Generation and intramolecular reactivity of acyl radicals from alkynylthiol esters under reducing tin-free conditions

[reaction: see text] The radical chain reaction of benzenethiol with alkynylthiol esters provides a new, valuable protocol for the tin-free generation of acyl radicals that arise from intramolecular substitution at sulfur by the initial sulfanylvinyl radicals.     

A Converse Hawking-Unruh Effect and dS<Superscript>2</Superscript>/CFT Correspondence

Given a local quantum field theory net $ \mathcal{A} $ on the de Sitter spacetime dS ^d , where geodesic observers are thermalized at Gibbons-Hawking temperature, we look for observers that feel to be in a ground state, i.e., particle evolutions with positive generator, providing a sort of converse to the Hawking-Unruh effect. Such positive energy evolutions always exist as noncommutative flows, but have only a partial geometric meaning, yet they map localized observables into localized observables. We characterize the local conformal nets on dS ^d . Only in this case our positive energy evolutions have a complete geometrical meaning. We show that each net has a unique maximal expected conformal subnet, where our evolutions are thus geometrical. In the two-dimensional case, we construct a holographic one-to-one correspondence between local nets $ \mathcal{A} $ on dS ² and local conformal non-isotonic families (pseudonets) $ \mathcal{B} $ on S ¹. The pseudonet $ \mathcal{B} $ gives rise to two local conformal nets $ \mathcal{B}_\pm $ on S ¹, that correspond to the $ \frak{H}_\pm $ horizon components of $ \mathcal{A} $, and to the chiral components of the maximal conformal subnet of $ \mathcal{A} $. In particular, $ \mathcal{A} $ is holographically reconstructed by a single horizon component, namely the pseudonet is a net, iff the translations on $ \frak{H}_\pm $ have positive energy and the translations on $ \frak{H}_\mp $ are trivial. This is the case iff the one-parameter unitary group implementing rotations on dS ² has positive/negative generator. Communicated by Klaus Fredenhagen submitted 07/02/03, accepted: 07/07/03     

Enhanced nonlinear effects in pulse propagation through epsilon‐near‐zero media

In recent years, unconventional metamaterial properties have triggered a revolution of electromagnetic research which has unveiled novel scenarios of wave‐matter interaction. A very small dielectric permittivity is a leading example of such unusual features, since it produces an exotic static‐like regime where the electromagnetic field is spatially slowly‐varying over a physically large region. The so‐called epsilon‐near‐zero metamaterials thus offer an ideal platform where to manipulate the inner details of the “stretched” field. Here we theoretically prove that a standard nonlinearity is able to operate such a manipulation to the point that even a thin slab produces a dramatic nonlinear pulse transformation, if the dielectric permittivity is very small within the field bandwidth. The predicted non‐resonant releasing of full nonlinear coupling produced by the epsilon‐near‐zero condition does not resort to any field enhancement mechanism and opens novel routes to exploiting matter nonlinearity for steering the radiation by means of ultra‐compact structures.

     

"Supramolecular" assembly of gold nanorods end-terminated with polymer "pom-poms": effect of pom-pom structure on the association modes

We report a predefined self-organization of gold nanorods (NRs) end-terminated with multiple polymer arms ("pom-poms") in higher-order structures. The assembly of polymer-tethered NRs was controlled by changing the structure of the polymer pom-poms. We show that the variation in the molecular weight of the polymer molecules and their relative location with respect to the long side of the NRs resulted in two competing association modes of the nanorods, that is, their side-by-side and end-to-end assembly, and produced bundles, chains, rings, and bundled chains of the NRs. The superposition of the two variables controlling the organization of NRs allowed us to create a map showing the variation in the longitudinal plasmonic bands of the NRs achieved by their self-assembly.     

Design and performance of BOREAS,the beamline for resonant X‐ray absorption and scattering experiments at the ALBA synchrotron light source

The optical design of the BOREAS beamline operating at the ALBA synchrotron radiation facility is described. BOREAS is dedicated to resonant X‐ray absorption and scattering experiments using soft X‐rays, in an unusually extended photon energy range from 80 to above 4000 eV, and with full polarization control. Its optical scheme includes a fixed‐included‐angle, variable‐line‐spacing grating monochromator and a pair of refocusing mirrors, equipped with benders, in a Kirkpatrick–Baez arrangement. It is equipped with two end‐stations, one for X‐ray magnetic circular dichroism and the other for resonant magnetic scattering. The commissioning results show that the expected beamline performance is achieved both in terms of energy resolution and of photon flux at the sample position.     

<Emphasis Type="Italic">ABCD</Emphasis>-<Emphasis Type="Italic">Tool</Emphasis>, a software suite for the analysis of α/β spectra from liquid scintillation counting

This paper presents the alpha/beta complete deconvolution tool (ABCD-Tool), a C++ application for the analysis of spectra from liquid scintillation counting (LSC) measurements. In addition to the basic algorithms for standard gross alpha/beta analysis and the determination of the counting efficiency, the software implements a recent unfolding technique based on Fourier transforms, which gives precise and reliable results even in the case of complex, strongly overlapping spectra. The application is designed to be used with alpha/beta spectra generated from Perkin Elmer Wallac Quantulus 1220. However, future upgrades are scheduled in order to extend the compatibility to spectra from other LSC instruments in commerce.     

Polymeric photoinitiators based on side-chain benzoin methyl ether and tertiary amine moieties for fast UV curable coatings

The synthesis is reported of a new series of polymeric photoinitiators obtained by copolymerization of a-methylolbenzoin methyl ether acrylate (MBA) with different N,N-dialkylamino alkyl acrylates. The copolymers have been fully characterized and employed in the photoinitiated polymerization and crosslinking reactions of a standard acrylic formulation for clear curable coatings. The photoinitiation activity of the above systems has been measured by using microwave dielectrometry and differential photocalorimetry, and compared with that found for the corresponding low-molecular-weight models. The results clearly indicate that the copolymeric systems display a remarkable decrease of the induction period and an improved overall activity in the UV curing of the acrylic coatings. An interpretation of the experimental findings is also reported.