Assessment and control of organic and other contaminants associated with the Stardust sample return from comet 81P/Wild 2

Abstract– Numerous potential sources of organic contaminants could have greatly complicated the interpretation of the organic portions of the samples returned from comet 81P/Wild 2 by the Stardust spacecraft. Measures were taken to control and assess potential organic (and other) contaminants during the design, construction, and flight of the spacecraft, and during and after recovery of the sample return capsule. Studies of controls and the returned samples suggest that many of these potential sources did not contribute any significant material to the collectors. In particular, contamination from soils at the recovery site and materials associated with the ablation of the heatshield do not appear to be significant problems. The largest source of concern is associated with the C present in the original aerogel. The relative abundance of this carbon can vary between aerogel tiles and even within individual tiles. This C was fortunately not distributed among a complex mixture of organics, but was instead largely present in a few simple forms (mostly as Si‐CH₃ groups). In most cases, the signature of returned cometary organics can be readily distinguished from contaminants through their different compositions, nonterrestrial isotopic ratios, and/or association with other cometary materials. However, some conversion of the carbon indigenous to the flight aerogel appears to have happened during particle impact, and some open issues remain regarding how this C may be processed into new forms during the hypervelocity impact collection of the comet dust.     

1750?years of large rainfall events inferred from particle size at East Lake, Cape Bounty, Melville Island, Canada

Annual grain-size variation was measured on the varved (annually laminated) lacustrine sediment from Cape Bounty East Lake using an innovative image analysis system. About 7100 images were acquired using a scanning electron microscope and processed to obtain measurement of particles from 2845 varves. Several particle-size distributions indices were calculated and can be linked to high-energy sedimentary facies. Moreover, the coarse grain size (98th percentile) of these high-energy facies is strongly correlated with summer rainfall (and also summer temperature) of instrumental data from nearby stations. Particle-size distributions show a similar trend through time, especially for the standard deviation and the 98th percentile. Climatic reconstruction suggests that Cape Bounty recently experienced an unprecedented increase of rainfall events since ~AD 1920. On the other hand, changes in varve thickness are weakly correlated with the particle-size distribution. Altogether, these results highlight the need to obtain annual grain-size data to identify a meteorological signal.     

Mechanism of light curve variability in the gamma ray bursts

In this paper we investigate the variability of the gamma ray burst light curve. It is generally known that this fluctuation arise in the second phase of a GRB event, when two shock waves of different Lorentz factors collide. This is so called internal shock scenario. We have developed a simple model which includes dynamical and radiating part, to simulate shock wave evolution and collision. By specifying the model parameters, we show that this scenario could be used to describe variability of GRB light curve. We then use the model to simulate peeks in several different long GRB events from the BATSE database, which show us that some of the basic parameters have a very narrow range of values.      

Dissolved iron distributions in the central region of the Gulf of California,México

We report dissolved iron (Fe_d) concentrations measured in the upper 600 m in the central region of the Gulf of California (GC) under spring conditions. Our results showed the complex nature of Fe cycling within the GC. In the northern region of the study area, surface waters were relatively enriched, with Fe_d concentrations >5.0 nM, which can be partially explained by an atmospheric source. These concentrations are 12 times higher than those found in the adjacent Pacific Ocean. In contrast, Fe_d depth profiles in the southern region did not show any Fe_d surface enrichment (concentrations <1.5 nM) because of particle scavenging and higher stratification of the water-column. The most southern station in our area of study was the most stratified and showed an excess Fe_d and PO₄ with respect to NO₃, conditions favorable for nitrogen fixation. This station also showed the least negative surface value of N* of all stations. However, despite the adequate levels of Fe_d and PO₄ at that location, the surface temperature (22.6 °C) was probably not high enough for diazotrophs to develop. A slight increase in Fe_d levels in intermediate waters at the southern region was associated with the oxygen minimum zone. Finally, our results suggest that remineralization of organic matter is probably the major source of Fe_d in subsurface waters of the GC.     

Assessment of chlorophyll variability along the Louisiana coast using multi-satellite data

Variability in surface chlorophyll (Chl) concentrations derived from the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) were examined in conjunction with river discharge, QuikSCAT satellite-derived winds, and sea surface height (SSH) anomaly data along the Louisiana coast, USA. Surface Chl distributions exhibited rapid response to strong northerly winds following a frontal passage. A comparison of time series (1998–2010) river discharge and monthly Chl data indicated Chl variability to be well correlated to seasonal river discharge only for locations near the two river deltas, while offshore, enhancements in Chl during fall–winter was likely due to cross-shelf transport or mixing associated with strong northerly wind stress. Variance in Chl examined using wavelet analysis applied to nearly 10 years (1998–2007) of SeaWiFS data indicated patterns of significant Chl variability due to combined enhanced wind and river discharge, offshore flows associated with Ekman transport and coastal wind convergence, and the effect of Hurricane Rita in 2005. Instances of significant Chl variance were also observed to occur during years of large hypoxic zone size suggesting potential linkages to hypoxia. SSH anomaly imagery indicated the presence of warm-core eddies that were responsible for the offshore dispersal of elevated Chl observed in the monthly SeaWiFS imagery. Overall, the use of multi-satellite data better described the forcing and patterns of Chl distributions along the river-dominated Louisiana coast and shelf.     

Modelling outsourceable transactions on polygon-based cadastral parcels

Modern land administration systems must fulfil the emerging need for a faster and more efficient processing of real estate transactions. In order to achieve such a goal, one way to go can be to outsource a larger segment of the cadastral geometry updating process to the actors external to the organisation maintaining the data. In case the spatial component of the combined legal–spatial transactions is to be outsourced, the underlying transaction processing system must be able to autonomously handle all possible cases in a safe and consistent manner. In this paper we developed a framework that can be used to design a system that is based on standard database transaction concepts and guarantees the safe processing of externally prepared transactions on polygon-based cadastral parcels. In order to be able to detach the process of editing from the consistency control, we adjusted our basic concepts to only consider the net effect of a transaction. In creating the framework we first detect all possible types of transactions. We do that by observing the cardinalities of the transaction’s affected and the resulting sets of parcels and the identities of each set’s members. Following the detection, we attach the basic integrity constraints to each of the transaction types. Finally we classify the detected transaction types into two subtypes with the primary criteria being the strict or relaxed requirements regarding the planar partition correctness. A strict definition of what can be done within each such transaction type provides a reference that can be used for linking the legal and the spatial component of a combined legal–spatial transaction. In order to substantiate the developed framework, we describe the implementation of a proof of the concept system.     

短时空基线PS-InSAR在北京地面沉降监测中的应用

短时空基线PS-InSAR采用同时控制时间基线和垂直基线的方法,在一定程度上避免了时空失相关问题。文中采用短时空基线PS-InSAR的方法监测北京区域地面沉降,分析了区域地面沉降中的时间序列演化特征,以及抽取地下水、断裂带对地面沉降的影响。结果发现时间序列上的地面沉降存在明显的季节性变化特征,抽取地下水作为导致地面沉降的主要原因,在一定程度上还取决于断裂带的影响,地面沉降中心区域并没有完全与地下水漏斗吻合,这可能与可压缩土层的厚度有关。     

A geological data logger

A novel data logger has been designed and tested for logging data from a satellite navigator, magnetometer, and a deep-sea echosounder. The logger exploits the interrupt structure of an in-house 8085 single-board computer (SBC) to service requests from the satellite navigator and real-time clock chip. The real-time clock interrupt forces the 8085 central processing unit (CPU) to fetch data from the magnetometer and echosounder at a user-selected interval. At present, up to four days of data can be stored on a single DC-100 tape cartridge. All recorded data are displayed on a dumb CRT terminal. The data-logging software is written in PLM/85-a higher level language for the 8085 microprocessor.     

SLRES地震储层反演及油气检测软件系统研制

本文介绍了地震储层反演及油气检测软件系统的构成和功能。