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The half-life of the yrast IΠ = 2+ state in the neutron-rich nucleus 188W has been measured using fast-timing techniques with the HPGe and LaBniCe array at the National Institute of Physics and Nuclear Engineering, Bucharest. The resulting value of t1/2 = 0.87(12) ns is equivalent to a reduced transition probability of B(E2;21 →01 +) = 85(12) W.u. for this transition. The B(E2;21 →01 +) is compared to neighboring tungsten isotopes and nuclei in the Hf, Os, and Pt isotopic chains. Woods-Saxon potential energy surface (PES ) calculations have been performed for nuclei in the tungsten isotopic chain and predict prolate deformed minima with rapidly increasing y softness for l84-192W and an oblate minimum for l94W. [ABSTRACT FROM AUTHOR]

Excited states in 212Po were populated by alpha transfer using the 208Pb(18O,14C) reaction, and their deexcitation gamma rays were studied with the Euroball array. Several levels were found to decay by a unique E1 transition (Egamma<1 MeV) populating the yrast state with the same spin value. Their lifetimes were measured by the Doppler-shift attenuation method. The values, found in the range 0.1-1.4 ps, lead to very enhanced transitions, B(E1)=2x10(-2)-1x10(-3) W.u. These results are discussed in terms of an alpha-cluster structure which gives rise to states with non-natural-parity values, provided that the composite system cannot rotate collectively, as expected in the "alpha+208Pb" case. Such states due to the oscillatory motion of the alpha-core distance are observed for the first time.

A very simple formula is presented that relates the logarithm of the half-life, corrected by the centrifugal barrier, with the Coulomb parameter in proton decay processes. The corresponding experimental data lie on two straight lines which appear as a result of a sudden change in the nuclear shape marking two regions of deformation independently of the angular momentum of the outgoing proton. This feature provides a powerful tool to assign experimentally quantum numbers in proton emitters.

It is known that impact forces increase with running velocity as well as when stride length increases. Since stride length naturally changes with changes in submaximal running velocity, it was not clear which factor, running velocity or stride length, played a critical role in determining impact characteristics. The aim of the study was to investigate whether or not stride length influences the relationship between running velocity and impact characteristics. Eight volunteers (mass=72.4 ± 8.9 kg; height = 1.7 ± 0.1 m; age = 25 ± 3.4 years) completed two running conditions: preferred stride length (PSL) and stride length constrained at 2.5 m (SL2.5). During each condition, participants ran at a variety of speeds with the intent that the range of speeds would be similar between conditions. During PSL, participants were given no instructions regarding stride length. During SL2.5, participants were required to strike targets placed on the floor that resulted in a stride length of 2.5 m. Ground reaction forces were recorded (1080 Hz) as well as leg and head accelerations (uni-axial accelerometers). Impact force and impact attenuation (calculated as the ratio of head and leg impact accelerations) were recorded for each running trial. Scatter plots were generated plotting each parameter against running velocity. Lines of best fit were calculated with the slopes recorded for analysis. The slopes were compared between conditions using paired t-tests. Data from two subjects were dropped from analysis since the velocity ranges were not similar between conditions resulting in the analysis of six subjects. The slope of impact force vs. velocity relationship was different between conditions (PSL: 0.178 ± 0.16 BW/m·s(-1); SL2.5: -0.003 ± 0.14 BW/m·s(-1); p < 0.05). The slope of the impact attenuation vs. velocity relationship was different between conditions (PSL: 5.12 ± 2.88 %/m·s(-1); SL2.5: 1.39 ± 1.51 %/m·s(-1); p < 0.05). Stride length was an important factor that determined impact force magnitude. It is likely that lower extremity posture is a determining factor influencing impact characteristics. Key PointsAs running velocity increased, the magnitude of the vertical ground reaction impact force increased as expected.As running velocity increased, stride length increased as expected.When stride length was constrained to be 2.5 m for all running velocities, the magnitude of the vertical ground reaction impact force did not increase as expected.When running different velocities, the changes in the magnitude of the vertical ground reaction impact force was related to stride length changes.