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‘Mammographic density’ (MD) is a concept that has entered medical practice since 2017. as a marker of breast cancer risk factor (BC) according to the international classifiation of NCCN. The term reflcts the degree of severity of benign diffuse breast dysplasia in women of post-reproductive age. MD is determined by the ratio of stromal, epithelial, and adipose tissue. According to the literature, in young women, high MD limits the possibilities of X-ray mammography, reducing its effectiveness in oncomammoscreening, leading to the detection of advanced forms of breast cancer. Post-reproductive women with high MD are more likely to develop breast cancer than those with low MD. In this regard, MD is of particular interest for studying its role in oncogenesis. Recent molecular genetic studies of the differences between high and low MD explain the main biological reasons why post-reproductive women with dense breast structure are at a higher risk of developing breast cancer. The aim is to identify the factors that inflence the relationship of MD with the risk of developing breast cancer based on a comparative analysis of molecular genetic studies and radiological manifestations of MD of different severity and to identify the factors that contribute to the formation of MD variants.

Diagnostic efficiency of breast cancer screening remains one of the most important issues in oncology and radiology. Artificial intelligence technologies are widely used in clinical medicine to effectively solve a number of technological and diagnostic problems. The aim. To develop segmentation neural network model for breast plain radiographs analysis with subsequent study of its clinical effectiveness. Materials and methods. The artificial intelligence-based system was developed to analyze X-ray mammography, аnd included a segmentation neural network with the U-Net architecture, a classification neural architecture ResNet50 with outputting the result using gradient boosting. 15486 X-ray cases were used for training, estimation of diagnostic accuracy and validation of the developed segmental model. All cases were labeled in specially developed software environment LabelCMAITech. The segmentation accuracy was determined by Intersection over Union (IoU) similarity coefficient, the probability of malignancy was calculated using the binary classification metrics. Results. The developed system is represented by a segmentation model based on neural network architecture. The model allows, with high accuracy of 0.8176 and higher, at threshold values on the output neurons of the network of 0.1 and 0.15, to localize X-ray findings that have diagnostic value for determining the likelihood of the presence of breast cancer signs in an X-ray mammographic study — focus, architecture distortion, local asymmetry, calcifications. When comparing the results of machine segmentation and marking of images by a radiologist, it was found that the model is not inferior to the doctor in the accuracy of determining the formations, extra-focal calcifications and intraglandular lymph nodes. Conclusion. The results of this study allow considering the model as an intelligent assistant to a radiologist in the analysis of screening mammographic cases.

The goal. To show the variety of manifestations of non-palpablebreast cancer, which create difficulties in diagnostics and thechoice of treatment tactics, to focus on the need to accelerate theintroduction of the latest organ-saving treatment and diagnostictechnologies and prevention into the system of mammary cancerscreening. The main provisions. The epidemiology of cancer, riskfactors, positive trends in mammary cancer screening in Russia arepresented. A description is given of the diversity of X-ray sonographic and molecular biological manifestations of non-palpable breastcancer based on the results of the analysis of a complex clinicalX-ray sonographic pathomorphological and molecular geneticexamination of 1,212 patients with clinically latent breast diseases,including 708 patients with non-palpable cancer of various molecular subtypes, manifested by a variety of options – a nodulargrowth (40.1%), an accumulation of microcalcifications (17.5%), asite of local heavy rearrangement of the structure (31.2%), canceraccompanied by pathological secretion (6.6%), X-ray negativecancer (4.6%). When distributed by stages, 70.3% had T1N0M0, 25%had TisN0M0 and microinvasive cancer. For differential diagnosis,high-tech radiological techniques were used – 3D X-ray and ultrasound tomosynthesis. Effective preoperative diagnostics allowed foradequate organ-saving treatment, including oncoplastic surgery,high-power radiation therapy and modern targeted drug treatment,timely rehabilitation and prevention. Conclusion. Non-palpablebreast cancer has many faces. Knowledge of the variants of itsmanifestations and the use of modern diagnostic methods arenecessary for mammary cancer screening, which creates thepreconditions for adequate timely organ-saving treatment thatpreserves the life of patients and its quality.

The rate of detection of breast cancer by MRI, while other methods of radiological diagnosis are not sufficiently informative, ranges from 5.2 to 26.3 per cent. Suspicious breast tumors of category BI-RADS 4, 5 show morphological image-guided biopsy verification, in particular MRI with contrast. Purpose. To show the possibilities and features of carrying out MRI-guided vacuum breast biopsy, including after aesthetic breast augmentation. Material and methods. A comprehensive X-ray, ultrasound and MRI examination of 54 women aged between 28 and 70 years with different breast tumors was conducted. Of these, five were detected only by breast MRI with contrast, and were morphologically verified by MRI-guided vacuum aspiration biopsy. Results. 14 of the 54 patients with breast mass were diagnosed with breast cancer and 26 were diagnosed with benign diseases. The effectiveness of comprehensive examination and low-invasive high-tech MRI-guided procedures in early refined screening for breast cancer, including after aesthetic breast augmentation, has been demonstrated. MRI-guided vacuum-assisted breast biopsy is a fast, safe and accurate diagnostic method of morphological verification of suspicious breast tumors that do not have X-ray and ultrasound.

The review presents the latest data on the development of a new direction of interdisciplinary integration of radiation and molecular biological technologies ‘omi с s', including high technologies in the field of genomics, transcriptomics, proteomics and metabo-lomics, which are the basis of systems biology and the future of medicine. The integration of medical imaging and advances in genetics have created a new direction of research - radiogenomics, which is a key step in the development of omhs-technologies. Radiogenomics - phenotype imaging, computer vision - is an interdisciplinary integration of visual radiology and biological systems that study biomedical imaging involving phenotypic and genotypic parameters that reflect the molecular and genotypic basis of tissue from which to predict patient risk and outcomes. Coupled with state-of-the-art analytical software, quantitative and qualitative imaging biomarkers bring unprecedented insight into complex tumor biology and contribute to a deeper understanding of cancer development and progression. Using the latest advances in digital, information and molecular biological technology, is an active convergence of specialties radiologist and genetics, giving the opportunity at the stage of studying medical images of the breast to obtain information about the biological characteristics of the tumor molecular subtype of cancer, determining prognosis, evaluating risk of recurrence, which is important for the choice of adequate tactics of individual monitoring and selection of medical benefits. Development of visual symptom medical images of the breast, characteristic for different molecular subtypes of cancer, will contribute to more accurate diagnosis of different manifestations of cancer, the choice of adequate treatment tactics that increase the duration and preservation of the high quality of a woman s life.

[EN] Novel hierarchical micro-meso-macroporous fluorine-doped silicon oxycarbide derived materials have been obtained by HF etching of silicon oxycarbides pyrolyzed at different temperatures. The influence of etching time (1 or 24 h) and pyrolysis temperature (from 1100 to 1400 °C) on the selective removal of the silica nano-domains present in the silicon oxycarbide and the appearance of oxygen and fluorine functionalities have been determined and evaluated in terms of their electrochemical response. The insertion of fluorine in the silicon oxycarbide matrix (Si–O(F) bonds) and free carbon phase (C–F semi-ionic and C–F covalent bonds) was corroborated. The materials pyrolyzed at 1300–1400 °C and etched during 24 h show values of specific capacitance as high as 225-165 Fg (0.1–30 Ag) using a symmetrical configuration and HSO 1 M as electrolyte. These materials displayed energy density values of 28-19 Whkg (0.1–45 kWkg). The hierarchical microstructure in conjunction with the oxygen and fluorine functionalities are essential in order to explain their good electrochemical response. In particular, those materials present the highest amount of meso (3–10 nm) and larger meso-macropores and the highest content of fluorine in their composition. Then, fluorine-doped silicon oxycarbide derived materials can be potentially used as electrodes for supercapacitors in the field of energy storage applications., This work was supported by project MAT2016-78700-R financed by Spanish Research Agency and European Regional Development Fund (AEI/FEDER, EU). The authors are also grateful to C. Díaz Dorado for her help with the revision of the figures. We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).

The structure and properties of polysiloxane dendrimer melts are studied by extensive atomistic molecular dynamics simulations. Two homologous series differing in the spacer length are considered. In the first series the dendrimer spacers are the shortest ones, comprising only one oxygen atom, while in the second series the spacers consist of two oxygen atoms with the silicon atom in between. Melts of the dendrimers from the 3rd up to the 6th generation number are modelled in a wide temperature range from 273 to 600 K. A comparative study of the macroscopic melt characteristics such as the melt density and thermal expansion coefficients is performed for the two series. Analysis of the dendrimer structure in melts and in the isolated state shows that intermolecular interactions and interpenetration of dendrimer molecules in melts hardly affect the dendrimer interior organization. However, the presence of neighboring molecules significantly slows down their intramolecular dynamics in melts in comparison with that of isolated dendrimers. An increasing generation number causes an increase of the radius of the dendrimer interior region unavailable for neighboring molecules, which starts to exceed the length of the peripheral interpenetration layer for high-generation dendrimers; this fact could lead to different mechanisms of melt dynamics for lower and higher generation dendrimers.

The aim: study of the effectiveness of the combined treatment of cysts in women after cosmetic breast endoprosthesis with the help of ozone therapy and drug Mastodinon. Material and methods. For 1.5 years with dynamic control after 6-12 months. clinical-x-ray-sonographic examination of the mammary glands of 21 women aged 34 to 42 years with different variants of mastopathy and cysts after cosmetic endoprosthesis was carried out. For therapeutic purposes, a fine needle aspiration biopsy of breast cysts was performed under ultrasound control, followed by the introduction of an ozone-oxygen mixture into the cavity at a concentration of 40-80 mcg/ml, in parallel, a herbal preparation Mastodinon was prescribed for 1 tab. X 2 times a day for 3 months. Results. The examined patients complained of pain, a feeling of swelling, the presence of insomnia, periodic feeling of heaviness and swelling, a sense of fear, apprehension and uncertainty associated with the surgical intervention to install implants. Clinical-x-ray-sonographic examination in all patients revealed fibrocystic mastopathy of varying severity with cysts from 0.5 to 2 cm. Control studies every 6 months during the year showed positive dynamics of combined treatment of breast cysts after ozone therapy and the use of Mastodinon as a stable therapeutic effect in 91% of cases. In 20 of the 21 cases, the cysts did not recur, the clinical symptoms of mastalgia did not bother. Conclusion. Combined conservative treatment of breast cysts after cosmetic endoprosthesis with sequential introduction into the emptied cavity of ozone-oxygen mixture at a concentration of at least 70-80 mcg/ml with the appointment of the drug Mastodinon for 3 months. Stably reduces clinical manifestations of fibrocystic mastitis and eliminates recurrence of cysts in 91% of cases, improves the quality of life of patients.

Characteristics of instantaneous (I), vibration-average (V), and frozen (F) structures of liquid ethylene glycol (EG), monoethanolamine (MEA), and ethylenediamine (ED) are obtained by means of molecular dynamics in the temperature range of 273–453 K. Structures are described by plotting Voronoi polyhedra and Delaunay simplexes. The distributions of volumes of Voronoi polyhedra and the radii of the spheres of Delaunay simplexes were obtained in the temperature range of liquid phase EG, MEA, and ED. A comparative analysis of these characteristics of three studied liquids is performed with different averaging over time and space. It is shown that describing the structure of liquids according to Voronoi and Delaunay allows us to compare the characteristics of spatial networks of hydrogen bonds in them very clearly.

The purpose of the studywasto examine the effectiveness of the drug Mastodynon® for the treatment of mastopathy in pre- and perimenopausal women. Materials and methods.The research was carried out within 12 months. Patient presenting complaints of pain in the breast, passed a comprehensive examination (clinical and Х-ray and/or sonographic) and questionnaires at the first visit and every 6 months. The plant-based drug Mastodynon®. Results.We examined 38 patients aged 45–56 years. Most women in this group for many years were observed due to mastopathy of different forms and degrees of severity. After 6 months after start of treatment with Mastodynon® the majority of patients reported decrease or absence of pain in the breasts, improvement of psycho-emotional condition. The positive effect of various degree was observed in 71,05% of the patients. After 1 year revealed a stabilization of the therapeutic effect of the drug Mastodynon® in 83,3% of cases. Mastodynon® has shown high effectiveness, good tolerability in the treatment of mastopathy in women of pre- and perimenopausal age, it has improved thepatients quality of life.

We studied the conformational behavior of silicon-containing dendrimers during their adsorption onto a flat impenetrable surface by molecular dynamics (MD) simulations. Four homologous series of dendrimers from the 4th up to the 7th generations were modeled, namely, two types of carbosilane dendrimers differing by the functionality of the core Si atom and two types of siloxane dendrimers with different lengths of the spacers. Comparative analysis of the fractions of adsorbed atoms belonging to various structural layers within dendrimers as well as density profiles allowed us to elucidate not only some general trends but also the effects determined by dendrimer specificity. In particular, it was found that in contrast to the carbosilane dendrimers interacting with the adsorbing surface mainly by their peripheral layers, the siloxane dendrimers with the longer –O–Si(CH3)2–O spacers expose atoms from their interior to the surface spreading out on it. These findings are important for the design of functional materials on the basis of silicon-containing dendrimers.

Dendrimers are perfect tree-like radially symmetric macromolecules with regular branching. Due to their architecture, dendrimers possess a set of unique properties, including high penetrating ability and a large number of functionalizable terminal groups. Practical use of dendrimers as delivery agents or nanoreactors in many cases involves a free space in a dendrimer interior. The question about presence of a hollow core (a cavity) inside the dendrimer molecule placed in a solvent attracts interest of researchers since the discovery of dendrimers. This review presents a rigorous discussion on the dendrimer structure in solution. The main objective is to draw attention to the difference in the structure of homopolymer and copolymer dendrimers. Theoretical studies typically consider homopolymer dendrimers (with similar inner and terminal segments), whereas experiments often examine dendrimers with massive terminal groups which chemical structure is different from the structure of the dendrimer inner groups. In the latter case, dendrimer is a copolymer macromolecule, and its conformation can depend on additional factors, such as solvent selectivity, or poor compatibility of terminal and core groups. The influence of these factors can lead to the formation of a region with a lower polymer density inside the dendrimer.

El pensamiento crítico y sus habilidades deberían ser un componente fundamental de la educación universitaria; especialmente en la administración. En este documento se analizarán las competencias y habilidades del pensamiento crítico y su utilidad para la enseñanza, la investigación y el desempeño profesional en administración de empresas. Al final se concluye que el pensamiento crítico podría manifestarse como el sexto modo de ser de los gerentes en las organizaciones; modo de ser crítico. Y se sugiere ahondar en estudios que busquen su plena implementación y desarrollo en este campo del conocimiento.

A simplified model of the in-plane molecular chain, allowing the description of folded and scrolled packings of molecular nanoribbons of different structures, is proposed. Using this model, possible steady states of single-layer nanoribbons scrolls of graphene, graphane, fluorographene, and fluorographane (graphene hydrogenated on the one side and fluorinated on the other side) are obtained. Their stability is demonstrated and their energy is calculated as a function of the nanoribbon length. It is shown that the scrolled packing is the most energetically favorable nanoribbon conformation at long lengths. The existences of scrolled packings for fluorographene nanoribbons and the existence of two different scroll types corresponding to left- and right-hand Archimedean spirals for fluorographane nanoribbons in the chain model are shown for the first time. The simplicity of the proposed model makes it possible to consider the dynamics of scrolls of rather long molecular nanoribbons at long enough time intervals.

This review summarizes the data published over the past two and a half decades on the mechanism of plastic deformation of bulk isotropic linear glassy polymers in uniaxial tension, compression, and shear at low deformation temperatures (Тdef < 0.6Тg) and moderate loading rates. The main attention is focused on studies concerning the numerical computer simulations of plasticity of organic polymer glasses. The plastic behavior of glassy polymers at nano-, micro-, and macrolevels in the range of macroscopic strains up to ≈100% is discussed. Plasticity mechanisms are compared for organic, inorganic, metallic, polymer, and nonpolymer glasses with different chemical structures and types of interparticle interactions. The general common mechanism of plasticity of glassy compounds, the nucleation of plasticity carriers in them, and the structure of such carriers and their dynamics are covered. Within the framework of the common plasticity mechanism, the specific features of deformation in glassy polymers are analyzed. Specifically, the participation of conformational transformations in macromolecules in the deformation response of polymer glasses, change in intensity of the yield peak with the thermomechanical prehistory of the sample, and the role of van der Waals interactions in the accumulation of excess potential energy by the sample under loading are considered. The role of free volume and structural and dynamic heterogeneities in the plasticity of glasses is also discussed.

We have derived effective potentials of Na+ and Cl— ions in implicit water at temperatures from 273 to 340 K and concentrations between 0,3 and 1 M. We divide the potentials into two parts: slowly decreasing Coulomb function and solvation energy. The primary dependence of the effective potentials on the parameters proved to be in the dependence on them of the dielectric constant. Slight temperature dependence of the solvation is present for the pairs Na+ — Na+ and Na+ — Cl— only.

Carbon nanofibers (CNFs) were grown in situ on porous glass at different temperatures and times using a Ni acetate catalyst and CH4/N2 as a carbon source. The porous glass was obtained by acid leaching of phase separated borosilicate glass, which generates a broad size distribution of mesopores (≈20 nm). Subsequent impregnation with Ni acetate reduces the pore size to ≈ 4 nm but also creates new micropores, thus increasing the surface area. During thermal treatment the surface area decreases as temperature rises, mainly due to shrinkage of the glassy matrix; however new pores are created at ≈ 70 nm (mainly at 600 oC) associated to the generation of CNFs on the glass surface, indicating this temperature offers the best conditions. The CNFs grow inside and fill in the micro-mesopores in the porous glass. They do not grow at 500 oC as the Ni acetate is not transformed into metallic Ni. Ni deactivation occurs at temperatures over 700 oC, thus reducing the formation of CNFs. At 1000 oC the degradation of CH4 leads to a thickening of the CNFs. The thermal degradation of the CNFs occurs in two steps, the first (360-416oC) corresponding to CNFs grown on the glass surface and the second (518-649oC) to CNFs grown inside the glass pores. Treatment times over 2 h lead to the deactivation of Ni, pore shrinkage and hence lower CNF yields.

A molecular mechanical model has been proposed for nanoribbons of graphone (graphene with single-sided hydrogenation), which takes into account deformations of valence bonds, valence and torsion angles, as well as non-bonded van der Waals and Coulomb interactions of atoms in a graphone nanoribbon. The ground states of the nanoribbons have been found using the proposed model. It has been shown that a rectangular fragment of graphone on a substrate formed by an infinite planar graphene sheet forms a flat monolayer, whereas a fragment that does not interact with the substrate takes a convex shape, the outer side of which contains the attached hydrogen atoms. The simulation of the dynamics has demonstrated that the single-sided structure of a graphone sheet is resistant to thermal vibrations (at temperatures T < 900 K, hydrogen atoms do not migrate from one side of the sheet to the other). The difference between the sides leads to a rapid folding of long-length free-standing graphone nanoribbons into scrolled structures. Thermal vibrations do not prevent the formation of scrolls, and the scrolls themselves are resistant to these vibrations.

In order to obtain dense silicon oxycarbide (SiOC) materials that maintain the properties of glass, non-conventional spark plasma sintering was used to sinter SiOC powders from 1300 to 1700 °C and with 40 MPa of pressure. The concurrence of electrical current, high pressure and low vacuum while the material is being heating produces a dense SiOC-derived material composed of a SiO 2 glassy matrix reinforced with SiC nanowires grown in situ , graphene-like carbon and turbostratic graphite. SiOC materials with high electrical and thermal response are obtained as a result of this new processing technique. Electrical resistivity undergoes an extraordinary decrease of five orders of magnitude from 1300 (1.0 × 10 5 Ω m) to 1700 °C (0.78 Ω m), ranging from insulate to semiconductor material; and thermal conductivity increases by 30%, for these sintering temperatures.

Our previous paper (E.A. Zubova, I.A. Strelnikov, N.K. Balabaev, A.V. Savin, M.A. Mazo, and L.I. Manevich, Polym. Sci., Ser. A 59 (1) (2017)) addressed the simplest coarse-grained model of polyethylene and alkanes. The CH2 group in this united-atom model is replaced with a bead. In the framework of the model, nonbonded interactions are described by the Lennard-Jones potential (6–12), whereas the potential for bonded interactions accounts for the bonds between beads and for coarse grained angles and dihedral angles but not for the cross terms between them. We found the area of geometrical parameters of the model where all the three known crystalline phases of polyethylene are stable at low temperatures. We parametrized the force field of the model using the dynamic properties of the system, namely, the inelastic neutron scattering spectrum of the orthorhombic phase of polyethylene. However, the simplest model underestimates the value of the elastic modulus along the chains of the crystal by a factor of two. The derived setting angle of the molecules also differs appreciably from the experimental data. Moreover, the acoustic dispersion curves for the modes with the wave vector directed along the chain axis deviate from the experimental data at low frequencies. In the present study, we included the cross terms into the bonded interactions. This made it possible to reproduce the experimental elastic modulus along the chains of the crystal and to decrease the frequency range for the optical skeletal dispersion curve to proper values. As for the beads, we separated force centers for the bonded and nonbonded interactions, which enabled us to reproduce the optical skeletal curve and to bring the anisotropy of interchain interactions in line with the experiment. However, the model fails to reproduce the balance of interactions between the neighboring chains in the crystal. For this, a different form of the potential energy of van der Waals interactions seems to be needed.

The position of a graphene nanoribbon on a solid substrate allows the chemical modification of only one of the nanoribbon sides. A method was proposed that enables the chemical modification of the other side, too. It was numerically modeled how a nanoribbon separated from a substrate rolls up into a roll and how the roll unrolls on a flat substrate. The dependences of the number of coils and the radii of rolls forming by hydrogenation on the nanoribbon length and width were determined.

[En] Cobalt-silicon oxycarbide materials (Co–SiOC) have been produced through the polymer-derived ceramic route by incorporating Cobalt acetate in different proportions. HF etching of the obtained materials leads to obtaining C-rich Co–SiOC materials where the constituent phases present different characteristics. The SiO units that were the most vulnerable to the chemical attack were the most tensioned ones which are connected at the edges of the graphitic planes. The carbonaceous nanostructures in the HF-etched materials present a different ordering degree which is related with the microstructural characteristics of the pyrolyzed precursors. In addition, the electrochemical performance turns out to be dependent not solely on the Co content but also to the graphitization degree of the carbonaceous phase., A. Tamayo acknowledges the financial support from Fundacion General CSIC and the program COMFUTURO. This research has been developed under the frame of the project MAT2016-78700-R from the Spanish Ministry of Economics and Competitiveness. We want to acknowledge Lucia Salvador for her inestimable assistance in the electrochemical measurements.

Hierarchically micro/mesoporous silicon oxycarbide derived carbon (SiOC-DC) materials have been successfully prepared by HF selective removing of silica nano-domains present in SiOC. Dense carbon enriched SiOC materials are obtained by pyrolysis from 1100 to 1400 °C of novel sol-gel hybrids which contain both Si-H and Si-Ph bonds. The pyrolysis temperature deeply affects the etching process, major differences are observed between the sample pyrolyzed at 1100 °C and at higher temperatures. Those differences are directly associated to the evolution of the phase separation of SiOC into SiO2 and SiC, which facilitates the selective extraction of silica nano-domains and the formation of micro/mesoporous SiOC-DC materials with high specific surface areas (SSAs) and high pore volumes. The SiOC-DC sample pyrolyzed at 1200 °C displays very promising results of specific capacitance (90-100 Fg-1 at 40 Ag-1), relatively high energy density (28 W.h.Kg-1) at a low power density (0.10 kW.kg-1), and a significant performance at high power density (10 W.h.Kg-1 at 49 kW.kg-1), taking into account the low potential window of inorganic liquid electrolyte used (0.9 V). We have found that the presence of micropores but even more, the presence of slit-shape mesopores (Dmeso 3-10 nm) is crucial in order to explain the electrochemical response of these materials.

The potential application of silicon oxycarbonitride (SiOCN), silicon oxycarbide (SiOC) and silicon oxycarbide¿SiC (SiOC¿SiC) for photothermal devices such as volumetric solar absorbers has been studied evaluating the response to thermal shock from a Fresnel lens. The accelerated ageing test comprises fast heating (32¿C min¿1 ) and cooling rates (27¿C min¿1 ) from 100 to 1000¿C and dwelling times of 10 min. Porous materials (SiOCNp and SiOCp) failed the thermal shock tests; they were massively degraded by the formation of a large depression in the focus of solar radiation. Dense materials (SiOCd and SiOC¿SiCd) withstood 100 cycles of thermal shock ageing tests due to the formation of a protective silica layer. The absorptance values for dense materials remained fairly constant before and after thermal shock tests: from 94.5 to 94.3% for SiOCd and from 93.3 to 93.3% for SiOC¿SiCd . These preliminary studies indicate their potential for high-temperature solar receiver applications., This research was funded by MINISTERIO DE ECONOMÍA, INDUSTRIA Y COMPETITIVIDAD OF SPAIN, [ENE2012-39385-CO3-01] and SPANISH RESEARCH AGENGY AND THE EUROPEAN REGIONAL DEVELOPMENT FUND (AEI/FEDER, UE), [MAT2016-78700-R].We acknowledge support of the publication fee by the Spanish National Research Council (CSIC) Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).

The coarse-grained model of polyethylene and alkanes (the united-atom model, in which each CH2 group is represented by a single bead) was proposed several decades ago. It is widely applied in molecular dynamics simulations. For different tasks, the models with different geometrical and force parameters are used. Until now, it was thought that the coarse-grained model of polyethylene cannot reproduce the orthorhombic crystalline phase, which is typical of this polymer. In the present study, we analyze the simplest coarse-grained model of polyethylene. In this model, the Lennard-Jones potential (6–12) is adopted for van der Waals interactions between the beads of different chains. Of the bonded interactions, only the “valence” bonds between beads and the “bond” and “torsion” angles are taken into account, whereas the cross terms between them are disregarded. We consider the model variation in which the bead (the force center with the mass of a CH2 group) is displaced from the center of the carbon atom and all the interactions, both bonded and nonbonded, are defined by the positions of these beads. For this model, we find the area of geometrical parameters (the displacement value and the van der Waals radius of the bead) in which all the three known crystalline phases of polyethylene are at equilibrium at low temperatures. We choose the force field constants for the model so that its oscillation spectrum reproduces the low-frequency part of the inelastic neutron scattering spectrum of the orthorhombic polyethylene. It proved to be that this choice can be made unambiguously. We compare the dispersion curves in the terahertz range with experimental data on the Raman scattering and infrared spectroscopy, and discuss the advantages and disadvantages of the analyzed simplest coarse model.

Extensive molecular dynamics simulations of polybutylcarbosilane dendrimer melts were performed in a wide temperature range from 300 to 600 K. The melt macroscopic and structural characteristics were analyzed for the third up to the eighth generation dendrimers for the systems consisting of 8 and 27 dendrimer molecules in the simulation box. For every system, averaging was performed over 8 independent simulation runs and along equilibrium time trajectories of up to 5 ns. Calculated values of the thermal expansion coefficients, heat capacity, and self-diffusion coefficients are in a good agreement with experimental observations. Analysis of the molecular mass dependence of the gyration radius and shape factor, detailed radial density distributions of dendrimer structural units, mobility of the branching points, and intermolecular interaction energy allowed to shed light on the basics of distinction in behavior of low and high generation dendrimer melts and formulate the directions of further research.

Highly densified bulk silicon oxycarbide—carbon composites (SiOC-C) reinforced with carbon black (CB), active carbon (AC) or graphite (GR) have been obtained through spark plasma sintering. Structural, mechanical, tribological and thermal properties of SiOC-C composites were researched. The SiOC-C composites reinforced with GR and CB tended to give β-SiC. Wear behavior at room temperature under dry conditions was determined by using a ball on plate configuration and stainless steel balls as counter bodies. The coefficient of friction of the composites decreases down to 40% and the wear rate is also reduced by 1 in the order of magnitude when compared to SiOC. A graphite-like carbon tribolayer is probably formed in the composites; this layer could be responsible for the observed enhancement of such tribological properties. These SiOC-C composites are promising candidates for use in harsh enviroments where an adequate tribological response is required at high temperatures.