Double Vivaldi antenna for wireless optical networks on chip

In this paper we present a double plasmonic Vivaldi antenna for on-chip optical wireless communication. The proposed antenna is a two-element broadside array fed by a silicon waveguide. The designs of the power splitter and of the hybrid Si-plasmonic coupler used for antenna excitation are described in detail. The array radiation characteristics are optimized through Finite Difference Time Domain simulations and the performance of a point-to-point link is evaluated. The proposed double Vivaldi array increases the gain of 3 dB with respect to a single antenna, improving the received power on a link of 6 dB when the double antenna is used for both transmitting and receiving sections.     

Vertical link solutions for multilayer optical-networks-on-chip topologies

This paper presents two different approaches that may allow the optical interconnection between superposed levels of multilayer photonic circuits as, for example, in optical-networks-on-chip. The first configuration is based on multi-mode interference devices, while the second one exploits multiple stacked directional couplers. The issues concerning the analytical and numerical design of such devices are discussed, together with a performance analysis in terms of efficiency and footprint.     

Broad‐Band Time‐Resolved Near Infrared Spectroscopy in the TJ‐II Stellarator

First experimental results on broad‐band, time‐resolved Near Infrared (NIR;here loosely defined as covering from 750 to 1650 nm) passive spectroscopy using a high sensitivity InGaAs detector are reported for the TJ‐II Stellarator. Experimental set‐up is described together with its main characteristics, the most remarkable ones being its enhanced NIR response, broadband spectrum acquisition in a single shot, and time‐resolved measurements with up to 1.8 kHz spectral rate. Prospects for future work and more extended physics studies in this newly open spectral region in TJ‐II are discussed. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The quest for new mild and selective modifications of natural structures: laccase-catalysed oxidation of ergot alkaloids leads to unexpected stereoselective C-4 hydroxylation

Laccase-catalysed oxidation of ergot alkaloids in the absence of chemical mediators allowed the unexpected isolation of the mono-hydroxylated derivatives of compounds 2-7. Structure determination by NMR techniques clearly indicated that hydroxylation took place at the C-4 benzylic position. Quite notably, the proposed protocol allowed, for the first time, functionalisation at the C-4 position of the ergoline skeleton. Depending on the absence or on the presence of a C-10 α-methoxy substituent, hydroxylation was either stereoselective (furnishing C-4α OH derivatives) or gave rise to a C-4α/C-4β OH mixture in a 2:1 ratio, respectively.     

The low-pressure focal plane detector of the MAGNEX spectrometer

The focal plane detector of the MAGNEX large acceptance magnetic spectrometer is presented. It is based on a large low-pressure gas-filled tracker followed by a wall of silicon detectors to stop the particles. It has been designed for the stringent requirements from the ion optics and the foreseen use with heavy ions. The performances of the device are demonstrated using 4MeV/u oxygen beams. The results of the tests are described and discussed in view of the application of the particle identification and trajectory reconstruction techniques to recover the kinematic properties of the reaction products. They demonstrate the suitability of such detector in a wide range of experiments where low-energy thresholds, large-accepted solid angle, precise momentum measurement and good particle identification are needed.     

Fano varieties of cubic fourfolds containing a plane

We prove that the Fano variety of lines of a generic cubic fourfold containing a plane is isomorphic to a moduli space of twisted stable complexes on a K3 surface. On the other hand, we show that the Fano varieties are always birational to moduli spaces of twisted stable coherent sheaves on a K3 surface. The moduli spaces of complexes and of sheaves are related by wall-crossing in the derived category of twisted sheaves on the corresponding K3 surface.     

1,1‐Di(9‐fluorenyl)­ethanol,a ­by‐­product from the acetyl­ation of 9‐fluorenyl­lithium

Treatment of 9‐fluorenyl­lithium with acetyl chloride produces 9‐acetyl­fluorene, (I), and several by‐products. Among them is a compound unequivocally identified for the first time as the addition product of (I) with 9‐fluorenyl­lithium, 1,1‐di(9‐fluorenyl)­ethanol, C₂₈H₂₂O, (II). The two fluorene‐ring planes of (II) are essentially perpendicular [89.90 (9)°]. A number of intermolecular non‐bonding distances are well within or close to the sum of their respective van der Waals radii and may be responsible for the rarely observed large bowing of one of the fluorene rings. This bowing apparently arises from two mol­ecules impinging on the convex face of the bowed ring, augmented by hydrogen bonding between the peripheral π electrons of the concave face and the hydroxyl H atom of another mol­ecule adjacent to that face.     

On the convergence of the MG/OPT method

Global convergence of the MG/OPT method for optimization is discussed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Zinc Interactions with a Soluble Mutated Rat Amylin to Mimic Whole Human Amylin: An Experimental and Simulation Approach to Understand Stoichiometry,Speciation and Coordination of the Metal Complexes

Islet amyloid polypeptide (IAPP) is a hormone co-secreted with insulin and zinc from pancreatic β-cells. To overcome the low solubility of human IAPP, we characterized zinc complexes species formed with 1) a mutated form of rat-IAPP(1–37; R18 H) able to mimic the human IAPP, 2) the r-IAPP(1–37) and the IAPP(1–8) fragment. Stoichiometry, speciation and coordination features of zinc(II) complexes were unveiled by ESI-MS, potentiometry and NMR measurements combined with DFT and free-energy simulations. Mononuclear species start to form around pH 6; Zn²⁺ binds both His18 and N-amino terminus in rat-IAPP(1–37; R18 H). The in silico study allows us to assess not only a structured turn compact domain in r-IAPP(1–37) and r-IAPP(1–37; R18 H) featured by a different free energy barrier for the transition from the compact to elongated conformation upon the coordination of Zn²⁺, but also to bring into light a coordination shell further stabilized by noncovalent interactions.     

On the Cheney and Sharma Operator

In this paper, we consider the double-indexed Bernstein power series operatorP_{a, t}introduced by Cheney and Sharma and related to the classical Laguerre polynomials. We obtain sharp estimates of the first two moments which allow us to prove that, when acting on a continuous functionf, the convergence ofP_{a, t}ftofis uniform on the whole interval [0, 1]. Moreover, we show that the rates of convergence depend on the way in whicht/agoes to 0. We also show thatP_{a, t}preserves monotonicity and global smoothness. Finally, we consider the monotonicity properties ofP_{a, t}with respect to both parameters. To achieve the mentioned results, we use a probabilistic approach based on the representation of the operator in terms of a suitable multi-indexed stochastic process. The path properties and the martingale-type properties of this process are key points to give short proofs.