Membrane extraction of a new antibiotic (Shengjimycin): equilibrium and mass transfer analysis

BACKGROUND: During the last two decades, separations based on liquid membrane technology have been demonstrated to be a potentially attractive process for a large number of industrial separations. The advantages of this technology over the current separation processes allowed its commercialization in the area of chemical/environmental applications (for the removal of toxic metals). Efforts are being devoted to biotechnological processes where membrane extraction has an added advantage of improving the productivity by removing inhibitory product during its production cycle. In this article the applicability of a membrane extraction technique based on hollow‐fibre membrane modules is investigated to extract a new antibiotic, Shengjimycin (SJM). SJM is produced in a multicomponent fermentation broth, from which the main components required to be separated selectively. RESULTS: From equilibrium experiments, sunflower oil, a cheap and less toxic solvent, was found to be good for the extraction of SJM at its natural pH of 7.2–7.8. Addition of a small amount (1.5%) of Amberlite LA‐2 (a carrier) in the solvent could intensify the process to achieve a high distribution coefficient. The process using this organic phase (Amberlite LA‐2 in sunflower oil) gave good extraction (ca 70%) within 3–4 h in a pilot‐scale hollow‐fibre membrane module. This new system is preferred over the toxic solvents being used or tried because of its cost, less toxicity, low environmental impact and operator‐friendliness. CONCLUSIONS: Because of the above‐mentioned favourable characteristics this membrane extraction method has the potential to be sustainable and effective as it has shown selective separation of the desired component from a multicomponent mixture. Copyright © 2011 Society of Chemical Industry     

Effects of Surface Processing on the Response of CZT Gamma Detectors: Studies with a Collimated Synchrotron X-Ray Beam

Using a microscale X-ray mapping technique incorporating a synchrotron beam, we are able to reveal the fine details of the surface properties in cadmium zinc telluride (CZT) semiconductor detectors. A detector, with various degrees of surface roughness, was irradiated by a high-spatial-resolution X-ray beam. The detector’s response was analyzed and displayed as a two-dimensional (2-D) map, and the charge collection was obtained from the peak positions in the spectra versus the beam’s location, which reflects the local material properties. We noted the correlation between the 2-D image and the spectral response of the charge collection at different locations on the surface area, which indicates that a rough surface tends to contain trapping centers, thereby enhancing leakage current and distorting the signal. We also discuss our observations on the transition effect at the boundary area of a rough and a smooth surface under identical conditions.     

Seebeck Coefficient in Nonparabolic Bulk Materials

We address a simplified formulation of the Seebeck coefficient (S) in degenerate bulk III–V and skutterudite materials within the framework of the k·p formalism, the conduction-band electrons of which obey Kane’s second-order energy dispersion relation. Incorporation of longitudinal acoustic phonon, screened ionized impurity, and polar optical phonon scatterings explains the origin of the experimentally determined change of sign of S in a skutterudite material such as CoSb₃. The use of an overlap function due to band nonparabolicity significantly affects the carrier relaxation time when compared with the corresponding parabolic energy dispersion relation. The well-known expression of S for nondegenerate wide-band-gap materials is obtained as a special case, and this compatibility is an indirect test of the generalized theoretical analysis. The present model of S also agrees well with the available experimental data on such materials over a wide range of temperatures and can be carried forward for accurate analysis of the thermoelectric figure of merit.     

To What Extent Do Whey and Casein Micelle Proteins Influence the Morphology and Properties of the Resulting Powder?

How the type of protein influences particle morphology remains a hot topic of debate. In this study we focused on the drying behavior of two major milk protein types; that is, whey protein and native micellar caseins. To improve understanding of the role of each protein in the particle-forming mechanisms, seven mixtures containing different whey proteins to caseins ratios were investigated. A monodisperse spray dryer (MDSD) was used to produce uniform particles by drying monodispersed droplets in a hot, dry air flow. Single particles were also obtained from the same material using single droplet drying in a pendant configuration. Powders were characterized according to their physical characteristics and their rehydration properties. It was demonstrated that particle morphology was mainly governed by the type of protein matrix, almost regardless of the drying kinetics, which differed considerably between MDSD and single droplet drying. Controlling product formulation thus represents a potential means by which to tune particle morphology and therefore the functional properties of powder.     

Optical characterisation of materials and systems for daylighting

The measurement of BRTF (Bi-directional reflectance and transmittance function) is described using a new instrument which is capable of supplying BRTF data and algorithms for use in computer simulations directly on diffuse materials and indirectly on large samples and sub-systems. A high sensitivity and dynamic range is needed to achieve low minimum observable BRTF and the role of angular resolution are discussed with examples. Forward scattering with extended tails is found to dominate pigmented polycarbonate. Slatted blinds are discussed as examples of systems where azimuth is important.     

Free convection from a vertical permeable circular cone with non-uniform surface temperature

Summary Laminar free convection from a vertical permeable circular cone maintained at nonuniform surface temperature is considered. Non-similar solutions for boundary-layer equations are found to exist when the surface temperature follows the power law variations with the distance measured from the leading edge. The numerical solutions of the transformed non-similar boundary-layer equations are obtained by using three methods, namely, (i) a finite difference method, (ii) a series solution method, and (iii) an asymptotic solution method. Solutions are obtained in terms of skin friction, heat transfer, velocity profile and temperature profile for smaller values of Prandtl number and temperature gradient are displayed in both tabular and graphical forms. Finite difference solutions are compared with the solutions obtained by perturbation and asymptotic techniques and found to be in excellent agreement.     

Wall-slip effects in SnAgCu solder pastes used in electronics assembly applications

Solder paste is the most important strategic bonding material used in the assembly of surface mount components in electronics manufacturing. As the trend towards miniaturisation of electronic products continues, there is an increasing demand for better understanding of the flow and deformation that is, the rheological behaviour of solder paste formulations. Wall slip plays an important role in characterising the flow behaviour of solder paste materials. The problem of wall slip arises due to the various attractive and repulsive forces acting between the solder particles and the walls of the measuring geometry. These interactions could lead to the presence of a thin solvent layer adjacent to the wall, which gives rise to slippage. In rheological measurements, slip effects can generally be avoided by using roughened surfaces for measuring geometries. In this paper, a novel technique is developed to study the effect of wall slip in the rheological measurements of lead-free solder paste. The viscosity and oscillatory data obtained for three different solder paste samples (from measuring geometries of different surface roughness) have been analysed and compared. In viscosity measurements, slip effects were dominant at low shear rates and the use of serrated surfaces was found to be quite effective in minimizing slip effects. Oscillatory measurements were also affected by roughening the surfaces of measuring geometries.     

Effect of sintering parameters (time and temperature) upon the fabrication process of organic binder-based metallic hollow sphere

Metallic hollow spheres (MHSs) are developed to be used in structural applications in syntactic and metal foams. These foams are lightweight and energy-absorbing structures which also can be used for acoustic insulation. In this study, the fabrication process of MHSs with optimum mechanical properties has been investigated. To achieve this goal, polystyrene spheres were coated with iron powder and an organic binder. During the multi-stage heat treatment, the green spheres were sintered into MHSs. Sintering was done at various temperatures (1125, 1150, 1175 and 1200°C) at different durations (3:30, 4:30 and 5:30?h). The influence of the different sintering durations and temperatures on mechanical features, microstructure and density was studied as well. The obtained results indicate that samples that were sintered at the temperature of 1175°C for 4:30?h resulted in superior mechanical and physical properties.