科研成果

Lab-on-a-chip has been used widely in rapid, high-throughput and low-consumption analysis of samples in biochemistry. The ion concentration polarization (ICP) produced by ion-selective transport of nanochannels provides a novel solution for problems in ultra-low concentration sample detection, systems biology and desalination. This paper reviews the applications of ion transport based on the principle of ICP in micro-nanofluidic systems. First, the fundamental governing equations of ICP are described. Then, the applications of nano-electrokinetic ion enrichment and ion current rectification (ICR) are introduced. Nano-electrokinetic ion enrichment is used mainly in the fields of molecular enrichment, ultra-low concentration sample detection and seawater desalination. ICR is applied mainly to the sensitive detection of analytical substances such as proteins, nucleic acids and small molecules. The application of ion transport based on ICP principle is summarized and the possible directions worthy of further research are proposed. (c) 2019 Society of Chemical Industry

Geoffrey Robinson’s The Killing Season is one of the most-awaited books by the Southeast Asian studies community in 2018. The 456-page monograph explores in great detail the anti-communist massacres of Indonesia in 1965-66 and the long-term repercussions in the following decades. As one of the worst human atrocities in the 20th century, the mass killing led to the death of some half a million real and alleged communist members and sympathizers. After more than 50 years, however, reflections on this tragic event are far from sufficient. Although academic work in recent years spurred growing discussions within small circles, the mass violence has not received adequate attention from the international audience. Worse still, a troubling silence permeates Indonesia even today, as many of those who committed the atrocities have stayed in power. While victims struggled to find viable ways to pursue justice, numerous murderers managed to get away with impunity.

An accurate determination of the minimum miscibility pressure (MMP) is required for the miscible gas injection project in oilfield. The experimental methods are usually considered to be an available and appropriate way to determine the MMPs, while so far few study has been found to systematically review and evaluate the experimental MMP determination methods. In this study, for the first time, ten existing experimental methods and their three important technical aspects, including the experimental design, operating procedure, and MMP criterion, are critically reviewed for determining the MMPs. Then, the three technical parts for each experimental method are specifically evaluated and scored from thirteen factors. On the basis of the evaluation results, a novel and effective screening table, which is coupled with the weight analysis, is initially developed to assist the selection of the most appropriate MMP experiment for different specific conditions. From the previously published studies, the conventional slim-tube tests, rising-bubble apparatus (RBA), and vanishing interfacial tension (VIT) technique are still the three most widely-used experimental methods for the MMP determinations. Results from this study indicate that the slim-tube and coreflood tests are the best experimental methods for the MMP determinations, which are followed by the RBA, VIT technique, and microfluidic test. Future work with respect to the experimental design, operating procedure, and MMP criteria are expected to improve the existing experimental methods and possibly initiate a completely standardized experimental method for the MMP determinations.

As recent trends in comparing the Han and Roman empires from primarily the point of view of literary evidence has brought forth new frameworks and opportunities of research, one asks how these developments could contribute to the comparison of the two empires' governance behaviors. The paper first surveys current literature published in the past decade and identify common themes in the scholarship on the Han and the Roman metallurgical advances and aspects of their iron industries. Of particular focus is the gradual awareness in the importance of iron semi-products in the Han and the Roman domains. In the second and third section, literary sources from the Qin-Han and the Roman domains are reviewed in order to identify general trends that can be juxtaposed for closer discussion. Particular emphasis is placed on the relationship between the private iron operators with generational legacies in the iron industries even be fore the formation of the Qin-Han and the Roman states, and how the state administrators engage with and adapt to the sophisticated and complex traditions of the Qin-Han and Roman iron industries. The fourth section provides a comparative discussion on issues concerning the states' juridical or statutory approaches to regulating iron mining and smelting operations, and observations on the intersect between semi-products, local ironworks andsmithies, and the needs of agricultural producers.

Body-mass index (BMI) has increased steadily in most countries in parallel with a rise in the proportion of the population who live in cities. This has led to a widely reported view that urbanization is one of the most important drivers of the global rise in obesity. Here we use 2,009 population-based studies, with measurements of height and weight in more than 112 million adults, to report national, regional and global trends in mean BMI segregated by place of residence (a rural or urban area) from 1985 to 2017. We show that, contrary to the dominant paradigm, more than 55% of the global rise in mean BMI from 1985 to 2017-and more than 80% in some low- and middle-income regions-was due to increases in BMI in rural areas. This large contribution stems from the fact that, with the exception of women in sub-Saharan Africa, BMI is increasing at the same rate or faster in rural areas than in cities in low- and middle-income regions. These trends have in turn resulted in a closing-and in some countries reversal-of the gap in BMI between urban and rural areas in low- and middle-income countries, especially for women. In high-income and industrialized countries, we noted a persistently higher rural BMI, especially for women. There is an urgent need for an integrated approach to rural nutrition that enhances financial and physical access to healthy foods, to avoid replacing the rural undernutrition disadvantage in poor countries with a more general malnutrition disadvantage that entails excessive consumption of low-quality calories.

Nitrous oxide (N2O) emission from wastewater treatment plants (WWTPs) has become a focus of attention due to its significant greenhouse effect. In this study, the role of sludge retention time (SRT) in mitigation of N2O emission from a pilot-scale oxidation ditch was systematically investigated. The activated sludge system that operated at SRT of 25 days demonstrated significantly lower N2O emission factor, higher resistance to ammonia overload and aeration failure shock than those obtained at SRT of 15 days no matter which hydraulic retention time (HRT) was adopted. Batch experiments revealed that nitrifier denitrification (ND) was the primary mechanism of N2O generation. However, more microbes affiliated with Nitrospira genera were harbored in the system at SRT 25 d, which could effectively avoid nitrite accumulation, a key factor promoting N2O generation by ND. PICRUSt results further suggested the system at SRT 25 d possessed higher genetic potential for N2O reduction reflected by the more abundant nitrous-oxide reductase.

Oil-sands (OS) operations in Alberta, Canada, are a large source of secondary organic aerosol (SOA). However, the SOA formation process from OS-related precursors remains poorly understood. In this work, a newly developed oxidation flow reactor (OFR), the Environment and Climate Change Canada OFR (ECCC-OFR), was characterized and used to study the yields and composition of SOA formed from OH oxidation of alpha-pinene, selected alkanes, and the vapors evolved from five OS-related samples (OS ore, naphtha, tailings pond water, bitumen, and dilbit). The derived SOA yields from alpha-pinene and selected alkanes using the ECCC-OFR were in good agreement with those of traditional smog chamber experiments but significantly higher than those of other OFR studies under similar conditions. The results also suggest that gas-phase reactions leading to fragmentation (i.e., C-C bond cleavage) have a relatively small impact on the SOA yields in the ECCC-OFR at high photochemical ages, in contrast to other previously reported OFR results. Translating the impact of fragmentation reactions in the ECCC-OFR to ambient atmospheric conditions reduces its impact on SOA formation even further. These results highlight the importance of careful evaluation of OFR data, particularly when using such data to provide empirical factors for the fragmentation process in models. Application of the ECCC-OFR to OS-related precursor mixtures demonstrated that the SOA yields from OS ore and bitumen vapors (maximum of similar to 0.6-0.7) are significantly higher than those from the vapors from solvent use (naphtha), effluent from OS processing (tailings pond water), and from the solvent diluted bitumen (dilbit; maximum of similar to 0.2-0.3), likely due to the volatility of each precursor mixture. A comparison of the yields and elemental ratios (H/C and O/C) of the SOA from the OS-related precursors to those of linear and cyclic alkane precursors of similar carbon numbers suggests that cyclic alkanes play an important role in the SOA formation in the OS. The analysis further indicates that the majority of the SOA formed downwind of OS facilities is derived from open-pit mining operations (i.e., OS ore evaporative emissions) rather than from higher-volatility precursors from solvent use during processing and/or tailings management. The current results have implications for improving the regional modeling of SOA from OS sources, for the potential mitigation of OS precursor emissions responsible for observed SOA downwind of OS operations, and for the understanding of petrochemical- and alkane-derived SOA in general.

The fast progressing electronic skins are spreading their applications into many aspects of human life. In terms of motion sensing, drawbacks exist in state-of-the-art approach of integrating sensing units into arrays e.g. the tradeoff between resolution and effective area, power consumption and interacting experience. This paper presents a novel self-powered digital-analog hybrid electronic skin for measuring noncontact linear planar displacement which achieves a high resolution of (0.75 mm, 1.07 mm, 2.20°) in a large area of 100 cm2 in three degrees of freedom. Owing to utilization of masked silver nanowires (AgNWs) spray coating and corona charging techniques in the fabrication process, this electronic skin is transparent and stretchable, while realizing self-powered sensing of an electret based on electrostatic inductions. Theory and localizing functions are proposed and proved by accordance with simulation and standard testing results. This electronic skin is capable of acting as an effective human-machine interface, which shows its future potential of practical usage in portable electronics, healthcare devices, and artificial intelligence, etc.

Human skin is the largest organ, which covers the human body and provides us the mechanical stimuli to help us interact with the outer environment. Inspired from the properties of human skin, imitating of the complicated human sensation using stretchable electronic devices becomes one of the most exciting research fields due to its vast potential application fields like wearable electronics, healthcare monitoring and artificial intelligence. To mimic real human skin, the huge sensor network is required to attach the body, where it seems critical to guarantee the energy supply at the same time. Nowadays, the emerging triboelectric nanogenerator (TENG), which can transduce the mechanical energy into the electrical energy based on the contact electrification and electrostatic induction, provides an attractive solution for the energy problem to work as the self-powered sensor. The self-powered sensor can generate electrical signal by itself, responsing to the stimulation from the environment without further energy supply devices. With four fundamental working modes and three main detection modes, TENG could develop versatile configurations to realize the various kinds of sensation. The mechanical compliance and stretchability together with the electrical conductance can be fulfilled beneficial from the advancement of material and micro/nano fabrication technology. In this way, the TENG based self-powered electronic skins (e-skins) have been developed with rational design to accomplish multifunctions of sensing including the pressure, position, strain, sliding and so on. It is expected that the self-powered e-skin will continue its fast development and make more progress to make the e-skin come into human life in the near future.

This paper reports a novel self-powered three-dimension motion sensor capable of independently detecting contact trajectory, pressure and velocity based on triboelectrification and electrostatic induction synchronously. Motion trajectories in the full plane can be identified by using a unique net-cross electrodes configuration design. In addition, the patterned silver nanowires (AgNWs) electrodes are sprayed onto the polydimethylsilane (PDMS) substrate to achieve good transparency and stretchability. By attaching the 3D motion sensor on human skin or robot surface directly, the 3D motion information of the object could be acquired including pressure, velocity and trajectory. The self-powered 3D motion sensor is a promising candidate in terms of human-computer interaction, anti-counterfeiting signatures, etc.

Abstract Surface tensions (STs) are of critical importance to numerous natural phenomena and practical applications while most existing ST correlations are in the empirical formulations and limited to the bulk phase. In this study, a new semi-analytical correlation based on the perturbation theory from the statistical thermodynamics is initially developed to calculate the STs of the various components in bulk and nanoconfined pores. The newly developed ST correlation is validated to be accurate and generalized in bulk and nanoconfined pores in comparison with the experimentally measured results at a wide range of temperatures. Furthermore, three important patterns with respect to the STs are determined: first, the STs are found to be reduced with the temperature increase but increase when the components become heavier in both bulk and nanoconfined pores; second, the STs of the mixtures tend to be more sensitive to the feed ratios at higher temperatures; last but not least, the nanoscale STs of the pure components are slightly lower than the bulk results at the same conditions.

Glyoxal (GLY) acts as a key contributor to tropospheric ozone production and secondary organic aerosol (SOA) formation on local to regional scales. The detection of GLY provides useful indicators of fast photochemistry occurring in the lower troposphere. The fast and sensitive detection of GLY is thus important, while traditional chemical ionization such as the proton-transfer reaction (PTR) is extremely limited by the poor detection limit and extensive fragmentation. To address these limitations, electron attachment reaction (EAR) ionization was applied to detect GLY. The generation of parent anions (GLY–) without fragmentation was observed, and cryogenic photoelectron imaging spectroscopy further characterized the structure of GLY–. The detection limit was estimated to be as low as (52 ± 1) pptv (parts per trillion by volume) with 1 min measurements. Other components in ambient air, such as water, carbon dioxide, and trace gases (acetone, propanal, etc.) have no effect on the detection of GLY. The EAR ionization is more promising than PTR ionization in detecting GLY. The detection of GLY in ambient air by the EAR ionization has been demonstrated.

Technetium (99Tc) typically exists as pertechnetate (TcO4−) and hydrated oxide (TcO2·nH2O) in soil and groundwater. While the former, Tc(VII), is very soluble and mobile in the environment, the latter is considered sparingly soluble and immobile. Consequently, immobilization of Tc(VII) can be achieved through conversion of Tc(VII) into Tc(IV). In this study, carboxymethyl cellulose (CMC) stabilized FeS nanoparticles (CMC-FeS) were prepared and tested for reductive immobilization of Tc(VII). Effects of nanoparticle dosage and water chemistry, including pH, humic acid and Ca2+ ions, were examined. At a dosage of 100 mg/L of CMC-FeS as Fe, CMC-FeS rapidly removed >96% of 1.2 μM of Tc(VII) within 1 h, with a retarded first-order rate constant (ka) of 150.32 h-1. Higher pH in the range of 5.0–9.0 favored the reaction, with an optimal pH range of 8.0–9.0. While Ca2+ (up to 2 mM) only modestly affected the Tc(VII) removal, high concentrations of humic acid (up to 10 mg/L as TOC) showed increased inhibition on the Tc(VII) removal rate. FTIR and XPS analyses indicated that CMC-FeS immobilized TcO4− through reductive conversion of TcO4− into TcO2(s) and formation of Tc2S7 precipitate. The immobilized Tc remained insoluble when aged for 100 days under anoxic conditions, whereas up to 22.9% of the immobilized Tc was remobilized when it was exposed to air for 100 days.