Equilibration kinetics in isolated and membrane-bound photosynthetic reaction centers upon illumination: a method to determine the photoexcitation rate

Kinetics of electron transfer, following variation of actinic light intensity, for photosynthetic reaction centers (RCs) of purple bacteria (isolated and membrane-bound) were analyzed by measuring absorbance changes in the primary photoelectron donor absorption band at 865 nm. The bleaching of the primary photoelectron donor absorption band in RCs, following a sudden increase of illumination from the dark to an actinic light intensity of Iexp, obeys a simple exponential law with the rate constant \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$(\alpha I_{\exp } \; + \;k_{\text{rec}} )$$\end{document}, in which α is a parameter relating the light intensity, measured in mW/cm2, to a corresponding theoretical rate in units of reciprocal seconds, and krec is the effective rate constant of the charge recombination in the photosynthetic RCs. In this work, a method for determining the α parameter value is developed and experimentally verified for isolated and membrane-bound RCs, allowing for rigorous modeling of RC macromolecule dynamics under varied photoexcitation conditions. Such modeling is necessary for RCs due to alterations of the forward photoexcitation rates and relaxation rates caused by illumination history and intramolecular structural dynamics effects. It is demonstrated that the classical Bouguer–Lambert–Beer formalism can be applied for the samples with relatively low scattering, which is not necessarily the case with strongly scattering media or high light intensity excitation

Периферическая ритмическая магнитная стимуляция при нейрогенных расстройствах мочеиспускания: обзор литературы и результаты клинического исследования

Urinary disorders caused by peripheral nervous system injury are characterized by weakness of neural control of lower urinary tract. Clinical and urodynamic examination demonstrate detrusor-hyporeflexia and its reduced contractility. Magnetic stimulation influences autonomic and somatic nerves innervating pelvic organs but the mechanism of action is still unclear. This paper presents literature review on diagnostics and treatment of neurogenic urinary disorders by using magnetic stimulation and the results of our investigational study. 7 patients with neurogenic urinary retention were included in a prospective study of peripheral repetitive magnetic stimulation. Prolonged clinical improvement during the follow-up of 3 months was observed in all patients.Расстройства мочеиспускания, обусловленные повреждением периферической нервной системы, характеризуются ослаблением активной иннервации нижних мочевых путей. Клинико-уродинамическая картина соответствует гипорефлекторному мочевому пузырю, при котором наблюдается нарушение сократительной активности детрузора. Магнитная стимуляция оказывает воздействие на вегетативные и соматические нервные волокна, участвующие в иннервации органов малого таза, однако в настоящее время механизм действия остается неизученным. В статье представлены обзор данных литературы, касающейся диагностики и лечения нейрогенных расстройств мочеиспускания с помощью магнитной стимуляции, а также результаты собственного клинического исследования. Были выполнены обследование и наблюдение 7 пациентов с нейрогенной задержкой мочеиспускания вследствие поражения периферической нервной системы. Больным проводили процедуры периферической ритмической магнитной стимуляции ежедневно, на курс 10 сеансов. У всех пациентов наблюдался клинический результат в течение 3 мес. 

Nanocrystals Growth Control during Laser Annealing of Sn:(α-Si) Composites

An efficient technique for low temperature metal-induced nanocrystalline silicon fabrication is presented. The technique is based on laser annealing of thin films of “amorphous silicon-tin” composites combined with in situ control and monitoring with Raman technique. Laser annealing was shown to provide the possibility of fine-tuning the nanocrystals size and concentration, which is important in photovoltaic and thermoelectric devices fabrication

Role of Laser Power, Wavelength, and Pulse Duration in Laser Assisted Tin-Induced Crystallization of Amorphous Silicon

This work describes tin-induced crystallization of amorphous silicon studied with Raman spectroscopy in thin-film structures Si-Sn-Si irradiated with pulsed laser light. We have found and analyzed dependencies of the nanocrystals’ size and concentration on the laser pulse intensity for 10 ns and 150 μm duration laser pulses at the wavelengths of 535 nm and 1070 nm. Efficient transformation of the amorphous silicon into a crystalline phase during the 10 ns time interval of the acting laser pulse in the 200 nm thickness films of the amorphous silicon was demonstrated. The results were analyzed theoretically by modeling the spatial and temporal distribution of temperature in the amorphous silicon sample within the laser spot location. Simulations confirmed importance of light absorption depth (irradiation wavelength) in formation and evolution of the temperature profile that affects the crystallization processes in irradiated structures