Time-domain Fourier optics for polarization-mode dispersion compensation

We report on a novel technique to compensate for all-order polarization-mode dispersion. By means of this technique, based on a suitable combination of phase modulation and group-velocity dispersion, we compensated for as much as 60 ps of differential group delay that affected a 10-Gbit/s return-to-zero data stream.     

Characterization based on conditional expectations of adjacent order statistics: A unified approach

In this paper, we show a unified approach to the problem of characterizing general distribution functions based on the conditional expectation between adjacent order statistics, or , where is a real, continuous and strictly monotonic function. We have the explicit expression of the distribution function from the above order mean function, and , and we give necessary and sufficient conditions so that any real function can be an order mean function. Our results generalize the results given for the discrete, absolutely continuous and continuous cases. Further, we show stability theorems for these characterizations.

     

Application of the density matrix multipole expansion to stark quantum beats from beam-foil-excited hydrogen atoms

Summary The density matrix multipolar-expansion theory, as applied to radiation from polarized atoms, is outlined. A calculation is performed for Stark quantum beats from beam-foil-excited hydrogen atoms, and comparison is good with experimental results.

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Riassunto Si sottolinea la teoria dello sviluppo multipolare della matrice di densità applicata alla radiazinone da atomi polarizzati. Si effettua un calcolo per i colpi quantici di Stark da atomi di idrogeno eccitati dal ?beam-foil? e il confronto con i risultati sperimentali è buono.

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Резюме Обсуждается применение теории мультипольного разложения матрицы потности к излчению поляризованных атомов. Вычсления проводятся для квантовых биений Штарка у атомов водорода, возбужденных при пролете через фольгу. Получается хорошее сравнение с экспериметальными результатами.

     

Vanishings for the cohomology of certain families of stable rank two vector bundles onP 3

Sunto Si analizzano delle condizioni per l'annullamento della coomologia di fibrati stabili di rango 2su P ³.Dopo i primi risultati di annullamento dovuti principalmente ad Hartshorne, Chang congetturò che alcune disuguaglianze sulle, classi di Chern fossero sufficienti per l'annullamento del primo gruppo di coomologia. La congettura finora è provata solo in alcuni casi particolari. Nel lavoro si dimostra la congettura in molti altri casi. In particolare si completano alcuni risultati recenti dovuti ad Ellia affrontando il caso in cui la prima classe di Chern è dispari.     

Finding the contour of a union of iso-oriented rectangies

Let R₁,…,R_m be rectangles on the plane with sides parallel to the coordinate axes. An algorithm is described for finding the contour of F = R₁ ∪ … ∪ R_m in $\text{O(m}\text{log}\text{m + p}\text{log}\text{(}\text{2m}{}^2\text{p}\text{))}$ time, where p is the number of edges in the contour. This is O(m²) in the general case, and O(m log m) when F is without holes (then p ≤ 8m ? 4); both of these performances are optimal.     

Dynamics of TMMC at low temperature: A new approach to the N-pole approximation

In this paper we study the conditions to be satisfied in order to use a N-pole truncation to the continued-frac$\text{t}$ ion expansion. We show the correct way to do the cut off and apply the result to analyse experimental data for the one-dimensional antiferromagnet TMMC, at low temperatures.     

Synthesis of alpha,beta-unsaturated 4,5-disubstituted gamma-lactones via ring-closing metathesis catalyzed by the first-generation Grubbs' catalyst

[reaction: see text] 4-Methyl-5-alkyl-2(5H)-furanones have been prepared by ruthenium-catalyzed ring-closing metathesis of the suitable methallyl acrylates. Despite the electron deficiency of the conjugated double bond and of the gem-disubstitution of the allylic alkene moiety in the starting acrylates, the first-generation Grubbs' catalyst I proved to be an effective promoter for the ring closure, affording the expected butenolides in good to high yields.     

Complete single-photon counting and timing module in a microchip

A complete module for single-photon counting and timing is demonstrated in a single chip. Features comparable with or better than commercially available macroscopic modules are obtained by integration of an active-quenching and active-reset circuit in complementary metal-oxide semiconductor technology together with a single-photon avalanche diode (SPAD). The integrated SPAD has a 12-microm-diameter sensitive area and operates with an overvoltage above breakdown adjustable up to 20 V. With a 5-V overvoltage the photon detection efficiency peaks above 40% around 500 nm, and the dark-counting rate is lower than 600 counts/s at room temperature. The overall counting dead time is 33 ns.