High accuracy CMOS position-sensitive photodetector (PSD)

A high-accuracy position-sensitive photodetector (PSD) for integrated sensor systems is presented. A 2-axis PSD composed of a dense array of vertical phototransistors and two arrays of polysilicon resistors was implemented using standard CMOS technology. Test results show better resolution and linearity as compared to a high-quality conventional PSD     

Effects of the feedlot contaminant 17alpha-trenbolone on reproductive endocrinology of the fathead minnow

Trenbolone acetate is a growth promoter widely used for beef production in the U.S. Two biologically active metabolites of the acetate, 17beta- and 17alpha-trenbolone, are ligands of vertebrate androgen receptors and comparatively stable in the waste of treated animals. Both have been detected in surface water associated with beef feedlots, suggesting a potential risk to aquatic animals. In previous work we evaluated the effects of beta-trenbolone on reproductive endocrinology of the fathead minnow (Pimephales promelas) in a 21-day test. The purpose of the present study was to conduct a similar set of experiments with alpha-trenbolone which, based on binding to mammalian androgen receptors, was expected to be less potent than beta-trenbolone. Fecundity of the fish was significantly reduced by alpha-trenbolone with an EC50 (95% confidence interval) of 0.011 (0.007-0.016) microg/L. In females, alpha-trenbolone reduced plasma vitellogenin and steroid concentrations and also induced the production of dorsal nuptial tubercles, structures normally present only in spawning males. Overall, effects of alpha-trenbolone on the reproductive system of the fish were qualitatively and quantitatively quite similar to those caused by beta-trenbolone. Part of this similarity might arise from the fact that a substantial amount of the alpha-trenbolone appeared to be converted to beta-trenbolone by the fish. Tissue concentrations of the beta-isomer were consistently similar to or greater than concentrations of alpha-trenbolone, despite the fact that no beta-trenbolone was detected in the exposure water. The present study demonstrates the importance of considering both alpha- and beta-trenbolone in assessing the potential ecological risk of androgens associated with beef feedlot discharges.     

Displacement sensing resolution of position-sensitive detectors inatmospheric turbulence using retroreflected beam

The position sensing resolution of a lateral-effect photodiode (LEP) and a four-quadrant (4Q) photodetector used as the position sensitive detector (PSD) in a sensor which measures the lateral displacement of a corner cube reflector (CCR) by illuminating it and detecting the position of the reflected light spot with the PSD is studied. An LEP is much noisier than a 4Q detector, but in an outdoor environment the sensitivity of the 4Q detector to atmospheric turbulence due to defocusing makes its resolution worse than that of an LEP. Submillimeter resolutions at the target distances of several hundreds of meters are electrically achievable with an LEP. Outdoors, however, its resolution is also bounded by the atmospheric turbulence. In turbulent measurement conditions, standard deviations of better than 1 cm were typically achievable up to the distance of 300 m and about 10 cm up to half a kilometer     

Evaluation of the model anti-androgen flutamide for assessing the mechanistic basis of responses to an androgen in the fathead minnow (Pimephales promelas)

In this study, we characterized the effects of flutamide, a model mammalian androgen receptor (AR) antagonist, on endocrine function in the fathead minnow (Pimephales promelas), a small fish species that is widely used for testing endocrine-disrupting chemicals (EDCs). Binding assays with whole cells transiently transfected with cloned fathead minnow AR indicated that flutamide binds competitively to the receptor. However, as is true in mammalian systems, a 2-hydroxylated metabolite of flutamide binds to the AR with a much higher affinity than the parent chemical. Mixture experiments with flutamide and the androgen 17beta-trenbolone demonstrated that the anti-androgen effectively blocked trenbolone-induced masculinization (nuptial tubercle production) of female fathead minnows, indicating antagonism of an AR receptor-mediated response in vivo. Conversely, reductions in vitellogenin in trenbolone-exposed females were not blocked by flutamide, suggesting that the vitellogenin response is not directly mediated through the AR. The results of these studies provide data demonstrating the validity of using the fathead minnow as a model species for detecting EDCs that exert toxicity through interactions with the AR.     

A Bayesian classification model for sea ice roughness fromscatterometer data

For sea ice in the Baltic Sea, surface scattering can be regarded as the dominant scattering mechanism at C-band. In this paper, a new statistical method is introduced for making statistical inferences about the underlying ice surface roughness on the basis of one-dimensional (1D) scatterometer data y. The central parameter in the hierarchical model applied in the context is a mixture parameter p, which indicates the degree of surface roughness in ice surface. Several questions related to the occurrence of different ice classes on a transect can be solved with the aid of the posterior distribution [p|y]. An empirical approximation for the posterior distribution is computed by using Markov Chain Monte Carlo methodology. The efficiency of the suggested approach is investigated by analyzing a C-band HH-polarization helicopter-borne HUTSCAT scatterometer data. The results provided by the statistical model show good agreement with a video-based ice type classification     

Incidence angle dependence of the statistical properties of C-band HH-polarization backscattering signatures of the Baltic Sea ice

Incidence angle dependence of three statistical parameters-the mean of the backscattering coefficient (/spl sigma//spl deg/), standard deviation, and autocorrelation coefficient of texture (/spl sigma//sub T/ and /spl rho//sub T/)-of the C-band horizontal-horizontal (HH) polarization backscattering signatures of the Baltic Sea ice are investigated using RADARSAT ScanSAR Narrow images and helicopter-borne Helsinki University of Technology Scatterometer (HUTSCAT) data. The analysis of the large amount of data shows that the relationship between the mean /spl sigma//spl deg/ in decibel scale and the incidence angle in the range from 19/spl deg/ to 46/spl deg/ is usually well described by a linear model. In general, the RADARSAT and HUTSCAT results agree with each other, and they are also supported by theoretical backscattering model calculations; the more deformed the ice, the smaller the slope between /spl sigma//spl deg/ and the incidence angle, and the higher the moisture content of snow or ice, the larger the slope. The derived /spl sigma//spl deg/ incidence angle dependencies can be used to roughly compensate the /spl sigma//spl deg/ incidence angle variation in the SAR images to help their visual and automated classification. The variability of /spl sigma//sub T/ and /spl rho//sub T/ with the increasing incidence angle is insignificant compared to the variability within each ice type. Their average changes with the incidence angle are so small that, in practice, their trends do not need to be compensated. The results of this study can be utilized when developing classification algorithms for the RADARSAT ScanSAR and ENVISAT HH-polarization Wide Swath images of the Baltic Sea ice.     

A high-resolution lateral displacement sensing method using activeillumination of a cooperative target and a focused four-quadrantposition-sensitive detector

A method for high-resolution lateral displacement sensing is proposed. The sensor includes an optical transceiver and a piece of reflective sheeting fixed to the object to be measured. The reflector position is measured by illuminating the reflector and focusing the reflected light on a four-quadrant (4Q) position-sensitive detector (PSD). The method provides true lateral displacement in a large working volume without calibration due to the property of a focused 4Q detector in which the size of the measurement span is determined solely by the size of the reflector, thus providing inherently accurate, constant scaling independent of distance. Experimental results obtained with a laboratory prototype show an air turbulence-limited resolution of a few micrometers (s value) and integral and differential nonlinearities better than ±1% and ±7%, respectively, when a square reflector of 1 cm² is used at a distance of 2.5 m. The main systematic source of error seems to be the spatial nonuniformity of the reflector specific radiance