Free Vibration of Axially Functionally Graded Timoshenko Circular Arch

Functionally graded materials are innovative composites of hybrid ceramics and metals that exhibit excellent mechanical performance in harsh temperature environments and under various external loads. In this study, the free vibrations of Timoshenko circular arches, made of functionally graded materials in the axial direction, are investigated. The material properties of Young's modulus and mass density of the arch vary according to a symmetric quadratic function along the arch axis. Differential equations governing the free vibration of the arch including the rotatory inertia and shear deformation, called the Timoshenko arch, are derived. A novel numerical solution method is developed to calculate the natural frequencies and mode shapes of the arch. Parametric studies of the modular ratio, shear correction factor, shear modulus ratio, and slenderness ratio on the natural frequencies are conducted, and the results are reported in the tables and figures

Shuttle-effect-free sodium–sulfur batteries derived from a Tröger's base polymer of intrinsic microporosity

Room-temperature sodium-sulfur (RT Na-S) batteries have recently gained attention as next-generation energy storage devices owing to their low cost, the abundance of sodium, and the high theoretical capacity of sulfur. However, the notorious shuttle effect, caused by the dissolution of intermediate polysulfides during cycling, limits the long-term performance of Na-S batteries. In this study, intrinsically microporous Tro center dot ger's base based polymer (PIM-EA-TB)-based carbon-sulfur composites are prepared for shuttle-effect-free RT Na-S batteries by utilizing the combination of physical confinement and covalent bonding in a single material. The composites demonstrate excellent electrochemical performance, including a negligible capacity fading over 350 cycles and a high coulombic efficiency of approximately greater than 99%.

Embedding Covalency into Metal Catalysts for Efficient Electrochemical Conversion of CO_2

CO_2 conversion is an essential technology to develop a sustainable carbon economy for the present and the future. Many studies have focused extensively on the electrochemical conversion of CO_2 into various useful chemicals. However, there is not yet a solution of sufficiently high enough efficiency and stability to demonstrate practical applicability. In this work, we use first-principles-based high-throughput screening to propose silver-based catalysts for efficient electrochemical reduction of CO_2 to CO while decreasing the overpotential by 0.4–0.5 V. We discovered the covalency-aided electrochemical reaction (CAER) mechanism in which p-block dopants have a major effect on the modulating reaction energetics by imposing partial covalency into the metal catalysts, thereby enhancing their catalytic activity well beyond modulations arising from d-block dopants. In particular, sulfur or arsenic doping can effectively minimize the overpotential with good structural and electrochemical stability. We expect this work to provide useful insights to guide the development of a feasible strategy to overcome the limitations of current technology for electrochemical CO_2 conversion

Solution-processed near-infrared Cu(In,Ga)(S,Se)(2) photodetectors with enhanced chalcopyrite crystallization and bandgap grading structure via potassium incorporation

Although solution-processed Cu(In,Ga)(S,Se)(2) (CIGS) absorber layers can potentially enable the low-cost and large-area production of highly stable electronic devices, they have rarely been applied in photodetector applications. In this work, we present a near-infrared photodetector functioning at 980 nm based on solution-processed CIGS with a potassium-induced bandgap grading structure and chalcopyrite grain growth. The incorporation of potassium in the CIGS film promotes Se uptake in the bulk of the film during the chalcogenization process, resulting in a bandgap grading structure with a wide space charge region that allows improved light absorption in the near-infrared region and charge carrier separation. Also, increasing the Se penetration in the potassium-incorporated CIGS film leads to the enhancement of chalcopyrite crystalline grain growth, increasing charge carrier mobility. Under the reverse bias condition, associated with hole tunneling from the ZnO interlayer, the increasing carrier mobility of potassium-incorporated CIGS photodetector improved photosensitivity and particularly external quantum efficiency more than 100% at low light intensity. The responsivity and detectivity of the potassium-incorporated CIGS photodetector reach 1.87 A W-1 and 6.45 x 10(10) Jones, respectively, and the - 3 dB bandwidth of the device extends to 10.5 kHz under 980 nm near-infrared light

Peritonsillar Abscess in a 40-Day-Old Infant

A peritonsillar abscess is one of the most commonly occurring deep space infections of the head and neck in adults and children. A peritonsillar abscess that appears in newborns, however, is extremely rare. The treatment of a peritonsillar abscess requires both the selection of appropriate antibiotics and the best procedure to remove the abscessed material. We report a case of a peritonsillar abscess in a 40-day-old infant who was treated with antibiotic therapy alone

Possible Mechanism on Enhanced Blood Compatibility, Biostability, and Anticalcification of Sulfonated Polyethyleneoxide-Grafted Polyurethane

To investigate the correlation between blood compatibility and biostability as well as the calcification-resistance of polymers, the surface of polyurethane (PU) was grafted with hydrophilic polyethyleneoxide (PEO), and further negatively charged sulfonate groups (S03) to produce PU-PEOIOOO and PU-PEOIOOOS03, respectively. PEO-S03 grafted PU surface showed great smoothness and high hydrophilicity. PU-PEOIOOO-S03 was much more blood compatible than untreated PU and PU-PEOlOOO from the results of in vitro platelet adhesion test and blood clotting times and ex vivo occlusion times. After 6 months implantation in rats, the degree of surface cracking and calcification on explanted PUs was decreased in the following order: PU ) PU-PEOIOOO ) PU-PEOlOOO-S03, meaning that PU-PEOlOOO-S03 is most promising as a biostable and calcification-resistant polymer. It is suggested that the more blood compatible modified PUs are, the more biostable and calcification-resistant. Such superior blood compatibility, biostability, and anticalcification of PU-PEOlOO 0-S03 might be attributed to the synergistic effect of nonadhesive and mobile PEO and negative sulfonate acid groups. Therefore, surface-modified PU-PEO-S03is expected to be useful for blood/tissue contacting biomedical material