7 research outputs found
Recommended from our members
Epitaxial growth of the first two members of the Ban +1InnO2.5 n +1Ruddlesden-Popper homologous series
We demonstrate the epitaxial growth of the first two members, and the n = β member of the homologous Ruddlesden-Popper series of Ba n + 1 In n O 2.5 n + 1 of which the n = 1 member was previously unknown. The films were grown by suboxide molecular-beam epitaxy where the indium is provided by a molecular beam of indium-suboxide [In 2O (g)]. To facilitate ex situ characterization of the highly hygroscopic barium indate films, a capping layer of amorphous SiO 2 was deposited prior to air exposure. The structural quality of the films was assessed by x-ray diffraction, reflective high-energy electron diffraction, and scanning transmission electron microscopy
Telephone Consultation for Improving Health of People Living with or at Risk of HIV: A Systematic Review
BACKGROUND: Low cost, effective interventions are needed to deal with the major global burden of HIV/AIDS. Telephone consultation offers the potential to improve health of people living with HIV/AIDS cost-effectively and to reduce the burden on affected people and health systems. The aim of this systematic review was to assess the effectiveness of telephone consultation for HIV/AIDS care. METHODS: We undertook a comprehensive search of peer-reviewed and grey literature. Two authors independently screened citations, extracted data and assessed the quality of randomized controlled trials which compared telephone interventions with control groups for HIV/AIDS care. Telephone interventions were voice calls with landlines or mobile phones. We present a narrative overview of the results as the obtained trials were highly heterogeneous in design and therefore the data could not be pooled for statistical analysis. RESULTS: The search yielded 3321 citations. Of these, nine studies involving 1162 participants met the inclusion criteria. The telephone was used for giving HIV test results (one trial) and for delivering behavioural interventions aimed at improving mental health (four trials), reducing sexual transmission risk (one trial), improving medication adherence (two trials) and smoking cessation (one trial). Limited effectiveness of the intervention was found in the trial giving HIV test results, in one trial supporting medication adherence and in one trial for smoking cessation by telephone. CONCLUSIONS: We found some evidence of the benefits of interventions delivered by telephone for the health of people living with HIV or at risk of HIV. However, only limited conclusions can be drawn as we only found nine studies for five different interventions and they mainly took place in the United States. Nevertheless, given the high penetration of low-cost mobile phones in countries with high HIV endemicity, more evidence is needed on how telephone consultation can aid in the delivery of HIV prevention, treatment and care
Effect of Nanocrystal Size and Carbon on Grain Growth during Annealing of Copper Zinc Tin Sulfide Nanocrystal Coatings
Polycrystalline
films were prepared by annealing coatings cast from colloidal dispersions
of Cu<sub>2</sub>ZnSnS<sub>4</sub> (CZTS) nanocrystals in sulfur vapor.
This nanocrystal dispersion-based route is a promising potential low-cost
approach for production of low-cost thin-film solar cells. We studied
the effects of nanocrystal size, sulfur pressure, and carbon concentration
on the microstructure development and grain growth during annealing.
Coatings prepared from dispersions of CZTS nanocrystals with an average
diameter of either 5 or 35 nm were annealed for 10β60 min at
600 Β°C in 50 or 500 Torr of sulfur. The CZTS nanocrystal size
influenced both the rate and mechanism of grain growth. When coatings
composed of 5 nm nanocrystals are annealed, abnormal grain growth
forms micrometer-scale CZTS grains on the surface of the coating.
In contrast, when CZTS coatings composed of 35 nm nanocrystals are
annealed, grains grow uniformly via normal grain growth. Grain growth
rates increased with sulfur pressure regardless of the nanocrystal
size. The presence of carbon, originating from ligands used to stabilize
nanocrystal dispersions, enhances abnormal grain growth, but too much
carbon eventually inhibits all grain growth. On the basis of these
observations, we propose a mechanism for microstructure development
during annealing of CZTS nanocrystal coatings in sulfur. While much
research effort has been expended on the reduction of carbon from
nanocrystal coatings prior to sulfidation or selenization by means
of ligand exchange or preannealing treatments in the belief that reduced
carbon concentration aids CZTS microstructure development and solar
cell efficiencies, this work indicates that carbon plays a more complex
and significant role in CZTS grain growth than previously assumed:
carbon may be beneficial or even required for rapid grain growth during
sulfidation
Formation of Copper Zinc Tin Sulfide Thin Films from Colloidal Nanocrystal Dispersions via Aerosol-Jet Printing and Compaction
A three-step
method to create dense polycrystalline semiconductor thin films from
nanocrystal liquid dispersions is described. First, suitable substrates
are coated with nanocrystals using aerosol-jet printing. Second, the
porous nanocrystal coatings are compacted using a weighted roller
or a hydraulic press to increase the coating density. Finally, the
resulting coating is annealed for grain growth. The approach is demonstrated
for making polycrystalline films of copper zinc tin sulfide (CZTS),
a new solar absorber composed of earth-abundant elements. The range
of coating morphologies accessible through aerosol-jet printing is
examined and their formation mechanisms are revealed. Crack-free albeit
porous films are obtained if most of the solvent in the aerosolized
dispersion droplets containing the nanocrystals evaporates before
they impinge on the substrate. In this case, nanocrystals agglomerate
in flight and arrive at the substrate as solid spherical agglomerates.
These porous coatings are mechanically compacted, and the density
of the coating increases with compaction pressure. Dense coatings
annealed in sulfur produce large-grain (>1 ΞΌm) polycrystalline
CZTS films with microstructure suitable for thin-film solar cells