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Hi, Daniel

A couple of quick comments:
Re: Uranyl glass ... because it emits low doses of radiation, it is 
not considered safe here in the US.  We have some sources overseas, 
but they have told us that they would probably be picked up as 
terrorists if they started exporting to the US.

Re: "Use a power meter and measure the power at the objective" and 
"not as practical":
Take a look a the new XP750 from Lumen Dynamics (formerly 
EXFO).  This neat little power meter was specifically designed to 
mimic a microscope slide so that it sits flat on the stage and 
measures the intensity right where you want it: at the sample 
plane.  You can use it on an inverted or upright and with any type of 
illuminator (lamp, LED, laser).  For those of you who took part in 
our Illumination Study in 2008, you might have noticed two sneaky 
questions about this device.  The response were huge.. and now it's 
available... for real.

For further information, you can visit their website ( 
http://www.ldgi-xcite.com/products-xr2100-xp750.php).  Also, I have 
an article coming out next month (July) in BioPhotonics written 
around interviews from users in three key labs (Jen Waters' NIC at 
Harvard, the YIP lab in Canada, and LBL).  If you want to chat with 
someone, get in touch with their Sr. Apps Scientist, Dr. Kavita 
Aswant (P:  1 905 812-3342, E: [log in to unmask]).  I know she'd 
welcome hearing from you.

Caveat: No commercial interest.

Good hunting!
Barbara Foster, President and Sr. Consultant

M icroscopy/Microscopy Education
P: (972)924-5310
W: <http://www.microscopyeducation.com/>www.MicroscopyEducation.com


At 05:09 PM 6/2/2011, Martin Wessendorf wrote:
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>
>Dear Daniel--
>
>On 6/2/2011 1:59 PM, Daniel Gitler wrote:
>
>>I am in need of either beads or a fluorophore in solution which is 
>>exited consistently by both the 405nm and 488nm lines of a confocal 
>>microscope. What I really need is that the ratio of excitation 
>>should be constant, in which case two separate dyes are probably 
>>not a good choice, unless their molar ratio can be quite consistent 
>>(perhaps in beads?). I also need that the efficiency of excitation 
>>for both lines be quite decent (doesn't have to be maximal, just 
>>decent). Finally (it appears I have a lot of requisites) the 
>>dye/beads should be as insensitive as possible to environmental 
>>changes (i.e., pH etc). The idea is to have a good standard in 
>>order to calibrate the ratio of the power of these two lines when 
>>imaging a sample (I do not need to know the actual number, just a 
>>relative measure will do fine).
>
>Based on a quick search, uranium glass looks like a 
>possibility.  The absorbance is perhaps 2x better at 488 than 
>405.  However, if you're imaging with a confocal, you would probably 
>need to use point-scanning, since uranium has a loooong fluorescence 
>time-constant (e.g. 170 usec in solution).
>
>Here are a few (mediocre) references--they might be a starting point:
>
>http://pubs.acs.org/doi/abs/10.1021/ac00230a029
>http://webhost.bridgew.edu/cnoda/research/uranyl/index.html
>http://onlinelibrary.wiley.com/doi/10.1002/pssa.2211150136/pdf
>
>Good luck!
>
>Martin
>--
>Martin Wessendorf, Ph.D.                   office: (612) 626-0145
>Assoc Prof, Dept Neuroscience                 lab: (612) 624-2991
>University of Minnesota             Preferred FAX: (612) 624-8118
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