125 research outputs found
Nonresonant self-injection seeding of a gain-switched diode laser
We demonstrate step-tunable single-mode operation of a gain-switched diode laser by nonresonant self-injection seeding from an uncoated glass slide used as an external cavity reflector. A spectral bandwidth reduction from 11 mn to 0.05 nm and wavelength tunability has been achieved for picosecond (near-transform-limited) pulses with little effect on other laser characteristics. Good agreement with numerical simulations based on a compound-cavity laser model is also reported
Estimating Small Area Income Deprivation: An Iterative Proportional Fitting Approach
Small area estimation and in particular the estimation of small area income deprivation has
potential value in the development of new or alternative components of multiple deprivation
indices. These new approaches enable the development of income distribution threshold based
as opposed to benefit count based measures of income deprivation and so enable the
alignment of regional and national measures such as the Households Below Average Income
with small area measures. This paper briefly reviews a number of approaches to small area
estimation before describing in some detail an iterative proportional fitting based spatial
microsimulation approach. This approach is then applied to the estimation of small area HBAI
rates at the small area level in Wales in 2003-5. The paper discusses the results of this
approach, contrasts them with contemporary ‘official’ income deprivation measures for the
same areas and describes a range of ways to assess the robustness of the results
The emerging geography of e-commerce in British retailing
This paper explores the growth of e-commerce in British grocery retailing and examines the spatial variations in e-commerce usage. The main data source is a large commercial consumer survey (Acxiom’s Research Opinion Data) rarely used by academics to date. Using these data in combination with census data, the paper addresses a number of key questions. After outlining key trends in the dataset on e-commerce usage (by product and over time) the first research question is: How do e-commerce purchases vary by geodemographic group? To answer this question, we explore e-commerce usage by age, sex and social class. The second key question is: Does e-commerce usage vary by type of geographical region? Thus, we explore variations in usage for urban and rural areas. The dynamics of urban–rural diffusion are also addressed here – by examining, in addition, the spread of broadband use across Britain. The last question is: To what degree do e-commerce sales vary by access to physical stores? This is addressed by examining consumers’ home locations in relation to geographical accessibility. The results show that age and income are crucial demographic discriminators of e-commerce usage, as is rural location versus urban, and distance from physical stores
Developing an Individual-level Geodemographic Classification
Geodemographics is a spatially explicit classification of socio-economic data, which can be used to describe and analyse individuals by where they live. Geodemographic information is used by the public sector for planning and resource allocation but it also has considerable use within commercial sector applications. Early geodemographic systems, such as the UK’s ACORN (A Classification of Residential Neighbourhoods), used only area-based census data, but more recent systems have added supplementary layers of information, e.g. credit details and survey data, to provide better discrimination between classes. Although much more data has now become available, geodemographic systems are still fundamentally built from area-based census information. This is partly because privacy laws require release of census data at an aggregate level but mostly because much of the research remains proprietary. Household level classifications do exist but they are often based on regressions between area and household data sets. This paper presents a different approach for creating a geodemographic classification at the individual level using only census data. A generic framework is presented, which classifies data from the UK Census Small Area Microdata and then allocates the resulting clusters to a synthetic population created via microsimulation. The framework is then applied to the creation of an individual-based system for the city of Leeds, demonstrated using data from the 2001 census, and is further validated using individual and household survey data from the British Household Panel Survey
Energy Density of Non-Minimally Coupled Scalar Field Cosmologies
Scalar fields coupled to gravity via in arbitrary
Friedmann-Robertson-Walker backgrounds can be represented by an effective flat
space field theory. We derive an expression for the scalar energy density where
the effective scalar mass becomes an explicit function of and the scale
factor. The scalar quartic self-coupling gets shifted and can vanish for a
particular choice of . Gravitationally induced symmetry breaking and
de-stabilization are possible in this theory.Comment: 18 pages in standard Late
Enabling quantitative data analysis through e-infrastructures
This paper discusses how quantitative data analysis in the social sciences can engage with and exploit an e-Infrastructure. We highlight how a number of activities which are central to quantitative data analysis, referred to as ‘data management’, can benefit from e-infrastructure support. We conclude by discussing how these issues are relevant to the DAMES (Data Management through e-Social Science) research Node, an ongoing project that aims to develop e-Infrastructural resources for quantitative data analysis in the social sciences
KAOSS: turbulent, but disc-like kinematics in dust-obscured star-forming galaxies at z ∼ 1.3–2.6
We present spatially resolved kinematics of 27 ALMA-identified dust-obscured star-forming galaxies (DSFGs) at z ∼ 1.3–2.6, as traced by Hα emission using VLT/KMOS near-infrared integral field spectroscopy from the ‘KMOS-ALMA Observations of Submillimetre Sources’ (KAOSS) Large Programme. We derive Hα rotation curves and velocity dispersion profiles for the DSFGs, and find that among the 27 sources with bright, spatially extended Hα emission, 24 display evidence for disc-like kinematics. We measure a median inclination-corrected velocity at 2.2 Rd of vrot = 190 ± 40 km s−1 and intrinsic velocity dispersion of σ0 = 87 ± 6 km s−1 for these disc-like sources. The kinematics yield median circular velocities of vcirc = 230 ± 20 km s−1 and dynamical masses within 2Re (∼ 7 kpc radius) of Mdyn = (1.1 ± 0.2) × 1011 M⊙. Compared to less actively star-forming galaxies, KAOSS DSFGs are both faster rotating with higher intrinsic velocity dispersions, but have similar vrot/σ0 ratios, median v/σ0 = 2.5 ± 0.5. We suggest that the kinematics of the DSFGs are primarily rotation supported but with a non-negligible contribution from pressure support, which may be driven by star formation or mergers/interactions. We estimate the normalization of the stellar mass Tully–Fisher relation (sTFR) for the disc-like DSFGs and compare it with local studies, finding no evolution at fixed slope between z ∼ 2 and z ∼ 0. Finally, we show that the kinematic properties of the DSFG population are consistent with them evolving into massive early-type galaxies, the dominant z ∼ 0 population at these masses
KAOSS: turbulent, but disc-like kinematics in dust-obscured star-forming galaxies at 1.3-2.6
We present spatially resolved kinematics of 31 ALMA-identified dust-obscured
star-forming galaxies (DSFGs) at 1.3-2.6, as traced by H
emission using VLT/KMOS near-infrared integral field spectroscopy from our
on-going Large Programme ''KMOS-ALMA Observations of Submillimetre Sources''
(KAOSS). We derive H rotation curves and velocity dispersion profiles
for the DSFGs. Of the 31 sources with bright, spatially extended H
emission, 25 display rotation curves that are well fit by a Freeman disc model,
enabling us to measure a median inclination-corrected velocity at 2.2 of = 190 30 kms and a median intrinsic velocity
dispersion of = 87 6 kms for these
sources. By comparison with less actively star-forming galaxies, KAOSS DSFGs
are both faster rotating and more turbulent, but have similar ratios, median 2.4 0.5. We suggest that alone is insufficient to describe the kinematics of DSFGs, which
are not kinematically ''cold'' discs, and that the individual components
and indicate that they are in fact turbulent, but
rotationally supported systems in 50 per cent of cases. This turbulence
may be driven by star formation or mergers/interactions. We estimate the
normalisation of the stellar Tully-Fisher relation (sTFR) for the disc-like
DSFGs and compare it with local studies, finding no evolution at fixed slope
between 2 and 0. Finally, we use kinematic estimates of DSFG halo
masses to investigate the stellar-to-halo mass relation, finding our sources to
be consistent with shock heating and strong feedback which likely drives the
declining stellar content in the most massive halos.Comment: 20 pages, 12 figures, submitted to MNRAS, updated author lis
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