Gerardo Giordano

Mechanical monolithic horizontal sensor for low frequency seismic noise measurement

This paper describes a mechanical monolithic horizontal sensor for geophysical applications developed at the University of Salerno. The instrument is basically a monolithic tunable folded pendulum, shaped with precision machining and electric discharge machining, that can be used both as seismometer and, in a force-feedback configuration, as accelerometer. The monolithic mechanical design and the introduction of laser interferometric techniques for the readout implementation makes it a very compact instrument, very sensitive in the low frequency seismic noise band, with a very good immunity to environmental noises. Many changes have been produced since last version (2007), mainly aimed to the improvement of the mechanics and of the optical readout of the instrument. In fact, we have developed and tested a prototype with elliptical hinges and mechanical tuning of the resonance frequency together with a laser optical lever and a new laser interferometer readout system. The theoretical sensitivity curve for both laser optical lever and laser interferometric readouts, evaluated on the basis of suitable theoretical models, shows a very good agreement with the experimental measurements. Very interesting scientific result is the measured natural resonance frequency of the instrument of 70 mHz with a Q=140 in air without thermal stabilization. This result demonstrates the feasibility of a monolithic folded pendulum sensor with a natural resonance frequency of the order of millihertz with a more refined mechanical tuning.

Tunable mechanical monolithic sensor with interferometric readout for low frequency seismic noise measurement

Abstract This paper describes a mechanical horizontal monolithic sensor developed at the University of Salerno. The instrument is basically a monolithic tunable folded pendulum, shaped with precision machining and electric-discharge-machining, that can be used both as seismometer and, in a force-feedback configuration, as accelerometer. It is a very compact instrument, very sensitive in the low-frequency band, with a very good immunity to environmental noises, with tunable resonance frequency and integrated laser optical readout.

Low Frequency - High Sensitivity Horizontal Inertial Sensor based on Folded Pendulum

This paper describes a new implementation of monolithic horizontal sensor, developed at the University of Salerno, based on the Folded Pendulum architecture, configurable both as seismometer and as accelerometer. The large low-frequency band (10-6 ÷ 10Hz), the high sensitivity ( in the band 0.1 ÷ 10 Hz) and the high quality factor in air (Q > 1500) are largely better than all the previous Folded Pendulum implementations. Moreover its monolithic implementation of the whole mechanics, coupled with a full tunability of its resonance frequency (70 mHz ÷ 1.2 Hz) obtained with a specially designed calibration procedure and with an integrated laser optical readout, guarantees both compactness, robustness and immunity to environmental noises. This makes this sensor suitable for a large number of scientific applications, also in high vacuum and cryogeny. Applications of this sensor are already started in the field of geophysics, including the study of seismic and newtonian noise for characterization of suitable sites for future underground interferometric detectors of gravitational waves.

Tunable mechanical monolithic horizontal sensor with high Q for low frequency seismic noise measurement

A tunable mechanical horizontal monolithic seismometer/accelerometer, developed for applications in the fields of geophysics and interferometric detection of gravitational waves of second and third generation, is described. The large measurement band (10−3 ÷ 10 Hz) with sensitivities of ≈ 10−12m/, as seismometer, and better than 10−11 m/s2/, as accelerometer, have been obtained with an optimised mechanical design and the introduction of a very sensitive laser interferometric optical readout, the latter aimed also to ensure a very good immunity to environmental noises. Prototypes of seismometers are operational in selected sites both to acquire seismic data for scientific analysis of seismic noise and to collect all the useful information to understand their performances in the very low frequency band (10−6 ÷ 10−3 Hz).

Microseismic studies of an underground site for a new interferometric gravitational wave detector

To improve the sensitivity of the future generation of gravitational wave interferometers in the frequency range around 1 Hz it is necessary to decrease the seismic and Newtonian noise affecting the detector performance. This goal is achieved by installing the experimental apparatus in an appropriate underground site, where the Rayleigh surface wave of the microseismic motion should be attenuated. Here we report the results of an experimental campaign devoted to a long term characterization of one of the potential sites for the construction of a third generation of gravitational wave detector: the former mine of Sos Enattos (Sardinia, Italy). We analyzed the seismic stability within the low-frequency sensitivity band of a third generation gravitational observatory and the correlation between the microseismic band and the weather conditions, in particular focusing on the Tyrrhenian sea status.

Low frequency, high sensitive tunable mechanical monolithic horizontal sensors

This paper describes an optimized version of the mechanical version of the monolithic tunable folded pendulum, developed at the University of Salerno, configurable both as seismometer and, in a force-feedback configuration, as accelerometer. Typical application of the sensors are in the field of geophysics, including the study of seismic and newtonian noise for characterization of suitable sites for underground interferometer for gravitational waves detection. The sensor, shaped with precision machining and electric-discharge-machining, like the previous version, is a very compact instrument, very sensitive in the low-frequency seismic noise band, with a very good immunity to environmental noises. Important characteristics are the tunability of the resonance frequency and the integrated laser optical readout, consisting of an optical lever and an interferometer. The theoretical sensitivity curves, largely improved due to a new design of the pendulum arms and of the electronics, are in a very good agreement with the measurements. The very large measurement band (10-6 ± 10Hz) is couple to a very good sensitivity (10-12 m/√Hz in the band 0.1 ± 10Hz), as seismometer. Prototypes of monolithic seismometers are already operational in selected sites around the world both to acquire seismic data for scientific analysis of seismic noise and to collect all the useful information to understand their performances in the very low frequency band (f < 1mHz). The results of the monolithic sensor as accelerometer (force feed-back configuration) are also presented and discussed. Particular relevance has their sensitivity that is better than 10-11 m/s2/√Hz in the band 0.1 ± 10Hz. Finally, hypotheses are made on further developments and improvements of monolithic sensors.

Low frequency seismic characterization of underground sites with tunable mechanical monolithic sensors

This paper describes the application on a new mechanical implementation of an inertial seismic sensor, configurable also as an force-balanced accelerometer, consisting of monolithic full symmetric Folded Pendulum equipped with an high sensitivity optical readout. The seismic sensor is, therefore, compact, light, scalable, resonant frequency tunable, with large measurement band, low thermal noise and with good immunity to environmental noises. The measured minimum displacement noise is in very good agreement with the theoretical ones. Typical applications are in the field of earthquake engineering, geophysics, civil engineering and in all applications requiring large band-low frequency performances coupled with high sensitivities.

A principal components algorithm for spectra normalisation

There is an increasing use of spectroscopic techniques, such as high-resolution NMR spectroscopy, to examine variations in cell metabolism and/or structure in response to numerous physical, chemical, and biological agents. In these types of studies, in order to obtain relative quantitative information, a comparison between signal intensities of control samples and treated or exposed ones is often conducted. A possible strategy is to estimate, by an opportune algorithm, a normalisation constant which takes into consideration all cell metabolites in the sample. In this paper, a new normalisation algorithm based on Principal Component Analysis (PCA) is presented. PRICONA (PRIncipal COmponent Normalisation Algorithm) is advantageous in normalising simultaneously great data sets of spectra, in individuating signals that could have been affected by the agent, and in allowing to measure their quantitative variation. The algorithm was tested by Monte Carlo simulations as well as experimentally.

Low frequency inertial control strategy for seismic attenuation with multi-stage mechanical suspensions

In this paper we present preliminary experimental results relative to the control of a multi-stage seismic attenuators and inertial platforms in the band 0:01±10Hz, using a open loop monolithic folded pendulum as inertial sensors. In fact, beyond the obvious compactness and robustness of monolithic implementations of folded pendulum, the main advantages of this class of sensors are the tune-ability of the resonance frequency, the high sensitivity, due to integrated laser optical readout, in a large measurement band. The results are presented and discussed in this paper together with the planned further developments and improvements.

Comparison of 1H-NMR spectra by normalisation algorithms for studying amyloid toxicity in cells

A range of debilitating human diseases is associated with the formation of stable, highly organised, protein aggregates, the amyloid fibrils. Substantial evidence suggests that Prefibrillar Oligomeric Aggregates (PFAs), preceding mature fibrils formation, are the crucial species in the onset of the neuronal degeneration even if with mechanisms to be further cleared. In this work, we show how 1H-NMR cell spectral analysis methods can prove to be very effective tools to clear the PFAs amyloid cytotoxicity mechanisms. Following the same method shown by Vilasi, we apply a new 1H-NMR analysis algorithm to identify the metabolites significantly varied in cells incubated with toxic oligomers from the amyloidogenic W7FW14F mutant of apomyoglobin. Our main aim is to confirm the results obtained by Vilasi et al., normalising a set of different data spectra with the new PRICONA algorithm here described, thus contributing to strengthen the general framework of metabolites and proteins involved in cellular amyloid toxicity.