bluuebunny/crossref_metadata_2025 huggingface dataset:
Is climate change the number one threat to humanity?
Authors: Goklany Indur M.
Published: October 2012

This paper challenges claims that global warming outranks other threats facing humanity through the foreseeable future (assumed to be 2085–2100). World Health Organization and British government‐sponsored global impact studies indicate that, relative to other factors, global warming's impact on key determinants of human and environmental well‐being should be small through 2085 even under the warmest Intergovernmental Panel on Climate Change (IPCC) scenario. Specifically, over 20 other health risks currently contribute more to death and disease worldwide than global warming. Through 2085, only 13% of mortality from hunger, malaria, and extreme weather events (including coastal flooding from sea level rise) should be from warming. Moreover, warming should reduce future global population at risk of water stress, and pressures on ecosystems and biodiversity (by increasing net biome productivity and decreasing habitat conversion). That warming is not fundamental to human well‐being is reinforced by lower bound estimates of net gross domestic product (GDP) per capita. This measure adjusts GDP downward to account for damages from warming due to market, health, and environmental impacts, and risk of catastrophe. For both developing and industrialized countries, net GDP per capita—albeit an imperfect surrogate for human well‐being—should be (1) double the current US level by 2100 under the warmest scenario, and (2) lowest under the poorest IPCC scenario but highest under the warmest scenario through 2200. The warmest world, being wealthier, should also have greater capacity to address any problem, including warming. Therefore, other problems and, specifically, lowered economic development are greater threats to humanity than global warming. WIREs Clim Change 2012, 3:489–508. doi: 10.1002/wcc.194

This article is categorized under:

Social Status of Climate Change Knowledge > Knowledge and Practice
QCD in the color-flow representation
Authors: Kilian W. , Ohl T. , Reuter J. , Speckner C.
Published: October 2012

Abstract

For many practical purposes, it is convenient to formulate unbroken non-abelian gauge theories like QCD in a color-flow basis. We present a new derivation of SU(N) interactions in the color-flow basis by extending the gauge group to U(N) × U(1)′ in such a way that the two U(1) factors cancel each other. We use the quantum action principles to show the equivalence to the usual basis to all orders in perturbation theory. We extend the known Feynman rules to exotic color representations (e.g. sextets) and discuss practical applications as they occur in automatic computation programs.
Surgeon Migration Between Developing Countries and the United States: Train, Retain, and Gain from Brain Drain
Authors: Hagander Lars E. , Hughes Christopher D. , Nash Katherine , Ganjawalla Karan , Linden Allison , Martins Yolanda , Casey Kathleen M. , Meara John G.
Published: October 2012

Background

The critical shortage of surgeons in many low‐ and middle‐income countries (LMICs) prevents adequate responses to surgical needs, but the factors that affect surgeon migration have remained incompletely understood. The goal of this study was to examine the importance of personal, professional, and infrastructural factors on surgeon migration from LMICs to the United States. We hypothesized that the main drivers of surgeon migration can be addressed by providing adequate domestic surgical infrastructure, surgical training programs, and viable surgical career paths.

Methods

We conducted an internet‐based nationwide survey of surgeons living in the US who originated from LMICs.

Results

66 surgeons completed the survey. The most influential factors for primary migration were related to professional reasons (p ≤ 0.001). Nonprofessional factors, such as concern for remuneration, family, and security were significantly less important for the initial migration decisions, but adopted a more substantial role in deciding whether or not to return after training in the United States. Migration to the United States was initially considered temporary (44 %), and a majority of the surveyed surgeons have returned to their source countries in some capacity (56 %), often on multiple occasions (80 %), to contribute to clinical work, research, and education.

Conclusions

This study suggests that surgically oriented medical graduates from LMICs migrate primarily for professional reasons. Initiatives to improve specialist education and surgical infrastructure in LMICs have the potential to promote retention of the surgical workforce. There may be formal ways for LMICs to gain from the international pool of relocated surgeons.
Predicting Hollow Viscus Injury in Blunt Abdominal Trauma with Computed Tomography
Authors: Bhagvan Savitha , Turai Matthew , Holden Andrew , Ng Alexander , Civil Ian
Published: October 2012

Background

Evaluation of blunt abdominal trauma is controversial. Computed tomography (CT) of the abdomen is commonly used but has limitations, especially in excluding hollow viscus injury in the presence of solid organ injury. To determine whether CT reports alone could be used to direct operative treatment in abdominal trauma, this study was undertaken.

Methods

The trauma database at Auckland City Hospital was accessed for patients who had abdominal CT and subsequent laparotomy during a five‐year period. The CT scans were reevaluated by a consultant radiologist who was blinded to operative findings. The CT findings were correlated with the operative findings.

Results

Between January 2002 and December 2007, 1,250 patients were evaluated for blunt abdominal injury with CT. A subset of 78 patients underwent laparotomy, and this formed the study group. The sensitivity and specificity of CT scan in predicting hollow viscus injury was 55.33 and 92.06 % respectively. The positive and negative predictive values were 61.53 and 89.23 % respectively. Presence of free fluid in CT scan was sensitive in diagnosing hollow viscus injury (90 %). Specific findings for hollow viscus injuries on CT scan were free intraperitoneal air (93 %), retroperitoneal air (100 %), oral contrast extravasation (100 %), bowel wall defect (98 %), patchy bowel enhancement (97 %), and mesenteric abnormality (94 %).

Conclusions

CT alone cannot be used as a screening tool for hollow viscus injury. The decision to operate in hollow viscus injury has to be based on mechanism of injury and clinical findings together with radiological evidence.
Endothelin‐1 induces hypoxia inducible factor 1α expression in pulmonary artery smooth muscle cells
Authors: Li Manxiang , Liu Yuan , Jin Faguang , Sun Xiuzhen , Li Zongfang , Liu Yun , Fang Ping , Shi Hongyang , Jiang Xingtang
Published: October 2012

Endothelin‐1 (ET‐1) dose‐dependently increased HIF1α expression in pulmonary artery smooth muscle cells (PASMCs). Inhibition of protein synthesis did not affect ET‐1‐induced HIF1α expression. The maximum effect of ET‐1 was similar to that caused by proteasome inhibitor MG132. Further study indicates that ET‐1 also dose‐dependently stimulated calcineurin activation, specific calcineurin inhibitor cyclosporine A (CsA), abolished ET‐1‐induced HIF1α elevation, and reversed ET‐1‐induced RACK1 (receptor of activated protein kinase C 1) de‐phosphorylation. Endothelin receptor A was found to specifically mediate the effects of ET‐1. To examine whether RACK1 is particularly involved in proteasome‐dependent HIF1α degradation, RACK1 was silenced by siRNA transfection. Cells lacking RACK1 exhibited significant elevation of HIF1α protein level. Taken together, our study suggests that ET‐1 suppressed proteasome‐dependent HIF1α degradation by calcineurin‐dependent RACK1 de‐phosphorylation.
Harmonizing Leibniz’s Ontology
Authors: STUMPF ANDREW D. H.
Published: October 2012

I propose a novel compatibilist interpretation of Leibniz’s mature views concerning what is metaphysically basic. Drawing on a compatibilist reading of Aristotle on primary substance in the Categories and Metaphysics Z, I argue that Leibniz is working with two complementary ways of being metaphysically basic—one applying to immaterial monads, the other to corporeal substances. Although corporeal substances derive their status as basic from their dominant monads, they are nevertheless fully real, unified, and genuinely capable of acting. This perspective respects Leibniz’s idealist tendencies and his commitment to the reality of bodies without (implausibly) attributing inconsistency to his considered views.
Generating the mapping class group by torsion elements of small order
Authors: MONDEN NAOYUKI
Published: October 2012

We show that the mapping class group of a closed, connected, oriented surface of genus at least three is generated by 3 elements of order 3. Moreover, we show that the mapping class group of a closed, connected, oriented surface of genus at least three is generated and by 4 elements of order 4.
The Conley–Zehnder indices of the rotating Kepler problem
Authors: ALBERS PETER , FISH JOEL W. , FRAUENFELDER URS , VAN KOERT OTTO
Published: October 2012

We determine the Conley–Zehnder indices of all periodic orbits of the rotating Kepler problem for energies below the critical Jacobi energy. Consequently, we show the universal cover of the bounded component of the regularized energy hypersurface is dynamically convex. Moreover, in the universal cover there is always precisely one periodic orbit with Conley–Zehnder index 3, namely the lift of the doubly covered retrograde circular orbit.
Optimal Redundant Sensor Configuration for Accuracy and Reliability Increasing in Space Inertial Navigation Systems
Authors: Jafari Mahdi , Roshanian Jafar
Published: October 2012

A redundant Inertial Measurement Unit (IMU) is an inertial sensing device composed of more than three accelerometers and three gyroscopes. This paper analyses the performance of redundant IMUs and their various sensor configurations. The inertial instruments can achieve high reliability for long periods of time only by redundancy. By suitable geometric configurations it is possible to extract the maximum amount of reliability and accuracy from a given number of redundant single-degree-of-freedom gyros or accelerometers. This paper gives a general derivation of the optimum matrix which can be applied to the outputs of any combination of three or more sensors to obtain three orthogonal vector components based on their geometric configuration and error characteristics. Certain combinations of four or more instruments are able to detect an instrument malfunction, and combinations of five have the additional capability of isolating that malfunction to a particular sensor. Finally, this paper offers a major improvement in reliability, although the improvement in accuracy is minor.
CO2-C losses and carbon quality of selected Maritime Antarctic soils
Authors: Carvalho Juliana Vanir De Souza , Mendonça Eduardo De Sá , La Scala Newton , Reis César , Reis Efrain Lázaro , Schaefer Carlos E.G.R.
Published: October 2012

Polar Regions are the most important soil carbon reservoirs on Earth. Monitoring soil carbon storage in a changing global climate context may indicate possible effects of climate change on terrestrial environments. In this regard, we need to understand the dynamics of soil organic matter in relation to its chemical characteristics. We evaluated the influence of chemical characteristics of humic substances on the process of soil organic matter mineralization in selected Maritime Antarctic soils. A laboratory assay was carried out with soils from five locations from King George Island. We determined the contents of total organic carbon, oxidizable carbon fractions of soil organic matter, and humic substances. Two in situ field experiments were carried out during two summers, in order to evaluate the CO2-C emissions in relation to soil temperature variations. The overall low amounts of soil organic matter in Maritime Antarctic soils have a low humification degree and reduced microbial activity. CO2-C emissions showed significant exponential relationship with temperature, suggesting a sharp increase in CO2-C emissions with a warming scenario, and Q10 values (the percentage increase in emission for a 10°C increase in soil temperature) were higher than values reported from elsewhere. The sensitivity of the CO2-C emission in relation to temperature was significantly correlated with the humification degree of soil organic matter and microbial activity for Antarctic soils.
Local fibred right adjoints are polynomial
Authors: KOCK ANDERS , KOCK JOACHIM
Published: October 2012

For any locally cartesian closed category ℰ, we prove that a local fibred right adjoint between slices of ℰ is given by a polynomial. The slices in question are taken in a well-known fibred sense.
Embedding Spanning Bipartite Graphs of Small Bandwidth
Authors: KNOX FIACHRA , TREGLOWN ANDREW
Published: October 2012

Böttcher, Schacht and Taraz (Math. Ann., 2009) gave a condition on the minimum degree of a graph G on n vertices that ensures G contains every r-chromatic graph H on n vertices of bounded degree and of bandwidth o(n), thereby proving a conjecture of Bollobás and Komlós (Combin. Probab. Comput., 1999). We strengthen this result in the case when H is bipartite. Indeed, we give an essentially best-possible condition on the degree sequence of a graph G on n vertices that forces G to contain every bipartite graph H on n vertices of bounded degree and of bandwidth o(n). This also implies an Ore-type result. In fact, we prove a much stronger result where the condition on G is relaxed to a certain robust expansion property. Our result also confirms the bipartite case of a conjecture of Balogh, Kostochka and Treglown concerning the degree sequence of a graph which forces a perfect H-packing.
The Rio+20 Process: Forward Movement for the Environment?
Authors: Powers Ann
Published: October 2012

This commentary summarizes the events at the recent UN Conference on Sustainable Development, commonly referred to as Rio+20, noting both the role of official national delegations and the diversity of non-state parties that were involved in a variety of venues at and around Rio+20. It sketches the background of sustainable development efforts, maps the road from the original 1992 Rio Earth Summit to the 20th anniversary gathering, and comments on the Conference’s outcomes and their implications for international law and legal institutions. In answer to the much debated question of whether the Rio+20 was a success or a failure, or something in between, the author concludes that the Conference, while disappointing to many, may have furthered the cause of sustainable development by producing a document which reflects a baseline of international norms and by fostering the increasingly important role of civil society action, commitments and partnerships, and of transnational governance.
A Genome-Wide Association Study of Monozygotic Twin-Pairs Suggests a Locus Related to Variability of Serum High-Density Lipoprotein Cholesterol
Authors: Surakka Ida , Whitfield John B. , Perola Markus , Visscher Peter M. , Montgomery Grant W. , Falchi Mario , Willemsen Gonneke , de Geus Eco J. C. , Magnusson Patrik K. E. , Christensen Kaare , Sørensen Thorkild I. A. , Pietiläinen Kirsi H. , Rantanen Taina , Silander Kaisa , Widén Elisabeth , Muilu Juha , Rahman Iffat , Liljedahl Ulrika , Syvänen Ann-Christine , Palotie Aarno , Kaprio Jaakko , Kyvik Kirsten O. , Pedersen Nancy L. , Boomsma Dorret I. , Spector Tim , Martin Nicholas G. , Ripatti Samuli , Peltonen Leena
Published: October 2012

Genome-wide association analysis on monozygotic twin-pairs offers a route to discovery of gene–environment interactions through testing for variability loci associated with sensitivity to individual environment/lifestyle. We present a genome-wide scan of loci associated with intra-pair differences in serum lipid and apolipoprotein levels. We report data for 1,720 monozygotic female twin-pairs from GenomEUtwin project with 2.5 million SNPs, imputed or genotyped, and measured serum lipid fractions for both twins. We found one locus associated with intra-pair differences in high-density lipoprotein cholesterol,rs2483058in an intron ofSRGAP2, where twins carrying the C allele are more sensitive to environmental factors (P= 3.98 × 10−8). We followed up the association in further genotyped monozygotic twins (N= 1,261), which showed a moderate association for the variant (P= 0.200, same direction of an effect). In addition, we report a new association on the level of apolipoprotein A-II (P= 4.03 × 10−8).
Evaluation einer Sprachfördermaßnahme für Vorschulkinder
Authors: Sachse Steffi , Budde Nora , Rinker Tanja , Groth Katarina
Published: October 2012

Adäquate sprachliche Fähigkeiten werden als zentral für einen gelingenden Schulstart und die gesamte schulische Laufbahn erachtet. Gerade für mehrsprachige Kinder wurden in den einzelnen Bundesländern Sprachkurse und Förderprogramme eingerichtet, die darauf abzielen, Kinder vor Schulbeginn im Deutschen sprachlich zu fördern, um deren Bildungschancen zu erhöhen. Allerdings ist die Wirksamkeit solcher additiver Sprachfördermaßnahmen bislang kaum erforscht. In der vorliegenden Studie wurde untersucht, welche Effekte ein in hessischen Vorlaufkursen eingesetztes, sprachwissenschaftlich fundiertes Förderprogramm hat und welche Sprachleistungen Kinder am Ende der Vorlaufkurse zeigen. Dafür wurden 125 mehrsprachige Kinder in Vorlaufkursen einbezogen, die entweder nach dem spezifischen Förderprogramm oder nach dem bisherigen Vorgehen der Lehrkräfte gefördert wurden. Im Ergebnis konnte keine Überlegenheit einer der beiden Varianten der Vorlaufkurse gezeigt werden. Auch die von den Kindern nach Beendigung der Vorlaufkurse gezeigten sprachlichen Leistungen fielen im Hinblick auf eine unproblematische Unterrichtsteilhabe sehr schwach aus.
Evaluating participation in water resource management: A review
Authors: Carr G. , Blöschl G. , Loucks D. P.
Published: October 2012

Key documents such as the European Water Framework Directive and the U.S. Clean Water Act state that public and stakeholder participation in water resource management is required. Participation aims to enhance resource management and involve individuals and groups in a democratic way. Evaluation of participatory programs and projects is necessary to assess whether these objectives are being achieved and to identify how participatory programs and projects can be improved. The different methods of evaluation can be classified into three groups: (i) process evaluation assesses the quality of participation process, for example, whether it is legitimate and promotes equal power between participants, (ii) intermediary outcome evaluation assesses the achievement of mainly nontangible outcomes, such as trust and communication, as well as short‐ to medium‐term tangible outcomes, such as agreements and institutional change, and (iii) resource management outcome evaluation assesses the achievement of changes in resource management, such as water quality improvements. Process evaluation forms a major component of the literature but can rarely indicate whether a participation program improves water resource management. Resource management outcome evaluation is challenging because resource changes often emerge beyond the typical period covered by the evaluation and because changes cannot always be clearly related to participation activities. Intermediary outcome evaluation has been given less attention than process evaluation but can identify some real achievements and side benefits that emerge through participation. This review suggests that intermediary outcome evaluation should play a more important role in evaluating participation in water resource management.
Modeling soil heating and moisture transport under extreme conditions: Forest fires and slash pile burns
Authors: Massman W. J.
Published: October 2012

Heating any soil during a sufficiently intense wildfire or prescribed burn can alter it irreversibly, causing many significant, long‐term biological, chemical, and hydrological effects. Given the climate‐change‐driven increasing probability of wildfires and the increasing use of prescribed burns by land managers, it is important to better understand the dynamics of the coupled heat and moisture transport in soil during these extreme heating events. Furthermore, improved understanding and modeling of heat and mass transport during extreme conditions should provide insights into the associated transport mechanisms under more normal conditions. The present study describes a numerical model developed to simulate soil heat and moisture transport during fires where the surface heating often ranges between 10,000 and 100,000 W m−2 for several minutes to several hours. Basically, the model extends methods commonly used to model coupled heat flow and moisture evaporation at ambient conditions into regions of extreme dryness and heat. But it also incorporates some infrequently used formulations for temperature dependencies of the soil specific heat, thermal conductivity, and the water retention curve, as well as advective effects due to the large changes in volume that occur when liquid water is rapidly volatilized. Model performance is tested against laboratory measurements of soil temperature and moisture changes at several depths during controlled heating events. Qualitatively, the model agrees with the laboratory observations, namely, it simulates an increase in soil moisture ahead of the drying front (due to the condensation of evaporated soil water at the front) and a hiatus in the soil temperature rise during the strongly evaporative stage of the soil drying. Nevertheless, it is shown that the model is incapable of producing a physically realistic solution because it does not (and, in fact, cannot) represent the relationship between soil water potential and soil moisture at extremely low soil moisture contents (i.e., residual or bound water: θ < 0.01 m3 m−3, for example). Diagnosing the model's performance yields important insights into how to make progress on modeling soil evaporation and heating under conditions of high temperatures and very low soil moisture content.
Complex characteristics of slow slip events in subduction zones reproduced in multi‐cycle simulations
Authors: Colella Harmony V. , Dieterich James H. , Richards‐Dinger Keith , Rubin Allan M.
Published: October 2012

Since the discovery of slow slip events along subduction zone interfaces worldwide, dense geodetic and seismic networks have illuminated detailed characteristics of these events and associated tremor. High‐resolution observations of tremor, where the spatial‐temporal evolution is presumed to reflect that of the underlying slow slip events, show highly complex patterns in which the origins remain poorly understood. We present a new, computationally efficient modeling technique that reproduces many features of observed slow slip events, including slow initiation, coalescence of separate events, and rapid back‐propagation of renewed slip over previously slipped regions. Rapid back propagation speeds are explained as a consequence of rate‐ and state‐dependent frictional healing, consistent with analytical solutions developed in support of the simulations.
Increasing frequency, intensity and duration of observed global heatwaves and warm spells
Authors: Perkins S. E. , Alexander L. V. , Nairn J. R.
Published: October 2012

Using the latest HadGHCND daily temperature dataset, global trends in observed summertime heatwaves and annually calculated warm spells for 1950–2011 are analysed via a multi‐index, multi‐aspect framework. Three indices that separately focus on maximum temperature (TX90pct), minimum temperature (TN90pct) and average temperature (EHF) were studied with respect to five characteristics of event intensity, frequency and duration. Despite which index is employed, increases in heatwave/warm spell intensity, frequency and duration are found. Furthermore, TX90pct and TN90pct trends are larger and exhibit more significance for warm spells, implying that non‐summer events are driving annual trends over some regions. Larger increases in TN90pct aspects relative to EHF and TX90pct are also observed. While qualitative information on event trends is similar across the indices, quantitative values vary. This result highlights the importance of employing the most appropriate index when assessing the impact of sustained extreme temperature events.
The amplitude of decadal to multidecadal variability in precipitation simulated by state‐of‐the‐art climate models
Authors: Ault T. R. , Cole J. E. , St. George S.
Published: October 2012

We assess the magnitude of decadal to multidecadal (D2M) variability in Climate Model Intercomparison Project 5 (CMIP5) simulations that will be used to understand, and plan for, climate change as part of the Intergovernmental Panel on Climate Change's 5th Assessment Report. Model performance on D2M timescales is evaluated using metrics designed to characterize the relative and absolute magnitude of variability at these frequencies. In observational data, we find that between 10% and 35% of the total variance occurs on D2M timescales. Regions characterized by the high end of this range include Africa, Australia, western North America, and the Amazon region of South America. In these areas D2M fluctuations are especially prominent and linked to prolonged drought. D2M fluctuations account for considerably less of the total variance (between 5% and 15%) in the CMIP5 archive of historical (1850–2005) simulations. The discrepancy between observation and model based estimates of D2M prominence reflects two features of the CMIP5 archive. First, interannual components of variability are generally too energetic. Second, decadal components are too weak in several key regions. Our findings imply that projections of the future lack sufficient decadal variability, presenting a limited view of prolonged drought and pluvial risk.
The extreme melt across the Greenland ice sheet in 2012
Authors: Nghiem S. V. , Hall D. K. , Mote T. L. , Tedesco M. , Albert M. R. , Keegan K. , Shuman C. A. , DiGirolamo N. E. , Neumann G.
Published: October 2012

The discovery of the 2012 extreme melt event across almost the entire surface of the Greenland ice sheet is presented. Data from three different satellite sensors – including the Oceansat‐2 scatterometer, the Moderate‐resolution Imaging Spectroradiometer, and the Special Sensor Microwave Imager/Sounder – are combined to obtain composite melt maps, representing the most complete melt conditions detectable across the ice sheet. Satellite observations reveal that melt occurred at or near the surface of the Greenland ice sheet across 98.6% of its entire extent on 12 July 2012, including the usually cold polar areas at high altitudes like Summit in the dry snow facies of the ice sheet. This melt event coincided with an anomalous ridge of warm air that became stagnant over Greenland. As seen in melt occurrences from multiple ice core records at Summit reported in the published literature, such a melt event is rare with the last significant one occurring in 1889 and the next previous one around seven centuries earlier in the Medieval Warm Period. Given its rarity, the 2012 extreme melt across Greenland provides an exceptional opportunity for new studies in broad interdisciplinary geophysical research.
Seismic velocity constraints on the material properties that control earthquake behavior at the Quebrada‐Discovery‐Gofar transform faults, East Pacific Rise
Authors: Roland Emily , Lizarralde Dan , McGuire Jeffrey J. , Collins John A.
Published: October 2012

Mid‐ocean ridge transform faults (RTFs) vary strongly along strike in their ability to generate large earthquakes. This general observation suggests that local variations in material properties along RTFs exert a primary control on earthquake rupture dynamics. We explore these relationships by examining the seismic structure of two RTFs that have distinctly different seismic coupling. We determine the seismic velocity structure at the Gofar and Quebrada faults on the East Pacific Rise (EPR) using P wave traveltime tomography with data from two active‐source wide‐angle refraction lines crossing the faults. We image low‐velocity zones (LVZs) at both faults, where P wave velocities are reduced by as much as 0.5–1.0 km/s (∼10–20%) within a several kilometer wide region. At the Gofar fault, the LVZ extends through the entire crust, into the seismogenic zone. We rule out widespread serpentinization as an explanation for the low velocities, owing to the lack of a corresponding signal in the locally measured gravity field. The reduced velocities can be explained if the plate boundary region is composed of fault material with enhanced fluid‐filled porosity (1.5–8%). Local seismic observations indicate that the high‐porosity region lies within a ∼10 km long portion of the fault that fails in large swarms of microearthquakes and acts as a barrier to the propagation of large (M ∼ 6.0) earthquakes. Tomographic images of fault structure combined with observed earthquake behavior suggest that EPR transform segments capable of generating large earthquakes have relatively intact gabbro within the seismogenic zone, whereas segments that slip aseismically or via earthquake swarms are composed of highly fractured, ≥2 km wide damage zones that extend throughout the crust.
Effects of anisotropic viscosity and texture development on convection in ice mantles
Authors: Rudolph M. L. , Manga M.
Published: October 2012

Convection may occur in the ice shells of satellites in the outer solar system. The style of convection, rate of heat transport, and resulting surface features depend on the rheology of ice, which in turn depends on temperature, grain size, stress, and crystallographic preferred orientation (CPO). Here we study the effect of CPO development and anisotropic viscosity on convection by coupling a model of polycrystalline ice deformation with a macroscopic flow model. Despite having a first‐order effect on velocities and heat transport in a convecting ice shell, fabric development is unlikely to be observable either directly by spacecraft‐based radar or indirectly based on changes in the wavelength or amplitude of dynamic topography.
The CH4structure in Titan's upper atmosphere revisited
Authors: Cui J. , Yelle R. V. , Strobel D. F. , Müller‐Wodarg I. C. F. , Snowden D. S. , Koskinen T. T. , Galand M.
Published: October 2012

In this study, we reanalyze the CH4structure in Titan's upper atmosphere combining the Cassini Ion Neutral Mass Spectrometer (INMS) data from 32 flybys and incorporating several updates in the data reduction algorithms. We argue that based on our current knowledge of eddy mixing and neutral temperature, strong CH4escape must occur on Titan. Ignoring ionospheric chemistry, the optimal CH4loss rate is ∼3 × 1027 s−1or 80 kg s−1in a globally averaged sense, consistent with the early result of Yelle et al. (2008). The considerable variability in CH4structure among different flybys implies that CH4escape on Titan is more likely a sporadic rather than a steady process, with the CH4profiles from about half of the flybys showing evidence for strong escape and most of the other flybys consistent with diffusive equilibrium. CH4inflow is also occasionally required to interpret the data. Our analysis further reveals that strong CH4escape preferentially occurs on the nightside of Titan, in conflict with the expectations of any solar‐driven model. In addition, there is an apparent tendency of elevated CH4escape with enhanced electron precipitation from the ambient plasma, but this is likely to be a coincidence as the time response of the CH4structure may not be fast enough to leave an observable effect during a Titan encounter.
Modeling morphodynamic processes in meandering rivers with spatial width variations
Authors: Zolezzi G. , Luchi R. , Tubino M.
Published: October 2012

Most morphodynamic models of river meandering assume spatially constant width; depending on the intensity of spatial width variations, different meandering styles actually exist, often associated with midchannel bars and islands. When intense enough, width oscillations characterize transitional planforms between meandering and braiding. We investigate, on a modeling basis, morphodynamic feedbacks between spatial curvature and width oscillations in river meanders and related bedform patterns. Our review of existing mathematical models suggests that width‐curvature interactions can be comprehensively analyzed by a hierarchy of models that descend from a two‐parameter perturbation solution of the governing depth‐averaged morphodynamic model. The focus is on in‐stream, autogenic hydromorphodynamic processes, and not explicitly on bank processes. Curvature‐width interactions are fundamentally nonlinear: the perturbation approach allows us to investigate the key effects at the first nonlinear interaction. In meanders with initially constant width, curvature nonlinearly forces midchannel bar growth, promoting symmetrical bank erosion further downstream, possibly triggering width oscillations. These in turn can significantly affect the process of bend stability and therefore condition the curvature dynamics. Wider‐at‐bends meanders develop shorter bends and are morphologically more active compared to equiwidth meanders, coherently with the few available field observations. River evolution models aiming to separately simulate bank erosion and accretion processes should incorporate these autogenic flow‐bed nonlinearities. Because of its focus on meandering morphologies close to the transition with braiding, the proposed approach can be taken as a novel, physically based viewpoint to the long‐debated subject of channel pattern selection.
Neurovascular Coupling Varies with Level of Global Cerebral Ischemia in a Rat Model
Authors: Baker Wesley B , Sun Zhenghui , Hiraki Teruyuki , Putt Mary E , Durduran Turgut , Reivich Martin , Yodh Arjun G , Greenberg Joel H
Published: October 2012

In this study, cerebral blood flow, oxygenation, metabolic, and electrical functional responses to forepaw stimulation were monitored in rats at different levels of global cerebral ischemia from mild to severe. Laser speckle contrast imaging and optical imaging of intrinsic signals were used to measure changes in blood flow and oxygenation, respectively, along with a compartmental model to calculate changes in oxygen metabolism from these measured changes. To characterize the electrical response to functional stimulation, we measured somatosensory evoked potentials (SEPs). Global graded ischemia was induced through unilateral carotid artery occlusion, bilateral carotid artery occlusion, bilateral carotid and right subclavian artery (SCA) occlusion, or carotid and SCA occlusion with negative lower body pressure. We found that the amplitude of the functional metabolic response remained tightly coupled to the amplitude of the SEP at all levels of ischemia observed. However, as the level of ischemia became more severe, the flow response was more strongly attenuated than the electrical response, suggesting that global ischemia was associated with an uncoupling between the functional flow and electrical responses.
Prevention of JNK Phosphorylation as a Mechanism for Rosiglitazone in Neuroprotection after Transient Cerebral Ischemia: Activation of Dual Specificity Phosphatase
Authors: Okami Nobuya , Narasimhan Purnima , Yoshioka Hideyuki , Sakata Hiroyuki , Kim Gab Seok , Jung Joo Eun , Maier Carolina M , Chan Pak H
Published: October 2012

Rosiglitazone, a synthetic peroxisome proliferator-activated receptor-γ (PPARγ) agonist, prevents cell death after cerebral ischemia in animal models, but the underlying mechanism has not been clarified. In this study, we examined how rosiglitazone protects neurons against ischemia. Mice treated with rosiglitazone were subjected to 60 minutes of focal ischemia followed by reperfusion. Rosiglitazone reduced infarct volume after ischemia and reperfusion. We show that this neuroprotective effect was reversed with a PPARgM antagonist. Western blot analysis showed a significant increase in expression of phosphorylated stress-activated protein kinases (c-Jun N-terminal kinase (JNK) and p38) in ischemic brain tissue. Rosiglitazone blocked this increase. Furthermore, we observed that rosiglitazone increased expression of the dual-specificity phosphatase 8 (DUSP8) protein and messenger RNA in ischemic brain tissue. Dual-specificity phosphatase 8 is a mitogen-activated protein kinase phosphatase that can dephosphorylate JNK and p38. Another key finding of the present study was that knockdown of DUSP8 in primary cultured cortical neurons that were subjected to oxygen–glucose deprivation diminished rosiglitazone's effect on downregulation of JNK phosphorylation. Thus, rosiglitazone's neuroprotective effect after ischemia is mediated by blocking JNK phosphorylation induced by ischemia via DUSP8 upregulation.
Role of Met58 in the regulation of electron/proton transfer in trihaem cytochrome PpcA from Geobacter sulfurreducens
Authors: Morgado Leonor , Dantas Joana M. , Simões Telma , Londer Yuri Y. , Pokkuluri P. Raj , Salgueiro Carlos A.
Published: October 2012

The bacterium Gs (Geobacter sulfurreducens) is capable of oxidizing a large variety of compounds relaying electrons out of the cytoplasm and across the membranes in a process designated as extracellular electron transfer. The trihaem cytochrome PpcA is highly abundant in Gs and is most probably the reservoir of electrons destined for the outer surface. In addition to its role in electron transfer pathways, we have previously shown that this protein could perform e−/H+ energy transduction. This mechanism is achieved by selecting the specific redox states that the protein can access during the redox cycle and might be related to the formation of proton electrochemical potential gradient across the periplasmic membrane. The regulatory role of haem III in the functional mechanism of PpcA was probed by replacing Met58, a residue that controls the solvent accessibility of haem III, with serine, aspartic acid, asparagine or lysine. The data obtained from the mutants showed that the preferred e−/H+ transfer pathway observed for PpcA is strongly dependent on the reduction potential of haem III. It is striking to note that one residue can fine tune the redox states that can be accessed by the trihaem cytochrome enough to alter the functional pathways.
The structural physical approximations and optimal entanglement witnesses
Authors: Ha Kil-Chan , Kye Seung-Hyeok
Published: October 2012

We introduce the notions of positive and copositive types for entanglement witnesses, depending on the distance to the positive part and copositive part. An entanglement witness W is of positive type if and only if its partial transpose \documentclass[12pt]{minimal}\begin{document}$W^\Gamma$\end{document}WΓ is of copositive type. We show that if the structural physical approximation (SPA) of W is separable, then W should be of copositive type, and the SPA of \documentclass[12pt]{minimal}\begin{document}$W^\Gamma$\end{document}WΓ is never separable unless W is of both positive and copositive types. This shows that the SPA conjecture is meaningful only for those of copositive type. We provide examples to show that the SPA conjecture fails even for the case of copositive types.
The 14th biennial Center for Turbulence Research Summer Program
Authors: Kim John
Published: October 2012

This is a brief account of the 14th biennial Summer Program of the Center for Turbulence Research, which was held at Stanford University from June 25 to July 20, 2012. Key accomplishments achieved during the summer program were presented at the conclusion of the program, and a few highlights are reported here. More detailed results are to be reported at the annual American Physical Society–Division of Fluid Dynamics meeting in San Diego, November 18-20, 2012, and in Proceedings of the 2012 Summer Program to be published in December 2012 by the Center for Turbulence Research of Stanford University. A repeating theme of the 2012 Summer Program was applications of the dynamic mode decomposition analysis, which revealed important dynamical information of flow physics. Other new findings are highlighted.
Electronically active defects in the Cu2ZnSn(Se,S)4 alloys as revealed by transient photocapacitance spectroscopy
Authors: Miller D. Westley , Warren Charles W. , Gunawan Oki , Gokmen Tayfun , Mitzi David B. , Cohen J. David
Published: October 2012

Transient photocapacitance (TPC) spectra were obtained on a series of Cu2ZnSn(Se,S)4 absorber devices with varying Se:S ratios, providing bandgaps (Eg) between 1 eV and 1.5 eV. Efficiencies varied between 8.3% and 9.3% for devices with Eg ≤ 1.2 eV and were near 6.5% for devices with Eg ≥ 1.4 eV. The TPC spectra revealed a band-tail region with Urbach energies at or below 18 meV for the first group, but in the 25-30 meV range for the higher band-gap samples. A deeper defect band centered near 0.8 eV was also observed in most samples. We identified a correlation between the Urbach energies and the voltage deficit in these devices.
Effect of temperature, strain, and strain rate on the flow stress of aluminum under shock-wave compression
Authors: Zaretsky E. B. , Kanel G. I.
Published: October 2012

The evolution of elastic-plastic shock waves with the propagation distance has been studied in 99.99% purity aluminum and in annealed 6061 aluminum alloy. The free surface velocity histories of shock-loaded samples, 0.1–2.0 mm thick and with initial temperature from 296 to 932 K, have been recorded using velocity interferometer system for any reflector (VISAR). The measured amplitudes of the elastic precursor waves have been approximated by power functions of the propagation distance, and these data have been converted into relationships between the shear stress at the top of elastic precursor wave and the initial plastic strain rate. The latter was found to decrease from 106 to 104 s−1 over 0.1 to 2-mm precursor traverse, while the density of mobile dislocations corresponding to these strain rates varied from 2 × 108 to 5 × 106 cm−2. At fixed strain rates, the flow stress of aluminum grows linearly with temperature. An analysis of the rise times of the plastic shock waves has shown that, for the same level of shear stress, the plastic strain rate at the shock front is by an order of magnitude higher and the density of mobile dislocations is 2-3 times higher than their initial values behind the elastic precursor front.
An alternative method for the measurement of the microwave temperature coefficient of resonant frequency (τf)
Authors: Silva M. A. S. , Fernandes T. S. M. , Sombra A. S. B.
Published: October 2012

In this paper an alternative method for the measurement of the temperature coefficient of resonant frequency (τf), is presented. The traditional method (based on the Courtney method) present some limitations of measuring the values of τf, for samples with high dielectric loss due to their inability to observe clearly the TE011 mode. The alternative experimental setup, to measure the τf value, is based on the variation of the temperature of the dominant mode of a dielectric resonator antenna. The method is quite compatible with the measurement of τf, based on the Courtney method. It presents the advantage that it is less sensitive to the sample loss. In the studied samples, with loss higher than 10−2, the τf were obtained. Samples of known τf were measured in both methods, using the configuration proposed by Courtney and the present study. The alumina (Al2O3) and calcium titanate (CaTiO3) were selected because they have well known values of τf and have low dielectric losses, the bismuth niobate and titanium (Bi3NbTiO9) was chosen because it is not possible to measure its τf by the traditional method due to its high dielectric loss. The obtained results, by measuring, the τf value of CaTiO3 and Al2O3, in this proposed method, present excellent agreement when compared to the traditional Courtney, transmission method. It was also very efficient for measurements of the τf value, of high dielectric loss materials (>10−2), as for the bismuth and titanium niobate (Bi3NbTiO9). The analysis of the temperature coefficient of resonant frequency (τf) in dielectric resonators is an important property for the development of electronic devices. This is because the τf is a fundamental parameter, for the production of new components like filters, oscillators and antennas, with high thermal stability.
High-resolution charge exchange measurements at ASDEX Upgrade
Authors: Viezzer E. , Pütterich T. , Dux R. , McDermott R. M. ,   ASDEX Upgrade Team
Published: October 2012

The charge exchange recombination spectroscopy (CXRS) diagnostics at ASDEX Upgrade (AUG) have been upgraded and extended to provide high-resolution measurements of impurity ion temperature, density, and rotation profiles. The existing core toroidal CXRS diagnostic has been refurbished to increase the level of signal, thus enabling shorter exposure times down to 3.5 ms. Additional lines of sight provide more detailed profiles and enable simultaneous measurements of multiple impurities. In addition, a new CXRS system has been installed, which allows for the measurement of poloidal impurity ion rotation in the plasma edge with high temporal (1.9 ms) and spatial resolution (down to 5 mm). A new wavelength correction method has been implemented to perform in situ wavelength calibrations on a shot-to-shot basis. Absolute measurements of the poloidal impurity ion rotation with uncertainties smaller than 1.5 km/s have been obtained. Comparison of all the CXRS measurements provides a consistency check of the diagnostics and good agreement has been found for all of the CXRS systems.
Revisiting aqueous-acetone mixtures through the concept of molecular emulsions
Authors: Kežić Bernarda , Perera Aurélien
Published: October 2012

Aqueous acetone mixtures represent a good example of perfectly miscible liquids in reality, and that hard to mix in silico. This is related to a key problem in molecular simulations, which is to distinguish between strongly micro-segregated mixtures from phase-separated ones. The Kirkwood-Buff integrals of in silico aqueous mixtures are often found to be dramatically higher than the experimental ones, hinting at a possible underlying phase separation. This is the case for many combinations of the force field models chosen for water or for acetone. Herein, we demonstrate, through a proper handling of the tail of the correlation functions, that these high values of the Kirkwood-Buff integrals represent in fact a transient regime within the segregated spatial domains, and that they asymptotically settle down to values in much better agreement with the experimental ones. The concept central to this new approach is that of molecular emulsions, where the long range part of the correlations is modulated by the micro-segregated domains, and that it is necessary to take into this modulation in order to recover the correct thermodynamical properties.
Geometric percolation in polydisperse systems of finite-diameter rods: Effects due to particle clustering and inter-particle correlations
Authors: Chatterjee Avik P.
Published: October 2012

The impact of particle clustering and correlation upon the percolation behavior of polydisperse cylinders with finite hard core diameter is examined within an analogy to a lattice percolation problem. Percolation thresholds and percolation and backbone probabilities are explored as functions of the degree of clustering and extent of correlation among the inter-particle contacts. The percolation threshold and volume fractions occupied by the infinite network and by the cluster backbone are shown to be quite sensitive to the formation of inter-connected cliques of particles and to the presence of correlation among particle contacts.