Topographic Controls on N2O and N2 Efflux in a Temperate Forest

The release of greenhouse gases into the atmosphere is becoming an increasingly important problem due to the overwhelming evidence of the relationship between rising greenhouse gas concentrations and increased global temperatures. It is important that we gain a better understanding of the processes controlling the release of N2O, a powerful greenhouse gas. Topographic influences on soil temperature, moisture, reduction-oxidation (redox) potential, dissolved organic carbon, and nitrate conditions, which in turn influence N2O release, were investigated in a natural temperate forest ecosystem in Ontario, Canada. Wetland positions were observed to have the conditions most suited for N2O production (redox potential between +100 and -100 mV). More N2O was released during the summer from the inner (IW) and outer (OW) wetland positions than from lowland and upland topographic positions. Significant positive relationships between N2O efflux and precipitation events in both the IW and OW were observed, suggesting that precipitation creates conditions that promote bursts of N2O release. In addition, substantial biogeochemical activities were observed during the non-growing season under a snow-pack, including denitrification, which can produce N2O. It is important that we gain a better understanding of the processes controlling the release of N2O during the non-growing season. Fluxes of N2 were estimated using the acetylene inhibition technique from wetland positions that had the optimal redox conditions. Adding N2 and N2O fluxes to catchment N export not only reduced the discrepancy in N export observed among catchments but also between N inputs and outputs. During summer months, rainfall events can be used to predict N2O fluxes from the wetland positions within catchments in temperate forests and the IW position had greater potential of reducing N2O to N2 compared to the OW and the lowland and upland areas. Failing to account for winter denitrification products may lead to underestimation of annual N losses

E. Williams, Lyneise, Latin Blackness in Parisian Visual Culture, 1852-1932

La culture visuelle française, encore parsemée de zones non explorées, est empreinte de stigmates liés à son histoire coloniale. L’écriture de son évolution est un phénomène récent et s’inspire des renommées visual et cultural studies, initiées en Grande-Bretagne, puis exportées aux Etats-Unis. Les dernières manifestations culturelles, à l’instar de l’exposition Le Modèle noir : de Géricault à Matisse au musée d’Orsay (2019), témoignent de l’intérêt grandissant que porte la France aux histoir..

Charles Fréger : Cimarron, mascarade et liberté

Les stratégies de résistance à la domination coloniale ont pris des formes multiples depuis le XVIe siècle. Pour certains peuples, notamment du côté des Amériques, « résister » consistait à reprendre possession de leur propre corps en maintenant la singularité de leur tradition et en affirmant leur culture à travers les costumes, les accessoires et les masques, aux antipodes de la vision occidentale. Dans sa traversée des Etats-Unis jusqu’au Brésil, le photographe Charles Fréger part à la ren..

Fashion and Postcolonial Critique

Fashion and Postcolonial Critique est le 22e volume de la série d’ouvrages de l’Académie des beaux-arts de Vienne. Il ne réunit pas moins de vingt-six contributeurs autour de trois axes principaux : la décolonisation des archives sur la mode à l’échelle globale ; les conditions de la postcolonialité ; la mise en regard des histoires de la mode avec des approches critiques contemporaines. L’intention au fondement de ce volume émerge lors du symposium intitulé Re-visioning Fashion Theories : Po..

USE OF HIGHLIGHTING STRATEGIES IN READING COMPREHENSION AND EFFECTS ON ATTAINMENT IN SELECTED READING SKILLS

This study had two specific research objectives, two research questions and four specific research hypotheses. The study used quasi-experimental research designs. Data were collected using a standardized test. The study had a population of English Language students from secondary schools. The purposive sampling technique was used. The sample consisted of 40 students. The reliability of the instruments was established using Cronbach Alpha, which yielded a reliability coefficient of .70. Data collected were analyzed using the Statistical Package for Social Sciences (SPSS version 24.00). Findings revealed that reading comprehension performances of students taught skimming and scanning in the highlighting strategies were significantly higher than those who were not taught using the highlighting strategies

Summer storms trigger soil N₂O efflux episodes in forested catchments

Climate change and climate-driven feedbacks on catchment hydrology and biogeochemistry have the potential to alter the aquatic versus atmospheric fate of nitrogen (N) in forests. This study investigated the hypothesis that during the forest growth season, topography redistributes water and water-soluble precursors (i.e., dissolved organic carbon and nitrate) for the formation of gaseous N species. Soil nitrous oxide (N₂O) and nitrogen (N₂) efflux and soil physical and chemical properties were measured in a temperate forest in Central Ontario, Canada from 2005 to 2010. Hotspots and hot moments of soil N₂O and N₂ efflux were observed in topographic positions that accumulate precipitation, which likely triggered the formation of redox conditions and in turn intercepted the conversion of nitrate N flowing to the stream by transforming it to N₂O and N₂. There was a strong relationship between precipitation and N₂O efflux (y = 0.44x1.22, r² = 0.618, p<0.001 in the inner wetland; y = 1.30x^{1.16} r² = 0.72, p<0.001 in the outer wetland) and significantly different N₂:N₂O ratios in different areas of the wetland (19.6 in the inner wetland and 10.1 in the outer wetland). Soil N₂O+N₂ efflux in response to precipitation events accounted for 16.1% of the annual N input. A consequence of the higher frequency of extreme precipitation events predicted under climate change scenarios is the shift from an aquatic to atmospheric fate for N, resulting in a significant forest N efflux. This in turn creates feedbacks for even warmer conditions due to increased effluxes of potent greenhouse gases."This research was funded by an NSERC Discovery grant to IFC (217053‐2009 RGPIN)."https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015JG00302

Nitro drugs for the treatment of trypanosomatid diseases:past, present, and future prospects

There is an urgent need for new, safer, and effective treatments for the diseases caused by the protozoan parasites Trypanosoma brucei, Trypanosoma cruzi, and Leishmania spp. In the search for more effective drugs to treat these ‘neglected diseases’ researchers have chosen to reassess the therapeutic value of nitroaromatic compounds. Previously avoided in drug discovery programs owing to potential toxicity issues, a nitro drug is now being used successfully as part of a combination therapy for human African trypanosomiasis. We describe here the rehabilitation of nitro drugs for the treatment of trypanosomatid diseases and discuss the future prospects for this compound class

Using detergent to enhance detection sensitivity of African trypanosomes in human CSF and blood by Loop-Mediated Isothermal Amplification (LAMP)

&lt;p&gt;&lt;b&gt;Background:&lt;/b&gt; The loop-mediated isothermal amplification (LAMP) assay, with its advantages of simplicity, rapidity and cost effectiveness, has evolved as one of the most sensitive and specific methods for the detection of a broad range of pathogenic microorganisms including African trypanosomes. While many LAMP-based assays are sufficiently sensitive to detect DNA well below the amount present in a single parasite, the detection limit of the assay is restricted by the number of parasites present in the volume of sample assayed; i.e. 1 per µL or 103 per mL. We hypothesized that clinical sensitivities that mimic analytical limits based on parasite DNA could be approached or even obtained by simply adding detergent to the samples prior to LAMP assay.&lt;/p&gt; &lt;p&gt;&lt;b&gt;Methodology/Principal Findings:&lt;/b&gt; For proof of principle we used two different LAMP assays capable of detecting 0.1 fg genomic DNA (0.001 parasite). The assay was tested on dilution series of intact bloodstream form Trypanosoma brucei rhodesiense in human cerebrospinal fluid (CSF) or blood with or without the addition of the detergent Triton X-100 and 60 min incubation at ambient temperature. With human CSF and in the absence of detergent, the LAMP detection limit for live intact parasites using 1 µL of CSF as the source of template was at best 103 parasites/mL. Remarkably, detergent enhanced LAMP assay reaches sensitivity about 100 to 1000-fold lower; i.e. 10 to 1 parasite/mL. Similar detergent-mediated increases in LAMP assay analytical sensitivity were also found using DNA extracted from filter paper cards containing blood pretreated with detergent before card spotting or blood samples spotted on detergent pretreated cards.&lt;/p&gt; &lt;p&gt;&lt;b&gt;Conclusions/Significance:&lt;/b&gt; This simple procedure for the enhanced detection of live African trypanosomes in biological fluids by LAMP paves the way for the adaptation of LAMP for the economical and sensitive diagnosis of other protozoan parasites and microorganisms that cause diseases that plague the developing world.&lt;/p&gt

Fexinidazole – A New Oral Nitroimidazole Drug Candidate Entering Clinical Development for the Treatment of Sleeping Sickness

This article describes the preclinical profile of fexinidazole, a new drug candidate with the potential to become a novel, oral, safe and effective short-course treatment for curing both stage 1 and 2 human African trypanosomiasis and replace the old and highly problematic treatment modalities available today. Fexinidazole is orally available and rapidly metabolized in two metabolites having equivalent biological activity to the parent and contributing significantly to the in vivo efficacy in animal models of both stage 1 and 2 HAT. Animal toxicology studies indicate that fexinidazole has an excellent safety profile, with no particular issues identified. Fexinidazole is a 5-nitroimidazole and, whilst it is Ames-positive, it is devoid of any genetic toxicity in mammalian cells and therefore does not pose a genotoxic risk for use in man. Fexinidazole, which was rediscovered through a process of compound mining, is the first new drug candidate for stage 2 HAT having entered clinical trials in thirty years, and has the potential to revolutionize therapy of this fatal disease at a cost that is acceptable in the endemic regions

Megazol and its bioisostere 4H-1,2,4-triazole: comparing the trypanocidal, cytotoxic and genotoxic activities and their in vitro and in silico interactions with the Trypanosoma brucei nitroreductase enzyme

Megazol (7) is a 5-nitroimidazole that is highly active against Trypanosoma cruzi and Trypanosoma brucei, as well as drug-resistant forms of trypanosomiasis. Compound 7 is not used clinically due to its mutagenic and genotoxic properties, but has been largely used as a lead compound. Here, we compared the activity of 7 with its 4H-1,2,4-triazole bioisostere (8) in bloodstream forms of T. brucei and T. cruzi and evaluated their activation by T. brucei type I nitroreductase (TbNTR) enzyme. We also analysed the cytotoxic and genotoxic effects of these compounds in whole human blood using Comet and fluorescein diacetate/ethidium bromide assays. Although the only difference between 7 and 8 is the substitution of sulphur (in the thiadiazole in 7) for nitrogen (in the triazole in 8), the results indicated that 8 had poorer antiparasitic activity than 7 and was not genotoxic, whereas 7 presented this effect. The determination of Vmax indicated that although 8 was metabolised more rapidly than 7, it bounds to the TbNTR with better affinity, resulting in equivalent kcat/KM values. Docking assays of 7 and 8 performed within the active site of a homology model of the TbNTR indicating that 8 had greater affinity than 7