CaCu3Ti4O12 ceramics from co-precipitation method: Dielectric properties of pellets and thick films

Dielectric properties of CaCu3Ti4O12 (CCTO)-based ceramics and thick films (e ∼50m) prepared from powders synthesized by a soft chemistry method (co-precipitation) are presented and discussed. The characteristics of pellets and thick films are compared. The pellets exhibit high values of the dielectric permittivity (εr ∼1.4×105) and relatively small dielectric losses (tan δ ∼0.16) at 1 kHz and room temperature. These properties are independent of the nature of the metallization of the electrodes. In addition, the dielectric permittivity decreases when the diameter of the electrodes of the pellets increases, while the losses remain constant. This result, which is strongly related to the nature of the dielectric material in between the electrodes, constitutes a strong indication that the high dielectric permittivity values observed in this material are not related to an interfacial (electrode material) related mechanism but is an internal barrier layer capacitor (IBLC) type. Very high values of the dielectric permittivity of CCTO thick films are measured (εr ∼5×104). The differences in dielectric permittivity between thick films and dense pellets may be attributed to the difference in grain size due to different CuO contents, and to the different reactivity of the materials

The Dry Season in Haiti: a Window of Opportunity to Eliminate Cholera Citation Revisions Authors

International audienceBACKGROUND:Since the beginning of the cholera epidemic in Haiti, attack rates have varied drastically with alternating peak and lull phases, which were partly associated with the fluctuating dry, rainy and cyclonic seasons. According to a study conducted in 2012, the toxigenic V. cholerae O1 strain responsible for the outbreak did not settle at a significant level in the Haitian aquatic environment. Therefore, we hypothesize that some areas of lingering cholera transmission during the dry season could play an important role in the re-emergence of outbreaks during the rainy season. Our objective was therefore to describe the dynamics of cholera and assess the fight against the disease during the dry season.METHODS:A field study was conducted from February 19 to March 29, 2013. After identifying the affected communes by analyzing the national cholera database, we visited corresponding health facilities to identify patient origins. We then conducted a field assessment of these foci to confirm the presence of cholera, assess factors associated with transmission and examine the activities implemented to control the epidemic since the beginning of the current dry season.RESULTS:We found that the great majority of Haitian communes (109/140) presented no sign of cholera transmission in February and March 2013. Suspected cases were concentrated in a small number of urban and rural areas, almost all of which were located in the northern half of the country and often in inland locales. In these areas, community health activities appeared insufficient and were often inappropriately targeted. Out of 49 analyzed foci, only 10 had benefited from at least one intervention involving the distribution of water treatment products together with an awareness campaign since December 2012.CONCLUSION:Cholera continues to affect Haiti as observed in early 2013; however, activities implemented to interrupt cholera transmission appear insufficient and poorly suited. This deficiency in the fight against cholera, especially at a period when transmission is weak, may explain the persistence of cholera even in the absence of significant aquatic reservoirs in Haiti

A data science approach for exploring differential expression profiles of genes in transcriptomic studies-Application to the understanding of ageing in obese and lean rats in the FIGHT-HF project

International audienc

Plasma protein biomarkers and their association with mutually exclusive cardiovascular phenotypes: the FIBRO‑TARGETS case–control analyses

International audienceBackground Hypertension, obesity and diabetes are major and potentially modifiable "risk factors" for cardiovascular diseases. Identification of biomarkers specific to these risk factors may help understanding the underlying pathophysiological pathways, and developing individual treatment. Methods The FIBRO-TARGETS (targeting cardiac fibrosis for heart failure treatment) consortium has merged data from 12 patient cohorts in 1 common database of > 12,000 patients. Three mutually exclusive main phenotypic groups were identified ("cases"): (1) "hypertensive"; (2) "obese"; and (3) "diabetic"; age-sex matched in a 1:2 proportion with "healthy controls" without any of these phenotypes. Proteomic associations were studied using a biostatistical method based on LASSO and confronted with machine-learning and complex network approaches. Results The case:control distribution by each cardiovascular phenotype was hypertension (50:100), obesity (50:98), and diabetes (36:72). Of the 86 studied proteins, 4 were found to be independently associated with hypertension: GDF-15, LEP, SORT-1 and FABP-2; 3 with obesity: CEACAM-8, LEP and PRELP; and 4 with diabetes: GDF-15, REN, CXCL-1 and SCF. GDF-15 (hypertension + diabetes) and LEP (hypertension + obesity) are shared by 2 different phenotypes. A machine-learning approach confirmed GDF-15, LEP and SORT-1 as discriminant biomarkers for the hypertension group, and LEP plus PRELP for the obesity group. Complex network analyses provided insight on the mechanisms underlying these disease phenotypes where fibrosis may play a central role.ConclusionPatients with “mutually exclusive” phenotypes display distinct bioprofiles that might underpin different biological pathways, potentially leading to fibrosis

Sex differences in circulating proteins in heart failure with preserved ejection fraction

Background Many patients with heart failure with preserved ejection fraction (HFpEF) are women. Exploring mechanisms underlying the sex differences may improve our understanding of the pathophysiology of HFpEF. Studies focusing on sex differences in circulating proteins in HFpEF patients are scarce. Methods A total of 415 proteins were analyzed in 392 HFpEF patients included in The Metabolic Road to Diastolic Heart Failure: Diastolic Heart Failure study (MEDIA-DHF). Sex differences in these proteins were assessed using adjusted logistic regression analyses. The associations between candidate proteins and cardiovascular (CV) death or CV hospitalization (with sex interaction) were assessed using Cox regression models. Results We found 9 proteins to be differentially expressed between female and male patients. Women expressed more LPL and PLIN1, which are markers of lipid metabolism; more LHB, IGFBP3, and IL1RL2 as markers of transcriptional regulation; and more Ep-CAM as marker of hemostasis. Women expressed less MMP-3, which is a marker associated with extracellular matrix organization; less NRP1, which is associated with developmental processes; and less ACE2, which is related to metabolism. Sex was not associated with the study outcomes (adj. HR 1.48, 95% CI 0.83–2.63), p = 0.18. Conclusion In chronic HFpEF, assessing sex differences in a wide range of circulating proteins led to the identification of 9 proteins that were differentially expressed between female and male patients. These findings may help further investigations into potential pathophysiological processes contributing to HFpEF

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 < 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

X-Ray Absorption Spectroscopy Study of the Structural and Electronic Changes upon Cycling of LiNiVO₄ as a Battery Electrode

International audienceLiNiVO4 is among the transition metal oxides which are candidates as negative electrode materials in lithium-ion batteries. This study describes the cycling behavior of LiNiVO4 synthesized by a soft chemistry method, X-ray absorption spectroscopy has been used to characterize the structural and electronic modifications induced in the first cycle of a LiNiVO4/Li battery. The experiments were performed at both vanadium and nickel K edges. During the first discharge, the vanadium atoms shift from their pristine tetrahedral sites to distorted octahedra, and a short Ni-Ni distance occurs. During the recharge, the vanadium comes back to a tetrahedral environment. At the same time, the short Ni-Ni distance is always observed. Changes in the edge indicate that both vanadium and nickel are reduced upon lithiation. Vanadium is reduced reversibly at oxidation state two. Nickel reaches a very low oxidation state close to zero and does not recover the pristine oxidation state two upon charging

Parameters that influence silica dissolution in alkaline media

International audienceGeopolymers have been the object of numerous studies because of their low environmental impact. The synthesis of these geomaterials is achieved by the alkaline activation of aluminosilicates. Alkaline activation is typically accomplished by the activation of potassium silicate or sodium silicate. These alkaline silicate solutions are relatively expensive. We thus attempted to create these solutions by the dissolution of potassium hydroxide and silica in water. This study focuses on the various parameters that can influence the dissolution of silica in basic media (pH>13). The samples used were amorphous silica, quartz sand and quartz ground to five different size distributions. The study of the dissolution of siliceous species was performed mainly by infrared spectroscopy by varying several factors. Stirring and solution volume played no significant role. However, the size distribution and crystallinity of silica were observed to significantly affect the kinetics of dissolution and the quantities of siliceous species in solution, which varied greatly according to the quantity of KOH introduced

Role of the silica source on the geopolymerization rate: A thermal analysis study

International audiencencreasing the amount of amorphous silica in a mixture containing silica and quartz favors a polycondensation reaction (i.e., geopolymerization) and improves the mechanical properties of the synthesized materials. The study aimed to investigate the polycondensation reaction during the consolidation step of geopolymer formation and examine the various equilibriums at different temperatures. In total, eleven compositions with various amounts of amorphous silica S (high reactivity) and quartz Q (low reactivity) (from 100%Q to 100%S) were synthesized in basic media with metakaolin. The synthesized samples were characterized by thermal analyses and mercury porosimetry. Correlations between the loss of water and the molar ratio of each composition were investigated. The existence of four reactions during the consolidation process was demonstrated: (i) the reorganization of the species; (ii) the dissolution of the metakaolin; (iii) the formation of oligomers; and (iv) the reaction of polycondensation. Moreover, two types of networks were shown, a silicate solution network for quartz-rich samples and a geopolymeric network for amorphous silica-rich samples. The nature of the primary network and the reactivity of the synthesized sample depend on the reactivity of the silica source used. © 2013 Elsevier B.V

Role of the silica source on the geopolymerization rate ALL or

International audienceThe synthesis of geopolymer-silica composites was achieved at room temperature to determine the role of the silica source (quartz or amorphous silica) on the polycondensation rate and the mechanical properties of synthesized materials. Then, samples with a composition range from 100% quartz to 100% amorphous silica were formed, compared and characterized by XRD, infrared spectroscopy, thermal analysis, SEM, and compression tests. The results give evidence that the increase of amorphous silica in the mixture favors the polycondensation reaction (i.e., "geopolymerization") to form consolidated materials whereas quartz led to heterogeneous materials without cohesion. These facts are explained by the modification of the Si/Al ratio in the geopolymer matrix due to the increase of quartz in the mixtur