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Peter Fromherz

Bio: Peter Fromherz is an academic researcher from Max Planck Society. The author has contributed to research in topics: Transistor & Field-effect transistor. The author has an hindex of 56, co-authored 177 publications receiving 9646 citations. Previous affiliations of Peter Fromherz include University of Ulm & Technical University of Berlin.


Papers
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Journal ArticleDOI
31 May 1991-Science
TL;DR: An identified neuron of the leech, a Retzius cell, has been attached to the open gate of a p-channel field-effect transistor, and weak signals that resemble the first derivative of the action potential were observed.
Abstract: An identified neuron of the leech, a Retzius cell, has been attached to the open gate of a p-channel field-effect transistor. Action potentials, spontaneous or stimulated, modulate directly the source-drain current in silicon. The electronic signals match the shape of the action potential. The average voltage on the gate was up to 25 percent of the intracellular voltage change. Occasionally weak signals that resemble the first derivative of the action potential were observed. The junctions can be described by a model that includes capacitive coupling of the plasma membrane and the gate oxide and that accounts for variable resistance of the seal.

564 citations

Journal ArticleDOI
TL;DR: In this paper, two types of fluorescent pH indicators, a hydroxycoumarin and an aminoc-marin dye, are incorporated by means of long paraffinic chain substituents to neutral, anionic, and cationic micelles.
Abstract: Two types of fluorescent pH indicators, a hydroxycoumarin and an aminocoumarin dye, are incorporated by means of long paraffinic chain substituents to neutral, anionic, and cationic micelles. The apparent pK values for the dyes in the micelles are compared to the pK values in aqueous solution. Shifts of the apparent pK are found for charged as well as for uncharged micelles, being different for the two indicators. A comparison of the pK shifts of the indicators in neutral micelles to pK shifts in a series of mixed solvents of different dielectric constant (e) leads us to attribute the shifts in the neutral system to a reduced polarity at the micelle surface for which a value of e 32 is estimated. With respect to charged micelles this polarity effect is responsible for part of the apparent pK shift. It may be revealed by comparing the results for the two indicator types. The value of the effective dielectric constant is found to be similar to that in the neutral micelle. The remaining part of the apparent pK shift may be taken as a measure of the electrical potential at the surface of the charged micelles. Some examples of potential measurements for various counterions are presented. A thermodynamical section attempts to present clear definitions of (and relations between) terms as “apparent pK”, “interfacial pK”, “interfacial pH”, and “acidity function”.

548 citations

Proceedings ArticleDOI
09 Feb 2003
TL;DR: Results from first biological experiments are presented, which prove full functionality of the chip, and related circuit and system issues as well as process aspects are discussed.
Abstract: Sensor arrays are a key tool in the field of neuroscience for noninvasive recording of the activity of biological networks, such as dissociated neurons or neural tissue. A high-density sensor array complementary metal–oxide–semiconductor chip is presented with 16 K pixels, a frame rate of 2 kiloframes per second, and a pitch of 7.8 m 7.8 m for imaging of neural activity. The related circuit and system issues as well as process aspects are discussed. A mismatch-canceling calibration circuitry with current mode signal representation is used. Results from first biological experiments are presented, which prove full functionality of the chip.

409 citations

Journal ArticleDOI
01 Dec 2003
TL;DR: A CMOS sensor array for monitoring neural signals of living cells with 128 /spl times/ 128 pixels in a 1 mm/sup 2/ area is described, using a sensor-MOSFET mismatch-compensating current-mode technique.
Abstract: Sensor arrays are a key tool in the field of neuroscience for noninvasive recording of the activity of biological networks, such as dissociated neurons or neural tissue. A high-density sensor array complementary metal-oxide-semiconductor chip is presented with 16 K pixels, a frame rate of 2 kiloframes per second, and a pitch of 7.8 /spl mu/m /spl times/ 7.8 /spl mu/m for imaging of neural activity. The related circuit and system issues as well as process aspects are discussed. A mismatch-canceling calibration circuitry with current mode signal representation is used. Results from first biological experiments are presented, which prove full functionality of the chip.

362 citations

Journal ArticleDOI
TL;DR: A hybrid circuit of a semiconductor chip and synaptically connected neurons was implemented and characterized and constitutes a proof-of-principle experiment for the development of neuroelectronic systems to be used in studies on neuronal signal processing, neurocomputation, and neuroprosthetics.
Abstract: A hybrid circuit of a semiconductor chip and synaptically connected neurons was implemented and characterized. Individual nerve cells from the snail Lymnaea stagnalis were immobilized on a silicon chip by microscopic picket fences of polyimide. The cells formed a network with electrical synapses after outgrowth in brain conditioned medium. Pairs of neurons were electronically interfaced for noninvasive stimulation and recording. Voltage pulses were applied to a capacitive stimulator on the chip to excite the attached neuron. Signals were transmitted in the neuronal net and elicited an action potential in a second neuron. The postsynaptic excitation modulated the current of a transistor on the chip. The implementation of the silicon-neuron-neuron-silicon circuit constitutes a proof-of-principle experiment for the development of neuroelectronic systems to be used in studies on neuronal signal processing, neurocomputation, and neuroprosthetics.

318 citations


Cited by
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Journal ArticleDOI
29 Aug 1997-Science
TL;DR: In this article, a general approach for multilayers by consecutive adsorption of polyanions and polycations has been proposed and has been extended to other materials such as proteins or colloids.
Abstract: Multilayer films of organic compounds on solid surfaces have been studied for more than 60 years because they allow fabrication of multicomposite molecular assemblies of tailored architecture. However, both the Langmuir-Blodgett technique and chemisorption from solution can be used only with certain classes of molecules. An alternative approach—fabrication of multilayers by consecutive adsorption of polyanions and polycations—is far more general and has been extended to other materials such as proteins or colloids. Because polymers are typically flexible molecules, the resulting superlattice architectures are somewhat fuzzy structures, but the absence of crystallinity in these films is expected to be beneficial for many potential applications.

9,593 citations

Journal ArticleDOI
TL;DR: Fundamental concepts of nonlinear microscopy are reviewed and conditions relevant for achieving large imaging depths in intact tissue are discussed.
Abstract: With few exceptions biological tissues strongly scatter light, making high-resolution deep imaging impossible for traditional⎯including confocal⎯fluorescence microscopy. Nonlinear optical microscopy, in particular two photon–excited fluorescence microscopy, has overcome this limitation, providing large depth penetration mainly because even multiply scattered signal photons can be assigned to their origin as the result of localized nonlinear signal generation. Two-photon microscopy thus allows cellular imaging several hundred microns deep in various organs of living animals. Here we review fundamental concepts of nonlinear microscopy and discuss conditions relevant for achieving large imaging depths in intact tissue.

3,781 citations

Journal ArticleDOI
TL;DR: Graphene and its derivatives are being studied in nearly every field of science and engineering as mentioned in this paper, and recent progress has shown that the graphene-based materials can have a profound impact on electronic and optoelectronic devices, chemical sensors, nanocomposites and energy storage.

3,118 citations

Journal ArticleDOI
TL;DR: The Rehybridization of the Acceptor (RICT) and Planarization ofThe Molecule (PICT) III is presented, with a comparison of the effects on yield and radiationless deactivation processes.
Abstract: 6. Rehybridization of the Acceptor (RICT) 3908 7. Planarization of the Molecule (PICT) 3909 III. Fluorescence Spectroscopy 3909 A. Solvent Effects and the Model Compounds 3909 1. Solvent Effects on the Spectra 3909 2. Steric Effects and Model Compounds 3911 3. Bandwidths 3913 4. Isoemissive Points 3914 B. Dipole Moments 3915 C. Radiative Rates and Transition Moments 3916 1. Quantum Yields and Radiationless Deactivation Processes 3916

2,924 citations