MicroRNA expression in lymphocyte development and malignancy

This article is available open access through the publisher’s website. Copyright @ 2008 Macmillan Publishers Limited.No abstract available.The Leukemia Research Fund, the Julian Starmer-Smith Memorial Fund, and the Medical Research Council

First genetic data for the critically endangered Cuban endemic Zapata Rail Cyanolimnas cerverai, and the taxonomic implications

Funding Information: GMK and AK are grateful to staff, particularly Ianela García-Lau, Manolo Barro and volunteers at the Museo de Historia Natural ‘Felipe Poey’, La Habana, Cuba, for access to relevant specimens. This study was funded by University of Aberdeen (AB) and The Sound Approach Ph.D. Studentship (TJS).Peer reviewedPublisher PD

Static and Dynamic Critical Phenomena at a Second Order QCD Phase Transition

In QCD with two flavors of massless quarks, the chiral phase transition is plausibly in the same universality class as the classical four component Heisenberg antiferromagnet. Therefore, renormalization group techniques developed in the study of phase transitions can be applied to calculate the critical exponents which characterize the scaling behaviour of universal quantities near the critical point. This approach to the QCD phase transition has implications both for lattice gauge theory and for heavy ion collisions. Future lattice simulations with longer correlation lengths will be able to measure the various exponents and the equation of state for the order parameter as a function of temperature and quark mass which we describe. In a heavy ion collision, the consequence of a long correlation length would be large fluctuations in the number ratio of neutral to charged pions. Unfortunately, we show that this phenomenon will not occur if the plasma stays close to equilibrium as it cools. If the transition is far out of equilibrium and can be modelled as a quench, it is possible that large volumes of the plasma with the pion field correlated will develop, with dramatic phenomenological consequences. }Comment: phyzzx, 41 pages, 4 figures available as a postscript file from K.R., PUPT-1347, IASSNS-HEP-92/6

Mapping the QCD Phase Diagram

I review recent theoretical developments which show how a key qualitative feature of the QCD phase diagram, namely a critical point which in a sense defines the landscape which heavy ion collision experiments are seeking to map, can be discovered. The map of the phase diagram which I sketch is based on reasonable inference from universality, lattice gauge theory and models; the discovery of the critical point would provide an experimental foundation for the central qualitative feature of the landscape. I also review recent progress in our understanding of cold, dense quark matter, as may occur in the cores of neutron stars. In this regime, quarks form Cooper pairs. The formation of such superconducting phases requires only weak attractive interactions, as provided by one-gluon exchange at asymptotically high density; these phases may nevertheless break chiral symmetry (by locking flavor symmetries to color symmetry) and may have excitations which are indistinguishable from those in a confined phase. Mapping this part of the phase diagram will require a better understanding of how the presence of color superconductivity and color-flavor locking affects neutron star phenomenology.Comment: Contribution to proceedings of Quark Matter '99, Torino, Italy. 12 pages. 4 figure

Quantum fields in disequilibrium: neutral scalar bosons with long-range, inhomogeneous perturbations

Using Schwinger's quantum action principle, dispersion relations are obtained for neutral scalar mesons interacting with bi-local sources. These relations are used as the basis of a method for representing the effect of interactions in the Gaussian approximation to field theory, and it is argued that a marked inhomogeneity, in space-time dependence of the sources, forces a discrete spectrum on the field. The development of such a system is characterized by features commonly associated with chaos and self-organization (localization by domain or cell formation). The Green functions play the role of an iterative map in phase space. Stable systems reside at the fixed points of the map. The present work can be applied to self-interacting theories by choosing suitable properties for the sources. Rapid transport leads to a second order phase transition and anomalous dispersion. Finally, it is shown that there is a compact representation of the non-equilibrium dynamics in terms of generalized chemical potentials, or equivalently as a pseudo-gauge theory, with an imaginary charge. This analogy shows, more clearly, how dissipation and entropy production are related to the source picture and transform a flip-flop like behaviour between two reservoirs into the Landau problem in a constant `magnetic field'. A summary of conventions and formalism is provided as a basis for future work.Comment: 23 pages revte

Plant exudates may stabilize or weaken soil depending on species, origin and time

We hypothesized that plant exudates could either gel or disperse soil depending on their chemical characteristics. Barley (Hordeum vulgare L. cv. Optic) and maize (Zea mays L.cv. Freya) root exudates were collected using an aerated hydroponic method and compared to chia (Salvia hispanica L.) seed exudate, a commonly used root exudate analogue. Sandy loam soil passed through a 500-μm mesh was treated with each exudate at a concentrationof 4.6 mg exudate g-1 dry soil. Two sets of soil samples were prepared, One set of treated soil samples was maintained at 4oC to suppress microbial processes. To characterize the effect of decomposition, the second set of samples was incubated at 16C for 2 weeks at – 30 kPa matric potential. Gas chromatography–mass spectrometry (GC–MS) analysis of the exudates found that barley had the largest organic acid content and chia the largest content of sugars (polysaccharide-derived or free), and maize was in between barley and chia. Yield stress of amended soil samples was measured by an oscillatory strain sweep test with a cone plate rheometer. When microbial decomposition was suppressed at 4oC, yield stress increased 20-fold for chia seed exudate and two-fold for maize root exudate compared to the control, whereas for barley root exudate it decreased to half. The yield stress after 2 weeks of incubation compared to soil with suppressed microbial decomposition increased by 85% for barley root exudate, but for chia and maize it decreased to by 87% and 54%, respectively. Barley root exudation might therefore disperse soil and this could facilitate nutrient release. The maize root and chia seed exudates gelled soil, which could create a more stable soil structure around roots or seeds

Casimir Forces at Tricritical Points: Theory and Possible Experiments

Using field-theoretical methods and exploiting conformal invariance, we study Casimir forces at tricritical points exerted by long-range fluctuations of the order-parameter field. Special attention is paid to the situation where the symmetry is broken by the boundary conditions (extraordinary transition). Besides the parallel-plate configuration, we also discuss the geometries of two separate spheres and a single sphere near a planar wall, which may serve as a model for colloidal particles immersed in a fluid. In the concrete case of ternary mixtures a quantitative comparison with critical Casimir and van der Waals forces shows that, especially with symmetry-breaking boundaries, the tricritical Casimir force is considerably stronger than the critical one and dominates also the competing van der Waals force.Comment: 18 pages, Latex, 3 postscript figures, uses Elsevier style file

Imaging microstructure of the barley rhizosphere:particle packing and root hair influences

Soil adjacent to roots has distinct structural and physical properties from bulk soil, affecting water and solute acquisition by plants. Detailed knowledge on how root activity and traits such as root hairs affect the three-dimensional pore structure at a fine scale is scarce and often contradictory. Roots of hairless barley (Hordeum vulgare L. cv Optic) mutant (NRH) and its wildtype (WT) parent were grown in tubes of sieved (&lt;250 μm) sandy loam soil under two different water regimes. The tubes were scanned by synchrotron-based X-ray computed tomography to visualise pore structure at the soil–root interface. Pore volume fraction and pore size distribution were analysed vs distance within 1 mm of the root surface. Less dense packing of particles at the root surface was hypothesised to cause the observed increased pore volume fraction immediately next to the epidermis. The pore size distribution was narrower due to a decreased fraction of larger pores. There were no statistically significant differences in pore structure between genotypes or moisture conditions. A model is proposed that describes the variation in porosity near roots taking into account soil compaction and the surface effect at the root surface.</p