Missense Mutations Modify the Conformational Ensemble of the α-Synuclein Monomer Which Exhibits a Two-Phase Characteristic

α-Synuclein is an intrinsically disordered protein occurring in different conformations and prone to aggregate in β-sheet structures, which are the hallmark of the Parkinson disease. Missense mutations are associated with familial forms of this neuropathy. How these single amino-acid substitutions modify the conformations of wild-type α-synuclein is unclear. Here, using coarse-grained molecular dynamics simulations, we sampled the conformational space of the wild type and mutants (A30P, A53P, and E46K) of α-synuclein monomers for an effective time scale of 29.7 ms. To characterize the structures, we developed an algorithm, CUTABI (CUrvature and Torsion based of Alpha-helix and Beta-sheet Identification), to identify residues in the α-helix and β-sheet from Cα-coordinates. CUTABI was built from the results of the analysis of 14,652 selected protein structures using the Dictionary of Secondary Structure of Proteins (DSSP) algorithm. DSSP results are reproduced with 93% of success for 10 times lower computational cost. A two-dimensional probability density map of α-synuclein as a function of the number of residues in the α-helix and β-sheet is computed for wild-type and mutated proteins from molecular dynamics trajectories. The density of conformational states reveals a two-phase characteristic with a homogeneous phase (state B, β-sheets) and a heterogeneous phase (state HB, mixture of α-helices and β-sheets). The B state represents 40% of the conformations for the wild-type, A30P, and E46K and only 25% for A53T. The density of conformational states of the B state for A53T and A30P mutants differs from the wild-type one. In addition, the mutant A53T has a larger propensity to form helices than the others. These findings indicate that the equilibrium between the different conformations of the α-synuclein monomer is modified by the missense mutations in a subtle way. The α-helix and β-sheet contents are promising order parameters for intrinsically disordered proteins, whereas other structural properties such as average gyration radius, Rg, or probability distribution of Rg cannot discriminate significantly the conformational ensembles of the wild type and mutants. When separated in states B and HB, the distributions of Rg are more significantly different, indicating that global structural parameters alone are insufficient to characterize the conformational ensembles of the α-synuclein monomer.

Диагностика вибрационного состояния роторов двухконтурного турбореактивного двигателя с применением фазочастотной характеристики, полученной без использования датчика положения вала

This paper considers theoretical and practical approaches to the construction of amplitude-frequency phase characteristics of turbofan engines and presents the results of the experiments. The novelty lies in excluding usage of information from the sensor of its initial position for the construction of the rotor phase characteristic. To determine the instantaneous value of the phase angle of the rotor oscillations, the method of orbital vibration analysis is used. Using the analysis of phase change of rotor fluctuation allows to define availability of resonance as well as defects and malfunctions that cause induce stiffness and damping of the rotor. Examples of turbofan engines diagnostics by means of the analysis of amplitude-frequency phase characteristics are given.

Detection of Constellation-Modulated Wireless Covert Channel Based on Adjusted CNN Model

With the development of wireless communication technology, more and more information leakage is realized through a wireless covert channel, which brings great challenges to the security of wireless communication. Compared with the wireless covert channel on the upper layer, the wireless covert channel based on the physical layer (WCC-P) has better concealment and greater capacity. As the most widely used scheme of WCC-P, the wireless covert channel with the modulation of the constellation point (WCC-MC) has attracted more and more attention. In this paper, a deep learning scheme based on amplitude-phase characteristics is proposed to detect and classify the WCC-MC scheme. We first extract the amplitude and phase characteristic of error vector magnitude (EVM) and constellation points and then map the amplitude and phase characteristic to the grayscale image, respectively. Finally, the generated feature images are trained, detected, and classified with the adjusted convolution neural network. The experimental results show that the detection accuracy of our proposed scheme can reach 98.5%, and the classification accuracy can reach 81.7%.

THE CHOICE OF SIGNALS FOR HYDROACOUSTIC NAVIGATION SYSTEM OF TRANSFORMATION UNDERWATER APPARATUS TO DOCKING MODULE

The proposed work is the first part of the overall work on the development of the structure of the hydroacoustic navigation system (HNST) for bringing the autonomous underwater vehicle (AUV) to the docking module (DM). The second (final) part will be published in the next issue of the journal. The purpose of this work is to select signals for building HNST providing reduction in a near zone at the distances not exceeding 300 m, an AUV and its docking with the carrier is considered. Mutual definition of a distance and angular position DM of the carrier and AUV relative to each other is carried out for this purpose. Determination of mutual angular coordinates can be carried out with use of HNST with short and ultra-short base. HNST with short base is preferable for realization from the point of view of simplicity. However, its installation on the AUV can be impossible because of rather small sizes of the device, and on AUV should be installed HNST with ultra-short base. HNST with short base can be established on the docking module. Since there are no reasons to assume the high speed of change of the phase characteristic of the developed high-frequency channel of transformation therefore the interval of stationarity of the phase characteristic should be significantly more than duration of a symbol at a speed of transfer of 4 kBit/s. Therefore, it is advisable to exchange measurement data between AUV and DM in the composition of HNST by relative phase modulation (DPSM). Reception of signals is performed by a suboptimal incoherent receiver on which entrance deep restriction of an entrance signal is carried out. The use of deep signal limitation at the receiver input allows to exclude operation of automatic control of strengthening at a stage of entry into communication, as a result, it is possible to reduce the duration of communication sessions. In the combined information navigation system, it is expedient: to apply as navigation signals of data exchanged between AUV and DM based on the results of mutual measurement of navigation parameters; to carry out data exchange between AUV and DM by method DPSM with a speed V = 4 kBit/s; to carry out transfer of the block of data with application of the correcting block cyclic code ; to apply to reception of a block of data diversity reception in combination with majority decoding characters, and then correct errors in the data block with the help of code, and to accompany the issuance of data to the user sign detection code errors in the block.

Using Hilbert Transform in Diagnostic of Composite Materials by Impedance Method

The article is devoted to the problem of the increasing of information quality for the impedance method of nondestructive testing. The purpose of this article is to get for the pulsed impedance method of nondestructive testing the additional informative parameters. Instantaneous values of the information signal's amplitude is a sensitive parameter to the effects of interference, in particular friction, which necessitates the use of additional informative features. It was experimentally measured signals from defective and defectless areas of the test pattern. Using of the Hilbert transform gave possibility to determine phase characteristics of these signals and realize demodulation to extract a low-frequency envelope for further analysis of its shape. It was received the informative features as a result of researches. Among them are instantaneous frequency of a signal, the integral of a phase characteristic on the selected interval and the integral of a difference signal phase characteristics. In order to compare quality of the defect detection using selected parameters it was carried out evaluation of the testing result reliability for a product fragment made of a composite material. Considering the influence of the change in the mechanical impedance of the researched area on the phase-frequency characteristics of the output signal of the converter, it is proposed to use as the diagnostic signs: the instantaneous frequency and the value of the phase characteristic of the current signal for certain points in time. The proposed informative features enable to increase general reliability of composite materials testing by the pulsed impedance method.

Designing a Low Frequency Delay Line

Expressions were obtained for the phase characteristic of the delay line with active losses. Linearity of the phase characteristic is estimated. The experimental results are presented.