Cratering and plastic deformation in polystyrene induced by MeV heavy ions : dependence on the molecular weight

Cratering and plastic deformation induced by individual MeV ions on the surface of polystyrene thin films of different molecular weights (Mw) (from 3250 to 2 X 10⁷u) are investigated using scanning force microscopy. 20 MeV, 85 MeV and 197 MeV gold ions are used to bombard the targets at grazing incidence (79° to the surface normal). Induced surface tracks consist of an elliptical crater followed by a hillock elongated in the direction of the ion incidence. For a given ion energy, the crater size is largest on the lowest Mw film. Crater dimensions are systematically reduced on films of heavier macro-molecules, up to a molecular weight of about 1.6 X 10⁵u. For Mw>1.6 X 10⁵u, the crater size remains approximately constant. The difference observed for the lateral dimensions of the craters are about 50% when comparing the lowest and the highest Mw films at a fixed energy. The observed saturation of the crater size for high Mw values coincides with the onset of entanglement effects in the polymer, which influences the viscosity and the compliance of the material. Moreover, the curve of the crater size versus Mw follows the same trend as the reciprocal viscosity (ηˉ¹) versus Mw , indicating that the viscosity is governing the final lateral dimensions of the craters. The hillock dimensions present a weak dependence on Mw , above a threshold at 3250u. The different behavior observed for craters and hillocks is discussed based on the viscoelastic properties of the polymer at different Mw and on the transient heating occurring close to the ion impact site

Cratering and plastic deformation in polystyrene induced by MeV heavy ions : dependence on the molecular weight

Cratering and plastic deformation induced by individual MeV ions on the surface of polystyrene thin films of different molecular weights (Mw) (from 3250 to 2 X 10⁷u) are investigated using scanning force microscopy. 20 MeV, 85 MeV and 197 MeV gold ions are used to bombard the targets at grazing incidence (79° to the surface normal). Induced surface tracks consist of an elliptical crater followed by a hillock elongated in the direction of the ion incidence. For a given ion energy, the crater size is largest on the lowest Mw film. Crater dimensions are systematically reduced on films of heavier macro-molecules, up to a molecular weight of about 1.6 X 10⁵u. For Mw>1.6 X 10⁵u, the crater size remains approximately constant. The difference observed for the lateral dimensions of the craters are about 50% when comparing the lowest and the highest Mw films at a fixed energy. The observed saturation of the crater size for high Mw values coincides with the onset of entanglement effects in the polymer, which influences the viscosity and the compliance of the material. Moreover, the curve of the crater size versus Mw follows the same trend as the reciprocal viscosity (ηˉ¹) versus Mw , indicating that the viscosity is governing the final lateral dimensions of the craters. The hillock dimensions present a weak dependence on Mw , above a threshold at 3250u. The different behavior observed for craters and hillocks is discussed based on the viscoelastic properties of the polymer at different Mw and on the transient heating occurring close to the ion impact site

Detrapping of vacancies at in/sup 111/ in quenched silver

The isothermal recovery of a quenched Ag foil doped with 111 ln has been studied through the time-differential perturbed-angular-correlation technique. A nearest-neighbor-vacancy configuration has produced a quadrupole interaction frequency, v0 = 166±3 MHz, and a detrapping vacancy process has been detected with Ed = 1.09±0.05 e V. The results are discussed and compared with previous measurements

Detrapping of vacancies at in/sup 111/ in quenched silver

The isothermal recovery of a quenched Ag foil doped with 111 ln has been studied through the time-differential perturbed-angular-correlation technique. A nearest-neighbor-vacancy configuration has produced a quadrupole interaction frequency, v0 = 166±3 MHz, and a detrapping vacancy process has been detected with Ed = 1.09±0.05 e V. The results are discussed and compared with previous measurements

Surgical site infection after gastrointestinal surgery in children : an international, multicentre, prospective cohort study

Introduction 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. Methods A 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). Results Of 1159 children across 181 hospitals in 51 countries, 523 (45 center dot 1%) children were from high HDI, 397 (34 center dot 2%) from middle HDI and 239 (20 center dot 6%) from low HDI countries. The 30-day SSI rate was 6.3% (33/523) in high HDI, 12 center dot 8% (51/397) in middle HDI and 24 center dot 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. Conclusion The 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.Peer reviewe

Exploring the cost-effectiveness of high versus low perioperative fraction of inspired oxygen in the prevention of surgical site infections among abdominal surgery patients in three low- and middle-income countries

Background: This study assessed the potential cost-effectiveness of high (80–100%) vs low (21–35%) fraction of inspired oxygen (FiO2) at preventing surgical site infections (SSIs) after abdominal surgery in Nigeria, India, and South Africa. Methods: Decision-analytic models were constructed using best available evidence sourced from unbundled data of an ongoing pilot trial assessing the effectiveness of high FiO2, published literature, and a cost survey in Nigeria, India, and South Africa. Effectiveness was measured as percentage of SSIs at 30 days after surgery, a healthcare perspective was adopted, and costs were reported in US dollars ($). Results: High FiO2 may be cost-effective (cheaper and effective). In Nigeria, the average cost for high FiO2 was$216 compared with $222 for low FiO2 leading to a −$6 (95% confidence interval [CI]: −$13 to −$1) difference in costs. In India, the average cost for high FiO2 was $184 compared with$195 for low FiO2 leading to a −$11 (95$15 to −$6) difference in costs. In South Africa, the average cost for high FiO2 was$1164 compared with $1257 for low FiO2 leading to a −$93 (95% CI: −$132 to −$65) difference in costs. The high FiO2 arm had few SSIs, 7.33% compared with 8.38% for low FiO2, leading to a −1.05 (95% CI: −1.14 to −0.90) percentage point reduction in SSIs. Conclusion: High FiO2 could be cost-effective at preventing SSIs in the three countries but further data from large clinical trials are required to confirm this

Use of Telemedicine for Post-discharge Assessment of the Surgical Wound: International Cohort Study, and Systematic Review with Meta-analysis

Objective: This study aimed to determine whether remote wound reviews using telemedicine can be safely upscaled, and if standardised assessment tools are needed. Summary background data: Surgical site infection is the most common complication of surgery worldwide, and frequently occurs after hospital discharge. Evidence to support implementation of telemedicine during postoperative recovery will be an essential component of pandemic recovery. Methods: The primary outcome of this study was surgical site infection reported up to 30-days after surgery (SSI), comparing rates reported using telemedicine (telephone and/or video assessment) to those with in-person review. The first part of this study analysed primary data from an international cohort study of adult patients undergoing abdominal surgery who were discharged from hospital before 30-days after surgery. The second part combined this data with the results of a systematic review to perform a meta-analysis of all available data conducted in accordance with PRIMSA guidelines (PROSPERO:192596). Results: The cohort study included 15,358 patients from 66 countries (8069 high, 4448 middle, 1744 low income). Of these, 6907 (45.0%) were followed up using telemedicine. The SSI rate reported using telemedicine was slightly lower than with in-person follow-up (13.4% vs. 11.1%, P<0.001), which persisted after risk adjustment in a mixed-effects model (adjusted odds ratio: 0.73, 95% confidence interval 0.63-0.84, P<0.001). This association was consistent across sensitivity and subgroup analyses, including a propensity-score matched model. In nine eligible non-randomised studies identified, a pooled mean of 64% of patients underwent telemedicine follow-up. Upon meta-analysis, the SSI rate reported was lower with telemedicine (odds ratio: 0.67, 0.47-0.94) than in-person (reference) follow-up (I2=0.45, P=0.12), although there a high risk of bias in included studies. Conclusions: Use of telemedicine to assess the surgical wound post-discharge is feasible, but risks underreporting of SSI. Standardised tools for remote assessment of SSI must be evaluated and adopted as telemedicine is upscaled globally