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.

Characteristics of long recovery early VLF events observed by the North African AWESOME Network

Abstract: [1] Lightning strokes are capable of initiating disturbances in the lower ionosphere, whose recoveries persist for many minutes. These events are remotely sensed via monitoring subionospherically propagating very low frequency (VLF) transmitter signals, which are perturbed as they pass through the region above the lightning stroke. In this paper we describe the properties and characteristics of the early VLF signal perturbations, which exhibit long recovery times using subionospheric VLF transmitter data from three identical receivers located at Algiers (Algeria), Tunis (Tunisia), and Sebha (Libya). The results indicate that the observation of long recovery events depends strongly on the modal structure of the signal electromagnetic field and the distance from the disturbed region and the receiver or transmitter locations. Comparison of simultaneously collected data at the three sites indicates that the role of the causative lightning stroke properties (e.g., peak current and polarity), or that of transient luminous events may be much less important. The dominant parameter which determines the duration of the recovery time and amplitude appears to be the modal structure of the subionospheric VLF probe signal at the ionospheric disturbance, where scattering occurs, and the subsequent modal structure that propagates to the receiver location.

Low-cycle thermal mechanical fatigue testing

Abstract: A test method is described for performing uniaxial low-cycle thermal mechanical fatigue tests at elevated temperatures on nickel-base superalloys. Both smooth specimen crack initiation and notched specimen crack propagation testing is discussed. Standard closed loop servohydraulic testing machines with closed loop electric induction heaters are utilized. The temperature and mechanical strain are independently controlled, allowing for a wide range of relationships between temperature and mechanical strain. Tubular specimens are directly inductively heated in air and cooled with compressed air. The temperature is measured with a radiation pyrometer which eliminates thermocouples and premature failures caused by welded thermocouples. Axial strain in the specimen is measured from machined internal ridges on the specimen utilizing a linear variable differential transformer and a quartz internal extensometer. An electronic system compensates for the thermal expansion component of strain for both the control loop and the recorders. This system permits direct recording of the load-induced mechanical strain. Load-strain hysteresis loops and strain-temperature plots can simply be recorded during the test.

Just a Cog in the Machine? The Individual Responsibility of Researchers in Nanotechnology is a Duty to Collectivize

Abstract: Responsible Research and Innovation (RRI) provides a framework for judging the ethical qualities of innovation processes, however guidance for researchers on how to implement such practices is limited. Exploring RRI in the context of nanotechnology, this paper examines how the dispersed and interdisciplinary nature of the nanotechnology field somewhat hampers the abilities of individual researchers to control the innovation process. The ad-hoc nature of the field of nanotechnology, with its fluid boundaries and elusive membership, has thus far failed to establish a strong collective agent, such as a professional organization, through which researchers could collectively steer technological development in light of social and environmental needs. In this case, individual researchers cannot innovate responsibly purely by themselves, but there is also no structural framework to ensure that responsible development of nanotechnologies takes place. We argue that, in such a case, individual researchers have a duty to collectivize. In short, researchers in situations where it is challenging for individual agents to achieve the goals of RRI are compelled to develop organizations to facilitate RRI. In this paper we establish and discuss the criteria under which individual researchers have this duty to collectivize.

Use of Monte Carlo Simulation Techniques in Accident Reconstruction

Abstract: A straight-forward, automated approach to performing sensitivity analyses using Monte Carlo simulation techniques is described in this paper. Probability distributions are assigned to key input parameters, and results are expressed in the form of probability distributions of each of the desired output parameters. With this technique, it is possible to obtain quantitative results regarding the probability of results being within selected ranges. The approach is fast and automated, and provides a rational basis for dealing with uncertainty and ranges of parameters in accident reconstruction analyses.

Critical Review of Read-Across Potential in Testing for Endocrine-Related Effects in Vertebrate Ecological Receptors

Abstract: Recent regulatory testing programs have been designed to evaluate whether a chemical has the potential to interact with the endocrine system and could cause adverse effects. Some endocrine pathways are highly conserved among vertebrates, providing a potential to extrapolate data generated for one vertebrate taxonomic group to others (i.e., biological read-across). To assess the potential for biological read-across, we reviewed tools and approaches that support species extrapolation for fish, amphibians, birds, and reptiles. For each of the estrogen, androgen, thyroid, and steroidogenesis (EATS) pathways, we considered the pathway conservation across species and the responses of endocrine-sensitive endpoints. The available data show a high degree of confidence in the conservation of the hypothalamus-pituitary-gonadal axis between fish and mammals and the hypothalamus-pituitary-thyroid axis between amphibians and mammals. Comparatively, there is less empirical evidence for the conservation of other EATS pathways between other taxonomic groups, but this may be due to limited data. Although more information on sensitive pathways and endpoints would be useful, current developments in the use of molecular target sequencing similarity tools and thoughtful application of the adverse outcome pathway concept show promise for further advancement of read-across approaches for testing EATS pathways in vertebrate ecological receptors. Environ Toxicol Chem 2020;39:739-753. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.