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991.
Jaeger A Lecomte VJ Weimerskirch H Richard P Cherel Y 《Rapid communications in mass spectrometry : RCM》2010,24(23):3456-3460
Stable isotopes are increasingly being used to trace wildlife movements. A fundamental prerequisite of animal isotopic tracking is a good knowledge of spatial isotopic variations in the environment. Few accessible reference maps of the isotopic landscape ("isoscapes") are available for marine predators. Here, we validate for the first time an isotopic gradient for higher trophic levels by using a unique combination of a large number of satellite-tracks and subsequent blood plasma isotopic signatures from a wide-ranging oceanic predator. The plasma δ(13)C and δ(15)N values of wandering albatrosses (n = 45) were highly and positively correlated to the Southern Ocean latitudes at which the satellite-tracked individuals foraged. The well-defined latitudinal baseline carbon isoscapes in the Southern Ocean is thus reflected in the tissue of consumers, but with a positive shift due to the cumulative effect of a slight (13)C-enrichment at each trophic level. The data allowed us to estimate the carbon isotopic position of the main oceanic fronts in the area, and thus to delineate robust isoscapes of the main foraging zones for top predators. The plasma δ(13)C and δ(15)N values were positively and linearly correlated, thus suggesting that latitudinal isoscapes also occur for δ(15)N at the base of the food web in oceanic waters of the Southern Ocean. The combination of device deployments with sampling of relevant tissues for isotopic analysis appears to be a powerful tool for investigating consumers' isoscapes at various spatio-temporal scales. 相似文献
992.
Vincent B. F. Mathot 《Journal of Thermal Analysis and Calorimetry》2010,102(2):403-412
In the past 35 years, the emphasis of the activities has been doing and stimulating of fundamental research; managing research
toward improvement and development of polymer systems and industrial applications of polymers; and providing analytical support
by utilization and development of characterization techniques and methods. Throughout, the research activities concerned the
study of molecular structure, crystallization and melting, morphology, and thermal properties of polymeric systems, and to
study and understand the relations between these topics. With respect to Thermal Analysis & Calorimetry (TA&C), quantitative
research has been realized in the field of crystallization of polymers of which a choice of recent work is discussed. 相似文献
993.
Clayden J Hennecke U Vincent MA Hillier IH Helliwell M 《Physical chemistry chemical physics : PCCP》2010,12(45):15056-15064
Poly aromatic ureas and poly aromatic amides are important classes of foldamers-oligomers with well defined conformations. We have explored the origins of the conformational preference of some N,N'-diaryl-N,N'-dimethyl ureas by a combination of NMR spectroscopy and electronic structure calculations using both a recently developed density functional (M06-2X) and a DFT approach (DFT-D) having empirical corrections for dispersive interactions. We have validated the DFT-D approach for structures of this type using high level wavefunction calculations, (CCSD(T)), of the unsubstituted N,N'-diphenyl-N,N'-dimethyl urea. For the N,N'-diaryl-N,N'-dimethyl ureas we have identified a number of 'endo' conformers (i.e. having an E,E geometrical conformation about the two urea C-N bonds), both π- and tert-butyl-stacked, as well as 'exo' structures (having a Z geometrical conformation about at least one of the C-N bonds), and have computed the relative energies of these conformers as well as the barriers for their interconversion. We find that the relative energies of the 'endo' structures closely follow the relative values of the dispersive interactions. The calculations have allowed us to associate different conformers with the various peaks in the NMR spectra, which point to relatively small differences in energy between the conformers. Somewhat larger energy differences are predicted by the two computational approaches, with the M06-2X functional performing the better of the two. It is suggested that the continuum model employed may not be sufficiently accurate to reflect the solvation of the various conformers. 相似文献
994.
Asymmetrical-flow field flow fractionation (AFFF) separates constituents based on hydrodynamic size and is emerging as a powerful
tool for obtaining high-resolution information on the size, molecular weight, composition, and stability of nanoscale particles
in liquid media. We employ a customized AFFF system combining on-line detectors for multi-angle light scattering, dynamic
light scattering, and UV–Vis absorption. Our objective is to develop optimized measurement protocols for the characterization
of gold nanoparticles (GNPs), which are widely utilized in biomedical research and other nanotechnology applications. Experimental
conditions have been optimized by controlling key parameters, including injection volume and solids concentration, mobile
phase composition, membrane type and pore size, and ratio of channel-to-cross-flow rates. Individual citrate-stabilized GNP
components (nominally 10, 20, 30, 40, and 60 nm) and GNPs functionalized with polyethylene glycol were separated from multicomponent
GNP mixtures by AFFF and subsequently characterized. We discuss the effects due to variations in measurement parameters and
GNP surface modification on observed retention, recovery, and peak resolution. 相似文献
995.
O. Abbas J. A. Fernández Pierna A. Boix C. von Holst P. Dardenne V. Baeten 《Analytical and bioanalytical chemistry》2010,397(5):1965-1973
The aim of this work is to show new advances in the analytical methods developed in the frame of the ban of processed animal
by-products in compound feed that is currently applied within the European Union. With this aim, studies to develop a quantitative
near infrared microscopy (NIRM) approach have been undertaken in order to fulfil future requirements of European legislation
like the introduction of tolerance levels that would require for official control purposes the availability of specific quantitative
methods. The capabilities of the NIRM method have been improved; no sample preparation is required and the acquisition parameters
are optimised. Both the gross and the fine fractions of the samples are considered; the reflexion mode was used to analyse
the gross raw fraction and the transmission mode was chosen to analyse the fine raw fraction. Parameters for reflexion analyses
were already fixed in our previous studies while those of transmission mode have been determined in the present study. Because
particles are too small, it is difficult to mark them; spectra were collected using the mapping technique. Quantitative analyses
have been carried out for different percentages of adulteration (0.5, 1, 2 and 5%). Results were depending on the particle
size distribution of the feed and of the fish meal which led to experimental values of adulteration varying between 0.13–0.92%,
0.93–3.7%, 2.42–5.83% and 1.95–9.39% for theoretical percentages of adulteration equal to 0.5, 1, 2 and 5%, respectively.
The established protocol with the key parameters proposed has to be considered for the development of an accurate method of
quantification. 相似文献
996.
We describe a spectroscopic comparative analysis based on the optoacoustic technique over the wavelength range from 410nm to 1000nm using a Q-switched Nd:YAG pumped optical parametric oscillator tunable source on a gold nanostructure solution located within a highly scattering medium. The advantages of this method over standard spectroscopy techniques are the possibility to localize and monitor the spectroscopic response of absorbing materials located within turbid media. The operation is confirmed using a comparative analysis with the spectroscopic results obtained from a reference measurement scheme, based on a highly sensitive collimated optical transmission setup in parallel and under the same experimental conditions as the optoacoustic technique. 相似文献
997.
We report a simple, compact electronic speckle-pattern interferometer (ESPI) incorporating holographic optical elements (HOEs) for the study of out-of-plane vibration. Reflection and transmission HOEs provide reference and object beams in the interferometer. The alignment difficulties with conventional ESPI systems are minimized using HOEs. The time-average ESPI subtraction method is used to generate the fringe pattern and remove background speckle noise by introducing a phase shift between consecutive images. The amplitude and phase maps are obtained using path-difference modulation. 相似文献
998.
We report on experiments performed with a cladding-pumped single-mode Er:Yb-codoped single-frequency fiber amplifier simultaneously seeded by a distributed-feedback diode at 1556 nm and a tunable external-cavity diode laser emitting at a wavelength of about 1 μm wavelength. The influence of the output wavelength of the external-cavity laser on amplification and reabsorption behavior of the Yb emission as well as the amplifier performance at a wavelength of 1556 nm is examined experimentally. 相似文献
999.
Both the formation energy and the diffusive activation energy of a single vacancy migrating in the first four atomic layers intra- and inter-layer near Cu Σ = 9 [110] twist GB have been investigated by using the MAEAM. The formation of the vacancy is favorable on the first layer (1L) near the GB plane and is spontaneous on sites ‘2’–‘5’ especially ‘2’ and ‘4’. The effects of the GB on the intra- as well as inter-layer migration are mainly for 1L–1L as well as for 1L–1L′, 2L–1L and 3L–1L related to the 1L, respectively. Furthermore, the vacancy in 1L is favorable to migrate in 1L (intra-layer) or through GB plane to 1L′, the one in either 2L or 3L is favorable to migrate to 1L. So the vacancy tends to converge to the first layer near the GB plane. 相似文献
1000.
Vincent Lavallo C. Adam Dyker Dr. Bruno Donnadieu Guy Bertrand Prof. 《Angewandte Chemie (International ed. in English)》2009,48(9):1540-1542
The true ground state of 1 is a matter of debate, but for clarity and convenience the allene resonance form 1 a , is the most appropriate. The arguments for aromaticity made by Christl and Engels are shown to be incorrect.