Single-modulator, direct frequency comb spectroscopy via serrodyne modulation.

Traditional electro-optic frequency comb spectrometers rely upon the use of an acousto-optic modulator (AOM) to provide a differential frequency shift between probe and local oscillator (LO) legs of the interferometer. Here we show that these modulators can be replaced by an electro-optic phase modulator (EOM) which is driven by a sawtooth waveform to induce serrodyne modulation. This approach enables direct frequency comb spectroscopy to be performed with a single dual-drive Mach-Zehnder modulator (DD-MZM), allowing for lower differential phase noise. Further, this method allows for simpler production of integrated photonic comb spectrometers on the chip scale.

Porous superhydrophobic membranes: hydrodynamic anomaly in oscillating flows.

We have fabricated and characterized a novel superhydrophobic system, a meshlike porous superhydrophobic membrane with solid area fraction Φ(s), which can maintain intimate contact with outside air and water reservoirs simultaneously. Oscillatory hydrodynamic measurements on porous superhydrophobic membranes as a function of Φ(s) reveal surprising effects. The hydrodynamic mass oscillating in phase with the membranes stays constant for 0.9≲Φ(s)≤1, but drops precipitously for Φ(s)<0.9. The viscous friction shows a similar drop after a slow initial decrease proportional to Φ(s). We attribute these effects to the percolation of a stable Knudsen layer of air at the interface.

Resolved sideband emission of InAs/GaAs quantum dots strained by surface acoustic waves.

The dynamic response of InAs/GaAs self-assembled quantum dots (QDs) to strain is studied experimentally by periodically modulating the QDs with a surface acoustic wave and measuring the QD fluorescence with photoluminescence and resonant spectroscopy. When the acoustic frequency is larger than the QD linewidth, we resolve phonon sidebands in the QD fluorescence spectrum. Using a resonant pump laser, we have demonstrated optical frequency conversion via the dynamically modulated QD, which is the physical mechanism underlying laser sideband cooling a nanomechanical resonator by means of an embedded QD.

Observation of optomechanical buckling transitions.

Correlated phases of matter provide long-term stability for systems as diverse as solids, magnets and potential exotic quantum materials. Mechanical systems, such as buckling transition spring switches, can have engineered, stable configurations whose dependence on a control variable is reminiscent of non-equilibrium phase transitions. In hybrid optomechanical systems, light and matter are strongly coupled, allowing engineering of rapid changes in the force landscape, storing and processing information, and ultimately probing and controlling behaviour at the quantum level. Here we report the observation of first- and second-order buckling transitions between stable mechanical states in an optomechanical system, in which full control of the nature of the transition is obtained by means of the laser power and detuning. The underlying multiwell confining potential we create is highly tunable, with a sub-nanometre distance between potential wells. Our results enable new applications in photonics and information technology, and may enable explorations of quantum phase transitions and macroscopic quantum tunnelling in mechanical systems.

Psychiatric presentations of seizure disorders.

Seizure disorders may present with signs and symptoms that are usually associated with psychiatric disorders. Physicians must be alert to this possibility; they should use careful history taking in conjunction with EEGs to avoid misdiagnosing certain cases of psychomotor, petit male, and grand mal epilepsy.

The psychiatric resident as an ex-officio community board member.

The authors describe a program in which third-year psychiatric residents participate as ex-officio members on the boards of community service agencies. Experience as board members gives residents a broad understanding of issues related to the delivery of community mental health services and encourages them to continue community involvment after their training is completed.

Conjoint therapy of psychiatric problems in the elderly.

In treating elderly psychiatric patients, interviewing spouses together may be the most useful setting. Data gathering, reality testing and reality orientation can all be enhanced by the "well" spouse. The physician also can assess the value of the "well" spouse as a co-therapist. Two case reports illustrate this method of aiding treatment.

Single case study basilar artery migraine presenting as conversion hysteria.

A case of basilar migraine headache in a young woman is presented. Although the patient had been treated by a neurologist for 2 years, the diagnosis was not established. When she presented to the emergency room of a local hospital, another neurologist diagnosed conversion reaction. Although there had been problems in the family, neurological examination during an episode of headache revealed the typical features of basilar migraine headache. This case illustrates the need for sharp neurological diagnostic skills among psychiatrists, as well as the need to avoid mind-body dichotomies when possible. With treatment for migraine, the patient has done well for several months posthospitalization.

Heterodyne interferometer with subatomic periodic nonlinearity.

A new, to our knowledge, heterodyne interferometer for differential displacement measurements is presented. It is, in principle, free of periodic nonlinearity. A pair of spatially separated light beams with different frequencies is produced by two acousto-optic modulators, avoiding the main source of periodic nonlinearity in traditional heterodyne interferometers that are based on a Zeeman split laser. In addition, laser beams of the same frequency are used in the measurement and the reference arms, giving the interferometer theoretically perfect immunity from common-mode displacement. We experimentally demonstrated a residual level of periodic nonlinearity of less than 20 pm in amplitude. The remaining periodic error is attributed to unbalanced ghost reflections that drift slowly with time.