Reinforcement Learning by Guided Safe Exploration

Safety is critical to broadening the application of reinforcement learning (RL). Often, we train RL agents in a controlled environment, such as a laboratory, before deploying them in the real world. However, the real-world target task might be unknown prior to deployment. Reward-free RL trains an agent without the reward to adapt quickly once the reward is revealed. We consider the constrained reward-free setting, where an agent (the guide) learns to explore safely without the reward signal. This agent is trained in a controlled environment, which allows unsafe interactions and still provides the safety signal. After the target task is revealed, safety violations are not allowed anymore. Thus, the guide is leveraged to compose a safe behaviour policy. Drawing from transfer learning, we also regularize a target policy (the student) towards the guide while the student is unreliable and gradually eliminate the influence of the guide as training progresses. The empirical analysis shows that this method can achieve safe transfer learning and helps the student solve the target task faster.Comment: Accecpted at ECAI 202

the case of classical ballet dancers

This study examines how employees assess demands-abilities and needs-supplies across their work lifespan, and how they better adjust to their work. Based on person-environment fit theory, the job design and the lifespan literatures, and using interviews with a sample of 40 professional ballet dancers, our research shows how the interplay between demands, abilities, needs, organizational resources, and regulation strategies contributes to a process of adjustment, and consequently enhances psychological well-being across the work lifespan. Additionally, we contribute to literature on well-being by presenting evidence of how organizational resources are perceived differently across the work lifespan and why. We also extend theory on job crafting by showing that crafting is partly a function of the phases of one's lifetime and by presenting evidence of forms of crafting among older workers. With increased longevity, individuals will need to remain working or recraft a career after reaching retirement age. Addressing age-related changes and considering the importance of organizational resources to well-being can help promote active aging.preprintpublishe

Diagnostic Accuracy of Raman Spectroscopy Integrated With Polarized Light Microscopy for Calcium Pyrophosphate–Associated Arthritis

Objective: We studied the performance of integrated Raman polarized light microscopy (iRPolM) for the identification of calcium pyrophosphate (CPP)–associated arthritis (CPPD). Methods: This is a diagnostic accuracy study including 400 consecutive synovial fluid samples from a single hospital in the Netherlands. Accuracy measures were calculated against polarized light microscopy (PLM) and the 2023 American College of Rheumatology (ACR)/EULAR criteria set for CPPD. Results: The interrater reliability between iRPolM and the 2023 ACR/EULAR criteria set for CPPD was strong (κ = 0.88). The diagnostic performance of iRPolM compared to the 2023 ACR/EULAR criteria set was sensitivity 86.0% (95% confidence interval [CI] 73.3–94.2), specificity 99.1% (95% CI 97.5–99.8), positive likelihood ratio 100.33 (95% CI 32.3–311.3), negative likelihood ratio 0.14 (95% CI 0.07–0.28), positive predictive value 93.5% (95% CI 82.2–97.8), negative predictive value 98.0% (95% CI 82.2–97.8), and accuracy 97.5% (95% CI 95.5–98.8). We allowed rheumatologists to rate the certainty of their microscopic identification of CPP and found a large correspondence between iRPolM and a certain identification (κ = 0.87), whereas only 10% of the uncertain CPP identifications could be confirmed with iRPolM. We identified several novel particle types in synovial fluid analysis, including calcium carbonate crystals, deposited carotenoids, microplastics, and three types of Maltese cross birefringent objects. Conclusion: iRPolM can easily identify CPP crystals with a strong diagnostic performance. PLM alone is not specific enough to reliably resolve complicated cases, and the implementation of Raman spectroscopy in rheumatology practice can be of benefit to patients with suspected CPPD.</p

Влияние параметров одномассной системы с упругими ограничителями на характер ее колебаний

У статті розглянуто одномасну систему з пружними обмежувачами. Побудовано області існування різних режимів коливань системи, а також визначено вплив параметрів системи на межі цих областей.A one-mass system with elastic constraints is studied. Areas of existing of different oscillation modes are built. Also an influence of system parameters on limits of these areas is determined

Ultrafast element-resolved magneto-optics using a fiber-laser-driven extreme ultraviolet light source

We present a novel setup to measure the transverse magneto-optical Kerr effect in the extreme ultraviolet spectral range at exceptionally high repetition rates based on a fiber laser amplifier system. This affords a very high and stable flux of extreme ultraviolet light, which we use to measure element-resolved demagnetization dynamics with unprecedented depth of information. Furthermore, the setup is equipped with a strong electromagnet and a cryostat, allowing measurements between 10 and 420 K using magnetic fields up to 0.86 T. The performance of our setup is demonstrated by a set of temperature- and time-dependent magnetization measurements showing distinct element-dependent behavior

A state-of-the-art review on studies examining the psychological contract

The psychological contract describes the perceived mutual obligations between an employee and the organization (Rousseau, 1989, 2001). Since 1990 numerous studies have been published examining the effects of psychological contracts. Previous reviews on these studies have focused on the history of the term ‘psychological contract’(Roehling, 1997), and on explaining the description, meaning, and usefulness of the psychological contract (Anderson & Schalk, 1998; Taylor & Tekleab, 2004; Van den Brande, 1999). Guest and Conway (2003) published the first review in which an actual overview of studies on psychological contracts was presented. However, the sample of reviewed studies was rather small (k=9) and only operationalizations of the psychological contract and correlations with dependent variables were reported. A review on more specific information, like survey design, sample, and measurement of the psychological contract is still lacking. As a consequence, the aim of this review was to examine the conceptualization and measurement of the psychological contract