Variability and polarization in the inner jet of 3C395

We present new results on the parsec-scale jet of the quasar 3C395, derived from VLBI polarization sensitive observations made in 1995.91 and 1998.50 at 8.4, 15.4 and 22.2 GHz. The observations show a complex one-sided jet extending up to 20 mas, with a projected magnetic field essentially aligned with the radio jet. The emission is strongly dominated, in total intensity and polarization, by the core and the inner jet region (of ~3 mas length). We have studied the details of this dominant region finding clear structural variations during this ~2.5 years period, in contrast with the apparent quietness of the jet structure inferred from lower resolution VLBI observations. We observe the ejection of a new component from the core and variations in the degree of polarization of the inner jet components. We estimate a high Faraday Rotation Measure close to the core, with a strong decrease along the inner jet.Comment: 7 pages, 4 figures, A&A in pres

The inner kiloparsec of the jet in 3C264

We present new multi-frequency EVN, MERLIN and VLA observations of the radio source 3C264, sensitive to linear scales ranging from the parsec to several kiloparsecs. The observations confirm the existence of regions with different properties in the first kiloparsec of the jet. The most remarkable feature is the transition between a well collimated narrow jet at distances from the core below 80 pc, to a conical-shaped wide jet, with an opening angle of 20 degrees. Another change of properties, consisting of an apparent deflection of the jet ridge line and a diminution of the surface brightness, occurs at a distance of 300 pc from the core, coincident with the radius of a ring observed at optical wavelengths. Our observations add new pieces of information on the spectrum of the radio-optical jet of 3C264, with results consistent with a synchrotron emission mechanism and a spectrum break frequency in the infrared. Brightness profiles taken perpendicularly to the jet of 3C264 are consistent with a spine brightened jet at distances below 100 pc from the core, and an edge-brightened jet beyond, which can be interpreted as evidence of a transverse jet velocity structure. Our observations do not allow us to distinguish between the presence of a face--on dust and gas disk at the center of the host galaxy of 3C264, or rather an evacuated bubble. However, the properties of the jet structure, the changes in the polarization angle, and the plausible jet orientation can be naturally brought into agreement in the bubble scenario.Comment: 10 pages, 9 figures, accepted in A&

Performance of a Pilot-Scale Air Sparged Continuous Flow Reactor and Hydrocyclone for Struvite Precipitation and Removal from Liquid Swine Manure

The objective of this research was to test a pilot-scale air sparged tank reactor (ASTR) and the ASTR in combination with a hydrocyclone (called the pilot-scale ASTR-hydrocyclone system) on two swine manure slurries for struvite-based (MgNH4PO4-6H2O) phosphorus removal and recovery. The pilot-scale ASTR system operated at flow rates of 80 to 115 L/min and was based on the bench-scale design from Shepherd et al. (2007). The ASTR effluent was processed using a hydrocyclone separator for struvite separation and total phosphorus (TP) recovery. The pilot-scale ASTR-hydrocyclone system provided a 92% reduction of dissolved reactive phosphorus (DRP) in manure slurry from a swine finishing facility concrete storage tank and a 91% reduction of DRP in manure slurry collected from a swine finishing facility deep-pit under floor collection system. The pilot-scale ASTR-hydrocyclone system removed 18% of TP in swine manure from a concrete storage tank and 9% to 14% of TP in swine manure slurry from a deep-pit under floor collection system. The low TP recovery was attributed to the hydrocyclones inability to provide effective struvite separation as operated. Full-scale economics and implementation of the tested struvite-based phosphorus removal is discussed. A case study of a typical Iowa deep-pit swine production facility (10,000 head/year) indicated that the annual cost of struvite-based phosphorus removal using this system would be approximately $8.88/finished pig or$0.035/L manure slurry treated ($ 0.134/gal). This cost often exceeds producer\u27s profit margins; this indicates that struvite-based phosphorus removal using this ASTR-hydrocyclone system in swine finisher manure slurries is not currently economically viable

Investigating Conductivity to Predict Magnesium Addition Requirements for Struvite Precipitation in Swine Manure Slurries

The goal of this project was to develop a system that identified magnesium demand for struvite formation by monitoring conductivity changes during continuous injection of magnesium chloride in several swine manure slurries. The conductivity of six manure slurries was monitored to identify the response due to magnesium chloride injection (MgCl2) and struvite precipitation. Struvite precipitation is a technically feasible treatment method for phosphorus removal and recovery from manure slurries (Burns et al., 2003; Bowers and Westerman, 2005a). Swine manure slurries often require the addition of magnesium (Mg2+) to force struvite precipitation. The quantity of Mg2+ required for maximized phosphorus removal can be determined through laboratory tests. Optimized struvite precipitation in a field setting requires a real-time method to determine Mg2+ addition rates during a land application event. This article discusses the requirements of an automated control system which monitors and controls the injection of Mg2+ to force struvite precipitation, accounting for real-time variations of magnesium demand. Theoretical predictions and pure solution tests provided information capable of determining the magnesium demand for struvite precipitations. After testing six different manures in triplicate, the conductivity responses did not follow theoretical predictions and failed to provide any indication of optimum magnesium injection rates for phosphorus removal

Development of an Air Sparged Continuous Flow Reactor for Struvite Precipitation from Two Different Liquid Swine Manure Storage Systems

Forced precipitation of struvite (MgNH4PO4*6H2O) has been demonstrated to be an effective method to reduce dissolved reactive phosphorus (DRP) from swine manure. The development of a robust and flexible continuous flow struvite precipitation reactor is essential to the application of this method to modern livestock operations. Swine manure generally requires pH adjustment, magnesium amendment and a sufficient reaction time to create optimum conditions for struvite precipitation. A bench-scale (14-L) continuous flow reactor was developed to force struvite precipitation and reduce DRP. The bench scale system was developed to quantify system performance prior to building a much larger pilot-scale unit. The bench-scale reactor used air sparging to provide pH adjustment and mixing. Influent manure slurry was continuously amended with magnesium chloride (MgCl2 . 6H2O) to promote maximum DRP removal. During continuous flow operation, a 10-minute hydraulic retention time was provided for struvite precipitation. This paper discusses the design and development of the continuous flow air sparged tank reactor (ASTR) and reports on the reactor\u27s DRP reduction capabilities on manure collected from two commercially utilized swine manure storage systems; 1) a concrete storage tank with a permeable cover, and 2) a shallow under floor pit manure collection system. Continuous flow ASTR treatment provided a 95% reduction of DRP from the covered storage tank manure and a 78% reduction of DRP from the under floor pit manure

Validation of a Low Cost Flow Measurement System for Monitoring Vegetative Treatment System Performance

In 2006, the Iowa Department of Natural Resources issued National Pollution Discharge Elimination System (NPDES) permits to six feedlots participating in research on the use of vegetative treatment systems (VTSs) to control beef feedlot runoff. While Iowa State University monitors releases from the research portion of these sites, the producers are required to monitor releases from the non-research portions. Additionally, non-research site producers with VTSs and NPDES permits are required to monitor system releases. They are required to measure release volume and collect a sample for analysis. Automated, research oriented open channel flow measurement systems typically cost $7,500 to employ. Muhlbauer et. al (2007) developed a low cost monitoring system (LMS) designed to measure open channel flow from a VTS with a total cost of$1,600. Testing of the LMS by Muhlbauer et. al. (2007) across flow events ranging from one to six hours indicated a mean accuracy of 90.6% in comparison to a flow meter equipped ISCO 6712 portable sampler using a .46m (18”) fiberglass H-flume. Further cost reduction options for a producer include fabrication of a metal H-flume, reducing total system cost to $850. This paper compares the performance of the LMS for estimating both short and longer duration flow events and performance of the fabricated metal flume. The LMS flow measurements were compared to an ISCO 6712 portable sampler and a Krohne Optiflux 4000 flow meter in twelve field tests lasting one and six hours with an accuracy of 88.5% in comparison to the Krohne. Relative to a commercial fiberglass flume, the three fabricated flumes had a mean percent accuracy of 98%

Magnetic Fields in Quasar Cores II

Multi-frequency polarimetry with the Very Long Baseline Array (VLBA) telescope has revealed absolute Faraday Rotation Measures (RMs) in excess of 1000 rad/m/m in the central regions of 7 out of 8 strong quasars studied (e.g., 3C 273, 3C 279, 3C 395). Beyond a projected distance of ~20 pc, however, the jets are found to have |RM| < 100 rad/m/m. Such sharp RM gradients cannot be produced by cluster or galactic-scale magnetic fields, but rather must be the result of magnetic fields organized over the central 1-100 pc. The RMs of the sources studied to date and the polarization properties of BL Lacs, quasars and galaxies are shown to be consistent so far with the predictions of unified schemes. The direct detection of high RMs in these quasar cores can explain the low fractional core polarizations usually observed in quasars at centimeter wavelengths as the result of irregularities in the Faraday screen on scales smaller than the telescope beam. Variability in the RM of the core is reported for 3C 279 between observations taken 1.5 years apart, indicating that the Faraday screen changes on that timescale, or that the projected superluminal motion of the inner jet components samples a new location in the screen with time. Either way, these changes in the Faraday screen may explain the dramatic variability in core polarization properties displayed by quasars.Comment: Accepted to the ApJ. 27 pages, 9 figures including figure 6 in colo

Radio interferometric observations of two core-dominated triple radio sources at z>3

Aims. We selected two radio quasars (J1036+1326 and J1353+5725) based on their 1.4-GHz radio structure, which is dominated by a bright central core and a pair of weaker and nearly symmetric lobes at ~10" angular separation. They are optically identified in the Sloan Digital Sky Survey (SDSS) at spectroscopic redshifts z>3. We investigate the possibility that their core-dominated triple morphology can be a sign of restarted radio activity in these quasars, involving a significant repositioning of the radio jet axis. Methods. We present the results of high-resolution radio imaging observations of J1036+1326 and J1353+5725, performed with the European Very Long Baseline Interferometry (VLBI) Network (EVN) at 1.6 GHz. These data are supplemented by archive observations from the Very Large Array (VLA).We study the large- and small-scale radio structures and the brightness temperatures, then estimate relativistic beaming parameters. Results. We show that the central emission region of these two high-redshift, core-dominated triple sources is compact but resolved at ~10 milli-arcsecond resolution. We find that it is not necessary to invoke large misalignment between the VLBI jet and the large-scale radio structure to explain the observed properties of the sources.Comment: 5 pages, 4 figures, accepted for publication in A&

8.4GHz VLBI observations of SN2004et in NGC6946

We report on 8.4GHz Very Long Baseline Interferometry (VLBI) observations of the type II-P supernova SN2004et in the spiral galaxy NGC 6946, made on 20 February 2005 (151 days after explosion). The Very Large Array (VLA) flux density was 1.23$\pm$0.07 mJy, corresponding to an isotropic luminosity at 8.4GHz of (4.45$\pm$0.3)$\times10^{25}$ erg s$^{-1}$ Hz$^{-1}$ and a brightness temperature of (1.3$\pm$0.3)$\times10^{8}$ K. We also provide an improved source position, accurate to about 0.5 mas in each coordinate. The VLBI image shows a clear asymmetry. From model fitting of the size of the radio emission, we estimate a minimum expansion velocity of 15,700$\pm$2,000 km s$^{-1}$. This velocity is more than twice the expected mean expansion velocity estimated from a synchrotron self-absorbed emission model, thus suggesting that synchrotron self-absorption is not relevant for this supernova. With the benefit of an optical spectrum obtained 12 days after explosion, we favor an emission model which consists of two hot spots on an underlying expanding shell of width comparable to that of SN 1993J.Comment: Accepted for publication in A&A (22/05/07