Directed self-assembly of a colloidal kagome lattice

A challenging goal in materials chemistry and physics is spontaneously to form intended superstructures from designed building blocks. In fields such as crystal engineering and the design of porous materials, this typically involves building blocks of organic molecules, sometimes operating together with metallic ions or clusters. The translation of such ideas to nanoparticles and colloidal-sized building blocks would potentially open doors to new materials and new properties, but the pathways to achieve this goal are still undetermined. Here we show how colloidal spheres can be induced to self-assemble into a complex predetermined colloidal crystal-in this case a colloidal kagome lattice-through decoration of their surfaces with a simple pattern of hydrophobic domains. The building blocks are simple micrometre-sized spheres with interactions (electrostatic repulsion in the middle, hydrophobic attraction at the poles, which we call 'triblock Janus') that are also simple, but the self-assembly of the spheres into an open kagome structure contrasts with previously known close-packed periodic arrangements of spheres. This open network is of interest for several theoretical reasons. With a view to possible enhanced functionality, the resulting lattice structure possesses two families of pores, one that is hydrophobic on the rims of the pores and another that is hydrophilic. This strategy of 'convergent' self-assembly from easily fabricated colloidal building blocks encodes the target supracolloidal architecture, not in localized attractive spots but instead in large redundantly attractive regions, and can be extended to form other supracolloidal networks.     

Addition of cerium and yttrium to ferritic steel weld metal to improve hydrogen trapping efficiency

The applicability of Ce and Y as promising candidate elements to form irreversible traps in weld metal was investigated by thermal desorption spectroscopy (TDS) with gas chromatography (GC).The precise nature of the precipitate particles newly formed in the weld metal by the addition of Ce and Y to a certain alloy system was characterized.Moreover,the hydrogen trapping efficiency expressed as the reduction of the diffusible hydrogen in the weld metal was analyzed.The results showed that the addition of Ce and/or Y to this alloy system led to the formation of a mixed type of (Ce,Ti)-based oxide,(Y,Ni)-based carbide,or (Ce,Y,Ti)-based oxide particles.Because of the high activation energy of the mixed type of particles (≥ 150 kJ/mol),the trapping efficiency for hydrogen was considered to be sufficiently high to effectively reduce the diffusible hydrogen content.     

Rational design of carbon shell-encapsulated cobalt nanospheres to enhance microwave absorption performance

Co@C core–shell nanospheres highly dispersed on carbon supports were rationally designed to improve the microwave absorbing property of the composite material, and fabricated by one pot thermal decomposition and simple annealing process. The Co nanospheres were completely encapsulated with thin carbon shells, which can effectively prevent the oxidation of the Co surface. Additionally, the particle size of Co nanospheres were properly controlled to optimize the electromagnetic property of the composite material. As a result, the lightweight Co@C/C composites with the particle size of 20 nm exhibited much enhanced microwave absorption properties. The improved microwave absorption performance is attributed mainly to the enhanced isotropic ratio and impedance matching of magnetic composites via tuning the Co particle size. Therefore, the welldesigned core-shell Co@C composite structure will provide a new insight for the development of high performance microwave absorbers.     

一种对松材线虫具有强感染性的内生真菌,Esteya vermicola

2006年在韩国松林土壤中分离出来一种稀有的丝孢菌(分离物CNU 120806)。该菌具有两种孢子,但是仅月型孢子能黏附于线虫虫体上,并感染线虫。该菌消耗线虫营养并生长出线虫虫体,形成新孢子,然后进行新的感染循环。基于形态和分子生物学特征,该菌被鉴定为Esteya vermicola,它是已经被报道过的首例松材线虫的内寄生菌。由于其高度侵染性,有希望成为防控毁灭性的松萎蔫病害的生防菌。生测表明,E.vermicola CBS 115803在4~5 d内就能感染致死几乎全部松材线虫,这是由于其产生了较多的月型孢子。研究还表明,应用该菌的配方具有防控松萎蔫病的生防商业化前景。     

Flexible metal-oxide devices made by room-temperature photochemical activation of sol-gel films

Amorphous metal-oxide semiconductors have emerged as potential replacements for organic and silicon materials in thin-film electronics. The high carrier mobility in the amorphous state, and excellent large-area uniformity, have extended their applications to active-matrix electronics, including displays, sensor arrays and X-ray detectors. Moreover, their solution processability and optical transparency have opened new horizons for low-cost printable and transparent electronics on plastic substrates. But metal-oxide formation by the sol-gel route requires an annealing step at relatively high temperature, which has prevented the incorporation of these materials with the polymer substrates used in high-performance flexible electronics. Here we report a general method for forming high-performance and operationally stable metal-oxide semiconductors at room temperature, by deep-ultraviolet photochemical activation of sol-gel films. Deep-ultraviolet irradiation induces efficient condensation and densification of oxide semiconducting films by photochemical activation at low temperature. This photochemical activation is applicable to numerous metal-oxide semiconductors, and the performance (in terms of transistor mobility and operational stability) of thin-film transistors fabricated by this route compares favourably with that of thin-film transistors based on thermally annealed materials. The field-effect mobilities of the photo-activated metal-oxide semiconductors are as high as 14 and 7?cm(2)?V(-1)?s(-1) (with an Al(2)O(3) gate insulator) on glass and polymer substrates, respectively; and seven-stage ring oscillators fabricated on polymer substrates operate with an oscillation frequency of more than 340?kHz, corresponding to a propagation delay of less than 210?nanoseconds per stage.     

Phosphorylation of WAVE1 regulates actin polymerization and dendritic spine morphology

WAVE1--the Wiskott-Aldrich syndrome protein (WASP)--family verprolin homologous protein 1--is a key regulator of actin-dependent morphological processes in mammals, through its ability to activate the actin-related protein (Arp2/3) complex. Here we show that WAVE1 is phosphorylated at multiple sites by cyclin-dependent kinase 5 (Cdk5) both in vitro and in intact mouse neurons. Phosphorylation of WAVE1 by Cdk5 inhibits its ability to regulate Arp2/3 complex-dependent actin polymerization. Loss of WAVE1 function in vivo or in cultured neurons results in a decrease in mature dendritic spines. Expression of a dephosphorylation-mimic mutant of WAVE1 reverses this loss of WAVE1 function in spine morphology, but expression of a phosphorylation-mimic mutant does not. Cyclic AMP (cAMP) signalling reduces phosphorylation of the Cdk5 sites in WAVE1, and increases spine density in a WAVE1-dependent manner. Our data suggest that phosphorylation/dephosphorylation of WAVE1 in neurons has an important role in the formation of the filamentous actin cytoskeleton, and thus in the regulation of dendritic spine morphology.     

Multi-Quality Properties Capability Analysis for Prestressing Strand of Prestressed Concrete

Prestressed concrete structures are main conformati on for the construction of high way bridges. The quality of prestressed concrete s tructures is mainly affected by the tensile strength of prestressing strand. In order to attain the purpose of economic design and long life span of prestressin g strand, the less relaxation property of strand type is suitable for constructi on and usage. Thus, the research and development of prestressing strand is requi red to reach the goals of high tensile strength and ...     

Renaturation of DNA catalysed by yeast DNA repair and recombination protein RAD10.

The RAD10 gene of Saccharomyces cerevisiae is required for the incision step of excision repair of ultraviolet-damaged DNA, and it functions in mitotic recombination. RAD10 has homology to the human excision repair gene ERCC-1. Here we describe the purification of the protein encoded by RAD10 and show that it is a DNA-binding protein with a strong preference for single-stranded DNA. We also show that RAD10 promotes the renaturation of complementary DNA strands.     

DNA helicase Srs2 disrupts the Rad51 presynaptic filament

Mutations in the Saccharomyces cerevisiae gene SRS2 result in the yeast's sensitivity to genotoxic agents, failure to recover or adapt from DNA damage checkpoint-mediated cell cycle arrest, slow growth, chromosome loss, and hyper-recombination. Furthermore, double mutant strains, with mutations in DNA helicase genes SRS2 and SGS1, show low viability that can be overcome by inactivating recombination, implying that untimely recombination is the cause of growth impairment. Here we clarify the role of SRS2 in recombination modulation by purifying its encoded product and examining its interactions with the Rad51 recombinase. Srs2 has a robust ATPase activity that is dependent on single-stranded DNA (ssDNA) and binds Rad51, but the addition of a catalytic quantity of Srs2 to Rad51-mediated recombination reactions causes severe inhibition of these reactions. We show that Srs2 acts by dislodging Rad51 from ssDNA. Thus, the attenuation of recombination efficiency by Srs2 stems primarily from its ability to dismantle the Rad51 presynaptic filament efficiently. Our findings have implications for the basis of Bloom's and Werner's syndromes, which are caused by mutations in DNA helicases and are characterized by increased frequencies of recombination and a predisposition to cancers and accelerated ageing.