671 research outputs found
Cross-interval histogram analysis of neuronal activity on multi-electrode arrays
Cross-neuron-interval histogram (CNIH) analysis has been performed in order to study correlated activity and connectivity between pairs of neurons in a spontaneously active developing cultured network of rat cortical cells. Thirty-eight histograms could be analyzed using two parameters, one for the shape and one for the average number per interval bin. The histogram shape varied gradually between flat and clearly peaked around zero interval, indicating no/abundant connectivity and direct connection pathways, respectively
Feature combinations and the Bhattacharyya criterion
A procedure for calculating a kxn rank k matrix B for data compression using the Bhattacharyya bound on the probability of error and an iterative construction using Householder transformation was developed. Two sets of remotely sensed agricultural data are used to demonstrate the application of the procedure. The results of the applications gave some indication of the extent to which the Bhattacharyya bound on the probability of error is affected by such transformations for multivariate normal populations
GRB Spikes Could Resolve Stars
GRBs vary more rapidly than any other known cosmological phenomena. The lower
limits of this variability have not yet been explored. Improvements in
detectors would reveal or limit the actual rate of short GRBs. Were microsecond
"spike" GRBs to exist and be detectable, they would time-resolve stellar mass
objects throughout the universe by their gravitational microlensing effect.
Analyzing the time structure of sufficient numbers of GRB spikes would reveal
or limit , , and/or .Comment: 18 pages, 2 figures, in press: ApJ (Letters
Gravitationally Lensed Gamma-Ray Bursts as Probes of Dark Compact Objects
If dark matter in the form of compact objects comprises a large fraction of
the mass of the universe, then gravitational lensing effects on gamma-ray
bursts are expected. We utilize BATSE and Ulysses data to search for lenses of
different mass ranges, which cause lensing in the milli, pico, and femto
regimes. Null results are used to set weak limits on the cosmological abundance
of compact objects in mass ranges from 10 to 10 . A
stronger limit is found for a much discussed universe dominated
by black holes of masses , which is ruled out at the
90% confidence level.Comment: 14 pages, 4 figures, fixed minor corrections. Accepted for
publication in ApJ(L
Limits on the cosmological abundance of supermassive compact objects from a millilensing search in gamma-ray burst data
A new search for the gravitational lens effects of a significant cosmological
density of supermassive compact objects (SCOs) on gamma-ray bursts has yielded
a null result. We inspected the timing data of 774 BATSE-triggered GRBs for
evidence of millilensing: repeated peaks similar in light-curve shape and
spectra. Our null detection leads us to conclude that, in all candidate
universes simulated, is favored for , while in some universes and mass ranges the density
limits are as much as 10 times lower. Therefore, a cosmologically significant
population of SCOs near globular cluster mass neither came out of the
primordial universe, nor condensed at recombination.Comment: 14 pages including 3 figures, appeared 2001 January 2
(Ti,Sn) solid solution-based gas sensors for new monitoring of hydraulic oil degradation
The proper operation of a fluid power system in terms of efficiency and reliability is directly related to the fluid state; therefore, the monitoring of fluid ageing in real time is fundamental to prevent machine failures. For this aim, an innovative methodology based on fluid vapor analysis through metal oxide (shortened: MOX) gas sensors has been developed. Two apparatuses were designed and realized: (i) a dedicated test bench to fast-age the fluid under controlled conditions; (ii) a laboratory MOX sensor system to test the headspace of the aged fluid samples. To prepare the set of MOX gas sensors suitable to detect the analytesâ concentrations in the fluid headspace, different functional materials were synthesized in the form of nanopowders, characterizing them by electron microscopy and X-ray diffraction. The powders were deposited through screen-printing technology, realizing thick-film gas sensors on which dynamical responses in the presence of the fluid headspace were obtained. It resulted that gas sensors based on solid solution TixSn1âxO2 with x = 0.9 and 0.5 offered the best responses toward the fluid headspace with lower response and recovery times. Furthermore, a decrease in the responses (for all sensors) with fluid ageing was observed
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