859 research outputs found
Angular resolution improvement of slumped thin glass optics for x-ray telescopes.
No full textCurrent X-ray telescopes such as Chandra and XMM were designed and built to privilege the angular resolution or the collecting area respectively, but using two different manufacturing techniques, and these two key aspects could not be optimised at the same time. The result is that the high-redshift X-ray Universe is still too unresolved to provide us with the understanding of the time evolution of the universe as we see it nowadays. Now the ATHENA mission, approved for the L2 slot in the Cosmic Vision program, is required to have an effective area of 2 m2 at 1 keV and an angular resolution better than 5 arcsec Half-Energy Width (HEW). At this regard, in addition to the baseline solution based on Silicon Pore Optics (SPO), thin glass foils are considered a viable alternative. Slumped glass foils are also considered as substrates for X-ray optics being developed in other projects; for example, the X-ray Surveyor mission being developed at SAO/CfA in USA, and the AXYOM project being developed in Italy. They both foresee the use of piezo-electric actuators to correct the shape errors of the mirrors.
The Brera Astronomical Observatory (INAF-OAB, Merate - Italy) has been working, from 2009 till 2013, under ESA contract aimed to develop in Europe a Slumped Glass Optics (SGO) technology, alternative to the one based on silicon pores, and based on the slumping of thin glass foils, in parallel to the work being carried out at NASA/GSFC and other institutes. The INAFOAB innovation is the use of pressure in the hot slumping process to replicate the mould figure.
This technology is coupled with an integration process able to damp low frequency errors. My Ph.D. activity, carried out at the INAF-OAB, is devoted to the advancement in the hot slumping technology assisted by pressure, for the production of glass mirrors for future X-ray telescopes. As a preliminary work, I have developed a new method to precisely characterise the mid frequency errors of the glass foils. An existing model, developed by Jimenez-Garate in 2003 to account for the relaxation of ripples in the slumped glass foil when in contact with the slumping mould, was modified to include the application of pressure, and the model was compared to the experimental results. The pressure was found to be essential, also from the the theory viewpoint, to reduce mid-frequency errors in the profile of slumped glass foils, which crucially degrade the performances of the optics. As for the slumping process, I have introduced a new glass material (Corning Eagle XG) combined with the Schott Zerodur K20, already chosen at earlier times as slumping mould material for its anti-sticking properties. I have developed cleaning protocols, used different thermal cycles and different pressures conditions, and reconditioned the pressure control system. I have also optimised the mould height with experiments based on Finite Element Analysis, and reduced the thermal gradients inside the mould and the glass foils.
The final result obtained in this research are slumped glass foils with angular resolution improved from the initial 7 arcsec to 2.2±0.3 arcsec in single reflection, as expected from metrology at 1 keV X-ray energy and 0.7 incidence angle, and computed by simulating a perfect integration.
This result has to be compared with 2 arcsec defined as the error budget allocated for the slumped glass foils. About 1 arcsec is due to replication of the mid-frequency errors in the slumping mould which, owing to the improved result in the slumping, are now a limiting factor in the quality of the slumped glass foils. From the roughness point of view, the contribution to the HEW is guaranteed to be less then 1 arcsec at 1 keV, with an rms improvement from 21 to 11 Å throughout my Ph.D.
Moreover, the last tests carried out proved that the roughness of the slumped glass foils can be further reduced to _ 7 Å, making the technology attractive also for higher X-ray energies and higher incidence angles.
The glass foils slumped during this Ph.D. have been used for the production of two SGO Proof Of Concept prototypes (POC) for the ATHENA mission: the POC#3, (with 2 glass foils assembled) is characterised by HEW value of 5.5 arcsec at 0.27 keV in the best portion of the module, as tested at the PANTER facility; the POC#4 (with 8 glass foils) has expected HEW of about 15 arcsec from metrological data, but the result in X-ray was much higher because of accidental problems during the integration. The next prototype, the POC#5 (with the best eight glass foils produced during my Ph.D. activity), will soon be integrated and tested in X-rays, to assess the improvement already proven by metrology and simulations. Some of the produced slumped glass foils have also been used for studies of active profile corrections with piezoelectric elements, both for the AXYOM project and X-ray Surveyor mission.
Alternative materials and techniques have been used in this research to further improve the result. To reduce the surface micro-roughness of the slumped glass foils, I have proven that the slumping technique with pressure application can also be suited in the indirect slumping, in which the optical surface of the glass is not in contact with the mould, thus preserving its initial surface smoothness. Moreover, the dip coating technique was studied to fill the micro-pores present on the surface of the glass foils slumped with the direct technique. Alternative materials for the slumping mould were tested, defining Si3N4 as a very promising candidate, owing to its higher rigidity with respect to Zerodur K20 and therefore preferable to avoid mould deformations with the slumping, as experienced with K20. The Gorilla glass (normally used for smartphones and tablets), was proven to preserve the surface quality of the glass foils, once slumped and chemically tempered to increase the mirror endurance against the vibrations experienced at launch.
Finally, I have also studied the scattering and the reflectivity properties of multilayer coatings for X-ray optics. I have upgraded an IDL code to simulate the roughness growth in the multilayer deposition process, extending the computations from periodic to the more general case of graded multilayers. I have also contributed to the X-ray measurements at the BEAR beamline of the Elettra synchrotron in Trieste, on multilayers deposited on glass, silicon and electroformed nickel, for the polarimetric LAMP projec
Modeling and measurement of the scattering properties of the source pinhole in the BEaTriX facility
No full textThe purpose of this brief technical note is to provide an assessment of the performance of the tungsten pinhole placed in front of the microfocus Incoatec X-ray source with Titanium anode in the BEaTriX X-ray facility. The pinhole is a part of the collimator kit by Amptek purchased years ago to collimate a solid-state detector, and consists of a small (1/2 inch) tungsten disk with a 2.2 mm thickness and a 450 μm diameter. The pinhole is placed at a 20 mm distance from the source and limits the beam along the short arm of the facility, avoiding so the X-ray incidence on the tube walls which might cause unwanted X-ray reflection/scattering or diffuse background. At the same time, the pinhole located near the X-ray source provides visual reference for the parabolic mirror alignment.
Pinholes are crucial optical components, as they have to diaphragm an X-ray beam without degrading it. Due to the closeness of the lateral walls of the pinhole to the X-rays, the surface has to be properly ruggedized in order to avoid unwanted reflections or diffuse scattering when X-rays impinge on it in grazing incidence conditions. Should this condition not be fulfilled, the pinhole would cause a broadening of the X- ray source and a consequent worsening of the finally collimated X-ray beam in BEaTriX. In this short note, we will show measurements of the X-ray beam in the BEaTriX facility aiming at ascertaining the scattering properties of the pinhole surface. The conclusion is that the amount of scattered/reflected radiation off the pinhole is hardly detectable and that the pinhole appears perfectly suitable for the collimation of the X-ray beam in the short arm of BEaTriX
Test plan of the BEaTriX paraboloidal mirror at PANTER
No full textScope of this technical note is the definition of a test plan for the X-ray characterization campaign of the BEaTriX paraboloidal mirror at PANTER. The collimating mirror is a core component of the 4.51 keV beamline of the BEaTriX expanded X-ray beam facility; indeed, the optical quality of the mirror will directly affect the collimation and the uniformity of the final beam that will be used to characterize the focusing performance of SPO MM for ATHENA. The mirror is made of HOQ 310 fused quartz, procured from Zeiss in a preliminary grinding and lapping state, and subsequently finished by a sequence of polishing at the Zeeko robotic machine installed at INAF-OAB. Improvement of the mirror figure has been achieved across several runs of IBF process, using the dedicated facility at INAF-OAB. At each polishing/figuring step, the mirror profile and surface roughness have been characterized using suitable metrology tools at MediaLario
Genepool variation and phylogenetic relationships of an indigenous north-east Italian grapevine collection revealed by nuclear and chloroplast SSRs.
No full textA germplasm safeguard programme was set up with 19 grapevine varieties considered as indigenous to northeastern
Italy. To better estimate how genetic structure can be used to obtain a conservation perspective of local varieties,
genetic variability was examined at 30 nuclear and 3 chloroplast polymorphic microsatellite loci in the native varieties plus 7 European cultivars taken as reference. The genetic profiles of all the cultivars were searched for possible parentage relationships and several suspected cases of the same variety having different names were investigated. The alleles shared at the loci suggest a parent–offspring relationship between Merlot and Cabernet Franc, ‘Gruaja’ and ‘Negrara Veronese’, and Marzemina Nera and Marzemina Bianca. Alleles at the 30 nuclear loci are consistent with Raboso Veronese being the progeny of Marzemina Bianca and Raboso Piave. Chloroplast-specific haplotypes were singled out for the first time in this indigenous germplasm and should be considered typical of the region. It is hypothesized that there are many specific haplotypes for the local varieties due to a past contribution of wild grapevine to the cultivated gene pool. The majority of investigated cultivars were demonstrated to constitute an independent source of genetic variation, and therefore a possible valuable resource of genetic traits for breeders
Test results of the BEaTriX paraboloidal mirror at PANTER
No full textScope of this technical note is to report on the X-ray tests of the BEaTriX collimating mirror that have been carried out at the PANTER X-ray facility, before (May 4th-17th 2021) and after the coating with a Cr+Pt reflective layer at DTU, in the framework of the joint activities on optics for the ATHENA X-ray telescope. The tests planned before the deposition of the coating were aimed at confirming the mirror’s imaging quality expectations from the metrology tests, performed along with the polishing and finishing processes. Post-coating tests are oriented to the final qualification of the mirror and to ascertain that the mirror has maintained the focusing properties. Prior to coating, only tests at 1.49 keV are possible on the mirror. At this energy, PANTER can test the mirror in either diverging beam setup or making the beam parallel by means of a dedicated zone plate, canceling in this way the focus aberrations due to the finite distance of the source. After coating, in addition to the same tests at 1.49 keV, a test in diverging beam will be performed at 4.51 keV. The ZP cannot be used to collimate the 4.51 keV beam, but a comparison of the best focus at 1.49 keV and 4.51 keV will allow us to estimate the X-ray scattering that can be expected in the operation of the BEaTriX parabolic mirror. Simulations carried out from metrology on the uncoated mirror currently demonstrate a very low impact of the roughness on the mirror focusing performance
Bianca Garavelli studiosa e scrittrice
No full textBianca Garavelli (Vigevano, 1958-2021) was a highly regarded figure in the literary world, both on the critical and creative side. Author of important critical studies on Dante and of a successful commentary on the Commediam (begun under the supervision of Maria Corti but then continued independently), as well as critic and reviewer for newspapers and periodicals, Garavelli also wrote and published poems, novels and short stories. This article offers an exhaustive bio-bibliographical profile of Bianca Garavelli, whose literary work in various fields is reconstructed and critically examined
Let´s (watch me) play : which factors relate to Let´s Play addiction?
No full textAuthor Bianca Haun, BScZusammenfassungen in englischer SpracheMasterarbeit Universität Linz 201
A combined intervention for executive deficits and anxiety in Parkinson's patients: a case study
No full textParkinson’s disease (PD) is a neurodegenerative disorder most commonly associated with motor symptomatology, yet often presenting with deficits in attention, executive functioning (EF; e.g., planning, mental flexibility, complex attention), anxiety, and depression, with debilitating effects on patients’ quality of life. Current interventions, including pharmacological and surgical methods show efficacy in motor symptom management, yet produce equivocal results in addressing non-motor dysfunction. The goal of this paper was to describe and investigate the efficacy and patient acceptance of a nonpharmacological intervention for treatment of executive dysfunction (ED) and anxiety in PD, in the context of a case study (the case of Mr. K). Brain and Mind Fitness Program (BMFP) is a short-term intervention, consisting of a combination of cognitive remediation and cognitive behavioral therapy (CBT). BMFP was demonstrated to be fully acceptable to Mr. K, based on ratings of 4 feasibility dimensions (fatigue, effort, progress, and enjoyment). The program also proved to be efficacious in alleviating Mr. K’s anxiety and depression symptoms, with benefits extending over the treatment period. BMFP, elsewhere shown to be an effective cognitive re-training of EF in PD patients, exhibited limited gains in the case of Mr. K., possibly due to his relatively intact cognitive abilities at baseline. Despite its limitations, the case of Mr. K presents a novel approach to treatment of PD non-motor symptoms and a learning opportunity for researchers and clinicians interested in expanding their knowledge across disciplines.Psy. D.Includes bibliographical referencesby Bianca R. Georgesc
BIANCA (Brain Intensity AbNormality Classification Algorithm): a new tool for automated segmentation of white matter hyperintensities
No full textReliable quantification of white matter hyperintensities of presumed vascular origin (WMHs) is increasingly needed, given the presence of these MRI findings in patients with several neurological and vascular disorders, as well as in elderly healthy subjects. We present BIANCA (Brain Intensity AbNormality Classification Algorithm), a fully automated, supervised method for WMH detection, based on the k-nearest neighbour (k-NN) algorithm. Relative to previous k-NN based segmentation methods, BIANCA offers different options for weighting the spatial information, local spatial intensity averaging, and different options for the choice of the number and location of the training points. BIANCA is multimodal and highly flexible so that the user can adapt the tool to their protocol and specific needs. We optimised and validated BIANCA on two datasets with different MRI protocols and patient populations (a “predominantly neurodegenerative” and a “predominantly vascular” cohort). BIANCA was first optimised on a subset of images for each dataset in terms of overlap and volumetric agreement with a manually segmented WMH mask. The correlation between the volumes extracted with BIANCA (using the optimised set of options), the volumes extracted from the manual masks and visual ratings showed that BIANCA is a valid alternative to manual segmentation. The optimised set of options was then applied to the whole cohorts and the resulting WMH volume estimates showed good correlations with visual ratings and with age. Finally, we performed a reproducibility test, to evaluate the robustness of BIANCA, and compared BIANCA performance against existing methods. Our findings suggest that BIANCA, which will be freely available as part of the FSL package, is a reliable method for automated WMH segmentation in large cross-sectional cohort studies. © 2016 The Author
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