Optimal distillation of a greenberger-horne-zeilinger state

We present the optimal local protocol to distill a Greenberger-Horne-Zeilinger state from a single copy of any pure state of three qubits.     

Enhanced Karush–Kuhn–Tucker Conditions for Mathematical Programs with Equilibrium Constraints

In this paper, we study necessary optimality conditions for nonsmooth mathematical programs with equilibrium constraints. We first show that, unlike the smooth case, the mathematical program with equilibrium constraints linear independent constraint qualification is not a constraint qualification for the strong stationary condition when the objective function is nonsmooth. We then focus on the study of the enhanced version of the Mordukhovich stationary condition, which is a weaker optimality condition than the strong stationary condition. We introduce the quasi-normality and several other new constraint qualifications and show that the enhanced Mordukhovich stationary condition holds under them. Finally, we prove that quasi-normality with regularity implies the existence of a local error bound.     

Studies on pyridazine azide cyclisation reactions

Reaction of sodium azide with 4-methyl-3,5,6-tribromopyridazine results in the formation of 3,5,6-triazide intermediate which could cyclise to give two possible bicyclic products while ab initio calculations show that the formation of a tricyclic compound is extremely energetically unfavourable. However, experimentally, only one major product is isolated. The structure of this unstable product has been conclusively established by X-ray crystallography as 3,5-diazido-4-methyl[1,5-b]tetrazolopyridazine confirming theoretical predictions.     

Elemental mapping and quantitative analysis of Cu, Zn, and Fe in rat brain sections by laser ablation ICP-MS

This report details the application of laser ablation quadrupole ICP-MS for the (multi)elemental mapping of 100-μm-thick sections of rat brain. The laser spot size used was 60 μm, and the laser scan speed was 120 μm s⁻¹. The analysis was relatively rapid, allowing mapping of a whole brain thin section (≈1 cm²) in about 2 h. Furthermore, the method was amenable to multi-element data collection including the physiologically important elements P and S and afforded sub μg g⁻¹ detection limits for the important trace elements Cu and Zn. Calibrations were performed with pressed pellets of biological certified reference materials, and the elemental distributions and concentrations of Cu, Zn, and Fe were determined in whole rat brain sections. The distributions and concentration ranges for these elements were consistent with previous studies and demonstrate the utility of this technique for rapid mapping of brain thin sections.     

Antiaromaticity in relation to 1,3,5,7-cyclooctatetraene structures

An isodesmic energy analysis has been carried out at the MP 2/6–31G *//HF /3–21G level for the nonplanar ground state ( 1 ) of 1,3,5,7-cyclooctateraene and for two planar forms, one having complete π delocalization ( 2 ) and the other having alternating single and double bonds ( 3 ). 1 is found to have a considerable degree of stabilization, which is attributed to limited π delocalization. The polyene 3 is the more stable of the two planar forms; it is a transition state in the inversion between two possible nonplanar structures. 2 is found to be a triplet at the Hartree–Fock level and is a critical point on an alternate pathway between the two possible arrangements of alternating single and double bonds in 3 . Both 2 and 3 have negative isodesmic energies, indicating the presence of stabilizing factors. Our results for 3 show that an “antiaromatic” system need not necessarily show a net destabilization. © 1994 John Wiley & Sons, Inc.     

A Poly(cobaloxime)/Carbon Nanotube Electrode: Freestanding Buckypaper with Polymer‐Enhanced H2‐Evolution Performance

A freestanding H₂‐evolution electrode consisting of a copolymer‐embedded cobaloxime integrated into a multiwall carbon nanotube matrix by π–π interactions is reported. This electrode is straightforward to assemble and displays high activity towards hydrogen evolution in near‐neutral pH solution under inert and aerobic conditions, with a cobalt‐based turnover number (TON_Co) of up to 420. An analogous electrode with a monomeric cobaloxime showed less activity with a TON_Co of only 80. These results suggest that, in addition to the high surface area of the porous network of the buckypaper, the polymeric scaffold provides a stabilizing environment to the catalyst, leading to further enhancement in catalytic performance. We have therefore established that the use of a multifunctional copolymeric architecture is a viable strategy to enhance the performance of molecular electrocatalysts.     

Synthesis and properties of alkylated imidazoles

Alkylation of 4(5)-nitroimidazole-5(4)-sulfonamide with benzyl bromide occurred on both ring nitrogens. The structures of the products could be assigned by comparison of the chemical shifts of the sulfonamide hydrogens in the nmr spectra with those of the isomeric methyl derivatives, which were prepared by differing routes. Uv and nmr spectral data are reported for a number of bromo-, nitro-, mercapto-, sulfamyl- and amino- substituted imidazoles as well as for both of the isomeric methylated derivatives of the series.     

Halichonadins G-J, new sesquiterpenoids from a sponge Halichondria sp.

Three new dimeric sesquiterpenoids, halichonadins G-I (1-3), and one new eudesmane sesquiterpenoid possessing a 1-phenethyl urea moiety, halichonadin J (4), were isolated from a marine sponge Halichondria sp. Halichonadins G (1) and H (2) are homo-dimers of eudesmane sesquiterpenoid, linked through a methyl 2-{1-(2-amino-2-oxoethyl)ureido}acetate fragment and a 2-hydroxymalonamide fragment, respectively, while halichonadin I (3) is a new hetero-dimer of eudesmane sesquiterpenoid linked through a urea fragment. The structures of 1-4 were elucidated on the basis of spectroscopic data.     

Molecular surface electrostatic potentials of anticonvulsant drugs

The computed molecular surface electrostatic potentials of a group of anticonvulsants of various chemical types were investigated with the objective of identifying common features that may be related to their activities. The calculations were carried out with the density functional B3P86/6-31G* procedure, using HF/STO-3G*-optimized geometries. Analysis of several statistically based properties of the surface potentials indicates that the negative regions are of primary importance and that an optimum intermediate level of local polarity, or internal charge separation, is required. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 70: 1137–1143, 1998     

Enhanced detonation sensitivities of silicon analogs of PETN: reaction force analysis and the role of σ–hole interactions

Si-pentaerythritol tetranitrate (PETN), Si[CH₂ONO₂]₄, is a silicon analog of the widely used explosive PETN, C[CH₂ONO₂]₄. Si-PETN is extremely sensitive to impact, much more so than PETN. This was attributed by Liu et al. to Si-PETN having a much lower activation barrier to decomposition, via a facile rearrangement that is not as readily available to PETN, and which releases considerable energy that can promote further steps. We have investigated computationally why the barrier to the rearrangement is so much lower for Si-PETN than for PETN, using 5, (H₃C)₃C–CH₂ONO₂, and 6, (H₃C)₃Si–CH₂ONO₂, as models for PETN and Si-PETN. Reaction force analysis shows that most of the difference between the rearrangement barriers for 5 and 6 comes about in the initial (reactant) stages of the processes, in which 6 benefits from a 1,3 electrostatic interaction involving a positive σ–hole on the silicon and the negative linking oxygen. The analogous interaction is weaker in 5, since the central carbon does not have positive σ–holes; furthermore, this carbon is less able than silicon to temporarily expand its coordination sphere. A similar explanation involving a positive silicon σ–hole and a linking oxygen is proposed for Si-PETN. The greater exothermicity of the rearrangement of 6 (and also Si-PETN) can be rationalized, following Liu et al., in terms of the formation of the strong Si–O bond.