1,243 research outputs found
A 16-channel Digital TDC Chip with internal buffering and selective readout for the DIRC Cherenkov counter of the BABAR experiment
A 16-channel digital TDC chip has been built for the DIRC Cherenkov counter
of the BaBar experiment at the SLAC B-factory (Stanford, USA). The binning is
0.5 ns, the conversion time 32 ns and the full-scale 32 mus. The data driven
architecture integrates channel buffering and selective readout of data falling
within a programmable time window. The time measuring scale is constantly
locked to the phase of the (external) clock. The linearity is better than 80 ps
rms. The dead time loss is less than 0.1% for incoherent random input at a rate
of 100 khz on each channel. At such a rate the power dissipation is less than
100 mw. The die size is 36 mm2.Comment: Latex, 18 pages, 13 figures (14 .eps files), submitted to NIM
Direct visualization of G-quadruplexes in DNA using atomic force microscopy
The formation of G-quadruplexes in G-rich regions of DNA is believed to affect DNA transcription and replication. However, it is currently unclear how this formation occurs in the presence of a complementary strand. We have used atomic force microscopy (AFM) to image stable RNA/DNA hybrid loops generated by transcription of the plasmid pPH600, which contains a 604-bp fragment of the murine immunoglobulin SÎł3 switch region. We show that the non-RNA-containing portion folds into G-quadruplexes, consistent with computational predictions. We also show that hybrid formation prevents further transcription from occurring, implying a regulatory role. After in vitro transcription, almost all (93%) of the plasmids had an asymmetric loop, a large asymmetric blob or a spur-like projection at the appropriate position on the DNA contour. The loops disappeared following treatment of the transcribed plasmid with RNase H, which removes mRNA hybridized with the template strand. Replacement of K+ in the transcription buffer with either Na+ or Li+ caused a reduction in the percentage of plasmids containing loops, blobs or spurs, consistent with the known effects of monovalent cations on G-quadruplex stability. The minimal sample preparation required for AFM imaging has permitted direct observation of the structural changes resulting from G-quadruplex formation
On Nichols algebras over PGL(2,q) and PSL(2,q)
We compute necessary conditions on Yetter-Drinfeld modules over the groups
\mathbf{PGL}(2,q)=\mathbf{PGL}(2,\FF_q) and
\mathbf{PSL}(2,q)=\mathbf{PSL}(2,\FF_q) to generate finite dimensional
Nichols algebras. This is a first step towards a classification of pointed Hopf
algebras with group of group-likes isomorphic to one of these groups.
As a by-product of the techniques developed in this work, we prove that there
is no non-trivial finite-dimensional pointed Hopf algebra over the Mathieu
groups and .Comment: Minor change
Solving Nonlinear Parabolic Equations by a Strongly Implicit Finite-Difference Scheme
We discuss the numerical solution of nonlinear parabolic partial differential
equations, exhibiting finite speed of propagation, via a strongly implicit
finite-difference scheme with formal truncation error . Our application of interest is the spreading of
viscous gravity currents in the study of which these type of differential
equations arise. Viscous gravity currents are low Reynolds number (viscous
forces dominate inertial forces) flow phenomena in which a dense, viscous fluid
displaces a lighter (usually immiscible) fluid. The fluids may be confined by
the sidewalls of a channel or propagate in an unconfined two-dimensional (or
axisymmetric three-dimensional) geometry. Under the lubrication approximation,
the mathematical description of the spreading of these fluids reduces to
solving the so-called thin-film equation for the current's shape . To
solve such nonlinear parabolic equations we propose a finite-difference scheme
based on the Crank--Nicolson idea. We implement the scheme for problems
involving a single spatial coordinate (i.e., two-dimensional, axisymmetric or
spherically-symmetric three-dimensional currents) on an equispaced but
staggered grid. We benchmark the scheme against analytical solutions and
highlight its strong numerical stability by specifically considering the
spreading of non-Newtonian power-law fluids in a variable-width confined
channel-like geometry (a "Hele-Shaw cell") subject to a given mass
conservation/balance constraint. We show that this constraint can be
implemented by re-expressing it as nonlinear flux boundary conditions on the
domain's endpoints. Then, we show numerically that the scheme achieves its full
second-order accuracy in space and time. We also highlight through numerical
simulations how the proposed scheme accurately respects the mass
conservation/balance constraint.Comment: 36 pages, 9 figures, Springer book class; v2 includes improvements
and corrections; to appear as a contribution in "Applied Wave Mathematics II
The camera of the fifth H.E.S.S. telescope. Part I: System description
In July 2012, as the four ground-based gamma-ray telescopes of the H.E.S.S.
(High Energy Stereoscopic System) array reached their tenth year of operation
in Khomas Highlands, Namibia, a fifth telescope took its first data as part of
the system. This new Cherenkov detector, comprising a 614.5 m^2 reflector with
a highly pixelized camera in its focal plane, improves the sensitivity of the
current array by a factor two and extends its energy domain down to a few tens
of GeV.
The present part I of the paper gives a detailed description of the fifth
H.E.S.S. telescope's camera, presenting the details of both the hardware and
the software, emphasizing the main improvements as compared to previous
H.E.S.S. camera technology.Comment: 16 pages, 13 figures, accepted for publication in NIM
Experimental investigation of the initial regime in fingering electrodeposition: dispersion relation and velocity measurements
Recently a fingering morphology, resembling the hydrodynamic Saffman-Taylor
instability, was identified in the quasi-two-dimensional electrodeposition of
copper. We present here measurements of the dispersion relation of the growing
front. The instability is accompanied by gravity-driven convection rolls at the
electrodes, which are examined using particle image velocimetry. While at the
anode the theory presented by Chazalviel et al. describes the convection roll,
the flow field at the cathode is more complicated because of the growing
deposit. In particular, the analysis of the orientation of the velocity vectors
reveals some lag of the development of the convection roll compared to the
finger envelope.Comment: 11 pages, 15 figures, REVTEX 4; reference adde
Wellbeing: The Challenge of âOperationalisingâ an Holistic Concept within a Reductionist Public Health Programme
Background
Wellbeing is a concept that, whilst contested, recognises individual and wider social, economic, political and environmental contextual influences â and is of growing interest and relevance locally and globally. In this paper, we report on one aspect of an evaluative research study conducted on a public health programme in North West England.
Aims
Within the context of a process evaluation that explored the delivery of a public health programme and sought to increase understanding of how and why different approaches worked well or not so well, this paper focuses specifically on the concept of wellbeing, examining perceptions of multiple stakeholders.
Methods
Interviews and focus groups were undertaken with 52 stakeholders involved in managing and facilitating the programme and its composite projects and with 90 community members involved as project participants. Data were subjected to thematic analysis, crossâcheck and refining.
Findings
Findings highlight stakeholdersâ diverse understandings of wellbeing, the complex relationship between health and wellbeing, and the perceived dissonance between the holistic concept of wellbeing and the reductionist design of the programme.
Conclusions
Wellbeing was understood to be âmore than healthâ and âmore than happinessâ, concerned with effective functioning, sense of purpose and flourishing. Essentially holistic, wellbeing offers opportunities to transcend clinical/pathogenic conceptions of âhealthâ and resonate with individuals, communities and local authorities. This raises concerns about how wellbeing can be meaningfully realised without compromising the concept, particularly when programmes are structured in reductionist ways requiring monitoring against discrete outcomes. Implications for practice include: utilising wellbeing as a driver for crossâcutting public health in challenging economic and organisational contexts; acknowledging that wellbeing is essentially social as well as individual; appreciating that wellbeing is experienced in relation to contexts and surroundings; and recognising that wellbeing defined in terms of individual happiness risks compromising the future wellbeing of societies and the planet
Mental status and health-related quality of life in an elderly population 15 years after limited cerebral ischaemia
BACKGROUND: Stroke has a major impact on survivors. Our study was designed to describe the mental status and health-related quality of life (HRQoL) in long-term survivors of TIA or minor ischaemic stroke (MIS) and evaluate associations of mental and physical factors with HR-QoL.
METHODS: A random sample of the 10-year survivors of the Dutch TI
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