444 research outputs found

    A Measurement of the Interference Structure Function, R_LT, for the 12C(e,e'p) reaction in the Quasielastic Region

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    The coincidence cross-section and the interference structure function, R_LT, were measured for the 12C(e,e'p) 11B reaction at quasielastic kinematics and central momentum transfer of q=400 MeV/c. The measurement was at an opening angle of theta_pq=11 degrees, covering a range in missing energy of E_m = 0 to 65 MeV. The R_LT structure function is found to be consistent with zero for E_m > 50 MeV, confirming an earlier study which indicated that R_L vanishes in this region. The integrated strengths of the p- and s-shell are compared with a Distorted Wave Impulse Approximation calculation. The s-shell strength and shape are compared with a Hartree Fock-Random Phase Approximation calculation. The DWIA calculation overestimates the cross sections for p- and s-shell proton knockout as expected, but surprisingly agrees with the extracted R_LT value for both shells. The HF-RPA calculation describes the data more consistently, which may be due to the inclusion of 2-body currents in this calculation.Comment: 8 Pages LaTex, 5 postscript figures. Submitted to Phys. Rev.

    Exponential Distribution of Locomotion Activity in Cell Cultures

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    In vitro velocities of several cell types have been measured using computer controlled video microscopy, which allowed to record the cells' trajectories over several days. On the basis of our large data sets we show that the locomotion activity displays a universal exponential distribution. Thus, motion resulting from complex cellular processes can be well described by an unexpected, but very simple distribution function. A simple phenomenological model based on the interaction of various cellular processes and finite ATP production rate is proposed to explain these experimental results.Comment: 4 pages, 3 figure

    Relativistic effects and two-body currents in 2H(e⃗,eâ€Čp)n^{2}H(\vec{e},e^{\prime}p)n using out-of-plane detection

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    Measurements of the 2H(e⃗,eâ€Čp)n{^2}H(\vec{e},e^{\prime}p)n reaction were performed using an 800-MeV polarized electron beam at the MIT-Bates Linear Accelerator and with the out-of-plane magnetic spectrometers (OOPS). The longitudinal-transverse, fLTf_{LT} and fLTâ€Čf_{LT}^{\prime}, and the transverse-transverse, fTTf_{TT}, interference responses at a missing momentum of 210 MeV/c were simultaneously extracted in the dip region at Q2^2=0.15 (GeV/c)2^2. On comparison to models of deuteron electrodisintegration, the data clearly reveal strong effects of relativity and final-state interactions, and the importance of the two-body meson-exchange currents and isobar configurations. We demonstrate that these effects can be disentangled and studied by extracting the interference response functions using the novel out-of-plane technique.Comment: 4 pages, 4 figures, and submitted to PRL for publicatio

    Radiotherapy quality assurance in paediatric clinical trials: first report from six QUARTET-affiliated trials

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    Background and Purpose: SIOP Europe's QUARTET project launched in 2016; aiming to improve access to high-quality radiotherapy for children and adolescents treated within clinical trials across Europe. The aim of this report is to present the profile of institutions participating in six QUARTET-affiliated trials and a description of the initial individual case review (ICR) outcomes. Methods: This is a two-part analysis. Firstly, using facility questionnaires, beam output audit certificates, and advanced technique credentialing records to create a profile of approved institutions, and secondly, collating trial records for ICRs submitted prior to 31/10/2022. Trials included are: SIOPEN HR-NBL1, SIOPEN-LINES, SIOPEN- VERITAS, SIOP-BTG HRMB, EpSSG-FaR-RMS, and SIOPEN HR-NBL2. Results: By 31/10/2022, a total of 103 institutions had commenced QUARTET site approval procedures to participate in QUARTET-affiliated trials; 66 sites across 20 countries were approved. These participating institutions were often paediatric referral sites with intensity modulated radiotherapy or proton beam therapy, designated paediatric radiation oncologists, and paediatric adapted facilities and imaging protocols available. In total, 263 patient plans were submitted for ICR, 254 ICRs from 15 countries were completed. ICRs had a rejection rate of 39.8%, taking an average of 1.4 submissions until approval was achieved. Target delineation was the most frequent reason for rejection. Conclusion: The QUARTET facility questionnaire is a valuable tool for mapping resources, personnel, and technology available to children and adolescents receiving radiotherapy. Prospective ICR is essential for paediatric oncology clinical trials and should be prioritised to reduce protocol violations

    Non-parameningeal head and neck rhabdomyosarcoma in children, adolescents, and young adults: Experience of the European paediatric Soft tissue sarcoma Study Group (EpSSG) – RMS2005 study

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    BACKGROUND/OBJECTIVES: The primary aim of this study was to analyse and evaluate the impact of different local treatments on the pattern of relapse in children with primary head and neck non-parameningeal (HNnPM) rhabdomyosarcoma (RMS), treated in the European paediatric Soft tissue sarcoma Study Group (EpSSG) RMS2005 study. The secondary aim was to assess whether current risk stratification is valid for this specific site. DESIGN/METHODS: This study includes all patients with localised HNnPM RMS enrolled in the RMS2005 study between 2005 and 2016. Treatment comprised chemotherapy adapted to risk group, with local surgery and/or radiation therapy. The main outcome measures were event-free survival (EFS) and overall survival (OS). RESULTS: A total of 165 patients were identified; the median age was 6.4 years (range, 0.1–25). The most common tumour sites were cheek/chin (22%) and nasal ala/nasolabial fold (20%). Histology was unfavourable for 40%, and regional nodal involvement present in 26%. Local therapy included surgery (58%) and/or radiotherapy (72%) to primary tumour and/or regional lymph nodes. After a median follow-up of 66 months (range, 6–158), 42 patients experienced an event, and 17 are still alive. Tumour events were frequent in oral primary (36%), parotid site (26%), cheek/chin (24%), and nasal ala/nasolabial fold (24%) and included locoregional failure in 84% of cases. The 5-year EFS and OS were 75% (95% confidence interval [CI]: 67.3–81.2) and 84.9% (95% CI: 77.5–89.7), respectively. Favourable histology was associated with a better EFS (82.3% versus 64.6%; p = 0.02) and nodal spread with a worse OS (88.6% versus 76.1%; p = 0.04). Different sublocations within the HNnPM primary did not have significant impact on outcome. CONCLUSION: Locoregional relapse/progression is the main tumour failure event in this site. Despite frequent unfavourable risk factors, HNnPM RMS remains a favourable location in the context of a risk-adapted strategy

    Meson Exchange Currents in (e,e'p) recoil polarization observables

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    A study of the effects of meson-exchange currents and isobar configurations in A(e⃗,eâ€Čp⃗)BA(\vec{e},e'\vec{p})B reactions is presented. We use a distorted wave impulse approximation (DWIA) model where final-state interactions are treated through a phenomenological optical potential. The model includes relativistic corrections in the kinematics and in the electromagnetic one- and two-body currents. The full set of polarized response functions is analyzed, as well as the transferred polarization asymmetry. Results are presented for proton knock-out from closed-shell nuclei, for moderate to high momentum transfer.Comment: 44 pages, 18 figures. Added physical arguments explaining the dominance of OB over MEC, and a summary of differences with previous MEC calculations. To be published in PR

    Measurement of the Transverse-Longitudinal Cross Sections in the p (e,e'p)pi0 Reaction in the Delta Region

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    Accurate measurements of the p(e,e?p)pi0 reaction were performed at Q^2=0.127(GeV/c)^2 in the Delta resonance energy region. The experiments at the MIT-Bates Linear Accelerator used an 820 MeV polarized electron beam with the out of plane magnetic spectrometer system (OOPS). In this paper we report the first simultaneous determination of both the TL and TL? (``fifth" or polarized) cross sections at low Q^{2} where the pion cloud contribution dominates the quadrupole amplitudes (E2 and C2). The real and imaginary parts of the transverse-longitudinal cross section provide both a sensitive determination of the Coulomb quadrupole amplitude and a test of reaction calculations. Comparisons with model calculations are presented. The empirical MAID calculation gives the best overall agreement with this accurate data. The parameters of this model for the values of the resonant multipoles are |M_{1+}(I=3/2)|= (40.9 \pm 0.3)10^{-3}/m_pi, CMR= C2/M1= -6.5 \pm 0.3%, EMR=E2/M1=-2.2 \pm 0.9%, where the errors are due to the experimental uncertainties.Comment: 10 pages, 3 figures, minor corrections and addition
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