Modelling and reducing gas emissions from naturally ventilated livestock buildings

Livestock buildings are identified to be a major source of ammonia emissions. About 30% of the total ammonia emission within livestock sectors is from naturally ventilated dairy cattle buildings. The main objectives of this study are to predict emissions from naturally ventilated dairy cattle buildings and to establish a systematic approach to curtail the emissions.Gas concentrations were measured inside two dairy cattle buildings in mid-Jutland, Denmark. CO2 balance method was thus applied to estimate ventilation and emission rates. Computational fluid dynamics (CFD) was used to find the optimum gas sampling positions for outlet CO2 concentration. The gas sampling positions should be located adjacent to the openings or even in the openings. The NH3 emission rates varied from 32 to77 g HPU-1 d-1 in building 1 and varied from 18 to30 g HPU-1 d-1 in building 2.Scale model experiment showed that partial pit ventilation was able to remove a large portion of polluted gases under the slatted floor. In the full scale simulations, a pit exhaust with a capacity of 37.3 m3 h-1 HPU-1 may reduce ammonia emission only by 3.16% compared with the case without pit ventilation. When the external wind was decreased to 1.4 m s-1 and the sidewall opening area were reduced to half, such a pit ventilation capacity can reduce ammonia emission by 85.2%. The utilization of pit ventilation system must be integrated with the control of the natural ventilation rates of the building

Efficient Algorithms for Node Disjoint Subgraph Homeomorphism Determination

Recently, great efforts have been dedicated to researches on the management of large scale graph based data such as WWW, social networks, biological networks. In the study of graph based data management, node disjoint subgraph homeomorphism relation between graphs is more suitable than (sub)graph isomorphism in many cases, especially in those cases that node skipping and node mismatching are allowed. However, no efficient node disjoint subgraph homeomorphism determination (ndSHD) algorithms have been available. In this paper, we propose two computationally efficient ndSHD algorithms based on state spaces searching with backtracking, which employ many heuristics to prune the search spaces. Experimental results on synthetic data sets show that the proposed algorithms are efficient, require relative little time in most of the testing cases, can scale to large or dense graphs, and can accommodate to more complex fuzzy matching cases.Comment: 15 pages, 11 figures, submitted to DASFAA 200

Recovery from acidosis is a robust trigger for loss of force in murine hypokalemic periodic paralysis.

Periodic paralysis is an ion channelopathy of skeletal muscle in which recurrent episodes of weakness or paralysis are caused by sustained depolarization of the resting potential and thus reduction of fiber excitability. Episodes are often triggered by environmental stresses, such as changes in extracellular K+, cooling, or exercise. Rest after vigorous exercise is the most common trigger for weakness in periodic paralysis, but the mechanism is unknown. Here, we use knock-in mutant mouse models of hypokalemic periodic paralysis (HypoKPP; NaV1.4-R669H or CaV1.1-R528H) and hyperkalemic periodic paralysis (HyperKPP; NaV1.4-M1592V) to investigate whether the coupling between pH and susceptibility to loss of muscle force is a possible contributor to exercise-induced weakness. In both mouse models, acidosis (pH 6.7 in 25% CO2) is mildly protective, but a return to pH 7.4 (5% CO2) unexpectedly elicits a robust loss of force in HypoKPP but not HyperKPP muscle. Prolonged exposure to low pH (tens of minutes) is required to cause susceptibility to post-acidosis loss of force, and the force decrement can be prevented by maneuvers that impede Cl- entry. Based on these data, we propose a mechanism for post-acidosis loss of force wherein the reduced Cl- conductance in acidosis leads to a slow accumulation of myoplasmic Cl- A rapid recovery of both pH and Cl- conductance, in the context of increased [Cl]in/[Cl]out, favors the anomalously depolarized state of the bistable resting potential in HypoKPP muscle, which reduces fiber excitability. This mechanism is consistent with the delayed onset of exercise-induced weakness that occurs with rest after vigorous activity