Identification of compounds from Etonia rosemary (Conradina etonia)

Mosquitoes transmit pathogens that result in diseases harmful to human, livestock, and wildlife hosts. Numerous measures can be used to reduce insect-borne disease risk to humans, and one approach is the use of topical repellents to prevent host-seeking arthropods from taking a blood meal. A current emphasis in the development of new repellents is that they be safe. Therefore, natural products sources are increasingly being explored. Compounds from plants of the mint family (Lamiaceae) have been demonstrated to be insect repellents. This study examines compounds from Etonia rosemary (Conradina etonia) to identify compounds for examination as insect repellents. Samples of Etonia rosemary were passively extracted with hexane, dichloromethane, and methanol and analyzed by GC/MS. This extraction method was chosen to eliminate thermal degradation of plant components that can occur during the distillation procedure. Additional headspace volatile compounds from this plant were identified using microscale purge-and-trap GC/MS. A variety of terpenes, terpenic alcohols, ketones, and aldehydes were identified in the extracts with terpenes and short-chained aldehydes detected in greatest abundance.     

Next generation, sequentially assembled ultrathin films: beyond electrostatics

Over the last 15 years, the layer-by-layer (LbL) assembly technology has proven to be a versatile method for surface modification. This approach is likely to find widespread application because of its simplicity and versatility; however, the conventional use of highly charged materials with limited responsive behaviour presents some key limitations. In this tutorial review, the formation of multilayer thin films prepared through non-electrostatic interactions is reviewed. We discuss the assembly of films via a number of different methodologies, with particular emphasis on those that provide enhanced orientational control, stimuli-responsive behaviour, and improved film stability.     

Ballistic focusing of polyenergetic protons driven by petawatt laser pulses

By using a thick (250 μm) target with 350 μm radius of curvature, the intense proton beam driven by a petawatt laser is focused at a distance of ～1 mm from the target for all detectable energies up to ～25 MeV. The thickness of the foil facilitates beam focusing as it suppresses the dynamic evolution of the beam divergence caused by peaked electron flux distribution at the target rear side. In addition, reduction in inherent beam divergence due to the target thickness relaxes the curvature requirement for short-range focusing. Energy resolved mapping of the proton beam trajectories from mesh radiographs infers the focusing and the data agree with a simple geometrical modeling based on ballistic beam propagation.     

Effect of lattice structure on energetic electron transport in solids irradiated by ultraintense laser pulses

The effect of lattice structure on the transport of energetic (MeV) electrons in solids irradiated by ultraintense laser pulses is investigated using various allotropes of carbon. We observe smooth electron transport in diamond, whereas beam filamentation is observed with less ordered forms of carbon. The highly ordered lattice structure of diamond is shown to result in a transient state of warm dense carbon with metalliclike conductivity, at temperatures of the order of 1-100?eV, leading to suppression of electron beam filamentation.     

Conics and caps

In this article, we begin with arcs in PG(2, q ⁿ ) and show that they correspond to caps in PG(2n, q) via the André/Bruck?CBose representation of PG(2, q ⁿ ) in PG(2n, q). In particular, we show that a conic of PG(2, q ⁿ ) that meets ?_?? in x points corresponds to a (q ⁿ ?+?1 ? x)-cap in PG(2n, q). If x?=?0, this cap is the intersection of n quadrics. If x?=?1 or 2, this cap is contained in the intersection of n quadrics and we discuss ways of extending these caps. We also investigate the structure of the n quadrics.     

Regioselective Synthesis of Allyl Trimethylsilanes from Allylic Halides

Treatment of an allylic halide 1 with a trimethylsilyl metal reagent affords either trans allyl trimethylsilane 4 or the regioisomeric allyl trimethylsilane 3 with proper choice of reaction conditions.     

Living Free Radical Polymerisation Under a Constant Source of Gamma Radiation – An Example of Reversible Addition‐Fragmentation Chain Transfer or Reversible Termination?

The primary mechanism for living polymerisation under a source of gamma radiation at low dose rates is shown to be reversible addition‐fragmentation chain transfer. This was demonstrated by showing that the initial transfer step determines the success of the polymerisation. When an inappropriate leaving group is chosen for the RAFT agent, the polymerisation is non‐living. Under a reversible termination mechanism the ‘living’‐ness should be independent of this initial transfer step.