225 research outputs found
cis-Dihydroxylation and Epoxidation of Alkenes by Manganese Catalysts - Selectivity, Reactivity and Mechanism
Strategies to Maintain Natural Biocontrol of Soil-Borne Crop Diseases During Severe Drought and Rainfall Events
In many parts of the world, agricultural ecosystems are increasingly exposed to severe drought, and rainfall events due to climate changes. This coincides with a higher vulnerability of crops to soil-borne diseases, which is mostly ascribed to decreased resistance to pathogen attacks. However, loss of the natural capacity of soil microbes to suppress soil-borne plant pathogens may also contribute to increased disease outbreaks. In this perspectives paper, we will discuss the effect of extreme weather events on pathogen-antagonist interactions during drought and rainfall events and upon recovery. We will focus on diseases caused by root-infecting fungi and oomycetes. In addition, we will explore factors that affect restoration of the balance between pathogens and other soil microbes. Finally, we will indicate potential future avenues to improve the resistance and/or recovery of natural biocontrol during, and after water stresses. As such, our perspective paper will highlight a knowledge gap that needs to be bridged to adapt agricultural ecosystems to changing climate scenarios
cis-Dihydroxylation and Epoxidation of Alkenes by Manganese Catalysts - Selectivity, Reactivity and Mechanism
Oxidation reactions are among the most elementary of organic transformations and are essential in biology, chemical industry and (synthetic organic) chemistry. Selective oxidation of hydrocarbons, such as cis-dihydroxylation and epoxidation of alkenes, introduces functional groups and yields useful products or intermediates which in turn can be used as building blocks for more complex chemical structures. Despite considerable advances in recent years, major challenges remain in oxidation chemistry. The need for increased atom efficiency demands the use of oxidants, which do not generate stoichiometric amounts of by-products. From an environmental and atom economy perspective, the two most desirable oxidants to use are molecular oxygen (O2) and hydrogen peroxide (H2O2). Selectivity is another key issue. In order to develop a useful process, the introduction of oxygen atom(s) to the substrate should occur only at the desired position(s) in the molecule. Furthermore, the catalyst used to activate the oxidant (O2 or H2O2) should be cheap, non-toxic and robust. This thesis describes both the development of new methods for the selective and environmentally benign cis-dihydroxylation and epoxidation of alkenes and the mechanistic studies of these new processes. Since the catalyst used is based on manganese and hydrogen peroxide is employed as oxidant, this new method is a more environmentally benign alternative for the currently existing technology
Factors Associated With Glaucoma Surgery in Pediatric Non-Infectious Uveitis
Purpose: To identify factors associated with glaucoma surgery in pediatric uveitis. Methods: Patients diagnosed with uveitis before their 18th birthday and with an observation period of at least one year were included in a retrospective case-control study. Results: A total of 185 patients were included, 84 of whom had undergone glaucoma surgery. Juvenile idiopathic arthritis (JIA)-related uveitis was associated with undergoing glaucoma surgery (p = .002). In the JIA-subgroup, the presence of anterior segment complications (OR 3.1 (95% CI 1.0 to 9.6); P = .045) and an IOP > 21 mmHg during the first uveitis remission (OR 4.5 (95% CI 1.3 to 15.2); P = .015) were associated with an increased risk of glaucoma surgery. Sixty-eight percent of the cases needed glaucoma surgery within one year after they started IOP-lowering triple therapy. Conclusion: The risk profile for undergoing glaucoma surgery as outlined in this study is a valuable help to recognize and treat secondary glaucoma in a timely manner.</p
Factors Associated With Glaucoma Surgery in Pediatric Non-Infectious Uveitis
Purpose: To identify factors associated with glaucoma surgery in pediatric uveitis. Methods: Patients diagnosed with uveitis before their 18th birthday and with an observation period of at least one year were included in a retrospective case-control study. Results: A total of 185 patients were included, 84 of whom had undergone glaucoma surgery. Juvenile idiopathic arthritis (JIA)-related uveitis was associated with undergoing glaucoma surgery (p = .002). In the JIA-subgroup, the presence of anterior segment complications (OR 3.1 (95% CI 1.0 to 9.6); P = .045) and an IOP > 21 mmHg during the first uveitis remission (OR 4.5 (95% CI 1.3 to 15.2); P = .015) were associated with an increased risk of glaucoma surgery. Sixty-eight percent of the cases needed glaucoma surgery within one year after they started IOP-lowering triple therapy. Conclusion: The risk profile for undergoing glaucoma surgery as outlined in this study is a valuable help to recognize and treat secondary glaucoma in a timely manner.</p
Plant–soil feedbacks of exotic plant species across life forms: a meta-analysis
Invasive exotic plant species effects on soil biota and processes in their new range can promote or counteract invasions via changed plant–soil feedback interactions to themselves or to native plant species. Recent meta-analyses reveale that soil influenced by native and exotic plant species is affecting growth and performance of natives more strongly than exotics. However, the question is how uniform these responses are across contrasting life forms. Here, we test the hypothesis that life form matters for effects on soil and plant–soil feedback. In a meta-analysis we show that exotics enhanced C cycling, numbers of meso-invertebrates and nematodes, while having variable effects on other soil biota and processes. Plant effects on soil biota and processes were not dependent on life form, but patterns in feedback effects of natives and exotics were dependent on life form. Native grasses and forbs caused changes in soil that subsequently negatively affected their biomass, whereas native trees caused changes in soil that subsequently positively affected their biomass. Most exotics had neutral feedback effects, although exotic forbs had positive feedback effects. Effects of exotics on natives differed among plant life forms. Native trees were inhibited in soils conditioned by exotics, whereas native grasses were positively influenced in soil conditioned by exotics. We conclude that plant life form matters when comparing plant–soil feedback effects both within and between natives and exotics. We propose that impact analyses of exotic plant species on the performance of native plant species can be improved by comparing responses within plant life form
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