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331.
We have obtained a large number of solutions to the aesthetic field equations. We discuss 19 solutions which appear to lead to bounded particle systems. One of the solutions is more complex (although only slightly) than the solution discussed in detail in Muraskin and Ring (1975). The solutions we have found have varied mathematical properties.  相似文献   
332.
333.
The combination of pharmacologic and endoscopic therapies is the gold standard for treating intestinal failures. The possibility of chemical solubility in water is mandatory for intelligent capsules. Functionalised silk fibroin with peptides and covalently linking different molecular entities to its structure make this protein a platform for preparing gels dissolving in the small and large intestine for drug delivery. In the present study, we linked a peptide containing the cell-adhesive motif Arginine–Glycine–Aspartic acid (RGD) to degummed silk fibres (DSF). Regenerated silk fibroin (RS) films obtained by dissolving functionalised DSF in formic acid were used to prepare composite gelatin. We show that such composite gelatin remains stable and elastic in the simulated gastric fluid (SGF) but can dissolve in the small and large intestines’ neutral-pH simulated intestine fluid (SIF). These findings open up the possibility of designing microfabricated and physically programmable scaffolds that locally promote tissue regeneration, thanks to bio-enabled materials based on functionalised regenerated silk.  相似文献   
334.
Tetramercaptotetrathiacalix[4]arene ( LH4 ) can be used as a coordination platform to bind four CuI ions at the thiolate and thioether S atoms. Donor ligands such as phosphanes can stabilize the resulting [LCu4] units, which then remain monomeric ( [(Ph3PCu)4L] ). In the absence of donor ligands, they aggregate, providing a hexamer ( [LCu4]6 ) in high yields, with a hollow‐sphere structure formed by an unprecedented Cu24S48 cage that is surrounded by the organic framework of the calixarene chalices. Preliminary NMR experiments with regard to the host‐guest chemistry in solution showed that the compound represents a polytopic host for acetonitrile and methane.  相似文献   
335.
1,3 Dipolar cycloaddition of Fmoc‐amino azides and acetylenic amides produces under solvent free irradiation a mixture of 1,4 or 1,5 substituted [1,2,3]‐triazoles. The presence of copper (I) iodide, plays a central role on regioselectivity. Four Fmoc‐amino azides characterized by different steric hindrance in side chains, and three different terminal alkynes, provided only the 1,4 substituted regioisomer under thermal microwave heating. Good yields, low consumption of organic solvents and short reaction times are the main aspects of our procedure. Reactions are compared to regioselective copper (I) catalysed solution synthesis performed at room temperature.  相似文献   
336.
Proton-donor ability of carboxylic groups incorporated by co-condensation into SBA-15 and ethane-bridged periodic mesoporous organosilica (PMO) has been studied through IR spectroscopy by dosing ammonia, which forms reversibly COO(-) groups and NH(4)(+) ions. The related equilibrium constants, determined by elaboration of IR data, reveal a lower reactivity of -COOH groups at the surface of PMO than on SBA-15, when the two samples have been outgassed at the same temperature. This finding is interpreted in terms of different dielectric constants and intermolecular interactions engaged with the surface species. Carboxylic groups on ethane-bridged organosilica react with silanols upon thermal treatment at 473 K to form a mixed anhydride species Si-O-C(O)-, at variance with the same groups on SBA-15.  相似文献   
337.

Various fundamental biologic roles of milk oligosaccharides have been recognized; however, their structure‐affinity relationship is still not fully revealed. Herein, we describe the synthesis of the fluorescent‐labeled milk oligosaccharides 3‐(5‐dimethylaminonaphthalene‐1‐sulfonylamino)propyl β‐D‐galactopyranosyl‐(1→3)‐[α‐L‐fucopyranosyl‐(1→4)]‐2‐acetamido‐2‐deoxy‐β‐D‐glucopyranoside (1) and 3‐(5‐dimethylamino‐naphthalene‐1‐sulfonylamino)propyl β‐D‐galactopyranosyl‐(1→3)‐[α‐L‐fucopyranosyl‐(1→4)]‐β‐D-glucopyranoside (2) as useful tools for synthetic, analytic, and biologic applications. For the fucosylation of lactose and lacto‐N‐biose, the chemical and the enzymatic syntheses using fucosyltransferase III were compared.  相似文献   
338.
Basic hydrogen peroxide and sodium perborate were found to be cheap and efficient alternatives for the conversion of primary and secondary nitro to carbonyl compounds (Nef reaction) in ionic liquids.  相似文献   
339.
A reliable, catalytic asymmetric vinylogous Mukaiyama-Mannich reaction of pyrrole-based silyl dienolates is introduced that is particularly apt for alkyl- and α-alkoxyalkyl-substituted aldehydes. The reaction course is effectively orchestrated by the Hoveyda-Snapper amino acid-based chiral ligand/silver(I) catalyst combination to produce valuable vicinal diamino carbonyl compounds in high yields, with virtually complete γ-site- and anti-selectivity and significant catalyst-to-product chirality transfer. The utility of the Mannich products can be seen in the synthesis of an unprecedented perhydrofuro[3,2-b]pyrrolone product, an aza-analogue of naturally occurring (+)-goniofufurone.  相似文献   
340.
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