Control of Intense Laser- Atom Processes With Strong Static Fields

Atomic processes in the presence of intense fields continue to attract a great deal of attention [1-3]. Key goals of research in this area are to increase the intensities and frequencies of coherent light produced in these processes. In two recent works [4,5] we have demonstrated theoretically the possibility of controlling intense laser-atom interaction processes by employing strong, but experimentally feasible, static electric or magnetic fields. Thus, in Ref. [4] we demonstrated how a strong static electric field may induce a high-energy plateau for scattered x-ray photons in laser-assisted, x-ray-atom scattering in which the incident x-rays were assumed to have an energy of 50 eV. The scattered x-rays were shown to have energies up to well over 200 eV, making such a process an attractive one for realizing coherent x-rays in the water window [between the K shell absorption edges of C (284 eV) and 0 (532 eV)], which would have important applications to imaging living biological structures by means of x-ray holography [6]. In Ref. [5], we demonstrated control of high-harmonic generation (HHG) by a linearly polarized laser field using a uniform static magnetic field parallel to the laser polarization. We predicted that particular values of the magnetic field can increase harmonic intensities by orders of magnitude. Our classical orbit calculations showed that these magnetic-field-induced intensity revivals occur when the return time for laserdriven motion of the electron back to the origin is a multiple of the cyclotron period for motion perpendicular to the laser polarization direction. We present here further results [7-9] on using strong electric and magnetic fields to control these two intense laser-atom processes

Static-Electric-Field-Induced Polarization Effects in Harmonic Generation

Two static-electric-field-induced effects on harmonic generation are demonstrated analytically and numerically: elliptic dichroism (in which the harmonic yield is different for right and left elliptically polarized laser fields) and elliptical polarization of harmonics produced by linearly polarized driving laser fields. Both effects stem from interference of real and imaginary parts of the nonlinear atomic susceptibilities. Possibilities for experimentally measuring these effects are discussed

Налоговая оптимизация налога на добавленную стоимость в условиях реформирования налоговой системы Республики Беларусь

Материалы XI Междунар. науч. конф. студентов, аспирантов и молодых ученых, Гомель, 17-18 мая 2018 г

The role of hyperhomocysteinemia in the development of postoperative vascular complications

© 2016, Serbian Medical Society. All rights reserved. Hyperhomocysteinemia is one of the unconventional risk factors of cardiovascular morbidity – it is causally associated in both directions with oxidative stress, endothelial dysfunction, mechanisms of cell signaling and apoptosis. Numerous clinical and experimental studies have explained the mechanisms and clinical expression of atherosclerotic and prothrombotic effects of homocysteine. The main pathological substrate, previous therapy, and surgical procedure-intervention itself are associated with the state of oxidative stress and endothelial dysfunction, which is one of important factors for elevated plasma homocysteine levels. Recent studies point to the possibility of a successful correction of hyperhomocysteinemia, especially secondary one

Malignant fibrous histiocytoma of the right upper leg – A case report

© 2018, Inst. Sci. inf., Univ. Defence in Belgrade. All rights reserved. Introduction. Malignant fibrous histiocytoma is a fast spreading pleomorphic sarcoma with a high malignant potential. Its spreading is characterized with local invasion and distant metastazes with early onset. Most common localisations of development are extremities, trunk and retroperitoneum. Given the line of rare case and specimen, lack of a clear etiology and mechanisms of this disease, as well as adequate histopathologic findings and intraoperative documentation, we presented current status, discuss putative etiology, histopathology with variant morphology, differential diagnosis and treatment modalities. Case report. We presented a 56-years-old female Serbian with tumor in the thigh that clinically resembles incapsulated hematoma. Computed tomography revealed intramuscular tumor with a heterodense structure and compression on surround tissue. Ex tempore biopsy specimen showed malignant potential of the tumor. Wide and radical excision of the nodule has been done, and definitive histopathological verification revealed malignant fibrous histiocytoma. Conclusion. Malignant fibrous histiocytoma is a most common type of soft tissue sarcomas in adults. Frequent localization is on lower extremities, and every rapidly enlarging nodule in this localization that on computed tomography is like incapsulated hematoma with necrotic zone should alert suspicion on presence of this type of sarcoma

Bright circularly polarized soft X-ray high harmonics for X-ray magnetic circular dichroism

We demonstrate, to our knowledge, the first bright circularly polarized high-harmonic beams in the soft X-ray region of the electromagnetic spectrum, and use them to implement X-ray magnetic circular dichroism measurements in a tabletop-scale setup. Using counterrotating circularly polarized laser fields at 1.3 and 0.79 mu m, we generate circularly polarized harmonics with photon energies exceeding 160 eV. The harmonic spectra emerge as a sequence of closely spaced pairs of left and right circularly polarized peaks, with energies determined by conservation of energy and spin angular momentum. We explain the single-atom and macroscopic physics by identifying the dominant electron quantum trajectories and optimal phase-matching conditions. The first advanced phase-matched propagation simulations for circularly polarized harmonics reveal the influence of the finite phase-matching temporal window on the spectrum, as well as the unique polarization-shaped attosecond pulse train. Finally, we use, to our knowledge, the first tabletop X-ray magnetic circular dichroism measurements at the N-4,N-5 absorption edges of Gd to validate the high degree of circularity, brightness, and stability of this light source. These results demonstrate the feasibility of manipulating the polarization, spectrum, and temporal shape of high harmonics in the soft X-ray region by manipulating the driving laser waveform