bluuebunny/crossref_metadata_2025 huggingface dataset:
Local sensitivity analysis for compositional data with application to soil texture in hydrologic modelling
Authors: Loosvelt L. , Vernieuwe H. , Pauwels V. R. N. , De Baets B. , Verhoest N. E. C.
Published: February 2013

Abstract. Compositional data, such as soil texture, are hard to deal with in the geosciences as standard statistical methods are often inappropriate to analyse this type of data. Especially in sensitivity analysis, the closed character of the data is often ignored. To that end, we developed a method to assess the local sensitivity of a model output with resect to a compositional model input. We adapted the finite difference technique such that the different parts of the input are perturbed simultaneously while the closed character of the data is preserved. This method was applied to a hydrologic model and the sensitivity of the simulated soil moisture content to local changes in soil texture was assessed. Based on a high number of model runs, in which the soil texture was varied across the entire texture triangle, we identified zones of high sensitivity in the texture triangle. In such zones, the model output uncertainty induced by the discrepancy between the scale of measurement and the scale of model application, is advised to be reduced through additional data collection. Furthermore, the sensitivity analysis provided more insight into the hydrologic model behaviour as it revealed how the model sensitivity is related to the shape of the soil moistureretention curve.
Improving soil moisture profile prediction from ground-penetrating radar data: a maximum likelihood ensemble filter approach
Authors: Tran A. P. , Vanclooster M. , Lambot S.
Published: February 2013

Abstract. The vertical profile of root zone soil moisture plays a key role in many hydro-meteorological and agricultural applications. We propose a closed-loop data assimilation procedure based on the maximum likelihood ensemble filter algorithm to update the vertical soil moisture profile from time-lapse ground-penetrating radar (GPR) data. A hydrodynamic model is used to propagate the system state in time and a radar electromagnetic model to link the state variable with the observation data, which enables us to directly assimilate the GPR data. Instead of using the surface soil moisture only, the approach allows to use the information of the whole soil moisture profile for the assimilation. We validated our approach by a synthetic study. We constructed a synthetic soil column with a depth of 80 cm and analyzed the effects of the soil type on the data assimilation by considering 3 soil types, namely, loamy sand, silt and clay. The assimilation of GPR data was performed to solve the problem of unknown initial conditions. The numerical soil moisture profiles generated by the Hydrus-1D model were used by the GPR model to produce the "observed" GPR data. The results show that the soil moisture profile obtained by assimilating the GPR data is much better than that of an open-loop forecast. Compared to the loamy sand and silt, the updated soil moisture profile of the clay soil converges to the true state much more slowly. Increasing update interval from 5 to 50 h only slightly improves the effectiveness of the GPR data assimilation for the loamy sand but significantly for the clay soil. The proposed approach appears to be promising to improve real-time prediction of the soil moisture profiles as well as to provide effective estimates of the unsaturated hydraulic properties at the field scale from time-lapse GPR measurements.
Errors in climate model daily precipitation and temperature output: time invariance and implications for bias correction
Authors: Maurer E. P. , Das T. , Cayan D. R.
Published: February 2013

Abstract. When correcting for biases in general circulation model (GCM) output, for example when statistically downscaling for regional and local impacts studies, a common assumption is that the GCM biases can be characterized by comparing model simulations and observations for a historical period. We demonstrate some complications in this assumption, with GCM biases varying between mean and extreme values and for different sets of historical years. Daily precipitation and maximum and minimum temperature from late 20th century simulations by four GCMs over the United States were compared to gridded observations. Using random years from the historical record we select a "base" set and a 10-yr independent "projected" set. We compare differences in biases between these sets at median and extreme percentiles. On average a base set with as few as 4 randomly-selected years is often adequate to characterize the biases in daily GCM precipitation and temperature, at both median and extreme values; 12 yr provided higher confidence that bias correction would be successful. This suggests that some of the GCM bias is time invariant. When characterizing bias with a set of consecutive years, the set must be long enough to accommodate regional low frequency variability, since the bias also exhibits this variability. Newer climate models included in the Intergovernmental Panel on Climate Change fifth assessment will allow extending this study for a longer observational period and to finer scales.
Effect of higher-order stress gradients on the centennial mass evolution of the Greenland ice sheet
Authors: Fürst J. J. , Goelzer H. , Huybrechts P.
Published: February 2013

Abstract. We use a three-dimensional thermo-mechanically coupled model of the Greenland ice sheet to assess the effects of marginal perturbations on volume changes on centennial timescales. The model is designed to allow for five ice dynamic formulations using different approximations to the force balance. The standard model is based on the shallow ice approximation for both ice deformation and basal sliding. A second model version relies on a higher-order Blatter/Pattyn type of core that resolves effects from gradients in longitudinal stresses and transverse horizontal shearing, i.e. membrane-like stresses. Together with three intermediate model versions, these five versions allow for gradually more dynamic feedbacks from membrane stresses. Idealised experiments are conducted on various resolutions to compare the time-dependent response to imposed accelerations at the marine ice front. If such marginal accelerations are to have an appreciable effect on total mass loss on a century timescale, a fast mechanism to transmit such perturbations inland is required. While the forcing is independent of the model version, inclusion of direct horizontal coupling allows the initial speed-up to reach several tens of kilometres inland. Within one century, effects from gradients in membrane stress alter the inland signal propagation and transmit additional dynamic thinning to the ice sheet interior. But the centennial overall volume loss differs only by some percents from the standard model, as the dominant response is a diffusive inland propagation of geometric changes. For the experiments considered, this volume response is even attenuated by direct horizontal coupling. The reason is a faster adjustment of the sliding regime by instant stress transmission in models that account for the effect of membrane stresses. Ultimately, horizontal coupling decreases the reaction time to perturbations at the ice sheet margin. These findings suggest that for modelling the mass evolution of a large-scale ice sheet, effects from diffusive geometric adjustments dominate effects from successively more complete dynamic approaches.
Brief Communication "Expansion of meltwater lakes on the Greenland Ice Sheet"
Authors: Howat I. M. , de la Peña S. , van Angelen J. H. , Lenaerts J. T. M. , van den Broeke M. R.
Published: February 2013

Abstract. Forty years of satellite imagery reveal that meltwater lakes on the margin of the Greenland Ice Sheet have expanded substantially inland to higher elevations with warming. These lakes are important because they provide a mechanism for bringing water to the ice bed, causing sliding. Inland expansion of lakes could accelerate ice flow by bringing water to previously frozen bed, potentially increasing future rates of mass loss. Increasing lake elevations closely follow the rise of the mass balance equilibrium line over much of the ice sheet, suggesting no physical limit on lake expansion. Data are not yet available to detect a corresponding change in ice flow, and the potential effects of lake expansion on ice sheet dynamics are not included in ice sheet models.
Analysis of the snow-atmosphere energy balance during wet-snow instabilities and implications for avalanche prediction
Authors: Mitterer C. , Schweizer J.
Published: February 2013

Abstract. Wet-snow avalanches are notoriously difficult to predict; their formation mechanism is poorly understood since in situ measurements representing the thermal and mechanical evolution are difficult to perform. Instead, air temperature is commonly used as a predictor variable for days with high wet-snow avalanche danger – often with limited success. As melt water is a major driver of wet-snow instability and snow melt depends on the energy input into the snow cover, we computed the energy balance for predicting periods with high wet-snow avalanche activity. The energy balance was partly measured and partly modelled for virtual slopes at different elevations for the aspects south and north using the 1-D snow cover model SNOWPACK. We used measured meteorological variables and computed energy balance and its components to compare wet-snow avalanche days to non-avalanche days for four consecutive winter seasons in the surroundings of Davos, Switzerland. Air temperature, the net shortwave radiation and the energy input integrated over 3 or 5 days showed best results in discriminating event from non-event days. Multivariate statistics, however, revealed that for better predicting avalanche days, information on the cold content of the snowpack is necessary. Wet-snow avalanche activity was closely related to periods when large parts of the snowpack reached an isothermal state (0 °C) and energy input exceeded a maximum value of 200 kJ m−2 in one day, or the 3-day sum of positive energy input was larger than 1.2 MJ m−2. Prediction accuracy with measured meteorological variables was as good as with computed energy balance parameters, but simulated energy balance variables accounted better for different aspects, slopes and elevations than meteorological data.
Desigualdades laborales de género, disponibilidad temporal y normativa social
Authors: Prieto Rodríguez Carlos , Pérez de Guzmán Eugenia Sofía
Published: February 2013

La fi nalidad de este artículo es analizar las desigualdades entre hombres ymujeres en el mercado de trabajo español desde una particular perspectivade género. Partimos de la tesis de que solo es posible entender y explicarestas desigualdades si se las analiza teniendo en cuenta su articulacióncon las que se dan en el espacio de las relaciones domésticas de género.Consideramos que en la actualidad son el resultado del encuentro entre ladinámica de las empresas del «nuevo capitalismo», caracterizada por exigira los trabajadores asalariados una «disponibilidad máxima», y las relacionesasimétricas de género que permean la totalidad del orden social y semuestran particularmente activas en el ámbito doméstico-familiar. Metodológicamenteesta articulación se argumenta recurriendo a la dimensión dela temporalidad, en base al análisis de los resultados de la Encuesta deEmpleo del Tiempo realizada por el INE en 2009-2010.
Sociología de la evaluación médica: estudio de casos
Authors: Sánchez Carrión Juan Javier
Published: February 2013

En un artículo anterior mostrábamos el contexto socio-económico en elque se realizan, evalúan y publican los ensayos clínicos, al tiempo queexponíamos algunas de sus limitaciones metodológicas. En este,después de mostrar dos modelos posibles de evaluación (metodológicoy cognitivo), analizamos la confl ictiva evaluación de tres medicamentos:dos que fueron sometidos a la prueba de un ensayo clínico y otro queno, a pesar del deseo del laboratorio de que así fuera. Como resultadode nuestra investigación comprobamos que en la decisión de aprobar orechazar los medicamentos estudiados tuvo una gran infl uencia lo quesuele llamarse el componente socio-económico de la evaluación, frenteal tecnológico, que es el que se supone que ha de primar a la hora detomar una decisión. Este resultado nos lleva a cuestionar el modelometodológico de evaluación y a pensar tentativamente en otro alternativo:el modelo cognitivo de evaluación.
Archaeologies of Persistence: Reconsidering the Legacies of Colonialism in Native North America
Authors: Panich Lee M.
Published: February 2013

This article seeks to define common ground from which to build a more integrated approach to the persistence of indigenous societies in North America. Three concepts are discussed—identity, practice, and context—that may prove useful for the development of archaeologies of persistence by allowing us to counter terminal narratives and essentialist concepts of cultural identity that are deeply ingrained in scholarly and popular thinking about Native American societies. The use of these concepts is illustrated in an example that shows how current archaeological research is challenging long-held scholarty and popular beliefs about the effects of colonialism in coastal California, where the policies of Spanish colonial missionaries have long been thought to have driven local native peoples to cultural extinction. By exploring how the sometimes dramatic changes of the colonial period were internally structured and are just one part of long and dynamic native histories, archaeologies of persistence may help to bring about a shift in how the archaeology of colonialism presents the histories of native peoples in North America—one that can make archaeology more relevant to descendant communities.
Picturing the Past: Gender inNational GeographicReconstructions of Prehistoric Life
Authors: Solometo Julie , Moss Joshua
Published: February 2013

Artistic reconstructions of ancient life are powerful blends of archaeological interpretation and imagination. Like other narratives about the past, they can project contemporary gender roles and relations on ancient peoples, and can reinforce or transform ideas about gender in the present. This article examines the construction of gender ideologies inNational Geographicillustrations of prehistoric life. Our analysis of 204 pictorial reconstructions from 1936 to 2007 reveals that women and women’s work are significantly underrepresented and undervalued, while exhibiting evidence of temporal change in response to societal factors and editorial influences. A vigorous archaeology of gender has had little impact on the magazine’s imagined past; in some respects, the ancient women depicted in the last twenty years are just as scarce, passive, and subordinate as they were in the postwar “backlash” of the 1950s.
Were Bifaces used as Mobile Cores by Clovis Foragers in the North American Lower Great Lakes Region? An Archaeological Test of Experimentally Derived Quantitative Predictions
Authors: Eren Metin I. , Andrews Brian N.
Published: February 2013

The notion that Paleoindians used bifaces as “mobile cores” is widespread in Late Pleistocene lithic research, although it can be difficult to test empirically. Here, we use experimental replication to establish two quantitative predictions that would be indicative of biface-core transport. If bifaces are being used as mobile cores, then we should see among a group of sites of varying toolstone procurement distances (a) a negative relationship between toolstone procurement distance and the mean unifacial tool maximum-thickness value from each site; and (b) a negative relationship between toolstone procurement distance and the variability (standard deviation) of maximum flake thickness values from each site. We then test these predictions against data from six Clovis sites of varying toolstone procurement distance in the Lower Great Lakes region. The results show that both sets of data possess a strong, positive relationship with increasing toolstone procurement distance, which is inconsistent with the notion that biface-cores were transported. Since the Clovis presence in the Lower Great Lakes is widely acknowledged to be a colonization pulse, we conclude that the lack of biface-core transport there is an economizing and risk-mitigating behavior consistent with the models of Kuhn (1994) and Meltzer (2002, 2003, 2004).
Challenging the Evidence for Prehistoric Wetland Maize Agriculture at Fort Center, Florida
Authors: Thompson Victor D. , Gremillion Kristen J. , Pluckhahn Thomas J.
Published: February 2013

The early evidence (2400 ± 105 B.P.) for wetland maize agriculture at the archaeological site of Fort Center, a large earth-work site in South Florida, USA, is frequently cited in discussions of the emergence of agriculture in the Eastern Woodlands of North America. The evidence for maize, however, rests on controversial pollen data; some researchers accept it, others remain skeptical of its identification or chronological placement. We present microbotanical data (pollen and phytoliths), macrobotanical data, and radiocarbon dates from recent excavations from this site. We argue that maize agriculture did not occur until the historic period at this site and that the identification of maize in earlier deposits is likely a result of contamination.
Recognizing Ritual Action and Intent in Communal Mourning Features on the Southern California Coast
Authors: Hull Kathleen L. , Douglass John G. , York Andrew L.
Published: February 2013

Recent excavations at two sites located along the coastal margin of the Los Angeles basin revealed three features created as a result of communal mourning ritual during the Intermediate Period (ca. 3000–1000 cal B.P.). Detailed analysis of constituents, structure, and context indicates that formation of these dense concentrations of ground stone implements, unmodified cobbles, other artifacts, and cremated human remains involved deliberate equipment production, sequential implement fragmentation and treatment including burning and pigmentation of items, and secondary interment of incomplete objects and bodies in pits within locales often used for this purpose over many generations. The large size and evident manipulation of objects as part of communal mourning ritual indicates that actions would have been readily visible to a gathered assembly. Thus, while the meaning and significance of these practices remains to be thoroughly explored, the data suggest that communal mourning ritual may have played a significant role in community-building and the maintenance of identity within a region with a dynamic population history.
Time, Oral Tradition, and Archaeology at Xakwnoowú, A Little Ice Age Fort in Southeastern Alaska
Authors: Crowell Aron L. , Howell Wayne K.
Published: February 2013

As a linguistic medium, oral tradition conveys rich and specific detail about past events but is also subject to alteration in the course of transmission between generations. As a source for indigenous history, spoken heritage is characteristically specific in geographic attribution and thus definitive of cultural landscapes, but it is temporally under-defined because it is unconstrained by calendrical dates. We consider these qualities in relation to Tlingit oral accounts that refer to Xak-wnoowú, an 850-year-old fort in the Glacier Bay region of southeastern Alaska. The site is narratively linked to the origins of Tlingit warfare and of the Kaagwaantaan clan, and remains a landmark of historical consciousness for contemporary descendants. We apply archaeological and geological evidence to date and verify key oral narratives, finding substantial convergence with scientific data and a complementarity of perspective that potentiates fuller understandings of both Tlingit history and environmental change during the Little Ice Age. We conclude that the historicity of oral tradition—a topic of wide current debate—is clearly demonstrated at Xakwnoowú, although instances of chronological compression are revealed by the analysis.
Les projets d’investissement internationalement mobiles : recours au yield management pour les politiques territoriales d’attractivité ?
Authors: Carluer Frédéric , Foignet Jean-Jacques
Published: February 2013

Cet article montre l’intérêt du yield management comme outil d’appariement des stratégies de localisation des entreprises multinationales et des politiques territoriales d’attractivité tout en optimisant les budgets publics qui y sont consacrés. A partir d’un échantillon de 69 projets d’investissements directs étrangers et de trois exemples de projets d’investissement mobiles internationalement, les pratiques actuelles de commercialisation du produit-territoire sont mises en perspective et leur impact évalué en termes de retour sur investissement.
La survie des joint ventures internationales : une étude de l’industrie pétrolière en Russie
Authors: Prévot Frédéric , Guallino Gabriel
Published: February 2013

Cette étude a pour objectif d’analyser l’influence du nombre de partenaires sur la survie des joint ventures. Les résultats montrent que plus le nombre de partenaires est élevé, plus la probabilité de survie est faible. Cependant, lorsque l’âge de la joint venture augmente, un nombre élevé de partenaires a alors un effet positif sur la survie. La prise en compte de l’effet du temps permet de réconcilier l’approche fondée sur les coûts de transaction, qui suppose un effet négatif du nombre de partenaires, et l’approche relationnelle, qui suppose un effet positif lié à la combinaison des ressources.
Les relations siège-filiales dans les firmes multinationales : vers une approche différenciée ?
Authors: Beddi Hanane
Published: February 2013

Cet article examine la diversité potentielle dans les relations entre le siège et les filiales des firmes multinationales. Pour faire face aux défis liés à la dispersion géographique de leurs activités, les firmes multinationales peuvent opter pour un management différencié selon les filiales au sein d’un même groupe. L’étude empirique est fondée sur trois études de cas : France Télécom, Schneider Electric et Publicis. Les résultats montrent la possibilité d’avoir un management uniforme ou différencié des filiales et identifient les différentes modalités qui entrent en ligne de compte tout en questionnant la place de la filiale et du siège.
Transfert de responsabilités dans les projets de coopération au développement : le cas d’une ONG franco-malgache
Authors: Chevrier Sylvie
Published: February 2013

Dans les organisations internationales, le transfert de responsabilités du personnel expatrié vers le personnel local ne va pas de soi. Il se heurte en particulier à des difficultés d’ordre culturel liées aux représentations que les parties se font de la délégation. Cet article présente une recherche-intervention dans une ONG franco-malgache qui a pour but d’accompagner les acteurs dans la compréhension de leurs représentations culturelles de la délégation et dans la construction de nouvelles pratiques favorisant le transfert de responsabilités.
Top‐Emission Organic Light‐Emitting Diode with a Novel Copper/Graphene Composite Anode
Authors: Meng Hu , Luo Jianxing , Wang Wei , Shi Zujin , Niu Qiaoli , Dai Lun , Qin Guogang
Published: January 2013

The relatively high sheet resistance of graphene compared with indium tin oxide (ITO) blocks the applications of graphene as transparent electrodes in organic light‐emitting diodes. A novel copper (Cu)/graphene composite electrode is presented and employed as the anode of a top‐emission organic light‐emitting diode with the structure of Cu/graphene/V2O5/NPB/Alq3/Alq3: C545T/Bphen: Cs2CO3/Sm/Au. The Cu/graphene composite electrodes are fabricated by growing graphene directly on Cu substrates via the chemical vapor deposition method without any transfer process. The maxima of current efficiency and power efficiency of a typical Cu/graphene composite anode device reach 6.1 cd/A and 7.6 lm/W, respectively, which are markedly higher than those of the control devices with a graphene anode, a Cu anode or an ITO anode. The low sheet resistance of the composite electrode, the high quality of graphene without any transfer process and the avoidance of wave guiding loss in glass or polyethylene terephthalate substrates result in the improvements of light emission efficiencies.
Water‐Soluble Conjugated Polymers for Simultaneous Two‐Photon Cell Imaging and Two‐Photon Photodynamic Therapy
Authors: Shen Xiaoqin , Li Lin , Min Chan Agnes Chow , Gao Nengyue , Yao Shao Q. , Xu Qing‐Hua
Published: January 2013

Conventional photosensitizers generally suffer from low efficiency in novel non‐invasive two‐photon photodynamic cancer therapy due to their small two‐photon absorption cross section and they lack an imaging capability for therapy guiding due to their low fluorescence yield. Demonstrated here is the first water‐soluble conjugated polymers as direct two‐photon photosensitizers with dual capability of two‐photon cell imaging and two‐photon photodynamic therapy. By introducing a strong electron‐withdrawing cyano group into the phenyl ring of the backbone, the cyano‐substituted poly(fluorene‐2,7‐ylenevinylene‐co‐phenylene) (PFVCN) displays a 2.4 times higher maximum two‐photon absorption cross section per repeat unit and significantly higher fluorescence quantum yield in water than the unsubstituted PFV. The large two‐photon absorption cross section of PFVCN allows it to efficiently generate singlet oxygen under two‐photon excitation, which is critical for two‐photon photodynamic therapy. Two‐photon excitation cell imaging and efficient two‐photon‐induced photodynamic therapy effect on cancer cells of PFVCN are successfully demonstrated. These studies provide insight in designing novel photosensitizing agents for simultaneous two‐photon imaging and two‐photon photodynamic therapy, which allows two‐photon imaging guided therapy to fully take the unique advantages of two‐photon excitation such as deep penetration and 3D selectivity.
Improvement of Transparent Metal Top Electrodes for Organic Solar Cells by Introducing a High Surface Energy Seed Layer
Authors: Schubert Sylvio , Meiss Jan , Müller‐Meskamp Lars , Leo Karl
Published: January 2013

We present highly transparent and conductive silver thin films in a thermally evaporated dielectric/metal/dielectric (DMD) multilayer architecture as top electrode for efficient small molecule organic solar cells. DMD electrodes are frequently used for optoelectronic devices and exhibit excellent optical and electrical properties. Here, we show that ultrathin seed layers such as calcium, aluminum, and gold of only 1 nm thickness strongly influence the morphology of the subsequently deposited silver layer used as electrode. The wetting of silver on the substrate is significantly improved with increasing surface energy of the seed material resulting in enhanced optical and electrical properties. Typically thermally evaporated silver on a dielectric material forms rough and granular layers which are not closed and not conductive below thicknesses of 10 nm. With gold acting as seed layer, the silver electrode forms a continuous, smooth, conductive layer down to a silver thickness of 3 nm. At 7 nm silver thickness such an electrode exhibits a sheet resistance of 19 Ω/□ and a peak transmittance of 83% at 580 nm wavelength, both superior compared to silver electrodes without seed layer and even to indium tin oxide (ITO). Top‐illuminated solar cells using gold/silver double layer electrodes achieve power conversion efficiencies of 4.7%, which is equal to 4.6% observed in bottom‐illuminated reference devices employing conventional ITO. The top electrodes investigated here exhibit promising properties for semitransparent solar cells or devices fabricated on opaque substrates.
Formaldehyd in der Umgebungsluft: von der Innenluftverunreinigung zur Außenluftverunreinigung?
Authors: Salthammer Tunga
Published: January 2013

Formaldehyd wird seit Jahrzehnten als typische Innenraumverunreinigung diskutiert. Gesetzliche Auflagen und kontinuierlich sinkende Richtwerte für die Innenraumluft haben dazu geführt, dass die Freisetzungsraten von Formaldehyd aus Einrichtungsgegenständen sowie Bau‐ und Haushaltsprodukten seit geraumer Zeit rückläufig sind. Langsam, und von der Innenraumforschung weitgehend unbemerkt, vollzieht sich allerdings ein Paradigmenwechsel. In manchen urbanen Gebieten liegen die Formaldehydkonzentrationen in der Außenluft bereits auf dem Niveau der Innenraumluftkonzentrationen, was im Wesentlichen auf photochemische Prozesse und die zunehmende Verwendung von Biokraftstoffen zurückzuführen ist. Mittelfristig wird diese Entwicklung zu Konsequenzen bezüglich der Lüftung von Gebäuden und zum Umdenken bei der Expositionsbewertung führen.
Effects of curing program on mechanical behavior and water absorption of DGEBA/TETa epoxy network
Authors: Dang D. Nguyen , Cohendoz S. , Mallarino S. , Feaugas X. , Touzain S.
Published: January 2013

Water uptake in organic coatings remains an interesting challenge for fundamental and applied researches because chemical, physical, and mechanical properties are concerned. The polymer network, which is affected by the curing program, is a key factor for water absorption. In this work, an epoxy network based on diglycidyl ether of bisphenol A and a hardener triethylentetramine was cured at different temperatures: below Tg (protocol 1) and above Tg (protocol 2). DMA, Differential Scanning Calorimetry (DSC), and FT‐IR measurements showed that both protocols allow to obtain totally cured networks. However, DSC and DMA results revealed that both cured networks present different levels of homogeneity, depending on the different curing conditions, which affect the free volume and the activation volume associated with visco‐elastic properties. The mechanical properties of free films and water sorption behaviors were investigated as function of cured conditions. It was found that protocol 1‐cured networks present higher mechanical properties and was less affected by water ingress than protocol 2‐cured systems, leading to better barrier properties. These results highlight the influence of the curing program onto the heterogeneous distribution of the epoxy network. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Amphiphilic poly(vinyl chloride)‐g‐poly[poly(ethylene glycol) methylether methacrylate] copolymer for the surface hydrophilicity modification of poly(vinylidene fluoride) membrane
Authors: Shao Xi‐Sheng , Li Jian‐Hua , Zhou Qing , Miao Jing , Zhang Qi‐Qing
Published: January 2013

In this study, a comblike amphiphilic graft copolymer containing poly(vinyl chloride) (PVC) backbones and poly(oxyethylene methacrylate) [poly(ethylene glycol) methylether methacrylate (PEGMA)] side chains was facilely synthesized via an atom transfer radical polymerization method. Secondary chlorines in PVC were used as initial sites to graft a poly[poly(ethylene glycol) methylether methacrylate] [P(PEGMA)] brush. The synthesized PVC‐g‐P(PEGMA) graft copolymer served as an efficient additive for the hydrophilicity modification of the poly(vinylidene fluoride) (PVDF) membrane via a nonsolvent‐induced phase‐inversion technique. A larger pore size, higher porosity, and better connectivity were obtained for the modified PVDF membrane; this facilitated the permeability compared to the corresponding virgin PVDF membrane. In addition, the modified PVDF membrane showed a distinctively enhanced hydrophilicity and antifouling resistance, as suggested by the contact angle measurement and flux of bovine serum albumin solution tests, respectively. Accordingly, the PVC‐g‐P(PEGMA) graft copolymer was demonstrated as a successful additive for the hydrophilicity modification, and this study will likely open up new possibilities for the development of efficient amphiphilic PVC‐based copolymers for the excellent hydrophilicity modification of PVDF membranes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
The effect of twin screw extrusion on structural, electrical, and rheological properties in carbon nanotube poly‐ether‐ether‐ketone nanocomposites
Authors: Guehenec Matthieu , Tishkova Victoria , Dagreou Sylvie , Leonardi Frederic , Derail Christophe , Puech Pascal , Pons François , Gauthier Benedicte , Cadaux Pierre‐Henri , Bacsa Wolfgang
Published: January 2013

The influence of twin screw extruder dispersion of multiwalled carbon nanotubes (CNTs) on the structural, electrical, and rheological properties in poly(ether ether ketone) is studied. Intermediate rotational speeds (200 rpm) of co‐rotating twin screws yield higher electrical conductivity and dynamic shear modulus than for lower or higher speeds when using 3 wt % multiwall CNTs. These improved properties at intermediate speeds are correlated with the dispersion state of nanotubes in the polymer matrix by using transmission electron microscopy and multispectral Raman mapping. We find that the complex shear modulus near structural percolation depends on the dispersion of the CNTs and the residence time in the extruder plays an important role in the final properties of the nanocomposite. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Studies on usage of acrylamide copolymers for textile effluent treatment
Authors: Jain Mukul R. , Jain Chhavi , Jain R. C.
Published: January 2013

The copolymers of acrylamide–maleic anhydride and acrylamide–diallyl dimethyl ammonium chloride of different ionicities were used for the removal of color, solids, etc., from effluent generated from textile industry. The studies have been carried out to remove color generated in the effluent. To estimate dye content, we prepared standard curve using UV‐vis spectrophotometer at different dye concentration following the Beer Lambert's Law. The copolymers of acrylamide–maleic anhydride and acrylamide–diallyl dimethyl ammonium chloride of known concentration were dosed in the known concentration of the dye. These polymers made flocks by adsorption with dyes and these colored flocks were filtered out. The intensity of the color of water went down on increasing the concentration of the polymers. The color of the textile effluent was removed to the extent of 97% using above mentioned polymers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Ultrasound initiated functionalization of SEBS with maleic anhydride
Authors: Shen Liyuan , Zhang Xianlong , Wu Hong , Guo Shaoyun
Published: January 2013

The functionalization of styrene‐b‐(ethylene‐co‐1‐butene)‐b‐styrene tri‐block copolymer with maleic anhydride (MAH) in melt state through ultrasound initiation was studied in this article. The effects of plasticizer content and types, MAH content, ultrasound power, and die temperature on grafting ratio of MAH were investigated by means of acid–base titration. Functionalized products were confirmed by new absorption bands in Fourier‐transform infrared spectroscopy. The experimental results showed that the ultrasound initiated products had lower complex viscosity (η*), lower gel content as well as lower molecular weight than peroxide initiated products, indicating that the ultrasound could cause chain scission and suppress the crosslinking side reaction to gain functionalized products, which have less gel content and high grafting ratio. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Congenital heart defects and major structural noncardiac anomalies in Alberta, Canada, 1995–2002
Authors: Lowry R. Brian , Bedard Tanya , Sibbald Barbara , Harder Joyce R. , Trevenen Cynthia , Horobec Vera , Dyck John D.
Published: February 2013

BACKGROUND

Although the majority of congenital heart defects (CHDs) occur in isolation, a significant number occur with noncardiac anomalies. This study determined the proportion of noncardiac anomalies among CHD cases in Alberta.

METHODS

Records of infants and children born in Alberta between January 1, 1995, to December 31, 2002, were searched using multiple sources of ascertainment in addition to the Alberta Congenital Anomalies Surveillance System (ACASS) (Alberta Health and Wellness, 2012). Each case was assigned to one CHD category and was further categorized into one of the following groups: isolated CHD, syndromes, chromosomal, associations and sequences, teratogens, Mendelian, neoplasia, heterotaxy, multiple minor anomalies, and multiple major anomalies.

RESULTS

Of all 3751 CHD cases (prevalence 12.42/1000 total births: confidence interval, 12.03–12.83), 75% were isolated, 10% had a chromosomal etiology, and 9% had multiple major anomalies. All other categories accounted for <2% each. The most commonly associated major noncardiac anomalies were musculoskeletal (MSK) (24%) followed by anomalies of the urinary tract (14%), gastrointestinal system (GI) (11%), and central nervous system (CNS) (11%).

CONCLUSIONS

This is both a population‐based and clinical study using a classification scheme that could help to determine possible etiologic factors contributing to CHD. By eliminating known etiologies such as chromosomal and single gene, future studies can focus on the remainder to evaluate possible preventive measures. The most commonly associated major noncardiac anomalies involve the MSK system, followed by the urinary, GI, and CNS systems. Birth Defects Research (Part A) 2013. © 2013 Wiley Periodicals, Inc.
Insights into CC Coupling in CO2 Electroreduction on Copper Electrodes
Authors: Montoya Joseph H. , Peterson Andrew A. , Nørskov Jens K.
Published: January 2013

We present a first‐principles theoretical study of carbon–carbon coupling in CO2 electroreduction on the copper 2 1 1 surface. Using DFT, we have determined kinetic barriers to the formation of a CC bond between adsorbates derived from CO. The results of our nudged elastic band calculations demonstrate that kinetic barriers to CC coupling decrease significantly with the degree of hydrogenation of reacting adsorbates. We also show that this trend is not affected by the electrical fields present at the solid‐electrolyte interface during electrocatalysis. Our results explain how copper can catalyze the production of higher hydrocarbons and oxygenates in the electrochemical environment, despite producing only single carbon atom products in gas‐phase catalysis, and how CC bonds can be formed at room temperature in the electrochemical environment, whereas substantially higher temperatures are needed in the Fischer–Tropsch catalysis. The unique feature of the electrochemical environment is that the chemical potential of hydrogen (electrons and protons) can be varied through the applied potential. This allows a variation of the degree of hydrogenation of the reactants and thus the activation barrier for CC coupling.
Telomerase Inhibitors from Cyanobacteria: Isolation and Synthesis of Sulfoquinovosyl Diacylglycerols from Microcystis aeruguinosa PCC 7806
Authors: Makhlouf Brahmi Malika , Portmann Cyril , D'Ambrosio Danilo , Woods Tom M. , Banfi Damiano , Reichenbach Patrick , Da Silva Laeticia , Baudat Emilie , Turcatti Gerardo , Lingner Joachim , Gademann Karl
Published: January 2013

By using the Telospot assay, 27 different extracts of cyanobacteria were evaluated for telomerase inhibition. All extracts showed varying, but significant activity. We selected Microcystis aeruguinosa PCC 7806 to identify the active compound and a bioassay guided fractionation led us to isolate mixtures of sulfoquinovosyl diacylglycerols (SQDGs), which were identified by 2D NMR and MS/MS experiments. Pure SQDG derivatives were then synthesized. The IC50 values of pure synthetic sulfoquinovosyl dipalmitoylglycerol and the monopalmitoylated derivative against telomerase were determined to be 17 and 40 μM, respectively. A structure–activity relationship study allowed the identification of compounds with modified lipophilic acyl groups that display improved activity.
On the Mechanism of the Dehydroaromatization of Hexane to Benzene by an Iridium Pincer Catalyst
Authors: Thawani Akanksha , Rajeev Ramanan , Sunoj Raghavan B.
Published: January 2013

The developments in the area of transition‐metal pincer complexes have opened up new avenues for conversion of saturated hydrocarbons to more useful aromatic compounds under homogeneous reaction conditions. In the backdrop of an interesting series of conversions of unbranched alkanes to benzene, toluene, and xylene (known as the BTX family aromatics) reported by Goldman and co‐workers (Nature Chem. 2011, 3, 167), we herein present a comprehensive mechanistic picture obtained by using density functional computations. The reaction involves an iridium–PCP‐pincer‐catalyzed dehydroaromatization of hexane to benzene (in which PCP=η3‐C6H3(iPrP)2‐1,3) by using tert‐butylethylene (TBE) as a sacrificial acceptor. The most energetically preferred pathway for a sequence of dehydrogenations is identified to begin with a terminal CH bond activation of n‐hexane leading to the formation of hex‐1‐ene. Although the initial dehydrogenation of n‐hexane was found to be endergonic, the accompanying exoergic hydrogenation of TBE to tert‐butylethane (TBA) compensates the energetics to keep the catalytic cycle efficient. Subsequent dehydrogenations provide a hexa‐1,3‐diene and then a hexa‐1,3,5‐triene. The pincer bound triene is identified to undergo cyclization to furnish cyclohexadiene. Eventually, dehydrogenation of cyclohexa‐1,3‐diene offers benzene. In the most preferred pathway, the Gibbs free energy barrier for cyclization leading to the formation of cyclohexa‐1,3‐diene is found to exhibit the highest barrier (21.7 kcal mol−1).
Templating Irreversible Covalent Macrocyclization by Using Anions
Authors: Kataev Evgeny A. , Kolesnikov Grigory V. , Arnold Rene , Lavrov Herman V. , Khrustalev Victor N.
Published: January 2013

Inorganic anions were used as templates in the reaction between a diamine and an activated diacid to form macrocyclic amides. The reaction conditions were found to perform the macrocyclization sufficiently slow to observe a template effect. A number of analytical methods were used to clarify the reaction mechanisms and to show that the structure of the intermediate plays a decisive role in determining the product distribution. For the macrocyclization under kinetic control, it was shown that the amount of a template, the conformational rigidity of building blocks, and the anion affinities of reaction components and intermediates are important parameters that one should take into consideration to achieve high yields.
Evolution of hierarchical‐structured CaCO3 in binary mixed solvent
Authors: Wang Lina , Jin Dalai , Wang Longcheng
Published: January 2013

Calcium carbonate with hierarchical structure was synthesized in water/organic compound binary soluvent by a chemical solution process within CaCl2/NaCO3 reaction system. Acetone, isopropanol, glycol, tetrahydrofuran were selected as the organic compound. Evolution of the hierarchical structure of CaCO3 was investigated. The as‐prepared products were characterized by X‐ray diffraction (XRD) and scanning electron microscopy (SEM). CaCO3 aggregations with spicate hierarchical structure were obtained with a high volume fraction of the organic solvent. Aspect ratio of the hierarchical structure increases to the highest when the volume fraction was 50%. Solvent with low dielectric constant was conducive to the oriented aggregation of the CaCO3 grains.
Robust Cycling of Li–O2 Batteries through the Synergistic Effect of Blended Electrolytes
Authors: Kim Byung Gon , Lee Je‐Nam , Lee Dong Jin , Park Jung‐Ki , Choi Jang Wook
Published: February 2013

Despite their exceptionally large specific capacities, the use of Li–O2 batteries has been limited because of their poor cycle lives, which originates from irreversible reaction processes during each cycle. Recent investigations have found that electrolyte decomposition is one of the most critical reasons for capacity decay. Herein, we report that a blended electrolyte, consisting of a carbonate solvent and an ionic liquid, improves the cycle lives of Li–O2 batteries remarkably through a synergistic effect from both components. Both electrolyte components perform complementary functions to each other: The ionic liquid suppresses the decomposition of the carbonate solvent, and the carbonate solvent resolves the poor ionic conductivity of the ionic liquid. This study confirms the importance and opportunities for the use of electrolytes in Li–O2 batteries.
X‐Ray Diagnostics of Ultrashort Laser‐Driven Plasma: Experiment and Simulations
Authors: Ivanov K.A. , Shulyapov S.A. , Turinge A.A. , Brantov A.V. , Uryupina D.S. , Volkov R.V. , Rusakov A.V. , Djilkibaev R.M. , Nedorezov V.G. , Bychenkov V.Yu. , Savel'ev A.B.
Published: January 2013

The complex approach combining experimental data on X‐ray diagnostics of plasma, the results of the numerical PIC simulation of laser‐plasma interaction (namely – fast electron spectra), as well as Monte‐Carlo calculation of the resulted X‐ray spectrum is presented. Direct comparison of the experimental and simulated X‐ray spectra (obtained at laser pulse intensity of 2.5 × 1018 W/cm2) revealed differences in the mean slope and cutoff of the two spectra. In particular experimental data exhibited twice higher slope. The possible explanations of the observed discrepancies are further discussed. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
RFNC–VNIIEF Study Into Interaction Between Intense Laser Pulses and Matter
Authors: Belkov S. A. , Rukavishnikov N. N. , Garanin S. G.
Published: January 2013

The results of petawatt laser system development in RFNC–VNIIEF and preliminary experiments of laser‐matter interaction at intencity about 1019 W/cm2 are presented. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Atomistic Modeling of Warm Dense Matter in the Two‐Temperature State
Authors: Norman G. E. , Starikov S. V. , Stegailov V. V. , Saitov I. M. , Zhilyaev P. A.
Published: January 2013

Warm dense matter is the state between the heated condensed matter and plasma. The importance of the development of warm dense matter theoretical description is determined by the fact that such conditions may arise in the variety of different scientific and industrial applications. For instance, warm dense matter is formed: in the matter impacted by femto‐ and picoseconds laser pulses; in nuclear materials at the formation of radiation track, etc. In these phenomena, the initial state of the system is a two‐temperature state and the electron temperature may be several orders higher than the ion one. In this work, the attempt of development of the united atomistic model of a warm dense matter is carried out. The special consideration is given to the twotemperature effects and the influence of the electron pressure on the behavior of ions. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐Intensity Laser Triggered Proton Acceleration from Ultrathin Foils
Authors: Brantov A. , Bychenkov V. Yu. , Romanov D. V. , Dollar F. , Maksimchuk A. , Krushelnick K.
Published: January 2013

The recently developed PIC code MANDOR features arbitrary target design including 3D preplasma and the 6‐component laser fields of a tightly focused laser beam. The 3D simulations have been performed to model recent HERCULES experiments on proton acceleration, where protons with energy greater than 20 MeV were produced using just 1.5 J laser pulses focused to intensity of 2 × 1021 W/cm2. By adapting the 3D target geometry relating to ps‐prepulse effect, reasonable agreement with experimental data for the proton energy spectrum has been achieved. The effect of the 3D preplasma shape on efficiency of proton acceleration is discussed. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)