Mechanical properties and microstructure characterisation of Au-Pt dental alloy

Development of a dental alloy with high Au content is based on the ternary system of Au-Pt-Zn with a nominal composition of 86,9Au-9,9Pt-1,5Zn, and about 1,5 wt.% micro-alloying elements (in, Ir, Rh). The results analyses of different heat-treated states showed that the optimal mechanical properties and hardness of an Au-Pt-Zn alloy can be reached with combinations of heat treatment for 20 minutes at 723 K and then slowly cooling, if the alloy was annealed at 1223 K for 30 minutes and the water quenched. Research results confirmed that the microstructure of the Au-Pt-Zn alloy consists of two phases: alpha(1)-phase rich in Au (main phase) and alpha(2)-phase rich in Pt (minor phase). During XRD analysis and use of the Rietveld method, it was found that the alpha(1)-phase content is about 98,5 wt.% while the content of alpha(2)-phase is 1,5 wt.%. STA analyses show that the Au-Pt-Zn alloy has a solidus temperature of about 1292 K and a liquidus temperature of about 1412 K

Rank-(n – 1) convexity and quasiconvexity for divergence free fields

The CAST experiment at CERN (European Organization of Nuclear Research) searches for axions from the sun. The axion is a pseudoscalar particle that was motivated by theory thirty years ago, with the intention to solve the strong CP problem. Together with the neutralino, the axion is one of the most promising dark matter candidates. The CAST experiment has been taking data during the last two years, setting an upper limit on the coupling of axions to photons more restrictive than from any other solar axion search in the mass range below 0.1 eV. In 2005 CAST will enter a new experimental phase extending the sensitivity of the experiment to higher axion masses. The CAST experiment strongly profits from technology developed for high energy physics and for X-ray astronomy: A superconducting prototype LHC magnet is used to convert potential axions to detectable X-rays in the 1-10 keV range via the inverse Primakoff effect. The most sensitive detector system of CAST is a spin-off from space technology, a Wolter I type X-ray optics in combination with a prototype pn-CCD developed for ESA's XMM-Newton mission. As in other rare event searches, background suppression and a thorough shielding concept is essential to improve the sensitivity of the experiment to the best possible. In this context CAST offers the opportunity to study the background of pn-CCDs and its long term behavior in a terrestrial environment with possible implications for future space applications. We will present a systematic study of the detector background of the pn-CCD of CAST based on the data acquired since 2002 including preliminary results of our background simulations.Comment: 11 pages, 8 figures, to appear in Proc. SPIE 5898, UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XI

The imaging properties of the Gas Pixel Detector as a focal plane polarimeter

X-rays are particularly suited to probe the physics of extreme objects. However, despite the enormous improvements of X-ray Astronomy in imaging, spectroscopy and timing, polarimetry remains largely unexplored. We propose the photoelectric polarimeter Gas Pixel Detector (GPD) as an instrument candidate to fill the gap of more than thirty years of lack of measurements. The GPD, in the focus of a telescope, will increase the sensitivity of orders of magnitude. Moreover, since it can measure the energy, the position, the arrival time and the polarization angle of every single photon, allows to perform polarimetry of subsets of data singled out from the spectrum, the light curve or the image of source. The GPD has an intrinsic very fine imaging capability and in this work we report on the calibration campaign carried out in 2012 at the PANTER X-ray test facility of the Max-Planck-Institut f\"ur extraterrestrische Physik of Garching (Germany) in which, for the first time, we coupled it to a JET-X optics module with a focal length of 3.5 m and an angular resolution of 18 arcsec at 4.5 keV. This configuration was proposed in 2012 aboard the X-ray Imaging Polarimetry Explorer (XIPE) in response to the ESA call for a small mission. We derived the imaging and polarimetric performance for extended sources like Pulsar Wind Nebulae and Supernova Remnants as case studies for the XIPE configuration, discussing also possible improvements by coupling the detector with advanced optics, having finer angular resolution and larger effective area, to study with more details extended objects.Comment: Accepted for publication in The Astrophysical Journal Supplemen

Simbol-X Hard X-ray Focusing Mirrors: Results Obtained During the Phase A Study

Simbol-X will push grazing incidence imaging up to 80 keV, providing a strong improvement both in sensitivity and angular resolution compared to all instruments that have operated so far above 10 keV. The superb hard X-ray imaging capability will be guaranteed by a mirror module of 100 electroformed Nickel shells with a multilayer reflecting coating. Here we will describe the technogical development and solutions adopted for the fabrication of the mirror module, that must guarantee an Half Energy Width (HEW) better than 20 arcsec from 0.5 up to 30 keV and a goal of 40 arcsec at 60 keV. During the phase A, terminated at the end of 2008, we have developed three engineering models with two, two and three shells, respectively. The most critical aspects in the development of the Simbol-X mirrors are i) the production of the 100 mandrels with very good surface quality within the timeline of the mission; ii) the replication of shells that must be very thin (a factor of 2 thinner than those of XMM-Newton) and still have very good image quality up to 80 keV; iii) the development of an integration process that allows us to integrate these very thin mirrors maintaining their intrinsic good image quality. The Phase A study has shown that we can fabricate the mandrels with the needed quality and that we have developed a valid integration process. The shells that we have produced so far have a quite good image quality, e.g. HEW <~30 arcsec at 30 keV, and effective area. However, we still need to make some improvements to reach the requirements. We will briefly present these results and discuss the possible improvements that we will investigate during phase B.Comment: 6 pages, 3 figures, invited talk at the conference "2nd International Simbol-X Symposium", Paris, 2-5 december, 200

The liver transplant waiting list—a single-center analysis

At this transplant center 1340 patients were entered on the liver transplant waiting list during the first 25 months (October 1987 to November 1989) after the initiation of the UNOS allocation system for liver grafts. Of these 972 (72.5%) of the patients received a graft, 120 (9.0%) died waiting for a graft, 109 (8.1%) remained on the active list as of the study endpoint of December 15, 1989, 123 (9.2%) were withdrawn from candidacy, and 16 (1.2%) received a transplant at another center. A total of 1201 patients were candidates for a first graft. Of the 812 primary candidates who received a graft, 64.8% received their graft within one month of entry on the waiting list. Of the 109 primary candidates who died before a graft could be found, 79.0% died within a month of entry onto the waiting list. At time of transplantation, 135 (16.6%) primary recipients of a graft were UNOS class 1, 326 (40.1%) were UNOS class 2, 190 (23.4%) were UNOS class 3, and 161 (19.8%) were UNOS class 4. Actuarial survival rates (percentage) at 6 months for recipients in UNOS class 1, class 2, class 3, and class 4 were 88.7±2.9, 82.6+2.1, 78.4±3.2, and 68.4±3.9, respectively (P<0.001). At the time of death of recipients who failed to get a graft, 6 (5.5%) were UNOS class 1, 14 (12.8%) were UNOS class 2, 23 (21.1%) were UNOS class 3, and 66 (60.6%) were UNOS class 4. These results indicate that a high proportion of liver transplant candidates are in urgent need of a graft and that the UNOS system succeeds in giving these patients high priority. However patient mortality on the waiting list and after transplantation would lessen significantly if more patients with end-stage liver disease were referred to the transplant center in a timely manner before their condition reaches the point where the probability of survival is diminished. © 1991 by Williams & Wilkins

First Light Measurements of Capella with the Low Energy Transmission Grating Spectrometer aboard the Chandra X-ray Observatory

We present the first X-ray spectrum obtained by the Low Energy Transmission Grating Spectrometer (LETGS) aboard the Chandra X-ray Observatory. The spectrum is of Capella and covers a wavelength range of 5-175 A (2.5-0.07 keV). The measured wavelength resolution, which is in good agreement with ground calibration, is $\Delta \lambda \simeq$ 0.06 A (FWHM). Although in-flight calibration of the LETGS is in progress, the high spectral resolution and unique wavelength coverage of the LETGS are well demonstrated by the results from Capella, a coronal source rich in spectral emission lines. While the primary purpose of this letter is to demonstrate the spectroscopic potential of the LETGS, we also briefly present some preliminary astrophysical results. We discuss plasma parameters derived from line ratios in narrow spectral bands, such as the electron density diagnostics of the He-like triplets of carbon, nitrogen, and oxygen, as well as resonance scattering of the strong Fe XVII line at 15.014 A.Comment: 4 pages (ApJ letter LaTeX), 2 PostScript figures, accepted for publication in ApJ Letters, 200

Mehanička svojstva i mikrostrukturna karakterizacija Au-Pt dentalne slitine

Development of a dental alloy with high Au content is based on the ternary system of Au-Pt-Zn with a nominal composition of 86,9Au-9,9Pt-1,5Zn, and about 1,5 wt.% micro-alloying elements (In, Ir, Rh). The results analyses of different heat-treated states showed that the optimal mechanical properties and hardness of an Au-Pt-Zn alloy can be reached with combinations of heat treatment for 20 minutes at 723 K and then slowly cooling, if the alloy was annealed at 1223 K for 30 minutes and the water quenched. Research results confirmed that the microstructure of the Au-Pt-Zn alloy consists of two phases: _1-phase rich in Au (main phase) and _2-phase rich in Pt (minor phase). During XRD analysis and use of the Rietveld method, it was found that the _1-phase content is about 98,5 wt.% while the content of _2-phase is 1,5 wt.%. STA analyses show that the Au-Pt-Zn alloy has a solidus temperature of about 1292 K and a liquidus temperature of about 1412 K.Razvoj dentalne slitine s visokim sadržajem zlata zasnovan je na ternarnom sustavu Au-Pt-Zn s nominalnim sastavom 86,9Au-9,9Pt-1,5Zn i oko 1,5 mas. % mikrolegirajučih elemenata (In, Ir, Rh). Rezultati analize su pokazali da se u slučaju slitine odžarene kod 1223 K u trajanju od 30 minuta i zakaljena u vodi optimalna mehanička svojstva i tvrdoća Au-Pt-Zn slitine mogu postići kombinacijom toplinske obrade na 720 oC u trajanju 20 minuta s naknadnim sporim hlađenjem. Rezultati istraživanja su potvrdili da se mikrostruktura Au-Pt-Zn slitine sastoji od dvije faze: _1-faze bogate sa zlatom (primarna faza) i _2 - faze bogate s platinom (sekundarna faza). Tijekom XRD analize i primjenom Rietveldove metode utvrđeno je da je sadržaj _1-faze oko 98,5 mas. %, dok je sadržaj _2-faze iznosio oko 1,5 mas. %. STA analiza je pokazala da je Au-Pt-Zn slitina imala solidus temperaturu oko 1292 K, a likvidus temperaturu oko 1412 K

RNA editing signature during myeloid leukemia cell differentiation

Adenosine deaminases acting on RNA (ADARs) are key proteins for hematopoietic stem cell self-renewal and for survival of differentiating progenitor cells. However, their specific role in myeloid cell maturation has been poorly investigated. Here we show that ADAR1 is present at basal level in the primary myeloid leukemia cells obtained from patients at diagnosis as well as in myeloid U-937 and THP1 cell lines and its expression correlates with the editing levels. Upon phorbol-myristate acetate or Vitamin D3/granulocyte macrophage colony-stimulating factor (GM-CSF)-driven differentiation, both ADAR1 and ADAR2 enzymes are upregulated, with a concomitant global increase of A-to-I RNA editing. ADAR1 silencing caused an editing decrease at specific ADAR1 target genes, without, however, interfering with cell differentiation or with ADAR2 activity. Remarkably, ADAR2 is absent in the undifferentiated cell stage, due to its elimination through the ubiquitin–proteasome pathway, being strongly upregulated at the end of the differentiation process. Of note, peripheral blood monocytes display editing events at the selected targets similar to those found in differentiated cell lines. Taken together, the data indicate that ADAR enzymes play important and distinct roles in myeloid cells