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Lithium-sulfur batteries (LSBs) are one of the most promising energy storage devices because of their high theoretical energy density; however, inherent issues including poor electrical conductivity and severe dissolution of S and its discharged products hinder their practical applications. MXenes have metallic conductivity, ultra-thin two-dimensional (2D) structures, rich surface functional groups, and macrostructural adjustability and have been widely used to design advanced sulfur hosts. 3D network structures assembled by 2D MXene nanosheets have shown superior performance for improving reaction kinetics, accommodating and dispersing sulfur at the micro-/nanoscale, and capturing polysulfides due to their porous interconnected structure. Herein, the applications of MXene architectures related to 2D layered structures, 3D multilayered structures, and 3D spherical structures as sulfur hosts are reviewed. The structure-performance relationship, challenges for current designs, and opportunities for future 3D architectures for LSBs are also analyzed.

A formal (2 + 1) annulation and three-component (1 + 1 + 1) cascade cyclisation via sulphur ylide cyclopropanation under mild conditions is described, with the spiro-cyclopropyl iminoindoline moiety transformed into pyrrolo[3,4-c]quinoline through a novel rearrangement process.

An acylative Suzuki-type cross-coupling of alkyl trifluoroborates and acid fluorides was developed by merging NHC organocatalysis with photoredox catalysis. A broad spectrum of ketones could be facilely synthesised under mild reaction conditions.

A novel Co(III) complex [Co(chda)(nta)] (1) (chda = trans-(1R,2R)-1,2-cyclohexanediamine, H3nta = nitrilotriacetic acid) was synthesized based on chda and H3nta ligands at room temperature. Complex 1 was structurally identified by single-crystal X-ray diffraction, elemental analysis, FT-IR and Raman spectrum. Complex 1 was connected by the intermolecular N–H···O hydrogen bonds to form a 2D supramolecular structure. The 3D Hirshfeld surface and 2D fingerprint plots were used to further study the intermolecular interactions of complex 1. The intermolecular O···H and H···H contacts were the most significant interactions in the crystal, which comprised 96.6% of the total Hirshfeld surface. In addition, complex 1 exhibited excellent photocatalytic activity for the removal of methylene blue under UV light. The possible photocatalytic mechanism and reaction kinetics were also discussed.

The chemical speciation of metal (Fe, Al, Mn and Cr) elements in agricultural and non-agricultural soils was investigated in upstream of the Pearl River, China. The result showed that Fe, Al and Cr in most of the samples, residual fractions accounted for more than 80% of their total concentrations. Mn in most of the samples, the reducible fractions were more than 40%, and generally more than residual fractions, oxidizable and weak acid soluble fractions. The mobility factors (MF) of Mn were the highest in both agricultural and non-agricultural soils, suggesting that the mobility of Mn were the strongest among the four metal elements. The MFs of Fe and Cr were almost zero, suggesting their mobility were low.

The concentration and distribution of metal (Mg, K, Ca and Na) elements in agricultural and non-agricultural soils were investigated in upstream of the Pearl River, China. The result showed that total Mg, K, Ca and Na concentrations in agricultural soils were higher than those in non-agricultural soils, indicating that agricultural input, such as water irrigation, fertilizer and pesticide application, may have led to the accumulation of Mg, K, Ca and Na in agricultural soils. Total concentrations of the metal elements in agricultural and non-agricultural soils were compared with the background values of Yunnan soil, the result showed Mg, K and Na were lower in both agricultural and non-agricultural soils in the study area, while Ca was relatively higher, which were possibly due to Karsts geographic environment in the study area.

The concentration and distribution of metal (Fe, Al, Mn and Cr) elements in agricultural and non-agricultural soils were investigated in upstream of the Pearl River, China. The result showed that total Fe, Al and Cr concentrations in agricultural soils were higher than those in non-agricultural soils, while total Mn concentrations in agricultural soils were lower than those in non-agricultural soils, indicating that agricultural input, such as water irrigation, fertilizer and pesticide application, may have led to the accumulation of Fe, Al and Cr in agricultural soils. Total concentrations of the metal elements in agricultural and non-agricultural soils were compared with the background values of Yunnan soil, the result showed Fe, Al, Mn and Cr were lower in both agricultural and non-agricultural soils in the study area.

The chemical speciation of metal (Mg, K, Ca and Na) in agricultural and non-agricultural soils was investigated in upstream of the Pearl River, China. The result showed that the four metals speciation distributions of the agricultural soils were similar to those of the non-agricultural soils. Mg were dominated by the residual fraction, the order of Mg in each fraction was residual fraction > weak acid soluble fraction reducible fraction > oxidizable fraction. The distribution patterns of Na and K were similar, in most of the samples, the orders of Na and K in each fraction were residual fraction > weak acid soluble fraction > oxidizable fraction > reducible fraction. The order of Ca in each fraction was weak acid soluble fraction > reducible fraction > oxidizable fraction residual fraction. The bioavailability of Ca in the area was very high in both agricultural and non-agricultural soils.

The Cycas pectinata complex is a group of poorly understood Asian cycads threatened by habitat destruction and overcollecting. We estimated the genetic variation in 17 isozyme loci across 39 populations representing 10 taxa in this complex from China, India, Thailand, and Vietnam. Three species from Thailand and an Indian endemic were also examined for comparison. Lower levels of intrapopulation variation than those reported for other gymnosperms were found in the C. pectinata complex. Our results support the hypothesis that low intrapopulation variation with relatively high spatial differentiation is a biological and evolutionary characteristic typical of cycads, unlike other gymnosperms. Large numbers of historically shared alleles and high genetic identities confirmed the close relationships of taxa in the complex. Strong gene flow occurred among local populations 2-7 km apart. Long-distance gene flow was restricted. The estimates of gene flow among taxa were generally low except between C. pectinata v...

China, as one of the ancient centers for diversity of domesticated plants, has a rich germplasm resource in vegetable and fruit crops. The Cucurbitaceae is one of the three most important families in that country as sources of vegetables. In a continuing effort to inform the West on Chinese uses of the Cucurbitaceae, we update a 1989 description of cucurbits in China with the inclusion of information from untranslated Chinese literature and further field observations. Included are 63 species valued as fruits, vegetables, and/or medicinal herbs. Each of these species is discussed in the context of its usages in China. We summarize the economic role of cultivated cucurbits in present day China. Finally, the infraspecific variation within the economically important domesticated cucurbits (Citrullus lanatus, Cucumis melo, Cucumis sativus, Cucurbita spp.,Lagenaria siceraria, Luffa spp., andMomordica charantia) is discussed.

Analysis of three plastid DNA sequences for a broad sampling of Amaryllidaceae resolve the American genera of the Amaryllidaceae as a clade that is sister to the Eurasian genera of the family, but base substitution rates for these genes are too low to resolve much of the intergeneric relationships within the American clade. We obtained ITS rDNA sequences for 76 species of American Amaryllidaceae and analyzed the aligned matrix cladistically, both with and without gaps included, using two species of Pancratium as outgroup taxa. ITS resolves two moderately to strongly supported groups, an Andean tetraploid clade, and a primarily extra-Andean “hippeastroid” clade. Within the hippeastroid clade, the tribe Griffineae is resolved as sister to the rest of Hippeastreae. The genera Rhodophiala and Zephyranthes are resolved as polyphyletic, but the possibility of reticulation within this clade argues against any re-arrangement of these genera without further investigation. Within the Andean subclade, Euste...

Observations were conducted in southern Florida on Aulacaspis yasumatsui Takagi (Hemiptera: Sternorrhyncha: Diaspididae), a recently introduced armored scale insect native to Southeast Asia. The insect's host plants, exclusively cycads, were identified in the following genera: Cycas (Cycadaceae); Dioon, Encephalartos, Microcycas, (Zamiaceae), and Stangeria (Stangeriaceae). Cycas spp. seemed to be preferred over other cycad genera by this insect. Aulacaspis yasumatsui infested pinnae, rachides, strobili, stems, and roots of various species of cycads. It generally infested all above-ground plant parts of Cycas spp. and sometimes the primary and secondary roots to a soil depth of 60 cm. No morphological differences in the frond- and root-infesting forms were noted. At an ambient temperature of about 24.5C, eggs hatched in 8-12 days. In the field, some individuals developed to second instars in 16 days and third instars in 28 days. Third instars (mature females) laid >100 eggs. Most of the females of a generation did not live longer than 75 days. No natural enemies were observed. The scale insect populations became extremely dense and killed 100% of 15 Cycas revoluta Thunburg within a year of infestation. Between 1996 and June 1998 the insect spread from a limited area in southern Miami to various sites as far as 120 km north, probably by movement of plants.

A new species, Cycas lindstromii, is described from Binh Thuan in southern Vietnam. It is allied to C. siamensis, but distinguished by its subterranean trunk, elongated megasporophyll, and shorter, keeled leaf. The new species is illustrated, and its distribution, ecology, and conservation status are discussed. The senior author studied wild cycad populations in Vietnam during the periods 16 October to 2 December 1994 and 18 February to 1 March 1995 (Yang, 1996). One discovery was a distinct species occurring in arid coastal areas in southern Vietnam, where it is under threat of extinction from land clearing and collection for sale as a garden plant. Systematic studies by the authors have shown that this taxon is as yet undescribed. It is here described as a new species in order to draw attention to its conservation requirements, and to provide a valid name for regulatory usage. Cycas lindstromii S.-L. Yang, K. D. Hill & N. T. Hiep, sp. nov. TYPE: Vietnam. Binh Thuan, Tuy Phong, Xa Chi Cong, near Doc Bao Da, 11013'N, 108038'E, alt. 25 m, 11 Nov. 1994, S.-L. Yang 557 (holotype, FTG; isotypes, NSW, S). Figure 1. Species similis C. siamensis Miquel, sed trunco subterraneo, foliis brevibus, megasporophylla lamina terminali elongata angusta differt. Stem subterranean, often branched at apex, to 15-23 cm long, 13-25 cm diam., base swollen, surface white-gray, smooth. Leaves 2-12 , deep green adaxially, yellowish green abaxially, highly glossy, 50-78 cm long, strongly keeled (opposite pinnae inserted at 40-600 on rachis), with 18-60 pinnae. Petiole 6.0-15 cm long, glabrous, spinescent for 50-100% of length. Basal pinnae not gradually reducing to spines, occasionally forked. Median pinnae simple, glabrous, 100-130 x 7-10 mm, crowded and overlapping, 7-12 mm apart on rachis; section flat, margins flat, apices acute. Tomentum on cataphylls brown. Cataphylls narrowly triangular, soft, 20-50 x 3-7 mm at base. Microsporangiate cones fusiform, coriaceous, yellow, 1620 cm long, 4-5 cm diam., peduncle length 3.0 cm. Microsporophyll lamina 10-16 X 11-15 mm, apical spine sharply upturned, 1-8 mm long. Megasporangiate cones 12 cm high, 7-9 cm diam.; megasporophylls 8-12 cm long, lamina ovate, 5.5-10 X 1.8-3.0 cm, deeply pectinate, with 6-13 pairs of soft lateral spines 8-12 x 4-5 mm; apical spine distinct from lateral spines, 30 x 4-5 mm at base. Ovules 2, glabrous. Seeds ovoid, 31-35 X 20-30 mm; sarcotesta reddish orange, not pruinose, 3-7 mm thick; fibrous layer present; spongy layer absent. Cycas lindstromii is nearest to C. siamensis (Miquel, 1863) but differs in its subterranean and frequently branched trunk, its shorter, keeled leaves with basal pinnae not progressively reducing to spines, its more slender male cone, and its relatively narrower and more elongated megasporophyll lamina. The two are placed in Cycas sect. Indosinenses. This section is defined by the pectinate megasporophyll lamina, the coriaceous male cone, and the glabrous ovules. Within the section, these two species make up subsection Indosinenses, defined by the small, narrow male cones and the short NovoN 7: 213-215. 1997. This content downloaded from 157.55.39.120 on Mon, 05 Sep 2016 06:04:20 UTC All use subject to http://about.jstor.org/terms