A study of TiO2/carbon black composition as counter electrode materials for dye-sensitized solar cells

This study describes a systematic approach of TiO₂/carbon black nanoparticles with respect to the loading amount in order to optimize the catalytic ability of triiodide reduction for dye-sensitized solar cells. In particular, the cell using an optimized TiO₂ and carbon black electrode presents an energy conversion efficiency of 7.4% with a 5:1 ratio of a 40-nm TiO₂ to carbon black. Based on the electrochemical analysis, the charge-transfer resistance of the carbon counter electrode changed based on the carbon black powder content. Electrochemical impedance spectroscopy and cyclic voltammetry study show lower resistance compared to the Pt counter electrode. The obtained nanostructures and photo electrochemical study were characterized.     

The Perspective of Arbuscular Mycorrhizal Symbiosis in Rice Domestication and Breeding

In nature, symbiosis with arbuscular mycorrhizal (AM) fungi contributes to sustainable acquisition of phosphorus and other elements in over 80% of plant species; improving interactions with AM symbionts may mitigate some of the environmental problems associated with fertilizer application in grain crops such as rice. Recent developments of high-throughput genome sequencing projects of thousands of rice cultivars and the discovery of the molecular mechanisms underlying AM symbiosis suggest that interactions with AM fungi might have been an overlooked critical trait in rice domestication and breeding. In this review, we discuss genetic variation in the ability of rice to form AM symbioses and how this might have affected rice domestication. Finally, we discuss potential applications of AM symbiosis in rice breeding for more sustainable agriculture.     

Magic Number Stabilities of Small para-H2 Clusters Doped by a Single ortho-D2

Path-integral Monte Carlo calculations have been performed to study superfluid behavior of small para-H₂ clusters doped by a single impurity molecule of ortho-D₂ at a low temperature of 1.6 K. It is found that the D₂ molecule is located near the center of mass of the cluster and H₂ molecules are distributed around the D₂ molecule to form a shell structure. All the clusters considered here show significant superfluid fractions at this temperature but superfluidity is found to be noticeably quenched at specific sizes of the clusters. The different superfluid propensity depending on the cluster size is understood to be related to the magic number behavior of the para-H₂ clusters.      

Isolation and identification of antioxidant producing marine-source actinomycetes and optimal medium conditions

Actinomycetes strain S-1 containing antioxidant components was isolated from the coast of Jeju Island in Korea and identified to the genus level using 16S ribosomal DNA sequencing and cellular fatty acids analysis as Nocardiopsis sp. (S-1). S-1 cultured supernatants showed high DPPH radical scavenging activities and hydroxyl radical scavenging abilities of up to 53%. Nutritional and culture conditions for antioxidant production were optimized. Galactose and yeast extracts were the best carbon and nitrogen sources for growth and antioxidant production. An initial medium acidity of pH 7.6, an incubation temperature of 25°C, a sodium chloride concentration of 2.5%, and an incubation time of 8 days were optimal. The DPPH scavenging activity of culture supernatants was 88% under optimum conditions. The S-1 strain can be useful for the functional fermented food and medicine industries.     

A Fully Integrated UHF CMOS Power Amplifier for Spacecraft Applications

A power amplifier (PA) is designed for a surface-to-orbit proximity link microtransceiver on Mars exploration rovers, aerobots, and small networked landers and works in conjunction with a 0.2-dB loss transmit/receive switch to allow nearly the full 1 W to reach the antenna. The fully integrated UHF CMOS PA with more than 30-dBm output is reported for the first time. A differential pMOS structure with floating-bias cascode transistors and 1:3-turn ratio output transformer are chosen to overcome low breakdown voltage (V _bk) of CMOS and chip area consumption issues at UHF frequencies. The high-Q on-chip transformer on a sapphire substrate enables the differential PA to drive a single-ended antenna effectively at 400 MHz. The PA in a standard package delivers 30-dBm output with 27% power-added efficiency. No performance degradation was observed in continuous-wave operation and the design has been tested to 136% of its nominal 3.3-V supply without failure.     

Quantum Conductance Probing of Oxygen Vacancies in SrTiO3 Epitaxial Thin Film using Graphene

Quantum Hall conductance in monolayer graphene on an epitaxial SrTiO₃ (STO) thin film is studied to understand the role of oxygen vacancies in determining the dielectric properties of STO. As the gate‐voltage sweep range is gradually increased in the device, systematic generation and annihilation of oxygen vacancies, evidenced from the hysteretic conductance behavior in the graphene, are observed. Furthermore, based on the experimentally observed linear scaling relation between the effective capacitance and the voltage sweep range, a simple model is constructed to manifest the relationship among the dielectric properties of STO with oxygen vacancies. The inherent quantum Hall conductance in graphene can be considered as a sensitive, robust, and noninvasive probe for understanding the electronic and ionic phenomena in complex transition‐metal oxides without impairing the oxide layer underneath.