Relaxed Byzantine Vector Consensus

Exact Byzantine consensus problem requires that non-faulty processes reach agreement on a decision (or output) that is in the convex hull of the inputs at the non-faulty processes. It is well-known that exact consensus is impossible in an asynchronous system in presence of faults, and in a synchronous system, n>=3f+1 is tight on the number of processes to achieve exact Byzantine consensus with scalar inputs, in presence of up to f Byzantine faulty processes. Recent work has shown that when the inputs are d-dimensional vectors of reals, n>=max(3f+1,(d+1)f+1) is tight to achieve exact Byzantine consensus in synchronous systems, and n>= (d+2)f+1 for approximate Byzantine consensus in asynchronous systems. Due to the dependence of the lower bound on vector dimension d, the number of processes necessary becomes large when the vector dimension is large. With the hope of reducing the lower bound on n, we consider two relaxed versions of Byzantine vector consensus: k-Relaxed Byzantine vector consensus and (delta,p)-Relaxed Byzantine vector consensus. In k-relaxed consensus, the validity condition requires that the output must be in the convex hull of projection of the inputs onto any subset of k-dimensions of the vectors. For (delta,p)-consensus the validity condition requires that the output must be within distance delta of the convex hull of the inputs of the non-faulty processes, where L_p norm is used as the distance metric. For (delta,p)-consensus, we consider two versions: in one version, delta is a constant, and in the second version, delta is a function of the inputs themselves. We show that for k-relaxed consensus and (delta,p)-consensus with constant delta>=0, the bound on n is identical to the bound stated above for the original vector consensus problem. On the other hand, when delta depends on the inputs, we show that the bound on n is smaller when d>=3

Linear and Range Counting under Metric-based Local Differential Privacy

Local differential privacy (LDP) enables private data sharing and analytics without the need for a trusted data collector. Error-optimal primitives (for, e.g., estimating means and item frequencies) under LDP have been well studied. For analytical tasks such as range queries, however, the best known error bound is dependent on the domain size of private data, which is potentially prohibitive. This deficiency is inherent as LDP protects the same level of indistinguishability between any pair of private data values for each data downer. In this paper, we utilize an extension of $\epsilon$-LDP called Metric-LDP or $E$-LDP, where a metric $E$ defines heterogeneous privacy guarantees for different pairs of private data values and thus provides a more flexible knob than $\epsilon$ does to relax LDP and tune utility-privacy trade-offs. We show that, under such privacy relaxations, for analytical workloads such as linear counting, multi-dimensional range counting queries, and quantile queries, we can achieve significant gains in utility. In particular, for range queries under $E$-LDP where the metric $E$ is the $L^1$-distance function scaled by $\epsilon$, we design mechanisms with errors independent on the domain sizes; instead, their errors depend on the metric $E$, which specifies in what granularity the private data is protected. We believe that the primitives we design for $E$-LDP will be useful in developing mechanisms for other analytical tasks, and encourage the adoption of LDP in practice

Regular solutions of the stationary Navier-Stokes equations on high dimensional Euclidean space

We study the existence of regular solutions of the incompressible stationary Navier-Stokes equations in $n$-dimensional Euclidean space with a given bounded external force of compact support. In dimensions $n\le 5$, the existence of such solutions was known. In this paper, we extend it to dimensions $n\le 15$.Comment: Exposition improved. To appear in Comm. Math. Phy

Performance of EdDSA and BLS Signatures in Committee-Based Consensus

We present the first performance comparison of EdDSA and BLS signatures in committee-based consensus protocols through large-scale geo-distributed benchmarks. Contrary to popular beliefs, we find that small deployments (less than 40 validators) can benefit from the small storage footprint of BLS multi-signatures while larger deployments should favor EdDSA to improve performance. As an independent contribution, we present a novel way for committee-based consensus protocols to verify BLS multi-signed certificates by manipulating the aggregated public key using pre-computed values

Can I See Beyond What You See? Blending Machine Learning and Econometrics to Discover Household TV Viewing Preferences

This article discusses the emergence of a computational social science analytics fusion as a mainstream scientific approach involving machine-based methods and explanatory empiricism as a basis for the discovery of new policy-related insights for business, consumer and social settings. It reflects the interdisciplinary background of the new approaches that the Hawaii International Conference on Systems Science has embraced over the years, and especially some of the recent development and shifts in the scientific study of technology-related phenomena. It also has evoked new forms of research inquiry, blended approaches to research methodology, and more pointed interest in the production of research results that have direct application in various industry contexts. We review background knowledge to showcase the methods shifts, and demonstrate the new forms of research, by showcasing contemporary applications that will be interesting to the audience on the occasion of the HICSS 50th anniversary

Étude structurale de deux complexes macromoléculaires biologiques : FANCD2/FANCI et la Phosphorylase Kinase par cryo microscopie électronique

During my thesis work, I have investigated the structure of two protein complexes, the FANCD2/FANCI complex and the Phosphorylase Kinase complex (PhK). Both complexes were studied using cryo electron microscopy combined with image analysis. The Fanconi Anemia (FA) pathway has been implied to play a significant role in DNA interstrand crosslink repair and may be the coordinator between different DNA damage repair pathways. Within the FA pathway, the FANCD2 and FANCI proteins are key players. In my thesis work, I have calculated the structure of the human FANCD2/FANCI complex. It possesses an inner cavity, large enough to accommodate a double stranded DNA helix. We also discovered a protruding tower domain, which our collaborator (M. Cohn, Oxford) has shown to be critical for the recruitment of the complex to DNA. PhK is one of the most complex kinases. It is composed of four subunits (αβγδ)4. PhK regulates glycogenolysis, it integrates various signals to catalyze the conversion of glycogen phosphorylase (GP) b to GP a (active), and the subsequent breakdown of glycogen. PhK is a potential target for glycemic control in diseases such as diabetes. Using state of the art electron microscope with a direct electron detection camera, after multiple image processing steps and correction of beams induced motion of films, I obtained a structure of the complexe at 7Å (FSC gold standard).Au cours de mon travail de thèse, j’ai étudié la structure des deux complexes de protéines, le complexe FANCD2/FANCI et la Phosphorylase kinase (PhK). Les deux complexes ont été étudiés en utilisant la cryo-microscopie électronique combinée à l’analyse d'image. La voie anémie de Fanconi (FA) a été reconnue comme jouant un rôle important dans la réparation de liaisons inter-brin de l'ADN. Dans cette voie, les protéines FANCD2 et FANCI sont des acteurs clés. Dans mon travail de thèse, j’ai calculé la structurale du complexe FANCD2/FANCI humaine. La structure montre une cavité intérieure, assez grande pour accueillir une hélice d'ADN double brin. Nous avons aussi mis en évidence un domaine en forme de tour. Notre collaborateur (M. Cohn, Oxford) a montré que celui-ci est essentiel pour le recrutement du complexe sur l'ADN. La PhK est l'une des kinases les plus complexes. Elle est composée de quatre sous-unités (αβγδ)4. PhK régule le métabolisme du glycogène, intègre divers signaux pour catalyser la conversion du glycogène phosphorylase b (GP) vers la GP a (actif), et la dégradation ultérieure de glycogène. En utilisant un microscope performant et une caméra de détection d'électrons directe puis après plusieurs étapes de traitement d’image, de correction de mouvement de films induits par les faisceaux d'électrons, j’ai obtenu une structure du complexe en 7Å (FSC gold standard)