Dynamic response of simply supported beams excited by piezoelectric actuators

The use of piezoelectric devices for the purposes of active noise or vibration control has become attractive in recent times. These small, power to weight efficient devices have had some success in active vibration control; however, the force transfer mechanism by which they interact with the structure to which they are attached needs to be understood to optimise the efficiency of their use. Various modelling approaches have been used over the past six (6) years to try and understand the force transfer mechanism in beams and plates, and in this work an adaptation of a published model is presented, and compared with experimental data and other published models. The force transfer mechanism between the piezoelectric actuator and the beam is found to be dependent upon the impedance of the beam. At resonance, the free edge condition of the piezoelectric actuator does not affect the strain field close to the free edge. Away from resonances, the force transfer mechanism is different and less efficient, and the free edge condition of the piezoelectric actuator does affect the strain field close to the free edge of the actuator. Further experimental work, investigating the power flow from the piezoelectric actuators to the beam, emphasises some of the differences found between the theory and experiments, and between the performance of piezoelectric actuators and electrodynamic actuatorsThesis (MESc.)--University of Adelaide, Dept. of Mechanical Engineering, 1993

The COlorectal NEoplasia Endoscopic Classification to Choose the Treatment classification for identification of large laterally spreading lesions lacking submucosal carcinomas: A prospective study of 663 lesions

International audienceAbstract Introduction Optical diagnosis is necessary when selecting the resection modality for large superficial colorectal lesions. The CO lorectal NE oplasia Endoscopic C lassification to C hoose the T reatment (CONECCT) encompasses overt (irregular pit or vascular pattern) and covert (macroscopic features) signs of carcinoma in an all‐in‐one classification using validated criteria. The CONECCT IIC subtype corresponds to adenomas with a high risk of superficial carcinoma that should be resected en bloc with free margins. Methods This prospective multicentre study investigated the diagnostic accuracy of the CONECCT classification for predicting submucosal invasion in colorectal lesions >20 mm. Optical diagnosis before en bloc resection by endoscopic submucosal dissection (ESD) was compared with the final histological diagnosis. Diagnostic accuracy for the CONECCT IIC subtype was compared with literature‐validated features of concern considered to be risk factors for submucosal invasion (non‐granular large spreading tumour [NG LST], macronodule >1 cm, SANO IIIA area, and Paris 0‐IIC area). Results Six hundred 63 lesions removed by ESD were assessed. The en bloc, R0, and curative resection rates were respectively 96%, 85%, and 81%. The CONECCT classification had a sensitivity (Se) of 100%, specificity (Sp) of 26.2%, positive predictive value of 11.6%, and negative predictive value (NPV) of 100% for predicting at least submucosal adenocarcinoma. The sensitivity of CONECCT IIC (100%) to predict submucosal cancer was superior to all other criteria evaluated. COlorectal NEoplasia Endoscopic Classification to Choose the Treatment IIC lesions constituted 11.5% of all submucosal carcinomas. Conclusion The CONECCT classification, which combines covert and overt signs of carcinoma, identifies with very perfect sensitivity (Se 100%, NPV 100%) the 30% of low‐risk adenomas in large laterally spreading lesions treatable by piecemeal endoscopic mucosal resection or ESD according to expertise without undertreatment. However, the low specificity of CONECCT leads to a large number of potentially not indicated ESDs for suspected high‐risk lesions

On the Potential of Bulk Metallic Glasses for Dental Implantology: Case Study on Ti40Zr10Cu36Pd14

Ti40Zr10Cu36Pd14 Bulk Metallic Glass (BMG) appears very attractive for future biomedical applications thanks to its high glass forming ability, the absence of toxic elements such as Ni, Al or Be and its good mechanical properties. For the first time, a complete and exhaustive characterization of a unique batch of this glassy alloy was performed, together with ISO standard mechanical tests on machined implant-abutment assemblies. The results were compared to the benchmark Ti-6Al-4V ELI (Extra-Low-Interstitial) to assess its potential in dental implantology. The thermal stability, corrosion and sterilization resistance, cytocompatibility and mechanical properties were measured on samples with a simple geometry, but also on implant-abutment assemblies’ prototypes. Results show that the glassy alloy exhibits a quite high thermal stability, with a temperature range of 38 °C between the glass transition and crystallization, a compressive strength of 2 GPa, a certain plastic deformation (0.7%), a hardness of 5.5 GPa and a toughness of 56 MPa.√m. Moreover, the alloy shows a relatively lower Young’s modulus (96 GPa) than the Ti-6Al-4V alloy (110–115 GPa), which is beneficial to limit bone stress shielding. The BMG shows a satisfactory cytocompatibility, a high resistance to sterilization and a good corrosion resistance (corrosion potential of −0.07 V/SCE and corrosion current density of 6.0 nA/cm2), which may ensure its use as a biomaterial. Tests on dental implants reveal a load to failure 1.5-times higher than that of Ti-6Al-4V and a comparable fatigue limit. Moreover, implants could be machined and sandblasted by methods usually conducted for titanium implants, without significant degradation of their amorphous nature. All these properties place this metallic glass among a promising class of materials for mechanically-challenging applications such as dental implants

Clinical outcome of non-curative endoscopic submucosal dissection for early colorectal cancer

International audienceObjective Endoscopic submucosal dissection (ESD) in a curative intent for submucosa-invasive early (T1) colorectal cancers (T1-CRCs) often leads to subsequent surgical resection in case of histologic parameters indicating higher risk of nodal involvement. In some cases, however, the expected benefit may be offset by the surgical risks, suggesting a more conservative approach. Design Retrospective analysis of consecutive patients with T1-CRC who underwent ESD at 13 centres ending inclusion in 2019 (n=3373). Cases with high risk of nodal involvement (non-curative ESD: G3, submucosal invasion>1000 µm, lymphovascular involvement, budding or incomplete resection/R1) were analysed if follow-up data (endoscopy/imaging) were available, regardless of the postendoscopic management (follow-up vs surgery) selected by the multidisciplinary teams in these institutions. Comorbidities were classified according to Charlson Comorbidity Index (CCI). Outcomes were disease recurrence, death and disease-related death rates in the two groups. Rate of residual disease (RD) at both the previous resection site and regional lymph nodes was assessed in the surgical cases as well as from follow-up in the follow-up group. Results Of 604 patients treated by colorectal ESD for submucosally invasive cancer, 207 non-curative resections (34.3%) were included (138 male; mean age 67.6±10.9 years); in 65.2% of cases, no complete resection was achieved (R1). Of the 207 cases, 60.9% (n=126; median CCI: 3; IQR: 2–4) underwent surgical treatment with RD in 19.8% (25/126), while 39.1% (n=81, median CCI: 5; IQR: 4–6) were followed up by endoscopy in all cases. Patients in the follow-up group had a higher overall mortality (HR=3.95) due to non-CRC causes (n=9, mean survival after ESD 23.7±13.7 months). During this follow-up time, tumour recurrence and disease-specific survival rates were not different between the groups (median follow-up 30 months; range: 6–105). Conclusion Following ESD for a lesion at high risk of RD, follow-up only may be a reasonable choice in patients at high risk for surgery. Also, endoscopic resection quality should be improved. Trial registration number NCT03987828

Low incidence of SARS-CoV-2, risk factors of mortality and the course of illness in the French national cohort of dialysis patients

International audienceThe aim of this study was to estimate the incidence of COVID-19 disease in the French national population of dialysis patients, their course of illness and to identify the risk factors associated with mortality. Our study included all patients on dialysis recorded in the French REIN Registry in April 2020. Clinical characteristics at last follow-up and the evolution of COVID-19 illness severity over time were recorded for diagnosed cases (either suspicious clinical symptoms, characteristic signs on the chest scan or a positive reverse transcription polymerase chain reaction) for SARS-CoV-2. A total of 1,621 infected patients were reported on the REIN registry from March 16th, 2020 to May 4th, 2020. Of these, 344 died. The prevalence of COVID-19 patients varied from less than 1% to 10% between regions. The probability of being a case was higher in males, patients with diabetes, those in need of assistance for transfer or treated at a self-care unit. Dialysis at home was associated with a lower probability of being infected as was being a smoker, a former smoker, having an active malignancy, or peripheral vascular disease. Mortality in diagnosed cases (21%) was associated with the same causes as in the general population. Higher age, hypoalbuminemia and the presence of an ischemic heart disease were statistically independently associated with a higher risk of death. Being treated at a selfcare unit was associated with a lower risk. Thus, our study showed a relatively low frequency of COVID-19 among dialysis patients contrary to what might have been assumed