The direct photodissociation process SO+a4Π +hv → S+ (4S0) + O(3P) via the repulsive SO+ 14Σ+ state has been studied using a laser-ion photofragment spectrometer with coaxial beams. The kinetic energy distribution of the S+ photofragments has been measured at a laser wavelength of λ=488 nm (hv=2.54 eV). The spectrum shows vibrational structure which can be assigned to transitions from the vibrational levelsv = 7–13 of the initiala4Π state. The experimental data are used along with semi-empirical calculations to locate the potential curve of the repulsive 14Σ+ state in the Franck-Condon region. The results are compared with data obtained from photopredissociation studies of SO+ and with theoretical calculations for the 14Σ+ state. 相似文献
Determination of iron speciation in water is one of the major challenges in environmental analytical chemistry. Here, we present and discuss a method for sampling and analysis of dissolved Fe(II), Fe(III), and Fetotal concentrations in natural thermal water covering a wide range of temperature, pH, chemical composition, and redox conditions. Various methods were tried in the collection, preservation, and storage of natural thermal water samples for the Fe(II) and Fe(III) determinations, yet the resultant Fe speciation determined was often found to be significantly affected by the methodology applied. Due to difficulties in preserving accurate Fe speciation in natural samples for later laboratory analysis, a field-deployed on-site method using ion-chromatography and spectrophotometry was developed and tested. The IC-Vis method takes advantage of ion chromatographic separation of Fe(II) and Fe(III), followed by post-column colour reaction and spectrophotometric detection, thus allowing analysis of Fe(II) and Fe(III) in a single 15-minute run. Additionally, Fetotal can be determined after sample oxidation. The analytical detection limits are ~2 µg L?1 (LOD) using 200–1000 µL injection volumes and depend on the blank and reagent quality. The power of this method relies on the capability to directly determine a wide range of absolute and relative concentrations of Fe(II) and Fe(III) in the field. The field-deployed IC-Vis method was applied for the determination of Fe(II) and Fe(III) concentrations in natural thermal water with discharge temperatures ranging from 12°C to 95°C, pH between 2.46 and 9.75, and Fetotal concentrations ranging from a few μg L?c up to 8.3 mg L?1. 相似文献
The conversion of isothiazoles into pyrazoles on treatment with hydrazine is investigated. The influence of various C-3, C-4 and C-5 isothiazole substituents and some limitations of this ring transformation are examined. When the isothiazole C-3 substituent is a good nucleofuge, 3-aminopyrazoles are obtained. However, when the 3-substituent is not a leaving group it is retained in the pyrazole product. Treatment of 4-bromo-3-chloro-5-phenylisothiazole 56 or 3-chloro-4,5-diphenylisothiazole 57 with anhydrous hydrazine at ca. 200 °C for a few minutes gives the corresponding 3-hydrazinoisothiazoles 61 and 64 respectively in high yields; the stability of these new hydrazines is investigated. 5,5′-Diphenyl-3,3′-biisothiazole-4,4′-dicarbonitrile 78 reacts with hydrazine to give 5,5′-diphenyl-3,3′-bi(1H-pyrazole)-4,4′-dicarbonitrile 79. Methylhydrazine reacts with 3-chloro-5-phenylisothiazole-4-carbonitrile 1 to give 3-(1-methylhydrazino)-5-phenylisothiazole-4-carbonitrile 83 and 3-amino-1-methyl-5-phenylpyrazole-4-carbonitrile 84. All products are fully characterised and rational mechanisms for the isothiazole into pyrazole transformation are proposed. 相似文献
131I, 137Cs and 134Cs were observed in environmental samples in Milano (40°N), Italy and Thessaloniki (45°N), Greece, soon after the nuclear accident in Fukushima, Japan. The radionuclide concentrations were determined and studied as a function of time. In Thessaloniki the 131I in air was observed for the first time on March 24, 2011. In Milano, the first evidence of Fukushima fallout has been confirmed with 131I and 137Cs measured in wet precipitation collected 2 days later. The maximum 131I activity concentration in air of 467 ± 25 μBq m?3, observed in Milano on April 3–4, 2011, was almost similar to the highest value of 497 ± 53 μBq m?3 observed in Thessaloniki. The 134Cs/137Cs activity ratio values in air were around 1 in both regions. Soil, grass and milk samples were contaminated with 131I and 137Cs at a low level. Finally, a dose assessment for these two areas showed clearly that the detected activities in all environmental samples were far below levels of concern. 相似文献
The results of theoretical calculations of associative desorption of CH(4) and H(2) from the Ni(111) surface are presented. Both minimum-energy paths and classical dynamics trajectories were generated using density-functional theory to estimate the energy and atomic forces. In particular, the recombination of a subsurface H atom with adsorbed CH(3) (methyl) or H at the surface was studied. The calculations do not show any evidence for enhanced CH(4) formation as the H atom emerges from the subsurface site. In fact, there is no minimum-energy path for such a concerted process on the energy surface. Dynamical trajectories started at the transition state for the H-atom hop from subsurface to surface site also did not lead to direct formation of a methane molecule but rather led to the formation of a thermally excited H atom and CH(3) group bound to the surface. The formation (as well as rupture) of the H-H and C-H bonds only occurs on the exposed side of a surface Ni atom. The transition states are quite similar for the two molecules, except that in the case of the C-H bond, the underlying Ni atom rises out of the surface plane by 0.25 A. Classical dynamics trajectories started at the transition state for desorption of CH(4) show that 15% of the barrier energy, 0.8 eV, is taken up by Ni atom vibrations, while about 60% goes into translation and 20% into vibration of a desorbing CH(4) molecule. The most important vibrational modes, accounting for 90% of the vibrational energy, are the four high-frequency CH(4) stretches. By time reversibility of the classical trajectories, this means that translational energy is most effective for dissociative adsorption at low-energy characteristic of thermal excitations but energy in stretching modes is also important. Quantum-mechanical tunneling in CH(4) dissociative adsorption and associative desorption is estimated to be important below 200 K and is, therefore, not expected to play an important role under typical conditions. An unexpected mechanism for the rotation of the adsorbed methyl group was discovered and illustrated a strong three-center C-H-Ni contribution to the methyl-surface bonding. 相似文献
An overview of opportunities of contemporary planar chromatography in pattern recognition and fingerprint analysis is presented. The most used chemometric methods are highlighted and their main advantages and drawbacks are underlined. In addition a cross section of the application of planar chromatographic fingerprinting in food, pharmaceutical, environmental, and forensic analysis is given. 相似文献
Insect flight research is propelled by their unmatched flight capabilities. However, complex underlying aerodynamic phenomena make computational modeling of insect-type flapping flight a challenging task, limiting our ability in understanding insect flight and producing aerial vehicles exploiting same aerodynamic phenomena. To this end, novel mid-fidelity approach to modeling insect-type flapping vehicles is proposed. The approach is computationally efficient enough to be used within optimal design and optimal control loops, while not requiring experimental data for fitting model parameters, as opposed to widely used quasi-steady aerodynamic models. The proposed algorithm is based on Helmholtz–Hodge decomposition of fluid velocity into curl-free and divergence-free parts. Curl-free flow is used to accurately model added inertia effects (in almost exact manner), while expressing system dynamics by using wing variables only, after employing symplectic reduction of the coupled wing-fluid system at zero level of vorticity (thus reducing out fluid variables in the process). To this end, all terms in the coupled body-fluid system equations of motion are taken into account, including often neglected terms related to the changing nature of the added inertia matrix (opposed to the constant nature of rigid body mass and inertia matrix). On the other hand—in order to model flapping wing system vorticity effects—divergence-free part of the flow is modeled by a wake of point vortices shed from both leading (characteristic for insect flight) and trailing wing edges. The approach is evaluated for a numerical case involving fruit fly hovering, while quasi-steady aerodynamic model is used as benchmark tool with experimentally validated parameters for the selected test case. The results indicate that the proposed approach is capable of mid-fidelity accurate calculation of aerodynamic loads on the insect-type flapping wings.
Using analytic methods, we present integrable solutions of the Bogomolny Yang–Mills–Higgs equations in 2+1 anti-de Sitter space. In particular, families of soliton solutions are constructed explicitly and their dynamics is investigated in some detail. 相似文献