Absolute accuracy in membrane-based ac nanocalorimetry

To achieve accurate results in nanocalorimetry a detailed analysis and understanding of the behavior of the calorimetric system is required. There are especially two system-related aspects that should be taken in consideration: the properties of the empty cell and the effect of the thermal link between sample and cell. Here we study these two aspects for a membrane-based system where heater and thermometer are both in good contact with each other and the center of the membrane. Practical, analytical expressions for describing the frequency dependence of heat capacity, thermal conductance, and temperature oscillation of the system are formulated and compared with measurements and numerical simulations. We finally discuss the experimental conditions for an optimal working frequency, where high resolution and good absolute accuracy are combined

Theoretical tools for atom laser beam propagation

We present a theoretical model for the propagation of non self-interacting atom laser beams. We start from a general propagation integral equation, and we use the same approximations as in photon optics to derive tools to calculate the atom laser beam propagation. We discuss the approximations that allow to reduce the general equation whether to a Fresnel-Kirchhoff integral calculated by using the stationary phase method, or to the eikonal. Within the paraxial approximation, we also introduce the ABCD matrices formalism and the beam quality factor. As an example, we apply these tools to analyse the recent experiment by Riou et al. [Phys. Rev. Lett. 96, 070404 (2006)]

Synthesis, structural and spectral studies of 5-methyl 2-furaldehyde thiosemicarbazone and its Co, Ni, Cu and Cd complexes

The reaction of cobalt, nickel, copper and cadmium chlorides and bromides with 5-methylfurfural thiosemicarbazone (M5FTSC) leads to the formation of two series of new complexes: [M(M5FTSC)2X2], [M(M5FTSC)X2]. They have been characterized by spectroscopic studies (infrared, 1H NMR, and electronic spectra). The crystal structures of the free ligand M5FTSC and of the compound [CuCl2(M5FTSC)] have been determined by X-ray diffraction methods. For the Co(II), Ni(II) and Cu(II) complexes, the central atom is coordinated through the sulphur atom and the azomethine nitrogen atom whilst for the Cd(II) complexes, the coordination atoms are the sulphur and furanic oxygen atoms instead of the azomethine nitrogen

Estimating the cumulative incidence of SARS-CoV-2 with imperfect serological tests: Exploiting cutoff-free approaches.

Large-scale serological testing in the population is essential to determine the true extent of the current SARS-CoV-2 pandemic. Serological tests measure antibody responses against pathogens and use predefined cutoff levels that dichotomize the quantitative test measures into sero-positives and negatives and use this as a proxy for past infection. With the imperfect assays that are currently available to test for past SARS-CoV-2 infection, the fraction of seropositive individuals in serosurveys is a biased estimator of the cumulative incidence and is usually corrected to account for the sensitivity and specificity. Here we use an inference method-referred to as mixture-model approach-for the estimation of the cumulative incidence that does not require to define cutoffs by integrating the quantitative test measures directly into the statistical inference procedure. We confirm that the mixture model outperforms the methods based on cutoffs, leading to less bias and error in estimates of the cumulative incidence. We illustrate how the mixture model can be used to optimize the design of serosurveys with imperfect serological tests. We also provide guidance on the number of control and case sera that are required to quantify the test's ambiguity sufficiently to enable the reliable estimation of the cumulative incidence. Lastly, we show how this approach can be used to estimate the cumulative incidence of classes of infections with an unknown distribution of quantitative test measures. This is a very promising application of the mixture-model approach that could identify the elusive fraction of asymptomatic SARS-CoV-2 infections. An R-package implementing the inference methods used in this paper is provided. Our study advocates using serological tests without cutoffs, especially if they are used to determine parameters characterizing populations rather than individuals. This approach circumvents some of the shortcomings of cutoff-based methods at exactly the low cumulative incidence levels and test accuracies that we are currently facing in SARS-CoV-2 serosurveys

Direct and indirect effects of the COVID-19 pandemic on mortality in Switzerland

The direct and indirect impact of the COVID-19 pandemic on population-level mortality is of concern to public health but challenging to quantify. Using data for 2011–2019, we applied Bayesian models to predict the expected number of deaths in Switzerland and compared them with laboratory-confirmed COVID-19 deaths from February 2020 to April 2022 (study period). We estimated that COVID-19-related mortality was underestimated by a factor of 0.72 (95% credible interval [CrI]: 0.46–0.78). After accounting for COVID-19 deaths, the observed mortality was −4% (95% CrI: −8 to 0) lower than expected. The deficit in mortality was concentrated in age groups 40–59 (−12%, 95%CrI: −19 to −5) and 60–69 (−8%, 95%CrI: −15 to −2). Although COVID-19 control measures may have negative effects, after subtracting COVID-19 deaths, there were fewer deaths in Switzerland during the pandemic than expected, suggesting that any negative effects of control measures were offset by the positive effects. These results have important implications for the ongoing debate about the appropriateness of COVID-19 control measures

Tracing carbon assimilation in endosymbiotic deep-sea hydrothermal vent mytilid fatty acids by ¹³C-fingerprinting

Bathymodiolus azoricus mussels thrive at Mid-Atlantic Ridge hydrothermal vents, where part oftheir energy requirements are met via an endosymbiotic association with chemolithotrophic and methanotrophic bacteria. In an effort to describe phenotypic characteristics of the two bacterial endosymbionts and to assesstheir ability to assimilate CO2, CH4 and multi-carbon compounds, we performed experiments in aquaria using 13C-labeled NaHCO3 (in the presence of H2S), CH4 or amino-acids and traced the incorporation of 13C into total and phospholipid fatty acids (tFA and PLFA, respectively). 14:0; 15:0; 16:0; 16:1(n - 7)c+t; 18:1(n - 13)c+t and (n - 7)c+t; 20:1(n - 7); 20:2(n - 9,15); 18:3(n - 7) and (n - 5,10,13) PLFA were labeled in the presence of H13CO3- (+H2S) and 13CH4, while the 12:0 compound became labeled only in the presence ofH13CO3- (+H2S). In contrast, the 17:0; 18:0; 16:1(n - 9); 16:1(n - 8) and (n - 6); 18:1(n - 8); and 18:2(n - 7) PLFA were only labeled in the presence of 13CH4. Some of these symbiont-specific fatty acids also appeared to be labeled in mussel gill tFA when incubated with 13C-enriched amino acids, and so were mussel-specific fatty acids such as 22:2(n - 7,15). Our results provide experimental evidence for the potential of specific fatty acid markers to distinguish between the two endosymbiotic bacteria, shedding new light on C1 and multi-carbon compound metabolic pathways in B. azoricus and its symbionts

Matter-wave laser Interferometric Gravitation Antenna (MIGA): New perspectives for fundamental physics and geosciences

The MIGA project aims at demonstrating precision measurements of gravity with cold atom sensors in a large scale instrument and at studying the associated applications in geosciences and fundamental physics. The first stage of the project (2013-2018) will consist in building a 300-meter long optical cavity to interrogate atom interferometers and will be based at the low noise underground laboratory LSBB in Rustrel, France. The second stage of the project (2018-2023) will be dedicated to science runs and data analyses in order to probe the spatio-temporal structure of the local gravity field of the LSBB region, a site of high hydrological interest. MIGA will also assess future potential applications of atom interferometry to gravitational wave detection in the frequency band $\sim 0.1-10$ Hz hardly covered by future long baseline optical interferometers. This paper presents the main objectives of the project, the status of the construction of the instrument and the motivation for the applications of MIGA in geosciences. Important results on new atom interferometry techniques developed at SYRTE in the context of MIGA and paving the way to precision gravity measurements are also reported.Comment: Proceedings of the 50th Rencontres de Moriond "100 years after GR", La Thuile (Italy), 21-28 March 2015 - 10 pages, 5 figures, 23 references version2: added references, corrected typo