Programmatic Imitation Learning from Unlabeled and Noisy Demonstrations

Imitation Learning (IL) is a promising paradigm for teaching robots to perform novel tasks using demonstrations. Most existing approaches for IL utilize neural networks (NN), however, these methods suffer from several well-known limitations: they 1) require large amounts of training data, 2) are hard to interpret, and 3) are hard to repair and adapt. There is an emerging interest in programmatic imitation learning (PIL), which offers significant promise in addressing the above limitations. In PIL, the learned policy is represented in a programming language, making it amenable to interpretation and repair. However, state-of-the-art PIL algorithms assume access to action labels and struggle to learn from noisy real-world demonstrations. In this paper, we propose PLUNDER, a novel PIL algorithm that integrates a probabilistic program synthesizer in an iterative Expectation-Maximization (EM) framework to address these shortcomings. Unlike existing PIL approaches, PLUNDER synthesizes probabilistic programmatic policies that are particularly well-suited for modeling the uncertainties inherent in real-world demonstrations. Our approach leverages an EM loop to simultaneously infer the missing action labels and the most likely probabilistic policy. We benchmark PLUNDER against several established IL techniques, and demonstrate its superiority across five challenging imitation learning tasks under noise. PLUNDER policies achieve 95% accuracy in matching the given demonstrations, outperforming the next best baseline by 19%. Additionally, policies generated by PLUNDER successfully complete the tasks 17% more frequently than the nearest baseline

Incommensurate charge-stripe correlations in the kagome superconductor CsV3_3Sb5−x_{5-x}Snx_x

We track the evolution of charge correlations in the kagome superconductor CsV$_3$Sb$_5$ as its parent, long-ranged charge density order is destabilized. Upon hole-doping doping, interlayer charge correlations rapidly become short-ranged and their periodicity is reduced by half along the interlayer direction. Beyond the peak of the first superconducting dome, the parent charge density wave state vanishes and incommensurate, quasi-1D charge correlations are stabilized in its place. These competing, unidirectional charge correlations demonstrate an inherent electronic rotational symmetry breaking in CsV$_3$Sb$_5$, independent of the parent charge density wave state and reveal a complex landscape of charge correlations across the electronic phase diagram of this class of kagome superconductors. Our data suggest an inherent 2$k_f$ charge instability and the phenomenology of competing charge instabilities is reminiscent of what has been noted across several classes of unconventional superconductors.Comment: 6 pages, 4 figure

Integrated spatial genomics reveals global architecture of single nuclei

Identifying the relationships between chromosome structures, nuclear bodies, chromatin states and gene expression is an overarching goal of nuclear-organization studies. Because individual cells appear to be highly variable at all these levels, it is essential to map different modalities in the same cells. Here we report the imaging of 3,660 chromosomal loci in single mouse embryonic stem (ES) cells using DNA seqFISH+, along with 17 chromatin marks and subnuclear structures by sequential immunofluorescence and the expression profile of 70 RNAs. Many loci were invariably associated with immunofluorescence marks in single mouse ES cells. These loci form ‘fixed points’ in the nuclear organizations of single cells and often appear on the surfaces of nuclear bodies and zones defined by combinatorial chromatin marks. Furthermore, highly expressed genes appear to be pre-positioned to active nuclear zones, independent of bursting dynamics in single cells. Our analysis also uncovered several distinct mouse ES cell subpopulations with characteristic combinatorial chromatin states. Using clonal analysis, we show that the global levels of some chromatin marks, such as H3 trimethylation at lysine 27 (H3K27me3) and macroH2A1 (mH2A1), are heritable over at least 3–4 generations, whereas other marks fluctuate on a faster time scale. This seqFISH+-based spatial multimodal approach can be used to explore nuclear organization and cell states in diverse biological systems

Integrated spatial genomics reveals global architecture of single nuclei

Identifying the relationships between chromosome structures, nuclear bodies, chromatin states and gene expression is an overarching goal of nuclear-organization studies. Because individual cells appear to be highly variable at all these levels, it is essential to map different modalities in the same cells. Here we report the imaging of 3,660 chromosomal loci in single mouse embryonic stem (ES) cells using DNA seqFISH+, along with 17 chromatin marks and subnuclear structures by sequential immunofluorescence and the expression profile of 70 RNAs. Many loci were invariably associated with immunofluorescence marks in single mouse ES cells. These loci form ‘fixed points’ in the nuclear organizations of single cells and often appear on the surfaces of nuclear bodies and zones defined by combinatorial chromatin marks. Furthermore, highly expressed genes appear to be pre-positioned to active nuclear zones, independent of bursting dynamics in single cells. Our analysis also uncovered several distinct mouse ES cell subpopulations with characteristic combinatorial chromatin states. Using clonal analysis, we show that the global levels of some chromatin marks, such as H3 trimethylation at lysine 27 (H3K27me3) and macroH2A1 (mH2A1), are heritable over at least 3–4 generations, whereas other marks fluctuate on a faster time scale. This seqFISH+-based spatial multimodal approach can be used to explore nuclear organization and cell states in diverse biological systems

Disentangling participatory ICT design in socioeconomic development

Participatory design in socioeconomic development is an invariably political activity fraught with both political as well as ethical entanglements. ICT for development (ICTD) - often involved in contexts of great inequality and heteogeneity - places these in especially sharp relief. This paper draws attention to these entanglements as well as what they mean for the role and practice of designer-researchers practicing PD. We then draw upon our experiences in an active PD project to highlight approaches that serve as a partial response to these entanglements. These presents both limitations as well as orientations for our role as designer-researchers in engaging with and organising PD work in ICTD - providing a starting point for answering the question “who participates with whom in what and why?

Examining the generalizability of research findings from archival data

This initiative examined systematically the extent to which a large set of archival research findings generalizes across contexts. We repeated the key analyses for 29 original strategic management effects in the same context (direct reproduction) as well as in 52 novel time periods and geographies; 45% of the reproductions returned results matching the original reports together with 55% of tests in different spans of years and 40% of tests in novel geographies. Some original findings were associated with multiple new tests. Reproducibility was the best predictor of generalizability—for the findings that proved directly reproducible, 84% emerged in other available time periods and 57% emerged in other geographies. Overall, only limited empirical evidence emerged for context sensitivity. In a forecasting survey, independent scientists were able to anticipate which effects would find support in tests in new samples

Cost-benefit analysis of two possible deposit-refund systems for reuse and recycling of plastic packaging in Sweden

Plastic packaging is a major contributor to the environmental impacts associated with the linear plastic production and consumption system due to the prevalence of short-lived single-use plastic (SUP) packaging. Deposit-refund system (DRS), as an alternative policy instrument to Extended Producer Responsibility in waste management, is deemed as a potentially promising way to address the failure of the current plastic waste management and facilitate circular plastic packaging production and consumption for food contact use. In this paper, two DRS scenarios for recycling and reuse respectively are explored, with PET trays for food-grade use in Sweden in focus. Their costs and benefits are investigated relative to the business-as-usual scenario over a 25-year period. Results show that the costs are greater than the benefits for the recycling scenario but not for the reuse scenario and that the benefit-cost ratio (1,67) of the reuse scenario is 2.3 times as high as that (0,73) of the recycling scenario. The distributive analysis reveals major cost drivers such as deposit handling and recycling in the recycling case and deposit handling, dishwashing and packaging in the reuse case and major cost takers such as materials industry and hospitality/supermarkets in both scenarios. However, the results are uncertain, as is indicated by sensitivity analysis. Several parameters with high uncertainty are identified and highlighted for system development and innovation.QC 20221201</p