New electron source concept for single-shot sub-100 fs electron diffraction in the 100 keV range

We present a method for producing sub-100 fs electron bunches that are suitable for single-shot ultrafast electron diffraction experiments in the 100 keV energy range. A combination of analytical results and state-of-the-art numerical simulations show that it is possible to create 100 keV, 0.1 pC, 20 fs electron bunches with a spotsize smaller than 500 micron and a transverse coherence length of 3 nm, using established technologies in a table-top set-up. The system operates in the space-charge dominated regime to produce energy-correlated bunches that are recompressed by established radio-frequency techniques. With this approach we overcome the Coulomb expansion of the bunch, providing an entirely new ultrafast electron diffraction source concept

Concept of a laser-plasma based electron source for sub-10 fs electron diffraction

We propose a new concept of an electron source for ultrafast electron diffraction with sub-10~fs temporal resolution. Electrons are generated in a laser-plasma accelerator, able to deliver femtosecond electron bunches at 5 MeV energy with kHz repetition rate. The possibility of producing this electron source is demonstrated using Particle-In-Cell simulations. We then use particle tracking simulations to show that this electron beam can be transported and manipulated in a realistic beamline, in order to reach parameters suitable for electron diffraction. The beamline consists of realistic static magnetic optics and introduces no temporal jitter. We demonstrate numerically that electron bunches with 5~fs duration and containing 1.5~fC per bunch can be produced, with a transverse coherence length exceeding 2~nm, as required for electron diffraction

Compression of sub-relativistic space-charge-dominated electron bunches for single-shot femtosecond electron diffraction

We demonstrate compression of 95 keV, space-charge-dominated electron bunches to sub-100 fs durations. These bunches have sufficient charge (200 fC) and are of sufficient quality to capture a diffraction pattern with a single shot, which we demonstrate by a diffraction experiment on a polycrystalline gold foil. Compression is realized by means of velocity bunching as a result of a velocity chirp, induced by the oscillatory longitudinal electric field of a 3 GHz radio-frequency cavity. The arrival time jitter is measured to be 80 fs

Detecting multivariate interactions in spatial point patterns with Gibbs models and variable selection

We propose a method for detecting significant interactions in very large multivariate spatial point patterns. This methodology develops high dimensional data understanding in the point process setting. The method is based on modelling the patterns using a flexible Gibbs point process model to directly characterise point-to-point interactions at different spatial scales. By using the Gibbs framework significant interactions can also be captured at small scales. Subsequently, the Gibbs point process is fitted using a pseudo-likelihood approximation, and we select significant interactions automatically using the group lasso penalty with this likelihood approximation. Thus we estimate the multivariate interactions stably even in this setting. We demonstrate the feasibility of the method with a simulation study and show its power by applying it to a large and complex rainforest plant population data set of 83 species

Prognostic factors associated with a restricted mouth opening (trismus) in patients with head and neck cancer:Systematic review

BACKGROUND: To prescribe early trismus therapy, prognostic factors influencing the restricted mouth opening should be identified first. Our aim is to present an overview of these factors in patients with head and neck cancer. METHODS: PubMed, Cochrane, EMBASE, and CINAHL were searched using terms related to head and neck cancer and mouth opening. Risk of bias was assessed using the "Quality in Prognosis Studies" tool. A best evidence synthesis was performed. RESULTS: Of the identified 1418 studies, 53 were included. Three studies contained a prognostic multivariate model for a restricted mouth opening. CONCLUSIONS: Patients with head and neck cancer will most likely develop a restricted mouth opening when they have a large tumor near the masticatory muscles that requires extensive cancer treatment. A restricted mouth opening most likely occurs within 6 months after cancer treatment. Further research is necessary on factors related to healing tendency or pain intensity

Simulating Electron Impact Ionization Using a General Particle Tracer (GPT) Custom Element

A new C++ custom element has been developed with the framework of General Particle Tracer (GPT) to simulate electron impact ionization of residual gas molecules. The custom element uses Monte-Carlo routines to determine both the ion production rate and the secondary electron kinetic energy based on user-defined gas densities and theoretical values for the ionization cross section and the secondary electron differential cross section. It then uses relativistic kinematics to track the secondary electron, the scattered electron, and the newly formed ion after ionization. The ion production rate and the secondary electron energy distribution determined by the custom element have been benchmarked against theoretical calculations and against simulations made using the simulation package IBSimu. While the custom element was originally built for particle accelerator simulations, it is readily extensible to other applications. The custom element will be described in detail and examples of applications at the Thomas Jefferson National Accelerator Facility will be presented for ion production in a DC high voltage photo-gun

Criterion for trismus in head and neck cancer patients:a verification study

Several cut-off points for trismus in head and neck cancer patients have been used. A mouth opening of 35 mm or less is most frequently used as cut-off point. Due to the variation in cut-off points, prevalence, risk factors and treatment outcomes of trismus cannot be studied in a uniform manner. To provide uniformity, we aimed to verify the cut-off point of 35 mm or less. Additionally, we aimed to determine associated covariates with reported difficulties when opening the mouth

Indole-3-thio­uronium nitrate

In the title compound, C9H10N3S+·NO3 −, the indole ring system and the thiouronium group are nearly perpendicular, with a dihedral angle of 88.62 (6)°. Hydrogen bonding generates two-dimensional networks which are linked to each other via π stacking inter­actions of the indole groups [average inter-planar ring–ring distance of 3.449 (2) Å]