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821.
Isabella M. Burtscher Edvin Johansson Stig Holts Freddy Sthlberg 《Magnetic resonance imaging》1999,17(10):351-1519
A new phantom and evaluation method for experimental evaluation of 1H-magnetic resonance spectroscopy single volume localization techniques regarding signal contamination (C), defined as the part of the signal originating outside the volume of interest, is presented. The quality assessment method is based on a spherical phantom with an oil/water interface in order to reduce susceptibility effects, and applied for stimulated-echo acquisition method (STEAM) and spin-echo (SE) sequences, echo times of 270, 135, and 10 ms, and cubic volumes of interest (VOI) of 13, 1.53, 23, 2.53, and 33 cm3. To be able to mimic measurements of the contamination in three dimensions the physical gradients representing the three orthogonal directions for slice selection were shifted in the pulse sequences. Contamination values in one dimension differed between 6.5% and 8.4% in SE sequences, and between 0.7% and 13.8% in STEAM sequences. In STEAM sequences a decrease of C with increasing VOI size was observed while SE sequences showed comparable C values for the different VOI sizes tested. The total contamination in three dimensions were 19% and 18% in SE and STEAM sequences with a TE of 270 ms, and 7% in a STEAM sequence with a TE of 10 ms, respectively. The presented evaluation method is easily applied to the new phantom and showed high reproducibility. 相似文献
822.
E. Roissé V. Couderc A. Barthélémy F. Louradour 《Applied physics. B, Lasers and optics》1999,69(2):89-91
We report the first diode-pumped solid-state laser operating in cw-mode-locked regime and simultaneously achieving intracavity
frequency-tripling. This laser provide UV picosecond pulses (λ=355 nm) of 10 ps duration with 0.5 mW average power at 150 MHz
repetition rate. A different set of adjustments gave rise to a Q-switched mode-locked regime. Trains of hundred UV pulses
of 60 ps duration and 4 W peak power were produced in this latter case at 50 kHz repetition rate.
Received: 12 October 1998 / Revised version: 12 December 1998 / Published online: 26 May 1999 相似文献
823.
A home made hydrogen/carbon analyser was used to determine the portion of exchangeable protons in aquatic humic substances.
For this purpose, equal sample amounts were dissolved in H2O and D2O, respectively, dried and combusted in a stream of oxygen. The amount of water resulting from combustion was measured by
an infrared detector which recorded the OH bending vibration of H2O. The bands stemming from HOD or D2O were not registered by the detection unit. Thus, combustion of organic samples containing exchangeable protons dissolved
in D2O resulted in a significantly smaller signal compared to the signal observed for the same sample dissolved in H2O. The relative intensity loss of the H2O signal observed after combustion was used to derive the portion of exchangeable protons in a standard reference material,
a humic substance isolated by the International Humic Substances Society (Suwannee River fulvic acid). According to this method
about 20% of the sample protons could be identified as exchangeable protons. With regard to titration data the portion of
protons bound to non acidic hydroxy functions could be estimated. The validity of this procedure was proved by combustion
experiments using commercially available deuterated substances as well as organic model compounds dissolved in D2O and H2O, respectively.
Received: 31 August 2000 / Revised: 11 October 2000 / Accepted: 14 October 2000 相似文献
824.
C. Müntz P. Baltes H. Oeschler A. Sartorius A. Wagner W. Ahner R. Barth M. Cieślak M. Debowski E. Grosse W. Henning P. Koczoń D. Miśkowiec R. Schicker P. Senger C. Bormann D. Brill Y. Shin J. Stein R. Stock H. Ströbele B. Kohlmeyer H. Pöppl F. Pühlhofer J. Speer K. Völkel W. Waluś 《Zeitschrift für Physik A Hadrons and Nuclei》1995,352(2):175-179
Positively charged pions and protons from collisions of Ne+NaF and Au+Au at 1 GeV/nucleon incident energy were measured near midrapidity. The center-of-mass pion spectra deviate from a Maxwell-Boltzmann distribution. The slope of the high-energy part of the pion spectra varies significantly with the system mass and little with the size of the reaction zone. While the total pion yield rises linearly with the number of participant nucleons, the highenergy component increases more than linearly. 相似文献
825.
Hannah Weiler-Feilchenfeld Robert E. Linder Günter Barth Edward Bunnenberg Carl Djerassi 《Theoretical chemistry accounts》1977,46(2):79-88
The magnetic circular dichroism spectra of 9-methyl-8-azapurine and of 7-, 8-, and 9-methyl-8-azaadenine have been found to be well resolved; as many as four distinct electronic bands are observable in the 200–350 nm spectral region. CNDO calculations indicate that * excitations are responsible for almost all of the MCD intensity. A comparison of four different parameterizations shows that a modification of Del Bene and Jaffé's CNDO/S procedure correctly predicts, with one exception, the sign of the observed B-terms and is therefore the most satisfactory method.Part LIII in the Stanford Series on Magnetic Circular Dichroism Studies. For Part LII, see J. H. Dawson, J. R. Trudell, R. E. Linder, G. Barth, E. Bunnenberg and C. Djerassi, submitted to Biochemistry. 相似文献
826.
Ohne Zusammenfassung 相似文献
827.
Zusammenfassung Das Verhalten der Spurenelemente Au, Cd, Co, Cu, Fe, Ir, La, Mn, Na, Sb, Se, Ta, W und Zn wurde bei der Chlorierung der Niob-Matrix im Cl2-Strom, und nachfolgender Abtrennung der Niob-Säure durch homogene Fällung untersucht. Die optimalen Bedingungen zur Abtrennung der Niob-Matrix von einigen Spurenelementen sowohl bei dem Aufschluß als auch bei der Fällung wurden ermittelt.
Digestion of niobium by chlorination and separation of the trace contaminants from the matrix by homogeneous precipitation
Summary The behaviour of fourteen trace elements (Au, Cd, Co, Cu, Fe, Ir, La, Mn, Na, Sb, Se, Ta, W, and Zn) was investigated during the chlorination of the niobium matrix in a Cl2-stream and in the separation of the niobium acid from a number of trace elements by homogeneous precipitation. The optimum conditions for the separation of the niobium matrix from the trace elements for both steps are given.相似文献
828.
J. Barth W. Braun J. Ernst K.-H. Glander J. Hannappel N. Jöpen F.J. Klein F. Klein H. Kalinowsky E. Klempt R. Lawall J. Link D. Menze W. Neuerburg M. Ostrick E. Paul H. van Pee I. Schulday W.J. Schwille B. Wiegers F.W. Wieland J. Wißkirchen C. Wu 《The European Physical Journal A - Hadrons and Nuclei》2003,17(2):269-274
Photoproduction of Φ-vector-mesons has been studied from reaction threshold up to W = 2.4 GeV with the SAPHIR spectrometer at the Bonn electron stretcher ring ELSA. Total cross-sections, differential cross-sections
and decay angular distributions were measured. We find evidence for strong non-diffractive contributions to Φ photoproduction.
Received: 12 December 2002 / Accepted: 13 March 2003 / Published online: 20 May 2003 相似文献
829.
L.I. Johansson A. Flodström S.-E. Hörnström B. Johansson J. Barth F. Gerken 《Solid State Communications》1982,41(5):427-430
Chemically shifted surface core-level binding energies are observed for the rare-earth alloy component in Eu1?xAux and Yb1?xAux. Furthermore, these shifts are different from the chemical shifts of the bulk 4f levels. The surface core-levels are used to identify surface segregation of the lanthanide metal in the present alloys. 相似文献
830.
Benjamin Balke Siham Ouardi Tanja Graf Joachim Barth Christian G.F. Blum Gerhard H. Fecher Andrey Shkabko Anke Weidenkaff Claudia Felser 《Solid State Communications》2010,150(11-12):529-532
In this article the Co2 based Heusler compounds are discussed as potential materials for spin voltage generation. The compounds were synthesized by arc melting and consequent annealing. Band structure calculations were performed which revealed the compounds to be half-metallic ferromagnets. Magnetometry was performed on the samples and the Curie temperatures and the magnetic moments were determined. The Seebeck coefficients were measured from low to ambient temperatures for all compounds. For selected compounds high temperature measurements up to 900 K were performed. 相似文献