Corrosives
Bev-Lorraine True, Robert H. Dreisbach in Dreisbach’s HANDBOOK of POISONING, 2001
The concentration of ozone does not begin to rise until nitric oxide (NO) has been completely converted to nitrogen dioxide (NO2). Although nitrogen dioxide alone contributes to the formation of a small amount of ozone, the levels found in urban atmospheres do not occur unless some of the carbon compounds indicated in the above schemes are present. These include aldehydes, ketones, and unsaturated hydrocarbons. The reactivity of these substances in atmospheres forms the basis for the restriction of their use in various solvents for paints, lacquers, and other finishes. Methane (CH4), which makes up about half of the organic compounds in the atmosphere, does not react. Some of the reaction intermediates are possible contributors to eye irritation, but they are so unstable that analysis or experimental testing has not been possible. PAN has been tested in volunteers and found to be irritating to the eyes at concentrations of 0.5 ppm, a concentration higher than that likely to occur in the atmosphere. A mixture of chemicals may be more irritating than the individual substances.
Composting
Sandy Cairncross, Richard Feachem in Environmental Health Engineering in the Tropics, 2018
Anaerobic composting or digestion, also known as fermentation or putrefaction, takes place in the absence of air or oxygen. It is the process by which organic muds are broken down by bacteria in marshes, producing marsh gas, consisting mainly of methane (CH4), but also of ammonia (NH3) and various sulfur-containing gases, which smell unpleasantly. A small amount of warmth is produced, but more of the energy is stored in the methane gas, which may be used for cooking or heating. Anaerobic composting is slow and unreliable as a method of pathogen destruction because it does not achieve sufficiently high temperatures. One method, the Bangalore method, requires alternate layers of refuse and nightsoil to be buried in trenches and left for at least six months.
Bowel disorders
Henry J. Woodford in Essential Geriatrics, 2022
There is an increased risk of small bowel bacterial overgrowth in people with diabetes, prior intestinal surgery or diverticulosis. Gastric atrophy or proton pump inhibitor (PPI) use may also be factors. Resulting symptoms include diarrhoea, weight loss and abdominal pain, or symptoms secondary to nutrient deficiencies. Bacteria can metabolise bile salts, leading to a reduction in the absorption of fat-soluble vitamins, and also metabolise vitamin B12 which could result in deficiency. The bacteria can produce folate and levels of this vitamin may become elevated (seeTable 12.3). Diagnosis can be achieved by culture of small bowel aspirates, or more commonly, by a hydrogen breath test. In this latter test the patient is administered glucose or lactulose and breath hydrogen and methane are measured. These gases can only originate from abnormal metabolism by bacteria in the small bowel. However, these investigations can be unreliable and, when suspicion is high, guidelines recommend a trial of antibiotics.24
Human keratinocytes adapt to ZnO nanoparticles induced toxicity via complex paracrine crosstalk and Nrf2-proteasomal signal transduction
Published in Nanotoxicology, 2018
Zhuoran Wu, Haibo Yang, Gautam Archana, Moumita Rakshit, Kee Woei Ng, Chor Yong Tay
To the transwell experimental set-up, 0.5 µg/ml of Nano-ZnO was added into the upper chamber with or without the fully confluent cell monolayer barrier. After 4 h of exposure, the culture medium in the bottom chamber was harvested and further diluted with DI water to make the tested solution with a final volume of 10 ml. Samples under different conditions were then analyzed via Perkin-Elmer SCIEX Elan DRCII ICP-MS. Prior to the analysis, smart tune was conducted using a standard solution containing Mg 24, In 115, and U 238 for systemic calibration. Methane was used as a reaction gas. The Zn2+ concentration was determined from the Zn isotope with a mass to charge ratio (m/z) of 66. The standard curve was derived from the Zn standard solution (in 1% HNO3). Sample readout was averaged from three repeated experiments.
Bioaugmentation of the green alga to enhance biogas production in an anaerobic hollow-fiber membrane bioreactor
Published in Biofouling, 2023
Sevcan Aydin, Hadi Fakhri, Nalan Tavsanli
Another contrast was seen in the Proteobacteria, which declined in the biofilm layer in the existence of H. pluvialis while mostly remaining unaffected in the sludge. A higher degree of dissociation was also seen in the HP reactor’s sludge and biofilm layer, with Firmicutes and Proteobacteria accounting for more than half of the total community in the sludge but less than 25% in the biofilm layer. Acetothermia and Cloacimonetes, neither of which were present in the biofilm layers of the C1 and C2 reactors, predominated in the biofilm layer of the HP reactor. The phyla Acetothermia, Acidobacteria, Armatimonadetes, and Chloroflexi were barely detectable in the sludge samples from the C1 and C2 reactors, whereas their presence in the HP reactor was much higher. Acetothermia spp. produce acetate, which is utilized in the formation of methane, thus enhancing biogas production. Phylum Thermotogae, previously reported to be correlated with hydrogenotrophic methane formation, did not change in the sludge samples, however decreased within the biofilm layer with the addition of antibiotics; and was completely diminished in the HP reactor in both sludge and biofilm layers. Citrobacter, Fervidobacterium, Klebsiella, Clostridium sensu stricto 5 and 8, Raoultella and Coprothermobacter were the most abundant genera in biofilm layers of the C1 and C2 reactors. Further, Acholeplasma was the most abundant genus in the biofilm layer of the HP reactor.
The rumen microbiome: a crucial consideration when optimising milk and meat production and nitrogen utilisation efficiency
Published in Gut Microbes, 2019
Chloe Matthews, Fiona Crispie, Eva Lewis, Michael Reid, Paul W. O’Toole, Paul D. Cotter
Methane production through fermentation involves the conversion of almost all polymers to methane and carbon dioxide under anaerobic conditions. It is the result of a number of metabolic interactions among the microbial ecosystem described above. As reviewed by Sirohi et al.,35 Wolfe began the first studies of CO2 reduction to methane in the early 1970s, discovering six new coenzymes in the following years. He found that the process of methanogenesis requires seven coenzymes and eight enzymes.35 CO2 and methane are removed by eructation to the atmosphere while acetate, propionate and butyrate travel across the rumen wall to the blood stream. Methane is produced by utilising simple substrates at low reduction potential to produce cellular energy.35 Methane synthesis contributes to the efficiency of the entire system and avoids the build-up of H2, which would inhibit the normal function of microbial enzymes involved in electron transfer.8 Indeed, if ruminants did not produce any methane, the rumen pH would drop and fibre digestion would no longer be feasible.
Related Knowledge Centers
- Alkane
- Chemical Compound
- Chemical Formula
- Carbon
- Hydrogen
- Group 14 Hydride
- Standard Temperature & Pressure
- Methane Clathrate
- Atmospheric Methane
- Methane Emissions