A revision of the Sclerocoelus galapagensis group (Diptera: Sphaeroceridae: Limosininae)

The Sclerocoelus galapagensis group is defined and revised, including the description of S. galapagensis new species from the Galapagos Islands; S. caribensis new species from the Caribbean and adjacent areas; S. brasilensis new species from Brazil, Ecuador, Colombia, and Panama; S. hemorrhoidal is new species from Ecuador and Venezuela; and S. andensis new species from Argentina, Bolivia, and Venezuela. The south Atlantic species Sclerocoelus subbrevipennis (Frey), new combination, is redescribed as a member of the S. galapagensis group, and is considered the sister species to the rest of the species group. A key to species, character matrix, and cladogram are provided

Medical image enhancement using threshold decomposition driven adaptive morphological filter

One of the most common degradations in medical images is their poor contrast quality. This suggests the use of contrast enhancement methods as an attempt to modify the intensity distribution of the image. In this paper, a new edge detected morphological filter is proposed to sharpen digital medical images. This is done by detecting the positions of the edges and then applying a class of morphological filtering. Motivated by the success of threshold decomposition, gradientbased operators are used to detect the locations of the edges. A morphological filter is used to sharpen these detected edges. Experimental results demonstrate that the detected edge deblurring filter improved the visibility and perceptibility of various embedded structures in digital medical images. Moreover, the performance of the proposed filter is superior to that of other sharpener-type filters

Spectrum of the Intensity of Modulated Noisy Light After Propagation in Dispersive Fiber

The spectral density of the optical intensity which results after modulated noisy light is propagated in dispersive single-mode fiber is investigated theoretically and experimentally. An exact general result is obtained for the case of lowest-order-only group velocity dispersion and is applied to light from a 1550-nm distributed-feedback semiconductor laser which is large-signal phase modulated and then propagated through 50 km of standard single-mode fiber. Experimental results demonstrate the effect of dispersion on the intensity spectrum (and thus, on lightwave system characteristics such as modulation response, relative intensity noise, carrier-to-noise ratio, and harmonic distortion) in this situation and provide confirmation of the theoretical results

Zero-field Time Correlation Functions of Four Classical Heisenberg Spins on a Ring

A model relevant for the study of certain molecular magnets is the ring of N=4 classical spins with equal near-neighbor isotropic Heisenberg exchange interactions. Assuming classical Heisenberg spin dynamics, we solve explicitly for the time evolution of each of the spins. Exact triple integral representations are derived for the auto, near-neighbor, and next-nearest-neighbor time correlation functions for any temperature. At infinite temperature, the correlation functions are reduced to quadrature. We then evaluate the Fourier transforms of these functions in closed form, which are double integrals. At low temperatures, the Fourier transform functions explicitly demonstrate the presence of magnons. Our exact results for the infinite temperature correlation functions in the long-time asymptotic limit differ qualitatively from those obtained assuming diffusive spin dynamics. Whether such explicitly non-hydrodynamic behavior would be maintained for large-N rings is discussed.Comment: 18 pages, 21 figure

The crisis of 1998 and the role of the central bank

Following the Russian default and devaluation in August 1998, financial markets were characterized by a withdrawal of liquidity, a flight to the safest assets, increased concerns about credit quality, and large declines in asset values. However, the crisis ended following a rather modest interest rate cut by the Federal Reserve. Why did the central bank's action have this effect? This article argues that the crisis was an episode of potential coordination failure, triggered by, but distinct from, the events in Russia. The Federal Reserve's action signaled a policy change that serve to eliminate the coordination failure equilibrium.Financial crises ; Banks and banking, Central

The Limit Behavior Of The Trajectories of Dissipative Quadratic Stochastic Operators on Finite Dimensional Simplex

The limit behavior of trajectories of dissipative quadratic stochastic operators on a finite-dimensional simplex is fully studied. It is shown that any dissipative quadratic stochastic operator has either unique or infinitely many fixed points. If dissipative quadratic stochastic operator has a unique point, it is proven that the operator is regular at this fixed point. If it has infinitely many fixed points, then it is shown that $\omega-$ limit set of the trajectory is contained in the set of fixed points.Comment: 14 pages, accepted in Difference Eq. App

Inverse Medea as a Novel Gene Drive System for Local Population Replacement: A Theoretical Analysis

One strategy to control mosquito-borne diseases, such as malaria and dengue fever, on a regional scale is to use gene drive systems to spread disease-refractory genes into wild mosquito populations. The development of a synthetic Medea element that has been shown to drive population replacement in laboratory Drosophila populations has provided encouragement for this strategy but has also been greeted with caution over the concern that transgenes may spread into countries without their consent. Here, we propose a novel gene drive system, inverse Medea, which is strong enough to bring about local population replacement but is unable to establish itself beyond an isolated release site. The system consists of 2 genetic components—a zygotic toxin and maternal antidote—which render heterozygous offspring of wild-type mothers unviable. Through population genetic analysis, we show that inverse Medea will only spread when it represents a majority of the alleles in a population. The element is best located on an autosome and will spread to fixation provided any associated fitness costs are dominant and to very high frequency otherwise. We suggest molecular tools that could be used to build the inverse Medea system and discuss its utility for a confined release of transgenic mosquitoes