Hydrogen isotope exchange reaction rate in tritium and methane mixed gas

Hydrogen isotope exchange reaction rate in tritium and methane mixed gas, as induced by tritium decay and beta radiation, has been experimentally measured. Initially T₂ gas was filled to 40 kPa and 20 kPa of CH₄ gas was added. The mixed gas spectrum was analyzed periodically by laser Raman spectrometry. The first order HT and H₂ formation rates and T₂ and CH₄ decay rates by hydrogen isotope exchange reaction were observed between 2.9·10^–3 h^–1 and 4.8·10^–3 h^–1. Although the estimated hydrogen isotope exchange reaction rate was 1/20–1/10 slower than the rate of H₂+T₂ mixed gases, it was nearly equivalent to the ion formation rate by tritium beta radiation. This suggested that isotopic hydrogen radicals formed via ionization would disappear in the presence of methane.     

Thermodynamic characterization of binding of DNA with cisplatin in aqueous solution by calorimetry

The behaviour of cis-diamminedichloroplatinum(II) (cisplatin) binding to DNA was studied thermodynamically by calorimetric methods such as flow microcalorimetry and differential scanning calorimetry (DSC). The thermodynamic quantities of binding of cisplatin to DNA were determined from the measurement of the heat of mixing. From the results obtained, it was suggested that the complex formation by the interaction of DNA with cisplatin may be influenced by the entropy term as a dominant factor. UV spectral measurement on solutions having a known concentration of DNA and cisplatin solutions of various concentrations was carried out at room temperature, and the difference of absorption, Δ A ₂₆₀ at wavelength 260 nm between DNA solutions with and without cisplatin was estimated. From the results obtained, a hyperchromic effect in the DNA solution containing cisplatin was found to exist. The appearance of the hyperchromic effect may be considered to originate from the disturbance of the base stacking between adjacent base pairs of DNA by the interaction of DNA with cisplatin. In addition, the thermal stability of the DNA-cisplatin complex was also studied by DSC method. The binding of cisplatin decreases the thermal stability of DNA; the transition temperature and the heat of the helix-coil transition of DNA decrease accompanying the binding of cisplatin. The decrease of the transition temperature is caused by the kinked DNA(helix') accompanying the appearance of the hyperchromic effect by binding cisplatin; also, the decrease of the heat of helix-coil transition may be based on the cooperative action between the heat of helix-coil transition of the kinked DNA(helix') and the heat of dissociation when cisplatin is dissociated from the DNA-cisplatin complex. By taking into consideration these results, the heat of binding of cisplatin to DNA was estimated to be about −106 kJ per mole of cisplatin.     

Design of a new axially chiral molecule by conformational fixation: 2,6-dithiaspiro[3.3]heptane 2,6-dioxide and its heavier analogues

We have designed a new axially chiral bis(sulfoxide) molecule with conformational rigidity: 2,6-dithiaspiro[3.3]heptane 2,6-dioxide 2a. This molecule has axial asymmetry due to two puckered thietane ring systems. The lone pairs on the sulfur show a strong s-character, which was expected to result in a high barrier to racemization, that is, inversion at the sulfur. We confirmed this prediction by calculations and experimentation. The lone pairs of the sulfur in 2a are sp^1.00 and the enthalpy of activation (ΔH³) for inversion is 47.5 kcal/mol (B3LYP/6-31G(d)). The ¹H NMR spectra of 2a showed two doublets and two doubled doublet peaks, which resulted from the rigidity of the four-membered ring frameworks without flipping. We separated the enantiomers of 2a by HPLC with a chiral stationary phase column to observe a set of complementary peaks. We also calculated the diselena- and ditellura congeners and confirmed that they also show axial chirality.     

Using sorbents to control heavy metals and particulate matter emission during solid fuel combustion

Some of the heavy metals in coal and wastes vaporize during combustion, concentrate in fine particulates, and emit with the flue gas into the atmosphere, to produce adverse effect on environment and health. This study first investigates the fate of the heavy metal species, especially Pb, Cd and Cr, known as semi-volatile, in various flue gases, especially in the presence of HCI and SO2, by chemical equilibrium calculation, in which, Si and Ca were proposed as base sorbent materials to capture Pb, Cd and Cr. Then Si- and Ca-based compounds as well as waste materials used as sorbents were optimized to capture the heavy metals. Finally, the optimal sorbent was tested in actual burning of dried sewage sludge as solid fuel, to evaluate the effectiveness of the sorbent. Calculated results show that Cl increases the volatility of most heavy metals, while SO2 enhances formation of condensed phases. Among the sorbents tested, kaolin appears most efficient to capture Pb and Cd. For sludge combustion with kaolin addition, both Pb and Cd were shifted from sub-micron to macro-sized particles, and accompanied by considerable decrease of 0.1 μm particles.     

Direct observation of optical excitation transfer based on resonant optical near-field interaction

This article reports the direct observation of long-distance optical excitation transfer based on resonant optical near-field interactions in randomly distributed quantum dots (QDs). We fabricated optical excitation transfer paths based on randomly distributed QDs by using CdSe/ZnS core?Cshell QDs and succeeded for the first time in obtaining output signals resulting from a unidirectional optical excitation transfer length of 2.4???m. Furthermore, we demonstrate that the optical excitation transfer occurs via the resonant excited levels of the QDs with a comparative experiment using non-resonant QDs. This excitation-transfer mechanism allows for intersecting, non-interacting nano-optical wires.     

Two-dimensional array of room-temperature nanophotonic logic gates using InAs quantum dots in mesa structures

We present a detailed study of the dynamics of light in passive nonlinear resonators with shallow and deep intracavity periodic modulation of the refractive index in both longitudinal and transverse directions of the resonator. We investigate solutions localized in the transverse direction (so-called Bloch cavity solitons) by means of envelope equations for underlying linear Bloch modes and solving Maxwell’s equations directly. Using a round-trip model for forward and backward propagating waves we review different types of Bloch cavity solitons supported by both focusing (at normal diffraction) and defocussing (at anomalous diffraction) nonlinearities in a cavity with a weak-contrast modulation of the refractive index. Moreover, we identify Bloch cavity solitons in a Kerr-nonlinear all-photonic crystal resonator solving Maxwell’s equations directly. In order to analyze the properties of Bloch cavity solitons and to obtain analytical access we develop a modified mean-field model and prove its validity. In particular, we demonstrate a substantial narrowing of Bloch cavity solitons near the zero-diffraction regime. Adjusting the quality factor and resonance frequencies of the resonator optimal Bloch cavity solitons in terms of width and pump energy are identified.     

Insight of arsenic transformation behavior during high-arsenic coal combustion

The release of arsenic vapors (As³⁺) during high-arsenic coal combustion not only raises serious environmental concerns, but also causes catalyst deactivation in selective catalytic reduction (SCR) systems. To illuminate the mechanisms involved in the transformation of arsenic vapors towards less troublesome arsenates (As⁵⁺) during coal combustion, the accessory minerals in the high-arsenic coal were identified and the association relationship of these compounds with arsenic in fly ash was estimated. The results showed that Si/Al were the main inorganic elements in high-arsenic coal while the content of Ca was quite low. Ca was mostly transformed into sulfates during coal combustion and the effect of Ca on the arsenic transformation was limited. Al/Fe played a more significant role in arsenic speciation transformation and arsenic in the fly ash was predominantly bound with Al/Fe-oxides as arsenates. It was further confirmed that Al in kaolin/metakaolin showed good capacity on arsenic capture. In addition, few arsenic vapors were captured through the physical adsorption mechanism and the large fraction of As³⁺ in some fine particles was mostly attributed to the chemical reactions between arsenic vapors and Al-compounds. Meanwhile, a certain amount of arsenic vapors were converted into As₂O₅(s) under the influence of SCR catalyst and then carried by flue gas to participate in fly ash. Besides, part of arsenic distributed in the fly ash was through the stabilization of ash matrix in high temperature conditions. The transformation of arsenic from vapors towards particulate arsenic favored arsenic emission control by particulate matter control devices.