Abstract When evaluating a two-phase intervention, the cumulative average treatment effect (ATE) is often the primary causal estimand of interest. However, some individuals who do not respond well to the Phase I treatment may subsequently display noncompliant behaviours. At the same time, exposure to the Phase I treatment is expected to directly influence an individual's potential outcomes, thereby violating the exclusion restriction. Building on an instrumental variable strategy for multisite trials, we clarify the conditions under which the cumulative ATE of a two-phase treatment can be identified by employing the random assignment of the Phase I treatment as the instrument. Our strategy relaxes both the conventional exclusion restriction and sequential ignorability assumptions. We assess the performance of the new strategy through simulation studies. Additionally, we reanalyse data from the Tennessee class size study, in which students and teachers were randomly assigned to either small or regular class types in kindergarten (Phase I) with noncompliance emerging in Grade 1 (Phase II). Applying our new strategy, we estimate the cumulative ATE of receiving two consecutive years of instruction in a small versus regular class.

Liquid metals (LMs), renowned for their high conductivity and large deformability, find increasing applications including in flexible electronics and soft robotics. One critical process in these applications is the precise patterning of LMs into desired shapes. Yet, existing LM patterning techniques predominantly focus on 2D patterns due to challenges posed by the inherent fluidity and leakage of LMs. Here, we introduce an approach that bypasses these limitations, enabling the creation of complex 3D leakage-free LM structures. This is achieved through mechanical programming of 2D magnetically immobilized LM paste formed via incorporating magnetic particles into LMs. Such composite effectively resists leakage due to the combined effect of strong magnetic inter-attraction within the porous magnetic networks and the high surface tension of LMs, while retaining the high conductivity. Diverse freestanding magnetic LM structures, obtained upon LM solidification at ambient temperature, dynamically morph between their 2D and various 3D configurations through multiple cycles of induction heating and magnetic-assisted reprogramming, featuring large compression resistance and self-healing capabilities. Potential applications of these leakage-resistant, shape-adaptable structures are demonstrated through a helical magnetic LM antenna, which showcases its efficiency in wireless communication and energy harvesting.

This mixed-method study focuses on young children's engagement in engineering design activities through the lens of goal orientation. The purpose is to build evidence-based knowledge for educators and researchers to better support children's motivation in engineering. The preliminary results indicate that young children (7-14 years old) have multifaceted goal orientations while engaging in engineering activities, and their goal orientations may be related to the context and setting of the activities (e.g., physical and social environments). The data also indicate differences between families of historically minoritized communities and general museum visitors and caregivers' goal orientations for their children's learning.

The diffusion and use of new ideas is critical for producing innovations and realizing their potential.We explore how characteristics of innovators and potential adopters affect the adoption of important, new scientific ideas in networks.Using rich data on biomedical researchers and their networks, natural language processing, and a novel two-way fixed effects strategy, we find that new ideas introduced by female scientists are under-utilized for two reasons.First, female innovators are less connected than men.Second, at short network distances, researchers (especially men) adopt women's ideas less.Similar gaps hold for underrepresented racial and ethnic minorities.