The simple SDD.

We describe the fabrication and characterisation of the SIMPLE superheated droplet detector, a 10 g active mass device of C(2)ClF(5) in 1-3% weight concentrations currently employed in a direct search for spin-dependent astroparticle dark matter candidates.

Neutron spectrometry with large volume, heavy-loaded superheated droplet detectors: a simple spin-off.

SIMPLE is a superheated droplet detector (SDD) experiment designed to search for the evidence of spin-dependent weakly interacting neutralino dark matter (WIMPs). SDDs, a type of emulsion detector, consist of a uniform suspension of superheated liquid droplets in a compliant material such as a polymeric or aqueous gel. We report on the first neutron spectrometry experiments with SIMPLE SDDs, a spin-off of the neutron detector calibrations performed at the Portuguese Research Reactor. SIMPLE SDDs differ from most SDDs available commercially as they have a 10 times higher loading factor, containing 10(3) times more freon than their commercial counterparts and a 100 times larger volume. We have analysed the response of SIMPLE SDDs to two quasi-monochromatic neutron beams of energies 54 and 144 keV obtained with passive filters. Results show that the characteristic peaks in the fluence distribution of both filters could be determined and their energy position obtained using a simple thermodynamic relation.

First dark matter limits from a large-mass, low-background, superheated droplet detector.

We report on the fabrication aspects and calibration of the first large active mass ( approximately 15 g) modules of SIMPLE, a search for particle dark matter using superheated droplet detectors (SDDs). While still limited by the statistical uncertainty of the small data sample on hand, the first weeks of operation in the new underground laboratory of Rustrel-Pays d'Apt already provide a sensitivity to axially coupled weakly interacting massive particles (WIMPs) competitive with leading experiments, confirming SDDs as a convenient, low-cost alternative for WIMP detection.

Transient synaptic redundancy in the developing cerebellum and isostatic random stacking of hard spheres.

We propose an automaton for the simulation of the distribution of the number of climbing fibers (CF) making synapses on each Purkinje cell (PC) at the maximum of the synaptic redundancy that exists transiently in the newborn cerebellum. This automaton is based on the hypothesis that the synaptic maximum is limited by topological constraints and can be described by an isostatic random stacking of hard spheres. There is convincing agreement between the simulated distribution of the number of CF axons per Purkinje cell and the distribution experimentally obtained by electrophysiological techniques.