Borylstannylation of alkynes with inverse regioselectivity: copper-catalyzed three-component coupling using a masked diboron

A variety of terminal alkynes are facilely convertible into cis-boryl(stannyl)alkenes with inverse regioselectivity to those of the previous borylstannylation by the copper-catalyzed three-component reaction using a masked diboron. The synthetic utility of the resulting boryl(stannyl)alkenes has been demonstrated by chemoselective coupling reactions

Visualization and Interpretation of Attosecond Electron Dynamics in Laser-Driven Hydrogen Molecular Ion using Bohmian Trajectories

We analyze the attosecond electron dynamics in hydrogen molecular ion driven by an external intense laser field using ab-initio numerical simulations of the corresponding time-dependent Schr{\"{o}}dinger equation and Bohmian trajectories. To this end, we employ a one-dimensional model of the molecular ion in which the motion of the protons is frozen. The results of the Bohmian trajectory calculations do agree well with those of the ab-initio simulations and clearly visualize the electron transfer between the two protons in the field. In particular, the Bohmian trajectory calculations confirm the recently predicted attosecond transient localization of the electron at one of the protons and the related multiple bunches of the ionization current within a half cycle of the laser field. Further analysis based on the quantum trajectories shows that the electron dynamics in the molecular ion can be understood via the phase difference accumulated between the Coulomb wells at the two protons. Modeling of the dynamics using a simple two-state system leads us to an explanation for the sometimes counter-intuitive dynamics of an electron opposing the classical force of the electric field on the electron.Comment: 8 pages, 6 figures. The following article has been submitted to The Journal of Chemical Physics. After it is published, it will be found at http://jcp.aip.org

Fast Purcell-enhanced single photon source in 1,550-nm telecom band from a resonant quantum dot-cavity coupling

High-bit-rate nanocavity-based single photon sources in the 1,550-nm telecom band are challenges facing the development of fibre-based long-haul quantum communication networks. Here we report a very fast single photon source in the 1,550-nm telecom band, which is achieved by a large Purcell enhancement that results from the coupling of a single InAs quantum dot and an InP photonic crystal nanocavity. At a resonance, the spontaneous emission rate was enhanced by a factor of 5 resulting a record fast emission lifetime of 0.2 ns at 1,550 nm. We also demonstrate that this emission exhibits an enhanced anti-bunching dip. This is the first realization of nanocavity-enhanced single photon emitters in the 1,550-nm telecom band. This coupled quantum dot cavity system in the telecom band thus provides a bright high-bit-rate non-classical single photon source that offers appealing novel opportunities for the development of a long-haul quantum telecommunication system via optical fibres.Comment: 16 pages, 4 figure

Polycation-siRNA nanoparticles can disassemble at the kidney glomerular basement membrane

Despite being engineered to avoid renal clearance, many cationic polymer (polycation)-based siRNA nanoparticles that are used for systemic delivery are rapidly eliminated from the circulation. Here, we show that a component of the renal filtration barrier—the glomerular basement membrane (GBM)—can disassemble cationic cyclodextrin-containing polymer (CDP)-based siRNA nanoparticles and, thereby, facilitate their rapid elimination from circulation. Using confocal and electron microscopies, positron emission tomography, and compartment modeling, we demonstrate that siRNA nanoparticles, but not free siRNA, accumulate and disassemble in the GBM. We also confirm that the siRNA nanoparticles do not disassemble in blood plasma in vitro and in vivo. This clearance mechanism may affect any nanoparticles that assemble primarily by electrostatic interactions between cationic delivery components and anionic nucleic acids (or other therapeutic entities)

Measurement of the double-\beta decay half-life of ^{136}Xe with the KamLAND-Zen experiment

We present results from the KamLAND-Zen double-beta decay experiment based on an exposure of 77.6 days with 129 kg of $^{136}$Xe. The measured two-neutrino double-beta decay half-life of $^{136}$Xe is $T_{1/2}^{2\nu} = 2.38 \pm 0.02(stat) \pm 0.14(syst) \times 10^{21}$ yr, consistent with a recent measurement by EXO-200. We also obtain a lower limit for the neutrinoless double-beta decay half-life, $T_{1/2}^{0\nu} > 5.7 \times 10^{24}$ yr at 90% confidence level (C.L.), which corresponds to almost a five-fold improvement over previous limits.Comment: 6 pages, 4 figures. Version as published in PR

Measurement of 1.7 to 74 MeV polarised gamma rays with the HARPO TPC

Current {\gamma}-ray telescopes based on photon conversions to electron-positron pairs, such as Fermi, use tungsten converters. They suffer of limited angular resolution at low energies, and their sensitivity drops below 1 GeV. The low multiple scattering in a gaseous detector gives access to higher angular resolution in the MeV-GeV range, and to the linear polarisation of the photons through the azimuthal angle of the electron-positron pair. HARPO is an R&D program to characterise the operation of a TPC (Time Projection Chamber) as a high angular-resolution and sensitivity telescope and polarimeter for {\gamma} rays from cosmic sources. It represents a first step towards a future space instrument. A 30 cm cubic TPC demonstrator was built, and filled with 2 bar argon-based gas. It was put in a polarised {\gamma}-ray beam at the NewSUBARU accelerator in Japan in November 2014. Data were taken at different photon energies from 1.7 MeV to 74 MeV, and with different polarisation configurations. The electronics setup is described, with an emphasis on the trigger system. The event reconstruction algorithm is quickly described, and preliminary measurements of the polarisation of 11 MeVphotons are shown.Comment: Proceedings VCI201