A characteristic lengthscale causes anomalous size effects and boundary programmability in mechanical metamaterials

The architecture of mechanical metamaterialsis designed to harness geometry, non-linearity and topology to obtain advanced functionalities such as shape morphing, programmability and one-way propagation. While a purely geometric framework successfully captures the physics of small systems under idealized conditions, large systems or heterogeneous driving conditions remain essentially unexplored. Here we uncover strong anomalies in the mechanics of a broad class of metamaterials, such as auxetics, shape-changers or topological insulators: a non-monotonic variation of their stiffness with system size, and the ability of textured boundaries to completely alter their properties. These striking features stem from the competition between rotation-based deformations---relevant for small systems---and ordinary elasticity, and are controlled by a characteristic length scale which is entirely tunable by the architectural details. Our study provides new vistas for designing, controlling and programming the mechanics of metamaterials in the thermodynamic limit.Comment: Main text has 4 pages, 4 figures + Methods and Supplementary Informatio

Initial oak regeneration responses to experimental warming along microclimatic and macroclimatic gradients

Quercus spp. are one of the most important tree genera in temperate deciduous forests in terms of biodiversity, economic and cultural perspectives. However, natural regeneration of oaks, depending on specific environmental conditions, is still not sufficiently understood. Oak regeneration dynamics are impacted by climate change, but these climate impacts will depend on local forest management and light and temperature conditions. Here, we studied germination, survival and seedling performance (i.e. aboveground biomass, height, root collar diameter and specific leaf area) of four oak species (Q. cerris, Q. ilex, Q. robur and Q. petraea). Acorns were sown across a wide latitudinal gradient, from Italy to Sweden, and across several microclimatic gradients located within and beyond the species' natural ranges. Microclimatic gradients were applied in terms of forest structure, distance to the forest edge and experimental warming. We found strong interactions between species and latitude, as well as between microclimate and latitude or species. The species thus reacted differently to local and regional changes in light and temperature ; in southern regions the temperate Q. robur and Q. petraea performed best in plots with a complex structure, whereas the Mediterranean Q. ilex and Q. cerris performed better in simply structured forests with a reduced microclimatic buffering capacity. The experimental warming treatment only enhanced height and aboveground biomass of Mediterranean species. Our results show that local microclimatic gradients play a key role in the initial stages of oak regeneration; however, one needs to consider the species-specific responses to forest structure and the macroclimatic context

Human enteric glia diversity in health and disease:new avenues for the treatment of Hirschsprung disease

BACKGROUND AND AIMS: The enteric nervous system (ENS), comprised of neurons and glia, regulates intestinal motility. Hirschsprung disease (HSCR) results from defects in ENS formation, yet while neuronal aspects have been extensively studied, enteric glia remain disregarded. This study aimed to explore enteric glia diversity in health and disease.METHODS: Full-thickness intestinal resection material from pediatric controls and HSCR patients was collected, dissociated and enriched for the ENS population through fluorescence-activated cell sorting. Single-cell RNA sequencing was performed to uncover the transcriptomic diversity of the ENS in HSCR patients and controls, as well as in wildtype and ret mutant zebrafish. Immunofluorescence and fluorescence in situ hybridization confirmed the presence of distinct subtypes.RESULTS: Two major enteric glial classes emerged in the pediatric intestine: Schwann-like enteric glia, reminiscent of Schwann cells, and Enteric glia, expressing classical glial markers. Comparative analysis with previously published datasets confirmed our classification and revealed that whilst classical enteric glia are predominant prenatally, Schwann-like enteric glia become more abundant postnatally. In HSCR, ganglionic segments mirrored controls, while aganglionic segments, only featured Schwann-like enteric glia. Leveraging the regenerative potential of Schwann cells, we explored therapeutic options using a ret mutant zebrafish. Prucalopride, a serotonin-receptor (5-HT) agonist, induced neurogenesis partially rescuing the HSCR phenotype in ret+/- mutants.CONCLUSION: Two major enteric glial classes were identified in the pediatric intestine, highlighting the significant postnatal contribution of Schwann-like enteric glia to glial heterogeneity. Crucially, these glial subtypes persist in aganglionic segments of HSCR patients, offering a new target for their treatment using 5-HT agonists.</p

Dying at home in Belgium: a descriptive GP interview study

<p>Abstract</p> <p>Background</p> <p>While increasing attention is being paid to enabling terminal patients to remain at home until death, limited information is available on the circumstances in which people at home actually die. Therefore this study aims to describe patient characteristics, functional and cognitive status and physical and psychological symptom burden in the last three months of life among Belgian patients dying at home, according to their GPs.</p> <p>Methods</p> <p>In 2005, a nationwide and retrospective interview study with GPs took place on people dying at home in Belgium as reported by Sentinel Network of GPs in Belgium. GPs registered all deaths (patients aged 1 year or more) weekly and were interviewed about all patients dying non-suddenly at home, using face-to-face structured interviews.</p> <p>Results</p> <p>Interviews were obtained on 205 patients (90% response rate). Between the second and third month before death, 55% were fully invalid or limited in self-care. In the last week of life, almost all were fully invalid. Fifty four percent were unconscious at some point during the last week; 46% were fully conscious. Most frequently reported symptoms were lack of energy, lack of appetite and feeling drowsy. Conditions most difficult for GPs to manage were shortness of breath, lack of energy and pain.</p> <p>Conclusions</p> <p>Many people dying at home under the care of their GPs in Belgium function relatively well until the last week of life and cognitive status seems to be preserved until the end in many cases. However, symptoms which GPs find difficult to control still manifest in many patients in the final week of life.</p

Change-of-state Paradigms and the middle in Kinyarwanda

This paper investigates the derivational relationships among members of verbal paradigms in Kinyarwanda (Bantu JD.61; Rwanda) by pursuing two interrelated goals. First, I describe a variety of derivational strategies for marking transitive and intransitive variants in change-of-state verb paradigms. Second, I focus on the detransitivizing morpheme –ik which serves as one possible marking for intransitive members of these paradigms. Ultimately, I argue that this morpheme is a marker of middle voice, and the variety of readings which appear with this form can be subsumed under a single operation of argument suppression. Finally, I provide a discussion of reflexives and the apparent lack of a reflexive reading with –ik by arguing that this reading is blocked by either lexical reflexives or the reflexive prefix i–

Cementitious Barriers Partnership FY2013 End-Year Report

In FY2013, the Cementitious Barriers Partnership (CBP) demonstrated continued tangible progress toward fulfilling the objective of developing a set of software tools to improve understanding and prediction of the long‐term structural, hydraulic and chemical performance of cementitious barriers used in nuclear applications. In November 2012, the CBP released “Version 1.0” of the CBP Software Toolbox, a suite of software for simulating reactive transport in cementitious materials and important degradation phenomena. In addition, the CBP completed development of new software for the “Version 2.0” Toolbox to be released in early FY2014 and demonstrated use of the Version 1.0 Toolbox on DOE applications. The current primary software components in both Versions 1.0 and 2.0 are LeachXS/ORCHESTRA, STADIUM, and a GoldSim interface for probabilistic analysis of selected degradation scenarios. The CBP Software Toolbox Version 1.0 supports analysis of external sulfate attack (including damage mechanics), carbonation, and primary constituent leaching. Version 2.0 includes the additional analysis of chloride attack and dual regime flow and contaminant migration in fractured and non‐fractured cementitious material. The LeachXS component embodies an extensive material property measurements database along with chemical speciation and reactive mass transport simulation cases with emphasis on leaching of major, trace and radionuclide constituents from cementitious materials used in DOE facilities, such as Saltstone (Savannah River) and Cast Stone (Hanford), tank closure grouts, and barrier concretes. STADIUM focuses on the physical and structural service life of materials and components based on chemical speciation and reactive mass transport of major cement constituents and aggressive species (e.g., chloride, sulfate, etc.). THAMES is a planned future CBP Toolbox component focused on simulation of the microstructure of cementitious materials and calculation of resultant hydraulic and constituent mass transfer parameters needed in modeling. Two CBP software demonstrations were conducted in FY2013, one to support the Saltstone Disposal Facility (SDF) at SRS and the other on a representative Hanford high‐level waste tank. The CBP Toolbox demonstration on the SDF provided analysis on the most probable degradation mechanisms to the cementitious vault enclosure caused by sulfate and carbonation ingress. This analysis was documented and resulted in the issuance of a SDF Performance Assessment Special Analysis by Liquid Waste Operations this fiscal year. The two new software tools supporting chloride attack and dual‐regime flow will provide additional degradation tools to better evaluate performance of DOE and commercial cementitious barriers. The CBP SRNL experimental program produced two patent applications and field data that will be used in the development and calibration of CBP software tools being developed in FY2014. The CBP software and simulation tools varies from other efforts in that all the tools are based upon specific and relevant experimental research of cementitious materials utilized in DOE applications. The CBP FY2013 program involved continuing research to improve and enhance the simulation tools as well as developing new tools that model other key degradation phenomena not addressed in Version 1.0. Also efforts to continue to verify the various simulation tools through laboratory experiments and analysis of field specimens are ongoing and will continue into FY2014 to quantify and reduce the uncertainty associated with performance assessments. This end‐year report summarizes FY2013 software development efforts and the various experimental programs that are providing data for calibration and validation of the CBP developed software

Cementitious Barriers Partnership (CBP): Training and Release of CBP Toolbox Software, Version 1.0 -13480

ABSTRACT The Cementitious Barriers Partnership (CBP) Project is a multi-disciplinary, multi-institutional collaboration supported by the Office of Tank Waste Management within the Office of Environmental Management of U.S. Department of Energy (US DOE). The CBP program has developed a set of integrated tools (based on state-of-the-art models and leaching test methods) that improve understanding and predictions of the long-term hydraulic and chemical performance of cementitious barriers used in nuclear applications. Tools selected for and developed under this program are intended to evaluate and predict the behavior of cementitious barriers used in near-surface engineered waste disposal systems for periods of performance up to or longer than 100 years for operating facilities and longer than 1,000 years for waste management purposes. CBP software tools were made available to selected DOE Office of Environmental Management and field site users for training and evaluation based on a set of important degradation scenarios, including sulfate ingress/attack and carbonation of cementitious materials. The tools were presented at two-day training workshops held at U.S. National Institute of Standards and Technology (NIST), Savannah River, and Hanford included LeachXS™/ORCHESTRA, STADIUM®, and a CBP-developed GoldSim Dashboard interface. Collectively, these components form the CBP Software ToolBox. The new U.S. Environmental Protection Agency leaching test methods based on the Leaching Environmental Assessment Framework (LEAF) were also presented. The CBP Dashboard uses a custom Dynamic-link library developed by CBP to couple to the LeachXS™/ORCHESTRA and STADIUM® codes to simulate reactive transport and degradation in cementitious materials for selected performance assessment scenarios. The first day of the workshop introduced participants to the software components via presentation materials, and the second day included hands-on tutorial exercises followed by discussions of enhancements desired by participants. Tools were revised based on feedbac