The Third-Annual Abolitionists’ Day Event

Three years ago, Adams County declared the first ever Abolitionists Day—a day dedicated to honoring the lives of the county’s abolitionists. The county’s abolitionists were a varied group, comprised of both whites and free blacks, men and women. Through their efforts, thousands of slaves were able to find their freedom in the North. One impressive couple, William and Phebe Wright, helped approximately one thousand men, women, and children to freedom. Adams County was also home to Thaddeus Stevens, a Gettysburg resident who used his position in the US House of Representatives to fight against the institution of slavery. With people as distinguished as these in the county’s history, it is fitting that the county has set aside a day to commemorate them. To aid in this commemoration, several groups from the county came together to create a two-hour program that honored these abolitionists and educated modern county residents about their legacy in a performance that featured a collection of skits, talks, and music. [excerpt

A Song for Jennie

The simple tune was created by lyricist E. B. Dewing and composer J. P. Webster who hoped they would inspire patriotism in their female audience while they worked to become accomplished musicians. When the Civil War broke out, the young women who played the piece had been left behind on the home front, only to imagine what horrors their men were facing. The government and the warfront alike relied on the homefront to present a brave and loyal face in order to maintain support for the war effort through the fostering of a nationalistic, sentimental culture that bled into all aspects of Union life. Music was a feminine expression of patriotic devotion that many women used to empathize with those on the battle front as well as to inspire themselves and their peers toward acts of patriotic sacrifice on behalf of their war-torn nation. After the war ended and America moved into Reconstruction, music like “Jennie Wade, the Heroine of Gettysburg” continued to inspire women, who were busy honoring the dead and healing the country’s gaping wounds. [excerpt

The aerobic treatment of reverse osmosis permeate for reuse : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Technology in Environmental Engineering

The reduction of effluent streams and the demand for freshwater intake in the dairy industry, may be accomplished by the segregation and reuse of streams that can be readily treated. This study assessed the biodegradability and suitability for reuse of reverse osmosis (R/O) permeate from Kiwi Dairies Ltd processing factory (Hawera), using aerobic treatment. Analysis of the permeate showed that there was a direct relationship between chemical oxygen and lactose concentration. The chemical oxygen demand of R/O permeate from two reverse osmosis membrane plants operating in parallel varied widely during the period of study. This wide variation in permeate chemical oxygen was directly related to the membrane efficiency. Elemental analysis of the R/O permeate showed that iron and phosphorous would need to be supplemented to ensure balanced microbial growth. The biodegradability was characterised by a series of batch tests to determine the biokinetic constants µm, Ks, qsm and Yt. These tests showed that the biodegradability of reverse osmosis permeate is comparable to general dairy wastes. Batch tests were also performed on permeate from R/O membranes of varying performance efficiency, with different lactose and mineral concentrations. There were no conclusive variations in biokinetic constants between permeates from R/O membranes of varying performance efficiency. Operation of a model activated sludge pilot plant showed that soluble COD removal efficiencies of over 90% could be achieved at hydraulic retention times of 10 and 20 hours. The sludge settling characteristics were more favourable at a 10 hour hydraulic retention time. Sudden fluctuations in membrane efficiency caused shock loads resulting in a deterioration in treatment efficiency and sludge settling characteristics. Although the pilot plant achieved satisfactory reductions, soluble COD levels were not decreased to the level of 10 to 15 mg l -1 required to enable the reuse of the permeate. In order to determine if low substrate levels could be achieved when aerobically treating R/O permeate from an efficient membrane plant, a laboratory scale reactor was used to treat permeate with a COD of 200 mg l-1. It was established that R/O permeate could be aerobically treated to levels suitable for reuse, provided the previous membrane processes performed efficiently

A planar diagram approach to the correlation problem

We transpose an idea of 't Hooft from its context of Yang and Mills' theory of strongly interacting quarks to that of strongly correlated electrons in transition metal oxides and show that a Hubbard model of N interacting electron species reduces, to leading orders in N, to a sum of almost planar diagrams. The resulting generating functional and integral equations are very similar to those of the FLEX approximation of Bickers and Scalapino. This adds the Hubbard model at large N to the list of solvable models of strongly correlated electrons. PACS Numbers: 71.27.+a 71.10.-w 71.10.FdComment: revtex, 5 pages, with 3 eps figure

Theory for the Doping Dependence of Spin Fluctuation Induced Shadow States in High-Tc_{c} Superconductors

We analyze the doping dependence of the intensity and energetical position of shadow states in high -T$_{c}$ superconductors within the 2D Hubbard model and using our recently developed numerical method for the self consistent summation of bubble and ladder diagrams. It is shown that shadow states resulting from short range antiferromagnetic correlations occur for small but finite excitation energies which decrease for decreasing doping, reflecting a dynamically broken symmetry with increasing lifetime. Simultanously, the intensity of these new states increases, the quasiparticle dispersion is strongly flattened, and a pseudogap in the density of states occurs. Finally, we discuss the importance of flat bands at the Fermi level and nesting of the Fermi surface as general prerequisites for the observability of shadow states.Comment: 9 pages (TeX) with 3 figures (Postscript

A new approach to strongly correlated fermion systems: the spin-particle-hole coherent-state path integral

We describe a new path integral approach to strongly correlated fermion systems, considering the Hubbard model as a specific example. Our approach is based on the introduction of spin-particle-hole coherent states which generalize the spin-1/2 coherent states by allowing the creation of a hole or an additional particle. The action of the fermion system $S[\gamma^*,\gamma;{\bf\Omega}]$ can be expressed as a function of two Grassmann variables ($\gamma_\uparrow$,$\gamma_\downarrow$) describing particles propagating in the lower and upper Hubbard bands, and a unit vector field ${\bf\Omega}$ whose dynamics arises from spin fluctuations. In the strong correlation limit, $S[\gamma^*,\gamma;{\bf\Omega}]$ can be truncated to quartic order in the fermionic fields and used as the starting point of a strong-coupling diagrammatic expansion in $t/U$ ($t$ being the intersite hopping amplitude and $U$ the on-site Coulomb repulsion). We discuss possible applications of this formalism and its connection to the t-J model and the spin-fermion model.Comment: 20 pages RevTex, 10 figure

Measuring the Relative Phase of the Energy Gap in a High-Temperature Superconductor with EELS

A method of measuring the relative phase of the energy gap in a high-temperature superconductor is suggested for electron energy loss spectroscopy. Energy-resolved measurements of off-specular scattering should show a feature similar to the specular feature associated with the gap. Unlike the specular feature, which reflects an average of the gap over the (normal) Fermi surface, the energy loss of the off-specular feature depends on the superconducting energy gap at only two locations on the Fermi surface. The onset of the feature reflects the relative phase between these two points. This result is independent of surface characteristics. Such characteristics affect the {\it magnitude} of the off-specular feature, not its location or onset. The size of the feature is estimated for a simple surface model. Implications of specific measurements on $\rm Bi_2Sr_2CaCu_2O_8$ are discussed

Theory for the Interdependence of High-Tc_c Superconductivity and Dynamical Spin Fluctuations

The doping dependence of the superconducting state for the 2D one-band Hubbard Hamiltonian is determined. By using an Eliashberg-type theory, we find that the gap function $\Delta_{\bf k}$ has a $d_{x^2-y^2}$ symmetry in momentum space and T$_c$ becomes maximal for $13 \; \%$ doping. Since we determine the dynamical excitations directly from real frequency axis calculations, we obtain new structures in the angular resolved density of states related to the occurrence of {\it shadow states} below T$_c$. Explaining the anomalous behavior of photoemission and tunneling experiments in the cuprates, we find a strong interplay between $d$-wave superconductivity and dynamical spin fluctuations.Comment: 4 pages (REVTeX) with 4 figures (Postscript