Spatiotemporal characterization of PM2.5, O3, and trace gases associated with East Asian continental outflows via drone sounding.

East Asian continental outflows with PM2.5, O3, and other species may determine the baseline conditions and affect the air quality in downwind areas via long-range transport (LRT). To gain insight into the impact and spatiotemporal characteristics of airborne pollutants in East Asian continental outflows, a versatile multicopter drone sounding platform was used to simultaneously observe PM2.5, O3, CO2, and meteorological variables (temperature, specific humidity, pressure, and wind vector) above the northern tip of Taiwan, Cape Fuiguei, which often encounters continental outflows during winter monsoon periods. By coordinating hourly high-spatial-resolution profiles provided by drone soundings, WRF/CMAQ model air quality predictions, HYSPLIT-simulated backward trajectories, and MERRA-2 reanalysis data, we analyzed two prominent phenomena of airborne pollutants in continental outflows to better understand their physical/chemical characteristics. First, we found that pollutants were well mixed within a sounding height of 500 m when continental outflows passed through and completely enveloped Cape Fuiguei. Eddies induced by significant fluctuations in wind speeds coupled with minimal temperature inversion and LRT facilitated vertical mixing, possibly resulting in high homogeneity of pollutants within the outflow layer. Second, the drone soundings indicated exceptionally high O3 concentrations (70-100 ppbv) but relatively low concentrations of PM2.5 (10-20 µg/m3), CO2 (420-425 ppmv), and VOCs in some air masses. The low levels of PM2.5, CO2, and VOCs ruled out photochemistry as the cause of the formation of high-level O3. Further coordination of spatiotemporal data with air mass trajectories and O3 cross sections provided by MERRA-2 suggested that the high O3 concentrations could be attributed to stratospheric intrusion and advection via continental outflows. High-level O3 concentrations persisted in the lower troposphere, even reaching the surface, suggesting that stratospheric intrusion O3 may be involved in the rising trend in O3 concentrations in parts of East Asia in recent years in addition to surface photochemical factors.

Using drone soundings to study the impacts and compositions of plumes from a gigantic coal-fired power plant.

The immense impacts of coal-fired power plant plumes on the atmospheric environment have caused great concern linked to climate and health issues. However, studies on the field observations of aerial plumes are relatively limited, mainly due to the lack of suitable plume observation tools and techniques. In this study, we use a multicopter unmanned aerial vehicle (UAV) sounding technique to study the influences of the aerial plumes of the world's fourth-largest coal-fired power plant on the atmospheric physical/chemical conditions and air quality. A set of species, including 106 volatile organic compounds (VOCs), CO, CO2, CH4, PM2.5, and O3, and meteorological variables of temperature (T), specific humidity (SH), and wind data, are collected by the UAV sounding technique. The results reveal that the large-scale plumes of the coal-fired power plant cause local temperature inversion and humidity changes, and even affect the dispersion of pollutants below. The chemical compositions of coal-fired power plant plumes are significantly different from those of another ubiquitous vehicular source. High fractions of ethane, ethene, and benzene and low fractions of n-butane and isopentane found in plumes could serve as the key features to help distinguish the influences of coal-fired power plant plumes from other pollution sources in a particular area. By taking the ratios of pollutants (e.g., PM2.5, CO, CH4, and VOCs) to CO2 in plumes and the CO2 emission amounts of the power plant into calculation, we enable the easy quantification of the specific pollutant emissions released from power plant plumes to the atmosphere. In summary, observation by using drone soundings dissecting the aerial plumes provides a new methodology that allows aerial plumes to be readily detected and characterized. Furthermore, the influences of the plumes on the atmospheric physical/chemical conditions and air quality can be assessed rather straightforwardly, which was not easily achievable in the past.

A study of the vertical homogeneity of trace gases in East Asian continental outflow.

East Asian continental outflows containing with pollutants may deteriorate air quality in the downwind region via long-range transport (LRT). In particular, cold fronts with high wind speeds generally promote the LRT of air pollutants to further downwind areas, including Taiwan. To gain an insightful understanding of the characteristics and vertical homogeneity of trace gases in East Asian continental outflows, as well as their relation with atmospheric meteorological conditions, whole air samples were collected above a cape at the northern tip of the island of Taiwan during frontal passages. Aerial samples were collected at multiple altitudes from the surface to a maximum height of 700 m with a multicopter sounding platform carrying a robotic whole air sampling device. Simultaneously, aerial meteorological variables of temperature and wind vector from near the surface to a maximum height of 1000 m were also measured during the whole air sampling periods. An array of 106 volatile organic compounds (VOCs) as well as CO, CO2, and CH4 were analyzed to characterize the air composition and vertical homogeneity of trace gases. The results revealed rather homogeneous vertical distributions of most VOCs, CO, CO2, and CH4 in the frontal passages, indicating well-mixed conditions of trace gases in the East Asian continental outflows. The strong wind shear and minimal temperature inversion associated with the frontal passage likely induced turbulence and increased vertical mixing. Furthermore, higher levels of species characteristic of the East Asian continent were observed from the surface up to hundreds of meters above the cape, revealing a strong inflow of polluted air masses from the East Asian continent brought by cold frontal passages.

Parameter Optimization of Laser Direct-Write Patterning on Indium Tin Oxide/Polycarbonate Thin Films Using Multi-Performance Characteristics Analysis.

Indium tin oxide (ITO) thin films on polycarbonate (PC) substrates were patterned using the laser direct-write (LDW) technique to form an isolation line. The effect of the LDW parameters (power, pulse repetition rate, and defocusing distance) on the isolation line width, depth and roughness of the PC within the line was investigated. Additionally, the Taguchi method of experimental design was applied to determine the optimal parameters of LDW. Results showed that increasing the power led to an increase in the isolation line width and decrease in the surface roughness of the PC within the line. The increase in the pulse repetition rate and defocusing distance caused a decrease in the isolation line width. The optimal parameters were found to be A2B3C3, consisting of power of 5 W, pulse repetition rate of 100 kHz, and defocusing distance of +3 mm. Under these parameters, we obtained an isolation line width of 48.4 µm, and a surface roughness of Ra 38 nm of the PC within the isolation line. We confirmed that the ITO films separated by the isolation lines attained electrical isolation.

Nonuniform Heating Method for Hot Embossing of Polymers with Multiscale Microstructures.

The hot embossing of polymers is one of the most popular methods for replicating high-precision structures on thermoplastic polymer substrates at the micro-/nanoscale. However, the fabrication of hybrid multiscale microstructures by using the traditional isothermal hot embossing process is challenging. Therefore, in this study, we propose a novel nonuniform heating method for the hot embossing of polymers with multiscale microstructures. In this method, a thin graphene-based heater with a nonuniform heating function, a facility that integrates the graphene-based heater and gas-assisted hot embossing, and a roll of thermoplastic film are employed. Under appropriate process conditions, multiscale polymer microstructure patterns are fabricated through a single-step hot embossing process. The quality of the multiscale microstructure patterns replicated is uniform and high. The technique has great potential for the rapid and flexible fabrication of multiscale microstructure patterns on polymer substrates.

Do holometabolous insects molt spontaneously after adulthood? An exceptional case report in fireflies (Coleoptera: Lampyridae), with discussion of its inferred endocrine regulation especially in relation to neoteny.

It has been a traditionally held view that winged insects stop molting after they reach adulthood. We observed a fascinating phenomenon of a post-imago molt occurring in the neotenic females of a firefly species in Taiwan over the last two years. By rearing Lamprigera minor larvae to adults, four out of the five unmated females studied were found undergoing an extra molt 8-18 days after adult eclosion. They were reproductively mature when the post-imago molt occurred, as evidenced by the eggs inside their bodies. The four females died without oviposition whereas the only normal female laid eggs. A comparison of exuviae of different stages confirmed the existence of post-imago ecdysis. The adult skin differed from the pupal one mainly in the mouthparts and leg structures. No mix of pupal and adult traits was seen in the adult skin. The females retained the same morphology after the extra molt. A close examination of the post-imago molting females revealed that their oviduct openings were all blocked by larval or pupal skin and thus unable to lay eggs. The reproductive stress may invoke an endocrine disorder and lead to an extra molt. We propose that L. minor females retain their prothoracic glands even as adults, allowing them to molt as adults under certain environmental or physiological conditions. Thus, neoteny of L. minor is reflected in both the external morphology as well as the internal physiology. The possible developmental changes associated with the evolution of neoteny are discussed.

An optimized multicopter UAV sounding technique (MUST) for probing comprehensive atmospheric variables.

The unique maneuverability, ease of deployment, simplicity in logistics, and relatively low costs of multicopters render them effective vehicles for low atmospheric research. While many efforts have contributed to the fundamental success of atmospheric applications of multicopters in the past, several challenges remain, including limited measurable variables, possible response-delay in real-time observations, insufficient measurement accuracy, endurance of harsh conditions and tolerance towards interferences. To address these challenges and further fortify the applicability in diversified research disciplines, this study developed an optimized multicopter UAV sounding technique (MUST). The MUST serves as an integrated platform by combining self-developed algorithms, optimized working environments for sensors/monitors, and retrofitted sampling devices to probe a comprehensive set of atmospheric variables. These variables of interest include meteorological parameters (temperature, relative humidity, pressure, wind direction and speed), the chemical composition (speciated VOCs, CO, CO2, CH4, CO2 isotopologues, O3, PM2.5, and black carbon), and the radiation flux, as well as visible and thermal images. The aim of this study is to achieve the following objectives: 1. to easily probe a comprehensive set of near-surface atmospheric variables; 2. to improve data quality by correcting for sensors' delay in real-time observations and minimizing environmental interferences; and 3. to enhance the versatility and applicability of aerial measurements by incorporating necessary hardware and software. Field launching cases from the surface to a maximum height of 1000 m were conducted to validate the robustness of the integrated MUST platform with sufficient speed, accuracy and resolution for the target variables.

Enhanced exopolysaccharide production by Cordyceps militaris using repeated batch cultivation.

Cordyceps militaris exo-polysaccharides (EPS) have been reported to possess many benefits, such as anti-tumor, anti-inflammatory and antioxidant activities. In this study, the production of EPS via cultivation in a bioreactor was investigated. Glucose and yeast extract were determined to be the most suitable carbon and nitrogen sources for EPS production. The appropriate levels of glucose and yeast extract were 40 g/L and 10 g/L, respectively, resulting in EPS production of 1.686 g/L in a submerged culture. In the stirred-tank fermentor, an agitation rate of 150 rpm and aeration rate of 1.5 vvm were the most effective for EPS production. Due to the anchoring of mycelial cells on the wall of fermentor, a repeated batch approach was used. EPS production of C. militaris could be enhanced to a maximum of 5.713 g/L, with a productivity of 476 mg/L/day in the second run. The repeated batch approach was expected to generate higher EPS production, increase EPS yield and productivity and further simplify cultivation operations for bio-industrial application.

Innovative Strain Sensing for Detection of Exterior Wall Tile Lesion: Smart Skin Sensory System.

Tiles are commonly used to cover the exteriors of buildings in Taiwan. However, older buildings in Taiwan encounter the problem of tiles falling off due to natural deterioration, which is unsightly, and more importantly, a threat to public safety. Nevertheless, no current method exists that can effectively detect flaws in building tiles in real time. This study combined the fields of civil engineering and automatic control to reduce risks caused by falling tiles by improving real-time detection of at-risk areas. Micro-resistance was combined with fuzzy theory as the logical foundation for evaluating tile status. String-type strain gauges were adopted as sensors to design a smart skin sensory system that could measure signs of deterioration in tile surface lesions. The design was found to be feasible. In the future, it can be further developed for facile real-time assessment of tile status.

Applicability of a linear diffusion model to determination of the height of the potential barrier at the grain boundaries of Fe-doped SrTiO3.

The potential barrier formed at the grain boundaries in Fe-doped SrTiO3 is reported to be one of the main reasons of the exceptionally large grain boundary resistivity of the material. Of particular interest is thus how to accurately quantify the potential barrier height, Ψgb, in such electronic conductors. This study aims to expand the applicability of a linear diffusion model (namely I-V model) to electronic conductors. The I-V model has previously proven its success in accurate determination of Ψgb in popular ionic conductors. By employing 1 mol% Fe-doped SrTiO3 as a model material, the current-voltage characteristics of the grain boundary investigated demonstrate the power law behavior predicted by the I-V model, verifying the applicability of this model. The Ψgb estimated from the I-V model at different temperatures are compared with those from the resistivity ratio of the grain boundary to the bulk. The resistivity ratio has been exclusively used to determine Ψgb in various conductors over several decades and yet has limitations in its accuracy. The Ψgb determined by the I-V model are found to be substantially lower than those from the resistivity ratio; such discrepancy implies that the potential barrier only partially contributes to the high grain boundary resistivity of a lightly doped electron-hole conducting SrTiO3.

The exceptionally large height of the potential barrier at the grain boundary of a LaGaO3-based solid solution deduced from a linear diffusion model.

The extent of the influence of space charge on the electric current through the grain boundary in solid electrolytes can be parameterized by the grain boundary potential, i.e. the height of the potential barrier formed at the grain boundary. Previously the value of this parameter has been estimated exclusively by the ratio of the grain boundary resistivity to the bulk counterpart over several decades. We recently demonstrated that it can be alternatively determined by analyzing the current-voltage characteristic of the grain boundary. Furthermore, we theoretically justified that the conventional method is in fact a subset of the new method, therefore, the latter is a more reliable and comprehensive approach to determine the grain boundary potential. Here, we present the experimental results that verify our theoretical justification. The values of the grain boundary potential determined for 1 mol% Sr-doped LaGaO3 (LSG1) employing both methods are in excellent agreement with one another. Such a consistency has not been reported for other solid electrolytes to date and we provide an explanation for it. Our data also indicate that for the case of LSG1, the Nernst-Einstein relation is preserved at the electric field exceeding 900 kV cm-1.

Study on the Correlation between Humidity and Material Strains in Separable Micro Humidity Sensor Design.

Incidents of injuries caused by tiles falling from building exterior walls are frequently reported in Taiwan. Humidity is an influential factor in tile deterioration but it is more difficult to measure the humidity inside a building structure than the humidity in an indoor environment. Therefore, a separable microsensor was developed in this study to measure the humidity of the cement mortar layer with a thickness of 1.5-2 cm inside the external wall of a building. 3D printing technology is used to produce an encapsulation box that can protect the sensor from damage caused by the concrete and cement mortar. The sensor is proven in this study to be capable of measuring temperature and humidity simultaneously and the measurement results are then used to analyze the influence of humidity on external wall tile deterioration.

Development of a multicopter-carried whole air sampling apparatus and its applications in environmental studies.

To advance the capabilities of probing chemical composition aloft, we designed a lightweight remote-controlled whole air sampling component (WASC) and integrated it into a multicopter drone with agile maneuverability to perform aerial whole air sampling. A field mission hovering over an exhaust shaft of a roadway tunnel to collect air samples was performed to demonstrate the applicability of the multicopter-carried WASC apparatus. Ten aerial air samples surrounding the shaft vent were collected by the multicopter-carried WASC. Additional five samples were collected manually inside the shaft for comparison. These samples were then analyzed in the laboratory for the chemical composition of 109 volatile organic compounds (VOCs), CH4, CO, CO2, or CO2 isotopologues. Most of the VOCs in the upwind samples (the least affected by shaft exhaust) were low in concentrations (5.9 ppbv for total 109 VOCs), posting a strong contrast to those in the shaft exhaust (235.8 ppbv for total 109 VOCs). By comparing the aerial samples with the in-shaft samples for chemical compositions, the influence of the shaft exhaust on the surrounding natural air was estimated. Through the aerial measurements, three major advantages of the multicopter-carried WASC were demonstrated: 1. The highly maneuverable multicopter-carried WASC can be readily deployed for three-dimensional environmental studies at a local scale (0-1.5 km); 2. Aerial sampling with superior sample integrity and preservation conditions can now be performed with ease; and 3. Data with spatial resolution for a large array of gaseous species with high precision can be easily obtained.

Changes in the levels and variability of halocarbons and the compliance with the Montreal Protocol from an urban view.

Ambient levels and variability of major atmospheric halocarbons, i.e. CFC-12, CFC-11, CFC-113, CCl4, CH3CCl3, C2HCl3, and C2Cl4 in a major metropolis (Taipei, Taiwan) were re-investigated after fourteen years by flask sampling in 2012. Our data indicates that the variability expressed as standard deviations (SD) of CFC-113 and CCl4 remained small (2.0 ppt and 1.9 ppt, respectively) for the 10th-90th percentile range in both sampling periods; whereas the variability of CFC-12, CFC-11, C2HCl3, and C2Cl4 measured in 2012 became noticeably smaller than observed in 1998, suggesting their emissions were reduced over time. By comparing with the background data of a global network (NOAA/ESRL/GMD baseline observatories), the ambient levels and distribution of these major halocarbons in Taipei approximated those at a background site (Mauna Loa) in 2012, suggesting that the fingerprint of the major halocarbons in a used-to-be prominent source area has gradually approached to that of the background atmosphere.

Determination of band alignment in the single-layer MoS2/WSe2 heterojunction.

The emergence of two-dimensional electronic materials has stimulated proposals of novel electronic and photonic devices based on the heterostructures of transition metal dichalcogenides. Here we report the determination of band offsets in the heterostructures of transition metal dichalcogenides by using microbeam X-ray photoelectron spectroscopy and scanning tunnelling microscopy/spectroscopy. We determine a type-II alignment between MoS2 and WSe2 with a valence band offset value of 0.83 eV and a conduction band offset of 0.76 eV. First-principles calculations show that in this heterostructure with dissimilar chalcogen atoms, the electronic structures of WSe2 and MoS2 are well retained in their respective layers due to a weak interlayer coupling. Moreover, a valence band offset of 0.94 eV is obtained from density functional theory, consistent with the experimental determination.

Ultrafast generation of pseudo-magnetic field for valley excitons in WSe2 monolayers.

The valley pseudospin is a degree of freedom that emerges in atomically thin two-dimensional transition metal dichalcogenides (MX2). The capability to manipulate it, in analogy to the control of spin in spintronics, can open up exciting opportunities. Here, we demonstrate that an ultrafast and ultrahigh valley pseudo-magnetic field can be generated by using circularly polarized femtosecond pulses to selectively control the valley degree of freedom in monolayer MX2. Using ultrafast pump-probe spectroscopy, we observed a pure and valley-selective optical Stark effect in WSe2 monolayers from the nonresonant pump, resulting in an energy splitting of more than 10 milli-electron volts between the K and K' valley exciton transitions. Our study opens up the possibility to coherently manipulate the valley polarization for quantum information applications.

Atomically thin heterostructures based on single-layer tungsten diselenide and graphene.

Heterogeneous engineering of two-dimensional layered materials, including metallic graphene and semiconducting transition metal dichalcogenides, presents an exciting opportunity to produce highly tunable electronic and optoelectronic systems. In order to engineer pristine layers and their interfaces, epitaxial growth of such heterostructures is required. We report the direct growth of crystalline, monolayer tungsten diselenide (WSe2) on epitaxial graphene (EG) grown from silicon carbide. Raman spectroscopy, photoluminescence, and scanning tunneling microscopy confirm high-quality WSe2 monolayers, whereas transmission electron microscopy shows an atomically sharp interface, and low energy electron diffraction confirms near perfect orientation between WSe2 and EG. Vertical transport measurements across the WSe2/EG heterostructure provides evidence that an additional barrier to carrier transport beyond the expected WSe2/EG band offset exists due to the interlayer gap, which is supported by theoretical local density of states (LDOS) calculations using self-consistent density functional theory (DFT) and nonequilibrium Green's function (NEGF).

Hot carriers in epitaxial graphene sheets with and without hydrogen intercalation: role of substrate coupling.

The development of graphene electronic devices produced by industry relies on efficient control of heat transfer from the graphene sheet to its environment. In nanoscale devices, heat is one of the major obstacles to the operation of such devices at high frequencies. Here we have studied the transport of hot carriers in epitaxial graphene sheets on 6H-SiC (0001) substrates with and without hydrogen intercalation by driving the device into the non-equilibrium regime. Interestingly, we have demonstrated that the energy relaxation time of the device without hydrogen intercalation is two orders of magnitude shorter than that with hydrogen intercalation, suggesting application of epitaxial graphene in high-frequency devices which require outstanding heat exchange with an outside cooling source.

Effect of paeonol on tissue destruction in experimental periodontitis of rats.

We evaluated the effects of paeonol, a phenolic compound of Moutan Cortex, on the tissue inflammation and destruction in experimental periodontitis of rats. The maxillary palatal bony surfaces of 18 rats received injections of lipopolysaccharide (LPS, 5 mg/mL), PBS or LPS-plus-paeonol (40 mg/kg, intra-peritoneal injection) for three days. Five days later, the osteoclasts were examined and compared after tartrate-resistant acid phosphatase staining. In another 36 rats, the experimental periodontitis was induced by placing the ligatures around the maxillary second and mandibular first molars. Seven days later, the periodontal destruction and inflammation in rats with paeonol (40 mg/kg or 80 mg/kg) and those who had no ligature or without paeonol were compared by dental radiography, micro-computerized tomography (micro-CT), and histology. Gingival mRNA expressions of pre-inflammatory cytokines, including IL-1ß' IL-6 and TNF-α were also examined. Compared to the effect of the LPS positive control, the paeonol injection significantly reduced the induced osteoclast formation. In ligature-induced periodontitis, the periodontal bone supporting ratio was significantly higher in the ligature-plus-paeonol groups compared to that of the ligature group, although they were still less than those in the non-ligature group. By micro-CT and by histology/histometry, a consistent anti-destructive effect was observed when paeonol was added. Moreover, less amount of inflammatory cell-infiltrated connective tissue area, connective tissue attachment, and mRNA expressions of pro-inflammatory cytokines were presented in the ligature-plus-paeonol groups than those in the ligature group. These results suggested that paeonol might have a protective potential on gingival tissue inflammation and alveolar bone loss during the process of periodontitis by inhibiting pro-inflammatory cytokines.

Analysis of building envelope insulation performance utilizing integrated temperature and humidity sensors.

A major cause of high energy consumption for air conditioning in indoor spaces is the thermal storage characteristics of a building's envelope concrete material; therefore, the physiological signals (temperature and humidity) within concrete structures are an important reference for building energy management. The current approach to measuring temperature and humidity within concrete structures (i.e., thermocouples and fiber optics) is limited by problems of wiring requirements, discontinuous monitoring, and high costs. This study uses radio frequency integrated circuits (RFIC) combined with temperature and humidity sensors (T/H sensors) for the design of a smart temperature and humidity information material (STHIM) that automatically, regularly, and continuously converts temperature and humidity signals within concrete and transmits them by radio frequency (RF) to the Building Physiology Information System (BPIS). This provides a new approach to measurement that incorporates direct measurement, wireless communication, and real-time continuous monitoring to assist building designers and users in making energy management decisions and judgments.