High sensitivity tool for geophysical applications: a geometrically locked ring laser gyroscope.

We demonstrate that a middle sized ring laser gyroscope (RLG) can be a very sensitive and robust instrument for rotational seismology, even if it operates in a quite noisy environment. The RLG has a square cavity, 1.60×1.60m 2, and it lies in a plane orthogonal to the Earth's rotational axis. The Fabry-Perot optical cavities along the diagonals of the square were accessed, and their lengths were locked to a reference laser. Through a quite simple locking circuit, we were able to keep the sensor fully operative for 14 days. We verified that the prototype properties are compatible with the seismic requirements. The obtained long term stability is of the order of 3 nanorad/s, and the short term sensitivity is close to 2n a n o r a d/s⋅H z -1/2. These results are limited only by the noisy environment; our laboratory is located in a building downtown.

Influence of the photon orbital angular momentum on electric dipole transitions: negative experimental evidence.

We describe an experiment of atomic spectroscopy devoted to ascertaining whether the orbital angular momentum (OAM) of photons has the same property of interacting with atoms or molecules as occurs for the spin angular momentum (SAM). In our experiment, rubidium vapors are excited by means of laser radiation with different combinations of OAM and SAM, particularly selected to inhibit or enhance the fluorescence according to the selection rules for the electric dipole transitions between the fundamental state and the first excited doublet. Our results clearly show that an electric-dipole-type transition is insensitive to the OAM value, and provide an original validation of a problem long debated in theoretical works.

Sensitive and robust second-harmonic interferometer for measuring the dispersion of the electro-optic coefficients in bulk materials.

Second-harmonic interferometry (SHI) is proposed for measuring the electro-optic (EO) coefficients of massive media. It combines the advantages of interferometric techniques with the mechanical stability of single-beam methods, simultaneously skimming the wavelength dispersion of the EO response. For demonstrating the effectiveness of the SHI technique, the EO coefficients r(33)(T) and r(13)(T) of the EO crystal lithium niobate are measured simultaneously at 1064 and 532 nm.

Dynamic formation of a hot field reversed configuration with improved confinement by supersonic merging of two colliding high-ß compact toroids.

A hot stable field-reversed configuration (FRC) has been produced in the C-2 experiment by colliding and merging two high-ß plasmoids preformed by the dynamic version of field-reversed θ-pinch technology. The merging process exhibits the highest poloidal flux amplification obtained in a magnetic confinement system (over tenfold increase). Most of the kinetic energy is converted into thermal energy with total temperature (T{i}+T{e}) exceeding 0.5 keV. The final FRC state exhibits a record FRC lifetime with flux confinement approaching classical values. These findings should have significant implications for fusion research and the physics of magnetic reconnection.

Jet outflow and open field line measurements on the C-2U advanced beam-driven field-reversed configuration plasma experiment.

Knowledge and control of the axial outflow of plasma particles and energy along open-magnetic-field lines are of crucial importance to the stability and longevity of the advanced beam-driven field-reversed configuration plasma. An overview of the diagnostic methods used to perform measurements on the open field line plasma on C-2U is presented, including passive Doppler impurity spectroscopy, microwave interferometry, and triple Langmuir probe measurements. Results of these measurements provide the jet ion temperature and axial velocity, electron density, and high frequency density fluctuations.

Preparation of small size palladium nanoparticles by picosecond laser ablation and control of metal concentration in the colloid.

We assessed a method for the preparation of small, highly stable and unprotected Pd nanoparticles by picosecond laser ablation in 2-propanol. The nanoparticles can be extracted from 2-propanol by centrifugation and redispersed in water, where a strongly negative ζ-potential assures long term stability. The proposed procedure permits reduction of particle size down to 1.6nm and optimization of the Pd(0):Pd(II) ratio which, in the best cases, was of the order of 6:1. The increase of this ratio with ablation times has been correlated to the high temperature conversion of PdO to metallic Pd by a simple theoretical model. A study of the relationship between colloid absorption at 400nm and Pd concentration permitted the role of PdO in the determination of the UV-vis spectra to be clarified and the limits of the Mie theory for the evaluation of colloid concentration to be established. The absorption at 400nm can be used as a fast method to estimate the Pd content in the colloids, provided that a calibration of the ablation process is preliminarily performed.

Bioelectrical impedance techniques in medicine. Part III: Impedance imaging. Second section: reconstruction algorithms.

This section is devoted to the reconstruction algorithms published in the literature and developed for reconstructing the electrical conductivity and permittivity inside a body from measurements made on the body surface. These algorithms fall into two main categories. The first, based on linear approximations, are noniterative methods assuming that conductivity does not differ very much from a constant. Examples of noniterative methods are the Barber-Brown back-projection method and related methods, the Calderon's approach, the moment method, and one-step Newton methods. The second class of methods consists of iterative methods, which typically include output least squares for various functions. A related class includes the adaptive methods, in which the applied patterns of current are adjusted to get the best signal. A review of all these different alternatives is presented.

Using the Hilbert uniqueness method in a reconstruction algorithm for electrical impedance tomography.

This paper presents a new version of the layer stripping algorithm in the sense that it works essentially by repeatedly stripping away the outermost layer of the medium after having determined the conductivity value in this layer. In order to stabilize the ill posed boundary value problem related to each layer, we base our algorithm on the Hilbert uniqueness method (HUM) and implement it with the boundary element method (BEM).

A direct sensitivity matrix approach for fast reconstruction in electrical impedance tomography.

In electrical impedance imaging, several proposed reconstruction algorithms have employed the concept of a sensitivity matrix, which can be used to relate the magnitude of a boundary voltage change of a 2D object to the change in conductivity inside the object that has given rise to it. The search for an appropriate inversion of the sensitivity matrix is the key to these algorithms. In this work, a method called the direct sensitivity matrix (DSM) approach for fast image reconstruction is proposed. Both theoretical and experimental results showing the efficiency of this proposed method are also presented.

3D reconstruction in electrical impedance imaging using a direct sensitivity matrix approach.

This paper represents a reconstruction algorithm using a direct sensitivity matrix (DSM) approach for fast 3D image reconstruction in electrical impedance imaging. The boundary element method (BEM) is used in the construction of this matrix. The first images of a conductivity perturbation inside a sphere are reconstructed, using theoretical data.

[Efficacy and tolerability of nicardipine retard and captopril in hypertension in the aged. Results of a multicenter study]. / Efficacia e tollerabilità della nicardipina retard e del captopril nell'ipertensione dell'anziano. Risultati di uno studio multicentrico.

The efficacy and tolerability of nicardipine retard and captopril were assessed in 174 over-60-year-olds suffering from slight or moderate essential hypertension. After 2-3 weeks of wash out the patients were randomly assigned to calcium antagonist (40 mg twice a day) or ace-inhibitor (25 mg twice a day) treatment which continued for 180 days. Monotherapy was combined with hydrochlorothiazide (12.5 mg/day) after 2 months in the event of an unsatisfactory reduction of arterial pressure in relation to basal values. Systolic and diastolic blood pressure was measured (1st and 5th Korotkoff's tone) at monthly intervals while lying and standing; heart rate was also measured using a palpatory method. Both nicardipine retard (no. 86) and captopril (no. 88) caused a significant reduction of clino- and orthostatic systolic and diastolic arterial pressure during the first two months of treatment. Respectively 70% and 51% of patients responded to treatment and the blood pressure reductions achieved using monotherapy remained unchanged during the course of the study. The association of hydrochlorothiazide resulted in a significant decrease in arterial pressure in non-responders, an effect which was observed with both nicardipine retard and captopril. No significant variation in heart rate was recorded between the two groups. Twenty-one patients in the nicardipine retard group and 16 in the captopril group suffered from slight to moderate side effects. Six patients dropped out of the nicardipine retard group and 15 patients out of the captopril group, an event for which side-effects were responsible in 1 and 3 cases respectively. In conclusion, nicardipine retard and captopril represent an efficacious form of treatment for geriatric hypertension and possess a satisfactory level of tolerability.

Spectroscopic measurement of ion temperature and ion velocity distributions in the flux-coil generated FRC.

One aim of the flux-coil generated field reversed configuration at Tri Alpha Energy (TAE) is to establish the plasma where the ion rotational energy is greater than the ion thermal energy. To verify this, an optical diagnostic was developed to simultaneously measure the Doppler velocity-shift and line-broadening using a 0.75 m, 1800 groves/mm, spectrometer. The output spectrum is magnified and imaged onto a 16-channel photomultiplier tube (PMT) array. The individual PMT outputs are coupled to high-gain, high-frequency, transimpedance amplifiers, providing fast-time response. The Doppler spectroscopy measurements, along with a survey spectrometer and photodiode-light detector, form a suite of diagnostics that provide insights into the time evolution of the plasma-ion distribution and current when accelerated by an azimuthal-electric field.

Doppler spectroscopy and D-alpha emission diagnostics for the C-2 FRC plasma.

Two Doppler spectroscopy diagnostics with complementary capabilities are developed to measure the ion temperatures and velocities of FRC plasmas in the C-2 device. First, the multichord ion doppler diagnostic can simultaneously measure 15 chords of the plasma using an image intensified camera. Second, a single-chord fast-response ion Doppler diagnostic provides much higher faster time response by using a 16-channel photo-multiplier tube array. To study the neutral density of deuterium under different wall and plasma conditions, a highly sensitive eight-channel D-alpha diagnostic has been developed and calibrated for absolute radiance measurements. These spectroscopic diagnostics capabilities, combined with other plasma diagnostics, are helping to understand and improve the field reversed configuration plasmas in the C-2 device.

Modì: a new mobile instrument for in situ double-pulse LIBS analysis.

Laser-induced breakdown spectroscopy (LIBS) is a promising technique for in situ elemental analysis. A new mobile instrument for LIBS analysis, developed in a collaboration between Marwan Technology s.r.l. and the Applied Laser Spectroscopy Laboratory in Pisa, is presented, and some applications of it and results from it are outlined. The innovative experimental set-up, based on the use of two suitably retarded laser pulses and a standardless analysis procedure, which overcomes problems related to matrix effects, greatly improves the potential of this technique for accurate quantitative analysis.

Conductivity interface modelling with dipoles by means of optimal control and boundary element methods in impedance tomography.

Optimal control techniques have been combined with Alessandrini's singular perturbation method and Wexler's algorithm to reconstruct images in impedance imaging. We have also considered an integral formulation of the potential problem, which has led us to introduce an array of dipoles whose position, orientation and length can be optimised to model the conductivity discontinuities.