飞秒化学的先驱者--记诺贝尔化学奖得主Ahmed H.Zewail教授

1999年10月12日,瑞典皇家科学院将今年的诺贝尔化学奖授予埃及和美国双重国籍的物理化学和化学物理学家Ahmed H.Zewail,以表彰他在利用飞秒激光脉冲研究化学反应方面的开拓性工作.各国科学家都认为这是一个众望所归的结果.在最近几年里,Zewail教授一直是诺贝尔化学奖呼声很高的候选人,并得到多次提名.     

Interweaving of triple-helical and extended metal-O-metal single-helical chains with the same helix axis in a 3D metal-organic framework

A novel 3D metal-organic framework [Cd2(m-bptc)(4,4'-bpy)(0.5)(H2O)4].H2O (1; m-H4bptc = 1,1'-biphenyl-2,3',3,4'-tetracarboxylic acid, 4,4'-bpy = 4,4'-bipyridine) with interweaving of triple- and single-helical chains has been obtained based on hydro(solvo)thermal reactions.     

Tanshinone IIA inhibits osteoclast differentiation through down-regulation of c-Fos and NFATc1

Bone is a dynamic tissue that is regulated by the activity of bone-resorbing osteoclasts and bone-forming osteoblasts. Excessive osteoclast formation causes diseases such as osteoporosis and rheumatoid arthritis. Natural substances may be useful as therapeutic drugs to prevent many diseases in humans because they avoid the many side effects of treatment with chemical compounds. Here we show that tanshinone IIA isolated from Salvia miltiorrhiza Bunge inhibits the receptor activator of NF-kappaB ligand (RANKL)-mediated osteoclast differentiation of osteoclast precursors. Tanshinone IIA suppressed the expression levels of c-Fos and NFATc1 induced by RANKL. However, retrovirus-mediated overexpression of c-Fos induced the expression of NFATc1 despite the presence of tanshinone IIA and reversed the inhibitory effect of tanshinone IIA on osteoclast differentiation. Also, the introduction of osteoclast precursors with the NFATc1 retrovirus led to osteoclast differentiation in the presence of tanshinone IIA. Our results suggest that tanshinone IIA may have a role as a therapeutic drug in the treatment of bone disease such as osteoporosis.     

Syntheses and characterization of two oxoborates, (Pb3O)2(BO3)2MO4 (M=Cr, Mo)

Two oxoborates, (Pb₃O)₂(BO₃)₂MO₄ (M=Cr, Mo), have been prepared by solid-state reactions below 700 °C. Single-crystal XRD analyses showed that the Cr compound crystallizes in the orthorhombic group Pnma with a=6.4160(13) Å, b=11.635(2) Å, c=18.164(4) Å, Z=4 and the Mo analog in the group Cmcm with a=18.446(4) Å, b=6.3557(13) Å, c=11.657(2) Å, Z=4. Both compounds are characterized by one-dimensional chains formed by corner-sharing OPb₄ tetrahedra. BO₃ and CrO₄ (MoO₄) groups are located around the chains to hold them together via Pb–O bonds. The IR spectra further confirmed the presence of BO₃ groups in both structures and UV–vis diffuse reflectance spectra showed band gaps of about 1.8 and 2.9 eV for the Cr and Mo compounds, respectively. Band structure calculations indicated that (Pb₃O)₂(BO₃)₂MoO₄ is a direct semiconductor with the calculated energy gap of about 2.4 eV.     

A new phenylethanoid glycoside from Rabdosia lophanthoides （Buch.-Ham.ex D.Don） Hara.

A new phenylethanoid glycoside,3-hydroxy-4-methoxy-β-phenylethoxy-O-α-L-rhamnopyranosyl-(1→3)-2-O-acetyl-O-β-D-glucopyranoside, named lophanthoside A,was isolated from Rabdosia lophanthoides(Buch.-Ham.ex D.Don) Hara.Its structure was determined by spectroscopic evidences.     

气质联用法测定复合食品包装袋中的二氨基甲苯

建立复合食品包装袋中二氨基甲苯气相色谱一质谱测定方法.样品用4%乙酸提取,加三氟乙酸酐进行衍生化,用气相色谱-质谱联用仪测定.二氨基甲苯含量在0. 002～0. 05μg/mL范围内与离子蜂面积呈良好的线性关系,相关系数r=0. 9998,检出限低于0. 0004 mg/L.测定结果的相对标准偏差为2. 98%～5. 50%(n=6),加标回收率为82%～92%.该方法快速、灵敏、测定结果准确.     

Excess of a class of g-frames

In this paper, we study the relationship between frames for the super Hilbert space H⊕H and g-frames for H with respect to C². We show that a g-frame associated with a frame for H⊕H remains a g-frame whenever any one of its elements is removed. Furthermore, we show that the excess of such a g-frame is at least dimH.     

Packing circuits in matroids

The purpose of this paper is to characterize all matroids M that satisfy the following minimax relation: for any nonnegative integral weight function w defined on E(M),

Simultaneous determination of 103 pesticide residues in tea samples by LC‐MS/MS

A simple and sensitive method was developed and validated for the simultaneous determination of 103 pesticide residues in tea by LC‐MS/MS. For the analysis of the pesticide with polarity, thermal lability or low volatility, this LC‐MS/MS method has an advantage over GC. In this work, residual pesticides were extracted from the tea sample with ACN and then purified using Carb‐NH₂ SPE cartridges. Using the multiple reaction monitoring mode, the pesticides were quantified and identified by the most abundant and characteristic fragment ions. The recoveries obtained for each pesticide ranged between 65 and 114% at three spiked concentration levels. The intra‐day precisions were lower than 19.6%. Good linear relationships were observed with the correlation coefficients r² >0.996 for all analytes. The established method was successfully applied to the determination of pesticide residues in real tea samples.     

Graphene nanoribbon-based supramolecular ensembles with dual-receptor targeting function for targeted photothermal tumor therapy

Triple negative breast cancer (TNBC) is one of the most malignant subtypes of breast cancer. Here, we report the construction of graphene nanoribbon (GNR)-based supramolecular ensembles with dual-receptor (mannose and α_vβ₃ integrin receptors) targeting function, denoted as GNR-Man/PRGD, for targeted photothermal treatment (PTT) of TNBC. The GNR-Man/PRGD ensembles were constructed through the solution-based self-assembly of mannose-grafted GNRs (GNR-Man) with a pyrene-tagged α_vβ₃ integrin ligand (PRGD). Enhanced PTT efficacies were achieved both in vitro and in vivo compared to that of the non-targeting equivalents. Tumor-bearing live mice were administered (tail vein) with GNR-Man/PRGD and then each mice group was subjected to PTT. Remarkably, GNR-Man/PRGD induced complete ablation of the solid tumors, and no tumor regrowth was observed over a period of 15 days. This study demonstrates a new and promising platform for the development of photothermal nanomaterials for targeted tumor therapy.

Dual receptor-targeting supramolecular glycomaterials are constructed based on graphene nanoribbons for the targeted photothermal therapy of triple-negative breast cancer in vivo.