Speckle removal from SAR images in the undecimated wavelet domain

Speckle reduction is approached as a minimum mean-square error (MMSE) filtering performed in the undecimated wavelet domain by means of an adaptive rescaling of the detail coefficients, whose amplitude is divided by the variance ratio of the noisy coefficient to the noise-free one. All the above quantities are analytically calculated from the speckled image, the variance and autocorrelation of the fading variable, and the wavelet filters only, without resorting to any model to describe the underlying backscatter. On the test image Lena corrupted by synthetic speckle, the proposed method outperforms Kuan's local linear MMSE filtering by almost 3-dB signal-to-noise ratio. When true synthetic aperture radar (SAR) images are concerned, empirical criteria based on distributions of multiscale local coefficient of variation, calculated in the undecimated wavelet domain, are introduced to mitigate the rescaling of coefficients in highly heterogeneous areas where the speckle does not obey a fully developed model, to avoid blurring strong textures and point targets. Experiments carried out on widespread test SAR images and on a speckled mosaic image, comprising synthetic shapes, textures, and details from optical images, demonstrate that the visual quality of the results is excellent in terms of both background smoothing and preservation of edge sharpness, textures, and point targets. The absence of decimation in the wavelet decomposition avoids typical impairments often introduced by critically subsampled wavelet-based denoising.     

Fast calculation of co-occurrence matrix parameters for image segmentation

Image segmentation methods based only on grey level information are not suitable for pictures in which regions exhibit almost the same average grey level and differ only for local variations or texture. By extending these methods to textural features, better results are expected. Among textural features, those extracted from co-occurrence matrices are quite effective. A fast algorithm for the calculation of these parameters for windows centred on each pixel of the image is presented.<>     

Girls' math performance under stereotype threat: The moderating role of mothers' gender stereotypes.

Previous research on stereotype threat in children suggests that making gender identity salient disrupts girls' math performance at as early as 5 to 7 years of age. The present study (n = 124) tested the hypothesis that parents' endorsement of gender stereotypes about math moderates girls' susceptibility to stereotype threat. Results confirmed that stereotype threat impaired girls' performance on math tasks among students from kindergarten through 2nd grade. Moreover, mothers' but not fathers' endorsement of gender stereotypes about math moderated girls' vulnerability to stereotype threat: Performance of girls whose mothers strongly rejected the gender stereotype about math did not decrease under stereotype threat. These findings are important because they point to the role of mothers' beliefs in the development of girls' vulnerability to the negative effects of gender stereotypes about math. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Information-theoretic heterogeneity measurement for SAR imagery

A heterogeneity feature, calculable from synthetic aperture radar (SAR) images on a per-pixel basis, but relying on global image statistics, is defined and discussed. Starting from the multiplicative speckle and texture models relating the amount of texture and speckle to the local mean and variance at every pixel, such a feature is rigorously derived from Shannon's information theory as the conditional information of local standard deviation to local mean. Thanks to robust statistical estimation, it is very little sensitive to the noise affecting SAR data, and thus capable of capturing subtle variations of texture whenever they are embedded in a heavy speckle. Experimental results carried out on two SAR images with different degrees of noisiness demonstrate that the proposed feature is likely to be useful for a variety of automated segmentation and classification tasks.     

Electronic polarizability as a predictor of biodegradation rates of dimethylnaphthalenes. an ab initio and density functional theory study

Geometries, relative stabilities, electronic excited states, atomic charges, and electronic dipole polarizabilities of dimethylnaphthalene (DMN) isomers have been calculated in gas and aqueous phases by ab initio and DFT methods. At the highest levels of calculation, alpha,alpha-DMN (2,6-DMN, 2,7-DMN, and 2,3-DMN) are the lowest energy isomers, while 1,8-DMN is the less stable by 7-8 kcal mol(-1). The averaged electronic polarizability, , is dependent on the position of the methyl substituents, increasing in the order alpha, alpha-DMN < (a, beta-DMN < beta, beta-DMN, with the largest values being obtained for 2,6-DMN and 2,7-DMN, while the lowest value is calculated for 1,8-DMN isomer. Polarizability differences among the isomers have been related to their spectroscopic properties. The computed value of DMN isomers, with the notable exception of 2,7-DMN, is in excellent linear relationship with the observed first-order biomass-normalized rate coefficient, a parameter related to the rate of biodegradation of polycyclic aromatic hydrocarbons (PAHs). This result suggests that electronic polarizability may be a useful tool for prediction of biodegradation trends of series of compounds, and inductive and dispersive interactions play a fundamental role in the biodegradation process of DMNs. The present approach is potentially suitable for applications on PAHs with higher molecular weight.     

Prediction of mutagenic activity of nitronaphthalene isomers by infrared and Raman spectroscopy

IR and Raman spectra of 1- and 2-nitronaphthalene isomers (1-NN and 2-NN) have been investigated to obtain more insight into the effect of the structure on mutagenic properties. To this purpose we have performed density functional theory calculations using B3LYP functional with cc-pVDZ basis set. The results have shown that IR and Raman spectra of nitronaphthalene isomers are somewhat similar to each other. A notable exception regards the symmetrical NO bonds stretching +CN bond stretching vibration (nusNO2+nuCN), which appears as very intense peak near 1350 cm(-1) in IR and Raman spectra of both isomers. Present calculations predict that for 2-NN isomer IR and Raman absorptions of this vibration are more intense by ca. 50 and 60%, respectively, than those of 1-NN isomer. The noticeably higher IR and Raman intensity values of the nusNO2+nuCN mode for 2-NN originate, respectively, from large dipole moment and polarizability changes with respect to the normal mode, suggesting that intermolecular interactions are especially favoured along this coordinate. These results are consistent with higher mutagenic activities of 2-NN in comparison to 1-NN isomer, supporting the binding to enzyme mechanism as a determining step in mutagenic pathways for this series of nitroaromatic compounds.     

Comparison of Pansharpening Algorithms: Outcome of the 2006 GRS-S Data-Fusion Contest

In January 2006, the Data Fusion Committee of the IEEE Geoscience and Remote Sensing Society launched a public contest for pansharpening algorithms, which aimed to identify the ones that perform best. Seven research groups worldwide participated in the contest, testing eight algorithms following different philosophies [component substitution, multiresolution analysis (MRA), detail injection, etc.]. Several complete data sets from two different sensors, namely, QuickBird and simulated Pleiades, were delivered to all participants. The fusion results were collected and evaluated, both visually and objectively. Quantitative results of pansharpening were possible owing to the availability of reference originals obtained either by simulating the data collected from the satellite sensor by means of higher resolution data from an airborne platform, in the case of the Pleiades data, or by first degrading all the available data to a coarser resolution and saving the original as the reference, in the case of the QuickBird data. The evaluation results were presented during the special session on data fusion at the 2006 international geoscience and remote sensing symposium in Denver, and these are discussed in further detail in this paper. Two algorithms outperform all the others, the visual analysis being confirmed by the quantitative evaluation. These two methods share the same philosophy: they basically rely on MRA and employ adaptive models for the injection of high-pass details.     

The role of electronic properties to the mutagenic activity of 1,6- and 3,6-dinitrobenzo[a]pyrene isomers

Equilibrium geometries, infrared spectra, vertical first ionization potential (IP), electronic affinity (EA), dipole moment (mu) and electronic dipole polarizability (alpha) of 1,6- and 3,6-dinitrobenzo[a]pyrene isomers (1,6-DNBaP and 3,6-DNBaP) were evaluated by means of Density Functional Theory (DFT) and recent semiempirical PM6 method. Structural, energetic and vibrational properties of DNBaP isomers are substantially similar to each other. Calculated IP, EA and alpha values of these isomers are practically identical, while mu of 3,6-DNBaP (8.2 D at DFT level) is predicted to be ca. 4 times the value of 1,6-DNBaP isomer (1.9 D at DFT level), owing to favorable mutual orientation of the individual nitro group vectors. Higher direct-mutagenic activities of 3,6-DNBaP with respect to 1,6-DNBaP isomer by 1-2 orders of magnitude might be determined by its peculiar electronic charge distribution, which through stronger electrostatic and inductive interactions, can promote much more effectively binding to active-site of enzymes involved in mutagenic pathways. On the other hand, orientation of the nitro substituents relatively to the plane of the aromatic moiety, molecular sizes, as well as nitroreduction and oxidation reactions seem not to have a key role in the determination of the different mutagenic behaviour of these isomers.