Inorganic Surface Passivation of PbS Nanocrystals resulting in Strong Photoluminescent Emission

Strong photoluminescent emission has been obtained from 3 nm PbS nanocrystals in aqueous colloidal solution, following treatment with CdS precursors. The observed emission can extend across the entire visible spectrum and usually includes a peak near 1.95 eV. We show that much of the visible emission results from absorption by higher-lying excited states above 3.0 eV with subsequent relaxation to and emission from states lying above the observed band-edge of the PbS nanocrystals. The fluorescent lifetimes for this emission are in the nanosecond regime, characteristic of exciton recombination.Comment: Preprint, 23 pages, 6 figure

A Combined EIS-NVSS Survey Of Radio Sources (CENSORS) III: Spectroscopic observations

The Combined EIS-NVSS Survey Of Radio Sources (CENSORS) is a 1.4GHz radio survey selected from the NRAO VLA Sky Survey (NVSS) and complete to a flux-density of 7.2mJy. It targets the ESO Imaging Survey (EIS) Patch D, which is a 3 by 2 square degree field centred on 09 51 36.0, -21 00 00 (J2000). This paper presents the results of spectroscopic observations of 143 of the 150 CENSORS sources. The primary motivation for these observations is to achieve sufficient spectroscopic completeness so that the sample may be used to investigate the evolution of radio sources. The observations result in secure spectroscopic redshifts for 63% of the sample and likely redshifts (based on a single emission line, for example) for a further 8%. Following the identification of the quasars and star-forming galaxies in the CENSORS sample, estimated redshifts are calculated for the remainder of the sample via the K-z relation for radio galaxies. Comparison of the redshift distribution of the CENSORS radio sources to distributions predicted by the various radio luminosity function evolution models of Dunlop & Peacock 1990, results in no good match. This demonstrates that this sample can be used to expand upon previous work in that field.Comment: Accepted for publication in MNRAS. This version has some reduced resolution figures and 13 associated gif files. A version with all figures incorporated (at full resolution) is available at http://www.roe.ac.uk/~pnb/papers/censors_spectro.pd

Direct imaging of a digital-micromirror device for configurable microscopic optical potentials

Programable spatial light modulators (SLMs) have significantly advanced the configurable optical trapping of particles. Typically, these devices are utilized in the Fourier plane of an optical system, but direct imaging of an amplitude pattern can potentially result in increased simplicity and computational speed. Here we demonstrate high-resolution direct imaging of a digital micromirror device (DMD) at high numerical apertures (NA), which we apply to the optical trapping of a Bose-Einstein condensate (BEC). We utilise a (1200 x 1920) pixel DMD and commercially available 0.45 NA microscope objectives, finding that atoms confined in a hybrid optical/magnetic or all-optical potential can be patterned using repulsive blue-detuned (532 nm) light with 630(10) nm full-width at half-maximum (FWHM) resolution, within 5% of the diffraction limit. The result is near arbitrary control of the density the BEC without the need for expensive custom optics. We also introduce the technique of time-averaged DMD potentials, demonstrating the ability to produce multiple grayscale levels with minimal heating of the atomic cloud, by utilising the high switching speed (20 kHz maximum) of the DMD. These techniques will enable the realization and control of diverse optical potentials for superfluid dynamics and atomtronics applications with quantum gases. The performance of this system in a direct imaging configuration has wider application for optical trapping at non-trivial NAs.Comment: 9 page

Towards efficient modelling of optical micromanipulation of complex structures

Computational methods for electromagnetic and light scattering can be used for the calculation of optical forces and torques. Since typical particles that are optically trapped or manipulated are on the order of the wavelength in size, approximate methods such as geometric optics or Rayleigh scattering are inapplicable, and solution or either the Maxwell equations or the vector Helmholtz equation must be resorted to. Traditionally, such solutions were only feasible for the simplest geometries; modern computational power enable the rapid solution of more general--but still simple--geometries such as axisymmetric, homogeneous, and isotropic scatterers. However, optically-driven micromachines necessarily require more complex geometries, and their computational modelling thus remains in the realm of challenging computational problems. We review our progress towards efficient computational modelling of optical tweezers and micromanipulation, including the trapping and manipulation of complex structures such as optical micromachines. In particular, we consider the exploitation of symmetry in the modelling of such devices.Comment: 5 pages, 4 figure

The final two redshifts for radio sources from the equatorial BRL sample

Best, Rottgering and Lehnert (1999, 2000a) defined a new sample of powerful radio sources from the Molonglo Reference Catalogue, for which redshifts were compiled or measured for 177 of the 178 objects. For the final object, MRC1059-010 (3C249), the host galaxy is here identified using near-infrared imaging, and the redshift is determined from VLT spectroscopy. For one other object in the sample, MRC0320+053 (4C05.14), the literature redshift has been questioned: new spectroscopic observations of this object are presented, deriving a corrected redshift. With these two results, the spectroscopic completeness of this sample is now 100%. New redshifts are also presented for PKS0742+10 from the Wall & Peacock 2.7 GHz catalogue, and PKS1336+003 from the Parkes Selected Regions. PKS0742+10 shows a strong neutral hydrogen absorption feature in its Lyman-alpha emission profile.Comment: 4 pages. LaTeX. Accepted for publication in MNRA

Fringe spacing and phase of interfering matter waves

We experimentally investigate the outcoupling of atoms from Bose-Einstein condensates using two radio-frequency (rf) fields in the presence of gravity. We show that the fringe separation in the resulting interference pattern derives entirely from the energy difference between the two rf fields and not the gravitational potential difference. We subsequently demonstrate how the phase and polarisation of the rf radiation directly control the phase of the matter wave interference and provide a semi-classical interpretation of the results.Comment: 4 pages, 3 figure

T-PHOT version 2.0: improved algorithms for background subtraction, local convolution, kernel registration, and new options

We present the new release v2.0 of T-PHOT, a publicly available software package developed to perform PSF-matched, prior-based, multiwavelength deconfusion photometry of extragalactic fields. New features included in the code are presented and discussed: background estimation, fitting using position dependent kernels, flux prioring, diagnostical statistics on the residual image, exclusion of selected sources from the model and residual images, individual registration of fitted objects. These new options improve on the performance of the code, allowing for more accurate results and providing useful aids for diagnostics.Comment: 7 pages, 8 figure

Histopathologic parameters as predictors of response to endoscopic sinus surgery in nonallergic patients with chronic rhinosinusitis

OBJECTIVE: To estimate the predictable value of histopathologic parameters in chronic rhinosinusitis (CRS) for response to endoscopic sinus surgery (ESS). - - - - - STUDY DESIGN: Symptomatology was rated in 100 patients prior to as well as 12 and 24 months after surgery. Specimens taken during the procedure were examined and scored for goblet cells, subepithelial thickening, mast cells, and eosinophils. Multiple regression analysis was performed to predict the total score of subjective symptoms before treatment by histopathologic parameters. The correlation between histopathologic parameters and postoperative symptoms was then evaluated. - - - - - RESULTS: Goblet cells were the best predictor correlating with 5 symptoms. Subepithelial thickening correlated with 4 symptoms. Mast cell infiltration correlated with 3 symptoms. Eosinophilic infiltration correlated with only one symptom (P<0.05). - - - - - CONCLUSION: Certain histopathologic parameters in CRS are predictive of favorable response to ESS. - - - - - SIGNIFICANCE: Pathologic evaluation may help the ENT surgeon to predict the persistence of certain CRS symptoms after ESS, even in patients at low risk for surgical failure. - - - - - EBM rating: C-4