ater‐solu le photose sitizer  were also proposed based on lutetium.
As a result of these wide variety of applications based on lutetium isotopes, the demand has increased dramatically for the high precision and accuracy determination of isotope
composition of lutetium. Thermal ionization mass spectrometry (TIMS) has been traditionally used for this purpose. Recent years have witnessed a major growth in the applications of multi- collector inductively coupled plasma mass spectrometry (MC-ICPMS) for the high precision determination of isotope ratios, because of its simple sample introduction, high ionization efficiency and high sensitivity. However, MC-ICPMS exhibits larger (10-fold) mass bias as compared to TIMS, which needs to be properly corrected for the accurate isotope ratio measurements. Various mass bias correction models, such as the linear, power-law , exponential , standard-sample bracketing (SSB), and combined SSB with internal standard models  have been employed. Majority geological applications in previous works were based on use of other elements such as W [26, 27], Yb  or Er  to correct the mass bias using the exponential law with the assumption of identical mass bias for the analyte and the reference isotope ratios. However, this assumption of identical mass bias for the analyte and the reference isotope ratios has been realized to be wrong, after all the mass bias for the Li is not the same for U , which in turn would produce biased results for the absolute isotope ratio measurements by MC-ICPMS.
Another improvement consists in the hyphenation of HPLC with MC-ICPMS, which has also been widely developed during the last two decades. 16 In the particular case of nuclear fuel samples, several studies have evaluated the performance of HPLC-MC-ICPMS for isotope ratio measurements of U, Pu, Nd, Eu, Gd, Sm in nuclear fuel samples or simulated solutions. 17-20 After taking into account the drift phenomenon occurring when transient signals are acquired 21-23 , isotope ratios are measured with uncertainties on the order of or lower than 1‰. This approach is particularly attractive for reducing the analysis time and consequently the analyst’s exposure to ionizing radiation. Nevertheless, considering the typical flow rates of the chromatographic systems which are usually on the order of several hundreds of microliters per minute, further developments are required to reduce the associated liquid waste volumes. Since electrokinetic methods only involve ion migration under the influence 3
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Use of Ga for mass bias correction for the accurate determination of copper isotope ratio in the NIST SRM 3114 Cu standard and geological samples by MC-ICPMS
repeated 10 4 times, and the best estimate of the calibrated
Figure 3. Typical regression plots of NRC HIPB-1 lead against NIST SRM 997 thallium using MC-ICPMS.
Figure 4. Relative isotope ratio diﬀerences (isotope deltas) of HIPB-1 samples Pb 1 −Pb 15 against their mixed blend (Pb mix ) using the combined
standard-sample bracketing and internal normalization (with thallium) isotopic fractionation correction model. Isotope deltas are expressed as relative deviations from the Pb mix in parts per million.
Isotopic ratios determined on MC instruments (TIMS, MC-ICPMS). Minor isotopes are generally measured SEM or Daly electrode coupled to a photomultiplier
Drawbacks: - Many settings must be performed (linearity, dead time, gain between SEM or Daly electrode and Faraday cup)
indeed observed in MC-ICPMS for magnetic isotopes (for example,
73 Ge and 201 Hg), in this study, mass-independent fractionation is also
observed for “even” isotopes (for example, 200 Hg and 204 Pb). Thus, mass-bias behavior of all isotopes cannot be divided into two distinct categories: one for all nonmagnetic nuclei and another for all magnetic nuclei. Rather, the magnitude of the observed departures is haphazard both in time and nuclide mass domains and is clearly not governed by the presence of the magnetic moment of the nuclides alone.
2. EXPERIMENTAL SECTION
2.1. Instrumentation. A Thermo Fisher Scientiﬁc Neptune Plus (Bremen, Germany) MC-ICPMS equipped with nine Faraday cups and a combined Scott-type on the top of a cyclonic spray chamber with a PFA self-aspirating nebulizer (Elemental Scientiﬁc, Omaha NE, USA), operating at 50 μL min −1 , was used for all osmium isotope ratio measurements. A platinum guard electrode was ﬁtted to the plug-in quartz torch with quartz injector. The instrument was operated under low mass resolution mode to perform isotope ratio measurements. Brieﬂy, the instrument was tuned for maximum sensitivity and optimal peak shape as well as stable signals using a 1.0 mg kg −1 osmium solution. The gain calibration of the Faraday cups was then performed to ensure normalization of their eﬃciencies. Typical operating conditions are summarized in Table S1 . Under these experimental conditions, acquisition of each measurement point takes
The in-situ measurement of isotopic compositions of Nd is suitable in minerals rich in this element (e.g. monazite, titanite, apatite). Apatite is an ideal candidate as its Nd concentrations are generally greater than several hundreds of ppm, and it is an ubiquitous phase in most rocks (magmatic, metamorphic and sedimentary), giving wide field of application in geology. Several laboratories have already developed the in-situ analysis of Nd isotopic ratios in this mineral. Analytical protocols are nearly similar at some extent, but diverge on other points such as correction for instrumental Sm-Nd fractionation ( Fisher et al., 2011; Iizuka et al., 2011 ). Moreover, the accuracy and precision of isotopic measurements seem to be strongly dependent on the instrumentation used (laser system + MC-ICPMS), as well as the number and diversity of isotopic ratios analyzed on, leading to the necessity for each laboratory to justify for its own protocol. Here, we present new Sm-Nd results acquired on the Thermo Fisher Scientific™ Neptune Plus™ instrument at the Laboratoire Magmas et Volcans (LMV), Clermont-Ferrand, France, on apatite crystals from three different localities (Durango apatite and two carbonatite apatites). We detail the different corrections needed to obtain accurate and precise Nd isotopic ratios with a focus on the laser (size of the spot, fluence, frequency and He/N 2 gas flows) and MC-ICPMS parameters (X vs. H skimmer cones) and their influence on the meas-
Institute for National Measurement To whom correspondences should be Standards, National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada
A procedure is described for precise Hg isotope ratio measurements by solution nebulization multicollector inductively coupled plasma mass spectrometry (MC- ICPMS). Hg was released from geological samples using aqua regia extraction and then separated from other matrix elements with the aid of anion-exchange chroma- tography using strongly basic Dowex 1-X8 anion-exchange resin. Performance of the chromatographic procedure was evaluated using various types of replacement anions for elution of mercury, including L -cysteine, thiourea, NO 3 - ,
invariability of the ratio of the fractionation coeﬃcients and is
capable of correcting both mass-dependent and mass- independent isotope ratio fractionation occurring in MC- ICPMS. 26 In this vein, the regression model does not invoke traditional mass fractionation assumptions and it allows one to compare isotope ratio measurements between various elements regardless of the fact that each element undergoes slightly diﬀerent isotope ratio fractionation. Taking advantage of these features, in this study, we test the reliability of the regression model using two independent primary isotope ratio calibrators, NIST SRM 997 thallium and NIST SRM 989 rhenium, for the characterization of irridum isotopic compisition.
Instrumentation. A Thermo Fisher Scientific Neptune MC-ICPMS (Bremen, Germany) equipped with nine Faraday cups and a combination of cyclonic and Scott-type spray chambers with a self-aspirating nebulizer MCN50 (Elemental Scientific, Omaha NE, USA) made from perfluoroalkoxy polymer and operating at 50 µL min –1 was used in all
Ce chapitre présente le principe de la technique MC-CDMA. Cette technique se caractérise par l’ajout d’une composante CDMA aux modulations à porteuses multiples OFDM. Les avantages associés expliquent l’intérêt porté à son application dans le cas des liaisons descendantes des futurs réseaux sans fil (4G). Les différentes techniques de détection du signal MC-CDMA reçu ont été présentées. Les résultats obtenus sur les canaux Rayleigh et Ric montrent que les détecteurs basés sur le critère de minimisation de l’erreur quadratique moyenne, MMSE et sur la combinaison à restauration d’orthogonalité, ORC, offrent les meilleures performances quelque soit la structure du récepteur, pour le dernier résultat on peut déduire que les systèmes MC-CDMA sont plus sensibles à l'effet Doppler. Le chapitre suivant sera consacré sur l’application du codage de canal en vue d’améliorer les performances du système MC- CDMA.
Chapter 7 Conclusion
This thesis presents the design of a system that allows programmers to visualize which parts of their code achieve modified condition/decision coverage (MC/DC) after that run their test suite. This tool is built on top of the Green Hills C/C++ compiler. I inserted static instrumentation by modifying the abstract syntax tree (AST) generated in the computer back end. I also modified some of the compiler front end code to maintain and propagate position information for each such expression. I wrote a separate utility program that interprets the extra data generated by the instrumented code and uses the associated position information to produce human readable output.
Design of a variable frequency transmitter in the region 75 to 95 mc Parsons, J.S.
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every X-ray tube incidence used by the simulated imaging protocol.
While in-room Magnetic Resonance Imaging starts becoming part of radiotherapy (RT) treatments, the use of X-ray imaging equipment in Image- Guided RT (IGRT) is still growing and with it, the need to evaluate the additional dose-to-organs it delivers. This study aims to verify the accuracy of Monte Carlo (MC) calculation of the patient’s dose-to-organs delivered by four commercially available kV imaging systems: XVI CBCT (Elekta), OBI CBCT (Varian), ExacTrac 2D-kV system (Brainlab) and 2D-kV CyberKnife imaging system (Accuray). Simulations were validated against OSL
An accurate and precise method has been developed for the determination of Ag isotope ratios in environmental samples by MC-ICP-MS. Mass discrimination and instrument drift were corrected by a combination of internal normalization with Pd and standard-sample-standard bracketing, without assuming identical mass bias for Pd and Ag. Efficient purification of Ag from sample matrices was obtained by a two stage tandem column setup with use of anion and cation exchange resin, subsequently. High precision of better than ±0.015‰ (2SD, n=4) obtained in real sample matrices makes the present method suitable for monitoring small degrees (e.g. less than 0.1 ‰ of 107/109 Ag) of Ag isotope fractionation that may be found in nature.
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A proposed two-dimensional array for reception in the 2-6 mc/s band
Cumming, W.A.; McCaskill, D.R.