Search

In this paper, we report the synthesis and transmittance of a titanium–indium–tin oxide (TITO) film, fabricated through a low-temperature process. The TITO film was fabricated by incorporating a 2-nm-thick titanium barrier at the bottom of an ITO film. The transmittance characteristics of the TITO film were examined for light-emitting diodes (LEDs) of various wavelengths at different post-annealing temperatures. A saturated high transmittance was observed at a temperature of 550 °C, which is relatively low when compared to that in the case of a conventional ITO film. Photoluminescence studies demonstrated that a 450-nm-thick TITO film, fabricated at 550 °C, was highly effective in improving the performance of the LED, when compared to conventional ITO films. The X-ray diffraction peaks, scanning electron microscopy images, and transmittance electron microscopy images confirmed that titanium atoms could improve the crystallization of ITO. It was found that non-crystallization in ITO was effectively activated by the titanium barrier. Furthermore, the optical bandgap (3.77 eV for the conventional ITO film) was improved to 3.92 eV in the TITO film. An infrared LED fabricated with a TITO film displayed 70% higher light output power than that with a conventional ITO film. These results suggest that using a titanium barrier is essential to effectively improve inactive nucleation sites in ITO films grown at low temperatures.

A highly doped emitting window for a vertical-cavity surface-emitting laser (VCSEL) was fabricated and its effect on the output power at a wavelength of 860-nm was investigated. The highly doped emitting window, which limited in required specific area, could be obtained by using various thermal conditions for patterned zinc oxide (ZnO). Experimental measurements showed that the highest doping concentration of 1.02 × 1019/cm3 was observed from patterned ZnO treated at 600 °C. The highly doped emitting window obtained by Zn diffusion effectively improved the real emission region confined by the current window owing to increase in the central concentration of the current injected from the top electrode. Among the developed VCSEL chips, the highest output power of 110 mW was observed with the use of a Zn-doped emitting widow at 600 °C, indicating an increase 47% compared with the output power of conventional chips (75 mW). For temperatures other than 600 °C, a relatively lower output power was obtained. The results show that the use of an emitting window highly doped with Zn can improve the output power of the VCSEL at a wavelength of 860-nm. It was verified that there exists an optimal thermal condition for the zinc diffusion process for patterned ZnO film required.

A new technique was used to directly measure O3 response to changes in precursor NOx and volatile organic compound (VOC) concentrations in the atmosphere using three identical Teflon smog chambers equipped with UV lights. One chamber served as the baseline measurement for O3 formation, one chamber added NOx, and one chamber added surrogate VOCs (ethylene, m-xylene, n-hexane). Comparing the O3 formation between chambers over a 3-hour UV cycle provides a direct measurement of O3 sensitivity to precursor concentrations. Measurements made with this system at Sacramento, California, between April–December 2020 revealed that the atmospheric chemical regime followed a seasonal cycle. O3 formation was VOC-limited (NOx-rich) during the early spring, transitioned to NOx-limited during the summer due to increased concentrations of ambient VOCs with high O3 formation potential, and then returned to VOC-limited (NOx-rich) during the fall season as the concentrations of ambient VOCs decreased and NOx increased. This seasonal pattern of O3 sensitivity is consistent with the cycle of biogenic emissions in California. The direct chamber O3 sensitivity measurements matched semi-direct measurements of HCHO/NO2 ratios from the TROPOspheric Monitoring Instrument (TROPOMI) aboard the Sentinel-5 Precursor (Sentinel-5P) satellite. Furthermore, the satellite observations showed that the same seasonal cycle in O3 sensitivity occurred over most of the entire state of California, with only the urban cores of the very large cities remaining VOC-limited across all seasons. The O3-nonattainment days (MDA8 O3>70 ppb) have O3 sensitivity in the NOx-limited regime, suggesting that a NOx emissions control strategy would be most effective at reducing these peak O3 concentrations. In contrast, a large portion of the days with MDA8 O3 concentrations below 55 ppb were in the VOC-limited regime, suggesting that an emissions control strategy focusing on NOx reduction would increase O3 concentrations. This challenging situation suggests that emissions control programs that focus on NOx reductions will immediately lower peak O3 concentrations but slightly increase intermediate O3 concentrations until NOx levels fall far enough to re-enter the NOx-limited regime. The spatial pattern of increasing and decreasing O3 concentrations in response to a NOx emissions control strategy should be carefully mapped in order to fully understand the public health implications.

The effect of laminar flow fluctuation on the indium composition of In0.07GaAs quantum wells was investigated in order to obtain a higher output power from infrared lighting-emitting diodes (IR-LEDs) having a 940-nm wavelength. By controlling the injection pressure, we obtained various laminar flow conditions. Through subsequent photoluminescence (PL) and X-ray diffraction (XRD) measurements, a noticeable improvement in the optical and the crystalline characteristics of the In0.07GaAs quantum wells was observed at an optimum laminar flow. This result could be attributed to a reduction of non-crystallization in InGaAs quantum wells that had their indium composition improved via the optimized laminar flow. Overall, a significantly improved output power (11.2 mW) was obtained from a 940-nm IR-LED chip fabricated at an optimum laminar flow of 500 sccm, and a remarkable increase of approximately 250% was displayed compared to a conventional chip (3.9 mW) fabricated at a laminar flow of 100 sccm.

In recent years, multipollutant approaches have been employed to investigate the association with health outcomes to better represent real-world conditions than more traditional analysis that considers a single pollutant. With regard to the exposure assessment of a mixture of air pollutants, it is critical to understand the spatial variability in multipollutant relations in order to assess their potential health implications. In this study, we investigated the spatial relations of multiple pollutant concentrations (i.e., NOx, NOy, black carbon, carbon monoxide, acetaldehyde, formaldehyde, toluene, xylenes/ethylbenzene, ozone, water-soluble organic carbon, and aerosol extinction) observed from the P-3B aircraft in the 2011 NASA field campaign in Baltimore/Washington D.C. areas during July 2011. The between-pollutant Pearson correlations and Z-scores (calculated from log-transformed concentrations) between near-highways and non-highways and between near-urban centers and non-urban centers varied by pollutant pair and space. We found generally lower correlations between NOx and other pollutants for near-highways (average r = 0.36) than for non-highways (average r = 0.41) and also for non-urban centers (average r = 0.37) than for near-urban centers (average r = 0.41). This indicated that the temporal associations between NOx and health outcomes might be less affected by other pollutants, which were also related to same health outcomes, for near-highways and non-urban centers. The analysis of between-pollutant Z-scores showed varying spatial relations for popular traffic-related pollutants with the Z-score differences of 0.43 (NOx-carbon monoxide), 0.29 (NOx-black carbon), and 0.17 (black carbon-carbon monoxide) between near-highways and non-highways. This result exhibited heterogeneous traffic-related pollutant mixtures with the proximity to highways, potentially leading to the diverse extent of health associations. Furthermore, a mixed effects model presented pollutant-specific associations between the concentrations and the proximity to highways and urban centers, showing larger declines for NOx, xylenes/ethylbenzene, toluene, and NOy than those for the pollutants related to secondary pollutant formation. The model also demonstrated the different sensitivity of each pollutant to meteorological parameters, which may modify the spatial and temporal variability in the relations between the pollutants. Our findings provide insights for exposure assessment studies to better understand the cumulative health consequences associated with multiple air pollutants simultaneously.

As part of the research on cement composites using cellulose nanocrystal (CNC) aqueous solution instead of general water, this study produced high-toughness cement composites reinforced with flax and steel fibers to improve the tensile deformation capacity, assessing the isothermal conduction calorimetry analysis, drying shrinkage, and strength characteristics. The mixing amount of CNCs was 0.4, 0.8, and 1.2 vol.% by volume of cement, and an aqueous solution was prepared using the ultrasonication dispersion method. When comparing the results of the experiment according to the CNC mixing ratio, CNCs at 0.8 vol.% led to an improvement in the shrinkage rate and mechanical performance compared with the plain specimen.

The importance of indoor air quality in a subway system is growing rapidly because passengers' health and displeasure are interrelated. Among diverse indoor pollutants, nitrogen dioxide (NO2) emitted from automobiles may flow into a platform of underground subway through ventilation holes or stairs. The level of NO2 in an underground subway station should be managed to prevent its adverse effects because NO2 is harmful to health. In this study, a novel control system (self-control system) equipped with panel-type hybrid activated carbon beds were developed and applied to remove NO2 and save energy for ventilation from underground subway stations. To evaluate the removal efficiency by varying influential factors such as superficial gas velocity and relative humidity, we measured the NO2 concentration from diverse sampling points (ambient, platform, and before and after the hybrid activated carbon bed) before and after operating the self-control system. As a result, the NO2 concentration at the ventilation hole of the subway station (12.3–113.6 ppb) was higher than that at the air monitoring station (9.2–68.4 ppb, AIRKOREA operated by Ministry of Environment in Korea). The level of NO2 was changed by varying the relative humidity in ambient air. The removal efficiency of NO2 decreased from 66.3% to 60.5% and the pressure drop of hybrid activated carbon bed in the system increased from 2.2 mmAq to 5.4 mmAq when the superficial gas velocity (depending on inverter frequency) increased from 1.04 m/s to 1.82 m/s. Additionally, the removal efficiency of NO2 rapidly decreased with elapsed time and was affected by relative humidity and weather conditions. Finally, the level of NO2 in the platform was less than 50 ppb (which is the standard value recommended by the Ministry of Environment, Korea), when the hybrid activated carbon bed was set to 90° (vertical direction on air flow). When the self-control system was operated in the heating ventilating, and air conditioning system of the underground subway station, the NO2 level in the platform was considerably controlled to below 50 ppb and the power consumption for ventilation reduced.

In this study, we investigated the development of titanium-indium-tin oxide (TITO) film for low-temperature near-infrared light-emitting diodes (NIR-LEDs) and studied their transmittance and conductivity characteristics. To fabricate the TITO structure, a 2 nm-thick titanium barrier, which exhibits high transparency in the visible-light region, was inserted between the ITO film and the top layer of the LED structure. The inclusion of Ti activated crystallization in the ITO films and improved their optical characteristics. Spectrometric analysis indicated outstanding transparency (nearly 93%) for 300 nm- and 450 nm-thick TITO films annealed at 550 °C in the NIR range (>700 nm). Furthermore, IR-LEDs with TITO films exhibited a 150% higher light output power than IR-LEDs with conventional ITO films. Therefore, we posit that using titanium as an activation barrier delivers effective crystalline ITO films for application in NIR devices.

In this paper, we reviewed the existing literature on the fabrication of nanocomposites based on cellulose and cellulose nanocrystals (CNCs), and analyzed their dispersion mechanism with respect to their use in the field of construction. First, the existing literature on CNC-based nanocomposites that exhibit the physical and chemical properties of nanocellulose and CNCs was reviewed. Next, keeping the use of these nanocomposites in the field of construction in mind, we determined the optimal mechanical method for their dispersion as an alternative to the currently used harmful chemical techniques. To this end, we evaluated the dispersibility of colloidal CNCs using two dispersion methods: magnetic stirring (for stirring times of 60 min, 120 min, and 180 min) and high-pressure dispersion (at pressures of 345 &times, 105 Pa, 1035 &times, 105 Pa, and 1587 &times, 105 Pa, and one to three dispersion passes). The optimal dispersion conditions were determined by analyzing the size and zeta potential of the CNC particles. It was found that the difference in the average diameter was reduced by approximately 76% at 1587 &times, 105 Pa during high-pressure dispersion.

As part of the study for the development of sustainable construction new materials for fiber reinforced high-toughness cement composite (ECC) using wood-based cellulose nanocrystals (hereinafter referred to as CNCs), this study assessed the applicability of CNCs through epidemiological performance assessment and long-term durability assessment. CNCs were prepared in the form of suspensions after dispersion and replaced with mixing water. The mixing rate of CNCs was 0.4, 0.8, 1.2 vol% Compared to cement, and the fiber types were Flax and Steel fiber. First, the amount of hydration products produced by the addition of CNCs was up to about 7% higher than that of plain specimen, and the value of strength was up to 20% at 0.8 vol%. Of steel fiber reinforced. Therefore, to evaluate the long-term durability according to the optimum mixing ratio of CNCs 0.8 vol%, compressive strength after freezing and thawing, acceleration carbonation, and chloride ion penetration resistance test were conducted. In the case of freezing-thawing, the strength ratio was lower than that of plain specimen, but the strength value itself increased by about 20% after freezing thawing. In the carbonation promotion test, the carbonation depth was reduced by about 60% compared to plain specimen. In the case of chlorine ion penetration resistance, the fiber-reinforced test specimens showed high value due to voids in the adhesion surface with cement due to the use of chlorine ions, but the C08 test specimen showed a resistance value of 5% lower than plain specimen confirming the validity of CNCs.

Transposable element (TE)-derived sequences comprise half of the human genome and DNA methylome and are presumed to be densely methylated and inactive. Examination of genome-wide DNA methylation status within 928 TE subfamilies in human embryonic and adult tissues identified unexpected tissue-specific and subfamily-specific hypomethylation signatures. Genes proximal to tissue-specific hypomethylated TE sequences were enriched for functions important for the relevant tissue type, and their expression correlated strongly with hypomethylation within the TEs. When hypomethylated, these TE sequences gained tissue-specific enhancer marks, including monomethylation of histone H3 at lysine 4 (H3K4me1) and occupancy by p300, and a majority exhibited enhancer activity in reporter gene assays. Many such TEs also harbored binding sites for transcription factors that are important for tissue-specific functions and showed evidence of evolutionary selection. These data suggest that sequences derived from TEs may be responsible for wiring tissue type-specific regulatory networks and may have acquired tissue-specific epigenetic regulation.

A single crystal of excessively Pb2+-exchanged zeolite Y (|Pb 15.5 2+ (Pb4O4(Pb 16/19 2+ Pb 3/19 4+ )4)4.75|[Si117Al75O384]-FAU) was prepared by exchange of Na–Y (|Na75|[Si117Al75O384]-FAU, Si/Al = 1.56) with an aqueous stream 0.05 M Pb(C2H3O2)2 at 294 K, followed by vacuum dehydration at 1 × 10−6 Torr and 693 K. Its structure was determined at 100 K, by X-ray diffraction techniques in the cubic space group Fd $$ \overline{3} $$ m and was refined to the final error indices R 1/wR 2 = 0.0639/0.1323. About 53.5 Pbn+ ions per unit cell occupy three different equipoints; 26 are at site I′, 19 are at site II, and the remaining 8.5 are at another site II. Three Pb4+ ions at some of the positions must have higher oxidation states due to elevated dehydration temperature; Pb(IIa) is supposed to coexist with Pb2+ and Pb4+ ions assuming the charge balance of the zeolite framework. A distorted Pb4O4 cube, alternating Pb2+ at Pb(I′) and O2− at O(5), coordinates with four Pb2+ and/or Pb4+ ions through its oxygen atoms to give a [Pb 4 2+ O 4 2− (Pb 16/19 2+ Pb 3/19 4+ )4]176/19+ cluster in 4.75 of eight sodalite cavities per unit cell in zeolite Y.

We investigate Ga0.33In0.67P quantum dot structures appropriate for special lighting applications in terms of structural and optical behaviors. The Ga0.33In0.67P materials form from 2-dimentional to 3-dimensional dots as the nominal growth thickness increases from 0.5 nm to 6.0 nm, indicating a Stranski-Krastanov growth mode. As the ambient temperature is increased to 300 K, the PL spectrum of the B-type dots is annihilated quickly because the large dot size induces a defect-related nonradiative recombination process. In contrast, the PL spectrum of the A-type dots is well maintained to 300 K. These data indicate that the Ga0.33In0.67P material is appropriate for an active layer of 700 nm light emitters.

The sintering behavior and dielectric characteristics of a titanium dioxide (TiO2) were investigated by adding CuO. The addition of CuO lowered the sintering temperature of the TiO2. At a given temperature, the densification and grain growth rate for a TiO2 with CuO were enhanced, compared with those of pure TiO2. The results suggest that CuO acts as an activator for the sintering of TiO2. Dielectric constant and loss were also examined for both pure and CuO added TiO2 samples. The variations of dielectric constant and loss were discussed in terms of grain size, porosity, and oxygen deficiency.

Among various materials suitable for an electrorheological (ER) fluid, polyaniline and its many derivatives based upon modification of oxidation state, dopant and polymerization conditions are of technological interest for their adaptation into ER fluids. This is because they have better thermal stability and smaller density than other potential ER materials. Furthermore, polyaniline is easy to polymerize by oxidation polymerization at relatively low temperature and can be doped from a conducting emeraldine hydrochloride form to an insulating state using simple protonic acids. In this study, we adapted the polyaniline based ER fluids for semi-active cylindrical flow-mode type ER damper. A cylindrical flow-mode type ER damper was chosen in this study because it has similar geometrical configuration to the conventional damper normally used for passenger vehicle. The damping forces measured using a semi-active ER damper with polyaniline based ER fluids were found to be controlled by tuning an applied electric field for different piston velocity.

The effectiveness of air pollution emission control policies can be evaluated by examining ambient pollutant concentration trends that are observed at a large number of ground monitoring sites over time. In this paper, we used ground monitoring measurements in conjunction with satellite aerosol optical depth (AOD) data to investigate fine particulate matter (PM2.5; particulate matter with aerodynamic diameter ≤ 2.5 µm) trends and their spatial patterns over a large U.S. region, New England, during 2000-2008. We examined the trends in rural and urban areas to get a better insight about the trends of regional and local source emissions. Decreases in PM2.5 concentrations (µg/m(3)) were more pronounced in urban areas than in rural ones. In addition, the highest and lowest PM2.5 decreases (µg/m(3)) were observed for winter and summer, respectively. Together, these findings suggest that primary particle concentrations decreased more relative to secondary ones. This is also supported by the analysis of the speciation data which showed that downward trends of primary pollutants including black carbon were stronger than those of secondary pollutants including sulfate. Furthermore, this study found that ambient primary pollutants decreased at the same rate as their respective source emissions. This was not the case for secondary pollutants which decreased at a slower rate than that of their precursor emissions. This indicates that concentrations of secondary pollutants depend not only on the primary emissions but also on the availability of atmospheric oxidants which might not change during the study period. This novel approach of investigating spatially varying concentration trends, in combination with ground PM2.5 species trends, can be of substantial regulatory importance.

We present a novel approach for generating targeted deletions of genomic segments in human and other eukaryotic cells using engineered zinc finger nucleases (ZFNs). We found that ZFNs designed to target two different sites in a human chromosome could introduce two concurrent DNA double-strand breaks (DSBs) in the chromosome and give rise to targeted deletions of the genomic segment between the two sites. Using this method in human cells, we were able to delete predetermined genomic DNA segments in the range of several-hundred base pairs (bp) to 15 mega-bp at frequencies of 10−3 to 10−1. These high frequencies allowed us to isolate clonal populations of cells, in which the target chromosomal segments were deleted, by limiting dilution. Sequence analysis revealed that many of the deletion junctions contained small insertions or deletions and microhomologies, indicative of DNA repair via nonhomologous end-joining. Unlike other genome engineering tools such as recombinases and meganucleases, ZFNs do not require preinsertion of target sites into the genome and allow precise manipulation of endogenous genomic scripts in animal and plant cells. Thus, ZFN-induced genomic deletions should be broadly useful as a novel method in biomedical research, biotechnology, and gene therapy.

The positions of PbI 2 molecule synthesized into the molecular-dimensioned cavities of |K 6 (Pb 4 I 2 )(PbI 2 ) 0.67 -(H 2 O) 2 |[Si 12 Al 12 O 48 ]-LTA have been determined. A single crystal of |Pb 6 |[Si 12 Al 12 O 48 ]-LTA, prepared by the dynamic ion-exchange of |Na 12 |Si 12 Al 12 O 48 -LTA with aqueous 0.05 M Pb(NO 3 ) 2 and washed with deionized water, was placed in a stream of flowing aqueous 0.05 M KI at 294 K for three days. The resulting crystal structure of the product (|K 6 (Pb 4 I 2 )(PbI 2 ) 0.67 (H 2 O) 2 |[Si 12 Al 12 O 48 ]-LTA, a = 12.353(1) A) was determined at 294 K by single-crystal X-ray diffraction in the space group Pm 3m. It was refined with all measured reflections to the final error index R 1 = 0.062 for 623 reflections which F o > 4σ(F o ). 4.67 Pb 2+ and six K + ions per unit cell are found at three crystallographically distinct positions: 3.67 Pb 2+ and three K + ions on the 3-fold axes opposite six-rings in the large cavity, three K + ions off the plane of the eight-rings, and the remaining one Pb 2+ ion lies opposite four-ring in the large cavity. 0.67 Pb 2+ ions and 1.34 I - ions per unit cell are found in the sodalite units, indicating the formation of a PbI 2 molecule in 67% of the sodalite units. Each PbI 2 (Pb-I = 3.392(7) A) is held in place by the coordination of its one Pb 2+ ion to the zeolite framework (a Pb 2+ cation is 0.74 A from a six-ring oxygens) and by the coordination of its two I - ions to K + ions through six-rings (I-K = 3.63(4) A). Two additional I - ions per unit cell are found opposite a four-ring in the large cavity and form Pb 2 K 2 I 5+ and PbK 2 I 3+ moieties, respectively, and two water molecules per unit cell are also found on the 3-fold axes in the large cavity.

Metal organic chemical vapor deposition (MOCVD) based aluminum gallium arsenide (AlGaAs) used as the bottom window (BW), which was inserted between the light-emitting diode (LED) structure and the absorbing substrate, has been proposed to improve the extraction efficiency of 630 nm AlGaInP LEDs. In an AlGaInP LED with this AlGaAs BW, enhanced light extraction efficiency was observed, as some of the light emitted from the active region to the absorbing substrate could pass out of the LED through the BW. In addition, it was found that a output power of 8 mW was obtained from an AlGaInP LED with both a BW and a distribution Bragg reflector (DBR), a nearly two fold improvement of over 4.2 mW that was obtained from a conventional one at an injection current of 80 mA.

This paper reports on the effect of Ni particle structures on the light extraction in 600 nm AlGaInP light-emitting diodes (LEDs). A Ni film was deposited on top of a gallium phosphide (GaP) layer and the surface texture was improved by an ammonia (NH3) plasma etching process into a chamber resulting in the formation of Ni particles with an average size of 10 nm. AlGaInP LED with the Ni particle shows an increase in the light extraction by 75% and a higher emission intensity with a percentage increase of 112.5% as compared with the conventional AlGaInP LEDs.