bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal etching process of microscale pits on the GaAs(001) surface
Authors: Li Shibin , Wu Jiang , Wang Zhiming , Li Zhenhua , Su Yuanjie , Wu Zhiming , Jiang Yadong , Salamo Gregory J.
Published: October 2011

When a GaAs(001) substrate is heated up to 650 °C in a scanning electron microscope (SEM) vacuum chamber with vacuum range from 10–4 Torr to 10–5 Torr, real‐time SEM observation reveals microscale pits on GaAs substrate surface. The annealing process of GaAs substrate in vacuum causes excess evaporation of arsenic and accumulation of gallium as liquid droplets on the surface. As the function of electrochemical drills, the gallium droplets etch away GaAs beneath the surface to make microscale holes on GaAs substrate. With small amount of oxygen in the chamber acting as etching catalyst, gallium droplets etch GaAs much faster than in ultra‐high vacuum (UHV) MBE chamber. This process provides an easy technique to fabricate microscale pits on GaAs(001) surface.

magnified image

Top view of microscale pits, (a) 8000× magnification view of pit; (b) 15000× magnification view of pit.

(© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Potent α‐Glucosidase Inhibitors from Safflower (Carthamus tinctorius L.) Seed
Authors: Takahashi Toshiyuki , Miyazawa Mitsuo
Published: October 2011

As part of the search for naturally derived α‐glucosidase inhibitors, the chemical components isolated from safflower seed (Carthamus tinctorius L.) were evaluated. The compounds active as α‐glucosidase inhibitors were serotonin derivatives (e.g. N‐p‐coumaroyl serotonin (1) and N‐feruloyl serotonin (2)). These compounds showed a potent inhibitory activity, the 50% inhibitory concentration (IC50) values were calculated as 47.2 µm (1) and 99.8 µm (2) while that of the reference drugs acarbose and 1‐deoxynojirimycin were evaluated as 907.5 µm and 278.0 µm, respectively. Regarding the structure of the serotonin derivative, the existence of the hydroxyl group at 5‐position in the serotonin moiety and the linkage of cinnamic acid and serotonin are essential for α‐glucosidase inhibitory activities. These results are helpful for the proper use of safflower seed as traditional medicine for the treatment of diabetes, moreover, it could serve to develop medicinal preparations as supplements and functional foods for diabetes. In particular, the serotonin compounds could be used as a lead compound for a new potential α‐glucosidase inhibitor derived from the plant. Copyright © 2011 John Wiley & Sons, Ltd.
Topography and field effects in secondary ion mass spectrometry Part II: insulating samples
Authors: Lee J. L. S. , Gilmore I. S. , Seah M. P. , Levick A. P. , Shard A. G.
Published: October 2011

A study is conducted on the effects of sample topography on the secondary ion mass spectrometry (SIMS) analysis of insulating samples, using poly(ethylene terephthalate) fibres (100 µm diameter) as a model system and simulations of the ion extraction field using finite element analysis. We focus on two significant issues: topographic field effects caused by the penetration of the extraction field into the sample, and the effect of charge compensation on the secondary ion images. Guidance is provided for setting the reflector voltage correctly for insulating fibres in reflectron SIMS instruments. The presence of the topographic sample distorts the extraction field, causing the secondary ions to be deflected laterally. This results in the severe loss of ion signals from the sides of the fibres because of the limited angular acceptance of the analyser. Strategies to reduce topographic field effects, including alternative sample mounting methods, are discussed. We also find that, in general, insulating samples are charged by the flood gun electrons resulting in a negative surface potential. This causes large variations in the SIMS images depending on the electron current, electron energy, raster mode and secondary ion polarity. Recommendations are given for analysts to obtain more reproducible images and reduce the effect of differential electron charging, for example by using a lower electron flood beam energy. © 2011 Crown copyright.
From Second‐order Cybernetics to Enactive Cognitive Science: Varela's Turn From Epistemology to Phenomenology
Authors: Froese Tom
Published: October 2011

Varela is well known in the systems sciences for his work on second‐order cybernetics, biology of cognition and especially autopoietic theory. His concern during this period was to find an appropriate epistemological foundation for the self‐reference inherent in life and mind. In his later years, Varela began to develop the so‐called ‘enactive’ approach to cognitive science, which sets itself apart from other sciences by promoting a careful consideration of concrete experiential insights. His final efforts were thus dedicated to finding a pragmatic phenomenological foundation for life and mind. It is argued that Varela's experiential turn—from epistemology to phenomenology—can be seen as a natural progression that builds on many ideas that were already implicit in second‐order cybernetics and biology of cognition. It is also suggested that the rigorous study of conscious experience may enable us to refine our theories and systemic concepts of life, mind and sociality. Copyright © 2011 John Wiley & Sons, Ltd.
Comparison of earthquake behavior of reinforced concrete minarets using fiber‐reinforced polymer composite
Authors: Altunişik Ahmet Can
Published: October 2011

This paper presents the comparison of the earthquake behavior of reinforced concrete (RC) minarets using fiber‐reinforced polymer (FRP) composite. A Turkish‐style RC minaret with two balconies of a mosque located in Trabzon, Turkey, was selected as an application. A 3D finite element model of the minaret was created using ansys finite element program to determine the earthquake behavior. The earthquake behavior of the minaret was investigated using the 1992 Erzincan earthquake ground motion record. Also, the cylindrical body of the minaret (below the first balcony, between two balconies and above the second balcony) was wrapped by four layers of FRP, and earthquake behavior was determined. Total thickness of the FRP was selected as 6.0 mm. At the end of the study, earthquake responses of the RC minaret such as displacements and maximum–minimum principal stresses before and after using FRP composite were compared with each other. It was seen from the earthquake analyses that using FRP is very effective on the earthquake responses of the minaret. Copyright © 2011 John Wiley & Sons, Ltd.
A geometry of the correlation space and a nonlocal degenerate parabolic equation from isotropic turbulence
Authors: Grebenev V.N. , Oberlack M.
Published: October 2011

Considering the metric tensor ds2(t), associated with the two‐point velocity correlation tensor field (parametrized by the time variable t) in the space 𝒦3of correlation vectors, at the first part of the paper we construct the Lagrangian system (Mt,ds2(t)) in the extended space 𝒦3 × R+ for homogeneous isotropic turbulence. This allows to introduce into the consideration common concept and technics of Lagrangian mechanics for the application in turbulence. Dynamics in time of (Mt,ds2(t)) (a singled out fluid volume equipped with a family of pseudo‐Riemannian metrics) is described in the frame of the geometry generated by the 1‐parameter family of metrics ds2(t) whose components are the correlation functions that evolve according to the von Kármán‐Howarth equation. This is the first step one needs to get in a future analysis the physical realization of the evolution of this volume. It means that we have to construct isometric embedding of the manifold Mt equipped with metric ds2(t) into R3 with the Euclidean metric. In order to specify the correlation functions, at the second part of this paper we study in details an initial‐boundary value problem to the closure model [19,26] for the von Kármán‐Howarth equation in the case of large Reynolds numbers limit.
Parameter determination of an evolution model for phase transformations in steel
Authors: Streckenbach T.
Published: October 2011

The paper is concerned with a general ansatz of a phenomenological evolution model for solid‐solid phase transformation kinetics in steel. To model the phase transition of austenite‐ferrite, ‐pearlite, or ‐bainite, a first order nonlinear ordinary differential equation (ODE) is considered. The main goal of this paper is to derive certain conditions for parameters that are based on data obtained from transformation diagrams. This leads to a set of independent parameters for which the inverse problem has a unique solution.
Husbandry and growth rates of neonate epaulette sharks, Hemiscyllium ocellatum in captivity
Authors: Payne Eric J.
Published: October 2011

In this report, I describe husbandry techniques that are used to successfully hatch and raise epaulette sharks, Hemiscyllium ocellatum, in captivity. Egg cases and hatchlings were held in floating baskets within a 1,306‐L tank, at water temperatures of 24.4–25.5°C. From 56 egg cases, 27 neonates successfully hatched, and 22 survived. Based on seven tagged egg cases, the average gestation time was 140.3 ± 4.6 days with a range of 134 and 148 days. Upon hatching, neonate length was 16.2 ± 0.522 cm, with a range of 15.24–17.30 cm, and weight was 19.9 ± 2.06 g, with a range of 16.50–24.5 g. Growth rates of four individuals were recorded over time. Finely chopped capelin, Mallotus villosus, fillets, supplemented with a multivitamin were the primary food items accepted by neonates. The success in rearing H. ocellatum can likely be attributed to a low stress environment, limited disruption, an easy to consume diet, multivitamin supplementation, and excellent water quality. Zoo Biol 31:718‐724, 2012. © 2011 Wiley Periodicals, Inc.
Fabry disease, enzyme replacement therapy and the significance of antibody responses
Authors: Deegan Patrick B.
Published: October 2011

Fabry disease is an X‐linked disorder caused by a deficiency of α‐galactosidase A. This leads to a progressive accumulation of globotriaosylceramide in tissues throughout the body. Cardiac, renal and neurological manifestations are common and life expectancy is significantly reduced relative to the general population. Management of Fabry disease involves the administration of intravenous enzyme replacement therapy (ERT). Two forms – agalsidase alfa and agalsidase beta – have been licensed in certain jurisdictions and are generally well tolerated; however, some patients develop antibodies to the infused enzyme, which may impair the efficacy and safety of treatment. Agalsidase alfa and agalsidase beta are produced in different systems; this leads to certain differences in post‐translational modification that may affect immunogenicity. Immunoglobulin (Ig) G antibodies have frequently been reported in patients with Fabry disease receiving ERT; IgG responses are reported in a greater proportion of patients receiving agalsidase beta than in patients receiving agalsidase alfa. IgE antibodies are less common than IgG antibodies, and have not been observed in patients receiving agalsidase alfa. However, these data are difficult to interpret due to methodological differences in the assessment of seropositivity, and in the doses of enzyme used. The clinical impact of the development of IgG antibodies to ERT in patients with Fabry disease remains unclear, due to lack of data and to the marked heterogeneity of patients both in terms of disease manifestations and response to therapy. Further studies that examine the development of antibodies in patients with Fabry disease and the potential impact of such antibodies on the outcome of ERT are necessary.
Fentanyl administration in infant rats produces long‐term behavioral responses
Authors: Medeiros Liciane Fernandes , de Souza Ana Cláudia , de Souza Andressa , Cioato Stefania Giotti , Scarabelot Vanessa Leal , Caumo Wolnei , Fernandes Luciana Carvalho , Torres Iraci L.S.
Published: October 2011

Considering the importance of studies in animal models that are focused on systems involved in pain mechanisms, this investigation aimed to evaluate the effects of pharmacological treatments on the behavioral responses of younger animals. To this end, we evaluated the effect of an acute dose of fentanyl (FEN) or S(+)‐ketamine (KET) at postnatal day 14 (P14) upon behavioral responses in the short‐ (P14), medium‐ (P30) and long‐term (P60) using the open field (OF), elevated plus‐maze (EPM) and formalin tests (FT) and tail‐flick latency. Fourteen‐day‐old male Wistar rats were divided into three groups: control (CT), fentanyl (FEN) and S(+)ketamine (KET) groups for statistical analysis, it was performed two‐way ANOVA followed by Bonferroni. We found that, regardless of the test performed (OF or EPM), between‐group differences occurred over time in all behaviors analyzed, including in the second phase of FT. In addition, EPM showed significant differences in behavioral responses related to acute administration (at P14) of fentanyl or S(+)‐ketamine, in behaviors such as number of entries in open and closed arms, time spent in open and closed arms, and number of head‐dipping. In relation to nociceptive response, the FEN group exhibited a decrease in the first phase of FT. These results indicate that unique administration of fentanyl or S(+)ketamine in an early period of life (P14) can promote changes in behavioral responses. In addition, our findings highlight the importance of extending the investigation of the effect of drug administration in young rats into adulthood.
Frequency spectra evolution of two-dimensional focusing wave groups in finite depth water
Authors: Tian Zhigang , Perlin Marc , Choi Wooyoung
Published: October 2011

An experimental and numerical study of the evolution of frequency spectra of dispersive focusing wave groups in a two-dimensional wave tank is presented. Investigations of both non-breaking and breaking wave groups are performed. It is found that dispersive focusing is far more than linear superposition, and that it undergoes strongly nonlinear processes. For non-breaking wave groups, as the wave groups propagate spatial evolution of wave frequency spectra, spectral bandwidth, surface elevation skewness, and kurtosis are examined. Nonlinear energy transfer between the above-peak ($f/ {f}_{p} = 1. 2{{\ndash}}1. 5$) and the higher-frequency ($f/ {f}_{p} = 1. 5\text{{\ndash}} 2. 5$) regions, with ${f}_{p} $ being the spectral peak frequency, is demonstrated by tracking the energy level of the components in the focusing and defocusing process. Also shown is the nonlinear energy transfer to the lower-frequency components that cannot be detected easily by direct comparisons of the far upstream and downstream measurements. Energy dissipation in the spectral peak region ($f/ {f}_{p} = 0. 9\text{{\ndash}} 1. 1$) and the energy gain in the higher-frequency region ($f/ {f}_{p} = 1. 5\text{{\ndash}} 2. 5$) are quantified, and exhibit a dependence on the Benjamin–Feir Index (BFI). In the presence of wave breaking, the spectral bandwidth reduces as much as 40 % immediately following breaking and eventually becomes much smaller than its initial level. Energy levels in different frequency regions are examined. It is found that, before wave breaking onset, a large amount of energy is transferred from the above-peak region ($f/ {f}_{p} = 1. 2\text{{\ndash}} 1. 5$) to the higher frequencies ($f/ {f}_{p} = 1. 5\text{{\ndash}} 2. 5$), where energy is dissipated during the breaking events. It is demonstrated that the energy gain in the lower-frequency region is at least partially due to nonlinear energy transfer prior to wave breaking and that wave breaking may not necessarily increase the energy in this region. Complementary numerical studies for breaking waves are conducted using an eddy viscosity model previously developed by the current authors. It is demonstrated that the predicted spectral change after breaking agrees well with the experimental measurements.
Cotton radiation use efficiency response to plant growth regulators
Authors: GONIAS E. D. , OOSTERHUIS D. M. , BIBI A. C.
Published: October 2011

Plant growth regulators are widely used in cotton production to improve crop management. Previous research has demonstrated changes in crop growth, dry matter (DM) partitioning and lint yield of cotton after the application of plant growth regulators. However, no reports are available demonstrating the effect of plant growth regulators on light interception and radiation use efficiency (RUE). Field studies were conducted in Fayetteville, Arkansas, USA in 2006 and 2007. RUE was estimated for the period between the pinhead square stage (PHS) of growth and 3 weeks after first flower (FF+3) from plots receiving three applications of the nitrophenolate and mepiquat chloride with Bacillus cereus plant growth regulators (Chaperone™) at 7·19 g a.i./ha and Pix Plus® at 41·94 g a.i./ha compared with an untreated control. No differences between the Chaperone treatment and the untreated control were found in the present study. However, Pix Plus significantly reduced plant height (both 2006 and 2007) and leaf area (2007 only), and altered the canopy structure of the crop as recorded by increased values of canopy extinction coefficient. Although DM accumulation was found not to be affected by plant growth regulator treatments, RUE was significantly increased after Pix Plus application, by 33·2%. RUE was increased because less light was intercepted by the Pix Plus treatment for the same biomass production, and this is probably a result of changes in photosynthetic capacity of the leaves and changes in light distribution throughout the canopy.
Delayed tail loss during the invasion of mouse skin by cercariae of Schistosoma japonicum
Authors: WANG TING , FANG ZHENG-MING , LEI JIA-HUI , GUAN FEI , LIU WEN-QI , BARTLETT ANN , WHITFIELD PHIL , LI YONG-LONG
Published: October 2011

A traditional assumption is that schistosome cercariae lose their tails at the onset of penetration. It has, however, recently been demonstrated that, for Schistosoma mansoni, cercarial tails were not invariably being shed as penetration took place and a high proportion of tails entered human skin under experimental conditions. This phenomenon was termed delayed tail loss (DTL). In this paper, we report that DTL also happens with S. japonicum cercariae during penetration of mouse skin. It occurred at all cercarial densities tested, from as few as 10 cercariae/2·25 cm2 of mouse skin up to 200 cercariae. Furthermore, it was demonstrated that there was a density-dependent increase in DTL as cercarial densities increased. No such density-dependent enhancement was shown for percentage attachment over the same cercarial density range.
Anticoccidial activity of herbal complex in broiler chickens challenged withEimeria tenella
Authors: ZAMAN MUHAMMAD A. , IQBAL ZAFAR , ABBAS RAO Z. , KHAN MUHAMMAD N.
Published: October 2011

The objective of the present study was to evaluate the anticoccidial effect of different concentrations of the herbal complex of 4 plants (leaves ofAzadirachta indicaandNicotiana tabacum,flowers ofCalotropis proceraand seeds ofTrachyspermum ammi) in broiler chickens in comparison with amprolium anticoccidial. Three concentrations (2 g, 4 g and 6 g) of herbal complex were given to the experimental groups once a day and amprolium (at the dose rate of 125 ppm) was given orally in drinking water from the 14th to the 21st days of age. One group was kept as infected, non-medicated control and one as non-infected, non-medicated control. All groups were inoculated orally with 75 000 sporulated oocysts on the 14th day of age except the non-infected, non-medicated control. Among herbal complex medicated groups, the maximum anticoccidial effect was seen in the group medicated with 6 g herbal complex followed by 4 g and 2 g herbal complex medicated groups. Treatment with 6 g of the herbal complex significantly reduced the negative performance and pathogenic effects associated withEimeria tenellachallenge at a level that was comparable with amprolium when using a largely susceptible recent field isolate. In summary, concentration-dependent anticoccidial activity of the studied herbal complex suggests its use as an alternative anticoccidial agent to chemotherapeutic drugs forEimeria tenellacontrol.
Naturalistic Study of Winter Driving Practices by Older Men and Women: Examination of Weather, Road Conditions, Trip Purposes, and Comfort
Authors: Myers Anita M. , Trang Aileen , Crizzle Alexander M.
Published: October 2011

La plupart des études sur les pratiques de conduite des aînés sont basées sur des données d’autoévaluation ; aucune n’a examiné objectivement leurs habitudes de conduite hivernale. Nous avons utilisé des appareils électroniques associés à des journaux de voyages, des cartes numériques et des archives météorologiques, afin d’examinerétudier les modes de conduite des personnes âgées de 65 à 91 sur deux semaines consécutives entre novembre 2008 et mars 2009. La conduite de nuit différait selon le mois, montrant l’importance des facteurs saisonniers, en particulier la quantité de lumière du jour. Bien que 69 pour cent de notre échantillon ait conduit les jours de mauvais temps, les aînés ont montré être significativement plus susceptibles de faire des voyages à des fins sociales ou de divertissement les jours de beau temps, et ils ont entrepris des voyages plus longs les jours offrant de bonnes conditions routières. Les scores de confort de conduite, notamment pour la conduite de nuit, étaient liés de manière significative aux indicateurs multiples de l’exposition et des habitudes, y compris au rayon autour du domicile. Comparativement aux hommes, les femmes ont obtenu des scores de conduite significativement plus bas, et ont été moins susceptibles de conduire quand les conditions metéorologiques et routières étaient défavorables.
Food intake in Slovenian adolescents and adherence to the Optimized Mixed Diet: a nationally representative study
Authors: Kobe Helena , Štimec Matevž , Ribič Cirila Hlastan , Fidler Mis Nataša
Published: October 2011

Objectives

To investigate the food intake of Slovenian adolescents and to compare it with food-based dietary guidelines developed for children and adolescents, named the Optimized Mixed Diet (OMD). The OMD is a useful tool for the evaluation of food intake of adolescents.

Design

All adolescents completed an FFQ at a regional health centre; a subgroup also completed a 3 d weighed dietary protocol at home.

Setting

This study is a part of the first national representative study on the dietary habits of Slovenian adolescents.

Subjects

This cross-sectional study included a representative sample of 2813 Slovenian adolescents entering high school, aged 14–17 years, from all ten geographical regions of Slovenia.

Results

The greatest deviations from the recommended intakes of the main food groups in the OMD were significantly lower intakes of (P < 0·001, mean): vegetables (179 and 163 g/d in boys and girls, respectively), bread/cereals (271 and 226 g/d), potatoes/rice/pasta (212 and 163 g/d); in boys also a significantly lower intake of fruits (mean: 321 g/d, P < 0·001) and a significantly higher intake of meat/meat products (mean: 126 g/d, P < 0·001). Additionally, the results show too high intake of sugar-sweetened beverages and too low intakes of fish and plant oils in both genders.

Conclusions

The food intake pattern of Slovenian adolescents deviates markedly from a healthy eating pattern. Nutrition education and interventions are needed for Slovenian adolescents.
PAYING ATTENTION TO WHITENESS AND CLASS
Authors: Golash-Boza Tanya
Published: October 2011

Juliet Hooker's Race and the Politics of Solidarity and Stanley R. Bailey's Legacies of Race both tackle the crucial question of what kinds of policies states with diverse populations and histories of social inequality should enact in the effort to move towards racial justice. Hooker bases her claims on a case study of multicultural reforms in Nicaragua. Bailey uses survey data to analyze racial attitudes and race-based policies in Brazil. Both Hooker and Bailey critique prior efforts to make generalizations about racial boundaries and multicultural politics on the basis of the U.S. case, and both contend that their arguments will apply beyond the particular case they analyze.
“WALK WITH ME IN WHITE”
Authors: Steedman Marek D.
Published: October 2011

This article argues that Americans operate with a concept and practice of political autonomy centered on a notion of “mastery,” which is inextricably linked to race, gender, and class hierarchy. I adopt Max Weber's concept of mastery and use it to broaden the construct of aHerrenvolkdemocracy beyond its traditional association with White supremacy. I then use this theoretical framework to illuminate the emergence of segregation in Atlanta between 1880 and 1910. This period marks a crucial transformation in the concept of race in the United States, as the paternalism of Southern agricultural relations is transposed by Southern Progressives into more urban and industrial settings. I conclude by raising the possibility that the concept of political autonomy currently operative in the United States shares important common ground with the ideological achievements of the Southern Progressives, confounding institutional attempts to foster citizen autonomy.
The Color Line Reconsidered
Authors: Dawson Michael C.
Published: October 2011

It is fitting that in the same issue that we present a previously unpublished article by W. E. B. Du Bois and host a symposium reviewing new major works on his political philosophy, we also present major essays debating the contours of the color line in the twenty-first century. Immigration and a strong rightward movement in American society are rapidly remaking the demographic and political configuration of the color line in the United States. Several essays in this issue debate critical aspects of this reconfiguration such as the relative importance of cultural versus structural causes of continued racial disparities; the role, if any, that racialization plays in shaping the modern immigrant incorporation into U.S. society; and, the legacy of the Moynihan report. Complementing these essays is a symposium on two major new books that provide fresh takes on the philosophical and theoretical relevance of Du Bois's thought for our times. We are also proud, for the first time anywhere, to publish Du Bois's essay, “The Social Significance of Booker T. Washington,” with an accompanying analytical introduction by Robert Brown.
INTRODUCTION TO “THE SOCIAL SIGNIFICANCE OF BOOKER T. WASHINGTON” By W. E. B. DU BOIS
Authors: Brown Robert
Published: October 2011

The Du Bois Review is pleased to publish, for the first time, this significant reflection on “the meaning of Booker T. Washington to America,” and in so doing highlight Du Bois's desire to see courage, rather than sacrifice, prevail in the face of injustice. This previously unpublished essay is among the W. E. B. Du Bois Papers housed in the Special Collections and University Archives at the University of Massachusetts, Amherst. It was brought to our attention by Robert Brown, who provides an introductory essay including an analysis of the likely date the essay was penned. We present it to our readers with the permission of The David Graham Du Bois Trust.
Integrating and scaling carbon, water, and energy fluxes with optical measurements
Authors: Koteen Laurie , Baldocchi Dennis , Gamon John
Published: October 2011

FLUXNET and Remote Sensing Open Workshop: Towards Upscaling Flux Information From Towers to the Globe; Berkeley, California, 7–9 June 2011 About 140 scientists from 15 countries, representing the remote sensing and land‐atmosphere flux measurement and modeling communities, attended a workshop to address the technical, methodological, and scientific challenges to integrating flux and optical measurements across a spectrum of spatial and temporal scales.
Rainfall: State of the science
Authors: Schultz Colin
Published: October 2011

In textbooks, rain is often considered either the first or final step in the Earth's global water cycle, either way marking a role of special significance. Its presence brings a nurturing flow of fresh water or a devastating flood. Its absence can parch the land. But while rain is spawned from large clouds, its measurement and detection hinge on the small‐scale wobbles and interactions described by rainfall microphysics. In the AGU monograph Rainfall: State of the Science, editors Firat Y. Testik and Mekonnen Gebremichael explore the diverse body of research on all aspects of rainfall science. In this interview, Eos talks to Firat Testik.
Planktonic foraminifera shells record seasonal temperature changes
Authors: Balcerak Ernie
Published: October 2011

When planktonic foraminifera calcify, the magnesium to calcium (Mg/Ca) ratios in their shells are sensitive to water temperature. This has enabled paleoceanographers to use Mg/Ca ratios measured from multiple fossil foraminifera shells in sediments as a proxy for average water temperatures in the past. Now Haarmann et al. show that some foraminifera Mg/Ca ratios can also be used to determine seasonal variations in temperature. The authors suggest that because planktonic foraminifera calcify over a period of a few weeks to months, the Mg/Ca ratios in single specimens could capture seasonal temperature variations. They tested this in samples of three different foraminifera species collected off the coast of northwestern Africa, where there is strong seasonal sea surface temperature variability. The researchers found that one of the three species, Globigerinoides ruber (pink), did show strong variations in Mg/Ca that tracked seasonal temperature changes and thus could potentially be used to reconstruct seasonality in the near and distant past. (Paleoceanography, doi:10.1029/2010PA002091, 2011)
Discrete element modeling of boudinage: Insights on rock rheology, matrix flow, and evolution of geometry
Authors: Abe Steffen , Urai Janos L.
Published: October 2011

We use discrete element model simulations to model the full boudinage process from initial fracturing of intact material to post‐fracture flow of material into gaps between fragments and to investigate the role which the material properties of the weak and strong layers play in this process. The models are deformed in 2D plane strain under a range of confining stresses, in coaxial bulk flow. Results show that the material properties, i.e. Mohr‐Coulomb or quasi‐viscous for the matrix and elastic‐brittle for the competent layer, lead to the development of natural looking boudin morphologies and deformation patterns in the matrix. The details of the matrix rheology only have a minor influence on the morphology of the boudins. By varying the material properties of the competent layer between fully brittle and semi‐ductile we obtain a wide range of deformation patterns ranging from pinch‐and‐swell structures to a variety of boudin types including drawn, shear band and straight sided torn boudins. In a number of models we observe rotation of the boudin blocks despite the applied deformation being purely coaxial. These rotations are generally related to asymmetrical (rhombic) boudin shapes. Some features observed in natural boudins such as concave block faces or the formation of veins between fragments are not modeled because pore fluids are not yet included in our model.
Lognormal Kalman filter for assimilating phase space density data in the radiation belts
Authors: Kondrashov D. , Ghil M. , Shprits Y.
Published: October 2011

Data assimilation combines a physical model with sparse observations and has become an increasingly important tool for scientists and engineers in the design, operation, and use of satellites and other high‐technology systems in the near‐Earth space environment. Of particular importance is predicting fluxes of high‐energy particles in the Van Allen radiation belts, since these fluxes can damage spaceborne platforms and instruments during strong geomagnetic storms. In transiting from a research setting to operational prediction of these fluxes, improved data assimilation is of the essence. The present study is motivated by the fact that phase space densities (PSDs) of high‐energy electrons in the outer radiation belt—both simulated and observed—are subject to spatiotemporal variations that span several orders of magnitude. Standard data assimilation methods that are based on least squares minimization of normally distributed errors may not be adequate for handling the range of these variations. We propose herein a modification of Kalman filtering that uses a log‐transformed, one‐dimensional radial diffusion model for the PSDs and includes parameterized losses. The proposed methodology is first verified on model‐simulated, synthetic data and then applied to actual satellite measurements. When the model errors are sufficiently smaller then observational errors, our methodology can significantly improve analysis and prediction skill for the PSDs compared to those of the standard Kalman filter formulation. This improvement is documented by monitoring the variance of the innovation sequence.
The full-length Streptococcus pneumoniae major pilin RrgB crystallizes in a fibre-like structure, which presents the D1 isopeptide bond and provides details on the mechanism of pilus polymerization
Authors: El Mortaji Lamya , Contreras-Martel Carlos , Moschioni Monica , Ferlenghi Ilaria , Manzano Clothilde , Vernet Thierry , Dessen Andrea , Di Guilmi Anne Marie
Published: October 2011

RrgB is the major pilin which forms the pneumococcal pilus backbone. We report the high-resolution crystal structure of the full-length form of RrgB containing the IPQTG sorting motif. The RrgB fold is organized into four distinct domains, D1–D4, each of which is stabilized by an isopeptide bond. Crystal packing revealed a head-to-tail organization involving the interaction of the IPQTG motif into the D1 domain of two successive RrgB monomers. This fibrillar assembly, which fits into the electron microscopy density map of the native pilus, probably induces the formation of the D1 isopeptide bond as observed for the first time in the present study, since neither in published structures nor in soluble RrgB produced in Escherichia coli or in Streptococcus pneumoniae is the D1 bond present. Experiments performed in live bacteria confirmed that the intermolecular bond linking the RrgB subunits takes place between the IPQTG motif of one RrgB subunit and the Lys183 pilin motif residue of an adjacent RrgB subunit. In addition, we present data indicating that the D1 isopeptide bond is involved in RrgB stabilization. In conclusion, the crystal RrgB fibre is a compelling model for deciphering the molecular details required to generate the pneumococcal pilus.
Facile fabrication of lateral nanowire wrap-gate devices with improved performance
Authors: Dhara Sajal , Sengupta Shamashis , Solanki Hari S. , Maurya Arvind , Pavan R. Arvind , Gokhale M. R. , Bhattacharya Arnab , Deshmukh Mandar M.
Published: October 2011

We present a simple fabrication technique for lateral nanowire wrap-gate devices with high capacitive coupling and field-effect mobility. Our process uses e-beam lithography with a single resist-spinning step and does not require chemical etching. We measure, in the temperature range 1.5–250 K, a subthreshold slope of 5–54 mV/decade and mobility of 2800–2500 cm2/Vs—significantly larger than previously reported lateral wrap-gate devices. At depletion, the barrier height due to the gated region is proportional to applied wrap-gate voltage.
Structure and dynamics of 1,2-dimethoxyethane and 1,2-dimethoxypropane in aqueous and non-aqueous solutions: A molecular dynamics study
Authors: Hezaveh Samira , Samanta Susruta , Milano Giuseppe , Roccatano Danilo
Published: October 2011

Herein, we report a comparative modelling study of 1,2-dimethoxyethane (DME) and 1,2-dimethoxypropane (DMP) at 298 K and 318 K in the liquid state, water mixtures, and at infinite dilution condition in water, methanol, carbon tetrachloride, and n-heptane. Both DME and DMP are united-atom models compatible with GROMOS/OPLS force fields. Calculated thermodynamic and structural properties of the pure DME and DMP liquids resulted in excellent agreement with the experimental data. In aqueous solutions, densities, diffusion coefficients, and concentration dependent conformers of DME, were in agreement with experimental data. The calculated free energy of solvation (ΔGhyd) at 298 K is equal to –22.1 ± 0.8 kJ mol−1 in good agreement with the experimental value of 20.2 kJ mol−1. In addition, the free energy of solvation of DME in non-aqueous solvents follows the trend methanol ≈ water < carbon tetrachloride < n-heptane, consistently with the dielectric constant of the solvents. On contrary, the presence of an extra methyl group on chiral carbon makes DMP less soluble than DME in water (ΔGhyd = −16.0 ± 1.1 kJ mol−1) but more soluble in non-polar solvents as n-heptane. Finally, for the DMP the chiral discrimination of the two enantiomers was calculated as solvation free energy difference of one DMP isomer in the solution of the other. The obtained value of ΔΔGRS = –3.7 ± 1.4 kJ mol−1 indicates a net chiral discrimination of the two enantiomers.
Thermocapillary instabilities in a laterally heated liquid bridge with end wall rotation
Authors: Kahouadji L. , Houchens B. C. , Witkowski L. Martin
Published: October 2011

The effect of rotation on the stability of thermocapillary driven flow in a laterally heated liquid bridge is studied numerically using the full-zone model of the floating-zone crystal growth technique. A small Prandtl number (0.02) fluid, relevant for semiconductor melts, is studied with an aspect ratio (height to diameter of the melt) equal to one. Buoyancy is neglected. A linear stability analysis of three-dimensional perturbations is performed and shows that for any ratio of angular velocities, a weak rotation rate has the surprising effect of destabilizing the base flow. By systematically varying the rotation rate and ratio of angular velocities, the critical threshold and azimuthal wave number of the most unstable mode is found over a wide range of this two parameter space. Depending on these parameters, the leading eigenmode is a wave propagating either in the positive or negative azimuthal direction, with kinetic energy typically localized close to one of the end walls. These results are of practical interest for industrial crystal growth applications, where rotation is often used to obtain higher quality crystals.
Role of the pressure force in the explosive dynamics of magnetic islands in double tearing modes
Authors: Janvier M. , Ishizawa A. , Li J. , Kishimoto Y.
Published: October 2011

The evolution of magnetic islands at two resonant surfaces during the development of a global tearing mode is investigated via numerical simulations of a reduced set of magneto-hydrodynamic equations in slab plasmas. The explosive dynamics of the islands resulting in an interchange follows a Rutherford-like regime, also referred to as a weakly coupled double tearing mode. It is found that the latent mechanism of this dynamics is the reduction of the total pressure around the opposite X-point and the abrupt growth is associated with an imbalance of the pressure around the islands. Once this imbalance is well established, each plasmoid is pushed to the opposite X-point, increasing the drive for the field merging. A feedback loop then takes place as the reconnection itself decreases the strength of the magnetic field between the tearing layers, i.e., reinforces the pressure imbalance. This loop accelerates reconnection, thus leading to the observed explosive growth.
Note: Mechanical and electrical characterization of nanowires in scanning electron microscope
Authors: Ru Changhai , Sun Lining
Published: October 2011

This note presents two experimental techniques for mechanical and electrical characterization of individual nanowires inside a scanning electron microscope (SEM). Tensile testing is realized by transferring a nanowire to a microelectromechanical systems device that stretches the nanowire and measures the elongations and tensile forces. The device consists of an electrostatic actuator and two capacitive sensors, capable of acquiring all measurement data (force and displacement) electronically without relying on electron microscopy imaging. For electrical characterization, four-point probe measurement of individual nanowires is performed automatically by controlling four nanomanipulators with SEM visual feedback. A feedforward controller is incorporated into the control system to improve the response time. This work represents advances in nanomaterial testing and automated nanomanipulation.
Characterization of near-terahertz complementary metal-oxide semiconductor circuits using a Fourier-transform interferometer
Authors: Arenas D. J. , Shim Dongha , Koukis D. I. , Seok Eunyoung , Tanner D. B. , O Kenneth K.
Published: October 2011

Optical methods for measuring of the emission spectra of oscillator circuits operating in the 400–600 GHz range are described. The emitted power from patch antennas included in the circuits is measured by placing the circuit in the source chamber of a Fourier-transform interferometric spectrometer. The results show that this optical technique is useful for measuring circuits pushing the frontier in operating frequency. The technique also allows the characterization of the circuit by measuring the power radiated in the fundamental and in the harmonics. This capability is useful for oscillator architectures designed to cancel the fundamental and use higher harmonics. The radiated power was measured using two techniques: direct measurement of the power by placing the device in front of a bolometer of known responsivity, and by comparison to the estimated power from blackbody sources. The latter technique showed that these circuits have higher emission than blackbody sources at the operating frequencies, and, therefore, offer potential spectroscopy applications.
On the dispersion features of whistler waves in almost pure ion plasmas
Authors: Lundin B. V. , Krafft C.
Published: October 2011

It is shown that in a multi-ion plasma of moderate density enriched by a large amount of negatively charged ions and/or heavy particulates, the lower cutoff frequencies of the electron whistler and the Z-mode (extraordinary) waves tend to each other, approaching the ion plasma frequency ωpi. The evolution of the dispersion curves ω(k, θ) of both wave modes is studied as a function of the relative electron density, beginning from the case of a moderate density plasma with comparable values of electron gyro- and plasma frequencies and ωpi essentially exceeding the ions’ gyrofrequencies. When the fraction of free electrons is very small the transparency frequency domain of the electron whistler mode becomes very narrow, being located in the vicinity of ωpi. If the negatively charged ions have the smallest specific charges among other ion species then, under similar conditions, the so-called crossover effect and the accompanying polarization sense reverse can occur at frequencies essentially greater than the ions’ gyrofrequencies. The revealed effects are characteristic of plasmas with excess of electronegative gas molecules or dust particulates highly adhesive to electrons, i.e., almost pure ion plasmas and/or pair-ion plasmas with extra small fractions of free electrons. Moreover, it is found that the vanishingly small electron fraction providing the same value of the electron whistler ion cutoff frequency normalized to the ion plasma frequency is essentially less for pair fullerene C60± than for pair hydrogen H± plasmas. The technique to determine ωpi using the evolution of the whistler wave magnetic field polarization ellipse is also described.
A few simple rules governing hydrogenation of graphene dots
Authors: Bonfanti M. , Casolo S. , Tantardini G. F. , Ponti A. , Martinazzo R.
Published: October 2011

We investigated binding of hydrogen atoms to small polycyclic aromatic hydrocarbons (PAHs)—i.e., graphene dots with hydrogen-terminated edges—using density functional theory and correlated wavefunction techniques. We considered a number of PAHs with three to seven hexagonal rings and computed binding energies for most of the symmetry unique sites, along with the minimum energy paths for significant cases. The chosen PAHs are small enough to not present radical character at their edges, yet show a clear preference for adsorption at the edge sites which can be attributed to electronic effects. We show how the results, as obtained at different levels of theory, can be rationalized in detail with the help of a few simple concepts derivable from a tight-binding model of the π electrons.
Phase behaviour and phase separation kinetics measurement using acoustic arrays
Authors: Khammar M. , Shaw J. M.
Published: October 2011

Speed of sound and acoustic wave attenuation are sensitive to fluid phase composition and to the presence of liquid-liquid interfaces. In this work, the use of an acoustic array comprising 64 elements as a non-intrusive sensor for liquid-liquid interface, phase separation kinetics measurement in bulk fluids, and local composition measurement in porous media is illustrated. Three benchmark examples: the phase behaviour of methanol + mixed hexanes and methanol + heptane mixtures at 25.0 °C and 1 bar, and Athabasca bitumen + heptane in a synthetic silica porous medium at 22.5 °C and 1 bar, illustrate the accuracy of liquid-liquid interface and potential research and industrial applications of the technique. Liquid-liquid interfaces can be detected independently using both speed of sound and acoustic wave attenuation measurements. The precision of the interface location measurement is 300 μm. As complete scans can be performed at a rate of 1 Hz, phase separation kinetics and diffusion of liquids within porous media are readily tracked. The technique is expected to find application where the fluids or porous media are opaque to visible light and where other imaging techniques are not readily applied, or are too costly. A current limitation is that the acoustic probes must be cooled to less than 315 K in order for them to operate.
High frequency response of carbon nanotube thin film speaker in gases
Authors: Xiao Lin , Liu Peng , Liu Liang , Li Qunqing , Feng Zhenghe , Fan Shoushan , Jiang Kaili
Published: October 2011

The thermoacoustic response of carbon nanotube (CNT) thin films at frequencies ranging from 300 Hz up to 100 kHz has been studied in a variety of gaseous mediums. Theoretical derivations show that the sound pressure generated by CNT thin films is approximately proportional to the inverse of the heat capacity of the gas within the audible frequency range of human hearing, which is consistent with the experimental results in argon, air, and helium. For large size CNT films, a decrease in sound pressure is observed within a higher frequency range in air, which is attributed to the destructive interference of sound waves in the near field zone according to the theoretical calculations.
Directional elliptically polarized terahertz emission from air plasma produced by circularly polarized intense femtosecond laser pulses
Authors: Jahangiri Fazel , Hashida Masaki , Tokita Shigeki , Nagashima Takeshi , Hangyo Masanori , Sakabe Shuji
Published: October 2011

We have observed directional elliptically polarized terahertz (THz) waves emitted from air plasma produced by circularly polarized femtosecond laser pulses. The spatial distribution of the THz waves shows that the radiation is strongly directed forward with a peak around the laser propagation direction. Measured THz power shows a square dependence on laser energy. We consider the parametric decay of laser light to R-waves in plasma in the presence of a spontaneous magnetic field as a possible explanation for the polarization, power dependence, and direction of the THz beam.