Using artificial neural networks to predict future dryland responses to human and climate disturbances

Land degradation and sediment remobilisation in dryland environments is considered to be a significant global environmental problem. Given the potential for currently stabilised dune systems to reactivate under climate change and increased anthropogenic pressures, identifying the role of external disturbances in driving geomorphic response is vitally important. We developed a novel approach, using artificial neural networks (ANNs) applied to time series of historical reactivation-deposition events from the Nebraska Sandhills, to determine the relationship between historic periods of sand deposition in semi-arid grasslands and external climatic conditions, land use pressures and wildfire occurrence. We show that both vegetation growth and sediment re-deposition episodes can be accurately estimated. Sensitivity testing of individual factors shows that localised forcings (overgrazing and wildfire) have a statistically significant impact when the climate is held at present-day conditions. However, the dominant effect is climate-induced drought. Our approach has great potential for estimating future landscape sensitivity to climate and land use scenarios across a wide range of potentially fragile dryland environments

Hydrology of Southwestern Connecticut

Guidebook for field trips in Connecticut: New England Intercollegiate Geological Conference 60th annual meeting, Yale University, New Haven, Connecticut, October 25-27, 1968: Trip B-

Resource Recovery from Wastewater Treatment Sludge Containing Gypsum

The disposal of wastewater treatment sludge generated at the Radford Army Ammunition Plant (RAAP) is a serious problem. The sludge is produced by neutralizing spent acid contained in the wastewater with lime, and consists principally of very finely divided wet gypsum (calcium sulfate dihydrate). Although the sludge is presently being disposed of in a landfill, the sludge is difficult to handle and convert into a load-bearing material. Therefore an alternative method of disposal is being developed and evaluated. The alternative method involves drying and granulating the sludge, followed by high temperature calcination in a fluidized bed reactor to recover usable sulfur dioxide and lime. If the method is adopted, these products would be used within the plant with considerable cost savings. The sulfur dioxide would be added to the feed stream of an oleum manufacturing facility and the lime would be reused in wastewater treatment

Excited Baryon Decay Widths in Large N_c QCD

We study excited baryon decay widths in large N_c QCD. It was suggested previously that some spin-flavor mixed-symmetric baryon states have strong couplings of O(N_c^{-1/2}) to nucleons [implying narrow widths of O(1/N_c)], as opposed to the generic expectation based on Witten's counting rules of an O(N_c^0) coupling. The calculation obtaining these narrow widths was performed in the context of a simple quark-shell model. This paper addresses the question of whether the existence of such narrow states is a general property of large N_c QCD. We show that a general large N_c QCD analysis does not predict such narrow states; rather they are a consequence of the extreme simplicity of the quark model.Comment: 9 page

Calcite–magnesite solid solutions : using genetic algorithms to understand non-ideality

We show how a genetic algorithm (GA) generates efficiently the energy landscape of the equimolar calcite–magnesite (CaCO3—MgCO3) solid solution. Starting from a random configuration of cations and a supercell containing 480 atoms, the lowest energy form of ordered dolomite was found in all runs, in 94% of which it was located with less than 20,000 fitness evaluations. Practical implementation and operation of the GA are discussed in detail. The method can also generate both low-lying and high-lying excited states. Detailed analysis of the energy-minimised structures of the different configurations reveals that low energies are associated with reduction of strain associated with rotation of the carbonate groups, a mechanism possible only when a carbonate layer lies between a layer of just Ca and a layer of just Mg. Such strain relief is not possible in the equimolar MgO–CaO solid solution despite the similarity of the crystal structures of these binary oxides to calcite–magnesite, and therefore, the enthalpy of mixing is very high. Implications for thermodynamic configurational averaging over the minima in the energy landscape are briefly considered. Overall, the genetic algorithm is shown to be a powerful tool in probing non-ideality in solid solutions and revealing the ordering patterns that give rise to such behaviour

Canonical Interpretation of the D_{sJ}(2860) and D_{sJ}(2690)

The spectrum and decay properties of radially excited $D_s$ states are examined in a new model. Good agreement is obtained with the properties of two recently announced $D_s$ mesons identified as $D_{s0}(2860) = c\bar{s}(2P)$ and $D^*_{s}(2690) = c\bar{s}$ as a possible mixture of $(2S;{}^3S_1)$ and $(1D;{}^3D_1)$. Searching for these mesons in B decays is advocated due to large predicted branching ratios.Comment: 6 pages, 2 ps figures, revte

Excited Baryons in Large N_c QCD Revisited: The Resonance Picture Versus Single-Quark Excitations

We analyze excited baryon properties via a 1/N_c expansion from two perspectives: as resonances in meson-nucleon scattering, and as single-quark excitations in the context of a simple quark model. For both types of analysis one can derive novel patterns of degeneracy that emerge as N_c --> \infty, and that are shown to be compatible with one another. This helps justify the single-quark excitation picture and may give some insight into its successes. We also find that in the large N_c limit one of the S_{11} baryons does not couple to the pi-N channel but couples to the eta-N channel. This is empirically observed in the N(1535), which couples very weakly to the pi-N channel and quite strongly to the eta-N channel. The comparatively strong coupling of the N(1650) to the pi-N channel and weak coupling to eta-N channel is also predicted. In the context of the simple quark model picture we reproduce expressions for mixing angles that are accurate up to O(1/N_c) corrections and are in good agreement with mixing angles extracted phenomenologically.Comment: 13 pages, ReVTeX

Actors that Unify Threads and Events

There is an impedance mismatch between message-passing concurrency and virtual machines, such as the JVM. VMs usually map their threads to heavyweight OS processes. Without a lightweight process abstraction, users are often forced to write parts of concurrent applications in an event-driven style which obscures control flow, and increases the burden on the programmer. In this paper we show how thread-based and event-based programming can be unified under a single actor abstraction. Using advanced abstraction mechanisms of the Scala programming language, we implemented our approach on unmodified JVMs. Our programming model integrates well with the threading model of the underlying VM

2D and 3D Polar Plume Analysis from the Three Vantage Positions of STEREO/EUVI A, B, and SOHO/EIT

Polar plumes are seen as elongated objects starting at the solar polar regions. Here, we analyze these objects from a sequence of images taken simultaneously by the three spacecraft telescopes STEREO/EUVI A and B, and SOHO/EIT. We establish a method capable of automatically identifying plumes in solar EUV images close to the limb at 1.01 - 1.39 R in order to study their temporal evolution. This plume-identification method is based on a multiscale Hough-wavelet analysis. Then two methods to determined their 3D localization and structure are discussed: First, tomography using the filtered back-projection and including the differential rotation of the Sun and, secondly, conventional stereoscopic triangulation. We show that tomography and stereoscopy are complementary to study polar plumes. We also show that this systematic 2D identification and the proposed methods of 3D reconstruction are well suited, on one hand, to identify plumes individually and on the other hand, to analyze the distribution of plumes and inter-plume regions. Finally, the results are discussed focusing on the plume position with their cross-section area.Comment: 22 pages, 10 figures, Solar Physics articl