A NOVEL METHOD OF FITTING SPATIO‐TEMPORAL MODELS TO DATA,WITH APPLICATIONS TO THE DYNAMICS OF MOUNTAIN PINE BEETLES

Abstract We develop a modular landscape model for the mountain pine beetle (Dendroctonus ponderosae Hopkins) infestation of a stage‐structured forest of lodgepole pine (Pinus contorta Douglas). Beetle attack dynamics are modeled using response functions and beetle movement using dispersal kernels. This modeling technique yields four model candidates. These models allow discrimination between four broad possibilities at the landscape scale: whether or not beetles are subject to an Allee effect at the landscape scale and whether or not host selection is random or directed. We fit the models with aerial damage survey data to the Sawtooth National Recreation Area using estimating functions, which allows for more rapid and complete parameter determination. We then introduce a novel model selection procedure based on facial recognition technology to compliment traditional nonspatial selection metrics. Together with these we are able to select a best model and draw inferences regarding the behavior of the beetle in outbreak conditions.     

XERODERMA PIGMENTOSUM FIBROBLASTS INCLUDING CELLS FROM XP VARIANTS ARE ABNORMALLY SENSITIVE TO THE MUTAGENIC AND CYTOTOXIC ACTION OF BROAD SPECTRUM SIMULATED SUNLIGHT

Abstract— The cytotoxic and mutagenic effects of broad spectrum simulated sunlight, as delivered by a Westinghouse Sun Lamp FS 20 filtered to eliminate wavelengths below 290 nm, were determined in diploid human skin fibroblasts which differ in their ability to repair pyrimidine dimers, and compared with results obtained with UV 254 nm radiation. The cell strains tested included normal fibroblasts; excision repair-deficient xeroderma pigmentosum (XP) cells from patients XP12BE (complementation group A). XP7BE (group D). and XP2BI (group G): and an XP variant patient (XP4BE) whose cells excise pyrimidinc dimers at a normal rate, but exhibit abnormal replication of DNA containing unexcised lesions. Cytotoxicity was assayed from loss of colony-forming ability. The group A cells were most sensitive to the killing effect of the Sun Lamp; the group D and G cells were slightly less sensitive; the XP variant cells showed intermediate sensitivity; and normal cells were most resistant. When the Sun Lamp survival curves for the group A, group D, the XP variant and normal cells were compared with their respective UV 254 nm survival curves, the relationships between the strains were virtually identical (i. e. the curves were related by a constant fluence modification factor). suggesting a common lesion for cell killing. The marker for mutagenesis was resistance to 6-thioguanine. The group A XP cells proved most sensitive to mutations induced by the simulated sunlight: the variant cells were intermediate; and the normal cells were the most resistant. Again, when the curves for mutations induced in these cell strains by simulated sunlight were compared with their respective 254 nm UV mutation curves, these were related by a constant fluence modification factor. suggesting a common lesion for mutagenesis. These results. taken together with published data indicating that at equicytotoxic levels of UV254 nm radiation and the filtered Sun Lamp. the number of pyrimidine dimers in the DNA of XP12BE cells was equal. support the hypothesis that the dimer is the lesion principally involved in both effects. Our data also support the hypothesis that mutations are involved in the sunlight-induced skin cancer of XP patients.     

EPR of an exchange-coupled,hydrogen-bridged one-dimensional Cu(II) complex containing both octahedral and square pyramidal geometries in the same unit cell

Single-crystal X and Q band EPR of a hydrogen-bridged l-dimensional Cu(II) complex, [Cu(stpy)₂(CH₃COO)₂(H₂O)₂] [CU(stpy)₂(CH₃COO) ₂(H₂O)], containing both octahedral and square pyramidal geometries in the same unit cell, has been studied at 300 K. EPR of powder samples at X band frequencies at 300 K and 77 K show exchange-narrowed resonance. The peak-to-peak linewidths of the signals are 80 G and 85 G, respectively. However, at Q band frequencies it exhibits an axially symmetric spectrum with spin Hamiltonian parameters g_|| = 2.303 and g_⊥ = 2.077, corresponding to an |x² ? y²〉 ground state. Single-crystal X band EPR spectra show a single resonance line for all the orientations, indicating the complex to be in the strong exchange regime. On the other hand, Q band spectra exhibit two lines corresponding to the weak exchange regime. An estimate of the interchain-site exchange coupling constant J′ = 0.0125(3) cm^?1 also reveals weak coupling between the magnetically distinct Cu(II) centres. The ratio of J′/J = 8.25 × 10^?2 is low enough to make the interactions almost l-dimensional, in agreement with X-ray data. EPR linewidth and lineshape analyses also support l-dimensional behaviour of the system.