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Socioeconomic achievement gaps have long been a central focus of educational research. However, not much is known about how (and why) between-district gaps vary among states, even though states are a primary organizational level in the decentralized education system in the United States. Using data from the Stanford Education Data Archive (SEDA), this study describes state-level socioeconomic achievement gradients and the growth of these gradients from Grades 3 to 8. We also examine state-level correlates of the gradients and their growth, including school system funding equity, preschool enrollment patterns, the distribution of teachers, income inequality, and segregation. We find that socioeconomic gradients and their growth rates vary considerably among states, and that between-district income segregation is positively associated with the socioeconomic achievement gradient.

Over the years, anaerobic digestion (AD) has evolved as a competent technology to retrieve energy potential from various organic substrates, including wastewater. However, the energy metabolisms of anaerobic microorganisms, biochemical reactions, and biogas production are affected by various parameters, including heavy metals. It is important to understand the interaction of heavy metals with anaerobes and their potential influence on the process to enhance energy potential. This review methodically outlines the occurrence and role of heavy metals in the AD process. Additionally, the repercussions of the most common heavy metals (i.e., Cu, Zn, Cd, Fe, and Ni) on each stage of AD (i.e., hydrolysis, acidogenesis, and methanogenesis) have been discussed. We found that traces of heavy metals can endorse anaerobic digestion, but inhibition increases with increasing concentration. Methanogenic archaea are more susceptible to heavy metal inhibition than hydrolytic and acidogenic archaea. An improved understanding and relevant intuition will help to promote biogas production along with heavy metal management.

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