On Comparison of Exponential and Hyperbolic Exponential Growth Models in Height/Diameter Increment of PINES (Pinus caribaea)

A new tree growth model called the hyperbolic exponential nonlinear growth model is suggested. Its ability in model prediction was compared with the Malthus or exponential growth model an approach which mimicked the natural variability of heights/diameter increment with respect to age and therefore provides more realistic height/diameter predictions as demonstrated by the results of the Kolmogorov Smirnov test and Shapiro-Wilk test. The mean function of top height/Dbh over age using the two models under study predicted closely the observed values of top height/Dbh in the Hyperbolic exponential nonlinear growth models better than the ordinary exponential growth model without violating most of the assumptions about the error term

Elucidating the Structural Chemistry of a Hysteretic Iron(II) Spin‐Crossover Compound From its Copper(II) and Zinc(II) Congeners

Annealing [Fe L 2 ][BF 4 ] 2 ∙2H 2 O ( L = 2,6‐ bis ‐[5‐methyl‐1 H ‐pyrazol‐3‐yl]pyridine) affords an anhydrous material, which undergoes a spin‐transition at T ½ = 205 K with a 65 K thermal hysteresis loop. This occurs via a sequence of phase changes, which were monitored by powder diffraction in an earlier study. [Cu L 2 ][BF 4 ] 2 ∙2H 2 O and [Zn L 2 ][BF 4 ] 2 ∙2H 2 O are not perfectly isostructural but, unlike the iron compound, they undergo single‐crystal‐to‐single‐crystal dehydration upon annealing. All the annealed compounds initially adopt the same tetragonal phase, but undergo a phase change near room temperature upon recooling. The low‐temperature phase of [Cu L 2 ][BF 4 ] 2 involves ordering of its Jahn‐Teller distortion, to a monoclinic lattice with three unique cation sites. The zinc compound adopts a different, triclinic low‐temperature phase with significant twisting of its coordination sphere, which unexpectedly becomes more pronounced as the crystal is cooled. Synchrotron powder diffraction data confirm the structural changes in the anhydrous zinc complex are reproduced in the high‐spin iron compound, before the onset of spin‐crossover. This will contribute to the wide hysteresis in the spin transition of the iron complex. EPR spectra of copper‐doped [Fe 0.97 Cu 0.03 L 2 ][BF 4 ] 2 imply its low spin phase contains two distinct cation environments in a 2:1 ratio

Obtaining Proportion of Optimum Yield when Full Yield is unattainable

In a situation where it is not feasible to obtain full yield at harvest time because it is unattainable or simply unavoidable; combined methods of calculus of variation and maximum likelihood estimates are used to obtain a proportion of this yield. This is obtained for both known (desired) and unknown (estimable) proportions of the maximum yield on rectangular and square plot – formations. The reference model is that due to Berry (1967) on intra-row and inter-row spacing experiment. Keywords: Berry's model, Calculus of variations, Maximum likelihood, Plot-formations. (Global Journal of Mathematical Sciences: 2002 1 (1&2): 21-26

International Journal of Physical Sciences Full Length Research Paper Lehmann Type II weighted Weibull distribution

Copyright © 2014 Author(s) retain the copyright of this articl

Systematic investigation of the physicochemical factors that contribute to the toxicity of ZnO nanoparticles.

ZnO nanoparticles (NPs) are prone to dissolution, and uncertainty remains whether biological/cellular responses to ZnO NPs are solely due to the release of Zn(2+) or whether the NPs themselves have additional toxic effects. We address this by establishing ZnO NP solubility in dispersion media (Dulbecco's modified Eagle's medium, DMEM) held under conditions identical to those employed for cell culture (37 °C, 5% CO2, and pH 7.68) and by systematic comparison of cell-NP interaction for three different ZnO NP preparations. For NPs at concentrations up to 5.5 μg ZnO/mL, dissolution is complete (with the majority of the soluble zinc complexed to dissolved ligands in the medium), taking ca. 1 h for uncoated and ca. 6 h for polymer coated ones. Above 5.5 μg/mL, the results are consistent with the formation of zinc carbonate, keeping the solubilized zinc fixed to 67 μM of which only 0.45 μM is as free Zn(2+), i.e., not complexed to dissolved ligands. At these relatively high concentrations, NPs with an aliphatic polyether-coating show slower dissolution (i.e., slower free Zn(2+) release) and reprecipitation kinetics compared to those of uncoated NPs, requiring more than 48 h to reach thermodynamic equilibrium. Cytotoxicity (MTT) and DNA damage (Comet) assay dose-response curves for three epithelial cell lines suggest that dissolution and reprecipitation dominate for uncoated ZnO NPs. Transmission electron microscopy combined with the monitoring of intracellular Zn(2+) concentrations and ZnO-NP interactions with model lipid membranes indicate that an aliphatic polyether coat on ZnO NPs increases cellular uptake, enhancing toxicity by enabling intracellular dissolution and release of Zn(2+). Similarly, we demonstrate that needle-like NP morphologies enhance toxicity by apparently frustrating cellular uptake. To limit toxicity, ZnO NPs with nonacicular morphologies and coatings that only weakly interact with cellular membranes are recommended