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- Fusai, Giuseppe Kito, et al.
(författare)
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Pancreatic surgery outcomes: multicentre prospective snapshot study in 67 countries
- 2023
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Ingår i: British Journal of Surgery. - : OXFORD UNIV PRESS. - 0007-1323 .- 1365-2168.
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Tidskriftsartikel (refereegranskat)abstract
- Background: Pancreatic surgery remains associated with high morbidity rates. Although postoperative mortality appears to have improved with specialization, the outcomes reported in the literature reflect the activity of highly specialized centres. The aim of this study was to evaluate the outcomes following pancreatic surgery worldwide. Methods: This was an international, prospective, multicentre, cross-sectional snapshot study of consecutive patients undergoing pancreatic operations worldwide in a 3-month interval in 2021. The primary outcome was postoperative mortality within 90 days of surgery. Multivariable logistic regression was used to explore relationships with Human Development Index (HDI) and other parameters. Results: A total of 4223 patients from 67 countries were analysed. A complication of any severity was detected in 68.7 percent of patients (2901 of 4223). Major complication rates (Clavien-Dindo grade at least IIIa) were 24, 18, and 27 percent, and mortality rates were 10, 5, and 5 per cent in low-to-middle-, high-, and very high-HDI countries respectively. The 90-day postoperative mortality rate was 5.4 per cent (229 of 4223) overall, but was significantly higher in the low-to-middle-HDI group (adjusted OR 2.88, 95 per cent c.i. 1.80 to 4.48). The overall failure-to-rescue rate was 21 percent; however, it was 41 per cent in low-to-middle-compared with 19 per cent in very high-HDI countries. Conclusion: Excess mortality in low-to-middle-HDI countries could be attributable to failure to rescue of patients from severe complications. The authors call for a collaborative response from international and regional associations of pancreatic surgeons to address management related to death from postoperative complications to tackle the global disparities in the outcomes of pancreatic surgery (NCT04652271; ISRCTN95140761).
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- Chao, Yimin, et al.
(författare)
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Evaporation and deposition of alkyl-capped silicon nanocrystals in ultrahigh vacuum
- 2007
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Ingår i: Nature Nanotechnology. - : Springer Science and Business Media LLC. - 1748-3395 .- 1748-3387. ; 2:8, s. 486-489
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Tidskriftsartikel (refereegranskat)abstract
- Nanocrystals are under active investigation because of their interesting size- dependent properties(1,2) and potential applications(3-5). Silicon nanocrystals have been studied for possible uses in optoelectronics(6), and may be relevant to the understanding of natural processes such as lightning strikes(7). Gas-phase methods can be used to prepare nanocrystals, and mass spectrometric techniques have been used to analyse Au-8,(9) and CdSe clusters(10). However, it is difficult to study nanocrystals by such methods unless they are synthesized in the gas phase(11). In particular, pre-prepared nanocrystals are generally difficult to sublime without decomposition. Here we report the observation that films of alkyl-capped silicon nanocrystals evaporate upon heating in ultrahigh vacuum at 200 degrees C, and the vapour of intact nanocrystals can be collected on a variety of solid substrates. This effect may be useful for the controlled preparation of new quantum-confined silicon structures and could facilitate their mass spectroscopic study and size- selection(12).
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- Mittal, Nitesh, et al.
(författare)
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Numerical Simulation of Mixed-Convection Flow in a Lid-Driven Porous Cavity Using Different Nanofluids
- 2014
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Ingår i: Heat Transfer-Asian Research. - : Wiley Periodicals. - 1099-2871 .- 1523-1496. ; 43:1, s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the effect of mixed convection flow in a lid-driven porous cavity using different nanoparticles, such as aluminum oxide (Al 2 O 3), copper (Cu), silver (Ag), and titanium dioxide (TiO 2), are investigated. The base fluid is considered as water. The transport equations are solved numerically by finite volume method on a co-located grid arrangement using quadratic upwind interpolation for convective kinematics (QUICK) scheme. A two-dimensional square cavity is considered for the present investigation whose horizontal walls are insulated. The cold left wall is moving up and hot right wall is moving down with equal velocities. The variations of temperature distribution, stream function, and Nusselt number (Nu) are analyzed at constant Grashof numbers (Gr), Richardson numbers (Ri), and Darcy numbers (Da) as 1 × 10 4, 100, and 0.1, respectively, for different nanoparticles. The present results are validated by favorable comparison with previously published literature. The predicted results clearly indicate that the presence of nanoparticles inside the porous media enhances the heat transfer significantly. It is observed from the numerical results that the average Nusselt numbers (Nu) were found to increase linearly with an increase in volume fraction (χ). For the given volume fraction, the average Nu is maximum for a silver-based nanoparticle.
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- Mittal, Nitesh, et al.
(författare)
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Numerical simulation of mixed convection in a porous medium filled with water/Al2 O3 nanofluid
- 2013
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Ingår i: Heat Transfer-Asian Research. - : Wiley Periodicals. - 1099-2871 .- 1523-1496. ; 42:1, s. 46-59
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Tidskriftsartikel (refereegranskat)abstract
- The present work encloses the application of a Brinkman-extended Darcy model in a problem concerning mixed convection ina lid-driven porous cavity using nanofluids. The transport equations are solved numerically by the finite volume method on a co-located grid arrangement using the Quadratic Upstream Interpolation for Convective Kinematics (QUICK) scheme. The effects of governing parameters, namely, Grashof number (Gr), Darcy number (Da), and solid volume fraction $(\chi)$, on the streamlines and the isotherms are studied. The present results are validated by favorable comparisons with previously published results and are in good agreement with them. The present numerical results show that the addition of nanoparticles to a base fluid has produced an augmentation of the heat transfer coefficient and it is found to increase significantly with an increase of the particle volume concentration. It is observed from the results that at the higher value of the Grashof number (Gr = 104), the average Nusselt number increases with an increase in the Darcy number for a constant solid volume fraction. The detailed results are reported by means of streamlines, isotherms, and Nusselt numbers
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