Resolving MISS conceptions and misconceptions: A geological approach to sedimentary surface textures generated by microbial and abiotic processes

The rock record contains a rich variety of sedimentary surface textures on siliciclastic sandstone, siltstone and mudstone bedding planes. In recent years, an increasing number of these textures have been attributed to surficial microbial mats at the time of deposition, resulting in their classification as microbially induced sedimentary structures, or MISS. Research into MISS has developed at a rapid rate, resulting in a number of misconceptions in the literature. Here, we attempt to rectify these MISS misunderstandings. The first part of this paper surveys the stratigraphic and environmental range of reported MISS, revealing that contrary to popular belief there are more reported MISS-bearing rock units of Phanerozoic than Precambrian age. Furthermore, MISS exhibit a pan-environmental and almost continuous record since the Archean. Claims for the stratigraphic restriction of MISS to intervals prior to the evolution of grazing organisms or after mass extinction events, as well as claims for the environmental restriction of MISS, appear to result from sampling bias. In the second part of the paper we suggest that raised awareness of MISS has come at the cost of a decreasing appreciation of abiotic processes that may create morphologically similar features. By introducing the umbrella term ‘sedimentary surface textures’, of which MISS are one subset, we suggest a practical methodology for classifying such structures in the geological record. We illustrate how elucidating the formative mechanisms of ancient sedimentary surface textures usually requires consideration of a suite of sedimentological evidence from surrounding strata. Resultant interpretations, microbial or non-microbial, should be couched within a reasonable degree of uncertainty. This approach recognizes that morphological similarity alone does not constitute scientific proof of a common origin, and reinstates a passive descriptive terminology for sedimentary surface textures that cannot be achieved with the current MISS lexicon. It is hoped that this new terminology will reduce the number of overly sensational and misleading claims of MISS occurrence, and permit the means to practically separate initial observation from interpretation. Furthermore, this methodology offers a scientific approach that appreciates the low likelihood of conclusively identifying microbial structures from visual appearance alone, informing the search for true MISS in Earth's geological record and potentially on other planetary bodies such as Mars.Instances of sedimentary surface textures in the field were identified coincidentally during multiple seasons of varied field investigations primarily funded for NSD by a variety of organisations including a George Frederic Matthew Research Grant from the New Brunswick Museum for 2012, and a Discovery Grant from the Natural Sciences and Engineering Research Council of Canada to MRG. AGL is supported by the Natural Environment Research Council [grant number NE/L011409/1].This is the final version of the article. It first appeared from Elsevier via http://dx.doi.org/10.1016/j.earscirev.2016.01.00

The Algorithmic Origins of Life

Although it has been notoriously difficult to pin down precisely what it is that makes life so distinctive and remarkable, there is general agreement that its informational aspect is one key property, perhaps the key property. The unique informational narrative of living systems suggests that life may be characterized by context-dependent causal influences, and in particular, that top-down (or downward) causation -- where higher-levels influence and constrain the dynamics of lower-levels in organizational hierarchies -- may be a major contributor to the hierarchal structure of living systems. Here we propose that the origin of life may correspond to a physical transition associated with a shift in causal structure, where information gains direct, and context-dependent causal efficacy over the matter it is instantiated in. Such a transition may be akin to more traditional physical transitions (e.g. thermodynamic phase transitions), with the crucial distinction that determining which phase (non-life or life) a given system is in requires dynamical information and therefore can only be inferred by identifying causal architecture. We discuss some potential novel research directions based on this hypothesis, including potential measures of such a transition that may be amenable to laboratory study, and how the proposed mechanism corresponds to the onset of the unique mode of (algorithmic) information processing characteristic of living systems.Comment: 13 pages, 1 tabl

T-cell reconstitution after thymus xenotransplantation induces hair depigmentation and loss

Here we present a mouse model for T-cell targeting of hair follicles, linking the pathogenesis of alopecia to that of depigmentation disorders. Clinically, thymus transplantation has been successfully used to treat T-cell immunodeficiency in congenital athymia, but is associated with autoimmunity. We established a mouse model of thymus transplantation by subcutaneously implanting human thymus tissue into athymic C57BL/6 nude mice. These xenografts supported mouse T-cell development. Surprisingly, we did not detect multiorgan autoimmune disease. However, in all transplanted mice, we noted a striking depigmentation and loss of hair follicles. Transfer of T cells from transplanted nudes to syngeneic black-coated RAG(-/-) recipients caused progressive, persistent coat-hair whitening, which preceded patchy hair loss in depigmented areas. Further transfer experiments revealed that these phenomena could be induced by CD4+ T cells alone. Immunofluorescent analysis suggested that Trp2+ melanocyte-lineage cells were decreased in depigmented hair follicles, and pathogenic T cells upregulated activation markers when exposed to C57BL/6 melanocytes in vitro, suggesting that these T cells are not tolerant to self-melanocyte antigens. Our data raise interesting questions about the mechanisms underlying tissue-specific tolerance to skin antigens

Evaluating the efficacy of thoracoscopy and talc poudrage versus pleurodesis using talc slurry (TAPPS trial): protocol of an open-label randomised controlled trial

INTRODUCTION: The management of recurrent malignant pleural effusions (MPE) can be challenging. Various options are available, with the most efficacious and widely used being talc pleurodesis. Talc can either be applied via a chest drain in the form of slurry, or at medical thoracoscopy using poudrage. Current evidence regarding which method is most effective is conflicting and often methodologically flawed. The TAPPS trial is a suitably powered, multicentre, open-label, randomised controlled trial designed to compare the pleurodesis success rate of medical thoracoscopy and talc poudrage with chest drain insertion and talc slurry. METHODS AND ANALYSIS: 330 patients with a confirmed MPE requiring intervention will be recruited from UK hospitals. Patients will be randomised (1:1) to undergo either small bore (<14 Fr) Seldinger chest drain insertion followed by instillation of sterile talc (4 g), or to undergo medical thoracoscopy and simultaneous poudrage (4 g). The allocated procedure will be performed as an inpatient within 3 days of randomisation taking place. Following discharge, patients will be followed up at regular intervals for 6 months. The primary outcome measure is pleurodesis failure rates at 3 months. Pleurodesis failure is defined as the need for further pleural intervention for fluid management on the side of the trial intervention. ETHICS AND DISSEMINATION: The trial has received ethical approval from the National Research Ethics Service Committee North West-Preston (12/NW/0467). There is a trial steering committee which includes independent members and a patient and public representative. The trial results will be published in a peer-reviewed journal and presented at international conferences, as well as being disseminated via local and national charities and patient groups. All participants who wish to know the study results will also be contacted directly on their publication. TRIAL REGISTRATION NUMBER: ISRCTN47845793

Iron oxidation at low temperature (260–500 C) in air and the effect of water vapor

The oxidation of iron has been studied at low temperatures (between 260 and 500 C) in dry air or air with 2 vol% H2O, in the framework of research on dry corrosion of nuclear waste containers during long-term interim storage. Pure iron is regarded as a model material for low-alloyed steel. Oxidation tests were performed in a thermobalance (up to 250 h) or in a laboratory furnace (up to 1000 h). The oxide scales formed were characterized using SEM-EDX, TEM, XRD, SIMS and EBSD techniques. The parabolic rate constants deduced from microbalance experiments were found to be in good agreement with the few existing values of the literature. The presence of water vapor in air was found to strongly influence the transitory stages of the kinetics. The entire structure of the oxide scale was composed of an internal duplex magnetite scale made of columnar grains and an external hematite scale made of equiaxed grains. 18O tracer experiments performed at 400 C allowed to propose a growth mechanism of the scale

Fundamental Strings, Holography, and Nonlinear Superconformal Algebras

We discuss aspects of holography in the AdS_3 \times S^p near string geometry of a collection of straight fundamental heterotic strings. We use anomalies and symmetries to determine general features of the dual CFT. The symmetries suggest the appearance of nonlinear superconformal algebras, and we show how these arise in the framework of holographic renormalization methods. The nonlinear algebras imply intricate formulas for the central charge, and we show that in the bulk these correspond to an infinite series of quantum gravity corrections. We also makes some comments on the worldsheet sigma-model for strings on AdS_3\times S^2, which is the holographic dual geometry of parallel heterotic strings in five dimensions.Comment: 25 page

Measuring processes and the Heisenberg picture

In this paper, we attempt to establish quantum measurement theory in the Heisenberg picture. First, we review foundations of quantum measurement theory, that is usually based on the Schr\"{o}dinger picture. The concept of instrument is introduced there. Next, we define the concept of system of measurement correlations and that of measuring process. The former is the exact counterpart of instrument in the (generalized) Heisenberg picture. In quantum mechanical systems, we then show a one-to-one correspondence between systems of measurement correlations and measuring processes up to complete equivalence. This is nothing but a unitary dilation theorem of systems of measurement correlations. Furthermore, from the viewpoint of the statistical approach to quantum measurement theory, we focus on the extendability of instruments to systems of measurement correlations. It is shown that all completely positive (CP) instruments are extended into systems of measurement correlations. Lastly, we study the approximate realizability of CP instruments by measuring processes within arbitrarily given error limits.Comment: v