			Home About us Contact

Different Process Parameters (different + process_parameter)

Distribution by Scientific Domains

Chemistry	50%

Selected Abstracts

Production, purification and thermal characterisation of invertase from a newly isolated Fusarium sp. under solid-state fermentation

INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 7 2008
Iram Shaheen
Summary Production of invertase employing a newly isolated Fusarium sp. under solid-state fermentation was optimised. Different process parameters were optimised. The maximum enzyme activity under optimum conditions was 47.23 ± 2.12 U gds,1 with nitrogen additives. The enzyme was purified by ammonium sulphate precipitation, diethylaminoethyl cellulose ion-exchange chromatography and Sephadex gel filtration. This protocol gave 20.25-fold purification and 5.53% recovery. The optimum pH and temperature for activity were 5.0 and 50 °C. The Km and Vmax values for the enzyme were 8.33 mm and 21.48 ,mol min,1, respectively. A detailed kinetic study of thermal inactivation has been carried out. Enthalpy of activation (,H*) decreased when entropy (,S*) of activation increased at higher temperatures. Moreover, free energy of denaturation (,G*) increased at higher temperature making the enzyme thermally stable. A possible explanation for the thermal inactivation of invertase at higher temperatures is also discussed. [source]

Dehydration studies using a novel multichamber microscale fluid bed dryer with in-line near-infrared measurement

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2003
Eetu Räsänen
Abstract The purpose of this research was to study the effect of two process parameters (temperature and moisture content) on dehydration behavior of different materials using a novel multichamber microscale fluid bed dryer with a process air control unit and in-line near-infrared (NIR) spectroscopy. The materials studied were disodium hydrogen phosphates with three different levels of hydrate water and wet theophylline granules. Measured process parameters of fluid bed drying were logged, including in-line NIR signals. Off-line analyses consisted of X-ray powder diffraction patterns, Fourier transform NIR spectra and moisture contents of studied materials. During fluid bed drying, the stepwise dehydration of materials was observed by the water content difference of inlet and outlet air, the pressure difference over the bed, and the in-line NIR spectroscopy. The off-line analysis confirmed the state of solid materials. The temperature and the moisture content of the process air were demonstrated to be significant factors for the solid-state stability of theophylline. The presented setup is a material and cost-saving approach for studying the influence of different process parameters on dehydration behavior during pharmaceutical processing. © 2003 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 92:2074,2081, 2003 [source]

Long-Term Properties of Butt-Welded Poly(propylene)

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 4 2003
Ernst Schmachtenberg
Abstract It is still not clear why the long-term properties of plastic weld seams can only be differentiated by the very expensive medium tensile creep tests. One hypothesis for justifying this is based on the change in the structure of the weld seam surroundings, another cites the consumption of antioxidants and the following ageing in the weld seam area to be responsible for this. Butt-welded weld seams made of poly(propylene) were systematically produced under different process parameters. Corresponding to the particular hypothesis, these weld seams were then analyzed in various ways to find correlations or to prove one of the hypotheses. Regarding their short-term weld seam quality, the analyzed weld seams could not be differentiated through short-term tensile or short-term bend test. However, the medium tensile creep tests showed significant differences in both time until failure and long-term weld seam quality. Under long-term loading, the start of the brittle crack could be detected in most weld seams in the fine spherulite-zone or between this zone and the area of the flow lines. This demonstrated again that only long-term tests are suitable for examining different weld seam qualities. Depending on the welding parameters, times until failure decline with increasing heated-tool temperature and heating time. Though these parameters lead to a higher consumption of antioxidants in the weld seam, a degradation was not detected in the breaking area. In fact, increasing heated-tool temperatures and heating times, as well as higher joining pressures lead to a change in the internal structure of the material. This can be seen in morphological structure analyses in the larger bend of the entire weld seam area. A larger bend, however, correlates with higher residual stresses in the weld seam. In the medium tensile creep tests, these residual stresses as well as the tensile stress in the border region and the compressive stress in the middle are superimposed by the tensile stress resulting from the test stress. Thus a greater bend of the weld seam area and higher residual stresses in the weld seam itself lead to shorter times until failure in medium tensile creep tests. Schematic representation of the formation of residual stresses in a weld seam and residual stresses in the different bended weld seam areas. [source]

Characterization of cell viability during bioprinting processes

BIOTECHNOLOGY JOURNAL, Issue 8 2009
Kalyani Nair
Abstract Bioprinting is an emerging technology in the field of tissue engineering and regenerative medicine. The process consists of simultaneous deposition of cells, biomaterial and/or growth factors under pressure through a micro-scale nozzle. Cell viability can be controlled by varying the parameters like pressure and nozzle diameter. The process itself can be a very useful tool for evaluating an in vitro cell injury model. It is essential to understand the cell responses to process-induced mechanical disturbances because they alter cell morphology and function. We carried out analysis and quantification of the degree of cell injury induced by bioprinting process. A parametric study with different process parameters was conducted to analyze and quantify cell injury as well as to optimize the parameters for printing viable cells. A phenomenological model was developed correlating the percentage of live, apoptotic and necrotic cells to the process parameters. This study incorporates an analytical formulation to predict the cell viability through the system as a function of the maximum shear stress in the system. The study shows that dispensing pressure has a more significant effect on cell viability than the nozzle diameter. The percentage of live cells is reduced significantly (by 38.75%) when constructs are printed at 40 psi compared to those printed at 5 psi. [source]