Electronic phase separation in correlated oxides: the phenomenon, its present status and future prospects.

Many transition metal oxide materials of high chemical purity are not necessarily monophasic. Thus, single crystals of chemically pure rare earth manganites and cobaltates of the general formula Ln(1-x)A(x)MO(3) (Ln=rare earth metal, A=alkaline earth metal, M=Mn, Co) exhibit the phenomenon of electronic phase separation wherein "phases" of different electronic and magnetic properties coexist. Such phase separation, the length scale of which can vary anywhere between a few nanometers to microns, gives distinct signatures in X-ray and neutron diffraction patterns, electrical and magnetic properties, as well as in NMR and other spectroscopies. While the probe one employs to investigate electronic phase separation depends on the length scale, it is noteworthy that direct imaging of the inhomogeneities has been accomplished. Some understanding of this phenomenon has been possible on the basis of some of the theoretical models, but we are far from unraveling the varied aspects of this new phenomenon. Herein, we present the highlights of experimental techniques and theoretical approaches, and comment on the future outlook for this fascinating phenomenon.     

High-performance liquid chromatographic method for determination of reversible isomers of SU5416

SU5416 shows light-induced reversible geometric isomerism. A simple, reliable, isocratic HPLC method using an UV-vis detector at lambda(425nm) was developed. The method provides efficient (R(S)=3.5) analysis of the two isomers with retention of the isomeric integrity. Additionally, the method has linearity over a wide range (50-1000microg/mL, r(2)=0.99), is accurate (99-102%, RSD <4%), and reproducible (RSD <0.8%). The method was used for analyzing pharmaceutical samples and understanding the kinetics of SU5416 isomers in methanol. In addition, this method can be used for quantifying the non-isolatable E-isomer.     

Nucleophilic additions of trimethylsilyl cyanide to cyclic oxocarbenium ions: evidence for the loss of stereoselectivity at the limits of diffusion control

The limitations of stereoelectronic models in assessing the stereoselective nucleophilic substitution reactions of cyclic oxocarbenium ions at high reaction rates are discussed. Evidence is provided suggesting that the diastereoselectivity of nucleophilic substitution reactions is attenuated at the limits of diffusion control. The low diastereoselectivities observed in the reactions of trimethylsilyl cyanide with five- and six-membered ring oxocarbenium ions are attributed to the high reactivity of the nucleophile and its reactions with these electrophiles at diffusion control rates.     

Supercontinuum generation in a Bragg fiber：a novel proposal

Nonlinear optical effects such as self-phase modula-tion,four-wave mixing,cross-phase modulation,sti mula-ted Raman scattering,together with appropriate tempo-ral dispersion profileinan optical fiber couldsignificant-ly broaden ( >100 nm) the spectrumof a…