28 research outputs found

    Piezoelectric Property of Electrospun PVDF Nanofibers as Linking Tips of Artificial-Hair-Cell Structures in Cochlea

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    The death of hair cells and damage of natural tip links is one of the main causes of hearing-loss disability, and the development of an advanced artificial hearing aid holds the key to assisting those suffering from hearing loss. This study demonstrates the potential of using electrospun polyvinylidene fluoride (PVDF) fibers to serve as the artificial tip links, for long-term hearing-aid-device development based on their piezoelectric properties. We have shown that the electrospun PVDF-fiber web, consisting of fibers ranging from 30–220 nm in diameter with high ÎČ-phase content, possesses the high piezoresponse of 170 mV. Analyses based on combined characterization methods including SEM, TEM, XRD, FTIR, Raman, DSC, XPS, PFM and piezoelectricity have confirmed that an optimized value of 15 wt.% PVDF could act as an effective candidate for a tip-link connector in a vibration-frequency prototype. Based on this easily reproducible electrospinning technique and the multifunctionalities of the resulting PVDF fibers, this fundamental study may shed light on the bio-inspired design of artificial, self-powered, high performance, hair-cell-like sensors in cochlea to tackle the hearing loss issue

    Elective cancer surgery in COVID-19-free surgical pathways during the SARS-CoV-2 pandemic: An international, multicenter, comparative cohort study

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    PURPOSE As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19–free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19–free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19–free surgical pathways. Patients who underwent surgery within COVID-19–free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19–free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score–matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19–free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION Within available resources, dedicated COVID-19–free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

    Elective Cancer Surgery in COVID-19-Free Surgical Pathways During the SARS-CoV-2 Pandemic: An International, Multicenter, Comparative Cohort Study.

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    PURPOSE: As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19-free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS: This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19-free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS: Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19-free surgical pathways. Patients who underwent surgery within COVID-19-free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19-free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score-matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19-free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION: Within available resources, dedicated COVID-19-free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

    Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

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    Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

    Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

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    Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

    Evaluation of some models of gas transport at different scales in a deep geological repository

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    International audienceThe aim of this talk is to present some examples of two-phase flow and two-component (gas-water) transport problems at different scales based on TOUGH code capabilities, which have been studied in the framework of a safety case of a high level waste (HLW) repository. The first example presented at small scale (meters and days) is that of the simulation of the in-situ PGZ-experiment of nitrogen transport in the Callovo-Oxfordian (COx) argillite. This example shows the importance of air-entry pressure as a parameter in the COx-hydraulic properties for enhancing simulation of nitrogen pressure in the COx. The second example is that of hydrogen transport at cell and module scales (dozen to hundred of meters, thousands of years) of a HLW repository site, where the problem of interfaces is invoked. The last example deals with the problem of the impact of piston flow of hydrogen on radionuclides transport at the scale of the repository site (kilometers, thousands of years), where a simplified repository model is used in order to study this impact. Finally, discussions about some studies on progress are presented, especially modelling of hysteresis, gas-solubility, and geo-mechanics which can have a great impact on gas transport at different scales

    A revisited compositional 2 phase flow model for gas transport at various scales in heterogeneous porous structures in a deep geological radioactive waste disposal facility

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    International audienceThere is a considerable challenge in modelling gas transport at different (spatial-time) scales in the saturated-unsaturated heterogeneous porous structure of a deep geological high-level radioactive waste disposal facility (HLW DF). Inconsistencies in the conceptual physical two-phase flow models and uncertainties in the input parameters of such models (lack of knowledge, spatial variability
) can lead to misunderstanding of physical phenomena occurring in a HLW DF, which may affect its performance during the post-closure phase. Therefore, there is a need for developing new physical approaches, and to account for uncertainties, in order to enhance the mathematical modelling of compositional two-phase flow models applied to gas migration in a HLW DF.The purpose of this work is twofold: (i) to study the sensitivity to gas entry pressure, as a parameter in the hydraulic properties of clay-based materials, on the modelling of gas transport in a state of near full water saturation, and (ii) to analyze the propagation of uncertainty of the input parameters of gas transport models at various scales. Based on the codes iTOUGH2 (Finsterle et al., 2007) and TOUGH2-MP (Zhang et al., 2008), three test problems are studied in this work.The first test problem is based on a 2-phase flow experiment carried out during 1.5 years in a deep borehole inside the Callovo Oxfordian (COx) clay rock, located in the Andra’s underground laboratory (De La Vaissiùre, 2011). This modelling study reveals that the gas-entry pressure plays an important role in this experiment. This was demonstrated by an optimal fit of the hydraulic parameters of the van Genuchten-Mualem model (modified by Vogel et al., 2001). The least squares optimization was carried out through a single objective function, using measured points of water retention and of relative permeability (to gas and water) vs. capillary pressure in the COx clay rock.The second test problem consists in the simulation of gas migration in a “module” composed of hundreds of waste cells, in a HLW DF during 100 000 years. The heterogeneous porous structure in each waste cell is modeled in detail (host rock, EDZ, bentonite, concrete, backfill
). Simulations are run with zero and non-zero gas entry pressure to show the impact of this parameter to gas pressure inside the access drifts and main drift of the facility.Finally, the third test problem consists in an application of uncertainty propagation methods in order to assess the uncertainty of model predictions due to input parameters uncertainty. Simulation results of gas and water fluxes during 100 000 years are presented using a simplified model of hydrogen migration in a HLW DF (Sañdi et al., 2018), with appropriate probability density functions for the uncertain parameters (including the hydrogen source term, gas-entry pressure, intrinsic permeability and porosity)

    Evaluation of some models of gas transport at different scales in a deep geological repository

    No full text
    International audienceThe aim of this talk is to present some examples of two-phase flow and two-component (gas-water) transport problems at different scales based on TOUGH code capabilities, which have been studied in the framework of a safety case of a high level waste (HLW) repository. The first example presented at small scale (meters and days) is that of the simulation of the in-situ PGZ-experiment of nitrogen transport in the Callovo-Oxfordian (COx) argillite. This example shows the importance of air-entry pressure as a parameter in the COx-hydraulic properties for enhancing simulation of nitrogen pressure in the COx. The second example is that of hydrogen transport at cell and module scales (dozen to hundred of meters, thousands of years) of a HLW repository site, where the problem of interfaces is invoked. The last example deals with the problem of the impact of piston flow of hydrogen on radionuclides transport at the scale of the repository site (kilometers, thousands of years), where a simplified repository model is used in order to study this impact. Finally, discussions about some studies on progress are presented, especially modelling of hysteresis, gas-solubility, and geo-mechanics which can have a great impact on gas transport at different scales

    A revisited compositional 2 phase flow model for gas transport at various scales in heterogeneous porous structures in a deep geological radioactive waste disposal facility

    No full text
    International audienceThere is a considerable challenge in modelling gas transport at different (spatial-time) scales in the saturated-unsaturated heterogeneous porous structure of a deep geological high-level radioactive waste disposal facility (HLW DF). Inconsistencies in the conceptual physical two-phase flow models and uncertainties in the input parameters of such models (lack of knowledge, spatial variability
) can lead to misunderstanding of physical phenomena occurring in a HLW DF, which may affect its performance during the post-closure phase. Therefore, there is a need for developing new physical approaches, and to account for uncertainties, in order to enhance the mathematical modelling of compositional two-phase flow models applied to gas migration in a HLW DF.The purpose of this work is twofold: (i) to study the sensitivity to gas entry pressure, as a parameter in the hydraulic properties of clay-based materials, on the modelling of gas transport in a state of near full water saturation, and (ii) to analyze the propagation of uncertainty of the input parameters of gas transport models at various scales. Based on the codes iTOUGH2 (Finsterle et al., 2007) and TOUGH2-MP (Zhang et al., 2008), three test problems are studied in this work.The first test problem is based on a 2-phase flow experiment carried out during 1.5 years in a deep borehole inside the Callovo Oxfordian (COx) clay rock, located in the Andra’s underground laboratory (De La Vaissiùre, 2011). This modelling study reveals that the gas-entry pressure plays an important role in this experiment. This was demonstrated by an optimal fit of the hydraulic parameters of the van Genuchten-Mualem model (modified by Vogel et al., 2001). The least squares optimization was carried out through a single objective function, using measured points of water retention and of relative permeability (to gas and water) vs. capillary pressure in the COx clay rock.The second test problem consists in the simulation of gas migration in a “module” composed of hundreds of waste cells, in a HLW DF during 100 000 years. The heterogeneous porous structure in each waste cell is modeled in detail (host rock, EDZ, bentonite, concrete, backfill
). Simulations are run with zero and non-zero gas entry pressure to show the impact of this parameter to gas pressure inside the access drifts and main drift of the facility.Finally, the third test problem consists in an application of uncertainty propagation methods in order to assess the uncertainty of model predictions due to input parameters uncertainty. Simulation results of gas and water fluxes during 100 000 years are presented using a simplified model of hydrogen migration in a HLW DF (Sañdi et al., 2018), with appropriate probability density functions for the uncertain parameters (including the hydrogen source term, gas-entry pressure, intrinsic permeability and porosity)
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