OSCR wave measurements-some preliminary results

OSCR is an HF radar system that has been developed for high spatial resolution coastal surface current measurement. This paper describes preliminary results that demonstrate that wave measurement can be successfully obtained from suitably processed OSCR data. Comparisons with data from a WAVEC directional buoy are presented and show encouraging agreement. Some of the limitations to the measurement process are discussed and indicate a maximum range of about 20 km. Surface current variability on short time scales presents the most serious obstacle to wave measurement. This appears to be more of a problem when the mean currents are large, in that in these circumstances the data fail initial quality control criteria. However, in lower mean currents, the effect is often still present and leads to errors in long wave measurement     

Application of an improved self-starter to geoacoustic inversion

The self-starter is improved using the operator of the split-step Pade solution. In addition to providing greater stability and being applicable closer to the source, the improved self-starter is an efficient forward model for geoacoustic inversion. It is necessary to solve only O(10) tridiagonal systems of equations to obtain the acoustic field on a vertical array located O(10) wavelengths from a source. This experimental configuration is effective for geoacoustic inverse problems involving unknown parameters deep in the ocean bottom. For problems involving depth-dependent acoustic parameters, the improved self-starter can be used to solve nonlinear inverse problems involving O(10) unknown sediment parameters in less than a minute on the current generation of workstations     

MAXIPOL: a balloon-borne experiment for measuring the polarization anisotropy of the cosmic microwave background radiation

We discuss MAXIPOL, a bolometric balloon-borne experiment designed to measure the E-mode polarization anisotropy of the cosmic microwave background radiation (CMB) on angular scales of 10^′ to 2°. MAXIPOL is the first CMB experiment to collect data with a polarimeter that utilizes a rotating half-wave plate and fixed wire-grid polarizer. We present the instrument design, elaborate on the polarimeter strategy and show the instrument performance during flight with some time domain data. Our primary dataset was collected during a 26 h turnaround flight that was launched from the National Scientific Ballooning Facility in Ft. Sumner, New Mexico in May 2003. During this flight five regions of the sky were mapped. Data analysis is in progress.     

A high-velocity ionized outflow and XUV photosphere in the narrow emission line quasar PG1211+143

We report on the analysis of a ∼60-ks XMM–Newton observation of the bright, narrow emission line quasar PG1211+143. Absorption lines are seen in both European Photon Imaging Camera and Reflection Grating Spectrometer spectra corresponding to H- and He-like ions of Fe, S, Mg, Ne, O, N and C. The observed line energies indicate an ionized outflow velocity of ∼24 000 km s⁻¹. The highest energy lines require a column density of   N _H∼ 5 × 10²³ cm⁻²  , at an ionization parameter of  log ξ∼ 3.4  . If the origin of this high-velocity outflow lies in matter being driven from the inner disc, then the flow is likely to be optically thick within a radius of ∼130 Schwarzschild radii, providing a natural explanation for the big blue bump (and strong soft X-ray) emission in PG1211+143.     

Hysteresis‐based analysis of overland metal transport

Introducing a concept of equivalent mass depth of flow, this study describes the phenomenon of non‐point source pollutant (metal) transport for pavement (or overland) flow in analogy with wave propagation in wide open channels. Hysteretic and normal mass rating curves are developed for runoff rate and mass of 12 dissolved and particulate‐bound metal elements (pollutants) using the rainfall‐runoff and water quality data of the 15 × 20 m² instrumented pavement in Cincinnati, USA. Normal mass rating curves developed for easy computation of pollutant load are found to be of a form similar to Manning's, which is valid for open channel flows. Based on the hysteresis analysis, wave types for dissolution and mixing of particulate‐bound metals are identified. The analysis finds that the second‐order partial‐differential equation normally used for metal transport does not have the efficacy to describe fully the strong non‐linear phenomena such as is described for various metal elements by dynamic waves. In addition, the proportionality concept of the popular SCS‐CN concept is extended for determining the potential maximum metal mass M_p of all the 12 elements transported by a rain storm and related to the antecedent dry period (ADP). For the primary metal zinc element, M_p is found to increase with the ADP and vice versa. Copyright © 2003 John Wiley & Sons, Ltd.     

Swimming with…Devonian fish

Armoured jawless fish, or 'ostracoderms', lived 450–360 million years ago, and display unusual morphologies, unlike any modern fish group. Since they left no living descendants, their mode of swimming has, until recently, remained speculative, although this is a crucial question as the first true pectoral fins evolved within the 'ostracoderms'. The discovery of the oldest-known fish trails, from the Early Devonian (400 million year old) 'Lower Old Red Sandstone' of south-east Wales offers new insights into the swimming behaviour of these early fish, notably the osteostracan 'ostracoderms' (or cephalaspids), whose horseshoe-shaped head and paddle-shaped pectoral fins have remained a functional riddle.