Molecular fingerprinting with the resolved modes of a femtosecond laser frequency comb

The control of the broadband frequency comb emitted from a mode-locked femtosecond laser has permitted a wide range of scientific and technological advances--ranging from the counting of optical cycles for next-generation atomic clocks to measurements of phase-sensitive high-field processes. A unique advantage of the stabilized frequency comb is that it provides, in a single laser beam, about a million optical modes with very narrow linewidths and absolute frequency positions known to better than one part in 10(15) (ref. 5). One important application of this vast array of highly coherent optical fields is precision spectroscopy, in which a large number of modes can be used to map internal atomic energy structure and dynamics. However, an efficient means of simultaneously identifying, addressing and measuring the amplitude or relative phase of individual modes has not existed. Here we use a high-resolution disperser to separate the individual modes of a stabilized frequency comb into a two-dimensional array in the image plane of the spectrometer. We illustrate the power of this technique for high-resolution spectral fingerprinting of molecular iodine vapour, acquiring in a few milliseconds absorption images covering over 6 THz of bandwidth with high frequency resolution. Our technique for direct and parallel accessing of stabilized frequency comb modes could find application in high-bandwidth spread-spectrum communications with increased security, high-resolution coherent quantum control, and arbitrary optical waveform synthesis with control at the optical radian level.     

A minimum column density of 1 g cm(-2) for massive star formation

Massive stars are very rare, but their extreme luminosities make them both the only type of young star we can observe in distant galaxies and the dominant energy sources in the Universe today. They form rarely because efficient radiative cooling keeps most star--forming gas clouds close to isothermal as they collapse, and this favours fragmentation into stars of one solar mass or lower. Heating of a cloud by accreting low-mass stars within it can prevent fragmentation and allow formation of massive stars, but the necessary properties for a cloud to form massive stars-and therefore where massive stars form in a galaxy--have not yet been determined. Here we show that only clouds with column densities of at least 1 g cm(-2) can avoid fragmentation and form massive stars. This threshold, and the environmental variation of the stellar initial mass function that it implies, naturally explain the characteristic column densities associated with massive star clusters and the difference between the radial profiles of Halpha and ultraviolet emission in galactic disks. The existence of a threshold also implies that the initial mass function should show detectable variation with environment within the Galaxy, that the characteristic column densities of clusters containing massive stars should vary between galaxies, and that star formation rates in some galactic environments may have been systematically underestimated.     

（s）—2—氨基—3—（2—氯苯基）—1,1—二苯基—1—丙醇的合成

标题化合物８－一种新的手性催化剂，通过丙二酸酯法及酶解拆分合成（ｓ）－３－（２－氯苯基）丙氨酸甲酯，进一步与溴苯发生格氏反应而成。     

G_n~(d,s)图的(n-1)-角色分配

Everett和Borgatti引入了k-角色分配的概念。进一步,他们引入并研究了图G的k-角色可分配程度来表示图G可以在多大程度上进行k-角色分配,记作αk(G).他们还给出了k=2时的k-角色可分配程度α2 (G)的下确界,并回答了什么时候α2(G)达到下确界。本文证明了k≥3时,αk(G)的下确界为0,并证明了当图G为Gk+1l,s图且α(s+1)≠0(mod k+1)(a=2,3,4)时,αk(G)达到下确界;最后还刻画了能够(n-1)-角色分配的Gn1,s图。     

基于径向基函数的点插值(RPIM)无网格法

基于径向函数的点插值法（RPIM）是一种新型无网格法。它有效地解决了点插值法（PIM）中遇到的最大困难：系数矩阵奇异性问题。此外，由于插值具有巧函数的性质，从而克服了以往无网格法中难以实现的位移边界条件的难点。本文简单介绍了PIM，重点阐述了RPIM的基本原理，并用算例表明了该法具有效率高、精度高和稳定性好等优点，在工程中具有广阔的应用前景。     

A low density of 0.8 g cm(-3) for the Trojan binary asteroid 617 Patroclus

The Trojan population consists of two swarms of asteroids following the same orbit as Jupiter and located at the L4 and L5 stable Lagrange points of the Jupiter-Sun system (leading and following Jupiter by 60 degrees ). The asteroid 617 Patroclus is the only known binary Trojan. The orbit of this double system was hitherto unknown. Here we report that the components, separated by 680 km, move around the system's centre of mass, describing a roughly circular orbit. Using this orbital information, combined with thermal measurements to estimate the size of the components, we derive a very low density of 0.8(- 0.1)+0.2 g cm(-3). The components of 617 Patroclus are therefore very porous or composed mostly of water ice, suggesting that they could have been formed in the outer part of the Solar System.     

A Sultone Route to the Antileukemic 1 ,1O-Seco-Eudesmanolides (-)-Eriolanin and (-)-Eriolangin

1Introduction The highly oxygenated 1,10-seco-eudesmanolides ( - )-eriolanin (1) and ( - )-eriolangin (2) isolated from the plant Eriophyllum lanatum (Asteraceae) inhibit the growth of the human KB tumor cell line in vitro and additionally display a significant antileukemic activity in vivo in mice (Scheme 1)[1]. Using novel methods for the synthetic elaboration of sultones[2], the first enantioselective total syntheses of 1 and 2 have been accomplished, which also established the hitherto unknown absolute configuration of these natural products[3].     

PAN及其衍生物的研究进展

本文就PAN及其衍生物作为分析试剂的研究进展作了综合评述 ,并介绍了它们在分析化学中的理论研究和应用     

Hn(-1)到Hn+1(-1)中的等距浸入

主要研究Hn(-1)到Hn+1(-1)中的具有奇异点和特殊第二基本形式的等距浸入.通过求解一组偏微分方程,得到了这些等距浸入的特殊例子.     

1-(4-硝基苯基)-3-(4-安替吡啉基)-三氮烯的合成

通过重氮盐的氮偶联反应,合成三氮烯类新试剂.质谱、红外光谱和核磁共振数据证实产物为1-(4-硝基苯基)-3-(4-安替吡啉基)-三氮烯.     

1-(4-硝基苯)-3-(3-甲基吡啶)三氮烯的合成及其与镉的显色反应

文章报道了新显色剂1-(4-硝基苯)-3-(3-甲基吡啶)三氮烯(NPMPDT)的合成及其与镉的显色反应。在Triton X—100的存在下,pH11.5的Na2B4O7-NaOH缓冲溶液中,该试剂能与镉发生显色反应,镉与NPMPDT形成摩尔比为4:1型的黄色配合物,在450nm处有一最大正吸收,在540nm处有一最大负吸收。以450nm为参比波长,540nm为测量波长进行双波长测定,其摩尔表观吸光系数ε=2.45×105 L.mol-1.cm-1,镉量在0~12.0μg/25mL范围内符合比尔定律,用其测定人发及废水中微量的镉,结果满意。     

A flexible adhesive with a conductivity of 5240 S/cm

Conductive adhesives (CAs) providing reliable connections between electronic components, have been widely used in solar cells [1], light emitting diodes (LEDs) ...     

[1-(5-氟戊基)-1H-吲哚-3-基](2-碘苯基)甲酮的合成

合成了具有较强的医学活性的[1-(5-氟戊基)-1H-吲哚-3-基](2-碘苯基)甲酮(AM-694)。首先以吲哚为起始原料,苯磺酰氯保护吲哚的1-位,AlCl3催化在吲哚3-位傅克酰基化的进行,避免了文献中通过格氏镁试剂(RMgX)对1-位的保护对无水、无氧的高要求,再将1-位保护脱掉,然后在1-位进行N-烷基化、酯基水解、甲磺酯化,最后用四正丁基氟化铵氟化。通过液相色谱(HPLC)进行含量分析,且利用核磁(NMR)和质谱(MS)进行了表征,反应总收率高达41.8%。与以往路线相比,文中方法步骤简单,成本较低,收率很高。     

1-(4-硝基苯基)-3-(5-氯吡啶)三氮烯的合成及其与铜的显色反应

报道了 1 - (4-硝基苯基 ) - 3 - (5 -氯吡啶 )三氮烯 (NPCPDT)的合成及其与铜的显色反应 .在OP存在下 ,在pH为 1 1 .0的硼砂 -氢氧化钠缓冲溶液中 ,该试剂能与铜发生显色反应 ,铜与NPCPDT形成摩尔比为 1∶3型的黄色配合物 ,在 4 5 0nm处有一最大正吸收 ,在 5 3 5nm处有一最大负吸收 .以 4 5 0nm为参比波长 ,5 3 5nm为测量波长进行双波长测定 ,表观摩尔吸光系数为 2 .4 2× 1 0 5L·mol-1 ·cm-1 ,铜的浓度在0～ 0 .6 μg/mL范围内符合比尔定律 .用拟定方法测定人发中的微量铜 ,结果满意     

1-(2-氯苄基)-2-(2-氯苯基)-苯并咪唑的合成及晶体结构

以邻氯苯甲醛和邻苯二胺直接关环合成了1-(2-氯苄基)-2-(2-氯苯基)-苯并咪唑.通过元素分析、红外分析对其进行了表征,并通过X-射线单晶衍射方法确定了其晶体结构.     

液-固流态化系统固体颗粒特性研究(1):颗粒的初始流态化速度v_(mf)

为数众多的计算颗粒初始流态化速度的公式大体上分为三类:第一类以Ergun公式为基础,引入经验系数加以修正;第二类以某种流体力学关系为基础;第三类属于纯经验公式。这三种类型中,以第一类式子有较大范围之Ar适应性,比较适用。本文提出的计算式子也属于Ergun型,从目前掌握的实验数据看来,比工程界广泛应用的Wen and Yu式子用于计算液-固流态化系统有更高的精确性,而且对球形与非球形颗粒都适用。     

基于4-(2,5-二甲基-4-羟基苯基)二氮杂萘酮的新型聚芳醚

目的合成一种新型既可溶解又耐高温的聚芳醚。方法从分子设计的角度出发,研究最佳合成方法及合成途径。结果合成了一种新型不对称杂环类双酚单体4-(2,5-二甲基-4-羟基苯基)二氮杂萘酮,分别与4种活性双卤单体经芳香亲核取代缩聚,制备了一系列聚芳醚聚合物。该系列聚芳醚特性粘度范围在0．39-0．79dL／g,玻璃化温度在232-284℃,氮气中5％和10％热失重温度分别是421-440℃和434-453℃,表现出良好的热性能。它们均为无定形结构,在室温下易溶于NMP、DMAc、DMF、Py、CHC13等有机溶剂中。结论该方法适宜于合成既可溶解又耐高温的聚芳醚。     

中频差Zeeman双折射双频激光干涉系统的实验研究

Zeeman双折射双频激光器能够输出3~40 MHz频差的双频激光,可用作高测速双频激光干涉仪的光源。针对这种激光器的特点,以频差约7 MHz的Zeeman双折射双频激光器为干涉仪的光源,建立了中频差双频激光干涉仪测量系统。经过与商用HP5528A双频激光干涉仪的比对测量实验得出,中频差双频激光干涉仪实验测量系统测量线性度小于0.002%,测量的标准不确定度小于0.1μm,证明了中频差双频激光干涉系统的可行性和针对这种光源采用的设计方案的正确性。