Simple model of the rf noise generated by multipacting electrons

A simplified analytical model is developed to predict the spectrum of electric current induced by the multipacting electrons between two parallel electrodes exposed to an rf voltage of fixed amplitude. The model is based on the resonant multipactor theory and makes it possible to calculate the relative spectral amplitudes of electric current at different harmonics and sub-harmonics of the applied rf frequency. The theoretical predictions are confirmed by numerical simulations of multipactor inside a rectangular waveguide. Specifically it is seen that the relative height of the spectral peaks decreases with increasing gap height

An approximate general model for multipactor in curved geometries

Abstract In order to formulate practical guidelines to avoid multipactor in a quadri-filar helix antenna we have developed a simplified statistical treatment of the electron dynamics between two opposing conducting surfaces of arbitrary curvature. The model allows us to judge the effect of the curvature and the inhomogeneous electric field on the electron density between the conductors. It is found that the parameter regions in these types of systems where multipactor will be possible are quite restricted. In particular it was found that multipactor will not be possible in any realistic helix antenna configuration

Detection of some genes encoding pathogenicity factors in the typical isolates of Escherichia coli

Using polymerase chain reaction 316 strains of E. coli (strains with normal enzymatic activity, strains with weak enzymatic activity and strains with hemolytic activity) were examined for the presence of pathogenicity genes. They were isolatedfrom healthy children and children with functional disorders of the gastro-intestinal tract. The studies have shown that strains of Escherichia coli have pathogenic potential, as evidenced by the presence of genetic pathogenicity markers in them

Invasive mosquito species Aedes albopictus and Aedes aegypti on the Black Sea coast of the Caucasus: genetics (COI, ITS2), Wolbachia and Dirofilaria infections

The area of invasive species Aedes albopictus and Aedes aegypti is expanding. Precise identification and understanding of the genetic diversity of invasive mosquito populations allows us to develop appropriate control methods. Endosymbiotic bacterium Wolbachia pipientis has different effects on their arthropod hosts and can influence the transmission and spread of the pathogens. The objective of the presented study was molecular-genetic identification of the Aedes mosquitoes collected in sampling sites on the Black Sea coast from 2007 to 2017; determination of genetic variability of Ae. aegypti, Ae. albopictus and their symbiotic bacteria Wolbachia; assessment of mosquitoes ability to be infected and to spread parasitic Dirofilaria. Another objective was obtaining the genetic characteristic of laboratory strain Ae. aegypti IMPITM. We investigated two markers of nuclear and mitochondrial DNA from Ae. albopictus and Ae. aegypti and compared them to DNA from Ae. cretinus and Ae. koreiсus sympatrically inhabiting the territory, as well as to one of Ae. aegypti from a laboratory line. The study of nuclear and mitochondrial DNA revealed a low level of variability in the invasive mosquitoes Ae. albopictus and Ae. aegypti collected at different collection sites and in different years. More than a half of Ae. albopictus were infected with Wolbachia, two strains of bacteria, wAlbA and wAlbB, occur in the Ae. albopictus population on the Black Sea coast. Total infection of Ae. aegypti and Ae. albopictus with dirofilariae was 1.8 %. Dirofilaria immitis was found only in mosquito abdomen, larvae of infective stage L3 were not found. D. repens larvae developed to the infective stage in the mosquitoes of both species

SPECIES DIVERSITY OF BIFIDOBACTERIA IN CHILDREN WITH FUNCTIONAL DISORDERS OF GASTROINTESTINAL TRACT

The main aim of this research was to identify species ratio and compatibility in children with functional disorders of gastrointestinal tract (GIT) using PCR method, with, species-specific primers for bifidobacteria. The assessment of intestinal microbiota symbionts composition, was made simultaneously. Dysbiosis changes of I—II degree in large intestine microbiocenosis in 86 children examined, were detected. The definition, of bifidobacteria species profile with, the dominance of B. longum, B. catenulatum. and B. bifidum. will allow to optimize the treatment of this pathology

REGIONAL FEATURES OF BIFIDOBACTERIA ANTAGONISTIC ACTIVITY IN INTESTINAL MICROBIOTA OF CHILDREN LIVING IN SIBERIA

Antagonistic properties of bifidobacteria to opportunistic microorganisms in vitro and mechanism of antagonistic activity decreasing were studied and. analyzed. Great percentage of bifidobacteria regional population strains with low antagonistic activity to transitional opportunistic microorganisms is registered. It results to colonization. resistance decreasing and. requires development of the preventive probiotics therapy methods to correct

Microecological and associative structure of intestinal biocenosis in children with functional gastrointestinal disorders

The article is devoted to one of actual problems of gastroenterology - study of microbiocenosis of gastrointestinal tract in functional disorders. Functional gastrointestinal disorders (FGID) or minimal dysfunctions of digestion are frequent in the first months of child's life and provoke anxiety both in parents and in pediatricians. Aim: to explore the microbial landscape and the associative structure of the microbiota of the large intestine in children with functional disorders of the gastrointestinal tract. Subjects and methods: Intestinal microbiota composition of 225 children with functional gastrointestinal disorders and 100 healthy children was studied using bacteriological method. Results. The 88.4 % frequency of detection of intestinal eubiosis disorders is discussed. Information is provided on the species composition of the major opportunistic organisms that inhabit this biotope. According to the results, decrease of bifidobacteria amount in structure of large intestine microbiota increases rate of detection of opportunistic microorganisms - predominantly, Klebsiella genus bacteria and Staphylococcus aureus. The intestinal microbial community is dominated by multicomponent transient association. The frequency of detection of pathogenic Staphylococcus in children under one year is discussed in detail. Conclusions. A distinctive feature of the intestinal biocenosis microecological status is significantly greater spread of enterococci than in healthy children, which can be a risk for the emergence of strains with the presence of a number of pathogenecity factors that cause infectious processes

Preliminary results on the Multipactor effect prediction in RF components with ferrites

This paper deals with the analysis of the Multipactor effect in RF components with ferrites performed through the preliminary measurements of ferrites secondary emission coefficient and the simulations of the effect of a continuous magnetic field on the electron bunch spread. The impact of this effect on the Multipactor threshold was quantified. \ua9 2013 IEEE

Analysis of phagoand antibiotic sensitivity of Enterobacteriaceae bacteria isolated from women of reproductive age

Pelvic inflammatory diseases occupy a special place in the structure of general morbidity, and are polymicrobial in nature with dominance of opportunistic microorganisms, in particular bacteria of the family Enterobacteriaceae. The aim was to study the composition of the vaginal microbiota in women of reproductive age with pelvic inflammatory diseases, as well as to determine the sensitivity of isolated microorganisms to antibiotics and bacteriophages. The study included 70 women of reproductive age, among them 37 were diagnosed with colpitis and cervicitis, 33 women in the comparison group (women screened for a diagnosis). Isolated microorganisms were identified by abdominoperineal methods, including the disk diffusion method to determine the sensitivity of microorganism cultures of Enterobacteriaceae family to antibiotics, and the method of crosses (evaluation of lytic activity of bacteriophages by the number of crosses) to determine the sensitivity to specific therapeutic bacteriophages. Vaginal biocenosis was characterized by deficit of lactobacilli (< 106 CFU/ml in 100 %), the presence of conditionally pathogenic microflora: bacteria of Enterobacteriaceae family, coccal flora and Candida fungi. From 60.0 to 89.3 % of Enterobacteria strains were resistant to aminoglycosides and quinolones, but also had a low level of sensitivity to therapeutic bacteriophages. The obtained data indicate the reduction of colonization resistance of vaginal mucosa in pelvic inflammatory diseases and specify the need to use medicinal drugs only under medical supervision to prevent clinically significant drug resistance

Regularities of disorders in large intestine microbiocenosis under the influence of Klebsiella oxytoca in children 6-12 months old with functional gastrointestinal disorders

Background. Functional disorders of the gastrointestinal tract represent one of the most urgent problems among children in the first year of life. Aim: to determine the peculiarities of microbiocenosis of large intestine in children with varying degrees of dysbiotic conditions of the gastrointestinal tract. Materials and methods. Material for the study included 354 coprological samples isolated from children with functional disorders of the gastrointestinal tract. Depending on the degree of dysbiotic disorders of the colon, the children were divided into comparison groups: group 1 - children with grade 1 dysbiosis (n = 15), group 2 - 45 children with grade 2 dysbiosis, group 3 consisted of 149 children with grade 3, and group 4 consisted of 145 children with grade 3 of dysbiotic disturbances and K. оxytoca vegetation. Identification was performed by standard methods. Results. All four groups were characterized with changes in the qualitative composition of the indigenous biota with predominance of E. coli with atypical properties (haemolytic (up to 26,7 %) and labourmigration activity (to 33,3 %)). Groups with grade 3 dysbiosis were characterized by the presence of aggressive symbiotes in diagnostically significant concentration of S. aureus, Clostridium spp., Candida spp., Enterobacter spp., Proteusspp., P. aeruginosa. Conclusion. The emergence of Klebsiella oxytoca in the colon of children is an evidence of the violation of compensatory-adaptive reactions of the organism, which in turn is characterized by a decrease and a change in the qualitative composition of the indigenous biota by connecting the more aggressive representatives of the bacterial agents