ANALYTICAL MODEL OF TEMPERATURE DISTRIBUTION OVER AN ELECTRONIC CIRCUIT BOARD

The thermal model of an electronic circuit board with installed heat dissipating components is presented as a two-dimension steady-state heat conduction problem with multiple sources distributed over a rectangular region. The corresponding energy equation includes a source term and a temperature-dependent term to account for linear heat transfer in z-direction. Boundary conditions are of first type with unique temperature along the perimeter. The integral-transform technique is applied to obtain closed-form integral solution. Assuming that all dissipated components have a rectangular contact area with the plate, multiple integrals for each dissipated sub-region are easily found. A temperature map over the board is calculated from the closed expression with a triple sum of series with respect to each coordinate and source. The error is evaluated by the estimation of the truncated terms. The solution was applied to obtain the temperature distribution over the electronic Driver Plate of the CEP block of the CIMEX Brazilian experiment for flight qualifying of the Optical Block Detector Assembling

Mini-ribozymes and freezing environment: a new scenario for the early RNA world

International audienceThe RNA World hypothesis states that the present-day life, which is based on DNA genomes and protein enzymes, was preceded by a simpler life form based primarily on RNA. During this era, the genetic information resided in the sequence of RNA molecules and the phenotype derived from the catalytic properties of RNA. Though it is a widely accepted scenario, a number of problems remain unsolved. One of the biggest questions is how complex RNAs could evolve, survive and replicate under typically assumed ''warm and wet'' conditions, taking into account that the RNA phosphodiester backbone is chemically unstable under these conditions. We suggest that prebiotic conditions associated with freezing could have been of key importance in the early RNA World, and discuss the role of primitive catalytic RNA in the evolution of RNA size and complexity

Current Development of siRNA Bioconjugates: From Research to the Clinic

Small interfering RNAs (siRNAs) acting via RNA interference mechanisms are able to recognize a homologous mRNA sequence in the cell and induce its degradation. The main problems in the development of siRNA-based drugs for therapeutic use are the low efficiency of siRNA delivery to target cells and the degradation of siRNAs by nucleases in biological fluids. Various approaches have been proposed to solve the problem of siRNA delivery in vivo (e.g., viruses, cationic lipids, polymers, nanoparticles), but all have limitations for therapeutic use. One of the most promising approaches to solve the problem of siRNA delivery to target cells is bioconjugation; i.e., the covalent connection of siRNAs with biogenic molecules (lipophilic molecules, antibodies, aptamers, ligands, peptides, or polymers). Bioconjugates are “ideal nanoparticles” since they do not need a positive charge to form complexes, are less toxic, and are less effectively recognized by components of the immune system because of their small size. This review is focused on strategies and principles for constructing siRNA bioconjugates for in vivo use

TURBULENT STRESS DISTRIBUTION IN THE TURBULENT BOUNDARY LAYER ON A PERMEABLE POROUS PLATE

In this paper the results of experimental tests on turbulent boundary layer on a plate with air blowing through permeable porous wall are presented. Tests were performed in an aerodynamic tunnel varying the blowing rate within the range of 0 to 2.5% of the air flow velocity in the tunnel, using thermoanemometers of constant temperature. It has been determined that the blowing increases the boundary layer thickness and strongly transforms the boundary layer inner part and turbulent nucleus, while the outer part remains not deformed. An increase in blowing causes an abrupt viscous stress decrease, also decreasing skin friction. Thick boundary layers (up to 120 mm) allowed a profound analysis of Reynolds' turbulent stresses. It has been found a general distribution of turbulent stress in the turbulent layer which is independent of blowing velocity. It has been established for the turbulent characteristics that the determining coordinate is the relative horizontal velocity, not the distance from the wall. With a turbulent stress database obtained from turbulent stresses direct measurements, it has been proposed a flow model for boundary layer on a permeable porous plate. It has also been demonstrated that in high blowing conditions the horizontal velocity profile in the boundary layer becomes equal to the velocity profile in a plane jet

Site-Selective Artificial Ribonucleases: Oligonucleotide Conjugates Containing Multiple Imidazole Residues in the Catalytic Domain

Design of site-selective artificial ribonucleases (aRNases) is one of the most challenging tasks in RNA targeting. Here, we designed and studied oligonucleotide-based aRNases containing multiple imidazole residues in the catalytic part and systematically varied structure of cleaving constructs. We demonstrated that the ribonuclease activity of the conjugates is strongly affected by the number of imidazole residues in the catalytic part, the length of a linker between the catalytic imidazole groups of the construct and the oligonucleotide, and the type of anchor group, connecting linker structure and the oligonucleotide. Molecular modeling of the most active aRNases showed that preferable orientation(s) of cleaving constructs strongly depend on the structure of the anchor group and length of the linker. The inclusion of deoxyribothymidine anchor group significantly reduced the probability of cleaving groups to locate near the cleavage site, presumably due to a stacking interaction with the neighbouring nucleotide residue. Altogether the obtained results show that dynamics factors play an important role in site-specific RNA cleavage. Remarkably high cleavage activity was displayed by the conjugates with the most flexible and extended cleaving construct, which presumably provides a better opportunity for imidazole residues to be correctly positioned in the vicinity of scissile phosphodiester bond

Circulating microRNAs in lung cancer: prospects for diagnosis, prognosis, and prediction of antitumor treatment efficacy

The review considers the main techniques to extract microRNA (miRNA) from various biological fluids (in particular, the serum and plasma), approaches to the analysis of miRNA concentration and composition, and methods to normalize the results in data analyses. Advantages and drawbacks of the methods are described. Special attention is given to circulating miRNAs, which can be used as markers for minimally invasive diagnosis, prediction of antitumor treatment efficacy, and disease prognosis in lung cancer. The review discusses the prospects and limitations that arise as the clinical significance is evaluated for miRNAs as potential tumor markers and a better understanding is gained for the roles various miRNAs play in the pathogenesis of lung cancer

Quality improvement in hospitals in the Russian Federation, 2000-2016: a systematic review.

We reviewed published evidence on quality improvement in hospitals in the Russian Federation since 2000. We used three data sources: MEDLINE, 'Rossiiskaia Meditsina' (Central Scientific Medical Library), and elibrary.ru using specific search terms. No language or study design restrictions were imposed. In total, 1717 articles were identified; 51 met the inclusion criteria and were thematically analysed. Russian legislation, government acts and grey literature were sourced to contextualise identified themes. Since 2010, the Federal Ministry of Health has increasingly sought to improve quality of care, providing additional resources and new initiatives across the health system. These include clinical practice guidelines, pay for performance schemes, electronic medical records, more specialist care, paraclinical care, and quality control systems. Quality of care, increasingly a concern of the Russian government, is said to be improving. Yet most initiatives have rarely been evaluated. This reflects the limited capacity for health services research in Russia. It seems likely that the full potential for improvements in quality of care in Russia is still to be realised

Biomedical journals and databases in Russia and Russian language in the former Soviet Union and beyond

In the 20th century, Russian biomedical science experienced a decline from the blossom of the early years to a drastic state. Through the first decades of the USSR, it was transformed to suit the ideological requirements of a totalitarian state and biased directives of communist leaders. Later, depressing economic conditions and isolation from the international research community further impeded its development. Contemporary Russia has inherited a system of medical education quite different from the west as well as counterproductive regulations for the allocation of research funding. The methodology of medical and epidemiological research in Russia is largely outdated. Epidemiology continues to focus on infectious disease and results of the best studies tend to be published in international periodicals. MEDLINE continues to be the best database to search for Russian biomedical publications, despite only a small proportion being indexed. The database of the Moscow Central Medical Library is the largest national database of medical periodicals, but does not provide abstracts and full subject heading codes, and it does not cover even the entire collection of the Library. New databases and catalogs (e.g. Panteleimon) that have appeared recently are incomplete and do not enable effective searching

Rationing of medical care: how medical care to be distributed in conditions of limited resources

Background. Rationing of health care—restricting patients’ access to potentially beneficial health care interventions through non-market instruments—is a natural feature of all health care systems as they operate under resource constraints. The purpose of this study is to characterize rationing practices and the attitude of doctors themselves to it, with an emphasis on comparing Russia and the United States and on changes in the perception of rationing during the COVID-19 pandemic. Methods. We conducted a bibliometric analysis of publications in the medical scientific literature since 1989 on the issue of rationing of medical care. To characterize rationing practices in Russia and the United States and the attitudes of doctors towards them, we used data from published studies and data from semi-structured in-depth interviews with 28 Russian doctors. Results. Despite the increasing frequency of publications related to the topic of resource allocation over the past 20 years, studies using the term “rationing” are rare. Both Russia and the USA have practices of explicit and implicit rationing. In Russia they are more diverse and widespread. In both countries, doctors prefer implicit rationing and do not want open discussion of these issues. The practice of rationing is institutionalized. In Russian medical organizations its most common form is a chain of permissions for the use of resources. But most doctors believe they are not rationing care. The pandemic briefly brought the topic of rationing into the public sphere, but then its discussion was limited. The probable reason is that medical practice during the pandemic was carried out within the previous legal framework. Professional organizations have developed several recommendations for rationing, but their usefulness and level of acceptance by professionals and the public is unclear. Conclusions The transition from implicit to explicit rationing is extremely difficult, but is necessary to ensure equitable patient access to scarce medical resources and the effective functioning of health care systems. A major barrier to the explicit and informed use of rationing instrument is the limited public acceptance of it and the reluctance of professional communities to make public decisions that maximize public benefit by prioritizing access to effective interventions