Nitrogen‐enriched nonporous carbon materials derived from melamine–mica composites are subjected to ammonia treatment to further increase the nitrogen content. For samples preoxidized prior to the ammonia treatment, the nitrogen content is doubled and is mainly incorporated in pyrrol‐like groups. The materials are tested as electrodes for supercapacitors, and in acidic or basic electrolytes, the gravimetric capacitance of treated samples is three times higher than that of untreated samples. This represents a tenfold increase of the capacitance per surface area (3300 µF cm−2) in basic electrolyte. Due to the small volume of the carbon materials, high volumetric capacitances are achieved in various electrolytic systems: 280 F cm−3 in KOH, 152 F cm−3 in H2SO4, and 92 F cm−3 in tetraethylammonium tetrafluoroborate/propylene carbonate.
Carbon materials with significant nitrogen contents were investigated as the electrode materials of
supercapacitors. The preparation procedure involved the polymerization of melamine in the interlayer
space of template fluorine mica and carbonization at 750, 850, and 1000 °C. Some samples were also
stabilized prior to carbonization. We have shown previously that these carbons possess very interesting
capacitive behavior in an acidic medium despite small surface areas. High capacitance values in H2SO4
were attributed to the pseudocapacitive interactions between the protons and nitrogen atoms. This paper
further discusses the results obtained in a base and an aprotic electrolyte, KOH and TEABF4/PC,
respectively. Electrochemical properties were evaluated with cycling voltammetry, a galvanostatic charge/discharge technique, and electrochemical impedance spectroscopy. High capacitance values were obtained
in proton-free KOH, and the presence of pseudocapacitive interactions between the ions of the electrolyte
and the nitrogen atoms of the carbon matrix is proposed. Compared to those in sulfuric acid, greater
capacitances of nonstabilized samples were obtained in KOH, i.e., for the sample carbonized at 1000 °C,
the capacitance was 84.61 F/g in KOH vs 47.92 F/g in H2SO4. On the other hand, less porous but more
nitrogen-rich stabilized samples gave better performances in H2SO4, i.e., 62.24 F/g in H2SO4 compared
to 49.86 F/g in KOH for the sample stabilized and carbonized at 1000 °C. The sample heat-treated at
750 °C with a surface area of ca. 400 m2/g performs similarly in both electrolytes, i.e., ∼200 F/g.
Significantly lower gravimetric capacitances were obtained in TEABF4/PC from the samples carbonized
at 750 °C. On the other hand, the almost nonporous sample subjected to stabilization prior to carbonization
at 1000 °C gave a capacitance of ∼20 F/g. Hence, we suggest that the faradaic interactions between the
carbon electrode material and the electrolyte, although much less significant than those in H2SO4 and
KOH, play an important role in the nonaqueous electrolyte as well. Narrow micropores were detected by
CO2 adsorption/desorption, and their importance to the interpretation of capacitive behavior is also
discussed.
Glutaraldehyde crosslinking of native or reconstituted collagen fibrils and tissues rich in collagen significantly reduces biodegradation. Other aldehydes are less efficient than glutaraldehyde in generating chemically, biologically, and thermally stable crosslinks. Tissues crosslinked with glutaraldehyde retain many of the viscoelastic properties of the native collagen fibrillar network which render them suitable for bioprostheses. Implants of collagenous materials crosslinked with glutaraldehyde are subject long-term to calcification, biodegradation, and low-grade immune reactions. We have attempted to overcome these problems by enhancing crosslinking through bridging of activated carboxyl groups with diamines and using glutaraldehyde to crosslink the epsilon-NH2 groups in collagen and the unreacted amines introduced by aliphatic diamines. This crosslinking reduces tissue degradation and nearly eliminates humoral antibody induction. Covalent binding of diphosphonates, specifically 3-amino-1-hydroxypropane-1, 1-diphosphonic acid (3-APD), and chondroitin sulfate to collagen or to the crosslink-enhanced collagen network reduces its potential for calcification. Platelet aggregation is also reduced by glutaraldehyde crosslinking and nearly eliminated by the covalent binding of chondroitin sulfate to collagen. The cytotoxicity of residual glutaraldehyde--leaching through the interstices of the collagen fibrils or the tissue matrix--and of reactive aldehydes associated with the bound polymeric glutaraldehyde can be minimized by neutralization and thorough rinsing after crosslinking and storage in a nontoxic bacteriostatic solution.
The oxidized octaethyltetraphenylporphyrin (1, OETPP) and the corresponding newly prepared octaisobutyltetraphenylporphyrin (3, OisoBuTPP) could be isolated from the reaction of OETPPLi2 (or OisoBuTPPLi2) with SOCl2. The X-ray analysis and the characteristic UV-vis spectra of 1 and 3 revealed that these are the first examples of 16 pi nonaromatic porphyrins.
Myo18B is an unconventional myosin family protein expressed predominantly in muscle cells. Although conventional myosins are known to be localized on the A‐bands and function as a molecular motor for muscle contraction, Myo18B protein was localized on the Z‐lines of myofibrils in striated muscles. Like Myo18A, another 18th class of myosin, the N‐terminal unique domain of the protein and not the motor domain and the coiled‐coil tail is critical for its localization to F‐actin in myocytes. Myo18B expression was induced by myogenic differentiation through the binding of myocyte‐specific enhancer factor‐2 to its promoter. Deficiency of Myo18B caused an embryonic lethality in mice accompanied by disruption of myofibrillar structures in cardiac myocytes at embryonic day 10.5. Thus, Myo18B is a unique unconventional myosin that is predominantly expressed in myocytes and whose expression is essential for the development and/or maintenance of myofibrillar structure.
Phenol-formaldehyde polymers and surfactant assembly was structuralized into lamella and disordered mesophases depending on the surfactant/phenol molar ratio at the synthesis.
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