Organometallic Pt(II) containing polymer as silver protection against sulfide tarnishing

In this work, the use of a film of an organometallic polymer, namely Pt‐DEBP, has been tested for the selective capture of sulfides with the aim of protecting silver object. Ag foils were exposed to different environmental conditions in the presence of Pt‐DEBP films. Scanning electron microscopy, energy dispersive spectrometry, and colorimetric studies allowed to assess that the polymeric layer selectively captures H₂S, preventing the tarnishing of the silver substrate over a period at least of 2 months, without any manipulation of the sample. This approach open new perspectives for the prevention of aging effects on silver objects of artistic interest, for which cleaning or coating procedures should be avoid. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Vector Quantization-Based Motion Field Segmentation under the Entropy Criterion

This paper proposes a segmentation of block-based motion fields under the constraint of the entropy criterion. The segmentation is performed by a vector quantization technique which associates the segmentation pattern to an element of a codebook. Optimization of the bit rate as a trade-off between motion and segmentation on the one hand and prediction error on the other hand is addressed. An estimation of the amount of information to code the displaced frame difference is derived, making it possible to control the segmentation process. Simulation results show the efficiency of the segmentation method combined with the entropy criterion in a video coding scheme.     

Survival of Lactobacillus rhamnosus strains in the upper gastrointestinal tract

In the present study six probiotic Lactobacillus rhamnosus strains were investigated for their ability to survive in the human upper gastrointestinal tract through a dynamic gastric model of digestion. MRS broth was used as delivery vehicle and survival was investigated during in vitro gastric and gastric plus duodenal digestion. Results highlighted that all tested strains showed good survival rate during both gastric and duodenal digestion. In particular, three strains exhibited a great survival showing a recovery percentage in the range between 117 and 276%. In agreement with survival data, high lactic acid production was detected for all strains, confirming their metabolic activity during digestion.     

Core shell hybrids based on noble metal nanoparticles and conjugated polymers: synthesis and characterization

Noble metal nanoparticles of different sizes and shapes combined with conjugated functional polymers give rise to advanced core shell hybrids with interesting physical characteristics and potential applications in sensors or cancer therapy. In this paper, a versatile and facile synthesis of core shell systems based on noble metal nanoparticles (AuNPs, AgNPs, PtNPs), coated by copolymers belonging to the class of substituted polyacetylenes has been developed. The polymeric shells containing functionalities such as phenyl, ammonium, or thiol pending groups have been chosen in order to tune hydrophilic and hydrophobic properties and solubility of the target core shell hybrids. The Au, Ag, or Pt nanoparticles coated by poly(dimethylpropargylamonium chloride), or poly(phenylacetylene-co-allylmercaptan). The chemical structure of polymeric shell, size and size distribution and optical properties of hybrids have been assessed. The mean diameter of the metal core has been measured (about 10-30 nm) with polymeric shell of about 2 nm.     

MPEG-4 video verification model: Status and directions

This article describes the current status and future directions of the emerging ISO MPEG-4 audiovisual coding standard. The article first presents an overview of the different aspects of the standard and then focuses on the video coding aspects. The current status of the Video Verification Model (VM) (a completely defined encoder and decoder specification) is described in detail and its performance is presented. The new functionalities supported by this emerging standard and their potential applications are highlighted. © 1997 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 8, 468–479, 1997     

Survival of Lactobacillus rhamnosus strains inoculated in cheese matrix during simulated human digestion

Survival of probiotic bacteria during transit through the gastrointestinal (GI) tract is influenced by a number of environmental variables including stomach acidity, bile salts, digestive enzymes and food matrix. This study assessed survival of seven selected Lactobacillus rhamnosus strains delivered within a model cheese system to the human upper GI tract using a dynamic gastric model (DGM). Good survival rates for all tested strains were recorded during both simulated gastric and duodenal digestion. Strains H12, H25 and N24 demonstrated higher survival capacities during gastric digestion than L. rhamnosus GG strain used as control, with H12 and N24 continuing to grow during duodenal digestion. Strains L. rhamnosus F17, N24 and R61 showed adhesion properties to both HT-29 and Caco-2 cells. The ability to attach to the cheese matrix during digestion was confirmed by scanning electron microscopy, also indicating production of extracellular polysaccharides as a response to acid stress.     

Soluble polymers of monosubstituted acetylenes with quaternary ammonium pendant groups: structure and morphology

Soluble conjugated polymers were obtained in the presence of Pd(II), Pt(II) and Rh(I) complexes from monosubstituted acetylene 3‐dimethylamino‐1‐propyne (H? C≡CCH₂N(CH₃)₂, 1 ) and the corresponding hydrochloride (H? C≡CCH₂N(CH₃)₂·HCl, 2 ) and hydrobromide (H? C≡CCH₂N(CH₃)₂·HBr, 3 ) derivatives. A series of reactions were performed to achieve the optimization of the polymerization conditions. The highest yields were found for polymers synthesized using Pd(II) bisacetylides specially prepared, i.e. trans‐[Pd(PPh₃)₂(C≡CCH₂N(CH₃)₂)₂], trans‐[Pd(PPh₃)₂(C≡CCH₂N(CH₃)₂)₂HCl] and trans‐[Pd(PPh₃)₂(C≡CCH₂N(CH₃)₂)₂HBr], respectively. The dimension and size distribution of the polymers were investigated using dynamic light scattering. Polymers containing quaternary ammonium groups showed evidence of a hydrodynamic radius of about 300 nm if prepared with the Rh(I) catalyst and of 160 nm if prepared with the Pd(II) catalysts. Polymers obtained from 1 showed smaller hydrodynamic radius compared to polymers obtained from 2 and 3 , regardless the polymerization catalyst. The ionic polymeric materials were soluble in organic solvents and, more interestingly, in water. The formation of nanoparticles with pearl‐like morphology was achieved using a recently developed osmosis‐based method, with dimensions varying from 60 nm up to micrometres. Copyright © 2011 Society of Chemical Industry     

Biopreservation of minimally processed iceberg lettuces using a bacteriocin produced by Lactococcus lactis wild strain

The industry of minimally processed vegetables (MPV) is constantly searching new technologies for maintaining quality and for inhibiting undesired microbial growth in all steps of production and distribution chain. Among the proposed new technologies, biopreservation, such as bacteriocin-based strategy, is recently considered as a promising perspective in order to reduce the application of chemical preservatives. In the present study the effect of the bacteriocin RUC9 produced by a wild strain of Lactococcus lactis was tested in minimally processed lettuce iceberg samples artificially inoculated with a wild strain of Listeria monocytogenes during storage at 4 °C and compared to that of commercial nisin. Moreover the microbial group dynamics were evaluated by conventional and molecular approaches. Although the treatment did not completely eliminate the pathogen on the produce, the results showed that the bacteriocin reduced the L. monocytogenes viable count of 2.7 log unit in 7 days of storage at 4 °C, suggesting that the treatment can be used as sanitizer to improve microbial safety and to reduce the chemical treatment in MPV processing.     

Effect of wild strains used as starter cultures and adjunct cultures on the volatile compounds of the Pecorino Siciliano cheese

The effect of six wild strains on the volatile profile of the PS cheese was investigated and compared to that generated from industrial starters generally used to produce PS cheese. All cheeses were subjected to microbiological, physicochemical, and volatile compounds analyses. The DGGE of the 16S rDNA analysis was also applied. The volatile compounds generated during ripening were studied through the SPME and the GC-MS methods. No difference was detected between the experimental and control cheeses throughout chemical and microbiological analyses, while the DGGE results showed the presence of Streptococcus thermophilus in all cheeses, and the dominance of Enterococcus durans, Lactobacillus rhamnosus, and Lactobacillus casei in most of the experimental cheeses. Moreover, the presence of Lactococcus lactis species as in the control and in the experimental P2 and P4 cheeses was also revealed. The SPME results showed more pronounced volatile compounds in the experimental cheese samples than in the control ones.