Distribution of lattice-strain on partly nitrogen-covered Cu(0 0 1) surfaces

In-plane elastic lattice strain on the Cu(0 0 1)-c(2 × 2)N surfaces is investigated by scanning tunneling microscopy on the surface where nitrogen-adsorbed patches with average size of 5 × 5 nm² (c(2 × 2)N patches) are well separated by wide clean Cu surface. The lattice distortion on clean Cu surface is recognized in the vicinity of the boundary to a c(2 × 2)N patch. The positions of the protrusions observed on the c(2 × 2)N patch are compared with the surrounding undistorted (1 × 1) lattice of the clean Cu surface. Most of the protrusions on the c(2 × 2)N patches locate on the fourfold hollow sites of the undistorted Cu lattice. The lattice distortion is significant only near the boundary to the surrounding clean Cu surface.     

Anomalous nuclear spin-lattice relaxation in copper small particles

Anomalously long nuclear spin-lattice relaxation time is expected in small metallic particles when the life time width of the conduction electron energy levels is smaller than their mean spacing. A new method for setting nuclear magnetization to zero is developed in order to measure the relaxation time in Cu small particles. The anomaly is observed in the relaxation of⁶³Cu in the particles with the diameters smaller than 100 A at temperatures below 0.5 K.     

The kinetics of the thermal pyridine dissociation of pyridine[N,N′-ethylenebis(salicylideneaminato)]-alkylcobalt(III) in the solid state. Kinetic trans effect of alkyl group

The thermal behavior of RCo(salen)py (R = Me, Et, nPr, iPr, n-Bu, iBu; salen = N,N′-ethylenebis(salicylideneaminate) dianion; py = pyridine) has been investigated by means of TG, DSC, and isothermal weight-loss measurements. These complexes dissociate 1 mol of pyridine per mole of complex in the temperature range 365–445 K, which is followed by the dissociation of the alkyl group. Kinetic analysis has revealed that the pyridine dissocation reactions fit the contracting disc equation. The electronic nature of the alkyl group has been found to affect the kinetic stability of the Co(III)-alkyl bonding; the more electron-donating group labilizes the Co(III)-py bonding. A linear correlation has been observed between the inductive substitution constants of alkyl groups and the pyridine-dissociation rates at 400 K.     

Preconcentration of antimony(III) from water with thionalide loaded on glass beads with the aid of collodion

2-Mercapto-N-2-naphthylacetamide (thionalide) loaded on glass beads with the aid of collodion is used for preconcentration of microgram levels of antimony(III) from aqueous solution. Antimony is quantitatively retained on the loaded beads from 0.4–0.8 mol l^?1 hydrochloric acid solutions; equilibration is achieved within 1 min. The retention capacity of the beads is 0.2 μml Sb g^?1 at 0.6 mol l^?1 hydrochloric acid. The maximum flow rate for quantitative retention is 1.27 ml min^?1 cm^?2. Antimony retained on the column is completely eluted with 10 ml of 6.0 mol l^?1 hydrochloric acid at flow rates<1.9 ml min^?1 cm^?2.     

Field desorption mass spectrometry of natural products—II: Physiologically active pennogenin—and hederagenin-glycosides

Field desorption mass spectra of underivatized saponios, naturel oligoglycosides of physiological activity, showed intense ions formed by attachment of alkali cations to the neutral molecule and to structurally highly significant subunits. This cationization was generated by small amounts of alkali salts which were present in samples after isolation from biological material. When the mass spectre were produced by laser-supported desorption and were recorded at high resolution on vapor-deposited AgBr plates unambiguous determination of the molecular weghts (in the mass range from 700 to 1400) was performed. Moreover, ions formed by direct bond cleavages in the oligosaccharide moiety of the natural saponins clearly gave information about the sequence of the sugar units in the molecule and their individual chemical structures. The formation of these fragments in FD-MS is discussed in relation to the well established mechanism of glycosidic bond cleavage by acidic solvolysis. In principle this comparison showed the usefulness of this approach for the interpretation of FD mass spectra of substances containing heteroatom linkages e.g., glycosides, esters, amides, imines, mercaptans, etc.     

Simultaneous determination of preservatives in beverages,vinegar, aqueous sauces,and quasi-drug drinks by stir-bar sorptive extraction (SBSE) and thermal desorption GC-MS

A method for the simultaneous determination of seven preservatives - sorbic acid, benzoic acid, and p-hydroxybenzoic acid ethyl, isopropyl, propyl, isobutyl, and butyl esters - in beverages, vinegar, aqueous sauces, and quasi-drug drinks has been developed using the stir-bar sorptive extraction technique then thermal desorption GC-MS analysis. The extraction conditions - pH, sample volume, extraction temperature, salt addition, and extraction time - were examined. d5-Benzoic acid and p-hydroxybenzoic acid sec-butyl ester were added as surrogate internal standards to compensate for the effect of sample matrix and coexisting analytes on the sorptive extraction. The linearity of the method was good over the concentration range from 1 to 1000 microg mL(-1) for sorbic acid, 10-1000 microg mL(-1) for benzoic acid, and 0.1-100 microg mL(-1) for p-hydroxybenzoic acid ethyl, isopropyl, propyl, isobutyl, and butyl esters, and the correlation coefficients were higher than 0.9984. The limit of detection ranged from 0.015 to 3.3 microg mL(-1). The recoveries (95-105%) and precision (RSD: 0.86-6.0%) of the method were examined by analyzing a sparkling soft drink, white wine, red wine, balsamic vinegar, soy sauce, and quasi-drug drink samples fortified at the 5 to 50 microg mL(-1) level.     

Swelling of sodium acrylate gels

The swelling process of sodium acrylate gel is experimentally investigated. It is found that sodium acrylate gels weakly crosslinked with N,N-methylene-bis-acrylamide may undergo volume phase transition and that different kinds of mechanical instabilities occur in sequence at the transition. Peculiar wrinkle patterns appear on the free surface of an unstable gel and are changed in geometry as swelling proceeds. Cellular patterns seen at various instances in the late period of swelling are ascertained to be geometrically similar to each other and different only in size. The radii of spherical acrylate gels allowed to swell in water are measured as functions of time. The results are discussed and compared with the kinetic theories of swelling. As a result, these theories are proved to be unsatisfactory to fully describe the experimental facts.