12,763 research outputs found
Aditional Ultra-High-Resolution Observations of Ca+ Ions in the Local Insterstellar Medium
We present ultra-high-resolution (0.35 km s−1 FWHM) observations of the interstellar Ca K line towards seven nearby stars. The spectral resolution was sufficient to resolve the line profiles fully, thereby enabling us to detect hitherto unresolved velocity components, and to obtain accurate measurements of the velocity dispersions (b values). Absorption components with velocities similar to those expected for the Local Interstellar Cloud (LIC) and the closely associated ‘G cloud’ were identified towards six of the seven stars. However, in most cases the b values deduced for these components were significantly larger than the b ≈ 2.2 km s−1 (i.e. Tk ≈ 7000 K, vt ≈ 1 km s−1) expected for the LIC, and it is argued that this results from the presence of additional, spectrally unresolved, components having similar velocities and physical conditions. For two stars (δ Vel and α Pav) we detect interstellar components with much smaller b values (1.1 ± 0.3 and 0.8 ± 0.1 km s−1, respectively) than are expected for low-density clouds within the Local Bubble. In the case of the narrow α Pav component, we also find an anomalously large Na i/Ca ii column density ratio, which is indicative of a relatively high density. Thus it is possible that, in addition to LIC-type clouds, the local interstellar medium contains a population of previously undetected cooler and denser interstellar clouds
Reweighted nuclear norm regularization: A SPARSEVA approach
The aim of this paper is to develop a method to estimate high order FIR and
ARX models using least squares with re-weighted nuclear norm regularization.
Typically, the choice of the tuning parameter in the reweighting scheme is
computationally expensive, hence we propose the use of the SPARSEVA (SPARSe
Estimation based on a VAlidation criterion) framework to overcome this problem.
Furthermore, we suggest the use of the prediction error criterion (PEC) to
select the tuning parameter in the SPARSEVA algorithm. Numerical examples
demonstrate the veracity of this method which has close ties with the
traditional technique of cross validation, but using much less computations.Comment: This paper is accepted and will be published in The Proceedings of
the 17th IFAC Symposium on System Identification (SYSID 2015), Beijing,
China, 201
Gas Absorption Detected from the Edge-on Debris Disk Surrounding HD32297
Near-infrared and optical imaging of HD32297 indicate that it has an edge-on
debris disk, similar to beta Pic. I present high resolution optical spectra of
the NaI doublet toward HD32297 and stars in close angular proximity. A
circumstellar absorption component is clearly observed toward HD32297 at the
stellar radial velocity, which is not observed toward any of its neighbors,
including the nearest only 0.9 arcmin away. An interstellar component is
detected in all stars >90 pc, including HD32297, likely due to the interstellar
material at the boundary of the Local Bubble. Radial velocity measurements of
the nearest neighbors, BD+07 777s and BD+07 778, indicate that they are
unlikely to be physically associated with HD32297. The measured circumstellar
column density around HD32997, log N(NaI) ~ 11.4, is the strongest NaI
absorption measured toward any nearby main sequence debris disk, even the
prototypical edge-on debris disk, beta Pic. Assuming that the morphology and
abundances of the gas component around HD32297 are similar to beta Pic, I
estimate an upper limit to the gas mass in the circumstellar disk surrounding
HD32297 of ~0.3 M_Earth.Comment: 13 pages, 2 figures; Accepted for publication in ApJ Letter
"Asthma can take over your life but having the right support makes that easier to deal with." Informing research priorities by exploring the barriers and facilitators to asthma control: a qualitative analysis of survey data.
BACKGROUND: Involving patients and the public in research prioritisation is important. Cochrane Airways works with authors to produce systematic reviews of evidence related to chronic airways disease. Cochrane Airways has undertaken activities to identify research priorities, including workshops with stakeholders and consultation with experts. We present the findings of an online survey, designed to align our work with the priorities of people affected by asthma. METHODS: We promoted a survey comprising open-ended questions via social media to people affected by asthma. We compiled the free-text responses and conducted an exploratory thematic analysis to identify important barriers and facilitators to asthma control. We triangulated findings with other research prioritisation activities to produce new review questions. RESULTS: We received 57 survey responses. Eight main themes emerged, most encompassing both facilitators and barriers: attitudes and knowledge; financial costs; environmental factors and triggers; healthcare systems; lifestyle factors; medication; self-care; and support. Barriers were more frequently mentioned than facilitators and many related to healthcare systems. CONCLUSIONS: These findings offer valuable insights into the challenges faced by individuals affected by asthma in the UK, and possibly further afield. We developed a list of priority reviews based on what was said by people in this survey and at a workshop. This demonstrates the real impact that people affected by asthma have on the research agenda of Cochrane Airways. Over the next 2-3 years we will produce reviews that address some of these questions hopefully leading to health benefits
Energy and width measurements of low-Z pionic X-ray transitions
High resolution spectrometric measurement of energy and natural line widths of 2p-1s pionic X ray transitions, as well as muonic transition energies in Li, Be, B, and C isotope
Solar energy conversion through the interaction of plasmons with tunnel junctions. Part A: Solar cell analysis. Part B: Photoconductor analysis
A solar cell utilizing guided optical waves and tunnel junctions was analyzed to determine its feasibility. From this analysis, it appears that the limits imposed upon conventional multiple cell systems also limit this solar cell. Due to this limitation, it appears that the relative simplicity of the conventional multiple cell systems over the solar cell make the conventional multiple cell systems the more promising candidate for improvement. It was discovered that some superlattice structures studied could be incorporated into an infrared photodetector. This photoconductor appears to be promising as a high speed, sensitive (high D sup star sub BLIP) detector in the wavelength range from 15 to over 100 micrometers
An analysis of the SPARSEVA estimate for the finite sample data case
In this paper, we develop an upper bound for the SPARSEVA (SPARSe Estimation
based on a VAlidation criterion) estimation error in a general scheme, i.e.,
when the cost function is strongly convex and the regularized norm is
decomposable for a pair of subspaces. We show how this general bound can be
applied to a sparse regression problem to obtain an upper bound for the
traditional SPARSEVA problem. Numerical results are used to illustrate the
effectiveness of the suggested bound
Space shuttle engineering and operations support. Avionics system engineering
The shuttle avionics integration laboratory (SAIL) requirements for supporting the Spacelab/orbiter avionics verification process are defined. The principal topics are a Spacelab avionics hardware assessment, test operations center/electronic systems test laboratory (TOC/ESL) data processing requirements definition, SAIL (Building 16) payload accommodations study, and projected funding and test scheduling. Because of the complex nature of the Spacelab/orbiter computer systems, the PCM data link, and the high rate digital data system hardware/software relationships, early avionics interface verification is required. The SAIL is a prime candidate test location to accomplish this early avionics verification
Design and technology GCE AS and A Level subject content
The AS and A level subject content sets out the knowledge, understanding and skills common to all AS and A level specifications in design and technology. It provides the framework within which awarding organisations create the detail of the subject specification. AS and A Level specifications in design and technology must reflect the subject aims and objectives. Aims and objectives Design and technology is an inspiring, rigorous and practical subject. Specifications in design and technology should encourage students to use creativity and imagination when applying iterative design processes to develop and modify designs, and to design and make prototypes/products1 that solve real world problems, considering their own and others’ needs, wants, aspirations and values. Specifications should enable students to identify market needs and opportunities for new products, initiate and develop design solutions, and make and test prototypes/products. Students should acquire subject knowledge in design and technology, including how a product can be developed through the stages of prototyping, realisation and commercial manufacture. Students should take every opportunity to integrate and apply their understanding and knowledge from other subject areas studied during Key Stage 4, with a particular focus on science and mathematics, and those subjects they are studying alongside AS and A level design and technology
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