IN a confocal scanning laser microscope 1,2 (CSLM), the detector pinhole is confocal with the illuminated spot on the sample, and rejects light reflected from objects that are not in the focal plane. This results in i...
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IN a confocal scanning laser microscope 1,2 (CSLM), the detector pinhole is confocal with the illuminated spot on the sample, and rejects light reflected from objects that are not in the focal plane. This results in images that contain only sharp or empty areas, as opposed to non-confocal images which contain sharp and blurry areas, and allows the CSLM to perform optical sectioning. Individual optical sections can be used to produce a true three-dimensional image or can be added together to produce an extended-depth-of-focus image. For biological specimens, the intensity of the reflected-light (or fluorescence) signal decreases with increasing penetration into the sample, and self-shadowing also limits the information in the image. Moreover, many biological specimens are only weak reflectors, but produce transmission images with good contrast. The only confocal transmission images reported previously have used scanning-stage microscopes 3,4, although Goldstein 5 has reported a confocal scanning-beam microscope that should in principle work in transmission. Here we describe a microscope that produces true confocal images in transmission, and also forms a reflected-light image from both the top and bottom of the specimen. The optical slices produced in transmission do not change in average intensity with depth in the specimen, and as the microscope can also examine the specimen from the bottom in reflected light, loss of data by self-shadowing is minimized. All of the original contrast modes of the CSLM (reflected light, fluorescence, differential phase contrast and so on) are also available using this new microscope.
It is demonstrated that the specific heat behaves as a monotonically increasing function of temperature with failing temperature for those supercooled metallic liquids, which can be laboratory glasses. This is in cont...
It is demonstrated that the specific heat behaves as a monotonically increasing function of temperature with failing temperature for those supercooled metallic liquids, which can be laboratory glasses. This is in contrast to cases where supercooled metallic liquids do not become laboratory glasses. In addition, a comment is made on the specific heat of a supercooled Lennard-Jones liquid.
Accurate tail-to-peak intensity ratios are extracted from the spectra produced in a Si(Li) detector by x-rays of energies 2-10 keV. The widely used model of a surface layer of incomplete charge collection fails to exp...
Accurate tail-to-peak intensity ratios are extracted from the spectra produced in a Si(Li) detector by x-rays of energies 2-10 keV. The widely used model of a surface layer of incomplete charge collection fails to explain the energy dependence of these data. The model is augmented to include loss of photoelectrons travelling back into the ICC layer from an interaction in the active silicon region;this gives excellent agreement with experiment. It is shown that the detection efficiency in the region of low x-ray energy may be deduced from the tail-to-peak ratios, together with measurement of the thicknesses of the beryllium window and the metal contact;a potential source of error in measuring the latter by the popular fluorescence technique is demonstrated.
Using Leibbrandt's general prescription for regularizing (n.q)-1 poles in momentum intergrals in axial-type non-covariant gauges we show that the difference between two linearly divergent integrals which arise in ...
Using Leibbrandt's general prescription for regularizing (n.q)-1 poles in momentum intergrals in axial-type non-covariant gauges we show that the difference between two linearly divergent integrals which arise in such gauges yield a surface term which is logarithmically divergent. The form of divergence of this term is shown to be independent of the choice of non-covariant gauge. We show that such a term modifies the expression for the one-loop Yang-Mills self-energy evaluated using a cutoff scheme of adding to it a divergent part.
The Guelph proton microprobe has provided several thousand spot analyses of mineralogical, geochemical and metallurgical specimens, mainly through contract arrangements. User-friendly target chamber design with color ...
The Guelph proton microprobe has provided several thousand spot analyses of mineralogical, geochemical and metallurgical specimens, mainly through contract arrangements. User-friendly target chamber design with color TV viewing of the incident beam spot at magnification x 300 is crucial in this work. A new PC-based data accumulation system for both spot analysis and elemental mapping is described. Various enhancements to the GUPIX software for spectrum fitting and standardization are reviewed.
We present a Monte Carlo simulation of X-ray interaction with a Si(Li) detector which includes for the first time both a detailed description of the atomic excitation and de-excitation and also a physically realistic ...
We present a Monte Carlo simulation of X-ray interaction with a Si(Li) detector which includes for the first time both a detailed description of the atomic excitation and de-excitation and also a physically realistic model of the frontal region of incomplete charge collection. Simulated lineshapes are in good agreement with those measured by using monoenergetic X-rays of energy 1-10 keV and by varying the two parameters of the model we can generate lineshapes very similar to those reported in the literature for other Si(Li) detectors.
The electric modulus representation is used to display conductivity and dielectric relaxation occurring in poly(propylene glycol)-4000 (PPG) complexed with LiCF3SO3, as the ether oxygen to lithium (O:Li) ratio is vari...
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The electric modulus representation is used to display conductivity and dielectric relaxation occurring in poly(propylene glycol)-4000 (PPG) complexed with LiCF3SO3, as the ether oxygen to lithium (O:Li) ratio is varied from 300:1 to 12:1. The frequency range covered is 10 to 10(7) Hz. Results are obtained for temperatures above the glass transition temperature appropriate for each PPG-LiCF3SO3 complex. For O:M = 300:1, the conductivity peak and the alpha and alpha' relaxation are clearly resolved. As the concentration is increased, there is a coupling between the structural and the conductivity relaxations;the various peaks begin to overlap. The coupling is greatest for an O:Li ratio in the range 30:1 to 12:1, where the highest conductivity is measured. Below room temperature, the 30:1 complex has the highest conductivity, above room temperature the 12:1 complex has the highest. At any particular temperature there is a concentration above which the conductivity drops. This drop is due to reduced ion mobility resulting from a dramatic increase in viscosity to values above approximately 100 poise.
作者：
SIMPSON, JJDepartment of Physics
University of Guelph and Guelph-Waterloo Program for Graduate Work in Physics Guelph Ontario Canada N1G 2W1
It is suggested that the late neutrino events from supernova SN1987A detected by the Kamiokande and IMB detectors can be understood as arising from massive neutrinos decaying in flight. If the neutrino mass is 17 keV,...
It is suggested that the late neutrino events from supernova SN1987A detected by the Kamiokande and IMB detectors can be understood as arising from massive neutrinos decaying in flight. If the neutrino mass is 17 keV, the estimated mean life is (0.6-1.6) x 10(4) s. The shorter prompt pulse then implies an upper limit to the mass of the lightest neutrino of 13 eV.
Deuterium nuclear magnetic resonance (NMR) spectra and spin-lattice relaxation times were determined in order to study the dynamics of t-butyl groups in butylated hydroxytoluene. The results are consistent with a mode...
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Deuterium nuclear magnetic resonance (NMR) spectra and spin-lattice relaxation times were determined in order to study the dynamics of t-butyl groups in butylated hydroxytoluene. The results are consistent with a model first proposed by Beckmann et al. [J. Magn. Reson. 36, 199 (1979)], where there is an inequivalence between the methyl groups within each t-butyl group. While two methyl groups reorient rapidly relative to the whole t-butyl rotation, the remaining methyl group is more restricted in its motion, reorienting at a rate comparable to that of the t-butyl group itself. The spin-lattice relaxation data show two T1 minima, the high temperature minimum (40-degrees-C) corresponding to the combined t-butyl and "slow" methyl rotations, and the low temperature minimum corresponding to "fast" methyl group rotation. Using an explicitly defined T1 fitting function, the T1 data yield activation energies of 2.2 and 6.0 kcal/mol for the fast methyl and t-butyl rotations, respectively, both in agreement with Beckmann's values obtained from proton T1 experiments. It was also possible to simulate the low temperature deuterium NMR spectra from T = - 160-degrees-C to T = - 80-degrees-C using the aforementioned dynamical inequivalence between the t-butyl methyl groups. While the fast methyl group rotation was in the motional narrowing region for T > - 160-degrees-C, it was possible, from the simulations, to determine the t-butyl exchange rates to within 10%. The jump rates are remarkably close to the values predicted from the T1 results. Above - 80-degrees-C, the spectra could not be simulated, implying that a third motion must be present to further alter the high temperature line shapes. The effective axial asymmetry of the T > - 20-degrees spectra indicates that the additional motion involves a two site exchange.
13 C-NMR is used to probe the motion and orientation of the car☐yl group in a 70% potassium palmitate/30% water mixture. An increase in Δσ with increasing temperature corresponds to a change of orientation of the ca...
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13 C-NMR is used to probe the motion and orientation of the car☐yl group in a 70% potassium palmitate/30% water mixture. An increase in Δσ with increasing temperature corresponds to a change of orientation of the car☐yl group. Comparison with 2 H-NMR and lineshape simulations show that near 57°C the molecules exchange between two orientations at a rate between 10–500 Hz.
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