New type of Bernstein modes in two-dimensional electron liquid

Bernstein modes are formed as a result of non-local coupling of collective excitations and cyclotron harmonics in magnetized plasma. In degenerate solid state plasma they are typically associated with magnetoplasmons. A new type of Bernstein modes arises in two-dimensional electron liquid at sufficiently strong quasiparticle interaction. We consider Bernstein modes originating from coupling between quasiparticle cyclotron harmonics and shear magnetosound waves. The latter may be responsible for the giant peak in radio-frequency photoresistance observed in high-quality GaAs quantum wells. Using Landau-Silin kinetic equation with an arbitrary strength of the interparticle Landau interaction, we trace the reconstruction of Bernstein mode spectrum in high-quality 2D electron systems across the crossover between weakly interacting degenerate electron gas and the correlated electron liquid. Sensitivity of Bernstein modes to the strength of quasiparticle interaction allows one to use them for spectroscopy of Landau interaction function in the electron Fermi liquids.Comment: 6 pages, 4 figure

Quantum Oscillations of Photocurrents in HgTe Quantum Wells with Dirac and Parabolic Dispersions

We report on the observation of magneto-oscillations of terahertz radiation induced photocurrent in HgTe/HgCdTe quantum wells (QWs) of different widths, which are characterized by a Dirac-like, inverted and normal parabolic band structure. The photocurrent data are accompanied by measurements of photoresistance (photoconductivity), radiation transmission, as well as magneto-transport. We develop a microscopic model of a cyclotron-resonance assisted photogalvanic effect, which describes main experimental findings. We demonstrate that the quantum oscillations of the photocurrent are caused by the crossing of Fermi level by Landau levels resulting in the oscillations of spin polarization and electron mobilities in spin subbands. Theory explains a photocurrent direction reversal with the variation of magnetic field observed in experiment. We describe the photoconductivity oscillations related with the thermal suppression of the Shubnikov-de Haas effect.Comment: 16 pages, 13 figure

Effects of Size Polydispersity on the Extinction Spectra of Colloidal Nanoparticle Aggregates

We investigate the effect of particle polydispersity on the optical extinction spectra of colloidal aggregates of spherical metallic (silver) nanoparticles, taking into account the realistic interparticle gaps caused by layers of stabilizing polymer adsorbed on the metal surface (adlayers). The spectra of computer-generated aggregates are computed using two different methods. The coupled-multipole method is used in the quasistatic approximation and the coupled-dipole method beyond the quasistatics. The latter approach is applicable if the interparticle gaps are sufficiently wide relative to the particle radii. Simulations are performed for two different particle size distribution functions (bimodal and Gaussian), varying the number of particles per aggregate, and different distribution functions of the interparticle gap width. The strong influence of the latter factor on the spectra is demonstrated and investigated in detail

Exciton-polaritons in CsPbBr3_3 crystals revealed by optical reflectivity in high magnetic fields and two-photon spectroscopy

Cesium lead bromide (CsPbBr$_3$) is a representative material of the emerging class of lead halide perovskite semiconductors that possess remarkable optoelectronic properties. Its optical properties in the vicinity of the band gap energy are greatly contributed by excitons, which form exciton-polaritons due to strong light-matter interactions. We examine exciton-polaritons in solution-grown CsPbBr$_3$ crystals by means of circularly-polarized reflection spectroscopy measured in high magnetic fields up to 60 T. The excited 2P exciton state is measured by two-photon absorption. Comprehensive modeling and analysis provides detailed quantitative information about the exciton-polariton parameters: exciton binding energy of 32.5 meV, oscillator strength characterized by longitudinal-tranverse splitting of 5.3 meV, damping of 6.7 meV, reduced exciton mass of $0.18 m_0$, exciton diamagnetic shift of 1.6 $\mu$eV/T$^2$, and exciton Land\'e factor $g_X=+2.35$. We show that the exciton states can be well described within a hydrogen-like model with an effective dielectric constant of 8.7. From the measured exciton longitudinal-transverse splitting we evaluate the Kane energy of $E_p=15$ eV, which is in reasonable agreement with values of $11.8-12.5$ eV derived from the carrier effective masses.Comment: 16 pager, 7 figure

СРАВНИТЕЛЬНЫЙ АНАЛИЗ ЭКЗОСОМ КЛЕТОК ЭСТРОГЕН-РЕЗИСТЕНТНОГО РАКА МОЛОЧНОЙ ЖЕЛЕЗЫ

The exosomes involvement in the pathogenesis of tumors is based on their property to incorporate into the recipient cells resulting in the both genomic and epigenomic changes.  Earlier we have shown that exosomes from different types of estrogen-independent breast  cancer cells (MCF-7/T developed by long-term tamoxifen treatment, and MCF-7/M)  developed by metformin treatment were able to transfer resistance to the parent MCF-7  cells. To elucidate the common features of the both types of resistant exosomes, the  proteome and microRNA cargo of the control and both types of the resistant exosomes were  analyzed. Totally, more than 400 proteins were identified in the exosome samples. Of these  proteins, only two proteins, DMBT1 (Deleted in Malignant Brain Tumors 1) and THBS1  (Thrombospondin-1), were commonly expressed in the both resistant exosomes (less than  5% from total DEPs) demonstrating the unique protein composition of each type of the resistant exosomes. The comparative analysis of the miRNA differentially expressed in  the both MCF-7/T and MCF-7/M resistant exosomes revealed 180 up-regulated and 202  down-regulated miRNAs. Among them, 4 up-regulated and 8 down-regulated miRNAs were  associated with progression of hormonal resistance of breast tumors. The bioinformatical  analysis of 4 up-regulated exosomal miRNAs revealed 2 miRNAs, mir- 101and mir-181b, which up-regulated PI3K signaling  supporting the key role of PI3K/Akt in the development of the resistant phenotype of breast cancer cells.Участие экзосом в патогенезе злокачественных опухолей основано на их способности проникать внутрь  клеток-реципиентов, вызывая в последних каскад генетических и эпигенетических изменений. Ранее мы  показали, что экзосомы, продуцируемые различными вариантами эстроген-независимых сублиний клеток  рака молочной железы (MCF-7/T, полученной в результате длительного культивирования клеток в  присутствии антиэстрогена тамоксифена, и MCF-7/M, полученной в результате культивирования клеток с  метформином), способны индуцировать резистентность в родительских клетках MCF-7. В настоящей работе  для исследования характерных особенностей состава экзосом резистентных клеток был проведен  сравнительный анализ протеома и профиля микроРНК контрольных экзосом и экзосом, полученных от  резистентных сублиний. В целом в образцах экзосом было идентифицировано более 400 белков, из которых  только 2 белка, DMBT1 (Deleted in Malignant Brain Tumors 1) и THBS1 (Thrombospondin-1), были  гиперэкспрессированы в обоих типах резистентных экзосом (менее 5 % от общего количества белков,  дифференциально экспрессированных в экзосомах резистетных клеток), что свидетельствует об уникальном  составе экзосомальных белков для каждого типа резистентных клеток. Сравнительный анализ  состава микроРНК, дифференциально экспрессированных в обоих вариантах экзосом резистентных клеток,  выявил 180 гиперэкспрессированных микроРНК и 202 микроРНК с пониженной экспрессией. Среди них 4  гиперэкспрессированных и 8 гипоэкспрессированных микроРНК оказались ассоциированы с развитием  гормональной резистентности клеток рака молочной железы. Биоинформатический анализ 4  гиперэкспрессированных микроРНК выявил 2 микроРНК, mir-101и mir-181b, участвующих в стимуляции PI3K  сигналинга, свидетельствуя о важной роли последнего в развитии гормональной резистентности  клеток рака молочной железы.

Molecular genetic and bacteriological methods of bovine mycoplasmosis diagnosis

Mycoplasmas are bacteria that are extremely unstable in vitro as they lack a rigid cell wall. They are most often detected in association with other pathogens, including those that can become L-forms if treated with antibiotics. Mycoplasma colonies, as well as colonies of L-form bacteria, have a typical «fried egg» appearance, therefore it is necessary to differentiate them for the accurate diagnosis and choice of treatment. The paper presents data on mycoplasma infection diagnosis in cattle and results of differentiation of isolated mycoplasma and L-form bacteria colonies using multiple passaging and real-time polymerase chain reaction. For that, 177 samples were collected from animals with mycoplasmosis clinical signs, 45 of them were tested using molecular genetic method, 132 samples were subjected to bacteriological testing. Mycoplasma DNA was detected in 71.1% of samples, and specific colonies were detected in 3.8% of samples. Such biochemical tests of mycoplasma species identification as arginine hydrolysis, blood serum liquefaction, film and grain formation, inoculation into Tween-80-containing medium, hemadsorption and hemolysis of erythrocytes do not allow an objective assessment of the species belonging to mycoplasmas, but, according to the results obtained, the isolated species most likely belongs to Mycoplasma dispar, which is pathogenic for cattle. Real-time polymerase chain reaction is undoubtedly the most accurate and rapid diagnostic method for mycoplasmosis, but a preliminary diagnosis can also be established bacteriologically within 2–7 days. In addition, during microbiological testing, it is possible to assess the antibiotic resistance of mycoplasma isolates, thereby developing an optimal and high-quality scheme of the disease treatment and prevention

MIP/Aquaporin 0 Represents a Direct Transcriptional Target of PITX3 in the Developing Lens

The PITX3 bicoid-type homeodomain transcription factor plays an important role in lens development in vertebrates. PITX3 deficiency results in a spectrum of phenotypes from isolated cataracts to microphthalmia in humans, and lens degeneration in mice and zebrafish. While identification of downstream targets of PITX3 is vital for understanding the mechanisms of normal ocular development and human disease, these targets remain largely unknown. To isolate genes that are directly regulated by PITX3, we performed a search for genomic sequences that contain evolutionarily conserved bicoid/PITX3 binding sites and are located in the proximity of known genes. Two bicoid sites that are conserved from zebrafish to human were identified within the human promoter of the major intrinsic protein of lens fiber, MIP/AQP0. MIP/AQP0 deficiency was previously shown to be associated with lens defects in humans and mice. We demonstrate by both chromatin immunoprecipitation and electrophoretic mobility shift assay that PITX3 binds to MIP/AQP0 promoter region in vivo and is able to interact with both bicoid sites in vitro. In addition, we show that wild-type PITX3 is able to activate the MIP/AQP0 promoter via interaction with the proximal bicoid site in cotransfection experiments and that the introduction of mutations disrupting binding to this site abolishes this activation. Furthermore, mutant forms of PITX3 fail to produce the same levels of transactivation as wild-type when cotransfected with the MIP/AQP0 reporter. Finally, knockdown of pitx3 in zebrafish affects formation of a DNA-protein complex associated with mip1 promoter sequences; and examination of expression in pitx3 morphant and control zebrafish revealed a delay in and reduction of mip1 expression in pitx3-deficient embryos. Therefore, our data suggest that PITX3 is involved in direct regulation of MIP/AQP0 expression and that the alteration of MIP/AQP0 expression is likely to contribute to the lens phenotype in cataract patients with PITX3 mutations