Linearization of holomorphic germs with quasi-Brjuno fixed points

Let f be a germ of holomorphic diffeomorphism of mathbb Cⁿ{mathbb {C}^{n}} fixing the origin O, with d f _O diagonalizable. We prove that, under certain arithmetic conditions on the eigenvalues of d f _O and some restrictions on the resonances, f is locally holomorphically linearizable if and only if there exists a particular f -invariant complex manifold. Most of the classical linearization results can be obtained as corollaries of our result.     

Characterization of Cyclic N-Acyliminium Ions by Infrared Ion Spectroscopy

N-Acyliminium ions are highly reactive intermediates that are important for creating CC-bonds adjacent to nitrogen atoms. Here we report the characterization of cyclic N-acyliminium ions in the gas phase, generated by collision induced dissociation tandem mass spectrometry followed by infrared ion spectroscopy using the FELIX infrared free electron laser. Comparison of DFT calculated spectra with the experimentally observed IR spectra provided valuable insights in the conformations of the N-acyliminium ions.     

Spectrofluorimetric Method for Determination and Validation of Cefixime in Pharmaceutical Preparations Through Derivatization with 2-Cyanoacetamide

A simple, sensitive and accurate method has been developed for spectrofluorimetric determination of cefixime in pure form and pharmaceutical preparations. The method is based on the reaction of cefixime with 2-cyanoacetamide in the presence of 21% ammonia at 100 °C. The fluorescent reaction product showed maximum fluorescence intensity at λ 378 nm after excitation at λ 330 nm. The factors affecting the derivatization reaction were carefully studied and optimized. The fluorescence intensity versus concentration plot was rectilinear over the range of 0.02 to 4 μg mL⁻¹ with correlation coefficient of 0.99036. The limit of detection (LOD) and limit of quantification (LOQ) was found to be 2.95 ng mL⁻¹ and 9.84 ng mL⁻¹, respectively. The proposed method was validated statistically and through recovery studies. The method was successfully applied for the determination of cefixime in pure and dosage form with percent recoveries from 98.117% to 100.38%. The results obtained from the proposed method have been compared with the official HPLC method and good agreement was found between them.     

Backward iteration in strongly convex domains

We prove that a backward orbit with bounded Kobayashi step for a hyperbolic, parabolic or strongly elliptic holomorphic self-map of a bounded strongly convex C² domain in Cd necessarily converges to a repelling or parabolic boundary fixed point, generalizing previous results obtained by Poggi-Corradini in the unit disk and by Ostapyuk in the unit ball of Cd.     

Biocatalytic organic synthesis of optically pure (S)-scoulerine and berbine and benzylisoquinoline alkaloids

A chemoenzymatic approach for the asymmetric total synthesis of the title compounds is described that employs an enantioselective oxidative C-C bond formation catalyzed by berberine bridge enzyme (BBE) in the asymmetric key step. This unique reaction yielded enantiomerically pure (R)-benzylisoquinoline derivatives and (S)-berbines such as the natural product (S)-scoulerine, a sedative and muscle relaxing agent. The racemic substrates rac-1 required for the biotransformation were prepared in 4-8 linear steps using either a Bischler-Napieralski cyclization or a C1-Cα alkylation approach. The chemoenzymatic synthesis was applied to the preparation of fourteen enantiomerically pure alkaloids, including the natural products (S)-scoulerine and (R)-reticuline, and gave overall yields of up to 20% over 5-9 linear steps.     

Spectrofluorimetric determination of cephradine in commercial formulation using ethylacetoacetate-formaldehyde as fluorogenic agent

A simple, precise and sensitive spectrofluorimetric method was developed for the determination of cephradine in pharmaceutical formulations. The method is based on reaction of cephradine with ethyl acetoacetate (EAA) in the presence of formaldehyde in acidic media. The fluorescence intensity of the resultant fluorescent derivative was measured at 443 nm after excitation at 350 nm. The effects of various experimental parameters on the formation of the fluorescent product were studied and optimized. A linear relationship between concentration of cephradine and fluorescence intensity was found over the range of 0.1–5.0 μg/mL. The limit of detection and quantification were calculated an found 1.09 × 10^?2 ± 3.64 × 10^?3 μg/mL and 3.64 × 10^?2 ± 3.64 × 10^?3 μg/mL, respectively and with relative standard deviation (RSD) 4.14%. Accuracy of the method was checked by standard addition method and applied to four different commercial formulations. The percentage recovery was found in the range of 97.03 to 103.80% for Velora suspension, 98.16 to 102.90% for velocef injection, 99.00 to 108.10% for Velora capsule and 99.06 to 104.90% for Cefradin capsule. The good percentage recoveries from all samples indicated that there were no interferences from the common excipients of formulations. The proposed method was successfully applied to the analysis of commercial suspension, capsule and injections. The result obtained by the proposed method was statistically validated with reference HPLC method. No significant difference in the results of the two methods was found regarding accuracy and precision using Student’s t-test and the variance ratio F-test.     

Effect of annealing on the supercapacitor performance of CuO-PAA/CNT films

We report the synthesis of CuO-poly(acrylic) acid/CNT hybrid thin films by a cost-effective spin-coating technique for supercapacitor application. Hybrid films were annealed at 300, 400, and 500 °C to study its effect on the supercapacitor behavior. X-ray photoelectron spectroscopy and Fourier transform-infrared spectroscopy techniques were used for the phase identification and determination of the organic component in the hybrid films, respectively. Surface morphology of the films was examined by scanning electron microscopy and revealed the novel ring-like structures. The average diameter of the ring changes from 0.5 to 1.2 μm with increase in annealing temperature. Cyclic voltammetry is employed to estimate the specific capacitance (C _sp) of the films in 1 M H₂SO₄ electrolyte. It is observed that the C _sp increases from 188 to 258 Fg⁻¹ with increase in annealing temperature.     

Spectrophotometric determination of methylamine moiety containing pesticides using ninhydrine reagent

A spectrophotometric method has been proposed for the determination of pesticides containing methylamine moiety. These pesticides afforded methylamine upon alkaline hydrolysis, which was subsequently reacted with ninhydrin in the presence of pyridine. The absorbance of the resulting blue-purple product was measured spectrophotometrically at 570 nm. The Beer??s law showed a linear relationship between absorbance and concentration of the pesticide in the range 0.04?C5.0 ??g/mL. The limit of detection and limit of quantification were 0.012 and 0.02 ??g/mL, respectively. The repeatability was 0.22 expressed as RSD. The performance of this newly developed method was compared with the established spectrophotometric methods for the determination of these pesticides. The method has been successfully applied to the evaluation of these pesticides in commercial pesticide formulation and to the determination of monocrotophos in fruit samples.