Knowledge intensive service activities (KISAs) in Korea's innovation system

노트 : This is submitted to the Korea Development Institute as the Final Report of “Analysis on Knowledge-Intensive Service Activities in Korea’s Innovation System”, in fulfillment of the Contract between KDI and STEPI. This Research is Fully Sponsored by Strategic Research Partnership of Korea Development Institute

A carbon nanotubes-silicon nanoparticles network for high performance lithium rechargeable battery anodes

As an effort to address the chronic capacity fading of Si anodes and thus achieve their robust cycling performance, herein, we develop a unique electrode in which silicon nanoparticles are embedded in the carbon nanotubes network. Utilizing robust contacts between silicon nanoparticles and carbon nanotubes, the composite electrodes exhibit excellent electrochemical performance : 95.5% capacity retention after 140 cycles as well as rate capability such that at the C-rate increase from 0.1C to 1C to 10C, the specific capacities of 850, 698, and 312 mAh/g are obtained, respectively. The present investigation suggests a useful design principle for silicon as well as other high capacity alloying electrodes that undergo large volume expansions during battery operations.

Rho-kinase Regulates Energy Balance by Targeting Hypothalamic Leptin Receptor Signaling

Leptin regulates energy balance. However, knowledge of the critical intracellular transducers of leptin signaling remains incomplete. Here we report that Rho-kinase 1 (ROCK1) regulates leptin action on body weight homeostasis by activating JAK2, an initial trigger of leptin receptor signaling. Leptin promotes the physical interaction of JAK2 and ROCK1, thereby increasing phosphorylation of JAK2 and downstream activation of Stat3 and FOXO1. Mice lacking ROCK1 in either POMC or AgRP neurons, mediators of leptin action, display obesity and impaired leptin sensitivity. In addition, deletion of ROCK1 in the arcuate nucleus markedly enhances food intake, resulting in severe obesity. Of note, ROCK1 is a specific mediator of leptin, but not insulin, regulation of POMC neuronal activity. Our data identify ROCK1 as a key regulator of leptin action on energy homeostasis

Silicon@porous nitrogen-doped carbon spheres through a bottom-up approach are highly robust lithium-ion battery anodes

Due to its excellent capacity, around 4000 mA h g(-1), silicon has been recognized as one of the most promising lithium-ion battery anodes, especially for future large-scale applications including electrical vehicles and utility power grids. Nevertheless, Si suffers from a short cycle life as well as limitations for scalable electrode fabrication. Herein, we report a novel design for highly robust and scalable Si anodes: Si nanoparticles embedded in porous nitrogen-doped carbon spheres (NCSs). The porous nature of NCSs buffers the volume changes of Si nanoparticles and thus resolves critical issues of Si anode operations, such as pulverization, vulnerable contacts between Si and carbon conductors, and an unstable solid-electrolyte interphase. The unique electrode structure exhibits outstanding performance with a gravimetric capacity as high as 1579 mA h g(-1) at a C/10 rate based on the mass of both Si and C, a cycle life of 300 cycles with 94% capacity retention, as well as a discharge rate capability of 6 min while retaining a capacity of 702 mA h g(-1). Significantly, the coulombic efficiencies of this structure reach 99.99%. The assembled structure suggests a design principle for high capacity alloying electrodes that suffer from volume changes during battery operations.

Plant growth promotion and Penicillium citrinum

<p>Abstract</p> <p>Background</p> <p>Endophytic fungi are known plant symbionts. They produce a variety of beneficial metabolites for plant growth and survival, as well as defend their hosts from attack of certain pathogens. Coastal dunes are nutrient deficient and offer harsh, saline environment for the existing flora and fauna. Endophytic fungi may play an important role in plant survival by enhancing nutrient uptake and producing growth-promoting metabolites such as gibberellins and auxins. We screened roots of <it>Ixeris repenes </it>(L.) A. Gray, a common dune plant, for the isolation of gibberellin secreting endophytic fungi.</p> <p>Results</p> <p>We isolated 15 endophytic fungi from the roots of <it>Ixeris repenes </it>and screened them for growth promoting secondary metabolites. The fungal isolate IR-3-3 gave maximum plant growth when applied to waito-c rice and <it>Atriplex gemelinii </it>seedlings. Analysis of the culture filtrate of IR-3-3 showed the presence of physiologically active gibberellins, GA₁, GA₃, GA₄and GA₇(1.95 ng/ml, 3.83 ng/ml, 6.03 ng/ml and 2.35 ng/ml, respectively) along with other physiologically inactive GA₅, GA₉, GA₁₂, GA₁₅, GA₁₉, GA₂₀and, GA₂₄. The plant growth promotion and gibberellin producing capacity of IR-3-3 was much higher than the wild type <it>Gibberella fujikuroi</it>, which was taken as control during present study. GA₅, a precursor of bioactive GA₃was reported for the first time in fungi. The fungal isolate IR-3-3 was identified as a new strain of <it>Penicillium citrinum </it>(named as <it>P. citrinum </it>KACC43900) through phylogenetic analysis of 18S rDNA sequence.</p> <p>Conclusion</p> <p>Isolation of new strain of <it>Penicillium citrinum </it>from the sand dune flora is interesting as information on the presence of <it>Pencillium </it>species in coastal sand dunes is limited. The plant growth promoting ability of this fungal strain may help in conservation and revegetation of the rapidly eroding sand dune flora. <it>Penicillium citrinum </it>is already known for producing mycotoxin citrinin and cellulose digesting enzymes like cellulase and endoglucanase, as well as xylulase. Gibberellins producing ability of this fungus and the discovery about the presence of GA₅will open new aspects of research and investigations.</p

Multistep Deposition of Gold Nanoparticles on Single-Walled Carbon Nanotubes for High-Performance Transparent Conducting Films

We report a dual-coating method for the deposition of gold nanoparticles on single-walled carbon nanotubes (SWNTs) to improve the electrical conductivities of SWNT network films. The deposition is achieved via a two-step process: (i) pretreatment, mixing gold precursor (HAuCl₄•3H₂O) with a dispersion of SWNTs containing sodium cholate or sodium dodecyl sulfate surfactants, and (ii) post-treatment, immersion of SWNT network films functionalized with gold ions (Au³⁺) in a gold salt solution. SWNT films doubly hybridized with gold nanoparticles exhibited a 20% reduced sheet resistance in comparison with SWNT films that were post-treated with Au alone. Optical spectroscopy and UPS results show that such enhanced electrical properties can be attributed to additional p-type doping of the SWNTs upon treatment with gold. These results are important for the development of efficient transparent conducting SWNT films for optoelectronic device applications

Electrospun Core-Shell Fibers for Robust Silicon Nanoparticle-Based Lithium Ion Battery Anodes

Because of its unprecedented theoretical capacity near 4000 mAh/g, which is approximately 10-fold larger compared to those of the current commercial graphite anodes, silicon has been the most promising anode for lithium ion batteries, particularly targeting large-scale energy storage applications including electrical vehicles and utility grids. Nevertheless, Si suffers from its short cycle life as well as the limitation for scalable electrode fabrication. Herein, we develop an electrospinning process to produce core shell fiber electrodes using a dual nozzle in a scalable manner. In the core shell fibers, commercially available nanoparticles in the core are wrapped by the carbon shell. The unique core shell structure resolves various issues of Si anode operations, such as pulverization, vulnerable contacts between Si and carbon conductors, and an unstable sold-electrolyte interphase, thereby exhibiting outstanding cell performance: a gravimetric capacity as high as 1384 mAh/g, a 5 min discharging rate capability while retaining 721 mAh/g, and cycle life of 300 cycles with almost no capacity loss. The electrospun core shell one-dimensional fibers suggest a new design principle for robust and scalable lithium battery electrodes suffering from volume expansion.