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1.
A series of dioxouranium(VI) complexes was synthesised with some Schiff base ligands containing substituent groups at para positions to CHN groups. These molecules were obtained by the condensation of para-nitro, chloro, bromo, hydroxy, methyl and methoxy aniline with salicylaldehyde. The bidentate ligands formed complexes of the type UO2(NCS)2 (X-N-Sal)n·mH2O, where n = 2, m = 3, x = NO2, Cl, Br and OH; n = 3, m = 2, x = CH3 and OCH3.Conductivity measurements indicate that all the complexes are non-electrolytes in nitromethane solution, whereas in DMF they correspond to 1:1 electrolytes.IR spectral data suggest that the molecules and not the anions of the Schiff base are coordinated to the central uranium atom. IR and Raman spectra suggest that the complexes UO2(NCS)2(X-N-Sal)2· 3H2O (X = NO2, Cl, Br) have C2h molecular symmetry, whereas UO2(NCS)2(X-N-Sal)3·2H2O (X = OCH3, CH3) have C2v symmetry.The frequencies of UO2(asym) (IR) and UO2(sym) (R) in the complexes seem to vary with the various substituents of the Schiff base ligand, in the order:NO2 > Cl > Br > OH > CH3 > OCH3 相似文献
2.
Butyl acetate holds great potential as a sustainable biofuel additive. Heterogeneously catalyzed transesterification of biobutanol and bioethylacetate can produce butyl acetate. This route is eco-friendly and offers several advantages over the commonly used Fischer Esterification. The Amberlite IR 120- and Amberlyst 15-catalyzed transesterification is studied in a batch reactor over a range of catalyst loading (6–12 wt.%), alcohol to ester feed ratio (1:3 to 3:1), and temperature (303.15–333.15 K). A butanol mole fraction of 0.2 in the feed is found to be optimum. Amberlite IR 120 promotes faster kinetics under these conditions. The transesterifications studied are slightly exothermic. The moles of solvent sorbed per gram of catalyst decreases (ethanol > butanol > ethyl acetate > butyl acetate) with decrease in solubility parameter. The dual site models, the Langmuir Hinshelwood and Popken models, are the most successful in correlating the kinetics over Amberlite IR 120 and Amberlyst 15, respectively. 相似文献
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In the dry savannas of West and Central Africa, where low soil fertility, unpredictable rainfall, weed competition and recurrent
drought are major constraints to maize production, the development of tropical maize genotypes with high and stable yields
under drought and low-nitrogen condition is very important since access to these improved genotypes may be the only affordable
alternative to many small scale farmers. Field trials were conducted in 2002 and 2003 at Ikenne southwestern Nigeria to investigate
the effect of weed pressures and drought stress on 2 maize (Zea mays L.) hybrids (9134-14, 9803-9) and 2 open-pollinated varieties (STREVIWD, IYFDCO1). Irrigation was withdrawn 4 weeks after
planting (about four weeks to mid-flowering) in the drought stress while the adjacent watered treatment had irrigation throughout
the growing period. The weed pressures were the completely weeded plots (hand weeding every week) and weedy plots (weeded
once, 2 weeks after planting). The experiment was a split plot in a randomized complete block design with four replicates.
Drought stress reduced the stover weight and grain yield of the maize cultivars by 6% and 34% respectively. Weed-free plots
had maize with higher agronomic traits than unweeded treatments. Hybrid 9803-9 was more susceptible to drought and weed stress
as indicated in the stover weight and grain yield. STREVIWD an open-pollinated variety (OPV) and Hybrid 9134-14 had superior
performances in terms of grain yield and shorter anthesis silking interval. Soil moisture content was higher in the unweeded
plots while the uptake of moisture was highest in drought susceptible hybrid 9803-9. Irrespective of the genotypes, maize
(hybrid and OPV) was more tolerant to drought in a weed-free environment than in unweeded conditions. There existed a negative
but significant correlation between weed biomass and chlorophyll content (−0.29, P < 0.01), grain yield (−0.45, P < 0.05), ear plant−1 (−0.27, P < 0.05) and kernel-number (−0.366 P < 0.01). 相似文献
5.
The foraging habitat selections of brown-eared pheasant (Crossoptilon mantchuricum) and the common pheasant (Phasianus colchicus) were studied in Huanglongshan Nature Reserve Shaanxi, China. Foraging habitat characteristics were measured on the basis of expected differences between species at 183 sites from November to December 2006 and January 2007. The results showed that both species selected foraging habitats with altitude (<1200 m), conifer forest, half sunny and half shady slope, sunny slope, density of trees (<5 individuals/100 m2), cover of shrub (>50%), visibility class (<10%) and distance to water source (<300 m). However, the brown-eared pheasant selected habitats with cover of trees (30–50%), middle or lower slope location, distance to edge of woods (<300 m) and human disturbance (<500 m), and the selection on density of shrub was not observed, compared to the selections on cover of trees (<30%), lower slope location, distance to edge of woods (<500 m) and human disturbance (<300 m), and density of shrub (>500 individuals/100 m2) for common pheasant. We also found that the common pheasant avoid predators by concealment whereas brown-eared pheasant evade predations by running away strategy. 相似文献
6.
Prey capture and digestion in Nepenthes spp. through their leaf-evolved biological traps involve a sequence of exciting events. Sugar-rich nectar, aroma chemicals, narcotic alkaloid secretions, slippery wax crystals, and other biochemicals take part in attracting, capturing, and digesting preys in Nepenthes pitchers. Here we report the distribution of three potent naphthoquinones in Nepenthes khasiana and their roles in prey capture. Plumbagin was first detected in N. khasiana, and its content (root: 1.33 ± 0.02%, dry wt.) was the highest found in any natural source. Chitin induction enhanced plumbagin levels in N. khasiana (root: 2.17 ± 0.02%, dry wt.). Potted N. khasiana plants with limited growth of roots and aerial parts, showed higher levels of plumbagin accumulation (root: 1.92 ± 0.02%; root, chitin induction: 3.30 ± 0.21%, dry wt.) compared with field plants. Plumbagin, a known toxin, insect ecdysis inhibitor, and antimicrobial, was also found embedded in the waxy layers at the top prey capture region of N. khasiana pitchers. Chitin induction, mimicking prey capture, produced droserone and 5-O-methyl droserone in N. khasiana pitcher fluid. Both these naphthoquinone derivatives provide antimicrobial protection to the pitcher fluid from visiting preys. A two-way barrier was found between plumbagin and its two derivatives. Plumbagin was never detected in the pitcher fluid whereas both its derivatives were only found in the pitcher fluid on chitin induction or prey capture. The three naphthoquinones, plumbagin, droserone, and 5-O-methyl droserone, act as molecular triggers in prey capture and digestion in the carnivorous plant, N. khasiana. 相似文献
7.
Azeez Adebimpe Ardalan Aarabi Emilie Bourel-Ponchel Mahdi Mahmoudzadeh Fabrice Wallois 《PloS one》2015,10(10)
There is growing evidence that brain networks are altered in epileptic subjects. In this study, we investigated the functional connectivity and brain network properties of benign childhood epilepsy with centrotemporal spikes using graph theory. Benign childhood epilepsy with centrotemporal spikes is the most common form of idiopathic epilepsy in young children under the age of 16 years. High-density EEG data were recorded from patients and controls in resting state with eyes closed. Data were preprocessed and spike and spike-free segments were selected for analysis. Phase locking value was calculated for all paired combinations of channels and for five frequency bands (δ, θ, α, β1 and β2). We computed the degree and small-world parameters—clustering coefficient (C) and path length (L)—and compared the two patient conditions to controls. A higher degree at epileptic zones during interictal epileptic spikes (IES) was observed in all frequency bands. Both patient conditions reduced connection at the occipital and right frontal regions close to the epileptic zone in the α band. The “small-world” features (high C and short L) were deviated in patients compared to controls. A changed from an ordered network in the δ band to a more randomly organized network in the α band was observed in patients compared to healthy controls. These findings show that the benign epileptic brain network is disrupted not only at the epileptic zone, but also in other brain regions especially frontal regions. 相似文献
8.
Jamiu Oladipupo Azeez Olabisi Adenike Hassan Johnson Kayode Adesodun Toyin Ayodele Arowolo 《Soil & Sediment Contamination》2013,22(8):930-957
Heavy metal pollution in soils and the high costs of remediation necessitate the evaluation of cheaper alternatives. The aim of this experiment was to evaluate Cd, Pb, Zn, and Cu sorption characteristics of three soils and their influence on the comparative effectiveness of EDTA and legume intercrop on the remediative abilities of maize, mucuna, okra, and kenaf. The sorption studies were done using standard procedures. The EDTA-assisted phytoextraction (6 mmol kg?1) and the cowpea intercrop trials were conducted in triplicate. The metal-spiked soils were planted with maize, kenaf, and mucuna in the EDTA trial and maize, kenaf, and okra were planted in the cowpea intercrop experiment. Cadmium was prefentially sorbed in acid and alkaline soils and Cu in slightly acid soil. Cadmium uptake was significantly lower (P < 0.05) in all the plants. Bioconcentration factors of Pb, Cu, and Zn were higher (P < 0.05) in maize compared with other plants. Phytoremediative ability of the plants in trials were maize > kenaf > mucuna and okra > maize > kenaf, respectively. It was concluded that a legume intercrop can substitute EDTA- assisted phytoextraction to prevent groundwater contamination resulting from high solubility of metals by EDTA. 相似文献
9.
Plants have to cope with changing seasons and adverse environmental conditions. Being sessile, plants have developed elaborate mechanisms for their survival that allow them to sense and adapt to the environment and reproduce successfully. A major adaptive trait for the survival of trees of temperate and boreal forests is the induction of growth cessation in anticipation of winters. In the last few years enormous progress has been made to elucidate the molecular mechanisms underlying SDs induced growth cessation in model perennial tree hybrid aspen (Populus tremula × P. tremuloides). In this review we discuss the molecular mechanism underlying photoperiodic control of growth cessation and adaptive responses. 相似文献
10.
Life with and without AtTIP1;1, an Arabidopsis aquaporin preferentially localized in the apposing tonoplasts of adjacent vacuoles 总被引:2,自引:0,他引:2
Azeez Beebo Dominique Thomas Christophe Der Lisa Sanchez Nathalie Leborgne-Castel Francis Marty Benoît Schoefs Karim Bouhidel 《Plant molecular biology》2009,70(1-2):193-209
The Arabidopsis thaliana Tonoplast Intrinsic Protein 1;1 (AtTIP1;1) is a member of the tonoplast aquaporin family. The tissue-specific expression pattern and intracellular localization of AtTIP1;1 were characterized using GUS and GFP fusion genes. Results indicate that AtTIP1;1 is expressed in almost all cell types with the notable exception of meristematic cells. The highest level of AtTIP1;1 expression was detected in vessel-flanking cells in vascular bundles. AtTIP1;1-GFP fusion protein labelled the tonoplast of the central vacuole and other smaller peripheral vacuoles. The fusion protein was not found evenly distributed along the tonoplast continuum but concentrated in contact zones of tonoplasts from adjacent vacuoles and in invaginations of the central vacuole. Such invaginations may result from partially engulfed small vacuoles. A knockout mutant was isolated and characterized to gain insight into AtTIP1;1 function. No phenotypic alteration was found under optimal growth conditions indicating that AtTIP1;1 function is not essential to the plant and that some members of the TIP family may act redundantly to facilitate water flow across the tonoplast. However, a conditional root phenotype was observed when mutant plants were grown on a glycerol-containing medium. 相似文献