DETERMINATION OF OPTIMUM SELECTIVE FLOTATION CONDITIONS OF KOYULHISAR Pb-Cu-Zn ORE BY GUM ARABIC

Bu çalıĞ¢mada, Sivas-Koyulhisar yöresinden temin edilen Pb-Cu-Zn kompleks cevherinin gang bastırıcı olarak Gum Arabic kullanılarak selektif flotasyonla zenginleĞ¢tirilmesinde optimum flotasyon koĞ¢ulları belirlenmeye çalıĞ¢ılmıĞ¢tır. Deneylerde kullanılan Koyulhisar Pb-Cu-Zn kompleks cevherinin %6.54 Pb, %1.45 Cu ve %7.47 Zn tenörlü olduğu kimyasal analiz ile tespit edilmiĞ¢tir. Selektif flotasyonun ilk kademesinde Pb, ikinci kademesinde Cu ve üçüncü kademesinde ise Zn kaba konsantresi eldesinde en uygun flotasyon koĞ¢ulları belirlenmiĞ¢tir. Elde edilen kaba konsantreler daha sonra temizleme flotasyonlarına tabi tutulmuĞ¢tur. Selektif flotasyonla kazanılan Pb, Cu ve Zn kaba konsantrelerinin tenör değerleri sırasıyla; %24.33 Pb, %15.10 Cu ve %41.43 Zn, konsantre verim değerleri ise sırasıyla %93.45, %78.52 ve %89.57'dir. Deneyler sonucunda bu cevherin selektif flotasyonu için belirlenen optimum koĞ¢ullar: Pb kaba flotasyonu için; pH=8, 600 gr/ton Gum Arabic, 40 gr/ton NaCN, 600 gr/ton ZnSO4, 120 gr/ton KAX, 90 gr/ton 2 Etil Hekzanol, köpük alma süresi 5 dakika, Cu kaba flotasyonu için; pH=8, 400 gr/ton Gum Arabic, 20 gr/ton NaCN, 800 gr/ton ZnSO4, 100 gr/ton Na2Cr2O7, 60 gr/ton KAX, 40 gr/ton 2 Etil Hekzanol, köpük alma süresi 5 dakika, Zn kaba flotasyonu için; pH=11, 400 gr/ton Gum Arabic, 60 gr/ton NaCN, 80 gr/ton Na2Cr2O7, 250 gr/ton CuSO4, 100 gr/ton KAX, 90 gr/ton 2 Etil Hekzanol, köpük alma süresi 5 dakika, olarak bulunmuĞ¢tur. Kaba konsantrelerin temizleme flotasyonuna tabi tutulmasıyla elde edilen Pb, Cu ve Zn nihai konsantrelerinin tenörleri sırasıyla; %69.26 Pb, %29.52 Cu ve %58.14 Zn, konsantre verim değerleri ise %72.33, %66.16 ve %75.65'dir. In this study, optimum flotation conditions for Koyulhisar Pb-Cu-Zn ore was determined using by Gum Arabic as depressant. Ore sample's grade is 6.54% Pb, 1.45% Cu and 7.47% Zn from chemical analysis. The most suitable conditions were fixed for Pb, Cu, and Zn rough flotation in first, second and third stage respectively and cleaning experiments were carried out for each of these concentrates. The grade of Pb, Cu and Zn rough concentrates are 24.33% Pb, 15.10% Cu and 41.43% Zn were obtained with recoveries 93.45%, 78.52% and 89.57% respectively. The optimum conditions for selective flotation are below: Pb rough flotation: pH=8, 600 gr/ton Gum Arabic, 40 gr/ton NaCN, 600 gr/ton ZnSO4, 120 gr/ton KAX, 90 gr/ton 2 Etil Hekzanol, flotation time 5 min. Cu rough flotation: pH=8, 400 gr/ton Gum Arabic, 20 gr/ton NaCN, 800 gr/ton ZnSO4, 100 gr/ton Na2Cr2O7, 60 gr/ton KAX, 40 gr/ton 2 Etil Hekzanol, flotation time 5 min. Zn rough flotation: pH=11, 400 gr/ton Gum Arabic, 60 gr/ton NaCN, 80 gr/ton Na2Cr2O7, 250 gr/ton CuSO4, 100 gr/ton KAX, 90 gr/ton 2 Etil Hekzanol, flotation time 5 min. The grades of concentrates after cleaning flotation 69.26% Pb, 29.52% Cu and 58.14% Zn were obtained with recoveries 72.33%, 66.16% and 75.65% respectively

A focal plane detector design for a wide-band Laue-lens telescope

The energy range above 60 keV is important for the study of many open problems in high energy astrophysics such as the role of Inverse Compton with respect to synchrotron or thermal processes in GRBs, non thermal mechanisms in SNR, the study of the high energy cut-offs in AGN spectra, and the detection of nuclear and annihilation lines. Recently the development of high energy Laue lenses with broad energy bandpasses from 60 to 600 keV have been proposed for a Hard X ray focusing Telescope (HAXTEL) in order to study the X-ray continuum of celestial sources. The required focal plane detector should have high detection efficiency over the entire operative range, a spatial resolution of about 1 mm, an energy resolution of a few keV at 500 keV and a sensitivity to linear polarization. We describe a possible configuration of the focal plane detector based on several CdTe/CZT pixelated layers stacked together to achieve the required detection efficiency at high energy. Each layer can operate both as a separate position sensitive detector and polarimeter or work with other layers to increase the overall photopeak efficiency. Each layer has a hexagonal shape in order to minimize the detector surface required to cover the lens field of view. The pixels would have the same geometry so as to provide the best coupling with the lens point spread function and to increase the symmetry for polarimetric studies.Comment: 10 pages, 9 figure

Gamma-ray Astrophysics in the MeV Range: the ASTROGAM Concept and Beyond

The energy range between about 100 keV and 1 GeV is of interest for a vast class of astrophysical topics. In particular, (1) it is the missing ingredient for understanding extreme processes in the multi-messenger era; (2) it allows localizing cosmic-ray interactions with background material and radiation in the Universe, and spotting the reprocessing of these particles; (3) last but not least, gamma-ray emission lines trace the formation of elements in the Galaxy and beyond. In addition, studying the still largely unexplored MeV domain of astronomy would provide for a rich observatory science, including the study of compact objects, solar- and Earth-science, as well as fundamental physics. The technological development of silicon microstrip detectors makes it possible now to detect MeV photons in space with high efficiency and low background. During the last decade, a concept of detector ("ASTROGAM") has been proposed to fulfil these goals, based on a silicon hodoscope, a 3D position-sensitive calorimeter, and an anticoincidence detector. In this paper we stress the importance of a medium size (M-class) space mission, dubbed "ASTROMEV", to fulfil these objectives

Observing GRBs with the LOFT Wide Field Monitor

LOFT (Large Observatory For X-ray Timing) is one of the four candidate missions currently under assessment study for the M3 mission in ESAs Cosmic Vision program to be launched in 2024. LOFT will carry two instruments with prime sensitivity in the 2-30 keV range: a 10 m2 class large area detector (LAD) with a <1° collimated field of view and a wide field monitor (WFM) instrument. The WFM is based on the coded mask principle, and 5 camera units will provide coverage of more than 1/3 of the sky. The prime goal of the WFM is to detect transient sources to be observed by the LAD. With its wide field of view and good energy resolution of <500 eV, the WFM will be an excellent instrument for detecting and studying GRBs and X-ray flashes. The WFM will be able to detect ~150 gamma ray bursts per year, and a burst alert system will enable the distribution of ~100 GRB positions per year with a ~1 arcmin location accuracy within 30 s of the burst

A new method for chlorhexidine (CHX) determination: CHX release after application of differently concentrated CHX-containing preparations on artificial fissures

Aims of the study were (1) to establish a method for quantification of chlorhexidine (CHX) in small volumes and (2) to determine CHX release from differently concentrated CHX-containing preparations, varnishes, and a CHX gel applied on artificial fissures. CHX determination was conducted in a microplate reader using polystyrene wells. The reduced intensity of fluorescence of the microplates was used for CHX quantification. For verification of the technique, intra- and inter-assay coefficients of variation were calculated for graded series of CHX concentrations, and the lower limit of quantification (LLOQ) was determined. Additionally, artificial fissures were prepared in 50 bovine enamel samples, divided into five groups (A–E, n = 10) and stored in distilled water (7 days); A: CHX-varnish EC40; B: CHX-varnish Cervitec; C: CHX-gel Chlorhexamed; D: negative control, no CHX application; and E: CXH-diacetate standard (E1, n = 5) or CHX-digluconate (E2, n = 5) in the solution. The specimens were brushed daily, and CHX in the solution was measured. The method showed intra- and inter-assay coefficients of variation of <10 and <20%, respectively; LLOQ was 0.91–1.22 nmol/well. The cumulative CHX release (mean ± SD) during the 7 days was: EC40 (217.2 ± 41.8 nmol), CHX-gel (31.3 ± 8.5 nmol), Cervitec (18.6 ± 1.7 nmol). Groups A–C revealed a significantly higher CHX release than group D and a continuous CHX-release with the highest increase from day 0 to 7 for EC40 and the lowest for Chlorhexamed. The new method is a reliable tool to quantify CHX in small volumes. Both tested varnishes demonstrate prolonged and higher CHX release from artificial fissures than the CHX-gel tested

Understanding the origin of the positron annihilation line and the physics of supernova explosions

Nuclear astrophysics, and particularly nuclear emission line diagnostics from a variety of cosmic sites, has remained one of the least developed fields in experimental astronomy, despite its central role in addressing a number of outstanding questions in modern astrophysics. Radioactive isotopes are co-produced with stable isotopes in the fusion reactions of nucleosynthesis in supernova explosions and other violent events, such as neutron star mergers. The origin of the 511 keV positron annihilation line observed in the direction of the Galactic Center is a 50-year-long mystery. In fact, we still do not understand whether its diffuse large-scale emission is entirely due to a population of discrete sources, which are unresolved with current poor angular resolution instruments at these energies, or whether dark matter annihilation could contribute to it. From the results obtained in the pioneering decades of this experimentally-challenging window, it has become clear that some of the most pressing issues in high-energy astrophysics and astro-particle physics would greatly benefit from significant progress in the observational capabilities in the keV-to-MeV energy band. Current instrumentation is in fact not sensitive enough to detect radioactive and annihilation lines from a wide variety of phenomena in our and nearby galaxies, let alone study the spatial distribution of their emission. In this White Paper (WP), we discuss how unprecedented studies in this field will become possible with a new low-energy gamma-ray space experiment, called ASTENA (Advanced Surveyor of Transient Events and Nuclear Astrophysics), which combines new imaging, spectroscopic and polarization capabilities. In a separate WP (Guidorzi et al. 39), we discuss how the same mission concept will enable new groundbreaking studies of the physics of Gamma–Ray Bursts and other high-energy transient phenomena over the next decades

The Large Observatory For X-ray Timing: LOFT

LOFT, the Large Observatory for X-ray Timing, is a new space mission concept devoted to observations of Galactic and extra-Galactic sources in the X-ray domain with the main goals of probing gravity theory in the very strong field environment of black holes and other compact objects, and investigating the state of matter at supra-nuclear densities in neutron stars. The instruments on-board LOFT, the Large area detector and the Wide Field Monitor combine for the first time an unprecedented large effective area (~10 m2 at 8 keV) sensitive to X-ray photons mainly in the 2-30 keV energy range and a spectral resolution approaching that of CCD-based telescopes (down to 200 eV at 6 keV). LOFT is currently competing for a launch of opportunity in 2022 together with the other M3 mission candidates of the ESA Cosmic Vision Progra