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排序方式: 共有46条查询结果,搜索用时 15 毫秒
1.
Zhaohua Dai Carl C. Trettin Changsheng Li Harbin Li Ge Sun Devendra M. Amatya 《Water, air, and soil pollution》2012,223(1):253-265
Emissions of methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) from a forested watershed (160 ha) in South Carolina, USA, were estimated with a spatially explicit watershed-scale modeling
framework that utilizes the spatial variations in physical and biogeochemical characteristics across watersheds. The target
watershed (WS80) consisting of wetland (23%) and upland (77%) was divided into 675 grid cells, and each of the cells had unique
combination of vegetation, hydrology, soil properties, and topography. Driven by local climate, topography, soil, and vegetation
conditions, MIKE SHE was used to generate daily flows as well as water table depth for each grid cell across the watershed.
Forest-DNDC was then run for each cell to calculate its biogeochemistry including daily fluxes of the three greenhouse gases
(GHGs). The simulated daily average CH4, CO2 and N2O flux from the watershed were 17.9 mg C, 1.3 g C and 0.7 mg N m−2, respectively, during the period from 2003–2007. The average contributions of the wetlands to the CH4, CO2 and N2O emissions were about 95%, 20% and 18%, respectively. The spatial and temporal variation in the modeled CH4, CO2 and N2O fluxes were large, and closely related to hydrological conditions. To understand the impact of spatial heterogeneity in
physical and biogeochemical characteristics of the target watershed on GHG emissions, we used Forest-DNDC in a coarse mode
(field scale), in which the entire watershed was set as a single simulated unit, where all hydrological, biogeochemical, and
biophysical conditions were considered uniform. The results from the field-scale model differed from those modeled with the
watershed-scale model which considered the spatial differences in physical and biogeochemical characteristics of the catchment.
This contrast demonstrates that the spatially averaged topographic or biophysical conditions which are inherent with field-scale
simulations could mask “hot spots” or small source areas with inherently high GHGs flux rates. The spatial resolution in conjunction
with coupled hydrological and biogeochemical models could play a crucial role in reducing uncertainty of modeled GHG emissions
from wetland-involved watersheds. 相似文献
2.
3.
Nanominerals, mineral nanoparticles, and Earth systems 总被引:4,自引:0,他引:4
Hochella MF Lower SK Maurice PA Penn RL Sahai N Sparks DL Twining BS 《Science (New York, N.Y.)》2008,319(5870):1631-1635
Minerals are more complex than previously thought because of the discovery that their chemical properties vary as a function of particle size when smaller, in at least one dimension, than a few nanometers, to perhaps as much as several tens of nanometers. These variations are most likely due, at least in part, to differences in surface and near-surface atomic structure, as well as crystal shape and surface topography as a function of size in this smallest of size regimes. It has now been established that these variations may make a difference in important geochemical and biogeochemical reactions and kinetics. This recognition is broadening and enriching our view of how minerals influence the hydrosphere, pedosphere, biosphere, and atmosphere. 相似文献
4.
With a view to select potato varieties possessing resistance to charcoal rot, laboratory tests were carried out at the Central Potato Research Institute, Simla (India). Five hundred and twenty six clones comprising tuber-bearing species ofSolanum and varieties and hybrids of potato were screened for their reaction toMacrophomina phaseoli (Maubl.) Ashby. A high degree of resistance was observed in six clones ofSolanum chacoense and four hybrids withS. chacoense germ plasm, while moderate susceptibility was observed in another six clones ofS. chacoense, three clones ofSolanum tuberosum ssp.andigena and nineteen hybrids produced at the Institute. 相似文献
5.
On microscopic examination after experimental infection with Paramphistomum cervi, tissue reactions in the duodenum were more pronounced during early stages of the infection (20th day post-infection (DPI)). Immature parasites were seen migrating to the muscularis layer, and focal infiltration of macrophages and lymphocytes was observed in the lamina propria and in the interstitial tissue of Brunner's gland. At places, there was cystic dilatation of Brunner's gland. At 40 DPI, the parasite was not present in the duodenal sections, and cellular infiltration was more diffuse and consistent. With the passage of time, the tissue reactions and cellular infiltration in the duodenum became less pronounced, but at 80 days parasites were attached to the villi of the rumen. Infiltration of mononuclear cells in the supporting connective tissue of the rumen was also observed. Thus, it is concluded that the immature forms of Paramphistomum cervi caused more severe damage in the duodenal tissue, whereas the adult form inflicted mild tissue damage in the rumen of the experimental kids. 相似文献
6.
Singh SK Dimri U Sharma MC Swarup D Kumar M Tiwary R 《Tropical animal health and production》2012,44(1):43-48
The oxidant/antioxidant balance of rabbits naturally infected with Psoroptes cuniculi and treated with ivermectin +/− vitamins A, D3, E, and H supplementation was investigated. Two groups of seven mixed ♂ and ♀, 6-to-8 month-old New Zealand White rabbits,
diagnosed Psoroptes mites-positive by skin scraping examination and seven clinically healthy control rabbits were examined. Blood samples were
obtained on day 0 and at 28 days post-therapy to determine oxidative stress indices. On day 0, the levels of lipid peroxides
were significantly higher (P ≤ 0.01) in the Psoroptes-infected rabbits compared with the healthy controls while those of reduced glutathione and the activities of the antioxidant
enzymes glutathione peroxidase, glutathione-S-transferase, catalase, and superoxide dismutase were significantly lower (P ≤ 0.01). Vitamin supplementation of the ivermectin-treated rabbits revealed both faster clinical (14 days) and parasitological
(10 days) recovery. It was concluded that significant alteration of oxidant/antioxidant balance is a factor in the pathogenesis
of P. cuniculi infestation of rabbits, and recovery can be enhanced by combining ivermectin treatment with vitamin A, D3, E, and H supplementation. 相似文献
7.
Crystalline properties of native starch granule fractions that varied in apparent density and size were investigated using differential scanning calorimetry (DSC). Endotherms obtained at 80% hydration showed significant variations in enthalpy between the six fractions. Typical bi-phasic endotherms exhibiting significant variation in start temperature were obtained for the six fractions at 50% hydration. However, on annealing at 50°C/50% hydration for 48 hr, all fractions showed a single endotherm without any significant variability in endotherm characteristics. At 10% hydration, the six fractions exhibited single high-temperature endotherms with significant differences in their peak temperatures. It was observed that mechanically damaging starch, resulted in the disappearance of any enthalpic transition. These observations could not be satisfactorily explained on the basis of prevailing concepts about DSC enthalpic transitions. 相似文献
8.
Singh SK Dimri U Sharma MC Swarup D Sharma B Pandey HO Kumari P 《Veterinary immunology and immunopathology》2011,144(3-4):487-492
The aim of the present study was to evaluate the status of apoptosis in peripheral blood leukocytes of dogs with demodicosis. A total of 26 dogs suffering from demodicosis, and positive for Demodex canis mites by skin scraping, participated in the study, 13 with localized demodicosis (LD) and 13 with generalized demodicosis (GD). A further 13 clinically healthy dogs, all of whom were negative for mites upon skin scraping, were used as controls. The dogs with GD revealed significantly higher (P ≤ 0.0001) percentage of leukocytes with externalization of phosphatidylserine (PS) and depolarized mitochondrial membrane potentials (ΔΨm) as compared with the dogs with LD and healthy controls. These dogs also revealed significantly lower values (P ≤ 0.0001) of hematological parameters viz. hemoglobin, total erythrocytes count total leukocytes count, lymphocytes, monocytes and neutrophils. Significantly higher (P ≤ 0.0001) percentages of leukocytes with externalization of PS and depolarized ΔΨm were also found in dogs with LD as compared with the healthy controls. These dogs also revealed significantly lower values of Hb (P ≤ 0.0001), TEC (P=0.025), TLC (P ≤ 0.0001), lymphocytes (P=0.008), monocytes (P ≤ 0.0001) and neutrophils (P=0.03). It is concluded that premature apoptosis of PBL may be implicated in the immunosuppression of the dogs with demodicosis. 相似文献
9.
Kritima Kapoor Opinder Singh Devendra Pathak 《Reproduction in domestic animals》2020,55(10):1393-1403
Tumour necrosis factor-α (TNF-α) is a cytokine that plays multiple important roles in corpus luteum (CL). Immunolocalization of expression of TNF-α in CL of buffalo was studied in different stages of its development and regression. Corpus luteum of healthy buffaloes (24) was collected from local slaughterhouses and categorized into early (stage I, 1–5 days, n = 6), mid (stage II, 6–11 days, n = 6), late luteal (stage III, 12–16 days, n = 6) and regressing phase (stage IV, 17–20 days, n = 6). In earliest phase of cyclic CL, per cent immunoexpression of TNF-α was significantly (p < .05) lower as compared to all phases with its expression being restricted to few developing luteal cells, usually in neutrophils. A significantly (p < .05) higher number of neutrophils with TNF-α immunoexpression were observed as compared to mid-luteal phase that indicated its role in initiation of angiogenesis at this stage. TNF-α immunoexpression almost doubled in mid-luteal phase, but the number of neutrophils exhibiting TNF-α was significantly (p < .05) lower with respect to all phases of CL. Immunoexpression percentage in late luteal phase increased sharply being significantly (p < .05) higher than earlier two phases of CL. In regressing phase, per cent immunostaining was maximum with highly significant (p < .05) difference as compared to all other stages, observed in all degrading luteal cells, abundant immune cells, that is neutrophils and macrophages which finally led to apoptosis and phagocytosis. Immunoexpression of TNF-α in early luteal phases served its role in initiation of angiogenesis, and its intense expression in regressing phase of CL suggested a shift in its role to apoptosis and structural luteal regression signifying both luteotropic and luteolytic roles in buffalo. This is probably the first study of its kind in buffaloes. 相似文献
10.
Ning-Jun Jiang Chao-Sheng Tang Toshiro Hata Benoît Courcelles Osama Dawoud Devendra N. Singh 《Soil Use and Management》2020,36(2):185-188
Bio-mediated soil improvement involves the usage of microbes to improve soil engineering performance through a series of bio-geochemical processes. In particular, Microbially Induced Calcite Precipitation (MICP), a ubiquitous bio-geochemical process that occurs in soil and results in permanent inorganic cementation between soil grains, has received the greatest research focus. While substantial progress has been made to develop MICP as a mainstream soil improvement technique, we still need to: (a) improve our understanding of the fundamental microbial, chemical and flow processes involved; (b) achieve multi-functionality by coupling engineering performance enhancement with ecological, environmental and carbon footprint benefits; and (c) maintain ecological balance and environmental friendliness, avoid long-term deterioration and lower the energy demand. 相似文献