Large-amplitude plasma wave generation with a high-intensity short-pulse beat wave

A short-pulse laser beat wave scheme for advanced particle accelerator applications is examined. A short, intense (3-ps, >10(18)-W cm(-2)) two-frequency laser pulse is produced by use of a modified chirped-pulse amplification scheme and is shown to produce relativistic plasma waves during interactions with low-density plasmas. The generation of plasma waves was observed by measurement of forward Raman scattering. Resonance was found to occur at an electron density many times that expected, owing to ponderomotive displacement of plasma within the focal region.     

Reduction of constrained mechanical systems and stability of relative equilibria

A mechanical system with perfect constraints can be described, under some mild assumptions, as a constrained Hamiltonian system(M, , H, D, W): (M, ) (thephase space) is a symplectic manifold,H (theHamiltonian) a smooth function onM, D (theconstraint submanifold) a submanifold ofM, andW (theprojection bundle) a vector sub-bundle ofT _D M, the reduced tangent bundle alongD. We prove that when these data satisfy some suitable conditions, the time evolution of the system is governed by a well defined differential equation onD. We define constrained Hamiltonian systems with symmetry, and prove a reduction theorem. Application of that theorem is illustrated on the example of a convex heavy body rolling without slipping on a horizontal plane. Two other simple examples show that constrained mechanical systems with symmetry may have an attractive (or repulsive) set of relative equilibria.     

Determination of binding affinity of enantiomers to albumin by liquid chromatography

The principles of the determination of the binding affinity constants of small molecules to albumin by liquid chromatography, using albumin as a mobile phase additive, are outlined. Chromatographic conditions for determinations of constants are presented and applied to enantiomers of tryptophan and omeprazole. The influence of albumin on the retaining properties of LiChrosorb RP-8, Phenyl Hypersil and LiChrosorb Diol was studied.     

Ion heating and thermonuclear neutron production from high-intensity subpicosecond laser pulses interacting with underdense plasmas

Thermonuclear fusion neutrons produced by D(d,n)3He reactions have been measured from the interaction of a high-intensity laser with underdense deuterium plasmas. For an input laser energy of 62 J, more than (1.0+/-0.2)x10(6) neutrons with a mean kinetic energy of (2.5+/-0.2) MeV were detected. These neutrons were observed to have an isotropic angular emission profile. By comparing these measurements with those using a secondary solid CD2 target it was determined that neutrons are produced from direct ion heating during this interaction.     

The Inception of Symplectic Geometry: the Works of Lagrange and Poisson During the Years 1808–1810

We analyse articles by Lagrange and Poisson written two 200 years ago which are the foundation of present-day symplectic and Poisson geometry.     

SEC–MS as an Approach to Isolate and Directly Identifying Small Molecular GPCR–Ligands from Complex Mixtures Without Labeling

G protein coupled receptors (GPCRs) belong to the most successful targets in drug discovery. However, the development of assays with an appropriately labeled high affinity reporter compound is laborious. In the present study an MS-based binding assay is described using the rat histamine receptor 2 (rH2) as a model GPCR system. Instead of using a purified receptor it is demonstrated that it is possible to use an unpurified receptor to extract active compounds from a solution or small mixture of compounds. By using SEC it is possible to separate the bound ligand from the unbound ligand. The major advantage of this approach is that there is no labeling of ligands required (direct monitoring based on the appropriate m/z values).     

The Schouten-Nijenhuis bracket and interior products

The main properties of the Schouten-Nijenhuis bracket are reviewed and a new formula is proven, which relates that bracket with the right interior product of multivectors by one-forms.     

Cellulases as chiral selectors

Cellulases are powerful chiral selectors especially for the separation of basic drugs. They have found applications both in liquid chromatography and capillary electrophoresis. Cellulases, which are produced in large amounts, are well characterised and thus useful for fundamental studies of the chiral recognition mechanism using, for instance, computer graphics.

In this article, some guidelines and procedures are given for the optimisation of enantioselective separations by the mobile phase composition (e.g. pH, charged and uncharged organic modifiers). The influence of solute structure on the enantioselectivity obtained on the cellulase phase is also discussed.     

Solvent extraction of tricyclic amines from blood plasma and liquid chromatographic determination

The extraction of seven tricyclic antidepressant amines from human plasma at different pH values was investigated for dichloromethane, diethyl ether and hexane--1-pentanol (95:5). The amines were extracted as bases and back-extracted to sulphuric acid, 0.10 mol/l, prior to the separation by bonded-phase liquid chromatography. Ether and hexane--1-pentanol (95:5) were most suitable, tertiary amines being best extracted at pH 8, and secondary amines at pH 10. Using ether, both while 15 min ws sufficient for hexane--1-pentanol (95:5). UV detection allowed concentrations down to 10 ng in 1 ml of plasma to be determined. Three ammonium ions--octylammonium, dimethylammonium, and trimethylammonium--were added as modifiers to the mobile phase containing acetonitrile in phosphoric acid, 0.10 mol/l. In the concentration interval 0.010--0.030 mol/l all of the amine modifiers gave on Polygosil C8 peak asymmetry factors of sufficiently low magnitude, while on Li-Chrosorb RP-18 this was so only for di- and trimethylammonium in a concentration of 0.030 mol/l.