Regional distribution of manganese,iron, copper,and zinc in the rat brain during development

Manganese (Mn), iron (Fe), copper (Cu), and zinc (Zn) concentrations were determined in the brain regions of normal 1-, 3-, 5-, 7-, 14-, 21-, 42-, 77-, and 147-day-old Wistar rats using inductively coupled plasma mass spectrometry (ICP-MS), and their maps were illustrated in color to visually compare the distribution of the elements at various stages of the growth process. Sagittal slices (1-mm thickness) sectioned at the level of the substantia nigra were divided into 18 regions, and the small slice samples were digested in microwave-assisted closed vessels for ICP-MS measurement. Mn, Fe, Cu, and Zn concentrations increased region-specifically with age, and their distributional maps showed some characteristics. These findings are discussed in terms of needs for these trace elements in the normal brain. Among new findings about their brain distribution, it is especially noteworthy that higher concentrations of Mn, Fe, and Zn were observed in the substantia nigra compared with those in neighboring regions. The mapping method in this work is expected to open up possibilities for screening of the in vivo element–element interrelationships among these essential elements.     

13C-NMR studies on the cevanine alkaloids : the application of 13C-NMR spectrum for structure elucidation of new alkaloids,baimonidine and isoverticine

The ¹³C-NMR spectra of seven cavanine alkaloids isolated from Veratrum and Fritillaria plants were measured and their signals were assigned, and these results were applicated for structure elucidation of two new cevanine alkaloids, baimonidine and isoverticine, isolated from mature Fritillaria verticillata.     

Stereoselective ring-opening polymerization of racemic lactide using aluminum-achiral ligand complexes: exploration of a chain-end control mechanism

Stereoselective polymerization of racemic lactide (rac-LA) was examined using Al-achiral ligand complexes. By introduction of substituents in aromatic rings of Schiff base ligands, a higher selectivity was obtained without any chiral auxiliaries in the catalyst via a chain-end control mechanism. The T(m) values (T(m) 170-192 degrees C) were comparable to or higher than that of homochiral polymer, poly(L-LA) (T(m) 162 degrees C), and a thermally more stable polylactide than poly(L-LA) was prepared from rac-LA.     

Preparation and thermosensitivity of naturally occurring polypeptide poly(gamma-glutamic acid) derivatives modified by propyl groups

Poly(gamma-glutamic acid) (gamma-PGA) is a biosynthetic polymer, and the carboxyl groups are able to undergo a chemical modification. In this study, poly(alpha-propyl gamma-glutamate) (gamma-PGA propylate) was synthesized by the esterification of these carboxyl groups to yield a thermosensitive and biodegradable polymer. In aqueous solution, the gamma-PGA propylate can impart thermosensitivity by controlling the hydrophobic-hydrophilic balance of the gamma-PGA polymeric chains.     

Modeling the adsorption of U(VI) onto animal chitin using coupled mass transfer and surface complexation

This paper reports the development of a treatment system, using animal chitin as a passive biosorbent, for removing U(VI) from aqueous waste streams. An integral part of this system is a model that provides for the optimization of the treatment system through simulation of U(VI) removal efficiency based on the characteristics of the influent waste stream. The model accounts for changing solution matrix conditions through the coupling of surface complexation and mass transfer models. Complexation of U(VI) by chitin surface sites was modeled using FITEQL. Application of FITEQL in the “forward” mode provided the sorbed and aqueous phase concentrations needed for the mass transfer model. The mass transfer model was derived for both batch and continuously stirred tank reactor (CSTR) configurations using Fick's Law, reactor mass balances and rate law expressions. The coupled model was successfully validated using CSTR data at pH 6.5 and rate constants determined from batch sorption experiments. The CSTR configuration yields a steady-state, eighty percent U(VI) removal for 1 μM influent U(VI) with a solution-phase pH of 6.5 and 3.9 g l⁻¹ chitin.     

Isotone solutions of parametric linear complementarity problems

The parametric linear complementarity problem is given by the conditions:q + p + Mz 0, 0,z 0,z ^T (q + p + Mz) = 0. Under the assumption thatM is a P-matrix, Cottle proved that the solution mapz() of the above problem is montonically nondecreasing in the parameter for every nonnegativeq and everyp if and only ifM is a Minkowski matrix. This paper examines whether a similar result holds in various other settings including a nonlinear case.     

A practical synthesis of 4′-thioribonucleosides

A practical synthesis of 4′-thioribonucleosides starting from inexpensive l-arabinose is described. 1,4-Anhydro-2,3-O-isopropylidene-4-thioribitol, which was prepared by using a novel reductive ring-contraction reaction, was converted to the 5-O-silylated sulfoxides. The Pummerer-type thioglycosylation of the sulfoxides gave the 4′-thioribonucleosides stereoselectively.     

Affinity transformation from hydrophilicity to hydrophobicity of water molecules on the basis of adsorption of water in graphitic nanopores

The interaction of water with hydrophobic surfaces is quite important in a variety of chemical and biochemical phenomena. The coexistence of water and oil can be realized by introduction of surfactants. In the case of water vapor adsorption on graphitic nanopores, plenty of water can be adsorbed in graphitic nanopores without surfactants, although the graphitic surface is not hydrophilic. Why are water molecules adsorbed in hydrophobic nanopores remarkably? This work can give an explicit insight to water adsorption in hydrophobic graphite nanopores using experimental and theoretical approaches. Water molecules are associated with each other to form the cluster of 1 nm in size, leading to a significant stabilization of the cluster in the graphitic nanopores. This mechanism can be widely applied to interfacial phenomena relating to coexistence of water and nanostructural materials of hydrophobicity.     

Micropore Filling of Supercritical Xe in Micropores of Activated Carbon Fibers

The adsorption isotherms of Xe vapor at 196 K and supercritical Xe at 300 K on activated carbon fibers of different pore widths were gravimetrically measured. The adsorption isotherms of Xe vapor were compared with the N(2) adsorption isotherms. A Dubinin-Radushkevich (DR) plot of the adsorption isotherms of Xe vapor showed a good linearity, indicating that Xe vapor is adsorbed by the representative micropore filling mechanism. The adsorption isotherms of supercritical Xe were approximated by the Langmuir equation. The saturated adsorption amounts of supercritical Xe, W(L), were in the range of 0.14 to 0.22 ml g(-1). The adsorption isotherms of supercritical Xe were described by the supercritical DR equation, which provides the quasisaturated vapor pressure P(0q). Both P(0q) and W(L) lead to the reduced isotherm, which can describe three isotherms. The obtained reduced isotherm derived from the isotherms of supercritical Xe could describe even those of Xe vapor. Hence, both Xe vapor and supercritical Xe should be adsorbed by the same mechanism. The isosteric heat of Xe adsorption was greater than the enthalpy of vaporization of Xe by more than 12 kJ mol(-1). These results suggest that Xe molecules are stabilized in the form of a cluster in micropores even at 300 K. Copyright 2000 Academic Press.