Intrinsic promotion mechanism of calcium oxide on ketone production during catalytic fast pyrolysis of biomass via experiment and density functional theory simulation.

CaO modified with acetic acid solution or sodium hydroxide (H-CaO/OH-CaO) was used to explore the relationship between the physical and chemical properties of CaO and the components of bio-oil during the pyrolysis of rice straw (RS) and model compounds via experiment and density functional theory(DFT) simulation. The results showed that the modification changed the properties of CaO, and thus the catalytic performance on production of bio-oil components. H-CaO with the larger number of strong basic sites (1.10 âˆ¼ 2 times than commercial CaO) and the longer Ca-O bond length showed the better selectivity and performance on formation of ketones (the maximum relative content in bio-oil reached 43 %). The conversion pathway of cellulose/hemicellulose was changed by H-CaO, which promoted the formation of ketones. The easier combining of H-CaO with the pyrolysis primary products due to the longer Ca-O bond was the key to its better performance.

Effects of light-emitting diode spectral combinations on growth and quality of pea sprouts under long photoperiod.

Pea sprouts have rich nutrition and are considered good for heart health. In this study, the kaspa peas and black-eyed peas were chosen to clarify the effect of different LED spectral combinations on the growth, yield, and nutritional quality of pea sprouts under long photoperiod (22 h light/2 h dark). The results showed that the two pea varieties responded differently to light spectral combinations. Black-eyed pea sprouts had higher plant height, fresh weight per plant, dry weight per plant, soluble sugar content, and lower malondialdehyde (MDA) content than kaspa peas under the same light treatment. Compared with white light, red-to-blue ratio of 2:1 significantly increased peroxidase (POD) and superoxide dismutase (SOD) activity, soluble sugar and soluble protein content of kaspa pea sprouts, and decreased MDA content of black-eyed pea sprouts. Blue light was negatively correlated with the plant height of pea sprouts and positively correlated with SOD activity, vitamin C, soluble sugar, and soluble protein content. Antioxidant capacity, yield, and nutritional quality of black-eyed pea sprouts were higher than those of kaspa pea sprouts under the same light treatment. Blue light improved the nutritional quality of pea sprouts. Compared with other light treatments, the red-to-blue ratio of 2:1 was more conducive to improving the antioxidant capacity and nutritional quality of pea sprouts under long photoperiod.

Metastable Dissolution Regularity of Nd3+ in Na2CO3 Solution and Mechanism.

The carbonate solution-dissolved rare earth showed some metastable chemical characteristics. In this paper, the systematic investigation of metastable dissolution regularity of Nd3+ in Na2CO3 solution was carried out. The results showed that Nd3+ has an instantaneous saturated solubility in Na2CO3 solution. When the amount of the dissolution Nd3+ did not reach the instantaneous saturated solubility, the solution was in a stable-state period. Once the concentration of Nd3+ exceeded the instantaneous saturated solubility, the solution was no longer in the metastable state and generated the neodymium double salt of carbonate precipitates rapidly. The molecular dynamics simulation of the solution in the metastable state was carried out. In high concentration Na2CO3 solution, dissolved Nd3+ had a coordination reaction with the CO3 2-. Also, there was a stronger interaction between Na+ and CO3 2-, which caused the effective concentration of free CO3 2- which could react with Nd3+ to become lower. Thus, these reasons make the solution exhibit a metastable state. In that metastable period, the dissolved Nd3+ becomes steady and hard to generate the neodymium double salt of carbonate precipitates.

Parallel beamlet dose calculation via beamlet contexts in a distributed multi-GPU framework.

PURPOSE: Dose calculation is one of the most computationally intensive, yet essential tasks in the treatment planning process. With the recent interest in automatic beam orientation and arc trajectory optimization techniques, there is a great need for more efficient model-based dose calculation algorithms that can accommodate hundreds to thousands of beam candidates at once. Foundational work has shown the translation of dose calculation algorithms to graphical processing units (GPUs), lending to remarkable gains in processing efficiency. But these methods provide parallelization of dose for only a single beamlet, serializing the calculation of multiple beamlets and under-utilizing the potential of modern GPUs. In this paper, the authors propose a framework enabling parallel computation of many beamlet doses using a novel beamlet context transformation and further embed this approach in a scalable network of multi-GPU computational nodes. METHODS: The proposed context-based transformation separates beamlet-local density and TERMA into distinct beamlet contexts that independently provide sufficient data for beamlet dose calculation. Beamlet contexts are arranged in a composite context array with dosimetric isolation, and the context array is subjected to a GPU collapsed-cone convolution superposition procedure, producing the set of beamlet-specific dose distributions in a single pass. Dose from each context is converted to a sparse representation for efficient storage and retrieval during treatment plan optimization. The context radius is a new parameter permitting flexibility between the speed and fidelity of the dose calculation process. A distributed manager-worker architecture is constructed around the context-based GPU dose calculation approach supporting an arbitrary number of worker nodes and resident GPUs. Phantom experiments were executed to verify the accuracy of the context-based approach compared to Monte Carlo and a reference CPU-CCCS implementation for single beamlets and broad beams composed by addition of beamlets. Dose for representative 4π beam sets was calculated in lung and prostate cases to compare its efficiency with that of an existing beamlet-sequential GPU-CCCS implementation. Code profiling was also performed to evaluate the scalability of the framework across many networked GPUs. RESULTS: The dosimetric accuracy of the context-based method displays <1.35% and 2.35% average error from the existing serialized CPU-CCCS algorithm and Monte Carlo simulation for beamlet-specific PDDs in water and slab phantoms, respectively. The context-based method demonstrates substantial speedup of up to two orders of magnitude over the beamlet-sequential GPU-CCCS method in the tested configurations. The context-based framework demonstrates near linear scaling in the number of distributed compute nodes and GPUs employed, indicating that it is flexible enough to meet the performance requirements of most users by simply increasing the hardware utilization. CONCLUSIONS: The context-based approach demonstrates a new expectation of performance for beamlet-based dose calculation methods. This approach has been successful in accelerating the dose calculation process for very large-scale treatment planning problems - such as automatic 4π IMRT beam orientation and VMAT arc trajectory selection, with hundreds of thousands of beamlets - in clinically feasible timeframes. The flexibility of this framework makes it as a strong candidate for use in a variety of other very large-scale treatment planning tasks and clinical workflows.

Molecular dynamics simulations of Y(iii) coordination and hydration properties.

Y mainly exists in ionic rare-earth resources. During rare-earth carbonate precipitation, rare-earth ion loss in the precipitated rare-earth mother liquor often occurs due to CO3 2- coordination and Y(iii) hydration. Microscopic information on the coordination and hydration of CO3 2- and H2O to Y(iii) has not yet been elucidated. Therefore, in this study, the macroscopic dissolution of Y(iii) in different aqueous solutions of Na2CO3 was studied. The radial distribution function and coordination number of Y(iii) by CO3 2- and H2O were systematically analyzed using molecular dynamics (MD) simulations to obtain the complex ion form of Y(iii) in carbonate solutions. Density functional theory (DFT) was used to geometrically optimize and calculate the UV spectrum of Y(iii) complex ions. This spectrum was then analyzed and compared with experimentally determined ultraviolet-visible spectra to verify the reliability of the MD simulation results. Results showed that Y(iii) in aqueous solution exists in the form of [Y·3H2O]3+ and that CO3 2- is present in the bidentate coordination form. In 0-0.8 mol L-1 CO3 2- solutions, Y(iii) was mainly present as the 5-coordinated complex [YCO3·3H2O]+. When the concentration of CO3 2- was increased to 1.2 mol L-1, [YCO3·3H2O]+ was converted into a 6-coordinated complex [Y(CO3)2·2H2O]-. Further increases in CO3 2- concentration promoted Y(iii) dissolution in solution in the form of complex ions. These findings can be used to explain the problem of incomplete precipitation of rare earths in carbonate solutions.

A novel Cs2NbOF5:Mn4+ oxyfluoride red phosphor for light-emitting diode devices.

The addition of a red-emitting phosphor to YAG:Ce3+-based white light-emitting diodes (WLEDs) greatly facilitates their applications in the field of high-color-rendering-index warm solid-state lighting. It is highly desirable to develop a red phosphor with satisfactory spectral features and low synthesis cost. In this study, a novel non-rare-earth and nonequivalent doping type of Cs2NbOF5:Mn4+ oxyfluoride red-emitting phosphor with high luminous efficiency was obtained via a facile room-temperature co-precipitation method, and its morphology and luminescent properties were investigated in detail. The Cs2NbOF5:Mn4+ phosphor with micro-rod-like morphology exhibited broad band absorption at blue light region (∼474 nm) and narrow bandwidth emissions at red region (∼633 nm). The color purity of the Cs2NbOF5:Mn4+ phosphor was calculated to be about 99%, and the internal quantum yield (QY) under 474 nm excitation was 63.4%. The concentration quenching of Mn4+ in Cs2NbOF5 matrix was mainly due to dipole-dipole interactions, and the activation energy of temperature quenching was calculated to be ∼0.2610 eV. The demonstration of a blue InGaN LED chip in combination with a blend of newly developed Cs2NbOF5:Mn4+ red phosphor and YAG:Ce3+ yellow phosphor greatly decreased the correlated color temperature (CCT) from 6255 to 3517 K while significantly improving the color rendering index (CRI) from 72.5 to 87.5. It deserves to be mentioned that the brand-new matrix to phosphor in the present study can be extended to various niobium/tantalum oxyfluoride series, which is very helpful for developing and designing new red phosphors.

ARCHERRT - a GPU-based and photon-electron coupled Monte Carlo dose computing engine for radiation therapy: software development and application to helical tomotherapy.

PURPOSE: Using the graphical processing units (GPU) hardware technology, an extremely fast Monte Carlo (MC) code ARCHERRT is developed for radiation dose calculations in radiation therapy. This paper describes the detailed software development and testing for three clinical TomoTherapy® cases: the prostate, lung, and head & neck. METHODS: To obtain clinically relevant dose distributions, phase space files (PSFs) created from optimized radiation therapy treatment plan fluence maps were used as the input to ARCHERRT. Patient-specific phantoms were constructed from patient CT images. Batch simulations were employed to facilitate the time-consuming task of loading large PSFs, and to improve the estimation of statistical uncertainty. Furthermore, two different Woodcock tracking algorithms were implemented and their relative performance was compared. The dose curves of an Elekta accelerator PSF incident on a homogeneous water phantom were benchmarked against DOSXYZnrc. For each of the treatment cases, dose volume histograms and isodose maps were produced from ARCHERRT and the general-purpose code, GEANT4. The gamma index analysis was performed to evaluate the similarity of voxel doses obtained from these two codes. The hardware accelerators used in this study are one NVIDIA K20 GPU, one NVIDIA K40 GPU, and six NVIDIA M2090 GPUs. In addition, to make a fairer comparison of the CPU and GPU performance, a multithreaded CPU code was developed using OpenMP and tested on an Intel E5-2620 CPU. RESULTS: For the water phantom, the depth dose curve and dose profiles from ARCHERRT agree well with DOSXYZnrc. For clinical cases, results from ARCHERRT are compared with those from GEANT4 and good agreement is observed. Gamma index test is performed for voxels whose dose is greater than 10% of maximum dose. For 2%/2mm criteria, the passing rates for the prostate, lung case, and head & neck cases are 99.7%, 98.5%, and 97.2%, respectively. Due to specific architecture of GPU, modified Woodcock tracking algorithm performed inferior to the original one. ARCHERRT achieves a fast speed for PSF-based dose calculations. With a single M2090 card, the simulations cost about 60, 50, 80 s for three cases, respectively, with the 1% statistical error in the PTV. Using the latest K40 card, the simulations are 1.7-1.8 times faster. More impressively, six M2090 cards could finish the simulations in 8.9-13.4 s. For comparison, the same simulations on Intel E5-2620 (12 hyperthreading) cost about 500-800 s. CONCLUSIONS: ARCHERRT was developed successfully to perform fast and accurate MC dose calculation for radiotherapy using PSFs and patient CT phantoms.

The MYB transcription factor GhMYB25 regulates early fibre and trichome development.

Little is still known about the developmental control of the long seed coat trichomes of cotton (Gossypium hirsutum L.). In Arabidopsis, leaf trichome initiation is regulated by a group of well-defined transcription factors that includes MYB and homeodomain types. Many MYBs are expressed in fibres, but their roles in fibre development remain unclear. We analysed the function of one MYB transcription factor, GhMYB25, identified from transcriptome comparisons between wild-type and fibreless cotton mutants. A GhMYB25 promoter-GUS construct in transgenic cotton was expressed in the epidermis of ovules, developing fibre initials and fibres, in the trichomes of a number of tissues including leaves, stems and petals, as well as in the anthers, pollen and the epidermal layers of roots and root initials, but not in root hairs. Cotton is an allotetraploid with two very similar GhMYB25 genes that were silenced by a single RNAi construct. GhMYB25-silenced cotton showed alterations in the timing of rapid fibre elongation, resulting in short fibres, dramatic reductions in trichomes on other parts of the plant, and reductions in seed production. Reciprocal crosses between transgenic and non-transgenic plants indicated that pollen and ovule viability per se were not disrupted. Ectopic over-expression of GhMYB25 had more subtle impacts, with increases in cotton fibre initiation and leaf trichome number. High expression appeared to adversely affect fertility. Our results provide convincing evidence for a role of GhMYB25, like other MIXTA-like MYBS, in regulating specialized outgrowths of epidermal cells, including, in this case, cotton fibres.