Spintrapping of intermediateradicals in the solid state gamma radiolysis of perfluoropolyethers

Significant features of the mechanism of the solid state gamma radiolysis of perfluoropolyethers was elecidated by trapping of reactive radicalsintermediates as spin adducts with 2-Methylnitrosopropane (MNP) or in solid matrices at low temperature. Polyethers with repeating units -[(OCF2CF2)x(OCF2)-y]n (A), yield radicals of type ROCF2• and ROCF2CF2•, which are identified from their nitroxyls derivatives. Clear evidence for radical ROCF2• was also obtained from its polycrystalline spectrum. Polyethers of formula -[(OCF2CF(CF3))x-(OCF2)y−]n (B), yield radicals ROCF2Ċ(CF3)-, as major product, togheter with minor amount of ROCF2. The polycrystalline ESR spectrum of the pure compound show the presence of ROCF2• and ROĊF(CF3)- as major products whilst the tertiary radical is not observed. These observations suggest that prominent processes in the radiolysis of A are CC and CO bond homolysis followed by β scission of the resulting a alkoxy radicals. The same type of reaction may be invoqued to rationalize the formation of ROCF2• and ROĊCF(CF3) in the radiolysis of B; however the identification of the tertiary radical implies either the partecipation of a dissociative elctron capture during the irradiation or Fluorine abstraction by primay ROCF2• species during the warm up above 77 K. A slow thermal reaction of MNP with polyethers, yielding nitroxyls, has been observed and it is actually being investigated

The structure of alkoxyfluoroalkyl radicals as studied by M.O. and computer simulation of polycrystalline spectra

A novel approach to the structure of Alkoxyfluoroalkyl radicals (1,2), based on the analysis of the anisotropy of polycrystalline ESR spectra and on M.O. calculations to the INDO level of approximation, is presented. Polymeric primary and secondary perfluoroalkoxyalkyl radicals of type ROCF2· and ROCF(CF3) were prepared by UV photolysis at 77 K of peroxidic perfluoropolyethers (2) and their ESR spectra were analyzed by computer simulation with the spin Hamiltonian (3): A satisfactory computer simulation of ROCF2· polycrystalline spectrum was obtained by assuming a pyramidal structure with a degree of bending of ∼19° and with an axially symmetric h.f. tensor.The ESR spectrum of the ROĊF(CF3)- radicals was accounted for in terms of a pyramidal radical centre with a degree of bending of about 11° and a locked orientation of the CF3 group with a Fluorine in the eclipsed position in respect to the half filled orbital. INDO calculations, performed to match the experimental anisotropic components of the h.f. tensor support the above conclusions and further show that a major contribute (>90%) to the dipolar tensor tij arises from the one-centre integrals of the F-2p orbitals, followed by (<10%) the two-centre integrals related to the u.s. population at the hybrid orbital of the adjacent carbon atom. The coefficients C(2p)=0.33 and C(2s)=0.086 for the Fluorine orbitals in the LCAO of the u. electron M.O. have been obtained, for radicals ROCF2·

Purification of plasmid DNA from clarified and non-clarified Escherichia coli lysates by berenil pseudo-affinity chromatography

In this study, berenil was tested as a ligand, specifically to purify plasmids of different sizes pVAX1-LacZ (6.05 Kbp) and pCAMBIA-1303 (12.361 Kbp) from clarified Escherichia coli alkaline lysates. For this purpose, chromatographic experiments were performed using Sepharose derivatized with berenil. The results showed that both pDNA molecules are completely purified using lower amounts of salt in the eluent than those previously reported for other pseudo-affinity and hydrophobic interaction chromatography based processes. Total retention of all lysate components was achieved with 1.3 M ammonium sulphate in the eluent buffer and pDNA elution was obtained by decreasing the salt concentration to 0.55 M. All impurities were eluted after decreasing the concentration to 0 M. The recovery yield for pCAMBIA-1303 (45%) was lower than that obtained for pVAX1-LacZ (85%), however the larger pDNA showed a higher purity level. Purification of pVAX1-LacZ was also performed using non-clarified E. coli process streams, replacing the clarification step with a second chromatographic run on the berenil-Sepharose. Using the same binding and elution conditions as before, a pure plasmid sample was obtained with a 33% yield and with all host impurity levels in accordance with the requirements established by the regulatory agencies. These results suggest that this chromatographic method is a promising alternative to purify pDNA for therapeutic use.Fundação para a Ciência e Tecnologia (FCT) - PTDC/QUI-QUI/100896/2008, SFRH/BD/64918/200

DUNE Phase II: Scientific Opportunities, Detector Concepts, Technological Solutions

International audienceThe international collaboration designing and constructing the Deep Underground Neutrino Experiment (DUNE) at the Long-Baseline Neutrino Facility (LBNF) has developed a two-phase strategy toward the implementation of this leading-edge, large-scale science project. The 2023 report of the US Particle Physics Project Prioritization Panel (P5) reaffirmed this vision and strongly endorsed DUNE Phase I and Phase II, as did the European Strategy for Particle Physics. While the construction of the DUNE Phase I is well underway, this White Paper focuses on DUNE Phase II planning. DUNE Phase-II consists of a third and fourth far detector (FD) module, an upgraded near detector complex, and an enhanced 2.1 MW beam. The fourth FD module is conceived as a "Module of Opportunity", aimed at expanding the physics opportunities, in addition to supporting the core DUNE science program, with more advanced technologies. This document highlights the increased science opportunities offered by the DUNE Phase II near and far detectors, including long-baseline neutrino oscillation physics, neutrino astrophysics, and physics beyond the standard model. It describes the DUNE Phase II near and far detector technologies and detector design concepts that are currently under consideration. A summary of key R&amp;D goals and prototyping phases needed to realize the Phase II detector technical designs is also provided. DUNE's Phase II detectors, along with the increased beam power, will complete the full scope of DUNE, enabling a multi-decadal program of groundbreaking science with neutrinos

The DUNE Far Detector Vertical Drift Technology. Technical Design Report

DUNE is an international experiment dedicated to addressing some of the questions at the forefront of particle physics and astrophysics, including the mystifying preponderance of matter over antimatter in the early universe. The dual-site experiment will employ an intense neutrino beam focused on a near and a far detector as it aims to determine the neutrino mass hierarchy and to make high-precision measurements of the PMNS matrix parameters, including the CP-violating phase. It will also stand ready to observe supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector implements liquid argon time-projection chamber (LArTPC) technology, and combines the many tens-of-kiloton fiducial mass necessary for rare event searches with the sub-centimeter spatial resolution required to image those events with high precision. The addition of a photon detection system enhances physics capabilities for all DUNE physics drivers and opens prospects for further physics explorations. Given its size, the far detector will be implemented as a set of modules, with LArTPC designs that differ from one another as newer technologies arise. In the vertical drift LArTPC design, a horizontal cathode bisects the detector, creating two stacked drift volumes in which ionization charges drift towards anodes at either the top or bottom. The anodes are composed of perforated PCB layers with conductive strips, enabling reconstruction in 3D. Light-trap-style photon detection modules are placed both on the cryostat's side walls and on the central cathode where they are optically powered. This Technical Design Report describes in detail the technical implementations of each subsystem of this LArTPC that, together with the other far detector modules and the near detector, will enable DUNE to achieve its physics goals