This article reports a new phosphorescent material, CaZnOS:Cu, that exhibits two types of mechano-optical conversion: mechanical quenching and mechanoluminescence. An intense mechanical quenching of phosphorescence corresponding to mechanical stimuli can be achieved in CaZnOS:Cu within a short decay time period. Over time, it gradually changes to mechanoluminescence when a mechanical load is applied. We propose that the mechanical quenching and mechanoluminescence arise from the different roles of shallow and deep traps in CaZnOS:Cu. CaZnOS:Cu has promising applications in monitoring mechanical stress in industrial plants, structures, and living bodies. Keywords: mechanical quenching; mechanoluminescence; phosphorescence; traps INTRODUCTIONAdjusting and controlling the optical properties of materials by altering environmental factors are important in the development of various applications in sensing, memory, detection, and display devices [1][2][3][4][5][6] . Mechanical stress is the most common external stimulus, and thus materials that exhibit mechano-optical conversion are promising for practical applications in science and engineering [7][8][9][10][11][12] .Mechanoluminescent (ML) materials emit light when mechanical energy is applied and are effective for mechano-optical conversion 1,9,13,14 . Therefore, ML materials have been used as optical sensors for monitoring changes in mechanical stress. 25 , have been explored. Recently, our group has discovered another type of mechano-optical conversion, which is referred to as mechanical quenching (MQ) 26 . In contrast to ML, MQ is the quenching of phosphorescence intensity by using mechanical stimuli. Previously, we reported that CaZnOS:Cu exhibited MQ under applied mechanical stress. However, to understand the MQ process and mechanism further and use it for practical applications, the crystal structure, phosphorescence properties, and MQ properties of CaZnOS:Cu must be determined.Here, we carry out further study on MQ in a phosphorescent material, CaZnOS:Cu. We examine the change in crystal structure that is caused by changing the Cu concentration, the phosphorescence properties, and the MQ mechanism. We find that CaZnOS:Cu exhibits a variety of mechano-optical conversions depending on the experimental conditions. MATERIALS AND METHODSCaZnOS:Cu was synthesized by a solid-state reaction method. Highpurity CaCO 3 (50 mol% excess) and appropriate amounts of ZnS and Cu 2 O were weighed and ground in an agate mortar with ethanol and then sintered under an air flow at 1100 6 C for 5 h. The excess calcium compounds were removed from the sample by washing with an aqueous solution of acetic acid. After filtration and drying, CaZnOS:Cu was ground again and then pulverized for measurement.The crystalline phase of CaZnOS:Cu was characterized by using X-ray powder diffraction (XRD; RINT-2000, Rigaku Co., Tokyo, Japan) with CuKa radiation (1.5418 Å ; cathode voltage, 40 kV; current, 40 mA) at room temperature. As reported previously, CaZnOS has an unusual structure with the...

TO ESTABLISH a sterilization method with minimal heating, the effect of high pressure on bacteriostasis was studied using thermoduric spores of Bacillus stearofhennophilus. After exposure to 800 MPa for 60 min at 6O"C, the spore count decreased from lo6 to 102/mL. However, exposure to the same pressure at room temperature did not cause significant change in spore numbers. The synergistic effect of high pressurization on the bacteriostatic action of sucrose fatty acid ester at low concentration (< 10 ppm) was pronounced with sucrose palmitic acid ester but not with sucrose stearic acid ester. Oscillatory pressurization was more effective for spore sterilization. Six cycles oscillation of S-min pressurization with 400 MPa at 70°C decreased the spore count from 10" to 102/mL, and with 600 MPa, complete sterilization was achieved.

A new non-destructive evaluation technique to detect cracks emanating from the inner surface (inner cracks) of a high-pressure hydrogen storage cylinder was developed by means of mechanoluminescence (ML) sensor consisting of SrAl 2 O 4 :EuML material and epoxy resin. To visualize the inner crack,a sheet ML sensor was attached onto the outer surface of the storage cylinder subjected to hydraulic pressure cycling with the maximum pressure of 45 MPa. The ML pattern was changed with an increase in the cycle number and the ML sensor could visualize the inner crack. The stress analysis by the finite element method clarified that the ML sensor provided unique equivalent strain distribution associated with stress concentration at the crack tip, i.e. the distance between two points having high equivalent strains was inversely proportional to the crack depth;consequently, the growth behavior of the inner crack was non-destructively quantified with the ML sensor attached on the outer surface.

Aluminum nitride (AlN) is one of piezoelectric materials, which are eagerly anticipated for use in microelectromechanical systems (MEMS) applications such as communication resonators, sensors, and energy harvesters. AlN is particularly excellent in generated voltage characteristics for the MEMS rather than oxide piezoelectric materials such as lead zirconium titanate Pb(Zr, Ti)O3. However, it is necessary to improve the piezoelectric properties of AlN in order to advance the performance of the MEMS. We dramatically increased the piezoelectric coefficient d33 of AlN films by simultaneously adding magnesium (Mg) and niobium (Nb). The d33 of Mg39.3Nb25.0Al35.7N is 22 pC/N, which is about four times that of AlN. The d33 is increased by Mg and Nb simultaneous addition, and is not increased by Mg or Nb single addition. Interestingly, the Nb has multiple chemical states, and which are influenced by the Mg concentration.

MATERIALS & METHODSBoth native and denatured protein samples were examined by determining fluorescence and specific rotation, and by polyacrylamide gel electrophoresis (PAGE) and differential scanning calorimetry (DSC). Denaturation of ovalbumin by pressure was much less than by heat or by the chemical denaturants. Gvalbumin was denatured under high pressure, as confirmed by the decrease in its a-helical content to 72% and DSC endothermic enthalpy to 61%, but it showed no change in the PAGE pattern. With bovine serum albumin decrease in fluorescence was observed after denaturation by chemicals, but it did not change under high pressure.

Our objective was to develop a method of sterilizing Bucillur steurothermophilus spores with minimal heating. Inactivation was achieved by spore destruction through six cycles of oscillatory pressurization at 70°C and 600 MPa, but inactivation was not complete within 60min with continuous pressurization. Four pressurization cycles at 600 MPa and 5 min/cycle decreased the spore count from lo6 to lO*/mL, and six cycles decreased the count from 10" to

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