Quantum Phase Transition of 3He in Aerogel at a Nonzero Pressure

金沢大学理学部We present evidence for a nonzero pressure, T ­ 0 superfluid phase transition of 3He in 98.2% open aerogel. Unlike bulk 3He which is a superfluid at T ­ 0 at all pressures (densities) between zero and the melting pressure, 3He in aerogel is not superfluid unless the 3He density exceeds a critical value rc. About 90% of the 3He added above rc contributes to the superfluid density. [S0031-9007(97)03585-0

Mass coupling and Q−1ofimpurity−limitednormalQ^{-1} of impurity-limited normal ^3$He in a torsion pendulum

We present results of the $Q^{-1}$ and period shift, $\Delta P$, for $^3$He confined in a 98% nominal open aerogel on a torsion pendulum. The aerogel is compressed uniaxially by 10% along a direction aligned to the torsion pendulum axis and was grown within a 400 $\mu$m tall pancake (after compression) similar to an Andronikashvili geometry. The result is a high $Q$ pendulum able to resolve $Q^{-1}$ and mass coupling of the impurity-limited $^3$He over the whole temperature range. After measuring the empty cell background, we filled the cell above the critical point and observe a temperature dependent period shift, $\Delta P$, between 100 mK and 3 mK that is 2.9$$ of the period shift (after filling) at 100 mK. The $Q^{-1}$ due to the $^3$He decreases by an order of magnitude between 100 mK and 3 mK at a pressure of $0.14\pm0.03$ bar. We compare the observable quantities to the corresponding calculated $Q^{-1}$ and period shift for bulk $^3$He.Comment: 8 pages, 3 figure

Propolis extract as a feed additive of the Nile tilapia juveniles

ABSTRACT This study was conducted to investigate the effects of dietary propolis alcohol extract supplementation on growth performance, digestibility, intestinal morphometry, and physiologic parameters Nile tilápia (Oreochromis niloticus L.) juveniles. For performance experiment and intestinal morphometry, 120 fish averaging 1.41±0.3g were randomly distributed into 24 tanks (70L each) in a closed recirculation water system with constant aeration and biofilter. The animals were distributed into four treatments using a completely randomized design with six replicates per treatment. The treatments consisted of four pellet feeds with different alcohol propolis concentrations extract (AEP) (0.0, 0.5, 1.0 and 1.5gkg-1). The performance experiment period was conducted for 45 days. For the digestibility experiment, an inert marker in the feed and the adapted Guelph feces collecting system were used. The results showed no differences in the performance parameters, crude protein apparent digestibility and dry matter of the feeds, intestinal morphometry, and physiologic parameters. However, there was an increasing linear effect on the energy digestibility with increasing PAE concentrations in the fish feed. The usage of the propolis extract supplementation levels of 1% is recommended for optimum effect on villus morphometry in Nile tilapia

Quasi-long-range order in the random anisotropy Heisenberg model: functional renormalization group in 4-\epsilon dimensions

The large distance behaviors of the random field and random anisotropy O(N) models are studied with the functional renormalization group in 4-\epsilon dimensions. The random anisotropy Heisenberg (N=3) model is found to have a phase with the infinite correlation radius at low temperatures and weak disorder. The correlation function of the magnetization obeys a power law < m(x) m(y) >\sim |x-y|^{-0.62\epsilon}. The magnetic susceptibility diverges at low fields as \chi \sim H^{-1+0.15\epsilon}. In the random field O(N) model the correlation radius is found to be finite at the arbitrarily weak disorder for any N>3. The random field case is studied with a new simple method, based on a rigorous inequality. This approach allows one to avoid the integration of the functional renormalization group equations.Comment: 12 pages, RevTeX; a minor change in the list of reference

Local mean-field study of capillary condensation in silica aerogels

We apply local mean-field (i.e. density functional) theory to a lattice model of a fluid in contact with a dilute, disordered gel network. The gel structure is described by a diffusion-limited cluster aggregation model. We focus on the influence of porosity on both the hysteretic and the equilibrium behavior of the fluid as one varies the chemical potential at low temperature. We show that the shape of the hysteresis loop changes from smooth to rectangular as the porosity increases and that this change is associated to disorder-induced out-of-equilibrium phase transitions that differ on adsorption and on desorption. Our results provide insight in the behavior of $^4$He in silica aerogels.Comment: 19 figure