Listeria monocytogenes in Aquatic Food Products—A Review

With the increased demand for lightly preserved and/or ready‐to‐eat (RTE) food products, the prevalence of the foodborne pathogen Listeria monocytogenes has increased, which is a public health concern. The goal for this review is to discuss the incidence, epidemiological importance, and contamination routes of L. monocytogenes in various aquatic ecosystems, seafood products, and processing environments and to summarize the data obtained since the 1990s. L. monocytogenes primarily enters the food‐production chain by cross‐contamination in production plants, making this pathogen a major threat to the seafood industry. This pathogen generally contaminates food products at low or moderate levels, but the levels involved in listeriosis outbreaks are significantly higher. The majority of isolates from aquatic products belong to serotype 1/2a, and outbreaks have been linked to highly similar or even indistinguishable strains. Several seafood‐processing plants are colonized by specific “in‐house” flora containing special DNA subtypes of L. monocytogenes. In such cases, L. monocytogenes populations can persist and/or multiply despite the inherent obstacles to their growth in food preservation and manufacturing operations. Therefore, food‐processing facilities must be designed carefully with an emphasis on effective cleaning and disinfecting operations in the production line.     

Graph-Laplacian features for neural waveform classification

Analysis of extracellular recordings of neural action potentials (known as spikes) is highly dependent upon the accuracy of neural waveform classification, commonly referred to as spike sorting. Feature extraction is an important stage of this process because it can limit the quality of clustering that is performed in the feature space. Principal components analysis (PCA) is the most commonly used feature extraction method employed for neural spike recordings. To improve upon PCA's feature extraction performance for neural spike sorting, we revisit the PCA procedure to analyze its weaknesses and describe an improved feature extraction method. This paper proposes a linear feature extraction technique that we call graph-Laplacian features, which simultaneously minimizes the graph Laplacian and maximizes variance. The algorithm's performance is compared with PCA and a wavelet-coefficient-based feature extraction algorithm on simulated single-electrode neural data. A cluster-quality metric is proposed to quantitatively measure the algorithm performance. The results show that the proposed algorithm produces more compact and well-separated clusters compared to the other approaches.     

Best packetisation scheme for H.263 Internet video communication

The H.263 codec is an efficient way to stream variable bit-rate video sequences. It is proposed that, for equivalent bandwidth and frame rate, a two-slice packetisation scheme results in superior peak signal-to-noise ratio, rather than the conventional one-slice scheme, and that constant inter-packet gap rather than 'bursty' delivery is preferable.     

Controlling the Diffusion of Runaway Electrons by Safety Factor Changes in IR-T1 Tokamak

The high-energy current of runaway electrons during a major disruption in tokamak reactors can cause serious damage to the first wall of the reactor and reduce its lifetime. Therefore, it is important to find methods for decreasing the generation of runaway electrons and their energy. The safety factor plays an important role in determining the stability criteria for a wide range of MHD modes. Since runaway electrons suffer only rarely from collisions and are hardly sensitive to electrostatic turbulence, their transport is governed by the magnetic lines structure. On the other hand, since the safety factor is related to the magnetic lines structure, changes in safety factor may have important effects on the diffusion of runaway electrons. In this paper, the generation of runaway electrons and their transport is investigated theoretically. Moreover, by changing the discharge voltage of ohmic and toroidal capacitors, different values of the edge safety factor is generated. In fact, in this experiment, the researchers try to increase the diffusion of runaway electrons by using safety factor changes in the IR-T1 tokamak.     

Grafting of ion-imprinted polymers on the surface of silica gel particles through covalently surface-bound initiators: a selective sorbent for uranyl ion

A new ion imprinted polymer coated silica gel sorbent has been prepared using the radical "grafting from" polymerization method through surface-bound azo initiators for selective uranyl uptake. The introduction of azo initiator onto the silica surface was achieved by the reaction of surface amino groups with 4,4'-azobis(4-cyanopentanoic acid chloride). The grafting step was then carried out in a stirred solution of initiator-modified silica particles in the presence of uranyl ion and functional and cross-linking monomers. The prepared sorbent was characterized using FT-IR spectroscopy, scanning electron microscopy (SEM), elemental analysis (EA), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and BET adsorption isotherm analysis. The influence of the uranyl concentration, pH, and flow rate of solution on the grafted polymer affinity has been investigated. Maximum uptake of uranyl ion was observed at a pH 3.0. The rebinding behavior of the sorbent has been successfully described by the Langmuir-Freundlich isotherm. The dynamic column capacity of sorbent and enrichment factor for uranyl ion were 52.9 +/- 3.4 micromol g(-1) and 52, respectively. It was found that imprinting results in increased affinity of the sorbent toward uranyl ion over strong competitor metal ions such as Fe(III) and Th(IV). The sorbent was repeatedly used and regenerated for 3 months without any significant decrease in polymer binding affinities. Finally the sorbent was applied to the preconcentration and determination of uranyl ion in real water samples.     

Highly selective and sensitive voltammetric sensor based on modified multiwall carbon nanotube paste electrode for simultaneous determination of ascorbic acid,acetaminophen and tryptophan

A carbon-paste electrode modified with multiwall carbon nanotubes (MWCNTs) was used for the sensitive and selective voltammetric determination of ascorbic acid (AA) in the presence of 3,4-dihydroxycinnamic acid (3,4-DHCA) as mediator. The mediated oxidation of AA at the modified electrode was investigated by cyclic voltammetry (CV), chronoamperommetry and electrochemical impedance spectroscopy (EIS). Also, the values of catalytic rate constant (k), and diffusion coefficient (D) for AA were calculated. Using square wave voltammetry (SWV), a highly selective and simultaneous determination of AA, acetaminophen (AC) and tryptophan (Trp) has been explored at the modified electrode. The modified electrode displayed strong function for resolving the overlapping voltammetric responses of AA, AC and Trp into three well-defined voltammetric peaks. In the mixture containing AA, AC and Trp, the three compounds can well separate from each other with potential differences of 200, 330 and 530 mV between AA and AC, AC and Trp and AA and Trp, respectively, which was large enough to determine AA, AC and Trp individually and simultaneously.     

Experiments on conical shell reducers under uniform external pressure

In previous studies, a proliferation of research work has been undertaken on the buckling behavior of shell structures particularly conical shells. Nonetheless, no experimental studies are found in the literature on the buckling of a full and real configured model of a slender shell reducer with two cylindrical end boundaries. To this end, buckling behavior of three conical shell reducers under uniform peripheral pressure was investigated and evaluated experimentally in this paper. In addition, relevant FE simulations as well as theoretical predictions were taken into account to compare buckling load and modes of deformation. Derived results were aimed at generalizing the data for conical reducers in full scale within the range of this study.     

Influence of the Polyvinyl Pyrrolidone Concentration on Particle Size and Dispersion of ZnS Nanoparticles Synthesized by Microwave Irradiation

Zinc sulfide semiconductor nanoparticles were synthesized in an aqueous solution of polyvinyl pyrrolidone via a simple microwave irradiation method. The effect of the polymer concentration and the type of sulfur source on the particle size and dispersion of the final ZnS nanoparticle product was carefully examined. Microwave heating generally occurs by two main mechanisms: dipolar polarization of water and ionic conduction of precursors. The introduction of the polymer affects the heating rate by restriction of the rotational motion of dipole molecules and immobilization of ions. Consequently, our results show that the presence of the polymer strongly affects the nucleation and growth rates of the ZnS nanoparticles and therefore determines the average particle size and the dispersion. Moreover, we found that PVP adsorbed on the surface of the ZnS nanoparticles by interaction of the C–N and C=O with the nanoparticle’s surface, thereby affording protection from agglomeration by steric hindrance. Generally, with increasing PVP concentration, mono-dispersed colloidal solutions were obtained and at the optimal PVP concentration (5%), sufficiently small size and narrow size distributions were obtained from both sodium sulfide and thioacetamide sulfur sources. Finally, the sulfur source directly influences the reaction mechanism and the final particle morphology, as well as the average size.