Formation of "Lightnings" in a Neutron Star Magnetosphere and the Nature of RRATs

The connection between the radio emission from "lightnings" produced by the absorption of high-energy photons from the cosmic gamma-ray background in a neutron star magnetosphere and radio bursts from rotating radio transients (RRATs) is investigated. The lightning length reaches 1000 km; the lightning radius is 100 m and is comparable to the polar cap radius. If a closed magnetosphere is filled with a dense plasma, then lightnings are efficiently formed only in the region of open magnetic field lines. For the radio emission from a separate lightning to be observed, the polar cap of the neutron star must be directed toward the observer and, at the same time, the lightning must be formed. The maximum burst rate is related to the time of the plasma outflow from the polar cap region. The typical interval between two consecutive bursts is ~100 s. The width of a single radio burst can be determined both by the width of the emission cone formed by the lightning emitting regions at some height above the neutron star surface and by a finite lightning lifetime. The width of the phase distribution for radio bursts from RRATs, along with the integrated pulse width, is determined by the width of the bundle of open magnetic field lines at the formation height of the radio emission. The results obtained are consistent with the currently available data and are indicative of a close connection between RRATs, intermittent pulsars, and extreme nullers.Comment: 24 pages, no figures, references update

On the possible observational manifestation of supernova shock impact on the neutron star magnetosphere

Impact of supernova explosion on the neutron star magnetosphere in a massive binary system is considered. The supernova shock striking the NS magnetosphere filled with plasma can lead to the formation of a magnetospheric tail with significant magnetic energy. The magnetic field reconnection in the current sheet formed can convert the magnetic energy stored in the tail into kinetic energy of accelerated charged particles. Plasma instabilities excited by beams of relativistic particles can lead to the formation of a short pulse of coherent radio emission with parameters similar to those of the observed bright extragalactic millisecond radio burst (Lorimer et al. 2007).Comment: 8 pages, Astron. Lett. in pres

Influence of photon energy on the efficiency of photochemotherapy

It is found that when indotricarbocyanine dye in HeLa cells is exposed to photons with different energies the efficiency of cell damage is wavelength independent provided the photosensitizer absorbs the same number of photons per unit time. In vivo animal experiments with two strains of tumor show that when the wavelength of the irradiating light is increased (668, 740, and 780 nm) and the number of photons absorbed per unit time per unit volume of the tumors is held constant, the damage depth increases by a factor of 1.5 and 3, respectively. The observed changes are related both to differences in the in vivo tissue optical transmission with increasing wavelength and an increased local concentration of oxygen owing to photodissociation of oxy-hemoglobin

Spectral luminescence properties of indotricarbocyanine dye in biological tissues

We have established that the shape and position of the maximum in the fluorescence spectrum of an indotricarbocyanine dye in tumor and normal tissues in vivo change over time after intravenous injection of the dye. Based on analysis of the spectral properties of the dye in vivo and in blood plasma, the dependence of the properties on the time since injection has shown that in the living body, the environment of the dye molecule changes as the photosensitizer goes from the skin into the tissue. We have established that in tissues in vivo, the dye molecules are localized in a region with low dielectric constant of the medium. We have shown that the change in the ratio of the concentrations of the different forms of hemoglobin in the blood has an effect on the absorption and shape of the fluorescence spectrum of the dye in tissues in vivo

Influence of photon energy on the efficiency of photochemotherapy

It is found that when indotricarbocyanine dye in HeLa cells is exposed to photons with different energies the efficiency of cell damage is wavelength independent provided the photosensitizer absorbs the same number of photons per unit time. In vivo animal experiments with two strains of tumor show that when the wavelength of the irradiating light is increased (668, 740, and 780 nm) and the number of photons absorbed per unit time per unit volume of the tumors is held constant, the damage depth increases by a factor of 1.5 and 3, respectively. The observed changes are related both to differences in the in vivo tissue optical transmission with increasing wavelength and an increased local concentration of oxygen owing to photodissociation of oxy-hemoglobin

Absorption of Gamma-Ray Photons in a Vacuum Neutron Star Magnetosphere: I. Electron-Positron Pair Production

The production of electron-positron pairs in a vacuum neutron star magnetosphere is investigated for both low (compared to the Schwinger one) and high magnetic fields. The case of a strong longitudinal electric field where the produced electrons and positrons acquire a stationary Lorentz factor in a short time is considered. The source of electron-positron pairs has been calculated with allowance made for the pair production by curvature and synchrotron photons. Synchrotron photons are shown to make a major contribution to the total pair production rate in a weak magnetic field. At the same time, the contribution from bremsstrahlung photons may be neglected. The existence of a time delay due to the finiteness of the electron and positron acceleration time leads to a great reduction in the electron-positron plasma generation rate compared to the case of a zero time delay. The effective local source of electron-positron pairs has been constructed. It can be used in the hydrodynamic equations that describe the development of a cascade after the absorption of a photon from the cosmic gamma-ray background in a neutron star magnetosphere.Comment: 29 pages, 1 figur

МНОГОКУРСОВАЯ ФОТОДИНАМИЧЕСКАЯ ТЕРАПИЯ ВЕРРУКОЗНОЙ ФОРМЫ ЛЕЙКОПЛАКИИ СЛИЗИСТОЙ ОБОЛОЧКИ ТЕЛА ЯЗЫКА (КЛИНИЧЕСКОЕ НАБЛЮДЕНИЕ)

The results of treatment of the patient with verrucous luekoplakia of mucous membrane of body of the tongue with photodynamic therapy are represented. In 2015 the patient underwent 4 courses of photodynamic therapy with photosensitizer photolon. Photolon was injected at dose of 2 mg/kg 3 h before irradiation (laser output power was 0.262 W, light dose – 50 and 100 J/cm2). The result of treatment was assessed as complete regression: 4 months after multiple-course photodynamic therapy there were no clinical and histological signs of luekoplakia.Приведены результаты лечения пациента с веррукозной формой лейкоплакии слизистой оболочки тела языка методом фотодинамической терапии. В 2015 г. пациенту было проведено 4 курса фотодинамической терапии с фотосенсибилизатором фотолон. Фотолон вводили в дозе 2 мг/кг за 3 ч до проведения облучения (мощность лазерного излучения 0,262 Вт на выходе световода, плотность энергии лазерного излучения – 50 и 100 Дж/см2). Эффект лечения оценен, как полная регрессия: при контрольном осмотре через 4 мес после завершения многокурсовой фотодинамической терапии клинических и гистологических признаков лейкоплакии не обнаружено

Фотодинамическая терапия лейкоплакии слизистой оболочки полости рта с фотосенсибилизатором фотолон

The objective – to assess tolerability, safety and immediate results of treatment of patients with oral leukoplakia using photodynamic therapy (PDT) with a photosensitizer photolon. The study included 40 patients (7 men, 33 women) with morphologically verified leukoplakia of the oral mucosa. The average age – 55±14 years. Number of treated foci – 109 (1 to 8). Photolon was administered intravenously at doses of 1.7-2.5 mg/kg. Photoirradiation («UPL PDT», Belarus, λ = 660±5 nm) was performed 2.5-3 h after administration: light exposure dose varied from 25 to 100 J/cm2, power density of 0.07 to 0.32 W/cm2, the duration of one field photoirradiation – from 2 to 13.5 min and according to its linear dimensions. The effectiveness of treatment was assessed 1-2 months after PDT by clinical data. Complete regression of foci recorded in 95% of cases (n=38), partial – in 5% (n=2).The follow-up period varied from 1 to 30 months. Full-epithelialization of the wound defect occurred within the period of 3-6 weeks after treatment. Photodynamic therapy may be recommended for patients with circumscribed or widespread oral leukoplakia as a simple, well-tolerated and effective option. Keywords: photodynamic therapy, photolon, oral leukoplakia.Целью исследования являлась оценка переносимости, безопасности и непосредственных результатов лечения пациентов с лейкоплакией слизистой оболочки полости рта методом фотодинамической терапии с фотосенсибилизатором фотолон. В исследование включено 40 пациентов (7 мужчин, 33 женщины) с морфологически верифицированной лейкоплакией слизистой оболочки полости рта. Средний возраст – 55±14 лет. Суммарное количество пролеченных очагов – 109 (от 1 до 8). Фотолон вводили внутривенно капельно в дозах от 1,7 мг/кг до 2,5 мг/кг. Сеанс облучения (лазер «УПЛ ФДТ», Республика Беларусь, λ=660±5 нм) проводили через 2,5-3 ч после введения препарата: плотность энергии лазерного излучения варьировала от 25 до 100 Дж/см2 , плотность мощности лазерного излучения от 0,07 до 0,32 Вт/см2 , продолжительность облучения одного поля, в зависимости от размеров очага лейкоплакии – от 2 до 13,5 мин. Эффективность лечения оценивали через 1-2 мес после ФДТ на основании клинических данных. Полная регрессия патологически измененных очагов зафиксирована в 95% случаев (n=38), частичная – в 5% (n=2). Срок наблюдения варьирует от 1 до 30 мес. Полная эпителизация раневого дефекта получена в течение 3-6 нед после проведенного лечения. Полученные результаты позволяют рекомендовать фотодинамическую терапию пациентам с ограниченной или распространенной лейкоплакией полости рта как простой, хорошо переносимый и эффективный метод лечения

ИССЛЕДОВАНИЕ СПЕКТРАЛЬНЫХ ХАРАКТЕРИСТИК НОРМАЛЬНЫХ И ОПУХОЛЕВЫХ ТКАНЕЙ В МИЛЛИМЕТРОВОМ ДИАПАЗОНЕ ЧАСТОТ

The regularities of differences are identified and the prospects marked for the use of extremely high frequency to detail representations about the features of the spectral characteristics of the tumor and non-tumor tissues.Выявлены закономерные отличия и отмечены перспективы использования крайне высоких частот для детализации представлений об особенностях спектральных характеристик опухолевых и неопухолевых тканей

Modular prediction of protein structural classes from sequences of twilight-zone identity with predicting sequences

<p>Abstract</p> <p>Background</p> <p>Knowledge of structural class is used by numerous methods for identification of structural/functional characteristics of proteins and could be used for the detection of remote homologues, particularly for chains that share twilight-zone similarity. In contrast to existing sequence-based structural class predictors, which target four major classes and which are designed for high identity sequences, we predict seven classes from sequences that share twilight-zone identity with the training sequences.</p> <p>Results</p> <p>The proposed MODular Approach to Structural class prediction (MODAS) method is unique as it allows for selection of any subset of the classes. MODAS is also the first to utilize a novel, custom-built feature-based sequence representation that combines evolutionary profiles and predicted secondary structure. The features quantify information relevant to the definition of the classes including conservation of residues and arrangement and number of helix/strand segments. Our comprehensive design considers 8 feature selection methods and 4 classifiers to develop Support Vector Machine-based classifiers that are tailored for each of the seven classes. Tests on 5 twilight-zone and 1 high-similarity benchmark datasets and comparison with over two dozens of modern competing predictors show that MODAS provides the best overall accuracy that ranges between 80% and 96.7% (83.5% for the twilight-zone datasets), depending on the dataset. This translates into 19% and 8% error rate reduction when compared against the best performing competing method on two largest datasets. The proposed predictor provides accurate predictions at 58% accuracy for membrane proteins class, which is not considered by majority of existing methods, in spite that this class accounts for only 2% of the data. Our predictive model is analyzed to demonstrate how and why the input features are associated with the corresponding classes.</p> <p>Conclusions</p> <p>The improved predictions stem from the novel features that express collocation of the secondary structure segments in the protein sequence and that combine evolutionary and secondary structure information. Our work demonstrates that conservation and arrangement of the secondary structure segments predicted along the protein chain can successfully predict structural classes which are defined based on the spatial arrangement of the secondary structures. A web server is available at <url>http://biomine.ece.ualberta.ca/MODAS/</url>.</p