Separatrix splitting at a Hamiltonian 02iω0^2 i\omega bifurcation

We discuss the splitting of a separatrix in a generic unfolding of a degenerate equilibrium in a Hamiltonian system with two degrees of freedom. We assume that the unperturbed fixed point has two purely imaginary eigenvalues and a double zero one. It is well known that an one-parametric unfolding of the corresponding Hamiltonian can be described by an integrable normal form. The normal form has a normally elliptic invariant manifold of dimension two. On this manifold, the truncated normal form has a separatrix loop. This loop shrinks to a point when the unfolding parameter vanishes. Unlike the normal form, in the original system the stable and unstable trajectories of the equilibrium do not coincide in general. The splitting of this loop is exponentially small compared to the small parameter. This phenomenon implies non-existence of single-round homoclinic orbits and divergence of series in the normal form theory. We derive an asymptotic expression for the separatrix splitting. We also discuss relations with behaviour of analytic continuation of the system in a complex neighbourhood of the equilibrium

Synthesis of Carbon Nanotubes and Nanofibers on Silica and Cement Matrix Materials

In order to create strong composite materials, a good dispersion of carbon nanotubes (CNTs) and nanofibers (CNFs) in a matrix material must be obtained. We proposed a simple method of growing the desirable carbon nanomaterial directly on the surface of matrix particles. CNTs and CNFs were synthesised on the surface of model object, silica fume particles impregnated by iron salt, and directly on pristine cement particles, naturally containing iron oxide. Acetylene was successfully utilised as a carbon source in the temperature range from 550 to 750 C. 5–10 walled CNTs with diameters of 10–15 nm at 600 C and 12–20 nm at 750 C were synthesised on silica particles. In case of cement particles, mainly CNFs with a diameter of around 30 nm were grown. It was shown that high temperatures caused chemical and physical transformation of cement particles.Peer reviewe

Coagulation Disorders in Infective Endocarditis: Role of Pathogens, Biomarkers, Antithrombotic Therapy (Systematic Review)

The issue of antithrombotic therapy in patients with infective endocarditis has been studied for over 75 years. During that time studying of pathogenesis of the disease and its embolic complications, lead to the introduction of the concept of “immunothrombosis”. That mechanism allows infective agents (mostly bacteria) to be cloaked from the immune system and to multiply freely, leading to growth of vegetation, thus resulting in higher chance of fragmentation. Small-scale experimental and clinical studies on the correction of hemostatic disorders in infective endocarditis, that were performed in 20th century, didn’t show any significant results, that could affect clinical practice. However, reinterpretation of available data on coagulative system will allow to have elements of hemostasis as an application point in treating infective endocarditis. The article will discuss latest insights on the role of hemostasis system in pathophysisology of infective endocarditis, its effects on the development of the embolic complications, perspectives for diagnostics and treatment

Hyperexpression of TLR2 and TLR4 in patients with ischemic stroke in acute period of the disease

Pathogenesis of ischemic stroke  is actively  involved  in the  system  of innate immunity. Under conditions of cerebral  ischemia, a number of biologically  active  substances are  released  that  interact with innate immunity receptors, in particular TLR2  and  TLR4, which  exacerbate inflammation in brain  tissue. Identification of predictor markers  at the level of the innate immunity system may foresee the clinical course of ischemic stroke and ensure timely treatment. Our objective was to study expression of TLR2 and TLR4 receptors in peripheral blood leukocytes  in patients with ischemic stroke in the dynamics of the disease. 27 people  were included in the study. The main  group consisted of patients with ischemic stroke of varying severity (n = 19). Patients of the main  group were divided into two subgroups:  with an NIHSS index value of < 10 (n = 10) and > 10 (n = 9). The control group included healthy  donors  with no history  of acute  and chronic inflammatory diseases (n = 8). Peripheral blood  leukocytes  were used as the  test material. To determine expression  of the TLR2  and TLR4  genes, RT-PCR in real time was used. Surface  expression  of TLRs was determined by flow cytometry. A study of the TLR2 and TLR4 gene expression showed that on the 1st, 3rd  and 7th  day post-stroke, the TLR4 gene expression  in patients was significantly  increased, when compared to the control group (p < 0.01), whereas TLR2 gene expression on the 3rd  day of the disease was not statistically different from the control group. A study of surface expression  of receptors showed that the average TLR2 fluorescence intensity on the patients’ peripheral blood monocytes was significantly  increased on the 1st  and 3rd  day of disease when compared to the control group.  The  surface  expression  of TLR4  on monocytes has a statistically significant  increase  only on day 7. Assessment  of surface expression  of TLRs in subgroups  with different  severity values by NIHSS showed that  patients with a NIHSS index > 10 had a significantly  higher  level of surface of TLR2  expression  over the observation period, while the largest difference in TLR4  expression  in the subgroups  was observed  on the 1st day of the disease (p < 0.05). Patients with ischemic stroke showed an increase  in TLR2 and TLR4 expression at the gene and protein level, compared to healthy  donors. These indices can be considered possible predictors for clinical  prognosis  of ischemic stroke

Молекулярная диагностика онкологических заболеваний: перспективы разработки стандартного образца содержания гена HER2

Cancer is the leading cause of death in the world. The development of oncopathology is closely related to various changes in the genetic material that occur in malignantly transformed cells. Medical decision-making requires a clear differentiation between normal and pathological indicators, which are, among other things, the results of application of quantitative methods in laboratory medicine. Studies of DNA isolated from a patient’s biological material, identification and measurement of the content of nucleotide sequences acting as oncopathology biomarkers allow to solve the problems of determining the genetic prerequisites for cancer, its early diagnosis, determining the treatment strategy, monitoring, and confirming the patient’s cure.The purpose of this research is to develop the main approaches to the design of DNA reference materials (RMs) for metrological support of molecular diagnostics of oncopathology through the example of the RM for the HER2 gene sequence content in the human genome, with the value of «the number of copies of the DNA sequence» which is metrologically traceable to the natural SI unit «one».In the course of the research, a technique for measuring the HER2 gene amplification (the number of copies of the gene sequence per genome) was developed based on the use of the digital PCR method (dPCR). Comparability of measurement results for the method developed by the authors, and the results obtained using a commercial kit by the MLPA method on samples of human biological material is shown.Five permanent cell lines obtained from the CUC «Vertebrate Cell Culture Collection» were characterized in relation to the copy number ratios of HER2 gene sequence and CEP17 and RPPH1 genes sequences. A cell line with the HER2 gene amplification was identified. The results obtained will be used to create the RM for the copy number ratio of the HER2 gene sequences and the RPPH1 and CEP17 gene sequences. Creation of matrix DNA RMs based on human cell cultures certified using dPCR will allow transferring the unit of copy numbers of the DNA sequence to calibrators included in medical devices, thereby ensuring the required reliability and comparability of measurement results in the laboratory diagnostics of oncopathology, as well as the possibility of calibrating routine methods of DNA diagnostics and intralaboratory quality control.Онкологические заболевания являются основной причиной смертности в мире. Развитие онкопатологий тесно связано с различными изменениями генетического материала, возникающими в злокачественно трансформированных клетках. Принятие медицинских решений требует четкой дифференциации нормальных и патологических показателей, являющихся в том числе результатами применения количественных методов в лабораторной медицине. Исследования ДНК, выделенной из биологического материала пациента, выявление и измерения содержания последовательностей нуклеотидов, выступающих в роли биомаркеров онкопатологий, позволяют решать задачи определения генетических предпосылок развития рака, его диагностики на ранней стадии, определения стратегии лечения, его мониторинга, подтверждения излечения пациента.Целью данного исследования является выработка основных подходов к созданию стандартных образцов (СО) ДНК для метрологического обеспечения молекулярной диагностики онкопатологий на примере СО содержания последовательности гена HER2 в составе генома человека, значение величины «число копий последовательности ДНК» которого метрологически прослеживается к естественной единице SI «один».В ходе исследования разработана методика выполнения измерений копийности (числа копий последовательности гена на геном) гена HER2, основанная на применении метода цифровой ПЦР (цПЦР). Показана сходимость результатов измерений для разработанной авторами методики и результатов, полученных с использованием коммерческого набора, использующего метод MLPA на образцах биологического материала человека.Охарактеризованы пять постоянных клеточных линий из ЦКП «Коллекция культур клеток позвоночных» по отношению числа копий последовательностей гена HER2 и генов CEP17 и RPPH1. Выявлена клеточная линия с повышенной копийностью гена HER2. Полученные результаты будут использованы при создании СО отношения числа копий последовательностей гена HER2 и генов RPPH1 и CEP17. Создание матричных СО ДНК на основе культур клеток человека, аттестованных с применением цПЦР, позволит передавать единицу величины числа копий последовательности ДНК калибраторам, входящим в состав медицинских изделий, обеспечивая тем самым требуемую достоверность и сопоставимость результатов измерений в лабораторной диагностике онкопатологий, а также возможность калибровки рутинных методик ДНК-диагностики и внутрилабораторного контроля качества