10,840 research outputs found
Classification of subwatershed slopes and geotechnical characterization of steep slopes on reclaimed mine lands in East Tennessee
Mining and logging activity in the Appalachian region create both excessive runoff and sedimentation in local streams and rivers. Also, the Surface Mining Control and Reclamation Act of 1977 led to over compaction of mine spoil which has led to reclaimed mine lands which will not grow economically viable native hardwood forests. In recent years a construction technique known as low compaction grading has allowed for suitable tree growth but stability and sedimentation have not yet been explored. The purpose of this paper is to create a rapid assessment method to classify the characteristics of watersheds based upon their geomorphology, and then to match this process to the established Rapid Geomorphic Assessment (RGA) method; these methods are intended to correspond to the tendency for a given slope to produce sediment. Also, this research attempts to match upland disturbance areas common in East Tennessee to sediment production characteristics.Lastly, mine spoil physical characteristics were determined and used to determine slope stability on steep reclaimed mine slopes using the low compaction grading technique, and to determine the medium\u27s suitability for tree growth. No correlations were found between the developed Rapid Slope Assessment and the established RGA method. Sediment production characteristics were measured and compared for several land use disturbance areas common to East Tennessee and it was determined that logging roads were the most prone to high sediment production and then mining roads, logged areas, and mined areas followed in that order. Lastly, dry and wet unit weights, moisture contents, and grain size distributions were measured for reclaimed mine slopes using the low compaction grading method, and slope stability was assessed using an infinite slope analysis. It was determined that the nuclear density gauge was the most reliable and convenient way to measure unit weight.Furthermore the factor of safety against slope failure ranged from 1.9 to 1.4. These relatively low factors of safety are acceptable due to the low cost and consequence of slope failure on surface mine sites
Identifying key belief-based targets for promoting regular physical activity among mothers and fathers with young children
We investigated the key beliefs to target in interventions aimed at increasing physical activity (PA) among mothers and fathers of young children. Parents (288 mothers and 292 fathers) completed a Theory of Planned Behaviour belief-based questionnaire and a 1-week follow-up of PA behaviour. We found that a range of behavioural, normative, and control beliefs were significantly correlated with parentsâ PA intentions and behaviour, with only a few differences observed in correlations between PA beliefs and intention and behaviour by gender. A range of key beliefs was identified as making independent contributions to parentsâ PA intentions; however, the behavioural beliefs about improving parenting practices (ÎČ = 0.13), interfering with other commitments (ÎČ = â0.29); normative beliefs about people I exercise with (ÎČ = 0.20); and control beliefs about lack of time (ÎČ = â0.24), inconvenience (ÎČ = â0.14), lack of motivation (ÎČ = â0.34), were revealed as significant independent predictors of actual PA behaviour. Furthermore, we found that a limited amount of parents already hold these beliefs, suggesting that these key beliefs warrant changing and, therefore, are appropriate targets for subsequent intervention. The current study fills an empirical gap in the PA literature by investigating an at-risk group and using a well established theoretical framework to identify key beliefs that guide parentsâ PA decision-making. Overall, we found support for parents being a unique group who hold distinctive behavioural, normative, and control beliefs toward PA. Attention to these key underlying beliefs will assist intervention work aimed at combating inactivity among this at-risk population
Scale-dependent bias and the halo model
We use a simplified version of the halo model with a power law power spectrum
to study scale dependence in galaxy bias at the very large scales relevant to
baryon oscillations. In addition to providing a useful pedagogical explanation
of the scale dependence of galaxy bias, the model provides an analytic tool for
studying how changes in the Halo Occupation Distribution (HOD) impact the scale
dependence of galaxy bias on scales between 10 and 1000 Mpc/h, which is useful
for interpreting the results of complex N-body simulations. We find that
changing the mean number of galaxies per halo of a given mass will change the
scale dependence of the bias, but that changing the way the galaxies are
distributed within the halo has a smaller effect on the scale dependence of
bias at large scales. We use the model to explain the decay in amplitude of the
baryon oscillations as k increases, and generalize the model to make
predictions about scale dependent galaxy bias when redshift space distortions
are introduced.Comment: 13 pages, 2 figures; corrected typos, extended discussion of redshift
space distortions, matches published versio
Constraining Anisotropic Baryon Oscillations
We present an analysis of anisotropic baryon acoustic oscillations and
elucidate how a mis-estimation of the cosmology, which leads to incorrect
values of the angular diameter distance, d_A, and Hubble parameter, H, manifest
themselves in changes to the monopole and quadrupole power spectrum of biased
tracers of the density field. Previous work has focused on the monopole power
spectrum, and shown that the isotropic "dilation" combination d_A^2/H is
robustly constrained by an overall shift in the scale of the baryon feature. We
extend this by demonstrating that the quadrupole power spectrum is sensitive to
an anisotropic "warping" mode d_A H, allowing one to break the degeneracy
between d_A and H. We describe a method for measuring this warping, explicitly
marginalizing over the form of redshift space distortions. We verify this
method on N-body simulations and estimate that d_A H can be measured with a
fractional accuracy of ~ 3/sqrt(V) % where the survey volume is estimated in
(Gpc/h)^3.Comment: 4 pages, 2 fig
A polymer gel index-matched to water enables diverse applications in fluorescence microscopy [preprint]
We demonstrate diffraction-limited and super-resolution imaging through thick layers (tens-hundreds of microns) of BIO-133, a biocompatible, UV-curable, commercially available polymer with a refractive index (RI) matched to water. We show that cells can be directly grown on BIO-133 substrates without the need for surface passivation and use this capability to perform extended time-lapse volumetric imaging of cellular dynamics 1) at isotropic resolution using dual-view light-sheet microscopy, and 2) at super-resolution using instant structured illumination microscopy. BIO-133 also enables immobilization of 1) Drosophila tissue, allowing us to track membrane puncta in pioneer neurons, and 2) Caenorhabditis elegans, which allows us to image and inspect fine neural structure and to track pan-neuronal calcium activity over hundreds of volumes. Finally, BIO-133 is compatible with other microfluidic materials, enabling optical and chemical perturbation of immobilized samples, as we demonstrate by performing drug and optogenetic stimulation on cells and C. elegans
Measuring the galaxy power spectrum with future redshift surveys
Precision measurements of the galaxy power spectrum P(k) require a data
analysis pipeline that is both fast enough to be computationally feasible and
accurate enough to take full advantage of high-quality data. We present a
rigorous discussion of different methods of power spectrum estimation, with
emphasis on the traditional Fourier method, the linear (Karhunen-Loeve; KL),
and quadratic data compression schemes, showing in what approximations they
give the same result. To improve speed, we show how many of the advantages of
KL data compression and power spectrum estimation may be achieved with a
computationally faster quadratic method. To improve accuracy, we derive
analytic expressions for handling the integral constraint, since it is crucial
that finite volume effects are accurately corrected for on scales comparable to
the depth of the survey. We also show that for the KL and quadratic techniques,
multiple constraints can be included via simple matrix operations, thereby
rendering the results less sensitive to galactic extinction and mis-estimates
of the radial selection function. We present a data analysis pipeline that we
argue does justice to the increases in both quality and quantity of data that
upcoming redshift surveys will provide. It uses three analysis techniques in
conjunction: a traditional Fourier approach on small scales, a pixelized
quadratic matrix method on large scales and a pixelized KL eigenmode analysis
to probe anisotropic effects such as redshift-space distortions.Comment: Major revisions for clarity. Matches accepted ApJ version. 23 pages,
with 2 figs included. Color figure and links at
http://www.sns.ias.edu/~max/galpower.html (faster from the US), from
http://www.mpa-garching.mpg.de/~max/galpower.html (faster from Europe) or
from [email protected]
Understanding the PSCz Galaxy Power Spectrum with N-body Simulations
By comparing the PSCz galaxy power spectrum with the results of nested pure
dark matter N-body simulations, we try to understand how infrared-selected
galaxies populate dark-matter haloes, paying special attention to the method of
halo identification in the simulations. We thus test the hypothesis that
baryonic physics negligibly affects the distribution of galaxies down to the
smallest scales yet observed. We are successful in reproducing the PSCz power
spectrum on scales < ~40 h/Mpc, near our resolution limit, by imposing a
central density cut-off on simulated haloes, which gives a rough minimum mass
and circular velocity of haloes in which PSCz galaxies formed.Comment: 12 pages, 16 figures (one added), conforms to version in MNRA
Sensitivity of a Bolometric Interferometer to the CMB power spectrum
Context. The search for B-mode polarization fluctuations in the Cosmic
Microwave Background is one of the main challenges of modern cosmology. The
expected level of the B-mode signal is very low and therefore requires the
development of highly sensitive instruments with low systematic errors. An
appealing possibility is bolometric interferometry. Aims. We compare in this
article the sensitivity on the CMB angular power spectrum achieved with direct
imaging, heterodyne and bolometric interferometry. Methods. Using a simple
power spectrum estimator, we calculate its variance leading to the counterpart
for bolometric interferometry of the well known Knox formula for direct
imaging. Results. We find that bolometric interferometry is less sensitive than
direct imaging. However, as expected, it is finally more sensitive than
heterodyne interferometry due to the low noise of the bolometers. It therefore
appears as an alternative to direct imagers with different and possibly lower
systematic errors, mainly due to the absence of an optical setup in front of
the horns.Comment: 5 pages, 3 figures. This last version matches the published version
(Astronomy and Astrophysics 491 3 (2008) 923-927). Sensitivity of Heterodyne
Interferometers modified by a factor of tw
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