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141.
142.
G. Klingelhöfer R. V. Morris P. A. De Souza Jr. D. Rodionov C. Schröder 《Hyperfine Interactions》2006,170(1-3):169-177
The element iron plays a crucial role in the study of the evolution of matter from an interstellar cloud to the formation and evolution of the planets. In the Solar System iron is the most abundant metallic element. It occurs in at least three different oxidation states: Fe(0) (metallic iron), Fe(II) and Fe(III). Fe(IV) and Fe(VI) compounds are well known on Earth, and there is a possibility for their occurrence on Mars. In January 2004 the USA space agency NASA landed two rovers on the surface of Mars, both carrying the Mainz Mössbauer spectrometer MIMOS II. They performed for the first time in-situ measurements of the mineralogy of the Martian surface, at two different places on Mars, Meridiani Planum and Gusev crater, respectively, the landing sites of the Mars-Exploration-Rovers (MER) Opportunity and Spirit. After about two Earth years or one Martian year of operation the Mössbauer (MB) spectrometers on both rovers have acquired data from more than 150 targets (and more than thousand MB spectra) at each landing site. The scientific measurement objectives of the Mössbauer investigation are to obtain for rock, soil, and dust (1) the mineralogical identification of iron-bearing phases (e.g., oxides, silicates, sulfides, sulfates, and carbonates), (2) the quantitative measurement of the distribution of iron among these iron-bearing phases (e.g., the relative proportions of iron in olivine, pyroxenes, ilmenite and magnetite in a basalt), (3) the quantitative measurement of the distribution of iron among its oxidation states (e.g., Fe2+, Fe3+, and Fe6+), and (4) the characterization of the size distribution of magnetic particles. Special geologic targets of the Mössbauer investigation are dust collected by the Athena magnets and interior rock and soil surfaces exposed by the Athena Rock Abrasion Tool and by trenching with rover wheels. The Mössbauer spectrometer on Opportunity at Meridiani Planum, identified eight Fe-bearing phases: jarosite (K,Na,H3O)(Fe,Al)(OH)6(SO4)2, hematite, olivine, pyroxene, magnetite, nanophase ferric oxides (npOx), an unassigned ferric phase, and a metallic Fe–Ni alloy (kamacite) in a Fe–Ni-meteorite. Outcrop rocks consist of hematite-rich spherules dispersed throughout S-rich rock that has nearly constant proportions of Fe3+ from jarosite, hematite, and npOx (28%, 35%, and 19% of total Fe). Jarosite is mineralogical evidence for aqueous processes under acid–sulfate conditions because it has structural hydroxide and sulfate and it forms at low pH. Hematite-rich spherules, eroded from the outcrop, and their fragments are concentrated as hematite-rich soils (lag deposits) on ripple crests (up to 68% of total Fe from hematite). Olivine, pyroxene, and magnetite are primarily associated with basaltic soils and are present as thin and locally discontinuous cover over outcrop rocks, commonly forming aeolian bedforms. Basaltic soils are more reduced (Fe3+/Fetotal ~0.2?0.4), with the fine-grained and bright aeolian deposits being the most oxidized. Basaltic soil at Meridiani Planum and Gusev crater have similar Fe-mineralogical compositions. At Gusev crater, the Mössbauer spectrometer on the MER Spirit rover has identified 8 Fe-bearing phases. Two are Fe2+ silicates (olivine and pyroxene), one is a Fe2+ oxide (ilmenite), one is a mixed Fe2+ and Fe3+ oxide (magnetite), two are Fe3+ oxides (hematite and goethite), one is a Fe3+ sulfate (mineralogically not constrained), and one is a Fe3+ alteration product (npOx). The surface material in the plains have a olivine basaltic signature (Morris, et al., Science, 305: 833, 2004; Morris, et al., J. Geophys. Res., 111, 2006, Ming, et al., J. Geophys. Res., 111, 2006) suggesting physical rather than chemical weathering processes present in the plains. The Mössbauer signature for the Columbia Hills surface material is very different ranging from nearly unaltered material to highly altered material. Some of the rocks, in particular a rock named Clovis, contain a significant amount of the Fe oxyhydroxide goethite, α-FeOOH, which is mineralogical evidence for aqueous processes because it is formed only under aqueous conditions. 相似文献
143.
Water-soluble organic matter (WSOM) from air particles plays a potentially important role in the climate system, yet little is known about its molecular composition and physico-chemical properties. During the past decade, the rapidly-evolving field of analytical instrumentation has produced sophisticated tools capable of providing molecular level information on this organic-aerosol fraction.This article presents a critical review of the major applications of these advanced analytical methods in WSOM analysis. We emphasize off-line methods relying on nuclear magnetic resonance and infrared spectroscopies, and high-resolution mass spectrometry. We also discuss the most prominent analytical methods for near real-time measurements of particulate WSOM. We address the limitations of advanced off-line and on-line instrumental techniques, and, finally, outline the major challenges ahead to improve the current knowledge on the chemical structures of aerosol WSOM. 相似文献
144.
ZHAO Li CHEN Liaoyuan LUO Cuiwen LIYongge PAN Wei SONG Xianming WANG Minghong 《核工业西南物理研究院年报(英文版)》2005,(1):79-81
HL-2A DAPS is a large scale special data system for HL-2A tokamak . Technology of network, communication, data acquisition, data processing, real-time display, data management and systems management have been used in this system. With higher quality products and lower design costs, virtual instrumentation has been widely used in HL-2A DAPS. Vh-tual instrumentation combines mainstream commercial technologies, with flexible software and a wide variety of measurement and control hardware. It's easily to create user-defined systems that meet the exact application needs for the experiment. 相似文献
145.
J. A. Pomarico D. I. Iriarte H. O. Di Rocco 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(1):65-72
In this paper we analyze the variations in line intensities ratios due to a non-equilibrium situation and to optical depth
effects. A four level model is proposed and the two particular situations for the possible transitions are considered. Electron
density and temperature as well as the source thickness are used as independent parameters to find out in which way and extent
they modify the ratios of levels populations compared with the ideal case of an equilibrium state and optically thin source.
Accordingly with the ion of interest, electron temperatures ranging from I/20 to I/7 eV (I being the ionization energy), whereas electron densities in the interval from 1014 to 1020 cm-3 will be considered. These ranges are of special interest for diverse applications such as LIBS and measurement of transition
probabilities. Some results are presented for real ions and a new expression for the escape factor is also proposed for general
plasma conditions.
Received 12 June 2001 and Received in final form 24 October 2001 相似文献
146.
Summary An infra-red detector produced by the Elettronica SPA Company for the European Space Agency to be used in the Earth surface
mapping from aircraft has been tested in our laboratory. We present the characteristics of the detector working in the spectral
range (1÷2.5) μm. The acquisition system and the electronics are discussed and a detailed study of all the noise sources is
presented; the measured NEP is 3.2·10−14W Hz−1/2 at a temperature of 108 K.
Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990. 相似文献
147.
148.
A kit for the conversion of an X-bandesr spectrometer for K-band operation is described and its performance has been tested withp-benzosemiquinone, vanadyl acetyl acetonate and 2, 5-ditertiary butyl semiquinone. The easy conversion of the X-band spectrometer
to K-band operation enables us to distinguish between magnetic field dependent and field independent parameters. A varactor
harmonic generator is used as a frequency doubler driving the fundamental power from the existing X-band source to give a
power output at K-band without having to modify the electronic circuit; the modification of the microwave circuitry is proposed. 相似文献
149.
U. Bottigli P. Camici C. R. Bellina P. A. Salvadori R. A. Mazzarisi R. Barsacchi M. Quaglia F. Ursini 《Il Nuovo Cimento D》1984,3(5):936-944
Summary This paper describes the use of a single-photon counting apparatus (SPCA) for the continuous monitoring of the ultraweak chemiluminescence
(UWC) emitted by isolated and perfused rat hearts and deriving from phospholipid peroxydation. Specifically the SPCA was used
to assess the peroxidative stress induced in the heart by the addition of an hydroperoxide to the perfusing medium. To this
purpose, different hydroperoxides were used and each one produced a tipical and highly reliable temporal evolution of UWC.
It was also found that the oxygen availability strongly influences the intensity and the kinetic of the UWC emission. UWC
was proved to be a very interesting and promising tool for monitoring the peroxidative damage of biological membranes, both
because it makes a continuous assessment possible and because the sensitivity of this method is approximately ten times greater
than usual analytical chemistry methods.
Riassunto è stato usato un apparato di misurazione a un fotone per misurare la chemiluminescenza emessa durante la perossidazione dei fosfolipidi della membrana cellulare di un cuore di ratto isolato e perfuso sottoposto ad uno stress perossidativo. Lo stress perossidativo è stato ottenuto aggiungendo idroperossidi al liquido di perfusione. I differenti idroperossidi usati hanno prodotto tipiche evoluzioni temporali di chemi-luminescenza altamente riproducibili. La disponibilità di ossigeno influenza fortemente l'intensità e la cinetica di emissione della chemiluminescenza. Nell'àmbito di uno studio sull'effetto di differenti idroperossidi sul cuore di ratto isolato e perfuso, la misura della chemiluminescenza si è dimostrata un interessante e promettente strumento per il monitoraggio in continuo dei danni perossidativi nelle membrane biologiche. La sensibilità di questo metodo per la valutazione della perossidazione dei fosfolipidi delle biomembrane è circa dieci volte maggiore rispetto agli ordinari metodi di chimica analitica.
Резюме В этой статъе описывается аппаратура для ретистрации отделъных фотонов для непрерывного мониторнта улътраслабой хемилюминесценции, испус-каемой во время пероксидации фосфолипидов клеточной мембраны изолированного и перфузированного сердца крысы. В частности, аппаратура для ретистрации отделъ-ных фотонов исполъзуется для оценки напряжениь, индуцированных в сердце при добавлении тидроперекиси в пербузирующую жидкостъ. для этого исполъзуутся различные тидропероксиды, которые дают типичные временные эволюции улътса-слабой хемиюминесценции. Также получается, что наличие кислорода силъно влияет на интенсивиостъ и кинетику улътраслабои хемилюминесценции. Показывается, что улътраслабая хемилюминесценция представляет оченъ интересный и перспективный инструмент для мониторинга пероксидативных повреждений биологических мембран. Чувствителъностъ этого метода для пценки пероксидации босболинидов биомембран почти в десятъ раз выше, чем обычнын методов аналитической химии.相似文献
150.
M P Seah 《Surface and interface analysis : SIA》2012,44(7):879-880
This International Standard revises ISO 18115:2001 and the two subsequent amendments by bringing the material up to date and by separating the general terms and terms used in spectroscopy into Part 1 and terms relating to scanning probe microscopy into Part 2. This part, Part 2, covers 227 terms used in scanning probe microscopy as well as 86 acronyms. The terms cover words or phrases used in describing the samples, instruments and theoretical concepts involved in surface chemical analysis. Copyright © 2012 Crown copyright. 相似文献