Analysis of Alpha Activity Levels and Dependence on Meteorological Factors over a Complex Terrain in Northern Iberian Peninsula (2014–2018)

Alpha ambient concentrations in ground-level air were measured weekly in Bilbao (northern Spain) by collecting aerosols in filters between 2014 and 2018. Over this period, the alpha activity concentrations in the aerosol’s samples range from 13.9 µBq/m3 to 246.5 µBq/m3, with a mean of 66.49 ± 39.33 µBq/m3. The inter-annual and intra-annual (seasonal and monthly) variations are analyzed, with the highest activity in autumn months and the lowest one in winter months. Special attention has been paid to alpha peak concentrations (weekly concentrations above the 90th percentile) and its relationship with regional meteorological scenarios by means of air mass trajectories and local meteorological parameters. The meteorological analysis of these high alpha concentrations has revealed two airflow patterns-one from the south with land origin and one from the north with maritime origin-mainly associated with these alpha peak concentrations. Surface winds during representative periods of both airflow patterns are also analyzed in combination with 222Rn concentrations, which demonstrated the different daily evolution associated with each airflow pattern. The present results are relevant in understanding trends and meteorological factors affecting alpha activity concentrations in this area, and hence, to control potential atmospheric environmental releases and ensure the environmental and public health

Out of equilibrium dynamics of poly(vinyl methyl ether) segments in miscible poly(styrene)-poly(vinyl methyl ether) blends

The local dynamics of the low-Tg component in a polymer blend, dynamically asymmetric poly(styrene)-poly(vinyl methyl ether) (PS-PVME), is studied below the glass transition, via dielectric relaxation spectroscopy. A particular attention has been paid to blends with a high PS content (PS weight fraction higher than 50%). A relaxation process, slower than the localized motions inducing the PVME secondary relaxations, is detected. Even though these blends fall out of equilibrium in this temperature regime, the structural recovery process is not efficient on the time scale of this PVME motional process. This relaxation is attributed to rather localized, weakly cooperative PVME motions resulting from the topological constraints imposed by the frozen PS chains.The authors acknowledge the University of the Basque Country (Project No. 9/UPV00206.215-13568/2001) and the Spanish Ministry of Science and Technology (Project No. MAT 2001/0070) for their support.Peer reviewe

Chain dynamics on crossing the glass transition: Nonequilibrium effects and recovery of the temperature dependence of the structural relaxation

In this paper we report thermally stimulated depolarization current results on the chain and segmental dynamics of two monodisperse polyisoprenes accessing both dynamics at ultralow frequency range and exploring the relationship between segmental and chain time scales when crossing the glass transition. In this range, we have recorded experimental evidence of nonequilibrium effects on the slowest chain mode dynamics. The nonequilibrium effects seem to occur simultaneously for both chain and α-relaxation. Moreover, detailed analysis strongly indicates the recovery of an even T-dependence for the chain and α-relaxation dynamics on crossing glass transition and in the glassy state. The obtained results can be understood taking into account the different temperature dependences of the length scales involved in the segmental and chain relaxations.We acknowledge the support of the following research projects MAT2012-31088 supported by the Spanish Ministry "Ministerio de Economía y Competitividad" and IT-654-13 supported by the Basque Government.Peer Reviewe

Polymer chain dynamics: Evidence of nonexponential mode relaxation using thermally stimulated depolarization current techniques

The slowest (p=1) mode relaxation of several polyisoprenes has been experimentally isolated by thermally stimulated depolarization current techniques. Close to the glass transition the p=1 mode deviates from the exponential behavior assumed by Rouse and tube-reptation theories. This effect is found to be a consequence of the closeness of τp=1 and α-relaxation time scales. The scenario resembles that of broadened fast component dynamics in polymer blends with high dynamic asymmetry and suggests a possible general interpretation in terms of the effect of local density fluctuations (α relaxation) on chain dynamics.We acknowledge the support from the following research projects: MAT2012-31088, supported by the Spanish Ministry “Ministerio de Economía y Competitividad,” and IT-654-13, supported by the Basque Government.Peer Reviewe

Dynamics of cyclic polyethers by broadband dielectric spectroscopy

Resumen del trabajo presentado al International Chemical Congress of Pacific Basin Societies, celebrado en Honolulu, Hawai (USA) del 15 al 20 de diciembre de 2015.Peer Reviewe

Dielectric relaxation of 2-ethyl-1-hexanol around the glass transition by thermally stimulated depolarization currents

We explore new routes for characterizing the Debye-like and α relaxation in 2-ethyl-1-hexanol (2E1H) monoalcohol by using low frequency dielectric techniques including thermally stimulated depolarization current (TSDC) techniques and isothermal depolarization current methods. In this way, we have improved the resolution of the overlapped processes making it possible the analysis of the data in terms of a mode composition as expected for a chain-like response. Furthermore the explored ultralow frequencies enabled to study dynamics at relatively low temperatures close to the glass transition (Tg ). Results show, on the one hand, that Debye-like and α relaxation timescales dramatically approach to each other upon decreasing temperature to Tg . On the other hand, the analysis of partial polarization TSDC data confirms the single exponential character of the Debye-like relaxation in 2E1H and rules out the presence of Rouse type modes in the scenario of a chain-like response. Finally, on crossing the glass transition, the Debye-like relaxation shows non-equilibrium effects which are further emphasized by aging treatment and would presumably emerge as a result of the arrest of the structural relaxation below Tg.We acknowledge the support of the following research projects MAT2012-31088 supported by the Spanish Ministry “Ministerio de Economía y Competitividad” and IT-654-13 supported by the Basque Government.Peer Reviewe

Investigation of water diffusion mechanisms in relation to polymer relaxations in polyamides

et al.Diffusion in semicrystalline polymers is a complex phenomenon because of the existence of specific interactions (nonpolar or polar), dynamic heterogeneities, and crystalline phases. The diffusion of water in two semicrystalline polyamides (PA6,6 and PA6,10) was investigated in order to determine the diffusion mechanisms and the influence of polymer relaxations on this process. Liquid water diffusion follows a Fickian mechanism in PA6,10 and a non-Fickian or anomalous mechanism in PA6,6. Through a quasi-equilibrium experiment in dynamic vapor sorption, it is shown that this difference results from the dependence of the diffusion coefficients on water concentration. Moreover, the influence of the polymer relaxations was assessed by broadband dielectric spectroscopy. The dielectric characteristic relaxation times of the α relaxation, associated with the glass transition, and of the β relaxation, related to more local dynamics, have been measured. A simple comparison with the time scale of diffusion suggests that diffusion and polyamide α relaxation should not be directly correlated. However, diffusion is correlated to the secondary β relaxation, which encompasses the local chain dynamics of hydrogen-bonded amide groups in the presence of water. A mechanism of diffusion based on the trapping of water molecules between neighboring sorption sites (amide groups) is proposed in these strongly interacting polymers. It is suggested that diffusion is limited by the relaxation time of hydrogen bonds between water molecules and amide groups and the change in conformation of these amide groups present in polyamides.Funded by the European Soft Matter Infrastructure (ESMI) program (grant no. 262348).Peer Reviewe

Characterization of ESBL-producing Escherichia spp. and report of an mcr-1 colistin-resistance Escherichia fergusonni strain from minced meat in Pamplona, Colombia

[EN] Foods of animal origin are increasingly considered a source of extended spectrum β-lactamase (ESBL) producing bacteria which can disseminate throughout the food chain and become a health concern for humans. This work aimed to evaluate the occurrence of ESBL-producing Escherichia coli in 100 retail minced meat samples taken in markets in Pamplona, Colombia. A total of 19 ESBL-producing isolates were obtained, 18 identified as E. coli and one as E. fergusonii. Fifteen isolates (78.9 %) carried blaCTX-M and blaTEM genes, one (5.2 %) blaSHV and blaTEM genes, one isolate (5.2 %) carried blaCTX-M and one (5.2 %) blaSHV alone. The majority of CTX-M-positive E. coli isolates carried the blaCTX-M-15 gene (13 isolates), being the blaCTX-M-9, blaCTX-M-2, and blaCTX-M-8 (one isolate each) also detected. Two SHV-positive isolates presented the blaSHV-5 and blaSHV-12 allele. The isolate identified as E. fergusonii was positive for blaCTX-M-65 gene and mcr-1 gene. Sixteen isolates (84.2 %) belonged to phylogroups A and B1 and grouped together in the phylogenetic tree obtained by MLST; phylogroups E and F were also detected. Transfer of ESBL resistance was demonstrated for the E. fergusonii isolate. Whole genome sequencing of this isolate revealed the presence of plasmids carrying additional resistance genes. This investigation showed the high prevalence of ESBL-producing E. coli in retail samples of minced meat. Also, the isolation of a strain of E. fergusonii is an additional concern, as some resistance genes are located in mobile elements, which can be transmitted to other bacteria. These evidences support the increasing public health concern considering the spreading of resistance genes through the food chain.S

Free volume holes diffusion to describe physical aging in poly(mehtyl methacrylate)/silica nanocomposites

9 páginas, 5 figuras, 3 tablas.-- Trabajo presentado al "MACRO2010: 43rd IUPAC World Polymer Congress" celebrado en Glasgow (U.K.) del 11 al 16 de julio de 2010.The spontaneous thermodynamically driven densification, the so-called physical aging, of glassy poly(mehtyl methacrylate) (PMMA) and its nanocomposites with silica has been described by means of the free volume holes diffusion model. This mechanism is able to account for the partial decoupling between physical aging and segmental dynamics of PMMA in nancomposites. The former has been found to be accelerated in PMMA/silica nanocomposites in comparison to “bulk” PMMA, whereas no difference between the segmental dynamics of bulk PMMA and that of the same polymer in nanocomposites has been observed. Thus, the rate of physical aging also depends on the amount of interface polymer/nanoparticles, where free volume holes disappear after diffusing through the polymer matrix. The free volume holes diffusion model is able to nicely capture the phenomenology of the physical aging process with a structure dependent diffusion coefficient.The authors acknowledge the University of the Basque Country and Basque Country Government (Ref. No. IT- 436-07, Depto. Educación, Universidades e Investigación) and Spanish Minister of Education (Grant Nos. MAT 2007- 63681 and CSD2006-00053) for their support. The support of the Basque Government within the Etortek program is also acknowledged.Peer reviewe

Nanodielectric mapping of a model polystyrene-poly(vinyl acetate) blend by electrostatic force microscopy

4 páginas, 4 figuras.-- PACS number(s): 61.41.+e, 62.23.-c.-- et al.We present a simple method to quantitatively image the dielectric permittivity of soft materials at nanoscale using electrostatic force microscopy (EFM) by means of the double pass method. The EFM experiments are based on the measurement of the frequency shifts of the oscillating tip biased at two different voltages. A numerical treatment based on the equivalent charge method allows extracting the values of the dielectric permittivity at each image point. This method can be applied with no restrictions of film thickness and tip radius. This method has been applied to image the morphology and the nanodielectric properties of a model polymer blend of polystyrene and poly(vinyl acetate).The financial support of Donostia International Physics Center (DIPC) is acknowledged. The authors would like to acknowledge the financial support provided by the Basque Country Government (Reference No. IT-436-07, Depto. Educación, Universidades e Investigación), the Spanish Ministry of Science and Innovation (Grant No. MAT 2007-63681), the European Community (SOFTCOMP program), and the PPF Rhéologie et plasticité des matériaux mous hétérogènes 2007–2010 Contract No. 20071656.Peer reviewe