Seven-minute synthesis of pure C(s)-C60Cl6 from [60]fullerene and iodine monochloride: first IR, Raman, and mass spectra of 99 mol % C60Cl6

Three previously reported procedures for the synthesis of pure C(s)-C60Cl6 from C60 and ICl dissolved in benzene or 1,2-dichlorobenzene were shown to actually yield complex mixtures of products that contain, at best, 54-80% C(s)-C60Cl6 based on HPLC integrated intensities. MALDI mass spectrometry was used for the first time to identify other components of the reaction mixtures. An improved synthetic procedure was developed for the synthesis of about 150 mg batches of chlorofullerenes containing 90% C(s)-C60Cl6 based on HPLC intensities. The optimum reaction time was decreased from several days to seven minutes. Small amounts of the product were purified by HPLC (toluene eluent) to 99% purity. The pure compound C(s)-C60Cl6 is stable for at least three months as a solvent-free powder at 25 degrees C. The Raman, far-IR, and MALDI mass spectra of pure C(s)-C60Cl6 are reported for the first time. The Raman and far-IR spectra, the first reported for any C60Cl(n) chlorofullerene, were used to carry out a vibrational analysis of C(s)-C60Cl6 at the DFT level of theory.     

Stieltjes polynomials and Gauss-Kronrod quadrature formulae for measures induced by Chebyshev polynomials

Given a fixedn1, and a (monic) orthogonal polynomial _n (·)= _n (·;d) relative to a positive measured on the interval [a, b], one can define the nonnegative measure , to which correspond the (monic) orthogonal polynomials . The coefficients in the three-term recurrence relation for , whend is a Chebyshev measure of any of the four kinds, were obtained analytically in closed form by Gautschi and Li. Here, we give explicit formulae for the Stieltjes polynomials whend is any of the four Chebyshev measures. In addition, we show that the corresponding Gauss-Kronrod quadrature formulae for each of these , based on the zeros of and , have all the desirable properties of the interlacing of nodes, their inclusion in [–1, 1], and the positivity of all quadrature weights. Exceptions occur only for the Chebyshev measured of the third or fourth kind andn even, in which case the inclusion property fails. The precise degree of exactness for each of these formulae is also determined.     

Reactions of peroxyacetyl radicals with reduced sulfur compounds

Summary The reaction of peroxyacetyl radicals with reduced sulfur compounds was studied at 55°C in N₂ at 1 000 mbar total pressure. The radicals were generated in equilibrium with peroxyacetyl nitrate and NO₂ in large excess. The pseudo first order decay ofPAN was measured in the absence and presence of several 100 ppm CH₃SH, C₂H₅SH,n-C₄H₉SH, (CH₃)₂S, and (CH₃S)₂. Computer simulations yielded the following rate constants of peroxyacetyl radicals with the above mentioned sulfur compounds: 3.7, 2.8, 13.0, 0.9, and 1.8·10^–16 cm³/s, respectively. An electron capturing compound of the thiols with NO₂ was observed.

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Reaktionen von Peroxyacetylradikalen mit reduzierten Schwefelverbindungen

Zusammenfassung Die Reaktionen von Peroxyacetylradikalen mit reduzierten Schwefelverbindungen wurden bei 55°C in NO₂ bei einem Totaldruck von 1 000 mbar untersucht. Die Radikale wurden im Gleichgewicht mit Peroxyacetylnitrat und NO₂ in großem Überschuß generiert. Der nach erster Ordnung verlaufende Zerfall vonPAN wurde in Abwesenheit und Anwesenheit und von einigen ppm CH₃SH, C₂H₅SH,n-C₄H₉SH, (CH₃)₂S und (CH₃S)₂ gemessen. Computersimulierung der Geschwindigkeitskonstanten für die Peroxyacetylradikale ergab mit den genannten Schwefelverbindungen 3.7, 2.8, 13.0, 0.9 und 1.8·10^–16 ch³/s. Eine elektronenfangende Verbindung der Thiole mit NO₂ wurde beobachtet.

     

Steroidal imidazopyridines and lactam imidazopyridines

Condensation of 17β-acetoxy-2α-bromo-5α-androstan-3-one with unsubstituted and substituted amino-pyridines, gives the corresponding 17β-acetoxy-5α-androstanimidazo[1,2-a]pyridines. Treatment of 16α-bromo-3-aza-A-homo-4α-androsten-4,17-dione with 2-aminopyridine or methyl-2-aminopyridine produces the corresponding 3-aza-A-homo-4α-androsten[16,17:2′,3′]imidazo[1,2-a]pyridines. Similarly, from 2α-bromo-17β-acetamido-5α-androstan-3-one and methylaminopyridine the 17β-acetamido-5α-androstan[2,3:2′,3′]imidazo[1,2-a]methylpyridine has been obtained. The structure of the compounds was apparent from their chemical properties and spectral data (ir, uv and nmr).     

Home-built integrated microarray system (IMAS). A three-laser confocal fluorescence scanner coupled with a microarray printer

Microarray technology covers the urgent need to exploit the accumulated genetic information from large-scale sequencing projects and facilitate investigations on a genome-wide scale. Although most applications focus on DNA microarrays, the technology has expanded to microarrays of proteins, peptides, carbohydrates, and small molecules aiming either at detection/quantification of biomolecules or investigation of biomolecular interactions in a massively parallel manner. Microarray experiments require two specialized instruments: An arrayer (or printer), for construction of microarrays, and a readout instrument (scanner). We have designed, constructed, and characterized the first integrated microarray system (IMAS) that combines the functions of a microarrayer and a three-laser confocal fluorescence scanner into a single instrument and provides excellent flexibility for the researcher. The three-axis robotic system that moves the printing head carrying multiple pins for arraying is also used for moving the microarray slide in front of a stationary optical system during scanning. Since the translation stages are the most expensive and crucial components of microarray printers and scanners, the proposed design reduces considerably the cost of the instrument and enhances remarkably its operative flexibility. Experiments were carried out at resolutions of 2.5, 5, 10, and 20 μm. The scanner detects 0.128 nmol L⁻¹ carboxyfluorescein (spots with diameters of 70 μm) corresponding to 1.8 molecules μm⁻². The linear range extends over 3.5 orders of magnitude (R ² = 0.997) and the dynamic range covers almost five orders of magnitude. DNA microarray model experiments were carried out, including staining with SYBR Green I and hybridization with oligonucleotides labeled with the fluorescent dyes Alexa 488, Alexa 594, and Alexa 633. Figure Lay-out of the home-built integrated microarray system (IMAS). For the first time, the functions of a microarrayer (printer) and a three-laser confocal fluorescence scanner are combined into a single instrument. The three-axis robotic system that moves the printing head for arraying is also used to move the microarray slide in front of a stationary optical system during scanning. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

pH/Thermosensitive Hydrogels Formed at Low pH by a PMMA‐PAA‐P2VP‐PAA‐PMMA Pentablock Terpolymer

A poly(methyl methacrylate)‐block‐poly(acrylic acid)‐block‐poly(2‐vinyl pyridine)‐block‐poly(acrylic acid)‐block‐poly(methyl methacrylate) (PMMA‐PAA‐P2VP‐PAA‐PMMA), pentablock terpolymer has been synthesized by anionic polymerization with sequential addition of monomers and studied in aqueous media at low pH. The system exhibits combined properties and adopts the behavior of ‘telechelic’ polyelectrolytes and that of double hydrophilic polyampholytes. This complex behavior leads to the pentablock terpolymer forming a pH and temperature sensitive reversible hydrogel at very low polymer concentration.

     

Bivariate Distributions with Pearson Type VII Conditionals

In this article the most general class of bivariate distributions such that both conditional densities are Pearson Type VII, with fixed shape parameter, is fully characterized. Some of its properties and relations with other distributions are explored. The estimation of parameters is considered by the methods of maximum likelihood and pseudolikelihood and a method for random variate generation is presented along with a simulation experiment. Bivariate and multivariate extensions of the Pearson Type VII conditionals distribution are also discussed.     

Preface to the special issue NODYCON 2021, Second International Nonlinear Dynamics Conference,Feb. 16–19, 2021

Nonlinear Dynamics -     

Dual-cardiac marker capillary waveguide fluoroimmunosensor based on tyramide signal amplification

The early diagnosis of acute myocardial infarction requires the determination of several markers in serum shortly after its incidence. The markers most widely employed are the isoenzyme MB of creatine kinase (CK-MB) and the cardiac troponin I (cTnI). In the present work, a capillary waveguide fluoroimmunosensor for fast and highly sensitive simultaneous determination of these markers in serum samples is demonstrated. The dual-analyte immunosensor was realized using glass capillaries internally modified with an ultrathin poly(dimethylsiloxane) film by creating discrete bands of analyte-specific antibodies. The capillary was then filled with a mixture of sample and biotinylated detection antibodies followed by reaction with streptavidin–horseradish peroxidase and incubation with a fluorescently labeled tyramide derivative to accumulate fluorescent labels onto immunoreaction bands. Upon scanning the capillary with a laser beam, part of the emitted fluorescence is trapped and waveguided through the capillary wall to a photomultiplier placed on one of its ends. The employment of tyramide signal amplification provided detection limits of 0.2 and 0.5 ng/mL for cTnI and CK-MB, respectively, in a total assay time of 30 min compared to 0.8 and 0.6 ng/mL obtained for the corresponding assays when the conventional fluorescent label R-phycoerythrin was used in a 65-min assay. In addition, the proposed immunosensor provided accurate and repeatable measurements (intra-assay and interassay coefficients of variation lower than 10%), and the values determined in serum samples were in good agreement with those obtained with commercially available enzyme immunoassays. Thus, the proposed capillary waveguide fluoroimmunosensor has all the required characteristics for fast and reliable diagnosis of acute myocardial infarction.      

Tar analysis from biomass gasification by means of online fluorescence spectroscopy

Optical methods in gas analysis are very valuable mainly due to their non-intrusive character. That gives the possibility to use them for in-situ or online measurements with only optical intervention in the measurement volume. In processes like the gasification of biomass, it is of high importance to monitor the gas quality in order to use the product gas in proper machines for energy production following the restrictions in the gas composition but also improving its quality, which leads to high efficient systems. One of the main problems in the biomass gasification process is the formation of tars. These higher hydrocarbons can lead to problems in the operation of the energy system. Up to date, the state of the art method used widely for the determination of tars is a standardized offline measurement system, the so-called “Tar Protocol”. The aim of this work is to describe an innovative, online, optical method for determining the tar content of the product gas by means of fluorescence spectroscopy. This method uses optical sources and detectors that can be found in the market at low cost and therefore it is very attractive, especially for industrial applications where cost efficiency followed by medium to high precision are of high importance.