866 research outputs found
Quantum Phase Transitions and Bipartite Entanglement
We develop a general theory of the relation between quantum phase transitions
(QPTs) characterized by nonanalyticities in the energy and bipartite
entanglement. We derive a functional relation between the matrix elements of
two-particle reduced density matrices and the eigenvalues of general two-body
Hamiltonians of -level systems. The ground state energy eigenvalue and its
derivatives, whose non-analyticity characterizes a QPT, are directly tied to
bipartite entanglement measures. We show that first-order QPTs are signalled by
density matrix elements themselves and second-order QPTs by the first
derivative of density matrix elements. Our general conclusions are illustrated
via several quantum spin models.Comment: 5 pages, incl. 2 figures. v3: The version published in PRL, including
a few extra comments and clarifications for which there was no space in the
PR
Spin orbit coupling at the level of a single electron
We utilize electron counting techniques to distinguish a spin conserving fast
tunneling process and a slower process involving spin flips in
AlGaAs/GaAs-based double quantum dots. By studying the dependence of the rates
on the interdot tunnel coupling of the two dots, we find that as many as 4% of
the tunneling events occur with a spin flip related to spin-orbit coupling in
GaAs. Our measurement has a fidelity of 99 % in terms of resolving whether a
tunneling event occurred with a spin flip or not
Distribution and Excretion of TEGDMA in Guinea Pigs and Mice
The monomer triethyleneglycoldimethacrylate (TEGDMA) is used as a diluent in many resin-based dental materials. It was previously shown in vitro that TEGDMA was released into the adjacent biophase from such materials during the first days after placement. In this study, the uptake, distribution, and excretion of 14C-TEGDMA applied via gastric, intradermal, and intravenous administration at dose levels well above those encountered in dental care were examined in vivo in guinea pigs and mice as a test of the hypothesis that TEGDMA reaches cytotoxic levels in mammalian tissues. 14C-TEGDMA was taken up rapidly from the stomach and small intestine after gastric administration in both species and was widely distributed in the body following administration by each route. Most 14C was excreted within one day as 14 CO2. The peak equivalent TEGDMA levels in all mouse and guinea pig tissues examined were at least 1000-fold less than known toxic levels. The study therefore did not support the hypothesis
Lamination And Microstructuring Technology for a Bio-Cell Multiwell array
Microtechnology becomes a versatile tool for biological and biomedical
applications. Microwells have been established long but remained
non-intelligent up to now. Merging new fabrication techniques and handling
concepts with microelectronics enables to realize intelligent microwells
suitable for future improved cancer treatment. The described technology depicts
the basis for the fabrication of a elecronically enhanced microwell. Thin
aluminium sheets are structured by laser micro machining and laminated
successively to obtain registration tolerances of the respective layers of
5..10\^Am. The microwells lasermachined into the laminate are with
50..80\^Am diameter, allowing to hold individual cells within the well.
The individual process steps are described and results on the microstructuring
are given.Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/EDA-Publishing
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