4,539 research outputs found
The impact of rain water on soil pore networks following irrigation with saline-sodic water
The soil pore network is an important factor affecting soil hydraulic conductivity (Ksat). In this study we examine the effect on the soil pore network of a Red Ferrosol caused by irrigation with good quality irrigation water (GQW), as well as saline-sodic water with varying sodium absorption ratios (SAR; 10, 50 and 120) and constant electrical conductivity (EC; 2 dS m-1), followed by application of distilled water (simulating rain water). The Ksat was measured for the different waters before and after applying the rain water to the soil. Soil samples were taken from different depths (1, 4 and 8 cm) for exchangeable cations measurement and the changes in ESP of the soil. Soil horizontal cross-sections were taken from the first 2 cm of the soil cores after drying with acetone and impregnation with polyester resin mixed with green fluorescent dye catalyst and hardener. These sections were polished and visualized under a microscope to investigate the changes in the soil pore network. By increasing the SAR of the water applied from 0.11 (GQW) to SAR 50 and 120, a significant reduction in Ksat was found, alongside a significant increase in the ESP of the soil from 3 to 10 and 11, respectively; this was most evident near the soil surface. After applying rain water, the Ksat reduced significantly approaching 0 mm h-1 where soil was treated with water of SAR 120. Visualisation of the soil pore network of the treated soils following the application of deionised water clearly showed a reduction in soil macroporosity where water quality of SAR â„10 was applied, even where soils were non-sodic. Where irrigation occurred with good quality, low SAR water, this reduction was not evident
Radiation Induced Damage in GaAs Particle Detectors
The motivation for investigating the use of GaAs as a material for detecting
particles in experiments for High Energy Physics (HEP) arose from its perceived
resistance to radiation damage. This is a vital requirement for detector
materials that are to be used in experiments at future accelerators where the
radiation environments would exclude all but the most radiation resistant of
detector types.Comment: 5 pages. PS file only - original in WORD Also available at
http://ppewww.ph.gla.ac.uk/preprints/97/06
Characterisation of low pressure VPE GaAs diodes before and after 24 GeV/c proton irradiation
GaAs Schottky diode detectors have been fabricated upon Low Pressure Vapour Phase Epitaxial GaAs. The devices were characterised before and after a 0.81\pm0.0050.85\pm0.012.8 \pm 0.2 \times 10^{14}^{-3}^{o}32\pm5$% at a reverse bias of 200V.GaAs Schottky diode particle detectors have been fabricated upon low-pressure vapour-phase epitaxial GaAs. The devices were characterised with both electrical and charge collection techniques. The height of the TiGaAs barrier used was determined via two electrical methods to be (0.81±0.005) and (0.85±0.01) eV. The current density was greater than that expected for an ideal Schottky barrier and the excess current was attributed to generation current in the bulk of the material. A space charge density of (2.8±0.2)Ă10 14 cm â3 was determined from capacitance voltage characterisation. The charge collection efficiency was determined from front alpha illumination and 60 keV gamma irradiation to be greater than 95% at a reverse bias of 50 V. The diodes were characterised after an exposure to a radiation fluence of 1.25Ă10 14 24 GeV/ c protons cm â2 . The reverse current measured at 20°C increased from 90 to 1500nA at an applied reverse bias of 200 V due to the radiation induced creation of extra generation centres. The capacitance measurements showed a dependence upon the test signal frequency which is a characteristic of deep levels. The capacitance measured at 5 V reverse bias with a test frequency of 100 Hz fell with radiation from 300 to 40pF due to the removal of measurable free carriers. The charge collection of the device determined from front alpha illumination also fell to (32±5)% at a reverse bias of 200 V
Assessing DNA methylation in the developing human intestinal epithelium: potential link to inflammatory bowel disease.
DNA methylation is one of the major epigenetic mechanisms implicated in regulating cellular development and cell-type-specific gene expression. Here we performed simultaneous genome-wide DNA methylation and gene expression analysis on purified intestinal epithelial cells derived from human fetal gut, healthy pediatric biopsies, and children newly diagnosed with inflammatory bowel disease (IBD). Results were validated using pyrosequencing, real-time PCR, and immunostaining. The functional impact of DNA methylation changes on gene expression was assessed by employing in-vitro assays in intestinal cell lines. DNA methylation analyses allowed identification of 214 genes for which expression is regulated via DNA methylation, i.e. regulatory differentially methylated regions (rDMRs). Pathway and functional analysis of rDMRs suggested a critical role for DNA methylation in regulating gene expression and functional development of the human intestinal epithelium. Moreover, analysis performed on intestinal epithelium of children newly diagnosed with IBD revealed alterations in DNA methylation within genomic loci, which were found to overlap significantly with those undergoing methylation changes during intestinal development. Our study provides novel insights into the physiological role of DNA methylation in regulating functional maturation of the human intestinal epithelium. Moreover, we provide data linking developmentally acquired alterations in the DNA methylation profile to changes seen in pediatric IBD.This study was supported by funds obtained from The Evelyn Trust, Crohnâs in Childhood Research Association (CICRA) and Crohnâs and Colitis in Childhood (3Cs) charity. J.K. was funded by a PhD studentship from CICRA. Funding for E.C. was provided by the Deutsche Forschungsgemeinschaft (Grant CA226/4-3) and Interne Forschungsförderung Essen (IFORES).This is the final version of the article. It first appeared from Nature Publishing Group via http://dx.doi.org/10.1038/mi.2015.8
Multifunctional Biocomposites Based on Polyhydroxyalkanoate and Graphene/Carbon Nanofiber Hybrids for Electrical and Thermal Applications
Most polymers are long-lasting and produced from monomers derived from fossil
fuel sources. Bio-based and/or biodegradable plastics have been proposed as a
sustainable alternative. Amongst those available, polyhydroxyalkanoate (PHA)
shows great potential across a large variety of applications but is currently
limited to packaging, cosmetics and tissue engineering due to its relatively
poor physical properties. An expansion of its uses can be accomplished by
developing nanocomposites where PHAs are used as the polymer matrix. Herein, a
PHA biopolyester was melt blended with graphene nanoplatelets (GNPs) or with a
1:1 hybrid mixture of GNPs and carbon nanofibers (CNFs). The resulting
nanocomposites exhibited enhanced thermal stability while their Young's modulus
roughly doubled compared to pure PHA. The hybrid nanocomposites percolated
electrically at lower nanofiller loadings compared to the GNP-PHA system. The
electrical conductivity at 15 wt.% loading was ~ 6 times higher than the
GNP-based sample. As a result, the electromagnetic interference shielding
performance of the hybrid material was around 50% better than the pure GNPs
nanocomposites, exhibiting shielding effectiveness above 20 dB, which is the
threshold for common commercial applications. The thermal conductivity
increased significantly for both types of bio-nanocomposites and reached values
around 5 W K-1 m-1 with the hybrid-based material displaying the best
performance. Considering the solvent-free and industrially compatible
production method, the proposed multifunctional materials are promising to
expand the range of application of PHAs and increase the environmental
sustainability of the plastic and plastic electronics industry.Comment: 26 page
Clumps into Voids
We consider a spherically symmetric distribution of dust and show that it is
possible, under general physically reasonable conditions, for an overdensity to
evolve to an underdensity (and vice versa). We find the conditions under which
this occurs and illustrate it on a class of regular Lemaitre-Tolman-Bondi
solutions. The existence of this phenomenon, if verified, would have the result
that the topology of density contours, assumed fixed in standard structure
formation theories, would have to change and that luminous matter would not
trace the dark matter distribution so well.Comment: LaTeX, 17 pages, 4 figures. Submitted to GRG 20/4/200
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MEDICATION ABORTION WITH PHARMACIST DISPENSING OF MIFEPRISTONE: A COHORT STUDY
Proteomic analysis of Plasmodium in the mosquito: progress and pitfalls
Here we discuss proteomic analyses of whole cell preparations of the mosquito stages of malaria parasite development (i.e. gametocytes, microgamete, ookinete, oocyst and sporozoite) of Plasmodium berghei. We also include critiques of the proteomes of two cell fractions from the purified ookinete, namely the micronemes and cell surface. Whereas we summarise key biological interpretations of the data, we also try to identify key methodological constraints we have met, only some of which we were able to resolve. Recognising the need to translate the potential of current genome sequencing into functional understanding, we report our efforts to develop more powerful combinations of methods for the in silico prediction of protein function and location. We have applied this analysis to the proteome of the male gamete, a cell whose very simple structural organisation facilitated interpretation of data. Some of the in silico predictions made have now been supported by ongoing protein tagging and genetic knockout studies. We hope this discussion may assist future studie
Monitoring Flower Visitation Networks and Interactions between Pairs of Bumble Bees in a Large Outdoor Flight Cage
This research was supported by a combined grant from the Wellcome Trust, the Biotechnology and Biological Sciences Research Council, and the Engineering and Physical Sciences Research Council (BB/F52765X/1). While writing, ML was supported by the IDEX of the Federal University of Toulouse (Starting and Emergence grants), the Fyssen foundation and the CNRS. NER was supported as the Rebanks Family Chair in Pollinator Conservation by The W. Garfield Weston Foundation. LC was supported by ERC Advanced Grant SpaceRadarPollinator and by a Royal Society Wolfson Research Merit Award
Cosmic Microwave Background, Accelerating Universe and Inhomogeneous Cosmology
We consider a cosmology in which a spherically symmetric large scale
inhomogeneous enhancement or a void are described by an inhomogeneous metric
and Einstein's gravitational equations. For a flat matter dominated universe
the inhomogeneous equations lead to luminosity distance and Hubble constant
formulas that depend on the location of the observer. For a general
inhomogeneous solution, it is possible for the deceleration parameter to differ
significantly from the FLRW result. The deceleration parameter can be
interpreted as ( for a flat matter dominated universe) in a
FLRW universe and be as inferred from the inhomogeneous enhancement
that is embedded in a FLRW universe. A spatial volume averaging of local
regions in the backward light cone has to be performed for the inhomogeneous
solution at late times to decide whether the decelerating parameter can be
negative for a positive energy condition. The CMB temperature fluctuations
across the sky can be unevenly distributed in the northern and southern
hemispheres in the inhomogeneous matter dominated solution, in agreement with
the analysis of the WMAP power spectrum data by several authors. The model can
possibly explain the anomalous alignment of the quadrupole and octopole moments
observed in the WMAP data.Comment: 20 pages, no figures, LaTex file. Equations and typos corrected and
references added. Additional material and some conclusions changed. Final
published versio
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