Energy-momentum conservation in pre-metric electrodynamics with magnetic charges

A necessary and sufficient condition for energy-momentum conservation is proved within a topological, pre-metric approach to classical electrodynamics including magnetic as well as electric charges. The extended Lorentz force, consisting of mutual actions by F=(E, B) on the electric current and G=(H, D) on the magnetic current, can be derived from an energy-momentum "potential" if and only if the constitutive relation G=G(F) satisfies a certain vanishing condition. The electric-magnetic reciprocity introduced by Hehl and Obukhov is seen to define a complex structure on the tensor product of 2-form pairs (F,G) which is independent of but consistent with the Hodge star operator defined by any Lorentzian metric. Contrary to a recent claim in the literature, it does not define a complex structure on the space of 2-forms itself.Comment: 8 pages, 1 fugur

Can Health Care Services Attract Retirees And Contribute to the Economic Sustainability of Rural Places?

The search for engines to power rural economic growth has gone beyond the traditional boundaries of the food and fiber sector to industries such as tourism and to schemes such as attracting metropolitan workers to commuter communities with rural amenities. A group that has been somewhat overlooked is retirees, who may wish to trade in urban or suburban life-styles for a more peaceful rural retirement. An industry that has been neglected is the health care industry, which is the most rapidly growing industry nationally and of particular interest to retirees and aging populations. This paper examines the importance of rural health care services in attracting migrants age 65+ to rural counties in Michigan. Results indicate that the number of health care workers has a positive effect on net in-migration, and that this effect is large and statistically significant for the 70+ age group. Implications for rural development strategies are discussed.elder migration, health care, rural development, Community/Rural/Urban Development,

Infinite families of superintegrable systems separable in subgroup coordinates

A method is presented that makes it possible to embed a subgroup separable superintegrable system into an infinite family of systems that are integrable and exactly-solvable. It is shown that in two dimensional Euclidean or pseudo-Euclidean spaces the method also preserves superintegrability. Two infinite families of classical and quantum superintegrable systems are obtained in two-dimensional pseudo-Euclidean space whose classical trajectories and quantum eigenfunctions are investigated. In particular, the wave-functions are expressed in terms of Laguerre and generalized Bessel polynomials.Comment: 19 pages, 6 figure

A generalized photon propagator

A covariant gauge independent derivation of the generalized dispersion relation of electromagnetic waves in a medium with local and linear constitutive law is presented. A generalized photon propagator is derived. For Maxwell constitutive tensor, the standard light cone structure and the standard Feynman propagator are reinstated

Cation Nuclear Magnetic Resonance (NMR). 7Li- and 23Na-NMR Results Obtained with Human Erythrocytes

A short discussion of practical results and theoretical aspects of nuclear magnetic resonance (NMR) on intracellular monovalent cations is presented. 7Li- and 23Na-NMR relaxation studies on human erythrocytes are described which indicate that lithium and sodium ions are essentially free inside the cell. However, there is a contribution to transverse relaxation originating from cations diffusing through electric field gradients imposed by the cytoskeleton, which is reflected in the NMR line shape. 39K-NMR results obtained by other authors for intracellular potassium are compared with the 7Li- and 23Na-NMR results presented here. The few 39K-NMR results obtained so far do not suggest that significant differences in dynamic behavior exist between intracellular potassium and sodium. 39K-NMR studies will, in the future, certainly enhance our understanding of the intracellular state of potassium ions

Internet Entrepreneurship and Economic Growth

This paper looks at national attempts to promote economic growth through the Internet. Growth can be driven through service exports or internally through increased service transactions and fostering entrepreneurship. India is often held as an example of service exports, but economic statistics show that India might not be a good example for other nations because net service trade is negative and wages have been economically distorted. Ultimately, developing nations need to find internal growth models. Internal growth could be driven though increased consumption due to improved information, or increased investment expenditures from infrastructure investments

Indenture Between Albertus C. Van Raalte and Christian Johanna, His wife, and the Consistory of the First Reformed Dutch Church of Holland

An indenture between Albertus C. Van Raalte and Christian Johanna, his wife, and the consistory of the First Reformed Dutch Church of Holland. The Van Raaltes receive one dollar for the lots one, two, fifteen and sixteen in block 41 from the congregation for the site on which they plan to build a church. The indenture was witnessed by Anna F Post and H[enry] De. Post. As Justice of the Peace, Post also handled the transaction. The consistory members who signed were elders: H. Broek, J. A. Verhorst, Jeltje Broersma, Gerrit Jan Hekhuis, J. Labots, J. A. Wilterdink, and W. V. Appeldoorn. The deacons were: A. De Weerd, G. W. Wilterdink, A. Plugger, and P. VandenBerg.https://digitalcommons.hope.edu/vrp_1850s/1219/thumbnail.jp