Gate-tuned negative differential resistance observed at room temperature in an array of gold nanoparticles

We fabricated a single-electron (SE) device using gold nanoparticles (Au NPs). Drain, source, and gate electrodes on a SiO2/Si substrate were formed using electron beam lithography (EBL) and thermal evaporation of Au. Subsequently, solutions of 3-nm-diameter and 5-nm-diameter Au NPs were dropped on the device to make current paths through Au NPs among the electrodes. Measurements of the device exhibited negative differential resistance (NDR) in the current-voltage characteristics between the drain and source electrodes at room temperature (298 K). The NDR behavior was tuned by applying a gate voltage

Fabrication of resistively-coupled single-electron device using an array of gold nanoparticles

We demonstrated one type of single-electron device that exhibited electrical characteristics similar to those of resistively-coupled SE transistor (R-SET) at 77 K and room temperature (287 K). Three Au electrodes on an oxidized Si chip served as drain, source, and gate electrodes were formed using electron-beam lithography and evaporation techniques. A narrow (70-nm-wide) gate electrode was patterned using thermal evaporation, whereas wide (800-nm-wide) drain and source electrodes were made using shadow evaporation. Subsequently, aqueous solution of citric acid and 15-nm-diameter gold nanoparticles (Au NPs) and toluene solution of 3-nm-diameter Au NPs chemisorbed via decanethiol were dropped on the chip to make the connections between the electrodes. Current–voltage characteristics between the drain and source electrodes exhibited Coulomb blockade (CB) at both 77 and 287 K. Dependence of the CB region on the gate voltage was similar to that of an R-SET. Simulation results of the model based on the scanning electron microscopy image of the device could reproduce the characteristics like the R-SET

Fluctuated spin-orbital texture of Rashba-split surface states in real and reciprocal space

Spin-orbit interaction (SOI) in low-dimensional systems, namely Rashba systems and the edge states of topological materials, is extensively studied in this decade as a promising source to realize various fascinating spintronic phenomena, such as the source of the spin current and spin-mediated energy conversion. Here, we show the odd fluctuation in the spin-orbital texture in a surface Rashba system on Bi/InAs(110)-(2$\times$1) by spin- and angle-resolved photoelectron spectroscopy and a numerical simulation based on a density-functional theory (DFT) calculation. The surface state shows a paired parabolic dispersion with the spin degeneracy lifted by the Rashba effect. Although its spin polarization should be fixed in a particular direction based on the Rashba model, the observed spin polarization varies greatly and even reverses its sign depending on the wavenumber. DFT calculations also reveal that the spin directions of two inequivalent Bi chains on the surface change from nearly parallel (canted-parallel) to anti-parallel in real space in the corresponding wavevector region. These results point out an oversimplification of the nature of spin in Rashba and Dirac systems and provide more freedom than expected for spin manipulation of photoelectrons.Comment: 23 pages, 7 figure

車椅子利用下における路面の影響調査

【目的】車椅子利用者の安楽に及ぼす影響の１つとして「声かけ」に注目して，バリアが車椅子利用者の体感にどのような影響を及ぼすのかを知ることとを目的とした研究を行った． 【方法】対象者は，２０歳代女性の看護学生で，車椅子利用時の体感に体重が影響することを考慮し標準体重に近い者を選定した．路面の状態については，観察，自走介助兼用車椅子に装着した振動計，座席用振動ピックアップを用い客観的測定を行った．声かけによる路面の状態による主観的反応の相違は，対象者６０人を無作為にA群の「声かけあり群（n＝３０）」と，B群の「声かけなし群（n＝３０）」の２群に分けて把握した． 【倫理的配慮】対象者に本研究の目的及び方法を説明し，同意書に署名してもらった． 【分析方法】アンケート調査結果について２群を比較した．ゆれ・恐怖感・乗り心地の段階評価においてはウィルコクソンの符号順位和検定を行った． 【結果および考察】路面の見かけと振動値は概ね一致していたが，見かけは平らであっても振動値は高い場所もあった．路面に対する反応は以下の通りである． １．振動が大きいところでは対象者の全身に振動を与え，不快をもたらしていた． ２．傾斜があるところでは対象者に恐怖感をもたらしていた． ３．声かけは対象者が振動を予測して，態勢を整えることに役立っていた． ４．声かけは安心感や気分転換等にもつながっていた． 以上のことから，車椅子利用者の介助に当たって声かけをすることは重要であることが明らかになった．また，多様な路面の性状下でも快適な車椅子利用ができるような介助の方法を探究していきたい．さらに，今回の結果は，車椅子以外にもシルバーカーや自走車椅子利用者の支援のあり方を示唆するものと考えられる．Aim : A research was conducted to investigate the influence by barriers of road surface on the bodily sensation of wheelchair users, while paying attention to “calling” as a factor influencing the comfort of the users. Method : The subjects were chosen from student nurses in their twenties. The objective measurement of the conditions of road surface was carried out through the use of observation, a vibrograph equipped on wheelchairs designed for both self-propelling and attendant-propelling, and a vibration pickup set on the seat of the wheelchairs. In order to grasp the differences emerged from calling in the subjective responses to road surface conditions, the 60 subjects were divided randomly into 2 groups of A and B, the former was “the group with calling（n=30）” whereas the latter was “the group without calling（n=30）”. Ethical consideration : The subjects were explained about the aim and method of the research, and requested to sign the agreement of participation. Analysis method : A comparison between the two groups on the results of the questionnaire was carried out. For the stage assessment of the vibration, fear and feeling of using a wheelchair, the Wilcoxon signedrank test was performed. Results and Discussion : There was a general concordance between the appearance of the road surface and the vibration level, but there were some spots where the vibrational levels were high although the surface appeared to be flat. The followings were the responses to the road surface. 1. Where the vibration levels were high, shakes were caused to the subjects’ bodies and made them feel uncomfortable. 2. Besides vibration, slopes on the road also caused the feeling of fear to the subjects. 3. Calling helped the subjects to predict a vibration and to be ready for it. 4. Calling related to the feeling of relief and mood changes, as well. From those findings, it has been clarified that calling is essential in assisting a wheelchair user. Also, it is a future theme to search for a way to assist in a comfortable use of wheelchairs under various conditions of the road surface

車椅子利用下における路面の影響調査

【目的】車椅子利用者の安楽に及ぼす影響の１つとして「声かけ」に注目して，バリアが車椅子利用者の体感にどのような影響を及ぼすのかを知ることとを目的とした研究を行った． 【方法】対象者は，２０歳代女性の看護学生で，車椅子利用時の体感に体重が影響することを考慮し標準体重に近い者を選定した．路面の状態については，観察，自走介助兼用車椅子に装着した振動計，座席用振動ピックアップを用い客観的測定を行った．声かけによる路面の状態による主観的反応の相違は，対象者６０人を無作為にA群の「声かけあり群（n＝３０）」と，B群の「声かけなし群（n＝３０）」の２群に分けて把握した． 【倫理的配慮】対象者に本研究の目的及び方法を説明し，同意書に署名してもらった． 【分析方法】アンケート調査結果について２群を比較した．ゆれ・恐怖感・乗り心地の段階評価においてはウィルコクソンの符号順位和検定を行った． 【結果および考察】路面の見かけと振動値は概ね一致していたが，見かけは平らであっても振動値は高い場所もあった．路面に対する反応は以下の通りである． １．振動が大きいところでは対象者の全身に振動を与え，不快をもたらしていた． ２．傾斜があるところでは対象者に恐怖感をもたらしていた． ３．声かけは対象者が振動を予測して，態勢を整えることに役立っていた． ４．声かけは安心感や気分転換等にもつながっていた． 以上のことから，車椅子利用者の介助に当たって声かけをすることは重要であることが明らかになった．また，多様な路面の性状下でも快適な車椅子利用ができるような介助の方法を探究していきたい．さらに，今回の結果は，車椅子以外にもシルバーカーや自走車椅子利用者の支援のあり方を示唆するものと考えられる．Aim : A research was conducted to investigate the influence by barriers of road surface on the bodily sensation of wheelchair users, while paying attention to “calling” as a factor influencing the comfort of the users. Method : The subjects were chosen from student nurses in their twenties. The objective measurement of the conditions of road surface was carried out through the use of observation, a vibrograph equipped on wheelchairs designed for both self-propelling and attendant-propelling, and a vibration pickup set on the seat of the wheelchairs. In order to grasp the differences emerged from calling in the subjective responses to road surface conditions, the 60 subjects were divided randomly into 2 groups of A and B, the former was “the group with calling（n=30）” whereas the latter was “the group without calling（n=30）”. Ethical consideration : The subjects were explained about the aim and method of the research, and requested to sign the agreement of participation. Analysis method : A comparison between the two groups on the results of the questionnaire was carried out. For the stage assessment of the vibration, fear and feeling of using a wheelchair, the Wilcoxon signedrank test was performed. Results and Discussion : There was a general concordance between the appearance of the road surface and the vibration level, but there were some spots where the vibrational levels were high although the surface appeared to be flat. The followings were the responses to the road surface. 1. Where the vibration levels were high, shakes were caused to the subjects’ bodies and made them feel uncomfortable. 2. Besides vibration, slopes on the road also caused the feeling of fear to the subjects. 3. Calling helped the subjects to predict a vibration and to be ready for it. 4. Calling related to the feeling of relief and mood changes, as well. From those findings, it has been clarified that calling is essential in assisting a wheelchair user. Also, it is a future theme to search for a way to assist in a comfortable use of wheelchairs under various conditions of the road surface

UCP1-dependent and UCP1-independent metabolic changes induced by acute cold exposure in brown adipose tissue of mice

Background: Brown adipose tissue (BAT) is a site of metabolic thermogenesis mediated by mitochondrial uncoupling protein 1 (UCP1) and represents a target for a therapeutic intervention in obesity. Cold exposure activates UCP1-mediated thermogenesis in BAT and causes drastic changes in glucose, lipid, and amino acid metabolism; however, the relationship between these metabolic changes and UCP1-mediated thermogenesis is not fully understood. Methods: We conducted metabolomic and GeneChip array analyses of BAT after 4-h exposure to cold temperature (10 °C) in wild-type (WT) and UCP1-KO mice. Results: Cold exposure largely increased metabolites of the glycolysis pathway and lactic acid levels in WT, but not in UCP1-KO, mice, indicating that aerobic glycolysis is enhanced as a consequence of UCP1-mediated thermogenesis. GeneChip array analysis of BAT revealed that there were 2865 genes upregulated by cold exposure in WT mice, and 838 of these were upregulated and 74 were downregulated in UCP1-KO mice. Pathway analysis revealed the enrichment of genes involved in fatty acid (FA) β oxidation and triglyceride (TG) synthesis in both WT and UCP1-KO mice, suggesting that these metabolic pathways were enhanced by cold exposure independently of UCP1-mediated thermogenesis. FA and cholesterol biosynthesis pathways were enhanced only in UCP1-KO mice. Cold exposure also significantly increased the BAT content of proline, tryptophan, and phenylalanine amino acids in both WT and UCP1-KO mice. In WT mice, cold exposure significantly increased glutamine content and enhanced the expression of genes related to glutamine metabolism. Surprisingly, aspartate was almost completely depleted after cold exposure in UCP1-KO mice. Gene expression analysis suggested that aspartate was actively utilized after cold exposure both in WT and UCP1-KO mice, but it was replenished from intracellular N-acetyl-aspartate in WT mice. Conclusions: These results revealed that cold exposure induces UCP1-mediated thermogenesis-dependent glucose utilization and UCP1-independent active lipid metabolism in BAT. In addition, cold exposure largely affects amino acid metabolism in BAT, especially UCP1-dependently enhances glutamine utilization. These results contribute a comprehensive understanding of UCP1-mediated thermogenesis-dependent and thermogenesis-independent metabolism in BAT

Fabrication of single-electron devices using dispersed nanoparticles and fitting experimental results to values calculated based on percolation model

We calculated the connection probability, P C, between electrodes on the basis of the triangular lattice percolation model for investigating the effect of distance variation between electrodes and the electrode width on fabricated capacitively coupled single-electron transistors. Single-electron devices were fabricated via the dispersion of gold nanoparticles (NPs). The NPs were dispersed via the repeated dropping of an NP solution onto a chip. The experimental results were fitted to the calculated values, and the fitting parameters were compared with the occupation probability, P O, which was estimated for one drop of the NP solution. On the basis of curves of the drain current versus the drain-source voltage (I D−V DS) measured at 77 K, the current was suppressed at approximately 0 V

Induced cancer stem-like cells as a model for biological screening and discovery of agents targeting phenotypic traits of cancer stem cell

Cancer stem cells (CSCs) retain the capacity to propagate themselves through self-renewal and to produce heterogeneous lineages of cancer cells constituting the tumor. Novel drugs that target CSCs can potentially eliminate the tumor initiating cell population therefore resulting in complete cure of the cancer. We recently established a CSC-like model using induced pluripotent stem cell (iPSC) technology to reprogram and partially differentiate human mammary epithelial MCF-10A cells. Using the induced CSC-like (iCSCL) model, we developed a phenotypic drug assay system to identify agents that inhibit the stemness and self-renewal properties of CSCs. The selectivity of the agents was assessed using three distinct assays characterized by cell viability, cellular stemness and tumor sphere formation. Using this approach, we found that withaferin A (WA), an Ayurvedic medicine constituent, was a potent inhibitor of CSC stemness leading to cellular senescence primarily via the induction of p21Cip1 expression. Moreover, WA exhibited strong anti-tumorigenic activity against the iCSCL. These results indicate that our iCSCL model provides an innovative high throughput platform for a simple, easy, and cost-effective method to search for novel CSC-targeting drugs. Furthermore, our current study identified WA as a putative drug candidate for abrogating the stemness and tumor initiating ability of CSCs