3,766 research outputs found
A New Approximation Scheme for Monte Carlo Applications
Approximation algorithms employing Monte Carlo methods, across application domains, often require as a subroutine the estimation of the mean of a random variable with support on [0,1]. One wishes to estimate this mean to within a user-specified error, using as few samples from the simulated distribution as possible. In the case that the mean being estimated is small, one is then interested in controlling the relative error of the estimate. We introduce a new (epsilon, delta) relative error approximation scheme for [0,1] random variables and provide a comparison of this algorithm\u27s performance to that of an existing approximation scheme, both establishing theoretical bounds on the expected number of samples required by the two algorithms and empirically comparing the samples used when the algorithms are employed for a particular application
Recommended from our members
Whole-cell 3D STORM reveals interactions between cellular structures with nanometer-scale resolution.
The ability to directly visualize nanoscopic cellular structures and their spatial relationship in all three dimensions will greatly enhance our understanding of molecular processes in cells. Here we demonstrated multicolor three-dimensional (3D) stochastic optical reconstruction microscopy (STORM) as a tool to quantitatively probe cellular structures and their interactions. To facilitate STORM imaging, we generated photoswitchable probes in several distinct colors by covalently linking a photoswitchable cyanine reporter and an activator molecule to assist bioconjugation. We performed 3D localization in conjunction with focal plane scanning and correction for refractive index mismatch to obtain whole-cell images with a spatial resolution of 20-30 nm and 60-70 nm in the lateral and axial dimensions, respectively. Using this approach, we imaged the entire mitochondrial network in fixed monkey kidney BS-C-1 cells, and studied the spatial relationship between mitochondria and microtubules. The 3D STORM images resolved mitochondrial morphologies as well as mitochondria-microtubule contacts that were obscured in conventional fluorescence images
Recommended from our members
Severity of Visual Field Loss at First Presentation to Glaucoma Clinics in England and Tanzania
Purpose: To compare severity of visual field (VF) loss at first presentation in glaucoma clinics in England and Tanzania.
Methods: Large archives of VF records from automated perimetry were used to retrospectively examine vision loss at first presentation in glaucoma clinics in Tanzania (N = 1,502) and England (N = 9,264). Mean deviation (MD) of the worse eye at the first hospital visit was used as an estimate of detectable VF loss severity.
Results: In Tanzania, 44.7% {CI95%: 42.2, 47.2} of patients presented with severe VF loss (< −20 dB), versus 4.6% {4.1, 5.0} in England. If we consider late presentation to also include cases of advanced loss (-12.01 dB to -20 dB), then the proportion of patients presenting late was 58.1% {55.6, 60.6} and 14.0% {13.3, 14.7}, respectively. The proportion of late presentations was greater in Tanzania at all ages, but the difference was particularly pronounced among working-age adults, with 50.3% {46.9, 53.7} of 18–65-year-olds presenting with advanced or severe VF loss, versus 10.2% {9.3, 11.3} in England. In both countries, men were more likely to present late than women.
Conclusions: Late presentation of glaucoma is a problem in England, and an even greater challenge in Tanzania. Possible solutions are discussed, including increased community eye-care, and a more proactive approach to case finding through the use of disruptive new technologies, such as low-cost, portable diagnostic aids
Polysaccharide Multilayer Nanoencapsulation of Insulin-Producing beta-Cells Grown as Pseudoislets for Potential Cellular Delivery of Insulin
Landfill capping stability: tapered solution with seepage
The capping system is one of the major structural elements in modern landfills. When using artificial sealing materials
(e.g. a geomembrane) as the capping liner, the stability of the cover soils and integrity of the geosynthethics need
to be assessed. Traditional design methods only consider uniform cover soil thickness with different degrees of
saturation and seepage build-up (i.e. parallel submergency ratio). This paper proposes an analytical method which
includes the seepage build-up in the stability analysis for the capping slope with a tapered cover soil profile, that is
when cover soils become thicker from top to bottom. Both the parallel (modified) and horizontal seepage force
build-up patterns have been considered and analysed. The proposed analytical methods are applied to a design case
in which uniform thickness cover soils are considered. The results are comparable to those of the traditional methods
and therefore they are verified. Parametric analyses have confirmed the tapered profile can effectively improve the
capping slope stability and indicated that the interface shear strength (between the cover soil and the underlying
geosynthetic) and cover soil shear strength have the most significant effects on the capping slope stability
- …