Effective Rheology of Bubbles Moving in a Capillary Tube

We calculate the average volumetric flux versus pressure drop of bubbles moving in a single capillary tube with varying diameter, finding a square-root relation from mapping the flow equations onto that of a driven overdamped pendulum. The calculation is based on a derivation of the equation of motion of a bubble train from considering the capillary forces and the entropy production associated with the viscous flow. We also calculate the configurational probability of the positions of the bubbles.Comment: 4 pages, 1 figur

Human Antimicrobial Peptide LL-37 Inhibits Adhesion of Candida albicans by Interacting with Yeast Cell-Wall Carbohydrates

Candida albicans is the major fungal pathogen of humans. Fungal adhesion to host cells is the first step of mucosal infiltration. Antimicrobial peptides play important roles in the initial mucosal defense against C. albicans infection. LL-37 is the only member of the human cathelicidin family of antimicrobial peptides and is commonly expressed in various tissues and cells, including epithelial cells of both the oral cavity and urogenital tract. We found that, at sufficiently low concentrations that do not kill the fungus, LL-37 was still able to reduce C. albicans infectivity by inhibiting C. albicans adhesion to plastic surfaces, oral epidermoid OECM-1 cells, and urinary bladders of female BALB/c mice. Moreover, LL-37-treated C. albicans floating cells that did not adhere to the underlying substratum aggregated as a consequence of LL-37 bound to the cell surfaces. According to the results of a competition assay, the inhibitory effects of LL-37 on cell adhesion and aggregation were mediated by its preferential binding to mannan, the main component of the C. albicans cell wall, and partially by its ability to bind chitin or glucan, which underlie the mannan layer. Therefore, targeting of cell-wall carbohydrates by LL-37 provides a new strategy to prevent C. albicans infection, and LL-37 is a useful, new tool to screen for other C. albicans components involved in adhesion

Alignment of the ALICE Inner Tracking System with cosmic-ray tracks

37 pages, 15 figures, revised version, accepted by JINSTALICE (A Large Ion Collider Experiment) is the LHC (Large Hadron Collider) experiment devoted to investigating the strongly interacting matter created in nucleus-nucleus collisions at the LHC energies. The ALICE ITS, Inner Tracking System, consists of six cylindrical layers of silicon detectors with three different technologies; in the outward direction: two layers of pixel detectors, two layers each of drift, and strip detectors. The number of parameters to be determined in the spatial alignment of the 2198 sensor modules of the ITS is about 13,000. The target alignment precision is well below 10 micron in some cases (pixels). The sources of alignment information include survey measurements, and the reconstructed tracks from cosmic rays and from proton-proton collisions. The main track-based alignment method uses the Millepede global approach. An iterative local method was developed and used as well. We present the results obtained for the ITS alignment using about 10^5 charged tracks from cosmic rays that have been collected during summer 2008, with the ALICE solenoidal magnet switched off.Peer reviewe

Particle identification in ALICE : a Bayesian approach

Peer reviewe

Flow Dominance and Factorization of Transverse Momentum Correlations in Pb-Pb Collisions at the LHC

We present the first measurement of the two-particle transverse momentum differential correlation function, P2≡ ΔpTΔpT/ pT2, in Pb-Pb collisions at sNN=2.76 TeV. Results for P2 are reported as a function of the relative pseudorapidity (Δη) and azimuthal angle (Δφ) between two particles for different collision centralities. The Δφ dependence is found to be largely independent of Δη for |Δη|≥0.9. In the 5% most central Pb-Pb collisions, the two-particle transverse momentum correlation function exhibits a clear double-hump structure around Δφ=π (i.e., on the away side), which is not observed in number correlations in the same centrality range, and thus provides an indication of the dominance of triangular flow in this collision centrality. Fourier decompositions of P2, studied as a function of the collision centrality, show that correlations at |Δη|≥0.9 can be well reproduced by a flow ansatz based on the notion that measured transverse momentum correlations are strictly determined by the collective motion of the system

K*(892)(0) and phi(1020)meson production at high transverse momentum in pp and Pb-Pb collisions at root sNN=2.76 TeV

The production of K∗(892)0 and φ(1020) mesons in proton-proton (pp) and lead-lead (Pb-Pb) collisions at √sNN = 2.76 TeV has been analyzed using a high luminosity data sample accumulated in 2011 with the ALICE detector at the Large Hadron Collider (LHC). Transverse momentum (pT) spectra have been measured for K∗(892)0 and φ(1020) mesons via their hadronic decay channels for pT up to 20 GeV/c. The measurements in pp collisions have been compared to model calculations and used to determine the nuclear modification factor and particle ratios. The K∗(892)0/K ratio exhibits significant reduction from pp to central Pb-Pb collisions, consistent with the suppression of the K∗(892)0 yield at low pT due to rescattering of its decay products in the hadronic phase. In central Pb-Pb collisions the pT dependent φ(1020)/π and K∗(892)0/π ratios show an enhancement over pp collisions for pT ≈ 3 GeV/c, consistent with previous observations of strong radial flow. At high pT, particle ratios in Pb-Pb collisions are similar to those measured in pp collisions. In central Pb-Pb collisions, the production of K∗(892)0 and φ(1020) mesons is suppressed for pT > 8 GeV/c. This suppression is similar to that of charged pions, kaons, and protons, indicating that the suppression does not depend on particle mass or flavor in the light quark sector

清涼飮料税論

The production of J/\).psi\) and $\psi(2S)$ was measured with the ALICE detector in Pb-Pb collisions at the LHC. The measurement was performed at forward rapidity 2.5 < y < 4 \() down to zero transverse momentum \(p_{\rm T} in the dimuon decay channel. Inclusive J/\).psi\) yields were extracted in different centrality classes and the centrality dependence of the average $p_{\rm T}$ is presented. The J/\).psi\) suppression, quantified with the nuclear modification factor $R_{\rm AA}$ , was studied as a function of centrality, transverse momentum and rapidity. Comparisons with similar measurements at lower collision energy and theoretical models indicate that the J/\).psi\) production is the result of an interplay between color screening and recombination mechanisms in a deconfined partonic medium, or at its hadronization. Results on the $\psi(2S)$ suppression are provided via the ratio of $\psi(2S)$ over J/\).psi\) measured in pp and Pb-Pb collisions