A mathematical characterization of vegetation effect on microwave remote sensing from the Earth

In passive microwave remote sensing of the earth, a theoretical model that utilizes the radiative transfer equations was developed to account for the volume scattering effects of the vegetation canopy. Vegetation canopies such as alfalfa, sorghum, and corn are simulated by a layer of ellipsoidal scatterers and cylindrical structures. The ellipsoidal scatterers represent the leaves of vegetation and are randomly positioned and oriented. The orientation of ellipsoids is characterized by a probability density function of Eulerian angles of rotation. The cylindrical structures represent the stalks of vegetation and their radii are assumed to be much smaller than their lengths. The underlying soil is represented by a half-space medium with a homogeneous permittivity and uniform temperature profile. The radiative transfer quations are solved by a numerical method using a Gaussian quadrature formula to compute both the vertical and horizontal polarized brightness temperature as a function of observation angle. The theory was applied to the interpretation of experimental data obtained from sorghum covered fields near College Station, Texas

New Estimates of Disability-Related Wage Discrimination with Controls for Job Demands

Using data from 2004 SIPP, matched to job demands from O*Net, we provide new estimates of disability-related wage discrimination. We apply state-of-the-art econometric methods to wage models which include job demands and interactions between demands and functional limitations. The interaction terms are interpreted as measures of how well disabled workers ?match? to jobs which minimize the effects of functional limitations. The results suggest traditional discrimination models underestimate potential effects of disability-related discrimination by penalizing workers for limitations which may not affect their job performance. The bias is greater for men, who generally appear to find better matches than do women.Job demand; Disability; Wage Discrimination

Estimates of Wage Discrimination Against Workers with Sensory Disabilities, with Controls for Job Demands

We provide the first-ever estimates of wage discrimination against workers with sensory (hearing, speech, vision) disabilities. Workers with sensory disabilities have lower probabilities of employment and lower wages, on average, than nondisabled workers. Their poor labor market outcomes are explained, at least in part, by the negative productivity effects of sensory limitations in jobs that require good communication skills, but disabilityrelated discrimination may also be a contributing factor. To separate productivity vs. discrimination effects, we decompose the wage differential between workers with and without sensory disabilities into an ?explained? part attributed to differences in productivity-related characteristics, and an ?unexplained? part attributed to discrimination. The decomposition is based on human capital wage equations with controls for job-specific demands related to sensory abilities, and interactions between job demands and sensory limitations. The interactions are interpreted as measures of the extent to which a worker?s sensory limitations affect important job functions. The results indicate approximately 1/3 (1/10) of the disability-related wage differential for men (women) is attributed to discrimination. The estimates are quite different from estimates of discrimination against workers with physical disabilities obtained by the same methods, underscoring the importance of accounting for heterogeneity of the disabled population in discrimination studies.Job demand; Sensory disability; Wage discrimination

The Nuclease Activity of the Yeast Dna2 Protein, Which Is Related to the RecB-like Nucleases, Is Essential in Vivo

Saccharomyces cerevisiae Dna2 protein is required for DNA replication and repair and is associated with multiple biochemical activities: DNA-dependent ATPase, DNA helicase, and DNA nuclease. To investigate which of these activities is important for the cellular functions of Dna2, we have identified separation of function mutations that selectively inactivate the helicase or nuclease. We describe the effect of six such mutations on ATPase, helicase, and nuclease after purification of the mutant proteins from yeast or baculovirus-infected insect cells. A mutation in the Walker A box in the C-terminal third of the protein affects helicase and ATPase but not nuclease; a mutation in the N-terminal domain (amino acid 504) affects ATPase, helicase, and nuclease. Two mutations in the N-terminal domain abolish nuclease but do not reduce helicase activity (amino acids 657 and 675) and identify the putative nuclease active site. Two mutations immediately adjacent to the proposed nuclease active site (amino acids 640 and 693) impair nuclease activity in the absence of ATP but completely abolish nuclease activity in the presence of ATP. These results suggest that, although the Dna2 helicase and nuclease activities can be independently affected by some mutations, the two activities appear to interact, and the nuclease activity is regulated in a complex manner by ATP. Physiological analysis shows that both ATPase and nuclease are important for the essential function of DNA2 in DNA replication and for its role in double-strand break repair. Four of the nuclease mutants are not only loss of function mutations but also exhibit a dominant negative phenotype

Controlling synchrony by delay coupling in networks: from in-phase to splay and cluster states

We study synchronization in delay-coupled oscillator networks, using a master stability function approach. Within a generic model of Stuart-Landau oscillators (normal form of super- or subcritical Hopf bifurcation) we derive analytical stability conditions and demonstrate that by tuning the coupling phase one can easily control the stability of synchronous periodic states. We propose the coupling phase as a crucial control parameter to switch between in-phase synchronization or desynchronization for general network topologies, or between in-phase, cluster, or splay states in unidirectional rings. Our results are robust even for slightly nonidentical elements of the network.Comment: 4 pages, 4 figure

Modeling, Estimation, and Pattern Analysis of Random Texture on 3-D Surfaces

To recover 3-D structure from a shaded and textural surface image involving textures, neither the Shape-from-shading nor the Shape-from-texture analysis is enough, because both radiance and texture information coexist within the scene surface. A new 3-D texture model is developed by considering the scene image as the superposition of a smooth shaded image and a random texture image. To describe the random part, the orthographical projection is adapted to take care of the non-isotropic distribution function of the intensity due to the slant and tilt of a 3-D textures surface, and the Fractional Differencing Periodic (FDP) model is chosen to describe the random texture, because this model is able to simultaneously represent the coarseness and the pattern of the 3-D texture surface, and enough flexible to synthesize both long-term and short-term correlation structures of random texture. Since the object is described by the model involving several free parameters and the values of these parameters are determined directly from its projected image, it is possible to extract 3-D information and texture pattern directly from the image without any preprocessing. Thus, the cumulative error obtained from each pre-processing can be minimized. For estimating the parameters, a hybrid method which uses both the least square and the maximum likelihood estimates is applied and the estimation of parameters and the synthesis are done in frequency domain. Among the texture pattern features which can be obtained from a single surface image, Fractal scaling parameter plays a major role for classifying and/or segmenting the different texture patterns tilted and slanted due to the 3-dimensional rotation, because of its rotational and scaling invariant properties. Also, since the Fractal scaling factor represents the coarseness of the surface, each texture pattern has its own Fractal scale value, and particularly at the boundary between the different textures, it has relatively higher value to the one within a same texture. Based on these facts, a new classification method and a segmentation scheme for the 3-D rotated texture patterns are develope