112 research outputs found

    Improving proton therapy by metal-containing nanoparticles:Nanoscale insights

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    The use of nanoparticles to enhance the effect of radiation-based cancer treatments is a growing field of study and recently, even nanoparticle-induced improvement of proton therapy performance has been investigated. Aiming at a clinical implementation of this approach, it is essential to characterize the mechanisms underlying the synergistic effects of nanoparticles combined with proton irradiation. In this study, we investigated the effect of platinum- and gadolinium-based nanoparticles on the nanoscale damage induced by a proton beam of therapeutically relevant energy (150 MeV) using plasmid DNA molecular probe. Two conditions of irradiation (0.44 and 3.6 keV/mu m) were considered to mimic the beam properties at the entrance and at the end of the proton track. We demonstrate that the two metal-containing nanoparticles amplify, in particular, the induction of nanosize damages (&gt;2 nm) which are most lethal for cells. More importantly, this effect is even more pronounced at the end of the proton track. This work gives a new insight into the underlying mechanisms on the nanoscale and indicates that the addition of metal-based nanoparticles is a promising strategy not only to increase the cell killing action of fast protons, but also to improve tumor targeting.</p

    Characterization of a Recombinant Adeno-Associated Virus Type 2 Reference Standard Material

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    A recombinant adeno-associated virus serotype 2 Reference Standard Material (rAAV2 RSM) has been produced and characterized with the purpose of providing a reference standard for particle titer, vector genome titer, and infectious titer for AAV2 gene transfer vectors. Production and purification of the reference material were carried out by helper virus–free transient transfection and chromatographic purification. The purified bulk material was vialed, confirmed negative for microbial contamination, and then distributed for characterization along with standard assay protocols and assay reagents to 16 laboratories worldwide. Using statistical transformation and modeling of the raw data, mean titers and confidence intervals were determined for capsid particles ({X}, 9.18 × 1011 particles/ml; 95% confidence interval [CI], 7.89 × 1011 to 1.05 × 1012 particles/ml), vector genomes ({X}, 3.28 × 1010 vector genomes/ml; 95% CI, 2.70 × 1010 to 4.75 × 1010 vector genomes/ml), transducing units ({X}, 5.09 × 108 transducing units/ml; 95% CI, 2.00 × 108 to 9.60 × 108 transducing units/ml), and infectious units ({X}, 4.37 × 109 TCID50 IU/ml; 95% CI, 2.06 × 109 to 9.26 × 109 TCID50 IU/ml). Further analysis confirmed the identity of the reference material as AAV2 and the purity relative to nonvector proteins as greater than 94%. One obvious trend in the quantitative data was the degree of variation between institutions for each assay despite the relatively tight correlation of assay results within an institution. This relatively poor degree of interlaboratory precision and accuracy was apparent even though attempts were made to standardize the assays by providing detailed protocols and common reagents. This is the first time that such variation between laboratories has been thoroughly documented and the findings emphasize the need in the field for universal reference standards. The rAAV2 RSM has been deposited with the American Type Culture Collection and is available to the scientific community to calibrate laboratory-specific internal titer standards. Anticipated uses of the rAAV2 RSM are discussed

    Search for electron antineutrino appearance in a long-baseline muon antineutrino beam

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    Electron antineutrino appearance is measured by the T2K experiment in an accelerator-produced antineutrino beam, using additional neutrino beam operation to constrain parameters of the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixing matrix. T2K observes 15 candidate electron antineutrino events with a background expectation of 9.3 events. Including information from the kinematic distribution of observed events, the hypothesis of no electron antineutrino appearance is disfavored with a significance of 2.40σ and no discrepancy between data and PMNS predictions is found. A complementary analysis that introduces an additional free parameter which allows non-PMNS values of electron neutrino and antineutrino appearance also finds no discrepancy between data and PMNS predictions

    Measurement of neutrino and antineutrino neutral-current quasielasticlike interactions on oxygen by detecting nuclear deexcitation γ rays

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    Neutrino- and antineutrino-oxygen neutral-current quasielastic-like interactions are measured at Super-Kamiokande using nuclear de-excitation γ\gamma-rays to identify signal-like interactions in data from a $14.94 \ (16.35)\times 10^{20}protonsontargetexposureoftheT2Kneutrino(antineutrino)beam.Themeasuredfluxaveragedcrosssectionsonoxygennucleiare protons-on-target exposure of the T2K neutrino (antineutrino) beam. The measured flux-averaged cross sections on oxygen nuclei are \langle \sigma_{\nu {\rm -NCQE}} \rangle = 1.70 \pm 0.17 ({\rm stat.}) ^{+ {\rm 0.51}}_{- {\rm 0.38}} ({\rm syst.}) \times 10^{-38} \ {\rm cm^2/oxygen}withafluxaveragedenergyof0.82GeVand with a flux-averaged energy of 0.82 GeV and \langle \sigma_{\bar{\nu} {\rm -NCQE}} \rangle = 0.98 \pm 0.16 ({\rm stat.}) ^{+ {\rm 0.26}}_{- {\rm 0.19}} ({\rm syst.}) \times 10^{-38} \ {\rm cm^2/oxygen}$ with a flux-averaged energy of 0.68 GeV, for neutrinos and antineutrinos, respectively. These results are the most precise to date, and the antineutrino result is the first cross section measurement of this channel. They are compared with various theoretical predictions. The impact on evaluation of backgrounds to searches for supernova relic neutrinos at present and future water Cherenkov detectors is also discussed

    Contributions from the DISC to accomplish the Aeolus mission objectives

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    The Aeolus Data Innovation and Science Cluster (DISC) supports the Aeolus mission with a wide range of activities from instrument and product quality monitoring over retrieval algorithm improvements to numerical weather prediction (NWP) impact assessments for wind and aerosols. The Aeolus DISC provides support to ESA, Cal/Val teams, numerical weather prediction (NWP) centers, and scientific users for instrument special operations and calibration, for the re-processing of Aeolus products from the past and through the provision of bi-annual updates of the L1A, L1B, L2A and L2B operational processors. The Aeolus DISC is coordinated by DLR with partners from ECMWF, KNMI, Météo-France, TROPOS, DoRIT, ABB, s&t, serco, OLA, Physics Solutions, IB Reissig and Les Myriades involving more than 40 scientists and engineers. The presentation will highlight the Aeolus DISC activities with a focus for the year 2021 and early 2022 since the last Aeolus workshop in November 2020. This covers the evolution of the instrument performance including investigations of the cause of the on-going signal loss and the achieved improvement via dedicated laser tests in 2021. In addition, refinements of algorithms and correction of the wind bias will be discussed - including a known remaining seasonal bias in October and March as encountered during the re-processing campaigns. Finally, the strategy for the on-going and future re-processing campaigns will be addressed to inform the scientific community about the availability and quality of the re-processed data products. The Aeolus mission has fully achieved its mission objectives including the unprecedented demonstration of direct-detection Doppler wind lidar technology and high-power laser operation in space in the ultraviolet spectral region over its planned full mission lifetime of 3 years and 3 months. Aeolus wind products have clearly demonstrated positive impact on forecasts using several NWP models. Since early 2020, and thus only 1.5 years after launch, the Aeolus wind products are used in operation at various NWP centers worldwide. This was achieved even despite the larger than expected wind random errors due to lower initial atmospheric signal levels and the observed signal losses during the operation of the first and second laser. In addition to this incredible success, first scientific studies demonstrated the use of Aeolus for atmospheric dynamics research in the stratosphere and for the analysis of aerosol transport. These achievements of the Aeolus mission and its success were only possible with the essential and critical contributions from the Aeolus DISC. This demonstrates the need and potential for setting up such scientific consortia covering a wide range of expertise from instrument, processors, and scientific use of products for Earth Explorer type missions. The invaluable experience gained by the Aeolus DISC during the more then 3 years of Aeolus mission in orbit (preceded by a period of 20 years before launch by a similar study team) is a pre-requisite for a successful preparation of an operational follow-on Aeolus-2 mission

    Search for light sterile neutrinos with the T2K far detector Super-Kamiokande at a baseline of 295 km

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    We perform a search for light sterile neutrinos using the data from the T2K far detector at a baseline of 295 km, with an exposure of 14.7ð7.6Þ × 1020 protons on target in neutrino (antineutrino) mode. A selection of neutral-current interaction samples is also used to enhance the sensitivity to sterile mixing. No evidence of sterile neutrino mixing in the 3 þ 1 model was found from a simultaneous fit to the charged-current muon, electron and neutral-current neutrino samples. We set the most stringent limit on the sterile oscillation amplitude sin2 θ24 for the sterile neutrino mass splitting Δm241 < 3 × 10−3 eV2=c4

    Measurement of the muon neutrino charged-current cross sections on water, hydrocarbon and iron, and their ratios, with the T2K on-axis detectors

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    We report a measurement of the flux-integrated νμ charged-current cross sections on water, hydrocarbon, and iron in the T2K on-axis neutrino beam with a mean neutrino energy of 1.5 GeV. The measured cross sections on water, hydrocarbon, and iron are σH2OCC=(0.840±0.010(stat.)+0.10−0.08(syst.))×10−38cm2/nucleon, σCHCC=(0.817±0.007(stat.)+0.11−0.08(syst.))×10−38cm2/nucleon, and σFeCC=(0.859±0.003(stat.)+0.12−0.10(syst.))×10−38cm2/nucleon, respectively, for a restricted phase space of induced muons: θμ0.4 GeV/c in the laboratory frame. The measured cross section ratios are σH2OCC/σCHCC=1.028±0.016(stat.)±0.053(syst.)⁠, σFeCC/σH2OCC=1.023±0.012(stat.)±0.058(syst.)⁠, and σFeCC/σCHCC=1.049±0.010(stat.)±0.043(syst.)⁠. These results, with an unprecedented precision for the measurements of neutrino cross sections on water in the studied energy region, show good agreement with the current neutrino interaction models used in the T2K oscillation analyses
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