A Novel Route to Calculate the Length Scale for the Glass Transition in Polymers

The occurrence of glass transition is believed to be associated to cooperative motion with a growing length scale with decreasing temperature. We provide a novel route to calculate the size of cooperatively rearranging regions CRR of glass-forming polymers combining the Adam-Gibbs theory of the glass transition with the self-concentration concept. To do so we explore the dynamics of glass-forming polymers in different environments. The material specific parameter $\alpha$ connecting the size of the CRR to the configurational entropy is obtained in this way. Thereby, the size of CRR can be precisely quantified in absolute values. This size results to be in the range 1 $\div$ 3 nm at the glass transition temperature depending on the glass-forming polymer

Reproductive strategy of white anglerfish (Lophius piscatorius) in Mediterranean waters: implications for management

14 pages, 7 figures, 2 tablesReproductive parameters of the white anglerfish (Lophius piscatorius) in the northwestern Mediterranean Sea were studied in 556 specimens collected monthly aboard commercial fishing vessels that were trawling at depths of 12-836 m. The main spawning season occurred from February through June. The size at maturity was estimated to be 48.8 cm in total length (TL) for males, 59.9 cm TL for females, and 51.3 cm TL for both sexes combined. The white anglerfish has group-synchronous oocyte development and determinate fecundity. It is a total spawner (spawns all its eggs once during a spawning season) and has a batch fecundity ranging from 661,647 to 885,214 oocytes, a relative batch fecundity of 66-128 oocytes per gram of female gutted weight, and a potential fecundity with values from 54,717 to 104,506 oocytes per kilogram of female total weight. This study is the first to provide the reproductive biology of white anglerfish in the northwestern Mediterranean Sea and provide valuable information that can be used to improve the stock assessment and ensure proper management of this speciesPeer Reviewe

Tests of mode coupling theory in a simple model for two-component miscible polymer blends

We present molecular dynamics simulations on the structural relaxation of a simple bead-spring model for polymer blends. The introduction of a different monomer size induces a large time scale separation for the dynamics of the two components. Simulation results for a large set of observables probing density correlations, Rouse modes, and orientations of bond and chain end-to-end vectors, are analyzed within the framework of the Mode Coupling Theory (MCT). An unusually large value of the exponent parameter is obtained. This feature suggests the possibility of an underlying higher-order MCT scenario for dynamic arrest.Comment: Revised version. Additional figures and citation

Nuevas citas de Parasquilla ferussaci (Roux, 1830) (Crustacea, Stomatopoda) en el Atlántico oriental y Mediterráneo occidental

En esta nota se informa sobre la presencia del estoma­tópodo Parasquilla ferussaci en las costas de la península ibérica. La documentación está basada en tres especímenes capturados, respectivamente, en Isla Cristina (Huelva) en el Golfo de Cádiz, Fuengirola (Málaga) en el Mar de Alborán y en Gavà (Barcelona) en el Me­diterráneo noroccidental. Se amplia la distribución conocida de la especie completando así el vacío existente hasta el momento entre las citas atlánticas y las del Mediterráneo central. Palabras clave: Parasquilla ferussaci, Estomatópodo, Mediterráneo occidental, Golfo de Cádiz.We report the occurrence of the little known stomatopod Parasquilla ferussaci on the Atlantic and Mediterranean coasts of the Iberian peninsula. Documentation is based on three specimens captured off Isla Cristina (Huelva) in the Gulf of Cadiz, off Fuengirola (Málaga) in the Alboran Sea and off Gavà (Barcelona) in the North-Western Mediterranean. These reports fill the distribution gap between Eastern Central Atlantic reports and previous Mediterranean reports east of the Balearic Islands. Key words: Parasquilla ferussaci, Stomatopoda, Western Mediterranean, Gulf of Cadiz.En esta nota se informa sobre la presencia del estoma­tópodo Parasquilla ferussaci en las costas de la península ibérica. La documentación está basada en tres especímenes capturados, respectivamente, en Isla Cristina (Huelva) en el Golfo de Cádiz, Fuengirola (Málaga) en el Mar de Alborán y en Gavà (Barcelona) en el Me­diterráneo noroccidental. Se amplia la distribución conocida de la especie completando así el vacío existente hasta el momento entre las citas atlánticas y las del Mediterráneo central. Palabras clave: Parasquilla ferussaci, Estomatópodo, Mediterráneo occidental, Golfo de Cádiz

Primera cita del elusivo calamar oceánico Thysanoteuthis rhombus Troschel, 1857 (Cephalopoda: Thysanoteuthidae) en la costa catalana

The diamondback squid Thysanoteuthis rhombus Troschel, 1857 is a large and elusive oceanic squid species. Here, we provide the first record of the species for the Catalan coast and integrate this finding in the current knowledge of the species in close areas.El chipirón volantín (Thysanoteuthis rhombus Troschel, 1857) es una especie de calamar oceánico grande y elusivo. En este trabajo se proporciona el primer registro de la especie para la costa catalana y se discute en el contexto de registros de la especie en zonas cercanas

La pesca de tiburones y rayas en el noroeste del Mediterráneo, una situación compleja

El mar Mediterráneo alberga una gran diversidad de tiburones y rayas, sin embargo, el conocimiento que se tiene de la pesca de estas especies es ambiguo y existe un gran vacío en el noroeste del Mediterráneo. En este trabajo detectamos que en las capturas aparecen muchas más especies de tiburones y rayas de las que se reportan en las estadísticas pesqueras, varias amenazadas de extinción, por lo que puede estar ocurriendo una desaparición de especies sin que se reporten adecuadamente. Encontramos que muchas especies son etiquetadas con otros nombres genéricos y puede ser que se produzcan cambios de nombres en los históricos de las estadísticas. Por otro lado, observamos que las estadísticas podrían tener un grado de incertidumbre alto debido a que algunas especies son procesadas a bordo por lo que los individuos llegan incompletos a la lonja. Finalmente detectamos que se está produciendo "finning" de rayas, lo que conlleva a problemas en las estadísticas y también desde un punto de vista ético ya que los individuos son procesados vivos a bordo. Estos problemas pueden estar ocurriendo en otras partes del mundo y es muy importante que se realicen estudios dirigidos a identificarlos para gestionar de mejor manera las poblaciones de elasmobranquios.The Mediterranean Sea is home to a great diversity of sharks and rays, however, the knowledge of fishing for these species is ambiguous and there is a great gap in the northwestern Mediterranean. In this work, we detected that many species of sharks and rays appeared in the catch than those reported in fisheries statistics, several threatened with extinction, and thus a disappearance of species may be occurring without being properly reported. We found many species labeled with other generic names and changes in names from historical statistics may occur. On the other hand, we observed that the statistics could have a high degree of uncertainty, because some species are processed on board and the individuals arrive incompletely at the market. Finally, we detected that ray "finning" is taking place, which leads to problems in statistics and from an ethical point of view since individuals are processed alive on board. These problems may be occurring in other parts of the world and it is very important that studies be conducted to identify them to better manage elasmobranch populations

X-ray Spectra of the RIXOS source sample

We present results of an extensive study of the X-ray spectral properties of sources detected in the RIXOS survey, that is nearly complete down to a flux limit of 3e-14 cgs (0.5-2 keV). We show that for X-ray surveys containing sources with low count rate spectral slopes estimated using simple hardness ratios in the ROSAT band can be biased. Instead we analyse three-colour X-ray data using statistical techniques appropriate to the Poisson regime which removes the effects of this bias. We have then applied this technique to the RIXOS survey to study the spectral properties of the sample. For the AGN we find an average energy index of 1.05+-0.05 with no evidence for spectral evolution with redshift. Individual AGN are shown to have a range of properties including soft X-ray excesses and intrinsic absorption. Narrow Emission Line Galaxies also seem to fit to a power-law spectrum, which may indicate a non-thermal origin for their X-ray emission. We infer that most of the clusters in the sample have a bremsstrahlung temperature >3 keV, although some show evidence for a cooling flow. The stars deviate strongly from a power-law model but fit to a thermal model. Finally, we have analysed the whole RIXOS sample containing 1762 sources. We find that the mean spectral slope of the sources hardens at lower fluxes in agreement with results from other samples. However, a study of the individual sources demonstrates that the hardening of the mean is caused by the appearance of a population of very hard sources at the lowest fluxes. This has implications for the nature of the soft X-ray background.Comment: 31,LaTeX file, 2 PS files with Table 2 and 22 PS figures. MNRAS in pres

Composite Cements Using Ground Granulated Blast Furnace Slag, Fly Ash, and Geothermal Silica with Alkali Activation

[EN] In recent decades, alkali activated and blended cements have attracted great interest worldwide due to their advantages of low energy cost, high strength, and good durability. This study evaluated the effects of replacing 50% of Portland cement with a mixture of three waste materials: ground granulated blast furnace slag (GGBFS), fly ash (FA), and geothermal waste (GS), with and without external alkaline activation, and activated with different alkali agents: 4 and 7% Na2O equivalent of sodium hydroxide, sodium silicate (water glass), and sodium sulfate. After 90 days of curing, samples were characterized using compressive strength tests, scanning electron microscopy, X-ray diffraction, and thermogravimetric analyses. The results showed that sodium hydroxide caused an alkali-silica reaction and reduced the strength, while sodium silicate and sodium sulfate improved the strength and hydration products formation. Moreover, the addition of fly ash decreased the compressive strength but increased the workability, while the addition of slag and geothermal waste increased strength and densified the matrix with the formation of additional hydration products. The blended cements without activation also showed better performance than pure cement and a more compact matrix of hydration products. The study demonstrated the feasibility of using waste materials to produce blended cements with low energy costs and high durability.This research was funded by CONAHCYT (National Council of Humanities, Science and Technology, Consejo Nacional de Humanidades, Ciencia y Tecnología México) and UANL (PAICYT). This research was conducted at FIME-UANL, the authors acknowledge the support that has made the laboratory and the operation possible; to Universidad Nacional de Colombia, and María Zambrano (UPV, Ministry of Universities, Recovery, Transformation, and Resilience Plan Funded by the European Union Next Generation EU) of the Institute of Materials Technology of the Polytechnic University of Valencia (Spain); and UPV s Aid to Promote Postdoctoral Research (PAIDPD-22).Salas Montoya, A.; Rodríguez-Barboza, LI.; Colmenero-Fonseca, F.; Cárcel-Carrasco, J.; Gómez-Zamorano, LY. (2023). Composite Cements Using Ground Granulated Blast Furnace Slag, Fly Ash, and Geothermal Silica with Alkali Activation. Buildings. 13(7). https://doi.org/10.3390/buildings1307185413

High and low molecular weight crossovers in the longest relaxation time dependence of linear cis-1,4 polyisoprene by dielectric relaxations

The dielectric relaxation of cis-1,4 Polyisoprene [PI] is sensitive not only to the local and segmental dynamics but also to the larger scale chain (end-to-end) fluctuations. We have performed a careful dielectric investigation on linear PI with various molecular weights in the range of 1 to 320 kg/mol. The broadband dielectric spectra of all samples were measured isothermally at the same temperature to avoid utilizing shift factors. For the low and medium molecular weight range, the comparisons were performed at 250 K to access both the segmental relaxation and normal mode peaks inside the available frequency window (1 mHz–10 MHz). In this way, we were able to observe simultaneously the effect of molecular mass on the segmental dynamics—related with the glass transition process—and on the end-to-end relaxation time of PI and thus decouple the direct effect of molecular weight on the normal mode from that due to the effect on the monomeric friction coefficient. The latter effect is significant for low molecular weight (M w < 33 kg/mol), i.e., in the range where the crossover from Rouse dynamics to entanglement limited flow occurs. Despite the conductivity contribution at low frequency, careful experiments allowed us to access to the normal mode signal for molecular weights as high as M w = 320 kg/mol, i.e., into the range of high molecular weights where the pure reptation behavior could be valid, at least for the description of the slowest chain modes. The comparison between the dielectric relaxations of PI samples with medium and high molecular weight was performed at 320 K. We found two crossovers in the molecular weight dependence of the longest relaxation time, the first around a molecular weight of 6.5 ± 0.5 kg/mol corresponding to the end of the Rouse regime and the second around 75 ± 10 kg/mol. Above this latter value, we find a power law compatible with exponent 3 as predicted by the De Gennes theory