Ultra-violet and mid-infrared continuum generation by cross-phase modulation between red-shifted solitons and blue-shifted dispersive waves in a photonic crystal fiber

Using a photonic crystal fiber with a zero dispersion wavelength of the fundamental mode at 780 nm designed and fabricated in our lab, the ultraviolet and mid-infrared continua are generated by cross-phase modulation between red-shift solitons and blue-shift dispersive waves. The dependences of continuum on the pump power and wavelength are investigated. With the pump working at 820 nm, when the pump power increases from 300 to 500 mW, the bandwidths of ultraviolet and mid-infrared continua change from 80 to 140 nm and 100 to 200 nm, respectively. The wavelength of ultraviolet continuum is below 246 nm, and the wavelength of mid-infrared continuum exceeds 2500 nm. Moreover, the influences of pump power on wavelength and conversion efficiency of different parts of continua are also demonstrated.     

Pentacyclic Triterpenoids,Phytosteroids and Fatty Acid Isolated from the Stem-bark of Cola lateritia K. Schum. (Sterculiaceae) of Cameroon origin; Evaluation of Their Antibacterial Activity

The phytochemical investigation on the chemical constituents of dichloromethane-methanol (1:1) stem-bark extract of Cola lateritia K. Schum. (Sterculiaceae) led to the isolation and characterization of five pentacyclic triterpenoids, one fatty acid and two phytosteroids. The compounds were identified as heptadecanoic acid (1), maslinic acid (2), betulinic acid (3), lupenone (4), lupeol (5), friedelin (6), β-stigmasterol (7) and ß-sitosterol-3-O-ß-D-glucoside (8). Their structures were determined by NMR analysis (¹H, ¹³C, DEPT-135, COSY, HMBC and HSQC), high-resolution mass spectrometry (HR-ESI-MS) and comparisons with published data in the literature. This work, to the best of our knowledge, is the first isolation and identification of these compounds in pure forms from Cola lateritia. Also, compounds 1–3 are reported for the first time from Cola genus. In vitro antibacterial activity of the isolated compounds (1–8) and the crude extract were evaluated against Bacillus subtilis, Staphylococcus epidermidis, Enterococcus faecalis, Mycobacterium smegmatis, Staphylococcus aureus, Enterobacter cloacae, Klebsiella oxytoca, Proteus vulgaris, Klebsiella pneumonia, Escherichia coli, Proteus mirabilis and Klebsiella aerogenes with streptomycin, nalidixic acid and ampicillin as standard antibacterial drugs. Compound 2 was active against E. faecalis (MIC = 18.5 µg/mL), and it was 6.9 and 28 times lower and active than that of streptomycin (MIC 128 µg/mL) and nalidixic acid (MIC > 512 µg/mL) respectively. All the isolated compounds and crude extract showed significant activities against the tested bacterial strains.     

LiBaF3:Eu2+真空紫外光谱研究

在室温下，二价稀土离了 杂的LiBaF3:Eu^2 粉末样品中，Eu^2 的发射呈现双峰结构，有一峰值波长约为410nm的宽峰，对应于Eu^2 的5d-4f跃迁，以及另一峰值波长约为360nm的窄峰，对应于Eu^2 的4f-4f跃迁。在50－400nm波长范围，测量了样品的反射光谱，并利用Kramers-Kroenig关系，计算了吸收光谱。从吸收光谱中，可以看到在102nm处有明显的吸收边，得到LiBaF3材料的禁带宽度Eg约为12.1eV。在高能端有53.4,59.4,65.3,69.2和76.5nm的吸收峰，它们对应于Ba^2 的5p电子和F的2p电子芯能级之间的跃迁，在低能量的183.4nm处，有很明显的吸收峰，推测这对应于本征缺陷的吸收。更低能量的吸收峰，则对应于禁带中的一些杂质能级，在未经紫外光或X射线辐照之前，用长波长（＞450nm）光激发LiBaF3:Eu^2 粉末样品，可以观测到Eu^2 离子的360nm和410m发光，亦表现出光激励发光特性。     

Online coupling of high-resolution chromatography with extreme UV photon activation tandem mass spectrometry: Application to the structural investigation of complex glycans by dissociative photoionization

The activation of ions by extreme-energy photons (XUV) produced by a synchrotron radiation beamline is a powerful method for characterizing complex glycans using tandem mass spectrometry (MS). As previously described, this activation method leads to rich fragmentation spectra with many structurally valuable cross-ring cleavages while maintaining labile modifications on the glycan structures. However, until now, the tandem MS event was too long to be compatible with liquid chromatography elution times. In this work, the duty cycle of the activation and detection of fragments was shortened, and the background signal on the spectra was drastically reduced. Both improvements allowed, for the first time, the successful coupling of a UHPLC system to XUV-activated tandem MS. The approach was used to characterize a complex mixture of oligo-porphyrans, which are a class of highly sulfated oligosaccharides, in a fully automated way. Due to an enhanced dynamic range and an increased sensitivity, some hypothetical structures of low abundance have been unequivocally confirmed in this study and others have been revised. Some previously undescribed species of oligo-porphyrans that exhibit lateral branching have been fully resolved. This work contributes to the scarce knowledge of the structure of porphyrans in red algae and pushes the current capacities of XUV-activation tandem MS by demonstrating the possibility of a direct coupling with UHPLC. This study will considerably broaden the applicability and practicality of this method in many fields of analytical biology.     

Simulation of NEXAFS spectra of a photo-reactive copolymer with considerably large monomer units: An ab initio molecular orbital study

We performed the simulation of near edge X-ray absorption fine structure (NEXAFS) spectra of a photo-reactive copolymer with considerably large monomer units by ab initio molecular orbital calculation, in order to explain the spectral change induced by irradiation of the linearly polarized near ultra-violet (LPNUV) light. The “building block approach” is applied for the theoretical calculation to calculate the core-excited states of the polymer with such large monomer units; the monomer unit is divided into subunits, whose core-excited states are calculated individually, and the results are summed up to simulate the spectra of the polymer. With the result of the simulation, the peaks in the observed spectra were assigned. The spectral change after the LPNUV-irradiation is attributed to the change in the electronic structure caused by the breakdown of the π-conjugation system of chalconyl group after photo-dimerization.     

用受激喇曼散射方法产生紫外皮秒激光探针测量

将波长1053nm、能量60～100mJ、脉冲宽度800ps的基频光,经二倍频、四倍频转换作为H2喇曼池的泵浦光,基于后向喇曼散射光的压缩原理,获得了波长296nm、能量约2mJ、脉冲宽度81ps的紫外超短脉冲激光,可用于ICF物理诊断实验。     

钇对苯甲酸芳香体系的效应钇在镧系元素中的位置

钇对苯甲酸芳香体系的效应加以研究并与碱和碱土金属以及若干过渡金属和有毒的重金属的效应相比较。钇与镧系元素相似,具有稳定苯甲酸体系的效应。芳香体系的微扰作用随着金属离子势的减小而增大。红外谱带强度的详细分析表示钇的位置是在铒与铥之间。芳香环谱带的相对强度和频率对于镧系元素原子序数的依赖关系表明双-双效应的存在。     

A constituent analysis of semiconductors using intense visible laser radiation

It is shown that the constituent surface atoms of several binary semiconductors vaporized by intense visible laser light can be easily identified by their characteristic radiation in the ultra-violet. These lines, between 200 nm and 400 nm, originate from the recombination of neutral excited atoms. The measurements were performed at room temperature and at liquid He temperature. This may represent an explanation for the very strongly intensity dependent ultra-violet signals occurring in recent SHG examinations of surface order in GaAs with illumination in the visible.     

大分子紫外线吸收剂的制备及其在聚偏氟乙烯中的应用

通过原子转移自由基聚合(ATRP)方法,将反应型紫外线吸收剂2-羟基-4-(3-甲基丙烯酸酯基-2-羟基丙氧基)二苯甲酮(BPMA)与甲基丙烯酸甲酯(MMA)共聚合成紫外线吸收剂P(MMA-co-BPMA),然后共混涂膜制备出具有紫外线吸收性能的聚偏氟乙烯(PVDF)复合膜。 通过核磁共振谱(NMR)、凝胶渗透色谱(GPC)、差示扫描量热仪(DSC)等技术手段对BPMA及P(MMA-co-BPMA)的结构和性能进行表征,通过紫外-可见光谱(UV-Vis)对制备的复合膜的紫外线吸收性能进行表征。 结果表明,大分子紫外线吸收剂P(MMA-co-BPMA)相对分子量分布较窄,为1.11。 当BPMA质量分数为0.68%时,P(MMA-co-BPMA)/PVDF复合膜在200~345 nm范围内透过率可降至0.4%以下,能够实现对紫外线的完全吸收。 抽提实验表明紫外线吸收剂大分子化可有效地防止外迁移。     

ZnO薄膜的激光辐照效应研究

研究了KrF准分子激光辐照对ZnO薄膜的本征缺陷.紫外（UV）发光以及表面形貌的影响,并对室温下ZnO的UV发射机理进行了详细探讨.结果表明激光辐照打断了薄膜内Zn—O键,氧空位（锌填隙）增多,导致表面电阻率下降,载流子浓度升高,调节激光辐照能量密度,可在较大范围内调控ZnO薄膜中的施主缺陷浓度;同时在激光热效应作用下,薄膜晶粒熔融长大,表面粗糙度大大降低;室温下ZnO薄膜的UV发光包括自由激子复合发光（FX）及其声子伴线（FX-LO）,缺陷浓度决定了FX与FX-LO的相对强度比,进而影响UV发射峰的强度以及位置.因此,激光辐照可以快速、有效地对ZnO薄膜内的缺陷浓度进行调控,从而控制其室温下的UV发射强度,这对于提高ZnO基光电器件的性能具有重要意义. 关键词： ZnO薄膜 激光辐照 紫外发光 缺陷浓度