Educational experiments on ESR imaging with a portable ESR spectrometer

A light-weight portable electron spin resonance (ESR) spectrometer with the permanent magnet of Nd-B-Fe (Neomax) and field sweep coils was used as a demonstration tool of ESR microscopy for student’s experiments. Educational experiments on one-and two-dimensional ESR imaging are made by inserting field gradient coils or field scanning wire arrays into the cavity using test samples of DPPH. A preliminary work on double frequency modulation is described for two-dimensional imaging using microwire arrays.     

Effect of molecular weight on the morphology of polystyrene/poly(methyl methacrylate) composite particles prepared by the solvent evaporation method

The effect of molecular weight on the morphology of polystyrene (PS)/poly(methyl methacrylate) (PMMA) composite particles was investigated. PS/PMMA composite particles with different molecular weights (M*=MwPS+MwPMMA)/2 approximately 2x10(4)-1x10(6) g.mol(-1)) were prepared by the release of toluene (T) from PS/PMMA/T (1/1/24, w/w/w) droplets dispersed in an aqueous solution of polyoxyethylene nonylphenyl ether nonionic surfactant (Emulgen 911). As T evaporated, the spherical droplets phase separated, resulting in snowmanlike composite particles with Janus morphology. The nonspherical shape was closely related to the morphology, which depended on M*. The interfacial tension between the phase-separated PS and PMMA phases increased with an increase in M*, and this would allow the formation of the snowmanlike shape to decrease the interfacial area between the PS and the PMMA phases.     

Triterpene glycosides from the roots of Codonopsis lanceolata

In the course of the development of new designer foods using the roots of Codonopsis lanceolata, we found that hot-water extracts of C. lanceolata recovered decreased testosterone levels in the blood and accelerated the restoration of reproductive dysfunction induced by hyperthermic treatment in male mice. Thus we studied the constituents of the polar fraction of the roots of C. lanceolata and identified six new triterpene saponins, lancemasides B (2), C (3), D (4), E (5), F (6), and G (7), along with the known saponin lancemasaide A (1) and phenylpropanoid glycosides 8-10. The structures of the new compounds 2-7 were determined by means of spectral data including 2D-NMR studies and chemical reactions to be oleanan-type bisdesmoside with sugars at C-3 and C-28. Compounds 2-6 have echinocystic acid as an aglycone, and compound 7 has asterogenic acid as an aglycone. Identification of the sugars and determination of their D,L-chiralities were carried out by application of the exciton chirality method to the per-O-p-bromobenzoylmethyl sugar derived from saponins.     

A single-cell drug efflux assay in bacteria by using a directly accessible femtoliter droplet array

Active efflux of drugs, such as antibiotics, from a cell is one of the major mechanisms that cause multi-drug resistance in bacteria. Here we report a method to assess drug efflux activity in individual Escherichia coli cells enclosed and isolated in a directly accessible femtoliter droplet array with a fluorogenic compound. The inhibitory effect of a chemical compound on an exogenously expressed efflux pump system from pathogenic bacteria was easily detected at the single-cell level. We also present a proof-of-principle experiment to screen for the gene encoding a drug efflux pump by collecting individual droplets containing single cells in which the drug efflux activity was restored after introduction of the exogenous gene from pathogenic bacteria. Our approach will be a useful tool to screen novel pump inhibitors and efflux pump genes, and to overcome infectious diseases caused by multi-drug-resistant bacteria.     

Nuclear spin maser and experimental search for 129 Xe atomic EDM

The present status of an active spin maser which is being developed for an experimental search for ¹²⁹Xe atomic electric dipole moment (EDM) is presented. In order to realize the long term stability of maser frequency, systematic effects for the spin maser operation were investigated. The correlations in the maser frequency with the solenoid current, the environmental field and the cell temperature were found. With the solenoid current and environmental field being stabilized and the cell temperature lowered, a frequency precision of 7.9 nHz has been achieved for the maser operation.     

Upper Bounds on the Paired Domination Subdivision Number of a Graph

A paired dominating set of a graph G with no isolated vertex is a dominating set S of vertices such that the subgraph induced by S in G has a perfect matching. The paired domination number of G, denoted by γ _pr(G), is the minimum cardinality of a paired dominating set of G. The paired domination subdivision number ${{\rm sd}_{\gamma _{\rm pr}}(G)}$ is the minimum number of edges to be subdivided (each edge of G can be subdivided at most once) in order to increase the paired domination number. In this paper, we show that if G is a connected graph of order at least 4, then ${{\rm sd}_{\gamma _{\rm pr}}(G)\leq 2|V(G)|-5}$ . We also characterize trees T such that ${{\rm sd}_{\gamma _{\rm pr}}(T) \geq |V(T)| /2}$ .     

4-factors in 2-connected star-free graphs

Let t≥3 be an integer. We show that if G is a 2-connected K_1,t-free graph with minimum degree at least (3t+1)/2, then G has a 4-factor.