Reply to discussion by G. Carosi and H. Chanson on "Turbulence characteristics in skimming flows on stepped spillways"

A main technical issue seems to be associated with the structure of the two-phase air–water flow skimming over the pseudo-bottom formed by the step edges. This is a difficult topic. In the air–water skimming flow, the microscopic structure of the gas–liquid mixture is closely linked with the interactions between turbulent vortices and air–water entities (bubbles, droplets, packets) (e.g., Chanson and Toombes 2002; Carosi and Chanson 2008; Gonzalez and Chanson 2008). In the high-velocity free-surface flow, the strong interactions between the turbulent waters and the atmosphere lead to a complete deformation at the interface. Through the free-surface, air is continuously trapped, and the resulting air–water mixture extends through the entire flow (Rao and Kobus 1971; Wood 1991; Chanson 1997). The air–water flow is characterized a complicated two-phase turbulent motion with void fractions ranging from some small, often nonzero values close to the invert to 100% above a pseudo "free-surface" that is usually defined as the location where the void fraction equals 90% (Cain and Wood 1981; Wood 1991; Chanson 1997; Matos 2000). The notion of "effective homogenous flow" contradicts detailed measurements conducted with accurate instrumentations in large-size facilities with well-controlled flow conditions and it is obsolete. Recent findings (Carosi and Chanson 2008) demonstrated in fact a marked changed in flow properties for C ~ 0.95 to 0.97, that is consistent with earlier studies suggesting the use of Y95 or even Y98 as the characteristic air–water flow thickness (Jevdjevich and Levin 1953; Aivazyan 1986)

Noradrenaline inhibits exocytosis via the G protein βγ subunit and refilling of the readily releasable granule pool via the αi1/2 subunit.

The molecular mechanisms responsible for the ‘distal’ effect by which noradrenaline (NA) blocks exocytosis in the β-cell were examined by whole-cell and cell-attached patch clamp capacitance measurements in INS 832/13 β-cells. NA inhibited Ca2+-evoked exocytosis by reducing the number of exocytotic events, without modifying vesicle size. Fusion pore properties also were unaffected. NA-induced inhibition of exocytosis was abolished by a high level of Ca2+ influx, by intracellular application of antibodies against the G protein subunit Gβ and was mimicked by the myristoylated βγ-binding/activating peptide mSIRK. NA-induced inhibition was also abolished by treatment with BoNT/A, which cleaves the C-terminal nine amino acids of SNAP-25, and also by a SNAP-25 C-terminal-blocking peptide containing the BoNT/A cleavage site. These data indicate that inhibition of exocytosis by NA is downstream of increased [Ca2+]i and is mediated by an interaction between Gβγ and the C-terminus of SNAP-25, as is the case for inhibition of neurotransmitter release. Remarkably, in the course of this work, a novel effect of NA was discovered. NA induced a marked retardation of the rate of refilling of the readily releasable pool (RRP) of secretory granules. This retardation was specifically abolished by a Gαi1/2 blocking peptide demonstrating that the effect is mediated via activation of Gαi1 and/or Gαi2

Image resonance in the many-body density of states at a metal surface

The electronic properties of a semi-infinite metal surface without a bulk gap are studied by a formalism that is able to account for the continuous spectrum of the system. The density of states at the surface is calculated within the GW approximation of many-body perturbation theory. We demonstrate the presence of an unoccupied surface resonance peaked at the position of the first image state. The resonance encompasses the whole Rydberg series of image states and cannot be resolved into individual peaks. Its origin is the shift in spectral weight when many-body correlation effects are taken into account

Less Minimal Flavour Violation

We consider the approximate U(2)^3 flavour symmetry exhibited by the quark sector of the Standard Model and all its possible breaking terms appearing in the quark Yukawa couplings. Taking an Effective Field Theory point of view, we determine the current bounds on these parameters, assumed to control the breaking of flavour in a generic extension of the Standard Model at a reference scale Lambda. In particular, a significant bound from epsilon'/epsilon is derived, which is relevant to Minimal Flavour Violation as well. In the up-quark sector, the recently observed CP violation in D -> pi+ pi-, K+ K- decays might be accounted for in this generic framework, consistently with any other constraint.Comment: 15 pages, 1 figur

Possible Dibaryons with Strangeness s=-5

In the framework of $RGM$, the binding energy of the six quark system with strangeness s=-5 is systematically investigated under the SU(3) chiral constituent quark model. The single $\Xi^*\Omega$ channel calculation with spins S=0 and 3 and the coupled $\Xi\Omega$ and $\Xi^*\Omega$ channel calculation with spins S=1 and 2 are considered, respectively. The results show following observations: In the spin=0 case, $\Xi^* \Omega$ is a bound dibaryon with the binding energy being $80.0 \sim 92.4 MeV$. In the S=1 case, $\Xi\Omega$ is also a bound dibaryon. Its binding energy is ranged from $26.2 MeV$ to $32.9 MeV$. In the S=2 and S=3 cases, no evidence of bound dibaryons are found. The phase shifts and scattering lengths in the S=0 and S=1 cases are also given.Comment: 10 pages, late

ARIS-Campaign: intercomparison of three ground based 22 GHz radiometers for middle atmospheric water vapor at the Zugspitze in winter 2009

This paper presents the Alpine Radiometer Intercomparison at the Schneefernerhaus (ARIS), which took place in winter 2009 at the high altitude station at the Zugspitze, Germany (47.42° N, 10.98° E, 2650 m). This campaign was the first direct intercomparison between three new ground based 22 GHz water vapor radiometers for middle atmospheric profiling with the following instruments participating: MIRA 5 (Karlsruhe Institute of Technology), cWASPAM3 (Max Planck Institute for Solar System Research, Katlenburg-Lindau) and MIAWARA-C (Institute of Applied Physics, University of Bern). Even though the three radiometers all measure middle atmospheric water vapor using the same rotational transition line and similar fundamental set-ups, there are major differences between the front ends, the back ends, the calibration concepts and the profile retrieval. The spectrum comparison shows that all three radiometers measure spectra without severe baseline artifacts and that the measurements are in good general agreement. The measurement noise shows good agreement to the values theoretically expected from the radiometer noise formula. At the same time the comparison of the noise levels shows that there is room for instrumental and calibration improvement, emphasizing the importance of low elevation angles for the observation, a low receiver noise temperature and an efficient calibration scheme. <br><br> The comparisons of the retrieved profiles show that the agreement between the profiles of MIAWARA-C and cWASPAM3 with the ones of MLS is better than 0.3 ppmv (6%) at all altitudes. MIRA 5 has a dry bias of approximately 0.5 ppm (8%) below 0.1 hPa with respect to all other instruments. The profiles of cWASPAM3 and MIAWARA-C could not be directly compared because the vertical region of overlap was too small. The comparison of the time series at different altitude levels show a similar evolution of the H<sub>2</sub>O volume mixing ratio (VMR) for the ground based instruments as well as the space borne sensor MLS

Pd/Cu Site Interchange and Non-Fermi-Liquid Behavior in UCu_4Pd

X-ray-absorption fine-structure measurements of the local structure in UCu_4Pd are described which indicate a probable lattice-disorder origin for non-Fermi-liquid behavior in this material. Short Pd-Cu distances are observed, consistent with 24 +/- 3% of the Pd atoms occupying nominally Cu sites. A "Kondo disorder" model, based on the effect on the local Kondo temperature T_K of this interchange and some additional bond-length disorder, agrees quantitatively with previous experimental susceptibility data, and therefore also with specific heat and magnetic resonance experiments.Comment: 4 pages, 3 PostScript figures, to be published in PR

Investigation of fiber/matrix adhesion: test speed and specimen shape effects in the cylinder test

The cylinder test, developed from the microdroplet test, was adapted to assess the interfacial adhesion strength between fiber and matrix. The sensitivity of cylinder test to pull-out speed and specimen geometry was measured. It was established that the effect of test speed can be described as a superposition of two opposite, simultaneous effects which have been modeled mathematically by fitting two parameter Weibull curves on the measured datas. Effects of the cylinder size and its geometrical relation on the measured strength values have been analyzed by finite element method. It was concluded that the geometry has a direct influence on the stress formation. Based on the results achieved, recommendations were given on how to perform the novel single fiber cylinder test

Gauged flavour symmetry for the light generations

We study the phenomenology of a model where an SU(2)^3 flavour symmetry acting on the first two generation quarks is gauged and Yukawa couplings for the light generations are generated by a see-saw mechanism involving heavy fermions needed to cancel flavour-gauge anomalies. We find that, in constrast to the SU(3)^3 case studied in the literature, most of the constraints related to the third generation, like electroweak precision bounds or B physics observables, can be evaded, while characteristic collider signatures are predicted.Comment: 16 pages, 3 figure

Spin-orbit splitting of image states

We quantify the effect of the spin-orbit interaction on the Rydberg-like series of image state electrons at the (111) and (001) surface of Ir, Pt and Au. Using relativistic multiple-scattering methods we find Rashba-like dispersions with Delta E(K)=gamma K with values of gamma for n=1 states in the range 38-88 meV Angstrom. Extending the phase-accumulation model to include spin-orbit scattering we find that the splittings vary like 1/(n+a)^3 where a is the quantum defect and that they are related to the probability of spin-flip scattering at the surface. The splittings should be observable experimentally being larger in magnitude than some exchange-splittings that have been resolved by inverse photoemission, and are comparable to linewidths from inelastic lifetimes.Comment: 10 pages, 4 figure