Colorimetry and efficiency of white LEDs : Spectral width dependence

The potential colour rendering capability and efficiency of white LEDs constructed by a combination of individual red, green and blue (RGB) LEDs are analysed. The conventional measurement of colour rendering quality, the colour rendering index (CRI), is used as well as a recently proposed colour quality scale (CQS), designed to overcome some of the limitations of CRI when narrow-band emitters are being studied. The colour rendering performance is maximised by variation of the peak emission wavelength and relative intensity of the component LEDs, with the constraint that the spectral widths follow those measured in actual devices. The highest CRI achieved is 89.5, corresponding to a CQS value of 79, colour temperature of 3800 K and a luminous efficacy of radiation (LER) of 365 lm/W. By allowing the spectral width of the green LED to vary the CRI can be raised to 90.9, giving values of 82.5 and 370 lm/W for the CQS and LER, respectively. The significance of these values are discussed in terms of optimising the possible performance of RGB LEDs

Cosmic Rays from Decaying Vortons

The flux of high energy cosmic rays coming from the decay of vortons is estimated. If the abundance of loops corresponding to a superconductivity scale coincident with that of the string formation is corrected to be compatible with the critical density of universe, it is found that the emission of one carrier per vorton may produce a flux of one cosmic ray event per $km^2$ of detector and per year.Comment: 8 pages, Latex, no figure

Revisiting Parsons: a wartime map classification system in the Digital Age

The Manual of Map Classification and Cataloguing, known colloquially as the ‘Parsons’ classification, is a geographic-based scheme for structuring a map collection using a sequence of alphanumeric classes and subdivisions. The system was published in 1946 after being devised by Captain Edward J.S. Parsons RE, the inaugural Curator of Maps at the Bodleian Library, University of Oxford. Although originally adopted by Parsons within the map collection of the British War Office, the system was later used to classify the Bodleian’s own map collections, where it remains the basis of the organization of over two million maps, atlases and cartographic books today. This paper explores how the role of the Parsons classification within the Bodleian Library has changed significantly since its genesis in the 1940s. It then outlines recent work undertaken at the library to consolidate and digitize the system so that it better serves a map collection whose infrastructure is now largely digital

The Rent-Price Ratio for the Aggregate Stock of Owner-Occupied Housing

We construct a time series of the rent-price ratio for the owner- occupied stock of housing, starting in 1960:1, by merging micro data from the last five Decennial Censuses of Housing with price indexes for house prices and rents.House Prices, Housing, Rents, CMHPI, Capitalization Rates

Molecular Gas Properties of the Giant Molecular Cloud Complexes in the Arms and Inter-arms of the Spiral Galaxy NGC 6946

Combining observations of multiple CO lines with radiative transfer modeling is a very powerful tool to investigate the physical properties of the molecular gas in galaxies. Using new observations as well as literature data, we provide the most complete CO ladders ever generated for eight star-forming regions in the spiral arms and inter-arms of the spiral galaxy NGC 6946, with observations of the CO(1-0), CO(2-1), CO(3-2), CO(4-3), CO(6-5), 13CO(1-0) and 13CO(2-1) transitions. For each region, we use the large velocity gradient assumption to derive beam-averaged molecular gas physical properties, namely the gas kinetic temperature (T_K), H2 number volume density n(H2) and CO number column density N(CO). Two complementary approaches are used to compare the observations with the model predictions: chi-square minimisation and likelihood. The physical conditions derived vary greatly from one region to the next: T_K=10-250 K, n(H2)=10^2.3-10^7.0 cm^-3 and N(CO)=10^15.0-10^19.3 cm^-2. The spectral line energy distribution (SLED) of some of these extranuclear regions indicates a star-formation activity that is more intense than that at the centre of our own Milky Way. The molecular gas in regions with a large SLED turnover transition (J_max>4) is hot but tenuous with a high CO column density, while that in regions with a low SLED turnover transition (J_max<=4) is cold but dense with a low CO column density. We finally discuss and find some correlations between the physical properties of the molecular gas in each region and the presence of young stellar population indicators (supernova remnants, HII regions, HI holes, etc.)Comment: 23 pages, 11 figures, MNRAS, Accepte

Combination of geodetic observations and models for glacial isostatic adjustment fields in Fennoscandia

We demonstrate a new technique for using geodetic data to update a priori predictions for Glacial Isostatic Adjustment (GIA) in the Fennoscandia region. Global Positioning System (GPS), tide gauge, and Gravity Recovery and Climate Experiment (GRACE) gravity rates are assimilated into our model. The technique allows us to investigate the individual contributions from these data sets to the output GIA model in a self-consistent manner. Another benefit of the technique is that we are able to estimate uncertainties for the output model. These are reduced with each data set assimilated. Any uncertainties in the GPS reference frame are absorbed by reference frame adjustments that are estimated as part of the assimilation. Our updated model shows a spatial pattern and magnitude of peak uplift that is consistent with previous models, but our location of peak uplift is slightly to the east of many of these. We also simultaneously estimate a spatially averaged rate of local sea level rise. This regional rate (similar to 1.5 mm/yr) is consistent for all solutions, regardless of which data sets are assimilated or the magnitude of a priori GPS reference frame constraints. However, this is only the case if a uniform regional gravity rate, probably representing errors in, or unmodeled contributions to, the low-degree harmonic terms from GRACE, is also estimated for the assimilated GRACE data. Our estimated sea level rate is consistent with estimates obtained using a more traditional approach of direct "correction" using collocated GPS and tide gauge site

A black-hole mass measurement from molecular gas kinematics in NGC4526

The masses of the supermassive black-holes found in galaxy bulges are correlated with a multitude of galaxy properties, leading to suggestions that galaxies and black-holes may evolve together. The number of reliably measured black-hole masses is small, and the number of methods for measuring them is limited, holding back attempts to understand this co-evolution. Directly measuring black-hole masses is currently possible with stellar kinematics (in early-type galaxies), ionised-gas kinematics (in some spiral and early-type galaxies) and in rare objects which have central maser emission. Here we report that by modelling the effect of a black-hole on the kinematics of molecular gas it is possible to fit interferometric observations of CO emission and thereby accurately estimate black hole masses. We study the dynamics of the gas in the early-type galaxy NGC4526, and obtain a best fit which requires the presence of a central dark-object of 4.5(+4.2-3.0)x10^8 Msun (3 sigma confidence limit). With next generation mm-interferometers (e.g. ALMA) these observations could be reproduced in galaxies out to 75 megaparsecs in less the 5 hours of observing time. The use of molecular gas as a kinematic tracer should thus allow one to estimate black-hole masses in hundreds of galaxies in the local universe, many more than accessible with current techniques.Comment: To appear in Nature online on 30/01/2013. 3 Pages, 2 Figures (plus two pages of supplementary information