Optical Spectroscopy of Comet C/2000 WM1 (LINEAR) at the Guillermo Harro Astrophysical Observatory in Mexico

We present a preliminary analysis of medium resolution optical spectra of comet C/2000 WM1 (LINEAR) obtained on 22 November 2001. Theemission lines of the molecules C₂, C₃, CN, NH₂,H₂O⁺ and presumably CO (Asundi and triplet bands) and C₂ ^-were identified in these spectra. By analysing the brightnessdistributions of the C₂, C₃, CN emission lines along theslit of the spectrograph we determined some physical parameters of theseneutrals, such as their lifetimes and expansion velocities inthe coma. The Franck–Condon factors for the CO Asundi bands and C₂ ^- bands were calculated using a Morse potential model.     

Imaging Borrelly

The nucleus, coma, and dust jets of short-period Comet 19P/Borrelly were imaged from the Deep Space 1 spacecraft during its close flyby in September 2001. A prominent jet dominated the near-nucleus coma and emanated roughly normal to the long axis of nucleus from a broad central cavity. We show it to have remained fixed in position for more than 34 hr, much longer than the 26-hr rotation period. This confirms earlier suggestions that it is co-aligned with the rotation axis. From a combination of fitting the nucleus light curve from approach images and the nucleus' orientation from stereo images at encounter, we conclude that the sense of rotation is right-handed around the main jet vector. The inferred rotation pole is approximately perpendicular to the long axis of the nucleus, consistent with a simple rotational state. Lacking an existing IAU comet-specific convention but applying a convention provisionally adopted for asteroids, we label this the north pole. This places the sub-solar latitude at ∼60° N at the time of the perihelion with the north pole in constant sunlight and thus receiving maximum average insolation.     

Optical Spectroscopy and Near-Infrared Observations of Comet C/2000 Wm1 (Linear) in December 2001 from Chile and Brazil

We report on the preliminary analysis of the high-resolution spectrum of CometC/2000 WM1 (LINEAR), obtained on Dec. 1, 2001 with the Fiber fed ExtendedRange Optical Spectrograph (FEROS) installed on the 1.52-m telescope of ESO(Chile). Many emission lines of the molecules C₂, C₃, CN, CH, CH⁺,NH₂, CO, CO⁺, H₂O⁺ and, presumably, C₂ ^- were identifiedin the spectral range 400–900 nm. Also, near-infrared photometry was performed on Dec. 2 and 3, with the infraredcamera (CamIV) attached to the 0.60-m Boller and Chivens telescope of the Picodos Dias Observatory (LNA/MCT), Brazil. We report the preliminary and comparativeanalysis of the I-J and J-H color indices.     

平板冻结器超压事故的原因分析

平板冻结器超压事故的发生主要由于使用设备时操作不当和设备质量不过关而引起。对设备超压原理分析和平板冻结器在不同温度条件下的充液比例进行理论计算 ,结果表明 ,停机时 ,在室温 35℃的条件下 ,蒸发器中的充液比例达到 0 .86 0 5时 ,会引起蒸发器发生超压而爆炸。当蒸发器中充液比例在 0 .86 0 5以下时发生的超压事故 ,肯定存在设备质量不过关的因素 ;而当充液比例在 0 .86 0 5或以上时发生的超压事故 ,则是由误操作引起。。     

Suspended sediment and phosphorus in proglacial rivers: bioavailability and potential impacts upon the P status of ice‐marginal receiving waters

This paper adopts standard tests developed in temperate catchment research to determine the total phosphorus (TP) and the algal available (base‐extractable) phosphorus (NaOH–P) content of a wide range of glaciofluvial sediments from the Northern Hemisphere. We find that the TP content of these sediments is broadly similar to the P content of major rock types in Earth's crust (230–670 µgP/g) and so the TP yields of glacier basins may be high owing to the efficacy of suspended sediment evacuation by glacial meltwaters. We show that this is best achieved where subglacial drainage systems are present. The NaOH–P pool of the sediments is found to be low (1–23 µgP/g) relative to the TP pool and also to the NaOH–P pool of suspended sediments in temperate, non‐glacierized catchments. This most probably reflects the restricted duration of intimate contact between dilute meltwaters and glacial suspended sediments during the ablation season. Thus, despite the high surface‐area:volume ratio of glacial suspended sediments, the potential for P adsorption to mineral surfaces following release by dissolution is also low. Further, sorption experiments and sequential extraction tests conducted using glacial suspended sediments from two Svalbard catchments indicate that the generation of reactive secondary minerals (e.g. Fe‐ and other hydroxides) with a strong capacity to scavenge P from solution (and thereby promote the continued dissolution of P) may also be limited by the short residence times. Most P is therefore associated with poorly weathered, calcite/apatite‐rich mineral phases. However, we use examples from the Svalbard glacier basins (Austre Brøggerbreen and Midre Lovénbreen) to show that the high sediment yields of glaciers may result in appreciable NaOH–P loading of ice‐marginal receiving waters. Again, the importance of subglacial drainage is highlighted, as it produces a major, episodic release of NaOH–P at Midre Lovénbreen that results in a yield (8·2 kg NaOH–P/km²/year) more than one order of magnitude greater than that at Austre Brøggerbreen (where subglacial drainage is absent and the yield is 0·48 kg NaOH‐P/km²/year). Therefore, as since both detrimental and beneficial effects of sediment‐bound P loading in ice marginal receiving waters are possible (i.e. either reduced primary productivity owing to increased turbidity or P fertilization following desorption) there is a pressing need to assess the ambient P status of such environments and also the capacity for ice‐marginal ecosystems to adapt to such inputs. Copyright © 2004 John Wiley & Sons, Ltd.     

X Per新发射相的不寻常变化

对ＸＰｅｒ新发射相连续四年的光学光谱和近红外光度监测结果，ＸＰｅｒ近两年的变化不同寻常，主要表现以下两点：（１）尽管它的光学光度Ｖ星等只恢复至失去气壳前的亮度，但Ｈａ发射线等值宽度和近红外，Ｊ，Ｈ和Ｋ光度地超过了历史记录的最大值，分别达到了１６．３４Ａ和５．３＾ｍ，５．３＾ｍ和５．１＾ｍ，表明ＸＰｅｒ新发射相气南的密度和尺度较都大，（２）我们首次观测到ＸＰｅｒ近红外光度和Ｈα发射线等值宽度变化趋势     

步进电机步距角的正余弦细分原理

步进电机的步距角由于受到机械结构和经典细分驱动电路的限制，只能适量的减小，但对于许多精密设备的控制及高精度的定位系统，其步距角的分辨率还应提高，正金弦细分驱动电路很好地解决了这一问题。它的主要特点是和计算机或单片机的接口简单、转速连续可调；增减EPROM的地址线可灵活改变细分数；电机运行平稳、振动小、噪声低。     

Comment on the paper “Fast tidal cycling and the origin of life” by Richard Lathe

We show that the fast tidal cycling postulated by Lathe [Lathe, R., 2004. Icarus 168, 18-22] is not a plausible mechanism to explain the origin of life on Earth about 3.9 Ga ago. The value of LOD at this remote epoch was probably comprised between 15 to 17 h, and the Earth-Moon distance was only about 20% smaller than nowadays, implying that the tidal frequencies and amplitudes were not so dramatically different from the present ones as stated in Lathe's paper.