Comparison of fragment partitions production in peripheral and central collisions

Ensembles of single-source events, produced in peripheral and central collisions and correponding respectively to quasi-projectile and quasi-fusion sources, are analyzed. After selections on fragment kinematic properties, excitation energies of the sources are derived using the calorimetric method and the mean behaviour of fragments of the two ensembles are compared. Differences observed in their partitions, especially the charge asymmetry, can be related to collective energy deposited in the systems during the collisions.Comment: 7 pages, 2 figures, presented at the International Workshop on Multifragmentation and Related Topics, Caen France, 4-7th november 2007 (IWM2007

Bose-enhanced chemistry: Amplification of selectivity in the dissociation of molecular Bose-Einstein condensates

We study the photodissociation chemistry of a quantum degenerate gas of bosonic triatomic $ABC$ molecules, assuming two open rearrangement channels ($AB+C$ or $A+BC$). The equations of motion are equivalent to those of a parametric multimode laser, resulting in an exponential buildup of macroscopic mode populations. By exponentially amplifying a small differential in the single-particle rate-coefficients, Bose stimulation leads to a nearly complete selectivity of the collective $N$-body process, indicating a novel type of ultra-selective quantum degenerate chemistry.Comment: 5 pages, 3 figure

Characterisation of friction and lubrication regimes in premium tubular connections

A friction test rig has been developed to carry out repeated sliding friction tests for premium tubular connections. The test rig enables accurate measurement of friction in various contact regimes which are relevant to the threaded connections between tubular components. Higher load tests can simulate the contact in metal-to-metal seals under very high contact pressures by using perpendicular pin-on-pin tests. The contact in the thread loading flank under intermediate pressures can be simulated by using larger radius coupon-on-coupon tests. The measured coefficient of friction is well correlated with a lubrication parameter combining lubricant film thickness and initial surface roughness. © 2012 Elsevier Ltd. All rights reserved

Break-up fragments excitation and the freeze-out volume

We investigate, in microcanonical multifragmentation models, the influence of the amount of energy dissipated in break-up fragments excitation on freeze-out volume determination. Assuming a limiting temperature decreasing with nuclear mass, we obtain for the Xe+Sn at 32 MeV/nucleon reaction [J. D. Frankland et al., Nucl. Phys. A689, 905 (2001); A689, 940 (2001)] a freeze-out volume almost half the one deduced using a constant limiting temperature.Comment: 11 pages, 6 figure