排序方式: 共有24条查询结果,搜索用时 15 毫秒
21.
Sidorov-Biryukov DA Fernandez A Zhu L Verhoef A Dombi P Pugzlys A Serebryannikov EE Zheltikov AM Knight JC Baltuska A 《Optics letters》2008,33(5):446-448
A linear technique of phase measurement based on spectral interferometry is employed to visualize the fine details in the spectral phase of a soliton produced in a highly nonlinear photonic crystal fiber (PCF) with a resolution better than 0.1 nm. Gigahertz features have been resolved in the spectral phase of the soliton PCF output, allowing the accuracy of time-domain soliton envelope reconstruction to be improved on the timescale of a few femtoseconds. 相似文献
22.
The quantification of monoclonal immunoglobulins by protein electrophoresis has been helpful in determining the prognosis for the patient. In a 65-year old man with documented IgG lambda monoclonal gammopathy, a discrepancy in the detection and quantification of this M-protein was found when studied by four different electrophoretic methods. On a high-resolution agarose method with acid violet staining a prominent peak was seen in the fast gamma-region. A lower resolution agarose method using an amido black staining showed a small mid-gamma restriction, and no spike was detected by high-resolution or lower resolution capillary zone electrophoresis. The discrepancy was not attributable to a migration in the beta-region leading to masking by transferrin or C3 peak, incorrect separation on CZE due to a high isoelectric point (pI > 8.5) or pentamerization of IgM M-proteins. Therefore, other causes for discrepancies should be investigated. 相似文献
23.
Verhoef A. J. Mitrofanov A. V. Nguyen X. T. Krikunova M. Fritzsche S. Kabachnik N. M. Drescher M. Baltuška A. 《Laser Physics》2011,21(7):1270-1274
The cascaded Auger decay following ionization or excitation with 94 eV soft-X-ray pulses from the 3d subshell in krypton has been energy-and-time-resolved for the first time. The decay time of the 4s
−14p
−2
nl → 4p
−3 + e and/or 4s
−14p
−1
nl → 4p
−2 + e transition is measured to be 74 ± 20 fs. Furthermore, our data shows that the electrons with a kinetic energy around 25 eV
(generally assigned as 3d
−1
np → 4s
−2
n′p + e) emitted after core excitation are emitted in a second decay step suggesting an alternative assignment of the form 4s
−2
np 4p
−2 + e. 相似文献
24.
Pectin, a versatile polysaccharide present in plant cell walls 总被引:2,自引:0,他引:2
Alphons G. J. Voragen Gerd-Jan Coenen René P. Verhoef Henk A. Schols 《Structural chemistry》2009,20(2):263-275
Pectin or pectic substances are collective names for a group of closely associated polysaccharides present in plant cell walls
where they contribute to complex physiological processes like cell growth and cell differentiation and so determine the integrity
and rigidity of plant tissue. They also play an important role in the defence mechanisms against plant pathogens and wounding.
As constituents of plant cell walls and due to their anionic nature, pectic polysaccharides are considered to be involved
in the regulation of ion transport, the porosity of the walls and in this way in the control of the permeability of the walls
for enzymes. They also determine the water holding capacity. The amount and composition of pectic molecules in fruits and
vegetables and other plant produce strongly determine quality parameters of fresh and processed food products. Pectin is also
extracted from suitable agro-by-products like citrus peel and apple pomace and used in the food industry as natural ingredients
for their gelling, thickening, and stabilizing properties. Some pectins gain more and more interest for their health modulating
activities. Endogenous as well as exogenous enzymes play an important role in determining the pectic structures present in
plant tissue, food products, or ingredients at a given time. In this paper functional and structural characteristics of pectin
are described with special emphasis on the structural elements making up the pectin molecule, their interconnections and present
models which envisage the accommodation of all structural elements in a macromolecule. Attention is also given to analytical
methods to study the pectin structure including the use of enzymes as analytical tools. 相似文献