Effect of polymer structure on the molecular dynamics and thermal behavior of poly(allyl acetoacetate) and copolymers

In this paper, dielectric and calorimetric studies of the small-molecule glass former allyl acetoacetate monomers as well as its newly synthetized homopolymer and copolymers with different styrene composition were performed in both the liquid and glassy states. The molecular dynamics studies by the broadband dielectric spectroscopy and the stochastic temperature modulated differential scanning calorimetry enabled us to explore relaxation processes of examined materials in the wide frequency range. We found that the copolymers reveal two co-existing glass transitions characterized by the glass transition temperatures, which are very close to those of the corresponding homopolymers. These results suggest that the copolymers exhibited some sequences of acetoacetate units with a microphase-separated morphology in agreement with the value of reactivity ratio previously determined. We investigated effects of copolymerization compositions on the glass transition temperature, the isobaric fragility index, the dielectric and calorimetric intensity, and the dynamic heterogeneity on the glass transitions of the materials.     

Complete Characterization of the O-Antigen from the LPS of Aeromonas bivalvium

Aeromonas species are found in the aquatic environment, drinking water, bottled mineral water, and different types of foods, such as meat, fish, seafood, or vegetables. Some of these species are primary or opportunistic pathogens for invertebrates and vertebrates, including humans. Among the pathogenic factors associated with these species, there are the lipopolysaccharides (LPSs). LPSs are the major components of the external leaflet of Gram-negative bacterial outer membrane. LPS is a glycoconjugate, generally composed of three portions: lipid A, core oligosaccharide, and O-specific polysaccharide or O-antigen. The latter, which may be present (smooth LPS) or not (rough LPS), is the most exposed part of the LPS and is involved in the pathogenicity by protecting infecting bacteria from serum complement killing and phagocytosis. The O-antigen is a polymer of repeating oligosaccharide units with high structural variability, particularly the terminal sugar, that confers the immunological specificity to the O-antigen. In this study, we established the structure of the O-chain repeating unit of the LPS from Aeromonas bivalvium strain 868 E^T (=CECT 7113^T = LMG 23376^T), a mesophilic bacterium isolated from cockles (Cardium sp.) and obtained from a retail market in Barcelona (Spain), whose biosynthesis core LPS cluster does not contain the waaE gene as most of Aeromonas species. After mild acid hydrolysis, the lipid A was removed by centrifugation and the obtained polysaccharide was fully characterized by chemical analysis and NMR spectroscopy. The polymer consists of a heptasaccharide repeating unit containing D-GalNAc, L-Rha, D-GlcNAc, and D-FucNAc residues.     

Changes in polyphenolic content and antioxidant activity after thermal treatments of grape seed extract and grape pomace

This study was undertaken to investigate the effect of heat treatment on polyphenolic content and antioxidant activity in grape pomace (GP) and grape seed extract (GSE). GP and GSE were heat treated in a furnace or autoclaved at 100 °C for 15, 30 and 60 min. Structural modifications of the polyphenols during thermal processes were determined by HPLC–MS, and the antioxidant activity was determined by ABTS, DPPH and photochemiluminescence methods. In general, furnace thermal treatment of GSE and GP did not affect the total extractable polyphenols content, tannin content, procyanidin components and the antioxidant activity. Autoclave treatment caused an extensive hydrolysis of gallocatechin (70%), catechin (61%), epicatechin (65%), procyanidin B1 (75%) and procyanidin B2 (73%) in GSE, and an increase in gallic acid (71%), gallocatechin (100%) and epicatechin gallate (129%) in GP. Autoclave treatment did not affect the antioxidant activity of GSE or GP. It can be concluded that the effect of autoclave was more severe than furnace heat treatment modifying the phenolic profile in a different manner depending on the grape seed product used. These modifications were not related with changes in antioxidant activity.     

Laser‐induced surface structures on gold‐coated polymers: Influence of morphology on surface‐enhanced Raman scattering enhancement

The fabrication of highly sensitive and reproducible substrates for Surface‐Enhanced Raman Scattering (SERS) remains a challenging scientific and technological issue. In this work, laser‐induced periodic surface structures are generated on poly(trimethylen terephthalate) films upon laser irradiation with the linearly polarized beams of a Nd:YAG laser (4th harmonic, 266 nm), an ArF excimer laser (193 nm), and a Titanium:sapphire laser (795 nm), resulting in periods close to the laser wavelength when irradiating at normal incidence, and larger periods for different angles of incidence. Additional irradiation with a circularly polarized beam at 266 nm produces superficial circular structures. The nanostructured polymers are coated with a nanoparticle assembled gold layer by pulsed laser deposition at 213 nm. The capabilities of these substrates for SERS are evaluated using benzenethiol as a test molecule and different degrees of Raman signal enhancement are observed depending on the nanostructure type. The highest enhancement factor is obtained by for nanostructured substrates with the highest values of period, depth, and roughness. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42770.     

Assessment of heavy metal levels in Almendares River sediments--Havana City, Cuba

The Almendares River watershed covers a large portion of Havana, Cuba and is centrally important to both recreational and other activities in the region. In order to assess current water quality conditions prior to planned remediation efforts, the spatial distribution of six heavy metals and other compounds were determined in river sediments at fifteen sampling stations in the watershed. Metal concentrations in sediments ranged from 86.1 to 708.8 for Zn, 39.3 to 189.0 for Pb, 71.6 to 420.8 for Cu, 84.4 to 209.7 Cr, 1.5 to 23.4 for Co, and 1.0 to 4.3 for Cd microg/g dry weight sediment. Calculated enrichment factors (EF; measured metal versus background mineral conditions) were almost always greater than 1.0, suggesting significant anthropogenic impact on metal levels in the river. The highest EF values were seen immediately below Cotorro (EF>10 for Pb, Cu, and Cd), a suburban town that has an active secondary smelter, and below the largest municipal landfill in Havana (EF>10 for Pb, Cu, Cd, and Zn). Further, three sampling stations had multiple metals at concentrations higher than probable effects concentrations (PEC), implying possible local ecotoxicological impacts. Finally, sequential extractions of the sediments indicated that heavy metals were largely associated with the organic fraction, and it was estimated that up to 62% of metals in the sediments would be susceptible to release back into the water column if hydraulic or other changes occurred in the river. These data are being used to prioritize decisions related to the remediation of the river system.     

Differential and scanning-mode external PIXE for the analysis of the painting “Ritratto Trivulzio” by Antonello da Messina

Extensive PIXE investigations have been performed at the LABEC accelerator laboratory in Florence on the painting “Ritratto Trivulzio” by Antonello da Messina, one of the great Italian masters of XV Century and a pioneer in modern oil painting.It is well known that a complete and unambiguous characterisation of materials in paintings is often difficult, owing to their complex structure. For the “Ritratto Trivulzio”, the combination of advanced variants of PIXE, such as differential and scanning-mode analysis, provided a relevant contribution to the characterisation of paint layers, in terms of composition and structure, in a totally non-invasive and non-destructive way.Single-spot mode PIXE with external proton beams of about half millimetre diameter was first used for a general characterisation of different areas of the painting. Differential PIXE performed in many spots led to reconstruct the sequence of paints employed by the artist and to estimate in some cases the local paint layer thickness.A second run carried out with the external scanning microbeam facility, using a 3 MeV proton beam of about 80 μm size, was then crucial to clarify some issues raised by the first analysis. In particular, elemental maps from selected areas helped to understand the way some colour shades had been obtained on the red mantle of the portrayed gentleman, using different pigments irregularly distributed on the surface.     

Synthesis of polar vinyl monomer–olefin copolymers by α‐diimine nickel catalyst

Vinyl acetate, methyl methacrylate, acrylonitrile and methyl vinyl ketone were investigated for co‐ and terpolymerization with ethylene and ethylene–propylene. Precursor [bis(N,N ′‐dimesitylimino)acenaphthene]dibromonickel, activated by methylaluminoxane was used as a catalyst system and trialkylaluminium was employed to block the polar groups for these polymerizations. Polymerization activities of the order of magnitude of 10⁶ in the case of vinyl acetate and methyl methacrylate, and 10⁵ in the case of acrylonitrile were achieved. Microanalysis and GPC of acrylonitrile copolymers found about 17 units of acrylonitrile per polymer chain. Copolymers with very different properties from the parent homopolymers were obtained in all cases except that of methyl vinyl ketone. © 2001 Society of Chemical Industry     

La CLAve to increase psychosis literacy of Spanish-speaking community residents and family caregivers.

The authors developed and tested a 35-min psychoeducational program with the goal of increasing Spanish-speaking persons’ literacy of psychosis. The program uses popular cultural icons derived from music, art, and videos, as well as a mnemonic device—La CLAve (The Clue)—to increase (a) knowledge of psychosis, (b) efficacy beliefs that one can identify psychosis in others, (c) attributions to mental illness, and (d) professional help-seeking. Assessments were conducted before and after administering the program to both community residents (n = 57) and family caregivers of persons with schizophrenia (n = 38). For community residents, the authors observed increases across the 4 domains of symptom knowledge, efficacy beliefs, illness attributions, and recommended help-seeking. For caregivers, increases were observed in symptom knowledge and efficacy beliefs. La CLAve is a conceptually informed psychoeducational tool with a developing empirical base aimed at helping Spanish-speaking Latinos with serious mental illness obtain care in a timely manner. (PsycINFO Database Record (c) 2010 APA, all rights reserved)