Organic Matter
Michael J. Kennish in Ecology of Estuaries Physical and Chemical Aspects, 2019
The relative importance of organic carbon sources in the estuarine carbon cycle has been a matter of controversy. While photosynthesis is an instrumental mechanism in the formation of organic carbon in estuaries, natural external sources (e.g., fluvial, groundwater, and oceanic inflow) and anthropogenic influxes (e.g., wastewater discharges and man-made hydrocarbons) can also be significant. A secondary, internal source of organic carbon compounds — those resulting from the degradation of dead organisms or excretion of molecules synthesized by organisms — cannot be discounted from analyses of carbon cycling. Counteracting the formation and introduction of organic carbon in estuaries are losses of organic carbon to heterotrophic consumption, sedimentation, and export to nearshore oceanic waters.
Organo-Modified Siloxane Polymers for Conditioning Skin and Hair
Randy Schueller, Perry Romanowski in Conditioning Agents for Hair and Skin, 2020
For an understanding of the physical properties of organo-modified siloxane compounds, one needs to understand the molecular architecture (15) of silicon-oxygen and silicon-carbon compounds compared to organic carbon-carbon and carbon-oxygen compounds. Low bond energy and low bond rotational energy contribute to a high degree of rotation of a Si-O-Si backbone. This freedom of rotation leads to a unique flexibility of a siloxane molecule. A siloxane molecule can be compared to a spring, Slinky, or accordion as its relates to back-and-forth and twisting motion. This bond flexibility is an important aspect of organo-siloxane polymers. It is believed that the freedom of rotation of a Si-O-Si backbone allows for an organo-cloud orientation [see Figure 1 (16)] that facilitates an effective spatial orientation/alignment at the interface of the surface to which an organo-siloxane polymer is exposed (lines A and B in Figure 1 represent interfaces). This freedom of rotation allows for maximizing surface activity, aligning the inorganic backbone (high-surface-energy Si-O-Si backbone) to high-polarity surfaces (line B in Figure 1) and organo-groups (low-surface-energy CH3 groups) to low-polarity surfaces (line A in Figure 1).
Radiometry
Michael Ljungberg in Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Organic scintillators usually contain aromatic carbon compounds, consisting of carbon and hydrogen. In these compounds, the carbon atoms form benzene rings, each containing six carbon atoms and a carbon atom in the ring is thus bound to two carbon atoms and one hydrogen atom. This molecule is planar, that is, the orbitals of the bound electrons all lie in the same plane with a bond angle of 120°. However, one of the electrons in the carbon L-shell does not take part in the bonds, and these six electrons form orbitals that are orthogonal to the molecular plane. These π-electrons make it possible for the benzene molecule to bind to another benzene molecule. Absorption of energy may cause excitation of a π-electron, followed by emission of light upon de-excitation.
Bioactivation of herbal constituents: mechanisms and toxicological relevance
Published in Drug Metabolism Reviews, 2019
Sesquiterpene lactones (SLs) are a large group of natural compounds containing α, β-unsaturated carbonyls, with over 5000 compounds reported to date. SLs are prevalent in plants of Asteraceae family where they can be found in almost all genera, notably in Artemisia, Arnica, Ambrosia, Helenium, Tanacetum, and Vernonia (Marles et al. 1995). They are 15-carbon compounds formed from condensation of three isoprene units, followed by cyclization and oxidative transformation to make a cis or trans-fused lactone. Sesquiterpene lactones exhibit a wide range of biological activities, such as antitumor, anti-inflammatory, analgesic, antibacterial, antifungal, antiviral, and insect deterrent, and many of them are used in traditional medicines worldwide to treat conditions such as fever, malaria, inflammation, ulcer, diabetes, and intestinal worms (Marles et al. 1995). The biological activity of SLs is mainly attributed to the α-methylene-γ-lactone group which covalently alkylates free sulfhydryl or amino groups in proteins via a Michael addition (Zhang et al. 2005). The intrinsic reactivity of the α-methylene-γ-lactone group also makes SLs the anti-herbivory and antimicrobial substance in plants, protecting from chewing insects and birds and inhibiting growth of competing plants.
Treatment of carbon monoxide poisoning: high-flow nasal cannula versus non-rebreather face mask
Published in Clinical Toxicology, 2021
Onder Yesiloglu, Muge Gulen, Salim Satar, Akkan Avci, Selen Acehan, Haldun Akoglu
Carbon monoxide (CO) is a colorless, odorless gas resulting from the incomplete combustion of carbon compounds. CO binds to hemoglobin competitively with oxygen (O2), causes a decrease in the oxygen content of blood and tissue hypoxia. Patients may present to the emergency department with severe symptoms ranging from ones similar to flu to coma and death. Clinical findings are non-specific such as dizziness, headache, nausea, vomiting, changes in consciousness, and can mimic many diseases. The clinical findings associated with poisoning are just loosely correlated with blood carboxyhemoglobin (COHb) levels [1].
Nanoparticles as a potential teratogen: a lesson learnt from fruit fly
Published in Nanotoxicology, 2019
Bedanta Kumar Barik, Monalisa Mishra
Nanoparticles (NPs) are engineered materials having one or multiple components and its size varies from 1 to 100 nanometer (nm) (Savolainen et al. 2010). NPs include various carbon compounds, nanocrystals, metal oxide, quantum dots, silica, and transition metals (Murray et al. 2000; Dreher 2003). The large surface area and high reactivity offer a characteristic physical, chemical, and biological properties (Dobrovolskaia and McNeil 2007; Hirano 2009) to the NPs used in various technological, medicinal and industrial applications.
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