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Zhizhenkov V.V.,RAS Ioffe Physical - Technical Institute | Grebennikov S.F.,Saint Petersburg University for Technology and Design | Busygin K.N.,Saint Petersburg University for Technology and Design | Kvachadze N.G.,RAS Ioffe Physical - Technical Institute | And 2 more authors.
Polymer Science - Series A | Year: 2017

It is shown that the sorption method makes it possible to quantitatively estimate the presence of ordered structures in the supramolecular structure of partially crystalline and liquid-crystalline paraamide polymers. Using 1H NMR spectroscopy and the sorption method, the growth of liquid-crystalline type structures during spinning and thermal treatment of the poly(paraamide) fiber is analyzed. A comparison of the 1H NMR spectra of the as-spun and heat-treated fibers at low temperatures (110–210 K) in a rigid lattice reveals that “loose” disordered microregions occur in the fiber before thermal treatment. Thermal treatment results in the “healing” of structural defects and leads to the appearance of liquid-crystalline-type structures owing to the large-scale quasi-segmental motion at a high temperature. © 2017, Pleiades Publishing, Ltd.


Smotrina T.V.,Volga State University of Technology | Grebennikov S.F.,Saint Petersburg University for Technology and Design | Busygin K.N.,Saint Petersburg University for Technology and Design | Smotrin V.A.,Kazan State Technological University | And 2 more authors.
Polymer Science - Series A | Year: 2017

It is shown that the sorption of water vapor in the amorphous regions of a liquid-crystalline polymer is accompanied by its swelling and the swelling pressure is responsible for the first stage of destruction of the most defective regions in the mesomorphous phase. The long-term swelling of the polymer in water leads to partial destruction of liquid-crystalline structures. The mechanism of water sorption and the dynamics of macromolecules in the liquid-crystalline paraamide polymers are studied by the method of proton magnetic resonance. © 2017, Pleiades Publishing, Ltd.


Zaitsev A.N.,Natural History Museum in London | Williams C.T.,Natural History Museum in London | Britvin S.N.,Saint Petersburg State University | Kuznetsova I.V.,Saint Petersburg University for Technology and Design | And 3 more authors.
Mineralogical Magazine | Year: 2010

Kerimasite, ideally Ca3Zr2(Fe3+ 2Si)O12, is a new calcium zirconium silicate-ferrite member of the garnet group from the extinct nephelinitic volcano Kerimasi and surrounding explosion craters in northern Tanzania. The mineral occurs as subhedral crystals up to 100 μm in size in calcite carbonatites, and as euhedral to subhedral crystals up to 180 μm in size in carbonatite eluvium. Kerimasite is light to dark-brown in colour and transparent with a vitreous lustre. No cleavage or parting was observed and the mineral is brittle. The calculated density is 4.105(1) g/cm3. The micro-indentation, VHN 25, ranges from 1168 to 1288 kg/mm2. Kerimasite is isotropic with n = 1.945(5). The average chemical formula of the mineral derived from electron microprobe analyses (sample K 94-25) and calculated for O = 12 and all Fe as Fe2O3 is (Ca3.00Mn 0.01Ce0.01Nd0.01)Σ3.03(Zr 1.72Nb0.14Ti0.08Mg0.02Y 0.02)Σ1.98(Fe3+ 1.23Si 0.86Al0.82Ti0.09)Σ3.00O 12. The largest Fe content determined in kerimasite is 21.6 wt.% Fe2O3 and this value corresponds to 1.66 a.p.f.u. in the tetrahedral site. Kerimasite is cubic, space group Ia3d with a = 12.549(1) Å , V = 1976.2(4) Å 3 and Z = 8. The five strongest powder-diffraction lines [d in Å , (I/Io), hkl] are: 4.441 (49) (220), 3.140 (91) (400), 2.808 (70) (420), 2.564 (93) (422) and 1.677 (100) (642). Single-crystal structure refinement revealed the typical structure of the garnet-group minerals. The name is given after the locality, Kerimasi volcano, Tanzania. © 2010 Mineralogical Society.


Vakulenko S.,Saint Petersburg National Research University of Information Technologies | Morozov I.,Saint Petersburg University for Technology and Design | Radulescu O.,Montpellier University
Nonlinearity | Year: 2016

We consider continuous time Hopfield-like recurrent networks as dynamical models for gene regulation and neural networks. We are interested in networks that contain n high-degree nodes preferably connected to a large number of N s weakly connected satellites, a property that we call n/N s-centrality. If the hub dynamics is slow, we obtain that the large time network dynamics is completely defined by the hub dynamics. Moreover, such networks are maximally flexible and switchable, in the sense that they can switch from a globally attractive rest state to any structurally stable dynamics when the response time of a special controller hub is changed. In particular, we show that a decrease of the controller hub response time can lead to a sharp variation in the network attractor structure: we can obtain a set of new local attractors, whose number can increase exponentially with N, the total number of nodes of the nework. These new attractors can be periodic or even chaotic. We provide an algorithm, which allows us to design networks with the desired switching properties, or to learn them from time series, by adjusting the interactions between hubs and satellites. Such switchable networks could be used as models for context dependent adaptation in functional genetics or as models for cognitive functions in neuroscience. © 2016 IOP Publishing Ltd & London Mathematical Society.


Andreeva O.A.,RAS Institute of Macromolecular Compounds | Burkova L.A.,Saint Petersburg University for Technology and Design
Physics of the Solid State | Year: 2011

The mechanisms of chemical dedoping of conductive polypyrrole with the initial conductivity values differing by an order of magnitude have been studied using EPR spectroscopy. An analysis of the temperature dependences of the electrical resistance of the initial highly conductive samples and dedoped samples has revealed a transition from three-dimensional conduction in the initial samples to one-dimensional conduction in the dedoped samples. This transition is caused by the transformation of transverse bipolarons into longitudinal bipolarons and ipolarons. It has been established that transverse and longitudinal quasiparticles are stabilized by counterions involving iron ions in different spin states: the spin of iron in the counterion of a transverse bipolaron is 2 and iron is inactive in the EPR spectrum, whereas in the counterion of longitudinal quasiparticles, the spin of iron is 5/2 and iron becomes paramagnetic. © 2011 Pleiades Publishing, Ltd.


Ivanov K.,Almaty University of Power Engineering and Telecommunications | Dinassylov A.,Almaty University of Power Engineering and Telecommunications | Yaroslavceva E.,Saint Petersburg University for Technology and Design
Mechanisms and Machine Science | Year: 2015

Gear adaptive variator is the toothed transmission with the variable transfer ratio which is adapting to the variable loading. Unsuccessful attempts of creation of a gear variator were undertaken repeatedly. The main problem is— maintenance of constant engagement of cogwheels of a variator. The decision of this problem can be based on use of a kinematic chain with two degrees of freedom. Earlier it was proved that this kinematic chain with closed contour possesses the effect of force adaptation. The gear variator can be performed in the form of the closed differential mechanism. The external variable technological loading changes the transfer ratio itself without any control system. The gear variator opens essentially new concept of creation of adaptive engineering for machines with variable technological resistance (for example, adaptive gearbox of car). The theory of a gear variator is based on discovery «Effect of force adaptation in mechanics » which is published in leading editions of world press. In the paper the bases of the theory of a gear adaptive variator are presented. © Springer International Publishing Switzerland 2015.


Andreeva O.A.,Russian Academy of Sciences | Burkova L.A.,Saint Petersburg University for Technology and Design | Podeshvo I.V.,Russian Academy of Sciences
Russian Journal of Physical Chemistry B | Year: 2015

Four aromatic amino acids (p-aminobenzoic, 4,6-diaminoisophthalic, o-aminobenzoic, and methylene-bis-anthranilic) were studied by FTIR spectroscopy. The first two molecules were found to exist in the solid phase exclusively in neutral form and the latter two in coexisting neutral and ionic forms. The shift of the tautomeric equilibrium from neutral molecule to zwitterion is determined by the character of substitution, molecular conformation, and the possibility of noncovalent bonds formed between the functional groups. The separation of charges becomes possible only if the conformers of the molecule include a structure with an OH….N intramolecular hydrogen bond. The proton is completely transferred from the acid group to the amino group when the strong intermolecular hydrogen bonds can stabilize the formed zwitterion. Otherwise, uncharged complexes with different degrees of proton transfer to the amino group are formed. © 2015, Pleiades Publishing, Ltd.


Vakulenko S.,Saint Petersburg University for Technology and Design | Radulescu O.,Montpellier University
Fundamenta Informaticae | Year: 2012

We investigate the possibility of programming arbitrarily complex space-time patterns, and transitions between such patterns, by gene networks. We consider networks with two types of nodes. The u-nodes, called centers, are hyperconnected and interact one to another via u-nodes, called satellites. This centralized architecture realizes a bow-tie scheme and possesses interesting properties. Namely, this organization creates feedback loops that are capable to generate any prescribed patterning dynamics, chaotic or periodic, or stabilize a number of prescribed equilibrium states. We show that activation or silencing of a node can sharply switch the network dynamics, even if the activated or silenced node is weakly connected. Centralized networks can keep their flexibility, and still be protected against environmental noises. Finding an optimized network that is both robust and flexible is a computationally hard problem in general, but it becomes feasible when the number of satellites is large. In theoretical biology, this class of models can be used to implement the Driesch-Wolpert program, allowing to go from morphogen gradients to multicellular organisms.


Perepelkin K.E.,Saint Petersburg University for Technology and Design
Fibre Chemistry | Year: 2010

The current types of ultrastrong and high-modulus fibres made from linear fibre-forming polymers - structure, principles of fabrication, properties, and basic areas of application - are examined. Most of the attention is focused on carbocyclic and heterocyclic para-aramid fibres, whose production capacities have reached 60,000 tons a year, the features of their structure and properties and areas of application. High-strength fibres made from other types of aromatic polymers (poly-p-phenylene benzobisoxazoles and thiazoles, polyarylates, polyvinyl alcohol, ultrahigh-molecular-weight polyethylene) are also briefly examined. © 2010 Springer Science+Business Media, Inc.


Shlyahtenko P.G.,Saint Petersburg University for Technology and Design | Suharev P.A.,Saint Petersburg University for Technology and Design
Izvestiya Vysshikh Uchebnykh Zavedenii, Seriya Teknologiya Tekstil'noi Promyshlennosti | Year: 2013

The paper presents a non-automatic method of control of textile fiber twist direction and values of its geometrical parameters (fiber diameter and twist amount) on the basis of the two-dimensional Fourier analysis of digital micro-images of its surface. Different ways of lighting while receiving digital images have been studied. Experiments, carried out with model samples of metal fibers twisted from metal wires of the same diameter, have confirmed the efficiency of the offered method.

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