11,694 research outputs found
SenseCam image localisation using hierarchical SURF trees
The SenseCam is a wearable camera that automatically takes photos of the wearer's activities, generating thousands of images per day.
Automatically organising these images for efficient search and retrieval is a challenging task, but can be simplified by providing
semantic information with each photo, such as the wearer's location during capture time. We propose a method for automatically determining the wearer's location using an annotated image database, described using SURF interest point descriptors. We show that SURF out-performs SIFT in matching SenseCam images and that matching can be done efficiently using hierarchical trees of SURF descriptors. Additionally, by re-ranking the top images using bi-directional SURF matches, location matching performance is improved further
The Impact of Gender and Location on the Willingness to Accept Overseas Assignments
Abstract: Business students in two universities were queried regarding their willingness to accept international postings. In contrast to Adler's (1984a, 19 86) findings, gender was a significant predictor when specific referent countries were identified. Country characteristics considered here included cultural distance (or the difference between the cultures of the respondent's home country and that of the referent location) and the levels of development and political risk in the referent country. Differences among countries on indices of cultural distance and human development explained substantial variance among males and females in their willingness to accept international assignments. Political risk, however, was not significant in explaining these gender differences
Affine Subspace Representation for Feature Description
This paper proposes a novel Affine Subspace Representation (ASR) descriptor
to deal with affine distortions induced by viewpoint changes. Unlike the
traditional local descriptors such as SIFT, ASR inherently encodes local
information of multi-view patches, making it robust to affine distortions while
maintaining a high discriminative ability. To this end, PCA is used to
represent affine-warped patches as PCA-patch vectors for its compactness and
efficiency. Then according to the subspace assumption, which implies that the
PCA-patch vectors of various affine-warped patches of the same keypoint can be
represented by a low-dimensional linear subspace, the ASR descriptor is
obtained by using a simple subspace-to-point mapping. Such a linear subspace
representation could accurately capture the underlying information of a
keypoint (local structure) under multiple views without sacrificing its
distinctiveness. To accelerate the computation of ASR descriptor, a fast
approximate algorithm is proposed by moving the most computational part (ie,
warp patch under various affine transformations) to an offline training stage.
Experimental results show that ASR is not only better than the state-of-the-art
descriptors under various image transformations, but also performs well without
a dedicated affine invariant detector when dealing with viewpoint changes.Comment: To Appear in the 2014 European Conference on Computer Visio
Positron emission tomography PET/CT harmonisation study of different clinical PET/CT scanners using commercially available software
Objectives: Harmonisation is the process whereby
standardised uptake values from different scanners can
be made comparable. This PET/CT pilot study aimed to
evaluate the effectiveness of harmonisation of a modern
scanner with image reconstruction incorporating resolution recovery (RR) with another vendor older scanner operated in two-dimensional (2D) mode, and for both against a European standard (EARL). The vendor-proprietary software EQ•PET was used, which achieves harmonisation with a Gaussian smoothing. A substudy investigated effect of RR on harmonisation.
Methods: Phantom studies on each scanner were
performed to optimise the smoothing parameters
required to achieve successful harmonisation. 80
patients were retrospectively selected; half were imaged
on each scanner. As proof of principle, a cohort of 10
patients was selected from the modern scanner subjects
to study the effects of RR on harmonisation.
Results: Before harmonisation, the modern scanner
without RR adhered to EARL specification. Using the
phantom data, filters were derived for optimal harmonisation between scanners and with and without RR as
applicable, to the EARL standard. The 80-patient
cohort did not reveal any statistically significant differences. In the 10-patient cohort SUVmax for RR > no RR irrespective of harmonisation but differences lacked statistical significance (one-way ANOVA F(3.36) = 0.37, p = 0.78). Bland-Altman analysis showed that harmonisation reduced the SUVmax ratio between RR and no RR to 1.07 (95% CI 0.96–1.18) with no outliers.
Conclusions: EQ•PET successfully enabled harmonisation
between modern and older scanners and against
the EARL standard. Harmonisation reduces SUVmax and
dependence on the use of RR in the modern scanner.
Advances in knowledge: EQ•PET is feasible to harmonise
different PET/CT scanners and reduces the effect of
RR on SUVmax
Matrix Regularization of an Open Supermembrane ---towards M-theory five-branes via open supermembranes ---
We study open supermembranes in 11 dimensional rigid superspace with 6
dimensional topological defects (M-theory five-branes). After rederiving in the
Green-Schwarz formalism the boundary conditions for open superstrings in the
type IIA theory, we determine the boundary conditions for open supermembranes
by imposing kappa symmetry and invariance under a fraction of 11 dimensional
supersymmetry. The result seems to imply the self-duality of the three-form
field strength on the five-brane world volume. We show that the light-cone
gauge formulation is regularized by a dimensional reduction of a 6 dimensional
N=1 super Yang-Mills theory with the gauge group SO(N\to\infty). We also
analyze the SUSY algebra and BPS states in the light-cone gauge.Comment: 30 pages, Latex, references and Appendix E added, some minor changes
mad
The Waters of The Third Pole: Sources of Threat, Sources of Survival
The purpose of this report is to open up a dialogue
on an issue that could put the lives and livelihoods
of millions of people at risk in the foreseeable future.
This issue is water – water as a vital resource and as
a potential crisis driver in the Hindu-Kush Himalaya
(HKH) region. In seeking to foster that dialogue,
the report has three specific objectives: [i] to survey
various types of potential water-related hazards and
crisis drivers that could affect the region; [ii] to foster new types of alliances – including greater attention to what will be called humanitarian policy-maker/ science dialogues – for addressing the threats that the region may face; and [iii] to propose first steps that must be taken now to lead to prevention and
preparedness measures commensurate with the nature and scale of threats facing the region
An investigation into linearity with cumulative emissions of the climate and carbon cycle response in HadCM3LC
We investigate the extent to which global mean temperature, precipitation, and the carbon cycle are constrained by cumulative carbon emissions throughout four experiments with a fully coupled climate-carbon cycle model. The two paired experiments adopt contrasting, idealised approaches to climate change mitigation at different action points this century, with total emissions exceeding two trillion tonnes of carbon in the later pair. Their initially diverging cumulative emissions trajectories cross after several decades, before diverging again. We find that their global mean temperatures are, to first order, linear with cumulative emissions, though regional differences in temperature of up to 1.5K exist when cumulative emissions of each pair coincide. Interestingly, although the oceanic precipitation response scales with cumulative emissions, the global precipitation response does not, due to a decrease in precipitation over land above cumulative emissions of around one trillion tonnes of carbon (TtC). Most carbon fluxes and stores are less well constrained by cumulative emissions as they reach two trillion tonnes. The opposing mitigation approaches have different consequences for the Amazon rainforest, which affects the linearity with which the carbon cycle responds to cumulative emissions. Averaged over the two fixed-emissions experiments, the transient response to cumulative carbon emissions (TCRE) is 1.95 K TtC-1, at the upper end of the IPCC’s range of 0.8-2.5 K TtC-1
OH(6-2) spectra and rotational temperature measurements at Davis, Antarctica
International audienceThe OH(6-2) band was monitored during 1990 at Davis, Antarctica (68.6°S, 78.0°E) using a Czerny-Turner scanning spectrometer. Spectra obtained with a 0.15-nm bandwidth and wavelength steps of 0.005 nm have been recorded in an attempt to isolate auroral features. This has enabled detailed study of weak features in the region ?837.5?855.5 nm. These weak features can contribute to the apparent intensity of P-branch lines and to the background. Their presence is allowed for in our calculation of rotational temperature, but the P1(3) line is excluded because of significant contamination. An average temperature of 221±2 K is obtained from a selected data set of 104 spectra. The mid-winter average temperature, for the months of May, June and July, is 224±2 K, which is consistent with the 1986 CIRA model values for mid-winter at this height and latitude, but this result is dependent on the choice of transition probabilities. Preliminary assessments of seasonal and diurnal variations in rotational temperature and intensity are presented
Reversible suppression of an essential gene in adult mice using transgenic RNA interference
RNAi has revolutionized loss-of-function genetics by enabling sequence-specific suppression of virtually any gene. Furthermore, tetracycline response elements (TRE) can drive expression of short hairpin RNAs (shRNAs) for inducible and reversible target gene suppression. Here, we demonstrate the feasibility of transgenic inducible RNAi for suppression of essential genes. We set out to directly target cell proliferation by screening an RNAi library against DNA replication factors and identified multiple shRNAs against Replication Protein A, subunit 3 (RPA3). We generated transgenic mice with TRE-driven Rpa3 shRNAs whose expression enforced a reversible cell cycle arrest. In adult mice, the block in cell proliferation caused rapid atrophy of the intestinal epithelium which led to weight loss and lethality within 8-11 d of shRNA induction. Upon shRNA withdrawal, villus atrophy and weight loss were fully reversible. Thus, shRpa3 transgenic mice provide an interesting tool to study tissue maintenance and regeneration. Overall, we have established a robust system that serves the purpose of temperature-sensitive alleles in other model organisms, enabling inducible and reversible suppression of essential genes in a mammalian system
Dynamic behaviour of the silica-water-bio electrical double layer in the presence of a divalent electrolyte
Electronic devices are becoming increasingly used in chemical- and bio-sensing applications and therefore understanding the silica-electrolyte interface at the atomic scale is becoming increasingly important. For example, field-effect biosensors (BioFETs) operate by measuring perturbations in the electric field produced by the electrical double layer due to biomolecules binding on the surface. In this paper, explicit-solvent atomistic calculations of this electric field are presented and the structure and dynamics of the interface are investigated in different ionic strengths using molecular dynamics simulations. Novel results from simulation of the addition of DNA molecules and divalent ions are also presented, the latter of particular importance in both physiological solutions and biosensing experiments. The simulations demonstrated evidence of charge inversion, which is known to occur experimentally for divalent electrolyte systems. A strong interaction between ions and DNA phosphate groups was demonstrated in mixed electrolyte solutions, which are relevant to experimental observations of device sensitivity in the literature. The bound DNA resulted in local changes to the electric field at the surface; however, the spatial- and temporal-mean electric field showed no significant change. This result is explained by strong screening resulting from a combination of strongly polarised water and a compact layer of counterions around the DNA and silica surface. This work suggests that the saturation of the Stern layer is an important factor in determining BioFET response to increased salt concentration and provides novel insight into the interplay between ions and the electrical double layer
- …