Properties of electrons scattered on a strong plane electromagnetic wave with a linear polarization: classical treatment

The relations among the components of the exit momenta of ultrarelativistic electrons scattered on a strong electromagnetic wave of a low (optical) frequency and linear polarization are established using the exact solutions to the equations of motion with radiation reaction included (the Landau-Lifshitz equation). It is found that the momentum components of the electrons traversed the electromagnetic wave depend weakly on the initial values of the momenta. These electrons are mostly scattered at the small angles to the direction of propagation of the electromagnetic wave. The maximum Lorentz factor of the electrons crossed the electromagnetic wave is proportional to the work done by the electromagnetic field and is independent of the initial momenta. The momentum component parallel to the electric field strength vector of the electromagnetic wave is determined only by the diameter of the laser beam measured in the units of the classical electron radius. As for the reflected electrons, they for the most part lose the energy, but remain relativistic. There is a reflection law for these electrons that relates the incident and the reflection angles and is independent of any parameters.Comment: 12 pp, 3 fig

Effective dynamics of an electrically charged string with a current

Equations of motion for an electrically charged string with a current in an external electromagnetic field with regard to the first correction due to the self-action are derived. It is shown that the reparametrization invariance of the free action of the string imposes constraints on the possible form of the current. The effective equations of motion are obtained for an absolutely elastic charged string in the form of a ring (circle). Equations for the external electromagnetic fields that admit stationary states of such a ring are revealed. Solutions to the effective equations of motion of an absolutely elastic charged ring in the absence of external fields as well as in an external uniform magnetic field are obtained. In the latter case, the frequency at which one can observe radiation emitted by the ring is evaluated. A model of an absolutely nonstretchable charged string with a current is proposed. The effective equations of motion are derived within this model, and a class of solutions to these equations is found.Comment: 14 pages, 3 figures, format changed, minor change

Radiation reaction for multipole moments

We propose a Poincare-invariant description for the effective dynamics of systems of charged particles by means of intrinsic multipole moments. To achieve this goal we study the effective dynamics of such systems within two frameworks -- the particle itself and hydrodynamical one. We give a relativistic-invariant definition for the intrinsic multipole moments both pointlike and extended relativistic objects. Within the hydrodynamical framework we suggest a covariant action functional for a perfect fluid with pressure. In the case of a relativistic charged dust we prove the equivalence of the particle approach to the hydrodynamical one to the problem of radiation reaction for multipoles. As the particular example of a general procedure we obtain the effective model for a neutral system of charged particles with dipole moment.Comment: 12 pages, 1 figure, RevTeX 4; references updated, minor textual correction

Новые подходы к оценке функционального статуса пациентов с хронической обструктивной болезнью легких

The aim of this study was to study the relationship between heart rate variability (HRV), 6-minute walking test (6-MWT) and ergoreflex to assess the functional status of patients with chronic obstructive pulmonary disease (COPD). Methods. The study included men with COPD (n = 64; mean age 64.98 ± 8.67) and control group volunteers without respiratory disease (n = 41; mean age 61.68 ± 9.21). Spirometry, 6-MWT, HRV analysis before, during, and after the external peripheral vascular occlusion test were performed in all patients and subjects of the control group to evaluate ergoreflex (reflex regulation of the body by means of the reaction of ergoreceptors located in muscles to the accumulation of metabolic products and mechanical muscle stretching). Results. The distance covered during the 6-MWT differed significantly between patients with COPD and those in the control group (p < 0.01). In 22 (34.4%) of the 64 patients with COPD, a decrease in saturation rate (SpO2) of ≥ 4% (p < 0.01) was observed during 6-MWT, while no data for SpO2 reduction at rest were obtained. During evaluation of ergoreflex by HRV changes in patients with COPD the data testifying to its hyperactivity, causing persistent predominance of the sympathetic VNS in patients with COPD, that is reflected in "deterrence" of HRV changes during the external peripheral vascular occlusion test. Correlations between 6-MWT, spirometry and HRV have been found, indicating a high level of adherence to 6-MWT in assessing the functional status of patients with COPD. Conclusion. Differences in results of external peripheral vascular occlusion test in COPD patients and healthy subjects are interpreted by hyperactivation of ergoreflex in COPD patients, which is consistent with the increase of muscle fatigue during 6-MWT. The data of 6-MWT correlate with HRV indices, and when the techniques are applied together, the possibilities of estimating the functional status of patients during the load tests are extended. Evaluation of ergoreflex is recommended for objectification of ideas about functional status of patients with COPD before implementation of basic rehabilitation programs.Целью данного исследования явилось изучение взаимоотношения показателей вариабельности сердечного ритма (ВСР), 6-минутного шагового теста (6-МШТ) и эргорефлекса для оценки функционального статуса больных хронической обструктивной болезнью легких (ХОБЛ). Материалы и методы. В исследование включены мужчины с ХОБЛ (n = 64; средний возраст – 64,98 ± 8,67 года) и добровольцы контрольной группы без заболеваний органов дыхания (n = 41; средний возраст – 61,68 ± 9,21 года). У всех пациентов и лиц контрольной группы проводились спирометрия, 6-МШТ, анализ показателей ВСР до, во время и после пробы с внешней периферической сосудистой окклюзией (ВПСО) для оценки эргорефлекса (рефлекторная регуляция организма посредством реакции эргорецепторов, расположенных в мышечной ткани, на накопление продуктов метаболизма и механическое растяжение мышцы). Результаты. При проведении 6-МШТ пройденная дистанция достоверно различалась между пациентами с ХОБЛ и лицами контрольной группы (p < 0,01). У 22 (34,4 %) из 64 пациентов с ХОБЛ при выполнении 6-МШТ отмечено снижение уровня сатурации (SpO2) ≥ 4 % (p < 0,01), в то время как данных за снижение SpO2 в покое не получено. При оценке эргорефлекса по изменению ВСР у пациентов с ХОБЛ получены данные, свидетельствующие о его гиперактивности, вызывающей стойкое преобладание симпатического отдела ВНС у больных ХОБЛ, что находит отражение в «сдерживании» изменений ВСР при проведении пробы с ВПСО. Выявлены корреляции между показателями 6-МШТ, спирометрии и ВСР, что свидетельствует о высоком уровне приверженности 6-МШТ при оценке функционального статуса пациентов с ХОБЛ. Заключение. Различия результатов пробы с ВПСО у пациентов с ХОБЛ и здоровых добровольцев трактуются гиперактивацией эргорефлекса у больных ХОБЛ, что согласуется с нарастанием мышечной усталости при 6-МШТ. Данные 6-МШТ коррелируют с показателями ВСР, а при совместном применении методик расширяются возможности оценки функционального статуса пациентов при проведении нагрузочных проб. Для объективизации представлений о функциональном статусе пациентов с ХОБЛ перед реализацией основных реабилитационных программ рекомендуется проводить оценку эргорефлекса

From least action in electrodynamics to magnetomechanical energy -- a review

The equations of motion for electromechanical systems are traced back to the fundamental Lagrangian of particles and electromagnetic fields, via the Darwin Lagrangian. When dissipative forces can be neglected the systems are conservative and one can study them in a Hamiltonian formalism. The central concepts of generalized capacitance and inductance coefficients are introduced and explained. The problem of gauge independence of self-inductance is considered. Our main interest is in magnetomechanics, i.e. the study of systems where there is exchange between mechanical and magnetic energy. This throws light on the concept of magnetic energy, which according to the literature has confusing and peculiar properties. We apply the theory to a few simple examples: the extension of a circular current loop, the force between parallel wires, interacting circular current loops, and the rail gun. These show that the Hamiltonian, phase space, form of magnetic energy has the usual property that an equilibrium configuration corresponds to an energy minimum.Comment: 29 pages, 9 figures, 65 reference

Electrospray Ionization with High-Resolution Mass Spectrometry as a Tool for Lignomics: Lignin Mass Spectrum Deconvolution

Capability to characterize lignin, lignocellulose, and their degradation products is essential for development of new renewable feedstocks. Electrospray ionization high-resolution time-offlight mass spectrometry (ESI HR TOF MS) method was developed expanding the lignomics toolkit while targeting the simultaneous detection of low and high molecular weight (MW) lignin species. The effect of a broad range of electrolytes and various ionization conditions on ion formation and ionization effectiveness was studied using a suite of mono-, di- and triarene lignin model compounds as well as intact lignin. Contrary to the previous studies, the positive ionization mode was found to be more effective for methoxy-substituted arenes and polyphenols, i.e., species of a broadly varied MW structurally similar to the native lignin. For the first time, we report an effective formation of multiply charged species of lignin with the subsequent mass spectrum deconvolution in the presence of 100 mmol·L-1 formic acid in the positive ESI mode. The developed method enabled the detection of lignin species with an MW between 150 and 9,000 Da or higher, depending on the mass analyzer. The obtained Mn and Mw values of 1,500 and 2,500 Da, respectively, were in good agreement with those determined by gel permeation chromatography. Furthermore, the deconvoluted ESI mass spectrum was similar to that obtained with matrixassisted laser desorption/ionization (MALDI) TOF MS, yet featuring a higher signal-to-noise ratio. The formation of multiply charged species was confirmed with ESI ion mobility HR Q-TOF MS