bluuebunny/crossref_metadata_2025 huggingface dataset:
High sensitivity steroid analysis using liquid chromatography/solvent‐assisted inlet ionization mass spectrometry
Authors: Chubatyi Nicholas D. , Pagnotti Vincent S. , Bentzley Catherine M. , McEwen Charles N.
Published: March 2012

RATIONALE

Steroids can be injected to behave as therapeutic agents to promote muscle growth and strength. Areas of concern include synthetic steroids in consumer meat and milk products and the presence of anabolic steroids in athletes. Here we demonstrate a new ionization method for high sensitivity steroid analysis using liquid chromatography/mass spectrometry (LC/MS).

METHODS

Solvent‐assisted inlet ionization (SAII) mass spectrometry was coupled directly to an infusion pump or to a liquid chromatograph to determine the limits of detection and quantitation for selected steroids. LC/MS/MS data was acquired on a quadrupole time‐of‐flight (QTOF) mass spectrometer and high resolution‐accurate mass LC/MS data was obtained on an Orbitrap mass spectrometer.

RESULTS

The SAII limit of detection for infusion into the Orbitrap using high mass resolution and accurate mass was shown, for the steroids studied, to be low ppqt and the limit of quantitation using LC/MS was low ppt. Low ppb levels were detected with high signal‐to‐noise from spiked urine using a simple Ziptip procedure without sample concentration.

CONCLUSIONS

LC/SAII‐MS is more sensitive than electrospray ionization (ESI) at similar mobile phase flow rates for the analysis of steroids. Previous studies have shown LC/SAII‐MS to have high sensitivity for analysis of peptides. The combined results suggests this easy to implement ionization method may advantageously replace ESI for a wide range of analyses. Copyright © 2012 John Wiley & Sons, Ltd.
Fragmentation investigation of seven arylnaphthalide lignans using liquid chromatography/tandem quadrupole time‐of‐flight mass spectrometry
Authors: Li Wei , Yang Meihua , Zheng Yuguo
Published: March 2012

RATIONALE

The combination of fragmentation patterns in positive and negative ion modes could be helpful in understanding the structural features of these arylnaphthalide lignans.

METHODS

Fragmentation patterns of seven arylnaphthalide lignans were investigated using liquid chromatography/tandem time‐of‐flight mass spectrometry, and their fragmentation pathways were comprehensively characterized.

RESULTS

In the positive ion mode, the cleavage of the C‐1′–C‐7′ bond was the most characteristic fragmentation pattern of the lignans with both 2′‐hydroxy and 4′,5′‐methylenedioxy groups on the B ring. Arylnaphthalide lignans containing a methylenedioxy group on the B ring could lose C2H2O2 easily. The characteristic mass losses of 58 Da (C2H2O2) could indicate the presence of a methylenedioxy group on the B ring. In the negative ion mode, the type of substituents at C‐7 could affect the cleavage pattern of the lactone ring.

CONCLUSIONS

In search for new compounds, and also in quality control, there is a need to have reliable methodology for the analysis of arylnaphthalide lignans. These results should be useful in the analysis of natural products with similar substructures from Chinese herbs in the future. Copyright © 2012 John Wiley & Sons, Ltd.
Dynamics of large Ar cluster bombardment of organic solids
Authors: Postawa Z. , Paruch R. , Rzeznik L. , Garrison B. J.
Published: March 2012

Molecular dynamics computer simulations are used to investigate the ejection process of molecules from a benzene crystal bombarded with keV large Ar clusters. The effect of projectile size, the kinetic energy and the impact angle on the sputtering efficiency is investigated. The results show that although the sputtering yield depends on all projectile parameters, this dependence can be greatly simplified if the sputtering yield per projectile nucleon is expressed as a function of projectile kinetic energy per nucleon. A different dependence of the total sputtering yield on the impact angle has been observed for small and large projectiles. This effect is attributed to a ‘washing out’ mechanism. For large projectiles most of the organic molecules are ejected by gentle collective action of argon atoms. Proper selection of the projectile parameters allows for achieving conditions where only intact molecules are emitted. Copyright © 2012 John Wiley & Sons, Ltd.
Sticky Bio‐inspired Micropillars: Finding the Best Shape
Authors: Carbone Giuseppe , Pierro Elena
Published: March 2012

Very recently, both experimental and theoretical investigations have shown that microstructured surfaces covered with mushroom‐shaped micropillars present strongly enhanced adhesive properties if compared to flat surfaces made of the same material. However, different geometries lead to different adhesive performance, and finding the optimal solution has become of utmost importance. This paper presents on which physical basis the optimal mushroom pillar shape should be sought, and it provides a relatively simple methodology to achieve the result. Calculations demonstrate that the adhesive performance of the pillar strongly depends on the geometry of the terminal plate. The best performance is achieved when the ratio s/Ri between the plate thickness (s) and the pillar internal radius (Ri) is close to 0.2–0.3, and the ratio Re/Ri is larger than 2, where Re is the external radius of the plate.
Liquid Crystal Order in Colloidal Suspensions of Spheroidal Particles by Direct Current Electric Field Assembly
Authors: Shah Aayush A. , Kang Heekyoung , Kohlstedt Kevin L. , Ahn Kyung Hyun , Glotzer Sharon C. , Monroe Charles W. , Solomon Michael J.
Published: March 2012

DC electric fields are used to produce colloidal assemblies with orientational and layered positional order from a dilute suspension of spheroidal particles. These 3D assemblies, which can be visualized in situ by confocal microscopy, are achieved in short time spans (t < 1 h) by the application of a constant voltage across the capacitor‐like device. This method yields denser and more ordered assemblies than had been previously reported with other assembly methods. Structures with a high degree of orientational order as well as layered positional order normal to the electrode surface are observed. These colloidal structures are explained as a consequence of electrophoretic deposition and field‐assisted assembly. The interplay between the deposition rate and the rotational Brownian motion is found to be critical for the optimal ordering, which occurs when these rates, as quantified by the Peclet number, are of order one. The results suggest that the mechanism leading to ordering is equilibrium self‐assembly but with kinetics dramatically accelerated by the application of the DC electric field. Finally, the crystalline symmetry of the densest structure formed is determined and compared with previously studied spheroidal assemblies.
Zähigkeitsdargebote kaltgefertigter Hohlprofile bei tiefen Temperaturen
Authors: Eichler Björn , Feldmann Markus , Sedlacek Gerhard
Published: March 2012

Kaltgefertigte Hohlprofile europäischer Hersteller weisen in der Regel bessere Zähigkeitseigenschaften auf als in DIN EN 10219 gefordert. Gleichwohl treten häufig Schwierigkeiten beim Einsatz kaltgefertigter Hohlprofile auf, da die Nachweisregeln zur Stahlgütewahl nach DIN EN 1993‐1‐10 dafür nicht anwendbar sind. Deswegen wurde ein Bemessungskonzept zur Stahlgütewahl entwickelt, welches auf realen Zähigkeitsmessungen an kaltgefertigten Hohlprofilen und effektiver Dehnungen beruht. Diese plastischen Dehnungen in den gebogenen Bereichen können zu einem Abfall der Materialzähigkeit führen. Für kreisförmige und rechteckige kaltgefertigte Hohlprofile wurde infolgedessen ein Verschiebungsterm DTcf zur Berücksichtigung dieser Zähigkeitsreduktion in Analogie zum temperaturbasierten Sprödbruchkonzept in DIN EN 1993‐1‐10 abgeleitet.

Toughness performance of cold‐formed structural hollow sections for low temperatures. European cold‐formed hollow sections in general exhibit better toughness properties than required by EN 10219. However, limits in applying the toughness related rules for the choice of steel material in EN 1993‐1‐10 to cold‐formed hollow sections still constitute barriers to free marketing. An assessment procedure has been developed which is based on toughness measurements and effective strains. Such plastic strains may occur in the bent areas associated with a toughness reduction. For the degradation of these toughness properties an appropriate temperature shift DTcf has been derived for both circular and rectangular hollow sections.
Risikoorientierte Bemessung von Tragstrukturen
Authors: Pertermann Ines , Puthli Ram , Ummenhofer Thomas , Vrouwenvelder A.C.W.M (Ton)
Published: March 2012

Der Eurocode DIN EN 1990 [1] eröffnet in Anhang B, Abschnitt B.3 mit der Definition verschiedener Schadensfolgeklassen (Consequences Classes CC1 bis CC3; deutsches Synonym: Versagensfolgeklasse) eine Möglichkeit zur risikoorientierten Festlegung des erforderlichen Zuverlässigkeitsniveaus. Dies kann durch Anpassung, d. h. Abminderung oder Erhöhung der Teilsicherheitsbeiwerte auf der Einwirkungs‐ oder der Widerstandsseite erfolgen. Soll das Zuverlässigkeitsniveau einzelner Bauteile oder einzelner Bauteilnachweise angepasst werden, so ist die Berücksichtigung auf der Widerstandsseite zweckmäßig. Ist das gesamte Tragwerk einer Schadensfolgeklasse zuzuordnen oder betrifft die Festlegung des Zuverlässigkeitsniveaus eine bestimmte Einwirkung, so ist die Berücksichtigung auf der Einwirkungsseite zweckmäßig. Transparenter ist jedoch die Erfassung in einem eigenständigen Faktor KFI (FI: Force Importance), auch Bedeutungsbeiwert genannt. Die Teilsicherheitsbeiwerte können dann unverändert bleiben. Im folgenden Artikel werden Hintergründe und Herleitung dieses Bedeutungsbeiwertes erläutert.

Risk oriented design of structures – Force importance factors KFI for differentiating the reliability levels of the different Consequences Classes. The Eurocode EN 1990 [1] Annex B Clause B.3 allows a risk oriented differentiation of the reliability levels with the definition of different consequences classes CC1 to CC3. This can occur through decrease or increase of the safety factor for either the action or the resistance. Should the reliability level of an individual structural component or individual structural check need to be differentiated, it is appropriate to consider the resistance side. If the whole structure is to be assigned a certain consequences class, or if the reliability level relates to a particular action, it is appropriate to consider the action side. In any case the inclusion in an independent factor KFI provides more transparency. The partial factors can then remain unchanged. This article describes the background and derivation of these force importance factors.
Development of spatial cognition
Authors: Vasilyeva Marina , Lourenco Stella F.
Published: March 2012

Spatial cognition plays an essential role in everyday functioning and provides a foundation for successful performance in scientific and technological fields. Reasoning about space involves processing information about distance, angles, and direction. Starting from infancy, children display sensitivity to these spatial properties, although their initial skills are quite limited. Subsequent development during early childhood and through the elementary school years involves gradual improvement in the use of individual frames of reference (i.e.,egocentricandallocentric), as well as in the ability to flexibly combine different types of spatial information. Similarly, there is a relatively long progression from the starting points, when infants and young children display sensitivity to distance and form simple spatial categories, to more mature spatial competence when older children and adults integrate distance and categorical information hierarchically. Such developments are associated with both the maturation of specific brain regions and accumulating experience, including interactions with the physical world and the acquisition of cultural tools. In particular, the mastery of symbolic spatial representations, such as maps and models, significantly augments basic spatial capabilities. While growing evidence implicates both biological and experiential factors in the development of spatial cognition, a deeper understanding of the mechanisms that underlie the developmental process requires further investigation of how such factors interact to produce organisms that function competently in their environments.WIREs Cogn Sci2012, 3:349–362. doi: 10.1002/wcs.1171

This article is categorized under:

Psychology > Development and Aging
A mixture model with evolving mass densities for describing synthesis and resorption phenomena in bones reconstructed with bio‐resorbable materials
Authors: Lekszycki T. , dell'Isola F.
Published: March 2012

The multiform bio‐mechanical phenomena occurring in bones grafted with the addition of artificial materials urge for the formulation of models which are sophisticated enough to describe their complexity. In the present paper we present a continuum poro‐elastic mixture model in which two apparent mass densities are introduced to describe, at a macroscopic length scale, situations in which bone tissues and artificial materials coexist and interact. We focus on the final healing stage process when the bone remodelling becomes the dominant phenomenon. Artificial materials used are obviously to be bio‐compatible and must resist to externally applied mechanical loads. More recently in order to favour bone tissue re‐growth in grafts, which improves the long term performances of grafted bones, it has been conceived to use substitute materials which may be, similarly to bone tissue, bio‐resorbed by osteoclasts and eventually replaced by newly synthesised living tissue. To account for resorption and synthesis phenomena suitable evolution equations are introduced for Lagrangian mass densities of the mixture constituents in which an integrodifferential operator defined on deformation fields appears. This operator is chosen to model some features of the coupling between mechanical compliance and biological bone tissue activity. The obtained system of integrodifferential equations is not trivial also when one considers one dimensional cases. Treating this simplified situations will allow us to individuate more easily some important remodelling scenarios. The numerical simulations which we present here show that the introduced model is promising and deserves to be developed to give previsions in more realistic applications.
Spatial structure, rock type, and local environmental conditions drive moss and lichen distribution on calcareous boulders
Authors: Spitale Daniel , Nascimbene Juri
Published: March 2012

Although mosses and lichens are a relevant component of the biota of rock habitats targeted for biodiversity conservation in Europe, the ecological factors driving their distribution are still poorly known. In this work, we examined the epilithic moss and lichen assemblages colonizing boulders of different types of calcareous rocks co‐occurring in the same area in the Italian Alps. The goals were: (1) to evaluate if and to what extent different calcareous rocks host different assemblages; (2) to identify species associated to each rock type; (3) to quantify the relative importance of rock type, local environmental factors, and habitat spatial structure in explaining species distribution. Our results demonstrated that different calcareous rocks host different moss and lichen assemblages with some typical species, indicating that each rock type contributes to the total diversity of both mosses and lichens. Local environmental conditions influenced mosses and not lichens whose distribution is mainly associated to rock type. The patterns of both organism groups were also significantly related to habitat spatial structure, species assemblages tending to have a patchy distribution, which may reflect dispersal dynamics. Our results have implications for conservation: (1) each rock type may play a relevant role in maintaining the overall diversity contributing with unique assemblages and typical species; (2) the patchy distribution of both moss and lichen assemblages should warn from considering rock patches as a monotonous repetition of the same habitat across space.
Lagrangian and spectral analysis of the forced flow past a circular cylinder using pulsed tangential jets
Authors: Jardin T. , Bury Y.
Published: March 2012

We numerically investigate the influence of pulsed tangential jets on the flow past a circular cylinder. To this end a spectral-Lagrangian dual approach is used on the basis of time-series data. The analysis reveals that the flow response to unsteady forcing is driven by strong interactions between shear layers and pulsed jets. The latter preferentially lead to either the lock-on regime or the quasi-steady vortex feeding regime whether the excitation frequency is of the order of, or significantly greater than, the frequency of the natural instability. The intensity of the wake vortices is mainly influenced by the momentum coefficient through the introduction of opposite-sign vorticity in the shear layers. This feature is emphasized using a modal-based time reconstruction, i.e. by reconstructing the flow field upon a specific harmonic spectrum associated with a characteristic time scale. The quasi-steady regime exhibits small-scale counter-rotating vortices that circumscribe the separated region. In the lock-on regime, atypical wake patterns such as 2P or $\mathrm{P} + \mathrm{S} $ can be observed, depending on the forcing frequency and the momentum coefficient, highlighting remarkable analogies with oscillating cylinders.
Optimal inflow boundary condition perturbations in steady stenotic flow
Authors: Mao X. , Blackburn H. M. , Sherwin S. J.
Published: March 2012

We determine optimal inflow boundary perturbations to steady flow through a straight inflexible tube with a smooth axisymmetric stenosis at a bulk-flow Reynolds number $\mathit{Re}= 400$, for which the flow is asymptotically stable. The perturbations computed produce an optimal gain, i.e. kinetic energy in the domain at a given time horizon normalized by a measure of time-integrated energy on the inflow boundary segment. We demonstrate that similarly to the optimal initial condition problem, the gain can be interpreted as the leading singular value of the forward linearized operator that evolves the boundary conditions to the final state at a fixed time. In this investigation we restrict our attention to problems where the temporal profile of the perturbations examined is a product of a Gaussian bell and a sinusoid, whose frequency is selected to excite axial wavelengths similar to those of the optimal initial perturbations in the same geometry. Comparison of the final state induced by the optimal boundary perturbation with that induced by the optimal initial condition demonstrates a close agreement for the selected problem. Previous works dealing with optimal boundary perturbation considered a prescribed spatial structure and computed an optimal temporal variation of a wall-normal velocity component, whereas in this paper we consider the problem of a prescribed temporal structure and compute the optimal spatial variation of velocity boundary conditions over a one-dimensional inflow boundary segment. The methodology is capable of optimizing boundary perturbations in general non-parallel two- and three-dimensional flows.
Roles of mating behavioural interactions and life history traits in the competition between alien and indigenous whiteflies
Authors: Wang P. , Crowder D.W. , Liu S.-S.
Published: March 2012

Interference competition between closely related alien and indigenous species often influences the outcome of biological invasions. The whitefly Bemisia tabaci species complex contains ≥28 putative species and two of them, Mediterranean (MED, formally referred to as the ‘Q biotype’) and Middle East-Asia Minor 1 (MEAM1, formally referred to as the ‘B biotype’), have recently spread to much of the world. In many invaded regions, these species have displaced closely related indigenous whitefly species. In this study, we integrated laboratory population experiments, behavioural observations and simulation modelling to investigate the capacity of MED to displace Asia II 1 (AII1, formally referred to as the ‘ZHJ2 biotype’), an indigenous whitefly widely distributed in Asia. Our results show that intensive mating interactions occur between MED and AII1, leading to reduced fecundity and progeny female ratio in AII1, as well as an increase in progeny female ratio in MED. In turn, our population cage experiments demonstrated that MED has the capacity to displace AII1 in a few generations. Using simulation models, we then show that both asymmetric mating interactions and differences in life history traits between the two species contribute substantially to the process of displacement. These findings would help explain the displacement of AII1 by MED in the field and, together with earlier studies on mating interactions between other species of the B. tabaci complex, indicate the widespread significance of asymmetric mating interactions in whitefly species exclusions.
UNDERSTANDING THE ASSOCIATION BETWEEN MATERNAL EDUCATION AND USE OF HEALTH SERVICES IN GHANA: EXPLORING THE ROLE OF HEALTH KNOWLEDGE
Authors: SMITH GREENAWAY EMILY , LEON JUAN , BAKER DAVID P.
Published: March 2012

This paper examines the role of health knowledge in the association between mothers' education and use of maternal and child health services in Ghana. The study uses data from a nationally representative sample of female respondents to the 2008 Ghana Demographic and Health Survey. Ordered probit regression models evaluate whether women's health knowledge helps to explain use of three specific maternal and child health services: antenatal care, giving birth with the supervision of a trained professional and complete child vaccination. The analyses reveal that mothers' years of formal education are strongly associated with health knowledge; health knowledge helps explain the association between maternal education and use of health services; and, net of a set of stringent demographic and socioeconomic controls, mothers' health knowledge is a key factor associated with use of health services.
Effects of environmental policy on consumption: lessons from the Chinese plastic bag regulation
Authors: He Haoran
Published: March 2012

To reduce plastic bag litter, China introduced a nationwide regulation requiring all retailers to charge for plastic shopping bags on 1 June 2008. By using the policy implementation as a natural experiment and collecting individual-level data before and after the implementation, we investigate the impacts of the regulation on consumers’ bag use. We find that the regulation implementation caused a 49 per cent reduction in the use of new bags. Besides regulation enforcement, consumers’ attitude toward the regulation and some consumers’ socioeconomic characteristics also affected bag consumption. However, the regulation effects differ largely among consumer groups and among regions and shopping occasions.
Environmental policy in a linear city model of product differentiation
Authors: Espínola-Arredondo Ana , Zhao Huan
Published: March 2012

This paper analyzes how a tax/subsidy policy affects consumers' behavior when choosing between green (pollution-free goods) and conventional products, and its effects on welfare when a proportion of consumers have strong preferences for green goods. We analyze a Hotelling's linear city model where final products by two firms are symmetric in all dimensions except for the externality their production process generates. Our efficiency comparisons suggest that, under a setting of horizontal product differentiation, an environmental regulation (either on polluting firms or consumers buying their products) yields higher social welfare than the absence of policy. Moreover, the proportion of consumers who prefer green products affects the welfare gains from a subsidy or tax policy.
The Emergence and Maintenance of Ethical Leadership in Organizations
Authors: Eisenbeiß Silke Astrid , Giessner Steffen R.
Published: March 2012

The present paper gives a review of empirical research on ethical leadership and shows that still little is known known about the contextual antecedents of ethical leadership. To address this important issue, a conceptual framework is developed that analyzes the embeddedness of organizational ethical leadership. This framework identifies manifest and latent contextual factors on three different levels of analysis – society, industry, and organization – which can affect the development and maintenance of ethical leadership. In particular, propositions are offered about how (1) societal characteristics, notably the implementation and the spirit of human rights in a society and societal cultural values of responsibility, justice, humanity, and transparency; (2) industry characteristics such as environmental complexity, the content of the organizational mandate, and the interests of stakeholder networks; and (3) intra-organizational characteristics, including the organizational ethical infrastructure and the ethical leadership behavior of a leader’s peer group, influence the development and maintenance of ethical leadership in organizations. This list of factors is not exhaustive, but illustrates how the three levels may impact ethical leadership. Implications for managerial practice and future research are discussed.
Gasoline emissions dominate over diesel in formation of secondary organic aerosol mass
Authors: Bahreini R. , Middlebrook A. M. , de Gouw J. A. , Warneke C. , Trainer M. , Brock C. A. , Stark H. , Brown S. S. , Dube W. P. , Gilman J. B. , Hall K. , Holloway J. S. , Kuster W. C. , Perring A. E. , Prevot A. S. H. , Schwarz J. P. , Spackman J. R. , Szidat S. , Wagner N. L. , Weber R. J. , Zotter P. , Parrish D. D.
Published: March 2012

Although laboratory experiments have shown that organic compounds in both gasoline fuel and diesel engine exhaust can form secondary organic aerosol (SOA), the fractional contribution from gasoline and diesel exhaust emissions to ambient SOA in urban environments is poorly known. Here we use airborne and ground‐based measurements of organic aerosol (OA) in the Los Angeles (LA) Basin, California made during May and June 2010 to assess the amount of SOA formed from diesel emissions. Diesel emissions in the LA Basin vary between weekdays and weekends, with 54% lower diesel emissions on weekends. Despite this difference in source contributions, in air masses with similar degrees of photochemical processing, formation of OA is the same on weekends and weekdays, within the measurement uncertainties. This result indicates that the contribution from diesel emissions to SOA formation is zero within our uncertainties. Therefore, substantial reductions of SOA mass on local to global scales will be achieved by reducing gasoline vehicle emissions.
Period doubling in magnetospheric convection cycle
Authors: Liu W. William
Published: March 2012

A gedanken investigation is performed on magnetospheric complexity. In an attempt to separate complexities due to external (solar wind) and internal (magnetospheric) dynamics, we hold the solar wind condition constant and investigate how the open flux in the magnetosphere changes from one convection cycle to the next. The change of open flux is related to the time integral of the tail electric field. This field, in turn, is proportional to the product of the normal (x) and tangential (z) components of the tail magnetic field. As the magnetosphere evolves, the magnetic components typically vary in opposite directions. We show that this competition leads to a magnetic flux cycle described by the classical logistic equation xn+1 = r(1 − xn)xn, where x is a linear function of open flux, the much researched route to chaos through period‐doubling. The result could provide a possible explanation of the steady magnetospheric convection, sawtooth events, and other observed manifestations of nonlinearity.
Understanding shock dynamics in the inner heliosphere with modeling and Type II radio data: The 2010‐04‐03 event
Authors: Xie H. , Odstrcil D. , Mays L. , St. Cyr O. C. , Gopalswamy N. , Cremades H.
Published: March 2012

The 2010 April 03 solar event was studied using observations from STEREO SECCHI, SOHO LASCO, and Wind kilometric Type II data (kmTII) combined with WSA‐Cone‐ENLIL model simulations performed at the Community Coordinated Modeling Center (CCMC). In particular, we identified the origin of the coronal mass ejection (CME) using STEREO EUVI and SOHO EIT images. A flux‐rope model was fit to the SECCHI A and B, and LASCO images to determine the CME's direction, size, and actual speed. J‐maps from STEREO COR2/HI‐1/HI‐2 and simulations from CCMC were used to study the formation and evolution of the shock in the inner heliosphere. In addition, we also studied the time‐distance profile of the shock propagation from kmTII radio burst observations. The J‐maps together with in‐situ data from the Wind spacecraft provided an opportunity to validate the simulation results and the kmTII prediction. Here we report on a comparison of two methods of predicting interplanetary shock arrival time: the ENLIL model and the kmTII method; and investigate whether or not using the ENLIL model density improves the kmTII prediction. We found that the ENLIL model predicted the kinematics of shock evolution well. The shock arrival times (SAT) and linear‐fit shock velocities in the ENLIL model agreed well with those measurements in the J‐maps along both the CME leading edge and the Sun‐Earth line. The ENLIL model also reproduced most of the large scale structures of the shock propagation and gave the SAT prediction at Earth with an error of ∼1 ± 7 hours. The kmTII method predicted the SAT at Earth with an error of ∼15 hours when using n0 = 4.16 cm−3, the ENLIL model plasma density near Earth; but it improved to ∼2 hours when using n0 = 6.64 cm−3, the model density near the CME leading edge at 1 AU.
Complexity of the Mw 6.3 2009 L'Aquila (central Italy) earthquake: 1. Multiple finite‐extent source inversion
Authors: Gallovič F. , Zahradník J.
Published: March 2012

Strong ground motion recordings of the Mw 6.3 2009 L'Aquila earthquake are analyzed by a newly proposed slip inversion technique. The source model consists of Multiple Finite‐Extent (MuFEx) subsources. The slip amplitude, rupture velocity, rake and risetime are assumed constant within each subsource. The size and location of the MuFEx subsources have to be inferred independently from other methods, preferably those free of strong constraints (such as constant rupture velocity over the whole fault, etc); here we use two published approaches satisfying such requirement: the truncated singular value decomposition and the iterative multiple‐point source deconvolution. Each MuFEx subsource is characterized by an individual set of trial nucleation points, rupture velocities and nucleation times, which are grid‐searched. For each combination of these parameters, the subsources' slip is determined by the least squares approach. This procedure thus provides not only the best fitting model, but also a whole range of acceptable models, allowing for the uncertainty analysis. The method is demonstrated on three synthetic tests. When applied to the L'Aquila data, both the best fitting model and the uncertainty analysis suggest that the event consisted of two major episodes, one with the rupture propagating immediately after the nucleation in the updip direction, the other being delayed by 3–4 s with dominant propagation toward the SE along the deeper part of the fault. The retrieved complexity of the rupture propagation warns against attempts to stabilize inversions by the use of a constant rupture velocity over the whole fault.
Seasonal variability of upper ocean heat content in Drake Passage
Authors: Stephenson Gordon R. , Gille Sarah T. , Sprintall Janet
Published: March 2012

Mixed‐layer depth (MLD) is often used in a mixed‐layer heat budget to relate air‐sea exchange to changes in the near‐surface ocean temperature. In this study, reanalysis heat flux products and profiles from a 15 year time series of high‐resolution, near‐repeat expendable bathythermograph/expendable conductivity‐temperature‐depth (XBT/XCTD) sampling in Drake Passage are used to examine the nature of MLD variations and their impact on a first‐order, one‐dimensional heat budget for the upper ocean in the regions north and south of the Polar Front. Results show that temperature and density criteria yield different MLD estimates, and that these estimates can be sensitive to the choice of threshold. The difficulty of defining MLD in low‐stratification regions, the large amplitude of wintertime MLD (up to 700 m in Drake Passage), and the natural small‐scale variability of the upper ocean result in considerable cast‐to‐cast variability in MLD, with changes of up to 200 m over 10 km horizontal distance. In contrast, the heat content over a fixed‐depth interval of the upper ocean shows greater cast‐to‐cast stability and clearly measures the ocean response to surface heat fluxes. In particular, an annual cycle in upper ocean heat content is in good agreement with the annual cycle in heat flux forcing, which explains ∼24% of the variance in heat content above 400 m depth north of the Polar Front and ∼63% of the variance in heat content south of the Polar Front.
Estimating surface longwave radiative fluxes from satellites utilizing artificial neural networks
Authors: Nussbaumer Eric A. , Pinker Rachel T.
Published: March 2012

A novel approach for calculating downwelling surface longwave (DSLW) radiation under all sky conditions is presented. The DSLW model (hereafter, DSLW/UMD v2) similarly to its predecessor, DSLW/UMD v1, is driven with a combination of Moderate Resolution Imaging Spectroradiometer (MODIS) level‐3 cloud parameters and information from the European Centre for Medium‐Range Weather Forecasts (ECMWF) ERA‐Interim model. To compute the clear sky component of DSLW a two layer feed‐forward artificial neural network with sigmoid hidden neurons and linear output neurons is implemented; it is trained with simulations derived from runs of the Rapid Radiative Transfer Model (RRTM). When computing the cloud contribution to DSLW, the cloud base temperature is estimated by using an independent artificial neural network approach of similar architecture as previously mentioned, and parameterizations. The cloud base temperature neural network is trained using spatially and temporally co‐located MODIS and CloudSat Cloud Profiling Radar (CPR) and the Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) Cloud‐Aerosol Lidar with Orthogonal Polarization (CALIOP) observations. Daily average estimates of DSLW from 2003 to 2009 are compared against ground measurements from the Baseline Surface Radiation Network (BSRN) giving an overall correlation coefficient of 0.98, root mean square error (rmse) of 15.84 W m−2, and a bias of −0.39 W m−2. This is an improvement over an earlier version of the model (DSLW/UMD v1) which for the same time period has an overall correlation coefficient 0.97 rmse of 17.27 W m−2, and bias of 0.73 W m−2.
Density and lithospheric thickness of the Tharsis Province from MEX MaRS and MRO gravity data
Authors: Beuthe M. , Le Maistre S. , Rosenblatt P. , Pätzold M. , Dehant V.
Published: March 2012

Radio science tracking of Mars Express (MaRS experiment) and Mars Reconnaissance Orbiter produced high resolution Martian gravity data. Applying localized spectral analysis on the new gravity data sets, we study the surface density and lithospheric elastic thickness in the Tharsis province. The gravity signal is predicted with geophysical models either including bottom loading (top/bottom model) or taking into account the loading history (top/top model). Volcanic shields are mainly composed of high‐density lava but their construction could have begun with lower density lava, with the exception of Ascraeus Mons which has a top of lower density. Buoyant bottom loading may have been present in the form of a mantle plume under Olympus Mons. The elastic thickness was much larger at Olympus Mons than at other volcanoes, suggesting large spatial variations of heat flux during the Hesperian. Alternatively, small elastic thicknesses could be artifacts reflecting the presence of very localized high‐density crustal intrusions beneath the volcanoes. Thaumasia highlands were probably supported by a mantle plume at the time of formation. In Valles Marineris, top/bottom models predict low densities and large elastic thicknesses, in conflict with the basaltic rock composition and Hesperian age of the valley. Dense mafic dikes underlie the western part of the valley. The top/top model serves to test another scenario in which the trough is formed with sedimentary infilling removed much later by erosion, the elastic thickness increasing in between. At the large volcanoes, the relation between gravity and topography is anisotropic probably because of density variations.
“Super‐parameterization”: A better way to simulate regional extreme precipitation?
Authors: Li Fuyu , Rosa Daniele , Collins William D. , Wehner Michael F.
Published: March 2012

Extreme precipitation is generally underestimated by current climate models relative to observations of present‐day rainfall distributions. Possible causes of this systematic error include the convective parameterization in these models that have been designed to reproduce measurements of climatological mean precipitation. One possible approach to improve the interaction of subgrid‐scale physical processes and large‐scale climate is to replace the conventional convective parameterizations with a high‐resolution cloud‐system resolving model. A “super‐parameterized” Community Atmosphere Model (SP‐CAM) utilizing this approach is used in this study to investigate the distribution of extreme precipitation in the United States. Results show that SP‐CAM better simulates the distributions of both light and intense precipitation compared to the standard version of CAM based upon conventional parameterizations. The improvements are mostly seen in regions dominated by convective precipitation, suggesting that super‐parameterization provides a better representation of subgrid convective processes.
Vibrational relaxation of CO2(ν2) by O(3P) in the 142–490 K temperature range
Authors: Castle Karen J. , Black Labe A. , Simione Michael W. , Dodd James A.
Published: March 2012

Laboratory measurements of the quenching of CO2(ν2) by O atoms are presented over the 142–490 K temperature range relevant to the 75–120 km altitude region of the terrestrial atmosphere. The primary cooling mechanism in this region occurs when CO2 is efficiently excited through collisions with ambient O atoms, populating the bending vibrational (ν2) modes. A significant fraction of the vibrationally excited CO2 relaxes through spontaneous 15‐μm emission that escapes into space, thereby removing kinetic energy from this region of the atmosphere and generating a local cooling effect. The rate coefficient for the vibrational relaxation of CO2(ν2) by O atoms, kO(ν2), is measured using transient diode laser absorption spectroscopy. A slight negative temperature dependence is observed for kO(ν2), with values ranging from 2.7 (±0.4) × 10−12 cm3 s−1 at 142 K to 1.3 (±0.2) × 10−12 cm3 s−1 at 490 K.
Protein phosphatases and their regulation in the control of mitosis
Authors: Mochida Satoru , Hunt Tim
Published: March 2012

Cell cycle transitions depend on protein phosphorylation and dephosphorylation. The discovery of cyclin‐dependent kinases (CDKs) and their mode of activation by their cyclin partners explained many important aspects of cell cycle control. As the cell cycle is basically a series of recurrences of a defined set of events, protein phosphatases must obviously be as important as kinases. However, our knowledge about phosphatases lags well behind that of kinases. We still do not know which phosphatase(s) is/are truly responsible for dephosphorylating CDK substrates, and we know very little about whether and how protein phosphatases are regulated. Here, we summarize our present understanding of the phosphatases that are important in the control of the cell cycle and pose the questions that need to be answered as regards the regulation of protein phosphatases.
Metagenomic and metaproteomic insights into bacterial communities in leaf-cutter ant fungus gardens
Authors: Aylward Frank O , Burnum Kristin E , Scott Jarrod J , Suen Garret , Tringe Susannah G , Adams Sandra M , Barry Kerrie W , Nicora Carrie D , Piehowski Paul D , Purvine Samuel O , Starrett Gabriel J , Goodwin Lynne A , Smith Richard D , Lipton Mary S , Currie Cameron R
Published: March 2012

Herbivores gain access to nutrients stored in plant biomass largely by harnessing the metabolic activities of microbes. Leaf-cutter ants of the genus Atta are a hallmark example; these dominant neotropical herbivores cultivate symbiotic fungus gardens on large quantities of fresh plant forage. As the external digestive system of the ants, fungus gardens facilitate the production and sustenance of millions of workers. Using metagenomic and metaproteomic techniques, we characterize the bacterial diversity and physiological potential of fungus gardens from two species of Atta. Our analysis of over 1.2 Gbp of community metagenomic sequence and three 16S pyrotag libraries reveals that in addition to harboring the dominant fungal crop, these ecosystems contain abundant populations of Enterobacteriaceae, including the genera Enterobacter, Pantoea, Klebsiella, Citrobacter and Escherichia. We show that these bacterial communities possess genes associated with lignocellulose degradation and diverse biosynthetic pathways, suggesting that they play a role in nutrient cycling by converting the nitrogen-poor forage of the ants into B-vitamins, amino acids and other cellular components. Our metaproteomic analysis confirms that bacterial glycosyl hydrolases and proteins with putative biosynthetic functions are produced in both field-collected and laboratory-reared colonies. These results are consistent with the hypothesis that fungus gardens are specialized fungus–bacteria communities that convert plant material into energy for their ant hosts. Together with recent investigations into the microbial symbionts of vertebrates, our work underscores the importance of microbial communities in the ecology and evolution of herbivorous metazoans.
A less expensive NiMnGa based Heusler alloy for magnetic refrigeration
Authors: Mejía C. Salazar , Gomes A. M. , de Oliveira L. A. S.
Published: March 2012

We present a study of the substitution of Mn by Cu on the compound Ni2Mn1-xCuxGa0.9Al0.1, showing that the substitution of a small amount of Al on the Ga site does not affect the magnetic and magnetocaloric potential compared to Ni2(Mn,Cu)Ga alloy. The samples were prepared with 10% substitution of Al and with Cu concentrations of x = 0.0, 0.2, and 0.3. Magnetization measurements as a function of temperature performed from 10 to 400 K, with an applied field of 0.02 T showed a ferromagnetic state, with critical temperature Tc = 295 and 300 K for the samples with Cu, x = 0.2 and 0.3, respectively. For the sample without Cu, a complex behavior is observed at Tc = 370 K, with martensitic transition at 220 K and a premartensitic at 250 K. Analysis of x-rays diffractograms at room temperature show a L21 structure for x = 0.0, while for x = 0.2 a mixture of L21 and martensitic is present, and the sample with x = 0.3 it is in a fully martensitic phase. Heat capacity measurements were performed in order to calculate magnetocaloric effect in the samples. The results indicate that in Ni(Mn,Cu)Ga alloys, a partial substitution of Ga by Al still produce a high refrigerant capacity while reducing the costs of fabrication.
Prediction of iron losses in doubly salient permanent magnet machine with rectangular current waveform
Authors: Zhang Jianzhong , Wang Minxi , Cheng Ming
Published: March 2012

Iron losses in doubly salient permanent magnet (DSPM) machine are difficult to predict, as the flux waveforms are complex and dc bias existed. This paper measures iron losses at no load for different rotor speeds and these measured loss data are used to calibrate the iron loss model of the DSPM machine. Then the iron losses at rated load are predicted under three phase rectangular currents exerting on the armature windings. The result shows that small increment of iron losses is in the rotor at rated load which do benefit to the rotor thermal dissipation design.
Nonlinear theory of mode conversion at plasma frequency
Authors: Bang Wu Kai , Hsu Jang Yu
Published: March 2012

An electromagnetic (EM) wave at the mode conversion layer transfers its energy to the electrostatic (ES) wave whose amplitude can be greatly enhanced due to its slow group velocity near the cut off layer. The large amplitude ES wave produces the density compression, indispensable for the nonlinear coupling in the EM wave, leading to the localized vortex flow. A dc magnetic field, tantamount to the vorticity, is generated as a result of the conservation of canonical momentum.
Molecular dynamics and kinetic study of carbon coagulation in the release wave of detonation products
Authors: Chevrot Guillaume , Sollier Arnaud , Pineau Nicolas
Published: March 2012

We present a combined molecular dynamics and kinetic study of a carbon cluster aggregation process in thermodynamic conditions relevant for the detonation products of oxygen deficient explosives. Molecular dynamics simulations with the LCBOPII potential under gigapascal pressure and high temperatures indicate that (i) the cluster motion in the detonation gas is compatible with Brownian diffusion and (ii) the coalescence probability is 100% for two clusters entering the interaction cutoff distance. We used these results for a subsequent kinetic study with the Smoluchowski model, with realistic models applied for the physical parameters such as viscosity and cluster size. We found that purely aggregational kinetics yield too fast clustering, with moderate influence of the model parameters. In agreement with previous studies, the introduction of surface reactivity through a simple kinetic model is necessary to approach the clustering time scales suggested by experiments (1000 atoms after 100 ns, 10 000 atoms after 1 μs). However, these models fail to reach all experimental criteria simultaneously and more complex modelling of the surface process seems desirable to go beyond these current limitations.
Hard x-ray photoelectron spectroscopy of chalcopyrite solar cell components
Authors: Gloskovskii A. , Jenkins C. A. , Ouardi S. , Balke B. , Fecher G. H. , Dai X.-F. , Gruhn T. , Johnson B. , Lauermann I. , Caballero R. , Kaufmann C. A. , Felser C.
Published: March 2012

Hard x-ray photoelectron spectroscopy is used to examine the partial density of states of Cu(In,Ga)Se2 (CIGSe), a semiconducting component of solar cells. The investigated, thin Cu(In,Ga)Se2 films were produced by multi-stage co-evaporation. Details of the measured core level and valence band spectra are compared to the calculated density of states. The semiconducting type electronic structure of Cu(In,Ga)Se2 is clearly resolved in the hard x-ray photoelectron spectra.
Tuning the electronic and magnetic properties of carbon-doped ZnO nanosheets: First-principles prediction
Authors: Zheng Fu-bao , Zhang Chang-wen , Wang Pei-ji , Luan Hang-xing
Published: March 2012

Using the full-potential linearized augmented plane wave (FLAPW) method, we study the electronic and magnetic properties of C-doped graphene-like ZnO nanosheets (NSs). The results show that in a specimen with isolated C-doping, there is a spontaneous polarization with a magnetic moment 2.0μB/C. In two C-doped systems the antiferromagnetic (AFM) coupling is more favorable in energy and C ions tend to form a cluster, while the metastable states are ferromagnetic (FM) order with a magnetic moment about 4.0μB/2 C. More importantly, the long-range FM order appears due to a p-p coupling interaction and p-d exchange hybridization, and the p-p coupling is the dominant mechanism.