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1.
Nat Commun ; 9(1): 2226, 2018 06 08.
Article in English | MEDLINE | ID: mdl-29884892

ABSTRACT

The Amazon rainforest is the world's largest source of reactive volatile isoprenoids to the atmosphere. It is generally assumed that these emissions are products of photosynthetically driven secondary metabolism and released from the rainforest canopy from where they influence the oxidative capacity of the atmosphere. However, recent measurements indicate that further sources of volatiles are present. Here we show that soil microorganisms are a strong, unaccounted source of highly reactive and previously unreported sesquiterpenes (C15H24; SQT). The emission rate and chemical speciation of soil SQTs were determined as a function of soil moisture, oxygen, and rRNA transcript abundance in the laboratory. Based on these results, a model was developed to predict soil-atmosphere SQT fluxes. It was found SQT emissions from a Terra Firme soil in the dry season were in comparable magnitude to current global model canopy emissions, establishing an important ecological connection between soil microbes and atmospherically relevant SQTs.

2.
Sci Rep ; 8(1): 1877, 2018 01 30.
Article in English | MEDLINE | ID: mdl-29382914

ABSTRACT

Nitrous acid (HONO) is an important precursor of the hydroxyl radical (OH), the atmosphere´s primary oxidant. An unknown strong daytime source of HONO is required to explain measurements in ambient air. Emissions from soils are one of the potential sources. Ammonia-oxidizing bacteria (AOB) have been identified as possible producers of these HONO soil emissions. However, the mechanisms for production and release of HONO in soils are not fully understood. In this study, we used a dynamic soil-chamber system to provide direct evidence that gaseous emissions from nitrifying pure cultures contain hydroxylamine (NH2OH), which is subsequently converted to HONO in a heterogeneous reaction with water vapor on glass bead surfaces. In addition to different AOB species, we found release of HONO also in ammonia-oxidizing archaea (AOA), suggesting that these globally abundant microbes may also contribute to the formation of atmospheric HONO and consequently OH. Since biogenic NH2OH is formed by diverse organisms, such as AOB, AOA, methane-oxidizing bacteria, heterotrophic nitrifiers, and fungi, we argue that HONO emission from soil is not restricted to the nitrifying bacteria, but is also promoted by nitrifying members of the domains Archaea and Eukarya.


Subject(s)
Bacteria/metabolism , Hydroxylamine/metabolism , Nitrification/physiology , Ammonia/metabolism , Archaea/metabolism , Atmosphere , Gases/metabolism , Hydroxyl Radical/metabolism , Nitrous Acid/metabolism , Oxidation-Reduction , Soil , Soil Microbiology
3.
Science ; 341(6151): 1233-5, 2013 Sep 13.
Article in English | MEDLINE | ID: mdl-24031015

ABSTRACT

Abiotic release of nitrous acid (HONO) in equilibrium with soil nitrite (NO2(-)) was suggested as an important contributor to the missing source of atmospheric HONO and hydroxyl radicals (OH). The role of total soil-derived HONO in the biogeochemical and atmospheric nitrogen cycles, however, has remained unknown. In laboratory experiments, we found that for nonacidic soils from arid and arable areas, reactive nitrogen emitted as HONO is comparable with emissions of nitric oxide (NO). We show that ammonia-oxidizing bacteria can directly release HONO in quantities larger than expected from the acid-base and Henry's law equilibria of the aqueous phase in soil. This component of the nitrogen cycle constitutes an additional loss term for fixed nitrogen in soils and a source for reactive nitrogen in the atmosphere.


Subject(s)
Nitrogen Fixation , Nitrogen/metabolism , Nitrosomonas europaea/metabolism , Nitrous Acid/metabolism , Reactive Nitrogen Species/metabolism , Soil Microbiology , Ammonia/metabolism , Atmosphere/chemistry , Oxidation-Reduction
4.
Prim Care ; 17(4): 775-91, 1990 Dec.
Article in English | MEDLINE | ID: mdl-2290874

ABSTRACT

This article provides an overview of the diagnosis and treatment of eye infections. The seriousness of eye infections can range from benign and self-limiting to lethal. The primary care physician must determine the seriousness of each particular infection and then, based on that determination, must treat or refer the patient.


Subject(s)
Eye Infections , Eye Infections/diagnosis , Eye Infections/drug therapy , Eye Infections/surgery , Humans
5.
Int Ophthalmol Clin ; 16(2): 95-100, 1976.
Article in English | MEDLINE | ID: mdl-939656

ABSTRACT

It can be seen that the technique of using properly selected filters to provide rigidly defined monochromatic bands with which to observe the fundus presents interesting and challenging information that is as yet mainly untapped. The applications quoted present only a small part of the areas that can be investigated. The technique is basically standard, but advances can still be made in optimizing filters. The question of what band width to use for a given application is by no means solved and presents a challenging avenue of inquiry. It should be pointed out that the use of color film with interference filters offers no advantage. The only dimension being recorded at each point in the film is reflectivity of the structure at the wavelength of the filter being used. Documenting the color of this wavelength by the use of color film is a fruitless exercise.


Subject(s)
Fundus Oculi , Photography/methods , Humans , Light , Photography/instrumentation
11.
Arch Ophthalmol ; 85(3): 355-8, 1971 Mar.
Article in English | MEDLINE | ID: mdl-5542875

Subject(s)
Argon
17.
Can J Ophthalmol ; 3(2): 138-42, 1968 Apr.
Article in English | MEDLINE | ID: mdl-5660425
20.
Am J Ophthalmol ; 63(5): 946-50, 1967 May.
Article in English | MEDLINE | ID: mdl-6024425
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