Mapping the Asymmetric Thick Disk: The Hercules Thick Disk Cloud

The stellar asymmetry of faint thick disk/inner halo stars in the first quadrant first reported by Larsen & Humphreys (1996) and investigated further by Parker et al. (2003, 2004) has been recently confirmed by SDSS (Juric et al. 2008). Their interpretation of the excess in the star counts as a ringlike structure, however, is not supported by critical complimentary data in the fourth quadrant not covered by SDSS. We present stellar density maps from the Minnesota Automated Plate Scanner (MAPS) Catalog of the POSS I showing that the overdensity does not extend into the fourth quadrant. The overdensity is most probably not a ring. It could be due to interaction with the disk bar, evidence for a triaxial thick disk, or a merger remnant/stream. We call this feature the Hercules Thick Disk Cloud.Comment: 11 pages, 5 figures, to be published in Astrophysical Journal Letter

D-branes and Strings as Non-commutative Solitons

The non-commutative geometry of a large auxiliary $B$-field simplifies the construction of D-branes as solitons in open string field theory. Similarly, fundamental strings are constructed as localized flux tubes in the string field theory. Tensions are determined exactly using general properties of non-BPS branes, and the non-Abelian structure of gauge fields on coincident D-branes is recovered.Comment: 31 pages, 2 figures, harvmac; v2: crucial sign error in vortex solution corrected, additional comments on electric flux tube, references adde

Mapping the Asymmetric Thick Disk I. A Search for Triaxiality

A significant asymmetry in the distribution of faint blue stars in the inner Galaxy, Quadrant 1 (l = 20 to 45 degrees) compared to Quadrant 4 was first reported by Larsen & Humphreys (1996). Parker et al (2003, 2004) greatly expanded the survey to determine its spatial extent and shape and the kinematics of the affected stars. This excess in the star counts was subsequently confirmed by Juric et al. (2008) using SDSS data. Possible explanations for the asymmetry include a merger remnant, a triaxial Thick Disk, and a possible interaction with the bar in the Disk. In this paper we describe our program of wide field photometry to map the asymmetry to fainter magnitudes and therefore larger distances. To search for the signature of triaxiality, we extended our survey to higher Galactic longitudes. We find no evidence for an excess of faint blue stars at l > 55 degrees including the faintest magnitude interval. The asymmetry and star count excess in Quadrant 1 is thus not due to a triaxial Thick Disk.Comment: 36 pages, 8 figures. Accepted by Astronomical Journa

Mapping the Asymmetric Thick Disk: II Distance, Size and Mass of the Hercules Thick Disk Cloud

The Hercules Thick Disk Cloud (Larsen et al. 2008) was initially discovered as an excess in the number of faint blue stars between quadrants 1 and 4 of the Galaxy. The origin of the Cloud could be an interaction with the disk bar, a triaxial thick disk or a merger remnant or stream. To better map the spatial extent of the Cloud along the line of sight, we have obtained multi-color UBVR photometry for 1.2 million stars in 63 fields approximately 1 square degree each. Our analysis of the fields beyond the apparent boundaries of the excess have already ruled out a triaxial thick disk as a likely explanation (Larsen, Humphreys and Cabanela 2010) In this paper we present our results for the star counts over all of our fields, determine the spatial extent of the over density across and along the line of sight, and estimate the size and mass of the Cloud. Using photometric parallaxes, the stars responsible for the excess are between 1 and 6 kiloparsecs from the Sun, 0.5 -- 4 kpc above the Galactic plane, and extends approximately 3-4 kiloparsecs across our line of sight. It is thus a major substructure in the Galaxy. The distribution of the excess along our sight lines corresponds with the density contours of the bar in the Disk, and its most distant stars are directly over the bar. We also see through the Cloud to its far side. Over the entire 500 square degrees of sky containing the Cloud, we estimate more than 5.6 million stars and 1.9 million solar masses of material. If the over density is associated with the bar, it would exceed 1.4 billion stars and more than than 50 million solar masses. Finally, we argue that the Hercules-Aquila Cloud (Belokurov et al. 2007) is actually the Hercules Thick Disk Cloud.Comment: 52 pages, 13 figure

Ca_3AlSb_3: an inexpensive, non-toxic thermoelectric material for waste heat recovery

Thermoelectric materials directly convert thermal energy into electrical energy, offering a promising solid-state solution for waste heat recovery. For thermoelectric devices to make a significant impact on energy and the environment the major impediments are the efficiency, availability and toxicity of current thermoelectric materials. Typically, efficient thermoelectric materials contain heavy elements such as lead and tellurium that are toxic and not earth abundant. Many materials with unusual structures containing abundant and benign elements are known, but remain unexplored for thermoelectric applications. In this paper we demonstrate, with the discovery of high thermoelectric efficiency in Ca_3AlSb_3, the use of elementary solid-state chemistry and physics to guide the search and optimization of such materials

Virtual Briefing at the Supreme Court

The open secret of Supreme Court advocacy in a digital era is that there is a new way to argue to the Justices. Today\u27s Supreme Court arguments are developed online: they are dissected and explored in blog posts, fleshed out in popular podcasts, and analyzed and re-analyzed by experts who do not represent the parties or have even filed a brief in the case at all. This virtual briefing (as we call it) is intended to influence the Justices and their law clerks but exists completely outside of traditional briefing rules. This article describes virtual briefing and makes a case that the key players inside the Court are listening. In particular, we show that the Twitter patterns of law clerks indicate they are paying close attention to producers of virtual briefing, and threads of these arguments (proposed and developed online) are starting to appear in the Court\u27s decisions. We argue that this crowdsourcing dynamic to Supreme Court decision-making is at least worth a serious pause. There is surely merit to enlarging the dialogue around the issues the Supreme Court decides; maybe the best ideas will come from new voices left out of the traditional briefing process. But the confines of the adversarial process have been around for centuries, and there are significant risks that come with operating outside of them, particularly given the unique nature and speed of online discussions. We analyze those risks in this Article and suggest it is time to think hard about embracing virtual briefing, truly assessing what can be gained and what will be lost along the way

Exact Noncommutative Solitons

We find exact solitons in a large class of noncommutative gauge theories using a simple solution generating technique. The solitons in the effective field theory description of open string field theory are interpreted as D-branes for any value of the noncommutativity. We discuss the vacuum structure of open string field theory in view of our results.Comment: 23 pages. v3: correction in section 3.

Effects of caffeine on reading performance on the Visagraph2

Caffeine is a drug that wakes people up and stimulates the central nervous system. It is frequently found in many beverages and other consumed products. It also comes as an over-the-counter supplement. Since it is so common and gets used to help people stay awake during reading tasks, we wanted to see what effect it has on comprehension, attention and eye movements when reading. To do this we screened 27 optometry students for health problems and tested them twice on the Visagraph2, an instrument that objectively monitors eye movements and tests comprehension of material read. Tests were conducted when subjects had no caffeine in their system and when caffeine was at its highest concentration in their blood. Some started on caffeine and others did not in an attempt to limit a learning affect. In an analysis of our data, we found better performance when not on caffeine that was statistically significant in the number of fixations, regressions and percent of directional attack. Span of recognition, comprehension, rate with comprehension and grade level efficiency were also better when not on caffeine, but they were not statistically significant. Reading rate without comprehension was slower and the average duration of fixation was longer when not on caffeine. However, since comprehension was better and their were fewer fixations when not on caffeine it can be concluded that caffeine made reading more erratic and less efficient. In short, not using caffeine makes reading more efficient and improves comprehension. Using caffeine makes reading quicker, but less efficient and decreases comprehension. This means that caffeine keeps the mind and body awake, but may not make you a better reader