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Introduction: Many aspects of teacher competency have been previously examined, particularly a teacher's ability to give commands effectively. Teachers' instructions to students within the classroom, aid in the acquisition of both the students' academic and nonacademic skills. Teachers' commands promote verbal and social skills, and facilitate appropriate classroom behavior. In this respect, compliance to teacher commands is an integral aspect of classroom behavior management. Method: Naturally occurring levels of teacher commands were studied across three ages of preschool classrooms; toddlers, 3-4 year olds, and 4-6 year olds. Commands were identified through a review of the literature in coordination with preschool classroom observation and observation protocol development. Levels of fifteen different identifiable types of commands were measured across six different types of preschool activities. Results: Results showed that there is a clear difference in the rates of commands across age levels and activities, and that specific types of commands occur at significantly higher percentages in differing age level preschool classrooms. Discussion and Conclusion: Types of commands elicited by teachers and the rate of command elicitation are seen as having implications for classroom compliance levels. (Contains 2 figures and 7 tables.)

Silver (Ag) engineered nanomaterials (ENMs) are being released into waste streams and are being discharged, largely as Ag 2 S aged-ENMs (a-ENMs), into agroecosystems receiving biosolids amendments. Recent research has demonstrated that biosolids containing an environmentally relevant mixture of ZnO, TiO 2 , and Ag ENMs and their transformation products, including Ag 2 S a-ENMs, disrupted the symbiosis between nitrogen-fixing bacteria and legumes. However, this study was unable to unequivocally determine which ENM or combination of ENMs and a-ENMs was responsible for the observed inhibition. Here, we examined further the effects of polyvinylpyrollidone (PVP) coated pristine Ag ENMs (PVP-Ag), Ag 2 S a-ENMs, and soluble Ag (as AgSO 4 ) at 1, 10, and 100 mg Ag kg −1 on the symbiosis between the legume Medicago truncatula and the nitrogen-fixing bacterium, Sinorhizobium melliloti in biosolids-amended soil. Nodulation frequency, nodule function, glutathione reductase production, and biomass were not significantly affected by any of the Ag treatments, even at 100 mg kg −1 , a concentration analogous to a worst-case scenario resulting from long-term, repeated biosolids amendments. Our results provide additional evidence that the disruption of the symbiosis between nitrogen-fixing bacteria and legumes in response to a mixture of ENMs in biosolids-amended soil reported previously may not be attributable to Ag ENMs or their transformation end-products. We anticipate these findings will provide clarity to regulators and industry regarding potential unintended consequences to terrestrial ecosystems resulting from of the use of Ag ENMs in consumer products. [ABSTRACT FROM AUTHOR]

Manufactured nanoparticles (MNP) rapidly undergo aging processes once released from products. Silver sulfide (Ag 2 S) is the major transformation product formed during the wastewater treatment process for Ag-MNP. We examined toxicogenomic responses of pristine Ag-MNP, sulfidized Ag-MNP (sAg-MNP), and AgNO 3 to a model soil organism, Caenorhabditis elegans . Transcriptomic profiling of nematodes which were exposed at the EC 30 for reproduction for AgNO 3 , Ag-MNP, and sAg-MNP resulted in 571 differentially expressed genes. We independently verified expression of 4 genes ( numr-1 , rol-8 , col-158 , and grl-20 ) using qRT-PCR. Only 11% of differentially expressed genes were common among the three treatments. Gene ontology enrichment analysis also revealed that Ag-MNP and sAg-MNP had distinct toxicity mechanisms and did not share any of the biological processes. The processes most affected by Ag-MNP relate to metabolism, while those processes most affected by sAg-MNP relate to molting and the cuticle, and the most impacted processes for AgNO 3 exposed nematodes was stress related. Additionally, as observed from qRT-PCR and mutant experiments, the responses to sAg-MNP were distinct from AgNO 3 while some of the effects of pristine MNP were similar to AgNO 3 , suggesting that effects from Ag-MNP is partially due to dissolved silver ions. [ABSTRACT FROM AUTHOR]

We investigated effects of Ag 2 S engineered nanomaterials (ENMs), polyvinylpyrrolidone (PVP) coated Ag ENMs (PVP-Ag), and Ag + on arbuscular mycorrhizal fungi (AMF), their colonization of tomato (S olanum lycopersicum ), and overall microbial community structure in biosolids-amended soil. Concentration-dependent uptake was measured in all treatments. Plants exposed to 100 mg kg −1 PVP-Ag ENMs and 100 mg kg −1 Ag + exhibited reduced biomass and greatly reduced mycorrhizal colonization. Bacteria, actinomycetes and fungi were inhibited by all treatment classes, with the largest reductions measured in 100 mg kg −1 PVP-Ag ENMs and 100 mg kg −1 Ag + . Overall, Ag 2 S ENMs were less toxic to plants, less disruptive to plant-mycorrhizal symbiosis, and less inhibitory to the soil microbial community than PVP-Ag ENMs or Ag + . However, significant effects were observed at 1 mg kg −1 Ag 2 S ENMs, suggesting that the potential exists for microbial communities and the ecosystem services they provide to be disrupted by environmentally relevant concentrations of Ag 2 S ENMs. [ABSTRACT FROM AUTHOR]

Sulfidation is a major transformation product for manufactured silver nanoparticles (Ag-MNPs) in the wastewater treatment process. We studied the dissolution, uptake, and toxicity of Ag-MNP and sulfidized Ag-MNPs (sAg-MNPs) to a model soil organism, Caenorhabditis elegans . Our results show that reproduction was the most sensitive endpoint tested for both Ag-MNPs and sAg-MNPs. We also demonstrate that sulfidation not only decreases solubility of Ag-MNP, but also reduces the bioavailability of intact sAg-MNP. The relative contribution of released Ag + compared to intact particles to toxicity was concentration dependent. At lower total Ag concentration, a greater proportion of the toxicity could be explained by dissolved Ag, whereas at higher total Ag concentration, the toxicity appeared to be dominated by particle specific effects. [ABSTRACT FROM AUTHOR]