Assessing the Antimicrobial Activity of Polyisoprene Based Surfaces

There has been an intense research effort in the last decades in the field of biofouling prevention as it concerns many aspects of everyday life and causes problems to devices, the environment, and human health. Many different antifouling and antimicrobial materials have been developed to struggle against bacteria and other micro- and macro-organism attachment to different surfaces. However the “miracle solution” has still to be found. The research presented here concerns the synthesis of bio-based polymeric materials and the biological tests that showed their antifouling and, at the same time, antibacterial activity. The raw material used for the coating synthesis was natural rubber. The polyisoprene chains were fragmented to obtain oligomers, which had reactive chemical groups at their chain ends, therefore they could be modified to insert polymerizable and biocidal groups. Films were obtained by radical photopolymerization of the natural rubber derived oligomers and their structure was altered, in order to understand the mechanism of attachment inhibition and to increase the efficiency of the anti-biofouling action. The adhesion of three species of pathogenic bacteria and six strains of marine bacteria was studied. The coatings were able to inhibit bacterial attachment by contact, as it was verified that no detectable leaching of toxic molecules occurred.     

Docosahexaenoic Acid Levels in Blood and Metabolic Syndrome in Obese Children: Is There a Link?

Prevalence of metabolic syndrome is increasing in the pediatric population. Considering the different existing criteria to define metabolic syndrome, the use of the International Diabetes Federation (IDF) criteria has been suggested in children. Docosahexaenoic acid (DHA) has been associated with beneficial effects on health. The evidence about the relationship of DHA status in blood and components of the metabolic syndrome is unclear. This review discusses the possible association between DHA content in plasma and erythrocytes and components of the metabolic syndrome included in the IDF criteria (obesity, alteration of glucose metabolism, blood lipid profile, and blood pressure) and non-alcoholic fatty liver disease in obese children. The current evidence is inconsistent and no definitive conclusion can be drawn in the pediatric population. Well-designed longitudinal and powered trials need to clarify the possible association between blood DHA status and metabolic syndrome.     

Volatile and semi-volatile components of oak wood chips analysed by Accelerated Solvent Extraction (ASE) coupled to gas chromatography–mass spectrometry (GC–MS)

Volatile and semi-volatile compounds of French and American oak wood used in wine and spirits ageing were extracted by an Accelerated Solvent Extractor (ASE) and analysed by gas chromatography–mass spectrometry. More than 90 compounds were isolated, characterised and quantified after being separated on two chromatographic columns with distinct polarity. The main oak wood components were quantitatively determined by using standard reference compounds. In addition, a number of compounds, mainly guaiacol and syringol derivatives, were detected and characterised. In particular, 10 compounds were tentatively identified as lignin dimers derivatives, whose presence in oak wood chips or barrels for wine and spirits ageing had not been previously described. Several of the characterised compounds enabled a distinction to be drawn between medium and high toasted wood chips, independently of their geographical origin.     

Full bulk spin polarization and intrinsic tunnel barriers at the surface of layered manganites.

Transmission of information using the spin of the electron as well as its charge requires a high degree of spin polarization at surfaces. However, at surfaces this degree of polarization can be quenched by competing interactions. Using a combination of surface-sensitive X-ray and tunnelling probes, we show for the quasi-two-dimensional bilayer manganites that only the outermost Mn-O bilayer is affected: it is a 1-nm-thick insulator that exhibits no long-range ferromagnetic order, whereas the next bilayer displays the full spin polarization of the bulk. Such an abrupt localization of the surface effects is due to the two-dimensional nature of the layered manganite, and the loss of ferromagnetism is attributed to weakened double exchange in the reconstructed surface bilayer and a resultant antiferromagnetic phase. The creation of a well-defined surface insulator atop a fully spin-polarized bulk demonstrates the ability of two of the most demanding components of an ideal magnetic tunnel junction to self-assemble naturally.     

A series of yeast shuttle vectors for expression of cDNAs and other DNA sequences

Expression/shuttle vectors for the yeast Saccharomyces cerevisiae have usually been large plasmids with only one or a small number of sites that are suitable for cloning and expression. We report here the construction and properties of a series of 12 expression vectors with multiple (four to eight) unique sites in their polylinkers which allow directional cloning and expression of DNA sequences under four different promoters. Eleven of these plasmids replicate at high copy number in Escherichia coli, and all have the yeast TRP1 gene, and the 2 μm origin including REP3 sequence, allowing selection and high copy number replication in yeast. Six of the plasmids are designed for the construction and selection of cDNA libraries from various eukaryotic organisms, allowing directional cloning and expression of cDNAs. All of these six have similar polylinkers containing a unique promoter proximal EcoRI site and a unique promoter distal XhoI site, allowing for directional cloning and expression of ‘ZAP’-type cDNAs. cDNAs that complement a wide variety of yeast mutants can be selected from libraries constructed in this way. The four alternative promoters, ADH2, PGK, GAL10 and SV40 were compared for their relative activity, both in E. coli and in yeast. All yeast promoters showed substantial activity in E. coli with ADH2 showing the highest activity. ADH2 also was well-regulated in yeast, showing very high relative activity under derepressing conditions. cDNAs selected by genetic complementation from libraries constructed in these vectors should be easily subclonable into other vectors, allowing expression in different eukaryotic organisms, DNA sequencing or site-directed mutagenesis.     

Photoluminescence of hydrophilic silicon nanocrystals in aqueous solutions

Stable aqueous solutions of undecylenic-acid-grafted silicon nanocrystals (Si-nc) were prepared. The time evolution of the photoluminescence properties of these hydrophilic silicon nanocrystals has been followed on different timescales (hours and days). On a short timescale (hours), Si-nc tend to agglomerate while the PL lineshape and intensity are stable. Agglomeration can be reduced by using suitable surfactants. On a long timescale (days), oxidation of Si-nc occurs even in the presence of surfactants. These two observations render Si-nc very useful as a labeling agent for biosensing.     

杰昆·索罗拉火车站,巴伦西亚,西班牙

何谓永恒城市与火车之间的爱恨情仇/关系源远流长,有过激情四溢的乐章,也有过痛苦折磨的片断,有过甜蜜美好的瞬间,也有公诸于众的背叛。而今,两者之间的关系历经变化,今非昔比。然而在巴伦西亚的杰昆·索罗拉火车站,城市与火车之间的激情烈焰仍在燃烧。新车站在允许高速火车进行停靠的同时,完成了将铁轨迁入地下的工程:     

广告,从中国文化中脱颖而出

广告是源于生活,又从生活中升华的艺术.中国广告的奇花异葩也只有在中国肥沃的历史文化土壤中才能茁壮成长.在这则美的空调的广告中,聪明又简单的创意,直接而真实的视觉演绎以及亲切又幽默的概念传达,让你看后回味无穷.     

Impact modification of polypropylene

This paper compares the modification mechanism provided by ethylene‐octene (EO) copolymer to that of ethylene‐propylene‐diene terpolymer (EPDM) rubber. Within the limits of this study, the highest impact strength was achieved at 30–40% rubber content, regardless of the rubber type. An increase in rubber melt viscosity resulted in overall greater impact strength. At the optimum concentration, the high‐viscosity (MFI = 1 to 5) EO rubber provided modification mainly via a crazing mechanism, while the EPDM rubber functioned by energy dissipation through the three‐dimensional network structure formed with the polypropylene matrix. This paper also discusses the effects of the processing conditions on the physical properties of PP/EPR copolymer. An increase in processing temperature and screw speed resulted in a reduced number of discrete rubber particles and nearly no or very slight increase in impact strength, but a very significant reduction in tensile strength and tensile modulus.     

Polymere und Copolymere mit reaktionsfähigen Gruppen. Copolymerisation von Glycidyl-β-methylitaconat und Styrol

In part I of this series the results of sedimentation velocity experiments with the polyelectrolyte Polyvinylpyrrolidone-Blancophor are described. The combination of the Svedberg formula and an equation of Tiselius describing the charge- and salt-effects gives the possibility to describe the change of the frictional coefficient as a function of charge and screening quantitatively. The resulting frictional coefficients resp. the dimensions of the coil of this polyelectrolyte change in a wide range with the charge density and the counterion concentration.