Synthesis of Propylene Oxide – Styrene Copolymers

The copolymerization of propylene oxide (PO) with styrene (St) catalyzed by Maghnite-H+ (Mag-H+) was investigated. Mag-H+, a nontoxic catalyst for cationic polymerization of vinylic and heterocyclic monomers, is a montmorillonite silicate sheet clay. This catalyst was prepared through a straight forward proton exchange process. It was found that Mag-H+ initiates the copolymerization in bulk at room temperature. Various techniques, including H1NMR, 13C-NMR, FT-IR spectroscopy, and Ubbelohde viscometer, were used to elucidate the resulting copolymers' structural characteristics. The effects of the amount of Mag-H+ and propylene oxide were studied. The yield of copolymerization depends on the amount of Mag-H+ used and the reaction time.

Fast simulation of Time-of-Flight detectors at the LHC

The modelling of Cherenkov based detectors is traditionally done using Geant4 toolkit. In this work, we present another method based on Python programming language and Numba high performance compiler to speed up the simulation. As an example we take one of the Forward Proton Detectors at the CERN LHC - ATLAS Forward Proton (AFP) Time-of-Flight, which is used to reduce the background from multiple proton-proton collisions in soft and hard diffiractive events. We describe the technical details of the fast Cherenkov model of photon generation and transportation through the optical part of the ToF detector. The fast simulation is revealed to be about 200 times faster than the corresponding Geant4 simulation, and provides similar results concerning length and time distributions of photons. The study is meant as the first step in a construction of a building kit allowing creation of a fast simulation of an arbitrary shaped optical part of detectors.

Central exclusive production of W boson pairs in pp collisions at the LHC in hadronic and semi-leptonic final states

We present a phenomenology study on central exclusive production of W+W− boson pairs in proton-proton collisions at the Large Hadron Collider at 14 TeV using the forward proton detectors, such as the ATLAS Forward Proton or the CMS-TOTEM Precision Proton Spectrometer detectors. Final states where at least one of the W bosons decay hadronically in a large-radius jet are considered. The latter extends previous efforts that consider solely leptonic final states. A measurement of exclusive W+W− also allows us to further constrain anomalous quartic gauge boson interactions between photons and W bosons. Expected limits on anomalous quartic gauge couplings $$ {a}_{0,C}^W $$ a 0 , C W associated to dimension-six effective operators are derived for the hadronic, semi-leptonic, and leptonic final states. It is found that the couplings can be probed down to one-dimensional values of $$ {a}_0^W=3.7\times {10}^{-7}{\mathrm{GeV}}^{-2} $$ a 0 W = 3.7 × 10 − 7 GeV − 2 and $$ {a}_C^W=9.2\times {10}^{-7}{\mathrm{GeV}}^{-7} $$ a C W = 9.2 × 10 − 7 GeV − 7 at 95% CL at an integrated luminosity of 300 fb−1 by combining all final states, compared to values of about $$ {a}_0^W=4\times {10}^{-6}{\mathrm{GeV}}^{-2} $$ a 0 W = 4 × 10 − 6 GeV − 2 and $$ {a}_C^W=1\times {10}^{-5}{\mathrm{GeV}}^{-2} $$ a C W = 1 × 10 − 5 GeV − 2 at 95% CL expected for the leptonic channel alone.

Formation of an unusual glutamine tautomer in a blue light using flavin photocycle characterizes the light-adapted state

Blue light using flavin (BLUF) photoreceptor proteins are critical for many light-activated biological processes and are promising candidates for optogenetics because of their modular nature and long-range signaling capabilities. Although the photocycle of the Slr1694 BLUF domain has been characterized experimentally, the identity of the light-adapted state following photoexcitation of the bound flavin remains elusive. Herein hybrid quantum mechanical/molecular mechanical (QM/MM) molecular dynamics simulations of this photocycle provide a nonequilibrium dynamical picture of a possible mechanism for the formation of the light-adapted state. Photoexcitation of the flavin induces a forward proton-coupled electron transfer (PCET) process that leads to the formation of an imidic acid tautomer of Gln50. The calculations herein show that the subsequent rotation of Gln50 allows a reverse PCET process that retains this tautomeric form. In the resulting purported light-adapted state, the glutamine tautomer forms a hydrogen bond with the flavin carbonyl group. Additional ensemble-averaged QM/MM calculations of the dark-adapted and purported light-adapted states demonstrate that the light-adapted state with the imidic acid glutamine tautomer reproduces the experimentally observed spectroscopic signatures. Specifically, the calculations reproduce the red shifts in the flavin electronic absorption and carbonyl stretch infrared spectra in the light-adapted state. Further hydrogen-bonding analyses suggest the formation of hydrogen-bonding interactions between the flavin and Arg65 in the light-adapted state, providing a plausible explanation for the experimental observation of faster photoinduced PCET in this state. These characteristics of the light-adapted state may also be essential for the long-range signaling capabilities of this photoreceptor protein.