Structure comparison between Th2Zn17-type and TbCu7-type Sm–Fe intermetallic compounds and their nitrides by means of 57Fe-Mössbauer spectroscopy

Samarium–iron intermetallic compounds were prepared by a melt spinning method with low and high wheel speeds, which resulted in a Th₂Zn₁₇-type and a TbCu₇-type structure, respectively. Structure comparison between these types was investigated for Sm–Fe intermetallic compounds and their nitrides by ⁵⁷Fe-Mössbauer spectroscopy.     

COMPARTMENTALIZATION OF ZINQII) TETRAPHENYLPORPHYRIN IN A HYDROPHOBIC MICRODOMAIN OF AN AMPHIPHILIC POLYELECTROLYTE: A PHYSICOCHEMICAL MODEL OF BIOLOGICAL METALLOPORPHYRIN SYSTEMS

Abstract— Small mole fractions of zinc(II) tetraphenylporphyrin (ZnTPP) moieties were covalently incorporated into amphiphilic polysulfonates having bulky hydrophobic groups such as lauryl, cyclododecyl, and (2-naphthyi)methyl (Np) groups in their side chains. The ZnTPP moieties are "compartmentalized" in the hydrophobic domains of these amphiphilic polyelectrolytes in aqueous solution. For comparison, the ZnTPP moieties were covalently incorporated into a polysulfonate without hydrophobic groups. The ZnTPP moieties in this reference polymer are exposed to water in aqueous solution. The compartmentalized ZnTPP systems in aqueous fluid solution emitted phosphorescence and thermally activated delayed fluorescence at room temperature. This is due to an extremely long-lived triplet excited state in the compartmentalized systems at room temperature in aqueous solution, e.g. 19 ms for ZnTPP compartmentalized in Np domains, compared with 3 ms for ZnTPP in the reference polymer. These remarkable compart-mentalization effects may be attributed to a restriction of motional freedom of the ZnTPP moiety isolated in a rigid and hydrophobic microenvironment provided by the amphiphilic polyelectrolytes in aqueous solution.     

A new tomato pregnane glycoside from the overripe fruits

A new pregnane glycoside has been isolated from the overripe fruits of Cherry tomato (Mini tomato), Lycopersicon esculentum var. cerasiforme (DUNAL) ALEF. The structure was determined to be 3-O-beta-lycotetraosyl 3beta-hydroxy-5alpha-pregn-16-en-20-one on the basis of spectroscopic analysis. The seasonal variation of the tomato saponin is discussed.     

Rheological behavior in water of complexes formed from poly(sodium 2-(acrylamido)-2-methylpropanesulfonate) and positively charged rodlike micelles

The viscoelastic behavior of aqueous solutions of an ionic complex formed from poly(sodium 2-(acrylamido)-2-methylpropanesulfonate) and rodlike mixed micelles of dimethyloleylamine oxide (DMOAO) and hexadecyltrimethylammonium chloride (CTAC) was investigated under oscillatory conditions. The DMOAO/CTAC mixed micelles exhibited high zero-shear viscosities (eta0) depending on the mole fraction of CTAC in the mixed micelle (Y) in the range 0Y0.25. The addition of the polyanion had no effect on the rheological behavior of the mixed micelles when Y<0.02 at an ionic strength (mu) of 0.2. However, when Y was increased to a certain level (Yc), eta0 decreased drastically; Yc depended on mu but not on the polymer concentration. These observations indicate the formation of an ionic complex between the polymer and micelle when YYc. The reciprocal of steady-state compliance (Je(-1)) began to decrease gradually at Y approximately Yc and then leveled off at Y>0.06. The relaxation time (tau) was found to be more strongly dependent on Y. Thus, the large decrease in eta0 was attributed mainly to a decrease in tau while the number density of junctions decreased only slightly. Therefore, it is concluded that polymer-micelle complex maintains a rodlike structure with some entanglements remaining at Y<0.12.     

A self-consistent cluster theory of amorphous materials

A cluster method for the electronic structure of amorphous materials is presented with an application to amorphous diamond. Eight-atom cluster model gives a pseudogap in the density of states.     

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.