Scale free interval graphs

Scale free graphs have attracted attention by their non-uniform structure that can be used as a model for various social and physical networks. In this paper, we propose a natural and simple random model for generating scale free interval graphs. The model generates a set of intervals randomly under a certain distribution, which defines a random interval graph. The main advantage of the model is its simpleness. The structure/properties of generated graphs are analyzable by relatively simple probabilistic and/or combinatorial arguments, which is different from many other models. Based on such arguments, we show for our random interval graph that its degree distribution follows a power law, and that it has a large average clustering coefficient.     

Rotary scanning wireless temperature measurement method for hyperthermia using ferromagnetic implants

Recently, the use of a ferromagnetic material in a soft‐heating method has garnered much attention as a novel method for cancer treatment. By concurrently using this material as a thermal probe, we are currently developing a minimally invasive heating and wireless temperature measurement system. To make the approach feasible in a clinical setting, it is vital to overcome the key challenge of heating the local tumor at a constant temperature. In previous conventional approaches, it was necessary to switch the induction‐heating power supply on/off after the target tumor temperature was reached. However, it cannot determine the temperature of the material during the power‐off period. Therefore, we changed this approach and found that by adjusting the distance between the heating coil and the material while maintaining a constant current flow in heating coil, the drift problem, which happened just after power is supplied during the on/off operation, did not occur any longer. Accordingly, it was not required to use multiple sensors to reduce the drift, thereby minimizing the cost. This study verifies the validity of our wireless thermometry approach while performing rotary scanning and proposes a technique for determining achievement of the target temperature. This knowledge complements other approaches for cancer treatment utilizing hyperthermia. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

An analytical method for thermal-hydraulic transients in piping networks

To predict the thermal-hydraulic transients, an analytical method has been developed for single and two-phase flow in arbitrary piping networks. In this method the piping network is represented by vessels and flow channels. The thermal-hydraulic transients in the channel are described by partial differential equations derived from mass, momentum and energy conservation laws. The partial differential equations are solved implicitly, simultaneously for the whole network, with the ordinary differential equations that describe the change of vessel pressures and enthalpies.Numerical calculation error is evaluated in the implicit method for the integration of partial differential equations of channel flow. In the numerical calculation an artificial diffusion appers with a diffusion coefficient Δt λ²/2, where Δt is a time step and λ denotes the propagation velocity of the perturbation.     

Micropatterned organoid culture of rat hepatocytes and HepG2 cells

The culture of liver cell organoids (multicellular aggregates) such as spheroids or cylindroids, which can strongly express liver functions, has been advocated as a useful technique that has advantages over monolayer culture. This paper describes a micropatterning technique for obtaining spheroids and cylindroids by using rat hepatocytes or HepG2 cells. We developed culture chips that comprised multiple, circular or rectangular microwells; the bottom surface of each microwell was modified with collagen to create a cell adhesion area, and the entire microwell, excluding the collagen-coated spots, was modified with polyethylene glycol (PEG) to create a nonadhesive area. Rat hepatocytes and HepG2 cells formed uniform spheroids and cylindroids on the circular and rectangular chips, respectively. Consequently, two-dimensional micropatterned chips containing homogeneous spheroids or cylindroids were generated. The expression of liver functions (protein secretion and ammonia removal) was greater in the spheroids and cylindroids than in the monolayer culture, and this expression was maintained for at least 2 weeks of culture. Thus, this chip technology has potential for use in various applications that involve organoid culture.     

Synthesis and antibacterial activity of 1-substituted-methyl carbapenems

The synthesis of the 1 alpha- and the 1 beta-substituted (fluoro, cyano, hydroxy and acetoxy)-methyl carbapenems having a 2-(1,3,4-thiadiazol-2-yl)thiomethyl side chain are described, and their in vitro antibacterial activities are compared with the corresponding 1 beta-methyl carbapenems together with imipenem. The synthesis and antibacterial activity of the 1 beta-substituted (fluoro and cyano)-methyl carbapenems having 2-(1-alkyl-4-pyridinio)thiomethyl side chains are also described.     

Evidence that Crystal Facet Orientation Dictates Oxygen Evolution Intermediates on Rutile Manganese Oxide

Elucidating the mechanism that differentiates the oxygen‐evolving center of photosystem II with its inorganic counterpart is crucial to develop efficient catalysts for the oxygen evolution reaction (OER). Previous studies have suggested that the larger overpotential for MnO₂ catalysts under neutral conditions may result from the instability of the Mn³⁺ intermediate to charge disproportionation. Here, by monitoring the surface intermediates of electrochemical OER on rutile MnO₂ with different facet orientations, a correlation between the stability of the intermediate species and crystal facets is confirmed explicitly for the first time. The coverage of the Mn³⁺ intermediate is found to be 11‐fold higher on the metastable (101) surfaces compared to (110) surfaces, leading to the superior OER activity of (101) surfaces. The difference in OER activity may result from the difference in surface electronic states of Mn³⁺, where interlayer charge comproportionation of Mn²⁺ and Mn⁴⁺ to generate two Mn³⁺ species is favored on (101) facets. Considering the fact that the OER enzyme accommodates Mn³⁺ stably during the Kok cycle, the enhanced OER activity of the rutile MnO₂ catalyst with a metastable surface highlights the importance of mimicking not only the crystal structure but also the electronic structure of the targeted natural enzyme.     

Novel electrochemical surface modification method of carbon fiber and its utilization to the preparation of functional electrode

The electrooxidative and -reductive methods for the surface modification of carbon fiber were developed. The carbon fiber surface was first oxidized under anodic conditions to introduce phenolic hydroxyl groups on the carbon fiber, and then the resulting oxidized carbon fiber was treated under cathodic conditions in the presence of various kinds of electrophiles such as alkyl halides and alkyl tosylates introducing the alkyl groups on the carbon fiber. The changes of the functional groups on the carbon fibers were confirmed by the X-ray photoelectron spectroscopy (XPS) study and the observation of the hydrophilicity. The functional carbon fiber electrode introduced β-cyclodextrin (β-CD) was then prepared by this electrochemical method. The electroreduction of acetophenone (1) was carried out using the resulting carbon fibers as cathodes. The use of the carbon fiber modified with β-CD gave relatively high dl selectivity of the reductive coupling products 2 (the dl/meso ratio: 5.2), while the dl/meso ratio using the untreated carbon fiber was 3.0, and the formation of 1-phenyl ethanol (3) was observed only by using the β-CD-modified carbon fiber. The observed products selectivity is discussed from the viewpoints of the interaction between the electrogenerated species and the functional groups on the carbon fibers.