18,662 research outputs found
Polymer Translocation througha Pore in a Membrane
We construct a new statistical physical model of polymer translocation
through a pore in a membrane treated as the diffusion process across a free
energy barrier. We determine the translocation time in terms of chain
flexibility yielding an entropic barrier, as well as in terms of the driving
mechanisms such as transmembrane chemical potential difference and Brownian
ratchets. It turns out that, while the chemical potential differences induce
pronounced effects on translocation due to the long-chain nature of the
polymer, the ratchets suppress this effect and chain flexibility.Comment: 4 pages, 5 figures, published in Phys. Rev. Lett. 77, 783(1996
Comparative Investigation of the High Pressure Autoignition of the Butanol Isomers
Investigation of the autoignition delay of the butanol isomers has been
performed at elevated pressures of 15 bar and 30 bar and low to intermediate
temperatures of 680-860 K. The reactivity of the stoichiometric isomers of
butanol, in terms of inverse ignition delay, was ranked as n-butanol >
sec-butanol ~ iso-butanol > tert-butanol at a compressed pressure of 15 bar but
changed to n-butanol > tert-butanol > sec-butanol > iso-butanol at 30 bar. For
the temperature and pressure conditions in this study, no NTC or two-stage
ignition behavior were observed. However, for both of the compressed pressures
studied in this work, tert-butanol exhibited unique pre-ignition heat release
characteristics. As such, tert-butanol was further studied at two additional
equivalence ratios ( = 0.5 and 2.0) to help determine the cause of the
heat release.Comment: 4 pages, 4 figures, presented at the 2011 Meeting of the Eastern
States Sections of the Combustion Institut
UConnRCMPy: Python-based data analysis for rapid compression machines
The ignition delay of a fuel/air mixture is an important quantity in
designing combustion devices, and these data are also used to validate chemical
kinetic models for combustion. One of the typical experimental devices used to
measure the ignition delay is called a Rapid Compression Machine (RCM). This
paper presents UConnRCMPy, an open-source Python package to process
experimental data from the RCM at the University of Connecticut. Given an
experimental measurement, UConnRCMPy computes the thermodynamic conditions in
the reaction chamber of the RCM during an experiment along with the ignition
delay. UConnRCMPy implements an extensible framework, so that alternative
experimental data formats can be incorporated easily. In this way, UConnRCMPy
improves the consistency of RCM data processing and enables the community to
reproduce data analysis procedures.Comment: 8 pages, 3 figures, presented at the 10th US National Combustion
Meetin
Polymer Release out of a Spherical Vesicle through a Pore
Translocation of a polymer out of curved surface or membrane is studied via
mean first passage time approach. Membrane curvature gives rise to a constraint
on polymer conformation, which effectively drives the polymer to the outside of
membrane where the available volume of polymer conformational fluctuation is
larger. Considering a polymer release out of spherical vesicle, polymer
translocation time is changed to the scaling behavior for
, from for , where is the polymer contour
length and , are vesicle radius and polymer radius of gyration
respectively. Also the polymer capture into a spherical budd is studied and
possible apparatus for easy capture is suggested.Comment: 14 pages RevTeX, 6 postscript figures, published in Phys. Rev. E 57,
730 (1998
Rich variety of defects in ZnO via an attractive interaction between O-vacancies and Zn-interstitials
As the concentration of intrinsic defects becomes sufficiently high in
O-deficient ZnO, interactions between defects lead to a significant reduction
in their formation energies. We show that the formation of both O-vacancies and
Zn-interstitials becomes significantly enhanced by a strong attractive
interaction between them, making these defects an important source of n-type
conductivity in ZnO.Comment: 12 pages, 4 figure
Fourth Generation Parity
We present a very simple 4th-generation (4G) model with an Abelian gauge
interaction under which only the 4G fermions have nonzero charge. The U(1)
gauge symmetry can have a Z_2 residual discrete symmetry (4G-parity), which can
stabilize the lightest 4G particle (L4P). When the 4G neutrino is the L4P, it
would be a neutral and stable particle and the other 4G fermions would decay
into the L4P leaving the trace of missing energy plus the standard model
fermions. Because of the new symmetry, the 4G particle creation and decay modes
are different from those of the sequential 4G model, and the 4G particles can
be appreciably lighter than typical experimental bounds.Comment: Version accepted for publication in PR
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