Unambiguous detection of target DNAs by excimer-monomer switching molecular beacons

A new class of molecular beacons were developed in which pyrene fluorophores were connected both at 3' and 5' ends of a single-stranded oligonucleotide. The two pyrene-based fluorophores were synthesized from the same starting material, so that the preparation of the beacons was simplified. The detection strategy of the beacons for target DNAs is based on "excimer-monomer emission switching" of the pyrene fluorophores: excimer emission of the pyrene moieties changed to monomer one when the beacons hybridized with the targets. This type of two-state mode of fluorescence allows unambiguous detection of the target DNAs because strict 1:1 correlation between the nonhybridized and the hybridized beacons can be monitored by the presence of isoemissive points of the fluorescence changes. The beacons can detect target 19-mer DNAs and can discriminate the targets from their single-nucleotide mismatches at 1 nM concentration. Advantages of the excimer-monomer switching molecular beacons were discussed in comparison with conventional ones.     

Iridium complex-catalyzed highly enantio- and diastereoselective [2+2+2] cycloaddition for the synthesis of axially chiral teraryl compounds

An asymmetric [2+2+2] cycloaddition of an alpha,omega-diyne, possessing ortho-substituted aryl groups on its terminus, and a monoalkyne with oxygen functionalities gave various axially chiral teraryl compounds. The coupling proceeded with extremely high enantio- (>99.5% ee) and diastereoselectivities (dl/meso = >95/5) when catalyzed by an iridium-chiral phosphine complex. As the products were readily transformed into diol compounds by deprotection without racemization, the present procedure provides access to a new chiral pool of diol compounds with C2 symmetry.     

Tin(IV) chloride-chiral pyrogallol derivatives as new Lewis acid-assisted chiral Brønsted acids for enantioselective polyene cyclization

[reaction: see text] New Lewis acid-assisted Br?nsted acids (LBAs), tin(IV) chloride-2,6-dialkoxyphenols, serve as artificial cyclases for biomimetic polyene cyclization. For example, the enantioselective cyclization of 4-(homogeranyl)toluene using tin(IV) chloride-2,6-di[(1'R,2'R)-trans-2'-(3' ',5' '-xylyl)cyclohexanoxy]phenol gave a trans-fused tricyclic compound with 85% ee.     

Generation of 360-nm ultraviolet light in first-order periodically poled bulk MgO:LiNbO3

Ultraviolet second-harmonic generation in first-order periodically poled MgO:LiNbO3 is presented. Using a high-voltage multipulse application method, we fabricated a first-order nonlinear grating with a period of 1.8 microm and depth of approximately 150 microm over 10-mm interaction length in a 1-mm-thick MgO:LiNbO3 substrate. In a single-pass configuration, continuous-wave 30-mW UV light at 362.5 nm was generated for a fundamental power of 522 mW, corresponding to a normalized conversion efficiency of 11%/W.     

Observation of the "self-healing" of an error field island in the large helical device

It was observed that the vacuum magnetic island produced by an external error magnetic field in the large helical device shrank in the presence of plasma. This was evidenced by the disappearance of flat regions in the electron temperature profile obtained by Thomson scattering. This island behavior depended on the magnetic configuration in which the plasmas were produced.     

Voltammetric Determination of Boric Acid Using the Ternary Complexation System with Salicylaldehyde and H‐Acid

A square‐wave voltammetric method for the determination of boric acid in water has been described based on the new understanding of the electrochemical behavior of boric acid‐Azomethine H complexation. Salicylaldehyde and H‐acid were used as the starting materials of boric acid‐Azomethine H complex and their concentrations were optimized for boric acid determination in water. A glassy carbon electrode, instead of a conventional mercury electrode, was used in the measurement. The detection limit of the proposed method was 0.10 mg B dm^?3. The proposed method was successfully used for boric acid determination in the water from a seawater desalination RO plant.     

超短脉冲强激光与固体靶相互作用中Kα射线的实验研究

在相对论激光强度下，对p偏振30 fs激光与固体Cu靶相互作用中产生的Kα射线进行了实验研究.采用刀边成像技术和单光子计数X射线CCD相结合的探测装置，在单发激光脉冲打靶时同时得到X射线源的尺寸、能谱以及Kα光子的转换效率等多种信息.实验结果与Reich等人的理论计算结果有明显的差异，Kα光子的能量转换效率在激光功率密度为1.6×10¹⁸W/cm²的条件下达到最大值7.08×10^-6/sr.根据这一结果并结合蒙特卡罗程序，推断出在这一聚焦光强下激光能量转换为前向超热电子的效率约为10%.