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241.
S. Siljamki A. Harju E. Rsnen J. Suorsa R.M. Nieminen 《Physica E: Low-dimensional Systems and Nanostructures》2005,26(1-4):441
Unsymmetrical quantum-dot systems are generally difficult to study using wave-function techniques, like quantum Monte Carlo (QMC) or exact diagonalization (ED) methods. The initial trial wave function for Monte Carlo methods is difficult to find, and the exact diagonalization method can only handle very few particles.In this article a two-dimensional semiconductor quantum dot containing a non-centered impurity ion is studied, using a new exact wave-function method. Results are analyzed and compared to density-functional-theory calculations. The computational method allows one to relax the commonly used lowest-Landau level (LLL) approximation, and it's effects are studied, e.g., on the charge and current density profiles.The method, which is a combination of QMC and ED methods, is described. It combines the scalability of Monte Carlo methods with the benefits of exact diagonalization, and allows one to accurately obtain the wave function for unsymmetrical quantum dots up to more than ten electrons. Also, excited states are accessible and are analyzed in this article. 相似文献
242.
The photoabsorption spectra of a continuous series of Na(n) clusters (n相似文献
243.
We investigate via density functional theory (DFT) the appearance of small MgO-supported gold clusters with 8 to 20 atoms in a scanning tunneling microscope (STM) experiment. Comparison of simulations of ultrathin films on a metal support with a bulk MgO leads to similar results for the cluster properties relevant for STM. Simulated STM pictures show the delocalized states of the cluster rather than the atomic structure. This finding is due to the presence of s- derived delocalized states of the cluster near the Fermi energy. The properties of theses states can be understood from a jellium model for monovalent gold. 相似文献
244.
It is well-known that (ℤ+, |) = (ℤ+, GCD, LCM) is a lattice, where | is the usual divisibility relation and GCD and LCM stand for the greatest common divisor
and the least common multiple of positive integers.
The number $
d = \prod\nolimits_{k = 1}^r {p_k^{d^{(k)} } }
$
d = \prod\nolimits_{k = 1}^r {p_k^{d^{(k)} } }
is said to be an exponential divisor or an e-divisor of $
n = \prod\nolimits_{k = 1}^r {p_k^{n^{(k)} } }
$
n = \prod\nolimits_{k = 1}^r {p_k^{n^{(k)} } }
(n > 1), written as d |
e
n, if d
(k) for all prime divisors p
k
of n. It is easy to see that (ℤ+\{1}, |
e
is a poset under the exponential divisibility relation but not a lattice, since the greatest common exponential divisor (GCED)
and the least common exponential multiple (LCEM) do not always exist. 相似文献
245.
Timo Tossavainen Pentti Haukkanen Martti Pesonen 《International Journal of Mathematical Education in Science & Technology》2013,44(8):1117-1130
In this paper, we investigate which aspects are overriding in the concept images of monotonicity of Finnish tertiary mathematics students, i.e., on which aspects of monotonicity they base their argument in different types of exercises related to that concept. Further, we examine the relationship between the quality of principal aspects and the success in solving monotonicity exercises and a few other standard problems in calculus. Our findings indicate that a mathematics student's conception about monotone functions is often restricted to continuous or differentiable functions and the algebraic aspect – the nearest one to the formal definition of monotonicity – is rare. 相似文献
246.
247.
Knöner G Ratnapala A Nieminen TA Vale CJ Heckenberg NR Rubinsztein-Dunlop H 《Lab on a chip》2006,6(12):1545-1547
We present a method for characterizing microscopic optical force fields. Two dimensional vector force maps are generated by measuring the optical force applied to a probe particle for a grid of particle positions. The method is used to map out the force field created by the beam from a lensed fiber inside a liquid filled microdevice. We find transverse gradient forces and axial scattering forces on the order of 2 pN per 10 mW laser power which are constant over a considerable axial range (>35 microm). These findings suggest future useful applications of lensed fibers for particle guiding/sorting. The propulsion of a small particle at a constant velocity of 200 microm s(-1) is shown. 相似文献
248.
Saggu S Hung HI Quiogue G Lemasters JJ Nieminen AL 《Photochemistry and photobiology》2012,88(2):461-468
In photodynamic therapy (PDT), light activates a photosensitizer added to a tissue, resulting in singlet oxygen formation and cell death. The photosensitizer phthalocyanine 4 (Pc 4) localizes primarily to mitochondrial membranes in cancer cells, resulting in mitochondria-mediated cell death. The aim of this study was to determine how lysosomes contribute to PDT-induced cell killing by mitochondria-targeted photosensitizers such as Pc 4. We monitored cell killing of A431 cells after Pc 4-PDT in the presence and absence of bafilomycin, an inhibitor of the vacuolar proton pump of lysosomes and endosomes. Bafilomycin was not toxic by itself, but greatly enhanced Pc 4-PDT-induced cell killing. To investigate whether iron loading of lysosomes affects bafilomycin-induced killing, cells were incubated with ammonium ferric citrate (30 μM) for 30 h prior to PDT. Ammonium ferric citrate enhanced Pc 4 plus bafilomycin-induced cell killing without having toxicity by itself. Iron chelators (desferrioxamine and starch-desferrioxamine) and the inhibitor of the mitochondrial calcium (and ferrous iron) uniporter, Ru360, protected against Pc 4 plus bafilomycin toxicity. These results support the conclusion that chelatable iron stored in the lysosomes enhances the efficacy of bafilomycin-mediated PDT and that lysosomal disruption augments PDT with Pc 4. 相似文献
249.
Juhani Nieminen 《manuscripta mathematica》1977,21(1):51-57
The latticeU(S) of the filters of a finite joinsemilattice S is considered and it is shown when the Hasse diagram graph of S generates a simple graphic algebra. 相似文献
250.
Juhani Nieminen 《Proceedings Mathematical Sciences》1985,94(1):43-45
Semimodular, modular and distributive finite lattices are characterized by means of convex sublattices and distance closed
sets of the Hasse diagram graphs. 相似文献