Front propagation in certain one-dimensional exclusion models

Recent results on two interacting particle systems on are summarized, the asymmetric simple exclusion process and the branching exclusion process.     

Germacreme derivatives from diverse marine soft-corals (octocorallia)

Examinations of the extracts of 8 taxonomically-diverse marine soft-corals (Orders Gorgonaceae, Alcyonaceae and Stolonifera, Subclass Octocorallia, Phylum Cnidaria), have resulted in the isolation of 4 new sesquiterpenoids (1–4) of the germacrene type. Three previously known germacrene derivatives (5–7), and the elemane 8, have also been isolated, and complete ¹H and ¹³C NMR assignments for these compounds are reported.     

Asymmetric Synthesis of alpha-Amino Phosphonic Acids by Diastereoselective Addition of Trimethyl Phosphite onto Chiral Oxazolidines(1)

A simple and general asymmetric synthesis of alpha-amino phosphonic acids is described. The method involves the highly selective addition of trialkyl phosphite onto various chiral oxazolidines. Oxazaphosphorinanes thus obtained with an excellent diastereoselectivity furnish the corresponding (S)-alpha-substituted amino phosphonic acids in good overall yields and high ee (77-->97%) after simple deprotection.     

Actinide bioassays by ICPMS

The ever-increasing sensitivity of ICPMS continues to expand the technique’s application in the field of health physics. Enhancements in sample introduction and instrument design over the last few years have resulted in improving the ICPMS detection limit from ∼10 ng/l to≤0.1 ng/l. This additional sensitivity provides greater flexibility in the analysis of long-lived radionuclides in biological fluids, and requires only minimal sample preparation of urine for uranium analysis; the described 3-minute abbreviated matrix separation provides detection limits that are comparable to or better than alpha counting. For urine samples tested having concentrations that exceed the accepted administrative limit for total uranium (0.2 μg/day), isotopic analysis by ICPMS (e.g., determining the presence of²³⁶U, or measuring appropriate uranium isotope ratios) provides a reliable indication of occupational exposure. Our laboratory also utilizes ICPMS in a study examining uranium dissolution rate classification of dust collected at the perimeter of a nuclear facility. Specific details regarding these and other health physics applications are featured, including our group’s participation in assisting the DOE with the evaluation of ICPMS as a cost-effective alternative to fission-track analysis for the routine determination of²³⁹Pu in urine.     

Zinc(II) as a versatile template for the design of dipolar and octupolar NLO-phores

Thermally stable dipolar and octupolar (D2d, D3) NLO-phores are readily accessible by combining one, two, or three 4,4'-bis(dialkylaminostyryl)-[2,2']-bipyridyl ligands with zinc(II) salts. The off-resonant beta0 values point out the superiority of octupoles versus dipoles in terms of nonlinearity/transparency tradeoff. The octahedral tris(bipyridyl)zinc(II) complex exhibits a very large beta0 value (241 x 10-30 esu), which is the largest ever reported for octupolar molecules.     

Synthesis and evaluation of new lipomonosaccharide-imprinted polymers as MISPE supports

Molecular imprinted polymers (MIP) were prepared by the copolymerization of styrene (S) or methyl methacrylate (MMA) and methacrylic acid (MAA) using ethylene glycol dimethacrylate (EGDMA) as the crosslinker with molar ratios of [monomer]/[crosslinker] and [MAA]/[template] of 3:7 (to obtain a rigid structure) and 1:6 (to optimise hydrogen interactions), respectively. The polymerizations occurred in presence of the template molecule (MIP) - GlcNcouma - an amphiphilic monosaccharide. The same materials, non-imprinted polymers (NIP), were also prepared in absence of the template. These MIPs were characterized and used as SPE supports for selective enrichment. The results showed the correlation between retention efficiency and the porogen character of the polymerization solvent.     

Synthesis, linear, and quadratic-nonlinear optical properties of octupolar D3 and D2d bipyridyl metal complexes

A series of D3 (Fe(II), Ru(II), Zn(II), Hg(II)) and D2d (Cu(I), Ag(I), Zn(II)) octupolar metal complexes featuring different functionalized bipyridyl ligands has been synthesized, and their thermal, linear (absorption and emission), and nonlinear optical (NLO) properties were determined. Their quadratic NLO susceptibilities were determined by harmonic light scattering at 1.91 microm, and the molecular hyperpolarizability (beta0) values are in the range of 200-657 x 10(-30) esu for octahedral complexes and 70-157 x 10(-30) esu for tetrahedral complexes. The octahedral zinc(II) complex 1 e, which contains a 4,4'-oligophenylenevinylene-functionalized 2,2'-bipyridine, exhibits the highest quadratic hyperpolarizability ever reported for an octupolar derivative (lambdamax=482 nm, beta1.91(1 e)=870 x 10(-30) esu, beta0(1 e)=657 x 10(-30) esu). Herein, we demonstrate that the optical and nonlinear optical (NLO) properties are strongly influenced by the symmetry of the complexes, the nature of the ligands (donor endgroups and pi linkers), and the nature of the metallic centers. For example, the length of the pi-conjugated backbone, the Lewis acidity of the metal ion, and the increase of ligand-to-metal ratio result in a substantial enhancement of beta. The contribution of the metal-to-ligand (MLCT) transition to the molecular hyperpolarizability is also discussed with respect to octahedral d6 complexes (M=Fe, Ru).