UCL University College London Eprints
UCL Eprints collects the work of UCL researchers and makes it freely available over the web, helping the worldwide scholarly community to discover UCL research. Institutional repositories like UCL Eprints complement the traditional academic publishing and scholarly communications processes. They raise the visibility of research and help to maximise its impact. UCL researchers are encouraged to deposit a copy of each journal article, conference paper, working paper, and any other research output, in the UCL Eprints at the earliest opportunity, ensuring that their research reaches as wide an audience as possible.
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MUC1 polymorphism in relation to susceptibility to Helicobacter pylori gastritis. - Santos Teixeira, A.S.
The gene MUC1 encodes a transmembrane mucin glycoprotein that is expressed on the apical surface of most epithelia and is aberrantly expressed in cancer. MUC1 contains an extended domain of tandemly repeated (TR) amino-acid sequence, which acts as the backbone for a large amount of O-linked glycosylation, and which varies in length and sequence in different alleles. Previous studies on MUC1 tandem repeat variation in patients with gastritis (Vinall et al, 2002) and gastric cancer (Carvalho et al, 1997) showed an overrepresentation of short TR alleles in the patient groups when compared with normal controls. The major aim of this...
Forced displacements in Cambodia: Creative re-appropriation practices versus current models of urban development - Boano, C; Talocci,, G
Forced evictions are commonplace in the developing world, mainly due to the need to repurpose land for allegedly higher order enterprises. In this post, Camillo Boano and Giorgio Talocci discuss their research with two relocation sites that originated from the same eviction in Phnom Penh, Cambodia. By looking at these cases, they show how newly-formed settlements can follow diametrically different paths: whereas one conforms to the current model of social development, the other one contests this model through home-grown urbanity practices. A longer version of this post appeared in Pacific Geographies (2015), 43(1), 15-20.
"Pick it up with light!"- An Advanced Summer Program for secondary school students - Mathew, M; Kumar, SC; Valencia, A; Volpe, G; Carrasco, S
A project to introduce secondary school students to statistical physics and biophotonics by means of an optical tweezers is presented. Interestingly, the project is completely experimental and no advanced calculus or physics knowledge is necessary. The project starts from the construction of the optical tweezers itself and therefore is also useful to introduce basic concepts of optics.
Dual-mechanism antimicrobial polymer-ZnO nanoparticle and crystal violet-encapsulated silicone - Noimark, S; Noor, N; Parkin, IP; Weiner, J; Williams, CK; Shaffer, MSP; Allan, E
The prevalence of healthcare-associated infection caused by multidrug-resistant bacteria is of critical concern worldwide. It is reported on the development of a bactericidal surface prepared by use of a simple, upscalable, two-step dipping strategy to incorporate crystal violet and di(octyl)-phosphinic- acid-capped zinc oxide nanoparticles into medical grade silicone, as a strategy to reduce the risk of infection. The material is characterized by UV-vis absorbance spectroscopy, X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectroscopy (ICP-OES) and transmission electron microscopy (TEM) and confirmed the incorporation of the ZnO nanoparticles in the polymer. The novel system proves to be a highly versatile...
Breakdown of Stokes-Einstein relation in the supercooled liquid state of phase change materials - Sosso, GC; Behler, J; Bernasconi, M
The application of amorphous chalcogenide alloys as data-storage media relies on their ability to undergo an extremely fast (10-100 ns) crystallisation once heated at sufficiently high temperature. However, the peculiar features that make these materials so attractive for memory devices still lack a comprehensive microscopic understanding. By means of large scale molecular dynamics simulations, we demonstrate that the supercooled liquid of the prototypical compound GeTe shows a very high atomic mobility (D \sim 10^(-6) cm2/s) down to temperatures close to the glass transition temperatures. This behaviour leads to a breakdown of the Stokes-Einstein relation between the self- diffusion coefficient and...
A neural network interatomic potential for the phase change material GeTe - Sosso, GC; Miceli, G; Caravati, S; Behler, J; Bernasconi, M
GeTe is a prototypical phase change material of high interest for applications in optical and electronic non-volatile memories. We present an interatomic potential for the bulk phases of GeTe, which is created using a neural network (NN) representation of the potential-energy surface obtained from reference calculations based on density functional theory. It is demonstrated that the NN potential provides a close to ab initio quality description of a number of properties of liquid, crystalline and amorphous GeTe. The availability of a reliable classical potential allows addressing a number of issues of interest for the technological applications of phase change materials,...
The Swift UVOT grism calibration and example spectra - Kuin, P; Breeveld, A; Page, M
The calibration of the two UVOT grisms which provide slitless spectroscopy in the 170-500 nm (UV grism) and 295-660 nm (visible grism) ranges has been completed. The UV grism has a spectral resolution ($\lambda/\Delta\lambda$) of 75 at $\lambda$2600 \AA\ for source magnitudes of u=10-16 mag, while the visible grism has a spectral resolution of 100 at $\lambda$4000 \AA\ for source magnitudes of b=12-17 mag. For brighter spectra, coincidence loss (pile-up) occurs in the photon-counting detector. A correction for the coincidence loss in grism spectra has been developed, and limits have been established above which that correction fails. After discussing the...
Space Telescope and Optical Reverberation Mapping Project. I. Ultraviolet Observations of the Seyfert 1 Galaxy NGC 5548 with the Cosmic Origins Spectrograph on Hubble Space Telescope - Rosa, GD; Peterson, BM; Ely, J; Kriss, GA; Crenshaw, DM; Horne, K; Korista, KT; Netzer, H; Pogge, RW; Arevalo, P; Barth, AJ; Bentz, MC; Brandt, WN; Breeveld, AA; Brewer, BJ; Bonta, ED; Lorenzo-Caceres, AD; Denney, KD; Dietrich, M; Edelson, R; Evans, PA; Fausnaugh, MM; Gehrels, N; Gelbord, JM; Goad, MR; Grier, CJ; Grupe, D; Hall, PB; Kaastra, J; Kelly, BC; Kennea, JA; Kochanek, CS; Lira, P; Mathur, S; McHardy, IM; Nousek, JA; Pancoast, A; Papadakis, I; Pei, L; Schimoia, JS; Siegel, M; Starkey, D; Treu, T; Uttley, P; Vaughan, S; Vestergaard, M; Villforth, C; Yan, H; Young, S; Zu, Y
We describe the first results from a six-month long reverberation-mapping experiment in the ultraviolet based on 170 observations of the Seyfert 1 galaxy NGC 5548 with the Cosmic Origins Spectrograph on the Hubble Space Telescope. Significant correlated variability is found in the continuum and broad emission lines, with amplitudes ranging from ~30% to a factor of two in the emission lines and a factor of three in the continuum. The variations of all the strong emission lines lag behind those of the continuum, with He II 1640 lagging behind the continuum by ~2.5 days and Lyman alpha 1215, C IV...
Space Telescope and Optical Reverberation Mapping Project. II. Swift and HST Reverberation Mapping of the Accretion Disk of NGC 5548 - Edelson, R; Gelbord, JM; Horne, K; McHardy, IM; Peterson, BM; Arevalo, P; Breeveld, AA; DeRosa, G; Evans, PA; Goad, MR; Kriss, GA; Brandt, WN; Gehrels, N; Grupe, D; Kennea, JA; Kochanek, CS; Nousek, JA; Papadakis, I; Siegel, M; Starkey, D; Uttley, P; Vaughan, S; Young, S; Barth, AJ; Bentz, MC; Brewer, BJ; Crenshaw, DM; Bonta, ED; Lorenzo-Caceres, AD; Denney, KD; Dietrich, M; Ely, J; Fausnaugh, MM; Grier, CJ; Hall, PB; Kaastra, J; Kelly, BC; Korista, KT; Lira, P; Mathur, S; Netzer, H; Pancoast, A; Pei, L; Pogge, RW; Schimoia, JS; Treu, T; Vestergaard, M; Villforth, C; Yan, H; Zu, Y
Recent intensive Swift monitoring of the Seyfert 1 galaxy NGC 5548 yielded 282 usable epochs over 125 days across six UV/optical bands and the X-rays. This is the densest extended AGN UV/optical continuum sampling ever obtained, with a mean sampling rate < 0.5-day. Approximately daily HST UV sampling was also obtained. The UV/optical light curves show strong correlations (r_max = 0.57 - 0.90) and the clearest measurement to date of interband lags. These lags are well-fit by a lambda^4/3 wavelength dependence, with a normalization that indicates an unexpectedly large disk size of ~0.35 +/- 0.05 lt-day at 1367 A, assuming...
The Swift-UVOT ultraviolet and visible grism calibration - Kuin, NPM; Landsman, W; Breeveld, AA; Page, MJ; James, C; Lamoureux, H; Mehdipour, M; Still, M; Yershov, V; Brown, PJ; Carter, M; Mason, KO; Kennedy, T; Marshall, F; Roming, PWA; Siegel, M; Oates, S; Smith, PJ; Pasquale, MD
We present the calibration of the Swift UVOT grisms, of which there are two, providing low-resolution field spectroscopy in the ultraviolet and optical bands respectively. The UV grism covers the range 1700-5000 Angstrom with a spectral resolution of 75 at 2600 Angstrom for source magnitudes of u=10-16 mag, while the visible grism covers the range 2850-6600 Angstrom with a spectral resolution of 100 at 4000 Angstrom for source magnitudes of b=12-17 mag. This calibration extends over all detector positions, for all modes used during operations. The wavelength accuracy (1-sigma) is 9 Angstrom in the UV grism clocked mode, 17 Angstrom...
The strength of actinide-element bonds from the quantum theory of atoms-in-molecules. - Huang, QR; Kingham, JR; Kaltsoyannis, N
[AnX(3)](2)(μ-η(2):η(2)-N(2)) (An = Th-Pu; X = F, Cl, Br, Me, H, OPh) have been studied using relativistic density functional theory. Geometric and vibrational data suggest that metal→N(2) charge transfer maximises at the protactinium systems, which feature the longest N-N bonds and the smallest σ(N-N), as a result of partial population of the N-N π* orbitals. There is very strong correlation of the standard quantum theory of atoms-in-molecules (QTAIM) metrics - bond critical point ρ, ∇(2)ρ and H and delocalisation indices - with An-N and N-N bond lengths and σ(N-N), but the correlation with An-N interaction energies is very poor. A...
Against Nietzsche's 'Theory' of the Drives - Stern, TJ
Nietzsche, we are often told, had an account of ‘self’ or ‘mind’ or a ‘philosophical psychology’, in which what he calls our ‘drives’ play a highly significant role. This underpins not merely his understanding of mind—in particular, of consciousness and action—but also his positive ethics, be they understood as authenticity, freedom, (self-)knowledge, autonomy, self-creation, or power. But Nietzsche did not have anything like a coherent account of ‘the drives’ according to which the self, the relationship between thought and action, or consciousness could be explained; consequently, he did not have a stable account of drives on which his positive ethics...