169 research outputs found
Electromagnetically induced transparency in inhomogeneously broadened Lambda-transition with multiple excited levels
Electromagnetically induced transparency (EIT) has mainly been modelled for
three-level systems. In particular, a considerable interest has been dedicated
to the Lambda-configuration, with two ground states and one excited state.
However, in the alkali-metal atoms, which are commonly used, hyperfine
interaction in the excited state introduces several levels which simultaneously
participate in the scattering process. When the Doppler broadening is
comparable with the hyperfine splitting in the upper state, the three-level
Lambda model does not reproduce the experimental results. Here we theoretically
investigate the EIT in a hot vapor of alkali-metal atoms and demonstrate that
it can be strongly reduced due to the presence of multiple excited levels.
Given this model, we also show that a well-designed optical pumping enables to
significantly recover the transparency
Quantum memory for light via stimulated off-resonant Raman process: beyond the three-level Lambda-scheme approximation
We consider a quantum memory scheme based on the conversion of a signal pulse
into a long-lived spin coherence via stimulated off-resonant Raman process. For
a storing medium consisting of alkali atoms, we have calculated the
Autler-Townes resonance structure created by a strong control field. By taking
into account the upper hyperfine states of the D1 optical transition, we show
important deviations from the predictions of the usual three-level
Lambda-scheme approximation and we demonstrate an enhancement of the process
for particular detunings of the control. We estimate the memory efficiency one
can obtain using this configuration.Comment: 8 pages, 6 figure
Measurement of intracellular concentration of fluorescently-labeled targets in living cells
Estimations of intracellular concentrations of fluorescently-labeled molecules within living cells are very important for guidance of biological experiments and interpretation of their results. Here we propose a simple and universal approach for such estimations. The approach is based upon common knowledge that the dye fluorescence is directly proportional to its quantum yield and the number of its molecules and that a coefficient of proportionality is determined by spectral properties of the dye and optical equipment used to record fluorescent signals. If two fluorescent dyes are present in the same volume, then a ratio of their concentrations is equal to a ratio of their fluorescence multiplied by some dye- and equipment-dependent coefficient. Thus, if the coefficient and concentration of one dye is known then the concentration of another dye can be determined. Here we have demonstrated how to calculate this coefficient (called a ratio factor) and how to use it for concentration measurements of fluorescently tagged molecules. As an example of how this approach can be used, we estimated a concentration of exogenously expressed neuronal Ca2+ sensor protein, hippocalcin, tagged by a fluorescent protein in a dendritic tree of rat hippocampal neurons loaded via a patch pipette with Alexa Fluor dye of known concentration. The new approach should allow performing a fast, inexpensive and reliable quantitative analysis of fluorescently-labeled targets in different parts of living cells
Associations of BCL-2 (RS17759659), CTLA-4 (RS231775), APO-1/FAS (RS2234767) genes polymorphisms with activity of proliferation and apoptosis in thyroid tissue of patients with nodular forms of goiter combined with autoimmune thyroiditis and thyroid adenoma
The study of apoptosis and proliferative activity in the thyroid gland (TG) tissue of patients with nodular goiter and autoimmune thyroiditis (NGAIT) and thyroid adenoma (TA) is based on the expression/density of Fas/FasL, BCL-2, p53, and Ki-67 markers assessment depending on the genetic polymorphisms of BCL-2 (rs17759659), CTLA-4 (rs231775) and APO-1/Fas (rs2234767) genes.Several mechanisms of thyroid cells' programmed killing are activated in NGAIT and TA with domination of Fas-induced apoptosis, which strongly associates with the BCL-2 gene's (rs17759659) promoter (F=25.33; p<0.001) and almost six fold weaker associates with the CTLA-4 gene's (rs231775) promoter (F=4.23, p=0.017). Factors that decrease the likelihood of NGAIT and TA regardless of the CTLA-4 (rs231775) and APO-1/Fas (rs2234767) genes' genotypes are the high Ki-67 density and reduction of cells containing p53 or BCL-2 proteins (OR=0.07-0.17; 95% CI OR: 0.03-0.36; p<0.001, and OR=0.08-0.11; 95% CI OR: 0.02-0.31; p<0.001, respectively). High expression of surface Fas and FasL in lymphoid infiltration and destruction of thyroid cells (stronger in GG-genotype carriers of the BCL-2 gene by 18.54% (pAA=0.043) and 36.18% (pAG=0.018), respectively) indicates the initiation of the external pathway of apoptosis through the caspase mechanism (effector caspase- 8)
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