This study evaluated the influence of different light sources on the efficiency of an office bleaching agent containing visible-light activating titanium dioxide photocatalyst (VL-TiO2) using an artificial discoloration tooth model. Extracted bovine teeth were stained by black tea. The CIE L*a*b* values were measured before and after nine consecutive treatments by the VL-TiO2-containing bleaching agent (TiON in Office, GC, Tokyo, Japan). A halogen light unit (CB; CoBee, GC) or an LED unit (G-light, GC) with two modes (blue and violet: GL-BV, blue: GL-B) were used to activate the bleaching agent in three groups (n=8). Brightness (ΔL) and color difference (ΔE) increased as bleaching repeated in all groups. Two-way ANOVA showed that both number of treatments and light sources significantly affected ΔE (p<0.05). GL-BV showed better bleaching effect than GL-B. In measurement of irradiation spectra, CB showed a wide spectrum (380-530 nm), GL-B had a sharp peak at 470 nm and GL-BV showed an additional peak at 405 nm. It was concluded that the light source influenced the efficiency of the tooth bleaching with VL-TiO2.
We investigate energy band structures of the Si1−xSnx compound alloy in the zincblende structure using interacting quasi‐band (IQB) theory. We first extend the IQB theory for four‐element compounds and subsequently calculate the electronic structures of the virtual Si1−xSnxSi1−ySny alloy where x = y. Diagonalizing a 20 × 20 non‐Hermitian Hamiltonian matrix using sp3s* empirical tight‐binding model with parameters obtained for the Si, Sn, and SiSn (zincblende) crystals, we obtain the electronic energy spectrum of the Si1−xSnx alloy for arbitrary x. Comparing the band structures, we reveal that the indirect–direct gap crossover in Si1−xSnx alloys occurs around x = 0.67 with Eg = 0.87 eV.
Calculated Sn concentration dependence of energy gaps in Si1−xSnx alloy.
This paper reports on the electronic states of compound semiconductor alloys of wurtzite structure calculated by the recently proposed interacting quasi-band (IQB) theory combined with empirical sp3 tight-binding models. Solving derived quasi-Hamiltonian 24 × 24 matrix that is characterized by the crystal parameters of the constituents facilitates the calculation of the conduction and valence bands of wurtzite alloys for arbitrary concentrations under a unified scheme. The theory is applied to III–V and II–VI wurtzite alloys: cation-substituted Al1−xGaxN and Ga1−xInxN and anion-substituted CdS1−xSex and ZnO1−xSx. The obtained results agree well with the experimental data, and are discussed in terms of mutual mixing between the quasi-localized states (QLS) and quasi-average bands (QAB): the latter bands are approximately given by the virtual crystal approximation (VCA). The changes in the valence and conduction bands, and the origin of the band gap bowing are discussed on the basis of mixing character.
Percutaneous endoscopic gastrostomy (PEG) is often performed for nutritional management in advanced esophageal cancer. We here report a patient who initially received enteral nutrition via a nasogastric tube and in whom the subsequent use of percutaneous transesophageal gastro-tubing (PTEG) circumvented the need for a gastrostomy. It is believed that PEG is less painful than a nasogastric tube. However, we selected PTEG because a PEG would have been within the planned irradiation field and there was concern about radiation dermatitis. We were able to administer chemoradiotherapy with sufficient nutrition via an enteral feeding tube via esophagostomy. PTEG is a very useful tool in patients at risk of radiation dermatitis of the abdomen.
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