Detection of pulsed gamma rays above 100 GeV from the Crab pulsar

We report the detection of pulsed gamma rays from the Crab pulsar at energies above 100 giga-electron volts (GeV) with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) array of atmospheric Cherenkov telescopes. The detection cannot be explained on the basis of current pulsar models. The photon spectrum of pulsed emission between 100 mega-electron volts and 400 GeV is described by a broken power law that is statistically preferred over a power law with an exponential cutoff. It is unlikely that the observation can be explained by invoking curvature radiation as the origin of the observed gamma rays above 100 GeV. Our findings require that these gamma rays be produced more than 10 stellar radii from the neutron star.     

Discovery of pulsed OH maser emission stimulated by a pulsar

Stimulated emission of radiation has not been directly observed in astrophysical situations up to this time. Here we demonstrate that photons from pulsar B1641-45 stimulate pulses of excess 1720-megahertz line emission in an interstellar hydroxyl (OH) cloud. As this stimulated emission is driven by the pulsar, it varies on a few-millisecond time scale, which is orders of magnitude shorter than the quickest OH maser variations previously detected. Our 1612-megahertz spectra are inverted copies of the 1720-megahertz spectra. This "conjugate line" phenomenon enables us to constrain the properties of the interstellar OH line-producing gas. We also show that pulsar signals undergo significantly deeper OH absorption than do other background sources, which confirms earlier tentative findings that OH clouds are clumpier on small scales than are neutral hydrogen clouds.     

Gamma-ray flares from the Crab Nebula

A young and energetic pulsar powers the well-known Crab Nebula. Here, we describe two separate gamma-ray (photon energy greater than 100 mega-electron volts) flares from this source detected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The first flare occurred in February 2009 and lasted approximately 16 days. The second flare was detected in September 2010 and lasted approximately 4 days. During these outbursts, the gamma-ray flux from the nebula increased by factors of four and six, respectively. The brevity of the flares implies that the gamma rays were emitted via synchrotron radiation from peta-electron-volt (10(15) electron volts) electrons in a region smaller than 1.4 × 10(-2) parsecs. These are the highest-energy particles that can be associated with a discrete astronomical source, and they pose challenges to particle acceleration theory.     

Magnetar-like emission from the young pulsar in Kes 75

We report the detection of magnetar-like x-ray bursts from the young pulsar PSR J1846-0258, at the center of the supernova remnant Kes 75. This pulsar, long thought to be exclusively rotation-powered, has an inferred surface dipolar magnetic field of 4.9 x 10(13) gauss, which is higher than those of the vast majority of rotation-powered pulsars, but lower than those of the approximately 12 previously identified magnetars. The bursts were accompanied by a sudden flux increase and an unprecedented change in timing behavior. These phenomena lower the magnetic and rotational thresholds associated with magnetar-like behavior and suggest that in neutron stars there exists a continuum of magnetic activity that increases with inferred magnetic field strength.     

Discovery of powerful gamma-ray flares from the Crab Nebula

The well-known Crab Nebula is at the center of the SN1054 supernova remnant. It consists of a rotationally powered pulsar interacting with a surrounding nebula through a relativistic particle wind. The emissions originating from the pulsar and nebula have been considered to be essentially stable. Here, we report the detection of strong gamma-ray (100 mega-electron volts to 10 giga-electron volts) flares observed by the AGILE satellite in September 2010 and October 2007. In both cases, the total gamma-ray flux increased by a factor of three compared with the non-flaring flux. The flare luminosity and short time scale favor an origin near the pulsar, and we discuss Chandra Observatory x-ray and Hubble Space Telescope optical follow-up observations of the nebula. Our observations challenge standard models of nebular emission and require power-law acceleration by shock-driven plasma wave turbulence within an approximately 1-day time scale.     

An x-ray nebula associated with the millisecond pulsar B1957+20

We have detected an x-ray nebula around the binary millisecond pulsar B1957+20. A narrow tail, corresponding to the shocked pulsar wind, is seen interior to the known Halpha bow shock and proves the long-held assumption that the rotational energy of millisecond pulsars is dissipated through relativistic winds. Unresolved x-ray emission likely represents the shock where the winds of the pulsar and its companion collide. This emission indicates that the efficiency with which relativistic particles are accelerated in the postshock flow is similar to that for young pulsars, despite the shock proximity and much weaker surface magnetic field of this millisecond pulsar.     

Parameters of the plasma affecting the radiation of pulsar 1

Analysis of the relation between time delay and frequency for pulses from Pulsar 1 shows that the dispersive region of the ray path must exceed 300 astronomical units and have an average electron number density less than 8000 per cubic centimeter and average magnetic field strength less than 2 x 10(-3) gauss. These requirements almost guarantee that the observed dispersion takes place in the interstellar medium.     

蟹池主养泥鳅生态高效养殖试验

[目的]提高蟹池水体的利用率以及饲料转化率、养殖模式的抗风险能力。[方法]在江苏省宿迁市宿城区中扬镇养殖基地开展了蟹池主养泥鳅生态高效养殖试验。[结果]蟹池主养泥鳅生态高效养殖模式推荐苗种放养模式为:放养160只/kg的扣蟹21 000只/hm2,放养260尾/kg的泥鳅苗种78 000尾/hm2(300 kg/hm2)。[结论]与河蟹单养模式相比,蟹池主养泥鳅养殖模式饲料系数大幅度下降,可以明显提高蟹池的综合生产能力、生态效益和总体经济效益,是一种生态高效养殖模式。     

商品蟹冬季暂养技术研究

在相同地点、时间和水源的条件下 ,进行了池塘和大水面中网箱冬季暂养商品蟹的研究。结果表明 ,网箱中暂养的商品蟹暂养成活率平均高出池塘 4.6 % ,由于网箱中暂养的商品蟹活力强 ,品质明显好于池塘蟹 ,因此经济效益也高出池塘蟹。经过平均约 2个月的暂养 ,池塘蟹和网箱蟹平均实际增加经济收入分别为 19%和 6 7%。     

潮汕地区虾蟹壳提取甲壳素的工艺优化

采用传统酸碱法提取潮汕地区虾蟹壳中甲壳素,对HCl溶液浓度、HCl溶液用量、酸浸时间3个因素进行正交试验,确定虾壳中脱钙的最佳工艺为提取5.00 g虾壳需HCl溶液浓度1.50 mol/L,酸浸时间6 h,HCl溶液用量50.00 m L,氢氧化钠溶液浓度为2.00%,碱浸时间24 h时,平氢氧化钠溶液用量36.30 m L,甲壳素含量为22.40%;蟹壳中脱钙的最佳工艺为5.00 g蟹壳需HCl溶液浓度1.50 mol/L,酸浸时间6 h,HCl溶液用量75.00 m L,氢氧化钠溶液浓度2.00%,碱浸时间24 h,平均氢氧化钠溶液用量25.03 m L,甲壳素含量为19.80%。     

山区池塘河蟹生态养殖试验

2003～2004年在贵阳市花溪区鱼种场进行池塘河蟹生态养殖试验,其结果为：蟹鱼套养2004年总产值达到105315．75元,纯收入2764．43元／667m^2,蟹平均规格为128．15g,最大个体210g,平均单产115．33kg／667m^2,回捕率45％,鲢鳙鱼303．75kg,投入产出比为1：1．65。河蟹单养总产值达到32340元,纯收入2475．37元／667m^2,蟹平均规格为125.35g,最大个体为190g,平均单产为107．8kg／667m^2,回捕率为43％,投入产出比1：1．62。完成了该项目的各项指标,并取得了较好的经济效益和社会效益。     

Absorption features in the x-ray spectrum of an ordinary radio pulsar

The vast majority of known nonaccreting neutron stars (NSs) are rotation-powered radio and/or γ-ray pulsars. So far, their multiwavelength spectra have all been described satisfactorily by thermal and nonthermal continuum models, with no spectral lines. Spectral features have, however, been found in a handful of exotic NSs and were thought to be a manifestation of their unique traits. Here, we report the detection of absorption features in the x-ray spectrum of an ordinary rotation-powered radio pulsar, J1740+1000. Our findings bridge the gap between the spectra of pulsars and other, more exotic, NSs, suggesting that the features are more common in the NS spectra than they have been thought so far.     

河蟹营养需要研究进展

近些年来,随着河蟹规模化人工养殖的迅速发展,国内外均在河蟹营养需要方面开展了相应的探索与研究;河蟹营养需要的研究在蛋白质、必需氨基酸、碳水化合物、能量、维生素、矿物元素等营养素方面取得了一定的进展。     

超细蟹粉对污染水体重金属的吸附作用研究

[目的]研究超细蟹粉对污染水体重金属的吸附作用,使重金属回收再利用,解决水体重金属污染问题。[方法]将废弃蟹壳通过超细技术处理,以超细蟹粉为吸附剂,对水体中Pb2＋、Ni2＋、Cu2＋的去除进行静态吸附试验,研究蟹粉的细度、超细蟹粉用量、溶液初始pH、吸附时间、吸附温度等对吸附作用的影响,并确定最佳的吸附条件,以测定工业废水中Pb2＋、Ni2＋、Cu2＋的吸附率。[结果]超细蟹粉对Pb2＋、Ni2＋、Cu2＋吸附作用的最佳吸附条件为：在常温（25℃）,pH为6.0时,0.8 g超细蟹粉对Ni2＋和Cu2＋的吸附时间为120 min,而Pb2＋的吸附时间为150 min,可使吸附达到最佳状态。[结论]超细蟹粉对Pb2＋、Ni2＋、Cu2＋有很强的吸附能力,是一种有效的生物吸附剂。     

长春地区池塘养殖扣蟹的试验研究

１９９４年夏季，作者在长春首次进行扣蟹养殖试验。共投放三期蟹苗２．５ｋｇ，约６０００只。出池时，回捕扣蟹６．４ｋｇ，回捕率为６．１％，扣蟹平均体重为１８．５ｇ／只。文中对养殖扣蟹的投饲，清塘，蟹池建设等问题进行了探讨。     

对河蟹养殖业可持续发展若干问题的思考

依据河蟹生物学特性 ,结合河蟹养殖科研与生产的实践 ,针对当前河蟹养殖生产实践的现状 ,就当前河蟹养殖生产中存在的种质资源利用与保护、养殖技术的普及与提高、病害防治的途径和适度发展规模等问题进行了评述     

锯缘青蟹血细胞酚氧化酶活力及主要影响因子

研究了温度、pH、促进剂、抑制剂、菌体及免疫多糖对锯缘青蟹(Scylla serrata)血细胞裂解物(HLS)酚氧化酶(phenoloxidase,PO)活力的影响。试验结果表明:锯缘青蟹PO的最适作用温度为25℃,最适pH值为7.8;SDS、Ca2 、Mg2 均可提高PO的活力,其中Ca2 和Mg2 的最佳反应浓度分别为50 mmol/L和150 mmol/L,SDS的最佳反应浓度为2.5 mg/mL;叠氮钠、二乙基二硫代氨基甲酸钠、乙二胺四乙酸、Cu2 对PO活力有不同的抑制作用。发现拟态弧菌SS060818、气单胞菌Mr M0602、金黄色葡萄球菌ATCC25923、溶壁微球菌AS1.634对PO有激活作用,其中拟态弧菌和气单胞菌激活作用显著,金黄色葡萄球菌、溶壁微球菌对PO有弱激活作用;肽聚糖、拟态弧菌脂多糖粗提物可显著提高PO活力,肽聚糖、脂多糖的最佳激活浓度分别为2.7mg/mL、0.5 mg/mL。     

垫形双皮菌原质团发育形成子实体的观察

经过基物培养获得垫形双皮菌[Diderma effusum (Schw.) Morgan]原质团,将原质团转移到琼脂培养基上进行继代培养,采用多因子试验筛选子实体形成的条件,观察子实体发育过程的形态变化.结果表明:垫形双皮菌子实体为垫状孢囊至联囊体.原质团扇面完整浓厚、饥饿、湿润、20～25℃是垫形双皮菌子实体发育形成所必需的,而黑暗与散射光交替更利于子实体的形成.