Respiratory Deposition of Fibers in the Non-Inertial Regime—Development and Application of a Semi-Analytical Model

A semi-analytical model describing the motion of fibrous particles ranging from nano- to micro scale was developed, and some important differences in respiratory tract transport and deposition between fibrous particles of various sizes and shapes were elucidated. The aim of this work was to gain information regarding health risks associated with inhalation exposure to small fibers such as carbon nanotubes. The model, however, is general in the sense that it can be applied to arbitrary flows and geometries at small fiber Stokes and Reynolds numbers. Deposition due to gravitational settling, Brownian motion and interception was considered, and results were presented for steady, laminar, fully developed parabolic flow in straight airways. Regarding particle size, our model shows that decrease in particle size leads to reduced efficiency of sedimentation but increased intensity of Brownian diffusion, as expected. We studied the effects due to particle shape alone by varying the aspect ratios and diameters of the microfibers simultaneously, such that the effect of particle mass does not come into play. Our model suggests that deposition both due to gravitational settling and Brownian diffusion decreases with increased fiber aspect ratio. Regarding the combined effect of fiber size and shape, our results suggest that for particles with elongated shape the probability of reaching the vulnerable gas-exchange region in the deep lung is highest for particles with diameters in the size range 10–100 nm and lengths of several micrometers. Note that the popular multi-walled carbon nanotubes fall into this size-range.     

An application of the Error-in-Variables Model—parameter estimation from Van Ness-type vapour-liquid equilibrium experiments

The Error-in-Variables Model (EVM) provides a means for estimating parameter values in mathematical models where there is error in every measured variable. This is a distinct improvement over the Method of Least Squares in most situations because the latter requires that there be error in measuring only one of the variables. As an example of the use of EVM, a method is presented for estimating Wilson equation parameters in binary and ternary vapour-liquid equilibrium where the data are obtained using the Van Ness experimental technique. The application presents unusual difficulties in that the compositions of the phases are not measured directly and the total quantity of one component is only measured as the sum of a series of increments. Data for the ternary system n-heptane/n-propanol/1-chlorobutane and the binary system n-heptane/1-chlorobutane are analysed by the proposed method, and the results are compared with the empirical results of Sayegh et al. (1979). The results of the EVM analysis are considerably more accurate. Analysis of the residuals obtained by the EVM procedure suggest serious deficiencies in the thermodynamic model.     

Model of morphology evolution in the growth of polycrystalline β-SiC films

The growth of β-SiC films via chemical vapor deposition (CVD) has been under intensive investigation because this is viewed to be an enabling material for a variety of new semiconductor devices in areas where silicon cannot effectively compete. However, the difficulty in achieving single-crystal or highly textured surface morphology in films with low bulk defect density has limited the use of β-SiC films in electronic devices. Although several researchers have reported results relating the morphology of β-SiC films to deposition parameters, including substrate temperature and gas composition, detailed knowledge of the effects of deposition parameters on film morphology and crystallographic texture is still lacking. If these relationships between deposition parameters and film morphology can be quantified, then it may be possible to obtain optimal β-SiC film morphologies via CVD for specific applications such as high-power electronic devices.The purpose of this study is to predict the dependence of the surface morphology of β-SiC films grown by CVD on substrate temperature and inlet atom ratio of Si:C, and to model the morphological evolution of the growing polycrystalline film. The Si:C ratio is determined by the composition of the reactant gases, propane (C₃H₈) and silane (SiH₄). A two-dimensional numerical model based on growth rate parameters has been developed to predict the evolution of the surface morphology. The model calculates the texture, surface roughness, and grain size of continuous polycrystalline β-SiC films resulting from growth competition between nucleated seed crystals of known orientation. Crystals with the fastest growth direction perpendicular to the substrate surface are allowed to overgrow all other crystal orientations. When a continuous polycrystalline film is formed, the facet orientations of crystals are represented on the surface. In the model, the growth parameter α_2D, the ratio of the growth rates of the {10} and {11} faces, determines the crystal shapes and, thus, the facet orientations of crystals. The growth rate parameter α_2D used in the model has been derived empirically from the textures of continuous β-SiC films reported in the literature.     

Research on the Degradation Kinetics Model in the Drying Process of Chinese Herb

Curative compositions such as catolpol in Rehmannia Glutinosa, flavone in Ophiopogon Japonicus and ginsenoside Re in Panax Ginseng in Chinese herbs were measured as the experimental indices by the method of high performance liquid chromatography under different drying conditions. The reaction order and parameters of the degradation kinetics model were determined and the model was verified by experiments. It was indicated that by comparing with the thin drying method, the prospective model could predict the degradation of curative compositions with drying time, temperature and moisture content of herbal materials with enough precision and could be used to simulate the degradation in the drying process of Chinese herb.     

Wind energy — the fuel of the future

Over the last six years wind power has become the world's fastest growing energy technology, and growth rates of 20% a year are predicted for the next     

A Micro-layer Model for the Lubrication Effect Near Collisions of Immersed Particles

A micro-layer model is proposed to account for the lubrication effect of liquid layer near collisions of immersed particles at moderate particle Reynolds number. This new model is to allow determination of the pressure profile within the micro-layer including the fluid inertia and viscosity. Then a correction based on the micro-layer model is applied to unsteady 3-D direct simulation of a particle approaching another one. The simulation is based on a modified immersed boundary method with direct force scheme. The quantitative agreement between numerical and experimental results validates the model presented in the study. The simulation results show that the fluid is squeezed prior to contact. When a particle approaches a flat wall or another particle, the lubrication force, obtained by integrating the pressure profile over the particle surface, is increased and prevents the particle from approaching. The model predicts that the velocity of approaching particle starts to decrease when separation distance of particles is less than 0.1dp, where dp is the particle diameter.     

Mathematical Modeling of Gas Flow in the Separation Zone of a Cocurrent Vortex Apparatus in Terms of the kT–ε Turbulence Model

A mathematical model of the gas flow in vortex apparatuses is proposed, which is based on numerically solving a set of Navier–Stokes and continuity differential equations for the k _T– turbulence model. The model enables one to reveal specific features of the aerodynamic interaction of two flows swirling in the same direction. Gas streamlines, turbulent kinetic energy isolines, and turbulent viscosity isolines are determined at various operating and design parameters. The parameters that ensure a high separation efficiency of an apparatus are found.     

Structure Optimization of the Toxic Conformation Model of Amyloid β42 by Intramolecular Disulfide Bond Formation

Amyloid β (Aβ) oligomers play a critical role in the pathology of Alzheimer's disease. Recently, we reported that a conformation-restricted Aβ42 with an intramolecular disulfide bond through cysteine residues at positions 17/28 formed stable oligomers with potent cytotoxicity. To further optimize this compound as a toxic conformer model, we synthesized three analogues with a combination of cysteine and homocysteine at positions 17/28. The analogues with Cys-Cys, Cys-homoCys, or homoCys-Cys, but not the homoCys-homoCys analogue, exhibited potent cytotoxicity against SH-SY5Y and THP-1 cells even at 10 nM. In contrast, the cytotoxicity of conformation-restricted analogues at positions 16/29 or 18/27 was significantly weaker than that of wild-type Aβ42. Furthermore, thioflavin-T assay, non-denaturing gel electrophoresis, and morphological studies suggested that the majority of these conformation-restricted analogues exists in an oligomeric state in cell culture medium, indicating that the toxic conformation of Aβ42, rather than the oligomeric state, is essential to induce cytotoxicity.     

HKT Transporters—State of the Art

The increase in soil salinity poses a serious threat to agricultural yields. Under salinity stress, several Na⁺ transporters play an essential role in Na⁺ tolerance in plants. Amongst all Na⁺ transporters, HKT has been shown to have a crucial role in both mono and dicotyledonous plants in the tolerance to salinity stress. Here we present an overview of the physiological role of HKT transporters in plant Na⁺ homeostasis. HKT regulation and amino acids important to the correct function of HKT transporters are reviewed. The functions of the most recently characterized HKT members from both HKT1 and HKT2 subfamilies are also discussed. Topics that still need to be studied in future research (e.g., HKT regulation) as well as research suggestions (e.g., generation of HKT mutants) are addressed.     

Application of the Maxwell–Stefan theory to the membrane electrolysis process: Model development and simulations

A model is developed which describes the mass transfer in ion-selective membranes as used in the chloralkali electrolysis process. The mass transfer model is based on the Maxwell–Stefan theory, in which the membrane charged groups are considered as one of the components in the aqueous mixture. The Maxwell–Stefan equations are re-written in such a way that the current density can be used as an input parameter in the model, which circumvents an extensive numerical iterative process in the numerical solution of the equations. Because the Maxwell–Stefan theory is in fact a force balance, and the clamping force needed to keep the membrane charged groups in its place is not taken into account, the model is basically over-dimensioned: the mole fraction of the membrane can be calculated by using the equivalent weight (EW) of the membrane or by using the equations of continuity. In this work, the latter method has been chosen. The results of the computer model were verified in several ways, which show that the computer model gives reliable results. Several exploratory simulations have been carried out for a sulfonic layer membrane and the conditions as encountered in the chloralkali electrolysis process. As there are no (reliable) Maxwell–Stefan diffusivities available for a Nafion membrane, in this trend study the diffusivities were all chosen equal at a more or less arbitrary value of 1.10⁻¹⁰ m² s⁻¹. Due to this, the absolute values of several performance parameters are incorrect as compared with industrial chloralkali operation (e.g. an unrealistically high current efficiency of 95.7% was found), but the model can still be used to obtain trends. For example, it is shown that the thickness of the membrane hardly increases the current efficiency (CE), however, the required potential drop proportionally increases with thickness. The pH rapidly increases to values greater than 12 just inside the membrane at the anolyte side. Moreover, for different values of the pH in the anolyte, the pH profiles inside the membrane nearly coincide with each other. A change in the anolyte strength does not have a significant effect on the performance of the membrane. At low values of the current density, a high value of the current efficiency is found. However, this is not due to a low OH⁻ counter flux, but to the simultaneous transport of OH⁻ and Cl⁻ towards the catholyte.     

Influence of the nature of the activating molecules on the catalytic activity of cobalt—molybdenum/alumina catalysts

The effectiveness of the activation of a commercial CoMo/Al₂O₃ catalyst was evaluated using five different sulphiding agents (carbon disulphide, dimethyldisulphide, butanethiol, thiophene and hydrogen sulphide) at high pressure (3 MPa) in the 300–450°C temperature range. The results indicate that the behaviour of the cobalt—molybdenum catalysts depends strongly on the nature of the activating molecule as well as the pretreatment temperature. The catalyst exhibited two different patterns, below and above 400°C. At 300°C, differences in the degree of sulphidation and in activities were observed when using different activating molecules. The most efficient of the sulphiding agents used was butanethiol while the least efficient one was thiophene. The activity of the catalyst was a maximum when carbon disulphide was used at 350°C or the other sulphiding agents at 400°C. We attributed the differences of effects of the various molecules to coupling effects between reduction and sulphidation reactions. Under the activation giving excellent activities, the coupling effect is optimal. Using carbon disulphide or thiophene at temperatures higher than 400°C, a catalyst with strongly decreased activity was produced. This behaviour is attributed to coke formation during sulphidation.     

Inhalation of Silver Nanomaterials—Seeing the Risks

Demand for silver engineered nanomaterials (ENMs) is increasing rapidly in optoelectronic and in health and medical applications due to their antibacterial, thermal, electrical conductive, and other properties. The continued commercial up-scaling of ENM production and application needs to be accompanied by an understanding of the occupational health, public safety and environmental implications of these materials. There have been numerous in vitro studies and some in vivo studies of ENM toxicity but their results are frequently inconclusive. Some of the variability between studies has arisen due to a lack of consistency between experimental models, since small differences between test materials can markedly alter their behaviour. In addition, the propensity for the physicochemistry of silver ENMs to alter, sometimes quite radically, depending on the environment they encounter, can profoundly alter their bioreactivity. Consequently, it is important to accurately characterise the materials before use, at the point of exposure and at the nanomaterial-tissue, or “nanobio”, interface, to be able to appreciate their environmental impact. This paper reviews current literature on the pulmonary effects of silver nanomaterials. We focus our review on describing whether, and by which mechanisms, the chemistry and structure of these materials can be linked to their bioreactivity in the respiratory system. In particular, the mechanisms by which the physicochemical properties (e.g., aggregation state, morphology and chemistry) of silver nanomaterials change in various biological milieu (i.e., relevant proteins, lipids and other molecules, and biofluids, such as lung surfactant) and affect subsequent interactions with and within cells will be discussed, in the context not only of what is measured but also of what can be visualized.     

Diffusion behaviour of the lead—acetate system

Variations in polarographic diffusion current constants for the lead—acetate system at constant ionic strength are shown to correlate with published equilibrium data. There is evidence that different types of solute—solute and solute—solvent interactions can be detected and distinguished by means of diffusion parameters.     

Report of the Oil Color Committee—1948

Conclusions The data completed on oils and on nickel sulfate solutions indicate that there is a standard deviation of up to 2% transmittance between measurements made by different laboratories on different instruments. This standard deviation is decreased by one-half when measurements are made by a single laboratory on a single instrument. The data indicate that nickel sulfate may be a satisfactory solution to use in standardizing the instruments in use in the various laboratories. The results obtained on the 12 oils submitted for readings indicate that about the same degree of reliability is obtained spectrophotometrically as with the Lovibond system at low color levels. At high color levels the spectrophotometer shows considerably more reproducibility. It is impossible to tell from the data obtained whether a single number system, such as a density measurement of 550 mμ., or a color index value, consisting of some function of measurements at two or more wavelengths, would be the most suitable for general measurements.