Search results for "trap"
showing 10 items of 2144 documents
Photodissociation of small group-11 metal cluster ions: Fragmentation pathways and photoabsorption cross sections
2003
Noble metal cluster ions Cu(n)(+), Ag(n)(+) and Au(n)(+) (n = 3-21) have been stored in a Penning trap and photodissociated by low intensity laser pulses of 10 ns at photon energies of 3.49 eV and 4.66 eV. The fragmentation pathways, neutral monomer and dimer evaporation, have been monitored as a function of cluster size, excitation energy and element. It is found that the behavior of the branching ratio between monomer and dimer evaporation as a function of excitation energy depends on the metal under investigation. In particular, the slope of the energy dependence is positive for silver but negative for gold and copper cluster ions. Furthermore, photoabsorption cross sections are determin…
Fragmentation pattern of gold clusters collided with xenon atoms
1994
Abstract The dissociation channels of gold cluster ions Au n + (2 ≤ n ≤ 23) have been investigated via collision induced dissociation in a Penning trap. Excited odd cluster ions with n ≤ 15 decay by evaporation of dimers, all others decay by monomer evaporation. Information on the binding energies is deduced from these dissociation channels.
Photo fragmentation of metal clusters stored in a penning trap
1996
Photo fragmentation studies of stored mass selected metal cluster ions of a large size range are reported. The experimental method and the data evaluation are described in detail. Gold cluster ions were produced by laser vaporization and stored in a Penning trap. After size selection they were electronically excited by irradiation with a pulsed laser beam. Relaxation by evaporation of neutral atoms and dimers was observed as a function of photon energy. From these data upper and lower limits for dissociation energies are determined for Aun + (n=3 to 23).
Electron impact ionization/dissociation of size selected gold cluster cations
2000
Abstract Singly charged gold clusters, Au n + in the size range n =12 to 72 have been captured and stored in a Penning trap, size selected and subjected to an electron beam. This interaction leads to further ionization as well as dissociation. The resulting abundance spectra of doubly and triply charged clusters show (a) a lower size limit for the production of multiply charged clusters from an ensemble of hot precursors, which can be understood in terms of the respective decay pathways, (b) an odd/even alternation of singly and doubly charged clusters in the size range below n =30, which inverses sign with change of charge state, and (c) magic numbers, i.e. prominent signals for particular…
Au n+-induced decomposition of N2O
1994
Reactions between small gold cluster ions, Au, and N2O were studied in a Penning trap mass spectrometer. Gold clusters were produced by laser vaporization and injected into a Penning trap. After reaction times of 50–7000ms the products were detected by time-of-flight mass spectrometry. For the major reaction channel, Au + N2OAu1,2N + NO+, rates of (0.9±0.1)×10−12 cm3 s−1 and (2.4±0.4)×10−12 cm3 s−1 were determined which are about a factor 500 below the collision rate. The corresponding activation energies for N2O decomposition were estimated to lie below 0.6 eV and 0.3 eV. Additional products with small branching ratios were detected, viz. the ions Au1O+, Au1N2O+, Au2N+, Au2NO+, Au2N2O+, Au…
Dopētu un nedopētu bismuta selenīda nanolaminātu veidošana un raksturošana
2019
Dopētu un nedopētu bismuta selenīdu nanolaminātu veidošana un raksturošana. Britāla L., zinātniskie vadītāji Dr. phys., vadošā pētniece Andžāne J., Dr. chem., asoc. prof. Erts D. Bakalaura darbs, -- lappuses, -- attēli, -- tabulas, -- literatūras avoti, -- pielikumi. Latviešu valodā. Šajā pētījumā tiek izstrādāta metode ar alvu dopētu un nedopētu Bi2Se3 ultraplānu kārtiņu, ar biezumu 10 nm, sintēzei uz grafēna virsmas. Secīgi sintezējot šādi strukturētus bismuta selenīda slāņus, uz grafēna pamatnes tiek izveidots nanolamināts, kurš sastāv no dopētām un nedopētām ultraplānām bismuta selenīda kārtiņām. Noteiktas šo nanolaminātu termoelektriskās īpašības un tos ietekmējošie faktori.
Transfection analysis of expression of mRNA isoforms encoding the nuclear autoantigen La/SS-B
1997
Transcription of the gene encoding for the nuclear autoantigen La resulted in La mRNA isoforms. A promoter switching combined with an alternative splicing pathway replaced the exon 1 with the exon 1'. The exon 1' contained GC-rich regions and an oligo(U) tail of 23 uridine residues. Moreover, it encoded for three open reading frames upstream of the La protein reading frame. Despite this unusual structure, when exon 1' La mRNAs were expressed in transfected cells, both exon 1 and 1' La mRNAs were translated to La protein, whereas the upstream open reading frames of the exon 1' were not translated. In addition to full-length exon 1' La mRNAs 5'-shortened exon 1' La mRNAs were detected. The ex…
Extrapyramidal Symptoms and their Relationship to Clinical Efficacy under Perphenazine Treatment*
1991
In order to verify the hypothesis of a strict relationship between clinical improvement and extrapyramidal side-effects, especially micrographia, twenty-two acutely ill schizophrenics were treated with perphenazine in a controlled prospective 28-day trial. During the study period, psychopathometric data, prolactin plasma levels, and handwriting samples were collected. According to the remission criteria fixed before the study began (both BPRS ≤ 25 and GAS ≥ 80 points), 45.5% (10/22) of the total patient sample were classified as treatment responders. Handwriting tests were quantified in 21 patients. "Positive" handwriting results, i. e., a reduction of at least 13% in the overall area of 50…
Efecto del pedaleo de brazos sobre el sistema cardiorrespiratorio de las personas con tetraplejia. (Effect of armcrank pedaling on the cardiorespirat…
2010
Objetivos: Determinar el efecto de un programa de entrenamiento de pedaleo de brazos (PB) estacionario, sobre el sistema cardiorrespiratorio de personas con tetraplejia. Metodo: Se estudiaron 11 participantes con tetraplejia por lesion medular (LM) de origen traumatico a niveles entre C4 y C6. Se midieron variables espirometricas (VC, FVC y MVV) y de Variabilidad de la Frecuencia Cardiaca VFC (HR, STDHR, RMSSD, LF, HF y HRVPOWER), antes y despues de 8 semanas de entrenamiento. Resultados: Todas las variables mostraron cambios significativos (p < 0,05) despues del programa de entrenamiento aumentando su valor, excepto la FC que disminuyo. Las personas con las LM mas bajas mostraron valores m…
Bioactive Compounds and Antioxidant Properties with Involved Mechanisms of Eugenia involucrata DC Fruits
2022
In this study, the phytochemical profile and the antioxidative properties of Eugenia involucrata fruits were evaluated. Spectrophotometric assays indicated that these berries are a rich source of polyphenols with very high radical-scavenging and metal-reducing activities. High-performance liquid chromatography–Orbitrap analysis was able to carry out the annotation of 36 different compounds, mainly belonging to the flavonol, flavan-3-ol, and anthocyanin families. Antioxidant activity of the fruit extract was evaluated in a cell-based lipid peroxidation model. Obtained data showed that the extract, at very low concentration, was able to prevent oxidative damage in HepG2 cells exposed to oxida…