Efficiency of application of different DNA probes in identifying marker chromosomes

The presence of marker chromosomes in the human karyotype always requires a special diagnostic approach. Determination of the marker chromosome type and structure is of great diagnostic and prognostic importance. There are several methods of marker chromosomes identification, which differ in their informative value. The paper presents the results of cytogenetic and FISH diagnostics of supernumerical marker chromosomes (SMC) cases in patients’ karyotype. Aim. To analyze the results of the cytogenetic and molecular cytogenetic diagnostics for patients with marker chromosomes, and to evaluate and compare the efficiency of the methods used. Methods. Karyotyping was done according to the standard methods. GTG, CBG, QFQ and NOR-Ag methods of differential staining were used. FISH was performed according to the manufacturer’s instructions for CEP, LSI and WCP DNA-probes. Results. Marker chromosome was found in 15 of 7989 patients. Application of standard staining methods was effective in 66.6 % of cases. Combination of differential staining and FISH allowed identifying a marker chromosome in 83.3 %. 90 % of all marker chromosomes were identified as isochromosomes and 60 % of them were derivative from chromosome 15. Conclusions. The use of WCP probes is a main step in the marker chromosome identification with further application of CEP/LSI probes. If a marker chromosome has nonspecific DNA sequences more sensitive methods should be use.Наявність маркерних хромосом в каріотипі людини завжди вимагає особливого діагностичного підходу. Визначення типу і структури маркерної хромосоми має велике діагностичне і прогностичне значення. Існує кілька методів ідентифікації маркерних хромосом, але різні методи мають різний рівень інформативності. В роботі наведені результати цитогенетичної та FISH діагностики випадків із надчисельними маркерними хромосомами в каріотипі пацієнтів. Мета. Аналіз результатів цитогенетичних і молекулярно-цитогенетичних досліджень каріотипів пацієнтів з маркерними хромосомами, а також оцінка і порівняння ефективності використаних методів. Методи. Каріотипування було виконано у відповідності до стандартних методів. Були використані GTG, CBG, QFQ і NOR-Ag методи диференціального фарбування. FISH була виконана відповідно до інструкцій виробника для CEP, LSI та WCP ДНК-проб. Результати. Маркерна хромосома була виявлена у 15 з 7989 пацієнтів. Застосування стандартних методів фарбування було ефективним у 66,6% випадків. Поєднання диференціального фарбування та FISH дозволило ідентифікувати маркерні хромосоми у 83,3 %. 90 % всіх маркерних хромосом були визначені як ізохромосоми і 60 % з них були похідними від хромосоми 15. Висновки. Використання WCP ДНК-проб є основним етапом ідентифікації маркерних хромосом з наступним застосуванням CEP та LSI ДНК-проб. Якщо маркерна хромосома має неспецифічні послідовності ДНК, то у таких випадках повинні бути застосовані більш чутливі методи.Наличие маркерных хромосом в кариотипе человека всегда требует особого диагностического подхода. Определение типа и структуры маркерной хромосомы имеет большое диагностическое и прогностическое значение. Существует несколько методов идентификации маркерных хромосом, но разные методы имеют разный уровень информативности. В работе приведены результаты цитогенетической и FISH диагностики случаев со сверхчисленными маркерными хромосомами в кариотипе пациентов. Цель. Анализ результатов цитогенетических и молекулярно-цитогенетических исследований кариотипов пациентов с маркерным хромосомами, а также оценка и сравнение эффективности использованных методов. Методы. Кариотипирование выполнено согласно стандартных методик. Использованы GTG, CBG, QFQ и NOR-Ag методы дифференциального окрашивания. FISH выполнена в соответствии с инструкциями производителя для CEP, LSI и WCP ДНК-проб. Результаты. Маркерная хромосома обнаружена у 15 из 7989 пациентов. Применение стандартных методов окрашивания было эффективным в 66,6 % случаев. Сочетание дифференциального окрашивания и FISH позволило идентифицировать маркерные хромосомы в 83,3 %. 90 % всех маркерных хромосом были определены как изохромосомы и 60 % из них были производными от хромосомы 15. Выводы. Использование WCP ДНК-проб является основным этапом идентификации маркерных хромосом с последующим применением CEP и LSI ДНК-проб. Если маркерная хромосома имеет неспецифические последовательности ДНК, то в таких случаях должны быть применены более чувствительные методы

Ultrarelativistic electron-hole pairing in graphene bilayer

We consider ground state of electron-hole graphene bilayer composed of two independently doped graphene layers when a condensate of spatially separated electron-hole pairs is formed. In the weak coupling regime the pairing affects only conduction band of electron-doped layer and valence band of hole-doped layer, thus the ground state is similar to ordinary BCS condensate. At strong coupling, an ultrarelativistic character of electron dynamics reveals and the bands which are remote from Fermi surfaces (valence band of electron-doped layer and conduction band of hole-doped layer) are also affected by the pairing. The analysis of instability of unpaired state shows that s-wave pairing with band-diagonal condensate structure, described by two gaps, is preferable. A relative phase of the gaps is fixed, however at weak coupling this fixation diminishes allowing gapped and soliton-like excitations. The coupled self-consistent gap equations for these two gaps are solved at zero temperature in the constant-gap approximation and in the approximation of separable potential. It is shown that, if characteristic width of the pairing region is of the order of magnitude of chemical potential, then the value of the gap in the spectrum is not much different from the BCS estimation. However, if the pairing region is wider, then the gap value can be much larger and depends exponentially on its energy width.Comment: 13 pages with 8 figures; accepted to Eur. Phys. J.

Multi-wavelength observations of blazar AO 0235+164 in the 2008-2009 flaring state

The blazar AO 0235+164 (z = 0.94) has been one of the most active objects observed by Fermi Large Area Telescope (LAT) since its launch in Summer 2008. In addition to the continuous coverage by Fermi, contemporaneous observations were carried out from the radio to γ-ray bands between 2008 September and 2009 February. In this paper, we summarize the rich multi-wavelength data collected during the campaign (including F-GAMMA, GASP-WEBT, Kanata, OVRO, RXTE, SMARTS, Swift, and other instruments), examine the cross-correlation between the light curves measured in the different energy bands, and interpret the resulting spectral energy distributions in the context of well-known blazar emission models. We find that the γ-ray activity is well correlated with a series of near-IR/optical flares, accompanied by an increase in the optical polarization degree. On the other hand, the X-ray light curve shows a distinct 20 day high state of unusually soft spectrum, which does not match the extrapolation of the optical/UV synchrotron spectrum. We tentatively interpret this feature as the bulk Compton emission by cold electrons contained in the jet, which requires an accretion disk corona with an effective covering factor of 19% at a distance of 100 R g. We model the broadband spectra with a leptonic model with external radiation dominated by the infrared emission from the dusty torus. © 2012. The American Astronomical Society. All rights reserved

Insights into the high-energy γ-ray emission of Markarian 501 from extensive multifrequency observations in the Fermi era

We report on the γ-ray activity of the blazar Mrk 501 during the first 480 days of Fermi operation. We find that the average Large Area Telescope (LAT) γ-ray spectrum of Mrk 501 can be well described by a single power-law function with a photon index of 1.78 ± 0.03. While we observe relatively mild flux variations with the Fermi-LAT (within less than a factor of two), we detect remarkable spectral variability where the hardest observed spectral index within the LAT energy range is 1.52 ± 0.14, and the softest one is 2.51 ± 0.20. These unexpected spectral changes do not correlate with the measured flux variations above 0.3 GeV. In this paper, we also present the first results from the 4.5 month long multifrequency campaign (2009 March 15-August 1) on Mrk 501, which included the Very Long Baseline Array (VLBA), Swift, RXTE, MAGIC, and VERITAS, the F-GAMMA, GASP-WEBT, and other collaborations and instruments which provided excellent temporal and energy coverage of the source throughout the entire campaign. The extensive radio to TeV data set from this campaign provides us with the most detailed spectral energy distribution yet collected for this source during its relatively low activity. The average spectral energy distribution of Mrk 501 is well described by the standard one-zone synchrotron self-Compton (SSC) model. In the framework of this model, we find that the dominant emission region is characterized by a size ≲0.1 pc (comparable within a factor of few to the size of the partially resolved VLBA core at 15-43 GHz), and that the total jet power (≃1044 erg s-1) constitutes only a small fraction (∼10-3) of the Eddington luminosity. The energy distribution of the freshly accelerated radiating electrons required to fit the time-averaged data has a broken power-law form in the energy range 0.3 GeV-10 TeV, with spectral indices 2.2 and 2.7 below and above the break energy of 20 GeV. We argue that such a form is consistent with a scenario in which the bulk of the energy dissipation within the dominant emission zone of Mrk 501 is due to relativistic, proton-mediated shocks. We find that the ultrarelativistic electrons and mildly relativistic protons within the blazar zone, if comparable in number, are in approximate energy equipartition, with their energy dominating the jet magnetic field energy by about two orders of magnitude. © 2011. The American Astronomical Society

Tunneling ionization of deep centers in high-frequency electric fields

A theoretical and experimental study of the tunneling ionization of deep impurities in semiconductors has been carried out for high-frequency alternating electric fields. It is shown that tunneling ionization occurs by phonon-assisted tunneling which proceeds at high electric field strengths into direct tunneling without involving phonons. In the quasistatic regime of low frequencies the tunneling probability is independent of frequency. Raising the frequency leads to an enhancement of the tunneling ionization. The transition from the quasistatic limit to frequency-dependent tunneling is determined by the tunneling time which, in the case of impurities interacting with thermal phonons, is controlled by the temperature. In both the quasistatic and high-frequency limits, the application of an external magnetic field perpendicular to the electric field reduces the ionization probability when the cyclotron frequency becomes larger than the reciprocal tunneling time