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No full textDevelopment of near-white surface of Ca(OH)2-Na2CO3-activated coal bottom ash
No full textThis study demonstrated that the Ca(OH)2-Na2CO3 activation produced a near-white surface of hardened samples having a high lightness index using dark coal-fired bottom ash. In this study, the lightness index (L*) (index of black (0) to white (1 00)) of raw dark bottom ash was 36.73, but after the activation, the hardened sample showed a significantly increased L* (77.93) (i.e., 112.2% L* increase) with a near-white surface. The Ca(OH)2- Na2CO3-activation also decreased the values of a* (index of green to red) and b*(index of blue to yellow), implying the removal of chromatic colors. However, this whitening effect significantly depended on the particle size of raw bottom ash, controlled by the milling process, and the produced amounts of white reaction products (particularly, C-S-H (gel) and CaCO3), affected by the milling process and substituted ratios with fly ash and ground granulated blast furnace slag (GGBFS). The compressive strength of the 100 wt% bottom ash sample was only 5.3 MPa at three days, but it was enhanced to have enough strength over 7.4-10.3 MPa (adequate for structural bricks) without losing the surface brightness noticeably (L* > 70) by the milling process or by substituting bottom ash with fly ash or GGBFS
Guest distributions and dissociation enthalpy of fluorinated gas (CHF3 or C2F6)+N-2 hydrates for hydrate-based gas separation
No full textFluorinated gases (F-gases), such as CHF3 and C2F6, which are used in the semiconductor industry and have considerable global warming potential, can be recovered after use through a gas hydrate-based separation method to prevent their release into the atmosphere. In this study, the guest distributions and dissociation enthalpy (Delta H-d) of F-gas (CHF3 or C2F6)+N-2 hydrates with different F-gas concentrations (CHF3: 20%, 80%, and 100% and C2F6: 20%, 60%, 80%, and 100%) were experimentally investigated using a powder X-ray diffractometer and a high-pressure micro-differential scanning calorimeter, respectively. At high N-2 concentrations in the feed gas, the occupancy of N-2 in the small (5(12)) cages of the F-gas+N-2 hydrates increased significantly. As a result, the F-gas+N-2 hydrates exhibited reduced hydration numbers at high N-2 concentration. The Delta H-d values (in kJ/mol gas) of the F-gas (CHF3 or C2F6)+N-2 hydrates decreased with increased N-2 concentration. The overall experimental results provide useful insights into the design and operation of gas hydrate-based F-gas separation processes
Stoichiometric Engineering of Cs2AgBiBr6 for Photomultiplication- Type Photodetectors
No full textPhotomultiplication (PM)-type photodetectors with a high external quantum efficiency (EQE) can be realized through adequately engineered trap states and trap-assisted charge injection. By strategically introducing slightly rich Bi and highly rich Br stoichiometric conditions, efficient trap states are realized for holes in lead-free Cs1.98AgBi1.15Br7.9 double perovskite (DP). With the diode structure of ITO/SnO2/Cs1.98AgBi1.15Br7.9/poly(3-hexylthiophene) (P3HT)/MoOx/Ag, where SnO2 and P3HT layers are used as the hole-and electron-blocking layers, respectively, successful realization of the selective hole trap and the resulting band bending/electron injection at the anode interface is demonstrated. As a result, a high EQE of similar to 16,000%, responsivity of similar to 50 A W-1, and specific detectivity of over 1012 Jones at -3 V are demonstrated. The origin of the suggested PM mechanism is discussed using photophysical and optoelectronic measurements and theoretical studies. This work ensures the successful demonstration of PM-type photodetectors using lead-free Cs2AgBiBr6 DP through strategic trap engineering
Pairing Colicins B and E5 with Bdellovibrio bacteriovorus To Eradicate Carbapenem- and Colistin-Resistant Strains of Escherichia coli
No full textWhile diverse antibacterials are available in nature, each possesses their own strengths and limitations. One such antibacterial is colicins, proteinaceous toxins that are produced by strains of E. coli to subvert the growth or viability of other E. coli strains. Similarly, predatory bacteria, of which Bdellovibrio bacteriovorus is well-known, are microbes that actively predate on and consume other Gram-negative bacterial strains. While they are all quite active as antibacterials, they also present some limitations: rapid resistance development to colicins while predation does not completely kill their prey. Within this study, therefore, we evaluated the impact of two different colicins (colicin B [ColB] and colicin E5 [ColE5]) and B. bacteriovorus HD100 either individually or together against four clinical isolates of E. coli that are resistant to either colistin or carbapenem. While the ColB and ColE5 were quickly active when used alone, causing a significant loss in viability (>3-log) in susceptible populations after only 3 h, the pathogens always grew afterwards and had final cell densities that were similar with their respective controls. Predation with B. bacteriovorus HD100, in contrast, was most pronounced after 24 h (>3-log reduction in each pathogen viability but never complete). When combined, better killing efficiencies were observed with several of the pathogens, with complete eradication realized for two (<100 viable pathogens per mL). Given the diversity of colicins in nature and the broad-spectrum activities of B. bacteriovorus strains, the results presented here suggest there is a massive potential to control pathogens when they are used together