The center-of-mass ͑CM͒ dispersion of spatially indirect excitons ͑IE's͒ in biased GaAs/Al 0.35 Ga 0.65 As double quantum wells is determined by photoluminescence ͑PL͒ spectroscopy in an in-plane magnetic field B. The field rigidly shifts the IE dispersion in k space by an amount proportional to both B and the electron-hole separation. The PL emission arises from IE's with zero total momentum, corresponding to finite CM velocity, which allows the direct measurement of the IE CM dispersion. The observed PL energy increases quadratically in B, corresponding to the IE kinetic energy, whereas the PL intensity follows the thermal occupation of the optically active IE states and decreases as a Gaussian function of B.

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We describe the synthesis of tetrahydroisoquinolines and tetrahydroisoquinolinium salts together with their pharmacological properties at various nicotinic acetylcholine receptors. In general, the compounds were α4β2 nAChR antagonists, with the tetrahydroisoquinolinium salts being more potent than the parent tetrahydroisoquinoline derivatives. The most potent α4β2 antagonist, 6c, exhibited submicromolar binding K and functional IC values and high selectivity for this receptor over the α4β4 and α3β4 nAChRs. Whereas the (S)-6c enantiomer was essentially inactive at α4β2, (R)-6c was a slightly more potent α4β2 antagonist than the reference β2-nAChR antagonist DHβΕ. The observation that the α4β2 activity resided exclusively in the (R)-enantiomer was in full agreement with docking studies. Several of tetrahydroisoquinolinium salts also displayed agonist activity at the α7 nAChR. Preliminary in vivo evaluation revealed antidepressant-like effects of both (R)-5c and (R)-6c in the mouse forced swim test, supporting the therapeutic potential of α4β2 nAChR antagonists for this indication.

Transport properties of 2D hole gases in (001)GaAs/Al 0.5 Ga 0.5 As heterostructures in the [1 10] and [110] directions have been investigated. In-plane uniaxial compression up to 5 kbar was applied in one or the other of the two directions, and measurements were performed in the temperature range 1.4-60 K and in a magnetic field up to 6 T. Without uniaxial compression the mobility is largest in the [1 10] direction, the [1 10]: [110] mobilities ratio attaining its largest values at low temperatures and high carrier densities. Interface roughness scattering together with acoustic phonon scattering is suggested to be the underlying phenomenon. Under uniaxial compression the electrical resistance decreases in the direction parallel to the compression, and it increases in the direction perpendicular to the compression. This behaviour is found to be in qualitative agreement with recent band structure calculations.

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