Cold Positions of the Restricted Wythoff\u27s Game

Wythoff\u27s game is a kind of 2-pile Nim game, which admits taking the same number of stones from both piles. It differs only a little from the 2-pile Nim game, but their winning strategies are quite different from each other. Amazingly the winning strategy of Wythoff\u27s game is directly related to a real number, specifically the golden ratio. In this paper we add two restrictions to this game, and investigate the winning strategy of the revised game

Evolutionary Aspects and Regulation of Tetrapyrrole Biosynthesis in Cyanobacteria under Aerobic and Anaerobic Environments

Chlorophyll a (Chl) is a light-absorbing tetrapyrrole pigment that is essential for photosynthesis. The molecule is produced from glutamate via a complex biosynthetic pathway comprised of at least 15 enzymatic steps. The first half of the Chl pathway is shared with heme biosynthesis, and the latter half, called the Mg-branch, is specific to Mg-containing Chl a. Bilin pigments, such as phycocyanobilin, are additionally produced from heme, so these light-harvesting pigments also share many common biosynthetic steps with Chl biosynthesis. Some of these common steps in the biosynthetic pathways of heme, Chl and bilins require molecular oxygen for catalysis, such as oxygen-dependent coproporphyrinogen III oxidase. Cyanobacteria thrive in diverse environments in terms of oxygen levels. To cope with Chl deficiency caused by low-oxygen conditions, cyanobacteria have developed elaborate mechanisms to maintain Chl production, even under microoxic environments. The use of enzymes specialized for low-oxygen conditions, such as oxygen-independent coproporphyrinogen III oxidase, constitutes part of a mechanism adapted to low-oxygen conditions. Another mechanism adaptive to hypoxic conditions is mediated by the transcriptional regulator ChlR that senses low oxygen and subsequently activates the transcription of genes encoding enzymes that work under low-oxygen tension. In diazotrophic cyanobacteria, this multilayered regulation also contributes in Chl biosynthesis by supporting energy production for nitrogen fixation that also requires low-oxygen conditions. We will also discuss the evolutionary implications of cyanobacterial tetrapyrrole biosynthesis and regulation, because low oxygen-type enzymes also appear to be evolutionarily older than oxygen-dependent enzymes

Surface Modification of Carbon Fiber for Enhancing the Mechanical Strength of Composites

The surface of carbon fibers (CFs) is often modified by multi-walled carbon nanotubes (MWCNTs), and the effect of the interface on the mechanical properties has been reported mostly for epoxy matrices. We achieved effective surface modification of CFs by a simple two-step process to graft a large amount of MWCNTs using a highly reactive polymer to enhance the bonding between CFs and MWCNTs. The first step was the reactive mono-molecular coating of a reactive polymer (poly-2-isopropenyl-2-oxazoline; Pipozo) that has high reactivity with COOH from CFs and MWCNTs. The high reactivity between the oxazoline group and COOH or phenol OH was confirmed for low-molecular-weight reactions. The second step was the coating of MWCNTs from a dispersion in a solvent. This simple process resulted in a substantial amount of MWCNTs strongly bonded to CF, even after washing. The MWCNTs grafted onto CFs remained even after melt-mixing. The effect on the interface, i.e., physical anchoring, led to an improvement of the mechanical properties. The novelty of the present study is that Pipozo acted as a molecular bonding layer between CFs and MWCNTs as a physical anchoring structure formed by a simple process, and the interface caused a 20% improvement in the tensile strength and modulus. This concept of a composite having a physical anchoring structure of MWCNTs on CFs has potential applications for lightweight thermoplastics, such as in the automotive industry

Effects of infinitely fast chemistry on combustion behavior of coaxial diffusion flame predicted by large eddy simulation

Large eddy simulations (LES) based on turbulent combustion models aid the design and optimization of combustors. Of the various combustion models available, the eddy break up (EBU) model is widely used because it assumes an infinitely fast chemistry. However, omitting the actual chemical kinetics can cause unexpected behavior, and the characteristics of the combustion models need to be elucidated. Here, the effects of an infinitely fast chemistry on the combustion behavior of a coaxial diffusion flame as predicted by an LES were analyzed. Although the EBU model captured the overall behavior of the chemical species as well as the flow field, the gas temperature and mass fractions of the combustion products in the mixing region of the fuel and oxidizer streams were overestimated. In contrast, the flamelet/progress variable (FPV) model yielded results that were in better agreement with the experimental data, because while the EBU model assumes an infinitely fast chemistry, the look-up tables used in the FPV model are based on the actual chemical kinetics. As these models can be used for the CFD simulations of coal and spray combustion, the results of this study should be useful for efficiently simulating practical combustion systems

Fluorescence Tumor-Imaging Using a Thermo-Responsive Molecule with an Emissive Aminoquinoline Derivative.

We synthesized (2,4-trifluoromethyl-7--bis(2,5,8,11-tetraoxatridecane-13-yl)-aminoquinoline) TFMAQ-diEg4, an emissive aminoquinoline derivative that incorporated two tetraethyleneglycol chains into an amino group. TFMAQ-diEg4 showed fluorescence and thermo-responsive properties accompanied by a lower critical solution temperature (LCST), due to the introduction of the oligoethylene glycol chain. This thermo-responsive LCST behavior occurred at the border of a cloud point. Below and above the cloud point, self-assemblies of 6-7-nm nanoparticles and ~2000-nm microparticles were observed, in vitro. In addition, TFMAQ-diEg4 showed a high solubility, over 20 mM for aqueous solution, in vivo, which not only prevented thrombosis but also allowed various examinations, such as single intravenous administration and intravenous drips. Intravenous administration of TFMAQ-diEg4, to tumor-bearing, mice led to the accumulation of the molecule in the tumor tissue, as observed by fluorescence imaging. A subset of mice was treated with local heat around their tumor tissue and an intravenous drip of TFMAQ-diEg4, which led to a high intensity of TFMAQ-diEg4 emission within the tumor tissue. Therefore, we revealed that TFMAQ-diEg4 was useful as a fluorescence probe with thermo-responsive properties

Fluorescence Tumor-Imaging Using a Thermo-Responsive Molecule with an Emissive Aminoquinoline Derivative

We synthesized (2,4-trifluoromethyl-7-N-bis(2,5,8,11-tetraoxatridecane-13-yl)-aminoquinoline) TFMAQ-diEg4, an emissive aminoquinoline derivative that incorporated two tetraethyleneglycol chains into an amino group. TFMAQ-diEg4 showed fluorescence and thermo-responsive properties accompanied by a lower critical solution temperature (LCST), due to the introduction of the oligoethylene glycol chain. This thermo-responsive LCST behavior occurred at the border of a cloud point. Below and above the cloud point, self-assemblies of 6-7-nm nanoparticles and ~2000-nm microparticles were observed, in vitro. In addition, TFMAQ-diEg4 showed a high solubility, over 20 mM for aqueous solution, in vivo, which not only prevented thrombosis but also allowed various examinations, such as single intravenous administration and intravenous drips. Intravenous administration of TFMAQ-diEg4, to tumor-bearing, mice led to the accumulation of the molecule in the tumor tissue, as observed by fluorescence imaging. A subset of mice was treated with local heat around their tumor tissue and an intravenous drip of TFMAQ-diEg4, which led to a high intensity of TFMAQ-diEg4 emission within the tumor tissue. Therefore, we revealed that TFMAQ-diEg4 was useful as a fluorescence probe with thermo-responsive properties