The covariant, time-dependent Aharonov-Bohm Effect

We discuss two possible covariant generalizations of the Aharonov-Bohm effect - one expression in terms of the space-time line integral of the four-vector potential and the other expression in terms of the space-time "area" integral of the electric and magnetic fields written in terms of the Faraday 2-form. These expressions allow one to calculate the Aharonov-Bohm effect for time-dependent situations. In particular, we use these expressions to study the case of an infinite solenoid with a time varying flux and find that the phase shift is zero due to a cancellation of the Aharonov-Bohm phase shift with a phase shift coming from the Lorentz force associated with the electric field, ${\bf E} = - \partial_t {\bf A}$, outside the solenoid. This result may already have been confirmed experimentally.Comment: 11 pages, no figures, journal version, three added reference

Spectral Analysis of the Stromlo-APM Survey I. Spectral Properties of Galaxies

We analyze spectral properties of 1671 galaxies from the Stromlo-APM survey, selected to have 15 < b_J < 17.15 and having a mean redshift z = 0.05. This is a representative local sample of field galaxies, so the global properties of the galaxy population provide a comparative point for analysis of more distant surveys. We measure Halpha, Oii 3727, Sii 6716, 6731, Nii 6583 and Oi 6300 equivalent widths and the D_4000 break index. The 5A resolution spectra use an 8 arcsec slit, which typically covers 40-50% of the galaxy area. We find no evidence for systematic trends depending on the fraction of galaxy covered by the slit, and further analysis suggests that our spectra are representative of integrated galaxy spectra. We classify spectra according to their Halpha emission, which is closely related to massive star formation. Overall we find 61% of galaxies are Halpha emitters with rest-frame equivalent widths EW(Halpha) >= 2A. The emission-line galaxy (ELG) fraction is smaller than seen in the CFRS at z = 0.2 and is consistent with a rapid evolution of Halpha luminosity density. The ELG fraction, and EW(Halpha), increase at fainter absolute magnitudes, smaller projected area and smaller D_4000. In the local Universe, faint, small galaxies are dominated by star formation activity, while bright, large galaxies are more quiescent. This picture of the local Universe is quite different from the distant one, where bright galaxies appear to show rapidly-increasing activity back in time. (Abridged)Comment: 40 pages, 25 figures, MNRAS, in pres

A statistical model for the intrinsically broad superconducting to normal transition in quasi-two-dimensional crystalline organic metals

Although quasi-two-dimensional organic superconductors such as $\kappa$-(BEDT-TTF)$_2$Cu(NCS)$_2$ seem to be very clean systems, with apparent quasiparticle mean-free paths of several thousand \AA, the superconducting transition is intrinsically broad (e.g $\sim 1$ K wide for $T_c \approx 10$ K). We propose that this is due to the extreme anisotropy of these materials, which greatly exacerbates the statistical effects of spatial variations in the potential experienced by the quasiparticles. Using a statistical model, we are able to account for the experimental observations. A parameter $\bar{x}$, which characterises the spatial potential variations, may be derived from Shubnikov-de Haas oscillation experiments. Using this value, we are able to predict a transition width which is in good agreement with that observed in MHz penetration-depth measurements on the same sample.Comment: 8 pages, 2 figures, submitted to J. Phys. Condens. Matte

Glueball Spin

The spin of a glueball is usually taken as coming from the spin (and possibly the orbital angular momentum) of its constituent gluons. In light of the difficulties in accounting for the spin of the proton from its constituent quarks, the spin of glueballs is reexamined. The starting point is the fundamental QCD field angular momentum operator written in terms of the chromoelectric and chromomagnetic fields. First, we look at the restrictions placed on the structure of glueballs from the requirement that the QCD field angular momentum operator should satisfy the standard commutation relationships. This can be compared to the electromagnetic charge/monopole system, where the quantization of the field angular momentum places restrictions (i.e. the Dirac condition) on the system. Second, we look at the expectation value of this operator under some simplifying assumptions.Comment: 11 pages, 0 figures; added references and some discussio

Science on television : A representational site for mediating ideology

The emergence of a new science paradigm has been identified. It is characteristically described as structuring an organic, holistic and ecological framework for understanding the nature of reality. The modern scientific paradigm with its characteristic underlying inorganic, reductive, and mechanistic vision of reality, discursively dominates Western societies\u27 cultural sense-making with its attempts to unlock the \u27mysteries\u27 of nature. The radically different characteristics of the new paradigm science is linked to \u27rising culture\u27 articulated in the exploratory social change of alternative social movements. The holistic principles and ecological values found variously in the environment, feminist, and new age/holistic health, peace and indigenous people\u27s movements link to the new paradigm. Both factual and fictional television texts engaging discursively with science, present a representational site for different cultural expression of the preferred meanings of ideology of two radically different paradigmatic frameworks

Connect the Dots: Coupling Quantum Dots with Water-Soluble Porphyrins

Currently, advances in the area of photodynamic therapy (PDT) using porphyrin molecules are being made and not only in this arena, but in science and society overall, nanoparticles are of high interest. For perspective on the size of nanoscale products (such as porphyrins or quantum dots) present in society today, consider that 2 g of 100 nm-diameter nanoparticles contains enough material to provide every human worldwide with 300,000 particles each (Hardman 2006). Porphyrins are better suited for PDT than their organic dye predecessors due to their fluorescence intensity and longevity. Currently, Photofrin® and Visudyne®, both porphyrin-type derivatives are used in PDT. However, the fluorescence and longevity advantages could possibly be further improved by the successful coupling of the porphyrin molecule to nanoparticles known as quantum dots (QDs). QDs, types of phosphors, are miniscule crystals of semiconductor material such as zinc sulfide, cadmium sulfide, cadmium telluride, or cadmium selenide, with their overall structure being composed of a core surrounded by an outer shell. The nature of QDs may be altered upon modification of or additions to this outer shell - including the attachment of porphyrin molecules (Zenkevich 2006). The resulting QD-porphyrin complex is expected to have increased photo-efficiency and more selective biological cell imaging. Porphyrins are known to be tumor specific and therefore the QD-porphyrin complex should be as well. Continuing research may include the addition of zinc to the porphyrin complex followed by attempted coupling with QDs. A second area of further research will include the addition of hexadiamine through the aide of a BOC protecting group followed by attempted coupling with QDs, as well as investigations concerning the cellular uptake of many of these QD-porphyrin compounds