Stettler O.,University Paris Est Creteil |
Moya K.L.,The Interdisciplinary Center |
Moya K.L.,Research University
Seminars in Cell and Developmental Biology | Year: 2014
The construction of the brain is a highly regulated process, requiring coordination of various cellular and molecular mechanisms that together ensure the stability of the cerebrum architecture and functions. The mature brain is an organ that performs complex computational operations using specific sensory information from the outside world and this requires precise organization within sensory networks and a separation of sensory modalities during development. We review here the role of homeoproteins in the arealization of the brain according to sensorimotor functions, the micropartition of its cytoarchitecture, and the maturation of its sensory circuitry. One of the most interesting observation about homeoproteins in recent years concerns their ability to act both in a cell-autonomous and non-cell-autonomous manner. The highlights in the present review collectively show how these two modes of action of homeoproteins confer various functions in shaping cortical maps. © 2014 Elsevier Ltd.
Wiese K.J.,French National Center for Scientific Research |
Wiese K.J.,Research University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2016
We derive and study two different formalisms used for nonequilibrium processes: the coherent-state path integral, and an effective, coarse-grained stochastic equation of motion. We first study the coherent-state path integral and the corresponding field theory, using the annihilation process A+A→A as an example. The field theory contains counterintuitive quartic vertices. We show how they can be interpreted in terms of a first-passage problem. Reformulating the coherent-state path integral as a stochastic equation of motion, the noise generically becomes imaginary. This renders it not only difficult to interpret, but leads to convergence problems at finite times. We then show how alternatively an effective coarse-grained stochastic equation of motion with real noise can be constructed. The procedure is similar in spirit to the derivation of the mean-field approximation for the Ising model, and the ensuing construction of its effective field theory. We finally apply our findings to stochastic Manna sandpiles. We show that the coherent-state path integral is inappropriate, or at least inconvenient. As an alternative, we derive and solve its mean-field approximation, which we then use to construct a coarse-grained stochastic equation of motion with real noise. © 2016 American Physical Society.
Nature Photonics Light source for quicker computer chips Waveguide with integrated carbon nanotubes for conversion of electric signals into light quicker computer chips are feasible publication in Nature Photonics
Home > Press > Nature Photonics: Light source for quicker computer chips: Waveguide with integrated carbon nanotubes for conversion of electric signals into light / quicker computer chips are feasible / publication in Nature Photonics Abstract: Worldwide growing data volumes make conventional electronic processing reach its limits. Future information technology is therefore expected to use light as a medium for quick data transmission also within computer chips. Researchers under the direction of KIT have now demonstrated that carbon nanotubes are suited for use as on-chip light source for tomorrow's information technology, when nanostructured waveguides are applied to obtain the desired light properties. The scientists now present their results in Nature Photonics. DOI: 10.1038/NPHOTON. 2016.70 On the large scale, data transmission by light has long become a matter of routine: Glass fiber cables as light waveguides transmit telephone and internet signals, for instance. For using the advantages of light, i.e. speed and energy efficiency, also on the small scale of computer chips, researchers of KIT have made an important step from fundamental research towards application. By the integration of smallest carbon nanotubes into a nanostructured waveguide, they have developed a compact miniaturized switching element that converts electric signals into clearly defined optical signals. "The nanostructures act like a photonic crystal and allow for customizing the properties of light from the carbon nanotube," Felix Pyatkov and Valentin Fütterling, the first authors of the study of KIT's Institute of Nanotechnology, explain. "In this way, we can generate narrow-band light in the desired color on the chip." Processing of the waveguide precisely defines the wavelength at which the light is transmitted. By engravings using electron beam lithography, the waveguides of several micrometers in length are provided with finest cavities of a few nanometers in size. They determine the waveguide's optical properties. The resulting photonic crystals reflect the light in certain colors, a phenomenon observed in nature on apparently colorful butterfly wings. As novel light sources, carbon nanotubes of about 1 micrometer in length and 1 nanometer in diameter are positioned on metal contacts in transverse direction to the waveguide. At KIT, a process was developed, by means of which the nanotubes can be integrated specifically into highly complex structures. The researchers applied the method of dielectrophoresis for deposition of carbon nanotubes from the solution and their arrangement vertically to the waveguide. This way of separating particles using inhomogeneous electric fields was originally used in biology and is highly suited to deposit nanoscaled objects on carrier materials. The carbon nanotubes integrated into the waveguide act as a small light source. When electric voltage is applied, they produce photons. The compact electricity/light signal converter presented now meets the requirements of the next generation of computers that combine electronic components with nanophotonic waveguides. The signal converter bundles the light about as strongly as a laser and responds to variable signals with high speed. Already now, the optoelectronic components developed by the researchers can be used to produce light signals in the gigahertz frequency range from electric signals. Among the leading researchers involved in the project were Ralph Krupke, who conducts research at the KIT Institute of Nanotechnology and at the Institute of Materials Science of TU Darmstadt, Wolfram H.P. Pernice, who moved from the KIT to the University of Münster one year ago, and Manfred M. Kappes, Institute of Physical Chemistry and Institute of Nanotechnology of KIT. The project was funded by the Science and Technology of Nanosystems (STN) programme of the Helmholtz Association. It is aimed at studying nanosystems of unique functionality and the potential of materials of a few nanometers in structural size. The Volkswagen Foundation financed a Ph.D. student position for the research project. In addition, the project was supported by the Karlsruhe Nano Micro Facility (KNMF) platform. About Karlsruhe Institute of Technology (KIT) Karlsruhe Institute of Technology (KIT) pools its three core tasks of research, higher education, and innovation in a mission. With about 9,300 employees and 25,000 students, KIT is one of the big institutions of research and higher education in natural sciences and engineering in Europe. KIT - The Research University in the Helmholtz Association Since 2010, the KIT has been certified as a family-friendly university. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
Home > Press > Nanofur for oil spill cleanup: Materials researchers learn from aquatic ferns: Hairy plant leaves are highly oil-absorbing / publication in bioinspiration & biomimetics / video on absorption capacity Abstract: Some water ferns can absorb large volumes of oil within a short time, because their leaves are strongly water-repellent and, at the same time, highly oil-absorbing. Researchers of KIT, together with colleagues of Bonn University, have found that the oil-binding capacity of the water plant results from the hairy microstructure of its leaves. It is now used as a model to further develop the new Nanofur material for the environmentally friendly cleanup of oil spills. (DOI: 10.1088/1748-3190/11/5/056003) Damaged pipelines, oil tanker disasters, and accidents on oil drilling and production platforms may result in pollutions of water with crude or mineral oil. Conventional methods to clean up the oil spill are associated with specific drawbacks. Oil combustion or the use of chemical substances to accelerate oil decomposition cause secondary environmental pollution. Many natural materials to take up the oil, such as sawdust or plant fibers, are hardly effective, because they also absorb large amounts of water. On their search for an environmentally friendly alternative to clean up oil spills, the researchers compared various species of aquatic ferns. "We already knew that the leaves of these plants repel water, but for the first time now, we have studied their capacity to absorb oil," Claudia Zeiger says. She conducted the project at KIT's Institute of Microstructure Technology. Aquatic ferns originally growing in tropical and subtropical regions can now also be found in parts of Europe. As they reproduce strongly, they are often considered weed. However, they have a considerable potential as low-cost, rapid, and environmentally friendly oil absorbers, which is obvious from a short video at http://www.kit.edu/kit/english/pi_2016_115_nanofur-for-oil-spill-cleanup.php. "The plants might be used in lakes to absorb accidental oil spills," Zeiger says. After less than 30 seconds, the leaves reach maximum absorption and can be skimmed off together with the absorbed oil. The water plant named salvinia has trichomes on the leaf surface -- hairy extensions of 0.3 to 2.5 mm in length. Comparison of different salvinia species revealed that leaves with the longest hairs did not absorb the largest amounts of oil. "Oil-absorbing capacity is determined by the shape of the hair ends," Zeiger emphasizes. The largest quantity of oil was absorbed by leaves of the water fern salvinia molesta, whose hair ends are shaped like an eggbeater. Based on this new knowledge on the relationship between surface structure of leaves and their oil-absorbing capacity, the researchers improved the 'Nanofur' material developed at their institute. This plastic nanofur mimics the water-repellent and oil-absorbing effect of salvinia to separate oil and water. "We study nanostructures and microstructures in nature for potential technical developments," says Hendrik Hölscher, Head of the Biomimetic Surfaces Group of the Institute of Microstructure Technology of KIT. He points out that different properties of plants made of the same material frequently result from differences of their finest structures. ### Claudia Zeiger as the first author presents the study results in the journal Bioinspiration & Biomimetics under the heading of "Microstructures of superhydrophobic plant leaves -- inspiration for efficient oil spill cleanup materials." This study was carried out in cooperation with scientists of the Nees Institute for Biodiversity of Plants of Bonn University, which was established by bionics pioneer Wilhelm Barthlott. Research was supported by a Ph.D. grant of Carl Zeiss Foundation, the Brazilian research and exchange program Ciências sem Fronteiras, and the Karlsruhe Nano Micro Facility (KNMF) high-tech platform of KIT. About Karlsruhe Institute of Technology (KIT) Karlsruhe Institute of Technology (KIT) pools its three core tasks of research, higher education, and innovation in a mission. With about 9,300 employees and 25,000 students, KIT is one of the big institutions of research and higher education in natural sciences and engineering in Europe. KIT - The Research University in the Helmholtz Association Since 2010, the KIT has been certified as a family-friendly university. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
Home > Press > Nature Communications: Laser source for biosensors: KIT Researchers for the First time integrate organic lasers on a silicon photonic chip -- publication in nature communications Abstract: In the area of nano photonics, scientists for the first time succeeded in integrating a laser with an organic gain medium on a silicon photonic chip. This approach is of enormous potential for low-cost biosensors that might be used for near-patient diagnosis once and without any sterilization expenditure similar to today's strips for measuring blood sugar. The researchers now present the new laser in Nature Communications: DOI: 10.1038/ncomms10864 This is the first time organic lasers were integrated on a single silicon photonic chip, Christian Koos, researcher of KIT's Institute of Photonics and Quantum Electronics (IPQ) and Institute of Microstructure Technology (IMT), reports. "The main advantage of the lasers consists in the fact that production of large series is associated with low costs. In the long term, manufacture at a price of some cents per laser might be feasible." One of the major challenges associated with the fabrication of optical microchips consists in integrating a number of different components on one substrate at low cost. For some years now, it has been possible to produce optical components from silicon. This so-called silicon photonics uses highly developed nanotechnological fabrication processes of microelectronics and allows for the inexpensive production of large numbers of high-performance photonic components. Such components of fractions of a micrometer in size can contribute to making information technology more energy-efficient and are highly suited for compact biosensors. The problem of integrating light sources on the chip, however, still remained unsolved, as the silicon semiconductor is hardly suited as a light emitter due to its electronic structure. During electron transfer between energetically different states, the energy is preferably released in the form of heat rather than light. Researchers of KIT have now developed a new class of lasers in the infrared range. For this purpose, they combine silicon nano waveguides with a polymer doped with an organic dye. The energy to operate this "organic" laser is supplied from above, vertically to the chip surface, by a pulsed light source. The laser light produced is directly coupled into a silicon nano waveguide. The researchers succeeded in generating pulsed laser radiation with a wavelength of 1310 nm and a peak power of more than 1 Watt on one chip. The new infrared lasers are presented in the Nature Communications journal. By the use of various dyes and laser resonators, the wavelength of laser radiation can be varied over a wide range. ### Dietmar Korn, Matthias Lauermann, Sebastian Koeber, Patrick Appel, Luca Alloatti, Robert Palmer, Pieter Dumon, Wolfgang Freude, Juerg Leuthold & Christian Koos: Lasing in silicon-organic hybrid waveguides. Nature Communications, 2016. DOI: 10.1038/ncomms10864 About Karlsruhe Institute of Technology (KIT) Karlsruhe Institute of Technology (KIT) pools its three core tasks of research, higher education, and innovation in a mission. With about 9,300 employees and 25,000 students, KIT is one of the big institutions of research and higher education in natural sciences and engineering in Europe. KIT -- The Research University in the Helmholtz Association Since 2010, the KIT has been certified as a family-friendly university. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.