Antioxidant behaviour of 2′‐hydroxy‐chalcones: a study of their electrochemical properties

The electrochemical behaviour of 13 chalcone analogues was systematically studied by means of cyclic voltammetry and chronoamperometry at a glassy carbon (GC), gold and platinum working electrodes using two different supporting electrolyte/solvent combinations. It was found that chalcone analogues can be easily oxidized at both GC and gold working electrodes, but not at a platinum electrode. Principal component analysis was further employed to reveal similarities/dissimilarities between oxidation potentials, chronoamperometric signals and ability of the compounds to scavenge the reactive oxygen species H₂O₂. The study reveals the inverse proportional relationship between the scavenging ability of H₂O₂, expressed as IC₅₀, and chronoamperometric signal at 800 mV using gold as working electrode. Copyright © 2012 John Wiley & Sons, Ltd.     

Cyclic codes of length 2 m

In this paper explicit expressions ofm + 1 idempotents in the ring are given. Cyclic codes of length 2 ^m over the finite fieldF _q, of odd characteristic, are defined in terms of their generator polynomials. The exact minimum distance and the dimension of the codes are obtained.     

两相区轧制后淬火引入马氏体降低钢板屈强比

晶粒细化和分裂增韧可使两相区轧制的层状超细晶钢板具有高强度同时韧性优异.前期研究发现轧后空冷生成的层状超细晶钢板,存在屈强比偏高的问题,高达0.9.本研究通过轧后淬火在层状超细晶组织中引入马氏体的方法降低屈强比.研究发现,在750℃和810℃轧制后淬火,层状超细晶组织中可生成体积分数约为14%的马氏体.此部分马氏体使拉伸过程中呈现连续屈服行为,提高加工硬化率,使钢板的屈强比降至0.7以下,解决了屈强比偏高的问题.此外,实验钢在具有高强度的同时,韧性优良.     

Constraining Cyclic Peptides To Mimic Protein Structure Motifs

Many proteins exert their biological activities through small exposed surface regions called epitopes that are folded peptides of well‐defined three‐dimensional structures. Short synthetic peptide sequences corresponding to these bioactive protein surfaces do not form thermodynamically stable protein‐like structures in water. However, short peptides can be induced to fold into protein‐like bioactive conformations (strands, helices, turns) by cyclization, in conjunction with the use of other molecular constraints, that helps to fine‐tune three‐dimensional structure. Such constrained cyclic peptides can have protein‐like biological activities and potencies, enabling their uses as biological probes and leads to therapeutics, diagnostics and vaccines. This Review highlights examples of cyclic peptides that mimic three‐dimensional structures of strand, turn or helical segments of peptides and proteins, and identifies some additional restraints incorporated into natural product cyclic peptides and synthetic macrocyclic peptidomimetics that refine peptide structure and confer biological properties.     

Electron ionization mass spectra of organophosphorus compounds Part V: Mass fragmentation modes of some azolyl,azinyl, and azepinyl phosphonates as cyclic α-aminophosphonates

Mass fragmentation pathways of eight synthetic organophosphorus compounds, belonging to azolyl, azinyl, and azepinyl phosphonates as cyclic α-aminophosphonates 1a,b–4a,b were investigated by electron impact mass spectrometry with the aim of obtaining a better understanding of their fragmentation processes. The intensity of the recorded molecular ion peaks showed moderate values. Compounds 1a,b–3a,b have almost identical fragmentation routes via easy elimination of phosphonate groups which can be fragmented into the cation PO₂ as base peaks. On the contrary, compounds 4a,b started their fragmentation via removal of 4-chlorophenyl moieties.     

Electroreduction of cationic fluorene complexes of manganese

Using cyclic voltammetry method, the reduction of cationic η⁶-fluorene complexes of manganese [(η⁶-9-R-C₁₃H₉)Mn(CO)₂L]PF₆ (L = CO, R = H (1 ⁺); L = CO, R = CH₃ (2 ⁺); L = PⁿBu₃, R = H (3 ⁺); L = CO, R = ^tBu (4 ⁺)) is studied. It is shown that, depending on the nature of a substituent in the position 9 of the fluorene ligand, the reduction occurs either with the detachment of an H atom from position 9 to give zwitterion compounds (complexes 1 ^±, 2 ^±, 3 ^±) or with the attachment of an H atom into the coordinated ring of the fluorene ligand to given η⁵-cyclohexadienyl complex (η⁵-9-^tBu-C₁₃H₉)Mn(CO)₃ (5).     

Borylation of saturated heterocycles with several heteroatoms. (Review)

New examples of the borylation of a series of five-and six-membered saturated 1,3-and 1,3,2-heterocycles with the formation of cyclic boric esters are described. The probable mechanism of the reaction is discussed. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 643–654, May, 2006.     

Electrochemical behaviour of the LiF-(CaF2)-La2O3 system

The electrochemical behaviour of the LiF-La₂O₃ and LiF-CaF₂-La₂O₃ systems was investigated by means of cyclic voltammetry. Several types of working electrodes (spectrographic pure graphite, W, Mo, Ni, Cu) were used. It was found that chemical reactions take place in the system during the dissolution of lanthanum oxide. The reduction of lithium cations occurred at the most positive potential from the species formed in the melt on ‘inert’ cathodes (W, Mo). The reactive cathodes (Cu, Ni) allowed the lanthanum deposition with depolarisation.     

AFM studies of metal deposition: instantaneous nucleation and the growth of cobalt nanoparticles on boron-doped diamond electrodes.

In situ atomic force microscopy (AFM) is used to study the growth of cobalt nuclei on a boron doped diamond electrode under potentiostatic control. The rate of growth of the nuclei at the electrode surface is monitored using AFM as a function of time at different deposition potentials. The nucleation of cobalt nuclei is found to be "instantaneous" and the growth of the nuclei is shown to be kinetically rather than diffusionally controlled over periods of tens and hundreds of seconds. At very short times (<10 seconds) the kinetics of nucleation are apparent.