• Canada
• Publicationsclose
• Research dataclose
• GB close
• CN close
• FR close

Security is an interesting area, one in which we may well be guilty of misunderstanding the very people we are working for whilst trying to protect them. It is often said that people (users) are a weak link in the security chain. This may be true, but there are nuances. In this chapter, the authors discuss some of the work they have done and are doing to help users understand their information and device security and make informed, guided, and responsible decisions. This includes Device Comfort, Annoying Technologies, and Ten Commandments for designers and implementers of security and trust systems. This work is exploratory and unfinished (it should in fact never be finished), and this chapter presents a step along the way to better security users.

Abstract Discrete time-translational symmetry in a periodically driven many-body system can be spontaneously broken to form a discrete time crystal, an exotic new phase of matter. We present observations characteristic of discrete time crystalline order in a driven system of paramagnetic P-donor impurities in isotopically enriched 28Si cooled below 10 K. The observations exhibit a stable subharmonic peak at half the drive frequency which remains pinned even in the presence of pulse error, a signature of discrete time crystalline order. This signal has a finite lifetime of ∼100 Floquet periods, but this effect is long-lived relative to coherent spin–spin interaction timescales, lasting ∼104 times longer. We present simulations of the system based on the paradigmatic central spin model and show good agreement with experiment. We investigate the role of dissipation and interactions within this model, and show that both are capable of giving rise to discrete time crystal-like behaviour.

We present preliminary results on a study of the 2--850 micron SEDs of a sample of 30 FIRBACK galaxies selected at 170 micron. These sources are representative of the brightest ~10% of the Cosmic Infrared Background. They are a mixture of mostly local (z<~0.3) starforming galaxies, and a tail of ULIGs that extend up to z~1, and are likely to be a similar population to faint SCUBA sources. We use archival Spitzer IRAC and MIPS data to extend the spectral coverage to the mid-IR regime, resulting in an unprecended (for this redshift range) census of their infrared SEDs. This allows us to study in far greater detail this important population linking the near-IR stellar emission with PAH and thermal dust emission. We do this using a Markov Chain Monte Carlo method, which easily allows for the inclusion of ~6 free parameters, as well as an estimate of parameter uncertainties and correlations. Comment: 5 pages, 3 figures. Proceeding for the conference "Starbursts: From 30 Doradus to Lyman Break Galaxies", held in Cambridge (UK) in September, 2004

Aims Treatment of patients with heart failure (HF) relies on measurement of LVEF. However, the extent to which EF is recorded varies markedly. We sought to characterize the patient group that is missing a measure of EF, and to explore the association between missing EF and outcome. Methods and results Individual data on 30 445 patients from 28 observational studies in the Meta-Analysis Global Group in Chronic Heart Failure (MAGGIC) project were used to compare the prevalence of co-morbidities and outcome across three groups of HF patients: those with missing EF (HF-mEF), reduced EF (HF-REF), and preserved EF (HF-PEF). A total of 29% had HF-mEF, 52% HF-REF, and 19% HF-PEF. Compared with patients in whom EF was known, patients with HF-mEF were older, had a greater prevalence of COPD and previous stroke, and were smokers. Patients with HF-mEF were less likely to receive evidence-based treatment than those with HF-REF. Adjusted mortality in HF-mEF was similar to that in HF-REF and greater than that in HF-PEF at 3 years [HF-REF, hazard ratio (HR) 1.03, 95% confidence interval (CI) 0.95–1.12); HF-PEF, HR 0.78, 95% CI 0.71–0.86]. Conclusion Missing EF is common. The short- and long-term outcome of patients with HF-mEF is poor and they exhibit different co-morbidity profiles and treatment patterns compared with patients with known EF. HF patients with missing EF represent a high risk group.

We hypothesize that phytoplankton have the sequential nutrient uptake strategy to maintain nutrient stoichiometry and high primary productivity in the water column. According to this hypothesis, phytoplankton take up the most limiting nutrient first until depletion, continue to draw down non-limiting nutrients and then take up the most limiting nutrient rapidly when it is available. These processes would result in the variation of ambient nutrient ratios in the water column around the Redfield ratio. We used high-resolution continuous vertical profiles of nutrients, nutrient ratios and on-board ship incubation experiments to test this hypothesis in the Strait of Georgia. At the surface in summer, ambient NO3− was depleted with excess PO43− and SiO4− remaining, and as a result, both N : P and N : Si ratios were low. The two ratios increased to about 10 : 1 and 0. 45 : 1, respectively, at 20 m. Time series of vertical profiles showed that the leftover PO43− continued to be removed, resulting in additional phosphorus storage by phytoplankton. The N : P ratios at the nutricline in vertical profiles responded differently to mixing events. Field incubation of seawater samples also demonstrated the sequential uptake of NO3− (the most limiting nutrient) and then PO43− and SiO4− (the non-limiting nutrients). This sequential uptake strategy allows phytoplankton to acquire additional cellular phosphorus and silicon when they are available and wait for nitrogen to become available through frequent mixing of NO3− (or pulsed regenerated NH4). Thus, phytoplankton are able to maintain high productivity and balance nutrient stoichiometry by taking advantage of vigorous mixing regimes with the capacity of the stoichiometric plasticity. To our knowledge, this is the first study to show the in situ dynamics of continuous vertical profiles of N : P and N : Si ratios, which can provide insight into the in situ dynamics of nutrient stoichiometry in the water column and the inference of the transient status of phytoplankton nutrient stoichiometry in the coastal ocean.

Background : The prevalence of chronic rhinitis is increasing rapidly; its pathogenesis is to be further understood; immune inflammation is one of the possible causative factors. Antigen specific CD8+ T cells play a critical role in the induction of chronic inflammation. Aims : This study aimed to investigate the role of antigen specific CD8+ T cells in the pathogenesis of chronic atypical allergic rhinitis. Material and Methods : Nasal mucosal epithelial surface scratching samples were obtained from patients with chronic obstruction atypical allergic rhinitis. Exosomes were purified from the scratching samples and examined by immune gold electron microscopy. The effect of exosomes on modulating dendritic cell's properties, the effect of exosome-pulsed dendritic cells on naive T cell differentiation and the antigen specific CD8+ T cell activation were observed by cell culture models. Results : Exosomes purified from patients with chronic atypical allergic rhinitis carried microbial products, Staphylococcal enterotoxin B (SEB), and airborne antigen, Derp1. Dendritic cells pulsed by SEB/Derp1-carrying exosomes showed high levels of CD80, CD86 and the major histocompatibility class I (MHCI). Exosome-pulsed dendritic cells could induce the naive CD3+ T cells to differentiate into CD8+ T cells. Upon the exposure to a specific antigen, the CD8+ T cells released granzyme B and perforin; more than 30% antigen specific CD8+ T cells proliferated. Conclusions : Antigen specific CD8+ T cells play an important role in the pathogenesis of chronic obstruction atypical allergic rhinitis.

Abstract Interstitial deletions of the short arm of chromosome 6 are rare and have been associated with developmental delay, hypotonia, congenital anomalies, and dysmorphic features. We used array comparative genomic hybridization in a South Carolina Autism Project (SCAP) cohort of 97 subjects with autism spectrum disorders (ASDs) and identified an ~ 5.4 Mb deletion on chromosome 6p22.3-p23 in a 15-year-old patient with intellectual disability and ASDs. Subsequent database queries revealed five additional individuals with overlapping submicroscopic deletions and presenting with developmental and speech delay, seizures, behavioral abnormalities, heart defects, and dysmorphic features. The deletion found in the SCAP patient harbors ATXN1, DTNBP1, JARID2, and NHLRC1 that we propose may be responsible for ASDs and developmental delay.

This paper concerns reinforcement learning~(RL) of the document ranking models for information retrieval~(IR). One branch of the RL approaches to ranking formalize the process of ranking with Markov decision process~(MDP) and determine the model parameters with policy gradient. Though preliminary success has been shown, these approaches are still far from achieving their full potentials. Existing policy gradient methods directly utilize the absolute performance scores (returns) of the sampled document lists in its gradient estimations, which may cause two limitations: 1) fail to reflect the relative goodness of documents within the same query, which usually is close to the nature of IR ranking; 2) generate high variance gradient estimations, resulting in slow learning speed and low ranking accuracy. To deal with the issues, we propose a novel policy gradient algorithm in which the gradients are determined using pairwise comparisons of two document lists sampled within the same query. The algorithm, referred to as Pairwise Policy Gradient (PPG), repeatedly samples pairs of document lists, estimates the gradients with pairwise comparisons, and finally updates the model parameters. Theoretical analysis shows that PPG makes an unbiased and low variance gradient estimations. Experimental results have demonstrated performance gains over the state-of-the-art baselines in search result diversification and text retrieval.

We explore the application of phase diversity to calibrate the non common path aberrations (NCPA) in the Gemini Planet Imager (GPI). This is first investigated in simulation in order to characterize the ideal technique parameters with simulated GPI calibration source data. The best working simulation parameters are derived and we establish the algorithm's capability to recover an injected astigmatism. Furthermore, the real data appear to exhibit signs of de-centering between the in and out of focus images that are required by phase diversity; this effect can arise when the diverse images are acquired in closed loop and are close to the non-linear regime of the wavefront sensor. We show in simulation that this effect can inhibit our algorithm, which does not take into account the impact of de-centering between images. To mitigate this effect, we validate the technique of using a single diverse image with our algorithm; this is first demonstrated in simulation and then applied to the real GPI data. Following this approach, we find that we can successfully recover a known astigmatism injection using the real GPI data and subsequently apply an NCPA correction to GPI (in the format of offset reference slopes) to improve the relative Strehl ratio by 5%; we note this NCPA correction application is rudimentary and a more thorough application will be investigated in the near future. Finally, the estimated NCPA in the form of astigmatism and coma agree well with the magnitude of the same modes reported by Poyneer et al. 2016.

Abstract In this work, the beneficial effect of carbocation scavenger additives on hardwood pretreatment was revealed by significantly improved biomass saccharification: cellulose hydrolysis yield was increased by over 15% after steam pretreatment of poplar, while that was enhanced by more than 48% after dilute acid pretreatment. Besides, the relative contributions of lignin towards enzyme binding and physical barrier effect for proposed mechanisms were quantified. Results indicated that the addition of carbocation scavenger, 2-naphthol-7-sulfonate, resulted in acid groups incorporation of 62.36 mmol/kg to lignin, which mitigated enzyme non-productive binding. Moreover, enlarged biomass porosity and reduced surface lignin coverage were detected through BET and XPS analysis, respectively, which mostly related to the diminished physical barrier effect of lignin. As a result, the lignin inhibitions were significantly suppressed through the addition of carbocation scavenger, giving rise to significantly improved enzymatic hydrolysis of hardwood.