Deposition method,relative humidity,and surface property effects of bacterial spore reaerosolization via pulsed air jet

Biological warfare incidents generate both immediate and delayed hazards, potentially resulting from reaerosolization of deposited hazardous particles from surfaces. Understanding the causes and effects of the initial deposition method and environmental conditions on reaerosolization is important in hazard prediction and selection of mitigation approaches. This study was conducted to determine the amount of reaerosolization of various bacterial spores and 1 µm polystyrene latex microspheres deposited wet or dry and incubated at 20 or 80% relative humidity (RH). The organisms used in this study were Bacillus atrophaeus var. globigii (Bg), B. thuringiensis (Bt), B. anthracis ΔSterne (Ba-ΔSterne), Ba-ΔSterne ΔbclA mutant (BclA), and Ba-ΔSterne ΔcotE mutant (CotE). These organisms represent a range of spore types with different outer surfaces: spores with exosporium hairs and a basal layer (Ba-ΔSterne and Bt), spores with a basal layer (BclA), and spores with a spore coat only (no exosporium, Bg and CotE). A pulsed air impinging jet was used to reaerosolize particles from gridded glass surfaces. The amount of reaerosolization was determined by counting the number of particles on the gridded surface before and after applying the air jet. Results indicate that, in general, higher reaerosolization was observed when particles were deposited dry and incubated at lower RH conditions. Our results indicate that Bt (has exosporium) was reaerosolized more readily than Bg (no exosporium) in all cases studied. This method can be used in laboratory studies to compare bacterial spore behavior and to study the relative effects of different spore outer layers and surface types on reaerosolization.

© 2017 Leidos, Inc.     

Lamellar morphology of high molecular weight poly(ether ether ketone) after rolltrusion

A rolltrusion technique has been applied to impose high molecule orientation in unreinforced poly(ether ether ketone). The relationships among processing, microstructure and properties were characterized. The morphology was controlled and investigated in the microstructural levels of crystallinity, chain orientation, lamellae and spherulite colony. The density measurements detected an increase in crystallinity after rolltrusion. Wide-angle X-ray scattering (WAXS) diffraction experiments showed the preferred c-axis chain orientation along the rolltrusion direction. The internal microstructure, revealed by permanganic etching and scanning electron microscopy (SEM), changed from randomly distributed lamellae to a row structure. The lamella thickness was estimated to be about 100 Å.     

UV-C Decontamination of Aerosolized and Surface-Bound Single Spores and Bioclusters

Biological particles are rarely individual organisms, but are clusters of organisms physically bound to one another, or bound to other material present in the environment. The size and composition of these bioclusters contribute to the protection of the organisms within the core of cluster from the harmful effects of ambient UV light. The use of ultraviolet irradiation has been evaluated in the past as an option for decontaminating surfaces and air; however, previous studies were conducted with single spores, or poorly characterized polydispersed aerosols making comparisons between studies difficult. This study is intended to evaluate the effect of UV-C irradiation on monodispersed particles of spore clusters with mean diameters of 2.8 μm and 4.4 μm, and single spores of Bacillus atrophaeus var. globigii on fixed surfaces and as aerosol. The D₉₀, the UV-C irradiation doses at which 90% of the colony forming units were rendered nonculturable, for single spores and spore clusters of 2.8 and 4.4 μm on surfaces were 138, 725, and 1128 J/m², respectively. The respective values for airborne spores were 27, 42, and 86–94 J/m². The first-stage decay rate constant for the surface exposure ranged from 0.012 for single spores to 0.003 for 4.4 μm clusters. Similarly, the aerosol decay rate constant ranged from 0.12 for single spores to 0.04 for 4.4 μm clusters. The results of this study demonstrate that the decay rate of spores contained in clusters is proportional to the overall particle size, and that it is harder to inactivate large clusters on surfaces.

Copyright 2014 American Association for Aerosol Research     

A Puff of Air Sorts Bioaerosols for Pathogen Identification

Optical-based, real-time bioaerosol sensors are able to distinguish bioaerosols and nonbioaerosols but are unable to classify pathogens or even discriminate harmful from harmless bacteria. Biochemical techniques can identify genus and species of bacteria but cannot do so efficiently due to time limitation and the very high concentration of background aerosols. We report for the first time an efficient aerosol sorter consisting of an aerodynamic deflector that is cued from bioaerosol fluorescence. Bacillus subtilis (anthrax stimulant) aerosol was successfully separated from mixed aerosols. We achieved enrichment of the suspected bioaerosol concentration by at least 10³, thus leading us new perspectives in pathogen identification. Although, at the present stage, a complete characterization of bioaerosols in real time is not yet possible, this new early warning/alarm sensor can supply high concentration of suspect bioaerosol particles for further specific analysis via bio-chemical assay technology or other subtle optical methods such as Raman spectroscopy.     

Exposing water samples to ultraviolet light improves fluorometry for detecting human fecal contamination

Fluorometry identifies human fecal contamination by detecting optical brighteners in environmental waters. Because optical brighteners are sensitive to sunlight, we determined if we could improve fluorometry by exposing water samples to ultraviolet (UV) light to differentiate between optical brighteners and other fluorescing organic compounds. Optical brighteners were likely present when the relative percentage difference in fluorometric value of the water before and after UV light exposure was >30% (glass cuvettes, 30 min exposure) or >15% (polymethacrylate cuvettes, 5 min exposure). In a blind study, we correctly identified the presence or absence of optical brighteners in 178 of 180 (99%) of the samples tested with a more expensive field fluorometer and in 175 of 180 (97%) of the samples tested with a less expensive handheld fluorometer. In the field, the method correctly identified two negative and three positive locations for human fecal contamination. When combined with counts of fecal bacteria, the new fluorometric method may be a simple, quick, and easy way to identify human fecal contamination in environmental waters.     

ELISA as an affordable methodology for monitoring groundwater contamination by pesticides in low-income countries

The traditional instrumental technology for pesticide residue analysis is too expensive and labor-intense to meet the regional needs concerning environmental monitoring. ELISA methodology was used for a pilot scale study of groundwater quality in an agricultural region a few kilometers southwest of Montevideo, the capital city of Uruguay. The study spanned 2 years and examined concentrations (detection limits are given in [ppb]) of two triazine herbicides (simazine [0.3] and atrazine [0.4]) and the carbamate insecticide carbaryl [10] and its major metabolite 1-naphthol [17]. In general, pesticide concentrations were below detection limits in the samples tested and in all cases were well below the maximum contaminant levels set by the U.S. EPA. 1-Naphthol was detected frequently by ELISA, but the assay may have tended to systematically overestimate this analyte. To our knowledge, this is the first study of its type in Uruguay and perhaps the first systematic approach to monitoring for organic pesticides in groundwater water sources in the temperate region of South America.     

Effect of blend rheology on the transport property of oriented poly(ethylene terephthalate) blends

Rheological studies were performed to delineate appropriate stretching windows, and poly(ethylene terephthalate)/poly(ethylene-co-vinyl alcohol) blend films were extruded biaxially within such processing windows. The morphology and oxygen permeability properties of these films, with and without a compatibilizer, were characterized. The intent of this study was to achieve a blend oxygen permeability value (OPV) of less than 1. At a fixed draw ratio and draw temperature, appropriate rheological matching could lead to an increase in the aspect ratio of the EVOH phase and, thereby, of oxygen barrier properties. This study concludes that by melt viscosity matching it is not possible to obtain blends with OPV of less than 1. The model of Fricke, used to predict blend permeability, was found to be more accurate at the higher draw temperatures, with the measured values deviating increasingly negatively from the predicted values as the draw temperature is decreased. © 1995 John Wiley & Sons, Inc.     

Morphology and barrier properties of oriented blends of poly(ethylene terephthalate) and poly(ethylene 2,6-naphthalate) with poly(ethylene-co-vinyl alcohol)

Morphology and oxygen permeability studies were carried out for blends of poly(ethylene terephthalate), PET, and poly(ethylene 2,6-naphthalate), PEN, with poly(ethylene-co-vinyl alcohol), EVOH. PET/EVOH blends are seen as a possible substitute for poly(vinylidene chloride)-coated PET packaging films. The effects of several processing parameters such as draw temperature and draw ratio on blend morphology and barrier properties suggest that the morphology of the EVOH phase dictates to a large extent the oxygen permeabilities of these blends. The relationships between morphology and oxygen permeability and explained are explained by consideration of two-phase conduction models. The model of Fricke is found to be a good predictor of the barrier properties of the PET/EVOH system. The oxygen permeability of PET was reduced by a factor of 4.2 with the addition of 20 wt% EVOH and that of PEN by a factor of 2.7 with the addition of 15 wt% EVOH. Water vapor permeabilities and mechanical properties of PET and PEN were only slightly affected by the addition of 15 wt% EVOH.     

Experimental results of a sensible heat storage system for residential and light commercial application

This paper presents the performance results for a sensible heat storage system. The system under study operates as an air source heat pump which stores the compressor heat of rejection as domestic hot water or hot water in a storage tank that can be used as a heat source for providing building heating. Although measurements were made to quantify space cooling, space heating, and domestic water heating, this paper emphasizes the space heating performance of the unit. The heat storage system was tested for different indoor and outdoor conditions to determine parameters such as heating charge rate, compressor power, and coefficient of performance (COP). The thermal storage tank was able to store a full charge of heat. The rate of increase of storage tank temperature increased with outdoor temperature. The heating rate during a charge test, best shown by the normalized rate plots, increased with evaporating temperature due to the increasing mass flow rate and refrigerant density. At higher indoor temperature during the discharge tests, the rate of decrease of storage tank temperature was slower. Also, the discharge heating rate decreased with time since the thermal storage tank temperature decreased as less thermal energy became available for use. Copyright © 1999 John Wiley & Sons, Ltd.     

Structure development in the early stages of crystallization during melt spinning

The earliest stage of crystallization during melt spinning was examined for four polymers: HDPE, PVDF, nylon 6 and poly(oxymethylene). The four polymers have very similar melt viscosities. Of particular interest is the dependence of the time for the onset of detectable crystallization on the take-up speed. The results for all four polymers lie on the same onset time versus take-up speed curve, indicating that this condition depends chiefly upon chain orientation and not appreciably on chain chemistry or specific undercooling. The result is consistent with a condition of critical strain level. A similar, but less stringent, result is found for further crystallization in the spinline.