Sodium, cation exchange and crop response in acid KwaZulu-Natal soils.

Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2000.In many acid, highly leached South African soils, Na levels are very low. Applications of Na to highly leached soils may be advantageous in some situations as Na has been shown to interact with soil acidity, P availability, and K nutrition of plants. It was found that an increased level of Na at constant anion concentration in the soil solution resulted in lower soil solution pH and Al3 + activity, and improved maize root penetration into an acid subsoil (pot trial). In another pot trial, Na did not improve lucerne root growth into the same subsoil. In a field trial on a limed, low-Na soil with severe subsoil acidity, the effects off our rates of Na, three Na carriers, and three rates of gypsum on maize growth were compared. In three out of four seasons grain yield responses to the Na applications were positive, and of a similar magnitude to the response to gypsum (455-925 kg ha). In another field trial with maize, responses to Na (of up to 1027 kg grain ha) were recorded in two out of three years on plots with topsoil acid saturations of greater than 45%. The reason for the responses to Na was probably improved subsoil rooting as a result of modified soil solution composition in the presence of Na. In a field trial with Italian rye grass on an acid, highly weathered soil, the effect of sodium applications were investigated at different levels of lime and K. In the first season, 200 kg ha Na as NaCl increased dry matter yield from 11289 kg ha to 12815 kg ha , Sodium responses were possibly due to enhanced P uptake, or Na substitution for K, or a combination of the two mechanisms. No consistent lime x Na interaction was observed. Potassium and Na applications affected the mineral balance of the herbage produced. Potassium depressed herbage Ca, Mg and Na concentrations, and Na depressed herbage Ca and Mg where herbage K was low, but had no effect on herbage K. Where soil P and K reserves are marginal, rye grass pastures may benefit from Na applications

Mesospheric turbulence during PMWE-conducive conditions

International audienceStrong radar returns at VHF known as Polar Mesospheric Winter Echoes (PMWE) seem to occur during periods of intense ionisation of the mesosphere. Apart from a mechanism to produce such ionisation, viz. solar proton precipitation, other prerequisites have been proposed, such as neutral air turbulence. Here, we employ a medium frequency radar to examine whether the atmospheric state is conducive to the appearance of PMWE; echo power signatures (isolated lower mesospheric echoes ? "ILME") are indicators of the necessary ionisation at sufficient depth in the middle atmosphere, and also echo fading times give information on turbulence. We fail to find evidence for causal relationship between ILME and turbulence but suggest that on occasion turbulence may be enhanced related to proton precipitation. The results presented provide a basis for investigating whether turbulence is a prerequisite for PMWE

Oral prion neuroinvasion occurs independently of PrPC expression in the gut epithelium

The early replication of certain prion strains within Peyer’s patches in the small intestine is essential for the efficient spread of disease to the brain after oral exposure. Our data show that orally acquired prions utilize specialized gut epithelial cells known as M cells to enter Peyer’s patches. M cells express the cellular isoform of the prion protein, PrPC, and this may be exploited by some pathogens as an uptake receptor to enter Peyer’s patches. This suggested that PrPC might also mediate the uptake and transfer of prions across the gut epithelium into Peyer’s patches in order to establish infection. Furthermore, the expression level of PrPC in the gut epithelium could influence the uptake of prions from the lumen of the small intestine. To test this hypothesis, transgenic mice were created in which deficiency in PrPC was specifically restricted to epithelial cells throughout the lining of the small intestine. Our data clearly show that efficient prion neuroinvasion after oral exposure occurred independently of PrPC expression in small intestinal epithelial cells. The specific absence of PrPC in the gut epithelium did not influence the early replication of prions in Peyer’s patches or disease susceptibility. Acute mucosal inflammation can enhance PrPC expression in the intestine, implying the potential to enhance oral prion disease pathogenesis and susceptibility. However, our data suggest that the magnitude of PrPC expression in the epithelium lining the small intestine is unlikely to be an important factor which influences the risk of oral prion disease susceptibility. IMPORTANCE The accumulation of orally acquired prions within Peyer’s patches in the small intestine is essential for the efficient spread of disease to the brain. Little is known of how the prions initially establish infection within Peyer’s patches. Some gastrointestinal pathogens utilize molecules, such as the cellular prion protein PrPC, expressed on gut epithelial cells to enter Peyer’s patches. Acute mucosal inflammation can enhance PrPC expression in the intestine, implying the potential to enhance oral prion disease susceptibility. We used transgenic mice to determine whether the uptake of prions into Peyer’s patches was dependent upon PrPC expression in the gut epithelium. We show that orally acquired prions can establish infection in Peyer’s patches independently of PrPC expression in gut epithelial cells. Our data suggest that the magnitude of PrPC expression in the epithelium lining the small intestine is unlikely to be an important factor which influences oral prion disease susceptibility

Inner-shell photodetachment of na-using r-matrix methods

Inner-shell photodetachment of Na-near the L-edge threshold was investigated using the R-matrix method. Significant structure was found in the cross section, and this structure is shown to be related to the complicated correlated electron dynamics endemic in negative ions. Comparison with experiment suggests that the absolute values of the measured cross section might be too small by a factor of two. © 2020 by the authors

Gravity wave characteristics in the mesopause region revealed from OH airglow imager observations over Northern Colorado

Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Space Physics 119 (2014): 630-645, doi:10.1002/2013JA018955.Using 5 years of all-sky OH airglow imager data over Yucca Ridge Field Station, CO (40.7°N, 104.9°W), from September 2003 to September 2008, we extract and deduce quasi-monochromatic gravity wave (GW) characteristics in the mesopause region. The intrinsic periods are clustered between approximately 4 and 10 min, and many of them are unstable and evanescent. GW occurrence frequency exhibits a clear semiannual variation with equinoctial minima, which is likely related to the seasonal variation of background wind. The anomalous propagation direction in January 2006, with strong southward before major warming starting in 21 January and weak southward propagation afterward, was most likely affected by stratospheric sudden warming. The momentum fluxes show strongly anticorrelated with the tides, with ~180° out of phase in the zonal component. While in the meridional component, the easterly maximum occurred approximately 2–6 h after maximum easterly tidal wind. However, the anticorrelations are both weakest during the summer. The dissipating and breaking of small-scale and high-frequency GW's components could have a potential impact on the general circulation in the mesopause region.This work was carried out at the University of Science and Technology of China, with support from the National Natural Science Foundation of China grants (41025016, 41127901, 41225017, 41074108, and 41121003), the National Basic Research Program of China grant 2012CB825605, the Chinese Academy of Sciences Key Research Program KZZD-EW-01, and the Fundamental Research Funds for the Central Universities.2014-07-3

Long-term frequent fires do not decrease topsoil carbon and nitrogen in an Afromontane grassland

Fire has been an integral evolutionary force shaping and maintaining grassy biomes, such as the Afromontane grasslands of South Africa. Afromontane grasslands represent a large carbon reservoir, but it is uncertain how fire affects their long-term C storage. We investigated the effect of fire regime on soil organic C and N (SOC; SON) in a long-term (39-year) burning experiment in the Maloti-Drakensberg Park, South Africa. We compared SOC and SON sampled in 2004 and 2019 from six treatments differing in fire frequency (annual, biennial, five-year, infrequent) and season (spring, autumn). Average SOC increased significantly between 2004 and 2019. Average SON increased slightly, resulting in a significant increase in C:N ratio, indicating that soil organic matter is becoming less N-eutrophic. Importantly, burning annually in spring increased SOC and SON. This unexpected response is attributed to the aluandic (acidic, high organic matter) properties of Drakensberg soils. Burning in autumn did not increase SOC and SON. The lowest C stocks were observed in infrequently burnt plots. Average C sequestration across all fire treatments was 0.30 Mg ha(-1) y(-1). The observed increase in SOC under frequent fires is contrary to many findings from other studies in grassy ecosystems and notably driven by fire season

RPGR-associated retinal degeneration in human X-linked RP and a murine model

PURPOSE. We investigated the retinal disease due to mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene in human patients and in an Rpgr conditional knockout (cko) mouse model. METHODS. XLRP patients with RPGR-ORF15 mutations (n = 35, ages at first visit 5–72 years) had clinical examinations, and rod and cone perimetry. Rpgr-cko mice, in which the proximal promoter and first exon were deleted ubiquitously, were back-crossed onto a BALB/c background, and studied with optical coherence tomography and electroretinography (ERG). Retinal histopathology was performed on a subset. RESULTS. Different patterns of rod and cone dysfunction were present in patients. Frequently, there were midperipheral losses with residual rod and cone function in central and peripheral retina. Longitudinal data indicated that central rod loss preceded peripheral rod losses. Central cone-only vision with no peripheral function was a late stage. Less commonly, patients had central rod and cone dysfunction, but preserved, albeit abnormal, midperipheral rod and cone vision. Rpgr-cko mice had progressive retinal degeneration detectable in the first months of life. ERGs indicated relatively equal rod and cone disease. At late stages, there was greater inferior versus superior retinal degeneration. CONCLUSIONS. RPGR mutations lead to progressive loss of rod and cone vision, but show different patterns of residual photoreceptor disease expression. Knowledge of the patterns should guide treatment strategies. Rpgr-cko mice had onset of degeneration at relatively young ages and progressive photoreceptor disease. The natural history in this model will permit preclinical proof-of-concept studies to be designed and such studies should advance progress toward human therapy

Polar vortex evolution during Northern Hemispheric winter 2004/05

As a part of the project "Atmospheric Wave Influences upon the Winter Polar Vortices (0–100 km)" of the CAWSES program, data from meteor and Medium Frequency radars at 12 locations and MetO (UK Meteorological Office) global assimilated fields have been analyzed for the first campaign during the Northern Hemispheric winter of 2004/05. The stratospheric state has been described using the conventional zonal mean parameters as well as Q-diagnostic, which allows consideration of the longitudinal variability. The stratosphere was cold during winter of 2004/05, and the polar vortex was relatively strong during most of the winter with relatively weak disturbances occurring at the end of December and the end of January. For this winter the strongest deformation with the splitting of the polar vortex in the lower stratosphere was observed at the end of February. Here the results show strong latitudinal and longitudinal differences that are evident in the stratospheric and mesospheric data sets at different stations. Eastward winds are weaker and oscillations with planetary wave periods have smaller amplitudes at more poleward stations. Accordingly, the occurrence, time and magnitude of the observed reversal of the zonal mesospheric winds associated with stratospheric disturbances depend on the local stratospheric conditions. In general, compared to previous years, the winter of 2004/05 could be characterized by weak planetary wave activity at stratospheric and mesospheric heights