bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Gamma and Electron Radiation on the Strength Characteristics of Nonwoven SMS Materials Based on Polypropylene
Authors: Galimzyanova Rezeda Yu. , Lisanevich Maria S. , Khakimullin Yuri N.
Published: September 2021

Radiation sterilization is widely used to sterilize nonwoven SMS medical products. SMS materials have improved filtering and barrier properties, low bacteriopermeability and, due to these properties, are indispensable for medicine. They are used to make such important health care products as disposable surgical clothing and underwear. As a result of the research carried out, the effect of gamma and electron radiation, in the range of absorbed doses from 15 to 25 kGy, on the strength characteristics of nonwoven SMS materials based on polypropylene with a surface density of 35, 40, 50 g/cm2 was studied. It has been established that the strength characteristics (tensile strength, tensile strength, and tear strength) of nonwoven materials decrease after exposure to ionizing radiation. The higher the density of the material, the more its characteristics decrease after radiation sterilization. It was also found that gamma radiation, due to its nature, has a stronger effect on nonwoven materials based on polypropylene, and leads to a stronger decrease in strength characteristics. In general, for products sterilized by ionizing radiation and made from SMS materials, it is important to control the strength characteristics, primarily, the tensile strength in the transverse direction of the web stuff.
Influence of Injection Rate on Mechanical Properties of the Molding Composition Based on Polyamide 6 and Carbon Nanotubes
Authors: Kuzmin Anton M. , Vodyakov Vladimir N. , Radaykina Elena A. , Kuznetsov Vyacheslav V. , Murneva Mariya I.
Published: September 2021

This paper is devoted to obtaining and investigating polymer composites based on polyamide-6 and carbon nanotubes. Polyamide 6, type 210/310, was used as a polymer matrix, and carbon nanotubes manufactured by OcSiAl were used as a modifier. The components were compounded in a co-rotating twin-screw extruder HAAKE Rheomex OS PTW 16 to obtain granulate. The granulate was processed by injection molding on a Babyplast 6/10V machine to obtain test samples as double-sided blades (ISO-527-2, type 5A). Elastic strength tests were carried out on a Gotech UAI-7000M universal tensile-testing machine. It has been shown that introduction of 0.15% CNT promotes an increase in the yield point and the initial modulus of elasticity with a significant decrease in the ultimate strength. The maximum value of the tensile strength (161 MPa) has been obtained for the specified composition at an injection rate of 12.9 ml/s.
Research of Vegetable Silicon Dioxide as a Filler for Polymer Composite Material
Authors: Fazylova Dina I. , Zenitova Lyubov A.
Published: September 2021

Polymer composite materials based on low molecular weight silicone rubber SKTN-D have been developed, which are supposed to be used as impression materials in dentistry. Vegetable silicon dioxide obtained from rice husk waste was studied as a filler.
Mesogenic Properties of Aromatic Oligoesters Derived from Kink-Structured Monomers
Authors: Deberdeev T.R. , Akhmetshina Alsu I. , Karimova Liana K.
Published: September 2021

Novel liquid crystalline oligomers were prepared using different compositions of kink-structured aromatic dicarboxylic acids, aromatic diols, and 4-hydroxybenzoic acid via high-temperature polycondensation. The reaction products were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and polarized optical microscopy. As a result, the samples containing kinked units with phenyl or naphthalene moiety had a broad processing window limited by the melting process and the isotropization, whereas one based on diphenic acid was almost entirely in an amorphous state. The surface properties of the oligomers were evaluated by wetting measurements using a static contact angle analysis.
Activity of Manganese Carboxylates in the Process of Liquid-Phase Oxidation of Ethylbenzene with Atmospheric Oxygen
Authors: Mukhamedzyanov Rinat , Muzipov Zufar , Pham The Son , Vasilyeva Elina , Akhmedyanova Raisa
Published: September 2021

The process of oxidation of hydrocarbon with oxygen proceeds with formation of the corresponding hydroperoxide as the primary product [1,2]. A catalyst is the most important factor that influences on the direction of flow of the oxidation reaction. Catalysts based on metals of variable valency, and their derivatives are the most active in reactions of oxidation of hydrocarbon [3].
Investigation of the Regularities of the Synthesis of Unsaturated Polyesters by the Method of Acceptor-Catalytic Polycondensation
Authors: Sultigova Zakhirat , Inarkieva Zareta , Bazheva Rima , Kharaev Arsen , Yalkhoroeva Madina
Published: September 2021

The regularities of acceptor-catalytic polycondensation in the synthesis of copolymers containing arylate, sulfone, and dichloroethylene groups in the main chain have been studied. The optimal conditions for their production have been found. Infrared spectroscopy, elemental analysis, turbidimetric titration and other methods confirmed the formation of copolymers of the proposed structure.
Study of the Influence of the Chemical Resistance of Polyphenylenesulphone from Radel on Mechanical Properties
Authors: Rzhevskaya Elena V. , Davydova Vladlena V. , Dolbin Igor V.
Published: September 2021

The paper presents the results of a study of the chemical resistance and mechanical properties of polyphenylene sulfone manufactured by Solvay, Radel brand, obtained by injection molding. Chemical resistance was investigated in short-term tests (24 hours duration), standard (7 days) and long-term (16 weeks). The mechanics of PPSU samples after exposure to chemical reagents is presented. It was revealed in what chemical environments and how much the mechanical properties of polyphenylene sulfone are preserved.
Modification of the Hygroscopic Properties of Textile Materials Containing Polyurethane Threads
Authors: Azanova Albina A. , Abutalipova Ludmila N. , Khisamiyeva Lyutziya G.
Published: September 2021

The article discusses the influence of the presence of polyurethane (elastomeric) threads in the composition of a textile material on the effect of plasma modification of hygroscopic properties. The objects of the study were textile (knitted) fabrics based on cotton fibers with the addition of Dorlastan threads. The samples were processed in the plasma of a high-frequency capacitive discharge at a reduced pressure, as the plasma-forming gas was used air. Experiments have shown that the water absorption of the samples after plasma treatment is increased by an average of 1.5 times. The presence of Dorlastan thread does not significantly affect the result of the plasma modification, since the samples are completely immersed in water and the elastomeric threads do not limit the water absorption of its cotton component. The degree of capillary rise, on the contrary, depends on the presence of polyurethane threads. In samples made of 100% cotton, the increase occurs up to 190-. According to these samples, polyurethane threads prevent the capillarity of water by about 4 times. Kinetic curves of water absorption are given. The results suggest that other processing treatments are required to render the polyurethane threads hydrophilicity by plasma treatment. This should be considered in the development of plasma methods for treating textile materials, including in terms of matrix for composite materials.
Investigation of the Deformation and Strength Properties of Elastomeric Compositions with Urea-Based Additives
Authors: Shishkina Nelly N. , Zakirova Larisa Yuryevna
Published: September 2021

The effect of blocked diisocyanates on the elastic-strength properties of elastomeric compositions based on SKI-3 isoprene rubber has been investigated. The synthesized additives are 2-isocyanato-4-phenylcarbamidotoluene (IPCT) and 2,4-diphenylcarbamidotoluene (DPCT). Tests were carried out to determine the physical and mechanical (conditional tensile strength, elongation at break, hardness) properties depending on the type and dosage of additives. It was found that samples with synthesized additives have strength and elongation at break higher than those of a sample without additives by 30 % and 200 %, respectively. There was also an increase in the tear resistance of all samples compared to the control (from 49.9 to 81.9 kN/m). An assumption is made about the formation of a network of physical connections, which provides an increase in these indicators. TMA analysis results showed a wider temperature range for reversible deformations (up to 180 °С).
Epoxy Sulfur Containing Olygomers for Fire-Resistant Compounds Based on 2,2di-(4-Oxyphenil)Sulfone
Authors: Balaeva S.M. , Beeva Dzhul’etta A. , Balaeva Zh.T. , Mirzoeva N.M. , Kyarov A.A.
Published: September 2021

The article presents information on the synthesis of epoxy oligomers based on 2,2-di-(4-hydroxyphenyl) sulfone (DODPS) and hexachloroethane (HCE). We showed the results of a study of the adhesive properties and fire resistance of epoxy polymers. The synthesized sulfur-containing epoxy oligomers have a reasonably low viscosity and high fire resistance. Casting compounds obtained on their basis have improved performance characteristics.
Investigation of the Wetting Process of Glass Fiber with Oligophenylene Sulfide Sulfone
Authors: Kurdanova Zhanna I. , Shakhmurzova Kamila T. , Guchinov V.A. , Kobyhno Ilya , Bezborodov Andrey
Published: September 2021

The wettability of reinforcing fillers such as glass and carbon fibers is a significant factor influencing the mechanical properties of the composite. This study focuses on the effect of finishing glass fiber surfaces with different concentrations of oligophenylene sulfide sulfone solution on fiber wettability, which is determined by contact angle and wetting time. The Adam-Schütte method was chosen as a method for determining the contact angle. According to the study results a 1.5% solution of oligophenylene sulfide sulfone in N, N'-dimethylacetamide gives a contact angle of 45°, forming over time a thin film on the fiber surface, which indicates a sufficiently high sizing ability.
Impact of Modification on the Energy Characteristics of Surfaces and Matrix Properties of the New Effective Polymer Vascular Implants
Authors: Bogdanova Yulia G. , Antonova L.V. , Silnikov V.N. , Khanova M.Yu. , Senokosova E.A. , Barbarash L.S.
Published: September 2021

New tissue-engineered vascular prostheses of small diameter (4mm) based on biodegradable polymer backbone – poly (ε-caprolactone) (PCL) and its composition with poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV/ PCL) were created. The full cycle of surface modification of the backbone with polyvinylpyrrolidone and drugs permitted to increase significantly the atrombogenic and antimicrobial properties of prostheses and provide its effective matrix properties. Both types of the developed constructs are suitable for testing in vivo. The energy characteristics of the prosthesis surfaces at the different interfaces were determined. It was established that the value of the energy of the "polymer, saturated with octane/water" interface can be used as a parameter for predicting cell adhesion and proliferation in the case when it is difficult to determine or to distinguish the energy characteristics of the surfaces of tissue-engineered materials at the interface with air.
Effect of Carbon Nanoparticles on Properties of Polyetherimide Fibers
Authors: Vaganov Gleb , Ivan’kova Elena , Yudin Vladimir , Vaganov Vyacheslav
Published: September 2021

In the present work, fibers based on heat-resistant amorphous polyimide brand Ultem-1000 were prepared by melt extrusion. Vapor-grown carbon nanofibers (VGCFs) and single-wall carbon nanotubes (SWCNTs) were used to increase the mechanical characteristics of the polymer fibers. The fibers were characterized by scanning electron microscopy (SEM), thermophysical and mechanical tensile analysis. SEM study revealed very good distribution of the carbon nanofillers throughout the polyimide fiber volume. The mechanical testing of the unoriented nanocomposite fibers showed that the introduction of VGCFs or SWCNTs led to an increase in tensile strength and modulus. High-temperature drawing allows obtaining polyimide nanocomposite fibers with significantly increased mechanical properties (»300 MPa for strength and »4.6 GPa for modulus).
The Development of Effective Multifunctional Inhibiting Additives for Polymeric Materials
Authors: Murzakanova Marina M. , Mamkhegov Rustam M. , Mikitaev Muslim A.
Published: September 2021

The synthesis of polyphenylene sulfide in the presence of catalytic systems based on various lithium salts has been studied, and conditions have been identified that accelerate the process and obtain a polymer with a given microstructure. The rheological, thermal, and physicomechanical properties of the obtained polymers were studied and the optimum temperature () and pressure (9-10 atm) were established upon the production of polyphenylene sulfide by high-temperature polycondensation of sodium sulfide and 1,4-dichlorobenzene in a solution of N-methylpyrrolidone, which increase the effectiveness of its synthesis.
Monthmorillonite as an Effective Catalyst of the Polyphenences of Polyphenylene Sulphide
Authors: Murzakanova Marina M. , Mamkhegov Rustam M. , Malamatov Akhmed Kh.
Published: September 2021

The synthesis of polyphenylene sulfide in the presence of catalytic systems based on montmorillonite and various lithium salts has been studied, and conditions have been identified that accelerate the process and obtain a polymer with a given microstructure. The rheological, thermal, and physicomechanical.
Research on the Possibility of Recycling Medical Masks and their Use as Polymer Additives
Authors: Musov Khasan V. , Tlupov Aslanbek F.
Published: September 2021

This article studies the recycling of medical masks by the extrusion method. The main mechanical and physicochemical properties of recycled medical masks have been researched. It was revealed that the processed medical masks contain high physical and mechanical properties. The article shows the introduction of recycled masks leading to an increase in the manufacturability of the homo-and a block copolymer of polypropylene. In the case of a block copolymer, an increase in elastic-strength properties is observed. The introduction of recycled masks does not significantly affect the thermophysical properties of the homo-and a block copolymer of polypropylene.
Influence of Spinneret Dimensional Parameters on Gas Separation Properties of Polysulfone Hollow Fiber Membranes
Authors: Matveev Dmitry N. , Vasilevsky Vladimir P.
Published: September 2021

The design and dimensional characteristics of the spinneret affect not only the geometry of the hollow fiber, but also the transport properties of the hollow fiber membranes. In the literature available today, there is a limited number of works in which the influence of the design and dimensional characteristics of the spinneret is studied. In this work, using the example of polysulfone hollow fiber membranes, it was shown that the use of a spinneret with smaller annular diameters leads to an increase in the gas permeability of the hollow fiber membrane with a decrease in the value of the ideal selectivity for the He/CO2 gas pair. It was found that using the spinneret with large annular diameters, the hollow fiber membrane is obtained with a smaller value of the average pore size of the flow, which is in agreement with the obtained data on gas permeability.
Electrophysical Parameters of Nanofilled Polymer Composites Based on Polyethylene
Authors: Dokshukina M.A. , Kunizhev B.I. , Gaitukieva Z.Kh.
Published: September 2021

The features of the dependence of the dielectric constant and the specific volume resistance of the composite "80 wt. % SKI-3 + 20 % wt. % LDPE" from the content of nanosized filler particles - aluminum and black carbon. The use of modern methods for studying macroscopic properties and electron microscopy made it possible to study the structure and morphology of the supramolecular formations of the composite. Models and possible physical mechanisms leading to extreme changes in εʹ and ρV at low concentrations of nanoparticles are presented.
Features of the Polymethyl Methacrylate Destruction Process by Various Types of Dynamic Loading
Authors: Kunizhev B.I. , Kugotova A.M. , Torshhoeva Z.S. , Shetov Ruslan A.
Published: September 2021

The paper presents a comparative analysis of the dynamic loading of a polymethyl methacrylate (PMMA) target by a polyethylene (PE) projectile exposed to laser radiation with similar initial energy characteristics of the projectile and the laser pulse. The similarities and differences in the mechanisms of the target's response and its destruction to high-speed mechanical and laser action are shown. A higher efficiency of laser irradiation in the destruction of PMMA was found, and the conditions for the transition of the fracture mechanism from brittle to elastic-plastic were shown.
Composite Cerium Oxide Nanoparticles - Containing Polysaccharide Hydrogel as Effective Agent for Burn Wound Healing
Authors: Popov Anton L. , Khohlov Nikolai V. , Popova Nelli R. , Andreeva Victoria V. , Kamenskikh Kristina A. , Ermakov Artem M. , Ivanov Vladimir K.
Published: September 2021

A high risk of complications in burn injuries is associated with the development of systemic inflammatory response syndrome. Thermal injury (burn) causes the release of cytokines and prostaglandia, resulting in increased interaction between leukocytes, platelets and endothelial cells. Activation of leukocytes leads to an increase in the formation of reactive oxygen species (ROS) and nitrogen, which is normally compensated by the activation of protective antioxidant enzymes. An imbalance between the activity of the radical-producing and antioxidant systems leads to an excess of free radicals and the development of oxidative stress. Oxidative stress limits the repair of damaged tissue and also leads to localized chronic inflammation. Thus, the removal of inflammation and a decrease in the ROS level, which exceeds the physiological level in the burn zone, seems to be expedient for accelerating the healing process of burn injuries of the skin. In this study, we used a polysaccharide hydrogel modified with cerium dioxide (CeO2) nanoparticles, which have unique anti-inflammatory and antioxidant properties, as an effective agent for the treatment of thermal burns. It has been shown that modification of the hydrogel with CeO2 nanoparticles provides accelerated healing of a model burn wound in rats. Already on the 5th day after the treatment of damage to the skin with the modified hydrogel, a decrease in the area of ​​the burn wound that is different from the control is observed. The use of a hydrogel accelerates the healing process of a burn wound on the 25th day by 25.42% (p <0.05) and ensures complete healing of burn wounds on average 5 days earlier in comparison with the control group with Levomekol ointment. Treatment of burn wounds using a hydrogel leads to the formation of a small post-burn scar. Thus, a polysaccharide hydrogel modified with CeO2 nanoparticles can be considered as an effective wound healing agent in the treatment of thermal burns and skin lesions of various etiologies.
Study of the Influence of SBS and APDDR on the Low-Temperature Properties of Road Bitumen
Authors: Gorbatova V.N. , Dudareva Tatiana V. , Krasotkina Irina A. , Nikol'skii Vadim G. , Naumova Yulia A. , Polonik V.D. , Egorov D.Yu.
Published: September 2021

A comparative assessment of the effect of two modifiers on the low-temperature properties of BND 90/130 bitumen was investigated using Asphalt Binder Cracking Device (ABCD test) and Dynamic Shear Rheometer (DSR 4-mm test). These modifiers are styrene-butadiene-styrene block copolymer (SBS) and active powder of discretely devulcanized rubber (APDDR) - powder elastomeric modifier obtained by high-temperature shear grinding of waste tire crumb rubber. ABCD results of RTFO-aged samples showed clear and gradual decrease of the ABCD cracking temperature (improvement) for all BC as the modifier concentration increases. It is noteworthy that the Bitumen Composites (modified bitumens) were cracking at higher strain and fracture stress values compared to neat bitumen. Results of DSR-4 mm test showed a decrease in the complex shear modulus (G*), storage modulus (G¢) and loss modulus (G²) BC compared to the neat bitumen. It is shown that bituminous composites have no maximum on the Cole-Cole diagram (dynamic vitrification) at T = -28°C which is observed in the neat bitumen.
Atomic Force Microscopy of the Local Electrical Properties of Bilayer Polyaniline-Polystyrene/P(VDF-TrFE) Composite
Authors: Budaev Artem V. , Melnikovich Ivanna N. , Melnichenko Vasily E. , Emelianov Nikita A.
Published: September 2021

Atomic force microscopy techniques (conductive-AFM, I-V spectroscopy and PFM) were used for characterisation of the local electrical properties of bilayer polyaniline-polystyrene/P(VDF-TrFE) polymer nanocomposite. Observed hysteresis of current-voltage characteristics confirms its memristive properties. It was caused by the influence of the ferroelectric polarization of P(VDF-TrFE) layer, the domain structure of which was visualised by piezoelectric force microscopy on the transport of charge carriers at the interface.
Strength Characteristics of 3D-Printed PETG-Based Products Optimization
Authors: Vlasov Valeriy V. , Trutnev Pavel A.
Published: September 2021

The paper considers the dependence of the strength properties of 3D-printed parts on FDM printing modes (temperature and speed), as well as the layer arrangement. PETG (polyethylene glycol terephthalate) based filament was chosen as the basis. A 3D printer was used to produce samples with strictly defined orientation of layers — longitudinal and transverse tensile force at different temperature and printing speed. The experiment has established the effect of these two factors on the tensile strength. The strength of the samples printed transversely was higher than the strength of samples printed longitudinally. This indicates a higher interlayer adhesion.
Polyetheretherketone Composites with Appreted Carbon Fibers
Authors: Beev Aues A. , Beeva Dzhul’etta A. , Shokumova M.U. , Tlenkopachev M.R. , Oshkhunov Muaed M.
Published: September 2021

The paper investigates the processes of carbon fiber surface treatment and their influence on the properties of polyetheretherketone composites. It has been shown that preliminary thermal activation of carbon fiber followed by treatment with a dressing agent - polyhydroxyether makes it possible to create polyetheretherketone composite carbon-filled materials with an increased level of physical and mechanical properties.
Microencapsulated Aromatic Polyetheretherketones and Copolyetheretherketones for 3D-Printing
Authors: Beev Aues A. , Khashirov Azamat A. , Beeva Dzhul’etta A. , Slonov Azamat L. , Shokumova M.U.
Published: September 2021

The presented work presents the results of the studies carried out to elucidate the possibility of obtaining by the microencapsulation method of powdered polyetheretherketones and spherical copolyetheretherketones recommended for use in 3D-printing. The influence of temperature-time and concentration parameters, the reaction medium on the size of microencapsulated particles of polyetheretherketones and copolyetheretherketones was determined. It was determined that the bulk density of microencapsulated particles of polyetheretherketone and copolyetheretherketones is 8-10 times higher than similar unencapsulated ones.
Some Properties of Polyconjugated Polymers Obtained by Oxidative Polymerization of Benzylidene-m-Phenylenediamines
Authors: Borukaev Timur A. , Salamov A.Kh. , Orlov Andrei V.
Published: September 2021

New polyconjugated polymers have been synthesized by oxidative polymerization of benzylidene-m-phenylenediamines. The morphology, particle size distribution, thermal and electrical properties of the obtained polybenzylidene-m-phenylenediamines have been investigated. The morphology of the particles of the obtained polymers was determined. It was shown that the synthesized polybenzylidene-m-phenylenediamines exhibit noticeable thermal stability and electrical conductivity. In this case, the thermal stability and the process of decomposition of polybenzylidene-m-phenylenediamines substantially depend on the chemical structure of the side fragments of macromolecules.
Synthesis of Complex Oligoesters Based on Adipic Acid, Ethanediol and Butanediol-1,4 with Specified Characteristics
Authors: Borukaev Timur A. , Archakova Raisa D. , Uzhakhova Leila Ya. , Mashukov N.I.
Published: September 2021

Aliphatic linear oligoesters with terminal hydroxyl groups and given molecular weight characteristics, hydroxyl and acid numbers were synthesized by esterification of adipic acid, ethylene glycol and butanediol-1,4. It was found that the main properties of complex oligoesters largely depend on the ratio of the starting reagents. The kinetic regularities of the process of esterification of adipic acid, ethylene glycol and butanediol-1,4 have been studied and determined. It was found that the duration of the vacuum stage of esterification in the presence of organomodified montmorillonite is noticeably shorter than when using a commercial catalyst.
Methodological Aspects of Evaluating the Particle Size Distribution of Powder Elastomeric Materials
Authors: Gordeeva I.V. , Dudareva Tatiana V. , Krasotkina I.A. , Nikol'skii Vadim G. , Naumova Yulia A. , Sinkevich M.Yu. , Lobachev V.A.
Published: September 2021

The properties of crumb rubber (CR) of unsorted end-of-life tires and of gas masks face part crushed at ambient temperature, as well as powder elastomeric materials (PEM) obtained by high-temperature shear grinding (HTSG) of CR and high-temperature shear co-grinding of CR with thermoplastic elastomer have been investigated. The methods of dry screening with vibrating sieve, wet laser diffraction, scanning electron microscopy, determination of the specific surface area by the BET method by sorption nitrogen and powder agglomeration were used. The effect of an anti-agglomerating additive on the results of determining the particle size distribution by the methods of dry vibrating sieving and wet laser diffraction has been investigated. Methodological recommendations for determining the particle size distribution of powder elastomeric materials (PEM) obtained by the HTSG have been developed.
Influence of the Degree of Hydration on the Relaxation Microheterogeneity of Segmental Mobility in PVA
Authors: Abaturova Nina A. , Lomovskaya Nadezhda Yu. , Shatokhina Svetlana A. , Lomovskoy Viktor A.
Published: September 2021

The study of local dissipative processes by the method of free-damped torsional oscillations excited in polyvinyl alcohol (PVA) showed the presence of three loss peaks in the internal friction spectrum in different temperature ranges of this spectrum [1].
New Chain Extenders for Self-Healing Polymers
Authors: Zakharova Daria V. , Lok’yaeva Zalina A. , Pavlov Alexander A. , Polezhaev Alexander V.
Published: September 2021

We present here a small series of compounds designed to modify the polymer chain of various polyurethanes in order to introduce a structural fragment with the ability of thermally-triggered reversible covalent interactions. Bismaleimides (2a-2e) were synthesized from commercially available aromatic and aliphatic symmetric diamines (1a-1e) and were further introduced into the Diels-Alder reaction with furfuryl alcohol as dienophiles. The Diels-Alder adducts (3a-3e) were obtained as a mixture of endo- and exo-isomer. The presence of symmetrical hydroxyl groups in the structure of the obtained compounds makes them suitable as chain extenders of low molecular weight diisocyanate prepolymers. The presence of a thermally reversible Diels-Alder reaction adduct in the structure of potential chain-extenders opens a possibility to create unique materials with self-healing properties. All compounds obtained were characterized by 1H, 13C NMR, ESI-HRMS, and IR spectroscopy. The thermochemical parameters of the reverse Diels-Alder reaction were established using DSC analysis.
Synthesis and Investigation of pH-Switchable RAFT Agent in Polymerization of Styrene
Authors: Vlasov Artem , Grigoreva Alexandra O. , Zaitsev Sergey D.
Published: September 2021

pH-switchable chain transfer agent 1-cyano-1-methylethyl (phenyl)(pyridin-4-yl)-carbamodithioate (CMPC) was synthesized and reversible addition-fragmentation chain-transfer (RAFT) polymerization of styrene in presence of CMPC was studied. It was shown that presence of CMPC affects molar mass distribution and kinetic features and realizes supposed mechanism of RAFT polymerization. Different effect of CMPC on polymerization of styrene in presence of protic acids was studied.
Setting Time of Powder Composites and the Effect of Chemical Reagents
Authors: Negmatov Soyibon S. , Munavvarkhanov Zokirkhon T. , Boydadaev Murotbek B. , Madraximov Alloberdi M.
Published: September 2021

Additives were selected and a method for modifying the structure of gypsum-containing materials for construction purposes and a method for their dispersion were developed. Based on the selected modifiers, effective compositions of composite gypsum-containing materials based on local and secondary raw materials were developed, and an increase in their strength and resistance to water was established.
Comparative Efficiency of Physical and Physicochemical Microencapsulation of some Medicinal Substances
Authors: Grekhnyova Elena V. , Kudryavtseva Tatyana N. , Efanov Sergey A. , Klimova Lyudmila G.
Published: September 2021

Microencapsulation of drugs is used for a long time to improve their properties. It was carried out a comparative assessment of the physical and physicochemical methods of microencapsulation on the example of some drugs. The spray drying method was selected from the physical methods. Physicochemical method based on simple coacervation was implemented by changing the solvent. A study and comparison of the properties of the products were obtained by UV and IR spectroscopy, liquid chromatography, electron microscopy. It was carried out a comparative assessment of the release profile of the active substance from microcapsules obtained by various methods. Using the example of furacilin microcapsules has been shown an increase in the biological activity of substances encapsulated in water-soluble polymers. The particle size distribution was determined by analyzing their trajectories. The main advantages and disadvantages of the two investigated encapsulation methods are outlined.
Use of Polyester-Etherketone and Composites Based on it in Medical Practice
Authors: Vindizheva Amina , Kharaeva Zaira , Khashirova Seda , Danilova-Volkovskaya Galina M.
Published: September 2021

The article presents a scientific review of the literature on the known methods of producing polyetheretherketane and composites based on it used in the medical manufacture practice of implants. The main substances used in the synthesis of PEEK, as well as modifiers included in the PEEK-based composite material, are generalized.
Polyvinyl Chloride Biodegradable Composite Materials, the Analysis of Biodegradability Research Methods
Authors: Vindizheva Amina , Khashirov Azamat A. , Sapaev Khuisein , Kalabin Alexandr , Mikitaev Muslim A. , Tsurova Ashat T.
Published: September 2021

This article presents a scientific review of the literature on biodegradable polymer composite materials based on polyvinyl chloride. We summarized data on the effect of modifiers of natural and synthetic origin on the biodegradability of polyvinyl chloride material. The main methods for studying the biodegradability of polymeric materials are considered.
Electrical Properties of Composites Based on Low-Pressure Polyethylene and Carbon-Containing Fillers
Authors: Mikitaev Muslim A. , Borisov V.A. , Musov Ismel V. , Slonov Azamat L. , Khakulova Diana M.
Published: September 2021

We have obtained polymer composites based on low-pressure polyethylene and carbon-containing fillers: carbon black, carbon nanotubes. The electrical properties of the obtained polymer composites have been investigated. Obtained polymer composites have electrically conductive properties. This article shows that the electrical properties significantly depend on the concentration, type of carbon-containing filler, as well as on temperature and voltage. It was found that containment of a certain amount of carbon-containing fillers leads to a formation of conductive paths composites, leading to the manifestation of a positive temperature coefficient in electrical resistance by the material.
Crosslinked Sodium Alginate as a Material for Nanolfiltration Protonic and Aprotonic Solvents
Authors: Dmitrieva E.S. , Pankratova E.E. , Anokhina Tatyana S. , Vinokurov V.V. , Volkov Alexey V.
Published: September 2021

In this work, for the first time, salts of bivalent and trivalent metals were used as crosslinking agents for nanofiltration membranes based on sodium alginate. The developed membranes were investigated for chemical stability in protic and aprotic solvents, the dependence of the permeability of these solvents on their sorption into the membrane material was obtained. The separating properties of membranes based on sodium alginate crosslinked with metal cations were investigated. The retention coefficient of the model substance with a molecular weight of 626 g/mol, dissolved in ethanol, was 97%.
Fully Renewable Composites Based on Agricultural Waste
Authors: Klushin Victor , Tokarev Denis , Kashparova Vera , Kolesnik Svetlana , Brink Ivan
Published: September 2021

In the present work, composite materials with a two wastes - waste goose feather as a filler and resinous waste from HMF production as a binder - have been developed. The mechanical properties and water sorption in dependence with feather/HMF resin composite content were studied. The composites containing 50% of feather have high strength properties up to 46 N/mm2 and low water sorption (lower 1%), which results in high water resistance. Due to these properties, they can become an excellent alternative to urea-formaldehyde resins and plastics based on them.
Kinetics of Phase Separation Polyamic Acid (PAA) Solutions with Various Precipitants
Authors: Anokhina Tatyana S. , Borisov Ilya L. , Yushkin Alexey A. , Vaganov Gleb , Didenko Andrey , Volkov Alexey V.
Published: September 2021

A new method with limited layer of polymeric solution was used to study the kinetics of precipitation of highly concentrated solutions of PAA in various precipitants; it allows to quickly estimate the rate of formation of the polymer membrane, adequately evaluate its morphology without membrane casting and reduce the experimental time for the preparation of a membrane with required porous structure. It was shown that the rate of precipitation of 18 wt. % PAA solution and the morphology of a layer resulting from the phase separation formed upon contact with water differ significantly in a “limited” layer and in a layer of infinite thickness. It was shown that morphology of a layer formed during phase separation of 18 wt. % PAA solution with water in the “unlimited” layer corresponds to morphology, which is formed in precipitation by 50% NMP-water solution of the same polymer solution in a “limited” layer. This supports the assumption about the strong dilution of the precipitant with a solvent when an “unlimited” layer method is used. In addition, during the investigation of the kinetics of the phase separation by water it was found that the rate of precipitation of highly concentrated polymer solution in a “limited” layer (ν = 8.3 μm/s) is significantly higher than in “unlimited” (ν = 1.7 μm/s). Using this method with “limited” layer, the kinetics of the phase separation of 18 wt. % PAA solution in aliphatic alcohols was also investigated; the rate of precipitation of the polymer solution is inversely proportional to their viscosity. Approximately twofold increase of dynamic viscosity with the chain length for each subsequent alcohol in the homologous series, the rate of precipitation of the PAA solution in them was also reduced by about 2 times
pH-Sensitive Hydrogels Based on Copolymers of Chitosan with Acrylamide and Sodium Acrylate
Authors: Kropotova Lidia , Grigoreva Alexandra O. , Mochalova A.E.
Published: September 2021

pH-sensitive hydrogels based on chitosan-graft-poly(acrylamide-co-sodium acrylate) were synthesized via radical polymerization in solution. Ammonium persulfate was used as initiator, and various amounts of hexamine were used as a cross-linking agent. The structure of obtained hydrogels was characterized by Fourier transform infrared spectroscopy. Moisture-absorbing power of hydrogels in buffer solution with various pH value (pH = 1.65; 4.01; 12.43) was investigated. It is turned out that such a copolymers have a high moisture retention capacity (swelling index attains the value 1100%) and are capable for reusing, that makes it possible to apply the hydrogels in different areas.
KAP1-Mediated Epigenetic Suppression in Anti-RNA Viral Responses by Direct Targeting RIG-I and MDA5
Authors: Li Qi , Qin Ying , Wang Wenwen , Jia Mutian , Zhao Wei , Zhao Chunyuan
Published: September 2021

Retinoic acid–inducible gene-I (RIG-I)–like receptors (RLRs), including RIG-I (encoded by Ddx58) and melanoma differentiation–associated gene 5 (MDA5) (encoded by Ifih1), are crucial for initiating antiviral responses. Endogenous retroviral elements (ERVs) are transposable elements derived from exogenous retroviruses that are integrated into the genome. KRAB-associated protein 1 (KAP1) is a key epigenetic suppressor of ERVs that protects cells from detrimental genome instability. Increased ERV transcripts are sensed by RLRs and trigger innate immune signaling. However, whether KAP1 directly controls RLRs activity remains unclear. In this study, we show that KAP1 attenuates RNA viral infection–induced type I IFNs and facilitates viral replication by inhibiting RIG-I/MDA5 expression in primary peritoneal macrophages (PMs) of C57BL/6J mice. Kap1 deficiency increases IFN-β expression and inhibits vesicular stomatitis virus replication in C57BL/6J mice in vivo. Mechanistically, KAP1 binds to the promoter regions of Ddx58 and Ifih1 and promotes the establishment of repressive histone marks in primary PMs of C57BL/6J mice. Concordantly, KAP1 suppresses the expression of RIG-I and MDA5 at the transcriptional level in primary PMs of C57BL/6J mice. Our results establish that KAP1 epigenetically suppresses host antiviral responses by directly targeting RIG-1 and MDA5, thus facilitating the immune escape of RNA viruses.
Long noncoding RNA H19 accelerates tenogenic differentiation by modulating miR-140-5p/VEGFA signaling
Authors: Liu You-Jie , Wang Hua-Jun , Xue Zhao-Wen , Cheang Lek-Hang , Tam Man-Seng , Li Ri-Wang , Li Jie-Ruo , Hou Hui-Ge , Zheng Xiao-Fei
Published: September 2021

Rotator cuff tear (RCT) is a common tendon injury, but the mechanisms of tendon healing remain incompletely understood. Elucidating the molecular mechanisms of tenogenic differentiation is essential to develop novel therapeutic strategies in clinical treatment of RCT. The long noncoding RNA H19 plays a regulatory role in tenogenic differentiation and tendon healing, but its detailed mechanism of action remains unknown. To elucidate the role of H19 in tenogenic differentiation and tendon healing, tendon-derived stem cells were harvested from the Achilles tendons of Sprague Dawley rats and a rat model of cuff tear was established for the exploration of the function of H19 in promoting tenogenic differentiation. The results showed that H19 overexpression promoted, while H19 silencing suppressed, tenogenic differentiation of tendon-derived stem cells (TDSCs). Furthermore, bioinformatic analyses and a luciferase reporter gene assay showed that H19 directly targeted and inhibited miR-140-5p to promote tenogenic differentiation. Further, inhibiting miR-140-5p directly increased VEGFA expression, revealing a novel regulatory axis between H19, miR-140-5p, and VEGFA in modulating tenogenic differentiation. In rats with RTC, implantation of H19-overexpressing TDSCs at the lesion promoted tendon healing and functional recovery. In general, the data suggest that H19 promotes tenogenic differentiation and tendon-bone healing by targeting miR-140-5p and increasing VEGFA levels. Modulation of the H19/miR-140-5p/VEGFA axis in TDSCs is a new potential strategy for clinical treatment of tendon injury.
Minimum ignition temperature: an alternative small-scale flammability test for conveyor belting
Authors: Mintz K J , Inglis K V
Published: September 2021

Minimum ignition temperature (MIT) tests were carried out on 10 different conveyor beltings to determine if this test is useful for assessing the fire-resistance of belting. In all but one case, two different MIT values were obtained for each product: a lower
one, in which an exothermic reaction was observed, designated MITnon-fl and a higher one, in which the sample burst into flames, designated MTHfl. The correlation between these two parameters was poor, probably because of the different nature of fire-retardants incorporated into the various
formulations. The correlation between both MIT's and the results of the large-scale tests is only fair; the oxygen index test proved to be a much better predictor of large-scale performance than either MIT, because both the oxygen index and large-scale tests measure primarily flame propagation, and
the MIT's measure ignitability. The main usefulness of the MIT test would be to determine the ignitability of belting when exposed to a hot source.
Mining research challenges
Authors: Udd J E
Published: September 2021

Mining research at CANMET is accomplished through both the Coal Research Laboratories (CRL), and the Mining Research Laboratories (MRL) divisions. The work of CRL is commodity-specific to coal and oil sands. MRL addresses the needs of all others, and
particularly, hard-rock and evaporite miners.
In this talk, the author will give an overview of federal government hard rock mining research and identify areas in which efforts in the national interest are particularly needed at present.
Impact of a delayed diagnosis of vulvar cancer and its association with HIV infection: A 4-year review at a tertiary hospital in KwaZulu-Natal, South Africa
Authors: Hlapane Ramakhosana S. , Khumalo Thandekile L. , Makhathini Bongumusa S. , Moodley Jagidesa
Published: September 2021

Background: Vulvar cancer is becoming more common in young women owing to the increased prevalence of co-infection with human papillomavirus and HIV.Objectives: The aim of this study was to determine the impact of the time interval from the diagnosis of vulvar cancer at the referring institution to the tertiary hospital and to evaluate the impact of HIV infection in the study population.Method: This was a retrospective descriptive chart review.Results: A total of 86 cases of vulvar cancer were analysed. The mean age was 48.2 ± 12.5. Sixty (69.8%) patients were under 50 years of age and eight (9.3%) under 30 years. The interval from the onset of symptoms to the diagnosis of cancer was 12 months in 63 (73.3%) patients. Eighty-one (94.8%) had had symptoms treated multiple times prior to diagnosis. Seventy (81.4%) were referred to the tertiary institution within 3 months of the diagnosis of cancer. Seventy (81.4%) had concomitant HIV infection. Of those with CD4 counts of 200 cells/mm3, 61.7% had early-stage vulvar cancer, while 38.3% had late-stage disease (P = 0.048). There was no association between the viral load and the Federation of Gynaecology and Obstetrics stage (P = 0.401). The primary treatment was surgery in 50%.Conclusion: Although the study was retrospective, we found that vulvar cancer was prevalent in younger patients with HIV infection. Higher CD4 counts were associated with early-stage disease. Early sampling of suspicious lesions can ensure early diagnosis of vulvar cancer and the initiation of therapeutic interventions, particularly in HIV-infected patients.
Prevalence and types of color vision deficiency among primary school students in Alexandria
Authors: Elshazly Alaa A.B. , El-Hinnawi Hazem M. , Osman Ihab M.
Published: September 2021

Purpose

The aim of this study was to determine the prevalence and types of color vision deficiency (CVD) among primary school students in Alexandria, Egypt.

Setting

This study was carried out at three primary schools in Alexandria, Egypt.

Patients and methods

This cross-sectional study was carried out among three primary school students in Alexandria, Egypt. Ocular examination including visual acuity and color vision testing with Ishihara plates (38-plate edition) was performed for all the students included. Further assessment using the Farnsworth–Munsell 100-hue test was performed for students who failed the Ishihara plates test.

Results

A total of 1000 (495 males and 505 females) school students were screened for CVD. The mean age of the students was 9±2.16 years. The overall prevalence of CVD was 1.9%, with a prevalence of 2.8 and 0.9% in males and females, respectively, a statistically significant difference (P=0.04). Among the CVD students, 36.8% had deuteranopia, 31.5% had deuteranomaly, 26.3% had protanopia, and 5.3% had tritanopia.

Conclusion

The prevalence of CVD was 1.9%, with a male predominance, among primary school students in Alexandria. Deutan color vision defects were the most prevalent.
Buccal mucous membrane graft-assisted dacryocystorhinostomy for management of refractory acquired nasolacrimal duct obstruction
Authors: Tharwat Ahmed
Published: September 2021

Aim

The aim of this study was to evaluate the efficacy of buccal mucous membrane graft-assisted-dacryocystorhinostomy (DCR) for the treatment of refractory acquired nasolacrimal duct (NLD) obstruction.

Patients and methods

This is a prospective, interventional case series study that included 10 patients with acquired NLD obstruction (12 eyes), associated with expected poor mucosal flaps (either due to previous failed DCR or atrophic rhinitis). In nine eyes failed previous DCR procedures were reported, while three eyes had associated atrophic rhinitis evidenced by nasal examination. Two patients had bilateral obstruction. All eyes had symptomatic epiphora. All eyes were treated with modified DCR using a buccal mucous membrane graft. The outcome was assessed in terms of relief of epiphora, patency of irrigation testing, and patency of the osteotomy site assessed by rhinoscopy at the third postoperative month, in addition to the duration of the procedure and the postoperative complications.

Results

After a minimum follow-up period of 6 months, in 11 (91.7%) out of the 12 eyes with epiphora, there was complete relief of tearing. Lacrimal passages were patent to irrigation testing postoperatively. One case with late advanced atrophic rhinitis showed recurrence of tearing after silicone tube removal. No complications to the donor graft site or surgical site were observed.

Conclusion

Buccal mucous membrane grafting-assisted DCR (at the level of the flaps) is a safe and effective technique for the treatment of cases of refractory acquired NLD obstruction.