Preparation of bismuth nanowire encased in quartz template for Hall measurements using focused ion beam processing

ABSTRACT: Forming electrodes on opposite sides of an individual bismuth nanowire was attempted to prepare for Hall measurements. Although a 1-mm-long bismuth nanowire which is completely covered with a quartz template has been successfully fabricated to prevent oxidation, it is very difficult to attach Hall electrodes on the opposite sides of the nanowire due to the quartz covering. One side of the cylindrical quartz template was removed by polishing without exposure of the nanowire to the atmosphere; the thickness between the polished template surface and the nanowire was estimated to be several micrometers. Focused ion beam processing was successfully employed to expose both surfaces of the nanowire under high vacuum by removing part of the quartz template. A carbon thin film was then deposited in situ on the wire surface to fabricate an electrical contact on the bismuth nanowire sample. Furthermore, the energy dispersive X-ray analysis was performed to the area processed by focused ion beam, and the bismuth component of the nanowire was successfully detected. It was confirmed that the focused ion beam processing was applicable to attach electrodes to bismuth nanowire for Hall measurement.     

Measurement of Flow Stress in Supercooled Austenite for High Hardenability Steel

In this article, the isothermal flow stress in supercooled austenite was measured for a high hardenability steel. Supercooled austenite forms at the nonequilibrium phase and changes into other phases within a short time. It was confirmed that conventional tensile tests, which require maintaining a constant temperature before stretching, cannot accurately measure the flow stress in supercooled austenite. Therefore, a new tensile test named “the continuous cooling tensile test” was developed. In this test, stretching is conducted during continuous cooling. In the continuous cooling tensile test, the flow stress between 673 K and 973 K (400 °C and 700 °C) was measured. Microscopic observations of the continuous cooling test results verified that the microstructures were supercooled austenite.     

含黏粒砂土场地液化离心机振动台试验研究

提出了含黏粒砂土模型地基制备、饱和与均匀性监测技术,利用ZJU-400土工离心机振动台开展了相同相对密度含黏粒砂土（黏粒含量10%）和洁净砂的地震液化模型试验,再现了水平场地地震液化现象,揭示了含黏粒砂土场地液化灾变特点。弯曲元波速监测表明,模型制备均匀性良好,相同条件下含黏粒砂土剪切波速比洁净砂低。而根据超静孔压消散与固结沉降观测分析发现,含黏粒砂土渗透系数比洁净砂低一个数量级,从而影响其液化前后超静孔压响应和应力应变行为。渗透性差异导致模型内超静孔压产生模式和消散速率显著不同,振动时含黏粒砂土模型浅层超静孔压累积比洁净砂慢,而深层则相反;震后含黏粒砂土孔压消散时间是洁净砂的15倍。液化过程中含黏粒砂土剪应力应变响应比相同深度处的洁净砂更显著,液化后其滞回圈应变较大、割线模量较小且阻尼比较大。土体液化沉降主要发生在液化后超静孔压消散过程,含黏粒砂土模型超静孔压消散时间更长,沉降量更大。上述成果为进一步研究含黏粒砂土地震响应分析及其液化判别提供了科学依据。     

Improving the gas recovery and separation efficiency of a hydrate-based gas separation

Efficient gas recovery and separation in a hydrate-based system was investigated for a model gaseous mixture of R22 and nitrogen. The formed hydrate settled in the recovery vessel; excess water was recycled and the hydrate was subsequently decomposed by releasing pressure from the vessel. The gas uptake rate of R22 gas from the vapor phase and the gas recovery rate from the hydrate were determined from hydrate formation and decomposition, respectively. The gas recovery rate of R22 gas gradually increased with time. On the contrary, the nitrogen gas recovery rate was a maximum in the initial stage of hydrate decomposition. A high separation factor (S.F.) was achieved by first separating the N₂-rich gas generated during initial hydrate decomposition. An efficient hydrate-based gas separation and recovery process is proposed.     

Application of Near-Infrared Spectroscopy for Evaluation of Drying Stress on Lumber Surface: A Comparison of Artificial Neural Networks and Partial Least Squares Regression

This study aimed to examine the feasibility of evaluating the stress level at the surface of lumber during drying using near-infrared (NIR) spectroscopy combined with artificial neural networks (ANNs). Sugi (Cryptomeria japonica D. Don) lumber with an initial moisture content ranging from 41.1 to 85.8% was dried using a commercial drying schedule. An ANN model for predicting surface-released strain (SRS) was developed based on NIR spectra collected from the lumber during drying. The predictive ability of the ANN model was compared with a partial least squares (PLS) regression model.

The ANN model showed good correlation between laboratory-measured SRS and predicted SRS with an R ² of 0.79, a root mean square error of prediction (RMSEP) of 0.0009, and a ratio of performance to deviation (RPD) of 1.81. The PLS regression model gave a lower R ² of 0.69, a higher RMSEP of 0.0010, and a lower RPD of 1.38 than the ANN model, suggesting that the predictive performance of the ANN model was superior to the PLS regression model. The SRS evolution during drying as predicted by the models showed a similar trend to the laboratory-measured one. The predicted elapsed times to reach maximum tensile SRS and stress reversal roughly coincided with the laboratory-measured times. These results suggest that NIR spectroscopy combined with multivariate analysis has the potential to predict the drying stress level on the lumber surface and the critical periods during drying, such as the points of maximum tensile stress and stress reversal.     

The Association of Cholesterol Uptake and Synthesis with Histology and Genotype in Cortisol-Producing Adenoma (CPA)

Cortisol-producing adenoma (CPA) is composed of clear and compact cells. Clear cells are lipid abundant, and compact ones lipid poor but associated with higher production of steroid hormones. PRKACA mutation (PRKACA mt) in CPA patients was reported to be associated with more pronounced clinical manifestation of Cushing’s syndrome. In this study, we examined the association of histological features and genotypes with cholesterol uptake receptors and synthetic enzymes in 40 CPA cases, and with the quantitative results obtained by gas chromatography-mass spectrometry (GC-MS) analysis in 33 cases to explore their biological and clinical significance. Both cholesterol uptake receptors and synthetic enzymes were more abundant in compact cells. GC-MS analysis demonstrated that the percentage of compact cells was inversely correlated with the concentrations of cholesterol and cholesterol esters, and positively with the activity of cholesterol biosynthesis from cholesterol esters. In addition, hormone-sensitive lipase (HSL), which catalyzes cholesterol biosynthesis from cholesterol esters, tended to be more abundant in compact cells of PRKACA mt CPAs. These results demonstrated that both cholesterol uptake and biosynthesis were more pronounced in compact cells in CPA. In addition, more pronounced HSL expression in compact cells of PRKACA mt CPA could contribute to their more pronounced clinical manifestation.     

Dielectric study of β-relaxation in some cellulosic substances

6-(2-Cyanoethylamino)-6-deoxycellulose (Cell-CEA) as a novel cellulose derivative was prepared from 6-bromo-6-deoxycellulose. The influence of the reaction conditions on the degree of substitution was studied in detail. The dielectric characteristics of a Cell-CEA sample having degree of substitution of 0.86, together with those of microcrystalline and regenerated celluloses, have been investigated in the temperature range from −60 to 120°C, and frequency range 30 Hz to 100kHz. One relaxation process, designated as β, was recognised, which was attributed to side-group motions, probably −CH₂X (X = OH or NHCH₂CH₂CN). The higher activation energy of this process and the shift to higher temperature in Cell-CEA, compared with microcrystalline and regenerated celluloses, reflects the enhanced steric constraints involved in the motion of the bulkier, −CH₂NHCH₂CH₂CN, side groups. The results obtained are discussed in terms of the dielectric parameters ϵ″_max′ β and Δϵ.     

Structural and electrical characteristics of high-κ Er2O3 and Er2TiO5 gate dielectrics for a-IGZO thin-film transistors

In this letter, we investigated the structural and electrical characteristics of high-κ Er₂O₃ and Er₂TiO₅ gate dielectrics on the amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) devices. Compared with the Er₂O₃ dielectric, the a-IGZO TFT device incorporating an Er₂TiO₅ gate dielectric exhibited a low threshold voltage of 0.39 V, a high field-effect mobility of 8.8 cm²/Vs, a small subthreshold swing of 143 mV/decade, and a high I_on/I_off current ratio of 4.23 × 10⁷, presumably because of the reduction in the oxygen vacancies and the formation of the smooth surface roughness as a result of the incorporation of Ti into the Er₂TiO₅ film. Furthermore, the reliability of voltage stress can be improved using an Er₂TiO₅ gate dielectric.     

Stereocomplex crystallization and spherulite growth behavior of poly(l-lactide)-b-poly(d-lactide) stereodiblock copolymers

The non-isothermally and isothermally crystallized stereodiblock copolymers of poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) with equimolar l-lactyl and d-lactyl units and different number-average molecular weights (M_n) of 3.9 × 10³, 9.3 × 10³, and 1.1 × 10⁴ g mol⁻¹, which are abbreviated as PLLA-b-PDLA copolymers, contained only stereocomplex crystallites as crystalline species, causing higher melting temperatures of the PLLA-b-PDLA copolymers compared to those of PLLA homopolymers. In the case of non-isothermal crystallization, the cold crystallization temperatures of the PLLA-b-PDLA copolymers during heating and cooling were respectively lower and higher than those of PLLA homopolymers, indicating accelerated crystallization of PLLA-b-PDLA copolymers. In the case of isothermal crystallization, in the crystallizable temperature range, the crystallinity (X_c) values of the PLLA-b-PDLA copolymers were lower than those of the PLLA homopolymers, and were susceptible to the effect of crystallization temperature in contrast to that of homopolymers. The radial growth rate of the spherulites (G) of the PLLA-b-PDLA copolymers was the highest at the middle M_n of 9.3 × 10³ g mol⁻¹. This trend is different from that of the PLLA homopolymers where the G values increased monotonically with a decrease in M_n, but seems to be caused by the upper critical M_n values of PLLA and PDLA chains as in the case of PLLA/PDLA blends (in other papers), above which homo-crystallites are formed in addition to stereocomplex crystallites. The disturbed crystallization of PLLA-b-PDLA copolymers compared to that of the PLLA/PDLA blend is attributable to the segmental connection between the PLLA and PDLA chains, which interrupted the free movement of those chains of the PLLA-b-PDLA copolymers during crystallization. The crystallite growth mechanism of the PLLA-b-PDLA copolymers was different from that of the PLLA/PDLA blend.