Miranda Muller

Questions and Answers (14) View all

• Answer added in Biogeochemistry
  63 How does one grind leaf samples to a fine powder for analysis by ICP-MS?
  By Miranda Muller · University of the Witwatersrand
  Miranda Muller · University of the Witwatersrand

  I have stated that I am doing analysis by ICP-MS, and that I need to have my samples suitably homogenised so that I can subsample a representative sam... [more]

  I have stated that I am doing analysis by ICP-MS, and that I need to have my samples suitably homogenised so that I can subsample a representative sample set. As I am not the only person who will be using this sample set, I am preparing the samples by the most conservative methods possible. My objectives are somewhat convoluted, and the ICP-MS is only a small fraction of the analysis that I am doing.
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• Answer added in Biogeochemistry
  63 How does one grind leaf samples to a fine powder for analysis by ICP-MS?
  By Miranda Muller · University of the Witwatersrand
  Miranda Muller · University of the Witwatersrand

  Jerzy, I thought that would be the case, but I was told that it was categorically not possible to digest a larger amount of sample to make up for the ... [more]

  Jerzy, I thought that would be the case, but I was told that it was categorically not possible to digest a larger amount of sample to make up for the lack of homogeneity in the sample. Anyhow, what I have found that works best, and didn't require buying a new mill, was to sieve my leaf samples by punching tiny holes in weighing boats (one for each sample to avoid contam) and then using Liquid N to grind the samples in an agate Mortar and pestle, then sieve out the fines, regrind the remains, sieve, regrind, sieve, regrind, until the sample was sufficiently fine. It's tedious but effective.
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• Answer added in Geographic Information System (GIS)
  13 Is there any way in ArcGIS to calculate the Latitude and Longitude of each pixel?
  By Rakhshan Roohi · La Trobe University
  Miranda Muller · University of the Witwatersrand

  In ArcGIS raster calculator, use the expression "(((("MaxGain - MinGain)/255) * "Image") + (MinGain)) to convert to Radiance (these values are in you... [more]

  In ArcGIS raster calculator, use the expression "(((("MaxGain - MinGain)/255) * "Image") + (MinGain)) to convert to Radiance (these values are in your Metadata, but I assume you have them to do the calculations anyway? Then use the "Sin" and "Cos"tools in the spatial analyst toolbox to calculate the Sin and Cosine of the radiance image. I've never tried to calculate the solar incidence angle though... (but don't tell anyone that there is something I don't know!)
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• Answer added in Geographic Information System (GIS)
  13 Is there any way in ArcGIS to calculate the Latitude and Longitude of each pixel?
  By Rakhshan Roohi · La Trobe University
  Miranda Muller · University of the Witwatersrand

  Hi Rakhshan, Oooh! I understand now.. but would it not be easier and faster to just use raster calculator to do that? Cheers, Miranda 

  Hi Rakhshan, Oooh! I understand now.. but would it not be easier and faster to just use raster calculator to do that? Cheers, Miranda
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• Answer added in Geographic Information System (GIS)
  13 Is there any way in ArcGIS to calculate the Latitude and Longitude of each pixel?
  By Rakhshan Roohi · La Trobe University
  Miranda Muller · University of the Witwatersrand

  Hi Rakhshan, I know you have said that you want the Radiance value of each pixel, but what are you going to be using that data for that you need to h... [more]

  Hi Rakhshan, I know you have said that you want the Radiance value of each pixel, but what are you going to be using that data for that you need to have the XY coordinates in this format. Forgive me for asking, but it seems like a cumbersome and exhausting exercise, so I assume you have some cunning master plan in mind for this data? Miranda
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