@article{13395, abstract = {Metallic nanoparticles co-functionalised with monolayers of UV- and CO2-sensitive ligands were prepared and shown to respond to these two types of stimuli reversibly and in an orthogonal fashion. The composition of the coating could be tailored to yield nanoparticles capable of aggregating exclusively when both UV and CO2 were applied at the same time, analogously to the behaviour of an AND logic gate.}, author = {Lee, Ji-Woong and Klajn, Rafal}, issn = {1364-548X}, journal = {Chemical Communications}, keywords = {Materials Chemistry, Metals and Alloys, Surfaces, Coatings and Films, General Chemistry, Ceramics and Composites, Electronic, Optical and Magnetic Materials, Catalysis}, number = {11}, pages = {2036--2039}, publisher = {Royal Society of Chemistry}, title = {{Dual-responsive nanoparticles that aggregate under the simultaneous action of light and CO2}}, doi = {10.1039/c4cc08541h}, volume = {51}, year = {2015}, } @article{13396, abstract = {Photoswitching in densely packed azobenzene self-assembled monolayers (SAMs) is strongly affected by steric constraints and excitonic coupling between neighboring chromophores. Therefore, control of the chromophore density is essential for enhancing and manipulating the photoisomerization yield. We systematically compare two methods to achieve this goal: First, we assemble monocomponent azobenzene–alkanethiolate SAMs on gold nanoparticles of varying size. Second, we form mixed SAMs of azobenzene–alkanethiolates and “dummy” alkanethiolates on planar substrates. Both methods lead to a gradual decrease of the chromophore density and enable efficient photoswitching with low-power light sources. X-ray spectroscopy reveals that coadsorption from solution yields mixtures with tunable composition. The orientation of the chromophores with respect to the surface normal changes from a tilted to an upright position with increasing azobenzene density. For both systems, optical spectroscopy reveals a pronounced excitonic shift that increases with the chromophore density. In spite of exciting the optical transition of the monomer, the main spectral change in mixed SAMs occurs in the excitonic band. In addition, the photoisomerization yield decreases only slightly by increasing the azobenzene–alkanethiolate density, and we observed photoswitching even with minor dilutions. Unlike in solution, azobenzene in the planar SAM can be switched back almost completely by optical excitation from the cis to the original trans state within a short time scale. These observations indicate cooperativity in the photoswitching process of mixed SAMs.}, author = {Moldt, Thomas and Brete, Daniel and Przyrembel, Daniel and Das, Sanjib and Goldman, Joel R. and Kundu, Pintu K. and Gahl, Cornelius and Klajn, Rafal and Weinelt, Martin}, issn = {1520-5827}, journal = {Langmuir}, keywords = {Electrochemistry, Spectroscopy, Surfaces and Interfaces, Condensed Matter Physics, General Materials Science}, number = {3}, pages = {1048--1057}, publisher = {American Chemical Society}, title = {{Tailoring the properties of surface-immobilized azobenzenes by monolayer dilution and surface curvature}}, doi = {10.1021/la504291n}, volume = {31}, year = {2015}, } @article{13397, abstract = {Self-assembly of inorganic nanoparticles has been studied extensively for particles having different sizes and compositions. However, relatively little attention has been devoted to how the shape and surface chemistry of magnetic nanoparticles affects their self-assembly properties. Here, we undertook a combined experiment–theory study aimed at better understanding of the self-assembly of cubic magnetite (Fe3O4) particles. We demonstrated that, depending on the experimental parameters, such as the direction of the magnetic field and nanoparticle density, a variety of superstructures can be obtained, including one-dimensional filaments and helices, as well as C-shaped assemblies described here for the first time. Furthermore, we functionalized the surfaces of the magnetic nanocubes with light-sensitive ligands. Using these modified nanoparticles, we were able to achieve orthogonal control of self-assembly using a magnetic field and light.}, author = {Singh, Gurvinder and Chan, Henry and Udayabhaskararao, T. and Gelman, Elijah and Peddis, Davide and Baskin, Artem and Leitus, Gregory and Král, Petr and Klajn, Rafal}, issn = {1364-5498}, journal = {Faraday Discussions}, keywords = {Physical and Theoretical Chemistry}, pages = {403--421}, publisher = {Royal Society of Chemistry}, title = {{Magnetic field-induced self-assembly of iron oxide nanocubes}}, doi = {10.1039/c4fd00265b}, volume = {181}, year = {2015}, } @article{13398, author = {Sun, Yugang and Scarabelli, Leonardo and Kotov, Nicholas and Tebbe, Moritz and Lin, Xiao-Min and Brullot, Ward and Isa, Lucio and Schurtenberger, Peter and Moehwald, Helmuth and Fedin, Igor and Velev, Orlin and Faivre, Damien and Sorensen, Christopher and Perzynski, Régine and Chanana, Munish and Li, Zhihai and Bresme, Fernando and Král, Petr and Firlar, Emre and Schiffrin, David and Souza Junior, Joao Batista and Fery, Andreas and Shevchenko, Elena and Tarhan, Ozgur and Alivisatos, Armand Paul and Disch, Sabrina and Klajn, Rafal and Ghosh, Suvojit}, issn = {1364-5498}, journal = {Faraday Discussions}, keywords = {Physical and Theoretical Chemistry}, pages = {463--479}, publisher = {Royal Society of Chemistry}, title = {{Field-assisted self-assembly process: General discussion}}, doi = {10.1039/c5fd90041g}, volume = {181}, year = {2015}, } @article{1383, abstract = {In plants, vacuolar H+-ATPase (V-ATPase) activity acidifies both the trans-Golgi network/early endosome (TGN/EE) and the vacuole. This dual V-ATPase function has impeded our understanding of how the pH homeostasis within the plant TGN/EE controls exo- and endocytosis. Here, we show that the weak V-ATPase mutant deetiolated3 (det3) displayed a pH increase in the TGN/EE, but not in the vacuole, strongly impairing secretion and recycling of the brassinosteroid receptor and the cellulose synthase complexes to the plasma membrane, in contrast to mutants lacking tonoplast-localized V-ATPase activity only. The brassinosteroid insensitivity and the cellulose deficiency defects in det3 were tightly correlated with reduced Golgi and TGN/EE motility. Thus, our results provide strong evidence that acidification of the TGN/EE, but not of the vacuole, is indispensable for functional secretion and recycling in plants.}, author = {Yu, Luo and Scholl, Stefan and Doering, Anett and Yi, Zhang and Irani, Niloufer and Di Rubbo, Simone and Neumetzler, Lutz and Krishnamoorthy, Praveen and Van Houtte, Isabelle and Mylle, Evelien and Bischoff, Volker and Vernhettes, Samantha and Winne, Johan and Friml, Jirí and Stierhof, York and Schumacher, Karin and Persson, Staffan and Russinova, Eugenia}, journal = {Nature Plants}, number = {7}, publisher = {Nature Publishing Group}, title = {{V-ATPase activity in the TGN/EE is required for exocytosis and recycling in Arabidopsis}}, doi = {10.1038/nplants.2015.94}, volume = {1}, year = {2015}, } @phdthesis{1401, abstract = {The human ability to recognize objects in complex scenes has driven research in the computer vision field over couple of decades. This thesis focuses on the object recognition task in images. That is, given the image, we want the computer system to be able to predict the class of the object that appears in the image. A recent successful attempt to bridge semantic understanding of the image perceived by humans and by computers uses attribute-based models. Attributes are semantic properties of the objects shared across different categories, which humans and computers can decide on. To explore the attribute-based models we take a statistical machine learning approach, and address two key learning challenges in view of object recognition task: learning augmented attributes as mid-level discriminative feature representation, and learning with attributes as privileged information. Our main contributions are parametric and non-parametric models and algorithms to solve these frameworks. In the parametric approach, we explore an autoencoder model combined with the large margin nearest neighbor principle for mid-level feature learning, and linear support vector machines for learning with privileged information. In the non-parametric approach, we propose a supervised Indian Buffet Process for automatic augmentation of semantic attributes, and explore the Gaussian Processes classification framework for learning with privileged information. A thorough experimental analysis shows the effectiveness of the proposed models in both parametric and non-parametric views.}, author = {Sharmanska, Viktoriia}, issn = {2663-337X}, pages = {144}, publisher = {Institute of Science and Technology Austria}, title = {{Learning with attributes for object recognition: Parametric and non-parametrics views}}, doi = {10.15479/at:ista:1401}, year = {2015}, } @article{14013, abstract = {The ultrafast motion of electrons and holes after light-matter interaction is fundamental to a broad range of chemical and biophysical processes. We advanced high-harmonic spectroscopy to resolve spatially and temporally the migration of an electron hole immediately after ionization of iodoacetylene while simultaneously demonstrating extensive control over the process. A multidimensional approach, based on the measurement and accurate theoretical description of both even and odd harmonic orders, enabled us to reconstruct both quantum amplitudes and phases of the electronic states with a resolution of ~100 attoseconds. We separately reconstructed quasi-field-free and laser-controlled charge migration as a function of the spatial orientation of the molecule and determined the shape of the hole created by ionization. Our technique opens the prospect of laser control over electronic primary processes.}, author = {Kraus, P. M. and Mignolet, B. and Baykusheva, Denitsa Rangelova and Rupenyan, A. and Horný, L. and Penka, E. F. and Grassi, G. and Tolstikhin, O. I. and Schneider, J. and Jensen, F. and Madsen, L. B. and Bandrauk, A. D. and Remacle, F. and Wörner, H. J.}, issn = {1095-9203}, journal = {Science}, keywords = {Multidisciplinary}, number = {6262}, pages = {790--795}, publisher = {American Association for the Advancement of Science}, title = {{Measurement and laser control of attosecond charge migration in ionized iodoacetylene}}, doi = {10.1126/science.aab2160}, volume = {350}, year = {2015}, } @article{14014, abstract = {We have studied a coupled electronic-nuclear wave packet in nitric oxide using time-resolved strong-field photoelectron holography and rescattering. We show that the electronic dynamics mainly appears in the holographic structures whereas nuclear motion strongly modulates the angular distribution of the rescattered photoelectrons.}, author = {Walt, Samuel G and Ram, N Bhargava and von Conta, Aaron and Baykusheva, Denitsa Rangelova and Atala, Marcos and Wörner, Hans Jakob}, issn = {1742-6596}, journal = {Journal of Physics: Conference Series}, keywords = {General Physics and Astronomy}, number = {11}, publisher = {IOP Publishing}, title = {{Resolving the dynamics of valence-shell electrons and nuclei through laser-induced diffraction and holography}}, doi = {10.1088/1742-6596/635/11/112135}, volume = {635}, year = {2015}, } @article{14015, abstract = {We advance high-harmonic spectroscopy to resolve molecular charge migration in time and space and simultaneously demonstrate extensive control over the process. A multidimensional approach enables us to reconstruct both quantum amplitudes and phases with a resolution of better than 100 attoseconds and to separately reconstruct field-free and laser- driven charge migration. Our techniques make charge migration in molecules measurable on the attosecond time scale and open new avenues for laser control of electronic primary processes.}, author = {Kraus, P M and Mignolet, B and Baykusheva, Denitsa Rangelova and Rupenyan, A and Horný, L and Penka, E F and Tolstikhin, O I and Schneider, J and Jensen, F and Madsen, L B and Bandrauk, A D and Remacle, F and Wörner, H J}, issn = {1742-6596}, journal = {Journal of Physics: Conference Series}, keywords = {General Physics and Astronomy}, number = {11}, publisher = {IOP Publishing}, title = {{Attosecond charge migration and its laser control}}, doi = {10.1088/1742-6596/635/11/112136}, volume = {635}, year = {2015}, } @article{14016, abstract = {All attosecond time-resolved measurements have so far relied on the use of intense near-infrared laser pulses. In particular, attosecond streaking, laser-induced electron diffraction and high-harmonic generation all make use of non-perturbative light–matter interactions. Remarkably, the effect of the strong laser field on the studied sample has often been neglected in previous studies. Here we use high-harmonic spectroscopy to measure laser-induced modifications of the electronic structure of molecules. We study high-harmonic spectra of spatially oriented CH3F and CH3Br as generic examples of polar polyatomic molecules. We accurately measure intensity ratios of even and odd-harmonic orders, and of the emission from aligned and unaligned molecules. We show that these robust observables reveal a substantial modification of the molecular electronic structure by the external laser field. Our insights offer new challenges and opportunities for a range of emerging strong-field attosecond spectroscopies.}, author = {Kraus, P. M. and Tolstikhin, O. I. and Baykusheva, Denitsa Rangelova and Rupenyan, A. and Schneider, J. and Bisgaard, C. Z. and Morishita, T. and Jensen, F. and Madsen, L. B. and Wörner, H. J.}, issn = {2041-1723}, journal = {Nature Communications}, keywords = {General Physics and Astronomy, General Biochemistry, Genetics and Molecular Biology, General Chemistry, Multidisciplinary}, publisher = {Springer Nature}, title = {{Observation of laser-induced electronic structure in oriented polyatomic molecules}}, doi = {10.1038/ncomms8039}, volume = {6}, year = {2015}, } @article{14017, abstract = {The detection of electron motion and electronic wave-packet dynamics is one of the core goals of attosecond science. Recently, choosing the nitric oxide molecule as an example, we have introduced and demonstrated an experimental approach to measure coupled valence electronic and rotational wave packets using high-order-harmonic-generation (HHG) spectroscopy [Kraus et al., Phys. Rev. Lett. 111, 243005 (2013)]. A short outline of the theory to describe the combination of the pump and HHG probe process was published together with an extensive discussion of experimental results [Baykusheva et al., Faraday Discuss. 171, 113 (2014)]. The comparison of theory and experiment showed good agreement on a quantitative level. Here, we present the theory in detail, which is based on a generalized density-matrix approach that describes the pump process and the subsequent probing of the wave packets by a semiclassical quantitative rescattering approach. An in-depth analysis of the different Raman scattering contributions to the creation of the coupled rotational and electronic spin-orbit wave packets is made. We present results for parallel and perpendicular linear polarizations of the pump and probe laser pulses. Furthermore, an analysis of the combined rotational-electronic density matrix in terms of irreducible components is presented that facilitates interpretation of the results.}, author = {Zhang, Song Bin and Baykusheva, Denitsa Rangelova and Kraus, Peter M. and Wörner, Hans Jakob and Rohringer, Nina}, issn = {1094-1622}, journal = {Physical Review A}, keywords = {Atomic and Molecular Physics, and Optics}, number = {2}, publisher = {American Physical Society}, title = {{Theoretical study of molecular electronic and rotational coherences by high-order-harmonic generation}}, doi = {10.1103/physreva.91.023421}, volume = {91}, year = {2015}, } @inproceedings{1424, abstract = {We consider the problem of statistical computations with persistence diagrams, a summary representation of topological features in data. These diagrams encode persistent homology, a widely used invariant in topological data analysis. While several avenues towards a statistical treatment of the diagrams have been explored recently, we follow an alternative route that is motivated by the success of methods based on the embedding of probability measures into reproducing kernel Hilbert spaces. In fact, a positive definite kernel on persistence diagrams has recently been proposed, connecting persistent homology to popular kernel-based learning techniques such as support vector machines. However, important properties of that kernel enabling a principled use in the context of probability measure embeddings remain to be explored. Our contribution is to close this gap by proving universality of a variant of the original kernel, and to demonstrate its effective use in twosample hypothesis testing on synthetic as well as real-world data.}, author = {Kwitt, Roland and Huber, Stefan and Niethammer, Marc and Lin, Weili and Bauer, Ulrich}, location = {Montreal, Canada}, pages = {3070 -- 3078}, publisher = {Neural Information Processing Systems Foundation}, title = {{Statistical topological data analysis-A kernel perspective}}, volume = {28}, year = {2015}, } @inproceedings{1425, abstract = {In this work we aim at extending the theoretical foundations of lifelong learning. Previous work analyzing this scenario is based on the assumption that learning tasks are sampled i.i.d. from a task environment or limited to strongly constrained data distributions. Instead, we study two scenarios when lifelong learning is possible, even though the observed tasks do not form an i.i.d. sample: first, when they are sampled from the same environment, but possibly with dependencies, and second, when the task environment is allowed to change over time in a consistent way. In the first case we prove a PAC-Bayesian theorem that can be seen as a direct generalization of the analogous previous result for the i.i.d. case. For the second scenario we propose to learn an inductive bias in form of a transfer procedure. We present a generalization bound and show on a toy example how it can be used to identify a beneficial transfer algorithm.}, author = {Pentina, Anastasia and Lampert, Christoph}, location = {Montreal, Canada}, pages = {1540 -- 1548}, publisher = {Neural Information Processing Systems Foundation}, title = {{Lifelong learning with non-i.i.d. tasks}}, volume = {2015}, year = {2015}, } @inproceedings{1430, abstract = {Evolutionary algorithms (EAs) form a popular optimisation paradigm inspired by natural evolution. In recent years the field of evolutionary computation has developed a rigorous analytical theory to analyse their runtime on many illustrative problems. Here we apply this theory to a simple model of natural evolution. In the Strong Selection Weak Mutation (SSWM) evolutionary regime the time between occurrence of new mutations is much longer than the time it takes for a new beneficial mutation to take over the population. In this situation, the population only contains copies of one genotype and evolution can be modelled as a (1+1)-type process where the probability of accepting a new genotype (improvements or worsenings) depends on the change in fitness. We present an initial runtime analysis of SSWM, quantifying its performance for various parameters and investigating differences to the (1+1) EA. We show that SSWM can have a moderate advantage over the (1+1) EA at crossing fitness valleys and study an example where SSWM outperforms the (1+1) EA by taking advantage of information on the fitness gradient.}, author = {Paixao, Tiago and Sudholt, Dirk and Heredia, Jorge and Trubenova, Barbora}, booktitle = {Proceedings of the 2015 Annual Conference on Genetic and Evolutionary Computation}, location = {Madrid, Spain}, pages = {1455 -- 1462}, publisher = {ACM}, title = {{First steps towards a runtime comparison of natural and artificial evolution}}, doi = {10.1145/2739480.2754758}, year = {2015}, } @article{14303, abstract = {Scaffolded DNA origami enables the fabrication of a variety of complex nanostructures that promise utility in diverse fields of application, ranging from biosensing over advanced therapeutics to metamaterials. The broad applicability of DNA origami as a material beyond the level of proof-of-concept studies critically depends, among other factors, on the availability of large amounts of pure single-stranded scaffold DNA. Here, we present a method for the efficient production of M13 bacteriophage-derived genomic DNA using high-cell-density fermentation of Escherichia coli in stirred-tank bioreactors. We achieve phage titers of up to 1.6 × 1014 plaque-forming units per mL. Downstream processing yields up to 410 mg of high-quality single-stranded DNA per one liter reaction volume, thus upgrading DNA origami-based nanotechnology from the milligram to the gram scale.}, author = {Kick, B and Praetorius, Florian M and Dietz, H and Weuster-Botz, D}, issn = {1530-6992}, journal = {Nano Letters}, number = {7}, pages = {4672--4676}, publisher = {ACS Publications}, title = {{Efficient production of single-stranded phage DNA as scaffolds for DNA origami}}, doi = {10.1021/acs.nanolett.5b01461}, volume = {15}, year = {2015}, } @misc{1473, abstract = {In this paper we survey geometric and arithmetic techniques to study the cohomology of semiprojective hyperkähler manifolds including toric hyperkähler varieties, Nakajima quiver varieties and moduli spaces of Higgs bundles on Riemann surfaces. The resulting formulae for their Poincaré polynomials are combinatorial and representation theoretical in nature. In particular we will look at their Betti numbers and will establish some results and state some expectations on their asymptotic shape.}, author = {Tamas Hausel and Rodríguez Villegas, Fernando}, booktitle = {Asterisque}, number = {370}, pages = {113 -- 156}, publisher = {Societe Mathematique de France}, title = {{Cohomology of large semiprojective hyperkähler varieties}}, volume = {2015}, year = {2015}, } @inproceedings{1474, abstract = {Cryptographic access control offers selective access to encrypted data via a combination of key management and functionality-rich cryptographic schemes, such as attribute-based encryption. Using this approach, publicly available meta-data may inadvertently leak information on the access policy that is enforced by cryptography, which renders cryptographic access control unusable in settings where this information is highly sensitive. We begin to address this problem by presenting rigorous definitions for policy privacy in cryptographic access control. For concreteness we set our results in the model of Role-Based Access Control (RBAC), where we identify and formalize several different flavors of privacy, however, our framework should serve as inspiration for other models of access control. Based on our insights we propose a new system which significantly improves on the privacy properties of state-of-the-art constructions. Our design is based on a novel type of privacy-preserving attribute-based encryption, which we introduce and show how to instantiate. We present our results in the context of a cryptographic RBAC system by Ferrara et al. (CSF'13), which uses cryptography to control read access to files, while write access is still delegated to trusted monitors. We give an extension of the construction that permits cryptographic control over write access. Our construction assumes that key management uses out-of-band channels between the policy enforcer and the users but eliminates completely the need for monitoring read/write access to the data.}, author = {Ferrara, Anna and Fuchsbauer, Georg and Liu, Bin and Warinschi, Bogdan}, location = {Verona, Italy}, pages = {46--60}, publisher = {IEEE}, title = {{Policy privacy in cryptographic access control}}, doi = {10.1109/CSF.2015.11}, year = {2015}, } @inproceedings{1481, abstract = {Simple board games, like Tic-Tac-Toe and CONNECT-4, play an important role not only in the development of mathematical and logical skills, but also in the emotional and social development. In this paper, we address the problem of generating targeted starting positions for such games. This can facilitate new approaches for bringing novice players to mastery, and also leads to discovery of interesting game variants. We present an approach that generates starting states of varying hardness levels for player 1 in a two-player board game, given rules of the board game, the desired number of steps required for player 1 to win, and the expertise levels of the two players. Our approach leverages symbolic methods and iterative simulation to efficiently search the extremely large state space. We present experimental results that include discovery of states of varying hardness levels for several simple grid-based board games. The presence of such states for standard game variants like 4×4 Tic-Tac-Toe opens up new games to be played that have never been played as the default start state is heavily biased. }, author = {Ahmed, Umair and Chatterjee, Krishnendu and Gulwani, Sumit}, booktitle = {Proceedings of the Twenty-Ninth AAAI Conference on Artificial Intelligence}, location = {Austin, TX, USA}, pages = {745 -- 752}, publisher = {AAAI Press}, title = {{Automatic generation of alternative starting positions for simple traditional board games}}, volume = {2}, year = {2015}, } @inproceedings{1483, abstract = {Topological data analysis offers a rich source of valuable information to study vision problems. Yet, so far we lack a theoretically sound connection to popular kernel-based learning techniques, such as kernel SVMs or kernel PCA. In this work, we establish such a connection by designing a multi-scale kernel for persistence diagrams, a stable summary representation of topological features in data. We show that this kernel is positive definite and prove its stability with respect to the 1-Wasserstein distance. Experiments on two benchmark datasets for 3D shape classification/retrieval and texture recognition show considerable performance gains of the proposed method compared to an alternative approach that is based on the recently introduced persistence landscapes.}, author = {Reininghaus, Jan and Huber, Stefan and Bauer, Ulrich and Kwitt, Roland}, location = {Boston, MA, USA}, pages = {4741 -- 4748}, publisher = {IEEE}, title = {{A stable multi-scale kernel for topological machine learning}}, doi = {10.1109/CVPR.2015.7299106}, year = {2015}, } @inproceedings{1495, abstract = {Motivated by biological questions, we study configurations of equal-sized disks in the Euclidean plane that neither pack nor cover. Measuring the quality by the probability that a random point lies in exactly one disk, we show that the regular hexagonal grid gives the maximum among lattice configurations. }, author = {Edelsbrunner, Herbert and Iglesias Ham, Mabel and Kurlin, Vitaliy}, booktitle = {Proceedings of the 27th Canadian Conference on Computational Geometry}, location = {Ontario, Canada}, pages = {128--135}, publisher = {Queen's University}, title = {{Relaxed disk packing}}, volume = {2015-August}, year = {2015}, }