Search results for "lifetime"
showing 10 items of 212 documents
A high-accuracy calibration method for temperature dependent photoluminescence imaging
2019
This work demonstrates a novel technique for calibrating temperature dependent photoluminescence (PL) images of silicon wafers with high accuracy. The PL signal is calibrated using a heat-controlled photoconductance (PC) stage integrated into the PL imaging system. The PC signal is measured in true steady state condition and used to determine the calibration constant under the same temperature and illumination as the PL image, thus providing a high-precision calibration. This results in a robust method for imaging of important physical parameters, such as the minority carrier lifetime and the implied voltage at different temperatures, as well as the temperature coefficients and the recombin…
Quantum dynamics of the oxygen isotopic exchange : lifetimes of metastable states of the ozone intermediate complex
2021
This thesis aims to describe the ozone dynamics during the isotopic exchange reactions of oxygen of type xO + yO zO (xO yO zO)* xO yO + zO, where x, y and z are the atomic masses of the stable oxygen isotopes (16, 17, 18). Firstly, we analyze several methods of accurate description of the atom interactions and numerical schemes to obtain the observables for the collision. Then, in a full-quantum hyperspherical formalism, we study the actual dynamics of the reactive process O + O2 -> O3* -> O2 + O. The metastable ozone created can then either decompose into oxygen by the inverse reaction, or relax into stable ozone by exchanging energy with the environment, typically N2 or O2 molecules. Thes…
Use of Caffeine for Cognitive Enhancement
2015
Abstract Pharmacological cognitive enhancement (CE) refers to the use of divergent psychoactive substances with the purpose of enhancing one's own cognition (e.g., increasing vigilance, concentration, memory). The group of substances for CE includes divergent over-the-counter drugs. Caffeine-containing products such as coffee, caffeinated drinks, and caffeine tablets are integral part of this group of substances. Furthermore, prescription drugs as well as illicit drugs belong to this group of CE substances (e.g., [psycho-]stimulants, modafinil). The use of caffeine in normal healthy subjects has very limited procognitive effects. However, there are few procognitive effects in healthy but sl…
Peptide–Membrane Interactions Monitored by Fluorescence Lifetime Imaging: A Study Case of Transportan 10
2021
The interest on detailed analysis of peptide-membrane interactions is of great interest in both fundamental and applied sciences as these may relate to both functional and pathogenic events. Such interactions are highly dynamic and spatially heterogeneous, making the investigation of the associated phenomena highly complex. The specific properties of membranes and peptide structural details, together with environmental conditions, may determine different events at the membrane interface, which will drive the fate of the peptide-membrane system. Here, we use an experimental approach based on the combination of spectroscopy and fluorescence microscopy methods to characterize the interactions …
Photooxidations of Alkenes in Fluorinated Constrained Media: Fluoro-organically Modified NaY as Improved Reactors for Singlet Oxygen “Ene” Reactions
2007
Creating a stationary fluorinated environment inside the zeolite cavity can increase the reactivity observed for intrazeolite photooxidation of alkenes. Exchanging the zeolite with fluorinated organic cations is a much more effective strategy than simply using a fluorinated solvent for slurry irradiations. Use of cations containing C-F bonds is also more efficient than use of deuterated cations for creation of a singlet oxygen friendly environment where the quenching processes are slowed down. Doping the zeolite with fluoro-organic cation 4 resulted in an increase in the singlet oxygen lifetime to 12 micros.
Bioorthogonal red and far-red fluorogenic probes for wash-free live-cell and super-resolution microscopy
2020
AbstractSmall-molecule fluorophores enable the observation of biomolecules in their native context with fluorescence microscopy. Specific labelling via bioorthogonal tetrazine chemistry confers minimal label size and rapid labelling kinetics. At the same time, fluorogenic tetrazine-dye conjugates exhibit efficient quenching of dyes prior to target binding. However, live-cell compatible long-wavelength fluorophores with strong fluorogenicity have been difficult to realize. Here, we report close proximity tetrazine-dye conjugates with minimal distance between tetrazine and fluorophore. Two synthetic routes give access to a series of cell permeable and impermeable dyes including highly fluorog…
The Acceptable Alternative Vehicle Fuel Price
2019
Historically, petroleum fuels have been the dominant fuel used for land transport. However, the growing need for sustainable national economics has urged us to incorporate more economical and ecological alternative vehicle fuels. The advantages and disadvantages of them complicate the decision-making process and compel us to develop adequate mathematical methods. Alternative fuel (compressed natural gas, liquefied petroleum gas, and ethanol fuel mixtures), the standard prices and their ratios were investigated. A mathematical model to determine a critical ratio between alternative and conventional fuel prices had already been developed. The results of this were investigated. The results sho…
Deconstructing and reconstructing resilience: a dynamic network approach
2019
Resilience is still often viewed as a unitary personality construct that, as a kind of anti-nosological entity, protects individuals against stress-related mental problems. However, increasing evidence indicates that the maintenance of mental health in the face of adversity results from complex and dynamic processes of adaptation to stressors that involve the activation of several separable protective factors. Such resilience factors can reside at biological, psychological and social levels and may include stable predispositions (such as genotype or personality traits) and malleable properties, skills, capacities or external circumstances (such as gene expression patterns, emotion regulatio…
Maximum Lifetime Problem in Sensor Networks with Limited Channel Capacity
2016
We analyze the maximum lifetime problem in sensor networks with limited channel capacity for multipoint-to-multipoint and broadcast data transmission services. For the transmission model in which the transmitter adjust the power of its radio signal to the distance to the receiver we propose a new Signal to Interference plus Noise Ratio function and use it to modify the Shannon-Hartley channel capacity formula. We show, that in order to achieve an optimal data transmission regarding considered the maximum lifetime problem we cannot allow for any interference of signals. For considered transmission model and the modified capacity formula we solve the maximum lifetime problem in one dimensiona…
Glial Chloride Homeostasis Under Transient Ischemic Stress
2021
High water permeabilities permit rapid adjustments of glial volume upon changes in external and internal osmolarity, and pathologically altered intracellular chloride concentrations ([Cl–]int) and glial cell swelling are often assumed to represent early events in ischemia, infections, or traumatic brain injury. Experimental data for glial [Cl–]int are lacking for most brain regions, under normal as well as under pathological conditions. We measured [Cl–]int in hippocampal and neocortical astrocytes and in hippocampal radial glia-like (RGL) cells in acute murine brain slices using fluorescence lifetime imaging microscopy with the chloride-sensitive dye MQAE at room temperature. We observed s…