Моделі динаміки пружних збурень у неоднорідно деформованому континуумі

Розвинуто нелінійну теорію пружності стосовно задач томографії тензорних полів у неоднорідно деформованих твердих тілах. За визначальні параметри локального термодинамічного стану, що відповідають процесові деформування, прийнято тензорні характеристики, означені щодо актуальної (деформованої) конфігурації — тензор напружень Коші та міри деформації Альманзі або Фінґера. У рамках запропонованої нелінійної теорії побудовано декілька варіантів системи рівнянь динаміки малих пружних збурень у неоднорідно деформованому твердому континуумі, лінеаризованої стосовно деформації збурення. Коефіцієнти отриманих рівнянь залежать від локальних параметрів початкового напружено-деформованого стану, заданих в актуальній конфігурації. У такому вигляді їх зручно застосовувати для опису хвильових процесів, які збуджують у неоднорідно деформованих тілах, щоб отримати апостеріорну інформацію про актуальний напружено-деформований стан цих об’єктів.A nonlinear theory of elasticity as applied to problems of tensor fields tomography in non-uniformly strained solids has been developed. As constitutive thermodynamic parameters of the theory, corresponding the process of deformation, the tensor characteristics determinate in the actual configuration — tensors Almansi’s and Finger’s have been used. In the frame of the theory several variants of system equations for dynamics of small elastic disturbances in non-uniformly strained continuum, linearized with respect to the amplitude of the disturbance, have been built. These equations coefficients are depended on local parameters of the body stress-strained state, determined in local base of the actual configuration. In such a form they are convenient to use for describing of the wave processes in non-uniformly strained solids activated to obtain some a posteriori information about the actual stress-strained state of such objects.Развита нелинейная теория упругости применительно к задачам томографии тензорных полей в неоднородно деформированных твердых телах. В качестве определяющих параметров локального термодинамического состояния, соответствующих процессу деформирования, приняты тензорные характеристики, определяемые относительно актуальной (деформированной) конфигурации — тензор напряжений Коши и меры деформации Альманзи или Фингера. В рамках предложенной нелинейной теории построено несколько вариантов системы уравнений динамики малых упругих возмущений в неоднородно деформированном твердом континууме, линеаризированной относительно деформации возмущения. Коэффициенты полученных уравнений зависят от локальных параметров напряженно-деформированного состояния, заданных в актуальной конфигурации. В таком виде их удобно применять для описания волновых процессов, которые возбуждают в неоднородно деформированных телах для получения апостериорной информации об актуальном напряженно-деформированном состоянии этих объектов

Characterization of relativistic electron bunch duration and travelling wave structure phase velocity based on momentum spectra measurements on the ARES linac at DESY

The ARES linac at DESY aims to generate and characterize ultrashort electron bunches (fs to sub-fs duration) with high momentum and arrival time stability for the purpose of applications related to accelerator R&D, e.g. development of advanced and compact diagnostics and accelerating structures, test of new accelerator components, medical applications studies, machine learning, etc. During its commissioning phase, the bunch duration characterization of the electron bunches generated at ARES has been performed with an RF-phasing technique relying on momentum spectra measurements, using only common accelerator elements (RF accelerating structures and magnetic spectrometers). The sensitivity of the method allowed highlighting different response times for Mo and Cs2Te cathodes. The measured electron bunch duration in a wide range of machine parameters shows excellent agreement overall with the simulation predictions, thus demonstrating a very good understanding of the ARES operation on the bunch duration aspect. The importance of a precise in-situ experimental determination of the phase velocity of the first travelling wave accelerating structure after the electron source, for which we propose a simple new beam-based method precise down to sub-permille variation respective to the speed of light in vacuum, is emphasized for this purpose. A minimum bunch duration of 20 fs rms, resolution-limited by the space charge forces, is reported. This is, to the best of our knowledge, around 4 times shorter than what has been previously experimentally demonstrated based on RF-phasing techniques with a single RF structure. The present study constitutes a strong basis for future time characterization down to the sub-fs level at ARES, using dedicated X-band transverse deflecting structures.Comment: 17 pages, 11 figures. To be submitted to Physical Review Accelerators and Beam

Hypofractionated image-guided breath-hold SABR (Stereotactic Ablative Body Radiotherapy) of liver metastases - clinical results

Purpose: Stereotactic Ablative Body Radiotherapy (SABR) is a non-invasive therapy option for inoperable liver oligometastases. Outcome and toxicity were retrospectively evaluated in a single-institution patient cohort who had undergone ultrasound-guided breath-hold SABR. Patients and methods: 19 patients with liver metastases of various primary tumors consecutively treated with SABR (image-guidance with stereotactic ultrasound in combination with computer-controlled breath-hold) were analysed regarding overall-survival (OS), progression-free-survival (PFS), progression pattern, local control (LC), acute and late toxicity. Results: PTV (planning target volume)-size was 108 +/- 109cm(3) (median 67.4 cm(3)). BED2 (Biologically effective dose in 2 Gy fraction) was 83.3 +/- 26.2 Gy (median 78 Gy). Median follow-up and median OS were 12 months. Actuarial 2-year-OS-rate was 31%. Median PFS was 4 months, actuarial 1-year-PFS-rate was 20%. Site of first progression was predominantly distant. Regression of irradiated lesions was observed in 84% (median time to detection of regression was 2 months). Actuarial 6-month-LC-rate was 92%, 1- and 2-years-LC-rate 57%, respectively. BED2 influenced LC. When a cut-off of BED2 = 78 Gy was used, the higher BED2 values resulted in improved local control with a statistical trend to significance (p = 0.0999). Larger PTV-sizes, inversely correlated with applied dose, resulted in lower local control, also with a trend to significance (p-value = 0.08) when a volume cut-off of 67 cm(3) was used. No local relapse was observed at PTV-sizes < 67 cm(3) and BED2 > 78 Gy. No acute clinical toxicity > degrees 2 was observed. Late toxicity was also <= degrees 2 with the exception of one gastrointestinal bleeding-episode 1 year post-SABR. A statistically significant elevation in the acute phase was observed for alkaline-phosphatase; in the chronic phase for alkaline-phosphatase, bilirubine, cholinesterase and C-reactive protein. Conclusions: A trend to statistically significant correlation of local progression was observed for BED2 and PTV-size. Dose-levels BED2 > 78 Gy cannot be reached in large lesions constituting a significant fraction of this series. Image-guided SABR (igSABR) is therefore an effective non-invasive treatment modality with low toxicity in patients with small inoperable liver metastases

Nucleon form factors and moments of generalized parton distributions using Nf=2+1+1N_f=2+1+1 twisted mass fermions

Version accepted for publication in Phys. Rev. D. 23 pages, 27 figuresWe present results on the axial and the electromagnetic form factors of the nucleon, as well as, on the first moments of the nucleon generalized parton distributions using maximally twisted mass fermions. We analyze two N_f=2+1+1 ensembles having pion masses of 210 MeV and 354 MeV at two values of the lattice spacing. The lattice scale is determined using the nucleon mass computed on a total of 18 N_f=2+1+1 ensembles generated at three values of the lattice spacing, $a$. The renormalization constants are evaluated non-perturbatively with a perturbative subtraction of ${\cal O}(a^2)$-terms. The moments of the generalized parton distributions are given in the $\bar{\rm MS}$ scheme at a scale of $\mu=2$ GeV. We compare with recent results obtained using different discretization schemes. The implications on the spin content of the nucleon are also discussed

CMR findings in patients with hypertrophic cardiomyopathy and atrial fibrillation

<p>Abstract</p> <p>Objectives</p> <p>We sought to evaluate the relation between atrial fibrillation (AF) and the extent of myocardial scarring together with left ventricular (LV) and atrial parameters assessed by late gadolinium-enhancement (LGE) cardiovascular magnetic resonance (CMR) in patients with hypertrophic cardiomyopathy (HCM).</p> <p>Background</p> <p>AF is the most common arrhythmia in HCM. Myocardial scarring is also identified frequently in HCM. However, the impact of myocardial scarring assessed by LGE CMR on the presence of AF has not been evaluated yet.</p> <p>Methods</p> <p>87 HCM patients underwent LGE CMR, echocardiography and regular ECG recordings. LV function, volumes, myocardial thickness, left atrial (LA) volume and the extent of LGE, were assessed using CMR and correlated to AF. Additionally, the presence of diastolic dysfunction and mitral regurgitation were obtained by echocardiography and also correlated to AF.</p> <p>Results</p> <p>Episodes of AF were documented in 37 patients (42%). Indexed LV volumes and mass were comparable between HCM patients with and without AF. However, indexed LA volume was significantly higher in HCM patients with AF than in HCM patients without AF (68 ± 24 ml·m^-2versus 46 ± 18 ml·m^-2, p = 0.0002, respectively). The mean extent of LGE was higher in HCM patients with AF than those without AF (12.4 ± 14.5% versus 6.0 ± 8.6%, p = 0.02). When adjusting for age, gender and LV mass, LGE and indexed LA volume significantly correlated to AF (r = 0.34, p = 0.02 and r = 0.42, p < 0.001 respectively). By echocardiographic examination, LV diastolic dysfunction was evident in 35 (40%) patients. Mitral regurgitation greater than II was observed in 12 patients (14%). Multivariate analysis demonstrated that LA volume and presence of diastolic dysfunction were the only independent determinant of AF in HCM patients (p = 0.006, p = 0.01 respectively). Receiver operating characteristic curve analysis indicated good predictive performance of LA volume and LGE (AUC = 0.74 and 0.64 respectively) with respect to AF.</p> <p>Conclusion</p> <p>HCM patients with AF display significantly more LGE than HCM patients without AF. However, the extent of LGE is inferior to the LA size for predicting AF prevalence. LA dilation is the strongest determinant of AF in HCM patients, and is related to the extent of LGE in the LV, irrespective of LV mass.</p

Sigma terms and strangeness content of the nucleon with Nf=2+1+1Nf=2+1+1 twisted mass fermions

7 pages, 6 figures. Talk given at the XXX International Symposium on Lattice Field Theory - Lattice 2012, June 24-29, 2012 Cairns, AustraliaWe investigate excited state contaminations in a direct computation of the nucleon $\sigma$-terms. This is an important source of systematic effects that needs to be controlled besides the light quark mass dependence and lattice artefacts. We use maximally twisted mass fermions with dynamical light ($u$,$d$), strange and charm degrees of freedom. Employing an efficient stochastic evaluation of the disconnected contribution available for twisted mass fermions, we show that the effect of excited states is large in particular for the strange $\sigma$-terms, where it can be as big as $O(\gtrsim 40$). This leads to the unfortunate conclusion that even with a source-sink separation of \sim 1.5 \fm and a good statistical accuracy it is not clear, whether excited state effects are under control for this quantity

EXPERIMENTS WITH A FAST CHOPPER SYSTEM FOR INTENSE ION BEAMS

Abstract Chopper systems are used to pulse charged particle beams. In most cases, electric deflection systems are used to generate beam pulses of defined lengths and appropriate repetition rates. At high beam intensities, the field distribution of the chopper system needs to be adapted precisely to the beam dynamics in order to avoid aberrations For the Frankfurt Neutron Source FRAN

Tunable and precise two-bunch generation at FLASHForward

Beam-driven plasma-wakefield acceleration based on external injection has the potential to significantly reduce the size of future accelerators. Stability and quality of the acceleration process substantially depends on the incoming bunch parameters. Precise control of the current profile is essential for optimising energy-transfer efficiency and preserving energy spread. At the FLASHForward facility, driver--witness bunch pairs of adjustable bunch length and separation are generated by a set of collimators in a dispersive section, which enables fs-level control of the longitudinal bunch profile. The design of the collimator apparatus and its commissioning is presented.Comment: 7 pages, 5 figures, to be published in the proceedings of the 4th European Advanced Accelerator Concepts Workshop, 15-21 September 2019, La Biodola Bay, Isola d'Elba, Ital