10 research outputs found
Low Temperature Solution-Phase Deposition of SnS Thin Films
The solution-phase deposition of inorganic semiconductors
is a promising, scalable method for the manufacture of
thin film photovoltaics. Deposition of photovoltaic materials
from molecular or colloidal inks offers the possibility of
inexpensive, rapid, high-throughput thin film fabrication
through processes such as spray coating. For example, CdTe,
Cu(In,Ga)(S,Se)_2 (CIGS), and CH_3NH_3Pb(Cl,I)_3 perovskite-based
thin film solar cells have been previously deposited using
solution-based processes. Inks have also recently been
developed for the solution deposition of Cu_2ZnSn(S,Se)_4
(CZTS) and FeS_2 (iron pyrite) absorber layers for thin film
solar applications, in order to provide sustainable alternatives to
materials that contain environmentally harmful heavy metals
(e.g., Cd, Pb) and/or scarce elements (e.g., Te, In)
Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study
Summary
Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally.
Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies
have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of
the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income
countries globally, and identified factors associated with mortality.
Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to
hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis,
exomphalos, anorectal malformation, and Hirschsprungâs disease. Recruitment was of consecutive patients for a
minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical
status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary
intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause,
in-hospital mortality for all conditions combined and each condition individually, stratified by country income status.
We did a complete case analysis.
Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital
diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal
malformation, and 517 with Hirschsprungâs disease) from 264 hospitals (89 in high-income countries, 166 in middleincome
countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male.
Median gestational age at birth was 38 weeks (IQR 36â39) and median bodyweight at presentation was 2·8 kg (2·3â3·3).
Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income
countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups).
Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome
countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries;
pâ€0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients
combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88â4·11],
p<0·0001; middle-income vs high-income countries, 2·11 [1·59â2·79], p<0·0001), sepsis at presentation (1·20
[1·04â1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention
(ASA 4â5 vs ASA 1â2, 1·82 [1·40â2·35], p<0·0001; ASA 3 vs ASA 1â2, 1·58, [1·30â1·92], p<0·0001]), surgical safety
checklist not used (1·39 [1·02â1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed
(ventilation 1·96, [1·41â2·71], p=0·0001; parenteral nutrition 1·35, [1·05â1·74], p=0·018). Administration of
parenteral nutrition (0·61, [0·47â0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65
[0·50â0·86], p=0·0024) or percutaneous central line (0·69 [0·48â1·00], p=0·049) were associated with lower mortality.
Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome,
middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will
be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger
than 5 years by 2030
Solution-Phase Synthesis of Highly Conductive Tungsten Diselenide Nanosheets
Solution-Phase
Synthesis of Highly Conductive Tungsten
Diselenide Nanosheet
Patching of Lattice Defects in Two-Dimensional Diffusion Barriers
Two-dimensional crystals
offer promise as diffusion barriers that
can also facilitate electronic conduction through the barrier plane
via tunneling. We present barriers in which crystal imperfections
are patched, leaving the pristine regions of the crystal exposed and
able to both prevent diffusion and allow electronic conduction. This
is accomplished by atomic layer deposition, where nucleation of patch
material is inhibited on the pristine crystal and promoted elsewhere.
Demonstrations of the effectiveness of this technique are performed
in the contexts of sulfur diffusion control in photovoltaic kesterite
devices and oxygen diffusion control in oxide-based resistive switching
devices
Low Temperature Solution-Phase Deposition of SnS Thin Films
Low Temperature
Solution-Phase Deposition of SnS Thin
Film
Fused PorphyrinâSingle-Walled Carbon Nanotube Hybrids: Efficient Formation and Photophysical Characterization
A systematic study of the interaction between Ï-extended porphyrins and single-walled carbon nanotubes (SWNTs) is reported here. Zinc porphyrins with 1-pyrenyl groups in the 5,15-<i>meso</i> positions, <b>1</b>, as well as compounds where one or both of the pyrene groups have been fused at the <i>meso</i> and ÎČ positions of the porphyrin core, <b>2</b> and <b>3</b>, respectively, have been examined. The strongest binding to SWNTs is observed for porphyrin <b>3</b>, leading to debundling of the nanotubes and formation of stable suspensions of <b>3</b>âSWNT hybrids in a range of common organic solvents. Absorption spectra of <b>3</b>âSWNT suspensions are broad and continuous (λ = 400â1400 nm), and the Q-band of <b>3</b> displays a significant bathochromic shift of 33 nm. The surface coverage of the SWNTs in the nanohybrids was estimated by spectroscopic and analytical methods and found to reach 64% for (7,6) nanotubes. The size and shape of Ï-conjugated porphyrins were found to be important factors in determining the strength of the ÏâÏ interactions, as the linear <i>anti</i>-<b>3</b> isomer displays more than 90% binding selectivity compared to the bent <i>syn</i>-<b>3</b> isomer. Steady-state photoluminescence measurements show quenching of porphyrin emission from the nanohybrids. Femtosecond transient absorption spectroscopy reveals that this quenching results from ultrafast electron transfer from the photoexcited porphyrin to the SWNT (1/<i>k</i><sub>CT</sub> = 260 fs) followed by rapid charge recombination on a picosecond time scale. Overall, our data demonstrate that direct ÏâÏ interaction between fused porphyrins and SWNTs leads to electronically coupled stable nanohybrids
Nanoscale Characterization of Back Surfaces and Interfaces in Thin-Film Kesterite Solar Cells
Combinations
of sub 1 ÎŒm absorber films with high-work-function back surface
contact layers are expected to induce large enough internal fields
to overcome adverse effects of bulk defects on thin-film photovoltaic
performance, particularly in earth-abundant kesterites. However, there
are numerous experimental challenges involving back surface engineering,
which includes exfoliation, thinning, and contact layer optimization.
In the present study, a unique combination of nanocharacterization
tools, including nano-Auger, Kelvin probe force microscopy (KPFM),
and cryogenic focused ion beam measurements, are employed to gauge
the possibility of surface potential modification in the absorber
back surface via direct deposition of high-work-function metal oxides
on exfoliated surfaces. Nano-Auger measurements showed large compositional
nonuniformities on the exfoliated surfaces, which can be minimized
by a brief bromineâmethanol etching step. Cross-sectional nano-Auger
and KPFM measurements on Au/MoO<sub>3</sub>/Cu<sub>2</sub>ÂZnSnÂ(S,Se)<sub>4</sub> (CZTSSe) showed an upward band bending as large as 400 meV
within the CZTSSe layer, consistent with the high work function of
MoO<sub>3</sub>, despite Au incorporation into the oxide layer. Density
functional theory simulations of the atomic structure for bulk amorphous
MoO<sub>3</sub> demonstrated the presence of large voids within MoO<sub>3</sub> enabling Au in-diffusion. With a less diffusive metal electrode
such as Pt or Pd, upward band bending beyond this level is expected
to be achieved