Factors influencing the electrospray intrasource separation and selective ionization of glycerophospholipids

The external electric field induces a separation of cations from negative electrolyte ions in the infusate while differential ionization of molecular species that possess differential electrical propensities can be induced in either the positive- or negative-ion mode during the electrospray ionization process. These physical and electrical processes that occur in the electrospray ion source have been used to selectively ionize lipid classes possessing different electrical propensities that are now known as "intrasource separation and selective ionization". However, the chemical principles underlying charge-dependent alterations in ionization efficiencies responsible for the selective ionization of lipid classes are not known with certainty. Herein, we examined the multiple factors that contribute to intrasource separation and selective ionization of lipid classes under optimal instrumental conditions. We demonstrated that many different lipid classes could be selectively ionized in the ion source and that intrasource resolution of distinct molecular constituents was independent of lipid concentration, flow rate, and residual ions under most experimental conditions. Moreover, the presence of alkaline conditions facilitates the selective ionization of many lipid classes through a mechanism independent of the design of the ESI ion source. Collectively, this study provides an empirical foundation for understanding the chemical mechanisms underlying intrasource separation and selective ionization of lipid classes that can potentially be used for global analysis of cellular lipidomes without the need for chromatographic separation.     

Analysis of the impacts of mechanical errors on the RF performance of a single spoke cavity

Mechanical errors can not be avoided in fabrication. They will cause geometry errors and have impacts on the cavity performance. This paper systematically analyzes the impacts of mechanical errors on the RF performance of Peking University single spoke cavity. The various kinds of shape and size errors are considered, the influences on the resonation frequency and field flatness are studied by numerical simulation and the theoretical models are analyzed. The results show that the single spoke cavity is robust with respect to the mechanical tolerance. It also indicates the most essential factors for fabrication.     

The investigation of the interaction between oxybutynin hydrochloride and bovine serum albumin by spectroscopic methods

The mutual interaction of oxybutynin hydrochloride (OB) with bovine serum albumin (BSA) was investigated by fluorescence, UV–vis absorption, circular dichroism (CD), and Fourier transform infrared (FT-IR) spectroscopies under simulative physiological conditions. The results of fluorescence titration revealed that OB could quench the intrinsic fluorescence of BSA by static quenching and there was a single class of binding sites on BSA for this drug. The thermodynamic parameters ΔH, ΔS, and ΔG calculated at different temperatures indicated that hydrogen bonds and van der Waals interactions were the dominant intermolecular forces in stabilizing the OB–BSA complexes. According to the theory of Förster’s non-radiation energy transfer, the binding distance r between OB and BSA was evaluated to be 3.27 nm. The displacement experiments confirmed that OB could bind to site I of BSA. The FT-IR and CD spectra showed that the binding of OB to BSA induced conformational changes in BSA.     

血红蛋白在离子液体[BMIM]PF6碳糊电极上的直接电化学

制备了离子液体[BMIM]PF6修饰碳糊电极(CILE), 并对其形貌和电化学行为进行了表征. 采用涂布法利用壳聚糖-皂土有机-无机复合膜将血红蛋白(Hb)固定于CILE电极表面, 利用紫外可见光谱、红外光谱和电化学方法等手段对包埋于膜内的Hb的性质进行了表征. 结果表明, Hb在薄膜内保持了其原始构象与生物活性, 循环伏安实验表明, 在pH=7.0的Britton-Robinson (B-R)缓冲液中, Hb表现出一对峰形良好的准可逆氧化还原峰, 为Hb Fe(III)/Fe(II)电对的特征峰, 对其直接电化学行为进行了研究, 求出式电位为-0.352 V(vs SCE), 电子转移数为0.885, 电荷传递系数为0.578, 表观异相电子转移速率常数为0.149 s-1.     

Platinum(II) complexes with pi-conjugated, naphthyl-substituted, cyclometalated ligands (RC N N): structures and photo- and electroluminescence

The crystal structures and photophysical properties of mononuclear [(RC N N)PtX](ClO4)n ((RC N N)=3-(6'-(2'-naphthyl)-2'-pyridyl)isoquinolinyl and derivatives; X=Cl, n=0; X=PPh(3) or PCy(3), n=1), dinuclear [(RC N N)2Pt2(mu-dppm)](ClO4)2 (dppm=bis(diphenyphosphino)methyl) and trinuclear [(RC N N)3Pt3(mu-dpmp)](ClO4)3 (dpmp=bis(diphenylphosphinomethyl)phenylphosphine) complexes are presented. The crystal structures show extensive intra- and/or intermolecular pipi interactions; the two (RC N N) planes of [(RC N N)2Pt2(mu-dppm)](ClO4)2 (R=Ph, 3,5-tBu2Ph or 3,5-(CF3)2Ph) are in a nearly eclipsed configuration with torsion angles close to 0 degrees. [(RC N N)PtCl], [(RC N N)2Pt2(mu-dppm)](ClO4)2, and [(RC N N)3Pt3(mu-dpmp)](ClO4)3 are strongly emissive with quantum yields of up to 0.68 in CH2Cl2 or MeCN solution at room temperature. The [(RC N N)PtCl] complexes have a high thermal stability (T(d)=470-549 degrees C). High-performance light-emitting devices containing [(RC N N)PtCl] (R=H or 3,5-tBu2Ph) as a light-emitting material have been fabricated; they have a maximum luminance of 63,000 cd m(-2) and CIE 1931 coordinates at x=0.36, y=0.54.     

北京大学高功率相干Terahertz光源设计

给出北京大学射频超导组拟建的准单色、高平均功率、波长可调的相干THz光源的系统设计. 该装置是根据相干扭摆器自发辐射原理, 采用自主原创的DC-SC超导光阴极注入器提供的高品质电子束经过磁压缩单次通过扭摆器产生0.25—0.5THz之间的光. 该装置提供的THz光具有波长连续可调、功率高、相干性好、单色性好、线偏振等特点, 为生物、医学、材料科学、通信等领域提供强有力的研究工具.     

应用于投影显示系统的偏振分光镜的设计和制备

讨论了应用于投影显示系统的满足宽光谱范围、大的入射角、高的消光比的偏振分光镜的设计和制备。提出了一种偏振分光镜的新的设计方法 :采用多对迈克尼尔对组合来满足宽入射角范围的要求 ,采用多个中心波长不同的λ 4膜堆来满足宽光谱范围。设计的偏振分光镜在 42 0nm～ 6 70nm的波段范围内 ,在 41.34°～ 48.6 6°的入射角范围内 ,达到p偏振光的平均透过率大于 85 % ,p偏振光的平均透过率与s光的平均透过率之比大于 10 0 0。并给出了设计实例和样品的实测结果     

一种近似计算金属多层膜界面过渡层厚度的方法

在用小角射线衍射研究离子束溅射法制备的多层膜基本结构时,提出了一个可以计算界面过渡层厚度公式。由实验曲线和文中提出公式得到过渡层厚度,并与用实验曲线和理论曲线进行拟合所得值进行了对比,结果表明这两种方法得到的过渡层厚度基本一致。     

Degradation of PCDD/Fs in Fly Ash by Vortex-shaped Gliding Arc Plasma

PCDD/Fs in fly ash from municipal solid waste incinerators (MSWIs) can be decomposed in non-thermal plasma, more in particular in a vortex-shaped gliding arc. Typical operating conditions are 10 kV voltage, 40 kΩB external current-limited resistor, 11 L/min tangential gas and 2 L/min axial carrier gas flow rates. Degradation efficiencies of PCDD/Fs are respectively 54.9, 61.7 and 66.8 % on mass basis and 60.7, 73.3 and 70.1 % on toxicity basis under N₂, air and O₂ condition. After treatment the morphology of fly ash has changed: needle-shaped crystals increasing, pores and fragments appearing and high-temperature melting showing which is leaded by direct contact with high-temperature core of arc. The results are explained tentatively by the creation of reactive intermediates leading to dechlorination and oxidation of PCDD/Fs and finally producing end-products such as CO₂, CO, HCl and CH₄.     

算子代数上(m,n)-Jordan导子的刻画

设R是一个环,M是一个R-双边模,m和n是两个非负整数满足m+n≠0,如果δ是一个从R到M的可加映射满足对任意A∈R,(m+n)δ(A~2)=2mAδ(A)+2nδ(A)A,则称δ是一个(m,n)-Jordan导子.本文证明了,如果R是一个单位环,M是一个单位R-双边模含有一个由R中幂等元代数生成的左(右)分离集,那么,当m,n0且m≠n时,每一个从R到M的(m,n)-Jordan导子恒等于零.还证明了,如果A和B是两个单位环,M是一个忠实的单位(A,B)-双边模(N是一个忠实的单位(B,A)-双边模),m,n0且m≠n,U=[A N M B]是一个|mn(m-n)(m+n)|-无挠的广义矩阵环,那么每一个从U到自身的(m,n)-Jordan导子恒等于零.