Automated high-performance liquid chromatographic method with column switching for the determination of neurotransmitters and related compounds, ascorbic acid and uric acid in tissue extracts

An automated high-performance liquid chromatographic method with electrochemical and fluorimetric detection and on-line data evaluation is described for the simultaneous measurement of indoleaminergic and catecholaminergic neurotransmitters, some of their metabolites and precursors and ascorbic and uric acids. Deproteinized tissue extracts from the central nervous system or peripheral organs are injected without prior purification (recovery greater than 90%). A switching system enables the compounds to be passed as necessary through one, two or three reversed-phase columns, which are then eluted simultaneously (analysis time 25 min). Fifty samples per day can be analysed with a precision of 95% for neurotransmitters and about 90% for ascorbic and uric acids.     

Correlated strength in the nuclear spectral function

We have carried out an (e,e'p) experiment at high momentum transfer and in parallel kinematics to measure the strength of the nuclear spectral function S(k,E) at high nucleon momenta k and large removal energies E. This strength is related to the presence of short-range and tensor correlations, and was known hitherto only indirectly and with considerable uncertainty from the lack of strength in the independent-particle region. This experiment locates by direct measurement the correlated strength predicted by theory.     

Analysing the isotopic life history of the alpine ungulates Capra ibex and Rupicapra rupicapra rupicapra through their horns

The horn of ungulate grazers offers a valuable isotopic record of their diet and environment. However, there have been no reports of the spatio‐temporal variation of the isotopic composition of horns. We investigated patterns of carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopic composition along and perpendicular to the horn axis in Capra ibex and Rupicapra rupicapra rupicapra to assess the effects of animal age, within‐year (seasonal) and inter‐annual variation, natural contamination and sampling position on horn isotope composition. Horns of male C. ibex (n = 23) and R. r. rupicapra (n = 1) were sampled longitudinally on the front (only R. r. rupicapra) and back side and on the surface and sub‐surface. The sides of the R. r. rupicapra horn did not differ in δ¹³C. In both species, the horn surface had a 0.15‰ lower δ¹³C and a higher carbon‐to‐nitrogen (C/N) ratio than the sub‐surface. Washing the horn with water and organic solvents removed material that caused these differences. With age, the δ¹⁵N of C. ibex horns increased (+0.1‰ year^?1), C/N ratio increased, and ¹³C discrimination relative to atmospheric CO₂ (¹³Δ) increased slightly (+0.03‰ year^?1). Geostatistical analysis of one C. ibex horn revealed systematic patterns of inter‐annual and seasonal ¹³C changes, but ¹⁵N changed only seasonally. The work demonstrates that isotopic signals in horns are influenced by natural contamination (δ¹³C), age effects (¹³Δ and δ¹⁵N), and seasonal (δ¹³C and δ¹⁵N) and inter‐annual variation (δ¹³C). The methods presented allow us to distinguish between these effects and thus allow the use of horns as isotopic archives of the ecology of these species and their habitat. Copyright © 2009 John Wiley & Sons, Ltd.     

Interactions between Oxygen Lone-Pair Orbitals and Double-Bond π-Orbitals in β,γ-Unsaturated,Bicyclic Ketones; a PE-Spectroscopic Investigation

The HE(Iα) photoelectron (PE) spectra of 2,3,5,6-tetramethylidene-2-bicyclo[2.2.1]heptanone ( 12 ), 5,6-dimethylidene-2-bicyclo[2.2.1]heptanone ( 14 ), 5,6-dimethylidene-2-bicyclo[2.2.2]octanone ( 16 ), and 5,6,7,8-tetramethylidene-2-bicyclo[2.2.2]octanone ( 17 ) have been recorded, Comparison with the PE data of other β,γ-unsaturated ketones and parent alkenes, and with the result of ab initio STO-3G calculations, confirm the existence of significant interactions between the oxygen lone-pair orbital n_o and the double-bond π orbital(s). It is argued that the major contributions to the basis energy shifts and to the cross term between the n_o and π orbitals are due to a ‘through-bond’ mechanism.     

‘Lone Pair’ and ‘CI Bond’ Ionization Energies of exo- and endo-2-Norbornyl Iodides

A PE-spectroscopic study of exo- and endo-2-norbornyl iodides suggests that the relative ability of the 2-norbornyl group to stabilize an electron deficiency on a substituent X (e.g. I) in exo- or endo-position depends on the location of the positive charge. There is no difference if the positive hole is strongly localized on on the substituent X (e.g. the 5p^?1 state of the title compounds). On the other hand, our results indicate that teh positive hole semi-localized in an exo-C? X bond is better stabilized by the 2-norbornyl group than a semi-localized, positive hole in an endo-C? X bond.     

The extremal microscopic coherent boson states

In a recent paper, the Fock-normal (=microscopic) fully-coherent statesL _L ⁽⁾ (L denotes the factorizing linear form) have been completely characterized, and the existence of nonpure elements in the extreme boundary of the weak-*-compact, convex setL _L has been shown. This letter is devoted to an analysis of the extremal fully-coherent states, especially those which are not pure states. An affine isomorphism is constructed betweenL _L ⁽⁾ and a certain convex subset of the normal completely positive maps on the bounded operators on Fock space. Then the extreme boundary ofL _L ⁽⁾ is determined by results and techniques from the theory of completely positive operators.     

Photoelectron-Spectroscopic Characterization of 3,4-Dimethyl-2,4-hexadienes

The He(Ia) photoelectron (PE) spectra of the (E,E)-, (E,Z)- and (Z,Z)-isomers of the title compound have been recorded to obtain information about their conformation in the gas phase. For a valid correlation with the PE data of other dienes it is necessary to take the potentials V(φ) for internal rotation and the corresponding conformer population densities P (φ) into account, as well as the rather complicated way wy in which the π^?1 ionization energy gap ΔI(φ) depends on the direct π-orbital interaction and the long-range ‘through-space’ interaction between the semi-localized methyl-group orbitals and the π-orbitals. These factors being taken into account, the mean twist angles, φ , compatible with the PE-spectroscopic results are φ (E,E) ≈? O° ± 30°, φ (E,Z) ≈? 80° or 110° within ± 15°, and φ (Z,Z) ≈? 85° to 105°. These results are in rough agreement with electron diffraction data by Traetteberg [15], other spectroscopic results and, for the (E, E)- and (Z,Z)-isomers, internal rotation potentials V(φ) previously calculated by Roth [17]. On the other hand the potential V (φ) proposed for the (E,Z)-isomer does not seem to be compatible with our findings.     

High-speed photorefraction at telecommunication wavelength 1.55 microm in Sn2P2S6:Te

We demonstrated for what is the first time to our knowledge photorefractive two-wave mixing in a bulk ferroelectric crystal using cw light at the telecommunication wavelength 1.55 microm. In the Te-doped ferroelectric semiconductor Sn2P2S6 with absorption constant <0.1 cm(-1) at 1.55 microm, grating recording times of 10 ms and a two-beam coupling gain of 2.8 cm(-1) have been measured at 350 mW power (intensity 440 W/cm(2)) without a necessity to apply an external electric field. With a moving grating technique, a maximal gain of 6.0 cm(-1) has been obtained.