Efficiency of peroxyderivatives in the chemical modification of polyethylene

The thermal decomposition of dialkyl peroxides, peroxyketals, and peroxyesters was realized in order to study the functionalization of polyethylene in the molten state. Two radicals were produced: one to abstract a hydrogen to the polyolefin, the other to combine with such a macroradical. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2957–2963, 2000     

Global alignment of molecular sequences via ancestral state reconstruction

We consider the trace reconstruction problem on a tree (TRPT): a binary sequence is broadcast through a tree channel where we allow substitutions, deletions, and insertions; we seek to reconstruct the original sequence from the sequences received at the leaves. The TRPT is motivated by the multiple sequence alignment problem in computational biology. We give a simple recursive procedure giving strong reconstruction guarantees at low mutation rates. To our knowledge, this is the first rigorous trace reconstruction result on a tree in the presence of indels.     

Suppression of parasitic lasing in high energy, high repetition rate Ti:sapphire laser amplifiers

Transverse parasitic lasing is well known for limiting the signal gain and the pulse energy that can be extracted from Ti:sapphire petawatt amplifiers. We have developed a technique for suppressing these parasitic lasing modes based on perfect refractive index-matching liquid doped with a broad-bandwidth absorber to suppress the transverse lasing while ensuring proper heat removal from the Ti:sapphire crystal. The 800 nm laser output with a bandwidth of 41 nm (FWHM) and peak energy of 22.7 J at a repetition rate of 1 Hz is demonstrated.     

Synthesis and self-assembly of "tree-like" amphiphilic glycopolypeptides

Novel synthetic tree-like oligosaccharides-grafted-polypeptides were prepared by using Huisgen 1,3-dipolar cycloaddition between poly(γ-benzyl-L-glutamate)-block-poly(propargylglycine) and two different oligosaccharides, dextran or hyaluronan. By direct solubilisation in water, these tree-like glycopeptides spontaneously form very small assemblies with sizes below 50 nm and low polydispersity.     

Development of O–H insertion for the attachment of phosphonates to nucleosides; synthesis of α-carboxy phosphononucleosides

Development of rhodium catalysed O–H insertion reactions employing α-diazophosphonates with appropriately protected adenosine, uridine and thymidine derivatives is described. This synthetic methodology leads, following deprotection, to novel phosphononucleoside derivatives bearing a carboxylic acid moiety adjacent to the phosphonate. Protection strategies are critical to the success of the key O–H insertion. There are two important aspects: avoiding competing insertion pathways or catalyst poisoning, and being able to achieve deprotection without degradation of the phosphononucleosides.     

Spray-drying as a tool to disperse conductive carbon inside Na<Subscript>2</Subscript>FePO<Subscript>4</Subscript>F particles by addition of carbon black or carbon nanotubes to the precursor solution

In this work, Na₂FePO₄F-carbon composite powders were prepared by spray-drying a solution of inorganic precursors with 10 and 20 wt% added carbon black (CB) or carbon nanotubes (CNTs). In order to compare the effect of CB and CNT when added to the precursor solutions, the structural, electrochemical, and morphological properties of the synthesized Na₂FePO₄F-xCB and Na₂FePO₄F-xCNT samples were systematically investigated. In both cases, X-ray diffraction shows that calcination at 600 °C in argon leads to the formation of Na₂FePO₄F as the major inorganic phase. ⁵⁷Fe Mössbauer spectroscopy was used as complementary technique to probe the oxidation states, local environment, and identify the composition of the iron-containing phases. The electrochemical performance is markedly better in the case of Na₂FePO₄F-CNT (20 wt%), with specific capacities of about 100 mAh/g (Na₂FePO₄F-CNT) at C/4 rate vs. 50 mAh/g for Na₂FePO₄F-CB (20 wt%). SEM characterization of Na₂FePO₄F-CB particles revealed different particle morphologies for the Na₂FePO₄F-CNT and Na₂FePO₄F-CB powders. The carbon-poor surface observed for Na₂FePO₄F-CB could be due to a slow diffusion of carbon in the droplets during drying. On the contrary, Na₂FePO₄F-CNT shows a better CNT dispersion inside and at the surface of the NFPF particles that improves the electrochemical performance.     

Synthesis and biological evaluation of isoflavone analogues from Dalbergia oliveri

Mucronulatol 1 and violanone 2 isolated from Dalbergia oliveri Gamble, and the corresponding isoflavone 3 were prepared by ligand coupling reactions involving organolead reagent. Biological studies have shown a significant cytotoxic effect against an HBL100 leukemia cell line only for isoflavan 1 with an IC₅₀ value amounting to 5.7 μM. All the drugs modestly inhibit the in vitro microtubule assembly, independently of the cytotoxic ability. Natural compounds 1 and 2 have no antibacterial activity, but are potent inhibitors of the Fusarium oxysporum phytopathogenic fungal growth.