Spin echo in spinor dipolar Bose-Einstein condensates

We theoretically propose and numerically realize spin echo in a spinor Bose--Einstein condensate (BEC). We investigate the influence on the spin echo of phase separation of the condensate. The equation of motion of the spin density exhibits two relaxation times. We use two methods to separate the relaxation times and hence demonstrate a technique to reveal magnetic dipole--dipole interactions in spinor BECs.Comment: 4 pages, 5 figure

Vortex Multiplication in Applied Flow: the Precursor to Superfluid Turbulence

The dynamics of quantized vortices in rotating $^3$He-B is investigated in the low density (single-vortex) regime as a function of temperature. An abrupt transition is observed at $0.5 T_{\rm c}$. Above this temperature the number of vortex lines remains constant, as they evolve to their equilibrium positions. Below this temperature the number of vortices increases linearly in time until the vortex density has grown sufficiently for turbulence to switch on. On the basis of numerical calculations we suggest a mechanism responsible for vortex formation at low temperatures and identify the mutual friction parameter which governs its abrupt temperature dependence.Comment: 5 pages, 4 figures; version submitted to Phys. Rev. Let

Superconducting Nb-film LC resonator

Sputtered Nb thin-film LC resonators for low frequencies at 0.5 MHz have been fabricated and tested in the temperature range 0.05--1 K in magnetic fields up to 30 mT. Their Q value increases towards decreasing temperature as sqrt(T) and reaches 10^3 at 0.05 K. As a function of magnetic field Q is unstable and displays variations up to 50%, which are reproducible from one field sweep to the next. These instabilities are attributed to dielectric losses in the plasma deposited SiO_2 insulation layer, since the thin-film coil alone reaches a Q > 10^5 at 0.05 K.Comment: 6 pages, 7 figures, submitted to Review of Scientific Instrument

A new type of carbon resistance thermometer with excellent thermal contact at millikelvin temperatures

Using a new brand of commercially available carbon resistor we built a cryogenic thermometer with an extremely good thermal contact to its thermal environment. Because of its superior thermal contact the thermometer is insensitive to low levels of spurious radio frequency heating. We calibrated our thermometer down to 5mK using a quartz tuning fork He-3 viscometer and measured its thermal resistance and thermal response time.Comment: 5 pages, 4 figure

Dementia Caregiver Burden: A Research Update and Critical Analysis

Purpose of Review: This article provides an updated review of the determinants of caregiver burden and depression, with a focus on care demands and especially the differential effects of various neuropsychiatric symptoms or symptom clusters. Moreover, studies on caregivers for frontotemporal and Lewy body dementias were referred to in order to identify differences and similarities with the mainstream literature based largely on Alzheimer caregivers. Recent Findings: As a group, neuropsychiatric symptoms are most predictive of caregiver burden and depression regardless of dementia diagnosis, but the effects appear to be driven primarily by disruptive behaviors (e.g., agitation, aggression, disinhibition), followed by delusions and mood disturbance. Disruptive behaviors are more disturbing partly because of the adverse impact on the emotional connection between the caregiver and the care-recipient and partly because they exacerbate difficulties in other domains (e.g., caring for activities of daily living). In behavioral variant frontotemporal dementia, not only are these disruptive behaviors more prominent but they are also more disturbing due to the care-recipient’s insensitivity to others’ feelings. In Lewy body dementia, visual hallucinations also appear to be distressing. Summary: The disturbing nature of disruptive behaviors cuts across dementia conditions, but the roles played by symptoms that are unique or particularly serious in a certain condition need to be explored further

Propagation of first sound in liquid 3He

The dispersion of first (hydrodynamic) sound in normalfluid and superfluid 3He has been measured in a cylindrical resonator at a pressure of 18.8 bar in the frequency range between 85 kHz and 227 kHz and in the temperature range between 1.2 and 50 mK. The sound velocity measured in the normalfluid regime confirms recent theories of the slip effect in Fermi liquids; in superfluid 3He-B we find qualitative agreement between experiment and theoretical sound velocity

Hydrodynamic sound experiments in normal and superfluid 3He

In a cylindrical resonator the attenuation and the velocity of first sound in normal and superfluid 3He have been measured in the frequency range from 40 to 300 kHz and at pressures of 8, 18.8, and 28 bar. In the normal fluid the viscosity deduced from our data agrees with previously reported values; the sound velocity in this regime can be explained by taking into account mean-free-path effects and zero-sound corrections. The results for the viscosity in the superfluid confirm the previous observations of a continuous decrease down to the lowest temperatures in contradiction to theoretical predictions. The sound-velocity data in the superfluid regime indicate that specular reflection of the quasiparticles may occur at the resonator walls

HYPERFINE ENHANCED NUCLEAR MAGNETIC COOLING IN PrBe13

Dans le composé PrBe13, qui est un paramagnétique de Van Vleck à basse température, le renforcement du champ magnétique appliqué au noyau de Pr par rapport au champ externe est de 9,8. Les expériences de désaimantation adiabatique nucleaire indique une bonne réversibilité thermodynamique et on atteint des températures finales inférieures à 1 mK. La température calculée de la transition dans l'état nucléaire ordonnée est de 0,46 mK.In Van Vleck paramagnetic PrBe13, the hyperfine enhancement of the local field at the Pr nuclei is 9.8 times the external applied field. Nuclear demagnetization experiments show good thermodynamic reversibility and yield end-temperatures below 1 mK. The calculated nuclear ordering temperature is 0.46 mK

Josephson mass current dynamics in experiments and simulations within a new model concept

Josephson mass currents have been investigated in superfluid 3He-B with high temporal resolution. The experimentally observed dynamics of all DC and AC Josephson effects could be modeled in detail by solving the quantum-phase– controlled equations of motion which could be adjusted for other quantum condensates as well. We show that the 3He π-state, discussed in the literature, might not be a state of 3He but nonlinear dynamics which also dominates the apparent dissipation and oscillation in the Josephson device. Four different modes were identified for Cooper pair oscillations and a pure sinusoidal current phase relationship was found for temperatures down to 0.16 mK where the device can be used as a bolometric detector