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9 Oct 2006

Volume 89, Issue 15, Articles (15xxxx)

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Appl. Phys. Lett. 89, 151920 (2006); http://dx.doi.org/10.1063/1.2360906 (3 pages)

Aycan Yurtsever, Matthew Weyland, and David A. Muller
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Helicase mediated active DNA unwinding in a stochastic field

Tamal Das and Suman Chakraborty

Appl. Phys. Lett. 89, 153901 (2006); http://dx.doi.org/10.1063/1.2358846 (3 pages) | Cited 2 times

Online Publication Date: 10 October 2006

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The mechanism of unwinding of DNA by a class of motor proteins called helicase, in contact with a thermal bath, is theoretically investigated. The dynamic simulations, incorporating the considerations of externally applied unwinding forces as well as stochastically fluctuating Langevin interactions, are utilized to calculate the critical force required for the base pair opening, which comes out to be in close agreement with the experimentally obtained results. The simulation predictions effectively demonstrate how the thermal stochasticities can be overridden by directional openings, as an extended viewpoint of the classical Peyrard-Bishop [Phys. Rev. Lett. 62, 2755 (1989)] model.
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87.15.R- Reactions and kinetics
87.15.H- Dynamics of biomolecules
87.14.E- Proteins
87.14.G- Nucleic acids
87.15.A- Theory, modeling, and computer simulation
87.19.Pp Biothermics and thermal processes in biology

Lethality mechanisms in Escherichia coli induced by intense sub-microsecond electrical pulses

P. R. Chalise, S. Perni, G. Shama, B. M. Novac, I. R. Smith, and M. G. Kong

Appl. Phys. Lett. 89, 153902 (2006); http://dx.doi.org/10.1063/1.2361271 (3 pages) | Cited 5 times

Online Publication Date: 10 October 2006

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In this letter, the authors present the inactivation kinetics of cells of Escherichia coli and its mutants following treatment with high-intensity electrical pulses of 700 and 32 ns durations. Their experimental results suggest that bacterial inactivation by 700 ns pulses is consistent with a mechanism of reversible electroporation, whereas inactivation by 32 ns pulses may occur as a result of damage to intracellular components. They believe that their results represent a first step towards elucidating the mechanism of lethality of submicrosecond pulses of different durations in prokaryotes.
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87.50.C- Static and low-frequency electric and magnetic fields effects
87.16.-b Subcellular structure and processes

Positron emission tomographic map reconstruction using fuzzy-median filter

Partha Pratim Mondal

Appl. Phys. Lett. 89, 153903 (2006); http://dx.doi.org/10.1063/1.2358943 (3 pages) | Cited 2 times

Online Publication Date: 11 October 2006

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Positron emission tomography is widely used in medical physics for the reconstruction of the distribution of radionuclei molecules for analyzing regional physiological functions. The existing maximum a posteriori reconstruction methodologies produce artifacts such as oversmoothing and streaking. In this letter, the author proposes a potential function based on fuzzy-median filter for noise-free image reconstruction. The reconstruction methodology is therefore very useful for obtaining artifact-free reconstruction of biomedical specimens.
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87.57.uk Positron emission tomography (PET)
87.57.N- Image analysis
02.50.-r Probability theory, stochastic processes, and statistics

Ionic contrast terahertz time resolved imaging of frog auricular heart muscle electrical activity

Jean-Baptiste Masson, Martin-Pierre Sauviat, and Guilhem Gallot

Appl. Phys. Lett. 89, 153904 (2006); http://dx.doi.org/10.1063/1.2360931 (3 pages) | Cited 4 times

Online Publication Date: 12 October 2006

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The authors demonstrate the direct, noninvasive and time resolved imaging of functional frog auricular fibers by ionic contrast terahertz (ICT) near field microscopy. This technique provides quantitative, time-dependent measurement of ionic flow during auricular muscle electrical activity, and opens the way of direct noninvasive imaging of cardiac activity under stimulation. ICT microscopy technique was associated with full three-dimensional simulation enabling to measure precisely the fiber sizes. This technique coupled to waveguide technology should provide the grounds to development of advanced in vivo ion flux measurement in mammalian hearts, allowing the prediction of heart attack from change in K+ fluxes.
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87.63.L- Visual imaging
87.19.R- Mechanical and electrical properties of tissues and organs
87.19.Hh Cardiac dynamics
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
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