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1.
Sci Rep ; 11(1): 523, 2021 Jan 12.
Artigo em Inglês | MEDLINE | ID: mdl-33436865

RESUMO

We present a detailed analysis of experimental study, which shows clear evidence of a two-stage melting process of a quasi-two-dimensional dusty plasma system in a high-frequency gas discharge. We accurately calculated global parameters of the orientational and translational order, as well as their susceptibilities to determine two critical points, related to "solid-to-hexatic" and "hexatic-to-liquid" phase transitions. The nature of the emerging defects and changes in their mutual concentration, in addition to the estimate of core energy of free dislocations also counts in favor of the formation of an intermediate hexatic phase. These results are fully consistent with the Berezinsky-Kosterlitz-Thouless theory.

2.
Sci Rep ; 10(1): 13653, 2020 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-32788600

RESUMO

There is a variety of cases in nature when the action-reaction symmetry is broken. In particular, suitable conditions for this are realized in colloidal suspensions and complex plasmas. Since the first theories and simulations of the nonreciprocal effective interactions between microparticles in complex plasmas were published in 1995-1996, there have been hundreds of studies in the theoretical development of this theme. However, despite such a rich theoretical background, one of the important unsolved problems is a direct experimental determination of the nonreciprocal interparticle interaction forces. Here, we studied experimentally in detail the forces of the nonreciprocal effective interaction between microparticles suspended a radio-frequency produced plasma sheath. For this purpose, an experimental method based on an analysis of the spectral density of random processes in an open dissipative two-particle system was developed. In contrast to previous investigations, the proposed method takes into account random and dissipative processes in the system, does not require a special design of the experimental setup and any external perturbations, pre-measurements of external fields and any assumptions about the type of interaction. We found that even small charge changes of one particle, caused by its thermal motion in a wake field of another particle, can lead to a significant change in the effective (measurable) interaction between the particles.

3.
Phys Rev E ; 100(6-1): 063202, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31962420

RESUMO

The breaking of a plane self-excited dust-acoustic soliton in a dust cloud formed in stratified dc glow discharge plasma is studied. Both macroscopic and kinetic parameters of the dust component near the soliton are experimentally obtained. It is shown that the breaking of a soliton can accelerate charged particles to supersonic speeds. The theoretical interpretation of the experimental results is performed in the framework of the hydrodynamic plasma approach, as well as the single-particle approximation. Both dissipative and nondissipative cases are considered.

4.
Phys Rev E ; 95(6-1): 063207, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28709289

RESUMO

A self-consistent model of plasma polarization around an isolated micron-sized dust particle under the action of an external electric field is presented. It is shown that the quasineutral condition is fulfilled and the formed volume charge totally screens the dust particle. The ion focusing and wake formation behind the dust particle are demonstrated for different ion mean free paths and the external electric fields. It is obtained that at low values of the external electric field the trapped ions play the main role in the screening of the dust particle charge. For high external electric fields, the density of trapped ions decreases and the dust particle is screened mainly by the free ions.

5.
Klin Lab Diagn ; 62(6): 375-381, 2017.
Artigo em Russo | MEDLINE | ID: mdl-31505117

RESUMO

The article presents the results of clinical laboratory examination of women (n=104) with gynecological diseases for detection of Toxoplasma gondii. The antibodies to T. gondii were detected in 39.42% of women using enzyme-linked immunosorbent assay and indirect immuno-fluorescence test. In women with various gynecological diseases the toxoplasmosis is detected against the background of concomitant extra-genital pathology. This disease takes its course mostly latent together with urogenital infections being accompanied by hemostasis changes. The detection of antibodies to T. gondii in most cases of inflammation process in oviducts, uterus, ovaries can indicate the role of toxoplasma in development of inflammation diseases of female genitals.

6.
J Appl Microbiol ; 116(5): 1129-36, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-24517235

RESUMO

AIM: To study the effects exerted by argon microwave nonthermal plasma (NTP) on cell wall-lacking Mollicutes bacteria. METHODS AND RESULTS: 10(8) CFU ml(-1) agar plated Mycoplasma hominis and Acholeplasma laidlawii were treated with the nonthermal microwave argon plasma for 30-300 s. The maximal 10- and 100-fold drop was observed for A. laidlawii and Myc. hominis, respectively. Similarly treated Escherichia coli and Staphylococcus aureus demonstrated the 10(5) and 10(3) drop, respectively. Removal of cholesterol affected resistance of A. laidlawii. 10 mmol l(-1) antioxidant butylated hydroxytoluene decreased mortality by a factor of 25-200. UV radiation alone caused 25-85% mortality in comparison with the whole NTP. Exogenously added hydrogen peroxide H2O2 did not cause mortality. NTP treatment of Myc. hominis triggered growth of microcolonies, which were several tenfold smaller than a typical colony. CONCLUSIONS: Despite the lack of cell wall, A. laidlawii and Myc. hominis were more resistant to argon microwave NTP than other tested bacteria. Mycoplasma hominis formed microcolonies upon NTP treatment. A role of UV and active species was demonstrated. SIGNIFICANCE AND IMPACT OF THE STUDY: The first study of NTP effects on Mollicutes revealed importance of a membrane composition for bacterial resistance to NTP. New specific Myc. hominis morphological forms were observed. The study confirmed importance of the concerted action of reactive oxygen species (ROS) with UV and other plasma bioactive agents for NTP bactericidal action.


Assuntos
Acholeplasma laidlawii/efeitos dos fármacos , Antibacterianos/farmacologia , Mycoplasma hominis/efeitos dos fármacos , Gases em Plasma/farmacologia , Argônio , Colesterol/fisiologia , Viabilidade Microbiana/efeitos dos fármacos , Micro-Ondas , Mycoplasma hominis/crescimento & desenvolvimento , Mycoplasma hominis/ultraestrutura , Oxidantes/farmacologia , Raios Ultravioleta
7.
Acta Naturae ; 4(3): 82-7, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-23150806

RESUMO

Non-thermal plasma (NTP) consists of a huge amount of biologically active particles, whereas its temperature is close to ambient. This combination allows one to use NTP as a perspective tool for solving different biomedical tasks, including antitumor therapy. The treatment of tumor cells with NTP caused dose-dependent effects, such as growth arrest and apoptosis. However, while the outcome of NTP treatment has been established, the molecular mechanisms of the interaction between NTP and eukaryotic cells have not been thoroughly studied thus far. In this work, the mechanisms and the type of death of human colon carcinoma HCT 116 cells upon application of non-thermal argon plasma were studied. The effect of NTP on the major stress-activated protein p53 was investigated. The results demonstrate that the viability of HCT116 cells upon plasma treatment is dependent on the functional p53 protein. NTP treatment caused an increase in the intracellular concentration of p53 and the induction of the p53-controlled regulon. The p53-dependent accumulation of active proapoptotic caspase-3 was shown in NTP-treated cells. The study was the first to demonstrate that treatment of human colon carcinoma cells with NTP results in p53-dependent apoptosis. The results obtained contribute to our understanding of the applicability of NTP in antitumor therapy.

8.
Phys Rev E Stat Nonlin Soft Matter Phys ; 86(3 Pt 2): 036404, 2012 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23031031

RESUMO

We have performed experimental and theoretical investigation of the formation and behavior of Coulomb clusters of charged diamagnetic particles in a cusp magnetic trap under microgravity conditions aboard the International Space Station. Graphite particles of 100-400 µm in size were used in experiments due to the highest specific magnetic susceptibility. We have observed the formation of clusters in the shape of an oblate ellipsoid of revolution and their oscillations after dynamical action by changing the magnetic field. Observing the excitation and damping of oscillations we have made some estimations. Molecular dynamics simulations of the observed processes have been made. Their results are in reasonable agreement with experiments. Some differences are evidently due to some unaccounted-for reasons.


Assuntos
Poeira , Modelos Químicos , Gases em Plasma/química , Eletricidade Estática , Ausência de Peso , Simulação por Computador , Tamanho da Partícula
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