A Co-Crystallised Cobalt(II) Cluster of Pyridinedicarboxylic Acid (PDC) as a Luminescent Material for Selective Sensing of Methanol

A luminescent Cobalt(II) co-crystal [Co₁₃(PDC)₁₆(H₂O)₂₄.7H₂O] 1 (where H₂PDC?=?2,6-pyridinedicarboxylic acid) have been prepared by oven-heating and slow evaporation of solvent. Single crystal X-ray diffraction (SCXRD) analysis revealed that 1 is a mixture of complexes that crystallizes in the triclinic space group P-1 and the geometry around the Co(II) ions is octahedral. The structure is extensively imbued with hydrogen bonding that helps in stabilizing the complex. Thermogravimetric analysis indicates that 1 is thermally stable up to 364 ^οC. The luminescence properties of 1 revealed a strong emission centered at 437 nm (λex?=?345 nm) assigned to ligand to metal charge transfer (LMCT). The luminescence sensing of 1 towards volatile organic molecules were also examined. However, 1 displayed a turn off towards methanol compared to other molecules with high quenching efficiency and low limit of detection (3.5?×?10^?4 vol%). The results show excellent selectively and high sensitivity. Powder X-ray diffraction studies revealed that the structural integrity of the complex was maintained after exposure to methanol vapour. Theoretical studies also revealed small binding energy (?413.2 au) and low energy gap (1.19) for 1-CH₃OH adduct.

     

Mutable objects in R

Programming paradigms help us understand the differences and similarities between fundamental choices in language design. This paper looks at R in the context of three paradigms of object oriented programming: mutable versus immutable objects, generic-function versus message-passing methods, and class-based versus prototype-based inheritance. The paper also describes a new OO package for R, mutatr, which provides mutable objects with message-passing methods and prototype-based inheritance. The mutatr package is available on CRAN.     

Experimental investigation of a two-qubit decoherence-free subspace

We thoroughly explore the phenomenon of a decoherence-free subspace (DFS) for two-qubit systems. Specifically, we both collectively and noncollectively decohere entangled polarization-encoded two-qubit states using thick birefringent crystals. These results characterize the basis-dependent effect of decoherence on the four Bell states, the robustness of the DFS state against perturbations in the assumption of collective decoherence, and the existence of a DFS for each type of stable noncollective decoherence. Finally, we investigate the effects of collective and noncollective dissipation.     

Effect ofV K centers on positron annihilation in KCl and Ag-doped KCl

Positron lifetime spectra have been measured at 77 K for KCl and Ag-doped KCl before and after x-irradiation at 77 K and after annealing at room temperature. Radiation at 77 K reduces the intensity of the intermediate lifetime (τ₂) component. Radiation-induced defects were monitored optically and by ESR. The experiment shows that the changes observed in the positron decay are associated with the presence ofV _K centers.     

Collagen as a model system to investigate the use of aspirin as an inhibitor of protein glycation and crosslinking

Aspirin has been shown to be a powerful inhibitor of post-Amadori Maillard reactions, although the exact mechanism of this action remains unclear. We have used corneal and scleral collagen as a model system: (i) to assess how aspirin, either alone or in combination with sugars, affects the surface charge distribution along the collagen fibrils; (ii) to see how sugars and/or aspirin affect the swelling properties of the cornea; and (iii) to see if sugars and/or aspirin change the distribution of water within the corneal stroma as the tissue swells. Charge changes were detected by examining changes in the uptake of phosphotungstate ions as seen in the electron microscope. Swelling was measured by monitoring the uptake of water as a function of swelling time, and water distribution was determined by using synchrotron X-ray diffraction to follow changes in the interfibrillar Bragg spacing as the cornea swells. Aspirin has a marked effect on the positive staining pattern of scleral collagen. This is different to the changes in stain uptake produced by glycation. Incubation with both sugars and aspirin showed that the sugar binding takes precedence over the effects of aspirin which, in turn, suggests that protein acetylation by aspirin is unlikely under these circumstances. However, aspirin completely suppresses corneal swelling. Even when the aspirin is removed, swelling in distilled water is reduced, and this is accompanied by changes in the water distribution. The results suggest that water is more evenly distributed in aspirin-treated corneas that are subsequently swollen than in swollen glycated corneas. Fructation, glucation and ribation on their own have little effect on the uptake of water as the cornea swells. This suggests that any sugar-derived crosslinks formed at this stage do not limit swelling.     

Use of chiral zwitterionic surfactants for enantiomeric resolutions by capillary electrophoresis

The enantiomeric resolution of 1,1'-binaphthyl-2,2'-diamine and Tr?ger's base was investigated using the commercially available zwitterionic surfactants 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulphonate (CHAPS) and 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulphonate (CHAPSO). Resolution of the weakly basic chiral probes was achieved using varying concentrations of surfactant, above their critical micellar concentrations, in a phosphate buffer (pH 2.5; 100 mM) to ensure ionisation of the analytes. Both CHAPS and CHAPSO were employed in the absence of additional coselectors or surfactants as sole micellar-forming agents. The addition of organic modifiers, methanol and acetonitrile (ACN), to the background electrolyte (BGE) was found to have a detrimental effect on enantioselectivity presumably by alteration of the phase polarity.     

Synthesis and biological activity of the hexalin moiety of compactin (ML-236B)

Alcohols14and21and the derived half-glutarate esters15and22have been prepared and evaluated as inhibitors of HMG CoA reductase. Compound14, the hexalin moiety of the natural fungal metabolite compactin (ML-236B) and compound21, its isomeric diene, have essentially no inhibitory properties. Compounds15and22show definite activity, although several orders of magnitude lower than that shown by compactin.