Search

Single impurities in insulators are now often used for quantum sensors and single photon sources, while nanoscale semiconductor doping features are being constructed for electrical contacts in quantum technology devices, implying that new methods for sensitive, non‐destructive imaging of single‐ or few‐atom structures are needed. X‐ray fluorescence (XRF) can provide nanoscale imaging with chemical specificity, and features comprising as few as 100 000 atoms have been detected without any need for specialized or destructive sample preparation. Presently, the ultimate limits of sensitivity of XRF are unknown – here, gallium dopants in silicon are investigated using a high brilliance, synchrotron source collimated to a small spot. It is demonstrated that with a single‐pixel integration time of 1 s, the sensitivity is sufficient to identify a single isolated feature of only 3000 Ga impurities (a mass of just 350 zg). With increased integration (25 s), 650 impurities can be detected. The results are quantified using a calibration sample consisting of precisely controlled numbers of implanted atoms in nanometer‐sized structures. The results show that such features can now be mapped quantitatively when calibration samples are used, and suggest that, in the near future, planned upgrades to XRF facilities might achieve single‐atom sensitivity. [ABSTRACT FROM AUTHOR]

Featured Application: Plasma uric acid, lactate, and osmolality parameters can be used for screening and monitoring of colorectal cancer. Data about uric acid and lactate raise questions about the molecular mechanisms of their action in cancer development and the need for revisiting their importance, not only as metabolites but also as signaling molecules. The action of circulating plasma lactate may be different from those locally produced in tumor microenvironments. A complex evaluation of colorectal cancer (CRC) in relation to screening, diagnosis, stage determination, prognosis, and treatment requires valuable biomarkers. The aim of this study was to measure selected biomarkers—uric acid (UA), lactate, Na+, Cl−, and osmolality—in CRC patients and to assess their diagnostic value to distinguish between CRC and healthy controls. Plasma lactate (2.21 ± 0.11 vs. 2.88 ± 0.19, p < 0.01), Na+ (130.79 ± 0.42 vs. 133.23 ± 0.25, p < 0.001), Cl− (102.59 ± 0.45 vs. 103.94 ± 0.23, p < 0.01), and osmolality (266.44 ± 0.86 vs. 271.72 ± 0.62, p < 0.001) were found to be significantly lower in CRC patients as compared to the healthy controls group. Among them, with satisfactory diagnostic potential, were plasma Na+ concentrations and osmolality (AUCNa+ = 0.752, p < 0.0001; AUCosmolality = 0.757, p < 0.05), respectively. UA concentrations were detected at higher concentrations in CRC patients (333.67 ± 13.05 vs. 295.88 ± 13.78, p < 0.05). The results of this study contribute to the elucidation of molecular mechanisms of CRC pathogenesis and the role of studied metabolic parameters in this process. Plasma uric acid, lactate, and osmolality parameters can be used for screening and monitoring colorectal cancer. Further studies are required to elucidate the molecular mechanisms of their action in cancer development. The action of circulating plasma lactate may be different from those locally produced in the tumor microenvironment. [ABSTRACT FROM AUTHOR]

The objective of this paper is to analyze the ability of a VVER-1000 core and its control system to cope with a hypothetical main steam line break (MSLB) accident in case of multiple equipment failures. The study involves the use of advanced 3D core calculation models benchmarked and validated for reactivity accidents in preceding studies. A MSLB core boundary condition problem is solved on a coarse (nodal) mesh with the coupled COBAYA/CTF neutronic/thermal hydraulic codes. The core thermal-hydraulic boundary conditions are obtained from a preceding full-plant MSLB simulation. The assessment of the core safety parameters is supplemented by a fine-mesh (sub-channel) thermal-hydraulic analysis of the hottest assemblies with the CTF code using information from the 3D nodal COBAYA/CTF calculations. Thirteen variants of a pessimistic MSLB scenario are considered, each of them assuming a number of equipment failures aggravated by eight control rods stuck out of the core after scram at different locations in the overcooled sector. The results (within the limitations of the adopted modeling assumptions) show that the core safety parameters do not exceed the safety limits in the simulated aggravated reactivity accidents.