Layer-by-layer electrodeposition of copper in the presence of o-phenanthroline, caused by a new type of hidden NDR oscillation with the effective electrode surface area as the key variable

Electrochemical deposition of copper (Cu) from aqueous acidic Cu2+ solutions with o-phenanthroline (o-phen) shows both potential and current oscillations, together with a (partially hidden) N-shaped negative differential resistance (N-NDR), indicating that the oscillations are classified into hidden N-NDR (or HN-NDR) oscillations. The color and the surface morphology of Cu deposits oscillate in synchronization with the potential and current oscillations. Microscopic inspection has shown that dense round Cu leaflets, which look gray, grow in the positive side of the potential oscillation or in the high-current state of the current oscillation, whereas thin Cu leaflets, which look black, grow in the opposite-side stages of the potential and current oscillations, thus finally resulting in a layered Cu deposit with the layer thickness of about 5 microm. The appearance of the NDR is explained to be due to adsorption of the reduced form of a [Cu(II)(o-phen)2]2+ complex, which suppresses the Cu electrodeposition. The increase in the effective electrode surface area by growth of thin Cu leaflets, on the other hand, causes a current increase that can hide the NDR. This NDR-hiding mechanism is of a new type and the present oscillation is regarded as a new-type of HN-NDR oscillator.     

Electronic control of spin alignment in pi-conjugated molecular magnets

Intramolecular spin alignment in pi-conjugated molecules is studied theoretically in a model of a Peierls-Hubbard chain coupled with two localized spins. By means of the exact diagonalization technique, we demonstrate that a spin singlet (S=0) to quartet (S=3/2) transition can be induced by electronic doping, depending on the chain length, the positions of the localized spins, and the sign of the electron-spin coupling. The calculated results provide a theoretical basis for understanding the mechanism of spin alignment recently observed in a diradical donor molecule.     

Descent Kummer theory via Weil restriction of multiplicative groups

We prove a Kummer duality for certain fields without roots of unity by using the Weil restriction of the multiplicative groups. This is a natural generalization of the classical Kummer theory.     

Enantioseparation of nicotine alkaloids in cigarettes by CE using sulfated β‐CD as a chiral selector and a capillary coated with amino groups

Nicotine (NC) and its related compounds (cotinine (CN), nornicotine (NN), anatabine (AT) and anabasine (AB)) were simultaneously enantioseparated by CE using a capillary with amino groups and sulfated β‐CD as a chiral selector. The optimum running conditions were found to be 30 mM acetate buffer (pH 5.0) containing 8% sulfated β‐CD with an applied voltage of +15 kV at 30°C using direct detection at 260 nm. Using a capillary coated with amino groups, the EOF migrates toward the positive pole. However, when sulfated β‐CD was added to the BGE, it was found that the EOF migrated toward the negative pole due to ionic adsorption of sulfated β‐CD to amino groups on the capillary inner wall. All the cationic analytes migrated as anions, suggesting that they formed stable anionic complexes with sulfated β‐CD. With this system and a simple pretreatment with mini‐cartridges, NC alkaloids in five cigarette samples were enantioseparated. As a result, each of the compounds except for CN was detected. In the case of NC, only (S)‐NC was detected (more than 99.9%), but in the case of NN, AT and AB, the ratios of (S)‐isomer to total isomers were in the ranges 58–70, 81–85 and 59–65%, respectively. On the other hand, only NC was detected in cigarette smoke and the ratio of (S)‐ and (R)‐NCs was 96:4. The amounts of NC alkaloids in cigarettes suggest that the production of (R)‐NC resulted from racemization due to the high temperature/burning of the cigarette.     

Nonexistence of elliptic curves having good reduction everywhere over certain quadratic fields

The purpose of this paper is to show the nonexistence of elliptic curves having good reduction everywhere over certain quadratic fields.     

Mössbauer spectroscopic study of photo-sensitive organic–inorganic hybrid system, (SP)[Fe(II)Fe(III)(dto)3](dto = C2O2S2, SP = spiropyran)

A photo-sensitive organic–inorganic hybrid system (SP)[Fe^IIFe^III(dto)₃] (SP = spiropyran, dto = C₂O₂S₂), has recently been developed, where the photo-isomerization of the intercalated spiropyran in solid state triggers the change of the magnetic properties, including the ferromagnetic transition temperature from 5 to 22 K. We performed ⁵⁷Fe Mössbauer measurement in order to probe the microscopic states of iron ions in (SP)[Fe^IIFe^III(dto)₃] and have investigated the photo-induced effect on them. The sample without UV-irradiation shows the charge transfer phase transition between 200 and 70 K and the higher and lower temperature phases coexist below 70 K, whereas the UV-irradiated sample does not undergo the charge transfer phase transition and the higher temperature phase is stable between 200 and 6 K.