850 research outputs found
Modified Fuzzy ARTMAP Approaches Bayes Optimal Classification Rtaes: An Empirical Demonstration
This report examines the feasability of the fuzzt ARTMAP neural network for classifying statistical data and analyses the results according to the Bayes decision criterion. A binary decision with a single observation classification problem is chosen to demonstrate and assess the performance of fuzzy ARTMAP. In this task, fuzzy ARTMAP is used to categorise two classes of Gaussian-distributed continuous-valued random variables autonomously and on-line. Various configurations of the task have been investigated by varying the source (mean) separation, prior probabilities and variances of the two Gaussian sources. The results illustrate the limitations of fuzzy ARTMAP in this content. This in turn leads to a modificatin to the algorithm of fuzzy ARTMAP. Together with a proposed category selection scheme, fuzzy ARTMAP is better able to approach the Bayes optimal classification rates for a binary decision domain
Fatty acid metabolism of Mycobacterium tuberculosis: a double-edged sword
Mycobacterium tuberculosis can cocatabolize a range of carbon sources. Fatty acids are among the carbons available inside the host’s macrophages. Here, we investigated the metabolic changes of the fatty acid-induced dormancy-like state of M. tuberculosis and its involvement in the acquisition of drug tolerance. We conducted metabolomics profiling using a phosphoenolpyruvate carboxykinase (PEPCK)-deficient M. tuberculosis strain in an acetate-induced dormancy-like state, highlighting an overaccumulation of methylcitrate cycle (MCC) intermediates that correlates with enhanced drug tolerance against isoniazid and bedaquiline. Further metabolomics analyses of two M. tuberculosis mutants, an ICL knockdown (KD) strain and PrpD knockout (KO) strain, each lacking an MCC enzyme—isocitrate lyase (ICL) and 2-methylcitrate dehydratase (PrpD), respectively—were conducted after treatment with antibiotics. The ICL KD strain, which lacks the last enzyme of the MCC, showed an overaccumulation of MCC intermediates and a high level of drug tolerance. The PrpD KO strain, however, failed to accumulate MCC intermediates as it lacks the second step of the MCC and showed only a minor level of drug tolerance compared to the ICL KD mutant and its parental strain (CDC1551). Notably, addition of authentic 2-methylisocitrate, an MCC intermediate, improved the M. tuberculosis drug tolerance against antibiotics even in glycerol medium. Furthermore, wild-type M. tuberculosis displayed levels of drug tolerance when cultured in acetate medium significantly greater than those in glycerol medium. Taken together, the fatty acid-induced dormancy-like state remodels the central carbon metabolism of M. tuberculosis that is functionally relevant to acquisition of M. tuberculosis drug tolerance
Addendum to "Superimposed Oscillations in the WMAP Data?"
We elaborate further on the possibility that the inflationary primordial
power spectrum contains superimposed oscillations. We study various effects
which could influence the calculation of the multipole moments in this case. We
also present the theoretical predictions for two other cosmological
observables, the matter power spectrum and the EE polarization channel.Comment: 4 pages, 3 figures, uses RevTex4, matches published versio
Premelting of Thin Wires
Recent work has raised considerable interest on the nature of thin metallic
wires. We have investigated the melting behavior of thin cylindrical Pb wires
with the axis along a (110) direction, using molecular dynamics and a
well-tested many-body potential. We find that---in analogy with cluster
melting---the melting temperature of a wire with radius is lower
than that of a bulk solid, , by . Surface melting
effects, with formation of a thin skin of highly diffusive atoms at the wire
surface, is observed. The diffusivity is lower where the wire surface has a
flat, local (111) orientation, and higher at (110) and (100) rounded areas. The
possible relevance to recent results on non-rupturing thin necks between an STM
tip and a warm surface is addressed.Comment: 10 pages, 4 postscript figures are appended, RevTeX, SISSA Ref.
131/94/CM/S
Stability and pinning synchronization analysis of fractional order delayed Cohen–Grossberg neural networks with discontinuous activations
This article, we explore the asymptotic stability and asymptotic synchronization analysis of fractional order delayed Cohen–Grossberg neural networks with discontinuous neuron activation functions (FCGNNDDs). First, under the framework of Filippov theory and differ- ential inclusion theoretical analysis, the global existence of Filippov solution for FCGNNDDs is studied by means of the given growth condition. Second, by virtue of suitable Lyapunov functional, Young inequality and comparison theorem for fractional order delayed linear system, some global asymptotic stability conditions for such system is derived by limiting discontinuous neuron activations. Third, the global asymptotic synchronization condition for FCGNNDDs is obtained based on the pinning control. At last, two numerical simula- tions are given to verify the theoretical findings.N/
Unified selective sorting approach to analyse multi-electrode extracellular data
Extracellular data analysis has become a quintessential method for understanding the neurophysiological responses to stimuli. This demands stringent techniques owing to the complicated nature of the recording environment. In this paper, we highlight the challenges in extracellular multi-electrode recording and data analysis as well as the limitations pertaining to some of the currently employed methodologies. To address some of the challenges, we present a unified algorithm in the form of selective sorting. Selective sorting is modelled around hypothesized generative model, which addresses the natural phenomena of spikes triggered by an intricate neuronal population. The algorithm incorporates Cepstrum of Bispectrum, ad hoc clustering algorithms, wavelet transforms, least square and correlation concepts which strategically tailors a sequence to characterize and form distinctive clusters. Additionally, we demonstrate the influence of noise modelled wavelets to sort overlapping spikes. The algorithm is evaluated using both raw and synthesized data sets with different levels of complexity and the performances are tabulated for comparison using widely accepted qualitative and quantitative indicators
Neutrino Propagation Through Helioseismic Waves
Motivated by earlier calculations showing large effects when neutrinos
propagate through fluctuating media, we perform here a detailed analysis of how
density fluctuations in the sun in the form of helioseismic waves can modify
the MSW solution to the solar neutrino problem. We find negligible effects for
the MSW spectrum, even under extreme circumstances. There are two main reasons
why our conclusions differ from earlier analyses. First, most helioseismic
waves do not affect neutrino propagation because their amplitude is too small
in the MSW resonance region, which is the only region to whose fluctuations
neutrinos are sensitive. There is one class of waves which may be subject to an
instability, however, and so can have significantly larger amplitudes. But the
wavelength for these waves is so long that it invalidates the previous methods
of calculation. Our more complete calculation significantly reduces the
prediction for their influence on neutrino propagation.Comment: 27 pages, plain TeX, 10 figure
Finite temperature Casimir effect in piston geometry and its classical limit
We consider the Casimir force acting on a -dimensional rectangular piston
due to massless scalar field with periodic, Dirichlet and Neumann boundary
conditions and electromagnetic field with perfect electric conductor and
perfect magnetic conductor boundary conditions. It is verified analytically
that at any temperature, the Casimir force acting on the piston is always an
attractive force pulling the piston towards the interior region, and the
magnitude of the force gets larger as the separation gets smaller. Explicit
exact expressions for the Casimir force for small and large plate separations
and for low and high temperatures are computed. The limits of the Casimir force
acting on the piston when some pairs of transversal plates are large are also
derived. An interesting result regarding the influence of temperature is that
in contrast to the conventional result that the leading term of the Casimir
force acting on a wall of a rectangular cavity at high temperature is the
Stefan--Boltzmann (or black body radiation) term which is of order ,
it is found that the contributions of this term from the interior and exterior
regions cancel with each other in the case of piston. The high temperature
leading order term of the Casimir force acting on the piston is of order ,
which shows that the Casimir force has a nontrivial classical
limit
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