Contaminated drinking water in one town manifesting as an outbreak of cryptosporidiosis in another.

In early 1992 we identified an outbreak of cryptosporidiosis in Oregon and sought to identify and control its source. We used a series of studies to identify risk factors for illness: (i) a case-control study among employees of a long-term-care facility (LTCF); (ii) a matched case-control study of the general community; (iii) a cohort study of wedding attendees; and (iv) a cross-sectional survey of the general community. Drinking Talent water was associated with illness in the LTCF (OR = 22.7, 95 % CI = 2.7-1009.0), and in the community (matched OR = 9.5, 95% CI 2.3-84.1). Drinking Talent water was associated with illness only among non-Talent residents who attended the wedding (P < 0.001) and in the community (RR = 6.5, 95 % CI 3.3-12.9). The outbreak was caused by contaminated municipal water from Talent in the absence of a discernible outbreak among Talent residents, suggesting persons exposed to contaminated water may develop immunity to cryptosporidiosis.

Encapsulating bis(beta-ketoiminato) polyethers. Volatile, fluorine-free barium precursors for metal-organic chemical vapor deposition.

The synthesis, characterization, and incorporation in volatile metal-organic chemical vapor deposition (MOCVD) precursors of a new class of linked beta-ketoiminate-polyether-beta-ketoiminate ligands is presented. These ligands are designed to encapsulate alkaline-earth cations having low charges and large ionic radii. Barium complexes having the general formula Ba[(RCOCHC(R')N)2(R")] (R = tert-butyl or CF3; R' = tert-butyl, methyl, or CF3; R" = -(CH2CH2O)4CH2CH2- or -(CH2CH2O)5CH2CH2)-) were prepared and characterized by 1H and 13C NMR spectroscopy, elemental analysis, and mass spectrometry. Single-crystal X-ray diffraction analysis of 2,2,5,25,28,28-hexamethyl-9,12,15,18,21-pentaoxa-4,25-diene-6,24- diimino-3,27-pentacosadionatobarium(II) reveals a monomeric, nine-coordinate, tricapped trigonal prismatic coordination geometry. Single-crystal X-ray structural analysis of 1,1,1,24,24,24-hexafluoro-4,21-ditrifluoromethyl-8,11,14,17- tetraoxa-3,21-diene-5,20-diimino-2,23-tetracosadionatobarium(II).2DMSO reveals a monomeric, ten-coordinate, distorted tetracapped trigonal prismatic coordination geometry. Volatility data are presented for these barium complexes, demonstrating viability as MOCVD precursors. In addition, it is demonstrated that thin epitaxial films of BaTiO3 can be grown on (001) MgO by low-pressure MOCVD techniques using one of these barium complexes and Ti(dipivaloylmethanate)2(isopropoxide)2 as precursors.

Infrared optical properties of diesel smoke plumes.

Far IR optical properties have been measured for smoke from diesel fires. Concentrations of both gaseous and particulate combustion products have been measured and chemical species contributing to the optical effects identified. To obtain these results, a variety of sampling instruments were lofted into large plumes on a mobile and open structure. The smoke plumes of diesel fires have been found to consist largely of carbonaceous material (in fibrous form) and heavy liquid hydrocarbons infused with the expected gaseous products of the combustion process. Strong attenuation at a wavelength of 10.6 microm is found to be due largely to the carbonaceous aerosol. The absorption coefficient is typically ~500 km(-1) at 10 m from the source with a variable but often comparable total scattering coefficient. The extinction coefficient, normalized to the mass density of the aerosol in a unit volume of space, is found to be 1.2 m(2)-g(-1) with an estimated variance of 20%. luctuational spectra of the attenuation follow a form similar to turbulence spectra.

Explosion dust particle size measurements.

In situ measurements of the sizes and concentrations of dust particles generated by the detonation of high explosives in clay soil near Leesville, La., sandy clay soil near Huntsville, Ala., and sandy soils near Orogrande, N.M. are reported. Measurements were generally made within 1 m of the surface (in one case 10 m) at distances ranging from 10 to approximately 50 m from the detonation point with a combination of Knollenberg lightscattering counters (for particles with equivalent radius in the submicron to 15-microm range) and a Knollenberg optical array probe (for particles of 10-150 microm). Measurements were made for periods of several tens of seconds following detonation. All dust size distributions, irrespective of soil or explosive type, exhibit a bimodal character with mass mean radii of approximately 7 and 70 microm. Peak aerosol mass loadings inferred from the distributions have values ranging from 0.05 to 10 g gm-3 with the larger mode of particles contributing most to the mass loading. Predictions of dust extinction coefficients at visible (0.55-microm) and IR (10.4-microm) wavelengths were made using the measured size distributions together with estimates of dust refractive indices. These predictions suggest that extinction should be nearly neutral (wavelength independent) in agreement with transmission measurements made during some of the tests. Predicted mass extinction coefficients, under the assumption of dust material density of 2.5 g cm-3, are of the order of 0.05 m2 g-1 at both visible and IR wavelengths. This value is also in good agreement with a test-averaged measured value of 0.03 m3 g-1 (at lambda = 10.6 microm) obtained using a short path transmissometer and hi-vol sampler.