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The use of hyphenated LC-NMR and LC-MS techniques for the purpose of directly identifying the major constituents of Belamcanda chinensis was investigated. Reversed-phase isocratic chromatography was performed using an acetonitrile-water solvent system on a C18 column. The NMR spectrum yielded five main peaks, whose analysis revealed them to be 5, 6, 7, 3'-tetrahydroxy-4'-methoxyisoflavone (1), tectorigenin (2), iristectorigenin A (3), irigenin (4), and irisflorentine (5). The identification of these constituents was confirmed by performing LC-ESI-MS experiment. This study shows that hyphenated LC-NMR and LC-MS can be used for the rapid (70 min) identification of the isoflavonoids.

AbstractThe Ru‐catalyzed cleavage of title aryloxy arylethanols (I) as model compounds for lignin‐like substructures is smoothly achieved to give aromatic ketones (II) and phenol derivatives in good yields.

Abstract The albedo of a roof determines the fraction of incoming sunlight that is reflected, which affects heat transfer into the building and exchange of energy between the built environment and the atmosphere. While the albedo of individual roofs can be easily measured, roof albedo at the city scale is unknown. In this paper we characterize the albedos of roofs in seven cities in California: Los Angeles, Long Beach, Bakersfield, San Francisco, San Jose, Sacramento, and San Diego. The fraction of urban area covered by roofs ranged by city from 10% to 25%. City-wide average roof albedo ranged from 0.17 ± 0.08 to 0.20 ± 0.11 (mean ± standard deviation) for five of the cities; values were higher in Sacramento (0.24 ± 0.11) and San Diego (0.29 ± 0.15). Buildings with small roofs were found to constitute a large fraction of city roof area and to have low mean albedos. This suggests that efforts to increase urban albedo through the use of reflective roofs should include small roofs, which are presumably mostly residential. Roof albedos derived for Bakersfield were used in a regional climate model (Weather Research and Forecasting Model) to estimate temperature changes attainable by converting the current stock of roofs to “cool” high albedo roofs. It was found that seasonal mean afternoon (15:00 LST) temperatures could be reduced by up to 0.2 °C during both the summer and winter. Changes in precipitation were not significant at the 95% confidence level.

Due to their high surface areas and large pore volumes, porous carbons (PCs) are valuable materials for use as electrodes in energy storage and conversion devices. Biomass is an ideal precursor for the preparation of PCs in part because it is sustainable and eco-friendly. Herein, new methodology for converting agarose, a naturally occurring type of biomass that forms robust hydrogels, into PCs with tunable pore structures and high electrochemical performance is described. The synthetic process is straightforward and entails heating a gel that is composed of agarose and potassium oxalate (K 2 C 2 O 4 ). Since the salt transforms into gaseous byproducts at elevated temperatures, the decomposition process was harnessed to create activated, open pores as the hydrogel underwent carbonization. For example, a PC with a surface area of 1754.9 m 2 g –1 and a pore volume of 2.643 cm 3 g –1 was obtained by heating a mixture of agarose and K 2 C 2 O 4 in a 1:3 weight ratio at 700 °C. The material was subsequently used as the electrode material in a supercapacitor and found to display a specific capacitance of 166.0 F g –1 at 0.125 A g –1 . Varying the quantity of added K 2 C 2 O 4 resulted in predictable changes in porosity and thus offered a means to tune the textural properties and the electrochemical performance of the PCs. For example, changing the feed ratio of agarose to K 2 C 2 O 4 to 1:6 afforded a PC that exhibited a high persistent specific capacitance (64.1 F g –1 at 5 A g –1 after 10,000 cycles) and a high-power density (20 kW kg –1 at 10 A g –1 ).

Atmospheric mercury (Hg) cycling is sensitive to climate-driven changes, but links with various teleconnections remain unestablished. Here, we revealed the El Niño-Southern Oscillation (ENSO) influence on gaseous elemental mercury (GEM) concentrations recorded at a background station in East Asia using the Hilbert-Huang transform (HHT). The timing and magnitude of GEM intrinsic variations were clearly distinguished by ensemble empirical mode decomposition (EEMD), revealing the amplitude of the GEM concentration interannual variability (IAV) is greater than that for diurnal and seasonal variability. We show that changes in the annual cycle of GEM were modulated by significant IAVs at time scales of 2-7 years, highlighted by a robust GEM IAV-ENSO relationship of the associated intrinsic mode functions. With confirmation that ENSO modulates the GEM annual cycle, we then found that weaker GEM annual cycles may have resulted from El Niño-accelerated Hg evasion from the ocean. Furthermore, the relationship between ENSO and GEM is sensitive to extreme events (i.e., 2015-2016 El Niño), resulting in perturbation of the long-term trend and atmospheric Hg cycling. Future climate change will likely increase the number of extreme El Niño events and, hence, could alter atmospheric Hg cycling and influence the effectiveness evaluation of the Minamata Convention on Mercury.

AbstractThis paper presents an understanding of the fundamental carrier transport mechanism in hydrogenated amorphous silicon (a‐Si:H)‐based n/p junctions. These n/p junctions are, then, used as tunneling and recombination junctions (TRJ) in tandem solar cells, which were constructed by stacking the a‐Si:H‐based solar cell on the heterojunction with intrinsic thin layer (HIT) cell. First, the effect of activation energy (Ea) and Urbach parameter (Eu) of n‐type hydrogenated amorphous silicon (a‐Si:H(n)) on current transport in an a‐Si:H‐based n/p TRJ has been investigated. The photoluminescence spectra and temperature‐dependent current–voltage characteristics in dark condition indicates that the tunneling is the dominant carrier transport mechanism in our a‐Si:H‐based n/p‐type TRJ. The fabrication of a tandem cell structure consists of an a‐Si:H‐based top cell and an HIT‐type bottom cell with the a‐Si:H‐based n/p junction developed as a TRJ in between. The development of a‐Si:H‐based n/p junction as a TRJ leads to an improved a‐Si:H/HIT‐type tandem cell with a better open circuit voltage (Voc), fill factor (FF), and efficiency. The improvements in the cell performance was attributed to the wider band‐tail states in the a‐Si:H(n) layer that helps to an enhanced tunneling and recombination process in the TRJ. The best photovoltage parameters of the tandem cell were found to be Voc = 1430 mV, short circuit current density = 10.51 mA/cm2, FF = 0.65, and efficiency = 9.75%. Copyright © 2015 John Wiley & Sons, Ltd.

Trace elements can have profound adverse effects on the health of people burning coal in homes or living near coal deposits, coal mines, and coal-burning power plants. Trace elements such as arsenic emitted from coal-burning power plants in Europe and Asia have been shown to cause severe health problems. Perhaps the most widespread health problems are caused by domestic coal combustion in developing countries where millions of people suffer from fluorosis and thousands from arsenism. Better knowledge of coal quality characteristics may help to reduce some of these health problems. For example, information on concentrations and distributions of potentially toxic elements in coal may help delineate areas of a coal deposit to be avoided. Information on the modes of occurrence of these elements and the textural relations of the minerals in coal may help to predict the behavior of the potentially toxic trace metals during coal cleaning, combustion, weathering, and leaching.

Microbial fuel cell (MFC) has received much attention in the last decade as a promising technology to simultaneously generate electricity and decontaminate wastewater. This study aims to quantitatively review the published literature on MFC, published in the period of 1970–2020, based on the Web of Science (WoS) database. For the first time in literature, a comprehensive quantitative review of MFC has been conducted by employing the technique of bibliometric and content analyses. A total of 11,397 publications have been retrieved from WoS, out of which 81.6% are research articles. The evaluation in the field of MFC has been mapped in various categories, such as publication history, publication distribution, subject category distribution, leading journals, leading countries and leading organizations in MFC research. Additionally, content analysis has been conducted to unearth the research trends in MFC; and some hot research topics in MFC have been spotted. Results depict that the period 2011–2020 has been the most appreciating era for MFC research, as it contributed 87% of the total publications. Among the subject categories, energy fuel and microbiology lead with contributions of 26.5% for each, butthe overall growth of the energy fuel category in the last decade has been the highest. Out of 1,147 journals publishing MFC research, Bioresource Technology is the leading one; and countries like China, USA and India are the main hub of MFC research with 26.47%, 16.95% and 7.69% contributions in publications, respectively. The hottest topics in MFC research are nanoparticles, catalysts, air electrodes, graphene electrodes, power enhancement, air cathode and nitrogen removal. Moreover, major research areas are engineering, energy fuels and biotechnology with each contribution 26.5% of the total publications.