[Pachydermodactyly]. / Pachydermodaktylie.

The differential diagnosis of swelling of the small finger joints is broad. We report on two young men presenting with progressive painless swelling of the proximal interphalangeal (PIP) joints where the physical examination was otherwise inconspicuous. Laboratory investigations including auto- antibodies were all normal, x-rays and magnetic resonance imaging (MRI) revealed no joint pathologies but only increased skin thickening. Skin biopsy demonstrated hyperkeratosis and acanthosis without tissue inflammation. We thus diagnosed pachydermodactyly in both cases. This rare disease predominantly affects young males, can affect one or both hands and is often associated with mechanical stress due to repetitive movements in patients with obsessive-compulsive disorders. Occupational exposure by monotonous actions (e.g. poultry processing) may also be a cause. A specific therapy is unnecessary in most cases but may include intralesional steroid administration or surgical resection. Cessation of mechanical stress can significantly improve pachydermodactyly.

Kinetic temperature effects on 4He dimers in jets.

The formation of dimers in a free jet cryogenic expansion of 4He gas has been studied by measuring mole fractions as a function of source temperature and pressure using diffraction from a nanostructured transmission grating. The data sets are limited to low source pressures for which dimers and trimers are the only appreciable cluster populations in the beam. The final cluster mole fractions are corrected for residual gas attenuation in the source chamber by an extrapolation over several residual gas pressures. A set of rate equations used to model the cluster formation in a free jet expansion has been extended to include the departure of the ambient translational temperature from the isentropic-equilibrium values as the density decreases with increasing distance. The effect of collisions in restoring the equilibrium temperature is treated with a relaxation time approximation. There are distinct distance ranges where the dimer and trimer mole fractions and the ambient temperature near their asymptotic values. The present modeling reproduces the apparent threshold observed at low source pressures for the survival of dimers in the asymptotic beam. Except for these low source pressures, there are only small changes relative to results based on the isentropic temperature.