Preparation and characterization of poly(vinyl chloride)/polystyrene/poly(ethylene glycol) hollow‐fiber ultrafiltration membranes

Hollow‐fiber ultrafiltration (UF) membranes were prepared from blends of poly(vinyl chloride) (PVC) and polystyrene (PS) with a dry/wet phase inversion method. Poly(ethylene glycol) (PEG) and N,N‐dimethylacetamide were used as the additive and solvent, respectively. The effects of the PEG concentration in the dope solution as an additive on the cross sections and inner and outer surface morphologies, permeability, and separation performance of the hollow fibers were examined. The mean pore size, pore size distribution, and mean roughness of both the inner and outer surfaces of the produced hollow fibers were determined by atomic force microscopy. Also, the mechanical properties of the hollow‐fiber membranes were investigated. UF experiments were conducted with aqueous solutions of poly(vinyl pyrrolidone) (PVP; K‐90, M_w = 360 kDa). From the results, we found that the PVC/PS hollow‐fiber membranes had two layers with a fingerlike structure. These two layers were changed from a wide and long to a thin and short morphology with increasing PEG concentration. A novel and until now undescribed shape of the nodules in the outer surfaces, which was denoted as a sea‐waves shape, was observed. The outer and inner pore sizes both increased with increasing PEG concentration. The water permeation flux of the hollow fibers increased from 104 to 367 L m^?2 h^?1 bar^?1) at higher PEG concentrations. The PVP rejection reached the highest value at a PEG concentration of 4 wt %, whereas at higher values (from 4 to 9 wt %), the rejection decreased. The same trend was found also for the tensile stress at break, Young's modulus, and elongation at break of the hollow fibers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 989‐1004, 2013     

A Spanish Inter-laboratory Comparison on the Characterization of Sterilization Autoclaves

Sterilization autoclaves are devices used to sterilize equipment and supplies; their users require a periodic determination of their performance to ensure that the required temperature is reached and maintained for the predefined time interval. Within the ENAC (Entidad Nacional de Acreditación, Spanish national accreditation body) Temperature and Humidity Technical Subcommittee, it was decided to carry out an inter-laboratory comparison on the characterization of sterilization autoclaves aiming to demonstrate the equivalence among the test procedures of the different participants. This paper presents the data processing and the results of this comparison that showed some discrepancies in the stability and uniformity measurements due to different parameter definitions and a probable underestimation of some uncertainty sources. The results show good agreement among the participants in the estimation of the set-point correction, while the estimation of the device stability and uniformity was not compatible in some cases. The use of wired or wireless sensors did not bias the results, but the laboratories that used pt-100 obtained results that underestimated the value of the thermal stability, probably due to their higher thermal mass and response time.     

An algorithm for adaptive refinement of triangular element meshes

A simple algorithm is developed for adaptive and automatic h refinement of two-dimensional triangular finite element meshes. The algorithm is based on an element refinement ratio that can be calculated from an a posteriori error indicator. The element subdivision algorithm is robust and recursive. Smooth transition between large and small elements is achieved without significant degradation of the aspect ratio of the elements in the mesh. Several example problems are presented to illustrate the utility of the approach.     

Using distilled water for the extraction of mucosal antibodies and the subsequent application in RSV neutralization test

Virus neutralization (VN) is an important functional test for evaluating RSV vaccines, also encompassing in mucosal secretion of the respiratory tract considering the infection route. In our previous study, an immunoglobin extraction method described by Bergquist et al. was adopted for RSV ELISA, but it was not suitable for virus neutralization test due to the cell toxicity of the 2% saponin solution used for the antibody extraction. In order to overcome this problem, several solvents including distilled water were tested in the present study for the capacity to extract immunogloblins. Antibodies in the extracts were evaluated and compared by ELISA. Distilled water was as efficient as the 2% saponin solution for extraction of total IgA, RSV specific IgA and IgG. More importantly, the organ extracts obtained subsequently could be used for virus neutralization test without causing adverse effect on the cell culture. Therefore, distilled water was finally chosen as the solvent for immunoglobulin extraction from mucosal organs when both ELISA and virus neutralization test are required.     

Peptide polymerisation facilitates incorporation into ISCOMs and increases antigen-specific IgG2a production

Synthetic peptides can be tailor-made to include any B or T epitopes desired from a single or multiple antigens or organisms. However, peptides in general are not very immunogenic and have not proven easy to incorporate into immunogenic vaccines. ISCOMs is an adjuvant system that has the capability not only to enhance the humoral immunogenicity of a protein but has also been shown to induce cell-mediated immune responses in animals. Synthetic peptide ISCOM vaccines are few because of the difficulty in incorporation of these peptides into ISCOMs. We have shown in this study that non-immunogenic peptides could be made immunogenic by polymerisation, and these polymers could be incorporated into ISCOMs to give highly immunogenic vaccines. Synthetic 20mer peptides containing known B and T-helper epitopes from the E7 protein of the cervical cancer associated human papillomavirus type 16 (HPV16 E7) have been used here as model immunogens. We have compared the humoral immunity induced by these peptides as polymers or as copolymers with a lipid binding 20mer peptide (LAP 20), with or without incorporation into ISCOMs. Unpolymerised peptide elicited no measurable antibody. When polymerised peptide was administered with CFA, or in phosphate-buffered saline (PBS) without adjuvant, or incorporated into ISCOMs, antibodies recognising both the immunising peptide and HPV16 E7 protein were produced. For equal quantities of administered peptide (5 micrograms), ISCOMs gave higher titres of antibody than CFA or PBS. Polymerised peptides induced high antigen-specific IgG2a:IgG1 ratios, which increased with multiple immunisations. These data indicate that polymerised peptides could be incorporated into ISCOMs to form efficient immunogens which may elicit a Th1 type response.     

Optimizing discrete stochastic systems using simulated annealing and simulation

The objective of this paper is to present an integrated approach of two models: simulation and optimization. This approach is used to determine the design parameters of stochastically constrained systems where the measure of performance is available only via simulation. The optimization model is solved using simulated annealing (SA) for parameter selection followed by the use of Monte Carlo simulation to evaluate the measure of performance. Based on the expected simulation output, the parameter set is either accepted or rejected. A modified rejection/acceptance criterion is presented for the proposed SA algorithm taking into consideration the stochastic system constraints. Moreover, a control variate is employed as a variance reduction technique in order to obtain an efficient estimate of performance measure. The proposed approach is tested using three real cases of the multi-echelon repairable item inventory systems (MERIIS). The results show that the proposed method is efficient in determining an optimal choice of spares and repair channels in these systems.     

Evaluation of electrophoretic immunoblotting for the detection of antibodies against the bovine leukosis virus in cattle

Six antigen preparations of bovine leukemia virus, including affinity-purified glycoprotein gp51, gradient-purified fetal lamb kidney-bovine leukemia virus antigen, and four crude antigens, were used in combination with several groups of cattle sera, for the evaluation of electrophoretic immunoblotting as a serological test method. Sera (89) from cattle naturally-infected with bovine leukosis virus, a panel of reference sera from infected and uninfected cattle (18), and serial bleedings from experimentally-infected cows (4) were used. Major differences between the six antigen preparations were observed in their reactivity with the various sera. The immunological variabilities of these antigens were confirmed further by their reactions with a gp51-specific monoclonal antibody. The known immunodominant gp51 failed as a reliable indicator for the serological status of the sera in blots when compared to the results on the same sera, two gp51-specific ELISAs and the agar gel immunodiffusion test were used as reference tests. There was a lack of staining of gp51 antigen by many sera, probably due to the labile nature of the gp51 molecule. On the other hand, non-specific staining in the gp51 region appeared with high frequency in some antigens. Antibody staining of the internal viral protein p24 correlated well with the results of the three reference tests. Other bands stained infrequently and were of no diagnostic value.