A transient radio jet in an erupting dwarf nova

Astrophysical jets seem to occur in nearly all types of accreting objects, from supermassive black holes to young stellar objects. On the basis of x-ray binaries, a unified scenario describing the disc/jet coupling has evolved and been extended to many accreting objects. The only major exceptions are thought to be cataclysmic variables: Dwarf novae, weakly accreting white dwarfs, show similar outburst behavior to x-ray binaries, but no jet has yet been detected. Here we present radio observations of a dwarf nova in outburst showing variable flat-spectrum radio emission that is best explained as synchrotron emission originating in a transient jet. Both the inferred jet power and the relation to the outburst cycle are analogous to those seen in x-ray binaries, suggesting that the disc/jet coupling mechanism is ubiquitous.     

Very high energy gamma-ray binary stars

One of the major astronomical discoveries of the last two decades was the detection of luminous x-ray binary star systems in which gravitational energy from accretion is released by the emission of x-ray photons, which have energies in the range of 0.1 to 10 kiloelectron volts. Recent observations have shown that some of these binary sources also emit photons in the energy range of 10(12) electron volts and above. Such sources contain a rotating neutron star that is accreting matter from a companion. Techniques to detect such radiation are ground-based, simple, and inexpensive. Four binary sources (Hercules X-1, 4U0115+63, Vela X-1, and Cygnus X-3) have been observed by at least two independent groups. Although the discovery of such very high energy "gamma-ray binaries" was not theoretically anticipated, models have now been proposed that attempt to explain the behavior of one or more of the sources. The implications of these observations is that a significant portion of the more energetic cosmic rays observed on Earth may arise from the action of similar sources within the galaxy during the past few million years.     

Polarized gamma-ray emission from the galactic black hole Cygnus X-1

Because of their inherently high flux allowing the detection of clear signals, black hole x-ray binaries are interesting candidates for polarization studies, even if no polarization signals have been observed from them before. Such measurements would provide further detailed insight into these sources' emission mechanisms. We measured the polarization of the gamma-ray emission from the black hole binary system Cygnus X-1 with the International Gamma-Ray Astrophysics Laboratory Imager on Board the Integral Satellite (INTEGRAL/IBIS) telescope. Spectral modeling of the data reveals two emission mechanisms: The 250- to 400-keV (kilo-electron volt) data are consistent with emission dominated by Compton scattering on thermal electrons and are weakly polarized. The second spectral component seen in the 400-keV to 2-MeV band is by contrast strongly polarized, revealing that the MeV emission is probably related to the jet first detected in the radio band.     

Periodic emission from the gamma-ray binary 1FGL J1018.6-5856

Gamma-ray binaries are stellar systems containing a neutron star or black hole, with gamma-ray emission produced by an interaction between the components. These systems are rare, even though binary evolution models predict dozens in our Galaxy. A search for gamma-ray binaries with the Fermi Large Area Telescope (LAT) shows that 1FGL J1018.6-5856 exhibits intensity and spectral modulation with a 16.6-day period. We identified a variable x-ray counterpart, which shows a sharp maximum coinciding with maximum gamma-ray emission, as well as an O6V((f)) star optical counterpart and a radio counterpart that is also apparently modulated on the orbital period. 1FGL J1018.6-5856 is thus a gamma-ray binary, and its detection suggests the presence of other fainter binaries in the Galaxy.     

大孔吸附树脂纯化矮牵牛花红色素

比较了大孔吸附树脂D61和X-5对牵牛花红色素的吸附效果及纯化牵牛花红色素的方法。结果表明：X-5树脂吸附牵牛花红色素的能力较强，吸附量为76．1mg／g湿树脂；洗脱液以甲醇洗脱效果最佳，洗脱回收率92％左右。     

High-resolution x-ray imaging of a globular cluster core: compact binaries in 47Tuc

We have obtained high-resolution (approximately 1") deep x-ray images of the globular cluster 47Tucanae (NGC 104) with the Chandra X-ray Observatory to study the population of compact binaries in the high stellar density core. A 70-kilosecond exposure of the cluster reveals a centrally concentrated population of faint (Lx approximately 10(30-33) ergs per second) x-ray sources, with at least 108 located within the central 2' x 2.5' and greater, similar half with Lx approximately 10(30.5) ergs per second. All 15 millisecond pulsars (MSPs) recently located precisely by radio observations are identified, though 2 are unresolved by Chandra. The x-ray spectral and temporal characteristics, as well as initial optical identifications with the Hubble Space Telescope, suggest that greater, similar50 percent are MSPs, about 30 percent are accreting white dwarfs, about 15 percent are main-sequence binaries in flare outbursts, and only two to three are quiescent low-mass x-ray binaries containing neutron stars, the conventional progenitors of MSPs. An upper limit of about 470 times the mass of the sun is derived for the mass of an accreting central black hole in the cluster. These observations provide the first x-ray "color-magnitude" diagram for a globular cluster and census of its compact object and binary population.     

Discovery of very high energy gamma rays associated with an x-ray binary

X-ray binaries are composed of a normal star in orbit around a neutron star or stellar-mass black hole. Radio and x-ray observations have led to the presumption that some x-ray binaries called microquasars behave as scaled-down active galactic nuclei. Microquasars have resolved radio emission that is thought to arise from a relativistic outflow akin to active galactic nuclei jets, in which particles can be accelerated to large energies. Very high energy gamma-rays produced by the interactions of these particles have been observed from several active galactic nuclei. Using the High Energy Stereoscopic System, we find evidence for gamma-ray emission of >100 gigaelectron volts from a candidate microquasar, LS 5039, showing that particles are also accelerated to very high energies in these systems.     

大孔树脂对管花肉苁蓉2种苷类静态吸附分离特性研究

松果菊苷和毛蕊花糖苷为管花肉苁蓉主要活性成分。以松果菊苷和毛蕊花糖苷为标准品,通过高效液相色谱仪确定样品质量浓度,从而比较8种供试树脂的吸附性能,以筛选出适宜分离此2种成分的大孔树脂。结果表明,X-5和HP-20吸附性能较好,进一步研究表明,X-5对松果菊苷吸附量最大,为50.03 mg/g,其次是HP-20,为46.05 mg/g;HP-20对毛蕊花糖苷的吸附量最大,为32.65 mg/g,其次是X-5,为27.56 mg/g。X-5对松果菊苷的解析能力最强,为77.35%,HP-20次之,为60.36%;X-5对毛蕊花糖苷的解析效果最好,为72.57%,其次是HP-20,为63.40%。2种树脂吸附量在前1 h变化最快,随时间的变化吸附能力逐渐减弱。X-5对试样原液(pH 3.43)中松果菊苷和毛蕊花糖苷的吸附性能优于HP-20,且当pH=6.02时对松果菊苷和毛蕊花糖苷的吸附量最大。确定X-5与HP-20分别为松果菊苷和毛蕊花糖苷的理想吸附树脂。综合比较吸附量和解析率等因素,确定X-5为分离纯化松果菊苷和毛蕊花糖苷的首选树脂。     

梅花杂交种茎段培养影响因素的研究

对两个梅花杂交种优良单株‘X-9’、‘X-55’进行茎段培养的试验研究。通过对采枝时期、培养基种类、消毒方法的对比试验,探索影响梅杂交种茎段腋芽萌发及生长的因素。结果表明:5月上旬到6月中旬是茎段培养的最佳时期;污染率会因品种不同而有差异;消毒方法以0.1%升汞5min最好;两个杂交种最适启动培养基为WPM+0.5mgL6-BA+0.1mgLNAA。     

大孔树脂纯化盐地碱蓬红色素的工艺研究

为纯化盐地碱蓬红色素,提高其色价,选取X-5、HPD300、D101、HPD400、NKA-9和AB-8等6种大孔树脂对盐地碱蓬红色素进行静态吸附试验,筛选最佳纯化色素树脂,并研究最佳树脂对盐地碱蓬红色素的纯化工艺条件.结果表明,X-5大孔树脂对盐地碱蓬红色素的吸附和解吸效果较好.在动态吸附中,当上样液浓度为1 mg/mL、pH值为6、流速为5 BV/h时,X-5对盐地碱蓬红色素吸附效果最好;以60％乙醇溶液为洗脱剂,洗脱流速为5 BV/h时,解吸效果最好;盐地碱蓬红色素纯化后,色价提高了6.14倍.     

荨麻中3,4-二香草基四氢呋喃的提取及纯化

[目的]研究荨麻中3,4-二香草基四氢呋喃的提取以及纯化,为进一步研究荨麻中3,4-二香草基四氢呋喃的作用机制奠定基础。[方法]采用醇水溶液回流提取,研究大孔吸附树脂吸附和分离狭叶荨麻提取液中3,4-二香草基四氢呋喃的方法和条件,并采用超滤膜纯化技术对其进行纯化。[结果]X-5大孔吸附树脂对3,4-二香草基四氢呋喃有较好的吸附能力;乙醇浓度为60%时解吸效果最好,解析液浓缩,超滤膜纯化重结晶后,荨麻中3,4-二香草基四氢呋喃纯度可达85.3%。[结论]采用X-5大孔吸附树脂以及超滤膜纯化技术可有效地提取荨麻中3,4-二香草基四氢呋喃,为今后荨麻中有效成分的研究与开发应用提供理论依据。     

大孔吸附树脂纯化小米枣黄酮的初步研究

为探讨利用大孔吸附树脂分离纯化小米枣黄酮的最佳工艺条件,以湖南衡南县产的小米枣为试材,进行了不同大孔吸附树脂的静态吸附与解吸及动态吸附与解吸试验,同时考察了X-5大孔吸附树脂的动态吸附与解吸条件。结果表明:在供试的5种大孔吸附树脂中,以X-5大孔吸附树脂的吸附及解吸性能最佳,其对黄酮的动态吸附率为79.50%,动态解吸率为99.53%;其分离纯化小米枣黄酮的最佳工艺参数为:上样液浓度0.263 mg/m L,上样液p H值5.0,洗脱剂为70%乙醇,洗脱剂p H值6.0,经该工艺条件纯化后,黄酮的纯度达68.12%。     

Combinatorial electrochemistry: A highly parallel, optical screening method for discovery of better electrocatalysts

Combinatorial screening of electrochemical catalysts by current-voltage methods can be unwieldy for large sample sizes. By converting the ions generated in an electrochemical half-cell reaction to a fluorescence signal, the most active compositions in a large electrode array have been identified. A fluorescent acid-base indicator was used to image high concentrations of hydrogen ions, which were generated in the electrooxidation of methanol. A 645-member electrode array containing five elements (platinum, ruthenium, osmium, iridium, and rhodium), 80 binary, 280 ternary, and 280 quaternary combinations was screened to identify the most active regions of phase space. Subsequent "zoom" screens pinpointed several very active compositions, some in ternary and quaternary regions that were bounded by rather inactive binaries. The best catalyst, platinum(44)/ruthenium(41)/osmium(10)/iridium(5) (numbers in parentheses are atomic percent), was significantly more active than platinum(50)/ruthenium(50) in a direct methanol fuel cell operating at 60 degreesC, even though the latter catalyst had about twice the surface area of the former.     

Orbital motion in the radio galaxy 3C 66B: evidence for a supermassive black hole binary

Supermassive black hole binaries may exist in the centers of active galactic nuclei such as quasars and radio galaxies, and mergers between galaxies may result in the formation of supermassive binaries during the course of galactic evolution. Using the very-long-baseline interferometer, we imaged the radio galaxy 3C 66B at radio frequencies and found that the unresolved radio core of 3C 66B shows well-defined elliptical motions with a period of 1.05 +/- 0.03 years, which provides a direct detection of a supermassive black hole binary.     

大孔树脂纯化葛花总异黄酮的工艺条件研究

以葛花总异黄酮含量及回收率为考察指标,选用大孔树脂对葛花总异黄酮进行分离纯化。结果表明,X-5树脂对葛花总异黄酮有较好的吸附和解吸效果,最佳工艺条件为:洗脱剂为70%乙醇;洗脱剂用量为3倍树脂体积;流速为2 mL/min;葛花总异黄酮上样液的质量浓度为2 mg/mL,速率为2 mL/min;冲洗杂质用水体积为20 mL。试验表明,该法简单可行,分离效果好,经X-5处理后的葛花异黄酮含量可达54%。     

正交设计优化大孔吸附树脂提取分离刺山柑中总黄酮的研究

以新疆吐鲁番野生刺山柑果实为原料,分别比较了不同乙醇浓度、料液比、超声时间对刺山柑总黄酮的提取率的影响,以正交试验进行筛选分析,选择最佳的提取条件;利用静态及动态吸附-洗脱试验筛选出提取效果较好的大孔树脂对刺山柑总黄酮进行分离。结果表明,在室温下以乙醇浓度为70％、超声时间为60min、料液比1：20时提取效果最佳。静态吸附-洗脱试验筛选出H103、X-5和AB-8树脂对总黄酮的分离效果较好,从动态分离黄酮的实验表明H103型大孔树脂分离效果最佳,总黄酮含量达到63．98％。     

ASTRONOMY: The Distance to the Large Magellanic Cloud

The Large Magellanic Cloud (LMC), a satellite of the Milky Way, is an important yardstick by which most intergalactic distances are measured. But as Cole explains in this Perspective, how far away the LMC is remains a matter of dispute, with far reaching implications in cosmology. But observations of Cepheids and of eclipsing binaries, two types of stars that allow absolute luminosity and thus absolute distances to be determined, are promising to resolve this important issue in the not too distant future.     

塿土对阴－非离子表面活性剂的吸附特征研究

以平衡吸附法研究了塿土对阴离子表面活性剂(SDS)、非离子表面活性剂(TritonX-100、Tween80和Brij35)的吸附特征,考察了pH、阴-非离子表面活性剂混合对塿土吸附表面活性剂的影响.结果表明,非离子表面活性剂在填土上吸附等温线均呈L型,且均符合Freundlich和Langmuir方程;壤土对SDS的吸附等温线呈LS型,可用Freundlich方程来描述;塿土对4种表面活性剂吸附量的大小顺序为Tween80＞SDS＞Brij35＞TfitonX-100.当阴-非离子表面活性剂一起进入土壤中,SDS-Brij35之间的相互影响不大;TritonX-100与SDS相互作用较大,无论二者以何种方式混合都会使TritonX-100在壤土上的吸附量增加,SDS的吸附量下降;SDS与Tween80之间的相互作用最大,混合后吸附量均下降,但Tween80吸附量降低的幅度最大.pH对非离子表面活性剂的吸附影响不大,而随着pH的增加,塿土对SDS的吸附百分率明显下降;在pH为8.0时,填土对非离子表面活性剂的吸附百分率达到80%以上.因此在选择合适的表面活性剂进行有机污染土壤修复和治理时,考虑土壤的特性和表面活性剂的结构是非常重要的.     

豆杰添加不同助剂防除大豆田鸭跖草等阔叶杂草效果及安全性评价

为探讨豆杰添加不同助剂对大豆田阔叶杂草的防除效果及安全性,选用豆杰84WDG 22.5 g/hm2添加4种助剂Ecosurf SA-9、Triton X-100和Tergitol L-62、ULD-E于大豆出苗后喷施。结果表明：施药10天后目测各处理对大豆田鸭跖草、刺儿菜、苣买菜等的鲜重防效都达到了60%以上;但对藜、问荆无效,除ULD-E对大豆有触杀型药害,大豆叶部有黄裼色斑点外,其余3种助剂对大豆均安全。施药45天后各处理对各种杂草株防效均较差,对鸭跖草、刺儿菜的鲜重防效：豆杰+X-100分别达到89.7%、98.1%以上,豆杰+SA-9在95.9%、78.8%以上,豆杰+L-62在92.5%、97.2%以上,豆杰+ULD-E在91.5%、92.7%以上,各处理对苣荬菜的鲜重防效也较好,在85.2%以上,对苍耳、豨莶的防效均达到100%,各处理均好于豆杰单剂处理。从不同助剂的浓度看,以1000倍液对各杂草的防除效果最佳,其次是2000倍液,再次是500倍液。目测豆杰+助剂除草效果的依次为：Ecosurf SA-9> Triton X-100> Tergitol L-62 > ULD-E。     

Observation of charge transport by negatively charged excitons

We report transport of electron-hole complexes in semiconductor quantum wells under applied electric fields. Negatively charged excitons (X-), created by laser excitation of a high electron mobility transistor, are observed to drift upon applying a voltage between the source and drain. In contrast, neutral excitons do not drift under similar conditions. The X- mobility is found to be as high as 6.5 x 10(4) cm2 V-1 s-1. The results demonstrate that X- exists as a free particle in the best-quality samples and suggest that light emission from opto-electronic devices can be manipulated through exciton drift under applied electric fields.