Combining nonthermal technologies to control foodborne microorganisms

Novel nonthermal processes, such as high hydrostatic pressure (HHP), pulsed electric fields (PEFs), ionizing radiation and ultrasonication, are able to inactivate microorganisms at ambient or sublethal temperatures. Many of these processes require very high treatment intensities, however, to achieve adequate microbial destruction in low-acid foods. Combining nonthermal processes with conventional preservation methods enhances their antimicrobial effect so that lower process intensities can be used. Combining two or more nonthermal processes can also enhance microbial inactivation and allow the use of lower individual treatment intensities. For conventional preservation treatments, optimal microbial control is achieved through the hurdle concept, with synergistic effects resulting from different components of the microbial cell being targeted simultaneously. The mechanisms of inactivation by nonthermal processes are still unclear; thus, the bases of synergistic combinations remain speculative. This paper reviews literature on the antimicrobial efficiencies of nonthermal processes combined with conventional and novel nonthermal technologies. Where possible, the proposed mechanisms of synergy is mentioned.     

Assessing effectiveness of the various performance metrics for multi-response optimization using multiple regression

Several methods for optimization of multiple response problems using planned experimental data have been proposed in the literature. Among them, an integrated approach of multiple regression-based optimization using an overall performance criteria has become quite popular. In this article, we examine the effectiveness of five performance metrics that are used for optimization of multiple response problems. The usefulness of these performance metrics are compared with respect to a utility measure, namely, the expected total non-conformance (NC), for three experimental datasets taken from the literature. It is observed that multiple regression-based weighted signal-to-noise ratio as a performance metric is the most effective in finding an optimal solution for multiple response problems.     

Evaluating safety of tunneled small bore central venous catheters in chronic kidney disease population: A quality improvement initiative

Introduction: Peripherally inserted central venous catheters (PICCs) may adversely impact future successful arteriovenous fistulae (AVF). As part of a quality improvement project, the performance of tunneled small bore tunneled central venous catheters (TSB‐CVCs), as alternatives to PICCs, was evaluated. Methods: A retrospective observational study, involving individuals ≥18 years of age who underwent TSB‐CVC placement by Interventional Radiology at Mayo Clinic, Rochester, MN between 1/1/2010 and 8/30/2013. Findings: The study cohort included 92 patients with a median age of 55 (46–67) years, who underwent 108 TSB‐CVC placements. Baseline renal disease was present in 71% (77/108). Most TSB‐CVCs were placed in hospitalized patients (94%; 102/108); five French in diameter (61%; 66/108) and located in an internal jugular vein (84%; 91/108). Median catheter indwelling time was 20 (11–43) days (n = 84). TSB‐CVC‐related bloodstream infection, deep venous thrombosis (DVT), and superficial venous thrombosis (SpVT) rates per line were 0.009 (1/108), 0.018 (2/108), and 0.009 (1/108), respectively. Venous outcomes in a subgroup of 54 patients, who had documented PICC placements (n = 161) in addition to TSB‐CVC (n = 58) were compared. TSB‐CVC‐DVT rate was lower than the PICC‐DVT rate (0.017 [1/58] vs. 0.106 per line [17/161]; P = 0.04). The TSB‐CVC‐SpVT rate was not different from the PICC‐SpVT rate (0 [0/58] vs. 0.037 [6/161] per line; P = 0.14). Discussion: TSB‐CVCs demonstrated an excellent safety profile in our study. These catheters should be preferentially utilized for arm vein preservation in advanced kidney disease. Their impact on future AVF success needs further evaluation.     

Amberlite XAD-2 impregnated organophosphinic acid extractant for separation of uranium(VI) from rare earth elements

Amberlite XAD-2 resin was impregnated with Cyanex272 {bis (2,4,4-trimethylpentyl) phosphinic acid} and Cyanex302 {bis (2,4,4-trimethylpentyl) monothiophosphinic acid}. Systematic studies of Cyanex302 impregnated XAD-2 were carried out to develop optimum conditions for uranium(VI) sorption and devise its separation from rare earth elements. Amberlite XAD-2 impregnated with Cyanex302 had poor distribution coefficients for lanthanum(III) and neodymium(III) while uranium(VI) was quantitatively sorbed from 1×10–3 M HNO3 and was recovered with 1 M HCl from the solid phase. The method proposed is simple, selective and reproducible for determination of uranium(VI) with a relative standard deviation (RSD) of 0.4 %.     

Steady MHD mixed convection flow of a viscoelastic fluid over a magnetized convectively heated vertical surface with Hall current and induced magnetic field effects

In this paper, the steady magnetohydrodynamic mixed convection flow of a viscoelastic fluid over a magnetized vertical surface embedded in a uniform porous material with rotation is considered. The Hall and induced magnetic field effects are also considered in this investigation. The regular perturbation technique is used to find the solutions of flow governing equations. To analyze the consequences of flow-influencing parameters to the flow variables, numerical computation has been performed and the results are illustrated in graphical and tabular forms. It is interesting to note that magnetic diffusion leads to the increase of the fluid flow. It brings a decrement in the induced magnetic field in the vicinity of the magnetized vertical surface.     

Impacts of the periodic wall conditions on the hydromagnetic convective flow of viscoelastic fluid through a vertical channel with Hall current and induced magnetic field

In this study, a mathematical analysis is presented for the hydromagnetic convective flow of an incompressible, chemically reacting, and electrically and thermally conducting viscoelastic fluid through a vertical channel bounded by the porous regime under the action of an applied magnetic field with Hall current and induced magnetic field effects. The left wall of the channel is considered to be nonmagnetic, whereas the right wall of the channel is periodically magnetized. The flow within the channel is induced due to the nonuniform wall temperature and concentration, periodic pressure gradient, and periodic movement of the right wall. The method of separation of variable is used to convert the flow governing coupled partial differential equations into the ordinary differential equations that are solved analytically, and the solution for fluid velocity, induced magnetic field, temperature, and concentration is presented in a closed form. Numerical computation has been performed to demonstrate the impact of various system parameters on the fluid flow behavior. It is observed that oscillations increase the primary flow and primary induced magnetic field. Buoyancy forces have a tendency to lessen the secondary induced magnetic field. Furthermore, it is examined that magnetic diffusivity increases the primary flow, whereas it decreases the secondary flow and primary induced magnetic field.     

The study of a maintenance float model with gamma failure and two repair centres

This paper considers an operational system made up of a number of independent and identical units. A given number N must be in service and is supported by a maintenance float. Here, an attempt has been made to model and analyse the maintenance float problem assuming two types of repairs, namely minor and major repairs. For the sake of simplicity, the failure distributions are taken to be exponential and gamma while the repair distributions are exponential and lognormal.     

Free volume,adhesion, and viscoelastic properties of model nanostructured pressure‐sensitive adhesive based on stoichiometric complex of poly(N‐vinyl pyrrolidone) and poly(ethylene glycol) of disparate chain lengths

Positron annihilation lifetime spectroscopy was used to characterize the size and content of subnanoscopic free volume in a model pressure‐sensitive adhesive based on a stoichiometric hydrogen‐bonded network complex of poly(N‐vinyl pyrrolidone) (PVP) and oligomeric poly(ethylene glycol) (PEG). Adhesive properties were examined with peel and probe tack tests, and mechanical properties were studied with tensile test. Nonequimolar stoichiometry and the structure of PVP–PEG model pressure‐sensitive adhesive blends were found to be determined by the length of PEG short chains. The size and number density of free volume domains in the PVP–PEG blends were determined as functions of blend composition and relative humidity of the surrounding atmosphere, which controls the amount of absorbed water. Correlating the free volume, adhesion behaviors, and tensile properties of the blends, the range of free volume favoring pressure‐sensitive adhesion in examined compositions was established. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Optimization of supercritical fluid extraction of lycopene from tomato skin with central composite rotatable design model

Response surface methodology using the central composite rotatetable design (CCRD) model was used to optimize parameters for supercritical carbon dioxide extraction of lycopene (C₄₀H₅₆) from dried tomato skin. The CCRD consisting of three-factored factorial design with two levels was used in this study. The factors used were temperature of the extraction chamber (40 and 70 °C), pressure of the extraction fluid (25 and 45 MPa), and modifier concentration (5 and 15%). Judged by the lack-of-fit-test, coefficient of determination and the standard errors results from the analysis of variance have shown the model to be adequate. The linear, quadratic and cross-effects were 0.58, 0.28 and 0.05, respectively. The independent variables have significantly (p < 0.05) influenced the extraction of all trans-lycopene from tomato skin. Although, no significant (p > 0.05) individual effect of modifier concentration shown, a synergetic effect was observed. A second-degree polynomial equation was developed from a response surface analysis for all trans-lycopene yield and the highest yield was predicted at 62 °C, 45 MPa (450 bar) and 14% temperature, pressure and modifier concentration, respectively and the recovery of all trans-lycopene was 33%.