Sculplexity: Sculptures of Complexity using 3D printing

We show how to convert models of complex systems such as 2D cellular automata into a 3D printed object. Our method takes into account the limitations inherent to 3D printing processes and materials. Our approach automates the greater part of this task, bypassing the use of CAD software and the need for manual design. As a proof of concept, a physical object representing a modified forest fire model was successfully printed. Automated conversion methods similar to the ones developed here can be used to create objects for research, for demonstration and teaching, for outreach, or simply for aesthetic pleasure. As our outputs can be touched, they may be particularly useful for those with visual disabilities.Comment: Free access to article on European Physics Letter

Signal propagation and noisy circuits

The information carried by a signal decays when the signal is corrupted by random noise. This occurs when a message is transmitted over a noisy channel, as well as when a noisy component performs computation. We first study this signal decay in the context of communication and obtain a tight bound on the rate at which information decreases as a signal crosses a noisy channel. We then use this information theoretic result to obtain depth lower bounds in the noisy circuit model of computation defined by von Neumann. In this model, each component fails (produces 1 instead of 0 or vice-versa) independently with a fixed probability, and yet the output of the circuit is required to be correct with high probability. Von Neumann showed how to construct circuits in this model that reliably compute a function and are no more than a constant factor deeper than noiseless circuits for the function. We provide a lower bound on the multiplicative increase in circuit depth necessary for reliable computation, and an upper bound on the maximum level of noise at which reliable computation is possible

On the maximum tolerable noise of k-input gates for reliable computation by formulas

We determine the precise threshold of component noise below which formulas composed of odd degree components can reliably compute all Boolean functions

Information Theory and Noisy Computation

We report on two types of results. The first is a study of the rate of decay of information carried by a signal which is being propagated over a noisy channel. The second is a series of lower bounds on the depth, size, and component reliability of noisy logic circuits which are required to compute some function reliably. The arguments used for the circuit results are information-theoretic, and in particular, the signal decay result is essential to the depth lower bound. Our first result can be viewed as a quantified version of the data processing lemma, for the case of Boolean random variables

Quantum tunneling of the Neel vector in antiferromagnetic [3 x 3] grid molecules

Based on numerical calculations it is shown that the antiferromagnetic grid molecule Mn-[3 x 3] is a very promising candidate to experimentally detect the phenomenon of quantum tunneling of the Neel vector.Comment: 4 pages, 3 figures, REVTEX 4, to appear in PR

Smooth, identifiable supermodels of discrete DAG models with latent variables

We provide a parameterization of the discrete nested Markov model, which is a supermodel that approximates DAG models (Bayesian network models) with latent variables. Such models are widely used in causal inference and machine learning. We explicitly evaluate their dimension, show that they are curved exponential families of distributions, and fit them to data. The parameterization avoids the irregularities and unidentifiability of latent variable models. The parameters used are all fully identifiable and causally-interpretable quantities.Comment: 30 page

Nutritional and Post-Transplantation Outcomes of Enteral versus Parenteral Nutrition in Pediatric Hematopoietic Stem Cell Transplantation: A Systematic Review of Randomized and Nonrandomized Studies

Hematopoietic stem cell transplantation (HSCT) involves the administration of chemotherapy followed by the infusion of donor stem cells. After treatment, children can consequently experience nausea, vomiting, diarrhea, anorexia, and mucositis, which negatively impact oral intake, leading to rapid deterioration in nutritional status and risk of malnutrition. Nutrition support therefore becomes necessary to circumvent these adverse effects. This has traditionally been provided via parenteral nutrition (PN), but pediatric evidence is increasingly advocating enteral nutrition (EN) as a preferential alternative. The objective of this review is to determine the efficacy of any forms of EN versus PN provided during admission to children aged ≤ 18 years undergoing HSCT. Primary outcomes considered efficacy in relation to various nutritional parameters, and secondary outcomes included a range of post-transplantation parameters. Data sources included English and non-English articles from the start date of MEDLINE, EMBASE, AMED, CINAHL and Cochrane Controlled Trials register, up to July 2018. Key journals were also hand searched, reference lists scanned, clinical experts contacted, and gray literature searched using EThOS and Open Grey. Randomized and observational studies comparing any forms of EN versus PN in children aged ≤ 18 years undergoing HSCT investigating nutritional or post-transplantation outcomes were eligible. Data were extracted from included studies using a custom extraction form that had previously been piloted. Because included studies were observational, risk of bias was assessed using Risk of Bias in Non-randomised Studies of Interventions. Because only a small number of heterogenous studies reporting a wide range of differently defined outcomes were included, meta-analyses were not performed and data were presented in narrative form. Conflicting results in favor of either method of nutrition support or no difference between methods were seen for duration of interventions, nutritional intakes, biochemical and anthropometric changes, mortality, infections, length of admission, and neutrophil engraftment. EN may provide favorable benefits over PN regarding acute graft-versus-host-disease (aGVHD) and platelet engraftment. A paucity of studies was found investigating the question posed by this review. Included studies were clinically heterogenous regarding populations, interventions, and outcomes, at moderate to serious risk of bias due to the absence of randomization, confounding parameters, statistical control, retrospective designs, and participant selection. Some studies were more than 15 years old. Despite the limited number and poor quality of identified studies, results support the growing body of pediatric evidence that EN is feasible during HSCT. Similar differences regarding many nutritional and post-transplantation outcomes were seen in both forms of nutrition support, but EN could provide benefits above PN including reduced incidence of aGVHD and faster platelet engraftment