Automated source of squeezed vacuum states driven by finite state machine based software.

In the last few decades, much effort has been made for the production of squeezed vacuum states in order to reduce quantum noise in the audio-frequency band. This technique has been implemented in all running gravitational-wave interferometric detectors and helped to improve their sensitivity. While the detectors are acquiring data for astrophysical observations, they must be kept in the operating condition, also called "science mode," that is, a state that requires the highest possible duty-cycle for all the instrumental parts and controls. We report the development of a highly automated setup for the generation of optical squeezed states, where all the required control loops are supervised by a software based on finite state machines; we took special care to grant ease of use, stability of operation, and possibility of auto-recovery. Moreover, the setup has been designed to be compatible with the existing software and hardware infrastructure of the Virgo detector. In this paper, we discuss the optical properties of this squeezing setup, the locking techniques, and the automation algorithms.

A state observer for the Virgo inverted pendulum.

We report an application of Kalman filtering to the inverted pendulum (IP) of the Virgo gravitational wave interferometer. Using subspace method system identification techniques, we calculated a linear mechanical model of Virgo IP from experimental transfer functions. We then developed a Kalman filter, based on the obtained state space representation, that estimates from open loop time domain data, the state variables of the system. This allows the observation (and eventually control) of every resonance mode of the IP mechanical structure independently.

In-vacuum Faraday isolation remote tuning.

In-vacuum Faraday isolators (FIs) are used in gravitational wave interferometers to prevent the disturbance caused by light reflected back to the input port from the interferometer itself. The efficiency of the optical isolation is becoming more critical with the increase of laser input power. An in-vacuum FI, used in a gravitational wave experiment (Virgo), has a 20 mm clear aperture and is illuminated by an almost 20 W incoming beam, having a diameter of about 5 mm. When going in vacuum at 10(-6) mbar, a degradation of the isolation exceeding 10 dB was observed. A remotely controlled system using a motorized lambda=2 waveplate inserted between the first polarizer and the Faraday rotator has proven its capability to restore the optical isolation to a value close to the one set up in air.

Digital error-signal extraction technique for real-time automatic control of optical interferometers.

We describe an efficient and robust method for the extraction of the longitudinal error signal for the automatic control of optical interferometers, which can also be applied when the uncontrolled optical system spans hundreds of fringes. The method is based on classic modulation techniques (phase modulation, mechanical modulation, etc.), but extends their performances by the use of the information available only at the output photodiode. We digitally implemented such a method by following modular hardware and software architectures. We then tested the whole procedure in the automatic control of a suspended Michelson interferometer, showing its feasibility and the good performances.

Fringe-counting technique used to lock a suspended interferometer.

We implement a digital fringe-counting technique to measure in real time the relative mirror displacement of a suspended Michelson interferometer with modulated optical path length for oscillations much larger than the laser wavelength (λ). This provides the proper error signal for a servo mechanism that reduces the relative displacement within λ/2. The implemented technique does not require extra optics or polarizers and thus can be used for interferometric gravitational wave detectors as a starting procedure to get the system locked.

Cyclandelate versus flunarizine. A double-blind study in a selected group of patients with dementia.

A double-blind, double-dummy clinical trial was conducted in which the efficacy of cyclandelate 1600 mg daily was compared with that of flunarizine 10mg daily in 40 patients (25 men and 15 women) with dementia of cerebrovascular origin. Parameters were assessed before treatment, and after 45 and 90 days of therapy. At 90 days, significant improvements were observed in patients given cyclandelate in measurements of P100 latency in the left eye, neurological impairment, dementia scores, ischaemia scores, Gottfries mental deterioration scale, Hamilton depression scores, short term visual memory, long term memory, Bender-Gestalt test and Koh's blocks test. In flunarizine recipients, improvements were observed in neurological impairment, ischaemia scores, Gottfries scale and Hamilton depression scores. Patients treated with cyclandelate showed significantly greater ameliorations in symptoms as assessed by the ischaemia scale, evoked visual potential, visual memory and Koh's block test compared with those given flunarizine. However, in none of the parameters was flunarizine superior to cyclandelate.

Electromyographic study of diabetic and alcoholic polyneuropathic patients treated with gangliosides.

A double-blind, randomized electromyographic investigation was conducted of the effects of cerebral ganglioside treatment on patients suffering from diabetic or alcoholic polyneuropathy. Cerebral gangliosides (50 mg once a day) administered to 15 diabetic and to 15 alcoholic neuropathic patients for 40 days, facilitated the reappearance of sensory potentials and significantly increased the MAP amplitude in median, ulnar, and peroneal nerves. In relation to ganglioside treatment, there was no significant change in the conduction velocities or in the distal latencies of these nerves, nor was there a change in the duration of the MAPs. On the basis of these results, it is suggested that the cerebral gangliosides are capable of inducing an improvement in the excitability of nerve fibers and of facilitating the processes of reinnervation, probably by means of an enhancement of fiber sprouting.