Papers by David S Kessler
Short Note DMO velocity analysis with Jacubowicz's dip-decomposition method
Dip-moveout (DMO) velocity analysis (VA) may be per- formed in several ways. Using the Fourier tr... more Dip-moveout (DMO) velocity analysis (VA) may be per- formed in several ways. Using the Fourier transform-based DMO techniques (Hale 1984, Notfors and Godfrey 1987, Liner and Bleinstein 1988), VA is done iteratively where a sequence of VA, normal moveout (NMO), DMO, inverse NMO, and a second VA yields an estimate of the DMO velocities. Using an integral method for application
Two-feed distillation: Same-composition feeds with different enthalpies
Ind Eng Chem Res, 1993
Additional separation can be achieved in flash distillation by separating the liquid feed into tw... more Additional separation can be achieved in flash distillation by separating the liquid feed into two parts, vaporizing only one part, and feeding these (now) two feeds to the top and bottom of a column. The driving force for the additional separation is the difference in chemical potential between liquid and vapor feeds with the same composition. This idea of using two feeds with the same composition but different enthalpies (herein called two-enthalpy feed) is applied to stripping and enriching columns and fractional distillation. Two-enthalpy-feed distillation, a new method for using waste heat effectively, should be useful in heat-integrated plants. When an ordinary distillation column has a two-phase feed, the use of two-enthalpy feed increases separation (same N and L/D), or decreases the number of stages (same L/D, x{sub D}, and x{sub B}), or decreases the reflux ratio (same N, x{sub D}, and x{sub B}). The two-enthalpy-feed system has a lower minimum reflux ratio than ordinary distillation with a two-phase feed. For other types of feed, two-enthalpy-feed distillation requires either less energy or energy at a less extreme temperature (i.e., lower temperature for reboilers or higher temperature for condensers) than ordinary distillation. Examples are presented for constant relative volatilities, hydrocarbon systems, and ethanol-water.
J Statist Phys, 1997
We study in detail a recently proposed simple discrete model for evolution on smooth landscapes. ... more We study in detail a recently proposed simple discrete model for evolution on smooth landscapes. An asymptotic solution of this model for long times is constructed. We find that the dynamics of the population is governed by correlation functions that although being formally down by powers of N (the population size), nonetheless control the evolution process after a very short transient. The long-time behavior can be found analytically since only one of these higher order correlators (the two-point function) is relevant. We compare and contrast the exact findings derived herein with a previously proposed phenomenological treatment employing mean-field theory supplemented with a cutoff at small population density. Finally, we relate our results to the recently studied case of mutation on a totally flat landscape.
The dynamics of a local community of competing species with weak immigration from a static region... more The dynamics of a local community of competing species with weak immigration from a static regional pool is studied. Implementing the generalized competitive Lotka-Volterra model with demographic noise, a rich dynamics structure with four qualitatively distinct phases is unfolded. When the overall interspecies competition is weak, the island species are a sample of the mainland species. For higher values of the competition parameter the system still admit an equilibrium community, but now some of the mainland species are absent on the island. Further increase in competition leads to an intermittent "chaotic" phase, where the dynamics is controlled by invadable combinations of species and the turnover rate is governed by the migration. Finally, the strong competition phase is glassy, dominated by uninvadable state and noise-induced transitions. Our model contains, as a spatial case, the celebrated neutral island theories of Wilson-MacArthur and Hubbell. Moreover, we show that slight deviations from perfect neutrality may lead to each of the phases, as the Hubbell point appears to be quadracritical.
Biophysical Journal, Mar 11, 2010
Monte Carlo simulations are used to study the effect of spontaneous (intrinsic) twist on the conf... more Monte Carlo simulations are used to study the effect of spontaneous (intrinsic) twist on the conformation of topologically equilibrated minicircles of dsDNA. The twist, writhe, and radius of gyration distributions and their moments are calculated for different spontaneous twist angles and DNA lengths. The average writhe and twist deviate in an oscillatory fashion (with the period of the double helix) from their spontaneous values, as one spans the range between two neighboring integer values of intrinsic twist. Such deviations vanish in the limit of long DNA plasmids.
One of the most popular models for quantitatively understanding the emergence of drug resistance ... more One of the most popular models for quantitatively understanding the emergence of drug resistance both in bacterial colonies and in malignant tumors was introduced long ago by Luria and Delbr\"uck. Here, individual resistant mutants emerge randomly during the birth events of an exponentially growing sensitive population. A most interesting limit of this process occurs when the population size $N$ is large and mutation rates are low, but not necessarily small compared to $1/N$. Here we provide a scaling solution valid in this limit, making contact with the theory of Levy $\alpha$-stable distributions, in particular one discussed long ago by Landau. One consequence of this association is that moments of the distribution are highly misleading as far as characterizing typical behavior. A key insight that enables our solution is that working in the fixed population size ensemble is not the same as working in a fixed time ensemble. Some of our results have been presented previously in shortened form.
[The aging of the population is going to affect all intergenerational transfers]
Population Et Avenir, 1995
This supplementary information contains detailed derivations, comparison to experiment, and discu... more This supplementary information contains detailed derivations, comparison to experiment, and discussion of other miscellaneous issues omitted from the main text.
We study the steady-state motion of mode III cracks propagating on a lattice exhibiting viscoelas... more We study the steady-state motion of mode III cracks propagating on a lattice exhibiting viscoelastic dynamics. The introduction of a Kelvin viscosity $\eta$ allows for a direct comparison between lattice results and continuum treatments. Utilizing both numerical and analytical (Wiener-Hopf) techniques, we explore this comparison as a function of the driving displacement $\Delta$ and the number of transverse sites $N$. At any $N$, the continuum theory misses the lattice-trapping phenomenon; this is well-known, but the introduction of $\eta$ introduces some new twists. More importantly, for large $N$ even at large $\Delta$, the standard two-dimensional elastodynamics approach completely misses the $\eta$-dependent velocity selection, as this selection disappears completely in the leading order naive continuum limit of the lattice problem.
Bardeen-Moshe-Bander Fixed Point and the Ultraviolet Triviality of (Phi-->2)33
Phys Rev Lett, 1984
The three-dimensional (Φ-->2)3 theory is studied at large N. A complete mapping of the phase diag... more The three-dimensional (Φ-->2)3 theory is studied at large N. A complete mapping of the phase diagram and a detailed analysis of the renormalization-group flows is given. The recently found uv fixed point of Bardeen, Moshe, and Bander is investigated and it is pointed out that its characteristics seem to be somewhat nongeneric and might disappear at finite N. Our analysis is restricted to infinite N and hence no definitive conclusions are yet possible.
Portable chemical reactor for use as an artificial kidney
Phys Rev E, 1997
Spiral waves are a ubiquitous feature of the nonequilibrium dynamics of a great variety of excita... more Spiral waves are a ubiquitous feature of the nonequilibrium dynamics of a great variety of excitable systems. In the limit of a large separation in timescale between fast excitation and slow recovery, one can reduce the spiral problem to one involving the motion of a free surface separating the excited and quiescent phases. In this work, we study the free surface problem in the limit of small diffusivity for the slow field variable. Specifically, we show that a previously found spiral solution in the diffusionless limit can be extended to finite diffusivity, without significant alteration. This extension involves the creation of a variety of boundary layers which cure all the undesirable singularities of the aforementioned solution. The implications of our results for the study of spiral stability are briefly discussed.
Physica a Statistical Mechanics and Its Applications, Jan 2, 1998
Stable wrinkled fronts were often observed in experiments on uid invasion into porous media, when... more Stable wrinkled fronts were often observed in experiments on uid invasion into porous media, when the invaded phase is less viscous than the invading one. Recent experiments by a group at the Weizmann institute, show that capillary wetting of paper may also lead to rough self-a ne fronts. A dominant factor controlling the interface roughening in these systems is the nature of the two-dimensional viscous uid ow in the medium behind it. Since the disorder in the medium modiÿes this ow, it also determines the roughness of the interface. We present a theoretical analysis of the connection between the nature of randomness in the medium and the resulting roughness of the fronts.
Antibody to Physarum myosin. I. Preparation and functional effects
Immunology, Apr 1, 1976
Preparation of antibody to Physarum myosin is described, and evidence is presented that the antib... more Preparation of antibody to Physarum myosin is described, and evidence is presented that the antibody is specific for this molecule. A diffusion coefficient of 1 X 10(-7) cm2/s is estimated. The antibody interfered with myosin enzyme activity and with superprecipitation of actomyosin. It did not cross-react with rabbit striated muscle myosin.
J Statist Phys, 1998
The role of mutational bias in evolution on a smooth landscape is investigated. We consider both ... more The role of mutational bias in evolution on a smooth landscape is investigated. We consider both a finite-length genome where the bias increases linearly with the fitness, and an infinite genome with a fixed bias. We present simulations of finite populations in a waiting time model, showing both the nonequilibrium dynamics and the equilibrium fitness distributions that are reached. We compute the equilibrium analytically in several cases, using approximate direct solution of the master equations and truncated hierarchies.
Phase-?eld Model of Mode III Dynamic Fracture
Size distribution of ring polymers
Scientific reports, Jan 15, 2016
We present an exact solution for the distribution of sample averaged monomer to monomer distance ... more We present an exact solution for the distribution of sample averaged monomer to monomer distance of ring polymers. For non-interacting and local-interaction models these distributions correspond to the distribution of the area under the reflected Bessel bridge and the Bessel excursion respectively, and are shown to be identical in dimension d ≥ 2, albeit with pronounced finite size effects at the critical dimension, d = 2. A symmetry of the problem reveals that dimension d and 4 - d are equivalent, thus the celebrated Airy distribution describing the areal distribution of the d = 1 Brownian excursion describes also a polymer in three dimensions. For a self-avoiding polymer in dimension d we find numerically that the fluctuations of the scaled averaged distance are nearly identical in dimension d = 2, 3 and are well described to a first approximation by the non-interacting excursion model in dimension 5.
Flame Structures in Heated Nonpremixed Microburners
We investigate the structure and behavior of nonpremixed flames formed in a co-flow of fuel and o... more We investigate the structure and behavior of nonpremixed flames formed in a co-flow of fuel and oxidizer within a submillimeter- scale channel. Two configurations are considered. In the first, the channel walls are held at an elevated constant temperature. A ``tuning fork'' flame structure is developed that is controlled by the interaction of the thermal boundary layer and the chemical mixing layer. The second configuration allows heat conduction within the channel walls and finite levels of heat loss. Here, external heating is provided at the exit of the channel, and the stability of the tuning fork flame structure in the resulting axial temperature gradient is examined. Increasing levels of heat loss lead to the appearance of oscillating flame structures.
We show that in a large class of equations, solitons formed from generic initial conditions do no... more We show that in a large class of equations, solitons formed from generic initial conditions do not have infinitely long exponential tails, but are truncated by a region of Gaussian decay. This phenomenon makes it possible to treat solitons as localized, individual objects. For the case of the KdV equation, we show how the Gaussian decay emerges in the inverse scattering formalism.
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Papers by David S Kessler