A miniature, directional fibre-optic acoustic source is presented that employs geometrical focussing to generate a nearly-collimated acoustic pencil beam. When paired with a fibre-optic acoustic detector, an all-optical ultrasound probe with an outer diameter of 2.5 mm is obtained that acquires a pulse-echo image line at each probe position without the need for image reconstruction. B-mode imag...

We study the effect of the non-Gaussian clustering of galaxies on the statistics of pencil beam surveys. We find that the higher order moments of the galaxy distribution play an important role in the probability distribution for the power spectrum peaks. Taking into account the observed values for the kurtosis of galaxy distribution we derive the general probability distribution for the power s...

We create mock pencil-beam redshift surveys from very large cosmological N -body simulations of two Cold Dark Matter cosmogonies, an Einstein-de Sitter model (τCDM) and a flat model with Ω0 = 0.3 and a cosmological constant (ΛCDM). We use these to assess the significance of the apparent periodicity discovered by Broadhurst et al. (1990). Simulation particles are tagged as ‘galaxies’ so as to re...

Scatterometers are remote sensing radars designed to measure near-surface winds over the ocean. The difficulties of accommodating traditional fan-beam scatterometers on spacecraft has lead to the development of a scanning pencilbeam instrument known as SeaWinds. SeaWinds will be part of the Japanese Advanced Earth Observing Satellite II (ADEOSII) to be launched in 1999. To analyze the performan...

The fields produced by a long beam with a given transverse charge distribution in a homogeneous vacuum chamber are studied. Signals induced by the displaced finitesize beam on electrodes of a beam position monitor (BPM) are calculated and compared to those from a pencil beam. The non-linearities and corrections to BPM signals due to a finite transverse beam size are calculated for an arbitrary ...

BACKGROUND AND PURPOSE MR imaging is currently not used to evaluate CSF flow changes due to short-lasting physiological maneuvers. The purpose of this study was to evaluate the ability of MR imaging to assess the CSF flow response to a Valsalva maneuver in healthy participants. MATERIALS AND METHODS A cardiac-gated fast cine-PC sequence with ≤15-second acquisition time was used to assess CSF ...

Scanned carbon ion radiotherapy beams provide highly conformal dose distributions for stationary tumors and excellent sparing of nearby normal tissues due to the sharp energy-loss maximum (Bragg peak) near the end of the particle range and minimal lateral Coulomb scattering. For moving targets (e.g., respiratory motion) treatment delivery with scanned ion beams becomes considerably more complex...

Circular antenna array design is one of the most important electromagnetic optimization problems of current interest. The antenna must generate a pencil beam pattern in the vertical plane along with minimized side lobe level. In this paper we present non conventional method based on improved parameter of hyper beam exponent x. The circular array when implemented using hyper beam technique, ther...