3,224 research outputs found

    The Incomplete Rosetta Stone Problem: Identifiability Results for Multi-View Nonlinear ICA

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    We consider the problem of recovering a common latent source with independent components from multiple views. This applies to settings in which a variable is measured with multiple experimental modalities, and where the goal is to synthesize the disparate measurements into a single unified representation. We consider the case that the observed views are a nonlinear mixing of component-wise corruptions of the sources. When the views are considered separately, this reduces to nonlinear Independent Component Analysis (ICA) for which it is provably impossible to undo the mixing. We present novel identifiability proofs that this is possible when the multiple views are considered jointly, showing that the mixing can theoretically be undone using function approximators such as deep neural networks. In contrast to known identifiability results for nonlinear ICA, we prove that independent latent sources with arbitrary mixing can be recovered as long as multiple, sufficiently different noisy views are available

    The demand for crop genetic resources: international use of the U.S. National Plant Germplasm System

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    In contrast to a perception that ex situ collections of germplasm are rarely used, this empirical case study reveals large quantities of germplasm samples distributed by the U.S. National Germplasm System to many types of scientific institutions located in numerous countries around the world. Distributions favor developing countries in several ways including the numbers of samples shipped, utilization rates in crop breeding programs, and the secondary benefits brought about through sharing this germplasm with other scientists. Expected future demand is also greater among scientists in developing countries. These findings underscore the importance to global science and technology of retaining such resources in the public domain.Germplasm resources, Plant Research., Germplasm conservation., Germplasm resources, Plant International cooperation. ,

    Introduction: The expanded conception of security and institutions

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    This is the author accepted manuscript. The final version is available from CUP via the DOI in this recordIntroduction Security is a dynamic, context-dependent concept that is inevitably shaped by social conditions and practices. The socio-political perception of security threats influences our security policies relevant to political decisions about the design of social institutions specifically addressing those security concerns. Security is traditionally understood to be physical protection of national territory and its population from the destructive effects of warfare through military means. Social institutions including but not limited to national governing institutions, inter-governmental institutions and the military are all devices developed through human history to collectively address traditional security threats. Security is often considered to be an antithesis of the rule of law and civil liberty, justifying violation of rules and the restriction of freedom. However, the development of international law and the institutionalisation of international public authorities have contributed to the increased normalcy or containment of extra-legal responses to security threats. For example, the Charter of the United Nations (‘UN Charter’) provides institutionalised mechanisms as the means of regulating the behaviour of sovereign states and conflict among them. The nuclear non-proliferation regime establishes mechanisms for preventing the proliferation of nuclear weapons and facilitating the development of peaceful nuclear energy technology by institutionalising the asymmetric obligations between designated nuclear-weapon states and other non-nuclear-weapon states. Yet, towards the end of the Cold War the concept of security began to expand, which subsequently led to the proliferation of contemporary security issues such as economic security, environmental security, energy and resource security, health security and bio-security. The conception of security also took a dramatic turn following the 2001 terrorist attacks on New York and Washington, blurring the traditional boundaries between international security and national security threats. Those changes in the conception of security world-wide have tested the potential of existing institutions, such as the World Trade Organization (WTO), the World Health Organization (WHO), the International Maritime Organization (IMO), the Organization for Security and Co-operation in Europe (OSCE), the European Union (EU) and the Association of Southeast Asian Nations (ASEAN), to assume a new role in the changing security paradigms, both at international and domestic levels

    The Court as Archive

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    "Until the late 20th century, ‘an archive’ generally meant a repository for documents, as well as the generic name for the wide range of documents the repository might hold. An archive could be visited, and then also searched, to discover past actions or lives that had meaning for the present. While historians and historiographers have long understood the contests that archives contain and represent, the very idea of ‘the archive’ has, over the last 40 years, become the subject and object of widening and intensified consideration. This consideration has been intellectual (from scholars in a wide range of disciplines) and public (from communities and individuals whose stories are held captive, or sometimes hidden or excluded from official archives), as well as institutional. It has involved scrutiny and critique of official archives’ limitations and practices, as well as symbolic, affective and theoretical expansion and heightened expectation of what ‘the archive’ is or should be. The very language of ‘the archive’ now carries freight as administrative practice, normative value, metaphor, description and aspiration in different ways than it did in the 20th century. This collection offers a unique contribution to these reinvigorated and sometimes new conversations about what an archive might be, what it can do as a consequence, and to whom it bears custodial responsibilities. In particular, this collection addresses what it means for contemporary Australian superior courts of record to not only have constitutional and procedural duties to documents as a matter of law, but also to acknowledge obligations to care for those materials in a way that understands their public meaning and public value for the Australian people, in the past, in the present and for the future.

    Finite-Temperature Auxiliary-Field Quantum Monte Carlo for Bose-Fermi Mixtures

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    We present a quantum Monte Carlo (QMC) technique for calculating the exact finite-temperature properties of Bose-Fermi mixtures. The Bose-Fermi Auxiliary-Field Quantum Monte Carlo (BF-AFQMC) algorithm combines two methods, a finite-temperature AFQMC algorithm for bosons and a variant of the standard AFQMC algorithm for fermions, into one algorithm for mixtures. We demonstrate the accuracy of our method by comparing its results for the Bose-Hubbard and Bose-Fermi-Hubbard models against those produced using exact diagonalization for small systems. Comparisons are also made with mean-field theory and the worm algorithm for larger systems. As is the case with most fermion Hamiltonians, a sign or phase problem is present in BF-AFQMC. We discuss the nature of these problems in this framework and describe how they can be controlled with well-studied approximations to expand BF-AFQMC's reach. The new algorithm can serve as an essential tool for answering many unresolved questions about many-body physics in mixed Bose-Fermi systems.Comment: 19 pages, 6 figure

    Causal Consistency of Structural Equation Models

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    Complex systems can be modelled at various levels of detail. Ideally, causal models of the same system should be consistent with one another in the sense that they agree in their predictions of the effects of interventions. We formalise this notion of consistency in the case of Structural Equation Models (SEMs) by introducing exact transformations between SEMs. This provides a general language to consider, for instance, the different levels of description in the following three scenarios: (a) models with large numbers of variables versus models in which the `irrelevant' or unobservable variables have been marginalised out; (b) micro-level models versus macro-level models in which the macro-variables are aggregate features of the micro-variables; (c) dynamical time series models versus models of their stationary behaviour. Our analysis stresses the importance of well specified interventions in the causal modelling process and sheds light on the interpretation of cyclic SEMs.Comment: equal contribution between Rubenstein and Weichwald; accepted manuscrip
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