Nanorings and rods interconnected by self-assembly mimicking an artificial network of neurons

[EN] Molecular electronics based on structures ordered as neural networks emerges as the next evolutionary milestone in the construction of nanodevices with unprecedented applications. However, the straightforward formation of geometrically defined and interconnected nanostructures is crucial for the production of electronic circuitry nanoequivalents. Here we report on the molecularly fine-tuned self-assembly of tetrakis-Schiff base compounds into nanosized rings interconnected by unusually large nanorods providing a set of connections that mimic a biological network of neurons. The networks are produced through self-assembly resulting from the molecular conformation and noncovalent intermolecular interactions. These features can be easily generated on flat surfaces and in a polymeric matrix by casting from solution under ambient conditions. The structures can be used to guide the position of electron-transporting agents such as carbon nanotubes on a surface or in a polymer matrix to create electrically conducting networks that can find direct use in constructing nanoelectronic circuits.The research leading to these results has received funding from ICIQ, ICREA, the Spanish Ministerio de Economia y Competitividad (MINECO) through project CTQ2011-27385 and the European Community Seventh Framework Program (FP7-PEOPLE-ITN-2008, CONTACT consortium) under grant agreement number 238363. We acknowledge E. C. Escudero-Adan, M. Martinez-Belmonte and E. Martin from the X-ray department of ICIQ for crystallographic analysis, and M. Moncusi, N. Argany, R. Marimon, M. Stefanova and L. Vojkuvka from the Servei de Recursos Cientifics i Tecnics from Universitat Rovira i Virgili (Tarragona, Spain).Escarcega-Bobadilla, MV.; Zelada-Guillen, GA.; Pyrlin, SV.; Wegrzyn, M.; Ramos, MMD.; Giménez Torres, E.; Stewart, A.... (2013). 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Interface Circuits for Microsensor Integrated Systems

ca. 200 words; this text will present the book in all promotional forms (e.g. flyers). Please describe the book in straightforward and consumer-friendly terms. [Recent advances in sensing technologies, especially those for Microsensor Integrated Systems, have led to several new commercial applications. Among these, low voltage and low power circuit architectures have gained growing attention, being suitable for portable long battery life devices. The aim is to improve the performances of actual interface circuits and systems, both in terms of voltage mode and current mode, in order to overcome the potential problems due to technology scaling and different technology integrations. Related problems, especially those concerning parasitics, lead to a severe interface design attention, especially concerning the analog front-end and novel and smart architecture must be explored and tested, both at simulation and prototype level. Moreover, the growing demand for autonomous systems gets even harder the interface design due to the need of energy-aware cost-effective circuit interfaces integrating, where possible, energy harvesting solutions. The objective of this Special Issue is to explore the potential solutions to overcome actual limitations in sensor interface circuits and systems, especially those for low voltage and low power Microsensor Integrated Systems. The present Special Issue aims to present and highlight the advances and the latest novel and emergent results on this topic, showing best practices, implementations and applications. The Guest Editors invite to submit original research contributions dealing with sensor interfacing related to this specific topic. Additionally, application oriented and review papers are encouraged.

New Aspects of Optical Coherence and their Potential for Quantum Technologies

Currently, optical technology impacts most of our lives, from light used in scientific measurement to the fiber optic cables that makeup the backbone of the internet. However, as our current optical infrastructure grows, we discover that these technologies are not limitless. However, our current optical technology functions on classical principles, and can be easily improved by incorporating our knowledge of quantum optics. In order to implement quantum technologies, our understanding of quantum coherence must improve. Through this knowledge we can maintain quantum states, and therefore their information, longer. In this dissertation, I will demonstrate that with sufficient knowledge of coherent properties, a simple algebra can be derived which can provide rules for graph reductions on a quantum network graph. Using this knowledge, I then provide a rudimentary algorithm which can find the optimal subgraph for communication on a quantum network. Next, I demonstrate that by measuring the photon statistics and second-order quantum coherence of a field, one can create a neural network capable of distinguishing the light sources on a pixel. Which is then applied to develop an imaging scheme capable of surpassing the Abbe-Rayleigh Criterion. Lastly, I present a multiphoton quantum version of the van Cittert-Zernike theorem. This provides formalism capable of determining the propagation of quantum coherence throughout a system. I then demonstrate the usefulness of the theorem by demonstrating sub-Poissonian statistics created by a linear system with an incident thermal beam, obtainable only by post-selection. Altogether, this provides incite into new applications of coherence to quantum technologies and the formalism to extending our knowledge even further.Comment: PhD thesis, 86 pages, 10 figure

Investigations of topological phases for quasi-1D systems

For a long time, quantum states of matter have been successfully characterized by the Ginzburg-Landau formalism that was able to classify all different types of phase transitions. This view changed with the discovery of the quantum Hall effect and topological insulators. The latter are materials that host metallic edge states in an insulating bulk, some of which are protected by the existing symmetries. Complementary to the search of topological phases in condensed matter, great efforts have been made in quantum simulations based on cold atomic gases. Sophisticated laser schemes provide optical lattices with different geometries and allow to tune interactions and the realization of artificial gauge fields. At the same time, new concepts coming from quantum information, based on entanglement, are pushing the frontier of our understanding of quantum phases as a whole. The concept of entanglement has revolutionized the description of quantum many-body states by describing wave functions with tensor networks (TN) that are exploited for numerical simulations based on the variational principle. This thesis falls within the framework of the studies in condensed matter physics: it focuses indeed on the so-called synthetic realization of quantum states of matter, more specifically, of topological ones, which may have on the long-run outfalls towards robust quantum computers. We propose a theoretical investigation of cold atoms in optical lattice pierced by effective (magnetic) gauge fields and subjected to experimentally relevant interactions, by adding a modern numerical approach based on TN algorithms. More specifically, this work will focus on (i) interacting topological phases in quasi-1D systems and, in particular, the Creutz-Hubbard model, (ii) the connection between condensed matter and high energy physics studying the Gross-Neveu model and the discretization of Wilson-Hubbard model, (iii) implementing tensor network-based algorithms.Durante mucho tiempo, los estados cuánticos de la materia se han caracterizado con éxito por el formalismo de Ginzburg-Landau que permitió de clasificar todos los diferentes tipos de transiciones de fase. Esta visión cambió con el descubrimiento del efecto Hall cuántico y los aislantes topológicos. Estos últimos son materiales que albergan estados de borde metálicos en una masa aislante, algunos de los cuales están protegidos por las simetrías existentes. Conjuntamente a la búsqueda de fases topológicas en materia condensada, se han hecho grandes esfuerzos en simulaciones cuánticas basadas en gases atómicos fríos. Los sofisticados esquemas láser proporcionan redes ópticas con diferentes geometrías y permiten ajustar las interacciones y la realización de campos de gauge artificial. Al mismo tiempo, los nuevos conceptos que provienen de la información cuántica, basados en el entanglement, están empujando la frontera de nuestra comprensión de las fases cuánticas en su conjunto. El concepto de entanglement ha revolucionado la descripción de los estados cuánticos de muchos cuerpos al describir las funciones de onda con redes tensoras (TN) que se explotan para simulaciones numéricas basadas en el principio de variación. Esta tesis se enmarca en los estudios de física de la materia condensada: en particular, se centra en la llamada realización sintética de los estados cuánticos de la materia, más específicamente, de los topológicos, que pueden tener en las salidas a largo plazo hacia computadoras cuánticas robustas. Se propone una investigación teórica de los átomos fríos en la red óptica con campos de gauge efectivos y sometidos a interacciones relevantes experimentalmente, agregando un enfoque numérico moderno basado en algoritmos TN. Más específicamente, este trabajo se centrará en (i) fases topológicas en los sistemas cuasi-1D y, en particular, el modelo Creutz-Hubbard, (ii) la conexión entre la materia condensada y la física de alta energía estudiando el modelo Gross-Neveu y el discretización del modelo Wilson-Hubbard, (iii) implementación de algoritmos basados en redes tensoras

Symmetry and Asymmetry in Quasicrystals or Amorphous Materials

About forty years after its discovery, it is still common to read in the literature that quasicrystals (QCs) occupy an intermediate position between amorphous materials and periodic crystals. However, QCs exhibit high-quality diffraction patterns containing a collection of discrete Bragg reflections at variance with amorphous phases. Accordingly, these materials must be properly regarded as long-range ordered materials with a symmetry incompatible with translation invariance. This misleading conceptual status can probably arise from the use of notions borrowed from the amorphous solids framework (such us tunneling states, weak interference effects, variable range hopping, or spin glass) in order to explain certain physical properties observed in QCs. On the other hand, the absence of a general, full-fledged theory of quasiperiodic systems certainly makes it difficult to clearly distinguish the features related to short-range order atomic arrangements from those stemming from long-range order correlations. The contributions collected in this book aim at gaining a deeper understanding on the relationship between the underlying structural order and the resulting physical properties in several illustrative aperiodic systems, including the border line between QCs and related complex metallic alloys, hierarchical superlattices, electrical transmission lines, nucleic acid sequences, photonic quasicrystals, and optical devices based on aperiodic order designs

Flux-charge duality and topological quantum phase fluctuations in quasi-one-dimensional superconductors

It has long been thought that macroscopic phase coherence breaks down in effectively lower-dimensional superconducting systems even at zero temperature due to enhanced topological quantum phase fluctuations. In quasi-1D wires, these fluctuations are described in terms of "quantum phase-slip" (QPS): tunneling of the superconducting order parameter for the wire between states differing by $\pm2\pi$ in their relative phase between the wire's ends. Over the last several decades, many deviations from conventional bulk superconducting behavior have been observed in ultra-narrow superconducting nanowires, some of which have been identified with QPS. While at least some of the observations are consistent with existing theories for QPS, other observations in many cases point to contradictory conclusions or cannot be explained by these theories. Hence, a unified understanding of the nature of QPS, and its relationship to the various observations has yet to be achieved. In this paper we present a new model for QPS which takes as its starting point an idea originally postulated by Mooij and Nazarov [Nature Physics {\bf 2}, 169 (2006)]: that \textit{flux-charge duality}, a classical symmetry of Maxwell's equations, can be used to relate QPS to the well-known Josephson tunneling of Cooper pairs. Our model provides an alternative, and qualitatively different, conceptual basis for QPS and the phenomena which arise from it in experiments, and it appears to permit for the first time a unified understanding of observations across several different types of experiments and materials systems.Comment: 48 Institute of Physics pages, plus 7 pages of appendices and 7 pages of references. 12 figures. v7: additional experimental data considered, and overall improvement for final submissio

Microfluidic bubble logic

Thesis (Ph. D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2008."September 2008."Includes bibliographical references.In this thesis, I propose a new paradigm in computing where bits can simultaneously transport and manipulate materials and information. Information representation is invariably physical. Though this insight is fundamental to understanding the physical limits of computation, it has never been exploited as a scheme for material manipulation. Bringing together notions from computer science and fluid dynamics, I present a new logic family "Bubble Logic" capable of both universal computation and programmable material manipulation in an all-fluidic two-phase system. This removes the distinction between materials and mechanisms to control them, bringing the programmability of the digital world into the physical world - with a wide range of promising applications in biotechnology, highthroughput screening, genomics and fluidic control systems for soft robotics, printing and digital fabrication.Microfluidics, the art of handling nano-to pico-liter volume fluids, is leading to a revolution in large-scale automation of biology and analytical chemistry. However, current lab-on-chip technologies are dependent on external macro-scale control elements, thus requiring a lab to run the chip. Bubble logic provides a dropletel,internal, inherently digital flow control mechanism at kHz frequencies with no moving parts or off-chip components. Nonlinearity is introduced in an otherwise linear, reversible, low Reynolds number flow via bubble-tobubble hydrodynamic interactions. I demonstrate bubble logic AND/OR/NOT gates, a toggle flip-flop, a ripple counter, a timing restoration device, a ring oscillator, a bistable valve and an on-demand bubble generator. These show the nonlinearity, gain, bistability, synchronization, cascadability, feedback and programmability required for scalable universal computation and control.(cont.) The representation used in this thesis makes possible encapsulation and manipulation of a large variety of micro-to nanocale materials including single molecules like DNA or proteins, live cells, liquid crystals, nano-particles and other biological and chemical reagents. Bubble logic provides a scheme to transport, store and operate on this new class of "digital materials" in an integrated, high-throughput fashion. Furthermore, microfluidics has also been extensively employed in biological systems. This thesis describes the discovery of two new physical fluid dynamic mechanisms motivated by a common theme of microfluidics in biology. Firstly, I describe a new superhydrophobic waterrepelling surface that has a characteristic of directional anisotropy to fluid resistance. The discovery, made while studying the integument of water-walking insects, helps rationalize the origin of thrust and hence propulsion of water-walking insects on a fluid interface. Secondly, this thesis uncovers a new physical mechanism for directed droplet transport, which I term "Capillary ratchet". Discovered in a class of surface feeding shorebirds, it is the only physical mechanism that is known to exploit contact angle hysteresis for fluid transport. Capillary ratchet is a promising candidate for implementing global clocking for integrated microfluidic devices.by Manu Prakash.Ph.D

Toward a formal theory for computing machines made out of whatever physics offers: extended version

Approaching limitations of digital computing technologies have spurred research in neuromorphic and other unconventional approaches to computing. Here we argue that if we want to systematically engineer computing systems that are based on unconventional physical effects, we need guidance from a formal theory that is different from the symbolic-algorithmic theory of today's computer science textbooks. We propose a general strategy for developing such a theory, and within that general view, a specific approach that we call "fluent computing". In contrast to Turing, who modeled computing processes from a top-down perspective as symbolic reasoning, we adopt the scientific paradigm of physics and model physical computing systems bottom-up by formalizing what can ultimately be measured in any physical substrate. This leads to an understanding of computing as the structuring of processes, while classical models of computing systems describe the processing of structures.Comment: 76 pages. This is an extended version of a perspective article with the same title that will appear in Nature Communications soon after this manuscript goes public on arxi

Vlsi Implementation of Olfactory Cortex Model

This thesis attempts to implement the building blocks required for the realization of the biologically motivated olfactory neural model in silicon as the special purpose hardware. The olfactory model is originally developed by R. Granger, G. Lynch, and Ambros-Ingerson. CMOS analog integrated circuits were used for this purpose. All of the building blocks were fabricated using the MOSIS service and tested at our site. The results of this study can be used to realize a system level integration of the olfactory model.Electrical Engineerin

Organization and connectivity of premotor interneurons in the mouse spinal cord

Movement is the final behavioral output of neuronal activity in the spinal cord. In all vertebrates, motor neurons are grouped into motor neuron pools, the functional units innervating individual muscles. Spinal interneurons receive a variety of inputs from the brain, cerebellum and sensory afferents, process this information and as the final outcome, the information reaches the motor neurons that control the activation of the innervated muscles. For generation of movement, precise activation of distinct motor neuron pools at the right moment in time is crucial and this precision is possible due to the cohorts of spinal interneurons, connected with specificity to distinct motor neuron pools that regulate motor neuronal activity. How premotor circuits connect to distinct motor neuron pools with specificity is poorly understood and represented a main question of my PhD thesis work. In my thesis, I present the results of my studies on connectivity of premotor interneuron populations to specific motor neuron pools in two layers - as general distribution patterns specific to control the regulation of particular muscles and by closer examination of the connection specificity of one class of the spinal pre-motor interneurons, the cholinergic partition cells. One significant part of this project was to develop a tool that allowed studying the pre-motor interneurons innervating defined motor neuron pools. For this purpose, I have adapted a novel rabies virus based tool (Wickersham et al. (2007b)) for mono- transsynaptic tracing of neuronal circuits in the spinal cord in vivo. I was successful in establishing an anatomical rabies-virus based connectivity assay in early postnatal mice in order to study the connectivity scheme of premotor neurons, the neuronal cohorts monosynaptically connected to motor neurons. The main parts of my thesis focus on: 1) motor neuron pools connectivity with premotor interneurons that appear to be widely-distributed when analysed at the segmental level, yet group into stereotypic populations, and differing for pools innervating functionally-distinct muscles; 2) local or segmental distribution of interneurons depending on their molecular identity; 3) specificity of the connectivity of cholinergic partition cells involved in the regulation of motor neuron excitability - this subpopulation of premotor interneurons segregate into ipsilaterally and bilaterally projecting populations, the latter exhibiting preferential connections to equivalent motor neuron pools bilaterally. A minor part of my thesis is devoted to the connectivity of the spinal pre-motor interneurons in α2-chimaerin mutant mice. Data presented in this part are preliminary and this project needs continuation, but the results begin to provide insight into the function of the α2-chimaerin molecule in the axon guidance and perhaps connectivity process of the bilaterally projecting subclass of partition cells and a dorsal subgroup of premotor interneurons. I demonstrate that the distribution of cholinergic partition cells connected to a particular motor neuron pool is different in α2-chimaerin mutant mice than in the wild-type mice. I also show that the distribution pattern of ectopic bilaterally projecting premotor interneurons in α2-chimaerin mutant mice what concerns the dorsal population of premotor interneurons. These studies of premotor interneurons visualize the widespread but precise nature of connectivity with motor neuron pools, reveal exquisite synaptic specificity for bilaterally projecting cholinergic partition cells and show the importance of the α2-chimaerin molecule in axon guidance and connectivity processes for the establishment of the appropriate premotor circuits in the spinal cord