Perturbation theories for sine-Gordon soliton dynamics

Three recent perturbation assumptions for soliton dynamics on Josephson junctions are compared with direct numerical integrations of the perturbed sine-Gordon equation. The McLaughlin-Scott theory yields the better prediction of soliton transmission or pinning at a microshort in presence of loss and bias without or with surface resistance loss.     

A geometrical approach to the integrability of soliton equations

A separability criterion in one-degree-of-freedom dynamics, suitable for soliton equations, is given in terms of a geometrical structure on the phase manifold. For solitonic degrees of freedom, i.e., those corresponding to the discrete spectrum of the associated Lax operator, integrability is a priori proved.     

Enzymatic synthesis of caged NADP cofactors: aqueous NADP photorelease and optical properties

The synthesis of caged NADP analogues 18, 19, and 20 has been accomplished by utilizing the transglycosidase activity of solubilized NAD glycohydrolase (porcine brain) to incorporate caged nicotinamides 2, 3, and 4 into NADP. The synthesis of several nicotinamides modified at the carboxamide with o-nitrobenzyl photolabile groups is demonstrated as well as their potential for enzymatic transglycosidation. These results further demonstrate the feasibility of direct enzymatic transglycosidation of sterically hindered substrates into NAD(P), although high nicotinamide analogue water solubility was found to be a necessary trait for yield enhancement with certain analogues. Caged analogues were surveyed under aqueous conditions for net NADP photorelease, while the UV and fluorescent properties of both analogues and their photobyproducts were assessed for compatibility with systems that rely on optical monitoring of enzyme activity. A highly water-soluble alpha-methyl-o-nitrobenzyl group 8 was developed for the synthesis of 20 in order to enhance net NADP photorelease. Compound 20 demonstrated a high 75% net NADP photoreleased without substantial UV optical blackening or fluorescent byproducts. Analogues 18 and 19 were shown by ESI/MALDI-MS to photogenerate primarily adducts of NADP with deleterious UV and fluorescent properties. Our work stresses the superior release properties conferred by alpha-methyl substitution on aqueous carboxamide photorelease from o-nitrobenzyl compounds.     

Decomposition kinetic of a synthetic oil adsorbed on different silico-alumina

The thermooxidative degradation of three models of oily soils was studied under non-isothermal conditions, at heating rates of 5, 10, 15 and 20°C min⁻¹. Di-octyl-sebacate, as model for synthetic oil, was adsorbed on silica, alumina and silico-alumina, considered models for the inorganic micelle of a soil. For a kinetic analysis, the TG data were processed by three methods: Flynn-Wall-Ozawa, Friedman and NPK (Nomen-Sempere). The results indicate the NPK as the less speculative method that allows a separation of the elementary steps and at the same time a separation of the temperature, respective conversion dependent part of the reaction rate.     

Efficient and general synthesis of 5-(alkoxycarbonyl)methylene-3-oxazolines by palladium-catalyzed oxidative carbonylation of prop-2-ynylamides

A variety of prop-2-ynylamides have been carbonylated under oxidative conditions to give oxazolines, oxazolines with chelating groups, and bisoxazolines bearing an (alkoxycarbonyl)methylene chain at the 5 position in good yields. The cyclization-alkoxycarbonylation process was carried out in alcoholic media at 50-70 degrees C and under 24 bar pressure of 3:1 carbon monoxide/air in the presence of catalytic amounts of 10% Pd/C or PdI2 in conjunction with KI. Cyclization occurred by anti attack of an oxygen function on the palladium-coordinated triple bond, followed by stereospecific alkoxycarbonylation, strictly resulting in E-stereochemistry. The structures of representative oxazolines and bisoxazolines have been determined by X-ray diffraction analysis.     

Efficient synthesis of ureas by direct palladium-catalyzed oxidative carbonylation of amines

A general synthesis of symmetrically disubstituted ureas and trisubstituted ureas by direct Pd-catalyzed oxidative carbonylation of primary amines or of a mixture of a primary and a secondary amine, respectively, with unprecedented catalytic efficiencies for this kind of process, is reported. Reactions are carried out at 90-100 degrees C in DME as the solvent in the presence of PdI(2) in conjunction with an excess of KI as the catalytic system and under 20 atm of a 4:1 mixture of CO and air. In some cases, working in the presence of an excess of CO(2) (40 atm) in addition to CO and air (60 atm total) had a beneficial effect on substrate reactivity and product yield. Cyclic five-membered and six-membered ureas were easily formed from primary diamines. The methodology has been successfully applied to the synthesis of pharmacologically active ureas, such as those deriving from alpha-amino esters or urea NPY5RA-972, a potent antagonist of the neuropeptide Y5 receptor.     

Determination of rapamycin: quantification of the sodiated species by an ion trap mass spectrometer as an alternative to the ammoniated complex analysis by triple quadrupole

Rapamycin is a potent immunosuppressive drug capable of significantly reducing acute graft rejection in kidney, liver and heart transplant patients. Its immunosuppressive activity and adverse effects have been related to rapamycin concentration, and therapeutic drug monitoring of the drug is deemed appropriate. This work was aimed at developing a new quantification method based on the isolation of the [M+Na]+ ion as precursor and its further fragmentation through an ion trap mass spectrometer equipped with an electrospray ionization source. A limit of detection (LOD) of 0.7 ng/mL was obtained, while the lower limit of quantification (LLOQ) was 2.4 ng/mL. The accuracy and reproducibility of the responses were evaluated and compared with results obtained when the [M+NH4]+ ion was chosen as the precursor in a triple quadrupole mass spectrometer. In this case the LOD was 0.5 ng/mL and the LLOQ 1.7 ng/mL. Data showed that it would be possible to use the quantification of the sodiated species for the routine determination of rapamycin, as an alternative to the commonly adopted method based on the ammoniated complex.