33,241 research outputs found
Contributions to the width difference in the neutral system from hadronic decays
Recent studies of several multi-body meson decays have revealed that
the final states are dominantly -even. However, the small value of the
width difference between the two physical eigenstates of the
- system indicates that the total widths of decays to
-even and -odd final states should be the same to within about a
percent. The known contributions to the width difference from hadronic
decays are discussed, and it is shown that an apparent excess of
quasi--even modes is balanced, within current uncertainty, by interference
effects in quasi-flavour-specific decays. Decay modes which may significantly
affect the picture with improved measurements are considered.Comment: 17 pages including 3 tables. v2: Updated with published version
including new comments in summar
Spatial learning and memory in the tortoise (Geochelone carbonaria)
A single tortoise (Geochelone carbonaria) was trained in an eight-arm radial maze, with the apparatus and general procedures modeled on those used to demonstrate spatial learning in rats. The tortoise learned to perform reliably above chance, preferentially choosing baited arms, rather than returning to arms previously visited on a trial. Test sessions that examined control by olfactory cues revealed that they did not affect performance. No systematic, stereotyped response patterns were evident. In spite of differences in brain structure, the tortoise showed spatial learning abilities comparable to those observed in mammals
The bacillary and macrophage response to hypoxia in tuberculosis and the consequences for T cell antigen recognition
M. tuberculosis is a facultative anaerobe and its characteristic pathological hallmark, the granuloma, exhibits hypoxia in humans and in most experimental models. Thus the host and bacillary adaptation to hypoxia is of central importance in understanding pathogenesis and thereby to derive new drug treatments and vaccines
Absorption of Energy at a Metallic Surface due to a Normal Electric Field
The effect of an oscillating electric field normal to a metallic surface may
be described by an effective potential. This induced potential is calculated
using semiclassical variants of the random phase approximation (RPA). Results
are obtained for both ballistic and diffusive electron motion, and for two and
three dimensional systems. The potential induced within the surface causes
absorption of energy. The results are applied to the absorption of radiation by
small metal spheres and discs. They improve upon an earlier treatment which
used the Thomas-Fermi approximation for the effective potential.Comment: 19 pages (Plain TeX), 2 figures, 1 table (Postscript
Measurements of flow phenomena induced by suction through perforated and partially plugged surfaces
Efforts were directed towards completing construction of the windtunnel test section, assembling instrumentation, programming the data acquisition and reduction system, adjusting the streamwise pressure gradient of the test section, calibrating the hot-wire anemometer probe, and constructing and testing a smoke generator. The test section was installed in the wind tunnel and is completely operational. The streamwise pressure gradient was adjusted to be nominally zero at a free-stream velocity of 3.05 m/s (10 ft/s). This was accomplished by adjusting the upper wall of the test section to be slightly divergent. The change in static pressure between any two streamwise locations in the test section was less than one percent of the free-stream dynamic pressure. A suitable means was found for accurately calibrating the hot-wire probe which is used to measure boundary-layer velocity profiles and fluctuating velocities
Experimental study of flow due to an isolated suction hole and a partially plugged suction slot
Details for construction of a model of a partially plugged, laminar flow control, suction slot and an isolated hole are presented. The experimental wind tunnel facility and instrumentation is described. Preliminary boundary layer velocity profiles (without suction model) are presented and shown to be in good agreement with the Blasius laminar profile. Recommendations for the completion of the study are made. An experimental program for study of transition on a rotating disk is described along with preliminary disturbance amplification rate data
Ergodic and non-ergodic clustering of inertial particles
We compute the fractal dimension of clusters of inertial particles in mixing
flows at finite values of Kubo (Ku) and Stokes (St) numbers, by a new series
expansion in Ku. At small St, the theory includes clustering by Maxey's
non-ergodic 'centrifuge' effect. In the limit of St to infinity and Ku to zero
(so that Ku^2 St remains finite) it explains clustering in terms of ergodic
'multiplicative amplification'. In this limit, the theory is consistent with
the asymptotic perturbation series in [Duncan et al., Phys. Rev. Lett. 95
(2005) 240602]. The new theory allows to analyse how the two clustering
mechanisms compete at finite values of St and Ku. For particles suspended in
two-dimensional random Gaussian incompressible flows, the theory yields
excellent results for Ku < 0.2 for arbitrary values of St; the ergodic
mechanism is found to contribute significantly unless St is very small. For
higher values of Ku the new series is likely to require resummation. But
numerical simulations show that for Ku ~ St ~ 1 too, ergodic 'multiplicative
amplification' makes a substantial contribution to the observed clustering.Comment: 4 pages, 2 figure
Magnetic Dipole Absorption of Radiation in Small Conducting Particles
We give a theoretical treatment of magnetic dipole absorption of
electromagnetic radiation in small conducting particles, at photon energies
which are large compared to the single particle level spacing, and small
compared to the plasma frequency. We discuss both diffusive and ballistic
electron dynamics for particles of arbitrary shape.
The conductivity becomes non-local when the frequency is smaller than the
frequency \omega_c characterising the transit of electrons from one side of the
particle to the other, but in the diffusive case \omega_c plays no role in
determining the absorption coefficient. In the ballistic case, the absorption
coefficient is proportional to \omega^2 for \omega << \omega_c, but is a
decreasing function of \omega for \omega >> \omega_c.Comment: 25 pages of plain TeX, 2 postscipt figure
Sasanian hinterland fortresses, linear barriers and frontier landscapes: The 2007 season at the Great Wall of Gorgan and the Wall of Tammishe
Tobacco plain packaging, human rights and the object and purpose of international trade mark protection
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