Fluorescent Discrimination between Traces of Chemical Warfare Agents and Their Mimics

An array of fluorogenic probes is able to discriminate between nerve agents, sarin, soman, tabun, VX and their mimics, in water or organic solvent, by qualitative fluorescence patterns and quantitative multivariate analysis, thus making the system suitable for the inthe- field detection of traces of chemical warfare agents as well as to differentiate between the real nerve agents and other related compounds.Ministerio de Economía y Competitividad, Spain (Project CTQ2012- 31611), Junta de Castilla y León, Consejería de Educación y Cultura y Fondo Social Europeo (Project BU246A12-1), the European Commission, Seventh Framework Programme (Project SNIFFER FP7-SEC-2012-312411) and the Swedish Ministry of Defence (no. A403913

Ten-Year Responses of Underplanted Northern Red Oak to Silvicultural Treatments, Herbivore Exclusion, and Fertilization

Establishing adequate advanced oak reproduction prior to final overstory removal is crucial for regenerating oak forests in the eastern U.S. Many management approaches exist to this end, but benefits associated with any individual technique can depend on the suite of techniques employed and the geographic location. At four mixed-hardwood upland forest sites in central and southern Indiana, we tested factorial combinations of deer fencing, controlled-release fertilization, and various silvicultural techniques (midstory removal, crown thinning, and a shelterwood establishment cut) for promoting the growth and survival of underplanted red oak seedlings. Crown thinning resulted in slow growth and low survival. Midstory removal and the shelterwood establishment cut were nearly equally effective for promoting seedling growth. Seedling survival was strongly influenced by fencing, and differences in survival between silvicultural treatments were minimal when fencing was employed. Fertilization had minimal effects overall, only increasing the probability that unfenced seedlings were in competitive positions relative to surrounding vegetation. We suggest that underplanting oak seedlings can augment natural reproduction, but the practice should be accompanied by a combination of midstory removal and fencing, at a minimum, for adequate growth and survival

Hole Nucleation and Growth in Free-Standing Polystyrene Ultrathin Films

Nucleation and growth of holes in free-standing ultrathin (s 100 nm) polymer films are examined via optical microscopy in order to gain a better understanding of these phenomena. Hole nucleation is quantified with a free energy barrier based on a simple capillary model. Additionally, holes are found to grow exponentially in accordance with previous studies in the literature. Ultrathin films of polystyrene (between 50 and 100 nm) cast via flow coating are suspended atop lithographically patterned arrays of pillars. The films are then annealed above the glass transition temperature to study the nucleation and growth of holes via optical microscopy. Image analysis is performed to measure the density of nucleated holes as well as hole radius as a function of time. Holes are found to grow exponentially with time in a nonlinear viscoelastic, shear thinning regime under high shear strain. The energy barrier model is applied to the nucleation of holes in free-standing thin films and is found to describe the phenomenon well. This analysis of hole nucleation and growth extends the understanding of ongoing research into suspended fiber formation from the melting of free-standing polymer thin films

Confinement Effects on Chain Entanglement in Free-Standing Polystyrene Ultrathin Films

A study of the confinement effects on chain entanglements in free-standing ultrathin (s100 nm) polymer films is presented. Chain entanglements are probed by determining the lifetime and breakup time scale of a branched network of suspended fibers formed from the annealing of these films. Films of polystyrene (between SO and 100 nm) cast via flow coating are suspended atop lithographically patterned arrays of pillars. The films are then annealed above the glass transition temperature, where holes are randomly formed. The holes expand exponentially due to capillary forces and impinge upon each other to form a suspended, branched network of fibers. The thinning of fibers as well as the lifetime and breakup of this fiber network is observed via optical microscopy. A model for the viscoelastic-capillary thinning of fibers can be applied to determine a time scale for the breakup of individual samples. The decay of this time scale, below a critical parent film thickness, shows a transition between interchain and self-entanglements when crossing into a confined regime, illustrating a significantly decreased interchain entanglement density and breakdown in the entangled network of the polymer melt. This analysis of confinement effects on chain entanglement extends the understanding of ongoing studies into suspended fiber formation from the melting of freestanding polymer thin films. A better knowledge of chain entanglements in confined systems will make future fabrication of nanoscale suspended fibers, new architectures, and subsequent devices more controlled and accessible