Epitaxial refractory-metal buer layers with a chemical gradient for adjustable lattice parameter and controlled chemical interface

We have developed and characterized the structure and composition of nanometers-thick solid-solution epitaxial layers of (V,Nb) on sapphire (1120), displaying a continuous lateral gradient of composition from one to another pure element. Further covered with an ultrathin pseudomorphic layer of W, these provide a template for the fast combinatorial investigation of any growth or physical property depending of strain

Electron gas polarization effect induced by heavy H-like ions of moderate velocities channeled in a silicon crystal

We report on the observation of a strong perturbation of the electron gas induced by 20 MeV/u U$^{91+}$ ions and 13 MeV/u Pb$^{81+}$ ions channeled in silicon crystals. This collective response (wake effect) in-duces a shift of the continuum energy level by more than 100 eV, which is observed by means of Radiative Electron Capture into the K and L-shells of the projectiles. We also observe an increase of the REC probability by 20-50% relative to the probability in a non-perturbed electron gas. The energy shift is in agreement with calculations using the linear response theory, whereas the local electron density enhancement is much smaller than predicted by the same model. This shows that, for the small values of the adiabaticity parameter achieved in our experiments, the density fluctuations are not strongly localized at the vicinity of the heavy ions

Effect of pediatric physical therapy on deformational plagiocephaly in children with positional preference: a randomized controlled trial

Objective To study the effect of pediatric physical therapy on positional preference and deformational plagiocephaly.\ud \ud Design Randomized controlled trial.\ud \ud Setting Bernhoven Hospital, Veghel, the Netherlands.\ud \ud Participants Of 380 infants referred to the examiners at age 7 weeks, 68 (17.9%) met criteria for positional preference, and 65 (17.1%) were enrolled and followed up at ages 6 and 12 months.\ud \ud Intervention Infants with positional preference were randomly assigned to receive either physical therapy (n = 33) or usual care (n = 32).\ud \ud Main Outcome Measures The primary outcome was severe deformational plagiocephaly assessed by plagiocephalometry. The secondary outcomes were positional preference, motor development, and cervical passive range of motion.\ud \ud Results Both groups were comparable at baseline. In the intervention group, the risk for severe deformational plagiocephaly was reduced by 46% at age 6 months (relative risk, 0.54; 95% confidence interval, 0.30-0.98) and 57% at age 12 months (0.43; 0.22-0.85). The numbers of infants with positional preference needed to treat were 3.85 and 3.13 at ages 6 and 12 months, respectively. No infant demonstrated positional preference at follow-up. Motor development was not significantly different between the intervention and usual care groups. Cervical passive range of motion was within the normal range at baseline and at follow-up. When infants were aged 6 months, parents in the intervention group demonstrated significantly more symmetry and less left orientation in nursing, positioning, and handling.\ud \ud Conclusion A 4-month standardized pediatric physical therapy program to treat positional preference significantly reduced the prevalence of severe deformational plagiocephaly compared with usual care

Nuclear fission time measurements as a function of excitation energy - A crystal blocking experiment

CASFission times of lead and uranium nuclei have been measured at GANIL by the crystal blocking method. The inverse kinematics was used. Fragment atomic numbers and total excitation energies were determined. For data analysis, full Monte-Carlo trajectory calculations were used to simulate the blocking patterns. The effect of post-scission emissions, included in our simulations, is discussed. At high excitation energies, the scissions occur dominantly at times shorter than 10−19 s, whereas at low excitation energies (E∗<250–300 MeV), scissions occurring at much longer times with sizeable probabilities are observed both for uranium and for lead nuclei, leading to average scission times much longer than those inferred from pre-scission emission

Evidence of Z=120 compound nucleus formation from lifetime measurement in the 238^{238}U+Ni reaction at 6.62 MeV/nucleon

CAS NIMThe formation of compound nuclei with Z=120, followed by fission, has been evidenced in the 238U+Ni system at 6.62 MeV/nucleon by very long reaction times (t ~ 10-17s) measured by the blocking technique in single crystals

Fission time measurements: a new probe into super-heavy element stability

Accepted for publication in Physical Review LettersReaction mechanism analyses performed with a 4 $\pi$ detector for the systems $^{208}$Pb+Ge, $^{238}U+Ni and$^{238}$U+Ge, combined with analyses of the associated reaction time distributions, provide us with evidence for nuclei with Z=120 and 124 living longer than$10^−18$s and arising from highly excited compound nuclei. By contrast, the neutron deficient nuclei with Z=114 possibly formed in$^{208}$Pb+Ge reactions have shorter lifetimes, close to or below the sensitivity limit of the experiment

Ion slowing down and charge exchange at small impact parameters selected by channeling: superdensity effects

CASInternational audienceIn two experiments performed with 20-30 MeV/u highly charged heavy ions (Pb56+, U91+) channeled through thin silicon crystals, we observed the original features of superdensity, associated to the glancing collisions with atomic rows undergone by part of the incident projectiles. In particular the very high collision rate yields a quite specific charge exchange regime, that leads to a higher ionization probability than in random conditions. X-ray measurements show that electrons captured in outershells are prevented from being stabilized, which enhances the lifetime of the projectile innershell vacancies. The charge state distributions and the energy loss spectra are compared to Monte-Carlo simulations. These simulations confirm, extend and illustrate the qualitative analysis of the experimental results