Microbial reduction of Fe(III)-bearing clay minerals in the presence of humic acids.

Both Fe(III)-bearing clay minerals and humic acids (HAs) are abundant in the soils and sediments. Previous studies have shown that bioreduction of structural Fe(III) in clay minerals could be accelerated by adding anthraquinone compound as a redox-active surrogate of HAs. However, a quinoid analogue could not reflect the adsorption and complexation properties of HA, and little is known about the effects of real HAs at environmental concentration on bioreduction of clay minerals. Here, it was shown that 10-200 mg l-1 of natural or artificially synthesized HAs could effectively stimulate the bioreduction rate and extent of Fe(III) in both iron-rich nontronite NAu-2 and iron-deficient montmorillonite SWy-2. After adsorption to NAu-2, electron-transfer activities of different HA fractions were compared. Additionally, Fe(II) complexation by HAs also contributed to improvement of clay-Fe(III) bioreduction. Spectrosopic and morphological analyses suggested that HA addition accelerated the transformation of NAu-2 to illite, silica and siderite after reductive dissolution.

Fraunhofer computer-generated hologram for diffused 3D scene in Fresnel region.

A Fraunhofer computer-generated hologram (CGH) is proved to be valid in display for three-dimensional (3D) objects from the Fresnel to the far-field region without a Fourier lens for reconstruction. To quickly compute large and complicated 3D objects that consist of slanted diffused surfaces in the Fresnel region, a Fraunhofer-based analytical approach using a basic-triangle tiling diffuser is developed. Both theoretical and experimental results reveal that Fraunhofer CGH can perform the same effects as Fresnel CGH but require less calculation time. Impressive 3D solid effects are achieved in the Fresnel region.

Three-dimensional imaging with monocular cues using holographic stereography.

Two quantitative criteria are derived to evaluate monocular cues in holographic stereograms. We find that the reconstruction has correct monocular cues when the whole scene is located in a so-called "monocular cues area" with compatible monocular and binocular cues. In contrast, incorrect monocular cues appear when the scene is in the other two areas, namely, the "visible multi-imaging area" and the "lacking information area." A pupil-function integral imaging algorithm is developed to simulate monocular observation, and a holographic printing system is set up to fabricate full-parallax holographic stereograms. Both simulations and experiments agree with the criteria.

High-speed full analytical holographic computations for true-life scenes.

We develop a novel method to generate hologram of three-dimensional (3D) textured triangle-mesh-model that is reconstructed from ordinary digital photos. This method allows analytically encoding the 3D model consisting of triangles. In contrast to other polygon based holographic computations, our full analytical method will free oneself from the numerical error that is in the angular spectrum due to the Whittaker-Shannon sampling. In order to saving the computation time, we employ the GPU platform that is remarkably superior to the CPU's. We have rendered a true-life scene with colored textures as the first demo by our homemade software. The holographic reconstructed scene possesses high performances in many aspects such as depth cues, surface textures, shadings, and occlusions, etc. The GPU's algorithm performs hundreds of times faster than those of CPU.