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1.
Background
Growth hormone (GH) plays an incompletely understood role in the development of the central nervous system (CNS). In this study, we use transgenic mice expressing a growth hormone antagonist (GHA) to explore the role of GH in regulating postnatal brain, spinal cord and body growth into adulthood. The GHA transgene encodes a protein that inhibits the binding of GH to its receptor, specifically antagonizing the trophic effects of endogenous GH. 相似文献2.
The pulsed laser atom probe has been used to characterise III-V semiconductor epilayer and quantum-well structures. The combination of high spatial resolution and good chemical specificity makes it possible to observe very fine scale composition variations in epilayer materials, and also to assess the roughness of individual interfaces in quantum-well material. 相似文献
3.
A Mukherjee M Dasgupta DJ Hinde CR Morton AC Berriman RD Butt JO Newton H Timmers 《Pramana》2001,57(1):195-198
Fusion cross-sections for the 7Li + 12C reaction have been measured at energies above the Coulomb barrier by the direct detection of evaporation residues. The heavy
evaporation residues with energies below 3 MeV could not be separated out from the α-particles in the spectrum and hence their
contribution was estimated using statistical model calculations. The present work indicates that suppression of fusion cross-sections
due to the breakup of 7Li may not be significant for 7Li + 12C reaction at energies around the barrier. 相似文献
4.
New results are presented on the analysis of silicon surfaces in a Time-of-Flight Atom Probe. Comparison is made between the chemical data obtained from conventional voltage pulse and laser pulse desorption. 相似文献
5.
The ability to locate and quantify elemental distributions in plants is crucial to understanding plant metabolisms, the mechanisms
of uptake and transport of minerals and how plants cope with toxic elements or elemental deficiencies. High-resolution secondary
ion mass spectrometry (SIMS) is emerging as an important technique for the analysis of biological material at the subcellular
scale. This article reviews recent work using the CAMECA NanoSIMS to determine elemental distributions in plants. The NanoSIMS
is able to map elemental distributions at high resolution, down to 50 nm, and can detect very low concentrations (milligrams
per kilogram) for some elements. It is also capable of mapping almost all elements in the periodic table (from hydrogen to
uranium) and can distinguish between stable isotopes, which allows the design of tracer experiments. In this review, particular
focus is placed upon studying the same or similar specimens with both the NanoSIMS and a wide range of complementary techniques,
showing how the advantages of each technique can be combined to provide a fuller data set to address complex scientific questions.
Techniques covered include optical microscopy, synchrotron techniques, including X-ray fluorescence and X-ray absorption spectroscopy,
transmission electron microscopy, electron probe microanalysis, particle-induced X-ray emission and inductively coupled plasma
mass spectrometry. Some of the challenges associated with sample preparation of plant material for SIMS analysis, the artefacts
and limitations of the technique and future trends are also discussed. 相似文献
6.
K.D. Vernon-Parry L.T. Romano J.S. Lees C.R.M. Grovenor 《Physica C: Superconductivity and its Applications》1990,170(5-6):388-394
Degradation processes in 2212 thallium-based superconductors have been investigated using X-ray diffraction and electron microscopy techniques. It has been shown that the formation of amorphous or microcrystalline material by decomposition of the superconducting phase is followed by the crystallization of BaCo3 and other oxide compounds. The influence of preexisting BaCO3 on the rate of this degradation process has also been studied, and the results indicate that the removal of this stable precursor compound is an important step in improving the long term stability of the 2212 phase. 相似文献
7.
Background
The 5-HT3 receptor is a member of a neurotransmitter-gated ion channel family which includes nicotinic acetylcholine, GABAA, and glycine receptors. While antibodies specific for the 5-HT3A receptor subunit are plentiful, and have revealed a wealth of structural and functional information, few antisera exist for the detection of 5-HT3B receptor subunits. Here we describe the generation and characterisation of a rabbit polyclonal antiserum that specifically recognises 5-HT3B receptor subunits 相似文献8.
The reactivity of the 2,2′-, 2,4′-, 4,4′-dibenzyldiisocyanate (2,2′-, 2,4′-, 4,4′-DBDI) with n-butanol in benzene has been studied. The concentrations of all species were monitored by using high performance liquid chromatography (HPLC). The reactivity of 4,4′-DBDI is similar to that of 4,4′-diphenylmethanediisocyanate (4,4′-MDI). Very strong intramolecular catalytic effects were noticed in the case of 2,2′-DBDI, probably due to the variable molecular geometry. These effects are responsible for the whole reaction pattern. The 2,4′-DBDI NCO ortho and para groups reactivities are different and comparable to that of 2,4-toluylenediisocyanate (2,4-TDI). 相似文献
9.
F. Christien C. Downing K. L. Moore C. R. M. Grovenor 《Surface and interface analysis : SIA》2012,44(3):377-387
A technique for the quantification of equilibrium grain boundary segregation by high resolution secondary ion mass spectroscopy (NanoSIMS) on simple metallographically polished surfaces has been demonstrated for the model system of sulphur segregation to nickel grain boundaries. Samples of nickel containing 5.4 wt ppm of sulphur were annealed at different temperatures to achieve different equilibrium sulphur grain boundary concentrations, ranging from less than 1% to about 50% of a monolayer. Quantification was carried out from sulphur concentration profiles acquired across about 20 grain boundaries in each sample. An internal standard (nickel containing a known concentration of sulphur in solid solution) was used for calibration. It is found that, depending on the annealing temperature, the average grain boundary sulphur concentration ranges from 0.9 to 25.8 ng cm–2 (or 1.7 1013 to 4.8 1014 atoms cm–2), i.e. ~0.015 to ~0.43 monolayer. Thermodynamic analysis gives a segregation free energy of ?97.8 kJ mol–1 and a grain boundary sulphur concentration at saturation of 26.7 ng cm–2 (or 5.0×1014 atoms cm–2), i.e. ~0.44 monolayer, in good agreement with previous measurements on this system. The limit of detection of the technique is shown to be as low as 0.24 ng cm–2 (or 4.5×1012 atoms cm–2), i.e. ~0.004 monolayer, with a counting time of only 10 min. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
10.
Lawrence CR Tafoya C William Shuttleworth Yuchio Yanagawa Kunihiko Obata Michael C Wilson 《BMC neuroscience》2008,9(1):105