Search results for "Yield"
showing 10 items of 1338 documents
The Role of Site-Specific Hydrogen Bonding Interactions in the Solvation Dynamics of N-Acetyltryptophanamide
2012
Measurements of the ultrafast broadband UV fluorescence of N-acetyltryptophanamide (NATA) provide detailed information on its relaxation patterns in three different solvents: methanol (MeOH), water and acetonitrile (ACN). Several processes leading to excited state solvation and cooling are found to occur on different characteristic time scales and are thoroughly analyzed. Comparison between protic MeOH and aprotic ACN allows one to single out a 12 Ps component in the former, which is attributed to the rearrangement of H-bonds existing between the protic solvent and excited NATA. This significantly stabilizes the excited state and provides the molecule with an efficient cooling mechanism. Th…
Zeaxanthin Dependent and Zeaxanthin Independent Changes in Nonphotochemical Energy Dissipation
1994
Summary The influence of zeaxanthin on high-energy-state quenching (qE) of room temperature chlorophyll fluorescence and on the quantum yield of oxygen evolution(ФO2) has been studied with isolated spinach thylakoids. A set of three different pretreatments was tested which all led to thylakoids with high contents of zeaxanthin. Depending on the presence of light the pretreatments differed strongly with respect to their effect on nonphotochemical fluorescence quenching. Independently from the extent of changes in nonphotochemical energy dissipation in the membrane energized state as reflected by nonphotochemical quenching the light pretreatments caused also changes in nonphotochemical energy…
Interpretation of the photoluminescence decay kinetics in metal halide perovskite nanocrystals and thin polycrystalline films
2020
Abstract In this paper we present critical analysis of different points of view on interpretation of the photoluminescence (PL) decay kinetics in lead halide perovskites prepared in the form of well passivated nanocrystals (PNCs) or thin polycrystalline layers. In addition to the literature data, our own measurements are also considered. For PNCs, a strong dependence of the PL lifetimes on the type of passivating ligand was observed with a consistently high PL quantum yield. It is shown that such ligand effects, as well as a decrease in the PL lifetime with decreasing temperature, are well qualitatively explained by the phenomenological model of thermally activated delayed luminescence, in …
Ectopic expression of the AtCDF1 transcription factor in potato enhances tuber starch and amino acid contents and yield under open field conditions
2023
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Radiosynthesis of 3-indolyl[1-11C]acetic acid for phyto-PET-imaging: An improved production procedure and formulation method
2014
Abstract An improved production procedure and formulation method for the carbon-11 radiolabeled phytohormone, 3-indolyl-[l- 11 C]acetic acid ([ 11 C]IAA), was developed by modifying selected original reaction parameters. This updated procedure both doubled the yield (from 25.9±6.7% ( n =12) to 61.0±0.3% ( n =10)) and increased the concentration (0.2–0.4 GBq/0.15–0.3 mL), enabling us to provide the radiotracer [ 11 C]IAA suitable for in vivo phyto-PET-imaging studies. The specific activity was improved by more than a factor of three (26.7±5.6 GBq/µmol to 82.5±36.1 GBq/µmol). The total synthesis time for both production and formulation was 81.8±3.0 min ( n =10). In addition, a streamlined sem…
The energy transfer to the luminescence centers in PbWO4
1998
Abstract The luminescence spectra, rise and decay kinetics and the yield of luminescence in undoped PbWO 4 crystals were studied after pulsed electron beam irradiation. The luminescence intensity rise observed after irradiation pulse showed two mechanisms—excitonic relaxation and electron–hole recombination—were involved in the formation of the excited states of the blue luminescence centers. It is proposed that the excited states of WO 3 and WO 2− 4 luminescence centers were formed from some intermediate metastable state.
ESR response to 60Co-rays of ammonium tartrate pellets using as additive
2007
Abstract This work presents experimental results regarding a new ammonium tartrate blend for ESR dosimetry, with a higher sensitivity and a lower lowest detectable dose (LDD) to Co 60 γ -rays than the recently used pure ammonium tartrate. The blend composed by ammonium tartrate and gadolinium-oxide ( Gd 2 O 3 ) shows a greater sensitivity ( ∼ 2 times) and a smaller LDD than ammonium tartrate. The increased sensitivity was mainly attributed to the great atomic number ( Z = 64 ) of gadolinium, that increases the effective atomic number of the blend; the interaction probability with photons and consequently the radical yield is therefore enhanced. Moreover ammonium tartrate with Gd 2 O 3 has a…
Stimulated luminescence of AlN ceramics induced by ultraviolet radiation
2001
Abstract Properties of thermally stimulated luminescence (TL) and optically stimulated luminescence (OSL) of the ceramic material AlN-Y 2 O 3 have been studied after exposure to ultraviolet radiation (UVR). The dosemeter material Al 2 O 3 : C has been used for comparative measurements. The spectral sensitivity of the samples has been studied and compared with spectral effectiveness of the UVR-induced biological processes. It has been shown that a very high yield and linear dose response characterise the UVR-induced TL from AlN-Y 2 O 3 . Although lower than the TL, the OSL signal from UV-exposed AlN-Y 2 O 3 is still higher than that of Al 2 O 3 : C in a broad spectral region. The possibilit…
Role of ΔpH in the mechanism of zeaxanthin-dependent amplification of qE
1995
Abstract The influence of zeaxanthin on the high-energy-state fluorescence quenching (qE) and the pH dependence of the maximum chlorophyll fluorescence yield (Fm) was examined in spinach thylakoids. High contents of zeaxanthin were achieved using different pretreatments. A pronounced, zeaxanthin-dependent amplification of non-photochemical quenching (NPQ) was exclusively found in thylakoids containing zeaxanthin, synthesized in the dark via the buildup of an artificial ΔpH. These thylakoids also showed a significant quenching of chlorophyll fluorescence in the range pH 5.5–6.3, where no or only slight quenching was visible in zeaxanthin-free thylakoids. Thylakoids containing high amounts of…
Factors affecting the amount and the mode of merocyanine 540 binding to the membrane of human erythrocytes. A comparison with the binding to leukemia…
1995
Abstract In the presence of albumin Merocyanine 540 (MC540) exhibits a very limited binding to the outer surface of the membrane of normal erythrocytes, whereas pronounced binding is observed to leukemia cells. To find out whether this difference is due to differences in the composition or structural organization of the cell membrane we analyzed effects of a number of covalent and non-covalent perturbations of the red cell membrane on the binding and fluorescence characteristics of membrane-bound MC540. It is shown that exposure of the cells to cationic chlorpromazine, neuraminidase or photodynamic treatment with AlPcS 4 as sensitizer caused a limited increase (30–50%) of MC540 binding, tog…