bluuebunny/crossref_metadata_2025 huggingface dataset:
Survival of the Fittest: Overcoming Oxidative Stress at the Extremes of Acid, Heat and Metal
Authors: Maezato Yukari , Blum Paul
Published: August 2012

The habitat of metal respiring acidothermophilic lithoautotrophs is perhaps the most oxidizing environment yet identified. Geothermal heat, sulfuric acid and transition metals contribute both individually and synergistically under aerobic conditions to create this niche. Sulfuric acid and metals originating from sulfidic ores catalyze oxidative reactions attacking microbial cell surfaces including lipids, proteins and glycosyl groups. Sulfuric acid also promotes hydrocarbon dehydration contributing to the formation of black “burnt” carbon. Oxidative reactions leading to abstraction of electrons is further impacted by heat through an increase in the proportion of reactant molecules with sufficient energy to react. Collectively these factors and particularly those related to metals must be overcome by thermoacidophilic lithoautotrophs in order for them to survive and proliferate. The necessary mechanisms to achieve this goal are largely unknown however mechanistics insights have been gained through genomic studies. This review focuses on the specific role of metals in this extreme environment with an emphasis on resistance mechanisms in Archaea.
Hot Deformation Mechanisms in AZ31 Magnesium Alloy Extruded at Different Temperatures: Impact of Texture
Authors: Rao Kamineni Pitcheswara , Prasad Yellapregada Venkata Rama Krishna , Dzwonczyk Joanna , Hort Norbert , Kainer Karl Ulrich
Published: August 2012

The hot deformation characteristics of AZ31 magnesium alloy rod extruded at temperatures of 300 °C, 350 °C and 450 °C have been studied in compression. The extruded material had a fiber texture with parallel to the extrusion axis. When extruded at 450 °C, the texture was less intense and the direction moved away from the extrusion axis. The processing maps for the material extruded at 300 °C and 350 °C are qualitatively similar to the material with near-random texture (cast-homogenized) and exhibited three dynamic recrystallization (DRX) domains. In domains #1 and #2, prismatic slip is the dominant process and DRX is controlled by lattice self-diffusion and grain boundary self-diffusion, respectively. In domain #3, pyramidal slip occurs extensively and DRX is controlled by cross-slip on pyramidal slip systems. The material extruded at 450 °C exhibited two domains similar to #1 and #2 above, which moved to higher temperatures, but domain #3 is absent. The results are interpreted in terms of the changes in fiber texture with extrusion temperature. Highly intense texture, as in the rod extruded at 350 °C, will enhance the occurrence of prismatic slip in domains #1 and #2 and promotes pyramidal slip at temperatures >450 °C (domain #3).
Genetic Variation in Morphology, Seed Quality and Self-(in)Compatibility among the Inbred Lines Developed from a Population Variety in Outcrossing Yellow Mustard (Sinapis alba)
Authors: Cheng Bifang , Williams David J. , Zhang Yan
Published: August 2012

Yellow mustard (Sinapis alba L.) has been grown as an important source of condiment for the spice trade in the world. It is an obligate outcrossing species due to its sporophytic self-incompatibility (SI). To utilize heterosis for yield potential, we have attempted to develop elite component inbred lines for producing high-yielding synthetic varieties for this crop. The open-pollinated variety Andante was used as the initial population. To circumvent the SI barrier, bud-pollination for selfing was performed on the selected initial (S0) plants. Various types of inbreeding depression were observed in the S1 generation. Elite inbred lines tolerant to inbreeding were produced by purging the deleterious alleles in each inbred generation. Self-compatible (SC) lines were developed for the first time in this species. There were three types of erucic variants (high: 49.9%, median: 23.9% and low: 1.4%), three types of linolenic variants (high: 18.5%, median: 13.8% and low: 3.8%) and two types of mucliage variants (high: 164.0 cS*mL/g and low: 12.0 cS*mL/g) among the developed inbred lines. These variants are being used to investigate the genetic and molecular mechanism underpinning the phenotypic variation of the seed oil profile and SI/SC traits in yellow mustard.
Supersymmetric Sigma Model Geometry
Authors: Lindström Ulf
Published: August 2012

This is a review of how sigma models formulated in Superspace have become important tools for understanding geometry. Topics included are: The (hyper)kähler reduction; projective superspace; the generalized Legendre construction; generalized Kähler geometry and constructions of hyperkähler metrics on Hermitian symmetric spaces.
Flexibility of Hydrogen Bond and Lowering of Symmetry in Proton Conductor
Authors: Yoshida Yukihiko , Hatori Junko , Kawakami Hinako , Matsuo Yasumitsu , Ikehata Seiichiro
Published: August 2012

In order to investigate why crystal symmetry lowers with increasing temperature by phase transition of TII–III (=369 K) in Cs3H(SeO4)2, in spite of the fact that crystal symmetry in the high-temperature phase of many ionic conductors becomes higher by the phase transition, we have studied the relation between the change in crystal symmetry and the appearance of proton motion. It was found from the analysis of domains based on crystal structure that the number of possible geometrical arrangement of hydrogen bond in phase II becomes two times larger than that in phase III, derived from the lowering of crystal symmetry with increasing temperature. These results indicate that the lowering of crystal symmetry in phase II appears by the increase of the number of geometrical arrangements and by the enhancement of the flexibility of hydrogen bond. Considering that the enhancement of the flexibility of hydrogen bond yields mobile proton in phase II, it is deduced that mobile proton in phase II appears in exchange for the lowering of crystal symmetry at II–III phase transition.
Chronic HBV Infection outside Treatment Guidelines: Is Treatment Needed?
Authors: Evans Alison A , London W Thomas , Gish Robert G , Cohen Chari , Block Tim M
Published: August 2012

Background

There are now seven antivirals approved for use in the management of chronic HBV infection in the US. Current professional guidelines recommend the use of antiviral treatment in only a distinct subset of the total HBV chronically infected population, estimated to be more than 350 million worldwide. The subset of chronically HBV-infected individuals for whom the antivirals have been demonstrated to produce desirable outcomes are those with abnormal liver enzymes and a viral load above a defined threshold, presumably identifying those at highest risk for development of cirrhosis and hepatocellular carcinoma. However, some individuals whose clinical features place them outside these guidelines, for whom treatment is not recommended, are also at significant risk for liver disease complications and liver-related death.

Methods

In this report, we produce new estimates of the age-specific risks of liver-related death in people outside the current treatment guidelines using published data from multiple populations.

Results

Our results indicate that the age-specific 10-year risks of liver-related mortality in these individuals range from 0.3–4% in the West to 0.3–20% in Asia.

Conclusions

The magnitude of these risks and the estimated size of the global population that falls outside of current treatment guidelines have led us to consider whether medical interventions are also needed for these individuals, either with currently approved therapeutics or yet-to-be-discovered medications targeting new mechanisms of antiviral effect. Potential targets for development of new medications are discussed.
Productivity and Habitat Modeling of Wood Storks Nesting in North and Central Florida
Authors: Rodgers James A. , Brooks William B. , Barrett Mark
Published: August 2012

Rainfall, surface water levels, location within the state, and area and types of habitats (n  =  29) surrounding wood stork Mycteria americana colonies in North and Central Florida were analyzed at 10-km, 20-km, and 30-km radii around each colony to examine their relationship with fledging rate and number of nests during 2003–2005. Seven variables within 10 km, 14 variables within 20 km, and 6 variables within 30 km of colonies were correlated with fledging rates. Fledging rate and number of nests were significantly associated with both wetland and nonwetland area and habitats. Among all the variables, fledging rate was most strongly associated with rainfall during the preceding 12–24 mo. Both larger colonies and colonies in North Florida had higher fledging rates. Although some variables had a positive association and other variables had a negative correlation with fledging rates, results were not consistent across all three radii, which suggests that the effects of hydrologic and habitat variables differs with increasing distance from a colony. The size of a wood stork colony was sensitive to a larger number of variables and varied by distances from the colony. Colonies were smaller in the northern part of Florida, and coastal colonies were larger than interior colonies. Because wood storks often use ephemeral foraging sites closer to a colony early in the season and those sites may not be available later in the season, wood storks may shift to alternate, more distant sites and habitats later in the season. A hypothesis is proposed whereby wood storks establish their colonies using proximate clues of prey availability based on the effects of past rainfall and certain preferred habitat types. These proximate cues to prey availability and foraging substrate surrounding a colony are detected by wood storks before the onset and during the initial nesting season. However, the long-term stability of a colony may ultimately be determined by yearly rainfall patterns and habitat variables at larger distances and by fledging rates that contribute to recruitment of nesting birds and an increase in number of nests.
p40phoxExpression Regulates Neutrophil Recruitment and Function during the Resolution Phase of Intestinal Inflammation
Authors: Conway Kara L. , Goel Gautam , Sokol Harry , Manocha Monika , Mizoguchi Emiko , Terhorst Cox , Bhan Atul K. , Gardet Agnès , Xavier Ramnik J.
Published: August 2012

NADPH oxidase is a multisubunit complex that assembles during phagocytosis to generate reactive oxygen species. Several components of this complex have been implicated in chronic granulomatous disease and Crohn’s disease, highlighting the importance of reactive oxygen species in regulating host immune response. In this study, we use genetically deficient mice to elucidate how p40phox, one subunit of the NADPH oxidase complex, functions during intestinal inflammation. We show that p40phox deficiency enhances inflammation in both dextran sulfate sodium-induced and innate immune-mediated murine colitis models. This inflammation is characterized by severe colonic tissue injury, increased proinflammatory cytokines, and increased neutrophil recruitment. We demonstrate that neutrophils are essential during the recovery phase of intestinal inflammation and that p40phox expression is necessary for this restitution. Lastly, using an integrative bioinformatic approach, we show that p40phox deficiency leads to upregulation of chemokine receptor 1 and downregulation of enzymes involved in glycan modifications, including fucosyltransferases and sialyltransferases, during inflammation. We propose that p40phox deficiency enhances intestinal inflammation through the dysregulation of these two pathways in neutrophils.
Genetic Investigation of Major Histocompatibility Complex Class-I Related RAET1 Genes for Association in a Glomerulonephritis Population
Authors: Vance Dwaine R. , Bennett Theresa A. , Maxwell Alexander P. , McKnight Amy Jayne
Published: August 2012

Chromosome 6q22–27 harbors risk genes for kidney disease. We evaluated 1,434 individuals with glomerulonephritis (cases) and 603 unaffected individuals (controls) for RAET1 genes at 6q22–27 using samples from the Medical Research Council/Kidney Research UK Glomerulonephritis DNA bank in a 2-stage approach. Top ranked single nucleotide polymorphisms were also geno-typed in kidney transplant recipients (n=571) and their respective donors (n=520) as controls to evaluate association with end-stage renal disease (ESRD). Provisional data suggested that rs9397070 in the RAET1G gene was associated with susceptibility to glomerulonephritis [Odds ratio (OR) 1.24, 95%; confidence interval (CI): 1.01–1.54, P=0.04] and further supported by additional genotyping (OR 1.22, 95% CI: 1.03–1.42, P=0.02). Genotyping the renal transplant population did not identify any significant association with ESRD. The RAET1 gene family contains candidate genes for kidney disease; however, common RAET1 gene polymorphisms are not identified as strong genetic risk factors for glomerulonephritis in these white populations.
Prevalence of Cryptosporidium spp. and Giardia duodenalis in pigs in Lusaka, Zambia
Authors: Siwila Joyce , Mwape Kabemba E.
Published: August 2012

This study was aimed at determining the prevalence of Cryptosporidium spp. and Giardia duodenalis in pigs which were being raised in intensive management systems. Faecal samples were collected from pigs of all age groups from three different piggery units. Samples were collected directly from the rectum for piglets and weaners and from the floor within 2 min – 5 min of excretion for sows and boars. At the time of collection, faecal consistency was noted as being normal, pasty or diarrhoeic. Samples were analysed further using the Merifluor® Cryptosporidium/Giardia immunofluorescence assay. All piggeries had at least one pig infected with either parasite. From a total 217 samples collected, 96 (44.2%; confidence interval [CI] = 37.6% – 50.9%) were positive for Cryptosporidium spp., whilst 26 (12%; CI = 7.6% – 16.3%) had G. duodenalis parasites. Of all the pigs, 6.9% (15/217) harboured both parasites. With regard to Cryptosporidium spp. infection, statistically significant differences were observed amongst the three units (p = 0.001), whereas no significant differences were observed for G. duodenalis infection (p = 0.13). Prevalence was higher in weaners as compared to other pig classes for both parasites, with significant differences being observed for G. duodenalis infection (p = 0.013). There was, however, no difference in infection between male and female pigs for both parasites. Furthermore, most infections were asymptomatic. From the study results it was clear that Cryptosporidium spp. and G. duodenalis infections were prevalent amongst pigs in the piggeries evaluated and, as such, may act as a source of infection for persons who come into contact with them.
TAVR and SAVR: Current Treatment of Aortic Stenosis
Authors: Patrick P. Hu
Published: August 2012

Transcatheter aortic valve replacement (TAVR) was approved in the United States in late 2011, providing a critically needed alternative therapy for patients with severe aortic stenosis previously refused surgical aortic valve replacement (SAVR). Over 20,000 TAVR have been performed in patients worldwide since 2002 when Alain Cribier performed the first-in-man TAVR. This paper reviews the data from balloon expandable and self-expanding aortic stent valves as well as data comparing them with traditional surgical aortic valve replacement (SAVR). Complications using criteria established by the Valve Academic Research Consortium (VARC) are reviewed. Future challenges and possibilities are discussed and will make optimizing TAVR an important goal in the years to come.
Fluxon Centering in Josephson Junctions with Exponentially Varying Width
Authors: Semerdjieva E. G. , Todorov M. D.
Published: August 2012

Nonlinear eigenvalue problems for fluxons in long Josephson junctions with exponentially varying width are treated. Appropriate algorithms are created and realized numerically. The results obtained concern the stability of the fluxons, the centering both magnetic field and current for the magnetic flux quanta in the Josephson junction as well as the ascertaining of the impact of the geometric and physical parameters on these quantities. Each static solution of the nonlinear boundary-value problem is identified as stable or unstable in dependence on the eigenvalues of associated Sturm-Liouville problem. The above compound problem is linearized and solved by using of the reliable Continuous analogue of Newton method.
On Solution Regularity of Linear Hyperbolic Stochastic PDE Using the Method of Characteristics
Authors: Li Lizao
Published: August 2012

The generalized Polynomial Chaos (gPC) method is one of the most widely used numerical methods for solving stochastic differential equations. Recently, attempts have been made to extend the the gPC to solve hyperbolic stochastic partial differential equations (SPDE). The convergence rate of the gPC depends on the regularity of the solution. It is shown that the characteristics technique can be used to derive general conditions for regularity of linear hyperbolic PDE, in a detailed case study of a linear wave equation with a random variable coefficient and random initial and boundary data.
A Revisit of the Semi-Adaptive Method for Singular Degenerate Reaction-Diffusion Equations
Authors: Sheng Qin , Khaliq A. Q. M.
Published: August 2012

This article discusses key characteristics of a semi-adaptive finite difference method for solving singular degenerate reaction-diffusion equations. Numerical stability, monotonicity, and convergence are investigated. Numerical experiments illustrate the discussion. The study reconfirms and improves several of our earlier results.
Effect of a Motor-Based Role-Play Intervention on the Social Behaviors of Adolescents With High-Functioning Autism: Multiple-Baseline Single-Subject Design
Authors: Gutman Sharon A. , Raphael-Greenfield Emily I. , Rao Ashwini K.
Published: August 2012

OBJECTIVE. We examined the effect of a motor-based role-play intervention on the social skills of adolescents with high-functioning autism.

METHOD. An ABA multiple-baseline design with three 3-mo phases occurring over 12 mo was used with 7 participants. Frequency of targeted verbal and nonverbal behaviors was tallied in each phase. Frequency data were analyzed using repeated-measures analyses of variance with post hoc comparisons to examine differences in targeted behaviors over the three phases.

RESULTS. Three participants completed all three study phases, 2 completed Phase 2, and 2 completed Phase 1. All participants (N = 7) demonstrated improved social skill use in Phase 1. Participants completing Phase 2 (n = 5) further improved social skill use. Additional improvements were observed among participants (n = 3) who completed Phase 3.

CONCLUSION. The intervention helped participants improve targeted social skill use. Further testing with larger samples and intervention modifications is warranted.
Effect of Classroom Modification on Attention and Engagement of Students With Autism or Dyspraxia
Authors: Kinnealey Moya , Pfeiffer Beth , Miller Jennifer , Roan Cecilia , Shoener Rachel , Ellner Matt L.
Published: August 2012

Students with autism display sensory sensitivities to environmental stimuli that affect their attending and engagement in classroom learning activities. The purpose of the study was to determine whether attending of 4 male students, ages 13–20, increased after the installation of sound-absorbing walls and halogen lighting. The multiple single-subject, mixed-method design, AB(B+C), included a 2-wk baseline and two intervention phases: 2 wk after sound-absorbing wall installation using the Owens Corning Basement Finishing System™ (Owens Corning, Toledo, OH) and 2 wk after halogen light installation. We calculated nonattending frequencies from videotaped class sessions and used visual analysis to measure within-phase and between-phase characteristics. Results included increased frequency and stability of attending and engagement and improved classroom performance, comfort, and mood. Journaling provided students’ perspective on the modifications and reflected overall increased sensory comfort and themes of improved classroom environment, positive emotional response (mood), and improved classroom performance.
Comparing the Functional Performance of Children and Youths With Autism, Developmental Disabilities, and No Disability Using the Revised Pediatric Evaluation of Disability Inventory Item Banks
Authors: Kao Ying-Chia , Kramer Jessica M. , Liljenquist Kendra , Tian Feng , Coster Wendy J.
Published: August 2012

OBJECTIVE. We compared the functional performance of children with autism spectrum disorders (ASD), intellectual and developmental disabilities (IDD), and without disabilities using the revised Pediatric Evaluation of Disability Inventory–Computer Adaptive Test (PEDI–CAT) Social/Cognitive, Daily Activities, and Responsibility domains.

METHOD. A nationally representative sample of parents of children ages 0–21 without disabilities (n = 2,205), with ASD (n = 108), or with IDD (n = 150) completed an online survey. We obtained predicted PEDI–CAT scaled scores for three reference ages (5, 10, 15) from a modified analysis of covariance model and compared each group’s scores using contrasts of the regression parameters.

RESULTS. We found no significant differences between the ASD and IDD groups. The group with ASD demonstrated significantly lower performance than the group without disabilities across the three domains at ages 10 and 15.

CONCLUSION. Scores on the PEDI–CAT differentiated the group with ASD from the group without disabilities. Children with ASD and IDD did not demonstrate different performance profiles.
Cross-Cultural Comparison of Sensory Behaviors in Children With Autism
Authors: Caron Kristina G. , Schaaf Roseann C. , Benevides Teal W. , Gal Eynat
Published: August 2012

Parents of children with autism frequently report that their children exhibit unusual responses to sensory experiences. Little research is available, however, describing how parents’ and children’s culture and environment might influence parents’ reports of their children’s behaviors. This study compared the frequency of parent-reported responses to sensory experiences in children from two countries—Israel and the United States. We administered the Short Sensory Profile to primary caregivers of children with autism spectrum disorders (ASD) and typically developing peers. Results indicate that Israeli parents reported unusual responses to sensory experiences less frequently than U.S. parents for both ASD and typically developing children. U.S. children with ASD demonstrated significantly greater difficulty in the Auditory Filtering and Visual/Auditory Sensitivity domains than Israeli children with ASD. These findings indicate a need to further explore the influence of culture and environment on caregiver perceptions of the responses to sensory experiences of children with ASD.
Autonomic and Behavioral Responses of Children With Autism to Auditory Stimuli
Authors: Chang Megan C. , Parham L. Diane , Blanche Erna Imperatore , Schell Anne , Chou Chih-Ping , Dawson Michael , Clark Florence
Published: August 2012

OBJECTIVES. We examined whether children with and without autism spectrum disorder (ASD) differ in autonomic activity at rest and in response to auditory stimuli and whether behavioral problems related to sounds in everyday life are associated with autonomic responses to auditory stimuli.

METHOD. We measured skin conductance (SC) at rest and in response to auditory stimuli as well as behavioral responses using the Sensory Processing Measure (SPM) Home Form. Participants were 25 children with ASD and 25 typically developing (TD) children, aged 5–12 yr.

RESULTS. The ASD group had significantly higher resting SC and stronger SC reactivity to tones than the TD group. Correlations between SC and SPM indicated that more severe auditory behavioral difficulties were associated with higher sympathetic activation at rest and stronger sympathetic reactivity to sound.

CONCLUSION. High sympathetic reactivity to sound may underlie the difficult behavioral responses to sound that children with ASD often demonstrate.
Precursors and Trajectories of Sensory Features: Qualitative Analysis of Infant Home Videos
Authors: Freuler Ashley , Baranek Grace T. , Watson Linda R. , Boyd Brian A. , Bulluck John C.
Published: August 2012

OBJECTIVE. This study explored precursors and trajectories of extreme sensory patterns in children with autism spectrum disorders (ASD) compared with children with developmental delay (DD).

METHOD. We conducted a retrospective analysis of home videos of 12 infants who later displayed extreme presence or absence of three sensory patterns at preschool and school age.

RESULTS. In ASD, hyporesponsiveness was most evident in infancy, followed by sensory repetitions. Hyporesponsiveness appeared stable over time and also was a precursor of sensory seeking. Infants with DD had few sensory precursors.

CONCLUSION. Precursors of extreme sensory features emerge early in children with ASD and appear relatively stable over time for a pattern of hyporesponsiveness but less stable for patterns of hyperresponsiveness and sensory seeking. These findings highlight the emergent nature of sensory features that may inform early identification and intervention.
Sensory Overresponsivity and Anxiety in Typically Developing Children and Children With Autism and Attention Deficit Hyperactivity Disorder: Cause or Coexistence?
Authors: Lane Shelly J. , Reynolds Stacey , Dumenci Levent
Published: August 2012

OBJECTIVE. To explore the relationship between sensory overresponsivity (SOR) and anxiety in children with autism, attention deficit hyperactivity disorder, and typical development.

METHOD. Path analysis was used to examine the primary SOR model (Green & Ben-Sasson, 2010) using both physiological and behavioral data.

RESULTS. The magnitude of physiological responses to sensory challenge was a mediator variable between predictors (baseline arousal and attention) and outcomes (anxiety and physiological recovery). Behavioral SOR was correlated with anxiety but not with physiological variables.

CONCLUSION. The intensity or magnitude of sensory responsivity mediates the relationship between baseline arousal and attention and outcome anxiety and physiologic recovery from sensory challenge. Behavioral tools used to measure SOR do not reflect physiological responsiveness; this mismatch warrants further investigation. SOR can prevent children from participating in the occupations of childhood; the greater the understanding of SOR, the more successful occupational therapy practitioners will be in developing effective interventions.
A simple framework for modelling the photochemical response to solar spectral irradiance variability in the stratosphere
Authors: Muncaster R. , Bourqui M. S. , Chabrillat S. , Viscardy S. , Melo S. M. L. , Charbonneau P.
Published: August 2012

Abstract. The stratosphere is thought to play a central role in the atmospheric response to solar irradiance variability. Recent observations suggest that the spectral solar irradiance (SSI) variability involves significant time-dependent spectral variations, with variable degrees of correlation between wavelengths, and new reconstructions are being developed. In this paper, we propose a simplified modelling framework to characterise the effect of short term SSI variability on stratospheric ozone. We focus on the pure photochemical effect, for it is the best constrained one. The photochemical effect is characterised using an ensemble simulation approach with multiple linear regression analysis. A photochemical column model is used with interactive photolysis for this purpose. Regression models and their coefficients provide a characterisation of the stratospheric ozone response to SSI variability and will allow future inter-comparisons between different SSI reconstructions. As a first step in this study, and to allow comparison with past studies, we take the representation of SSI variability from the Lean (1997) solar minimum and maximum spectra. First, solar maximum-minimum response is analysed for all chemical families and partitioning ratios, and is compared with past studies. The ozone response peaks at 0.18 ppmv (approximately 3%) at 37 km altitude. Second, ensemble simulations are regressed following two linear models. In the simplest case, an adjusted coefficient of determination R2 larger than 0.97 is found throughout the stratosphere using two predictors, namely the previous day's ozone perturbation and the current day's solar irradiance perturbation. A better accuracy (R2 larger than 0.9992) is achieved with an additional predictor, the previous day's solar irradiance perturbation. The regression models also provide simple parameterisations of the ozone perturbation due to SSI variability. Their skills as proxy models are evaluated independently against the photochemistry column model. The bias and RMS error of the best regression model are found smaller than 1% and 15% of the ozone response, respectively. Sensitivities to initial conditions and to magnitude of the SSI variability are also discussed.
The physical and chemical characteristics of marine organic aerosols: a review
Authors: Gantt B. , Meskhidze N.
Published: August 2012

Abstract. Knowledge of the physical characteristics and chemical composition of marine organic aerosols is needed for the quantification of their effects on solar radiation transfer and cloud processes. Global emission estimates of marine organic aerosol are in a range of 2 to 70 Tg yr−1 and occur over regions most susceptible to aerosol perturbations. This review examines research pertinent to the chemical composition, size distribution, mixing state, emission mechanism, and climatic impact of marine primary organic aerosols associated with sea spray. Numerous measurements have shown that both the ambient mass concentration of marine organic aerosol and size-resolved organic mass fraction of sea spray aerosol are related to surface ocean biological activity. Recent studies have also indicated that fine mode (smaller than 200 nm in diameter) marine organic aerosols can have a size distribution independent from sea-salt, while coarse mode aerosols (larger than 1000 nm in diameter) are more likely to be internally-mixed with sea-salt. Climate studies have found that marine organic aerosols can cause large local increases in the cloud condensation nuclei concentration, with the potential to have a non-negligible influence on the anthropogenic aerosol indirect forcing. Despite these signs of climate-relevance for marine organic aerosols, the source strength, chemical composition, mixing state, hygroscopicity, cloud droplet activation potential, atmospheric aging, and removal of marine organic aerosols remain poorly quantified. Additional laboratory, field, and modeling studies focused on the chemistry, size distribution, and mixing state of sea spray aerosols are needed to better understand and quantify their importance.
Variations of ionospheric profile parameters during solar maximum and comparison with IRI-2007 over Chung-Li, Taiwan
Authors: Chuo Y. J.
Published: August 2012

Abstract. This paper studies the seasonal changes in the diurnal variation of ionospheric bottomside slab thickness (B0), based on observations during high solar activities at the equatorial ionization anomaly (EIA) area station of Chung-Li (121.1° E, 24.9° N), Taiwan. The data examined in this investigation are derived from ionograms recorded at Chung-Li in 1999, and are compared with International Reference Ionosphere (IRI-2007) model values. In our data set B0 shows largest values and biggest changes during the daytime (06:00–12:00 LT) particularly in the summer. Moreover, the diurnal variation of B0 shows an abnormal peak during the pre-sunrise period, especially in the winter. The variation in the F-peak height (hmF2) is related to a thermospheric wind traveling toward the equator, which also enhances B0 during the pre-sunrise period. The results of the comparison with the IRI model show that B0 is overestimated, in both the B0-table and the Gulyaeva option, after noon LT in the equinox (B0-table and Gulyaeva average values for the overestimation are 11 and 47 km, respectively) and summer (B0-table and Gulyaeva average values for the overestimation are 23 and 71 km, respectively) periods. Furthermore, the modeled values are underestimated at approximately 31 and 14 km for the table and Gulyaeva option during the daytime in the winter, respectively. The F2-layer maximum electron density (NmF2) data show reasonably favorable agreement with the model for a high correlation coefficient of approximately 0.97, with the major difference observed at approximately noon in the equinox and winter seasons. Regarding the hmF2 data, the model shows agreement with the observed values, and the largest discrepancy (average value is 39 km) was observed in the summer and the smallest (average value is 11 km) in the equinox season. This paper provides a comprehensive discussion on the relationship among B0, the NmF2 and the hmF2 for geomagnetic storm events.
A synthesis of carbon in international trade
Authors: Peters G. P. , Davis S. J. , Andrew R.
Published: August 2012

Abstract. In a globalised world, the transfer of carbon between regions, either physically or embodied in production, represents a substantial fraction of global carbon emissions. The resulting emission transfers are important for balancing regional carbon budgets and for understanding the drivers of emissions. In this paper we synthesise current understanding in two parts: (1) CO2 emissions embodied in goods and services that are produced in one country but consumed in others, and (2) carbon physically present in fossil fuels, petroleum-derived products, harvested wood products, crops, and livestock products. We describe the key differences between studies and provide a consistent set of estimates using the same definitions, modelling framework, and consistent data. We find the largest trade flows of carbon in international trade in 2004 were fossil fuels (2673 MtC, 37 % of global emissions), CO2 embodied in traded goods and services (1661 MtC, 22 % of global emissions), crops (522 MtC, 31 % of total harvested crop carbon), petroleum-based products (183 MtC, 50 % of their total production), harvested wood products (149 MtC, 40 % of total roundwood extraction), and livestock products (28 MtC, 22 % of total livestock carbon). We find that for embodied CO2 emissions, estimates from independent studies are robust, and that differences between individual studies are not a reflection of the uncertainty in consumption-based estimates, but rather these differences result from the use of different production-based emissions input data and different definitions for allocating emissions to international trade. After adjusting for these issues, results across independent studies converge to give less uncertainty than previously assumed. For physical carbon flows there are relatively few studies to be synthesised, but differences between existing studies are due to the method of allocating to international trade, with some studies using "apparent consumption" as opposed to "final consumption". While results across studies are sufficiently robust to be used in further applications, more research is needed to understand differences and to harmonise definitions for particular applications.
Evaluation of a regional air-quality model with bi-directional NH3 exchange coupled to an agro-ecosystem model
Authors: Bash J. O. , Cooter E. J. , Dennis R. L. , Walker J. T. , Pleim J. E.
Published: August 2012

Abstract. Atmospheric ammonia (NH3) is the primary atmospheric base and an important precursor for inorganic particulate matter and when deposited NH3 contributes to surface water eutrophication, soil acidification and decline in species biodiversity. Flux measurements indicate that the air-surface exchange of NH3 is bi-directional. However, the effects of bi-directional exchange, soil biogeochemistry and human activity are not parameterized in air quality models. The US Environmental Protection Agency (EPA)'s Community Multiscale Air-Quality (CMAQ) model with bi-directional NH3 exchange has been coupled with the United States Department of Agriculture (USDA)'s Environmental Policy Integrated Climate (EPIC) agro-ecosystem model's nitrogen geochemistry algorithms. CMAQ with bi-directional NH3 exchange coupled to EPIC connects agricultural cropping management practices to emissions and atmospheric concentrations of reduced nitrogen and models the biogeochemical feedback on NH3 air-surface exchange. This coupled modeling system reduced the biases and error in NHx (NH3 + NH4+) wet deposition and in ambient aerosol concentrations in an annual 2002 Continental US (CONUS) domain simulation when compared to a 2002 annual simulation of CMAQ without bi-directional exchange. Fertilizer emissions estimated in CMAQ 5.0 with bi-directional exchange exhibits markedly different seasonal dynamics than the US EPA's National Emissions Inventory (NEI), with lower emissions in the spring and fall and higher emissions in July.
Modeling the sensitivity of soil mercury storage to climate-induced changes in soil carbon pools
Authors: Hararuk O. , Obrist D. , Luo Y.
Published: August 2012

Abstract. Substantial amounts of mercury (Hg) in the terrestrial environment reside in soils and are associated with soil organic carbon (C) pools, where they accumulated due to increased atmospheric deposition due to anthropogenic activities. The purpose of this study was to examine potential sensitivity of surface soil Hg pools to global change variables, particularly affected by predicted changes in soil C pools, in the contiguous US. To investigate, we included a soil Hg component in the Community Land Model based on empirical statistical relationships between soil Hg / C ratios and precipitation, latitude and clay; and subsequently explored the sensitivity of soil C and soil Hg densities (i.e. areal-mass) to climate scenarios in which we altered annual precipitation, carbon dioxide (CO2) concentrations, and temperature. Our model simulations showed that current sequestration of Hg in the contiguous US accounted for 15 230 metric tons of Hg in the top 0–40 cm of soils. In the simulations, these soil Hg pools were most sensitive to changes in precipitation because of strong effects on soil C pools plus a direct effect of precipitation on soil Hg / C ratios. Soil Hg pools were predicted to increase beyond present-day values following an increase in precipitation amounts and decrease following a reduction in precipitation. We found pronounced regional differences in sensitivity of soil Hg to precipitation, which were particularly high along high-precipitation areas along the West and East Coasts. Modeled increases in CO2 concentrations to 700 ppm stimulated soil C and Hg densities, while increased air temperatures had small negative effects on soil C and Hg. The combined effects of increased CO2, increased temperature, and increased or decreased precipitation were strongly governed by precipitation and CO2 showing pronounced regional patterns. Based on these results, we conclude that the combination of precipitation and CO2 should be emphasized when assessing how climate-induced changes in soil C may affect sequestration of Hg in soils.
A review of the South American monsoon history as recorded in stable isotopic proxies over the past two millennia
Authors: Vuille M. , Burns S. J. , Taylor B. L. , Cruz F. W. , Bird B. W. , Abbott M. B. , Kanner L. C. , Cheng H. , Novello V. F.
Published: August 2012

Abstract. We review the history of the South American summer monsoon (SASM) over the past ~2000 yr based on high-resolution stable isotope proxies from speleothems, ice cores and lake sediments. Our review is complemented by an analysis of an isotope-enabled atmospheric general circulation model (GCM) for the past 130 yr. Proxy records from the monsoon belt in the tropical Andes and SE Brazil show a very coherent behavior over the past 2 millennia with significant decadal to multidecadal variability superimposed on large excursions during three key periods: the Medieval Climate Anomaly (MCA), the Little Ice Age (LIA) and the current warm period (CWP). We interpret these three periods as times when the SASM's mean state was significantly weakened (MCA and CWP) and strengthened (LIA), respectively. During the LIA each of the proxy archives considered contains the most negative δ18O values recorded during the entire record length. On the other hand, the monsoon strength is currently rather weak in a 2000-yr historical perspective, rivaled only by the low intensity during the MCA. Our climatic interpretation of these archives is consistent with our isotope-based GCM analysis, which suggests that these sites are sensitive recorders of large-scale monsoon variations. We hypothesize that these centennial-scale climate anomalies were at least partially driven by temperature changes in the Northern Hemisphere and in particular over the North Atlantic, leading to a latitudinal displacement of the ITCZ and a change in monsoon intensity (amount of rainfall upstream over the Amazon Basin). This interpretation is supported by several independent records from different proxy archives and modeling studies. Although ENSO is the main forcing for δ18O variability over tropical South America on interannual time scales, our results suggest that its influence may be significantly modulated by North Atlantic climate variability on longer time scales. Finally, our analyses indicate that isotopic proxies, because of their ability to integrate climatic information on large spatial scales, could complement more traditional proxies such as tree rings or documentary evidence. Future climate reconstruction efforts could potentially benefit from including isotopic proxies as large-scale predictors in order to better constrain past changes in the atmospheric circulation.
Drastic shrinking of the Hadley circulation during the mid-Cretaceous Supergreenhouse
Authors: Hasegawa H. , Tada R. , Jiang X. , Suganuma Y. , Imsamut S. , Charusiri P. , Ichinnorov N. , Khand Y.
Published: August 2012

Abstract. Understanding the behavior of the global climate system during extremely warm periods is one of the major themes of paleoclimatology. Proxy data demonstrate that the equator-to-pole temperature gradient was much lower during the mid-Cretaceous "supergreenhouse" period than at present, implying larger meridional heat transport by atmospheric and/or oceanic circulation. However, reconstructions of atmospheric circulation during the Cretaceous have been hampered by a lack of appropriate datasets based on reliable proxies. Desert distribution directly reflects the position of the subtropical high-pressure belt, and the prevailing surface-wind pattern preserved in desert deposits reveals the exact position of its divergence axis, which marks the poleward margin of the Hadley circulation. We reconstructed temporal changes in the latitude of the subtropical high-pressure belt and its divergence axis during the Cretaceous based on spatio-temporal changes in the latitudinal distribution of deserts and prevailing surface-wind patterns in the Asian interior. We found a poleward shift in the subtropical high-pressure belt during the early and late Cretaceous, suggesting a poleward expansion of the Hadley circulation. In contrast, an equatorward shift of the belt was found during the mid-Cretaceous "supergreenhouse" period, suggesting drastic shrinking of the Hadley circulation. These results, in conjunction with recent observations, suggest the existence of a threshold in atmospheric CO2 level and/or global temperature, beyond which the Hadley circulation shrinks drastically.
Regional wave propagation using the discontinuous Galerkin method
Authors: Wenk S. , Pelties C. , Igel H. , Käser M.
Published: August 2012

Abstract. We present an application of the discontinuous Galerkin (DG) method to regional wave propagation. The method makes use of unstructured tetrahedral meshes, combined with a time integration scheme solving the arbitrary high-order derivative (ADER) Riemann problem. The ADER-DG method is high-order accurate in space and time, beneficial for reliable simulations of high-frequency wavefields over long propagation distances. Due to the ease with which tetrahedral grids can be adapted to complex geometries, undulating topography of the Earth's surface and interior interfaces can be readily implemented in the computational domain. The ADER-DG method is benchmarked for the accurate radiation of elastic waves excited by an explosive and a shear dislocation source. We compare real data measurements with synthetics of the 2009 L'Aquila event (central Italy). We take advantage of the geometrical flexibility of the approach to generate a European model composed of the 3-D EPcrust model, combined with the depth-dependent ak135 velocity model in the upper-mantle. The results confirm the applicability of the ADER-DG method for regional scale earthquake simulations, which provides an alternative to existing methodologies.
Projecting Antarctic ice discharge using response functions from SeaRISE ice-sheet models
Authors: Levermann A. , Winkelmann R. , Nowicki S. , Fastook J. L. , Frieler K. , Greve R. , Hellmer H. H. , Martin M. A. , Mengel M. , Payne A. J. , Pollard D. , Sato T. , Timmermann R. , Wang W. L. , Bindschadler R. A.
Published: August 2012

Abstract. The largest uncertainty in projections of future sea-level change still results from the potentially changing dynamical ice discharge from Antarctica. While ice discharge can alter through a number of processes, basal ice-shelf melting induced by a warming ocean has been identified as a major if not the major cause for possible additional ice flow across the grounding line. Here we derive dynamic ice-sheet response functions for basal ice-shelf melting using experiments carried out within the Sea-level Response to Ice Sheet Evolution (SeaRISE) intercomparison project with five different Antarctic ice-sheet models. As used here these response functions provide separate contributions for four different Antarctic drainage regions. Under the assumptions of linear-response theory we project future ice-discharge for each model, each region and each of the four Representative Concentration Pathways (RCP) using oceanic temperatures from 19 comprehensive climate models of the Coupled Model Intercomparison Project, CMIP-5, and two ocean models from the EU-project Ice2Sea. Uncertainty in the climatic forcing, the oceanic response and the ice-model differences is combined into an uncertainty range of future Antarctic ice-discharge induced from basal ice-shelf melt. The additional ice-loss (Table 6) is clearly scenario-dependent and results in a median of 0.07 m (66%-range: 0.04–0.10 m; 90%-range: −0.01–0.26 m) of global sea-level equivalent for the low-emission RCP-2.6 scenario and yields 0.1 m (66%-range: 0.06–0.14 m; 90%-range: −0.01–0.45 m) for the strongest RCP-8.5. If only models with an explicit representation of ice-shelves are taken into account the scenario dependence remains and the values change to: 0.05 m (66%-range: 0.03–0.08 m) for RCP-2.6 and 0.07 m (66%-range: 0.04–0.11 m) for RCP-8.5. These results were obtained using a time delay between the surface warming signal and the subsurface oceanic warming as observed in the CMIP-5 models. Without this time delay the ranges for all ice-models changes to 0.10 m (66%-range: 0.07–0.12 m; 90%-range: 0.01–0.28 m) for RCP-2.6 and 0.15 m (66%-range: 0.10–0.21 m; 90%-range: 0.02–0.53 m) for RCP-8.5. All probability distributions as provided in Fig. 10 are highly skewed towards high values.
Iterative method for solving a problem with mixed boundary conditions for biharmonic equation arising in fracture mechanics
Authors: Quang A Dang , Xuan Thao Mai
Published: August 2012

In this paper we consider a mixed boundary value problem for biharmonic equation of the Airy stress function which models a crack problem of a solid elastic plate. An iterative method for reducing the problem to a sequence of mixed problems for Poisson equations is proposed and investigated. The convergence of the method is established theoretically and illustrated on many numerical experiments.