Uncertainty-driven Affordance Discovery for Efficient Robotics Manipulation

Robotics affordances, providing information about what actions can be taken in a given situation, can aid robotics manipulation. However, learning about affordances requires expensive large annotated datasets of interactions or demonstrations. In this work, we show active learning can mitigate this problem and propose the use of uncertainty to drive an interactive affordance discovery process. We show that our method enables the efficient discovery of visual affordances for several action primitives, such as grasping, stacking objects, or opening drawers, strongly improving data efficiency and allowing us to learn grasping affordances on a real-world setup with an xArm 6 robot arm in a small number of trials.Comment: Presented at the GMPL workshop @ RSS 202

Deconfounded Imitation Learning

Standard imitation learning can fail when the expert demonstrators have different sensory inputs than the imitating agent. This is because partial observability gives rise to hidden confounders in the causal graph. We break down the space of confounded imitation learning problems and identify three settings with different data requirements in which the correct imitation policy can be identified. We then introduce an algorithm for deconfounded imitation learning, which trains an inference model jointly with a latent-conditional policy. At test time, the agent alternates between updating its belief over the latent and acting under the belief. We show in theory and practice that this algorithm converges to the correct interventional policy, solves the confounding issue, and can under certain assumptions achieve an asymptotically optimal imitation performance

Water Resources Systems Planning and Management: An Introduction to Methods, Models and Applications

This 2005 version has been superseded by the 2017 edition, available in full here: http://hdl.handle.net/1813/48159Throughout history much of the world has witnessed ever-greater demands for reliable, high-quality and inexpensive water supplies for domestic consumption, agriculture and industry. In recent decades there have also been increasing demands for hydrological regimes that support healthy and diverse ecosystems, provide for water-based recreational activities, reduce if not prevent floods and droughts, and in some cases, provide for the production of hydropower and ensure water levels adequate for ship navigation. Water managers are challenged to meet these multiple and often conflicting demands. At the same time, public stakeholder interest groups have shown an increasing desire to take part in the water resources development and management decision making process. Added to all these management challenges are the uncertainties of natural water supplies and demands due to changes in our climate, changes in people's standards of living, changes in watershed land uses and changes in technology. How can managers develop, or redevelop and restore, and then manage water resources systems - systems ranging from small watersheds to those encompassing large river basins and coastal zones - in a way that meets society's changing objectives and goals? In other words, how can water resources systems become more integrated and sustainable

Disasters and History

This monograph provides an overview of research into disasters from a historical perspective, making two new contributions. First, it introduces the field of ‘disaster studies’ to history, showing how we can use history to better understand how societies deal with shocks and hazards and their potentially disastrous outcomes. Second, we introduce historians to the topic of disasters and the field of disaster studies, and explicitly show the relevance of studying past disasters to better understand the social, economic, and political functioning of past societies

The additional value of first pass myocardial perfusion imaging during peak dose of dobutamine stress cardiac MRI for the detection of myocardial ischemia

Purpose of this study was to assess the additional value of first pass myocardial perfusion imaging during peak dose of dobutamine stress Cardiac-MR (CMR). Dobutamine Stress CMR was performed in 115 patients with an inconclusive diagnosis of myocardial ischemia on a 1.5 T system (Magnetom Avanto, Siemens Medical Systems). Three short-axis cine and grid series were acquired during rest and at increasing doses of dobutamine (maximum 40 μg/kg/min). On peak dose dobutamine followed immediately by a first pass myocardial perfusion imaging sequence. Images were graded according to the sixteen-segment model, on a four point scale. Ninety-seven patients showed no New (Induced) Wall Motion Abnormalities (NWMA). Perfusion imaging showed absence of perfusion deficits in 67 of these patients (69%). Perfusion deficits attributable to known previous myocardial infarction were found in 30 patients (31%). Eighteen patients had NWMA, indicative for myocardial ischemia, of which 14 (78%) could be confirmed by a corresponding perfusion deficit. Four patients (22%) with NWMA did not have perfusion deficits. In these four patients NWMA were caused by a Left Bundle Branch Block (LBBB). They were free from cardiac events during the follow-up period (median 13.5 months; range 6–20). Addition of first-pass myocardial perfusion imaging during peak-dose dobutamine stress CMR can help to decide whether a NWMA is caused by myocardial ischemia or is due to an (inducible) LBBB, hereby preventing a false positive wall motion interpretation

Single molecule fluorescence for membrane proteins

The cell membrane is a complex milieu of lipids and proteins. In order to understand the behaviour of individual molecules is it often desirable to examine them as purified components in in vitro systems. Here, we detail the creation and use of droplet interface bilayers (DIBs) which, when coupled to TIRF microscopy, can reveal spatiotemporal and kinetic information for individual membrane proteins. A number of steps are required including modification of the protein sequence to enable the incorporation of appropriate fluorescent labels, expression and purification of the membrane protein and subsequent labelling. Following creation of DIBs, proteins are spontaneously incorporated into the membrane where they can be imaged via conventional single molecule TIRF approaches. Using this strategy, in conjunction with step-wise photobleaching, FRET and / or single particle tracking, a host of parameters can be determined such as oligomerisation state and dynamic information. We discuss advantages and limitations of this system and offer guidance for successful implementation of these approaches

Disasters and History

Disasters and History offers the first comprehensive historical overview of hazards and disasters. Drawing on a range of case studies, including the Black Death, the Lisbon earthquake of 1755 and the Fukushima disaster, the authors examine how societies dealt with shocks and hazards and their potentially disastrous outcomes. They reveal the ways in which the consequences and outcomes of these disasters varied widely not only between societies but also within the same societies according to social groups, ethnicity and gender. They also demonstrate how studying past disasters, including earthquakes, droughts, floods and epidemics, can provide a lens through which to understand the social, economic and political functioning of past societies and reveal features of a society which may otherwise remain hidden from view

Performance of adenosine “stress-only” perfusion MRI in patients without a history of myocardial infarction: a clinical outcome study

To assess the diagnostic value of adenosine “stress-only” myocardial perfusion MR for ischemia detection as an indicator for coronary angiography in patients without a prior myocardial infarction and a necessity to exclude ischemia. Adenosine perfusion MRI was performed at 1.5 T in 139 patients with a suspicion of ischemia and no prior myocardial infarction. After 3 min of adenosine infusion a perfusion sequence was started. Patients with a perfusion defect were referred to coronary angiography (CAG). Patients with a normal perfusion were enrolled in follow-up. Fourteen out of 139 patients (10.1%) had a perfusion defect indicative of ischemia. These patients underwent a coronary angiogram, which showed complete agreement with the perfusion images. 125 patients with a normal myocardial perfusion entered follow-up (median 672 days, range 333–1287 days). In the first year of follow-up one Major Adverse Coronary Event (MACE) occurred and one patient had new onset chest pain with a confirmed coronary stenosis. Reaching a negative predictive value for MACE of 99.2% and for any coronary event of 98.4%. At 2 year follow-up no additional MACE occurred. Sensitivity of adenosine perfusion MR for MACE is 93.3% and specificity and positive predictive value are 100%. Adenosine myocardial perfusion MR for the detection of myocardial ischemia in a “stress-only” protocol in patients without prior myocardial infarctions, has a high diagnostic accuracy. This fast examination can play an important role in the evaluation of patients without prior myocardial infarctions and a necessity to exclude ischemia

Early treatment versus expectative management of patent ductus arteriosus in preterm infants

_Background:_ Much controversy exists about the optimal management of a patent ductus arteriosus (PDA) in preterm infants, especially in those born at a gestational age (GA) less than 28weeks. No causal relationship has been proven between a (haemodynamically significant) PDA and neonatal complications related to pulmonary hyperperfusion and/or systemic hypoperfusion. Although studies show conflicting results, a common understanding is that medical or surgical treatment of a PDA does not seem to reduce the risk of major neonatal morbidities and mortality. As the PDA might have closed spontaneously, treated children are potentially exposed to iatrogenic adverse effects. A conservative approach is gaining interest worldwide, although convincing evidence to support its use is lacking. _Methods:_ This multicentre, randomised, non-inferiority trial is conducted in neonatal intensive care units. The study population consists of preterm infants (GA1.5mm. Early treatment (between 24 and 72h postnatal age) with the cyclooxygenase inhibitor(COXi) ibuprofen (IBU) is compared with an expectative management (no intervention intended to close a PDA). The primary outcome is the composite of mortality, and/or necrotising enterocolitis (NEC) Bell stage ≥ IIa, and/or bronchopulmonary dysplasia (BPD) defined as the need for supplemental oxygen, all at a postmenstrual age (PMA) of 36weeks. Secondary outcome parameters are short term sequelae of cardiovascular failure, comorbidity and adverse events assessed during hospitalization and long-term neurodevelopmental outcome assessed at a corrected age of 2 years. Consequences regarding health economics are evaluated by cost effectiveness analysis and budget impact analysis. _Discussion:_ As a conservative approach is gaining interest, we investigate whether in preterm infants, born at a GA less than 28weeks, with a PDA an expectative management is non-inferior to early treatment with IBU regarding to the composite outcome of mortality and/or NEC and/or BPD at a PMA of 36weeks

Why do people file share unlawfully? A systematic review, meta-analysis and panel study

Unlawful digital media sharing is common and believed to be extremely damaging to business. Understanding unlawful file sharers’ motivations offers the opportunity to develop business models and behavioral interventions to maximize consumers’ and businesses’ benefit. This paper uses a systematic review of unlawful file sharing research, and the Theory of Planned Behavior, to motivate a large-scale panel study in which initial determinants were used to predict subsequent behavior. A meta-analysis found Attitudes, Subjective Norms and Perceived Behavioral Control were all associated with unlawful file sharing. Media type and demographic differences in the importance of Perceived Behavioral Control were found and attributed to more accurate evaluation of familiar activities, i.e., greater experience increases the influence of Perceived Behavioral Control but age does not. The panel study confirmed that greater past experience was associated with Perceived Behavioral Control and Intention. We conclude that past experience increases the efficacy of the Theory of Planned Behavior and specifically Perceived Behavioral control in predicting behavior, contrary to some widely held beliefs about the role of experience. The role of experience is therefore crucial to understanding people’s choices. Practically, improving social approval, positive evaluation and access to lawful media should reduce unlawful behavior