A preliminary checklist of scale insects (Hemiptera: Coccoidea) intercepted in Korea on dracaena and ficus plants (Asparagales: Asparagaceae, Rosales: Moraceae) imported from southern Asia

The checklist revealed 40 species of scale insects (Hemiptera: Coccoidea) intercepted at Korean ports of entry on dracaena and ficus plants from southern Asia from 1996 to 2014. Brief diagnostic criteria and related information of the intercepted species are given to assist in the identifiation of specimens of scale insects intercepted from these plant hosts. Additionally, this preliminary checklist of scale insects could be utilized as a basis for preventive measures in quarantine

Growth of superconducting MgB2 thin films via postannealing techniques

We report the effect of annealing on the superconductivity of MgB2 thin films as functions of the postannealing temperature in the range from 700 C to 950 C and of the postannealing time in the range from 30 min to 120 min. On annealing at 900 C for 30 min, we obtained the best-quality MgB2 films with a transition temperature of 39 K and a critical current density of ~ 10^7 A/cm^2. Using the scanning electron microscopy, we also investigated the film growth mechanism. The samples annealed at higher temperatures showed the larger grain sizes, well-aligned crystal structures with preferential orientations along the c-axis, and smooth surface morphologies. However, a longer annealing time prevented the alignment of grains and reduced the superconductivity, indicating a strong interfacial reaction between the substrate and the MgB2 film.Comment: 7 pages, 4 figures include

Concurrent Magnetic and Metal-Insulator Transitions in (Eu,Sm)B_6 Single Crystals

The effects of magnetic doping on a EuB_6 single crystal were investigated based on magnetic and transport measurements. A modest 5% Sm substitution for Eu changes the magnetic and transport properties dramatically and gives rise to concurrent antiferromagnetic and metal-insulator transitions (MIT) from ferromagnetic MIT for EuB6. Magnetic doping simultaneously changes the itinerant carrier density and the magnetic interactions. We discuss the origin of the concurrent magnetic MIT in (Eu,Sm)B_6.Comment: 13 pages, 3 figures, final version to appear in Appl. Phys. Lett

Modulation of host metabolism by the human gastric pathogen Helicobacter pylori

Cellular homeostasis is important for retaining cellular viability and functions, and often manipulated by bacterial pathogens as an effective target for remodeling the host environment for colonization. Helicobacter pylori, a human gastric pathogen that impacts more than a half the human population as the only recognized biological carcinogen, colonizes the highly acidic human gastric environment by modulating host cellular homeostasis. Vacuolating cytotoxin A (VacA) is a pore-forming exotoxin of H. pylori, that, once secreted, enters the host cells and targets mitochondria. Previous studies revealed that VacA supports H. pylori colonization by altering host energy metabolism, specifically, by collapsing the proton gradients that are required for mitochondrial energy production. However, how such VacA cellular actions alter host cell biology during H. pylori infection has not been well understood, and was the major gap in knowledge addressed in this dissertation. Here, the studies revealed that VacA-induced metabolic stress is sensed by host cells in a manner mediated by mTORC1, a central metabolic sensor in mammalian cells. VacA-mediated inhibition of mTORC1, which is also a major metabolic regulator, indicated a global metabolic shift from a biosynthetic state to a catabolic state, as manifested by two major cellular changes; 1) induction of autophagy, a catabolic recycling mechanism that can generate extra carbon and energy sources to support a restoration of the metabolic balance, and, 2) inhibition of host protein synthesis. Furthermore, the studies unexpectedly revealed that cellular amino acids, which are the building blocks for de novo protein synthesis, also often utilized as carbon and energy sources at mitochondria, were depleted by H. pylori infection in a VacA-dependent manner. In addition, the amino acid deficiencies within VacA-intoxicated cells were largely attributed to the loss of cellular capabilities of importing extracellular amino acids in an energy-dependent manner, and the continuous consumption of amino acids at mitochondria resulted in the depletion of intracellular amino acid pools. Lastly, the studies provided the premise for evaluating how VacA manipulation of host metabolism alters host cell biology during H. pylori infection. In particular, reduction in host production of mucus proteins, key innate immune factors secreted to repel approaching pathogens, could possibly result in a VacA-dependent manner during H. pylori infection. In conclusion, the studies in this dissertation investigated how VacA could contribute to H. pylori infection biology, and revealed that VacA induces a global metabolic shift towards a less biosynthetic and more catabolic state, which could alter host effectiveness to respond to H. pylori infection. I speculate that future investigation on how the VacA-dependent metabolic shift within host cells alters host capacity to produce immune/protective factors against infection will extend our understanding in microbial infection biology, and, may contribute to developing more effective and comprehensive therapeutics against H. plyori infection