Creating ultracold molecules by collisions with ultracold rare gas atoms in an optical trap

We study collisions of para-H$_2$ with five rare gas atomic species (He, Ne, Ar, Kr and Xe) over the range from 1 K to 1 $\mu$ K and evaluate the feasibility of sympathetic cooling H$_2$ with ultracold ground state rare gas atoms co-trapped within a deep optical trap. Collision cross-sections over this large temperature range show that all of these species could be used to cool H$_2$ to ultracold temperatures and that argon and helium are the most promising species for future experiments.Comment: 5 pages, 1 figure, 1 table, submitted for publicatio

Towards sympathetic cooling of large molecules: Cold collisions between benzene and rare gas atoms

This paper reports on calculations of collisional cross sections for the complexes Z-CDH6 (X = 3He, 4He, Ne) at temperatures in the range 1)μK - 10K and shows that relatively large cross sections in the 103-105Å2 range are available for collisional cooling. Both elastic and inelastic processes are considered in this temperature range. The calculations suggest that sympathetically cooling benzene to microkelvin temperatures is feasible using these co-trapped rare gas atoms in an optical trap. © IOP Publishing Ltd and Deutsche Physikalische Gesellschan

Pupils or prisoners? Institutional geographies and internal exclusion in UK secondary schools

This is the accepted version of the following article: Barker, J., Alldred, P., Watts, M. and Dodman, H. (2010), Pupils or prisoners? Institutional geographies and internal exclusion in UK secondary schools. Area, 42: 378–386, which has been published in final form at the link below. Copyright © 2010 The Authors.A growing interest in the geographies of schooling has led to an exploration of a variety of school spaces. An increasing number of secondary schools offer internal fixed-term exclusions so that temporary removal from school is not seen as ‘time off’ for students. This particular strategy has led to the creation of a new type of space in schools. Drawing upon research undertaken in a London secondary school, this paper explores the geography of these new secluded spaces. We highlight that the configuration of physical space in Seclusion Units and the regulation of spatial practices create highly controlled and segregated spaces of punishment. We explore the powerful transformative effects of these spaces to change students' behaviour, social interaction and attitudes to learning. However, rather than simply creating docile subjects, we recognise that domination is never complete and we explore the extent and the limit of student resistance to the discipline and control of the Seclusion Unit

Exploiting correlogram structure for robust speech recognition with multiple speech sources

This paper addresses the problem of separating and recognising speech in a monaural acoustic mixture with the presence of competing speech sources. The proposed system treats sound source separation and speech recognition as tightly coupled processes. In the first stage sound source separation is performed in the correlogram domain. For periodic sounds, the correlogram exhibits symmetric tree-like structures whose stems are located on the delay that corresponds to multiple pitch periods. These pitch-related structures are exploited in the study to group spectral components at each time frame. Local pitch estimates are then computed for each spectral group and are used to form simultaneous pitch tracks for temporal integration. These processes segregate a spectral representation of the acoustic mixture into several time-frequency regions such that the energy in each region is likely to have originated from a single periodic sound source. The identified time-frequency regions, together with the spectral representation, are employed by a `speech fragment decoder' which employs `missing data' techniques with clean speech models to simultaneously search for the acoustic evidence that best matches model sequences. The paper presents evaluations based on artificially mixed simultaneous speech utterances. A coherence-measuring experiment is first reported which quantifies the consistency of the identified fragments with a single source. The system is then evaluated in a speech recognition task and compared to a conventional fragment generation approach. Results show that the proposed system produces more coherent fragments over different conditions, which results in significantly better recognition accuracy

Maternal Expression Relaxes Constraint on Innovation of the Anterior Determinant, bicoid

The origin of evolutionary novelty is believed to involve both positive selection and relaxed developmental constraint. In flies, the redesign of anterior patterning during embryogenesis is a major developmental innovation and the rapidly evolving Hox gene, bicoid (bcd), plays a critical role. We report evidence for relaxation of selective constraint acting on bicoid as a result of its maternal pattern of gene expression. Evolutionary theory predicts 2-fold greater sequence diversity for maternal effect genes than for zygotically expressed genes, because natural selection is only half as effective acting on autosomal genes expressed in one sex as it is on genes expressed in both sexes. We sample an individual from ten populations of Drosophila melanogaster and nine populations of D. simulans for polymorphism in the tandem gene duplicates bcd, which is maternally expressed, and zerknüllt (zen), which is zygotically expressed. In both species, we find the ratio of bcd to zen nucleotide diversity to be two or more in the coding regions but one in the noncoding regions, providing the first quantitative support for the theoretical prediction of relaxed selective constraint on maternal-effect genes resulting from sex-limited expression. Our results suggest that the accelerated rate of evolution observed for bcd is owing, at least partly, to variation generated by relaxed selective constraint

LANDSAT-4 multispectral scanner (MSS) subsystem radiometric characterization

The multispectral band scanner (mass) and its spectral characteristics are described and methods are given for relating video digital levels on computer compatible tapes to radiance into the sensor. Topics covered include prelaunch calibration procedures and postlaunch radiometric processng. Examples of current data resident on the MSS image processing system are included. The MSS on LANDSAT 4 is compared with the scanners on earlier LANDSAT satellites

Cavity cooling a single charged nanoparticle

The development of laser cooling coupled with the ability to trap atoms and ions in electromagnetic fields, has revolutionised atomic and optical physics, leading to the development of atomic clocks, high-resolution spectroscopy and applications in quantum simulation and processing. However, complex systems, such as large molecules and nanoparticles, lack the simple internal resonances required for laser cooling. Here we report on a hybrid scheme that uses the external resonance of an optical cavity, combined with radio frequency (RF) fields, to trap and cool a single charged nanoparticle. An RF Paul trap allows confinement in vacuum, avoiding instabilities that arise from optical fields alone, and crucially actively participates in the cooling process. This system offers great promise for cooling and trapping a wide range of complex charged particles with applications in precision force sensing, mass spectrometry, exploration of quantum mechanics at large mass scales and the possibility of creating large quantum superpositions.Comment: 8 pages, 5 figures Updated version includes additional references, new title, and supplementary information include

'Trying to keep up': Intersections of identity, space, time and rhythm in women student carer auto/biographical accounts

Geographies of Care and Caring is a burgeoning area of geographical thought, although auto/biographical caring accounts have been less explored. Drawing upon in-depth interviews with women students (from different generations) who are in education with a range of caring responsibilities (‘student carers’), this chapter explores how auto/biographies are laden with spatial and temporal rhythms. Drawing upon theorisations of time and rhythm (Lefebvre, 2013, Elden, 2004), and feminist work exploring the gendered emotional and temporal dynamics of care (Hochschild, 1989; Maher 2009; Rogers and Weller, 2013) we explore how participants negotiate complex, shifting and multiply-intersecting rhythms across space and time to undertake care and construct identities as student and carer. In doing so, we consider the benefits of incorporating spatial and temporal rhythms within auto/biographical accounts

The 8^8B Neutrino Spectrum

Knowledge of the energy spectrum of $^8$B neutrinos is an important ingredient for interpreting experiments that detect energetic neutrinos from the Sun. The neutrino spectrum deviates from the allowed approximation because of the broad alpha-unstable $^8$Be final state and recoil order corrections to the beta decay. We have measured the total energy of the alpha particles emitted following the beta decay of $^8$B. The measured spectrum is inconsistent with some previous measurements, in particular with a recent experiment of comparable precision. The beta decay strength function for the transition from $^8$B to the accessible excitation energies in $^8$Be is fit to the alpha energy spectrum using the R-matrix approach. Both the positron and neutrino energy spectra, corrected for recoil order effects, are constructed from the strength function. The positron spectrum is in good agreement with a previous direct measurement. The neutrino spectrum disagrees with previous experiments, particularly for neutrino energies above 12 MeV.Comment: 15 pages, 13 figures, 4 tables, submitted to Phys. Rev. C, typos correcte