Cation-pi interactions in aromatics of biological and medicinal interest: Electrostatic potential surfaces as a useful qualitative guide

The cation-pi interaction is an important, general force for molecular recognition in biological receptors. Through the sidechains of aromatic amino acids, novel binding sites for cationic ligands such as acetylcholine can be constructed. We report here a number of calculations on prototypical cation-pi systems, emphasizing structures of relevance to biological receptors and prototypical heterocycles of the type often of importance in medicinal chemistry. Trends in the data can be rationalized using a relatively simple model that emphasizes the electrostatic component of the cation-pi interaction. In particular, plots of the electrostatic potential surfaces of the relevant aromatics provide useful guidelines for predicting cation-pi interactions in new systems

Nonlinear propagation equations in fibers with multiple modes—Transitions between representation bases

The transverse pattern of the field that propagates in a fiber supporting multiple modes can always be described as a superposition of the patterns of the individual fiber modes. Yet, the use of other bases is often found to be more convenient, with the most famous example being that of linearly polarized modes in weakly guiding fibers. The nonlinear propagation equations contain coefficients that involve overlap integrals between the lateral profiles of multiple propagation modes. A fundamental question that has been raised in this context is whether it is legitimate to compute these coefficients from the overlap integrals between elements of alternative bases for the field representation. In this paper, we show that the answer to this question is positive in the most general sense. This result is significant in the context of space-division multiplexed transmission in multi-mode and multi-core fibers.The transverse pattern of the field that propagates in a fiber supporting multiple modes can always be described as a superposition of the patterns of the individual fiber modes. Yet, the use of other bases is often found to be more convenient, with the most famous example being that of linearly polarized modes in weakly guiding fibers. The nonlinear propagation equations contain coefficients that involve overlap integrals between the lateral profiles of multiple propagation modes. A fundamental question that has been raised in this context is whether it is legitimate to compute these coefficients from the overlap integrals between elements of alternative bases for the field representation. In this paper, we show that the answer to this question is positive in the most general sense. This result is significant in the context of space-division multiplexed transmission in multi-mode and multi-core fibers

Milano sepolta : Dieci anni di archeologia urbana a Milano

Le trasformazioni della citt\ue0 contemporanea sono un\u2019importante occasione per far riemergere tratti della Milano antica altrimenti impercettibili, sepolti sotto metri di stratigrafia e di vita urbana. In una realt\ue0 in perenne proiezione verso il futuro, queste tracce finiscono spesso per scomparire, sopraffatte dai ritmi della citt\ue0 moderna, nascoste dietro i muri dei palazzi e nei cantieri. La mostra fotografica \u201cMilano sepolta. Dieci anni di archeologia urbana a Milano" vuole rendere partecipe la collettivit\ue0 degli eccezionali tesori nascosti nel sottosuolo milanese, e del duro lavoro necessario a riportarli luce, tutelarli e valorizzarli. Un\u2019attenta selezione di immagini raccolte durante gli scavi archeologici condotti nel decennio 2005-2015, rievoca la memoria di questa realt\ue0, parte integrante dell\u2019anima della citt\ue0, prima che venga definitivamente perduta

Milano sepolta : Dieci anni di archeologia urbana a Milano

Le trasformazioni della citt\ue0 contemporanea sono un\u2019importante occasione per far riemergere tratti della Milano antica altrimenti impercettibili, sepolti sotto metri di stratigrafia e di vita urbana. In una realt\ue0 in perenne proiezione verso il futuro, queste tracce finiscono spesso per scomparire, sopraffatte dai ritmi della citt\ue0 moderna, nascoste dietro i muri dei palazzi e nei cantieri. La mostra fotografica \u201cMilano sepolta. Dieci anni di archeologia urbana a Milano" vuole rendere partecipe la collettivit\ue0 degli eccezionali tesori nascosti nel sottosuolo milanese, e del duro lavoro necessario a riportarli luce, tutelarli e valorizzarli. Un\u2019attenta selezione di immagini raccolte durante gli scavi archeologici condotti nel decennio 2005-2015, rievoca la memoria di questa realt\ue0, parte integrante dell\u2019anima della citt\ue0, prima che venga definitivamente perduta

Nonclassical correlations in damped quantum solitons

Using cumulant expansion in Gaussian approximation, the internal quantum statistics of damped soliton-like pulses in Kerr media are studied numerically, considering both narrow and finite bandwidth spectral pulse components. It is shown that the sub-Poissonian statistics can be enhanced, under certain circumstances, by absorption, which damps out some destructive interferences. Further, it is shown that both the photon-number correlation and the correlation of the photon-number variance between different pulse components can be highly nonclassical even for an absorbing fiber. Optimum frequency windows are determined in order to realize strong nonclassical behavior, which offers novel possibilities of using solitons in optical fibers as a source of nonclassically correlated light beams.Comment: 15 pages, 11 PS figures (color

Can apparent superluminal neutrino speeds be explained as a quantum weak measurement?

Probably not.Comment: 10 pages, 1 figur

The Gordon-Haus effect for modified NLS solitons

Random jitter in the soliton arrival time (the Gordon-Haus effect) is analyzed for solitons being solutions of the integrable modified nonlinear Schroedinger equation. It is shown that the mean square fluctuation of the soliton position depends on the soliton parameters which can be properly adjusted to suppress the Gordon-Haus jitter.Comment: LaTeX, 7 pages, 3 figures, to be published in Europhys. Let

Theory of quantum fluctuations of optical dissipative structures and its application to the squeezing properties of bright cavity solitons

We present a method for the study of quantum fluctuations of dissipative structures forming in nonlinear optical cavities, which we illustrate in the case of a degenerate, type I optical parametric oscillator. The method consists in (i) taking into account explicitly, through a collective variable description, the drift of the dissipative structure caused by the quantum noise, and (ii) expanding the remaining -internal- fluctuations in the biorthonormal basis associated to the linear operator governing the evolution of fluctuations in the linearized Langevin equations. We obtain general expressions for the squeezing and intensity fluctuations spectra. Then we theoretically study the squeezing properties of a special dissipative structure, namely, the bright cavity soliton. After reviewing our previous result that in the linear approximation there is a perfectly squeezed mode irrespectively of the values of the system parameters, we consider squeezing at the bifurcation points, and the squeezing detection with a plane--wave local oscillator field, taking also into account the effect of the detector size on the level of detectable squeezing.Comment: 10 figure

Generation and manipulation of squeezed states of light in optical networks for quantum communication and computation

We analyze a fiber-optic component which could find multiple uses in novel information-processing systems utilizing squeezed states of light. Our approach is based on the phenomenon of photon-number squeezing of soliton noise after the soliton has propagated through a nonlinear optical fiber. Applications of this component in optical networks for quantum computation and quantum cryptography are discussed.Comment: 12 pages, 2 figures; submitted to Journal of Optics

The Italian research project ROAD-NGN ‘Optical frequency/wavelength division multiple access techniques for next generation networks'

The paper describes the activities of the Italian national research project ROAD-NGN ‘Optical frequency/wavelength division multiple access techniques for next generation networks’; the project aims to investigate and experiment new technological solutions to facilitate the migration of access systems from copper to optical fibre, and to help the integration with broadband wireless architectures, with particular interest for the backhauling of the fourth generation (4G) Long Term Evolution (LTE) networks. The approaches, based on the orthogonal frequency division multiplexing (OFDM) and wavelength division multiplexing (WDM) techniques, can enable the unbundling of the local loop (ULL) and are upgradable toward very ultra wideband systems