Collection of Airborne Microorganisms into Liquid by Bubbling through Porous Medium

A new method for the removal of airborne particles by air bubbling through fibrous filters immersed into a liquid has recently been developed (Agranovski et al. 1999) and shown to be very efficient for cleaning air environments with ultra-fine aerosol particles. The principal objective of the present study was to evaluate the new bubbling technique for the collection of airborne bacteria into a liquid for subsequent physical and microbiological analysis. It was found that the technique is capable of achieving a physical collection efficiency of 98.5% or higher for particles larger than 0.3 w m in aerodynamic diameter. The physical collection efficiency of the prototype bubbler remained at that high level for 8 h of continuous operation with negligible variation of the pressure drop across the device. Evaporation of the collection fluid did not exceed 20% during 8 h, and the reaerosolization effect on the physical collection efficiency of the bubbler prototype was <8%. The recovery rate of gram-negative Pseudomonas fluorescens bacteria collected for 20 min was shown to be as high as 74% - 10%. Its decrease with time was not statistically significant: the recovery rate reached 63% - 15% and 58% - 16% after 4 and 8 h of continuous operation, respectively. Thus the bubbling technique was demonstrated to be suitable for collecting viable airborne bacteria even if they are sensitive to the stress.     

Milk protein-derived bioactive tripeptides Ile-Pro-Pro and Val-Pro-Pro protect endothelial function in vitro in hypertensive rats

Milk products containing casein-derived bioactive tripeptides Ile-Pro-Pro (isoleucine-proline-proline) and Val-Pro-Pro (valine-proline-proline) have been shown to lower blood pressure in animal models and clinical studies. In vitro experiments were performed to elucidate the effects of Ile-Pro-Pro, Val-Pro-Pro and Leu-Pro-Pro (leucine-proline-proline) on vascular function. Isolated spontaneously hypertensive rat (SHR) mesenteric arteries were stored in Krebs solution containing 1 mM of tripeptides at +4 °C for 1, 12 or 24 h. Thereafter, arteries were mounted in an organ bath chamber (+37 °C) for vascular reactivity measurements. Endothelium-dependent relaxation was better preserved (P < 0.05) in mesenteric arteries stored with tripeptides versus the control. Endothelium-independent relaxation remained unaltered. Endothelium-derived hyperpolarizing factor (EDHF)-related relaxation was more pronounced in arteries stored with Ile-Pro-Pro. Angiotensin-converting enzyme (ACE)-inhibitory activity of tripeptides was demonstrated after 24 h storage suggesting its role in improved relaxation. Thus, tripeptides do not affect smooth muscle but they protect endothelium in cold storage.     

Power Allocation in a Wireless Network Using Scheduling and Stochastic Programming with Penalty Functions

This paper studies the optimal allocation of transmit power in a wireless communication network. First, a stochastic programming formulation is introduced, based on penalizing violations of quality-of-service constraints. The maximization of the certainty equivalent signal-to-interference ratio under Rayleigh fading corresponds to a penalty model where (max-min) fairness is explicitly taken into consideration. Second, optimum dynamic power allocation is discussed. Efficient dynamic resource allocation under both linear and logarithmic utility functions is addressed. The dynamic model studies the optimal trade-off between instantaneous quality-of-service and a delay-penalized reliable quality-of-service. Related work on optimal stochastic power control is summarized.     

Perforated appendicitis in children: risk factors for the development of complications

BACKGROUND: Many aspects of the management of perforated appendicitis in children remain controversial. The objective of this study was to define risk factors associated with the development of postoperative complications in children undergoing treatment for perforated appendicitis. METHODS: We reviewed all children (age < 16 years) who were treated for perforated appendicitis at Cardinal Glennon Children's Hospital between 1988 and 1997. Inclusion criteria included either gross or microscopic evidence of appendiceal perforation. RESULTS: Of 285 children with perforated appendicitis, 279 underwent immediate operative treatment. Mean patient age was 7.7 years and there were no deaths. Major postoperative complications included intra-abdominal abscess (n = 17), ileus (n = 7), mechanical intestinal obstruction (n = 6), and wound infection (n = 4). All children who had a postoperative abscess had more than 5 days of symptoms before operation. Within this subgroup, drain placement was associated with not only decreased postoperative abscess formation and but also shorter duration of fever and length of hospitalization. The incidence of mechanical obstruction or ileus was not increased and the rate of wound infection was actually lower after drainage. CONCLUSIONS: Drain placement appears to be helpful in children with late diagnosis but is of little benefit when the duration of symptoms is less than 5 days. Thus it is likely that drains are most useful in patients with well-established and localized abscess cavities.     

Respiratory Symptoms and Infections among Children in a Day-Care Center with Mold Problems

The prevalence of irritative symptoms and the incidence of respiratory infections among children in a day-care center affected by mold were compared with those in a reference day-care center. A retrospective pilot study was made in the mold-problem day-care center. Analysis of absenteeism records and a one-year follow-up study were made in both day-care centers. In the pilot study, half of the exposed 41 children had prolonged or frequent symptoms and respiratory infections. In addition, the absenteeism in the mold-problem day-care center was nearly twice as high as in the reference day-care center. After cessation of the exposure, the occurrence of respiratory symptoms decreased and no lower respiratory tract infections appeared.     

Covalent biofunctionalization of cellulose acetate with thermostable chimeric avidin

A stable, bioactive cellulose acetate (CA) surface was developed by functionalizing the surface with highly thermostable avidin form. The CA films were first functionalized with a mixture of 3-aminopropyltrimethoxysilane and tetraethoxysilane to introduce free amino groups onto the surface of CA films. Free amino groups were functionalized with glutaraldehyde to obtain an activated surface for covalent biomolecule immobilization. A genetically engineered, high-affinity biotin-binding protein chimeric avidin, ChiAVD(I117Y), was used for biofunctionalization of the surface. The chimeric avidin protein has an increased stability in chemically harsh conditions and at high temperature when compared to wt (strept)avidin. The biological activity, i.e., biotin-binding capacity, of the immobilized protein was probed by [(3)H]-biotin. The activity of the chimeric avidin on functionalized CA films was fully retained over the three months' study period. The biotin-binding capacity of the immobilized chimeric avidin was compared to that of immobilized streptavidin, chicken avidin, and rhizavidin and significant differences between proteins were detected. The developed material offers a valuable platform for the development of inexpensive in vitro diagnostics and also supports biosensing applications that are required to operate under demanding conditions.     

Tailoring surface properties of paper using nanosized precipitated calcium carbonate particles

Pigment particles used in paper coatings are typically of micrometer size and consequently the thickness of the coatings is, even at its lowest, in micrometer scale. Progress in nanotechnology has given way to the development of nanosized materials to be used in coatings, yet their exploitation has not been studied to a great extent. This study examines utilization of nanosized precipitated calcium carbonate (nanoPCC) particles in nanoscale thin coating layers. In contrast to commonly used coatings, a thin nanoparticle-based coating was targeted to change the substrate surface characteristics via controlled surface structure rather than via high coat weight. A novel approach for stabilizing and modifying the nanoPCC particles with pectin and alkenyl succinic anhydride (ASA) was utilized and a nanoparticle coating with uniform particle distribution was created. The coating applied on paper substrate was hydrophobic, having a water contact angle of 125°. Particle surface modification provided dispersion stability, enabling control of the coating layer structure. The introduced concept provides a new approach to paper coatings utilizing controlled deposition of nanoparticles with extremely low coat weight, yet having high impact on substrate surface properties. Additionally, as paper is an environmentally sound product, the approach to form a controllable nanostructure on a green substrate has potential in applications outside the traditional paper products.     

Airborne enteric coliphages and bacteria in sewage treatment plants

The concentrations of airborne culturable microorganisms were determined in wastewater and sludge treatment processes of seven sewage treatment plants. Two types of coliphages, Salmonella and total viable bacteria were sampled by the BioSampler and the numbers of faecal coliforms and enterococci were obtained from the Andersen 6-stage impactor. The BioSampler recovered higher numbers of airborne coliphage viruses than has been measured with other liquid samplers in previous studies, suggesting that this sampler has improved efficiency for sampling airborne coliphages. Airborne coliphages were detected in many stages of the wastewater or sludge treatment process. The highest microbiological air contaminations were found in pre-treatment and aerated grit separation stages of the operation. This was attributed to aerosolisation of microorganisms by mechanical handling or forced aeration. Aeration and settling processes located outdoors caused low microbial concentrations, but the brush aerator released more microorganisms into the air. Our results emphasize the necessity for controlling the exposure of sewage workers to airborne microorganisms, especially in process areas that involve mechanical agitation or forced aeration of wastewater.