2,457 research outputs found
Click, play and save: The iGamelan as a tool for music-culture sustainability
This article explores the potential for web-based interactive music resources to represent and sustain music-culture heritage via digital means. Our focus is the University of Otago's virtual Indonesian gamelan (iGamelan): an immersive online resource featuring interactive musical instruments, an audio-video gallery, and information archive. Designed in 2010-2011 for use within the tertiary education context, the iGamelan stands alone as an innovative learning/teaching tool, and also enhances real-life instructional sessions with the University's pelog/slendro Central Javanese gamelan. This article illuminates the pitfalls and achievements of the iGamelan project and, at a broader level, demonstrates how contemporary technology can help sustain active music-making cultures
Turbulent Driving Scales in Molecular Clouds
Supersonic turbulence in molecular clouds is a dominant agent that strongly
affects the clouds' evolution and star formation activity. Turbulence may be
initiated and maintained by a number of processes, acting at a wide range of
physical scales. By examining the dynamical state of molecular clouds, it is
possible to assess the primary candidates for how the turbulent energy is
injected. The aim of this paper is to constrain the scales at which turbulence
is driven in the molecular interstellar medium, by comparing simulated
molecular spectral line observations of numerical magnetohydrodynamic (MHD)
models and molecular spectral line observations of real molecular clouds. We
use principal component analysis, applied to both models and observational
data, to extract a quantitative measure of the driving scale of turbulence. We
find that only models driven at large scales (comparable to, or exceeding, the
size of the cloud) are consistent with observations. This result applies also
to clouds with little or no internal star formation activity. Astrophysical
processes acting on large scales, including supernova-driven turbulence,
magnetorotational instability, or spiral shock forcing, are viable candidates
for the generation and maintenance of molecular cloud turbulence. Small scale
driving by sources internal to molecular clouds, such as outflows, can be
important on small scales, but cannot replicate the observed large-scale
velocity fluctuations in the molecular interstellar medium.Comment: 8 pages, 7 figures, accepted for publication in A&
CO Abundance Variations in the Orion Molecular Cloud
Infrared stellar photometry from 2MASS and spectral line imaging observations
of 12CO and 13CO J = 1-0 line emission from the FCRAO 14m telescope are
analysed to assess the variation of the CO abundance with physical conditions
throughout the Orion A and Orion B molecular clouds. Three distinct Av regimes
are identified in which the ratio between the 13CO column density and visual
extinction changes corresponding to the photon dominated envelope, the strongly
self-shielded interior, and the cold, dense volumes of the clouds. Within the
strongly self-shielded interior of the Orion A cloud, the 13CO abundance varies
by 100% with a peak value located near regions of enhanced star formation
activity. The effect of CO depletion onto the ice mantles of dust grains is
limited to regions with AV > 10 mag and gas temperatures less than 20 K as
predicted by chemical models that consider thermal-evaporation to desorb
molecules from grain surfaces.
Values of the molecular mass of each cloud are independently derived from the
distributions of Av and 13CO column densities with a constant 13CO-to-H2
abundance over various extinction ranges. Within the strongly self-shielded
interior of the cloud (Av > 3 mag), 13CO provides a reliable tracer of H2 mass
with the exception of the cold, dense volumes where depletion is important.
However, owing to its reduced abundance, 13CO does not trace the H2 mass that
resides in the extended cloud envelope, which comprises 40-50% of the molecular
mass of each cloud. The implied CO luminosity to mass ratios, M/L_{CO}, are 3.2
and 2.9 for Orion A and Orion B respectively, which are comparable to the value
(2.9), derived from gamma-ray observations of the Orion region. Our results
emphasize the need to consider local conditions when applying CO observations
to derive H2 column densities.Comment: Accepted for publication in MNRAS. 21 pages, 14 figure
A Range Correction for Icesat and Its Potential Impact on Ice-sheet Mass Balance Studies
We report on a previously undocumented range error in NASA's Ice, Cloud and land Elevation Satellite (ICESat) that degrades elevation precision and introduces a small but significant elevation trend over the ICESat mission period. This range error (the Gaussian-Centroid or 'G-C'offset) varies on a shot-to-shot basis and exhibits increasing scatter when laser transmit energies fall below 20 mJ. Although the G-C offset is uncorrelated over periods less than1 day, it evolves over the life of each of ICESat's three lasers in a series of ramps and jumps that give rise to spurious elevation trends of 0.92 to 1.90 cm yr(exp 1), depending on the time period considered. Using ICESat data over the Ross and Filchner-Ronne ice shelves we show that (1) the G-C offset introduces significant biases in ice-shelf mass balance estimates, and (2) the mass balance bias can vary between regions because of different temporal samplings of ICESat.We can reproduce the effect of the G-C offset over these two ice shelves by fitting trends to sample-weighted mean G-C offsets for each campaign, suggesting that it may not be necessary to fully repeat earlier ICESat studies to determine the impact of the G-C offset on ice-sheet mass balance estimates
Building finite element models to investigate zebrafish jaw biomechanics
Skeletal morphogenesis occurs through tightly regulated cell behaviors during development; many cell types alter their behavior in response to mechanical strain. Skeletal joints are subjected to dynamic mechanical loading. Finite element analysis (FEA) is a computational method, frequently used in engineering that can predict how a material or structure will respond to mechanical input. By dividing a whole system (in this case the zebrafish jaw skeleton) into a mesh of smaller 'finite elements', FEA can be used to calculate the mechanical response of the structure to external loads. The results can be visualized in many ways including as a 'heat map' showing the position of maximum and minimum principal strains (a positive principal strain indicates tension while a negative indicates compression. The maximum and minimum refer the largest and smallest strain). These can be used to identify which regions of the jaw and therefore which cells are likely to be under particularly high tensional or compressional loads during jaw movement and can therefore be used to identify relationships between mechanical strain and cell behavior. This protocol describes the steps to generate Finite Element models from confocal image data on the musculoskeletal system, using the zebrafish lower jaw as a practical example. The protocol leads the reader through a series of steps: 1) staining of the musculoskeletal components, 2) imaging the musculoskeletal components, 3) building a 3 dimensional (3D) surface, 4) generating a mesh of Finite Elements, 5) solving the FEA and finally 6) validating the results by comparison to real displacements seen in movements of the fish jaw
A geostatistical study of the Manhattan gold deposit
Online access for this thesis was created in part with support from the Institute of Museum and Library Services (IMLS) administered by the Nevada State Library, Archives and Public Records through the Library Services and Technology Act (LSTA). To obtain a high quality image or document please contact the DeLaMare Library at https://unr.libanswers.com/ or call: 775-784-6945.Geostatistical reserve estimation techniques are divided between those which assume an underlying distribution function for the data and those that do not. This thesis applies a parametric technique, Lognormal Kriging, and a non-parametric technique, Probability Kriging, to the structurally controlled Manhattan gold deposit located in Manhattan, Nevada. The average grade of the deposit is suitable for bulk mining and heap leaching, however, substantial portions of the deposit are high grade mill ore. These high grade pods are small in size relative to the dimensions of the exploration drilling grid. Therefore, interpretation of the exploration data by other than a probabilistic method will give no indication of the presence of a high grade pod other than the average grade of a block. Probability kriging estimates a distribution function for each estimated block. The estimated distribution may be used to determine average grades and tonnages of blocks above specified cutoff grades
Dispersion of Observed Position Angles of Submillimeter Polarization in Molecular Clouds
One can estimate the characteristic magnetic field strength in GMCs by
comparing submillimeter polarimetric observations of these sources with
simulated polarization maps developed using a range of different values for the
assumed field strength. The point of comparison is the degree of order in the
distribution of polarization position angles. In a recent paper by H. Li and
collaborators, such a comparison was carried out using SPARO observations of
two GMCs, and employing simulations by E. Ostriker and collaborators. Here we
reexamine this same question, using the same data set and the same simulations,
but using an approach that differs in several respects. The most important
difference is that we incorporate new, higher angular resolution observations
for one of the clouds, obtained using the Hertz polarimeter. We conclude that
the agreement between observations and simulations is best when the total
magnetic energy (including both uniform and fluctuating field components) is at
least as large as the turbulent kinetic energy.Comment: revised, accepted version; to appear in The Astrophysical Journal; 20
pages, 2 figures, 2 table
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