Comparison of inactivation of Listeria monocytogenes within a biofilm matrix using chlorine dioxide gas,aqueous chlorine dioxide and sodium hypochlorite treatments

The present research compared the effect of chlorine dioxide (CD) gas, aqueous CD and aqueous sodium hypochlorite (SHC) treatments on the inactivation of a five strain mixture of Listeria monocytogenes – containing biofilms. Four day old biofilms were developed on a stainless steel (SS 304) coupon by using a mixture of five cultures of L. monocytogenes (Scott A, N1-227, 103M, 82 and 311) using a 100% relative humidity (RH) dessicator for incubation at room temperature (22 ± 2 °C). After biofilm development, coupons were rinsed and dried for 2 h and treated with 0.3 mg/l CD gas at 75% RH, 7 mg/l of aqueous CD and 50 mg/l SHC. Initial log₁₀ population of biofilm cells before CD gas, aqueous CD and SHC treatment was 4.80, 5.09 and 4.95 log₁₀ CFU/cm². The Weibull model was used to fit non-linear survivor curves. Treatments and time points of 0.3 mg/l CD gas and 7 mg/l aq. CD solution were significantly different (p < 0.05). A 10 min treatment of 0.3 mg/l CD gas, 7 mg/l of aq. CD, and 50 mg/l SHC resulted in reductions of 3.21, 3.74 and 3.09 log₁₀ CFU/cm², respectively. At 10 min, all treatments were not statistically different (p > 0.05). Low levels of CD (0.3 mg/l CD gas and 7 mg/l aq. CD solution) for 10 min resulted in similar log reductions compared to 50 mg/l SHC.     

Improved adhesion of ultra-hard carbon films on cobalt–chromium orthopaedic implant alloy

While interfacial graphite formation and subsequent poor film adhesion is commonly reported for chemical vapor deposited hard carbon films on cobalt-based materials, we find the presence of O₂ in the feedgas mixture to be useful in achieving adhesion on a CoCrMo alloy. Nucleation studies of surface structure before formation of fully coalesced hard carbon films reveal that O₂ feedgas helps mask the catalytic effect of cobalt with carbon through early formation of chromium oxides and carbides. The chromium oxides, in particular, act as a diffusion barrier to cobalt, minimizing its migration to the surface where it would otherwise interact deleteriously with carbon to form graphite. When O₂ is not used, graphitic soot forms and films delaminate readily upon cooling to room temperature. Continuous 1 μm-thick nanostructured carbon films grown with O₂ remain adhered with measured hardness of 60 GPa and show stable, non-catastrophic circumferential micro-cracks near the edges of indent craters made using Rockwell indentation.     

Velocities of entrainment in liquid fluidized beds of mixed solids

Experimental data are reported on velocities of entrainment in liquid fluidized beds. Single as well as multicomponent mixtures of solids varying in size and/or density have been investigated. By drawing an analogy with partially fluidized bed systems, phase equilibrium diagrams of binary and ternary mixtures have been constructed and presented. Correlations have been developed for the prediction of velocities related to the beginning of entrainment, minimum entrainment and complete entrainment.     

Studies on the storage stability of oil-based paneer pickle

The recipe for oil-based paneer pickle was standardized on the basis of sensory evaluation. During storage, there was a significant decrease in moisture, fat and protein content and a significant increase in acidity, free fatty acids and peroxide value at both room temperature and refrigeration temperature in all the packaging materials. The sensory score of the pickle remained in the 'liked very much' range up to the end of the storage period. The pickle remained microbiologically safe and was acceptable up to 2 months of storage at both storage temperatures. The pickle packed in glass jars and stored at refrigeration temperature was found to be the most acceptable.     

Photochemical interaction of ascorbic acid with riboflavin, nicotinamide and alpha-tocopherol in cream formulations

The present work is based on a study of the effect of some vitamins such as riboflavin (RF), nicotinamide (NA) and alpha‐tocopherol (TP) on the photodegradation of ascorbic acid (vitamin C) (AH₂) in oil‐in‐water cream formulations using a UV irradiation source. A UV spectrophotometric and the official iodimetric methods have been used for the assay of AH₂ in cream formulations. These methods have been validated in the presence of RF, NA and TP before their application to the creams. The recoveries of AH₂ in the creams are in the range of 90–95% and the reproducibility of the method is within ±5%. The apparent first‐order rate constants (k_obs) for the photodegradation of AH₂ in the presence of RF, NA and TP, individually, in the creams have been obtained. The second‐order rate constants for the photochemical interaction of AH₂ and the vitamins RF, NA and TP have been determined from the plots of k_obs for AH₂ photolysis versus the individual vitamin concentration along with the values of k₀ from the intercept on the vertical axis. The values of k₀ in the presence of RF and NA are lower than those of the k_obs, indicating that these vitamins act as photosensitizers for the degradation of AH₂ in creams. On the contrary, the value of k₀ in the presence of TP is higher than that of the k_obs, suggesting a stabilizing effect of this vitamin on the degradation of AH₂ in creams. The mode of interaction of the individual vitamins with AH₂ on photolysis has been discussed.     

A reduced reaction mechanism for the simulation in ethylene flare combustion

Industrial ethylene flares are considered to be a probable major source of volatile organic compounds (VOCs) such as formaldehyde. VOCs are chemicals that are responsible for the formation of other atmospheric pollutants like ozone. Due to the difficulty and cost of field measurements, on-line monitoring is not practical and other methods must be employed. Current methodologies for calculating speciated and total VOC emissions from flaring activities generally apply a simple mass reduction to the VOC species sent to the flare that does not consider the production of incomplete combustion or other intermediates. There arises a need of a speciation study for the inspection of these flare for their emission. However, most of the detailed kinetic mechanisms for the speciation study of flaring events are too complex, consist of large number of reactions and species, and also are computationally expensive. A reduced mechanism will thus be desirable for improving computational efficiency. In this study, a reduced mechanism for simulating ethylene flare combustion is presented. By retaining the important features of the detailed mechanism in the form of elementary reactions, and satisfying the species constraint of commercial CFD packages, the reduced mechanism, thereby, is useful for speciation study of flaring event.     

High electric field effects in amorphous semiconducting (As2S3)1−x(PbS)x

High electric field measurements on (As₂S₃)_1?x(PbS)_x amorphous semiconductors have been made in sandwich geometry at 50 and 80°C. They reveal the non-linear effects associated with conduction in amorphous semiconductors. The x = 0.1 composition exhibits an anomalous increase in current at an applied field of about 22.5 KV/cm which is found to be independent of the temperature.     

Interaction Between Ionic Liquids and Gemini Surfactant: A Detailed Investigation into the Role of Ionic Liquids in Modifying Properties of Aqueous Gemini Surfactant

Tuning physicochemical properties of aqueous surfactant solutions comprised of normal or reverse micelles by external additives is of utmost importance due to the enormous application potential of surfactant‐based systems. Unusual and interesting properties of environmentally benign ionic liquids (IL) make them suitable candidates for this purpose. To understand and establish the role of IL in modifying properties of aqueous gemini surfactants, we studied the effect of the IL, 1‐hexyl‐3‐methylimidazolium bromide ([Hmim][Br]) and 1‐octyl‐3‐methylimidazolium bromide ([Omim][Br]) on the properties of the aqueous cationic gemini surfactant 1,6‐hexanediyl‐α,ω‐bis(dimethyltetradecyl)ammonium bromide (14‐6‐14,2Br^?). The behavioral changes were investigated by measuring the critical micelle concentration (CMC) using electrical conductance, surface tension, dye solubilization and fluorescence probe measurements at 298.15 K. It was observed that the CMC of 14‐6‐14,2Br^? gemini surfactant decreases with addition of IL, thus favoring the micellization process. An increase in micellar size was observed at lower IL concentration using dynamic light scattering, with a decrease in aggregation number (N_agg) determined from fluorescence probe quenching measurements. It is noteworthy that the extent of modulation of the micellar properties is different for both the IL due to their structural differences. IL behave like electrolytes at lower concentrations and cosurfactants at higher concentrations and form mixed micelles with the cationic gemini surfactant showing an increase in N_agg.     

The cross-flow filtration of an unstable β-lactam antibiotic fermentation broth

A ceramic cross-flow filter has been evaluated in a recycle loop connected to a bioreactor containing a viscous Streptomyces sp. broth. Because of the instability of the antibiotics formed, it would be advantageous to extract them continuously as they are produced. The performance of the filter, under conditions of high viscosity and suspended solids, has been calculated. Resistance to filtrate flux, distribution of the antibiotic and sterilisability within the system were also examined. An initial flux at a cross-flow velocity of 4 ms^?1 gave readings of 162 litres m^?2 h^?1, which dropped to 131 litres m^?1 h^?1 on subsequent runs because of ‘bedding-in’. Fluxes were improved by an increase of cross-flow velocity and, for short periods, by applying pressure. They were reduced by anti-foam agents and the gradual build-up of particle polarisation layers. Loop sterilisation and removal of the antibiotic in the filtrate stream were excellent.     

Acoustic diffraction by two concentric coaxial soft spherical caps

Summary The subject of this paper is the problem of diffraction of a time-harmonic axially symmetric acoustic wave by two concentric coaxial soft spherical caps. An integral equation technique is employed to solve such a boundary value problem involving two concentric coaxial spherical caps. Approximate expressions are derived for the far field amplitude as well as the scattering cross section for this problem when the incident wave is a low frequency axially symmetric plane wave travelling along the common axis of the two caps. By taking appropriate limits, the formulae for scattering cross section for the corresponding problems for a soft spherical cap, a soft sphere and a soft sphere bounded by a concentric soft spherical cap are also derived. Furthermore, the total electrostatic charge required to raise the two concentric coaxial spherical caps to unit potentials in a free space is readily evaluated from the analysis of this paper.