Human instrumental performance in ratio and interval contingencies:a challenge for associative theory

Associative learning theories regard the probability of reinforcement as the critical factor determining responding. However, the role of this factor in instrumental conditioning is not completely clear. In fact, a wealth of evidence from instrumental free-operant experiments has shown that participants respond at a higher rate on variable ratio than on variable interval schedules even though the reinforcement probability on the interval schedule is the same as or greater than that on the ratio schedule. This difference has been attributed to the differential reinforcement of long inter-response times (IRT) by interval schedules, which acts to slow responding. In the present study, we used a novel experimental design to investigate human responding under random ratio (RR) and regulated probability interval (RPI) schedules, a type of interval schedule that sets a reinforcement probability independently of the IRT duration. We trained participants separately on each type of schedule before a final choice test in which they distributed responding between two schedules similar to those experienced during training. Although response rates on the various schedules did not differ reliably during training, the participants responded at a lower rate on the RPI schedule than on the matched RR schedule during the choice test. This preference cannot be attributed to a higher probability of reinforcement for long IRTs and questions the idea that similar associative processes underlie instrumental and classical conditioning.</p

Functional connectivity between the entorhinal and posterior cingulate cortices underpins navigation discrepancies in at-risk Alzheimer’s disease

Navigation processes that are selectively mediated by functional activity in the entorhinal cortex may be a marker of preclinical Alzheimer's disease (AD). Here, we tested if a short path integration paradigm can detect the strongest genetic-risk phenotype of AD in large sample of apolipoprotein E (APOE)-genotyped individuals. We also examined the associations between APOE-mediated navigation process, subjective cognitive decline, and rest-stating network connectivity. Navigation discrepancies classified 77% the APOE-genotyped cohort into their respective low-risk ε3ε3 and high-risk ε3ε4 categories. When connectivity strength between entorhinal and the posterior cingulate cortices (also a functional correlate of strongest APOE-dependant behavioral characteristics) was considered, this classification accuracy increased to 85%. Our findings present a whole picture of at-genetic-risk AD, including select impairment in path integration, self-report cognitive decline, and altered network activity that is reminiscent of the pathological spread of preclinical AD disease. These findings may have important implications for the early detection of AD

The SPARC Toroidal Field Model Coil Program

The SPARC Toroidal Field Model Coil (TFMC) Program was a three-year effort between 2018 and 2021 that developed novel Rare Earth Yttrium Barium Copper Oxide (REBCO) superconductor technologies and then successfully utilized these technologies to design, build, and test a first-in-class, high-field (~20 T), representative-scale (~3 m) superconducting toroidal field coil. With the principal objective of demonstrating mature, large-scale, REBCO magnets, the project was executed jointly by the MIT Plasma Science and Fusion Center (PSFC) and Commonwealth Fusion Systems (CFS). The TFMC achieved its programmatic goal of experimentally demonstrating a large-scale high-field REBCO magnet, achieving 20.1 T peak field-on-conductor with 40.5 kA of terminal current, 815 kN/m of Lorentz loading on the REBCO stacks, and almost 1 GPa of mechanical stress accommodated by the structural case. Fifteen internal demountable pancake-to-pancake joints operated in the 0.5 to 2.0 nOhm range at 20 K and in magnetic fields up to 12 T. The DC and AC electromagnetic performance of the magnet, predicted by new advances in high-fidelity computational models, was confirmed in two test campaigns while the massively parallel, single-pass, pressure-vessel style coolant scheme capable of large heat removal was validated. The REBCO current lead and feeder system was experimentally qualified up to 50 kA, and the crycooler based cryogenic system provided 600 W of cooling power at 20 K with mass flow rates up to 70 g/s at a maximum design pressure of 20 bar-a for the test campaigns. Finally, the feasibility of using passive, self-protection against a quench in a fusion-scale NI TF coil was experimentally assessed with an intentional open-circuit quench at 31.5 kA terminal current.Comment: 17 pages 9 figures, overview paper and the first of a six-part series of papers covering the TFMC Progra

European Atlas of Natural Radiation

Natural ionizing radiation is considered as the largest contributor to the collective effective dose received by the world population. The human population is continuously exposed to ionizing radiation from several natural sources that can be classified into two broad categories: high-energy cosmic rays incident on the Earth’s atmosphere and releasing secondary radiation (cosmic contribution); and radioactive nuclides generated during the formation of the Earth and still present in the Earth’s crust (terrestrial contribution). Terrestrial radioactivity is mostly produced by the uranium and thorium radioactive families together with potassium. In most circumstances, radon, a noble gas produced in the radioactive decay of uranium, is the most important contributor to the total dose.This Atlas aims to present the current state of knowledge of natural radioactivity, by giving general background information, and describing its various sources. This reference material is complemented by a collection of maps of Europe displaying the levels of natural radioactivity caused by different sources. It is a compilation of contributions and reviews received from more than 80 experts in their field: they come from universities, research centres, national and European authorities and international organizations.This Atlas provides reference material and makes harmonized datasets available to the scientific community and national competent authorities. In parallel, this Atlas may serve as a tool for the public to: • familiarize itself with natural radioactivity;• be informed about the levels of natural radioactivity caused by different sources;• have a more balanced view of the annual dose received by the world population, to which natural radioactivity is the largest contributor;• and make direct comparisons between doses from natural sources of ionizing radiation and those from man-made (artificial) ones, hence to better understand the latter.Additional information at: https://remon.jrc.ec.europa.eu/About/Atlas-of-Natural-Radiatio

CALCULATION OF DOSE CONVERSION FACTORS BASED ON THE RESULTS OF GEOMETRIC MIXTURE MODELS FOR RISK ASSESSMENT OF RADON EXPOSURE

Abstract The results of the geometric mixture model by Tomasek (2011, 2013) were applied for the calculation of radiation risk at radon exposure at the assessment of dose conversion factors (DCF; mSv/WLM) from radon exposure to the effective dose-by-dose conversion convention approach for cohorts with different smoking status. It is shown that the use of a geometric mixture model results in a better agreement between DCF values for men and women.</jats:p