1,410 research outputs found
Centaurus A at Ultra-High Energies
We review the importance of Centaurus A in high energy astrophysics as a
nearby object with many of the properties expected of a major source of very
high energy cosmic rays and gamma-rays. We examine observational techniques and
the results so far obtained in the energy range from 200 GeV to above 100 EeV
and attempt to fit those data with expectations of Centaurus A as an
astrophysical source from VHE to UHE energies.Comment: 11 pages, 4 figures, accepted for publication in PAS
Structure and activity of DmmA, a marine haloalkane dehalogenase
DmmA is a haloalkane dehalogenase (HLD) identified and characterized from the metagenomic DNA of a marine microbial consortium. Dehalogenase activity was detected with 1,3âdibromopropane as substrate, with steadyâstate kinetic parameters typical of HLDs ( K m = 0.24 ± 0.05 mM, k cat = 2.4 ± 0.1 s â1 ). The 2.2âĂ
crystal structure of DmmA revealed a fold and active site similar to other HLDs, but with a substantially larger active site binding pocket, suggestive of an ability to act on bulky substrates. This enhanced cavity was shown to accept a range of linear and cyclic substrates, suggesting that DmmA will contribute to the expanding industrial applications of HLDs. PDB Code(s): 3U1TPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90241/1/PRO_2009_sm_suppinfo.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/90241/2/2009_ftp.pd
Patients' use of a home-based virtual reality system to provide rehabilitation of the upper limb following stroke
Background: A low cost, virtual reality system that translates movements of the hand, fingers and thumb into game play was designed to provide a flexible and motivating approach to increasing adherence to home based rehabilitation. Objective: Effectiveness depends on adherence, so did patients use the intervention to the recommended level. If not, what reasons did they give? Design: Prospective cohort study plus qualitative analysis of interviews. Methods: 17 patients recovering from stroke recruited to the intervention arm of a feasibility trial had the equipment left in their homes for eight weeks and were advised to use it three times a day for periods of no more than 20 minutes. Frequency and duration of use were automatically recorded. At the end of the intervention, participants were interviewed to determine barriers to using it in the recommended way. Results: Duration of use and how many days they used the equipment are presented for the 13 participants who successfully started the intervention. These figures were highly variable and could fall far short of our recommendations. There was a weak (p=0.053) positive correlation between duration and baseline reported activities of daily living. Participants reported familiarity with technology and competing commitments as barriers to use although appreciated the flexibility of the intervention and found it motivating
A Precision Calculation of the Next-to-Leading Order Energy-Energy Correlation Function
The O(alpha_s^2) contribution to the Energy-Energy Correlation function (EEC)
of e+e- -> hadrons is calculated to high precision and the results are shown to
be larger than previously reported. The consistency with the leading logarithm
approximation and the accurate cancellation of infrared singularities exhibited
by the new calculation suggest that it is reliable. We offer evidence that the
source of the disagreement with previous results lies in the regulation of
double singularities.Comment: 6 pages, uuencoded LaTeX and one eps figure appended Complete paper
as PostScript file (125 kB) available at:
http://www.phys.washington.edu/~clay/eecpaper1/paper.htm
The School Sport Co-ordinator Programme: Changing the Role of the Physical Education Teacher?
Over the last decade or so, young people have increasingly become a focus of UK sport policy. Fuelled in part by concerns such as the increasing levels of childhood inactivity and obesity, and the lack of international success in sport, a plethora of policy initiatives aimed at young people have been developed. In April 2000, the government published its sport strategy document, A Sporting Future for All, pulling together all the threads of recent policies, and in it, restating its commitment to youth sport, sport in education, excellence and sport in the community. One such policy initiative, the School Sport Co-ordinator programme, is the focus of this paper. The School Sport Co-ordinator programme, currently being introduced into schools in England, is an initiative that involves two government departments (sport and education) and a number of other agencies, reflecting the government's current agenda to ensure 'joined up policy' thinking. It aims to develop opportunities for youth sport through co-ordinated links between PE and sport in schools, both within and outside of the formal curriculum, with those in local community sports settings. The essence of the School Sport Co-ordinator programme is to free up nominated teachers in schools from teaching to allow them time for development activities, specifically to encourage schools and community sports providers to work in partnership. This paper draws on data from an ongoing research project examining the implementation of one School Sport Co-ordinator partnership, 'northbridge'. Drawing on in-depth interviews, it explores the perceptions of the newly established School Sport Co-ordinators of their changing role. The paper highlights some of the initial tensions and challenges for them in their task of working across different educational and sporting contexts
Hypoxia promotes breast cancer cell invasion through HIF-1a-mediated up-regulation of the invadopodial actin bundling protein CSRP2
Hypoxia is a common feature of solid tumours that promotes invasion and metastatic dissemination. Invadopodia are actin-rich membrane protrusions that direct extracellular matrix proteolysis and facilitate tumour cell invasion. Here, we show that CSRP2, an invadopodial actin bundling protein, is upregulated by hypoxia in various breast cancer cell lines, as well as in pre-clinical and clinical breast tumour specimens. We functionally characterized two hypoxia responsive elements within the proximal promoter of CSRP2 gene which are targeted by hypoxia-inducible factor-1 (HIF-1) and required for promoter transactivation in response to hypoxia. Remarkably, CSRP2 knockdown significantly inhibits hypoxia-stimulated invadopodium formation, ECM degradation and invasion in MDA-MB-231 cells, while CSRP2 forced expression was sufficient to enhance the invasive capacity of HIF-1a-depleted cells under hypoxia. In MCF-7 cells, CSRP2 upregulation was required for hypoxia-induced formation of invadopodium precursors that were unable to promote ECM degradation. Collectively, our data support that CSRP2 is a novel and direct cytoskeletal target of HIF-1 which facilitates hypoxia-induced breast cancer cell invasion by promoting invadopodia formation.The authors are grateful to Monika Dieterle, Arnaud Muller, Pter Nazarov and Muhammad Zaeem Noman (Oncology Department, LIH, Luxembourg) for technical assistance, support in statistical analyses and constructive discussions. The authors also warmly thank Sara A. Courtneidge for the gift of the Tks5-GFP construct (Oregon Health and Science University, Portland, USA). This work was mainly supported by a research grant from âFondation Cancerâ Luxembourg (FC/2016/02), and the National Research Fund (C16/ BM/11297905). Joshua Brown Clay is recipient of a Postdoctoral fellowship from âFonds De La Recherche Scientifqueâ - FNRS âTĂ©lĂ©vieâ (7.4512.16). Antoun Al Absi and Hannah Wurzer are recipients of PhD fellowships from the National Research Fund, Luxembourg (AFR7892325 and PRIDE15/10675146/CANBIO, respectively)
Morphological identification of Bighead Carp, Silver Carp, and Grass Carp eggs using random forests machine learning classification
Visual identification of fish eggs is difficult and unreliable due to a lack of information on the morphological egg characteristics of many species. We used random forests machine learning to predict the identity of genetically identified Bighead Carp Hypophthalmichthys nobilis, Grass Carp Ctenopharyngodon idella, and Silver Carp H. molitrix eggs based on egg morphometric and environmental characteristics. Family, genus, and species taxonomic-level random forests models were explored to assess the performance and accuracy of the predictor variables. The egg characteristics of Bighead Carp, Grass Carp, and Silver Carp were similar, and they were difficult to distinguish from one another. When combined into a single invasive carp class, the random forests models were â„ 97% accurate at identifying invasive carp eggs, with a â€5% false positive rate. Egg membrane diameter was the most important predictive variable, but the addition of ten other variables resulted in a 98% success rate for identifying invasive carp eggs from 26 other upper Mississippi River basin species. Our results revealed that a combination of morphometric and environmental measurements can be used to identify invasive carp eggs. Similar machine learning approaches could be used to identify the eggs of other fishes. These results will help managers more easily and quickly assess invasive carp reproduction
Characterization of Seven Ultra-Wide Trans-Neptunian Binaries
The low-inclination component of the Classical Kuiper Belt is host to a
population of extremely widely-separated binaries. These systems are similar to
other Trans-Neptunian binaries (TNBs) in that the primary and secondary
components of each system are of roughly equal size. We have performed an
astrometric monitoring campaign of a sample of seven wide-separation,
long-period TNBs and present the first-ever well-characterized mutual orbits
for each system. The sample contains the most eccentric (2006 CH69, e=0.9) and
the most widely-separated, weakly bound (2001 QW322, a/Rh~0.22) binary minor
planets known, and also contains the system with lowest-measured mass of any
TNB (2000 CF105, M~1.85E17 kg). Four systems orbit in a prograde sense, and
three in a retrograde sense. They have a different mutual inclination
distribution compared to all other TNBs, preferring low mutual-inclination
orbits. These systems have geometric r-band albedos in the range of 0.09-0.3,
consistent with radiometric albedo estimates for larger solitary
low-inclination Classical Kuiper Belt objects, and we limit the plausible
distribution of albedos in this region of the Kuiper Belt. We find that
gravitational collapse binary formation models produce a similar orbital
distribution to that currently observed, which along with a confluence of other
factors supports formation of the cold Classical Kuiper Belt in situ through
relatively rapid gravitational collapse rather than slow hierarchical
accretion. We show that these binary systems are sensitive to disruption via
collisions, and their existence suggests that the size distribution of TNOs at
small sizes remains relatively shallow.Comment: 22 pages, 14 Figures, in press in the Astrophysical Journal, updated
to reflect bibliographic corrections and additional table added in proo
The what and where of adding channel noise to the Hodgkin-Huxley equations
One of the most celebrated successes in computational biology is the
Hodgkin-Huxley framework for modeling electrically active cells. This
framework, expressed through a set of differential equations, synthesizes the
impact of ionic currents on a cell's voltage -- and the highly nonlinear impact
of that voltage back on the currents themselves -- into the rapid push and pull
of the action potential. Latter studies confirmed that these cellular dynamics
are orchestrated by individual ion channels, whose conformational changes
regulate the conductance of each ionic current. Thus, kinetic equations
familiar from physical chemistry are the natural setting for describing
conductances; for small-to-moderate numbers of channels, these will predict
fluctuations in conductances and stochasticity in the resulting action
potentials. At first glance, the kinetic equations provide a far more complex
(and higher-dimensional) description than the original Hodgkin-Huxley
equations. This has prompted more than a decade of efforts to capture channel
fluctuations with noise terms added to the Hodgkin-Huxley equations. Many of
these approaches, while intuitively appealing, produce quantitative errors when
compared to kinetic equations; others, as only very recently demonstrated, are
both accurate and relatively simple. We review what works, what doesn't, and
why, seeking to build a bridge to well-established results for the
deterministic Hodgkin-Huxley equations. As such, we hope that this review will
speed emerging studies of how channel noise modulates electrophysiological
dynamics and function. We supply user-friendly Matlab simulation code of these
stochastic versions of the Hodgkin-Huxley equations on the ModelDB website
(accession number 138950) and
http://www.amath.washington.edu/~etsb/tutorials.html.Comment: 14 pages, 3 figures, review articl
Probing potassium in the atmosphere of HD 80606b with tunable filter transit spectrophotometry from the Gran Telescopio Canarias
We report observations of HD 80606 using the 10.4-m Gran Telescopio Canarias
(GTC) and the OSIRIS tunable filter imager. We acquired very-high-precision,
narrow-band photometry in four bandpasses around the K I absorption feature
during the January 2010 transit of HD 80606b and during out-of-transit
observations conducted in January and April of 2010. We obtained differential
photometric precisions of \sim 2.08e-4 for the in-transit flux ratio measured
at 769.91-nm, which probes the K I line core. We find no significant difference
in the in-transit flux ratio between observations at 768.76 and 769.91 nm. Yet,
we find a difference of \sim 8.09 \pm 2.88e-4 between these observations and
observations at a longer wavelength that probes the K I wing (777.36 nm). While
the presence of red noise in the transit data has a non-negligible effect on
the uncertainties in the flux ratio, the 777.36-769.91 nm colour during transit
shows no effects from red noise and also indicates a significant colour change,
with a mean value of \sim 8.99\pm0.62e-4. This large change in the colour is
equivalent to a \sim 4.2% change in the apparent planetary radius with
wavelength, which is much larger than the atmospheric scale height. This
implies the observations probed the atmosphere at very low pressures as well as
a dramatic change in the pressure at which the slant optical depth reaches
unity between \sim770 and 777 nm. We hypothesize that the excess absorption may
be due to K I in a high-speed wind being driven from the exoplanet's exosphere.
We discuss the viability of this and alternative interpretations, including
stellar limb darkening, starspots, and effects from Earth's atmosphere. We
strongly encourage follow-up observations of HD 80606b to confirm the signal
measured here. Finally, we discuss the future prospects for exoplanet
characterization using tunable filter spectrophotometry.Comment: Accepted to MNRAS; revised version includes some major updates; now
21 pages, with 14 figures and 9 table
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