Методика оценки легочной перфузии у пациентов с ранее перенесенной COVID-19 пневмонией: клиническое контролируемое нерандомизированное исследование

INTRODUCTION: Evaluating pulmonary lung perfusion in patients with previously treated COVID-19 infection may lead to a better understanding of long-term consequences of the disease, as well as may identify the changes determined by their symptoms. Further research is required for optimization of lung perfusion’s design parameters’ methods in order to implement those in clinical practice.OBJECTIVE: To determine the possibilities of an alternative method for evaluation of relative lung perfusion using three-dimensional ultrafast contrast-enhanced MRI on patients with previously treated COVID-19 pneumonia.MATERIALS AND METHODS: We examined 100 patients (28 male and 72 female, aged 22 to 70) who had laboratory-confirmed COVID-19 infection. The research was conducted using the three-dimensional ultrafast dynamic contrast-enhanced MRI based on 3D T1-weighted images. During the postprocessing, we received the values of rPBF (relative pulmonary blood flow), rPBV (relative pulmonary blood volume), and rMTT (relative mean transit time).Statistics. For non-linear dependence modelling we used natural spline transformation for time and interaction effect with a group. Intergroup comparison on integral measures was based on Kruskall-Wallis test (χ2), pair comparisons were based on Conover’s test (Δ). For multiple hypothesis testing correction, we used the false discovery rate (FDR). Comparisons were determined as statistically significant when p<0.05.RESULTS: The differences in obtained values of lung perfusion among patient groups were confirmed both quantitatively (by rMTT, rPBV, rPBF) and qualitatively (by building the curves of contrast agent accumulation). Patients with previously treated COVID-19 demonstrate slower contrast agent transit and increased relative lung blood volume. Their accumulation curves have qualitative differences as well.DISCUSSION: We suggest a new method of evaluation of lung perfusion indicators in patients with previously treated COVID-19. We conducted an intergroup analysis based on the degree of lung damage during the acute phase of COVID-19 (with no infiltrativechanges, with minor lung damage, and major lung damage). The intergroup differences found are more significant for patients with lung damage (both minor and major) than for patients with no infiltrative lung changes during the acute phase of COVID-19.CONCLUSION: This method of evaluation of pulmonary perfusion is able to adequately characterize the functional lung conditions in patients with previously treated COVID-19 pneumonia. The chosen model is the most optimal.ВВЕДЕНИЕ: Оценка перфузии легких у людей с перенесенным COVID-19 может дать более четкое представление о долгосрочных последствиях болезни и выявить изменения, которые могут обусловливать их симптомы. Необходимы дальнейшие исследования с целью оптимизации методов расчета параметров легочной перфузии для внедрения их в клиническую практику.ЦЕЛЬ: Определить возможности альтернативного способа оценки относительной легочной перфузии с  использованием трехмерной сверхбыстрой динамической контрастной магнитно-резонансной томографии у пациентов с ранее перенесенной COVID-19 пневмонией.МАТЕРИАЛЫ И МЕТОДЫ: Проведено обследование 100 пациентов (28 мужчин и 72 женщин в возрасте от 22 до 70 лет), перенесших лабораторно подтвержденный COVID-19, с  использованием трехмерной сверхбыстрой динамической контрастной магнитно-резонансной томографии на базе градиентных 3D-Т1-взвешенных изображений. В ходе постпроцессинговой обработки изображений получены значения rPBF (относительная скорость кровотока), rPBV (относительный объем кровотока) и rMTT (относительное среднее время пассажа).Статистика. Для моделирования нелинейной зависимости использовалась натуральная сплайн-трансформация от времени с эффектом взаимодействия с групповой принадлежностью. Межгрупповое сравнение по интегральным показателям осуществлялось критерием Краскела–Уоллиса (χ2), попарные сравнения — критерием Коновера (Δ). Для коррекции множественного тестирования гипотез использовалась средняя доля ложных отклонений (FDR). Статистически значимыми различия признавались при p<0,05.РЕЗУЛЬТАТЫ: Различия показателей легочной перфузии между группами пациентов были подтверждены как количественно по параметрам rMTT, rPBV, rPBF, так и качественно при построении кривых накопления контрастного препарата. У пациентов с перенесенным COVID-19 наблюдается замедление пассажа контрастного препарата и увеличение относительного объема легочной крови, а кривые накопления контрастного препарата имеют качественные отличия.ОБСУЖДЕНИЕ: Предложен новый способ для оценки показателей легочной перфузии у  пациентов с  перенесенным COVID-19, проведен межгрупповой анализ групп в  зависимости от  степени поражения легких во время острой фазы COVID-19 (без инфильтративных изменений, с поражением легких легкой и тяжелой степени). Выявленные межгрупповые различия наиболее показательны для групп пациентов с  поражением легких (как легкой, так и  тяжелой степени) по сравнению с группой пациентов без инфильтративных изменений легких во время острой фазы COVID-19.ЗАКЛЮЧЕНИЕ: Данный способ оценки относительной легочной перфузии способен адекватно охарактеризовать функциональное состояние легких у  пациентов с  ранее перенесенной COVID-19 пневмонией, а  выбранная модель является оптимальной

Study of Leading Hadrons in Gluon and Quark Fragmentation

The study of quark jets in e+e- reactions at LEP has demonstrated that the hadronisation process is reproduced well by the Lund string model. However, our understanding of gluon fragmentation is less complete. In this study enriched quark and gluon jet samples of different purities are selected in three-jet events from hadronic decays of the Z collected by the DELPHI experiment in the LEP runs during 1994 and 1995. The leading systems of the two kinds of jets are defined by requiring a rapidity gap and their sum of charges is studied. An excess of leading systems with total charge zero is found for gluon jets in all cases, when compared to Monte Carlo Simulations with JETSET (with and without Bose-Einstein correlations included) and ARIADNE. The corresponding leading systems of quark jets do not exhibit such an excess. The influence of the gap size and of the gluon purity on the effect is studied and a concentration of the excess of neutral leading systems at low invariant masses (<~ 2 GeV/c^2) is observed, indicating that gluon jets might have an additional hitherto undetected fragmentation mode via a two-gluon system. This could be an indication of a possible production of gluonic states as predicted by QCD.Comment: 19 pages, 6 figures, Accepted by Phys. Lett.

Measurements of fiducial and differential cross sections for Higgs boson production in the diphoton decay channel at s√=8 TeV with ATLAS

Measurements of fiducial and differential cross sections are presented for Higgs boson production in proton-proton collisions at a centre-of-mass energy of s√=8 TeV. The analysis is performed in the H → γγ decay channel using 20.3 fb−1 of data recorded by the ATLAS experiment at the CERN Large Hadron Collider. The signal is extracted using a fit to the diphoton invariant mass spectrum assuming that the width of the resonance is much smaller than the experimental resolution. The signal yields are corrected for the effects of detector inefficiency and resolution. The pp → H → γγ fiducial cross section is measured to be 43.2 ±9.4(stat.) − 2.9 + 3.2 (syst.) ±1.2(lumi)fb for a Higgs boson of mass 125.4GeV decaying to two isolated photons that have transverse momentum greater than 35% and 25% of the diphoton invariant mass and each with absolute pseudorapidity less than 2.37. Four additional fiducial cross sections and two cross-section limits are presented in phase space regions that test the theoretical modelling of different Higgs boson production mechanisms, or are sensitive to physics beyond the Standard Model. Differential cross sections are also presented, as a function of variables related to the diphoton kinematics and the jet activity produced in the Higgs boson events. The observed spectra are statistically limited but broadly in line with the theoretical expectations

Search for squarks and gluinos in events with isolated leptons, jets and missing transverse momentum at s√=8 TeV with the ATLAS detector

The results of a search for supersymmetry in final states containing at least one isolated lepton (electron or muon), jets and large missing transverse momentum with the ATLAS detector at the Large Hadron Collider are reported. The search is based on proton-proton collision data at a centre-of-mass energy s√=8 TeV collected in 2012, corresponding to an integrated luminosity of 20 fb−1. No significant excess above the Standard Model expectation is observed. Limits are set on supersymmetric particle masses for various supersymmetric models. Depending on the model, the search excludes gluino masses up to 1.32 TeV and squark masses up to 840 GeV. Limits are also set on the parameters of a minimal universal extra dimension model, excluding a compactification radius of 1/R c = 950 GeV for a cut-off scale times radius (ΛR c) of approximately 30

Evidence for the Higgs-boson Yukawa coupling to tau leptons with the ATLAS detector

Results of a search for H → τ τ decays are presented, based on the full set of proton-proton collision data recorded by the ATLAS experiment at the LHC during 2011 and 2012. The data correspond to integrated luminosities of 4.5 fb−1 and 20.3 fb−1 at centre-of-mass energies of √s = 7 TeV and √s = 8 TeV respectively. All combinations of leptonic (τ → `νν¯ with ` = e, µ) and hadronic (τ → hadrons ν) tau decays are considered. An excess of events over the expected background from other Standard Model processes is found with an observed (expected) significance of 4.5 (3.4) standard deviations. This excess provides evidence for the direct coupling of the recently discovered Higgs boson to fermions. The measured signal strength, normalised to the Standard Model expectation, of µ = 1.43 +0.43 −0.37 is consistent with the predicted Yukawa coupling strength in the Standard Model

Measurement of the production of a W boson in association with a charm quark in pp collisions at √s = 7 TeV with the ATLAS detector

The production of a W boson in association with a single charm quark is studied using 4.6 fb−1 of pp collision data at s√ = 7 TeV collected with the ATLAS detector at the Large Hadron Collider. In events in which a W boson decays to an electron or muon, the charm quark is tagged either by its semileptonic decay to a muon or by the presence of a charmed meson. The integrated and differential cross sections as a function of the pseudorapidity of the lepton from the W-boson decay are measured. Results are compared to the predictions of next-to-leading-order QCD calculations obtained from various parton distribution function parameterisations. The ratio of the strange-to-down sea-quark distributions is determined to be 0.96+0.26−0.30 at Q 2 = 1.9 GeV2, which supports the hypothesis of an SU(3)-symmetric composition of the light-quark sea. Additionally, the cross-section ratio σ(W + +c¯¯)/σ(W − + c) is compared to the predictions obtained using parton distribution function parameterisations with different assumptions about the s−s¯¯¯ quark asymmetry

Measurement of χ c1 and χ c2 production with s√ = 7 TeV pp collisions at ATLAS

The prompt and non-prompt production cross-sections for the χ c1 and χ c2 charmonium states are measured in pp collisions at s√ = 7 TeV with the ATLAS detector at the LHC using 4.5 fb−1 of integrated luminosity. The χ c states are reconstructed through the radiative decay χ c → J/ψγ (with J/ψ → μ + μ −) where photons are reconstructed from γ → e + e − conversions. The production rate of the χ c2 state relative to the χ c1 state is measured for prompt and non-prompt χ c as a function of J/ψ transverse momentum. The prompt χ c cross-sections are combined with existing measurements of prompt J/ψ production to derive the fraction of prompt J/ψ produced in feed-down from χ c decays. The fractions of χ c1 and χ c2 produced in b-hadron decays are also measured

Search for squarks and gluinos with the ATLAS detector in final states with jets and missing transverse momentum using √s=8 TeV proton-proton collision data

A search for squarks and gluinos in final states containing high-p T jets, missing transverse momentum and no electrons or muons is presented. The data were recorded in 2012 by the ATLAS experiment in s√=8 TeV proton-proton collisions at the Large Hadron Collider, with a total integrated luminosity of 20.3 fb−1. Results are interpreted in a variety of simplified and specific supersymmetry-breaking models assuming that R-parity is conserved and that the lightest neutralino is the lightest supersymmetric particle. An exclusion limit at the 95% confidence level on the mass of the gluino is set at 1330 GeV for a simplified model incorporating only a gluino and the lightest neutralino. For a simplified model involving the strong production of first- and second-generation squarks, squark masses below 850 GeV (440 GeV) are excluded for a massless lightest neutralino, assuming mass degenerate (single light-flavour) squarks. In mSUGRA/CMSSM models with tan β = 30, A 0 = −2m 0 and μ > 0, squarks and gluinos of equal mass are excluded for masses below 1700 GeV. Additional limits are set for non-universal Higgs mass models with gaugino mediation and for simplified models involving the pair production of gluinos, each decaying to a top squark and a top quark, with the top squark decaying to a charm quark and a neutralino. These limits extend the region of supersymmetric parameter space excluded by previous searches with the ATLAS detector

Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC

The uncertainty on the calorimeter energy response to jets of particles is derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the calorimeter response to single isolated charged hadrons is measured and compared to the Monte Carlo simulation using proton-proton collisions at centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009 and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter response to specific types of particles (positively and negatively charged pions, protons, and anti-protons) is measured and compared to the Monte Carlo predictions. Finally, the jet energy scale uncertainty is determined by propagating the response uncertainty for single charged and neutral particles to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3% for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table, submitted to European Physical Journal

Measurement of the charge asymmetry in dileptonic Decays of top quark pairs in pp collisions at √ s = 7 TeV using the ATLAS detector

A measurement of the top-antitop (tt) charge asymmetry is presented using data corresponding to an integrated luminosity of 4.6 fb −1 of LHC pp collisions at a centre- of-mass energy of 7 TeV collected by the ATLAS detector. Events with two charged leptons, at least two jets and large missing transverse momentum are selected. Two observables are studied: A tt/C, based on the reconstructed tt final state. The asymmetries are measured to be A ll/C = 0.024 +/- 0.015 (stat.) +/- 0.009 (syst.) Att/C = 0.021 +/- 0.025 (stat.) +/- 0.017 (syst.) The measured values are in agreement with the Standard Model predictions