Amperometric detection of ascorbic acid in honey using ascorbate oxidase immobilised on amberlite IRA-743

A differential amperometric method for the specific determination of ascorbic acid in honey was developed by association of a flow injection analysis (FIA) system and a tubular reactor containing the ascorbate oxidase enzyme immobilised. A gold electrode modified by electrochemical deposition of palladium was employed as working electrode. Ascorbic acid was quantified in seven samples of commercial honeys using a potential of +0.60 V vs. Ag/AgCl_(sat). The linear dynamic range in ascorbic acid extends from 1 to 50 μmol L⁻¹, at pH 7.0. At flow rate of 1.5 mL min⁻¹ and injecting 250 μL sample volumes, a sampling frequency of 180 determinations per hour is afforded. The detection and quantification limit of this method are 0.14 and 0.49 μmol L⁻¹, respectively. The samples analyses were compared with the volumetric method, and showed an excellent correlation between the methods.     

Toward plasmonic polymers

We establish the concept of a plasmonic polymer, whose collective optical properties depend on the repeat unit. Experimental and theoretical analyses of the super- and sub- radiant plasmon response of plasmonic polymers comprising repeat units of single nanoparticles or dimers of gold nanoparticles show that (1) the redshift of the lowest energy coupled mode becomes minimal as the chain approaches the infinite chain limit at a length of ～10 particles, (2) the presence and energy of the modes are sensitive to the geometries of the constituents, that is, repeat unit, but (3) spatial disorder and nanoparticle heterogeneity have only small effects on the super-radiant mode.     

Crosslinkable coupling agents: Synthesis and use for modification of interfaces in polymer blends

A novel coupling agent containing 2-oxazoline and 2-oxazinone as well as hydrosilane moieties has been prepared by hydrosilylation of the corresponding allyl ether containing precursor with a methylhydrosiloxane-dimethylsiloxane copolymer. This hydrosiloxane containing coupling agent, termed as SCA, was characterized by ¹H NMR and its crosslinkability was proven by DSC. SCA was used for the modification of the interfaces in heterogeneous polymer blends. In a model blend system based on mono-carboxylic acid terminated polystyrene (PS-COOH) and mono-amino terminated poly(methyl methacrylate) (PMMA-NH₂) the 2-oxazoline and 2-oxazinone units of SCA can selectively react with the carboxylic groups or amino groups, respectively. The remaining hydrosilane units partially crosslink under the used mixing conditions.The morphology of the three-component blends prepared by melt mixing was evaluated. SCA is immiscible with the polymers and forms its own phase. The expected location of the SCA at the interface between the polymers was proven only in an annealed, strongly phase separated blend. Overall the effect of the compatibilizer on the morphology is very small. Neither the domain size nor the composition for phase inversion are significantly affected in this blend system by the presence of SCA.     

Fault management tools for a cooperative and decentralized networkoperations environment

Some institutions do not have centralized computer network operations. In the case of the Federal University of Rio Grande do Sul, some domains have their own group of people in charge of such a task locally and other domains do not. The paper describes the university's network approach, as well as the fault management tools to support such an approach. One of them, the CINEMA Alert System, analyzes the network after polling entities and generates alerts when required. Another, the CINEMA trouble ticket system, helps the decentralized operations staff in cooperating during network failure recovery processes. The main features of the tools and software modules' organization to achieve a cooperative integrated network management environment are presented     

Ferri-liposomes as an MRI-visible drug-delivery system for targeting tumours and their microenvironment

The tumour microenvironment regulates tumour progression and the spread of cancer in the body. Targeting the stromal cells that surround cancer cells could, therefore, improve the effectiveness of existing cancer treatments. Here, we show that magnetic nanoparticle clusters encapsulated inside a liposome can, under the influence of an external magnet, target both the tumour and its microenvironment. We use the outstanding T2 contrast properties (r2=573-1,286 s(-1) mM(-1)) of these ferri-liposomes, which are ～95 nm in diameter, to non-invasively monitor drug delivery in vivo. We also visualize the targeting of the tumour microenvironment by the drug-loaded ferri-liposomes and the uptake of a model probe by cells. Furthermore, we used the ferri-liposomes to deliver a cathepsin protease inhibitor to a mammary tumour and its microenvironment in a mouse, which substantially reduced the size of the tumour compared with systemic delivery of the same drug.     

Sex, BMI and age in addition to dietary intakes influence blood concentrations and congener profiles of dioxins and PCBs

Scope: The aim of this study was to i) characterize dietary polychlorinated biphenyls (PCBs) and dioxin exposure in consumers of fish from the PCB contaminated Lake Mjøsa in Norway ii) examine the influence of demographic factors on blood concentrations and congener composition of dioxins and PCBs, iii) characterize dietary sources and possible exposures above tolerable intake. Methods and results: Blood samples were analysed for dioxin‐like (dl) compounds (PCDD/Fs and dl‐PCBs) and non‐dl‐PCBs (ndl‐PCBs). Dietary exposures were calculated using food frequency questionnaires (n=64). Men had higher median intake of dl‐compounds than women (1.2 and 0.85 pg TEQ/kg bw/day), but similar blood concentrations (23.3 and 25.8, pg TEQ/g lipid weight (lw)). For non‐dl‐PCBs, intakes (6.5 and 4.5 ng/kg bw/day) and blood concentrations (381 and 224 ng/g lw) were higher in men than in women. Blood concentrations correlated with dietary intakes in men only. Increasing BMI and age elevated blood concentrations mainly in women. Men and women had different blood congener profiles, with a higher share of PCB‐126 in women, despite similar dietary congener profiles. Eleven participants exceeded the tolerable intake for dl‐compounds. Fish from Lake Mjøsa was the main dietary source. Conclusion: The higher influence of BMI and age for women than for men may have implications for risk assessment.     

Admission Control in Networks with Advance Reservations

The provisioning of quality-of-service for real-time network applications may require the network to reserve resources. A natural way to do this is to allow advance reservations of network resources prior to the time they are needed. We consider several two-dimensional admission control problems in simple topologies such as a line and a tree. The input is a set of connection requests, each specifying its spatial characteristics, that is, its source and destination; its temporal characteristics, that is, its start time and duration time; and, potentially, also a bandwidth requirement. In addition, each request is associated with a profit gained by accommodating it. We address the related admission control problem, where the goal is to maximize the total profit gained by the accommodated requests. We provide approximation algorithms for several problem variations. Our results imply a 4c-approximation algorithm for finding a maximum weight independent set of axis-parallel rectangles in the plane, where c is the size of a maximum set of overlapping rectangles.     

Hollow Poly(3‐hydroxybutyrate) Fibers Produced by Melt Spinning

Native and nucleated PHB has been melt‐spun and the properties of the resulting fibers have been investigated. Biocompatible nucleating agents such as HAP and THY were compared to BN as a reference material. DSC was used to investigate the non‐isothermal crystallization kinetics as a function of processing temperature and cooling rate. It was found that particularly the choice of process temperature can ensure sufficient primary crystallization of native PHB: heating not higher than 10–15 K above the melting temperature induced a favorable crystallization behavior of native PHB. Thus, melt spinning at low process temperatures without additives was demonstrated to be the key to the formation of well‐defined hollow PHB fibers.

     

Enterococcus faecium and Enterococcus durans isolated from cheese: Survival in the presence of medications under simulated gastrointestinal conditions and adhesion properties

In this study, we evaluated the survival of Enterococcus faecium and Enterococcus durans, isolated from cheese, in the presence of medications and under simulated in vitro gastrointestinal conditions. The presence of genes encoding virulence factors, the susceptibility to antimicrobial agents, and adhesion properties were also assessed. Enterococcus faecium and E. durans both exhibited resistance to most of the tested medications but showed a large sensitivity to analgesics and antihypertensives; they also showed wide susceptibility to antimicrobial agents. Enterococcus durans SJRP29 had greater resistance to the presence of medications in comparison with the probiotic Lactobacillus acidophilus La-5. The strains, except for E. durans SJRP05, did not harbor virulence genes. Enterococcus durans SJRP14, SJRP17, and SJRP26 were sensitive to all tested antimicrobial agents. Enterococcus faecium was more stable during the simulation of gastrointestinal tract and showed greater viability. At the end of the assay, except for E. durans SJRP17, all strains showed high viability (>7 log cfu/mL). Enterococcus durans SJRP29 stood out from the other strains and was selected for further evaluation; it tolerated up to 3.0% NaCl at 30 and 37°C, besides having good adhesion properties (high values of auto-aggregation, co-aggregation, and hydrophobicity). Additionally, the microorganism did not show bile salt hydrolase activity or mucin degradation. These results encourage carrying out additional tests to evaluate the probiotic features by using in vitro dynamic models and in vivo tests before applying these strains to a food system.