Chemiluminescent optical fiber immunosensor detection of Brucella cells presenting smooth-A antigen

Brucellosis is a worldwide distributed zoonotic re-emerging disease, causing abortions in domesticated animals and Malta fever in humans. Currently, the gold standard for confirmation of the existence of the causative agent genus Brucella is the isolation of the bacteria from body or liquid samples, whereas standard serological tests are used for diagnosis. The need for a rapid point of care identification of Brucella organisms has led us to develop a novel chemiluminescent optical fiber immunosensor. The immunosensor based on a conventional enzyme linked immunoassay (ELISA) technique was implemented on optical fibers and its performance was compared to the standard ELISA method. We show that depending on the detecting antibodies used specificity of the assay is achieved. Brucella cells presenting smooth-A O-chain determinant were detected at a minimal protein concentration of 1.098 ng/ml, correlating to 305 cfu/ml, while smooth-M O-chain cells, rough cells and two gram-negative bacteria other than Brucella sp. produced negative results, confirming the high specificity of the technique.     

Targeting implementation efforts for maximum satisfaction with new computer systems: Results from four human service agencies

Human service management needs to pinpoint the areas in which to concentrate computer implementation efforts in order to achieve maximum satisfaction with new systems. This study sought to identify the most salient factors affecting user satisfaction in management and client oriented computer systems in human services. Along with commonly used factors to assess user computer satisfaction (UCS), congruence with human service norms was added. UCS was evaluated in newly implemented computer systems in four human services. Two had introduced management oriented systems and two had introduced client oriented systems (N = 517). Hierarchical regression was conducted to assess the relative effects of four classes of variable (user, environmental, process, and system), on UCS. Contrary to expectations, results show that the two types of system were analogous with respect to contributing variables to UCS. Preparedness, importance to management, integration, usefulness, and technical support best predict UCS. Moreover, the systems did not differ with respect to congruence with human service norms, and this variable did not load on the regression. A discussion of the implications of these findings for implementation theory and human service management concludes the paper.     

The Thermal Effects of Nucleation and Crystallization of KBr and KCl Solutions. II. The Heat Of Nucleation and the Supersaturated Solution

It is shown that the induction period commonly observed in the crystallization of salts from aqueous solutions is due to a heterogeneous nucleation process made apparent by the release of heat. The metastable supersaturated solution is therefore a solution of particles, and the supersaturation limit can be extended by the addition of a good nucleator. In the case of KBr and KCl the halogenoplumbate complex ions are good nucleators. The heat evolved during the nucleation process is proportional to the concentration of the lead ions and the supersaturation limit is a kinetic function of the concentration of the lead ions. The size of the fine particles that can be held in a supersaturated solution and σ, “the crystal-liquid surface tension”, were determined by the use of the Ostwald-Freundlich equation. The thermal effects can thus be quantitatively accounted for.     

Impact of humic acid fouling on membrane performance and transport of pharmaceutically active compounds in forward osmosis

The impact of humic acid fouling on the membrane transport of two pharmaceutically active compounds (PhACs) – namely carbamazepine and sulfamethoxazole – in forward osmosis (FO) was investigated. Deposition of humic acid onto the membrane surface was promoted by the complexation with calcium ions in the feed solution and the increase in ionic strength at the membrane surface due to the reverse transport of NaCl draw solute. The increase in the humic acid deposition on the membrane surface led to a substantial decrease in the membrane salt (NaCl) permeability coefficient but did not result in a significant decrease in the membrane pure water permeability coefficient. As the deposition of humic acid increased, the permeation of carbamazepine and sulfamethoxazole decreased, which correlated well with the decrease in the membrane salt (NaCl) permeability coefficient. It is hypothesized that the hydrated humic acid fouling layer hindered solute diffusion through the membrane pore and enhanced solute rejection by steric hindrance, but not the permeation of water molecules. The membrane water and salt (NaCl) permeability coefficients were fully restored by physical cleaning of the membrane, suggesting that humic acid did not penetrate into the membrane pores.     

Mathematical model for analysis of recirculating vertical flow constructed wetlands

The recirculating vertical flow constructed wetland (RVFCW) was developed for the treatment of domestic wastewater (DWW). In this system, DWW is applied to a vertical flow bed through which it trickles into a reservoir located beneath the bed. It is then recirculated back to the root zone of the bed. In this study, a compartmental model was developed to simulate the RVFCW. The model, which addresses transport and removal kinetics of total suspended solids, 5-day biological oxygen demand and nitrogen, was fitted to kinetical results obtained from pilot field setups and a local sensitivity analysis was performed on the model parameters and operational conditions. This analysis showed that after 5 h of treatment water quality is affected more by stochastic events than by the model parameter values, emphasizing the stability of the RVFCW system to large variations in operational conditions. Effluent quality after 1 h of treatment, when the sensitivity analysis showed the parameter impacts to be largest, was compared to model predictions. The removal rate was found to be dependent on the recirculation rate. The predictions correlated well with experimental observations, leading to the conclusion that the proposed model is a satisfactory tool for studying RVFCWs.     

Clinical characteristics of Crohn's disease in children and adults

There are few reports contrasting the clinical characteristics of Crohn's disease in different age groups. We therefore compared retrospectively children and adults with Crohn's disease. 23 children (mean age: 12.8 +/- 2.5 years) and 66 adults (mean age: 27.0 +/- 4.0 years) were studied. Presenting symptoms of abdominal pain and diarrhea were significantly more common in adults, while in children anorexia and weight loss were more frequent. Children tended to present with extra-gastrointestinal tract symptoms as well, mainly anemia and joint involvement. Common symptoms during active disease did not differ between groups, except that weight loss, evident in all children, was found in only 70% of adults. Anemia was present during active disease in all pediatric cases but in only 62% of adults. There were no significant differences between groups regarding disease location, gastrointestinal complications and extra-intestinal manifestations. We conclude that in children Crohn's disease may differ significantly, mainly presenting with nonclassical symptoms, such as anemia and joint involvement. The primary care physician should be aware of these differences.     

Some comments on the modes of action of nanocomposites in the flame retardancy of polymers

Nanocomposites of polymers with montmorillonite (MMT) yield upon pyrolysis and combustion an MMT‐rich surface of the char. The prevalent approach considers this accumulation as due to the gasification of the polymer and subsequent gradual precipitation of the MMT on the surface. According to the present paper, the enrichment in MMT is postulated to be due to a migration or convection of the MMT to the surface driven mainly by the lower surface free energy of the MMT. The role of the surface free energy in the surface structure of polymer blends, especially those involving a silicon‐containing component, is discussed. The enrichment occurs above the glass transition temperature and is temperature dependent. XPS evidence for the accumulation of MMT on the surface of a polystyrene/MMT nanocomposite is reviewed. Its dependence on the stability of the nanocomposite structure, and particularly on the stability of the quaternary ammonium compounds that bind the polymer to the MMT, is pointed out. The importance of the surface free energy in the flame retardancy of polymer blends as well as polymer‐additive mixtures is discussed. Copyright © 2003 John Wiley & Sons, Ltd.     

Grain refinement and mechanical properties enhancement of AZ91E alloy by addition of ceramic particles

Improved mechanical properties and structural uniformity of Mg-based alloys can be achieved by use of grain-refining additives prior to casting. Ceramic particles of α-Al₂O₃ and SiC can serve as such additives to refine the microstructure of Mg–Al-based alloys. However, direct introduction of ceramic particles into Mg matrix is limited by the poor wetting of those particles by liquid Mg and their massive agglomeration. Mg/α-Al₂O₃ and Mg/SiC master alloys were prepared using a method based on the insertion of the ceramic particles into a molten Mg bath through a Mg-nitride layer formed on the surface of the molten bath. The mixture of Mg/ceramic particles was cooled to room temperature under a nitrogen atmosphere. Mg-15%Al₂O₃ and AZ91E + 10%SiC master alloys were obtained. These master alloys were used to refine AZ91E alloys by introducing various amounts of ceramic particles to manufacture AZ91E + 1%Al₂O₃, AZ91E + 1%SiC, and AZ91E + 3%SiC alloys. These were cast using high-pressure die casting and gravity die casting. The alloy AZ91E + 1%Al₂O₃ was grain refined to ~20 μm and the alloys AZ91E + SiC were grain refined to ~50 μm as against 110 μm in non-refined counterparts. The mechanical properties of the modified alloys are substantially better than those of a non-refined AZ91E alloy which is the result of a combination of grain refinement and reinforcement of the matrix by ceramic particles. Alloy AZ91E + 1%Al₂O₃ exhibited the best mechanical properties.     

Antifouling ultrafiltration membranes via post-fabrication grafting of biocidal nanomaterials

Ultrafiltration (UF) membranes perform critical pre-treatment functions in advanced water treatment processes. In operational systems, however, biofouling decreases membrane performance and increases the frequency and cost of chemical cleaning. The present work demonstrates a novel technique for covalently or ionically tethering antimicrobial nanoparticles to the surface of UF membranes. Silver nanoparticles (AgNPs) encapsulated in positively charged polyethyleneimine (PEI) were reacted with an oxygen plasma modified polysulfone UF membrane with and without 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) present. The nucleophilic primary amines of the PEI react with the electrophilic carboxyl groups on the UF membrane surface to form electrostatic and covalent bonds. The irreversible modification process imparts significant antimicrobial activity to the membrane surface. Post-synthesis functionalization methods, such as the one presented here, maximize the density of nanomaterials at the membrane surface and may provide a more efficient route for fabricating diverse array of reactive nanocomposite membranes.