THE USE OF TELESCOPING SPATIAL SCALES TO CAPTURE INSHORE TO SLOPE DYNAMICS IN MARINE ECOSYSTEM MODELING

Abstract Ecosystem processes function at many scales, and capturing these processes is a challenge for ecosystem models. Nevertheless, it is a necessary step for considering many management issues pertaining to shelf and coastal systems. In this paper, we explore one method of modeling large areas with a focus at a range of scales. We develop an ecosystem model that can be used for strategic management decision support by modeling the waters off southeastern Australia using a polygon telescoping approach, which incorporates fine‐scale detail at the coastal zone, increasing in scale to a very coarse scale in the offshore areas. This telescoping technique is a useful tool for incorporating a wide range of habitats at different scales into a single model.     

MODELING THE EVOLUTION OF NATURAL ORGANIC MATTER IN THE ENVIRONMENT WITH AN AGENT‐BASED STOCHASTIC APPROACH

ABSTRACT. Natural organic matter (NOM) is ubiquitous in terrestrial and aquatic ecosystems, and it plays a crucial role in the evolution of soils, the transport of pollutants, and the global carbon cycle. NOM is a complex mixture of molecules and is thus heterogeneous in structure and composition. As NOM passes through an ecosystem, it is acted upon by a variety of processes, such as microbial degradation, adsorption to mineral surfaces, and photochemical reactions that can change its properties and reactivity. The evolution of NOM in space and time thus is an important research area in biology, geochemistry, ecology, soil science, and water resources. Due to its complex structural and chemical heterogeneity, new simulation approaches are needed to help better understand the evolution of NOM properties and reactivity as it passes through an ecosystem. We present a new stochastic model, which explicitly treats NOM as a large number of discrete heterogeneous molecules (“agents”) with different probabilities of transformations or reactions. The NOM, the microorganisms, and their environment are taken together as a complex system, with the NOM interactions within this system simulated using an agent‐based stochastic modeling approach. The initial users of the NOM simulations include a geographically separated group of NSF‐sponsored scientists and engineers from different research disciplines, including both academics and U.S. government scientists. A Web‐based interface serves as a prototype NOM “collaboratory” designed to promote collaboration among the various researchers and to allow them to share their data, model results, and suggested approaches or improvements across distributed sites. This Web‐based interface has been designed to allow researchers to access the simulation model remotely from a standard Web browser. The Web‐based interface thus allows researchers at distant locations to provide parameters for their simulations, to start and stop simulations, and to plot and view results, all remotely.     

Point source excitation in direct and inverse scattering: The soft and the hard small sphere

A spherical wave emanating from a point source is scatteredby either a soft or a hard body. The incident spherical wavehas a wavelength which is much larger than the characteristicdimension of the scatterer and it is modified in such a wayas to recover the plane wave incidence when the source pointrecedes to infinity. Using low frequency expansions the scatteringproblem is transformed to a sequence of exterior potential problemsin the presence of a monopole singularity located at the sourceof the incident wave field. Complete expansions for the scatteringamplitude are provided. The method is applied to the cases ofa soft and a hard sphere and the first three approximationsfor the near, as well as the far, field are evaluated. It isobserved that every one, after the first, low frequency approximationof the far field, involves one spherical multipole more thanthe corresponding approximation for the case of an incidentplane wave. As the point singularity tends to infinity, therelative results recover all the known expressions for planeincidence. It is shown that for point excitation the Rayleighapproximation of the scattering amplitude for a hard sphereis of the second order, in contrast to the case of plane excitationwhich is of the third order. Simple algorithms that specifythe radius and the position of a soft and a hard sphere areproposed, which are based on the additional dependence of thescattering amplitude represented by the distance from the pointsource to the centre of the scatterer. The inversion algorithmis shown to be stable whenever the source point is not too faraway from the target sphere. A simple way to decide whetherthe sphere is a soft or a hard body is also provided.     

Using Natural and Artificial Light Sources to Illustrate Quantum Mechanical Concepts

We present here a discovery-based laboratory project that introduces elementary quantum mechanical concepts using the spectral distributions of natural and artificial light sources. The measured emission spectra of sunlight and interior/exterior lighting are explained using the electromagnetic spectrum, the phenomenon of blackbody radiation, and the quantization of light. This 4–5 week experiment is appropriate for the general chemistry laboratory or can be expanded for use in upper-division chemistry laboratories, and it uses modern spectroradiometric equipment that is readily available and increasingly used in the physical and biological sciences.     

Multiple quantum nuclear magnetic resonance spectra of partially oriented styrene in a nematic phase

Proton multiple-quantum nuclear magnetic resonance (MQNMR) spectra of styrene partially oriented in a nematic liquid crystal were acquired using the magnetic field gradient method. Six-, seven- and eight-quantum spectra were iteratively solved to yield all intramolecular dipolar couplings (D_ij) which were used to determine the molecular shape of styrene. The dipolar couplings were fitted to a model averaging between four equivalent non-planar conformations of the molecule. Ignoring vibrational corrections, the analysis was consistent with a non-planar molecular geometry with a dihedral angle of approximately 16 degrees between the olefinic fragment and the aromatic ring.     

A detailed study of CHB bridge bonding in the simplest carborane: H2C(H2)BH2 +

The structure, energetics, and bonding of the simplest carborane, H₂C(H₂)BH₂ ⁺, is determined by high level ab initio calculations. The molecule is bound by 35.5 kcalmol^?1 with respect to the lowest energy dissociation products, CH₄ + BH₂ ⁺ which are produced without a dissociation barrier (i.e. no reverse activation energy) along the minimum energy pathway. A detailed analysis of the occupied valence orbitals shows that the bonding arises from three-centre-two-electron bonding through an unusual carbon-hydrogen-boron (CHB) bridge bond explaining the strong binding energy and the absence of a dissociation barrier. The possibility that CHB bridge bonds may play a role in CH sigma bond activation is discussed. Harmonic vibrational frequencies, infrared absorption intensities, and frequency shifts occurring for ¹⁰B, ¹³C, and D isotopic substitution are reported.     

The Determination of Derivative Parameters for a Monotonic Rational Quadratic Interpolant

Explicit formulae are developed for determining the derivativeparameters of a monotonic interpolation method of Gregory &Delbourgo (1982).     

SKIN PHOTOSENSITIVITY AND PHOTODESTRUCTION OF SEVERAL POTENTIAL PHOTODYNAMIC SENSITIZERS

The major side effect associated with porphyrins (Photofrin II) in clinical photodynamic therapy is skin photosensitivity. In order to avoid this deleterious reaction, patients must remain out of the sunlight for approximately 1 month. A possible procedure to reduce the amount of skin photosensitivity is to photodegrade (photobleach) the compound in the skin. In this study, we report a series of experiments describing the photodegradation rates of two photosensitizers currently receiving attention due to their potential for use in PDT (mono L-aspartyl chlorin e6 and chloroaluminum sulfonated phthalocyanine). These compounds are compared to Photofrin II (PfII). Experiments consisted of determining photodegradation rates and efficiencies of the sensitizers in (i) phosphate buffered saline (PBS), (ii) PBS with fetal calf serum (to enhance absorption and simulate cellular binding or deaggregation), (iii) Chinese Hamster Ovary cells, and (iv) Balb/c mice. We performed two standardized skin sensitivity assays using the Hartely albino guinea pig irradiated with a UV blue point lamp and Balb/c mice irradiated with the therapeutic wavelength of each sensitizer. In addition, we performed a cell clonogenicity assay comparing photodegraded and fresh PfII on CHO cells. The photodegraded PfII exhibited significant phototoxicity, although the fluorescence was bleached by more than 70%. The results show that PfII causes major skin photosensitization and that the other compounds produce no substantial skin sensitivity. Our studies suggest that photodegradation of PfII with 630 nm light has little influence on the phototoxicity of the compound. In addition, skin sensitivity was not alleviated with prior photobleaching with 405 nm light.     

A multiple-criteria decision model with ranked inputs

Address for correspondence: G. Gregory, Laburnum Cottage, 10 Main Street, Milnthorpe, Cumbria, LA7 7PN. A model for multiple-criteria decision analysis is proposedwhere the input data consist of rankings of criteria and ofalternatives within each criterion. The analysis uses the approachof data-envelopment analysis, summing over the scores obtainedby this method. Examples of further assessment of the best alternativesare presented.     

FOREST ROTATIONS AND STAND INTERDEPENDENCY: OWNERSHIP STRUCTURE AND TIMING OF DECISIONS

ABSTRACT. This paper extends the Hartman model to study the optimal rotation age of two interdependent stands at the steady state, when the rotation ages of the two stands are equal and the stream of amenities produced from the two stands may be complements or substitutes, both in space and over time. In the presence of stand interdependence both the ownership structure and the sequence of decision making matters. Rotation age choices are examined and compared under a variety of equilibria, including Nash, Stackelberg and sole owner cases. We show that the sole owner's rotation age is longer than the rotation age under both Nash and Stackelberg assumptions if the stands are spatial complements but shorter if they are spatial substitutes. The precise relationship between the Nash and Stackelberg rotation ages and the qualitative properties of rotation ages in terms of timber prices, regeneration costs and interest rates also depend on how spatial substitutability and complementarity between stands evolves through time.