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Clostridium difficile infection (CDI) has been extensively described in healthcare settings; however, risk factors associated with community-acquired (CA) CDI remain uncertain. This study aimed to synthesize the current evidence for an association between commonly prescribed medications and comorbidities with CA-CDI.
A systematic search was conducted in 5 electronic databases for epidemiologic studies that examined the association between the presence of comorbidities and exposure to medications with the risk of CA-CDI. Pooled odds ratios were estimated using 3 meta-analytic methods. Subgroup analyses by location of studies and by life stages were conducted.
Twelve publications (n=56,776 patients) met inclusion criteria. Antimicrobial (odds ratio, 6.18; 95% CI, 3.80–10.04) and corticosteroid (1.81; 1.15–2.84) exposure were associated with increased risk of CA-CDI. Among the comorbidities, inflammatory bowel disease (odds ratio, 3.72; 95% CI, 1.52–9.12), renal failure (2.64; 1.23–5.68), hematologic cancer (1.75; 1.02–5.68), and diabetes mellitus (1.15; 1.05–1.27) were associated with CA-CDI. By location, antimicrobial exposure was associated with a higher risk of CA-CDI in the United States, whereas proton-pump inhibitor exposure was associated with a higher risk in Europe. By life stages, the risk of CA-CDI associated with antimicrobial exposure greatly increased in adults older than 65 years.
Antimicrobial exposure was the strongest risk factor associated with CA-CDI. Further studies are required to investigate the risk of CA-CDI associated with medications commonly prescribed in the community. Patients with diarrhea who have inflammatory bowel disease, renal failure, hematologic cancer, or diabetes are appropriate populations for interventional studies of screening.
Many of the high temperature superconductor phases degrade rapidly when in the presence of water, acids, carbon dioxide or carbon monoxide. In order to foster more rapid developments in the area of high-Tc research, it will be necessary to acquire a more complete understanding of the surface chemistry of these superconducting materials. In this paper, the relative reactivity of the common cuprate phases toward water is reported. X-ray powder diffraction and scanning electron microscopy measurements are utilized here to establish the reactivity trends.
Electrochemical techniques are exploited to fabricate conductive polymer/high-Tcsuperconductor sandwich structures. In such hybrid polymer/superconductor systems, it is found that when the polymer is oxidized to its conductive state, the transition temperature (Tc) and critical current (Jc) of the underlying superconductor film are suppressed. Reversible Modulations in the values of the transition temperatures up to 50 K are noted for these structures. Upon reduction of the conductive polymer layer back to its non-conductive form, Tc is found to return to values close to those acquired for the underivatized YBa2Cu3O7-δ film. Thus, the principle of a Molecular/superconductor switch for controlling superconductivity is demonstrated.
The preparation of a hybrid conducting polymer/high-temperature superconductor device consisting of a polypyrrole coated YBa2Cu3O7-δ microbridge is reported. Electrochemical techniques are exploited to alter the oxidation state of the polymer and, in doing so, it is found for the first time that superconductivity can be modulated in a controllable and reproducible fashion by a polymer layer. Whereas the neutral (insulating) polypyrrole only slightly influences the electrical properties of the underlying YBa2Cu3O7-δ film, the oxidized (conductive) polymer depresses Tc by up to 15K. Thus, a new type of molecular switch for controlling superconductivity is demonstrated.
Multilayer assemblies of epitaxially-grown, Ill-V semiconductor materials are being investigated for use in thermophotovoltaic (TPV) energy conversion applications. It has been observed that thick, highly-doped semiconductor layers within cell architectures dominate the parasitic free-carrier absorption (FCA) of devices at wavelengths above the bandgap of the semiconductor material. In this work, the wavelength-dependent, free-carrier absorption of p- and n-type InGaAs layers grown epitaxially onto semi-insulating InP substrates has been measured and related to the total absorption of long-wavelength photons in thermophotovoltaic devices. The optical responses of the TPV cells are then used in the calculation of spectral utilization factors and device efficiencies.
Solid bodies immersed in hot fluids may melt. The molten material produced can then mix with, and be assimilated into, the fluid influencing its compositional and thermal states. Compositional convection of melt and thermal convection of cooled fluid around the solid determine the heat flux from the fluid to the solid's surface. This, together with the thermal properties of the solid, controls the rate of melting. Experiments on melting wax spheres into water are described; these have shown how variations in the nature of melt flow round the sphere cause differing melting rates and hence the development of a distinctive melting morphology. Melting rates are calculated by a simple theoretical analysis which estimates melt layer thickness and the heat flux from the fluid. Melting rate predictions agree well with the experimental data. A geological application occurs when magma incorporates blocks of its surrounding wall rock. Relatively rapid melting rates are estimated, typically in the order of a half metre per day. Such fast rates indicate that this method of contamination may be an important influence on magmatic evolution in continental environments.
Individual herbicides and all double combinations of imazaquin, imazethapyr, and imazapyr were applied alone and in combination to the foliage of pitted morningglory plants in order to evaluate potential influences on translocation. Unlabeled imazethapyr at 5.62 μg plant−1 stimulated basipetal translocation of both 14C-imazaquin and 14C–imazapyr. Unlabeled imazaquin at 7.49 μg plant−1 also increased basipetal translocation of 14C–imazethapyr but did not influence 14C–imazapyr translocation. No combination affected the amount of 14C herbicide remaining in treated leaves or moving into foliage above treated leaves. Unlabeled imazapyr at 0.11 μg plant−1 did not affect movement of either imazaquin or imazethapyr.
Imazaquin and imazethapyr were applied postemergence to soybeans for control of 8- to 12-leaf rhizome johnsongrass and pitted morningglory in the field. At 8 weeks, johnsongrass control was 70% with 70 g ai/ha imazaquin plus 105 g ai/ha imazethapyr but was no more than 50% with a single application of either herbicide. Imazaquin at 70 g/ha plus imazethapyr at 35 g/ha interacted synergistically to provide 90% pitted morningglory control, while 140 g/ha imazaquin controlled 77%. Imazaquin at 70 g/ha with imazethapyr from 18 to 105 g/ha controlled both weed species equal to or better than that obtained with 140 g/ha imazaquin.
Field experiments were conducted to evaluate postemergence combinations of imazethapyr, imazquin, or chlorimuron with low rates of imazapyr for Johnsongrass and pitted morningglory control. Imazapyr applied alone at rates up to 4 g ai/ha gave little or no control of either weed species. However, the addition of imazapyr to various rates of imazethapyr or imazaquin synergistically increased both johnsongrass and pitted morningglory control 8 weeks after treatment. The rates of imazethapyr or imazaquin required for significant enhancement of johnsongrass control were higher than those required for pitted morningglory control. No synergistic increases in control of either weed species were noted with mixtures of imazapyr and chlorimuron. Although not synergistic in every case, the mixtures of imazapyr at 4 g/ha with imazethapyr, imazaquin, or chlorimuron gave johnsongrass and pitted morningglory control equal to or better than the next higher rate of these herbicides applied alone. Imazapyr did not increase soybean injury or decrease yield provided by chlorimuron, imazaquin, or imazethapyr.
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