Analysis and implications of aircraft disinsectants

Aircraft disinsection is required by various countries. In-flight spraying with a 2% phenothrin aerosol exposes passengers and crew directly. Residual spaying uses a permethrin emulsions in the absence of passengers and crew and results in dermal and oral exposures. Exposed passengers and crew often complain of, skin rashes, respiratory problems, tingling and numbness in fingertips and lips and burning eyes. A number of formulations were analyzed for their constituents using GLC-Mass. spec. Volatile organic compounds (VOCs) were found in all aerosol preparations including, ethyl benzene and xylene isomers along with phenothrin. Residual sprays contained, cis-, and trans-, permethrins, palmidrol, and occasionally naphthalene. Headspace analysis found methylene chloride and hexene derivatives but not the active ingredients. The known synergistic effects between organophosphates and pyrethrins, based on carboxyesterases inhibition, can be expected in the presence of Tricresylphosphates (TCPs), constituents found in jet engine oils and in some hydraulic fluids. During oil seal failure, the presence of TCP in the ventilation air could explain the increased sensitivity of some crew members and passengers to disinsectants.     

Prediction of ammonia emission from dairy barns using feed characteristics part 1: Relation between feed characteristics and urinary urea concentration

Urinary urea concentration is an important predictor of NH3 emission from dairy barns. To reduce urinary urea concentration, accurate and precise prediction of urea concentration for different feeding regimes is a prerequisite. The objective of this research, therefore, was to predict urinary urea concentration of a cow using feed characteristics. To compute urinary urea concentration of a cow, we predicted: urine volume; urinary N excretion, using a regression or a mechanistic model; and the relationship between urinary urea concentration and urinary N concentration, which was derived from experimental data. Model results were validated using experimental data. Cows were fed one of nine diets, which was a combination of one of three rumen-degradable protein balances, and one of three roughage compositions. Each diet was repeated once. Measured parameters included herd, diet, and urine characteristics. Observed urinary urea concentration can be predicted with reasonable accuracy from existing models to predict urine volume and urinary N excretion using feed characteristics. The regression model predicted N excretion slightly better than the mechanistic model. In addition, input parameters required for the regression model are recorded at each dairy farm in The Netherlands. This regression model, therefore, can be used by animal nutritionists and producers to determine diets that result in a reduced NH3 emission.     

Variables influencing food perception reviewed for consumer-oriented product development

Consumer wishes have to be translated into product characteristics to implement consumer-oriented product development. Before this step can be made, insight in food-related behavior and perception of consumers is necessary to make the right, useful, and successful translation. Food choice behavior and consumers' perception are studied in many disciplines. Models of food behavior and preferences therefore were studied from a multidisciplinary perspective. Nearly all models structure the determinants related to the person, the food, and the environment. Consequently, the overview of models was used as a basis to structure the variables influencing food perception into a model for consumer-oriented product development. To this new model, referred to as food perception model, other variables like time and place as part of consumption moment were added. These are important variables influencing consumers' perception, and therefore of increasing importance to consumer-oriented product development nowadays. In further research, the presented food perception model is used as a tool to implement successful consumer-oriented product development.     

Polysaccharides as excipients for colon-specific coatings. Permeability and swelling properties of casted films

Oligosaccharides such as inulin (In) and polysaccharides such as galactomannans, combined with polymethacrylates on isolated films for film coatings, were obtained from aqueous-based solvents and investigated as potential vehicles for colonic drug delivery. These compositions, which are susceptible to fermentation by colonic microflora, constitute promising excipients for the development of new colon-specific therapeutic systems. The characteristics of several compositions have been demonstrated in permeability and swelling studies on isolated films composed of a polymethacrylate associated with In or galactomannans of mesquite seed gum (MSG). Results reported prove a dependency of the properties of mixed films on the polymethacrylate-polysaccharide concentration ratio and on the composition of the dissolution media. An increase in permeability through the mixed films was observed in a simulated colonic environment for the following compositions: Eudragit®RS30D-MSG 70 : 30 w/w; Eudragit® RS30D-In 90 : 10 w/w; Eudragit®RS30D-In 76 : 24 w/w.     

Auto-ignition hazard of mixtures of ammonia,hydrogen, methane and air in a urea plant

The auto-ignition of NH(3)/CH(4)/H(2)/air mixtures constitutes a hazard that is of much concern in urea plants. In this study, the auto-ignition behaviour of NH(3)/CH(4)/H(2)/air mixtures is investigated experimentally for pressures up to 7500 kPa. The experiments were carried out in a closed spherical vessel with a volume of 8 dm(3). The concentration and the pressure dependence of the auto-ignition temperature (AIT) were determined for four types of mixtures: NH(3)/air, NH(3)/CH(4)/air, NH(3)/H(2)/air and NH(3)/CH(4)/H(2)/air. The most ignitable NH(3)/air mixtures were situated between stoichiometry and the upper flammability limit. Small amounts of methane and hydrogen decrease the AIT of NH(3)/air mixtures to a large extent. The pressure dependence of the AIT could be correlated by a Semenov relationship. For the multi-fuel mixtures, a distinct deviation from the Semenov correlation was observed at the lowest temperatures. With respect to the explosion hazard in urea plants, the experimental results were used to assess realistic AIT values in the pool reactor and the ammonia scrubber, operating at a pressure of 15,000 kPa.     

Decorrelation-based blood flow velocity estimation: effect of spread of flow velocity,linear flow velocity gradients,and parabolic flow

In recent years, a new method to measure transverse blood flow, based on the decorrelation of the radio frequency (RF) signals has been developed. In this paper, we investigated the influence of nonuniform flow on the velocity estimation. The decorrelation characteristics of transverse blood flow using an intravascular ultrasound (IVUS) array catheter are studied by means of computer modeling. Blood was simulated as a collection of randomly located point scatterers; moving this scattering medium transversally across the acoustical beam represented flow. First-order statistics were evaluated, and the signal-to-noise ratio from the signals were measured. The correlation coefficient method was used to present the results. Three velocity profiles were simulated: random spread of blood-flow velocity, linear blood-flow velocity gradient, and parabolic blood-flow. Radio frequency and envelope signals were used to calculate the decorrelation pattern. The results were compared to the mean decorrelation pattern for plug blood-flow. The RF signals decorrelation patterns were in good agreement with those obtained for plug blood flow. Envelope decorrelation patterns show a close agreement with the one for plug blood flow. For axial blood flow, there is a discrepancy between decorrelation patterns. The results presented here suggest that the decorrelation properties of an IVUS array catheter for measuring quantitative transverse blood flow probably will not be affected by different transverse blood-flow conditions     

Evaluating 3D bone tissue engineered constructs with different seeding densities using the alamarBlue™ assay and the effect on in vivo bone formation

Bone tissue engineering using patient derived cells seeded onto porous scaffolds has gained much attention in recent years. Evaluating the viability of these 3D constructs is an essential step in optimizing the process. The alamarBlue (aB) assay was evaluated for its potential to follow in vitro cell proliferation on architecturally standardized hydroxyapatite scaffolds. The impact of the aB assayed and seeding density on subsequent in vivo bone formation was investigated. Twelve scaffolds were seeded with various densities from 250 to 2.5×10⁶ cells/scaffold and assay by aB at 5 time points during the 7-day culture period. Twelve additional scaffolds were seeded with 2.5×10⁵ cells/scaffold. Two control and 2 aB treated scaffolds were subcutaneously implanted into each of 6 nude mice for 6 weeks. Four observers ranked bone formation using a pair wise comparison of histological sections form each mouse. The aB assay successfully followed cell proliferation, however, the diffusion kinetics of the 3D constructs must be considered. The influence of in vitro aB treatment on subsequent in vivo bone formation cannot be ruled out but was not shown to be significant in the current study. The aB assay appears to be quite promising for evaluating a maximum or end-point viability of 3D tissue engineered constructs. Finally, higher seeding densities resulted in more observed bone formation.     

Wave-front sensing from defocused images by use of wave-front slopes

We describe a novel technique for deriving wave-front aberrations from two defocused intensity measurements. The intensity defines a probability density function, and the method is based on the evolution of the cumulative density function of the intensity with light propagation. In one dimension, the problem is easily solved with a histogram specification procedure, with a linear relationship between the wave-front slope and the difference in the abscissas of the histograms. In two dimensions, the method requires use of a Radon transform. Simulation results demonstrate that good reconstructions can be attained down to 100 photons in each detector. In addition, the method is insensitive to scintillation at the aperture.     

The principle cause for lower plate numbers in capillary zone electrophoresis with most organic solvents.

With longitudinal diffusion as an unavoidable source of peak broadening, the peak efficiency (expressed by the plate number, N) in capillary zone electrophoresis depends on the ratio of electrophoretic mobility, mu, and tracer- or self-diffusion coefficient, D. Both parameters are functions of the ionic strength of the electrolyte solution. According to theory, the mobility is decreased with increasing ionic strength by the relaxation effect (depending on the relative permittivity) and the electrophoretic effect (depending on the relative permittivity and the viscosity of the solvent), whereas the diffusion coefficient is decreased only by the relaxation effect. This allows the theoretical predictions that the plate number, which is proportional to the ratio mu/D, decreases with increasing ionic strength and that the magnitude of this reduction depends on the solvent. Taking the values for relative permittivity and viscosity allows forecasting that, in general, water as a solvent exhibits the smallest lowering of the plate number, as compared to organic solvents. The theoretical predictions are confirmed by the data for the ratio calculated from measured mobilities and diffusion coefficients for iodide as the analyte ion in water, methanol, and acetonitrile with ionic strength of the background electrolyte varying between 0.005 and 0.080 mol L(-1). Whereas the experimentally observed plate number per volt is reduced from its "ultimate value" of about 20 (analyte charge number z = 1, zero ionic strength) in water by only 10%, the decrease at the same ionic strength in methanol and acetonitrile reaches 25 to 30%. Thus, the maximum plate number should read Nmax approximately equals 13 zU (with U being the effective voltage) for these solvents with ionic strengths normally applied in capillary electrophoresis. This reduction is not stemming from inappropriate experimental conditions, but has fundamental physicochemical causes.     

Integrated microfluidic system enabling (bio)chemical reactions with on-line MALDI-TOF mass spectrometry

A continuous flow micro total analysis system (micro-TAS) consisting of an on-chip microfluidic device connected to a matrix assisted laser desorption ionization [MALDI] time-of-flight [TOF] mass spectrometer (MS) as an analytical screening system is presented. Reaction microchannels and inlet/outlet reservoirs were fabricated by powderblasting on glass wafers that were then bonded to silicon substrates. The novel lab-on-a-chip was realized by integrating the microdevice with a MALDI-TOFMS standard sample plate used as carrier to get the microfluidic device in the MALDI instrument. A novel pressure-driven pumping mechanism using the vacuum of the instrument as a driving force induces flow in the reaction microchannel in a self-activating way. Organic syntheses as well as biochemical reactions are carried out entirely inside the MALDI-MS ionization vacuum chamber and analyzed on-line by MALDI-TOFMS in real time. The effectiveness of the micro-TAS system has been successfully demonstrated with several examples of (bio)chemical reactions.