3,407 research outputs found
Microscopic Theory of Protein Folding Rates.I: Fine Structure of the Free Energy Profile and Folding Routes from a Variational Approach
A microscopic theory of the free energy barriers and folding routes for
minimally frustrated proteins is presented, greatly expanding on the
presentation of the variational approach outlined previously [J. J. Portman, S.
Takada, P. G. Wolynes, Phys. Rev. Lett. {\bf 81}, 5237 (1998)]. We choose the
-repressor protein as an illustrative example and focus on how the
polymer chain statistics influence free energy profiles and partially ordered
ensembles of structures. In particular, we investigate the role of chain
stiffness on the free energy profile and folding routes. We evaluate the
applicability of simpler approximations in which the conformations of the
protein molecule along the folding route are restricted to have residues that
are either entirely folded or unfolded in contiguous stretches. We find that
the folding routes obtained from only one contiguous folded region corresponds
to a chain with a much greater persistence length than appropriate for natural
protein chains, while the folding route obtained from two contiguous folded
regions is able to capture the relatively folded regions calculated within the
variational approach. The free energy profiles obtained from the contiguous
sequence approximations have larger barriers than the more microscopic
variational theory which is understood as a consequence of partial ordering.Comment: 16 pages, 11 figure
Game Based Learning for Safety and Security Education
Safety and security education are important part of technology related education, because of recent number of increase in safety and security related incidents. Game based learning is an emerging and rapidly advancing forms of computer-assisted instruction. Game based learning for safety and security education enables students to learn concepts and skills without the risk of physical injury and security breach. In this paper, a pedestal grinder safety game and physical security game have been developed using industrial standard modeling and game development software. The average score of the knowledge test of grinder safety game was 82%, which is higher than traditional lecture only instruction method. In addition, the survey of physical security game shows 84% average satisfaction ratio from high school students who played the game during the summer camp. The results of these studies indicated that game based learning method can enhance students' learning without potential harm to the students
Microscopic Theory of Protein Folding Rates.II: Local Reaction Coordinates and Chain Dynamics
The motion involved in barrier crossing for protein folding are investigated
in terms of the chain dynamics of the polymer backbone, completing the
microscopic description of protein folding presented in the previous paper.
Local reaction coordinates are identified as collective growth modes of the
unstable fluctuations about the saddle-points in the free energy surface. The
description of the chain dynamics incorporates internal friction (independent
of the solvent viscosity) arising from the elementary isomerizations of the
backbone dihedral angles. We find that the folding rate depends linearly on the
solvent friction for high viscosity, but saturates at low viscosity because of
internal friction. For -repressor, the calculated folding rate
prefactor, along with the free energy barrier from the variational theory,
gives a folding rate that agrees well with the experimentally determined rate
under highly stabilizing conditions, but the theory predicts too large a
folding rate at the transition midpoint. This discrepancy obtained using a
fairly complete quantitative theory inspires a new set of questions about chain
dynamics, specifically detailed motions in individual contact formation.Comment: 18 pages, 8 figure
Drag force on an oscillating object in quantum turbulence
This paper reports results of the computation of the drag force exerted on an
oscillating object in quantum turbulence in superfluid He. The drag force
is calculated on the basis of numerical simulations of quantum turbulent flow
about the object. The drag force is proportional to the square of the magnitude
of the oscillation velocity, which is similar to that in classical turbulence
at high Reynolds number. The drag coefficient is also calculated, and its value
is found to be of the same order as that observed in previous experiments. The
correspondence between quantum and classical turbulences is further clarified
by examining the turbulence created by oscillating objects.Comment: 7 pages, 5 figures, 1 tabl
Parametrizations of triaxial deformation and E2 transitions of the wobbling band
By the very definition the triaxial deformation parameter is related
to the expectation values of the K=0 and K=2 components of the intrinsic
quadrupole tensor operator. On the other hand, using the same symbol
"", various different parametrizations of triaxial deformation have
been employed, which are suitable for various types of the mean-field
potentials. It is pointed out that the values of various "" are quite
different for the same actual triaxial deformation, especially for the large
deformation; for example, the difference can be almost a factor two for the
case of the triaxial superdeformed bands recently observed in the Hf and Lu
nuclei. In our previous work, we have studied the wobbling band in Lu nuclei by
using the microscopic framework of the cranked Nilsson mean-field and the
random phase approximation, where the most serious problem is that the
calculated B(E2) value is about factor two smaller. It is shown that the origin
of this underestimation can be mainly attributed to the small triaxial
deformation; if is used the same triaxial deformation as in the analysis of the
particle-rotor model, the calculated B(E2) increases and gives correct
magnitude compared with the experimental data.Comment: 10 pages, 9 figure
Competing Ground States of a Peierls-Hubbard Nanotube
Motivated by iodo platinum complexes assembled within a quadratic-prism
lattice, [Pt(CHN)(CHN)I](NO), we
investigate the ground-state properties of a Peierls-Hubbard four-legged tube.
Making a group-theoretical analysis, we systematically reveal a variety of
valence arrangements, including half-metallic charge-density-wave states.
Quantum and thermal phase competition is numerically demonstrated with
particular emphasis on doping-induced successive insulator-to-metal transitions
with conductivity increasing stepwise.Comment: 6 pages, 4 figures. to be published in Europhys. Lett. 87 (2009)
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Length-weight relationship and relative condition factor of Stolephorus commersonii (Lacepede, 1803) exploited along Kerala coast
The length-weight relationship and relative condition factor
of Stolephorus commersonii was calculated to assess the
significance of allometric factor and the well being. The study
was carried out by using the data collected from ring seine
and purse seine catches during the year 2010-2011. The
length of species in catches ranged from 5 to 14.6 cm with
a mean length of 9.24 ┬▒ 1.83 cm and the weight ranged
from 1 to 25g with an average weight of 6.64 ┬▒ 3.96 g.
Length-weight relationship calculated for male, female and
pooled are W = 0.0070 L3.02, W = 0. 00756 L2.99 and W =
0. 0073 L3.006 respectively. The relative condition factor (Kn)
estimated separately for male and female showed monthly
fluctuation. The highest Kn values were observed in February
and August and the lowest in June for both the sexes
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Atomistic study on the pressure dependence of the melting point of NdFe12
We investigated, using molecular dynamics, how pressure affects the melting point of the recently theorised and epitaxially grown structure NdFe12. We modified Morse potentials using experimental constants and a genetic algorithm code, before running two-phase solid-liquid coexistence simulations of NdFe12 at various temperatures and pressures. The refitting of the Morse potentials allowed us to significantly improve the accuracy in predicting the melting temperature of the constituent elements
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