Exponent

About: Exponent is a company organization based out in Menlo Park, California, United States. It is known for research contribution in the topics: Population & Risk assessment. The organization has 1589 authors who have published 2680 publications receiving 88140 citations.

Isolation of carbon and grain boundary carbide effects on the creep and intergranular stress corrosion cracking behavior of Ni-16Cr-9Fe-xC alloys in 360 °C primary water

Abstract: The influence of carbon and grain boundary carbides on intergranular stress corrosion cracking (IGSCC) of controlled-purity Ni−16Cr−9Fe−xC alloys in 360 °C primary water was investigated using constant load tensile (CLT) and constant extension rate tensile (CERT) tests. The CLT test results confirmed that carbon in solution decreases the creep rate by several orders of magnitude, while grain boundary carbides serve to increase the creep susceptibility. Although carbon increases the work hardening rate, it is demonstrated, using the Bailey-Orowan creep model, that the primary effect of carbon in solution is to delay the recovery process of climb at the grain boundary, thereby reducing the creep rate. Grain boundary carbides produce a negligible contribution to the internal stress and may increase the creep rate by acting as dislocation sources. Grain boundary carbide precipitation increases IGSCC resistance in 360 °C primary water containing 0, 1, and 18 bar hydrogen, providing the highest overall resistance to both environmentally induced creep and cracking. The magnitude of the beneficial effect of grain boundary carbides is extremely sensitive to hydrogen overpressure, with the largest influence observed for 1 bar hydrogen. The detrimental effect of hydrogen on IGSCC shows consistencies with aspects of both film rupture/slip dissolution and hydrogen embrittlement models.

GEMS/Food Consumption Cluster Diets

Abstract: The World Health Organization (WHO) has developed the GEMS/Food Consumption Cluster Diets, which provides an overview of the food consumption patterns worldwide, through 13 dietary patterns covering 183 countries. Estimates of food consumption are necessary to assess the potential exposure of populations to chemical contaminants and certain nutrient substances in food. Based on Food Balance Sheet (FBS) data collected by the Food and Agriculture Organization of the United Nations (FAO), these diets are routinely used by international risk assessment bodies. The derivation of these diets is presented and the uses and limitations of the diets are discussed, including their application in total diet studies.

Analysis and modeling of Nannochloropsis growth in lab, greenhouse, and raceway experiments.

Abstract: Efficient production of algal biofuels could reduce dependence on foreign oil by providing a domestic renewable energy source. Moreover, algae-based biofuels are attractive for their large oil yield potential despite decreased land use and natural resource (e.g., water and nutrients) requirements compared to terrestrial energy crops. Important factors controlling algal lipid productivity include temperature, nutrient availability, salinity, pH, and the light-to-biomass conversion rate. Computational approaches allow for inexpensive predictions of algae growth kinetics for various bioreactor sizes and geometries without the need for multiple, expensive measurement systems. Parametric studies of algal species include serial experiments that use off-line monitoring of growth and lipid levels. Such approaches are time consuming and usually incomplete, and studies on the effect of the interaction between various parameters on algal growth are currently lacking. However, these are the necessary precursors for computational models, which currently lack the data necessary to accurately simulate and predict algae growth. In this work, we conduct a lab-scale parametric study of the marine alga Nannochloropsis salina and apply the findings to our physics-based computational algae growth model. We then compare results from the model with experiments conducted in a greenhouse tank and an outdoor, open-channel raceway pond. Results show that the computational model effectively predicts algae growth in systems across varying scale and identifies the causes for reductions in algal productivities. Applying the model facilitates optimization of pond designs and improvements in strain selection.

In vivo oxidation and surface damage in retrieved ethylene oxide-sterilized total knee arthroplasties.

Abstract: Background Gas sterilization (eg, ethylene oxide [EtO] and gas plasma) was introduced for polyethylene to reduce oxidation due to free radicals occurring during radiation sterilization. Recently, oxidation has been observed in polyethylenes with undetectable levels of free radicals, which were expected to be oxidatively stable. It is unclear whether in vivo oxidation will occur in unirradiated inserts sterilized with EtO.

Emissions associated with operations of four different additive manufacturing or 3D printing technologies

Abstract: In this pilot-scale study, a wide range of potential emissions were evaluated for four types of additive manufacturing (AM) machines These included material extrusion (using acrylonitrile-butadien