Ergodicity for the GI/G/1GI/G/1-type Markov Chain

Ergodicity is a fundamental issue for a stochastic process. In this paper, we refine results on ergodicity for a general type of Markov chain to a specific type or the $GI/G/1$-type Markov chain, which has many interesting and important applications in various areas. It is of interest to obtain conditions in terms of system parameters or the given information about the process, under which the chain has various ergodic properties. Specifically, we provide necessary and sufficient conditions for geometric, strong and polynomial ergodicity, respectively.Comment: 16 page

The linkages with fires, vegetation composition and human activity in response to climate changes in the Chinese Loess Plateau during the Holocene

Holocene paleo-records of the Chinese Loess Plateau loess-soil profiles were used to reconstruct wildfire patterns and landscape evolution. We examine black carbon and charcoal influx, combined with the Magnetic susceptibility, delta C-13 values of soil organic matter, pollen counts and other paleo-environmental proxies to discuss interactions with biomass-climate during the Holocene. The history of fires from the charcoal and black carbon (BC, char and soot) influx at the two sites demonstrates a transition from climate-controlled low amplitude variations with peaks during the Early and Middle Holocene (11-3.1kyearsB.P.) to higher amplitude variability in fire occurrence decoupled from climate and tied to human activities during the Late Holocene (3.1-0kyearsB.P.). The difference in fire patterns was attributed to regional effective moisture and human land use over the entre Loess Plateau; meanwhile, fire activities observed during the Holocene are consistent with variations in vegetation composition inferred from delta C-13 values in soil organic matter, pollen counts, and paleoclimate proxies. Regional wildfires rarely occurred on the desert steppe dominated by a weedy C-3 taxon (Artemisia, Compositae, and Chenopodiaceae dominated)during the late glacial period. A limited biomass would not meet fire propagation in the extreme colder and drier environment of the Loess Plateau during those periods, though. As the climate became ameliorated during the early Holocene, there was an increasing biomass and a sufficient contribution do to high fuel accumulation from C-4 taxon (Gramineae). As the middle Holocene progressed toward warmer and wetter conditions, fire events were less frequent on the steppe and forest-steppe (e.g. expansion of trees C-3,C- Quercus, Corylus) of the Loess Plateau. Subsequently, the number of local and regional fire events have largely increased with the colder and drier climate conditions (e.g. expansion of C-3 weedy), which have been decoupling with intensive anthropogenic burning for farming since the past 3kyr. These data suggests that the regional fire patterns vary strongly along environmental gradients in the effective moisture and regional fuel availability as well as the spatial and temporal distributions of Neolithic burning practices over the Loess Plateau in response to the weakening East Asian monsoon during the Holocene

Cardiovascular stability during arteriovenous extracorporeal therapy: a randomized controlled study in lambs with acute lung injury

INTRODUCTION: Clinical application of arteriovenous (AV) extracorporeal membrane oxygenation (ECMO) requires assessment of cardiovascular ability to respond adequately to the presence of an AV shunt in the face of acute lung injury (ALI). This ability may be age dependent and vary with the experimental model. We studied cardiovascular stability in a lamb model of severe ALI, comparing conventional mechanical ventilation (CMV) with AV-ECMO therapy. METHODS: Seventeen lambs were anesthetized, tracheotomized, paralyzed, and ventilated to maintain normocapnia. Femoral and jugular veins, and femoral and carotid arteries were instrumented for the AV-ECMO circuit, systemic and pulmonary artery blood pressure monitoring, gas exchange, and cardiac output determination (thermodilution technique). A severe ALI (arterial oxygen tension/inspired fractional oxygen <200) was induced by lung lavage (repeated three times, each with 5 ml/kg saline) followed by tracheal instillation of 2.5 ml/kg of 0.1 N HCl. Lambs were consecutively assigned to CMV treatment (n = 8) or CMV plus AV-ECMO therapy using up to 15% of the cardiac output for the AV shunt flow during a 6-hour study period (n = 9). The outcome measures were the degree of inotropic and ventilator support needed to maintain hemodynamic stability and normocapnia, respectively. RESULTS: Five of the nine lambs subjected to AV-ECMO therapy (56%) died before completion of the 6-hour study period, as compared with two out of eight lambs (25%) in the CMV group (P > 0.05; Fisher's exact test). Surviving and nonsurviving lambs in the AV-ECMO group, unlike the CMV group, required continuous volume expansion and inotropic support (P < 0.001; Fisher's exact test). Lambs in the AV-ECMO group were able to maintain normocapnia with a maximum of 30% reduction in the minute ventilation, as compared with the CMV group (P < 0.05). CONCLUSION: AV-ECMO therapy in lambs subjected to severe ALI requires continuous hemodynamic support to maintain cardiovascular stability and normocapnia, as compared with lambs receiving CMV support

Bioremediation of polycyclic aromatic hydrocarbon-contaminated soil by a bacterial consortium and associated microbial community changes

Bioremediation of a PAH-contaminated soil was carried out with a bacterial consortium enriched from the soil. The soil contained 9362.1 mu g kg(-1) of USEPA priority PAHs, 90.6% of which were 4- and 5-ring PAHs. After incubation for 56 days, 20.2% and 35.8% of total PAHs were removed from the soil with the addition of 10% and 20% of a bacterial consortium suspension. The soil microbial population increased in the early days but decreased by the end of the experiment. Denaturing gradient gel electrophoresis (DGGE) analysis of polymerase chain reaction (PCR)-amplified bacterial 165 rRNA gene fragments revealed that DGGE profiles of the soil with the addition of the consortium were clustered together and distinct from those of control soil. Sphingobacteria and Proteobacteria were found to be the dominant bacterial groups in the soil according to the sequence analysis of DGGE bands. The results indicate that incubation with a bacterial consortium may be a promising method for bioremediation of PAH-contaminated soils. (C) 2012 Elsevier Ltd. All rights reserved.Bioremediation of a PAH-contaminated soil was carried out with a bacterial consortium enriched from the soil. The soil contained 9362.1 mu g kg(-1) of USEPA priority PAHs, 90.6% of which were 4- and 5-ring PAHs. After incubation for 56 days, 20.2% and 35.8% of total PAHs were removed from the soil with the addition of 10% and 20% of a bacterial consortium suspension. The soil microbial population increased in the early days but decreased by the end of the experiment. Denaturing gradient gel electrophoresis (DGGE) analysis of polymerase chain reaction (PCR)-amplified bacterial 165 rRNA gene fragments revealed that DGGE profiles of the soil with the addition of the consortium were clustered together and distinct from those of control soil. Sphingobacteria and Proteobacteria were found to be the dominant bacterial groups in the soil according to the sequence analysis of DGGE bands. The results indicate that incubation with a bacterial consortium may be a promising method for bioremediation of PAH-contaminated soils. (C) 2012 Elsevier Ltd. All rights reserved