Analysis of pressurized and axially loaded orthotropic multicell tanks

Nondimensional stress resultants and displacements for multicell tanks of orthotropic construction loaded by internal pressure and axial compressio

The Stellar Content of Obscured Galactic Giant HII Regions. VI: W51A

We present K-band spectra of newly born OB stars in the obscured Galactic giant H II region W51A and ~ 0.8'' angular resolution images in the J, H and K_S-bands. Four objects have been spectroscopically classified as O-type stars. The mean spectroscopic parallax of the four stars gives a distance of 2.0 \pm 0.3 kpc (error in the mean), significantly smaller than the radio recombination line kinematic value of 5.5 kpc or the values derived from maser propermotion observations (6--8 kpc). The number of Lyman continuum photons from the contribution of all massive stars (NLyc ~ 1.5 x 10^{50} s^{-1}) is in good agreement with that inferred from radio recombination lines (NLyc = 1.3 x 10^{50} s^{-1}) after accounting for the smaller distance derived here. We present analysis of archival high angular resolution images (NAOS CONICA at VLT and T-ReCS at Gemini) of the compact region W51 IRS2. The K_S--band images resolve the infrared source IRS~2 indicating that it is a very young compact HII region. Sources IRS2E was resolved into compact cluster (within 660 AU of projected distance) of 3 objects, but one of them is just bright extended emission. W51d1 and W51d2 were identified with compact clusters of 3 objects (maybe 4 in the case of W51d1) each one. Although IRS~2E is the brightest source in the K-band and at 12.6 \micron, it is not clearly associated with a radio continuum source. Our spectrum of IRS~2E shows, similar to previous work, strong emission in Br$\gamma$ and HeI, as well as three forbidden emission lines of FeIII and emission lines of molecular hydrogen (H_2) marking it as a massive young stellar object.Comment: 31 pages and 9 figures, submitted to A

Lattice calculation of the lowest order hadronic contribution to the muon anomalous magnetic moment

We present a quenched lattice calculation of the lowest order (alpha^2) hadronic contribution to the anomalous magnetic moment of the muon which arises from the hadronic vacuum polarization. A general method is presented for computing entirely in Euclidean space, obviating the need for the usual dispersive treatment which relies on experimental data for e^+e^- annihilation to hadrons. While the result is not yet of comparable accuracy to those state-of-the-art calculations, systematic improvement of the quenched lattice computation to this level of accuracy is straightforward and well within the reach of present computers. Including the effects of dynamical quarks is conceptually trivial, the computer resources required are not.Comment: 12 pages, including two figures. Added reference and footnote Replaced with published version; minor changes asked for by referees and minor deletions to stay within page limi

Technology for large-scale translation of clinical practice guidelines : a pilot study of the performance of a hybrid human and computer-assisted approach

Background: The construction of EBMPracticeNet, a national electronic point-of-care information platform in Belgium, was initiated in 2011 to optimize quality of care by promoting evidence-based decision-making. The project involved, among other tasks, the translation of 940 EBM Guidelines of Duodecim Medical Publications from English into Dutch and French. Considering the scale of the translation process, it was decided to make use of computer-aided translation performed by certificated translators with limited expertise in medical translation. Our consortium used a hybrid approach, involving a human translator supported by a translation memory (using SDL Trados Studio), terminology recognition (using SDL Multiterm termbases) from medical termbases and support from online machine translation. This has resulted in a validated translation memory which is now in use for the translation of new and updated guidelines. Objective: The objective of this study was to evaluate the performance of the hybrid human and computer-assisted approach in comparison with translation unsupported by translation memory and terminology recognition. A comparison was also made with the translation efficiency of an expert medical translator. Methods: We conducted a pilot trial in which two sets of 30 new and 30 updated guidelines were randomized to one of three groups. Comparable guidelines were translated (a) by certificated junior translators without medical specialization using the hybrid method (b) by an experienced medical translator without this support and (c) by the same junior translators without the support of the validated translation memory. A medical proofreader who was blinded for the translation procedure, evaluated the translated guidelines for acceptability and adequacy. Translation speed was measured by recording translation and post-editing time. The Human Translation Edit Rate was calculated as a metric to evaluate the quality of the translation. A further evaluation was made of translation acceptability and adequacy. Results: The average number of words per guideline was 1,195 and the mean total translation time was 100.2 min/1,000 words. No meaningful differences were found in the translation speed for new guidelines. The translation of updated guidelines was 59 min/1,000 words faster (95% CI 2-115; P=.044) in the computer-aided group. Revisions due to terminology accounted for one third of the overall revisions by the medical proofreader. Conclusions: Use of the hybrid human and computer-aided translation by a non-expert translator makes the translation of updates of clinical practice guidelines faster and cheaper because of the benefits of translation memory. For the translation of new guidelines there was no apparent benefit in comparison with the efficiency of translation unsupported by translation memory (whether by an expert or non-expert translator

Weathering microenvironments on feldspar surfaces: implications for understanding fluid-mineral reactions in soils

The mechanisms by which coatings develop on weathered grain surfaces, and their potential impact on rates of fluid-mineral interaction, have been investigated by examining feldspars from a 1.1 ky old soil in the Glen Feshie chronosequence, Scottish highlands. Using the focused ion beam technique, electron-transparent foils for characterization by transmission electron microscopy were cut from selected parts of grain surfaces. Some parts were bare whereas others had accumulations, a few micrometres thick, of weathering products, often mixed with mineral and microbial debris. Feldspar exposed at bare grain surfaces is crystalline throughout and so there is no evidence for the presence of the amorphous 'leached layers' that typically form in acid-dissolution experiments and have been described from some natural weathering contexts. The weathering products comprise sub-μm thick crystallites of an Fe-K aluminosilicate, probably smectite, that have grown within an amorphous and probably organic-rich matrix. There is also evidence for crystallization of clays having been mediated by fungal hyphae. Coatings formed within Glen Feshie soils after ∼1.1 ky are insufficiently continuous or impermeable to slow rates of fluid-feldspar reactions, but provide valuable insights into the complex weathering microenvironments on debris and microbe-covered mineral surfaces

Testing formula satisfaction

We study the query complexity of testing for properties defined by read once formulae, as instances of massively parametrized properties, and prove several testability and non-testability results. First we prove the testability of any property accepted by a Boolean read-once formula involving any bounded arity gates, with a number of queries exponential in \epsilon and independent of all other parameters. When the gates are limited to being monotone, we prove that there is an estimation algorithm, that outputs an approximation of the distance of the input from satisfying the property. For formulae only involving And/Or gates, we provide a more efficient test whose query complexity is only quasi-polynomial in \epsilon. On the other hand we show that such testability results do not hold in general for formulae over non-Boolean alphabets; specifically we construct a property defined by a read-once arity 2 (non-Boolean) formula over alphabets of size 4, such that any 1/4-test for it requires a number of queries depending on the formula size

The Stellar Content of Obscured Galactic Giant H II Regions

Near infrared images of the Galactic giant HII region W43 reveal a dense stellar cluster at its center. Broad band JHK photometry of the young cluster and K-band spectra of three of its bright stars are presented. The 2 micron spectrum of the brightest star in the cluster is very well matched to the spectra of Wolf-Rayet stars of sub-type WN7. Two other stars are identified as O type giants or supergiants by their NIII and CIV emission. The close spatial clustering of O and the hydrogen WN type stars is analogous to the intense star burst clusters R136 in the Large Magellanic Cloud and NGC3603 in the Galaxy.Comment: 22 pages (LaTex), including 7 figures (eps

Matching Dynamics with Constraints

We study uncoordinated matching markets with additional local constraints that capture, e.g., restricted information, visibility, or externalities in markets. Each agent is a node in a fixed matching network and strives to be matched to another agent. Each agent has a complete preference list over all other agents it can be matched with. However, depending on the constraints and the current state of the game, not all possible partners are available for matching at all times. For correlated preferences, we propose and study a general class of hedonic coalition formation games that we call coalition formation games with constraints. This class includes and extends many recently studied variants of stable matching, such as locally stable matching, socially stable matching, or friendship matching. Perhaps surprisingly, we show that all these variants are encompassed in a class of "consistent" instances that always allow a polynomial improvement sequence to a stable state. In addition, we show that for consistent instances there always exists a polynomial sequence to every reachable state. Our characterization is tight in the sense that we provide exponential lower bounds when each of the requirements for consistency is violated. We also analyze matching with uncorrelated preferences, where we obtain a larger variety of results. While socially stable matching always allows a polynomial sequence to a stable state, for other classes different additional assumptions are sufficient to guarantee the same results. For the problem of reaching a given stable state, we show NP-hardness in almost all considered classes of matching games.Comment: Conference Version in WINE 201

\'Free Collisions in a Microgravity Many-Particle Experiment. II. The Collision Dynamics of Dust-Coated Chondrules

The formation of planetesimals in the early Solar System is hardly understood, and in particular the growth of dust aggregates above millimeter sizes has recently turned out to be a difficult task in our understanding [Zsom et al. 2010, A&A, 513, A57]. Laboratory experiments have shown that dust aggregates of these sizes stick to one another only at unreasonably low velocities. However, in the protoplanetary disk, millimeter-sized particles are known to have been ubiquitous. One can find relics of them in the form of solid chondrules as the main constituent of chondrites. Most of these chondrules were found to feature a fine-grained rim, which is hypothesized to have formed from accreting dust grains in the solar nebula. To study the influence of these dust-coated chondrules on the formation of chondrites and possibly planetesimals, we conducted collision experiments between millimeter-sized, dust-coated chondrule analogs at velocities of a few cm/s. For 2 and 3 mm diameter chondrule analogs covered by dusty rims of a volume filling factor of 0.18 and 0.35-0.58, we found sticking velocities of a few cm/s. This velocity is higher than the sticking velocity of dust aggregates of the same size. We therefore conclude that chondrules may be an important step towards a deeper understanding of the collisional growth of larger bodies. Moreover, we analyzed the collision behavior in an ensemble of dust aggregates and non-coated chondrule analogs. While neither the dust aggregates nor the solid chondrule analogs show sticking in collisions among their species, we found an enhanced sicking efficiency in collisions between the two constituents, which leads us to the conjecture that chondrules might act as "catalyzers" for the growth of larger bodies in the young Solar System