Iowa's Center for Agriculture Safety and Health Annual Report, 2003

I-CASH is to enhance the health and safety of Iowa's agricultural community by establishing and coordinating prevention and education programs. This annual report gives information about a variety of areas that participate in I-CASH

Iowa's Center for Agriculture Safety and Health Annual Report, 2005

I-CASH is to enhance the health and safety of Iowa's agricultural community by establishing and coordinating prevention and education programs. This annual report gives information about a variety of areas that participate in I-CASH

Iowa's Center for Agriculture Safety and Health Annual Report, 2006

I-CASH is to enhance the health and safety of Iowa's agricultural community by establishing and coordinating prevention and education programs. This annual report gives information about a variety of areas that participate in I-CASH

Iowa's Center for Agriculture Safety and Health Annual Report, 2007

I-CASH is to enhance the health and safety of Iowa's agricultural community by establishing and coordinating prevention and education programs. This annual report gives information about a variety of areas that participate in I-CASH

Iowa's Center for Agriculture Safety and Health Annual Report, 2009

I-CASH is to enhance the health and safety of Iowa's agricultural community by establishing and coordinating prevention and education programs. This annual report gives information about a variety of areas that participate in I-CASH

Iowa's Center for Agriculture Safety and Health Annual Report, 2010

I-CASH is to enhance the health and safety of Iowa's agricultural community by establishing and coordinating prevention and education programs. This annual report gives information about a variety of areas that participate in I-CASH

Iowa's Center for Agriculture Safety and Health Annual Report, 2011

I-CASH is to enhance the health and safety of Iowa's agricultural community by establishing and coordinating prevention and education programs. This annual report gives information about a variety of areas that participate in I-CASH

Iowa's Center for Agriculture Safety and Health Annual Report, 2012

I-CASH is to enhance the health and safety of Iowa's agricultural community by establishing and coordinating prevention and education programs. This annual report gives information about a variety of areas that participate in I-CASH

Iowa's Center for Agriculture Safety and Health Annual Report, 2013

I-CASH is to enhance the health and safety of Iowa's agricultural community by establishing and coordinating prevention and education programs. This annual report gives information about a variety of areas that participate in I-CASH

The data treatment dependent variability of U-Pb zircon ages obtained using mono-collector, sector field, laser ablation ICP-MS

U-Pb dating of zircons by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) is a widely used analytical technique in Earth Sciences. For U-Pb ages below 1 billion years (1 Ga), Pb-206/U-238 dates are usually used, showing the least bias by external parameters such as the presence of initial lead and its isotopic composition in the analysed mineral. Precision and accuracy of the Pb/U ratio are thus of highest importance in LA-ICPMS geochronology. We consider the evaluation of the statistical distribution of the sweep intensities based on goodness-of-fit tests in order to find a model probability distribution fitting the data to apply an appropriate formulation for the standard deviation. We then discuss three main methods to calculate the Pb/U intensity ratio and its uncertainty in the LA-ICPMS: (1) ratio-of-the-mean intensities method, (2) mean-of-the-intensity-ratios method and (3) intercept method. These methods apply different functions to the same raw intensity vs. time data to calculate the mean Pb/U intensity ratio. Thus, the calculated intensity ratio and its uncertainty depend on the method applied. We demonstrate that the accuracy and, conditionally, the precision of the ratio-of-the-mean intensities method are invariant to the intensity fluctuations and averaging related to the dwell time selection and off-line data transformation (averaging of several sweeps); we present a statistical approach how to calculate the uncertainty of this method for transient signals. We also show that the accuracy of methods (2) and (3) is influenced by the intensity fluctuations and averaging, and the extent of this influence can amount to tens of percentage points; we show that the uncertainty of these methods also depends on how the signal is averaged. Each of the above methods imposes requirements to the instrumentation. The ratio-of-the-mean intensities method is sufficiently accurate provided the laser induced fractionation between the beginning and the end of the signal is kept low and linear. We show, based on a comprehensive series of analyses with different ablation pit sizes, energy densities and repetition rates for a 193 nm ns-ablation system that such a fractionation behaviour requires using a low ablation speed (low energy density and low repetition rate). Overall, we conclude that the ratio-of-the-mean intensities method combined with low sampling rates is the most mathematically accurate among the existing data treatment methods for U-Pb zircon dating by sensitive sector field ICPMS.

Stories in Agriculture and Life Sciences, Fall 2007

Stories we hope will inform and inspire you. Stories about how the college is constantly striving to make new discoveries, encourage and educate students and serve Iowans. Stories of the people who make this college one of the premier institutions of agriculture and life sciences in the world.

Stories in Agriculture and Life Sciences, Fall 2008

Stories we hope will inform and inspire you. Stories about how the college is constantly striving to make new discoveries, encourage and educate students and serve Iowans. Stories of the people who make this college one of the premier institutions of agriculture and life sciences in the world.

Stories in Agriculture and Life Sciences, Fall 2009

Stories we hope will inform and inspire you. Stories about how the college is constantly striving to make new discoveries, encourage and educate students and serve Iowans. Stories of the people who make this college one of the premier institutions of agriculture and life sciences in the world.

Stories in Agriculture and Life Sciences, Spring 2009

Stories we hope will inform and inspire you. Stories about how the college is constantly striving to make new discoveries, encourage and educate students and serve Iowans. Stories of the people who make this college one of the premier institutions of agriculture and life sciences in the world.

Stories in Agriculture and Life Sciences, Fall 2010

Stories we hope will inform and inspire you. Stories about how the college is constantly striving to make new discoveries, encourage and educate students and serve Iowans. Stories of the people who make this college one of the premier institutions of agriculture and life sciences in the world.