7,014 research outputs found
Shocked molecular hydrogen towards the Tornado nebula
We present near-infrared and millimetre-line observations of the Tornado
nebula (G357.7-0.1). We detected 2.12 micron_m H2 1-0 S(1) line emission
towards the suspected site of interaction with a molecular cloud revealed by
the presence of an OH(1720 MHz) maser. The distribution of the H2 emission is
well correlated with the nonthermal radio continuum emission from the Tornado,
and the velocity of the H2 emission spans over 100 km/s, which both imply that
the H2 emission is shock excited. We also detected millimetre-lines from 12CO
and 13CO transitions at the velocity of the maser, and mapped the distribution
of the molecular cloud in a 2 x 2 arcmin^2 region around the maser. The peak of
the molecular cloud aligns well with an indentation in the nebula's radio
continuum distribution, suggesting that the nebula's shock is being decelerated
at this location, which is consistent with the presence of the OH(1720 MHz)
maser and shocked H2 emission at that location.Comment: 10 pages, 8 figures, minor changes, accepted to MNRA
Design of a five-axis ultra-precision micro-milling machineâUltraMill. Part 2: Integrated dynamic modelling, design optimisation and analysis
Using computer models to predict the dynamic performance of ultra-precision machine tools can help manufacturers to substantially reduce the lead time and cost of developing new machines. However, the use of electronic drives on such machines is becoming widespread, the machine dynamic performance depending not only on the mechanical structure and components but also on the control system and electronic drives. Bench-top ultra-precision machine tools are highly desirable for the micro-manufacturing of high-accuracy micro-mechanical components. However, the development is still at the nascent stage and hence lacks standardised guidelines. Part 2 of this two-part paper proposes an integrated approach, which permits analysis and optimisation of the entire machine dynamic performance at the early design stage. Based on the proposed approach, the modelling and simulation process of a novel five-axis bench-top ultra-precision micro-milling machine toolâUltraMillâis presented. The modelling and simulation cover the dynamics of the machine structure, the moving components, the control system and the machining process and are used to predict the entire machine performance of two typical configurations
Hall magnetohydrodynamics of partially ionized plasmas
The Hall effect arises in a plasma when electrons are able to drift with the
magnetic field but ions cannot. In a fully-ionized plasma this occurs for
frequencies between the ion and electron cyclotron frequencies because of the
larger ion inertia. Typically this frequency range lies well above the
frequencies of interest (such as the dynamical frequency of the system under
consideration) and can be ignored. In a weakly-ionized medium, however, the
Hall effect arises through a different mechanism -- neutral collisions
preferentially decouple ions from the magnetic field. This typically occurs at
much lower frequencies and the Hall effect may play an important role in the
dynamics of weakly-ionised systems such as the Earth's ionosphere and
protoplanetary discs.
To clarify the relationship between these mechanisms we develop an
approximate single-fluid description of a partially ionized plasma that becomes
exact in the fully-ionized and weakly-ionized limits. Our treatment includes
the effects of ohmic, ambipolar, and Hall diffusion. We show that the Hall
effect is relevant to the dynamics of a partially ionized medium when the
dynamical frequency exceeds the ratio of ion to bulk mass density times the
ion-cyclotron frequency, i.e. the Hall frequency. The corresponding length
scale is inversely proportional to the ion to bulk mass density ratio as well
as to the ion-Hall beta parameter.Comment: 11 page, 1 figure, typos removed, numbers in tables revised; accepted
for publication in MNRA
A Multi-Wavelength Study of Sgr A*: The Role of Near-IR Flares in Production of X-ray, Soft -ray and Sub-millimeter Emission
(abridged) We describe highlights of the results of two observing campaigns
in 2004 to investigate the correlation of flare activity in Sgr A* in different
wavelength regimes, using a total of nine ground and space-based telescopes. We
report the detection of several new near-IR flares during the campaign based on
{\it HST} observations. The level of near-IR flare activity can be as low as
mJy at 1.6 m and continuous up to about 40% of the total
observing time. Using the NICMOS instrument on the {\it HST}, the {\it
XMM-Newton} and CSO observatories, we also detect simultaneous bright X-ray and
near-IR flare in which we observe for the first time correlated substructures
as well as simultaneous submillimeter and near-IR flaring. X-ray emission is
arising from the population of near-IR-synchrotron-emitting relativistic
particles which scatter submillimeter seed photons within the inner 10
Schwarzschild radii of Sgr A* up to X-ray energies. In addition, using the
inverse Compton scattering picture, we explain the high energy 20-120 keV
emission from the direction toward Sgr A*, and the lack of one-to-one X-ray
counterparts to near-IR flares, by the variation of the magnetic field and the
spectral index distributions of this population of nonthermal particles. In
this picture, the evidence for the variability of submillimeter emission during
a near-IR flare is produced by the low-energy component of the population of
particles emitting synchrotron near-IR emission. Based on the measurements of
the duration of flares in near-IR and submillimeter wavelengths, we argue that
the cooling could be due to adiabatic expansion with the implication that flare
activity may drive an outflow.Comment: 48 pages, 12 figures, ApJ (in press
Self-lensing of a Singular Isothermal Sphere
Many astrophysical systems can be approximated as isothermal spheres. In an
isothermal sphere, the ``foreground'' objects can act as lenses on
``background'' objects in the same distribution. We study gravitational lensing
by a singular isothermal sphere analytically. Our results may have interesting
applications.Comment: 15 pages plus 2 figures. Revised final version to appear in Phys.
Rev. D (2000
Molecular Diagnostics of Supernova Remnant Shocks
We have undertaken a study of radio and infrared molecular-line emission
towards several SNRs in order to investigate molecular signatures of SNR
shocks, and to test models for OH maser production in SNRs. Here we present
results on G349.7+0.2.Comment: 4 pages, 3 figures, appears in "Neutron Stars in Supernova Remnants"
(ASP Conference Proceedings), eds P. O. Slane and B. M. Gaensler, 2002, p.39
Applied Interventions in the Prevention and Treatment of Obesity Through the Research of Professor Jane Wardle
Purpose of Review
Obesity presents a challenge for practitioners, policy makers, researchers and for those with obesity themselves. This review focuses on psychological approaches to its management and prevention in children and adults.
Recent Findings
Through exploring the work of the late Professor Jane Wardle, we look at the earliest behavioural treatment approaches and how psychological theory has been used to develop more contemporary approaches, for example incorporating genetic feedback and habit formation theory into interventions. We also explore how Jane has challenged thinking about the causal pathways of obesity in relation to eating behaviour. Beyond academic work, Jane was an advocate of developing interventions which had real-world applications.
Summary
Therefore, we discuss how she not only developed new interventions but also made these widely available and the charity that she established
Edging your bets: advantage play, gambling, crime and victimisation
Consumerism, industrial development and regulatory liberalisation have underpinned the ascendance of gambling to a mainstream consumption practice. In particular, the online gambling environment has been marketed as a site of âsafe risksâ where citizens can engage in a multitude of different forms of aleatory consumption. This paper offers a virtual ethnography of an online âadvantage playâ subculture. It demonstrates how advantage players have reinterpreted the online gambling landscape as an environment saturated with crime and victimisation. In this virtual world, advantage play is no longer simply an instrumental act concerned with profit accumulation to finance consumer desires. Rather, it acts as an opportunity for individuals to engage in a unique form of edgework, whereby the threat to oneâs well-being is tested through an ability to avoid crime and victimisation. This paper demonstrates how mediated environments may act as sites for edgeworking and how the potential for victimisation can be something that is actively engaged with
Shocked molecular gas towards the SNR G359.1-0.5 and the Snake
We have found a bar of shocked molecular hydrogen (H2) towards the OH(1720
MHz) maser located at the projected intersection of supernova remnant (SNR)
G359.1-0.5 and the nonthermal radio filament, known as the Snake. The H2 bar is
well aligned with the SNR shell and almost perpendicular to the Snake. The
OH(1720 MHz) maser is located inside the sharp western edge of the H2 emission,
which is consistent with the scenario in which the SNR drives a shock into a
molecular cloud at that location. The spectral-line profiles of 12CO, HCO+ and
CS towards the maser show broad-line absorption, which is absent in the 13CO
spectra and most probably originates from the pre-shock gas. A density gradient
is present across the region and is consistent with the passage of the SNR
shock while the H2 filament is located at the boundary between the pre--shocked
and post-shock regions.Comment: 8 pages, 12 figures, accepted by the MNRAS, typos fixe
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