Symmetry and Variation of Hodge Structures

The main problem addressed in the paper is the Torelli problem for n-dimensional varieties of general type, more specifically for varieties with ample canonical bundle. It asks under which geometrical condition for a variety the period map for the Hodge structure of weight n is a local embedding. We define a line bundle to be almost very ample iff the associated linear system is base point free and yields an injective morphism. We define instead a line bundle to be quasi very ample if it yields a birational morphism which is a local embedding on the complement of a finite set. Our main result is the existence of infinitely many families of surfaces of general type, with quasi very ample canonical bundle, each yielding an irreducible connected component of the moduli space, such that the period map has everywhere positive dimensional fibres. These surfaces are surfaces isogenous to a product, i.e., quotients of a product of curves by the free action of a finite group G. In the paper we also give some sufficient conditions in order that global double Torelli holds for these surfaces, i.e., the isomorphism type of the surface is reconstructed from the fundamental group plus the Hodge structure on the cohomology algebra. We do this via some useful lemmas on the action of an abelian group on the cohomology of an algebraic curve. We also establish a birational description of the moduli space of curves of genus 3 with a non trivial 3-torsion divisor.Comment: 38 pages, to appear in Asian J. Math., Volume in honour of Y.T. Siu's 60-th birthday. Revision, we correct the main theorem replacing almost very ample by quasi very ample, which is in one way better and in one way wors

Relation of agronomic and multispectral reflectance characteristics of spring wheat canopies

The relationships between crop canopy variables such as leaf area index (LAI) and their multispectral reflectance properties were investigated along with the potential for estimating canopy variables from remotely sensed reflectance measurements. Reflectance spectra over the 0.4 to 2.5 micron wavelength range were acquired during each of the major development stages of spring wheat canopies at Williston, North Dakota, during three seasons. Treatments included planting date, N fertilization, cultivar, and soil moisture. Agronomic measurements included development stage, biomass, LAI, and percent soil cover. High correlations were found between reflectance and percent cover, LAI, and biomass. A near infrared wavelength band, 0.76 to 0.90 microns, was most important in explaining variation in LAI and percent cover, while a middle infrared band, 2.08 to 2.35 microns, explained the most variation in biomass and plant water content. Transformations, including the near infrared/red reflectance ratio and greenness index, were also highly correlated to canopy variables. The relationship of canopy variables to reflectance decreased as the crop began to ripen. the canopy variables could be accurately predicted using measurements from three to five wavelength bands. The wavelength bands proposed for the thematic mapper sensor were more strongly related to the canopy variables than the LANDSAT MSS bands

Reducing the critical switching current in nanoscale spin valves

The current induced magnetization reversal in nanoscale spin valves is a potential alternative to magnetic field switching in magnetic memory devices. We show that the critical switching current can be decreased by an order of magnitude by strategically distributing the resistances in the magnetically active region of the spin valve. In addition, we simulate full switching curves and predict a new precessional state.Comment: mistake corrected, references added, 4 page

Sampling for area estimation: A comparison of full-frame sampling with the sample segment approach

The effect of sampling on the accuracy (precision and bias) of crop area estimates made from classifications of LANDSAT MSS data was investigated. Full-frame classifications of wheat and non-wheat for eighty counties in Kansas were repetitively sampled to simulate alternative sampling plants. Four sampling schemes involving different numbers of samples and different size sampling units were evaluated. The precision of the wheat area estimates increased as the segment size decreased and the number of segments was increased. Although the average bias associated with the various sampling schemes was not significantly different, the maximum absolute bias was directly related to sampling unit size

RPA quasi-elastic responses in infinite and finite nuclear systems

Quasi-elastic responses in nuclear matter and in $^{12}$C and $^{40}$Ca nuclei are calculated in ring approximation to investigate the finite size effects on the electromagnetic quasi-elastic responses. A method to simulate these effects in infinite systems calculations is proposed. The sensitivity of the results to the various terms of the residual interaction is studied. The results of nuclear matter RPA calculations are compared with those obtained in ring approximation to evidence the importance of the exchange terms.Comment: 14 pages, 8 figure

Light scattering by magnons in whispering gallery mode cavities

Brillouin light scattering is an established technique to study magnons, the elementary excitations of a magnet. Its efficiency can be enhanced by cavities that concentrate the light intensity. Here, we theoretically study inelastic scattering of photons by a magnetic sphere that supports optical whispering gallery modes in a plane normal to the magnetization. Magnons with low angular momenta scatter the light in the forward direction with a pronounced asymmetry in the Stokes and the anti-Stokes scattering strength, consistent with earlier studies. Magnons with large angular momenta constitute Damon Eschbach modes are shown to inelastically reflect light. The reflection spectrum contains either a Stokes or anti-Stokes peak, depending on the direction of the magnetization, a selection rule that can be explained by the chirality of the Damon Eshbach magnons. The controllable energy transfer can be used to manage the thermodynamics of the magnet by light

Research in the application of spectral data to crop identification and assessment, volume 2

The development of spectrometry crop development stage models is discussed with emphasis on models for corn and soybeans. One photothermal and four thermal meteorological models are evaluated. Spectral data were investigated as a source of information for crop yield models. Intercepted solar radiation and soil productivity are identified as factors related to yield which can be estimated from spectral data. Several techniques for machine classification of remotely sensed data for crop inventory were evaluated. Early season estimation, training procedures, the relationship of scene characteristics to classification performance, and full frame classification methods were studied. The optimal level for combining area and yield estimates of corn and soybeans is assessed utilizing current technology: digital analysis of LANDSAT MSS data on sample segments to provide area estimates and regression models to provide yield estimates

Multistage classification of multispectral Earth observational data: The design approach

An algorithm is proposed which predicts the optimal features at every node in a binary tree procedure. The algorithm estimates the probability of error by approximating the area under the likelihood ratio function for two classes and taking into account the number of training samples used in estimating each of these two classes. Some results on feature selection techniques, particularly in the presence of a very limited set of training samples, are presented. Results comparing probabilities of error predicted by the proposed algorithm as a function of dimensionality as compared to experimental observations are shown for aircraft and LANDSAT data. Results are obtained for both real and simulated data. Finally, two binary tree examples which use the algorithm are presented to illustrate the usefulness of the procedure

On Power Suppressed Operators and Gauge Invariance in SCET

The form of collinear gauge invariance for power suppressed operators in the soft-collinear effective theory is discussed. Using a field redefinition we show that it is possible to make any power suppressed ultrasoft-collinear operators invariant under the original leading order gauge transformations. Our manipulations avoid gauge fixing. The Lagrangians to O(lambda^2) are given in terms of these new fields. We then give a simple procedure for constructing power suppressed soft-collinear operators in SCET_II by using an intermediate theory SCET_I.Comment: 15 pages, journal versio

Into the Light: Diurnality has Evolved Multiple Times in Geckos

Geckos are the only major lizard group consisting mostly of nocturnal species. Nocturnality is presumed to have evolved early in gecko evolution and geckos possess numerous adaptations to functioning in low light and at low temperatures. However, not all gecko species are nocturnal and most diurnal geckos have their own distinct adaptations to living in warmer, sunlit environments. We reconstructed the evolution of gecko activity patterns using a newly generated time-calibrated phylogeny. Our results provide the first phylogenetic analysis of temporal activity patterns in geckos and confirm an ancient origin of nocturnality at the root of the gecko tree. We identify multiple transitions to diurnality at a variety of evolutionary time scales and transitions back to nocturnality occur in several predominantly diurnal clades. The scenario presented here will be useful in reinterpreting existing hypotheses of how geckos have adapted to varying thermal and light environments. These results can also inform future research of gecko ecology, physiology, morphology and vision as it relates to changes in temporal activity patterns