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• Girdling treatments were effective in killing Douglas-fir. • Improved effectiveness occurred when girdle width was equal to or greater than the tree diameter. • Most snags persisted up to 17 years after girdling. • Fuel loading and regeneration were not substantially affected by girdling treatments. The prolonged absence of fire in Oregon white oak (Quercus garryana) woodlands and savannas of the Pacific Northwest has resulted in substantial conifer encroachment over the past century. Use of low intensity prescribed burns often lacks sufficient intensity to kill larger encroached trees, requiring alternative approaches. In the Bald Hills region of Redwood National Park, managers have implemented girdling treatments to kill Douglas-fir (Pseudotsuga menziesii) over the past two decades with the objective of recovering remnant oaks and restoring historical woodland area. We surveyed 258 girdled Douglas-fir to examine the effectiveness of girdling treatments to create snags and the impacts of girdling on tree regeneration and fuel recruitment over a 17 year time since girdling chronosequence. Girdling was successful in killing 91% of the treated Douglas-fir independent of the method used (axe or chainsaw). Larger trees with a low girdle width-to-tree diameter ratio tended to survive girdling. Trees with a girdle width-to-tree diameter ratio ≥1 were most effective at killing trees. Snags generated through girdling decayed over time but did not significantly reduce in height over the time period examined. Bird activity was observed on 19% of snags across the chronosequence but 88% of 10 y old snags had signs of bird foraging. Fine woody fuel loading and fuelbed depths were potentially elevated 7 years after treatment but did not persist through the time period examined. Regeneration of Douglas-fir and oaks were highly variable and did not seem to be clearly linked to girdling activity. Our results indicate that girdling is a highly effective treatment to kill Douglas-fir and aid restoration of Oregon oak woodlands with limited negative impacts on surface fuel hazards or regeneration. [ABSTRACT FROM AUTHOR]

The relationship of environmental constraints with the differences between plant-level efficiency and the feasibility of enhancements in environmental performance and productivity are investigated. Results indicate that not all production inefficiencies can be attributed to environmental constraints. A 1990 estimate shows that the average production loss caused by environmental constraints is 9.4%.

Ink analysis is central to questioned document examination. We applied direct analysis in real time mass spectrometry (DART MS) to ballpoint, gel, and fluid writing ink analysis. DART MS acquires the mass spectrum of an ink while it is still on a document without altering the appearance of the document. Spectra were acquired from ink on a variety of papers, and the spectrum of the blank paper could be subtracted out to produce a cleanly isolated ink spectrum in most cases. Only certain heavy or heavily processed papers interfered. The time since an ink is written on paper has a large effect on its spectrum. DART spectra change radically during the first few months after an ink is written as the more volatile components evaporate, but the spectra stabilize after that. A library-search study involving 166 well- aged inks assessed the ability to identify inks from their DART spectra. The aggregate success rate was 92%. [ABSTRACT FROM AUTHOR]

The degradation of a thermally-aged bismaleimide-glass fiber composite system was assessed via spectroscopic methods. Composite samples were subjected to accelerated isothermal aging at temperatures (275, 300, 325, 350 and 375 ° C) near or above the suggested upper usage limit of 290 °C. Broadband dielectric spectroscopy was used to measure changes in the dielectric spectra of aged composites from 1 kHz to 2 MHz, while chemical changes in the resin were identified with Fourier transform infrared photoacoustic spectroscopy. Additionally, samples were mechanically assessed via a double-notch compression test. Relationships between the dielectric, photoacoustic, and mechanical properties were inferred from the results. [ABSTRACT FROM AUTHOR]

Here, we report the first study on the hole making performance of thermoplastic carbon fibre/polyetherketoneketone (CF/PEKK) composite. Different hole making methods (conventional drilling vs. helical milling) have been compared and the effect of different feed rates has been investigated. The effect of thermal-mechanical interaction on the resulting hole damage has been elucidated for the first time for carbon fibre reinforced thermoplastics (CFRTPs) hole making. In the material science dimension, advanced material characterization techniques have been deployed to reveal the material removal mechanisms at microscopic scale and unveil the underlying material structural change at a molecular level. Results show that the delamination damage of CF/PEKK is a result of the thermal-mechanical interaction. For conventional drilling, the high machining temperature (at low feed rate <0.1 mm/rev) has a stronger influence on the delamination damage and the delamination starts to show stronger dependence on the thrust force at high feed rate >0.1 mm/rev. In contrast, helical milling generates a much higher machining temperature which plays a more predominant role in the associated delamination damage. Microstructural analysis shows that all the hole surfaces feature matrix smearing, as a result of combined in-plane shear stress and high machining temperature. Conventional drilling leads to more severe hole wall microstructural damage (matrix loss and surface cavity) as compared to helical milling. Finally, thermal analysis reveals that the hole making process has led to significantly increased crystallinity in the PEKK matrix as a result of the strain-induced crystallization under the combined effect of shear stress and high temperature. [Display omitted] • Hole making performance of CF/PEKK is investigated for the first time. • A comparative study on conventional drilling and helical milling is reported. • The role of thermo-mechanical interaction is elucidated for CF/PEKK hole making. • Chip morphology and the associated material removal mechanism are revealed. • Shear-induced crystallization caused by hole making is reported for the first time. [ABSTRACT FROM AUTHOR]