The Rearrangement of 3, 4-Dihydro-2, 2-Dimethy-2H, 5H-Pyrano [2, 3-b][1] Benzopyran-5-Ones With DDQ

A novel rearrangement of 3, 4-dihydro-2, 2-dimethyl-2H, 5H-pyrano [2, 3-b] [1] benzopyran-5-ones (dihydropyranochromones) has been observed during the dehydrogenation with DDQ. The products obtained are found to be 2, 2-dimethyl-2H, 5H-pyrano [3, 2-c] [1] benzopyran-5-ones (pyranocoumarins).     

Synthesis of obtusinin and 7-(3′-hydroxymethylbut-2′-enyloxy)-6-methoxy-2H-1-benzopyran-2-one

Obtusinin (1) has been synthesised by the reaction of 6-methoxy-7-(3-methylbut-2-enyloxy)-2H-1-benzopyran-2-one (3) with OsO₄. Synthesis of 7-(3-hydroxymethylbut-2-enyloxy)-6-methoxy-2H-1-benzopyran-2-one (2) has been achieved by the regiospecific oxidation of3 with SeO₂ followed by reduction of the formed aldehyde with KBH₄.

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Synthese von Obtusinin und 7-(3-Hydroxymethylbut-2-enyloxy)-6-methoxy-2H-1-benzopyran-2-on

Zusammenfassung Obtusinin (1) wurde über 6-Methoxy-7-(3-methylbut-2-enyloxy)-2H-1-benzopyran-2-on (3) mit OsO₄ synthetisiert. Die Darstellung von 7-(3-Hydroxymethylbut-2-enyloxy)-6-methoxy-2H-1-benzopyran-2-on (2) wurde mittels regioselektiver Oxidation von3 mit SeO₂, gefolgt von Reduktion des gebildeten Aldehyds mit KBH₄, bewerkstelligt.

     

Partial molar heat capacities and volumes of transfer of nucleic acid bases,nucleosides and nucleotides from water to aqueous solutions of sodium and calcium chloride at 25°C

Partial molar heat capacities and volumes of some nucleic acid bases, nucleosides and nucleotides have been measured in 1m aqueous NaCl and CaCl₂ solutions using Picker flow microcalorimeter and a vibrating tube digital densimeter. The partial molar heat capacities of transfer and volumes of transfer from water to the electrolyte solutions were calculated using earlier data for these compounds in water. The values of these transfer parameters are positive. The higher values for transfer to aqueous CaCl₂ solutions reflect the stronger interactions of the constituents of the nucleic acids with Ca⁺² ions than with the Na⁺ ions.     

Electrical Resistivity of Na-K Binary Liquid Alloy Using Ab-Initio Pseudopotentials

The study of electrical resistivity of simple binary liquid alloy Na-K is presented as a function of concentration. Hard sphere diameters of sodium （Na） and potassium （K） are obtained through the inter ionic pair potentials evaluated using Troullier and Martins ab-initio pseudopotentials, which have been used to calculate partial structure factors S（q）. Tile Ziman formula for calculating resistivity of binary liquid alloys has been used. Form factors are calculated using ab-initio pseudopotentials. Tile results suggest that the first principle approach for calculating pseudopotentials with in the frame work of Ziman formalism is quite successful in explaining the electrical resistivity data of compound forming binary liquid alloys.     

Development and validation of a stability-indicating high-performance liquid chromatography method for the simultaneous determination of albuterol, budesonide, and ipratropium bromide in compounded nebulizer solutions

In recent years, there has been a large increase in the use of pharmaceutical compounding to prepare medications that are not commercially available. The treatment of asthma typically includes the use of albuterol (ALB), ipratropium bromide (IPB), and/or budesonide (BUD) nebulizer solutions. There is currently no commercially available nebulizer solution containing all three of these compounds, and patients must rely on often-unregulated compounding. There is a distinct need for methodologies that can be used to analyze compounded formulations to ensure patient safety. We report an HPLC-UV method to separate and quantitate ALB, IPB, and BUD in nebulizer solutions. The method used a gradient elution to achieve separation via an RP C18 column. The method was validated, showed good selectivity, and was linear over several orders of magnitude. The method was applied to the analysis of nebulizer solutions and determination of their storage stability. Significant ALB-dependent degradation occurred within 5 h in solutions formulated with the free base of ALB, while those containing the sulfate salt of ALB produced no degradation. Alkali solutions can cause base-catalyzed hydrolysis of IPB and degradation of BUD. Compounded formulations containing ALB need to include an acid to control pH and prevent degradation.     

Waveguide trapping of hollow glass spheres

Microparticles can be trapped and propelled by the evanescent field of optical waveguides. As the evanescent field only stretches 100-200?nm from the surface of the waveguide, only the lower caps of the microparticles interact directly with the field. This is taken advantage of by trapping hollow glass spheres on waveguides in the same way as solid glass spheres. For the chosen waveguide, numerical simulations show that hollow microspheres with a shell thickness above 60?nm can be stably trapped, while spheres with thinner shells are repelled. The average refractive index of the sphere-field intersection volume is used to explain the result in a qualitative way.     

Ab initio study of platinum induced reconstructions on Ge(001)-(1×2) surface with dimerization

We present first principle total energy calculation of Pt induced reconstructions on Ge(001)-(1×2) surface with dimerization. Study was undertaken using localized orbitals basis set DFT using SIESTA to compare pure Ge dimerized Ge(001)-(1×2) surface with 0.5 and 1.0 Pt covered dimerized Ge(001)-(1×2) surface with the possibility of homo (Ge-Ge and Pt-Pt) and hetro (Pt-Ge) dimers. From total energy calculation results we calculated dimer bond lengths, buckling angles and formation energy of dimers on Ge(001)-(1×2) surface. By calculating the formation energy of different configurations we find that Ge-Ge buckled dimerized surface has least (−1.23 eV/dimer) and Pt-Pt symmetric dimerized surface has largest (+0.09 eV/dimer) formation energy with respect to unreconstructed surface. We further calculated the electronic DOS and band structure of Ge dimerized as well as Pt dimerized surface to see the change in semiconducting behavior on dimerization. By comparing the DOS and electronic band structure of homo Ge dimerized surface, we found metallicity of Ge(001)-(1×2) surface results from dimer formation. Also by comparing the electronic band structure of homo Ge dimerized surface with unreconstructed surface we find that less number of bands crossing the Fermi level which is perhaps due to the saturation of one dangling bond per Ge surface atom. By introducing Pt at 0.5 and 1.0 coverage in place of Ge, except for homo Pt buckled dimerized surface having 1.0 coverage of Pt, we find in all other cases increase in number of bands are crossing the Fermi level, indicating strong metallic behavior of Ge(001)-(1×2) surface.     

Multistep transitions in collagens

It is well known that collagens exist in triple-helical form, and, on average, the individual chains have glycine at every third place. Collagens from different sources vary in distributions of other amino acids. They could also be different in the distribution of defects, which are generally nonhelical regions of low stability. Varying lengths of individual chains in the triple-helical system can also contribute to this variability. All these variations manifest themselves in the creation of a transition profile with undulations that are indicative of a multiphasic nature. In the present communication, we try to understand this variability by using essentially the Zimm and Bragg approach and suitably amending it for a triple-helical system. Factors that contribute to the multiphasic nature are incorporated into the transition model and discussed. Results obtained for collagen types I, II, III, V_x, V_y, and XI are in agreement with the experimental measurements. Transitions in the first three types can be interpreted on the basis of two-phase theory. Nucleation parameters, which are indicative of the sharpness of transition, are interpreted in terms of stability and possible amino acid composition.     

Tracing Robert's use of representations to solve counting problems: A 16-year case study

This study describes how Robert used his external representations (formulae, notations, sketches, models, and figures) to solve progressively more challenging counting tasks over a 16-year period. In his explorations of counting tasks, Robert discovered intricate connections between solutions to problems that looked different on the surface. Using video data from Robert's problem solving, analyses of his solutions are presented that shed light on how he built new ideas from existing ideas and how he modified external representations to make new mathematical discoveries and provide justifications for his solutions.