Michelle O Johnson

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While Amazonian forests are extraordinarily diverse, the abundance of trees is skewed strongly towards relatively few 'hyperdominant' species. In addition to their diversity, Amazonian trees are a key component of the global carbon cycle, assimilating and storing more carbon than any other ecosystem on Earth. Here we ask, using a unique data set of 530(More)
Understanding the processes that determine above-ground biomass (AGB) in Amazonian forests is important for predicting the sensitivity of these ecosystems to environmental change and for designing and evaluating dynamic global vegetation models (DGVMs). AGB is determined by inputs from woody productivity [woody net primary productivity (NPP)] and the rate(More)
We have developed two radiation-hard ASICs for optical data transmission in the ATLAS pixel detector at the CERN Large Hadron Collider (LHC). The first circuit is a driver chip for a Vertical Cavity Surface Emitting Laser (VCSEL) diode to be used for 80 Mbit/s data transmission from the detector. The second circuit is a Bi-Phase Mark, decoder chip to(More)
The on-detector optical link of the ATLAS pixel detector contains radiation-hard receiver chips to decode bi-phase marked signals received on PIN arrays and data transmitter chips to drive VCSEL arrays. The components are mounted on hybrid boards (optoboards). We present results from the irradiation studies with 24 GeV protons up to 32 Mrad (1.2 x 10 p/cm)(More)
The proposed International Linear Collider (ILC) will use tens of thousands of beam position monitors (BPMs) for precise beam alignment. The signal from each BPM is digitized and processed for feedback control. The demand on the digitizers depends on their location at the accelerator complex. The two large damping rings require the fastest high-precision(More)
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