An electron bunch passing through a dielectric-lined waveguide generates Čerenkov radiation that can result in a high-peak axial electric field suitable for acceleration of a subsequent bunch. Axial ...fields beyond gigavolt-per-meter are attainable in structures with sub-mm sizes depending on the achievement of suitable electron bunch parameters. A promising configuration consists of using a planar dielectric structure driven by flat electron bunches. In this paper we present a three-dimensional analysis of wakefields produced by flat beams in planar dielectric structures thereby extending the work of Tremaine, Rosenzweig, and Schoessow, Phys. Rev. E 56, 7204 (1997) on the topic. We especially provide closed-form expressions for the normal frequencies and field amplitudes of the excited modes and benchmark these analytical results with finite-difference time-domain particle-in-cell numerical simulations. Finally, we implement a semianalytical algorithm into a popular particle-tracking program thereby enabling start-to-end high-fidelity modeling of linear accelerators based on dielectric-lined planar waveguides.
We report on the successful experimental generation of electron bunches with ramped current profiles. The technique relies on impressing nonlinear correlations in the longitudinal phase space using a ...superconducing radio frequency linear accelerator operating at two frequencies and a current-enhancing dispersive section. The produced ~700-MeV bunches have peak currents of the order of a kilo-Ampère. Data taken for various accelerator settings demonstrate the versatility of the method and, in particular, its ability to produce current profiles that have a quasilinear dependency on the longitudinal (temporal) coordinate. The measured bunch parameters are shown, via numerical simulations, to produce gigavolt-per-meter peak accelerating electric fields with transformer ratios larger than 2 in dielectric-lined waveguides.
Flat beams—beams with asymmetric transverse emittances—have important applications in novel light-source concepts and advanced-acceleration schemes and could possibly alleviate the need for damping ...rings in lepton colliders. Over the last decade, a flat beam generation technique based on the conversion of an angular-momentum-dominated beam was proposed and experimentally tested. In this paper we explore the production of compressed flat beams. We especially investigate and optimize the flat beam transformation for beams with substantial fractional energy spread. We use as a simulation example the photoinjector of Fermilab’s Advanced Superconducting Test Accelerator. The optimizations of the flat beam generation and compression at Advanced Superconducting Test Accelerator were done via start-to-end numerical simulations for bunch charges of 3.2 nC, 1.0 nC, and 20 pC at ∼37MeV . The optimized emittances of flat beams with different bunch charges were found to be 0.25μm (emittance ratio is ∼400 ), 0.13μm , 15 nm before compression, and 0.41μm , 0.20μm , 16 nm after full compression, respectively, with peak currents as high as 5.5 kA for a 3.2−nC flat beam. These parameters are consistent with requirements needed to excite wakefields in asymmetric dielectric-lined waveguides or produce significant photon flux using small-gap micro-undulators.
Experimental results are reported for test beam acceleration and deflection in a two-channel, cm-scale, rectangular dielectric-lined wakefield accelerator structure energized by a 14-MeV drive beam. ...The dominant waveguide mode of the structure is at ∼30GHz , and the structure is configured to exhibit a high transformer ratio (∼12∶1 ). Accelerated bunches in the narrow secondary channel of the structure are continuously energized via Cherenkov radiation that is emitted by a drive bunch moving in the wider primary channel. Observed energy gains and losses, transverse deflections, and changes in the test bunch charge distribution compare favorably with predictions of theory.
Introduction Depression leads to substantial suffering for the patients, their families and becomes an economic burden for system 1,2. Patients and clinicians tend to rate the remission differently ...3. Objectives and methods We investigate if clinicians and patients rate different the treatment response. This study assed the evolution of major depressive episode (MDE) in patients treated with Agomelatine, in Romania. It was designed as a multicentre, observational study that included 1213 adult patients evaluated in 75 sites in 2014. The design included 3 visits (baseline (V1); visit at 2/3 weeks (V2); visit 6/8 weeks (V3)). The scales used were: MADRS, SHAPS, CGI-I, CGI-S, PGI-I, PGI-S. Results The MDE improvement was significant ( P < 0.001) for all aspects evaluated. At baseline, more clinicians vs. patients considered the moderately or markedly ill as best descriptors of the state. The difference between the two assessments was even higher for V2 and V3. During V2 clinicians reported “minimally improvement” while patients reported “much improvement” in higher percentage. During V3, both, clinicians and patients reported a “very much improved” clinical status. Of the patients 42.60% reported at V3 “normal”, not at all ill’ in comparison to 34.81% of clinicians who reported the same ( P < 0.001). Conclusions This could mean that patients are not aware of the severity of their disease. This data could be interpreted in the way that patients are more prone to rate higher the improvements as response to treatment and the clinicians to rate as response a more than 50% decrease of symptomatology. References not available.
We plan to use very small emittance electron beams created from our novel, single tip cathodes to make a channeling-radiation X-ray source for X-ray imaging, especially phase contrast imaging. We ...calculate that we can preserve the electron emittance from the source to the crystal, and focus to a 40nm spot on the crystal face for 40MeV electrons. This yields an X-ray source with good coherence properties. We discuss our plan for experiments at Fermilab with 4.5MeV electrons at the High Brightness Electron Source Laboratory, and with 40MeV electrons at the Advanced Superconducting Test Accelerator. We also present the state of our art with cathode construction and testing. Electrons come from the cathodes by field-emission, with the electric field enhanced by geometric properties of a very small, robust diamond tip. This can create an electron beam with very small emittance. We estimate that the normalized emittance of such a beam at the cathode is 3nmrad. We currently test the cathodes in DC, high-voltage test stands. We will begin experiments placing the cathodes in RF guns in early 2013.
Abstract
Funding Acknowledgements
Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Grant TE 137/2020
Background. In primary mitral regurgitation (PMR) left ...ventricular (LV) remodeling is an adaptive process with prognostic significance.
Aim. To characterize LV deformation parameters related to PMR severity for a better understanding of LV pathophysiology, in patients with mild to severe PMR and preserved LV ejection fraction (EF).
Methods. 48 patients (56 ± 14 years, 42% men) with PMR (mild - 12 patients, moderate - 12 patients, severe - 24 patients) and 50 age and sex matched-controls (56 ± 12 years, 48% men) were analyzed by 2-dimensional speckle-tracking echocardiography (2D STE) for LV endo, mid, and epicardial longitudinal strain (LS); endo, mid, and epicardial circumferential strain (CS); and radial strain (RS). LV volumes and EF, and LA volumes and emptying fraction (EmF) were measured by 3D echocardiography. MR severity was quantified by vena contracta (VC), PISA radius, MR regurgitant volume, and EROA measurements, according to the 2021 ESC guidelines.
Results. 3D LVEF had no significant difference between PMR patients and controls (p= 0.11). From control subjects to mild, moderate, and severe PMR, there was a progressive reduction of LS and RS (Figures 1 and 2), but not of CS. By 2D STE multilayer analysis, when compared to controls, PMR patients had decreased endo-, mid-, and epi-LS (p < 0.04), with a compensatory increase of endo-LS in mild PMR (Figure 2). Basal, middle, and apical segments LS decreased similarly and progressively from control subjects to PMR patients (p < 0.01). In addition, in patients with PMR only LS, but not RS or CS, correlated with MR severity (PISA radius, VC, and MR regurgitant volume: r= -0.43, r= -0.32, r= -0.38, all p < 0.01), and LA function (EmF: r = -0.41, p < 0.01).
Conclusion. When compared to normal subjects, patients with PMR and preserved LVEF have altered LV longitudinal and radial deformation, with preserved circumferential strain. All longitudinal layers and all LV segments were similarly affected. Only longitudinal strain correlates with MR severity and atrial function. Our study suggests that a comprehensive evaluation of the LV deformation should be included in the assessment of patients with PMR, in order to identify early stages of LV dysfunction, starting even from mild MR. Abstract Figure. LV deformation - PMR vs controls Abstract Figure. Multilayer LS in PMR patients
Abstract
RCHOP chemotherapy (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone) in non-Hodgkin's lymphoma (NHL) has a high risk of cardiotoxicity, with increased morbidity and ...mortality.
Aim
To define new parameters, such as 3D LV deformation, arterial stiffness and biomarkers able to detect late cardiotoxicity.
Methods
54 patients (26 men, 57±10 years) with NHL, scheduled to receive RCHOP, with LVEF>50%, were assessed at baseline, after the 4th cycle of RCHOP and 2 years after completion of therapy. Assessment included 3D echocardiography for LV EF and deformation - longitudinal, radial, circumferential, area strain (LS, RS, CS, AS), Arteriograph for pulse wave velocity (PWV) and biomarkers (troponin I, NT-pro-BNP). Cardiotoxicity was defined as a decrease of LVEF <50%, with >10% from the baseline value.
Results
11 patients (group I) developed cardiotoxicity, while 43 patients did not (group II) (LVEF decreased from 59±3 to 56±2 vs 58±3 to 47±2, p<0.0001). From baseline to 2 years there was a significant reduction of LS, CS and AS, and an increase of arterial stiffness and troponin I; however, changes were greater in group I vs group II (p=0.001) (see table). Even if NT-pro-BNP increased from baseline to 2 years, no significant changes were found between group I and II. Decrease of 3D LVEF correlated with changes of LS, AS, PWV, and troponin (r=0.64, r=0.42, r=−0.37 and r=−0.29, p<0.05). LS reduction after the 4th cycle was the best independent predictor for LVEF decrease after 2 years from therapy completion (R2=0.43, p=0.001); thus, decrease of LS with more than 26% after the 4th RCHOP cycle predicted late cardiotoxicity, after 2 years, with a sensitivity of 87% and specificity of 71% (AUC=0.867).
Conclusion
Assessment of 3D myocardial deformation, arterial stiffness and biomarkers is able to detect late cardiovascular toxicity, and to predict further decline of LVEF in patients with NHL. LS is the best independent predictor for late cardiotoxicity.
Funding Acknowledgement
Type of funding sources: None. 123 Cardiovascular toxicity parameters
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