Comparison of the equilibrium geometry of acetylene (C2H2) and disilyne (Si2H2)

The equilibrium geometry of disilyne is not linear, but is twisted. The potential surfaces of acetylene and disilyne have a critical internuclear distance between the central atoms, where the stable geometry changes from linear to twisted forms the R-dependence of the valence-shell electron energy causes the difference in the structure of the molecules.     

Selective 1,4-diacetoxylation of conjugated dienes with tellurium (IV) oxide

Oxidation of several linear conjugated dienes with tellurium (IV) oxide and lithium bromide in acetic acid affords an isomeric mixture of the corresponding diacetoxyalkenes (1,2- and 1,4-addition products), 1,4-isomer being highly selectively produced when the ratio of LiBr/TeO₂, is 5–10.     

Determination of nitrate in natural waters by flow-injection analysis

Summary Nitrate was determined in natural water samples by flow-injection spectrophotometry. It was reduced to nitrite with copperized cadmium and the nitrite thus produced reacted with p-aminoacetophenone and m-phenylenediamine. The limit of detection was about 1.5 g l^–1 for sample injections of 650 l. The sampling rate was about 40 samples h^–1 and the relative standard deviation was above 1% for 0.1–0.3 mg l^–1 nitratenitrogen. Nitrite present in the sample was determined separately and subtracted.

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Nitratbestimmung in natürlichen Wässern mit Hilfe der Fließinjektions-Analyse

Zusammenfassung Nitrat wird bei dieser Methode mit Hilfe einer Cu/Cd-Reduktionssäule zu Nitrit reduziert, das mit p-Aminoacetophenon und m-Phenylendiamin zur Reaktion gebracht wird. Die gebildete Verbindung wird spektral-photometrisch gemessen. Die Nachweisgrenze beträgt etwa 1,5 g/l bei injizierten Probevolumina von 650 l. Der Probendurchsatz beträgt 40/h. Die relative Standardabweichung liegt über 1% bei 0,1–0,3 mg/l Nitrat-Stickstoff. Vorhandenes Nitrit wird gesondert bestimmt und abgezogen.

     

Palladium-catalyzed allylic oxidation of olefins by t-butyl hydroperoxide and tellurium(IV) oxide

Treatment of several cyclic olefins, β-pinene, allylbenzene, and estragole with palladium(II) salt in acetic acid in the presence of t-butyl hydroperoxide and tellurium(IV) oxide afforded mainly the corresponding allylic acetates. The reaction proceeded catalytically with palladium(II) salt, t-BuOOH working as a reoxidizing agent.     

Interplay between structure and magnetism in Mo12S9I9 nanowires

We investigate the equilibrium geometry and electronic structure of Mo12S9I9 nanowires using ab initio density functional calculations. The skeleton of these unusually stable nanowires consists of rigid, functionalized Mo octahedra, connected by flexible, bistable sulfur bridges. This structural flexibility translates into a capability to stretch up to approximately 20% at almost no energy cost. The nanowires change from conductors to narrow-gap magnetic semiconductors in one of their structural isomers.     

Demonstration of a PDMS-based bio-microactuator using cultured cardiomyocytes to drive polymer micropillars

Natural cellular functions are increasingly exploited for integrated chemical systems such as biochemical reactors and biosensors. We propose to utilize the intrinsic mechanical function of cardiomyocytes, converting chemical energy into mechanical energy. In this report, we demonstrate the working principle of our proposed poly(dimethylsiloxane) (PDMS) based cardiomyocyte bio-microactuator using fabricated PDMS micropillars driven to repetitive motion by attached pulsating cardiomyocytes. Sheets of PDMS embedded with an array of micropillars were fabricated and modified for cardiomyocyte attachment in culture. Primary neonatal rat cardiomyocytes were cultured on the array, attaching to the micropillars and substratum successfully, and exhibiting their typical spontaneous, pulsatile phenotype. Micropillars beat with the coupled cells spontaneously without any triggers. The beat frequency was 1.4 Hz at 37 degrees C and the displacement of the top of the pillar that beat most strongly in our observation was 2.8+/-0.2 microm. From this result, contractile forces of cultured cardiomyocytes were estimated to exceed 3.5 microN. The estimated force is far greater than that of a previously described hydrogel-based cardiomyocyte bio-microactuator (K. Morishima et al., in Micro Total Analysis Systems 2003, ed. M. A. Northrup et al., The Transducers Research Foundation, San Diego, CA, vol. 2, pp. 1125-1128). PDMS compatibility as a base material for bio-microactuator design using cultured cardiomyocytes was verified. This PDMS-based cell microactuator worked for about one week without exchange of the culture medium, and this system could be developed for various purposes in the future as self-actuated and efficient mechanochemical transducers without external energy source requirements.