Mining electron density for functionally relevant protein polysterism in crystal structures.

This review focuses on conceptual and methodological advances in our understanding and characterization of the conformational heterogeneity of proteins. Focusing on X-ray crystallography, we describe how polysterism, the interconversion of pre-existing conformational substates, has traditionally been analyzed by comparing independent crystal structures or multiple chains within a single crystal asymmetric unit. In contrast, recent studies have focused on mining electron density maps to reveal previously 'hidden' minor conformational substates. Functional tests of the importance of minor states suggest that evolutionary selection shapes the entire conformational landscape, including uniquely configured conformational substates, the relative distribution of these substates, and the speed at which the protein can interconvert between them. An increased focus on polysterism may shape the way protein structure and function is studied in the coming years

A note on the 1-prevalence of continuous images with full Hausdorff dimension

We consider the Banach space consisting of real-valued continuous functions on an arbitrary compact metric space. It is known that for a prevalent (in the sense of Hunt, Sauer and Yorke) set of functions the Hausdorff dimension of the image is as large as possible, namely 1. We extend this result by showing that `prevalent' can be replaced by `1-prevalent', i.e. it is possible to \emph{witness} this prevalence using a measure supported on a one dimensional subspace. Such one dimensional measures are called \emph{probes} and their existence indicates that the structure and nature of the prevalence is simpler than if a more complicated `infinite dimensional' witnessing measure has to be used.Comment: 8 page

The Hausdorff dimension of graphs of prevalent continuous functions

We prove that the Hausdorff dimension of the graph of a prevalent continuous function is 2. We also indicate how our results can be extended to the space of continuous functions on $[0,1]^d$ for $d \in \mathbb{N}$ and use this to obtain results on the `horizon problem' for fractal surfaces. We begin with a survey of previous results on the dimension of a generic continuous function

Child death in high-income countries

Although high income countries have made substantial progress towards reducing child mortality over recent decades, rates vary markedly between and within countries, and modifiable factors continue to be identified in many deaths. A series of three articles in The Lancet has described the epidemiology of child mortality and a standardised approach to child death reviews in high income countries. Patterns of child mortality at different ages are delineated into five broad categories: perinatal, congenital, acquired natural, external, and unexplained; while contributory factors are described across four broad domains: factors intrinsic to the child, the physical environment, the social environment, and service delivery. This commentary attempts to draw on the conclusions of these three articles and make practical recommendations on strategies in three key areas with perhaps the greatest potential to further reduce child mortality in high income countries: perinatal conditions, particularly preterm birth; acquired natural conditions, such as sepsis or acute respiratory problems; and external causes, including road traffic fatalities

The Real Problem with Perturbative Quantum Field Theory

The perturbative approach to quantum field theory (QFT) has long been viewed with suspicion by philosophers of science. This paper offers a diagnosis of its conceptual problems. Drawing on Norton's ([2012]) discussion of the notion of approximation I argue that perturbative QFT ought to be understood as producing approximations without specifying an underlying QFT model. This analysis leads to a reassessment of common worries about perturbative QFT. What ends up being the key issue with the approach on this picture is not mathematical rigour, or the threat of inconsistency, but the need for a physical explanation of its empirical success

How to make a comet

The primary mandate of NASA is the study of the nature and origin of the solar system. The study of the comets provide information about conditions and processes at the beginning of the solar system. Short period comets and their relatives, the near Earth asteroids may prove to be second only to the sun in importance to the long term survival of civilization for two reasons. The short period comets and the near Earth asteroids are a possible candidate for the cause of mass extinctions of life on Earth; and they may provide the material means for the expansion of civilization into the solar system and beyond. The comets and near Earth asteroids almost certainly represent the most primitive material of the solar system, still tantalizingly unavailable until spacecraft bring first-hand information. In the meantime comets must be studied by remote means. Laboratory investigations using synthetic cometary materials may add to the knowledge of these interesting objects. Experimentation on comet synthesis is briefly discussed

Towards a Realist View of Quantum Field Theory

Quantum field theories (QFTs) seem to have all of the qualities that typically motivative scientific realism. Alongside general relativity, the standard model of particle physics, and its subsidiaries, like quantum electrodynamics (QED) and quantum chromodynamics (QCD), are our most fundamental physical theories. They have also produced some of the most accurate predictions in the history of science: QED famously gives a value for the anomalous magnetic moment of the electron that agrees with experiment at precisions better than one part in a trillion. When it comes to actually articulating a realist reading of these theories, however, we run into serious difficulties. This chapter puts forward what I take to be the most promising strategy for developing a realist epistemology in this context. I set up the discussion by highlighting the difficulty of making sense of QFT in orthodox realist terms if we restrict our attention to perturbative and axiomatic treatments of the theory. I then introduce the renormalization group, and argue, drawing on previous work by Wallace (2006, 2011) and Williams (2017), that it points to a way of rescuing a realist reading of QFT. I close by considering some challenges facing this renormalization group based realism. Besides some brief remarks in this final section, I will mostly be bracketing the measurement problem and associated interpretive puzzles inherited from non-relativistic quantum mechanics