Wyniki wyszukiwania - Biblioteka Nauki

1

LOcal Rovibrational Instability in a water Molecule

100%

Konarski J. , Mańkowski M.

Polish Journal of Chemistry

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2003

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tom Vol. 77 / nr 11

1615-1623

EN

Using the stability matrix method, the occurrence of locally unstable states in the water molecule has been shown. Detailed analysis of this problem reveals a dependence of the state stability on the rotational quantum numbers Jand k, as well as on the rotation about the z axis perpendicular to the molecular plane, i.e. on the rotation at which the Coriolis coupling reaches a maximum.

2

Structure and dynamics of water adsorbed on the lignite surface: Molecular dynamics simulation

80%

You X. , He M. , Cao X. , Lyu X. , Li L.

Physicochemical Problems of Mineral Processing

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2019

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tom Vol. 55, iss. 1

10--20

EN

The effects of oxygen-containing functional groups on the structure and dynamic properties of water molecules near a lignite surface were investigated through molecular dynamics (MD) simulations. Because of its complex composition and structure, a graphite surface containing hydroxyl, carboxyl, and carbonyl groups was used to represent the lignite surface model. According to X-ray photoelectron spectroscopic (XPS) results, the composing proportion of hydroxyl, carbonyl and carboxyl is 21:13:6. The density profiles of oxygen and hydrogen atoms indicate that the brown coal surface characteristics influence the structural and dynamic properties of water molecules. The interfacial water is much more ordered than bulk water. The results of the radial distribution functions, mean square displacements, and local self-diffusion coefficients for the water molecules in the vicinity of three oxygen-containing functional groups confirmed that carboxyl groups are the preferential adsorption sites.

3

The influence of hydrochloric acid treatment and temperature on the electro-physical properties of super-thin basalt fibers

80%

Nikoghosyan S. , Sahakyan A. , Gavalyan V. , Harutyunyan V. , Hovanisyan A. , Yeritsyan H. , Atoyan V. , Puskulyan K. , Gerchikov M. , Hakobyan N.

Open Physics

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2011

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tom 9

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nr 6

1482-1487

EN

Electro-physical parameters of super-thin basalt fiber (STBF) from Armenian basalt rocks are measured before and after hydrochloric acid treatment. It is shown that specific resistance and dielectric parameters of super-thin basalt fiber change essentially after hydrochloric acid treatment. The temperature dependence of these parameters was studied too. The probable cause of the change is an increase in the total amount of pores and modification of the share of pores of various sizes in STBF, followed by an increase of absorption of water molecules from the ambient medium. The results (in both alternating and direct electric fields) are interpreted within the framework of the dipole-relaxation mechanism of the polarization of water molecules in STBF pores.

4

Molecular simulation study on hydration of low-rank coal particles and formation of hydration film

80%

Xia Y. , Yang Z. , Xing Y. , Gui X.

Physicochemical Problems of Mineral Processing

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2019

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tom Vol. 55, iss. 2

586--596

EN

Water molecules in low-rank coal (LRC) significantly influence its upgrading and utilization. To investigate the hydration of LRC particles and the formation of a hydration film, molecular simulation techniques were innovatively used, including molecular dynamics (MD) simulations and density functional theory (DFT) calculations. The adsorption of water molecules on LRC and various oxygen-containing groups was analyzed. The results show that water molecules adsorb close to the LRC surface and form a large overlapping layer at the LRC/water interface. The radial distribution functions (RDFs) show that the adsorption affinity of water molecules on oxygen-containing sites is stronger than that on carbon-containing sites, and the RDF peaks indicate the existence of a hydration film. Moreover, the differences in adsorption between various oxygen-containing groups depend on both the number of hydrogen bonds and the adsorption distances. The calculated binding energies indicate that the adsorption capacity follows the order carboxyl > phenolic hydroxyl > alcoholic hydroxyl > ether linkage > carbonyl. Experimental results show that a high sorption rate exists between water vapor and LRC samples at the beginning of sorption, which verified the simulation results.

5

Struktura ciekłej wody. Cz.1. Modele struktury wody

60%

Dutkiewicz E. , Jakubowska A.

Wiadomości Chemiczne

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1998

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tom [Z] 52, 11-12

773--786

EN

Without doubt, water is the most studied system in chemistry. Despite this fact, water is still far from being satisfactorily described on the molecular level and continues to fascinate new generations of chemists. This situation reflects the difficulty of providing a structural description that accounts for the dynamic behaviour of the H-bonding ability of water, i.e., the ability of water molecules to from different structures. The aim of this work was to present different models describing: 1) a water molecule; 2) hydrogen-bond networks; 3) the water structure. The first model of a water molecule was created by Bjerrum. Various modifications of this model were proposed later. Water models proposed by Ben-Naim and Stillinger (BNS model) and Stillinger-Rahman (ST2 model)are typical ones among the four-point charge models. The model proposed by Rowlinson is a modified four-point charge model. Matsuoka-Clementi-Yoshimine's model is a three-point charge model of the water molecule. Jorgensen's model is also described in this work. Besides these rigid models of a water molecule, flexible models have also been introduced. Typical ones are the central force (CF) model and its modifications proposed by Bopp-Jancsó-Heinzinger (BJH). We present also different models describing hydrogen-bond networks: model based on polygons, bond percolation models and lattice models (square water, simplified square water, brick water). Models describing the water structure may be divided into two main classes: mixture models (a fluid composed of molecular clusters of various sizes) and continuum models. Continuum models are not sufficient to explain the unusual behaviour of H2O and D2O. Water can also appear to be a macroscopic, space-filling gel-like network. This structural picture of water combines ideas of continuum models with ideas of mixture models.

6

Kropla wody. Esej

51%

Wrembel H.

Ekologia i Technika

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2007

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tom R. 15, nr 5

179-190

PL

W pracy przedstawiono właściwości fizyczne wody, rozważono możliwość powstania jej na Ziemi, pokazano właściwości różnych odmian izotopowych wody, omówiono znaczenie jakości wody pitnej dla zdrowia ludzkiego.

EN

The aim of this work is to show some physical properties of water, Its occurrence on the Earth and diferennces in the behaviour of different isotopic water molecules. The irnportance on the health problerns of the quality of drinking water, is shown.

7

Wodna klatka

41%

Lipkowski J.

Academia. Magazyn Polskiej Akademii Nauk

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2005

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nr 1

34-36

8

Molecular dynamics simulation studies of lipid bilayer systems

41%

Pasenkiewicz-Gierula M. , Murzyn K. , Rog T. , Czaplewski C.

Acta Biochimica Polonica

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2000

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tom 47

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nr 3

EN

The main structural element of biological membranes is a liquid-crystalline lipid bilayer. Other constituents, i.e. proteins, sterols and peptides, either intercalate into or loosely attach to the bilayer. We applied a molecular dynamics simulation method to study membrane systems at various levels of compositional complexity. The studies were started from simple lipid bilayers containing a single type phosphatidylcholine (PC) and water molecules (PC bilayers). As a next step, cholesterol (Chol) molecules were introduced to the PC bilayers (PC-Chol bilayers). These studies provided detailed information about the structure and dynamics of the membrane/water interface and the hydrocarbon chain region in bilayers built of various types of PCs and Chol. This enabled studies of membrane systems of higher complexity. They included the investigation of an integral membrane protein in its natural environment of a PC bilayer, and the antibacterial activity of magainin-2. The latter study required the construction of a model bacterial membrane which consisted of two types of phospholipids and counter ions. Whenever published experimental data were available, the results of the simulations were compared with them.

9

Properties of starch - sugar - water systems studied by dynamic rheological measurements

41%

Sikora M.

Polish Journal of Food and Nutrition Sciences

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2001

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tom 10

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nr 1

EN

Saturated aqueous solutions of D-glucose, D-fructose and sucrose were blended with solid granules of corn, waxy corn and tapioca starches. Systems deficient in water were obtained, properties of which were studied by dynamic rheological measurements. The properties of systems obtained at different proportions of saturated sugar solutions to starch were characterized. It was concluded that desired rheological properties (fluidity of blends) can be achieved by adjusting relevant quantity of plasticizers (different sugars and water). Similarly, by adjusting the quality and quantity of plasticizers, the phenomenon of "magic trick" (viscoelastic behaviour) can be achieved in the studied systems, however, that property is manifested in a very narrow range of starch-to-saturated sugar solution ratio. For all systems under study, the quantity of saturated solutions of relevant sugars, needed to achieve plasticity of each systems, was depicted. It was also concluded that in order to achieve plasticity with tapioca starch granules, for each 2 g of this starch 1.83 and 1.99 g of saturated solution of D-glucose and sucrose, respectively, are needed. In order to achieve plasticity with granules of waxy corn starch - 2.63 and 2.35 g, respectively, and with granules of corn starch - 3.09 and 2.5 g of saturated solutions of D-glucose and sucrose, respectively, are needed. The systems containing saturated solutions of D-fructose have different relationships. In order to achieve plasticity of blends containing corn, waxy corn and tapioca starch, for each 2 g of starch 2.14; 2.13 and 2.33 g, respectively, of saturated fructose solution is needed.

PL

Nasycone roztwory D-glukozy, D-fruktozy oraz sacharozy mieszano z granulami skrobi kukurydzianej, kukurydzianej woskowej oraz tapioki. Otrzymywano ubogie w wodę mieszaniny, właściwości których badano przy pomocy dynamicznych pomiarów Teologicznych. Scharakteryzowano właściwości otrzymanych układów przy różnych proporcjach nasyconych roztworów cukrów do skrobi. Stwierdzono, że pożądane właściwości reologiczne (płynność układów), można osiągnąć poprzez dobranie odpowiednich ilości plastyfikatora (różnych cukrów i wody). Podobnie, przez regulację ilości i jakości plastyfikatora, można otrzymać w badanych układach zjawisko "magie trick" (właściwości sprężystolepkie), chociaż właściwości te przejawiają się w bardzo wąskim zakresie proporcji skrobi do nasyconego roztworu cukru. Dla wszystkich układów podano ilości nasyconych roztworów odpowiednich cukrów, potrzebne do osiągnięcia plastyczności danego układu. Stwierdzono, że w celu osiągnięcia plastyczności z granulami skrobi tapioki, na 2 g tej skrobi potrzeba 1,83 i 1,99 g nasyconych roztworów D-glukozy i sacharozy, z granulami skrobi kukurydzy woskowej - odpowiednio 2,63 i 2,35 g, a z granulami skrobi kukurydzianej - odpowiednio 3,09 i 2,5 g. Układy z nasyconymi roztworami D-fruktozy mają odmienne, wzajemne relacje. W celu osiągnięcia plastyczności układów skrobi kukurydzianej, kukurydzianej woskowej i tapiokowej, na każde 2 g tych skrob i potrzeba odpowiednio 2,14; 2,13 i 2,33 g nasyconego roztworu D-fruktozy.

10

Interaction of starch polysaccharides and their mixture with water molecules and model lipids. ESR study

41%

Wasserman L. A. , Aliev I. O. , Yuryev V. P.

Żywność Nauka Technologia Jakość. Suplement

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2002

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tom 09

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nr 4

EN

Electron spin resonance (ESR) was used in order to study interaction of starch polysaccharides (amylose and amylopectin), their mixture and gelatinized potato starch with water molecules and lipids upon cooling. Different spin probes were used, on the one hand spin-labelled stearic acid (5-DSA), which limited lipids, and on the other hand the water soluble probe 4-hydroxy-2,2,6,6-tetramethylpiperidine-1- oxyl (Tempol), which was sensitive to changes in dynamic water phase associated with the temperature- induced polysaccharide gel formation. It was shown that interaction between gelatinized starches and lipids related to mainly on presence of amylose macromolecules in the system. On the other hand, interaction between amylopectin macromolecules and lipids takes place also.

PL

Za pomocą elektronowego rezonansu spinowego (ESR) zbadano, powstające po chłodzeniu, oddziaływania między polisacharydami skrobiowymi (amylozą i amylopektyną), skrobią i z żelowaną skrobią ziemniaczaną a wodą i lipidami. Zastosowano różne wskaźniki spinowe pozwalające badać zmiany w dynamice fazy wodnej związane z powstawaniem indukowanych temperaturą żeli. Pokazano, że w oddziaływaniach między z żelowaną skrobią i lipidami uczestniczy głównie amyloza chociaż obserwuje się też oddziaływania między lipidami i amylopektyną.