@article{13416, abstract = {The reversible molecular template-directed self-assembly of gold nanoparticles (AuNPs), a process which relies solely on noncovalent bonding interactions, has been demonstrated by high-resolution transmission electron microscopy (HR-TEM). By employing a well-known host−guest binding motif, the AuNPs have been systemized into discrete dimers, trimers, and tetramers. These nanoparticulate twins, triplets, and quadruplets, which can be disassembled and reassembled either chemically or electrochemically, can be coalesced into larger, permanent polygonal structures by thermal treatment using a focused HR-TEM electron beam.}, author = {Olson, Mark A. and Coskun, Ali and Klajn, Rafal and Fang, Lei and Dey, Sanjeev K. and Browne, Kevin P. and Grzybowski, Bartosz A. and Stoddart, J. Fraser}, issn = {1530-6992}, journal = {Nano Letters}, keywords = {Mechanical Engineering, Condensed Matter Physics, General Materials Science, General Chemistry, Bioengineering}, number = {9}, pages = {3185--3190}, publisher = {American Chemical Society}, title = {{Assembly of polygonal nanoparticle clusters directed by reversible noncovalent bonding interactions}}, doi = {10.1021/nl901385c}, volume = {9}, year = {2009}, } @article{13417, abstract = {Mission Impossible: Metal nanoparticles (NPs) coated with photoresponsive ligands are used as “inks” for self-erasing “paper” whereby light-induced self-assembly of the NPs is transduced into local color changes (see picture). Depending on the degree of self-assembly, multicolor images can be written using only one type of NP ink. Duration of image erasure is regulated by the surface concentration of photoactive groups and can range from seconds to days.}, author = {Klajn, Rafal and Wesson, Paul J. and Bishop, Kyle J. M. and Grzybowski, Bartosz A.}, issn = {1521-3773}, journal = {Angewandte Chemie International Edition}, keywords = {General Chemistry, Catalysis}, number = {38}, pages = {7035--7039}, publisher = {Wiley}, title = {{Writing self-erasing images using metastable nanoparticle “inks”}}, doi = {10.1002/anie.200901119}, volume = {48}, year = {2009}, } @article{13418, abstract = {In traditional photoconductors1,2,3, the impinging light generates mobile charge carriers in the valence and/or conduction bands, causing the material’s conductivity to increase4. Such positive photoconductance is observed in both bulk and nanostructured5,6 photoconductors. Here we describe a class of nanoparticle-based materials whose conductivity can either increase or decrease on irradiation with visible light of wavelengths close to the particles’ surface plasmon resonance. The remarkable feature of these plasmonic materials is that the sign of the conductivity change and the nature of the electron transport between the nanoparticles depend on the molecules comprising the self-assembled monolayers (SAMs)7,8 stabilizing the nanoparticles. For SAMs made of electrically neutral (polar and non-polar) molecules, conductivity increases on irradiation. If, however, the SAMs contain electrically charged (either negatively or positively) groups, conductivity decreases. The optical and electrical characteristics of these previously undescribed inverse photoconductors can be engineered flexibly by adjusting the material properties of the nanoparticles and of the coating SAMs. In particular, in films comprising mixtures of different nanoparticles or nanoparticles coated with mixed SAMs, the overall photoconductance is a weighted average of the changes induced by the individual components. These and other observations can be rationalized in terms of light-induced creation of mobile charge carriers whose transport through the charged SAMs is inhibited by carrier trapping in transient polaron-like states9,10. The nanoparticle-based photoconductors we describe could have uses in chemical sensors and/or in conjunction with flexible substrates.}, author = {Nakanishi, Hideyuki and Bishop, Kyle J. M. and Kowalczyk, Bartlomiej and Nitzan, Abraham and Weiss, Emily A. and Tretiakov, Konstantin V. and Apodaca, Mario M. and Klajn, Rafal and Stoddart, J. Fraser and Grzybowski, Bartosz A.}, issn = {1476-4687}, journal = {Nature}, keywords = {Multidisciplinary}, number = {7253}, pages = {371--375}, publisher = {Springer Nature}, title = {{Photoconductance and inverse photoconductance in films of functionalized metal nanoparticles}}, doi = {10.1038/nature08131}, volume = {460}, year = {2009}, } @article{13419, abstract = {Reaction-diffusion (RD) processes initiated from the surfaces of mesoscopic particles can fabricate complex core-and-shell structures. The propagation of a sharp RD front selectively removes metal colloids or nanoparticles from the supporting gel or polymer matrix. Once fabricated, the core structures can be processed “remotely” via galvanic replacement reactions, and the composite particles can be assembled into open-lattice crystals.}, author = {Wesson, Paul J. and Soh, Siowling and Klajn, Rafal and Bishop, Kyle J. M. and Gray, Timothy P. and Grzybowski, Bartosz A.}, issn = {1521-4095}, journal = {Advanced Materials}, keywords = {Mechanical Engineering, Mechanics of Materials, General Materials Science}, number = {19}, pages = {1911--1915}, publisher = {Wiley}, title = {{“Remote” fabrication via three-dimensional reaction-diffusion: Making complex core-and-shell particles and assembling them into open-lattice crystals}}, doi = {10.1002/adma.200802964}, volume = {21}, year = {2009}, } @article{13420, abstract = {Weakly protected metal nanoparticles (MNPs) are used as precursors for the preparation of catenane- and pseudorotaxane-decorated NPs of various compositions (gold, palladium, platinum). When attached to the surface of MNPs, the molecular switches retain their switching abilities. The redox potentials of these switches depend on and can be regulated by the composition of the mixed self-assembled monolayers covering the MNPs.}, author = {Klajn, Rafal and Fang, Lei and Coskun, Ali and Olson, Mark A. and Wesson, Paul J. and Stoddart, J. Fraser and Grzybowski, Bartosz A.}, issn = {1520-5126}, journal = {Journal of the American Chemical Society}, keywords = {Colloid and Surface Chemistry, Biochemistry, General Chemistry, Catalysis}, number = {12}, pages = {4233--4235}, publisher = {American Chemical Society}, title = {{Metal nanoparticles functionalized with molecular and supramolecular switches}}, doi = {10.1021/ja9001585}, volume = {131}, year = {2009}, } @article{13421, abstract = {Side-chain poly[2]catenanes at the click of a switch! A bistable side-chain poly[2]catenane has been synthesized and found to form hierarchical self-assembled hollow superstructures of nanoscale dimensions in solution. Molecular electromechanical switching (see picture) of the material is demonstrated, and the ground-state equilibrium thermodynamics and switching kinetics are examined as the initial steps towards processible molecular-based electronic devices and nanoelectromechanical systems.}, author = {Olson, Mark A. and Braunschweig, Adam B. and Fang, Lei and Ikeda, Taichi and Klajn, Rafal and Trabolsi, Ali and Wesson, Paul J. and Benítez, Diego and Mirkin, Chad A. and Grzybowski, Bartosz A. and Stoddart, J. Fraser}, issn = {1521-3773}, journal = {Angewandte Chemie International Edition}, keywords = {General Chemistry, Catalysis}, number = {10}, pages = {1792--1797}, publisher = {Wiley}, title = {{A bistable poly[2]catenane forms nanosuperstructures}}, doi = {10.1002/anie.200804558}, volume = {48}, year = {2009}, } @article{17809, abstract = {Supermassive black hole binaries (SMBHBs) in galactic nuclei are thought to be a common by-product of major galaxy mergers. We use simple disk models for the circumbinary gas and for the binary–disk interaction to follow the orbital decay of SMBHBs with a range of total masses (M) and mass ratios (q), through physically distinct regions of the disk, until gravitational waves (GWs) take over their evolution. Prior to the GW-driven phase, the viscous decay is generically in the stalled "secondary-dominated" regime. SMBHBs spend a non-negligible fraction of a fiducial time of 107 yr at orbital periods between days ≲torb≲ yr, and we argue that they may be sufficiently common to be detectable, provided they are luminous during these stages. A dedicated optical or X-ray survey could identify coalescing SMBHBs statistically, as a population of periodically variable quasars, whose abundance obeys the scaling Nvar ∝ tαvar within a range of periods around tvar∼ tens of weeks. SMBHBs with M ≲ 107 M☉, with 0.5 ≲ α ≲ 1.5, would probe the physics of viscous orbital decay, whereas the detection of a population of higher-mass binaries, with α = 8/3, would confirm that their decay is driven by GWs. The lowest-mass SMBHBs (M ≲ 105–6 M☉) enter the GW-driven regime at short orbital periods, when they are already in the frequency band of the Laser Interferometric Space Antenna (LISA). While viscous processes are negligible in the last few years of coalescence, they could reduce the amplitude of any unresolved background due to near-stationary LISA sources. We discuss modest constraints on the SMBHB population already available from existing data, and the sensitivity and sky coverage requirements for a detection in future surveys. SMBHBs may also be identified from velocity shifts in their spectra; we discuss the expected abundance of SMBHBs as a function of their orbital velocity.}, author = {Haiman, Zoltán and Kocsis, Bence and Menou, Kristen}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {2}, pages = {1952--1969}, publisher = {American Astronomical Society}, title = {{The population of viscosity- and gravitational wave-driven supermassive black hole binaries among luminous active galactic nuclei}}, doi = {10.1088/0004-637x/700/2/1952}, volume = {700}, year = {2009}, } @article{1798, abstract = {The mammalian brain is assembled from thousands of neuronal cell types that are organized in distinct circuits to perform behaviorally relevant computations. Transgenic mouse lines with selectively marked cell types would facilitate our ability to dissect functional components of complex circuits. We carried out a screen for cell type-specific green fluorescent protein expression in the retina using BAC transgenic mice from the GENSAT project. Among others, we identified mouse lines in which the inhibitory cell types of the night vision and directional selective circuit were selectively labeled. We quantified the stratification patterns to predict potential synaptic connectivity between marked cells of different lines and found that some of the lines enabled targeted recordings and imaging of cell types from developing or mature retinal circuits. Our results suggest the potential use of a stratification-based screening approach for characterizing neuronal circuitry in other layered brain structures, such as the neocortex.}, author = {Sandra Siegert and Scherf, Brigitte G and Del Punta, Karina and Didkovsky, Nick and Heintz, Nathaniel M and Roska, Botond M}, journal = {Nature Neuroscience}, number = {9}, pages = {1197 -- 1204}, publisher = {Nature Publishing Group}, title = {{Genetic address book for retinal cell types}}, doi = {10.1038/nn.2370}, volume = {12}, year = {2009}, } @article{1799, abstract = {The detection of approaching objects, such as looming predators, is necessary for survival. Which neurons and circuits mediate this function? We combined genetic labeling of cell types, two-photon microscopy, electrophysiology and theoretical modeling to address this question. We identify an approach-sensitive ganglion cell type in the mouse retina, resolve elements of its afferent neural circuit, and describe how these confer approach sensitivity on the ganglion cell. The circuit's essential building block is a rapid inhibitory pathway: it selectively suppresses responses to non-approaching objects. This rapid inhibitory pathway, which includes AII amacrine cells connected to bipolar cells through electrical synapses, was previously described in the context of night-time vision. In the daytime conditions of our experiments, the same pathway conveys signals in the reverse direction. The dual use of a neural pathway in different physiological conditions illustrates the efficiency with which several functions can be accommodated in a single circuit.}, author = {Münch, Thomas A and Da Silveira, Ravá A and Sandra Siegert and Viney, Tim J and Awatramani, Gautam B and Roska, Botond M}, journal = {Nature Neuroscience}, number = {10}, pages = {1308 -- 1316}, publisher = {Nature Publishing Group}, title = {{Approach sensitivity in the retina processed by a multifunctional neural circuit}}, doi = {10.1038/nn.2389}, volume = {12}, year = {2009}, } @article{18028, abstract = {We measure the conductance and current–voltage characteristics of two amine-terminated molecular wires— 4,4'-diaminostilbene and bis-(4-aminophenyl)acetylene—by breaking Au point contacts in a molecular solution at room temperature. Histograms compiled from thousands of measurements show a slight increase in the molecular junction conductance (I/V) as the bias is increased to nearly 450 mV. Comparatively, similar conductance measurements made with 1,6-diaminohexane, a saturated molecule, demonstrate almost no bias dependence. We also present a new technique to measure a statistically defined current–voltage (I–V) curve. Application to all three molecules shows that 4,4'-diaminostilbene exhibits the largest increase in differential conductance as a function of applied bias. This indicates that the predominant transport channel for 4,4'-diaminostilbene (the highest occupied molecular orbital) is closer to the Fermi level of the metal than that of the other molecules, consistent with the trends observed in the molecular ionization potential. We find that junctions constructed with the conjugated molecules show greater noise in individual junctions and less structural stability, on average, at biases greater than 450 mV. In contrast, junctions formed with the alkane can sustain a bias of up to 900 mV. This significantly affects the statistically averaged I–V characteristic measured for the conjugated molecules at higher bias.}, author = {Widawsky, J R and Kamenetska, M and Klare, J and Nuckolls, C and Steigerwald, M L and Hybertsen, M S and Venkataraman, Latha}, issn = {1361-6528}, journal = {Nanotechnology}, number = {43}, publisher = {IOP Publishing}, title = {{Measurement of voltage-dependent electronic transport across amine-linked single-molecular-wire junctions}}, doi = {10.1088/0957-4484/20/43/434009}, volume = {20}, year = {2009}, } @article{18029, abstract = {We compare the conductance of 1,4-bis(methylthio)benzene with that of 2,3,6,7-tetrahydrobenzo[1,2-b:4,5-b′]dithiophene and the conductance of 1,4-bis(methylseleno)benzene with that of 2,3,6,7-tetrahydrobenzo[1,2-b:4,5-b′]diselenophene and show explicitly that the orientation of an Au−S or Au−Se bond relative to the aromatic π system controls electron transport through conjugated molecules. Specifically, we have found that the conduction pathway connects the Au electrodes to the aromatic π-system via the chalcogen p lone pairs, and greater overlaps among these components lead to higher conductivity through the molecular junction.}, author = {Park, Young S. and Widawsky, Jonathan R. and Kamenetska, Maria and Steigerwald, Michael L. and Hybertsen, Mark S. and Nuckolls, Colin and Venkataraman, Latha}, issn = {1520-5126}, journal = {Journal of the American Chemical Society}, number = {31}, pages = {10820--10821}, publisher = {American Chemical Society}, title = {{Frustrated rotations in single-molecule junctions}}, doi = {10.1021/ja903731m}, volume = {131}, year = {2009}, } @article{18030, abstract = {We analyze the formation and evolution statistics of single-molecule junctions bonded to gold electrodes using amine, methyl sulfide, and dimethyl phosphine link groups by measuring conductance as a function of junction elongation. For each link, the maximum elongation and formation probability increase with molecular length, strongly suggesting that processes other than just metal-molecule bond breakage play a key role in junction evolution under stress. Density functional theory calculations of adiabatic trajectories show sequences of atomic-scale changes in junction structure, including shifts in the attachment point, that account for the long conductance plateau lengths observed.}, author = {Kamenetska, M. and Koentopp, M. and Whalley, A. C. and Park, Y. S. and Steigerwald, M. L. and Nuckolls, C. and Hybertsen, M. S. and Venkataraman, Latha}, issn = {1079-7114}, journal = {Physical Review Letters}, number = {12}, publisher = {American Physical Society}, title = {{Formation and evolution of single-molecule junctions}}, doi = {10.1103/physrevlett.102.126803}, volume = {102}, year = {2009}, } @article{18031, abstract = {Molecular-scale components are expected to be central to the realization of nanoscale electronic devices1,2,3. Although molecular-scale switching has been reported in atomic quantum point contacts4,5,6, single-molecule junctions provide the additional flexibility of tuning the on/off conductance states through molecular design. To date, switching in single-molecule junctions has been attributed to changes in the conformation or charge state of the molecule7,8,9,10,11,12. Here, we demonstrate reversible binary switching in a single-molecule junction by mechanical control of the metal–molecule contact geometry. We show that 4,4'-bipyridine–gold single-molecule junctions can be reversibly switched between two conductance states through repeated junction elongation and compression. Using first-principles calculations, we attribute the different measured conductance states to distinct contact geometries at the flexible but stable nitrogen–gold bond: conductance is low when the N–Au bond is perpendicular to the conducting π-system, and high otherwise. This switching mechanism, inherent to the pyridine–gold link, could form the basis of a new class of mechanically activated single-molecule switches.}, author = {Quek, Su Ying and Kamenetska, Maria and Steigerwald, Michael L. and Choi, Hyoung Joon and Louie, Steven G. and Hybertsen, Mark S. and Neaton, J. B. and Venkataraman, Latha}, issn = {1748-3395}, journal = {Nature Nanotechnology}, number = {4}, pages = {230--234}, publisher = {Springer Nature}, title = {{Mechanically controlled binary conductance switching of a single-molecule junction}}, doi = {10.1038/nnano.2009.10}, volume = {4}, year = {2009}, } @article{1825, abstract = {Many membrane channels and receptors exhibit adaptive, or desensitized, response to a strong sustained input stimulus. A key mechanism that underlies this response is the slow, activity-dependent removal of responding molecules to a pool which is unavailable to respond immediately to the input. This mechanism is implemented in different ways in various biological systems and has traditionally been studied separately for each. Here we highlight the common aspects of this principle, shared by many biological systems, and suggest a unifying theoretical framework. We study theoretically a class of models which describes the general mechanism and allows us to distinguish its universal from system-specific features. We show that under general conditions, regardless of the details of kinetics, molecule availability encodes an averaging over past activity and feeds back multiplicatively on the system output. The kinetics of recovery from unavailability determines the effective memory kernel inside the feedback branch, giving rise to a variety of system-specific forms of adaptive response—precise or input-dependent, exponential or power-law—as special cases of the same model. }, author = {Tamar Friedlander and Brenner, Naama}, journal = {PNAS}, number = {52}, pages = {22558 -- 22563}, publisher = {National Academy of Sciences}, title = {{Adaptive response by state-dependent inactivation}}, doi = {10.1073/pnas.0902146106 }, volume = {106}, year = {2009}, } @article{18356, abstract = {Similarity is one of the most important abstract concepts in human perception of the world. In computer vision, numerous applications deal with comparing objects observed in a scene with some a priori known patterns. Often, it happens that while two objects are not similar, they have large similar parts, that is, they are partially similar. Here, we present a novel approach to quantify partial similarity using the notion of Pareto optimality. We exemplify our approach on the problems of recognizing non-rigid geometric objects, images, and analyzing text sequences.}, author = {Bronstein, Alexander and Bronstein, Michael M. and Bruckstein, Alfred M. and Kimmel, Ron}, issn = {1573-1405}, journal = {International Journal of Computer Vision}, number = {2}, pages = {163--183}, publisher = {Springer Nature}, title = {{Partial similarity of objects, or how to compare a centaur to a horse}}, doi = {10.1007/s11263-008-0147-3}, volume = {84}, year = {2009}, } @article{18357, abstract = {This paper explores the problem of similarity criteria between nonrigid shapes. Broadly speaking, such criteria are divided into intrinsic and extrinsic, the first referring to the metric structure of the object and the latter to how it is laid out in the Euclidean space. Both criteria have their advantages and disadvantages: extrinsic similarity is sensitive to nonrigid deformations, while intrinsic similarity is sensitive to topological noise. In this paper, we approach the problem from the perspective of metric geometry. We show that by unifying the extrinsic and intrinsic similarity criteria, it is possible to obtain a stronger topology-invariant similarity, suitable for comparing deformed shapes with different topology. We construct this new joint criterion as a tradeoff between the extrinsic and intrinsic similarity and use it as a set-valued distance. Numerical results demonstrate the efficiency of our approach in cases where using either extrinsic or intrinsic criteria alone would fail.}, author = {Bronstein, Alexander and Bronstein, Michael M. and Kimmel, Ron}, issn = {1573-1405}, journal = {International Journal of Computer Vision}, number = {3}, pages = {281--301}, publisher = {Springer Nature}, title = {{Topology-invariant similarity of nonrigid shapes}}, doi = {10.1007/s11263-008-0172-2}, volume = {81}, year = {2009}, } @inproceedings{18391, abstract = {We introduce a design of a coded light-based 3D color video camera optimized for build up cost as well as accuracy in depth reconstruction and acquisition speed. The components of the system include a monochromatic camera and an off-the-shelf LED projector synchronized by a miniature circuit. The projected patterns are captured and processed at a rate of 200 fps and allow for real-time reconstruction of both depth and color at video rates. The reconstruction and display are performed at around 30 depth profiles and color texture per second using a graphics processing unit (GPU).}, author = {Rubinstein, O. and Honen, Y. and Bronstein, Alexander and Bronstein, M. M. and Kimmel, R.}, booktitle = {12th International Conference on Computer Vision Workshops}, location = {Kyoto, Japan}, publisher = {IEEE}, title = {{3D-color video camera}}, doi = {10.1109/iccvw.2009.5457433}, year = {2009}, } @inproceedings{18392, abstract = {Feature-based methods have recently gained popularity in computer vision and pattern recognition communities, in applications such as object recognition and image retrieval. In this paper, we explore analogous approaches in the 3D world applied to the problem of non-rigid shape search and retrieval in large databases.}, author = {Ovsjanikov, Maks and Bronstein, Alexander and Bronstein, Michael M. and Guibas, Leonidas J.}, booktitle = {12th International Conference on Computer Vision Workshops}, isbn = {9781424444427}, location = {Kyoto, Japan}, publisher = {IEEE}, title = {{Shape Google: A computer vision approach to isometry invariant shape retrieval}}, doi = {10.1109/iccvw.2009.5457682}, year = {2009}, } @inproceedings{18393, abstract = {Shape-from-X is a generic type of inverse problems in computer vision, in which a shape is reconstructed from some measurements. A specially challenging setting of this problem is the case in which the reconstructed shapes are non-rigid. In this paper, we propose a framework for intrinsic regularization of such problems. The assumption is that we have the geometric structure of a shape which is intrinsically (up to bending) similar to the one we would like to reconstruct. For that goal, we formulate a variation with respect to vertex coordinates of a triangulated mesh approximating the continuous shape. The numerical core of the proposed method is based on differentiating the fast marching update step for geodesic distance computation.}, author = {Devir, Yohai S. and Rosman, Guy and Bronstein, Alexander and Bronstein, Michael M. and Kimmel, Ron}, booktitle = {12th International Conference on Computer Vision Workshops}, isbn = {9781424444427}, location = {Kyoto, Japan}, publisher = {IEEE}, title = {{On reconstruction of non-rigid shapes with intrinsic regularization}}, doi = {10.1109/iccvw.2009.5457688}, year = {2009}, } @article{18438, abstract = {Partial matching of geometric structures is important in computer vision, pattern recognition and shape analysis applications. The problem consists of matching similar parts of shapes that may be dissimilar as a whole. Recently, it was proposed to consider partial similarity as a multi-criterion optimization problem trying to simultaneously maximize the similarity and the significance of the matching parts. A major challenge in that framework is providing a quantitative measure of the significance of a part of an object. Here, we define the significance of a part of a shape by its discriminative power with respect do a given shape database — that is, the uniqueness of the part. We define a point-wise significance density using a statistical weighting approach similar to the term frequency-inverse document frequency (tf-idf) weighting employed in search engines. The significance measure of a given part is obtained by integrating over this density. Numerical experiments show that the proposed approach produces intuitive significant parts, and demonstrate an improvement in the performance of partial matching between shapes. }, author = {Bronstein, Alexander and Bronstein, Michael M. and Carmon, Yair and Kimmel, Ron}, issn = {1882-6695}, journal = {IPSJ Transactions on Computer Vision and Applications}, pages = {105--114}, publisher = {Information Processing Society of Japan}, title = {{Partial similarity of shapes using a statistical significance measure}}, doi = {10.2197/ipsjtcva.1.105}, volume = {1}, year = {2009}, }