Mechanical behaviour of vacuum chambers and beam screens under quench conditions in dipole and quadrupole fields

A method based on analytical formulas is described to calculate bending moments, stresses, and deformations of vacuum chambers and beam screens in dipole and in quadrupole fields during a magnet quench. Solutions are given for circular and racetrack shaped structures. Without the need of time consuming calculations the solutions enable a quick design and verification of vacuum chambers and beam screens

Transient pluripotent cell populations during primitive ectoderm formation: correlation of in vivo and in vitro pluripotent cell development.

Formation and differentiation of a pluripotent cell population is central to mammalian development, and the isolation, identification and manipulation of human pluripotent cells is predicted to be of therapeutic use. Within the early mammalian embryo, two distinct populations of pluripotent cells have been described: the inner cell mass (ICM), which differentiates to form a second pluripotent cell populations, the primitive ectoderm. Indirect evidence suggests the existence of temporally distinct intermediate pluripotent cell populations as primitive ectoderm is formed. We coupled an in vitro model of primitive ectoderm formation (the transition of embryonic stem cells to early primitive ectoderm-like (EPL) cells) with ddPCR-based techniques to identify three novel genes, Psc1, CRTR-1 and PRCE, that were expressed differently during pluripotent cell progression. Detailed mapping of these genes with Oct4, Rex1 and Fgf5 on pregastrulation embryos provided the first molecular evidence for the existence of successive, temporally distinct pluripotent cell populations in the embryo between the ICM and primitive ectoderm. No evidence was found for spatial heterogeneity within the Oct4+ pool. The transition between populations correlated with morphological or developmental alterations in pluripotent cells in vivo. Genes that are temporally expressed during pluripotent cell progression may provide an opportunity for molecular discrimination of pluripotent cells at different stages of maturation in vivo and an understanding of the cellular origins and properties of pluripotent cell lines isolated from diverse sources. Furthermore, the strong correlation of gene expression demonstrated between EPL cell formation in vitro and primitive ectoderm formation in vivo validates EPL cells as a model for primitive ectoderm, thereby providing a model system for the investigation of pluripotent differentiation and an opportunity for directed differentiation of pluripotent cells to therapeutically useful cell populations.T. A. Pelton, S. Sharma, T. C. Schulz, J. Rathjen and P. D. Rathje

Currents in, Forces on and Deformations/Displacements of the LHC Beam Screen Expected during a Magnet Quench

Due to the field asymmetry of the LHC dipoles, the magnetic field integral calculated from the centre of the aperture to the outside of the cold mass does not vanish. During a magnet quench this asymmetry generates an electromotive force and thus a current with a resultant lateral force on the beam screen. This induced force was observed indirectly when measuring the deformation of the beam screen cross-section during a quench using a precision displacement transducer, which will be described. The transducer (based on optical gratings) was developed specially to study the beam screen deformation in cryogenic environments and high magnetic fields. The results of the measurements are compared to calculations and to direct measurements of the induced voltage along the current path. An estimation of the forces exerted on the cold bore by the beam screen and of the actual current induced in the beam screen will be given

Cell-cell communication mediated by the CAR subgroup of immunoglobulin cell adhesion molecules in health and disease

The immunoglobulin superfamily represents a diverse set of cell-cell contact proteins and includes well-studied members such as NCAM1, DSCAM, L1 or the contactins which are strongly expressed in the nervous system. In this review we put our focus on the biological function of a less understood subgroup of Ig-like proteins composed of CAR (coxsackievirus and adenovirus receptor), CLMP (CAR-like membrane protein) and BT-IgSF (brain and testis specific immunoglobulin superfamily). The CAR-related proteins are type I transmembrane proteins containing an N-terminal variable (V-type) and a membrane proximal constant (C2-type) Ig domain in their extracellular region which are implicated in homotypic adhesion. They are highly expressed during embryonic development in a variety of tissues including the nervous system whereby in adult stages the protein level of CAR and CLMP decreases, only BT-IgSF expression increases within age. CAR-related proteins are concentrated at specialized cell-cell communication sites such as gap or tight junctions and are present at the plasma membrane in larger protein complexes. Considerable progress has been made on the molecular structure and interactions of CAR while research on CLMP and BT-IgSF is at an early stage. Studies on mouse mutants revealed biological functions of CAR in the heart and for CLMP in the gastrointestinal and urogenital systems. Furthermore, CAR and BT-IgSF appear to regulate synaptic function in the hippocampus

Dormancy in white-grained wheat: Mechanisms and genetic control

Dissertação de Mestrado em Ecologia, apresentada ao Departamento de Ciências da Vida da Faculdade de Ciências e Tecnologia da Universidade de Coimbra

The Receptor-Like Kinase SERK3/BAK1 Is Required for Basal Resistance against the Late Blight Pathogen Phytophthora infestans in Nicotiana benthamiana

BACKGROUND The filamentous oomycete plant pathogen Phytophthora infestans causes late blight, an economically important disease, on members of the nightshade family (Solanaceae), such as the crop plants potato and tomato. The related plant Nicotiana benthamiana is a model system to study plant-pathogen interactions, and the susceptibility of N. benthamiana to Phytophthora species varies from susceptible to resistant. Little is known about the extent to which plant basal immunity, mediated by membrane receptors that recognise conserved pathogen-associated molecular patterns (PAMPs), contributes to P. infestans resistance. PRINCIPAL FINDINGS We found that different species of Phytophthora have varying degrees of virulence on N. benthamiana ranging from avirulence (incompatible interaction) to moderate virulence through to full aggressiveness. The leucine-rich repeat receptor-like kinase (LRR-RLK) BAK1/SERK3 is a major modulator of PAMP-triggered immunity (PTI) in Arabidopsis thaliana and N. benthamiana. We cloned two NbSerk3 homologs, NbSerk3A and NbSerk3B, from N. benthamiana based on sequence similarity to the A. thaliana gene. N. benthamiana plants silenced for NbSerk3 showed markedly enhanced susceptibility to P. infestans infection but were not altered in resistance to Phytophthora mirabilis, a sister species of P. infestans that specializes on a different host plant. Furthermore, silencing of NbSerk3 reduced the cell death response triggered by the INF1, a secreted P. infestans protein with features of PAMPs. CONCLUSIONS/SIGNIFICANCE We demonstrated that N. benthamiana NbSERK3 significantly contributes to resistance to P. infestans and regulates the immune responses triggered by the P. infestans PAMP protein INF1. In the future, the identification of novel surface receptors that associate with NbSERK3A and/or NbSERK3B should lead to the identification of new receptors that mediate recognition of oomycete PAMPs, such as INF1.This work was supported by the Gatsby Charitable Foundation, BBSRC, Nuffield Foundation and the German Research Foundation (DFG). SS was supported by a personal research fellowship (SCHO1347/1-1). JPR is an Australian Research Council Future Fellow (FT0992129). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

A new foundational crisis in mathematics, is it really happening?

The article reconsiders the position of the foundations of mathematics after the discovery of HoTT. Discussion that this discovery has generated in the community of mathematicians, philosophers and computer scientists might indicate a new crisis in the foundation of mathematics. By examining the mathematical facts behind HoTT and their relation with the existing foundations, we conclude that the present crisis is not one. We reiterate a pluralist vision of the foundations of mathematics. The article contains a short survey of the mathematical and historical background needed to understand the main tenets of the foundational issues.Comment: Final versio

Intuitionistic sets and numbers: small set theory and Heyting arithmetic

It has long been known that (classical) Peano arithmetic is, in some strong sense, “equivalent” to the variant of (classical) Zermelo–Fraenkel set theory (including choice) in which the axiom of infinity is replaced by its negation. The intended model of the latter is the set of hereditarily finite sets. The connection between the theories is so tight that they may be taken as notational variants of each other. Our purpose here is to develop and establish a constructive version of this. We present an intuitionistic theory of the hereditarily finite sets, and show that it is definitionally equivalent to Heyting Arithmetic HA, in a sense to be made precise. Our main target theory, the intuitionistic small set theory SST is remarkably simple, and intuitive. It has just one non-logical primitive, for membership, and three straightforward axioms plus one axiom scheme. We locate our theory within intuitionistic mathematics generally

Mechanical Behaviour of the Short Models of LHC Main Dipole Magnets

A series of single and twin aperture 1 metre magnet models has been built and tested in the framework of the R&D program of main superconducting dipole magnets for the Large Hadron Collider project. The se models, designed for a nominal field of 8.3 T at 1.8 K, have been constructed to test the performance of SC coils and to optimise various design options for the full length 15 metre long dipoles. T he models have been extensively equipped with a specially developed mechanical instrumentation, enabling both the control of main assembly parameters - like coil azimuthal and axial pre-load, stress i n the outer shrinking cylinder - and also the monitoring of magnet behaviour during cooling and energising, under the action of electromagnetic forces. The instrumentation used, mainly based on strain gauge transducers, is described and the results of mechanical measurements obtained during power tests of the models are discussed and compared with the design predictions based on Finite Element calc ulations