A chiral route to negative refraction

Negative refraction is currently achieved by driving the magnetic permeability and electrical permittivity simultaneously negative, thus requiring two separate resonances in the refracting material. The introduction of a single chiral resonance leads to negative refraction of one polarization, resulting in improved and simplified designs of negatively refracting materials and opening previously unknown avenues of investigation in this fast-growing subject.     

Association of transfer RNA acceptor identity with a helical irregularity

The aminoacylation specificity ("acceptor identity") of transfer RNAs (tRNAs) has previously been associated with the position of particular nucleotides, as opposed to distinctive elements of three-dimensional structure. The contribution of a G.U wobble pair in the acceptor helix of tRNA(Ala) to acceptor identity was examined with synthetic amber suppressor tRNAs in Escherichia coli. The acceptor identity was not affected by replacing the G.U wobble pair in tRNA(Ala) with a G.A, C.A, or U.U wobble pair. Furthermore, a tRNA(Ala) acceptor identity was conferred on tRNA(Lys) when the same site in the acceptor helix was replaced with any of several wobble pairs. Additional data with tRNA(Ala) show that a substantial acceptor identity was retained when the G.U wobble pair was translocated to another site in the acceptor helix. These results suggest that the G.U wobble pair induces an irregularity in the acceptor helix of tRNA(Ala) to match a complementary structure in the aminoacylating enzyme.     

Helical polyacetylene synthesized with a chiral nematic reaction field

Helical polyacetylene was synthesized under an asymmetric reaction field consisting of chiral nematic (N*) liquid crystals (LCs). The chiral nematic LC was prepared by adding a chiroptical binaphthol derivative as a chiral dopant to a mixture of two nematic LCs. Acetylene polymerizations were carried out using the catalyst titanium tetra-n-butoxide-triethylaluminum dissolved in the chiral nematic LC solvent. The polyacetylene film was shown by scanning electron microscopy to consist of clockwise or counterclockwise helical structure of fibrils. A Cotton effect was observed in the region of the pi --> pi* transition of the polyacetylene chain in circular dichroism spectra. The high electrical conductivities of approximately 1500 to 1800 siemens per centimeter after iodine doping and the chiral helicity of these films may be exploited in electromagnetic and optical applications.     

A glycine-dependent riboswitch that uses cooperative binding to control gene expression

We identified a previously unknown riboswitch class in bacteria that is selectively triggered by glycine. A representative of these glycine-sensing RNAs from Bacillus subtilis operates as a rare genetic on switch for the gcvT operon, which codes for proteins that form the glycine cleavage system. Most glycine riboswitches integrate two ligand-binding domains that function cooperatively to more closely approximate a two-state genetic switch. This advanced form of riboswitch may have evolved to ensure that excess glycine is efficiently used to provide carbon flux through the citric acid cycle and maintain adequate amounts of the amino acid for protein synthesis. Thus, riboswitches perform key regulatory roles and exhibit complex performance characteristics that previously had been observed only with protein factors.     

Photoinduced electron transfer from a conducting polymer to buckminsterfullerene

Evidence for photoinduced electron transfer from the excited state of a conducting polymer onto buckminsterfullerene, C(60), is reported. After photo-excitation of the conjugated polymer with light of energy greater than the pi-pi* gap, an electron transfer to the C(60) molecule is initiated. Photoinduced optical absorption studies demonstrate a different excitation spectrum for the composite as compared to the separate components, consistent with photo-excited charge transfer. A photoinduced electron spin resonance signal exhibits signatures of both the conducting polymer cation and the C(60) anion. Because the photoluminescence in the conducting polymer is quenched by interaction with C(60), the data imply that charge transfer from the excited state occurs on a picosecond time scale. The charge-separated state in composite films is metastable at low temperatures.     

Chain walking: A new strategy to control polymer topology

Ethylene pressure has been used to control the competition between isomerization (chain walking) and monomer insertion processes for ethylene coordination polymerization catalyzed by a palladium-alpha-diimine catalyst. The topology of the polyethylene varies from linear with moderate branching to "hyperbranched" structures. Although the overall branching number and the distribution of short-chain branching change very slightly, the architecture or topology of the polyethylene changes from linear polyethylene with moderate branches at high ethylene pressures to a hyperbranched polyethylene at low pressures.     

Retention deficit correlated with a deficit in the corticoid response to stress

Previous research has indicated that intracerebral injection of potassium chloride, and the resultant electrical silence of the brain, lead to the attenuation of a previously conditioned emotional response; this response may reflect conditioned fear. The data reported here indicate that the normal mobilization of corticosteroids, perhaps a second index of emotionality, is also attenuated by such injections.     

A 160-femtosecond optical image processor based on a conjugated polymer

Degenerate ground-state conjugated polymers exhibit large third-order nonlinear optical susceptibilities, including substantial two-photon absorption. With the use of a machine architecture suited to these material properties, ultrafast optical processors are possible. A four-wave mixing optical correlator was built with an air-stable, processable, degenerate ground-state conjugated polymer, poly(1,6-heptadiester). The continuously updatable processor correlates two 5000-pixel images in less than 160 femtoseconds, achieving peak processing rates of 3 x 10(16) operations per second.     

A68: a major subunit of paired helical filaments and derivatized forms of normal Tau

Putative Alzheimer disease (AD)-specific proteins (A68) were purified to homogeneity and shown to be major subunits of one form of paired helical filaments (PHFs). The amino acid sequence and immunological data indicate that the backbone of A68 is indistinguishable from that of the protein tau (tau), but A68 could be distinguished from normal human tau by the degree to which A68 was phosphorylated and by the specific residues in A68 that served as phosphate acceptors. The larger apparent relative molecular mass (Mr) of A68, compared to normal human tau, was attributed to abnormal phosphorylation of A68 because enzymatic dephosphorylation of A68 reduced its Mr to close to that of normal tau. Moreover, the LysSerProVal motif in normal human tau appeared to be an abnormal phosphorylation site in A68 because the Ser in this motif was a phosphate acceptor site in A68, but not in normal human tau. Thus, the major subunits of a class of PHFs are A68 proteins and the excessive or inappropriate phosphorylation of normal tau may change its apparent Mr, thus transforming tau into A68.     

Identification of novel genes associated with duck OASL in response to influenza A virus

2′-5′-Oligoadenylate synthetase like protein(OASL) plays a key role in response to viral infections through selectively activating the OAS/RNase L or OASL/RIG-I signaling pathway. Although classic pathway of OASL is well-known, its regulated genes or co-actors are largely unknown. To study the possible molecular mechanism of duck OASL(dOASL), we performed RNA-sequencing(RNA-seq) and immunoprecipitation and mass spectrometry(IP-MS) at the level of mRNA and protein, respectively. For RNA-seq, we used DF1 cell lines(DF1 dO ASL+/+, DF1 cO ASL–/–, and DF1) with or without the CK/0513 H5 N1 virus(A/chicken/huabei/0513/2007) infection. 1 737 differentially expressed genes(DEGs) were identified as candidate target genes regulated by dOASL. Gene Ontology(GO), Kyoto Encyclopedia of Genes and Genomes(KEGG) analysis and Weighted Correlation Network Analysis(WGCNA) were performed. We identified one important yellow co-expression module correlated with antiviral immune response. In this module, Ankyrin repeat and FYVE domain containing 1(ANKFY1), harboring a BTB domain similar to the methyl CpG-binding protein 1(MBD1) which bound to OASL in human, was regulated by dOASL. At protein level, 133 host proteins were detected. Interestingly, ANKFY1 was one of them binding to dOASL protein. Further phylogenomic and chromosomal syntenic analysis demonstrated MBD1 was absent in birds, while mammals retained. It is suggested that OASL-ANKFY1 interaction might act as a compensatory mechanism to regulate gene expression in birds. Our findings will provide a useful resource for the molecular mechanism research of dOASL.     

探索产学结合途径, 建立合作运行机制,培养高等技术应用性人才

产学合作教育是高等学校全面贯彻党的教育方针 ,适应社会经济发展的需要 ,培养具有创新精神和实践能力的高素质人才的有效教学形式 ,是高等教育面向社会、服务社会的重要途径。发展高职高专教育 ,培养适应社会和经济发展需要的高等技术应用性人才 ,必需走产学结合的道路。我校多年来积极实施产学结合教育 ,探索产学结合途径 ,建立产学结合良性运行机制 ,取得了一定的效果。我们认为 ,实施产学结合不仅企业从学校得到了技术和人才回报 ,更重要的是增强了学校与社会的联系 ,提高了学校的知名度 ,锻炼了教师队伍 ,完成了培养高素质技术应用性人…     

常用聚合物(SBS)改性沥青稳定剂添加量的确定

本研究通过大量的试验阐明改性沥青制作设备加工核心均是如何将SBS充分的研磨、分散于基质沥青中,使之形成稳定的3维网状结构。但由于设备与工艺的不同会导致加工性能有所差异,所以投料的配比也是会有明显差距,据此根据现有的工艺情况及工程的重要性通过试验来确定物料最佳添加量。提出利用"离析试验"163℃、48h前后的软化点差值确定稳定剂添加量的观点。     

A dielectric polymer with high electric energy density and fast discharge speed

Dielectric polymers with high dipole density have the potential to achieve very high energy density, which is required in many modern electronics and electric systems. We demonstrate that a very high energy density with fast discharge speed and low loss can be obtained in defect-modified poly(vinylidene fluoride) polymers. This is achieved by combining nonpolar and polar molecular structural changes of the polymer with the proper dielectric constants, to avoid the electric displacement saturation at electric fields well below the breakdown field. The results indicate that a very high dielectric constant may not be desirable to reach a very high energy density.     

信息素养调查问卷的文献计量分析

目的: 通过对国内高校信息素养调查问卷进行文献计量学分析,为信息素养调查问卷的设计提供依据。方法: 搜集硕士学位论文和专业调查网站中的有效问卷,运用词频分析法,研究目前信息素养问卷调查的热点。结果: 学生组调查问卷中的热点包括信息处理使用能力、信息评价与分析、信息检索能力、信息意识与态度、信息伦理道德,教师调查问卷的热点包括信息处理使用能力、信息教育、信息的检索与收集、信息的评价与分析、信息意识与态度。结论: 目前国内信息素养调查的内容还不够全面,不能反映信息素养教育的重点。