Aspectos de la corrosión atmosférica de aceros autopasivables

Se estudia la corrosión de aceros Corten y Corcap en un medio que representa una atmósfera urbana industrial. Se compara el comportamiento frente a un acero al carbono corriente. La pasivación de los aceros especiales se logra mediante un ensayo acelerado de inmersiones y emersiones alternadas, la velocidad de corrosión instantánea se mide mediante técnicas electroquímicas de resistencia de polarización. Se discute el efecto que tiene un tratamiento térmico sobre el comportamiento a la corrosión. la capa de pasivaciónse determina mediante espectroscopia infrarroja y Mössbauer

Factors influencing variation in implementation outcomes of the redesigned community health fund in the Dodoma region of Tanzania: a mixed-methods study

INTRODUCTION: Micro-health insurance (MHI) has been identified as a possible interim solution to foster progress towards Universal Health Coverage (UHC) in low- and middle- income countries (LMICs). Still, MHI schemes suffer from chronically low penetration rates, especially in sub-Saharan Africa. Initiatives to promote and sustain enrolment have yielded limited effect, yet little effort has been channelled towards understanding how such initiatives are implemented. We aimed to fill this gap in knowledge by examining heterogeneity in implementation outcomes and their moderating factors within the context of the Redesigned Community Health Fund in the Dodoma region in Tanzania. METHODS: We adopted a mixed-methods design to examine implementation outcomes, defined as adoption and fidelity of implementation (FOI) as well as their moderating factors. A survey questionnaire collected individual level data and a document review checklist and in-depth interview guide collected district level data. We relied on descriptive statistics, a chi square test and thematic analysis to analyse our data. RESULTS: A review of district level data revealed high adoption (78%) and FOI (77%) supported also by qualitative interviews. In contrast, survey participants reported relatively low adoption (55%) and FOI (58%). Heterogeneity in adoption and FOI was observed across the districts and was attributed to organisational weakness or strengths, communication and facilitation strategies, resource availability (fiscal capacity, human resources and materials), reward systems, the number of stakeholders, leadership engagement, and implementer's skills. At an individual level, heterogeneity in adoption and FOI of scheme components was explained by the survey participant's level of education, occupation, years of stay in the district and duration of working in the scheme. For example, the adoption of job description was statistically associated with occupation (p = 0.001) and wworking in the scheme for more than 20 months had marginal significant association with FOI (p = 0.04). CONCLUSION: The study demonstrates that assessing the implementation processes helps to detect implementation weaknesses and therefore address such weaknesses as the interventions are implemented or rolled out to other settings. Attention to contextual and individual implementer elements should be paid in advance to adjust implementation strategies and ensure greater adoption and fidelity of implementation

Drug design and synthesis of first in class PDZ1 targeting NHERF1 inhibitors as anticancer agents

Targeted approaches aiming at modulating NHERF1 activity, rather than its overall expression, would be preferred to preserve the normal functions of this versatile protein. We focused our attention on the NHERF1/PDZ1 domain that governs its membrane recruitment/displacement through a transient phosphorylation switch. We herein report the design and synthesis of novel NHERF1 PDZ1 domain inhibitors. These compounds have potential therapeutic value when used in combination with antagonists of β-catenin to augment apoptotic death of colorectal cancer cells refractory to currently available Wnt/β-catenin-targeted agents

The deuterium-to-oxygen ratio in the interstellar medium

Because the ionization balances for HI, OI, and DI are locked together by charge exchange, D/O is an important tracer for the value of the D/H ratio and for potential spatial variations in the ratio. As the DI and OI column densities are of similar orders of magnitude for a given sight line, comparisons of the two values will generally be less subject to systematic errors than comparisons of DI and HI, which differ by about five orders of magnitude. Moreover, D/O is additionally sensitive to astration, because as stars destroy deuterium, they should produce oxygen. We report here the results of a survey of D/O in the interstellar medium performed with FUSE. We also compare these results with those for D/N. Together with a few results from previous missions, the sample totals 24 lines of sight. The distances range from a few pc to ~2000 pc and log N(DI) from ~13 to ~16 (cm-2). The D/O ratio is constant in the local interstellar medium out to distances of ~150 pc and N(DI) ~ 1x10^15 cm-2, i.e. within the Local Bubble. In this region of the interstellar space, we find D/O = (3.84+/-0.16)x10^-2 (1 sigma in the mean). The homogeneity of the local D/O measurements shows that the spatial variations in the local D/H and O/H must be extremely small, if any. A comparison of the Local Bubble mean value with the few D/O measurements available for low metallicity quasar sight lines shows that the D/O ratio decreases with cosmic evolution, as expected. Beyond the Local Bubble we detected significant spatial variations in the value of D/O. This likely implies a variation in D/H, as O/H is known to not vary significantly over the distances covered in this study. Our dataset suggests a present-epoch deuterium abundance below 1x10^-5, i.e. lower than the value usually assumed, around 1.5x10^-5.Comment: 17 pages, 9 figures, 4 tables, accepted for publication in the Astrophysical Journa

Spitzer-MIPS Observations of the eta Cha Young Association

We have mapped the eta Chamaeleontis young stellar association in the far-infrared with the Multiband Imaging Photometer for Spitzer (MIPS) on the Spitzer Space Telescope. All sixteen members within the map region were detected at 24 um, along with five members at 70 um and two at 160 um. Ten stars show far-infrared excess emission indicating the presence of circumstellar disks; six of these have central clearings as evidenced by the onset of excess emission at >5 um. No new infrared excess sources are identified among the 113 2MASS field stars with 24 um photometry but not seen as X-ray sources, indicating that membership lists derived from X-ray surveys are reasonably complete. Circumstellar disks in the eta Cha association span the range from 1e-1 to 1e-4 in their fractional infrared luminosity, with a median Ldust /Lstar of 0.04. The presence of optically thick, optically thin, and intermediate optical depth disks within the same stellar group, in combination with the large fraction of disks with inner holes, indicates that the Cha association represents a crucial stage in circumstellar disk evolution.Comment: To appear in The Astrophysical Journa

Low temperature transition to a superconducting phase in boron-doped silicon films grown on (001)-oriented silicon wafers

We report on a detailed analysis of the superconducting properties of boron-doped silicon films grown along the 001 direction by Gas Immersion Laser Doping. The doping concentration cB has been varied up to approx. 10 at.% by increasing the number of laser shots to 500. No superconductivity could be observed down to 40mK for doping level below 2.5 at.%. The critical temperature Tc then increased steeply to reach 0.6K for cB = 8 at%. No hysteresis was found for the transitions in magnetic field, which is characteristic of a type II superconductor. The corresponding upper critical field Hc2(0) was on the order of 1000 G, much smaller than the value previously reported by Bustarret et al. in Nature (London) 444, 465 (2006).Comment: 4 pages including 4 figures, submitted to PRB-Rapid Communicatio

Far Infrared Prperties of M Dwarfs

We report the mid- and far-infrared properties of nearby M dwarfs. Spitzer/MIPS measurements were obtained for a sample of 62 stars at 24 um, with subsamples of 41 and 20 stars observed at 70 um and 160 um respectively. We compare the results with current models of M star photospheres and look for indications of circumstellar dust in the form of significant deviations of K-[24 um] colors and 70 um / 24 um flux ratios from the average M star values. At 24 um, all 62 of the targets were detected; 70 um detections were achieved for 20 targets in the subsample observed; and no detections were seen in the 160 um subsample. No clear far-infrared excesses were detected in our sample. The average far infrared excess relative to the photospheric emission of the M stars is at least four times smaller than the similar average for a sample of solar-type stars. However, this limit allows the average fractional infrared luminosity in the M-star sample to be similar to that for more massive stars. We have also set low limits for the maximum mass of dust possible around our stars.Comment: 28 pages, 4 figures, to be published in The Astrophysical Journa