SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Base

224

The synchronization of two pendulum clocks hanging from a wall was first observed by Huygens during the XVII century. This type of synchronization is observed in other areas, and is fundamentally different from the problem of two clocks hanging from a moveable base. We present a model explaining the phase opposition synchronization of two pendulum clocks in those conditions. The predicted behaviour is observed experimentally, validating the model.

Concepts: Scientific method, Hypothesis, Das Model, Base, Problem of evil, Pendulum clock, Christiaan Huygens

178

To evaluate the evidence for a causal relationship between dietary acid/alkaline and alkaline water for the aetiology and treatment of cancer.

Concepts: Causality, Water, The Canon of Medicine, The Association, Philosophy of science, Base

175

Salt pollution and human-accelerated weathering are shifting the chemical composition of major ions in fresh water and increasing salinization and alkalinization across North America. We propose a concept, the freshwater salinization syndrome, which links salinization and alkalinization processes. This syndrome manifests as concurrent trends in specific conductance, pH, alkalinity, and base cations. Although individual trends can vary in strength, changes in salinization and alkalinization have affected 37% and 90%, respectively, of the drainage area of the contiguous United States over the past century. Across 232 United States Geological Survey (USGS) monitoring sites, 66% of stream and river sites showed a statistical increase in pH, which often began decades before acid rain regulations. The syndrome is most prominent in the densely populated eastern and midwestern United States, where salinity and alkalinity have increased most rapidly. The syndrome is caused by salt pollution (e.g., road deicers, irrigation runoff, sewage, potash), accelerated weathering and soil cation exchange, mining and resource extraction, and the presence of easily weathered minerals used in agriculture (lime) and urbanization (concrete). Increasing salts with strong bases and carbonates elevate acid neutralizing capacity and pH, and increasing sodium from salt pollution eventually displaces base cations on soil exchange sites, which further increases pH and alkalinization. Symptoms of the syndrome can include: infrastructure corrosion, contaminant mobilization, and variations in coastal ocean acidification caused by increasingly alkaline river inputs. Unless regulated and managed, the freshwater salinization syndrome can have significant impacts on ecosystem services such as safe drinking water, contaminant retention, and biodiversity.

Concepts: Acid, Water, United States, Chemistry, Potassium, Base, Ocean acidification, Alkalinity

42

Stromatolites are the oldest evidence for life on Earth, but modern living examples are rare and predominantly occur in shallow marine or (hyper-) saline lacustrine environments, subject to exotic physico-chemical conditions. Here we report the discovery of living freshwater stromatolites in cool-temperate karstic wetlands in the Giblin River catchment of the UNESCO-listed Tasmanian Wilderness World Heritage Area, Australia. These stromatolites colonize the slopes of karstic spring mounds which create mildly alkaline (pH of 7.0-7.9) enclaves within an otherwise uniformly acidic organosol terrain. The freshwater emerging from the springs is Ca-HCO3 dominated and water temperatures show no evidence of geothermal heating. Using 16 S rRNA gene clone library analysis we revealed that the bacterial community is dominated by Cyanobacteria, Alphaproteobacteria and an unusually high proportion of Chloroflexi, followed by Armatimonadetes and Planctomycetes, and is therefore unique compared to other living examples. Macroinvertebrates are sparse and snails in particular are disadvantaged by the development of debilitating accumulations of carbonate on their shells, corroborating evidence that stromatolites flourish under conditions where predation by metazoans is suppressed. Our findings constitute a novel habitat for stromatolites because cool-temperate freshwater wetlands are not a conventional stromatolite niche, suggesting that stromatolites may be more common than previously thought.

Concepts: Cyanobacteria, Carbon dioxide, Bacteria, Water, PH, Base, Fossil, Stromatolite

39

The combined effects of anthropogenic and biological CO2 inputs may lead to more rapid acidification in coastal waters compared to the open ocean. It is less clear, however, how redox reactions would contribute to acidification. Here we report estuarine acidification dynamics based on oxygen, hydrogen sulfide (H2S), pH, dissolved inorganic carbon and total alkalinity data from the Chesapeake Bay, where anthropogenic nutrient inputs have led to eutrophication, hypoxia and anoxia, and low pH. We show that a pH minimum occurs in mid-depths where acids are generated as a result of H2S oxidation in waters mixed upward from the anoxic depths. Our analyses also suggest a large synergistic effect from river-ocean mixing, global and local atmospheric CO2 uptake, and CO2 and acid production from respiration and other redox reactions. Together they lead to a poor acid buffering capacity, severe acidification and increased carbonate mineral dissolution in the USA’s largest estuary.The potential contribution of redox reactions to acidification in coastal waters is unclear. Here, using measurements from the Chesapeake Bay, the authors show that pH minimum occurs at mid-depths where acids are produced via hydrogen sulfide oxidation in waters mixed upward from anoxic depths.

Concepts: Oxygen, Carbon dioxide, Acid, Hydrogen, Carbon, PH, Base, Dead zone

34

To reduce the costs of maintaining a poliovirus immunization base in low-income areas, we assessed the extent of priming immune responses after the administration of inactivated poliovirus vaccine (IPV).

Concepts: Immune system, Vaccine, Vaccination, Polio vaccine, Immunology, Base, Poliovirus

28

There exists a misunderstanding on the TAED-activated peroxide system in the textile industry that H(2)O(2) used in excess of the stoichiometric amount could produce an addition effect on bleaching of cotton under alkaline conditions. In this study, a critical reinvestigation was carried out on the TAED-activated peroxide system for bleaching of cotton. It was found that the TAED-activated peroxide system achieved its best performance under near-neutral pH conditions. No addition effect was observed when an excessive amount of H(2)O(2) was used under alkaline conditions, which is probably due to the base-catalyzed bimolecular decomposition of peracetic acid and the nucleophilic attack by H(2)O(2) on peracetic acid. NaHCO(3) was shown to be a desired alkaline agent for maintaining near-neutral pH for the TAED-activated peroxide system. This study provides new insight into the application of the TAED-activated peroxide system for low-temperature bleaching of cotton under more environmentally benign conditions.

Concepts: Oxygen, Ammonia, Hydrogen peroxide, Cotton, PH, Textile, Base, Tetraacetylethylenediamine

28

The characterization of a spore laccase from Bacillus vallismortis fmb-103, isolated from textile industry disposal sites, is described. The activity was 6.5U/g of dry spore with ABTS as the substrate. The enzyme was quite stable at high temperature. It retained more than 90% of its initial activity after 10h at 70°C. The enzyme demonstrated broad pH stability in both acidic and alkaline conditions. There was almost no activity loss at pH 3 over an extended period of time, and the relative activity remained at 82% and 38% at pH 7 and pH 9 after 10days. NaN(3), SDS, l-cysterine, Dithiothreitol, EDTA and NaCl inhibit the enzyme activity. Triphenylmethane dyes, including malachite green, brilliant green and aniline blue were efficiently degraded by the enzyme after 24h in combination with a mediator with efficiencies of 76.84%, 96.56% and 81.17%, respectively. The reusability of spore laccase for decolorization dyes was also examined.

Concepts: Acid, Enzyme, PH, Sodium hydroxide, Base, PH indicator, Triarylmethane dyes, Hydrochloric acid

28

Grape anthocyanins reacted with diacetyl, a secondary metabolite of microorganisms involved in winemaking, to form 10-acetyl-pyranoanthocyanins, a type of anthocyanin-derived pigments similar to other vitisin-type pyranoanthocyanins found in red wines. The structures of 10-acetyl-pyranomalvidin-3-β-O-glucoside and 10-acetyl-pyranopeonidin-3-β-O-glucoside were confirmed by spectroscopic methods (UV-vis, MS/MS, and NMR) after their synthesis and isolation. In contrast to other vitisin-type pyranoanthocyanins, the newly described 10-acetyl-pyranoanthocyanins exhibited differentiated color-related properties. They showed an important tendency to occur as colorless hemiacetals at C-10 under wine pH conditions, while co-occurrence of flavylium cation and quinoidal base yield a broad visible absorbance band around 510-520 nm. Moreover, they easily reacted with bisulfite in acidic aqueous solution (pH 2.0), but the expected bleaching was not observed. Bisulfite bonded to the carbonyl of 10-acetyl substituent instead the expected C-10 position of the pyranoanthocyanin core, thus giving rise to a red pigment hypsochromically shifted towards orangish nuances (maximum absorbances at 487-491 nm).

Concepts: Spectroscopy, Chemistry, Color, Vermilion, Wine, Oenology, Base, Anthocyanin

28

Multiple pH-sensitive composites have been prepared through non-covalently functionalizing chemically converted graphene (CCG) with chitosan. Chtiosan exhibits as polybases and CCG shows characteristics of polyacids. Owing to the synergistic effects of chitosan and CCG, chitosan decorated graphene (CS-G) presents a multiple pH-responsive behavior that it can be dispersed well whether in acidic or in basic solution but aggregated in near-neutral solution. After CS-G was modified through a controlled deposition and cross-linking process of chitosan, the resultant cross-linked chitosan decorated graphene (CLCS-G) can be converted to a different pH-sensitive material that disperses only in acidic solution. Both CS-G and CLCS-G present a reversible switching between dispersed and aggregated states with pH as a stimulus. The unique pH response mechanisms of CS-G and CLCS-G have been further investigated by zeta potential analysis. Based on the unique pH-responsive property of CS-G, a stable and repeatable pH-driven switch was developed for monitoring pH change.

Concepts: Acid, Chemistry, Polymer chemistry, Colloid, PH, Base, Cross-link, Thermoplastic