955 research outputs found
Circularly polarized microwaves for magnetic resonance study in the GHz range: application to nitrogen-vacancy in diamonds
The ability to create time-dependent magnetic fields of controlled
polarization is essential for many experiments with magnetic resonance. We
describe a microstrip circuit that allows us to generate strong magnetic field
at microwave frequencies with arbitrary adjusted polarization. The circuit
performance is demonstrated by applying it to an optically detected magnetic
resonance and Rabi nutation experiments in nitrogen-vacancy color centers in
diamond. Thanks to high efficiency of the proposed microstrip circuit and
degree of circular polarization of 85% it is possible to address the specific
spin states of a diamond sample using a low power microwave generator.Comment: 4 pages, 7 figures, nitrogen-vacancy, microwave circular
polarization, spin-state addressin
Exploring risk factors at the molecular level
Risk factors for cardiovascular diseases trigger molecular changes that harm the endothelial cells in the heart, but exercise can suppress these effects
A fast and reliable method for the delineation of tree crown outlines for the computation of crown openness values and other crown parameters
Numerous crown parameters (e.g., leaf area index, diameter, height, volume) can be obtained via the analysis of tree crown photographs. In all cases, parameter values are functions of the position of the crown outline. However, no standardized method to delineate crowns exists. To explore the effect of different outlines on tree crown descriptors, in this case crown openness (CO), and facilitate the adoption of a standard method free of user bias, we developed the program Crown Delineator that automatically delineates any outline around tree crowns following predetermined sensibility settings. We used different outlines to analyze tree CO in contrasting settings: using saplings from four species in young boreal mixedwood forests and medium-sized hybrid poplar trees from a low-density plantation. In both cases, the estimated CO increases when calculated from a looser outline, which had a strong influence on understory available light simulations using a forest simulator. These results demonstrate that the method used to trace crown outlines is an important step in the determination of CO values. We provide a much-needed computer-assisted solution to help standardize this procedure, which can also be used in many other situations in which the delineation of tree crowns is needed (e.g., competition and crown shyness)
Coherent population oscillations with nitrogen-vacancy color centers in diamond
We present results of our research on two-field (two-frequency) microwave
spectroscopy in nitrogen-vacancy (NV-) color centers in a diamond. Both fields
are tuned to transitions between the spin sublevels of the NV- ensemble in the
3A2 ground state (one field has a fixed frequency while the second one is
scanned). Particular attention is focused on the case where two microwaves
fields drive the same transition between two NV- ground state sublevels (ms=0
-> ms=+1). In this case, the observed spectra exhibit a complex narrow
structure composed of three Lorentzian resonances positioned at the pump-field
frequency. The resonance widths and amplitudes depend on the lifetimes of the
levels involved in the transition. We attribute the spectra to coherent
population oscillations induced by the two nearly degenerate microwave fields,
which we have also observed in real time. The observations agree well with a
theoretical model and can be useful for investigation of the NV relaxation
mechanisms.Comment: 17 page
Invariant density and time asymptotics for collisionless kinetic equations with partly diffuse boundary operators
International audienceThis paper deals with collisionless transport equationsin bounded open domains with boundary , orthogonallyinvariant velocity measure \bm{m}(\d v) with support and stochastic partly diffuse boundary operators relating the outgoing andincoming fluxes. Under very general conditions, such equations are governedby stochastic -semigroups on We give a general criterion of irreducibility of and we show that, under very natural assumptions, if an invariant densityexists then converges strongly (notsimply in Cesar\`o means) to its ergodic projection. We show also that if noinvariant density exists then is\emph{sweeping} in the sense that, for any density , the total mass of concentrates near suitable sets of zero measure as We show also a general weak compactness theoremwhich provides a basis for a general theory on existence of invariantdensities. This theorem is based on a series of results on smoothness andtransversality of the dynamical flow associated to $\left( U_{\mathsf{H}}(t)\right) _{t\geq0}.
Histopathological evaluation of recurrent goiter.
The recurrent goiter is the regrowth of thyroid tissue after thyroidectomy. An inadequate surgical removal of the thyroid gland, lack of substitution therapy and pathological stimulation of the thyroid growth can all promote the recurrence. The aim of this study was to find the connection between the histopathological findings during the first and second operation and the recurrence of goiter. The study group consisted of 29 women and 1 man. The mean time to recurrence was 15 years. The most frequent histopathological finding during the first and second operation was struma nodosa. According to our observations different histopathological findings were found in 63.4% cases after primary and secondary thyroidectomy. Some genetic investigations showed that nodules in recurrent goiters did not derive from nodules left during the first operation but from a group of cells which had high growth potential. Thus, not only the operation technique and substitution after operation are key factors of successful therapy of goiter, but also other factors which stimulate the re-growth of thyroid tissue
Entropic trade-off relations for quantum operations
Spectral properties of an arbitrary matrix can be characterized by the
entropy of its rescaled singular values. Any quantum operation can be described
by the associated dynamical matrix or by the corresponding superoperator. The
entropy of the dynamical matrix describes the degree of decoherence introduced
by the map, while the entropy of the superoperator characterizes the a priori
knowledge of the receiver of the outcome of a quantum channel Phi. We prove
that for any map acting on a N--dimensional quantum system the sum of both
entropies is not smaller than ln N. For any bistochastic map this lower bound
reads 2 ln N. We investigate also the corresponding R\'enyi entropies,
providing an upper bound for their sum and analyze entanglement of the
bi-partite quantum state associated with the channel.Comment: 10 pages, 4 figure
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