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1.
In this research we study lasing without population inversion from a three-level atom interacting with two laser fields, in
the ladder or cascade scheme. We investigate counterintuitive sequencing as well as regular sequencing of the time of laser
fields application. In a counterintuitive sequence scheme a short probe pulse is introduced prior to the application of the
coupling field, in contrast, to a standard sequence scheme, where both fields are introduced at the same time. The influence
of varying the probe pulse width and time delay between the initiation of probe and coupling fields on transient probe gain
is investigated. The calculations indicate the potential of producing gain without inversion via counterintuitive sequence
scheme. 相似文献
2.
Two-photon enhancement of the optogalvanic signal is shown to be possible, both theoretically and experimentally, even in the case of population inversion of the first transition. This is shown, in particular, for the neon 1s2 → 2pi transitions. 相似文献
3.
Ultrashort pulse counterintuitive sequencing of three level lambda scheme shows five fold enhancement of the amplification
without inversion on the probe transition. Introducing a short pulse weak probe field prior to the strong pump field results
in an enhanced dispersion and stronger amplification on the probe field. The presence of an incoherent pump populating the
upper level is crucial to the amplification. Parametric study of this effect is briefly presented. 相似文献
4.
Soma Bahmany Lucia E.A. de Wit Dennis A. Hesselink Teun van Gelder Nauras M. Shuker Carla Baan Bart C.H. van der Nagel Birgit C.P. Koch Brenda C.M. de Winter 《Biomedical chromatography : BMC》2019,33(1)
After solid organ transplantation, tacrolimus is given to prevent rejection. Therapeutic drug monitoring is used to reach target concentrations of tacrolimus in whole blood. Because the site of action of tacrolimus is the lymphocyte, and tacrolimus binds ~80% to erythrocytes, the intracellular tacrolimus concentration in lymphocytes is possibly more relevant. For this purpose, we aimed to develop, improve and validate a UPLC–MS/MS method to measure tacrolimus concentrations in isolated peripheral blood mononuclear cells (PBMCs). PBMCs were isolated using a Ficoll separation technique, followed by a washing step using red blood cell lysis. A cell suspension of 50 μL containing 1 million PBMCs was used in combination with MagSiMUS‐TDMPREP. To each sample we added 30 μL lysis buffer, 20 μL reconstitution buffer containing 13C2H4‐tacrolimus as internal standard, 40 μL MagSiMUS‐TDMPREP Type I Particle Mix and 175 μL Organic Precipitation Reagent VI for methanol‐based protein precipitation. A 10 μL aliquot of the supernatant was injected into the UPLC–MS/MS system. The method was validated, resulting in high sensitivity and specificity. The method was linear (r2 = 0.997) over the range 5.0–1250 pg/1 × 106 PBMCs. The inaccuracy was <5% and the imprecision was <15%. The washing steps following Ficoll isolation could be performed at either room temperature or on ice, with no effect of the temperature on the results. A method for the analysis of tacrolimus concentrations in PBMCs was developed and successfully validated. Further research will be performed to investigate the correlation between concentrations in PBMCs and clinical outcome. 相似文献
5.
A general and unambiguous approach has been developed for structural elucidation of modified purine nucleosides using NMR spectroscopy. Systematic assignment of proton and carbon signals of modified nucleosides was firmly established by COSY and the anomerism of the glycosidic linkage of synthetic nucleosides clearly elucidated by NOESY experiments. Characteristic properties of 15N-isotopic labelling at specific positions of nucleosides were also employed for structural studies. The reported approach is applicable to other modified nucleosides and nucleotides, as well as nucleobases. 相似文献
6.
Mohammed Shuker Mahmood 《Numerische Mathematik》2009,112(4):601-636
We consider a scheme for nonlinear (degenerate) convection dominant diffusion problems that arise in contaminant transport in porous media with equilibrium adsorption isotherm. This scheme is based on a regularization relaxation scheme that has been introduced by Jäger and Ka?ur (Numer Math 60:407–427, 1991; M2AN Math Model Numer Anal 29(N5):605–627, 1995) with a type of numerical integration by Bermejo (SIAM J Numer Anal 32:425–455, 1995) to the modified method of characteristics with adjusted advection MMOCAA that was recently developed by Douglas et al. (Numer Math 83(3):353–369, 1999; Comput Geosci 1:155–190, 1997). We present another variant of adjusting advection method. The convergence of the scheme is proved. An error estimate of the approximated scheme is derived. Computational experiments are carried out to illustrate the capability of the scheme to conserve the mass. 相似文献
7.
8.
In a recent publication we have studied counterintuitive pulse sequence applied to a three level ladder scheme, utilizing
rectangular-shaped pulses. In this research we investigate amplification without population inversion in a three level ladder
system interacting with two electromagnetic fields, namely, the probe and coupling fields. We take both probe and drive fields
in the form of Gaussian shaped pulses. In a counterintuitive sequence scheme, the short probe pulse is introduced prior to
the application of the coupling field, in contrast to a regular sequence scheme, where both fields are introduced at the same
time. The influence of varying the probe pulse width and time delay between the initiation times of the probe and coupling
fields on transient probe gain is investigated. It is found that the system exhibits a kind of memory about previously applied
weak probe pulse. This may allow for detection of the past event by applying a strong drive pulse in the future. 相似文献
9.
Firstenberg O London P Yankelev D Pugatch R Shuker M Davidson N 《Physical review letters》2010,105(18):183602
Self-similar solutions of the coherent diffusion equation are derived and measured. The set of real similarity solutions is generalized by the introduction of a nonuniform phase, based on the elegant Gaussian modes of optical diffraction. In a light-storage experiment, the complex solutions are imprinted on a gas of diffusing atoms, and the self-similar evolution of both their amplitude and phase pattern is demonstrated. An algebraic decay depending on the mode order is measured. Notably, as opposed to the regular diffusion spreading, a subset of the solutions exhibits a self-similar contraction. 相似文献
10.