Selective Reflection Spectroscopy at the Interface between a Calcium Fluoride Window and Cs Vapour

A special vapour cell has been built, that allows the measurement of the atom-surface van der Waals interaction exerted by a CaF2 window at the interface with Cs vapour. Mechanical and thermal fragility of fluoride windows make common designs of vapour cells unpractical, so that we have developed an all-sapphire sealed cell with an internal CaF2 window. Although impurities were accidentally introduced when filling-up the prototype cell, leading to a line-broadening and shift, the selective reflection spectrum on the Cs D1 line (894 nm) makes apparent the weak van der Waals surface interaction. The uncertainties introduced by the effects of these impurities in the van der Waals measurement are nearly eliminated when comparing the selective reflection signal at the CaF2 interface of interest, and at a sapphire window of the same cell. The ratio of the interaction respectively exerted by a sapphire interface and a CaF2 interface is found to be 0.55 $\pm$ 0.25, in good agreement with the theoretical evaluation of ~0.67.Comment: soumis \`a Appl Phys B MS 4734

To the question regarding accuracy of COVID-2019 laboratory diagnostics

Issues of accuracy (sensitivity and specificity) of PCR-analysis depending on features of performing preanalytical and analytical stages of laboratory diagnostics of COVID-19, as well as comparing PCR and lung computed tomography (CT) results have been analyzed in the study. Currently, a molecular genetic test based on polymerase chain reaction (PCR) is used for diagnostics of a new coronavirus infection (COVID-19). As of November 1, 2020, more than 750 million PCR tests have been conducted globally. Evidence accumulated by now allows to estimate diagnostic sensitivity and specificity of the SARS-CoV-2-specific PCR as high as 82—91% and 99—100%, respectively. In addition, increased PCR sensitivity may be noted upon performing repeated testing of the upper respiratory tract samples comprising 82.2% during the primary analysis that was further elevated up to 90.6% after two consecutive tests. A whole set of factors affect the PCR accuracy. In particular, false negative data might result from insufficient amount of virus-coupled genetic material in the sample, timeframe and mistakes made upon selecting biological samples. It was found that SARS-CoV-2 virus RNA was detected at the maximum diagnostic sensitivity in the upper respiratory tract 1—3 days before the onset of symptoms and sustained within the 5—6 days after disease onset. Such period of time is associated with the peak risk of SARS-CoV-2 transmission. On week 2 after disease onset, there have been noted elevated rate of detecting viral RNA in bronchopulmonary samples. The duration of detecting virus-related markers (including those found in the absence of viable virus forms) correlates with disease severity and may last for as long as 1—2 months. Another real-world issue related to PCR analysis is posed by an opportunity of obtaining false positive data, which solution requires high level organized laboratory research, especially in case large-scale studies. Upon that, it is worth noting that positive PCR results may account for detecting solely certain RNA-related fragments present in any sample, rather than a viable virus. It was noted that PCR in comparison to CT analysis demonstrates higher specificity, but does not allow to distinguish pneumonia caused by SARS-CoV-2 from pneumonia caused by other etiological agents (up to 25% false positive results). However, the diagnostic CT sensitivity was 97.2% that exceeds such parameter for PCR by 10—15%. It was concluded that the approach combining use of both PCR and CT by taking into account their own features as well as factors affecting the accuracy of the data obtained, allows us to correctly interpret the diagnostical results

Erratum (astro-ph/0510172): Robust Limits on Lorentz Violation from Gamma-Ray Bursts

We correct the fitting formula used in refs. [1,2] to obtain a robust limit on a violation of Lorentz invariance that depends linearly on the photon energy. The correction leads to a slight increase of the limit on the scale of the violation, to M > 1.4 x 10^{16} GeV.Comment: four pages latex, two eps figures, uses special macro

Lorentz Invariance Violation induced time delays in GRBs in different cosmological models

Lorentz Invariance Violation (LIV) manifesting itself by energy dependent modification of standard relativistic dispersion relation has recently attracted a considerable attention. Ellis et al. previously investigated the energy dependent time offsets in different energy bands on a sample of gamma ray bursts and, assuming standard cosmological model, they found a weak indication for redshift dependence of time delays suggestive of LIV. Going beyond the $\Lambda$CDM cosmology we extend this analysis considering also four alternative models of dark energy (quintessence with constant and variable equation of state, Chaplygin gas and brane-world cosmology). It turns out that the effect noticed by Ellis et al. is also present in those models and is the strongest for quintessence with variable equation of state.Comment: 14 pages, 1 figur

GRB 051221A and Tests of Lorentz Symmetry

Various approaches to quantum gravity suggest the possibility of violation of Lorentz symmetry at very high energies. In these cases we expect a modification at low energies of the dispersion relation of photons that contains extra powers of the momentum suppressed by a high energy scale. These terms break boost invariance and can be tested even at relatively low energies. We use the light curves of the very bright short Gamma-Ray Burst GRB 051221A and compare the arrival times of photons at different energies with the expected time delay due to a modified dispersion relation. As no time delay was observed, we set a lower bound of 0.0066 E_{pl} \sim 0.66 10^{17} GeV on the scale of Lorentz invariance violation.Comment: 9 pages, 2 figure

COVID-19 as a zoonotic infection

Here we discuss the issues for attributing the new coronavirus infection COVID-19 to zoonoses based on the data on probable origin of the SARS-CoV-2 virus, the possible formation of its reservoir in animals (bats) as well as human susceptibility. Today, the dominant point of view is that the outbreak of COVID-19 arose as a result of the SARS-CoV-2 coronavirus overcoming the interspecies barrier, acquiring ability to infect and spread in human population. Comparative phylogenetic analysis at the molecular level showed that SARS-CoV-2 is genetically closest to bat coronaviruses, particularly to the RmYN02 and RaTG13 strains isolated from the horseshoe bat, a species considered to be the main host of SARSCoV and MERS-CoV coronaviruses. The ability of the SARS-CoV-2 coronavirus to infect various wild animal has been revealed. SARS-CoV-2 has been found in minks on farms in the Netherlands with mortality rates ranging from 1.2 to 2.4%. While infecting rhesus monkeys with the SARS-CoV-2, it resulted in productive infection and detected viremia. Cats have been found to be susceptible hosts for the human SARS-CoV-2 virus. A likely explanation for this lies in the high similarity between the human and feline counterpart of the ACE2 receptor. It has been shown that dogs can become infected but transmit no virus to other animals. To date, over the entire period of the pandemic the World Organization for Animal Health provides no information about cases of human infection transmitted from pets. Thus, there is no evidence that animals play a role in the spread of SARS-CoV-2 among people during the current period of the pandemic. Human outbreaks are caused by human-to-human virus transmission, and based on the currently available information, the risk of spreading COVID-19 from animals is considered low. More research is needed to understand how COVID-19 can affect animals of a wide variety of species and how big might be the risks of infection transmission from them to humans

Comparative evaluation of the effectiveness of a peptide-containing drug and polyoxydonium in the treatment of chronic parodontitis

Currently, the available methods of treating parodontitis are not able to have a complex effect. Therefore, in recent years, there has been an active search and development of new methods of treatment and new drugs that have a complex etiopathogenetic effect on this disease. This article provides a comparative evaluation of the classical and experimental methods of treating chronic periodontitis. Based on the reconstruction of an experimental model of chronic inflammation of periodontal tissues of the Wistar rat line, we compared methods of topical therapy by “Organosilicon Glycerohydrogel – Peptide” and “Polyoxidonium” compositions. A comparative assessment of the activity of these drugs with control groups, which were treated with “Organosilicon Glycerohydrogel” and “Metrogyl Denta”, was carried out. Previously, we carried out separate studies of the effectiveness of the use of the composition “organosilicon glycerohydrogel – peptide”, as well as the method of treatment of periodontitis, by injecting the drug “Polyoxidonium”. They have been compared with the classic treatment for this disease to obtain relevant data and results. In our opinion, the data obtained are of considerable interest. The assessment and comparison of clinical and histological data have been carried out, which showed that all drugs had a positive effect on the processes of tissue regeneration. However, the composition “Organosilicon Glycerohydrogel-peptide”, due to the characteristics of the hydrogel, which is acting as a transcutaneous conductor, showed a faster antimicrobial and pathogenetic effect, which allows a comprehensive approach to solving this problem. In comparison with the groups of “Organosilicon Glycerohydrogel” and “Polyoxidonium”, the period of clinical improvement increased by 57% in the group of “Glycerohydrogel-Peptide”, and, in the “Metrogyl Denta” group, the indicators improved by 15% approximately

The charge-dyon bound system in the spherical quantum well

The spherical wave functions of charge-dyon bounded system in a rectangular spherical quantum dot of infinitely and finite height are calculated. The transcendent equations, defining the energy spectra of the systems are obtained. The dependence of the energy levels from the wall sizes is found.Comment: 8 pages, 5 figure