Volumetric texture segmentation by discriminant feature selection and multiresolution classification

In this paper, a multiresolution volumetric texture segmentation (M-VTS) algorithm is presented. The method extracts textural measurements from the Fourier domain of the data via subband filtering using an orientation pyramid (Wilson and Spann, 1988). A novel Bhattacharyya space, based on the Bhattacharyya distance, is proposed for selecting the most discriminant measurements and producing a compact feature space. An oct tree is built of the multivariate features space and a chosen level at a lower spatial resolution is first classified. The classified voxel labels are then projected to lower levels of the tree where a boundary refinement procedure is performed with a three-dimensional (3-D) equivalent of butterfly filters. The algorithm was tested with 3-D artificial data and three magnetic resonance imaging sets of human knees with encouraging results. The regions segmented from the knees correspond to anatomical structures that can be used as a starting point for other measurements such as cartilage extraction.     

Retrieval of pigment concentrations and size structure of algal populations from their absorption spectra using multilayered perceptrons

Spectral absorption coefficients of phytoplankton can now be derived, under some assumptions, from hyperspectral ocean color measurements and thus become accessible from space. In this study, multilayer perceptrons have been developed to retrieve information on the pigment composition and size structure of phytoplankton from these absorption spectra. The retrieved variables are the main pigment groups (chlorophylls a, b, c, and photosynthetic and nonphotosynthetic carotenoids) and the relative contributions of three algal size classes (pico-, nano-, and microphytoplankton) to total chlorophyll a. The networks have been trained, tested, and validated using more than 3,700 simultaneous absorption and pigment measurements collected in the world ocean. Among pigment groups, chlorophyll a is the most accurately retrieved (average relative errors of 17% and 16% for the test and validation data subsets, respectively), while the poorest performances are found for chlorophyll b (average relative errors of 51% and 40%). Relative contributions of algal size classes to total chlorophyll a are retrieved with average relative errors of 19% to 33% for the test subset and of 18% to 47% for the validation subset. The performances obtained for the validation data, showing no strong degradation with respect to test data, suggest that these neural networks might be operated with similar performances for a large variety of marine areas.     

Humidity's influence on visible region refractive index structure parameter C(n)(2)

In the near-infrared and visible bandpasses optical propagation theory conventionally assumes that humidity does not contribute to the effects of atmospheric turbulence on optical beams. While this assumption may be reasonable for dry locations, we demonstrate that there is an unequivocal effect owing to the presence of humidity upon the strength of turbulence parameter, C(n)(2), from data collected in the Chesapeake Bay area over 100 m length horizontal propagation paths. We describe and apply a novel technique, Hilbert phase analysis, to the relative humidity, temperature, and C(n)(2) data to show the contribution of the relevant climate variable to C(n)(2) as a function of time.     

Numerical and experimental analysis of microstructure formation during stainless steels solidification

The aim of this work is to examine microstructure formation during the solidification of unidirectional solidified AISI 304 stainless steel. Numerical and experimental results indicate that this numerical model allows a precise analysis of the AISI 304 stainless steel microstructure formation. This model determines temperature profiles, position of liquid and solid isotherms, thermal parameters (thermal gradients, tip rate movement, rate cooling), and finally, the secondary inter dendritic spacing. This model was tested by comparing the experimental values results, and thus a reasonable correlation was found.     

Reversible toluene adsorption on monolithic carbon aerogels

Thirteen monolithic carbon aerogels with different pore textures were used as toluene adsorbents. Adsorption was carried out under both static and dynamic conditions. Under static conditions at 25 degrees C and at saturation, an adsorption capacity as high as 1.36 cm(3) g(-1) or 1180 mg g(-1) was obtained. Toluene adsorption was a reversible process in all carbon aerogels, and the adsorbed toluene was completely recovered by heating them at 400 degrees C. Regenerated adsorbents showed larger surface area and micropore width than the original samples, indicating that no pore blockage was produced. Adsorption under dynamic conditions at 100 degrees C was also completely reversible after at least three consecutive adsorption-desorption cycles. The ability of these carbon aerogels to reversibly adsorb toluene could be useful for their application in thermal swing adsorption or pressure swing adsorption equipment.     

EVA Nanocomposites Elaborated with Bentonite Organo‐Modified by Wet and Semi‐Wet Methods

EVA copolymer/organoclay nanocomposites were prepared using melt‐compounding. Organoclays were obtained using wet and semi‐wet modification methods. These methods enable us to obtain organoclays with adequate modifier incorporation, but organoclays with a homogeneous and narrow agglomeration size distribution were obtained only with the wet method. TS and EB were higher for nanocomposites obtained with organoclays prepared using the wet method. Analysis of Limiting Oxygen Index, UL94 test and Cone Calorimeter test showed that the retardant properties of nanocomposites were also influenced by the kind of modifiers and the modification method.

     

Indirect electrochemical oxidation of cyanide by hydrogen peroxide generated at a carbon cathode

The oxidation of cyanide was performed in aqueous sodium hydroxide solutions. Cyanide was oxidized over 90% to cyanate by hydrogen peroxide electrochemically generated at a 60 ppi reticulated vitreous carbon electrode from oxygen reduction. Cyanide depletion was recorded as a function of time from the analysis of cyanide based on the titration procedure using silver nitrate with p$p$-dimethylamino-benzal-rhodanine indicator. Cyanate was further oxidized to mineralization by decreasing the pH of the solution obtaining a recovery of carbon dioxide over 90%. The employment of copper together with hydrogen peroxide to increase the destruction of cyanide was also studied. Different molar ratios of hydrogen peroxide/cyanide and copper/cyanide were tested achieving over 98% of cyanide destruction in a time period of 40 min by increasing either the concentration of hydrogen peroxide or copper ion.     

Evidence for elevated production of methylmercury in salt marshes

Depth variations of total mercury (Hg) and methylmercury (MeHg) concentrations were obtained in cores from nonvegetated sediments, sediments colonized by Sarcocornia fruticosa, Halimione portulacoides, and Spartina maritima and below-ground biomass in three Portuguese estuaries. Similar analyses were also performed on the above-ground plant tissues. Concentrations in below-ground biomass exceeded up to 9 (Hg) and 44 (MeHg) times the levels in sediments. Mercury and MeHg in below-ground biomass were up to 400 (Hg) and 4700 (MeHg) times higher than those found in above-ground parts, indicating a weak upward translocation. Methylmercury in colonized sediments reached 18% of the total Hg, which was 70 times above the maximum values found in nonvegetated sediments. Concentrations of MeHg in vegetated sediments were not related to plant type but were linearly proportional to the total mercury levels. The analysis of below-ground biomass at high depth resolution (2 cm) provided evidence that Hg and MeHg were elevated. The higher enrichment factors were found where the shifting of redox conditions suggested high microbial activity. Mercury and MeHg in below-ground tissues were a function of total levels in sediments and again were not plant-specific. These results suggest that the bioremediation of mercury-contaminated sediments is likely to increase the formation of methylmercury.     

Application and validation of a clean-up tandem assay column for screening ochratoxin A in cocoa powder.

A rapid antibody-based assay for the detection of ochratoxin A in cocoa powder is described, involving sequential clean-up and visual detection of the toxin ("clean-up tandem assay column"). The screening test was developed to have a cut-off level of 2 microg kg(-1) and was shown to have false positive and false negative rates of 10 and 2%, respectively. Analysis of six samples can be carried out in the field in approximately 30 min by untrained workers. Using the proposed rapid screening test, 10 retail cocoa powders were found to contain no detectable levels of ochratoxin A (<2 microg kg(-1)). These samples were also found to be negative (<2 microg kg(-1)) when analysed using an LC-MS/MS method.