Specific Response Characteristics Research Articles

Sensing touch location on an elastic surface by monitoring structural vibrations

In recent years, touchscreens have become ubiquitous, and projected capacitance (p-cap) has arisen as the dominant touch-sensing technology. Though powerful, p-cap has some characteristics that make it less suited for certain applications. Active acoustic sensing (AAS) systems work by sensing the vibration response of an elastic surface to a system-generated excitation and associating specific response characteristics with touch locations on the surface. These systems have the potential to offer advantages over p-cap in terms of scalability, cost, and performance in harsh environments. AAS systems may also offer the ability to sense touch pressure as an additional input parameter. We developed an empirical model of surface vibrational response as a function of the location of an applied force and then used this model to inform the signal processing and machine learning approaches employed in a prototype AAS system. In this presentation, we provide results from our empirical model as well as details of the prototype system, including its construction and performance.

Soil enzyme kinetics and thermodynamics in response to long-term vegetation succession

Our current knowledge regarding soil organic matter (SOM) turnover during vegetation succession is often limited to conventional C decomposition models. However, microbial enzyme-mediated SOM degradation and nutrient cycling are mainly reflected in the kinetic parameters of these enzymes. Changes in the composition and structure of plant communities are typically accompanied by alterations in soil ecological functions. Therefore, it is important to clarify the kinetic parameters of soil enzymes and their temperature sensitivity in response to vegetation succession, especially under the current trend of climate change-related global warming; however, these are still understudied. Here, we examined the kinetic parameters of soil enzymes, their temperature sensitivity, and their associations with environmental variables over long-term (approximately 160 years) vegetation succession on the Loess Plateau using a space-for-time substitution method. We found that the kinetic parameters of soil enzymes changed significantly during vegetation succession. Specific response characteristics varied depending on the enzyme. Overall, the temperature sensitivity (Q10, 0.79–1.87) and activation energy (Ea, 8.69–41.49 kJ·mol−1) remained stable during long-term succession. Compared with N-acetyl-glucosaminidase and alkaline phosphatase, β-glucosidase was more sensitive to extreme temperatures. In particular, two kinetic parameters (i.e., maximum reaction rate, Vmax; half-saturation constant, Km) of β-glucosidase were decoupled at low (5 °C) and high (35 °C) temperatures. Overall, Vmax was the primary determinant of variations of enzyme catalytic efficiency (Kcat) during succession, and soil total nutrients had a greater impact on Kcat than available nutrients. Our results suggested that soil ecosystems played an increasingly important role as a C source during long-term vegetation succession, as indicated by the positive responses of the C cycling enzyme Kcat, while the factors related to soil N and P cycling remained relatively stable.

Structural variation between neuropeptide isoforms affects function in the lobster cardiac system

Neuronal responses to peptide signaling are determined by the specific binding of a peptide to its receptor(s). For example, isoforms of the same peptide family can drive distinct responses in the same circuit by having different affinities for the same receptor, by having each isoform bind to a different receptor, or by a combination of these scenarios. Small changes in peptide composition can alter the binding kinetics and overall physiological response to a given peptide. In the American lobster (Homarus americanus), native isoforms of C-type allatostatins (AST-Cs) usually decrease heartbeat frequency and alter contraction force. However, one of the three AST-C isoforms, AST-C II, drives a cardiac response distinct from the response elicited by the other two. To investigate the aspects of the peptide that might be responsible for these differential responses, we altered various features of each peptide sequence. Although the presence of an amide group at the end of a peptide sequence (amidation) is often essential for determining physiological function, we demonstrate that C-terminal amidation does not dictate the AST-C response in the lobster cardiac system. However, single amino acid substitution within the consensus sequence did account for many of the differences in specific response characteristics (e.g. contraction frequency or force).

Effects of Touch Location and Intensity on Interneurons of the Leech Local Bend Network

Touch triggers highly precise behavioural responses in the leech. The underlying network of this so-called local bend reflex consists of three layers of individually characterised neurons. While the population of mechanosensory cells provide multiplexed information about the stimulus, not much is known about how interneurons process this information. Here, we analyse the responses of two local bend interneurons (cell 157 and 159) to a mechanical stimulation of the skin and show their response characteristics to naturalistic stimuli. Intracellular dye-fills combined with structural imaging revealed that these interneurons are synaptically coupled to all three types of mechanosensory cells (T, P, and N cells). Since tactile stimulation of the skin evokes spikes in one to two cells of each of the latter types, interneurons combine inputs from up to six mechanosensory cells. We find that properties of touch location and intensity can be estimated reliably and accurately based on the graded interneuron responses. Connections to several mechanosensory cell types and specific response characteristics of the interneuron types indicate specialised filter and integration properties within this small neuronal network, thus providing evidence for more complex signal processing than previously thought.

Taguchi and ANOVA approach for optimization of flow characteristics of self-compacting concrete

Sand-rich self-compacting concrete (SCC) with high volume of fly ash requires specific experimental design for optimized response in freshened state. The analysis of the results of an experimental investigation by Taguchi method for optimization of the effect of size of coarse aggregate and fine aggregate content on the quality characteristics of SCC are presented in this study. Slump flow diameter, V-funnel flow time, U-box rise and segregation index are considered as the response parameters of the freshened SCC. The mixes were designed for a fixed water–powder ratio and aggregate–powder ratio to achieve the desired compressive strength. The basic mix was determined based on mortar trial test and for a larger context of a test program on hardened SCC. The analysis revealed size of coarse aggregate and fine aggregate contents for optimum response of freshened SCC. The individual significant levels of the controlling factors in relation to the specific response characteristics are obtained. Thus, an understanding was developed on how the controlling factors influenced the freshened quality characteristics of SCC with high volume of fly ash and sand content. The confirmation test further verified the optimized results.

Design and Color Response of Colorimetric Multilumophore Oxygen Sensors

The preparation of multilumophore colorimetric luminescent oxygen sensors exhibiting red-green, red-blue, and red-green-blue color space responses across oxygen partial pressures in the range of 0-760 Torr is described. We show how the relative lumophore concentration, emission lifetime, and permeability of the polymer host matrix to oxygen may be used to control both the color space response and the sensitivity of these sensors, thus enabling the device to be optimized for operation over a specific oxygen concentration range or application. The Commission Internationale de L'Eclairage (CIE) xy color space response and oxygen sensitivity of these experimental multilumophore sensors has been modeled using a combination of CIE color coordinates and Stern-Volmer quenching kinetics, and generally good agreement between the experimental and modeled response is obtained. This approach will therefore provide a useful preexperimentation tool for the design of sensors with specific response characteristics.

SECM visualization of spatial variability of enzyme–polymer spots: 1. Discretisation and interference elimination using artificial neural networks

Enzyme–polymer layers immobilized on an electrode surface often serve as basis for amperometric biosensors. Caused by the formation process they show spatial variability in the polymer thickness which corresponds to a variability of immobilized enzyme activity. The relationship between topography and localized enzymatic activity of enzyme–polymer spots was studied using scanning electrochemical microscopy (SECM) in the feedback mode and generator-collector mode. Discretisation with a grid size corresponding to the scanning parameters defined substructures which can be treated as individual microsensors with specific response characteristics. The local responses are mainly governed by the polymer thickness but also influenced by neighbouring sites. Thus, discretisation allowed us to treat an enzyme–polymer spot with dimensions of about 300 μm diameter like an array of more than 400 individual microsensors. Using suitable selection criteria and multivariate calibration it was possible to identify sensing sites which are optimal for the determination of glucose. It was demonstrated that an artificial neural network which was trained with the data provided by SECM images well predicted glucose concentration in the presence of ascorbic acid.

Real-Time Seismic Monitoring of the New Cape Girardeau Bridge and Preliminary Analyses of Recorded Data: An Overview

This paper introduces the state-of-the-art seismic monitoring system implemented for the 1,206-m-long (3,956 ft) cable-stayed Bill Emerson Memorial Bridge in Cape Girardeau (Missouri), a new Mississippi River crossing, approximately 80 km from the epicentral region of the 1811 and 1812 New Madrid earthquakes. The real-time seismic monitoring system for the bridge includes a broadband network consisting of superstructure and free-field arrays and comprises a total of 84 channels of accelerometers deployed on the superstructure (towers and deck), pier foundations (caisson tops and bents), and in the vicinity of the bridge (e.g., free-field, both surface and downhole). The paper also introduces the high-quality response data obtained from the broadband network that otherwise would not have been possible with older instruments. Such data is aimed to be used by the owner, researchers, and engineers to (1) assess the performance of the bridge, (2) check design parameters, including the comparison of dynamic characteristics with actual response, and (3) better design future similar bridges. Preliminary spectral analyses of low-amplitude ambient vibration data and that from a small earthquake reveal specific response characteristics of this new bridge and the free-field in its proximity. There is coherent tower-cable-deck interaction that sometimes results in amplified ambient motions. Also, while the motions at the lowest (triaxial) downhole accelerometers on both Missouri and Illinois sides are practically free from any feedback of motions of the bridge, the motions at the middle downhole and surface accelerometers are influenced significantly even by amplified ambient motions of the bridge.

Theoretical treatment and computer simulation of microelectrode arrays

New relations for and interrelations between the current responses of different microelectrode arrays are presented. Interdigitated microelectrode arrays (IDAs: alternating cathodes and anodes) and uniform microband electrode arrays (MEAs: only cathodes or anodes) are treated, and miniaturized systems with planar band electrodes or hemicylinder electrodes are discussed. A common basis was found for the specific response characteristics of IDAs and MEAs. The theoretical expressions were verified by results from computer modelling. The numerical simulations made use of finite-element procedures to evaluate steady-state and time-dependent mass fluxes and concentration profiles of electroactive species at the surfaces of different microelectrode arrays. It was shown that the response behavior of a given array can be exactly predicted from the current data of other arrays.

Dinamismo talamocortical: ¿Cómo se comunican el tálamo y la neocorteza durante los estados de procesamiento de información?

The thalamus is the gateway to the neocortex. Most of the information that reaches the neocortex is transmitted through thalamocortical fibres. The neocortex, in turn, sends massive feedback to the thalamus through corticothalamic fibres. The sensory input reaches the thalamus by means of the primary sensory fibres. When the properties of these pathways are explored, they are found to present specific response characteristics. These studies have generally been conducted during anaesthesia or other quiescent states. Yet when the properties of these synaptic connections are explored in the active states typical of information processing, their responses are substantially different.These changes appear to be necessary to set the pathways of the thalamocortical system in a state of sensory input processing and, therefore, could account for the transformations that take place in order to sustain attentional and perceptive processes.

Direct ex vivo analysis of human CD4(+) memory T cell activation requirements at the single clonotype level.

CD4(+) memory T cells continuously integrate signals transmitted through the TCR and costimulatory molecules, only responding when the intensity of such signals exceeds an intrinsic activation threshold. Recent data suggest that these activation thresholds can be regulated independently of TCR specificity, and that threshold tuning may constitute a major mechanism for controlling T cell effector activity. In this work we take advantage of the profound clonotypic hierarchies of the large human CD4(+) T cell response to CMV to study activation thresholds of fresh (unexpanded) memory T cells at the clonotypic level. We identified dominant responses to CMV matrix determinants mediated by single TCRB sequences within particular TCR-Vbeta families. The specific response characteristics of these single, Ag-specific, TCRB-defined clonotypes could be unequivocally determined in fresh PBMC preparations by cytokine flow cytometry with gating on the appropriate Vbeta family. These analyses revealed 1) optimal peptides capable of eliciting specific responses by themselves at doses as low as 2 pg/ml, with each log increase in dose eliciting ever-increasing frequencies of responding cells over a 4- to 5-log range; 2) significant augmentation of response frequencies at all submaximal peptide doses by CD28- and CD49d-mediated costimulation; 3) differential dose response and costimulatory characteristics for IFN-gamma and IL-2 responses; and 4) no association of activation requirements with the CD27-defined CD4(+) T cell memory differentiation pathway. Taken together these data confirm that triggering heterogeneity exists within individual CD4(+) memory T cell clonotypes in vivo and demonstrate that such single clonotypes can manifest qualitatively different functional responses depending on epitope dose and relative levels of costimulation.

Developmental changes in the density of ionic currents in antennal-lobe neurons of the sphinx moth, Manduca sexta.

Early in metamorphic adult development, action potentials elicited from Manduca sexta antennal lobe neurons are small in amplitude, long in duration, and calcium dependent. As development proceeds, the action potential waveform becomes larger in amplitude, shorter in duration, and increasingly sodium dependent. Whole cell voltage-clamp analysis of Manduca antennal-lobe neurons in vitro has been used to identify voltage-activated currents that contribute to developmental changes in the electrical excitability of these cells. Proximal Branching neurons [putative projection (output) neurons] and Rick Rack neurons (putative local antennal-lobe interneurons) are examined in detail early (pupal stage 5) and late (pupal stage 14) in adult metamorphosis. In both cell types, four voltage-gated and two calcium-dependent ionic currents have been identified. Cell-type-specific changes in the density of sodium, calcium, and potassium currents correlate temporally with changes in cell excitability and spike waveform. Developmental changes in ionic current profiles are accompanied also by the emergence of cell-type-specific response characteristics in the cells. Together with the accompanying paper, this study provides an important foundation for examining the impact of developmental changes in electrical excitability on the growth, electrical properties and connectivity of neurons in central olfactory pathways of the moth.

Market monitoring and control of ancillary services

In this paper, the problems of market monitoring and control of ancillary services of future energy systems are presented. We envision that future system operation of electric power systems will evolve into completely unbundled ancillary service markets that are governed by spot price signals. The grid operators need to acquire ancillary services through competitive markets for control of the system operation. With the above vision of the future, this paper presents the control of ancillary services based on a frequency regulation/load following (LFC) market, a load regulating (RL) market, and a base load (BL) market. In the LFC market, the units dispatched for generation must have specific response characteristics as determined by the nature of system loads. These units will be controlled by the grid operator. It is envisioned that LFC will be multi-time scale and decentralized. In the RL market, the units dispatched for generation will not participate in LFC. These units are dispatched for specific period of time for regulating system load. The BL units are dispatched daily to satisfy the BL of the day on a weekly or monthly basis. The locational market power associated with generators participating in LFC and in RL is even more critical than that for generators participating in satisfying the BL, since these units are required for frequency regulation, voltage support and relief of overload conditions. To create an efficient market for these services, we will propose and formulate the use of incentive strategies for the BL, RL and the LFC markets.

Indirect adaptive nonlinear control of drug delivery systems

This paper investigates the use of adaptive neural network techniques for modeling and automatic control of mean arterial pressure through the intravenous infusion of sodium nitroprusside. An indirect model reference-based adaptive nonlinear control scheme with neural networks approximating the unknown nonlinearities, is developed. In this formulation nonlinear estimators are used to adaptively approximate the system uncertainty and augment the linear control law for improved performance. The overall design is based on self-tuning the controller to the specific response characteristics of individual patients. Computer simulations illustrate the ability of radial basis function networks to model the unknown nonlinearities and improve the closed-loop system characteristics.

A climate hypothesis describing the solar‐terrestrial system as a frequency domain with specific response characteristics

The evidence for and against solar variability influencing weather and climate is beset by conflicting results (e.g., see Goldberg, 1982). This article will examine a new point of departure that is designed to complement simple cause‐and‐effect methodologies. The study is based upon an analogue to contemporary quantum physics.Individual atoms are known to exhibit discrete absorption and emission responses to incoming radiation. John Jacob Balmer's 1885 description of the visible lines in the hydrogen spectrum was soon extended by Lyman and Humphreys to include both the ultraviolet and infrared componems defining the simplest atomic element. In the late 1970's I decided to test a climate concept based upon the known variability of incoming UV radiation and outgoing infrared that also displays a similar discrete frequency response. This response is primarily controlled by the triatomic molecules O3, H20, and CO2 that exist as diabatically important trace gases within earth's atmosphere.

Retinal afferents to the pigeon optic tectum: Discharge characteristics in response to whole field illumination

Responses of pigeon retinotectal afferents to changes in whole field illumination are quantitatively analyzed for 313 units recorded in the stratum opticum. One hundred per cent of these units were responsive in unanesthetized birds and 92.9 percent in urethane anesthetized preparations. Of the responsive units, 92.4 percent (anesthetized) and 100 percent (unanesthetized) gave on-responses whose discharge characteristics showed an orderly relationship to stimulus intensity. Following the on-response, discharge generally ceased during sustained illumination. At stimulus termination off-responses frequently occurred, their probability being a function of stimulus intensity and duration. This probability, as well as specific response characteristics, could be predicted to a large extent from on-response characteristics. Anesthesia and level of background illumination predictably affected these response characteristics quantitatively but did not alter them qualitatively. It is hypothesized that with respect to whole field illumination the pigeon's retinotectal afferents constitute a homogeneous population continuously distributed according to threshold for intensity change.