The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Keith S Elmslie - One of the best experts on this subject based on the ideXlab platform.
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open State Occupancy prevents gating charge relaxation of n type cav2 2 calcium channels
Biophysical Journal, 2009Co-Authors: Viktor Yarotskyy, Keith S ElmslieAbstract:N-type and L-type channels have significant gating differences, and we wondered whether some of these differences are linked to the relationship between charge movement and channel opening. The time constants for N-channel closing (τDeact) and Off-gating charge movement (τQOff) were compared over a range of voltages. τQOff was significantly larger than τDeact at voltages < −10 mV, and the voltage dependence of the τQOff was less steep than that for τDeact, which suggests that gating charge relaxation does not limit channel closing. Roscovitine, a drug that slows N-channel closing by holding the channel in a high open-probability State, was found to slow both τQOff and τDeact, and thus the time courses of channel closing and gating charge relaxation were similar. Our gating current results were reproduced with the addition of a voltage-independent, closed-closed transition to our previously published two-open-State N-channel model. This work suggests that, like L-type channels, there is a voltage-independent transition along the N-channel activation/deactivation pathway, but this transition occurs between closed States instead of the closed-open States of the L-channel. Also unlike L-type channels, the gating charge appears to be locked into the activated position by the N-channel open State.
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gating charge movement is prevented by open State Occupancy of n type cav2 2 calcium channels
Biophysical Journal, 2009Co-Authors: Viktor Yarotskyy, Keith S ElmslieAbstract:L-type calcium channels show a loose coupling between channel closing and gating charge movement. There are significant gating differences between N-type and L-type channels and we wondered if some of these differences were linked to the relationship between charge movement and channel opening. This was accomplished by comparing the time constant (τ) for channel closing (τDeact) with that for Off-gating charge movement (τ QOff) over a range of voltages. Ionic currents were recorded in 5 mM Ca2+, while gating currents were recorded in 0.1 mM La3+ and 5 mM Mg2+ (La-Mg) from N-channels expressed in HEK 293 cells. τ QOff was larger than τDeact and the voltage dependence of the τ QOff was less steep than that for τDeact, which suggests that gating charge relaxation does not limit channel closing. To determine if the reverse was true, we used roscovitine, which slows N-channel closing by holding the channel in a high Po open State. We found that τ QOff was identical to τDeact in roscovitine. There was a risk that residual ionic tail current could contaminate Off-gating current, so we used an envelope protocol to measured the recovery time course of QOn (no ionic current contamination), and found the same τ as for both τ QOff and τDeact in roscovitine. This coincidence of τ QOff with τDeact suggests that transition out of the roscovitine-bound high Po open State becomes rate limiting to both QOff and channel closing. We conclude that, unlike L-channels, the high Po N-channel open State places the channel into a confirmation that locks gating charge into the activated position.
Pavel Sobotik - One of the best experts on this subject based on the ideXlab platform.
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role of dangling bond State Occupancy in adsorptionof copper phthalocyanine on si 111 sn 3 3
Journal of Physical Chemistry C, 2019Co-Authors: P Zimmermann, Karel Majer, Pavel Kocan, Ivan Ostadal, Pavel SobotikAbstract:Interaction of organic molecules with solid surfaces reflects the local electronic structure of nonequivalent surface sites. The Si(111)-Sn-√3 × √3 surface with intrinsic defects offers dangling bonds with various electron occupancies. In this study, we report on the interaction of copper phthalocyanine with this surface studied with scanning tunneling microscopy and spectroscopy. Sn atoms in the adlayer contain unpaired electrons in their dangling bonds. The molecules are found to adsorb on Sb and Si substitutional defects instead of the homogenous Sn areas. The symmetry of the molecules is lowered or lost after adsorption, and we find substantial differences in the electronic structure of the molecules adsorbed on either type of defects. Furthermore, the molecules preferentially adsorb on double Si substitutional defects where they can switch between a static and a fuzzy State, for both of which a corresponding bonding model is proposed. Our study shows a pivotal role of substitutional defects in the re...
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Role of Dangling Bond State Occupancy in Adsorptionof Copper Phthalocyanine on Si(111)-Sn-√3 × √3
Journal of Physical Chemistry C, 2019Co-Authors: P Zimmermann, Karel Majer, Pavel Kocan, Ivan Ošt’ádal, Pavel SobotikAbstract:Interaction of organic molecules with solid surfaces reflects the local electronic structure of nonequivalent surface sites. The Si(111)-Sn-√3 × √3 surface with intrinsic defects offers dangling bonds with various electron occupancies. In this study, we report on the interaction of copper phthalocyanine with this surface studied with scanning tunneling microscopy and spectroscopy. Sn atoms in the adlayer contain unpaired electrons in their dangling bonds. The molecules are found to adsorb on Sb and Si substitutional defects instead of the homogenous Sn areas. The symmetry of the molecules is lowered or lost after adsorption, and we find substantial differences in the electronic structure of the molecules adsorbed on either type of defects. Furthermore, the molecules preferentially adsorb on double Si substitutional defects where they can switch between a static and a fuzzy State, for both of which a corresponding bonding model is proposed. Our study shows a pivotal role of substitutional defects in the re...
Christoforos N Hadjicostis - One of the best experts on this subject based on the ideXlab platform.
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probabilistic detection of fsm single State transition faults based on State Occupancy measurements
IEEE Transactions on Automatic Control, 2005Co-Authors: Christoforos N HadjicostisAbstract:This note discusses a probabilistic methodology for detecting single permanent or transient functional changes in the State-transition mechanism of a deterministic finite-State machine (FSM). The associated probabilistic detector observes the empirical frequencies with which different States are occupied and detects faults by analyzing the discrepancy between the observed State Occupancy measurements and the expected frequencies. In addition to State Occupancy measurements, the detector requires a statistical characterization of the input, but does not need to know the order with which States appear or the exact input sequence that is applied to the FSM. These features can be useful in settings where the input/State order may not be known due to synchronization, communication or other constraints.
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Probabilistic fault detection in finite-State machines based on State Occupancy measurements
Proceedings of the 41st IEEE Conference on Decision and Control 2002., 2002Co-Authors: Christoforos N HadjicostisAbstract:This paper discusses a probabilistic methodology for detecting permanent or transient functional changes in the State-transition mechanism of a deterministic finite-State machine (FSM). The associated detector observes the frequencies with which States are occupied and detects faults by analyzing the deviation between the expected frequencies and actual measurements. In addition to stale Occupancy measurements, the detector requires a statistical characterization of the input, but does not need to know the order with which States appear or the input sequence that is applied to the FSM. The discussion in the paper focuses on the case of a single fault and on the performance of the fault detector in terms of the probabilities of detection and false alarm, the number of States, and the length of the observation window.
P Zimmermann - One of the best experts on this subject based on the ideXlab platform.
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Reactivity of Ethylene with Tin and Indium Modified Si(001) Surfaces
2020Co-Authors: P Zimmermann, P. SobotíkAbstract:In this STM study we investigate the interaction of ethylene with clean, indium and tin modified Si(001) surface. We find that ethylene chemically interacts with tin-modified Si(001)2×1 surface by (2+2) cycloaddition reaction — as in the case of adsorption on clean Si(001) — but the reactivity of the substrate is dramatically reduced. On the other hand, indium-modified Si(001)2×1 surface was found to be chemically inert to ethylene adsorption. We attribute the reactivity/inertness of the tin and indium modified surfaces to the difference in π-State Occupancy of their dimer structural unit.
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role of dangling bond State Occupancy in adsorptionof copper phthalocyanine on si 111 sn 3 3
Journal of Physical Chemistry C, 2019Co-Authors: P Zimmermann, Karel Majer, Pavel Kocan, Ivan Ostadal, Pavel SobotikAbstract:Interaction of organic molecules with solid surfaces reflects the local electronic structure of nonequivalent surface sites. The Si(111)-Sn-√3 × √3 surface with intrinsic defects offers dangling bonds with various electron occupancies. In this study, we report on the interaction of copper phthalocyanine with this surface studied with scanning tunneling microscopy and spectroscopy. Sn atoms in the adlayer contain unpaired electrons in their dangling bonds. The molecules are found to adsorb on Sb and Si substitutional defects instead of the homogenous Sn areas. The symmetry of the molecules is lowered or lost after adsorption, and we find substantial differences in the electronic structure of the molecules adsorbed on either type of defects. Furthermore, the molecules preferentially adsorb on double Si substitutional defects where they can switch between a static and a fuzzy State, for both of which a corresponding bonding model is proposed. Our study shows a pivotal role of substitutional defects in the re...
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Role of Dangling Bond State Occupancy in Adsorptionof Copper Phthalocyanine on Si(111)-Sn-√3 × √3
Journal of Physical Chemistry C, 2019Co-Authors: P Zimmermann, Karel Majer, Pavel Kocan, Ivan Ošt’ádal, Pavel SobotikAbstract:Interaction of organic molecules with solid surfaces reflects the local electronic structure of nonequivalent surface sites. The Si(111)-Sn-√3 × √3 surface with intrinsic defects offers dangling bonds with various electron occupancies. In this study, we report on the interaction of copper phthalocyanine with this surface studied with scanning tunneling microscopy and spectroscopy. Sn atoms in the adlayer contain unpaired electrons in their dangling bonds. The molecules are found to adsorb on Sb and Si substitutional defects instead of the homogenous Sn areas. The symmetry of the molecules is lowered or lost after adsorption, and we find substantial differences in the electronic structure of the molecules adsorbed on either type of defects. Furthermore, the molecules preferentially adsorb on double Si substitutional defects where they can switch between a static and a fuzzy State, for both of which a corresponding bonding model is proposed. Our study shows a pivotal role of substitutional defects in the re...
Viktor Yarotskyy - One of the best experts on this subject based on the ideXlab platform.
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open State Occupancy prevents gating charge relaxation of n type cav2 2 calcium channels
Biophysical Journal, 2009Co-Authors: Viktor Yarotskyy, Keith S ElmslieAbstract:N-type and L-type channels have significant gating differences, and we wondered whether some of these differences are linked to the relationship between charge movement and channel opening. The time constants for N-channel closing (τDeact) and Off-gating charge movement (τQOff) were compared over a range of voltages. τQOff was significantly larger than τDeact at voltages < −10 mV, and the voltage dependence of the τQOff was less steep than that for τDeact, which suggests that gating charge relaxation does not limit channel closing. Roscovitine, a drug that slows N-channel closing by holding the channel in a high open-probability State, was found to slow both τQOff and τDeact, and thus the time courses of channel closing and gating charge relaxation were similar. Our gating current results were reproduced with the addition of a voltage-independent, closed-closed transition to our previously published two-open-State N-channel model. This work suggests that, like L-type channels, there is a voltage-independent transition along the N-channel activation/deactivation pathway, but this transition occurs between closed States instead of the closed-open States of the L-channel. Also unlike L-type channels, the gating charge appears to be locked into the activated position by the N-channel open State.
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gating charge movement is prevented by open State Occupancy of n type cav2 2 calcium channels
Biophysical Journal, 2009Co-Authors: Viktor Yarotskyy, Keith S ElmslieAbstract:L-type calcium channels show a loose coupling between channel closing and gating charge movement. There are significant gating differences between N-type and L-type channels and we wondered if some of these differences were linked to the relationship between charge movement and channel opening. This was accomplished by comparing the time constant (τ) for channel closing (τDeact) with that for Off-gating charge movement (τ QOff) over a range of voltages. Ionic currents were recorded in 5 mM Ca2+, while gating currents were recorded in 0.1 mM La3+ and 5 mM Mg2+ (La-Mg) from N-channels expressed in HEK 293 cells. τ QOff was larger than τDeact and the voltage dependence of the τ QOff was less steep than that for τDeact, which suggests that gating charge relaxation does not limit channel closing. To determine if the reverse was true, we used roscovitine, which slows N-channel closing by holding the channel in a high Po open State. We found that τ QOff was identical to τDeact in roscovitine. There was a risk that residual ionic tail current could contaminate Off-gating current, so we used an envelope protocol to measured the recovery time course of QOn (no ionic current contamination), and found the same τ as for both τ QOff and τDeact in roscovitine. This coincidence of τ QOff with τDeact suggests that transition out of the roscovitine-bound high Po open State becomes rate limiting to both QOff and channel closing. We conclude that, unlike L-channels, the high Po N-channel open State places the channel into a confirmation that locks gating charge into the activated position.
