Cyclic Dependence Research Articles

Electrically-Excited Surface Plasmon Polaritons with Directionality Control

Compact electrical sources of surface plasmon polaritons (SPPs) are promising for integration with high-speed electronics. Being a highly compact source, the point dipole has the ability to directly couple to surface plasmon modes, and be electrically driven through the inelastic tunneling of electrons, for example, at the tip of a scanning tunneling microscope (STM). However, the directional control of electrically excited SPPs from such compact sources has not been demonstrated, despite its importance in controlling the optical energy flow on a chip. In this paper, we present a comprehensive analysis of the directional excitation of SPPs on Au 1D cavity by moving an STM tip relative to the edge of the cavity stripe and analyzing the light collected through an inverted microscope. The directional propagation of the SPP and its far-field emission exhibit a clear cyclic dependence on the relative distance from this edge. These results provide key steps toward realizing compact solid-state devices with the ...

Spectroscopic and Biochemical Studies of TRIP8b Regulation of HCN Channels

TRIP8b, an accessory subunit of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, alters both cell surface expression and cyclic nucleotide dependence of these channels. The mechanism through which TRIP8b exerts these dual effects is still poorly understood. Besides binding the terminal three residues of HCN channels, TRIP8b also binds directly to the cyclic nucleotide-binding domain (CNBD). A small central portion of TRIP8b, termed TRIP8bcore, is involved in this interaction. Binding of TRIP8bcore to the CNBD dramatically reduces the effects of cAMP on the channel. Using spectroscopic and biochemical techniques, we sought to understand how and where TRIP8b binds to the CNBD and how it reduces the cyclic nucleotide dependence of HCN channels. To closely examine the binding of TRIP8bcore to the CNBD, we used double electron-electron resonance (DEER) at Q-band frequencies to study conformational changes in the soluble CNBD of HCN2 in the presence of TRIP8b and cAMP. We show that the overall structure of the TRIP8b bound conformation of the CNBD closely resembles the apo state. In addition, we use DEER between the CNBD and TRIP8bcore and nuclear magnetic resonance (NMR) to localize the binding site for TRIP8b on the CNBD. Finally, to understand the mechanism of TRIP8b inhibition of cAMP regulation of HCN channels, we performed binding studies of cAMP and TRIP8b on the CNBD and developed a multi-state mathematical model to explore 1) whether cAMP and TRIP8b can bind simultaneously to HCN channels, 2) whether TRIP8b reduces the affinity for cAMP binding, and 3) whether TRIP8b reduces the effect of cAMP on HCN channels by preventing the structural rearrangements associated with channel opening.

Mechanistic Studies of Electrode-Assisted Catalytic Oxidation by Flavinium and Acridinium Cations

Electrochemical behavior of flavinium (Et-Fl+) and acridinium (Acr+) cations is presented, in order to investigate their activity toward catalytic water oxidation. Cyclic voltammograms of Acr+ and Et-Fl+ in acetonitrile are qualitatively similar, with oxidation peaks at highly positive potentials, and these oxidation peaks depend strongly on the type of the working electrode being used. However, the two model compounds exhibit different behaviors in the presence of water: while Et-Fl+ facilitates electrocatalytic water oxidation through an electrode-assisted mechanism, water oxidation is not accelerated in the presence of Acr+. A comparative study of variable scan-rate cyclic voltammetry, concentration dependence, and spectroelectrochemical behavior of two model compounds suggest that Et-Fl+ and Acr+ exhibit different reaction pathways with the electrode surface. On the basis of the experimental results, a mechanism is proposed to account for the observed differences in electrocatalysis.

Chemometrics quality assessment of wastewater treatment plant effluents using physicochemical parameters and UV absorption measurements

Chemometric techniques like Principal Component Analysis (PCA) and Partial Least Squares Regression (PLS) are used to explore, analyze and model relationships among different water quality parameters in wastewater treatment plants (WWTP). Different data sets generated by laboratory analysis and by an automatic multi-parametric monitoring system with a new designed optical device have been investigated for temporal variations on water quality parameters measured in the water influent and effluent of a WWTP over different time scales. The obtained results allowed the discovery of the more important relationships among the monitored parameters and of their cyclic dependence on time (daily, monthly and annual cycles) and on different plant management procedures.This study intended also the modeling and prediction of concentrations of several water components and parameters, especially relevant for water quality assessment, such as Dissolved Organic Matter (DOM), Total Organic Carbon (TOC) nitrate, detergent, and phenol concentrations. PLS models were built to correlate target concentrations of these constituents with UV spectra measured in samples collected at (1) laboratory conditions (in synthetic water mixtures); and at (2) WWTP conditions (in real water samples from the plant). Using synthetic water mixtures, specific wavelengths were selected with the aim to establish simple and reliable prediction models, which gave good relative predictions with errors of around 3–4% for nitrates, detergent and phenols concentrations and of around 15% for the DOM in external validation. In the case of nitrate and TOC concentrations modeling in real water samples from the effluent of the WWTP using the reduced spectral data set, results were also promising with low prediction errors (less than 20%).

Cyclic strain rate effects in fatigued face-centred and body-centred cubic metals

The present work deals mainly with the effect and the use of strain rate and temperature changes during cyclic deformation as a means to obtain valuable information on the thermally activated dislocation glide processes, based on the assessment of reversible changes of the thermal effective stress and of transient changes of the athermal stress. The importance of closed-loop testing in true plastic strain control with constant cyclic plastic strain rate throughout the cycle is explained and emphasized, especially with respect to the case of strain rate sensitive materials. Stress responses of face-centred cubic and body-centred cubic (bcc) metals to cyclic strain rate changes are presented to illustrate that the deformation modes of these two classes of materials differ characteristically at temperatures below that the so-called knee temperature of bcc metals. When such tests are performed in cyclic saturation, the temperature and strain rate dependence of bcc metals can be measured very accurately on one and the same specimen, permitting a thorough analysis of thermal activation.

Target Z dependence of Xe L x-ray emission in heavy ion–atom collision near the Bohr velocity: influence of level matching

X-ray yields for the projectile L-shell have been measured for collisions between Xe20+ and thick solid targets throughout the periodic table with incident energies near the Bohr velocity. The yields show a very pronounced cyclic dependence on the target atomic number. This result indicates that Xe L x-ray emission intensity is greatly enhanced either in near-symmetric collisions or if the binding energy of the Xe M-shell matches the L- or N-shell binding energy of the target.

Electroreduction of tungsten oxide(VI) in molten salts with added metaphosphate

Tungstate ions WO4 2− are not electrochemically active in chloride melts. Upon introduction of PO3 − ions into the melt, two waves appear in the voltammograms at potentials −0.1— −0.2 V and −0.3— −0.5 V vs. Pb/Pb2+ reference electrode. With a PO3 − concentration ratio of 0.01<[PO3 −]/[WO4 2−]<0.18, the potentiostatic electrolysis product of WO4 2− at the above mentioned potentials is metallic tungsten; a NaPO3 concentration increase for ratios [PO3 −]/[WO4 2−]≫ 0.18 results in tungsten phosphide in electrolysis product. Cyclic voltammograms and dependence of half-peak potentials on electrode polarization rate indicate the irreversible character of the electrode process. Electrode process modeling allows us to state that the first wave in the voltammogram of KCl-NaCl-Na2WO4-NaPO3 system corresponds to tungsten oxychlorides discharge while the second wave appears due to the discharge of ditungstate ions. In the voltammograms of Na2WO4-NaPO3 melts, reduction wave was observed at −1.1- −1.2 V potentials. Proportionality of limiting current to NaPO3 concentration, constancy of I d/v 1/2 ratio, and I d/nFc constant kinetic value equal to (8.3−9.5)×10−5 cm/s for steady-state wave indicate that electrode process rate is limited by electrochemically active particle diffusion to the electrode. Nascent ditungstate ions become electrochemically active in the overall electrode process. Charge transfer stage is reversible.

Dimeric TRIP8b Binds to the Cyclic Nucleotide Binding Domain of HCN Channels

The accessory protein TRIP8b has been shown to modulate expression level, cellular localization, and cyclic nucleotide-dependent regulation of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. The mechanism through which TRIP8b exerts these effects is poorly understood. Work from this lab, as well as others, has shown that TRIP8b and HCN2 interact in two places. The first site is between the terminal three residues of HCN and the tetratricopeptide repeat (TPR) domains of TRIP8b. We previously solved the X-ray crystal structure of this binding site bound to a peptide of the terminal 7 amino acids of HCN2. The second interaction involves the cyclic nucleotide-binding domain (CNBD) of HCN and a highly conserved region of TRIP8b N-terminal to the TPR domains. This binding site is sufficient to impact the cyclic nucleotide dependence of HCN channels. Here we use biochemical and biophysical techniques on isolated domains of each protein to begin to understand the second interaction site between the CNBD and the TRIP8b conserved domain. Light-scattering size-exclusion chromatography demonstrated that TRIP8b and HCN2 form a 2:1 complex when co-expressed and that TRIP8b, when expressed alone, forms both dimer and monomer. Surprisingly the CNBD of HCN2 interacts preferentially with the dimeric form of TRIP8b. In contrast, using a fluorescently labeled peptide of the terminal 7 amino acids of HCN2, we demonstrate that the carboxy terminal tripeptide of HCN2 is able to bind both the dimeric and monomeric forms of TRIP8b. The ability of the CNBD to discriminate between monomeric and dimeric TRIP8b suggests an interesting potential mechanism through which the impact of binding on the cyclic nucleotide-dependent regulation of HCN channels can be tuned by controlling the oligomeric state of TRIP8b.

A Peculiarity in Pearl’s Logic of Interventionist Counterfactuals

We examine a formal semantics for counterfactual conditionals due to Judea Pearl, which formalizes the interventionist interpretation of counterfactuals central to the interventionist accounts of causation and explanation. We show that a characteristic principle validated by Pearl’s semantics, known as the principle of reversibility, states a kind of irreversibility: counterfactual dependence (in David Lewis’s sense) between two distinct events is irreversible. Moreover, we show that Pearl’s semantics rules out only mutual counterfactual dependence, not cyclic dependence in general. This, we argue, suggests that Pearl’s logic is either too weak or too strong.

Cyclic creep and fatigue testing of nanocrystalline copper thin films

This study performed microtensile testing to investigate the mechanical properties of cyclic fatigue in freestanding nanocrystalline copper thin films of sub-micrometer thickness. We observed the mechanical response associated with tension–tension fatigue under various stress amplitudes and mean stress conditions at cyclic loading frequencies of up to 10Hz. Experiments were carried out using feedback to provide load control for sputter deposited 300, 500, and 700nm Cu thin films. Cu films were deposited on the Si substrate and then separated from the substrate following the completion of processing. The feedback control maintains the stress within the film at a constant value, even when the stress threatens to drop due to plastic deformation during the course of the experiment. As anticipated, the number of loading cycles to failure exceeded 106 under low mean loads at low amplitudes with an increase in the load leading to a decrease in the number of cycles to failure. These results provide clear evidence of cyclic creep rate dependence and changes in the failure mechanism from crack formation to extended plasticity following a decrease in the mean load or load amplitude. Moreover, we observed how the fatigue and cyclic creep of the tested films depended on the length scale.

Structure and stoichiometry of an accessory subunit TRIP8b interaction with hyperpolarization-activated cyclic nucleotide-gated channels

Ion channels operate in intact tissues as part of large macromolecular complexes that can include cytoskeletal proteins, scaffolding proteins, signaling molecules, and a litany of other molecules. The proteins that make up these complexes can influence the trafficking, localization, and biophysical properties of the channel. TRIP8b (tetratricopetide repeat-containing Rab8b-interacting protein) is a recently discovered accessory subunit of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels that contributes to the substantial dendritic localization of HCN channels in many types of neurons. TRIP8b interacts with the carboxyl-terminal region of HCN channels and regulates their cell-surface expression level and cyclic nucleotide dependence. Here we examine the molecular determinants of TRIP8b binding to HCN2 channels. Using a single-molecule fluorescence bleaching method, we found that TRIP8b and HCN2 form an obligate 4:4 complex in intact channels. Fluorescence-detection size-exclusion chromatography and fluorescence anisotropy allowed us to confirm that two different domains in the carboxyl-terminal portion of TRIP8b--the tetratricopepide repeat region and the TRIP8b conserved region--interact with two different regions of the HCN carboxyl-terminal region: the carboxyl-terminal three amino acids (SNL) and the cyclic nucleotide-binding domain, respectively. And finally, using X-ray crystallography, we determined the atomic structure of the tetratricopepide region of TRIP8b in complex with a peptide of the carboxy-terminus of HCN2. Together, these experiments begin to uncover the mechanism for TRIP8b binding and regulation of HCN channels.

OS2106 軸受鋼の応力漸減回転曲げ疲労挙動に対する高応力域繰返し数依存性の一考察

OS2106 軸受鋼の応力漸減回転曲げ疲労挙動に対する高応力域繰返し数依存性の一考察

Molecular Determinants of the Interaction Between HCN2 and its Accessory Subunit TRIP8b

Considerable evidence has shown that ion channels operate as part of large macromolecular complexes composed of channels, cytoskeletal proteins, scaffolding proteins, signaling molecules, and a litany of other molecules. The proteins that make up these complexes can influence trafficking, localization, and biophysical properties of the channel. Until recently, little was known about which proteins associate with and modulate hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. New studies have uncovered a cytosolic protein called Trip8b, which may contribute to the dendritic localization of HCN channels in many neurons. TRIP8b interacts with the carboxy terminus (C-terminus) of HCN channels at two sites and regulates the expression level and cyclic nucleotide dependence of the channel. Here we examine the molecular determinants of Trip8b binding to HCN2 channels using a combination of electrophysiology, single molecule fluorescence, and X-ray crystallography. We first determined the stoichiometry of the interaction using the single molecule bleaching method. We counted bleaching steps of EGFPs expressed as fusions with Trip8b in oocytes co-expressing HCN2 and found that Trip8b and HCN2 form a 4:4 complex in intact channels. Using isolated fragments of HCN2, we find that Trip8b and the C-terminus of HCN2 form a stable 2:1 Trip8b:HCN2 interaction and that removal of the downstream binding site on HCN2 does not alter this complex in solution. Combined with the single molecule fluorescence data, we believe this suggests a model wherebyTrip8b interacts with HCN2 in the cleft between two adjacent C-termini making multiple contacts with the each cyclic nucleotide binding domain on neighboring HCN2 molecules. To begin to understand the detailed molecular mechanism of the interaction between Trip8b and HCN2, we used X-ray crystallography to determine the structure of Trip8b in complex with a peptide of the last seven amino acids of HCN2.

On Periodic Register Need in Software Pipelining

This paper presents several theoretical and fundamental results on the register need in periodic schedules, also known as MAXLIVE. Our first contribution is a novel formula for computing the exact number of registers needed by a scheduled loop. This formula has two advantages: Its computation can be done by using a polynomial algorithm with O(n lg n) complexity (n is the number of instructions in the loop) and it allows the generalization of a previous result [13]. Second, during software pipelining, we show that the minimal number of registers needed may increase when incrementing the initiation interval (II), which is contrary to intuition. For the case of zero architectural delays in accessing registers, we provide a sufficient condition for keeping the minimal number of registers from increasing when incrementing the II. Third, we prove an interesting property that enables us to optimally compute the minimal periodic register sufficiency of a loop for all its valid periodic schedules, irrespective of II. Fourth and last, we prove that the problem of optimal stage scheduling under register constraints is polynomially solvable for a subclass of data dependence graphs, whereas this problem is known to be NP-complete for arbitrary dependence graphs [7]. Our latter result generalizes a previous achievement [13] which addressed data dependence trees and forest of trees. In this study, we consider cyclic data dependence graphs without taking into account any resource constraints. The aim of our theoretical results on the periodic register need is to help current and future software pipeliners achieve significant performance improvements by making better (if not the best) use of the available resources.

Dynamic gain scheduled control of a Hawk scale model

AbstractWhen designing flight control laws using linearisations of an aircraft model about different flight conditions, some form of scheduling of the resultant gains will often be required to implement the controller over wide operating regions. In practice, the controller gains are often scheduled against relatively slowly-varying system states such as altitude or velocity. However, it may also be desirable to schedule gains against rapidly-varying states such as angle-of-attack, thereby generating a cyclic dependence through hidden coupling terms. Previous published work at Bristol has developed a numerical method of accounting for this dependence when scheduling state feedback gains against coupled states. The resulting ‘dynamic gain schedule’ is shown to significantly improve the transient response of the aircraft model during rapid manoeuvring and to reduce the chances of control surface actuator position limit saturation. In this paper, the novel design process, using eigenstructure assignment, is applied to a mathematical second-order longitudinal aircraft model which represents an approximate BAe Hawk wind-tunnel model. The dynamic gain scheduled controller is shown to work extremely well in practice when applied to the closed-loop experimental rig. Despite the highly nonlinear characteristics of the model aerodynamics and tailplane actuation system, as well as unmodelled high turbulence levels, dynamic gain scheduling demonstrates stable closed loop control even in regions where the nonlinearities are such that conventional gain scheduling fails to produce a stable response.

EMI Shielding Effectiveness of Copper/Epoxy Composites

Samples of shaped and treated copper (Cu) fibre/brittle matrix composites have been fabricated with a variety of fibre shapes, treatments, diameters, and powder inclusions and tested for shielding effectiveness (SE) using the ASTM standard D4935-99 method over the frequency range 200 to 1500 MHz. A small amount of nickel (Ni) powder was included in some specimens to evaluate the effect of magnetic permeability on SE. Most tests were conducted at constant (15 vol%, “v%”) fibre volume fraction. Results show that a smaller fibre diameter results in significant SE improvements. SE was also substantially improved by relatively minor fibre shaping (which changes along the fibre length) or by fine-scale roughening via chemical treatment. Addition of small amounts of Cu powder leads to major improvements in SE. Most of the improvements are presumably due to the establishment of conductive networks, although fibre shaping or treatment allows greater scattering and thus more internal reflections with attendant absorption. The smaller diameter fibres consistently gave better SE. When a continuous fibre mesh was used, high SE resulted, showing the dominance of fibre connectivity for such materials; the surface condition of the mesh is relatively unimportant. The improvements in SE can be achieved with essentially identical mechanical properties, leading to an effective multifunctional material, although most of the SE values achieved so far are modest. Ni powder results in overall improvement in SE as well as a cyclic dependence of SE on frequency, which indicates phase interference at a scale of particle size not previously seen.

The Mn I 539.47 nm Line Variation in Solar Active Regions

It is a well-established fact that the Mn I 539.47 nm line exhibits significant cycle dependence similar to lines arising in the chromosphere which are affected by non-thermal heating in the chromospheric plages. Among these lines the case of the Mn I 539.47 nm line seems unique. It is of photospheric origin on the basis of theoretical calculations but its cyclic dependence hints at a chromospheric nature. The present work provides further evidence to both connections. The line exhibits asymmetry features and a center-to-limb variation as though influenced by the photospheric granulation. On the other hand an enhancement of the central intensity has been detected in a well identifiable Ca plage area. The line seems to be a promising candidate as an irradiance variation indicator.

수정 다층 모델을 이용한 이력곡선의 묘사

Overlay model had several advantages to describe hysteretic behavior of material and showed good capability for many engineering materials. However, this model is only applicable to material obeying Masing postulate. Some materials such as 316L stainless steel do not follow Masing postulate and show cyclic hardening(or softening) and strain range dependence. Low cycle fatigue tests of 316L stainless steel at 600℃ were performed to investigate the characteristics of cyclic behavior of non-Masing material. From all tests cyclic softening was observed. There were differences in elastic limit of hysteresis loop according to applied strain range. To consider these features, modified overlay model was developed. Yield stresses of subelements were divided into isotropic and anisotropic part to describe the non-Masing behavior. The plastic strain range memorization was introduced to consider the strain range dependence. The prediction using modified overlay model showed a good accordance to actual hysteresis loops.

Visualization of Electrochemical Measurements under Finite Conditions using JAVA and Its Application for Assisted Learning (2)

A program written in JAVA language was developed for the virtual electrochemical measurement of a modified electrode with a finite diffusion thickness, e.g., an electrode coated with polymer film in which functional molecules were dispersed. This program, called ES-2, can simulate cyclic voltammetry and potential-step chronoamperospectrometry by considering the rate of charge injection from the electrode to the functional molecule and the diffusion of charge. The results are shown by a voltammogram (I-V curve), and concentration distribution in the layer at a series of voltages at cyclic voltammogram mode, I-t curve, and time dependence of concentration distribution in the layer at potential step mode and a text of current values, the fraction of the oxidized molecules (RCT) and parameters used for the simulation in both modes. A dynamic textbook of electrochemistry can be constructed by this program combined with HTML text.

Bacterial luminescence: Luminescence mechanism with cyclic peroxide participation and dependence on reactive oxygen species (a hypothesis)

Chemically initiated exchange (CIEE) luminescence reactions were reviewed and a new mechanism of luminescence with peracid as an intermediate is proposed; bacterial luminescence is generally considered to be a case of dioxetane luminescence, or, to be more precise, CIEE-luminescence which includes the generation of a cyclic peroxide. In the hypothesis the monooxygenase reaction (aldehyde →fatty acid) should not be coupled with emitter generation as is usually believed, but only with the generation of peracid. As to the generation of the emitter, excited flavin, it is likely to occur later, during the interaction of flavin with cyclic peroxide. Its consequence is the breaking of two chemical bonds (O—O and C—C) in the cyclic peroxide and simultaneous generation of 4α-hydroxyflavin in exited state. In general, the generation of light includes three stages: 1) the monooxygenase reaction and the concurrent production of peracid; 2) the conversion of peracid to cyclic peroxide; and 3) the interaction of cyclic peroxide with flavin (through the CIEE mechanism).