A process of fabricating a seven layer microfluidic chip using CO2 laser processing and hot bonding technology is presented. The applied polymer substrates were poly(methyl-methacrylate) (PMMA), polycarbonate (PC), polystyrene (PS) and polyethylene terephthalate (PET). The results show the optimal combination of polymer substrates for the seven layer microfluidic chip at the hot bonding parameters of bonding temperature of 100 degrees C and bonding pressure of 1 MPa for maintaining times of nine minutes. Due to the different properties of the polymer substrates, the profile of the microchannel in the different polymer sheets for the same CO2 laser processing parameters. The maximum tensile strength of the microfluidic was measured as 1.0 MPa. The combined polymers with the minimum binding force were PC and PMMA. At the end, a mixing experiment was performed in the seven layer microfluidic chip with different fluid Re numbers.
Two-dimensional (2D) metallic transition metal dichalcogenides (MTMDCs), the complement of 2D semiconducting TMDCs, have attracted extensive attentions in recent years because of their versatile properties such as superconductivity, charge density wave, and magnetism. To promote the investigations of their fantastic properties and broad applications, the preparation of large-area, high-quality, and thickness-tunable 2D MTMDCs has become a very urgent topic and great efforts have been made. This topical review therefore focuses on the introduction of the recent achievements for the controllable syntheses of 2D MTMDCs (VS2, VSe2, TaS2, TaSe2, NbS2, NbSe2, etc). To begin with, some earlier developed routes such as chemical vapor transport, mechanical/chemical exfoliation, as well as molecular beam epitaxy methods are briefly introduced. Secondly, the scalable chemical vapor deposition methods involved with two sorts of metal-based feedstocks, including transition metal chlorides and transition metal oxidations mixed with alkali halides, are discussed separately. Finally, challenges for the syntheses of high-quality 2D MTMDCs are discussed and the future research directions in the related fields are proposed.
Reductive immobilization of radioactive pertechnetate (99TcO4−) in simulated groundwater was studied by prepared carboxymethyl cellulose (CMC) and starch stabilized zero valent iron nanoparticles (nZVI), and long-term remobilization of reduced Tc was also evaluated under anoxic and oxic conditions. The stabilized nZVI can effectively reduce soluble 99Tc(VII) to insoluble 99Tc(IV), and they can be easily delivered into a contaminated groundwater zone and facilitate in situ remediation. In this study, CMC-stabilized nZVI showed higher reactivity than that using starch as the stabilizer. Batch experiments indicated that more than 99% of 99Tc(VII) (C0=12mg/mL) was reduced and removed from groundwater by CMC-stabilized nZVI with a CMC content of 0.2% (w/w) at a broad pH of 5–8. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses further confirmed that 99Tc(VII)O4− transformed into 99Tc(IV)O2 (s). The presence of bicarbonate exhibited insignificant effect on Tc immobilization, while humic acid (HA) inhibited reaction mainly due to retardation on electron transfer and formation of Tc(IV)-HA complexes. More interesting, the immobilized Tc(IV) remained insoluble even after 120 d under anoxic condition, while only ∼21% was remobilized when exposed to air. Therefore, bio-macromolecules stabilized nZVI nanoparticles could be a viable alternative for in situ remediation of radioactive contamination in groundwater.
Abstract Aim Dryland ecosystems are exceedingly sensitive to climate change. Desertification induced by both climate changes and human activities seriously threatens dryland vegetation. However, the impact of climate change on distribution of dryland plant species has not been well documented. Here, we studied the potential distribution of four representative dryland plant species (Haloxylon ammodendron, Anabasis aphylla, Calligonum mongolicum, and Populus euphratica) under current and future climate scenarios in a temperate desert region, aiming to improve our understanding of the responses of dryland plant species to climate change and provide guidance for dryland conservation and afforestation. Location Junggar Basin, a large desert region in northwestern China. Methods Occurrence data of the studied species were collected from an extensive field investigation of 2,516 sampling sites in the Junggar Basin. Ensemble species distribution models using 10 algorithms were developed and used to predict the potential distribution of each studied species under current and future climate scenarios. Result Haloxylon ammodendron and A. aphylla were likely to lose most of their current suitable habitats under future climate scenarios, while C. mongolicum and P. euphratica were likely to expand their ranges or remain relatively stationary. Variable importance evaluation showed that the most important climate variables influencing species distribution differed across the studied species. These results may be explained by the different ecophysiological characteristics and adaptation strategies to the environment of the four studied species. Main conclusions We explored the responses of the representative dryland plant species to climate change in the Junggar Basin in northwestern China. The different changes in suitability of different species imply that policymakers may need to reconsider the selection and combination of the afforestation species used in this area. This study can provide valuable reference for the management and conservation of dryland ecosystems under future climate change scenarios.
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.