Effects of charcoal production on soil physical properties in Ghana   总被引：15，自引：0，他引：15  

Philip G. Oguntunde  Babatunde J. Abiodun  Ayodele E. Ajayi  Nick van de Giesen 《植物养料与土壤学杂志》2008,171(4):591-596

Charcoal production, widespread in Ghana like in other W African countries, is a major driver of land‐cover change. Effects of charcoal production on soil physical, including hydrological, properties, were studied in the forest–savannah transition zone of Ghana. Core and composite samples from 12 randomly selected sites across the width of Kotokosu watershed were taken from 0–10 cm layer at charcoal‐site soils and adjacent field soils (control). These were used to determine saturated hydraulic conductivity (K_sat), bulk density, total porosity, soil texture, and color. Infiltration rates, surface albedo, and soil‐surface temperature were also measured on both sites. The results showed that the saturated hydraulic conductivity of soils under charcoal kilns increased significantly (p < 0.01) from 6.1 ± 2.0 cm h^–1 to 11.4 ± 5.0 cm h^–1, resulting to a relative increase of 88%. Soil color became darkened under charcoal kilns with hue, value, and chroma decreasing by 8%, 20%, and 20%, respectively. Bulk density on charcoal‐site soils reduced by 9% compared to adjacent field soils. Total porosity increased from 45.7% on adjacent field soils to 50.6% on earth kilns. Surface albedo reduced by 37% on charcoal‐site soils while soil‐surface temperature increased up to 4°C on average. Higher infiltration rates were measured on charcoal‐site soils, which suggest a possible decrease in overland flow and less erosion on those kiln sites.  相似文献   

Thermal stability of anthocyanin extract of Hibiscus sabdariffa L. in the presence of beta-cyclodextrin     

Mourtzinos I  Makris DP  Yannakopoulou K  Kalogeropoulos N  Michali I  Karathanos VT 《Journal of agricultural and food chemistry》2008,56(21):10303-10310

The thermal stability of anthocyanin extract isolated from the dry calyces of Hibiscus sabdariffa L. was studied over the temperature range 60-90 degrees C in aqueous solutions in the presence or absence of beta-cyclodextrin (beta-CD). The results indicated that the thermal degradation of anthocyanins followed first-order reaction kinetics. The temperature-dependent degradation was adequately modeled by the Arrhenius equation, and the activation energy for the degradation of H. sabdariffa L. anthocyanins during heating was found to be approximately 54 kJ/mol. In the presence of beta-CD, anthocyanins degraded at a decreased rate, evidently due to their complexation with beta-CD, having the same activation energy. The formation of complexes in solution was confirmed by nuclear magnetic resonance studies of beta-CD solutions in the presence of the extract. Moreover, differential scanning calorimetry revealed that the inclusion complex of H. sabdariffa L. extract with beta-CD in the solid state was more stable against oxidation as compared to the free extract, as the complex remained intact at temperatures 100-250 degrees C where the free extract was oxidized. The results obtained clearly indicated that the presence of beta-CD improved the thermal stability of nutraceutical antioxidants present in H. sabdariffa L. extract, both in solution and in solid state.  相似文献   

Microbial and nematode communities associated with potatoes genetically modified to express the antimicrobial peptide magainin and unmodified potato cultivars     

Maureen O’Callaghan  Emily M. Gerard  Nigel L. Bell  Nick W. Waipara  Lee T. Aalders  David B. Baird  Anthony J. Conner 《Soil biology & biochemistry》2008,40(6):1446-1459

The antimicrobial peptide magainin II has activity against a range of micro-organisms. Tubers harvested from potatoes genetically modified (GM) to express a synthetic magainin gene show improved resistance to the bacterial pathogen Erwinia carotovora. The microbial and nematode communities associated with three magainin-expressing potato lines, their near-isogenic, unmodified parental cultivar (Iwa) and an unrelated cultivar (Karaka) were investigated on field-grown plants. Heterotrophic plate counts were used to enumerate aerobic culturable bacterial and fungal populations, while cultivation-independent analysis of bacterial communities was based on denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene fragments amplified from community DNA from phyllosphere, rhizosphere and geocaulosphere (tuber surface) samples. Small but statistically significant differences in the population sizes of culturable bacteria, fungi and yeast were detected among some GM magainin-expressing lines and the unmodified control. However, these differences were typically smaller than the differences between the unmodified parental line control (Iwa) and the unrelated cultivar control (Karaka). Similarly, the difference in the proportion of the nematode population belonging to the fungal feeding trophic group between Iwa and Karaka was greater than that amongst Iwa and its near-isogenic GM lines, and was significantly so for the genus Aphelenchus. The nematode channel ratio (NCR) indicated a more fungal-dominated decomposition channel in soil beneath Karaka compared to Iwa at harvest. In general, eubacterial phylloplane communities were similar for all lines, while the rhizosphere communities associated with two of the three GM lines differed from communities associated with their unmodified parental line control. When roots were senescent, there was no significant difference among potato lines in rhizosphere eubacterial communities or individual trophic groups of the nematode community. Greater diversity was found in geocaulosphere; α-proteobacteria and actinomycete communities of two of the three GM lines differed significantly from their unmodified parental line control and the unrelated cultivar control, while the communities associated with the third GM line were more similar to those of the two control lines. This highlights the importance of testing several GM lines when assessing non-target effects. Results suggest that there is little likelihood of any major sustained non-target effect of genetic modification using a magainin II transgene on plant-associated and soil microflora and function.  相似文献   

Comparison of high (5%) and low (1%) concentrations of micellar microemulsion propofol formulations with a standard (1%) lipid emulsion in horses     

Boscan P  Steffey EP  Farver TB  Mama KR  Huang NJ  Harris SB 《American journal of veterinary research》2006,67(9):1476-1483

OBJECTIVE: To compare anesthesia-related events associated with IV administration of 2 novel micellar microemulsion preparations (1% and 5%) and a commercially available formulation (1%) of propofol in horses. Animals-9 healthy horses. PROCEDURES: On 3 occasions, each horse was anesthetized with 1 of the 3 propofol formulations (1% or 5% microemulsion or 1% commercial preparation). All horses received xylazine (1 mg/kg, IV), and anesthesia was induced with propofol (2 mg/kg, IV). Induction and recovery events were quantitatively and qualitatively assessed. Venous blood samples were obtained before and at intervals following anesthesia for quantification of clinicopathologic variables. RESULTS: Compared with the commercial formulation, the quality of anesthesia induction in horses was slightly better with the micellar microemulsion formulas. In contrast, recovery characteristics were qualitatively and quantitatively indistinguishable among treatment groups (eg, time to stand after anesthesia was 34.3 +/- 7.3 minutes, 34.1 +/- 8.8 minutes, and 39.0 +/- 7.6 minutes in horses treated with the commercial formulation, 1% microemulsion, and 5% microemulsion, respectively). During recovery from anesthesia, all horses stood on the first attempt and walked within 5 minutes of standing. No clinically relevant changes in hematologic and serum biochemical analytes were detected during a 3-day period following anesthesia. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that the micellar microemulsion preparation of propofol (1% or 5%) has similar anesthetic effects in horses, compared with the commercially available lipid propofol formulation. Additionally, the micellar microemulsion preparation is anticipated to have comparatively low production costs and can be manufactured in various concentrations.  相似文献   

Mineralogy and petrology of comet 81P/Wild 2 nucleus samples     

Zolensky ME  Zega TJ  Yano H  Wirick S  Westphal AJ  Weisberg MK  Weber I  Warren JL  Velbel MA  Tsuchiyama A  Tsou P  Toppani A  Tomioka N  Tomeoka K  Teslich N  Taheri M  Susini J  Stroud R  Stephan T  Stadermann FJ  Snead CJ  Simon SB  Simionovici A  See TH  Robert F  Rietmeijer FJ  Rao W  Perronnet MC  Papanastassiou DA  Okudaira K  Ohsumi K  Ohnishi I  Nakamura-Messenger K  Nakamura T  Mostefaoui S  Mikouchi T  Meibom A  Matrajt G  Marcus MA  Leroux H  Lemelle L  Le L  Lanzirotti A  Langenhorst F  Krot AN  Keller LP  Kearsley AT 《Science (New York, N.Y.)》2006,314(5806):1735-1739

The bulk of the comet 81P/Wild 2 (hereafter Wild 2) samples returned to Earth by the Stardust spacecraft appear to be weakly constructed mixtures of nanometer-scale grains, with occasional much larger (over 1 micrometer) ferromagnesian silicates, Fe-Ni sulfides, Fe-Ni metal, and accessory phases. The very wide range of olivine and low-Ca pyroxene compositions in comet Wild 2 requires a wide range of formation conditions, probably reflecting very different formation locations in the protoplanetary disk. The restricted compositional ranges of Fe-Ni sulfides, the wide range for silicates, and the absence of hydrous phases indicate that comet Wild 2 experienced little or no aqueous alteration. Less abundant Wild 2 materials include a refractory particle, whose presence appears to require radial transport in the early protoplanetary disk.  相似文献   

Corridors increase plant species richness at large scales   总被引：1，自引：0，他引：1  

Damschen EI  Haddad NM  Orrock JL  Tewksbury JJ  Levey DJ 《Science (New York, N.Y.)》2006,313(5791):1284-1286

Habitat fragmentation is one of the largest threats to biodiversity. Landscape corridors, which are hypothesized to reduce the negative consequences of fragmentation, have become common features of ecological management plans worldwide. Despite their popularity, there is little evidence documenting the effectiveness of corridors in preserving biodiversity at large scales. Using a large-scale replicated experiment, we showed that habitat patches connected by corridors retain more native plant species than do isolated patches, that this difference increases over time, and that corridors do not promote invasion by exotic species. Our results support the use of corridors in biodiversity conservation.  相似文献   

SINGLE‐SHOT TURBO SPIN ECHO PULSE SEQUENCE FINDINGS IN DOGS WITH AND WITHOUT PROGRESSIVE MYELOMALACIA          下载免费PDF全文

Lindsey J. Gilmour  Nick D. Jeffery  Kristina Miles  Elizabeth Riedesel 《Veterinary radiology & ultrasound》2017,58(2):197-205

Progressive myelomalacia is an uncommon type of ischemic, hemorrhagic spinal cord infarction. Diagnosis can be difficult, but prompt recognition is important. We hypothesized that cerebrospinal fluid signal attenuation on magnetic resonance (MR) images would be more extensive in dogs that developed progressive myelomalacia vs. control dogs. A retrospective analytic cohort study was designed. Dogs were included if they presented for acute paraplegia and loss of deep pain perception and had undergone MR imaging using both sagittal single‐shot turbo spin echo (SSTSE) and standard sagittal T2‐weighted fast spin echo (T2W) pulse sequences. Dogs were divided into progressive myelomalacia and control groups for comparisons. All MR examinations were evaluated by three reviewers blinded to patient outcome. Length of cerebrospinal fluid attenuation was recorded as a ratio to the length of the L2 vertebral body in SSTSE and T2W sequences (CSF:L2_SSTSE and CSF:L2_T2, respectively). Length of intramedullary spinal cord hyperintensity was recorded as a ratio to the length of the L2 vertebral body in T2W sequences. A total of 21 dogs were included (five in the progressive myelomalacia group and 16 in the control group). The mean CSF:L2_SSTSE attenuation value was significantly higher in dogs that developed progressive myelomalacia (CSF:L2_SSTSE = 10.7) compared to controls (CSF:L2_SSTSE = 5.4; P = 0.015). A cut off ratio of attenuation >7.4 provided optimal differentiation between groups in this study. Findings supported the conclusion that dogs with CSF:L2_SSTSE ≤ 7.4 are unlikely to develop progressive myelomalacia while dogs with CSF:L2_SSTSE > 7.4 are indeterminate for progressive myelomalacia.  相似文献   

Nutritional potential of fodder trees on clay and sandy soils     

Boki Luske  Nick van Eekeren 《Agroforestry Systems》2018,92(4):975-986

In this paper we focus on the functional role of trees for livestock as fodder in silvopastoral systems, available for (dairy) cows within or around pastures. Farmers often report that cows browse from trees, however, little is known about the nutritional value of different tree species. Therefore, the objective of this study was to assess the effect of soil type and season on the nutritional potential of leaves from Fraxinus excelsior, Alnus glutinosa and Salix viminalis. Leaf samples were collected at 10 sites in the Netherlands on clay and on sandy soils in June, July and September and were analysed for digestibility, crude protein, macro and micro element concentrations. We conclude that the nutritional value of tree leaves differs between the studied tree species. Regarding the seasonal variation, we found a main effect of sampling period on the crude protein, calcium, phosphorus, copper and selenium concentration of leaves. No main effect of soil type was found on the nutritional value of leaves. Significant interactions were found for species × sampling period (digestibility, calcium, sulphur) and species × soil (digestibility, calcium). For the zinc and selenium concentration in tree leaves, a significant species × soil × sampling period interaction was found. We conclude that trees can play a role for supplying protein, and macro and micro elements to livestock, but that it depends on which tree species is used.  相似文献   

Characterization of the mechanism of action of the fungicide fenpicoxamid and its metabolite UK‐2A          下载免费PDF全文

David H Young  Nick X Wang  Stacy T Meyer  Cruz Avila‐Adame 《Pest management science》2018,74(2):489-498

BACKGROUND

Fenpicoxamid is a new fungicide for control of Zymoseptoria tritici, and is a derivative of the natural product UK‐2A. Its mode of action and target site interactions have been investigated.

RESULTS

UK‐2A strongly inhibited cytochrome c reductase, whereas fenpicoxamid was much less active, consistent with UK‐2A being the fungicidally active species generated from fenpicoxamid by metabolism. Both compounds caused rapid loss of mitochondrial membrane potential in Z. tritici spores. In Saccharomyces cerevisiae, amino acid substitutions N31K, G37C and L198F at the Qi quinone binding site of cytochrome b reduced sensitivity to fenpicoxamid, UK‐2A and antimycin A. Activity of fenpicoxamid was not reduced by the G143A exchange responsible for strobilurin resistance. A docking pose for UK‐2A at the Qi site overlaid that of antimycin A. Activity towards Botrytis cinerea was potentiated by salicylhydroxamic acid, showing an ability of alternative respiration to mitigate activity. Fungitoxicity assays against Z. tritici field isolates showed no cross‐resistance to strobilurin, azole or benzimidazole fungicides.

CONCLUSION

Fenpicoxamid is a Qi inhibitor fungicide that provides a new mode of action for Z. tritici control. Mutational and modeling studies suggest that the active species UK‐2A binds at the Qi site in a similar, but not identical, fashion to antimycin A. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.  相似文献   

Book Review: Social aspects of sustainable dry-land management,edited by D. Stiles. Wiley,Chichester, 1995. ISBN 0 471 95633 3, £45, $75,xiii + 313 pp.     

Nick Middleton 《Land Degradation \u0026amp; Development》1996,7(2):177-177

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