Origin of the overall water splitting activity of Ta3N5 revealed by ultrafast transient absorption spectroscopy

Tantalum nitride (Ta3N5) is one of the few visible light absorbing photocatalysts capable of overall water splitting (OWS), by which the evolution of both H2 and O2 is possible. Despite favourable energetics, realizing the OWS or efficient H2 evolution in Ta3N5 prepared by the nitridation of tantalum oxide (Ta2O5) or Ta foil remains a challenge even after 15 years of intensive research. Recently our group demonstrated OWS in Ta3N5 when prepared by the short time nitridation of potassium tantalate (KTaO3). To obtain a mechanistic insight on the role of Ta precursor and nitridation time in realizing OWS, ultrafast dynamics of electrons (3435 nm probe) and holes (545 nm probe) is investigated using transient absorption spectroscopy. Electrons decay majorly by trapping in Ta3N5 prepared by the nitridation of Ta2O5, which do not show OWS. However, OWS activity in Ta3N5 prepared by 0.25 hour nitridation of KTaO3 is particularly favoured by the virtually absent electron and hole trapping. On further increasing the nitridation time of KTaO3 from 0.25 to 10 hour, trapping of both electron and hole is enhanced which concurrently results in a reduction of the OWS activity. Insights from correlating the synthesis conditions—structural defects—carrier dynamics—photocatalytic activity is of importance in designing novel photocatalysts to enhance solar fuel production

トウケイテキ ドウリキガクテキ ケンチ ニ モトズク ソウキョクシケイ ジユウ エネルギーメン ノ カイセキ

京都大学0048新制・課程博士博士(理学)甲第13618号理博第3276号新制||理||1483(附属図書館)UT51-2008-C536京都大学大学院理学研究科化学専攻(主査)教授 谷村 吉隆, 教授 松本 吉泰, 教授 寺嶋 正秀学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDA

DESIGN OF SPINDLE SUPPORTED BY HIGH STIFFNESS WATER HYDROSTATIC THRUST BEARING

ABSTRACT A precision spindle is a key component of the ultra-precision machine tools that are used for machining precision molds for producing various lenses and other precise parts. The machining accuracy required for the parts now reaches several tens of nanometers. In order to achieve the desired machining accuracy, the precise spindle system with high stiffness bearings is inevitably needed for the ultra-precision machine tools. The paper thus deals with a design of a spindle supported by water hydrostatic bearings. An objective of the study is to design the precision spindle supported by the water hydrostatic bearings with the bearing stiffness of 1 kN/μm. Thus the paper presents the design procedure of the hydrostatic thrust bearings. In particular, the design of the bearing restrictors is introduced. The characteristics of water hydrostatic thrust bearings of the designed spindle are investigated theoretically. The influences of the gap sizes and the supply water pressure on the bearing stiffness are given. It is indicated that the bearing stiffness of 1 kN/μm can be obtained by the spindle design. Structure and materials of the developed spindle are also introduced

Proton Transfer in Bulk Water using the Full Adaptive QM/MM Method: Integration of Solute- and Solvent-Adaptive Approaches

The quantum mechanical/molecular mechanical (QM/MM) method is a hybrid molecular simulation technique that increases the accessibility of local electronic structures of large systems. The technique combines the benefit of accuracy found in the QM method and that of cost efficiency found in the MM method. However, it is difficult to directly apply the QM/MM method to the dynamics of solution systems, particularly for proton transfer. As explained in the Grotthuss mechanism, proton transfer is a structural interconversion between hydronium ions and solvent water molecules. Hence, when the QM/MM method is applied, an adaptive treatment, namely on-the-fly revisions on molecular definitions, is required for both the solute and solvent. Although several solvent-adaptive methods have been proposed, a full adaptive framework, which is an approach that also considers adaptation for solutes, remains untapped. In this paper, we propose a new numerical expression for the coordinates of the excess proton and its control algorithm. Furthermore, we confirm that this method can stably and accurately simulate proton transfer dynamics in bulk water.</div

後腹膜出血にて発症した腎血管筋脂肪種

47歳男, 左側腹部痛を主訴に入院した.画像診断上, 腎血管筋脂肪腫とその破裂による後腹膜血腫がもっとも疑われ, 迅速診断の上, 血腫除去と摘出術が行われたWe report a case of renal angiomyolipoma with retroperitoneal hemorrhage treated by enucleation in a 47 year-old male. The mass in the anterior side of the left kidney, revealed by sonography and CT, was diagnosed as angiomyolipoma with a retroperitoneal hematoma caused by its spontaneous rupture. Removal of hematoma and enucleation of the tumor were performed after the diagnosis. Diagnosis and treatment of ruptured renal angiomyolipoma are discussed