Negative polarizability of 2D electrons in HgTe quantum well

The polarizability of electrons occupying the lowest subband of spatial quantization in CdTe/Cd$_x$Hg$_{1-x}$Te/CdTe quantum wells is calculated. It is shown that polarizability in the quantum well without cadmium is negative, i.e., the displacement of an electron in an electric field applied perpendicularly to the quantum well plane is opposite to the force acting on it. The negative polarizability of 2D electrons can reduce the dielectric constant of quantum wells by up to $(10-15)$ percent.Comment: 4 pages, 4 figure

The valence band energy spectrum of HgTe quantum wells with inverted band structures

The energy spectrum of the valence band in HgTe/Cd$_x$Hg$_{1-x}$Te quantum wells with a width $(8-20)$~nm has been studied experimentally by magnetotransport effects and theoretically in framework $4$-bands $kP$-method. Comparison of the Hall density with the density found from period of the Shubnikov-de Haas (SdH) oscillations clearly shows that the degeneracy of states of the top of the valence band is equal to 2 at the hole density $p< 5.5\times 10^{11}$~cm$^{-2}$. Such degeneracy does not agree with the calculations of the spectrum performed within the framework of the $4$-bands $kP$-method for symmetric quantum wells. These calculations show that the top of the valence band consists of four spin-degenerate extremes located at $k\neq 0$ (valleys) which gives the total degeneracy $K=8$. It is shown that taking into account the "mixing of states" at the interfaces leads to the removal of the spin degeneracy that reduces the degeneracy to $K=4$. Accounting for any additional asymmetry, for example, due to the difference in the mixing parameters at the interfaces, the different broadening of the boundaries of the well, etc, leads to reduction of the valleys degeneracy, making $K=2$. It is noteworthy that for our case two-fold degeneracy occurs due to degeneracy of two single-spin valleys. The hole effective mass ($m_h$) determined from analysis of the temperature dependence of the amplitude of the SdH oscillations show that $m_h$ is equal to $(0.25\pm0.02)\,m_0$ and weakly increases with the hole density. Such a value of $m_h$ and its dependence on the hole density are in a good agreement with the calculated effective mass.Comment: 8 pages, 11 figure

BACTERIOPHAGES AND LACTIC ACID BACTERIA. UTERATURE REVIEW

The review of literature and own data analysis describe bacteriophages application for medical microbiology (especially in cases of multiple drug resistance of pathogens) and. industrial biotechnology (the problems of decontamination and. stabilization of foods). Prospects of bacteriophages for enzyme therapy are underlined

CO-FUNCTIONING OF LECTINS OF MULTICOMPONENT PROBIOTIC AND POTENTIAL PROBIOTIC COMPARTMENT OF BIOTOPE ON THE EXAMPLE OF AUTOREGULATOR LACTOBACILLUS SYSTEM

Using lectins of Acilact, clinical isolates of Lactobacillus from vaginal biotope were screened. Lactobacilli of the biotopes were classified to functional groups. Results indicate autoregulation signal properties of probiotic microbial lectins

Modulation of biofilms by microbial potential consortia of human: conception of extended probiotic compartment of biotope, prognostic patterns

The purpose of the investigation was development of screening visual and quantitative method of strain selection and potential consortium of normal human microflora (including one of probiotic orientation) for future creation of new synbiotic, symbiotic and acellular prophylactic and medicinal forms significant for therapy of endoceliac diseases. We used strains of yeast Candida and lactobacilli Lactobacillus, isolated from normal microflora of urogenital biotope of healthy donors. Suspensions of strains with turbidity 1 unit of Mcfarland standards were added with increasing doses to wells of polystyrene micropanels with surplus of MRS broth (variants A, B, C, D and E) and incubated 48 hours at 37 °C. Cultivated biofilms were stained with gentian violet and bottoms of wells in micropanels were photographed and scanned. Optical density of ethanol fixated stained biofilms in wells was registered with colour filter 620 nm. Visual evaluation was performed of influence of biofilm resolving activity and opposite action of polysaccharides and other adhesins. To assess ranging of expressiveness if biofilms growth in monocultures we suggested to use calculated coefficient (D + E)/(B + C), which reflects rectifying and decreasing of gradient of slope of dosage dependence of optical density in series of cultivations of microbial suspensions. The results make possible to perform monitoring of early film formation by strains of microorganisms and their mixtures. Micropanel is convenient for getting prognostic patterns of interference on film formation of co-existing in biotope consortiums of microorganisms populations and for evaluation of health status of biotope human microbiocenosises. It is possible to select strains biocompatible with human organism and their mixtures of probiotic orientation which are of great interest for prevention and therapy antibiofilm, antipathogenic, enzymatic, alternative to antibiotics, supporting adjuvant and combine