Soil adjusted vegetation water content retrievals in grasslands

Soil contamination of canopy reflectance over grasslands can cause errors in empirical vegetation water content (VWC) retrievals using the NDII (Normalized Difference Infrared Index, [ρ_0.86?ρ_1.64]/[ρ_0.86+ρ_1.64]). Minimization of soil contamination by NDII relies on the existence of a quasi straight soil line and quasi straight VWC isolines (lines of equal VWC) in the 1.64–0.86 µm reflectance space. Further the VWC isolines are expected to meet at the origin of the 1.64–0.86 µm reflectance space. Considering soil moisture as the primary determinant of soil reflectance variation at a given location, this study investigates the effect of soil moisture on the nature of soil lines and VWC isolines under grassland conditions. Reflectance simulations from coupled soil‐leaf‐canopy reflectance models under grassland conditions show that soil lines and VWC isolines are expected to be curved and may not converge at the origin. This behaviour is attributed to disproportionate soil moisture related absorption processes operating at 1.64 µm and 0.86 µm. A new technique that accounts for these inconsistencies in NDII assumptions is proposed for VWC retrievals. The technique consists of using separate regression relationships between VWC and a Soil Adjusted NDII (SANDII) based on the volumetric soil moisture category of the background. SANDII, based on the idea borrowed from the Soil Adjusted Vegetation Index (SAVI) is an origin shifted transformation of NDII. The optimum origin that reduces VWC retrieval errors is shown to be soil moisture category specific. The proposed technique requires categorical soil moisture information in order to decide which regression relationship to apply for VWC retrievals. Climatology, meteorological models or microwave observations are expected to be reliable resources for such categorical soil moisture information. Evaluations of the proposed technique using simulated reflectances showed that absolute errors in VWC retrievals were reduced by an average 20% as compared to the traditional NDII regression method. Such improvements are expected to be significant for fire‐risk applications. Finally supporting evidence for the need of an origin translated NDII is provided using data collected over pastures during the Soil Moisture Experiment 2003 (SMEX03) field campaign.     

Reverse Micelle-Mediated Synthesis and Characterization of Tricalcium Phosphate Nanopowder for Bone Graft Applications

Nanocrystalline β-tricalcium phosphate (β-TCP) powder was synthesized using reverse micelle as a template system. Cyclohexane was used as the oil phase, aqueous solutions of calcium nitrate and phosphoric acid as the aqueous phase, and poly(oxyethylene)₅ nonylphenol ether (NP-5) and/or poly(oxyethylene)₁₂ nonylphenol ether (NP-12) as the surfactants. The powder were synthesized at a fixed Ca/P molar ratio of 1.5 at a pH of 10. The synthesized powder were calcined at 800°C to obtain monophasic β-TCP. Particle size, morphology, and surface area of the synthesized powder were dependent on the chemistry of the surfactant and composition of the microemulsion. The powder were characterized using a BET surface area analyzer, powder X-ray diffraction, dynamic light scattering technique, and transmission electron microscopy. TCP nanoparticles had a particle size between 32 and 135 nm, and a BET-specific average surface area between 57 and 103 m²/g with controlled morphology. The powder were consolidated and sintered at 1250°C in a 3 kW microwave furnace in the form of a compact disk. Human osteoprecursor cells (osteoblastic precursor cell line 1 [OPC1]) were used to assess the biocompatibility of TCP disks after 1, 5, and 11 days in culture using scanning electron microscopy, MTT assay, and alkaline phosphatase expressions. Disk samples were biocompatible and showed excellent OPC1 cell adhesion, growth, and proliferation. Biocompatible β-TCP nanopowder were synthesized with controlled particle size, morphology, and surface area using a reverse micelle-mediated template system.     

Kinetics of Melt Crystallization of a Sunflower Oil‐Based Polyunsaturated Fatty Acid Mixture

Important parameters like supercooling and cooling rates affecting the melt crystallization of a polyunsaturated fatty acid (PUFA) mixture obtained from sunflower oil were investigated and compared via high‐resolution polarized‐light microscopy. PUFA was thermally characterized in a differential scanning calorimeter and the significant liquid‐solid‐phase transition temperatures determined were then implemented in the development of specific temperature profiles. Analyzed between two glass slides, induction times were found to decrease with low crystallization temperatures and the number of nuclei per unit area increased with higher supercooling and cooling rates. A comparison between the linear crystal growth rates of pure standards of each of the main fatty acids present in the PUFA mixture and the PUFA mixture itself indicated that the latter is much slower than that of each of its pure components.     

Biomedical applications of thermally activated shape memory polymers

Shape memory polymers (SMPs) are smart materials that can remember a primary shape and can return to this primary shape from a deformed secondary shape when given an appropriate stimulus. This property allows them to be delivered in a compact form via minimally invasive surgeries in humans, and deployed to achieve complex final shapes. Here we review the various biomedical applications of SMPs and the challenges they face with respect to actuation and biocompatibility. While shape memory behavior has been demonstrated with heat, light and chemical environment, here we focus our discussion on thermally stimulated SMPs.     

Analyzing the Structure and Evolution of Massive Telecom Graphs

With the ever-growing competition in telecommunications markets, operators have to increasingly rely on business intelligence to offer the right incentives to their customers. Existing approaches for telecom business intelligence have almost solely focused on the individual behavior of customers. In this paper, we use the call detail records of a mobile operator to construct call graphs, that is, graphs induced by people calling each other. We determine the structural properties of these graphs and also introduce the Treasure-Hunt model to describe the shape of mobile call graphs. Moreover, we determine how the structure of these call graphs evolve over time. Finally, since short messaging service (SMS) is becoming a preferred mode of communication among many sections of the society, we study the properties of the SMS graph. Our analysis indicates several interesting similarities and differences between the SMS graph and the corresponding call graph. We believe that our analysis techniques can allow telecom operators to better understand the social behavior of their customers and potentially provide major insights for designing effective incentives.     

A note on generalized hold functions

In this note, we study the generalized hold functions for use of digital control of continuous-time systems. First we define and solve the problem of simultaneous stabilization and minimization. It is shown that every plant with a strictly proper transfer function is simultaneously stabilizable and minimizable, provided that the sampling interval is small enough. We also consider robust designs of generalized hold functions. A condition is given for the stability of a system using generalized hold functions in the presence of uncertainty.     

Theoretical studies on VPI-5. 3. The MS-Q force field for aluminophosphate zeolites

Aluminophosphate zeolite is an artificial material which shows strange hydrophilicity. We have been investigating the reason by quantum mechanics, and found that the hydrophilicity of this zeolite depended on the local geometric deformation, and speculated that the site-specific hydrophilicity might be explained by differences in the stiffness of the local deformation determined by the location with the pore structure. In order to test these ideas, we construct a reliable force field based on the new MS-Q approach developed by Demiralp, Cagin, and Goddard. Our force field well reproduces the experimental structure of VPI-5.     

Improved Thermoelectric Performance of Higher Manganese Silicides with Ge Additions

Polycrystalline higher manganese silicides (HMS) with Ge additions were prepared by induction melting followed by hot-pressing. The phase structures and microstructure of the pellets were investigated, and their thermoelectric properties were measured from room temperature to 650°C. It was found that the solubility of Ge in HMS was limited to around 1.6%, beyond which an extra phase of Si _y Ge_1?y appeared. The electrical conductivity was continuously enhanced by Ge additions, while the Seebeck coefficient was slightly decreased. The thermal conductivity showed first a decreasing then an increasing relationship with increasing Ge additions. The HMS cells, mainly along the c-axis, were remarkably enlarged by the substitution of Ge, which probably resulted in the enhancement of phonon scattering due to an increased number of defects, reducing the phonon thermal conductivity. The dimensionless figure of merit of the optimized HMS polycrystals was improved by more than 30% compared with the pure HMS material.     

Vibration isolation using open or filled trenches

The problem of structural isolation from ground transmitted vibrations by open or infilled trenches under conditions of plane strain is numerically studied. The soil medium is assumed to be linear elastic or viscoelastic, homogeneous and isotropic. Horizontally propagating Rayleigh waves or waves generated by the motion of a rigid foundation or by surface blasting are considered in this work. The formulation and solution of the problem is accomplished by the boundary element method in the frequency domain for harmonic disturbances or in conjunction with Laplace transform for transient disturbances. The proposed method, which requires a discretisation of only the trench perimeter, the soil-foundation interface and some portion of the free soil surface on either side of the trench appears to be better than either finite element or finite difference techniques. Some parametric studies are also conducted to assess the importance of the various geometrical, material and dynamic input parameters and provide useful guidelines to the design engineer.