18,760 research outputs found
A Comment on "The Far Future of Exoplanet Direct Characterization" - the Case for Interstellar Space Probes
Following on from ideas presented in a recent paper by Schneider et al.
(2010) on "The Far Future of Exoplanet Direct Characterization", I argue that
they have exaggerated the technical obstacles to performing such 'direct
characterization' by means of fast (order 0.1c) interstellar space probes. A
brief summary of rapid interstellar spaceflight concepts that may be found in
the literature is presented. I argue that the presence of interstellar dust
grains, while certainly something which will need to be allowed for in
interstellar vehicle design, is unlikely to be the kind of 'show stopper'
suggested by Schneider et al. Astrobiology as a discipline would be a major
beneficiary of developing an interstellar spaceflight capability, albeit in the
longer term, and I argue that astrobiologists should keep an open mind to the
possibilities.Comment: Accepted for publication in Astrobiolog
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Petrography and bulk composition of Miller Range 05035: a new lunar VLT gabbro
Miller Range (MIL) 05035 is a crystalline lunar mare gabbroic meteorite collected in Antarctica in 2005 [1]. It is an important new sample in the lunar meteorite (LM) collection as it is only one of ~8 to be classified as basaltic in nature. MIL 05035 is coarsely grained with large pyroxene grains ( 8mm) subophitically enclosing plagioclase grains ( 6mm), and accessory ilmenite, spinel, silica and sulphide phases
Crime Prevention and Community Safety
This chapter traces and evaluates both the historic emergence of the modern ‘preventive turn’ as well as the elaboration and institutionalisation of crime prevention and community safety over the last thirty years or so. Focusing on the UK, the evolution and changes over time are situated, where relevant, in a broader international context. The chapter identifies three distinct periods of developments that structure the shifts in crime prevention policy and practices from the 1980s to the present day. It explores the conceptualisation, take-up and advancement of a preventive mentality and practices in relation to situational, social and developmental crime prevention as well as community safety. It goes on to assess the institutionalisation of preventive partnerships and early intervention as distinct forms of governance and their implications for ‘responsibilisation’ and ‘securitisation’. In conclusion, it reflects upon the journey travelled thus far as well as possible future directions in an age of austerity
Biological basis of child health 2: introduction to fertilisation, prenatal development and birth
This article is the second in a series called the biological basis of child health. It considers the period of development from fertilisation to birth, outlining the three stages of prenatal development - the germinal, embryonic and fetal stages. The article details how tissues and organs typically develop at each stage, and explains how and when deviations in development and congenital anomalies are likely to occur. It also describes some of the common congenital anomalies, their potential effects and their detection before or after birth. Information is also provided about the delivery of full-term infants, including the stages of labour
Universal trapping scaling on the unstable manifold for a collisionless electrostatic mode
An amplitude equation for an unstable mode in a collisionless plasma is
derived from the dynamics on the two-dimensional unstable manifold of the
equilibrium. The mode amplitude decouples from the phase due to the
spatial homogeneity of the equilibrium, and the resulting one-dimensional
dynamics is analyzed using an expansion in . As the linear growth rate
vanishes, the expansion coefficients diverge; a rescaling
of the mode amplitude absorbs these
singularities and reveals that the mode electric field exhibits trapping
scaling as . The dynamics for
depends only on the phase where is the derivative of the dielectric as
.Comment: 11 pages (Latex/RevTex), 2 figures available in hard copy from the
Author ([email protected]); paper accepted by Physical Review
Letter
AXJ1749+684: a narrow emission-line galaxy with a flat X-ray spectrum
We report the serendipitous detection of an X-ray source, AXJ1749+684, with
the ASCA Gas Imaging Spectrometer. AXJ1749+684 is identified with a
LINER/starburst-type spiral galaxy KUG 1750+683A at a redshift z = 0.05. It has
a hard X-ray spectrum, consistent with that of the X-ray background (XRB) in
the 1-10 keV band. Despite the optical classification, the X-ray luminosity
cannot be explained by starburst activity. Combined with spatial variations in
the optical emission line ratios, this suggests the presence of an obscured
Seyfert nucleus embedded within a starforming galaxy. Similar behaviour could
explain the ambiguous properties of the faint narrow-line X-ray galaxies
(NLXGs) emerging from deep X-ray surveys.Comment: MNRAS Letters in press, 6 pages, 7 figures in MNRAS LaTex styl
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