SciCombinator

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

Concept: Base

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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

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Silver nanoparticles were added into anaerobic batch reactors to enhance acidogenesis and fermentative hydrogen production simultaneously. The effects of silver nanoparticles concentration (0-200nmolL(-1)) and inorganic nitrogen concentration (0-4.125gL(-1)) on cell growth and hydrogen production were investigated using glucose-fed mixed bacteria dominated by Clostridium butyricum. The tests with silver nanoparticles exhibited much higher H2 yields than the blank, and the maximum hydrogen yield (2.48mol/molglucose) was obtained at the silver concentration of 20nmolL(-1). Presence of silver nanoparticles reduced the yield of ethanol, but increased the yield of acetic acid. The high silver nanoparticles had higher cell biomass production rate. Further study using the alkaline pretreated culture as inoculum was carried out to verify the positive effect of silver nanoparticles on H2 production. Results demonstrated that silver nanoparticles could not only increase the hydrogen yield, but reduce the lag phase for hydrogen production simultaneously.

Concepts: Oxygen, Hydrogen, Ethanol, Base, Fermentative hydrogen production, Hydrogen production, Dark fermentation, Biohydrogen

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5-(Tetrazol-1-yl)-2H-tetrazole (1), or 1,5'-bistetrazole, was synthesized by the cyclization of 5-amino-1H-tetrazole, sodium azide and triethyl orthoformate in glacial acetic acid. A derivative of 1, 2-methyl-5-(tetrazol-1-yl)tetrazole (2) can be obtained by this method starting from 5-amino-2-methyl-tetrazole. Furthermore, selected salts of 1 with nitrogen-rich and metal (alkali and transition metal) cations, including hydroxylammonium (4), triaminoguanidinium (5), copper(I) (8) and silver (9), as well as copper(II) complexes of both 1 and 2 were prepared. An intensive characterization of the compounds is given, including vibrational (IR, Raman) and multinuclear NMR spectroscopy, mass spectrometry, DSC and single-crystal X-ray diffraction. Their sensitivities towards physical stimuli (impact, friction, electrostatic) were determined according to Bundesamt für Materialforschung (BAM) standard methods. Energetic performance (detonation velocity, pressure, etc.) parameters were calculated with the EXPLO5 program, based on predicted heats of formation derived from enthalpies computed at the CBS-4M level of theory and utilizing the atomization energy method. From the analytical and calculated data, their potential as energetic materials in different applications was evaluated and discussed.

Concepts: Oxygen, Ethanol, Acetic acid, Vinegar, Base, Iridium, Rhodium, Acetate

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Endoscopic endonasal transpterygoid approaches (EETA) use the pneumatization of the sinonasal corridor to control lesions of the middle and posterior skull base. These surgical areas are complex and the required surgical corridors are difficult to predict.

Concepts: Forecasting, Base, Corridor

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The present investigation was aimed at optimizing the conditions for preparing sulfated derivative of gum obtained from partially ripe fruits of Aegle marmelos. Elemental analysis, FTIR-ATR and NMR studies confirmed successful sulfation. The ratio of chlorosulfonic acid to pyridine exerted maximum influence on the degree of substitution followed by reaction temperature and reaction time. The sulfated derivative showed higher swelling in both acidic and alkaline pH as compared to unmodified gum. It also possessed higher negative zeta potential, higher viscosity, work of shear, firmness, consistency, cohesiveness and index of viscosity as compared to both unmodified gum as well as sodium alginate. Sulfated derivative was superior to unmodified gum and sodium alginate in terms of antimicrobial and anticoagulant activity. The sulfated sample appears to be a potential substitute over the unmodified gum sample and sodium alginate for modulating physicochemical properties of food and drug release dosage forms.

Concepts: Acid, Ratio, Cell wall, PH, Physical chemistry, Materials science, Base, Natural gum

26

A process based on a steam explosion pretreatment and alkali solution post-treatment was applied to fractionate olive stones (whole and fragmented, without seeds) and olive cake into their main constitutive polymers of cellulose ©, hemicelluloses (H) and lignin (L) under the optimal conditions for each fraction according earlier works. The chemical characterization (chromatographic method and UV and IR spectroscopy) and the functional properties (water and oil-holding capacities, bile acid binding and glucose retardation index) of each fraction were analyzed. The in vitro studies showed a substantial bile acid binding activity in the fraction containing lignin from olive stones (L) and the alkaline extractable fraction from olive cake (Lp). Lignin bound significantly more bile acid than any other fraction and similar to cholestyramine (a cholesterol-lowering, bile acid-binding drug), especially when the cholic acid (CA) was tested. These results highlight the health promoting potential of lignin from olive stones and olive cake extracted from olive by-products.

Concepts: Water, PH, Bile acid, Cellulose, Base, Alkali, Bile acid sequestrant, Taurocholic acid

26

Bis-thiazolium salts constitute a new class of anti-hematozoan drugs that inhibit parasite phosphatidylcholine biosynthesis. They specifically accumulate in Plasmodium- and Babesia-infected erythrocytes. Here, we provide new insight on the choline analogue albitiazolium, which is currently clinically tested against severe malaria. Concentration-dependent accumulation in P. falciparum-infected erythrocytes reached steady-state after 90-120 min and was massive throughout the blood cycle, with cellular accumulation ratios of up to 1000. This could not occur through a lysosomotropic effect, and the extent did not depend on the food vacuole pH, which is the case for the weak base chloroquine. Analysis of albitiazolium accumulation in P. falciparum-IRBC revealed a high-affinity component, restricted to mature stages and suppressed by pepstatin A treatment, and thus likely related to drug accumulation in the parasite food vacuole. Albitiazolium also accumulated in a second high-capacity component present throughout the blood cycle, likely not related to the food vacuole and also observed with Babesia divergens- infected erythrocytes. Accumulation was strictly glucose dependent, drastically inhibited by H(+)/K(+) and Na(+) ionophores upon collapse of ionic gradients and appeared to be energized by the proton-motive force across the erythrocyte plasma membrane, indicating the importance of transport steps for this permanently charged new type of antimalarial. This specific, massive and irreversible accumulation allows albitiazolium to restrict its toxicity to hematozoan-infected erythrocytes. The intraparasitic compartmentation of albitiazolium corroborates a dual mechanism of action, which could make this new type of antimalarial resistant to parasite resistance.

Concepts: Blood, Malaria, Cell membrane, Red blood cell, Apicomplexa, PH, Base, Babesia divergens

26

In this work, we report a novel approach to fabricate hierarchical TiO2 microspheres (HTMS) assembled by ultrathin nanoribbons where an anatase/TiO2(B) heterojunction and high energy facet coexist. The as-adopted approach involves (1) nonaqueous solvothermal treatment of a mixture of tetrabutyl titanate and acetic acid and (2) topotactical transformation into HTMS via thermal annealing. By this approach, the TiO2(B) phase usually synthesized from an alkaline treatment route could be initially formed. Subsequently, phase transition from TiO2(B) to anatase TiO2 occurs upon thermal treatment. It is demonstrated that such phase transition is accompanied by crystallographic orientation along the c-axis of anatase and TiO2(B) crystals, resulting in not only a coherent interface between two phases but also oriented attachment of anatase mesocrystals along the [001] direction, and finally high-energy (001) facet exposure. Interestingly, this work provides an alternative fluorine-free route for the synthesis of TiO2 crystals with high-energy (001) facet exposure. The structural analysis reveals that lattice-match induced topotactic transformation from TiO2(B) to anatase is the sole reason for the (001) facet exposure of anatase TiO2. The photocatalytic test for acetaldehyde decomposition shows that HTMS with anatase/TiO2(B) heterojunction and high-energy (001) facet exhibits superior photocatalytic efficiency compared with the relevant commercial product P25, which can be ascribed to the synergistic effect of large surface area, anatase/TiO2(B) heterojunction as well as high-energy facet exposure.

Concepts: Crystallography, Ethanol, Acetic acid, Titanium dioxide, Photocatalysis, Acetaldehyde, Base, Anatase

26

The Fukushima nuclear accident has highlighted the importance of finding a better final storage method for radioactive cesium species. Cs is highly soluble in water, and can easily exchange with other alkali ions in zeolites or clays to form stable complexes. However, Cs(+) is released from Cs(+) complexes into water when surrounded by an excess of water. Pollucite may be the best final storage option for Cs(+), but its typical synthesis requires heating to about 1200°C in air. Here, we show that the hydrothermal synthesis of pollucite can be completed at 300°C in three hours from any zeolite or clay. Furthermore, our procedure does not require ion exchange before synthesis. Radioactive Cs is usually found in complexes with clays. At that time, this method only requires calcium hydroxide, water, and three hours of hydrothermal synthesis, so the process is both inexpensive and practical for large-scale application. Pollucite is an analog of analcime zeolite, and contains a channel system 2.8 Å in diameter, which is formed by 6-oxygen rings. As the diameter of Cs(+) is 3.34 Å and each Cs(+) exists independently within a separate portion of the channel, Cs(+) cannot exit the pollucite framework without breaking it.

Concepts: Water, Oxide, Base, Alkali metal, Zeolite, Zeolites, Pollucite, Analcime

26

An isotachophoresis (ITP) separation of eight lanthanides on a serpentine PMMA microchip with a tee junction and a 230 mm long serpentine channel is described. The cover of the PMMA chip is 175 μm thick so that a contactless conductivity detector (C(4) D) in microchip mode can be used to detect the lanthanides as they migrate by ITP through the microchannel. Acetate and α-hydroxyisobutyric acid (HIBA) are used as complexing agents to increase the electrophoretic mobility difference between the lanthanides. Eight lanthanides are concentrated within ∼ 6 min by ITP in the complex microchip using 10 mM ammonium acetate at pH 4.5 as the leading electrolyte (LE) and 10 mM acetic acid at ∼ pH 3.0 as the terminating electrolyte (TE) in ∼ 6 min. In addition, a 2D numerical simulation of the lanthanides undergoing ITP in the microchip is compared with experimental results using COMSOL Multiphysics v4.3a.

Concepts: Acid dissociation constant, Acetic acid, Electrophoresis, Base, COMSOL Multiphysics, Multiphysics, Isotachophoresis, Acetates