3,869 research outputs found
Utility Cost of Formal Privacy for Releasing National Employer-Employee Statistics
National statistical agencies around the world publish tabular summaries based on combined employer-employee (ER-EE) data. The privacy of both individuals and business establishments that feature in these data are protected by law in most countries. These data are currently released using a variety of statistical disclosure limitation (SDL) techniques that do not reveal the exact characteristics of particular employers and employees, but lack provable privacy guarantees limiting inferential disclosures. In this work, we present novel algorithms for releasing tabular summaries of linked ER-EE data with formal, provable guarantees of privacy. We show that state-of-the-art differentially private algorithms add too much noise for the output to be useful. Instead, we identify the privacy requirements mandated by current interpretations of the relevant laws, and formalize them using the Pufferfish framework. We then develop new privacy definitions that are customized to ER-EE data and satisfy the statutory privacy requirements. We implement the experiments in this paper on production data gathered by the U.S. Census Bureau. An empirical evaluation of utility for these data shows that for reasonable values of the privacy-loss parameter Ļµā„1, the additive error introduced by our provably private algorithms is comparable, and in some cases better, than the error introduced by existing SDL techniques that have no provable privacy guarantees. For some complex queries currently published, however, our algorithms do not have utility comparable to the existing traditiona
Genomic analysis of the role of transcription factor C/EBPĪ“ in the regulation of cell behaviour on nanometric grooves
C/EBPĪ“ is a tumour suppressor transcription factor that induces gene expression involved in suppressing cell migration. Here we investigate whether C/EBPĪ“-dependent gene expression also affects cell responses to nanometric topology. We found that ablation of the C/EBPĪ“ gene in mouse embryonal fibroblasts (MEFs) decreased cell size, adhesion and cytoskeleton spreading on 240 nm and 540 nm nanometric grooves. ChIP-SEQ and cDNA microarray analyses demonstrated that many binding sites for C/EBPĪ“, and the closely related C/EBPĪ², exist throughout the mouse genome and control the upregulation or downregulation of many adjacent genes. We also identified a group of C/EBPĪ“-dependent, trans-regulated genes, whose promoters contained no C/EBPĪ“ binding sites and yet their activity was regulated in a C/EBPĪ“-dependent manner. These genes include signalling molecules (e.g. SOCS3), cytoskeletal components (Tubb2, Krt16 and Krt20) and cytoskeletal regulators (ArhGEF33 and Rnd3) and are possibly regulated by cis-regulated diffusible mediators, such as IL6. Of particular note, SOCS3 was shown to be absolutely required for efficient cell spreading and contact guidance on 240 nm and 540 nm nanometric grooves. C/EBPĪ“ is therefore involved in the complex regulation of multiple genes, including cytoskeletal components and signalling mediators, which influence the nature of cell interactions with nanometric topology
Parameter Estimation with Increased Precision for Elliptic and Hypo-elliptic Diffusions
This work aims at making a comprehensive contribution in the general area of
parametric inference for discretely observed diffusion processes. Established
approaches for likelihood-based estimation invoke a time-discretisation scheme
for the approximation of the intractable transition dynamics of the Stochastic
Differential Equation (SDE) model over finite time periods. The scheme is
applied for a step-size that is either user-selected or determined by the data.
Recent research has highlighted the critical ef-fect of the choice of numerical
scheme on the behaviour of derived parameter estimates in the setting of
hypo-elliptic SDEs. In brief, in our work, first, we develop two weak second
order sampling schemes (to cover both hypo-elliptic and elliptic SDEs) and
produce a small time expansion for the density of the schemes to form a proxy
for the true intractable SDE transition density. Then, we establish a
collection of analytic results for likelihood-based parameter estimates
obtained via the formed proxies, thus providing a theoretical framework that
showcases advantages from the use of the developed methodology for SDE
calibration. We present numerical results from carrying out classical or
Bayesian inference, for both elliptic and hypo-elliptic SDEs
Sub-shot-noise shadow sensing with quantum correlations
The quantised nature of the electromagnetic field sets the classical limit to the sensitivity of position measurements. However, techniques based on the properties of quantum states can be exploited to accurately measure the relative displacement of a physical object beyond this classical limit. In this work, we use a simple scheme based on the split-detection of quantum correlations to measure the position of a shadow at the single-photon light level, with a precision that exceeds the shot-noise limit. This result is obtained by analysing the correlated signals of bi-photon pairs, created in parametric downconversion and detected by an electron multiplying CCD (EMCCD) camera employed as a split-detector. By comparing the measured statistics of spatially anticorrelated and uncorrelated photons we were able to observe a significant noise reduction corresponding to an improvement in position sensitivity of up to 17% (0.8dB). Our straightforward approach to sub-shot-noise position measurement is compatible with conventional shadow-sensing techniques based on the split-detection of light-fields, and yields an improvement that scales favourably with the detectorās quantum efficiency
Compatibility of the large quasar groups with the concordance cosmological model
We study the compatibility of large quasar groups with the concordance cosmological model. Large quasar groups are very large spatial associations of quasars in the cosmic web, with sizes of 50ā250 hā1 Mpc. In particular, the largest large quasar group known, named Huge-LQG, has a longest axis of ā¼860 hā1 Mpc, larger than the scale of homogeneity (ā¼260 Mpc), which has been noted as a possible violation of the cosmological principle. Using mock catalogues
constructed from the Horizon Run 2 cosmological simulation, we found that large quasar groups size, quasar member number and mean overdensity distributions in the mocks agree with observations. The Huge-LQG is found to be a rare group with a probability of 0.3 per cent of finding a group as large or larger than the observed, but an extreme value analysis shows that it is an expected maximum in the sample volume with a probability of 19 per cent of observing a largest quasar group as large or larger than Huge-LQG. The Huge-LQG is expected to be the largest structure in a volume at least 5.3 Ā± 1 times larger than the one currently studied
Adaptive foveated single-pixel imaging with dynamic super-sampling
As an alternative to conventional multi-pixel cameras, single-pixel cameras
enable images to be recorded using a single detector that measures the
correlations between the scene and a set of patterns. However, to fully sample
a scene in this way requires at least the same number of correlation
measurements as there are pixels in the reconstructed image. Therefore
single-pixel imaging systems typically exhibit low frame-rates. To mitigate
this, a range of compressive sensing techniques have been developed which rely
on a priori knowledge of the scene to reconstruct images from an under-sampled
set of measurements. In this work we take a different approach and adopt a
strategy inspired by the foveated vision systems found in the animal kingdom -
a framework that exploits the spatio-temporal redundancy present in many
dynamic scenes. In our single-pixel imaging system a high-resolution foveal
region follows motion within the scene, but unlike a simple zoom, every frame
delivers new spatial information from across the entire field-of-view. Using
this approach we demonstrate a four-fold reduction in the time taken to record
the detail of rapidly evolving features, whilst simultaneously accumulating
detail of more slowly evolving regions over several consecutive frames. This
tiered super-sampling technique enables the reconstruction of video streams in
which both the resolution and the effective exposure-time spatially vary and
adapt dynamically in response to the evolution of the scene. The methods
described here can complement existing compressive sensing approaches and may
be applied to enhance a variety of computational imagers that rely on
sequential correlation measurements.Comment: 13 pages, 5 figure
Measure Transport with Kernel Stein Discrepancy
Measure transport underpins several recent algorithms for posterior approximation in the Bayesian context, wherein a transport map is sought to minimise the Kullback--Leibler divergence (KLD) from the posterior to the approximation. The KLD is a strong mode of convergence, requiring absolute continuity of measures and placing restrictions on which transport maps can be permitted. Here we propose to minimise a kernel Stein discrepancy (KSD) instead, requiring only that the set of transport maps is dense in an sense and demonstrating how this condition can be validated. The consistency of the associated posterior approximation is established and empirical results suggest that KSD is competitive and more flexible alternative to KLD for measure transport
- ā¦