85 research outputs found
Separatrix splitting at a Hamiltonian 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
Seroimmunotyping of African swine fever virus
The extreme genetic and immunobiological heterogeneity exhibited by the African swine fever virus (ASFV) has been a significant impediment in the development of an efficacious vaccine against this disease. Consequently, the lack of internationally accepted protocols for the laboratory evaluation of candidate vaccines has become a major concern within the scientific community. The formulation of such protocols necessitates the establishment of a consensus at the international level on methods for the determination of homologous and heterologous isolates/strains of ASFV. The present article provides a comprehensive description of biological techniques employed in the classification of ASFV by seroimmunotypes. These techniques involve a holistic evaluation of ASFV isolates/strains based on their antigenic properties as determined by the hemadsorption inhibiting test (HAdI) using type-specific sera and an immunological test (IT) conducted on pigs inoculated with attenuated strains. The article outlines the methods for setting up the HAdI test, an IT on pigs, and the processes involved in the acquisition of type-specific serums for the HAdI test. It is pertinent to note that the definitive classification of seroimmunotype can only be ascertained after conducting an IT on pigs. The findings from the HAdI test or the phylogenetic analysis of the EP402R gene should be considered preliminary in nature
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
Democracy, protest and public sphere in Russia after the 2011–2012 anti-government protests: digital media at stake
The 2011–2012 Russian protest mobilisations were largely enabled by the rise of social networks. Social and technological advancements paired to pave the way for the ‘biggest protests since the fall of USSR’. Ubiquitous and uncensored social media facilitated the networking and mobilisation for this protest activity: Liberal masses were able to share and discuss their grievances, unite and coordinate online for the offline protest. The digitally savvy protest public developed to confront the government, which appeared to be astonished by the scale of protest. Those mobilisations marked an important gap between the government’s conception of the society and the real state of resistance. This article studies three main hypotheses regarding the potential of the protest movement in Russia. The hypotheses were drawn from recent sociological, political and media studies on Russian resistance. Current research aims to contribute to the debate from the digital media perspective. It therefore evaluates three main assumptions: Digital media have the potential to empower, dependent upon the relevant political, social and economic factors; digital media isolates protest publics and therefore may be more useful for the government than the resistance; and recent censorship of digital media communication signals a tightening of both formal and informal restrictions against opposition and protest politics. This article uses theoretical and factual evidence on the limitations of democracy and the public sphere and conceptualises the government’s management of resistance in Russia during and after the 2011–2012 protests. It studies how the hybrid political regime in Russia balances restrictions on freedom of speech with strengthened state propaganda and how it mediates media oppression and invites self-censorship. Finally, it examines how the state communication watchdog has recently focused its attention at the digital realm. This move confirms the importance of the online protest communication for the Russian political environment. Yet the state’s acknowledgement of digital political resistance may lead to further oppression and curbing of this emerging component of Russian politics
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
Изучение влияния антител к боковым карбогидратным звеньям аллергенов на популяционный профиль сенсибилизации пациентов в Юго-западном регионе Украины
Были обследованы на наличие IgE антител к 28 аллергенам методом иммуноблоттинга производства компании Mediwiss (Германия) 500 пациентов Юго-Западного региона Украины с подозрением либо клинически установленным диагнозом аллергического ринита, конъюнктивита,
бронхиальной астмы, поллиноза. У (21,1±2,00) % обследованных пациентов с наличием антител к различным аллергенам выявлялись антитела к ССD-маркеру, присутствовавшем на блоте. Такие пациенты значительно меняли эпидемиологическую картину сенсибилизации обследованной когорты за счет повышения процента положительных реакций на растительные, инсектные аллергены, а также на латекс. Использование ССD-блокера при повторном обследовании 84 пациентов с множественной сенсибилизацией достоверно снижало процент положительных реакций именно на вышеуказанные аллергены, содержащие боковые кроссреактивные карбогидратные цепочки. Это позволяет рекомендовать использование ССD-блокера для устранения перекрестных неспецифических реакций при рутинном обследовании пациентов с аллергическими заболеваниями. Следует учитывать также возможность неспецифических реакций при
эпидемиологическом анализе серопозитивности к аллергенам в популяции.500 patients from the South-Western region of Ukraine with suspected or clinically confirmed diagnosis of allergic rhinitis, conjunctivitis, bronchial asthma, pollinosis were examined for the presence
of IgE antibodies to 28 allergens by immunoblotting manufactured by Mediwiss (Germany). It was
shown that (21.10±2.00)% of the examined patients with antibodies to various allergens have also antibodies to the CСD-marker present on the blot. Such patients significantly changed the epidemiological pattern of sensitization of the examined cohort due to increase of the percentage of positive reactions to plant, insect allergens, and also to latex. The use of CСD-blocker in the re-examination of 84
patients with multiple sensitization significantly reduced the percentage of positive reactions particularly to the allergens containing cross-reactive carbohydrate chains. This makes it possible to recommend the use of CCD-blocker for the elimination of cross-nonspecific reactions during the routine
examination of patients with allergic diseases. The possibility of non-specific reactions in the epidemiological analysis of seropositivity to allergens in the population should also be taken into account
- …