Control of carbon incorporation in AlAs grown by atomic layer epitaxy using variously orientated substrates

We demonstrate a method for successfully controlling carbon incorporation in AlAs layers grown by atomic layer epitaxy (ALE) using various GaAs substrates with different orientations. The number of alkyl radicals attached to an Al atom at the surface, which is a main factor in carbon incorporation, can be intentionally controlled by changing substrate orientation. We found that the carbon incorporation in ALE-AlAs using the (3 1 1)B surface is 2 x 10¹⁷,cm^-3, which is the lowest value ever reported for ALE-AlAs that satisfies one-monolayer self-limiting growth conditions.     

Pb-free surface-finishing on electronic components’ terminals for Pb-free soldering assembly

Pb-free solderable surface finishing is essential to implement Pb-free solder assembly in order to meet with the growing demand of environmental consciousness to eliminate Pb from electronic products. Two types of widely applicable Pb-free surface finishing technologies are developed. One is the multilayer-system including Pd with Ni undercoat. Heat-resistance of Pd enables whole-surface-plating on to leadframe before IC-assembling process. The other is the double-layer-system with low-melting-point-materials, for example, thicker Sn underlayer and thinner Sn-Bi alloy overlayer, dilutes Sn-Bi alloy’s defects of harmful reactivity along with substrate metal and mechanical brittleness with keeping its advantages of solder-wettability and no whisker.     

Programmed High‐Hole‐Mobility Supramolecular Polymers from Disk‐Shaped Molecules

In this paper a simple, casting solution technique for the preparation of two‐dimensional (2D) arrays of very‐high molecular weight (MW) 1D‐Pc supramolecular inorganic polymers is described. The soluble fluoroaluminium tetra‐tert‐butylphthalocyanine (ttbPcAlF) is synthesized and characterized, which can be self‐assembled to form 2D arrays of very‐high‐MW 1D‐Pc supramolecular inorganic polymers. High‐resolution transmission electron microscopy (HRTEM) demonstrates that the 1D‐ttbPcAlF, having a cofacial ring spacing of ～0.36 nm and an interchain distance of ～1.7 nm, self‐assembles into 2D‐nanosheets (～140 nm in length, ～20 nm in width, and equivalent to MW of 3.2 × 10⁵ g mol^?1). The film cast from a 1,2‐dichloroethane (DCE) solution shows a minimum hole‐mobility of ～0.3 cm² V^?1 s^?1 at room temperature by flash‐photolysis time‐resolved microwave conductivity (TRMC) measurements and a fairly high dark dc‐conductivity of ～1 × 10^?3 S cm^?1.     

Study on the urban heat island mitigation effect achieved by converting to grass-covered parking

The urban heat island mitigation effect of conversion from asphalt-covered parking areas to grass-covered ones is estimated by observation and calculation. The mean surface temperature in a parking lot is calculated from a thermal image captured by an infrared camera. The sensible heat flux in each parking space is calculated based on the surface heat budget. The reduction in the sensible heat flux is estimated to be approximately 100-150 W m⁻² during the day and approximately 50 W m⁻² during the night, in comparison with an asphalt surface. The air temperature reduction by the spread of grass-covered parking areas is calculated to be about 0.1 °C. Furthermore, consideration is given to the appearance of the parking lot, the growth of grass, the effects of the weight of a car and the heat radiated from its engine, the costs of construction and maintenance, etc.     

Arterial-venous carbon dioxide tension difference after hypothermic cardiopulmonary bypass

Arterial-venous carbon dioxide tension difference (Pv-aCO2) is known to become high after severe hemorrhage shock and resuscitation. We hypothesized that Pv-aCO2 might be high after cardiac surgery because of the oxygen debt occurred during hypothermic cardiopulmonary bypass (CPB). Blood pressure, cardiac index, hemoglobin, the arterial and mixed venous blood gases were repeatedly measured every 6 hours for 24 hours following cardiac surgery in 60 adult patients who underwent hypothermic CPB. Immediately after the surgery, Pv-aCO2 was extremely high, then gradually decreased to within normal ranges 12 hours later (8.0 +/- 2.9 mmHg vs 5.9 +/- 3.1 mmHg. p < 0.01). Factors which significantly correlated to Pv-aCO2 were cardiac index, oxygen delivery, minimum rectal temperature and duration of CPB. Oxygen debt during hypothermic CPB might cause significantly high Pv-aDO2. At least 12 hours were necessary to recover from anaerobic status to physiological condition.     

Solid-state diffusion bonding of silicon nitride using titanium foils

This article presents an effective way to control the interfacial reaction during solid-state diffusion bonding of silicon nitride (Si₃N₄) using titanium foils. The interfacial structure and its growth kinetics were analyzed in detail with scanning electron microscopy (SEM), electron-probe microanalysis (EPMA), and X-ray diffraction (XRD). The actual phase sequence of the joint interfaces bonded at temperatures between 1473 and 1673 K is concluded to be Si₃N₄/Ti₅Si₃(N)/α-Ti(N)+Ti₅Si₃(N), which is different from the phase sequence observed at room temperature after bonding. The joints are very weak due to the formation of a brittle Ti₅Si₃(N) layer at the interface. To suppress the growth of the Ti₅Si₃ layer, a nitrogen-solution treatment of titanium foils prior to each bonding experiment is implemented. Although a perfect prevention of the Ti₅Si₃(N) layer formation is not achieved with this treatment, it is shown that the growth of the layer is effectively suppressed enough to improve the joint strength to a level 3 times higher than the case in which pure titanium is employed.     

Development of systems reliability analysis code SECOM-2 for seismic PSA

An integrated code system SECOM-2, developed at the Japan Atomic Energy Research Institute (JAERI), has the following functions for systems reliability analysis in seismic probabilistic safety assessments (PSAs): (1) calculation of component failure probability, (2) extraction of minimal cut sets (MCSs) from a given fault tree (FT), (3) calculation of frequencies of accident sequences and core damage, (4) importance analysis with several measures with consideration of unique parameters of seismic PSAs, (5) sensitivity analysis, and (6) uncertainty analysis. This paper summarizes the special features of SECOM-2 to perform the analyses mentioned above. At JAERI, using an integrated FT which represents seismically induced core damage due to all initiating events as a system model to calculate core damage frequency of a nuclear power plant, SECOM-2 can calculate conditional point estimate probabilities of system failures, losses of safety functions, and core damage as a function of earthquake motions. The point estimate is computed by a method which gives an exact numerical solution using the Boolean arithmetic model method. As for consideration of correlation of component failure, which has been an important issue in seismic PSAs, a new technique based on direct FT quantification by a Monte Carlo simulation is being added to SECOM-2. Adding this technique, the core damage frequency can be calculated not only with the upper bound approximation based on MCSs but also with a near exact solution taking into account the correlation among all components. This paper also presents the preliminary results of a seismic PSA of a generic BWR plant in Japan performed at JAERI to demonstrate the functions of the SECOM-2 code.     

D-aspartate modulates melatonin synthesis in rat pinealocytes

The effect of protection of dopaminergic neurons by talipexole, a dopamine (DA) agonist, is investigated on a methamphetamine (MA)-induced parkinsonism model of mice (C57BL/6N). The reduction of tyrosine hydroxylase activity in the striatum 72 h after MA (5 mg/kg every 2 h, four times) treatment was attenuated by the administration of talipexole (0.25 mg/kg or 1.0 mg/kg) prior to the administration of MA. In an in vitro experiment, talipexole inhibited the adduction reaction of hydroxyl radicals to salicylate. Taken together, these data suggest that the protective effect of talipexole on DA neurons is, in part, caused by the hydroxyl radical-scavenging action of the drug.