Loss of coherence in cavity-polariton condensates: effect of disorder vs. exciton reservoir

The work was supported by the Russian Science Foundation (Grant No. 14-12-01372) and the State of Bavaria.Time evolution of long-range spatial coherence in a freely decaying cavity-polariton condensate excited resonantly in a high-Q GaAs microcavity (MC) is found to be qualitatively different from that in nonresonantly excited condensates. The first-order spatial correlation function g(1)(r1, r2) in response to resonant 1.5 ps pump pulses at normal incidence leaving the exciton reservoir empty is found to be nearly independent of the excitation density. g(1) exceeds 0.7 within the excited spot and decreases very slowly in the decaying and expanding condensate. It remains above 0.5 until the polariton blueshift α|ψ2| gets comparable to the characteristic amplitude of the disorder potential δELP . The disorder is found to reveal itself at α|ψ2| ≤ δELP in fast and short-range phase fluctuations as well as vortex formation. They lead to oscillations in g(1)(t), but have little effect on the overall coherence, which is well reproduced in the framework of the Gross-Pitaevskii equations.PostprintPeer reviewe

Studies of non-autonomous effects of apoptosis in the course of in vitro apoptotic cell death initiation in healthy persons and patients with rheumatoid arthritis

The process of apoptosis is known that play an important role in cellular homeostasis, and the altered cell death may lead to development of pathological disorders. Evolving autoimmune conditions, in particular, rheumatoid arthritis, are associated with decreased rates of apoptosis as a form of programmed cell death. The aim of this study was to evaluate expression of activation and proliferation markers on T lymphocytes during initiation of apoptotic cell death under the conditions of “cell neighborhood” in healthy individuals and patients with rheumatoid arthritis. Patients and methods. The study was performed with blood samples of the patients with rheumatoid arthritis (RA) and healthy women of comparable age. During the study, we conducted experiments aimed to identify the in vitro influence of non-stimulated apoptosis-induced cells, as well as aCD3- and dexamethasone (Dexa)-stimulated apoptosis-induced cells upon autologous T lymphocytes cultured under physiological conditions. Development of a “cell neighborhood” model, i.e., co-cultures of CFSE- T cells subjected to incubation under crowding condition and depletion of the culture medium which is the most physiological variant of apoptosis activation, and CFSE+ autologous cells placed in the complete culture medium, has revealed some relationships. We have revealed an opportunity of secondary induction of early and late apoptosis by means of humoral and cellular components of autologous cell culture subjected to activation apoptosis. We determined the features of apoptosis in unstimulated, as well as aCD3- and dexamethasone-stimulated cultures, compared with controls. There were no differences in these parameters of apoptosis between RA patients and healthy people for all variants of cultures. An increased proportion of viale cells was found in the CFSE- culture of patients with RA when compared to donors. The donor group had more lymphocytes with activation parameters CD25+, CD69+ and low level of proliferation marker Ki-67 than patients. In contrast to healthy, the RA patients demonstrated a significantly increased expression of Ki 67 in T lymphocytes when co-culturing CFSE- and CFSE+ cells. An increased number of living cells in apoptotic cultures of patients with RA relative to healthy people, in absence of significant differences in the parameters of apoptosis and activation markers in dynamics, as well as pattern of changes in the Ki-67+ cell contents suggested a contribution of the non-autonomous effects of apoptosis to cellular homeostasis in RA patients

Studies of effector molecules exerting autonomous and nonautonomous influence of T lymphocyte apoptosis under the conditions of in vitro “cell neighborhood” in healthy people and patients with rheumatoid arthritis

Cellular homeostasis in the body is known to be maintained by the processes of cell proliferation and death, whereas apoptosis is the most frequent and physiological, “silent” mechanism of cell elimination. It has been currently shown that the process of apoptosis traditionally considered an autonomous event, has a pronounced non-autonomous effect on migration, proliferation, and death of the neighboring cells. This work was based on the data on impaired programmed death of mononuclear cells from the patients with rheumatoid arthritis (RA) leading to the evolving autoimmune inflammation. The aim of this study was to evaluate effector molecules exerting autonomous and non-autonomous influence of T cell apoptosis under the conditions of “cell neighborhood” in cell cultures of healthy people and RA patients. The studies were performed with blood samples of RA patients and healthy women of comparable age. These experiments were performed in order to assess the levels of main molecules mediating the in vitro receptor and mitochondrial apoptosis of T lymphocytes. In previous studies, using the original “cell neighborhood” model, no differences were found in parameters of early and late activation apoptosis between the groups of donors and RA patients. At the same time, 1-week incubation in apoptotic cultures of the patients was followed by significantly increased number of viable cells carrying the proliferation marker Ki-67. Different results of in vitro apoptosis induction in cultures under similar conditions of “cell neighborhood” in healthy people and patients with RA have revealed the importance of main effector molecules of apoptosis in the studied groups. In this study, we have revealed low potential of the receptor pathway for apoptosis activation in healthy people, due to suppression of TNFα production during cell incubation under the conditions of “cell neighborhood”, and in RA patients due to initially low TNFα in supernatants which did not change over time and in various incubation variants, along with low content of initiating caspase 8 in both groups. Significant suppression of effector molecules of mitochondrial pathway of apoptosis activation, i.e., Bcl-2 anti-apoptotic factor and p53 transcription factor was detected in cultures of apoptotic cells, as well as mixtures of proliferating and apoptotic cells under the conditions of “cell neighborhood” in RA patients. The amounts of these molecules did not change in healthy persons. At the same time, no differences in these molecules were found between individual variants of cell cultures from the patients with RA and healthy people. The both studied groups were characterized by a significant activation of IL-4 and IL-6 production, i.e., the cytokines with autonomous and non-autonomous protective and reparative properties, Hence, one may conclude that high levels of these cytokines had different effects in cell cultures under the conditions of “cell neighborhood”. Incubation of cells from healthy people under suboptimal conditions was associated with maintaining the balance of proliferation and apoptosis, whereas, in cell cultures of RA patients, this balance caused activation of proliferation processes, being accompanied by an increase in the number of living cells in apoptotic cultures

Hidden metabolic disorders in high-class athletes

Objective: to reveal the frequency of deviations occurrence in individual biochemical indicators, which can be markers of hidden metabolicconditioned deviations in the health of athletes.Materials and methods. Members of sports teams of Russia at the age of 16 to 38 years were examined. The total number of examined athletes was 5245: 3167 were male athletes and 2078 were female athletes. We studied 25 indicators of the biochemical composition of blood, showing latent metabolic disorders and the activity of its regulators, negative shifts in the functional state of individual physiological systems of the body and possible damage to tissues of individual organs.Results. Reference ranges and their centile gradations were calculated on the basis of a large array of data for 25 biochemical parameters. The use of centile gradations in assessing the values of blood biochemical parameters, recorded during the current monitoring in athletes, makes it possible to establish the vector of their changes and timely make changes in the volume and orientation of training loads, as well as to reasonably develop individualized programs for the athlete’s metabolic support. The use of the centile approach and the formation on its basis of gradation scales for each of the studied blood biochemical parameters also made it possible to establish the percentage of persons with significant deviations in certain biochemical parameters among the studied sample of athletes, admitted to the training process within the framework of in-depth medical examinations (DMO).Conclusion: such deviations from the norm may indicate hidden metabolic disorders that occur against the background of professional sports loads, and in the absence of timely compensation, they can lead to a breakdown in adaptation and the development of various metabolic-related pathologie

Blowup dynamics of coherently driven polariton condensates : experiment

The work was supported by the Russian Science Foundation (Grant No. 14-12-01372).We report an experimental verification of the recent prediction that sharp transitions between steady states in multistable cavity-polariton systems are mediated by intermode parametric scattering that triggers the accumulation of energy and, hence, lowers the threshold at the cost of extending the transition latency period [S. S. Gavrilov, Phys. Rev. B 90, 205303 (2014)]. The time-resolved measurements are performed using a high-Q GaAs microcavity pumped slightly above the lower polariton level at normal incidence.Publisher PDFPeer reviewe

Photorefractive polymer composites for the IR region based on carbon nanotubes

The photorefractive properties of polymer composites based on aromatic polyimide and single-wall carbon nanotubes are studied using radiation at a wavelength of 1064 nm. It is found that the nanotubes possess photoelectric sensitivity in this spectral region and that the kinetic photorefractive characteristics of the polymer composites are entirely determined by the photogeneration and charge transport characteristics of the layers. The two-beam gain coefficient of the signal beam measured for a composite consisting of aromatic polyimide and 0.25 wt % of single-wall carbon nanotubes in a constant electric field E 0 = 79 V/μm is equal to 84 cm -1 and exceeds the optical absorption coefficient by 59 cm -1 . The refractive index modulation is equal to Δn = 0.004 at E 0 = 54 V/μm. \ua9 2005 Pleiades Publishing, Inc