Search results for "Penn"
showing 10 items of 568 documents
Collision induced dissociation of stored gold cluster ions
1994
The stability of gold cluster ions Au + (2≦n≦23) has been investigated via collision induced dissociation in a Penning trap. Threshold energies and dissociation channels have been determined. The cluster stability exhibits a pronounced odd — even alternation: Clusters with an odd number of atoms,n, are more stable than the even-numbered ones. Enhanced stabilities are found for Au 3 + , Au 9 + , and Au 19 + in accordance with the Clemenger-Nilsson and the deformed jellium model of delocalized valence electrons. Excited odd cluster ions withn≦15 predominantly decay by evaporation of dimers; all others decay by monomer evaporation. From the dissociation channels estimates of the binding energi…
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…
COMPARISON OF CRIMSON FOUNTAINGRASS AND DISS FIBRES AS AGGREGATES FOR CEMENT MORTARS
2019
The use of natural fibres in cement composites is an expanding research field as their use can improve the mechanical and thermal behavior of cement mortars and reduce their carbon footprint. In this paper two different wild grasses, i.e. Pennisetum Setaceum, also known as crimson fountaingrass, and Ampelodesmos Mauritanicus, also called diss, are used as source of natural fibres for cement mortars. The principal aim is to evaluate the possibility of using the more invasive crimson fountaingrass in place of diss inside cement based vegetable concrete. The two plants’ fibres have been characterized by means of electron microscopy, helium picnometry; moreover, the thermal conductivity of fibr…
Individual differences in adaptive choice strategies
2003
Abstract Individual differences in compensatory and non-compensatory choice processes remain an unresolved issue for decision process researchers. This study investigates the stability and nature of individual differences in choice processes when individuals adapt to changes in the structure of the choice environment, namely the correlation among the choice attributes. By means of process tracing techniques, between-subjects differences in choice processing (option-based or attribute based) were found to be stable across different tasks. Individuals with higher openness to experience and ability to solve reasoning tasks were found to be more adaptive, that is to switch more promptly their c…
Discussing lifestyle behaviors: perspectives and experiences of general practitioners
2019
Background: Initiatives aimed at increasing participation in preventive health behaviors has been identified as a priority for addressing the increasing incidence of non-communicable chronic disease. General practice is an existing network that can be leveraged to intervene and promote messages for health behavior change. We aimed to explore the extent to which ‘lifestyle’ behaviors are discussed by general practitioners (GPs) with their patients in their practices, and the context and content of these discussions. Methods: GPs (N = 26) practising in Australian clinics participated in semi-structured interviews. Data were analyzed using an inductive thematic analysis. Results: Results showe…
Hilja Henkivartija : Hilja Ilveskeron henkilöhahmo Leena Lehtolaisen romaaneissa Henkivartija, Paholaisen pennut ja Oikeuden jalopeura
2013
Tutkin kandidaatintyössäni Leena Lehtolaisen romaanisarjassa esiintyvän päähenkilön Hilja Ilveskeron henkilöhahmoa ja sen kehittymistä erityisesti suhteessa dekkarin lajiin. Sisällytän tutkimukseeni romaanit Henkivartija, Oikeuden jalopeura ja Paholaisen pennut. Tutkin Hilja Ilveskeron henkilöhahmoa ja sen kehittymistä. Tutkimukseni aineistona olevat kolme kirjaa täyttävät selvästi dekkarin lajitunnusmerkit, joten vertaan myös henkilöhahmoa dekkarin tyypillisiin henkilöhahmoihin ja tutkin sen sijoittumista suhteessa niihin ja suhteessa dekkarin lajiin ja sen alalajeihin. Käytän lähteinäni Voitto Ruohosen ja Juha-Pekka Koskisen dekkareista tekemiä tutkimuksia ja teoksia ja vertailen Hiljan h…