@article{6678, abstract = {We survey coding techniques that enable reliable transmission at rates that approach the capacity of an arbitrary discrete memoryless channel. In particular, we take the point of view of modern coding theory and discuss how recent advances in coding for symmetric channels help provide more efficient solutions for the asymmetric case. We consider, in more detail, three basic coding paradigms. The first one is Gallager's scheme that consists of concatenating a linear code with a non-linear mapping so that the input distribution can be appropriately shaped. We explicitly show that both polar codes and spatially coupled codes can be employed in this scenario. Furthermore, we derive a scaling law between the gap to capacity, the cardinality of the input and output alphabets, and the required size of the mapper. The second one is an integrated scheme in which the code is used both for source coding, in order to create codewords distributed according to the capacity-achieving input distribution, and for channel coding, in order to provide error protection. Such a technique has been recently introduced by Honda and Yamamoto in the context of polar codes, and we show how to apply it also to the design of sparse graph codes. The third paradigm is based on an idea of Böcherer and Mathar, and separates the two tasks of source coding and channel coding by a chaining construction that binds together several codewords. We present conditions for the source code and the channel code, and we describe how to combine any source code with any channel code that fulfill those conditions, in order to provide capacity-achieving schemes for asymmetric channels. In particular, we show that polar codes, spatially coupled codes, and homophonic codes are suitable as basic building blocks of the proposed coding strategy. Rather than focusing on the exact details of the schemes, the purpose of this tutorial is to present different coding techniques that can then be implemented with many variants. There is no absolute winner and, in order to understand the most suitable technique for a specific application scenario, we provide a detailed comparison that takes into account several performance metrics.}, author = {Mondelli, Marco and Hassani, Hamed and Urbanke, Rudiger }, issn = {0018-9448}, journal = {IEEE Transactions on Information Theory}, number = {5}, pages = {3371--3393}, publisher = {IEEE}, title = {{How to achieve the capacity of asymmetric channels}}, doi = {10.1109/tit.2018.2789885}, volume = {64}, year = {2018}, } @article{690, abstract = {We consider spectral properties and the edge universality of sparse random matrices, the class of random matrices that includes the adjacency matrices of the Erdős–Rényi graph model G(N, p). We prove a local law for the eigenvalue density up to the spectral edges. Under a suitable condition on the sparsity, we also prove that the rescaled extremal eigenvalues exhibit GOE Tracy–Widom fluctuations if a deterministic shift of the spectral edge due to the sparsity is included. For the adjacency matrix of the Erdős–Rényi graph this establishes the Tracy–Widom fluctuations of the second largest eigenvalue when p is much larger than N−2/3 with a deterministic shift of order (Np)−1.}, author = {Lee, Jii and Schnelli, Kevin}, journal = {Probability Theory and Related Fields}, number = {1-2}, publisher = {Springer}, title = {{Local law and Tracy–Widom limit for sparse random matrices}}, doi = {10.1007/s00440-017-0787-8}, volume = {171}, year = {2018}, } @inproceedings{6675, abstract = {We present a coding paradigm that provides a new achievable rate for the primitive relay channel by combining compress-and-forward and decode-and-forward with a chaining construction. In the primitive relay channel model, the source broadcasts a message to the relay and to the destination; and the relay facilitates this communication by sending an additional message to the destination through a separate channel. Two well-known coding approaches for this setting are decode-and-forward and compress-and-forward: in the former, the relay decodes the message and sends some of the information to the destination; in the latter, the relay does not attempt to decode, but it sends a compressed description of the received sequence to the destination via Wyner-Ziv coding. In our scheme, we transmit over pairs of blocks and we use compress-and-forward for the first block and decode-and-forward for the second. In particular, in the first block, the relay does not attempt to decode and it sends only a part of the compressed description of the received sequence; in the second block, the relay decodes the message and sends this information plus the remaining part of the compressed sequence relative to the first block. As a result, we strictly outperform both compress-and- forward and decode-and-forward. Furthermore, this paradigm can be implemented with a low-complexity polar coding scheme that has the typical attractive features of polar codes, i.e., quasi-linear encoding/decoding complexity and super-polynomial decay of the error probability. Throughout the paper we consider as a running example the special case of the erasure relay channel and we compare the rates achievable by our proposed scheme with the existing upper and lower bounds.}, author = {Mondelli, Marco and Hassani, Hamed and Urbanke, Rudiger}, booktitle = {2018 IEEE International Symposium on Information Theory}, issn = {2157-8117}, location = {Vail, CO, United States}, pages = {351--355}, publisher = {IEEE}, title = {{A new coding paradigm for the primitive relay channel}}, doi = {10.1109/isit.2018.8437479}, year = {2018}, } @article{703, abstract = {We consider the NP-hard problem of MAP-inference for undirected discrete graphical models. We propose a polynomial time and practically efficient algorithm for finding a part of its optimal solution. Specifically, our algorithm marks some labels of the considered graphical model either as (i) optimal, meaning that they belong to all optimal solutions of the inference problem; (ii) non-optimal if they provably do not belong to any solution. With access to an exact solver of a linear programming relaxation to the MAP-inference problem, our algorithm marks the maximal possible (in a specified sense) number of labels. We also present a version of the algorithm, which has access to a suboptimal dual solver only and still can ensure the (non-)optimality for the marked labels, although the overall number of the marked labels may decrease. We propose an efficient implementation, which runs in time comparable to a single run of a suboptimal dual solver. Our method is well-scalable and shows state-of-the-art results on computational benchmarks from machine learning and computer vision.}, author = {Shekhovtsov, Alexander and Swoboda, Paul and Savchynskyy, Bogdan}, issn = {01628828}, journal = {IEEE Transactions on Pattern Analysis and Machine Intelligence}, number = {7}, pages = {1668--1682}, publisher = {IEEE}, title = {{Maximum persistency via iterative relaxed inference with graphical models}}, doi = {10.1109/TPAMI.2017.2730884}, volume = {40}, year = {2018}, } @article{7063, abstract = {The high-pressure synthesis and incommensurately modulated structure are reported for the new compound Sr2Pt8−xAs, with x = 0.715 (5). The structure consists of Sr2Pt3As layers alternating with Pt-only corrugated grids. Ab initio calculations predict a metallic character with a dominant role of the Pt d electrons. The electrical resistivity (ρ) and Seebeck coefficient confirm the metallic character, but surprisingly, ρ showed a near-flat temperature dependence. This observation fits the description of the Mooij correlation for electrical resistivity in disordered metals, originally developed for statistically distributed point defects. The discussed material has a long-range crystallographic order, but the high concentration of Pt vacancies, incommensurately ordered, strongly influences the electronic conduction properties. This result extends the range of validity of the Mooij correlation to long-range ordered incommensurately modulated vacancies. Motivated by the layered structure, the resistivity anisotropy was measured in a focused-ion-beam micro-fabricated well oriented single crystal. A low resistivity anisotropy indicates that the layers are electrically coupled and conduction channels along different directions are intermixed.}, author = {Martino, Edoardo and Arakcheeva, Alla and Autès, Gabriel and Pisoni, Andrea and Bachmann, Maja D. and Modic, Kimberly A and Helm, Toni and Yazyev, Oleg V. and Moll, Philip J. W. and Forró, László and Katrych, Sergiy}, issn = {2052-2525}, journal = {IUCrJ}, number = {4}, pages = {470--477}, publisher = {International Union of Crystallography (IUCr)}, title = {{Sr2Pt8−xAs: A layered incommensurately modulated metal with saturated resistivity}}, doi = {10.1107/s2052252518007303}, volume = {5}, year = {2018}, } @article{7062, abstract = {Weyl fermions are a recently discovered ingredient for correlated states of electronic matter. A key difficulty has been that real materials also contain non-Weyl quasiparticles, and disentangling the experimental signatures has proven challenging. Here we use magnetic fields up to 95 T to drive the Weyl semimetal TaAs far into its quantum limit, where only the purely chiral 0th Landau levels of the Weyl fermions are occupied. We find the electrical resistivity to be nearly independent of magnetic field up to 50 T: unusual for conventional metals but consistent with the chiral anomaly for Weyl fermions. Above 50 T we observe a two-order-of-magnitude increase in resistivity, indicating that a gap opens in the chiral Landau levels. Above 80 T we observe strong ultrasonic attenuation below 2 K, suggesting a mesoscopically textured state of matter. These results point the way to inducing new correlated states of matter in the quantum limit of Weyl semimetals.}, author = {Ramshaw, B. J. and Modic, Kimberly A and Shekhter, Arkady and Zhang, Yi and Kim, Eun-Ah and Moll, Philip J. W. and Bachmann, Maja D. and Chan, M. K. and Betts, J. B. and Balakirev, F. and Migliori, A. and Ghimire, N. J. and Bauer, E. D. and Ronning, F. and McDonald, R. D.}, issn = {2041-1723}, journal = {Nature Communications}, number = {1}, publisher = {Springer Nature}, title = {{Quantum limit transport and destruction of the Weyl nodes in TaAs}}, doi = {10.1038/s41467-018-04542-9}, volume = {9}, year = {2018}, } @article{7059, abstract = {Unusual behavior in quantum materials commonly arises from their effective low-dimensional physics, reflecting the underlying anisotropy in the spin and charge degrees of freedom. Here we introduce the magnetotropic coefficient k = ∂2F/∂θ2, the second derivative of the free energy F with respect to the magnetic field orientation θ in the crystal. We show that the magnetotropic coefficient can be quantitatively determined from a shift in the resonant frequency of a commercially available atomic force microscopy cantilever under magnetic field. This detection method enables part per 100 million sensitivity and the ability to measure magnetic anisotropy in nanogram-scale samples, as demonstrated on the Weyl semimetal NbP. Measurement of the magnetotropic coefficient in the spin-liquid candidate RuCl3 highlights its sensitivity to anisotropic phase transitions and allows a quantitative comparison to other thermodynamic coefficients via the Ehrenfest relations.}, author = {Modic, Kimberly A and Bachmann, Maja D. and Ramshaw, B. J. and Arnold, F. and Shirer, K. R. and Estry, Amelia and Betts, J. B. and Ghimire, Nirmal J. and Bauer, E. D. and Schmidt, Marcus and Baenitz, Michael and Svanidze, E. and McDonald, Ross D. and Shekhter, Arkady and Moll, Philip J. W.}, issn = {2041-1723}, journal = {Nature Communications}, number = {1}, pages = {3975}, publisher = {Springer Nature}, title = {{Resonant torsion magnetometry in anisotropic quantum materials}}, doi = {10.1038/s41467-018-06412-w}, volume = {9}, year = {2018}, } @article{7058, abstract = {We examine recent magnetic torque measurements in two compounds, γ−Li2IrO3 and RuCl3, which have been discussed as possible realizations of the Kitaev model. The analysis of the reported discontinuity in torque, as an external magnetic field is rotated across the c axis in both crystals, suggests that they have a translationally invariant chiral spin order of the form ⟨Si⋅(Sj×Sk)⟩≠0 in the ground state and persisting over a very wide range of magnetic field and temperature. An extraordinary |B|B2 dependence of the torque for small fields, beside the usual B2 part, is predicted by the chiral spin order. Data for small fields are available for γ−Li2IrO3 and are found to be consistent with the prediction upon further analysis. Other experiments such as inelastic scattering and thermal Hall effect and several questions raised by the discovery of chiral spin order, including its topological consequences, are discussed.}, author = {Modic, Kimberly A and Ramshaw, B. J. and Shekhter, A. and Varma, C. M.}, issn = {2469-9969}, journal = {Physical Review B}, number = {20}, publisher = {APS}, title = {{Chiral spin order in some purported Kitaev spin-liquid compounds}}, doi = {10.1103/physrevb.98.205110}, volume = {98}, year = {2018}, } @article{7060, abstract = {The anomalous metallic state in the high-temperature superconducting cuprates is masked by superconductivity near a quantum critical point. Applying high magnetic fields to suppress superconductivity has enabled detailed studies of the normal state, yet the direct effect of strong magnetic fields on the metallic state is poorly understood. We report the high-field magnetoresistance of thin-film La2–xSrxCuO4 cuprate in the vicinity of the critical doping, 0.161 ≤ p ≤ 0.190. We find that the metallic state exposed by suppressing superconductivity is characterized by magnetoresistance that is linear in magnetic fields up to 80 tesla. The magnitude of the linear-in-field resistivity mirrors the magnitude and doping evolution of the well-known linear-in-temperature resistivity that has been associated with quantum criticality in high-temperature superconductors.}, author = {Giraldo-Gallo, P. and Galvis, J. A. and Stegen, Z. and Modic, Kimberly A and Balakirev, F. F. and Betts, J. B. and Lian, X. and Moir, C. and Riggs, S. C. and Wu, J. and Bollinger, A. T. and He, X. and Božović, I. and Ramshaw, B. J. and McDonald, R. D. and Boebinger, G. S. and Shekhter, A.}, issn = {1095-9203}, journal = {Science}, number = {6401}, pages = {479--481}, publisher = {AAAS}, title = {{Scale-invariant magnetoresistance in a cuprate superconductor}}, doi = {10.1126/science.aan3178}, volume = {361}, year = {2018}, } @inproceedings{7116, abstract = {Training deep learning models has received tremendous research interest recently. In particular, there has been intensive research on reducing the communication cost of training when using multiple computational devices, through reducing the precision of the underlying data representation. Naturally, such methods induce system trade-offs—lowering communication precision could de-crease communication overheads and improve scalability; but, on the other hand, it can also reduce the accuracy of training. In this paper, we study this trade-off space, and ask:Can low-precision communication consistently improve the end-to-end performance of training modern neural networks, with no accuracy loss?From the performance point of view, the answer to this question may appear deceptively easy: compressing communication through low precision should help when the ratio between communication and computation is high. However, this answer is less straightforward when we try to generalize this principle across various neural network architectures (e.g., AlexNet vs. ResNet),number of GPUs (e.g., 2 vs. 8 GPUs), machine configurations(e.g., EC2 instances vs. NVIDIA DGX-1), communication primitives (e.g., MPI vs. NCCL), and even different GPU architectures(e.g., Kepler vs. Pascal). Currently, it is not clear how a realistic realization of all these factors maps to the speed up provided by low-precision communication. In this paper, we conduct an empirical study to answer this question and report the insights.}, author = {Grubic, Demjan and Tam, Leo and Alistarh, Dan-Adrian and Zhang, Ce}, booktitle = {Proceedings of the 21st International Conference on Extending Database Technology}, isbn = {9783893180783}, issn = {2367-2005}, location = {Vienna, Austria}, pages = {145--156}, publisher = {OpenProceedings}, title = {{Synchronous multi-GPU training for deep learning with low-precision communications: An empirical study}}, doi = {10.5441/002/EDBT.2018.14}, year = {2018}, } @article{7126, abstract = {In the Minimum Description Length (MDL) principle, learning from the data is equivalent to an optimal coding problem. We show that the codes that achieve optimal compression in MDL are critical in a very precise sense. First, when they are taken as generative models of samples, they generate samples with broad empirical distributions and with a high value of the relevance, defined as the entropy of the empirical frequencies. These results are derived for different statistical models (Dirichlet model, independent and pairwise dependent spin models, and restricted Boltzmann machines). Second, MDL codes sit precisely at a second order phase transition point where the symmetry between the sampled outcomes is spontaneously broken. The order parameter controlling the phase transition is the coding cost of the samples. The phase transition is a manifestation of the optimality of MDL codes, and it arises because codes that achieve a higher compression do not exist. These results suggest a clear interpretation of the widespread occurrence of statistical criticality as a characterization of samples which are maximally informative on the underlying generative process.}, author = {Cubero, Ryan J and Marsili, Matteo and Roudi, Yasser}, issn = {1099-4300}, journal = {Entropy}, keywords = {Minimum Description Length, normalized maximum likelihood, statistical criticality, phase transitions, large deviations}, number = {10}, publisher = {MDPI}, title = {{Minimum description length codes are critical}}, doi = {10.3390/e20100755}, volume = {20}, year = {2018}, } @article{7277, abstract = {Solid alkali metal carbonates are universal passivation layer components of intercalation battery materials and common side products in metal‐O2 batteries, and are believed to form and decompose reversibly in metal‐O2/CO2 cells. In these cathodes, Li2CO3 decomposes to CO2 when exposed to potentials above 3.8 V vs. Li/Li+. However, O2 evolution, as would be expected according to the decomposition reaction 2 Li2CO3→4 Li++4 e−+2 CO2+O2, is not detected. O atoms are thus unaccounted for, which was previously ascribed to unidentified parasitic reactions. Here, we show that highly reactive singlet oxygen (1O2) forms upon oxidizing Li2CO3 in an aprotic electrolyte and therefore does not evolve as O2. These results have substantial implications for the long‐term cyclability of batteries: they underpin the importance of avoiding 1O2 in metal‐O2 batteries, question the possibility of a reversible metal‐O2/CO2 battery based on a carbonate discharge product, and help explain the interfacial reactivity of transition‐metal cathodes with residual Li2CO3.}, author = {Mahne, Nika and Renfrew, Sara E. and McCloskey, Bryan D. and Freunberger, Stefan Alexander}, issn = {1433-7851}, journal = {Angewandte Chemie International Edition}, number = {19}, pages = {5529--5533}, publisher = {Wiley}, title = {{Electrochemical oxidation of Lithium Carbonate generates singlet oxygen}}, doi = {10.1002/anie.201802277}, volume = {57}, year = {2018}, } @article{7271, abstract = {The recent demand of multifunctional materials and devices for advanced applications in energy conversion and data storage resulted into a revival of multiferroics, that is, materials characterized by the coexistence of ferromagnetism and ferroelectricity. Despite intense efforts made in the past decade, single-phase room temperature multiferroics are yet to be discovered/fabricated. Nanostructured ferroic materials could potentially exhibit multiferroism since a high fraction of their atoms/ions are superficial, thereby altering significantly the properties of the bulk phase. Alternately, a magnetic order can be induced into ferroelectric materials upon aliovalent doping with magnetic ions. Here, we report on the synthesis of aggregate-free single-phase transition-metal-doped BaTiO3 quasi-monodisperse cuboidal nanocrystals (NC) which exhibit multiferroic properties at room temperature and can be suitable for applications in data storage. The proposed synthetic route allows the inclusion of a high concentration of magnetic ions such as Mn+ (M = Cr, Mn, Fe, Co) up to a nominal concentration of 4% without the formation of any secondary phase. The size of the nanocrystals was controlled in a wide range from ∼15 up to ∼70 nm by varying the reaction time from 48 to 144 h. The presence of unpaired electrons and their magnetic ordering have been probed by electron paramagnetic resonance spectroscopy (EPR), and a vibrating sample magnetometer (VSM). Likewise, an acentric structure, associated with the existence of a dielectric polarization, was observed by lattice dynamics analysis and piezoresponse force microscopy (PFM). These results show that high-quality titanium-containing perovskite nanocrystals which display multiferroic properties at room temperature can be fabricated via soft solution-based synthetic routes, and the properties of these materials can be modulated by changing the size of the nanocrystals and the concentration of the dopant thereby opening the door to the design and study of single-phase multiferroic materials.}, author = {Costanzo, Tommaso and McCracken, John and Rotaru, Aurelian and Caruntu, Gabriel}, issn = {2574-0970}, journal = {ACS Applied Nano Materials}, number = {9}, pages = {4863--4874}, publisher = {ACS}, title = {{Quasi-monodisperse transition-metal-doped BaTiO3 (M = Cr, Mn, Fe, Co) colloidal nanocrystals with multiferroic properties}}, doi = {10.1021/acsanm.8b01036}, volume = {1}, year = {2018}, } @article{7287, abstract = {Passivation layers on electrode materials are ubiquitous in nonaqueous battery chemistries and strongly govern performance and lifetime. They comprise breakdown products of the electrolyte including carbonate, alkyl carbonates, alkoxides, carboxylates, and polymers. Parasitic chemistry in metal–O2 batteries forms similar products and is tied to the deviation of the O2 balance from the ideal stoichiometry during formation/decomposition of alkaline peroxides or superoxides. Accurate and integral quantification of carbonaceous species and peroxides or superoxides in battery electrodes remains, however, elusive. We present a refined procedure to quantify them accurately and sensitively by pointing out and rectifying pitfalls of previous procedures. Carbonaceous compounds are differentiated into inorganic and organic ones. We combine mass and UV–vis spectrometry to quantify evolved O2 and complexed peroxide and CO2 evolved from carbonaceous compounds by acid treatment and Fenton’s reaction. The capabilities of the method are exemplified by means of Li–O2 and Na–O2 cathodes, graphite anodes, and LiNi0.8Co0.15Al0.05O2 cathodes.}, author = {Schafzahl, Bettina and Mourad, Eléonore and Schafzahl, Lukas and Petit, Yann K. and Raju, Anjana R. and Thotiyl, Musthafa Ottakam and Wilkening, Martin and Slugovc, Christian and Freunberger, Stefan Alexander}, issn = {2380-8195}, journal = {ACS Energy Letters}, number = {1}, pages = {170--176}, publisher = {ACS}, title = {{Quantifying total superoxide, peroxide, and carbonaceous compounds in metal–O2 batteries and the solid electrolyte interphase}}, doi = {10.1021/acsenergylett.7b01111}, volume = {3}, year = {2018}, } @article{7285, abstract = {Hydrogelation, the self-assembly of molecules into soft, water-loaded networks, is one way to bridge the structural gap between single molecules and functional materials. The potential of hydrogels, such as those based on perylene bisimides, lies in their chemical, physical, optical, and electronic properties, which are governed by the supramolecular structure of the gel. However, the structural motifs and their precise role for long-range conductivity are yet to be explored. Here, we present a comprehensive structural picture of a perylene bisimide hydrogel, suggesting that its long-range conductivity is limited by charge transfer between electronic backbones. We reveal nanocrystalline ribbon-like structures as the electronic and structural backbone units between which charge transfer is mediated by polar solvent bridges. We exemplify this effect with sensing, where exposure to polar vapor enhances conductivity by 5 orders of magnitude, emphasizing the crucial role of the interplay between structural motif and surrounding medium for the rational design of devices based on nanocrystalline hydrogels.}, author = {Burian, Max and Rigodanza, Francesco and Demitri, Nicola and D̵ord̵ević, Luka and Marchesan, Silvia and Steinhartova, Tereza and Letofsky-Papst, Ilse and Khalakhan, Ivan and Mourad, Eléonore and Freunberger, Stefan Alexander and Amenitsch, Heinz and Prato, Maurizio and Syrgiannis, Zois}, issn = {1936-0851}, journal = {ACS Nano}, number = {6}, pages = {5800--5806}, publisher = {ACS}, title = {{Inter-backbone charge transfer as prerequisite for long-range conductivity in perylene bisimide hydrogels}}, doi = {10.1021/acsnano.8b01689}, volume = {12}, year = {2018}, } @article{7286, abstract = {The solid electrolyte interphase (SEI) in Li and Na ion batteries forms when highly reducing or oxidizing electrode materials come into contact with a liquid organic electrolyte. Its ability to form a mechanically robust, ion-conducting, and electron-insulating layer critically determines performance, cycle life, and safety. Li or Na alkyl carbonates (LiAC and NaAC, respectively) are lead SEI components in state-of-the-art carbonate based electrolytes, and our fundamental understanding of their charge transport and mechanical properties may hold the key to designing electrolytes forming an improved SEI. We synthesized a homologous series of LiACs and NaACs from methyl to octyl analogues and characterized them with respect to structure, ionic conductivity, and stiffness. The compounds assume layered structures except for the lithium methyl carbonate. Room-temperature conductivities were found to be ∼10–9 S cm–1 for lithium methyl carbonate, <10–12 S cm–1 for the other LiACs, and <10–12 S cm–1 for the NaACs with ion transport mostly attributed to grain boundaries. While LiACs show stiffnesses of ∼1 GPa, NaACs become significantly softer with increasing chain lengths. These findings will help to more precisely interpret the complex results from charge transport and mechanical characterization of real SEIs and can give a rationale for influencing the SEI’s mechanical properties via the electrolyte.}, author = {Schafzahl, Lukas and Ehmann, Heike and Kriechbaum, Manfred and Sattelkow, Jürgen and Ganner, Thomas and Plank, Harald and Wilkening, Martin and Freunberger, Stefan Alexander}, issn = {1520-5002}, journal = {Chemistry of Materials}, number = {10}, pages = {3338--3345}, publisher = {ACS}, title = {{Long-chain Li and Na alkyl carbonates as solid electrolyte interphase components: Structure, ion transport, and mechanical properties}}, doi = {10.1021/acs.chemmater.8b00750}, volume = {30}, year = {2018}, } @inproceedings{7407, abstract = {Proofs of space (PoS) [Dziembowski et al., CRYPTO'15] are proof systems where a prover can convince a verifier that he "wastes" disk space. PoS were introduced as a more ecological and economical replacement for proofs of work which are currently used to secure blockchains like Bitcoin. In this work we investigate extensions of PoS which allow the prover to embed useful data into the dedicated space, which later can be recovered. Our first contribution is a security proof for the original PoS from CRYPTO'15 in the random oracle model (the original proof only applied to a restricted class of adversaries which can store a subset of the data an honest prover would store). When this PoS is instantiated with recent constructions of maximally depth robust graphs, our proof implies basically optimal security. As a second contribution we show three different extensions of this PoS where useful data can be embedded into the space required by the prover. Our security proof for the PoS extends (non-trivially) to these constructions. We discuss how some of these variants can be used as proofs of catalytic space (PoCS), a notion we put forward in this work, and which basically is a PoS where most of the space required by the prover can be used to backup useful data. Finally we discuss how one of the extensions is a candidate construction for a proof of replication (PoR), a proof system recently suggested in the Filecoin whitepaper. }, author = {Pietrzak, Krzysztof Z}, booktitle = {10th Innovations in Theoretical Computer Science Conference (ITCS 2019)}, isbn = {978-3-95977-095-8}, issn = {1868-8969}, location = {San Diego, CA, United States}, pages = {59:1--59:25}, publisher = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik}, title = {{Proofs of catalytic space}}, doi = {10.4230/LIPICS.ITCS.2019.59}, volume = {124}, year = {2018}, } @article{7458, abstract = {The coupling between magnetic and electric subsystems in composites of ferromagnetic and ferroelectric phases is a product property that is facilitated by mechanical strain that arises due to magnetostriction and the piezoelectric effect in the constituent phases. Such multiferroic composites are of immense interests for studies on the physics of electromagnetic coupling and for use in a variety of applications. Here, we focus on magneto-electric (ME) coupling in nanocomposites. Particular emphasis is on core-shell particles and coaxial fibers, thin film heterostructures, and planar structures with a variety of mechanical connectivity. A brief review of models that predict strong ME effects in nanostructures is followed by synthesis and characterization. Core-shell particulate composites can be prepared by hydrothermal processes and chemical or deoxyribonucleic acid-assisted assembly. Electrospinning techniques have been utilized to prepare defect free core-shell nanofibers. Core-shell particles and fibers can be assembled into superstructures with the aid of magnetic and electric fields and characterized for possible use in advanced technologies. Chemical-vapor deposition techniques have been shown to be effective for the preparation of heterostructures of ferrites and ferroelectrics. Exotic planar multiferroic structures with potential for enhancing ME coupling strengths are also considered. Scanning probe microscopy techniques are ideal for probing the nature of direct- and converse-ME coupling in individual nanostructures. Magnetoelectric characterization of assemblies of nanocomposites can be done by ME voltage coefficient, magnetic field induced polarization, and magneto-dielectric effects. We conclude with a brief discussion on possible avenues for strengthening the product properties in the nanocomposites.}, author = {Viehland, Dwight and Li, Jie Fang and Yang, Yaodong and Costanzo, Tommaso and Yourdkhani, Amin and Caruntu, Gabriel and Zhou, Peng and Zhang, Tianjin and Li, Tianqian and Gupta, Arunava and Popov, Maksym and Srinivasan, Gopalan}, issn = {0021-8979}, journal = {Journal of Applied Physics}, number = {6}, publisher = {AIP}, title = {{Tutorial: Product properties in multiferroic nanocomposites}}, doi = {10.1063/1.5038726}, volume = {124}, year = {2018}, } @article{7717, abstract = {Background: DNA methylation levels change along with age, but few studies have examined the variation in the rate of such changes between individuals. Methods: We performed a longitudinal analysis to quantify the variation in the rate of change of DNA methylation between individuals using whole blood DNA methylation array profiles collected at 2–4 time points (N = 2894) in 954 individuals (67–90 years). Results: After stringent quality control, we identified 1507 DNA methylation CpG sites (rsCpGs) with statistically significant variation in the rate of change (random slope) of DNA methylation among individuals in a mixed linear model analysis. Genes in the vicinity of these rsCpGs were found to be enriched in Homeobox transcription factors and the Wnt signalling pathway, both of which are related to ageing processes. Furthermore, we investigated the SNP effect on the random slope. We found that 4 out of 1507 rsCpGs had one significant (P < 5 × 10−8/1507) SNP effect and 343 rsCpGs had at least one SNP effect (436 SNP-probe pairs) reaching genome-wide significance (P < 5 × 10−8). Ninety-five percent of the significant (P < 5 × 10−8) SNPs are on different chromosomes from their corresponding probes. Conclusions: We identified CpG sites that have variability in the rate of change of DNA methylation between individuals, and our results suggest a genetic basis of this variation. Genes around these CpG sites have been reported to be involved in the ageing process.}, author = {Zhang, Qian and Marioni, Riccardo E and Robinson, Matthew Richard and Higham, Jon and Sproul, Duncan and Wray, Naomi R and Deary, Ian J and McRae, Allan F and Visscher, Peter M}, issn = {1756-994X}, journal = {Genome Medicine}, number = {1}, publisher = {Springer Nature}, title = {{Genotype effects contribute to variation in longitudinal methylome patterns in older people}}, doi = {10.1186/s13073-018-0585-7}, volume = {10}, year = {2018}, } @article{7718, abstract = {Flores Island, Indonesia, was inhabited by the small-bodied hominin species Homo floresiensis, which has an unknown evolutionary relationship to modern humans. This island is also home to an extant human pygmy population. Here we describe genome-scale single-nucleotide polymorphism data and whole-genome sequences from a contemporary human pygmy population living on Flores near the cave where H. floresiensis was found. The genomes of Flores pygmies reveal a complex history of admixture with Denisovans and Neanderthals but no evidence for gene flow with other archaic hominins. Modern individuals bear the signatures of recent positive selection encompassing the FADS (fatty acid desaturase) gene cluster, likely related to diet, and polygenic selection acting on standing variation that contributed to their short-stature phenotype. Thus, multiple independent instances of hominin insular dwarfism occurred on Flores.}, author = {Tucci, Serena and Vohr, Samuel H. and McCoy, Rajiv C. and Vernot, Benjamin and Robinson, Matthew Richard and Barbieri, Chiara and Nelson, Brad J. and Fu, Wenqing and Purnomo, Gludhug A. and Sudoyo, Herawati and Eichler, Evan E. and Barbujani, Guido and Visscher, Peter M. and Akey, Joshua M. and Green, Richard E.}, issn = {0036-8075}, journal = {Science}, number = {6401}, pages = {511--516}, publisher = {American Association for the Advancement of Science}, title = {{Evolutionary history and adaptation of a human pygmy population of Flores Island, Indonesia}}, doi = {10.1126/science.aar8486}, volume = {361}, year = {2018}, }