More than 8 million people fly on commercial aircraft each day with approximately 5% having a pre-existing respiratory disease. Thus it is necessary to provide high air quality in aircraft to protect public health. Volatile organic compounds (VOCs) present in aircraft cabins are suspected to contribute to the reported complaints. We investigated concentrations of VOCs, air temperature, relative humidity, and CO2 concentrations in a total of 46 flights, including 26 Chinese domestic flights and 20 international flights. We focused on the data from the cruising phase without meal serving in which the air supply and air recirculation were steady. A total of 284 passengers (i.e., 101 on international flights and 183 on Chinese domestic flights) were invited to participate in questionnaire surveys in this phase. We performed a linear mixed model analysis by controlling for potential confounders (age, gender, smoke habits, and history of allergy) to study associations between VOCs exposures and passengers' complaints. Xylene was significantly associated with irritations of the eyes, nose, and throat on both international and domestic flights, with antilog beta values from 1.12 to 1.28 (p < 0.05). The association of some aldehydes (i.e., nonanal, decanal, and heptanal), which are potential oxidation products with ozone, with passengers' sensory irritations was also significant, especially during international flights (antilog beta values: 1.19–1.22). It indicates that VOCs, especially xylene and aldehydes, in aircraft cabins may influence the perceived indoor air quality and complaints among passengers.
Sulfate scaling, as insoluble inorganic sulfate deposits, can cause serious operational problems in various industries, such as blockage of membrane pores and subsurface media and impairment of equipment functionality. There is limited article to bridge sulfate formation mechanisms with field scaling control practice. This article reviews the molecular-level interfacial reactions and thermodynamic basis controlling homogeneous and heterogeneous sulfate mineral nucleation and growth through classical and non-classical pathways. Common sulfate scaling control strategies were also reviewed, including pretreatment, chemical inhibition and surface modification. Furthermore, efforts were made to link the fundamental theories with industrial scale control practices. Effects of common inhibitors on different steps of sulfate formation pathways (i.e., ion pair and cluster formation, nucleation, and growth) were thoroughly discussed. Surface modifications to industrial facilities and membrane units were clarified as controlling either the deposition of homogeneous precipitates or the heterogeneous nucleation. Future research directions in terms of optimizing sulfate chemical inhibitor design and improving surface modifications are also discussed. This article aims to keep the readers abreast of the latest development in mechanistic understanding and control strategies of sulfate scale formation and to bridge knowledge developed in interfacial chemistry with engineering practice.
Background: Antibiotic resistome has been found to strongly interact with the core microbiota in the human gut, yet little is known about how antibiotic resistance genes (ARGs) correlate with certain microbes in large rivers that are regarded as "terrestrial gut." Results: By creating the integral pattern for ARGs and antibiotic-resistant microbes in water and sediment along a 4300-km continuum of the Yangtze River, we found that human pathogen bacteria (HPB) share 13.4% and 5.9% of the ARG hosts in water and sediment but contribute 64% and 46% to the total number of planktonic and sedimentary ARGs, respectively. Moreover, the planktonic HPB harbored 79 ARG combinations that are dominated by "natural" supercarriers (e.g., Rheinheimera texasensis and Noviherbaspirillum sp. Root189) in river basins. Conclusions: We confirmed that terrestrial HPB are the major ARG hosts in the river, rather than conventional supercarriers (e.g., Enterococcus spp. and other fecal indicator bacteria) that prevail in the human gut. The discovery of HPB as natural supercarriers in a world's large river not only interprets the inconsistency between the spatial dissimilarities in ARGs and their hosts, but also highlights the top priority of controlling terrestrial HPB in the future ARG-related risk management of riverine ecosystems globally.
A panel discussion on "Empire and Regional Order", in which I discussed two related issues: 1. how to do research on the history of regional politics? 2. how to make sense of the unwritten by following what Ann Laura Stoler called “archival grains”.
Polycyclic aromatic hydrocarbon (PAH) structures with suitable electron-withdrawing groups are useful building blocks for developing optical and electron-transporting materials. Here, we report the application of double benzannulation processes to synthesize PAH diimides with enlarged π-frameworks featuring a central anthracene moiety. The processes are realized by copper-catalyzed [4+2] cycloaddition of ethynyl-substituted aromatic dicarobximide to 2,5-bis(phenylethynyl)terephthalaldehyde, followed by intramolecular photocyclization or direct arylation via Heck cross coupling. Specifically, A central symmetric benzo[1,2- k :4,5- k ']-bis(fluoranthene)-3,4,12,13-tetracarboxyl diimide (BFDI) is acquired, with a single crystal revealing its completely planar polycyclic skeleton. Such a shape-persistent PAH expectedly exhibits a tendency to stack face-to-face and forms J-aggregates. Moreover, BFDI can be expediently difunctionalized site-selectively in reactive 9 and 10 positions of the anthracene unit and applied to prepare conjugated polymers. When coupled with 1,4-diketopyrrolo[3,4- c ]-pyrrole (DPP) via thiophene and dithiophene linkers, two significantly broadened absorption bands extended to the near-infrared regime appear, evidencing the effective π-conjugative extension ability of BFDI unit.
Conventionally, thermal technology of steam-assisted gravity drainage (SAGD) has been an effective method to unlock unconventional petroleum resources with extra-high viscosity. However, in the middle and late stages of SAGD, there are some problems such as low oil production rate and high water cut, and a large amount of greenhouse gases can be generated, which may disrupt the balance of the geo-energy supply and greenhouse-gas mitigation. Therefore, in this study, with a novel thermal SAGD technology with flue gas in the late stage of SAGD, the steam chamber and fluid-steam ratio could be substantially improved, which thereafter results in better production performance. Meanwhile, it can effectively use the flue gas produced by SAGD to reduce carbon emissions. A laboratory-scale three-dimensional (3-D) physical was manufactured to simulate the practical processes, including interwell warm-up, conventional and novel flue gas-assisted SAGD at high-pressure and high-temperature reservoir conditions. The experiments demonstrated the injected flue gas concentrated on the top of the physical model due to the gravity override, which contributes to control the heat loss to the atmosphere and subsurface systems. In this way, the thermal sweep efficiency was substantially increased since the heat retained was employed for the lateral-direction steam chamber development. Meanwhile, the addition of flue gas induced the reduction of steam partial pressure, which finally resulted in chamber temperature decreasing by approximately 10 °C. On the other hand, the instantaneous fluid-steam ratio was found to increase from 0.06 to 0.24 at the highest, while the water cut decreased by around 20%. All the aforementioned changes in physical parameters contribute to 7.75% higher petroleum fluid recovery. Overall, the newly-developed technology has been validated to significantly extend production lifetime and improved recovery efficiency. This study will support the foundation of more general application pertaining to greenhouse gases mitigation and sustainable productions in unconventional geo-energy.
As novel metal-free photocatalysts, covalent organic frameworks (COFs) have great potential to decontaminate pollutants in water. Fast charge recombination in COFs yet inhibits their photocatalytic performance. We found that the intramolecular charge transfer within COFs could be modulated via constructing a donor–acceptor (D–A) structure, leading to the improved photocatalytic performance of COFs toward pollutant degradation. By integrating electron donor units (1,3,4-thiadiazole or 1,2,4-thiadiazole ring) and electron acceptor units (quinone), two COFs (COF-TD1 and COF-TD2) with robust D–A characteristics were fabricated as visible-light-driven photocatalysts to decontaminate paracetamol. With the readily excited electrons in 1,3,4-thiadiazole rings, COF-TD1 exhibited efficient electron–hole separation through a push–pull electronic effect, resulting in superior paracetamol photodegradation performance (>98% degradation in 60 min) than COF-TD2 (∼60% degradation within 120 min). COF-TD1 could efficiently photodegrade paracetamol in complicated water matrices even in river water, lake water, and sewage wastewater. Diclofenac, bisphenol A, naproxen, and tetracycline hydrochloride were also effectively degraded by COF-TD1. Efficient photodegradation of paracetamol in a scaled-up reactor could be achieved either by COF-TD1 in a powder form or that immobilized onto a glass slide (to further ease recovery and reuse) under natural sunlight irradiation. Overall, this study provided an effective strategy for designing excellent COF-based photocatalysts to degrade emerging contaminants.
TikTok has enjoyed wide popularity in the Global South. But in the summer of 2020, a tit for tat altercation erupted over the use of the app in India against the backdrop of a border dispute between India and China. India banned TikTok, along with other Chinese mobile applications. This ban raised larger ongoing issues around user privacy, cybersecurity threats, and content regulation issues on social media platforms and telecommunications equipment around the world. In this paper we explore these issues and the wider debates on social media. To do so, we interviewed policymakers and academics as well as representatives from India’s technology industry. We also applied computational linguistic analysis on 6,388 Twitter posts about the ban by Indian users. The discourses on Twitter show intense nationalistic rhetoric and that Indian Twitter users were vocal in urging the government to ban TikTok. In-depth expert interviews suggested there were intense geopolitical conflicts behind the TikTok ban. We situate these findings with a broader analysis of the current geopolitics of social media platforms.
Full-waveform inversion (FWI) is considered as a high-resolution imaging technique to recover the geophysical parameters of the elastic subsurface from the entire content of the seismic signals. However, the subsurface material properties are less well estimated with elastic constraints, especially for the near-surface structure, which usually contains fluid contents. Since Biot theory has provided a framework to describe seismic wave propagations in the poroelastic media, in this work, we propose an algorithm for the 2-D time-domain (TD) poroelastic FWI (PFWI) when the fluid-saturated poroelastic equations are applied to carve the physical mechanism in the shallow subsurface. To detect the contribution of the poroelastic parameters to shallow seismic wavefields, the scattered P-SV\&SH wavefields corresponding to a single model parameter are derived explicitly by Born approximation and shown numerically afterward. The Fréchet kernels are also derived and exhibited in P-SV\&SH schemes to analyse the sensitivities of the objective function to different poroelastic parameters. Furthermore, we verify the accuracy of the derivations through model parameter reconstructions. We perform a series of numerical tests on gradients with respect to different model parameters to further evaluate inter-parameter trade-offs. PFWI holds potential possibilities to directly invert fluid-related physical parameters of the shallow subsurface.
Dielectric spectroscopy in the sub-THz regime is a promising candidate for microfluidic-based analysis of biological cells and bio-molecules, since multiple vibrational and rotational transition energy levels exist in this frequency range (P. Siegel, “Terahertz technology in biology and medicine,” IEEE Trans. Microw. Theor. Tech., vol. 52, pp. 2438–2447, 2004). This article presents our recent efforts in the implementation of microfluidic channel networks with silicon-based technologies to unleash the potential of an integrated sub-THz microfluidic sensor platform. Various aspects of dielectric sensors, readout systems, flowmeter design as well as implemention- and technology-related questions are addressed. Three dielectric sensor systems are presented operating at 240 GHz realizing transmission-based, reflection-based and full two-port architectures. Furthermore different silicon based microchannel integration techniques are discussed as well as a novel copper pillar-based PCB microchannel method is proposed and successfully demonstrated.
