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We model Covid-19 vaccine uptake as a reinforcement learning dynamic between two populations: the vaccine adopters, and the vaccine hesitant. Using data available from the Center for Disease Control (CDC), we estimate the payoff matrix governing the interaction between these two groups over time and show they are playing a Hawk-Dove evolutionary game with an internal evolutionarily stable Nash equilibrium (the asymptotic percentage of vaccinated in the population). We then ask whether vaccine adoption can be improved by implementing dynamic incentive schedules that reward/punish the vaccine hesitant, and if so, what schedules are optimal and how effective are they likely to be? When is the optimal time to start an incentive program, how large should the incentives be, and is there a point of diminishing returns? By using a tailored replicator dynamic reinforcement learning model together with optimal control theory, we show that well designed and timed incentive programs can improve vaccine uptake by shifting the Nash equilibrium upward in large populations, but only so much, and incentive sizes above a certain threshold show diminishing returns.

The Hawk-Dove mathematical game offers a paradigm of the trade-offs associated with aggressive and passive behaviors. When two (or more) populations of players (animals, insect populations, countries in military conflict, economic competitors, microbial communities, populations of co-evolving tumor cells, or reinforcement learners adopting different strategies) compete, their success or failure can be measured by their frequency in the population (successful behavior is reinforced, unsuccessful behavior is not), and the system is governed by the replicator dynamical system. We develop a time-dependent optimal-adaptive control theory for this nonlinear dynamical system in which the payoffs of the Hawk-Dove payoff matrix are dynamically altered (dynamic incentives) to produce (bang-bang) control schedules that (i) maximize the aggressive population at the end of timeT, and (ii) minimize the aggressive population at the end of timeT. These two distinct time-dependent strategies produce upper and lower bounds on the outcomes from all strategies since they represent two extremizers of the cost function using the Pontryagin maximum (minimum) principle. We extend the results forward to timesnT(n= 1, …, 5) in an adaptive way that uses the optimal value at the end of timenTto produce the new schedule for time (n+ 1)T. Two special schedules and initial conditions are identified that produce absolute maximizers and minimizers over an arbitrary number of cycles for 0 ≤T≤ 3. ForT> 3, our optimum schedules can drive either population to extinction or fixation. The method described can be used to produce optimal dynamic incentive schedules for many different applications in which the 2 × 2 replicator dynamics is used as a governing model.

Primary Water Stress Corrosion Cracking (PWSCC) has been observed in pressurized water reactor (PWR) coolant system pressure boundary components. Recently this cracking has been observed in Alloy 82/182 butt welds. Various repair and mitigation schemes have been proposed or employed to address this cracking. Case N-766 was developed as an alternative method for PWSCC mitigation. It is especially useful for applications in PWSCC susceptible regions where accessibility to the outer surfaces for performing other PWSCC mitigation techniques are difficult or impractical. The method in Case N-766 involves isolating the PWSCC susceptible material from its environment, in this case PWR reactor coolant fluid, thereby eliminating one of the three (3) simultaneous conditions that must exist for PWSCC to occur. Inlays provide for mitigation of flaws or repair of existing flaws and also permit maintaining the inside surface contour essentially in its original configuration, without flow path restriction. Onlays, which do not require an excavation into the pipe ID, permit maintaining the inside surface contour essentially in its original configuration, or permitting weld buildup on the inside surface. This paper presents the technical basis for the design, fabrication, and inspection requirements for inlays and onlays.Copyright © 2010 by ASME

Inflatable structures are being developed for use in space to take advantage of the potential for lower packaging volumes and lighter weights. These structures may consist of thin polymer membranes as well as more robust inflatable, then rigidizable, structural elements. For space applications, it must be shown that the materials can tolerate the orbital environment. This includes the effects of solar radiation and electron/proton radiation on the optical properties and mechanical response of the materials, as well as atomic oxygen effects for possible LEO applications. The highest radiation concern is with the thin-film materials, e.g., the canopy and reflector of an antenna or components of a sun shade or solar sail. All materials used in an inflatable structure need to be capable of tolerating the orbital environment and maintaining properties within the mission requirements. The approach to assessing the effects of space environment on materials begins with consideration of the orbital environment. The solar radiation spectrum is not orbital dependent, but the radiation from electrons and protons varies by orders of magnitude, depending on the particular orbit. The atomic oxygen environment is strongly dependent on altitude and solar activity. Once an orbit has been defined, the atmospheric models are available to calculate the flux and energy of the particle radiation. The orbital lifetime then is used to calculate dose levels and solar exposures that the materials must tolerate. With the environment specified, the expected dose in the materials can then be calculated. If damage thresholds are available for the particular materials involved, possible degradation can be predicted; if not, a ground or orbital test is needed. For a ground test to assess the durability of a material in orbit, the methodology is to predict the dose levels in the materials, which then drive the test parameters.

A survey of 376 women who met the DSM III criteria for bulimia is presented. The purpose of the survey is to provide information regarding the demographics of this population, the total extent of food-related behavior and basic indices of psychiatric symptoms. The results indicate that the typical bulimic surveyed was a single,Caucasian woman in her early 20's who was well educated and of average weight for her height. Most of the women were binge eating and using evacuation techniques such as self-induced vomiting on a daily to more than daily basis and had engaged in this behavior for 51/2 years. Despite the severity of the disturbed eating behavior, the sample was relatively symptom free on standard indices of psychiatric symptoms when compared to other psychiatric populations.

This brief report presents preliminary findings regarding the use of short-term group treatment for bulimia. Ten patients who met the Diagnostic and Statistical Manual III (DSM-III) criteria for bulimia were treated in a 12-session psycho-educational format. Results indicated that all patients reduced the frequency of their bulimic behavior and showed change in attitudes related to pathological eating behavior. The preliminary results suggest that short-term group treatment may be a moderately effective treatment intervention for bulimia.

To investigate the incidence and correlates of bulimic behavior, 1268 high school females were surveyed. A 47-item questionnaire was used to identify a group of students that would meet the DSM-III criteria for a probable diagnosis of bulimia. Students were then compared across the four content areas of demographics; body perception and weight information; dieting, exercise and menstrual behavior; and frequency of bingeing and purging behavior. Results indicated that 4.9% of the students met rigorous criteria for the diagnosis of bulimia. Between-group comparisons indicated that body dissatisfaction, drive for thinness, and chronicity of dieting differentiated the two groups.

ELECTRON impact processes give rise to both positive and negative ions. The negative ions are, in general, only about 10−3 times as intense as the positive ions. In contrast with positive ions, only singly charged negative ions have previously been reported. Calculations involving the crystalline state, where doubly charged negative ions (such as O = and S =) apparently do exist, indicate that the formation of O = from O − requires 7.8 eV in the gas phase1. The lifetime of a doubly charged ion in the gas phase would be expected to be short and has been predicted to be 10−10 sec or less2—too short for observation in the usual mass spectrometer. This communication reports the observation of doubly charged negative ions of oxygen, fluorine, chlorine and bromine, with indications that the lifetimes are of the order of 10−4 sec (the ion collection time in the mass spectrometer used).