11,937 research outputs found
Time-resolved measurement of single pulse femtosecond laser-induced periodic surface structure formation
Time-resolved diffraction microscopy technique has been used to observe the
formation of laser-induced periodic surface structures (LIPSS) from the
interaction of a single femtosecond laser pulse (pump) with a nano-scale groove
mechanically formed on a single-crystal Cu substrate. The interaction dynamics
(0-1200 ps) was captured by diffracting a time-delayed, frequency-doubled pulse
from nascent LIPSS formation induced by the pump with an infinity-conjugate
microscopy setup. The LIPSS ripples are observed to form sequentially outward
from the groove edge, with the first one forming after 50 ps. A 1-D analytical
model of electron heating and surface plasmon polariton (SPP) excitation
induced by the interaction of incoming laser pulse with the groove edge
qualitatively explains the time-evloution of LIPSS formation.Comment: 4 pages, 5 figure
Dynamic instability of microtubules: effect of catastrophe-suppressing drugs
Microtubules are stiff filamentary proteins that constitute an important
component of the cytoskeleton of cells. These are known to exhibit a dynamic
instability. A steadily growing microtubule can suddenly start depolymerizing
very rapidly; this phenomenon is known as ``catastrophe''. However, often a
shrinking microtubule is ``rescued'' and starts polymerizing again. Here we
develope a model for the polymerization-depolymerization dynamics of
microtubules in the presence of {\it catastrophe-suppressing drugs}. Solving
the dynamical equations in the steady-state, we derive exact analytical
expressions for the length distributions of the microtubules tipped with
drug-bound tubulin subunits as well as those of the microtubules, in the
growing and shrinking phases, tipped with drug-free pure tubulin subunits. We
also examine the stability of the steady-state solutions.Comment: Minor corrections; final published versio
Comprehensive Approach of Groundwater Resource Evaluation: A Case Study in the Chippewa Creek Watershed in Ohio
Author Institution: Department of Geological Sciences, State University of New York - New Paltz ; Department of Earth Science, University of Northern Iowa ; Department of Geology, University of AkronA groundwater resource evaluation of Chippewa Creek watershed in Wayne and Medina counties, OH, shows continued availability of groundwater for agriculture and domestic uses. Two major hydrogeologic units in this watershed supply groundwater. A 100 to 150 ft (30 to 46 m) thick outwash deposit of sand and gravel, occupying a buried valley underlying Chippewa Creek, forms a highly permeable aquifer for agricultural, municipal, and domestic purposes. In some areas bedrock aquifers, mostly composed of sandstone of Pennsylvanian and Mississippian age, are used for industrial and domestic purposes. Mean transmissivity of the outwash aquifer is 25,000 gpd/ft (310 mVday). The hydraulic conductivity of the aquifer has a mean value of 250 gpd/ft2 (10 m/day). The total calculated volume of annual net recharge is 4.2 x 108 ft3 (1.2 107 m3) and the mean specific capacity of the wells completed in aquifer is 5.0 gpm/ft (1.03 1/sec/m). The groundwater quality is suitable for drinking and agricultural use and contains mostly Ca++, Na+, K+ and HCO3~ ions. Groundwater pollution potential of the study area was evaluated using DRASTIC. Chippewa Creek watershed lies within the Glaciated Central Ground Water Region. Seven mappable units from DRASTIC were defined in the study area based on seven hydrogeologic settings. The units are: 1) 7Aa, glacial till over bedded sedimentary rocks (DRASTIC designation); 2) 7Ad, glacial till over sandstone; 3) 7Af, sand and gravel interbedded in glacial till; 4) 7Ba, outwash; 5) 7D, buried valley; 6) 7Eb, alluvium without overbank deposits; 7) 7Ec, alluvium over bedded sedimentary rocks. The outwash aquifer has a moderate to high pollution potential and the underlying sandstone and shale deposits show relatively low pollution potentials. The alluvium in valleys exhibits moderately high susceptibility to contamination
Logarithmic Correction to BPS Black Hole Entropy from Supersymmetric Index at Finite Temperature
It has been argued by Iliesiu, Kologlu and Turiaci in arXiv:2107.09062 that
one can compute the supersymmetric index of black holes using black hole
geometry carrying finite temperature but a specific complex angular velocity.
We follow their prescription to compute the logarithmic correction to the
entropy of BPS states in four dimensions, defined as the log of the index of
supersymmetric black holes, and find perfect agreement with the previous
results for the same quantity computed using the near horizon geometry of zero temperature black holes. Besides giving an independent
computation of supersymmetric black hole entropy, this analysis also provides a
test of the procedure used previously for computing logarithmic corrections to
Schwarzschild and other non-extremal black hole entropy.Comment: 23 page
Pax2, a new murine paired-box-containing gene and its expression in the developing excretory system.
The consequences of SU(3) colorsingletness, Polyakov Loop and Z(3) symmetry on a quark-gluon gas
Based on quantum statistical mechanics we show that the color singlet
ensemble of a quark-gluon gas exhibits a symmetry through the normaized
character in fundamental representation and also becomes equivalent, within a
stationary point approximation, to the ensemble given by Polyakov Loop. Also
Polyakov Loop gauge potential is obtained by considering spatial gluons along
with the invariant Haar measure at each space point. The probability of the
normalized character in vis-a-vis Polyakov Loop is found to be maximum
at a particular value exhibiting a strong color correlation. This clearly
indicates a transition from a color correlated to uncorrelated phase or
vise-versa. When quarks are included to the gauge fields, a metastable state
appears in the temperature range due to the
explicit symmetry breaking in the quark-gluon system. Beyond
MeV the metastable state disappears and stable domains appear. At low
temperature a dynamical recombination of ionized color charges to a
color singlet confined phase is evident along with a confining
background that originates due to circulation of two virtual spatial gluons but
with conjugate phases in a closed loop. We also discuss other possible
consequences of the center domains in the color deconfined phase at high
temperature.Comment: Version published in J. Phys.
Instability of dilute granular flow on rough slope
We study numerically the stability of granular flow on a rough slope in
collisional flow regime in the two-dimension. We examine the density dependence
of the flowing behavior in low density region, and demonstrate that the
particle collisions stabilize the flow above a certain density in the parameter
region where a single particle shows an accelerated behavior. Within this
parameter regime, however, the uniform flow is only metastable and is shown to
be unstable against clustering when the particle density is not high enough.Comment: 4 pages, 6 figures, submitted to J. Phys. Soc. Jpn.; Fig. 2 replaced;
references added; comments added; misprints correcte
A (Running) Bolt for New Reasons
We construct a four-parameter family of smooth, horizonless, stationary
solutions of ungauged five-dimensional supergravity by using the
four-dimensional Euclidean Schwarzschild metric as a base space and
"magnetizing" its bolt. We then generalize this to a five-parameter family
based upon the Euclidean Kerr-Taub-Bolt. These "running Bolt" solutions are
necessarily non-static. They also have the same charges and mass as a
non-extremal black hole with a classically-large horizon area. Moreover, in a
certain regime their mass can decrease as their charges increase. The existence
of these solutions supports the idea that the singularities of non-extremal
black holes are resolved by low-mass modes that correct the singularity of the
classical black hole solution on large (horizon-sized) scales.Comment: 25 pages, 3 figures, LaTeX; v2: minor changes, references adde
Inverse flux quantum periodicity of magnetoresistance oscillations in two-dimensional short-period surface superlattices
Transport properties of the two-dimensional electron gas (2DEG) are
considered in the presence of a perpendicular magnetic field and of a {\it
weak} two-dimensional (2D) periodic potential modulation in the 2DEG plane. The
symmetry of the latter is rectangular or hexagonal. The well-known solution of
the corresponding tight-binding equation shows that each Landau level splits
into several subbands when a rational number of flux quanta pierces the
unit cell and that the corresponding gaps are exponentially small. Assuming the
latter are closed due to disorder gives analytical wave functions and
simplifies considerably the evaluation of the magnetoresistivity tensor
. The relative phase of the oscillations in and
depends on the modulation periods involved. For a 2D modulation
with a {\bf short} period nm, in addition to the Weiss oscillations
the collisional contribution to the conductivity and consequently the tensor
show {\it prominent peaks when one flux quantum passes
through an integral number of unit cells} in good agreement with recent
experiments. For periods nm long used in early experiments, these
peaks occur at fields 10-25 times smaller than those of the Weiss oscillations
and are not resolved
On the kinks and dynamical phase transitions of alpha-helix protein chains
Heuristic insights into a physical picture of Davydov's solitonic model of
the one-dimensional protein chain are presented supporting the idea of a
non-equilibrium competition between the Davydov phase and a complementary,
dynamical- `ferroelectric' phase along the chainComment: small latex file with possible glue problems, just go on !, no
figures, small corrections with respect to the published text, follow-up work
to cond-mat/9304034 [PRE 47 (June 1993) R3818
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