An eco-solution for track & trace of goods and third party logistics

This paper presents a new economic cost-effective solution known as the Web and telephony based method for tracking and tracing of goods and small and medium sized third party logistic providers. Considering that these companies usually operate on very flat margins, a comparison is made of the available track and trace technologies like GPS, mobile phone approximated GPS and Java based cell tracking in terms of costs, operating risks, and other evaluation criteria

^25Mg NMR study of the MgB_2 superconductor

^25Mg NMR spectra and nuclear spin-lattice relaxation time, T_1, have been measured in polycrystalline ^25MgB_2 with a superconducting transition temperature T_c = 39.0 K in zero magnetic field. From the first order and second order quadrupole perturbed NMR spectrum a quadrupole coupling frequency nu_Q = 222(1.5) kHz is obtained. T_1T = 1090(50) sK and Knight shift K_c = 242(4) ppm are temperature independent in the normal conducting phase. The ^25Mg Korringa ratio equals to 0.95 which is very close to the ideal value of unity for s-electrons. The comparison of the experimental nu_Q, T_1T, and K_c with the corresponding values obtained by LDA calculations shows an excellent agreement for all three quantities.Comment: 4 pages including 4 eps-figures, revtex

High-fidelity ion-trap quantum computing with hyperfine clock states

We propose the implementation of a geometric-phase gate on magnetic-field-insensitive qubits with $\hat{\sigma}^z$-dependent forces for trapped ion quantum computing. The force is exerted by two laser beams in a Raman configuration. Qubit-state dependency is achieved by a small frequency detuning from the virtually-excited state. Ion species with excited states of long radiative lifetimes are used to reduce the chance of a spontaneous photon emission to less than 10$^{-8}$ per gate-run. This eliminates the main source of gate infidelity of previous implementations. With this scheme it seems possible to reach the fault tolerant threshold.Comment: 4 pages, 1 figur

Photoinitiated processes in functionally diverse organic molecules elucidated by theoretical methods

In this thesis reaction mechanisms of organic compounds with applications in different areas, such as kinetic studies, labeling, and battery electrolytes, are investigated with theoretical methods from quantum chemistry, quantum dynamics, and molecular dynamics. The variety of the investigated molecules ranges from polycyclic hydrocarbons, dyes, electrolytes to precursors of reactive species. The work was performed either in close collaboration with experimentalists or based on experimental results and in this way allows an in-depth look at the occurring chemistry. In the first part the concept of adapted reactive coordinates for reduced dimensional quantum dynamics is presented necessary for the studies in the following part. It relies on the Wilson G-matrix method as formulation of the kinetic part of the Hamiltonian and allows to include the relaxation of background coordinates besides the identified main reactive coordinates without optimizations for each grid point. The concept is shown for a photodissociation involving complex structural changes and the G-matrix elements and their influence on the dynamics are discussed. In the second part the photoinitated bond cleavage reaction for diphenylmethyl chloride and diphenylmethyl bromide is studied. Based on the reactive coordinate system presented before, quantum dynamical simulations enlighten the path of the wave packet, which passes through two consecutive conical intersections—a three-state and a two-state one—as decisive elements for the product splitting. In the case of chlorine, the experimental signal is modeled from the simulated data to further prove the mechanism. For the bromine case, additionally non-adiabatic mixed quantum-classical dynamics is used to clarify the role of vibrations during the bond cleavage, which are responsible for small amplitude oscillations of the experimental signals. Throughout this part the “our own n-layered integrated molecular orbital and molecular mechanics” (ONIOM) method is used to reduce the involved computational cost. The third part is dedicated to the photophysics of elongated π systems in organic molecules discussing two examples. The first one is the polycyclic hydrocarbon pyrene, the second one covalently linked constructs of DNA and the dye Cyanine 3. For pyrene, the ultrafast transition from the photo-accessible S2 state to the fluorescent S1 is simulated for the first time using two complementary dynamical methods. It is shown that both methods yield comparable results and demonstrate the strong coupling between the two states. The constructs in the second example are investigated experimentally and theoretically. Simulated spectra for a model system help attributing an occurring blue-shift to dimerization. Circular dichroism measurements and molecular dynamics simulations further characterize the formed dimers. The last part comprises a joint experimental and theoretical study concerning the chemical stability of two electrolytes commonly used in lithium-ion batteries towards singlet oxygen. It is shown that singlet oxygen is reactive towards the electrolyte ethylene carbonate. Ab initio calculations suggest a concerted double hydrogen abstraction by the singlet oxygen as mechanism, which is not possible for the second electrolyte dimethyl carbonate. It is an example for the unusual reaction of an alkyl group with singlet oxygen and yields hydrogen peroxide. Ground state mixed quantum-classical dynamics verify the further decay of the reaction intermediate vinylene carbonate to carbon dioxide, which is found experimentally. The theoretically predicted intermediate formation of hydrogen peroxide is detected colorimetrically proving the reaction mechanism and its detrimental effect is investigated experimentally

Sammandrag från föredrag hållet av K. G. R005 Vid Scand-LAS symposium i Köpenhamn, 18—19/4 1977

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Irreversible nucleation in molecular beam epitaxy: From theory to experiments

Recently, the nucleation rate on top of a terrace during the irreversible growth of a crystal surface by MBE has been determined exactly. In this paper we go beyond the standard model usually employed to study the nucleation process, and we analyze the qualitative and quantitative consequences of two important additional physical ingredients: the nonuniformity of the Ehrlich-Schwoebel barrier at the step-edge, because of the existence of kinks, and the steering effects, due to the interaction between the atoms of the flux and the substrate. We apply our results to typical experiments of second layer nucleation.Comment: 11 pages. Table I corrected and one appendix added. To be published in Phys. Rev. B (scheduled issue: 15 February 2003

Theoretical calculations for solid oxygen under high pressure

The crystal structure of solid oxygen at low temperatures and at pressures up to 7 GPa is studied by theoretical calculations. In the calculations, the adiabatic potential of the crystal is approximated by a superposition of pair-potentials between oxygen molecules calculated by an ab-initio method. The monoclinic alpha structure is stable up to 6 GPa and calculated lattice parameters agree well with experiments. The origin of a distortion and that of an anisotropic lattice compressibility of the basal plane of alpha-O2 are clearly demonstrated. In the pressure range from 6 to 7 GPa, two kinds of structures are proposed by X-ray diffraction experiments: the alpha and orthorhombic delta structures. It is found that the energy difference between these structures becomes very small in this pressure range. The relation between this trend and the incompatible results of X-ray diffraction experiments is discussed.Comment: 12 pages, 6 figure

Weighted Bergman kernels and virtual Bergman kernels

We introduce the notion of "virtual Bergman kernel" and apply it to the computation of the Bergman kernel of "domains inflated by Hermitian balls", in particular when the base domain is a bounded symmetric domain.Comment: 12 pages. One-hour lecture for graduate students, SCV 2004, August 2004, Beijing, P.R. China. V2: typo correcte

Influence of adatom interactions on second layer nucleation

We develop a theory for the inclusion of adatom interactions in second layer nucleation occurring in epitaxial growth. The interactions considered are due to ring barriers between pairs of adatoms and binding energies of unstable clusters. The theory is based on a master equation, which describes the time development of microscopic states that are specified by cluster configurations on top of an island. The transition rates are derived by scaling arguments and tested against kinetic Monte-Carlo simulations. As an application we reanalyze experiments to determine the step edge barrier for Ag/Pt(111).Comment: 4 pages, 4 figure