Thermoelectric properties of Bi and Cu co-doped Ca3Co2O6single crystals

Single crystals of Bi and Cu-doped Ca₃Co₂O₆were synthesized in a molten K₂CO₃flux. Using an obtained single crystal of (Ca_0.985(5)Bi_0.015(5))₃(Co_0.990(3)Cu_0.010(3))₂O₆elongated to the c-axis direction of the crystal structure, the electric resistivity (ρ) and Seebeck coefficient (S) were measured from room temperature to over 1000 K in air. The single crystal showed p-type semiconducting behavior with ρ values of 1.8 Ω cm at 303 K and 0.017 Ω cm at 1000 K. The S values were +254 μ VK^{− 1} at 325 K, +360 μ VK^{− 1} at 420 K, and +214 μ VK^{− 1} at 1000 K. The power factor (S ² ρ ^{− 1}) increased with an increase of temperature and attained 2.70 × 10^{− 4} Wm^{− 1}K^{− 2} at 1000 K.     

Nyquist stability criterion of intrinsic zeros for continuous-time pure imaginary zeros

This note treats a stability condition of the zeros of sampled systems corresponding to continuous-time pure imaginary zeros with multiplicity one for systems with the relative degree one. It is shown that the Nyquist plot can be used to check the stability condition.     

Wavelength dependence of repetitive-pulse laser-induced damage threshold in beta-BaB2O4

The dependence on wavelength of repetitive-pulse (10 Hz, 8-10 ns) laser-induced damage on beta barium metaborate (BBO) has been investigated. The thresholds of dielectric breakdown in bulk crystal have been found to be 0.3 GW/cm(2) at 266 nm, 0.9 GW/cm(2) at 355 nm, 2.3 GW/cm(2) at 532 nm, and 4.5 GW/cm(2) at 1064 nm. Results indicate two-photon absorption at 266 and 355 nm, which helps to produce an avalanche effect that causes breakdown at each of the four wavelengths tested. Neither the BBO refractive indices nor the absorption spectrum change until breakdown occurs.     

A new artificial life body: biologically inspired dynamic bipedal humanoid robots

Recently, a biologically inspired, bipedal, dynamic, humanoid robot was developed at the Artificial Life and Robotics Laboratory of Oita University. This bipedal humanoid robot is able to walk dynamically and to go up and down stairs. The central pattern generator developed produces various types of walking pattern. This robot has a pair of small CMOS color CCD cameras, a speaker, and a microphone in the head part, and will have a GPS, a portable telephone, and other sensors in the body part, so that the integration of locomotion and behavior to achieve specific demonstrations will be realized. This project develops dynamic mobility and the ability for autonomous recognition and navigation using the biological central nervous system, the brain system, and the real-time control system. Also, the design principles that demonstrate the dynamic interaction between neural and mechanical controls will be clarified. In Phase I, the platform of a small, bipedal, humanoid robot is used to develop autonomous locomotion and autonomous sensing and navigation. In Phase II of the project, an iteration on the platform design for human-size, bipedal, humanoid robots will be performed for operational testing. The development of bipedal humanoid robots that capture biological systems with unique principles and practices could dramatically increase their performance in tasks for national security needs.This work was presented in part at the 8th International Symposium on Artificial Life and Robotics, Oita, Japan, January 24–26, 2003     

Parameter’s setting of the ant colony algorithm applied in preventive maintenance optimization

Meta-heuristic applications have evolved a lot nowadays and have been used in many domains. However, their parameter setting stills, till now, a serious problem which influences their efficiency and their attitude. Under the title of preventive maintenance optimization, the Ant Colony (AC) is used as a search technique for the best intervention dates to preventively maintain a series-parallel system. The AC proves once again its efficiency (Samrout, M., Yalaoui, F., Chatelet, E., & Chebbo, N. (2005). Reliability Engineering & System Safety, 89, 346–354), but the parameter setting’s issue persists as a critical issue which needs more analysis. This paper offers a detailed study about the influence of the parameters on the AC operation. An experimental plan design is done. Obtained results are coherent with the convergence conditions of the ant colony algorithms. Based on those latter, improvements are done to the original ant colony algorithm and interesting results are obtained.     

Carbon doping and etching in GaxIn1−xAsyP1−y on GaAs substrates using CBr4 by metalorganic chemical vapor deposition

Carbon doping and etching by CBr₄ were studied for Ga_xIn_1−xAs_yP_1−y (0≤y≤1) on GaAs grown by metalorganic chemical vapor deposition. It was found that the hole concentration drastically decreases with decreasing y when the flow rate of CBr₄ is constant. When y is under 0.5, the conduction type of GaInAsP changes ton-type. In the region of 0<y<0.6, the surface morphology was degraded and the carrier compensation became higher than could be estimated from the C concentration. This seems to be due to the micro defects because this range of composition is within the unstable region which is theoretically predicted. The etching effect by CBr₄ was observed during the growth. The rate of etching for InAsP component is about three times larger than that for the GaAsP component. The thermodynamic analysis suggests that the etching is due to the increase of the partial pressure of GaBr and InBr.     

Enzymatic Properties of β‐1,3‐Glucanase from Streptomyces sp Mo.

Streptomyces sp Mo endo‐β‐1,3‐glucanase was found to have hydrolyzing activity toward curdlan and released laminarioligosaccharides selectively. The molecular weight was estimated to be 36000 Da and its N‐terminal amino acid sequence was VTPPDISVTN. The optimal pH was 6 and the enzyme was found to be stable from pH 5 to 8. The optimal temperature was 60 °C and the activity was stable below 50 °C. The enzyme hydrolyzed selectively curdlan containing only β‐1,3 linkages. The enzyme had 89% relative activity toward Laminaria digitata laminarin, which contains a small amount of β‐1,6 linkages compared with curdlan, while Eisenia bicyclis laminarin with a higher amount of β‐1,6‐linkages, was not hydrolyzed. Mo enzyme adsorbed completely on curdlan powder. The enzymatic hydrolysis of curdlan powder resulted in the accumulation of laminaribiose (yield 81.7%). Trisaccharide was inevitably released from the hydrolysis of laminarioligosaccharides with 5 to 7 degrees of polymerization (DP). Although the enzyme cleaved off disaccharide (DP 2) from tetrasaccharide (DP 4), the reaction rate was lower than those of DP 5 to 7. The results indicated that the active site of Mo endo‐β‐1,3‐glucanase can efficiently recognize glucosyl residue chain of greater than DP 5 and hydrolyzes the β‐1,3 linkage between the 3rd and 4th glucosyl residue.     

Optimization of maintenance policy using the proportional hazard model

The evolution of system reliability depends on its structure as well as on the evolution of its components reliability. The latter is a function of component age during a system's operating life. Component aging is strongly affected by maintenance activities performed on the system. In this work, we consider two categories of maintenance activities: corrective maintenance (CM) and preventive maintenance (PM). Maintenance actions are characterized by their ability to reduce this age. PM consists of actions applied on components while they are operating, whereas CM actions occur when the component breaks down. In this paper, we expound a new method to integrate the effect of CM while planning for the PM policy. The proportional hazard function was used as a modeling tool for that purpose. Interesting results were obtained when comparison between policies that take into consideration the CM effect and those that do not is established.     

VLS growth of alternating InAsP/InP heterostructure nanowires for multiple-quantum-dot structures

We investigated the Au-assisted growth of alternating InAsP/InP heterostructures in wurtzite InP nanowires on InP(111)B substrates for constructing multiple-quantum-dot structures. Vertical InP nanowires without stacking faults were obtained at a high PH(3)/TMIn mole flow ratio of 300-1000. We found that the growth rate changed largely when approximately 40 min passed. Ten InAsP layers were inserted in the InP nanowire, and it was found that both the InP growth rate and the background As level increased after the As supply. We also grew the same structure using TBAs/TBP and could reduce the As level in the InP segments. A simulation using a finite-difference time-domain method suggests that the nanowire growth was dominated by the diffusion of the reaction species with long residence time on the surface. For TBAs/TBP, when the source gases were changed, the formed surface species showed a short diffusion length so as to reduce the As background after the InAsP growth.     

Building siRNAs with Cubes: Synthesis and Evaluation of Cubane-Modified siRNAs

Cubane molecules hold great potential for medicinal chemistry applications due to their inherent stability and low toxicity. In this study, we report the synthesis of a cubane derivative phosphoramidite for the incorporation of cubane into small interfering RNAs (siRNAs). Synthetic siRNAs rely on chemical modifications to improve their pharmacokinetic profiles. However, they are still able to mediate sequence-specific gene silencing via the endogenous RNA interference pathway. We designed a library of siRNAs bearing cubane at different positions within the sense and antisense strands. All siRNAs showed excellent gene-silencing activity, with IC₅₀ values ranging from 45.4 to 305 pM. Incorporating the cubane modification in both the sense and antisense strand led to viable duplexes with good biological activity. To the best of our knowledge, this is the first report of siRNAs bearing a cubane derivative within the backbone.