Fabrication and characterization of ZrO2–CaO–P2O5–Na2O–SiO2 bioactive glass ceramics

SiO₂–CaO–Na₂O–P₂O₅–ZrO₂ based bioactive glasses with different compositions of SiO₂ and yttrium stabilized ZrO₂ were prepared by the conventional melt quenching technique. The effects on the chemical–mechanical properties of bioactive glasses due to the addition of ZrO₂ by replacing SiO₂ were investigated. Microstructure and phase behavior were studied by scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction analysis. Compressive strength, porosity, Vickers hardness, and Young’s modulus were measured as mechanical properties. Bioactivity and cell viability were investigated by immersion in simulated body fluid and MTT assay analysis. Osteosarcoma cell proliferation on the specimen surfaces was examined by confocal laser scanning microscopy. The results showed that replacing SiO₂ with ZrO₂ helps the bioactive glass to be completely vitrified at comparatively lower sintering temperature than conventional Bioglass^®. The mechanical properties were also improved without compromising biocompatibility. Bioactive glass containing 10 wt% ZrO₂ and 35 wt% SiO₂ showed compressive strength of 399.71 MPa, Young's modulus of 22.3 GPa, Vicker’s hardness of 502.54 HV, and porosity of 26 vol%.     

Channel width dependence of hot electron injection program/hot hole erase cycling behavior in silicon-oxide-nitride-oxide-silicon (SONOS) memories

The channel width dependence of hot electron injection program/hot hole erase cycling behavior in silicon-oxide-nitride-oxide-silicon (SONOS) memories is investigated. While the trapped charge profile-dependent overerasure is observed in 10-μm-wide device, it is suppressed in 0.22-μm-wide device. Both the overerasure suppression and gradual positive threshold voltage shift in narrow device are explained as an elevated hot hole injection efficiency followed by more pronounced redistribution of the hole profile in the channel-center and the suppression of the lateral migration of injected holes in the channel-edge, by combining the measured endurance characteristics and TCAD simulation results. Main physical mechanisms are three-dimensional distribution of the electric field by gate/drain voltage, increasing interface states, and their trapped charge with cycling in the channel-edge.     

Characterization of dose delivery in a hard X-ray irradiation facility

The Radiation Bioengineering Laboratory at Seoul National University (SNU) operates a user-constructed hard X-ray irradiation facility for radiation biology and radiation therapy physics studies. The system package of YXLON model 450-D08 operating at the anode voltage of up to 450 kV is a key part of the facility, which enables in vitro cell irradiation and animal irradiation for in vivo studies. In this article, dose delivery in the hard X-ray irradiation facility was characterized in terms of the dose vs. operational parametric combination of the facility. The operational parameters included beam tube anode voltage, beam tube current, irradiation time, and beam exit-to-sample distance. Bremsstrahlung X-rays at energy below approximately 20 keV were filtered out by a 3 mm-thick aluminum plate fitted over the 5 mm-thick beryllium window. Gafchromic EBT films were used as radiation sensor materials in dose measurement. The characterization was validated via experimental observation of the in vitro biological responses of cells to radiation exposure. The biological responses obtained using the new hard X-ray irradiator were highly comparable with those obtained using a commercial gamma-ray irradiator.     

New Multidrug Efflux Systems in a Microcystin-Degrading Bacterium Blastomonas fulva and Its Genomic Feature

A microcystin-degrading bacterial strain, Blastomonas fulva T2, was isolated from the culture of a microalgae Microcystis. The strain B. fulva T2 is Gram-stain-negative, non-motile, aerobic, non-spore-forming and phototrophic. The cells of B. fulva T2 are able to grow in ranges of temperature from 15 to 37 °C, with a pH of 6 to 8 and a salinity of 0 to 1% NaCl. Here, we sequenced the complete genome of B. fulva T2, aiming to better understand the evolutionary biology and the function of the genus Blastomonas at the molecular level. The complete genome of B. fulva T2 contained a circular chromosome (3,977,381 bp) with 64.3% GC content and a sizable plasmid (145.829 bp) with 60.7% GC content which comprises about 3.5% of the total genetic content. A total of 3842 coding genes, including 46 tRNAs and 6 rRNAs, were predicted in the genome. The genome contains genes for glycolysis, citric acid cycle, Entner–Doudoroff pathways, photoreaction center and bacteriochlorophylla synthesis. A 7.9 K gene cluster containing mlrA, mlrB, mlrC and mlrD_1,2,3,4 of microcystin-degrading enzymes was identified. Notably, eight different efflux pumps categorized into RND, ABC and MFS types have been identified in the genome of strain T2. Our findings should provide new insights of the alternative reaction pathway as well as the enzymes which mediated the degradation of microcystin by bacteria, as well as the evolution, architectures, chemical mechanisms and physiological roles of the new bacterial multidrug efflux system.     

Methylglyoxal-derived advanced glycation end products induce matrix metalloproteinases through activation of ERK/JNK/NF-κB pathway in kidney proximal epithelial cells

Food Science and Biotechnology - The accumulation of reactive α-dicarbonyl leading to advanced glycation end products (AGEs) have been linked to pathophysiological diseases in many studies,...     

Nitrifying bacterial communities and its activities in aerobic biofilm reactors under different temperature conditions

Tests were performed to investigate nitrifying bacterial communities and activities in aerobic biofilm reactors with different temperature conditions, denaturing gradient gel electrophoresis (DGGE) based on polymerase chain reaction targeting 16S rRNA and amoA gene, fluorescence in situ hybridization (FISH) and dehydrogenase activity (DHA). T1, T2 and T3 reactors operated at different temperatures (5, 10 and 30 °C, respectively) were set up in the thermostat and acclimated. Nitrification was considerably limited in T1 and T2 reactors. DGGE revealed specific genera of ammonium-oxidizing bacteria (AOB) and some Nitrosomonas genera endured at the low temperatures. FISH revealed a decreased distribution ratio between AOB and nitrate-oxidizing bacteria at 5 °C, and showed that the decrease of AOB also affected the nitrification failure in the aerobic biofilm reactor. The mean attached biomass of the T1, T2 and T3 reactors was 69.6, 80.6 and 112.9 mg/L, respectively, and the 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium chloride dehydrogenase activity of the respective reactors was 73.6, 87.4 and 134.2 mgO₂^*/g VSS/day. The results demonstrate that a low temperature condition in an aerobic biofilm reactor decreases the attached biomass, distribution ratio and activity of nitrifying bacteria, and produces a change in the composition of the AOB species, which results in the failure of nitrification.     

Physicochemical stability and virucidal effect of diluted,slightly acidic electrolyzed water against human norovirus

Food Science and Biotechnology - This study aimed to evaluate the virucidal effect and potential use as a disinfectant of undiluted and diluted slightly acidic electrolyzed water (SAEW) on human...     

Use of spent sulfidic caustic for autotrophic denitrification in the biological nitrogen removal processes: Lab-scale and pilot-scale experiments

Caustic is utilized in petrochemical plants for the removal of hydrogen sulfide (H₂S) from a variety of hydrocarbon streams. Because spent sulfidic caustic (SSC) harbors a high level of H₂S and high alkalinity, it was injected into the anoxic zones of the biological nitrogen removal process as the electron donor and buffering agent for sulfur-based autotrophic denitrificaton. In order to determine the optimal SSC dosage, a modified Ludzack–Ettinger (MLE) process was first conducted at laboratory scale. As the result of the lab-scale experiments, the chemical oxygen demand (COD) increment of effluent and nitrification failure were observed, because SSC harbors barely biodegradable matter, and the caustic content was high, in accordance with the requirements. Thus, during the pilot-scale experiments, a hybrid Bardenpho process was designed and the SSC was neutralized from pH 13.3 to 11.5. These strategies were successful because no COD increment of effluent was observed and the pH of the unit process was stable. The heterotrophic and autotrophic denitrification ratios at each condition were calculated and, as the end product of sulfur-based autotrophic denitrification, the sulfate concentration was monitored.