Periodic Boundary Value Problems for a Class of Functional Differential Equations

In this paper we show that the method of upper and lower solutions coupled with the monotone iterative technique is valid to obtain constructive proofs of existence of solutions for nonlinear periodic boundary value problems of functional differential equations without assuming properties of monotonicity in the nonlinear part.     

Rational ligand design for metal ion recognition. Synthesis of a N-benzylated N2S3-donor macrocycle for enhanced silver(I) discrimination

Four previously documented ligand design strategies for achieving Ag(I) discrimination have been applied to the design of a new N-benzylated N2S3-donor macrocycle; the latter shows high selectivity for Ag(I) over Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) in log K and bulk membrane transport studies.     

GIS-based model of stable hydrogen isotope ratios in North American growing-season precipitation for use in animal movement studies

Stable hydrogen isotope ratios of precipitation (δD_p) show distinct geographic patterns across North America. Over the last decade, ecologists have utilized growing-season δD_p patterns to study the movements of migratory animals. The accuracy and precision of such studies is, in part, contingent upon the accuracy and precision of growing-season δD_p maps. Previous mapping efforts have employed simple kriging procedures to produce smooth contor maps of growing-season δD_p. We attempted to improve these maps by incorporating the effects of altitude on both δD_p values and growing season length. This involved producing elevation-corrected monthly δD_p, temperature, and precipitation amount values for 1-km grid cells across the continental United States and Canada using recently developed interpolation procedures. We used a geographic information system (GIS) to calculate a weighted-average growing-season δD_p value for each grid cell using δD_p and precipitation amount values for all months in which the mean temperature was greater than 0 °C. We used seven independent data sets to compare the precision of the resulting altitude-corrected map with another that did not account for altitude. Overall, predicted δD_p values from the altitude-corrected map more closely matched observed values, and correspondence was more pronounced at finer spatial scales. Digital versions of the GIS-based maps generated during this effort are available via the Internet at http://biology.unm.edu/wolf/precipitationD.htm. These δD_p layers can be combined with other types of spatial information, such as species' geographic ranges and habitat associations, to further improve our understanding of animal movements.     

Prediction-based control of chaos and a dynamic Parrondoʼs paradox

We analyze the stabilization of an unstable periodic orbit (UPO) by periodic prediction-based control (PBC). We rigorously prove that, for 2-periodic orbits, a pulse strategy reduces the necessary control strength to stabilize the UPO. Moreover, we find that in some cases the periodic control prevents some undesirable effects induced by the PBC method. In this way, we provide an example of a dynamic Parrondo?s paradox: the switching between two undesirable dynamics results in a nicely periodic dynamic behavior.     

Investigation of chaotic instabilities in railway wheel squeal

Nonlinear Dynamics - The occurrence of chaotic motion in a railway instability phenomenon known as wheel squeal is investigated. The analysis is motivated and applied to predicting the large...