Permafrost and wildlife influences on stream nutrient dynamics and metabolism in boreal forest watersheds of Interior Alaska

Thesis (M.S.) University of Alaska Fairbanks, 2006In the boreal forest of interior Alaska, both permafrost and wildfire impact stream solute concentrations, but their effect on stream function is unknown. This research focused on the effects of wildfire and permafrost on stream nutrient dynamics and metabolism in the Caribou Poker Creeks Research Watershed (CPCRW) in interior Alaska. Wildfire impact on chemistry was determined through comparison of pre- and post-fire stream chemistry in a control and a burned watershed. We predicted that increased nutrient and decreased dissolved organic carbon (DOC) delivery to streams after fire would stimulate gross primary productivity (GPP) and reduce ecosystem respiration in burned watersheds. Fire resulted in higher stream nitrate, sulfate, and cation concentrations, and lower DOC concentration, at the burned site than at the control site. Streams draining burned watersheds had higher summer GPP (2.4 gO₂ m⁻² day⁻¹) than the unburned sites (1.2 gO₂ m⁻² day⁻¹). Respiration was also higher in burned than unburned watersheds (3.9 and 3.0 gO₂ m⁻² day⁻¹, respectively). Metabolism was not correlated with the increased nutrient concentrations observed after fire. Instead, we suggest GPP was stimulated through increased soluble reactive phosphorus availability after fire, whereas respiration was likely controlled by pre-existing differences in stream physical or chemical characteristics.1. Background -- 2. Permafrost and wildlife influences on stream nutrient dynamics and metabolism in boreal forest watersheds of interior Alaska -- 3. Conclusions

Cluster states in nuclei as representations of a U(n+1) group

We propose a description of cluster states in nuclei in terms of representations of unitary algebras U(n+1), where n is the number of space degrees of freedom. Within this framework, a variety of situations including both vibrational and rotational spectra, soft and rigid configurations, identical and non-identical constituents can be described. As an example, we show how the method can be used to study alpha-clustering configurations in 12C with point group symmetry D(3h).Comment: 5 pages, 2 figures, Phys. Rev. C, in pres

Optimal control technique for Many Body Quantum Systems dynamics

We present an efficient strategy for controlling a vast range of non-integrable quantum many body one-dimensional systems that can be merged with state-of-the-art tensor network simulation methods like the density Matrix Renormalization Group. To demonstrate its potential, we employ it to solve a major issue in current optical-lattice physics with ultra-cold atoms: we show how to reduce by about two orders of magnitudes the time needed to bring a superfluid gas into a Mott insulator state, while suppressing defects by more than one order of magnitude as compared to current experiments [1]. Finally, we show that the optimal pulse is robust against atom number fluctuations.Comment: 5 pages, 4 figures, published versio

Exploring the impact of stakeholder pressure on environmental management strategies at the plant level: What does industry have to do with it?

Stakeholder theory and empirical evidence confirm the positive relationship between stakeholder pressure and the implementation of environmental practices and strategies. However, the specific mechanisms and impact of selected stakeholder groups on environmental management strategies are relatively underexplored. In this paper, this shortcoming is addressed by exploring the impact of selected stakeholder groups on environmental management strategies taking the contingency factor industry into consideration (i.e., dynamic vs. static industries). Basing the arguments primarily on stakeholder theory, it is suggested that stakeholder pressures are perceived differently in plants in dynamic versus static industries. Similarly, it is suggested that the influence of stakeholder pressures on the implementation of environmental strategies is influenced by industry type. To test the proposed research model, primary survey data from 502 plants collected in the United States across multiple industries is used. Thus, this paper contributes to the sustainability operations management literature through exploring the relationship between stakeholder pressure, environmental strategy implementation and contextual factors (i.e., industry type) through hypotheses testing. Results indicate that industry type does indeed affect stakeholder pressure, and the relationship between stakeholder pressure and environmental strategy implementation. Plants situated in dynamic industries experience a significantly higher level of stakeholder pressures as opposed to plants situated in static industries across an array of environmental strategies

High magnetic field thermal-expansion and elastic properties of CeRhIn5_5

We report high magnetic field thermal-expansion and magnetostriction results on CeRhIn$_5$ single crystals. Several transitions, both first and second order, are observed when the field is applied perpendicular to the crystallographic c-axis. The magnetic field dependence of the thermal-expansion coefficient above 15 K, where the magnetic correlations are negligible, can be explained supposing an almost pure $| \pm 5/2>$ ground state doublet, in apparent contradiction with neutron scattering experiments. Although the spin-lattice interaction is relevant in this compound, the effect of the magnetic correlations on the elastic properties is relatively weak, as revealed by resonant ultrasound spectroscopy experiments.Comment: 5 pages, 6 figure

Trajectory generation for road vehicle obstacle avoidance using convex optimization

This paper presents a method for trajectory generation using convex optimization to find a feasible, obstacle-free path for a road vehicle. Consideration of vehicle rotation is shown to be necessary if the trajectory is to avoid obstacles specified in a fixed Earth axis system. The paper establishes that, despite the presence of significant non-linearities, it is possible to articulate the obstacle avoidance problem in a tractable convex form using multiple optimization passes. Finally, it is shown by simulation that an optimal trajectory that accounts for the vehicle’s changing velocity throughout the manoeuvre is superior to a previous analytical method that assumes constant speed