Enhancement of chi((2)) cascading processes in one-dimensional photonic bandgap structures

We theoretically analyze the nonlinear phase shifts induced by cascaded chi((2)):chi((2)) processes in one-dimensional photonic bandgap structures. We find that the enhancement of the density of modes near the band edge, coupled with a suitable choice of relative phase mismatch, leads to a remarkable new effect: The relative phase shift of the fundamental field on transmission can be of the order of pi over a distance of 7mum , with input intensities of the order of only 10 MW/cm(2).     

Nordehydrocyclodercitin, a hexacyclic pyridoacridine alkaloid from the marine ascidian, Aplidium sp

A new hexacyclic pyridoacridine alkaloid, nordehydrocyclodercitin (1), from an ascidian, Aplidium sp., cf. Aplidium cratiferum collected at Arab Reef, Great Barrier Reef, Australia is reported. Nordehydrocyclodercitin is structurally related to stellettamine (2) and cyclodercitin (3), which are sponge metabolites, and cycloshermilamine D (4) which was isolated from the marine tunicate Cystodytes violatinctus. The structure of nordehydrocyclodercitin was determined by interpretation of spectroscopic data, particularly those obtained from HMBC correlations, and by comparison with reported data for known related pyridoacridine alkaloids.     

Synthesis of the first poly(diaminosulfide)s and an investigation of their applications as drug delivery vehicles

This paper reports the first examples of poly(diaminosulfide)s that were synthesized by the reaction of a sulfur transfer reagent and several secondary diamines. The diaminosulfide group has the general structure of R(2)N-S-NR(2) and, although it has been used in the synthesis of small molecules, it has never been utilized in the synthesis of macromolecules until this report. A series of poly(diaminosulfide)s were synthesized at elevated temperatures, and the molecular weights of the polymers were as high as 12,400 g mol(-1) with conversions for the polymerization reaction up to 99%. The rate constants for the transamination reactions that lead to the polymers were measured in several solvents to provide an understanding the reaction conditions necessary to polymerize the monomers. The degradation of diaminosulfides were studied in D(2)O, C(6)D(6), CD(3)OD, CDCl(3), and DMSO-d(6)/D(2)O to demonstrate that they were very stable in organic solvents but degraded within hours under aqueous conditions. These results clearly demonstrated that diaminosulfides are very stable in organic solvents under ambient conditions. Poly(diaminosulfide)s have sufficient stabilities to be useful for many applications. The ability of these polymers to function as drug delivery vehicles were studied by the fabrication of nanoparticles of a water-insoluble poly(diaminosulfide) with a dye. The microparticles were readily absorbed into human embryonic 293 cells and possessed no measureable toxicity towards these same cells.     

A new rearranged dolabellane diterpene from the soft coral Clavularia inflata

A new dolabellane type diterpene 1 has been isolated through its acetate 1a. The structure of 1a was elucidated by extensive 1D and 2D NMR spectroscopy and confirmed by mass spectrometry. The structure of 1 was deduced by comparison of its NMR spectral data with those of 1a, while its relative stereochemistry was deduced by NOESY. The absolute stereochemistry of C-7 was determined by analyses of 1 separately esterified with R and S O-mandelic acids.     

Third-harmonic generation and self-channeling in air using high-power femtosecond laser pulses

It is shown, both theoretically and experimentally, that during laser pulse filamentation in air an intense ultrashort third-harmonic pulse is generated forming a two-colored filament. The third-harmonic pulse maintains both its peak intensity and energy over distances much longer than the characteristic coherence length. We argue that this is due to a nonlinear phase-locking mechanism between the two pulses in the filament and is independent of the initial material wave-vector mismatch. A rich spatiotemporal propagation dynamics of the third-harmonic pulse is predicted. Potential applications of this phenomenon to other parametric processes are discussed.     

Retention of palladium and phosphine ligands using nanoporous polydicyclopentadiene thimbles

Thimbles composed of polydicyclopentadiene retained Pd and phosphines used in Buchwald-Hartwig and Sonogashira coupling reactions but allowed the products to permeate. The products were isolated in high yields on the exteriors of the thimbles with no detectable contamination from phosphine and with Pd loadings as low as < 5.5 ppm.     

Improving the Molecular Ion Signal Intensity for In Situ Liquid SIMS Analysis

In situ liquid secondary ion mass spectrometry (SIMS) enabled by system for analysis at the liquid vacuum interface (SALVI) has proven to be a promising new tool to provide molecular information at solid–liquid and liquid–vacuum interfaces. However, the initial data showed that useful signals in positive ion spectra are too weak to be meaningful in most cases. In addition, it is difficult to obtain strong negative molecular ion signals when m/z>200. These two drawbacks have been the biggest obstacle towards practical use of this new analytical approach. In this study, we report that strong and reliable positive and negative molecular signals are achievable after optimizing the SIMS experimental conditions. Four model systems, including a 1,8-diazabicycloundec-7-ene (DBU)-base switchable ionic liquid, a live Shewanella oneidensis biofilm, a hydrated mammalian epithelia cell, and an electrolyte popularly used in Li ion batteries were studied. A signal enhancement of about two orders of magnitude was obtained in comparison with non-optimized conditions. Therefore, molecular ion signal intensity has become very acceptable for use of in situ liquid SIMS to study solid–liquid and liquid–vacuum interfaces.

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