Dynamical systems with relaxation time

We define mathematically a class of dynamical systems that exhibit relaxation corresponding to that observed in physical systems, and then show that this class is identical with the class ofK-mixing dynamical systems.     

Simple functional-differential equations for the bound-state wave-function components

We present a new method of a direct derivation of differential equations for the wave-function components of identical-pariticles systems. The method generates in a simple manner all the possible variants of these equations. In some cases they are the differential equations of Faddeev of Yakubovskii. It is shown that the case of the bound states allows to formulate very simple equations for the components which are equivalent to the Schrödinger equation for the complete wave function. The components with a minimal antisymmetry are defined and the corresponding equations are derived.     

冰晶石-氧化铝熔体结构的计算机模拟研究

用Monte Carlo法对冰晶石-氧化铝系熔体结构作了计算机模拟研究。结果表明: 熔体中既有含“氧桥”和“氟桥”的“多核”离子集团, 如F3Al-O-AlF_3、F_3Al-AlF_3、F_3Al—F—AlF_3—F等; 也有“单核”离子集团如AlF_5~(2-)、AlOF_3~(2-)等。熔体中还存在较松散的xNa~+·yF~-离子集团。熔体中不存在AlO_2~-或AlO_3~(3-)集团。     

226Ra and possible water contamination due to phosphate fertilizer production

The raw material used in the production of fetilizers is phosphate ore containing various amounts of naturally radioactive elements. During phosphate ore processing, owing to chemical properties of radium, practically all²²⁶Ra gets incorporated into phosphogypsum and becomes the main source of radioactivity. This study was carried out in a fertilizer factory in central Croatia, which may represent a site of significant environmental contamination due to fertilizer production and phosphogypsum deposition in the area. The purpose of this paper was to determine whether ingestion of drinking water in this area poses a health risk for the inhabitants. The results of our study confirmed the occurrence of²²⁶Ra in elevated concentrations in the samples of trickling waters. However, concurrent analyses of drinking water indicated that the risk of adverse health effects for the population living in the vicinity of a phosphate fertilizer plant is negligible.     

Isoperichoric focusing field-flow fractionation and thin layer isoperichoric focusing based on coupling of gradient generated by primary field with secondary field action: general principles and performances

The primary field forces can generate spatially oriented gradient of the effective property of a continuum or pseudo-continuum fluid (carrier liquid). When this gradient is coupled with the action of a secondary field of identical or different nature the isoperichoric focused zones of the dispersed species can appear. Consequently, they can be separated according to differences responding to the property gradient of the carrier liquid. This concept can be applied under static (non-flow) conditions in thin layer focusing as well as under dynamic conditions with the elution due to the carrier liquid flow in focusing field-flow fractionation. The gradient established by the action of the primary field and the concentration distribution of the isoperichoric focused zone formed by the coupled effect of the gradient and of the primary or secondary field are described theoretically. The rigorous relationship describing the shape of the focused zone is compared with the approximate solutions. The performances of the proposed principle were evaluated by model calculations. Potential experimental configurations considering the implementation of the static and dynamic conditions are discussed. The generalized isoperichoric focusing theory can be applied to describe the particular processes operating in analytical and preparative focusing separations of the particles of various, but especially of biological origin.     

Photodissociation dynamics of pyridine

Photodissociation of pyridine, 2,6-d2-pyridine, and d5-pyridine at 193 and 248 nm was investigated separately using multimass ion imaging techniques. Six dissociation channels were observed at 193 nm, including C5NH5 --> C5NH4 + H (10%) and five ring opening dissociation channels, C5NH5 --> C4H4 + HCN, C5NH5 --> C3H3 + C2NH2, C5NH5 --> C2H4 +C3NH, C5NH5 --> C4NH2 + CH3 (14%), and C5NH5 --> C2H2 + C3NH3. Extensive H and D atom exchanges of 2,6-d2-pyridine prior to dissociation were observed. Photofragment translational energy distributions and dissociation rates indicate that dissociation occurs in the ground electronic state after internal conversion. The dissociation rate of pyridine excited by 248-nm photons was too slow to be measured, and the upper limit of the dissociation rate was estimated to be 2x10(3) s(-1). Comparisons with potential energies obtained from ab initio calculations and dissociation rates obtained from the Rice-Ramsperger-Kassel-Marcus theory have been made.     

Enantiomers of sterically hindered n-aryl-4-pyridones: Chromatographic enrichment and thermal interconversion

N-Aryl-4-pyridones 1–6 were synthesized by condensation of the corresponding 4-pyrone with anilines. The enrichment of the enantiomers was achieved by liquid chromatography on triacctylcellulose, enantiomeric purities of(+)-1 and (+ )-2 being measured by ¹H-NMR in the presence of an optically active auxiliary. Barriers to partial rotation about the C-N bond in 1-4 were determined and compared with corresponding biphenyls.     

Gel permeation chromatographic characterization of sodium hyaluronate and its fractions prepared by ultrasonic degradation

Summary High-molecular-weight sodium hyaluronate isolated from rooster combs was degraded by ultrasonication. The molecular weight of hyaluronate and its polydispersity was determined by gel-permeation chromatography. During 75-min treatment the molecular weight value decreased from 1.39×10⁶ Da to 2.25×10⁵ Da while the polydispersity of the molecular weight increased from 1.29 to 2.36. The reciprocal value of the square of the hyaluronate's molecular weight was linearly proportional to the time of ultrasonication.     

Size exclusion chromatographic characterization of sodium hyaluronate fractions prepared by high energetic sonication

Summary A high molecular weight sodium hyaluronate isolated from rooster combs was degraded by ultrasonication. High-performance size exclusion chromatography allowed rapid and accurate determination of molecular weight parameters (M_z, M_w, M_n) and distributions. The time dependence of hyaluronan ultrasonication to the molecular characteristics of the polymer was investigated. A non-random nature of the degradation process was demonstrated and the reciprocal M_n value was found to be linearly proportional to the time of ultrasonication.     

Binding of high-mannose-type oligosaccharides and synthetic oligomannose clusters to human antibody 2G12: implications for HIV-1 vaccine design

Human antibody 2G12 broadly neutralizes human immunodeficiency virus type 1 (HIV-1) isolates and shows protective activity against viral challenge in animal models. Previous mutational analysis suggested that 2G12 recognized a novel cluster of high-mannose type oligosaccharides on HIV-1 gp120. To explore the carbohydrate antigen for HIV-1 vaccine design, we have studied the binding of 2G12 to an array of HIV-1 high-mannose type oligosaccharides by competitive ELISAs and found that Man9GlcNAc is 210- and 74-fold more effective than Man5GlcNAc and Man6GlcNAc in binding to 2G12. The results establish that the larger high-mannose oligosaccharide on HIV-1 is the favorable subunit for 2G12 recognition. To mimic the putative epitope of 2G12, we have created scaffold-based multivalent Man9 clusters and found that the galactose-scaffolded bi-, tri-, and tetra-valent Man9 clusters are 7-, 22-, and 73-fold more effective in binding to 2G12 than the monomeric Man9GlcNAc2Asn. The experimental data shed light on further structural optimization of epitope mimics for developing a carbohydrate-based HIV-1 vaccine.