Turing Instability in a Boundary-fed System

The formation of localized structures in the chlorine dioxide-idodine-malonic acid (CDIMA) reaction-diffusion system is investigated numerically using a realistic model of this system. We analyze the one-dimensional patterns formed along the gradients imposed by boundary feeds, and study their linear stability to symmetry-breaking perturbations (Turing instability) in the plane transverse to these gradients. We establish that an often-invoked simple local linear analysis which neglects longitudinal diffusion is inappropriate for predicting the linear stability of these patterns. Using a fully nonuniform analysis, we investigate the structure of the patterns formed along the gradients and their stability to transverse Turing pattern formation as a function of the values of two control parameters: the malonic acid feed concentration and the size of the reactor in the dimension along the gradients. The results from this investigation are compared with existing experiments.Comment: 41 pages, 18 figures, to be published in Physical Review

Dynamic carbon and sulfur cycling in the aftermath of the Lomagundi-Jatuli Event: Evidence from the Paleoproterozoic Hutuo Supergroup, North China Craton

The unprecedented positive δ13C excursion in carbonates deposited between 2.2 and 2.0 Ga, known as the Lomagundi-Jatuli Event (LJE), has been documented globally and linked to the rise of atmospheric oxygen. Increasing oxidation inevitably changed the atmosphere-hydrosphere system, but few chemostratigraphic or quantitative constraints for the aftermath of this event exists. Here, we describe a ~200 m-thick carbonate succession in the Huaiyincun Formation, Hutuo Supergroup, ~2.0–1.9 Ga, from the North China Craton. There is a lithological transition from pink-purple dolostones to grey dolostones at ca. 91.6 m above the base of the Huaiyincun Formation. The former are more enriched in hematite and detrital minerals, whereas the latter contain more organic matter but almost no detrital phases. Meanwhile, the frequent occurrence of tempesite structures, along with the abrupt decline of stromatolites in the upper Huaiyincun Formation, suggest a storm-dominated environment. These distinct features within the Huaiyincun Formation reveal increased water depth during a transgression event. Two types of Raman spectra of organic matter were found in the lower and upper Huaiyincun Formation, respectively, which is proposed to be the result of variable oxidation. At 65.6 m, 26 m below the lithological transition (~91.6 m), remarkable decreases in both δ13Ccarb and δ34SCAS are observed. This discordance between C-S isotopic excursions and sedimentological and mineralogical variations argues against a seawater depth gradient effect of the δ13Ccarb and δ34SCAS curves. Instead, the decline of δ13Ccarb rather correlates with the negative δ13Ccarb excursions in ca. 2.0 Ga carbonates from Gabon and Russia, known as the Shunga-Francevillian Event (SFE). The result of the quantitatively constrained paleo-seawater [SO42−]sw suggests a crash of the seawater sulfate reservoir compared with that during the preceding LJE. However, the decreased δ34SCAS and increased CAS concentration towards the top of the study unit represent the recovery of seawater sulfate reservoir. The coordinated decline in δ34SCAS and δ13Ccarb values is likely related to enhanced oxidation of continental pyrite and organic matter in the aftermath of the LJE. The Huaiyincun Formation therefore represents a critical interval that recorded dynamic carbon and sulfur cycles after the LJE

Existence and Stability of Symmetric Periodic Simultaneous Binary Collision Orbits in the Planar Pairwise Symmetric Four-Body Problem

We extend our previous analytic existence of a symmetric periodic simultaneous binary collision orbit in a regularized fully symmetric equal mass four-body problem to the analytic existence of a symmetric periodic simultaneous binary collision orbit in a regularized planar pairwise symmetric equal mass four-body problem. We then use a continuation method to numerically find symmetric periodic simultaneous binary collision orbits in a regularized planar pairwise symmetric 1, m, 1, m four-body problem for $m$ between 0 and 1. Numerical estimates of the the characteristic multipliers show that these periodic orbits are linearly stability when $0.54\leq m\leq 1$, and are linearly unstable when $0<m\leq0.53$.Comment: 6 figure

Evolution of tourism in a flagship protected area of China

Nature-based tourism in protected areas, which is growing worldwide, offers much potential to enhance biodiversity conservation, poverty alleviation, and ultimately sustainable development. Understanding the evolution of protected areas as tourism destinations and the causes and consequences of changing supply and demand elements is an essential step toward sustainably managing tourism in these critical ecosystems. This research applied the Tourism Area Life Cycle (TALC) model to illustrate and analyze the 30-year evolution of tourism in Wolong Nature Reserve. Being inscribed in UNESCO Biosphere Reserve and World Heritage programmes, Wolong is a flagship protected area in China. We showed that the Reserve experienced exploration, involvement, and development stages of the TALC before tourism growth was completely halted by the Wenchuan Earthquake in 2008. We systematically investigated the changes related to the evolution of tourism and identified various internal and external driving forces. We examined the dynamics of politics, economy, and tourism growth that might propel the Reserve through the life cycle and identified significant tourism governance structural changes through the stages. The results have implications for sustainable tourism development in China's protected areas and also contribute to a broader and general understanding of the complex relationships between protected areas, sustainable tourism, and community development

N=1 gauge superpotentials from supergravity

We review the supergravity derivation of some non-perturbatively generated effective superpotentials for N=1 gauge theories. Specifically, we derive the Veneziano-Yankielowicz superpotential for pure N=1 Super Yang-Mills theory from the warped deformed conifold solution, and the Affleck-Dine-Seiberg superpotential for N=1 SQCD from a solution describing fractional D3-branes on a C^3 / Z_2 x Z_2 orbifold.Comment: LaTeX, iopart class, 8 pages, 3 figures. Contribution to the proceedings of the workshop of the RTN Network "The quantum structure of space-time and the geometric nature of fundamental interactions", Copenhagen, September 2003; v2: published version with minor clarification

ML-NA: A Machine Learning Based Node Performance Analyzer Utilizing Straggler Statistics

Current Cloud clusters often consist of heterogeneous machine nodes, which can trigger performance challenges such as the task straggler problem, whereby a small subset of parallel tasks running abnormally slower than the other sibling ones. The straggler problem leads to extended job response and deteriorates system throughput. Poor performance nodes are more likely to engender stragglers, and can undermine straggler mitigation effectiveness. For example, as the dominant mechanism for straggler alleviation, speculative execution functions by creating redundant task replicas on other machine nodes as soon as a straggler is detected. When speculative copies are assigned onto the poor performance nodes, it is hard for them to catch up with the stragglers compared to replicas run on fast nodes. And due to the fact that the performance heterogeneity is caused not only by static attribute variations such as physical capacity, but also dynamic characteristic uctuations such as contention level, analyzing node performance is important yet challenging. In this paper we develop ML-NA, a Machine Learning based Node performance Analyzer. By leveraging historical parallel tasks execution log data, ML-NA classies cluster nodes into different categories and predicts their performance in the near future as a scheduling guide to improve speculation effectiveness and minimize task straggler generation. We consider MapReduce as a representative framework to perform our analysis, and use the published OpenCloud trace as a case study to train and to evaluate our model. Results show that ML-NA can predict node performance categories with an average accuracy up to 92.86%

White Lines and 3d-Occupancy for the 3d Transition-Metal Oxides

Electron energy-loss spectrometry was employed to measure the white lines at the L23 absorption edges of the 3d transition-metal oxides and lithium transition-metal oxides. The white-line ratio (L3/L2) was found to increase between d^0 and d^5 and decrease between d^5 and d^10, consistent with previous results for the transition metals and their oxides. The intensities of the white lines, normalized to the post-edge background, are linear for the 3d transition-metal oxides and lithium transition-metal oxides. An empirical correlation between normalized white-line intensity and 3d occupancy is established. It provides a method for measuring changes in the 3d-state occupancy. As an example, this empirical relationship is used to measure changes in the transition-metal valences of Li_{1-x}Ni_{0.8}Co_{0.2}O_2 in the range of 0 < x < 0.64. In these experiments the 3d occupancy of the nickel ion decreased upon lithium deintercalation, while the cobalt valence remained constant.Comment: 6 pages, 7 figure

Leakage Inductance Calculation for Planar Transformers with a Magnetic Shunt

The magnetic shunt is generally inserted in a planar transformer to increase the leakage inductance, which can be utilized as the series inductor in resonant circuits such as the LLC resonant converter. This paper presents a calculation methodology for the leakage inductance of the transformer with a magnetic shunt by means of the stored magnetic energy in the primary and secondary sides of the transformer using the magnetomotive force (MMF) variation method, as well as the stored energy in the shunt based on the reluctance model. The detailed calculation method is described. Both the finite-element analysis simulation and the experimental results have proven the validity of the proposed calculation method for leakage inductance

Apatite-glaucony association in the Ediacaran Doushantuo Formation, South China and implications for marine redox conditions

Major phosphogenic events took place in the late Paleoproterozoic and the Ediacaran, both of which followed an episode of atmospheric oxygenation. These apparent coincidences have led to suggestions that the Precambrian phosphorus cycle was partly regulated by oceanic redox conditions, although direct evidence is lacking. In this paper, we report the discovery of glaucony in drill cores from the phosphorite-rich Ediacaran Doushantuo Formation at Weng'an, South China, which provides new insights into redox conditions and geochemical cycles during the deposition and early diagenesis of the lower Doushantuo Formation. The presence of flaser and lenticular bedding in the sandstones suggests deposition in a tidally-influenced shallow water environment. Apatite is present as millimeter-scale flasers in sandstones, but more commonly as intraclastic grains. Glaucony typically occurs as interstitial aggregates cementing and replacing detrital minerals and phosphatic grains, with an upsection decrease in abundance. The Doushantuo glauconies have consistently high K2O (7.5–9.6 wt%). In particular, phosphorite-hosted glaucony has generally higher total iron (TFe2O3) than sandstone-hosted glaucony, consistent with Al3+–Fe3+ substitution in the octahedral site, as supported by Raman peaks slightly shifted towards lower wavenumbers for higher Fe content. A decrease in detrital input probably resulted in limited Al availability during early diagenesis, which in turn led to the waning of glaucony upsection. The phosphate grains do not show any negative Ce anomalies, consistent with precipitation of authigenic apatite in suboxic environments with insignificant preferential remobilisation of Ce during deposition and early diagenesis. REE + Y features show variable diagenetic REE enrichment in phosphorites, but identical concave-down patterns. The wide occurrence of glaucony cement further documents the presence of a generally suboxic early diagenetic environment on the seafloor, which was in active exchange with bottom seawater. Slight fluctuations of redox states in the porewater and bottom water would have promoted the cycling of Fe, enrichment of phosphate and REE, and extensive glaucony authigenesis. Therefore, the glaucony-bearing phosphorites in the Doushantuo Formation are a direct result of Fe-redox driven diagenesis. Apatite-glaucony association likely forms in suboxic environments and is considered as a useful mineralogical proxy for paleoredox conditions on the Precambrian ocean floors