In this report, amorphous silica powder was extracted from an open atmosphere burned wild barley (Hordeum murinum ssp. leporinum) straw using the alkali leaching method. Nitrogen adsorption-desorption measurements, energy dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) results, and analysis reveal that the as-extracted amorphous silica is mesoporous with a large surface area (357 m(2)/g) and somewhat high content of carbon. X-ray diffraction (XRD) patterns showed that the extracted silica crystallized into the cristobalite phase, on heating it in an air atmosphere for 90 min at 1000 C. The effect of the crystallization process on morphological and structural properties of porous silicon (PSi) produced from the extracted silica by magnesiothermic reduction has been investigated. The reduction process of the amorphous extracted silica resulted in the formation of a mixed phase of cubic Si and silicon carbide (SiC), which has a crystallinity index of 52 %, meso/micropores embedded in macro-size voids, average size of Si crystallites of similar to 70 nm, and specific surface area of similar to 160 m(2)/g. In comparison, the PSi produced from the crystallized silica exhibited a single cubic silicon nanocrystalline phase, higher purity, better crystallinity and a smaller average size of Si nano-crystallites. These suggest that the pre-crystallization of agriculture-derived silica precursor can be used as an effective way to produce high-quality PSi. The present work contributes to the previous reported literature on HF-free synthesis of PSi, a promising material for a wide range of applications.
A benchmark-based neutronic and steady-state thermal-hydraulic assessment was performed to evaluate beryllium reflector configurations for enhancing irradiation capability in the MTR-10 MW research reactor. The reference one-trap core was modified to a symmetric four-trap layout, and a constrained sequence of graphite and beryllium reflector substitutions was assessed with MCNP4C2/MTRMC. The four-trap configuration reduced the initial excess reactivity from 141.71 to 82.85 mk. The selected 22-block beryllium reflector recovered the excess reactivity to 139.38 mk, corresponding to 96.04% recovery of the reactivity loss relative to the shifted four-trap base case. The four-site average thermal neutron flux increased from the reference central-trap mean of 1.055 × 10 14 to 1.319 × 10 14 n·cm -2 ·s -1 , an average gain of 25.0%, while the maximum site reached 1.904 × 10 14 n·cm -2 ·s -1 . After applying a comparable active neutron-history basis, OpenMC reproduced the same recovery trend, giving 96.94% recovered reactivity. The steady-state thermal-hydraulic assessment used CAUDVAP/TERMIC-1H at 550 m 3 /h, giving a total mass flow rate of 151.607 kg/s and a mean pressure drop of 5.372 kPa. The maximum plate power in the hottest fuel element was 28.93 kW, giving a hot-plate peaking factor of 1.24 and a hot-plate heat-flux input of 49.4 W/cm 2 . The TERMIC-B2 case at 50 W/cm 2 therefore represents the rounded-up hot-plate condition for the final configuration, with redistribution and DNB ratios above unity over the assessed hot-channel velocity interval.
Abstract Extended post-anthesis moisture largely enhances aggressiveness of Fusarium head blight (FHB) pathogens; however, no information is available if this aggressiveness increase arose only from humidity effect or humidity leads to changes in Fusarium fungi resulting in higher aggressiveness. To this end, we re-isolated 16 fungal cultures of four Fusarium species subjected to duration of spray-irrigation of 21 days and compared their in vitro aggressiveness with the same Fusarium fungi not-subjected to prolonged post-anthesis moisture, i.e. duration of spray-irrigation of 0/7 days. Differences in latent period (LP), area under disease progress curve (AUDPC) and coleoptile length reduction (CLR) were observed on wheat detached leaves and seedlings in the aggressiveness of Fusarium -moisture treatments relative to fungal-non-moisture treatments. Prolonged humidity application did increase Fusarium aggressiveness measured in vitro ; FHB subjected to duration of spray-irrigation of 21 days had significantly lesser LP and higher AUDPC and CLR in compared with FHB subjected to duration of spray-irrigation of 0/7 days. This is the first report showing that aggressiveness increase arises from pathogenic changes in Fusarium fungi enhanced under prolonged humidity conditions. When considering FHB disease prevention strategies, the environmental conditions in which fungi grow need to be taken into consideration.
The aim of this paper is to evaluate the vulnerability of groundwater to contamination by adapting aquifer vulnerability index (AVI) approach, based mainly on the hydraulic conductivity (K) of the aquifer and overburden layers' thickness (h). The technique of vertical electrical sounding (VES) with the configuration of Schlumberger was applied to model the Quaternary aquifer and its overburden layers in the Khanasseer Valley area in Northern Syria. According to AVI classification, 5.88% of the study area is hugely polluted, 67.00% highly polluted, 23.53% moderately polluted, and 2.94% lowly polluted. Several hydro-geoelectrical parameters which affect the Aquifer Vulnerability Index (AVI) (such as anisotropy (lambda) of the subsurface hydrogeological layers, thickness (hOverb), resistivity (rho Overb), hydraulic conductivity (K), and hydraulic resistance (C) of the protecting layers) are statistically analyzed. Different mutual empirical relationships between the above parameters are established through analyzing their statistical correlation matrix. The derived empirical relationships highlight the mutual hydrological processes and the lithological connectivity nature between the study Quaternary aquifer and its overlaying layers. The obtained results highlighted the importance of safeguarding groundwater resources, and outlined resource allocation to protect the aquifer zones, for decision-makers. This was the first time that AVI approach is applied in Syria, and can be consequently extended to other Syrian aquifers. AVI can be also applied worldwide to estimate the conditions dominating the aquifer's protectivity in semi-arid regions.
Spot blotch (SB) disease caused by the fungus Cochliobolus sativus is one of the most devastating diseases of barley (Hordeum vulgare L.) worldwide. Using barley varieties resistant to SB could be part of an integrated control strategy. Currently, resistance is determined based on symptom assessment in infected plants, but molecular measurements may provide a more effective screening method. We hypothesized that the degree of SB disease resistance in barley genotypes is associated with defense related gene expression levels and salicylic acid (SA) content. Two barley cultivars exhibiting moderate and severe symptoms of SB on leaves were used. Our data showed that gene responses to SB infection were differentially regulated depending on the susceptibility levels of the barley cultivars. The resistant cultivar exhibited significantly higher levels of constitutive gene expression for the PR1, PR2, PR3, and PR5 genes as compared with the susceptible one. It is noteworthy that the expression level of the PR1 gene was significantly higher in the resistant cultivar compared to the expression levels of other genes. Furthermore, the SA level was significantly higher (P = 0.001) in the resistant cultivar (102 ng/g) than in the susceptible cultivar (25.5 ng/g) at 96 hpi. These results indicate that the expression levels of defense-related genes and the SA content in barely plants can serve as reliable predictors for predicting resistance to SB disease.
