Limits to growth of forest biomass carbon sink under climate change.

Widely recognized as a significant carbon sink, North American forests have experienced a history of recovery and are facing an uncertain future. This growing carbon sink is dictated by recovery from land-use change, with growth trajectory modified by environmental change. To address both processes, we compiled a forest inventory dataset from North America to quantify aboveground biomass growth with stand age across forest types and climate gradients. Here we show, the biomass grows from 90 Mg ha-1 (2000-2016) to 105 Mg ha-1 (2020 s), 128 Mg ha-1 (2050 s), and 146 Mg ha-1 (2080 s) under climate change scenarios with no further disturbances. Climate change modifies the forest recovery trajectory to some extent, but the overall growth is limited, showing signs of biomass saturation. The future (2080s) biomass will only sequester at most 22% more carbon than the current level. Given such a strong sink has limited growth potential, our ground-based analysis suggests policy changes to sustain the carbon sink

Topological Anderson Insulator

Disorder plays an important role in two dimensions, and is responsible for striking phenomena such as metal insulator transition and the integral and fractional quantum Hall effects. In this paper, we investigate the role of disorder in the context of the recently discovered topological insulator, which possesses a pair of helical edge states with opposing spins moving in opposite directions and exhibits the phenomenon of quantum spin Hall effect. We predict an unexpected and nontrivial quantum phase termed "topological Anderson insulator," which is obtained by introducing impurities in a two-dimensional metal; here disorder not only causes metal insulator transition, as anticipated, but is fundamentally responsible for creating extended edge states. We determine the phase diagram of the topological Anderson insulator and outline its experimental consequences.Comment: 4 pages, 4 figure

Proof of Concept: Biocement for Road Repair

Road repair is an expensive operation every year. This cost can be greatly reduced if waste materials from the mining and biofuel industries can be used to substitute conventional materials for road repair or construction. The objective of this project is to develop methods to produce a new construction material, biocement, using waste products and apply the new material for road repair and construction. Two types of waste were used in this study. One is limestone fines produced from a limestone mine in Iowa. Another is organic acids, a byproduct produced from a pyrolysis-based biofuel manufacturing process. The limestone fines and organic acids can be used to produce biocement under ambient temperature in an inexpensive way. The cost-effective biocement can be used as a substitute for expensive cement for road repairs and construction. Biocement grout, or biogrout, can be injected directly into cavities or cracks in pavement for road repair. As the viscosity of biogrout is low, biogrout can penetrate better into the road pavement than cement grout. Biocement-mixed aggregate can be used for road base or subbase construction. Biocement solutions can also be applied directly on shoulders as a stabilizer or on unpaved roads as a dust control agent. The focus of this project is on the development of cost-effective biocement products and their effectiveness for road repair. Once the methods for biocement production and applications are established in laboratory scale, field experiments can be carried out as a follow-up study