356 research outputs found
Searching for the B0d,s → ∅π+ π- decays
No full textUsing 3 fb-1 of pp collision data collected at √s = 7 and 8 TeV by the LHCb
experiment in the 2011 and 2012 data taking periods, the decays B⁰s → ϕπ+π-
and B⁰d → ϕπ+π- have been studied in the π+π- invariant mass range below
1600 MeV/c². The B⁰s,d → ϕπ+π- branching fractions are determined to be:
B(B⁰s → ϕπ+π-;mππ < 1600) = [3:72 ± 0:18 ± 0:38 ± 0:38] x 10-6
B(B⁰d → ϕπ+π-,mππ < 1600) = [1:75 ± 0:25 ± 0:42 ± 0:14] x 10-7
where the first uncertainty is statistical, the second is systematic, and the third
comes from the normalisation mode B⁰s → ϕϕ. From the π+π- mass distribution
and fits to angular distributions, the resonant decay mode B⁰s → ϕf₀(980) is observed and the branching fraction is measured to be:
B(B⁰s → ϕf₀(980); f₀(980) → π+π-) = [1:23 ± 0:15 ± 0:12 ± 0:12] x 10-6
The fit also requires contributions from B⁰s → ϕf2(1270). A search for a P-wave contribution from B⁰s → ϕρ⁰(770) finds evidence at ~ 4σ but confirmation will require more data. An upper limit of the B⁰s → ϕρ⁰(770) decay branching fraction
at 90% C.L. is measured to be:
B(B⁰s → ϕρ⁰(770)) < 4 x 10-
Characteristics and magnetic field properties of the Hamamatsu R11265 Multi-Anode Photomultiplier Tubes
No full text<b>Telomere-to-telomere genome of the allotetraploid legume</b><b> </b><b><i>Sesbania cannabina</i></b><b><i> </i></b><b>reveals transposon-driven subgenome divergence and mechanisms of alkaline stress tolerance</b>
No full textTelomere-to-telomere genome of the allotetraploid legume Sesbania cannabina reveals transposon-driven subgenome divergence and mechanisms of alkaline stress tolerance</p
On the initial configurations of collapsible channel flow
No full textThis paper studies the effect of the initial configurations of the governing equations on flows in a collapsible channel where the upper elastic wall is replaced by a pre-stretched beam. The aim is to check the existence of a “tongue” shaped neutral stability curve in the Reynolds number–tension space from a fluid-beam model [Luo XY, Cai ZX. Effects of wall stiffness on the linear stability of flow in an elastic channel. In: de Langre E, Axisa F, editors. Proceedings of the eighth international conference on flow-induced vibrations, FIV2004, vol. II. Paris, France: 2004. p. 167–70], in a properly formulated initial strain configuration. It was found that, for a given Reynolds number, as the tension is lowered to a critical value, the system becomes unstable, which is to be expected. However, a further decrease of the tension re-stabilizes the system before it becomes unstable again. It was possible that this puzzling finding was an artefact since the elastic equations used in the model were not properly derived from the zero initial stress configuration (Ogden, private communication). To check this, in this paper, a range of steady solutions are studied with both zero and non-zero initial wall tension. These are compared with the results using the finite element package Adina 8.3 using both the initial strain and initial stress configurations. As expected, the fluid-beam model agrees with Adina when using the initial stress configuration, but not when using the initial strain configuration. For cases with a small initial tension or small deformation (very large initial tension), both initial stress and initial strain configurations lead to very similar results, however, when the initial tension is comparable with the stretching induced tension, there are obvious differences in these two configurations. The “tongue” stability curve is then re-calculated with a zero initial tension, and re-plotted in the Reynolds number–effective tension space. It is interesting to see that though slightly different in shape, the “tongue” stable zone appears again when the zero initial tension is used. Thus it is highly likely that the puzzling “tongue” in the neutral stability curve is not due to the modelling approximation, but indicating a real, interesting physical phenomenon
Do-It-Yourself Transfer of Large-Area Graphene Using an Office Laminator and Water
No full textWe demonstrate a simple method for transferring large areas (up to A4-size sheets) of CVD graphene from copper foils onto a target substrate using a commercially available polyvinyl alcohol polymer foil as a carrier substrate and commercial hot-roll office laminator. Through the use of terahertz time-domain spectroscopy and Raman spectroscopy, large-area quantitative optical contrast mapping, and the fabrication and electrical characterization of ∼50 individual centimeter-scale van der Pauw field effect devices, we show a nondestructive technique to transfer large-area graphene with low residual doping that is scalable, economical, reproducible, and easy to use and that results in less doping and transfer-induced damage than etching or electrochemical delamination transfers. We show that the copper substrate can be used multiple times with minimal loss of material and no observable reduction in graphene quality. We have additionally demonstrated the transfer of multilayer hexagonal boron nitride from copper and iron foils. Finally, we note that this approach allows graphene to be supplied on stand-alone polymer supports by CVD graphene manufacturers to end users, with the only equipment and consumables required to transfer graphene onto target substrates being a commercial office laminator and water.</p
Numerical simulation of the instabilities of a 2D collapsible channel flow
No full textCollapsible channel flows that originated from physiological applications have many intriguing dynamic system behaviours. In this thesis, the stability of a two-dimensional collapsible channel flow is studied numerically. Three approaches are adopted to investigate the fluid-structure interaction problem: an in-house Finite Element Method (FE) based Fluid-Beam model (FBM), a commercial FE based code, ADINA, and an eigensolver derived from the FBM (linear analysis). Two types of inlet boundary conditions are considered. One is the flow-driven system where the inlet flow rate is specified, and the other is the pressure-driven where the pressure drop is given. It turns out that these two systems yield very different dynamical features even though the steady solutions are the same. For the flow-driven system, a range of steady solutions are studied with both zero and non-zero initial wall tension by means of both FBM (using initial stress configuration) and ADINA (equipped with both initial strain and initial stress configurations). As expected, the FBM agrees with ADINA when using the initial stress configuration, but not when the initial strain configuration is adopted. This established the importance of the initial configuration. The effects of different wall thicknesses on the steady wall performance have also been shown as significant. Fully-coupled unsteady simulations have also been performed with FBM (Bernoulli-Euler beam) and ADINA (Timoshenko beam) to demonstrate significant influences of modelling assumptions on the dynamical behaviour. In addition to unsteady simulations, linear stability analysis is also carried out to identify the critical parameter values that occur when the system is in the neutrally stable state. Using the faster Fourier transform, the unsteady results are then compared with the linear stability analysis results. Excellent agreements are achieved in terms of frequencies of modes of instabilities. Finally, we focus on the dynamical behaviour of collapsible channel flows in a pressure-driven system, and the differences with those of the flow-driven system (Luo et al. 2008). It is found that the stability structure for the pressure-driven system is no longer cascade as in the flow-driven case. Instead, the mode-1 instability is the dominating unstable mode in the pressure-driven system. In the pressure drop and wall stiffness space, neutrally stable mode-2 curve is completely enclosed by the mode-1 neutral curve, and there is no purely mode-2 unstable solution in the parameter space investigated. Interesting mode-switch is also observed. By analysing the energy budgets at the neutral stable points, we confirmed that in the high tension region (on the upper branch of the mode-1 neutral curve), the stability mechanism is the same as that of Jensen & Heil (2003). Namely, self-excited oscillations can grow by extracting kinetic energy from the mean flow, with exactly two thirds of the net kinetic energy flux dissipated by the dissipations and the remainder balanced by increased dissipation in the mean flow. However, the mechanism doesn’t apply for the lower branch of the mode-1 neutral curve. In addition, energy balance changes further for the mode-2 curves in the flow-driven system. It is clear that different mechanisms are operating in different regions of the parameter space, and for different boundary conditions
Focal length modulation based on a metallic slit surrounded with grooves in curved depths
No full textSystematic Reconstruction of Molecular Cascades Regulating GP Development Using Single-Cell RNA-Seq
No full textSummaryThe growth plate (GP) comprising sequentially differentiated cell layers is a critical structure for bone elongation and regeneration. Although several key regulators in GP development have been identified using genetic perturbation, systematic understanding is still limited. Here, we used single-cell RNA-sequencing (RNA-seq) to determine the gene expression profiles of 217 single cells from GPs and developed a bioinformatics pipeline named Sinova to de novo reconstruct physiological GP development in both temporal and spatial high resolution. Our unsupervised model not only confirmed prior knowledge, but also enabled the systematic discovery of genes, potential signal pathways, and surface markers CD9/CD200 to precisely depict development. Sinova further identified the effective combination of transcriptional factors (TFs) that regulates GP maturation, and the result was validated using an in vitro EGFP-Col10a screening system. Our case systematically reconstructed molecular cascades in GP development through single-cell profiling, and the bioinformatics pipeline is applicable to other developmental processes.Video Abstrac
Characterisation and magnetic field properties of multianode photomultiplier tubes
No full textWe report on studies of the Hamamatsu model R11265 Multianode Photomultiplier as part of the effort to qualify their use in the upgrade of the LHCb Ring Imaging Cherenkov Detectors. Comparisons with the known model R7600 are also made. Of particular interest is the behaviour of the MaPMT in magnetic fields comparable to the residual fringe field of the LHCb bending magnet ranging up to 25 Gauss
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