Magnitude and mechanisms of disequilibrium between predawn plant and soil water potentials

Journal ArticlePredawn plant water potential (Uw, measured with leaf psychrometers) and surrogate measurements made with the pressure chamber (termed Upc here) are used to infer comparative ecological performance, based on the expectation that these plant potentials reflect the wettest soil Uw accessed by roots. There is growing evidence, however, that some species exhibit substantial predawn disequilibrium (PDD), defined as plant Uw or Upc at predawn substantially more negative than the Uw of soil accessed by roots

Magnetic Flux Tube Reconnection: Tunneling Versus Slingshot

The discrete nature of the solar magnetic field as it emerges into the corona through the photosphere indicates that it exists as isolated flux tubes in the convection zone, and will remain as discrete flux tubes in the corona until it collides and reconnects with other coronal fields. Collisions of these flux tubes will in general be three dimensional, and will often lead to reconnection, both rearranging the magnetic field topology in fundamental ways, and releasing magnetic energy. With the goal of better understanding these dynamics, we carry out a set of numerical experiments exploring fundamental characteristics of three dimensional magnetic flux tube reconnection. We first show that reconnecting flux tubes at opposite extremes of twist behave very differently: in some configurations, low twist tubes slingshot while high twist tubes tunnel. We then discuss a theory explaining these differences: by assuming helicity conservation during the reconnection one can show that at high twist, tunneled tubes reach a lower magnetic energy state than slingshot tubes, whereas at low twist the opposite holds. We test three predictions made by this theory. 1) We find that the level of twist at which the transition from slingshot to tunnel occurs is about two to three times higher than predicted on the basis of energetics and helicity conservation alone, probably because the dynamics of the reconnection play a large role as well. 2) We find that the tunnel occurs at all flux tube collision angles predicted by the theory. 3) We find that the amount of magnetic energy a slingshot or a tunnel reconnection releases agrees reasonably well with the theory, though at the high resistivities we have to use for numerical stability, a significant amount of magnetic energy is lost to diffusion, independent of reconnection.Comment: 21 pages, 15 figures, submitted to Ap

Identification and characterization of a novel extracellular matrix protein nephronectin that is associated with integrin alpha8beta1 in the embryonic kidney.

The epithelial-mesenchymal interactions required for kidney organogenesis are disrupted in mice lacking the integrin alpha8beta1. None of this integrin's known ligands, however, appears to account for this phenotype. To identify a more relevant ligand, a soluble integrin alpha8beta1 heterodimer fused to alkaline phosphatase (AP) has been used to probe blots and cDNA libraries. In newborn mouse kidney extracts, alpha8beta1-AP detects a novel ligand of 70-90 kD. This protein, named nephronectin, is an extracellular matrix protein with five EGF-like repeats, a mucin region containing a RGD sequence, and a COOH-terminal MAM domain. Integrin alpha8beta1 and several additional RGD-binding integrins bind nephronectin. Nephronectin mRNA is expressed in the ureteric bud epithelium, whereas alpha8beta1 is expressed in the metanephric mesenchyme. Nephronectin is localized in the extracellular matrix in the same distribution as the ligand detected by alpha8beta1-AP and forms a complex with alpha8beta1 in vivo. Thus, these results strongly suggest that nephronectin is a relevant ligand mediating alpha8beta1 function in the kidney. Nephronectin is expressed at numerous sites outside the kidney, so it may also have wider roles in development. The approaches used here should be generally useful for characterizing the interactions of novel extracellular matrix proteins identified through genomic sequencing projects

Review of 99 self-report measures for assessing well-being in adults: exploring dimensions of well-being and developments over time

This is the final version. Available from BMJ Publishing Group via the DOI in this record.OBJECTIVE: Investigators within many disciplines are using measures of well-being, but it is not always clear what they are measuring, or which instruments may best meet their objectives. The aims of this review were to: systematically identify well-being instruments, explore the variety of well-being dimensions within instruments and describe how the production of instruments has developed over time. DESIGN: Systematic searches, thematic analysis and narrative synthesis were undertaken. DATA SOURCES: MEDLINE, EMBASE, EconLit, PsycINFO, Cochrane Library and CINAHL from 1993 to 2014 complemented by web searches and expert consultations through 2015. ELIGIBILITY CRITERIA: Instruments were selected for review if they were designed for adults (≥18 years old), generic (ie, non-disease or context specific) and available in an English version. RESULTS: A total of 99 measures of well-being were included, and 196 dimensions of well-being were identified within them. Dimensions clustered around 6 key thematic domains: mental well-being, social well-being, physical well-being, spiritual well-being, activities and functioning, and personal circumstances. Authors were rarely explicit about how existing theories had influenced the design of their tools; however, the 2 most referenced theories were Diener's model of subjective well-being and the WHO definition of health. The period between 1990 and 1999 produced the greatest number of newly developed well-being instruments (n=27). An illustration of the dimensions identified and the instruments that measure them is provided within a thematic framework of well-being. CONCLUSIONS: This review provides researchers with an organised toolkit of instruments, dimensions and an accompanying glossary. The striking variability between instruments supports the need to pay close attention to what is being assessed under the umbrella of 'well-being' measurement.This research was supported by a University of Exeter Medical School PhD Studentship

Characterization of a 5-eV neutral atomic oxygen beam facility

An experimental effort to characterize an existing 5-eV neutral atomic oxygen beam facility being developed at Princeton Plasma Physics Laboratory is described. This characterization effort includes atomic oxygen flux and flux distribution measurements using a catalytic probe, energy determination using a commercially designed quadrupole mass spectrometer (QMS), and the exposure of oxygen-sensitive materials in this beam facility. Also, comparisons were drawn between the reaction efficiencies of materials exposed in plasma ashers, and the reaction efficiencies previously estimated from space flight experiments. The results of this study show that the beam facility is capable of producing a directional beam of neutral atomic oxygen atoms with the needed flux and energy to simulate low Earth orbit (LEO) conditions for real time accelerated testing. The flux distribution in this facility is uniform to +/- 6 percent of the peak flux over a beam diameter of 6 cm

Nonparametric Euler Equation Identification andEstimation

We consider nonparametric identification and estimation of pricing kernels, or equivalently of marginal utility functions up to scale, in consumption based asset pricing Euler equations.Ours is the first paper to prove nonparametric identification of Euler equations under low level conditions (without imposing functional restrictions or just assuming completeness). We also propose a novel nonparametric estimator based on our identification analysis, which combines standard kernel estimation with the computation of a matrix eigenvector problem. Our esti-mator avoids the ill-posed inverse issues associated with existing nonparametric instrumental variables based Euler equation estimators. We derive limiting distributions for our estimator and for relevant associated functionals. We provide a Monte Carlo analysis and an empirical application to US household-level consumption data.nonparametric identificatio

Chromosomal integration vectors allowing flexible expression of foreign genes in Campylobacter jejuni.

BACKGROUND: Campylobacter jejuni is a major cause of human gastroenteritis yet there is limited knowledge of how disease is caused. Molecular genetic approaches are vital for research into the virulence mechanisms of this important pathogen. Vectors that allow expression of genes in C. jejuni via recombination onto the chromosome are particularly useful for genetic complementation of insertional knockout mutants and more generally for expression of genes in particular C. jejuni host backgrounds. METHODS: A series of three vectors that allow integration of genes onto the C. jejuni chromosome were constructed by standard cloning techniques with expression driven from three different strong promoters. Following integration onto the C. jejuni chromosome expression levels were quantified by fluorescence measurements and cells visualized by fluorescence microscopy. RESULTS: We have created plasmid, pCJC1, designed for recombination-mediated delivery of genes onto the C. jejuni chromosome. This plasmid contains a chloramphenicol resistance cassette (cat) with upstream and downstream restriction sites, flanked by regions of the C. jejuni pseudogene Cj0223. Cloning of genes immediately upstream or downstream of the cat gene allows their subsequent introduction onto the C. jejuni chromosome within the pseudogene. Gene expression can be driven from the native gene promoter if included, or alternatively from the cat promoter if the gene is cloned downstream of, and in the same transcriptional orientation as cat. To provide increased and variable expression of genes from the C. jejuni chromosome we modified pCJC1 through incorporation of three relatively strong promoters from the porA, ureI and flaA genes of C. jejuni, Helicobacter pylori and Helicobacter pullorum respectively. These promoters along with their associated ribosome binding sites were cloned upstream of the cat gene on pCJC1 to create plasmids pCJC2, pCJC3 and pCJC4. To test their effectiveness, a green fluorescent protein (gfp) reporter gene was inserted downstream of each of the three promoters and following integration of promoter-gene fusions onto the C. jejuni host chromosome, expression levels were quantified. Expression from the porA promoter produced the highest fluorescence, from flaA intermediate levels and from ureI the lowest. Expression of gfp from the porA promoter enabled visualization by fluorescent microscopy of intracellular C. jejuni cells following invasion of HeLa cells. CONCLUSIONS: The plasmids constructed allow stable chromosomal expression of genes in C. jejuni and, depending on the promoter used, different expression levels were obtained making these plasmids useful tools for genetic complementation and high level expression