40,125 research outputs found
A Report on a Long Term Research Program on the Bowman site in Arkansas
The Bowman (3LR46) and Bowman/Wallace (3LR50) sites represent a Caddo multi-mound center on the Red River in Little River County, Arkansas. Southeastern researchers may recognize the site name from an engraved shell cup and several additional “SECC” objects found in Mound 2. Hoffman provides a brief summary of digging at the sites and offers a proposed site organization of eight mounds (both burial and “temple mounds”) surrounding a possible plaza area and at least three offmound cemeteries. Material collected from Mounds 1 and 2 and two off-mound cemeteries suggest Haley phase (ca. A.D. 1200-1400) occupations. Additionally, data from Mound 1 have the potential to “reveal a solid sequence of [Caddo] burial and mortuary artifact styles” beginning with the earliest Caddo occupations in the Red River region
'Oligarchs', Business and Russian Foreign Policy: From El'tsin to Putin
The paper investigates the role of private and state-controlled business in the formation and implementation of Russian foreign policy since the collapse of the Soviet Union. The extent to which the 'oligarchs' and business more generally followed their own interests in their external relations or acted as tools of the Russian state is a particular focus. Under President Boris El'tsin, Boris Berezovskii was the only one of the oligarchs to have significant influence on Russian foreign policy. President Vladimir Putin's moves against the oligarchs were motivated partly by the desire to restrict political debate, including on foreign policy, and partly to prevent Mikhail Khodorkovskii from creating a private oil pipeline system which would have subverted Putin's foreign policy, but the main reason was probably the desire to restore state control over key industrial sectors. Under El'tsin, business had followed its own interests, which sometimes conflicted with Russian foreign policy and sometimes reinforced it; but after Putin's attacks on the oligarchs, business seemed more integrated into policy implementation, while still following its own interests where they did not conflict with those of the state, as is suggested by a discussion of Gazprom's foreign policy role
Current Research: Toward a Collaborative Development of a Truly Comprehensive Multi-State Material Culture Database
Throughout the past several years, I have been compiling, with the help of several Caddo researchers, a comprehensive multi-state database primarily composed of whole Caddo vessels from published excavations, private collections, and archaeological reports. At present, the database contains over 13,000 vessel entries from over 500 sites ranging from a single vessel recorded at a site to hundreds. Over the years, the database has evolved to contain, where applicable, attribute fields on type, variety, motif designs (largely using the Glossary of Motifs published in the Spiro shell engravings, collegiate assignment, form, temper, decorative method (incised, brushed, etc.), context (burial #, site #, intra site location), pigment, archaeological phase, collector, repository, associated photographs, and reference citations. The database is managed using Microsoft Access where data are imported into ESRI ArcGIS and spatial analyses can be conducted.
This is a continual, and perhaps never-ending, work in progress where attribute fields are added, types are vetted, and new sites are included. In some cases, “Caddo-like” vessels from sites outside the Caddo Archaeological Area, or Caddo Homeland, are included in order to evaluate social interaction and exchange of ideas. Through this process, some initial insights into landscape scale social interactions and interregional relationships using this growing comprehensive database have been explored
Citizenship, community, and counter-terrorism : UK security discourse, 2001-2011
This paper analyses a corpus of UK policy documents which sets out national security policy as an exemplar of the contemporary discourse of counter-terrorism in Europe, the USA and worldwide. A corpus of 148 documents (c. 2.8 million words) was assembled to reflect the security discourse produced by the UK government before and after the 7/7 attacks on the London Transport system. To enable a chronological comparison, the two sub-corpora were defined: one relating to a discourse of citizenship and community cohesion (2001-2006); and one relating to the ‘Preventing Violent Extremism’ discourse (2007-2011). Wordsmith Tools (Scott 2008) was used to investigate keywords and patterns of collocation. The results present
themes emerging from a comparative analysis of the 100 strongest keywords in each sub- corpus; as well as a qualitative analysis of related patterns of the collocation, focusing inparticular on features of connotation and semantic prosody
Water does partially dissociate on the perfect TiO2(110) surface : a quantitative structure determination
There has been a long-standing controversy as to whether water can dissociate on perfect areas of a TiO2(110) surface; most early theoretical work indicated this dissociation was facile, while experiments indicated little or no dissociation. More recently the consensus of most theoretical calculations is that no dissociation occurs. New results presented here, based on analysis of scanned-energy mode photoelectron diffraction data from the OH component of O 1s photoemission, show the coexistence of molecular water and OH species in both atop (OHt) and bridging (OHbr) sites. OHbr can arise from reaction with oxygen vacancy defect sites (Ovac), but OHt have only been predicted to arise from dissociation on the perfect areas of the surface. The relative concentrations of OHt and OHbr sites arising from these two dissociation mechanisms are found to be fully consistent with the initial concentration Ovac sites, while the associated Ti-O bondlengths of the OHt and OHbr species are found to be 1.85±0.08Å and 1.94±0.07 Å, respectively
Hubble Space Telescope Imaging of the Globular Cluster System around NGC 5846
Bimodal globular cluster metallicity distributions have now been seen in a
handful of large ellipticals. Here we report the discovery of a bimodal
distribution in the dominant group elliptical NGC 5846, using the Hubble Space
Telescope's Wide Field and Planetary Camera 2 (WFPC2). The two peaks are
located at V-I = 0.96 and 1.17, which roughly correspond to metallicities of
[Fe/H] = -1.2 and -0.2 respectively. The luminosity functions of the blue and
red subpopulations appear to be the same, indicating that luminosity does not
correlate with metallicity within an individual galaxy's globular cluster
system. Our WFPC2 data cover three pointings allowing us to examine the spatial
distribution of globular clusters out to 30 kpc (or 2.5 galaxy effective
radii). We find a power law surface density with a very flat slope, and a
tendency for globular clusters to align close to the galaxy minor axis. An
extrapolation of the surface density profile, out to 50 kpc, gives a specific
frequency S_N = 4.3 +/- 1.1. Thus NGC 5846 has a much lower specific frequency
than other dominant ellipticals in clusters but is similar to those in groups.
The central galaxy regions reveal some filamentary dust features, presumably
from a past merger or accretion of a gas-rich galaxy. This dust reaches to the
very nucleus and so provides an obvious source of fuel for the radio core. We
have searched for proto-globular clusters that may have resulted from the
merger/accretion and find none. Finally, we briefly discuss the implications of
our results for globular cluster formation mechanisms.Comment: 22 pages, Latex. To be published in the Astronomical Journal. Full
paper available at http://www.ucolick.org/~forbes/home.htm
Scalable Robust Kidney Exchange
In barter exchanges, participants directly trade their endowed goods in a
constrained economic setting without money. Transactions in barter exchanges
are often facilitated via a central clearinghouse that must match participants
even in the face of uncertainty---over participants, existence and quality of
potential trades, and so on. Leveraging robust combinatorial optimization
techniques, we address uncertainty in kidney exchange, a real-world barter
market where patients swap (in)compatible paired donors. We provide two
scalable robust methods to handle two distinct types of uncertainty in kidney
exchange---over the quality and the existence of a potential match. The latter
case directly addresses a weakness in all stochastic-optimization-based methods
to the kidney exchange clearing problem, which all necessarily require explicit
estimates of the probability of a transaction existing---a still-unsolved
problem in this nascent market. We also propose a novel, scalable kidney
exchange formulation that eliminates the need for an exponential-time
constraint generation process in competing formulations, maintains provable
optimality, and serves as a subsolver for our robust approach. For each type of
uncertainty we demonstrate the benefits of robustness on real data from a
large, fielded kidney exchange in the United States. We conclude by drawing
parallels between robustness and notions of fairness in the kidney exchange
setting.Comment: Presented at AAAI1
Cold gas and star formation in a merging galaxy sequence
We explore the evolution of the cold gas and star-formation activity during
galaxy interactions, using a merging galaxy sequence comprising both pre- and
post-mergers. Data for this study come from the literature but supplemented by
new radio observations presented here. Firstly, we confirm that the
star-formation efficiency (SFE) increases close to nuclear coalescence. At
post-merger stages there is evidence that the SFE declines to values typical of
ellipticals. This trend can be attributed to M(H_2) depletion due to
interaction induced star-formation. However, there is significant scatter,
likely to arise from differences in the interaction details of individual
systems. Secondly, we find that the central molecular hydrogen surface density,
increases close to the final stages of the merging of the two nuclei. Such a
trend is also predicted by numerical simulations. Furthermore, there is
evidence for a decreasing fraction of cold gas mass from early interacting
systems to merger remnants, attributed to gas conversion into other forms. The
evolution of the total-radio to blue-band luminosity ratio, reflecting the
disk+nucleus star-formation activity, is also investigated. Although this ratio
is on average higher than that of isolated spirals, we find a marginal increase
along the merging sequence, attributed to the relative insensitivity of disk
star-formation to interactions. However, a similar result is also obtained for
the nuclear radio emission, although galaxy interactions are believed to
significantly affect the activity in the central galaxy regions. Finally, we
find that the FIR--radio flux ratio distribution of interacting galaxies is
consistent with star-formation being the main energising source.Comment: 18 pages, 17 figures, accepted for publication in MNRA
Keck Imaging of the Globular Cluster Systems in the Early--type Galaxies NGC 1052 and NGC 7332
The presence of two globular cluster subpopulations in early-type galaxies is
now the norm rather than the exception. Here we present two more examples for
which the host galaxy appears to have undergone a recent merger. Using
multi-colour Keck imaging of NGC 1052 and NGC 7332 we find evidence for a
bimodal globular cluster colour distribution in both galaxies, with roughly
equal numbers of blue and red globular clusters. The blue ones have similar
colours to those in the Milky Way halo and are thus probably very old and
metal-poor. If the red GC subpopulations are at least solar metallicity, then
stellar population models indicate young ages. We discuss the origin of
globular clusters within the framework of formation models. We conclude that
recent merger events in these two galaxies have had little effect on their
overall GC systems. We also derive globular cluster density profiles, global
specific frequencies and in the case of NGC 1052, radial colour gradients and
azimuthal distribution. In general these globular cluster properties are normal
for early-type galaxies.Comment: 11 pages, Latex, 15 figures, 2 tables, accepted by MNRA
Compensation for time fluctuations of phase modulation in a liquid-crystal-on-silicon display by process synchronization in laser materials processing
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