Pool boiling on modified surfaces using R-123

This article has been made available through the Brunel Open Access Publishing Fund.Saturated pool boiling of R-123 was investigated for five horizontal copper surfaces modified by different treatments, namely, an emery-polished surface, a fine sandblasted surface, a rough sandblasted surface, an electron beam-enhanced surface, and a sintered surface. Each 40-mm-diameter heating surface formed the upper face of an oxygen-free copper block, electrically heated by embedded cartridge heaters. The experiments were performed from the natural convection regime through nucleate boiling up to the critical heat flux, with both increasing and decreasing heat flux, at 1.01 bar, and additionally at 2 bar and 4 bar for the emery-polished surface. Significant enhancement of heat transfer with increasing surface modification was demonstrated, particularly for the electron beam-enhanced and sintered surfaces. The emery-polished and sandblasted surface results are compared with nucleate boiling correlations and other published data. © 2014 Syed W. Ahmad, John S. Lewis, Ryan J. McGlen, and Tassos G. Karayiannis Published with license by Taylor & Francis

Imaging X-ray, Optical, and Infrared Observations of the Transient Anomalous X-ray Pulsar XTE J1810-197

We report X-ray imaging, timing, and spectral studies of XTE J1810-197, a 5.54s pulsar discovered by Ibrahim et al. (2003) in recent RXTE observations. In a set of short exposures with the Chandra HRC camera we detect a strongly modulated signal (55+/-4% pulsed fraction) with the expected period located at (J2000) 18:09:51.08, -19:43:51.7, with a uncertainty radius of 0.6 arcsec (90% C.L.). Spectra obtained with XMM-Newton are well fitted by a two-component model that typically describes anomalous X-ray pulsars (AXPs), an absorbed blackbody plus power law with parameters kT = 0.67+/-0.01 keV, Gamma=3.7+/-0.2, N_H=(1.05+/-0.05)E22 cm^-2, and Fx(0.5-10 keV) = 3.98E-11 ergs/cm2/s. Alternatively, a 2T blackbody fit is just as acceptable. The location of CXOU J180951.1-194351 is consistent with a point source seen in archival Einstein, Rosat, & ASCA images, when its flux was nearly two orders-of-magnitude fainter, and from which no pulsations are found. The spectrum changed dramatically between the "quiescent" and "active" states, the former can be modeled as a softer blackbody. Using XMM timing data, we place an upper limit of 0.03 lt-s on any orbital motion in the period range 10m-8hr. Optical and infrared images obtained on the SMARTS 1.3m telescope at CTIO show no object in the Chandra error circle to limits V=22.5, I=21.3, J=18.9, & K=17.5. Together, these results argue that CXOU J180951.1-194351 is an isolated neutron star, one most similar to the transient AXP AX J1844.8-0256. Continuing study of XTE J1810-197 in various states of luminosity is important for understanding and possibly unifying a growing class of isolated, young neutron stars that are not powered by rotation.Comment: 12 pages, 7 figures, AAS LaTex, uses emulateapj5.sty. Updated to include additional archival data and a new HRC observation. To appear in The Astrophysical Journa

Functional Task Test: 3. Skeletal Muscle Performance Adaptations to Space Flight

The functional task test is a multi-disciplinary study investigating how space-flight induced changes to physiological systems impacts functional task performance. Impairment of neuromuscular function would be expected to negatively affect functional performance of crewmembers following exposure to microgravity. This presentation reports the results for muscle performance testing in crewmembers. Functional task performance will be presented in the abstract "Functional Task Test 1: sensory motor adaptations associated with postflight alternations in astronaut functional task performance." METHODS: Muscle performance measures were obtained in crewmembers before and after short-duration space flight aboard the Space Shuttle and long-duration International Space Station (ISS) missions. The battery of muscle performance tests included leg press and bench press measures of isometric force, isotonic power and total work. Knee extension was used for the measurement of central activation and maximal isometric force. Upper and lower body force steadiness control were measured on the bench press and knee extension machine, respectively. Tests were implemented 60 and 30 days before launch, on landing day (Shuttle crew only), and 6, 10 and 30 days after landing. Seven Space Shuttle crew and four ISS crew have completed the muscle performance testing to date. RESULTS: Preliminary results for Space Shuttle crew reveal significant reductions in the leg press performance metrics of maximal isometric force, power and total work on R+0 (p<0.05). Bench press total work was also significantly impaired, although maximal isometric force and power were not significantly affected. No changes were noted for measurements of central activation or force steadiness. Results for ISS crew were not analyzed due to the current small sample size. DISCUSSION: Significant reductions in lower body muscle performance metrics were observed in returning Shuttle crew and these adaptations are likely contributors to impaired functional tasks that are ambulatory in nature (See abstract Functional Task Test: 1). Interestingly, no significant changes in central activation capacity were detected. Therefore, impairments in muscle function in response to short-duration space flight are likely myocellular rather than neuromotor in nature

A review of fMRI simulation studies

Simulation studies that validate statistical techniques for fMRI data are challenging due to the complexity of the data. Therefore, it is not surprising that no common data generating process is available (i.e. several models can be found to model BOLD activation and noise). Based on a literature search, a database of simulation studies was compiled. The information in this database was analysed and critically evaluated focusing on the parameters in the simulation design, the adopted model to generate fMRI data, and on how the simulation studies are reported. Our literature analysis demonstrates that many fMRI simulation studies do not report a thorough experimental design and almost consistently ignore crucial knowledge on how fMRI data are acquired. Advice is provided on how the quality of fMRI simulation studies can be improved

Formation of the compact jets in the black hole GX 339-4

Galactic black hole binaries produce powerful outflows with emit over almost the entire electromagnetic spectrum. Here, we report the first detection with the Herschel observatory of a variable far-infrared source associated with the compact jets of the black hole transient GX 339-4 during the decay of its recent 2010-2011 outburst, after the transition to the hard state. We also outline the results of very sensitive radio observations conducted with the Australia Telescope Compact Array, along with a series of near-infrared, optical (OIR) and X-ray observations, allowing for the first time the re-ignition of the compact jets to be observed over a wide range of wavelengths. The compact jets first turn on at radio frequencies with an optically thin spectrum that later evolves to optically thick synchrotron emission. An OIR reflare is observed about ten days after the onset of radio and hard X-ray emission, likely reflecting the necessary time to build up enough density, as well as to have acceleration (e.g. through shocks) along an extended region in the jets. The Herschel measurements are consistent with an extrapolation of the radio inverted power-law spectrum, but they highlight a more complex radio to OIR spectral energy distribution for the jets.Comment: Accepted for publication in MNRAS Letter, 6 pages, 3 Figures + 1 online Tabl

The 2002 Outburst of the Black-Hole X-ray Binary 4U 1543-47: Optical and Infrared Light Curves

We have obtained simultaneous optical and near infrared observations of 4U 1543-47 during its 2002 outburst. The most striking feature of the outburst light curve is the secondary maximum which appears after the object transitions into the low-hard state. This secondary maximum is much stronger in the infrared bands than optical. We suggest that the origin of the secondary maximum flux may be synchrotron radiation associated with a jet. Close infrared monitoring may lead to reliable triggers for simultaneous multiwavelength campaigns to study jet formation processes.Comment: Accepted for publication in Ap

Learning Behavioural Context

The original publication is available at www.springerlink.co

Market trends and outlook

1 online resource (PDF, 2 pages)This archival publication may not reflect current scientific knowledge or recommendations. Current information available from the University of Minnesota Extension: https://www.extension.umn.edu