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1.
de Lecea AM Smit AJ Fennessy ST 《Rapid communications in mass spectrometry : RCM》2011,25(23):3640-3649
Stable isotopes are an increasingly important tool in trophic linkage ecological studies. In studies of large marine animals, isotopic sampling is often given secondary priority to sampling for diversity and biomass aspects. Consequently, isotopic samples are frequently collected subsequent to repeated freezing and thawing of animals, and the results of these studies are often based on the assumption that this pre-treatment does not affect the isotopic values. Our study tested this assumption and examined the difference between oven- and freeze-drying on isotopic values and elemental carbon-to-nitrogen (C:N) ratios. The values for δ(15)N and δ(13)C, percentage nitrogen and carbon, and the C:N ratios were determined from the tissues of six marine species, including invertebrates and fish, as (1) fresh samples, (2) samples thawed once, and (3) samples thawed twice. The drying method, thawing treatment and their interaction did significantly affect the δ(15)N and δ(13)C isotope values for all species. Oven-dried samples had slightly higher δ(13)C and δ(15)N values than freeze-dried samples, although not significant in most instances. For most species, oven-drying produced lower carbon and nitrogen percentage than freeze-drying for samples that had been thawed once, but the C:N ratio was unaffected by the drying method. Repeated freezing and thawing did not affect the isotope values, but it did decrease the percentage carbon and nitrogen for both desiccation methods. We recommend drying samples from fresh wherever possible, and careful choice of desiccation method in light of the fact that most lipid models are based on oven-dried samples and oven-drying could cause enrichment of (15)N or (13)C through evaporation of volatile compounds richer in lighter isotopes such as some lipids. Finally, we recommend that further studies on the specific effects of freezing and desiccation on elasmobranchs is needed. Overall we recommend the use of freeze-drying when possible and to use the samples from freshly caught organisms. 相似文献
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Andriy Fedorov Jacob Fluckiger Gregory D. Ayers Xia Li Sandeep N. Gupta Clare Tempany Robert Mulkern Thomas E. Yankeelov Fiona M. Fennessy 《Magnetic resonance imaging》2014
Multi-parametric Magnetic Resonance Imaging, and specifically Dynamic Contrast Enhanced (DCE) MRI, play increasingly important roles in detection and staging of prostate cancer (PCa). One of the actively investigated approaches to DCE MRI analysis involves pharmacokinetic (PK) modeling to extract quantitative parameters that may be related to microvascular properties of the tissue. It is well-known that the prescribed arterial blood plasma concentration (or Arterial Input Function, AIF) input can have significant effects on the parameters estimated by PK modeling. The purpose of our study was to investigate such effects in DCE MRI data acquired in a typical clinical PCa setting. First, we investigated how the choice of a semi-automated or fully automated image-based individualized AIF (iAIF) estimation method affects the PK parameter values; and second, we examined the use of method-specific averaged AIF (cohort-based, or cAIF) as a means to attenuate the differences between the two AIF estimation methods. 相似文献
3.
ChemInform Abstract: X-Ray Structural Studies of the Polymorphic Elpasolites K2LiAlF6 and Rb2LiGaF6.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献
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An efficient method for calculating the Lagrange multipliers and the analytical gradients of one state included in a state average MCSCF wave function is presented. It is demonstrated that the state average energy of an ‘equal-weight’ scheme is invariant to rotations within the state average subspace and that the corresponding rotations should be eliminated from the Lagrangian equations. Finally, a diagnostic is presented, which gauges the energy difference between a state defined by a state average calculation and the corresponding fully variational multi-configurational SCF state. 相似文献
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The thin-film spinel-forming solid state reaction between Al2O3 and MgO has been studied under initially non-coherent conditions. MgO films in (001) orientation on
-cut sapphire single crystals were heated at 1100°C for 30 min or 1h. The film/substrate reaction proceeds via cation counterdiffusion as was revealed by a marker experiment. The MgAl2O4 films formed were predominantly (001) oriented, with an additional systematic tilt of about 5° of the spinel lattice around the [010] axis. The structure of the Al2O3
/MgAl2O4(001) and MgAl2O4(001)/MgO(001) reaction fronts has been investigated on cross section samples by high-resolution electron microscopy. It appeared that after starting from an incoherent interface, the Al2O3
/MgAl2O4(001) front assumes an almost fully coherent structure during the reaction. As a result the lattice misfit is reduced to 1%, and interfacial ledges are formed. The latter most probably play an active role in the necessary c.p.h. f.c.c. reconstruction of the oxygen sublattice. The MgAl2O4(001)/MgO(001) reaction front consists of coherent regions divided by misfit dislocations. During the reaction the former run ahead whereas the latter lag behind. As a result the morphology of the reaction front is bowed. The results confirm earlier observations of Carter and Schmalzried of the semicoherent Al2O3(00.1)/CoAl2O4(111) interface, thus strongly supporting the conclusion of a fundamental new phase transformation mechanism specific to oxide systems.Presented at the workshop on High-Voltage and High-Resolution Electron Microscopy, February 21–24, 1994, Stuttgart, Germany. 相似文献
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RIVLIN T. J.; RUSCHEWEYH ST.; SHAFFER D.; WIRTHS K. J. 《IMA Journal of Numerical Analysis》1983,3(3):327-332
Given (1, 0), n N, we discuss the optimal recoveryof (), for analytic and bounded in < 1, from the knowledge of the values of at n points z1,.zm[0,l),where these points are chosen to produce the least possibleintrinsic error. The optimal algorithms are explicitly determined. 相似文献
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A FORTRAN computer program for automatic neutron activation analysis is presented. The program locates and identifies peaks
in a gamma-ray spectrum, calculates peak areas and the concentrations of the elements of interest in the sample. This program
was specifically designed for the SLOWPOKE reactor, it uses a semi-absolute method and does not need standards or flux monitors.
The program was written so as to minimize the computation time, and a typical 4096-channel spectrum is processed in five seconds
by an IBM 360/75 computer. 相似文献
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M. Dülk ST. Fischer M. Bitter M. Caraccia W. Vogt E. Gini H. Melchior W. Hunziker A. Buxens H.N. Poulsen A.T. Clausen 《Optical and Quantum Electronics》2001,33(7-10):899-906
A monolithically integrated and fully packaged Mach–Zehnder interferometer with semiconductor optical amplifiers (MZI-SOA) is demonstrated as polarisation-independent high-speed demultiplexer for up to 160 Gbit/s optical time division multiplexed (OTDM) data streams. 相似文献