Onset of Superfluidity in 4He Films Adsorbed on Disordered Substrates

We have studied 4He films adsorbed in two porous glasses, aerogel and Vycor, using high precision torsional oscillator and DC calorimetry techniques. Our investigation focused on the onset of superfluidity at low temperatures as the 4He coverage is increased. Torsional oscillator measurements of the 4He-aerogel system were used to determine the superfluid density of films with transition temperatures as low as 20 mK. Heat capacity measurements of the 4He-Vycor system probed the excitation spectrum of both non-superfluid and superfluid films for temperatures down to 10 mK. Both sets of measurements suggest that the critical coverage for the onset of superfluidity corresponds to a mobility edge in the chemical potential, so that the onset transition is the bosonic analog of a superconductor-insulator transition. The superfluid density measurements, however, are not in agreement with the scaling theory of an onset transition from a gapless, Bose glass phase to a superfluid. The heat capacity measurements show that the non-superfluid phase is better characterized as an insulator with a gap.Comment: 15 pages (RevTex), 21 figures (postscript

Identification of the unfavored N=7 superdeformed band in Hg191

A new superdeformed band has been identified in Hg191 bringing the total number of bands observed in this nucleus to four. The new band has properties similar to those of a superdeformed band reported recently in Hg193. Both bands are believed to be built on the unfavored signature of the j15/2 intruder configuration. Comparisons between the data and cranked Woods-Saxon calculations highlight the strengths and weaknesses of theory in describing high-N orbitals at large deformation

New features of superdeformed bands in Hg194

Two new features of superdeformed (SD) bands in the A190 region emerge from a study of Hg194 with the Gammasphere detector array. A decrease of the dynamic moment of inertia is observed for rotational frequencies Latin small letter h with strokeω0.4 MeV, confirming long standing expectations based on mean field calculations with pairing. Evidence for a small staggering in the SD transition energies is also observed, suggesting the presence of terms with fourfold symmetry in the SD Hamiltonian

Identification of 181Hg and shape coexistence in odd-A Hg isotopes

In-beam γ-ray transitions in 181Hg, the lightest odd-A Hg isotope known thus far, have been identified from fragment mass-γ and γ-γ coincidence measurements. Five prolate deformed rotational bands were placed in the level scheme. A decoupled band built on the strongly prolate deformed 1/2-[521] ground state was observed up to 29/2-. A 5/2-[512] configuration is suggested for a pair of strongly coupled bands displaying no signature splitting. The other two bands are also signature partner bands. They are populated with the largest intensity and exhibit splitting. They have been associated with the mixed neutron i13/2 orbitals and are proposed to decay to an i13/2 isomeric state associated with an oblate state

Neural Reward Responsiveness in Children who Engage in Nonsuicidal Self‐Injury: An ERP Study

Background: A better understanding of the correlates of nonsuicidal self‐injury (NSSI) in children is important for the identification and prevention of future suicide risk. However, although abnormalities in reward responsiveness might constitute one potential transdiagnostic mechanism of risk for NSSI, no studies have examined initial response to reward in children with a history of NSSI. The goal of the present study was to address this important gap in the literature. To objectively assess initial response to reward, we utilized the feedback negativity (FN) event‐related potential, a well‐established psychophysiological marker of reward responsiveness. Methods: Participants were 57 children (19 with a history of NSSI and 38 demographically matched controls) between the ages of 7 and 11. Diagnostic interviews were used to assess for current and past DSM‐IV mood and anxiety diagnoses and NSSI history. Children also completed a guessing task, during which continuous electroencephalography was recorded. Results: Children with a history of NSSI exhibited significantly more negative ΔFN (i.e., FN to losses minus FN to gains) than children without NSSI. These findings appeared to be at least partially independent of children\u27s history of psychopathology and current symptoms, suggesting their specificity to NSSI. Conclusions: These results provide initial evidence for heightened neural initial reward responsiveness to losses versus rewards in children with a history of NSSI. Pending replications and longitudinal studies, the ΔFN might represent a psychophysiological marker of risk for self‐harm