Infectivity of Trichinella nativa in traditional northern (country) foods prepared with meat from experimentally infected seals

The infectivity of Trichinella nativa larvae in three traditional northern (country) foods was assessed. Foods were prepared with meat from seals experimentally infected with Trichinella nativa and evaluated over a 317-day period during which this food was fed directly to cats while mice were orally inoculated with larvae recovered following the digestion of the food in a solution containing 1% pepsin and 1% HCl at 37 degrees C. Foods examined were igunaq (meat and blubber placed in a seal skin bag and allowed to ferment), nikku (air-dried meat), and sausage (meat, fillers, salt, and spices). Sausage was examined both in a raw state and after partial cooking. Infective T. nativa larvae survived in igunaq, nikku, raw frozen sausage, and poorly cooked sausage for at least 5 months under controlled laboratory conditions. Core temperatures of partially cooked sausage never exceeded 50 degrees C. Caution should be exercised in using these data to establish guidelines for the consumption of raw products, since the survival of infective larvae could be unpredictably extended under field conditions. These data indicate significant food safety risks associated with igunaq, nikku, and sausage prepared with Trichinella-infected meat and provide information for use in risk management and in directing future research.     

Glucose decomposition at high temperature, mild acid, and short residence times

Glucose is an intermediate product in the conversion of biomass to liquid fuels and chemicals via H₂SO₄ hydrolysis and subsequent fermentation. Unfortunately, glucose is destroyed as well as formed in this reaction. This study of glucose decomposition kinetics can be used to more accurately determine the kinetics of glucose formation from cellulosic biomass. The results demonstrate the importance of parallel reversion reactions in explaining the higher rates of disappearance of glucose found in this study as compared to earlier studies. An heuristic set of decomposition rate constants, applicable to conditions likely to be found in a flow reactor, are presented.     

An Experimental Study of Indoor and Outdoor Concentrations of Fine Particles Through Nonisothermal Cracks

It has been shown that a substantial proportion of indoor exposure is from particles originating outdoors. Idealized cracks have been used to study penetration under laboratory settings and all previous studies assumed isothermal conditions. There can be 10–20°C difference between indoor and outdoor temperatures even in mild climate zones. This is the first study to investigate the influence of thermophoresis on the penetration of particles through cracks. A sandwich design consisting of two chambers (each 0.325 [W] × 0.125 [L] × 0.11 [H] m³) and a crack module was used to measure indoor-to-outdoor particle concentrations under practical indoor and outdoor conditions. An idealized aluminum smooth crack of 90 mm crack length was tested under three different pressures ranging from 4 to 8 Pa. Submicron sodium chloride particles were generated and a scanning mobility particle sizer was used to scan the concentration in outdoor and indoor chambers. To mimic summer and winter conditions in temperate climatic zones, two sets of temperature differences (indoor–outdoor) were used: +18°C and ?10°C. I/O ratio and relative difference of I/O ratio compared to the isothermal condition were calculated. Inferring from the results, it can be observed that the I/O ratios under the winter scenario are substantially higher than those under the summer and isothermal scenarios for particle sizes less than 100 nm and the influence of temperature on I/O ratios diminishes with increasing particle sizes.

Copyright 2013 American Association for Aerosol Research     

Genetic variation of lodgepole pine, Pinus contorta var. latifolia, chemical and physical defenses that affect mountain pine beetle, Dendroctonus ponderosae, attack and tree mortality

Plant secondary chemistry is determined by both genetic and environmental factors, and while large intraspecific variation in secondary chemistry has been reported frequently, the levels of genetic variation of many secondary metabolites in forest trees in the context of potential resistance against pests have been rarely investigated. We examined the effect of tree genotype and environment/site on the variation in defensive secondary chemistry of lodgepole pine, Pinus contorta var. latifolia, against the fungus, Grosmannia clavigera (formerly known as Ophiostoma clavigerum), associated with the mountain pine beetle, Dendroctonus ponderosae. Terpenoids were analyzed in phloem samples from 887, 20-yr-old trees originating from 45 half-sibling families planted at two sites. Samples were collected both pre- and post-inoculation with G. clavigera. Significant variation in constitutive and induced terpenoid compounds was attributed to differences among families. The response to the challenge inoculation with G. clavigera was strong for some individual compounds, but primarily for monoterpenoids. Environment (site) also had a significant effect on the accumulation of some compounds, whereas for others, no significant environmental effect occurred. However, for a few compounds significant family x environment interactions were found. These results suggest that P. c. latifolia secondary chemistry is under strong genetic control, but the effects depend on the individual compounds and whether or not they are expressed constitutively or following induction.     

Extended hydrophobicity and self-cleaning performance of waterborne PDMS/TiO<Subscript>2</Subscript> nanocomposite coatings under accelerated laboratory and outdoor exposure testing

It has been shown that incorporation of TiO₂ nanoparticles into hydrophobic coatings can show self-cleaning performance. Accelerated laboratory testing indicated that the coats retain their hydrophobic nature for an extended time period. In this paper, hydrophobic polydimethylsiloxane (PDMS)/TiO₂ nanocomposite coatings with a TiO₂ content of 0–40% were fabricated by simple blending of a PDMS dispersion with an aqueous TiO₂ nanoparticle dispersion. Their long-term hydrophobicity and self-cleaning performance were investigated both in laboratory and real-world outdoor testing. As expected, TiO₂ nanoparticle-based coatings exhibited better self-cleaning relative to the TiO₂-free PDMS control coating as measured by methylene blue degradation testing. Excellent long-term hydrophobicity was observed in accelerated weathering testing when they contained the appropriate levels of TiO₂ nanoparticles (i.e., 0–30%). However, the same PDMS/TiO₂ coatings did not show self-cleaning performance, and instead, exhibited improved dirt pickup resistance, in outdoor exposure testing. Sustained hydrophobicity was observed in outdoor exposure testing for the clear films except when TiO₂ levels were at 40%. The hysteresis of water contact angle (HWCA) significantly increased for the PDMS control coating, and water beading was lost as the film surface picked up dirt. In contrast, the TiO₂-based coatings with appropriate TiO₂ levels maintained a relatively low HWCA after outdoor exposure and no water sheeting on rainy days was observed. This result demonstrates that while photocatalytic TiO₂ nanoparticles can maintain coating hydrophobicity upon outdoor exposure, long-term self-cleaning performance in polluted environments has not yet been achieved with this type of coating under real-world conditions.     

Quantitative Measurements of the Critical Impeller Speed for Solid‐Liquid Suspensions

A quantitative methodology for particle suspension assessment is presented. A new parameter, f_mov/tot, the ratio of the mean number of moving particles to the total number of particles, is introduced to evaluate the minimum speed required to just suspend solids. This approach is tested to investigate the impact of impeller clearance on the minimum impeller speed, N_js, in a vessel when using a radial flow Rushton turbine. Flow patterns and power numbers obtained experimentally and computationally support the suspension findings. Image analysis is an appropriate method for determining N_js. Lowering the impeller clearance reduces the speed required for particle suspension with a change of flow pattern from a radial discharge with two loops to a single loop scouring the vessel base. The power number also falls markedly at the two‐to‐one loop transition as does the strain rate near the base.     

The effects of the azimuthal position of the measurement plane on the flow parameters determined by PIV within a stirred vessel

Two-dimensional particle image velocimetry (PIV) is usually used to determine the complex flow field in mechanically agitated vessels on the basis of measurements taken in a single vertical plane, thus, assuming axial symmetry. In this paper, we use 2D PIV to investigate the effects of the azimuthal position of the measurement plane in a fully baffled vessel agitated by a pitched blade turbine. Seventeen planes located at 5 degree intervals between two adjacent baffles are analysed. To maintain a high spatial resolution of ～1 mm when examining each plane, a two-block approach is employed combining data from two fields of view to reconstruct the whole flow field. Time-averaged velocity and turbulent kinetic energy fields are obtained under fully turbulent conditions as a function of the azimuthal position of the laser plane. It is shown that the assumption of axial symmetry for such Eulerian fields is not fully justified within a fully baffled vessel, as there are considerable differences between planes. The results also show for the type and size of impeller used here, the importance of including both the axial and radial discharge contributions for an accurate evaluation of the flow number, otherwise it can be underestimated by up to 60%. The three-dimensional nature of the PIV measurements has also enabled the mass continuity to be accurately verified throughout the vessel.     

Shannon entropy for local and global description of mixing by Lagrangian particle tracking

If 100 dice cannot be cast simultaneously, one single die can be cast 100 times. On the basis of this simple principle, the experimental technique of positron emission particle tracking has been used to develop and implement a new methodology for quantifying the local and global mixing characteristics within a mechanically agitated fluid batch system. This Lagrangian technique uses a single positron-emitting particle as flow follower. Using a high data acquisition rate, such a tracer is continuously tracked in 3D space and time to accurately determine its trajectory over a considerable period of time. By partitioning its long trajectory, the single particle tracer can be regarded as thousands of simultaneously tracked particles which are instantaneously, locally and non-invasively injected in the mixing system at varying feed positions. A large amount of PEPT data were collected for impeller rotational speeds ranging from 100 to 500 rpm which allowed new statistical tools derived from information theory, such as Shannon entropy and uncertainty, to be implemented in the data analysis. Thus, measurements of entropy mixing indices were obtained as a function of position, time and impeller speed. The method also allowed the determination of characteristic time parameters including the macroscale mixing time which agreed very well with correlations of the dimensionless mixing time available in the mixing literature. Detailed local information is provided on minimum mixing time positions for feed and withdrawal of material, which can be used to optimise the design or operation of stirred batch mixing systems.     

The Impact of Fluid Dynamic Stress in Stirred Bioreactors – The Scale of the Biological Entity: A Personal View

From the start of industrial biotechnology, there has been a perception that biological entities are damaged by stirring, so-called ‘shear damage'. Often, it was the soft option to explain a loss of performance when it was due to other factors, such as bubble ingestion with proteins or on scale-up, where tip speed increased when it was due to decreased homogeneity, especially in pH. For many years, poor control and the range of analytical tools available made a more in-depth explanation difficult; and the concepts of ‘high' and ‘low shear' impellers, now largely disproven, increased it. Here, the size of the biological entity is compared to the Kolmogorov microscale of turbulence leading to a reasonably clear picture emerging. The article starts with the author's introduction to the issue approximately 42 year ago with enzymes, conveniently also the smallest entity; and finishes with the largest, filamentous fungi.