bluuebunny/crossref_metadata_2025 huggingface dataset:
Article Commentary: Dealing with Diversity in Computational Cancer Modeling
Authors: Johnson David , McKeever Steve , Stamatakos Georgios , Dionysiou Dimitra , Graf Norbert , Sakkalis Vangelis , Marias Konstantinos , Wang Zhihui , Deisboeck Thomas S.
Published: May 2013

This paper discusses the need for interconnecting computational cancer models from different sources and scales within clinically relevant scenarios to increase the accuracy of the models and speed up their clinical adaptation, validation, and eventual translation. We briefly review current interoperability efforts drawing upon our experiences with the development of in silico models for predictive oncology within a number of European Commission Virtual Physiological Human initiative projects on cancer. A clinically relevant scenario, addressing brain tumor modeling that illustrates the need for coupling models from different sources and levels of complexity, is described. General approaches to enabling interoperability using XML-based markup languages for biological modeling are reviewed, concluding with a discussion on efforts towards developing cancer-specific XML markup to couple multiple component models for predictive in silico oncology.
Isometric group actions and the cohomology of flat fiber bundles
Authors: Banagl Markus
Published: May 2013

Using methods originating in the theory of intersection spaces, specifically a de Rham type description of the real cohomology of these spaces by a complex of global differential forms, we show that the Leray–Serre spectral sequence with real coefficients of a flat fiber bundle of smooth manifolds collapses if the fiber is Riemannian and the structure group acts isometrically. The proof is largely topological and does not need a metric on the base or total space. We use this result to show further that if the fundamental group of a smooth aspherical manifold acts isometrically on a Riemannian manifold, then the equivariant real cohomology of the Riemannian manifold can be computed as a direct sum over the cohomology of the group with coefficients in the (generally twisted) cohomology modules of the manifold. Our results have consequences for the Euler class of flat sphere bundles. Several examples are discussed in detail.
Highly transitive actions of $\operatorname{Out}(F_n)$
Authors: Garion Shelly , Glasner Yair
Published: May 2013

An action of a group on a set is called

k

-
transitive
if it is transitive on ordered

k

-tuples and
highly transitive
if it is

k

-transitive for every

k

. We show that for

n \ge 4

the group

\operatorname{Out}(F_n) = \operatorname{Aut}(F_n) / \mathrm{Inn}(F_n)

admits a faithful highly transitive action on a countable set.
Cubulating rhombus groups
Authors: Janzen David , Wise Daniel T.
Published: May 2013

We study CAT(0) 2-complexes all of whose polygons are Euclidean rhombi. We describe walls in these complexes, and examine the dual CAT(0) cube complex. Our viewpoint relates Sageev’s dual cube complexes to de Bruijn’s approach to the Penrose tilings
O Processo de Decisão de Compra em Supermercados On-Line: Uma Pesquisa Qualitativa com Clientes do Zona Sul Atende
Authors: Moreira André Barcelos , Chauvel Marie Agnes , Silva Renata Céli Moreira da
Published: May 2013

O Zona Sul foi o primeiro supermercado no Rio de Janeiro a oferecer serviços de venda pela Internet e é líder nesse segmento na cidade. Assim, foi escolhido como objeto deste estudo, que buscou descrever e analisar o processo de decisão dos consumidores que utilizam a Internet para fazer compras de supermercado. Foram realizadas 20 entrevistas em profundidade com esses consumidores. As entrevistas foram feitas durante a realização da compra e a navegação dos entrevistados foi gravada com o uso de um software. Os resultados apontaram que os entrevistados buscam conveniência, rapidez e facilidade para comprar. Foram identificados aspectos do site que comprometem parcialmente esse objetivo. As conclusões trazem sugestões para facilitar o processo de compra e torná-lo mais ágil.
Erratum: Aragonite saturation states at cold‐water coral reefs structured by Lophelia pertusa in the Northern Gulf of Mexico
Authors: Lunden Jay J. , Georgian Samuel E. , Cordes Erik E.
Published: May 2013

Please refer to the complete text available via the link at right.
The Wicketkeeper and Injury
Authors: Dhillon Mandeep , Prabhakar Sharad , Raj Nirmal
Published: May 2013

Cricket injury has become a significant issue in recent times with many high profile players getting injured during the game. Injury surveillance programs have recently been started and have documented a high injury rate in fast bowlers. One of the most tasking player positions in cricket is wicketkeeping; despite the best protective wear used by them, the nature of the game would imply a high attrition rate due to injury. We looked at the published literature and our own experience, and found little documented data for this subgroup of players. The types of injury recorded and the problems therein are discussed; it is proposed that future focus should be on short-term analysis of injury profiles so as to improve preventive methods, and long-term evaluation of overuse injury or degenerative changes in the body due to the prolonged abnormal posture maintained by wicketkeepers.

How to cite this article

Dhillon MS, Prabhakar S, Raj N. The Wicketkeeper and Injury. J Postgrad Med Edu Res 2013;47(2):99-102.
Is a “Firm” a Firm? A Stackelberg Experiment
Authors: Hildenbrand Andreas
Published: May 2013

Industrial organization is mainly concerned with the behavior of large firms, especially when it comes to oligopoly theory. Experimental industrial organization, therefore, faces a problem: How can firms be brought into the laboratory? The main approach relies on framing: Call individuals “firms”! This experimental approach is not in line with modern industrial organization, according to which a firm’s market behavior is also determined by its organizational structure. In this paper, a Stackelberg experiment is considered in order to answer the question whether framing individual decision making as firm decision making or implementing an organizational structure is more effective for generating profit-maximizing behavior. Firms are either represented by individuals or by teams. Teams are organized according to a parsimonious version of Alchian and Demsetz’s (Production, Information Costs, and Economic Organization, 1972) contractual model of the firm. The author finds teams’ quantity choices are more in line with the assumption of profit maximization than individuals’ choices. Compared to individuals, teams appear to be less inequality averse.
Leucaena lanceolata S. Watson ssp. lanceolata, ESPECIE FORESTAL CON POTENCIAL PARA SER INTRODUCIDA EN SISTEMAS SILVOPASTORILES
Authors: Román-Miranda María L. , Martínez-Rosas Luis A. , Mora-Santacruz Antonio , Torres-Morán Pablo , Gallegos-Rodríguez Agustín , Avendaño-López Adriana
Published: May 2013

La utilización de especies forestales en los sistemas de producción agropecuaria contribuye a reducir la presión en los bosques naturales y se pueden incorporar en áreas no arboladas. El objetivo de este estudio fue evaluar la calidad nutritiva, germinación, desarrollo de plántula en vivero y diversidad de usos de Leucaena lanceolata S. Watson ssp. lanceolata. El material comestible y las semillas se colectaron en Tomatlán, Jalisco. Se realizaron análisis bromatológicos, pruebas de escarificación y evaluación de plántula en vivero sobre tres suelos con diferente pH. El experimento se analizó en un diseño completamente al azar con comparación de medias de Tukey (P ≤ 0.05). Además, se hicieron entrevistas a productores, una revisión bibliográfica y consulta de ejemplares en los herbarios para conocer los usos locales y potenciales de la especie. Los resultados indican alto contenido de materia seca (97.40 %) y proteína cruda (29.05 %), mayor germinación en los tratamientos térmicos, mejor desarrollo de la plántula en el suelo ligeramente ácido (6.57) y la diversidad de usos incluye leña, forraje y madera, entre otros. Por el alto valor nutritivo y diversidad de usos en el medio rural, L. lanceolata representa una opción viable para utilizarse en sistemas silvopastoriles del trópico seco.
ESTRUCTURA Y COMPOSICIÓN ARBÓREA DE UN FRAGMENTO DE BOSQUE MESÓFILO DE MONTAÑA EN EL ESTADO DE VERACRUZ
Authors: García-De la Cruz Yureli , Olivares-López Luis A. , Ramos-Prado José M.
Published: May 2013

La estructura y composición arbórea se analizaron en un fragmento de bosque mesófilo de montaña en la zona centro del estado de Veracruz. Para ello, se establecieron tres transectos de 2,000 m2, en los cuales se tomaron datos dasométricos a todos los individuos con diámetro normal mayor de 10 cm. Se encontraron 239 individuos pertenecientes a 14 especies, 12 géneros y 12 familias. La familia Fagaceae fue dominante en las áreas de muestreo. Quercus salicifolia, Liquidambar styraciflua, Quercus leiophylla y Alchornea latifolia fueron las especies más importantes. Éstas presentaron relaciones alométricas significativas entre las variables cobertura-diámetro normal, y altura-diámetro normal (excepto A. latifolia). Se plantea una posible variante sinecológica de bosque mesófilo de montaña, a través de la asociación Q. salicifolia-L. styraciflua, lo cual refleja la baja riqueza florística reportada.
CONTENIDO DE CARBONO ORGÁNICO EN EL SUELO BAJO DIFERENTES CONDICIONES FORESTALES: RESERVA DE LA BIOSFERA MARIPOSA MONARCA, MÉXICO
Authors: Pérez-Ramírez Silvia , Ramírez M. Isabel , Jaramillo-López Pablo F. , Bautista Francisco
Published: May 2013

A nivel mundial, el suelo almacena dos veces más carbono que la atmósfera y casi el doble de la cantidad almacenada en la vegetación. La capacidad de almacenamiento de carbono de los suelos depende de sus propiedades y usos. El objetivo del presente trabajo fue analizar el contenido de carbono orgánico del suelo (COS), bajo diferentes condiciones forestales dentro de la Reserva de la Biósfera Mariposa Monarca en México. Para ello se definieron seis grupos de muestreo, basándose en tres condiciones del arbolado (conservado, aprovechado y perturbado) y dos tipos de vegetación (oyamel y pino-encino). Para cada grupo se calculó el contenido de carbono en cuatro perfiles de suelo completos (N=24), comenzando en el horizonte A. Los resultados muestran diferencias en el contenido de COS en suelos que se encuentran bajo diferentes tipos de vegetación y condiciones del arbolado. Los rodales de oyamel conservado tienen en promedio 153 MgC·ha-1 de COS, mientras que los aprovechados y perturbados tienen 95 y 125 MgC·ha-1, respectivamente. Los resultados muestran que el promedio de COS en bosques conservados de pino-encino es de 103 MgC·ha-1, mientras que los aprovechados y perturbados tienen 39 y 13 MgC·ha-1, respectivamente. Los bosques conservados almacenan entre 40-80 % del COS en los horizontes A del suelo. El contenido de COS debería ser considerado para determinar el impacto del manejo forestal o de cualquier otra política de conservación.
Aerosol size-resolved trace metal composition in remote northern tropical Atlantic marine environment: case study Cape Verde islands
Authors: Fomba K. W. , Müller K. , van Pinxteren D. , Herrmann H.
Published: May 2013

Abstract. Size-resolved trace metal concentrations of 15 elements in aerosol particles at the Cape Verde Atmospheric Observatory (CVAO) under remote background conditions were investigated through analysis of aerosol samples collected during intensive field studies from January 2007 to November 2011 using total reflection x-ray fluorescence (TXRF). The identification of the main air mass origin that influence remote marine aerosol in the northern tropical Atlantic has been investigated. In total, 317 samples were collected. The dataset was analyzed according to the main air mass inflow at the station. We found that remote conditions make up about 45% of the meteorological conditions in a year at CVAO and thus the northern tropical Atlantic. Surprisingly, air masses from North America are often responsible for higher trace metal concentrations in this region. Elements such as Zn, Pb, Cu, Cr, Ni, and V were mostly found in the submicron size fractions, while elements with dominant crustal or oceanic origin such as Fe, Ti, Mn, Sr, and Rb were found in the coarse fractions (>1 μm). The highest metal concentrations, especially for Zn (3.23 ng m−3), Cu (0.81 ng m−3), Sr (2.63 ng m−3), and Cr (0.53 ng m−3), were observed in air masses originating from North America and the concentrations were within the same concentration range to those reported previously in the literature for remote marine aerosols. Fe (12.26 ng m−3), Ti (0.91 ng m−3), and Mn (0.35 ng m−3) showed higher concentrations when air mass came from Europe and the Canary Islands. Pb concentration was low (<0.20 ng m−3) and did not vary significantly with air mass direction. The low Pb concentration is indicative of the complete phase-out of leaded gasoline even in African countries. Crustal enrichment factor values decreased from fine to coarse-mode particles with low values (<4) observed for Fe, Mn, and Rb, and high values (>20) for Zn, Cu, Ni, Cr, Pb, and Se. The observed enrichment of the elements was attributed to crustal, marine, anthropogenic, and biogenic sources, as well as long-range transport and resuspension. Zn, Cu and Pb were indicators of anthropogenic activities, while Ti and Sr were indicators of crustal and marine origin, respectively. Oceanic and biogenic emissions might have contributed to most of the Se observed. This work provides the first long-term size-resolved trace metals study for remote tropical northern Atlantic marine aerosols and the dataset could serve as good initiation of yearly flux estimates.
Implications of elevated CO2 on pelagic carbon fluxes in an Arctic mesocosm study – an elemental mass balance approach
Authors: Czerny J. , Schulz K. G. , Boxhammer T. , Bellerby R. G. J. , Büdenbender J. , Engel A. , Krug S. A. , Ludwig A. , Nachtigall K. , Nondal G. , Niehoff B. , Silyakova A. , Riebesell U.
Published: May 2013

Abstract. Recent studies on the impacts of ocean acidification on pelagic communities have identified changes in carbon to nutrient dynamics with related shifts in elemental stoichiometry. In principle, mesocosm experiments provide the opportunity of determining temporal dynamics of all relevant carbon and nutrient pools and, thus, calculating elemental budgets. In practice, attempts to budget mesocosm enclosures are often hampered by uncertainties in some of the measured pools and fluxes, in particular due to uncertainties in constraining air–sea gas exchange, particle sinking, and wall growth. In an Arctic mesocosm study on ocean acidification applying KOSMOS (Kiel Off-Shore Mesocosms for future Ocean Simulation), all relevant element pools and fluxes of carbon, nitrogen and phosphorus were measured, using an improved experimental design intended to narrow down the mentioned uncertainties. Water-column concentrations of particulate and dissolved organic and inorganic matter were determined daily. New approaches for quantitative estimates of material sinking to the bottom of the mesocosms and gas exchange in 48 h temporal resolution as well as estimates of wall growth were developed to close the gaps in element budgets. However, losses elements from the budgets into a sum of insufficiently determined pools were detected, and are principally unavoidable in mesocosm investigation. The comparison of variability patterns of all single measured datasets revealed analytic precision to be the main issue in determination of budgets. Uncertainties in dissolved organic carbon (DOC), nitrogen (DON) and particulate organic phosphorus (POP) were much higher than the summed error in determination of the same elements in all other pools. With estimates provided for all other major elemental pools, mass balance calculations could be used to infer the temporal development of DOC, DON and POP pools. Future elevated pCO2 was found to enhance net autotrophic community carbon uptake in two of the three experimental phases but did not significantly affect particle elemental composition. Enhanced carbon consumption appears to result in accumulation of dissolved organic carbon under nutrient-recycling summer conditions. This carbon over-consumption effect becomes evident from mass balance calculations, but was too small to be resolved by direct measurements of dissolved organic matter. Faster nutrient uptake by comparatively small algae at high CO2 after nutrient addition resulted in reduced production rates under future ocean CO2 conditions at the end of the experiment. This CO2 mediated shift towards smaller phytoplankton and enhanced cycling of dissolved matter restricted the development of larger phytoplankton, thus pushing the system towards a retention type food chain with overall negative effects on export potential.
The impact of land-use change on floristic diversity at regional scale in southern Sweden 600 BC–AD 2008
Authors: Fredh D. , Broström A. , Rundgren M. , Lagerås P. , Mazier F. , Zillén L.
Published: May 2013

Abstract. This study explores the relationship between land-use and floristic diversity between 600 BC and AD 2008 in the uplands of southern Sweden. We use fossil pollen assemblages and the Regional Estimates of Vegetation Abundance from Large Sites (REVEALS) model to quantitatively reconstruct land cover at a regional scale. Floristic richness and evenness are estimated using palynological richness and REVEALS-based evenness, respectively. We focus on the period AD 350 to 750 to investigate the impact of an inferred, short-lived (< 200 yr) period of land-use expansion and subsequent land abandonment on vegetation composition and floristic diversity. The observed vegetation response is compared to that recorded during the transition from traditional to modern land-use management at the end of the 19th century. Our results suggest that agricultural land use was most widespread between AD 350 and 1850, which correlates broadly with high values of palynological richness. REVEALS-based evenness was highest between AD 500 and 1600 which indicates a more equal cover among taxa during this time interval. Palynological richness increased during the inferred land-use expansion after AD 350 and decreased during the subsequent regression AD 550–750, while REVEALS-based evenness increased throughout this period. The values of palynological richness during the last few decades are within the range observed during the last 1650 yr. However, REVEALS-based evenness shows much lower values during the last century compared to the previous ca. 2600 yr, which indicates that the composition of present-day vegetation is unusual in a millennial perspective. Our results show that regional scale changes in land use have had clear impacts on floristic diversity in southern Sweden, with a vegetation response time of less than 20 to 50 yr. We show the importance of traditional land use to attain high biodiversity and suggest that ecosystem management should include a regional landscape perspective.
Modeling ocean circulation and biogeochemical variability in the Gulf of Mexico
Authors: Xue Z. , He R. , Fennel K. , Cai W.-J. , Lohrenz S. , Hopkinson C.
Published: May 2013

Abstract. A three-dimensional coupled physical-biogeochemical model is applied to simulate and examine temporal and spatial variability of circulation and biogeochemical cycling in the Gulf of Mexico (GoM). The model is driven by realistic atmospheric forcing, open boundary conditions from a data assimilative global ocean circulation model, and observed freshwater and terrestrial nutrient input from major rivers. A 7 yr model hindcast (2004–2010) was performed, and validated against satellite observed sea surface height, surface chlorophyll, and in-situ observations including coastal sea-level, ocean temperature, salinity, and nutrient concentration. The model hindcast revealed clear seasonality in nutrient, phytoplankton and zooplankton distributions in the GoM. An Empirical Orthogonal Function analysis indicated a phase-locked pattern among nutrient, phytoplankton and zooplankton concentrations. The GoM shelf nutrient budget was also quantified, revealing that on an annual basis ~80% of nutrient input was denitrified on the shelf and ~17% was exported to the deep ocean.
Eurasian Arctic climate over the past millennium as recorded in the Akademii Nauk ice core (Severnaya Zemlya)
Authors: Opel T. , Fritzsche D. , Meyer H.
Published: May 2013

Abstract. The chronology of the Akademii Nauk (AN) ice core from Severnaya Zemlya (SZ) has been expanded to the last 1100 yr. Here, we present the easternmost high-resolution ice-core climate-proxy records (δ18O and sodium) from the Arctic that provide new perspectives on past climate fluctuations in the Barents and Kara seas region. Multi-annual AN δ18O data as near-surface air-temperature proxy reveal major temperature changes over the last millennium, including the absolute minimum around 1800 and the exceptional warming to a double-peak maximum in the early 20th century. Neither a pronounced Medieval Climate Anomaly nor a Little Ice Age are detectable in the AN δ18O record. In contrast, there is evidence for several abrupt warming and cooling events such as in the 15th and 16th centuries. These abrupt changes are probably caused by shifts in the atmospheric circulation patterns and accompanied sea-ice feedbacks in the Barents and Kara seas region that highlight the role of the internal variability of the Arctic climate system.
Spatial models for monitoring the spatio-temporal evolution of ashes after fire – a case study of a burnt grassland in Lithuania
Authors: Pereira P. , Cerdà A. , Úbeda X. , Mataix-Solera J. , Martin D. , Jordán A. , Burguet M.
Published: May 2013

Abstract. Ash thickness is a key variable in the protection of soil against erosion agents after planned and unplanned fires. Ash thickness measurements were conducted along two transects (flat and sloping areas) following a grided experimental design. In order to interpolate data with accuracy and identify the techniques with the least bias, several interpolation methods were tested in the grided plot. Overall, the fire had a low severity. However, the fire significantly reduced the ground cover, especially on sloping areas, owing to the higher fire severity and/or less biomass previous to the fire. Ash thickness depended on fire severity and was thin where fire severity was higher and thicker in lower fire severity sites. The ash thickness decreased with time after the fire. Between 4 and 16 days after the fire, ash was transported by wind. The greatest reduction took place between 16 and 34 days after the fire as a result of rainfall, and was more efficient where fire severity was higher. Between 34 and 45 days after the fire, no significant differences in ash thickness were identified among ash colours and only traces of the ash layer remained. The omni-directional experimental variograms showed that variable structure did not change significantly with time. The ash spatial variability increased with time, particularly on the slope, as a result of water erosion.
Las publicaciones científicas médicas impresas y su evolución hacia la era digital
Authors: Hernández Tunia Gil , Martínez Ruiz Vivian , García Ferrer Guillermo , Quesada Ravelo Odalys
Published: May 2013

En este artículo se analiza la evolución histórica de las publicaciones médicas cubanas a través del tiempo, desde su aparición en formato impreso hasta la era digital. Se hace referencia a las primeras formas de comunicación científica en el mundo, la aparición de la imprenta en América y a los acontecimientos históricos y sociales que favorecieron el nacimiento y desarrollo de las publicaciones impresas en la isla de Cuba, así como su desarrollo en la era digital.
Búsqueda de descriptores que caractericen una disciplina emergente en WoS y SCOPUS: el caso de la Educación Matemática
Authors: Adamuz-Povedano Natividad , Jiménez-Fanjul Noelia , Maz-Machado Alexander
Published: May 2013

Con la complejidad que van adquiriendo ciertas disciplinas al tener conexiones y relaciones con otras ramas del conocimiento de las que reciben aportes, se hace necesario identificar cuáles son los descriptores que caractericen de forma específica su producción científica. Tomamos como ejemplo prototipo a la Educación Matemática por la existencia de ambigüedad de criterio en la concreción de los términos clave para la producción científica de esta disciplina. Todo esto hace pues necesario el establecimiento de un listado de descriptores que la caracterice. Presentamos un desarrollo metodológico para obtener un listado de descriptores básicos de la producción científica publicados en revistas científicas indexadas en las bases de datos de la Web of Science (WoS) y SCOPUS durante un periodo de 30 años, de 1980 a 2009, para esta disciplina.
Tratamiento de la investigación científica sobre los estudios de mujer, género y feminismo
Authors: Salvai María Eugenia
Published: May 2013

La investigación se propuso, luego de buscar en los catálogos de todas las bibliotecas de la Universidad Nacional de Córdoba, analizar el estado de la investigación elaborada desde la misma universidad, referida a estudios de mujer, género y feminismo entre los años 2000 y 2009. La hipótesis planteó que los documentos no resultan accesibles. En el presente artículo se analizan las posibles causas por las cuales la investigación sobre estudios de mujer, género y feminismo resulta invisibilizada.
COMPUTATIONAL SIMULATION OF ELASTOMER NANOCOMPOSITES: CURRENT PROGRESS AND FUTURE CHALLENGES
Authors: Liu Jun , Zhang Liqun , Cao Dapeng , Shen Jianxiang , Gao Yangyang
Published: May 2013

In the field of elastomer nanocomposites (ENCs), computational simulation technique is becoming more and more essential, as a result of its ability to provide important and clear information at the molecular level, which is always difficult to obtain or not accessible through experimental investigations. We focus on summarizing the progress achieved in the simulation research of three critical topics of ENCs, namely, (i) the dispersion mechanism (particularly polymer-mediated interparticle interaction, the “many-body” effect at high filler loading), (ii) the characterization of the nanoscale/microscale structure and dynamics [the modified chain configuration in the presence of nanoparticles (NPs), the interfacial binding strength determining the efficiency of the stress transfer, the possibly altered interfacial chain structure, interfacial segmental dynamics leading to the shift of the glass transition temperature Tg, the formation of the filler network and its structure, the chemical cross-linking process], and (iii) the macroscopic viscoelasticity (the Payne effect), mechanical reinforcement, and physical property (thermal conductivity). Since recently only limited simulation work has been carried out pertaining to ENCs, we discuss these three topics in light of the simulation and theoretical achievements of polymer nanocomposites (mainly polymer melts filled with NPs). Meanwhile, some relevant experimental studies are also included for better illustration. Furthermore, for each topic, three typically different reinforcing fillers, such as three-dimensional spherical, two-dimensional sheet, and one-dimensional rod NPs, separately corresponding to carbon black or silica, clay sheets, and carbon nanotubes intensively used in the practical applications of ENCs, are illustrated in order. In order to realize a comprehensive understanding of the structure–property relation and in the meantime to provide more practical guidelines for the engineering applications of ENCs, we investigate future simulation opportunities and difficulties.
X-RAY COMPUTED MICROTOMOGRAPHY OF RUBBER
Authors: Jago Karine Le Gorju
Published: May 2013

In rubber science, X-ray computed microtomography (micro CT) is becoming an increasingly used technique to characterize 3D microstructures. As a first step, experimental methods, limitations, and data analysis are described. A review of published micro CT studies for rubber is reported. Examples of our recent works are presented, including investigations on samples or complex structures, for compact or foam rubbers. Micro CT is used to describe the evolution of microstructures relative to different processing steps, to environmental interaction, and to adaptation to a mechanical deformation. New insights and better understanding of damage mechanisms due to quasistatic, creep, and fatigue solicitations are presented from in situ micro CT experiments. Perspective studies are outlined.
GLASS TRANSITION IN RUBBERY MATERIALS
Authors: Roland C. Michael
Published: May 2013

When the perturbation frequency imposed on a rubber falls within the glass transition zone of its viscoelastic spectrum, energy absorption is maximized. This phenomenon is the operative mechanism for various applications of elastomers requiring large energy dissipation. Nevertheless, a fundamental understanding of the glass transition is lacking. The diversity of properties that depend both on chemical structure and thermodynamic conditions makes modeling difficult and a first principles theory perhaps unachievable; indeed, the number of models for the glass transition seems to be inversely proportional to their ability to accurately describe the myriad behaviors. The progress made at quantifying the role of the thermodynamic variables temperature, T, and density, ρ, on the dynamics is described. An important aspect of the work was the discovery that relaxation times and viscosities of molecular liquids and polymers superpose when plotted against the scaling variable T/ργ, with the scaling exponent γ a material constant sensibly related to the nature of the intermolecular repulsive potential; thus, dynamic spectroscopy measurements can be used to quantify the forces between molecules. Other properties derive from the scaling behavior, including the Boyer-Spencer rule and the correlation of fluctuations in the potential energy with fluctuations in the virial pressure.
MICROSTRUCTURE AND MOLECULAR DYNAMICS OF ELASTOMERS AS STUDIED BY ADVANCED LOW-RESOLUTION NUCLEAR MAGNETIC RESONANCE METHODS
Authors: Saalwächter Kay
Published: May 2013

Nuclear magnetic resonance (NMR) certainly belongs to the most powerful spectroscopic tools in rubber science. Yet the often high level of experimental and in particular instrumental sophistication represents a barrier to its widespread use. Recent advances in low-resolution, often low-field, proton NMR characterization methods of elastomeric materials are reviewed. Chemical detail, as normally provided by chemical shifts in high-resolution NMR spectra, is often not needed when just the (average) molecular motions of the rubber components are of interest. Knowledge of the molecular-level dynamics enables the quantification and investigation of coexisting rigid and soft regions, as often found in filled elastomers, and is further the basis of a detailed analysis of the local density of cross-links and the content of nonelastic material, all of which sensitively affect the rheological behavior. In fact, specific static proton NMR spectroscopy techniques can be thought of as molecular rheology, and they open new avenues toward the investigation of inhomogeneities in elastomers, the knowledge of which is key to improving our theoretical understanding and creating new rational-design principles of novel elastomeric materials. The methodological advances related to the possibility of studying not only the cross-link density on a molecular scale but also its distribution and the option to quantitatively detect the fractions of polymer in different states of molecular mobility and estimate the size and arrangement of such regions are illustrated with different examples from the rubber field. This concerns, among others, the influence of the vulcanization system and the amount and type of filler particles on the spatial (in)homogeneity of the cross-link density, the amount of nonelastic network defects, and the relevance of glassy regions in filled elastomers.
ASSIGNMENT OF NMR SIGNALS FOR CHLOROPRENE RUBBER BY TWO-DIMENSIONAL NMR SPECTROSCOPY
Authors: Saito Takayuki , Kawahara Seiichi , Ohtake Yoshito
Published: May 2013

Various pulse techniques of NMR spectroscopy were applied to CR to assign some small signals in 13C and 1H NMR spectra for the rubber. First, the rubber was subjected to distortionless enhancement by polarization transfer and attached proton test. The small signals in the 13C NMR spectrum were assigned to secondary, tertiary, and quaternary carbons. Second, correlations between 13C and 1H were investigated by heteronuclear multiple quantum correlation, heteronuclear two bond correlation, and heteronuclear multiple bond correlation measurements to assign the small signals in the 13C NMR spectrum in detail. By using the resulting correlations between 13C and 1H, the small unassigned signals in 1H NMR spectrum were assigned to methylene and methine protons of the rubber.
SOYBEAN OIL PLASTICIZERS AS REPLACEMENT OF PETROLEUM OIL IN RUBBER
Authors: Petrović Zoran S. , Ionescu Mihail , Milić Jelena , Halladay James R.
Published: May 2013

Polymerized soybean oils of different molecular weights were used as plasticizers in NR/SBR compositions. The oils of different molecular weights and viscosities were synthesized by cationic polymerization using a proprietary technology. Because vegetable oils have double bonds, they are not only viscosity depressants but also active participants in cross-linking reactions. Properties of elastomers extended with different concentrations of mineral oil or pure soybean oil were compared with elastomers extended by polymerized oils of different molecular weights at the same concentrations. It was found that polymerized soybean oil could be substituted for naphthenic process oil with minimal differences in mechanical and dynamic properties.
EXPERIMENTAL CHARACTERIZATION AND MODELLING OF LARGE-STRAIN VISCOELASTIC BEHAVIOR OF A THERMOPLASTIC POLYURETHANE ELASTOMER
Authors: Bartolomé L. , Aginagalde A. , Martínez A. B. , Urchegui M. A. , Tato W.
Published: May 2013

Thermoplastic polyurethane elastomers (TPUs) are a kind of elastomer that can be processed as thermoplastics. These elastomers exhibit a highly nonlinear behavior characterized by hyper-elastic deformability. Furthermore, the mechanical behavior of these elastomers is time-dependent, that is, they exhibit a viscoelastic behavior. We describe the material response of a TPU under moderate strains (ɛ < 1) by using an overlay visco-hyperelastic model assuming separation of time dependence from nonlinear stress–strain behavior. To achieve this goal, cyclic loading–unloading experimental tests are carried out for two homogeneous deformation states, uniaxial tension and pure shear, and the strain–stress data are then analyzed to fit a hyperelastic model. Conversely, a viscoelastic model is obtained from relaxation tests. Finally, the visco-hyperelastic model is implemented in a finite element calculation tool (ABAQUS), and the numerical results show a reasonable correlation with experimental data. As a result, a overlay visco-hyperelastic model depending on maximum strain is proposed.
NBR-PANI.DBSA BLENDS: EFFECT OF ELECTRON BEAM IRRADIATION
Authors: Yong K. C.
Published: May 2013

The electron beam irradiation technique was successfully used to cross-link poly(butadiene-co-acrylonitrile)-polyaniline dodecylbenzenesulfonate [NBR-PAni.DBSA] blends. Significant increase in cross-linking densities of all blends with doses of irradiation (up to 200 kGy) was observed, and a reasonably high cross-linking density level (in the order of 1030 m−3) also was achieved. All electron beam–irradiated NBR-PAni.DBSA blends exhibited good tensile properties (with tensile strength up to ∼20 MPa), with values that are comparable to those of similar blends cross-linked with either conventional sulfur or peroxide techniques. This kind of irradiation-induced cross-linking technique (at doses up to 200 kGy) also did not interrupt the blends' electrical properties after the blends were sufficiently stabilized for at least 24 h. The irradiated NBR-PAni.DBSA blends also possessed good electrical properties, that is, a single conductivity percolation threshold and high conductivities up to the order of 10−2 S.cm−1. All of these findings indicate a good potential for using the electron beam irradiation technique to prepare highly cross-linked, electrically conductive NBR-PAni.DBSA blends.
DRYING KINETICS AND CROSS-LINKING OF SULFUR PREVULCANIZED THICK NATURAL RUBBER LATEX FILM
Authors: Jing Chen , Lei Yang , Jieping Zhong , Sidong Li , Yongjun Chen , Kui Xu
Published: May 2013

In order to investigate drying kinetics of thick natural latex (NR) samples after film formation and the effect on cross-linking of NR latex during the drying process, we employed drying experiment methods, swelling methods, and Fourier transform infrared spectroscopy (FTIR) methods to study the drying and vulcanizing characteristics of NR latex. The results show that the drying temperature and thickness of film have obviously affected drying characteristics. The drying kinetic equation is achieved by mathematic fitting, and the Henderson and Pabis model MR = a exp(−kt) was the best fitted model for the thick NR latex film. The effect of the drying temperature on the drying constant was assessed employing an Arrhenius type equation, which can be expressed as k = 6746 exp[−39.9 × 103/(RT)] (R = 8.314 J mol−1 K−1). The drying constant exponentially decreased with the increasing film thickness. At the beginning of drying, the cross-link density increases rapidly, and up to the maximum value, it would slightly decrease with the prolonged drying time, which the results of FTIR also agree with.
DURABILITY TESTING OF SILICONE MATERIALS FOR PROTON EXCHANGE MEMBRANE FUEL CELL USE
Authors: Bhargava S. , O'Leary K. A. , Jackson T. C. , Lakshmanan B.
Published: May 2013

Silicone resins are ideal candidates for proton exchange membrane fuel cells (PEMFC) sealing and gasketing. They have many advantages for PEMFC application, such as superior stability and longevity under harsh environments, low water absorption, and broad temperature range. However, as this work shows, silicone-based materials have one big drawback: low molecular weight siloxanes, oligomers, and/or degradation byproducts may readily migrate from the base material into the fuel cell membrane, forming glassy structures, reducing the mechanical durability, and ultimately fracturing the proton exchange membrane (PEM). A novel, in situ testing method has been developed to test the effect of siloxanes on PEMFCs. The mechanism for migration of cyclic siloxanes to the PEM interface, causing it to fail in a brittle fashion, is presented. A commercially available silicone gasket material was used as a case study to validate the mechanism. Optical microscopy, scanning electron microscopy, and inductively coupled plasma were used to perform failure analysis of the tested samples. Thermogravimetric analysis was used to measure the removal rate of low molecular weight cyclic siloxanes. Gas chromatography–mass spectrometry was used to separate the organic molecules off-gassing from the material at temperature and provide a mass spectrum of each component.
CRACK GROWTH BEHAVIOR OF STYRENE-BUTADIENE RUBBER, NATURAL RUBBER, AND POLYBUTADIENE RUBBER COMPOUNDS: COMPARISON OF PURE-SHEAR VERSUS STRIP TENSILE TEST
Authors: Andreini G. , Straffi P. , Cotugno S. , Gallone G. , Polacco G.
Published: May 2013

Fatigue crack growth experiments on different carbon black–filled rubber compounds have been carried out to evaluate the influence of pure-shear and strip tensile testing mode by using sine and pulse as waveforms. In a previous set of experimental investigations regarding the influence of both waveform and tested material, it was found that the mode I of crack opening sometimes propagates too quickly to be properly monitored in tests involving strip-tensile specimens. An alternative test methodology based on pure-shear test mode has been investigated, optimizing both the shape of the specimen and the test equipment. Data obtained from the different compound formulations were consistent with the theoretical background and resulted in similar ranking of compound crack growth resistance for the two testing modes; in addition, pure-shear mode showed a higher sensitivity to formula variations.
OVERCOMING INCOMPATIBILITY PROBLEMS IN ELASTOMER BLENDS BY TAILORED SURFACE PROPERTIES OF RUBBER ADDITIVES
Authors: Dierkes W. , Tiwari M. , Guo R. , Datta R. , Talma A. , Noordermeer J. , van Ooij W.
Published: May 2013

Rubber is a challenging composite material, whose functionality strongly depends on the affinity of the different materials in the composite and its morphology. One way to tailor polarity and chemistry of the filler surface is plasma coating. When using acetylene, thiophene, or pyrrole as monomers, the coating results in a reduced polarity of the filler compared with untreated silica, and unsaturated C–C bonds are formed on the surface. This improves the compatibility of the filler–polymer blends. In a SBR/EPDM blend, the filler–polymer compatibility is improved for all plasma-coated fillers compared with untreated silica. The best dispersion is achieved by plasma–pyrrole coating, as measured by the Payne effect and reinforcement parameter. The rubber–filler interaction is also highest for this blend, as measured by the bound rubber content. As expected, this results in improved tensile properties. In NBR/EPDM, the filler–filler interaction is significantly reduced by the plasma–pyrrole coating, which indicates a balanced compatibility of the pyrrole-treated silica in both polymers. The properties of the vulcanizate show the combinatorial effect of dispersion, filler–polymer interaction, polymer entanglements, and cross-link density. All plasma-treated, silica-filled NBR/EPDM materials show a considerable increase in tensile strength compared with untreated silica, with polyacetylene-treated silica resulting in the best properties. When plasma-coated curatives are used in SBR/EPDM blends, the scorch safety of the compounds is increased and the rupture energy is enhanced. In NBR/EPDM blends, all packages of the modified curatives provide an increased maximum torque compared with the control. Mechanical properties of the NBR/EPDM blend are improved even more than they are with SBR/EPDM. This indicates a more-balanced distribution of cross-links, along with a more-homogeneous carbon black dispersion over the different rubber phases. A better polarity match between additives and polymers usually results in improved material properties. The wide variety of monomers for the plasma polymerization allows researchers to tailor the surface properties of the additives.
Vitis vinifera SPECTRAL RESPONSE TO THE INCREASE OF CO2
Authors: Galvíncio Josiclêda Domiciano , Naue Carine Rosa , Angelotti Francilene , Moura Magna Soelma Beserra de
Published: May 2013

Hyperspectral remote sensing (HRS) is a useful method to monitor spectral changes in vegetation. HRS contains significant spectral information for detecting plant stress. The specific aims were: (1) to assess the changes in Vitis vinifera plant chlorophyll content due to the leakage of CO2 into the plant-air environment, and (2) to analyze an vegetation index derived from the first derivative reflectance values for use in detecting Vitis vinifera plant stress due to elevated concentrations of air CO2. Spectral reflectance was measured between 336 and 1045 nm with a spectral resolution of 1 nm, covering visible and near-infrared portions of the electromagnetic spectrum. The amount of chlorophyll decreased about 50% in the open top chamber modified (OTC modified) + CO2 injection when compared to natural condition. The difference in chlorophyll between OTC modified + no CO2 injection and natural condition was 24%. The concentration of chlorophyll a and b decreased and concentration of carotenoids increases of Vitis vinifera in initial stage of growth, with increase in CO2 to 550 ppm. In the end, the remote sensing hyperspectral presents itself as a great tool to assist in studies of global climate change and its impacts on the biomes of the world.
HYPERSPECTRAL VERSUS MULTISPECTRAL DATA FOR ZONATION OF VEGETABLE SPECIES: A ABSTRACT
Authors: Galvíncio Josicleda Domiciano
Published: May 2013

Motivated by the increasing importance of hyperspectral remote sensing data and encouraged to improve the use of physical-mathematical models that a necessity multispectral image, this text wants to perform a abstract of correspondence between hyperspectral and multispectral information to improve of zonation environmental and plant species. In order, the use hyperspectral remote sensing has been promising in to characterize chemical and physical properties of vegetation. When combined with multispectral remote sensing may promote progress in monitoring the physical and chemical properties of spatial and temporal scale.
LEAF SPECTRAL BEHAVIOR AND CHLOROPHYLL CONTENT OF MIMOSA HOSTILIS CANOPY IN A SEMIARID ENVIRONMENT
Authors: Galvíncio Josicleda Domiciano , Pimentel Rejane MM
Published: May 2013

Insurance and efficiency to monitoring and the use of interacting methods for an accurate diagnosis of the vegetation, mainly those from tropical regions, are essentials to contribute to future development management actions. Remote sensing, biological traits associating structural and biochemical data will permit evaluate the behavioral picture of a dominant specie in vegetation that cover great areas. This study aimed to identify the leaf spectral signature features and structural traits related to dominant specie and photosynthesis implications, relating it with environmental stress consequences and discussing critically monitoring using remote sensing methods. Multispectral analysis and hyperspectral spectroradiometer “FieldSpec Handheld” by Analytical Spectral Devices (ASD) from georeferenced points were made. Perceptible differences were detected for mean values of chlorophyll a and b from field data. The use of Hyperion hyperspectral image showed potential to infer the condition of vegetation regeneration analyzed and different intensities of chlorophyll
CLIMATE CHARACTERIZATION USING WATER BALANCE AND NDVI FOR CITY OF PAULISTA-PE
Authors: França Luciana Mayla de Aquino , Pereira João Antonio dos Santos , Galvíncio Josiclêda Domiciano
Published: May 2013

The State of Pernambuco is composed of five meso-regions established according to the IBGE (Brazilian Institute of geography and statistics), among them, the metropolitan region of Recife (RMR) that contains 14 municipalities. With urban development and technological, it became increasingly easy study that focuses on the physical characteristics of the environment, such as mulching, soil, hydrological and climatic characteristics. The destruction of plant cover to the urbanization is the factor that starts to trigger adverse processes in any region of the planet. Currently, are widely used techniques of satellite monitoring to track the environmental situation in the regions. With this, this article presents a study that evaluates the environmental and climatic characteristics, using tools such as the water balance and the NDVI for the municipality of Paulista – PE. The results showed that the municipality features compatible with the climate, being a moist spot and with dense vegetation. Keywords: Municipality, NDVI, satellite monitoring, water balance.