Vibrational analysis of isopropyl nitrate and isobutyl nitrate

Raman and infrared spectra of isopropyl nitrate and isobutyl nitrate are reported. These spectra are used in combination with computational studies employing density functional theory at the B3-LYP/6-31G* level to assign the vibrational transitions to their corresponding normal coordinates. Similar to other alkyl nitrates, the frequency of the NO2 symmetric stretch remains relatively unchanged while the asymmetric stretch shifts to lower frequency with increasing alpha-carbon substitution. The mode assignments involving the photochemically relevant -ONO2 chromophore agree well with those from previous infrared work. Raman depolarization ratios are also presented, and provide evidence that the condensed phase, ground-state molecular structure of isobutyl nitrate is of Cs symmetry. In contrast, the minimum energy structure of isopropyl nitrate is predicted to contain a pronounced twist around the C-O bond relative to the Cs-symmetry structure that lies 2.6 kcal/mol higher in energy. Infrared intensities of isopropyl nitrate are consistent with the twisted geometry, demonstrating that this conformer is favored in solution.     

Differential branching fraction and angular analysis of the decay B0 → K*0 μ+ μ-

The angular distributions and the partial branching fraction of the decay B0 → K*0 μ+ μ- are studied by using an integrated luminosity of 0.37 fb(-1) of data collected with the LHCb detector. The forward-backward asymmetry of the muons, A(FB), the fraction of longitudinal polarization, F(L), and the partial branching fraction dB/dq2 are determined as a function of the dimuon invariant mass. The measurements are in good agreement with the standard model predictions and are the most precise to date. In the dimuon invariant mass squared range 1.00-6.00 GeV2/c4, the results are A(FB)=-0.06(-0.14)(+0.13)±0.04, F(L)=0.55±0.10±0.03, and dB/dq2=(0.42±0.06±0.03)×10(-7) c4/GeV2. In each case, the first error is statistical and the second systematic.     

Measurement of the CP-violating phase ϕ(s) in the decay B(s)(0) → J/ψϕ

We present a measurement of the time-dependent CP-violating asymmetry in B(s)(0) → J/ψ? decays, using data collected with the LHCb detector at the LHC. The decay time distribution of B(s)(0) → J/ψ? is characterized by the decay widths Γ(H) and Γ(L) of the heavy and light mass eigenstates, respectively, of the B(s)(0) - B(s)(0) system and by a CP-violating phase ?(s). In a sample of about 8500 B(s)(0) → J/ψ? events isolated from 0.37 fb(-1) of pp collisions at sqrt[s] = 7 TeV, we measure ?(s) = 0.15 ± 0.18(stat) ± 0.06(syst) rad. We also find an average B(s)(0) decay width Γ(s) ≡ (Γ(L) + Γ(H))/2 = 0.657 ± 0.009(stat) ± 0.008(syst) ps(-1) and a decay width difference ΔΓ(s) ≡ Γ(L) - Γ(H) = 0.123 ± 0.029(stat) ± 0.011(syst) ps(-1). Our measurement is insensitive to the transformation (?(s),ΔΓ(s)) ? (π - ?(s), -ΔΓ(s)).     

Observation of B(s)(0) → J/ψf(2)'(1525) in J/ψK+ K- final states

The decay B(s)(0) → J/ψK+ K- is investigated using 0.16 fb(-1) of data collected with the LHCb detector using 7 TeV pp collisions. Although the J/ψ? channel is well known, final states at higher K+ K- masses have not previously been studied. In the K+ K- mass spectrum we observe a significant signal in the f(2)'(1525) region as well as a nonresonant component. After subtracting the nonresonant component, we find B(B(s)(0) → J/ψf(2)'(1525))/B(B(s)(0) → J/ψ?) = (26.4 ± 2.7 ± 2.4)%.     

First observation of the decays B(0) → D(+)K(-)π(+)π(-) and B(-) → D(0)K(-)π(+)π(-)

First observations of the Cabibbo-suppressed decays B(0) → D(+)K(-)π(+)π(-) and B(-) → D(0)K(-)π(+)π(-) are reported using 35 pb(-1) of data collected with the LHCb detector. Their branching fractions are measured with respect to the corresponding Cabibbo-favored decays, from which we obtain B(B(0) → D(+)K(-)π(+)π(-))/B(B(0) → D(+)π(-)π(+)π(-))=(5.9±1.1±0.5)×10(-2) and B(B(-) → D(0)K(-)π(+)π(-))/B(B(-) → D(0)π(-)π(+)π(-))=(9.4±1.3±0.9)×10(-2), where the uncertainties are statistical and systematic, respectively. The B(-) → D(0)K(-)π(+)π(-) decay is particularly interesting, as it can be used in a similar way to B(-) → D(0)K(-) to measure the Cabibbo-Kobayashi-Maskawa phase γ.     

Experimental Control of Turbulent Boundary Layers with In-plane Travelling Waves

The experimental control of turbulent boundary layers using streamwise travelling waves of spanwise wall velocity, produced using a novel active surface, is outlined in this paper. The innovative surface comprises a pneumatically actuated compliant structure based on the kagome lattice geometry, supporting a pre-tensioned membrane skin. Careful design of the structure enables waves of variable length and speed to be produced in the flat surface in a robust and repeatable way, at frequencies and amplitudes known to have a favourable influence on the boundary layer. Two surfaces were developed, a preliminary module extending 152 mm in the streamwise direction, and a longer one with a fetch of 2.9 m so that the boundary layer can adjust to the new surface condition imposed by the forcing. With a shorter, 1.5 m portion of the surface actuated, generating an upstream-travelling wave, a drag reduction of 21.5% was recorded in the boundary layer with Re _τ =?1125. At the same flow conditions, a downstream-travelling produced a much smaller drag reduction of 2.6%, agreeing with the observed trends in current simulations. The drag reduction was determined with constant temperature hot-wire measurements of the mean velocity gradient in the viscous sublayer, while simultaneous laser Doppler vibrometer measurements of the surface recorded the wall motion. Despite the mechanics of the dynamic surface resulting in some out-of-plane motion (which is small in comparison to the in-plane streamwise movement), the positive drag reduction results are encouraging for future investigations at higher Reynolds numbers.     

The formation and structure of phenylcamphoric acid and related compounds

The complete structure and stereochemistry of (+)-phenylcamphoric acid has been determined. The acid obtained from the Friedel-Crafts reaction of benzene with isolauronolic acid is identified as (±)-phenylcamphoric acid, α-Campholytic acid is shown to be a likely precursor of phenylcamphoric acid in these reactions. The Friedel-Crafts reaction of 3-cyano-1,2,2-trimethylcyclopentanecarbonyl chloride or 3-cyano-2,2-dimethyl-1-methylenecyclopentane with benzene provides a mixture of phenylcamphornitrile and an isomer. Isofenchocamphoric anhydride similarly provides a mixture of the epimeric 4-phenyl-2,2,4-trimethylcyclopentanecarboxylic acids.