Thermodynamic Characterization of Polymeric Materials Subjected to Non-isothermal Flows: Experiment, Theory and Simulation

Frictional or viscous heating phenomena are found in virtually every industrial operation dealing with processing of polymeric materials. This work is aimed at addressing some of the existing shortcomings in modeling non-isothermal polymer flowing processes. Specifically, existing theories suggest that when a polymer melt is subjected to deformation, its internal energy changes very little compared to its conformational entropy. This statement forms the definition of the Theory of Purely Entropic Elasticity (PEE) applied to polymer melts. Under the auspices of this theory, the temperature evolution equation for modeling the polymer melt under an applied deformation is greatly simplified. In this study, using a combination of experimental measurements, continuum-based computer modeling and molecular simulation techniques, the validity of this theory is tested for a wide range of processing conditions. First, we present experimental evidence that this theory is only valid for low deformation regimes. Furthermore, using molecular theory, a direct correlation is found between the relaxation characteristics of the polymer and the flow regime where this theory stops being valid. We present a new and improved form of the temperature equation containing an extra term previously neglected under the PEE assumption, followed by a recipe for evaluating the extra term. The corrected temperature equation is found to give more accurate predictions for the temperature profiles in the high flow rate regimes, in excellent agreement with our experimental measurements. Next, in order to gain a molecular-level understanding of our experimental findings, a series of polydisperse linear alkane systems with average chain lengths between 24 and 78 carbon atoms are modeled with an applied “orienting field” using a highly efficient non- equilibrium Monte Carlo scheme. Our simulation results appear to substantiate our experimental findings. The internal energy change of the oriented conformations is found to be similar in magnitude with the free energy change, indicating that it is not reasonable to be neglected from a macroscopic energy balance. Furthermore, the inter- molecular interactions are found to play a crucial role in the energy balance of the system, which explains why PEE is not obeyed when high degrees of orientation are achieved. In the end, a structural study is performed on highly oriented configurations of n-eicosane generated through steady-state non-equilibrium molecular dynamics (NEMD). We compare the simulated oriented structures to x-ray diffraction data for crystalline n-eicosane, and conclude that a crystalline precursor is formed during the simulations

Challenges in Dental Imaging – Edge and Texture Analysis in Caries Detection

One of the most frequent diseases all over the world is represented by dental caries, hence it is of utmost importance to detect them as early as possible, in order to prevent massive tooth decay. Next to clinical examination, radiographic images are essential in identifying caries, especially for lesions located on the contact surface between the posterior teeth. Incipient caries are difficult to identify, sometimes even for specialists, so segmentation and detection through various image processing techniques may be useful. This paper presents an analysis of edge and texture parameters in X-rays containing caries, based on Sobel and Canny operators, Gabor filters and local binary pattern (LBP) operator. Our study set consisted in 80 X-rays from Bitewing Radiography Caries Detection Challenge 2015. Final results align with literature results and confirm the fact that caries segmentation in X-rays is a difficult task, with an average of less than 35% edge pixels correctly identified and poor results for texture segmentation; they also motivate us to refine our work in search of new algorithms and methods for caries segmentation and detection

Global patient outcomes after elective surgery: prospective cohort study in 27 low-, middle- and high-income countries.

BACKGROUND: As global initiatives increase patient access to surgical treatments, there remains a need to understand the adverse effects of surgery and define appropriate levels of perioperative care. METHODS: We designed a prospective international 7-day cohort study of outcomes following elective adult inpatient surgery in 27 countries. The primary outcome was in-hospital complications. Secondary outcomes were death following a complication (failure to rescue) and death in hospital. Process measures were admission to critical care immediately after surgery or to treat a complication and duration of hospital stay. A single definition of critical care was used for all countries. RESULTS: A total of 474 hospitals in 19 high-, 7 middle- and 1 low-income country were included in the primary analysis. Data included 44 814 patients with a median hospital stay of 4 (range 2-7) days. A total of 7508 patients (16.8%) developed one or more postoperative complication and 207 died (0.5%). The overall mortality among patients who developed complications was 2.8%. Mortality following complications ranged from 2.4% for pulmonary embolism to 43.9% for cardiac arrest. A total of 4360 (9.7%) patients were admitted to a critical care unit as routine immediately after surgery, of whom 2198 (50.4%) developed a complication, with 105 (2.4%) deaths. A total of 1233 patients (16.4%) were admitted to a critical care unit to treat complications, with 119 (9.7%) deaths. Despite lower baseline risk, outcomes were similar in low- and middle-income compared with high-income countries. CONCLUSIONS: Poor patient outcomes are common after inpatient surgery. Global initiatives to increase access to surgical treatments should also address the need for safe perioperative care. STUDY REGISTRATION: ISRCTN5181700

Preliminary results of proton inelastic scattering on 57^{57}Fe

International audienceA proton inelastic scattering experiment on a 57Fe target was performed at the 9 MV TANDEM facility of Horia Hulubei-National Institute of Physics and Nuclear Engineering, Bucharest-Măgurele, Romania. The purpose was to determine the γ-production cross sections of the transitions observed in the 57Fe(p, p’γ)57Fe reaction. The detection system consisted of 4 HPGe detectors for detection and a Faraday cup for beam integration. The proton energy was varied from 5 to 16 MeV, in 1-MeV steps. In the current analysis, experimental cross sections were determined only for the high-volume detectors, placed at 110◦ and 150◦ with respect to the beam axis. This work presents the data analysis procedure and the preliminary experimental cross sections for the most intense transitions decaying from the first seven excited states in 57Fe. The results are compared with TALYS 1.9 theoretical calculations performed using default input parameters

Absolute cross sections of the

Absolute cross sections for the 86Sr(α,n)89Zr reaction at energies close to the Gamow window are reported. Three thin SrF2 targets were irradiated using the 9 MV Tandem facility in IFIN-HH Bucharest that delivered α beams for the activation process. Two high-purity Germanium detectors were used to measure the induced activity of 89Zr in a low background environment. The experimental results are in very good agreement with Hauser-Feshbach statistical model calculations performed with the TALYS code

Absolute cross sections of the 86Sr(α,n)89Zr reaction at energies of astrophysical interest

Absolute cross sections for the 86Sr(α,n)89Zr reaction at energies close to the Gamow window are reported. Three thin SrF2 targets were irradiated using the 9 MV Tandem facility in IFIN-HH Bucharest that delivered α beams for the activation process. Two high-purity Germanium detectors were used to measure the induced activity of 89Zr in a low background environment. The experimental results are in very good agreement with Hauser-Feshbach statistical model calculations performed with the TALYS code

Incidence of severe critical events in paediatric anaesthesia (APRICOT): a prospective multicentre observational study in 261 hospitals in Europe

Background Little is known about the incidence of severe critical events in children undergoing general anaesthesia in Europe. We aimed to identify the incidence, nature, and outcome of severe critical events in children undergoing anaesthesia, and the associated potential risk factors. Methods The APRICOT study was a prospective observational multicentre cohort study of children from birth to 15 years of age undergoing elective or urgent anaesthesia for diagnostic or surgical procedures. Children were eligible for inclusion during a 2-week period determined prospectively by each centre. There were 261 participating centres across 33 European countries. The primary endpoint was the occurence of perioperative severe critical events requiring immediate intervention. A severe critical event was defined as the occurrence of respiratory, cardiac, allergic, or neurological complications requiring immediate intervention and that led (or could have led) to major disability or death. This study is registered with ClinicalTrials.gov, number NCT01878760. Findings Between April 1, 2014, and Jan 31, 2015, 31â127 anaesthetic procedures in 30â874 children with a mean age of 6·35 years (SD 4·50) were included. The incidence of perioperative severe critical events was 5·2% (95% CI 5·0â5·5) with an incidence of respiratory critical events of 3·1% (2·9â3·3). Cardiovascular instability occurred in 1·9% (1·7â2·1), with an immediate poor outcome in 5·4% (3·7â7·5) of these cases. The all-cause 30-day in-hospital mortality rate was 10 in 10â000. This was independent of type of anaesthesia. Age (relative risk 0·88, 95% CI 0·86â0·90; p<0·0001), medical history, and physical condition (1·60, 1·40â1·82; p<0·0001) were the major risk factors for a serious critical event. Multivariate analysis revealed evidence for the beneficial effect of years of experience of the most senior anaesthesia team member (0·99, 0·981â0·997; p<0·0048 for respiratory critical events, and 0·98, 0·97â0·99; p=0·0039 for cardiovascular critical events), rather than the type of health institution or providers. Interpretation This study highlights a relatively high rate of severe critical events during the anaesthesia management of children for surgical or diagnostic procedures in Europe, and a large variability in the practice of paediatric anaesthesia. These findings are substantial enough to warrant attention from national, regional, and specialist societies to target education of anaesthesiologists and their teams and implement strategies for quality improvement in paediatric anaesthesia. Funding European Society of Anaesthesiology