Low-temperature processed InGaZnO MES-FET for flexible device applications

Amorphous oxide semiconductor (AOSs) of an In-Ga-Zn-O (IGZO)1) is expected to be used as a channel material for thin-film transistors (TFTs) because the IGZO TFTs exhibit field-effect motility (μFE) of over 10 cm2/Vs and good uniformity even fabricate at room temperature. The oxide TFTs with metal-insulator-semiconductor (MIS) structure have been employed widely; however, maximum processing temperature of 300-400 °C is required to guarantee the performance and reliability of the TFTs. In contrast, metal-semiconductor field effect transistor (MES-FET) has several advantages especially for flexible devices since a Schottky gate can be formed at low temperature with AOSs. There are a few reports of AOSs based MES-FET2, 3); however, it has remained an issue to form stable and good Schottky contact on the AOSs. We reported the top-gated MES-FET with the IGZO channel, which was deposited by mist chemical vapour deposition at 350 °C, and sputtered silver oxide (AgOx) Schottky gate4). The μFE of 3.2 cm2/Vs and subthreshold swing (SS) of 356 mV/decade were achieved. However, a maximum processing temperature of the MES-FET was 350 °C, which was not suitable for flexible device applications. In this presentation, the IGZO MES-FET with AgOx Schottky gate was fabricated at a maximum processing temperature of 150 °C. We investigated the influences of deposition conditions and post-deposition annealing on electrical properties of the low-temperature processed IGZO MES-FET. Figure 1 shows a cross sectional view of the IGZO MES-FET. First, a 100 nm-thick IGZO film was deposited on glass substrate by DC magnetron sputtering without intentional substrate heating from InGaZnO (In:Ga:Zn=1:1:1 mol.%) target. Deposition pressure was kept at 1.0 Pa, while the O2 gas ratio [R(O2)=O2/(Ar+O2)] was varied at 0.66, 0.80, and 1.00%. The IGZO film was patterned into an active channel by conventional photolithography and wet etching. The IGZO channel was then annealed at 100 or 150 ºC for 1h in ambient air. A 120 nm-thick AgOx was deposited by DC reactive sputtering, and Au was deposited on the AgOx by thermal evaporation. The AgOx/Au stacked Schottky gate was patterned by lift-off. Finally, Mo source and drain electrodes was formed by lift-off. Channel width/length of the MES-FET was 100/10 μm. Figure 2 shows the (a) forward and reverse currents of the IGZO/AgOx Schottky diode and (b) on and off current of the IGZO MES-FET, as a function of the Hall carrier concentration (NHall) in the IGZO channel. The diode properties were well correlated with the NHall; however, on-current of the MES-FET depended on not only NHall but also the R[O2] of the IGZO deposition. Carrier transport mechanism of the IGZO MES-FET and control methods of electrical properties will be discussed at the conference. Please click Additional Files below to see the full abstract

PACAP is Implicated in the Stress Axes

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a highly conserved pleiotropic neuropeptide that functions as a neurotransmitter, neuromodulator and neurotrophic factor. Accumulating evidence implicates PACAP as an important regulator of both central and/or peripheral components of the stress axes, particularly exposure to prolonged or traumatic stress. Indeed, PACAP and its cognate receptors are widely expressed in the brain regions and peripheral tissues that mediate stress-related responses. In the sympathoadrenomedullary system, PACAP is required for sustained epinephrine secretion during metabolic stress. It is likely that PACAP regulates autonomic function and contributes to peripheral homeostasis by maintaining a balance between sympathetic and parasympathetic activity, favoring stimulation of the sympathetic system. Furthermore, PACAP is thought to act centrally on the paraventricular nucleus of the hypothalamus to regulate both the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system. Intriguingly, PACAP is also active in brain structures that mediate anxiety- and fear-related behaviors, and the expression of PACAP and its receptors are dynamically altered under pathologic conditions. Thus PACAP may influence both hard-wired (genetically determined) stress responses and gene-environment interactions in stress-related psychopathology. This article aims to overview the molecular mechanisms and psychiatric implications of PACAP-dependent stress responses

A Case of Hypocalcaemia Due to Vitamin D Deficiency in ‘Hikikomori’ Syndrome

Objective: To describe hypocalcaemia due to vitamin D deficiency in ‘hikikomori’ syndrome. Materials and methods: A 37-year-old man with ‘hikikomori’ syndrome for a year was admitted with hypocalcaemia (serum ionic calcium 1.17 mmol/l). Serum 1,25(OH)2-vitamin D3 determined by liquid chromatography–tandem mass spectrometry was depressed at 12.1 pg/ml (29.0 pmol/l) and plasma intact PTH elevated at 324 ng/l. Administration of 1 μg/day 1α(OH)-vitamin D3 and 1 g/day calcium lactate for 1 week normalized calcium and PTH, and raised 1,25(OH)2-vitamin D3 to low normal levels. Conclusion: This is the first report of hypocalcaemia due to vitamin D deficiency in a patient with ‘hikikomori’ syndrome

Polyunsaturated fatty acids-enriched lipid from reduced sugar alcohol mannitol by marine yeast Rhodosporidiobolus fluvialis Y2

Brown macroalgae is a promising marine biomass for the production of bioethanol and biodiesel fuels. Here we investigate the biochemical processes used by marine oleaginous yeast for assimilating the major carbohydrate found in brown macroalgae. Briefly, yeast Rhodosporidiobolus fluvialis strain Y2 was isolated from seawater and grown in minimal medium containing reduced sugar alcohol mannitol as the sole carbon source with a salinity comparable to seawater. Conditions limiting nitrogen were used to facilitate lipid synthesis. R. fluvialis Y2 yielded 55.1% (w/w) and 39.1% (w/w) of lipids, per dry cell weight, from mannitol in the absence and presence of salinity, respectively. Furthermore, mannitol, as a sugar source, led to an increase in the composition of polyunsaturated fatty acids, linoleic acid (C18:2) and linolenic acid (C18:3), compared to glucose. This suggests that oxidation of mannitol leads to the activation of NADH-dependent fatty acid desaturases in R. fluvialis Y2. Such fatty acid composition may contribute to the cold-flow properties of biodiesel fuels. Our results identified a salt-tolerant oleaginous yeast species with unique metabolic traits, demonstrating a key role as a decomposer in the global carbon cycle through marine ecosystems. This is the first study on mannitol-induced synthesis of lipids enriched with polyunsaturated fatty acids by marine yeast

Substrate size-dependent conformational changes of bacterial pectin-binding protein crucial for chemotaxis and assimilation

Gram-negative Sphingomonas sp. strain A1 exhibits positive chemotaxis toward acidic polysaccharide pectin. SPH1118 has been identified as a pectin-binding protein involved in both pectin chemotaxis and assimilation. Here we show tertiary structures of SPH1118 with six different conformations as determined by X-ray crystallography. SPH1118 consisted of two domains with a large cleft between the domains and substrates bound to positively charged and aromatic residues in the cleft through hydrogen bond and stacking interactions. Substrate-free SPH1118 adopted three different conformations in the open form. On the other hand, the two domains were closed in substrate-bound form and the domain closure ratio was changed in response to the substrate size, suggesting that the conformational change upon binding to the substrate triggered the expression of pectin chemotaxis and assimilation. This study first clarified that the solute-binding protein with dual functions recognized the substrate through flexible conformational changes in response to the substrate size