Breaking the light speed barrier

As it is well known, classical special relativity allows the existence of three different kinds of particles: bradyons, luxons and tachyons. Bradyons have non-zero mass and hence always travel slower than light. Luxons are particles with zero mass, like the photon, and they always travel with invariant velocity. Tachyons are hypothetical superluminal particles that always move faster than light. The existence of bradyons and luxons is firmly established, while the tachyons were never reliably observed. In quantum field theory, the appearance of tachyonic degrees of freedom indicates vacuum instability rather than a real existence of the faster-than-light particles. However, recent controversial claims of the OPERA experiment about superluminal neutrinos triggered a renewed interest in superluminal particles. Driven by a striking analogy of the old Frenkel-Kontorova model of a dislocation dynamics to the theory of relativity, we conjecture in this note a remarkable possibility of existence of the fourth type of particles, elvisebrions, which can be superluminal. The characteristic feature of elvisebrions, distinguishing them from tachyons, is that they are outside the realm of special relativity and their energy remains finite (or may even turn to zero) when the elvisebrion velocity approaches the light velocity.Comment: 37 pages, no figures, two last sections extended, to be published in Acta Physica Polonica

Expanding space, quasars and St. Augustine's fireworks

An attempt is made to explain time non-dilation allegedly observed in quasar light curves. The explanation is based on the assumption that quasar black holes are, in some sense, foreign for our Friedmann-Robertson-Walker universe and do not participate in the Hubble flow. Although at first sight such a weird explanation requires unreasonably fine-tuned Big Bang initial conditions, we find a natural justification for it using the Milne cosmological model as an inspiration.Comment: 36 pages, 4 figures, some text and references added, published versio

The dog-and-rabbit chase problem as an exercise in introductory kinematics

The purpose of this article is to present a simple solution of the classic dog-and-rabbit chase problem which emphasizes the use of concepts of elementary kinematics and, therefore, can be used in introductory mechanics course. The article is based on the teaching experience of introductory mechanics course at Novosibirsk State University for first year physics students which are just beginning to use advanced mathematical methods in physics problems. We hope it will be also useful for students and teachers at other universities too.Comment: 11 pages, 3 figures, authorship changed to match the published versio

The effect of diet on the qualitative and quantitative composition of the human microbiota

The purpose of the study is to identify the prevalence of different types of diets among students of the 1st–4th year of USMU and to assess their impact on the composition of the human microbiota.Цель исследования – выявить распространенность разных видов диет среди студентов 1-4 курса УГМУ и оценить их влияние на состав микробиоты человека

Phenomenology of the Lense-Thirring effect in the Solar System

Recent years have seen increasing efforts to directly measure some aspects of the general relativistic gravitomagnetic interaction in several astronomical scenarios in the solar system. After briefly overviewing the concept of gravitomagnetism from a theoretical point of view, we review the performed or proposed attempts to detect the Lense-Thirring effect affecting the orbital motions of natural and artificial bodies in the gravitational fields of the Sun, Earth, Mars and Jupiter. In particular, we will focus on the evaluation of the impact of several sources of systematic uncertainties of dynamical origin to realistically elucidate the present and future perspectives in directly measuring such an elusive relativistic effect.Comment: LaTex, 51 pages, 14 figures, 22 tables. Invited review, to appear in Astrophysics and Space Science (ApSS). Some uncited references in the text now correctly quoted. One reference added. A footnote adde

Низкая эффективность антибиотиков, назначаемых амбулаторно детям с пневмонией и острым средним отитом, как следствие несоблюдения клинических рекомендаций

Background: Amoxicillin is the drug of choice for treating the majority of community-acquired respiratory tract infections in children, including pneumonia and acute otitis media according to both international and national guidelines. Nevertheless, the practice of not following these guidelines is widespread.Objective: Our aim was to study a range of antibiotics prescribed prior to hospitalization to children with community-acquired pneumonia (CAP) and acute otitis media (AOM), and to evaluate their effectiveness.Methods. Observational study of children with hospital-verified diagnosis CAP or AOM.Results. Amoxicillin was prescribed to only 4.5% of children with CAP and 1% of patients with AOM; along with parenteral cephalosporines and amoxicillin/clavulanate in adequate doses therapy was started in 34 and 25% respectively. Other children received 3d generation oral cephalosporines or macrolides, which rendered a very low effectiveness (19 and 10% respectively). In view of a flagrant inconformity of the prescribed antibiotics and their doses to the guidelines, non-effective prescriptions were made for 72% of children with CAP and 69% — with AOM. For children with atypical pneumonia macrolides were prescribed in only 19%.Conclusion. Since amoxicillin remains the main drug for treating infections caused by an ever increasing number of resistant strains of S. pneumonia and S. pyogenes, it should be prescribed to children with CAP and AOM: its doses (as well as doses of amoxicillin/clavulanate) should be not less than 45 mg/kg/d, and in risk group patients — 80–100 mg/kg/d. The pediatricians’ skills of differentiating atypical pneumonia should be improved.Амоксициллин, согласно как международным, так и отечественным рекомендациям, является препаратом выбора для лечения большинства внебольничных инфекций респираторного тракта у детей. Тем не менее практика назначения антибиотиков на догоспитальном этапе в разных странах демонстрирует низкий уровень следования стандартам лечения внебольничных пневмоний и острого среднего отита (ОСО).Цель исследования: изучить спектр антибиотиков, назначаемых на амбулаторном этапе детям с пневмонией и ОСО, а также оценить их эффективность.Методы. Дизайн работы — наблюдательное исследование когорты детей, госпитализированных с диагнозом внебольничной пневмонии (n = 261) и ОСО (n = 225) в 2008–2015 гг.Результаты. Амоксициллин был назначен только 4,5% детей с типичной внебольничной пневмонией и 1% — с ОСО; вместе с парентеральными цефалоспоринами и амоксициллином/ клавуланатом в адекватных дозировках стартовая терапия была начата всего в 34 и 25% случаев соответственно. Остальные дети лечились оральными цефалоспоринами 3-го поколения и макролидами с крайне низкой эффективностью (19 и 10% соответственно). Ввиду выраженного несоответствия спектра антибиотиков и их доз современным рекомендациям неэффективные стартовые назначения были сделаны при типичной пневмонии в 72%, а при ОСО — в 69% случаев. При атипичных пневмониях макролиды были назначены всего 19% больным.Заключение. Поскольку амоксициллин остается основным препаратом для лечения инфекций, вызванных Streptococcus pneumoniae и Streptococcus pyogenes в эпоху роста их резистентности, он должен использоваться в качестве стартового препарата при типичных пневмониях и ОСО. Дозы амоксициллина, в т. ч. защищенного, не должны быть ниже 45 мг/кг в сут, а при риске устойчивости пневмококков — 80–100 мг/кг в сут. Следует также повышать знания педиатров в дифференциальной диагностике атипичных пневмоний

Immunoglobulin, glucocorticoid, or combination therapy for multisystem inflammatory syndrome in children: a propensity-weighted cohort study

Background: Multisystem inflammatory syndrome in children (MIS-C), a hyperinflammatory condition associated with SARS-CoV-2 infection, has emerged as a serious illness in children worldwide. Immunoglobulin or glucocorticoids, or both, are currently recommended treatments. Methods: The Best Available Treatment Study evaluated immunomodulatory treatments for MIS-C in an international observational cohort. Analysis of the first 614 patients was previously reported. In this propensity-weighted cohort study, clinical and outcome data from children with suspected or proven MIS-C were collected onto a web-based Research Electronic Data Capture database. After excluding neonates and incomplete or duplicate records, inverse probability weighting was used to compare primary treatments with intravenous immunoglobulin, intravenous immunoglobulin plus glucocorticoids, or glucocorticoids alone, using intravenous immunoglobulin as the reference treatment. Primary outcomes were a composite of inotropic or ventilator support from the second day after treatment initiation, or death, and time to improvement on an ordinal clinical severity scale. Secondary outcomes included treatment escalation, clinical deterioration, fever, and coronary artery aneurysm occurrence and resolution. This study is registered with the ISRCTN registry, ISRCTN69546370. Findings: We enrolled 2101 children (aged 0 months to 19 years) with clinically diagnosed MIS-C from 39 countries between June 14, 2020, and April 25, 2022, and, following exclusions, 2009 patients were included for analysis (median age 8·0 years [IQR 4·2–11·4], 1191 [59·3%] male and 818 [40·7%] female, and 825 [41·1%] White). 680 (33·8%) patients received primary treatment with intravenous immunoglobulin, 698 (34·7%) with intravenous immunoglobulin plus glucocorticoids, 487 (24·2%) with glucocorticoids alone; 59 (2·9%) patients received other combinations, including biologicals, and 85 (4·2%) patients received no immunomodulators. There were no significant differences between treatments for primary outcomes for the 1586 patients with complete baseline and outcome data that were considered for primary analysis. Adjusted odds ratios for ventilation, inotropic support, or death were 1·09 (95% CI 0·75–1·58; corrected p value=1·00) for intravenous immunoglobulin plus glucocorticoids and 0·93 (0·58–1·47; corrected p value=1·00) for glucocorticoids alone, versus intravenous immunoglobulin alone. Adjusted average hazard ratios for time to improvement were 1·04 (95% CI 0·91–1·20; corrected p value=1·00) for intravenous immunoglobulin plus glucocorticoids, and 0·84 (0·70–1·00; corrected p value=0·22) for glucocorticoids alone, versus intravenous immunoglobulin alone. Treatment escalation was less frequent for intravenous immunoglobulin plus glucocorticoids (OR 0·15 [95% CI 0·11–0·20]; p<0·0001) and glucocorticoids alone (0·68 [0·50–0·93]; p=0·014) versus intravenous immunoglobulin alone. Persistent fever (from day 2 onward) was less common with intravenous immunoglobulin plus glucocorticoids compared with either intravenous immunoglobulin alone (OR 0·50 [95% CI 0·38–0·67]; p<0·0001) or glucocorticoids alone (0·63 [0·45–0·88]; p=0·0058). Coronary artery aneurysm occurrence and resolution did not differ significantly between treatment groups. Interpretation: Recovery rates, including occurrence and resolution of coronary artery aneurysms, were similar for primary treatment with intravenous immunoglobulin when compared to glucocorticoids or intravenous immunoglobulin plus glucocorticoids. Initial treatment with glucocorticoids appears to be a safe alternative to immunoglobulin or combined therapy, and might be advantageous in view of the cost and limited availability of intravenous immunoglobulin in many countries. Funding: Imperial College London, the European Union's Horizon 2020, Wellcome Trust, the Medical Research Foundation, UK National Institute for Health and Care Research, and National Institutes of Health

Immunoglobulin, glucocorticoid, or combination therapy for multisystem inflammatory syndrome in children: a propensity-weighted cohort study

Background Multisystem inflammatory syndrome in children (MIS-C), a hyperinflammatory condition associated with SARS-CoV-2 infection, has emerged as a serious illness in children worldwide. Immunoglobulin or glucocorticoids, or both, are currently recommended treatments. Methods The Best Available Treatment Study evaluated immunomodulatory treatments for MIS-C in an international observational cohort. Analysis of the first 614 patients was previously reported. In this propensity-weighted cohort study, clinical and outcome data from children with suspected or proven MIS-C were collected onto a web-based Research Electronic Data Capture database. After excluding neonates and incomplete or duplicate records, inverse probability weighting was used to compare primary treatments with intravenous immunoglobulin, intravenous immunoglobulin plus glucocorticoids, or glucocorticoids alone, using intravenous immunoglobulin as the reference treatment. Primary outcomes were a composite of inotropic or ventilator support from the second day after treatment initiation, or death, and time to improvement on an ordinal clinical severity scale. Secondary outcomes included treatment escalation, clinical deterioration, fever, and coronary artery aneurysm occurrence and resolution. This study is registered with the ISRCTN registry, ISRCTN69546370. Findings We enrolled 2101 children (aged 0 months to 19 years) with clinically diagnosed MIS-C from 39 countries between June 14, 2020, and April 25, 2022, and, following exclusions, 2009 patients were included for analysis (median age 8·0 years [IQR 4·2–11·4], 1191 [59·3%] male and 818 [40·7%] female, and 825 [41·1%] White). 680 (33·8%) patients received primary treatment with intravenous immunoglobulin, 698 (34·7%) with intravenous immunoglobulin plus glucocorticoids, 487 (24·2%) with glucocorticoids alone; 59 (2·9%) patients received other combinations, including biologicals, and 85 (4·2%) patients received no immunomodulators. There were no significant differences between treatments for primary outcomes for the 1586 patients with complete baseline and outcome data that were considered for primary analysis. Adjusted odds ratios for ventilation, inotropic support, or death were 1·09 (95% CI 0·75–1·58; corrected p value=1·00) for intravenous immunoglobulin plus glucocorticoids and 0·93 (0·58–1·47; corrected p value=1·00) for glucocorticoids alone, versus intravenous immunoglobulin alone. Adjusted average hazard ratios for time to improvement were 1·04 (95% CI 0·91–1·20; corrected p value=1·00) for intravenous immunoglobulin plus glucocorticoids, and 0·84 (0·70–1·00; corrected p value=0·22) for glucocorticoids alone, versus intravenous immunoglobulin alone. Treatment escalation was less frequent for intravenous immunoglobulin plus glucocorticoids (OR 0·15 [95% CI 0·11–0·20]; p<0·0001) and glucocorticoids alone (0·68 [0·50–0·93]; p=0·014) versus intravenous immunoglobulin alone. Persistent fever (from day 2 onward) was less common with intravenous immunoglobulin plus glucocorticoids compared with either intravenous immunoglobulin alone (OR 0·50 [95% CI 0·38–0·67]; p<0·0001) or glucocorticoids alone (0·63 [0·45–0·88]; p=0·0058). Coronary artery aneurysm occurrence and resolution did not differ significantly between treatment groups. Interpretation Recovery rates, including occurrence and resolution of coronary artery aneurysms, were similar for primary treatment with intravenous immunoglobulin when compared to glucocorticoids or intravenous immunoglobulin plus glucocorticoids. Initial treatment with glucocorticoids appears to be a safe alternative to immunoglobulin or combined therapy, and might be advantageous in view of the cost and limited availability of intravenous immunoglobulin in many countries. Funding Imperial College London, the European Union's Horizon 2020, Wellcome Trust, the Medical Research Foundation, UK National Institute for Health and Care Research, and National Institutes of Health