Gas chromatography on 10 um silica particles

Summary Porous silica microparticles designed for modern liquid chromatography have proven effective in gas chromatography. Columns of 35–50 cm gave plate heights as low as 3.3 particle diameters and speeds of 2400 theoretical plates per second or 500 effective theoretical plates per second. Inlet pressures up to 70 atmospheres were required using hydrogen as carrier gas. The particles as received were too retentive for fast chromatography and gave asymmetric peaks. A coating of fluorosilicone oil overcame both problems. Other coatings were less effective. Bonded phases proved less satisfactory on both counts and also gave substantially less efficient columns and greater flow resistance. Column efficiency and flow resistance were sharply dependent on physical properties of the particles. The most efficient packing was clearly spherical particles of 5–10 μm diameter with narrow size distribution, pore diamters about 50 nm, BET surface areas of 25–50 m²/g and surfaces modified with trifluoropropyl silicone. A six-component hydrocarbon sample was separated in 33 s with a resolution of 4 for the most difficult pair and in 2.6 s with a minimal resolution. Performance was limited by end effects and by available pressure so that much better performance can be expected from longer columns and higher pressures.     

Measurements of branching fractions, polarizations, and direct CP-violation asymmetries in B-->rhoK* and B-->f0(980)K* decays

We report searches for B-meson decays to the charmless final states rhoK* and f0(980)K* with a sample of 232x10(6) BB pairs collected with the BABAR detector at the PEP-II e+e- collider. We measure in units of 10(-6) the following branching fractions, where the first error quoted is statistical and the second systematic, or upper limits are given at the 90% confidence level: B(B+-->rho0K*+)<6.1, B(B+-->rho+K*0)=9.6+/-1.7+/-1.5, B(B0-->rho-K*+)<12.0, B(B0-->rho0K*0)=5.6+/-0.9+/-1.3, B(B+-->f0(980)K*+)=5.2+/-1.2+/-0.5, and B(B0-->f0(980)K*0)<4.3. For the significant modes, we also measure the fraction of longitudinal polarization and the charge asymmetry: fL(B+-->rho+K*0)=0.52+/-0.10+/-0.04, fL(B0-->rho0K*0)=0.57+/-0.09+/-0.08, ACP(B+-->rho+K*0)=-0.01+/-0.16+/-0.02, ACP(B0-->rho0K*0)=0.09+/-0.19+/-0.02, and ACP(B+-->f0(980)K*+)=-0.34+/-0.21+/-0.03.     

Measurement of branching fractions and charge asymmetries in B decays to an eta meson and a K* meson

We present measurements of branching fractions and charge asymmetries for the decays B-->etaK*, where K* indicates a spin 0, 1, or 2 Kpi system. The data sample corresponds to 344x10(6) BB pairs collected with the BABAR detector at the PEP-II asymmetric-energy e+ e- collider at SLAC. We measure the branching fractions (in units of 10(-6): B(B0-->etaK*0(892))=16.5+/-1.1+/-0.8, B(B+-->etaK*+(892))=18.9+/-1.8+/-1.3, B(B0-->eta(Kpi)0*0)=11.0+/-1.6+/-1.5, B(B+-->eta(Kpi)0*+)=18.2+/-2.6+/-2.6, B(B0-->etaK2*0(1430))=9.6+/-1.8+/-1.1, and B(B+-->etaK2*+(1430))=9.1+/-2.7+/-1.4. We also determine the charge asymmetries for all decay modes.     

Probing internal transport barriers with heat pulses in JET

The first electron temperature modulation experiments in plasmas characterized by strong and long-lasting electron and ion internal transport barriers (ITB) have been performed in JET using ion cyclotron resonance heating in mode conversion scheme. The ITB is shown to be a well localized narrow layer with low heat diffusivity, characterized by subcritical transport and loss of stiffness. In addition, results from cold pulse propagation experiments suggest a second order transition process for ITB formation.     

Viscosities of carrier gases at gas chromatograph temperatures and pressures

Summary Equations are derived for viscosities of H₂, He, N₂ and Ar for use at chromatographic temperatures which are accurate to within 0.3% for H₂, and 0.1% for the other gases. The effect of pressure is usually negligible but may increase the viscosity of N₂ or Ar by as much as 0.5% at 25°C or lower and 5 atm or higher.     

NMR investigation into the dynamic behaviour of a novel C2-symmetric macrocyclic ligand

The variable-temperature (1)H NMR spectra of a tosylated triazacyclononane are reported. The spectra show a dynamic process which is assigned to hindered rotation about the amide-like N--S bonds, and a value for the free energy of activation for the rotations is derived, DeltaG* = 50.2 kJ mol(-1) at 273 K. Steric and electronic factors which influence the barrier are discussed.     

Measurement of the branching fraction and polarization for the decay B--->D*0K*-

We present a study of the decay B--->D(*0)K(*-) based on a sample of 86 x 10(6) Upsilon(4S)-->BBmacr; decays collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We measure the branching fraction B(B--->D(*0)K(*-))=(8.3+/-1.1(stat)+/-1.0(syst)) x 10(-4), and the fraction of longitudinal polarization in this decay to be Gamma(L)/Gamma=0.86+/-0.06(stat)+/-0.03(syst).