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The Layer-Oriented Simulation Tool (LOST) is a numerical simulation code developed for analysis of the performance of multiconjugate adaptive optics modules following a layer-oriented approach. The LOST code computes the atmospheric layers in terms of phase screens and then propagates the phase delays introduced in the natural guide stars’ wave fronts by using geometrical optics approximations. These wave fronts are combined in an optical or numerical way, including the effects of wave-front sensors on measurements in terms of phase noise. The LOST code is described, and two applications to layer-oriented modules are briefly presented. We have focus on the Multiconjugate adaptive optics demonstrator to be mounted upon the Very Large Telescope and on the Near-IR-Visible Adaptive Interferometer for Astronomy (NIRVANA) interferometric system to be installed on the combined focus of the Large Binocular Telescope.

Layer Oriented represented in the last few years a new and promising aproach to solve the problems related to the limited field of view achieved by classical Adaptive Optics systems. It is basically a different approach to multi conjugate adaptive optics, in which pupil plane wavefront sensors (like the pyramid one) are conjugated to the same altitudes as the deformable mirrors. Each wavefront sensor is independently driving its conjugated deformable mirror thus simplifying strongly the complexity of the wavefront computers used to reconstruct the deformations and drive the mirror themselves, fact that can become very important in the case of extremely large telescopes where the complexity is a serious issue. The fact of using pupil plane wavefront sensors allow for optical co-addition of the light at the level of the detector thus increasing the SNR of the system and permitting the usage of faint stars, improving the efficiency of the wavefront sensor. Furthermore if coupled to the Pyramid wavefront sensor (because of its high sensitivity), this technique is actually peforming a very efficient usage of the light leading to the expectation that, even by using only natural guide stars, a good sky coverage can be achieved, above all in the case of giant telescopes. These are the main reasons for which in the last two years several projects decided to make MCAO systems based on the Layer Oriented technique. This is the case of MAD (an MCAO demonstrator that ESO is building with one wavefront sensing channel based on the Layer Oriented concept) and NIRVANA (an instrument for LBT). Few months ago we built and successfully tested a first prototype of a layer oriented wavefront sensor and experiments and demonstrations on the sky are foreseen even before the effective first light of the above mentioned instruments. The current situation of all these projects is presented, including the extensive laboratory testing and the on-going experiments on the sky.

MAD’s mission is to demonstrate the feasibility of Multi-Conjugate Adaptive Optics (MCAO) as a prerequisite for the 100-m OWL telescope, as well as several 2nd Generation VLT Instruments. It aims at comparing the relative merits of different methods and, therefore, alternatively employs multiple Shack-Hartmann and layer-oriented wavefront sensors requiring 3 and 2 detector units respectively. The 5 detector heads will be identical and equipped with CCD50 devices from Marconi, which have already been successfully tested with the VLT AO instrument NAOS-CONICA. ESO’s standard CCD controller FIERA will be utilized in its new version, upgraded to a PCI bus board.

This study describes the evolution of the concept of health in Italian occupational health legislation (1900-2001). Mental health dimensions at work (such as reduction in monotony and repetitiveness, mental risks in pregnancy and so on) were introduced only recently. This can be explained with: 1) poor working conditions; 2) the delay of the occupational health community in including mental health in the concept of health; 3) the gap between scientific knowledge of risk factors for mental health and legislation aimed at prevention.

Over the past two years ESO has reinforced its efforts in the field of Adaptive Optics. The AO team has currently the challenging objectives to provide 8 Adaptive Optics systems for the VLT in the coming years and has now a world-leading role in that field. This paper will review all AO projects and plans. We will present an overview of the Nasmyth Adaptive Optics System (NAOS) with its infrared imager CONICA installed successfully at the VLT last year. Sodium Laser Guide Star plans will be introduced. The status of the 4 curvature AO systems (MACAO) developed for the VLT interferometer will be discussed. The status of the SINFONI AO module developed to feed the infrared integral field spectrograph (SPIFFI) will be presented. A short description of the Multi-conjugate Adaptive optics Demonstrator MAD and its instrumentation will be introduced. Finally, we will present the plans for the VLT second-generation AO systems and the researches performed in the frame of OWL.

The Adaptive Optics for the Telescopio Nazionale Galileo module (namely AdOpt@TNG) implements the pyramid wavefront sensor as a unique feature. This allows to get valuable information on its performance on the sky. An updated overview of the results obtained so far is shown, including a discussion on the sources of errors in the closed loop operation, distinguishing them between the ones specific of the pyramid wavefront sensor and the one more related to the system as a whole. This system allows also for a number of experiments and check of the sensitivity of such a wavefront sensor, especially in comparison with other types of sensing units. The ways to accomplish such an experiment in a convincing way are shown along with the first results obtained so far. Finally, we describe how and up to which extent a number of practical problems encountered in the near past can be solved implementing the recent new ideas on the pyramid theme, many of which popped up from our "lessons learned".

Layer Oriented MCAO is a promising technique attempting to perform wide field of view correction with Natural Guide Stars. In the extended concept of Multiple Field of View Layer Oriented MCAO the wavefront sensor field of view is enlarged to collect more photons from more Natural Guide Stars and, in principle, significant sky coverages at any galactic latitude are achieved using only Natural Guide Stars. In this paper we address the problem of finding the best magnitude range for the Natural Guide Stars in order to achieve the best correction with the largest sky coverage in the Layer Oriented Multiple Field of View. For a given Field of View and sky direction we consider only the Natural Guide Stars within a given brightness range and we compute the equivalent integrated magnitude. Then we correlate the contribution in sky coverage of the previously considered Natural Guide Stars and we extrapolate which is the magnitude class giving the largest sky coverage. Once identified the more suitable Natural Guide Star magnitude class we discuss the possible implications in the design of a Multiple Field of View Layer Oriented wavefront sensor and we give the order of magnitude for the main parameters, i.e., maximum number of Natural Guide Stars and detector characteristics.

A demonstrator of the multi-conjugate adaptive optics concept is under construction at ESO and will be installed on the Nasmyth focus of the VLT. This demonstrator called MAD will have two different wavefront sensor channels: Shack-Hartmann and Layer-Oriented; in this article we only describe the Layer-Oriented one. The Layer-Oriented wavefront sensor can select eight reference stars in the two arc-minutes corrected field of view in order to have a maximum of two references in each quarter of the field. XY stages will remotely adjust the position of each reference star selector. The starlight will be fed onto two detectors and two completely independent loops will drive the deformable mirrors, one conjugated to the ground and the other to an altitude of approximately 8 km. The Layer-Oriented wavefront sensor will use the same CCDs than the Shack-Hartmann channel and the pupil will be divided into 9×9 subapertures both for the high and for the ground layer. The spatial sampling of the subapertures will be different for the two CCDs and their integration time will be tuned to typical values of the conjugated altitudes characteristic wind speed. The overall status of the instrument with respect to optics, mechanics, electronics and software is given hereafter. We also summarize the progress on the procurement phase and give the time schedule for the assembling, integration and testing phases.

In this paper, we review the salient facts for a range of available atmosphere emulation technologies, and in the framework of the ESO Multi-Conjugate-AO demonstrator project, aptly called MAD, we present our phase screen test results for silver-sodium ion-exchange, transmissive phase screens. We find (a) that the measured power spectrum of phase fluctuations is consistent with the input Von Karman spectrum and (b) that by tracking the best focus of ten spots formed by a silver-sodium ion-exchange micro-lens array, it was found that the wavelength dependence of 1.266μm of phase-shift is 1.5±2.5% relative to air in the wavelength range 550nm to 800μm. Additionally, we present our optical design and specifications for MAPS, the Multi-Atmospheric Phase screens and Stars instrument that will be used to test MAD before shipment to the VLT. It includes glass screens conjugate to the 0.25km, 3.0km, and 9.0km atmospheric layers above the telescope. We explain the reasoning behind the choice of pupil size and implications for phase screen proximity, footprint sizes, and wind speed gradients. Our design mimics the VLT Nasmyth F/15 focal plane in terms of plate scale, field of view, high Strehl, and field curvature.

Multi-Conjugate Adaptive Optics (MCAO) is working on the principle to perform wide field of view atmospheric turbulence correction using many Guide Stars located in and/or surrounding the observed target. The vertical distribution of the atmospheric turbulence is reconstructed by observing several guide stars and the correction is applied by some deformable mirrors optically conjugated at different altitudes above the telescope. The European Southern Observatory together with external research institutions is going to build a Multi-Conjugate Adaptive Optics Demonstrator (MAD) to perform wide field of view adaptive optics correction. The aim of MAD is to demonstrate on the sky the feasibility of the MCAO technique and to evaluate all the critical aspects in building such kind of instrument in the framework of both the 2nd generation VLT instrumentation and the 100-m telescope OWL. In this paper we present the conceptual design of the MAD module that will be installed at one of the VLT unit telescope in Paranal to perform on-sky observations. MAD is based on a two deformable mirrors correction system and on two multi-reference wavefront sensors capable to observe simultaneously some pre-selected configurations of Natural Guide Stars. MAD is expected to correct up to 2 arcmin field of view in K band.

Layer-Oriented MCAO is a promising technique that can scale up easily compared to similar competing techniques. The Multiple-Field-of-View Layer-Oriented make a further step employing more guide stars to sample the turbulence with the net effect of increasing the sky coverage enabling MCAO systems based only natural guide stars. However even a simple estimation of Layer-Oriented M-FoV MCAO performance for the Extremely Large Telescopes, in particular for OWL, has not been attempted yet. The main problem is the enormous amount of computing power (processor and memory) required to properly carry out an accurate simulation for ELTs. In this work we perform a numerical simulation using some shortcuts to simplify the problem and achieve a first cut of what the performance of Layer-Oriented M-FoV MCAO could be for a 100m-class telescope. We take a mixed analytical-numerical approach in order to significantly reduce the amount of computing power required while maintaining a good level of accuracy.

Preliminary requirements and possible technological solutions for the next generation of ground-based optical telescopes were laid down at ESO in 1998. Since then, a phase A study has been commissioned, the objective of which is to produce a conceptual design compatible, to the maximum possible extent, with proven technology, and establish realistic plans for detailed design, site selection, construction and operation for a 100-m class optical, diffraction-limited telescope. There was no doubt about how daunting such a challenge would be, but, somewhat surprisingly, it turns out to be firmly confined to adaptive optics concepts and technologies. The telescope itself appears to be feasible within the allocated budget and without reliance on exotic assumptions. Fabrication of key subsystems is fully within the reach of a properly engineered, industrialized process. A consolidated baseline is taking shape, and alternative system and subsystem solutions are being explored, strengthening the confidence that requirements could be met. Extensive development of wavefront measurement techniques enlarges the palette of solutions available for active wavefront control of a segmented, active telescope. At system level, ESO is developing enabling experiments to validate multi-conjugate adaptive optics (MAD for Multi-conjugate Adaptive optics Demonstrator) and telescope wavefront control (APE, for Active Phasing Experiment).

The concept of Pyramid Wavefront sensor has been introduced as a more compact and flexible alternative to Shack--Hartmann wavefront sensing. In the past five years, however, such a novel concept promised a much larger sensitivity and an inherent easiness to be implemented in a multiple reference wavefront sensor. AdOptTNG, a natural guide star based adaptive optics module implemented at the 3.5m TNG telescope is equipped with such a sensor. We report here on the updated status, including on-sky experimental verification of various of the several features of such a sensor. We discuss the results obtained, their scalability and the lessons learned in building, aligning and operating it. Some comparison with theoretical and laboratory-based result, is also tentatively reported.

In layer-oriented adaptive optics, multiconjugation is performed in a much more efficient way than conventional wavefront sensing. This improved efficiency is impressive for high altitude layers and moderate for ground ones. On the other hand high altitude layers can be covered with only a limited field of view (where one can search for natural guide stars) while for ground layers the usable field of view is limited essentially by practical reasons. We introduce the further concept of multiple field of view layer oriented where a combination of sampling and covered field leads easily to sky coverages that nearly approach the whole sky with the usage of solely natural guide stars for 8m class telescopes.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The Galileo Telescope is a Ritchey-Chretienne telescope with an aperture of 3.58 meters and is located in La Palma Island. Since the first light in June 1998, several nights have been used to calibrate and to test the active optics systems, an operation involving also the control and reduction software and the optics of the de-rotator system. At the moment the active optics system routinely works at the beginning of the nights to support both technical and scientific observations. The ultimate tests on the control system are here reported and its performances are analyzed in order to quantify the final optical quality. Also a brief report on the effects of the serrourier temperature is reported. A comparison between Shack-Hartmann analysis performed on the rotator adapter bench and wavefront analysis on the instrument focal plane (at Nasmith station) is also reported. Some images taken in the visible and near infrared ranges during the same night are shown.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The European Southern Observatory is developing a medium order curvature adaptive optics system designed to be operable with minimal modification at any focus of the Very Large telescope (VLT). The first application of this AO system (MACAO) is to equip all four VLT Unit Telescope (UT) Coude foci with 60 element AO systems capable of delivering to the VLT Interferometer (VLTI) > 50% K band Strehl. The AO system being used by an interferometer is constrained to introduce minimal piston and operating as a sub-system of a large and complex instrument to have a robust architecture and simple operation. Installation of the first AO system is scheduled to begin first Quarter 2002 with completion of all four UTs by early 2004. Other applications of the MACAO system will be for use by the CRIRES and SPIFFI spectrographs.

For giant, 100 m-class, telescopes, a completely new class of problems arises. Trying to solve them adopting the techniques used for the classical 4 ... 10 m-class telescope systems is indeed a reductive approach. Because of the cone effect and of the difficulties in retrieving the tilt due to the use of LGSs, tomography and multiconjugation will play a central role in the development of these systems. We review the tomographic concept and we report about recent experiments to validate the concept using sky observations. The Field of View requirement is another crucial step in the design of the optical system of these telescopes and hence it needs to be attacked in a detailed and as wide as possible approach. The adoption of classical wavefront sensors looking to different stars is here overcome with wavefront sensors directly conjugated to different layers, with big advantages in term of intrinsic complication of the system, both from the optomechanical point of view (less complexity and saving of a huge amount of light) and from the computational point of view. The adoption of these new sensing techniques (that, gaining from the close loop situation, can be efficiently coupled to a number of very faint stars, whose complexity does not scale with the number of references but, rather, to the number of sensed layers) is here reviewed. This concept of multiple object wavefront sensing leads to an example of a system with a minimum number of independent adaptive optics loop, in which each layer represented in a wavefront sensor can be conjugated to a specifically conjugated deformable mirror.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The AdOptTNG module is an adaptive optics facility permanently mounted at the Nasmyth focus of the 4m-class Telescopio Nazionale Galileo (TNG). Its integration on the telescope started in late November 1998 and first-light of the speckle and tip-tilt modes took place shortly after. Both modes have been offered to the astronomical community and turned out to provide performances close to the expectations. Double stars with separation below 0.1 arcsec have been resolved by the speckle facility. Improvement of the Strehl ratio of a factor two and enhancement in the FWHM from 0.65 arcsec to 0.35 arcsec have been obtained on relatively faint reference stars. The high-speed low noise CCD, namely an 80 X 80 pixel read from the four corners, has been mounted and aligned with the Shack-Hartmann wavefront sensor. A Xinetics mirror with 96 actuators has been calibrated against the wavefront sensor with on-board alignment fibers. This has been done using a modal approach and using Singular Value Decomposition in order to get a reliable interaction matrix. Filtering can be modal too, using a default integrative filter coupled with a limited FIR-fashioned technique. Open loop measurements on the sky provide data to establish open loop transfer functions and realistic estimates of limiting magnitude. High-order wavefront correction loop has been successfully tested on the sky. In this paper we give a description of the overall functionality of the module and of the procedure required to acquire targets to be used as reference in the correction. A brief overview of the very first astronomical results obtained so far on angular size and shape measurements of a few asteroids and sub-arcsec imaging of Planetary Nebulae and Herbig Haro objects is also given.

The pyramid wavefront sensor is a novel concept device whose features are attractive for adaptive optics for several reasons. We show here the first loop closure of an AO system using this kind of sensor at the focal plane of a 4m-class telescope. One of the critical optical elements of our wavefront sensor is the pyramid that splits the light from the star used for the wavefront correction. This component is essentially a four faces prism having actually a full vertex angle of 7 degrees with specifications on its edges and roof of 4 - 5 microns or better. The best turned edges obtained on the prototypes already built have shown values of the order of 6 microns, with roofs of the same order, not far from the required tolerances. In this article we describe the techniques and the system used for the construction of this optical component and the improvements to the polishing procedure that we plan to adopt in order to increase the quality of its edges and optical surfaces. Pixel processing is suitable to fit with existing Shack-Hartmann systems, making this device an attractive add-on option for existing SH-based AO systems. The plans for future developments in order to firmly establish the performances of the pyramid wavefront sensor are briefed out.

In this paper we integrate the dynamic models formulated by the microeconomic theory of trade unions and the differential games approach. We demonstrate that the results of the dynamic monopoly union model, elaborated by Kidd and Oswald (1987) and Jones and McKenna (1994), can be obtained as solutions of a Stackelberg differential game between firms and unions under particular assumptions on union’s membership dynamic. We also develop a Nash differential game whose solutions imply a cycle in wage share of product and employment rate which resembles Goodwin’s (1967) cyclical growth path. This result is obtained by use of the Hopf theorem on local bifurcations, under particular hypotheses on the membership dynamics.

The use of a Laser Guide Star (LGS) in an Adaptive Optics system in order to increase the sky coverage, leads to a degradation of correction performances caused by the focus anisoplanatism, or cone effect, the LGS upward tilt indetermination and the defocusing produced by the non-constant altitude of the LGS. If the Adaptive Optics system has the typical configuration of a Shack-Hartmann wavefront sensor and a piezo-stack deformable mirror, a possible partial solution to solve the problem is to add a low order curvature wavefront sensor able to look at an off-axis a natural guide star close enough to the observed object. In fact the very low order modes (tip-tilt, defocus and astigmatism) are the most degraded by the LGS use but they have also the largest isoplanatic patch especially in the near infrared (H,K bands) wavelengths. With this configuration the Shack-Hartmann sensor provides the coefficients for the higher order modes while the curvature sensor provide the coefficients for the lower order ones. In this way the tilt and conical anisoplanatisms are partially reduced and there is also a continuos monitoring of the sodium layer altitude. Furthermore another aspect is the comparison of the performances at very faint magnitudes between a Shack-Hartmann and a low order curvature sensor in order to check if the reduced pupil sampling provides a better correction. In this framework a simulation work has been developed to study the coupling performances of a curvature sensor with a piezo-stack mirror; the code has been written in IDL. Keywords: adaptive optics, laser guide stars, numerical simulations, curvature wavefront sensors, deformable mirrors

We describe in this paper the development of a simulation tool for modeling any kind of adaptive optic system with laser guide star within the framework of the European network Laser Guide Star for 8-m Class Telescopes. This is intended to support investigations about laser guide stars problems line cone effect and tip-tilt determination. The different kinds of software modules to be developed are listed and the libraries already distributed among the network are described: phase screen generation, downward propagation, wavefront sensing and reconstruction. The future studies for solving the cone effect are also presented.

The adaptive optics modules for the Italian Telescopio Nazionale Galileo, namely AdOptTNG, is ready to be mounted at the telescope. First light will take place with the tip- tilt loop working, about which further laboratory test has been made during the last month. Also, the speckle camera with the real time autocorrelation feature has been completely finished and tested. The tracking system which allow to use moving references has been completed. For what regards the higher order loop the contracts about the DM and the CCD controller have been successfully concluded. Moreover, the wavefront sensing unit has been in large part built and tested in the laboratory. Details of the integration in the Nasmith Interface carrying the CCD scientific camera and the IR Imager are given together with a thorough description of the internal acceptance test of the optomechanical module comprising more than 20 motorized axes and several functioning modes.

In this paper we compare the impact on the turbulent wavefront Zernike modes, of a Kolmogorov and a Von Karman spectrum atmosphere with finite outer scale. We have simulated these effects analytically and numerically, for Natural and Laser Guide Star AO system, on axis and off- axis. The goal is to compare the effects of anisoplanatism, and re-evaluate the discussions on the pro's and con's of LGS vs. NGS on a perspective which includes also the presence of the outer scale.

AdOpt@TNG is the Adaptive Optics module for the Italian “Telescopio Nazionale Galileo" (TNG), a 4m? class telescope that will have its first light in late 1997. This module incorporates a number of peculiar features such as the adoption of an electro-magnetically driven tip-tilt mirror, a continuously adjustable offset between the reference and the scientific objects (in a way to deal, for instance, with moving references, like asteroids, or targets, like comets), a built-in speckle camera with an on-line autocorrelator and others. The speckle camera has been tested at the 1.82m telescope of the Astronomical Observatory of Asiago, a short account of the results obtained is given. Most of the elements of the AdOpt@TNG module have been manufactured and tested. The up-to-date status report of the module is briefly given.

The possibility of improving the image quality of the Italian Telescopio Nazionale Galileo (TNG) by means of real-time on- line image selection by using a fast shutter is studied. The tip-tilt signal is checked against a user defined threshold to trigger on rejection of those images which would significantly degrade the long-exposure point spread function because of jitter broadening. The dependency of the achievable improvements on the rejection threshold, on the shutter opening and closing times, and on the atmosphere conditions (ro) is analyzed. The pros and cons of a ferroelectric liquid crystal shutter are discussed.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In the framework of the adaptive optics for TNG the mechanical, optical and engineering aspects of the laser projection system for the TNG are briefly shown. The laser beam is projected through the elevation axis on the Nasmith foci usually devoted for spectroscopic purposes and otherwise unused during imaging scientific activities. The optical design of the projector is also outlined. It is foreseen that in the very first phase a Rayleigh laser will be operated at TNG, later replaced by a mesospheric sodium LGS generator.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Switching-on an adaptive optics loop, the system usually rapidly locks the target in the correction mode. When the sky background contribution is not negligible, the SNR may depend upon the correction status. While in an already closed loop, the SNR could be high enough to maintain the situation of good correction by the adopt system, during the switching-on phase, this condition could be far from true, because it is possible that the SNR isn't enough to lock the loop, starting from the open loop situation. We discuss this problem (called the bootstrap problem for adaptive optics) with particular attention on some filtering system working in the described situation and tuned to solve the problem.

The authors describe characteristics and key results of the optical design for adaptive optics at the Galileo telescope. Two off axis parabolae are used to image the pupil on the deformable mirror, and in order to keep to a minimum the number of reflections, one of them is used as tip-tilt mirror. The several constraints, both mechanical and optical, which led to the definitive design are reported (pupil position, effective focal ratio, off axis performances, size of the module . . .). Because tip-tilt is realized through tilting of a non-flat mirror care has been given to the deterioration and distortion of the image for a given range of misalignment of the off axis parabola.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A new concept for a device able to simulate evolving atmospherically distorted wavefronts for the adaptive optics system of the Italian facility Telescopio Nazionale Galileo (TNG) is presented. The goodness of performances of an adaptive optics system depends upon the testing accuracy of its components made under different seeing conditions. Moreover, in order to not loose good seeing nights, the possibility to perform tests during day-light can become strongly important. Introducing a simulator able to generate the image of an astronomical object deformed by atmosphere can help to solve many such problems. In order to create the wanted distortion we use phase changing plate (PCP) screens. A system of moving screens and adjustable zooms provides to change, over a wide range, some fundamental parameters of the atmosphere turbulence like fired parameter ro, Greenwood frequency fG and the isoplanatic angle (theta) o.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The status report of the adaptive optics module for the 3.5 m TNG telescope is briefly given together with the description of three important subsystems: the off-axis tracking capability of the wavefront sensor; the CCD to be used for the wavefront sensor and the modal filtering approach to be implemented in the module.

ThermoTrex Corporation has designed and built a prototype of the fast steering mirror to be used for image motion control in the TNG adaptive optics system. The principal characteristic of this mirror is the use of voice coil actuators whose positions are controlled with closed loops based on capacitive sensors. Here we report the main features of the mirror assembly and laboratory measurements done to characterize the mirror behavior. The Bode diagram of the mirror is reported and discussed.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

An all-reflective, unobstructed and unvignetted optical design for a wide field of view (12 degree(s) squared) camera is described. The camera is obtained by two sections of conical surfaces and allows an efficient stray light rejection, in order to detect faint gaseous features in the neighborhood of the comet nucleus against its bright body. Very good optical performances are obtained with a 2048 X 2048 CCD array detector allowing more than 90% of the encircled energy into a single 12 micrometers squared pixel over the whole detector area. Distortion is kept to a few percent allowing a backup operation of this camera for navigation purposes. Also an add-on option of an off-Rowland quasi-stigmatic spectrograph is described. The optical design is such that this spectrograph is fed by a plane mirror mounted on the camera filter wheel, and the spectrum is sent on the same CCD detector of the imaging mode in a similar way. Thus a very low resource additional spectroscopic option is obtained. This channel mounts a 4 degree(s) length entrance slit, and permits to obtain a very good spectral and spatial resolution.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A description of the main results of a theoretical study on the required power and coils to drive a large ferrimagnetic liquid mirror are briefly sketched and discussed. A number of possible options are evaluated and a case-study for the International Space Station Alpha is also given.

During day-light adaptive optics systems usually needs an artificial source in order to close the loop and provide checks for tests, upgrades and performances verifications. In this work the wavefront simulator for the Adaptive Optics system of the Telescopio Nazionale Galileo (TNG).

Electromagnetic forces can be used to deform the free surface of a reflective liquid. Such forces can be obtained through flowing of electrical current in the liquid itself or using its ferro-magnetic properties. For the first approach a ground-based experiment to characterize an adaptive mirror is briefly reported. For the second approach a technique to deploy in nearly- zero gravity environment a large concave mirror is shown. For this space-based application an example of case study is briefly given.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Some preliminary optical designs for three wide field cameras are briefly reported for the space missions Plures and Rosetta. Plures is a proposal to the European Space Agency (ESA) for a wide field telescope able to detect Supernova explosions with a time resolution of the order of a fraction of a minute. After the Supernova detection the telescope should switch to a narrow, single-object mode in order to probe the event in a photometric and spectroscopic mode. Plures should continuously monitor the Virgo cluster with a field of view of the order of 100 squared degrees. Rosetta is a cornerstone mission of ESA for the approaching of a cometary body, after the fly-by with two asteroids. In the approach phase Rosetta should orbit around the comet. Two cameras will map and probe the surface of the comet nucleus. For the three optics all-reflective unobstructed solutions are presented.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Some solutions for the case of two—mirror three—reflection telescope assuming to use really two mirrors (firstreflection on a surface strictly equal to the one related to the third reflection) are briefly described. This work is aby—product of the efforts of a larger team for the conceptual design of wide field UV space mission. 1. INTRODUCTION Ultraviolet sky—surveys from space requires all—reflective solutions able to cover a moderate to large Field of View (FoV hereafter). The quest for wide—field ultraviolet Astronomy is long standing. In the past years, indeed, there havebeen more proposals to space agencies and assessments study about wide field telescopes than substantial realization.Among endehavour, at international level, of exploiting of wide fields from space systematically, it may be recalledthe accomodation study of UTEX on SpaceLab (ESA, 1976), the assessment study of SWAT (NASA, 1979) andSpace—Schmidt (ESA, 1979) and proposals ASCHOT on MIR (USSR, 1988), UTEF on Space Station Freedom (ESA,1990), the SMEX—type mission UVSE, now renamed JUNO1, to NASA, MOUSE2'3 to ESA.Meanwhile UV astronomy aimed at single light sources in the spectroscopy or photometric mode as been having its

The active real-time cophasing of an interferometer, that is, the fulfillment of the condition (Delta) (OPD) >> (lambda) (OPD is the Optical Path Difference between every pair of light beams, each coming from every telescope of the array is a crucial requirement for high resolution and long exposure image formation. So the optical concept is a possible design of a Cophasing System (CS hereafter) for a space interferometer, e.g. the Multimirror Ultraviolet Solar Telescope (MUST), will be presented. A collimator and a pair of achromatic wedges are two of its components; the former has the target to collimate light beams which enter in the CS preserving the instrumental errors due to aberrations much less than (lambda) in the Optical Path Length (OPL) of the light beams; the latter allows to choose any region of the Field of View (FoV) of the beams by their simple rotation (two degree of freedom correspond to a FoV point) in order to have high contrast features used in telescopes pre- alignment subsystem included in the CS. Ray tracing results on these optical components will be show. Their tolerance analysis will also be discussed. A mechanical approach for each wedge rotation will be shown together with a preliminary CAD arrangement of the subsystem in a cylindrical package of diameter approximately equals 300 mm and approximately equals 100 mm height.

A European collaboration has been formed to mitigate risks associated with LGS AO systems planned on the E-ELT. A Nasmyth platform on the 4.2m WHT will develop into a testbed. A seven year programme of work has been drafted to provide test infrastructure including the controlled environment GRAIL to support a set of risk mitigation developments and experiments.

Research into the monitoring and control of oral malodor has nowadays received new stimulus from the importance gained by this phenomenon as a medical and social problem. In this paper the performance of an electronic nose to detect this manifestation has been investigated in order to explore the possibility of using this instrument as a complement to those already existing for the assessment of oral malodor. In particular, a breath sampling procedure has been optimized to maximize the transfer to the sensors of those molecules that are known to be associated with the malodor. The sensitivity of electronic nose sensors to hydrogen sulfide, butyric acid and valeric acid-three compounds known to play a major role in halitosis-has been measured and the results indicate that the threshold limits are compatible with halitosis detection. An experiment with real and artificial samples indicates the possibility of identifying halitosis-affected individuals and of discriminating them according to breath composition.

This paper presents the integration and first results for the CAMCAO NIR camera. The camera was built for the ESO Multi-conjugate Adaptive optics Demonstrator, where it is presently operating, to evaluate the feasibility of this Adaptive Optics technique. On a second phase it will work directly at the Nasmyth focus of the VLT. CAMCAO is a high resolution, wide field of view NIR camera, that is using the 2k×2k HgCdTe HAWAII- 2 infrared detector from Rockwell Scientific, controlled by the ESO IRACE system. The camera operates in the near infrared region between 1.0 μm and 2.5 μm wavelength using an eight position filter wheel with J, H, K', K-continuum and Brγ filters. Both the integration experience and the results obtained in the mechanical, vacuum, cryogenics and optical tests are presented, including all relevant parameters in the ESO specifications. The requirement of mechanical stiffness together with light weight was achieved yielding a total weight of less than 90 Kg. The camera fulfills both cryogenic and vacuum stability requirements. The temperature within the detector is maintained at 80K by an accurate control loop, ensuring mK stability, after cooling down the detector at a rate kept below 0.5 K/min. The optical performance tests were made using a Fizeau interferometer both for the individual optical components and complete setup. The infrared optical validation measurements were performed by re-imaging a point source in the camera focal plane and measuring the PSF with the detector. The computed Strehl ratio reached 95% in the central region of the FoV, with values larger than 90% in a area covering 88% of the focal plane.

This was the radiographic evaluation of 15 maxillary incisors apexification treatment carried out on 7-9 years old patients with periapical pathology due to pulpal necrosis after dental trauma.The treatment consisted of two phases. The aim of first phase was the formation of a calcified apical barrier through calcium hydroxide medications repeated twice with a three months interval. The aim of the second phase was the obturation of the root canal system once achieved a radiographic evidence of the formation of an apical barrier. The treated teeth were radiographed at six months and then periodically once a year for a period of 7 and 13 years.The radiographic analysis allowed to underline three different kinds of apical formation: a physiological development of the apical portion with a final root length equal to the contralateral tooth; the formation of a cap tissue and an apical development with the final root length slightly shorter than the contralateral tooth; or the formation of different layers of mineralised tissue that aggregate together trough the years.Apexification is not a static phenomenon and the apexified area undergoes through the years to a conspicuous readjustment involving bone, apical root tissues and root filling material.

Background The aim of this study was to evaluate the antiplaque effect of a new alcohol free essential oil mouthwash with respect to a control of an essential oil with alcohol mouthwash, using an in vivo plaque regrowth model of 3-days. Methods The study was designed as a double-masked, randomized, crossover clinical trial, involving 30 volunteers to compare two different essential oil containing mouthwashes, during a 3-day plaque accumulation model. After receiving a thorough professional prophylaxis at the baseline, over the next 3-days each volunteer refrained from all oral hygiene measures and had two daily rinses with 20 ml of the test mouthwash (alcohol free essential oil) or the control mouthwash (essential oil with alcohol). At the end of the each experimental period, plaque was assessed and the panelists filled out a questionnaire. Each subject underwent a 14 days washout period and there was a second allocation. Results The essential oil mouthwash with ethanol shows a better inhibitory effect of plaque regrowth in 3-days than the mouthwash test with only essential oil in the whole mouth (plaque index = 2.18 against 2.46, respectively, p < 0.05); for the lower jaw (plaque index = 2.28 against 2.57, respectively, p < 0.05); for the upper jaw (plaque index = 2.08 against 2.35, respectively, p < 0.05); for the incisors (plaque index = 1.93 against 2.27, respectively, p < 0.05); and the canines (plaque index = 1.99 against 2.47, respectively, p < 0.05). Conclusion The essential oil containing mouthwash without alcohol seems to have a less inhibiting effect on the plaque regrowth than the traditional alcoholic solution. Trial Registration ClinicalTrials.gov NCT01411618

The MAD demonstrator performed on-sky observations at VLT telescope for validating Ground-Layer, Laser Tomography and Multi-Conjugate Adaptive Optics correction. Here we present the results obtained on the sky and in laboratory for Star Oriented mode. Article not available.

The present study evaluated the durability of bond strength between zirconia and 3 different resin cements. Thirty stabilized tetragonal zirconium-dioxide blocks were duplicated in dual-curing resin core build-up material specimens. Resin blocks were randomly luted to zirconium surfaces using 1) Clearfil Esthetic Cement (CLF), 2) RelyX Unicem Aplicap (RELX), or 3) Multilink Automix (MLA). After 24 h, half of the specimens from each of the 3 groups were loaded in tension until fracture (0.5 mm/min). The remaining half were tested after 6,000 thermal cycles (5 to 55°C). Data were analyzed using 2-way ANOVA and the Tukey test (α = 0.05). Fractographic analysis was performed using a stereomicroscope. Tensile bond strength values were significantly affected by the luting agent system employed and by thermal aging (P < 0.001). The highest tensile bond strength values in non-thermal-aged groups were observed for specimens from the RELX and CLF groups. In contrast, in the thermal-aged groups, the highest tensile bond strength values were for the MLA and RELX groups. Moreover, while thermocycling significantly affected bond strengths in the RELX and CLF groups, the mean strength of the MLA group did not significantly change after aging. There was little difference in the distribution of failure modes in any group.