1,038 research outputs found
Roadmaps to Utopia: Tales of the Smart City
Notions of the Smart City are pervasive in urban development discourses. Various frameworks for the development of smart cities, often conceptualized as roadmaps, make a number of implicit claims about how smart city projects proceed but the legitimacy of those claims is unclear. This paper begins to address this gap in knowledge. We explore the development of a smart transport application, MotionMap, in the context of a £16M smart city programme taking place in Milton Keynes, UK. We examine how the idealized smart city narrative was locally inflected, and discuss the differences between the narrative and the processes and outcomes observed in Milton Keynes. The research shows that the vision of data-driven efficiency outlined in the roadmaps is not universally compelling, and that different approaches to the sensing and optimization of urban flows have potential for empowering or disempowering different actors. Roadmaps tend to emphasize the importance of delivering quick practical results. However, the benefits observed in Milton Keynes did not come from quick technical fixes but from a smart city narrative that reinforced existing city branding, mobilizing a growing network of actors towards the development of a smart region. Further research is needed to investigate this and other smart city developments, the significance of different smart city narratives, and how power relationships are reinforced and constructed through them
Vernalization-Repression of Arabidopsis FLC Requires Promoter Sequences but Not Antisense Transcripts
The repression of Arabidopsis FLC expression by vernalization (extended cold) has become a model for understanding polycomb-associated epigenetic regulation in plants. Antisense and sense non-coding RNAs have been respectively implicated in initiation and maintenance of FLC repression by vernalization. We show that the promoter and first exon of the FLC gene are sufficient to initiate repression during vernalization; this initial repression of FLC does not require antisense transcription. Long-term maintenance of FLC repression requires additional regions of the gene body, including those encoding sense non-coding transcripts
A connection between star formation activity and cosmic rays in the starburst galaxy M 82
Although Galactic cosmic rays (protons and nuclei) are widely believed to be
dominantly accelerated by the winds and supernovae of massive stars, definitive
evidence of this origin remains elusive nearly a century after their discovery
[1]. The active regions of starburst galaxies have exceptionally high rates of
star formation, and their large size, more than 50 times the diameter of
similar Galactic regions, uniquely enables reliable calorimetric measurements
of their potentially high cosmic-ray density [2]. The cosmic rays produced in
the formation, life, and death of their massive stars are expected to
eventually produce diffuse gamma-ray emission via their interactions with
interstellar gas and radiation. M 82, the prototype small starburst galaxy, is
predicted to be the brightest starburst galaxy in gamma rays [3, 4]. Here we
report the detection of >700 GeV gamma rays from M 82. From these data we
determine a cosmic-ray density of 250 eV cm-3 in the starburst core of M 82, or
about 500 times the average Galactic density. This result strongly supports
that cosmic-ray acceleration is tied to star formation activity, and that
supernovae and massive-star winds are the dominant accelerators.Comment: 18 pages, 4 figures; published in Nature; Version is prior to
Nature's in-house style editing (differences are minimal
Discovery of very high energy gamma rays from PKS 1424+240 and multiwavelength constraints on its redshift
We report the first detection of very-high-energy (VHE) gamma-ray emission
above 140 GeV from PKS 1424+240, a BL Lac object with an unknown redshift. The
photon spectrum above 140 GeV measured by VERITAS is well described by a power
law with a photon index of 3.8 +- 0.5_stat +- 0.3_syst and a flux normalization
at 200 GeV of (5.1 +- 0.9_stat +- 0.5_syst) x 10^{-11} TeV^-1 cm^-2 s^-1, where
stat and syst denote the statistical and systematical uncertainty,
respectively. The VHE flux is steady over the observation period between MJD
54881 and 55003 (2009 February 19 to June 21). Flux variability is also not
observed in contemporaneous high energy observations with the Fermi Large Area
Telescope (LAT). Contemporaneous X-ray and optical data were also obtained from
the Swift XRT and MDM observatory, respectively. The broadband spectral energy
distribution (SED) is well described by a one-zone synchrotron self-Compton
(SSC) model favoring a redshift of less than 0.1. Using the photon index
measured with Fermi in combination with recent extragalactic background light
(EBL) absorption models it can be concluded from the VERITAS data that the
redshift of PKS 1424+240 is less than 0.66.Comment: accepted for publication, Ap
Status of the VERITAS Observatory
VERITAS, an Imaging Atmospheric Cherenkov Telescope (IACT) system for
gammma-ray astronomy in the GeV-TeV range, has recently completed its first
season of observations with a full array of four telescopes. A number of
astrophysical gamma-ray sources have been detected, both galactic and
extragalactic, including sources previously unknown at TeV energies. We
describe the status of the array and some highlight results, and assess the
technical performance, sensitivity and shower reconstruction capabilities.Comment: Submitted to Proceedings of "4th Heidelberg International Symposium
on High Energy Gamma-Ray Astronomy 2008
Evidence for long-term Gamma-ray and X-ray variability from the unidentified TeV source HESS J0632+057
HESS J0632+057 is one of only two unidentified very-high-energy gamma-ray
sources which appear to be point-like within experimental resolution. It is
possibly associated with the massive Be star MWC 148 and has been suggested to
resemble known TeV binary systems like LS I +61 303 or LS 5039. HESS J0632+057
was observed by VERITAS for 31 hours in 2006, 2008 and 2009. During these
observations, no significant signal in gamma rays with energies above 1 TeV was
detected from the direction of HESS J0632+057. A flux upper limit corresponding
to 1.1% of the flux of the Crab Nebula has been derived from the VERITAS data.
The non-detection by VERITAS excludes with a probability of 99.993% that HESS
J0632+057 is a steady gamma-ray emitter. Contemporaneous X-ray observations
with Swift XRT reveal a factor of 1.8+-0.4 higher flux in the 1-10 keV range
than earlier X-ray observations of HESS J0632+057. The variability in the
gamma-ray and X-ray fluxes supports interpretation of the ob ject as a
gamma-ray emitting binary.Comment: 8 pages, 3 figures, Accepted for publication in The Astrophysical
Journa
Plant-RRBS, a bisulfite and next-generation sequencing-based methylome profiling method enriching for coverage of cytosine positions
Background: Cytosine methylation in plant genomes is important for the regulation of gene transcription and transposon activity. Genome-wide methylomes are studied upon mutation of the DNA methyltransferases, adaptation to environmental stresses or during development. However, from basic biology to breeding programs, there is a need to monitor multiple samples to determine transgenerational methylation inheritance or differential cytosine methylation. Methylome data obtained by sodium hydrogen sulfite (bisulfite)-conversion and next-generation sequencing (NGS) provide genome- wide information on cytosine methylation. However, a profiling method that detects cytosine methylation state dispersed over the genome would allow high-throughput analysis of multiple plant samples with distinct epigenetic signatures. We use specific restriction endonucleases to enrich for cytosine coverage in a bisulfite and NGS-based profiling method, which was compared to whole-genome bisulfite sequencing of the same plant material.
Methods: We established an effective methylome profiling method in plants, termed plant-reduced representation bisulfite sequencing (plant-RRBS), using optimized double restriction endonuclease digestion, fragment end repair, adapter ligation, followed by bisulfite conversion, PCR amplification and NGS. We report a performant laboratory protocol and a straightforward bioinformatics data analysis pipeline for plant-RRBS, applicable for any reference-sequenced plant species.
Results: As a proof of concept, methylome profiling was performed using an Oryza sativa ssp. indica pure breeding line and a derived epigenetically altered line (epiline). Plant-RRBS detects methylation levels at tens of millions of cytosine positions deduced from bisulfite conversion in multiple samples. To evaluate the method, the coverage of cytosine positions, the intra-line similarity and the differential cytosine methylation levels between the pure breeding line and the epiline were determined. Plant-RRBS reproducibly covers commonly up to one fourth of the cytosine positions in the rice genome when using MspI-DpnII within a group of five biological replicates of a line. The method predominantly detects cytosine methylation in putative promoter regions and not-annotated regions in rice.
Conclusions: Plant-RRBS offers high-throughput and broad, genome- dispersed methylation detection by effective read number generation obtained from reproducibly covered genome fractions using optimized endonuclease combinations, facilitating comparative analyses of multi-sample studies for cytosine methylation and transgenerational stability in experimental material and plant breeding populations
Discovery of Very High-Energy Gamma-Ray Radiation from the BL Lac 1ES 0806+524
The high-frequency-peaked BL-Lacertae object \objectname{1ES 0806+524}, at
redshift z=0.138, was observed in the very-high-energy (VHE) gamma-ray regime
by VERITAS between November 2006 and April 2008. These data encompass the two-,
and three-telescope commissioning phases, as well as observations with the full
four-telescope array. \objectname{1ES 0806+524} is detected with a statistical
significance of 6.3 standard deviations from 245 excess events. Little or no
measurable variability on monthly time scales is found. The photon spectrum for
the period November 2007 to April 2008 can be characterized by a power law with
photon index between
300 GeV and 700 GeV. The integral flux above 300 GeV is
which corresponds to 1.8% of the Crab Nebula flux. Non contemporaneous
multiwavelength observations are combined with the VHE data to produce a
broadband spectral energy distribution that can be reasonably described using a
synchrotron-self Compton model.Comment: 14 pages, 4 figures, accepted to APJ
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