongly, the evidence suggests that international judges are policy seekers. Judges vary in their inclination to defer to member states in the implementation of human rights. Moreover, judges from former socialist countries are more likely to find violations against their own government and against other former socialist governments, suggesting that they are motivated by rectifying a particular set of injustices. I conclude that the overall picture is mostly positive for the possibility of impartial review of government behavior by judges on an international court. Like judges on domestic review courts, ECtHR judges are politically motivated actors in the sense that they have policy preferences on how to best apply abstract human rights in concrete cases, not in the sense that they are using their judicial power to settle geopolitical scores.
A comparison of the effects of soya isoflavonoids and fish oil on cell proliferation, apoptosis and the expression of oestrogen receptors α and β in the mammary gland and colon of the rat
Authors: Kramer Franziska , Johnson Ian T. , Doleman Joanne F. , Lund Elizabeth K.
Published: December 2008

Isoflavonoids and fish oil may be protective against colorectal cancer, but the evidence in relation to breast cancer risk is ambiguous. In the present study, we have investigated the impact of soya-derived isoflavonoids andn-3 fatty acids from fish oil, both individually and in combination, on apoptosis, cell proliferation and oestrogen receptor (ER) expression in the colon and mammary gland of the rat. Female rats were fed diets high inn-3 fatty acids (80 g/kg diet) or soya protein (765 mg/kg diet isoflavones) for 2 weeks, and then killed before the removal of the colon and mammary glands. Cell proliferation and apoptosis were quantified morphologically in whole crypts and terminal end buds. The expressions ofERαandERβwere measured in colon tissue scrapes and the mammary gland. Fish oil significantly increased apoptosis and decreased mitosis in both tissues, an effect associated with a decrease in the expressions ofERα andERβ. Soya had no effect on apoptosis in either tissue, but reduced mitosis in the colon (P < 0·001) while increasing it in the mammary gland (P = 0·001). The changes in proliferation were associated with contrasting changes in theERexpression such that fish oil significantly decreased bothERβandERα, while soya increasedERαand decreasedERβ. The results may provide a novel mechanism by whichn-3 fatty acids could reduce cancer risk, but the interpretation of the results in relation to soya consumption and breast cancer risk requires further investigation.
Nutrition in early life, and risk of cancer and metabolic disease: alternative endings in an epigenetic tale?
Authors: Burdge Graham C. , Lillycrop Karen A. , Jackson Alan A.
Published: December 2008

There is substantial evidence which shows that constraints in the early life environment are an important determinant of risk of metabolic disease and CVD. There is emerging evidence that higher birth weight, which reflects a more abundant prenatal environment, is associated with increased risk of cancer, in particular breast cancer and childhood leukaemia. Using specific examples from epidemiology and experimental studies, this review discusses the hypothesis that increased susceptibility to CVD, metabolic disease and cancer have a common origin in developmental changes induced in the developing fetus by aspects of the intra-uterine environment including nutrition which involve stable changes to the epigenetic regulation of specific genes. However, the induction of specific disease risk is dependent upon the nature of the environmental challenge and interactions between the susceptibility set by the altered epigenome and the environment throughout the life course.
Putting accent in its place: Rethinking obstacles to communication
Authors: Derwing Tracey M. , Munro Murray J.
Published: December 2008

One of the most salient aspects of speech is accent – either dialectal differences attributable to region or class, or phonological variations resulting from L1 influence on the L2. Our primary concern is with the latter, because of the strong social, psychological, and communicative consequences of speaking with an L2 accent. The decline of audiolingualism led to a concomitant marginalization of pronunciation research and teaching. It was believed that pronunciation instruction could not be effective, in part because of the unrealistic goal of native-like speech in L2 learners, and also because of research findings that suggested that instruction had a negligible impact on oral production. The recent revival of interest in pronunciation research has brought a change of focus away from native-like models toward easy intelligibility. The effects of this change have yet to be fully realized in L2 classrooms. However, many L2 students themselves are keenly interested in pronunciation instruction, a fact not lost on individuals who have recognized a lucrative marketing niche in ‘accent reduction/elimination’ programs that may do more harm than good. Our presentation will relate the core issues of intelligibility, identity, social evaluation, and discrimination to appropriate pronunciation pedagogy for L2 learners.
Conditions that alter saccadic eye movement latencies and affect target choice to visual stimuli and to electrical stimulation of area V1 in the monkey
Authors: SCHILLER PETER H. , KENDALL GEOFFREY L. , SLOCUM WARREN M. , TEHOVNIK EDWARD J.
Published: December 2008

In this study, we examined procedures that alter saccadic latencies and target selection to visual stimuli and electrical stimulation of area V1 in the monkey. It has been shown that saccadic eye movement latencies to singly presented visual targets form a bimodal distribution when the fixation spot is turned off a number of milliseconds prior to the appearance of the target (the gap period); the first mode has been termed express saccades and the second regular saccades. When the termination of the fixation spot is coincident with the appearance of the target (0 ms gap), express saccades are rarely generated. We show here that a bimodal distribution of saccadic latencies can also be obtained when an array of visual stimuli is presented prior to the appearance of the visual target, provided the elements of the array overlap spatially with the visual target. The overall latency of the saccadic eye movements elicited by electrical stimulation of area V1 is significantly shortened both when a gap is introduced between the termination of the fixation spot and the stimulation and when an array is presented. However, under these conditions, the distribution of saccadic latencies is unimodal. When two visual targets are presented after the fixation spot, introducing a gap has no effect on which target is chosen. By contrast, when electrical stimulation is paired with a visual target, introducing a gap greatly increases the frequency with which the electrical stimulation site is chosen.
Economic valuation of flood risk exposure and reduction in a severely flood prone developing country
Authors: BROUWER ROY , AKTER SONIA , BRANDER LUKE , HAQUE ENAMUL
Published: December 2008

This paper presents the results of a dichotomous choice contingent valuation (CV) study of reduced flood risks in Bangladesh. Sensitivity of willingness to pay (WTP) to varying risk exposure levels is tested in a ‘natural experiment’, targeting floodplain residents facing regular annual flooding and a disaster flood once every five to ten years. Accounting for price, income and education levels, both subjective risk aversion and objective baseline risk exposure affect stated WTP for a common level of flood protection. We find a number of problems with the CV application in this specific developing country context. Half of the respondents are unable to pay in financial terms, but are willing to contribute in kind. The combined use of a monetary and non-monetary measure of WTP would have lowered the number of zero bids considerably. A test-retest carried out six months after the original survey shows that the stated WTP values are reliable.
Exact 2‐D scattering from a slot in a ground plane backed by a semielliptical cavity and covered with a multilayer isorefractive diaphragm
Authors: Canta S. M. , Erricolo D.
Published: December 2008

A semielliptical channel flush‐mounted under a metal plane and slotted along the interfocal distance of its cross section is separated from the half‐space above by a multilayer diaphragm. The cavity, the diaphragm, and the half‐space are all isorefractive to each other. Both the cavity and the multilayer diaphragm are filled with materials isorefractive to the medium in the half‐space above. This is a two‐dimensional geometry where the source is invariant with respect to the axial variable. The resulting electromagnetic boundary‐value problem is solved exactly in terms of Mathieu functions, when the excitation source is either a plane wave or a line source. For plane wave incidence, the polarization is with either the electric or the magnetic field parallel to the axis of the structure and the direction of incidence is arbitrary in a plane perpendicular to the axis. For line source excitation, the polarization is with either the electric or the magnetic field parallel to the axis of the structure and the source is arbitrarily located. Numerical results are also provided.
Tectonic control on the late stage exhumation of the Aar Massif (Switzerland): Constraints from apatite fission track and (U‐Th)/He data
Authors: Reinecker John , Danišík Martin , Schmid Claudia , Glotzbach Christoph , Rahn Meinert , Frisch Wolfgang , Spiegel Cornelia
Published: December 2008

We examine the hypothesis that Pliocene exhumation of the external massifs in the central Alps is controlled by climatic change. New thermochronological data from the western Gastern‐Aar massif are used to investigate the timing, extent, and reasons for Neogene exhumation. Our data reveal that exhumation was constant with 0.5 km/Ma over the last 10 Ma in the north. In the southern part, exhumation was of the same order until ∼3.5 Ma but then increased gradually toward the south to values of up to 1.2 km/Ma, resulting in overall northward tilting of the western Aar massif. We explain this accelerated exhumation in the south after ∼3.5 Ma mainly by tectonic denudation in the footwall of the Rhône‐Simplon fault and discuss changes in deep crustal configuration, which may have triggered south directed normal faulting. We propose that the Rhône river was structurally trapped by the Rhône‐Simplon normal fault zone, which additionally enhanced erosion in the southern section of the Aar massif. Climatic forcing may have an impact in the very late stage of exhumation due to Alpine glaciation in the late Pliocene.
A spatial regularization approach to parameter estimation for a distributed watershed model
Authors: Pokhrel P. , Gupta H. V. , Wagener T.
Published: December 2008

Environmental models have become increasingly complex with greater attention being given to the spatially distributed representation of processes. Distributed models have large numbers of parameters to be specified, which is typically done either by recourse to a priori methods based on observable physical watershed characteristics, by calibration to watershed input‐state‐output data, or by some combination of both. In the case of calibration, the high dimensionality of the parameter search space poses a significant identifiability problem. This article discusses how this problem can be addressed, utilizing additional information about the parameters through a process known as regularization. Regularization, in its broadest sense, is a mathematical technique that utilizes additional information or constraints about the parameters to reduce problems related to over‐parameterization. This article develops and applies a regularization approach to the calibration of a version of the Hydrology Laboratory Distributed Hydrologic Model (HL‐DHM) developed by the US National Weather Service. A priori parameter estimates derived using the approach by Koren et al. (2000) were used to develop regularization relationships to constrain the feasible parameter space and enable existing global optimization techniques to be applied to solve the calibration problem. In a case study for the Blue River basin, the number of unknowns to be estimated was reduced from 858 to 33, and this calibration strategy improved the model performance while preserving the physical realism of the model parameters. Our results also suggest that the commonly used parameter field “multiplier” approach may often not be appropriate.
Turbulent dissipation on the margins of the South China Sea
Authors: St. Laurent Louis
Published: December 2008

Measurements of turbulence along the continental slope, shelfbreak, and shelf of the northern South China Sea are presented from a 10‐day measurement program during April 2005. The shelfbreak region was characterized by a deep stratification that appears to be typical of the late winter‐monsoon. This appears to shift the wave field at the shelfbreak from the soliton‐like depression anomalies observed in previous years to a more complex wave field, supporting high‐frequency waves in both upper and lower depth‐intervals of the water column. On average, 30% of the depth‐integrated turbulent dissipation occurs within 10 m of the bottom, where baroclinic energy is preferentially dissipated. Dissipation levels, reaching 50 mW/m2, are an order of magnitude larger than those attainable through frictional dissipation of the local barotropic tide, and an order of magnitude larger than levels typical in the open ocean.
Paleointensity of the ancient Martian magnetic field
Authors: Weiss Benjamin P. , Fong Luis E. , Vali Hojatollah , Lima Eduardo A. , Baudenbacher Franz J.
Published: December 2008

Mars today has no core dynamo magnetic field. However, the discovery of remanent magnetization in Martian meteorites and intense crustal magnetization suggests that Mars once had a global field. Here we present high resolution maps of the magnetic field of Martian meteorite ALH 84001. These maps are the most sensitive yet quantitative study of natural remanent magnetization (with resolved anomalies as weak as 1 × 10−14 Am2). ALH 84001 likely contains a 4 billion year old (Ga) thermoremanence partially overprinted by one or more poorly understood secondary components. Our data suggest that the paleointensity of the local paleofield was within an order of magnitude of that of the present‐day Earth. If this field were global in extent, it should have played a key role in Martian atmospheric and climatic evolution. However, it is still too weak to easily explain the intensity of Martian crustal paleomagnetic anomalies.
Low‐frequency variations of the large‐scale ocean circulation and heat transport in the North Atlantic from 1955–1998 in situ temperature and salinity data
Authors: Huck T. , de Verdière A. Colin , Estrade P. , Schopp R.
Published: December 2008

Low‐frequency variations of the large‐scale ocean circulation in the Atlantic are reconstructed from NODC pentadal anomalies of temperature and salinity from 1955 to 1998 based on hydrographic data, in addition to atmospheric reanalysis surface forcing. Diagnostic ocean circulations are estimated from simple methods using dynamical model integrations: namely diagnostic, robust diagnostic, and short prognostic. Mean transports of heat and mass are sensitive to the method and model configuration, but their decadal variability is much more coherent and does not depend explicitly on the variations of the surface forcing, its influence being imprinted in the thermohaline structure. Multidecadal variations are of the order of 20%, with large transports in the subpolar gyre in the early 1960's and mid 1990's, and low values in the mid 1970's. By reducing the influence of subgrid‐scale parameterizations and surface forcings, these methods offer alternatives to exhaustive GCM simulations.
Ways in which ICME sheaths differ from magnetosheaths
Authors: Siscoe G. , Odstrcil D.
Published: December 2008

Because the material that constitutes a coronal mass ejection expands as it propagates into interplanetary space (where it is referred to as an interplanetary coronal mass ejection, ICME), its sheath differs from other heliophysical sheaths in three ways: (1) the lateral deflection of the solar wind away from the nose of an ICME is reduced; (2) the solar wind tends to pile up in front of an ICME instead of flowing around it; and (3) the ICME sheath is thinner. (We refer here to ICME sheaths that have a preceding bow shock and that therefore are analogous to other heliophysical sheaths.) These three differences are explained here by physical arguments and illustrated with an MHD simulation.
Lightning‐driven electric fields measured in the lower ionosphere: Implications for transient luminous events
Authors: Thomas Jeremy N. , Barnum Benjamin H. , Lay Erin , Holzworth Robert H. , Cho Mengu , Kelley Michael C.
Published: December 2008

Transient luminous events above thunderstorms such as sprites, halos, and elves require large electric fields in the lower ionosphere. Yet very few in situ measurements in this region have been successfully accomplished, since it is typically too low in altitude for rockets and satellites and too high for balloons. In this article, we present some rare examples of lightning‐driven electric field changes obtained at 75–130 km altitude during a sounding rocket flight from Wallops Island, Virginia, in 1995. We summarize these electric field changes and present a few detailed case studies. Our measurements are compared directly to a 2D numerical model of lightning‐driven electromagnetic fields in the middle and upper atmosphere. We find that the in situ electric field changes are smaller than predicted by the model, and the amplitudes of these fields are insufficient for elve production when extrapolated to a 100 kA peak current stroke. This disagreement could be due to lightning‐induced ionospheric conductivity enhancement, or it might be evidence of flaws in the electromagnetic pulse mechanism for elves.
Have tropical cyclones been feeding more extreme rainfall?
Authors: Lau K.‐M. , Zhou Y. P. , Wu H.‐T.
Published: December 2008

We have conducted a study of the relationship between tropical cyclone (TC) and extreme rain events using GPCP and TRMM rainfall data, and storm track data for July through November (JASON) in the North Atlantic (NAT) and the western North Pacific (WNP). Extreme rain events are defined in terms of percentile rainrate, and TC‐rain by rainfall associated with a named TC. Results show that climatologically, 8% of rain events and 17% of the total rain amount in NAT are accounted by TCs, compared to 9% of rain events, and 21% of rain amount in WNP. The fractional contribution of accumulated TC‐rain to total rain, Ω, increases nearly linearly as a function of rainrate. Extending the analyses using GPCP pentad data for 1979–2005, and for the post‐SSM/I period (1988–2005), we find that while there is no significant trend in the total JASON rainfall over NAT or WNP, there is a positive significant trend in heavy rain over both basins for the 1979–2005 period, but not for the post‐SSM/I period. Trend analyses of Ω for both periods indicate that TCs have been feeding increasingly more to rainfall extremes in NAT, where the expansion of the warm pool area can explain slightly more than 50% of the change in observed trend in total TC rainfall. In WNP, trend signals for Ω are mixed, and the long‐term relationship between TC rain and warm pool area is strongly influenced by interannual and interdecadal variability.
Extratropical waves transport boreal wildfire emissions and drive regional air quality dynamics
Authors: Bein Keith J. , Zhao Yongjing , Johnston Murray V. , Evans Greg J. , Wexler Anthony S.
Published: December 2008

A synthesis of data and analyses identified eight separate wildfire events (five in boreal Canada and three in the western United States) that impacted the Pittsburgh Supersite, as well as Toronto, during June and July 2002. These data also revealed a larger structure in the nature of pollution episodes in Pittsburgh characterized by alternating periods of stagnation and cleansing. Stagnation resulted in significant and sustained increases in pollutant concentrations that were eventually flushed by clean air transported from Canada. Stagnation events were further characterized by decreases in wind speed, increases in ambient temperature, and enhanced atmospheric processing. Reverse trends were observed during the “clean” periods. Wildfire emissions consistently arrived immediately prior to the stagnation events and tended to be trapped and recirculated by the associated surface high pressure system, prolonging their impact. These receptor site dynamics were correlated to the structure and propagation of transient extratropical synoptic‐scale waves, which were characterized by eastward propagating transcontinental trough‐ridge‐trough configurations. Temporal patterns observed in the Pittsburgh data (a repeating sequence of long‐range transport followed by stagnation and then flushing) were in phase with alternating synoptic structures of the propagating waves. Northwesterly subsiding flow between the ridge and trough transported wildfire emissions from the injection height above the fires down into the Pittsburgh and Toronto air sheds. As the wave propagated, the surface high associated with the upper‐level ridge passed Pittsburgh, initiating a stagnation event. The cold front associated with the approaching trough flushed the stagnant air but reset the sequence of events as emissions from new wildfires were again transported behind the front. The sequence consistently repeated throughout the study period with a frequency directly correlated to the frequency of extratropical wave formation. Stagnation severity was related to the speed and maturity of the synoptic disturbances while wildfire impact severity corresponded to fire size.
Volcanic forcing of climate over the past 1500 years: An improved ice core‐based index for climate models
Authors: Gao Chaochao , Robock Alan , Ammann Caspar
Published: December 2008

Understanding natural causes of climate change is vital to evaluate the relative impacts of human pollution and land surface modification on climate. We have investigated one of the most important natural causes of climate change, volcanic eruptions, by using 54 ice core records from both the Arctic and Antarctica. Our recently collected suite of ice core data, more than double the number of cores ever used before, reduces errors inherent in reconstructions based on a single or small number of cores, which enables us to obtain much higher accuracy in both detection of events and quantification of the radiative effects. We extracted volcanic deposition signals from each ice core record by applying a high‐pass loess filter to the time series and examining peaks that exceed twice the 31‐year running median absolute deviation. We then studied the spatial pattern of volcanic sulfate deposition on Greenland and Antarctica and combined this knowledge with a new understanding of stratospheric transport of volcanic aerosols to produce a forcing data set as a function of month, latitude, and altitude for the past 1500 years. We estimated the uncertainties associated with the choice of volcanic signal extraction criteria, ice core sulfate deposition to stratospheric loading calibration factor, and the season for the eruptions without a recorded month. We forced an energy balance climate model with this new volcanic forcing data set, together with solar and anthropogenic forcing, to simulate the large‐scale temperature response. The results agree well with instrumental observations for the past 150 years and with proxy records for the entire period. Through better characterization of the natural causes of climate change, this new data set will lead to improved prediction of anthropogenic impacts on climate. The new data set of stratospheric sulfate injections from volcanic eruptions for the past 1500 years, as a function of latitude, altitude, and month, is available for download in a format suitable for forcing general circulation models of the climate system.
Relationship between MODIS fire hot spot count and burned area in a degraded tropical peat swamp forest in Central Kalimantan, Indonesia
Authors: Tansey K. , Beston J. , Hoscilo A. , Page S. E. , Paredes Hernández C. U.
Published: December 2008

A number of space‐borne sensors observe radiant energy at thermal wavelengths. Thermal anomaly data, otherwise known as hotspot data, have been shown to be particularly correlated with the occurrence of active fires (a fire normally with a flaming component and/or smoldering component). Because of a lack of high‐quality burned area data, recent studies have used hotspot data as a proxy for burned area when calculating gas emissions or atmospheric pollutants as a result of biomass burning. We argue that the relationship between hotspot data and burned area is spatially variable and strongly dependent on the vegetation type and function. In this article, we explore the relationship between hotspot data and burned area for a region of degraded and partially altered tropical peat swamp forest in southern Kalimantan, Indonesia. MODIS thermal anomaly (MOD14A1) data were used, alongside disaster monitoring constellation (DMC) and Landsat TM data that were used to derive the burnt area, to calculate a figure indicating the average burned area per hotspot (AR). Two different levels of hotspot detection confidence are examined in order to ascertain which confidence levels best describe fires in a tropical peat swamp forest environment. Only a relatively small number of fires were detected at the lowest confidence level, but these small number of hotspots improved results. Results for the estimation of burnt area for each hotspot were found to vary between 15 and 16 ha. Omission errors are of the order of 60%; hotspot commission rates are of the order of 8%.
Consistency of scaling relations among bedrock and alluvial channels
Authors: Wohl Ellen , David Gabrielle C. L.
Published: December 2008

This paper presents field data on channel geometry and potential control variables from 47 field settings representing a diverse range of environments. These data are used to evaluate existing scaling relationships used in models of the evolution of bedrock channel geometry and to test the hypothesis that channel width (w) increases more slowly and depth (d) more rapidly in relation to discharge (Q) or drainage area (A) as substrate resistance increases. For this data set, w ∼ A0.3, w ∼ Q0.5, d ∼ A0.2, and d ∼ Q0.3. The w‐A and w‐Q relations are close to those found by previous investigators. The d‐A and d‐Q relations have not previously been reported for bedrock channels. Examination of trends within the data does not support the hypothesis and, instead, suggests that the erosional resistance of channel boundaries is not the primary control on scaling relations for channel geometry.
Conceptual model uncertainty in groundwater modeling: Combining generalized likelihood uncertainty estimation and Bayesian model averaging
Authors: Rojas Rodrigo , Feyen Luc , Dassargues Alain
Published: December 2008

Uncertainty assessments in groundwater modeling applications typically attribute all sources of uncertainty to errors in parameters and inputs, neglecting what may be the primary source of uncertainty, namely, errors in the conceptualization of the system. Confining the set of plausible system representations to a single model leads to underdispersive and prone‐to‐bias predictions. In this work, we present a general and flexible approach that combines generalized likelihood uncertainty estimation (GLUE) and Bayesian model averaging (BMA) to assess uncertainty in model predictions that arise from errors in model structure, inputs, and parameters. In a prior analysis, a set of plausible models is selected, and the joint prior input and parameter space is sampled to form potential simulators of the system. For each model, the likelihood measures of acceptable simulators, assigned to them based on their ability to reproduce observed system behavior, are integrated over the joint input and parameter space to obtain the integrated model likelihood. The latter is used to weight the predictions of the respective model in the BMA ensemble predictions. For illustrative purposes, we applied the methodology to a three‐dimensional hypothetical setup. Results showed that predictions of groundwater budget terms varied considerably among competing models; despite this, a set of 16 head observations used for conditioning did not allow differentiating between the models. BMA provided average predictions that were more conservative than individual predictions obtained for individual models. Conceptual model uncertainty contributed up to 30% of the total uncertainty. The results clearly indicate the need to consider alternative conceptualizations to account for model uncertainty.
Tree rainfall interception measured by stem compression
Authors: Friesen J. , van Beek C. , Selker J. , Savenije H. H. G. , van de Giesen N.
Published: December 2008

A method for measuring whole‐tree interception of precipitation is presented which employs mechanical displacement sensors to measure trunk compression caused by the water captured by the tree. This direct and nondestructive method is demonstrated to be sensitive to less than 5 kg of interception field tests in Netherlands and Ghana.
Measurement & Prediction of Phase Behaviour of Carbon Dioxide Mixtures
Authors: Forte Esther , Galindo Amparo , Ruffine Livio , Trusler J.P. Martin
Published: December 2008

Acquiring a comprehensive understanding of the behaviour of carbon dioxide under reservoir conditions is essential for optimizing its usage in enhanced oil recovery (EOR) and for developing sequestration schemes. In order to obtain this understanding, it is necessary to study the physical properties and phase behaviour of mixtures of carbon dioxide with hydrocarbons and brines under conditions of high pressure. In this work we are addressing both the experimental and the theoretical aspects of this problem. A new apparatus, based on the static-analytical method, has been developed to measure phase equilibrium. The equipment comprises a high-pressure cell with sapphire windows for visual observation and phase sampling, with on-line gas chromatography analysis, for measuring the phase compositions. The experimental work is complemented with a theoretical modelling for these mixtures, using the statistical association fluid theory for potentials of variable range (SAFT-VR). As an example of the predictive capabilities of the equation, the fluid phase behaviour of the mixture (carbon dioxide + n-decane) is presented.
The chemical and electronic surface and interface structure of CuGaSe2 thin-film solar cell absorbers
Authors: Bär M. , Rusu M. , Lehmann S. , Schedel-Niedrig Th. , Lauermann I. , Lux-Steiner M. C.
Published: December 2008

The chemical and electronic surface and interface structure of CuGaSe2 thin films was investigated by photoelectron spectroscopy. With bulk [Ga]/[Cu] ratios increasing from 0.94 to 1.39 a transition of the Cu:Ga:Se surface composition from 1:1:2 to 1:3:5 and a downward shift of the valence band maximum with respect to the Fermi energy were observed. The comparison with the conduction band minimum (CBM) of CdS reveals that at the CdS/CuGaSe2 interface the recombination barrier height simultaneously increases and a “clifflike” offset is formed to the CBM of CuGaSe2.
Angle-resolved photoelectron study on the structures of silicon nitride films and Si3N4/Si interfaces formed using nitrogen-hydrogen radicals
Authors: Aratani Takashi , Higuchi Masaaki , Sugawa Shigetoshi , Ikenaga Eiji , Ushio Jiro , Nohira Hiroshi , Suwa Tomoyuki , Teramoto Akinobu , Ohmi Tadahiro , Hattori Takeo
Published: December 2008

Soft x-ray-excited angle-resolved photoemission results for nitride films formed using nitrogen–hydrogen radicals on Si(100), Si(111), and Si(110) are reported. The data were obtained using synchrotron radiation, which allowed the Si 2p, N 1s, and O 1s levels to be investigated with the same probing depth. The following main results were obtained: (1) the Si3N4 film is covered with one monolayer of Si–(OH)3N. Its areal density is 15% smaller on Si(111) than on Si(100) and Si (110), (2) the Si3N4/Si interfaces on all three surfaces are compositionally abrupt. This conclusion is based on the observation that no Si atoms bonded with three N atoms and one Si atom were detected, and (3) the observation that the number of Si–H bonds at the Si3N4/Si(110) interface is 38%–53% larger than those at the Si3N4/Si(100) and Si3N4/Si(111) interfaces indicates a dependence of the interface structure on the orientation of the substrate.
Computation of vibrational energy levels and eigenstates of fluoroform using the multiconfiguration time-dependent Hartree method
Authors: Doriol Loïc Joubert , Gatti Fabien , Iung Christophe , Meyer Hans-Dieter
Published: December 2008

A theoretical study of the vibrational spectrum of the CHF3 molecule is carried out with the aid of the multiconfiguration time-dependent Hartree (MCTDH) algorithm. In order to obtain the eigenvalues and the eigenstates, recent developments in the MCTDH improved relaxation method in a block form are exploited. Around 80 eigenvalues are reported, which are converged with a very high accuracy. The results obtained with our study are compared with those of a previous work using the wave operator sorting algorithm approach. The present investigation exemplifies the robustness and the accuracy of the improved relaxation method.
High performance ambient processed inverted polymer solar cells through interfacial modification with a fullerene self-assembled monolayer
Authors: Hau Steven K. , Yip Hin-Lap , Ma Hong , Jen Alex K.-Y.
Published: December 2008

The performance of inverted bulk-heterojunction solar cells with zinc oxide nanoparticles as the electron selective contact is compared to those modified with a fullerene self-assembled monolayer (C60-SAM). The devices modified with a C60-SAM show very significant improvement in conversion efficiencies compared to unmodified devices leading to efficiencies as high as 4.9%. This is due to enhanced electronic coupling of the inorganic/organic interface from the C60-SAM leading to improved fill factor and photocurrent. Furthermore, devices fabricated in an inert environment were compared to those fabricated in ambient showing comparable device performance.
Molecular dynamics calculation of the fluorine ions’ potential energies in AlGaN/GaN heterostructures
Authors: Yuan L. , Wang M. J. , Chen K. J.
Published: December 2008

Fluorine ions can be effectively incorporated into AlGaN/GaN high electron mobility transistors (HEMTs), enabling the modulation of local potential and carrier density. The physical mechanism of fluorine incorporation in AlGaN/GaN heterojunctions is of fundamental importance to the stability of fluorine ions in AlGaN/GaN HEMTs. In this work, the molecular dynamics simulation method is used to calculate the potential energies of interstitial and substitutional fluorine ions in AlGaN/GaN material system. It is revealed that the fluorine ions are most likely located at the substitutional group-III cation sites S(III), and the diffusion of fluorine ions in implanted III-nitride semiconductors should be dominated by S(III)-interstitial process.
Ferroelectric and anisotropic electrical properties of BaMgF4 single crystal for vacuum UV devices
Authors: Kannan C. V. , Shimamura K. , Zeng H. R. , Kimura H. , Villora E. G. , Kitamura K.
Published: December 2008

Ferroelectric and anisotropic electrical behaviors of barium magnesium fluoride (BaMgF4) single crystal grown under CF4 atmosphere by the Czochralski method are comprehensively studied by polarization hysteresis and impedance spectroscopy measurements, respectively. The coercive field (Ec) varies not only with applied frequency but also with ramp rates, while spontaneous polarization Ps∼6.9 C/cm2 remains the same. Dielectric polarization and ionic conductivity measurements at various temperatures and frequencies reveal quasi-one-dimensional ionic conduction phenomena along the c-axis and non-Debye dielectric relaxation along the axes.