DNA logic gates

A conceptually new logic gate based on DNA has been devised. Methoxybenzodeazaadenine ((MD)A), an artificial nucleobase which we recently developed for efficient hole transport through DNA, formed stable base pairs with T and C. However, a reasonable hole-transport efficiency was observed in the reaction for the duplex containing an (MD)A/T base pair, whereas the hole transport was strongly suppressed in the reaction using a duplex where the base opposite (MD)A was replaced by C. The influence of complementary pyrimidines on the efficiency of hole transport through (MD)A was quite contrary to the selectivity observed for hole transport through G. The orthogonality of the modulation of these hole-transport properties by complementary pyrimidine bases is promising for the design of a new molecular logic gate. The logic gate system was executed by hole transport through short DNA duplexes, which consisted of the "logic gate strand", containing hole-transporting nucleobases, and the "input strand", containing pyrimidines which modulate the hole-transport efficiency of logic bases. A logic gate strand containing multiple (MD)A bases in series provided the basis for a sharp AND logic action. On the other hand, for OR logic and combinational logic, conversion of Boolean expressions to standard sum-of-product (SOP) expressions was indispensable. Three logic gate strands were designed for OR logic according to each product term in the standard SOP expression of OR logic. The hole-transport efficiency observed for the mixed sample of logic gate strands exhibited an OR logic behavior. This approach is generally applicable to the design of other complicated combinational logic circuits such as the full-adder.     

Electronic structure of dendrimer-encapsulated Au nanocluster

We have carried out optical and X-ray photoemission studies of the dendrimer-encapsulated Au nanoclusters. The dendrimer-encapsulated Au nanoclusters are prepared by the chemical reduction of Au ions loaded within the dendrimer templates. Photoluminescence spectrum of the dendrimer-encapsulated Au nanoclusters with diameter of about 1.0 nm shows the visible luminescence centered at about 2.8 eV. In addition, we have measured the nanocluster-size dependent photoemission spectra in the valence-band region. From line shape analysis of Au 4f X-ray photoemission spectra, Au 4f core-level spectra of the dendrimer-encapsulated Au nanoclusters reflect the size dependent chemical-states. From these results, we discuss electronic structures and chemical states of the dendrimer-encapsulated Au nanoclusters.     

Hard protective waterproof coating for high-power laser optical elements

We developed a new method for making a waterproof coating by photooxidation of silicone oil. The silicone oil was spin coated onto the surfaces of optical elements, i.e., a plastic lens, a laser mirror, and a nonlinear optical crystal, and then irradiated with a xenon excimer lamp in air, which transformed the organic silicone oil into an amorphous glass film. This technique has enabled an optical thin film to transmit ultraviolet rays of wavelengths below 200 nm and to exhibit the characteristics of homogeneity, high density, and resistance to environmental effects and to corrosion by water, and a Mohs scale value of 5.     

Effects of ultrasonic intensity and reactor scale on kinetics of enzymatic saccharification of various waste papers in continuously irradiated stirred tanks

Based on the enzymatic saccharification of the various pulps in the previous 0.8 l ultrasonic stirred tank reactor, the ultrasound-enhanced saccharification of waste papers such as newspaper, carton paper, office paper etc. was carried out in the same reactor as well as larger scale stirred tank reactors of size 3.2 and 6.4 l. The saccharification of each waste paper was less enhanced in the larger reactor at a given ultrasonic intensity. This could be attributed to the decrease in the ultrasonic intensity per reaction volume, i.e., the specific ultrasonic intensity. Most waste papers were more efficiently hydrolyzed with increasing specific ultrasonic intensities, although newspaper was less efficiently done for a too high specific intensity. Such an adverse effect might be due to the fact that some impurities in the newspaper such as lignin were activated by an intensive ultrasonic irradiation to form a rigid and closed network, which inhibited the access and adsorption of cellulase on to the substrate surface. The previous kinetic model was found to be applicable to analyze and simulate the saccharification of each waste paper in the different ultrasonic reactors. The ultimate conversion of a substrate based on the total sugar concentration estimated for an infinite reaction time could be correlated as a function of the ratio of initial substrate to enzyme concentrations at a fixed specific ultrasonic intensity. Either the apparent rate constant or the ultimate conversion increased and tended to approach a constant with an increase in the specific ultrasonic intensity except for the case of newspaper, while neither the apparent Michaelis constant, product inhibition constant nor glucose formation equilibrium constant was influenced by the specific ultrasonic intensity.     

Evidence for strong-coupling s-wave superconductivity in MgB2: (11)B NMR Study

We have investigated a gap structure in a newly discovered superconductor, MgB2, through measurement of the (11)B nuclear spin-lattice relaxation rate, (11)(1/T(1)). (11)(1/T(1)) is proportional to the temperature (T) in the normal state, and decreases exponentially in the superconducting (SC) state, revealing a tiny coherence peak just below T(c). The T dependence of 1/T(1) in the SC state can be accounted for by an s-wave SC model with a large gap size of 2Delta/k(B)T(c) approximately 5 which suggests it is in a strong-coupling regime.     

Magnetic and microwave absorption properties of BaFe12−x (Mn0.5Cu0.5Zr)x/2O19 synthesized by sol–gel processing

BaFe_12−x (Mn_0.5Cu_0.5Zr)_x/2O₁₉ hexaferrites with x=1, 2 and 3 were prepared by sol–gel process. The ferrite powders possess hexagonal shape and are well separated from one another. The powders of these ferrites were mixed with polyvinylchloride (PVC) plasticizer to be converted into a microwave absorbing composite ferrite with a thickness of 1.8 mm. X-ray diffractometer (XRD), scanning electron microscope (SEM), ac susceptometer, vibrating sample magnetometer and vector network analyzer were used to analyze its structure, electromagnetic and microwave absorption properties. The results showed that magnetoplumbite structures for all samples were formed. The sample with higher magnetic susceptibility and coercivity exhibits a larger microwave absorbing ability. Also the present investigation demonstrates that a microwave absorber using BaFe_12−x(Mn_0.5Cu_0.5Zr)_x/2O₁₉ (x=2 and 3)/PVC with a matching thickness of 1.8 mm can be fabricated for applications over 15 GHz, with reflection loss more than −25 dB for specific frequencies, by controlling the molar ratio of the substituted ions.     

Submillimeter wave esr and far infrared spectroscopy measurements of CuGeO3

Submillimeter wave ESR and far infrared transmission measurements of first inorganic spin-Peierls system CuGeO₃ have been performed using the single crystals. Our new results are discussed in connection with the magnetic properties of the spin-Peierls systems and the recent neutron measurements of CuGeO₃.     

Preparation of molecularly imprinted polymers with thiourea group for phosphate

Molecularly imprinted polymers selective for phosphate were prepared with the two types of functional monomers, 1-allyl-2-thiourea and N-methyl-N′-(4-vinylphenyl)-thiourea, and the binding abilities of the polymers were evaluated. Phenylphosphonic acid or diphenyl phosphate were used as the template molecules and the imprinted polymers prepared with 1-allyl-2-thiourea as functional monomer showed high binding ability to phosphate in aqueous media and nearly 90% of phosphate could be recovered. Also, the imprinted polymer prepared with N-methyl-N′-(4-vinylphenyl)-thiourea as functional monomer had a high binding ability and specific interaction with phosphate in acetonitrile solution and over 90% of phosphate-derivatives could be recovered selectively.     

Molecular recognition by indoleacetic acid-imprinted polymers – effects of 2-hydroxyethyl methacrylate content

Molecularly imprinted polymers for indole-acetic acid were prepared by co-polymerizing N,N-dimethylaminoethyl methacrylate, 2-hydroxyethyl methacrylate (HEMA), and ethylene glycol dimethacrylate. The dependence of the affinity and selectivity of the imprinted polymers on HEMA content was evaluated chromatographically. The affinity was improved by increasing the HEMA content; the selectivity of the imprinted polymer was best when the HEMA content was approximately 30%, irrespective of monomer content.