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We examine the DC and radio frequency (RF) response of superconducting transmission line resonators comprised of very thin NbTiN films, [Formula: see text] in thickness, in the high-temperature limit, where the photon energy is less than the thermal energy. The resonant frequencies of these superconducting resonators show a significant nonlinear response as a function of RF input power, which can approach a frequency shift of [Formula: see text] in a [Formula: see text] span in the thinnest film. The strong nonlinear response allows these very thin film resonators to serve as high kinetic inductance parametric amplifiers.

Active mirror structures based on a dielectric high-contrast grating reflector combined with optical gain are proposed. Design parameters are found that work for III-V based compounds on diamond substrates, thus allowing semiconductor disk lasers with kW output power. Preliminary fabrications validates the concept by exhibiting a passive reflectivity ~99%.

Modulation doping is a commonly adopted technique to create two-dimensional (2D) electrons or holes in semiconductor heterostructures. One constraint, however, is that the intentional dopants required for modulation doping are controlled and incorporated during the growth of heterostructures. Using undoped strained germanium quantum wells as the model material system, we show, in this work, that modulation doping can be achieved post-growth of heterostructures by ion implantation and dopant-activation anneals. The carrier density is controlled ex situ by varying the ion fluence and implant energy, and an empirical calibration curve is obtained. While the mobility of the resulting 2D holes is lower than that in undoped heterostructure field-effect transistors built using the same material, the achievable carrier density is significantly higher. Potential applications of this modulation-doping technique are discussed.

We report the preparation, crystallization, and solid-state characterization of the first members of a new family of spiro-bis-(1,9-diamino-substituted-phenalenyl)boron neutral radicals. The crystal structures show that the three radicals are monomeric and without close contacts in the crystal lattice. In all cases magnetic susceptibility measurements confirm the presence of free radicals with one unpaired spin per molecule. Two of the new radical compounds are among the most highly conducting neutral organic solids, with room-temperature conductivities reaching sigma(RT) = 4 x 10(-2) S/cm. The measured conductivities correlate with the closest intermolecular contacts in the solid state and with the calculated band dispersions, even though the bandwidths are much smaller than those found in other organic conductors.

The ground-state and thermal properties of a two-dimensional array of Josephson coupled superconducting wires is studied. For rational values of the magnetic flux per plaquette, mean-field theory provides an accurate description and the system makes a transition to a vortex state. For small values of the magnetic flux per plaquette, mean-field theory also provides an adequate description. The measurement of critical currents can provide information on the ground state.

A simple analytical model for the signal acquisition range for a laser guided mortar is presented. The signal consists of a repetitively pulsed laser of fixed pulse duration and fixed pulse repetition frequency. The pulses are detected by a seeker consisting of a quadrant photodiode and a trans-impedance amplifier. Noise is introduced from solar irradiance and from the detector/amplifier electronics. The model maximizes the acquisition range by optimizing trans-impedance amplifier circuit components. A comparison of integrating multiple low energy pulses (MPLD) versus detecting each pulse individually (conventional) is made.

BackgroundWe compared the anti-depressant and cognitive effects of up to eight sessions of bilateral, brief pulse electroconvulsive therapy (ECT) administered twice (ECT x 2) or three times weekly (ECT x 3), to confirm that ECT x 3 acts more rapidly although the two schedules are equivalent in antidepressant outcome, and to establish whether ECT x 3 is indeed associated with more severe memory impairment.MethodPatients with major depression, endogenous subtype were randomly assigned to ECT x 3 or ECT x 2 plus one simulated ECT per week, both up to a maximum of eight real ECT. Depression was evaluated by the Hamilton Depression Scale the day after each treatment and cognitive function by a test battery administered before and after the ECT series and at one month follow-up.ResultsAssessed categorically or parametrically, there was no significant difference in antidepressant outcome between the two schedules. Rate of response was significantly more rapid with ECT x 3 but was associated with more severe memory impairment.ConclusionsTwice weekly administration is an optimum schedule for bilateral ECT unless clinical indications require the more rapid antidepressant effect of three times weekly treatment.