University of Camerino

The performance of direct tests, such as bacteriological culture and qPCR, for the diagnosis of brucellosis has been evaluated in a limited number of studies, often based on small sample sizes. Moreover, the absence of a gold standard makes this assessment even more challenging. A potential alternative for evaluating the performance of direct tests is Bayesian latent class analysis (BLCA), which does not require prior knowledge of disease status or a gold standard. This study aimed to estimate the sensitivity (Se) and specificity (Sp) of bacteriological culture for brucellosis diagnosis. In a brucellosis-endemic area, a large number of seronegative and seropositive buffaloes and cattle were tested using bacteriological culture and qPCR. BLCA was applied to estimate the performance of both tests. The median Se of bacteriological culture was estimated at 61.3%, compared to 70.9% of qPCR. The median Sp was 99.6% for bacteriological culture and 89.3% for qPCR. Bacteriological culture demonstrated a higher Positive Predictive Value (PPV) than qPCR in both buffaloes and cattle, whereas the Negative Predictive Value (NPV) of the two methods did not differ significantly. These results suggest that, in settings of low brucellosis prevalence, a positive bacteriological culture has a greater predictive value than qPCR .

Carbon has a central role in biology and organic chemistry, and its solid allotropes provide the basis of much of our modern technology1. However, the liquid form of carbon remains nearly uncharted2, and the structure of liquid carbon and most of its physical properties are essentially unknown3. But liquid carbon is relevant for modelling planetary interiors4,5 and the atmospheres of white dwarfs6, as an intermediate state for the synthesis of advanced carbon materials7,8, inertial confinement fusion implosions9, hypervelocity impact events on carbon materials10 and our general understanding of structured fluids at extreme conditions11. Here we present a precise structure measurement of liquid carbon at pressures of around 1 million atmospheres obtained by in situ X-ray diffraction at an X-ray free-electron laser. Our results show a complex fluid with transient bonding and approximately four nearest neighbours on average, in agreement with quantum molecular dynamics simulations. The obtained data substantiate the understanding of the liquid state of one of the most abundant elements in the universe and can test models of the melting line. The demonstrated experimental abilities open the path to performing similar studies of the structure of liquids composed of light elements at extreme conditions.