Experimental Study of Heat Pump Thermodynamic Cycles Using CO 2 Based Mixtures -Methodology and First Results

The aim of this work is to study heat pump cycles, using CO 2 based mixtures as working fluids. Since adding other chemicals to CO 2 moves the critical point and generally equilibrium lines, it is expected that lower operating pressures as well as higher global efficiencies may be reached. A simple stage pure CO 2 cycle is used as reference, with fixed external conditions. Two scenarios are considered: water is heated from 10 {\textdegree}C to 65 {\textdegree}C for Domestic Hot Water scenario and from 30 {\textdegree}C to 35 {\textdegree}C for Central Heating scenario. In both cases, water at the evaporator inlet is set at 7 {\textdegree}C to account for such outdoor temperature conditions. In order to understand the dynamic behaviour of thermodynamic cycles with mixtures, it is essential to measure the fluid circulating composition. To this end, we have developed a non intrusive method. Online optical flow cells allow the recording of infrared spectra by means of a Fourier Transform Infra Red spectrometer. A careful calibration is performed by measuring a statistically significant number of spectra for samples of known composition. Then, a statistical model is constructed to relate spectra to compositions. After calibration, compositions are obtained by recording the spectrum in few seconds, thus allowing for a dynamic analysis. This article will describe the experimental setup and the composition measurement techniques. Then a first account of results with pure CO 2 , and with the addition of propane or R-1234yf will be given

Low GWP Refrigerant and Partial Miscible Lubricant

Lubricant selection is based on several lubricant properties to satisfied compressor and system reliability, longevity and energy efficiency performances. The use of non-miscible or low soluble lubricant can bring some technical advantage for the compressor and the system. This paper presents investigations results on low GWP refrigerant alternatives for light commercial and commercial applications. The work also targets the reduction refrigerant charge associated with the compressor characteristics

Vaccine breakthrough hypoxemic COVID-19 pneumonia in patients with auto-Abs neutralizing type I IFNs

Life-threatening `breakthrough' cases of critical COVID-19 are attributed to poor or waning antibody response to the SARS- CoV-2 vaccine in individuals already at risk. Pre-existing autoantibodies (auto-Abs) neutralizing type I IFNs underlie at least 15% of critical COVID-19 pneumonia cases in unvaccinated individuals; however, their contribution to hypoxemic breakthrough cases in vaccinated people remains unknown. Here, we studied a cohort of 48 individuals ( age 20-86 years) who received 2 doses of an mRNA vaccine and developed a breakthrough infection with hypoxemic COVID-19 pneumonia 2 weeks to 4 months later. Antibody levels to the vaccine, neutralization of the virus, and auto- Abs to type I IFNs were measured in the plasma. Forty-two individuals had no known deficiency of B cell immunity and a normal antibody response to the vaccine. Among them, ten (24%) had auto-Abs neutralizing type I IFNs (aged 43-86 years). Eight of these ten patients had auto-Abs neutralizing both IFN-a2 and IFN-., while two neutralized IFN-omega only. No patient neutralized IFN-ss. Seven neutralized 10 ng/mL of type I IFNs, and three 100 pg/mL only. Seven patients neutralized SARS-CoV-2 D614G and the Delta variant (B.1.617.2) efficiently, while one patient neutralized Delta slightly less efficiently. Two of the three patients neutralizing only 100 pg/mL of type I IFNs neutralized both D61G and Delta less efficiently. Despite two mRNA vaccine inoculations and the presence of circulating antibodies capable of neutralizing SARS-CoV-2, auto-Abs neutralizing type I IFNs may underlie a significant proportion of hypoxemic COVID-19 pneumonia cases, highlighting the importance of this particularly vulnerable population

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

COVID-19 symptoms at hospital admission vary with age and sex: results from the ISARIC prospective multinational observational study

Background: The ISARIC prospective multinational observational study is the largest cohort of hospitalized patients with COVID-19. We present relationships of age, sex, and nationality to presenting symptoms. Methods: International, prospective observational study of 60 109 hospitalized symptomatic patients with laboratory-confirmed COVID-19 recruited from 43 countries between 30 January and 3 August 2020. Logistic regression was performed to evaluate relationships of age and sex to published COVID-19 case definitions and the most commonly reported symptoms. Results: ‘Typical’ symptoms of fever (69%), cough (68%) and shortness of breath (66%) were the most commonly reported. 92% of patients experienced at least one of these. Prevalence of typical symptoms was greatest in 30- to 60-year-olds (respectively 80, 79, 69%; at least one 95%). They were reported less frequently in children (≤ 18 years: 69, 48, 23; 85%), older adults (≥ 70 years: 61, 62, 65; 90%), and women (66, 66, 64; 90%; vs. men 71, 70, 67; 93%, each P &lt; 0.001). The most common atypical presentations under 60 years of age were nausea and vomiting and abdominal pain, and over 60 years was confusion. Regression models showed significant differences in symptoms with sex, age and country. Interpretation: This international collaboration has allowed us to report reliable symptom data from the largest cohort of patients admitted to hospital with COVID-19. Adults over 60 and children admitted to hospital with COVID-19 are less likely to present with typical symptoms. Nausea and vomiting are common atypical presentations under 30 years. Confusion is a frequent atypical presentation of COVID-19 in adults over 60 years. Women are less likely to experience typical symptoms than men

Pompe à chaleur : technologies et applications dans le résidentiel

La pompe à chaleur nécessite une bonne compréhension des composants technologiques ainsi que du besoin à satisfaire afin d’être correctement dimensionnée et ainsi optimiser sa consommation énergétique. Cet article traite du secteur résidentiel (le chauffage et/ou l’eau chaude sanitaire). Après une présentation du principe de fonctionnement, les composants technologiques sont décrits. Le dimensionnement de la pompe à chaleur est ensuite présenté en prenant en compte ou non la présence d’un appoint énergétique. Enfin, des règles d’installation sont proposées en mettant en avant les avantages et contraintes des solutions existantes

Online, Non-Intrusive Composition Measurements Of Circulating Co2 Based Mixtures In An Experimental Heat Pump By Means Of Infra-Red Spectroscopy.

Using CO2 based mixtures as a working fluid in refrigeration and heat pumps is a potential alternative to the use of traditional fluids (HFC, HFO, …) which are environmentally problematic. In order to investigate the efficiency of such systems, we have designed an experimental heat pump equipped with different measurement devices. In the present article, we will focus on the mixture composition measurement technique. In order to fully understand the behaviour of such a heat pump, it is necessary to measure the composition of the mixture at each point of the cycle. In order to do so, we have used a technique based on infra-red spectroscopy and chemometry. At each point in the loop, we have installed optical cells equipped with transparent windows and optical fibres. The spectra are recorded by a Fourier transform infra-red spectrometer. The mixtures composition is then extracted from the spectra by the partial least squares (PLS) method which is a now common method in analytical chemistry. But, beforehand, the PLS method has to be calibrated. This is done by recording a statistically meaningful set of spectra on samples of known composition. Then a model can be derived to relate the compositions to the characteristics of the spectra. The calibration stage can be performed independently on separate well controlled samples. In our case, the calibration has been carried out directly on the experimental loop. To this end, micro sampling devices (ROLSI TM) have been installed in different places next to the optical cells. During this calibration process, the composition of the fluid is measured by gas chromatography at varying conditions and compositions along with the recording of the spectra. Once this calibration is done, the composition can be measured in short times, typically of the order of the second by the spectroscopic technique. This allows for a dynamic analysis of the working conditions. This article will describe in detail the experimental set up and the calibration process for a mixture of CO2 and ethanol on the composition range of interest at temperatures ranging from -20°C to +100°C and pressures from 20 to 120 bars and the expected accuracy will be discussed

Online composition measurements of refrigerant mixtures by optical fibres and infrared spectroscopy

International audienceAs refrigeration and heat pump industries use more and more mixtures as refrigerants it is useful to measure the composition of the fluid at different locations in the machine. For our own research purposes on mixture based cycles, we have implemented an online non-intrusive technique basedon infrared spectroscopy. This paper describes the apparatus used and also the data treatment that allows to extract valuable information from the recorded spectra. The calibration of the method for a given mixture is obtained by recording spectra with known concentrations, pressure and temperature. Partial least squares (PLS) or principal component regression (PCR) statistical methods are used to build a model. Then compositions can be determined for unknown mixtures. Results are presented for CO2+Propane mixtures. The sensitivity of the method to baseline treatment is tested. The best accuracy obtained so far is of the order of 2%The method is well tested and can be applied to other mixtures

Méthodologie et banc d'essais relatifs à l'étude expérimentale de cycles thermodynamiques de pompe à chaleur utilisant des mélanges à base de CO2.

International audienceThe aim of this work is to study heat pump cycles, using CO2 based mixtures as working fluids. Since adding other chemicals to CO2 moves the critical point and generally equilibrium lines, it is expected that lower operating pressures as well as higher global efficiencies may be reached. A simple stage pure CO2 cycle is used as reference, with fixed external conditions. Two scenarios are considered: water is heated from 283 K to 338 K (10 °C to 65 °C) for Domestic Hot Water scenario and from 303 K to 308 K (30 °C to 35 °C) for Central Heating scenario. In both cases, water at the evaporator inlet is set at 280 K (7 °C) to account for such outdoor temperature conditions. In order to understand the dynamic behaviour of thermodynamic cycles with mixtures, it is essential to measure the fluid circulating composition. To this end, we have developed a non intrusive method. Online optical flow cells allow the recording of infrared spectra by means of a Fourier Transform Infra Red spectrometer. A careful calibration is performed by measuring a statistically significant number of spectra for samples of known composition. Then, a statistical model is constructed to relate spectra to compositions. After calibration, compositions are obtained by recording the spectrum in few seconds, thus allowing for a dynamic analysis. This article will describe the experimental setup and the composition measurement techniques. Then a first account of results with pure CO2, and with the addition of propane will be given