共查询到20条相似文献，搜索用时 345 毫秒
1.
The physical nature of ultraluminous x-ray sources is uncertain. Stellar-mass black holes with beamed radiation and intermediate black holes with isotropic radiation are two plausible explanations. We discovered radio emission from an ultraluminous x-ray source in the dwarf irregular galaxy NGC 5408. The x-ray, radio, and optical fluxes as well as the x-ray spectral shape are consistent with beamed relativistic jet emission from an accreting stellar black hole. If confirmed, this would suggest that the ultraluminous x-ray sources may be stellar-mass rather than intermediate-mass black holes. However, interpretation of the source as a jet-producing intermediate-mass black hole cannot be ruled out at this time. 相似文献
2.
The ultraluminous x-ray source (ULX) in the galaxy M82 has been identified as a possible intermediate-mass black hole formed in stellar collisions in the super star cluster MGG 11. The x-ray flux from M82 is modulated, with a peak-to-peak amplitude corresponding to an isotropic luminosity of 2.4 _ 1040 erg s-1 in M82 and a period of 62.0 +/- 2.5 days, which we interpret as the orbital period of the ULX binary. This orbital period implies that the mass-donor star must be a giant or supergiant. Large mass-transfer rates, sufficient to fuel the ULX, are expected for a giant-phase mass donor in an x-ray binary. The giant phase has a short lifetime, indicating that we see the ULX in M82 in a brief and unusual period of its evolution. 相似文献
3.
【目的】研究不同密度处理下对花生农艺性状及产量的影响,分析密度与产量的最佳配置。【方法】选取3种花育系列花生品种(花育25号、花育33号和花育36号),设置4个种植密度水平(1.2×105、1.5×105、1.8×105和2.1×105穴/hm2)处理进行列区设计试验,测定不同种植密度下各花生品种的主茎高、侧枝长等主要农艺性状以及产量,筛选最佳种植密度。【结果】密度为1.2×105~1.5×105穴/hm2主茎高要显著大于密度为1.8×105~2.1×105穴/hm2;密度处理为1.5×105穴/hm2的侧枝长比其他处理显著高出1~6.8 cm;单株果数和饱果数均在低密度下最大,随密度的增大而减小;种植密度对总分枝和结果枝影响差异不显著;花育33号在种植密度为1.5×105穴/hm2时产量为最大,为4 555.58 kg/hm2,其次是花育36号、密度为1.8×105穴/hm2处理,第三是花育25号、密度为1.5×105穴/hm2处理。【结论】花育系列花生品种种植密度为1.5×105~1.8×105穴/hm2。 相似文献
4.
We show that the black hole in the x-ray binary Cygnus X-1 was formed in situ and did not receive an energetic trigger from a nearby supernova. The progenitor of the black hole had an initial mass greater than 40 solar masses, and during the collapse to form the approximately 10-solar mass black hole of Cygnus X-1, the upper limit for the mass that could have been suddenly ejected is approximately 1 solar mass, much less than the mass ejected in a supernova. The observations suggest that high-mass stellar black holes may form promptly, when massive stars disappear silently. 相似文献
5.
The origin of jets emitted from black holes is not well understood; however, there are two possible energy sources: the accretion disk or the rotating black hole. Magnetohydrodynamic simulations show a well-defined jet that extracts energy from a black hole. If plasma near the black hole is threaded by large-scale magnetic flux, it will rotate with respect to asymptotic infinity, creating large magnetic stresses. These stresses are released as a relativistic jet at the expense of black hole rotational energy. The physics of the jet initiation in the simulations is described by the theory of black hole gravitohydromagnetics. 相似文献
6.
研究以减毒沙门氏菌为载体的生长抑素基因疫苗对肉鸡的血浆生化指标和免疫器官指数的影响。将28日龄的150只肉鸡随机分为5个组,每组30只,A、B、C组口服生长抑素基因疫苗,剂量分别为8×109CFU/只、4×109CFU/只、1×109CFU/只,D组口服生理盐水,作为对照组,E组口服减毒沙门氏菌CS022,2周后加强免疫1次。结果表明:口服pcS/2SS基因疫苗后,C组(1×109CFU/只)肉鸡的白蛋白含量较D组明显增加(P<0.05),8周龄时和10周龄时尿素氮含量较D组明显降低(P<0.05)。pcS/2SS基因疫苗对血浆总蛋白、葡萄糖、游离脂肪酸的含量影响不明显。免疫器官指数方面,各组差异不显著(P>0.05),但1×109CFU/只剂量组较对照组(D组)有升高趋势。由以上结果可以看出,口服生长抑素基因疫苗可以提高肉鸡血浆白蛋白的含量,降低肉鸡血浆尿素氮含量,对血浆总蛋白、葡萄糖、游离脂肪酸的含量影响不明显,免疫器官指数有升高趋势,1×109CFU/只为较适宜剂量。 相似文献
7.
Black holes are most often detected by the radiation produced when they gravitationally pull in surrounding gas, in a process called accretion. The efficiency with which the hot gas radiates its thermal energy strongly influences the geometry and dynamics of the accretion flow. Both radiatively efficient thin disks and radiatively inefficient thick disks are observed. When the accreting gas gets close to the central black hole, the radiation it produces becomes sensitive to the spin of the hole and the presence of an event horizon. Analysis of the luminosities and spectra of accreting black holes has yielded tantalizing evidence for both rotating holes and event horizons. Numerical simulations imply that the relativistic jets often seen from accreting black holes may be powered in part by the spin of the hole. 相似文献
8.
RC Reis JM Miller MT Reynolds K Gültekin D Maitra AL King TE Strohmayer 《Science (New York, N.Y.)》2012,337(6097):949-951
Supermassive black holes (SMBHs; mass is greater than or approximately 10(5) times that of the Sun) are known to exist at the center of most galaxies with sufficient stellar mass. In the local universe, it is possible to infer their properties from the surrounding stars or gas. However, at high redshifts we require active, continuous accretion to infer the presence of the SMBHs, which often comes in the form of long-term accretion in active galactic nuclei. SMBHs can also capture and tidally disrupt stars orbiting nearby, resulting in bright flares from otherwise quiescent black holes. Here, we report on a ~200-second x-ray quasi-periodicity around a previously dormant SMBH located in the center of a galaxy at redshift z = 0.3534. This result may open the possibility of probing general relativity beyond our local universe. 相似文献
9.
不同种植方式密植对花生开花结实的影响 总被引：1，自引：1，他引：0
以珍珠豆型花生远杂6号为研究材料,采用裂区试验,调查了夏直播花生在不同密度和不同种植模式下的开花物候、群体开花规律、群体成针、成果特性及产量性状等指标的变化,探讨了合理密植对花生群体生殖生长及产量的影响。结果表明:2.25×10~5穴/hm~2密度种植比1.80×10~5穴/hm~2始花时间晚1～2 d;第一对侧枝基部10 cm内节数减少了10.29%;有效分枝比率提高8.50%;饱果率和出仁率分别提高3.81%、2.25%。宽窄行种植比等行距种植始花时间提前2～3 d,饱果率和出仁率分别提高3.03%、1.58%。双粒播种比单粒播种有效分枝比率提高10.60%,饱果率和出仁率分别提高3.70%、1.43%。2.25×~穴/hm~2宽窄行双粒种植的群体开花总量最高(1 873.31万朵/hm~2),群体果针数和结果数也最多,分别达1 365万个/hm~2和488万个/hm~2。远杂6号为耐密品种,夏直播种植,适当增加种植密度可有效提高产量,改善荚果商品性。 相似文献
10.
11.
Begelman MC 《Science (New York, N.Y.)》2003,300(5627):1898-1903
Black holes are common objects in the universe. Each galaxy contains large numbers-perhaps millions-of stellar-mass black holes, each the remnant of a massive star. In addition, nearly every galaxy contains a supermassive black hole at its center, with a mass ranging from millions to billions of solar masses. This review discusses the demographics of black holes, the ways in which they interact with their environment, factors that may regulate their formation and growth, and progress toward determining whether these objects really warp spacetime as predicted by the general theory of relativity. 相似文献
12.
Mazzali PA Valenti S Della Valle M Chincarini G Sauer DN Benetti S Pian E Piran T D'Elia V Elias-Rosa N Margutti R Pasotti F Antonelli LA Bufano F Campana S Cappellaro E Covino S D'Avanzo P Fiore F Fugazza D Gilmozzi R Hunter D Maguire K Maiorano E Marziani P Masetti N Mirabel F Navasardyan H Nomoto K Palazzi E Pastorello A Panagia N Pellizza LJ Sari R Smartt S Tagliaferri G Tanaka M Taubenberger S Tominaga N Trundle C Turatto M 《Science (New York, N.Y.)》2008,321(5893):1185-1188
The only supernovae (SNe) to show gamma-ray bursts (GRBs) or early x-ray emission thus far are overenergetic, broad-lined type Ic SNe (hypernovae, HNe). Recently, SN 2008D has shown several unusual features: (i) weak x-ray flash (XRF), (ii) an early, narrow optical peak, (iii) disappearance of the broad lines typical of SN Ic HNe, and (iv) development of helium lines as in SNe Ib. Detailed analysis shows that SN 2008D was not a normal supernova: Its explosion energy (E approximately 6x10(51) erg) and ejected mass [ approximately 7 times the mass of the Sun (M(middle dot in circle))] are intermediate between normal SNe Ibc and HNe. We conclude that SN 2008D was originally a approximately 30 M(middle dot in circle) star. When it collapsed, a black hole formed and a weak, mildly relativistic jet was produced, which caused the XRF. SN 2008D is probably among the weakest explosions that produce relativistic jets. Inner engine activity appears to be present whenever massive stars collapse to black holes. 相似文献
13.
【目的】选用自选育成的16个玉米自交系进行配合力和聚类分析,为玉米自交系的利用和强优势组合的选配提供参考。【方法】以5个玉米自交系为测验种,按NCⅡ遗传交配设计配制55个测交组合,进行产量配合力效应及聚类分析。【结果】16个玉米自交系的产量配合力差异显著,M9、M3、M1和F3、F2的GCA较高;组合M10×F3、M9×F3、M1×F3、M3×F2、M4×F2、M9×F2、M3×F3、M6×F3、M5×F3、M11×F2的配合力总效应较高,为强优势组合,其利用潜力较大。根据产量SCA进行聚类分析,可将16个自交系分为5类：M1、M6为第Ⅰ类群;M2、M7、M9、M3、M5为第Ⅱ类群;M8、M11、F1为第Ⅲ类群;F2、F3为第Ⅳ类群;M4、M10、F4、F5为第Ⅴ类群。【结论】自交系M3、M9和F2、F3的GCA和SCA效应均较高,具有较高的利用价值,与其他自交系组配,较易选育出较高产的玉米杂交组合。 相似文献
14.
We review the likely population, observational properties, and broad implications of stellar-mass black holes and ultraluminous x-ray sources. We focus on the clear empirical rules connecting accretion and outflow that have been established for stellar-mass black holes in binary systems in the past decade and a half. These patterns of behavior are probably the keys that will allow us to understand black hole feedback on the largest scales over cosmological time scales. 相似文献
15.
Lo KY 《Science (New York, N.Y.)》1986,233(4771):1394-1403
Studies of active galactic nuclei constitute one of the major efforts in astronomy. Massive black holes are the most likely source for the enormous energy radiated from such nuclei. Observations reviewed here suggest unusual activity and the possible existence of a massive black hole in the nucleus of our galaxy. Because of its proximity to Earth, our galactic nucleus can be observed in unsurpassed detail and may serve as the Rosetta stone both for deciphering active galactic nuclei and for confirming the existence of a massive black hole. 相似文献
16.
由黑洞的熵计算其温度 总被引：1，自引：0，他引：1
通过黑洞热力学第一定律,由黑洞的熵来计算黑洞的温度．由此方法算出的史瓦西黑洞和克尔-纽曼黑洞的温度与以前的结果相符,Vaidya黑洞的温度与引入新的乌龟坐标变换后算得的结果一致． 相似文献
17.
[目的]研究蜡蚧轮枝菌MZ041024菌株对平菇厉眼蕈蚊成虫的致病力。[方法]以采集于蒙自食用菌栽培地的菌袋上的平菇厉眼蕈蚊为试材,蜡蚧轮枝菌MZ041024菌株的分生孢子浓度共设5．0×10^4～5．0×10^8个／ml的5个处理浓度,对平菇厉眼蕈蚊成虫进行室内毒力测定。[结果]蜡蚧轮枝菌MZ041024菌株对平菇厉眼蕈蚊成虫的毒力随分生孢子浓度的增加而增强,第2天开始出现平菇厉眼蕈蚊成虫死亡,在5．0×10^4～5．0×10^8个/ml的5个浓度处理的成虫死亡率分别为31．92％、45．16％、62．25％、73．03％和79．78％;第4～7天的致死中浓度（LC50）分别为3．581×10^8、2．451×10^7、4．218×10^6和2．648×10^5个／ml;5．0×10^5～5．0×10^8个／ml浓度下成虫的致死中时间（LT50）随着分生孢子浓度的增加而逐渐缩短,由7．5d缩短到4．8d。[结论]蜡蚧轮枝菌MZ041024菌株在室内对平菇厉眼蕈蚊成虫具有较强的毒力和较好的防治效果。 相似文献
18.
About 20% of all massive stars in the Milky Way have unusually high velocities, the origin of which has puzzled astronomers for half a century. We argue that these velocities originate from strong gravitational interactions between single stars and binaries in the centers of star clusters. The ejecting binary forms naturally during the collapse of a young (≤1 million years old) star cluster. This model replicates the key characteristics of OB runaways in our galaxy, and it explains the presence of runaway stars of ≥100 solar masses (M(⊙)) around young star clusters, such as R136 and Westerlund 2. The high proportion and the distributions in mass and velocity of runaways in the Milky Way are reproduced if the majority of massive stars are born in dense and relatively low-mass (5000 to 10,000 M(⊙)) clusters. 相似文献
19.
20.
［目的］ 报道了粉拟青霉（Isaria farinosa）对菜蚜（Lipaphis erysimi）的致病力,为探索对菜蚜的有效生物防治方法提供参考。［方法］用无菌水将粉拟青霉分生孢子从PDA平板上洗出,配制成1.5×10^8孢子/ml的高浓度孢子悬浮液用于蚜虫感染试验;将配制成的孢子悬浮液按梯度稀释法制成孢子数分别为1.5×10^4（pf1）、1.5×10^5（pf2）、1.5×10^6（pf3）、1.5×10^7（pf4）、1.5×10^8（pf5）孢子/ml 的5个浓度用于毒力测定。［结果］在用粉拟青霉1.5×10^8孢子/ml的孢子悬浮液处理7 d后,菜蚜的感染率达到9222%,死亡率为100%,校正死亡率为83.33%。说明粉拟青霉菌株PFCB001对菜蚜易造成侵染,并具有很高的毒力。粉拟青霉对菜蚜的毒力回归方程为：y=0.595 7x-3.324 0,LC50为3.799 0×10^5孢子/ml,随着孢子浓度升高,蚜虫的死亡率也随之升高,时间越长,菜蚜死亡率越高。［结论］粉拟青霉对菜蚜具有良好的致病性,运用粉拟青霉防治菜蚜具有很大的潜力。 相似文献