Simulating chromatographic separation of topologically different polymers

AbstractChromatography which is sensitive to the sizes of macromolecules and to their adsorption serves as an appropriate method to separate complex polymers. Unfortunately, the molar mass also influences the chromatographic retention, thus making quite difficult the problem of separation of polydisperse polymers by their topology.By using a theory of chromatographic behavior of macromolecules, we simulate chromatograms of polydisperse polymers that differ solely in their topology, and discuss possibilities to separate complex polymers (such as eight-, tadpole-, theta-, manacle-shaped polymers, etc.) from their linear, branched, or macrocyclic precursors or topo-isomeric products.As follows from the simulations, two approaches towards the separation of polydisperse polymers by topology are especially promising. The first one is the chromatography at optimized (critical or near-critical) interaction conditions, where molar-mass effects are minimized; The second one consists in combing different chromatographic modes, which allows obtaining a separation by both molar mass and topology in a 2D chromatogram.Some of the simulated chromatographic separations are qualitatively very similar to the real ones, the others are the theoretical prediction

Temperature independent diffuse scattering and elastic lattice deformations in relaxor PbMg1/3Nb2/3O3

The results of diffuse neutron scattering experiment on PbMg1/3Nb2/3O3 single crystal above the Burns temperature are reported. It is shown that the high temperature elastic diffuse component is highly anisotropic in low-symmetry Brillouin zones and this anisotropy can be described using Huang scattering formalism assuming that the scattering originates from mesoscopic lattice deformations due to elastic defects. The qualitative agreement between this model and the experimental data is achieved with simple isotropic defects. It is demonstrated that weak satellite maxima near the Bragg reflections can be interpreted as the finite resolution effect.Comment: 7 pages, 7 figure

Direct evidence of soft mode behavior near the Burns' temperature in PbMg1/3_{1 / 3}Nb2/3_{2 / 3}O3_{3} (PMN) relaxor ferroectric

Inelastic neutron scattering measurements of the relaxor ferroelectric PbMg$_{1 / 3}$Nb$_{2 / 3}$O$_{3}$ (PMN) in the temperature range 490~K$<$T$<$880~K directly observe the soft mode (SM) associated with the Curie-Weiss behavior of the dielectric constant $\varepsilon$(T). The results are treated within the framework of the coupled SM and transverse optic (TO1) mode and the temperature dependence of the SM frequency at q=0.075 a* is determined. The parameters of the SM are consistent with the earlier estimates and the frequency exhibits a minimum near the Burns temperature ($\approx$ 650K)Comment: 6 figure

DOXORUBICIN SORPTION/DESORPTION ON MODIFIED SILICA-MAGNETITE NANOCOMPOSITES

This work was supported by the Ministry of Science and Higher Education, project №075-15-2020-777 and project AAAA-A19-119012490007-8

Clinical symptoms and ECG data in women with acute coronary syndrome

Background. There are many differences in chest pain symptoms between men and women in terms of location, nature, and additional symptoms. The issue of describing the differences in chest pain in men and women with acute coronary syndrome (ACS), as well as their correlation with changes in the electrocardiogram (ECG) and coronary angiography (CAG) remains relevant.Methods. The study included 588 patients of the cardiology department of the Novokuznetsk City Clinical Hospital No. 1 from 2013 to 2017 with a diagnosis of ACS. Depending on the gender, the subjects were divided into two groups: Group I – 330 men; Group II – 258 women.Results. ACS with ST elevation was more common in men (45.8 %) than in women (33.3 %; p = 0.002). There were no pathological ECG changes in women in 58.1 % of cases, in men – in 45.5 % (p &lt; 0.001). ECG type Q/ST elevation was detected more often in men (45.8 %) than in women (33.3 %; p = 0.002). The absence of coronary artery lesions was observed in 27.9 % of men and 44.2 % of women (p &lt; 0.001). Hemodynamically significant coronary artery stenosis was more common in men (57.6 %) than in women (38.7 %; p &lt; 0.001). In a typical angina clinic, hemodynamically significant coronary artery disease in patients with Q/without ST elevation ACS was detected in 40.2 % of men and in 58.5 % of women (p = 0.002). In the atypical angina clinic, hemodynamically significant lesions of coronary artery were more common in men (40.6 %) than in women (34.1 %; p = 0.02).Conclusion. In women atypical chest pains and intact coronary arteries were detected more often than in men, and hemodynamically significant coronary artery stenosis were found less often than in men. In men, a more pronounced pathology of the coronary arteries in ACS was revealed, in women – great difficulties in diagnosing ACS

Spatial development of tourism based on the structure model of the territorial tourist complex

The article examines the problem of spatial tourism planning. The authors note that the possibility of tourist activities in different territorial zones requires functional zoning. The study justifies the use of a territorial tourist complex concept. The authors propose using the model of functional and planning complexes as a basis for understanding the structure of the territorial tourist complex, as well in the spatial development of tourism. Spatial planning of tourism implements various approaches. However, the main problem of the territorial tourist complexes’ development arises because tourist activity can be carried out in the territories of various purposes. Multi-functional zones are important for tourism as this determines their specialization and tourist flows. The study of territorial tourist complexes is related to the problem of using this concept in the practice of spatial development. Therefore, an urgent task is to develop a model that characterizes the structure of the tourist complex, which will enable moving on to an understanding of tourism development planning.peer-reviewe

Nanocapsule for Safe and Effective Methane Storage

A nanocapsule for safe and effective methane storage is investigated by the method of molecular dynamics. The mass content of methane in the nanocapsule reaches the value of 14.5 mass%. The nanocapsule consists of two parts: a locking chamber and a storage area. The locking chamber is the nanotube (10.10), open at one end, with a K@C601+endohedral complex inside it. The storage area is a nanotube (20.20). The locking chamber and the storage area are joined with each other and form T-junction. The locking chamber is opened at the methane filling and the discharge stages, and it is closed at the storage stage. Thanks to the locking chamber, methane molecules are stored in the nanocapsules under normal external conditions. Opening and closing of the locking chamber are carried out by the K@C601+endohedral complex displacement, which is done by the electric field action. The specific structure of the nanocapsule allows two aims to be reached: a high methane mass content and significant level of safety

Microbiota of the upper respiratory tract in children with chronic adenoiditis

Background. Routine application of the GC-MS method to assess the URT microbiota can potentially improve the efficacy and safety of treatment for chronic respiratory diseases. Aim. To perform a comparative analysis of the microbiota from the surface of the pharyngeal tonsil, from the deep parts of the nose, and saliva in children with chronic adenoiditis. Materials and methods. The study included 90 patients with chronic adenoiditis (CA) and/or pharyngeal tonsil hypertrophy (PTH). All study participants had swabs taken from the surface of the pharyngeal tonsil, from the deep parts of the nasal cavity, and saliva as a biological fluid of the oral cavity. Microorganisms were identified by specific fatty acids using GC-MS to assess the composition of the microbial community on the surface of the pharyngeal tonsil. Results. The study showed that the microbiota of the nasopharynx is identical in its qualitative composition to microorganisms from the deep parts of the nose. However, according to the results of the analysis of microbial markers of saliva, the oral microbiota showed significant differences in the quantitative and qualitative composition of microorganisms compared with the nasopharyngeal microbiota. Conclusion. The introduction of the GC-MS method for assessing the URT microbiota enables its monitoring in clinical practice for the treatment of chronic respiratory system diseases without disturbing the ecology of the mucous membranes and the whole body

Temperature Evolution of Sodium Nitrite Structure in a Restricted Geometry

The NaNO$_{2}$ nanocomposite ferroelectric material in porous glass was studied by neutron diffraction. For the first time the details of the crystal structure including positions and anisotropic thermal parameters were determined for the solid material, embedded in a porous matrix, in ferro- and paraelectric phases. It is demonstrated that in the ferroelectric phase the structure is consistent with bulk data but above transition temperature the giant growth of amplitudes of thermal vibrations is observed, resulting in the formation of a "premelted state". Such a conclusion is in a good agreement with the results of dielectric measurements published earlier.Comment: 4 pages, 4 figure