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- Ademuyiwa, Adesoji O., et al.
(author)
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Determinants of morbidity and mortality following emergency abdominal surgery in children in low-income and middle-income countries
- 2016
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In: BMJ Global Health. - : BMJ Publishing Group Ltd. - 2059-7908. ; 1:4
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Journal article (peer-reviewed)abstract
- Background: Child health is a key priority on the global health agenda, yet the provision of essential and emergency surgery in children is patchy in resource-poor regions. This study was aimed to determine the mortality risk for emergency abdominal paediatric surgery in low-income countries globally.Methods: Multicentre, international, prospective, cohort study. Self-selected surgical units performing emergency abdominal surgery submitted prespecified data for consecutive children aged <16 years during a 2-week period between July and December 2014. The United Nation's Human Development Index (HDI) was used to stratify countries. The main outcome measure was 30-day postoperative mortality, analysed by multilevel logistic regression.Results: This study included 1409 patients from 253 centres in 43 countries; 282 children were under 2 years of age. Among them, 265 (18.8%) were from low-HDI, 450 (31.9%) from middle-HDI and 694 (49.3%) from high-HDI countries. The most common operations performed were appendectomy, small bowel resection, pyloromyotomy and correction of intussusception. After adjustment for patient and hospital risk factors, child mortality at 30 days was significantly higher in low-HDI (adjusted OR 7.14 (95% CI 2.52 to 20.23), p<0.001) and middle-HDI (4.42 (1.44 to 13.56), p=0.009) countries compared with high-HDI countries, translating to 40 excess deaths per 1000 procedures performed.Conclusions: Adjusted mortality in children following emergency abdominal surgery may be as high as 7 times greater in low-HDI and middle-HDI countries compared with high-HDI countries. Effective provision of emergency essential surgery should be a key priority for global child health agendas.
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- Baran, Jakub D., et al.
(author)
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A Case of Unusually Large Density of States Changes For Physisorption - TetraPhenyl-Porphyrins on Cu(111)
- 2015
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Conference paper (other academic/artistic)abstract
- Conformational changes caused by surface adsorption can dramatically affect a molecule’s properties. The conformational flexibility of the porphyrin family of molecules has been exploited particularly well in a number of contexts, including prototypical molecular switches. Despite this level of study, however, the exact mechanisms underpinning conformational switching are often unclear. We show that the conformation of the tetra(4-bromophenyl) porphyrin (Br4TPP) on Cu(111) depends critically on the precise adsorption site of the molecule, and that, remarkably, large conformational changes are driven entirely by van der Waals (vdW) interactions between the molecule and the substrate surface. A combination of scanning probe microscopy, low temperature single molecule manipulation, dispersion-corrected density functional theory (DFT) and molecular dynamics (MD) simulations shows that van der Waals forces dominate the adsorption of TPP molecules, causing significant distortions of the molecular architecture so that the porphyrin can adopt one of two low energy conformations. In addition, scanning probe manipulation has been used to translate and switch the Br4TPP molecule between conformations via an intermediary, ‘hybrid’ structure. We have used the generalized gradient approximation (GGA) parameterization by Perdew—Burke—Ernzerhof (PBE), and the sparse-matter optBP86b-vdW20 (vdW-DFT) exchange and correlation functional to account for the missing dispersion forces. In order to check for the presence of chemical bonding we have analyzed the molecule-surface complexes using electron localization function (ELF) and Bader charges. We find that vdW-forces alone are capable of causing large shifts in the molecular density of states, despite the complete absence of chemical interactions.
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| 8. |
- Gannon, Greg, et al.
(author)
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Modelling ink spreading on self-assembled monolayers for nanopatterning applications
- 2008
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Conference paper (peer-reviewed)abstract
- Alkanethiol self-assembled monolayers (SAMs) on gold; specifically the Au(111) surface; have been widely studied since their discovery in the early 1980 s. The interest in SAMs is due in part to their ease of production but also due to their present and potential application in technologies as diverse as biosensors; corrosion protection and nanolithography. Spreading of ink outside the desired printed area is one of the major limitations of microcontact printing (m-CP) with alkanethiol self-assembled monolayers (SAMs) on gold.1;2 We use molecular dynamics (MD) computer simulations to quantify the temperature and concentration dependence of hexadecanethiol (HDT) ink spreading on HDT SAMs; modelling 18 distinct printing conditions using periodic simulation cells of ~7 nm edge length and printing conditions ranging from 7 ink molecules per cell at 270 K to 42 ink molecules per cell at 371K.3 The computed alkanethiol ink diffusion rates on the SAM are of the same order of magnitude as bulk liquid alkanethiol diffusion rates at all but the lowest ink concentrations and highest temperatures; with up to 20-30 times increases in diffusion rates at the lowest concentration-highest temperature conditions. We show that although alkanethiol surfaces are autophobic; autophobicity is not enough to pin the ink solutions on the SAM and so any over-inking of the SAM will lead to spreading of the printed pattern. Comparison of experimental and calculated diffusion data supports an interpretation of pattern broadening as a mixture of spreading on fully- and partially-formed SAMs; and the calculated spreading rates establish some of the fundamental limitations of m-CP in terms of stamp contact time and desired pattern width
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| 9. |
- Gannon, Greg, et al.
(author)
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Molecular dynamics simulations of self-assembled monolayers for nanopatterning applications
- 2007
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Conference paper (peer-reviewed)abstract
- Self-Assembled Monolayers (SAMs) are used in areas as diverse as corrosion protection; nanodevices and biotechnology. Despite a wealth of both experimental and theoretical studies of SAM structure and behaviour[1]; there still remain some unanswered questions. Alkanethiol molecular ink diffusion on alkanethiol SAMs is one such area; and one amenable to computational study. Ink diffusion is an important consideration when one performs microcontact printing - "... the quality of the printed pattern strongly depends on the mobility of the ink compound ..."[2]. An understanding of ink diffusion is therefore crucial to the production of stable; high-resolution nanopatterns. We first of all calculated alkanethiol self-diffusion coefficients in bulk liquid and obtained good agreement with measured values. The Einstein diffusion equation was used to calculate the diffusion coefficients from 1 nanosecond molecular dynamics (MD) simulations Simulations of alkanethiol SAMs were performed and the temperature dependence of the SAM tilt angle found to be in good agreement with literature values. Having validated our method both for calculating diffusion and the SAM structural models; we calculated the diffusion of both a single alkanethiol molecule and a 75-molecule drop ; on a range of perfect and defect SAMs; establishing a range for ink diffusion in different environments and; ultimately; allowing identification of optimum ink molecular weights for microcontact printing applications
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