Experimental Investigations of Whisker Formation on Tin Platings

With the global transition to lead-free electronics, the electronic component market has seen an increase in the selection of pure tin and tin-rich alloys as lead-free component finishes. The adoption of tin-rich finishes has enhanced a reliability issue associated with the formation of electrically conductive whiskers, emanating from tin finished surface. A spontaneous growth of whisker may bridge adjacent conductors, leading to current leakage or electrical shorts. Whiskers tend to grow over many months. However, due to a lack of the factors accelerating whisker growth, prediction of whisker formation is extremely difficult. Therefore, the effective mitigation strategies are necessary, particularly for high-reliability applications, which require a long product operational life. The objective of this study is to investigate a method for characterizing whisker growth, which can further enable measuring the effectiveness of mitigation strategies. To achieve this objective, a set of experiments was conducted using matte and bright tin platings on copper, Alloy-42, and brass metal coupons. The plated coupons were subjected to high temperature exposures, including annealing (at 150ºC/one hour). Whisker growth on tin-plated samples was characterized using environmental scanning electron microscopy, in terms of the maximum whisker length, length distribution, and whisker density, at different time periods up to 24 months. The experimental results have shown different behaviors of whisker growth (length and density) between bright and matte tin, depending on the materials and exposure conditions. It was experimentally demonstrated that bright tin over brass could be considered a worst-case scenario for assessing the risks associated with tin whiskers. This work has further revealed that the current industry practice of testing for 3000 hours for monitoring the propensity of tin whiskers is insufficient to cover a saturation of whisker density and capture the temporal nature of whiskers. In order to overcome such insufficiencies, the use of time-based distribution data for whisker length and whisker density was proposed as an alternative method for characterizing whisker growth. With the application of this proposed method, the effect of annealing (150ºC/one hour) and its effect under the presence of electrical current were investigated for retarding whisker formation and growth on tin-plating

Monotonicity for Multiobjective Accelerated Proximal Gradient Methods

Accelerated proximal gradient methods, which are also called fast iterative shrinkage-thresholding algorithms (FISTA) are known to be efficient for many applications. Recently, Tanabe et al. proposed an extension of FISTA for multiobjective optimization problems. However, similarly to the single-objective minimization case, the objective functions values may increase in some iterations, and inexact computations of subproblems can also lead to divergence. Motivated by this, here we propose a variant of the FISTA for multiobjective optimization, that imposes some monotonicity of the objective functions values. In the single-objective case, we retrieve the so-called MFISTA, proposed by Beck and Teboulle. We also prove that our method has global convergence with rate $O(1/k^2)$, where $k$ is the number of iterations, and show some numerical advantages in requiring monotonicity.Comment: - Added new numerical experiment

Differences in the Composition of Activated Partial Thromboplastin Time (APTT) Reagents Affect Clot Waveform Analysis

Background Clot waveform analysis (CWA) based on activated partial thromboplastin time (APTT) is a useful assay for hemostasis. However, the effects of activators and phospholipid conditions on CWA have not been adequately investigated. Therefore, we characterized CWA using four different APTT reagents. Methods: We used 39 archived plasma samples from patients with hemophilia A (HA), 16 samples from patients with HA under emicizumab treatment, and 10 samples from healthy individuals for CWA with four different types of APTT reagents (reagents A, B, C, and D). We then compared Ad|min1|, Ad|min2|, and Ad|max2| from the CWA, which reflect the maximum velocity, maximum acceleration, and maximum deceleration, respectively, among the four reagents. Results: Similar clot waveform shapes were observed for each reagent in the healthy donor group, HA group, and HA under emicizumab group, and the waveform was different for each target group. Significant changes were found in clotting time (CT) (s), Ad|min1| (%/s), Ad|min2| (%/s2), and Ad|max2| (%/s2). The waveform pattern for the coagulation reaction by reagent D, comprising silica and synthetic phospholipids, was the fastest among the reagents examined. Further, the difference in Ad|min1| (%/s) and Ad|min2| (%/s2) was larger than that in CT depending on the reagent used(s), indicating that the measured value of CWA was affected by the reagent composition. Conclusion: Our results showed a significant difference among reagents with varying composition and concentration; this was found to affect the parameters obtained from CWA. Thus, the differences between reagents hinder standardization of quantitative evaluation using these parameters; further, this highlights the necessity of understanding the characteristics of APTT reagents and determining the reference range in individual facilities

A RecA-mediated exon profiling method

We have developed a RecA-mediated simple, rapid and scalable method for identifying novel alternatively spliced full-length cDNA candidates. This method is based on the principle that RecA proteins allow to carry radioisotope-labeled probe DNAs to their homologous sequences, resulting in forming triplexes. The resulting complex is easily detected by mobility difference on electrophoresis. We applied this exon profiling method to four selected mouse genes as a feasibility study. To design probes for detection, the information on known exonic regions was extracted from public database, RefSeq. Concerning the potentially transcribed novel exonic regions, RNA mapping experiment using Affymetrix tiling array was performed. As a result, we were able to identify alternative splice variants of Thioredoxin domain containing 5, Interleukin1β, Interleukin 1 family 6 and glutamine-rich hypothetical protein. In addition, full-length sequencing demonstrated that our method could profile exon structures with >90% accuracy. This reliable method can allow us to screen novel splice variants from a huge number of cDNA clone set effectively

Identification of cyst nematode B-type CLE peptides and modulation of the vascular stem cell pathway for feeding cell formation.

Stem cell pools in the SAM (shoot apical meristem), RAM (root apical meristem) and vascular procambium/cambium are regulated by CLE-receptor kinase-WOX signaling modules. Previous data showed that cyst nematode CLE-like effector proteins delivered into host cells through a stylet, act as ligand mimics of plant A-type CLE peptides and are pivotal for successful parasitism. Here we report the identification of a new class of CLE peptides from cyst nematodes with functional similarity to the B-type CLE peptide TDIF (tracheary element differentiation inhibitory factor) encoded by the CLE41 and CLE44 genes in Arabidopsis. We further demonstrate that the TDIF-TDR (TDIF receptor)-WOX4 pathway, which promotes procambial meristem cell proliferation, is involved in beet cyst nematode Heterodera schachtii parasitism. We observed activation of the TDIF pathway in developing feeding sites, reduced nematode infection in cle41 and tdr-1 wox4-1 mutants, and compromised syncytium size in cle41, tdr-1, wox4-1 and tdr-1 wox4-1 mutants. By qRT-PCR and promoter:GUS analyses, we showed that the expression of WOX4 is decreased in a clv1-101 clv2-101 rpk2-5 mutant, suggesting that WOX4 is a potential downstream target of nematode CLEs. Exogenous treatment with both nematode A-type and B-type CLE peptides induced massive cell proliferation in wild type roots, suggesting that the two types of CLEs may regulate cell proliferation during feeding site formation. These findings highlight an important role of the procambial cell proliferation pathway in cyst nematode feeding site formation

Children with unilateral aural atresia

The effects of FM system fitted into the normal hearing ear (NHE) or a cartilage conduction hearing aid (CCHA) fitted into the affected ear (AE) on the speech recognition ability in noise were examined in children with unilateral congenital aural atresia (UCAA). In children with bilateral normal hearing (BNH), speech recognition score (SRS) was significantly decreased in the noisy environment of -5 dB signal-to-noise ratio (SNR), compared with those in quiet. In children with UCAA, SRS was significantly decreased in noisy environments of 0 and -5 dB SNR, compared with those in quiet. In noisy environments of 0 and -5 dB SNR, SRS in children with UCAA was significantly decreased, compared those in children with BNH. In the noisy environment of -5 dB SNR, SRS in UCAA children aided by FM system fitted into NHE was significantly better than those in unaided children in the same group. In the noisy environment of 0 dB SNR, SRS in UCAA children aided by CCHA into AE tended to be higher than those in unaided children in the same group. FM system and CCHA can be recommended as an audiological management for the improvement of speech recognition in children with UCHL in classrooms

The Development of Lesson Plans to Enable Diversity and Collaboration (II): Focusing on Ways to Elicit Unique Modes of Expression of Each Student

In this study, the authors aimed to develop lessons in which diversity and collaboration were ensured through children's cooperative involvement in a special class for students with intellectual disabilities. To bring out unique modes of expression for each student, the authors framed two practices and analyzed, as a lesson study, children's activities and the teacher's support in an unformulated communicative learning process. The authors found three key results. First, children's expressions deepen through a combination of both imitation and exploration, and collaboration emerged through this deepening process. Second, the pursuit of a teaching practice oriented toward diversity and collaboration contributes to the growth and development of both children and teachers, through discussing the learning environment, the teacher's actions, and the processes through which children explore their expressions. Third, children's motives for expression can be encouraged through intellectual curiosity and interest in musical instruments, the creation of an atmosphere where children can feel comfortable and the creation of positive relationships and a sense of partnership among the children and teacher. Their need for competence, then, can be stimulated by activities such as imitating each other's expression

Transcription and Annotation of “Memorandum on Adam Smith\u27s Library in 1950s”

特集 東京大学経済学図書館所蔵貴重図書の研究Special Feature Studies on the Rare Books of the Library of Economics掲載写真をカラーで提供（冊子体はモノクロ

Biorhythm-Based Awakening Timing Modulation

Abstract-The purpose of the present study is to control human biological rhythm and life cycle by optimization of awakening timing. We developed a wearable interface for controlling awakening time named "BRAC (Biological Rhythm based Awakening timing Controller)". BRAC could estimate bio-rhythm by pulse wave from finger tip and send awake signal to user. An ordinary alarm clock operates according to set times that have to be set in advance. However, humans have a rhythm in their sleep, which affects one's sleep depth and wake-up timing. We consider the simplest way to control or reset human's biorhythm or life style is to optimize the awakening timing and the sleeping hours. We examined the relationship between controlling awakening timing based on autonomous nerve rhythm and equilibrium function. Our findings suggest indicate that the prototype "BRAC" could evaluate user's biological rhythm and awakes user at the time optimized for physical function of equilibrium