The objective of this study was to determine whether statistically valid correlations could be shown between enterococcal counts of samples from creek and coastal sites and the presence of two molecular, library-independent markers that specify human and/or sewage pollution. Four hundred ninety samples were collected between August 2007 and April 2009 to determine enterococcal counts and the presence of genetic markers for the sewage indicator organisms Methanobrevibacter smithii and Bacteroidales. The presence of human/sewage markers and enterococcal counts were higher in creek samples than coastal samples, but the higher creek levels did not statistically correlate with the either enterococcal count or the presence of the markers present in coastal samples. Furthermore, there was no correlation between enterococcal counts in coastal samples and either marker at any of the beach sites tested. The results of this investigation in Mississippi coastal waters suggest that human/sewage markers are unlikely to correlate with enterococci counts in the nearshore environment and that enterococcal counts may be indicative of other animal or environmental sources. Additionally, a study comparing conventional gel electrophoresis with capillary electrophoresis did not convincingly establish that one method was better than the other in regard to the results obtained. The capillary method does allow reproducibility of results and the ability to analyze multiple samples in a short period of time; however, the operational expenditures exceed the cost of traditional gel electrophoresis.

Surface integral equations become cumbersome to solve when arbitrary combinations of materials, and complicated arrangements of junctions between those materials, are considered. This paper describes a straightforward approach for generalizing integral equation techniques to handle any combinations of materials with junctions. Particular attention is focused on a unique, easily implemented junction resolution algorithm that maps each basis function coefficient to one or more unknowns. Three examples are presented for validation purposes.

This paper describes a simple physically-motivated "near-field" preconditioning scheme that is effective in accelerating convergence of surface, volume, and combined surface/volume integral equations for a broad variety of electromagnetic scattering problems. It can be easily implemented numerically in method of moment (MoM) solvers (both conventional and those employing matrix-compression techniques), irrespective of the analytical form of the integral-equation kernel. It has low memory and CPU requirements, both of which scale linearly with the number of unknowns, and is easily amenable to efficient parallelization. We demonstrate the preconditioner's performance (in conjunction with the BiCGstab(ell) iterative solver) on two representative geometries, and observe a significant reduction in the number of iterations required for convergence.

Motivated by the desire to image exosolar planets, recent work by us and others has shown that high-contrast imaging can be achieved using specially shaped pupil masks. The objective of a shaped pupil coronagraph is to design an aperture that results in a system point spread function (PSF) with the needed contrast allowing planet discovery at the smallest inner working distance (IWD) in the shortest integration time. To do this, we optimize throughput with contrast and IWD constraints. In this paper we summarize the various optimal shaped pupils we have created to date, comparing their performance. We also present preliminary results on stochastic wavefront estimation and control algorithms, an essential capability for any coronagraphic planet finding system.

A new method is presented for amplitude and phase control using two liquid crystal spatial light modulators in conjunction with a white light Michelson interferometer. Preliminary proof-of-concept measurements are given showing the prospect of using this method for correction of amplitude errors in telescopes.

An experimental proof using two liquid crystal spatial light modulators in conjunction with a white light Michelson interferometer to correct amplitude error in telescopes is presented. The principle is reviewed, and then the experiment for a monochromatic closed loop is detailed.

In modeling geometries that involve two or more distinct partitions, an iterative field bouncing (IFB) method can be applied to substantially reduce total memory requirements. This approach also makes possible the use of several different techniques simultaneously, where the optimal analysis method can be chosen for each partition. Application of IFB accelerates solutions particularly in situations where each partition is moving with a velocity independent of the others. Results are shown for a typical application of IFB.

Generating accurate, high‐resolution time‐frequency distributions (TFD) is a critical aspect of dynamic radar scattering analysis. Well‐formed TFD's can be used for target identification, target acquisition in high‐noise environments, or extending the range of radar systems. In this paper, we diverge from traditional methods employing complex signal‐processing methods and propose a simple approach for constructing the TFD for computational electromagnetic (CEM) targets based on the physics of the problem. The proposed method allows for an arbitrarily high resolution at any single look angle. Several examples are presented to validate the method. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 186–189, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10552

The adaptive integral method (AIM) is a fast method associated with O(N1.5) or less complexity. It has been extensively used for the analysis of metallic scatterers on the basis of the electric field integral equation (EFIE), and the AIM implementation is extended to include more general surface types such as impedance, resistive, dielectric and others. The associated multipole expansions of the basis functions are presented for all integral operators, and examples of perfect electrically conducting (PEC) and dielectric surfaces are given for validation

Like the fast multipole method (FMM), the adaptive integral method (AlM) is a fast integral method that has O(N/sup /spl alpha//logN), /spl alpha/<1.5 computational complexity and O(N/sup /spl alpha//), /spl alpha/<1.5 memory requirements. AlM achieves its memory and complexity reduction by mapping the original edge-basis functions onto a regular grid and then using the Toeplitz property of the Green's function along with the fast Fourier transform (FFT) for a fast execution of the matrix-vector products in the iterative solver. So far, application of AIM has been restricted to metallic structures. In this paper, we extend AIM to modeling scattering by three dimensional multi-layered surfaces. For validation RCS results are given for layered and coated spheres and for composite wing-like structures.

We examine the object-oriented programming (OOP) capabilities of FORTRAN 90 and their applications to numerical electromagnetic codes. Specifically, we will define an object representing a three-dimensional vector, and illustrate how objects can streamline code development by reducing the number of subroutines and the potential for programmer errors.

Many scatterers such as cavities, jet engines, antennas, appendages on large vehicles and small perturbations in an otherwise homogenous medium are best characterized by distinct higher order scattering phenomena. Their scattering contributions can have significant influence on the overall scattering of the structure and may also contain unique attributes/features that can be exploited for various post-processing functions. Available radar imaging methods based on SAR and traditional time-frequency methods do not possess the necessary resolution needed to extract features in some cases. The authors introduce the adaptive optimal kernel spectrogram approach and discuss higher order mechanisms.

We have constructed a large-format mosaic CCD camera for the Sloan Digital Sky Survey. The camera consists of two arrays, a photometric array that uses 30 2048 x 2048 SITe/Tektroniu CCDs (24 mu m pixels) with an effective imaging area of 720 cm(2) and an astrometric array that uses 24 400 x 2048 CCDs with the same pixel size, which will allow us to tie bright astrometric standard stars to the objects imaged in the photometric camera. The instrument will be used to carry out photometry essentially simultaneously in five color bands spanning the range accessible to silicon detectors on the ground in the time-delay-and-integrate (TDI) scanning mode. The photometric detectors are arrayed in the focal plane in six columns of five chips each such that two scans cover a filled stripe 2." 5 wide. This paper presents engineering and technical details of the camera.

This article addresses a freely available application programming interface (API) for three-dimensional graphics, known as OpenGL. This API bridges the gap between piles of raw data and extremely complicated three-dimensional animation in a way that requires only a few hours to learn. It is can be used for EM field visualization. In this article, we try to take most of the "leg-work" out of learning OpenGL, by presenting a tutorial that will get you started in the right direction. Some other interesting OpenGL-related technologies are also mentioned.

The Low Resolution Imaging Spectrometer (LRIS) for the Cassegrain focus of the Keck 10-meter telescope on Mauna Kea is described. It has an imaging mode so it can also be used for taking direct images. The field of view in both spectrographic and imaging modes is 6 by 7.8 arcmin. It can be used with both conventional slits and custom-punched slit masks. The optical quality of the spectrograph is good enough to take full advantage of the excellent imaging properties of the telescope itself. The detector is a cooled back-illuminated Tektronics Inc. 2048 CCD which gives a sampling rate of 4.685 pixels per arcsec. In the spectrographic mode the spectrograph has a maximum efficiency at the peak of the grating blaze of 32-34% for the two lowest resolution gratings and 28% for the 1200 g/mm grating. This efficiency includes the detector but not the telescope or the atmosphere.

The Low Resolution Imaging Spectrometer is designed for use at the Cassegrain focus of the Keck 10-m telescope. It provides the capability of acquiring low resolution (R equals 1000 to 5000) digital spectra, as well as 6 X 8 arc-minute moderately high spatial resolution (4.65 pixels/arc-second) direct images. Spectroscopy can be carried out with single slits which are 3 arc-minutes long. In addition punched multi-slits can also be employed which allow for the acquisition of at least forty spectra simultaneously. Since the instrument is designed to be as efficient as possible, it is a double spectrograph, with a dichroic splitting the blue and red light into separate optical paths after the collimator. Only the red side has been constructed thus far. With a 2048 by 2048 thinned Tektronix CCD as the detector the total efficiency of the red side at the peak of the grating blaze is predicted to be nearly 40%. Results of the commissioning observing runs will be described.

We describe an astronomical camera for the 200-in. Hale telescope using four 800 X800 Texas Instruments CCDs in an optical arrangement that allows imaging of a contiguous 1600-pixel-square region of sky. The system employs reimaging optics to yield a scale of 0.33 arcsec per pixel, a good match to the best seeing conditions at Palomar Observatory. Modern high-efficiency coatings are used in the complex optical system to yield a throughput at peak efficiency of nearly 50% (including the losses in the telescope), corresponding to a quantum efficiency on the sky of about 30%. The system uses a fifth CCD in a spectroscopic channel, and it is possible to obtain simultaneous imaging and spectroscopic observations with the system. The camera may also be used in a scanning mode, in which the telescope tracking rate is offset, and the charge is clocked in the chips in such a manner as to keep the charge image aligned with the optical image. In this way, a survey for high-redshift quasars has been carried out over a large area of sky. The instrument has produced images for the most distant clusters of galaxies yet discovered as well as spectra of the most distant galaxies yet observed.

The Shaped Pupil Coronagraph (SPC) is a high-contrast imaging system pioneered at Princeton and designed for the TPF-C telescope. In this document, we summarize the work done to date on the SPC to date and evaluate its current and projected performance. What makes the SPC attractive for TPF is that it is very simple to make and set up, and it is inherently broadband. Owing to the simplicity of the SPC, it is quickly becoming a relatively mature technology with theoretical and experimental validations of its performance. Many shaped pupils have been designed to various specifications and tools are in place to quickly turn out more. Full vector-field simulations show that realistic shaped pupils can already achieve 1010 contrast in the absence of aberrations. A manufacturing process has been developed to make shaped pupils for as little as a few thousand dollars, at JPL and NIST. Shaped pupils have also been shown to be very insensitive to aberrations, and especially low order aberrations such as tilt and defocus. The SPC is undergoing extensive studies in the lab, and so far a suppression of 4 × 10-8 has been achieved in 10% broadband light (averaged across a region between 4 and 9 λ/D), after speckle-nulling-based wavefront correction. The limiting factor is now believed to be well-understood and is primarily the inability of the speckle nulling algorithm to correct for manufacturing errors in the mask. It was shown that this limitation can be overcome by using a more sophisticated estimation algorithm called peak-a- boo, or by using a shaped pupil design that is insensitive to manufacturing defects. The SPC lends itself well to many wavefront estimation and correction schemes. Simulations show that realistic shaped pupil manufacturing errors and realistic wavefront error can be corrected with a single DM at one wavelength, and 2 or 3 DMs in broadband. The main disadvantages of the SPC is throughput, sharpness, and working angle, but the throughput disadvantage may be counterbalanced to an extent by the fact that SPC requires very few optical components and the fact that the light blocked by the mask may still be used to sense aberrations.