A novel reagent combination for the oxidation of highly electron deficient pyridines to N-oxides: trifluoromethanesulfonic anhydride/sodium percarbonate

A novel reagent combination, Tf₂O/Na₂CO₃·1.5H₂O₂, has been developed for the oxidation of highly electron deficient pyridines to their corresponding N-oxides. The N-oxidation reaction, utilizing the in situ generated peracid, proceeds under mild conditions that allow for a number of functional groups and substitution patterns on the pyridine ring.     

Accurate determination of an immunosuppressant in stented swine tissues with LC–MS/MS

During stent development, accurate monitoring of the drug concentration in animal tissues can provide critical information on how the drug is released into the circulation and the surrounding tissues. To establish the relationship between the drug concentration and the distance from the stent to the target tissue, a comprehensive strategy was developed for sample collection, sample homogenization and sample storage as well as sample analysis. This strategy was developed with the analytical chemists and animal surgical specialists working together as a team. The optimized sampling process was designed to yield a representative sample, appropriately located and of an appropriate size. The sampling process was also designed to eliminate the potential for carryover and cross-contamination. During sample processing, the analyte solution was spiked into blank tissues using a sharp needle and a gas-tight syringe to prepare tissue quality control samples. These tissue quality controls were then used to evaluate the stability of the drug in solid tissue and homogenate, the homogenization carryover, the cross-contamination and the recovery of the drug during method validation and to monitor the overall process of drug analysis of the swine tissues. This thorough strategy has been applied to the accurate determination of zotarolimus in swine tissues for regulated toxicology studies. The entire process was controlled, including precise tissue sampling, compound-based tissue homogenization, method validation, and the application of the method to regulated toxicokinetics studies. The results demonstrate that analytical chemistry concepts can be successfully integrated into toxicokinetics studies in order to collect precise samples and obtain meaningful results. The strategy can be applied to similar toxicokinetics studies of locally administrated drugs in tissues.     

Lateralization of acoustic signals by dichotically listening budgerigars (Melopsittacus undulatus)

Sound localization allows humans and animals to determine the direction of objects to seek or avoid and indicates the appropriate position to direct visual attention. Interaural time differences (ITDs) and interaural level differences (ILDs) are two primary cues that humans use to localize or lateralize sound sources. There is limited information about behavioral cue sensitivity in animals, especially animals with poor sound localization acuity and small heads, like budgerigars. ITD and ILD thresholds were measured behaviorally in dichotically listening budgerigars equipped with headphones in an identification task. Budgerigars were less sensitive than humans and cats, and more similar to rabbits, barn owls, and monkeys, in their abilities to lateralize dichotic signals. Threshold ITDs were relatively constant for pure tones below 4 kHz, and were immeasurable at higher frequencies. Threshold ILDs were relatively constant over a wide range of frequencies, similar to humans. Thresholds in both experiments were best for broadband noise stimuli. These lateralization results are generally consistent with the free field localization abilities of these birds, and add support to the idea that budgerigars may be able to enhance their cues to directional hearing (e.g., via connected interaural pathways) beyond what would be expected based on head size.     

A combined SAMO-ZDO method for the evaluation of ionization potentials

A scheme for the ab initio calculation of vertical ionization potentials without the necessity to compute two-electron repulsion integrals is discussed. The method employs the simulated ab initio molecular orbital (SAMO) method to generate Koopman's theorem eigenvalues. These are then corrected for the change in relaxation and correlation effects due to ionization by a Green's function perturbation scheme, in which all necessary integrals are evaluated using the zero differential overlap (ZDO) approximations, in this case the complete neglect of differential overlap (CNDO) method.     

1-alkoxyallene as an effective precursor for regio- and stereocontrolled allylation reactions with aliphatic aldehydes via bis-stannylation

Bis-stannylation of 1-(methoxy)methoxyallene yields (E)-(3-(methoxymethoxy)prop-2-ene-1,2-diyl) bis-tributylstannane (2) as a highly reactive allylation reagent. Stereoselective reactions of functionalized stannane 2 with a variety of aldehydes provide good yields of 1,2-diol derivatives. Reactions with alpha-alkoxyaldehydes proceed with chelation-controlled addition to afford efficient constructions of 3,4-anti-4,5-syn-relationships in stereotriads bearing three differentiated oxygen (alkoxy and hydroxy) substituents. Mechanistic considerations are presented, and derivatives for NMR experiments support the stereochemical assignments. An X-ray diffraction study is included.     

Nanoparticle Modified Cellulose Fibres

Summary: The dissolution of cellulose in N-methylmorpholine-N-oxide monohydrate exhibits a remarkable acceptance towards well ground organic or inorganic additives up to high concentrations. Particle sizes generally in the lower micrometer range have been the most common features of all additives applied up to now. With the assumption, that it would succeed to exploit the capabilities to a surface and matrix manipulation already described for combinations of synthetic fibres and polymer bulk materials for cellulose as well, then very interesting opportunities for the development of shaped cellulosic bodies would result that possess improved product characteristics. Inorganic, hydrophilic nanoclays and different organic modified nanoparticles of various manufacturers were chosen for the investigation. The effect of the different nanoparticle types on the matrix structure after the incorporation was determined by means of X-ray wide angle scattering. Nanoadditives did not influence the structural formation of cellulose shapes significantly. Compared to a film forming process, in case of fibre spinning it was found that the nanoclays obviously underwent a preferred orientation as a result of the solvent extraction after a dry-wet extrusion process.