In this paper, MnO2 nanomaterials of different crystallographic types and crystal morphologies have been selectively synthesized via a facile hydrothermal route and electrochemically investigated as the cathode active materials of primary and rechargeable batteries. Beta-MnO2 nano/microstructures, including one-dimensional (1-D) nanowires, nanorods, and nanoneedles, as well as 2-D hexagramlike and dendritelike hierarchical forms, were obtained by simple hydrothermal decomposition of an Mn(NO3)2 solution under controlled reaction conditions. Alpha- and gamma-MnO2 nanowires and nanorods were also prepared on the basis of previous literature. The as-synthesized samples were characterized by instrumental analyses such as XRD, SEM, TEM, and HRTEM. Furthermore, the obtained 1-D alpha- and gamma-MnO2 nanostructures were found to exhibit favorable discharge performance in both primary alkaline Zn-MnO2 cells and rechargeable Li-MnO2 cells, showing their potential applications in high-energy batteries.

Rechargeable lithium-ion batteries are considered intriguing power sources for a wide variety of applications because of their high energy density, lightweight design and environmental friendliness.[1] With respect to the anode of Li-ion batteries, silicon-based materials have attracted tremendous interest owing to their extremely high theoretical capacity of about 4200 mAh g -1 (with the formation of Li 4.2 Si alloy), [2] which is much higher than that of commercialized graphitic carbon (372 mAh g -1 for compound LiC 6 ) and other Li alloys. [3,4] However, Si suffers from serious irreversible capacity and poor cyclability, which result from the huge volume swings during lithium ion insertion/extraction process. This pulverization disadvantage is the obstacle for practical application of Si as the anode materials of rechargeable Li-ion batteries. The current strategies to overcome the so-called pulverization of Si are focusing on two issues: reducing the alloy particle size and using composite materials. [5][6][7][8] For example,Wilson and Dahn prepared carbon-containing nanodispersed Si with reversible specific capacity of 500 mAh g -1 in the former case, [5] and Holzapfel et al. prepared nanosized Si/graphite composites with a stable capacity of 1000 mAh g -1 in the latter. [7] Recently, Liu's group reported on the synthesis of carbon-coated 44 wt % Si nanocomposites, exhibiting a capacity of 1489 mAh g -1 after 20 cycles. [8] In view of the literature, the significant improvement on the electrochemical performance of Si is still necessary to achieve larger gravimetric capacity, higher coulombic efficiency and better cylability. It is noted that hollow nanomaterials of metals and transition-metal oxides are promising candidates as high-energy electrode materials. [9][10][11][12] In particular, Archer and co-workers reported that hollow SnO 2 nanospheres exhibited superior cycling properties and high initial discharge capacity of 1140 mAh g -1 .[12] On the other hand, although many methods for the preparation of Si nanocrystals have been described, [13,14] controlled synthesis of hollow Si nanospheres still remains a great challenge. Herein, we report on the preparation of nest-like Si nanospheres and their highly reversible lithium storage and excellent high-rate capability. This result suggests that the as-prepared nest-like Si nanospheres are promising candidates as the anode materials of rechargeable Li-ion batteries. The nest-like Si nanospheres were prepared by a solvothermal method, [14] with modified experimental setup (Fig. S1, Supporting Information and Experimental Sec.). It was found that the size and morphology of the products are greatly dependent on the experimental conditions. The direct reaction of NaSi and NH 4 Br under the solvothermal conditions, in which no cotton bags and LaNi 5 alloys were added in the reaction system, only led to Si nanosparticles ( Fig. S2a-c, Supporting Information). If the cotton bags are added into the system but without the addition of LaNi 5 alloys, the product is ...

In this work, we report on the preparation of nanoporous γ-MnO 2 with different morphologies and their application in rechargeable Li-ion batteries. Nanoporous γ-MnO 2 has been successfully synthesized via a facile route using a hydrothermal treatment and sequential thermal decomposition without employing any template or surfactant. Through simply altering the reactant, nanoporous hollow microspheres and nanocubes can be selectively prepared. The influence caused by different reaction conditions on the structure and morphology of the products has been discussed in detail. It is found that the reactant NH 4 HCO 3 and hydrothermal treatment are necessary for preparing the hollow microspheres. The thermal decomposition of the precursor leads to formation of the nanoporous structure. Both the as-prepared γ-MnO 2 hollow microspheres and the nanocubes exhibit promising electrochemical properties as the anode materials of rechargeable Li-ion batteries. In particular, the initial reversible capacity for the hollow microspheres and nanocubes were 1071.1 mAh g -1 and 1041.9 mAh g -1 , respectively, showing their potential application in Li-ion batteries.

BackgroundMicrobial production of monoterpenes provides a promising substitute for traditional chemical-based methods, but their production is lagging compared with sesquiterpenes. Geraniol, a valuable monoterpene alcohol, is widely used in cosmetic, perfume, pharmaceutical and it is also a potential gasoline alternative. Previously, we constructed a geraniol production strain by engineering the mevalonate pathway together with the expression of a high-activity geraniol synthase.ResultsIn this study, we further improved the geraniol production through reducing the endogenous metabolism of geraniol and controlling the precursor geranyl diphosphate flux distribution. The deletion of OYE2 (encoding an NADPH oxidoreductase) or ATF1 (encoding an alcohol acetyltransferase) both involving endogenous conversion of geraniol to other terpenoids, improved geraniol production by 1.7-fold or 1.6-fold in batch fermentation, respectively. In addition, we found that direct down-regulation of ERG20 expression, the branch point regulating geranyl diphosphate flux, does not improve geraniol production. Therefore, we explored dynamic control of ERG20 expression to redistribute the precursor geranyl diphosphate flux and achieved a 3.4-fold increase in geraniol production after optimizing carbon source feeding. Furthermore, the combination of dynamic control of ERG20 expression and OYE2 deletion in LEU2 prototrophic strain increased geraniol production up to 1.69 g/L with pure ethanol feeding in fed-batch fermentation, which is the highest reported production in engineered yeast.ConclusionAn efficient geraniol production platform was established by reducing the endogenous metabolism of geraniol and by controlling the flux distribution of the precursor geranyl diphosphate. The present work also provides a production basis to synthesis geraniol-derived chemicals, such as monoterpene indole alkaloids.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-017-0641-9) contains supplementary material, which is available to authorized users.

A new hydrogen storage system of poly(methyl acrylate)‐confined ammonia borane, which has been prepared by a solution‐blending method, has shown the characteristics of controllable dehydrogenation performance and water resistance.

Monoterpenes have wide applications in the food, cosmetics, and medicine industries and have recently received increased attention as advanced biofuels. However, compared with sesquiterpenes, monoterpene production is still lagging in Saccharomyces cerevisiae. In this study, geraniol, a valuable acyclic monoterpene alcohol, was synthesized in S. cerevisiae. We evaluated three geraniol synthases in S. cerevisiae, and the geraniol synthase Valeriana officinalis (tVoGES), which lacked a plastid-targeting peptide, yielded the highest geraniol production. To improve geraniol production, synthesis of the precursor geranyl diphosphate (GPP) was regulated by comparing three specific GPP synthase genes derived from different plants and the endogenous farnesyl diphosphate synthase gene variants ERG20 (G) (ERG20 (K197G) ) and ERG20 (WW) (ERG20 (F96W-N127W) ), and controlling endogenous ERG20 expression, coupled with increasing the expression of the mevalonate pathway by co-overexpressing IDI1, tHMG1, and UPC2-1. The results showed that overexpressing ERG20 (WW) and strengthening the mevalonate pathway significantly improved geraniol production, while expressing heterologous GPP synthase genes or down-regulating endogenous ERG20 expression did not show positive effect. In addition, we constructed an Erg20p(F96W-N127W)-tVoGES fusion protein, and geraniol production reached 66.2 mg/L after optimizing the amino acid linker and the order of the proteins. The best strain yielded 293 mg/L geraniol in a fed-batch cultivation, a sevenfold improvement over the highest titer previously reported in an engineered S. cerevisiae strain. Finally, we showed that the toxicity of geraniol limited its production. The platform developed here can be readily used to synthesize other monoterpenes.

Osteoblast induction and differentiation in developing long bones is dynamically controlled by the opposing action of transcriptional activators and repressors. In contrast to the long list of activators that have been discovered over past decades, the network of repressors is not well-defined. Here we identify the expression of Foxp1/2/4 proteins, comprised of Forkhead-box (Fox) transcription factors of the Foxp subfamily, in both perichondrial skeletal progenitors and proliferating chondrocytes during endochondral ossification. Mice carrying loss-of-function and gain-of-function Foxp mutations had gross defects in appendicular skeleton formation. At the cellular level, over-expression of Foxp1/2/4 in chondroctyes abrogated osteoblast formation and chondrocyte hypertrophy. Conversely, single or compound deficiency of Foxp1/2/4 in skeletal progenitors or chondrocytes resulted in premature osteoblast differentiation in the perichondrium, coupled with impaired proliferation, survival, and hypertrophy of chondrocytes in the growth plate. Foxp1/2/4 and Runx2 proteins interacted in vitro and in vivo, and Foxp1/2/4 repressed Runx2 transactivation function in heterologous cells. This study establishes Foxp1/2/4 proteins as coordinators of osteogenesis and chondrocyte hypertrophy in developing long bones and suggests that a novel transcriptional repressor network involving Foxp1/2/4 may regulate Runx2 during endochondral ossification.

Organisms respond to tissue damage through the upregulation of protective responses which restore tissue structure and metabolic function. Mitochondria are key sources of intracellular oxidative metabolic signals that maintain cellular homeostasis. Here we report that tissue and cellular wounding triggers rapid and reversible mitochondrial fragmentation. Elevated mitochondrial fragmentation either in fzo-1 fusion-defective mutants or after acute drug treatment accelerates actin-based wound closure. Wounding triggered mitochondrial fragmentation is independent of the GTPase DRP-1 but acts via the mitochondrial Rho GTPase MIRO-1 and cytosolic Ca2+. The fragmented mitochondria and accelerated wound closure of fzo-1 mutants are dependent on MIRO-1 function. Genetic and transcriptomic analyzes show that enhanced mitochondrial fragmentation accelerates wound closure via the upregulation of mtROS and Cytochrome P450. Our results reveal how mitochondrial dynamics respond to cellular and tissue injury and promote tissue repair.