4,760 research outputs found
A Simple Noise Model with Memory for Biological Systems
A noise source model, consisting of a pulse sequence at random times with
memory, is presented. By varying the memory we can obtain variable randomness
of the stochastic process. The delay time between pulses, i. e. the noise
memory, produces different kinds of correlated noise ranging from white noise,
without delay, to quasi-periodical process, with delay close to the average
period of the pulses. The spectral density is calculated. This type of noise
could be useful to describe physical and biological systems where some delay is
present. In particular it could be useful in population dynamics. A simple
dynamical model for epidemiological infection with this noise source is
presented. We find that the time behavior of the illness depends on the noise
parameters. Specifically the amplitude and the memory of the noise affect the
number of infected people.Comment: 8 pages, 4 figure
Dynamics and fragmentation mechanism of (CH3-C5H4)Pt(CH3)3 on SiO2 Surfaces
The interaction of (CH3-C5H4)Pt(CH3)3
((methylcyclopentadienyl)trimethylplatinum)) molecules on fully and partially
hydroxylated SiO2 surfaces, as well as the dynamics of this interaction were
investigated using density functional theory (DFT) and finite temperature
DFT-based molecular dynamics simulations. Fully and partially hydroxylated
surfaces represent substrates before and after electron beam treatment and this
study examines the role of electron beam pretreatment on the substrates in the
initial stages of precursor dissociation and formation of Pt deposits. Our
simulations show that on fully hydroxylated surfaces or untreated surfaces, the
precursor molecules remain inactivated while we observe fragmentation of
(CH3-C5H4)Pt(CH3)3 on partially hydroxylated surfaces. The behavior of
precursor molecules on the partially hydroxylated surfaces has been found to
depend on the initial orientation of the molecule and the distribution of
surface active sites. Based on the observations from the simulations and
available experiments, we discuss possible dissociation channels of the
precursor.Comment: 18 Pages, 5 Figure
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