2,800 research outputs found
Interface relaxation in electrophoretic deposition of polymer chains: Effects of segmental dynamics, molecular weight, and field
Using different segmental dynamics and relaxation, characteristics of the
interface growth is examined in an electrophoretic deposition of polymer chains
on a three (2+1) dimensional discrete lattice with a Monte Carlo simulation.
Incorporation of faster modes such as crankshaft and reptation movements along
with the relatively slow kink-jump dynamics seems crucial in relaxing the
interface width. As the continuously released polymer chains are driven (via
segmental movements) and deposited, the interface width grows with the
number of time steps , (--,
which is followed by its saturation to a steady-state value . Stopping the
release of additional chains after saturation while continuing the segmental
movements relaxes the saturated width to an equilibrium value ().
Scaling of the relaxed interface width with the driving field , remains similar to that of the steady-state width. In
contrast to monotonic increase of the steady-state width , the relaxed
interface width is found to decay (possibly as a stretched exponential)
with the molecular weight.Comment: 5 pages, 7 figure
Supersymmetric version of a hydrodynamic system in Riemann invariants and its solutions
In this paper, a supersymmetric extension of a system of hydrodynamic type
equations involving Riemann invariants is formulated in terms of a superspace
and superfield formalism. The symmetry properties of both the classical and
supersymmetric versions of this hydrodynamical model are analyzed through the
use of group-theoretical methods applied to partial differential equations
involving both bosonic and fermionic variables. More specifically, we compute
the Lie superalgebras of both models and perform classifications of their
respective subalgebras. A systematic use of the subalgebra structures allow us
to construct several classes of invariant solutions, including travelling
waves, centered waves and solutions involving monomials, exponentials and
radicals.Comment: 30 page
Biomechanical Differences Between the Bulgarian Split-Squat and Back Squat
International Journal of Exercise Science 14(1): 533-543, 2021. The Bulgarian split squat (BSS) is a unilateral lower extremity strength exercise; however, the mechanical demands have not been fully elucidated. The purpose of this study was to compare ankle, knee, and hip joint net joint moment impulse (NJMI), work (NJW), peak net joint moment (NJM) and peak displacement between the BSS and traditional bilateral back squat (BS). Following a practice and 1-repetition maximum (1-RM) session, 2x3 BS (70% 1-RM) and BSS (35% 1-RM) were completed by twenty resistance trained males (24.20 ± 2.50 yrs, 1.76 ± 0.06m, 85.3 ± 13.90 kg). Significant squat type x joint interactions were revealed for NJMI (p \u3c 0.001), NJW (p \u3c 0.001), peak NJM (p \u3c 0.001), and peak displacement (p = 0.011). For both squats, hip NJMI, NJW, and peak NJM was significantly greater than both ankle (d = 5.50-9.40) and knee (d = 7.50-8.50). While knee NJMI (d = 2.80) and peak NJM (d = 2.10) during the BSS was statistically less compared to ankle, during BS knee NJMI was statistically greater than ankle (d = 3.00). Ankle and knee NJW were statistically similar during BSS (d = 0.30), whereas knee NJW was statistically greater than ankle during BS (d = 3.20). Comparing between squat types within each joint demonstrated statistically equal peak displacement for the ankle (d = 0.14) and hip (d = 0.11), whereas knee joint peak displacement was significantly less for the BSS compared to BS (d = 0.82). Both the BSS and BS are hip dominant exercises. The BSS may best be used in circumstances to focus on hip extension while minimizing the knee joint demands, such as the early phases of knee rehabilitation or when addressing isolated hip extension deficiencies
Hydrodynamic Waves in Regions with Smooth Loss of Convexity of Isentropes. General Phenomenological Theory
General phenomenological theory of hydrodynamic waves in regions with smooth
loss of convexity of isentropes is developed based on the fact that for most
media these regions in p-V plane are anomalously small. Accordingly the waves
are usually weak and can be described in the manner analogous to that for weak
shock waves of compression. The corresponding generalized Burgers equation is
derived and analyzed. The exact solution of the equation for steady shock waves
of rarefaction is obtained and discusses.Comment: RevTeX, 4 two-column pages, no figure
Physics in Riemann's mathematical papers
Riemann's mathematical papers contain many ideas that arise from physics, and
some of them are motivated by problems from physics. In fact, it is not easy to
separate Riemann's ideas in mathematics from those in physics. Furthermore,
Riemann's philosophical ideas are often in the background of his work on
science. The aim of this chapter is to give an overview of Riemann's
mathematical results based on physical reasoning or motivated by physics. We
also elaborate on the relation with philosophy. While we discuss some of
Riemann's philosophical points of view, we review some ideas on the same
subjects emitted by Riemann's predecessors, and in particular Greek
philosophers, mainly the pre-socratics and Aristotle. The final version of this
paper will appear in the book: From Riemann to differential geometry and
relativity (L. Ji, A. Papadopoulos and S. Yamada, ed.) Berlin: Springer, 2017
Intersubband absorption linewidth in GaAs quantum wells due to scattering by interface roughness, phonons, alloy disorder, and impurities
We calculate the intersubband absorption linewidth in quantum wells (QWs) due
to scattering by interface roughness, LO phonons, LA phonons, alloy disorder,
and ionized impurities, and compare it with the transport energy broadening
that corresponds to the transport relaxation time related to electron mobility.
Numerical calculations for GaAs QWs clarify the different contributions of each
individual scattering mechanism to absorption linewidth and transport
broadening. Interface roughness scattering contributes about an order of
magnitude more to linewidth than to transport broadening, because the
contribution from the intrasubband scattering in the first excited subband is
much larger than that in the ground subband. On the other hand, LO phonon
scattering (at room temperature) and ionized impurity scattering contribute
much less to linewidth than to transport broadening. LA phonon scattering makes
comparable contributions to linewidth and transport broadening, and so does
alloy disorder scattering. The combination of these contributions with
significantly different characteristics makes the absolute values of linewidth
and transport broadening very different, and leads to the apparent lack of
correlation between them when a parameter, such as temperature or alloy
composition, is changed. Our numerical calculations can quantitatively explain
the previously reported experimental results.Comment: 17 pages, including 15 figure
On the Nature of the Cosmological Constant Problem
General relativity postulates the Minkowski space-time to be the standard
flat geometry against which we compare all curved space-times and the
gravitational ground state where particles, quantum fields and their vacuum
states are primarily conceived. On the other hand, experimental evidences show
that there exists a non-zero cosmological constant, which implies in a deSitter
space-time, not compatible with the assumed Minkowski structure. Such
inconsistency is shown to be a consequence of the lack of a application
independent curvature standard in Riemann's geometry, leading eventually to the
cosmological constant problem in general relativity.
We show how the curvature standard in Riemann's geometry can be fixed by
Nash's theorem on locally embedded Riemannian geometries, which imply in the
existence of extra dimensions. The resulting gravitational theory is more
general than general relativity, similar to brane-world gravity, but where the
propagation of the gravitational field along the extra dimensions is a
mathematical necessity, rather than being a a postulate. After a brief
introduction to Nash's theorem, we show that the vacuum energy density must
remain confined to four-dimensional space-times, but the cosmological constant
resulting from the contracted Bianchi identity is a gravitational contribution
which propagates in the extra dimensions. Therefore, the comparison between the
vacuum energy and the cosmological constant in general relativity ceases to be.
Instead, the geometrical fix provided by Nash's theorem suggests that the
vacuum energy density contributes to the perturbations of the gravitational
field.Comment: LaTex, 5 pages no figutres. Correction on author lis
Reconstructing a Z' Lagrangian using the LHC and low-energy data
We study the potential of the LHC and future low-energy experiments to
precisely measure the underlying model parameters of a new Z' boson. We
emphasize the complimentary information obtained from both on- and off-peak LHC
dilepton data, from the future Q-weak measurement of the weak charge of the
proton, and from a proposed measurement of parity violation in low-energy
Moller scattering. We demonstrate the importance of off-peak LHC data and
Q-weak for removing sign degeneracies between Z' couplings that occur if only
on-peak LHC data is studied. A future precision measurement of low-energy
Moller scattering can resolve a scaling degeneracy between quark and lepton
couplings that remains after analyzing LHC dilepton data, permitting an
extraction of the individual Z' couplings rather than combinations of them. We
study how precisely Z' properties can be extracted for LHC integrated
luminosities ranging from a few inverse femtobarns to super-LHC values of an
inverse attobarn. For the several example cases studied with M_Z'=1.5 TeV, we
find that coupling combinations can be determined with relative uncertainties
reaching 30% with 30 fb^-1 of integrated luminosity, while 50% is possible with
10 fb^-1. With SLHC luminosities of 1 ab^-1, we find that products of quark and
lepton couplings can be probed to 10%.Comment: 36 pages, 17 figure
- …