Although graphene oxide (GO) has been used in many applications to improve human life quality, its environmental fate and behavior are still largely unknown. In this work, a novel approach that combines experimental measurements and theoretical calculations was used to determine the aggregation kinetics of GO sheets in aqueous solutions under different chemistry conditions (e.g., cation valence and pH). Experimental data showed that both cation valence and pH showed significant effect on the aggregation of GO sheets. The measured critical coagulation concentrations were in good agreement with the predictions of the extended Schulze-Hardy rule. Ca(2+) and Mg(2+) were more effective than Na(+) in aggregating the GO sheets, which could be attributed to the cross-linking between GO sheets by the divalent cations through "bridging" the functional groups at the edges of the GO sheets. When solution pH increases, deprotonation of carboxylic groups was found to play a key role in increasing GO sheet stability and surface charge development. These results suggested that edge-to-edge and face-to-face interactions were the dominant modes of GO aggregation in the presence of divalent metal ions and H(+), respectively. A modified attachment efficiency (α) model was developed on the basis of the Maxwell approach with considerations of both primary and secondary minima. The model predictions matched the experimental measurements of the aggregation kinetics of GO sheets in aqueous solutions under all of the tested experimental conditions well.

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Compost stability/maturity has become a critical issue for land application of compost because immature compost can be detrimental to plant growth and the soil environment. We compared several methods of evaluating the stability/maturity of biosolids compost: chemical properties, microbial respiration activity (CO2 evolution), seed germination tests, and dissolved organic carbon (DOC) as determined by its concentration and mass‐specific absorbence (MSA) at 420 nm. Two to five biosolids compost samples were collected during compost curing stages from three full‐scale composting facilities in Florida. The compost samples from two facilities were in the stabilization/maturation process. With curing time, electrical conductivity (EC), DOC concentration, and CO2 evolution rate decreased, whereas pH, seed germination rate, and the MSA of DOC increased in these samples. Compost samples from the third facility exhibited distinctly different behavior. Relatively high seed phytotoxicity, with no consistent trends of other parameters, suggested that these samples may have not been in a real curing process, despite the generally low CO2 evolution rate and DOC content. Based on these results, we concluded that pH, EC, CO2 evolution rate, seed germination rate, and DOC (concentration and MSA) could be used to monitor stabilization and maturation processes. Compost stability and maturity are different characteristics and both are needed for compost quality control. Dissolved organic carbon analysis is promising as a simple but comprehensive index for compost stability/maturity.

In this paper we report the design, testing and use of a scannerless probe specifically for minimally invasive imaging of deep tissue in vivo with an epi-fluorescence modality. The probe images a 500 µm diameter field of view through a 710 µm outer diameter probe with a maximum tissue penetration depth of 15 mm specifically configured for eGFP imaging. Example results are given from imaging the pituitary gland of rats and zebrafish hearts with lateral resolution of 2.5 µm., "Real-time visualization of human prolactin alternate promoter usage in vivo using a double-transgenic rat model," Mol. Endocrinol.Fast handheld two-photon fluorescence microendoscope with a 475 μm × 475 μm field of view for in vivo imaging," Opt.

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