Effects of deposition parameters on SiCln (n=0-2) densities in SiCl4 glow discharge plasma

The relative densities of SiCl_n (n=0-2) in SiCl₄ radio frequency (rf) glow discharge plasma are measured by mass spectrometry. The effects of discharge parameters, including rf power, discharge pressure, substrate temperature and SiCl₄ flow rate on the relative densities of SiCl_n (n=0-2) are investigated in detail. The experimental results demonstrate that the relative densities of SiCl_n (n=0-2) in SiCl₄ plasma are dependent strongly on these discharge parameters. An optimum configuration of discharge parameters (low rf power, high discharge pressure, low substrate temperature and low flow rate), which enhanced the formation of SiCl_n (n=0-2) radicals, was searched. Further, researching of SiCl_n (n=0-2) spatial distribution for seeking a suitable deposition condition is beneficial for understanding the deposition mechanism of thin films.     

The sensitivity of the calculation of ΔV to vehicle and impact parameters

ΔV is frequently used to describe collision severity, and is often used by accident investigators to estimate speeds of vehicles prior to a collision, and by researchers looking for correlations between severity and outcome. This study identifies how ΔV varies over a wide range of input uncertainties allowing the direct comparison of different methods of input data collection in terms of their effect on uncertainty in the calculation of ΔV.     

Characterization and mapping of carotenoids in the algae Dunaliella and Phaeodactylum using Raman and target orthogonal partial least squares

A method was developed for the characterisation of carotenoid pigments in algal species using Raman spectroscopy in combination with multivariate hyperspectral analysis. Target orthogonal partial least squares (T-OPLS) operates by designating one known reference spectrum as the target. The target spectrum is put as the single y column in an OPLS regression model where the X matrix consists of the unfolded image spectra as variables in its columns. The spectral shape of the OPLS first orthogonal target score enabled us to verify the peak positions of the standard, and detect new peaks, not present in the reference standard. It was shown that the mixture of carotenoids present in the algae did not fully match the reference spectrum, however, the method provided enough information to make an analysis possible also in this case. The image results were constructed from the OPLS loading vectors that were showing a correlation map for the reference spectrum from the predictive loadings and maps of the occurrence of deviations from the orthogonal loadings.     

Antioxidant enzyme status in Azolla microphylla in relation to salinity and possibilities of environmental monitoring

The rice field biofertilizer Azolla microphylla was subjected to salinity treatment (EC 4.70 and 8.72 ds/m) and growth, nitrogen fixation and the activity of antioxidant enzymes such as superoxide dismutase, ascorbate peroxidase and catalase were studied. Salinity exposure resulted in decreased growth rate and nitrogen fixation by the organism. Further a positive correlation between the peroxide content, and antioxidant enzyme activity in relation to the level of salinity was also observed. From the results we conclude that the observed changes in the antioxidant enzyme profile of A. microphylla could be effectively used to bio-monitor the toxic effect due to salinity. An increase in the activity of antioxidant enzymes could be therefore exploited further to develop biosensors to detect harmful free radicals and the extent of cell damage in the cells.     

Retention of oxalates in frozen products of three brassica species depending on the methods of freezing and preparation for consumption

The investigation showed that fresh brassicas: Brussels sprouts, broccoli, green cauliflower and white cauliflower respectively contained 50 mg, 67 mg, 72 mg and 95 mg oxalates in 100 g fresh matter. Soluble oxalates constituted 70%, 40%, 40% and 54% of total oxalates respectively. The cooked product obtained from traditionally prepared frozen vegetables (blanching-freezing-refrigerated storage-cooking) contained 45-66% of soluble oxalates. The product obtained from frozen vegetables produced using the modified method (cooking-freezing-refrigerated storage-defrosting and heating in a microwave oven) contained more oxalates than that obtained using the traditional method. The oxalate: calcium ratio in fresh vegetables varied considerably: 0.63 (Brussels sprouts); 1.10 (broccoli); 1.27 (green cauliflower); and 2.42 (white cauliflower). In products prepared for consumption the ratios were lower. The proportion of calcium bound as calcium oxalate differed between the vegetables investigated, but the treatments applied did not influence this parameter. The apparent retention of oxalate overestimated the true retention.     

A scheme for solving strongly coupled chemical reaction equations appearing in the removal of SO2 and NOx from flue gases

The removal of NO_x from mixtures of NO-NO₂-N₂ and NO-NO₂-O₂-H₂O is discussed theoretically in this study, and the removal of ₂SO and xNO is further discussed when a gas system of NO_x-N₂-O₂-H₂O contains CO₂ and SO₂. The involved chemical reaction rate equations in the process of SO₂/NO_x removal are solved numerically using Treanor's method, in which a scheme separating chemical reactions into fast and slow groups has been proposed for improving the numerical stability. Numerical results show that the contribution of ion reactions to xNO removal is negligible, and that high temperature is not beneficial for the NO oxidation. However, high concentration of O₂ is conducive to the NO oxidation. Addition of water facilitates the NO_x removal, and increasing water vapor concentration enhances the NO_x removal efficiency; inclusion of CO₂ and SO₂ into the system favors the NO removal.     

Influence of Se on the electron mobility in thermal evaporated Bi2(Te1−xSex)3 thin films

Thermoelectric solid solutions of Bi₂ (Te_1−xSe_x)₃ with x = 0, 0.2, 0.4, 0.6, 0.8 and 1 were grown using the Bridgman technique. Thin films of these materials of different compositions were prepared by conventional thermal evaporation of the prepared bulk materials. The temperature dependence of the electrical conductivity σ, free carriers concentration n, mobility μ_H, and seebeck coefficient S, of the as-deposited and films annealed at different temperatures, have been studied at temperature ranging from 300 to 500 K. The temperature dependence of σ revealed an intrinsic conduction mechanism above 400 K, while for temperatures less than 400 K an extrinsic conduction is dominant.The activation energy, ΔE, and the energy gap, E_g, were found to increase with increasing Se content. The variation of S with temperature revealed that the samples with different compositions x are degenerate semiconductors with n-type conduction. Both, the annealing and composition effects on Hall constant, R_H, density of electron carriers, n, Hall mobility, μ_H, and the effective mass, m^∗/m₀ are studied in the above temperature range.     

Fabrication of a novel micro-nano fibrous nonwoven scaffold with Antheraea assama silk fibroin for use in tissue engineering

The success of developing artificial organs by tissue engineering depends on scaffold properties and architecture. Here, we describe the fabrication of an Antheraea assama fibroin based novel micro-nano fibrous nonwoven scaffold. The morphological and chemical characterization was done by scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR) respectively, which demonstrated the formation of scaffold with micro-nano architecture. The biocompatibility was assessed in vitro by haemolysis and cytotoxicity assays, whereby the scaffold was found to be nontoxic and efficient in supporting cell adhesion and growth.     

The reaction mechanism of the spray Ion Layer Gas Reaction process to deposit In2S3 thin films

The spray Ion Layer Gas Reaction (ILGAR) is a well-established, patented and commercial process used primarily to deposit In₂S₃ as buffer layers in thin film solar cells. In this paper we investigate the growth mechanism of the spray In₂S₃ ILGAR process by characterising the intermediate growth stages of films, following the growth mechanism with a quartz crystal microbalance and tracking the gaseous side-and-intermediate products during film growth, using a mass spectrometer. A basic growth mechanism model is then proposed based on an aerosol assisted chemical vapour deposition of an In(O_x,Cl_y,(OH)_z) film, as the first stage process, followed by the conversion of the intermediate film using H₂S gas to In₂S₃.     

Preparation of H-bar cross-sectional specimen for in situ TEM straining experiments: A FIB-based method applied to a nitrided Ti-6Al-4V alloy

The in situ tensile straining of cross-sectional specimens inside a TEM is intrinsically very difficult to perform despite its obvious interest to study interfaces of surface treated materials. We have combined a FIB-based method to produce H-bar specimens of a nitrided Ti-6Al-4V alloy and in situ TEM straining stage, to successfully study the plastic deformation mechanisms that are activated close to the nitrided surface in the Ti-based alloy.     

Wavelet neural networks for modelling high pressure inactivation kinetics of Listeria monocytogenes in UHT whole milk

The aim of the present work was to investigate the applicability of a Wavelet Neural Network to describe the inactivation pattern of Listeria monocytogenes by high hydrostatic pressure in ultra high temperature (UHT) whole milk, and evaluate its performance against models used in predictive microbiology such as the re-parameterized Gompertz and modified Weibull equations. A comparative study with linear partial least squares regression (PLS-R) as well as neural network (NN) models demonstrated on the same dataset has been also considered. Milk was artificially inoculated with an initial population of the pathogen of ca. 10⁷ CFU/ml and exposed to a range of high pressures (350, 450, 550, 600 MPa) for up to 40 min at ambient temperature (ca. 25 °C). Typical survival curves were obtained including a shoulder, a log-linear and a tailing phase. Increasing the magnitude of the applied pressure resulted in increasing levels of inactivation. Modelling approaches provided good fit to experimental training data as inferred by the low values of the root mean squared error (RMSE) and the high values of regression coefficient (R²). Models were validated at 400 and 500 MPa with independent experimental data. First or second order polynomial models were employed to relate the inactivation parameters to pressure, whereas the wavelet network as well as the PLS and NN models were utilised as a one-step modelling approach. The prediction performance of the proposed learning-based network was better at both validation pressures. The development of accurate models to describe the survival curves of micro-organisms in high pressure treatment would be very important to the food industry for process optimisation, food safety and would eventually expand the applicability of this non-thermal process.     

Investigation of the tribological behavior and its relationship to the microstructure and mechanical properties of a-SiC:H films elaborated by low frequency plasma assisted chemical vapor deposition

Amorphous hydrogenated silicon carbide (a-SiC:H) coatings are promising candidates for tribological applications in the mechanical and aeronautical industries. Alternately high values of hardness H (15 < H < 32 GPa) and elastic modulus E contribute to their good wear resistance as well as to a low friction coefficient. The latter has been found to vary in the range 0.1 < μ < 0.65, depending upon the microstructure of the layers. The roughness of the films determined by atomic force microscopy is in all cases low (Ra ~ 5 nm). Comparisons between the tests carried out in air and those performed under vacuum conditions point to a substantial role of the adhesive part of the friction coefficient in vacuum. They also highlight the role played by the transfer layer between the film and the pin in producing a low friction coefficient for several coatings. This transfer layer consists chiefly of silicon and oxygen (O/Si ~ 2), whilst low quantities of carbon are also present.