474 research outputs found
The Faustian Grip of Academic Publishing
The journal acquisition budget of libraries is not increasing at the same rate as subscription rates creating the serials' crisis. Many solutions have been proposed including the freely available electronic journal. However, all the solutions suffer the same Faustian Grip - namely that the actors in the academic publishing game have little or no incentive to stop publishing in the current journals. We examine those incentives concluding that even with a better more efficient technology, the actors will not change from the current academic publishing institution, and the serials' crisis will remain.serials crisis journal pricing academic publishing
Uniform hydrogen fuel layers for inertial fusion targets by microgravity
A critical concern in the fabrication of targets for inertial confinement fusion (ICF) is ensuring that the hydrogenic (D(sub 2) or DT) fuel layer maintains spherical symmetry. Solid layered targets have structural integrity, but lack the needed surface smoothness. Liquid targets are inherently smooth, but suffer from gravitationally induced sagging. One method to reduce the effective gravitational field environment is freefall insertion into the target chamber. Another method to counterbalance field gravitational force is to use an applied magnetic field combined with a gradient field to induce a magnetic dipole force on the liquid fuel layer. Based on time dependent calculations of the dynamics of the liquid fuel layer in microgravity environments, we show that it may be possible to produce a liquid layered ICF target that satisfies both smoothness and symmetry requirements
Interferometry of Aurigae: Characterization of the asymmetric eclipsing disk
We report on a total of 106 nights of optical interferometric observations of
the Aurigae system taken during the last 14 years by four beam
combiners at three different interferometric facilities. This long sequence of
data provides an ideal assessment of the system prior to, during, and after the
recent 2009-2011 eclipse. We have reconstructed model-independent images from
the 10 in-eclipse epochs which show that a disk-like object is indeed
responsible for the eclipse. Using new 3D, time-dependent modeling software, we
derive the properties of the F-star (diameter, limb darkening), determine
previously unknown orbital elements (, ), and access the global
structures of the optically thick portion of the eclipsing disk using both
geometric models and approximations of astrophysically relevant density
distributions. These models may be useful in future hydrodynamical modeling of
the system. Lastly, we address several outstanding research questions including
mid-eclipse brightening, possible shrinking of the F-type primary, and any
warps or sub-features within the disk.Comment: 105 pages, 57 figures. This is an author-created, un-copyedited
version of an article accepted for publication in Astrophysical Journal
Supplement Series. IOP Publishing Ltd is not responsible for any errors or
omissions in this version of the manuscript or any version derived from i
A Controlled Study on the Characterisation of Bioaerosols Emissions from Compost
Bioaerosol emissions arising from biowaste treatment are an issue of public concern. To better characterise the bioaerosols, and to assess a range of measurement methods, we aerosolised green waste compost under controlled conditions. Viable and non-viable Andersen samplers, cyclone samplers and a real time bioaerosol detection system (Spectral Intensity Bioaerosol Sensor (SIBS)) were deployed simultaneously. The number-weighted fraction of fluorescent particles was in the range 22–26% of all particles for low and high emission scenarios. Overall fluorescence spectral profiles seen by the SIBS exhibited several peaks across the 16 wavelength bands from 298 to 735 nm. The size-fractionated endotoxin profile showed most endotoxin resided in the 2.1–9 μm aerodynamic diameter fraction, though up to 27% was found in a finer size fraction. A range of microorganisms were detected through culture, Matrix Assisted Laser Desorption and Ionisation Time of Flight Mass Spectrometry (MALDI-TOF) and quantitative polymerase chain reaction (qPCR), including Legionella pneumophila serogroup 1. These findings contribute to our knowledge of the physico-chemical and biological characteristics of bioaerosols from composting sites, as well as informing future monitoring approaches and data interpretation for bioaerosol measurement
Stellar Diameters and Temperatures. I. Main-Sequence A, F, and G Stars
We have executed a survey of nearby, main-sequence A-, F-, and G-type stars with the CHARA Array, successfully measuring the angular diameters of forty-four stars with an average precision of ~1.5%. We present new measures of the bolometric flux, which in turn leads to an empirical determination of the effective temperature for the stars observed. In addition, these CHARA-determined temperatures, radii, and luminosities are fit to Yonsei-Yale model isochrones to constrain the masses and ages of the stars. These results are compared to indirect estimates of these quantities obtained by collecting photometry of the stars and applying them to model atmospheres and evolutionary isochrones. We find that for most cases, the models overestimate the effective temperature by ~1.5%-4% when compared to our directly measured values. The overestimated temperatures and underestimated radii in these works appear to cause an additional offset in the star's surface gravity measurements, which consequently yield higher masses and younger ages, in particular for stars with masses greater than ~1.3 M_☉. Additionally, we compare our measurements to a large sample of eclipsing binary stars, and excellent agreement is seen within both data sets. Finally, we present temperature relations with respect to (B – V) and (V – K) colors as well as spectral type, showing that calibration of effective temperatures with errors ~1% is now possible from interferometric angular diameters of stars
New Tetrahedral Global Minimum for the 98-atom Lennard-Jones Cluster
A new atomic cluster structure corresponding to the global minimum of the
98-atom Lennard-Jones cluster has been found using a variant of the
basin-hopping global optimization algorithm. The new structure has an unusual
tetrahedral symmetry with an energy of -543.665361, which is 0.022404 lower
than the previous putative global minimum. The new LJ_98 structure is of
particular interest because its tetrahedral symmetry establishes it as one of
only three types of exceptions to the general pattern of icosahedral structural
motifs for optimal LJ microclusters. Similar to the other exceptions the global
minimum is difficult to find because it is at the bottom of a narrow funnel
which only becomes thermodynamically most stable at low temperature.Comment: 3 pages, 2 figures, revte
The current system associated with the boundary of plasma bubbles
The current system associated with the boundary of plasma bubbles in the Earth's magnetotail has been studied by employing Cluster multipoint observations. We have investigated the currents in both the dipolarization front (DF, leading edge of the plasma bubble) and the trailing edge of the plasma bubble. The distribution of currents at the edge indicates that there is a current circuit in the boundary of a plasma bubble. The field‐aligned currents in the trailing edge of the plasma bubble are flowing toward the ionosphere (downward) on the dawnside and away from the ionosphere (upward) on the duskside, in the same sense as region‐1 current. Together with previous studies of the current distributions in the DF and magnetic dip region, we have obtained a more complete picture of the current system surrounding the boundary of plasma bubble. This current system is very similar to the substorm current wedge predicted by MHD simulation models but with much smaller scale.Key PointsWe have obtained a current circuit in the boundary of plasma bubbleThe FACs in the trailing edge of plasma bubble is also region‐1‐senseThe current and FACs system is similar to SCW but with much smaller scalePeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110641/1/grl52338.pd
Quantum interference experiments, modular variables and weak measurements
We address the problem of interference using the Heisenberg picture and
highlight some new aspects through the use of pre-selection, post-selection,
weak measurements, and modular variables, We present a physical explanation for
the different behaviors of a single particle when the distant slit is open or
closed: instead of having a quantum wave that passes through all slits, we have
a localized particle with non-local interactions with the other slit(s). We
introduce a Gedankenexperiment to measure this non-local exchange. While the
Heisenberg picture and the Schrodinger pictures are equivalent formulations of
quantum mechanics, nevertheless, the results discussed here support a new
approach which has led to new insights, new intuitions, new experiments, and
even the possibility of new devices that were missed from the old perspective
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