Use of frit-disc crucibles for routine and exploratory solution growth of single crystalline samples

Solution growth of single crystals from high temperature solutions often involves the separation of residual solution from the grown crystals. For many growths of intermetallic compounds, this separation has historically been achieved with the use of plugs of silica wool. Whereas this is generally efficient in a mechanical sense, it leads to a significant contamination of the decanted liquid with silica fibers. In this paper we present a simple design for frit-disc alumina crucible sets that has made their use in the growth single crystals from high temperature solutions both simple and affordable. An alumina frit-disc allows for the clean separation of the residual liquid from the solid phase. This allows for the reuse of the decanted liquid, either for further growth of the same phase, or for subsequent growth of other, related phases. In this paper we provide examples of the growth of isotopically substituted TbCd$_{6}$ and icosahedral i-$R$Cd quasicrystals, as well as the separation of (i) the closely related Bi$_{2}$Rh$_{3}$S$_{2}$ and Bi$_{2}$Rh$_{3.5}$S$_{2}$ phases and (ii) PrZn$_{11}$ and Pr$_{2}$Zn$_{17}$.Comment: submitted to Philosophical Magazin

Dynamics and Control of Tethered Formation Flight Spacecraft Using the SPHERES Testbed

This paper elaborates on the theory and experiment of controlling tethered spacecraft formation without depending on thrusters. In dealing with such underactuated systems, much emphasis is placed on complete decentralization of the control and estimation algorithms in order to reduce the dimensionality and complication. The nonlinear equations of motions of multi-vehicle tethered spacecraft are derived by Lagrange’s equations. Decentralization is then realized by the diagonalization technique and its stability is proven by contraction theory. The preliminary analysis predicts unstable dynamics depending on the direction of the tether motor. The controllability analysis indicates that both array resizing and spin-up are fully controllable only by the reaction wheels and the tether motor, thereby eliminating the need for thrusters. Based upon this analysis, gain-scheduling LQR controllers and nonlinear controllers by feedback linearization have been successfully implemented into the tethered SPHERES testbed, and tested at the NASA MSFCs flat floor facility using two and three SPHERES configurations. The relative sensing mechanism employing the ultrasound ranging system and the inertial gyro is also described

SPHERES Tethered Formation Flight Testbed: Application to NASA’s SPECS Mission

This paper elaborates on theory and experiment of the formation flight control for the future space-borne tethered interferometers. The nonlinear equations of multi-vehicle tethered spacecraft system are derived by Lagrange equations and decoupling method. The preliminary analysis predicts unstable dynamics depending on the direction of the tether motor. The controllability analysis indicates that both array resizing and spin-up are fully controllable only by the reaction wheels and the tether motor, thereby eliminating the need for thrusters. Linear and nonlinear decentralized control techniques have been implemented into the tethered SPHERES testbed, and tested at the NASA MSFC's flat floor facility using two and three SPHERES configurations. The nonlinear control using feedback linearization technique performed successfully in both two SPHERES in-line configuration and three triangular configuration while varying the tether length. The relative metrology system, using the ultra sound metrology system and the inertial sensors as well as the decentralized nonlinear estimator, is developed to provide necessary state information

Curcumin Suppresses the Activity of Inhibitor-κB Kinase in an in vitro Inflamed Human Intestinal Mucosa Model by S-nitrosylation

Abstract In previous study, we found curcumin to possess anti-inflammatory properties in lipopolysaccharide (LPS)-induced macrophage cells due to the involvement of curcumin and S-nitrosylation in the NF-κB pathway. However, the role of curcumin on regulation of NF-κB signaling pathway through S-nitrosylation in an in vitro inflamed human intestinal mucosa model has not yet been elucidated. This study aimed to concern inhibitory effects of curcumin on NF-κB pathway in two type of inflamed human intestinal cells, Caco-2 and HT-29. Western blot presented the protein expression of iNOS can be reduced by treated curcumin with 30 μM for 12h. Consistently, pro-inflammatory cytokines, such as IL-1β, IL-6, TNFα and IFN-γ was also repressed. The results also shows curcumin reduced the amount of nitrite and nitrate in inflamed human intestinal cells, Caco-2 and HT-29, maintained total S-nitrosylation level on proteins. Furthermore, the protection of S-nitrosylation on IKKβ in inflamed Caco-2 and HT-29 cells by curcumin caused the repression of IκB phosphorylation and NF-κB activation. In conclusion, this study verified that curcumin-mediated S-nitrosylation may be as an important regulator for anti-inflammation in an in vitro inflamed human intestinal mucosa model. Keywords: curcumin, S-nitrosylation, inflamed human intestinal cells, NF-κB, IκB, IKK, nitric oxide Cite This Article: Ning-Jo Kao, and Zwe-Ling Kong, "Curcumin Suppresses the Activity of Inhibitor-κB Kinase in an in vitro Inflamed Human Intestinal Mucosa Model by S-nitrosylatio

Thin-Film Sensor for Fatigue Crack Sensing and Monitoring in Steel Bridges under Varying Crack Propagation Rates and Random Traffic Loads

Fatigue cracks are critical structural concerns for steel highway bridges, and fatigue initiation and propagation activity continues undetected between physical bridge inspections. Monitoring fatigue crack activity between physical inspections can provide far greater reliability in structural performance and can be used to prevent excessive damage and repair costs. In this paper, a thin-film strain sensor, called a soft elastomeric capacitor (SEC) sensor, is evaluated for sensing and monitoring fatigue cracks in steel bridges. The SEC is a flexible and mechanically robust strain sensor, capable of monitoring strain over large structural surfaces. By deploying multiple SECs in the form of dense sensor arrays, it is possible to detect fatigue cracks over large regions of a structural member such as a bridge girder. Previous studies have verified the SEC’s capability to monitor fatigue cracks under idealized harmonic load cycles with a constant crack propagation rate. Here, an investigation is performed under more complex and realistic situations to translate the SEC technology from laboratory testing to field applications—specifically, as cracking propagates under (1) a decreasing crack propagation rate, and (2) random traffic load cycles with stochastic peak-to-peak amplitudes and periods. An experimental program was developed which included an efficient data collection strategy, new loading protocols, and crack-sensing algorithms. The experimental results showed an increasing trend of the fatigue damage feature, crack growth index (CGI), under crack initiation and propagation, despite decreasing crack propagation rates or random traffic load cycles. In addition, the results also showed that the SEC did not produce false-positive results when cracks stopped growing. The findings of this study significantly enhance the SEC’s fatigue sensing and monitoring capability under more realistic loading conditions, which is a critical step toward field applications of this technology

A large-area strain sensing technology for monitoring fatigue cracks in steel bridges

This paper presents a novel large-area strain sensing technology for monitoring fatigue cracks in steel bridges. The technology is based on a soft elastomeric capacitor (SEC), which serves as a flexible and large-area strain gauge. Previous experiments have verified the SEC\u27s capability to monitor low-cycle fatigue cracks experiencing large plastic deformation and large crack opening. Here an investigation into further extending the SEC\u27s capability for long-term monitoring of fatigue cracks in steel bridges subject to traffic loading, which experience smaller crack openings. It is proposed that the peak-to-peak amplitude (pk–pk amplitude) of the sensor\u27s capacitance measurement as the indicator of crack growth to achieve robustness against capacitance drift during long-term monitoring. Then a robust crack monitoring algorithm is developed to reliably identify the level of pk–pk amplitudes through frequency analysis, from which a crack growth index (CGI) is obtained for monitoring fatigue crack growth under various loading conditions. To generate representative fatigue cracks in a laboratory, loading protocols were designed based on constant ranges of stress intensity to limit plastic deformations at the crack tip. A series of small-scale fatigue tests were performed under the designed loading protocols with various stress intensity ratios. Test results under the realistic fatigue crack conditions demonstrated the proposed crack monitoring algorithm can generate robust CGIs which are positively correlated with crack lengths and independent from loading conditions

Dynamics and Control of Tethered Formation Flight Spacecraft Using the SPHERES Testbed

This paper elaborates on the theory and experiment of controlling tethered spacecraft formation without depending on thrusters. In dealing with such underactuated systems, much emphasis is placed on complete decentralization of the control and estimation algorithms in order to reduce the dimensionality and complication. The nonlinear equations of motions of multi-vehicle tethered spacecraft are derived by Lagrange’s equations. Decentralization is then realized by the diagonalization technique and its stability is proven by contraction theory. The preliminary analysis predicts unstable dynamics depending on the direction of the tether motor. The controllability analysis indicates that both array resizing and spin-up are fully controllable only by the reaction wheels and the tether motor, thereby eliminating the need for thrusters. Based upon this analysis, gain-scheduling LQR controllers and nonlinear controllers by feedback linearization have been successfully implemented into the tethered SPHERES testbed, and tested at the NASA MSFCs flat floor facility using two and three SPHERES configurations. The relative sensing mechanism employing the ultrasound ranging system and the inertial gyro is also described

Growth and characterization of BaZnGa

We report the growth, structure and characterization of BaZnGa, identifying it as the sole known ternary compound in the Ba-Zn-Ga system. Single crystals of BaZnGa can be grown out of excess Ba-Zn and adopt a tI36 structure type. There are three unique Ba sites and three M\,=\,Zn/Ga sites. Using DFT calculations we can argue that whereas one of these three M sites is probably solely occupied by Ga, the other two M sites, most likely, have mixed Zn/Ga occupancy. Temperature dependent resistivity and magnetization measurements suggest that BaZnGa is a poor metal with no electronic or magnetic phase transitions between 2\,K and 300\,K