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Delayed tree mortality and Chinese tallow (Triadica sebifera) population explosion in a Louisiana bottomland hardwood forest following Hurricane Katrina
Assessing long-term effects of hurricane damage in bottomland hardwood forests is important to detect any permanent, long lasting changes to the forest. Two 75 × 75 m plots were established in a Louisiana bottomland hardwood forest in 2004 and all adult trees were measured. The plots were resurveyed in 2006 after Hurricane Katrina passed over the plots in 2005, and in 2011, to gain an understanding of mortality over time. Species composition, mortality and biomass change were assessed over the study period from 2004 to 2011. Sweetgum, water oak, and laurel oak were the most important overstory species in 2004, and American holly and American hornbeam were the most important understory species. In the more damaged plot, there was a shift in dominant species as 63 new Chinese tallow individuals recruited into the adult class (>10 cm) between 2004 and 2011. Chinese tallow is an invasive tree species that often out-competes native species in bottomland hardwood forests. Annual mortality in the bottomland hardwood forest plots between 2004 and 2011 was 6% per year, 11% per year from 2004 to 2006 (representing direct hurricane mortality), and 5% between 2006 and 2011 (delayed tree mortality). Approximately 53% of the total biomass (188,000 kg) was lost between 2004 and 2011. A plot in a cypress tupelo forest was added in 2006 and very little damage or mortality was observed. This study revealed that delayed mortality to hurricane-damaged trees is a significant factor in the long-term dynamics of bottomland hardwood forests and represents an amplification of the effects of the hurricane over time. The fact that direct and delayed mortality is different by species indicates that the measurement only of direct mortality can lead to false conclusions about which species are resistant to hurricanes. Hurricane damage opened up new habitat for invasion by Chinese tallow which grew prolifically in highly damaged, low elevation, wet areas, indicating that large disturbances are an important factor in accelerating the population expansion of this invasive species. The high mortality and low recruitment of some species into the sapling and adult layers and the corresponding expansion of Chinese tallow indicates that species composition will differ from pre-hurricane composition for some time in the future.
Experimental study on explosion characteristics of DME-blended LPG mixtures in a closed vessel
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An extension of high-order shock-fitted detonation propagation in explosives
An update to the numerical shock-fitting scheme from [1] is proposed. The updated scheme locally lowers the order of the scheme in the region of secondary non-fitted waves that interact with the fitted front. In addition, it utilizes a non-uniform mapping from the physical space to the computational space along the streamline direction to offer computational savings over the use of an uniform spacing. The utility of the scheme is first demonstrated on planar ideal gas detonating flows. It is then applied to detonation propagation in a two-dimensional axisymmetric geometry while utilizing an Arrhenius Wescott-Stewart-Davis model for PBX 9502.
Measurements of Argon-39 at the U20az underground nuclear explosion site
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The characteristic release of noble gases from an underground nuclear explosion
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Cavity-melt partitioning of refractory radionuclides and implications for detecting underground nuclear explosions
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Nuclear explosion monitoring network design considerations
Design of an efficient monitoring network requires information on the type and size of releases to be detected, the accuracy and reliability of the measuring equipment, and the desired network performance. This work provides a scientific basis for optimizing or minimizing networks of 133 Xe samplers to achieve a desired performance level for different levels of release. The approach of this work varies the density of sampling locations to find optimal location subsets, and to explore the properties of variations of those subsets – how crucial is a specific subset; are substitutions problematic? The choice of possible station locations is arbitrary but constrained to some extent by the location of islands, land masses, difficult topography (mountains, etc.) and the places where infrastructure exists to run and support a sampler. Performance is evaluated using hypothetical releases and atmospheric transport models that cover an entire year.
Explosive welding of aluminium to stainless steel using carbon steel and niobium interlayers
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Eruption dynamics and explosive-effusive transitions during the 1400 cal BP eruption of Opala volcano, Kamchatka, Russia
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Laboratory biological safety cabinet (BSC) explosion
Scientists at universities across Iraq are actively working to report actual incidents and accidents occurring in their laboratories in order to raise awareness and encourage openness, leading to widespread adoption of robust Chemical Safety and Security (CSS) practices. This manuscript is the first in a series of five case studies describing laboratory incidents and accidents in Iraqi university laboratories in order to share lessons learned and minimize the possibility of similar incidents in the future. In this study, we describe a serious event that resulted in a postgraduate student sustaining serious injuries when the biological safety cabinet (BSC) she was using exploded. Of particular note, the paper highlights how a combination of failures and deficiencies at many levels within an organization and its technical community (rather than a single piece of faulty equipment or the careless behavior of one person) can lead to a dangerous, potentially life-threatening incident. By openly sharing what happened along with the lessons learned from the accident, we hope to minimize the possibility of another researcher being injured in a similar incident in the future.