2,340 research outputs found
Probabilistic Phase Space Trajectory Description for Anomalous Polymer Dynamics
It has been recently shown that the phase space trajectories for the
anomalous dynamics of a tagged monomer of a polymer --- for single polymeric
systems such as phantom Rouse, self-avoiding Rouse, Zimm, reptation, and
translocation through a narrow pore in a membrane; as well as for
many-polymeric system such as polymer melts in the entangled regime --- is
robustly described by the Generalized Langevin Equation (GLE). Here I show that
the probability distribution of phase space trajectories for all these
classical anomalous dynamics for single polymers is that of a fractional
Brownian motion (fBm), while the dynamics for polymer melts between the
entangled regime and the eventual diffusive regime exhibits small, but
systematic deviations from that of a fBm.Comment: 8 pages, two figures, 3 eps figure files, minor changes,
supplementary material included moved to the appendix, references expanded,
to appear in J. Phys.: Condens. Matte
Pore-blockade Times for Field-Driven Polymer Translocation
We study pore blockade times for a translocating polymer of length ,
driven by a field across the pore in three dimensions. The polymer performs
Rouse dynamics, i.e., we consider polymer dynamics in the absence of
hydrodynamical interactions. We find that the typical time the pore remains
blocked during a translocation event scales as ,
where is the Flory exponent for the polymer. In line with our
previous work, we show that this scaling behaviour stems from the polymer
dynamics at the immediate vicinity of the pore -- in particular, the memory
effects in the polymer chain tension imbalance across the pore. This result,
along with the numerical results by several other groups, violates the lower
bound suggested earlier in the literature. We discuss why
this lower bound is incorrect and show, based on conservation of energy, that
the correct lower bound for the pore-blockade time for field-driven
translocation is given by , where is the viscosity of
the medium surrounding the polymer.Comment: 14 pages, 6 figures, slightly shorter than the previous version; to
appear in J. Phys.: Cond. Ma
Simulations of Two-Dimensional Unbiased Polymer Translocation Using the Bond Fluctuation Model
We use the Bond Fluctuation Model (BFM) to study the pore-blockade times of a
translocating polymer of length in two dimensions, in the absence of
external forces on the polymer (i.e., unbiased translocation) and hydrodynamic
interactions (i.e., the polymer is a Rouse polymer), through a narrow pore.
Earlier studies using the BFM concluded that the pore-blockade time scales with
polymer length as , with , whereas some
recent studies with different polymer models produce results consistent with
, originally predicted by us. Here is the Flory exponent of
the polymer; in 2D. In this paper we show that for the BFM if the
simulations are extended to longer polymers, the purported scaling ceases to hold. We characterize the finite-size effects, and study
the mobility of individual monomers in the BFM. In particular, we find that in
the BFM, in the vicinity of the pore the individual monomeric mobilities are
heavily suppressed in the direction perpendicular to the membrane. After a
modification of the BFM which counters this suppression (but possibly
introduces other artifacts in the dynamics), the apparent exponent
increases significantly. Our conclusion is that BFM simulations do not rule out
our theoretical prediction for unbiased translocation, namely .Comment: minor proofreading corrections, 23 pages (double spacing), 7 figures,
published versio
CAUSES OF DISPOSAL OF MURRAH BUFFALO FROM AN ORGANISED HERD
The present study comprised of 602 disposal records of adult Murrah buffaloes , spread over a period of 16 years
from 1985 to 2000 at NDRI, Karnal, Haryana. Analysed data showed that the reproductive problems (38.62),
low milk production (24.01) and udder problems (22.76) were the three major reasons of culling in adult Murrah
buffaloes . The culling of cows due to involuntary reason (reproductive problems, udder problems and locomotive
disorders) accounted for nearly 63.68 percent of total culling in Murrah buffaloes in the NDRI herd. The data
revealed that maximum mortality occurred due to digestive problems accounting for 30.89 percent followed by
cardio-vascular problems (26.02 percent), respiratory problems (21.14 percent), parasitic problems (8.13 percent)
and uro-genital problems (5.69 percent). The results showed that there is a scope for further improvement in
production and reproductive efficiency through better monitoring of reproduction and udder health status of the
buffaloes. The high involuntary culling rate not only makes the dairy enterprises economically less profitable but
also reduces the genetic improvement by lowering the selection differential for milk production
Polymers grafted to porous membranes
We study a single flexible chain molecule grafted to a membrane which has
pores of size slightly larger than the monomer size. On both sides of the
membrane there is the same solvent. When this solvent is good, i.e. when the
polymer is described by a self avoiding walk, it can fairly easily penetrate
the membrane, so that the average number of membrane crossings tends, for chain
length , to a positive constant. The average numbers of monomers on
either side of the membrane diverges in this limit, although their ratio
becomes infinite. For a poor solvent, in contrast, the entire polymer is
located, for large , on one side of the membrane. For good and for theta
solvents (ideal polymers) we find scaling laws, whose exponents can in the
latter case be easily understood from the behaviour of random walks.Comment: 4 pages, 6 figure
Temporal criticality in socio-technical systems
Socio-technical systems, where technological and human elements interact in a
goal-oriented manner, provide important, functional support to our societies.
We draw specific attention to the concept of timeliness that has been
ubiquitously and integrally adopted as a quality standard in the {\it modus
operandi\/} of socio-technical systems, but remains an underappreciated aspect.
We point out that a variety of incentives, often reinforced by competitive
pressures, prompt system operators to myopically optimize for cost- and
time-efficiencies, running the risk of inadvertently pushing the systems
towards the proverbial `edge of a cliff'. Invoking a stylized model for
operational delays, we argue that this cliff edge is a true critical point --
identified as {\it temporal criticality\/} -- implying that system efficiency
and robustness to perturbation are in tension with each other. Specifically for
firm-to-firm production networks, we suggest that the proximity to temporal
criticality is a possible route for solving the fundamental ``excess volatility
puzzle'' in economics. Further, in generality for optimizing socio-technical
systems, we propose that system operators incorporate a measure of resilience
in their welfare functions.Comment: 9 pages, 3 figures, perspective paper, corrected copy-paste error in
the abstrac
Near-infrared photoabsorption by C(60) dianions in a storage ring
We present a detailed study of the electronic structure and the stability of C(60) dianions in the gas phase. Monoanions were extracted from a plasma source and converted to dianions by electron transfer in a Na vapor cell. The dianions were then stored in an electrostatic ring, and their near-infrared absorption spectrum was measured by observation of laser induced electron detachment. From the time dependence of the detachment after photon absorption, we conclude that the reaction has contributions from both direct electron tunneling to the continuum and vibrationally assisted tunneling after internal conversion. This implies that the height of the Coulomb barrier confining the attached electrons is at least similar to 1.5 eV. For C(60)(2-) ions in solution electron spin resonance measurements have indicated a singlet ground state, and from the similarity of the absorption spectra we conclude that also the ground state of isolated C(60)(2-) ions is singlet. The observed spectrum corresponds to an electronic transition from a t(1u) lowest unoccupied molecular orbital (LUMO) of C(60) to the t(1g) LUMO+1 level. The electronic levels of the dianion are split due to Jahn-Teller coupling to quadrupole deformations of the molecule, and a main absorption band at 10723 cm(-1) corresponds to a transition between the Jahn-Teller ground states. Also transitions from pseudorotational states with 200 cm(-1) and (probably) 420 cm(-1) excitation are observed. We argue that a very broad absorption band from about 11 500 cm(-1) to 13 500 cm(-1) consists of transitions to so-called cone states, which are Jahn-Teller states on a higher potential-energy surface, stabilized by a pseudorotational angular momentum barrier. A previously observed, high-lying absorption band for C(60)(-) may also be a transition to a cone state
Hubungan Laju Pertumbuhan Dengan Saat Berbunga Untuk Seleksi Kegenjahan Tanaman Pepaya
. The research has been conducted at Aripan Experimental Station , Indone- sian Fruit Research Institute at Solok from August 1999 to February 2000 in randomized block design with three repli- cations and 40 accessions of papaya as treatments were collected from West Sumatera, Bengkulu, South Sumatera, Lampung, and East Jawa. The research was using container trial in field. The parameters observed were relative growth rate, net assimilation rate, plant dry weight, plant height, leaf number, stem diameter, and flowering time. The results of the experiment indicated that growth rate and flowering time among accessions are enough variations. No correlation between growth rate component and flowering time of papaya. The experiment results indicated that selec- tion of early flowering papaya by exploited of plant growth rate can not be applied. Accesion No. 029 which indicated faster growth and early flowering can be used as an candidate of superior variety
Response of a Hexagonal Granular Packing under a Localized External Force: Exact Results
We study the response of a two-dimensional hexagonal packing of massless,
rigid, frictionless spherical grains due to a vertically downward point force
on a single grain at the top layer. We use a statistical approach, where each
mechanically stable configuration of contact forces is equally likely. We show
that this problem is equivalent to a correlated -model. We find that the
response is double-peaked, where the two peaks, sharp and single-grain diameter
wide, lie on the two downward lattice directions emanating from the point of
the application of the external force. For systems of finite size, the
magnitude of these peaks decreases towards the bottom of the packing, while
progressively a broader, central maximum appears between the peaks. The
response behaviour displays a remarkable scaling behaviour with system size
: while the response in the bulk of the packing scales as , on
the boundary it is independent of , so that in the thermodynamic limit only
the peaks on the lattice directions persist. This qualitative behaviour is
extremely robust, as demonstrated by our simulation results with different
boundary conditions. We have obtained expressions of the response and higher
correlations for any system size in terms of integers corresponding to an
underlying discrete structure.Comment: Accepted for publication in JStat; 33 pages, 10 figures; Section 2.2
reorganized and rewritten; Details about the simulation procedure added in
Sec.3.1. ; A new section, summarizing the final results and the calculation
procedure adde
Sensitivity of the stress response function to packing preparation
A granular assembly composed of a collection of identical grains may pack
under different microscopic configurations with microscopic features that are
sensitive to the preparation history. A given configuration may also change in
response to external actions such as compression, shearing etc. We show using a
mechanical response function method developed experimentally and numerically,
that the macroscopic stress profiles are strongly dependent on these
preparation procedures. These results were obtained for both two and three
dimensions. The method reveals that, under a given preparation history, the
macroscopic symmetries of the granular material is affected and in most cases
significant departures from isotropy should be observed. This suggests a new
path toward a non-intrusive test of granular material constitutive properties.Comment: 15 pages, 11 figures, some numerical data corrected, to appear in J.
Phys. Cond. Mat. special issue on Granular Materials (M. Nicodemi Editor
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