Making Market Rule(s)

This is the introductory essay for a special issue on the geographies of market construction and market regulation. It argues that in an age of markets, geographers ought to pay more attention to the seemingly mundane, but nevertheless socially constructed, rules that are necessary for any market to operate

Dose-Dependent Thresholds of 10-ns Electric Pulse Induced Plasma Membrane Disruption and Cytotoxicity in Multiple Cell Lines

In this study, we determined the LD50 (50% lethal dose) for cell death, and the ED50 (50% of cell population staining positive) for propidium (Pr) iodide uptake, and phosphatidylserine (PS) externalization for several commonly studied cell lines (HeLa, Jurkat, U937, CHO-K1, and GH3) exposed to 10-ns electric pulses (EP). We found that the LD50 varied substantially across the cell lines studied, increasing from 51 J/g for Jurkat to 1861 J/g for HeLa. PS externalized at doses equal or lower than that required for death in all cell lines ranging from 51 J/g in Jurkat, to 199 J/g in CHO-K1. Pr uptake occurred at doses lower than required for death in three of the cell lines: 656 J/g for CHO-K1, 634 J/g for HeLa, and 142 J/g for GH3. Both Jurkat and U937 had a LD50 lower than the ED50 for Pr uptake at 780 J/g and 1274 J/g, respectively. The mechanism responsible for these differences was explored by evaluating cell size, calcium concentration in the exposure medium, and effect of trypsin treatment prior to exposure. None of the studied parameters correlated with the observed results suggesting that cellular susceptibility to injury and death by 10-ns EP was largely determined by cell physiology. In contrast to previous studies, our findings suggest that permeabilization of internal membranes may not necessarily be responsible for cell death by 10-ns EP. Additionally, a mixture of Jurkat and HeLa cells was exposed to 10-ns EP at a dose of 280 J/g. Death was observed only in Jurkat cells suggesting that 10-ns EP may selectively kill cells within a heterogeneous tissue

KH 15D: Gradual Occultation of a Pre-Main-Sequence Binary

We propose that the extraordinary ``winking star'' KH 15D is an eccentric pre-main-sequence binary that is gradually being occulted by an opaque screen. This model accounts for the periodicity, depth, duration, and rate of growth of the modern eclipses; the historical light curve from photographic plates; and the existing radial velocity measurements. It also explains the re-brightening events that were previously observed during eclipses, and the subsequent disappearance of these events. We predict the future evolution of the system and its full radial velocity curve. Given the small velocity of the occulting screen relative to the center of mass of the binary, the screen is probably associated with the binary, and may be the edge of a precessing circumbinary disk.Comment: ApJ Letters, in press [11 pp., 5 figs]. Revision is shorter and incorporates suggestions from the referee and other colleague

Spectroscopic Discovery of the Broad-Lined Type Ic Supernova 2010bh Associated with the Low-Redshift GRB 100316D

We present the spectroscopic discovery of a broad-lined Type Ic supernova (SN 2010bh) associated with the nearby long-duration gamma-ray burst (GRB) 100316D. At z = 0.0593, this is the third-nearest GRB-SN. Nightly optical spectra obtained with the Magellan telescopes during the first week after explosion reveal the gradual emergence of very broad spectral features superposed on a blue continuum. The supernova features are typical of broad-lined SNe Ic and are generally consistent with previous supernovae associated with low-redshift GRBs. However, the inferred velocities of SN 2010bh at 21 days after explosion are a factor of ~2 times larger than those of the prototypical SN 1998bw at similar epochs, with v ~ 26,000 km/s, indicating a larger explosion energy or a different ejecta structure. A near-infrared spectrum taken 13.8 days after explosion shows no strong evidence for He I at 1.083 microns, implying that the progenitor was largely stripped of its helium envelope. The host galaxy is of low luminosity (M_R ~ -18.5 mag) and low metallicity (Z < 0.4 Z_solar), similar to the hosts of other low-redshift GRB-SNe.Comment: 6 pages, 4 figures, 1 table, submitted to ApJ Letter

Orientation uncertainty reduces perceived obliquity

The influence of prejudice on perception should be greatest when certainty about stimulus identity is least. We exploited this relationship to reveal visual biases for the cardinal orientations: vertical and horizontal. Specifically, when we increased the variance of orientations in an array of grating patches, estimates of the mean became less oblique. This result is consistent with a stable prior, or prejudice, for those orientations most prevalent in natural scenes

Probing Sub-Micron Forces by Interferometry of Bose-Einstein Condensed Atoms

We propose a technique, using interferometry of Bose-Einstein condensed alkali atoms, for the detection of sub-micron-range forces. It may extend present searches at 1 micron by 6 to 9 orders of magnitude, deep into the theoretically interesting regime of 1000 times gravity. We give several examples of both four-dimensional particles (moduli), as well as higher-dimensional particles -- vectors and scalars in a large bulk-- that could mediate forces accessible by this technique.Comment: 32 pages, 5 figures, RevTeX4, expanded discussion of interactions, references added, to appear in PR

Ringed, Bearded, and Ribbon Seal Vocalizations North of Barrow, Alaska: Seasonal Presence and Relationship with Sea Ice

The acoustic repertoires of ringed, bearded, and ribbon seals are described, along with their seasonal occurrence and relationship to sea ice concentration. Acoustic recordings were made between September and June over three years (2006 – 09) along the continental slope break in the Chukchi Sea, 120 km north-northwest of Barrow, Alaska. Vocalizations of ringed and bearded seals occurred in winter and during periods of 80% – 100% ice cover but were mostly absent during open water periods. The presence of ringed and bearded seal calls throughout winter and spring suggests that some portion of their population is overwintering. Analysis of the repertoire of ringed and bearded seal calls shows seasonal variation. Ringed seal calls are primarily barks in winter and yelps in spring, while bearded seal moans increase during spring. Ribbon seal calls were detected only in the fall of 2008 during the open water period. The repertoire of known ribbon seal vocalizations was expanded to include three additional calls, and two stereotyped call sequences were common. Retrospective analyses of ringed seal recordings from 1982 and ribbon seal recordings from 1967 showed a high degree of stability in call repertoire across large spatial and temporal scales.Le répertoire acoustique des phoques annelés, des phoques barbus et des phoques à bandes sont décrits, de même que leur présence saisonnière et leur rapport avec la concentration de glace de mer. Des enregistrements acoustiques ont été effectués entre septembre et juin sur une période de trois ans (2006 – 2009), le long de la rupture de la pente continentale, dans la mer des Tchouktches, à 120 km au nord-nord-ouest de Barrow, en Alaska. Les vocalisations de phoques annelés et de phoques barbus étaient présentes pendant l’hiver et pendant les périodes où la concentration de glace était de 80 % à 100 %, mais elles se faisaient rares pendant les périodes d’eau libre. La présence des cris de phoques annelés et de phoques barbus tout au long de l’hiver et du printemps suggère qu’une partie de leur population hiverne. L’analyse du répertoire de cris de phoques annelés et de phoques barbus indique une variation saisonnière. L’hiver, le cri du phoque annelé prend principalement la forme d’aboiements, tandis que le printemps, il prend la forme de glapissements. Les gémissements du phoque barbu s’intensifient au printemps. Le cri des phoques à bandes n’a été capté qu’à l’automne 2008, pendant la période des eaux libres. Le répertoire des vocalisations connues du phoque à bandes a été élargi pour inclure trois autres cris, bien que deux séquences de cris stéréotypées étaient courantes. L’analyse rétrospective des enregistrements de cris de phoques annelés de 1982 et de phoques à bandes de 1967 a laissé entrevoir une grande stabilité du point de vue du répertoire des cris, et ce, sur de vastes échelles spatiales et temporelles

The Peculiar SN 2005hk: Do Some Type Ia Supernovae Explode as Deflagrations?

We present extensive u'g'r'i'BVRIYJHKs photometry and optical spectroscopy of SN 2005hk. These data reveal that SN 2005hk was nearly identical in its observed properties to SN 2002cx, which has been called ``the most peculiar known type Ia supernova.'' Both supernovae exhibited high ionization SN 1991T-like pre-maximum spectra, yet low peak luminosities like SN 1991bg. The spectra reveal that SN 2005hk, like SN 2002cx, exhibited expansion velocities that were roughly half those of typical type Ia supernovae. The R and I light curves of both supernovae were also peculiar in not displaying the secondary maximum observed for normal type Ia supernovae. Our YJH photometry of SN 2005hk reveals the same peculiarity in the near-infrared. By combining our optical and near-infrared photometry of SN 2005hk with published ultraviolet light curves obtained with the Swift satellite, we are able to construct a bolometric light curve from ~10 days before to ~60 days after B maximum. The shape and unusually low peak luminosity of this light curve, plus the low expansion velocities and absence of a secondary maximum at red and near-infrared wavelengths, are all in reasonable agreement with model calculations of a 3D deflagration which produces ~0.25 M_sun of 56Ni.Comment: Accepted by PASP, to appear in April 2007 issue, 63 pages, 16 figures, 11 table