Surface photovoltages in Si wafers excited with a chopped 559 nm-wavelength photon beam are analysed using a new half-sided junction model. In this model, the wafer surface with the depletion layer is considered to be one half of the p-n junction. Chopping frequency ranges from 2 Hz through 20 kHz. Four 76 mm-diameter p-type Si wafers having resistivities of 260, 92, 17 and 1.0 mΩ m are used after forming 360 nm-thick wet-oxide layer on their front surfaces. In these wafers, photovoltage increases with resistivity. In three high-resistivity wafers with strongly-inverted surfaces, the inversion capacitances and conductances limit the photovoltages at low frequencies. The obtained inversion time-constant is 7 s for the 17 mΩ m wafer.

Tetragenococcus halophila D10 catalyzes the decarboxylation of L-aspartate with nearly stoichiometric release of L-alanine and CO 2 . This trait is encoded on a 25-kb plasmid, pD1. We found in this plasmid a putative asp operon consisting of two genes, which we designated aspD and aspT, encoding an L-aspartate-␤-decarboxylase (AspD) and an aspartate-alanine antiporter (AspT), respectively, and determined the nucleotide sequences. The sequence analysis revealed that the genes of the asp operon in pD1 were in the following order: promoter 3 aspD 3 aspT. The deduced amino acid sequence of AspD showed similarity to the sequences of two known L-aspartate-␤-decarboxylases from Pseudomonas dacunhae and Alcaligenes faecalis. Hydropathy analyses suggested that the aspT gene product encodes a hydrophobic protein with multiple membrane-spanning regions. The operon was subcloned into the Escherichia coli expression vector pTrc99A, and the two genes were cotranscribed in the resulting plasmid, pTrcAsp. Expression of the asp operon in E. coli coincided with appearance of the capacity to catalyze the decarboxylation of aspartate to alanine. Histidine-tagged AspD (AspDHis) was also expressed in E. coli and purified from cell extracts. The purified AspDHis clearly exhibited activity of L-aspartate-␤-decarboxylase. Recombinant AspT was solubilized from E. coli membranes and reconstituted in proteoliposomes. The reconstituted AspT catalyzed self-exchange of aspartate and electrogenic heterologous exchange of aspartate with alanine. Thus, the asp operon confers a proton motive metabolic cycle consisting of the electrogenic aspartate-alanine antiporter and the aspartate decarboxylase, which keeps intracellular levels of alanine, the countersubstrate for aspartate, high.The gram-positive lactic acid bacterium Tetragenococcus halophila is used to ferment soy sauce, which contains large amounts of amino acids, including L-aspartate (aspartate), sugars, such as hexoses and pentoses, and sodium chloride (ca. 17%) (27). Some strains of T. halophila catalyze decarboxylation of aspartate with nearly stoichiometric release of L-alanine (alanine) and CO 2 (11,27). Based on analogy to our previous work on Lactobacillus subspecies M3 (1), aspartate decarboxylation is thought to be advantageous for tetragenococcal cells because aspartate consumption concomitant with release of alanine generates rather than consumes metabolic energy and regulates the intracellular pH. The net charge movement during the exchange of aspartate with alanine results in a membrane potential of physiological polarity. Furthermore, decarboxylation reactions consume scalar protons and thus generate a pH gradient of physiological polarity. The combined activities of the precursor-product exchange and decarboxylation result in a proton motive force (PMF) that is sufficiently high to drive ATP synthesis via FoF1 ATPase. Such metabolic systems are proposed as proton motive metabolic cycles, and the prototype model is found in the oxalate-formate exchange system of Oxalobacter...

BackgroundBacterial biofilms that develop on root surfaces outside apical foramens have been found to be associated with refractory periapical periodontitis. However, several other factors cause endodontic failures apart from extraradicular biofilms. The aim of this study was to identify the factors causing endodontic failures in general practices in Japan.MethodsPatients diagnosed as having refractory periapical periodontitis by general practitioners and who requested endodontic treatment at Osaka University Dental Hospital were selected by checking medical records from April 2009 to March 2013. Factors causing endodontic failures were identified.ResultsA total of 103 teeth were selected, and 76 teeth completed root-canal treatment. Tooth extractions were required for 18 teeth after or without endodontic treatment. Six teeth required apicoectomy after endodontic treatment. One tooth needed hemisection. One tooth needed intentional replantation. One tooth needed adhesion and replantation. The main causes of treatment failure were open apices (24 teeth), perforation (18 teeth), and root fracture (13 teeth). In six teeth with open apices that required apicoectomy or extraction, extraradicular biofilms may have been related to endodontic failure.ConclusionsMost endodontic cases diagnosed with refractory periapical periodontitis by general practitioners were compromised by any other factors rather than extraradicular biofilms.Electronic supplementary materialThe online version of this article (10.1186/s12903-018-0530-6) contains supplementary material, which is available to authorized users.

The SiO2/Si interface structure of thin oxide films thermally grown on Si(100), (111), and (110) surfaces under device processing conditions has been investigated using high-resolution photoemission spectroscopy with synchrotron radiation. The intensity distribution of the so-called suboxides, Si1+, Si2+, Si3+, displays a strong dependence on the crystallographic orientation of the substrate over the oxidation temperature range from 600 to 900 °C; Si1+ is enhanced in intensity on Si(111) and (110), while the Si2+ intensity is larger than the Si1+ one on Si(100). This orientation dependence is explained in terms of the bond topology of the substrate surface. A Si(110) surface exhibits a rather large Si3+ intensity as compared to Si(100), (111) surfaces, suggesting that Si–Si bonds on the outermost layer of a Si(110) surface are easily broken by oxygen atoms to generate the bridge bond Si–O–Si. The presence of an interfacial Si atom to which hydrogen is bonded is clearly observed. The total suboxide intensity, i.e., the sum of the suboxide intensities depends on both oxidation temperature and substrate orientation, which is interpreted by means of the interfacial roughness and the surface Si atom density of the substrate. It is shown that an ordered crystalline phase of SiO2 is present at the interfacial region. The generation of this phase has a Si(111)-preferred orientation.

A superconducting field-effect transistor (FET) with a 0.1pm-length gate electrode was fabricated and tested at liquid-helium temperature. Two superconducting electrodes (source and drain) were formed on the same Si substrate surface with an oxide-insulated gate electrode by a self-aligned fabrication process. Superconducting current flowing through the semiconductor (Si) between the two superconducting electrodes (Nb) was controlled by a gate-bias voltage.superconducting device with three terminals using dc A power is desired for development of superconducting integrated circuits. Several types of three-terminal superconducting devices have been proposed and experimentally tested [ 11-[5]. Superconducting field-effect transistors (FET's) have excellent input/output isolation compared with others. The first experimental superconducting FET was realized by the authors [6]. The gate electrode was formed on the opposite side of the Si single-crystal film from the two superconducting electrodes, so these devices were not suitable for integrated circuits. Takayanagi and Kawakami [7] and Ivanov et al. [8],[9] reported on superconducting FET's using compound semiconductors. The gate lengths of their devices were about 0.5 and 0.4 pm, respectively, much larger than that of shortchannel Si MOSFET's. A smaller gate length is necessary to improve the switching speed of the superconducting FET's and to realize highly integrated circuits, because a small gatelength superconducting FET has a larger superconducting current to drive the next stage. However, planar devices with a short gate length have been difficult to fabricate on one side of a Si single crystal because the two superconducting electrodes are less than 0.2 pm apart in a Si semiconductor substrate and the gate electrodes must lie between the two.In this paper we describe the fabrication and operation of a superconducting FET with a gate length as short as 0.1 pm. This FET has a planar structure with a gate electrode between the two superconducting electrodes on the same side of a Si single crystal. The electric characteristics are measured at 4.2 K and the static characteristics are discussed.A cross-sectional view is shown in Fig. 1. The device has a single-crystal Si substrate, two As+ ion-implanted areas, a gate oxide, a poly-Si gate electrode, and a superconducting source and drain. The original aspect of this structure is the 0.1 -pm-length gate electrode with an overhang and insulating sidewalls of very thin Si3N4 film. A top view of the device and a scanning-electron micrograph of the gate structure are shown in Fig. 2(a) and (b), respectively. Fig. 1. Cross-sectional view of the superconducting FET with 0.1-pm gate \ , / Sdurce electrode(Nb1 Drain electrode(Nb) (a) -150nm (b) scanning electron micrograph of the gate structure (cross-sectional view).Fig. 2. (a) Micrograph of the superconducting FET (top view) and (b)A multilayer of gate oxide, doped poly-Si, and Si3N4 was formed on a surface of the p-Si single-crystal substrate. The gate oxide was a therma...