bluuebunny/crossref_metadata_2025 huggingface dataset:
Cdc42 and Gsk3 modulate the dynamics of radial glial growth, inter-radial glial interactions and polarity in the developing cerebral cortex
Authors: Yokota Yukako , Eom Tae-Yeon , Stanco Amelia , Kim Woo-Yang , Rao Sarada , Snider William D. , Anton E. S.
Published: November 2010

Polarized radial glia are crucial to the formation of the cerebral cortex. They serve as neural progenitors and as guides for neuronal placement in the developing cerebral cortex. The maintenance of polarized morphology is essential for radial glial functions, but the extent to which the polarized radial glial scaffold is static or dynamic during corticogenesis remains an open question. The developmental dynamics of radial glial morphology, inter-radial glial interactions during corticogenesis, and the role of the cell polarity complexes in these activities remain undefined. Here, using real-time imaging of cohorts of mouse radial glia cells, we show that the radial glial scaffold, upon which the cortex is constructed, is highly dynamic. Radial glial cells within the scaffold constantly interact with one another. These interactions are mediated by growth cone-like endfeet and filopodia-like protrusions. Polarized expression of the cell polarity regulator Cdc42 in radial glia regulates glial endfeet activities and inter-radial glial interactions. Furthermore, appropriate regulation of Gsk3 activity is required to maintain the overall polarity of the radial glia scaffold. These findings reveal dynamism and interactions among radial glia that appear to be crucial contributors to the formation of the cerebral cortex. Related cell polarity determinants (Cdc42, Gsk3) differentially influence radial glial activities within the evolving radial glia scaffold to coordinate the formation of cerebral cortex.
Genomic Differentiation Between Temperate and Tropical Australian Populations ofDrosophila melanogaster
Authors: Kolaczkowski Bryan , Kern Andrew D , Holloway Alisha K , Begun David J
Published: November 2010

Determining the genetic basis of environmental adaptation is a central problem of evolutionary biology. This issue has been fruitfully addressed by examining genetic differentiation between populations that are recently separated and/or experience high rates of gene flow. A good example of this approach is the decades-long investigation of selection acting along latitudinal clines in Drosophila melanogaster. Here we use next-generation genome sequencing to reexamine the well-studied Australian D. melanogaster cline. We find evidence for extensive differentiation between temperate and tropical populations, with regulatory regions and unannotated regions showing particularly high levels of differentiation. Although the physical genomic scale of geographic differentiation is small—on the order of gene sized—we observed several larger highly differentiated regions. The region spanned by the cosmopolitan inversion polymorphism In(3R)P shows higher levels of differentiation, consistent with the major difference in allele frequencies of Standard and In(3R)P karyotypes in temperate vs. tropical Australian populations. Our analysis reveals evidence for spatially varying selection on a number of key biological processes, suggesting fundamental biological differences between flies from these two geographic regions.
Réﬂexion philosophique sur la crise financière
Authors: Lázaro Raquel
Published: November 2010

Résumé Pour Adam Smith observe que la majeure partie de l’humanité n’aspire pas à la perfection. Elle recherche ses propres intérêts. Les relations économiques excluent la fraternité et la gratuité et elles sont basées seulement sur l’intérêt particulier de chacun. Il n’y a donc pas de bien commun, mais un intérêt général résultant de la somme des intérêts particuliers. Comment atteindre la paix sociale lorsque les hommes sont tous égoïstes ? Il est nécessaire de revaloriser le savoir philosophique : l’homme n’est pas en essence ni principalement un être commercial, mais bien un être politique, donc un être sociétal.
CD137-Mediated Pathogenesis from Chronic Hepatitis to Hepatocellular Carcinoma in Hepatitis B Virus-Transgenic Mice
Authors: Wang Jun , Zhao Wenxia , Cheng Liang , Guo Mingzhou , Li Dongling , Li Xiaozhu , Tan Yi , Ma Suping , Li Suyun , Yang Yunsheng , Chen Lieping , Wang Shengdian
Published: November 2010

Chronic hepatitis B virus (HBV) infection is characterized by sustained liver inflammation with an influx of lymphocytes, which contributes to the development of cirrhosis and hepatocellular carcinoma. The mechanisms underlying this immune-mediated hepatic pathogenesis remain ill defined. We report in this article that repetitive infusion of anti-CD137 agonist mAb in HBV-transgenic mice closely mimics this process by sequentially inducing hepatitis, fibrosis, cirrhosis, and, ultimately, liver cancer. CD137 mAb initially triggers hepatic inflammatory infiltration due to activation of nonspecific CD8+ T cells with memory phenotype. CD8+ T cell-derived IFN-γ plays a central role in the progression of chronic liver diseases by actively recruiting hepatic macrophages to produce fibrosis-promoting cytokines and chemokines, including TNF-α, IL-6, and MCP-1. Importantly, the natural ligand of CD137 was upregulated significantly in circulating CD14+ monocytes in patients with chronic hepatitis B infection and closely correlated with development of liver cirrhosis. Thus, sustained CD137 stimulation may be a contributing factor for liver immunopathology in chronic HBV infection. Our studies reveal a common molecular pathway that is used to defend against viral infection but also causes chronic hepatic diseases.
Temperature Measurement Reliability and Validity With Thermocouple Extension Leads or Changing Lead Temperature
Authors: Jutte Lisa S. , Long Blaine C. , Knight Kenneth L.
Published: November 2010

Context:

Thermocouples' leads are often too short, necessitating the use of an extension lead.

Objective:

To determine if temperature measures were influenced by extension-lead use or lead temperature changes.

Design:

Descriptive laboratory study.

Setting:

Laboratory.

Other Participants:

Experiment 1: 10 IT-21 thermocouples and 5 extension leads. Experiment 2: 5 IT-21 and PT-6 thermocouples.

Methods:

In experiment 1, temperature data were collected on 10 IT-21 thermocouples in a stable water bath with and without extension leads. In experiment 2, temperature data were collected on 5 IT-21 and PT-6 thermocouples in a stable water bath before, during, and after ice-pack application to extension leads.

Results:

In experiment 1, extension leads did not influence IT-21 validity (P  =  .45) or reliability (P  =  .10). In experiment 2, postapplication IT-21 temperatures were greater than preapplication and application measures (P < .05).

Conclusions:

Extension leads had no influence on temperature measures. Ice application to leads may increase measurement error.
Implementing efficient and effective learnerships in the construction industry
Authors: Mummenthey Claudia , Du Preez Ronel
Published: November 2010

Orientation: Overcoming skills deficits has been a major concern in South Africa since the advent of democracy in 1994.Research purpose: This study investigated the current state of the learnership system in the construction sector and identified the major obstacles.Motivation for the study: The study was an attempt to illustrate why it is necessary to implement efficient and effective learnerships in the construction industry.Research design, approach and method: A learnership evaluation framework was developed and indicated the critical factors for efficient and effective learnership implementation as well as the roles of the various key stakeholders. The sample included respondents from building and civil companies (n = 90), learners (n = 135), accredited training providers (n = 14) and Construction Education and Training Authority and industry-related bodies (n = 10).Main findings: It was found that descriptive statistics, non-parametric tests and a content analysis of the Western Cape data indicated that, despite low satisfaction with the system in the workplace and among institutional providers, the learnership system was nevertheless regarded as an appropriate means to develop artisans.Practical/managerial implications: Companies were motivated to offer learnerships but felt inadequately prepared for actual implementation. Learnerships were felt to demonstrate effectiveness in terms of employability and skills enhancement.Contribution/value-add: This research provides a theoretical framework to understand, describe and assess the implementation of efficient and effective learnerships in the construction industry.
Ceramics with Regularly Arranged Tubular Pores by Electrophoretic Deposition at Gauze Electrodes
Authors: Moritz Kirsten , Aneziris Christos G.
Published: November 2010

The fabrication of planar zirconia green bodies with unidirectionally aligned pore channels by electrophoretic deposition with simultaneous electrolytic gas bubble formation using different platinum gauzes and, for comparison, platinum foil as deposition electrodes is described. The electrode has a strong influence on the pore structure. At suitable mesh sizes, a very regular arrangement of the tubular pores corresponding to the gauze structure can be obtained.
Metal‐Polymer Nanocomposites for Functional Applications
Authors: Faupel Franz , Zaporojtchenko Vladimir , Strunskus Thomas , Elbahri Mady
Published: November 2010

Nanocomposites combine favorable features of the constituents on the nanoscale to obtain new functionalities. The present paper is concerned with the preparation of polymer‐based nanocomposites consisting of metal nanoparticles in a polymer matrix and the resulting functional properties. Emphasis is placed on vapor phase deposition which inter alia allows the incorporation of alloy clusters with well defined composition and tailored filling factor profiles. Examples discussed here include optical composites with tuned particle surface plasmon resonances for plasmonic applications, magnetic high frequency materials with cut‐off frequencies well above 1 GHz, sensors that are based on the dramatic change in the electronic properties near the percolation threshold, and antibacterial coatings which benefit from the large effective surface of nanoparticles and the increased chemical potential which both strongly enhance ion release.
One‐Pot Hydroxy Group Activation/Carbon‐Carbon Bond Forming Sequence Using a Brønsted Base/Brønsted Acid System
Authors: Devineau Alice , Pousse Guillaume , Taillier Catherine , Blanchet Jérôme , Rouden Jacques , Dalla Vincent
Published: November 2010

A new sequential two‐step multicatalytic strategy is presented consisting in the efficient DBU‐catalysed trichloroacetimidation of an alcohol followed by a ditriflylamine (Tf2NH)‐catalysed intermolecular alkylation by silicon‐based nucleophiles and CH nucleophiles. The distinct feature of the trichloroacetimidate group allows use of weaker acid catalysts such as 1,1′‐bi‐2‐naphthol (BINOL)‐derived phosphoric acid, pointing out the possible development of an enantioselective variant. This unprecedented sequential one‐pot Brønsted base‐Brønsted acid catalysis further expands the synthetic scope of the trichloroacetimidate group.
Preparation, characterization, and properties of crosslinked hydroxylated poly(styrene‐b‐butadiene‐b‐styrene) triblock copolymer
Authors: Wu Guoliang , Zeng Songjun , Ou Encai , Yu Puren , Xiong Yuanqin , Xu Weijian
Published: November 2010

Hydroxylated poly(styrene‐b‐butadiene‐b‐styrene) triblock copolymer (HO‐SBS), with crosslinked networks, was prepared using various amounts of toluene diisocyanate (TDI). The amount of TDI was 0, 0.5, 1, 2, and 5 wt %. The effects of different contents of TDI on the microstructure, thermal properties, and mechanical properties of the crosslinked networks were investigated in detail. Fourier transform infrared spectra indicates that the reaction between OH and NCO have take place, and the solid‐state nuclear magnetic resonance spectra confirms that the crosslinked structure has been obtained. The results of scanning electron microscopy show that the mode of fracture surfaces transmits gradually from tough fracture to brittle fracture, but the structure of microphase separation is still observed at the same time. Mechanical test indicates that crosslinking is a useful method to regulate mechanical properties of the HO‐SBS. The results of dynamic mechanical thermal analysis display that there are two glass transition temperatures, which also means that the microphase separation is still in existence. Moreover, the glass transition temperature of the polybutadiene domains shifts to higher temperature. Accordingly, the microstructure, glass transition temperature, solvent resistance, and mechanical properties of the HO‐SBS are influenced obviously by the crosslinking of TDI. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
CSTR‐based modelling for the continuous carbonation of sodium aluminate solution
Authors: Wang Xiaoli , Yang Chunhua , Gui Weihua , Young Brent R. , Chen Xiao Dong
Published: November 2010

A continuous stirred‐tank reactor (CSTR) model has been developed for the continuous carbonation of the sodium aluminates solution (SAS) which is a key process in sintered alumina production. Based on the mechanistic analysis of the continuous carbonation, a kinetic model established at laboratory scale was scaled up to the industrial continuous carbonation of SAS. A CSTR model was formulated for the process under normal operation conditions. The remaining unknown model parameters were estimated from the industrial data and the validation results show that the model can predict the composition concentrations in the carbonated solution by 90% majority with the relative errors within ±5% compared to industrial data. The model developed will be further evaluated for on‐line prediction and control in the corresponding industrial process.

Un modèle de réacteur à cuve agitée continu (RCAC) a été conçu pour la carbonation continue de la solution d'aluminate de sodium (SAS), qui est un processus essentiel à la production d'alumine frittée. Selon une analyse mécaniste de la carbonation continue, un modèle cinétique établi à l'échelle laboratoire a été adapté au processus industriel de carbonation continue de la SAS. Un modèle de RCAC a été proposé pour fonctionner dans les conditions normales d'exploitation de ce processus. Les autres paramètres inconnus du modèle ont été estimés à partir des données industrielles et les résultats de la validation ont montré que le modèle peut prévoir les concentrations de la composition de la solution de carbone dans 90 % des cas avec une marge d'erreur de ±5 % par rapport aux données industrielles. Afin d'évaluer plus en détail le modèle proposé, la prédiction et le contrôle en ligne du processus industriel correspondant seront analysés. Can. J. Chem. Eng. © 2010 Canadian Society for Chemical Engineering
Parental divorce and disordered eating: An investigation of a gene‐environment interaction
Authors: Suisman Jessica L. , Alexandra Burt S. , McGue Matt , Iacono William G. , Klump Kelly L.
Published: November 2010

Objective:

We investigated gene‐environment interactions (GxE) for associations between parental divorce and disordered eating (DE).

Method:

Participants were 1,810 female twins from the Michigan State University Twin Registry and the Minnesota Twin Family Study. The Minnesota Eating Behaviors Survey was used to assess DE. We tested for GxE by comparing the heritability of DE in twins from divorced versus intact families. It was hypothesized that divorce would moderate the heritability of DE, in that heritability would be higher in twins from divorced than twins from intact families.

Results:

As expected, the heritability of body dissatisfaction was significantly higher in twins from divorced than intact families. However, genetic influences were equal in twins from divorced and intact families for all other forms of DE.

Discussion:

Although divorce did not moderate heritability of most DE symptoms, future research should replicate GxEs for body dissatisfaction and identify factors underlying this unique relationship. © 2010 by Wiley Periodicals, Inc. (Int J Eat Disord 2010)
Modular Total Syntheses of Lamellarin G Trimethyl Ether and Lamellarin S
Authors: Hasse Katrin , Willis Anthony C. , Banwell Martin G.
Published: November 2010

Modular total syntheses of the title compounds 2 and 3 are reported. The key pyrrolic building block 8 was prepared from the readily accessible pyrrole 6 via a di‐iodination/mono‐deiodination sequence. Suzuki–Miyaura cross‐coupling of compound 8 with boronate ester 9 afforded lactone 10. Bromination of compound 10 followed by N‐alkylation under Mitsunobu conditions afforded the fully substituted pyrrole 13 that engaged in a second Suzuki–Miyaura cross‐coupling reaction with boronic acid 14 to give compound 15. Hydrolysis of the ester moiety within the last compound afforded acid 16 that engaged in a decarboxylative Heck cyclization process to give lamellarin G trimethyl ether (3). A related sequence of reactions starting from building block 8 and using the isopropoxy‐substituted arenes 22, 25 and 27 has allowed for the completion of the first total synthesis of lamellarin S (2).
The role of methacrylate polymerized as porous‐layered and nanoparticle‐bound phases for open‐tubular capillary electrochromatography: Substitution of a charged monomer for a bulk monomer
Authors: Chen Jian‐Lian , Lin Yi‐Chen
Published: November 2010

The bulk monomer, butyl methacrylate (BMA), was copolymerized with an ionizable monomer (mono‐(2‐(methacryloyloxy)ethyl) succinate (MES)) and carbon nanotubes (CNTs) by ethylene dimethacrylate (EDMA) crosslinking to form the porous‐layered and nanoparticle‐bound stationary phases for open‐tubular CEC. Here, two new phases were synthesized to check the role of BMA on the BMA‐MES and BMA‐CNT phases and the suitability of the MES monomer for concurrently acting as a bulk monomer. One phase, MES‐EDMA, was simply composed of MES monomer and EDMA crosslinker and exhibited a phase construction of molecular layers, in contrast to the polymeric phases of BMA‐MES. Another phase studied was MES‐CNT, which SEM images showed that MES could be a good bulk monomer for a CNT‐polyacrylate composite phase with embedded CNTs. For all the modified capillaries, the EOF profiles observed in phosphate buffers between pH 3.6 and 9.6 were comparable with each other and conformed to their corresponding SEM images. The residual silanols retained their influence on the EOF profiles in the MES‐EDMA and BMA‐MES capillaries, but diminished in the CNT‐bound capillaries. In a comparison with the MES‐EDMA capillary, the BMA‐MES capillary afforded a stronger interaction with flavonoids and phenolic acids and still retained positive capacity factor values. Additionally, the capacity factors obtained from the BMA‐CNT capillary were higher than those from the MES‐CNT capillary, as the BMA‐CNT phase had hydrophobic BMA units and a high surface contact area of bound CNTs.
Influence of slip condition on the peristaltic transport in an asymmetric channel with heat transfer: An exact solution
Authors: Hayat T. , Hussain Q. , Qureshi M. Umar , Ali N. , Hendi Awatif A.
Published: November 2010

The mechanism of peristaltic magnetohydrodynamic (MHD) flow based on slip and heat transfer effects is studied in an asymmetric channel. An incompressible viscous fluid fills the porous space inside the channel. Long wavelength and zero Reynolds number approximation are used in the flow modeling. Expressions of stream function, longitudinal pressure gradient, and temperature are developed. Various interesting phenomena associated with peristalsis, such as pumping and trapping, are discussed in detail. Further the effects of various pertinent parameters on temperature field and heat transfer coefficient are explained with the help of graphs and tables. It is found that pressure rise over one wavelength decreases in pumping region for large values of slip parameter. Similar behavior is observed for temperature field by increasing the slip parameter. However, the volume of trapped bolus decreases by increasing the slip parameter. Copyright © 2010 John Wiley & Sons, Ltd.
Infant‐directed media: an analysis of product information and claims
Authors: Fenstermacher Susan K. , Barr Rachel , Salerno Katherine , Garcia Amaya , Shwery Clay E. , Calvert Sandra L. , Linebarger Deborah L.
Published: November 2010

Infant DVDs typically have titles and even company names that imply some educational benefit. It is not known whether these educational claims are reflected in actual content. The present study examined this question. Of 686 claims (across 58 programs) listed on packaging, websites and promotional materials, implicit claims were most frequent (37%) followed by uncodable/vague claims (25%), a list of included content (24%), and explicit claims (14%). The most frequently targeted educational domain was general knowledge claim (32%), followed by language/literacy claim (29%), social–emotional claim (15%), physical claim (12%), and cognitive development claim (12%). Number of claims in a domain was positively associated with the percentage of scenes featuring that domain content (Mean r = 0.52), indicating a moderate degree of match between claims and DVD content. Overall, both claims and content were disproportionately targeted to language and general knowledge content areas, relative to social, physical and cognitive domains. Even when claims are developmentally appropriate, there is some difficulty in translating of producer claims into educational DVD content. Copyright © 2010 John Wiley & Sons, Ltd.
Risk factors for breast cancer among young women in southern Iran
Authors: Ghiasvand Reza , Maram Esfandiar Setoudeh , Tahmasebi Sedigheh , Tabatabaee Seyed Hamid Reza
Published: November 2010

Age standardized incidence rates of breast cancer in developed countries is nearly threefold higher than in developing countries. Iran has had one of the lowest incidence rates for breast cancer in the world, but during the last four decades increasing incidence rates of breast cancer made it the most prevalent cancer in Iranian women. After adjustment for age, Iranian young women are at relatively higher risk of breast cancer than their counterparts in developed countries. The purpose of this study was to investigate some established risk factors of breast cancer in Iranian young women. A hospital‐based case control study comprising 521 women with histologically confirmed, incident breast cancer and 521 controls frequency‐matched by age and province of residence was conducted. Logistic regression performed to investigate associations of reproductive and anthropometric factors with breast cancer risk. In multivariate analysis, family history [odds ratio (OR): 1.61; 95% confidence interval (CI): 1.07–2.42], oral contraceptives (OC) usage (OR: 1.52; 95% CI: 1.11–2.08), low parity (OR parity ≥ 3 vs. 1–2: 0.33; 95% CI: 0.23–0.49), employment (OR: 1.83; 95% CI: 1.05–3.23) and shorter period of breast feeding (OR ≥ 37 months vs. < 37: 0.61; 95% CI: 0.44–0.84) were related to a higher risk of breast cancer in young women. This was the first study focusing on risk factors of breast cancer in Iranian young women. The trend of decreasing parity and shortened duration of breast feeding along with OC usage might partly explain the rapid rising of breast cancer incidence in Iranian young women.
Early life exposure to infections and risk of childhood acute lymphoblastic leukemia
Authors: Urayama Kevin Y. , Ma Xiaomei , Selvin Steve , Metayer Catherine , Chokkalingam Anand P. , Wiemels Joseph L. , Does Monique , Chang Jeffrey , Wong Alan , Trachtenberg Elizabeth , Buffler Patricia A.
Published: November 2010

Evidence from a growing number of studies indicates that exposure to common infections early in life may be protective against childhood acute lymphoblastic leukemia (ALL). We examined the relationship between three measures of early life exposure to infections—daycare attendance, birth order and common childhood infections in infancy—with the risk of ALL in non‐Hispanic white and Hispanic children, two ethnicities that show sociodemographic differences. The analysis included 669 ALL cases (284 non‐Hispanic whites and 385 Hispanics) and 977 controls (458 non‐Hispanic whites and 519 Hispanics) ages 1–14 years enrolled in the Northern California Childhood Leukemia Study (NCCLS). When the three measures were evaluated separately, daycare attendance by the age of 6 months (odds ratio [OR] for each thousand child‐hours of exposure = 0.90, 95% confidence interval [CI]: 0.82–1.00) and birth order (OR for having an older sibling = 0.68, 95% CI: 0.50–0.92) were associated with a reduced risk of ALL among non‐Hispanic white children but not Hispanic children, whereas ear infection before age 6 months was protective in both ethnic groups. When the three measures were assessed simultaneously, the influence of daycare attendance (OR = 0.83, 95% CI: 0.73–0.94) and having an older sibling (OR = 0.59, 95% CI: 0.43–0.83) became stronger for non‐Hispanic white children. In Hispanic children, a strong reduction in risk associated with ear infections persisted (OR = 0.45, 95% CI: 0.25–0.79). Evidence of a protective role for infection‐related exposures early in life is supported by findings in both the non‐Hispanic white and Hispanic populations within the NCCLS.
Articular cartilage repair using an intra‐articular magnet and synovium‐derived cells
Authors: Hori Junji , Deie Masataka , Kobayashi Takaaki , Yasunaga Yuji , Kawamata Seiichi , Ochi Mitsuo
Published: November 2010

The purpose of this study was to investigate the chondrogenic potential of magnetically labeled synovium‐derived cells (M‐SDCs) and examine whether M‐SDCs could repair the articular cartilage using an intra‐articular magnet after delivery to the lesion. Synovium‐derived cells (SDCs) were cultured from the synovium of a rat knee, and were magnetically labeled with ferumoxides. M‐SDCs were examined with a transmission electron microscope. A pellet culture system was used to evaluate the chondrogenic potential of M‐SDCs in a magnetic field. In a rat model, allogeneic M‐SDCs were injected into the knee after we made an osteochondral defect on the patellar groove and implanted an intra‐articular magnet at the bottom of the defect. We histologically examined the defects at 48 h, 4 weeks, 8 weeks, and 12 weeks after treatment. Electron microscopy showed the transfection of ferumoxides into SDCs. The pellet cultures revealed the chondrogenic potential of M‐SDCs in a magnetic field. M‐SDCs accumulated in the osteochondral defect at 48 h after treatment, and we confirmed the regeneration of the articular cartilage at 4 weeks, 8 weeks, and 12 weeks after treatment using an intra‐articular magnet. We demonstrated that articular cartilage defects could be repaired using an intra‐articular magnet and M‐SDCs. We believe that this system will be useful to repair human articular cartilage defects. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:531–538, 2011
Substandard models of finite set theory
Authors: Kirby Laurence
Published: November 2010

A survey of the isomorphic submodels of Vω, the set of hereditarily finite sets. In the usual language of set theory, Vω has 2ℵ0 isomorphic submodels. But other set‐theoretic languages give different systems of submodels. For example, the language of adjunction allows only countably many isomorphic submodels of Vω (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bound biexciton luminescence in nitrogen δ‐doped GaAs
Authors: Harada Yukihiro , Kojima Osamu , Kita Takashi , Wada Osamu
Published: November 2010

We have studied the detailed fine structure splitting of the photoluminescence lines exhibiting the superlinear excitation power dependence in nitrogen δ‐doped GaAs. The symmetric splitting energy observed between the 1.493 and 1.509 eV lines suggests that these two lines originate from the same impurity center because the mixing of the bright‐ and dark‐exciton components depends on the electron‐hole exchange energy and the local‐strain field. The excitation power dependence of these two lines indicates that the 1.509 eV line is attributed to the biexciton luminescence corresponding to the 1.493 eV line.
Geographic accessibility to obstetric care and maternal mortality in a large metropolitan area of Brazil
Authors: Simões Patrícia P. , Almeida Renan M.V.R.
Published: November 2010

Objective

To assess maternal mortality and its association with accessibility to obstetric care in the metropolitan region of Rio de Janeiro, Brazil.

Methods

Maternal mortality was assessed from 2 national databases, one administrative and the other designed for epidemiologic purposes. Distances traveled from residence to hospital via the transit network were calculated using a specialized information system. Deaths were grouped by area of residence, and maternal mortality ratios (number of deaths per 100,000 live births) as well as death incidence ratios (deaths/live births in 2 regions or hospital types) were calculated for these areas.

Results

We identified 236 deaths and estimated under‐reporting at 30%. The most common causes of death were hypertension‐related disorders, “other obstetric conditions,” and complications from abortion; the longest traveled distance was 66.43 km (mean, 13.65 km); and maternal mortality ratios varied between 25.54% and 56.45%, the highest values being for areas with the lowest municipal human development index. The highest death incidence ratios were found at general hospitals without specialized obstetric care.

Conclusion

Maternal mortality is still a serious problem in the studied region. The wide variations among areas of different socioeconomic conditions suggest the need for a better allocation of health care resources.
Vitamin D deficiency in pregnant women and their newborns as seen at a tertiary‐care center in Karachi, Pakistan
Authors: Karim Saadiya A. , Nusrat Uzma , Aziz Sina
Published: November 2010

Objective

To estimate the prevalence of vitamin D deficiency among pregnant women in Karachi, Pakistan; correlate maternal and cord blood vitamin D deficiency; and assess possible predictors of vitamin D deficiency.

Methods

This observational, analytical, cross‐sectional study was conducted with 50 consecutive women in labor presenting with a singleton term pregnancy at a large tertiary center in Karachi. Data were recorded on a special form, maternal blood was taken before delivery and cord blood was taken at delivery. All blood samples were analyzed for 25‐hydroxy vitamin D levels. Comparisons were made using the Χ2 test.

Results

The mean vitamin D levels were 24 ng/mL for the participants and 20 ng/mL for the newborns. Vitamin D sufficiency was noted in 11 (22%), insufficiency in 16 (32%), and deficiency in 23 (46%) of the 50 participants whereas sufficiency and deficiency, respectively, were noted in 6 (12%) and 44 (88%) of the newborns. There was a positive correlation between the vitamin D levels in maternal and cord blood (r = 0.03; P < 0.003). Maternal vitamin D levels were significantly affected by sunlight exposure (P < 0.007) and quality of diet P < 0.01).

Conclusion

Vitamin D deficiency is high among pregnant urban Pakistani women and their newborns. This public health problem needs urgent attention.
Remembering Positive and Negative Life Events
Authors: Leist Anja K. , Ferring Dieter , Filipp Sigrun-Heide
Published: November 2010

We examined distributions of remembered negative and positive life events across the lifespan in a sample of adults in middle and old age. Distributions of positive, but not negative, life events showed a significant reminiscence bump, replicating earlier findings. Gender differences occurred with respect to distribution of memories of positive life events of the first four decades of life. Furthermore, we found substantial associations of number and valence of remembered life events with future time perspective and functions of autobiographical memory to create meaning, which remained significant after controlling for age and health. The number and valence of negative and positive life events across the lifespan reflect, to a certain extent, the age and time perspective of the remembering individual.
Steady state reach‐scale theory for radioactive tracer concentration in a simple channel/floodplain system
Authors: Lauer J. Wesley , Willenbring Jane
Published: November 2010

A steady state analytical model is presented for reach‐scale variation in the concentration of a decaying radioactive tracer associated with sediment particles that regularly pass through an off‐channel floodplain. The floodplain is represented as a series of well‐mixed sediment reservoirs that continually exchange sediment with the channel. The model allows for tributary input and valley‐wide aggradation or degradation. Tracer concentration depends on the upstream boundary concentration, the tracer and sediment load, floodplain geometry, and the rates of in‐floodplain tracer production and/or decay. The theory predicts relatively modest down‐channel change in the concentration of long‐lived isotopes but implies that significant change may occur for (1) tracers with a short‐enough half‐life (such as 14C) or (2) floodplains with sediment residence times that are large enough for cosmogenic production or meteoric fallout to increase tracer concentration in the down‐valley direction. The profiles are shown to be strongly dependent on the grain size distributions of both the sediment load and the floodplain. The results imply that down‐channel 14C profiles have the potential to constrain Holocene bed material loads in systems with sufficient storage. The theory concisely describes the general importance of a floodplain for modifying in situ produced cosmogenic tracer concentration and can also characterize floodplain importance for fallout radioisotopes (i.e., 10Be, 210Pb, or 7Be) or organic 14C.
Gas escape features off New Zealand: Evidence of massive release of methane from hydrates
Authors: Davy Bryan , Pecher Ingo , Wood Ray , Carter Lionel , Gohl Karsten
Published: November 2010

Multibeam swath bathymetry data from the southwest margin of the Chatham Rise, New Zealand, show gas release features over a region of at least 20,000 km2. Gas escape features, interpreted to be caused by gas hydrate dissociation, include an estimated a) 10 features, 8–11 km in diameter and b) 1,000 features, 1–5 km in diameter, both at 800–1,100 m water depth. An estimated 10,000 features, ∼150 m in diameter, are observed at 500–700 m water depth. In the latter depth range sub‐bottom profiles show similar gas escape features (pockmarks) at disconformities interpreted to mark past sea‐level low stands. The amount of methane potentially released from hydrates at each of the largest features is ∼7*1012 g. If the methane from a single event at one 8–11 km scale pockmark reached the atmosphere, it would be equivalent to ∼3% of the current annual global methane released from natural sources into the atmosphere.
Changes in distribution of brine waters on the Laptev Sea shelf in 2007
Authors: Bauch D. , Hölemann J. , Willmes S. , Gröger M. , Novikhin A. , Nikulina A. , Kassens H. , Timokhov L.
Published: November 2010

Combined salinity and δ18O data from summer 2007 reveal a significant change in brine production in the Laptev Sea relative to summer 1994. The distribution of river water and brine‐enriched waters on the Laptev Sea shelf is derived based on mass balance calculations using salinity and δ18O data. While in 1994 maximal influence of brines is seen within bottom waters, in 2007 the influence of brines is highest within the surface layer and only a moderate influence of brines is observed in the bottom layer. In contrast to 2007, salinity and δ18O data from summer 1994 clearly identify a locally formed brine‐enriched bottom water mass as mixing end‐member between surface layer and inner shelf waters on one side and with higher salinity water from the outer Laptev Sea on the other side. In 2007, the brine‐enriched waters are predominantly part of the surface regime, and the mixing end‐member between surface layer and outer shelf waters is replaced by a relatively salty bottom water mass. This relatively salty bottom water probably originates from the western Laptev Sea. The inverted distribution of brines in the water column in 2007 relative to 1994 suggests a less effective winter sea ice formation in winter 2006–2007 combined with advection of more saline waters from the western Laptev Sea or the outer shelf precedent to the climatically extreme summer 2007. The observed changes result in an altered export of waters from the Laptev Sea to the Arctic Ocean halocline.
Global estimates of gravity wave parameters from GPS radio occultation temperature data
Authors: Wang L. , Alexander M. J.
Published: November 2010

Gravity waves (GWs) play critical roles in the global circulation and the temperature and constituent structures in the middle atmosphere. They also play significant roles in the dynamics and transport and mixing processes in the upper troposphere and lower stratosphere and can affect tropospheric weather. Despite significant advances in our understanding of GWS and their effects in different regions of the atmosphere in the past few decades, observational constraints on GW parameters including momentum flux and propagation direction are still sorely lacking. Global Positioning System (GPS) radio occultation (RO) technique provides global, all‐weather, high vertical resolution temperature profiles in the stratosphere and troposphere. The unprecedentedly large number of combined temperature soundings from the Constellation Observing System for Meteorology, Ionosphere, and Climate and Challenging Minisatellite Payload GPS RO missions allows us to obtain GW perturbations by removing the gravest zonal modes using the wavelet method for each day. We extended the GW analysis method of Alexander et al. (2008) to three dimensions to estimate the complete set of GW parameters (including momentum flux and horizontal propagation direction) from the GW temperature perturbations thus derived. To demonstrate the effectiveness of the analysis, we showed global estimates of GW temperature amplitudes, vertical and horizontal wavelengths, intrinsic frequency, and vertical flux of horizontal momentum in the altitude range of 17.5–22.5 km during December 2006 to February 2007. Consistent with many previous studies, GW temperature amplitudes are a maximum in the tropics and are generally larger over land, likely reflecting convection and topography as main GW sources. GW vertical wavelengths are a minimum at equator, likely due to wave refraction, whereas GW horizontal wavelengths are generally longer in the tropics. Most of the waves captured in the analysis of the GPS data are low‐intrinsic frequency inertia‐GWs, and the estimated intrinsic frequencies scaled by the Coriolis parameter also show a strong maximum at equator. Enhanced wave fluxes are linked to convection, topography, and storm tracks, among others. As preliminary tests of the analysis in deriving horizontal propagation directions, we compared the GPS estimates with the corresponding estimates from the U.S. high vertical resolution radiosonde data using the conventional Stokes parameters method and we also conducted a separate analysis of the GPS data over the southern Andes in South America. We also showed the first global estimates of GW propagation directions from the GPS data. Finally, the sensitivity of the analysis to the temporal and spatial dimensions of the longitude × latitude × time cells and the uncertainties of the analysis and possible ways to reduce these uncertainties are discussed.
Older Adults Expend More Listening Effort Than Young Adults Recognizing Speech in Noise
Authors: Anderson Gosselin Penny , Gagné Jean-Pierre
Published: November 2010

Purpose

Listening in noisy situations is a challenging experience for many older adults. The authors hypothesized that older adults exert more listening effort compared with young adults. Listening effort involves the attention and cognitive resources required to understand speech. The purpose was (a) to quantify the amount of listening effort that young and older adults expend when they listen to speech in noise and (b) to examine the relationship between self-reported listening effort and objective measures.

Method

A dual-task paradigm was used to objectively evaluate the listening effort of 25 young and 25 older adults. The primary task involved a closed-set sentence-recognition test, and the secondary task involved a vibrotactile pattern recognition test. Participants performed each task separately and concurrently under 2 experimental conditions: (a) when the level of noise was the same and (b) when baseline word recognition performance did not differ between groups.

Results

Older adults expended more listening effort than young adults under both experimental conditions. Subjective estimates of listening effort did not correlate with any of the objective dual-task measures.

Conclusions

Older adults require more processing resources to understand speech in noise. Dual-task measures and subjective ratings tap different aspects of listening effort.
Temporal and Spectral Cues for Musical Timbre Perception in Electric Hearing
Authors: Kong Ying-Yee , Mullangi Ala , Marozeau Jeremy , Epstein Michael
Published: November 2010

Purpose

The purpose of this study was to investigate musical timbre perception in cochlear-implant (CI) listeners using a multidimensional scaling technique to derive a timbre space.

Methods

Sixteen stimuli that synthesized western musical instruments were used (McAdams, Winsberg, Donnadieu, De Soete, & Krimphoff, 1995). Eight CI listeners and 15 normal-hearing (NH) listeners participated. Each listener made judgments of dissimilarity between stimulus pairs. Acoustical analyses that characterized the temporal and spectral characteristics of each stimulus were performed to examine the psychophysical nature of each perceptual dimension.

Results

For NH listeners, the timbre space was best represented in three dimensions, one correlated with the temporal envelope (log-attack time) of the stimuli, one correlated with the spectral envelope (spectral centroid), and one correlated with the spectral fine structure (spectral irregularity) of the stimuli. The timbre space from CI listeners, however, was best represented by two dimensions, one correlated with temporal envelope features and the other weakly correlated with spectral envelope features of the stimuli.

Conclusions

Temporal envelope was a dominant cue for timbre perception in CI listeners. Compared to NH listeners, CI listeners showed reduced reliance on both spectral envelope and spectral fine structure cues for timbre perception.
Versatile optical access to the tunnel gap in a low-temperature scanning tunneling microscope
Authors: Kuhnke K. , Kabakchiev A. , Stiepany W. , Zinser F. , Vogelgesang R. , Kern K.
Published: November 2010

We developed a setup that provides three independent optical access paths to the tunnel junction of an ultrahigh vacuum low temperature (4.2 K) scanning tunneling microscope (STM). Each path can be individually chosen to couple light in or out, or to image the tunnel junction. The design comprises in situ adjustable aspheric lenses to allow tip exchange. The heat input into the STM is negligible. We present in detail the beam geometry and the realization of lens adjustment. Measurements demonstrate the characterization of a typical light source exemplified by emission from tip-induced plasmons. We suggest employing the Fourier transforming properties of imaging lenses and polarization analysis to obtain additional information on the light emission process. Performance and future potential of the instrument are discussed.
Simulation of phonon transmission through graphene and graphene nanoribbons with a Green’s function method
Authors: Huang Zhen , Fisher Timothy S. , Murthy Jayathi Y.
Published: November 2010

In this paper, phonon transmission through a graphene sheet and graphene nanoribbons is investigated using an atomistic Green’s function method. Best-fit results from first-principles calculations using a fourth nearest neighbor force-constant model are used to establish the matrices that describe interactions among carbon atoms. The effect of carbon isotopes on thermal conductance is investigated, and the results reveal that isotopic doping moderately reduces both phonon transmission function and thermal conductance. The phonon transmission function of each vibrational branch in the heterogeneous interface is also calculated, and comparisons indicate the major and minor channels of phonon transport through graphene. Further, phonon wave effects in zigzag and armchair edge ribbons are investigated. Phonon transmission functions and thermal conductances are found to be sensitive to the edge shape of structures. The phonon transmission functions of nanoribbons with defects are evaluated by artificially creating mismatches at interfaces. By comparing the transmission function of different defect patterns and the corresponding thermal conductances, the reduction in phonon transport is quantified. The length of defects is found to be important to phonon transport. The results herein offer a useful reference and suggest directions for future research on thermal applications of this material.
Optical second harmonic generation at heterojunction interfaces of a molybdenum trioxide layer and an organic layer
Authors: El Basaty A. B. , Miyauchi Y. , Mizutani G. , Matsushima T. , Murata H.
Published: November 2010

We have observed optical second harmonic generation (SHG) from a space charge layer (SCL) in a stacked indium tin oxide (ITO)/molybdenum trioxide (MoO3)/N−N′-diphenyl-N−N′-bis(1-naphthly)-1,1′-biphenyl-4,4′-diamine (α-NPD) system. When the MoO3 thicknesses were increased, the SHG signals from this system decreased sharply at smaller MoO3 thicknesses, and were saturated at MoO3 thicknesses larger than 1 nm. These results prove the vital role of SCL in improvement of drive voltages of organic light-emitting diodes.
Deficits in axonal transport precede ALS symptoms in vivo
Authors: Bilsland Lynsey G. , Sahai Erik , Kelly Gavin , Golding Matthew , Greensmith Linda , Schiavo Giampietro
Published: November 2010

ALS is a fatal neurodegenerative disease characterized by selective motor neuron death resulting in muscle paralysis. Mutations in superoxide dismutase 1 (SOD1) are responsible for a subset of familial cases of ALS. Although evidence from transgenic mice expressing human mutant SOD1
G93A
suggests that axonal transport defects may contribute to ALS pathogenesis, our understanding of how these relate to disease progression remains unclear. Using an in vivo assay that allows the characterization of axonal transport in single axons in the intact sciatic nerve, we have identified clear axonal transport deficits in presymptomatic mutant mice. An impairment of axonal retrograde transport may therefore represent one of the earliest axonal pathologies in SOD1
G93A
mice, which worsens at an early symptomatic stage. A deficit in axonal transport may therefore be a key pathogenic event in ALS and an early disease indicator of motor neuron degeneration.