Impact of treated wastewater irrigation on water repellency of Mediterranean soils

Irrigation with treated wastewater (TWW) is gaining importance due to declining water availability in dry regions. TWW irrigation has various potential adverse effects on soil quality such as hydrophobic effects on soil surfaces, reducing initial sorptivity and promoting the formation of preferential flow paths. In May and June 2010, in situ infiltration measurements using mini disk tension infiltrometer were deployed in five different orchard plots in Israel to assess the impact of different irrigation water qualities on the soil water repellency index R. In most plantations, long-term test sites were accessed to compare adjacent plots irrigated with fresh water (FW) or TWW. Topsoil samples were analyzed for selected physical and chemical characteristics. The mean R values increased at all TWW sites, from +15 up to +55 % compared with FW sites. The water drop penetration time (WDPT) increased up to 30 fold at three of five TWW sites compared with FW sites. Subsequent U tests and multilevel analysis indicated an impact of the type of irrigation water on R and WDPT. Moreover, soil electrical conductivity and exchangeable sodium percentage were consistently higher at all TWW sites. These results show that irrigation water quality clearly influences physical and chemical properties of the soil.     

Do multipurpose companion trees affect high value timber trees in a silvopastoral plantation system?

Establishment of native timber trees on deforested land may contribute to the livelihood of farmers, to improved ecosystem services and to increased greenhouse gas uptake. Here, we present a new silvopastoral planting design to assess species performance and interspecific competition or facilitation effects among native timber and multipurpose trees in Central America. Two timber species, Tabebuia rosea and Cedrela odorata, were established in three low-density planting regimes allowing combined tree and future livestock production: (1) solitary planting, (2) companion planting with Guazuma ulmifolia, and (3) companion planting with the nitrogen-fixing Gliricidia sepium. We quantified survival, growth and reforestation potential of the two timber species subjected to the different planting regimes for the first 2 years after establishment. Nitrogen concentration as well as stable nitrogen and carbon isotope composition (δ¹⁵N, δ¹³C) of leaves of the timber saplings were determined. T. rosea showed higher survival and better growth than C. odorata under varying environmental conditions (soil, concomitant vegetation). Performance of the timber saplings was unaffected by either companion species. Planting regimes had no effect on foliar nitrogen concentration and δ¹⁵N of the two timber species, although δ¹⁵N values indicated nitrogen fixation activity in G. sepium trees. Planting regimes affected foliar δ¹³C values in T. rosea. δ¹³C values were significantly higher in solitarily growing individuals, suggesting lower exposition to water stress conditions in saplings surrounded by companion species. As we found positively correlated growth traits among timber and multipurpose trees, a combined planting may benefit farmers by providing additional goods and services.     

Structure determination of partially deuterated carotenoids from intrinsically labeled vegetables by HPLC-MS and 1H NMR

The structures of biosynthetic deuterated carotenoids in labeled vegetables were investigated: (all-E)-lutein and (all-E)-beta-carotene from spinach, and (all-E)-beta-carotene and (all-E)-alpha-carotene from carrots. The vegetables were grown hydroponically using a nutrient solution enriched with deuterium oxide (D(2)O) and were extracted using matrix solid-phase dispersion (MSPD). Deuterium enrichment in the carotenoid molecules was determined by liquid chromatography-mass spectrometry (LC-MS). (all-E)-Lutein and (all-E)-beta-carotene in spinach showed partial deuteration from (2)H(1) to (2)H(12), with the abundance maximum at (2)H(5). (all-E)-beta-Carotene and (all-E)-alpha-carotene from carrots showed partial deuteration from (2)H(1) to (2)H(17), with the abundance maximum at (2)H(11). The (1)H NMR spectra of the four deuterated carotenoids showed additional signals for all methyl groups and decreased signal intensity for the olefinic protons and the methylene protons in the ring. These differences are due to isotopic effects and are based on the substitution of protons by deuterium atoms. The deuteration was distributed randomly throughout the carotenoid molecules.     

Occurrence of zearalenone-4-beta-D-glucopyranoside in wheat

An LC-MS method was developed for the analysis of zearalenone-4-beta-D-glucopyranoside and zearalenone in wheat (Triticum aestivum). The limit of determination for zearalenone-4-beta-D-glucopyranoside and zearalenone was 10 microg/kg. The recovery rates were calculated to be 69% and 89% at a concentration of 100 microg/kg for zearalenone-4-beta-D-glucopyranoside and zearalenone, respectively. Twenty-four Bavarian wheat samples from a 1999 harvest were analyzed. Zearalenone was present in 22 of 24 field samples, the levels ranged from 11 to 860 microg/kg. Zearalenone-4-beta-D-glucopyranoside was found in 10 of the zearalenone positive samples (42%) at levels ranging from 17 to 104 microg/kg. The amounts of zearalenone-4-beta-D-glucopyranoside were correlated to those of zearalenone (r2 = 0.86, b = 0.10). After gastrointestinal hydrolyzation, zearalenone-4-beta-glucopyranoside might be implicated in the development of a zearalenone-syndrome. Therefore, more attention should be focused on conjugated mycotoxins in food and feed.     

A linear, O-coordinated eta1-CO2 bound to uranium

The electron-rich, six-coordinate tris-aryloxide uranium(III) complex [((AdArO)3tacn)U(III)] [where (AdArOH)3tacn = 1,4,7-tris(3-adamantyl-5-tert-butyl-2-hydroxybenzyl)1,4,7-triazacyclononane] reacts rapidly with CO2 to yield [((AdArO)3tacn)U(IV)(CO2)], a complex in which the CO(2) ligand is linearly coordinated to the metal through its oxygen atom (eta1-OCO). The latter complex has been crystallographically and spectroscopically characterized. The inequivalent O-C-O bond lengths [1.122 angstroms (A) for the O-C bond adjacent to uranium and 1.277 A for the other], considered together with magnetization data and electronic and vibrational spectra, support the following bonding model: U(IV)=O=C*-O- <--> U(IV)-OC-O-. In these charge-separated resonance structures, the uranium center is oxidized to uranium(IV) and the CO2 ligand reduced by one electron.     

A maximum in the strength of nanocrystalline copper

We used molecular dynamics simulations with system sizes up to 100 million atoms to simulate plastic deformation of nanocrystalline copper. By varying the grain size between 5 and 50 nanometers, we show that the flow stress and thus the strength exhibit a maximum at a grain size of 10 to 15 nanometers. This maximum is because of a shift in the microscopic deformation mechanism from dislocation-mediated plasticity in the coarse-grained material to grain boundary sliding in the nanocrystalline region. The simulations allow us to observe the mechanisms behind the grain-size dependence of the strength of polycrystalline metals.     

Spatial regulators for bacterial cell division self-organize into surface waves in vitro

In the bacterium Escherichia coli, the Min proteins oscillate between the cell poles to select the cell center as division site. This dynamic pattern has been proposed to arise by self-organization of these proteins, and several models have suggested a reaction-diffusion type mechanism. Here, we found that the Min proteins spontaneously formed planar surface waves on a flat membrane in vitro. The formation and maintenance of these patterns, which extended for hundreds of micrometers, required adenosine 5'-triphosphate (ATP), and they persisted for hours. We present a reaction-diffusion model of the MinD and MinE dynamics that accounts for our experimental observations and also captures the in vivo oscillations.     

Complex multicolor tilings and critical phenomena in tetraphilic liquid crystals

T-shaped molecules with a rod-like aromatic core and a flexible side chain form liquid crystal honeycombs with aromatic cell walls and a cell interior filled with the side chains. Here, we show how the addition of a second chain, incompatible with the first (X-shaped molecules), can form honeycombs with highly complex tiling patterns, with cells of up to five different compositions ("colors") and polygonal shapes. The complexity is caused by the inability of the side chains to separate cleanly because of geometric frustration. Furthermore, a thermoreversible transition was observed between a multicolor (phase-separated) and a single-color (mixed) honeycomb phase. This is analogous to the Curie transition in simple and frustrated ferro- and antiferromagnets; here spin flips are replaced by 180° reorientations of the molecules.