Multicolour correlative imaging using phosphor probes

Correlative light and electron microscopy exploits the advantages of optical methods, such as multicolour probes and their use in hydrated live biological samples, to locate functional units, which are then correlated with structural details that can be revealed by the superior resolution of electron microscopes. One difficulty is locating the area imaged by the electron beam in the much larger optical field of view. Multifunctional probes that can be imaged in both modalities and thus register the two images are required. Phosphor materials give cathodoluminescence (CL) optical emissions under electron excitation. Lanthanum phosphate containing thulium or terbium or europium emits narrow bands in the blue, green and red regions of the CL spectrum; they may be synthesised with very uniform-sized crystals in the 10- to 50-nm range. Such crystals can be imaged by CL in the electron microscope, at resolutions limited by the particle size, and with colour discrimination to identify different probes. These materials also give emissions in the optical microscope, by multiphoton excitation. They have been deposited on the surface of glioblastoma cells and imaged by CL. Gadolinium oxysulphide doped with terbium emits green photons by either ultraviolet or electron excitation. Sixty-nanometre crystals of this phosphor have been imaged in the atmospheric scanning electron microscope (JEOL ClairScope). This probe and microscope combination allow correlative imaging in hydrated samples. Phosphor probes should prove to be very useful in correlative light and electron microscopy, as fiducial markers to assist in image registration, and in high/super resolution imaging studies

Aboriginal youth, hip hop and the politics of identification

This paper explores the identity work taking place around contemporary subcultural hip hop amongst Australian indigenous youth in two disadvantaged urban locations. Previous work on Aboriginal hip hop has been attentive to the interface between tradition and modernity. However, existing scholarship has lacked a deeper ethnographic understanding of the dynamics between youth and parent cultures, and the tensions between the two generations. This article is based on research with young hip hop enthusiasts, community activists and educators. It deals with the cultural politics of identification and sees hip hop practice as associated with a process in which Aboriginality is crystallized as a principal affiliation and as offering an account for experiences of social marginalization. Far from being an outlet for expressing a prior or essential Aboriginality, hip hop as cultural practice is associated with the production of particular identifications

Neutrino physics and the flavour problem

We consider the problem of trying to understand the recently measured neutrino data simultaneously with understanding the hierarchical form of quark and charged lepton Yukawa matrices. We summarise the data that a successful model of neutrino mass must predict, and then move on to attempting to do so in the context of spontaneously broken 'family' symmetries. We consider first an abelian U(1) family symmetry, which appears in the context of a type I string model. Then we consider a model based on a non-abelian SU(3)_F, which is the maximal family group consistent with an SO(10) GUT. In this case the symmetry is more constraining, and is examined in the context of SUSY field theory