Low-power-loss and high voltage X-ray tube with graphite nanospines cold cathode

We report a low-power-loss and high voltage X-ray tubes with a graphite nanospines (GNS) cold cathode. The cathode is encapsulated in a glass tube having a Beryllium window with a Tantalum film to generate X-rays. The internal tube pressure was below 10⁻⁷ Pa and a tube current exceeding 1 mA at a tube voltage of 22.9 kV was observed in the fabricated X-ray tube. The tube current dispersion, defined as standard deviation/mean (σ/mean), was relatively small at 2.4%. An X-ray radiation dose rate exceeding 5 Sv/h was obtained from the X-ray tube and the radiation dose rate dispersion was also small (σ/mean=0.3%). As an application of the X-ray tube, we demonstrated radiography for the rapid inspection of organic products.     

Suppression of π/2−π Spin Echo in Solid 3He in High Fields

High demagnetizing field in solid ³ He leads to rich interesting phenomena such as multiple spin echoes. On the other hand, it has a severe influence on the appearance of the ordinary spin echo using /2– RF pulse sequence. We have observed spin echoes in solid ³ He in 7.4 Tesla, which appeared to decay on a much shorter time scale than T ₂ estimated from theories. This can be explained as follows. The angle made by the magnetization with the field after the -pulse differs a little from that before the pulse, because the -pulse employed in the experiment is inevitably not ideal. Since due to the demagnetizing field, the frequency of the precession motion depends on the angle between the magnetization and the field, the frequencies before and after the -pulse are different, which smeared out the spin echo. We have computed the damping time in various conditions, and found good agreement with experimental results.     

Silica and titanium dioxide nanoparticles cause pregnancy complications in mice

The increasing use of nanomaterials has raised concerns about their potential risks to human health. Recent studies have shown that nanoparticles can cross the placenta barrier in pregnant mice and cause neurotoxicity in their offspring, but a more detailed understanding of the effects of nanoparticles on pregnant animals remains elusive. Here, we show that silica and titanium dioxide nanoparticles with diameters of 70 nm and 35 nm, respectively, can cause pregnancy complications when injected intravenously into pregnant mice. The silica and titanium dioxide nanoparticles were found in the placenta, fetal liver and fetal brain. Mice treated with these nanoparticles had smaller uteri and smaller fetuses than untreated controls. Fullerene molecules and larger (300 and 1,000 nm) silica particles did not induce these complications. These detrimental effects are linked to structural and functional abnormalities in the placenta on the maternal side, and are abolished when the surfaces of the silica nanoparticles are modified with carboxyl and amine groups.     

Application of FIB microsampling technique to long-period ordered TiAl single crystal with composition gradient

Metastable long-period superstructures in an L10-TiAl single crystal with a composition gradient were observed successfully by transmission electron microscopy with a focused ion beam (FIB) microsampling technique. The composition gradient from 54.7 to 75 at.% Al with approximately 6 microm width was detected by electron probe microanalysis and foil specimens containing the composition-gradient area were fabricated by the FIB microsampling method. The foil specimens clearly exhibit sequential changes in long-period superstructure depending on the Al concentration.     

Electrical characteristics of Ge-based metal-insulator-semiconductor devices with Ge3N4 dielectrics formed by plasma nitridation

We have fabricated pure germanium nitrides (Ge3N4) using high-density plasma nitridation and investigated electrical properties of Au/Ge3N4/Ge capacitors. We achieved equivalent oxide thickness (EOT) of 1.4 nm, and dielectric constant of Ge3N4 was estimated to be 9.7. The gate leakage current density of 4.3 A/cm2 in the accumulation condition at V(fb)-1 V, where V(fb) is the flatband voltage, was one order of magnitude lower than that of conventional poly-Si/SiO2/Si stacks. The interface state density (D(it)) of Ge3N4/Ge interfaces evaluated by a low-temperature conductance method exhibited a minimum value of 9.4 x 10(11) cm(-2)eV(-1) at E - E(v) = 0.27 eV. Furthermore, the insulating property and interface quality of Ge3N4/Ge system was found to be thermally stable up to 650 degrees C. These results indicate that Ge3N4 is a promising candidate for either a gate insulator or an interfacial layer under high-k dielectrics for Ge-MIS devices.     

ACCELERATION OF CRACK GROWTH UNDER INTERMITTENT OVERLOADING AT ELEVATED TEMPERATURE

Abstract— Acceleration of crack growth by intermittent overloading was investigated at 650°C by using specimens of different thickness made of Type 304 stainless steel. When the hold time of overload was very short (∼20s), the crack growth rate was significantly accelerated (20–50 times) and the fracture surface morphology showed extremely ductile transgranular fracture by glide plane decohesion or microvoid coalescence, suggesting significant recovery of the material. In the thinner plate specimens, the crack growth rate under intermittent overloading was correlated well with the modified J -integral, i.e. J ( C %) and agreed with the growth rate of static creep cracks in a J versus d a /d t diagram. In the thicker plate specimens, however, this is not the case and the growth rate was about 20% of that in the thinner plate specimens in the J diagram. Transgranular fatigue type crack growth appeared in the low growth rate region.     

Effect of bubble nuclei on freezing of supercooled water

In order to clarify effects of bubble nuclei on freezing of supercooled water, various kinds of experiments were carried out with invisible sizes of bubbles in supercooled water. Water samples were kept in a test tube and cooled down at a constant cooling rate until the water solidified. The degree of supercooling at freezing was then measured. Two kinds of water surfaces were applied. One was exposure to the atmosphere, and the other was covered with silicone oil. Three kinds of pressure conditions were applied. The first type was atmospheric pressure. The second type was compression up to 6.0 atm. The third type was evacuated down to 0.02 atm. Two holding time periods before starting the experiments were applied. One was 30 min and the other was 24 h. It was found that the degree of supercooling at freezing is high in the case of the free surface compared to the one with oil–water surface. The reason suggested was that the bubbles in the water can be released from the surface in the case of normal atmospheric exposure and trapped at the oil–water interface in the case of water covered with oil. Hence, it was clarified that the freezing of supercooled water is affected by the existence of bubble nuclei.     

Biomechanical evaluation of regenerating long bone by nanoindentation

It is crucial to measure the mechanical function of regenerating bone in order to assess the mechanical performance of the regenerating portion as well as the efficiency of the regeneration methods. In this study, nanoindentation was applied to regenerating and intact rabbit ulnae to determine the material properties of hardness and elasticity; viscoelasticity was also investigated to precisely evaluate the material properties. Both intact and regenerating bones exhibited remarkable viscoelasticity manifested as a creep behavior during load hold at the maximum load, and the creep was significantly greater in the regenerating bone than the intact bone. The creep resulted in an overestimation of the hardness and Young’s modulus. Hence, during nanoindentation testing of bones, the effect of creep should be eliminated. Moreover, the regenerating bone had lower hardness and Young’s modulus than the intact bone. The nanoindentation technique proved to be a powerful approach for understanding the mechanical properties of regenerating bone.     

Mathematical Modeling of Metal Active Gas (MAG) Arc Welding

In the present paper. a numerical model for MAG (metal active gas) arc welding of thin plate has been developed. In MAG arc welding, the electrode wire is melted and supplied into the molten pool intermittently. Accordingly, it is assumed on the modeling that the thermal energy enters the base-plates through two following mechanisms, i.e., direct heating from arc plasma and "indirect" heating from the deposited metal. In the second part of the paper, MAG arc welding process is numerically-analyzed by using the model. and the calculated weld bead dimension and surface profile have been compared with the experimental MAG welds on steel plate. As the result. it is made clear that the model is capable of predicting the bead profile of thin-plate MAG arc welding, including weld bead with undercutting.     

基于望远镜搜索的块匹配运动估值的低功耗VLSI结构

在一种基于望远镜搜索的块匹配运动估值的 VL SI实现中 ,对用于加速搜索的传统心动阵列引擎进行了结构上的改进 ,从而能够显著地降低功耗 .方法是使用一种新的块匹配误差计算的提早跳出技术 ,并通过在阵列处理单元中屏蔽操作数来避免不必要的计算操作 .基于算法模拟结果的简单估计表明 :使用新结构搜索引擎的运动估值 ,功耗可降低到原来的 40 %左右 ,而仍然保持着相同的处理速度和相似的视频解码图质量 .