Phase transition in exotic nuclei along the N=ZN=Z line

The abrupt structure change from the nuclei of $N=Z \le 35$ to those of $N=Z \ge 36$ is investigated by means of shell model calculations. The basic features of the even-even and odd-odd nuclei under consideration are nicely reproduced. A sudden jump of nucleons into the upper $g_{9/2}d_{5/2}$ shell at $N=Z=36$ is found to be the main reason that causes the qualitative structure difference. It is argued that the structure change can be viewed as a decisive change of the mean field, or a phase transition, along the $N=Z$ line.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Let

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

Continuum quasiparticle random phase approximation and the time dependent Hartree-Fock-Bogoliubov approach

Quadrupole excitations of neutron-rich nuclei are analyzed by using the linear response method in the Quasiparticle Random Phase Approximation (QRPA). The QRPA response is derived starting from the time-dependent Hartree-Fock-Bogoliubov (HFB) equations. The residual interaction between the quasiparticles is determined consistently from the two-body force used in the HFB equations, and the continuum coupling is treated exactly. Calculations are done for the neutron-rich oxygen isotopes. It is found that pairing correlations affect the low-lying states, and that a full treatment of the continuum can change the structure of the states in the giant resonance region.Comment: 17 pages, 7 figures. Revised version with comments and references adde

Thermal diffusivity and Biot number: a new experimental method

A new simple method is presented for measuring thermal diffusivity and Biot number in cylindrical samples made of relatively highly conducting materials, subjected to laminar air flow. The basic idea is a heat source in the middle section of the sample, acting also as a thermocouple; only one additional temperature sensor at the cylinder basis is required to give all information, without requiring any hypothesis about the effective time dependence of the heat source

Neural cytoskeleton capabilities for learning and memory

This paper proposes a physical model involving the key structures within the neural cytoskeleton as major players in molecular-level processing of information required for learning and memory storage. In particular, actin filaments and microtubules are macromolecules having highly charged surfaces that enable them to conduct electric signals. The biophysical properties of these filaments relevant to the conduction of ionic current include a condensation of counterions on the filament surface and a nonlinear complex physical structure conducive to the generation of modulated waves. Cytoskeletal filaments are often directly connected with both ionotropic and metabotropic types of membrane-embedded receptors, thereby linking synaptic inputs to intracellular functions. Possible roles for cable-like, conductive filaments in neurons include intracellular information processing, regulating developmental plasticity, and mediating transport. The cytoskeletal proteins form a complex network capable of emergent information processing, and they stand to intervene between inputs to and outputs from neurons. In this manner, the cytoskeletal matrix is proposed to work with neuronal membrane and its intrinsic components (e.g., ion channels, scaffolding proteins, and adaptor proteins), especially at sites of synaptic contacts and spines. An information processing model based on cytoskeletal networks is proposed that may underlie certain types of learning and memory