Aluminum phosphate sealing to improve insulation resistance of plasma-sprayed alumina coating

The insulation resistance of conventional atmospheric plasma-sprayed alumina coatings with 10–15% porosity is ～10¹¹ Ω. The presence of pores, lamellae boundaries, and other non-fillings dampens the insulation resistance of the coating. In the present study, aluminum phosphate was used to seal the surface of plasma-sprayed alumina coating and evaluate the effect of sealing on the insulation resistance and its thermal cycling response. Sealing was carried out with three concentrations of sealant (P/Al molar ratio of 3, 10, and 15). Characterization by X-ray diffraction and scanning electron microscopy revealed the primary sealing phase as aluminum metaphosphate and effective sealing of the pores by the aluminum phosphate phases. Insulation resistance is improved by two orders of magnitude after sealing the coated samples. Sealing with P/Al molar ratio 3 exhibited maximum insulation resistance of ～10¹³ Ω at room temperature. Thermal cycling studies between 650°C and 200°C on the sealed samples showed deterioration in thermal cycling life after sealing.     

On global solutions to fractional functional differential equations with infinite delay in Fréchet spaces

In this paper, we investigate global uniqueness results for fractional functional differential equations with infinite delay in Fréchet spaces. We shall rely on a nonlinear alternative of Leray-Schauder type in Fréchet spaces due to Frigon and Granas. The results are obtained by using the α-resolvent family (S_α(t))_t≥0 on a complex Banach space X combined with the above-mentioned fixed point theorem. As an application, a controllability result with one parameter is also provided to illustrate the theory.     

Photocurrent enhancement of d.c. sputtered copper oxide thin films

Copper oxide (CuO) thin films with photocurrent as high as 25 μA/cm² were deposited on conductive glass substrates using d.c. reactive sputtering. This was the highest reported photocurrent for sputteredp- type copper oxide measured in the electrolyte KI. The photocurrent drastically increased up to 25 (μA/cm² as the sputtering pressure and the substrate temperature were increased up to 8.5 mbar and 192°C, respectively. All the synthesized films contained single phase of CuO in this range of pressure and substrate temperature. Variation of the photocurrent, photovoltage, structure and absorbance with deposition conditions were studied in detail.     

The impact of thermal conductivity and diffusion rates on water vapor transport through gas diffusion layers

Proper water management in a hydrogen-fueled polymer electrolyte membrane (PEM) fuel cell is critical for performance and durability. A mathematical model has been developed to elucidate the effect of thermal conductivity and water vapor diffusion coefficient in the gas diffusion layers (GDLs). The fraction of product water removed in the vapor phase through the GDL as a function of GDL properties/set of material and component parameters and operating conditions has been calculated. The current model enables identification of conditions wherein condensation occurs in each GDL component. The model predicts the temperature gradient across various components of a PEM fuel cell, providing insight into the overall mechanism of water transport in a given cell design. The water condensation conditions and transport mode in the GDL components depend on the combination of water vapor diffusion coefficients and thermal conductivities of the GDL components. Different types of GDLs and water transport scenarios are defined in this work, based on water condensation in the GDL and fraction of water that the GDL removes through the vapor phase, respectively.     

Characterisation of microstructural damage due to corrosion fatigue in AISI type 316 LN stainless steels with different nitrogen contents

Corrosion fatigue (CF) behaviour of AISI type 316 LN stainless steels (SS) with three different nitrogen contents was evaluated in a boiling aqueous solution of 5?M NaCl+0·15?M Na₂SO₄+2·5?ml?l^?1 HCl at a stress ratio of 0·5 and a frequency of 0·1?Hz. After the CF tests, the specimens were observed under a field emission gun scanning electron microscope (FEG-SEM) as well as an atomic force microscope (AFM) to understand the deformation mechanism which led to the failure. Slip character could be explained based on the surface deformation features observed using FEG-SEM and AFM. A slip irreversibility relation has been proposed which when applied could explain the CF behaviour of these steels with varying nitrogen contents. Increase in the nitrogen content increased the slip reversibility up to 0·14?wt-% nitrogen; however, further increase in nitrogen content had no beneficial effect on the slip reversibility.     

Structure‐Guided Design of Thiazolidine Derivatives as Mycobacterium tuberculosis Pantothenate Synthetase Inhibitors

The pantothenate biosynthetic pathway is essential for the persistent growth and virulence of Mycobacterium tuberculosis (Mtb) and one of the enzymes in the pathway, pantothenate synthetase (PS, EC: 6.3.2.1), encoded by the panC gene, has become an appropriate target for new therapeutics to treat tuberculosis. Herein, we report nanomolar thiazolidine inhibitors of Mtb PS developed by a rational inhibitor design approach. The thiazolidine compounds were discovered by using energy‐based pharmacophore modelling and subsequent in vitro screening, which resulted in compounds with a half maximal inhibitory concentration (IC₅₀) value of (1.12±0.12) μM . These compounds were subsequently optimised by a combination of modelling and synthetic chemistry. Hit expansion of the lead by chemical synthesis led to an improved inhibitor with an IC₅₀ value of 350 nM and an Mtb minimum inhibitory concentration (MIC) of 1.55 μM . Some of these compounds also showed good activity against dormant Mtb cells.     

Oxygen Potential in the System UMoO6/UMoO5 by the Solid Oxide Electrolyte Emf Method

The emf of the galvanic cell Pt|UMoO₆UMoO₅|ZrO₂-Y₂O₃|O₂(air, Po₂=0.21 atm)|Pt, measured from 776 to 1127 K, was determined to be E = 751.7−0.4909 ±4.3 mV. Using the standard Gibbs energy of formation, ^fΔG°, for UMoO₆ reported in the literature from transpiration studies, the ^fΔG° for UMoO₅ is calculated to be ^fΔG°〈UMoO₅〉=−1816.9+0.3748T±6.0 U-mol⁻¹ The magnitudes of the standard entropies of formation, ^fΔS°, for UMoO₆ and UMoO₅ were evaluated from those values reported for the binary oxides which constitute the ternary compounds.     

Porous Enzymatic Membrane for Nanotextured Glucose Sweat Sensors with High Stability toward Reliable Noninvasive Health Monitoring

Development of reliable glucose sensors for noninvasive monitoring without interruption or limiting users' mobility is highly desirable, especially for diabetes diagnostics, which requires routine/long‐term monitoring. However, their applications are largely limited by the relatively poor stability. Herein, a porous membrane is synthesized for effective enzyme immobilization and it is robustly anchored to the modified nanotextured electrode solid contacts, so as to realize glucose sensors with significantly enhanced sensing stability and mechanical robustness. To the best of our knowledge, this is the first report of utilizing such nanoporous membranes for electrochemical sensor applications, which eliminates enzyme escape and provides a sufficient surface area for molecular/ion diffusion and interactions, thus ensuring the sustainable catalytic activities of the sensors and generating reliable measureable signals during noninvasive monitoring. The as‐assembled nanostructured glucose sensors demonstrate reliable long‐term stable monitoring with a minimal response drift for up to 20 h, which delivers a remarkable enhancement. Moreover, they can be integrated into a microfluidic sensing patch for noninvasive sweat glucose monitoring. The as‐synthesized nanostructured glucose sensors with remarkable stability can inspire developments of various enzymatic biosensors for reliable noninvasive composition analysis and their ultimate applications in predictive clinical diagnostics, personalized health‐care monitoring, and chronic diseases management.