Nonadiabatic transitions in chemical reactions: A quantum mechanical study

This work presents an exact quantum mechanical treatment of a reactive three-atom collinear model system incorporating nonadiabatic couplings. It was assumed that nonadiabatic transitions are induced by the vibrational motion only. The main findings are: (i) The reaction process can create conditions in which weak nonadiabatic couplings terms ( for which the Massey parameter was round 10) may cause large probabilities (～0.5) for transitions from one electronic surface to the other. In other words, the reaction process is able in certain cases to create a near resonance situation which makes the non-adiabatic transition almost independent of the magnitude of the coupling term. For this to happen the two surfaces need not be proximate, nor need they “almost” cross along a certain line (ii) In cases where the main nonadiabatic transitions take place outside the interaction region one may, at least qualitatively, decouple the reaction process from the nonadiabatic one. Thus, under the conditions specified one may first treat the reactive system on the ground state surface without including the excited interacting surface and then treat the nonadiabatic process independently.     

Poisson source localization on the plane: change-point case

We present a detection problem where several spatially distributed sensors observe Poisson signals emitted from a single radioactive source of unknown position. The measurements at each sensor are modeled by independent inhomogeneous Poisson processes. A method based on Bayesian change-point estimation is proposed to identify the location of the source’s coordinates. The asymptotic behavior of the Bayesian estimator is studied. In particular, the consistency and the asymptotic efficiency of the estimator are analyzed. The limit distribution and the convergence of the moments are also described. The similar statistical model could be used in GPS localization problems.

     

Evanescent waves in FGM spherical curved plates: an analytical treatment

A deep understanding of both guided propagating and evanescent waves is very essential for non-destructive evaluation. Guided propagating waves have received considerable attention, but the research on guided evanescent waves is quite limited, especially for functionally graded structures. This paper presents an analytical approach, based on the orthogonal function technique, to solve the evanescent waves in a spherical curved plate with functionally graded material in the radial direction. The proposed approach can obtain all the real, imaginary and complex solutions but without iterative process. The validity of the proposed approach is illustrated by comparison with available results. The convergence of the approach is also discussed through a numerical example. Dispersion characteristics of the guided waves in various graded spherical curved plates are studied and three dimensional dispersion curves are plotted in frequency-complex wavenumber space. The effects of different radius-thickness ratios and graded fields on the dispersion curves of the guided evanescent waves are illustrated. The displacement distributions are also discussed to analyze the characteristics of the guided evanescent waves.     

Investigation of an alternative chemical agent to recover valuable metals from anode slime

Anode slime (AS) including high content of precious metals is a by-product obtained after the electro-refining stage in copper production. In this study, it is aimed to recover Cu, Au, and Ag from the AS by using 1-butyl-3-methyl-imidazolium hydrogen sulphate ([Bmim]HSO₄) ionic liquid (IL) as a green solvent. The effects of IL concentration, temperature, reaction time and pulp density on recovery of valuable metals were statistically investigated. A high copper recovery of 87.52% was obtained under optimum condition as in 60% (v/v) [Bmim]HSO₄ at 50 °C after 2 h, pulp density at 40 g/L (1/25 solid/liquid ratio). Also, a remarkable gold recovery as 97.32% has been achieved in 80% (v/v) [Bmim]HSO₄ at 95 °C after 4 h, pulp density at 40 g/L. Temperature and IL concentration were detected as the most effective parameters for copper and gold recovery from AS, respectively. Silver could not be recovered from the AS due to the lower solubility in [Bmim]HSO₄ IL media. According to experimental results, [Bmim]HSO₄ could be offered as an alternative leaching agent, instead of conventional solvents, to recover valuable metals from copper anode slime.     

Drinfeld modules and torsion in the Chow groups of certain threefolds

Let E B be an elliptic surface defined over the algebraic closureof a finite field of characteristic greater than 5. Let W bea resolution of singularities of E x _B E. We show that the l-adicAbel–Jacobi map from the l-power-torsion in the secondChow group of W to H³(W, _l(2)) _l/_l is an isomorphism for almostall primes l. A main tool in the proof is the assertion thatcertain CM-cycles in fibres of W B are torsion, which is provenusing results from the theory of Drinfeld modular curves.     

A new efficient route to chiral 1,3-disubstituted ferrocenes: application to the syntheses of (R(p))- and (S(p))-17alpha-[(3'-formylferrocenyl)ethynyl]estradiol

Starting from (2S,4S)-2-ferrocenyl-4-(methoxymethyl)-1,3-dioxane (4), use of the stereogenic ortho-directing menthyl para-tolyl sulfoxide group, which occupies the 2' position in the ferrocenyl ring and redirects subsequent lithiation to the 3' position, allowed the synthesis of optically pure (S(p))-1-formyl-3-iodoferrocene (8), that was characterized by single-crystal X-ray diffraction. Combination of this method with a protection-deprotection strategy, using trimethylsilyl as a temporary blocking group, yielded (R(p))-1-formyl-3-iodoferrocene (13). Separate Sonogashira coupling of each of the enantiomeric iodoformylferrocenes 8 and 13 with 17alpha-ethynyl-estradiol produced (R(p))-17alpha-[(3'-formylferrocenyl)ethynyl]estradiol (14) and (S(p))-17alpha-[(3'-formylferrocenyl)ethynyl]estradiol (15), respectively.     

Acetylene chemistry,part XXII [1, 2]: Synthesis of noracronycine and some of its analogs via Mitsunobu-reaction

Summary The natural product noracronycine as well as some of its analogs were synthesized by Mitsunobu-etherisation, using propinol derivatives.

---

Acetylenchemie, 22. Mitt.: Synthese von Noracronycin und einiger Analoga mittels Mitsunobu-Reaktion (Kurze Mitt.)

Zusammenfassung Der Naturstoff Noracronycin sowie einige seiner Analoga konnten durch Mitsunobu-Veretherung unter Verwendung von Propinol-Derivaten synthetisiert werden.

     

Deciphering the activation sequence of ferrociphenol anticancer drug candidates

The complete oxidation sequence of a model for ferrociphenols, a new class of anticancer drug candidate, is reported. Cyclic voltammetry was used to monitor the formation of oxidation intermediates on different timescales, thereby allowing the electrochemical characterization of both the short-lived and stable species obtained from the successive electron-transfer and deprotonation steps. The electrochemical preparation of the ferrocenium intermediate enabled a stepwise voltammetric determination of the stable oxidation compounds obtained upon addition of a base as well as the electron stoichiometry observed for the overall oxidation process. A mechanism has been established from the electrochemical data, which involves a base-promoted intramolecular electron transfer between the phenol and the ferrocenium cation. The resulting species is further oxidized then deprotonated to yield a stable quinone methide. To further characterize the transient species successively formed during the two-electron oxidation of the ferrociphenol to its quinone methide, EPR was used to monitor the fate of the paramagnetic species generated upon addition of imidazole to the electrogenerated ferrocenium. The study revealed the passage from an iron-centered to a carbon-centered radical, which is then oxidized to yield the quinone methide, namely, the species that interacts with proteins and so forth under biological conditions.