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排序方式: 共有526条查询结果,搜索用时 31 毫秒
91.
92.
Jean-Paul Laclau Joseph Levillain Philippe Deleporte Jean de Dieu Nzila Jean-Pierre Bouillet Laurent Saint André Antoine Versini Louis Mareschal Yann Nouvellon Armel Thongo M’Bou Jacques Ranger 《Forest Ecology and Management》2010
Tropical plantation forests are meeting an increasing proportion of global wood demand and comprehensive studies assessing the impact of silvicultural practices on tree and soil functioning are required to achieve sustainable yields. The objectives of our study were: (1) to quantify the effects of contrasting organic residue (OR) retention methods on tree growth and soil nutrient pools over a full Eucalyptus rotation and (2) to assess the potential of soil analyses to predict yields of fast-growing plantations established on tropical sandy soils. An experiment was set up in the Congo at the harvesting of the first rotation after afforestation of a native herbaceous savanna. Six treatments were set up in 0.26 ha plots and replicated in 4 blocks, with OR mass at planting ranging from 0 to 46.5 Mg ha−1. Tree growth over the whole rotation was highly dependent on OR management at planting. Over-bark trunk volume 7 years after planting ranged from 96 m3 ha−1 in the treatment with forest floor and harvest residue removal at planting to 164 m3 ha−1 in the treatment with the largest amount of OR. A comparison of nutrient stocks within the ecosystem at planting and at the end of the rotation suggested that nutrient contents in OR were largely involved in the different response observed between treatments. OR management treatments did not significantly modify most of the nutrient concentrations in the upper layers of the mineral soil. Conventional soil analyses performed before planting and at ages 1 and 3 years were unable to detect differences between treatments despite large differences in tree growth. In contrast, linear regressions between stand aboveground biomass at harvesting and OR mass at planting (independent variable) showed that OR mass was an excellent predictor of stand yield (R2 = 0.99). A large share of soil fertility comes from organic material above the mineral soil in highly weathered sandy soils and OR mass at planting might be used in conjunction with soil analyses to assess the potential of these soils to support forest plantations. 相似文献
93.
94.
We investigated the indirect effect of an insecticide spray against the European Corn Borer (Ostrinia nubilalis Hübner; Lepidoptera: Crambidae) on mycotoxin contaminations of grain maize at the harvest stage. Between 2004 and 2009, 45 paired plots comparing insecticide treatment with untreated control were studied in Alsace administrative region, in the northeast of France. An average reduction of 78% in O. nubilalis larval densities was observed in insecticide-treated plots compared with control plots. Mean levels of deoxynivalenol mycotoxin in harvested grain were significantly reduced from 849 ppb in the control samples to 152 ppb in the insecticide-treated samples. A statistical modelling approach involving Generalized Linear Models (GLMs) was employed to identify and rank the associated variables for damage and pest density on different plant parts, on deoxynivalenol levels in harvested grain at harvest. The modelling revealed that the occurrence and the density of O. nubilalis larvae in maize stalks and in ears are the best indicators for deoxynivalenol contamination. The identification of these deoxynivalenol contamination risk factors, along with other factors such as genetic background, harvest date and crop rotation allows improvement of the risk assessment and risk forecasting in maize crops in order to manage crop safety and maintain maize deoxynivalenol mycotoxin levels below the European Regulation (EC) No. 1126/2007 threshold. 相似文献
95.
Ferret-Bernard S Lacroix-Lamandé S Remot A Metton C Bernardet N Charley B Drouet F Laurent F 《Veterinary research》2011,42(1):19
ABSTRACT: At birth, the immune system is still in development making neonates more susceptible to infections. The recognition of microbial ligands is a key step in the initiation of immune responses. It can be mimicked to stimulate the immune system by the use of synthetic ligands recognising pattern recognition receptors. In human and mouse, it has been found that neonatal cytokine responses to toll-like receptor (TLR) ligands differ in many ways from those of adults but the relevant studies have been limited to cord blood and spleen cells. In this study, we compared the responses in neonate and adult sheep to CpG oligodeoxynucleotides (ODN), a TLR9 ligand, in both a mucosal and a systemic organ. We observed that in response to CpG-ODN more IL-12 was produced by neonatal than adult sheep cells from mesenteric lymph nodes (MLN) and spleen. This higher IL-12 response was limited to the first 20 days after birth for MLN cells but persisted for a longer period for spleen cells. The major IL-12-producing cells were identified as CD14+CD11b+. These cells were poor producers of IL-12 in response to direct stimulation with CpG-ODN and required the cooperation of other MLN cells. The difference in response to CpG-ODN between neonates and adults can be attributed to both a higher proportion of CD14+CD11b+ cells in neonate lambs and their higher capacity to produce IL-15. The IL-15 increases IL-12 production by an amplifying feedback loop involving CD40. 相似文献
96.
de Stefani A de Risio L Platt SR Matiasek L Lujan-Feliu-Pascual A Garosi LS 《Veterinary surgery : VS》2011,40(2):183-191
Objective: To report frequency and type of complications, and outcome in dogs with severe neurologic signs secondary to internal, suspected obstructive hydrocephalus treated by ventriculoperitoneal (VP) shunting. Study Design: Case series. Animals: Dogs (n=14). Methods: Medical records (2001–2006) was reviewed for dogs that had VP shunting. Inclusion criteria were complete medical record, progressive forebrain signs unresponsive to medical treatment, normal metabolic profile, negative antibody titers and/or cerebrospinal PCR for Toxoplasma gondii, Neospora caninum, and canine distemper virus, magnetic resonance images of the brain, confirmed diagnosis of VP shunting, and follow‐up information. Results: Hydrocephalus was idiopathic in 5 dogs and acquired (interventricular tumors, intraventricular hemorrhage, inflammatory disease) in 9 dogs. Four dogs developed complications 1 week to 18 months postoperatively, including ventricular catheter migration, infection, shunt under‐drainage, kinking of the peritoneal catheter, valve fracture, and abdominal skin necrosis. Three of these dogs had 1 or more successful revision surgeries and 1 dog was successfully treated with antibiotics. All, but 1 dog, were discharged within 1 week of surgery, and had substantial neurologic improvement. Median survival time for all dogs was 320 days (1–2340 days), for dogs with idiopathic hydrocephalus, 274 (60–420) days and for dogs with secondary hydrocephalus, 365 (1–2340) days. Conclusions: VP shunting was successful in relieving neurologic signs in most dogs and postoperative complications occurred in 29%, but were resolved medically or surgically. 相似文献
97.
Objective: To evaluate the clinical outcome of minimally invasive plate osteosynthesis (MIPO) for nonarticular tibial fractures stabilized using bone plates with or without an intramedullary rod (IMR). Study Design: Prospective study. Animals: Dogs (n=28) and 8 cats. Methods: After closed reduction, fracture fixation was achieved using an epiperiosteal plate inserted percutaneously through epiphyseal small incisions. In some fractures, an IMR was inserted via medial parapatellar arthrotomy. Radiographs were recommended every 3 weeks until clinical union. Postoperative tibial length and alignment were compared with contralateral measurements (P<.05). Time to clinical union and complications were recorded. Results: An IMR was used in 30.5% of the cases. Repaired tibiae were 1% shorter than contralateral tibiae (P<.05). Frontal and sagittal alignment were similar between repaired and contralateral tibiae (P>.05). Six dogs were lost for follow‐up; owners indicated normal function. In 30 cases for which bone healing was documented, mean±SD healing time was 45±20.8 days; however, when considering the 23 cases, which completed preestablished scheduled follow‐ups, healing time was 36±11.6 days. Minor complications occurred in 4 cases (11%). One major complication (3%) consisting of a plate fracture was successfully revised using MIPO with a larger plate. Conclusions: Consistent restoration of alignment was accomplished using MIPO techniques. Furthermore, MIPO appeared to yield faster healing times and lower complication rates than those reported with conventional plate osteosynthesis. 相似文献
98.
Doyen A Beaulieu L Saucier L Pouliot Y Bazinet L 《Journal of agricultural and food chemistry》2011,59(5):1784-1792
Electrodialysis with ultrafiltration membrane (EDUF) is a technology based on the separation of molecules according to their charge and molecular mass. Some works have already successfully demonstrated the recovery of bioactive peptide fractions. However, the impact of ultrafiltration membrane (UFM) material, used in the EDUF system, on the peptide migration has never been studied. Consequently, the objectives of this work were (1) to evaluate the effect of two different UFM materials on the selective separation of peptides from a snow crab byproduct hydrolysate by electrodialysis with ultrafiltration membranes and (2) to determine the effect of UFM material on their potential fouling by peptides. It appeared that, after 6 h of EDUF separation using polyether sulfone (PES) and cellulose acetate (CA) UFM, peptides with low molecular weights ranging from 300 to 700 Da represented the most abundant population in the KCl1 (compartment located near the anode for the recovery of anionic/acid peptide fractions) and KCl2 (compartment located near the cathode for the recovery of cationic/basic peptide fractions) permeates. Peptides with molecular weights ranging from 700 to 900 Da did not migrate during the EDUF treatment. Moreover, only CA UFM allowed the recovery of high molecular weight molecules (900-20000 Da) in both KCl compartments. Peptides desorbed from PES and CA UFM after 6 h of EDUF separation had low molecular weights and belonged mainly to the 600-700 Da molecular weight range. These peptides represented a low proportion of the peptides initially present in the snow crab byproduct hydrolysate with individual molecular weight range proportions from 1.52 ± 0.31 to 10.2 ± 2.32%. 相似文献
99.
Leah Tsror Valerie Hélias Sara Mordechai-Lebiush Orly Erlich Marina Hazanovsky Laura Chalupowicz Michal Reuven Orit Dror Lea Valinsky Angelique Laurent Shulamit Manulis-Sasson 《Plant pathology》2021,70(9):2179-2187
Pectobacterium brasiliense (Pbr) infects a wide range of crops worldwide, causing potato blackleg and soft rot and vegetable soft rots. This study aimed to characterize the genetic diversity and virulence variability among 68 Pbr strains isolated from either symptomless potato progeny tubers, diseased potato plants, ware potatoes wash water, or vegetables grown in Israel, as well as strains isolated from symptomless seed tubers grown in Europe, or diseased potato plants grown in France. The collection was typed using PCR and TaqMan real-time PCR analyses, dnaX sequence analysis, pulsed-field gel electrophoresis (PFGE), and pectolytic activity. dnaX phylogeny grouped almost all strains in a common genetic clade related to Pbr, which was distinct from the other Pectobacterium species. PFGE analysis identified two main clusters, including one major group of 47 strains with 95%–100% similarity. Maceration assays on two potato cultivars showed significant differences between strains but with no correlations with the source of the strains nor the status of the host (with/without symptoms). Molecular (dnaX sequences and PFGE profiles) and phenotypic analyses (tuber maceration tests) showed that the tested Pbr strains are not a homogeneous group. Analysis of the tested Pbr strains isolated from potato and vegetables grown in fields with a history of potato cultivation suggests that seed tubers imported from Europe may be the main source for Pbr in Israel. To the best of our knowledge, this is the first study that describes biodiversity and population structure of P. brasiliense isolated from potato and vegetables under hot climate conditions. 相似文献
100.
Jean-Etienne Poirrier Laurent Poirrier Pierre Leprince Pierre Maquet 《Journal of circadian rhythms》2006,4(1):10-10