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Search Results: 1 - 10 of 3992 matches for " Stephan Shuichi Haupt "
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Postsynaptic Odorant Concentration Dependent Inhibition Controls Temporal Properties of Spike Responses of Projection Neurons in the Moth Antennal Lobe
Terufumi Fujiwara, Tomoki Kazawa, Stephan Shuichi Haupt, Ryohei Kanzaki
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0089132
Abstract: Although odorant concentration-response characteristics of olfactory neurons have been widely investigated in a variety of animal species, the effect of odorant concentration on neural processing at circuit level is still poorly understood. Using calcium imaging in the silkmoth (Bombyx mori) pheromone processing circuit of the antennal lobe (AL), we studied the effect of odorant concentration on second-order projection neuron (PN) responses. While PN calcium responses of dendrites showed monotonic increases with odorant concentration, calcium responses of somata showed decreased responses at higher odorant concentrations due to postsynaptic inhibition. Simultaneous calcium imaging and electrophysiology revealed that calcium responses of PN somata but not dendrites reflect spiking activity. Inhibition shortened spike response duration rather than decreasing peak instantaneous spike frequency (ISF). Local interneurons (LNs) that were specifically activated at high odorant concentrations at which PN responses were suppressed are the putative source of inhibition. Our results imply the existence of an intraglomerular mechanism that preserves time resolution in olfactory processing over a wide odorant concentration range.
Development of a Scheme and Tools to Construct a Standard Moth Brain for Neural Network Simulations
Hidetoshi Ikeno,Tomoki Kazawa,Shigehiro Namiki,Daisuke Miyamoto,Yohei Sato,Stephan Shuichi Haupt,Ikuko Nishikawa,Ryohei Kanzaki
Computational Intelligence and Neuroscience , 2012, DOI: 10.1155/2012/795291
Abstract: Understanding the neural mechanisms for sensing environmental information and controlling behavior in natural environments is a principal aim in neuroscience. One approach towards this goal is rebuilding neural systems by simulation. Despite their relatively simple brains compared with those of mammals, insects are capable of processing various sensory signals and generating adaptive behavior. Nevertheless, our global understanding at network system level is limited by experimental constraints. Simulations are very effective for investigating neural mechanisms when integrating both experimental data and hypotheses. However, it is still very difficult to construct a computational model at the whole brain level owing to the enormous number and complexity of the neurons. We focus on a unique behavior of the silkmoth to investigate neural mechanisms of sensory processing and behavioral control. Standard brains are used to consolidate experimental results and generate new insights through integration. In this study, we constructed a silkmoth standard brain and brain image, in which we registered segmented neuropil regions and neurons. Our original software tools for segmentation of neurons from confocal images, KNEWRiTE, and the registration module for segmented data, NeuroRegister, are shown to be very effective in neuronal registration for computational neuroscience studies. 1. Introduction Insect brains are important model systems for analyzing neural function. This is due to their comparatively simple structure incorporating important brain functions such as sensory information processing, learning, and behavioral control mechanisms [1–3]. Analysis based on the morphologies of neurons and neuropils has greatly promoted the understanding of neural function. In particular, the existence of numerous identified neurons has consolidated the application of insect brains as model neural networks in the field of neuroethology [4, 5]. The detailed morphology of neurons can be captured more readily using recent fluorescence techniques and various genetic technologies in insects [6–9]. These methodological advances have resulted in new insights into brain mechanisms through the use of small and tractable insect brains. A well-known simple insect behavior is the unique orientation to pheromone stimuli displayed by the male silkmoth, Bombyx mori. This programmed behavior triggered by sensing pheromone consists of surge, zigzag, and looping locomotor components [10]. Sensory signal pathways for pheromone have already been identified and characterized by intra- and
A Single Sex Pheromone Receptor Determines Chemical Response Specificity of Sexual Behavior in the Silkmoth Bombyx mori
Takeshi Sakurai,Hidefumi Mitsuno,Stephan Shuichi Haupt,Keiro Uchino,Fumio Yokohari,Takaaki Nishioka,Isao Kobayashi,Hideki Sezutsu,Toshiki Tamura,Ryohei Kanzaki
PLOS Genetics , 2011, DOI: 10.1371/journal.pgen.1002115
Abstract: In insects and other animals, intraspecific communication between individuals of the opposite sex is mediated in part by chemical signals called sex pheromones. In most moth species, male moths rely heavily on species-specific sex pheromones emitted by female moths to identify and orient towards an appropriate mating partner among a large number of sympatric insect species. The silkmoth, Bombyx mori, utilizes the simplest possible pheromone system, in which a single pheromone component, (E, Z)-10,12-hexadecadienol (bombykol), is sufficient to elicit full sexual behavior. We have previously shown that the sex pheromone receptor BmOR1 mediates specific detection of bombykol in the antennae of male silkmoths. However, it is unclear whether the sex pheromone receptor is the minimally sufficient determination factor that triggers initiation of orientation behavior towards a potential mate. Using transgenic silkmoths expressing the sex pheromone receptor PxOR1 of the diamondback moth Plutella xylostella in BmOR1-expressing neurons, we show that the selectivity of the sex pheromone receptor determines the chemical response specificity of sexual behavior in the silkmoth. Bombykol receptor neurons expressing PxOR1 responded to its specific ligand, (Z)-11-hexadecenal (Z11-16:Ald), in a dose-dependent manner. Male moths expressing PxOR1 exhibited typical pheromone orientation behavior and copulation attempts in response to Z11-16:Ald and to females of P. xylostella. Transformation of the bombykol receptor neurons had no effect on their projections in the antennal lobe. These results indicate that activation of bombykol receptor neurons alone is sufficient to trigger full sexual behavior. Thus, a single gene defines behavioral selectivity in sex pheromone communication in the silkmoth. Our findings show that a single molecular determinant can not only function as a modulator of behavior but also as an all-or-nothing initiator of a complex species-specific behavioral sequence.
Edgeworth Approximation of a Finite Sample Distribution for an AR(1) Model with Measurement Error  [PDF]
Shuichi Nagata
Open Journal of Statistics (OJS) , 2012, DOI: 10.4236/ojs.2012.24046
Abstract: In this paper, we consider the finite sample property of the ordinary least squares (OLS) estimator for an AR(1) model with measurement error. We present the Edgeworth approximation for a finite distribution of OLS up to O(T1/2). We introduce an instrumental variable estimator that is consistent in the presence of measurement error. Finally, a simulation study is conducted to assess the theoretical results and to compare the finite sample performances of these estimators.
Price and Quantity Competition in a Mixed Duopoly with Emission Tax  [PDF]
Shuichi Ohori
Theoretical Economics Letters (TEL) , 2014, DOI: 10.4236/tel.2014.42020
Abstract:

This paper compares price and quantity competition in a mixed duopoly with emission tax; in a mixed duopoly, one public firm competes with one private firm in the market. We find that social welfare is the highest when both the firms simultaneously choose price levels. Then, the optimal emission tax is sufficiently lower than the marginal social damage.

Modeling geologically abrupt climate changes in the Miocene: Potential effects of high-latitudinal salinity changes  [PDF]
Bernd J. Haupt, Dan Seidov
Natural Science (NS) , 2012, DOI: 10.4236/ns.2012.43022
Abstract: The cooling of the Cenozoic, including the Miocene epoch, was punctuated by many geologically abrupt warming and cooling episodes— strong deviations from the cooling trend with time span of ten to hundred thousands of years. Our working hypothesis is that some of those warming episodes at least partially might have been caused by dynamics of the Antarctic Ice Sheet, which, in turn, might have caused strong changes of sea surface salinity in the Miocene Southern Ocean. Feasibility of this hypothesis is explored in a series of offline-coupled ocean-atmosphere computer experiments. The results suggest that relatively small and geologically short-lived changes in freshwater balance in the Southern Ocean could have significantly contributed to at least two prominent warming episodes in the Miocene. Importantly, the scenario-based experiments also suggest that the Southern Ocean was more sensitive to the salinity changes in the Miocene than today, which can attributed to the opening of the Central American Isthmus as a major difference between the Miocene and the present-day ocean-sea geometry.
Probing relaxation times in graphene quantum dots
Christian Volk,Christoph Neumann,Sebastian Kazarski,Stefan Fringes,Stephan Engels,Federica Haupt,André Müller,Christoph Stampfer
Physics , 2013, DOI: 10.1038/ncomms2738
Abstract: Graphene quantum dots are attractive candidates for solid-state quantum bits. In fact, the predicted weak spin-orbit and hyperfine interaction promise spin qubits with long coherence times. Graphene quantum dot devices have been extensively investigated with respect to their excitation spectrum, spin-filling sequence, and electron-hole crossover. However their relaxation dynamics remain largely unexplored. This is mainly due to challenges in device fabrication, in particular regarding the control of carrier confinement and the tunability of the tunnelling barriers, both crucial to experimentally investigate decoherence times. Here, we report on pulsed-gate transient spectroscopy and relaxation time measurements of excited states in graphene quantum dots. This is achieved by an advanced device design, allowing to tune the tunnelling barriers individually down to the low MHz regime and to monitor their asymmetry with integrated charge sensors. Measuring the transient currents through electronic excited states, we estimate lower limit of charge relaxation times on the order of 60-100 ns.
Clinical considerations in selecting and using atypical antipsychotics
Haupt Dan
Annals of General Psychiatry , 2006, DOI: 10.1186/1744-859x-5-s1-s35
Abstract:
Student Attitudes Towards Cooperative Construction Education Experiences
Theo Haupt
Australasian Journal of Construction Economics and Building , 2012,
Abstract: This paper reports on the findings of a study that examined the attitudes of students at a historically disadvantaged institution (HOI) compared with those at a previously advantaged institution (PAl) in South Africa. PAis in South Africa have been almost exclusively white in the past while HOls have been predominantly black-both with respect to their academic staffing and student population. It is argued that higher education institutions have given students in general too little that will be of real value beyond a credential that will help them get their first jobs. The opinions of first year students were surveyed before, and third and final year students after, their practical periods of employment in construction. The study concludes that all the cooperative partners in cooperative education can do much more to improve this approach to construction education.
Flip-Flop Flow Control inside Streamwise Diverging Diamond-Shaped Cylinder Bundles with Concavities  [PDF]
Shuichi Torii, Shizaburo Umeda
Journal of Flow Control, Measurement & Visualization (JFCMV) , 2013, DOI: 10.4236/jfcmv.2013.13010
Abstract: The flow visualization work with the aid of PIV and Piezometer deals with flip-flop flow around diamond-shaped cylinder bundle revised with concavities on both bundle walls. It is disclosed that 1) the concavity constructed on both side-walls of a diamond cylinder induces a substantial change in the flow patterns in the exit jet-stream field and jet- stream dispersion, 2) pressure characteristics are quantitatively measured in a diverging-flow region in diamond cylinder bundles with concavityand in its downstream region, and 3) flip-flop flow occurs in the flow passages and its occurrence condition is obtained.

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