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Where do electronic markets come from? Regulation and the transformation of financial exchanges
The practices of high-frequency trading (HFT) are dependent on automated financial markets, especially those produced by securities exchanges electronically interconnected with competing exchanges. How did this infrastructural and organizational state of affairs come to be? Employing the conceptual distinction between fixed-role and switch-role markets, we analyse the discourse surrounding the design and eventual approval of the Securities and Exchange Commissionâs Regulation of Exchanges and Alternative Trading Systems (Reg ATS). We find that the disruption of the exchange industry at the hands of automated markets was produced through an interweaving of both technological and political change. This processual redefinition of the âexchangeâ, in addition, may provide a suggestive precedent for understanding contemporary regulatory crises generated by other digital marketplace platforms
On the Nature of the Bursting X-Ray Pulsar GRO J1744-28
The unusual properties of the bursting X-ray pulsar GRO J1744-28 are
explained in terms of a low-mass X-ray binary system consisting of an evolved
stellar companion transferring mass through Roche-lobe overflow onto a neutron
star, implying that the inclination of the system is < 18 degrees.
Interpretation of the QPO at frequency nu(QPO) = 40 Hz using the beat-frequency
model of Alpar \& Shaham and the measured period derivative with the Ghosh \&
Lamb accretion-torque model implies that the persistent X-ray luminosity of the
source is approximately equal to the Eddington luminosity and that the neutron
star has a surface equatorial magnetic field = 2e10 [40 Hz/nu(QPO)] G for
standard neutron star parameters. This implies a distance to GRO J1744-28 of ~
5 [nu(QPO)/40 Hz]^{1/6} b^{1/2} kpc, where b < 1 is a correction factor that
depends on the orientation of the neutron star.Comment: 10 pages, 2 figures, uuencoded gzipped tarred file. Uses AAS macros
v. 4. Revised shortened paper, accepted for publication in Astrophysical
Journal Letter
A versatile, automated and high-throughput drug screening platform for zebrafish embryos
Zebrafish provide a unique opportunity for drug screening in living animals, with the fast developing, transparent embryos allowing for relatively high-throughput, microscopy-based screens. However, the limited availability of rapid, flexible imaging and analysis platforms has limited the use of zebrafish in drug screens. We have developed an easy-to-use, customisable automated screening procedure suitable for high-throughput phenotype-based screens of live zebrafish. We utilised the WiScanÂź Hermes High Content Imaging System to rapidly acquire brightfield and fluorescent images of embryos, and the WiSoftÂź Athena Zebrafish Application for analysis, which harnesses an Artificial Intelligence-driven algorithm to automatically detect fish in brightfield images, identify anatomical structures, partition the animal into regions, and exclusively select the desired side-oriented fish. Our initial validation combined structural analysis with fluorescence images to enumerate GFP-tagged haematopoietic stem and progenitor cells in the tails of embryos, which correlated with manual counts. We further validated this system to assess the effects of genetic mutations and x-ray irradiation in high content using a wide range of assays. Further, we performed simultaneous analysis of multiple cell types using dual fluorophores in high throughput. In summary, we demonstrate a broadly applicable and rapidly customisable platform for high-content screening in zebrafish
TLR7 ligation augments hematopoiesis in Rps14 (uS11) deficiency via paradoxical suppression of inflammatory signaling
Myelodysplastic syndrome (MDS) is a hematological malignancy characterized by blood cytopenias and predisposition to acute myeloid leukemia (AML). Therapies for MDS are lacking, particularly those that have an impact in the early stages of disease. We developed a model of MDS in zebrafish with knockout of Rps14, the primary mediator of the anemia associated with del(5q) MDS. These mutant animals display dose- and age-dependent abnormalities in hematopoiesis, culminating in bone marrow failure with dysplastic features. We used Rps14 knockdown to undertake an in vivo small-molecule screening, to identify compounds that ameliorate the MDS phenotype, and we identified imiquimod, an agonist of Toll-like receptor-7 (TLR7) and TLR8. Imiquimod alleviates anemia by promoting hematopoietic stem and progenitor cell expansion and erythroid differentiation, the mechanism of which is dependent on TLR7 ligation and Myd88. TLR7 activation in this setting paradoxically promoted an anti-inflammatory gene signature, indicating cross talk via TLR7 between proinflammatory pathways endogenous to Rps14 loss and the NF-ÎșB pathway. Finally, in highly purified human bone marrow samples from anemic patients, imiquimod led to an increase in erythroid output from myeloerythroid progenitors and common myeloid progenitors. Our findings have both specific implications for the development of targeted therapeutics for del(5q) MDS and wider significance identifying a potential role for TLR7 ligation in modifying anemia
Genetic Polymorphisms and Bacterial Infections in Neonates
© 2016, Springer Science+Business Media New York.Identifying single nucleotide polymorphisms (SNPs) in the genes involved in sepsis may help to clarify the pathophysiology of neonatal sepsis. The aim of this study was to evaluate the relationships between different forms of bacterial infections in neonates and genes potentially involved in the response to invasion by infectious agents. The study involved 20 neonates with a diagnosis of sepsis, 25 neonates with localized bacterial infections, and otherwise healthy neonates born during the study period. A total of eight SNPs in four candidate genes including Toll-like receptors (TLR2, TLR4) and pro-inflammatory cytokines (IL-1, Il-6) were genotyped. Genotypes CT and TT of IL-1ÎČ C3953T were associated with a significantly increased risk of developing sepsis (OR = 9.3; p = 0.02). The percentage of heterozygotes for the mutant allele was 65 %, while homozygotesâ5 %. Among the patients with localized bacterial infections, TLR4 Asp299Gly, genotypes CT and TT IL-1ÎČ C3953T, and genotypes GC and CC IL-1ÎČ G-1473C showed the association with an increased risk of developing diseases (p = 0.05, p = 0.04, p = 0,04, respectively). These results show that genetic variability seems to play a role in sepsis and localized bacterial infections in neonates by influencing susceptibility to the disease
Wigner Crystalline Edges in nu < 1 Quantum Dots
We investigate the edge reconstruction phenomenon believed to occur in
quantum dots in the quantum Hall regime when the filling fraction is nu < 1.
Our approach involves the examination of large dots (< 40 electrons) using a
partial diagonalization technique in which the occupancies of the deep interior
orbitals are frozen. To interpret the results of this calculation, we evaluate
the overlap between the diagonalized ground state and a set of trial
wavefunctions which we call projected necklace (PN) states. A PN state is
simply the angular momentum projection of a maximum density droplet surrounded
by a ring of localized electrons. Our calculations reveal that PN states have
up to 99% overlap with the diagonalized ground states, and are lower in energy
than the states identified in Chamon and Wen's study of the edge
reconstruction.Comment: 8 pages, 8 figures, to be published in Phys. Rev.
Stellar population and dust extinction in an ultraluminous infrared galaxy at z=1.135
We present the detailed optical to far-infrared observations of SST
J1604+4304, an ULIRG at z = 1.135. Analyzing the stellar absorption lines,
namely, the CaII H & K and Balmer H lines in the optical spectrum, we derive
the upper limits of an age for the stellar population. Given this constraint,
the minimum {chi}^2 method is used to fit the stellar population models to the
observed SED from 0.44 to 5.8um. We find the following properties. The stellar
population has an age 40 - 200 Myr with a metallicity 2.5 Z_{sun}. The
starlight is reddened by E(B-V) = 0.8. The reddening is caused by the
foreground dust screen, indicating that dust is depleted in the starburst site
and the starburst site is surrounded by a dust shell. The infrared (8-1000um)
luminosity is L_{ir} = 1.78 +/- 0.63 * 10^{12} L_{sun}. This is two times
greater than that expected from the observed starlight, suggesting either that
1/2 of the starburst site is completely obscured at UV-optical wavelengths, or
that 1/2 of L_{ir} comes from AGN emission. The inferred dust mass is 2.0 +/-
1.0 * 10^8 M_{sun}. This is sufficient to form a shell surrounding the galaxy
with an optical depth E(B-V) = 0.8. From our best stellar population model - an
instantaneous starburst with an age 40 Myr, we infer the rate of 19
supernovae(SNe) per year. Simply analytical models imply that 2.5 Z_{sun} in
stars was reached when the gas mass reduced to 30% of the galaxy mass. The gas
metallcity is 4.8 Z_{sun} at this point. The gas-to-dust mass ratio is then 120
+/- 73. The inferred dust production rate is 0.24 +/- 0.12 M_{sun} per SN. If
1/2 of L_{ir} comes from AGN emission, the rate is 0.48 +/- 0.24 M_{sun} per
SN. We discuss the evolutionary link of SST J1604+4304 to other galaxy
populations in terms of the stellar masses and the galactic winds.Comment: 11 pages, 9 figures, accepted for publication in MNRA
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