Morphology of the Nuclear Disk in M87

A deep, fuly sampled diffraction limited (FWHM ~ 70 mas) narrow-band image of the central region in M87 was obtained with the Wide Filed and Planetary Camera 2 of the Hubble Space Telescope using the dithering technique. The H-alpha+[NII] continuum subtracted image reveals a wealth of details in the gaseous disk structure described earlier by Ford et al. (1994). The disk morphology is dominated by a well defined three-arm spiral pattern. In addition, the major spiral arms contain a large number of small "arclets" covering a range of sizes (0.1-0.3 arcsec = 10-30 pc). The overall surface brightness profile inside a radius ~1.5" (100 pc) is well represented by a power-law I(mu) ~ mu^(-1.75), but when the central ~40 pc are excluded it can be equally well fit by an exponential disk. The major axis position angle remains constant at about PA_disk ~ 6 deg for the innermost ~1", implying the disk is oriented nearly perpendicular to the synchrotron jet (PA_jet ~ 291 deg). At larger radial distances the isophotes twist, reflecting the gas distribution in the filaments connecting to the disk outskirts. The ellipticity within the same radial range is e = 0.2-0.4, which implies an inclination angle of i~35 deg. The sense of rotation combined with the dust obscuration pattern indicate that the spiral arms are trailing.Comment: 5 pages, 3 postscript figures, to appear in the Proceedings of the M87 Workshop, Ringberg castle, Germany, 15-19 Sep 1997, also available from http://jhufos.pha.jhu.edu/~zlatan/papers.htm

HYDROMEDUSAE OFF THE ORANGE RIVER MOUTH, SOUTHERN AFRICA

A total of 242 zooplankton samples from the upper 100 m of the water column was collected discontinuously from March 1997 to January 1999 off the Orange River mouth on the west coast of southern Africa. Six species of hydromedusae were recovered at generally low abundance, of which Euphysa aurata, Leuckartia octona and Proboscidactyla menoni were dominant. E. aurata and L. octona showed evidence of seasonality in abundance. The low diversity of the fauna was remarkable and it is hypothesized that this might be attributable in part to sedimentation from the Orange River, and in part to locally weak circulation and the wide extent of the continental shelf

Lysine Requirement of the Gestating Sow Determined by Using Plasma Urea Nitrogen as a Rapid Response Criterion

Lysine requirements at two stages of gestation were estimated in adult sows who had been fed either low (LL) or high lysine (HL) diets in the previous lactation period. Sows fed LL lost more weight during lactation that sows fed HL. Also, sows fed LL diet had more days of anestrus than sows fed HL. There were no differences, however, in litter weight gain of sows fed LL and HL. Estimates of gestation lysine requirements for sows fed LL were 9.6 ± 1.5 and 12.2 ± 1.7 g/d for early gestation and late gestation, respectively. The plasma urea nitrigen (PUN) technique did not accurately or precisely estimate the lysine requirement of the sows fed the HL diet in lactation

X-ray absorption spectroscopic analysis of raw and processed hog manure

Non-Peer ReviewedAnaerobic digestion technology is a process that allows livestock producers to generate electricity and heat by digesting manure. Clear-Green Environmental Inc. uses this process to make biogas from hog manure. Raw manure is pumped into a digester where it is digested anaerobically by mesophyllic bacteria. The digested manure is transferred to a dual purpose tank (DPT) which serves as a secondary digester from which the biogas is collected. Carbon is the only nutrient consumed in the digester and the by-product of this process is used in fertilizers. It has not been shown if there is a change in speciation of key elements like nitrogen and phosphorus upon digestion. X-ray Absorption Near Edge Structure spectroscopy (XANES) was used to characterize the nitrogen, phosphorous and iron found in raw and digested hog manure. Two detection modes, Total Electron Yield (TEY) and Fluorescence Yield (FY) were used for data collection. Raw hog manure contained organic nitrogen, phosphates and ferrous iron. Digested hog manure contained organic and inorganic nitrogen, phosphates as well as a mix of ferrous and ferric iron

WFPC2 LRF Imaging of Emission Line Nebulae in 3CR Radio Galaxies

We present HST/WFPC2 Linear Ramp Filter images of high surface brightness emission lines (either [OII], [OIII], or H-alpha+[NII]) in 80 3CR radio sources. We overlay the emission line images on high resolution VLA radio images (eight of which are new reductions of archival data) in order to examine the spatial relationship between the optical and radio emission. We confirm that the radio and optical emission line structures are consistent with weak alignment at low redshift (z < 0.6) except in the Compact Steep Spectrum (CSS) radio galaxies where both the radio source and the emission line nebulae are on galactic scales and strong alignment is seen at all redshifts. There are weak trends for the aligned emission line nebulae to be more luminous, and for the emission line nebula size to increase with redshift and/or radio power. The combination of these results suggests that there is a limited but real capacity for the radio source to influence the properties of the emission line nebulae at these low redshifts (z < 0.6). Our results are consistent with previous suggestions that both mechanical and radiant energy are responsible for generating alignment between the radio source and emission line gas.Comment: 80 pages, 54 figures. Accepted for publication in ApJ

High Accuracy Near-infrared Imaging Polarimetry with NICMOS

The findings of a nine orbit calibration plan carried out during HST Cycle 15, to fully determine the NICMOS camera 2 (2.0 micron) polarization calibration to high accuracy, are reported. Recently Ueta et al. and Batcheldor et al. have suggested that NICMOS possesses a residual instrumental polarization at a level of 1.2-1.5%. This would completely inhibit the data reduction in a number of GO programs, and hamper the ability of the instrument to perform high accuracy polarimetry. We obtained polarimetric calibration observations of three polarimetric standards at three spacecraft roll angles separated by ~60deg. Combined with archival data, these observations were used to characterize the residual instrumental polarization in order for NICMOS to reach its full potential of accurate imaging polarimetry at p~1%. Using these data, we place an 0.6% upper limit on the instrumental polarization and calculate values of the parallel transmission coefficients that reproduce the ground-based results for the polarimetric standards. The uncertainties associated with the parallel transmission coefficients, a result of the photometric repeatability of the observations, are seen to dominate the accuracy of p and theta. However, the updated coefficients do allow imaging polarimetry of targets with p~1.0% at an accuracy of +/-0.6% and +/-15deg. This work enables a new caliber of science with HST.Comment: 13 pages, 9 figures, PASP accepte

High Accuracy Imaging Polarimetry with NICMOS

The ability of NICMOS to perform high accuracy polarimetry is currently hampered by an uncalibrated residual instrumental polarization at a level of 1.2-1.5%. To better quantify and characterize this residual we obtained observations of three polarimetric standard stars at three separate space-craft roll angles. Combined with archival data, these observations were used to characterize the residual instrumental polarization to enable NICMOS to reach its full polarimetric potential. Using these data, we calculate values of the parallel transmission coefficients that reproduce the ground-based results for the polarimetric standards. The uncertainties associated with the parallel transmission coefficients, a result of the photometric repeatability of the observations, dominate the accuracy of p and theta. However, the new coefficients now enable imaging polarimetry of targets with p~1.0% at an accuracy of +/-0.6% and +/-15 degrees.Comment: 5 pages, 2 figures. Contributed talk, "Astronomical Polarimetry 2008. Science from Small to Large Telescopes" La Malbaie, Quebec, Canada, 200

The Genesis of Intermediate and Silicic Magmas in Deep Crustal Hot Zones

A model for the generation of intermediate and silicic igneous rocks is presented, based on experimental data and numerical modelling. The model is directed at subduction-related magmatism, but has general applicability to magmas generated in other plate tectonic settings, including continental rift zones. In the model mantle-derived hydrous basalts emplaced as a succession of sills into the lower crust generate a deep crustal hot zone. Numerical modelling of the hot zone shows that melts are generated from two distinct sources; partial crystallization of basalt sills to produce residual H2O-rich melts; and partial melting of pre-existing crustal rocks. Incubation times between the injection of the first sill and generation of residual melts from basalt crystallization are controlled by the initial geotherm, the magma input rate and the emplacement depth. After this incubation period, the melt fraction and composition of residual melts are controlled by the temperature of the crust into which the basalt is intruded. Heat and H2O transfer from the crystallizing basalt promote partial melting of the surrounding crust, which can include meta-sedimentary and meta-igneous basement rocks and earlier basalt intrusions. Mixing of residual and crustal partial melts leads to diversity in isotope and trace element chemistry. Hot zone melts are H2O-rich. Consequently, they have low viscosity and density, and can readily detach from their source and ascend rapidly. In the case of adiabatic ascent the magma attains a super-liquidus state, because of the relative slopes of the adiabat and the liquidus. This leads to resorption of any entrained crystals or country rock xenoliths. Crystallization begins only when the ascending magma intersects its H2O-saturated liquidus at shallow depths. Decompression and degassing are the driving forces behind crystallization, which takes place at shallow depth on timescales of decades or less. Degassing and crystallization at shallow depth lead to large increases in viscosity and stalling of the magma to form volcano-feeding magma chambers and shallow plutons. It is proposed that chemical diversity in arc magmas is largely acquired in the lower crust, whereas textural diversity is related to shallow-level crystallizatio

Using Critical Integrative Argumentation to Assess Socioscientific Argumentation Across Decision-Making Contexts

Socioscientific issues (SSI) are often used to facilitate students’ engagement in multiple scientific practices such as decision-making and argumentation, both of which are goals of STEM literacy, science literacy, and integrated STEM education. Literature often emphasizes scientific argumentation over socioscientific argumentation, which involves considering social factors in addition to scientific frameworks. Analyzing students’ socioscientific arguments may reveal how students construct such arguments and evaluate pedagogical tools supporting these skills. In this study, we examined students’ socioscientific arguments regarding three SSI on pre- and post-assessments in the context of a course emphasizing SSI-based structured decision-making. We employed critical integrative argumentation (CIA) as a theoretical and analytical framework, which integrates arguments and counterarguments with stronger arguments characterized by identifying and refuting counterarguments. We hypothesized that engaging in structured decision-making, in which students integrate multidisciplinary perspectives and consider tradeoffs of various solutions based upon valued criteria, may facilitate students’ development of integrated socioscientific arguments. Findings suggest that students’ arguments vary among SSI contexts and may relate to students’ identities and perspectives regarding the SSI. We conclude that engaging in structured decision-making regarding personally relevant SSI may foster more integrated argumentation skills, which are critical to engaging in information-laden democratic societies