An information theoretic approach to the expressiveness of programming languages

The conciseness conjecture is a longstanding notion in computer science that programming languages with more built-in operators, that is more expressive languages with larger semantics, produce smaller programs on average. Chaitin defines the related concept of an elegant program such that there is no smaller program in some language which, when run, produces the same output. This thesis investigates the conciseness conjecture in an empirical manner. Influenced by the concept of elegant programs, we investigate several models of computation, and implement a set of functions in each programming model. The programming models are Turing Machines, λ-Calculus, SKI, RASP, RASP2, and RASP3. The information content of the programs and models are measured as characters. They are compared to investigate hypotheses relating to how the mean program size changes as the size of the semantics change, and how the relationship of mean program sizes between two models compares to that between the sizes of their semantics. We show that the amount of information present in models of the same paradigm, or model family, is a good indication of relative expressivity and average program size. Models that contain more information in their semantics have smaller average programs for the set of tested functions. In contrast, the relative expressiveness of models from differing paradigms, is not indicated by their relative information contents. RASP and Turing Machines have been implemented as Field Programmable Gate Array (FPGA) circuits to investigate hardware analogues of the hypotheses above. Namely that the amount of information in the semantics for a model directly influences the size of the corresponding circuit, and that the relationship of mean circuit sizes between models is comparable to the relationship of mean program sizes. We show that the number of components in the circuits that realise the semantics and programs of the models correlates with the information required to implement the semantics and program of a model. However, the number of components to implement a program in a circuit for one model does not relate to the number of components implementing the same program in another model. This is in contrast to the more abstract implementations of the programs. Information is a computational resource and therefore follows the rules of Blum’s axioms. These axioms and the speedup theorem are used to obtain an alternate proof of the undecidability of elegance. This work is a step towards unifying the formal notion of expressiveness with the notion of algorithmic information theory and exposes a number of interesting research directions. A start has been made on integrating the results of the thesis with the formal framework for the expressiveness of programming languages

Losing life and livelihood: A systematic review and meta-analysis of unemployment and all-cause mortality

Unemployment rates in the United States remain near a 25-year high and global unemployment is rising. Previous studies have shown that unemployed persons have an increased risk of death, but the magnitude of the risk and moderating factors have not been explored. The study is a random effects meta-analysis and meta-regression designed to assess the association between unemployment and all-cause mortality among working-age persons. We extracted 235 mortality risk estimates from 42 studies, providing data on more than 20 million persons. The mean hazard ratio (HR) for mortality was 1.63 among HRs adjusted for age and additional covariates. The mean effect was higher for men than for women. Unemployment was associated with an increased mortality risk for those in their early and middle careers, but less for those in their late career. The risk of death was highest during the first 10 years of follow-up, but decreased subsequently. The mean HR was 24% lower among the subset of studies controlling for health-related behaviors. Public health initiatives could target unemployed persons for more aggressive cardiovascular screening and interventions aimed at reducing risk-taking behaviors

ToyArchitecture: Unsupervised Learning of Interpretable Models of the World

Research in Artificial Intelligence (AI) has focused mostly on two extremes: either on small improvements in narrow AI domains, or on universal theoretical frameworks which are usually uncomputable, incompatible with theories of biological intelligence, or lack practical implementations. The goal of this work is to combine the main advantages of the two: to follow a big picture view, while providing a particular theory and its implementation. In contrast with purely theoretical approaches, the resulting architecture should be usable in realistic settings, but also form the core of a framework containing all the basic mechanisms, into which it should be easier to integrate additional required functionality. In this paper, we present a novel, purposely simple, and interpretable hierarchical architecture which combines multiple different mechanisms into one system: unsupervised learning of a model of the world, learning the influence of one's own actions on the world, model-based reinforcement learning, hierarchical planning and plan execution, and symbolic/sub-symbolic integration in general. The learned model is stored in the form of hierarchical representations with the following properties: 1) they are increasingly more abstract, but can retain details when needed, and 2) they are easy to manipulate in their local and symbolic-like form, thus also allowing one to observe the learning process at each level of abstraction. On all levels of the system, the representation of the data can be interpreted in both a symbolic and a sub-symbolic manner. This enables the architecture to learn efficiently using sub-symbolic methods and to employ symbolic inference.Comment: Revision: changed the pdftitl

PVR: Patch-to-Volume Reconstruction for Large Area Motion Correction of Fetal MRI

In this paper we present a novel method for the correction of motion artifacts that are present in fetal Magnetic Resonance Imaging (MRI) scans of the whole uterus. Contrary to current slice-to-volume registration (SVR) methods, requiring an inflexible anatomical enclosure of a single investigated organ, the proposed patch-to-volume reconstruction (PVR) approach is able to reconstruct a large field of view of non-rigidly deforming structures. It relaxes rigid motion assumptions by introducing a specific amount of redundant information that is exploited with parallelized patch-wise optimization, super-resolution, and automatic outlier rejection. We further describe and provide an efficient parallel implementation of PVR allowing its execution within reasonable time on commercially available graphics processing units (GPU), enabling its use in the clinical practice. We evaluate PVR's computational overhead compared to standard methods and observe improved reconstruction accuracy in presence of affine motion artifacts of approximately 30% compared to conventional SVR in synthetic experiments. Furthermore, we have evaluated our method qualitatively and quantitatively on real fetal MRI data subject to maternal breathing and sudden fetal movements. We evaluate peak-signal-to-noise ratio (PSNR), structural similarity index (SSIM), and cross correlation (CC) with respect to the originally acquired data and provide a method for visual inspection of reconstruction uncertainty. With these experiments we demonstrate successful application of PVR motion compensation to the whole uterus, the human fetus, and the human placenta.Comment: 10 pages, 13 figures, submitted to IEEE Transactions on Medical Imaging. v2: wadded funders acknowledgements to preprin

Comparison of the Hindin Proteins of Strongylocentrotus franciscanus, S. purpuratus, and Lytechinus variegatus: Sequences involved in the Species Specificity of Fertilization

Bindin is the sea urchin sperm acrosomal protein that is responsible for the species-specific adhesion of the sperm to the egg. Two new bindin cDNA sequences that contain the entire open reading frame for the binding precursor are reported: one for Strongylocentrotus franciscanus and one for Lytechinus variegatus. Both contain inverted repetitive sequences in their 3' untranslated regions, and the S. franciscanus cDNA contains an inverted repetitive sequence match between the 5' untranslated region and the coding region. The middle third of the mature bindin sequence is highly conserved in all three species, and the flanking sequences share short repeated sequences that vary in number between the species. Cross-fertilization data are reported for the species S. purpuratus, S. franciscanus, L. variegatus, and L. pictus. A barrier to cross-fertilization exists between the sympatric Strongylocentrotus species, but there is no barrier between the allopatric Lytechinus species