DIVERGENCE OF RADIATION TRANSMITTED BY DOUBLY CONNECTED APERTURES WITH ELLIPTIC OR RECTILINEAR CONTOURS.

An analysis is made of a radiator with an aperture which is a doubly connected region with elliptic or rectangular contours that are linked by the scaling transformation. The ratio of the sizes of the outer and inner contours is M greater than 1. A model of an ideal radiator (with a homogeneous distribution of the field over the aperture) is used in a study of the far-field distributions of the intensity and radiation energy. The intensity limits of the divergence angles are established. It is shown that variation of the shape of the aperture involving an increase in the eccentricity of the mutual positions of the contours can result in a considerable (by a factor of nearly 2 if 1 less than M APP 1STH 2) reduction in the divergence of the energy compared with a concentric aperture

Theoretical investigation of controlled generation of a dense attosecond relativistic electron bunch from the interaction of an ultrashort laser pulse with a nanofilm

For controllable generation of an isolated attosecond relativistic electron bunch [relativistic electron mirror (REM)] with nearly solid-state density, we propose using a solid nanofilm illuminated normally by an ultraintense femtosecond laser pulse having a sharp rising edge. With two-dimensional (2D) particle-in-cell (PIC) simulations, we show that, in spite of Coulomb forces, all of the electrons in the laser spot can be accelerated synchronously, and the REM keeps its surface charge density during evolution. We also developed a self-consistent 1D theory, which takes into account Coulomb forces, radiation of the electrons, and laser amplitude depletion. This theory allows us to predict the REM parameters and shows a good agreement with the 2D PIC simulations.open524

Flying mirror model for interaction of a super-intense laser pulse with a thin plasma layer: Transparency and shaping of linearly polarized laser pulses

A self-consistent one-dimensional (1D) flying mirror model is developed for description of an interaction of an ultra-intense laser pulse with a thin plasma layer (foil). In this model, electrons of the foil can have large longitudinal displacements and relativistic longitudinal momenta. An approximate analytical solution for a transmitted field is derived. Transmittance of the foil shows not only a nonlinear dependence on the amplitude of the incident laser pulse, but also time dependence and shape dependence in the high-transparency regime. The results are compared with particle-in-cell (PIC) simulations and a good agreement is ascertained. Shaping of incident laser pulses using the flying mirror model is also considered. It can be used either for removing a prepulse or for reducing the length of a short laser pulse. The parameters of the system for effective shaping are specified. Predictions of the flying mirror model for shaping are compared with the 1D PIC simulations, showing good agreement.open

Flying mirror model for interaction of a super-intense nonadiabatic laser pulse with a thin plasma layer: Dynamics of electrons in a linearly polarized external field

Interaction of a high-power laser pulse having a sharp front with a thin plasma layer is considered. General one-dimensional numerical-analytical model is elaborated, in which the plasma layer is represented as a large collection of electron sheets, and a radiation reaction force is derived analytically. Using this model, trajectories of the electrons of the plasma layer are calculated numerically and compared with the electron trajectories obtained in particle-in-cell simulations, and a good agreement is found. Two simplified analytical models are considered, in which only one electron sheet is used, and it moves transversely and longitudinally in the fields of an ion sheet and a laser pulse (longitudinal displacements along the laser beam axis can be considerably larger than the laser wavelength). In the model I, a radiation reaction is included self-consistently, while in the model II a radiation reaction force is omitted. For the two models, analytical solutions for the dynamical parameters of the electron sheet in a linearly polarized laser pulse are derived and compared with the numerical solutions for the central electron sheet (positioned initially in the center) of the real plasma layer, which are calculated from the general numerical-analytical model. This comparison shows that the model II gives better description for the trajectory of the central electron sheet of the real plasma layer, while the model I gives more adequate description for a transverse momentum. Both models show that if the intensity of the laser pulse is high enough, even in the field with a constant amplitude, the electrons undergo not only the transverse oscillations with the period of the laser field, but also large (in comparison with the laser wavelength) longitudinal oscillations with the period, defined by the system parameters and initial conditions of particular oscillation.open282

The clinical application of electrical impedance technology in the detection of malignant neoplasms: a systematic review

Background: Electrical impedance technology has been well established for the last 20 years. Recently research has begun to emerge into its potential uses in the detection and diagnosis of pre-malignant and malignant conditions. The aim of this study was to systematically review the clinical application of electrical impedance technology in the detection of malignant neoplasms. Methods: A search of Embase Classic, Embase and Medline databases was conducted from 1980 to 22/02/2018 to identify studies reporting on the use of bioimpedance technology in the detection of pre-malignant and malignant conditions. The ability to distinguish between tissue types was defined as the primary endpoint, and other points of interest were also reported. Results: 731 articles were identified, of which 51 reported sufficient data for analysis. These studies covered 16 different cancer subtypes in a total of 7035 patients. As the studies took various formats, a qualitative analysis of each cancer subtype’s data was undertaken. All the studies were able to show differences in electrical impedance and/or related metrics between malignant and normal tissue. Conclusions: Electrical impedance technology provides a novel method for the detection of malignant tissue, with large studies of cervical, prostate, skin and breast cancers showing encouraging results. Whilst these studies provide promising insights into the potential of this technology as an adjunct in screening, diagnosis and intra-operative margin assessment, customised development as well as multi-centre clinical trials need to be conducted before it can be reliably employed in the clinical detection of malignant tissue

DIVERGENCE OF RADIATION TRANSMITTED BY DOUBLY CONNECTED APERTURES WITH ELLIPTIC OR RECTILINEAR CONTOURS.

An analysis is made of a radiator with an aperture which is a doubly connected region with elliptic or rectangular contours that are linked by the scaling transformation. The ratio of the sizes of the outer and inner contours is M greater than 1. A model of an ideal radiator (with a homogeneous distribution of the field over the aperture) is used in a study of the far-field distributions of the intensity and radiation energy. The intensity limits of the divergence angles are established. It is shown that variation of the shape of the aperture involving an increase in the eccentricity of the mutual positions of the contours can result in a considerable (by a factor of nearly 2 if 1 less than M APP 1STH 2) reduction in the divergence of the energy compared with a concentric aperture

DIVERGENCE OF RADIATION TRANSMITTED BY DOUBLY CONNECTED APERTURES WITH ELLIPTIC OR RECTILINEAR CONTOURS.

An analysis is made of a radiator with an aperture which is a doubly connected region with elliptic or rectangular contours that are linked by the scaling transformation. The ratio of the sizes of the outer and inner contours is M greater than 1. A model of an ideal radiator (with a homogeneous distribution of the field over the aperture) is used in a study of the far-field distributions of the intensity and radiation energy. The intensity limits of the divergence angles are established. It is shown that variation of the shape of the aperture involving an increase in the eccentricity of the mutual positions of the contours can result in a considerable (by a factor of nearly 2 if 1 less than M APP 1STH 2) reduction in the divergence of the energy compared with a concentric aperture

DIVERGENCE OF RADIATION TRANSMITTED BY DOUBLY CONNECTED APERTURES WITH ELLIPTIC OR RECTILINEAR CONTOURS.

An analysis is made of a radiator with an aperture which is a doubly connected region with elliptic or rectangular contours that are linked by the scaling transformation. The ratio of the sizes of the outer and inner contours is M greater than 1. A model of an ideal radiator (with a homogeneous distribution of the field over the aperture) is used in a study of the far-field distributions of the intensity and radiation energy. The intensity limits of the divergence angles are established. It is shown that variation of the shape of the aperture involving an increase in the eccentricity of the mutual positions of the contours can result in a considerable (by a factor of nearly 2 if 1 less than M APP 1STH 2) reduction in the divergence of the energy compared with a concentric aperture