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Target Material (target + material)
Selected AbstractsLaser Ablation (193 nm), Purification and Determination of Very Low Concentrations of Solar Wind Nitrogen Implanted in Targets from the GENESIS SpacecraftGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 2 2009Laurent Zimmermann azote; ablation laser; purification; spectrométrie de masse; mission GENESIS The GENESIS space mission recovered ions emitted by the Sun during a 27 month period. In order to extract, purify and determine the very low quantities of solar nitrogen implanted in the GENESIS targets, a new installation was developed and constructed at the CRPG (Nancy, France). It permitted the simultaneous determination of nitrogen and noble gases extracted from the target by laser ablation. The extraction procedure used a 193 nm excimer laser that allowed for surface contamination in the outer 5 nm to be removed, followed by a step that removed 50 nm of the target material, extracting the solar nitrogen and noble gases implanted in the target. Following purification using Ti and Zr getters for noble gases and a Cu-CuO oxidation cycle for N2, the extracted gases were analysed by static mode (pumps closed) mass spectrometry using electron multiplier and Faraday cup detectors. The nitrogen blanks from the purification section and the static line (30 minutes) were only 0.46 picomole and 0.47 picomole, respectively. La mission GENESIS a récupéré des ions émis par le soleil pendant une période de 27 mois. Afin d'extraire, purifier et analyser de très faibles quantités d'azote solaire implantés dans des cibles GENESIS, une nouvelle installation a été développée et construite au CRPG. Elle a permis l'analyse simultanée de l'azote et des gaz nobles extraits de la couche d'or par ablation. La procédure d'extraction a utilisé un laser Excimer 193 nm qui a permis une étape d'extraction à 5 nm pour éliminer la pollution à la surface, suivie d'une étape qui a extrait jusqu'à une profondeur de 50 nm l'azote et les gaz rares solaires implantés dans la cible. Après une purification à l'aide de getters Ti et Zr pour les gaz rares et un cycle d'oxydation Cu-CuO pour N2, les gaz extraits ont été analysés en mode statique (pompage fermé) par spectrométrie de masse à l'aide d'un multiplicateur d'électrons et d'une cage de Faraday. Les blancs d'azote provenant de la partie purification et de la ligne en statique (30 minutes) étaient de seulement 0.46 et 0.47 picomole, respectivement. [source] Analysis of the steady-state flow of a compressible viscoplastic medium over a wedgeINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 6 2006Oana Cazacu Abstract A new model for calculating the resistance to penetration into geological or geologically derived materials is proposed. We assume steady-state flow of the target material over the penetrator. The target medium is described by a rate dependent constitutive equation that accounts for combined effects of strain rate and compaction on yielding. The wedge-shaped penetrator is considered to be rigid. The influence of the characteristics of the penetrator/target interface, impact velocity, target mechanical properties and nose geometry on the resistance to penetration is investigated. It is found that for low to intermediate impact velocities, accounting for friction results in a blunter optimal wedge geometry for optimal penetration performance. Copyright © 2005 John Wiley & Sons, Ltd. [source] Numerical analysis of Rayleigh,Plesset equation for cavitating water jetsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 7 2007H. Alehossein Abstract High-pressure water jets are used to cut and drill into rocks by generating cavitating water bubbles in the jet which collapse on the surface of the rock target material. The dynamics of submerged bubbles depends strongly on the surrounding pressure, temperature and liquid surface tension. The Rayleigh,Plesset (RF) equation governs the dynamic growth and collapse of a bubble under various pressure and temperature conditions. A numerical finite difference model is established for simulating the process of growth, collapse and rebound of a cavitation bubble travelling along the flow through a nozzle producing a cavitating water jet. A variable time-step technique is applied to solve the highly non-linear second-order differential equation. This technique, which emerged after testing four finite difference schemes (Euler, central, modified Euler and Runge,Kutta,Fehlberg (RKF)), successfully solves the Rayleigh,Plesset (RP) equation for wide ranges of pressure variation and bubble initial sizes and saves considerable computing time. Inputs for this model are the pressure and velocity data obtained from a CFD (computational fluid dynamics) analysis of the jet. Copyright © 2007 John Wiley & Sons, Ltd. [source] Synthesis of 13C-labelled cinnamonitrileJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 2 2002Elizabeth M. Zippi Abstract 13C-labelled cinnamonitrile, a compound that possesses both the aromatic functionality of styrene and the nitrile functionality of acrylonitrile has been synthesized in one step using , -bromostyrene and potassium [13C]cyanide. The preparation of a target material using 13C -labelled cinnamonitrile may provide a cost-effective method for producing nitrogen-13 via proton irradiation for Positron Emission Tomography. Copyright © 2002 John Wiley & Sons, Ltd. [source] Synthesis of Phenyl-13C6-etheneJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 11 2001Elizabeth M. Zippi Abstract In an effort to prepare an improved carbon-rich target material for the accelerator production of 13N labelled ammonia for use in positron emission tomography (PET), sulfonated poly(styrene/divinylbenzene) has been evaluated. The preparation of this target material using naturally abundant carbon-12 compounds was investigated in an effort to optimize conditions for the preparation of the analogous carbon-13 target material which may provide a cost-effective method for producing nitrogen-13 labelled ammonia via proton irradiation. As part of this study, phenyl-13C6-ethene was synthesized in three steps starting from benzene-13C6. Copyright © 2001 John Wiley & Sons, Ltd. [source] Hertzian Ring Crack Initiation in Hot-Pressed Silicon CarbidesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2009Andrew A. Wereszczak The use of Hertzian indentation to measure ring crack initiation force (RCIF) distributions in four hot-pressed silicon carbide (SiC) ceramics is described. Three diamond indenter diameters were used with each SiC; the RCIF in each test was identified with the aid of an acoustic emission system; and two-parameter Weibull RCIF distributions were determined for all 12 combinations. RCIF testing was found to be an effective discriminator of contact damage initiation and response. It consistently produced the same ranking of RCIF between the four SiCs, with all three different indenter diameters, which is noteworthy because Knoop hardness and fracture toughness measurements were only subtly different or equivalent for the four SiCs. However, because RCIF, like hardness, is a characteristic response of a target material to an applied indentation condition (e.g., a function of indenter diameter) and not a material property, the implications and possible limitations should be acknowledged when using RCIF to discriminate the target material response. [source] Australasian microtektites and associated impact ejecta in the South China Sea and the Middle Pleistocene supereruption of TobaMETEORITICS & PLANETARY SCIENCE, Issue 2 2006Billy P. Glass Unmelted ejecta were found associated with the microtektites at this site and with Australasian microtektites in Core SO95,17957,2 and ODP Hole 1144A from the central and northern part of the South China Sea, respectively. A few opaque, irregular, rounded, partly melted particles containing highly fractured mineral inclusions (generally quartz and some K feldspar) and some partially melted mineral grains, in a glassy matrix were also found in the microtektite layer. The unmelted ejecta at all three sites include abundant white, opaque grains consisting of mixtures of quartz, coesite, and stishovite, and abundant rock fragments which also contain coesite and, rarely, stishovite. This is the first time that shock-metamorphosed rock fragments have been found in the Australasian microtektite layer. The rock fragments have major and trace element contents similar to the Australasian microtektites and tektites, except for higher volatile element contents. Assuming that the Australasian tektites and microtektites were formed from the same target material as the rock fragments, the parent material for the Australasian tektites and microtektites appears to have been a fine-grained sedimentary deposit. Hole 1144A has the highest abundance of microtektites (number/cm2) of any known Australasian microtektite-bearing site and may be closer to the source crater than any previously identified Australasian microtektite-bearing site. A source crater in the vicinity of 22° N and 104° E seems to explain geographic variations in abundance of both the microtektites and the unmelted ejecta the best; however, a region extending NW into southern China and SE into the Gulf of Tonkin explains the geographic variation in abundance of microtektites and unmelted ejecta almost as well. The size of the source crater is estimated to be 43 ± 9 km based on estimated thickness of the ejecta layer at each site and distance from the proposed source. A volcanic ash layer occurs just above the Australasian microtektite layer, which some authors suggest is from a supereruption of the Toba caldera complex. We estimate that deposition of the ash occurred ,800 ka ago and that it is spread over an area of at least 3.7 times 107 km2. [source] Integrated deep drilling, coring, downhole logging, and data management in the Chicxulub Scientific Drilling Project (CSDP), MexicoMETEORITICS & PLANETARY SCIENCE, Issue 6 2004Lothar Wohlgemuth To date, a continuous scientific sampling of large impact craters from cover rocks to target material has only seldom been performed. The first project to deep-drill and core into one of the largest and well-preserved terrestrial impact structures was executed in the winter of 2001/2002 in the 65 Myr-old Chicxulub crater in Mexico using integrated coring sampling and in situ measurements. The combined use of different techniques allows a three-dimensional insight and a better understanding of impact processes. Here, we report the integration of conventional rotary drilling techniques with wireline mining coring technology that was applied to drill the 1510 m-deep Yaxcopoil-1 (Yax-1) well about 40 km southwest of Mérida, Yucatán, Mexico. During the course of the project, we recovered approximately 900 m of intact core samples including the transitions of reworked ejecta to post-impact sediments, and that one from large blocks of tilted target material to impact-generated rocks, i.e., impact melt breccias and suevites. Coring was complemented by wireline geophysical measurements to obtain a continuous set of in situ petrophysical data of the borehole walls. The data acquired is comprised of contents of a natural radioactive element, velocities of compressional sonic waves, and electrical resistivity values. All the digital data sets, including technical drilling parameters, initial scientific sample descriptions, and 360° core pictures, were distributed during the course of the operations via Internet and were stored in the ICDP Drilling Information System (http:www.icdp-online.org), serving the global community of cooperating scientists as a basic information service. [source] Mineralogy, petrology, and thermal evolution of the Benton LL6 chondriteMETEORITICS & PLANETARY SCIENCE, Issue S7 2003Erin L. WALTON Internally, the meteorite comprises light-colored, subangular to subrounded clasts embedded in a dark grey-colored matrix. Clasts comprise the same mineral phases as the matrix, as well as chondrules and larger (50,100 ,m) single mineral grains (mainly olivine and orthopyroxene). Composite (polyphase) clasts can be several millimeters in length. Numerous examples of post-brecciation and post-annealing shearing and displacement at the micron to millimeter scale occur in the form of shock veins. Benton is a shock stage S3 chondrite, which experienced shock pressures on the order of 15,20 GPa, with an estimated post-shock temperature increase of 100,150°C. Benton's history comprises a sequence of events as follows: 1) chondrule formation and initial assembly; 2) brecciation; 3) thermal metamorphism; and 4) shock veining. Events (2) and (4) can be equated with distinct impact events, the former representing bombardment of target material that remained in situ or collisionally fragmented during metamorphism, and then gravitationally reassembled, the latter probably with release from the source body to yield a meteorite. Thermal metamorphism post-dates brecciation. The mean equilibration temperature recorded in the Benton LL6 chondrite is 890°C, obtained using the two pyroxene geothermometer. [source] Positron annihilation spectroscopy using high-energy photonsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 2 2010Maik Butterling Abstract The superconducting electron accelerator ELBE (Electron Linac with high Brilliance and low Emittance) at the Research Centre Dresden-Rossendorf (Germany) serves as a high-intensity bremsstrahlung photon-source delivering a pulsed beam (26,MHz) with very short bunches (<5,ps). The photons are being converted into positrons by means of pair production inside the target material thus forming an intense positron source. The accelerator machine pulse is used as time reference allowing positron lifetime spectroscopy. We performed positron annihilation spectroscopy by pair production in different sample materials and used coincidence techniques to reduce the background due to scattered photons significantly in order resulting in spectra of extraordinary high quality. [source] Ion Energy Distributions in Magnetron Sputtering of Zinc Aluminium OxidePLASMA PROCESSES AND POLYMERS, Issue S1 2009Thomas Welzel Abstract Ion energy distributions have been measured with an energy-dispersive mass spectrometer during magnetron sputtering of Al doped ZnO. A d.c. and a pulsed d.c. discharge have been investigated. Different positive ions from the target material have been observed with low energies in d.c. and a second energy peak of about 30 eV in pulsed d.c. with only weak additional energy due to the sputter process. Negative ions are mainly O, with energies corresponding to the target voltage of several 100 eV. They originate from the target and barely from the (O2) gas and hit the substrate opposite the race track. In pulsed d.c., due to the varying target voltage, energies of up to 500 eV have been observed. With increasing pressure, negative ions at the substrate are reduced exponentially in their density but not in their energy. [source] Technical note: PCR analysis of minimum target amount of ancient DNAAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2010Daniela Woide Abstract The study of ancient DNA plays an important role in archaeological and palaeontological research as well as in pathology and forensics. Here, we present a new tool for ancient DNA analysis, which overcomes contamination problems, DNA degradation, and the negative effects of PCR inhibitors while reducing the amount of starting target material in the picogram range. Ancient bone samples from four Egyptian mummies were examined by combining laser microdissection, conventional DNA extraction, and low-volume PCR. Initially, several bone particles (osteons) in the micrometer range were extracted by laser microdissection. Subsequently, ancient DNA amplification was performed to verify our extraction method. Amelogenin and ,-actin gene specific fragments were amplified via low-volume PCR in a total reaction volume of 1 ,l. Results of microdissected mummy DNA samples were compared to mummy DNA, which was extracted using a standard DNA extraction method based on pulverization of bone material. Our results highlight the combination of laser microdissection and low-volume PCR as a promising new technique in ancient DNA analysis. Am J Phys Anthropol, 2010. © 2010 Wiley-Liss, Inc. [source] Determination of the Oxygen Deficiency in Vacuum-Hot-Pressed Ferroelectric Ceramics Using a Thermogravimetric TechniqueJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2000Qi Tan An attempt to measure the oxygen deficiency in vacuum-hot-pressed ferroelectric target materials was made, using a thermogravimetric method. The approach was intended to measure the relative mass increase of oxygen-deficient sheet samples, with respect to an oxidized reference that was annealed in air. A saturation of mass change was achieved, which indicated a saturated oxidation state and provided a basis for further calculation of the oxygen deficiency in the samples. Results were obtained for barium strontium titanate and lead lanthanum zirconate titanate compositions, which shows the feasibility of applying the thermogravimetric method to ferroelectric materials. [source] Impactites as a random medium,Using variations in physical properties to assess heterogeneity within the Bosumtwi meteorite impact craterMETEORITICS & PLANETARY SCIENCE, Issue 4-5 2007Elizabeth L'HEUREUX The damage induced by impact results in extensive fracturing and mixing of target materials. We discuss here a means of using sonic velocity and density logs from two boreholes through the Bosumtwi crater fill and basement to estimate the degree of heterogeneity and fracturing within the impacted target, in order to understand the discrepancy between the large impedances derived from the log data and the nonreflective zone of impactites observed in seismic sections. Based on an analysis of the stochastic fluctuations in the log data, the Bosumtwi impactites are characterized by vertical scale lengths of 2,3 m. From the resolution of the seismic data over the crater, horizontal scale lengths are estimated at <12 m. The impactites therefore fall within the quasi-homogeneous scattering regime, i.e., seismic energy will propagate through the medium with little disruption. Scale lengths as small as these are observed in the fractured basement rocks of impact structures, whereas non-impact related crystalline environments are characterized by scale lengths an order of magnitude larger. Assuming that the high-frequency fluctuations observed in the log data are more sensitive to fracture distribution than petrology, this suggests that the small scale lengths observed within impact structures are characteristic of impact-induced damage, and could be used to estimate the extent of fracturing undergone by the rocks at any depth below an impact structure. [source] Geological overview and cratering model for the Haughton impact structure, Devon Island, Canadian High ArcticMETEORITICS & PLANETARY SCIENCE, Issue 12 2005Gordon R. Osinski Regional geological mapping has refined the sedimentary target stratigraphy and constrained the thickness of the sedimentary sequence at the time of impact to ,1880 m. New 40Ar,39Ar dates place the impact event at ,39 Ma, in the late Eocene. Haughton has an apparent crater diameter of ,23 km, with an estimated rim (final crater) diameter of ,16 km. The structure lacks a central topographic peak or peak ring, which is unusual for craters of this size. Geological mapping and sampling reveals that a series of different impactites are present at Haughton. The volumetrically dominant crater-fill impact melt breccias contain a calcite-anhydrite-silicate glass groundmass, all of which have been shown to represent impact-generated melt phases. These impactites are, therefore, stratigraphically and genetically equivalent to coherent impact melt rocks present in craters developed in crystalline targets. The crater-fill impactites provided a heat source that drove a post-impact hydrothermal system. During this time, Haughton would have represented a transient, warm, wet microbial oasis. A subsequent episode of erosion, during which time substantial amounts of impactites were removed, was followed by the deposition of intra-crater lacustrine sediments of the Haughton Formation during the Miocene. Present-day intra-crater lakes and ponds preserve a detailed paleoenvironmental record dating back to the last glaciation in the High Arctic. Modern modification of the landscape is dominated by seasonal regional glacial and niveal melting, and local periglacial processes. The impact processing of target materials improved the opportunities for colonization and has provided several present-day habitats suitable for microbial life that otherwise do not exist in the surrounding terrain. [source] The Sirente crater field, ItalyMETEORITICS & PLANETARY SCIENCE, Issue 11 2002Jens ORMö They are located in the Sirente plain within the mountains of the Abruzzo region, central Italy. The craters are distributed in a field 450 m long and 400 m wide. This field consists of ,17 smaller craters close to a larger main crater. The main crater is located in the southern end of the crater field and is 140 m long and 115 m wide, measured rim-to-rim. It has a well-developed, saddle-shaped rim that rises at a maximum 2.2 m above the surrounding plain. Radiocarbon dating of the target surface preserved below the rim gave a calibrated age of formation at about a.d. 412 (1650 ± 40 radiocarbon years b.p.). This young age is consistent with the apparent little modification of the rim. The morphology of the main crater and its relation to a crater field strongly points to its origin by impact from a projectile that broke up during its passage through the atmosphere. Quartz is very rare in the target and no planar deformation features have been found so far. The rim material and the upper 4 m of the main crater infill are impregnated with ferric oxides, which gives a more reddish colour compared to the other sediments of the plain. Rusty crusts with high Fe and Mn content occur in the rim material, but have not been found in the plain's sediments. Some of these crusts can be separated by magnet, and have sporadic micron-sized Ni-rich granules. The main crater is in the size range of the craters with explosive dispersion of the projectile and has many features comparable to both large experimental and meteoritic impact craters formed in loose sediments. We suggest that this crater represents a rare example of well-preserved, small impact crater formed in unconsolidated target materials. [source] Electrospray ionization and atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry of antioxidants applied in lubricants,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2009Alexander Kassler The aim of this study was to investigate the utility of ion trap mass spectrometry (ITMS) in combination with the two desorption/ionization methods, electrospray (ESI) and atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI), for the detection of antioxidants which are applied in lubricants. These experiments should form the base for future investigations of antioxidants in tribologically formed thin layers on the surface of frictional systems. Seventeen different antioxidants were selected out of the group of hindered phenolic and aromatic aminic compounds. Practically all antioxidants could be characterized by positive ion ESI- and AP-MALDI-ITMS, forming various types/species of molecular ions (e.g. [M]+., [M+H]+, [M+Na]+ or [M,2H+H]+). A few compounds could be analyzed by negative ion ESI-MS, too, but none by negative ion AP-MALDI-MS. The influence of target materials in AP-MALDI-MS (gold- and titanium nitride (TiN)-covered stainless steel, micro-diamond-covered hard metal, hand-polished and sand-blasted stainless steel targets) with respect to the molecular ion intensity and type of molecular ion of two selected antioxidants was evaluated. The surface properties are of particular interest because in friction tests different materials with different surface characteristics are used. However, the MS results indicate that optimal target surfaces have to be found for individual antioxidants in AP-MALDI-MS but in general smooth surfaces were superior to rough surfaces. Finally the gold-covered stainless steel MALDI target provided the best mass spectra and was selected for all the antioxidants investigated. Copyright © 2009 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||