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June 2008

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Subject:
From:
Ellery Frahm <[log in to unmask]>
Reply To:
JEOL-Focused Probe Users List <[log in to unmask]>
Date:
Tue, 3 Jun 2008 21:49:14 -0500
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Moderator: Ellery Frahm, [log in to unmask],
Electron Microprobe Lab, University of Minnesota

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*

Colleagues,

I am working on a project that attempts to evaluate the effects of  
choices made in EMPA on the data and ultimately on the geological  
interpretations.  I want to analyze a set of geological specimens  
using three, four, maybe five analytical schemes, and I'll see how  
those different schemes affect the data and ultimate interpretations.   
Two or three of these schemes will be based on common approaches in  
the relevant literature.  The main goal is essentially to determine  
the robustness of the geological interpretations.  Can these  
interpretations withstand variations introduced by different  
analysts?  Are the ultimate interpretations vulnerable to the  
different "cultures" or analytical "traditions" of different labs?

Analysts carry out a series of actions and make a series of choices  
while doing an analysis.  This is considered an "operational sequence"  
by anthropologists who study technology, and such anthropologists are  
interested in the choices people make and the reasons for those  
choices.  Some of these choices, even in EMPA, are made for very  
technical and logical reasons (e.g., an accelerating voltage of 15 kV  
optimizes the overvoltage ratio for the main elements of interest),  
whereas other choices are made for outdated, arbitrary, or other  
reasons (e.g., we use Correction Method A, not Correction Method B, in  
this lab because it is what we've always done).  Both types of choices  
can be equally important in obtaining accurate data.

Back to my research project, I have ideas about what choices are most  
important and common in EMPA when deciding how to analyze a geological  
specimen.  But I'd like to not bias my project by investigating only  
my own ideas about important and common choices.  I haven't spent very  
much time in other microprobe labs, so I am embedded in the "culture"  
of the lab here at the University of Minnesota.

So I'd like to hear from my colleagues on this issue.  What do you  
think are the most important and common choices made when approaching  
an analysis?  Are there choices that you think almost all of your  
colleagues would make the same way?  Have researchers from other labs  
asked you to use conditions that boggle you?  If you have spent a lot  
of time in multiple labs, have you recognized the different "cultures"  
of the labs?  What choices do you think analysts make that aren't  
really important today but are based on habits or traditions from  
older machines or correction routines?  I will use any comments and  
criticisms I receive to select the choices on which this project  
should focus, probably just by tabulating the responses.

I apologize for being a bit vague, but I'm trying not to bias anyone's  
responses.  I welcome all input and opinions either on- or off-list.   
All comments or criticisms will remain anonymous unless you either  
respond on-list or give me explicit permission to cite you.

Thank you for your time and assistance.  I apologize if you have  
received this email more than once due to cross-list posting.

Best,
Ellery

--------------------
Ellery E. Frahm
Research Fellow & Manager
Electron Microprobe Laboratory
University of Minnesota - Twin Cities
Department of Geology & Geophysics
Lab Website: http://probelab.geo.umn.edu
Personal Website: http://umn.edu/~frah0010

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