Model-based fit procedure for power-law-like spectra

$1/f^\alpha$ noises are ubiquitous and affect many measurements. These noises are both a nuisance and a peculiarity of several physical systems; in dielectrics, glasses and networked liquids it is very common to study this noise to gather useful information. Sometimes it happens that the noise has a power-law shape only in a certain frequency range, and contains other important features, that are however difficult to study because simple fits often fail. Here I propose a model-based fit procedure that performs well on spectra obtained in a molecular dynamics simulation.Comment: 12 postscript figures, submitted to J. Comp. Phy

Effect of the Berendsen thermostat on dynamical properties of water

The effect of the Berendsen thermostat on the dynamical properties of bulk SPC/E water is tested by generating power spectra associated with fluctuations in various observables. The Berendsen thermostat is found to be very effective in preserving temporal correlations in fluctuations of tagged particle quantities over a very wide range of frequencies. Even correlations in fluctuations of global properties, such as the total potential energy, are well-preserved for time periods shorter than the thermostat time constant. Deviations in dynamical behaviour from the microcanonical limit do not, however, always decrease smoothly with increasing values of the thermostat time constant but may be somewhat larger for some intermediate values of $\tau_B$, specially in the supercooled regime, which are similar to time scales for slow relaxation processes in bulk water.Comment: 21 pages, 5 figures, To be published in Mol. Phy

KORELASI ANTARA BESAR ARUS LISTRIK MELALUI MEDIUM AIR DENGAN KERUSAKAN HISTOPATOLOGI OTOT GASTROKNEMIUS TIKUS WISTAR

Background: Death by electrocaution in the water is not always indicate a specific phenomenon. Electric shock can cause damage to limb muscles, so hystopathologic examination is necessary. This study aimed to determine how strong the correlation between the electric current through water conduction with the damage of Wistar rat’s gastrocnemius muscle in the form hypercontraction points number of muscle fibers that occur. Methods: This was an experimental study with post test only control group design, using Wistar rats as research samples. Thirty Wistar rats whose have inclusion and exclusion criterias was adapted for one week and then divided into five groups, each groups had six Wistar rats. One control group was not given the exposure of electric current and the four other groups were given exposure of electric current-rise, ranging from 10-30 mA, 31-60 mA, 61-90 mA and 91-120 mA. All of the samples was examined by counting the number of hypercontraction points of muscle fibers that occur. Hypothesis test uses Spearman test by SPSS for Windows 11.5. Result: Spearman test indicates p = 0.000 or there was a significant correlation between the exposure of electric current with the number of hypercontraction points of muscle fibers. The value had a very strong positive correlation (r = 0.852). Conclusion: The greater the exposure of electrical currents is given, the number of hypercontraction points of muscle fibers that occur is getting greater too. The number of hypercontraction points of muscle fibers can describe the damage of skeletal muscles are due to the electrical injuries. Key words: electric current, muscle hypercontraction, water conductio