Spike Model Research Articles

Modeling fast and slow gamma oscillations with interneurons of different subtype.

Experimental and theoretical studies demonstrate that neuronal gamma oscillations crucially depend on interneurons, but current models do not consider the diversity of known interneuron subtypes. Moreover, in CA1 of the hippocampus, experimental evidence indicates the presence of multiple gamma oscillators, two of which may be coordinated by differing interneuron populations. In this article, we show that models of networks with competing interneuron populations with different postsynaptic effects are sufficient to generate, within CA1, distinct oscillatory regimes. We find that strong mutual inhibition between the interneuron populations permits distinct fast and slow gamma states, whereas weak mutual inhibition generates mixed gamma states. We develop idealized firing rate models to illuminate dynamic properties of these competitive gamma networks, and reinforce these concepts with basic spiking models. The models make several explicit predictions about gamma oscillators in CA1. Specifically, interneurons of different subtype phase-lock to different gamma states, and one population of interneurons is silenced and the other active during fast and slow gamma events. Finally, mutual inhibition between interneuron populations is necessary to generate distinct gamma states. Previous experimental studies indicate that fast and slow gamma oscillations reflect different information processing modes, although it is unclear whether these rhythms are intrinsic or imposed. The models outlined demonstrate that basic architectures can locally generate these oscillations, as well as capture other features of fast and slow gamma, including theta-phase preference and spontaneous transitions between gamma states. These models may extend to describe general dynamics in networks with diverse interneuron populations.NEW & NOTEWORTHY The oscillatory coordination of neural signals is crucial to healthy brain function. We have developed an idealized neuronal model that generates distinct fast and slow gamma oscillations, a known feature of the rodent hippocampus. Our work provides a mechanism of this phenomenon, as well as a theoretical framework for future experiments concerning hippocampal gamma. It moreover offers a tractable model of competitive gamma oscillations that is generalizable across the nervous system.

Public's willingness to pay a premium for bioethanol in Korea: A contingent valuation study

Bioethanol (BE), a renewable energy, is well-known to mitigate the greenhouse gas emissions compared with conventional gasoline. Thus, the Korean government is considering the introduction of a BE mandate in which the legal blend is 5% BE and 95% gasoline (E5) until 2020 in order to expand BE use. We should examine the public acceptability of the introduction, which incurs a rise in the fuel price. This study attempts to assess the public's willingness to pay (WTP) a premium for introducing the E5 program in Korea. To this end, a contingent valuation (CV) survey of 1000 randomly selected consumers was conducted in 2014 across the nation. We used a one-and-one-half-bound dichotomous choice question in the CV survey and applied the spike model to handle the WTP data with zeros. The mean WTP, a premium for the E5 per liter, is estimated to be KRW 290 (USD 0.27), which is statistically meaningful at the 1% level. This value amounts to 15.6% of the gasoline retail price in 2014 (KRW 1856 or USD 1.70) and can be interpreted as the external benefit of BE. We can conclude that gasoline consumers in Korea are ready to pay a significant premium for the E5.

Anomalous effect of ion velocity on track formation in GeS

Systematic experiments were performed for studying the effect of the projectile velocity (velocity effect, VE) in GeS which has a highly anisotropic conductivity. The prethinned specimens were irradiated by Bi, Au, W, Xe, Ag, Kr, Ni and Fe ions of about E≈1MeV/nucleon energy. Track radii were measured by transmission electron microscopy. Compared to previous experiments performed with high velocity projectile, there is a marked VE for Se>20keV/nm (Se – electronic stopping power). However, the VE is gradually reduced and finally disappears as Se decreases. This effect is described for the first time. The predictions according to the Analytical Thermal Spike Model are in excellent quantitative agreement with the experiments in the range Se>20keV/nm. The anomalous behavior of track evolution at lower values of Se is attributed to the combination of semiconducting and insulating properties. An explanation of the VE is given based on the Coulomb explosion model.

Public Acceptability of Introducing a Biogas Mandate in Korea: A Contingent Valuation Study

Biogas (BG), a renewable form of energy, can mitigate greenhouse gas emissions, unlike conventional gas. Thus, the Korean Government is considering the introduction of a BG mandate, in which the legal blend is 2% BG and 98% conventional gas (BG2), by 2020 to expand BG use. We should examine the public acceptability of the introduction, which will incur a rise in the gas price. This study attempts to assess the public’s willingness to pay (WTP) for introducing the BG2 program in Korea. The WTP data were obtained from a one-and-one-half-bounded dichotomous choice contingent valuation survey of 1000 households. Because a considerable number of the respondents (63.4%) gave a zero WTP response, we applied a spike model to treat the WTP data with zero observations. The yearly mean WTP was computed as 2539 Korean won (KRW) (USD 2.5) per household for the next 10 years, which is also statistically meaningful at the 1% level. Expanding the value to the national population gives us KRW 50.7 billion (USD 49.5 million) per year. The present value of the total public WTP amounts to KRW 372.7 billion (USD 368.4 million) using a social discount rate of 5.5%. We can conclude that gas consumers in Korea are ready to shoulder some of the financial burden of expanding the use of BG.

Model-Driven Analysis of Eyeblink Classical Conditioning Reveals the Underlying Structure of Cerebellar Plasticity and Neuronal Activity.

The cerebellum plays a critical role in sensorimotor control. However, how the specific circuits and plastic mechanisms of the cerebellum are engaged in closed-loop processing is still unclear. We developed an artificial sensorimotor control system embedding a detailed spiking cerebellar microcircuit with three bidirectional plasticity sites. This proved able to reproduce a cerebellar-driven associative paradigm, the eyeblink classical conditioning (EBCC), in which a precise time relationship between an unconditioned stimulus (US) and a conditioned stimulus (CS) is established. We challenged the spiking model to fit an experimental data set from human subjects. Two subsequent sessions of EBCC acquisition and extinction were recorded and transcranial magnetic stimulation (TMS) was applied on the cerebellum to alter circuit function and plasticity. Evolutionary algorithms were used to find the near-optimal model parameters to reproduce the behaviors of subjects in the different sessions of the protocol. The main finding is that the optimized cerebellar model was able to learn to anticipate (predict) conditioned responses with accurate timing and success rate, demonstrating fast acquisition, memory stabilization, rapid extinction, and faster reacquisition as in EBCC in humans. The firing of Purkinje cells (PCs) and deep cerebellar nuclei (DCN) changed during learning under the control of synaptic plasticity, which evolved at different rates, with a faster acquisition in the cerebellar cortex than in DCN synapses. Eventually, a reduced PC activity released DCN discharge just after the CS, precisely anticipating the US and causing the eyeblink. Moreover, a specific alteration in cortical plasticity explained the EBCC changes induced by cerebellar TMS in humans. In this paper, for the first time, it is shown how closed-loop simulations, using detailed cerebellar microcircuit models, can be successfully used to fit real experimental data sets. Thus, the changes of the model parameters in the different sessions of the protocol unveil how implicit microcircuit mechanisms can generate normal and altered associative behaviors.The cerebellum plays a critical role in sensorimotor control. However, how the specific circuits and plastic mechanisms of the cerebellum are engaged in closed-loop processing is still unclear. We developed an artificial sensorimotor control system embedding a detailed spiking cerebellar microcircuit with three bidirectional plasticity sites. This proved able to reproduce a cerebellar-driven associative paradigm, the eyeblink classical conditioning (EBCC), in which a precise time relationship between an unconditioned stimulus (US) and a conditioned stimulus (CS) is established. We challenged the spiking model to fit an experimental data set from human subjects. Two subsequent sessions of EBCC acquisition and extinction were recorded and transcranial magnetic stimulation (TMS) was applied on the cerebellum to alter circuit function and plasticity. Evolutionary algorithms were used to find the near-optimal model parameters to reproduce the behaviors of subjects in the different sessions of the protocol. The main finding is that the optimized cerebellar model was able to learn to anticipate (predict) conditioned responses with accurate timing and success rate, demonstrating fast acquisition, memory stabilization, rapid extinction, and faster reacquisition as in EBCC in humans. The firing of Purkinje cells (PCs) and deep cerebellar nuclei (DCN) changed during learning under the control of synaptic plasticity, which evolved at different rates, with a faster acquisition in the cerebellar cortex than in DCN synapses. Eventually, a reduced PC activity released DCN discharge just after the CS, precisely anticipating the US and causing the eyeblink. Moreover, a specific alteration in cortical plasticity explained the EBCC changes induced by cerebellar TMS in humans. In this paper, for the first time, it is shown how closed-loop simulations, using detailed cerebellar microcircuit models, can be successfully used to fit real experimental data sets. Thus, the changes of the model parameters in the different sessions of the protocol unveil how implicit microcircuit mechanisms can generate normal and altered associative behaviors.

A comparison of the values of water inflows into selected South African estuaries: The Heuningnes, Kleinmond, Klein, Palmiet, Cefane, Kwelera and Haga-Haga

Abstract The functionality of estuaries is threatened by widespread and rapid transformation as a result of the significant reduction in the rate at which freshwater flows into them. We present standardized methods that combine freshwater abstraction and estuary functionality to estimate recreational values of freshwater inflow to households located in proximity to the seven selected South African estuaries while testing for the convergent validity of the contingent valuation method (CVM), zonal travel cost method (ZTCM) and the individual travel cost method (ITCM). Given that the dependent variable is the log transform, our dependent variable is not censored, so we use an OLS model for the regression, and model separately our zero values using a spike model. When running our regressions, we pool all observations from the seven estuaries and use dummy fixed effects for each estuary, and use interactions to model different effects of the covariates in each estuary. For travel costs analyses, we estimate truncated count data models of recreational demand taking into account the fact that the number of visitation trips taken is a non-negative integer. The CVM generated values per m 3 of freshwater inflow into the estuary ranges from R0.0022 to R0.0546 whereas the ZTCM values ranges from R0.0035 to R0.0499, while the ITCM generated value per m 3 of freshwater inflow is R0.003. The findings in this study are that some convergence of results is achieved.

Measuring the economic benefits of designating Baegnyeong Island in Korea as a marine protected area

ABSTRACTThe Korean Government is considering designating Baegnyeong Island, which has several distinguishing features (it is the habitat of endangered species such as the spotted seal and has unique marine scenery and ecosystem), as a marine protected area (MPA). The policymakers are demanding information on the economic benefits of designating the island as an MPA. Therefore, this paper describes an attempt to measure the economic benefits, using a contingent valuation (CV) survey of 600 randomly selected households in Korea in 2015. We used a one-and-one-half-bound dichotomous choice (DC) question to derive the willingness to pay (WTP) responses, and applied a spike model to deal with WTP responses of zero. The yearly mean WTP per household was computed to be KRW 3,590 (USD 3.15) for the next 10 years, an estimate that is statistically significant at the 1% level. Expanding the value to the national population gives us KRW 67.2 billion (USD 59.1 million) per year. The present value of the total economic benefits amounts to KRW 534.0 billion (USD 469.2 million) using a social discount rate of 5.5%. We can conclude that Korean households are ready to shoulder some of the financial burden of designating the island as an MPA.

Micro-structural origin of elongation in swift heavy ion irradiated Ni nanoparticles: A combined EXAFS and DFT study

Aiming for perpendicular magnetic storage usage, shape anisotropy is introduced in Ni nanoparticles (NPs) embedded inside a thin SiO2 matrix using swift heavy ion irradiation (SHI). Systematic increase in NPs' aspect ratio along the direction of incident SHI beam is observed up to 5 × 1013 ions/cm2 (5e13) fluence from grazing incidence small angle X-ray scattering measurements. Strikingly, at higher fluences the major dimension (along SHI beam) got reduced. This observation is totally intriguing as usually particle elongation increases with applied fluence. To understand this anomaly, as a first step, we have performed a combined near and far edge X-ray absorption spectroscopy (XANES and EXAFS) analysis. This shows irradiated Ni NPs sustain their metallic phase even with increased structural disorder and reduced atomic co-ordination. However an atypical reduction in local structural anisotropy beyond 5e13 fluence is observed from angle dependent EXAFS: following the same trend as NP elongation. To have a better insight, the role of the electronic spin of individual atoms in controlling particle shape is investigated. Using the lattice temperature profiles derived from thermal spike model, we have carried out ab initio molecular dynamics (MD) simulations to understand the structural distortion at higher temperatures. The experimentally observed structural and shape anisotropy in the irradiated NPs is only realized when spin polarization contributions were considered in our calculations. From the pair correlation function and atom-wise spin density plots, we conclude that presence of spin affects the second co-ordination shell and controls the atomic arrangements in such a manner that elongated structures are preferred in the irradiated system at intermediate fluence (i.e. 5e13). Further increase in MD temperature to 6000 K (corresponding to 1 × 1014 ions/cm2 fluence) results in disordered spin alignment and melting of moderately weak spin polarized Ni NPs: thus violating conventional trend of increasing particle elongation w.r.t SHI fluence.

The public value of contaminated soil remediation in Janghang copper smelter of Korea

The Korean government planned to remediate the soil contaminated with heavy metals, such as arsenic, cadmium, and lead, in Janghang copper smelter (JCS). The policy-makers are demanding a figure about the public value of the remediation. Therefore, this paper describes an attempt to measure the public value, applying the contingent valuation (CV) method. To this end, we conducted a CV survey of 1000 households in Korea in 2015. We used a one-and-one-half-bounded dichotomous choice question to derive the willingness to pay (WTP) responses, and utilized a spike model to analyze zero WTP responses. The mean WTP was computed to be KRW 1627 (USD 1.37) per household per year and statistically meaningful at the 1% level. Expanding the value to the national population gives us KRW 30.4 billion (USD 25.7 million) per year. The present value of the total public value for the next ten years reaches KRW 241.7 billion (USD 204.0 million), using a social discount rate of 5.5%. We can conclude that Korean households are ready to shoulder some of the financial burden for contaminated soil remediation in JCS. Moreover, we conducted economic feasibility analysis of the remediation and found that it is socially profitable.

Public Willingness to Pay for Transforming Jogyesa Buddhist Temple in Seoul, Korea into a Cultural Tourism Resource

The Jogyesa Buddhist Temple (JBT), located in Seoul, Korea, is the chief temple of the Jogye Order, which represents Korean Buddhism. The Seoul government plans to transform the JBT into a cultural tourism resource and a historical site. This study attempts to analyze the willingness to pay (WTP) for implementing the transformation, which includes building a new shopping arcade for Buddhist culture and tourism, constructing a museum for the teaching of history and an experience center for Korean traditional culture in the precincts of JBT, and making an open space for domestic and/or foreign visitors. To this end, the study looks into the WTP for the implementation, reporting on a contingent valuation (CV) survey that was conducted with 500 Seoul households. The single-bounded dichotomous choice CV model and a spike model were applied to derive the WTP responses and analyze the WTP data with zero observations, respectively. The mean yearly WTP was computed to be KRW 7129 (USD 6.30) per household for the next five years, with the estimate being statistically significant at the 1% level. Expanding the value to the Seoul population gives us KRW 25.4 billion (USD 22.5 million) per year. The present value of the total WTP amounts to KRW 114.6 billion (USD 101.3 million) using a social discount rate of 5.5%. We can conclude that Seoul households are ready to shoulder some of the financial burden of implementing the transformation.

The External Benefits of Research and Development Investment in Waste-to-Energy Technology in Korea

The Korean government considers expanding the WtE share of total energy from 1% to 5% by 2020 through research and development (R&D) in waste-to-energy (WtE) technologies. This study attempts to measure the external benefits of investing in R&D in these technologies. To this end, a contingent valuation (CV) is employed. More specifically, a 2016 national survey of randomly selected 1,000 households was carried out across the nation to gauge the willingness to pay (WTP) for the investment. One-and-one-half-bounded dichotomous choice question was used in the CV survey, and the spike model was applied to dealing with zero WTP responses. The mean yearly WTP is estimated to be KRW 4,175 (USD 3.57) per household, which is statistically significant at the 1% level. Expanding the value to the entire nation translates into an investment of about KRW 79.1 billion (USD 67.6 million), which can be interpreted as the annual external benefit of the R&D investment in WtE technology.

The Economic Value of the National Meteorological Service in the Korean Household Sector: A Contingent Valuation Study

The meteorological service (MS) in Korea is provided by the Korea Meteorological Administration (KMA), a governmental organization. This study attempts to measure the economic value of the national MS in the Korean household sector. Economic theory indicates that the economic value of a service is the area under the demand curve, which is the sum of the actual expenditure and the additional willingness to pay (WTP) for the service. The actual expenditure is well known, but the additional WTP is not. Thus, we assess the additional WTP for the national MS, conducting a contingent valuation survey of 1000 randomly selected households in Korea in 2014. We use a one-and-one-half-bound dichotomous choice question to derive the WTP responses and apply a spike model to deal with WTP responses of zero. The mean additional WTP per household is computed as KRW 860 (USD 0.75) per month and is statistically significant at the 1% level. Given that the monthly expenditure for the MS is KRW 1459 (USD 1.26) per household as of 2013, the economic value of the national MS is computed as KRW 2319 (USD 2.01) per household per month. Expanding the value to the national population gives us KRW 513.6 billion (USD 444.9 million) per year.

Sequential Pattern Formation in the Cerebellar Granular Layer.

Here, we introduce a novel mechanism for temporal recoding by the cerebellar granular layer based on three key properties: the granule cell-Golgi cell inhibitory feedback loop, bursting behaviour of granule cells and the large ratio of granule cells to Golgi cells. We propose that mutual inhibition of granule cells, mediated by Golgi cell feedback inhibition, prevents simultaneous activation. Granule cells are differentiated by firing threshold, resulting in sequential bursts of spikes. We demonstrate the plausibility of the mechanism through a computational simulation of a firing rate model, and further examine its robustness by developing a spiking model incorporating realistic postsynaptic potentials.

Ion channel noise can explain firing correlation in auditory nerves

Neural spike trains are commonly characterized as a Poisson point process. However, the Poisson assumption is a poor model for spiking in auditory nerve fibres because it is known that interspike intervals display positive correlation over long time scales and negative correlation over shorter time scales. We have therefore developed a biophysical model based on the well-known Meddis model of the peripheral auditory system, to produce simulated auditory nerve fibre spiking statistics that more closely match the firing correlations observed in empirical data. We achieve this by introducing biophysically realistic ion channel noise to an inner hair cell membrane potential model that includes fractal fast potassium channels and deterministic slow potassium channels. We succeed in producing simulated spike train statistics that match empirically observed firing correlations. Our model thus replicates macro-scale stochastic spiking statistics in the auditory nerve fibres due to modeling stochasticity at the micro-scale of potassium channels.

Alternative approaches to electronic damage by ion‐beam irradiation: Exciton models

The paper briefly describes the main features of the damage produced by swift heavy ion (SHI) irradiation. After a short revision of the widely used thermal spike concept, it focuses on cumulative mechanisms of track formation which are alternative to those based on lattice melting (thermal spike models). These cumulative mechanisms rely on the production of point defects around the ion trajectory, and their accumulation up to a final lattice collapse or amorphization. As to the formation of point defects, the paper considers those mechanisms relying on direct local conversion of the excitation energy into atomic displacements (exciton models). A particular attention is given to processes based on the non‐radiative recombination of excitons that have become self‐trapped as a consequence of a strong electron–phonon interaction (STEs). These mechanisms, although operative under purely ionizing radiation in some dielectric materials, have been rarely invoked, so far, to discuss SHI damage. They are discussed in this paper together with relevant examples to materials such as Cu3N, alkali halides, SiO2, and LiNbO3.

Functional Relevance of Different Basal Ganglia Pathways Investigated in a Spiking Model with Reward Dependent Plasticity.

The brain enables animals to behaviorally adapt in order to survive in a complex and dynamic environment, but how reward-oriented behaviors are achieved and computed by its underlying neural circuitry is an open question. To address this concern, we have developed a spiking model of the basal ganglia (BG) that learns to dis-inhibit the action leading to a reward despite ongoing changes in the reward schedule. The architecture of the network features the two pathways commonly described in BG, the direct (denoted D1) and the indirect (denoted D2) pathway, as well as a loop involving striatum and the dopaminergic system. The activity of these dopaminergic neurons conveys the reward prediction error (RPE), which determines the magnitude of synaptic plasticity within the different pathways. All plastic connections implement a versatile four-factor learning rule derived from Bayesian inference that depends upon pre- and post-synaptic activity, receptor type, and dopamine level. Synaptic weight updates occur in the D1 or D2 pathways depending on the sign of the RPE, and an efference copy informs upstream nuclei about the action selected. We demonstrate successful performance of the system in a multiple-choice learning task with a transiently changing reward schedule. We simulate lesioning of the various pathways and show that a condition without the D2 pathway fares worse than one without D1. Additionally, we simulate the degeneration observed in Parkinson's disease (PD) by decreasing the number of dopaminergic neurons during learning. The results suggest that the D1 pathway impairment in PD might have been overlooked. Furthermore, an analysis of the alterations in the synaptic weights shows that using the absolute reward value instead of the RPE leads to a larger change in D1.

Abstract 2244: Development of an automated device for size-based enrichment and isolation of circulating tumor cells in lung cancer patients

Abstract Background and Purpose: Circulating tumor cells (CTCs) are relatively rare cells defined as tumor cells circulating in the peripheral blood of patients with solid tumors. Diagnosis utilizing CTCs is expected to help guide decision-making for precision cancer medicine. We developed an automated microcavity array (MCA) system to detect CTCs based on the differences in size and deformability between tumor cells and normal blood cells. Here we evaluated its performance using preclinical spike-in model and blood samples from non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) patients. Material and method: The automated MCA system consists of components such as chambered cartridge containing micro metal filter, reagent and waste reservoirs, and peristaltic pump. To evaluate the recovery of CTCs, preclinical experiments using NSCLC cells, NCI-H820, A549, NCI-H441 and NCI-H23 spiked into peripheral whole blood from healthy volunteers were performed. For clinical evaluation, 6 mL of peripheral whole blood was collected from 50 advanced lung cancer patients prior to the initiation of chemotherapy and from 10 healthy donors. Samples were collected in an EDTA-containing tube and were processed within 3 hours of blood draw. Recovered cells on the filter were then fixed, permeabilized, and stained automatically and high-resolution fluorescent images were obtained using fluorescence microscope. We defined CTC as DAPI-positive, cytokeratin-positive and CD45-negative cell. Results: Results of the preclinical study showed that up to 90% of spiked-in tumor cells were recovered, confirming that the detection sensitivity by this automated device is on par with that by previous manual detection procedure. Demographics of 50 lung cancer patients enrolled in clinical study were as follows: median age 72 (range, 48 to 85); male 66%; stage III/IV 12/88%; NSCLC/SCLC 78/22%. Cells defined as CTC were detected in 2 cases out of 10 healthy volunteers, of which CTC count was 1 and 2 / 6 mL, respectively. Three or more CTCs were detected in 71% of patients with advanced lung cancer (39 out of 50) and five or more CTCs were detected in 52% of patients (26 out of 50) (median CTC count 13.5). Among stage IV NSCLC patients, patients with extrathoracic metastasis tend to have more CTCs than in those with intrathoracic metasitasis (median CTC count, 8 versus 4, p = 0.058). A head-to-head comparison between CellSearch system and our system was conducted in NSCLC patients, showing the superiority of our system (median CTC count, 0 versus 11.25, p = 0.0001, n = 17). Conclusions Our results suggest that the automated MCA device has a clinical potential for CTCs diagnosis towards precision medicine in lung cancer. This device also enables higher throughput owing to its automated procedure. Further clinical evaluation including the detection of PD-L1 expression will be performed in an expansion cohort. Citation Format: Satomi Yagi, Yasuhiro Koh, Hiroaki Akamatsu, Woong Kim, Ayaka Tanaka, Kuninobu Kanai, Atsushi Hayata, Ryota Shibaki, Masayuki Higuchi, Hisashige Kanbara, Takashi Kikuchi, Keiichiro Akamatsu, Masanori Nakanishi, Hiroki Ueda, Nobuyuki Yamamoto. Development of an automated device for size-based enrichment and isolation of circulating tumor cells in lung cancer patients. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2244.

Dynamic Signal Tracking in a Simple V1 Spiking Model.

This work is part of an effort to understand the neural basis for our visual system's ability, or failure, to accurately track moving visual signals. We consider here a ring model of spiking neurons, intended as a simplified computational model of a single hypercolumn of the primary visual cortex of primates. Signals that consist of edges with time-varying orientations localized in space are considered. Our model is calibrated to produce spontaneous and driven firing rates roughly consistent with experiments, and our two main findings, for which we offer dynamical explanation on the level of neuronal interactions, are the following. First, we have documented consistent transient overshoots in signal perception following signal switches due to emergent interactions of the E- and I-populations. Second, for continuously moving signals, we have found that accuracy is considerably lower at reversals of orientation than when continuing in the same direction (as when the signal is a rotating bar). To measure performance, we use two metrics, called fidelity and reliability, to compare signals reconstructed by the system to the ones presented and assess trial-to-trial variability. We propose that the same population mechanisms responsible for orientation selectivity also impose constraints on dynamic signal tracking that manifest in perception failures consistent with psychophysical observations.

Swift heavy ion induced structural phase generation and enhanced luminescence from CdS based nanocomposites

Abstract Synthesis and modification of CdS:SiO 2 and Cd 0.99 Ag 0.01 S:SiO 2 nanocomposite thin films grown at substrate temperature 200 °C by pulsed laser deposition (PLD) followed by swift heavy ion irradiation (SHII) using 120 MeV Ag 9 + ions is reported. The structural evolution of CdS phase in SiO 2 after SHII is illustrated by glancing angle x-ray diffraction patterns and micro-Raman spectra. Transmission electron microscopy (TEM) images clearly show the growth of CdS/Cd 0.99 Ag 0.01 S nanoparticles in SiO 2 matrix under the influence of SHII. Photoluminescence (PL) spectra show two emission peak at ~ 2.34 eV and ~ 3.05 eV assigned for green emission (GE) and violet emission (VE) respectively. The VE assumed to be originated due to the band edge emission and GE identified as the trap levels located between conduction band and valence band. The presence of emission from pristine films indicates that the crystalline domains are very small in films rather than the particles are amorphous in nature. A systematic increment in PL emission intensity corresponding to trap emission as a function of ion irradiation fluence is observed from the two nanocomposite systems. However, the behavior of band edge emission induced by SHII is quite different in two nanocomposite systems. SHII induced phase formation and emission intensity variation as a function of ion fluence are explained on the basis of thermal spike model.

Measuring benefits of providing water for environmental improvement in Daechi-stream and Ji-stream

This study attempts to estimate the benefits of using water ensuing from the Chilgap multipurpose reservoir for environmental improvement. The contingent valuation method (CVM) was used to elicit the willingness to pay (WTP) for providing environmental improvement water from the Chilgap reservoir to Daechi-stream and Ji-stream. The DCDB (double-bound dichotomous choice) survey method was used to collect data for the analysis. Due to the usually high cost of increasing the sample size, the use of follow-up questions was implemented as an inexpensive method of improving the efficiency of the estimation. A spike model was used in this study because a number of respondents showed zero WTP. The spike model can be estimated as easily as the conventional model. Results show that the average annual household’s WTP is 4,516 won using the conventional model and 8,644 won using the spike model. Applying the estimated average annual household’s WTP to the Chungnam and Daejeon regional levels, the benefits of environmental improvement water from the Chilgap reservoir is estimated at 11.9 billion won per year. The temporal benefits of providing water for environmental improvement, for a 50-year period at a 6.0% discount rate, is estimated at about 190 billion won in the Chungnam and Daejeon areas. These results could be useful especially when the government tries to determine an appropriate level of investment and to make a policy related to providing environmental improvement water.