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Trypanosoma cruzi has three biochemically and morphologically distinct developmental stages that are programmed to rapidly respond to environmental changes the parasite faces during its life cycle. Unlike other eukaryotes, Trypanosomatid genomes contain protein coding genes that are transcribed into polycistronic pre-mRNAs and have their expression controlled by post-transcriptional mechanisms. Transcriptome analyses comparing three stages of the T. cruzi life cycle revealed changes in gene expression that reflect the parasite adaptation to distinct environments. Several genes encoding RNA binding proteins (RBPs), known to act as key post-transcriptional regulatory factors, were also differentially expressed. We characterized one T. cruzi RBP, named TcZH3H12, which contains a zinc finger domain and is up-regulated in epimastigotes compared to trypomastigotes and amastigotes. TcZC3H12 knockout (KO) epimastigotes showed decreased growth rates and increased capacity to differentiate into metacyclic trypomastigotes. Transcriptome analyses comparing wild type and TcZC3H12 KOs revealed a TcZC3H12-dependent expression of epimastigote-specific genes such as genes encoding amino acid transporters and proteins associated with differentiation (PADs). RNA immunoprecipitation assays showed that transcripts from the PAD family interact with TcZC3H12. Taken together, these findings suggest that TcZC3H12 positively regulates the expression of genes involved in epimastigote proliferation and also acts as a negative regulator of metacyclogenesis.
Using stream water polluted with untreated wastewater in agriculture is controversial due to its combination of benefits and negative health impacts. Using data from a household survey, ‘wastewater’ and ‘freshwater’ farmers were analysed comparatively to examine the perceived impacts of irrigation water quality on farmers' health and to evaluate the extent of health damage. Probability of illness was estimated using the theory of utility-maximising behaviour of households subject to the conventional farm household production model, augmented by adding a health production function. Reduced model and instrumental variable probit specifications both show that perceived illness prevalence is significantly higher for household members working on wastewater irrigation farms than for those working with freshwater. Our data entails econometric complications (e.g., endogeneity of farmers' behaviour, unobserved location-specific characteristics). Ignoring these will result in underestimation of the value of policy interventions designed to reduce potential health damage of wastewater use in irrigation.
Between January 2006 and May 2008, 2624 pregnant S. Korean women between 35–37 weeks gestation were screened for group B streptococcus (GBS). Resistance to antimicrobials was tested by disk diffusion and serotype determined using co-agglutination assays and microarray methods. Overall, 8% of pregnant women were colonized. Serotype III was the predominant serotype (43·8%), followed by serotypes V (20·3%), Ia (12·1%), and Ib (9·5%). GBS was frequently resistant to clindamycin (54·0%) and erythromycin (25·6%); 3·7% were resistant to cefazolin. More than three-quarters of serotype V were resistant to clindamycin or erythromycin or both, and 71% of serotype III were resistant to clindamycin but only 12% were resistant to erythromycin. GBS prevalence exceeded earlier reports by one-third. This is the first report of cefazolin resistance in Korea. These results underscore the need to establish screening measures and chemoprophylaxis guidelines regarding GBS infections in Korea.
Inceptisols are the major forest soils in northern Taiwan. Some chemical, physical and morphological properties have been documented for these soils, yet there is little information on the mineralogy and the charge characteristics of their constituent 2:1 clay minerals. In this study we conducted a detailed characterization of the clay mineralogy of two Inceptisols. Two pedons were sampled at diagnostic horizons and the clay mineralogy was examined by X-ray diffraction. The magnitude of the layer charge of the 2:1 phyllosilicates was estimated using the alkylammonium exchange method (nC = 12). The clay mineralogy of both soils was dominated by vermiculite and mica with small amounts of kaolinite. The surface horizon contained more mica and kaolinite than the lower horizons. The mean layer charge of vermiculite ranged between 0.60 and 0.86 cmolc/(O10(OH)2). The distribution of clay layer charge decreased with increasing soil depth in two pedons. Differences in layer charge between samples are due to differences in weathering processes. The difference in the extent of clay mineral weathering in the A and Bsm horizons could be partly because the mineral surfaces in the Bsm horizon were coated with organo-Fe complexes which protected them from weathering.
Faculty members at the authors' institution are involved in multidisciplinary materials research through a National Science Foundation funded center. One goal of this center is to empower materials education through the incorporation of research outcomes into the undergraduate and graduate curricula. There are currently no MSE degree programs on this campus; therefore, a variety of means is being employed to infuse MSE information into non-MSE curricula. In addition to classroom lectures and case studies, students receive an extramural exposure to the multidisciplinary aspects of MSE by engaging in team or individual projects that exploit fully the center's facilities and resources. Benefits are being experienced in terms of a heightened enrollment of students in graduate MSE programs, and increased placement of students in materials related positions in industry. The paper describes the status of these efforts.
Amorphous Si/Ge artificial multilayers have been implanted with Si and B at liquid nitrogen temperature, and partially ion mixed with Ar at different temperatures. In all cases, the square of the mixing length was found to be proportional to the dose. Annealing of Si-implanted samples showed that after relaxation the diffusivity appeared unaffected by the implantation process. Annealing of the B-implanted samples showed an enhancement of the diffusivity at the higher dose. The diffusive component of the square of the mixing length in the Ar-ion mixed samples has an Arrhenius-type temperature dependence, with an activation enthalpy of 0.22 eV.
The use of spun-on liquids to form ohmic and Schottky barrier contacts on Si has been investigated. Two commercially available metallo-organic solutions containing Au or Pt were applied to Si substrates by spinning techniques. The Au or Pt contacts were then formed by annealing at 250°C or 450°C respectively. The metallurgical interactions between the spun-on Au or Pt layers and the Si substrate were investigated by MeV backscattering spectrometry and X-ray diffraction as a function of the annealing temperature. The resulting electrical characteristics were investigated with four point probe, I-V and C-V techniques. It was found that the spun-on Au or Pt films react with Si substrates at much higher temperatures than those deposited by vacuum evaporation. The diode characteristics of the spun-on Au films are comparable to those of evaporated Au films ( φB ∼0.85V, n ∼1.08), whereas diode characteristics of spunon Pt films show no linear region on the ln I-V curve. The application of spun-on Au also improves the bondability of Si chips on Mo headers.
Experiments in a in (6-35 mm) channel have yielded further information on the precision and convenience of the razor blade technique. It is shown that adhesive tape or carefully located cement can be used to secure a segment of razor blade over a static pressure hole: the resulting calibration for shear stress remains valid if the blade is removed and relocated over the same or a different, similar sized hole. Razor blade segments, calibrated in this manner, have been used to measure wall-shear stress in a turbulent boundary layer with tangential, secondary injection: the results indicate that V. C. Patel’s law of the wall is valid for such flows.
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