7,717 research outputs found
The inner kiloparsec of the jet in 3C264
We present new multi-frequency EVN, MERLIN and VLA observations of the radio
source 3C264, sensitive to linear scales ranging from the parsec to several
kiloparsecs. The observations confirm the existence of regions with different
properties in the first kiloparsec of the jet. The most remarkable feature is
the transition between a well collimated narrow jet at distances from the core
below 80 pc, to a conical-shaped wide jet, with an opening angle of 20 degrees.
Another change of properties, consisting of an apparent deflection of the jet
ridge line and a diminution of the surface brightness, occurs at a distance of
300 pc from the core, coincident with the radius of a ring observed at optical
wavelengths. Our observations add new pieces of information on the spectrum of
the radio-optical jet of 3C264, with results consistent with a synchrotron
emission mechanism and a spectrum break frequency in the infrared. Brightness
profiles taken perpendicularly to the jet of 3C264 are consistent with a spine
brightened jet at distances below 100 pc from the core, and an edge-brightened
jet beyond, which can be interpreted as evidence of a transverse jet velocity
structure. Our observations do not allow us to distinguish between the presence
of a face--on dust and gas disk at the center of the host galaxy of 3C264, or
rather an evacuated bubble. However, the properties of the jet structure, the
changes in the polarization angle, and the plausible jet orientation can be
naturally brought into agreement in the bubble scenario.Comment: 10 pages, 9 figures, accepted in A&
A cooperative-relational approach to digital libraries
Copyright @ 2007 Springer-Verlag, Berlin HeidelbergThis paper presents a novel approach to model-driven development of Digital Library (DL) systems. The overall idea is to allow Digital Library systems designers (e.g. information architects, librarians, domain experts) to easily design such systems by using a visual language. We designed a Domain Specific Visual Language for such a purpose and developed a framework supporting it; this framework helps designers by automatically generating code for the defined Digital Library system, so that they do not have to get involved into technical issues concerning its deployment. In our approach, both Human-Computer Interaction and Computer Supported Collaborative Work techniques are exploited when generating interfaces and services for the specific Digital Library domain
Vortex ratchet reversal: The role of interstitial vortices
Triangular arrays of Ni nanotriangles embedded in superconducting Nb films
exhibit unexpected dynamical vortex effects. Collective pinning with a vortex
lattice configuration different from the expected fundamental triangular
"Abrikosov state" is found. The vortex motion which prevails against the
triangular periodic potential is produced by channelling effects between
triangles. Interstitial vortices coexisting with pinned vortices in this
asymmetric potential, lead to ratchet reversal, i.e. a DC output voltage which
changes sign with the amplitude of an applied alternating drive current. In
this landscape, ratchet reversal is always observed at all magnetic fields (all
numbers of vortices) and at different temperatures. The ratchet reversal is
unambiguously connected to the presence of two locations for the vortices:
interstitial and above the artificial pinning sites.Comment: 21 pages, 4 figures, 1 Tabl
Rapid turnover of effector-memory CD4(+) T cells in healthy humans
Memory T cells can be divided into central-memory (T(CM)) and effector-memory (T(EM)) cells, which differ in their functional properties. Although both subpopulations can persist long term, it is not known whether they are maintained by similar mechanisms. We used in vivo labeling with deuterated glucose to measure the turnover of CD4(+) T cells in healthy humans. The CD45R0(+)CCR7(-) T(EM) subpopulation was shown to have a rapid proliferation rate of 4.7% per day compared with 1.5% per day for CD45R0(+)CCR7(+) T(CM) cells; these values are equivalent to average intermitotic (doubling) times of 15 and 48 d, respectively. In contrast, the CD45RA(+)CCR7(+) naive CD4(+) T cell population was found to be much longer lived, being labeled at a rate of only 0.2% per day (corresponding to an intermitotic time of approximately 1 yr). These data indicate that human CD4(+) T(EM) cells constitute a short-lived cell population that requires continuous replenishment in vivo
Ca impurity in small mixed He-He clusters
The structure of small mixed helium clusters doped with one calcium atom has
been determined within the diffusion Monte Carlo framework. The results show
that the calcium atom sits at the He-He interface. This is in agreement
with previous studies, both experimental and theoretical, performed for large
clusters. A comparison between the results obtained for the largest cluster we
have considered for each isotope shows a clear tendency of the Ca atom to
reside in a deep dimple at the surface of the cluster for He clusters, and
to become fully solvated for He clusters. We have calculated the absorption
spectrum of Ca around the transition and have found that
it is blue-shifted from that of the free-atom transition by an amount that
depends on the size and composition of the cluster.Comment: 24 pages, 11 figures. Accepted on Journal of Chemical Physic
Wearable Systems for Monitoring Mobility-Related Activities in Chronic Disease: A Systematic Review
The use of wearable motion sensing technology offers important advantages over conventional methods for obtaining measures of physical activity and/or physical functioning in individuals with chronic diseases. This review aims to identify the actual state of applying wearable systems for monitoring mobility-related activity in individuals with chronic disease conditions. In this review we focus on technologies and applications, feasibility and adherence aspects, and clinical relevance of wearable motion sensing technology. PubMed (Medline since 1990), PEdro, and reference lists of all relevant articles were searched. Two authors independently reviewed randomised trials systematically. The quality of selected articles was scored and study results were summarised and discussed. 163 abstracts were considered. After application of inclusion criteria and full text reading, 25 articles were taken into account in a full text review. Twelve of these papers evaluated walking with pedometers, seven used uniaxial accelerometers to assess physical activity, six used multiaxial accelerometers, and two papers used a combination approach of a pedometer and a multiaxial accelerometer for obtaining overall activity and energy expenditure measures. Seven studies mentioned feasibility and/or adherence aspects. The number of studies that use movement sensors for monitoring of activity patterns in chronic disease (postural transitions, time spent in certain positions or activities) is nonexistent on the RCT level of study design. Although feasible methods for monitoring human mobility are available, evidence-based clinical applications of these methods in individuals with chronic diseases are in need of further development
Ferromagnetic proximity effect in a-Co_xSi_(1-x)/Nb bilayers: Role of magnetic disorder and interface transparency
The superconducting and magnetic properties of a-Co_(x)Si_(1−x) /Nb bilayers have been studied as a function of Co content in order to analyze the superconducting/ferromagnetic proximity effect in a system with strong disorder in the magnetic layers. As Co atoms become more diluted, the magnetization of the amorphous a-CoxSi1−x alloy decreases gradually, whereas their resistivity increases and enters in a weak localization regime. The superconducting transition temperatures of the a-Co_(x)Si_(1−x) /Nb bilayers follow a decreasing trend as Co content is reduced, reaching the lowest value at the boundary between the ferromagnetic-nonmagnetic amorphous phases. These results can be understood in terms of the increase in interface transparency together with the changes in the spin-flip scatterin
Translating model simulators to analysis models
The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-540-78743-3_6Proceedings of 11th International Conference, FASE 2008, Held as Part of the Joint European Conferences on Theory and Practice of Software, ETAPS 2008, Budapest, Hungary, March 29-April 6, 2008.We present a novel approach for the automatic generation of model-to-model transformations given a description of the operational semantics of the source language by means of graph transformation rules. The approach is geared to the generation of transformations from Domain-Specific Visual Languages (DSVLs) into semantic domains with an explicit notion of transition, like for example Petri nets. The generated transformation is expressed in the form of operational triple graph grammar rules that transform the static information (initial model) and the dynamics (source rules and their execution control structure). We illustrate these techniques with a DSVL in the domain of production systems, for which we generate a transformation into Petri nets.Work sponsored by the Spanish Ministry of Science and Education, project MOSAIC (TSI2005-08225-C07-06
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