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101.
Laser-induced incandescence (LII) of soot has developed into a popular method for making in situ measurements of soot volume fraction and primary particle sizes. However, there is still a lack of understanding regarding the generation and interpretation of the cooling signals. To model heat transfer from the heated soot particles to the surrounding gas, knowledge of the collision-based cooling as well as reactive events, including oxidation (exothermic) and evaporation (endothermic) is essential. We have simulated LII of soot using the ReaxFF reactive force field for hydrocarbon combustion. Soot was modeled as a stack of four graphene sheets linked together using sp(3) hybridized carbon atoms. To calculate the thermal accommodation coefficient of various gases with soot, graphene sheets of diameter 40 ? were used to create a soot particle containing 2691 atoms, and these simulations were carried out using the ReaxFF version incorporated into the Amsterdam Density Functional program. The reactive force field enables us to simulate the effects of conduction, evaporation, and oxidation of the soot particle on the cooling signal. Simulations were carried out for both reactive and nonreactive gas species at various pressures, and the subsequent cooling signals of soot were compared and analyzed. To correctly model N(2)-soot interactions, optimization of N-N and N-C-H force field parameters against DFT and experimental values was performed and is described in this paper. Subsequently, simulations were performed in order to find the thermal accommodation coefficients of soot with various monatomic and polyatomic gas molecules like He, Ne, Ar, N(2), CO(2), and CH(4). For all these species we find good agreement between our ReaxFF results and previously published accommodation coefficients. We thus believe that Molecular Dynamics using the ReaxFF reactive force field is a promising approach to simulate the physical and chemical aspects of soot LII. 相似文献
102.
103.
Hayashi H Lightcap IV Tsujimoto M Takano M Umeyama T Kamat PV Imahori H 《Journal of the American Chemical Society》2011,133(20):7684-7687
A bottom-up strategy has been developed to construct a multiple electron transfer system composed of organic/inorganic ternary composites (porphyrin, zinc oxide nanoparticles, reduced graphene oxide) on a semiconducting electrode without impairing the respective donor-acceptor components. The hierarchical electron transfer cascade system exhibited remarkably high photocurrent generation with an incident-photon-to-current efficiency of up to ca. 70%. 相似文献
104.
Kamat SS Fan H Sauder JM Burley SK Shoichet BK Sali A Raushel FM 《Journal of the American Chemical Society》2011,133(7):2080-2083
Two enzymes of unknown function from the amidohydrolase superfamily were discovered to catalyze the deamination of N-6-methyladenine to hypoxanthine and methyl amine. The methylation of adenine in bacterial DNA is a common modification for the protection of host DNA against restriction endonucleases. The enzyme from Bacillus halodurans, Bh0637, catalyzes the deamination of N-6-methyladenine with a k(cat) of 185 s(-1) and a k(cat)/K(m) of 2.5 × 10(6) M(-1) s(-1). Bh0637 catalyzes the deamination of N-6-methyladenine 2 orders of magnitude faster than adenine. A comparative model of Bh0637 was computed using the three-dimensional structure of Atu4426 (PDB code: 3NQB) as a structural template and computational docking was used to rationalize the preferential utilization of N-6-methyladenine over adenine. This is the first identification of an N-6-methyladenine deaminase (6-MAD). 相似文献
105.
Jose C. J. M. D. S. Menezes Bikshandarkoil R. Srinivasan Pallepogu Raghavaiah Shashikumar K. Paknikar Shrivallabh P. Kamat 《Journal of heterocyclic chemistry》2011,48(4):952-956
Two new structurally isomeric, 2‐(2,4,4‐trimethyl‐3,4‐dihydro‐2H‐benzo[h]chromen‐2‐yl)‐1‐naphthol ( 1 ) and 3‐(2,4,4‐trimethyl‐3,4‐dihydro‐2H‐benzo[g]chromen‐2‐yl)‐2‐naphthol ( 3 ) have been synthesized from 2‐acetyl‐1‐naphthol and ethyl‐3‐hydroxy‐2‐naphthoate, respectively, involving Grignard reaction, dehydration of the corresponding tertiary alcohols, and hetero Diels–Alder dimerization. The two benzochromenes ( 1 and 3 ) have been fully characterized by IR, NMR, and HRESIMS data. Their structures are further supported by crystallography of their corresponding acetates ( 2 and 4 ). J. Heterocyclic Chem., (2011). 相似文献
106.
Molecular iodine as an inexpensive catalyst is described in the construction of 2-substituted or 2,2-disubstituted chromans and 4-aryl-3,4-dihydrobenzopyran-2-ones via [3+3] cyclocoupling. For the synthesis of chromans, phenols and allylic alcohols were refluxed in chloroform in presence of 20 mol % I2 while [3+3] cyclocoupling of phenols and cinnamic acids proceeded to give 4-aryl-3,4-dihydrobenzopyran-2-ones using 30 mol % I2. Later reaction occurs via a tandem hydroarylation–esterification process at 120–130 °C under solvent free conditions. Chromans were obtained in 20–92% yields and substituted 4-aryl-3,4-dihydrobenzopyran-2-ones were obtained in 5–85% yields. 相似文献
107.
Robert Kennedy Ignacio Martini Greg Hartland Prashant V Kamat 《Journal of Chemical Sciences》1997,109(6):497-507
Cds-capped SnO2 (CdS@SnO2) and SiO2 (CdS@SiO2) colloids of 50–80 ? in diameter have been prepared in aqueous medium. Significant quenching of CdS emission is observed
in the CdS@SnO2 system as the electrons are injected from the excited CdS shell into the SnO2 core. Photoinduced charge separation in this system also results in transient bleaching in the 450 nm region. Picosecond
laser flash photolysis studies of composite semiconductor nanoclusters that highlight the effect of the metal oxide core on
the photophysical properties of the outer CdS shell are described.
Contribution No. 3961 from the Notre Dame Radiation Laboratory, USA 相似文献
108.
109.
J. V. Kamat J. S. Gamare K. Jayachandran Suresh K. Aggarwal 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(2):1431-1434
A biamperometric methodology for the sequential determination of thorium (Th) and uranium (U) was developed. In the sample solution containing Th and U, Th was first determined by complexometric titration based on the electrochemical behaviour of EDTA maintaining a potential of ≥200 mV between the twin Pt electrodes. This was followed by the redox titrimetric determination of U employing biamperometry to detect the end point. Prior to the determination of U, EDTA was destroyed by fuming with concentrated HClO4 to eliminate its interference in the U determination. The method was tested for the determination of Th and U in (Th, U) O2 samples containing 4 mg of Th and 2–8 mg of U, with precision and accuracy of better than 0.3 %. 相似文献
110.
It is known that corresponding to a field theory of a tensor of arbitrary rank, there exists a direct-action theory under certain conditions. An attempt is therefore made to construct an explicit direct-action theory for a tensor field of rankN in such a form that the absorber theory of radiation may be worked out using the methods made so well known by Wheeler-Feynman and Hoyle-Narlikar. It is possible to recover the familiar electromagnetic theory corresponding to the case ofN = 1. 相似文献