Effect of milling and reinforcement on mechanical properties of nanostructured magnesium composite

Recycled Mg chips were used to synthesize nanostructured Mg composite of Mg–5 wt%Al reinforced with x wt% (x = 1, 2 and 5) in-situ formed AlN powder. Mechanical milling was employed to produce the composite powder of crystalline size 30–43 nm. The mechanically milled (MMed) powders were subjected to uniaxial pressing, sintering and hot extrusion processes to produce bulk solid samples. After sintering at 400 °C and hot extrusion at 350 °C, the crystalline size of the composite samples still remains in nanometer range from 52 to 84 nm. The effect of milling and the percentage of reinforced AlN on the mechanical properties such as tensile strength and ductility were discussed with the general explanation of deformation mechanisms involved.     

Thermal stability of cryomilled nanocrystalline aluminum containing diamantane nanoparticles

The thermal stability of nanoscale grains in cryomilled aluminum powders containing 1% diamantane was investigated. Diamantane is a diamondoid molecule consisting of 14 carbon atoms in a diamond cubic structure that is terminated by hydrogen atoms. The nanostructures of the resulting cryomilled powders were characterized using both transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. The average grain size was found to be on the order of 22 nm, a value similar to that obtained for cryomilled Al without diamantane. To determine thermal stability, the powders were heated in an inert gas atmosphere at constant temperatures between 423 and 773 K (0.51T _m to 0.83T _m) for exposure times of up to 10 h. The average grain size for all powders containing diamantane was observed to remain in the nanocrystalline range (1–100 nm) for all exposures and was generally less than half of that for cryomilled pure Al heated under the same conditions. The thermal stability data were found to be consistent with a grain growth model based on drag forces exerted by dispersed particles against grain boundary migration. The present findings indicate that the presence of diamantane results in a substantial increase in the thermal stability of nanoscale grains in Al.     

Haplotype Analysis of BADH1 by Next-Generation Sequencing Reveals Association with Salt Tolerance in Rice during Domestication

Betaine aldehyde dehydrogenase 1 (BADH1), a paralog of the fragrance gene BADH2, is known to be associated with salt stress through the accumulation of synthesized glycine betaine (GB), which is involved in the response to abiotic stresses. Despite the unclear association between BADH1 and salt stress, we observed the responses of eight phenotypic characteristics (germination percentage (GP), germination energy (GE), germination index (GI), mean germination time (MGT), germination rate (GR), shoot length (SL), root length (RL), and total dry weight (TDW)) to salt stress during the germination stage of 475 rice accessions to investigate their association with BADH1 haplotypes. We found a total of 116 SNPs and 77 InDels in the whole BADH1 gene region, representing 39 haplotypes. Twenty-nine haplotypes representing 27 mutated alleles (two InDels and 25 SNPs) were highly (p < 0.05) associated with salt stress, including the five SNPs that have been previously reported to be associated with salt tolerance. We observed three predominant haplotypes associated with salt tolerance, Hap_2, Hap_18, and Hap_23, which were Indica specific, indicating a comparatively high number of rice accessions among the associated haplotypes. Eight plant parameters (phenotypes) also showed clear responses to salt stress, and except for MGT (mean germination time), all were positively correlated with each other. Different signatures of domestication for BADH1 were detected in cultivated rice by identifying the highest and lowest Tajima’s D values of two major cultivated ecotypes (Temperate Japonica and Indica). Our findings on these significant associations and BADH1 evolution to plant traits can be useful for future research development related to its gene expression.     

Retrieval of chlorophyll fluorescence from reflectance spectra through polarization discrimination: modeling and experiments

The polarization discrimination technique we recently developed, shows that it is possible to separate the elastic scattering and the chlorophyll fluorescence signal from the water-leaving radiance by making use of the fact that the elastically scattered components are partially polarized, while the fluorescence signal is unpolarized. The technique has been shown to be applicable to a wide range of water conditions. We present an extension of experimental and analytical results, which serve to define the scope of this technique and its range of applicability. A new analysis, based on vector radiative transfer computations, and on laboratory and field measurements on eastern Long Island and in the Chesapeake Bay, shows that the technique is generally effective for both open ocean and coastal waters, but that it is limited if the ocean bottom albedo and/or multiple scattering due to very high mineral particle concentrations result in depolarizing the water-leaving radiance. In addition, we show that in contrast with the polarization-based retrieval, the traditional method of extracting fluorescence height using the baseline method can give significant errors, particularly for coastal waters where it strongly overestimates the fluorescence values.     

Action Research as a Proactive Research Method for Construction Engineering and Management

Academic research in applied disciplines such as construction engineering and management (CEM) has the dual mission of simultaneously contributing to the solution of practical problems and creating theoretical and conceptual knowledge. To do so, appropriate research approaches are needed. However, extant literature in the field has paid little attention to this issue and research methods used have been almost entirely either quantitative surveys or case studies. In this paper, action research (AR) is proposed as an answer to this knowledge gap. AR aims at building and testing theory within the context of solving an immediate practical problem in a real setting. The paper describes the underlying philosophy and application procedure of AR and highlights its strengths and weaknesses. Then, the applicability of the method to CEM is illustrated through a case study of improving access to information to support planning and decision making in a construction owner organization through designing and implementing a data warehouse. The findings indicate that AR is a reliable, structured, and rigorous research approach that is very useful for conducting applied research in construction and enabling academia to influence and improve construction industry practices. It can also effectively help to improve collaboration between academic researchers and industry practitioners in research and development projects.     

Delta excitations and shell-model information in heavy-ion, charge-exchange reactions

We calculate total cross sections for coherent pion production using localized plane-wave approximations for the shell-structure of valence nucleons that are excited to delta particles in the intermediate state in the (12C, 12B) and (12C, 12N) charge-exchange, heavy-ion reactions. We find comparable agreement to projectile downshift data for 12C(12C, 12B)12N. Then we improve the formalism by replacing the localized plane wave bound states with harmonic oscillator states which are imbedded in a multipole expansion approach and calculate pion differential cross sections to test for the sensitivity of the spectra to the single-particle mass parameter.     

Behaviour of ionized metal plasma deposited Ta diffusion barrier between Cu and SiO2

This work investigated the diffusion barrier properties of ionized metal plasma (IMP) deposited Ta between Cu and SiO₂. When Cu and Ta layers were formed by IMP sputtering, it was found that the Cu has the equilibrium f.c.c. structure with the grain size of 80 nm whereas Ta is in a metalstable tetragonal (-Ta) form with a grain size of around 10 nm. With the help of sheet resistance measurement, X-ray diffraction, cross-section transmission electron microscope analysis, Rutherford backscattering spectroscopy, secondary ion mass spectroscopy, and scanning electron microscopy, the Ta barrier layer was observed to fail at temperature above 650°C due to the reactions among Cu, Ta and O and formation of Cu _x Ta _y O _z . The phase transformation of -Ta into the stable phase (-Ta), in the presence of Cu was encountered when annealing the sample at above 800°C. The role of oxygen was also found to be important in the phase transformation, in the reactions and it seems to have a strong effect on the thermal stability of the barrier layer.