27,035 research outputs found
Inter-CubeSat Communication with V-band "Bull's eye" antenna
We present the study of a simple communication scenario between two CubeSats using a V-band “Bull's eye” antenna that we designed for this purpose. The return loss of the antenna has a -10dB bandwidth of 0.7 GHz and a gain of 15.4dBi at 60 GHz. Moreover, the low-profile shape makes it easily integrable in a CubeSat chassis. The communication scenario study shows that, using 0.01W VubiQ modules and V-band “Bull’s eye” antennas, CubeSats can efficiently transmit data within a 500 MHz bandwidth and with a 10-6 BER while being separated by up to 98m, under ideal conditions, or 50m under worst case operating conditions (5° pointing misalignment in E- and H-plane of the antenna, and 5° polarisation misalignment)
Compressing DNA sequence databases with coil
Background: Publicly available DNA sequence databases such as GenBank are large, and are
growing at an exponential rate. The sheer volume of data being dealt with presents serious storage
and data communications problems. Currently, sequence data is usually kept in large "flat files,"
which are then compressed using standard Lempel-Ziv (gzip) compression – an approach which
rarely achieves good compression ratios. While much research has been done on compressing
individual DNA sequences, surprisingly little has focused on the compression of entire databases
of such sequences. In this study we introduce the sequence database compression software coil.
Results: We have designed and implemented a portable software package, coil, for compressing
and decompressing DNA sequence databases based on the idea of edit-tree coding. coil is geared
towards achieving high compression ratios at the expense of execution time and memory usage
during compression – the compression time represents a "one-off investment" whose cost is
quickly amortised if the resulting compressed file is transmitted many times. Decompression
requires little memory and is extremely fast. We demonstrate a 5% improvement in compression
ratio over state-of-the-art general-purpose compression tools for a large GenBank database file
containing Expressed Sequence Tag (EST) data. Finally, coil can efficiently encode incremental
additions to a sequence database.
Conclusion: coil presents a compelling alternative to conventional compression of flat files for the
storage and distribution of DNA sequence databases having a narrow distribution of sequence
lengths, such as EST data. Increasing compression levels for databases having a wide distribution of
sequence lengths is a direction for future work
Can Economic Development Programs Be Evaluated?
The question addressed in this paper seems simple: Can economic development programs be evaluated? But the answer is not simple because of the nature of evaluation. To determine a program's effectiveness requires a sophisticated evaluation because it requires the evaluator to distinguish changes due to the program from changes due to nonprogram factors. The evaluator must focus on the outcomes caused by the program rather than the program's procedures. Evaluations can be divided into two categories process or formative evaluations and outcome, impact, or summative evaluations. Process evaluations focus on how a program is delivered. Impact evaluations focus on the program's results. Although process evaluations are important, the focus of this chapter is on program outcomes thus the concern with impact evaluations; however, both types of evaluations need to be defined.economic, development, programs, evaluate, Bartik, Bingham
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A seed specific dose kernel method for low-energy brachytherapy dosimetry.
We describe a method for independently verifying the dose distributions from pre- and post-implant brachytherapy source distributions. Monte Carlo calculations have been performed to characterize the three-dimensional dose distribution in water phantom from a low-energy brachytherapy source. The calculations are performed in a voxelized, Cartesian coordinate geometry and normalized based upon a separate Monte Carlo calculation for the seed specific air-kerma strength to produce an absolute dose grid with units of cGy hr(-1) x U(-1). The seed-specific, three-dimensional dose grid is stored as a text file for processing using a separate visual basic program. This program requires the coordinate positions of each seed in the pre- or post-plan and sums the kernel file for a three-dimensional composite dose distribution. A kernel matrix size of 81x81x81 with a voxel size of 1.0x1.0x1.0 mm3 was chosen as a compromise between calculation time, kernel size, and truncation of the stored dose distribution as a function of radial distance from the midpoint of the seed. Good agreement is achieved for a representative pre- and post-plan comparison versus a commercial implementation of the TG-43 brachytherapy dosimetry protocol
Earthshine as an Illumination Source at the Moon
Earthshine is the dominant source of natural illumination on the surface of
the Moon during lunar night, and at locations within permanently shadowed
regions that never receive direct sunlight. As such, earthshine may enable the
exploration of areas of the Moon that are hidden from solar illumination. The
heat flux from earthshine may also influence the transport and cold trapping of
volatiles present in the very coldest areas. In this study, Earth's spectral
radiance at the Moon is examined using a suite of Earth spectral models created
using the Virtual Planetary Laboratory (VPL) three dimensional modeling
capability. At the Moon, the broadband, hemispherical irradiance from Earth
near 0 phase is approximately 0.15 watts per square meter, with comparable
contributions from solar reflectance and thermal emission. Over the simulation
timeframe, spanning two lunations, Earth's thermal irradiance changes less than
a few mW per square meter as a result of cloud variability and the
south-to-north motion of sub-observer position. In solar band, Earth's
diurnally averaged light curve at phase angles < 60 degrees is well fit using a
Henyey Greenstein integral phase function. At wavelengths > 0.7 microns, near
the well known vegetation "red edge", Earth's reflected solar radiance shows
significant diurnal modulation as a result of the longitudinal asymmetry in
projected landmass, as well as from the distribution of clouds. A simple
formulation with adjustable coefficients is presented for estimating Earth's
hemispherical irradiance at the Moon as a function of wavelength, phase angle
and sub-observer coordinates. It is demonstrated that earthshine is
sufficiently bright to serve as a natural illumination source for optical
measurements from the lunar surface.Comment: 27 pages, 15 figures, 1 tabl
Allatostatin-A neurons inhibit feeding behavior in adult Drosophila
How the brain translates changes in internal metabolic state or perceived food quality into alterations in feeding behavior remains poorly understood. Studies in Drosophila larvae have yielded information about neuropeptides and circuits that promote feeding, but a peptidergic neuron subset whose activation inhibits feeding in adult flies, without promoting metabolic changes that mimic the state of satiety, has not been identified. Using genetically based manipulations of neuronal activity, we show that activation of neurons (or neuroendocrine cells) expressing the neuropeptide allatostatin A (AstA) inhibits or limits several starvation-induced changes in feeding behavior in adult Drosophila, including increased food intake and enhanced behavioral responsiveness to sugar. Importantly, these effects on feeding behavior are observed in the absence of any measurable effects on metabolism or energy reserves, suggesting that AstA neuron activation is likely a consequence, not a cause, of metabolic changes that induce the state of satiety. These data suggest that activation of AstA-expressing neurons promotes food aversion and/or exerts an inhibitory influence on the motivation to feed and implicate these neurons and their associated circuitry in the mechanisms that translate the state of satiety into alterations in feeding behavior
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