Preparation and application of monolithic beds in the separation of selected natural biologically important compounds

The importance of monolithic (continuous) beds is connected with their easy preparation and the far-reaching possibilities of modification of their surface and porous properties. These properties make them particularly attractive for the analysis of biologically important compounds characterized by a wide spectrum of physicochemical properties. This review summarizes their preparation methods as well as their application as continuous beds for determination of such biologically important compounds as catecholamines, vitamins, flavonoids, amino acids, peptides, and proteins.     

The effective sky temperature: an enigmatic concept

To properly simulate the condensation process and design a water recovery system from condensation of atmospheric water vapour on a surface maintained below the dew point by radiative heat loss from the surface to night sky, an accurate estimation of the effective sky temperature is required. To estimate the effective night sky temperature, an experimental system consisting of a series of metal plates embedded on a heat transfer panel, a weather station and a control system was used. The results obtained from theoretical analyses and preliminary experiments are presented and discussed. A special emphasis is given to a mathematical solution of the system of equations that need to be solved to obtain the effective sky temperature. It is shown that although the system of equations works well for the direct heat transfer problem, there is a serious difficulty to solve the inverse heat transfer problem to retrieve the desired parameters.     

Residual silanols at reversed-phase silica in HPLC--a contribution for a better understanding

As porous silica gel is the most common adsorbent and support for bonded stationary phase synthesis, residual silanol groups are a recurring problem in the field of liquid chromatography and other separation techniques. Residual silanols most often have a negative effect on the separation process by causing peak tailing. Therefore, there was an attempt to remove residual silanols during stationary-bonded phase synthesis. The type and surface concentration of residual silanols were measured using different instrumental techniques such as NMR and infrared spectroscopy, calorimetry, and various chromatographic methods. Residual silanols exhibit acidic characteristic and they can ionize depending on the environment. Thus, they posses cation-exchange properties and cause the zeta potential of silica particle in liquid environment. Presented review discusses the influence of the residual silanol groups on the solvation process and retention of polar compounds. The novel methodology of residual silanols determination is presented as well as the influence of the silanols on the zeta potential of the stationary-bonded phases in chromatographic conditions.     

Log-Sobolev inequalities for infinite one dimensional lattice systems

It is shown that a unique Gibbs measure of infinite spin system with short range interaction on one dimensional lattice satisfies log-Sobolev inequality.Supported by SFB 237     

The equivalence of the logarithmic Sobolev inequality and the Dobrushin-Shlosman mixing condition

Given a finite range lattice gas with a compact, continuous spin space, it is shown (cf. Theorem 1.2) that a uniform logarithmic Sobolev inequality (cf. 1.4) holds if and only if the Dobrushin-Shlosman mixing condition (cf. 1.5) holds. As a consequence of our considerations, we also show (cf. Theorems 3.2 and 3.6) that these conditions are equivalent to a statement about the uniform rate at which the associated Glauber dynamics tends to equilibrium. In this same direction, we show (cf. Theorem 3.19) that these ideas lead to a surprisingly strong large deviation principle for the occupation time distribution of the Glauber dynamics.During the period of this research, both authors were partially supported by grants DAAL 03-86-K-0171 and DMS-8913328     

Substitution electrophile du ferrocene et du dimethylferrocene par les derives carbonyles protones : II. Influence des effets stériques et conformationnels lors de la synthèse des α-ferrocénylcarbinols

In strongly acidic media ferrocene and dimethylferrocene react with carbonyl compounds to produce α-ferrocenylcarbinols. ¹H NMR studies show that the alcohols are quickly transformed into α-ferrocenylcarbenium ions which after hydrolysis afford the alcohols in high yields. In all cases mono-substitution products are only obtained. With dimethyl ferrocene the ratio of 2-isomer versus 3-isomer indicate a higher reactivity of the α position when small electrophiles are used ; on the contrary condensation of ketones occur preferentially at the β position.     

Chemistry of the μ-hydridobis[pentacarbonylchromium(0)] Species. Part II. Acidification reaction of its derivatives with hydrogen chloride

Summary The Bu₄N[Cr₂H(CO)₁₀] species reacts with hydrogen chloride in methanol to produce Bu₄N[Cr(CO)₅Cl].Analogous reactions using the complex K(phen)₃Cr₂H(CO)₁₀ and K(bpy)₂Cr₂H(CO)₁₀ salts (phen = 1,10-phenanthroline, bpy = 2,2-bipyridine) give the new (phen)₂H[Cr₂H(CO)₁₀], phenH[Cr₂H(CO)₁₀], (phenH)₂(Cl)[Cr₂H(CO)₁₀], and bpyH[Cr₂H(CO)₁₀] derivatives respectively.