4,018 research outputs found
An Age-Period-Cohort Database of Inter-Regional Migration in Australia and Britain, 1976-96
Report prepared as part of a collaborative project on "Migration Trends in Australia and Britain: Levels and Trends in an Age-Period-Cohort Framework" funded by the Economic and Social Research Council and the Australian Research Council.
This paper describes the way in which parallel databases of inter-regional migration flows for Australia and Britain, classified by five year ages and birth cohorts for four five year periods between 1976 and 1996. The data processing involves estimation of migration data for comparable spatial units, the reduction of the number of those units to a reduced set for ease of analysis, the extraction of migration data from official data files supplied by the Australian Bureau of Statistics and the Office for National Statistics, and the filling of gaps in these files through iterative proportional fitting for some of the British data. The final stage in preparation of the migration databases was to estimate the numbers of transitions (Australia) or movements (Britain) for age-period-cohort spaces. In principle, this last estimation involves a fairly simple interpolation or aggregation of age-time classified migration data, but in practice a great deal of detailed attention is required. A final section specifies the populations at risk to be used for each age-period-cohort observation plan to compute migration intensities
Harmonising Databases for the Cross National Study of Internal Migration: Lessons from Australia and Britain
This project involves the development of a Web interface to origin-destination statistics from the 1991 Census (in a form that will be compatible with planned 2001 outputs). It provides the user with a set of screen-based tools for setting the parameters governing each data extraction (data set, areas, variables) in the form of a query. Traffic light icons are used to signal what the user has set so far and what remains to be done. There are options to extract different types of flow data and to generate output in different formats. The system can now be used to access the interaction flow data contained in the 1991 Special Migration Statistics Sets 1 and 2 and Special Workplace Statistics Set C. WICID has been demonstrated at the Origin-Destination Statistics Roadshows organised by GRO Scotland and held during May/June 2000 and the Census Offices have expressed interest in using the software in the Census Access Project
Systems, interactions and macrotheory
A significant proportion of early HCI research was guided by one very clear vision: that the existing theory base in psychology and cognitive science could be developed to yield engineering tools for use in the interdisciplinary context of HCI design. While interface technologies and heuristic methods for behavioral evaluation have rapidly advanced in both capability and breadth of application, progress toward deeper theory has been modest, and some now believe it to be unnecessary. A case is presented for developing new forms of theory, based around generic “systems of interactors.” An overlapping, layered structure of macro- and microtheories could then serve an explanatory role, and could also bind together contributions from the different disciplines. Novel routes to formalizing and applying such theories provide a host of interesting and tractable problems for future basic research in HCI
Equidistribution of Heegner Points and Ternary Quadratic Forms
We prove new equidistribution results for Galois orbits of Heegner points
with respect to reduction maps at inert primes. The arguments are based on two
different techniques: primitive representations of integers by quadratic forms
and distribution relations for Heegner points. Our results generalize one of
the equidistribution theorems established by Cornut and Vatsal in the sense
that we allow both the fundamental discriminant and the conductor to grow.
Moreover, for fixed fundamental discriminant and variable conductor, we deduce
an effective surjectivity theorem for the reduction map from Heegner points to
supersingular points at a fixed inert prime. Our results are applicable to the
setting considered by Kolyvagin in the construction of the Heegner points Euler
system
Surface nano-patterning through styrene adsorption on Si(100)
We present an ab initio study of the structural and electronic properties of
styrene molecules adsorbed on the dimerized Si(100) surface at different
coverages, ranging from the single-molecule to the full monolayer. The
adsorption mechanism primarily involves the vinyl group via a [2+2]
cycloaddition process that leads to the formation of covalent Si-C bonds and a
local surface derelaxation, while it leaves the phenyl group almost
unperturbed. The investigation of the functionalized surface as a function of
the coverage (e.g. 0.5 -- 1 ML) and of the substrate reconstruction reveals two
major effects. The first results from Si dimer-vinyl interaction and concerns
the controlled variation of the energy bandgap of the interface. The second is
associated to phenyl-phenyl interactions, which gives rise to a regular pattern
of electronic wires at surface, stemming from the pi-pi coupling. These
findings suggest a rationale for tailoring the surface nano-patterning of the
surface, in a controlled way.Comment: 19 pages (preprint), 4 figures, supplementary materia
Gel-Electrophoresis and Diffusion of Ring-Shaped DNA
A model for the motion of ring-shaped DNA in a gel is introduced and studied
by numerical simulations and a mean-field approximation. The ring motion is
mediated by finger-shaped loops (hernias) that move in an amoeba-like fashion
around the gel obstructions. This constitutes an extension of previous
reptation tube treatments. It is shown that tension is essential for describing
the dynamics in the presence of hernias. It is included in the model as long
range interactions over stretched DNA regions. The mobility of ring-shaped DNA
is found to saturate much as in the well-studied case of linear DNA.
Experiments in polymer gels, however, show that the mobility drops
exponentially with the DNA ring size. This is commonly attributed to
dangling-ends in the gel that can impale the ring. The predictions of the
present model are expected to apply to artificial 2D obstacle arrays (W.D.
Volkmuth, R.H. Austin, Nature 358,600 (1992)) which have no dangling-ends. In
the zero-field case an exact solution of the model steady-state is obtained,
and quantities such as the average ring size are calculated. An approximate
treatment of the ring dynamics is given, and the diffusion coefficient is
derived. The model is also discussed in the context of spontaneous symmetry
breaking in one dimension.Comment: 8 figures, LaTeX, Phys. Rev. E - in pres
Magnetic Diode Effect in Double Barrier Tunnel Junctions
A quantum statistical theory of spin-dependent tunneling through asymmetric
magnetic double barrier junctions is presented which describes ballistic
and diffuse tunneling by a single analytical expression. It is evidenced that
the key parameter for the transition between these two tunneling regimes is the
electron scattering. For these junctions a strong asymmetric behaviour in the
I-V characteristics and the tunnel magnetoresistance (TMR) is predicted which
can be controlled by an applied magnetic field. This phenomenon relates to the
quantum well states in the middle metallic layer. The corresponding resonances
in the current and the TMR are drastically phase shifted under positive and
negative voltage.Comment: 10 pages, 4 Postscript figures, submitted to Europhys. Let
Modelling Molecular Motors as Folding-Unfolding Cycles
We propose a model for motor proteins based on a hierarchical Hamiltonian
that we have previously introduced to describe protein folding. The proposed
motor model has high efficiency and is consistent with a linear load-velocity
response. The main improvement with respect to previous models is that this
description suggests a connection between folding and function of allosteric
proteins.Comment: 5 pages RevTeX, 2 Postscript figures, replaced due to LaTeX proble
- …