Search results for "TRIPLE"
showing 10 items of 506 documents
Relaxation Mechanisms of 5-Azacytosine.
2015
The photophysics and deactivation pathways of the noncanonical 5-azacytosine nucleobase were studied using the CASPT2//CASSCF protocol. One of the most significant differences with respect to the parent molecule cytosine is the presence of a dark (1)(nNπ*) excited state placed energetically below the bright excited state (1)(ππ*) at the Franck-Condon region. The main photoresponse of the system is a presumably efficient radiationless decay back to the original ground state, mediated by two accessible conical intersections involving a population transfer from the (1)(ππ*) and the (1)(nNπ*) states to the ground state. Therefore, a minor contribution of the triplet states in the photophysics o…
Properties and performance of a quadrupole mass filter used for resonance ionization mass spectrometry
1998
Abstract The performance of commercial quadrupole mass spectrometers (QMS) with a number of imperfections, as compared to the ideal hyperbolic geometry, has been characterized using the computer simulation program simion 3d version 6.0. The analysis of simulated QMS geometries focuses primarily on modeling of the internal potential, the study of field deviations, and the influence of finite length on performance of the QMS. The computer simulation of ion trajectories in the QMS field yields predictions for optimum working conditions and provides estimates for the resolving power and the maximum isotopic abundance sensitivity. Experimental measurements that confirm these expectations are pre…
cis-Diazido[bis(diphenylphosphino)methane-κ2P,P′]ruthenium(II) dichloromethane 0.42-solvate
2006
Submitted by António Freitas (amsf@uma.pt) on 2019-06-13T13:44:22Z No. of bitstreams: 1 cis-Diazidobis(diphenylphosphino)methane-j2PP000ruthenium(II) dichloromethane 0.42-solvateJoãoRodrigues.pdf: 167616 bytes, checksum: 2ba0b7a76027be3eda26ce11d43fec66 (MD5) Made available in DSpace on 2019-06-13T13:44:22Z (GMT). No. of bitstreams: 1 cis-Diazidobis(diphenylphosphino)methane-j2PP000ruthenium(II) dichloromethane 0.42-solvateJoãoRodrigues.pdf: 167616 bytes, checksum: 2ba0b7a76027be3eda26ce11d43fec66 (MD5) Previous issue date: 2006 info:eu-repo/semantics/publishedVersion
Triplet exciplexes as energy transfer photosensitisers
2006
Experimental evidence is provided for the occurrence of triplet–triplet energy transfer from benzoylthiophene–indole exciplexes to naphthalenes with a remarkable stereodifferentiation; chiral recognition is also observed in the decay of the generated naphthalene triplets. Perez Prieto, Julia, Julia.Perez@uv.es ; Galian, Raquel Eugenia, Raquel.Galian@uv.es ; Morant Miñana, Maria Carmen, Maica.Morant@uv.es
Similarity and Specificity of Chlorophyll b Triplet State in Comparison to Chlorophyll a as Revealed by EPR/ENDOR and DFT Calculations
2019
An investigation of the photoexcited triplet state of chlorophyll (Chl) b has been carried out by means of electron nuclear double resonance, both in a frozen organic solvent and in a protein environment provided by the water-soluble chlorophyll protein of Lepidium virginicum. Density functional theory calculations have allowed the complete assignment of the observed hyperfine couplings corresponding to the methine protons and the methyl groups, leading to a complete picture of the spin density distribution of the triplet state in the tetrapyrrole macrocycle. The triplet-state properties of Chl b are found to be similar, in many respects, to those previously reported for Chl a, although som…
Optically Detected Magnetic Resonance of Chlorophyll Triplet States in Water-Soluble Chlorophyll Proteins from Lepidium virginicum: Evidence for Exci…
2018
Optically detected magnetic resonance of triplet states populated by photoexcitation in water-soluble chlorophyll proteins (WSCPs) from Lepidium virginicum has been performed using both absorption and fluorescence detection. Well resolved triplet-singlet (T-S) spectra have been obtained and interpreted in terms of electronic interactions among the four chlorophylls (Chls), forming two dimers in the WSCP tetramer. Localization of the triplet state on a single Chl leads to a redistribution of the oscillator strength in the remaining three Chls of the complex. By comparing the spectra with those obtained on a substoichiometric WSCP complex containing only 2 Chls per protein tetramer, we proved…
Gas chromatography and mass spectroscopy techniques for the detection of chemical contaminants and residues in foods
2017
Gas chromatography-mass spectrometry (GC-MS) is a cornerstone for qualitative and quantitative analysis of food contaminants and residues. It is fast and sensitive, provides a high peak capacity, and allows determination of thermally stable and volatile compounds. Recent research has resulted in better chromatographic columns and methods for sample preparation that enable a significant expansion of the application range of GC-MS, profiling strategies for sample characterization being identified as important future drivers. Newer detection/separation solutions, such as fast chromatography, comprehensive two-dimensional GC (GC × GC), triple quadrupole MS, time-of-flight MS or orbitrap, atmosp…
Follow up: palmitic acid ester of tetrahydrocannabinol (THC) and palmitic acid diester of 11-hydroxy-THC – unsuccessful search for additional THC met…
2020
Abstract Objectives In a previous investigation we searched for the occurrence of palmitic acid ester compounds of delta9-tetrahydrocannabinol (THC) and its primary metabolite 11-hydroxy-delta9-THC (11-OH-THC) in human body fluids and tissues (THC palmitic acid monoester [THC-Pal] and 11-OH-THC palmitic acid diester [11-OH-THC-DiPal]). As those esters could not be detected in various human body fluids (e.g. blood) or tissues (e.g. adipose tissue) we extended the investigation analyzing adipose tissue samples of mice previously given synthetic THC or a cannabis extract. Methods In total, 48 adipose tissue samples previously tested positive for THC by means of a liquid chromatographic triple …
Development of a new multi-analyte assay for the simultaneous detection of opioids in serum and other body fluids using liquid chromatography-tandem …
2015
Abstract A liquid chromatography–tandem mass spectrometry method using electrospray ionization in positive ionization mode was developed for the simultaneous detection of multiple opioid-type drugs in plasma. The presented assay allows the quantitative determination of alfentanil, buprenorphine, codeine, desomorphine, dextromethorphan, dextrorphan, dihydrocodeine, dihydromorphine, ethylmorphine, fentanyl, hydrocodone, hydromorphone, methadone, morphine, naloxone, naltrexone, oxycodone, oxymorphone, pentazocine, pethidine, pholcodine, piritramide, remifentanil, sufentanil, and tramadol as well as the metabolites 6-monoacetylmorphine, bisnortilidine, morphine-3-glucuronide, morphine-6-glucuro…
Determination of trichothecenes in chicken liver using gas chromatography coupled with triple-quadrupole mass spectrometry
2018
Abstract Chicken meat and edible offal are included in a wide number of preparations in the worldwide cuisine. Among the offal, the liver is one of the most consumed in some countries like Egypt since it is rich in proteins and is an economical source of many essential nutrients for humans. Mycotoxins, secondary toxic metabolites produced by fungi, have the potential to enter human food chain not only with cereal consumption but also through edible tissues from animals fed with mycotoxin-contaminated feed. Accordingly, a rapid method for the determination of eight trichothecenes in chicken liver was developed based on a quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction an…