Slope variations on the surface of Phobos     

Muinonen K  Lumme K  Irvine WM 《Planetary and Space Science》1991,39(1-2):327-334

It has been suggested that slope fluctuations on the scale of pixel dimensions could be determined by statistical photoclinometry. A closer study of the surface of Phobos reveals variations in the scattering properties of single particles and micro-structures formed by the particles. In the present context, the photoclinometric method of brightness moments is extended to account for these variations by allowing statistical fluctuations in the phase function of the assumed Lommel-Seeliger scattering law. The mean slope on the investigated regions of Phobos has been found to vary from approximately 12 degrees on a 61m scale to approximately 7 degrees on a 216-272m scale. On the same scales, a value of the order of 2% has been obtained for the standard deviation of the scattering phase function. Hints of a fractal-like scale-invariance have been noticed in the covariance function of brightness.  相似文献   

The organochlorine contamination history of the Mersey estuary, UK, revealed by analysis of sediment cores from salt marshes   总被引：2，自引：0，他引：2  

Fox WM  Connor L  Copplestone D  Johnson MS  Leah RT 《Marine environmental research》2001,51(3):213-227

Sediment profiles in the Banks, Ince and Widnes Warth salt marshes in Northwest England contain a mappable record of historic pollution. For persistent organochlorine compounds this stretches back over 90 years. The PCB and HCH profiles can be successfully rationalised by dating methods, and they can be related to the dates of initial production and subsequent withdrawal from use of these chemicals as a result of restrictive environmental legislation. HCB has a more complex pollution profile as it has been manufactured in Northwest England, both deliberately as a pesticide and accidentally as a by-product of several chlorination processes, dating back to the start of the 20th century. The concentrations of degradation products of DDT are relatively constant through the sediment profile and are dominated by op'- and pp'-DDD with only minor contributions from the most toxic species, pp'-DDT. The quantities of these compounds resident in the reservoir of pollutants under these marshes have been calculated, and have fallen progressively in the last 30-50 years.  相似文献   

中美海-气第四次西太平洋联合调查圆满结束     

刘纪元 《海洋预报》1988,(3)

中美热带西太平洋海-气相互作用合作研究第四次科学考察工作于1988年4月20日-6月8日,历时50天、船程1500余海里,获得了大量调查资料,达到了预期目的,圆满地完成了任务。 本次科学考察的科学家和技术人员,中方50名、美方12名。调查海区为18°20＇N—10°30＇S、122°-165°E,观测了298个XBT站、106个CTD站,在这些测站上同时进行了海洋生物学、海洋化学中的26个要素的观测、分析。并且顺利地回收、施放大洋长期锚定浮标各一个,布放漂流浮标8个,多普勒声学海流测量8000余海里。本航次增加了气象全天空照像、太阳辐射记录、大气凝结核记录和气溶胶——冰核取样等项目。还收集了热带西太平洋海域大量的气象情报资料,为研究海-气相互作用、诊断埃尔-尼诺现象提供了科学依据。 本次作业虽难度大,其中有四条调查断面的部分测站距海岸近(只有3海里)、漂流速度大,且海底地形复杂、气象变化多端,给调查工作带来了很大困难,但在中美双方科研工  相似文献   

海洋资料浮标工作会议在津召开     

刘纪元 《海洋预报》1993,(1)

国家海洋局海洋资料浮标工作会议于1992年7月14日至16日在天津召开,来自局内外的17单位和部门的37名代表出席了会议。国家海洋局陈炳鑫副局长到会并讲话,叶人秒副司长作“依靠科技进步、狠抓措施落实、提高整体效益、把浮标网建设提高到一个新水平”的工作报告。他说,从1985年决定建设国家海洋资料浮标网开始,在全局上下、局内局外的共同努力下,现在初步建成具有一定规模的、配套基本齐全的海洋资料浮标业务运行系统。海洋资料浮标是一个海上“无人观测站”,七年来,先后在12个浮标站位上布放37个站次浮标,其中9个站已经有一年连续或基本连续的海洋资料,截至1991年,共获得有效数据资料161兆字节。这些资料对海洋环境预报、海洋灾害警报,海洋资源开发、海洋工程建设和科学研究都是十分宝贵的。  相似文献   

发展与不发展热带扰动分析比较     

Gray  WH 刘纪元 《海洋技术学报》1997,16(2):90-94

发展与不发展热带扰动分析比较Ｗ·Ｍ·Ｇｒａｙ利用气象卫星可见光及红外数字化资料，结合探空资料，分析并比较了西北太平洋上发展和不发展扰动间的差别。结果表明：扰动的深对流量及其强度与扰动发展为热带风暴的潜势并没有良好的关系。热带风暴的“发生”与深对流的特...  相似文献   

在大西洋快速加强气旋试验期间海面温度分布对爆发性气旋生成的作用     

Lape.  WM 赵汉光 《气象科技》1993,(2):57-62

1 引言许多研究者提出墨西哥湾流的暖水对气旋爆发性加深提供了必需的能量,这种爆发性加深是冬季在美国和加拿大东海岸附近的海面上一种经常观测到的海洋气旋生成时所特有的现象。可是,许多研究(Nuss 和 An-thes,1987;Kuo 和 Low-Nam,1990;Kuo  相似文献   

The detection of interstellar methylcyanoacetylene     

Broten NW  MacLeod JM  Avery LW  Irvine WM  Hoglund B  Friberg P  Hjalmarson A 《The Astrophysical journal》1984,(1):L25-L29

A new interstellar molecule, methylcyanoacetylene (CH3C3N), has been detected in the molecular cloud TMC-1. The J = 8 --> 7, J = 7 --> 6, J = 6 --> 5, and J = 5 --> 4 transitions have been observed. For the first three of these, both the K = 0 and K = 1 components are present, while for J = 5 --> 4, only the K = 0 line has been detected. The observed frequencies were calculated by assuming a value of radial velocity VLSR = 5.8 km s-1 for TMC-1, typical of other molecules in the cloud. All observed frequencies are within 10 kHz of the calculated frequencies, which are based on the 1982 laboratory constants of Moises et al., so the identification is secure. The lines are broadened by hyperfine splitting, and the J = 5 --> 4, K = 0 transition shows incipient resolution into three hyperfine components. The rotational temperature determined for these observations is quite low, with 2.7 K < or = Trot < or = 4 K. the total column density is approximately 5 x 10(12) cm-2.  相似文献   

Detections of 13C-substituted C3H2 in astronomical sources     

Madden SC  Irvine WM  Matthews HE 《The Astrophysical journal》1986,311(1):L27-L31

We report observations of the 2(12)-1(01) rotational transition of the 13C isotopic species of cyclopropenylidene (C3H2) toward TMC-1, Sgr B2, and IRC +10216 using the laboratory rest frequencies which have recently become available. Our detections allow estimates to be made of the fractional abundance of the unsubstituted similar species in these sources. The fractional abundance relative to H2, f(C3H2), is 1-2 x 10(-8) in TMC-1, and this is similar to the abundance of HCN, one of the more abundant organic molecules in the interstellar medium. In IRC +10216 f(C3H2) is one order of magnitude greater than in TMC-1. The 12C species in Sgr B2 shows a self-absorbed profile and the relative abundance of C3H2 estimated to be about an order of magnitude less than in TMC-1.  相似文献   

A new interstellar polyatomic molecule: detection of propynal in the cold cloud TMC-1     

Irvine WM  Brown RD  Cragg DM  Friberg P  Godfrey PD  Kaifu N  Matthews HE  Ohishi M  Suzuki H  Takeo H 《The Astrophysical journal》1988,335(2):L89-L93

We report the detection of the acetylene derivative propynal (HC triple bond CCHO) in the cold cloud TMC-1, with an abundance that is very close to that for the related species tricarbon monoxide (C3O). Propadienone, an isomer of propynal with the formula H2C=C=C=O, was not detected and is hence less abundant than either C3O or HC2CHO.  相似文献   

Detection of interstellar ethylene oxide (c-C2H4O)     

Dickens JE  Irvine WM  Ohishi M  Ikeda M  Ishikawa S  Nummelin A  Hjalmarson A 《The Astrophysical journal》1997,489(2):753-757

We report the identification of 10 transitions that support the detection of the small cyclic molecule ethylene oxide (c-C2H4O) in Sgr B2N. Although one of these transitions is severely blended, so that an accurate intensity and line width could not be determined, and two other lines are only marginally detected, we have done Gaussian fits to the remaining seven lines and have performed a rotation diagram analysis. Our results indicate a rotation temperature T(rot) = 18 K and a molecular column density N(c-C2H4O) = 3.3 x 10(14) cm-2, corresponding to a fractional abundance relative to molecular hydrogen of order 6 x 10(-11). This is a factor of more than 200 higher than the abundance for this molecule suggested by the "new standard" chemistry model of Lee, Bettens, & Herbst. This result suggests that grain chemistry might play an effective role in the production of c-C2H4O. No transitions of this molecule were detected in either Sgr B2M or Sgr B2NW.  相似文献