News from Academy Bay

Donation Made in Memory of Last Grandchild of Ecuador's First President. Deaths of CDF Board Members. Major Gift by Mrs. Louise Van Straelen-Poirier. Itasca to Galápagos. Station Research Vessel

The Role of the Magnetorotational Instability in the Sun

We calculate growth rates for nonaxisymmetric instabilities including the magnetorotational instability (MRI) throughout the Sun. We first derive a dispersion relation for nonaxisymmetric instability including the effects of shear, convective buoyancy, and three diffusivities (thermal conductivity, resistivity, and viscosity). We then use a solar model evolved with the stellar evolution code MESA and angular velocity profiles determined by Global Oscillations Network Group (GONG) helioseismology to determine the unstable modes present at each location in the Sun and the associated growth rates. The overall instability has unstable modes throughout the convection zone and also slightly below it at middle and high latitudes. It contains three classes of modes: large-scale hydrodynamic convective modes, large-scale hydrodynamic shear modes, and small-scale magnetohydrodynamic (MHD) shear modes, which may be properly called MRI modes. While large-scale convective modes are the most rapidly growing modes in most of the convective zone, MRI modes are important in both stably stratified and convectively unstable locations near the tachocline at colatitudes theta less than 53 degrees. Nonaxisymmetric MRI modes grow faster than the corresponding axisymmetric modes; for some poloidal magnetic fields, the nonaxisymmetric MRI growth rates are similar to the angular rotation frequency Omega, while axisymmetric modes are stabilized. We briefly discuss the saturation of the field produced by MRI modes, finding that the implied field at the base of the convective zone in the Sun is comparable to that derived based on dynamos active in the tachocline and that the saturation of field resulting from the MRI may be of importance even in the upper convection zone.Comment: 20 pages, 11 figure

Building a Better mSUGRA: WIMP Dark Matter Without Flavor Violation

The appearance of a natural dark matter candidate, the neutralino, is among the principal successes of minimal supergravity (mSUGRA) and its descendents. In lieu of a suitable ultraviolet completion, however, theories of gravity-mediated supersymmetry breaking such as mSUGRA suffer from arbitrary degrees of flavor violation. Though theories of gauge-mediated supersymmetry breaking are free from such prohibitive flavor violation, they typically lack natural neutralino dark matter candidates. Yet this conventional dichotomy breaks down when the hidden sector is strongly coupled; in models of gauge-mediated supersymmetry breaking, the neutralino may be the lightest supersymmetric particle (LSP) if the fields of the hidden sector possess large anomalous dimensions. In fact, general models of so-called "sequestered" gauge mediation possess the full richness of neutralino dark matter found in mSUGRA without corresponding flavor problems. Here we explore generalized models of sequestered gauge mediation and the rich variety of neutralino dark matter they exhibit.Comment: 26 pages, 7 figure

An Annotated Checklist of Wisconsin Mutillidae (Hymenoptera)

A survey of Wisconsin velvet ants (Hymenoptera: Mutillidae) conducted from literature searches, collection inventories, and two years of field work (2001-2002) yielded 28 species in three subfamilies. Of these, 23 species (representing 82% of the Wisconsin fauna and a 460% increase in the known species richness) are new state species records, having not previously been recorded in the published literature from the state. The known distributions of all Wisconsin species are reported by region and county, along with pertinent phenological, natural history, and other collection information, when known

Bioaugmentation for Improved Recovery of Anaerobic Digesters After Toxicant Exposure

Bioaugmentation was investigated as a method to decrease the recovery period of anaerobic digesters exposed to a transient toxic event. Two sets of laboratory-scale digesters (SRT = 10 days, OLR = 2 g COD/L-day), started with inoculum from a digester stabilizing synthetic municipal wastewater solids (MW) and synthetic industrial wastewater (WW), respectively, were transiently exposed to the model toxicant, oxygen. Bioaugmented digesters received 1.2 g VSS/L-day of an H2-utilizing culture for which the archaeal community was analyzed. Soon after oxygen exposure, the bioaugmented digesters produced 25–60% more methane than non-bioaugmented controls (p \u3c 0.05). One set of digesters produced lingering high propionate concentrations, and bioaugmentation resulted in significantly shorter recovery periods. The second set of digesters did not display lingering propionate, and bioaugmented digesters recovered at the same time as non-bioaugmented controls. The difference in the effect of bioaugmentation on recovery may be due to differences between microbial communities of the digester inocula originally employed. In conclusion, bioaugmentation with an H2-utilizing culture is a potential tool to decrease the recovery period, decrease propionate concentration, and increase biogas production of some anaerobic digesters after a toxic event. Digesters already containing rapidly adaptable microbial communities may not benefit from bioaugmentation, whereas other digesters with poorly adaptable microbial communities may benefit greatly

Iris Recognition: The Consequences of Image Compression

Iris recognition for human identification is one of the most accurate biometrics, and its employment is expanding globally. The use of portable iris systems, particularly in law enforcement applications, is growing. In many of these applications, the portable device may be required to transmit an iris image or template over a narrow-bandwidth communication channel. Typically, a full resolution image (e.g., VGA) is desired to ensure sufficient pixels across the iris to be confident of accurate recognition results. To minimize the time to transmit a large amount of data over a narrow-bandwidth communication channel, image compression can be used to reduce the file size of the iris image. In other applications, such as the Registered Traveler program, an entire iris image is stored on a smart card, but only 4 kB is allowed for the iris image. For this type of application, image compression is also the solution. This paper investigates the effects of image compression on recognition system performance using a commercial version of the Daugman iris2pi algorithm along with JPEG-2000 compression, and links these to image quality. Using the ICE 2005 iris database, we find that even in the face of significant compression, recognition performance is minimally affected