1,600 research outputs found
Dynamical surface structures in multi-particle-correlated surface growths
We investigate the scaling properties of the interface fluctuation width for
the -mer and -particle-correlated deposition-evaporation models. These
models are constrained with a global conservation law that the particle number
at each height is conserved modulo . In equilibrium, the stationary
roughness is anomalous but universal with roughness exponent ,
while the early time evolution shows nonuniversal behavior with growth exponent
varying with models and . Nonequilibrium surfaces display diverse
growing/stationary behavior. The -mer model shows a faceted structure, while
the -particle-correlated model a macroscopically grooved structure.Comment: 16 pages, 10 figures, revte
Neutron Diffraction Study of Field Cooling Effects on Relaxor Ferroelectrics Pb[(Zn_{1/3} Nb_{2/3})_{0.92} Ti_{0.08}] O_{3}
High-temperature (T) and high-electric-field (E) effects on Pb[(Zn_{1/3}
Nb_{2/3})_{0.92} Ti_{0.08}]O_3 (PZN-8%PT) were studied comprehensively by
neutron diffraction in the ranges 300 <= T <= 550 K and 0 <= E <= 15 kV/cm. We
have focused on how phase transitions depend on preceding thermal and
electrical sequences. In the field cooling process (FC, E parallel [001] >= 0.5
kV/cm), a successive cubic (C) --> tetragonal (T) --> monoclinic (M_C)
transition was observed. In the zero field cooling process (ZFC), however, we
have found that the system does not transform to the rhombohedral (R) phase as
widely believed, but to a new, unidentified phase, which we call X. X gives a
Bragg peak profile similar to that expected for R, but the c-axis is always
slightly shorter than the a-axis. As for field effects on the X phase, we found
an irreversible X --> M_C transition via another monoclinic phase (M_A) as
expected from a previous report [Noheda et al. Phys. Rev. Lett. 86, 3891
(2001)]. At a higher electric field, we confirmed a c-axis jump associated with
the field-induced M_C --> T transition, which was observed by strain and x-ray
diffraction measurements.Comment: 8 pages, 9 figures, revise
Adsorption of Reactive Particles on a Random Catalytic Chain: An Exact Solution
We study equilibrium properties of a catalytically-activated annihilation reaction taking place on a one-dimensional chain of length () in which some segments (placed at random, with mean concentration
) possess special, catalytic properties. Annihilation reaction takes place,
as soon as any two particles land onto two vacant sites at the extremities
of the catalytic segment, or when any particle lands onto a vacant site on
a catalytic segment while the site at the other extremity of this segment is
already occupied by another particle. Non-catalytic segments are inert with
respect to reaction and here two adsorbed particles harmlessly coexist. For
both "annealed" and "quenched" disorder in placement of the catalytic segments,
we calculate exactly the disorder-average pressure per site. Explicit
asymptotic formulae for the particle mean density and the compressibility are
also presented.Comment: AMSTeX, 27 pages + 4 figure
Suppression of an absolute defect in Type IV pilus biogenesis by loss-of-function mutations in pilT, a twitching motility gene in Neisseria gonorrhoeae
Type IV pili of Neisseria gonorrhoeae, the Gram-negative etiologic agent of gonorrhea, facilitate colonization of the human host. Gonococcal PilT, a protein belonging to a large family of molecules sharing a highly conserved nucleotide binding domain motif, has been shown to be dispensable for organelle biogenesis but essential for twitching motility and competence for genetic transformation. Here, we show that the defect in pilus biogenesis resulting from mutations in the pilC gene, encoding a putative pilus-associated adhesin for human tissue, can be suppressed by the absence of functional PilT. These data conclusively demonstrate that PilT influences the Type IV pilus biogenesis pathway and strongly suggest that organelle expression is a dynamic process. In addition, these findings imply that PilT antagonizes the process of organelle biogenesis and provide the basis for a model for how the counteractive roles of PilT and PilC might relate mechanistically to the phenomenon of twitching motility
Statistical nature of non-Gaussianity from cubic order primordial perturbations: CMB map simulations and genus statistic
We simulate CMB maps including non-Gaussianity arising from cubic order
perturbations of the primordial gravitational potential, characterized by the
non-linearity parameter . The maps are used to study the characteristic
nature of the resulting non-Gaussian temperature fluctuations. We measure the
genus and investigate how it deviates from Gaussian shape as a function of
and smoothing scale. We find that the deviation of the non-Gaussian
genus curve from the Gaussian one has an antisymmetric, sine function like
shape, implying more hot and more cold spots for and less of both
for . The deviation increases linearly with and also
exhibits mild increase as the smoothing scale increases. We further study other
statistics derived from the genus, namely, the number of hot spots, the number
of cold spots, combined number of hot and cold spots and the slope of the genus
curve at mean temperature fluctuation. We find that these observables carry
signatures of that are clearly distinct from the quadratic order
perturbations, encoded in the parameter . Hence they can be very useful
tools for distinguishing not only between non-Gaussian temperature fluctuations
and Gaussian ones but also between and type
non-Gaussianities.Comment: 18+1 page
Theory of coherent acoustic phonons in InGaN/GaN multi-quantum wells
A microscopic theory for the generation and propagation of coherent LA
phonons in pseudomorphically strained wurzite (0001) InGaN/GaN multi-quantum
well (MQW) p-i-n diodes is presented. The generation of coherent LA phonons is
driven by photoexcitation of electron-hole pairs by an ultrafast Gaussian pump
laser and is treated theoretically using the density matrix formalism. We use
realistic wurzite bandstructures taking valence-band mixing and strain-induced
piezo- electric fields into account. In addition, the many-body Coulomb
ineraction is treated in the screened time-dependent Hartree-Fock
approximation. We find that under typical experimental conditions, our
microscopic theory can be simplified and mapped onto a loaded string problem
which can be easily solved.Comment: 20 pages, 17 figure
Influence of a Brane Tension on Phantom and Massive Scalar Field Emission
We elaborate the signature of the extra dimensions and brane tension in the
process of phantom and massive scalar emission in the spacetime of
(4+n)-dimensional tense brane black hole. Absorption cross section, luminosity
of Hawking radiation and cross section in the low-energy approximation were
found. We envisage that parameter connected with the existence of a brane
imprints its role in the Hawking radiation of the considered fields.Comment: 7 pages, * figures, RevTex, to be published in General Relativity and
Gravitatio
Свободные аминокислоты и их азотсодержащие метаболиты в гипоталамусе крыс при острой интоксикации динилом и их корреляция с аминокислотным спектром плазмы крови
аминокислотыгипоталамусдинилотравлениеплазм
Nonlinear wave transmission and pressure on the fixed truncated breakwater using NURBS numerical wave tank
Fully nonlinear wave interaction with a fixed breakwater is investigated in a numerical wave tank (NWT). The potential theory and high-order boundary element method are used to solve the boundary value problem. Time domain simulation by a mixed Eulerian-Lagrangian (MEL) formulation and high-order boundary integral method based on non uniform rational B-spline (NURBS) formulation is employed to solve the equations. At each time step, Laplace equation is solved in Eulerian frame and fully non-linear free-surface conditions are updated in Lagrangian manner through material node approach and fourth order Runge-Kutta time integration scheme. Incident wave is fed by specifying the normal flux of appropriate wave potential on the fixed inflow boundary. To ensure the open water condition and to reduce the reflected wave energy into the computational domain, two damping zones are provided on both ends of the numerical wave tank. The convergence and stability of the presented numerical procedure are examined and compared with the analytical solutions. Wave reflection and transmission of nonlinear waves with different steepness are investigated. Also, the calculation of wave load on the breakwater is evaluated by first and second order time derivatives of the potential
Do Relatively More Efficient Firms Demand Additional Audit Effort (Hours)?
We examine whether firms with higher relative efficiency (operational performance) require additional audit effort (hours) to signal audit quality to demonstrate that their financial reporting systems are robust. Therefore, we use a Korean sample of publicly listed firms because of the Korean audit hour policy which mandates that audit hour information be made available for market participants. We find that client firms with higher relative efficiency have higher audit hours, suggesting that management has an incentive to demand additional audit hours for signalling purposes, and that shareholders, amongst other stakeholders, have an incentive to demand external monitoring to reduce potential agency problems. The results show that relative efficiency is a unique measure of firm performance that can provide insights into a client firm's business and audit risk. We also find evidence suggesting that audit firms do not subject clients to a fee (fee per hour) premium based on relative efficiency, supporting our finding that client firms require audit effort for signalling purposes. Thus, our results have important implications for policymakers about audit effort demand
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