Undulation instabilities in the meniscus of smectic membranes

Using optical microscopy, phase shifting interferometry and atomic force microscopy, we demonstrate the existence of undulated structures in the meniscus of ferroelectric smectic-C* films. The meniscus is characterized by a periodic undulation of the smectic-air interface, which manifests itself in a striped pattern. The instability disappears in the untilted smectic-A phase. The modulation amplitude and wavelength both depend on meniscus thickness. We study the temperature evolution of the structure and propose a simple model that accounts for the observed undulations.Comment: Submitted to PR

Transcriptional adaptation of Mycobacterium tuberculosis within macrophages: Insights into the phagosomal environment

Little is known about the biochemical environment in phagosomes harboring an infectious agent. To assess the state of this organelle we captured the transcriptional responses of Mycobacterium tuberculosis (MTB) in macrophages from wild-type and nitric oxide (NO) synthase 2–deficient mice before and after immunologic activation. The intraphagosomal transcriptome was compared with the transcriptome of MTB in standard broth culture and during growth in diverse conditions designed to simulate features of the phagosomal environment. Genes expressed differentially as a consequence of intraphagosomal residence included an interferon � – and NO-induced response that intensifies an iron-scavenging program, converts the microbe from aerobic to anaerobic respiration, and induces a dormancy regulon. Induction of genes involved in the activation and �-oxidation of fatty acids indicated that fatty acids furnish carbon and energy. Induction of �E-dependent, sodium dodecyl sulfate–regulated genes and genes involved in mycolic acid modification pointed to damage and repair of the cell envelope. Sentinel genes within the intraphagosomal transcriptome were induced similarly by MTB in the lungs of mice. The microbial transcriptome thus served as a bioprobe of the MTB phagosomal environment

Informative modeling of subjective reality for intellectual anthropomorphic robots

This research is aimed at solving the problem of safeguarding robot operation by modeling the subjective reality of an intellectual anthropomorphic robot. Analysis has been carried out on trends in designing advanced robot control systems and methods of improving the safety of robot usage. The following conclusions are drawn: the risk of causing damage to human life, health or property increases when people interact with robots; it is necessary to combine neural network control systems with expert control systems in order to enhance the intellect of a robot and raise the level of trust held by humans towards robots; developing norms and regulations, designing collaborative robots, drawing visualization diagrams for safety zones cannot really provide the depth of robot socialization sufficient for the human society; an informative model of the subjective reality could be integrated into an intellectual anthropomorphic robot to provide a safer 'human-robot' interaction. Such an approach should result in achieving the greatest trust of humans and their safety due to anthropomorphic conversion of both the external design of a robot and its internal control structure. By its nature, the research is interdisciplinary - it is run in the fields of artificial intelligence and philosophy of subjective reality. © Published under licence by IOP Publishing Ltd

Structures and orientational transitions in thin films of tilted hexatic smectics

We present detailed systematic studies of structural transformations in thin liquid crystal films with the smectic-C to hexatic phase transition. For the first time all possible structures reported in the literature are observed for one material (5 O.6) at the variation of temperature and thickness. In unusual modulated structures the equilibrium period of stripes is twice with respect to the domain size. We interpret these patterns in the frame work of phenomenological Landau type theory, as equilibrium phenomena produced by a natural geometric frustration in a system having spontaneous splay distortion.Comment: 7 pages, 6 figure

Effective index of refraction, optical rotation, and circular dichroism in isotropic chiral liquid crystals

This paper concerns optical properties of the isotropic phase above the isotropic-cholesteric transition and of the blue phase BP III. We introduce an effective index, which describes spatial dispersion effects such as optical rotation, circular dichroism, and the modification of the average index due to the fluctuations. We derive the wavelength dependance of these spatial dispersion effects quite generally without relying on an expansion in powers of the chirality and without assuming that the pitch of the cholesteric $P$ is much shorter than the wavelength of the light $\lambda$, an approximation which has been made in previous studies of this problem. The theoretical predictions are supported by comparing them with experimental spectra of the optical activity in the BP III phase.Comment: 15 pages and 7 figures. Submitted to PR

Effect of Dipolar Interaction in Molecular Crystals

We investigate in this paper the ground state and the nature of the transition from an orientational ordered phase at low temperature to the disordered state at high temperature in a molecular crystal. Our model is a Potts model which takes into account the exchange interaction $J$ between nearest-neighbor molecules and a dipolar interaction between molecular axes in three dimensions. The dipolar interaction is characterized by two parameters: its amplitude $D$ and the cutoff distance $r_c$. If the molecular axis at a lattice site has three orientations, say the $x$, $y$ or $z$ axes, then when D=0, the system is equivalent to the 3-state Potts model: the transition to the disordered phase is known to be of first order. When $D\neq 0$, the ground-state configuration is shown to be composed of two independent interpenetrating layered subsystems which form a sandwich whose periodicity depends on $D$ and $r_c$. We show by extensive Monte Carlo simulation with a histogram method that the phase transition remains of first order at relatively large values of $r_c$.Comment: 6 pages, 7 figure

Analysis of kinematic and kinetic parameters of pace in cerebral palsy patients with internal torsion hip deformity

Literature data on the correlation between femoral torsion during clinical examination and during walking are different. Aim of the study was to compare kinetics and kinematics in cerebral palsy patients with iatrogenic crouch gait pattern with and without clinically diagnosed internal femoral torsion. Material and methods. Comparative analysis of clinical examination and three-dimensional gait analysis (3DGA) was performed in 61 subjects (122 limbs), GMFCS II with iatrogenic crouch gait pattern. The average age was 14.5 ± 2.5 years. This sample was formed in 2018–2021. Kinetic and kinematic data were recorded by Qualisys 7+ optical cameras (8 cameras) with passive marker video capture technology, synchronized with six KISTLER dyno platforms (Switzerland). The analysis was performed in the QTM (Qualisys) and Visual3D (C-Motion) programs with automated calculation of values. Based on the clinical data, all the patients were divided as follows: I – no clinically detected internal femoral torsion – 50 limbs, II – clinically detected internal femoral torsion – 68 limbs. Results. Comparison of the values of kinematics and kinetics in groups of patients according to the criterion of clinically detected/not detected had statistically significant differences in kinematics – the maximum and minimum values of femur and tibia torsion relative to the norm. Differential diagnosis of compensated/decompensated internal femoral torsion was represented by multidirectional values of the angle of foot positioning relative to the motion vector. The kinetic parameters in the groups were statistically doubtful, because they depended on the walking speed of patients, their ability to move. Conclusions. The values of maximum femoral torsion angle up to 22° were not clinically interpreted as internal femoral torsion, those from 22° to 28° can be interpreted both with clinically revealed femoral torsion (68 %) and with the absence of femoral torsion (22 %), which corresponds to the risk group, those more than 28° fell into the group of clinically diagnosed internal femoral torsion