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101.
Jorma Hölsä Taneli Laamanen Mika Lastusaari Marja Malkamäki Edmund Welter Dariusz A. Zajac 《Spectrochimica Acta Part B: Atomic Spectroscopy》2010
The existence of the different R2+/R3+/RIV (R: rare earth) ions as well as the modifications in the structural environment around the dopant and co-dopants in CaAl2O4:Eu2+,R3+ persistent luminescence materials was studied by LIII edge X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) measurements at Hamburger Synchrotronstrahlungslabor (HASYLAB) at Deutsches Elektronen-Synchrotron (DESY) (Hamburg, Germany). The measurements were carried out at 10 and 296 K for selected rare earth (co-)dopants (Eu2+; Ce3+, Nd3+, Sm3+, and Yb3+). 相似文献
102.
Jorma Hölsä Marco Kirm Mika Lastusaari Janne Niittykoski Pavel Novák 《Journal of luminescence》2009,129(12):1560-1563
The electronic structures of the distrontium magnesium disilicate (Sr2MgSi2O7(:Eu2+)) materials were studied by a combined experimental and theoretical approach. The UV-VUV synchrotron radiation was applied in the experimental study while the electronic structures were investigated theoretically by using the density functional theory. The structure of the valence and conduction bands and the band gap energy of the material as well as the position of the Eu2+ 4f ground state were calculated. The calculated band gap energy (6.7 eV) agrees well with the experimental value of 7.1 eV. The valence band consists mainly of the oxygen states and the bottom of the conduction band of the Sr states. The calculated occupied 4f ground state of Eu2+ lies in the energy gap of the host though the position depends strongly on the Coulomb repulsion strength. The position of the 4f ground state with respect to the valence and conduction bands is discussed using the theoretical and experimental evidence available. 相似文献
103.
Hellman H Laitinen RS Kaila L Jalonen J Hietapelto V Jokela J Sarpola A Rämö J 《Journal of mass spectrometry : JMS》2006,41(11):1421-1429
The hydrolysis reactions of FeCl3 in 0.1 mM aqueous solutions were monitored by electrospray ionisation time-of-flight mass spectrometry (ESI-ToF-MS). In contrast to the other ionisation techniques, electrospray ionisation provides information on the composition of the elemental cores even in water and salt cluster ions. Therefore, the technique facilitates detection of the bonding of the chloride ions in the oxo-hydroxo-iron cores. A variety of mononuclear and polynuclear iron-oxohydroxo-chloride complexes were characterised from the cationic and anionic mass spectra of iron(III) solutions. Oxidation and reduction reactions of iron, as well as competition between OH- and Cl- ions within one iron core, were also observed. 相似文献
104.
[structure: see text] The relative and absolute stereochemistry of the structurally unique 24-membered myxobacterial macrolides archazolid A and B, highly potent vacuolar-type ATPase (V-ATPase) inhibitors in vitro and in vivo, was determined on the basis of a combination of extensive high-field NMR studies, including J-based configuration analysis, molecular modeling, and chemical methods. 相似文献
105.
Z-configured 1,4-diene or β, γ-unsaturated carbonyl systems are readily available by the Wittig reaction. Isomerization required for access into the E-series can easily be accomplished by irradiation using an ordinary tungsten lamp and diphenyl disulphide sensitizer. There is very little formatation of conjugated isomers (less than 1%). 相似文献
106.
Hermi F. Brito Jukka Hassinen Jorma Hölsä Högne Jungner Taneli Laamanen Mika Lastusaari Marja Malkamäki Janne Niittykoski Pavel Novák Lucas C. V. Rodrigues 《Journal of Thermal Analysis and Calorimetry》2011,105(2):657-662
The details of the mechanism of persistent luminescence were probed by investigating the trap level structure of Sr2MgSi2O7:Eu2+,R3+ materials (R: Y, La-Lu, excluding Pm and Eu) with thermoluminescence (TL) measurements and Density Functional Theory (DFT)
calculations. The TL results indicated that the shallowest traps for each Sr2MgSi2O7:Eu2+,R3+ material above room temperature were always ca. 0.7 eV corresponding to a strong TL maximum at ca. 90 °C. This main trap
energy was only slightly modified by the different co-dopants, which, in contrast, had a significant effect on the depths
of the deeper traps. The combined results of the trap level energies obtained from the experimental data and DFT calculations
suggest that the main trap responsible for the persistent luminescence of the Sr2MgSi2O7:Eu2+,R3+ materials is created by charge compensation lattice defects, identified tentatively as oxygen vacancies, induced by the R3+ co-dopants. 相似文献
107.
An erasure correction strategy based on fountain coding is proposed for traffic with real-time requirements. A sliding window marks the range of non-expired data. Each new block entering the window is once sent as such, followed by probabilistically sending a repair packet. The repair packets are formed as a random combination of the blocks in the current window using a degree distribution as in LT coding. The performance of the method with a given channel loss probability is analyzed using a Markov chain model. The state space, however, has to be truncated for computational tractability. The truncation error is verified to be small enough by simulations. By using the analytical model the optimal degree distribution is found to be of single-degree type. The performance of the proposed scheme is compared with deterministic settings, in which repair packets are sent after fixed number of systematic packets. Further comparison is made against Raptor coding, and we note that using the presented strategy can result in better performance in some situations. 相似文献
108.
Fractional Brownian surfaces have frequently been used to model various physical processes and to generate artificial landscapes. We study a closely related process, called two-dimensional fractional Gaussian noise. We devise a method for generating realizations of this process using an approximate conditioning approach, motivated by results from the corresponding one-dimensional process applied in teletraffic modeling. 相似文献
109.
Evaluation of electrolessly deposited NiP integral resistors on flexible polyimide substrate 总被引:1,自引:0,他引:1
Tuomas F. Waris Markus P.K. Turunen Tomi Laurila Jorma K. Kivilahti 《Microelectronics Reliability》2005,45(3-4):665-673
Integral nickel–phosphorus (NiP) resistors were fabricated on flexible polyimide (PI) substrates by electroless NiP deposition. The deposition process was first set up for standard rigid epoxy substrates and then modified for the flexible substrates. The effects of the PI surface modifications on the interfacial adhesion (NiP/PI) were measured experimentally by the pull-off method. The process parameters were optimised to give good adhesion. The mechanical durability of the electrolessly deposited thin film NiP resistors was tested by measuring the electrical resistance during cyclic loading. The results showed the resistors to be mechanically stable. The electrical resistance was also monitored continuously during exposure to corrosive gas environment. The corrosive environment had no significant effect on the resistance of either the electrolessly deposited resistors or the commercial integral resistors used as a reference. The results show that resistors can be fabricated on flexible PI substrate by the described method. 相似文献
110.
Sarpola AT Saukkoriipi JJ Hietapelto VK Jalonen JE Jokela JT Joensuu PH Laasonen KE Rämö JH 《Physical chemistry chemical physics : PCCP》2007,9(3):377-388
ElectroSpray Ionization-Mass Spectrometry (ESI-MS) and computational methods (DFT, MP2, and COSMO) were used to investigate the hydrolysis products of aluminium chloride as a function of sulfate concentration at pH 3.7. With the aid of computational chemistry, structural information was deduced from the chemical compositions observed with ESI-MS. Many novel types of hydrolysis products were noted, revealing that our present understanding of aluminium speciation is too simple. The role of counterions was found to be critical: the speciation of aluminium changed markedly as a function of sulfate concentration. Ab initio calculations were used to reveal the energetically most favoured structures of aluminium sulfate anions and cations selected from the ESI-MS results. Several interesting observations were made. Most importantly, the bonding behaviour of the sulfate group changed as the number of aqua ligands increased. The accompanying structural rearrangement of the clusters revealed the highly active role of sulfate as a ligand. The gas phase calculations were expanded to the aquatic environment using a conductor-like screening model. As expected, the bonding behaviour of the sulfate group in the minimum energy structures was distinctly different in the aquatic environment compared to the gas phase. Together, these methods open a new window for research in the solution chemistry of aluminium species. 相似文献