On some Banach space properties sufficient for weak normal structure and their permanence properties

We consider Banach space properties that lie between conditions introduced by Bynum and Landes. These properties depend on the metric behavior of weakly convergent sequences. We also investigate the permanence properties of these conditions.

     

Lieb-Robinson Bounds and the Exponential Clustering Theorem

We give a Lieb-Robinson bound for the group velocity of a large class of discrete quantum systems which can be used to prove that a non-vanishing spectral gap implies exponential clustering in the ground state of such systems.     

Compton scattering from the deuteron and extracted neutron polarizabilities

Differential cross sections for Compton scattering from the deuteron were measured at MAX-Lab for incident photon energies of 55 and 66 MeV at nominal laboratory angles of 45 degrees, 125 degrees, and 135 degrees. Tagged photons were scattered from liquid deuterium and detected in three NaI spectrometers. By comparing the data with theoretical calculations in the framework of a one-boson-exchange potential model, the sum and the difference of the isospin-averaged nucleon polarizabilities, alpha(N)+beta(N)=17.4+/-3.7 and alpha(N)-beta(N)=6.4+/-2.4 (in units of 10(-4) fm(3)), have been determined. By combining the latter with the global-averaged value for alpha(p)-beta(p) and using the predictions of the Baldin sum rule for the sum of the nucleon polarizabilities, we have obtained values for the neutron electric and magnetic polarizabilities of alpha(n)=8.8+/-2.4(total)+/-3.0(model) and beta(n)=6.5-/+2.4(total)-/+3.0(model), respectively.     

Product systems over right-angled Artin semigroups

We build upon Mac Lane's definition of a tensor category to introduce the concept of a product system that takes values in a tensor groupoid . We show that the existing notions of product systems fit into our categorical framework, as do the -graphs of Kumjian and Pask. We then specialize to product systems over right-angled Artin semigroups; these are semigroups that interpolate between free semigroups and free abelian semigroups. For such a semigroup we characterize all product systems which take values in a given tensor groupoid . In particular, we obtain necessary and sufficient conditions under which a collection of -graphs form the coordinate graphs of a -graph.     

Liquid flow patterns about barbotage bubbles

This paper summarizes the results of a flow visualization study on the liquid motion around barbotage bubbles during growth and departure. Flow patterns, as well as for the first time, instantaneous velocities, are reported as a function of time and location about the bubbles. The experiments, employing the hydrogen-bubble technique and high-speed cine photography, were with: water as the liquid, air as the bubbled gas, orifice diameters of 0.116 and 0.252 cm, and different air flow rates; the two limiting cases of constant supply pressure and constant volumetric flow rate were covered. It was found that the liquid around a barbotage bubble assumes two velocity maxima, the first an outward maximum during bubble growth and the second in the opposite direction approximately at the time of bubble departure; further, liquid velocities were found to be higher close to the bubbling site. Certain differences in liquid velocities between the constant pressure and constant flow cases are explained in terms of available theoretical solutions to the bubble growth rate. Qualitative comparisons of the barbotage liquid flow patterns and those recently reported for boiling flow patterns are also presented.     

Two-phase flow in a horizontal equal-sided impacting tee junction

Pressure-drop and phase-distribution data were generated for air–water flows in a horizontal impacting tee junction. All three sides of the junction (37.8-mm i.d.) were oriented horizontally. The data correspond to a junction pressure of 1.5 bar (abs), ambient temperature, inlet flow regimes of wavy, stratified, and annular, and a wide range of mass splits at the junction. Most of the range for the phase-distribution data corresponds to conditions that were untested in previous investigations. In general, it was found that the phases did not distribute themselves evenly between the two outlets unless the mass split is equal. There is a serious lack of data in the literature on the two-phase pressure drop in impacting tee junctions and therefore, the present data add substantially to the existing data. A mechanistic model capable of predicting the phase distribution and pressure drop was developed and shown to be in general good agreement with the present data and others from the literature.