Some upper bounds on the total and list chromatic numbers of multigraphs

In this paper we discuss some estimates for upper bounds on a number of chromatic parameters of a multigraph. In particular, we show that the total chromatic number for an n-order multigraph exceeds the chromatic index by the smallest t such that t! > n.     

Detection and discrimination of simple and complex sounds by hearing-impaired Belgian Waterslager canaries

Belgian Waterslager canaries (BWC) are bred to produce a distinctive low-pitched song with energy restricted to a lower range of frequencies than in other types of canaries. Previous studies have shown a high frequency hearing loss primarily above 2000 Hz that is related to hair cell abnormalities in BWC, but little is known about auditory perception in these birds. Here, frequency, duration, and intensity discrimination, temporal integration, gap detection, and discrimination of temporally reversed harmonic complexes in BWC were measured and compared to normal-hearing non-BWC. BWC had excellent frequency discrimination ability at 1000 Hz, but showed poor frequency discrimination compared to non-BWC at frequencies in the region of hearing loss. Duration and intensity discrimination were not adversely affected in BWC. Temporal integration was reduced in BWC, except at 2000 Hz. Gap detection and discrimination of temporally reversed stimuli were somewhat better in BWC than in non-BWC. Those tests that relied primarily on temporal processing were less affected by the cochlear damage in BWC than tests that probably relied more on audibility and spectral analysis. Thus, despite significant high frequency hearing loss and extensive damage along the basilar papilla, BWC retain relatively good hearing abilities under many conditions.     

Stereochemical Studies of the Karlotoxin Class Using NMR Spectroscopy and DP4 Chemical‐Shift Analysis: Insights into their Mechanism of Action

After publication of karlotoxin 2 (KmTx2; 1 ), the harmful algal bloom dinoflagellate Karlodinium sp. was collected and scrutinized to identify additional biologically active complex polyketides. The structure of 1 was validated and revised at C49 using computational NMR tools including J‐based configurational analysis and chemical‐shift calculations. The characterization of two new compounds [KmTx8 ( 2 ) and KmTx9 ( 3 )] was achieved through overlaid 2D HSQC NMR techniques, while the relative configurations were determined by comparison to 1 and computational chemical‐shift calculations. The detailed evaluation of 2 using the NCI‐60 cell lines, NMR binding studies, and an assessment of the literature supports a mode of action (MoA) for targeting cancer‐cell membranes, especially of cytostatic tumors. This MoA is uniquely different from that of current agents employed in the control of cancers for which 2 shows sensitivity.     

The crystal structure of carbamoyl fluoride,NH<Subscript>2</Subscript>COF

Although first synthesized in 1940, the X-ray crystal structure of carbamoyl fluoride, NH₂COF, has until now remained unknown. [1] NH₂COF crystallizes in the orthorhombic space group Ibam, is planar, and exhibits a short C-N bond length, 1.3168(13) Å, implying a significant degree of donation from the nitrogen lone pair. The structure features one molecule in the asymmetric unit and eight molecules in the unit cell. There are four molecules in two planar layers that are connected by a network of NH·O hydrogen bonds with N·O distances of 2.987(2) Å and 2.945(2) Å. The compound was also studied by quantum chemical calculations at both the ab initio (MP2) and density functional theory (B3LYP) level.     

Influence of the purification process on the stability of <Emphasis Type="Italic">Jatropha curcas</Emphasis> biodiesel

The aim of this work was to evaluate the influence of the purification process on the stability of Jatropha curcas biodiesel. The biodiesel was obtained using a variety of purification processes: three wet methods with different drying processes (vacuum oven, conventional oven and anhydrous sodium sulfate) and one dry method (purification with adsorbent magnesium silicate). Biodiesel was characterized through the analysis of carbon residue, acidity index, infrared and gas chromatography. The composition J. curcas oil indicated 56.3 % of unsaturated fatty acids and 43.7 % of saturated fatty acids. Jatropha oil presented high quantity of saturated acids, which are less susceptible at oxidation. The biodiesel sample that was chemically purified (PUsq) presented better purity, indicating be the process more efficient in remove the residues of synthesis. Thermogravimetric curves of purified biodiesel by wet method, PUsq, with chemical drying using anhydrous sodium sulfate, and PUsv, with vacuum drying, showed the highest initial decomposition temperatures, indicating higher thermal stability. The carbon residue and infrared analyses suggested that contamination by catalyst residue is a determining factor in reduction of the oxidative stability of biodiesel. The oxidative stability was evaluated using Rancimat and pressure differential scanning calorimetry. Biodiesel samples showing better oxidative stability were purified using PUsq and PUsv, which obtained stability of 6 h using the Rancimat technique, the minimum limit set by Brazilian legislation, without the addition of antioxidant, suggesting that these methods least influenced the stability of biodiesel.     

Soft-lithographic approach to functionalization and nanopatterning oxide-free silicon

We report a simple, reliable high-throughput method for patterning passivated silicon with reactive organic monolayers and demonstrate selective functionalization of the patterned substrates with both small molecules and proteins. The approach completely protects silicon from chemical oxidation, provides precise control over the shape and size of the patterned features in the 100 nm domain, and gives rapid, ready access to chemically discriminated patterns that can be further functionalized with both organic and biological molecules.     

Drug discovery using very large numbers of patents. General strategy with extensive use of match and edit operations

A patent data base of 6.7 million compounds generated by a very high performance computer (Blue Gene) requires new techniques for exploitation when extensive use of chemical similarity is involved. Such exploitation includes the taxonomic classification of chemical themes, and data mining to assess mutual information between themes and companies. Importantly, we also launch candidates that evolve by “natural selection” as failure of partial match against the patent data base and their ability to bind to the protein target appropriately, by simulation on Blue Gene. An unusual feature of our method is that algorithms and workflows rely on dynamic interaction between match-and-edit instructions, which in practice are regular expressions. Similarity testing by these uses SMILES strings and, less frequently, graph or connectivity representations. Examining how this performs in high throughput, we note that chemical similarity and novelty are human concepts that largely have meaning by utility in specific contexts. For some purposes, mutual information involving chemical themes might be a better concept.     

Highly dispersed palladium(II) in a defective metal-organic framework: application to C-H activation and functionalization

High reversibility during crystallization leads to relatively defect-free crystals through repair of nonperiodic inclusions, including those derived from impurities. Microporous coordination polymers (MCPs) can achieve a high level of crystallinity through a related mechanism whereby coordination defects are repaired, leading to single crystals. In this work, we discovered and exploited the fact that this process is far from perfect for MCPs and that a minority ligand that is coordinatively identical to but distinct in shape from the majority linker can be inserted into the framework, resulting in defects. The reaction of Zn(II) with 1,4-benzenedicarboxylic acid (H(2)BDC) in the presence of small amounts of 1,3,5-tris(4-carboxyphenyl)benzene (H(3)BTB) leads to a new crystalline material, MOF-5(O(h)), that is nearly identical to MOF-5 but has an octahedral morphology and a number of defect sites that are uniquely functionalized with dangling carboxylates. The reaction with Pd(OAc)(2) impregnates the metal ions, creating a heterogeneous catalyst with ultrahigh surface area. The Pd(II)-catalyzed phenylation of naphthalene within Pd-impregnated MOF-5(O(h)) demonstrates the potential utility of an MCP framework for modulating the reactivity and selectivity of such transformations. Furthermore, this novel synthetic approach can be applied to different MCPs and will provide scaffolds functionalized with catalytically active metal species.