| 1. |
- Thomas, HS, et al.
(författare)
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- 2019
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swepub:Mat__t
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| 2. |
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| 3. |
- Drake, TM, et al.
(författare)
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Surgical site infection after gastrointestinal surgery in children: an international, multicentre, prospective cohort study
- 2020
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Ingår i: BMJ global health. - : BMJ. - 2059-7908. ; 5:12
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Tidskriftsartikel (refereegranskat)abstract
- Surgical site infection (SSI) is one of the most common healthcare-associated infections (HAIs). However, there is a lack of data available about SSI in children worldwide, especially from low-income and middle-income countries. This study aimed to estimate the incidence of SSI in children and associations between SSI and morbidity across human development settings.MethodsA multicentre, international, prospective, validated cohort study of children aged under 16 years undergoing clean-contaminated, contaminated or dirty gastrointestinal surgery. Any hospital in the world providing paediatric surgery was eligible to contribute data between January and July 2016. The primary outcome was the incidence of SSI by 30 days. Relationships between explanatory variables and SSI were examined using multilevel logistic regression. Countries were stratified into high development, middle development and low development groups using the United Nations Human Development Index (HDI).ResultsOf 1159 children across 181 hospitals in 51 countries, 523 (45·1%) children were from high HDI, 397 (34·2%) from middle HDI and 239 (20·6%) from low HDI countries. The 30-day SSI rate was 6.3% (33/523) in high HDI, 12·8% (51/397) in middle HDI and 24·7% (59/239) in low HDI countries. SSI was associated with higher incidence of 30-day mortality, intervention, organ-space infection and other HAIs, with the highest rates seen in low HDI countries. Median length of stay in patients who had an SSI was longer (7.0 days), compared with 3.0 days in patients who did not have an SSI. Use of laparoscopy was associated with significantly lower SSI rates, even after accounting for HDI.ConclusionThe odds of SSI in children is nearly four times greater in low HDI compared with high HDI countries. Policies to reduce SSI should be prioritised as part of the wider global agenda.
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| 4. |
- Syväjärvi, Mikael, et al.
(författare)
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Fluorescent SiC as a new material for white LEDs
- 2012
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Ingår i: Physica scripta. T. - 0281-1847 .- 0031-8949 .- 1402-4896. ; T148, s. 014002-
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Tidskriftsartikel (refereegranskat)abstract
- Current III–V-based white light-emitting diodes (LEDs) are available. However, their yellow phosphor converter is not efficient at high currents and includes rare-earth metals, which are becoming scarce. In this paper, we present the growth of a fluorescent silicon carbide material that is obtained by nitrogen and boron doping and that acts as a converter using a semiconductor. The luminescence is obtained at room temperature, and shows a broad luminescence band characteristic of donor-to-acceptor pair recombination. Photoluminescence intensities and carrier lifetimes reflect a sensitivity to nitrogen and boron concentrations. For an LED device, the growth needs to apply low-off-axis substrates. We show by ultra-high-resolution analytical transmission electron microscopy using aberration-corrected electrons that the growth mechanism can be stable and that there is a perfect epitaxial relation from the low-off-axis substrate and the doped layer even when there is step-bunching.
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| 5. |
- Gulbinas, Karolis, et al.
(författare)
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Raman Scattering and Carrier Diffusion Study in Heavily Co-doped 6H-SiC Layers
- 2014
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Ingår i: IOP Conference Series. - : Institute of Physics Publishing (IOPP). - 1757-8981 .- 1757-899X. ; 56:1, s. 012005-
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Tidskriftsartikel (refereegranskat)abstract
- Thick 6H-SiC epilayers were grown using the fast sublimation method on low-off-axis substrates. They were co-doped with N and B impurities of ≈1019 cm−3 and (41016–51018) cm−3 concentration, respectively. The epilayers exhibited donor-acceptor pair (DAP) photoluminescence. The micro-Raman spectroscopic study exposed a compensated n-6H-SiC epilayer of common quality with some 3C-SiC inclusions. The compensation ratio of B through 200 μm thick epilayer varied in 20-30% range. The free carrier diffusivity was studied by transient grating technique at high injection level. The determined ambipolar diffusion coefficient at RT was found to decrease from 1.15 cm2/s to virtually 0 cm2/s with boron concentration increasing by two orders.
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| 6. |
- Gavryushin, V., et al.
(författare)
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Examination of Photoluminescence Temperature Dependencies in N-B Co-doped 6H-SiC
- 2014
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Ingår i: IOP Conference Series. - : Institute of Physics Publishing (IOPP). - 1757-8981 .- 1757-899X. ; 56:1, s. 012003-
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Tidskriftsartikel (refereegranskat)abstract
- Two overlapping photoluminescent (PL) bands with a peaks (half-width) at 1.95 eV (0.45 eV) and 2.15 eV (0.25 eV), correspondingly at 300 K, are observed in heavily B-N co-doped 6H-SiC epilayers under high-level excitation condition. The low energy band dominates at low temperatures and decreases towards 300 K which is assigned to DAP emission from the nitrogen trap to the deep boron (dB) with phonon-assistance. The 2.15 eV band slightly increases with temperature and becomes comparable with the former one at 300 K. We present a modelling comprising electron de-trapping from the N-trap, i.e. calculating trapping and de-trapping probabilities. The T-dependence of the 2.15 eV band can be explained by free electron emission from the conduction band into the dB center provided by similar phonon-assistance
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| 7. |
- Grivickas, V., et al.
(författare)
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Carrier lifetimes and influence of in-grown defects in N-B Co-doped 6H-SiC
- 2014
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Ingår i: IOP Conference Series. - : Institute of Physics Publishing (IOPP). ; 56:1, s. 012004-
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Konferensbidrag (refereegranskat)abstract
- The thick N-B co-doped epilayers were grown by the fast sublimation growth method and the depth-resolved carrier lifetimes have been investigated by means of the free-carrier absorption (FCA) decay under perpendicular probe-pump measurement geometry. In some samples, we optically reveal in-grown carbon inclusions and polycrystalline defects of substantial concentration and show that these defects slow down excess carrier lifetime and prevent donor-acceptor pair photo luminescence (DAP PL). A pronounced electron lifetime reduction when injection level approaches the doping level was observed. It is caused by diffusion driven non-radiative recombination. However, the influence of surface recombination is small and insignificant at 300 K.
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| 8. |
- Grivickas, V., et al.
(författare)
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Fundamental band edge absorption in 3C-SiC : Phonon absorption assisted transitions
- 2010
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Ingår i: Silicon Carbide and Related Materials 2009, Pts 1 and 2. - : Trans Tech Publications Inc.. - 0878492798 - 9780878492794 ; , s. 231-234
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Konferensbidrag (refereegranskat)abstract
- An alternative approach based on non-equilibrium free-carrier density measurements was used to characterize the fundamental absorption edge of 3C-SiC at room and 77 K temperatures. At 77 K temperature the extracted absorption edge compared well to the previous literature data revealing characteristic thresholds due to the phonon emission assisted transitions. At room temperature the absorption tail due to the phonon absorption assisted transition was revealed up to the value of 0.01cm-1 exceeding the previous 5 cm -1 limit induced by unintentional sample doping.
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| 9. |
- Grivickas, V., et al.
(författare)
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Internal stress in freestanding 3C-SiC grown on Si and relation to carrier lifetime
- 2010
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Ingår i: 2010 Wide Bandgap Cubic Semiconductors. - : American Institute of Physics (AIP). - 9780735408470 ; , s. 91-94
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Konferensbidrag (refereegranskat)abstract
- Residual stress and carrier lifetime variation have been measured in free-standing n-type 3C-SiC wafer grown on undulated Si substrate. We identify extended regions of residual stress that lie parallel to epilayer surfaces. The opposite polarity of stress is identified toward the interface and toward the top surface. Integrated carrier lifetime has been determined by random defect density distribution which is enhanced in the areas of double-positioning boundary defects. It is shown that carrier lifetimes are severely reduced by the presence of residual stress towards epilayer surfaces. In this way lifetime depth-distribution can be mistakenly attributed to enhanced surface recombination.
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| 10. |
- Gulbinas, K., et al.
(författare)
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Conversion of laser pulse optical energy to photo-acoustic wave in nm-scale layered tlgase2 crystals
- 2014
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Ingår i: IOP Conference Series.
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Konferensbidrag (refereegranskat)abstract
- Experiments are presented that reveal an efficient optical energy conversion from the visible to the infrared wavelengths range as a result of photo-acoustic response (PAR) after light pulse incites onto the free surface of Tlgase2 crystal. Excitation was carried out with a tunable wavelength of ns-pulse laser and the PAR was detected laterally with a focused cw- probe. The observed properties can be related to variety of successive factors: high electron- hole-phonon deformation potential, a high factor of refraction coefficient dependency on pressure, the absence of surface recombination and the band filling effect, in relation with low absorption coefficient due to the forbidden direct-band optical transition in Tlgase2. All these ensure that the acoustic energy remain well confined under a wide pulse power and energy range suggesting that Tlgase2 is a promising material for dynamic optical energy conversion.
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