Ideal hierarchical secret sharing schemes

Hierarchical secret sharing is among the most natural generalizations of threshold secret sharing, and it has attracted a lot of attention from the invention of secret sharing until nowadays. Several constructions of ideal hierarchical secret sharing schemes have been proposed, but it was not known what access structures admit such a scheme. We solve this problem by providing a natural definition for the family of the hierarchical access structures and, more importantly, by presenting a complete characterization of the ideal hierarchical access structures, that is, the ones admitting an ideal secret sharing scheme. Our characterization deals with the properties of the hierarchically minimal sets of the access structure, which are the minimal qualified sets whose participants are in the lowest possible levels in the hierarchy. By using our characterization, it can be efficiently checked whether any given hierarchical access structure that is defined by its hierarchically minimal sets is ideal. We use the well known connection between ideal secret sharing and matroids and, in particular, the fact that every ideal access structure is a matroid port. In addition, we use recent results on ideal multipartite access structures and the connection between multipartite matroids and integer polymatroids. We prove that every ideal hierarchical access structure is the port of a representable matroid and, more specifically, we prove that every ideal structure in this family admits ideal linear secret sharing schemes over fields of all characteristics. In addition, methods to construct such ideal schemes can be derived from the results in this paper and the aforementioned ones on ideal multipartite secret sharing. Finally, we use our results to find a new proof for the characterization of the ideal weighted threshold access structures that is simpler than the existing one.Peer ReviewedPostprint (author's final draft

Genome-independent hypoxic repression of estrogen receptor alpha in breast cancer cells

Averages and standard deviations of band intensities calculated for all repeats of each western blot in Fig. 2a. Specific band intensities normalized to the loading control bands (β-actin). Calculations derived from at least three independent experiments. (DOCX 17 kb

Optimal non-perfect uniform secret sharing schemes

A secret sharing scheme is non-perfect if some subsets of participants that cannot recover the secret value have partial information about it. The information ratio of a secret sharing scheme is the ratio between the maximum length of the shares and the length of the secret. This work is dedicated to the search of bounds on the information ratio of non-perfect secret sharing schemes. To this end, we extend the known connections between polymatroids and perfect secret sharing schemes to the non-perfect case. In order to study non-perfect secret sharing schemes in all generality, we describe their structure through their access function, a real function that measures the amount of information that every subset of participants obtains about the secret value. We prove that there exists a secret sharing scheme for every access function. Uniform access functions, that is, the ones whose values depend only on the number of participants, generalize the threshold access structures. Our main result is to determine the optimal information ratio of the uniform access functions. Moreover, we present a construction of linear secret sharing schemes with optimal information ratio for the rational uniform access functions.Peer ReviewedPostprint (author's final draft

Smart sensing interoperability platforms in the scope of Atlantos

This paper aims to demonstrate the capabilities of a Smart Cable which aims to convert any commercial non-PUCK-enabled sensor in a Smart PUCK-enabled device. Through this development, it can be easily integrated on a sensor web platform in order to access the data in real time, and so there is no need to rely on each sensor manufacturer to comply with Sensor Web Enablement standards. The results presented in this paper were acquired during some real field experiments performed between the 24th and 28th of September at PLOCAN facilities in Gran Canaria. During these days three Turner Designs Cyclops sensors were successfully integrated and tested in a mission using an observing surface vehicle such as the Wave Glider SV-2.Peer Reviewe

Comprehensive Simultaneous Shipboard and Airborne Characterization of Exhaust from a Modern Container Ship at Sea

We report the first joint shipboard and airborne study focused on the chemical composition and water-uptake behavior of particulate ship emissions. The study focuses on emissions from the main propulsion engine of a Post-Panamax class container ship cruising off the central coast of California and burning heavy fuel oil. Shipboard sampling included micro-orifice uniform deposit impactors (MOUDI) with subsequent off-line analysis, whereas airborne measurements involved a number of real-time analyzers to characterize the plume aerosol, aged from a few seconds to over an hour. The mass ratio of particulate organic carbon to sulfate at the base of the ship stack was 0.23 ± 0.03, and increased to 0.30 ± 0.01 in the airborne exhaust plume, with the additional organic mass in the airborne plume being concentrated largely in particles below 100 nm in diameter. The organic to sulfate mass ratio in the exhaust aerosol remained constant during the first hour of plume dilution into the marine boundary layer. The mass spectrum of the organic fraction of the exhaust aerosol strongly resembles that of emissions from other diesel sources and appears to be predominantly hydrocarbon-like organic (HOA) material. Background aerosol which, based on air mass back trajectories, probably consisted of aged ship emissions and marine aerosol, contained a lower organic mass fraction than the fresh plume and had a much more oxidized organic component. A volume-weighted mixing rule is able to accurately predict hygroscopic growth factors in the background aerosol but measured and calculated growth factors do not agree for aerosols in the ship exhaust plume. Calculated CCN concentrations, at supersaturations ranging from 0.1 to 0.33%, agree well with measurements in the ship-exhaust plume. Using size-resolved chemical composition instead of bulk submicrometer composition has little effect on the predicted CCN concentrations because the cutoff diameter for CCN activation is larger than the diameter where the mass fraction of organic aerosol begins to increase significantly. The particle number emission factor estimated from this study is 1.3 × 10^(16) (kg fuel)^(−1), with less than 1/10 of the particles having diameters above 100 nm; 24% of particles (>10 nm in diameter) activate into cloud droplets at 0.3% supersaturation

Trends in Qualifying Biomarkers in Drug Safety. Consensus of the 2011 Meeting of the Spanish Society of Clinical Pharmacology

In this paper we discuss the consensus view on the use of qualifying biomarkers in drug safety, raised within the frame of the XXIV meeting of the Spanish Society of Clinical Pharmacology held in Málaga (Spain) in October, 2011. The widespread use of biomarkers as surrogate endpoints is a goal that scientists have long been pursuing. Thirty years ago, when molecular pharmacogenomics evolved, we anticipated that these genetic biomarkers would soon obviate the routine use of drug therapies in a way that patients should adapt to the therapy rather than the opposite. This expected revolution in routine clinical practice never took place as quickly nor with the intensity as initially expected. The concerted action of operating multicenter networks holds great promise for future studies to identify biomarkers related to drug toxicity and to provide better insight into the underlying pathogenesis. Today some pharmacogenomic advances are already widely accepted, but pharmacogenomics still needs further development to elaborate more precise algorithms and many barriers to implementing individualized medicine exist. We briefly discuss our view about these barriers and we provide suggestions and areas of focus to advance in the field

On the optimization of bipartite secret sharing schemes

Optimizing the ratio between the maximum length of the shares and the length of the secret value in secret sharing schemes for general access structures is an extremely difficult and long-standing open problem. In this paper, we study it for bipartite access structures, in which the set of participants is divided in two parts, and all participants in each part play an equivalent role. We focus on the search of lower bounds by using a special class of polymatroids that is introduced here, the bipartite ones. We present a method based on linear programming to compute, for every given bipartite access structure, the best lower bound that can be obtained by this combinatorial method. In addition, we obtain some general lower bounds that improve the previously known ones, and we construct optimal secret sharing schemes for a family of bipartite access structures.Postprint (author’s final draft

Efecto del manejo del suelo (laboreo vs. siembra directa) sobre la diversidad florística en campos de cereal

Postprint (published version

Glycosylated apolipoprotein J in cardiac ischaemia: molecular processing and circulating levels in patients with acute ischaemic events.

AIM: Using proteomics, we previously found that serum levels of glycosylated (Glyc) forms of apolipoprotein J (ApoJ), a cytoprotective and anti-oxidant protein, decrease in the early phase of acute myocardial infarction (AMI). We aimed to investigate: (i) ApoJ-Glyc intracellular distribution and secretion during ischaemia; (ii) the early changes in circulating ApoJ-Glyc during AMI; and (iii) associations between ApoJ-Glyc and residual ischaemic risk post-AMI. METHODS AND RESULTS: Glycosylated apolipoprotein J was investigated in: (i) cells from different organ/tissue origin; (ii) a pig model of AMI; (iii) de novo AMI patients (n = 38) at admission within the first 6 h of chest pain onset and without troponin T elevation at presentation (early AMI); (iv) ST-elevation myocardial infarction patients (n = 212) who were followed up for 6 months; and (v) a control group without any overt cardiovascular disease (n = 144). Inducing simulated ischaemia in isolated cardiac cells resulted in an increased intracellular accumulation of non-glycosylated ApoJ forms. A significant decrease in ApoJ-Glyc circulating levels was seen 15 min after ischaemia onset in pigs. Glycosylated apolipoprotein J levels showed a 45% decrease in early AMI patients compared with non-ischaemic patients (P < 0.0001), discriminating the presence of the ischaemic event (area under the curve: 0.934; P < 0.0001). ST-elevation myocardial infarction patients with lower ApoJ-Glyc levels at admission showed a higher rate of recurrent ischaemic events and mortality after 6-month follow-up (P = 0.008). CONCLUSIONS: These results indicate that ischaemia induces an intracellular accumulation of non-glycosylated ApoJ and a reduction in ApoJ-Glyc secretion. Glycosylated apolipoprotein J circulating levels are reduced very early after ischaemia onset. Its continuous decrease indicates a worsening in the evolution of the cardiac event, likely identifying patients with sustained ischaemia after AMI