BioNanoAdhesion: atomic force microscopy study of the electrostatic properties of pyridine-and imidazole-based polycationic surfaces

Self-assembled monolayers of pyridine- and imidazole-based disulfides are currently being produced on low roughness gold surfaces. The electrostatic interaction between these surfaces and an atomic force microscope cantilever, modified with a silica microparticle, will subsequently be investigated as a function of environmental pH. The results can be used towards the development of improved nanoparticulate non-viral gene delivery vectors

Increasing trap stiffness with position clamping in holographic optical tweezers

We present a holographic optical tweezers system capable of position clamping multiple particles. Moving an optical trap in response to the trapped object's motion is a powerful technique for optical control and force measurement. We have now realised this experimentally using a Boulder Nonlinear Systems Spatial Light Modulator (SLM) with a refresh rate of 203Hz. We obtain a reduction of 44% in the variance of the bead's position, corresponding to an increase in effective trap stiffness of 77%. This reduction relies on the generation of holograms at high speed. We present software capable of calculating holograms in under 1ms using a graphics processor unit. © 2009 Optical Society of America

Multilingual gendered identities: female undergraduate students in London talk about heritage languages

In this paper I explore how a group of female university students, mostly British Asian and in their late teens and early twenties, perform femininities in talk about heritage languages. I argue that analysis of this talk reveals ways in which the participants enact ‘culturally intelligible’ gendered subject positions. This frequently involves negotiating the norms of ‘heteronormativity’, constituting femininity in terms of marriage, motherhood and maintenance of heritage culture and language, and ‘girl power’, constituting femininity in terms of youth, sassiness, glamour and individualism. For these young women, I ask whether higher education can become a site in which they have the opportunities to explore these identifications and examine other ways of imagining the self and what their stories suggest about ‘doing being’ a young British Asian woman in London

GRB030406 an extremely hard burst outside of the INTEGRAL field of view

Using the IBIS Compton mode, the INTEGRAL satellite is able to detect and localize bright and hard GRBs, which happen outside of the nominal INTEGRAL telescopes field of view. We have developed a method of analyzing such INTEGRAL data to obtain the burst location and spectra. We present the results for the case of GRB030406. The burst is localized with the Compton events, and the location is consistent with the previous Interplanetary Network position. A spectral analysis is possible with the detailed modeling of the detector response for such a far off-axis source with the offset of 36.9 $^\circ$. The average spectrum of the burst is extremely hard: the photon index above 400 \kev is -1.7, with no evidence of a break up to 1.1 \mev at 90% confidence level.Comment: Astronomy and Astrophysics in pres

Bio-nanopatterning of Surfaces

Bio-nanopatterning of surfaces is a very active interdisciplinary field of research at the interface between biotechnology and nanotechnology. Precise patterning of biomolecules on surfaces with nanometre resolution has great potential in many medical and biological applications ranging from molecular diagnostics to advanced platforms for fundamental studies of molecular and cell biology. Bio-nanopatterning technology has advanced at a rapid pace in the last few years with a variety of patterning methodologies being developed for immobilising biomolecules such as DNA, peptides, proteins and viruses at the nanoscale on a broad range of substrates. In this review, the status of research and development are described, with particular focus on the recent advances on the use of nanolithographic techniques as tools for biomolecule immobilisation at the nanoscale. Present strengths and weaknesses, as well future challenges on the different nanolithographic bio-nanopatterning approaches are discussed

X-Ray Emission of Gamma-Ray Bursts

X-ray emission can provide a crucial diagnostic of gamma-ray bursts (GRBs). We calculate the X-ray and gamma-ray spectra of impulsive acceleration episodes related to GRB pulses. We use the synchrotron shock model (SSM) as a basis of our calculations. We show that the current data on soft-to-hard emission ratios of GRB pulse emission are in agreement with the SSM. In particular, GRB pulse emission detected by GINGA is in agreement with the SSM low-energy spectra. We deduce that GINGA detected the majority of bright GRBs detectable by BATSE. These results indicate that the physical environment surrounding the GRB emission site is optically thin to X-ray photon energies. We also calculate emission ratios in the Einstein, ROSAT, SAX and HETE energy bands, and discuss how future information on simultaneous soft/hard GRB emission can contribute in distinguishing different emission models. Two different components of X-ray emission may simultaneously exist in a fraction of GRBs. One component is clearly associated with the individual GRB pulses, and an additional component may be related to the pulse X-ray spectral upturns and/or the precursors/tails occasionally observed. We also show that a meaningful search of GRB-driven X-ray flashes in Andromeda (M31) can be carried out with existing ROSAT data and future SAX Wide Field Camera observations.Comment: 18 pages, 5 figures included as postscript files. Astrophysical Journal, in press, vol. 474 (10 April 1997