@article{12642, abstract = {Near-surface air temperature, typically measured at a height of 2 m, is the most important control on the energy exchange and the melt rate at a snow or ice surface. It is distributed in a simplistic manner in most glacier melt models by using constant linear lapse rates, which poorly represent the actual spatial and temporal variability of air temperature. In this paper, we test a simple thermodynamic model proposed by Greuell and Böhm in 1998 as an alternative, using a new dataset of air temperature measurements from along the flowline of Haut Glacier d’Arolla, Switzerland. The unmodified model performs little better than assuming a constant linear lapse rate. When modified to allow the ratio of the boundary layer height to the bulk heat transfer coefficient to vary along the flowline, the model matches measured air temperatures better, and a further reduction of the root-mean-square error is obtained, although there is still considerable scope for improvement. The modified model is shown to perform best under conditions favourable to the development of katabatic winds – few clouds, positive ambient air temperature, limited influence of synoptic or valley winds and a long fetch – but its performance is poor under cloudy conditions.}, author = {Petersen, Lene and Pellicciotti, Francesca and Juszak, Inge and Carenzo, Marco and Brock, Ben}, issn = {1727-5644}, journal = {Annals of Glaciology}, keywords = {Earth-Surface Processes}, number = {63}, pages = {120--130}, publisher = {International Glaciological Society}, title = {{Suitability of a constant air temperature lapse rate over an Alpine glacier: Testing the Greuell and Böhm model as an alternative}}, doi = {10.3189/2013aog63a477}, volume = {54}, year = {2013}, } @article{12643, abstract = {Parameterizations of incoming longwave radiation are increasingly receiving attention for both low and high elevation glacierized sites. In this paper, we test 13 clear-sky parameterizations combined with seven cloud corrections for all-sky atmospheric emissivity at one location on Haut Glacier d'Arolla. We also analyze the four seasons separately and conduct a cross-validation to test the parameters’ robustness. The best parameterization is the one by Dilley and O'Brien, B for clear-sky conditions combined with Unsworth and Monteith cloud correction. This model is also the most robust when tested in cross-validation. When validated at different sites in the southern Alps of Switzerland and north-western Italian Alps, all parameterizations show a substantial decrease in performance, except for one site, thus suggesting that it is important to recalibrate parameterizations of incoming longwave radiation for different locations. We argue that this is due to differences in the structure of the atmosphere at the sites. We also quantify the effect that the incoming longwave radiation parameterizations have on energy-balance melt modeling, and show that recalibration of model parameters is needed. Using parameters from other sites leads to a significant underestimation of melt and to an error that is larger than that associated with using different parameterizations. Once recalibrated, however, the parameters of most models seem to be stable over seasons and years at the location on Haut Glacier d'Arolla.}, author = {Juszak, I. and Pellicciotti, Francesca}, issn = {2169-897X}, journal = {Journal of Geophysical Research: Atmospheres}, keywords = {Space and Planetary Science, Earth and Planetary Sciences (miscellaneous), Atmospheric Science, Geophysics}, number = {8}, pages = {3066--3084}, publisher = {American Geophysical Union}, title = {{A comparison of parameterizations of incoming longwave radiation over melting glaciers: Model robustness and seasonal variability}}, doi = {10.1002/jgrd.50277}, volume = {118}, year = {2013}, } @article{1304, abstract = {When confronted with a large-field stimulus rotating around the vertical body axis, flies display a following behavior called "optomotor response." As neural control elements, the large tangential horizontal system (HS) cells of the lobula plate have been prime candidates for long. Here, we applied optogenetic stimulation of HS cells to evaluate their behavioral role in Drosophila. To minimize interference of the optical activation of channelrhodopsin-2 with the visual perception of the flies, we used a bistable variant called ChR2-C128S. By applying pulses of blue and yellow light, we first demonstrate electrophysiologically that lobula plate tangential cells can be activated and deactivated repeatedly with no evident change in depolarization strength over trials. We next show that selective optogenetic activation of HS cells elicits robust yaw head movements and yaw turning responses in fixed and tethered flying flies, respectively.}, author = {Haikala, Väinö and Maximilian Jösch and Borst, Alexander and Mauss, Alex S}, journal = {Journal of Neuroscience}, number = {34}, pages = {13927 -- 13934}, publisher = {Society for Neuroscience}, title = {{Optogenetic control of fly optomotor responses}}, doi = {10.1523/JNEUROSCI.0340-13.2013}, volume = {33}, year = {2013}, } @article{1305, abstract = {In the fly Drosophila melanogaster, photoreceptor input to motion vision is split into two parallel pathways as represented by first-order interneurons L1 and L2 (Rister et al., 2007; Joesch et al., 2010). However, how these pathways are functionally specialized remains controversial. One study (Eichner et al., 2011) proposed that the L1-pathway evaluates only sequences of brightness increments (ON-ON), while the L2-pathway processes exclusively brightness decrements (OFF-OFF). Another study (Clark et al., 2011) proposed that each of the two pathways evaluates both ON-ON and OFF-OFF sequences. To decide between these alternatives, we recorded from motionsensitive neurons in flies in which the output from either L1 or L2 was genetically blocked. We found that blocking L1 abolishes ON-ON responses but leaves OFF-OFF responses intact. The opposite was true, when the output from L2 was blocked. We conclude that the L1 and L2 pathways are functionally specialized to detect ON-ON and OFF-OFF sequences, respectively.}, author = {Maximilian Jösch and Weber, Franz and Eichner, Hubert and Borst, Alexander}, journal = {Journal of Neuroscience}, number = {3}, pages = {902 -- 905}, publisher = {Society for Neuroscience}, title = {{Functional specialization of parallel motion detection circuits in the fly}}, doi = {10.1523/JNEUROSCI.3374-12.2013}, volume = {33}, year = {2013}, } @article{1307, abstract = {We prove uniqueness of solutions of the DLSS equation in a class of sufficiently regular functions. The global weak solutions of the DLSS equation constructed by Jüngel and Matthes belong to this class of uniqueness. We also show uniqueness of solutions for the quantum drift-diffusion equation, which contains additional drift and second-order diffusion terms. The results hold in case of periodic or Dirichlet-Neumann boundary conditions. Our proof is based on a monotonicity property of the DLSS operator and sophisticated approximation arguments; we derive a PDE satisfied by the pointwise square root of the solution, which enables us to exploit the monotonicity property of the operator.}, author = {Julian Fischer}, journal = {Communications in Partial Differential Equations}, number = {11}, pages = {2004 -- 2047}, publisher = {Taylor & Francis}, title = {{Uniqueness of solutions of the Derrida-Lebowitz-Speer-Spohn equation and quantum drift diffusion models}}, doi = {10.1080/03605302.2013.823548}, volume = {38}, year = {2013}, } @article{1308, abstract = {We derive sufficient conditions for advection-driven backward motion of the free boundary in a chemotaxis model with degenerate mobility. In this model, a porous-medium-type diffusive term and an advection term are in competition. The former induces forward motion, the latter may induce backward motion of the free boundary depending on the direction of advection. We deduce conditions on the growth of the initial data at the free boundary which ensure that at least initially the advection term is dominant. This implies local backward motion of the free boundary provided the advection is (locally) directed appropriately. Our result is based on a new class of moving test functions and Stampacchia's lemma. As a by-product of our estimates, we obtain quantitative bounds on the spreading of the support of solutions for the chemotaxis model and provide a proof for the finite speed of the support propagation property of solutions.}, author = {Julian Fischer}, journal = {SIAM Journal on Mathematical Analysis}, number = {3}, pages = {1585 -- 1615}, publisher = {Society for Industrial and Applied Mathematics }, title = {{Advection-driven support shrinking in a chemotaxis model with degenerate mobility}}, doi = {10.1137/120874291}, volume = {45}, year = {2013}, } @article{1310, abstract = {We derive lower bounds on asymptotic support propagation rates for strong solutions of the Cauchy problem for the thin-film equation. The bounds coincide up to a constant factor with the previously known upper bounds and thus are sharp. Our results hold in case of at most three spatial dimensions and n∈. (1, 2.92). The result is established using weighted backward entropy inequalities with singular weight functions to yield a differential inequality; combined with some entropy production estimates, the optimal rate of propagation is obtained. To the best of our knowledge, these are the first lower bounds on asymptotic support propagation rates for higher-order nonnegativity-preserving parabolic equations.}, author = {Julian Fischer}, journal = {Journal of Differential Equations}, number = {10}, pages = {3127 -- 3149}, publisher = {Academic Press}, title = {{Optimal lower bounds on asymptotic support propagation rates for the thin-film equation}}, doi = {10.1016/j.jde.2013.07.028}, volume = {255}, year = {2013}, } @article{2107, abstract = {We present a method for fabrication-oriented design of actuated deformable characters that allows a user to automatically create physical replicas of digitally designed characters using rapid manufacturing technologies. Given a deformable character and a set of target poses as input, our method computes a small set of actuators along with their locations on the surface and optimizes the internal material distribution such that the resulting character exhibits the desired deformation behavior. We approach this problem with a dedicated algorithm that combines finite-element analysis, sparse regularization, and constrained optimization. We validate our pipeline on a set of two- and three-dimensional example characters and present results in simulation and physically-fabricated prototypes.}, author = {Skouras, Mélina and Thomaszewski, Bernhard and Coros, Stelian and Bickel, Bernd and Groß, Markus}, journal = {ACM Transactions on Graphics}, number = {4}, publisher = {ACM}, title = {{Computational design of actuated deformable characters}}, doi = {10.1145/2461912.2461979}, volume = {32}, year = {2013}, } @article{2108, abstract = {We present an interactive design system that allows non-expert users to create animated mechanical characters. Given an articulated character as input, the user iteratively creates an animation by sketching motion curves indicating how different parts of the character should move. For each motion curve, our framework creates an optimized mechanism that reproduces it as closely as possible. The resulting mechanisms are attached to the character and then connected to each other using gear trains, which are created in a semi-automated fashion. The mechanical assemblies generated with our system can be driven with a single input driver, such as a hand-operated crank or an electric motor, and they can be fabricated using rapid prototyping devices. We demonstrate the versatility of our approach by designing a wide range of mechanical characters, several of which we manufactured using 3D printing. While our pipeline is designed for characters driven by planar mechanisms, significant parts of it extend directly to non-planar mechanisms, allowing us to create characters with compelling 3D motions. }, author = {Coros, Stelian and Thomaszewski, Bernhard and Noris, Gioacchino and Sueda, Shinjiro and Forberg, Moira and Sumner, Robert W and Matusik, Wojciech and Bernd Bickel}, journal = {ACM Transactions on Graphics}, number = {4}, publisher = {ACM}, title = {{Computational design of mechanical characters}}, doi = {10.1145/2461912.2461953}, volume = {32}, year = {2013}, } @article{2109, abstract = {Most additive manufacturing technologies work by layering, i.e. slicing the shape and then generating each slice independently. This introduces an anisotropy into the process, often as different accuracies in the tangential and normal directions, but also in terms of other parameters such as build speed or tensile strength and strain. We model this as an anisotropic cubic element. Our approach then finds a compromise between modeling each part of the shape individually in the best possible direction and using one direction for the whole shape part. In particular, we compute an orthogonal basis and consider only the three basis vectors as slice normals (i.e. fabrication directions). Then we optimize a decomposition of the shape along this basis so that each part can be consistently sliced along one of the basis vectors. In simulation, we show that this approach is superior to slicing the whole shape in one direction, only. It also has clear benefits if the shape is larger than the build volume of the available equipment.}, author = {Hildebrand, Kristian and Bernd Bickel and Alexa, Marc}, journal = {Computers and Graphics (Pergamon)}, number = {6}, pages = {669 -- 675}, publisher = {Elsevier}, title = {{Orthogonal slicing for additive manufacturing}}, doi = {10.1016/j.cag.2013.05.011}, volume = {37}, year = {2013}, } @article{2110, abstract = {We present a method for practical physical reproduction and design of homogeneous materials with desired subsurface scattering. Our process uses a collection of different pigments that can be suspended in a clear base material. Our goal is to determine pigment concentrations that best reproduce the appearance and subsurface scattering of a given target material. In order to achieve this task we first fabricate a collection of material samples composed of known mixtures of the available pigments with the base material. We then acquire their reflectance profiles using a custom-built measurement device. We use the same device to measure the reflectance profile of a target material. Based on the database of mappings from pigment concentrations to reflectance profiles, we use an optimization process to compute the concentration of pigments to best replicate the target material appearance. We demonstrate the practicality of our method by reproducing a variety of different translucent materials. We also present a tool that allows the user to explore the range of achievable appearances for a given set of pigments. }, author = {Papas, Marios and Regg, Christian and Jarosz, Wojciech and Bernd Bickel and Jackson, Philip V and Matusik, Wojciech and Marschner, Steve and Groß, Markus S}, journal = {ACM Transactions on Graphics}, number = {4}, publisher = {ACM}, title = {{Fabricating translucent materials using continuous pigment mixtures}}, doi = {10.1145/2461912.2461974}, volume = {32}, year = {2013}, } @article{2111, abstract = {Animated animatronic figures are a unique way to give physical presence to a character. However, their movement and expressions are often limited due to mechanical constraints. In this paper, we propose a complete process for augmenting physical avatars using projector-based illumination, significantly increasing their expressiveness. Given an input animation, the system decomposes the motion into low-frequency motion that can be physically reproduced by the animatronic head and high-frequency details that are added using projected shading. At the core is a spatio-temporal optimization process that compresses the motion in gradient space, ensuring faithful motion replay while respecting the physical limitations of the system. We also propose a complete multi-camera and projection system, including a novel defocused projection and subsurface scattering compensation scheme. The result of our system is a highly expressive physical avatar that features facial details and motion otherwise unattainable due to physical constraints.}, author = {Bermano, Amit H and Bruschweiler, Philipp and Grundhöfer, Anselm and Iwai, Daisuke and Bernd Bickel and Groß, Markus S}, journal = {ACM Transactions on Graphics}, number = {6}, publisher = {ACM}, title = {{Augmenting physical avatars using projector-based illumination}}, doi = {10.1145/2508363.2508416}, volume = {32}, year = {2013}, } @article{21110, abstract = {The NAD(P)H-dependent carbonyl reductase from Candida parapsilosis ATCC 7330 catalyses the asymmetric reduction of ethyl 4-phenyl-2-oxobutanoate to ethyl (R)-4-phenyl-2-hydroxybutanoate, a precursor of angiotensin-converting enzyme inhibitors such as Cilazapril and Benazepril. The carbonyl reductase was expressed in Escherichia coli and purified by GST-affinity and size-exclusion chromatography. Crystals were obtained by the hanging-drop vapour-diffusion method and diffracted to 1.86 Å resolution. The asymmetric unit contained two molecules of carbonyl reductase, with a solvent content of 48%. The structure was solved by molecular replacement using cinnamyl alcohol dehydrogenase from Saccharomyces cerevisiae as a search model.}, author = {Aggarwal, Nidhi and Mandal, Pradeep K and Gautham, Namasivayam and Chadha, Anju}, issn = {1744-3091}, journal = {Acta Crystallographica Section F Structural Biology Communications}, number = {3}, pages = {313--315}, publisher = {International Union of Crystallography}, title = {{Expression, purification, crystallization and preliminary X-ray diffraction analysis of carbonyl reductase from Candida parapsilosis ATCC 7330}}, doi = {10.1107/s1744309113003667}, volume = {69}, year = {2013}, } @article{2112, abstract = {Force-deformation measurements of cloth exhibit significant hysteresis, and many researchers have identified internal friction as the source of this effect. However, it has not been incorporated into computer animation models of cloth. In this paper, we propose a model of internal friction based on an augmented reparameterization of Dahl's model, and we show that this model provides a good match to several important features of cloth hysteresis even with a minimal set of parameters. We also propose novel parameter estimation procedures that are based on simple and inexpensive setups and need only sparse data, as opposed to the complex hardware and dense data acquisition of previous methods. Finally, we provide an algorithm for the efficient simulation of internal friction, and we demonstrate it on simulation examples that show disparate behavior with and without internal friction.}, author = {Miguel, Eder and Tamstorf, Rasmus and Bradley, Derek J and Schvartzman, Sara C and Thomaszewski, Bernhard and Bernd Bickel and Matusik, Wojciech and Marschner, Steve and Otaduy, Miguel A}, journal = {ACM Transactions on Graphics}, number = {6}, publisher = {ACM}, title = {{Modeling and estimation of internal friction in cloth}}, doi = {10.1145/2508363.2508389 }, volume = {32}, year = {2013}, } @article{2113, abstract = {A new method fabricates custom surface reflectance and spatially varying bidirectional reflectance distribution functions (svBRDFs). Researchers optimize a microgeometry for a range of normal distribution functions and simulate the resulting surface's effective reflectance. Using the simulation's results, they reproduce an input svBRDF's appearance by distributing the microgeometry on the printed material's surface. This method lets people print svBRDFs on planar samples with current 3D printing technology, even with a limited set of printing materials. It extends naturally to printing svBRDFs on arbitrary shapes.}, author = {Rouiller, Olivier and Bernd Bickel and Kautz, Jan and Matusik, Wojciech and Alexa, Marc}, journal = {IEEE Computer Graphics and Applications}, number = {6}, pages = {48 -- 57}, publisher = {IEEE}, title = {{3D printing spatially varying BRDFs}}, doi = {10.1109/MCG.2013.82 }, volume = {33}, year = {2013}, } @article{2114, abstract = {3D printing is considered a disruptive technology with a potentially tremendous socioeconomic impact. The three articles in this special issue illustrate how novel computer graphics approaches are advancing such digital fabrication.}, author = {Bernd Bickel and Alexa, Marc}, journal = {IEEE Computer Graphics and Applications}, number = {6}, pages = {24 -- 25}, publisher = {IEEE}, title = {{Computational aspects of fabrication: Modeling, design and 3d printing}}, doi = {10.1109/MCG.2013.89}, volume = {33}, year = {2013}, } @article{2117, abstract = {We prove new upper and lower bounds for Banach space-valued stochastic integrals with respect to a compensated Poisson random measure. Our estimates apply to Banach spaces with non-trivial martingale (co)type and extend various results in the literature. We also develop a Malliavin framework to interpret Poisson stochastic integrals as vector-valued Skorohod integrals, and prove a Clark-Ocone representation formula.}, author = {Dirksen, Sjoerd and Jan Maas and van Neerven, Jan M}, journal = {Electronic Journal of Probability}, publisher = {Institute of Mathematical Statistics}, title = {{Poisson stochastic integration in Banach spaces}}, doi = {10.1214/EJP.v18-2945 }, volume = {18}, year = {2013}, } @article{2129, abstract = {This paper continues the investigation of `Wasserstein-like' transportation distances for probability measures on discrete sets. We prove that the discrete transportation metrics on the d-dimensional discrete torus with mesh size 1/N converge, when N→∞, to the standard 2-Wasserstein distance W_2 on the continuous torus in the sense of Gromov-Hausdorff. This is the first convergence result for the recently developed discrete transportation metrics. The result shows the compatibility between these metrics and the well-established 2-Wasserstein metric. }, author = {Gigli, Nicola and Jan Maas}, journal = {SIAM Journal on Mathematical Analysis}, number = {2}, pages = {879 -- 899}, publisher = {Society for Industrial and Applied Mathematics }, title = {{Gromov-Hausdorff convergence of discrete transportation metrics}}, doi = {10.1137/120886315 }, volume = {45}, year = {2013}, } @article{2139, abstract = {Recently it has been shown that pairs of atoms can form metastable bonds due to non-conservative forces induced by dissipation [Lemeshko&Weimer, Nature Comm. 4, 2230 (2013)]. Here we study the dynamics of interaction-induced coherent population trapping - the process responsible for the formation of dissipatively bound molecules. We derive the effective dissipative potentials induced between ultracold atoms by laser light, and study the time evolution of the scattering states. We demonstrate that binding occurs on short timescales of ~10 microseconds, even if the initial kinetic energy of the atoms significantly exceeds the depth of the dissipative potential. Dissipatively-bound molecules with preordained bond lengths and vibrational wavefunctions can be created and detected in current experiments with ultracold atoms.}, author = {Mikhail Lemeshko}, journal = {Frontiers Physics}, number = {17}, publisher = {Frontiers Media}, title = {{Manipulating scattering of ultracold atoms with light-induced dissipation}}, doi = {10.3389/fphy.2013.00017}, volume = {1}, year = {2013}, } @inproceedings{2182, abstract = {We propose a general framework for abstraction with respect to quantitative properties, such as worst-case execution time, or power consumption. Our framework provides a systematic way for counter-example guided abstraction refinement for quantitative properties. The salient aspect of the framework is that it allows anytime verification, that is, verification algorithms that can be stopped at any time (for example, due to exhaustion of memory), and report approximations that improve monotonically when the algorithms are given more time. We instantiate the framework with a number of quantitative abstractions and refinement schemes, which differ in terms of how much quantitative information they keep from the original system. We introduce both state-based and trace-based quantitative abstractions, and we describe conditions that define classes of quantitative properties for which the abstractions provide over-approximations. We give algorithms for evaluating the quantitative properties on the abstract systems. We present algorithms for counter-example based refinements for quantitative properties for both state-based and segment-based abstractions. We perform a case study on worst-case execution time of executables to evaluate the anytime verification aspect and the quantitative abstractions we proposed.}, author = {Cerny, Pavol and Henzinger, Thomas A and Radhakrishna, Arjun}, booktitle = {Proceedings of the 40th annual ACM SIGPLAN-SIGACT symposium on Principles of programming language}, location = {Rome, Italy}, pages = {115 -- 128}, publisher = {ACM}, title = {{Quantitative abstraction refinement}}, doi = {10.1145/2429069.2429085}, year = {2013}, }