Mixing Dynamics at the Large Confluence Between the Yangtze River and Poyang Lake

Mixing processes downstream of river confluences impacts the ecology and the related environmental management of river networks. A clear understanding of such processes is challenging, especially for confluences having width-to-depth ratios larger than 100, due to the limited available field data. In this study, four field surveys based on hydro-acoustic and conductivity measurements were conducted near the confluence between the Yangtze River and the Poyang Lake, which are the largest river and freshwater lake in China, respectively. It was found that mixing dynamics at the confluence were controlled by a complex interaction among the momentum flux ratio, secondary flow and the lock-exchange flow associated to the density contrast between the two tributaries. Slow mixing was observed during high-flow conditions that generated dual counter-rotating secondary cells, with the downwelling flow acting as a barrier in the post-confluence channel. In contrast, more rapid mixing was observed during low-flow conditions when only a single channel-scale secondary flow was identified. The mixing processes were also affected by the lock-exchange flow associated to the density difference between the two confluent flows. Such lock-exchange enhanced mixing when the Yangtze River waters had higher temperature, that is, lower density than that of the Poyang Lake. In low flow condition, the penetration of the much larger momentum flux of Yangtze River created a “two-layers” structure with the contribution of the density difference, which further enhanced the curvature-induced helicity. The findings from the present study improve our current understanding of mixing dynamics in large river confluences

Molecular traces of alternative social organization in a termite genome

Although eusociality evolved independently within several orders of insects, research into the molecular underpinnings of the transition towards social complexity has been confined primarily to Hymenoptera (for example, ants and bees). Here we sequence the genome and stage-specific transcriptomes of the dampwood termite Zootermopsis nevadensis (Blattodea) and compare them with similar data for eusocial Hymenoptera, to better identify commonalities and differences in achieving this significant transition. We show an expansion of genes related to male fertility, with upregulated gene expression in male reproductive individuals reflecting the profound differences in mating biology relative to the Hymenoptera. For several chemoreceptor families, we show divergent numbers of genes, which may correspond to the more claustral lifestyle of these termites. We also show similarities in the number and expression of genes related to caste determination mechanisms. Finally, patterns of DNAmethylation and alternative splicing support

OpenEventMap: A Volunteered Location-Based Service

Our lives are affected by myriads of events happening daily all over the world. For efficient planning and management of complex systems composed of various components, understanding relationships between an event and the reactive behaviour of involved components is vital. Analysing these complex relations demands a spatiotemporal event-based model, in which the event plays a central role. In this article we develop a framework which provides the possibility of mapping and storing event-related information on the OpenStreetMap (OSM) platform by volunteers. The study is divided into two different phases: first, mapping the event elements by adding new attributes adequately designed to encode spatiotemporal and semantic event information; and, second, representing the event-related information on a map by developing a Web application, offering a volunteered location-based service. To facilitate the event-mapping procedure, a Java OpenStreetMap (JOSM) plug-in was developed for volunteers. The plug-in was developed based on the notion of an event to adequately store and manipulate the semantic information of events in the OSM structure. The tool was used by more than 100 volunteers in Munich for the years 2012 to 2014. In addition to manual collection of event-related information by volunteers, a crawling framework was also developed to automatically collect freely available event information from various Web pages on the Internet. The framework extracts the same event elements as the plug-in. But the framework crawls each Web page according to some pre-defined rules and follows a post-processing step, if necessary. The manually collected events along with the crawled event information are visualized in a Web application. The study revealed that adding the possibility of event-oriented mapping to OSM empowers volunteers to collect a higher level of information (event information) for city maps. This information can furthermore be used for strategy development and service planning by decision-makers. </jats:p

Design and Control Strategy of Soft Robot Based on Gas–Liquid Phase Transition Actuator

In this paper, a soft robot driven by a gas–liquid phase transition actuator with a new structure is designed; The soft robot is driven by the pressure generated by electrically induced ethanol phase transition. The gas–liquid phase transition drive was found to be able to generate a larger driving force by using only low voltage. Compared with the gas drive of a traditional soft robot, gas–liquid phase transition-driven soft robot does not require a complex circuit system and a huge external energy supply air pump, making its overall structure more compact. At the same time, because of the new structure of the actuator on the soft robot, the soft robot has good gas tightness and less recovery time. A reinforcement depth learning control strategy is also added so that the soft robot with this actuator could better grip objects of different sizes and weights

A novel molybdenum-based nanocrystal decorated ceramic membrane for organics degradation via catalytic wet air oxidation (CWAO) at ambient conditions

Catalytic wet air oxidation (CWAO), one of the best-known methods for water treatment, has been intensely investigated for dyes degradation. However, the extreme operation conditions as well as the recovery of suspended catalyst are economically unattractive. In the current work, a novel Mo-based nanocrystal decorated ceramic membrane (Mo/Al2O3) has been prepared and applied for organics degradation via CWAO at ambient conditions for the first time. The catalytic Mo/Al2O3 membranes were prepared by an in-situ hydrothermal followed by calcination method. Their physical and chemical properties were characterized by field emission scanning electron microscope (FESEM), X-rays diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS). The catalytic performance of Mo/Al2O3 membranes were evaluated via organics (safranine O and humic acid) degradation under a home-made membrane filtration system. The effects of calcination temperature, catalyst loading amount, and trans-membrane pressure (TMP) were systematically investigated. The stability and durability of the catalytic Mo/Al2O3 membrane were examined in a long-term filtration system. Results showed that the performance of Mo/Al2O3 membrane would decrease with increasing of calcination temperature as well as TMP. However, the catalyst loading amount was not a major effect on the removal of organics in the system. For one-time loading membrane calcined at 300 °C (1x-Mo/Al2O3 membrane@300), the removal efficiency could achieve higher than 90 % in 40 min in a recycled filtration system with an initial safranine O concentration of 10 mg L−1. The chemical quenching experiment as well as radical quantification verified the main reactive oxygen species were 1O2 and [rad]O2− in the system. The ROS generation mechanism was proposed via the characterization of the catalyst after reaction. The deliberate combination of CWAO and membrane separation represents a new strategy that offers exciting possibilities for water treatment under ambient conditions.Nanyang Technological UniversityFinancial support for this project is provided by the Ph.D. research scholarship from NTU

Mechanically Robust Fluorinated Graphene/Poly(<i>p</i>‑Phenylene Benzobisoxazole) Nanofiber Films with Low Dielectric Constant and Enhanced Thermal Conductivity: Implications for Thermal Management Applications

Low-dielectric materials have found broad applications in microelectronics but are limited by poor mechanical properties and thermal conductivity. In this study, a class of nanocomposite films based on fluorinated graphene (FG) was developed by replacing the traditional polymer matrix with a 3D interconnected poly(p-phenylene benzobisoxazole) (PBO) nanofiber network. The FG nanosheets are uniformly distributed in the porous network of PBO nanofibers (PBONF) and stacked orderly to form a nacre-like layered structure while paving effective thermal conduction paths. Ultimately, the strong interfacial bonding and efficient synergy between FG and PBONF endow the composite films with unparalleled tensile properties (strength and modulus up to 295.4 MPa and 7.79 GPa, respectively) and folding endurance (no drop in tensile properties after 1000 folds), ultralow dielectric constant (as low as 1.71), and excellent thermal conductivity (12.13 W m–1 K–1). In addition, these FG/PBONF composite films also exhibit an ultrahigh thermal stability (5% weight loss temperature higher than 540 °C), which makes them promising for the heat dissipation of high-power electronic devices in extreme environments

Preparation, Structure, and Properties of Chitosan/Cellulose/Multiwalled Carbon Nanotube Composite Membranes and Fibers

Binary ionic liquids (ILs), 1-butyl-3-methylimidazolium chloride and 1-H-3-methylimidazolium chloride, were developed to dissolve chitosan and cellulose and disperse multiwalled carbon nanotubes (MWCNTs). The resulting mixed paste could be used to prepare chitosan/cellulose/MWCNT composite membranes and fibers. Fourier transform infrared spectroscopy, wide-angle X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, tensile testing, and conductivity measurements were used to evaluate the structure and properties of the composite materials and the effect of the incorporation of MWCNTs at various loadings. The characterization results indicate that the incorporation of MWCNTs improved the comprehensive performances of the composite materials, and the best loading of MWCNTs was 4 wt %. This IL dissolution method is a green and feasible method for preparing chitosan/cellulose/MWCNT composite membranes and fibers and will provide beneficial references for the preparation of similar materials. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 128: 1193-1199, 201