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Sample records for neuronal phase-response curves

  1. Linear control of neuronal spike timing using phase response curves.

    PubMed

    Stigen, Tyler; Danzl, Per; Moehlis, Jeff; Netoff, Theoden

    2009-01-01

    We propose a simple, robust, linear method to control the spike timing of a periodically firing neuron. The control scheme uses the neuron's phase response curve to identify an area of optimal sensitivity for the chosen stimulation parameters. The spike advance as a function of current pulse amplitude is characterized at the optimal phase and a linear least-squares regression is fit to the data. The inverted regression is used as the control function for this method. The efficacy of this method is demonstrated through numerical simulations of a Hodgkin-Huxley style neuron model as well as in real neurons from rat hippocampal slice preparations. The study shows a proof of concept for the application of a linear control scheme to control neuron spike timing in-vitro. This study was done on an individual cell level, but translation to a tissue or network level is possible. Control schemes of this type could be implemented in a closed loop implantable device to treat neuromotor disorders involving pathologically neuronal activity such as epilepsy or Parkinson's disease.

  2. On the Firing Rate Dependency of the Phase Response Curve of Rat Purkinje Neurons In Vitro

    PubMed Central

    Couto, João; Linaro, Daniele; De Schutter, E; Giugliano, Michele

    2015-01-01

    Synchronous spiking during cerebellar tasks has been observed across Purkinje cells: however, little is known about the intrinsic cellular mechanisms responsible for its initiation, cessation and stability. The Phase Response Curve (PRC), a simple input-output characterization of single cells, can provide insights into individual and collective properties of neurons and networks, by quantifying the impact of an infinitesimal depolarizing current pulse on the time of occurrence of subsequent action potentials, while a neuron is firing tonically. Recently, the PRC theory applied to cerebellar Purkinje cells revealed that these behave as phase-independent integrators at low firing rates, and switch to a phase-dependent mode at high rates. Given the implications for computation and information processing in the cerebellum and the possible role of synchrony in the communication with its post-synaptic targets, we further explored the firing rate dependency of the PRC in Purkinje cells. We isolated key factors for the experimental estimation of the PRC and developed a closed-loop approach to reliably compute the PRC across diverse firing rates in the same cell. Our results show unambiguously that the PRC of individual Purkinje cells is firing rate dependent and that it smoothly transitions from phase independent integrator to a phase dependent mode. Using computational models we show that neither channel noise nor a realistic cell morphology are responsible for the rate dependent shift in the phase response curve. PMID:25775448

  3. Functional phase response curves: a method for understanding synchronization of adapting neurons.

    PubMed

    Cui, Jianxia; Canavier, Carmen C; Butera, Robert J

    2009-07-01

    Phase response curves (PRCs) for a single neuron are often used to predict the synchrony of mutually coupled neurons. Previous theoretical work on pulse-coupled oscillators used single-pulse perturbations. We propose an alternate method in which functional PRCs (fPRCs) are generated using a train of pulses applied at a fixed delay after each spike, with the PRC measured when the phasic relationship between the stimulus and the subsequent spike in the neuron has converged. The essential information is the dependence of the recovery time from pulse onset until the next spike as a function of the delay between the previous spike and the onset of the applied pulse. Experimental fPRCs in Aplysia pacemaker neurons were different from single-pulse PRCs, principally due to adaptation. In the biological neuron, convergence to the fully adapted recovery interval was slower at some phases than that at others because the change in the effective intrinsic period due to adaptation changes the effective phase resetting in a way that opposes and slows the effects of adaptation. The fPRCs for two isolated adapting model neurons were used to predict the existence and stability of 1:1 phase-locked network activity when the two neurons were coupled. A stability criterion was derived by linearizing a coupled map based on the fPRC and the existence and stability criteria were successfully tested in two-simulated-neuron networks with reciprocal inhibition or excitation. The fPRC is the first PRC-based tool that can account for adaptation in analyzing networks of neural oscillators.

  4. Functional Phase Response Curves: A Method for Understanding Synchronization of Adapting Neurons

    PubMed Central

    Cui, Jianxia; Canavier, Carmen C.; Butera, Robert J.

    2009-01-01

    Phase response curves (PRCs) for a single neuron are often used to predict the synchrony of mutually coupled neurons. Previous theoretical work on pulse-coupled oscillators used single-pulse perturbations. We propose an alternate method in which functional PRCs (fPRCs) are generated using a train of pulses applied at a fixed delay after each spike, with the PRC measured when the phasic relationship between the stimulus and the subsequent spike in the neuron has converged. The essential information is the dependence of the recovery time from pulse onset until the next spike as a function of the delay between the previous spike and the onset of the applied pulse. Experimental fPRCs in Aplysia pacemaker neurons were different from single-pulse PRCs, principally due to adaptation. In the biological neuron, convergence to the fully adapted recovery interval was slower at some phases than that at others because the change in the effective intrinsic period due to adaptation changes the effective phase resetting in a way that opposes and slows the effects of adaptation. The fPRCs for two isolated adapting model neurons were used to predict the existence and stability of 1:1 phase-locked network activity when the two neurons were coupled. A stability criterion was derived by linearizing a coupled map based on the fPRC and the existence and stability criteria were successfully tested in two-simulated-neuron networks with reciprocal inhibition or excitation. The fPRC is the first PRC-based tool that can account for adaptation in analyzing networks of neural oscillators. PMID:19420126

  5. Influences of membrane properties on phase response curve and synchronization stability in a model globus pallidus neuron.

    PubMed

    Fujita, Tomohiro; Fukai, Tomoki; Kitano, Katsunori

    2012-06-01

    The activity patterns of the globus pallidus (GPe) and subthalamic nucleus (STN) are closely associated with motor function and dysfunction in the basal ganglia. In the pathological state caused by dopamine depletion, the STN-GPe network exhibits rhythmic synchronous activity accompanied by rebound bursts in the STN. Therefore, the mechanism of activity transition is a key to understand basal ganglia functions. As synchronization in GPe neurons could induce pathological STN rebound bursts, it is important to study how synchrony is generated in the GPe. To clarify this issue, we applied the phase-reduction technique to a conductance-based GPe neuronal model in order to derive the phase response curve (PRC) and interaction function between coupled GPe neurons. Using the PRC and interaction function, we studied how the steady-state activity of the GPe network depends on intrinsic membrane properties, varying ionic conductances on the membrane. We noted that a change in persistent sodium current, fast delayed rectifier Kv3 potassium current, M-type potassium current and small conductance calcium-dependent potassium current influenced the PRC shape and the steady state. The effect of those currents on the PRC shape could be attributed to extension of the firing period and reduction of the phase response immediately after an action potential. In particular, the slow potassium current arising from the M-type potassium and the SK current was responsible for the reduction of the phase response. These results suggest that the membrane property modulation controls synchronization/asynchronization in the GPe and the pathological pattern of STN-GPe activity.

  6. Phase response curve analysis of a full morphological globus pallidus neuron model reveals distinct perisomatic and dendritic modes of synaptic integration

    PubMed Central

    Schultheiss, Nathan W.; Edgerton, Jeremy R.; Jaeger, Dieter

    2010-01-01

    Synchronization of globus pallidus (GP) neurons and cortically-entrained oscillations between GP and other basal ganglia nuclei are key features of the pathophysiology of Parkinson's disease. Phase response curves (PRCs), which tabulate the effects of phasic inputs within a neuron's spike cycle on output spike timing, are efficient tools for predicting the emergence of synchronization in neuronal networks and entrainment to periodic input. In this study we apply physiologically realistic synaptic conductance inputs to a full morphological GP neuron model to determine the phase response properties of the soma and different regions of the dendritic tree. We find that perisomatic excitatory inputs delivered throughout the inter-spike interval advance the phase of the spontaneous spike cycle yielding a type I PRC. In contrast, we demonstrate that distal dendritic excitatory inputs can either delay or advance the next spike depending on whether they occur early or late in the spike cycle. We find this latter pattern of responses, summarized by a biphasic (type II) PRC, was a consequence of dendritic activation of the small conductance calcium-activated potassium current, SK. We also evaluate the spike-frequency dependence of somatic and dendritic PRC shapes, and we demonstrate the robustness of our results to variations of conductance densities, distributions, and kinetic parameters. We conclude that the distal dendrite of GP neurons embodies a distinct dynamical subsystem that could promote synchronization of pallidal networks to excitatory inputs. These results highlight the need to consider different effects of perisomatic and dendritic inputs in the control of network behavior. PMID:20164360

  7. Collective phase response curves for heterogeneous coupled oscillators

    NASA Astrophysics Data System (ADS)

    Hannay, Kevin M.; Booth, Victoria; Forger, Daniel B.

    2015-08-01

    Phase response curves (PRCs) have become an indispensable tool in understanding the entrainment and synchronization of biological oscillators. However, biological oscillators are often found in large coupled heterogeneous systems and the variable of physiological importance is the collective rhythm resulting from an aggregation of the individual oscillations. To study this phenomena we consider phase resetting of the collective rhythm for large ensembles of globally coupled Sakaguchi-Kuramoto oscillators. Making use of Ott-Antonsen theory we derive an asymptotically valid analytic formula for the collective PRC. A result of this analysis is a characteristic scaling for the change in the amplitude and entrainment points for the collective PRC compared to the individual oscillator PRC. We support the analytical findings with numerical evidence and demonstrate the applicability of the theory to large ensembles of coupled neuronal oscillators.

  8. Estimation of the phase response curve from Parkinsonian tremor

    PubMed Central

    Saifee, Tabish A.; Edwards, Mark J.; Kassavetis, Panagiotis

    2015-01-01

    Phase response curves (PRCs), characterizing the response of an oscillator to weak external perturbation, have been estimated from a broad range of biological oscillators, including single neurons in vivo. PRC estimates, in turn, provide an intuitive insight into how oscillatory systems become entrained and how they can be desynchronized. Here, we explore the application of PRC theory to the case of Parkinsonian tremor. Initial attempts to establish a causal effect of subthreshold transcranial magnetic stimulation applied to primary motor cortex on the filtered tremor phase were unsuccessful. We explored the possible explanations of this and demonstrate that assumptions made when estimating the PRC in a traditional setting, such as a single neuron, are not arbitrary when applied to the case of tremor PRC estimation. We go on to extract the PRC of Parkinsonian tremor using an iterative method that requires varying the definition of the tremor cycle and estimating the PRC at multiple peristimulus time samples. Justification for this method is supported by estimates of PRC from simulated single neuron data. We provide an approach to estimating confidence limits for tremor PRC and discuss the interpretational caveats introduced by tremor harmonics and the intrinsic variability of the tremor's period. PMID:26561596

  9. Phase response curves in the characterization of epileptiform activity

    NASA Astrophysics Data System (ADS)

    Perez Velazquez, J. L.; Galán, R. F.; Dominguez, L. Garcia; Leshchenko, Y.; Lo, S.; Belkas, J.; Erra, R. Guevara

    2007-12-01

    Coordinated cellular activity is a major characteristic of nervous system function. Coupled oscillator theory offers unique avenues to address cellular coordination phenomena. In this study, we focus on the characterization of the dynamics of epileptiform activity, based on some seizures that manifest themselves with very periodic rhythmic activity, termed absence seizures. Our approach consists in obtaining experimentally the phase response curves (PRCs) in the neocortex and thalamus, and incorporating these PRCs into a model of coupled oscillators. Phase preferences of the stationary states and their stability are determined, and these results from the model are compared with the experimental recordings, and interpreted in physiological terms.

  10. Phase response curves for models of earthquake fault dynamics.

    PubMed

    Franović, Igor; Kostić, Srdjan; Perc, Matjaž; Klinshov, Vladimir; Nekorkin, Vladimir; Kurths, Jürgen

    2016-06-01

    We systematically study effects of external perturbations on models describing earthquake fault dynamics. The latter are based on the framework of the Burridge-Knopoff spring-block system, including the cases of a simple mono-block fault, as well as the paradigmatic complex faults made up of two identical or distinct blocks. The blocks exhibit relaxation oscillations, which are representative for the stick-slip behavior typical for earthquake dynamics. Our analysis is carried out by determining the phase response curves of first and second order. For a mono-block fault, we consider the impact of a single and two successive pulse perturbations, further demonstrating how the profile of phase response curves depends on the fault parameters. For a homogeneous two-block fault, our focus is on the scenario where each of the blocks is influenced by a single pulse, whereas for heterogeneous faults, we analyze how the response of the system depends on whether the stimulus is applied to the block having a shorter or a longer oscillation period.

  11. Robust Entrainment of Circadian Oscillators Requires Specific Phase Response Curves

    PubMed Central

    Pfeuty, Benjamin; Thommen, Quentin; Lefranc, Marc

    2011-01-01

    The circadian clocks keeping time in many living organisms rely on self-sustained biochemical oscillations entrained by external cues, such as light, to the 24-h cycle induced by Earth's rotation. However, environmental cues are unreliable due to the variability of habitats, weather conditions, or cue-sensing mechanisms among individuals. A tempting hypothesis is that circadian clocks have evolved so as to be robust to fluctuations in the signal that entrains them. To support this hypothesis, we analyze the synchronization behavior of weakly and periodically forced oscillators in terms of their phase response curve (PRC), which measures phase changes induced by a perturbation applied at different times of the cycle. We establish a general relationship between the robustness of key entrainment properties, such as stability and oscillator phase, on the one hand, and the shape of the PRC as characterized by a specific curvature or the existence of a dead zone, on the other hand. The criteria obtained are applied to computational models of circadian clocks and account for the disparate robustness properties of various forcing schemes. Finally, the analysis of PRCs measured experimentally in several organisms strongly suggests a case of convergent evolution toward an optimal strategy for maintaining a clock that is accurate and robust to environmental fluctuations. PMID:21641300

  12. Robust Measurements of Phase Response Curves Realized via Multicycle Weighted Spike-Triggered Averages

    NASA Astrophysics Data System (ADS)

    Imai, Takashi; Ota, Kaiichiro; Aoyagi, Toshio

    2017-02-01

    Phase reduction has been extensively used to study rhythmic phenomena. As a result of phase reduction, the rhythm dynamics of a given system can be described using the phase response curve. Measuring this characteristic curve is an important step toward understanding a system's behavior. Recently, a basic idea for a new measurement method (called the multicycle weighted spike-triggered average method) was proposed. This paper confirms the validity of this method by providing an analytical proof and demonstrates its effectiveness in actual experimental systems by applying the method to an oscillating electric circuit. Some practical tips to use the method are also presented.

  13. Optimal Design for Hetero-Associative Memory: Hippocampal CA1 Phase Response Curve and Spike-Timing-Dependent Plasticity

    PubMed Central

    Miyata, Ryota; Ota, Keisuke; Aonishi, Toru

    2013-01-01

    Recently reported experimental findings suggest that the hippocampal CA1 network stores spatio-temporal spike patterns and retrieves temporally reversed and spread-out patterns. In this paper, we explore the idea that the properties of the neural interactions and the synaptic plasticity rule in the CA1 network enable it to function as a hetero-associative memory recalling such reversed and spread-out spike patterns. In line with Lengyel’s speculation (Lengyel et al., 2005), we firstly derive optimally designed spike-timing-dependent plasticity (STDP) rules that are matched to neural interactions formalized in terms of phase response curves (PRCs) for performing the hetero-associative memory function. By maximizing object functions formulated in terms of mutual information for evaluating memory retrieval performance, we search for STDP window functions that are optimal for retrieval of normal and doubly spread-out patterns under the constraint that the PRCs are those of CA1 pyramidal neurons. The system, which can retrieve normal and doubly spread-out patterns, can also retrieve reversed patterns with the same quality. Finally, we demonstrate that purposely designed STDP window functions qualitatively conform to typical ones found in CA1 pyramidal neurons. PMID:24204822

  14. The h channel mediates location dependence and plasticity of intrinsic phase response in rat hippocampal neurons.

    PubMed

    Narayanan, Rishikesh; Johnston, Daniel

    2008-05-28

    The presence of phenomenological inductances in neuronal membrane has been known for more than one-half a century. Despite this, the dramatic contributions of such inductive elements to the amplitude and, especially, phase of neuronal impedance, and their roles in modulating temporal dynamics of neuronal responses have surprisingly remained unexplored. In this study, we demonstrate that the h channel contributes a location-dependent and plastic phenomenological inductive component to the input impedance of CA1 pyramidal neurons. Specifically, we show that the h channels introduce an apparent negative delay in the local voltage response of these neurons with respect to the injected current within the theta frequency range. The frequency range and the extent of this lead expand with increases in h current either through hyperpolarization, or with increasing distance of dendritic location from the soma. We also demonstrate that a spatially widespread increase in this inductive phase component accompanies long-term potentiation. Finally, using impedance analysis, we show that both location and activity dependence of intrinsic phase response are attributable not to changes in a capacitive or a leak component, but to changes in h-channel properties. Our results suggest that certain voltage-gated ion channels can differentially regulate internal time delays within neurons, thus providing them with an independent control mechanism in temporal coding of neuronal information. Our analyses and results also establish impedance as a powerful measure of intrinsic dynamics and excitability, given that it quantifies temporal relationships among signals and excitability as functions of input frequency.

  15. Characterizing dynamic interactions between ultradian glucocorticoid rhythmicity and acute stress using the phase response curve.

    PubMed

    Rankin, James; Walker, Jamie J; Windle, Richard; Lightman, Stafford L; Terry, John R

    2012-01-01

    The hypothalamic-pituitary-adrenal (HPA) axis is a dynamic oscillatory hormone signalling system that regulates the pulsatile secretion of glucocorticoids from the adrenal glands. In addition to regulation of basal levels of glucocorticoids, the HPA axis provides a rapid hormonal response to stress that is vitally important for homeostasis. Recently it has become clear that glucocorticoid pulses encode an important biological signal that regulates receptor signalling both in the central nervous system and in peripheral tissues. It is therefore important to understand how stressful stimuli disrupt the pulsatile dynamics of this system. Using a computational model that incorporates the crucial feed-forward and feedback components of the axis, we provide novel insight into experimental observations that the size of the stress-induced hormonal response is critically dependent on the timing of the stress. Further, we employ the theory of Phase Response Curves to show that an acute stressor acts as a phase-resetting mechanism for the ultradian rhythm of glucocorticoid secretion. Using our model, we demonstrate that the magnitude of an acute stress is a critical factor in determining whether the system resets via a Type 1 or Type 0 mechanism. By fitting our model to our in vivo stress-response data, we show that the glucocorticoid response to an acute noise stress in rats is governed by a Type 0 phase-resetting curve. Our results provide additional evidence for the concept of a deterministic sub-hypothalamic oscillator regulating the ultradian glucocorticoid rhythm, which constitutes a highly responsive peripheral hormone system that interacts dynamically with hypothalamic inputs to regulate the overall hormonal response to stress.

  16. Multidimensional representations of the phase response curve for both type 1 and type 2 membrane excitability

    NASA Astrophysics Data System (ADS)

    Raidt, Robert; Smith, Andrew J.; Oprisan, Sorinel A.

    2012-02-01

    Neurons are complex excitable cells with a highly nonlinear response to external perturbations, such as presynaptic inputs and biological noise. Single-cell activity is determined by the properties of ionic channels and the ionic makeup of cell's environment and is mathematically described by coupled and nonlinear evolution equations. The phase resetting curve (PRC) reduces the complexity of the biophysical mechanisms involved in generating action potentials to tabulating advances or delays of subsequent spikes of a neuron due to an external perturbation. The PRC is widely used to predict the activity of large neural networks that by replacing the computationally intensive integration of evolution equations with lookup tables. The fundamental assumption of the PRC approach in predicting phase-locked modes in coupled neural networks is that the transient PRC measured for isolated and bursting neurons (open-loop) remains the same under the recurrent inputs of a phase-locked mode (close-loop). The novelties of our approach are: 1) the use of discrete sine transforms (DST's) to store the PRC's as a series of coefficients, and 2) the use of multidimensional stacks to represent multidimensional objects.

  17. Investigating inter-segmental connections between thoracic ganglia in the stick insect by means of experimental and simulated phase response curves.

    PubMed

    Tóth, Tibor I; Grabowska, Martyna; Rosjat, Nils; Hellekes, Katja; Borgmann, Anke; Daun-Gruhn, Silvia

    2015-06-01

    The neuronal networks that control the motion of the individual legs in insects, in particular in the stick insect, are located in the pro-, meso- and meta-thoracic ganglia. They ensure high flexibility of movement control. Thus, the legs can move in an apparently independent way, e.g., during search movements, but also in tight coordination during locomotion. The latter is evidently a very important behavioural mode. It has, therefore, inspired a large number of studies, all aiming at uncovering the nature of the inter-leg coordination. One of the basic questions has been as to how the individual control networks in the three thoracic ganglia are connected to each other. One way to study this problem is to use phase response curves. They can reveal properties of the coupling between oscillatory systems, such as the central pattern generators in the control networks in the thoracic ganglia. In this paper, we report results that we have achieved by means of a combined experimental and modelling approach. We have calculated phase response curves from data obtained in as yet unpublished experiments as well as from those in previously published ones. By using models of the connected pro- and meso-thoracic control networks of the protractor and retractor neuromuscular systems, we have also produced simulated phase response curves and compared them with the experimental ones. In this way, we could gain important information of the nature of the connections between the aforementioned control networks. Specifically, we have found that connections from both the protractor and the retractor "sides" of the pro-thoracic network to the meso-thoracic one are necessary for producing phase response curves that show close similarity to the experimental ones. Furthermore, the strength of the excitatory connections has been proven to be crucial, while the inhibitory connections have essentially been irrelevant. We, thus, suggest that this type of connection might also be present in

  18. Human phase response curve to intermittent blue light using a commercially available device.

    PubMed

    Revell, Victoria L; Molina, Thomas A; Eastman, Charmane I

    2012-10-01

    Light shifts the timing of the circadian clock according to a phase response curve (PRC). To date, all human light PRCs have been to long durations of bright white light. However, melanopsin, the primary photopigment for the circadian system, is most sensitive to short wavelength blue light. Therefore, to optimise light treatment it is important to generate a blue light PRC.We used a small, commercially available blue LED light box, screen size 11.2 × 6.6 cm at ∼50 cm, ∼200 μW cm(−2), ∼185 lux. Subjects participated in two 5 day laboratory sessions 1 week apart. Each session consisted of circadian phase assessments to obtain melatonin profiles before and after 3 days of free-running through an ultradian light–dark cycle (2.5 h wake in dim light, 1.5 h sleep in the dark), forced desynchrony protocol. During one session subjects received intermittent blue light (three 30 min pulses over 2 h) once a day for the 3 days of free-running, and in the other session (control) they remained in dim room light, counterbalanced. The time of blue light was varied among subjects to cover the entire 24 h day. For each individual, the phase shift to blue light was corrected for the free-run determined during the control session. The blue light PRC had a broad advance region starting in the morning and extending through the afternoon. The delay region started a few hours before bedtime and extended through the night. This is the first PRC to be constructed to blue light and to a stimulus that could be used in the real world.

  19. A three pulse phase response curve to three milligrams of melatonin in humans

    PubMed Central

    Burgess, Helen J; Revell, Victoria L; Eastman, Charmane I

    2008-01-01

    Exogenous melatonin is increasingly used for its phase shifting and soporific effects. We generated a three pulse phase response curve (PRC) to exogenous melatonin (3 mg) by administering it to free-running subjects. Young healthy subjects (n = 27) participated in two 5 day laboratory sessions, each preceded by at least a week of habitual, but fixed sleep. Each 5 day laboratory session started and ended with a phase assessment to measure the circadian rhythm of endogenous melatonin in dim light using 30 min saliva samples. In between were three days in an ultradian dim light (< 150 lux)–dark cycle (LD 2.5 : 1.5) during which each subject took one pill per day at the same clock time (3 mg melatonin or placebo, double blind, counterbalanced). Each individual's phase shift to exogenous melatonin was corrected by subtracting their phase shift to placebo (a free-run). The resulting PRC has a phase advance portion peaking about 5 h before the dim light melatonin onset, in the afternoon. The phase delay portion peaks about 11 h after the dim light melatonin onset, shortly after the usual time of morning awakening. A dead zone of minimal phase shifts occurred around the first half of habitual sleep. The fitted maximum advance and delay shifts were 1.8 h and 1.3 h, respectively. This new PRC will aid in determining the optimal time to administer exogenous melatonin to achieve desired phase shifts and demonstrates that using exogenous melatonin as a sleep aid at night has minimal phase shifting effects. PMID:18006583

  20. Evaluation of the Phase-Dependent Rhythm Control of Human Walking Using Phase Response Curves

    PubMed Central

    Yamamoto, Yuki; Aoi, Shinya; Imai, Takashi; Aoyagi, Toshio; Tomita, Nozomi; Tsuchiya, Kazuo

    2016-01-01

    Humans and animals control their walking rhythms to maintain motion in a variable environment. The neural mechanism for controlling rhythm has been investigated in many studies using mechanical and electrical stimulation. However, quantitative evaluation of rhythm variation in response to perturbation at various timings has rarely been investigated. Such a characteristic of rhythm is described by the phase response curve (PRC). Dynamical simulations of human skeletal models with changing walking rhythms (phase reset) described a relation between the effective phase reset on stability and PRC, and phase reset around touch-down was shown to improve stability. A PRC of human walking was estimated by pulling the swing leg, but such perturbations hardly influenced the stance leg, so the relation between the PRC and walking events was difficult to discuss. This research thus examines human response to variations in floor velocity. Such perturbation yields another problem, in that the swing leg is indirectly (and weakly) perturbed, so the precision of PRC decreases. To solve this problem, this research adopts the weighted spike-triggered average (WSTA) method. In the WSTA method, a sequential pulsed perturbation is used for stimulation. This is in contrast with the conventional impulse method, which applies an intermittent impulsive perturbation. The WSTA method can be used to analyze responses to a large number of perturbations for each sequence. In the experiment, perturbations are applied to walking subjects by rapidly accelerating and decelerating a treadmill belt, and measured data are analyzed by the WSTA and impulse methods. The PRC obtained by the WSTA method had clear and stable waveforms with a higher temporal resolution than those obtained by the impulse method. By investigation of the rhythm transition for each phase of walking using the obtained PRC, a rhythm change that extends the touch-down and mid-single support phases is found to occur. PMID:27203839

  1. Photic entrainment of Period mutant mice is predicted from their phase response curves

    PubMed Central

    Pendergast, Julie S.; Friday, Rio C.; Yamazaki, Shin

    2010-01-01

    A fundamental property of circadian clocks is that they entrain to environmental cues. The circadian genes, Period1 and Period2, are involved in entrainment of the mammalian circadian system. To investigate the roles of the Period genes in photic entrainment, we constructed phase response curves (PRC) to light pulses for C57BL/6J wild-type, Per1−/−, Per2−/−, and Per3−/− mice and tested whether the PRCs accurately predict entrainment to non-24 light-dark cycles (T-cycles) and constant light (LL). The PRCs of wild-type and Per3−/− mice are similar in shape and amplitude and have relatively large delay zones and small advance zones, resulting in successful entrainment to T26, but not T21, with similar phase angles. Per1−/− mice have a high-amplitude PRC, resulting in entrainment to a broad range of T-cycles. Per2−/− mice also entrain to a wide range of T-cycles because the advance portion of their PRC is larger than wild-types. Period aftereffects following entrainment to T-cycles were similar among all genotypes. We found that the ratio of the advance portion to the delay portion of the PRC accurately predicts the lengthening of the period of the activity rhythm in LL. Wild-type, Per1−/−, and Per3−/− mice had larger delay zones than advance zones and lengthened (>24hrs) periods in LL, while Per2−/− mice had delay and advance zones that were equal in size and no period lengthening in LL. Together, these results demonstrate that PRCs are powerful tools for predicting and understanding photic entrainment of circadian mutant mice. PMID:20826680

  2. A phase response curve to single bright light pulses in human subjects

    NASA Technical Reports Server (NTRS)

    Khalsa, Sat Bir S.; Jewett, Megan E.; Cajochen, Christian; Czeisler, Charles A.

    2003-01-01

    The circadian pacemaker is differentially sensitive to the resetting effects of retinal light exposure, depending upon the circadian phase at which the light exposure occurs. Previously reported human phase response curves (PRCs) to single bright light exposures have employed small sample sizes, and were often based on relatively imprecise estimates of circadian phase and phase resetting. In the present study, 21 healthy, entrained subjects underwent pre- and post-stimulus constant routines (CRs) in dim light (approximately 2-7 lx) with maintained wakefulness in a semi-recumbent posture. The 6.7 h bright light exposure stimulus consisted of alternating 6 min fixed gaze (approximately 10 000 lx) and free gaze (approximately 5000-9000 lx) exposures. Light exposures were scheduled across the circadian cycle in different subjects so as to derive a PRC. Plasma melatonin was used to determine the phase of the onset, offset, and midpoint of the melatonin profiles during the CRs. Phase shifts were calculated as the difference in phase between the pre- and post-stimulus CRs. The resultant PRC of the midpoint of the melatonin rhythm revealed a characteristic type 1 PRC with a significant peak-to-trough amplitude of 5.02 h. Phase delays occurred when the light stimulus was centred prior to the critical phase at the core body temperature minimum, phase advances occurred when the light stimulus was centred after the critical phase, and no phase shift occurred at the critical phase. During the subjective day, no prolonged 'dead zone' of photic insensitivity was apparent. Phase shifts derived using the melatonin onsets showed larger magnitudes than those derived from the melatonin offsets. These data provide a comprehensive characterization of the human PRC under highly controlled laboratory conditions.

  3. Effects of induced wheel running on the circadian activity rhythms of Syrian hamsters: entrainment and phase response curve.

    PubMed

    Reebs, S G; Mrosovsky, N

    1989-01-01

    The goal of this study was to provide an example of nonsocial and nonphotic entrainment in Syrian hamsters, together with a corresponding phase response curve (PRC). Fourteen male hamsters were given 2-hr bouts of induced activity (mostly wheel running) at 23.83-hr intervals in constant darkness (DD). The activity onsets of 10 hamsters entrained to this manipulation, with no anticipatory activity present. After entrainment, the rhythms resumed free-running from a time 0.66-3.91 hr after the onset of the last bout of induced activity. Postentrainment free-running periods were shorter than pre-entrainment values. The PRC for 2-hr pulses of induced activity in DD revealed phase advances induced in some animals between circadian time (CT) 4 and CT 11 (approximately the last half of the hamsters' rest period), and delays between CT 23 and CT 3 and between CT 17 and CT 20. The CTs for phase advances are compatible with the phase angle differences observed between rhythm and zeitgeber at the end of entrainment. Many features of the results (not all animals entraining, PRC characteristics, lack of observable anticipation to the daily stimuli, phase relationship between zeitgeber and activity rhythms) are similar to those from a previous study on social entrainment in this species (Mrosovsky, 1988). These similarities reinforce the idea that induced activity and social zeitgebers act on activity rhythms via a common mechanism.

  4. The h channel mediates location-dependence and plasticity of intrinsic phase response in rat hippocampal neurons

    PubMed Central

    Narayanan, Rishikesh; Johnston, Daniel

    2008-01-01

    The presence of phenomenological inductances in neuronal membrane has been known for more than half a century. In spite of this, the dramatic contributions of such inductive elements to the amplitude and, especially, phase of neuronal impedance, and their roles in modulating temporal dynamics of neuronal responses have surprisingly remained unexplored. In this study, we demonstrate that the h channel contributes a location-dependent and plastic phenomenological inductive component to the input impedance of CA1 pyramidal neurons. Specifically, we show that the h channels introduce an apparent negative delay in the local voltage response of these neurons with respect to the injected current within the theta frequency range. The frequency-range and the extent of this lead expand with increases in h current either through hyperpolarization, or with increasing distance of dendritic location from the soma. We also demonstrate that a spatially widespread increase in this inductive phase component accompanies long-term potentiation. Finally, employing impedance analysis, we show that both location- and activity-dependence of intrinsic phase response are not due to changes in a capacitive or a leak component, but due to changes in h channel properties. Our results suggest that certain voltage-gated ion channels can differentially regulate internal time delays within neurons, thus providing them with an independent control mechanism in temporal coding of neuronal information. Our analyses and results also establish impedance as a powerful measure of intrinsic dynamics and excitability, given that it quantifies excitability and temporal relationships among signals as functions of input frequency. PMID:18509046

  5. Human phase response curve to a single 6.5 h pulse of short-wavelength light

    PubMed Central

    Rüger, Melanie; St Hilaire, Melissa A; Brainard, George C; Khalsa, Sat-Bir S; Kronauer, Richard E; Czeisler, Charles A; Lockley, Steven W

    2013-01-01

    The photic resetting response of the human circadian pacemaker depends on the timing of exposure, and the direction and magnitude of the resulting shift is described by a phase response curve (PRC). Previous PRCs in humans have utilized high-intensity polychromatic white light. Given that the circadian photoreception system is maximally sensitive to short-wavelength visible light, the aim of the current study was to construct a PRC to blue (480 nm) light and compare it to a 10,000 lux white light PRC constructed previously using a similar protocol. Eighteen young healthy participants (18–30 years) were studied for 9–10 days in a time-free environment. The protocol included three baseline days followed by a constant routine (CR) to assess initial circadian phase. Following this CR, participants were exposed to a 6.5 h 480 nm light exposure (11.8 μW cm−2, 11.2 lux) following mydriasis via a modified Ganzfeld dome. A second CR was conducted following the light exposure to re-assess circadian phase. Phase shifts were calculated from the difference in dim light melatonin onset (DLMO) between CRs. Exposure to 6.5 h of 480 nm light resets the circadian pacemaker according to a conventional type 1 PRC with fitted maximum delays and advances of −2.6 h and 1.3 h, respectively. The 480 nm PRC induced ∼75% of the response of the 10,000 lux white light PRC. These results may contribute to a re-evaluation of dosing guidelines for clinical light therapy and the use of light as a fatigue countermeasure. PMID:23090946

  6. The Rhythm Aftereffect: Support for Time Sensitive Neurons with Broad Overlapping Tuning Curves

    ERIC Educational Resources Information Center

    Becker, Mark W.; Rasmussen, Ian P.

    2007-01-01

    Ivry [Ivry, R. B. (1996). The representation of temporal information in perception and motor control. Current Opinion in Neurobiology, 6, 851-857.] proposed that explicit coding of brief time intervals is accomplished by neurons that are tuned to a preferred temporal interval and have broad overlapping tuning curves. This proposal is analogous to…

  7. Determine Neuronal Tuning Curves by Exploring Optimum Firing Rate Distribution for Information Efficiency

    PubMed Central

    Han, Fang; Wang, Zhijie; Fan, Hong

    2017-01-01

    This paper proposed a new method to determine the neuronal tuning curves for maximum information efficiency by computing the optimum firing rate distribution. Firstly, we proposed a general definition for the information efficiency, which is relevant to mutual information and neuronal energy consumption. The energy consumption is composed of two parts: neuronal basic energy consumption and neuronal spike emission energy consumption. A parameter to model the relative importance of energy consumption is introduced in the definition of the information efficiency. Then, we designed a combination of exponential functions to describe the optimum firing rate distribution based on the analysis of the dependency of the mutual information and the energy consumption on the shape of the functions of the firing rate distributions. Furthermore, we developed a rapid algorithm to search the parameter values of the optimum firing rate distribution function. Finally, we found with the rapid algorithm that a combination of two different exponential functions with two free parameters can describe the optimum firing rate distribution accurately. We also found that if the energy consumption is relatively unimportant (important) compared to the mutual information or the neuronal basic energy consumption is relatively large (small), the curve of the optimum firing rate distribution will be relatively flat (steep), and the corresponding optimum tuning curve exhibits a form of sigmoid if the stimuli distribution is normal. PMID:28270760

  8. Determine Neuronal Tuning Curves by Exploring Optimum Firing Rate Distribution for Information Efficiency.

    PubMed

    Han, Fang; Wang, Zhijie; Fan, Hong

    2017-01-01

    This paper proposed a new method to determine the neuronal tuning curves for maximum information efficiency by computing the optimum firing rate distribution. Firstly, we proposed a general definition for the information efficiency, which is relevant to mutual information and neuronal energy consumption. The energy consumption is composed of two parts: neuronal basic energy consumption and neuronal spike emission energy consumption. A parameter to model the relative importance of energy consumption is introduced in the definition of the information efficiency. Then, we designed a combination of exponential functions to describe the optimum firing rate distribution based on the analysis of the dependency of the mutual information and the energy consumption on the shape of the functions of the firing rate distributions. Furthermore, we developed a rapid algorithm to search the parameter values of the optimum firing rate distribution function. Finally, we found with the rapid algorithm that a combination of two different exponential functions with two free parameters can describe the optimum firing rate distribution accurately. We also found that if the energy consumption is relatively unimportant (important) compared to the mutual information or the neuronal basic energy consumption is relatively large (small), the curve of the optimum firing rate distribution will be relatively flat (steep), and the corresponding optimum tuning curve exhibits a form of sigmoid if the stimuli distribution is normal.

  9. A broadly applicable 3-D neuron tracing method based on open-curve snake.

    PubMed

    Wang, Yu; Narayanaswamy, Arunachalam; Tsai, Chia-Ling; Roysam, Badrinath

    2011-09-01

    This paper presents a broadly applicable algorithm and a comprehensive open-source software implementation for automated tracing of neuronal structures in 3-D microscopy images. The core 3-D neuron tracing algorithm is based on three-dimensional (3-D) open-curve active Contour (Snake). It is initiated from a set of automatically detected seed points. Its evolution is driven by a combination of deforming forces based on the Gradient Vector Flow (GVF), stretching forces based on estimation of the fiber orientations, and a set of control rules. In this tracing model, bifurcation points are detected implicitly as points where multiple snakes collide. A boundariness measure is employed to allow local radius estimation. A suite of pre-processing algorithms enable the system to accommodate diverse neuronal image datasets by reducing them to a common image format. The above algorithms form the basis for a comprehensive, scalable, and efficient software system developed for confocal or brightfield images. It provides multiple automated tracing modes. The user can optionally interact with the tracing system using multiple view visualization, and exercise full control to ensure a high quality reconstruction. We illustrate the utility of this tracing system by presenting results from a synthetic dataset, a brightfield dataset and two confocal datasets from the DIADEM challenge.

  10. Interaction function of coupled bursting neurons

    NASA Astrophysics Data System (ADS)

    Xia, Shi; Jiadong, Zhang

    2016-06-01

    The interaction functions of electrically coupled Hindmarsh-Rose (HR) neurons for different firing patterns are investigated in this paper. By applying the phase reduction technique, the phase response curve (PRC) of the spiking neuron and burst phase response curve (BPRC) of the bursting neuron are derived. Then the interaction function of two coupled neurons can be calculated numerically according to the PRC (or BPRC) and the voltage time course of the neurons. Results show that the BPRC is more and more complicated with the increase of the spike number within a burst, and the curve of the interaction function oscillates more and more frequently with it. However, two certain things are unchanged: ϕ = 0, which corresponds to the in-phase synchronization state, is always the stable equilibrium, while the anti-phase synchronization state with ϕ = 0.5 is an unstable equilibrium. Project supported by the National Natural Science Foundation of China (Grant Nos. 11272065 and 11472061).

  11. Differential effects of conductances on the phase resetting curve of a bursting neuronal oscillator

    PubMed Central

    Prinz, Astrid A.

    2015-01-01

    The intrinsically oscillating neurons in the crustacean pyloric circuit have membrane conductances that influence their spontaneous activity patterns and responses to synaptic activity. The relationship between the magnitudes of these membrane conductances and the response of the oscillating neurons to synaptic input has not yet been fully or systematically explored. We examined this relationship using the phase resetting curve (PRC), which summarizes the change in the cycle period of a neuronal oscillator as a function of the input’s timing within the oscillation. We first utilized a large database of single-compartment model neurons to determine the effect of individual membrane conductances on PRC shape; we found that the effects vary across conductance space, but on average, the hyperpolarization-activated and leak conductances advance the PRC. We next investigated how membrane conductances affect PRCs of the isolated pacemaker kernel in the pyloric circuit of Cancer borealis by: (1) tabulating PRCs while using dynamic clamp to artificially add varying levels of specific conductances, and (2) tabulating PRCs before and after blocking the endogenous hyperpolarization-activated current. We additionally used a previously described four-compartment model to determine how the location of the hyperpolarization-activated conductance influences that current’s effect on the PRC. We report that while dynamic-clamp-injected leak current has much smaller effects on the PRC than suggested by the single-compartment model, an increase in the hyperpolarization-activated conductance both advances and reduces the noisiness of the PRC in the pacemaker kernel of the pyloric circuit in both modeling and experimental studies. PMID:25835323

  12. Segmentation of neuronal structures using SARSA (λ)-based boundary amendment with reinforced gradient-descent curve shape fitting.

    PubMed

    Zhu, Fei; Liu, Quan; Fu, Yuchen; Shen, Bairong

    2014-01-01

    The segmentation of structures in electron microscopy (EM) images is very important for neurobiological research. The low resolution neuronal EM images contain noise and generally few features are available for segmentation, therefore application of the conventional approaches to identify the neuron structure from EM images is not successful. We therefore present a multi-scale fused structure boundary detection algorithm in this study. In the algorithm, we generate an EM image Gaussian pyramid first, then at each level of the pyramid, we utilize Laplacian of Gaussian function (LoG) to attain structure boundary, we finally assemble the detected boundaries by using fusion algorithm to attain a combined neuron structure image. Since the obtained neuron structures usually have gaps, we put forward a reinforcement learning-based boundary amendment method to connect the gaps in the detected boundaries. We use a SARSA (λ)-based curve traveling and amendment approach derived from reinforcement learning to repair the incomplete curves. Using this algorithm, a moving point starts from one end of the incomplete curve and walks through the image where the decisions are supervised by the approximated curve model, with the aim of minimizing the connection cost until the gap is closed. Our approach provided stable and efficient structure segmentation. The test results using 30 EM images from ISBI 2012 indicated that both of our approaches, i.e., with or without boundary amendment, performed better than six conventional boundary detection approaches. In particular, after amendment, the Rand error and warping error, which are the most important performance measurements during structure segmentation, were reduced to very low values. The comparison with the benchmark method of ISBI 2012 and the recent developed methods also indicates that our method performs better for the accurate identification of substructures in EM images and therefore useful for the identification of imaging

  13. Seeing a straight line on a curved surface: decoupling of patterns from surfaces by single IT neurons

    PubMed Central

    Ratan Murty, N. Apurva

    2016-01-01

    We have no difficulty seeing a straight line drawn on a paper even when the paper is bent, but this inference is in fact nontrivial. Doing so requires either matching local features or representing the pattern after factoring out the surface shape. Here we show that single neurons in the monkey inferior temporal (IT) cortex show invariant responses to patterns across rigid and nonrigid changes of surfaces. We recorded neuronal responses to stimuli in which the pattern and the surrounding surface were varied independently. In a subset of neurons, we found pattern-surface interactions that produced similar responses to stimuli across congruent pattern and surface transformations. These interactions produced systematic shifts in curvature tuning of patterns when overlaid on convex and flat surfaces. Our results show that surfaces are factored out of patterns by single neurons, thereby enabling complex perceptual inferences. NEW & NOTEWORTHY We have no difficulty seeing a straight line on a curved piece of paper, but in fact, doing so requires decoupling the shape of the surface from the pattern itself. Here we report a novel form of invariance in the visual cortex: single neurons in monkey inferior temporal cortex respond similarly to congruent transformations of patterns and surfaces, in effect decoupling patterns from the surface on which they are overlaid. PMID:27733595

  14. The influence of population size, noise strength and behavioral task on best-encoded stimulus for neurons with unimodal or monotonic tuning curves

    PubMed Central

    Yarrow, Stuart; Seriès, Peggy

    2015-01-01

    Tuning curves and receptive fields are widely used to describe the selectivity of sensory neurons, but the relationship between firing rates and information is not always intuitive. Neither high firing rates nor high tuning curve gradients necessarily mean that stimuli at that part of the tuning curve are well represented by a neuron. Recent research has shown that trial-to-trial variability (noise) and population size can strongly affect which stimuli are most precisely represented by a neuron in the context of a population code (the best-encoded stimulus), and that different measures of information can give conflicting indications. Specifically, the Fisher information is greatest where the tuning curve gradient is greatest, such as on the flanks of peaked tuning curves, but the stimulus-specific information (SSI) is greatest at the tuning curve peak for small populations with high trial-to-trial variability. Previous research in this area has focussed upon unimodal (peaked) tuning curves, and in this article we extend these analyses to monotonic tuning curves. In addition, we examine how stimulus spacing in forced choice tasks affects the best-encoded stimulus. Our results show that, regardless of the tuning curve, Fisher information correctly predicts the best-encoded stimulus for large populations and where the stimuli are closely spaced in forced choice tasks. In smaller populations with high variability, or in forced choice tasks with widely-spaced choices, the best-encoded stimulus falls at the peak of unimodal tuning curves, but is more variable for monotonic tuning curves. Task, population size and variability all need to be considered when assessing which stimuli a neuron represents, but the best-encoded stimulus can be estimated on a case-by case basis using commonly available computing facilities. PMID:25774131

  15. Multipulse phase resetting curves

    NASA Astrophysics Data System (ADS)

    Krishnan, Giri P.; Bazhenov, Maxim; Pikovsky, Arkady

    2013-10-01

    In this paper, we introduce and study systematically, in terms of phase response curves, the effect of dual-pulse excitation on the dynamics of an autonomous oscillator. Specifically, we test the deviations from linear summation of phase advances resulting from two small perturbations. We analytically derive a correction term, which generally appears for oscillators whose intrinsic dimensionality is >1. The nonlinear correction term is found to be proportional to the square of the perturbation. We demonstrate this effect in the Stuart-Landau model and in various higher dimensional neuronal models. This deviation from the superposition principle needs to be taken into account in studies of networks of pulse-coupled oscillators. Further, this deviation could be used in the verification of oscillator models via a dual-pulse excitation.

  16. Transcranial electrical brain stimulation modulates neuronal tuning curves in perception of numerosity and duration

    PubMed Central

    Javadi, Amir Homayoun; Brunec, Iva K.; Walsh, Vincent; Penny, Will D.; Spiers, Hugo J.

    2014-01-01

    Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation method with many putative applications and reported to effectively modulate behaviour. However, its effects have yet to be considered at a computational level. To address this we modelled the tuning curves underlying the behavioural effects of stimulation in a perceptual task. Participants judged which of the two serially presented images contained more items (numerosity judgement task) or was presented longer (duration judgement task). During presentation of the second image their posterior parietal cortices (PPCs) were stimulated bilaterally with opposite polarities for 1.6 s. We also examined the impact of three stimulation conditions on behaviour: anodal right-PPC and cathodal left-PPC (rA-lC), reverse order (lA-rC) and no-stimulation condition. Behavioural results showed that participants were more accurate in numerosity and duration judgement tasks when they were stimulated with lA-rC and rA-lC stimulation conditions respectively. Simultaneously, a decrease in performance on numerosity and duration judgement tasks was observed when the stimulation condition favoured the other task. Thus, our results revealed a double-dissociation of laterality and task. Importantly, we were able to model the effects of stimulation on behaviour. Our computational modelling showed that participants' superior performance was attributable to a narrower tuning curve — smaller standard deviation of detection noise. We believe that this approach may prove useful in understanding the impact of brain stimulation on other cognitive domains. PMID:25130301

  17. Harmonic Phase Response of Nonlinear Radar Targets

    DTIC Science & Technology

    2015-10-01

    ARL-TR-7513 ● OCT 2015 US Army Research Laboratory Harmonic Phase Response of Nonlinear Radar Targets by Sean F McGowan, Dr...Laboratory Harmonic Phase Response of Nonlinear Radar Targets by Sean F McGowan and Kelly D Sherbondy Sensors and Electron Devices Directorate...

  18. Spike width and frequency alter stability of phase-locking in electrically coupled neurons.

    PubMed

    Dodla, Ramana; Wilson, Charles J

    2013-06-01

    The stability of phase-locked states of electrically coupled type-1 phase response curve neurons is studied using piecewise linear formulations for their voltage profile and phase response curves. We find that at low frequency and/or small spike width, synchrony is stable, and antisynchrony unstable. At high frequency and/or large spike width, these phase-locked states switch their stability. Increasing the ratio of spike width to spike height causes the antisynchronous state to transition into a stable synchronous state. We compute the interaction function and the boundaries of stability of both these phase-locked states, and present analytical expressions for them. We also study the effect of phase response curve skewness on the boundaries of synchrony and antisynchrony.

  19. Phase response theory extended to nonoscillatory network components

    PubMed Central

    Sieling, Fred H.; Archila, Santiago; Hooper, Ryan; Canavier, Carmen C.; Prinz, Astrid A.

    2012-01-01

    New tools for analysis of oscillatory networks using phase response theory (PRT) under the assumption of pulsatile coupling have been developed steadily since the 1980s, but none have yet allowed for analysis of mixed systems containing nonoscillatory elements. This caveat has excluded the application of PRT to most real systems, which are often mixed. We show that a recently developed tool, the functional phase resetting curve (fPRC), provides a serendipitous benefit: it allows incorporation of nonoscillatory elements into systems of oscillators where PRT can be applied. We validate this method in a model system of neural oscillators and a biological system, the pyloric network of crustacean decapods. PMID:23004844

  20. Predicting neural network firing pattern from phase resetting curve

    NASA Astrophysics Data System (ADS)

    Oprisan, Sorinel; Oprisan, Ana

    2007-04-01

    Autonomous neural networks called central pattern generators (CPG) are composed of endogenously bursting neurons and produce rhythmic activities, such as flying, swimming, walking, chewing, etc. Simplified CPGs for quadrupedal locomotion and swimming are modeled by a ring of neural oscillators such that the output of one oscillator constitutes the input for the subsequent neural oscillator. The phase response curve (PRC) theory discards the detailed conductance-based description of the component neurons of a network and reduces them to ``black boxes'' characterized by a transfer function, which tabulates the transient change in the intrinsic period of a neural oscillator subject to external stimuli. Based on open-loop PRC, we were able to successfully predict the phase-locked period and relative phase between neurons in a half-center network. We derived existence and stability criteria for heterogeneous ring neural networks that are in good agreement with experimental data.

  1. Synchronization properties of heterogeneous neuronal networks with mixed excitability type.

    PubMed

    Leone, Michael J; Schurter, Brandon N; Letson, Benjamin; Booth, Victoria; Zochowski, Michal; Fink, Christian G

    2015-03-01

    We study the synchronization of neuronal networks with dynamical heterogeneity, showing that network structures with the same propensity for synchronization (as quantified by master stability function analysis) may develop dramatically different synchronization properties when heterogeneity is introduced with respect to neuronal excitability type. Specifically, we investigate networks composed of neurons with different types of phase response curves (PRCs), which characterize how oscillating neurons respond to excitatory perturbations. Neurons exhibiting type 1 PRC respond exclusively with phase advances, while neurons exhibiting type 2 PRC respond with either phase delays or phase advances, depending on when the perturbation occurs. We find that Watts-Strogatz small world networks transition to synchronization gradually as the proportion of type 2 neurons increases, whereas scale-free networks may transition gradually or rapidly, depending upon local correlations between node degree and excitability type. Random placement of type 2 neurons results in gradual transition to synchronization, whereas placement of type 2 neurons as hubs leads to a much more rapid transition, showing that type 2 hub cells easily "hijack" neuronal networks to synchronization. These results underscore the fact that the degree of synchronization observed in neuronal networks is determined by a complex interplay between network structure and the dynamical properties of individual neurons, indicating that efforts to recover structural connectivity from dynamical correlations must in general take both factors into account.

  2. PDF neuron firing phase-shifts key circadian activity neurons in Drosophila.

    PubMed

    Guo, Fang; Cerullo, Isadora; Chen, Xiao; Rosbash, Michael

    2014-06-17

    Our experiments address two long-standing models for the function of the Drosophila brain circadian network: a dual oscillator model, which emphasizes the primacy of PDF-containing neurons, and a cell-autonomous model for circadian phase adjustment. We identify five different circadian (E) neurons that are a major source of rhythmicity and locomotor activity. Brief firing of PDF cells at different times of day generates a phase response curve (PRC), which mimics a light-mediated PRC and requires PDF receptor expression in the five E neurons. Firing also resembles light by causing TIM degradation in downstream neurons. Unlike light however, firing-mediated phase-shifting is CRY-independent and exploits the E3 ligase component CUL-3 in the early night to degrade TIM. Our results suggest that PDF neurons integrate light information and then modulate the phase of E cell oscillations and behavioral rhythms. The results also explain how fly brain rhythms persist in constant darkness and without CRY.

  3. Input-output relation and energy efficiency in the neuron with different spike threshold dynamics.

    PubMed

    Yi, Guo-Sheng; Wang, Jiang; Tsang, Kai-Ming; Wei, Xi-Le; Deng, Bin

    2015-01-01

    Neuron encodes and transmits information through generating sequences of output spikes, which is a high energy-consuming process. The spike is initiated when membrane depolarization reaches a threshold voltage. In many neurons, threshold is dynamic and depends on the rate of membrane depolarization (dV/dt) preceding a spike. Identifying the metabolic energy involved in neural coding and their relationship to threshold dynamic is critical to understanding neuronal function and evolution. Here, we use a modified Morris-Lecar model to investigate neuronal input-output property and energy efficiency associated with different spike threshold dynamics. We find that the neurons with dynamic threshold sensitive to dV/dt generate discontinuous frequency-current curve and type II phase response curve (PRC) through Hopf bifurcation, and weak noise could prohibit spiking when bifurcation just occurs. The threshold that is insensitive to dV/dt, instead, results in a continuous frequency-current curve, a type I PRC and a saddle-node on invariant circle bifurcation, and simultaneously weak noise cannot inhibit spiking. It is also shown that the bifurcation, frequency-current curve and PRC type associated with different threshold dynamics arise from the distinct subthreshold interactions of membrane currents. Further, we observe that the energy consumption of the neuron is related to its firing characteristics. The depolarization of spike threshold improves neuronal energy efficiency by reducing the overlap of Na(+) and K(+) currents during an action potential. The high energy efficiency is achieved at more depolarized spike threshold and high stimulus current. These results provide a fundamental biophysical connection that links spike threshold dynamics, input-output relation, energetics and spike initiation, which could contribute to uncover neural encoding mechanism.

  4. [Excitability curve of alpha motor neurons of the foot dorsal flexor in chemically induced parkinsonian rigidity prior to and following ethylbenzatropine administration].

    PubMed

    Zakrzewska, F

    1975-01-01

    For evaluation of the state of excitability of motoneurons in the dorsal flexor of the foot in patients with drug-induced muscle rigidity curves of excitability of motoneurons in the anterior tibial muscle were plotted in 10 patients not receiving psychotropic agents (controls) and 10 patients treated with chlorpromazine. Two variants of experiment wase used: in the 1st variant stimulation of the peroneal nerve behind the fibular capitulum served as the conditioning and testing stimulus, in the 2nd variant stimulation of the tibial nerve in the popliteal fossa was the conditioning stimulus and stimulation of the peroneal nerve in the above way was the testing stimulus. The investigations were carried out before and 30-50 min after intramuscular injection of ethylbenzatropine 5 mg. In the 1st variant the curve of excitability of the motoneurons of the anterior tibial muscle showed the same configuration as the curve of excitability of motoneurons of the soleus muscle in the control group as well as in the treated group. Similarly as in the excitability curve of the soleus muscle five phases could be differentiated in it. Phase III of depression was, however, deeper and phase IV of returning excitability was more evident. In variant II in phase III depression was observed lasting only 40 msec., then in place of return of excitability its decrease was observed. These results were similar to these obtained in the case of conditioning stimulation of afferent fibres of the anterior tibialis muscle, and testing stimulation of the afferent fibres of the soleus muscle. After ethylbenzatropine injection no changes were found in variant I, on the other hand, in variant II a rise of excitability was present in phase III in the control group and in phases III and IV in treated patients. Ethylbenzatropine seemed, thus, to have no effect on the excitability of motoneurons in the dorsal flexor of the foot in the case of conditioning afferent stimulation of the dorsae flexor of the

  5. Interplay between excitability type and distributions of neuronal connectivity determines neuronal network synchronization.

    PubMed

    Mofakham, Sima; Fink, Christian G; Booth, Victoria; Zochowski, Michal R

    2016-10-01

    While the interplay between neuronal excitability properties and global properties of network topology is known to affect network propensity for synchronization, it is not clear how detailed characteristics of these properties affect spatiotemporal pattern formation. Here we study mixed networks, composed of neurons having type I and/or type II phase response curves, with varying distributions of local and random connections and show that not only average network properties, but also the connectivity distribution statistics, significantly affect network synchrony. Namely, we study networks with fixed networkwide properties, but vary the number of random connections that nodes project. We show that varying node excitability (type I vs type II) influences network synchrony most dramatically for systems with long-tailed distributions of the number of random connections per node. This indicates that a cluster of even a few highly rewired cells with a high propensity for synchronization can alter the degree of synchrony in the network as a whole. We show this effect generally on a network of coupled Kuramoto oscillators and investigate the impact of this effect more thoroughly in pulse-coupled networks of biophysical neurons.

  6. Interplay between excitability type and distributions of neuronal connectivity determines neuronal network synchronization

    NASA Astrophysics Data System (ADS)

    Mofakham, Sima; Fink, Christian G.; Booth, Victoria; Zochowski, Michal R.

    2016-10-01

    While the interplay between neuronal excitability properties and global properties of network topology is known to affect network propensity for synchronization, it is not clear how detailed characteristics of these properties affect spatiotemporal pattern formation. Here we study mixed networks, composed of neurons having type I and/or type II phase response curves, with varying distributions of local and random connections and show that not only average network properties, but also the connectivity distribution statistics, significantly affect network synchrony. Namely, we study networks with fixed networkwide properties, but vary the number of random connections that nodes project. We show that varying node excitability (type I vs type II) influences network synchrony most dramatically for systems with long-tailed distributions of the number of random connections per node. This indicates that a cluster of even a few highly rewired cells with a high propensity for synchronization can alter the degree of synchrony in the network as a whole. We show this effect generally on a network of coupled Kuramoto oscillators and investigate the impact of this effect more thoroughly in pulse-coupled networks of biophysical neurons.

  7. Phase responses of harmonics reflected from radio-frequency electronics

    NASA Astrophysics Data System (ADS)

    Mazzaro, Gregory J.; McGowan, Sean F.; Gallagher, Kyle A.; Sherbondy, Kelly D.; Martone, Anthony F.; Narayanan, Ram M.

    2016-05-01

    The phase responses of nonlinear-radar targets illuminated by stepped frequencies are studied. Data is presented for an experimental radar and two commercial electronic targets at short standoff ranges. The amplitudes and phases of harmonics generated by each target at each frequency are captured over a 100-MHz-wide transmit band. As in the authors' prior work, target detection is demonstrated by receiving at least one harmonic of at least one transmit frequency. In the present work, experiments confirm that the phase of a harmonic reflected from a radio-frequency electronic target at a standoff distance is linear versus frequency. Similar to traditional wideband radar, the change of the reflected phase with respect to frequency indicates the range to the nonlinear target.

  8. Bradford Curves.

    ERIC Educational Resources Information Center

    Rousseau, Ronald

    1994-01-01

    Discussion of informetric distributions shows that generalized Leimkuhler functions give proper fits to a large variety of Bradford curves, including those exhibiting a Groos droop or a rising tail. The Kolmogorov-Smirnov test is used to test goodness of fit, and least-square fits are compared with Egghe's method. (Contains 53 references.) (LRW)

  9. Acute phase response in cattle infected with Anaplasma marginale.

    PubMed

    Nazifi, S; Razavi, S M; Kaviani, F; Rakhshandehroo, E

    2012-03-23

    This study was undertaken to evaluate the acute phase responses via the assessment of the concentration of serum sialic acids (total, lipid bound and protein bound), inflammatory mediators (IFN-γ and TNF-α) and acute phase proteins (Hp and SAA) in 20 adult crossbred cattle naturally infected by Anaplasma marginale. The infected animals were divided into 2 subgroups on the basis of parasitemia rate (<20% and >20%). Also, as a control group, 10 clinically healthy cattle from the same farms were sampled. Our data revealed significant decreases in red blood cell count (RBC), hematocrite (PCV) and hemoglobine (Hb) in infected cattle compared to healthy ones. Conversely, the concentrations of Hp, SAA, ceruloplasmin, fibrinogen, serum sialic acids and the circulatory IFN-γ and TNF-α were increased in the diseased cattle (P<0.05). In addition, it was evident that the progression of parasitemia in infected cattle did not induce any significant alterations in the hematological indices (RBCs, PCV and Hb) and the concentrations of Hp, SAA, ceruloplasmin and fibrinogen. SAA was the most sensitive factor to change in the diseased cattle. Therefore, increase in SAA concentration may be a good indicator of inflammatory process in cattle naturally infected with Anaplasma marginale.

  10. Nonsmooth dynamics in spiking neuron models

    NASA Astrophysics Data System (ADS)

    Coombes, S.; Thul, R.; Wedgwood, K. C. A.

    2012-11-01

    Large scale studies of spiking neural networks are a key part of modern approaches to understanding the dynamics of biological neural tissue. One approach in computational neuroscience has been to consider the detailed electrophysiological properties of neurons and build vast computational compartmental models. An alternative has been to develop minimal models of spiking neurons with a reduction in the dimensionality of both parameter and variable space that facilitates more effective simulation studies. In this latter case the single neuron model of choice is often a variant of the classic integrate-and-fire model, which is described by a nonsmooth dynamical system. In this paper we review some of the more popular spiking models of this class and describe the types of spiking pattern that they can generate (ranging from tonic to burst firing). We show that a number of techniques originally developed for the study of impact oscillators are directly relevant to their analysis, particularly those for treating grazing bifurcations. Importantly we highlight one particular single neuron model, capable of generating realistic spike trains, that is both computationally cheap and analytically tractable. This is a planar nonlinear integrate-and-fire model with a piecewise linear vector field and a state dependent reset upon spiking. We call this the PWL-IF model and analyse it at both the single neuron and network level. The techniques and terminology of nonsmooth dynamical systems are used to flesh out the bifurcation structure of the single neuron model, as well as to develop the notion of Lyapunov exponents. We also show how to construct the phase response curve for this system, emphasising that techniques in mathematical neuroscience may also translate back to the field of nonsmooth dynamical systems. The stability of periodic spiking orbits is assessed using a linear stability analysis of spiking times. At the network level we consider linear coupling between voltage

  11. Estimating mortality risk in preoperative patients using immunologic, nutritional, and acute-phase response variables.

    PubMed Central

    Christou, N V; Tellado-Rodriguez, J; Chartrand, L; Giannas, B; Kapadia, B; Meakins, J; Rode, H; Gordon, J

    1989-01-01

    We measured the delayed type hypersensitivity (DTH) skin test response, along with additional variables of host immunocompetence in 245 preoperative patients to determine which variables are associated with septic-related deaths following operation. Of the 14 deaths (5.7%), 12 were related to sepsis and in 2 sepsis was contributory. The DTH response (p less than 0.00001), age (p less than 0.0002), serum albumin (p less than 0.003), hemoglobin (p less than 0.02), and total hemolytic complement (p less than 0.03), were significantly different between those who died and those who lived. By logistic regression analysis, only the DTH skin test response (log likelihood = 41.7, improvement X2 = 6.24, p less than 0.012) and the serum albumin (log likelihood = 44.8, improvement X2 = 17.7, p less than 0.001) were significantly and independently associated with the deaths. The resultant probability of mortality calculation equation was tested in a separate validation group of 519 patients (mortality = 5%) and yielded a good predictive capability as assessed by (1) X2 = 0.08 between observed and expected deaths, NS; (2) Goodman-Kruskall G statistic = 0.673) Receiver-Operating-Characteristic (ROC) curve analysis with an area under the ROC curve, Az = 0.79 +/- 0.05. We conclude that a reduced immune response (DTH skin test anergy) plus a nutritional deficit and/or acute-phase response change are both associated with increased septic-related deaths in elective surgical patients. PMID:2472781

  12. Acute phase response in lame crossbred dairy cattle

    PubMed Central

    Bagga, A.; Randhawa, Swaran Singh; Sharma, S.; Bansal, B. K.

    2016-01-01

    Aim: The study was undertaken to study acute phase response based on acute phase proteins (APPs) such as C-reactive protein (CRP), haptoglobin (Hp), serum amyloid A (SAA), and fibrinogen in lame crossbred dairy cattle. Materials and Methods: Lame animals (n=30) were selected within 3-7 days of being noticed as lame by the farm veterinarian, from a local dairy farm in southeast Ludhiana over a period of 6 months, stratified proportionately with respect to stage of lactation with non-lame healthy cows (n=10). All the cows were otherwise healthy and did not have any other inflammatory problems such as pneumonia, enteritis, mastitis, or any kind of acute uterine inflammation. Blood samples were collected from all the animals; serum and plasma samples were separated and stored at −20°C. The levels of CRP, Hp, and SAA were estimated using Sandwich ELISA, whereas fibrinogen was estimated by heat precipitation method. Results: SAA levels in lame cows were significantly higher (22.19±0.85 µg/ml), approximately 3 times as compared to non-lame cows (8.89±0.72 µg/ml), whereas serum Hp concentration was approximately 20 times higher in the lame cattle (21.71±3.32 mg/dl) as compared to non-lame cows (1.17±0.07 mg/dl). Fibrinogen also increased in the lame cattle (3.97±0.22 g/L) as compared to non-lame group (1.40±0.17 g/L). Serum CRP levels analyzed in the lame cattle for the first time in the present study, and significant high concentration was appreciated in lame cattle (4.41±0.33 mg/L) as compared to non-lame cattle (0.61±0.14 mg/L). Lame cattle were having more of sole hemorrhages, sole ulcers, and white line lesions as compared to non-lame cattle. Conclusion: It can be concluded that lame cattle exhibit high levels of APPs including CRP, Hp, SAA, and fibrinogen as compared to non-lame cattle. PMID:27956769

  13. The Nonlinear Phase Response Curve of the Human Circadian Pacemaker and How Complex Behaviors Might Arise in Nature

    NASA Astrophysics Data System (ADS)

    Leder, Ron S.

    2002-08-01

    Our example from nature is two groups of about 10,000 cells in the brain called Suprachiasmatic Nuclei (SCN) and how light can entrain free running endogenous periodic behavior via the retina's connection to the SCN. Our major question is how a complex behavior like this can arise in nature. Finally presented is a mathematical model and simulation showing how simple periodic signals can be coupled to produce spatio-temporal chaotic behavior and how two complex signals can combine to produce simple coherent behavior with a hypothetical analogy to phase resetting in biological circadian pacemakers.

  14. Natural variations in the stress and acute phase responses of cattle

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The initial response of the innate immune system upon activation has been defined as the acute phase response (APR). Activation of the APR results in several responses that include fever, metabolic adaptations, and changes in behavior. The APR can be modulated by many factors, with stress being th...

  15. Modulation of the acute phase response in feedlot steers supplemented with Saccharomyces cerevisiae

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study was designed to determine the effect of supplementing feedlot steers with Saccharomyces cerevisiae CNCM I-1079 (SC) on the acute phase response to a lipopolysaccharide (LPS) challenge. Steers (n = 18; 266 ± 4 kilograms body weight) were separated into three treatment groups (n = 6/treatm...

  16. In Utero Exposure to Lipopolysaccharide Alters the Postnatal Acute Phase Response in Beef Heifers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study was designed to determine the potential effect of prenatal lipopolysaccharide (LPS) exposure on the postnatal acute phase response (APR) to an LPS challenge in heifers. Pregnant crossbred cows (n = 50) were separated into prenatal immune stimulation (PIS; n = 25; administered 0.1 microgr...

  17. Roles of STAT3 in Protein Secretion Pathways during the Acute-Phase Response

    PubMed Central

    Ahyi, Ayele-Nati N.; Quinton, Lee J.; Jones, Matthew R.; Ferrari, Joseph D.; Pepper-Cunningham, Zachary A.; Mella, Juan R.; Remick, Daniel G.

    2013-01-01

    The acute-phase response is characteristic of perhaps all infections, including bacterial pneumonia. In conjunction with the acute-phase response, additional biological pathways are induced in the liver and are dependent on the transcription factors STAT3 and NF-κB, but these responses are poorly understood. Here, we demonstrate that pneumococcal pneumonia and other severe infections increase expression of multiple components of the cellular secretory machinery in the mouse liver, including the endoplasmic reticulum (ER) translocon complex, which mediates protein translation into the ER, and the coat protein complexes (COPI and COPII), which mediate vesicular transport of proteins to and from the ER. Hepatocyte-specific mutation of STAT3 prevented the induction of these secretory pathways during pneumonia, with similar results observed following pharmacological activation of ER stress by using tunicamycin. These findings implicate STAT3 in the unfolded protein response and suggest that STAT3-dependent optimization of secretion may apply broadly. Pneumonia also stimulated the binding of phosphorylated STAT3 to promoter regions of secretion-related genes in the liver, supporting a direct role for STAT3 in their transcription. Altogether, these results identify a novel function of STAT3 during the acute-phase response, namely, the induction of secretory machinery in hepatocytes. This may facilitate the processing and delivery of newly synthesized loads of acute-phase proteins, enhancing innate immunity and preventing liver injury during infection. PMID:23460517

  18. Protective effect of resveratrol in endotoxemia-induced acute phase response in rats.

    PubMed

    Sebai, Hichem; Ben-Attia, Mossadok; Sani, Mamane; Aouani, Ezzedine; Ghanem-Boughanmi, Néziha

    2009-04-01

    Lipopolysaccharide (LPS), a glycolipid component of the cell wall of gram-negative bacteria can elicit a systemic inflammatory process leading to septic shock and death. Acute phase response is characterized by fever, leucocytosis, thrombocytopenia, altered metabolic responses and redox balance by inducing excessive reactive oxygen species (ROS) generation. Resveratrol (trans-3,5,4' trihydroxystilbene) is a natural polyphenol exhibiting antioxidant and anti-inflammatory properties. We investigated the protective effect of resveratrol on endotoxemia-induced acute phase response in rats. When acutely administered by i.p. route, resveratrol (40 mg/kg b.w.) counteracted the effect of a single injection of LPS (4 mg/kg b.w.) which induced fever, a decrease in white blood cells (WBC) and platelets (PLT) counts. When i.p. administered during 7 days at 20 mg/kg per day (subacute treatment), resveratrol abrogated LPS-induced erythrocytes lipoperoxidation and catalase (CAT) activity depression to control levels. In the plasma compartment, LPS increased malondialdehyde (MDA) via nitric monoxide (NO) elevation and decreased iron level. All these deleterious LPS effects were reversed by a subacute resveratrol pre-treatment via a NO independent way. Resveratrol exhibited potent protective effect on LPS-induced acute phase response in rats.

  19. Phase Response Design of Recursive All-Pass Digital Filters Using a Modified PSO Algorithm.

    PubMed

    Chang, Wei-Der

    2015-01-01

    This paper develops a new design scheme for the phase response of an all-pass recursive digital filter. A variant of particle swarm optimization (PSO) algorithm will be utilized for solving this kind of filter design problem. It is here called the modified PSO (MPSO) algorithm in which another adjusting factor is more introduced in the velocity updating formula of the algorithm in order to improve the searching ability. In the proposed method, all of the designed filter coefficients are firstly collected to be a parameter vector and this vector is regarded as a particle of the algorithm. The MPSO with a modified velocity formula will force all particles into moving toward the optimal or near optimal solution by minimizing some defined objective function of the optimization problem. To show the effectiveness of the proposed method, two different kinds of linear phase response design examples are illustrated and the general PSO algorithm is compared as well. The obtained results show that the MPSO is superior to the general PSO for the phase response design of digital recursive all-pass filter.

  20. Phase Response Design of Recursive All-Pass Digital Filters Using a Modified PSO Algorithm

    PubMed Central

    Chang, Wei-Der

    2015-01-01

    This paper develops a new design scheme for the phase response of an all-pass recursive digital filter. A variant of particle swarm optimization (PSO) algorithm will be utilized for solving this kind of filter design problem. It is here called the modified PSO (MPSO) algorithm in which another adjusting factor is more introduced in the velocity updating formula of the algorithm in order to improve the searching ability. In the proposed method, all of the designed filter coefficients are firstly collected to be a parameter vector and this vector is regarded as a particle of the algorithm. The MPSO with a modified velocity formula will force all particles into moving toward the optimal or near optimal solution by minimizing some defined objective function of the optimization problem. To show the effectiveness of the proposed method, two different kinds of linear phase response design examples are illustrated and the general PSO algorithm is compared as well. The obtained results show that the MPSO is superior to the general PSO for the phase response design of digital recursive all-pass filter. PMID:26366168

  1. Acute phase response induced following tumor treatment by photodynamic therapy: relevance for the therapy outcome

    NASA Astrophysics Data System (ADS)

    Korbelik, Mladen; Merchant, Soroush; Stott, Brandon; Cecic, Ivana; Payne, Peter; Sun, Jinghai

    2006-02-01

    Acute phase response is an effector process orchestrated by the innate immune system for the optimal mobilization of the resources of the organism distant from the local insult site needed in the execution of a host-protecting reaction. Our research has shown that mice bearing tumors treated by photodynamic therapy (PDT) exhibit the three major hallmarks of acute phase response: release of acute phase reactants, neutrophilia, and pituitary/adrenal axis activation. Of particular interest in this study were acute phase proteins that have a pivotal role in the clearance of dead cells, since the occurrence of this process in PDT-treated tumors emerges as a critical event in the course of PDT-associated host response. It is shown that this type of acute phase reactants, including complement proteins (C3, C5, C9, mannose-binding lectin, and ficolin A) and related pentraxins (serum amyloid P component and PTX3), are upregulated following tumor PDT and accumulate in the targeted lesions. Based on the recently accumulated experimental evidence it is definitely established that the acute phase response is manifested in the hosts bearing PDT-treated tumors and it is becoming clear that this effector process is an important element of PDT-associated host response bearing in impact on the eventual outcome of this therapy.

  2. Impact of neuronal heterogeneity on correlated colored noise-induced synchronization.

    PubMed

    Zhou, Pengcheng; Burton, Shawn D; Urban, Nathaniel N; Ermentrout, G Bard

    2013-01-01

    Synchronization plays an important role in neural signal processing and transmission. Many hypotheses have been proposed to explain the origin of neural synchronization. In recent years, correlated noise-induced synchronization has received support from many theoretical and experimental studies. However, many of these prior studies have assumed that neurons have identical biophysical properties and that their inputs are well modeled by white noise. In this context, we use colored noise to induce synchronization between oscillators with heterogeneity in both phase-response curves and frequencies. In the low noise limit, we derive novel analytical theory showing that the time constant of colored noise influences correlated noise-induced synchronization and that oscillator heterogeneity can limit synchronization. Surprisingly, however, heterogeneous oscillators may synchronize better than homogeneous oscillators given low input correlations. We also find resonance of oscillator synchronization to colored noise inputs when firing frequencies diverge. Collectively, these results prove robust for both relatively high noise regimes and when applied to biophysically realistic spiking neuron models, and further match experimental recordings from acute brain slices.

  3. [Neuronal ageing].

    PubMed

    Piechota, Małgorzata; Sunderland, Piotr

    2014-01-01

    Ageing leads to irreversible alterations in the nervous system, which to various extent impair its functions such as capacity to learn and memory. In old neurons and brain, similarly to what may take place in other cells, there is increased oxidative stress, disturbed energetic homeostasis and metabolism, accumulation of damage in proteins and nucleic acids. Characteristic of old neurons are alterations in plasticity, synaptic transmission, sensitivity to neurotrophic factors and cytoskeletal changes. Some markers of senescence, whose one of them is SA-beta-galactosidase were used to show the process of neuronal ageing both in vitro, and in vivo. Some research suggest that, despite the fact that neurons are postmitotic cells, it is cell cycle proteins which play a certain role in their biology, e.g. differentiation. However, their role in neuronal ageing is not known or explained. Ageing is the serious factor of development of neurodegenerative diseases among others Alzheimer disease.

  4. The Skipping Rope Curve

    ERIC Educational Resources Information Center

    Nordmark, Arne; Essen, Hanno

    2007-01-01

    The equilibrium of a flexible inextensible string, or chain, in the centrifugal force field of a rotating reference frame is investigated. It is assumed that the end points are fixed on the rotation axis. The shape of the curve, the skipping rope curve or "troposkien", is given by the Jacobi elliptic function sn. (Contains 3 figures.)

  5. Anodic Polarization Curves Revisited

    ERIC Educational Resources Information Center

    Liu, Yue; Drew, Michael G. B.; Liu, Ying; Liu, Lin

    2013-01-01

    An experiment published in this "Journal" has been revisited and it is found that the curve pattern of the anodic polarization curve for iron repeats itself successively when the potential scan is repeated. It is surprising that this observation has not been reported previously in the literature because it immediately brings into…

  6. Flow-duration curves

    USGS Publications Warehouse

    Searcy, James Kincheon

    1959-01-01

    The flow-duration curve is a cumulative frequency curve that shows the percent of time specified discharges were equaled or exceeded during a given period. It combines in one curve the flow characteristics of a stream throughout the range of discharge, without regard to the sequence of occurrence. If the period upon which the curve is based represents the long-term flow of a stream, the curve may be used to predict the distribution of future flows for water- power, water-supply, and pollution studies. This report shows that differences in geology affect the low-flow ends of flow-duration curves of streams in adjacent basins. Thus, duration curves are useful in appraising the geologic characteristics of drainage basins. A method for adjusting flow-duration curves of short periods to represent long-term conditions is presented. The adjustment is made by correlating the records of a short-term station with those of a long-term station.

  7. Simulating Supernova Light Curves

    SciTech Connect

    Even, Wesley Paul; Dolence, Joshua C.

    2016-05-05

    This report discusses supernova light simulations. A brief review of supernovae, basics of supernova light curves, simulation tools used at LANL, and supernova results are included. Further, it happens that many of the same methods used to generate simulated supernova light curves can also be used to model the emission from fireballs generated by explosions in the earth’s atmosphere.

  8. Tornado-Shaped Curves

    ERIC Educational Resources Information Center

    Martínez, Sol Sáez; de la Rosa, Félix Martínez; Rojas, Sergio

    2017-01-01

    In Advanced Calculus, our students wonder if it is possible to graphically represent a tornado by means of a three-dimensional curve. In this paper, we show it is possible by providing the parametric equations of such tornado-shaped curves.

  9. CURVES: curve evolution for vessel segmentation.

    PubMed

    Lorigo, L M; Faugeras, O D; Grimson, W E; Keriven, R; Kikinis, R; Nabavi, A; Westin, C F

    2001-09-01

    The vasculature is of utmost importance in neurosurgery. Direct visualization of images acquired with current imaging modalities, however, cannot provide a spatial representation of small vessels. These vessels, and their branches which show considerable variations, are most important in planning and performing neurosurgical procedures. In planning they provide information on where the lesion draws its blood supply and where it drains. During surgery the vessels serve as landmarks and guidelines to the lesion. The more minute the information is, the more precise the navigation and localization of computer guided procedures. Beyond neurosurgery and neurological study, vascular information is also crucial in cardiovascular surgery, diagnosis, and research. This paper addresses the problem of automatic segmentation of complicated curvilinear structures in three-dimensional imagery, with the primary application of segmenting vasculature in magnetic resonance angiography (MRA) images. The method presented is based on recent curve and surface evolution work in the computer vision community which models the object boundary as a manifold that evolves iteratively to minimize an energy criterion. This energy criterion is based both on intensity values in the image and on local smoothness properties of the object boundary, which is the vessel wall in this application. In particular, the method handles curves evolving in 3D, in contrast with previous work that has dealt with curves in 2D and surfaces in 3D. Results are presented on cerebral and aortic MRA data as well as lung computed tomography (CT) data.

  10. Presence of an acute phase response in sheep with clinical classical scrapie

    PubMed Central

    2012-01-01

    Background Work with experimental scrapie in sheep has been performed on-site for many years including studies on PrPSc dissemination and histopathology of organs and tissues both at preclinical and clinical stages. In this work serum was sampled at regular intervals from lambs which were infected immediately after birth and from parallel healthy controls, and examined for acute phase proteins. In contrast to earlier experiments, which extensively studied PrPSc dissemination and histopathology in peripheral tissues and brain, this experiment is focusing on examination of serum for non-PrPSc markers that discriminates the two groups, and give insight into other on-going processes detectable in serum samples. Results There was clear evidence of an acute phase response in sheep with clinical scrapie, both experimental and natural. All the three proteins, ceruloplasmin, haptoglobin and serum amyloid A, were increased at the clinical stage of scrapie. Conclusion There was evidence of a systemic measurable acute phase response at the clinical terminal end-stage of classical scrapie. PMID:22805457

  11. Mechanics of Curved Folds

    NASA Astrophysics Data System (ADS)

    Dias, Marcelo A.; Santangelo, Christian D.

    2011-03-01

    Despite an almost two thousand year history, origami, the art of folding paper, remains a challenge both artistically and scientifically. Traditionally, origami is practiced by folding along straight creases. A whole new set of shapes can be explored, however, if, instead of straight creases, one folds along arbitrary curves. We present a mechanical model for curved fold origami in which the energy of a plastically-deformed crease is balanced by the bending energy of developable regions on either side of the crease. Though geometry requires that a sheet buckle when folded along a closed curve, its shape depends on the elasticity of the sheet. NSF DMR-0846582.

  12. Energy Model of Neuron Activation.

    PubMed

    Romanyshyn, Yuriy; Smerdov, Andriy; Petrytska, Svitlana

    2017-02-01

    On the basis of the neurophysiological strength-duration (amplitude-duration) curve of neuron activation (which relates the threshold amplitude of a rectangular current pulse of neuron activation to the pulse duration), as well as with the use of activation energy constraint (the threshold curve corresponds to the energy threshold of neuron activation by a rectangular current pulse), an energy model of neuron activation by a single current pulse has been constructed. The constructed model of activation, which determines its spectral properties, is a bandpass filter. Under the condition of minimum-phase feature of the neuron activation model, on the basis of Hilbert transform, the possibilities of phase-frequency response calculation from its amplitude-frequency response have been considered. Approximation to the amplitude-frequency response by the response of the Butterworth filter of the first order, as well as obtaining the pulse response corresponding to this approximation, give us the possibility of analyzing the efficiency of activating current pulses of various shapes, including analysis in accordance with the energy constraint.

  13. Desynchronization boost by non-uniform coordinated reset stimulation in ensembles of pulse-coupled neurons.

    PubMed

    Lücken, Leonhard; Yanchuk, Serhiy; Popovych, Oleksandr V; Tass, Peter A

    2013-01-01

    Several brain diseases are characterized by abnormal neuronal synchronization. Desynchronization of abnormal neural synchrony is theoretically compelling because of the complex dynamical mechanisms involved. We here present a novel type of coordinated reset (CR) stimulation. CR means to deliver phase resetting stimuli at different neuronal sub-populations sequentially, i.e., at times equidistantly distributed in a stimulation cycle. This uniform timing pattern seems to be intuitive and actually applies to the neural network models used for the study of CR so far. CR resets the population to an unstable cluster state from where it passes through a desynchronized transient, eventually resynchronizing if left unperturbed. In contrast, we show that the optimal stimulation times are non-uniform. Using the model of weakly pulse-coupled neurons with phase response curves, we provide an approach that enables to determine optimal stimulation timing patterns that substantially maximize the desynchronized transient time following the application of CR stimulation. This approach includes an optimization search for clusters in a low-dimensional pulse coupled map. As a consequence, model-specific non-uniformly spaced cluster states cause considerably longer desynchronization transients. Intriguingly, such a desynchronization boost with non-uniform CR stimulation can already be achieved by only slight modifications of the uniform CR timing pattern. Our results suggest that the non-uniformness of the stimulation times can be a medically valuable parameter in the calibration procedure for CR stimulation, where the latter has successfully been used in clinical and pre-clinical studies for the treatment of Parkinson's disease and tinnitus.

  14. Acute phase response, inflammation and metabolic syndrome biomarkers of Libby asbestos exposure

    SciTech Connect

    Shannahan, Jonathan H.; Alzate, Oscar; Winnik, Witold M.; Andrews, Debora; Schladweiler, Mette C.; Ghio, Andrew J.; Gavett, Stephen H.; Kodavanti, Urmila P.

    2012-04-15

    Identification of biomarkers assists in the diagnosis of disease and the assessment of health risks from environmental exposures. We hypothesized that rats exposed to Libby amphibole (LA) would present with a unique serum proteomic profile which could help elucidate epidemiologically-relevant biomarkers. In four experiments spanning varied protocols and temporality, healthy (Wistar Kyoto, WKY; and F344) and cardiovascular compromised (CVD) rat models (spontaneously hypertensive, SH; and SH heart failure, SHHF) were intratracheally instilled with saline (control) or LA. Serum biomarkers of cancer, inflammation, metabolic syndrome (MetS), and the acute phase response (APR) were analyzed. All rat strains exhibited acute increases in α-2-macroglobulin, and α1-acid glycoprotein. Among markers of inflammation, lipocalin-2 was induced in WKY, SH and SHHF and osteopontin only in WKY after LA exposure. While rat strain- and age-related changes were apparent in MetS biomarkers, no LA effects were evident. The cancer marker mesothelin was increased only slightly at 1 month in WKY in one of the studies. Quantitative Intact Proteomic profiling of WKY serum at 1 day or 4 weeks after 4 weekly LA instillations indicated no oxidative protein modifications, however APR proteins were significantly increased. Those included serine protease inhibitor, apolipoprotein E, α-2-HS-glycoprotein, t-kininogen 1 and 2, ceruloplasmin, vitamin D binding protein, serum amyloid P, and more 1 day after last LA exposure. All changes were reversible after a short recovery regardless of the acute or long-term exposures. Thus, LA exposure induces an APR and systemic inflammatory biomarkers that could have implications in systemic and pulmonary disease in individuals exposed to LA. -- Highlights: ► Biomarkers of asbestos exposure are required for disease diagnosis. ► Libby amphibole exposure is associated with increased human mortality. ► Libby amphibole increases circulating proteins involved

  15. Highly curved microchannel plates

    NASA Technical Reports Server (NTRS)

    Siegmund, O. H. W.; Cully, S.; Warren, J.; Gaines, G. A.; Priedhorsky, W.; Bloch, J.

    1990-01-01

    Several spherically curved microchannel plate (MCP) stack configurations were studied as part of an ongoing astrophysical detector development program, and as part of the development of the ALEXIS satellite payload. MCP pairs with surface radii of curvature as small as 7 cm, and diameters up to 46 mm have been evaluated. The experiments show that the gain (greater than 1.5 x 10 exp 7) and background characteristics (about 0.5 events/sq cm per sec) of highly curved MCP stacks are in general equivalent to the performance achieved with flat MCP stacks of similar configuration. However, gain variations across the curved MCP's due to variations in the channel length to diameter ratio are observed. The overall pulse height distribution of a highly curved surface MCP stack (greater than 50 percent FWHM) is thus broader than its flat counterpart (less than 30 percent). Preconditioning of curved MCP stacks gives comparable results to flat MCP stacks, but it also decreases the overall gain variations. Flat fields of curved MCP stacks have the same general characteristics as flat MCP stacks.

  16. Cells and secretagogues involved in the human late-phase response.

    PubMed

    Charlesworth, E N; Iliopoulos, O; MacDonald, S M; Kagey-Sobotka, A; Lichtenstein, L M

    1989-01-01

    Those scientists interested in allergic inflammatory processes have recently been focusing on the late-phase response, since it appears most similar to the chronic disease states observed in allergic patients. In this review we will focus on the pattern of mediator release and cellular traffic observed in two in vivo human models of the late-phase reaction, one involving the upper airways and the other the skin. We have observed in these models, as had been observed earlier in blood, that the late-phase reaction is associated with a second increase in the level of mediators. We also describe our studies of the secretagogues responsible for this late-phase mediator release and, in so doing, introduce the subjects of histamine-releasing factors and IgE heterogeneity.

  17. The sales learning curve.

    PubMed

    Leslie, Mark; Holloway, Charles A

    2006-01-01

    When a company launches a new product into a new market, the temptation is to immediately ramp up sales force capacity to gain customers as quickly as possible. But hiring a full sales force too early just causes the firm to burn through cash and fail to meet revenue expectations. Before it can sell an innovative product efficiently, the entire organization needs to learn how customers will acquire and use it, a process the authors call the sales learning curve. The concept of a learning curve is well understood in manufacturing. Employees transfer knowledge and experience back and forth between the production line and purchasing, manufacturing, engineering, planning, and operations. The sales learning curve unfolds similarly through the give-and-take between the company--marketing, sales, product support, and product development--and its customers. As customers adopt the product, the firm modifies both the offering and the processes associated with making and selling it. Progress along the manufacturing curve is measured by tracking cost per unit: The more a firm learns about the manufacturing process, the more efficient it becomes, and the lower the unit cost goes. Progress along the sales learning curve is measured in an analogous way: The more a company learns about the sales process, the more efficient it becomes at selling, and the higher the sales yield. As the sales yield increases, the sales learning process unfolds in three distinct phases--initiation, transition, and execution. Each phase requires a different size--and kind--of sales force and represents a different stage in a company's production, marketing, and sales strategies. Adjusting those strategies as the firm progresses along the sales learning curve allows managers to plan resource allocation more accurately, set appropriate expectations, avoid disastrous cash shortfalls, and reduce both the time and money required to turn a profit.

  18. Dynamics of curved interfaces

    SciTech Connect

    Escudero, Carlos

    2009-08-15

    Stochastic growth phenomena on curved interfaces are studied by means of stochastic partial differential equations. These are derived as counterparts of linear planar equations on a curved geometry after a reparametrization invariance principle has been applied. We examine differences and similarities with the classical planar equations. Some characteristic features are the loss of correlation through time and a particular behavior of the average fluctuations. Dependence on the metric is also explored. The diffusive model that propagates correlations ballistically in the planar situation is particularly interesting, as this propagation becomes nonuniversal in the new regime.

  19. Graphing Polar Curves

    ERIC Educational Resources Information Center

    Lawes, Jonathan F.

    2013-01-01

    Graphing polar curves typically involves a combination of three traditional techniques, all of which can be time-consuming and tedious. However, an alternative method--graphing the polar function on a rectangular plane--simplifies graphing, increases student understanding of the polar coordinate system, and reinforces graphing techniques learned…

  20. Textbook Factor Demand Curves.

    ERIC Educational Resources Information Center

    Davis, Joe C.

    1994-01-01

    Maintains that teachers and textbook graphics follow the same basic pattern in illustrating changes in demand curves when product prices increase. Asserts that the use of computer graphics will enable teachers to be more precise in their graphic presentation of price elasticity. (CFR)

  1. Curve Fit Challenge

    ERIC Educational Resources Information Center

    Harper, Suzanne R.; Driskell, Shannon

    2005-01-01

    Graphic tips for using the Geometer's Sketchpad (GSP) are described. The methods to import an image into GSP, define a coordinate system, plot points and curve fit the function using a graphical calculator are demonstrated where the graphic features of GSP allow teachers to expand the use of the technology application beyond the classroom.

  2. The Bacterial Growth Curve.

    ERIC Educational Resources Information Center

    Paulton, Richard J. L.

    1991-01-01

    A procedure that allows students to view an entire bacterial growth curve during a two- to three-hour student laboratory period is described. Observations of the lag phase, logarithmic phase, maximum stationary phase, and phase of decline are possible. A nonpathogenic, marine bacterium is used in the investigation. (KR)

  3. Caffeine in hot drinks elicits cephalic phase responses involving cardiac activity.

    PubMed

    McMullen, Michael K; Whitehouse, Julie M; Shine, Gillian; Whitton, Peter A; Towell, Anthony

    2012-09-01

    Caffeine stimulates both oropharyngeal and gut bitter taste receptors (hTAS2Rs) and so has the potential to elicit reflex autonomic responses. Coffee containing 130 mg caffeine has been reported to increase heart rate for 30 min post-ingestion. Whereas added-caffeine, in doses of 25 to 200 mg, ingested with decaffeinated coffee/tea decreases heart rate 10 to 30 min post-ingestion. This study aimed to clarify caffeine's chemosensory impact. Double-espresso coffees were compared to a placebo-control capsule in a double-blind between-measures design. Coffees tested were regular coffee (130 mg caffeine) and decaffeinated coffee with added-caffeine (0, 67 and 134 mg). Cardiovascular measures from three post-ingestion phases: 1) 0 to 5; 2) 10 to 15; and 3) 25 to 30 min; were compared to pre-ingestion measures. Participants comprised 11 women in the control group and 10 women in the test group. Decaffeinated coffee elicited no changes. Decaffeinated coffee with 67 mg caffeine: decreased dp/dt in Phase 1. Decaffeinated coffee with 134 mg caffeine: increased heart rate in Phases 1 and 2; decreased spontaneous baroreflex sensitivity in Phase 1; and increased diastolic pressure in Phases 2 and 3. Regular coffee: increased heart rate in Phases 1 and 2; decreased dp/dt in all phases; and decreased systolic pressure in Phase 1. Caffeine is the substance in regular coffee which elicits chemosensory autonomic reflex responses, which involves heart activity and the baroreflex. Compared to the caffeine in regular coffee, added-caffeine elicits somewhat different chemosensory responses including a more pronounced pressor effect and resetting of the baroreflex. Caffeine in commonly consumed amounts, as well as modulating body processes by blocking adenosine receptors, can elicit reflex autonomic responses during the ingestion of caffeinated drinks. It is plausible that caffeine stimulates hTAS2Rs, during the ingestion of coffee, eliciting cephalic phase responses. These cephalic phase

  4. Acrolein-Induced Dyslipidemia and Acute Phase Response Independenly of HMG-CoA Reductase

    PubMed Central

    Conklin, Daniel J.; Prough, Russell A.; Juvan, Peter; Rezen, Tadeja; Rozman, Damjana; Haberzettl, Petra; Srivastava, Sanjay; Bhatnagar, Aruni

    2012-01-01

    Scope Aldehydes are ubiquitous natural constituents of foods, water and beverages. Dietary intake represents the greatest source of exposure to acrolein and related aldehydes. Oral acrolein induces dyslipidemia acutely and chronically increases atherosclerosis in mice, yet the mechanisms are unknown. Because lipid synthesis and trafficking are largely under hepatic control, we examined hepatic genes in murine models of acute and chronic oral acrolein exposure. Methods and results Changes in hepatic gene expression were examined using a Steroltalk microarray. Acute acrolein feeding modified plasma and hepatic proteins and increased plasma triglycerides within 15 min. By 6h, acrolein altered hepatic gene expression including Insig1, Insig2 and Hmgcr genes and stimulated an acute phase response (APR) with up-regulation of serum amyloid A genes (Saa) and systemic hypoalbuminemia. To test if decreased HMG-CoA reductase activity could modify acrolein-induced dyslipidemia or the APR, mice were pretreated with simvastatin. Statin treatment, however, did not alter acrolein-induced dyslipidemia or hypoalbuminemia associated with an APR. Few hepatic genes were dysregulated by chronic acrolein feeding in apoE-null mice. These studies confirmed that acute acrolein exposure altered expression of hepatic genes involved with lipid synthesis and trafficking and APR, and thus, indicated a hepatic locus of acrolein-induced dyslipidemia and APR that was independent of HMG CoA-reductase. Conclusion Dietary intake of acrolein could contribute to cardiovascular disease risk by disturbing hepatic function. PMID:21812109

  5. Acute exercise does not induce an acute phase response (APR) in Standardbred trotters.

    PubMed

    Kristensen, Lena; Buhl, Rikke; Nostell, Katarina; Bak, Lars; Petersen, Ellen; Lindholm, Maria; Jacobsen, Stine

    2014-04-01

    The purpose of the study was to investigate whether acute strenuous exercise (1600- to 2500-m race) would elicit an acute phase response (APR) in Standardbred trotters. Blood levels of several inflammatory markers [serum amyloid A (SAA), haptoglobin, fibrinogen, white blood cell count (WBC), and iron], muscle enzymes [creatinine kinase (CK) and aspartate transaminase (AST)], and hemoglobin were assessed in 58 Standardbred trotters before and after racing. Hemoglobin levels increased and iron levels decreased 12 to 14 h after racing and haptoglobin concentrations, white blood cell counts, and iron levels were decreased 2 and/or 7 d after racing. Concentrations of CK, AST, SAA, and fibrinogen were unaltered in response to racing. Acute strenuous exercise did not elicit an acute phase reaction. The observed acute increase in hemoglobin levels and decreases in haptoglobin and iron levels may have been caused by exercise-induced hemolysis, which indicates that horses might experience a condition similar to athlete's anemia in humans. The pathogenesis and clinical implications of the hematological and blood-biochemical changes elicited by acute exercise in Standardbred trotters in the present study warrant further investigation.

  6. Undernutrition, the Acute Phase Response to Infection, and Its Effects on Micronutrient Status Indicators12

    PubMed Central

    Bresnahan, Kara A.; Tanumihardjo, Sherry A.

    2014-01-01

    Infection and undernutrition are prevalent in developing countries and demonstrate a synergistic relation. Undernutrition increases infection-related morbidity and mortality. The acute phase response (APR) is an innate, systemic inflammatory reaction to a wide array of disruptions in a host’s homeostasis, including infection. Released from immune cells in response to deleterious stimuli, proinflammatory cytokines act on distant tissues to induce behavioral (e.g., anorexia, weakness, and fatigue) and systemic effects of the APR. Cytokines act to increase energy and protein requirements to manifest fever and support hepatic acute phase protein (APP) production. Blood concentrations of glucose and lipid are augmented to provide energy to immune cells in response to cytokines. Additionally, infection decreases intestinal absorption of nutrients and can cause direct loss of micronutrients. Traditional indicators of iron, zinc, and vitamin A status are altered during the APR, leading to inaccurate estimations of deficiency in populations with a high or unknown prevalence of infection. Blood concentrations of APPs can be measured in nutrition interventions to assess the time stage and severity of infection and correct for the APR; however, standardized cutoffs for nutrition applications are needed. Protein-energy malnutrition leads to increased gut permeability to pathogens, abnormal immune cell populations, and impaired APP response. Micronutrient deficiencies cause specific immune impairments that affect both innate and adaptive responses. This review describes the antagonistic interaction between the APR and nutritional status and emphasizes the need for integrated interventions to address undernutrition and to reduce disease burden in developing countries. PMID:25398733

  7. Acute-phase responses vary with pathogen identity in house sparrows (Passer domesticus).

    PubMed

    Coon, Courtney A C; Warne, Robin W; Martin, Lynn B

    2011-06-01

    Pathogens may induce different immune responses in hosts contingent on pathogen characteristics, host characteristics, or interactions between the two. We investigated whether the broadly effective acute-phase response (APR), a whole body immune response that occurs in response to constitutive immune receptor activation and includes fever, secretion of immune peptides, and sickness behaviors such as anorexia and lethargy, varies with pathogen identity in the house sparrow (Passer domesticus). Birds were challenged with a subcutaneous injection of either a glucan at 0.7 mg/kg (to simulate fungal infection), a synthetic double-stranded RNA at 25 mg/kg (to simulate viral infection), or LPS at 1 mg/kg (to simulate a gram-negative bacterial infection), and then body mass, core body temperature changes, sickness behaviors, and secretion of an acute-phase protein, haptoglobin, were compared. Despite using what are moderate-to-high pyrogen doses for other vertebrates, only house sparrows challenged with LPS showed measurable APRs. Febrile, behavioral, and physiological responses to fungal and viral mimetics had minimal effects.

  8. The acute phase response of cod (Gadus morhua L.): expression of immune response genes.

    PubMed

    Audunsdottir, Sigridur S; Magnadottir, Bergljot; Gisladottir, Berglind; Jonsson, Zophonias O; Bragason, Birkir Th

    2012-02-01

    An acute phase response (APR) was experimentally induced in Atlantic cod (Gadus morhua L.) by intramuscular injection of turpentine oil. The change in the expression of immune related genes was monitored in the anterior kidney and the spleen over a period of 7 days. The genes examined were two types of pentraxins, apolipoprotein A1 (ApoA-I), the complement component C3, interleukin-1β (IL-1β), transferrin, cathelicidin, and hepcidin. All genes were constitutively expressed in both organs and their expression amplified by the turpentine injection. A pattern of response was observed both with respect to the organ preference and to the timing of a maximum response. The increased gene expression of the pentraxins, ApoA-I and C3 was restricted to the anterior kidney, the gene expression of IL-1β, cathelicidin, and transferrin increased in both organs, while hepcidin gene expression was only significantly increased in the spleen. The pentraxins and ApoA-I appear to be early mediators of APR in cod, possibly stimulating C3 and IL-1β response, while the antimicrobial peptides may play a minor role. The increase in transferrin gene expression in both organs, and apparent indifference to cortisol release associated with the turpentine injection, suggests that this could be a typical acute phase protein in cod.

  9. Monitoring the acute phase response to vaso-occlusive crisis in sickle cell disease.

    PubMed Central

    Stuart, J; Stone, P C; Akinola, N O; Gallimore, J R; Pepys, M B

    1994-01-01

    AIMS--To identify suitable acute phase proteins as objective markers of tissue ischaemia during painful vaso-occlusive crises in sickle cell disease. METHODS--The prodromal and established phases of 14 vaso-occlusive crises were studied longitudinally in 10 patients with sickle cell anaemia. Automated solid phase enzyme immunoassays were used to measure the fast responding acute phase proteins C-reactive protein and serum amyloid A protein. Slower responding glycoproteins (fibrinogen, orosomucoid, sialic acid and concanavalin-A binding) were measured in parallel. RESULTS--C-reactive protein and serum amyloid A protein increased early in crisis, sometimes within the early (prodromal) phase. Crises that resolved within 24 hours in hospital showed a minor and transient rise compared with crises that required treatment for four days or more. In eight crises treated by patients at home the acute phase response ranged from minor to a level consistent with extensive tissue ischaemia. CONCLUSIONS--Sensitive enzyme immunoassays for C-reactive protein and serum amyloid A protein are of potential value for monitoring the onset of tissue ischaemia in sickle cell crisis and for confirming subsequent resolution. PMID:7510726

  10. Trishear for curved faults

    NASA Astrophysics Data System (ADS)

    Brandenburg, J. P.

    2013-08-01

    Fault-propagation folds form an important trapping element in both onshore and offshore fold-thrust belts, and as such benefit from reliable interpretation. Building an accurate geologic interpretation of such structures requires palinspastic restorations, which are made more challenging by the interplay between folding and faulting. Trishear (Erslev, 1991; Allmendinger, 1998) is a useful tool to unravel this relationship kinematically, but is limited by a restriction to planar fault geometries, or at least planar fault segments. Here, new methods are presented for trishear along continuously curved reverse faults defining a flat-ramp transition. In these methods, rotation of the hanging wall above a curved fault is coupled to translation along a horizontal detachment. Including hanging wall rotation allows for investigation of structures with progressive backlimb rotation. Application of the new algorithms are shown for two fault-propagation fold structures: the Turner Valley Anticline in Southwestern Alberta, and the Alpha Structure in the Niger Delta.

  11. Atlas of fatigue curves

    SciTech Connect

    Boyer, H.E.

    1986-01-01

    This Atlas was developed to serve engineers who are looking for fatigue data on a particular metal or alloy. Having these curves compiled in a single book will also facilitate the computerization of the involved data. It is pointed out that plans are under way to make the data in this book available in ASCII files for analysis by computer programs. S-N curves which typify effects of major variables are considered along with low-carbon steels, medium-carbon steels, alloy steels, HSLA steels, high-strength alloy steels, heat-resisting steels, stainless steels, maraging steels, cast irons, and heat-resisting alloys. Attention is also given to aluminum alloys, copper alloys, magnesium alloys, molybdenum, tin alloys, titanium and titanium alloys, zirconium, steel castings, closed-die forgings, powder metallurgy parts, composites, effects of surface treatments, and test results for component parts.

  12. Mouse Curve Biometrics

    SciTech Connect

    Schulz, Douglas A.

    2007-10-08

    A biometric system suitable for validating user identity using only mouse movements and no specialized equipment is presented. Mouse curves (mouse movements with little or no pause between them) are individually classied and used to develop classication histograms, which are representative of an individual's typical mouse use. These classication histograms can then be compared to validate identity. This classication approach is suitable for providing continuous identity validation during an entire user session.

  13. Quantization on Curves

    NASA Astrophysics Data System (ADS)

    Frønsdal, Christian; Kontsevich, Maxim

    2007-02-01

    Deformation quantization on varieties with singularities offers perspectives that are not found on manifolds. The Harrison component of Hochschild cohomology, vanishing on smooth manifolds, reflects information about singularities. The Harrison 2-cochains are symmetric and are interpreted in terms of abelian *-products. This paper begins a study of abelian quantization on plane curves over mathbb{C}, being algebraic varieties of the form {mathbb{C}}^2/R, where R is a polynomial in two variables; that is, abelian deformations of the coordinate algebra mathbb{C}[x,y]/(R). To understand the connection between the singularities of a variety and cohomology we determine the algebraic Hochschild (co)homology and its Barr Gerstenhaber Schack decomposition. Homology is the same for all plane curves mathbb{C}[x,y]/R, but the cohomology depends on the local algebra of the singularity of R at the origin. The Appendix, by Maxim Kontsevich, explains in modern mathematical language a way to calculate Hochschild and Harrison cohomology groups for algebras of functions on singular planar curves etc. based on Koszul resolutions.

  14. Prenatal transportation alters the acute phase response (APR) of bull calves exposed to a lipopolysaccharide (LPS) challenge

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study was designed to determine if prenatal transportation influences the acute phase response (APR) to a postnatal Lipopolysaccharide (LPS) challenge. Pregnant Brahman cows (n=96) matched by age and parity were separated into transported (TRANS; n=48; transported for 2 hours on gestational day...

  15. Supplementation of Lactobacillus acidophilus fermentation product can attenuate the acute phase response following a lipopolysaccharide challenge in pigs.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study was designed to determine if feeding a Lactobacillus acidophilus fermentation product to weaned pigs would reduce stress and acute phase responses (APR) following a lipopolysaccharide (LPS) challenge. Pigs (n=30; 6.4±0.1 kilograms body weight) were housed individually in pens with ad libi...

  16. Yeast cell wall supplementation alters the physiological and acute phase responses of crossbred heifers to an endotoxin challenge

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A study was conducted to determine the effect of feeding yeast cell wall (YCW) products on the physiological and acute phase responses of crossbred newly-received heifers to an endotoxin challenge. Heifers (n = 24; 219 ± 2.4 kg) were separated into treatment groups receiving a Control diet (n = 8), ...

  17. The effect of yeast cell wall supplementation on the physiological and acute phase responses of crossbred heifers to endotoxin challenge

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A study was conducted to determine the effect of feeding yeast cell wall (YCW) products on the physiological and acute phase responses of crossbred newly-received heifers to endotoxin (lipopolysaccharide; LPS) challenge. Heifers (n=24; 218.9+/-2.4 kg) were obtained from commercial sale barns and tra...

  18. OmniGen-AF supplementation modulated the physiological and acute phase responses of Brahman heifers to an endotoxin challenge

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study examined the effect of feeding OmniGen-AF (OG; Prince Agri Products) on the physiological and acute phase responses (APR) of newly-weaned heifers to an endotoxin (lipopolysaccharide; LPS) challenge. Brahman heifers (n=24; 183±5 kilograms) from the Texas AgriLife Research Center in Overton...

  19. Dried citrus pulp modulates the physiological and acute phase responses of crossbred heifers to an endotoxin challenge

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study examined the effect of feeding dried citrus pulp (CP) pellets on the physiological and acute phase responses (APR) of newly-received crossbred heifers to an endotoxin (lipopolysaccharide; LPS) challenge. Heifers (n=24; 218.3±2.4 kg) were obtained from commercial sale barns and transported...

  20. Acute phase response, inflammation and metabolic syndrome biomarkers of Libby asbestos exposure.

    PubMed

    Shannahan, Jonathan H; Alzate, Oscar; Winnik, Witold M; Andrews, Debora; Schladweiler, Mette C; Ghio, Andrew J; Gavett, Stephen H; Kodavanti, Urmila P

    2012-04-15

    Identification of biomarkers assists in the diagnosis of disease and the assessment of health risks from environmental exposures. We hypothesized that rats exposed to Libby amphibole (LA) would present with a unique serum proteomic profile which could help elucidate epidemiologically-relevant biomarkers. In four experiments spanning varied protocols and temporality, healthy (Wistar Kyoto, WKY; and F344) and cardiovascular compromised (CVD) rat models (spontaneously hypertensive, SH; and SH heart failure, SHHF) were intratracheally instilled with saline (control) or LA. Serum biomarkers of cancer, inflammation, metabolic syndrome (MetS), and the acute phase response (APR) were analyzed. All rat strains exhibited acute increases in α-2-macroglobulin, and α1-acid glycoprotein. Among markers of inflammation, lipocalin-2 was induced in WKY, SH and SHHF and osteopontin only in WKY after LA exposure. While rat strain- and age-related changes were apparent in MetS biomarkers, no LA effects were evident. The cancer marker mesothelin was increased only slightly at 1 month in WKY in one of the studies. Quantitative Intact Proteomic profiling of WKY serum at 1 day or 4 weeks after 4 weekly LA instillations indicated no oxidative protein modifications, however APR proteins were significantly increased. Those included serine protease inhibitor, apolipoprotein E, α-2-HS-glycoprotein, t-kininogen 1 and 2, ceruloplasmin, vitamin D binding protein, serum amyloid P, and more 1 day after last LA exposure. All changes were reversible after a short recovery regardless of the acute or long-term exposures. Thus, LA exposure induces an APR and systemic inflammatory biomarkers that could have implications in systemic and pulmonary disease in individuals exposed to LA.

  1. Rotation Curves of Galaxies

    NASA Astrophysics Data System (ADS)

    Kalnajs, Agris J.

    One can obtain a fairly good understanding of the relation between axially symmetric mass distributions and the rotation curves they produce without resorting to calculations. However it does require a break with tradition. The first step consists of replacing quantities such as surface density, volume density, and circular velocity with the mass in a ring, mass in a spherical shell, and the square of the circular velocity, or more precisely with 2 pi G r mu(r), 4 pi G r^2 rho(r), and Vc^2 (r). These three quantities all have the same dimensions, and are related to each other by scale-free linear operators. The second step consists of introducing ln(r) as the coordinate. On the log scale the scale-free operators becomes the more familiar convolution operations. Convolutions are easily handled by Fourier techniques and a surface density can be converted into a rotation curve or volume density in a small fraction of a second. A simple plot of 2 pi G r mu(r) as a function of ln(r) reveals the relative contributions of different radii to Vc^2(r). Such a plot also constitutes a sanity test for the fitting of various laws to photometric data. There are numerous examples in the literature of excellent fits to the tails that lack data or are poor fits around the maximum of 2 pi G r mu(r). I will discuss some exact relations between the above three quantities as well as some empirical observations such as the near equality of the maxima of 2 pi G r mu(r) and Vc^2 (r) curves for flat mass distributions.

  2. Curved PVDF airborne transducer.

    PubMed

    Wang, H; Toda, M

    1999-01-01

    In the application of airborne ultrasonic ranging measurement, a partially cylindrical (curved) PVDF transducer can effectively couple ultrasound into the air and generate strong sound pressure. Because of its geometrical features, the ultrasound beam angles of a curved PVDF transducer can be unsymmetrical (i.e., broad horizontally and narrow vertically). This feature is desired in some applications. In this work, a curved PVDF air transducer is investigated both theoretically and experimentally. Two resonances were observed in this transducer. They are length extensional mode and flexural bending mode. Surface vibration profiles of these two modes were measured by a laser vibrometer. It was found from the experiment that the surface vibration was not uniform along the curvature direction for both vibration modes. Theoretical calculations based on a model developed in this work confirmed the experimental results. Two displacement peaks were found in the piezoelectric active direction of PVDF film for the length extensional mode; three peaks were found for the flexural bending mode. The observed peak positions were in good agreement with the calculation results. Transient surface displacement measurements revealed that vibration peaks were in phase for the length extensional mode and out of phase for the flexural bending mode. Therefore, the length extensional mode can generate a stronger ultrasound wave than the flexural bending mode. The resonance frequencies and vibration amplitudes of the two modes strongly depend on the structure parameters as well as the material properties. For the transducer design, the theoretical model developed in this work can be used to optimize the ultrasound performance.

  3. Magnetism in curved geometries

    NASA Astrophysics Data System (ADS)

    Streubel, Robert; Fischer, Peter; Kronast, Florian; Kravchuk, Volodymyr P.; Sheka, Denis D.; Gaididei, Yuri; Schmidt, Oliver G.; Makarov, Denys

    2016-09-01

    Extending planar two-dimensional structures into the three-dimensional space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring the geometry of an object, e.g. its local curvature. In a generic electronic system, curvature results in the appearance of scalar and vector geometric potentials inducing anisotropic and chiral effects. In the specific case of magnetism, even in the simplest case of a curved anisotropic Heisenberg magnet, the curvilinear geometry manifests two exchange-driven interactions, namely effective anisotropy and antisymmetric exchange, i.e. Dzyaloshinskii-Moriya-like interaction. As a consequence, a family of novel curvature-driven effects emerges, which includes magnetochiral effects and topologically induced magnetization patterning, resulting in theoretically predicted unlimited domain wall velocities, chirality symmetry breaking and Cherenkov-like effects for magnons. The broad range of altered physical properties makes these curved architectures appealing in view of fundamental research on e.g. skyrmionic systems, magnonic crystals or exotic spin configurations. In addition to these rich physics, the application potential of three-dimensionally shaped objects is currently being explored as magnetic field sensorics for magnetofluidic applications, spin-wave filters, advanced magneto-encephalography devices for diagnosis of epilepsy or for energy-efficient racetrack memory devices. These recent developments ranging from theoretical predictions over fabrication of three-dimensionally curved magnetic thin films, hollow cylinders or wires, to their characterization using integral means as well as the development of advanced tomography approaches are in the focus of this review.

  4. Magnetism in curved geometries

    SciTech Connect

    Streubel, Robert; Fischer, Peter; Kronast, Florian; Kravchuk, Volodymyr P.; Sheka, Denis D.; Gaididei, Yuri; Schmidt, Oliver G.; Makarov, Denys

    2016-08-17

    Extending planar two-dimensional structures into the three-dimensional space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring the geometry of an object, e.g. its local curvature. In a generic electronic system, curvature results in the appearance of scalar and vector geometric potentials inducing anisotropic and chiral effects. In the specific case of magnetism, even in the simplest case of a curved anisotropic Heisenberg magnet, the curvilinear geometry manifests two exchange-driven interactions, namely effective anisotropy and antisymmetric exchange, i.e. Dzyaloshinskii–Moriya-like interaction. As a consequence, a family of novel curvature-driven effects emerges, which includes magnetochiral effects and topologically induced magnetization patterning, resulting in theoretically predicted unlimited domain wall velocities, chirality symmetry breaking and Cherenkov-like effects for magnons. The broad range of altered physical properties makes these curved architectures appealing in view of fundamental research on e.g. skyrmionic systems, magnonic crystals or exotic spin configurations. In addition to these rich physics, the application potential of three-dimensionally shaped objects is currently being explored as magnetic field sensorics for magnetofluidic applications, spin-wave filters, advanced magneto-encephalography devices for diagnosis of epilepsy or for energy-efficient racetrack memory devices. Finally, these recent developments ranging from theoretical predictions over fabrication of three-dimensionally curved magnetic thin films, hollow cylinders or wires, to their characterization using integral means as well as the development of advanced tomography approaches are in the focus of this review.

  5. Magnetism in curved geometries

    DOE PAGES

    Streubel, Robert; Fischer, Peter; Kronast, Florian; ...

    2016-08-17

    Extending planar two-dimensional structures into the three-dimensional space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring the geometry of an object, e.g. its local curvature. In a generic electronic system, curvature results in the appearance of scalar and vector geometric potentials inducing anisotropic and chiral effects. In the specific case of magnetism, even in the simplest case of a curved anisotropic Heisenberg magnet, the curvilinear geometry manifests two exchange-driven interactions, namely effective anisotropy and antisymmetric exchange, i.e. Dzyaloshinskii–Moriya-like interaction. Asmore » a consequence, a family of novel curvature-driven effects emerges, which includes magnetochiral effects and topologically induced magnetization patterning, resulting in theoretically predicted unlimited domain wall velocities, chirality symmetry breaking and Cherenkov-like effects for magnons. The broad range of altered physical properties makes these curved architectures appealing in view of fundamental research on e.g. skyrmionic systems, magnonic crystals or exotic spin configurations. In addition to these rich physics, the application potential of three-dimensionally shaped objects is currently being explored as magnetic field sensorics for magnetofluidic applications, spin-wave filters, advanced magneto-encephalography devices for diagnosis of epilepsy or for energy-efficient racetrack memory devices. Finally, these recent developments ranging from theoretical predictions over fabrication of three-dimensionally curved magnetic thin films, hollow cylinders or wires, to their characterization using integral means as well as the development of advanced tomography approaches are in the focus of this review.« less

  6. Complementary Curves of Descent

    DTIC Science & Technology

    2012-11-16

    provision of law , no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid...curves of descent 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR( S ) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT...NUMBER 7. PERFORMING ORGANIZATION NAME( S ) AND ADDRESS(ES) US Naval Academy,Physics Department,Annapolis,MD,21402-1363 8. PERFORMING ORGANIZATION

  7. Curved cap corrugated sheet

    NASA Technical Reports Server (NTRS)

    Davis, R. C.; Bales, T. T.; Royster, D. M.; Jackson, L. R. (Inventor)

    1984-01-01

    The report describes a structure for a strong, lightweight corrugated sheet. The sheet is planar or curved and includes a plurality of corrugation segments, each segment being comprised of a generally U-shaped corrugation with a part-cylindrical crown and cap strip, and straight side walls and with secondary corrugations oriented at right angles to said side walls. The cap strip is bonded to the crown and the longitudinal edge of said cap strip extends beyond edge at the intersection between said crown and said side walls. The high strength relative to weight of the structure makes it desirable for use in aircraft or spacecraft.

  8. Transforming Curves into Curves with the Same Shape.

    ERIC Educational Resources Information Center

    Levine, Michael V.

    Curves are considered to have the same shape when they are related by a similarity transformation of a certain kind. This paper extends earlier work on parallel curves to curves with the same shape. Some examples are given more or less explicitly. A generalization is used to show that the theory is ordinal and to show how the theory may be applied…

  9. The Characteristic Curves of Water

    NASA Astrophysics Data System (ADS)

    Neumaier, Arnold; Deiters, Ulrich K.

    2016-09-01

    In 1960, E. H. Brown defined a set of characteristic curves (also known as ideal curves) of pure fluids, along which some thermodynamic properties match those of an ideal gas. These curves are used for testing the extrapolation behaviour of equations of state. This work is revisited, and an elegant representation of the first-order characteristic curves as level curves of a master function is proposed. It is shown that Brown's postulate—that these curves are unique and dome-shaped in a double-logarithmic p, T representation—may fail for fluids exhibiting a density anomaly. A careful study of the Amagat curve (Joule inversion curve) generated from the IAPWS-95 reference equation of state for water reveals the existence of an additional branch.

  10. Multiple CubicBezier Curves.

    ERIC Educational Resources Information Center

    Khonsari, Michael M.; Horn, Douglas

    1990-01-01

    An algorithm is described for generating smooth curves of first-order continuity. The algorithm is composed of several cubic Bezier curves joined together at the user defined control points. Introduced is a tension control parameter which can be set thus providing additional flexibility in the design of free-form curves. (KR)

  11. Titration Curves: Fact and Fiction.

    ERIC Educational Resources Information Center

    Chamberlain, John

    1997-01-01

    Discusses ways in which datalogging equipment can enable titration curves to be measured accurately and how computing power can be used to predict the shape of curves. Highlights include sources of error, use of spreadsheets to generate titration curves, titration of a weak acid with a strong alkali, dibasic acids, weak acid and weak base, and…

  12. Quantum relative Lorenz curves

    NASA Astrophysics Data System (ADS)

    Buscemi, Francesco; Gour, Gilad

    2017-01-01

    The theory of majorization and its variants, including thermomajorization, have been found to play a central role in the formulation of many physical resource theories, ranging from entanglement theory to quantum thermodynamics. Here we formulate the framework of quantum relative Lorenz curves, and show how it is able to unify majorization, thermomajorization, and their noncommutative analogs. In doing so, we define the family of Hilbert α divergences and show how it relates with other divergences used in quantum information theory. We then apply these tools to the problem of deciding the existence of a suitable transformation from an initial pair of quantum states to a final one, focusing in particular on applications to the resource theory of athermality, a precursor of quantum thermodynamics.

  13. Optimal compensation for neuron loss

    PubMed Central

    Barrett, David GT; Denève, Sophie; Machens, Christian K

    2016-01-01

    The brain has an impressive ability to withstand neural damage. Diseases that kill neurons can go unnoticed for years, and incomplete brain lesions or silencing of neurons often fail to produce any behavioral effect. How does the brain compensate for such damage, and what are the limits of this compensation? We propose that neural circuits instantly compensate for neuron loss, thereby preserving their function as much as possible. We show that this compensation can explain changes in tuning curves induced by neuron silencing across a variety of systems, including the primary visual cortex. We find that compensatory mechanisms can be implemented through the dynamics of networks with a tight balance of excitation and inhibition, without requiring synaptic plasticity. The limits of this compensatory mechanism are reached when excitation and inhibition become unbalanced, thereby demarcating a recovery boundary, where signal representation fails and where diseases may become symptomatic. DOI: http://dx.doi.org/10.7554/eLife.12454.001 PMID:27935480

  14. Parvalbumin-immunoreactive neurons in the human claustrum.

    PubMed

    Hinova-Palova, D V; Edelstein, L; Landzhov, B V; Braak, E; Malinova, L G; Minkov, M; Paloff, A; Ovtscharoff, W

    2014-09-01

    The morphology and distribution of parvalbumin-immunoreactive neurons (PV-ir) were studied in the human claustrum. PV-ir neurons were observed throughout the claustrum, with the highest numbers noted in the central (broadest) portion as compared with the dorsal and ventral aspects. Reaction product was evident in the neuronal perikarya, dendritic processes, and spines. In the majority of these labeled neurons, the cytoplasm was devoid of lipofuscin pigment. Cell bodies varied widely in both shape and size, ranging from oval and small, to multipolar and large. PV-ir neurons were classified into two groups, primarily based on dendritic morphology: spiny neurons with long and straight dendrites, and aspiny neurons with thin and curving dendritic processes. PV-ir fibers were seen throughout the neuropil, with many immuno-positive puncta noted.

  15. Mechanism of Interaction of Sleep-Affecting Compounds With Neuronal Receptors

    DTIC Science & Technology

    2004-07-01

    elicited ion currents. Effect of uridine on ion current amplitude was non-monotonic showing a wave-like behavior of dose - response curve with two peaks at...potentiation occurs at the lowest dose of substance. Presence of several peaks in the dose - response curve suggests availability in neuron membrane of...somewhat from the effect in cortical neurons showing the wave-like dose - response curve and blocking effect of DSIP at concentrations higher than 1

  16. Automated reasoning about cubic curves.

    SciTech Connect

    Padmanabhan, R.; McCune, W.; Mathematics and Computer Science; Univ. of Manitoba

    1995-01-01

    It is well known that the n-ary morphisms defined on projective algebraic curves satisfy some strong local-to-global equational rules of derivation not satisfied in general by universal algebras. For example, every rationally defined group law on a cubic curve must be commutative. Here we extract from the geometry of curves a first order property (gL) satisfied by all morphisms defined on these curves such that the equational consequences known for projective curves can be derived automatically from a set of six rules (stated within the first-order logic with equality). First, the rule (gL) is implemented in the theorem-proving program Otter. Then we use Otter to automatically prove some incidence theorems on projective curves without any further reference to the underlying geometry or topology of the curves.

  17. Metabolizable protein supply modulated the acute-phase response following vaccination of beef steers.

    PubMed

    Moriel, P; Arthington, J D

    2013-12-01

    Our objective was to evaluate the effects of MP supply, through RUP supplementation, on the acute-phase response of beef steers following vaccination. On d 0, Brangus-crossbred steers (n = 24; 173 ± 31 kg; 175 ± 16 d of age) were randomly assigned to receive 1 of 3 isocaloric diets formulated to provide 85, 100, and 115% of the daily MP requirements of a beef steer gaining 0.66 kg of BW daily. Diets were limit-fed at 1.8% of BW (DM basis) and individually provided to steers once daily (0800 h) from d 0 to 29. Steers were weighed on d 0 and 29, following a 12-h period of feed and water withdrawal. On d 7, steers were vaccinated against Mannheimia haemolytica (OneShot, Pfizer), and blood samples were collected on d 0, 7, 8, 10, 14, 21, and 30. Plasma metabolites were analyzed as repeated measures using the MIXED procedure of SAS. Final BW and ADG were similar (P ≥ 0.50) among treatments (mean = 184 ± 9 kg and 0.5 ± 0.08 kg/d, respectively). Effects of time were detected (P < 0.01) for plasma concentrations of all acute-phase proteins, which peaked between d 7 to 14, returning to baseline concentrations by d 29. Treatment effects were not detected (P ≥ 0.19) for plasma concentrations of acid-soluble protein, albumin, fibrinogen, IGF-1 and serum amyloid-A. Plasma concentrations of total protein (TP) and plasma urea nitrogen (PUN) increased (P ≤ 0.05) with increasing supply of MP (87.1, 89.6, and 90.1 ± 1.09 mg TP/mL and 6.1, 8.3, and 10.3 ± 0.41 mg PUN/dL for 85, 100, and 115% MP steers, respectively). From d 10 to 29, steers provided 115% MP had less (P < 0.001) plasma concentrations of ceruloplasmin than steers fed 85 and 100% MP, which had similar plasma ceruloplasmin concentrations. On d 14, plasma concentrations of haptoglobin were greatest (P ≤ 0.06) for steers fed 115% MP, intermediate for 100% MP, and least for 85% MP (0.98, 0.71 and 0.44 ± 0.099 mg/mL, respectively). On d 10, plasma concentrations of creatinine were greater (P = 0.01) for steers

  18. Birational maps that send biquadratic curves to biquadratic curves

    NASA Astrophysics Data System (ADS)

    Roberts, John A. G.; Jogia, Danesh

    2015-02-01

    Recently, many papers have begun to consider so-called non-Quispel-Roberts-Thompson (QRT) birational maps of the plane. Compared to the QRT family of maps which preserve each biquadratic curve in a fibration of the plane, non-QRT maps send a biquadratic curve to another biquadratic curve belonging to the same fibration or to a biquadratic curve from a different fibration of the plane. In this communication, we give the general form of a birational map derived from a difference equation that sends a biquadratic curve to another. The necessary and sufficient condition for such a map to exist is that the discriminants of the two biquadratic curves are the same (and hence so are the j-invariants). The result allows existing examples in the literature to be better understood and allows some statements to be made concerning their generality.

  19. Langevin Equation on Fractal Curves

    NASA Astrophysics Data System (ADS)

    Satin, Seema; Gangal, A. D.

    2016-07-01

    We analyze random motion of a particle on a fractal curve, using Langevin approach. This involves defining a new velocity in terms of mass of the fractal curve, as defined in recent work. The geometry of the fractal curve, plays an important role in this analysis. A Langevin equation with a particular model of noise is proposed and solved using techniques of the Fα-Calculus.

  20. Reflection of curved shock waves

    NASA Astrophysics Data System (ADS)

    Mölder, S.

    2017-03-01

    Shock curvatures are related to pressure gradients, streamline curvatures and vorticity in flows with planar and axial symmetry. Explicit expressions, in an influence coefficient format, are used to relate post-shock pressure gradient, streamline curvature and vorticity to pre-shock gradients and shock curvature in steady flow. Using higher order, von Neumann-type, compatibility conditions, curved shock theory is applied to calculate the flow near singly and doubly curved shocks on curved surfaces, in regular shock reflection and in Mach reflection. Theoretical curved shock shapes are in good agreement with computational fluid dynamics calculations and experiment.

  1. Shape Preserving Interpolation by Curves

    DTIC Science & Technology

    2001-07-01

    curves Given data 1i E R2 , i = 0,..., N, we consider a curve r : [a, b] -- R2 satisfying r(ti) = Ii , i = 0,..., N, (3.1) for values a = to < tj...tN = b. For a closed curve the situation is extended periodically so that Ii +N =10, ti+N =ti, i E Z, r(t+b-a) =r(t), tc R. 3.1 Desirable properties...para- meterisation). When all vi = 0, r will reduce to the usual C2 cubic spline interpolant. As vi --+ oc, the curve is ’pulled tight’ at Ii and as

  2. Hepatic cytochrome P450 3A drug metabolism is reduced in cancer patients who have an acute-phase response

    PubMed Central

    Rivory, L P; Slaviero, K A; Clarke, S J

    2002-01-01

    Inflammatory disease states (infection, arthritis) are associated with reduced drug oxidation by the cytochrome P450 3A system. Many chemotherapy agents are metabolised through this pathway, and disease may therefore influence inter-individual differences in drug pharmacokinetics. The purpose of this study was to assess cytochrome P450 3A function in patients with advanced cancer, and its relation to the acute-phase response. We evaluated hepatic cytochrome P450 3A function in 40 patients with advanced cancer using the erythromycin breath test. Both the traditional C20min measure and the recently proposed 1/TMAX values were estimated. The marker of acute-phase response, C-reactive protein and the pro-inflammatory cytokines IL-6, IL-1β, TNFα and IL-8 were measured in serum or plasma at baseline. Cancer patients with an acute phase response (C-reactive protein >10 mg l−1, n=26) had reduced metabolism as measured with the erythromycin breath test 1/TMAX (Kruskal–Wallis Anova, P=0.0062) as compared to controls (C-reactive protein ⩽10 mg l−1, n=14). Indeed, metabolism was significantly associated with C-reactive protein over the whole concentration range of this acute-phase marker (r=−0.64, Spearman Rank Correlation, P<0.00001). C-reactive protein serum levels were significantly correlated with those of IL-6 (Spearman coefficient=0.58, P<0.0003). The reduction in cytochrome P450 3A function with acute-phase reaction was independent of the tumour type and C-reactive protein elevation was associated with poor performance status. This indicates that the sub-group of cancer patients with significant acute-phase response have compromised drug metabolism, which may have implications for the safety of chemotherapy in this population. British Journal of Cancer (2002) 87, 277–280. doi:10.1038/sj.bjc.6600448 www.bjcancer.com © 2002 Cancer Research UK PMID:12177794

  3. Multi-walled carbon nanotube-physicochemical properties predict the systemic acute phase response following pulmonary exposure in mice.

    PubMed

    Poulsen, Sarah S; Knudsen, Kristina B; Jackson, Petra; Weydahl, Ingrid E K; Saber, Anne T; Wallin, Håkan; Vogel, Ulla

    2017-01-01

    Pulmonary exposure to multi-walled carbon nanotubes (MWCNTs) has been linked to an increased risk of developing cardiovascular disease in addition to the well-documented physicochemical-dependent adverse lung effects. A proposed mechanism is through a strong and sustained pulmonary secretion of acute phase proteins to the blood. We identified physicochemical determinants of MWCNT-induced systemic acute phase response by analyzing effects of pulmonary exposure to 14 commercial, well-characterized MWCNTs in female C57BL/6J mice pulmonary exposed to 0, 6, 18 or 54 μg MWCNT/mouse. Plasma levels of acute phase response proteins serum amyloid A1/2 (SAA1/2) and SAA3 were determined on day 1, 28 or 92. Expression levels of hepatic Saa1 and pulmonary Saa3 mRNA levels were assessed to determine the origin of the acute phase response proteins. Pulmonary Saa3 mRNA expression levels were greater and lasted longer than hepatic Saa1 mRNA expression. Plasma SAA1/2 and SAA3 protein levels were related to time and physicochemical properties using adjusted, multiple regression analyses. SAA3 and SAA1/2 plasma protein levels were increased after exposure to almost all of the MWCNTs on day 1, whereas limited changes were observed on day 28 and 92. SAA1/2 and SAA3 protein levels did not correlate and only SAA3 protein levels correlated with neutrophil influx. The multiple regression analyses revealed a protective effect of MWCNT length on SAA1/2 protein level on day 1, such that a longer length resulted in lowered SAA1/2 plasma levels. Increased SAA3 protein levels were positively related to dose and content of Mn, Mg and Co on day 1, whereas oxidation and diameter of the MWCNTs were protective on day 28 and 92, respectively. The results of this study reveal very differently controlled pulmonary and hepatic acute phase responses after MWCNT exposure. As the responses were influenced by the physicochemical properties of the MWCNTs, this study provides the first step towards designing

  4. Learning curves in health care.

    PubMed

    Waldman, J Deane; Yourstone, Steven A; Smith, Howard L

    2003-01-01

    This article explores the uses of learning curve theory in medicine. Though effective application of learning curve theory in health care can result in higher quality and lower cost, it is seldom methodically applied in clinical practice. Fundamental changes are necessary in the corporate culture of medicine in order to capitalize maximally on the benefits of learning.

  5. Modulation of C4b-binding protein isoforms during the acute phase response caused by orthopedic surgery.

    PubMed

    Criado-García, O; González-Rubio, C; López-Trascasa, M; Pascual-Salcedo, D; Munuera, L; Rodríguez de Córdoba, S

    1997-01-01

    Orthopedic surgery is described as an event with a high risk of thromboembolic diseases. This is probably a consequence of a synergistic combination of different risk factors in the patients subjected to this type of surgery, including age, immobilization, anesthesia and different hypercoagulable states. After surgery patients develop an acute-phase response that leads to changes in several plasma proteins. One of these proteins is the complement regulator C4b-binding protein (C4BP). We have recently shown that in some acute-phase patients C4BP is incorrectly controlled (with elevation of the C4BP beta-containing isoforms), leading to a potential hypercoagulable state by decreasing the plasma levels of free (active) protein S. Here we have studied whether patients subjected to orthopedic surgery have an appropriate modulation of the C4BP isoforms during their postoperative acute-phase responses. We have analyzed the evolution of the C4BP isoforms in serial samples from 11 patients who have undergone knee (or hip) prosthesis surgery (mean age 70 years), or scoliosis surgery (mean age 18 years). Our data suggest a similar evolution of C4BP isoforms in all these patients, with an almost exclusive increase of C4BP isoforms lacking C4BP beta polypeptides and steady levels of free protein S.

  6. Neuronal Migration Disorders

    MedlinePlus

    ... Understanding Sleep The Life and Death of a Neuron Order Publications Support Resources Patient Organizations Professional Societies ... birth defects caused by the abnormal migration of neurons in the developing brain and nervous system. In ...

  7. Accelerating Around an Unbanked Curve

    DTIC Science & Technology

    2006-02-01

    FEB 2006 2. REPORT TYPE 3. DATES COVERED 00-00-2006 to 00-00-2006 4. TITLE AND SUBTITLE Accelerating Around an Unbanked Curve 5a. CONTRACT...December 2004 issue of TPT presented a problem concerning how a car should acceler-ate around an unbanked curve of constant radius r starting from rest...Accelerating Around an Unbanked Curve Carl E. Mungan, U.S. Naval Academy, Annapolis, MD 100 THE PHYSICS TEACHER ◆ Vol. 44, February 2006 The shapes

  8. Curved conveyor section guide assembly

    SciTech Connect

    Truszczinski, H.

    1981-02-03

    A guide assembly for a curved conveyor section of a scraperchain conveyor guides the scraper assembly from a first straight conveyor portion round the curved conveyor section to a second straight conveyor portion. This guiding is accomplished by a pair of independently rotatable pulley wheels. A further pair of independently rotatable pulley wheels are provided to guide the drive chain of a plough round the curved conveyor section. This enables the plough to be driven to and fro along the first straight conveyor portion by a drive station attached to the second straight conveyor portion adjacent to the guide assembly.

  9. Neurofibromin and Neuronal Apoptosis

    DTIC Science & Technology

    2005-07-01

    for these differences in the response of Nfl-/- neurons. "So What" Section. The learning disabilities associated with NF I constitute a highly variable...and +/+ neurons appear to become more significant with age. Our results may have implications for two areas: 1) the pathogenesis of learning ... disabilities in children with NF I, and 2) therapeutic strategies or targets for prolonging neuron survival, or for increasing neuronal response to protective

  10. Modifying the acute phase response of Jersey calves by supplementing milk replacer with omega-3 fatty acids from fish oil.

    PubMed

    Ballou, M A; Cruz, G D; Pittroff, W; Keisler, D H; DePeters, E J

    2008-09-01

    Fifty-one Jersey bull calves (5 +/- 1 d old) were assigned to 1 of 3 milk replacers to determine the effects of increasing doses of n-3 fatty acids from fish oil on the acute phase response after an endotoxin challenge. All calves were fed a 22.5% crude protein and 18% lipid milk replacer (Calva Products, Acampo, CA) supplemented with an additional 2% fatty acids. Treatments differed only in the supplemental lipid source and included a 3:1 mix of corn and canola oils, a 1:1 blend of fish oil (Omega Proteins, Houston, TX) and the 3:1 mix of corn and canola oils, and fish oil only. On d 23, each calf was injected subcutaneously with 4 microg/kg of body weight of Salmonella Typhimurium endotoxin. Clinical, hematological, and biochemical parameters were measured at 0, 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 18, 24, and 72 h post endotoxin challenge. Endotoxin caused a dramatic rise in respiratory rate; feeding fish oil significantly attenuated the increase. Heart rate and rectal temperature were not affected by treatment. Feeding fish oil attenuated the change in serum iron concentration over time. Endotoxin caused severe hypoglycemia, reaching a nadir at 4 h. Calves supplemented with fish oil had reduced concentrations of serum glucose for 8 to 24 h. Furthermore, calves supplemented with fish oil alone had reduced serum insulin at 12, 28, and 24 h. In contrast, endotoxin caused an acute increase in blood urea nitrogen and nonesterified fatty acids; there were significant linear effects of fish oil on both blood urea nitrogen and nonesterified fatty acids. Serum triglycerides were elevated beginning at 12 h after the endotoxin challenge and returned to baseline values within 72 h. Fish oil suppressed the rise in triglycerides during this period, and the effect was linear with increasing fish oil. Serum concentrations of leptin decreased after the endotoxin challenge; however, the treatment did not influence the response. There was no treatment effect on serum aspartate

  11. Flow over riblet curved surfaces

    NASA Astrophysics Data System (ADS)

    Loureiro, J. B. R.; Silva Freire, A. P.

    2011-12-01

    The present work studies the mechanics of turbulent drag reduction over curved surfaces by riblets. The effects of surface modification on flow separation over steep and smooth curved surfaces are investigated. Four types of two-dimensional surfaces are studied based on the morphometric parameters that describe the body of a blue whale. Local measurements of mean velocity and turbulence profiles are obtained through laser Doppler anemometry (LDA) and particle image velocimetry (PIV).

  12. Diminished acute phase response and increased hepatic inflammation of aged rats in response to intraperitoneal injection of lipopolysaccharide.

    PubMed

    Gomez, Christian R; Acuña-Castillo, Claudio; Pérez, Claudio; Leiva-Salcedo, Elías; Riquelme, Denise M; Ordenes, Gamaliel; Oshima, Kiyoko; Aravena, Mauricio; Pérez, Viviana I; Nishimura, Sumiyo; Sabaj, Valeria; Walter, Robin; Sierra, Felipe

    2008-12-01

    Aging is associated with a deterioration of the acute phase response to inflammatory challenges. However, the nature of these defects remains poorly defined. We analyzed the hepatic inflammatory response after intraperitoneal administration of lipopolysaccharide (LPS) given to Fisher 344 rats aged 6, 15, and 22-23 months. Induction of the acute phase proteins (APPs), haptoglobin, alpha-1-acid glycoprotein, and T-kininogen was reduced and/or retarded with aging. Initial induction of interleukin-6 in aged rats was normal, but the later response was increased relative to younger counterparts. An exacerbated hepatic injury was observed in aged rats receiving LPS, as evidenced by the presence of multiple microabscesses in portal tracts, confluent necrosis, higher neutrophil accumulation, and elevated serum levels of alanine aminotransferase, relative to younger animals. Our results suggest that aged rats displayed a reduced expression of APPs and increased hepatic injury in response to the inflammatory insult.

  13. Postpartum Circulating Markers of Inflammation and the Systemic Acute-Phase Response After Early-Onset Preeclampsia.

    PubMed

    van Rijn, Bas B; Bruinse, Hein W; Veerbeek, Jan H; Post Uiterweer, Emiel D; Koenen, Steven V; van der Bom, Johanna G; Rijkers, Ger T; Roest, Mark; Franx, Arie

    2016-02-01

    Preeclampsia is an inflammatory-mediated hypertensive disorder of pregnancy and seems to be an early indicator of increased cardiovascular risk, but mechanisms underlying this association are unclear. In this study, we identified levels of circulating inflammatory markers and dynamic changes in the systemic acute-phase response in 44 women with a history of severe early-onset preeclampsia, compared with 29 controls with only uneventful pregnancies at 1.5 to 3.5 years postpartum. Models used were in vivo seasonal influenza vaccination and in vitro whole-blood culture with T-cell stimulants and the toll-like receptor-4 ligand lipopolysaccharide. Outcome measures were C-reactive protein, interleukin-6 (IL-6), IL-18, fibrinogen, myeloperoxidase, and a panel of 13 cytokines representative of the innate and adaptive inflammatory response, in addition to established cardiovascular markers. The in vivo acute-phase response was higher for women with previous preeclampsia than that for controls without such a history, although only significant for C-reactive protein (P=0.04). Preeclampsia was associated with higher IL-1β (P<0.05) and IL-8 (P<0.01) responses to T-cell activation. Hierarchical clustering revealed 2 distinct inflammatory clusters associated with previous preeclampsia: an adaptive response cluster associated with increased C-reactive protein and IL-6 before and after vaccination, increased weight, and low high-density lipoprotein cholesterol; and a toll-like receptor-4 mediated the cluster associated with increased IL-18 before and after vaccination but not associated with other cardiovascular markers. Furthermore, we found interactions between previous preeclampsia, common TLR4 gene variants, and the IL-18 response to vaccination. In conclusion, preeclampsia is associated with alterations in the inflammatory response postpartum mostly independent of other established cardiovascular risk markers.

  14. Cochlear microphonic broad tuning curves

    NASA Astrophysics Data System (ADS)

    Ayat, Mohammad; Teal, Paul D.; Searchfield, Grant D.; Razali, Najwani

    2015-12-01

    It is known that the cochlear microphonic voltage exhibits much broader tuning than does the basilar membrane motion. The most commonly used explanation for this is that when an electrode is inserted at a particular point inside the scala media, the microphonic potentials of neighbouring hair cells have different phases, leading to cancelation at the electrodes location. In situ recording of functioning outer hair cells (OHCs) for investigating this hypothesis is exceptionally difficult. Therefore, to investigate the discrepancy between the tuning curves of the basilar membrane and those of the cochlear microphonic, and the effect of phase cancellation of adjacent hair cells on the broadness of the cochlear microphonic tuning curves, we use an electromechanical model of the cochlea to devise an experiment. We explore the effect of adjacent hair cells (i.e., longitudinal phase cancellation) on the broadness of the cochlear microphonic tuning curves in different locations. The results of the experiment indicate that active longitudinal coupling (i.e., coupling with active adjacent outer hair cells) only slightly changes the broadness of the CM tuning curves. The results also demonstrate that there is a π phase difference between the potentials produced by the hair bundle and the soma near the place associated with the characteristic frequency based on place-frequency maps (i.e., the best place). We suggest that the transversal phase cancellation (caused by the phase difference between the hair bundle and the soma) plays a far more important role than longitudinal phase cancellation in the broadness of the cochlear microphonic tuning curves. Moreover, by increasing the modelled longitudinal resistance resulting the cochlear microphonic curves exhibiting sharper tuning. The results of the simulations suggest that the passive network of the organ of Corti determines the phase difference between the hair bundle and soma, and hence determines the sharpness of the

  15. Macaque inferior temporal neurons are selective for three-dimensional boundaries and surfaces.

    PubMed

    Janssen, P; Vogels, R; Liu, Y; Orban, G A

    2001-12-01

    The lower bank of the superior temporal sulcus (TEs), part of the inferior temporal cortex, contains neurons selective for disparity-defined three-dimensional (3-D) shape. The large majority of these TEs neurons respond to the spatial variation of disparity, i.e., are higher-order disparity selective. To determine whether curved boundaries or curved surfaces by themselves are sufficient to elicit 3-D shape selectivity, we recorded the responses of single higher-order disparity-selective TEs neurons to concave and convex 3-D shapes in which the disparity varied either along the boundary of the shape, or only along its surface. For a majority of neurons, a 3-D boundary was sufficient for 3-D shape selectivity. At least as many neurons responded selectively to 3-D surfaces, and a number of neurons exhibited both surface and boundary selectivity. The second aim of this study was to determine whether TEs neurons can represent differences in second-order disparities along the horizontal axis. The results revealed that TEs neurons can also be selective for horizontal 3-D shapes and can code the direction of curvature (vertical or horizontal). Thus, TEs neurons represent both boundaries and surfaces curved in depth and can signal the direction of curvature along a surface. These results show that TEs neurons use not only boundary but also surface information to encode 3-D shape properties.

  16. Dynamic Input Conductances Shape Neuronal Spiking(1,2).

    PubMed

    Drion, Guillaume; Franci, Alessio; Dethier, Julie; Sepulchre, Rodolphe

    2015-01-01

    Assessing the role of biophysical parameter variations in neuronal activity is critical to the understanding of modulation, robustness, and homeostasis of neuronal signalling. The paper proposes that this question can be addressed through the analysis of dynamic input conductances. Those voltage-dependent curves aggregate the concomitant activity of all ion channels in distinct timescales. They are shown to shape the current-voltage dynamical relationships that determine neuronal spiking. We propose an experimental protocol to measure dynamic input conductances in neurons. In addition, we provide a computational method to extract dynamic input conductances from arbitrary conductance-based models and to analyze their sensitivity to arbitrary parameters. We illustrate the relevance of the proposed approach for modulation, compensation, and robustness studies in a published neuron model based on data of the stomatogastric ganglion of the crab Cancer borealis.

  17. Cajal bodies in neurons.

    PubMed

    Lafarga, Miguel; Tapia, Olga; Romero, Ana M; Berciano, Maria T

    2016-09-14

    Cajal is commonly regarded as the father of modern neuroscience in recognition of his fundamental work on the structure of the nervous system. But Cajal also made seminal contributions to the knowledge of nuclear structure in the early 1900s, including the discovery of the "accessory body" later renamed "Cajal body" (CB). This important nuclear structure has emerged as a center for the assembly of ribonucleoproteins (RNPs) required for splicing, ribosome biogenesis and telomere maintenance. The modern era of CB research started in the 1990s with the discovery of coilin, now known as a scaffold protein of CBs, and specific probes for small nuclear RNAs (snRNAs). In this review, we summarize what we have learned in the recent decades concerning CBs in post-mitotic neurons, thereby ruling out dynamic changes in CB functions during the cell cycle. We show that CBs are particularly prominent in neurons, where they frequently associate with the nucleolus. Neuronal CBs are transcription-dependent nuclear organelles. Indeed, their number dynamically accommodates to support the high neuronal demand for splicing and ribosome biogenesis required for sustaining metabolic and bioelectrical activity. Mature neurons have canonical CBs enriched in coilin, survival motor neuron protein and snRNPs. Disruption and loss of neuronal CBs associate with severe neuronal dysfunctions in several neurological disorders such as motor neuron diseases. In particular, CB depletion in motor neurons seems to reflect a perturbation of transcription and splicing in spinal muscular atrophy, the most common genetic cause of infant mortality.

  18. Relative Locality in Curved Spacetime

    NASA Astrophysics Data System (ADS)

    Kowalski-Glikman, Jerzy; Rosati, Giacomo

    2013-07-01

    In this paper we construct the action describing dynamics of the particle moving in curved spacetime, with a nontrivial momentum space geometry. Curved momentum space is the core feature of theories where relative locality effects are present. So far aspects of nonlinearities in momentum space have been studied only for flat or constantly expanding (de Sitter) spacetimes, relying on their maximally symmetric nature. The extension of curved momentum space frameworks to arbitrary spacetime geometries could be relevant for the opportunities to test Planck-scale curvature/deformation of particles momentum space. As a first example of this construction we describe the particle with κ-Poincaré momentum space on a circular orbit in Schwarzschild spacetime, where the contributes of momentum space curvature turn out to be negligible. The analysis of this problem relies crucially on the solution of the soccer ball problem.

  19. Phase nucleation in curved space

    NASA Astrophysics Data System (ADS)

    Gómez, Leopoldo; García, Nicolás; Vitelli, Vincenzo; Lorenzana, José; Daniel, Vega

    Nucleation and growth is the dominant relaxation mechanism driving first-order phase transitions. In two-dimensional flat systems, nucleation has been applied to a wide range of problems in physics, chemistry and biology. Here we study nucleation and growth of two-dimensional phases lying on curved surfaces and show that curvature modifies both critical sizes of nuclei and paths towards the equilibrium phase. In curved space, nucleation and growth becomes inherently inhomogeneous and critical nuclei form faster on regions of positive Gaussian curvature. Substrates of varying shape display complex energy landscapes with several geometry-induced local minima, where initially propagating nuclei become stabilized and trapped by the underlying curvature (Gómez, L. R. et al. Phase nucleation in curved space. Nat. Commun. 6:6856 doi: 10.1038/ncomms7856 (2015).).

  20. Supply curves of conserved energy

    NASA Astrophysics Data System (ADS)

    Meier, A. K.

    1982-05-01

    Supply curves of conserved energy provide an accounting framework that expresses the potential for energy conservation. The economic worthiness of a conservation measure is expressed in terms of the cost of conserved energy, and a measure is considered economical when the cost of conserved energy is less than the price of the energy it replaces. A supply curve of conserved energy is independent of energy prices; however, the economical reserves of conserved energy will depend on energy prices. Double-counting of energy savings and error propagation are common problems when estimating conservation potentials, but supply curves minimize these difficulties and make their consequences predictable. The sensitivity of the cost of conserved energy is examined, as are variations in the optimal investment strategy in response to changes in inputs. Guidelines are presented for predicting the consequences of such changes.

  1. Curve Fit Technique for a Smooth Curve Using Gaussian Sections.

    DTIC Science & Technology

    1983-08-01

    curve-fitting. Furthermore, the algorithm that does the fitting is simple enough to be used on a programmable calculator . 8 -I.F , A X i 4. Y-14 .4. - -* F.J OR;r IF 17 r*~~ , ac ~J ’a vt. . S ~ :.. *~All, a-4k .16’.- a1 1, t

  2. Harmonic Measure of Critical Curves

    SciTech Connect

    Bettelheim, E.; Rushkin, I.; Gruzberg, I.A.; Wiegmann, P.

    2005-10-21

    Fractal geometry of critical curves appearing in 2D critical systems is characterized by their harmonic measure. For systems described by conformal field theories with central charge c{<=}1, scaling exponents of the harmonic measure have been computed by Duplantier [Phys. Rev. Lett. 84, 1363 (2000)] by relating the problem to boundary two-dimensional gravity. We present a simple argument connecting the harmonic measure of critical curves to operators obtained by fusion of primary fields and compute characteristics of the fractal geometry by means of regular methods of conformal field theory. The method is not limited to theories with c{<=}1.

  3. Active particles on curved surfaces

    NASA Astrophysics Data System (ADS)

    Fily, Yaouen; Baskaran, Aparna; Hagan, Michael

    Active systems have proved to be very sensitive to the geometry of their environment. This is often achieved by spending significant time at the boundary, probing its shape by gliding along it. I will discuss coarse graining the microscopic dynamics of self-propelled particles on a general curved surface to predict the way the density profile on the surface depends on its geometry. Beyond confined active particles, this formalism is a natural starting point to study objects that cannot leave the boundary at all, such as cells crawling on a curved substrate, animals running on uneven ground, or active colloids trapped at an interface.

  4. Shock detachment from curved wedges

    NASA Astrophysics Data System (ADS)

    Mölder, S.

    2017-03-01

    Curved shock theory is used to show that the flow behind attached shocks on doubly curved wedges can have either positive or negative post-shock pressure gradients depending on the freestream Mach number, the wedge angle and the two wedge curvatures. Given enough wedge length, the flow near the leading edge can choke to force the shock to detach from the wedge. This local choking can preempt both the maximum deflection and the sonic criteria for shock detachment. Analytical predictions for detachment by local choking are supported by CFD results.

  5. NEXT Performance Curve Analysis and Validation

    NASA Technical Reports Server (NTRS)

    Saripalli, Pratik; Cardiff, Eric; Englander, Jacob

    2016-01-01

    Performance curves of the NEXT thruster are highly important in determining the thruster's ability in performing towards mission-specific goals. New performance curves are proposed and examined here. The Evolutionary Mission Trajectory Generator (EMTG) is used to verify variations in mission solutions based on both available thruster curves and the new curves generated. Furthermore, variations in BOL and EOL curves are also examined. Mission design results shown here validate the use of EMTG and the new performance curves.

  6. The role of GABAergic inhibition in shaping directional selectivity of bat inferior collicular neurons determined with temporally patterned pulse trains.

    PubMed

    Zhou, X M; Jen, P H-S

    2002-11-01

    This study examined the role of GABAergic inhibition in shaping directional selectivity of neurons in the inferior colliculus of the big brown bat, Eptesicus fuscus. When determined with temporally patterned pulse trains at different pulse repetition rates, 93 inferior colliculus neurons displayed three types of directional selectivity curves. A directionally selective curve always showed a maximum to a certain azimuthal angle (the best angle). A hemifield curve showed a maximum to a range of contralateral azimuthal angles. A non-directional curve did not show a maximum to any particular azimuthal angles. Directional selectivity curves of 42% neurons changed from hemifield or non-directional to directionally selective and the best angles of 16-21% neurons shifted toward the midline with increasing pulse repetition rate of pulse trains. Directional selectivity curves of most (74%) neurons that discharged impulses to each pulse of a pulse train also became sharper with increasing pulse repetition rate of pulse trains. Bicuculline application produced more pronounced broadening of directional selective curves of inferior colliculus neurons at higher than at lower pulse repetition rates. As a result, pulse repetition rate-dependent directional selectivity of inferior colliculus neurons was abolished. Possible mechanisms and biological significance of these findings are discussed.

  7. Descending protocerebral neurons related to the mating dance of the male silkworm moth.

    PubMed

    Kanzaki, R; Shibuya, T

    1986-07-09

    Descending protocerebral neurons in the male silkworm moth brain responding to the sexual pheromone (Bombykol) were identified. The neurons responded well with a tonic type of response and the high-frequency spikes evoked continued even after the end of the stimulus. Characteristics of the dose-response curves of the neurons to the pheromone remarkably resembled those of the wing vibration which is one of the mating behavioral components of the male moths.

  8. Supply Curves of Conserved Energy

    SciTech Connect

    Meier, Alan Kevin

    1982-05-01

    Supply curves of conserved energy provide an accounting framework that expresses the potential for energy conservation. The economic worthiness of a conservation measure is expressed in terms of the cost of conserved energy, and a measure is considered economical when the cost of conserved energy is less than the price of the energy it replaces. A supply curve of conserved energy is independent of energy prices; however, the economical reserves of conserved energy will depend on energy prices. Double-counting of energy savings and error propagation are common problems when estimating conservation potentials, but supply curves minimize these difficulties and make their consequences predictable. The sensitivity of the cost of conserved energy is examined, as are variations in the optimal investment strategy in response to changes in inputs. Guidelines are presented for predicting the consequences of such changes. The conservation supply curve concept can be applied to peak power, water, pollution, and other markets where consumers demand a service rather than a particular good.

  9. Interpolation and Polynomial Curve Fitting

    ERIC Educational Resources Information Center

    Yang, Yajun; Gordon, Sheldon P.

    2014-01-01

    Two points determine a line. Three noncollinear points determine a quadratic function. Four points that do not lie on a lower-degree polynomial curve determine a cubic function. In general, n + 1 points uniquely determine a polynomial of degree n, presuming that they do not fall onto a polynomial of lower degree. The process of finding such a…

  10. Variability among polysulphone calibration curves

    NASA Astrophysics Data System (ADS)

    Casale, G. R.; Borra, M.; Colosimo, A.; Colucci, M.; Militello, A.; Siani, A. M.; Sisto, R.

    2006-09-01

    Within an epidemiological study regarding the correlation between skin pathologies and personal ultraviolet (UV) exposure due to solar radiation, 14 field campaigns using polysulphone (PS) dosemeters were carried out at three different Italian sites (urban, semi-rural and rural) in every season of the year. A polysulphone calibration curve for each field experiment was obtained by measuring the ambient UV dose under almost clear sky conditions and the corresponding change in the PS film absorbance, prior and post exposure. Ambient UV doses were measured by well-calibrated broad-band radiometers and by electronic dosemeters. The dose-response relation was represented by the typical best fit to a third-degree polynomial and it was parameterized by a coefficient multiplying a cubic polynomial function. It was observed that the fit curves differed from each other in the coefficient only. It was assessed that the multiplying coefficient was affected by the solar UV spectrum at the Earth's surface whilst the polynomial factor depended on the photoinduced reaction of the polysulphone film. The mismatch between the polysulphone spectral curve and the CIE erythemal action spectrum was responsible for the variability among polysulphone calibration curves. The variability of the coefficient was related to the total ozone amount and the solar zenith angle. A mathematical explanation of such a parameterization was also discussed.

  11. Breakpoint chlorination curves of greywater.

    PubMed

    March, J G; Gual, M

    2007-08-01

    A study on chlorination of raw greywater with hypochlorite is reported in this paper. Samples were chlorinated in a variety of conditions, and residual chlorine (Cl2) was measured spectrophotometrically. For each sample, the chlorination curve (chlorine residuals versus chlorine dose) was obtained. Curves showed the typical hump-and-dip profile attributable to the formation and destruction of chloramines. It was observed that, after reactions with strong reductants and chloramines-forming compounds, the remaining organic matter exerted a certain demand of chlorine. The evolution of chlorination curves with addition of ammonia and dodecylbencene sulfonate sodium salt and with dilution of the greywater sample were studied. In addition, chlorination curves at several contact times have been obtained, resulting in slower chlorine decay in the hump zone than in the dip zone. In addition, the decay of coliforms in chlorinated samples was also investigated. It was found that, for a chlorination dosage corresponding to the maximum of the hump zone (average 8.9 mg Cl2/ L), samples were negative in coliforms after 10 to 30 minutes of contact time. After-growth was not observed within 3 days after chlorination. Implications in chlorination treatments of raw greywater can be derived from these results.

  12. Immunomodulatory properties of gamithromycin and ketoprofen in lipopolysaccharide-challenged calves with emphasis on the acute-phase response.

    PubMed

    Plessers, Elke; Wyns, Heidi; Watteyn, Anneleen; Pardon, Bart; De Baere, Siegrid; Sys, Stanislas U; De Backer, Patrick; Croubels, Siska

    2016-03-01

    Macrolide antibiotics and non-steroidal anti-inflammatory drugs (NSAIDs) have been reported to be modulators of the innate immune response, irrespectively of their antimicrobial and anti-inflammatory actions. Therefore, it was our objective to evaluate whether the macrolide gamithromycin (GAM) and the NSAID ketoprofen (KETO) attenuate the acute-phase response in calves, and whether their combined administration is beneficial due to synergistic and/or additive effects. To this end, both drugs, as well as their combination, were studied in a previously developed inflammation model, i.e., the induction of an acute-phase response by an intravenous lipopolysaccharide (LPS) challenge (0.5 μg/kg body weight). Sixteen 4-week-old Holstein-Friesian calves were randomized into 4 groups: a positive control (+CONTR) group, receiving LPS but no pharmacological treatment (n=4) and a GAM (n=4), a KETO (n=4) and a GAM-KETO (n=4) group, receiving the respective drugs 1h prior to LPS administration. Clinical scoring and blood collection were performed at regular time points until 72 h post LPS challenge. Plasma concentrations of the selected cytokines (tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6)), acute-phase protein (serum amyloid A (SAA)) and prostaglandin E2 (PGE2) were subsequently quantified. Pre-treatment with GAM had no effect in the inflammation model compared to the +CONTR group. KETO, on the other hand, completely inhibited depression, anorexia and fever. This remarkable influence was associated with a significant reduction of PGE2 synthesis by KETO, while the effect on TNF-α, IL-6 and SAA was not straightforward. The combined administration of GAM and KETO provided no synergistic or additive effects in this model, neither clinically nor regarding the studied inflammatory mediators. In conclusion, KETO entirely inhibited PGE2 synthesis, fever development and depression, while GAM did not exert any effect in this model. These results promote the concomitant

  13. Linear stability in networks of pulse-coupled neurons.

    PubMed

    Olmi, Simona; Torcini, Alessandro; Politi, Antonio

    2014-01-01

    In a first step toward the comprehension of neural activity, one should focus on the stability of the possible dynamical states. Even the characterization of an idealized regime, such as that of a perfectly periodic spiking activity, reveals unexpected difficulties. In this paper we discuss a general approach to linear stability of pulse-coupled neural networks for generic phase-response curves and post-synaptic response functions. In particular, we present: (1) a mean-field approach developed under the hypothesis of an infinite network and small synaptic conductances; (2) a "microscopic" approach which applies to finite but large networks. As a result, we find that there exist two classes of perturbations: those which are perfectly described by the mean-field approach and those which are subject to finite-size corrections, irrespective of the network size. The analysis of perfectly regular, asynchronous, states reveals that their stability depends crucially on the smoothness of both the phase-response curve and the transmitted post-synaptic pulse. Numerical simulations suggest that this scenario extends to systems that are not covered by the perturbative approach. Altogether, we have described a series of tools for the stability analysis of various dynamical regimes of generic pulse-coupled oscillators, going beyond those that are currently invoked in the literature.

  14. Comparison of Two Algebraic Methods for Curve/curve Intersection

    NASA Technical Reports Server (NTRS)

    Demontaudouin, Y.; Tiller, W.

    1985-01-01

    Most geometric modeling systems use either polynomial or rational functions to represent geometry. In such systems most computational problems can be formulated as systems of polynomials in one or more variables. Classical elimination theory can be used to solve such systems. Here Cayley's method of elimination is summarized and it is shown how it can best be used to solve the curve/curve intersection problem. Cayley's method was found to be a more straightforward approach. Furthermore, it is computationally simpler, since the elements of the Cayley matrix are one variable instead of two variable polynomials. Researchers implemented and tested both methods and found Cayley's to be more efficient. Six pairs of curves, representing mixtures of lines, circles, and cubic arcs were used. Several examples had multiple intersection points. For all six cases Cayley's required less CPU time than the other method. The average time ratio of method 1 to method 2 was 3.13:1, the least difference was 2.33:1, and the most dramatic was 6.25:1. Both of the above methods can be extended to solve the surface/surface intersection problem.

  15. Pacemaking Kisspeptin Neurons

    PubMed Central

    Kelly, Martin J.; Zhang, Chunguang; Qiu, Jian; Rønnekleiv, Oline K.

    2013-01-01

    Kisspeptin (Kiss1) neurons are vital for reproduction. GnRH neurons express the kisspeptin receptor, GPR 54, and kisspeptins potently stimulate the release of GnRH by depolarising and inducing sustained action potential firing in GnRH neurons. As such Kiss1 neurons may be the pre-synaptic pacemaker neurons in the hypothalamic circuitry that controls reproduction. There are at least two different populations of Kiss1 neurons: one in the rostral periventricular area (RP3V) that is stimulated by oestrogens and the other in the arcuate nucleus that is inhibited by oestrogens. How each of these Kiss1 neuronal populations participate in the regulation of the reproductive cycle is currently under intense investigation. Based on electrophysiological studies in the guinea pig and mouse, Kiss1 neurons in general are capable of generating burst firing behavior. Essentially all Kiss1 neurons, which have been studied thus far in the arcuate nucleus, express the ion channels necessary for burst firing, which include hyperpolarization-activated, cyclic nucleotide gated cation (HCN) channels and the T-type calcium (Cav3.1) channels. Under voltage clamp conditions, these channels produce distinct currents that under current clamp conditions can generate burst firing behavior. The future challenge is to identify other key channels and synaptic inputs involved in the regulation of the firing properties of Kiss1 neurons and the physiological regulation of the expression of these channels and receptors by oestrogens and other hormones. The ultimate goal is to understand how Kiss1 neurons control the different phases of GnRH neurosecretion and hence reproduction. PMID:23884368

  16. Vitamin B12 enhances the phase-response of circadian melatonin rhythm to a single bright light exposure in humans.

    PubMed

    Hashimoto, S; Kohsaka, M; Morita, N; Fukuda, N; Honma, S; Honma, K

    1996-12-13

    Eight young males were subjected to a single blind cross-over test to see the effects of vitamin B12 (methylcobalamin; VB12) on the phase-response of the circadian melatonin rhythm to a single bright light exposure. VB12 (0.5 mg/day) or vehicle was injected intravenously at 1230 h for 11 days, which was followed by oral administration (2 mg x 3/day) for 7 days. A serial blood sampling was performed under dim light condition (less than 200 lx) and plasma melatonin rhythm was determined before and after a single bright light exposure (2500 lx for 3 h) at 0700 h. The melatonin rhythm before the light exposure showed a smaller amplitude in the VB12 trial than in the placebo. The light exposure phase-advanced the melatonin rhythm significantly in the VB12 trail, but not in the placebo. These findings indicate that VB12 enhances the light-induced phase-shift in the human circadian rhythm.

  17. Effects of glutamine supplementation on gut barrier, glutathione content and acute phase response in malnourished rats during inflammatory shock

    PubMed Central

    Belmonte, Liliana; Coëffier, Moïse; Pessot, Florence Le; Miralles-Barrachina, Olga; Hiron, Martine; Leplingard, Antony; Lemeland, Jean-François; Hecketsweiler, Bernadette; Daveau, Maryvonne; Ducrotté, Philippe; Déchelotte, Pierre

    2007-01-01

    AIM: To evaluate the effect of glutamine on intestinal mucosa integrity, glutathione stores and acute phase response in protein-depleted rats during an inflammatory shock. METHODS: Plasma acute phase proteins (APP), jejunal APP mRNA levels, liver and jejunal glutathione concentrations were measured before and one, three and seven days after turpentine injection in 4 groups of control, protein-restricted, protein-restricted rats supplemented with glutamine or protein powder. Bacterial translocation in mesenteric lymph nodes and intestinal morphology were also assessed. RESULTS: Protein deprivation and turpentine injection significantly reduced jejunal villus height, and crypt depths. Mucosal glutathione concentration significantly decreased in protein-restricted rats. Before turpentine oil, glutamine supplementation restored villus heights and glutathione concentration (3.24 ± 1.05 vs 1.72 ± 0.46 μmol/g tissue, P < 0.05) in the jejunum, whereas in the liver glutathione remained low. Glutamine markedly increased jejunal α1-acid glycoprotein mRNA level after turpentine oil but did not affect its plasma concentration. Bacterial translocation in protein-restricted rats was not prevented by glutamine or protein powder supplementation. CONCLUSION: Glutamine restored gut glutathione stores and villus heights in malnourished rats but had no preventive effect on bacterial translocation in our model. PMID:17569119

  18. Corticospinal mirror neurons.

    PubMed

    Kraskov, A; Philipp, R; Waldert, S; Vigneswaran, G; Quallo, M M; Lemon, R N

    2014-01-01

    Here, we report the properties of neurons with mirror-like characteristics that were identified as pyramidal tract neurons (PTNs) and recorded in the ventral premotor cortex (area F5) and primary motor cortex (M1) of three macaque monkeys. We analysed the neurons' discharge while the monkeys performed active grasp of either food or an object, and also while they observed an experimenter carrying out a similar range of grasps. A considerable proportion of tested PTNs showed clear mirror-like properties (52% F5 and 58% M1). Some PTNs exhibited 'classical' mirror neuron properties, increasing activity for both execution and observation, while others decreased their discharge during observation ('suppression mirror-neurons'). These experiments not only demonstrate the existence of PTNs as mirror neurons in M1, but also reveal some interesting differences between M1 and F5 mirror PTNs. Although observation-related changes in the discharge of PTNs must reach the spinal cord and will include some direct projections to motoneurons supplying grasping muscles, there was no EMG activity in these muscles during action observation. We suggest that the mirror neuron system is involved in the withholding of unwanted movement during action observation. Mirror neurons are differentially recruited in the behaviour that switches rapidly between making your own movements and observing those of others.

  19. Culturing rat hippocampal neurons.

    PubMed

    Audesirk, G; Audesirk, T; Ferguson, C

    2001-01-01

    Cultured neurons are widely used to investigate the mechanisms of neurotoxicity. Embryonic rat hippocampal neurons may be grown as described under a wide variety of conditions to suit differing experimental procedures, including electrophysiology, morphological analysis of neurite development, and various biochemical and molecular analyses.

  20. Neuronal Mechanisms of Intelligence.

    DTIC Science & Technology

    1986-03-21

    The underlying premise of this research is that the neuron itself is the functional unit in the brain for positive reinforcement . Our early studies...preference studies (an alternative method to self-stimulation for measuring reward). Keywords: Neuronal conditioning; Positive reinforcement ; Learning; and Adaptive networks.

  1. K2 Mission Light Curves

    NASA Astrophysics Data System (ADS)

    Smith, Jeffrey C.; morris, robert; Bryson, Steve; Jenkins, Jon Michael; Caldwell, Douglas

    2015-08-01

    The K2 mission is now generating light curves for its ecliptic-field campaigns. Producing good photometry for K2 is more challenging than for Kepler’s prime mission because periodic thruster firings are used to compensate for the loss of two reaction wheels. These firings, referred to as "roll tweaks", result in spacecraft rotation along the barrel axis and high corresponding image motion. The resulting motion-dominated systematic errors are dramatically different than the focus-dominated systematic errors experienced during the prime mission. They also make it challenging to properly identify and remove flux from background objects present in the optimal apertures. We summarize these challenges and describe the resulting modifications to the Kepler pipeline for the processing of K2 data. The quality of the K2 mission light curves is characterized.

  2. Infinite swapping in curved spaces

    NASA Astrophysics Data System (ADS)

    Curotto, E.; Mella, Massimo

    2014-01-01

    We develop an extension of the infinite swapping and partial infinite swapping techniques [N. Plattner, J. D. Doll, P. Dupuis, H. Wang, Y. Liu, and J. E. Gubernatis, J. Chem. Phys. 135, 134111 (2011)] to curved spaces. Furthermore, we test the performance of infinite swapping and partial infinite swapping in a series of flat spaces characterized by the same potential energy surface model. We develop a second order variational algorithm for general curved spaces without the extended Lagrangian formalism to include holonomic constraints. We test the new methods by carrying out NVT classical ensemble simulations on a set of multidimensional toroids mapped by stereographic projections and characterized by a potential energy surface built from a linear combination of decoupled double wells shaped purposely to create rare events over a range of temperatures.

  3. Infinite swapping in curved spaces.

    PubMed

    Curotto, E; Mella, Massimo

    2014-01-07

    We develop an extension of the infinite swapping and partial infinite swapping techniques [N. Plattner, J. D. Doll, P. Dupuis, H. Wang, Y. Liu, and J. E. Gubernatis, J. Chem. Phys. 135, 134111 (2011)] to curved spaces. Furthermore, we test the performance of infinite swapping and partial infinite swapping in a series of flat spaces characterized by the same potential energy surface model. We develop a second order variational algorithm for general curved spaces without the extended Lagrangian formalism to include holonomic constraints. We test the new methods by carrying out NVT classical ensemble simulations on a set of multidimensional toroids mapped by stereographic projections and characterized by a potential energy surface built from a linear combination of decoupled double wells shaped purposely to create rare events over a range of temperatures.

  4. Analysis of Exoplanet Light Curves

    NASA Astrophysics Data System (ADS)

    Erdem, A.; Budding, E.; Rhodes, M. D.; Püsküllü, Ç.; Soydugan, F.; Soydugan, E.; Tüysüz, M.; Demircan, O.

    2015-07-01

    We have applied the close binary system analysis package WINFITTER to a variety of exoplanet transiting light curves taken both from the NASA Exoplanet Archive and our own ground-based observations. WINFitter has parameter options for a realistic physical model, including gravity brightening and structural parameters derived from Kopal's applications of the relevant Radau equation, and it includes appropriate tests for determinacy and adequacy of its best fitting parameter sets. We discuss a number of issues related to empirical checking of models for stellar limb darkening, surface maculation, Doppler beaming, microvariability, and transit time variation (TTV) effects. The Radau coefficients used in the light curve modeling, in principle, allow structural models of the component stars to be tested.

  5. Neuronal signaling through endocytosis.

    PubMed

    Cosker, Katharina E; Segal, Rosalind A

    2014-02-01

    The distinctive morphology of neurons, with complex dendritic arbors and extensive axons, presents spatial challenges for intracellular signal transduction. The endosomal system provides mechanisms that enable signaling molecules initiated by extracellular cues to be trafficked throughout the expanse of the neuron, allowing intracellular signals to be sustained over long distances. Therefore endosomes are critical for many aspects of neuronal signaling that regulate cell survival, axonal growth and guidance, dendritic branching, and cell migration. An intriguing characteristic of neuronal signal transduction is that endosomal trafficking enables physiological responses that vary based on the subcellular location of signal initiation. In this review, we will discuss the specialized mechanisms and the functional significance of endosomal signaling in neurons, both during normal development and in disease.

  6. Neuronal Signaling through Endocytosis

    PubMed Central

    Cosker, Katharina E.; Segal, Rosalind A.

    2014-01-01

    The distinctive morphology of neurons, with complex dendritic arbors and extensive axons, presents spatial challenges for intracellular signal transduction. The endosomal system provides mechanisms that enable signaling molecules initiated by extracellular cues to be trafficked throughout the expanse of the neuron, allowing intracellular signals to be sustained over long distances. Therefore endosomes are critical for many aspects of neuronal signaling that regulate cell survival, axonal growth and guidance, dendritic branching, and cell migration. An intriguing characteristic of neuronal signal transduction is that endosomal trafficking enables physiological responses that vary based on the subcellular location of signal initiation. In this review, we will discuss the specialized mechanisms and the functional significance of endosomal signaling in neurons, both during normal development and in disease. PMID:24492712

  7. NEURON and Python

    PubMed Central

    Hines, Michael L.; Davison, Andrew P.; Muller, Eilif

    2008-01-01

    The NEURON simulation program now allows Python to be used, alone or in combination with NEURON's traditional Hoc interpreter. Adding Python to NEURON has the immediate benefit of making available a very extensive suite of analysis tools written for engineering and science. It also catalyzes NEURON software development by offering users a modern programming tool that is recognized for its flexibility and power to create and maintain complex programs. At the same time, nothing is lost because all existing models written in Hoc, including graphical user interface tools, continue to work without change and are also available within the Python context. An example of the benefits of Python availability is the use of the xml module in implementing NEURON's Import3D and CellBuild tools to read MorphML and NeuroML model specifications. PMID:19198661

  8. Imaging calcium in neurons.

    PubMed

    Grienberger, Christine; Konnerth, Arthur

    2012-03-08

    Calcium ions generate versatile intracellular signals that control key functions in all types of neurons. Imaging calcium in neurons is particularly important because calcium signals exert their highly specific functions in well-defined cellular subcompartments. In this Primer, we briefly review the general mechanisms of neuronal calcium signaling. We then introduce the calcium imaging devices, including confocal and two-photon microscopy as well as miniaturized devices that are used in freely moving animals. We provide an overview of the classical chemical fluorescent calcium indicators and of the protein-based genetically encoded calcium indicators. Using application examples, we introduce new developments in the field, such as calcium imaging in awake, behaving animals and the use of calcium imaging for mapping single spine sensory inputs in cortical neurons in vivo. We conclude by providing an outlook on the prospects of calcium imaging for the analysis of neuronal signaling and plasticity in various animal models.

  9. NEURON and Python.

    PubMed

    Hines, Michael L; Davison, Andrew P; Muller, Eilif

    2009-01-01

    The NEURON simulation program now allows Python to be used, alone or in combination with NEURON's traditional Hoc interpreter. Adding Python to NEURON has the immediate benefit of making available a very extensive suite of analysis tools written for engineering and science. It also catalyzes NEURON software development by offering users a modern programming tool that is recognized for its flexibility and power to create and maintain complex programs. At the same time, nothing is lost because all existing models written in Hoc, including graphical user interface tools, continue to work without change and are also available within the Python context. An example of the benefits of Python availability is the use of the xml module in implementing NEURON's Import3D and CellBuild tools to read MorphML and NeuroML model specifications.

  10. Accelerating Around an Unbanked Curve

    NASA Astrophysics Data System (ADS)

    Mungan, Carl E.

    2006-02-01

    The December 2004 issue of TPT presented a problem concerning how a car should accelerate around an unbanked curve of constant radius r starting from rest if it is to avoid skidding. Interestingly enough, two solutions were proffered by readers.2 The purpose of this note is to compare and contrast the two approaches. Further experimental investigation of various turning strategies using a remote-controlled car and overhead video analysis could make for an interesting student project.

  11. Factors associated with acute-phase response of bisphosphonate-naïve or pretreated women with osteoporosis receiving an intravenous first dose of zoledronate or ibandronate.

    PubMed

    Popp, A W; Senn, R; Curkovic, I; Senn, C; Buffat, H; Popp, P F; Lippuner, K

    2017-03-15

    A first intravenous dose of bisphosphonates may be associated with an acute-phase response (APR). In bisphosphonate-naïve women with postmenopausal osteoporosis, the characteristics and frequency of APR may differ by compound. Prior bisphosphonate exposure was predictive of APR risk and severity.

  12. ROLE OF THE MATERNAL ACUTE PHASE RESPONSE AND TUMOR NECROSIS FACTOR ALPHA IN THE DEVELOPMENTAL TOXICITY OF LIPOPOLYSACCHARIDE IN THE CD-1 MOUSE

    EPA Science Inventory

    ABSTRACT
    The acute phase response (APR) functions to reset metabolic homeostasis following infectious, toxic or traumatic insult. TNF- , a putative mediator of the APR, has been associated with fetal death in rodents and preterm labor and delivery in humans. We hypothesized...

  13. Modulation of the acute phase response following a lipopolysaccharide challenge in pigs supplemented with an all-natural Saccharomyces cerevisiae fermentation product

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study was designed to determine if feeding a Saccharomyces cerevisiae fermentation product to weaned pigs would reduce the stress and acute phase responses (APR) following an acute lipopolysaccharide (LPS) challenge. Pigs (n = 20; 6.4 +/- 0.2 kg body weight) were obtained and transported to an ...

  14. Survival of Campylobacter jejuni during Stationary Phase: Evidence for the Absence of a Phenotypic Stationary-Phase Response

    PubMed Central

    Kelly, Alison F.; Park, Simon F.; Bovill, Richard; Mackey, Bernard M.

    2001-01-01

    When Campylobacter jejuni NCTC 11351 was grown microaerobically in rich medium at 39°C, entry into stationary phase was followed by a rapid decline in viable numbers to leave a residual population of 1% of the maximum number or less. Loss of viability was preceded by sublethal injury, which was seen as a loss of the ability to grow on media containing 0.1% sodium deoxycholate or 1% sodium chloride. Resistance of cells to mild heat stress (50°C) or aeration was greatest in exponential phase and declined during early stationary phase. These results show that C. jejuni does not mount the normal phenotypic stationary-phase response which results in enhanced stress resistance. This conclusion is consistent with the absence of rpoS homologues in the recently reported genome sequence of this species and their probable absence from strain NCTC 11351. During prolonged incubation of C. jejuni NCTC 11351 in stationary phase, an unusual pattern of decreasing and increasing heat resistance was observed that coincided with fluctuations in the viable count. During stationary phase of Campylobacter coli UA585, nonmotile variants and those with impaired ability to form coccoid cells were isolated at high frequency. Taken together, these observations suggest that stationary-phase cultures of campylobacters are dynamic populations and that this may be a strategy to promote survival in at least some strains. Investigation of two spontaneously arising variants (NM3 and SC4) of C. coli UA585 showed that a reduced ability to form coccoid cells did not affect survival under nongrowth conditions. PMID:11319108

  15. Incomplete suppression of distractor-related activity in the frontal eye field results in curved saccades.

    PubMed

    McPeek, Robert M

    2006-11-01

    Saccades in the presence of distractors show significant trajectory curvature. Based on previous work in the superior colliculus (SC), we speculated that curvature arises when a movement is initiated before competition between the target and distractor goals has been fully resolved. To test this hypothesis, we recorded frontal eye field (FEF) activity for curved and straight saccades in search. In contrast to the SC, activity in FEF is normally poorly correlated with saccade dynamics. However, the FEF, like the SC, is involved in target selection. Thus if curvature is caused by incomplete target selection, we expect to see its neural correlates in the FEF. We found that saccades that curve toward a distractor are accompanied by an increase in perisaccadic activity of FEF neurons coding the distractor location, and saccades that curve away are accompanied by a decrease in activity. In contrast, for FEF neurons coding the target location, there is no significant difference in activity between curved and straight saccades. To establish that the distractor-related activity is causally related to saccade curvature, we applied microstimulation to sites in the FEF before saccades to targets presented without distractors. The stimulation was subthreshold for evoking saccades and the temporal structure of the stimulation train resembled the activity recorded for curved saccades. The resulting movements curved toward the location coded by the stimulation site. These results support the idea that saccade curvature results from incomplete suppression of distractor-related activity during target selection.

  16. Compression of contour data through exploiting curve-to-curve dependence

    NASA Technical Reports Server (NTRS)

    Yalabik, N.; Cooper, D. B.

    1975-01-01

    An approach to exploiting curve-to-curve dependencies in order to achieve high data compression is presented. One of the approaches to date of along curve compression through use of cubic spline approximation is taken and extended by investigating the additional compressibility achievable through curve-to-curve structure exploitation. One of the models under investigation is reported on.

  17. NLINEAR - NONLINEAR CURVE FITTING PROGRAM

    NASA Technical Reports Server (NTRS)

    Everhart, J. L.

    1994-01-01

    A common method for fitting data is a least-squares fit. In the least-squares method, a user-specified fitting function is utilized in such a way as to minimize the sum of the squares of distances between the data points and the fitting curve. The Nonlinear Curve Fitting Program, NLINEAR, is an interactive curve fitting routine based on a description of the quadratic expansion of the chi-squared statistic. NLINEAR utilizes a nonlinear optimization algorithm that calculates the best statistically weighted values of the parameters of the fitting function and the chi-square that is to be minimized. The inputs to the program are the mathematical form of the fitting function and the initial values of the parameters to be estimated. This approach provides the user with statistical information such as goodness of fit and estimated values of parameters that produce the highest degree of correlation between the experimental data and the mathematical model. In the mathematical formulation of the algorithm, the Taylor expansion of chi-square is first introduced, and justification for retaining only the first term are presented. From the expansion, a set of n simultaneous linear equations are derived, which are solved by matrix algebra. To achieve convergence, the algorithm requires meaningful initial estimates for the parameters of the fitting function. NLINEAR is written in Fortran 77 for execution on a CDC Cyber 750 under NOS 2.3. It has a central memory requirement of 5K 60 bit words. Optionally, graphical output of the fitting function can be plotted. Tektronix PLOT-10 routines are required for graphics. NLINEAR was developed in 1987.

  18. Sound propagation over curved barriers

    NASA Technical Reports Server (NTRS)

    Pierce, Allan D.; Main, Geoffrey L.; Kearns, James A.; Hsieh, H.-A.

    1986-01-01

    Wide barriers with curved tops are studied with emphasis placed on circumstances whereby the local radius of curvature R of the barrier is continuous along the surface and is large compared to a wavelength. Results analogous to those given by Hayek et al. (1978) are reviewed and extended to cases where the radius of curvature and the surface impedance may vary with position. Circumstances not easily interpreted within the framework of the model proposed by Keller (1956) and Hayek et al. are also considered.

  19. Sound propagation over curved barriers

    NASA Astrophysics Data System (ADS)

    Pierce, Allan D.; Main, Geoffrey L.; Kearns, James A.; Hsieh, H.-A.

    Wide barriers with curved tops are studied with emphasis placed on circumstances whereby the local radius of curvature R of the barrier is continuous along the surface and is large compared to a wavelength. Results analogous to those given by Hayek et al. (1978) are reviewed and extended to cases where the radius of curvature and the surface impedance may vary with position. Circumstances not easily interpreted within the framework of the model proposed by Keller (1956) and Hayek et al. are also considered.

  20. Dirac's aether in curved spacetime.

    PubMed

    Oliveira; Teixeira

    2000-06-01

    Proca's equations for two types of fields in a Dirac's aether with electric conductivity sigma are solved exactly. The Proca electromagnetic fields are assumed with cylindrical symmetry. The background is a static, curved spacetime whose spatial section is homogeneous and has the topology of either the three-sphere S 3 or the projective three-space P 3. Simple relations between the range of Proca field lambda, the Universe radius R, the limit of photon rest mass mgamma and the conductivity sigma are written down.

  1. Curved microchannels and bacterial streamers

    NASA Astrophysics Data System (ADS)

    Rusconi, Roberto; Lecuyer, Sigolene; Guglielmini, Laura; Stone, Howard

    2010-03-01

    Bacterial biofilms are commonly identified as microbial communities attached to a surface and encased in a self-secreted extracellular matrix. Due to their increased resistance to antimicrobial agents, biofilms have an enormous impact on health and medicine (e.g., wound healing, implant-associated infections, disease transmission). On the other hand, they constitute a major component of the stream ecosystem by increasing transport of nutrients and retention of suspended particles. In this talk, we present an experimental study of bacterial biofilm development in a microfluidic device. In particular, we show the formation of filamentous structures, or streamers, in curved channels and how these suspended biofilms are linked to the underlying hydrodynamics.

  2. Dopaminergic neurons modulate GABA neuron migration in the embryonic midbrain.

    PubMed

    Vasudevan, Anju; Won, Chungkil; Li, Suyan; Erdélyi, Ferenc; Szabó, Gábor; Kim, Kwang-Soo

    2012-09-01

    Neuronal migration, a key event during brain development, remains largely unexplored in the mesencephalon, where dopaminergic (DA) and GABA neurons constitute two major neuronal populations. Here we study the migrational trajectories of DA and GABA neurons and show that they occupy ventral mesencephalic territory in a temporally and spatially specific manner. Our results from the Pitx3-deficient aphakia mouse suggest that pre-existing DA neurons modulate GABA neuronal migration to their final destination, providing novel insights and fresh perspectives concerning neuronal migration and connectivity in the mesencephalon in normal as well as diseased brains.

  3. Neuromorphic Silicon Neuron Circuits

    PubMed Central

    Indiveri, Giacomo; Linares-Barranco, Bernabé; Hamilton, Tara Julia; van Schaik, André; Etienne-Cummings, Ralph; Delbruck, Tobi; Liu, Shih-Chii; Dudek, Piotr; Häfliger, Philipp; Renaud, Sylvie; Schemmel, Johannes; Cauwenberghs, Gert; Arthur, John; Hynna, Kai; Folowosele, Fopefolu; Saighi, Sylvain; Serrano-Gotarredona, Teresa; Wijekoon, Jayawan; Wang, Yingxue; Boahen, Kwabena

    2011-01-01

    Hardware implementations of spiking neurons can be extremely useful for a large variety of applications, ranging from high-speed modeling of large-scale neural systems to real-time behaving systems, to bidirectional brain–machine interfaces. The specific circuit solutions used to implement silicon neurons depend on the application requirements. In this paper we describe the most common building blocks and techniques used to implement these circuits, and present an overview of a wide range of neuromorphic silicon neurons, which implement different computational models, ranging from biophysically realistic and conductance-based Hodgkin–Huxley models to bi-dimensional generalized adaptive integrate and fire models. We compare the different design methodologies used for each silicon neuron design described, and demonstrate their features with experimental results, measured from a wide range of fabricated VLSI chips. PMID:21747754

  4. Neuronal ubiquitin homeostasis

    PubMed Central

    Hallengren, Jada; Chen, Ping-Chung; Wilson, Scott M.

    2013-01-01

    Neurons have highly specialized intracellular compartments that facilitate the development and activity of the nervous system. Ubiquitination is a post-translational modification that controls many aspects of neuronal function by regulating protein abundance. Disruption of this signaling pathway has been demonstrated in neurological disorders such as Parkinson’s disease, Amyotrophic Lateral Sclerosis and Angleman Syndrome. Since many neurological disorders exhibit ubiquitinated protein aggregates, the loss of neuronal ubiquitin homeostasis may be an important contributor of disease. This review discusses the mechanisms utilized by neurons to control the free pool of ubiquitin necessary for normal nervous system development and function as well as new roles of protein ubiquitination in regulating synaptic activity. PMID:23686613

  5. Miniature curved artificial compound eyes

    PubMed Central

    Floreano, Dario; Pericet-Camara, Ramon; Viollet, Stéphane; Ruffier, Franck; Brückner, Andreas; Leitel, Robert; Buss, Wolfgang; Menouni, Mohsine; Expert, Fabien; Juston, Raphaël; Dobrzynski, Michal Karol; L’Eplattenier, Geraud; Recktenwald, Fabian; Mallot, Hanspeter A.; Franceschini, Nicolas

    2013-01-01

    In most animal species, vision is mediated by compound eyes, which offer lower resolution than vertebrate single-lens eyes, but significantly larger fields of view with negligible distortion and spherical aberration, as well as high temporal resolution in a tiny package. Compound eyes are ideally suited for fast panoramic motion perception. Engineering a miniature artificial compound eye is challenging because it requires accurate alignment of photoreceptive and optical components on a curved surface. Here, we describe a unique design method for biomimetic compound eyes featuring a panoramic, undistorted field of view in a very thin package. The design consists of three planar layers of separately produced arrays, namely, a microlens array, a neuromorphic photodetector array, and a flexible printed circuit board that are stacked, cut, and curved to produce a mechanically flexible imager. Following this method, we have prototyped and characterized an artificial compound eye bearing a hemispherical field of view with embedded and programmable low-power signal processing, high temporal resolution, and local adaptation to illumination. The prototyped artificial compound eye possesses several characteristics similar to the eye of the fruit fly Drosophila and other arthropod species. This design method opens up additional vistas for a broad range of applications in which wide field motion detection is at a premium, such as collision-free navigation of terrestrial and aerospace vehicles, and for the experimental testing of insect vision theories. PMID:23690574

  6. Improved capacitive melting curve measurements

    NASA Astrophysics Data System (ADS)

    Sebedash, Alexander; Tuoriniemi, Juha; Pentti, Elias; Salmela, Anssi

    2009-02-01

    Sensitivity of the capacitive method for determining the melting pressure of helium can be enhanced by loading the empty side of the capacitor with helium at a pressure nearly equal to that desired to be measured and by using a relatively thin and flexible membrane in between. This way one can achieve a nanobar resolution at the level of 30 bar, which is two orders of magnitude better than that of the best gauges with vacuum reference. This extends the applicability of melting curve thermometry to lower temperatures and would allow detecting tiny anomalies in the melting pressure, which must be associated with any phenomena contributing to the entropy of the liquid or solid phases. We demonstrated this principle in measurements of the crystallization pressure of isotopic helium mixtures at millikelvin temperatures by using partly solid pure 4He as the reference substance providing the best possible universal reference pressure. The achieved sensitivity was good enough for melting curve thermometry on mixtures down to 100 μK. Similar system can be used on pure isotopes by virtue of a blocked capillary giving a stable reference condition with liquid slightly below the melting pressure in the reference volume. This was tested with pure 4He at temperatures 0.08-0.3 K. To avoid spurious heating effects, one must carefully choose and arrange any dielectric materials close to the active capacitor. We observed some 100 pW loading at moderate excitation voltages.

  7. Wrinkling Crystallography on Curved Surfaces

    NASA Astrophysics Data System (ADS)

    Reis, Pedro; Brojan, Miha; Terwagne, Denis; Lagrange, Romain

    2014-03-01

    We present results on an experimental analysis of the morphology of wrinkling patterns on curved surfaces. Our experimental hemispherical samples are fabricated using rapid prototyping and consist of a thin-stiff shell adhered to a soft-thick substrate, both made out of silicone-based rubbers. Pressurizing an inner spherical air cavity enables compression of the samples, thereby morphing the outer thin shell from its initially smooth configuration into a wrinkled state. A variety of patterns with different morphologies can be observed depending on the combination of the sample's geometric and material properties. We focus our attention on the specific pattern mode of hexagonal-like dimples, which we characterize by analyzing their surface profile using a digital 3D scanner. Through digital image processing, we skeletonize these patterns by identifying both the location of the ridges and determining the positions of the dimples. We give emphasis to the effect of curvature on the morphology and topology of these wrinkled patterns and focus on the tiling of the wrinkling units and their statistics of defects. Our results are contrasted with other crystalline planar and curved systems.

  8. Miniature curved artificial compound eyes.

    PubMed

    Floreano, Dario; Pericet-Camara, Ramon; Viollet, Stéphane; Ruffier, Franck; Brückner, Andreas; Leitel, Robert; Buss, Wolfgang; Menouni, Mohsine; Expert, Fabien; Juston, Raphaël; Dobrzynski, Michal Karol; L'Eplattenier, Geraud; Recktenwald, Fabian; Mallot, Hanspeter A; Franceschini, Nicolas

    2013-06-04

    In most animal species, vision is mediated by compound eyes, which offer lower resolution than vertebrate single-lens eyes, but significantly larger fields of view with negligible distortion and spherical aberration, as well as high temporal resolution in a tiny package. Compound eyes are ideally suited for fast panoramic motion perception. Engineering a miniature artificial compound eye is challenging because it requires accurate alignment of photoreceptive and optical components on a curved surface. Here, we describe a unique design method for biomimetic compound eyes featuring a panoramic, undistorted field of view in a very thin package. The design consists of three planar layers of separately produced arrays, namely, a microlens array, a neuromorphic photodetector array, and a flexible printed circuit board that are stacked, cut, and curved to produce a mechanically flexible imager. Following this method, we have prototyped and characterized an artificial compound eye bearing a hemispherical field of view with embedded and programmable low-power signal processing, high temporal resolution, and local adaptation to illumination. The prototyped artificial compound eye possesses several characteristics similar to the eye of the fruit fly Drosophila and other arthropod species. This design method opens up additional vistas for a broad range of applications in which wide field motion detection is at a premium, such as collision-free navigation of terrestrial and aerospace vehicles, and for the experimental testing of insect vision theories.

  9. Motor neurone disease.

    PubMed

    2016-03-23

    Essential facts Motor neurone disease describes a group of related diseases, affecting the neurones in the brain and spinal cord. Progressive, incurable and life-limiting, MND is rare, with about 1,100 people developing it each year in the UK and up to 5,000 people affected at any one time. One third of people will die within a year of diagnosis and more than half within two years. About 5% to 10% are alive at ten years.

  10. Neuronal Mechanisms of Intelligence

    DTIC Science & Technology

    1987-11-01

    numbtr) FIELOD GROUP ]SUB-GROJP operant conditioning; neuronal conditioning; positive reinforcement ; reward; learning; adaptive networks; self...gratuitous capacity for operant conditioning, the individual neuron could be an important functional unit for positive reinforcement in the brain. These...the following conditions: 1) if a brain cell with the capacity for positive reinforcement discharges in a burst of activity, and 2) if that cell’s

  11. Ghrelin in Central Neurons

    PubMed Central

    Ferrini, F; Salio, C; Lossi, L; Merighi, A

    2009-01-01

    Ghrelin, an orexigenic peptide synthesized by endocrine cells of the gastric mucosa, is released in the bloodstream in response to a negative energetic status. Since discovery, the hypothalamus was identified as the main source of ghrelin in the CNS, and effects of the peptide have been mainly observed in this area of the brain. In recent years, an increasing number of studies have reported ghrelin synthesis and effects in specific populations of neurons also outside the hypothalamus. Thus, ghrelin activity has been described in midbrain, hindbrain, hippocampus, and spinal cord. The spectrum of functions and biological effects produced by the peptide on central neurons is remarkably wide and complex. It ranges from modulation of membrane excitability, to control of neurotransmitter release, neuronal gene expression, and neuronal survival and proliferation. There is not at present a general consensus concerning the source of ghrelin acting on central neurons. Whereas it is widely accepted that the hypothalamus represents the most important endogenous source of the hormone in CNS, the existence of extra-hypothalamic ghrelin-synthesizing neurons is still controversial. In addition, circulating ghrelin can theoretically be another natural ligand for central ghrelin receptors. This paper gives an overview on the distribution of ghrelin and its receptor across the CNS and critically analyses the data available so far as regarding the effects of ghrelin on central neurotransmission. PMID:19721816

  12. Ghrelin in central neurons.

    PubMed

    Ferrini, F; Salio, C; Lossi, L; Merighi, A

    2009-03-01

    Ghrelin, an orexigenic peptide synthesized by endocrine cells of the gastric mucosa, is released in the bloodstream in response to a negative energetic status. Since discovery, the hypothalamus was identified as the main source of ghrelin in the CNS, and effects of the peptide have been mainly observed in this area of the brain. In recent years, an increasing number of studies have reported ghrelin synthesis and effects in specific populations of neurons also outside the hypothalamus. Thus, ghrelin activity has been described in midbrain, hindbrain, hippocampus, and spinal cord. The spectrum of functions and biological effects produced by the peptide on central neurons is remarkably wide and complex. It ranges from modulation of membrane excitability, to control of neurotransmitter release, neuronal gene expression, and neuronal survival and proliferation. There is not at present a general consensus concerning the source of ghrelin acting on central neurons. Whereas it is widely accepted that the hypothalamus represents the most important endogenous source of the hormone in CNS, the existence of extra-hypothalamic ghrelin-synthesizing neurons is still controversial. In addition, circulating ghrelin can theoretically be another natural ligand for central ghrelin receptors. This paper gives an overview on the distribution of ghrelin and its receptor across the CNS and critically analyses the data available so far as regarding the effects of ghrelin on central neurotransmission.

  13. Neuron-Microdevice Connections.

    NASA Astrophysics Data System (ADS)

    Regehr, Wade Gordon

    1988-12-01

    A new method for long-term recording and stimulation applicable to cultured neurons has been developed. Silicon -based microelectrodes have been fabricated using integrated -circuit technology and micromachining. The chronic connection is made by positioning the electrode tip into contact with the cell body, and gluing the device to the bottom of the culture dish. These "diving-board electrodes" consist of an insulated lead exposed only at the tip sealed to the cell body of a cultured neuron: A two-way electrical connection to Helisoma B19 neurons has been established for up to four days. Preliminary experiments with cultured superior cervical ganglion neurons indicate diving-board electrodes can be used with cultured neurons larger than 20mum in diameter. In a related technique Helisoma neurons grown on a special dish containing a multielectrode array were found to seal to the dish electrodes, establishing similar long-term connections. This capability will make it possible to conduct experiments with either diving-board electrodes or dishes that cannot be performed using conventional techniques.

  14. Acute-phase response to benzo[a]pyrene and induction of rat ALDH3A1.

    PubMed

    Pappas, Periklis; Sotiropoulou, Marianthi; Karamanakos, Petros; Kostoula, Aggeliki; Levidiotou, Stamatia; Marselos, Marios

    2003-02-01

    The aldehyde dehydrogenase-3A1 (ALDH3A1) enzyme, encoded by a member of the [Ah]-gene family, is dramatically increased (more than 100-fold) by benzo[a]pyrene (BaP) and other polycyclic hydrocarbons. Although much is known regarding the mechanism for the drug-metabolizing enzymes up-regulated by the Ah receptor, the physiological role of that tremendously increased ALDH3A1 enzyme activity is not yet fully clarified. The aim of this study was to identify a possible acute-phase response to different classes of xenobiotics affecting the metabolic capacity of the hepatocyte, by studying possible changes of serum acute-phase proteins (APPs) of hepatic origin, before and after BaP administration. Male Wistar rats were used in different series of experiments. The effects of BaP were estimated in terms of dose-response and time-response, with regard to the serum level of several APPs such as alpha-1-acid-glycoprotein (AAG), alpha-1-antitrypsin (AAT), C-reactive protein (CRP), and haptoglobin (HPT). In parallel experiments, levels of the same proteins have been determined after a time-dependent treatment with lipopolysaccharide (LPS). The changes in serum proteins were compared with the results of BaP or LPS administration on both hepatic ALDH3A1 and total ALDH enzyme activities. The results showed that BaP induced CRP and HPT in a time-dependent way, proportional to that caused by LPS. Additionally, ALDH3A1, CRP, and HPT were induced by BaP subacute treatment, whereas another type of ALDH inducer, phenobarbital, did not affect the levels of APPs or ALDH3A1, but did increase ALDH1A3 activity. Former studies of our group have shown that the inhibitory effects of different non-steroidal anti-inflammatory drugs (NSAIDs) on the ALDH3A1 induction were most possibly due to a decreased formation of arachidonic products like prostaglandins. Considering the changes of APPs caused by BaP, this study further supports the suggestion that the induction of ALDH3A1 is related to an

  15. Cellular and molecular mechanisms regulating the hepatic erythropoietin expression during acute-phase response: a role for IL-6.

    PubMed

    Ramadori, Pierluigi; Ahmad, Ghayyor; Ramadori, Giuliano

    2010-09-01

    during acute-phase response. The increase of HIF-2alpha, predominantly expressed in endothelial cells and fibroblast-like cells, seems not to be affected by the lack of IL-6.

  16. NeuronBank: A Tool for Cataloging Neuronal Circuitry

    PubMed Central

    Katz, Paul S.; Calin-Jageman, Robert; Dhawan, Akshaye; Frederick, Chad; Guo, Shuman; Dissanayaka, Rasanjalee; Hiremath, Naveen; Ma, Wenjun; Shen, Xiuyn; Wang, Hsui C.; Yang, Hong; Prasad, Sushil; Sunderraman, Rajshekhar; Zhu, Ying

    2010-01-01

    The basic unit of any nervous system is the neuron. Therefore, understanding the operation of nervous systems ultimately requires an inventory of their constituent neurons and synaptic connectivity, which form neural circuits. The presence of uniquely identifiable neurons or classes of neurons in many invertebrates has facilitated the construction of cellular-level connectivity diagrams that can be generalized across individuals within a species. Homologous neurons can also be recognized across species. Here we describe NeuronBank.org, a web-based tool that we are developing for cataloging, searching, and analyzing neuronal circuitry within and across species. Information from a single species is represented in an individual branch of NeuronBank. Users can search within a branch or perform queries across branches to look for similarities in neuronal circuits across species. The branches allow for an extensible ontology so that additional characteristics can be added as knowledge grows. Each entry in NeuronBank generates a unique accession ID, allowing it to be easily cited. There is also an automatic link to a Wiki page allowing an encyclopedic explanation of the entry. All of the 44 previously published neurons plus one previously unpublished neuron from the mollusc, Tritonia diomedea, have been entered into a branch of NeuronBank as have 4 previously published neurons from the mollusc, Melibe leonina. The ability to organize information about neuronal circuits will make this information more accessible, ultimately aiding research on these important models. PMID:20428500

  17. Tuning Curves for Arm Posture Control in Motor Cortex Are Consistent with Random Connectivity

    PubMed Central

    Abbott, L. F.; Vaadia, Eilon

    2016-01-01

    Neuronal responses characterized by regular tuning curves are typically assumed to arise from structured synaptic connectivity. However, many responses exhibit both regular and irregular components. To address the relationship between tuning curve properties and underlying circuitry, we analyzed neuronal activity recorded from primary motor cortex (M1) of monkeys performing a 3D arm posture control task and compared the results with a neural network model. Posture control is well suited for examining M1 neuronal tuning because it avoids the dynamic complexity of time-varying movements. As a function of hand position, the neuronal responses have a linear component, as has previously been described, as well as heterogeneous and highly irregular nonlinearities. These nonlinear components involve high spatial frequencies and therefore do not support explicit encoding of movement parameters. Yet both the linear and nonlinear components contribute to the decoding of EMG of major muscles used in the task. Remarkably, despite the presence of a strong linear component, a feedforward neural network model with entirely random connectivity can replicate the data, including both the mean and distributions of the linear and nonlinear components as well as several other features of the neuronal responses. This result shows that smoothness provided by the regularity in the inputs to M1 can impose apparent structure on neural responses, in this case a strong linear (also known as cosine) tuning component, even in the absence of ordered synaptic connectivity. PMID:27224735

  18. The Aggregate Demand Curve: A Reply.

    ERIC Educational Resources Information Center

    Hansen, Richard B.; And Others

    1987-01-01

    Responds to claims about the instructional value of the downward-sloping aggregate demand curve in teaching principles of macroeconomics. Examines the effects of interest-rates and the role of money on demand curves. Concludes by arguing against the use of downward-sloping aggregate demand curves in textbooks. (RKM)

  19. Cubic spline functions for curve fitting

    NASA Technical Reports Server (NTRS)

    Young, J. D.

    1972-01-01

    FORTRAN cubic spline routine mathematically fits curve through given ordered set of points so that fitted curve nearly approximates curve generated by passing infinite thin spline through set of points. Generalized formulation includes trigonometric, hyperbolic, and damped cubic spline fits of third order.

  20. Simulation of Code Spectrum and Code Flow of Cultured Neuronal Networks.

    PubMed

    Tamura, Shinichi; Nishitani, Yoshi; Hosokawa, Chie; Miyoshi, Tomomitsu; Sawai, Hajime

    2016-01-01

    It has been shown that, in cultured neuronal networks on a multielectrode, pseudorandom-like sequences (codes) are detected, and they flow with some spatial decay constant. Each cultured neuronal network is characterized by a specific spectrum curve. That is, we may consider the spectrum curve as a "signature" of its associated neuronal network that is dependent on the characteristics of neurons and network configuration, including the weight distribution. In the present study, we used an integrate-and-fire model of neurons with intrinsic and instantaneous fluctuations of characteristics for performing a simulation of a code spectrum from multielectrodes on a 2D mesh neural network. We showed that it is possible to estimate the characteristics of neurons such as the distribution of number of neurons around each electrode and their refractory periods. Although this process is a reverse problem and theoretically the solutions are not sufficiently guaranteed, the parameters seem to be consistent with those of neurons. That is, the proposed neural network model may adequately reflect the behavior of a cultured neuronal network. Furthermore, such prospect is discussed that code analysis will provide a base of communication within a neural network that will also create a base of natural intelligence.

  1. Monocyte-conditioned medium, interleukin-1, and tumor necrosis factor stimulate the acute phase response in human hepatoma cells in vitro

    PubMed Central

    1986-01-01

    Human hepatoma cells mimic the acute phase response after treatment with monocyte-conditioned medium. Levels of secreted fibrinogen, alpha- 1 acid glycoprotein, C-reactive protein, haptoglobin, and the third component of complement were elevated compared with control levels after 48 h of incubation with conditioned supernatant medium from an enriched fraction of normal peripheral monocytes. Albumin levels declined and alpha-1 antitrypsin remained unchanged. Levels of specific mRNA were measured by hybridization to slot blots and Northern blots and changed in correspondence with protein alterations. Interleukin-1 and tumor necrosis factor stimulated the third component of complement, but did not elevate any other member of the acute phase group and were therefore only partially active in this system. The identification of an in vitro model of the human acute phase response will permit analysis of the molecular basis for coordinate regulation of this group of facultative genes. PMID:3017995

  2. Gain control of synaptic transfer from second- to third-order neurons of cockroach ocelli

    PubMed Central

    1996-01-01

    Synaptic transmission from second- to third-order neurons of cockroach ocelli occurs in an exponentially rising part of the overall sigmoidal characteristic curve relating pre- and postsynaptic voltage. Because of the nonlinear nature of the synapse, linear responses of second-order neurons to changes in ligh intensity are half-wave rectified, i.e., the response to a decrement in light is amplified whereas that to an increment in light is compressed. Here I report that the gain of synaptic transmission from second- to third-order neurons changes by ambient light levels and by wind stimulation applied to the cerci. Transfer characteristics of the synapse were studied by simultaneous intracellular recordings of second- and third-order neurons. Potential changes were evoked in second-order neurons by a sinusoidally modulated light with various mean luminances. With a decrease in the mean luminance (a) the mean membrane potential of second-order neurons was depolarized, (b) the synapse between the second- and third-order neurons operated in a steeper range of the exponential characteristic curve, where the gain to transmit modulatory signals was higher, and (c) the gain of third-order neurons to detect a decrement in light increased. Second-order neurons were depolarized when a wind or tactile stimulus was applied to various parts of the body including the cerci. During a wind-evoked depolarization, the synapse operated in a steeper range of the characteristic curve, which resulted in an increased gain of third-order neurons to detect light decrements. I conclude that the nonlinear nature of the synapse between the second- and third-order neurons provides an opportunity for an adjustment of gain to transmit signals of intensity change. The possibility that a similar gain control occurs in other visual systems and underlies a more advanced visual function, i.e., detection of motion, is discussed. PMID:8741734

  3. Curved film cooling admission tube

    NASA Technical Reports Server (NTRS)

    Graham, R. W.; Papell, S. S. (Inventor)

    1980-01-01

    Effective film cooling to protect a wall surface from a hot fluid which impinges on or flows along the surface is provided. A film of cooling fluid having increased area is provided by changing the direction of a stream of cooling fluid through an angle of from 135 deg. to 165 deg. before injecting it through the wall into the hot flowing gas. The 1, cooling fluid is injected from an orifice through a wall into a hot flowing gas at an angle to form a cooling fluid film. Cooling fluid is supplied to the orifice from a cooling fluid source via a turbulence control passageway having a curved portion between two straight portions. The angle through which the direction of the cooling fluid is turned results in less mixing of the cooling fluid with the hot gas, thereby substantially increasing the length of the film in a downstream direction.

  4. Laser-induced magnetization curve

    NASA Astrophysics Data System (ADS)

    Takayoshi, Shintaro; Sato, Masahiro; Oka, Takashi

    2014-12-01

    We propose an all optical ultrafast method to highly magnetize general quantum magnets using a circularly polarized terahertz laser. The key idea is to utilize a circularly polarized laser and its chirping. Through this method, one can obtain magnetization curves of a broad class of quantum magnets as a function of time even without any static magnetic field. We numerically demonstrate the laser-induced magnetization process in realistic quantum spin models and find a condition for the realization. The onset of magnetization can be described by a many-body version of Landau-Zener mechanism. In a particular model, we show that a plateau state with topological properties can be realized dynamically.

  5. Bacterial streamers in curved microchannels

    NASA Astrophysics Data System (ADS)

    Rusconi, Roberto; Lecuyer, Sigolene; Guglielmini, Laura; Stone, Howard

    2009-11-01

    Biofilms, generally identified as microbial communities embedded in a self-produced matrix of extracellular polymeric substances, are involved in a wide variety of health-related problems ranging from implant-associated infections to disease transmissions and dental plaque. The usual picture of these bacterial films is that they grow and develop on surfaces. However, suspended biofilm structures, or streamers, have been found in natural environments (e.g., rivers, acid mines, hydrothermal hot springs) and are always suggested to stem from a turbulent flow. We report the formation of bacterial streamers in curved microfluidic channels. By using confocal laser microscopy we are able to directly image and characterize the spatial and temporal evolution of these filamentous structures. Such streamers, which always connect the inner corners of opposite sides of the channel, are always located in the middle plane. Numerical simulations of the flow provide evidences for an underlying hydrodynamic mechanism behind the formation of the streamers.

  6. Caloric curve of star clusters.

    PubMed

    Casetti, Lapo; Nardini, Cesare

    2012-06-01

    Self-gravitating systems, such as globular clusters or elliptical galaxies, are the prototypes of many-body systems with long-range interactions, and should be the natural arena in which to test theoretical predictions on the statistical behavior of long-range-interacting systems. Systems of classical self-gravitating particles can be studied with the standard tools of equilibrium statistical mechanics, provided the potential is regularized at small length scales and the system is confined in a box. The confinement condition looks rather unphysical in general, so that it is natural to ask whether what we learn with these studies is relevant to real self-gravitating systems. In order to provide an answer to this question, we consider a basic, simple, yet effective model of globular clusters: the King model. This model describes a self-consistently confined system, without the need of any external box, but the stationary state is a nonthermal one. In particular, we consider the King model with a short-distance cutoff on the interactions, and we discuss how such a cutoff affects the caloric curve, i.e., the relation between temperature and energy. We find that the cutoff stabilizes a low-energy phase, which is absent in the King model without cutoff; the caloric curve of the model with cutoff turns out to be very similar to that of previously studied confined and regularized models, but for the absence of a high-energy gaslike phase. We briefly discuss the possible phenomenological as well as theoretical implications of these results.

  7. Caloric curve of star clusters

    NASA Astrophysics Data System (ADS)

    Casetti, Lapo; Nardini, Cesare

    2012-06-01

    Self-gravitating systems, such as globular clusters or elliptical galaxies, are the prototypes of many-body systems with long-range interactions, and should be the natural arena in which to test theoretical predictions on the statistical behavior of long-range-interacting systems. Systems of classical self-gravitating particles can be studied with the standard tools of equilibrium statistical mechanics, provided the potential is regularized at small length scales and the system is confined in a box. The confinement condition looks rather unphysical in general, so that it is natural to ask whether what we learn with these studies is relevant to real self-gravitating systems. In order to provide an answer to this question, we consider a basic, simple, yet effective model of globular clusters: the King model. This model describes a self-consistently confined system, without the need of any external box, but the stationary state is a nonthermal one. In particular, we consider the King model with a short-distance cutoff on the interactions, and we discuss how such a cutoff affects the caloric curve, i.e., the relation between temperature and energy. We find that the cutoff stabilizes a low-energy phase, which is absent in the King model without cutoff; the caloric curve of the model with cutoff turns out to be very similar to that of previously studied confined and regularized models, but for the absence of a high-energy gaslike phase. We briefly discuss the possible phenomenological as well as theoretical implications of these results.

  8. AKLSQF - LEAST SQUARES CURVE FITTING

    NASA Technical Reports Server (NTRS)

    Kantak, A. V.

    1994-01-01

    The Least Squares Curve Fitting program, AKLSQF, computes the polynomial which will least square fit uniformly spaced data easily and efficiently. The program allows the user to specify the tolerable least squares error in the fitting or allows the user to specify the polynomial degree. In both cases AKLSQF returns the polynomial and the actual least squares fit error incurred in the operation. The data may be supplied to the routine either by direct keyboard entry or via a file. AKLSQF produces the least squares polynomial in two steps. First, the data points are least squares fitted using the orthogonal factorial polynomials. The result is then reduced to a regular polynomial using Sterling numbers of the first kind. If an error tolerance is specified, the program starts with a polynomial of degree 1 and computes the least squares fit error. The degree of the polynomial used for fitting is then increased successively until the error criterion specified by the user is met. At every step the polynomial as well as the least squares fitting error is printed to the screen. In general, the program can produce a curve fitting up to a 100 degree polynomial. All computations in the program are carried out under Double Precision format for real numbers and under long integer format for integers to provide the maximum accuracy possible. AKLSQF was written for an IBM PC X/AT or compatible using Microsoft's Quick Basic compiler. It has been implemented under DOS 3.2.1 using 23K of RAM. AKLSQF was developed in 1989.

  9. Synapse-to-neuron ratio is inversely related to neuronal density in mature neuronal cultures.

    PubMed

    Cullen, D Kacy; Gilroy, Meghan E; Irons, Hillary R; Laplaca, Michelle C

    2010-11-04

    Synapse formation is a fundamental process in neurons that occurs throughout development, maturity, and aging. Although these stages contain disparate and fluctuating numbers of mature neurons, tactics employed by neuronal networks to modulate synapse number as a function of neuronal density are not well understood. The goal of this study was to utilize an in vitro model to assess the influence of cell density and neuronal maturity on synapse number and distribution. Specifically, cerebral cortical neurons were plated in planar culture at densities ranging from 10 to 5000 neurons/mm², and synapse number and distribution were evaluated via immunocytochemistry over 21 days in vitro (DIV). High-resolution confocal microscopy revealed an elaborate three-dimensional distribution of neurites and synapses across the heights of high-density neuronal networks by 21 DIV, which were up to 18 μm thick, demonstrating the complex degree of spatial interactions even in planar high-density cultures. At 7 DIV, the mean number of synapses per neuron was less than 5, and this did not vary as a function of neuronal density. However, by 21 DIV, the number of synapses per neuron had jumped 30- to 80-fold, and the synapse-to-neuron ratio was greatest at lower neuronal densities (< 500 neurons/mm²; mean approximately 400 synapses/neuron) compared to mid and higher neuronal densities (500-4500 neurons/mm²; mean of approximately 150 synapses/neuron) (p<0.05). These results suggest a relationship between neuronal density and synapse number that may have implications in the neurobiology of developing neuronal networks as well as processes of cell death and regeneration.

  10. Equine neuronal ceroid lipofuscinosis.

    PubMed

    Url, A; Bauder, B; Thalhammer, J; Nowotny, N; Kolodziejek, J; Herout, N; Fürst, S; Weissenböck, H

    2001-04-01

    Neuronal ceroid lipofuscinosis (NCL) is an inherited, neurodegenerative disorder with fatal outcome in humans. It has also been described in some animal species; this is the first report of NCL in equines. Three horses showed developmental retardation, slow movements and loss of appetite at the age of six months. Neurological symptoms, as well as visual failure in one case, were noticed at the age of 1 year. Due to slowly progressing deterioration, euthanasia was indicated 1.5 years after onset of conspicuous behavior. At necropsy, slight flattening of the gyri and discoloring of the brain was noticed. Histopathology revealed eosinophilic, autofluorescent material in the perikarya of neurons throughout the brain and spinal cord. Identical material was found in neurons of retina, submucous and myenteric ganglia, as well as in glial cells. Immunohistochemistry, using antiserum against subunit c of mitochondrial ATP synthase, showed positive signals in neurons and glial cells. Electron microscopical studies revealed fingerprint profiles mixed with rectilinear structures in markedly enlarged lysosomes of neurons and renal tubules, and rectilinear structures mixed with curvilinear bodies in macrophages and lymphocytes of lymph nodes. Thus, our study presents the first occurrence of lysosomal storage disease in horses, further characterized by immunohistochemical and electron microscopical investigations as NCL.

  11. Neuronal survival in the brain: neuron type-specific mechanisms.

    PubMed

    Pfisterer, Ulrich; Khodosevich, Konstantin

    2017-03-02

    Neurogenic regions of mammalian brain produce many more neurons that will eventually survive and reach a mature stage. Developmental cell death affects both embryonically produced immature neurons and those immature neurons that are generated in regions of adult neurogenesis. Removal of substantial numbers of neurons that are not yet completely integrated into the local circuits helps to ensure that maturation and homeostatic function of neuronal networks in the brain proceed correctly. External signals from brain microenvironment together with intrinsic signaling pathways determine whether a particular neuron will die. To accommodate this signaling, immature neurons in the brain express a number of transmembrane factors as well as intracellular signaling molecules that will regulate the cell survival/death decision, and many of these factors cease being expressed upon neuronal maturation. Furthermore, pro-survival factors and intracellular responses depend on the type of neuron and region of the brain. Thus, in addition to some common neuronal pro-survival signaling, different types of neurons possess a variety of 'neuron type-specific' pro-survival constituents that might help them to adapt for survival in a certain brain region. This review focuses on how immature neurons survive during normal and impaired brain development, both in the embryonic/neonatal brain and in brain regions associated with adult neurogenesis, and emphasizes neuron type-specific mechanisms that help to survive for various types of immature neurons. Importantly, we mainly focus on in vivo data to describe neuronal survival specifically in the brain, without extrapolating data obtained in the PNS or spinal cord, and thus emphasize the influence of the complex brain environment on neuronal survival during development.

  12. Simple models for reading neuronal population codes.

    PubMed Central

    Seung, H S; Sompolinsky, H

    1993-01-01

    In many neural systems, sensory information is distributed throughout a population of neurons. We study simple neural network models for extracting this information. The inputs to the networks are the stochastic responses of a population of sensory neurons tuned to directional stimuli. The performance of each network model in psychophysical tasks is compared with that of the optimal maximum likelihood procedure. As a model of direction estimation in two dimensions, we consider a linear network that computes a population vector. Its performance depends on the width of the population tuning curves and is maximal for width, which increases with the level of background activity. Although for narrowly tuned neurons the performance of the population vector is significantly inferior to that of maximum likelihood estimation, the difference between the two is small when the tuning is broad. For direction discrimination, we consider two models: a perceptron with fully adaptive weights and a network made by adding an adaptive second layer to the population vector network. We calculate the error rates of these networks after exhaustive training to a particular direction. By testing on the full range of possible directions, the extent of transfer of training to novel stimuli can be calculated. It is found that for threshold linear networks the transfer of perceptual learning is nonmonotonic. Although performance deteriorates away from the training stimulus, it peaks again at an intermediate angle. This nonmonotonicity provides an important psychophysical test of these models. PMID:8248166

  13. Orientation selectivity in inhibition-dominated networks of spiking neurons: effect of single neuron properties and network dynamics.

    PubMed

    Sadeh, Sadra; Rotter, Stefan

    2015-01-01

    The neuronal mechanisms underlying the emergence of orientation selectivity in the primary visual cortex of mammals are still elusive. In rodents, visual neurons show highly selective responses to oriented stimuli, but neighboring neurons do not necessarily have similar preferences. Instead of a smooth map, one observes a salt-and-pepper organization of orientation selectivity. Modeling studies have recently confirmed that balanced random networks are indeed capable of amplifying weakly tuned inputs and generating highly selective output responses, even in absence of feature-selective recurrent connectivity. Here we seek to elucidate the neuronal mechanisms underlying this phenomenon by resorting to networks of integrate-and-fire neurons, which are amenable to analytic treatment. Specifically, in networks of perfect integrate-and-fire neurons, we observe that highly selective and contrast invariant output responses emerge, very similar to networks of leaky integrate-and-fire neurons. We then demonstrate that a theory based on mean firing rates and the detailed network topology predicts the output responses, and explains the mechanisms underlying the suppression of the common-mode, amplification of modulation, and contrast invariance. Increasing inhibition dominance in our networks makes the rectifying nonlinearity more prominent, which in turn adds some distortions to the otherwise essentially linear prediction. An extension of the linear theory can account for all the distortions, enabling us to compute the exact shape of every individual tuning curve in our networks. We show that this simple form of nonlinearity adds two important properties to orientation selectivity in the network, namely sharpening of tuning curves and extra suppression of the modulation. The theory can be further extended to account for the nonlinearity of the leaky model by replacing the rectifier by the appropriate smooth input-output transfer function. These results are robust and do not

  14. Orientation Selectivity in Inhibition-Dominated Networks of Spiking Neurons: Effect of Single Neuron Properties and Network Dynamics

    PubMed Central

    Sadeh, Sadra; Rotter, Stefan

    2015-01-01

    The neuronal mechanisms underlying the emergence of orientation selectivity in the primary visual cortex of mammals are still elusive. In rodents, visual neurons show highly selective responses to oriented stimuli, but neighboring neurons do not necessarily have similar preferences. Instead of a smooth map, one observes a salt-and-pepper organization of orientation selectivity. Modeling studies have recently confirmed that balanced random networks are indeed capable of amplifying weakly tuned inputs and generating highly selective output responses, even in absence of feature-selective recurrent connectivity. Here we seek to elucidate the neuronal mechanisms underlying this phenomenon by resorting to networks of integrate-and-fire neurons, which are amenable to analytic treatment. Specifically, in networks of perfect integrate-and-fire neurons, we observe that highly selective and contrast invariant output responses emerge, very similar to networks of leaky integrate-and-fire neurons. We then demonstrate that a theory based on mean firing rates and the detailed network topology predicts the output responses, and explains the mechanisms underlying the suppression of the common-mode, amplification of modulation, and contrast invariance. Increasing inhibition dominance in our networks makes the rectifying nonlinearity more prominent, which in turn adds some distortions to the otherwise essentially linear prediction. An extension of the linear theory can account for all the distortions, enabling us to compute the exact shape of every individual tuning curve in our networks. We show that this simple form of nonlinearity adds two important properties to orientation selectivity in the network, namely sharpening of tuning curves and extra suppression of the modulation. The theory can be further extended to account for the nonlinearity of the leaky model by replacing the rectifier by the appropriate smooth input-output transfer function. These results are robust and do not

  15. What Gets a Cell Excited? Kinky Curves

    ERIC Educational Resources Information Center

    Kay, Alan R.

    2014-01-01

    Hodgkin and Huxley's (5) revealing the origins of cellular excitability is one of the great triumphs of physiology. In an extraordinarily deft series of papers, they were able to measure the essential electrical characteristics of neurons and synthesize them into a quantitative model that accounts for the excitability of neurons and other…

  16. Differentialless geometry of plane curves

    NASA Astrophysics Data System (ADS)

    Latecki, Longin J.; Rosenfeld, Azriel

    1997-10-01

    We introduce a class of planar arcs and curves, called tame arcs, which is general enough to describe the boundaries of planar real objects. A tame arc can have smooth parts as well as sharp corners; thus a polygonal arc is tame. On the other hand, this class of arcs is restrictive enough to rule out pathological arcs which have infinitely many inflections or which turn infinitely often: a tame arc can have only finitely many inflections, and its total absolute turn must be finite. In order to relate boundary properties of discrete objects obtained by segmenting digital images to the corresponding properties of their continuous originals, the theory of tame arcs is based on concepts that can be directly transferred from the continuous to the discrete domain. A tame arc is composed of a finite number of supported arcs. We define supported digital arcs and motivate their definition by the fact that hey can be obtained by digitizing continuous supported arcs. Every digital arc is tame, since it contains a finite number of points, and therefore it can be decomposed into a finite number of supported digital arcs.

  17. Learning curve of speech recognition.

    PubMed

    Kauppinen, Tomi A; Kaipio, Johanna; Koivikko, Mika P

    2013-12-01

    Speech recognition (SR) speeds patient care processes by reducing report turnaround times. However, concerns have emerged about prolonged training and an added secretarial burden for radiologists. We assessed how much proofing radiologists who have years of experience with SR and radiologists new to SR must perform, and estimated how quickly the new users become as skilled as the experienced users. We studied SR log entries for 0.25 million reports from 154 radiologists and after careful exclusions, defined a group of 11 experienced radiologists and 71 radiologists new to SR (24,833 and 122,093 reports, respectively). Data were analyzed for sound file and report lengths, character-based error rates, and words unknown to the SR's dictionary. Experienced radiologists corrected 6 characters for each report and for new users, 11. Some users presented a very unfavorable learning curve, with error rates not declining as expected. New users' reports were longer, and data for the experienced users indicates that their reports, initially equally lengthy, shortened over a period of several years. For most radiologists, only minor corrections of dictated reports were necessary. While new users adopted SR quickly, with a subset outperforming experienced users from the start, identification of users struggling with SR will help facilitate troubleshooting and support.

  18. Is the tautochrone curve unique?

    NASA Astrophysics Data System (ADS)

    Terra, Pedro; de Melo e Souza, Reinaldo; Farina, C.

    2016-12-01

    We show that there are an infinite number of tautochrone curves in addition to the cycloid solution first obtained by Christiaan Huygens in 1658. We begin by reviewing the inverse problem of finding the possible potential energy functions that lead to periodic motions of a particle whose period is a given function of its mechanical energy. There are infinitely many such solutions, called "sheared" potentials. As an interesting example, we show that a Pöschl-Teller potential and the one-dimensional Morse potentials are sheared relative to one another for negative energies, clarifying why they share the same oscillation periods for their bounded solutions. We then consider periodic motions of a particle sliding without friction over a track around its minimum under the influence of a constant gravitational field. After a brief historical survey of the tautochrone problem we show that, given the oscillation period, there is an infinity of tracks that lead to the same period. As a bonus, we show that there are infinitely many tautochrones.

  19. Simulations of Closed Timelike Curves

    NASA Astrophysics Data System (ADS)

    Brun, Todd A.; Wilde, Mark M.

    2017-03-01

    Proposed models of closed timelike curves (CTCs) have been shown to enable powerful information-processing protocols. We examine the simulation of models of CTCs both by other models of CTCs and by physical systems without access to CTCs. We prove that the recently proposed transition probability CTCs (T-CTCs) are physically equivalent to postselection CTCs (P-CTCs), in the sense that one model can simulate the other with reasonable overhead. As a consequence, their information-processing capabilities are equivalent. We also describe a method for quantum computers to simulate Deutschian CTCs (but with a reasonable overhead only in some cases). In cases for which the overhead is reasonable, it might be possible to perform the simulation in a table-top experiment. This approach has the benefit of resolving some ambiguities associated with the equivalent circuit model of Ralph et al. Furthermore, we provide an explicit form for the state of the CTC system such that it is a maximum-entropy state, as prescribed by Deutsch.

  20. Perineuronal Nets Enhance the Excitability of Fast-Spiking Neurons

    PubMed Central

    2016-01-01

    Perineuronal nets (PNNs) are specialized complexes of extracellular matrix molecules that surround the somata of fast-spiking neurons throughout the vertebrate brain. PNNs are particularly prevalent throughout the auditory brainstem, which transmits signals with high speed and precision. It is unknown whether PNNs contribute to the fast-spiking ability of the neurons they surround. Whole-cell recordings were made from medial nucleus of the trapezoid body (MNTB) principal neurons in acute brain slices from postnatal day 21 (P21) to P27 mice. PNNs were degraded by incubating slices in chondroitinase ABC (ChABC) and were compared to slices that were treated with a control enzyme (penicillinase). ChABC treatment did not affect the ability of MNTB neurons to fire at up to 1000 Hz when driven by current pulses. However, f–I (frequency–intensity) curves constructed by injecting Gaussian white noise currents superimposed on DC current steps showed that ChABC treatment reduced the gain of spike output. An increase in spike threshold may have contributed to this effect, which is consistent with the observation that spikes in ChABC-treated cells were delayed relative to control-treated cells. In addition, parvalbumin-expressing fast-spiking cortical neurons in >P70 slices that were treated with ChABC also had reduced excitability and gain. The development of PNNs around somata of fast-spiking neurons may be essential for fast and precise sensory transmission and synaptic inhibition in the brain. PMID:27570824

  1. Finite transformers for construction of fractal curves

    SciTech Connect

    Lisovik, L.P.

    1995-01-01

    In this paper we continue the study of infinite R{sup n}-transformers that can be used to define real functions and three-dimensional curves. An R{sup n}-transformer A generates an output n-tuple A(x) = (Y{sub 1},...,Y{sub n}), consisting of output binary representations. We have previously shown that finite R{sup n}-transformers with n = 1, 2 can be used to define a continuous, nowhere differentiable function and a Peano curve. Curves of this kind are objects of fractal geometry. Here we show that some other fractal curves, which are analogs of the Koch curve and the Sierpinski napkin, can be defined by finite R{sup 2}-transformers. R{sup n}-transformers (and also finite R{sup n}-transformers) thus provide a convenient tool for definition of fractal curves.

  2. Deployment of a Curved Truss

    NASA Technical Reports Server (NTRS)

    Giersch, Louis R.; Knarr, Kevin

    2010-01-01

    Structures capable of deployment into complex, three-dimensional trusses have well known space technology applications such as the support of spacecraft payloads, communications antennas, radar reflectors, and solar concentrators. Such deployable trusses could also be useful in terrestrial applications such as the rapid establishment of structures in military and emergency service situations, in particular with regard to the deployment of enclosures for habitat or storage. To minimize the time required to deploy such an enclosure, a single arch-shaped truss is preferable to multiple straight trusses arranged vertically and horizontally. To further minimize the time required to deploy such an enclosure, a synchronous deployment with a single degree of freedom is also preferable. One method of synchronizing deployment of a truss is the use of a series of gears; this makes the deployment sequence predictable and testable, allows the truss to have a minimal stowage volume, and the deployed structure exhibits the excellent stiffness-to-mass and strength-to-mass ratios characteristic of a truss. A concept for using gears with varying ratios to deploy a truss into a curved shape has been developed and appears to be compatible with both space technology applications as well as potential use in terrestrial applications such as enclosure deployment. As is the case with other deployable trusses, this truss is formed using rigid elements (e.g., composite tubes) along the edges, one set of diagonal elements composed of either cables or folding/hinged rigid members, and the other set of diagonal elements formed by a continuous cable that is tightened by a motor or hand crank in order to deploy the truss. Gears of varying ratios are used to constrain the deployment to a single degree of freedom, making the deployment synchronous, predictable, and repeatable. The relative sizes of the gears and the relative dimensions of the diagonal elements determine the deployed geometry (e

  3. Nanoresolution radiology of neurons

    NASA Astrophysics Data System (ADS)

    Wu, H. R.; Chen, S. T.; Chu, Y. S.; Conley, R.; Bouet, N.; Chien, C. C.; Chen, H. H.; Lin, C. H.; Tung, H. T.; Chen, Y. S.; Margaritondo, G.; Je, J. H.; Hwu, Y.

    2012-06-01

    We report recent advances in hard-x-ray optics—including record spatial resolution—and in staining techniques that enable synchrotron microradiology to produce neurobiology images of quality comparable to electron and visible microscopy. In addition, microradiology offers excellent penetration and effective three-dimensional detection as required for many neuron studies. Our tests include tomographic reconstruction based on projection image sets.

  4. The Reliability of Neurons

    PubMed Central

    Bullock, Theodore Holmes

    1970-01-01

    The prevalent probabilistic view is virtually untestable; it remains a plausible belief. The cases usually cited can not be taken as evidence for it. Several grounds for this conclusion are developed. Three issues are distinguished in an attempt to clarify a murky debate: (a) the utility of probabilistic methods in data reduction, (b) the value of models that assume indeterminacy, and (c) the validity of the inference that the nervous system is largely indeterministic at the neuronal level. No exception is taken to the first two; the second is a private heuristic question. The third is the issue to which the assertion in the first two sentences is addressed. Of the two kinds of uncertainty, statistical mechanical (= practical unpredictability) as in a gas, and Heisenbergian indeterminancy, the first certainly exists, the second is moot at the neuronal level. It would contribute to discussion to recognize that neurons perform with a degree of reliability. Although unreliability is difficult to establish, to say nothing of measure, evidence that some neurons have a high degree of reliability, in both connections and activity is increasing greatly. An example is given from sternarchine electric fish. PMID:5462670

  5. Nanoresolution radiology of neurons

    SciTech Connect

    Wu, H. R.; Chen, S. T.; Chu, Y. S.; Conley, R.; Bouet, N.; Chien, C. C.; Chen, H. H.; Lin, C. H.; Tung, H. T.; Chen, Y. S.; Margaritondo, G.; Je, J. H.; Hwu, Y.

    2012-05-29

    We report recent advances in hard-x-ray optics—including record spatial resolution—and in staining techniques that enable synchrotron microradiology to produce neurobiology images of quality comparable to electron and visible microscopy. In addition, microradiology offers excellent penetration and effective three-dimensional detection as required for many neuron studies. Our tests include tomographic reconstruction based on projection image sets.

  6. Nanoresolution radiology of neurons

    SciTech Connect

    Wu, H.R.; Chen, S.T.; Chu, Y.S.; Conley, R.; Bouet, N.; Chien, C.C.; Chen, H.H.; Lin, C.H.; Tung, H.T.; Chen, Y.S.; Margaritondo, G.; Je, J.H.; Hwu, Y.

    2013-04-08

    We report recent advances in hard-x-ray optics - including record spatial resolution - and in staining techniques that enable synchrotron microradiology to produce neurobiology images of quality comparable to electron and visible microscopy. In addition, microradiology offers excellent penetration and effective three-dimensional detection as required for many neuron studies. Our tests include tomographic reconstruction based on projection image sets.

  7. Clustered protocadherins and neuronal diversity.

    PubMed

    Hirayama, Teruyoshi; Yagi, Takeshi

    2013-01-01

    Neuronal diversity is a fundamental requirement for complex neuronal networks and brain function. The clustered protocadherin (Pcdh) family possesses several characteristic features that are important for the molecular basis of neuronal diversity. Clustered Pcdhs are expressed predominantly in the central nervous system, in neurites, growth cones, and synapses. They consist of about 60 isoforms, and their expression is stochastically and combinatorially regulated in individual neurons. The multiple clustered Pcdhs expressed in individual neurons form heteromultimeric protein complexes that exhibit homophilic adhesion properties. Theoretically, the clustered Pcdhs could generate more than 3×10(10) possible variations in each neuron and 12,720 types of cis-tetramers per neuron. The clustered Pcdhs are important for normal neuronal development. The clustered Pcdh genes have also attracted attention as a target for epigenetic regulation.

  8. The Effects of Guanfacine and Phenylephrine on a Spiking Neuron Model of Working Memory.

    PubMed

    Duggins, Peter; Stewart, Terrence C; Choo, Xuan; Eliasmith, Chris

    2017-01-01

    We use a spiking neural network model of working memory (WM) capable of performing the spatial delayed response task (DRT) to investigate two drugs that affect WM: guanfacine (GFC) and phenylephrine (PHE). In this model, the loss of information over time results from changes in the spiking neural activity through recurrent connections. We reproduce the standard forgetting curve and then show that this curve changes in the presence of GFC and PHE, whose application is simulated by manipulating functional, neural, and biophysical properties of the model. In particular, applying GFC causes increased activity in neurons that are sensitive to the information currently being remembered, while applying PHE leads to decreased activity in these same neurons. Interestingly, these differential effects emerge from network-level interactions because GFC and PHE affect all neurons equally. We compare our model to both electrophysiological data from neurons in monkey dorsolateral prefrontal cortex and to behavioral evidence from monkeys performing the DRT.

  9. Dissociative Recombination without a Curve Crossing

    NASA Technical Reports Server (NTRS)

    Guberman, Steven L.

    1994-01-01

    Ab initio calculations show that a curve crossing is not always needed for a high dissociative- recombination cross section. For HeH(+), in which no neutral states cross the ion potential curve, dissociative recombination is driven by the nuclear kinetic-energy operator on adiabatic potential curves. The kinetic-energy derivative operator allows for capture into repulsive curves that are outside of the classical turning points for the nuclear motion. The dominant dissociative route is the C (2)Sigma(+) state leading to H(n = 2) atoms. An analogous mechanism is proposed for the dissociative recombination of H3(+).

  10. A kill curve for Phanerozoic marine species

    NASA Technical Reports Server (NTRS)

    Raup, D. M.

    1991-01-01

    A kill curve for Phanerozoic species is developed from an analysis of the stratigraphic ranges of 17,621 genera, as compiled by Sepkoski. The kill curve shows that a typical species' risk of extinction varies greatly, with most time intervals being characterized by very low risk. The mean extinction rate of 0.25/m.y. is thus a mixture of long periods of negligible extinction and occasional pulses of much higher rate. Because the kill curve is merely a description of the fossil record, it does not speak directly to the causes of extinction. The kill curve may be useful, however, to li inverted question markmit choices of extinction mechanisms.

  11. Craniofacial Reconstruction Using Rational Cubic Ball Curves

    PubMed Central

    Majeed, Abdul; Mt Piah, Abd Rahni; Gobithaasan, R. U.; Yahya, Zainor Ridzuan

    2015-01-01

    This paper proposes the reconstruction of craniofacial fracture using rational cubic Ball curve. The idea of choosing Ball curve is based on its robustness of computing efficiency over Bezier curve. The main steps are conversion of Digital Imaging and Communications in Medicine (Dicom) images to binary images, boundary extraction and corner point detection, Ball curve fitting with genetic algorithm and final solution conversion to Dicom format. The last section illustrates a real case of craniofacial reconstruction using the proposed method which clearly indicates the applicability of this method. A Graphical User Interface (GUI) has also been developed for practical application. PMID:25880632

  12. Alterations in oxidant/antioxidant balance, high-mobility group box 1 protein and acute phase response in cross-bred suckling piglets suffering from rotaviral enteritis.

    PubMed

    Kumar De, Ujjwal; Mukherjee, Reena; Nandi, Sukdeb; Patel, Bhimnere Hanumatnagouda Manjunatha; Dimri, Umesh; Ravishankar, Chintu; Verma, Ashok Kumar

    2014-10-01

    Rotaviral enteritis has emerged as a major cause of morbidity and mortality in piglets during their post-natal life. The present study was carried out to examine high-mobility group box 1 (HMGB1) protein, acute phase response and oxidative stress indices in the serum of suckling piglets suffering from enteritis with or without association of porcine group A rotavirus infection. The present investigation utilized 23 clinical cases with signs of acute enteritis and 12 more healthy piglets of a similar age group as control animals. Out of 23 enteritis cases, 12 cases were found to be positive for porcine group A rotavirus infection as confirmed by reverse transcription-polymerase chain reaction (RT-PCR) using specific primers for group A rotavirus, and the rest were found negative. The acute enteritis cases in piglets were associated with an elevated level of HMGB1 protein and serum haptoglobin and ceruloplasmin suggestive of an acute phase response. Among the oxidative stress indices, the concentrations of malondialdehyde (MDA) and nitric oxide (NO) in serum were significantly increased. A pronounced drop of total antioxidant capacity and the activity of antioxidant enzymes such as catalase and superoxide dismutase in the serum of piglets suffering from acute enteritis compared to healthy ones were also noticed. The alterations in HMGB1 protein, acute phase response and oxidative stress indices were more pronounced in cases with the involvement of porcine rotavirus as compared to rotavirus-negative cases. It is concluded that HMGB1 protein, markers of oxidative stress and acute phase proteins might play an important role in the aetiopathogenesis of porcine diarrhoea caused by rotavirus and might be true markers in diagnosing the conditions leading to the extension of the prompt and effective therapeutic care.

  13. Neuronal cell cycle: the neuron itself and its circumstances.

    PubMed

    Frade, José M; Ovejero-Benito, María C

    2015-01-01

    Neurons are usually regarded as postmitotic cells that undergo apoptosis in response to cell cycle reactivation. Nevertheless, recent evidence indicates the existence of a defined developmental program that induces DNA replication in specific populations of neurons, which remain in a tetraploid state for the rest of their adult life. Similarly, de novo neuronal tetraploidization has also been described in the adult brain as an early hallmark of neurodegeneration. The aim of this review is to integrate these recent developments in the context of cell cycle regulation and apoptotic cell death in neurons. We conclude that a variety of mechanisms exists in neuronal cells for G1/S and G2/M checkpoint regulation. These mechanisms, which are connected with the apoptotic machinery, can be modulated by environmental signals and the neuronal phenotype itself, thus resulting in a variety of outcomes ranging from cell death at the G1/S checkpoint to full proliferation of differentiated neurons.

  14. LASER APPLICATIONS AND OTHER TOPICS IN LASER TECHNOLOGY: Influence of transitions between excited singlet and triplet states on the phase response of dye solutions

    NASA Astrophysics Data System (ADS)

    Kabanov, V. V.; Rubanov, A. S.; Tolstik, A. L.

    1988-08-01

    An investigation is made of the transitions between excited singlet and triplet states, and of the effects of stereoisomerism molecules on the light-induced change in the refractive index of a dye solution. It is shown that the contribution of the ground and excited channels to the total phase response varies within a wide range depending on the spectroscopic characteristics of the medium and the parameters of the exciting radiation. An estimate is obtained of the ratio of the contributions of the resonant and thermal nonlinearities to the total change in the refractive index.

  15. Forces in the complex octonion curved space

    NASA Astrophysics Data System (ADS)

    Weng, Zi-Hua

    2016-04-01

    The paper aims to extend major equations in the electromagnetic and gravitational theories from the flat space into the complex octonion curved space. Maxwell applied simultaneously the quaternion analysis and vector terminology to describe the electromagnetic theory. It inspires subsequent scholars to study the electromagnetic and gravitational theories with the complex quaternions/octonions. Furthermore Einstein was the first to depict the gravitational theory by means of tensor analysis and curved four-space-time. Nowadays some scholars investigate the electromagnetic and gravitational properties making use of the complex quaternion/octonion curved space. From the orthogonality of two complex quaternions, it is possible to define the covariant derivative of the complex quaternion curved space, describing the gravitational properties in the complex quaternion curved space. Further it is possible to define the covariant derivative of the complex octonion curved space by means of the orthogonality of two complex octonions, depicting simultaneously the electromagnetic and gravitational properties in the complex octonion curved space. The result reveals that the connection coefficient and curvature of the complex octonion curved space will exert an influence on the field strength and field source of the electromagnetic and gravitational fields, impacting the linear momentum, angular momentum, torque, energy, and force and so forth.

  16. Electrical-Discharge Machining Of Curved Passages

    NASA Technical Reports Server (NTRS)

    Guirguis, Kamal S.

    1993-01-01

    Electrical-discharge machining (EDM) used to cut deep hole with bends. EDM process done with articulating segmented electrode. Originally straight, electrode curved as it penetrates part, forming long, smoothly curving hole. After hole cut, honed with slurry to remove thin layer of recast metal created by EDM. Breakage of tools, hand deburring, and drilling debris eliminated.

  17. Mixture Modeling of Individual Learning Curves

    ERIC Educational Resources Information Center

    Streeter, Matthew

    2015-01-01

    We show that student learning can be accurately modeled using a mixture of learning curves, each of which specifies error probability as a function of time. This approach generalizes Knowledge Tracing [7], which can be viewed as a mixture model in which the learning curves are step functions. We show that this generality yields order-of-magnitude…

  18. Cost Curves and How They Relate.

    ERIC Educational Resources Information Center

    Mixon, J. Wilson; Tohemy, Soumaya M.

    2002-01-01

    Describes a Web site that contains Microsoft Excel workbooks that draft consistent short-run and long-run cost curves and the text describing them. Details a common error in representing the curves. Reports that the Web site also presents revenues and profits for a price taker and a price maker. (JEH)

  19. Forgetting Curves: Implications for Connectionist Models

    ERIC Educational Resources Information Center

    Sikstrom, Sverker

    2002-01-01

    Forgetting in long-term memory, as measured in a recall or a recognition test, is faster for items encoded more recently than for items encoded earlier. Data on forgetting curves fit a power function well. In contrast, many connectionist models predict either exponential decay or completely flat forgetting curves. This paper suggests a…

  20. Parallel Curves: Getting There and Getting Back

    ERIC Educational Resources Information Center

    Agnew, A. F.; Mathews, J. H.

    2006-01-01

    This note takes up the issue of parallel curves while illustrating the utility of "Mathematica" in computations. This work complements results presented earlier. The presented treatment, considering the more general case of parametric curves, provides an analysis of the appearance of cusp singularities, and emphasizes the utility of symbolic…

  1. Measuring Model Rocket Engine Thrust Curves

    ERIC Educational Resources Information Center

    Penn, Kim; Slaton, William V.

    2010-01-01

    This paper describes a method and setup to quickly and easily measure a model rocket engine's thrust curve using a computer data logger and force probe. Horst describes using Vernier's LabPro and force probe to measure the rocket engine's thrust curve; however, the method of attaching the rocket to the force probe is not discussed. We show how a…

  2. Remote sensing used for power curves

    NASA Astrophysics Data System (ADS)

    Wagner, R.; Jørgensen, H. E.; Paulsen, U. S.; Larsen, T. J.; Antoniou, I.; Thesbjerg, L.

    2008-05-01

    : Power curve measurement for large wind turbines requires taking into account more parameters than only the wind speed at hub height. Based on results from aerodynamic simulations, an equivalent wind speed taking the wind shear into account was defined and found to reduce the power standard deviation in the power curve significantly. Two LiDARs and a SoDAR are used to measure the wind profile in front of a wind turbine. These profiles are used to calculate the equivalent wind speed. The comparison of the power curves obtained with the three instruments to the traditional power curve, obtained using a cup anemometer measurement, confirms the results obtained from the simulations. Using LiDAR profiles reduces the error in power curve measurement, when these are used as relative instrument together with a cup anemometer. Results from the SoDAR do not show such promising results, probably because of noisy measurements resulting in distorted profiles.

  3. Curved and conformal high-pressure vessel

    SciTech Connect

    Croteau, Paul F.; Kuczek, Andrzej E.; Zhao, Wenping

    2016-10-25

    A high-pressure vessel is provided. The high-pressure vessel may comprise a first chamber defined at least partially by a first wall, and a second chamber defined at least partially by the first wall. The first chamber and the second chamber may form a curved contour of the high-pressure vessel. A modular tank assembly is also provided, and may comprise a first mid tube having a convex geometry. The first mid tube may be defined by a first inner wall, a curved wall extending from the first inner wall, and a second inner wall extending from the curved wall. The first inner wall may be disposed at an angle relative to the second inner wall. The first mid tube may further be defined by a short curved wall opposite the curved wall and extending from the second inner wall to the first inner wall.

  4. Dose-response curve for anaesthetics based on the Monod-Wyman-Changeux model.

    PubMed

    Iwai, T; Kihara, H; Imaiand, K; Uchida, M

    1996-10-01

    We have analysed the dose-response curve for halothane and isoflurane according to the Monod-Wyman-Changeux (MWC) model. This model describes the nature of the physiological data reported by Wakamori, Ikemoto and Akaike for inhibitory Cl currents induced by GABA or glycine in dissociated rat brain neurones and by Herrington and colleagues for Ca2+ currents in clonal pituitary cells. With some assumptions on the difference in response to anaesthetics between patients, the model is applicable in vivo, and it also describes well the human dose-response curve for isoflurane reported by Mather, Raftery and Prys-Roberts. However, the steeply sigmoidal dose-response curve in humans for halothane presented by deJong and Eger is difficult to understand with the same model, because it gives rise to unrealistic MWC variables.

  5. Add neurons, subtract anxiety

    PubMed Central

    Kheirbek, Mazen A.; Hen, René

    2014-01-01

    IN BRIEF To keep memories from becoming jumbled, the brain must encode the distinct features of events and situations in a way that allows them to be distinguished from one another—a process called pattern separation. Pattern separation enables us to distinguish dangerous situations from similar ones that pose no risk. People with defects in this ability may be prone to anxiety disorders. The process occurs in one of the two regions of the brain that generate neurons throughout life. These fledgling cells seem to be critical to pattern separation. Interventions that specifically boost the ranks of rookie neurons could provide new ways to regulate mood and possibly treat conditions such as post-traumatic stress disorder. PMID:24974712

  6. Micropatterning neuronal networks.

    PubMed

    Hardelauf, Heike; Waide, Sarah; Sisnaiske, Julia; Jacob, Peter; Hausherr, Vanessa; Schöbel, Nicole; Janasek, Dirk; van Thriel, Christoph; West, Jonathan

    2014-07-07

    Spatially organised neuronal networks have wide reaching applications, including fundamental research, toxicology testing, pharmaceutical screening and the realisation of neuronal implant interfaces. Despite the large number of methods catalogued in the literature there remains the need to identify a method that delivers high pattern compliance, long-term stability and is widely accessible to neuroscientists. In this comparative study, aminated (polylysine/polyornithine and aminosilanes) and cytophobic (poly(ethylene glycol) (PEG) and methylated) material contrasts were evaluated. Backfilling plasma stencilled PEGylated substrates with polylysine does not produce good material contrasts, whereas polylysine patterned on methylated substrates becomes mobilised by agents in the cell culture media which results in rapid pattern decay. Aminosilanes, polylysine substitutes, are prone to hydrolysis and the chemistries prove challenging to master. Instead, the stable coupling between polylysine and PLL-g-PEG can be exploited: Microcontact printing polylysine onto a PLL-g-PEG coated glass substrate provides a simple means to produce microstructured networks of primary neurons that have superior pattern compliance during long term (>1 month) culture.

  7. The frequency preference of neurons and synapses in a recurrent oscillatory network.

    PubMed

    Tseng, Hua-an; Martinez, Diana; Nadim, Farzan

    2014-09-17

    A variety of neurons and synapses shows a maximal response at a preferred frequency, generally considered to be important in shaping network activity. We are interested in whether all neurons and synapses in a recurrent oscillatory network can have preferred frequencies and, if so, whether these frequencies are the same or correlated, and whether they influence the network activity. We address this question using identified neurons in the pyloric network of the crab Cancer borealis. Previous work has shown that the pyloric pacemaker neurons exhibit membrane potential resonance whose resonance frequency is correlated with the network frequency. The follower lateral pyloric (LP) neuron makes reciprocally inhibitory synapses with the pacemakers. We find that LP shows resonance at a higher frequency than the pacemakers and the network frequency falls between the two. We also find that the reciprocal synapses between the pacemakers and LP have preferred frequencies but at significantly lower values. The preferred frequency of the LP to pacemaker synapse is correlated with the presynaptic preferred frequency, which is most pronounced when the peak voltage of the LP waveform is within the dynamic range of the synaptic activation curve and a shift in the activation curve by the modulatory neuropeptide proctolin shifts the frequency preference. Proctolin also changes the power of the LP neuron resonance without significantly changing the resonance frequency. These results indicate that different neuron types and synapses in a network may have distinct preferred frequencies, which are subject to neuromodulation and may interact to shape network oscillations.

  8. Statistical aspects of modeling the labor curve.

    PubMed

    Zhang, Jun; Troendle, James; Grantz, Katherine L; Reddy, Uma M

    2015-06-01

    In a recent review by Cohen and Friedman, several statistical questions on modeling labor curves were raised. This article illustrates that asking data to fit a preconceived model or letting a sufficiently flexible model fit observed data is the main difference in principles of statistical modeling between the original Friedman curve and our average labor curve. An evidence-based approach to construct a labor curve and establish normal values should allow the statistical model to fit observed data. In addition, the presence of the deceleration phase in the active phase of an average labor curve was questioned. Forcing a deceleration phase to be part of the labor curve may have artificially raised the speed of progression in the active phase with a particularly large impact on earlier labor between 4 and 6 cm. Finally, any labor curve is illustrative and may not be instructive in managing labor because of variations in individual labor pattern and large errors in measuring cervical dilation. With the tools commonly available, it may be more productive to establish a new partogram that takes the physiology of labor and contemporary obstetric population into account.

  9. Three-body choreographies in given curves

    NASA Astrophysics Data System (ADS)

    Ozaki, Hiroshi; Fukuda, Hiroshi; Fujiwara, Toshiaki

    2009-10-01

    As shown by Johannes Kepler in 1609, in the two-body problem, the shape of the orbit, a given ellipse, and a given non-vanishing constant angular momentum determine the motion of the planet completely. Even in the three-body problem, in some cases, the shape of the orbit, conservation of the center of mass and a constant of motion (the angular momentum or the total energy) determine the motion of the three bodies. We show, by a geometrical method, that choreographic motions, in which equal mass three bodies chase each other around the same curve, will be uniquely determined for the following two cases. (i) Convex curves that have point symmetry and non-vanishing angular momentum are given. (ii) Eight-shaped curves which are similar to the curve for the figure-eight solution and the energy constant are given. The reality of the motion should be tested whether the motion satisfies an equation of motion or not. Extensions of the method for generic curves are shown. The extended methods are applicable to generic curves which do not have point symmetry. Each body may have its own curve and its own non-vanishing masses.

  10. Investigation of learning and experience curves

    SciTech Connect

    Krawiec, F.; Thornton, J.; Edesess, M.

    1980-04-01

    The applicability of learning and experience curves for predicting future costs of solar technologies is assessed, and the major test case is the production economics of heliostats. Alternative methods for estimating cost reductions in systems manufacture are discussed, and procedures for using learning and experience curves to predict costs are outlined. Because adequate production data often do not exist, production histories of analogous products/processes are analyzed and learning and aggregated cost curves for these surrogates estimated. If the surrogate learning curves apply, they can be used to estimate solar technology costs. The steps involved in generating these cost estimates are given. Second-generation glass-steel and inflated-bubble heliostat design concepts, developed by MDAC and GE, respectively, are described; a costing scenario for 25,000 units/yr is detailed; surrogates for cost analysis are chosen; learning and aggregate cost curves are estimated; and aggregate cost curves for the GE and MDAC designs are estimated. However, an approach that combines a neoclassical production function with a learning-by-doing hypothesis is needed to yield a cost relation compatible with the historical learning curve and the traditional cost function of economic theory.

  11. Generating artificial light curves: revisited and updated

    NASA Astrophysics Data System (ADS)

    Emmanoulopoulos, D.; McHardy, I. M.; Papadakis, I. E.

    2013-08-01

    The production of artificial light curves with known statistical and variability properties is of great importance in astrophysics. Consolidating the confidence levels during cross-correlation studies, understanding the artefacts induced by sampling irregularities, establishing detection limits for future observatories are just some of the applications of simulated data sets. Currently, the widely used methodology of amplitude and phase randomization is able to produce artificial light curves which have a given underlying power spectral density (PSD) but which are strictly Gaussian distributed. This restriction is a significant limitation, since the majority of the light curves, e.g. active galactic nuclei, X-ray binaries, gamma-ray bursts, show strong deviations from Gaussianity exhibiting `burst-like' events in their light curves yielding long-tailed probability density functions (PDFs). In this study, we propose a simple method which is able to precisely reproduce light curves which match both the PSD and the PDF of either an observed light curve or a theoretical model. The PDF can be representative of either the parent distribution or the actual distribution of the observed data, depending on the study to be conducted for a given source. The final artificial light curves contain all of the statistical and variability properties of the observed source or theoretical model, i.e. the same PDF and PSD, respectively. Within the framework of Reproducible Research, the code and the illustrative example used in this paper are both made publicly available in the form of an interactive MATHEMATICA notebook.

  12. Existence and stability criteria for phase-locked modes in ring neural networks based on the spike time resetting curve method.

    PubMed

    Oprisan, Sorinel Adrian

    2010-01-21

    We developed a systematic and consistent mathematical approach to predicting 1:1 phase-locked modes in ring neural networks of spiking neurons based on the open loop spike time resetting curve (STRC) and its almost equivalent counterpart-the phase resetting curve (PRC). The open loop STRCs/PRCs were obtained by injecting into an isolated model neuron a triangular shaped time-dependent stimulus current closely resembling an actual synaptic input. Among other advantages, the STRC eliminates the confusion regarding the undefined phase for stimuli driving the neuron outside of the unperturbed limit cycle. We derived both open loop PRC and STRC-based existence and stability criteria for 1:1 phase-locked modes developed in ring networks of spiking neurons. Our predictions were in good agreement with the closed loop numerical simulations. Intuitive graphical methods for predicting phase-locked modes were also developed both for half-centers and for larger ring networks.

  13. Parvalbumin+ Neurons and Npas1+ Neurons Are Distinct Neuron Classes in the Mouse External Globus Pallidus

    PubMed Central

    Hernández, Vivian M.; Hegeman, Daniel J.; Cui, Qiaoling; Kelver, Daniel A.; Fiske, Michael P.; Glajch, Kelly E.; Pitt, Jason E.; Huang, Tina Y.; Justice, Nicholas J.

    2015-01-01

    Compelling evidence suggests that pathological activity of the external globus pallidus (GPe), a nucleus in the basal ganglia, contributes to the motor symptoms of a variety of movement disorders such as Parkinson's disease. Recent studies have challenged the idea that the GPe comprises a single, homogenous population of neurons that serves as a simple relay in the indirect pathway. However, we still lack a full understanding of the diversity of the neurons that make up the GPe. Specifically, a more precise classification scheme is needed to better describe the fundamental biology and function of different GPe neuron classes. To this end, we generated a novel multicistronic BAC (bacterial artificial chromosome) transgenic mouse line under the regulatory elements of the Npas1 gene. Using a combinatorial transgenic and immunohistochemical approach, we discovered that parvalbumin-expressing neurons and Npas1-expressing neurons in the GPe represent two nonoverlapping cell classes, amounting to 55% and 27% of the total GPe neuron population, respectively. These two genetically identified cell classes projected primarily to the subthalamic nucleus and to the striatum, respectively. Additionally, parvalbumin-expressing neurons and Npas1-expressing neurons were distinct in their autonomous and driven firing characteristics, their expression of intrinsic ion conductances, and their responsiveness to chronic 6-hydroxydopamine lesion. In summary, our data argue that parvalbumin-expressing neurons and Npas1-expressing neurons are two distinct functional classes of GPe neurons. This work revises our understanding of the GPe, and provides the foundation for future studies of its function and dysfunction. SIGNIFICANCE STATEMENT Until recently, the heterogeneity of the constituent neurons within the external globus pallidus (GPe) was not fully appreciated. We addressed this knowledge gap by discovering two principal GPe neuron classes, which were identified by their nonoverlapping

  14. Stimulus features coded by single neurons of a macaque body category selective patch.

    PubMed

    Popivanov, Ivo D; Schyns, Philippe G; Vogels, Rufin

    2016-04-26

    Body category-selective regions of the primate temporal cortex respond to images of bodies, but it is unclear which fragments of such images drive single neurons' responses in these regions. Here we applied the Bubbles technique to the responses of single macaque middle superior temporal sulcus (midSTS) body patch neurons to reveal the image fragments the neurons respond to. We found that local image fragments such as extremities (limbs), curved boundaries, and parts of the torso drove the large majority of neurons. Bubbles revealed the whole body in only a few neurons. Neurons coded the features in a manner that was tolerant to translation and scale changes. Most image fragments were excitatory but for a few neurons both inhibitory and excitatory fragments (opponent coding) were present in the same image. The fragments we reveal here in the body patch with Bubbles differ from those suggested in previous studies of face-selective neurons in face patches. Together, our data indicate that the majority of body patch neurons respond to local image fragments that occur frequently, but not exclusively, in bodies, with a coding that is tolerant to translation and scale. Overall, the data suggest that the body category selectivity of the midSTS body patch depends more on the feature statistics of bodies (e.g., extensions occur more frequently in bodies) than on semantics (bodies as an abstract category).

  15. Are driving and overtaking on right curves more dangerous than on left curves?

    PubMed

    Othman, Sarbaz; Thomson, Robert; Lannér, Gunnar

    2010-01-01

    It is well known that crashes on horizontal curves are a cause for concern in all countries due to the frequency and severity of crashes at curves compared to road tangents. A recent study of crashes in western Sweden reported a higher rate of crashes in right curves than left curves. To further understand this result, this paper reports the results of novel analyses of the responses of vehicles and drivers during negotiating and overtaking maneuvers on curves for right hand traffic. The overall objectives of the study were to find road parameters for curves that affect vehicle dynamic responses, to analyze these responses during overtaking maneuvers on curves, and to link the results with driver behavior for different curve directions. The studied road features were speed, super-elevation, radius and friction including their interactions, while the analyzed vehicle dynamic factors were lateral acceleration and yaw angular velocity. A simulation program, PC-Crash, has been used to simulate road parameters and vehicle response interaction in curves. Overtaking maneuvers have been simulated for all road feature combinations in a total of 108 runs. Analysis of variances (ANOVA) was performed, using two sided randomized block design, to find differences in vehicle responses for the curve parameters. To study driver response, a field test using an instrumented vehicle and 32 participants was reviewed as it contained longitudinal speed and acceleration data for analysis. The simulation results showed that road features affect overtaking performance in right and left curves differently. Overtaking on right curves was sensitive to radius and the interaction of radius with road condition; while overtaking on left curves was more sensitive to super-elevation. Comparisons of lateral acceleration and yaw angular velocity during these maneuvers showed different vehicle response configurations depending on curve direction and maneuver path. The field test experiments also showed

  16. Optoacoustic endoscopy in curved scanning mode

    NASA Astrophysics Data System (ADS)

    He, Hailong; Buehler, Andreas; Ntziachristos, Vasilis

    2016-03-01

    Optoacoustic technique has been shown to resolve anatomical, functional and molecular features at depths that go beyond the reach of epi-illumination optical microscopy offering new opportunities for endoscopic imaging. Herein, we interrogate the merits of optoacoustic endoscopy implemented by translating a sound detector in linear or curved geometries. The linear and curved detection geometries are achieved by employing an intravascular ultrasound transducer (IVUS) within a plastic guide shaped to a line or a curve. This concept could be used together with optical endoscopes to yield hybrid optical and optoacoustic imaging.

  17. Approximation of Dynamical System's Separatrix Curves

    NASA Astrophysics Data System (ADS)

    Cavoretto, Roberto; Chaudhuri, Sanjay; De Rossi, Alessandra; Menduni, Eleonora; Moretti, Francesca; Rodi, Maria Caterina; Venturino, Ezio

    2011-09-01

    In dynamical systems saddle points partition the domain into basins of attractions of the remaining locally stable equilibria. This problem is rather common especially in population dynamics models, like prey-predator or competition systems. In this paper we construct programs for the detection of points lying on the separatrix curve, i.e. the curve which partitions the domain. Finally, an efficient algorithm, which is based on the Partition of Unity method with local approximants given by Wendland's functions, is used for reconstructing the separatrix curve.

  18. Linear instability of curved free shear layers

    NASA Technical Reports Server (NTRS)

    Liou, William W.

    1993-01-01

    The linear inviscid hydrodynamic stability of slightly curved free mixing layers is studied in this paper. The disturbance equation is solved numerically using a shooting technique. Two mean velocity profiles that represent stably and unstably curved free mixing layers are considered. Results are shown for cases of five curvature Richardson numbers. The stability characteristics of the shear layer are found to vary significantly with the introduction of the curvature effects. The results also indicate that, in a manner similar to the Goertler vortices observed in a boundary layer along a concave wall, instability modes of spatially developing streamwise vortex pairs may appear in centrifugally unstable curved mixing layers.

  19. Heterogeneous Potassium Conductances Contribute to the Diverse Firing Properties of Postnatal Mouse Vestibular Ganglion Neurons

    PubMed Central

    Risner, Jessica R.; Holt, Jeffrey R.

    2009-01-01

    How mechanical information is encoded in the vestibular periphery has not been clarified. To begin to address the issue we examined the intrinsic firing properties of postnatal mouse vestibular ganglion neurons using the whole cell, tight-seal technique in current-clamp mode. We categorized two populations of neurons based on the threshold required to evoke an action potential. Low-threshold neurons fired with an average minimum current injection of −43 pA, whereas high-threshold neurons required −176 pA. Using sine-wave stimuli, we found that the neurons were inherently tuned with best frequencies that ranged up to 40 Hz. To investigate the membrane properties that contributed to the variability in firing properties we examined the same neurons in voltage-clamp mode. High-threshold neurons had larger cell bodies and whole cell capacitances but a resting conductance density of 0.18 nS/pF, nearly identical to that of low-threshold neurons, suggesting that cell size was an important parameter determining threshold. We also found that vestibular ganglion neurons expressed a heterogeneous population of potassium conductances. TEA-sensitive conductances contributed to the position of the tuning curve in the frequency domain. A 4-AP–sensitive conductance was active at rest and hyperpolarized resting potential, limited spontaneous activity, raised threshold, and prevented repetitive firing. In response to sine-wave stimulation 4-AP–sensitive conductances prevented action potential generation at low frequencies and thus contributed to the high-pass corner of the tuning curve. The mean low-pass corner (about 29 Hz) was determined by the membrane time constant. Together these factors contributed to the sharply tuned, band-pass characteristics intrinsic to postnatal vestibular ganglion neurons. PMID:16855108

  20. Heterogeneous potassium conductances contribute to the diverse firing properties of postnatal mouse vestibular ganglion neurons.

    PubMed

    Risner, Jessica R; Holt, Jeffrey R

    2006-11-01

    How mechanical information is encoded in the vestibular periphery has not been clarified. To begin to address the issue we examined the intrinsic firing properties of postnatal mouse vestibular ganglion neurons using the whole cell, tight-seal technique in current-clamp mode. We categorized two populations of neurons based on the threshold required to evoke an action potential. Low-threshold neurons fired with an average minimum current injection of -43 pA, whereas high-threshold neurons required -176 pA. Using sine-wave stimuli, we found that the neurons were inherently tuned with best frequencies that ranged up to 40 Hz. To investigate the membrane properties that contributed to the variability in firing properties we examined the same neurons in voltage-clamp mode. High-threshold neurons had larger cell bodies and whole cell capacitances but a resting conductance density of 0.18 nS/pF, nearly identical to that of low-threshold neurons, suggesting that cell size was an important parameter determining threshold. We also found that vestibular ganglion neurons expressed a heterogeneous population of potassium conductances. TEA-sensitive conductances contributed to the position of the tuning curve in the frequency domain. A 4-AP-sensitive conductance was active at rest and hyperpolarized resting potential, limited spontaneous activity, raised threshold, and prevented repetitive firing. In response to sine-wave stimulation 4-AP-sensitive conductances prevented action potential generation at low frequencies and thus contributed to the high-pass corner of the tuning curve. The mean low-pass corner (about 29 Hz) was determined by the membrane time constant. Together these factors contributed to the sharply tuned, band-pass characteristics intrinsic to postnatal vestibular ganglion neurons.

  1. Transmission of wave energy in curved ducts

    NASA Technical Reports Server (NTRS)

    Rostafinski, W.

    1973-01-01

    A formation of wave energy flow was developed for motion in curved ducts. A parametric study over a range of frequencies determined the ability of circular bends to transmit energy for the case of perfectly rigid walls.

  2. Solid-state curved focal plane arrays

    NASA Technical Reports Server (NTRS)

    Nikzad, Shouleh (Inventor); Hoenk, Michael (Inventor); Jones, Todd (Inventor)

    2010-01-01

    The present invention relates to curved focal plane arrays. More specifically, the present invention relates to a system and method for making solid-state curved focal plane arrays from standard and high-purity devices that may be matched to a given optical system. There are two ways to make a curved focal plane arrays starting with the fully fabricated device. One way, is to thin the device and conform it to a curvature. A second way, is to back-illuminate a thick device without making a thinned membrane. The thick device is a special class of devices; for example devices fabricated with high purity silicon. One surface of the device (the non VLSI fabricated surface, also referred to as the back surface) can be polished to form a curved surface.

  3. Modeling Type IIn Supernova Light Curves

    NASA Astrophysics Data System (ADS)

    De La Rosa, Janie; Roming, Peter; Fryer, Chris

    2016-01-01

    We present near-by Type IIn supernovae observed with Swift's Ultraviolet/Optical Telescope (UVOT). Based on the diversity of optical light curve properties, this Type II subclass is commonly referred to as heterogeneous. At the time of discovery, our IIn sample is ~ 2 magnitudes brighter at ultraviolet wavelengths than at optical wavelengths, and ultraviolet brightness decays faster than the optical brightness. We use a semi-analytical supernova (SN) model to better understand our IIn observations, and focus on matching specific observed light curves features, i.e peak luminosity and decay rate. The SN models are used to study the effects of initial SN conditions on early light curves, and to show the extent of the "uniqueness" problem in SN light curves. We gratefully acknowledge the contributions from members of the Swift UVOT team, the NASA astrophysics archival data analysis program, and the NASA Swift guest investigator program.

  4. Classification of ASKAP Vast Radio Light Curves

    NASA Technical Reports Server (NTRS)

    Rebbapragada, Umaa; Lo, Kitty; Wagstaff, Kiri L.; Reed, Colorado; Murphy, Tara; Thompson, David R.

    2012-01-01

    The VAST survey is a wide-field survey that observes with unprecedented instrument sensitivity (0.5 mJy or lower) and repeat cadence (a goal of 5 seconds) that will enable novel scientific discoveries related to known and unknown classes of radio transients and variables. Given the unprecedented observing characteristics of VAST, it is important to estimate source classification performance, and determine best practices prior to the launch of ASKAP's BETA in 2012. The goal of this study is to identify light curve characterization and classification algorithms that are best suited for archival VAST light curve classification. We perform our experiments on light curve simulations of eight source types and achieve best case performance of approximately 90% accuracy. We note that classification performance is most influenced by light curve characterization rather than classifier algorithm.

  5. Asymmetry Dependence of the Nuclear Caloric Curve

    NASA Astrophysics Data System (ADS)

    McIntosh, A. B.; Bonasera, A.; Cammarata, P.; Hagel, K.; Heilborn, L.; Kohley, Z.; Mabiala, J.; May, L. W.; Marini, P.; Raphelt, A.; Souliotis, G. A.; Wuenschel, S.; Zarrella, A.; Yennello, S. J.

    2013-03-01

    A basic feature of the nuclear equation of state is not yet understood: the dependence of the nuclear caloric curve on the neutron-proton asymmetry. Predictions of theoretical models differ on the magnitude and even the sign of this dependence. In this work, the nuclear caloric curve is examined for fully reconstructed quasi-projectiles around mass A = 50. Two independent thermometers, the momentum quadrupole fluctuation thermometer and the Albergo yield ratio thermometer, are used to extract the caloric curve. For both methods, the caloric curve extracted shows that the temperature varies linearly with quasi-projectile asymmetry For the momentum quadrupole fluctuation thermometer, an increase in asymmetry of 0.15 units corresponds to a decrease in temperature on the order of 1 MeV. These results also highlight the importance of a full quasi-projectile reconstruction in the study of thermodynamic properties of hot nuclei.

  6. Interactions of neurons with topographic nano cues affect branching morphology mimicking neuron-neuron interactions.

    PubMed

    Baranes, Koby; Kollmar, Davida; Chejanovsky, Nathan; Sharoni, Amos; Shefi, Orit

    2012-08-01

    We study the effect of topographic nano-cues on neuronal growth-morphology using invertebrate neurons in culture. We use photolithography to fabricate substrates with repeatable line-pattern ridges of nano-scale heights of 10-150 nm. We plate leech neurons atop the patterned-substrates and compare their growth pattern to neurons plated atop non-patterned substrates. The model system allows us the analysis of single neurite-single ridge interactions. The use of high resolution electron microscopy reveals small filopodia processes that attach to the line-pattern ridges. These fine processes, that cannot be detected in light microscopy, add anchoring sites onto the side of the ridges, thus additional physical support. These interactions of the neuronal process dominantly affect the neuronal growth direction. We analyze the response of the entire neuronal branching tree to the patterned substrates and find significant effect on the growth patterns compared to non-patterned substrates. Moreover, interactions with the nano-cues trigger a growth strategy similarly to interactions with other neuronal cells, as reflected in their morphometric parameters. The number of branches and the number of neurites originating from the soma decrease following the interaction demonstrating a tendency to a more simplified neuronal branching tree. The effect of the nano-cues on the neuronal function deserves further investigation and will strengthen our understanding of the interplay between function and form.

  7. The onset of the progression of acute phase response mechanisms induced by extreme impacts can be followed by the decrease in blood levels of positive acute phase proteins.

    NASA Astrophysics Data System (ADS)

    Larina, Olga; Bekker, Anna

    Studies performed at space flights and earth-based simulation models detected the plasma indices of acute phase reaction (APR), i.e. the increase of APR cytokine mediators and alterations in the production of blood acute phase proteins (APP) at the initial stages of adaptation to altered gravity conditions. Acute phase response is the principal constituent of the functional activity of innate immunity system. Changes in plasma APPs contents are considered to serve the restoration of homeostasis state. According to trends of their concentration shifts at the evolving of acute phase reaction APPs are denoted as positive, neutral, or negative. Plasma concentrations of positive acute phase proteins α1-acid glycoprotein (α1-AGP), α1-antitrypsin (α1-AT), and neutral α2-macroglobulin (α2-M) were measured in human study at 12-hour antiorthostatic position (AOP) with 15° head down tilt and hypoxia experiments at 14% oxygen in pressure chamber. Both of these impacts were shown to produce alterations in the APP levels indicative for acute phase response. Nevertheless, in AOP experiment noticeable decrease in α1-AGP concentration occurred by hour 12, and even more pronounced decline of α1-AGP and α1-AT were found on hypoxia hours 12 and 36. Acute phase proteins α1-AGP and α2-M possess the features of proteinase inhibitors. This function is implemented by the formation of complexes with the molecules of proteolytic enzymes which subsequently are removed from the blood flow. Transient decrease in plasma concentrations of protease inhibitors on early phases of APR development was reported to result from the growth of plasma protease activity due to cathepsin release from activated leukocytes, which had not yet been compensated by enhanced APP synthesis. Being a carrier protein for positively charged and neutral substances, α1-AGP shows pronounced elevation in its blood content during APR development. As assumed, it is required for the transportation of the increased

  8. Melatonin entrains free-running blind people according to a physiological dose-response curve.

    PubMed

    Lewy, Alfred J; Emens, Jonathan S; Lefler, Bryan J; Yuhas, Krista; Jackman, Angela R

    2005-01-01

    The specific circadian role proposed for endogenous melatonin production was based on a study of sighted people who took low pharmacological doses (500 microg) of this chemical signal for the "biological night": the magnitude and direction of the induced phase shifts were dependent on what time of day exogenous melatonin was administered and were described by a phase-response curve that turned out to be the opposite of that for light. We now report that lower (physiological) doses of up to 300 microg can entrain (synchronize) free-running circadian rhythms of 10 totally blind subjects that would otherwise drift later each day. The resulting log-linear dose-response curve in the physiological range adds support for a circadian function of endogenous melatonin in humans. Efficacy of exogenous doses in the physiological range are of clinical significance for totally blind people who will need to take melatonin daily over their entire lifetimes in order to remain entrained to the 24 h day. Left untreated, their free-running endocrine, metabolic, behavioral, and sleep/wake cycles can be almost as burdensome as not having vision.

  9. Characterization of Ca(2+) channels in rat subthalamic nucleus neurons.

    PubMed

    Song, W J; Baba, Y; Otsuka, T; Murakami, F

    2000-11-01

    The subthalamic nucleus (STN) plays a key role in motor control. Although previous studies have suggested that Ca(2+) conductances may be involved in regulating the activity of STN neurons, Ca(2+) channels in this region have not yet been characterized. We have therefore investigated the subtypes and functional characteristics of Ca(2+) conductances in STN neurons, in both acutely isolated and slice preparations. Acutely isolated STN cells were identified by retrograde filling with the fluorescent dye, Fluoro-Gold. In acutely isolated STN neurons, Cd(2+)-sensitive, depolarization-activated Ba(2+) currents were observed in all cells studied. The current-voltage relationship and current kinetics were characteristic of high-voltage-activated Ca(2+) channels. The steady-state voltage-dependent activation curves and inactivation curves could both be fitted with a single Boltzmann function. Currents evoked with a prolonged pulse, however, inactivated with multiple time constants, suggesting either the presence of more than one Ca(2+) channel subtype or multiple inactivation processes with a single channel type in STN neurons. Experiments using organic Ca(2+) channel blockers revealed that on average, 21% of the current was nifedipine sensitive, 52% was sensitive to omega-conotoxin GVIA, 16% was blocked by a high concentration of omega-agatoxin IVA (200 nM), and the remainder of the current (9%) was resistant to the co-application of all blockers. These currents had similar voltage dependencies, but the nifedipine-sensitive current and the resistant current activated at slightly lower voltages. omega-Agatoxin IVA at 20 nM was ineffective in blocking the current. Together, the above results suggest that acutely isolated STN neurons have all subtypes of high-voltage-activated Ca(2+) channels except for P-type, but have no low-voltage-activated channels. Although acutely isolated neurons provide a good preparation for whole cell voltage-clamp study, dendritic processes are

  10. Aging and Neuronal Vulnerability

    PubMed Central

    Mattson, Mark P.; Magnus, Tim

    2011-01-01

    Everyone ages, but only some will acquire a neurodegenerative disorder in the process. Disease might occur when cells fail to respond adaptively to age-related increases in oxidative, metabolic and ionic stress resulting in excessive accumulation of damaged proteins, DNA and membranes. Determinants of neuronal vulnerability might include cell size and location, metabolism of disease-specific proteins, and repertoire of signal transduction pathways and stress resistance mechanisms. Emerging evidence on protein interaction networks that monitor and respond to the normal aging process suggests that successful neural aging is possible for most, but also cautions that cures for neurodegenerative disorders are unlikely in the near future. PMID:16552414

  11. DNA Damage Induced Neuronal Death

    DTIC Science & Technology

    1999-10-01

    Experiments are proposed to examine the molecular mechanism by which mustard chemical warfare agents induce neuronal cell death . DNA damage is the...proposed underlying mechanism of mustard-induced neuronal cell death . We propose a novel research strategy to test this hypothesis by using mice with...perturbed DNA repair to explore the relationship between mustard-induced DNA damage and neuronal cell death . Initial in vitro studies (Years 1, 2 & 3

  12. Deformability curve for K18 steel

    SciTech Connect

    Pospiech, J.

    1999-12-01

    The problem of the best utilization of plasticity in plastic working processes of metals, at low resistance to deformation and maximum utilization of capacity of installations has gained great importance, especially in recent years. Determination of plasticity of materials by the method of Kolmogorow is described. Variation of the stress factor for several plastic working processes is also described. Tests to plot the deformability curve (also referred to as reserve of plasticity curve) were selected and proved.

  13. Neutron cross sections: Book of curves

    SciTech Connect

    McLane, V.; Dunford, C.L.; Rose, P.F.

    1988-01-01

    Neuton Cross Sections: Book of Curves represents the fourth edition of what was previously known as BNL-325, Neutron Cross Sections, Volume 2, CURVES. Data is presented only for (i.e., intergrated) reaction cross sections (and related fission parameters) as a function of incident-neutron energy for the energy range 0.01 eV to 200 MeV. For the first time, isometric state production cross sections have been included. 11 refs., 4 figs.

  14. On the Light Curves of AM CVn

    NASA Astrophysics Data System (ADS)

    Smak, J.

    2017-03-01

    Light curves of AM CVn are analyzed by decomposing them into their Fourier components. The amplitudes of the fundamental mode and overtones of the three components: the superhumps, the negative superhumps and the orbital variations, are found to be variable. This implies that variations in the shape of the observed light curve of AM CVn are not only due to the interference between those components, but also due to the intrinsic variability within these components.

  15. Isentropic fluid dynamics in a curved pipe

    NASA Astrophysics Data System (ADS)

    Colombo, Rinaldo M.; Holden, Helge

    2016-10-01

    In this paper we study isentropic flow in a curved pipe. We focus on the consequences of the geometry of the pipe on the dynamics of the flow. More precisely, we present the solution of the general Cauchy problem for isentropic fluid flow in an arbitrarily curved, piecewise smooth pipe. We consider initial data in the subsonic regime, with small total variation about a stationary solution. The proof relies on the front-tracking method and is based on [1].

  16. Topology of the Space of Nondegenerate Curves

    NASA Astrophysics Data System (ADS)

    Shapiro, M. Z.

    1994-04-01

    A curve on a sphere or on a projective space is called nondegenerate if it has a nondegenerate moving frame at every point. The number of homotopy classes of closed nondegenerate curves immersed in the sphere or projective space is computed. In the case of the sphere Sn, this turns out to be 4 for odd n>=3 and 6 for even n>=2 in the case of the projective space Pn, 10 for odd n>=3 and 3 for even n>=2.

  17. Geometric Observers for Dynamically Evolving Curves

    PubMed Central

    Niethammer, Marc; Vela, Patricio A.; Tannenbaum, Allen

    2009-01-01

    This paper proposes a deterministic observer design for visual tracking based on nonparametric implicit (level-set) curve descriptions. The observer is continuous discrete with continuous-time system dynamics and discrete-time measurements. Its state-space consists of an estimated curve position augmented by additional states (e.g., velocities) associated with every point on the estimated curve. Multiple simulation models are proposed for state prediction. Measurements are performed through standard static segmentation algorithms and optical-flow computations. Special emphasis is given to the geometric formulation of the overall dynamical system. The discrete-time measurements lead to the problem of geometric curve interpolation and the discrete-time filtering of quantities propagated along with the estimated curve. Interpolation and filtering are intimately linked to the correspondence problem between curves. Correspondences are established by a Laplace-equation approach. The proposed scheme is implemented completely implicitly (by Eulerian numerical solutions of transport equations) and thus naturally allows for topological changes and subpixel accuracy on the computational grid. PMID:18421113

  18. GPU accelerated curve fitting with IDL

    NASA Astrophysics Data System (ADS)

    Galloy, M.

    2012-12-01

    Curve fitting is a common mathematical calculation done in all scientific areas. The Interactive Data Language (IDL) is also widely used in this community for data analysis and visualization. We are creating a general-purpose, GPU accelerated curve fitting library for use from within IDL. We have developed GPULib, a library of routines in IDL for accelerating common scientific operations including arithmetic, FFTs, interpolation, and others. These routines are accelerated using modern GPUs using NVIDIA's CUDA architecture. We will add curve fitting routines to the GPULib library suite, making curve fitting much faster. In addition, library routines required for efficient curve fitting will also be generally useful to other users of GPULib. In particular, a GPU accelerated LAPACK implementation such as MAGMA is required for the Levenberg-Marquardt curve fitting and is commonly used in many other scientific computations. Furthermore, the ability to evaluate custom expressions at runtime necessary for specifying a function model will be useful for users in all areas.

  19. Piecewise power laws in individual learning curves.

    PubMed

    Donner, Yoni; Hardy, Joseph L

    2015-10-01

    The notion that human learning follows a smooth power law (PL) of diminishing gains is well-established in psychology. This characteristic is observed when multiple curves are averaged, potentially masking more complex dynamics underpinning the curves of individual learners. Here, we analyzed 25,280 individual learning curves, each comprising 500 measurements of cognitive performance taken from four cognitive tasks. A piecewise PL (PPL) model explained the individual learning curves significantly better than a single PL, controlling for model complexity. The PPL model allows for multiple PLs connected at different points in the learning process. We also explored the transition dynamics between PL curve component pieces. Performance in later pieces typically surpassed that in earlier pieces, after a brief drop in performance at the transition point. The transition rate was negatively associated with age, even after controlling for overall performance. Our results suggest at least two processes at work in individual learning curves: locally, a gradual, smooth improvement, with diminishing gains within a specific strategy, which is modeled well as a PL; and globally, a discrete sequence of strategy shifts, in which each strategy is better in the long term than the ones preceding it. The piecewise extension of the classic PL of practice has implications for both individual skill acquisition and theories of learning.

  20. Effectivizing the geometry of the curve complex

    NASA Astrophysics Data System (ADS)

    Aougab, Tarik

    This thesis is devoted to understanding how the geometry of the curve complex of a surface S, the Teichmuller space of S, and of the mapping class group of S explicitly depend on the underlying topology of S. Moreover, this thesis demonstrates that the geometry of the mapping class group, and the tools used to study this geometry such as Masur and Minsky's celebrated distance formula, can be used to answer basic, but surprisingly challenging questions related to the combinatorial properties of curves on surfaces. In particular, we prove that all curve graphs are uniformly hyperbolic, independent of the topology of the underlying surface. We also give effective versions of several results regarding train track splitting sequences, and the subset of the curve graph corresponding to curves which bound disks in a handlebody. Finally, we study the local geometry of a family of curve graphs all related to the same surface, and specifically we give upper and lower bounds on the maximum size of a complete subgraph for these graphs.

  1. Probing exoplanet clouds with optical phase curves.

    PubMed

    Muñoz, Antonio García; Isaak, Kate G

    2015-11-03

    Kepler-7b is to date the only exoplanet for which clouds have been inferred from the optical phase curve--from visible-wavelength whole-disk brightness measurements as a function of orbital phase. Added to this, the fact that the phase curve appears dominated by reflected starlight makes this close-in giant planet a unique study case. Here we investigate the information on coverage and optical properties of the planet clouds contained in the measured phase curve. We generate cloud maps of Kepler-7b and use a multiple-scattering approach to create synthetic phase curves, thus connecting postulated clouds with measurements. We show that optical phase curves can help constrain the composition and size of the cloud particles. Indeed, model fitting for Kepler-7b requires poorly absorbing particles that scatter with low-to-moderate anisotropic efficiency, conclusions consistent with condensates of silicates, perovskite, and silica of submicron radii. We also show that we are limited in our ability to pin down the extent and location of the clouds. These considerations are relevant to the interpretation of optical phase curves with general circulation models. Finally, we estimate that the spherical albedo of Kepler-7b over the Kepler passband is in the range 0.4-0.5.

  2. Single-shot curved slice imaging.

    PubMed

    Jochimsen, Thies H; Norris, David G

    2002-03-01

    The feasibility of imaging a curved slice with a single-shot technique so that the reconstructed image shows an un-warping of the slice is examined. This could be of practical importance when the anatomical structures of interest can be more efficiently covered with curved slices than with a series of flat planes. One possible example of such a structure is the cortex of the human brain. Functional imaging would especially benefit from this technique because several planar images can be replaced by a few curved slice images. A method is introduced that is based on multidimensional pulses to excite the desired curved slice profile. A GRASE imaging sequence is then applied that is tailored to the k-space representation of the curved slice. This makes it possible to capture the in-plane information of the slice with a single-shot technique. The method presented is limited to slices that are straight along one axis and can be approximated by a polygon. Reconstruction is performed using a simple numeric Fourier integration along the curved slice. This leads to an image that shows the desired un-warped representation of the slice. Experimental results obtained with this method from healthy volunteers are presented and demonstrate the feasibility of the proposed technique.

  3. [Neuronal plasticity and gene expression].

    PubMed

    Sokolova, O O; Shtark, M B; Lisachev, P D

    2010-01-01

    Neuronal plasticity--a fundamental feature of brain--provides adequate interactions with dynamic environment. One of the most deeply investigated forms of the neuronal plasticity is a long-term potentiation (LTP)--a phenomenon underlying learning and memory. Signal paths activated during LTP converge into the nuclear of the neuron, giving rise to launch of the molecular-genetic programs, which mediate structural and functional remodeling of synapses. In the review data concerning involvement of multilevel gene expression into plastic change under neuronal activation are summarized.

  4. The straintronic spin-neuron.

    PubMed

    Biswas, Ayan K; Atulasimha, Jayasimha; Bandyopadhyay, Supriyo

    2015-07-17

    In artificial neural networks, neurons are usually implemented with highly dissipative CMOS-based operational amplifiers. A more energy-efficient implementation is a 'spin-neuron' realized with a magneto-tunneling junction (MTJ) that is switched with a spin-polarized current (representing weighted sum of input currents) that either delivers a spin transfer torque or induces domain wall motion in the soft layer of the MTJ to mimic neuron firing. Here, we propose and analyze a different type of spin-neuron in which the soft layer of the MTJ is switched with mechanical strain generated by a voltage (representing weighted sum of input voltages) and term it straintronic spin-neuron. It dissipates orders of magnitude less energy in threshold operations than the traditional current-driven spin neuron at 0 K temperature and may even be faster. We have also studied the room-temperature firing behaviors of both types of spin neurons and find that thermal noise degrades the performance of both types, but the current-driven type is degraded much more than the straintronic type if both are optimized for maximum energy-efficiency. On the other hand, if both are designed to have the same level of thermal degradation, then the current-driven version will dissipate orders of magnitude more energy than the straintronic version. Thus, the straintronic spin-neuron is superior to current-driven spin neurons.

  5. The biophysics of neuronal growth

    NASA Astrophysics Data System (ADS)

    Franze, Kristian; Guck, Jochen

    2010-09-01

    For a long time, neuroscience has focused on biochemical, molecular biological and electrophysiological aspects of neuronal physiology and pathology. However, there is a growing body of evidence indicating the importance of physical stimuli for neuronal growth and development. In this review we briefly summarize the historical background of neurobiophysics and give an overview over the current understanding of neuronal growth from a physics perspective. We show how biophysics has so far contributed to a better understanding of neuronal growth and discuss current inconsistencies. Finally, we speculate how biophysics may contribute to the successful treatment of lesions to the central nervous system, which have been considered incurable until very recently.

  6. Circadian Periods of Sensitivity for Ramelteon on the onset of Running-wheel Activity and the Peak of Suprachiasmatic Nucleus Neuronal Firing Rhythms in C3H/HeN Mice

    PubMed Central

    Rawashdeh, Oliver; Hudson, Randall L.; Stepien, Iwona; Dubocovich, Margarita L.

    2016-01-01

    Ramelteon, an MT1/MT2 melatonin receptor agonist, is used for the treatment of sleep-onset insomnia and circadian sleep disorders. Ramelteon phase shifts circadian rhythms in rodents and humans when given at the end of the subjective day; however, its efficacy at other circadian times is not known. Here, the authors determined in C3H/ HeN mice the maximal circadian sensitivity for ramelteon in vivo on the onset of circadian running-wheel activity rhythms, and in vitro on the peak of circadian rhythm of neuronal firing in suprachiasmatic nucleus (SCN) brain slices. The phase response curve (PRC) for ramelteon (90 μg/mouse, subcutaneous [sc]) on circadian wheel-activity rhythms shows maximal sensitivity during the late mid to end of the subjective day, between CT8 and CT12 (phase advance), and late subjective night and early subjective day, between CT20 and CT2 (phase delay), using a 3-day-pulse treatment regimen in C3H/HeN mice. The PRC for ramelteon resembles that for melatonin in C3H/ HeN mice, showing the same magnitude of maximal shifts at CT10 and CT2, except that the range of sensitivity for ramelteon (CT8–CT12) during the subjective day is broader. Furthermore, in SCN brain slices in vitro, ramelteon (10 pM) administered at CT10 phase advances (5.6 ± 0.29 h, n = 3) and at CT2 phase delays (−3.2 ± 0.12 h, n = 6) the peak of circadian rhythm of neuronal firing, with the shifts being significantly larger than those induced by melatonin (10 pM) at the same circadian times (CT10: 2.7 ± 0.15 h, n = 4, p < .05; CT2: −1.13 ± 0.08 h, n = 6, p < .001, respectively). The phase shifts induced by both melatonin and ramelteon in the SCN brain slice at either CT10 or CT2 corresponded with the period of sensitivity observed in vivo. In conclusion, melatonin and ramelteon showed identical periods of circadian sensitivity at CT10 (advance) and CT2 (delay) to shift the onset of circadian activity rhythms in vivo and the peak of SCN neuronal firing rhythms in vitro

  7. Investigating the Stability and Accuracy of the Phase Response for NOx Sensing 5% Mg-modified LaCrO3 Electrodes

    SciTech Connect

    Murray, E P; Novak, R F; Kubinski, D J; Soltis, R E; Visser, J H; Woo, L Y; Martin, L P; Glass, R S

    2007-06-14

    Impedance spectroscopy measurements were carried out on LaCr{sub 0.95}Mg{sub 0.05}O{sub 3} (LCM) asymmetric interdigitated electrodes supported on fully stabilized 8-mol% Y{sub 2}O{sub 3}-stabilized ZrO{sub 2} (YSZ) electrolytes. Experiments were carried out using 0-50 ppm NO{sub x}, 5-15% O{sub 2} with N{sub 2} as the balance, over temperatures ranging from 600-700 C. AC measurements taken at a constant frequency between 1-100 Hz indicated the phase response of the sensor was less sensitive to fluctuations in the O{sub 2} concentration and the baseline drift was limited. Specific frequencies were observed where the sensor response was essentially temperature independent.

  8. Hippocampal neurons in schizophrenia

    PubMed Central

    Heckers, S.; Konradi, C.

    2014-01-01

    Summary The hippocampus is crucial for normal brain function, especially for the encoding and retrieval of multimodal sensory information. Neuropsychiatric disorders such as temporal lobe epilepsy, amnesia, and the dementias are associated with structural and functional abnormalities of specific hippocampal neurons. More recently we have also found evidence for a role of the hippocampus in the pathophysiology of schizophrenia. The most consistent finding is a subtle, yet significant volume difference in schizophrenia. Here we review the cellular and molecular basis of smaller hippocampal volume in schizophrenia. In contrast to neurodegenerative disorders, total hippocampal cell number is not markedly decreased in schizophrenia. However, the intriguing finding of a selective loss of hippocampal inter-neurons deserves further study. Two neurotransmitter receptors, the GABAA and AMPA/kainate glutamate receptors, appear to be abnormal, whereas changes of the NMDA glutamate receptor are less robust. The expression of several genes, including those related to the GABAergic system, neurodevelopment, and synaptic function, is decreased in schizophrenia. Taken together, recent studies of hippocampal cell number, protein expression, and gene regulation point towards an abnormality of hippocampal architecture in schizophrenia. PMID:12111476

  9. Vectorial moments of curves in Euclidean 3-space

    NASA Astrophysics Data System (ADS)

    Tunçer, Yılmaz

    In this study, we introduced the vectorial moments as a new curves as w-dual curve, where w ∈{T(s),N(s),B(s)}, constructed by the Frenet vectors of a regular curve in Euclidean 3-space and we gave the Frenet apparatus of w-dual curves and also we applied to helices and curve pairs of constant breadth.

  10. Curved-region-based ridge frequency estimation and curved Gabor filters for fingerprint image enhancement.

    PubMed

    Gottschlich, Carsten

    2012-04-01

    Gabor filters (GFs) play an important role in many application areas for the enhancement of various types of images and the extraction of Gabor features. For the purpose of enhancing curved structures in noisy images, we introduce curved GFs that locally adapt their shape to the direction of flow. These curved GFs enable the choice of filter parameters that increase the smoothing power without creating artifacts in the enhanced image. In this paper, curved GFs are applied to the curved ridge and valley structures of low-quality fingerprint images. First, we combine two orientation-field estimation methods in order to obtain a more robust estimation for very noisy images. Next, curved regions are constructed by following the respective local orientation. Subsequently, these curved regions are used for estimating the local ridge frequency. Finally, curved GFs are defined based on curved regions, and they apply the previously estimated orientations and ridge frequencies for the enhancement of low-quality fingerprint images. Experimental results on the FVC2004 databases show improvements of this approach in comparison with state-of-the-art enhancement methods.

  11. The Neuronal Ceroid-Lipofuscinoses

    ERIC Educational Resources Information Center

    Bennett, Michael J.; Rakheja, Dinesh

    2013-01-01

    The neuronal ceroid-lipofuscinoses (NCL's, Batten disease) represent a group of severe neurodegenerative diseases, which mostly present in childhood. The phenotypes are similar and include visual loss, seizures, loss of motor and cognitive function, and early death. At autopsy, there is massive neuronal loss with characteristic storage in…

  12. Synchronization by elastic neuronal latencies

    NASA Astrophysics Data System (ADS)

    Vardi, Roni; Timor, Reut; Marom, Shimon; Abeles, Moshe; Kanter, Ido

    2013-01-01

    Psychological and physiological considerations entail that formation and functionality of neuronal cell assemblies depend upon synchronized repeated activation such as zero-lag synchronization. Several mechanisms for the emergence of this phenomenon have been suggested, including the global network quantity, the greatest common divisor of neuronal circuit delay loops. However, they require strict biological prerequisites such as precisely matched delays and connectivity, and synchronization is represented as a stationary mode of activity instead of a transient phenomenon. Here we show that the unavoidable increase in neuronal response latency to ongoing stimulation serves as a nonuniform gradual stretching of neuronal circuit delay loops. This apparent nuisance is revealed to be an essential mechanism in various types of neuronal time controllers, where synchronization emerges as a transient phenomenon and without predefined precisely matched synaptic delays. These findings are described in an experimental procedure where conditioned stimulations were enforced on a circuit of neurons embedded within a large-scale network of cortical cells in vitro, and are corroborated and extended by simulations of circuits composed of Hodgkin-Huxley neurons with time-dependent latencies. These findings announce a cortical time scale for time controllers based on tens of microseconds stretching of neuronal circuit delay loops per spike. They call for a reexamination of the role of the temporal periodic mode in brain functionality using advanced in vitro and in vivo experiments.

  13. Neuronal avalanches and coherence potentials

    NASA Astrophysics Data System (ADS)

    Plenz, D.

    2012-05-01

    The mammalian cortex consists of a vast network of weakly interacting excitable cells called neurons. Neurons must synchronize their activities in order to trigger activity in neighboring neurons. Moreover, interactions must be carefully regulated to remain weak (but not too weak) such that cascades of active neuronal groups avoid explosive growth yet allow for activity propagation over long-distances. Such a balance is robustly realized for neuronal avalanches, which are defined as cortical activity cascades that follow precise power laws. In experiments, scale-invariant neuronal avalanche dynamics have been observed during spontaneous cortical activity in isolated preparations in vitro as well as in the ongoing cortical activity of awake animals and in humans. Theory, models, and experiments suggest that neuronal avalanches are the signature of brain function near criticality at which the cortex optimally responds to inputs and maximizes its information capacity. Importantly, avalanche dynamics allow for the emergence of a subset of avalanches, the coherence potentials. They emerge when the synchronization of a local neuronal group exceeds a local threshold, at which the system spawns replicas of the local group activity at distant network sites. The functional importance of coherence potentials will be discussed in the context of propagating structures, such as gliders in balanced cellular automata. Gliders constitute local population dynamics that replicate in space after a finite number of generations and are thought to provide cellular automata with universal computation. Avalanches and coherence potentials are proposed to constitute a modern framework of cortical synchronization dynamics that underlies brain function.

  14. Cryopreservation of adherent neuronal networks.

    PubMed

    Ma, Wu; O'Shaughnessy, Thomas; Chang, Eddie

    2006-07-31

    Neuronal networks have been widely used for neurophysiology, drug discovery and toxicity testing. An essential prerequisite for future widespread application of neuronal networks is the development of efficient cryopreservation protocols to facilitate their storage and transportation. Here is the first report on cryopreservation of mammalian adherent neuronal networks. Dissociated spinal cord cells were attached to a poly-d-lysine/laminin surface and allowed to form neuronal networks. Adherent neuronal networks were embedded in a thin film of collagen gel and loaded with trehalose prior to transfer to a freezing medium containing DMSO, FBS and culture medium. This was followed by a slow rate of cooling to -80 degrees C for 24 h and then storage for up to 2 months in liquid nitrogen at -196 degrees C. The three components: DMSO, collagen gel entrapment and trehalose loading combined provided the highest post-thaw viability, relative to individual or two component protocols. The post-thaw cells with this protocol demonstrated similar neuronal and astrocytic markers and morphological structure as those detected in unfrozen cells. Fluorescent dye FM1-43 staining revealed active recycling of synaptic vesicles upon depolarizing stimulation in the post-thaw neuronal networks. These results suggest that a combination of DMSO, collagen gel entrapment and trehalose loading can significantly improve conventional slow-cooling methods in cryopreservation of adherent neuronal networks.

  15. Tracing personalized health curves during infections.

    PubMed

    Schneider, David S

    2011-09-01

    It is difficult to describe host-microbe interactions in a manner that deals well with both pathogens and mutualists. Perhaps a way can be found using an ecological definition of tolerance, where tolerance is defined as the dose response curve of health versus parasite load. To plot tolerance, individual infections are summarized by reporting the maximum parasite load and the minimum health for a population of infected individuals and the slope of the resulting curve defines the tolerance of the population. We can borrow this method of plotting health versus microbe load in a population and make it apply to individuals; instead of plotting just one point that summarizes an infection in an individual, we can plot the values at many time points over the course of an infection for one individual. This produces curves that trace the course of an infection through phase space rather than over a more typical timeline. These curves highlight relationships like recovery and point out bifurcations that are difficult to visualize with standard plotting techniques. Only nine archetypical curves are needed to describe most pathogenic and mutualistic host-microbe interactions. The technique holds promise as both a qualitative and quantitative approach to dissect host-microbe interactions of all kinds.

  16. Probing exoplanet clouds with optical phase curves

    PubMed Central

    Muñoz, Antonio García; Isaak, Kate G.

    2015-01-01

    Kepler-7b is to date the only exoplanet for which clouds have been inferred from the optical phase curve—from visible-wavelength whole-disk brightness measurements as a function of orbital phase. Added to this, the fact that the phase curve appears dominated by reflected starlight makes this close-in giant planet a unique study case. Here we investigate the information on coverage and optical properties of the planet clouds contained in the measured phase curve. We generate cloud maps of Kepler-7b and use a multiple-scattering approach to create synthetic phase curves, thus connecting postulated clouds with measurements. We show that optical phase curves can help constrain the composition and size of the cloud particles. Indeed, model fitting for Kepler-7b requires poorly absorbing particles that scatter with low-to-moderate anisotropic efficiency, conclusions consistent with condensates of silicates, perovskite, and silica of submicron radii. We also show that we are limited in our ability to pin down the extent and location of the clouds. These considerations are relevant to the interpretation of optical phase curves with general circulation models. Finally, we estimate that the spherical albedo of Kepler-7b over the Kepler passband is in the range 0.4–0.5. PMID:26489652

  17. Updated U.S. Geothermal Supply Curve

    SciTech Connect

    Augustine, C.; Young, K. R.; Anderson, A.

    2010-02-01

    This paper documents the approach used to update the U.S. geothermal supply curve. The analysis undertaken in this study estimates the supply of electricity generation potential from geothermal resources in the United States and the levelized cost of electricity (LCOE), capital costs, and operating and maintenance costs associated with developing these geothermal resources. Supply curves were developed for four categories of geothermal resources: identified hydrothermal (6.4 GWe), undiscovered hydrothermal (30.0 GWe), near-hydrothermal field enhanced geothermal systems (EGS) (7.0 GWe) and deep EGS (15,900 GWe). Two cases were considered: a base case and a target case. Supply curves were generated for each of the four geothermal resource categories for both cases. For both cases, hydrothermal resources dominate the lower cost range of the combined geothermal supply curve. The supply curves indicate that the reservoir performance improvements assumed in the target case could significantly lower EGS costs and greatly increase EGS deployment over the base case.

  18. A pipeline for neuron reconstruction based on spatial sliding volume filter seeding.

    PubMed

    Sui, Dong; Wang, Kuanquan; Chae, Jinseok; Zhang, Yue; Zhang, Henggui

    2014-01-01

    Neuron's shape and dendritic architecture are important for biosignal transduction in neuron networks. And the anatomy architecture reconstruction of neuron cell is one of the foremost challenges and important issues in neuroscience. Accurate reconstruction results can facilitate the subsequent neuron system simulation. With the development of confocal microscopy technology, researchers can scan neurons at submicron resolution for experiments. These make the reconstruction of complex dendritic trees become more feasible; however, it is still a tedious, time consuming, and labor intensity task. For decades, computer aided methods have been playing an important role in this task, but none of the prevalent algorithms can reconstruct full anatomy structure automatically. All of these make it essential for developing new method for reconstruction. This paper proposes a pipeline with a novel seeding method for reconstructing neuron structures from 3D microscopy images stacks. The pipeline is initialized with a set of seeds detected by sliding volume filter (SVF), and then the open curve snake is applied to the detected seeds for reconstructing the full structure of neuron cells. The experimental results demonstrate that the proposed pipeline exhibits excellent performance in terms of accuracy compared with traditional method, which is clearly a benefit for 3D neuron detection and reconstruction.

  19. Convergent properties of vestibular-related brain stem neurons in the gerbil

    NASA Technical Reports Server (NTRS)

    Kaufman, G. D.; Shinder, M. E.; Perachio, A. A.

    2000-01-01

    Three classes of vestibular-related neurons were found in and near the prepositus and medial vestibular nuclei of alert or decerebrate gerbils, those responding to: horizontal translational motion, horizontal head rotation, or both. Their distribution ratios were 1:2:2, respectively. Many cells responsive to translational motion exhibited spatiotemporal characteristics with both response gain and phase varying as a function of the stimulus vector angle. Rotationally sensitive neurons were distributed as Type I, II, or III responses (sensitive to ipsilateral, contralateral, or both directions, respectively) in the ratios of 4:6:1. Four tested factors shaped the response dynamics of the sampled neurons: canal-otolith convergence, oculomotor-related activity, rotational Type (I or II), and the phase of the maximum response. Type I nonconvergent cells displayed increasing gains with increasing rotational stimulus frequency (0.1-2.0 Hz, 60 degrees /s), whereas Type II neurons with convergent inputs had response gains that markedly decreased with increasing translational stimulus frequency (0.25-2.0 Hz, +/-0.1 g). Type I convergent and Type II nonconvergent neurons exhibited essentially flat gains across the stimulus frequency range. Oculomotor-related activity was noted in 30% of the cells across all functional types, appearing as burst/pause discharge patterns related to the fast phase of nystagmus during head rotation. Oculomotor-related activity was correlated with enhanced dynamic range compared with the same category that had no oculomotor-related response. Finally, responses that were in-phase with head velocity during rotation exhibited greater gains with stimulus frequency increments than neurons with out-of-phase responses. In contrast, for translational motion, neurons out of phase with head acceleration exhibited low-pass characteristics, whereas in-phase neurons did not. Data from decerebrate preparations revealed that although similar response types could

  20. Cell biology of neuronal endocytosis.

    PubMed

    Parton, R G; Dotti, C G

    1993-09-01

    Endocytosis is the process by which cells take in fluid and components of the plasma membrane. In this way cells obtain nutrients and trophic factors, retrieve membrane proteins for degradation, and sample their environment. In neuronal cells endocytosis is essential for the recycling of membrane after neurotransmitter release and plays a critical role during early developmental stages. Moreover, alterations of the endocytic pathway have been attributed a crucial role in the pathophysiology of certain neurological diseases. Although well characterized at the ultrastructural level, little is known of the dynamics and molecular organization of the neuronal endocytic pathways. In this respect most of our knowledge comes from studies of non-neuronal cells. In this review we will examine the endocytic pathways in neurons from a cell biological viewpoint by making comparisons with non-neuronal cells and in particular with another polarized cell, the epithelial cell.

  1. Phenotypic checkpoints regulate neuronal development.

    PubMed

    Ben-Ari, Yehezkel; Spitzer, Nicholas C

    2010-11-01

    Nervous system development proceeds by sequential gene expression mediated by cascades of transcription factors in parallel with sequences of patterned network activity driven by receptors and ion channels. These sequences are cell type- and developmental stage-dependent and modulated by paracrine actions of substances released by neurons and glia. How and to what extent these sequences interact to enable neuronal network development is not understood. Recent evidence demonstrates that CNS development requires intermediate stages of differentiation providing functional feedback that influences gene expression. We suggest that embryonic neuronal functions constitute a series of phenotypic checkpoint signatures; neurons failing to express these functions are delayed or developmentally arrested. Such checkpoints are likely to be a general feature of neuronal development and constitute presymptomatic signatures of neurological disorders when they go awry.

  2. [Neurons and values].

    PubMed

    Camps, Victoria

    2013-09-01

    This article examines the advances made by neuroscience in the attempt to find an answer to the question regarding the origin and foundation of moral judgements and of human behaviour in compliance with them. The conception of the brain as something dynamic and capable of adapting to the social and cultural surroundings is seen to be an important point for philosophy. At the same time, the complexity of ethical issues that cannot be reduced to observations based strictly on neurons alone also becomes quite apparent. Nevertheless, scientists and philosophers should get together and communicate with one another so as to be able to pose their questions with greater rigour and take advantage of each other's respective knowledge.

  3. Neuron's function revealed

    SciTech Connect

    2009-01-01

    There's a new way to explore biologys secrets. With a flash of light, scientists from the U.S. Department of Energys Lawrence Berkeley National Laboratory and the University of California, Berkeley zeroed in on the type of neural cell that controls swimming in larval zebrafish. Using innovative light-activated proteins and gene expression techniques, the scientists zapped several zebrafish with a pulse of light, and initiated a swimming action in a subset of fish that was traced back to the type of neuron that drives the side-to-side motion of their tail fins. The technique behind this needle-in-haystack search for the neural roots of a specific behavior could become a powerful way to learn how any biological system works. http://newscenter.lbl.gov/press-releases/2009/09/16/light-activated-protein/

  4. Multiplying with Neurons

    NASA Astrophysics Data System (ADS)

    Gabbiani, F.; Krapp, H.; Koch, C.; Laurent, G.

    1998-03-01

    LGMD and DCMD are a pair of identified neurons in the locust brain thought to be involved in visually triggered escape behavior. LGMD integrates visual inputs in its dendritic arbor, converts them into spikes transmitted in a 1:1 manner to DCMD which relays this information to motor centers. We measured the spike activity of DCMD during simulated object approach and observed that its peak occured prior to the expected collision. The time difference between peak activity and collision depended linearly on the ratio of object size to approach velocity, as expected if LGMD/DCMD were detecting the moment in time when the approaching object reaches a fixed angular threshold θ_thresh on the locust's retina. The response of LGMD/DCMD could be fitted by multiplying the angular velocity at which an approaching object is increasing in size over the retina, dot θ, with an exponential function of the object's angular size, θ: f(t) = g(dot θ(t-δ) e^-α θ(t-δ)) where g is a static non-linearity, α a constant related to the angular threshold detected by LGMD/DCMD (θ_thresh = arctan (2/α)) and δ denotes the lag of the neuronal response with respect to the stimulus. This suggests that LGMD/DCMD derives its angular threshold sensitivity by multiplying dot θ with an exponential of θ. A biophysical implementation would be through linear summation of excitatory and inhibitory inputs proportional to log(dot θ) and -α θ, followed by a conversion to spike rate according to the static non-linearity (g circ exp). We have performed several experiments to test this hypothesis.

  5. Leptin excites POMC neurons via activation of TRPC channels

    PubMed Central

    Qiu, Jian; Fang, Yuan; Rønnekleiv, Oline K.; Kelly, Martin J.

    2010-01-01

    Leptin can exert its potent appetite-suppressing effects via activation of hypothalamic proopiomelanocortin (POMC) neurons. It depolarizes POMC neurons via activation of a yet unidentified non-selective cation current. Therefore, we sought to identify the conductance activated by leptin using whole cell recording in EGFP-POMC neurons from transgenic mice. The TRPC channel blockers SKF96365, FFA and 2-APB potently inhibited the leptin-induced current. Also, lanthanum (La3+) and intracellular Ca2+ potentiated the effects of leptin. Moreover, the DAG permeable analog OAG failed to activate any TRPC current. Using a Cs+-gluconate-based internal solution, leptin-activated current reversed near -20 mV. After replacement of external Na+ and K+ with Cs+, the reversal shifted to near 0 mV, and the I/V curve exhibited a negative slope conductance at voltages more negative than –40 mV. Based on scRT-PCR, TRPC1 and TRPC4-7 mRNA were expressed in POMC neurons with TRPC5 being the most prevalent. The leptin-induced current was blocked by Jak2 inhibitor AG490, the PI3 Kinase inhibitor wortmannin and the phospholipase C inhibitors, U73122 and ET-18-OCH3. Notably, we identified PLCγ1 transcripts in the majority of POMC neurons. Therefore, leptin through a Jak2-PI3 kinase-PLCγ pathway activates TRPC channels, and TRPC1, 4 and 5 appear to be the key channels mediating the depolarizing effects of leptin in POMC neurons. PMID:20107083

  6. Surface growth kinematics via local curve evolution.

    PubMed

    Moulton, Derek E; Goriely, Alain

    2014-01-01

    A mathematical framework is developed to model the kinematics of surface growth for objects that can be generated by evolving a curve in space, such as seashells and horns. Growth is dictated by a growth velocity vector field defined at every point on a generating curve. A local orthonormal basis is attached to each point of the generating curve and the velocity field is given in terms of the local coordinate directions, leading to a fully local and elegant mathematical structure. Several examples of increasing complexity are provided, and we demonstrate how biologically relevant structures such as logarithmic shells and horns emerge as analytical solutions of the kinematics equations with a small number of parameters that can be linked to the underlying growth process. Direct access to cell tracks and local orientation enables for connections to be made to the underlying growth process.

  7. Plasticity and rectangularity in survival curves

    NASA Astrophysics Data System (ADS)

    Weon, Byung Mook; Je, Jung Ho

    2011-09-01

    Living systems inevitably undergo a progressive deterioration of physiological function with age and an increase of vulnerability to disease and death. To maintain health and survival, living systems should optimize survival strategies with adaptive interactions among molecules, cells, organs, individuals, and environments, which arises plasticity in survival curves of living systems. In general, survival dynamics in a population is mathematically depicted by a survival rate, which monotonically changes from 1 to 0 with age. It would be then useful to find an adequate function to describe complicated survival dynamics. Here we describe a flexible survival function, derived from the stretched exponential function by adopting an age-dependent shaping exponent. We note that the exponent is associated with the fractal-like scaling in cumulative mortality rate. The survival function well depicts general features in survival curves; healthy populations exhibit plasticity and evolve towards rectangular-like survival curves, as examples in humans or laboratory animals.

  8. Mapping curved spacetimes into Dirac spinors

    PubMed Central

    Sabín, Carlos

    2017-01-01

    We show how to transform a Dirac equation in a curved static spacetime into a Dirac equation in flat spacetime. In particular, we show that any solution of the free massless Dirac equation in a 1 + 1 dimensional flat spacetime can be transformed via a local phase transformation into a solution of the corresponding Dirac equation in a curved static background, where the spacetime metric is encoded into the phase. In this way, the existing quantum simulators of the Dirac equation can naturally incorporate curved static spacetimes. As a first example we use our technique to obtain solutions of the Dirac equation in a particular family of interesting spacetimes in 1 + 1 dimensions. PMID:28074908

  9. Mapping curved spacetimes into Dirac spinors.

    PubMed

    Sabín, Carlos

    2017-01-11

    We show how to transform a Dirac equation in a curved static spacetime into a Dirac equation in flat spacetime. In particular, we show that any solution of the free massless Dirac equation in a 1 + 1 dimensional flat spacetime can be transformed via a local phase transformation into a solution of the corresponding Dirac equation in a curved static background, where the spacetime metric is encoded into the phase. In this way, the existing quantum simulators of the Dirac equation can naturally incorporate curved static spacetimes. As a first example we use our technique to obtain solutions of the Dirac equation in a particular family of interesting spacetimes in 1 + 1 dimensions.

  10. Geometric Mechanics of Curved Crease Origami

    NASA Astrophysics Data System (ADS)

    Dias, Marcelo A.; Dudte, Levi H.; Mahadevan, L.; Santangelo, Christian D.

    2012-09-01

    Folding a sheet of paper along a curve can lead to structures seen in decorative art and utilitarian packing boxes. Here we present a theory for the simplest such structure: an annular circular strip that is folded along a central circular curve to form a three-dimensional buckled structure driven by geometrical frustration. We quantify this shape in terms of the radius of the circle, the dihedral angle of the fold, and the mechanical properties of the sheet of paper and the fold itself. When the sheet is isometrically deformed everywhere except along the fold itself, stiff folds result in creases with constant curvature and oscillatory torsion. However, relatively softer folds inherit the broken symmetry of the buckled shape with oscillatory curvature and torsion. Our asymptotic analysis of the isometrically deformed state is corroborated by numerical simulations that allow us to generalize our analysis to study structures with multiple curved creases.

  11. Geometric mechanics of curved crease origami.

    PubMed

    Dias, Marcelo A; Dudte, Levi H; Mahadevan, L; Santangelo, Christian D

    2012-09-14

    Folding a sheet of paper along a curve can lead to structures seen in decorative art and utilitarian packing boxes. Here we present a theory for the simplest such structure: an annular circular strip that is folded along a central circular curve to form a three-dimensional buckled structure driven by geometrical frustration. We quantify this shape in terms of the radius of the circle, the dihedral angle of the fold, and the mechanical properties of the sheet of paper and the fold itself. When the sheet is isometrically deformed everywhere except along the fold itself, stiff folds result in creases with constant curvature and oscillatory torsion. However, relatively softer folds inherit the broken symmetry of the buckled shape with oscillatory curvature and torsion. Our asymptotic analysis of the isometrically deformed state is corroborated by numerical simulations that allow us to generalize our analysis to study structures with multiple curved creases.

  12. Experimental simulation of closed timelike curves

    NASA Astrophysics Data System (ADS)

    Ringbauer, Martin; Broome, Matthew A.; Myers, Casey R.; White, Andrew G.; Ralph, Timothy C.

    2014-06-01

    Closed timelike curves are among the most controversial features of modern physics. As legitimate solutions to Einstein’s field equations, they allow for time travel, which instinctively seems paradoxical. However, in the quantum regime these paradoxes can be resolved, leaving closed timelike curves consistent with relativity. The study of these systems therefore provides valuable insight into nonlinearities and the emergence of causal structures in quantum mechanics—essential for any formulation of a quantum theory of gravity. Here we experimentally simulate the nonlinear behaviour of a qubit interacting unitarily with an older version of itself, addressing some of the fascinating effects that arise in systems traversing a closed timelike curve. These include perfect discrimination of non-orthogonal states and, most intriguingly, the ability to distinguish nominally equivalent ways of preparing pure quantum states. Finally, we examine the dependence of these effects on the initial qubit state, the form of the unitary interaction and the influence of decoherence.

  13. Experimental simulation of closed timelike curves.

    PubMed

    Ringbauer, Martin; Broome, Matthew A; Myers, Casey R; White, Andrew G; Ralph, Timothy C

    2014-06-19

    Closed timelike curves are among the most controversial features of modern physics. As legitimate solutions to Einstein's field equations, they allow for time travel, which instinctively seems paradoxical. However, in the quantum regime these paradoxes can be resolved, leaving closed timelike curves consistent with relativity. The study of these systems therefore provides valuable insight into nonlinearities and the emergence of causal structures in quantum mechanics--essential for any formulation of a quantum theory of gravity. Here we experimentally simulate the nonlinear behaviour of a qubit interacting unitarily with an older version of itself, addressing some of the fascinating effects that arise in systems traversing a closed timelike curve. These include perfect discrimination of non-orthogonal states and, most intriguingly, the ability to distinguish nominally equivalent ways of preparing pure quantum states. Finally, we examine the dependence of these effects on the initial qubit state, the form of the unitary interaction and the influence of decoherence.

  14. Waveguide finite elements for curved structures

    NASA Astrophysics Data System (ADS)

    Finnveden, Svante; Fraggstedt, Martin

    2008-05-01

    A waveguide finite element formulation for the analysis of curved structures is introduced. The formulation is valid for structures that along one axis have constant properties. It is based on a modified Hamilton's principle valid for general linear viscoelastic motion, which is derived here. Using this principle, material properties such as losses may be distributed in the system and may vary with frequency. Element formulations for isoparametric solid elements and deep shell elements are presented for curved waveguides as well as for straight waveguides. In earlier works, the curved elements have successfully been used to model a passenger car tyre. Here a simple validation example and convergence study is presented, which considers a finite length circular cylinder and all four elements presented are used, in turn, to model this structure. Calculated results compare favourably to those in the literature.

  15. Energy dissipation in flows through curved spaces

    NASA Astrophysics Data System (ADS)

    Debus, J.-D.; Mendoza, M.; Succi, S.; Herrmann, H. J.

    2017-02-01

    Fluid dynamics in intrinsically curved geometries is encountered in many physical systems in nature, ranging from microscopic bio-membranes all the way up to general relativity at cosmological scales. Despite the diversity of applications, all of these systems share a common feature: the free motion of particles is affected by inertial forces originating from the curvature of the embedding space. Here we reveal a fundamental process underlying fluid dynamics in curved spaces: the free motion of fluids, in the complete absence of solid walls or obstacles, exhibits loss of energy due exclusively to the intrinsic curvature of space. We find that local sources of curvature generate viscous stresses as a result of the inertial forces. The curvature- induced viscous forces are shown to cause hitherto unnoticed and yet appreciable energy dissipation, which might play a significant role for a variety of physical systems involving fluid dynamics in curved spaces.

  16. Energy dissipation in flows through curved spaces

    PubMed Central

    Debus, J.-D.; Mendoza, M.; Succi, S.; Herrmann, H. J.

    2017-01-01

    Fluid dynamics in intrinsically curved geometries is encountered in many physical systems in nature, ranging from microscopic bio-membranes all the way up to general relativity at cosmological scales. Despite the diversity of applications, all of these systems share a common feature: the free motion of particles is affected by inertial forces originating from the curvature of the embedding space. Here we reveal a fundamental process underlying fluid dynamics in curved spaces: the free motion of fluids, in the complete absence of solid walls or obstacles, exhibits loss of energy due exclusively to the intrinsic curvature of space. We find that local sources of curvature generate viscous stresses as a result of the inertial forces. The curvature- induced viscous forces are shown to cause hitherto unnoticed and yet appreciable energy dissipation, which might play a significant role for a variety of physical systems involving fluid dynamics in curved spaces. PMID:28195148

  17. Statistics from dynamics in curved spacetime

    SciTech Connect

    Parker, L.; Wang, Y.

    1989-06-15

    We consider quantum fields of spin 0, 1/2, 1,3/2, and 2 with a nonzero mass in curved spacetime. We show thatthe dynamical Bogolubov transformations associated with gravitationally inducedparticle creation imply the connection between spin and statistics: Byembedding two flat regions in a curved spacetime, we find that only when oneimposes Bose-Einstein statistics for an integer-spin field and Fermi-Diracstatistics for a half-integer-spin field in the first flat region is the sametype of statistics propagated from the first to the second flat region. Thisderivation of the flat-spacetime spin-statistics theorem makes use ofcurved-spacetime dynamics and does not reduce to any proof given in flatspacetime. We also show in the same manner that parastatistics, up to thefourth order, are consistent with the dynamical evolution of curved spacetime.

  18. Asymmetry dependence of the nuclear caloric curve

    NASA Astrophysics Data System (ADS)

    McIntosh, A. B.; Bonasera, A.; Cammarata, P.; Hagel, K.; Heilborn, L.; Kohley, Z.; Mabiala, J.; May, L. W.; Marini, P.; Raphelt, A.; Souliotis, G. A.; Wuenschel, S.; Zarrella, A.; Yennello, S. J.

    2013-02-01

    A basic feature of the nuclear equation of state is not yet understood: the dependence of the nuclear caloric curve on the neutron-proton asymmetry. Predictions of theoretical models differ on the magnitude and even the sign of this dependence. In this work, the nuclear caloric curve is examined for fully reconstructed quasi-projectiles around mass A = 50. The caloric curve extracted with the momentum quadrupole fluctuation thermometer shows that the temperature varies linearly with quasi-projectile asymmetry N-Z/A. An increase in asymmetry of 0.15 units corresponds to a decrease in temperature on the order of 1 MeV. These results also highlight the importance of a full quasi-projectile reconstruction in the study of thermodynamic properties of hot nuclei.

  19. Plasticity and rectangularity in survival curves

    PubMed Central

    Weon, Byung Mook; Je, Jung Ho

    2011-01-01

    Living systems inevitably undergo a progressive deterioration of physiological function with age and an increase of vulnerability to disease and death. To maintain health and survival, living systems should optimize survival strategies with adaptive interactions among molecules, cells, organs, individuals, and environments, which arises plasticity in survival curves of living systems. In general, survival dynamics in a population is mathematically depicted by a survival rate, which monotonically changes from 1 to 0 with age. It would be then useful to find an adequate function to describe complicated survival dynamics. Here we describe a flexible survival function, derived from the stretched exponential function by adopting an age-dependent shaping exponent. We note that the exponent is associated with the fractal-like scaling in cumulative mortality rate. The survival function well depicts general features in survival curves; healthy populations exhibit plasticity and evolve towards rectangular-like survival curves, as examples in humans or laboratory animals. PMID:22355622

  20. Neuronal cell lines as model dorsal root ganglion neurons

    PubMed Central

    Yin, Kathleen; Baillie, Gregory J

    2016-01-01

    Background Dorsal root ganglion neuron-derived immortal cell lines including ND7/23 and F-11 cells have been used extensively as in vitro model systems of native peripheral sensory neurons. However, while it is clear that some sensory neuron-specific receptors and ion channels are present in these cell lines, a systematic comparison of the molecular targets expressed by these cell lines with those expressed in intact peripheral neurons is lacking. Results In this study, we examined the expression of RNA transcripts in the human neuroblastoma-derived cell line, SH-SY5Y, and two dorsal root ganglion hybridoma cell lines, F-11 and ND7/23, using Illumina next-generation sequencing, and compared the results with native whole murine dorsal root ganglions. The gene expression profiles of these three cell lines did not resemble any specific defined dorsal root ganglion subclass. The cell lines lacked many markers for nociceptive sensory neurons, such as the Transient receptor potential V1 gene, but expressed markers for both myelinated and unmyelinated neurons. Global gene ontology analysis on whole dorsal root ganglions and cell lines showed similar enrichment of biological process terms across all samples. Conclusions This paper provides insights into the receptor repertoire expressed in common dorsal root ganglion neuron-derived cell lines compared with whole murine dorsal root ganglions, and illustrates the limits and potentials of these cell lines as tools for neuropharmacological exploration. PMID:27130590

  1. Timelike curves can increase entanglement with LOCC

    NASA Astrophysics Data System (ADS)

    Moulick, Subhayan Roy; Panigrahi, Prasanta K.

    2016-11-01

    We study the nature of entanglement in presence of Deutschian closed timelike curves (D-CTCs) and open timelike curves (OTCs) and find that existence of such physical systems in nature would allow us to increase entanglement using local operations and classical communication (LOCC). This is otherwise in direct contradiction with the fundamental definition of entanglement. We study this problem from the perspective of Bell state discrimination, and show how D-CTCs and OTCs can unambiguously distinguish between four Bell states with LOCC, that is otherwise known to be impossible.

  2. Multivariate curve-fitting in GAUSS

    USGS Publications Warehouse

    Bunck, C.M.; Pendleton, G.W.

    1988-01-01

    Multivariate curve-fitting techniques for repeated measures have been developed and an interactive program has been written in GAUSS. The program implements not only the one-factor design described in Morrison (1967) but also includes pairwise comparisons of curves and rates, a two-factor design, and other options. Strategies for selecting the appropriate degree for the polynomial are provided. The methods and program are illustrated with data from studies of the effects of environmental contaminants on ducklings, nesting kestrels and quail.

  3. Relativistic rotation curve for cosmological structures

    NASA Astrophysics Data System (ADS)

    Razbin, Mohammadhosein; Firouzjaee, Javad T.; Mansouri, Reza

    2014-08-01

    Using a general relativistic exact model for spherical structures in a cosmological background, we have put forward an algorithm to calculate the test particle geodesics within such cosmological structures in order to obtain the velocity profile of stars or galaxies. The rotation curve thus obtained is based on a density profile and is independent of any mass definition which is not unique in general relativity. It is then shown that this general relativistic rotation curves for a toy model and a NFW density profile are almost identical to the corresponding Newtonian one, although the general relativistic masses may be quite different.

  4. Solitons in curved space of constant curvature

    SciTech Connect

    Batz, Sascha; Peschel, Ulf

    2010-05-15

    We consider spatial solitons as, for example, self-confined optical beams in spaces of constant curvature, which are a natural generalization of flat space. Due to the symmetries of these spaces we are able to define respective dynamical parameters, for example, velocity and position. For positively curved space we find stable multiple-hump solitons as a continuation from the linear modes. In the case of negatively curved space we show that no localized solution exists and a bright soliton will always decay through a nonlinear tunneling process.

  5. Making Curved Frequency-Selective Microwave Reflectors

    NASA Technical Reports Server (NTRS)

    Hickey, Gregory S.; Wu, Te-Kao

    1995-01-01

    Prototype curved lightweight dichroic microwave reflectors designed to be highly reflective in X and K(suba) frequency bands and highly transmissive in K(subu) and S bands. Conductive grid elements formed photolithographically on curved reflector surfaces. Intended for use as subreflectors of main paraboloidal antenna reflector to enable simultaneous operation in both prime-focus configuration in K(subu) and S bands and Cassegrain configuration in X and K(suba) bands. Basic concepts of reflectors described in "Frequency-Selective Microwave Reflectors" (NPO-18701). "Double Square-Loop Dichroic Microwave Reflector" (NPO-18676), "Triband Circular-Loop Dichroic Microwave Reflector" (NPO-18714), and "Improved Dichroic Microwave Reflector" (NPO-18664).

  6. Linear Titration Curves of Acids and Bases.

    PubMed

    Joseph, N R

    1959-05-29

    The Henderson-Hasselbalch equation, by a simple transformation, becomes pH - pK = pA - pB, where pA and pB are the negative logarithms of acid and base concentrations. Sigmoid titration curves then reduce to straight lines; titration curves of polyelectrolytes, to families of straight lines. The method is applied to the titration of the dipeptide glycyl aminotricarballylic acid, with four titrable groups. Results are expressed as Cartesian and d'Ocagne nomograms. The latter is of a general form applicable to polyelectrolytes of any degree of complexity.

  7. More Unusual Light Curves from Kepler

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2017-03-01

    Twenty-three new objects have been added to the growing collection of stars observed to have unusual dips in their light curves. A recent study examines these stars and the potential causes of their strange behavior.An Influx of DataThe primary Kepler mission provided light curves for over 100,000 stars, and its continuation K2 is observing another 20,000 stars every three months. As we enter an era where these enormous photometric data sets become commonplace Gaia will obtain photometry for millions of stars, and LSST billions its crucial that we understand the different categories of variability observed in these stars.The authors find three different types of light curves among their 23 unusual stars. Scallop-shell curves (top) show many undulations; persistent flux-dip class curves (middle) have discrete triangularly shaped flux dips; transient, narrow dip class curves (bottom) have only one dip that is variable in depth. The authors speculate a common cause for the scallop-shell and persistent flux-dip stars, and a different cause for the transient flux-dip stars. [Stauffer et al. 2017]After filtering out the stars with planets, those in binary systems, those with circumstellar disks, and those with starspots, a number of oddities remain: a menagerie of stars with periodic variability that cant be accounted for in these categories. Some of these stars are now famous (for instance, Boyajians star); some are lesser known. But by continuing to build up this sample of stars with unusual light curves, we have a better chance of understanding the sources of variability.Building the MenagerieTo this end, a team of scientists led by John Stauffer (Spitzer Science Center at Caltech) has recently hunted for more additions to this sample in the K2 data set. In particular, they searched through the light curves from stars in the Oph and Upper Scorpius star-forming region a data set that makes up the largest collection of high-quality light curves for low-mass, pre

  8. Cellinoid shape model for multiple light curves

    NASA Astrophysics Data System (ADS)

    Lu, Xiao-Ping; Ip, Wing-Huen

    2015-04-01

    Extended from the ellipsoid shape, cellinoid shape model consists of eight octants from eight different ellipsoids with the constraint that the adjacent octants have the same semi-axes in common. With the asymmetric shape, cellinoid shape model could be adopted in simulating the irregular shapes of asteroids. In this article, we attempt to apply cellinoid shape model to multiple light curves observed in various geometries and present some techniques to make the whole inverse process more efficient. Finally numerical experiments confirm that cellinoid shape model could derive the physical parameters of asteroids from both of synthetic and real light curves.

  9. Timelike curves can increase entanglement with LOCC

    PubMed Central

    Moulick, Subhayan Roy; Panigrahi, Prasanta K.

    2016-01-01

    We study the nature of entanglement in presence of Deutschian closed timelike curves (D-CTCs) and open timelike curves (OTCs) and find that existence of such physical systems in nature would allow us to increase entanglement using local operations and classical communication (LOCC). This is otherwise in direct contradiction with the fundamental definition of entanglement. We study this problem from the perspective of Bell state discrimination, and show how D-CTCs and OTCs can unambiguously distinguish between four Bell states with LOCC, that is otherwise known to be impossible. PMID:27897219

  10. A synthetic light curve solution of the OAO-2 ultraviolet light curves of u Herculis

    NASA Technical Reports Server (NTRS)

    Eaton, J. A.

    1978-01-01

    OAO 2 ultraviolet photometry of the eclipsing binary u Her is reported and interpreted. The light curve of u Her is found to be intrinsically variable, the variable light curve is rectified, and the adjusted light and color curves are plotted. A simultaneous solution to three adjusted OAO 2 light curves (at respective wavelengths of 3320, 1910, and 1550 A) is obtained by using the Roche model. The results indicate that the system is semidetached if the gravity darkening of the secondary is not significantly larger than expected. It is suggested that the primary is responsible for the variable light curve, that the monochromatic albedo of the secondary is very low at short wavelengths, and that the depth of primary eclipse is strongly dependent on the primary's limb darkening.

  11. Preliminary Investigation of Curved Liner Sample in the NASA LaRC Curved Duct Test Rig

    NASA Technical Reports Server (NTRS)

    Gerhold, Carl H.; Jones, Michael G.; Brown, Martha C.

    2007-01-01

    This viewgraph presentation reviews the preliminary investigation of the curved liner sample in the NASA LaRC Curved Duct Test Rig (CDTR). It reviews the purpose of the Curved Duct Test Rig. Its purpose is to develop capability to investigate acoustic and aerodynamic properties in ducts. It has several features to accomplish that purpose: (1) Large scale (2) Flow rate to M = 0.275 (3) Higher order mode control (4) Curved flow path (5) Adaptable test section (6) Flexible test configurations. The liner has minimal effect on turbulence or boundary layer growth in duct. The curved duct sample attenuation is affected by mode scattering. In conclusion, the CDTR is valid tool for aerodynamic and acoustic evaluation of duct treatment

  12. The Chandelier Neuron in Schizophrenia

    PubMed Central

    Lewis, David A.

    2010-01-01

    Markers of GABA neurotransmission between chandelier neurons and their synaptic targets, the axon initial segment (AIS) of pyramidal neurons, are altered in the dorsolateral prefrontal cortex (DLPFC) of subjects with schizophrenia. For example, immunoreactivity for the GABA membrane transporter (GAT1) is decreased in presynaptic chandelier neuron axon terminals, whereas immunoreactivity for the GABAA receptor α2 subunit is increased in postsynaptic AIS. These alterations are most marked in cortical layers 2–3. In addition, other determinants of the function of chandelier cell-pyramidal neuron synapses, such as ankyrin-G (which regulates the recruitment of sodium channels to the AIS), are also selectively altered in superficial layer pyramidal neurons in subjects with schizophrenia. Each of these components of chandelier cell-pyramidal neuron connectivity exhibits distinctive developmental trajectories in the primate DLPFC, suggesting that disturbances in these trajectories could contribute to the pathogenesis of schizophrenia. Recent findings that inputs from neocortical chandelier neurons are excitatory provide new ideas about the role of this circuitry in the pathophysiology of cortical dysfunction in schizophrenia. PMID:21154915

  13. The chandelier neuron in schizophrenia.

    PubMed

    Lewis, David A

    2011-01-01

    Markers of GABA neurotransmission between chandelier neurons and their synaptic targets, the axon initial segment (AIS) of pyramidal neurons, are altered in the dorsolateral prefrontal cortex (DLPFC) of subjects with schizophrenia. For example, immunoreactivity for the GABA membrane transporter (GAT1) is decreased in presynaptic chandelier neuron axon terminals, whereas immunoreactivity for the GABA(A) receptor α2 subunit is increased in postsynaptic AIS. These alterations are most marked in cortical layers 2-3. In addition, other determinants of the function of chandelier cell-pyramidal neuron synapses, such as ankyrin-G (which regulates the recruitment of sodium channels to the AIS), are also selectively altered in superficial layer pyramidal neurons in subjects with schizophrenia. Each of these components of chandelier cell-pyramidal neuron connectivity exhibits distinctive developmental trajectories in the primate DLPFC, suggesting that disturbances in these trajectories could contribute to the pathogenesis of schizophrenia. Recent findings that inputs from neocortical chandelier neurons are excitatory provide new ideas about the role of this circuitry in the pathophysiology of cortical dysfunction in schizophrenia.

  14. Changes in cholesterol homeostasis and acute phase response link pulmonary exposure to multi-walled carbon nanotubes to risk of cardiovascular disease

    SciTech Connect

    Poulsen, Sarah S.; Saber, Anne T.; Mortensen, Alicja; Szarek, Józef; Wu, Dongmei; Williams, Andrew; Andersen, Ole; Jacobsen, Nicklas R.; Yauk, Carole L.; Wallin, Håkan; Halappanavar, Sabina; Vogel, Ulla

    2015-03-15

    Adverse lung effects following pulmonary exposure to multi-walled carbon nanotubes (MWCNTs) are well documented in rodents. However, systemic effects are less understood. Epidemiological studies have shown increased cardiovascular disease risk after pulmonary exposure to airborne particles, which has led to concerns that inhalation exposure to MWCNTs might pose similar risks. We analyzed parameters related to cardiovascular disease, including plasma acute phase response (APR) proteins and plasma lipids, in female C57BL/6 mice exposed to a single intratracheal instillation of 0, 18, 54 or 162 μg/mouse of small, entangled (CNT{sub Small}, 0.8 ± 0.1 μm long) or large, thick MWCNTs (CNT{sub Large}, 4 ± 0.4 μm long). Liver tissues and plasma were harvested 1, 3 and 28 days post-exposure. In addition, global hepatic gene expression, hepatic cholesterol content and liver histology were used to assess hepatic effects. The two MWCNTs induced similar systemic responses despite their different physicochemical properties. APR proteins SAA3 and haptoglobin, plasma total cholesterol and low-density/very low-density lipoprotein were significantly increased following exposure to either MWCNTs. Plasma SAA3 levels correlated strongly with pulmonary Saa3 levels. Analysis of global gene expression revealed perturbation of the same biological processes and pathways in liver, including the HMG-CoA reductase pathway. Both MWCNTs induced similar histological hepatic changes, with a tendency towards greater response following CNT{sub Large} exposure. Overall, we show that pulmonary exposure to two different MWCNTs induces similar systemic and hepatic responses, including changes in plasma APR, lipid composition, hepatic gene expression and liver morphology. The results link pulmonary exposure to MWCNTs with risk of cardiovascular disease. - Highlights: • Systemic and hepatic alterations were evaluated in female mice following MWCNT instillation. • Despite being physicochemically

  15. Weight loss and low body cell mass in males with lung cancer: relationship with systemic inflammation, acute-phase response, resting energy expenditure, and catabolic and anabolic hormones.

    PubMed

    Simons, J P; Schols, A M; Buurman, W A; Wouters, E F

    1999-08-01

    The aim of the present study was to investigate, in human lung cancer, the relationship between weight loss and the existence of a low body cell mass (BCM) on the one hand, and the putative presence of systemic inflammation, an increased acute-phase response, anorexia, hypermetabolism and changes in circulating levels of several anabolic and catabolic hormones on the other. In 20 male lung cancer patients, pre-stratified by weight loss of >/=10% (n=10) or of <10% (n=10), the following measurements were performed: BCM (by dual-energy X-ray absorptiometry/bromide dilution), circulating levels of sTNF-R55 and sTNF-R75 (soluble tumour necrosis factor receptors of molecular masses 55 and 75 kDa respectively), interleukin-6, lipopolysaccharide-binding protein, albumin, appetite (scale of 0-10), resting energy expenditure (by indirect calorimetry) and circulating levels of catabolic (cortisol) and anabolic [testosterone, insulin-like growth factor-I (IGF-I)] hormones. Compared with the patients with a weight loss of <10%, those with a weight loss of >/=10% were characterized by higher levels of sTNF-R55 (trend towards significance; P=0.06), and lower levels of albumin (27.4 compared with 34.4 mmol/l; P=0.02), testosterone (13.2 compared with 21.5 nmol/l; P=0.01) and IGF-I (119 compared with 184 ng/ml; P=0.004). In the patient group as a whole, the percentage weight loss was significantly correlated with sTNF-R55 (r=0.59, P=0.02), albumin (r=-0.63, P=0.006) and IGF-I (r=-0.50, P=0.02) levels. Height-adjusted BCM was significantly correlated with sTNF-R55 (r=-0.57, P=0.03), sTNF-R75 (r=-0.50, P=0. 04), lipopolysaccharide-binding protein (r=-0.50, P=0.04), albumin (r=0.56, P=0.02) and resting energy expenditure/BCM (r=-0.54, P=0. 03), and there was a trend towards a correlation with IGF-I concentration (r=0.44, P=0.06). We conclude that, in human lung cancer, weight loss and the presence of a low BCM are associated with systemic inflammation, an increased acute-phase

  16. Dopaminergic regulation of orexin neurons.

    PubMed

    Bubser, Michael; Fadel, Jim R; Jackson, Lela L; Meador-Woodruff, James H; Jing, Deqiang; Deutch, Ariel Y

    2005-06-01

    Orexin/hypocretin neurons in the lateral hypothalamus and adjacent perifornical area (LH/PFA) innervate midbrain dopamine (DA) neurons that project to corticolimbic sites and subserve psychostimulant-induced locomotor activity. However, it is not known whether dopamine neurons in turn regulate the activity of orexin cells. We examined the ability of dopamine agonists to activate orexin neurons in the rat, as reflected by induction of Fos. The mixed dopamine agonist apomorphine increased Fos expression in orexin cells, with a greater effect on orexin neurons located medial to the fornix. Both the selective D1-like agonist, A-77636, and the D2-like agonist, quinpirole, also induced Fos in orexin cells, suggesting that stimulation of either receptor subtype is sufficient to activate orexin neurons. Consistent with this finding, combined SCH 23390 (D1 antagonist)-haloperidol (D2 antagonist) pretreatment blocked apomorphine-induced activation of medial as well as lateral orexin neurons; in contrast, pretreatment with either the D1-like or D2-like antagonists alone did not attenuate apomorphine-induced activation of medial orexin cells. In situ hybridization histochemistry revealed that LH/PFA cells rarely express mRNAs encoding dopamine receptors, suggesting that orexin cells are transsynaptically activated by apomorphine. We therefore lesioned the nucleus accumbens, a site known to regulate orexin cells, but this treatment did not alter apomorphine-elicited activation of medial or lateral orexin neurons. Interestingly, apomorphine failed to activate orexin cells in isoflurane-anaesthetized animals. These data suggest that apomorphine-induced arousal but not accumbens-mediated hyperactivity is required for dopamine to transsynaptically activate orexin neurons.

  17. Ensemble Neuron Tracer for 3D Neuron Reconstruction.

    PubMed

    Wang, Ching-Wei; Lee, Yu-Ching; Pradana, Hilmil; Zhou, Zhi; Peng, Hanchuan

    2017-02-09

    Tracing of neuron paths is important in neuroscience. Recent studies have shown that it is possible to segment and reconstruct three-dimensional morphology of axons and dendrites using fully automatic neuron tracing methods. A specific tracer may be better than others for a specific dataset, but another tracer could perform better for some other datasets. Ensemble of learners is an effective way to improve learning accuracy in machine learning. We developed automatic ensemble neuron tracers, which consistently perform well on 57 datasets of 5 species collected from 7 laboratories worldwide. Quantitative evaluation based on the data generated by human annotators shows that the proposed ensemble tracers are valuable for 3D neuron tracing and can be widely applied to different datasets.

  18. Neuronal pathway finding: from neurons to initial neural networks.

    PubMed

    Roscigno, Cecelia I

    2004-10-01

    Neuronal pathway finding is crucial for structured cellular organization and development of neural circuits within the nervous system. Neuronal pathway finding within the visual system has been extensively studied and therefore is used as a model to review existing knowledge regarding concepts of this developmental process. General principles of neuron pathway finding throughout the nervous system exist. Comprehension of these concepts guides neuroscience nurses in gaining an understanding of the developmental course of action, the implications of different anomalies, as well as the theoretical basis and nursing implications of some provocative new therapies being proposed to treat neurodegenerative diseases and neurologic injuries. These therapies have limitations in light of current ethical, developmental, and delivery modes and what is known about the development of neuronal pathways.

  19. Mass Distributions Implying Flat Galactic Rotation Curves

    ERIC Educational Resources Information Center

    Keeports, David

    2010-01-01

    The rotational speeds of stars in the disc of a spiral galaxy are virtually independent of the distances of the stars from the centre of the galaxy. In common parlance, the stellar speed versus distance plot known as a galactic rotation curve is by observation typically nearly flat. This observation provides strong evidence that most galactic…

  20. The Window Dressing Behind "The Bell Curve."

    ERIC Educational Resources Information Center

    Richardson, Tina Q.

    1995-01-01

    Critiques the conceptual framework of "The Bell Curve: Intelligence and Class Structure in American Life." Concludes evidence is grounded in the classical tradition, which may be the case for some of their data, but conclusions and policy recommendations are based on assumptions and not grounded in data. Discusses limitations of scientific…

  1. Liquefaction probability curves for surficial geologic deposits

    USGS Publications Warehouse

    Holzer, Thomas L.; Noce, Thomas E.; Bennett, Michael J.

    2011-01-01

    Liquefaction probability curves that predict the probability of surface manifestations of earthquake-induced liquefaction are developed for 14 different types of surficial geologic units. The units consist of alluvial fan, beach ridge, river delta topset and foreset beds, eolian dune, point bar, flood basin, natural river and alluvial fan levees, abandoned river channel, deep-water lake, lagoonal, sandy artificial fill, and valley train deposits. Probability is conditioned on earthquake magnitude and peak ground acceleration. Curves are developed for water table depths of 1.5 and 5.0 m. Probabilities are derived from complementary cumulative frequency distributions of the liquefaction potential index (LPI) that were computed from 927 cone penetration tests. For natural deposits with a water table at 1.5 m and subjected to a M7.5 earthquake with peak ground acceleration (PGA)  =  0.25g, probabilities range from 0.5 for beach ridge, point bar, and deltaic deposits. The curves also were used to assign ranges of liquefaction probabilities to the susceptibility categories proposed previously for different geologic deposits. For the earthquake described here, probabilities for susceptibility categories have ranges of 0–0.08 for low, 0.09–0.30 for moderate, 0.31–0.62 for high, and 0.63–1.00 for very high. Retrospective predictions of liquefaction during historical earthquakes based on the curves compare favorably to observations.

  2. Pleats in crystals on curved surfaces.

    PubMed

    Irvine, William T M; Vitelli, Vincenzo; Chaikin, Paul M

    2010-12-16

    Hexagons can easily tile a flat surface, but not a curved one. Introducing heptagons and pentagons (defects with topological charge) makes it easier to tile curved surfaces; for example, soccer balls based on the geodesic domes of Buckminster Fuller have exactly 12 pentagons (positive charges). Interacting particles that invariably form hexagonal crystals on a plane exhibit fascinating scarred defect patterns on a sphere. Here we show that, for more general curved surfaces, curvature may be relaxed by pleats: uncharged lines of dislocations (topological dipoles) that vanish on the surface and play the same role as fabric pleats. We experimentally investigate crystal order on surfaces with spatially varying positive and negative curvature. On cylindrical capillary bridges, stretched to produce negative curvature, we observe a sequence of transitions-consistent with our energetic calculations-from no defects to isolated dislocations, which subsequently proliferate and organize into pleats; finally, scars and isolated heptagons (previously unseen) appear. This fine control of crystal order with curvature will enable explorations of general theories of defects in curved spaces. From a practical viewpoint, it may be possible to engineer structures with curvature (such as waisted nanotubes and vaulted architecture) and to develop novel methods for soft lithography and directed self-assembly.

  3. Serial Position Curves in Free Recall

    ERIC Educational Resources Information Center

    Laming, Donald

    2010-01-01

    The scenario for free recall set out in Laming (2009) is developed to provide models for the serial position curves from 5 selected sets of data, for final free recall, and for multitrial free recall. The 5 sets of data reflect the effects of rate of presentation, length of list, delay of recall, and suppression of rehearsal. Each model…

  4. The wavelength dependence of Triton's light curve

    NASA Technical Reports Server (NTRS)

    Hillier, J.; Veverka, J.; Helfenstein, P.; Mcewen, A.

    1991-01-01

    Using Voyager observations, it is demonstrated that Triton's orbital light curve is strongly wavelength-dependent, a characteristic which readily explains some of the apparent discrepancies among pre-Voyager telescopic measurements. Specifically, a light curve amplitude (peak to peak) is found that decreases systematically with increasing wavelength from about 0.08 magnitude (peak to peak) near 200 nm to less than 0.02 magnitude near 1000 nm. Peak brightness occurs near 90 deg orbital longitude (leading hemisphere). The brightness variation across this hemisphere is close to sinusoidal; the variation across the darker hemisphere is more complex. The decrease in light curve amplitude with increasing wavelength appears to be due to a decrease in contrast among surface markings, rather than to atmospheric obscuration. The model also explains the observed decrease in the amplitude of Triton's light curve at visible wavelengths over the past decade, a decrease related to the current migration of the subsolar latitude toward the south pole; it is predicted that this trend will continue into the 1990s.

  5. Light extraction block with curved surface

    DOEpatents

    Levermore, Peter; Krall, Emory; Silvernail, Jeffrey; Rajan, Kamala; Brown, Julia J.

    2016-03-22

    Light extraction blocks, and OLED lighting panels using light extraction blocks, are described, in which the light extraction blocks include various curved shapes that provide improved light extraction properties compared to parallel emissive surface, and a thinner form factor and better light extraction than a hemisphere. Lighting systems described herein may include a light source with an OLED panel. A light extraction block with a three-dimensional light emitting surface may be optically coupled to the light source. The three-dimensional light emitting surface of the block may includes a substantially curved surface, with further characteristics related to the curvature of the surface at given points. A first radius of curvature corresponding to a maximum principal curvature k.sub.1 at a point p on the substantially curved surface may be greater than a maximum height of the light extraction block. A maximum height of the light extraction block may be less than 50% of a maximum width of the light extraction block. Surfaces with cross sections made up of line segments and inflection points may also be fit to approximated curves for calculating the radius of curvature.

  6. Jet flow on ribbed curved surfaces

    NASA Astrophysics Data System (ADS)

    Lashkov, Iu. A.; Sokolova, I. N.; Shumilkina, E. A.

    1992-02-01

    The objective of the study was to investigate the possibility of using microribbing to reduce turbulent friction in Coanda flows over curved surfaces. It is shown that ribs make it possible to reduce the effect of a jet impinging on an obstacle and to prevent the Coanda effect when jet attachment is undesirable. The optimal rib parameters are determined.

  7. Is the Water Heating Curve as Described?

    ERIC Educational Resources Information Center

    Riveros, H. G.; Oliva, A. I.

    2008-01-01

    We analysed the heating curve of water which is described in textbooks. An experiment combined with some simple heat transfer calculations is discussed. The theoretical behaviour can be altered by changing the conditions under which the experiment is modelled. By identifying and controlling the different parameters involved during the heating…

  8. Least-squares fitting Gompertz curve

    NASA Astrophysics Data System (ADS)

    Jukic, Dragan; Kralik, Gordana; Scitovski, Rudolf

    2004-08-01

    In this paper we consider the least-squares (LS) fitting of the Gompertz curve to the given nonconstant data (pi,ti,yi), i=1,...,m, m≥3. We give necessary and sufficient conditions which guarantee the existence of the LS estimate, suggest a choice of a good initial approximation and give some numerical examples.

  9. Measuring Systematic Error with Curve Fits

    ERIC Educational Resources Information Center

    Rupright, Mark E.

    2011-01-01

    Systematic errors are often unavoidable in the introductory physics laboratory. As has been demonstrated in many papers in this journal, such errors can present a fundamental problem for data analysis, particularly when comparing the data to a given model. In this paper I give three examples in which my students use popular curve-fitting software…

  10. Dual kinetic curves in reversible electrochemical systems

    PubMed Central

    Hankins, Michael J.; Yablonsky, Gregory S.

    2017-01-01

    We introduce dual kinetic chronoamperometry, in which reciprocal relations are established between the kinetic curves of electrochemical reactions that start from symmetrical initial conditions. We have performed numerical and experimental studies in which the kinetic curves of the electron-transfer processes are analyzed for a reversible first order reaction. Experimental tests were done with the ferrocyanide/ferricyanide system in which the concentrations of each component could be measured separately using the platinum disk/gold ring electrode. It is shown that the proper ratio of the transient kinetic curves obtained from cathodic and anodic mass transfer limited regions give thermodynamic time invariances related to the reaction quotient of the bulk concentrations. Therefore, thermodynamic time invariances can be observed at any time using the dual kinetic curves for reversible reactions. The technique provides a unique possibility to extract the non-steady state trajectory starting from one initial condition based only on the equilibrium constant and the trajectory which starts from the symmetrical initial condition. The results could impact battery technology by predicting the concentrations and currents of the underlying non-steady state processes in a wide domain from thermodynamic principles and limited kinetic information. PMID:28358881

  11. A Class Inquiry into Newton's Cooling Curve

    ERIC Educational Resources Information Center

    Bartholow, Martin

    2007-01-01

    Newton's cooling curve was chosen for the four-part laboratory inquiry into conditions affecting temperature change. The relationship between time and temperature is not foreseen by the average high school student before the first session. However, during several activities students examine the classic relationship, T = A exp[superscript -Ct] + B…

  12. The Ultimate Spitzer Phase Curve Survey

    NASA Astrophysics Data System (ADS)

    Stevenson, Kevin; Bean, Jacob; Deming, Drake; Desert, Jean-Michel; Feng, Y. Katherina; Fortney, Jonathan; Kataria, Tiffany; Kempton, Eliza; Lewis, Nikole; Line, Michael; Morley, Caroline; Rauscher, Emily; Showman, Adam

    2016-08-01

    Exoplanet phase curves are sure to be one of the main enduring legacies of Spitzer. They provide a wealth of information about exoplanet atmospheres, including longitudinal constraints on atmospheric composition, thermal structure, and energy transport, that will continue to open new doors of scientific inquiry and propel future investigations for years to come. The measured heat redistribution efficiency (or ability to transport energy from a planet's highly-irradiated dayside to its eternally-dark nightside) shows considerable variation between exoplanets. Theoretical models predict a correlation between heat redistribution efficiency and planet temperature; however, the latest results are inconsistent with current predictions. Instead, a new potential trend is emerging, one that connects heat redistribution efficiency with planet rotation rate. We will test this hypothesis by performing Spitzer phase curve observations of seven exoplanets with physical properties that span the parameter space. We have identified high-contrast targets with short orbital periods around bright host stars to ensure the observations reveal robust phase curve results. Spitzer is uniquely suited for this program because we can achieve our primary goals using broadband photometry. Part of the phase curve legacy will be to combine our archived Spitzer data with transmission and dayside emission spectra from HST and JWST. Adding energy transport and cloud coverage constraints to the measured dayside abundances and thermal profiles will yield a fundamental understanding of these exoplanets' atmospheres that can be leveraged into new avenues of investigation.

  13. Marginal Utility and Convex Indifference Curves.

    ERIC Educational Resources Information Center

    Jackson, A.A.

    1981-01-01

    Reviews discussion of the relationship between marginal utility and indifference curves which has been presented in recent issues of "Economics." Concludes that indifference analysis does not embody the assumptions of marginal utility theory and that there is no simple relationship between these concepts that does not entail unacceptable…

  14. Nonadiabatic transitions at potential curve crossings

    SciTech Connect

    Nakamura, Hiroki; Zhu, Chaoyuan

    1996-12-31

    Recently, the Landau-Zener-Stueckelberg problems have been completely solved in a form convenient for various applications. A summary of the results will be reported. Other related subjects such as multi-level curve crossing and conical intersection problems will also be briefly touched upon.

  15. Nonlinear Growth Curves in Developmental Research

    ERIC Educational Resources Information Center

    Grimm, Kevin J.; Ram, Nilam; Hamagami, Fumiaki

    2011-01-01

    Developmentalists are often interested in understanding change processes, and growth models are the most common analytic tool for examining such processes. Nonlinear growth curves are especially valuable to developmentalists because the defining characteristics of the growth process such as initial levels, rates of change during growth spurts, and…

  16. "The Bell Curve": Review of Reviews.

    ERIC Educational Resources Information Center

    Parker, Franklin; Parker, Betty J.

    This paper reviews the book "The Bell Curve" by Harvard psychologist Richard J. Herrnstein and political scientist Charles Alan Murray. The paper asserts as the book's main points and implications: (1) one's socioeconomic place in life is now determined by IQ rather than family wealth and influence; (2) ruling white elites, who have…

  17. Tumor Static Concentration Curves in Combination Therapy.

    PubMed

    Cardilin, Tim; Almquist, Joachim; Jirstrand, Mats; Sostelly, Alexandre; Amendt, Christiane; El Bawab, Samer; Gabrielsson, Johan

    2017-03-01

    Combination therapies are widely accepted as a cornerstone for treatment of different cancer types. A tumor growth inhibition (TGI) model is developed for combinations of cetuximab and cisplatin obtained from xenograft mice. Unlike traditional TGI models, both natural cell growth and cell death are considered explicitly. The growth rate was estimated to 0.006 h(-1) and the natural cell death to 0.0039 h(-1) resulting in a tumor doubling time of 14 days. The tumor static concentrations (TSC) are predicted for each individual compound. When the compounds are given as single-agents, the required concentrations were computed to be 506 μg · mL(-1) and 56 ng · mL(-1) for cetuximab and cisplatin, respectively. A TSC curve is constructed for different combinations of the two drugs, which separates concentration combinations into regions of tumor shrinkage and tumor growth. The more concave the TSC curve is, the lower is the total exposure to test compounds necessary to achieve tumor regression. The TSC curve for cetuximab and cisplatin showed weak concavity. TSC values and TSC curves were estimated that predict tumor regression for 95% of the population by taking between-subject variability into account. The TSC concept is further discussed for different concentration-effect relationships and for combinations of three or more compounds.

  18. Towards Automatic Classification of Neurons

    PubMed Central

    Armañanzas, Rubén; Ascoli, Giorgio A.

    2015-01-01

    The classification of neurons into types has been much debated since the inception of modern neuroscience. Recent experimental advances are accelerating the pace of data collection. The resulting information growth of morphological, physiological, and molecular properties encourages efforts to automate neuronal classification by powerful machine learning techniques. We review state-of-the-art analysis approaches and availability of suitable data and resources, highlighting prominent challenges and opportunities. The effective solution of the neuronal classification problem will require continuous development of computational methods, high-throughput data production, and systematic metadata organization to enable cross-lab integration. PMID:25765323

  19. A fish on the hunt, observed neuron by neuron

    SciTech Connect

    2010-01-01

    This three-dimensional microscopy image reveals an output neuron of the optic tectum lighting up in response to visual information from the retina. The scientists used this state-of-the-art imaging technology to learn how neurons in the optic tectum take visual information and convert it into an output that drives action. More information: http://newscenter.lbl.gov/feature-stories/2010/10/29/zebrafish-vision/

  20. Modeling and Fitting Exoplanet Transit Light Curves

    NASA Astrophysics Data System (ADS)

    Millholland, Sarah; Ruch, G. T.

    2013-01-01

    We present a numerical model along with an original fitting routine for the analysis of transiting extra-solar planet light curves. Our light curve model is unique in several ways from other available transit models, such as the analytic eclipse formulae of Mandel & Agol (2002) and Giménez (2006), the modified Eclipsing Binary Orbit Program (EBOP) model implemented in Southworth’s JKTEBOP code (Popper & Etzel 1981; Southworth et al. 2004), or the transit model developed as a part of the EXOFAST fitting suite (Eastman et al. in prep.). Our model employs Keplerian orbital dynamics about the system’s center of mass to properly account for stellar wobble and orbital eccentricity, uses a unique analytic solution derived from Kepler’s Second Law to calculate the projected distance between the centers of the star and planet, and calculates the effect of limb darkening using a simple technique that is different from the commonly used eclipse formulae. We have also devised a unique Monte Carlo style optimization routine for fitting the light curve model to observed transits. We demonstrate that, while the effect of stellar wobble on transit light curves is generally small, it becomes significant as the planet to stellar mass ratio increases and the semi-major axes of the orbits decrease. We also illustrate the appreciable effects of orbital ellipticity on the light curve and the necessity of accounting for its impacts for accurate modeling. We show that our simple limb darkening calculations are as accurate as the analytic equations of Mandel & Agol (2002). Although our Monte Carlo fitting algorithm is not as mathematically rigorous as the Markov Chain Monte Carlo based algorithms most often used to determine exoplanetary system parameters, we show that it is straightforward and returns reliable results. Finally, we show that analyses performed with our model and optimization routine compare favorably with exoplanet characterizations published by groups such as the

  1. A "chaos" of Phanerozoic eustatic curves

    NASA Astrophysics Data System (ADS)

    Ruban, Dmitry A.

    2016-04-01

    The knowledge of eustasy has changed during the past two decades. Although there is not any single global sea-level curve for the entire Phanerozoic, new curves have been proposed for all periods. For some geological time intervals, there are two and more alternative reconstructions, from which it is difficult to choose. A significant problem is the available eustatic curves are justified along different geological time scales (sometimes without proper explanations), which permits to correlate eustatic events with the possible error of 1-3 Ma. This degree of error permits to judge about only substage- or stage-order global sea-level changes. Close attention to two geological time slices, namely the late Cambrian (Epoch 3‒Furongian) and the Late Cretaceous, implies that only a few eustatic events (6 events in the case of the late Cambrian and 9 events in the case of the Late Cretaceous) appear on all available alternative curves for these periods, and different (even opposite) trends of eustatic fluctuations are shown on these curves. This reveals significant uncertainty in our knowledge of eustasy that restricts our ability to decipher factors responsible for regional transgressions and regressions and relative sea-level changes. A big problem is also inadequate awareness of the geological research community of the new eustatic developments. Generally, the situation with the development and the use of the Phanerozoic eustatic reconstructions seems to be "chaotic". The example of the shoreline shifts in Northern Africa during the Late Cretaceous demonstrates the far-going consequences of this situation. The practical recommendations to avoid this "chaos" are proposed. Particularly, these claim for good awareness of all eustatic developments, their critical discussion, and clear explanation of the employed geological time scale.

  2. Trend analyses with river sediment rating curves

    USGS Publications Warehouse

    Warrick, Jonathan A.

    2015-01-01

    Sediment rating curves, which are fitted relationships between river discharge (Q) and suspended-sediment concentration (C), are commonly used to assess patterns and trends in river water quality. In many of these studies it is assumed that rating curves have a power-law form (i.e., C = aQb, where a and b are fitted parameters). Two fundamental questions about the utility of these techniques are assessed in this paper: (i) How well to the parameters, a and b, characterize trends in the data? (ii) Are trends in rating curves diagnostic of changes to river water or sediment discharge? As noted in previous research, the offset parameter, a, is not an independent variable for most rivers, but rather strongly dependent on b and Q. Here it is shown that a is a poor metric for trends in the vertical offset of a rating curve, and a new parameter, â, as determined by the discharge-normalized power function [C = â (Q/QGM)b], where QGM is the geometric mean of the Q values sampled, provides a better characterization of trends. However, these techniques must be applied carefully, because curvature in the relationship between log(Q) and log(C), which exists for many rivers, can produce false trends in â and b. Also, it is shown that trends in â and b are not uniquely diagnostic of river water or sediment supply conditions. For example, an increase in â can be caused by an increase in sediment supply, a decrease in water supply, or a combination of these conditions. Large changes in water and sediment supplies can occur without any change in the parameters, â and b. Thus, trend analyses using sediment rating curves must include additional assessments of the time-dependent rates and trends of river water, sediment concentrations, and sediment discharge.

  3. Npas1+ Pallidal Neurons Target Striatal Projection Neurons

    PubMed Central

    Glajch, Kelly E.; Kelver, Daniel A.; Hegeman, Daniel J.; Cui, Qiaoling; Xenias, Harry S.; Augustine, Elizabeth C.; Hernández, Vivian M.; Verma, Neha; Huang, Tina Y.; Luo, Minmin; Justice, Nicholas J.

    2016-01-01

    Compelling evidence demonstrates that the external globus pallidus (GPe) plays a key role in processing sensorimotor information. An anatomical projection from the GPe to the dorsal striatum has been described for decades. However, the cellular target and functional impact of this projection remain unknown. Using cell-specific transgenic mice, modern monosynaptic tracing techniques, and optogenetics-based mapping, we discovered that GPe neurons provide inhibitory inputs to direct and indirect pathway striatal projection neurons (SPNs). Our results indicate that the GPe input to SPNs arises primarily from Npas1-expressing neurons and is strengthened in a chronic Parkinson's disease (PD) model. Alterations of the GPe-SPN input in a PD model argue for the critical position of this connection in regulating basal ganglia motor output and PD symptomatology. Finally, chemogenetic activation of Npas1-expressing GPe neurons suppresses motor output, arguing that strengthening of the GPe-SPN connection is maladaptive and may underlie the hypokinetic symptoms in PD. SIGNIFICANCE STATEMENT An anatomical projection from the pallidum to the striatum has been described for decades, but little is known about its connectivity pattern. The authors dissect the presynaptic and postsynaptic neurons involved in this projection, and show its cell-specific remodeling and strengthening in parkinsonian mice. Chemogenetic activation of Npas1+ pallidal neurons that give rise to the principal pallidostriatal projection increases the time that the mice spend motionless. This argues that maladaptive strengthening of this connection underlies the paucity of volitional movements, which is a hallmark of Parkinson's disease. PMID:27194328

  4. A cDNA microarray analysis to identify genes involved in the acute-phase response pathway of the olive flounder after infection with Edwardsiella tarda.

    PubMed

    Moon, Ji Young; Hong, Yong-Ki; Kong, Hee Jeong; Kim, Dong-Gyun; Kim, Young-Ok; Kim, Woo-Jin; Ji, Young Joo; An, Cheul Min; Nam, Bo-Hye

    2014-09-15

    The acute-phase response (APR) is an important systemic reaction that occurs within hours of an inflammatory signal caused by physical bodily injury or microbial infection. To investigate the APR of the olive flounder (Paralichthys olivaceus) following infection with a pathogen, we established an expressed sequence tag (EST)-based cDNA microarray chip composed of 13,061 PCR-amplified cDNAs encoding unique genes selected from an olive flounder EST analysis. Microarray analyses showed that the set of genes involved in the APR was strongly up-regulated in the liver of the olive flounder after infection with Edwardsiella tarda. Among the up-regulated genes, catechol-O-methyltransferase domain-containing protein 1, six-transmembrane prostate protein, haptoglobin precursor, and toll-like receptor 5 soluble form were particularly strongly up-regulated. Interestingly, the toll-like receptor 5 soluble form, which has not yet been detected in mammals, was up-regulated as much as 250-fold upon E. tarda infection. These results suggest that the APR mechanism of fish may be regulated differently from that of mammals. The data described here contribute toward our collective understanding of APR, especially in fish.

  5. Metabolic Cost of the Activation of Immune Response in the Fish-Eating Myotis (Myotis vivesi): The Effects of Inflammation and the Acute Phase Response.

    PubMed

    Otálora-Ardila, Aída; Herrera M, L Gerardo; Flores-Martínez, José Juan; Welch, Kenneth C

    2016-01-01

    Inflammation and activation of the acute phase response (APR) are energetically demanding processes that protect against pathogens. Phytohaemagglutinin (PHA) and lipopolysaccharide (LPS) are antigens commonly used to stimulate inflammation and the APR, respectively. We tested the hypothesis that the APR after an LPS challenge was energetically more costly than the inflammatory response after a PHA challenge in the fish-eating Myotis bat (Myotis vivesi). We measured resting metabolic rate (RMR) after bats were administered PHA and LPS. We also measured skin temperature (Tskin) after the LPS challenge and skin swelling after the PHA challenge. Injection of PHA elicited swelling that lasted for several days but changes in RMR and body mass were not significant. LPS injection produced a significant increase in Tskin and in RMR, and significant body mass loss. RMR after LPS injection increased by 140-185% and the total cost of the response was 6.50 kJ. Inflammation was an energetically low-cost process but the APR entailed a significant energetic investment. Examination of APR in other bats suggests that the way in which bats deal with infections might not be uniform.

  6. Acute phase response to Mycoplasma haemofelis and 'Candidatus Mycoplasma haemominutum' infection in FIV-infected and non-FIV-infected cats.

    PubMed

    Korman, R M; Cerón, J J; Knowles, T G; Barker, E N; Eckersall, P D; Tasker, S

    2012-08-01

    The pathogenicity of Haemoplasma spp. in cats varies with 'Candidatus Mycoplasma haemominutum' (CMhm) causing subclinical infection while Mycoplasma haemofelis (Mhf) often induces haemolytic anaemia. The aims of this study were to characterise the acute phase response (APR) of the cat to experimental infection with Mhf or CMhm, and to determine whether chronic feline immunodeficiency virus (FIV) infection influences this response. The acute phase proteins serum amyloid A (SAA), haptoglobin (Hp) and α-1-acid glycoprotein (AGP) concentrations were measured pre-infection and every 7-14 days up to day 100 post-infection (pi) in cats infected with either Mhf or CMhm. Half of each group of cats (6/12) were chronically and subclinically infected with FIV. Marbofloxacin treatment was given on days 16-44 pi to half of the Mhf-infected cats, and on days 49-77 pi to half of the CMhm-infected cats. FIV-infected animals had significantly lower AGP concentrations, and significantly greater Hp concentrations than non-FIV-infected cats when infected with CMhm and Mhf, respectively. Both CMhm and Mhf infection were associated with significant increases in SAA concentrations, while AGP concentrations were only significantly increased by Mhf infection. Mhf-infected cats had significantly greater SAA concentrations than CMhm-infected animals. Both Mhf and CMhm infections were associated with an APR, with Mhf infection inducing a greater response. Chronic FIV infection appeared to modify the APR, which varied with the infecting Haemoplasma species.

  7. Metabolic Cost of the Activation of Immune Response in the Fish-Eating Myotis (Myotis vivesi): The Effects of Inflammation and the Acute Phase Response

    PubMed Central

    Otálora-Ardila, Aída; Herrera M., L. Gerardo; Flores-Martínez, José Juan; Welch, Kenneth C.

    2016-01-01

    Inflammation and activation of the acute phase response (APR) are energetically demanding processes that protect against pathogens. Phytohaemagglutinin (PHA) and lipopolysaccharide (LPS) are antigens commonly used to stimulate inflammation and the APR, respectively. We tested the hypothesis that the APR after an LPS challenge was energetically more costly than the inflammatory response after a PHA challenge in the fish-eating Myotis bat (Myotis vivesi). We measured resting metabolic rate (RMR) after bats were administered PHA and LPS. We also measured skin temperature (Tskin) after the LPS challenge and skin swelling after the PHA challenge. Injection of PHA elicited swelling that lasted for several days but changes in RMR and body mass were not significant. LPS injection produced a significant increase in Tskin and in RMR, and significant body mass loss. RMR after LPS injection increased by 140–185% and the total cost of the response was 6.50 kJ. Inflammation was an energetically low-cost process but the APR entailed a significant energetic investment. Examination of APR in other bats suggests that the way in which bats deal with infections might not be uniform. PMID:27792729

  8. Guidelines on selection of laboratory tests for monitoring the acute phase response. International Committee for Standardization in Haematology (expert panel on blood rheology).

    PubMed Central

    1988-01-01

    These guidelines refer to laboratory tests for monitoring changes in acute phase proteins in patients with an inflammatory response to tissue damage. Quantitative measurements of acute phase proteins are a valuable indicator of the presence, extent, and response of inflammation to treatment. When short term (less than 24 hours) changes in the inflammatory response are expected, quantitative assay of C reactive protein is the test of choice. The hyperproteinaemia that develops in response to a longer term (more than 24 hours) inflammatory response is complex and may vary from one disease to another. A test that is sensitive to the combined effect of several plasma proteins is therefore indicated, and appropriate tests include the erythrocyte sedimentation rate and plasma viscosity--the latter having several advantages. Tests for monitoring short term and long term changes in acute phase proteins are complementary and should be used for different clinical purposes; no one test is ideal for all clinical situations. A quality control programme is an essential component of laboratory tests for monitoring the acute phase response. PMID:2463272

  9. Neuronal boost to evolutionary dynamics.

    PubMed

    de Vladar, Harold P; Szathmáry, Eörs

    2015-12-06

    Standard evolutionary dynamics is limited by the constraints of the genetic system. A central message of evolutionary neurodynamics is that evolutionary dynamics in the brain can happen in a neuronal niche in real time, despite the fact that neurons do not reproduce. We show that Hebbian learning and structural synaptic plasticity broaden the capacity for informational replication and guided variability provided a neuronally plausible mechanism of replication is in place. The synergy between learning and selection is more efficient than the equivalent search by mutation selection. We also consider asymmetric landscapes and show that the learning weights become correlated with the fitness gradient. That is, the neuronal complexes learn the local properties of the fitness landscape, resulting in the generation of variability directed towards the direction of fitness increase, as if mutations in a genetic pool were drawn such that they would increase reproductive success. Evolution might thus be more efficient within evolved brains than among organisms out in the wild.

  10. Neuronal boost to evolutionary dynamics

    PubMed Central

    de Vladar, Harold P.; Szathmáry, Eörs

    2015-01-01

    Standard evolutionary dynamics is limited by the constraints of the genetic system. A central message of evolutionary neurodynamics is that evolutionary dynamics in the brain can happen in a neuronal niche in real time, despite the fact that neurons do not reproduce. We show that Hebbian learning and structural synaptic plasticity broaden the capacity for informational replication and guided variability provided a neuronally plausible mechanism of replication is in place. The synergy between learning and selection is more efficient than the equivalent search by mutation selection. We also consider asymmetric landscapes and show that the learning weights become correlated with the fitness gradient. That is, the neuronal complexes learn the local properties of the fitness landscape, resulting in the generation of variability directed towards the direction of fitness increase, as if mutations in a genetic pool were drawn such that they would increase reproductive success. Evolution might thus be more efficient within evolved brains than among organisms out in the wild. PMID:26640653

  11. Neuronal migration and protein kinases

    PubMed Central

    Ohshima, Toshio

    2015-01-01

    The formation of the six-layered structure of the mammalian cortex via the inside-out pattern of neuronal migration is fundamental to neocortical functions. Extracellular cues such as Reelin induce intracellular signaling cascades through the protein phosphorylation. Migrating neurons also have intrinsic machineries to regulate cytoskeletal proteins and adhesion properties. Protein phosphorylation regulates these processes. Moreover, the balance between phosphorylation and dephosphorylation is modified by extracellular cues. Multipolar-bipolar transition, radial glia-guided locomotion and terminal translocation are critical steps of radial migration of cortical pyramidal neurons. Protein kinases such as Cyclin-dependent kinase 5 (Cdk5) and c-Jun N-terminal kinases (JNKs) involve these steps. In this review, I shall give an overview the roles of protein kinases in neuronal migration. PMID:25628530

  12. Polyphenolic Antioxidants and Neuronal Regeneration

    PubMed Central

    Ataie, Amin; Shadifar, Mohammad; Ataee, Ramin

    2016-01-01

    Many studies indicate that oxidative stress is involved in the pathophysiology of neurodegenerative diseases. Oxidative stress can induce neuronal damages, modulate intracellular signaling and ultimately leads to neuronal death by apoptosis or necrosis. To review antioxidants preventive effects on oxidative stress and neurodegenerative diseases we accumulated data from international medical journals and academic informations’ sites. According to many studies, antioxidants could reduce toxic neuronal damages and many studies confirmed the efficacy of polyphenol antioxidants in fruits and vegetables to reduce neuronal death and to diminish oxidative stress. This systematic review showed the antioxidant activities of phytochemicals which play as natural neuroprotectives with low adverse effects against some neurodegenerative diseases as Parkinson or Alzheimer diseases. PMID:27303602

  13. Duration sensitivity of neurons in the primary auditory cortex of albino mouse.

    PubMed

    Wang, Xin; Qi, Qiaozhen; Huang, Caifei; Chomiak, Taylor; Luo, Feng

    2016-02-01

    Many neurons in the central auditory system of a number of species have been found to be sensitive to the duration of sound stimuli. While previous studies have shown that γ-aminobutyric acid (GABA)-ergic inhibitory input is important for duration sensitivity in the inferior colliculus (IC), it is still unknown whether (GABA)-ergic inhibitory input plays an important role in generating duration sensitivity in the cortex. Using free-field sound stimulation and in vivo extracellular recording, we investigated duration sensitivity in primary auditory cortical (AI) neurons of the Nembutal anesthetized albino mouse (Mus musculus, Km) and examined the effect of the GABAA receptor antagonist bicuculline on AI neuron duration sensitivity. A total of 63 duration tuning curves were measured in AI neurons. Of these, 44% (28/63) exhibited duration sensitive responses, while 43% (27/63) lacked duration sensitivity. The remaining 13% (8/63) exhibited long-pass properties likely reflecting both duration sensitive and insensitive features. We found that duration sensitive neurons had shorter first spike latency (FSL) and longer firing duration (FD) when stimulated with best duration (p < 0.05), while duration insensitive neurons had invariable FSL and FD at different sound durations (p>0.05). Furthermore, 60% (6/10) of duration sensitive neurons and 75% (3/4) long-pass neurons lost duration sensitivity following bicuculline application. Taken together, our results show that cortical neurons in the albino mouse are sensitive to sound duration, and that GABAergic inhibition may play an important role in the formation of de novo duration sensitivity in AI. The possible mechanism and behavioral significance of duration sensitivity in AI neurons is discussed.

  14. [Some characteristics of vertigo in vestibular neuronitis].

    PubMed

    Skliut, I A; Likhachev, S A; Rybina, O V

    2004-01-01

    The authors present a detailed clinical analysis of objective neurological symptoms and vertigo in patients with vestibular neuronitis. Diagnostic criteria are specified allowing differentiation between vertigo and dizziness, pathognomonic signs of vestibular neuronitis are outlined. Peripheral location of the pathological process in vestibular neuronitis is suggested. How rotating vertigo is forming in patients with vestibular neuronitis is hypothesized.

  15. Bursting Types and Bifurcation Analysis in the Pre-Bötzinger Complex Respiratory Rhythm Neuron

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Lu, Bo; Liu, Shenquan; Jiang, Xiaofang

    Many types of neurons and excitable cells could intrinsically generate bursting activity, even in an isolated case, which plays a vital role in neuronal signaling and synaptic plasticity. In this paper, we have mainly investigated bursting types and corresponding bifurcations in the pre-Bötzinger complex respiratory rhythm neuron by using fast-slow dynamical analysis. The numerical simulation results have showed that for some appropriate parameters, the neuron model could exhibit four distinct types of fast-slow bursters. We also explored the bifurcation mechanisms related to these four types of bursters through the analysis of phase plane. Moreover, the first Lyapunov coefficient of the Hopf bifurcation, which can decide whether it is supercritical or subcritical, was calculated with the aid of MAPLE software. In addition, we analyzed the codimension-two bifurcation for equilibria of the whole system and gave a detailed theoretical derivation of the Bogdanov-Takens bifurcation. Finally, we obtained expressions for a fold bifurcation curve, a nondegenerate Hopf bifurcation curve, and a saddle homoclinic bifurcation curve near the Bogdanov-Takens bifurcation point.

  16. Spinal sensory projection neuron responses to spinal cord stimulation are mediated by circuits beyond gate control

    PubMed Central

    Zhang, Tianhe C.; Janik, John J.; Peters, Ryan V.; Chen, Gang; Ji, Ru-Rong

    2015-01-01

    Spinal cord stimulation (SCS) is a therapy used to treat intractable pain with a putative mechanism of action based on the Gate Control Theory. We hypothesized that sensory projection neuron responses to SCS would follow a single stereotyped response curve as a function of SCS frequency, as predicted by the Gate Control circuit. We recorded the responses of antidromically identified sensory projection neurons in the lumbar spinal cord during 1- to 150-Hz SCS in both healthy rats and neuropathic rats following chronic constriction injury (CCI). The relationship between SCS frequency and projection neuron activity predicted by the Gate Control circuit accounted for a subset of neuronal responses to SCS but could not account for the full range of observed responses. Heterogeneous responses were classifiable into three additional groups and were reproduced using computational models of spinal microcircuits representing other interactions between nociceptive and nonnociceptive sensory inputs. Intrathecal administration of bicuculline, a GABAA receptor antagonist, increased spontaneous and evoked activity in projection neurons, enhanced excitatory responses to SCS, and reduced inhibitory responses to SCS, suggesting that GABAA neurotransmission plays a broad role in regulating projection neuron activity. These in vivo and computational results challenge the Gate Control Theory as the only mechanism underlying SCS and refine our understanding of the effects of SCS on spinal sensory neurons within the framework of contemporary understanding of dorsal horn circuitry. PMID:25972582

  17. Properties of Neurons in External Globus Pallidus Can Support Optimal Action Selection

    PubMed Central

    Bogacz, Rafal; Martin Moraud, Eduardo; Abdi, Azzedine; Magill, Peter J.; Baufreton, Jérôme

    2016-01-01

    The external globus pallidus (GPe) is a key nucleus within basal ganglia circuits that are thought to be involved in action selection. A class of computational models assumes that, during action selection, the basal ganglia compute for all actions available in a given context the probabilities that they should be selected. These models suggest that a network of GPe and subthalamic nucleus (STN) neurons computes the normalization term in Bayes’ equation. In order to perform such computation, the GPe needs to send feedback to the STN equal to a particular function of the activity of STN neurons. However, the complex form of this function makes it unlikely that individual GPe neurons, or even a single GPe cell type, could compute it. Here, we demonstrate how this function could be computed within a network containing two types of GABAergic GPe projection neuron, so-called ‘prototypic’ and ‘arkypallidal’ neurons, that have different response properties in vivo and distinct connections. We compare our model predictions with the experimentally-reported connectivity and input-output functions (f-I curves) of the two populations of GPe neurons. We show that, together, these dichotomous cell types fulfil the requirements necessary to compute the function needed for optimal action selection. We conclude that, by virtue of their distinct response properties and connectivities, a network of arkypallidal and prototypic GPe neurons comprises a neural substrate capable of supporting the computation of the posterior probabilities of actions. PMID:27389780

  18. Centrosome localization determines neuronal polarity.

    PubMed

    de Anda, Froylan Calderon; Pollarolo, Giulia; Da Silva, Jorge Santos; Camoletto, Paola G; Feiguin, Fabian; Dotti, Carlos G

    2005-08-04

    Neuronal polarization occurs shortly after mitosis. In neurons differentiating in vitro, axon formation follows the segregation of growth-promoting activities to only one of the multiple neurites that form after mitosis. It is unresolved whether such spatial restriction makes use of an intrinsic program, like during C. elegans embryo polarization, or is extrinsic and cue-mediated, as in migratory cells. Here we show that in hippocampal neurons in vitro, the axon consistently arises from the neurite that develops first after mitosis. Centrosomes, the Golgi apparatus and endosomes cluster together close to the area where the first neurite will form, which is in turn opposite from the plane of the last mitotic division. We show that the polarized activities of these organelles are necessary and sufficient for neuronal polarization: (1) polarized microtubule polymerization and membrane transport precedes first neurite formation, (2) neurons with more than one centrosome sprout more than one axon and (3) suppression of centrosome-mediated functions precludes polarization. We conclude that asymmetric centrosome-mediated dynamics in the early post-mitotic stage instruct neuronal polarity, implying that pre-mitotic mechanisms with a role in division orientation may in turn participate in this event.

  19. Network synchronization in hippocampal neurons.

    PubMed

    Penn, Yaron; Segal, Menahem; Moses, Elisha

    2016-03-22

    Oscillatory activity is widespread in dynamic neuronal networks. The main paradigm for the origin of periodicity consists of specialized pacemaking elements that synchronize and drive the rest of the network; however, other models exist. Here, we studied the spontaneous emergence of synchronized periodic bursting in a network of cultured dissociated neurons from rat hippocampus and cortex. Surprisingly, about 60% of all active neurons were self-sustained oscillators when disconnected, each with its own natural frequency. The individual neuron's tendency to oscillate and the corresponding oscillation frequency are controlled by its excitability. The single neuron intrinsic oscillations were blocked by riluzole, and are thus dependent on persistent sodium leak currents. Upon a gradual retrieval of connectivity, the synchrony evolves: Loose synchrony appears already at weak connectivity, with the oscillators converging to one common oscillation frequency, yet shifted in phase across the population. Further strengthening of the connectivity causes a reduction in the mean phase shifts until zero-lag is achieved, manifested by synchronous periodic network bursts. Interestingly, the frequency of network bursting matches the average of the intrinsic frequencies. Overall, the network behaves like other universal systems, where order emerges spontaneously by entrainment of independent rhythmic units. Although simplified with respect to circuitry in the brain, our results attribute a basic functional role for intrinsic single neuron excitability mechanisms in driving the network's activity and dynamics, contributing to our understanding of developing neural circuits.

  20. Neuronal polarization in the developing cerebral cortex

    PubMed Central

    Sakakibara, Akira; Hatanaka, Yumiko

    2015-01-01

    Cortical neurons consist of excitatory projection neurons and inhibitory GABAergic interneurons, whose connections construct highly organized neuronal circuits that control higher order information processing. Recent progress in live imaging has allowed us to examine how these neurons differentiate during development in vivo or in in vivo-like conditions. These analyses have revealed how the initial steps of polarization, in which neurons establish an axon, occur. Interestingly, both excitatory and inhibitory cortical neurons establish neuronal polarity de novo by undergoing a multipolar stage reminiscent of the manner in which polarity formation occurs in hippocampal neurons in dissociated culture. In this review, we focus on polarity formation in cortical neurons and describe their typical morphology and dynamic behavior during the polarization period. We also discuss cellular and molecular mechanisms underlying polarization, with reference to polarity formation in dissociated hippocampal neurons in vitro. PMID:25904841

  1. Piecewise quartic polynomial curves with a local shape parameter

    NASA Astrophysics Data System (ADS)

    Han, Xuli

    2006-10-01

    Piecewise quartic polynomial curves with a local shape parameter are presented in this paper. The given blending function is an extension of the cubic uniform B-splines. The changes of a local shape parameter will only change two curve segments. With the increase of the value of a shape parameter, the curves approach a corresponding control point. The given curves possess satisfying shape-preserving properties. The given curve can also be used to interpolate locally the control points with GC2 continuity. Thus, the given curves unify the representation of the curves for interpolating and approximating the control polygon. As an application, the piecewise polynomial curves can intersect an ellipse at different knot values by choosing the value of the shape parameter. The given curve can approximate an ellipse from the both sides and can then yield a tight envelope for an ellipse. Some computing examples for curve design are given.

  2. Estimated hydrogeological parameters by artificial neurons network

    NASA Astrophysics Data System (ADS)

    Lin, H.; Chen, C.; Tan, Y.; Ke, K.

    2009-12-01

    In recent years, many approaches had been developed using artificial neurons network (ANN) model cooperated with Theis analytical solution to estimate the effective hydrological parameters for the homogenous and isotropic porous media, such as Lin and Chen approach [Lin and Chen, 2006] (or called the ANN approach hereafter), PC-ANN approach [Samani et al., 2008]. The above methods assumed a full superimposition of the type curve and the observed drawdown, and tried to use the first time-drawdown data as a match point to make a fine approximation of the effective parameters. However, using the first time-drawdown data or the early time-drawdown data is not always correct for the estimation of the hydrological parameters, especially for heterogeneous and anisotropic aquifers. Therefore, this paper mainly corrected the concept of superimposed plot by modifying the ANN approach and PC-ANN approach, as well as cooperating with Papadopoulos analytical solution, to estimate the transmissivities and storage coefficient for anisotropic, heterogeneous aquifers. The ANN model is trained with 4000 training sets of the well function, and tested with 1000 sets and 300 sets of synthetic time-drawdown generated from homogonous and heterogonous parameters, respectively. In-situ observation data, the time-drawdown at station Shi-Chou of the Chihuahua River alluvial fan, Taiwan, is further adopted to test the applicability and reliability of proposed methods, as well as comparing with Straight-line method and Type-curve method. Results suggested that both of the modified methods had better performance than the original ones. Using late time drawdown to optimize the effective parameters is shown better than using early-time drawdown. Additionally, results indicated that the modified ANN approach is better than the modified PC-ANN approach in terms of precision, while the efficiency of the modified PC-ANN approach is approximately three times better than the modified ANN approach.

  3. Curved butterfly bileaflet prosthetic cardiac valve

    DOEpatents

    McQueen, David M.; Peskin, Charles S.

    1991-06-25

    An annular valve body having a central passageway for the flow of blood therethrough with two curved leaflets each of which is pivotally supported on an accentric positioned axis in the central passageway for moving between a closed position and an open position. The leaflets are curved in a plane normal to the eccentric axis and positioned with the convex side of the leaflets facing each other when the leaflets are in the open position. Various parameters such as the curvature of the leaflets, the location of the eccentric axis, and the maximum opening angle of the leaflets are optimized according to the following performance criteria: maximize the minimum peak velocity through the valve, maximize the net stroke volume, and minimize the mean forward pressure difference, thereby reducing thrombosis and improving the hemodynamic performance.

  4. Curved contours and the associative response.

    PubMed

    Zusne, L

    1975-02-01

    72 random polygons and their curvilinear transformations were exposed for 3 sec. to 40 subjects who produced written associations during a 10-sec. interval. The number of associations varied, in general, directly with the amount of curved contour as well as with the degree of contour dispersion. The amount of variance accounted for by these two variables was small, however. Differences in curvature produced much greater differences in the content of the associations, greater degrees of curvature evoking more associations that were curved, man-made objects or living things and fewer associations that were straight-edged, man-made objects. A significant and inverse relationship was also established between contour dispersion and associations that were non-living, natural objects. It is concluded that physical form dimensions, especially curvature, affect less the association value (connotative meaning) of visual forms and much more their denotative meaning.

  5. Measuring Model Rocket Engine Thrust Curves

    NASA Astrophysics Data System (ADS)

    Penn, Kim; Slaton, William V.

    2010-12-01

    This paper describes a method and setup to quickly and easily measure a model rocket engine's thrust curve using a computer data logger and force probe. Horst describes using Vernier's LabPro2 and force probe to measure the rocket engine's thrust curve; however, the method of attaching the rocket to the force probe is not discussed. We show how a simple engine holder can be constructed and used with Vernier's LabPro and force probe to record data that students can use to compare to sample data from the rocket manufacturer or the National Association of Rocketry's3 engine certification sheets, calculate total impulse, and make predictions for model rocket launches. PASCO markets a rocket engine test bracket4 that mounts to its PASPORT force sensor for similar measurements. The engine holder described here is very economical, and all the parts can be obtained from a local hardware store or home center.

  6. Modeling Light Curves for Improved Classification

    NASA Astrophysics Data System (ADS)

    Faraway, Julian; Mahabal, Ashish; Sun, Jiayang; Wang, Xiaofeng; Yi; Zhang, Lingsong

    2016-02-01

    Many synoptic surveys are observing large parts of the sky multiple times. The resulting lightcurves provide a wonderful window to the dynamic nature of the universe. However, there are many significant challenges in analyzing these light curves. These include heterogeneity of the data, irregularly sampled data, missing data, censored data, known but variable measurement errors, and most importantly, the need to classify in astronomical objects in real time using these imperfect light curves. We describe a modeling-based approach using Gaussian process regression for generating critical measures representing features for the classification of such lightcurves. We demonstrate that our approach performs better by comparing it with past methods. Finally, we provide future directions for use in sky-surveys that are getting even bigger by the day.

  7. Radio light curves of V471 Tauri

    NASA Technical Reports Server (NTRS)

    Patterson, Joseph; Caillault, Jean-Pierre; Skillman, David R.

    1993-01-01

    We have acquired light curves at a wavelength of 6 cm of the eclipsing binary V471 Tauri around the orbit, in order to determine the geometrical location of the radio emission in the binary. Each light curve shows a broad minimum near the time of optical eclipse, suggesting that the radio luminosity originates between the two stars. Other observations at X-ray, UV, and visual wavelengths are also supportive of the idea of a gas cloud more or less permanently located between the stars. This could be explained if the radio emission arises from the interaction of the magnetic fields of the secondary and the white dwarf near the line of centers.

  8. Taurine-induced modulation of voltage-sensitive Na+ channels in rat dorsal root ganglion neurons.

    PubMed

    Yu, Shan-Shan; Yu, Kuai; Gu, Yan; Ruan, Di-Yun

    2005-08-15

    The physiological role of taurine, an abundant free amino acid in the neural system, is still poorly understood. The aim of this study was to investigate its effect on TTX-sensitive (TTX-S) and TTX-resistant (TTX-R) Na+ currents in enzymatically dissociated neurons from rat dorsal root ganglion (DRG) with conventional whole-cell recording manner under voltage-clamp conditions. A TTX-S Na+ current was recorded preferentially from large DRG neurons and a TTX-R Na+ current preferentially from small ones. For TTX-S Na+ channel, taurine of the concentration > or = 10 mM shifted the activation curve in the depolarizing direction and the inactivation curve in the hyperpolarizing direction. There was no change in the activation curve for TTX-R Na+ channel and the inactivation curve was shifted in the hyperpolarizing direction slightly in the presence of taurine > or = 20 mM. When the recovery kinetics was examined, the presence of taurine resulted in a slower recovery from inactivation of TTX-S currents and no change of TTX-R ones. All the effects of taurine were weakly concentration-dependent and partly recovered quite slowly after washout. Our data indicate that taurine alters the properties of Na+ currents in intact DRG neurons. These may contribute to the understanding of taurine as a natural neuroprotectant and the potential of taurine as a useful medicine for the treatment of sensory neuropathies.

  9. SS433 Trek 2: light curve analysis.

    NASA Astrophysics Data System (ADS)

    Fukue, J.; Obana, Y.; Okugami, M.

    The authors have calculated theoretical light curves of SS433 during eclipse and precession, using a model in which SS433 consists of a geometrically thick torus around a compact star and a companion star filling the Roche lobe. The favorite combination is that the mass ratio is about 2 (a compact star is a black hole) and the surface temperature of the companion is around 17000K.

  10. SPOTTED STAR LIGHT CURVES WITH ENHANCED PRECISION

    SciTech Connect

    Wilson, R. E.

    2012-09-15

    The nearly continuous timewise coverage of recent photometric surveys is free of the large gaps that compromise attempts to follow starspot growth and decay as well as motions, thereby giving incentive to improve computational precision for modeled spots. Due to the wide variety of star systems in the surveys, such improvement should apply to light/velocity curve models that accurately include all the main phenomena of close binaries and rotating single stars. The vector fractional area (VFA) algorithm that is introduced here represents surface elements by small sets of position vectors so as to allow accurate computation of circle-triangle overlap by spherical geometry. When computed by VFA, spots introduce essentially no noticeable scatter in light curves at the level of one part in 10,000. VFA has been put into the Wilson-Devinney light/velocity curve program and all logic and mathematics are given so as to facilitate entry into other such programs. Advantages of precise spot computation include improved statistics of spot motions and aging, reduced computation time (intrinsic precision relaxes needs for grid fineness), noise-free illustration of spot effects in figures, and help in guarding against false positives in exoplanet searches, where spots could approximately mimic transiting planets in unusual circumstances. A simple spot growth and decay template quantifies time profiles, and specifics of its utilization in differential corrections solutions are given. Computational strategies are discussed, the overall process is tested in simulations via solutions of synthetic light curve data, and essential simulation results are described. An efficient time smearing facility by Gaussian quadrature can deal with Kepler mission data that are in 30 minute time bins.

  11. Optical Phase Curves of Kepler Exoplanets

    NASA Astrophysics Data System (ADS)

    Esteves, Lisa J.; De Mooij, Ernst J. W.; Jayawardhana, Ray

    2013-07-01

    We conducted a comprehensive search for optical phase variations of all close-in (a/R sstarf < 10) planet candidates in 15 quarters of Kepler space telescope data. After correcting for systematics, we found eight systems that show secondary eclipses as well as phase variations. Of these, five (Kepler-5, Kepler-6, Kepler-8, KOI-64, and KOI-2133) are new and three (TrES-2, HAT-P-7, and KOI-13) have published phase curves, albeit with many fewer observations. We model the full phase curve of each planet candidate, including the primary and secondary transits, and derive their albedos, dayside and nightside temperatures, ellipsoidal variations, and Doppler beaming. We find that KOI-64 and KOI-2133 have nightside temperatures well above their equilibrium values (while KOI-2133 also has an albedo, >1), so we conclude that they are likely to be self-luminous objects rather than planets. The other six candidates have characteristics consistent with their being planets with low geometric albedos (<0.3). For TrES-2 and KOI-13, the Kepler bandpass appears to probe atmospheric layers hotter than the planet's equilibrium temperature. For KOI-13, we detect a never-before-seen third cosine harmonic with an amplitude of 6.7 ± 0.3 ppm and a phase shift of -1.1 ± 0.1 rad in the phase curve residual, possibly due to its spin-orbit misalignment. We report derived planetary parameters for all six planets, including masses from ellipsoidal variations and Doppler beaming, and compare our results to published values when available. Our results nearly double the number of Kepler exoplanets with measured phase curve variations, thus providing valuable constraints on the properties of hot Jupiters.

  12. Making Internal Molds Of Long, Curved Tubes

    NASA Technical Reports Server (NTRS)

    Burley, Richard K.

    1989-01-01

    Mold material carried to internal weld joint and removed after impression taken. Remotely operated device makes impression mold of interior surface of tube at weld joint. Mold provides indication of extent of mismatch between members at joint. Maneuvered to weld inspected through curved tube 3 in. in diameter by 50 in. long. Readily adapted to making molds to measure depth of corrosion in boiler tubes or other pipes.

  13. Analysis of light curve of LP Camelopardalis

    NASA Astrophysics Data System (ADS)

    Prudil, Z.; Skarka, M.; Zejda, M.

    2016-05-01

    We present photometric analysis of the RRab type pulsating star LP Cam. The star was observed at Brno Observatory and Planetarium during nine nights. Measurements were calibrated to the Johnson photometric system. Four captured and thirteen previously published maxima timings allowed us to refine the pulsation period and the zero epoch. The light curve was Fourier decomposed to estimate physical parameters using empirical relations. Our results suggest that LP Cam is a common RR Lyrae star with high, almost solar metallicity.

  14. The Astral Curved Disc of Chevroches (France)

    NASA Astrophysics Data System (ADS)

    Devevey, F. Rousseau, A.

    2009-08-01

    The excavation of the unexplored secondary agglomeration in Chevroches (Nièvre), from 2001 to 2002, directed by F. Devevey (INRAP), has led to the discovery of an astrological bronze curved disc of a type unknown in the ancient world; it is inscribed with three lines in Greek transcribing Egyptian an Roman months, and the twelve signs of the zodiac. This article presents the first observations.

  15. Delamination Analysis Of Composite Curved Bars

    NASA Technical Reports Server (NTRS)

    Ko, William L.; Jackson, Raymond H.

    1990-01-01

    Classical anisotropic elasticity theory used to construct "multilayer" composite semicircular curved bar subjected to end forces and end moments. Radial location and intensity of open-mode delamination stress calculated and compared with results obtained from anisotropic continuum theory and from finite element method. Multilayer theory gave more accurate predictions of location and intensity of open-mode delamination stress. Currently being applied to predict open-mode delamination stress concentrations in horse-shoe-shaped composite test coupons.

  16. Potential Energy Curves of Hydrogen Fluoride

    NASA Technical Reports Server (NTRS)

    Fallon, Robert J.; Vanderslice, Joseph T.; Mason, Edward A.

    1960-01-01

    Potential energy curves for the X(sup 1)sigma+ and V(sup 1)sigma+ states of HF and DF have been calculated by the Rydberg-Klein-Rees method. The results calculated from the different sets of data for HF and DF are found to be in very good agreement. The theoretical results of Karo are compared to the experimental results obtained here.

  17. OPTICAL PHASE CURVES OF KEPLER EXOPLANETS

    SciTech Connect

    Esteves, Lisa J.; De Mooij, Ernst J. W.; Jayawardhana, Ray E-mail: demooij@astro.utoronto.ca

    2013-07-20

    We conducted a comprehensive search for optical phase variations of all close-in (a/R{sub *} < 10) planet candidates in 15 quarters of Kepler space telescope data. After correcting for systematics, we found eight systems that show secondary eclipses as well as phase variations. Of these, five (Kepler-5, Kepler-6, Kepler-8, KOI-64, and KOI-2133) are new and three (TrES-2, HAT-P-7, and KOI-13) have published phase curves, albeit with many fewer observations. We model the full phase curve of each planet candidate, including the primary and secondary transits, and derive their albedos, dayside and nightside temperatures, ellipsoidal variations, and Doppler beaming. We find that KOI-64 and KOI-2133 have nightside temperatures well above their equilibrium values (while KOI-2133 also has an albedo, >1), so we conclude that they are likely to be self-luminous objects rather than planets. The other six candidates have characteristics consistent with their being planets with low geometric albedos (<0.3). For TrES-2 and KOI-13, the Kepler bandpass appears to probe atmospheric layers hotter than the planet's equilibrium temperature. For KOI-13, we detect a never-before-seen third cosine harmonic with an amplitude of 6.7 {+-} 0.3 ppm and a phase shift of -1.1 {+-} 0.1 rad in the phase curve residual, possibly due to its spin-orbit misalignment. We report derived planetary parameters for all six planets, including masses from ellipsoidal variations and Doppler beaming, and compare our results to published values when available. Our results nearly double the number of Kepler exoplanets with measured phase curve variations, thus providing valuable constraints on the properties of hot Jupiters.

  18. Icarus: Stellar binary light curve synthesis tool

    NASA Astrophysics Data System (ADS)

    Breton, Rene

    2016-11-01

    Icarus is a stellar binary light curve synthesis tool that generates a star, given some basic binary parameters, by solving the gravitational potential equation, creating a discretized stellar grid, and populating the stellar grid with physical parameters, including temperature and surface gravity. Icarus also evaluates the outcoming flux from the star given an observer's point of view (i.e., orbital phase and orbital orientation).

  19. Lower extremity kinematics of athletics curve sprinting.

    PubMed

    Alt, Tobias; Heinrich, Kai; Funken, Johannes; Potthast, Wolfgang

    2015-01-01

    Curve running requires the generation of centripetal force altering the movement pattern in comparison to the straight path run. The question arises which kinematic modulations emerge while bend sprinting at high velocities. It has been suggested that during curve sprints the legs fulfil different functions. A three-dimensional motion analysis (16 high-speed cameras) was conducted to compare the segmental kinematics of the lower extremity during the stance phases of linear and curve sprints (radius: 36.5 m) of six sprinters of national competitive level. Peak joint angles substantially differed in the frontal and transversal plane whereas sagittal plane kinematics remained unchanged. During the prolonged left stance phase (left: 107.5 ms, right: 95.7 ms, straight: 104.4 ms) the maximum values of ankle eversion (left: 12.7°, right: 2.6°, straight: 6.6°), hip adduction (left: 13.8°, right: 5.5°, straight: 8.8°) and hip external rotation (left: 21.6°, right: 12.9°, straight: 16.7°) were significantly higher. The inside leg seemed to stabilise the movement in the frontal plane (eversion-adduction strategy) whereas the outside leg provided and controlled the motion in the horizontal plane (rotation strategy). These results extend the principal understanding of the effects of curve sprinting on lower extremity kinematics. This helps to increase the understanding of nonlinear human bipedal locomotion, which in turn might lead to improvements in athletic performance and injury prevention.

  20. Operators and higher genus mirror curves

    NASA Astrophysics Data System (ADS)

    Codesido, Santiago; Gu, Jie; Mariño, Marcos

    2017-02-01

    We perform further tests of the correspondence between spectral theory and topological strings, focusing on mirror curves of genus greater than one with nontrivial mass parameters. In particular, we analyze the geometry relevant to the SU(3) relativistic Toda lattice, and the resolved C{^3}/Z_6 orbifold. Furthermore, we give evidence that the correspondence holds for arbitrary values of the mass parameters, where the quantization problem leads to resonant states. We also explore the relation between this correspondence and cluster integrable systems.

  1. PyCS : Python Curve Shifting

    NASA Astrophysics Data System (ADS)

    Tewes, Malte

    2015-09-01

    PyCS is a software toolbox to estimate time delays between multiple images of strongly lensed quasars, from resolved light curves such as obtained by the COSMOGRAIL monitoring program. The pycs package defines a collection of classes and high level functions, that you can script in a flexible way. PyCS makes it easy to compare different point estimators (including your own) without much code integration. The package heavily depends on numpy, scipy, and matplotlib.

  2. Random Matrix Theory and Elliptic Curves

    DTIC Science & Technology

    2014-11-24

    related to the intervals of prime numbers. 15. SUBJECT TERMS EOARD, Random Matrix theory, Riemann Hypothesis, Elliptic Curves 16. SECURITY...range of quantities of fundamental importance in number theory. In the cases of the Riemann zeta function and Dirichlet L-functions, this information...investigation using analytic techniques. As an indication of their significance, two of the Clay Millennium Prize Problems, the Riemann Hypothesis and the

  3. Science 101: What Makes a Curveball Curve?

    ERIC Educational Resources Information Center

    Robertson, William C.

    2009-01-01

    Ah, springtime, and young people's thoughts turn to... baseball, of course. But this column is not about "how" to throw a curveball, so you'll have to look that up on your own. Here, the focus is on the "why" of the curveball. There are two different things that cause a spinning ball to curve. One is known as the "Bernoulli effect" and the other…

  4. Least-Squares Curve-Fitting Program

    NASA Technical Reports Server (NTRS)

    Kantak, Anil V.

    1990-01-01

    Least Squares Curve Fitting program, AKLSQF, easily and efficiently computes polynomial providing least-squares best fit to uniformly spaced data. Enables user to specify tolerable least-squares error in fit or degree of polynomial. AKLSQF returns polynomial and actual least-squares-fit error incurred in operation. Data supplied to routine either by direct keyboard entry or via file. Written for an IBM PC X/AT or compatible using Microsoft's Quick Basic compiler.

  5. Ab-inition melting curve of titanium

    NASA Astrophysics Data System (ADS)

    Stutzmann, Vincent; Bouchet, Johann; Bottin, Francois

    2014-03-01

    Thermodynamical properties of titanium are of great interest for aerospace and aviation industries and many studies are done in order to understand its behaviour under pressure (P) and temperature (T) : phase transitions at low T, melting curve at high T and P. In this work we compute the first ab-initio melting curve of titanium. This one is obtained with the Abinit package using DFT, in the GGA approximation, and in the framework of the projector augmented wave method (PAW). At first, we perform ground state calculations and study the five allotropic phases of titanium. Two PAW atomic data are generated with two different cutoff radius. The larger one gives results near previews ab-initio calculations, whereas the smaller one gives results near all electron calculation. Using the second PAW atomic data and performing ab-initio molecular dynamic simulations, we then compute the melting curve of titanium with three different methods. Results show relevance of our calculations, but also discrepencies with experimental data.

  6. Light Curves of Type IA Supernovae

    NASA Astrophysics Data System (ADS)

    Ford, C. H.; Herbst, W.; Balonek, T. J.; Benson, P. J.; Chromey, F. R.; Ratcliff, S. J.

    1992-05-01

    VRI light curves of five Type Ia supernovae (1991B, 1991N, 1991T, 1991bg, and 1992G) have been obtained with CCDs attached to small telescopes at northeastern sites. The data have been carefully transformed to the standard system using images obtained with the 0.9m telescope at KPNO. The first three supernovae have faded sufficiently that we can carefully correct for the galactic background and, in particular, its effect on the determination of fade rates at late times. SN 1991bg clearly demonstrates that there can be gross differences among Type Ia's in the shape (and maximum brightness) of their light curves (Filippenko et al., preprint). We investigate whether a single "template" can be devised which fits the R and I light curve shapes of the other four supernovae in our sample, and the degree to which each fits the V template of Leibundgut (1988, Ph.D. thesis, U. of Basel). The distinctive secondary maximum seen in I (about 18 days after primary maximum; Balonek et al., preprint) should be useful for distinguishing peculiar Type Ia's like SN 1991bg, and for establishing the time of maximum brightness for supernovae that were discovered up to three weeks afterwards. We thank the W. M. Keck Foundation for their support of the Keck Northeast Astronomy Consortium. This project is an outgrowth of that support.

  7. Psychophysical tuning curves at very high frequencies

    NASA Astrophysics Data System (ADS)

    Yasin, Ifat; Plack, Christopher J.

    2005-10-01

    For most normal-hearing listeners, absolute thresholds increase rapidly above about 16 kHz. One hypothesis is that the high-frequency limit of the hearing-threshold curve is imposed by the transmission characteristics of the middle ear, which attenuates the sound input [Masterton et al., J. Acoust. Soc. Am. 45, 966-985 (1969)]. An alternative hypothesis is that the high-frequency limit of hearing is imposed by the tonotopicity of the cochlea [Ruggero and Temchin, Proc. Nat. Acad. Sci. U.S.A. 99, 13206-13210 (2002)]. The aim of this study was to test these hypotheses. Forward-masked psychophysical tuning curves (PTCs) were derived for signal frequencies of 12-17.5 kHz. For the highest signal frequencies, the high-frequency slopes of some PTCs were steeper than the slope of the hearing-threshold curve. The results also show that the human auditory system displays frequency selectivity for characteristic frequencies (CFs) as high as 17 kHz, above the frequency at which absolute thresholds begin to increase rapidly. The findings suggest that, for CFs up to 17 kHz, the high-frequency limitation in humans is imposed in part by the middle-ear attenuation, and not by the tonotopicity of the cochlea.

  8. Serial position curves in free recall.

    PubMed

    Laming, Donald

    2010-01-01

    The scenario for free recall set out in Laming (2009) is developed to provide models for the serial position curves from 5 selected sets of data, for final free recall, and for multitrial free recall. The 5 sets of data reflect the effects of rate of presentation, length of list, delay of recall, and suppression of rehearsal. Each model accommodates the serial position curve for first recalls (where those data are available) as well as that for total recalls. Both curves are fit with the same parameter values, as also (with 1 exception) are all of the conditions compared within each experiment. The distributions of numbers of recalls are also examined and shown to have variances increased above what would be expected if successive recalls were independent. This is taken to signify that, in those experiments in which rehearsals were not recorded, the retrieval of words for possible recall follows the same pattern that is observed following overt rehearsal, namely, that retrieval consists of runs of consecutive elements from memory. Finally, 2 sets of data are examined that the present approach cannot accommodate. It is argued that the problem with these data derives from an interaction between the patterns of (covert) rehearsal and the parameters of list presentation.

  9. Ultraviolet light curves of V535 Arae

    NASA Technical Reports Server (NTRS)

    Eaton, Joel A.

    1991-01-01

    The light curve of V535 Ara is determined from observations of this long-period W UMa binary in the UV, and its gravity darkening is estimated. The UV colors and spectral type correspond to (B - V)0 = 0.24, or A8V, and imply that the star should have very little residual convection in its envelope. It is concluded that the gravity darkening is large, as in a radiative star, unless it is modified by circulation in the common envelope, or unless all stars this warm are convective. Four solutions are obtained to a combination of optical and UV light curves, two for high radiative gravity darkening, and two for low convective gravity darkening. The light curves were fitted equally well in all four cases, while in all but the one with low-gravity darkening and a hot inner face there was a rather large global temperature difference between the two stars. It is suggested that the W UMa binaries are found only at spectral types later than about A8 because their outer envelopes must be convective to transfer luminosity.

  10. Spectral curve fitting of dielectric constants

    NASA Astrophysics Data System (ADS)

    Ruzi, M.; Ennis, C.; Robertson, E. G.

    2017-01-01

    Optical constants are important properties governing the response of a material to incident light. It follows that they are often extracted from spectra measured by absorbance, transmittance or reflectance. One convenient method to obtain optical constants is by curve fitting. Here, model curves should satisfy Kramer-Kronig relations, and preferably can be expressed in closed form or easily calculable. In this study we use dielectric constants of three different molecular ices in the infrared region to evaluate four different model curves that are generally used for fitting optical constants: (1) the classical damped harmonic oscillator, (2) Voigt line shape, (3) Fourier series, and (4) the Triangular basis. Among these, only the classical damped harmonic oscillator model strictly satisfies the Kramer-Kronig relation. If considering the trade-off between accuracy and speed, Fourier series fitting is the best option when spectral bands are broad while for narrow peaks the classical damped harmonic oscillator and the Triangular basis fitting model are the best choice.

  11. Open timelike curves violate Heisenberg's uncertainty principle.

    PubMed

    Pienaar, J L; Ralph, T C; Myers, C R

    2013-02-08

    Toy models for quantum evolution in the presence of closed timelike curves have gained attention in the recent literature due to the strange effects they predict. The circuits that give rise to these effects appear quite abstract and contrived, as they require nontrivial interactions between the future and past that lead to infinitely recursive equations. We consider the special case in which there is no interaction inside the closed timelike curve, referred to as an open timelike curve (OTC), for which the only local effect is to increase the time elapsed by a clock carried by the system. Remarkably, circuits with access to OTCs are shown to violate Heisenberg's uncertainty principle, allowing perfect state discrimination and perfect cloning of coherent states. The model is extended to wave packets and smoothly recovers standard quantum mechanics in an appropriate physical limit. The analogy with general relativistic time dilation suggests that OTCs provide a novel alternative to existing proposals for the behavior of quantum systems under gravity.

  12. Turbulence measurements in curved wall jets

    NASA Astrophysics Data System (ADS)

    Rodman, L. C.; Wood, N. J.; Roberts, L.

    1987-01-01

    Accurate turbulence measurements taken in wall jet flows are difficult to obtain, due to high intensity turbulence and problems in achieving two-dimensionality. The problem is compounded when streamwise curvature of the flow is introduced, since the jet entrainment and turbulence levels are greatly increased over the equivalent planar values. In this experiment, two-dimensional plane and curved wall jet flows are simulated by having a jet blow axially over a cylinder. In the plane case the cylinder has constant transverse radius, and in the curved cases the cylinder has a varying transverse radius. Although the wall jet in these cases is axisymmetric, adequate 'two-dimensional' flow can be obtained as long as the ratio of the jet width to the cylinder radius is small. The annular wall jet has several advantages over wall jets issuing from finite rectangular slots. Since the slot has no ends, three-dimensional effects caused by the finite length of the slot and side wall interference are eliminated. Also, the transverse curvature of the wall allows close optical access to the surface using a Laser Doppler Velocimetry (LDV) system. Hot wire measurements and some LDV measurements are presented for plane and curved wall jet flows. An integral analysis is used to assess the effects of transverse curvature on the turbulent shear stress. The analysis and the data show that the effects of transverse curvature on both the mean flow and the shear stress are small enough for two-dimensional flow to be approximately satisfactorily.

  13. PSD analysis of optical QSO light curves

    NASA Astrophysics Data System (ADS)

    Simm, Torben; Salvato, M.; Saglia, R.; Ponti, G.; Lanzuisi, G.; Trakhtenbrot, B.; Nandra, K.; Bender, R.

    2016-08-01

    One of the elementary properties of quasar activity is continuous variability in the UV/optical bands. The power spectral density (PSD) potentially contains information about the underlying processes connected to variability. We applied a novel method based on continuous-time autoregressive moving average (CARMA) models (Kelly et al. 2014) to derive the PSD even for irregularly sampled light curves. Using a sample of ~100 X-ray selected non-local QSOs from the XMM-COSMOS catalog and optical light curves provided by the Pan-STARRS1 MDF survey we find that the PSD resembles a broken power-law with a high-frequency slope significantly steeper than observed in X-ray studies. The PSD normalization is observed to scale inversely with bolometric luminosity and Eddington ratio, whereas there is no correlation between the characteristic bend timescale and black hole mass. We find a weak tendency for QSOs with higher black hole mass to have steeper high-frequency PSD slopes. In an ongoing work we extend these studies employing a sample of ~700 variable broad-line QSOs with high-quality black hole mass estimates and well-sampled light curves from the SDSS-RM project.

  14. The biology behind lichenometric dating curves.

    PubMed

    Loso, Michael G; Doak, Daniel F

    2006-03-01

    Lichenometry is used to date late-Holocene terminal moraines that record glacier fluctuations. Traditionally, it relies upon dating curves that relate diameters of the largest lichens in a population to surface ages. Although widely used, the technique remains controversial, in part because lichen biology is poorly understood. We use size-frequency distributions of lichens growing on well-dated surfaces to fit demographic models for Rhizocarpon geographicum and Pseudophebe pubescens, two species commonly used for lichenometry. We show that both species suffer from substantial mortality of 2-3% per year, and grow slowest when young-trends that explain a long-standing contradiction between the literatures of lichenometry and lichen biology. Lichenometrists interpret the shape of typical dating curves to indicate a period of rapid juvenile "great growth," contrary to the growth patterns expected by biologists. With a simulation, we show how the "great growth" pattern can be explained by mortality alone, which ensures that early colonists are rarely found on the oldest surfaces. The consistency of our model predictions with biological theory and observations, and with dozens of lichenometric calibration curves from around the world, suggests opportunities to assess quantitatively the accuracy and utility of this common dating technique.

  15. Capillary migration of microdisks on curved interfaces.

    PubMed

    Yao, Lu; Sharifi-Mood, Nima; Liu, Iris B; Stebe, Kathleen J

    2015-07-01

    The capillary energy landscape for particles on curved fluid interfaces is strongly influenced by the particle wetting conditions. Contact line pinning has now been widely reported for colloidal particles, but its implications in capillary interactions have not been addressed. Here, we present experiment and analysis for disks with pinned contact lines on curved fluid interfaces. In experiment, we study microdisk migration on a host interface with zero mean curvature; the microdisks have contact lines pinned at their sharp edges and are sufficiently small that gravitational effects are negligible. The disks migrate away from planar regions toward regions of steep curvature with capillary energies inferred from the dissipation along particle trajectories which are linear in the deviatoric curvature. We derive the curvature capillary energy for an interface with arbitrary curvature, and discuss each contribution to the expression. By adsorbing to a curved interface, a particle eliminates a patch of fluid interface and perturbs the surrounding interface shape. Analysis predicts that perfectly smooth, circular disks do not migrate, and that nanometric deviations from a planar circular, contact line, like those around a weakly roughened planar disk, will drive migration with linear dependence on deviatoric curvature, in agreement with experiment.

  16. A learning curve for solar thermal power

    NASA Astrophysics Data System (ADS)

    Platzer, Werner J.; Dinter, Frank

    2016-05-01

    Photovoltaics started its success story by predicting the cost degression depending on cumulated installed capacity. This so-called learning curve was published and used for predictions for PV modules first, then predictions of system cost decrease also were developed. This approach is less sensitive to political decisions and changing market situations than predictions on the time axis. Cost degression due to innovation, use of scaling effects, improved project management, standardised procedures including the search for better sites and optimization of project size are learning effects which can only be utilised when projects are developed. Therefore a presentation of CAPEX versus cumulated installed capacity is proposed in order to show the possible future advancement of the technology to politics and market. However from a wide range of publications on cost for CSP it is difficult to derive a learning curve. A logical cost structure for direct and indirect capital expenditure is needed as the basis for further analysis. Using derived reference cost for typical power plant configurations predictions of future cost have been derived. Only on the basis of that cost structure and the learning curve levelised cost of electricity for solar thermal power plants should be calculated for individual projects with different capacity factors in various locations.

  17. Nonmonotonic flow curves of shear thickening suspensions

    NASA Astrophysics Data System (ADS)

    Mari, Romain; Seto, Ryohei; Morris, Jeffrey F.; Denn, Morton M.

    2015-05-01

    The discontinuous shear thickening (DST) of dense suspensions is a remarkable phenomenon in which the viscosity can increase by several orders of magnitude at a critical shear rate. It has the appearance of a first-order phase transition between two hypothetical "states" that we have recently identified as Stokes flows with lubricated or frictional contacts, respectively. Here we extend the analogy further by means of stress-controlled simulations and show the existence of a nonmonotonic steady-state flow curve analogous to a nonmonotonic equation of state. While we associate DST with an S -shaped flow curve, at volume fractions above the shear jamming transition the frictional state loses flowability and the flow curve reduces to an arch, permitting the system to flow only at small stresses. Whereas a thermodynamic transition leads to phase separation in the coexistence region, we observe a uniform shear flow all along the thickening transition. A stability analysis suggests that uniform shear may be mechanically stable for the small Reynolds numbers and system sizes in a rheometer.

  18. Nonmonotonic flow curves of shear thickening suspensions.

    PubMed

    Mari, Romain; Seto, Ryohei; Morris, Jeffrey F; Denn, Morton M

    2015-05-01

    The discontinuous shear thickening (DST) of dense suspensions is a remarkable phenomenon in which the viscosity can increase by several orders of magnitude at a critical shear rate. It has the appearance of a first-order phase transition between two hypothetical "states" that we have recently identified as Stokes flows with lubricated or frictional contacts, respectively. Here we extend the analogy further by means of stress-controlled simulations and show the existence of a nonmonotonic steady-state flow curve analogous to a nonmonotonic equation of state. While we associate DST with an S-shaped flow curve, at volume fractions above the shear jamming transition the frictional state loses flowability and the flow curve reduces to an arch, permitting the system to flow only at small stresses. Whereas a thermodynamic transition leads to phase separation in the coexistence region, we observe a uniform shear flow all along the thickening transition. A stability analysis suggests that uniform shear may be mechanically stable for the small Reynolds numbers and system sizes in a rheometer.

  19. Incorporating Experience Curves in Appliance Standards Analysis

    SciTech Connect

    Garbesi, Karina; Chan, Peter; Greenblatt, Jeffery; Kantner, Colleen; Lekov, Alex; Meyers, Stephen; Rosenquist, Gregory; Buskirk, Robert Van; Yang, Hung-Chia; Desroches, Louis-Benoit

    2011-10-31

    The technical analyses in support of U.S. energy conservation standards for residential appliances and commercial equipment have typically assumed that manufacturing costs and retail prices remain constant during the projected 30-year analysis period. There is, however, considerable evidence that this assumption does not reflect real market prices. Costs and prices generally fall in relation to cumulative production, a phenomenon known as experience and modeled by a fairly robust empirical experience curve. Using price data from the Bureau of Labor Statistics, and shipment data obtained as part of the standards analysis process, we present U.S. experience curves for room air conditioners, clothes dryers, central air conditioners, furnaces, and refrigerators and freezers. These allow us to develop more representative appliance price projections than the assumption-based approach of constant prices. These experience curves were incorporated into recent energy conservation standards for these products. The impact on the national modeling can be significant, often increasing the net present value of potential standard levels in the analysis. In some cases a previously cost-negative potential standard level demonstrates a benefit when incorporating experience. These results imply that past energy conservation standards analyses may have undervalued the economic benefits of potential standard levels.

  20. Neuronize: a tool for building realistic neuronal cell morphologies

    PubMed Central

    Brito, Juan P.; Mata, Susana; Bayona, Sofia; Pastor, Luis; DeFelipe, Javier; Benavides-Piccione, Ruth

    2013-01-01

    This study presents a tool, Neuronize, for building realistic three-dimensional models of neuronal cells from the morphological information extracted through computer-aided tracing applications. Neuronize consists of a set of methods designed to build 3D neural meshes that approximate the cell membrane at different resolution levels, allowing a balance to be reached between the complexity and the quality of the final model. The main contribution of the present study is the proposal of a novel approach to build a realistic and accurate 3D shape of the soma from the incomplete information stored in the digitally traced neuron, which usually consists of a 2D cell body contour. This technique is based on the deformation of an initial shape driven by the position and thickness of the first order dendrites. The addition of a set of spines along the dendrites completes the model, building a final 3D neuronal cell suitable for its visualization in a wide range of 3D environments. PMID:23761740

  1. Spinal Cord Neuronal Precursors Generate Multiple Neuronal Phenotypes in Culture

    PubMed Central

    Kalyani, Anjali J.; Piper, David; Mujtaba, Tahmina; Lucero, Mary T.; Rao, Mahendra S.

    2010-01-01

    Neuronal restricted precursors (NRPs) (Mayer-Proschel et al., 1997) can generate multiple neurotransmitter phenotypes during maturation in culture. Undifferentiated E-NCAM+ (embryonic neural cell adhesion molecule) immunoreactive NRPs are mitotically active and electrically immature, and they express only a subset of neuronal markers. Fully mature cells are postmitotic, process-bearing cells that are neurofilament-M and synaptophysin immunoreactive, and they synthesize and respond to different subsets of neurotransmitter molecules. Mature neurons that synthesize and respond to glycine, glutamate, GABA, dopamine, and acetylcholine can be identified by immunocytochemistry, RT-PCR, and calcium imaging in mass cultures. Individual NRPs also generate heterogeneous progeny as assessed by neurotransmitter response and synthesis, demonstrating the multipotent nature of the precursor cells. Differentiation can be modulated by sonic hedgehog (Shh) and bone morphogenetic protein (BMP)-2/4 molecules. Shh acts as a mitogen and inhibits differentiation (including cholinergic differentiation). BMP-2 and BMP-4, in contrast, inhibit cell division and promote differentiation (including cholinergic differentiation). Thus, a single neuronal precursor cell can differentiate into multiple classes of neurons, and this differentiation can be modulated by environmental signals. PMID:9742154

  2. Neurons on Parafilm: versatile elastic substrates for neuronal cell cultures.

    PubMed

    Yoo, Sang Jin; Nam, Yoonkey

    2012-02-15

    A variety of materials has been applied to neuronal cell culture substrates to improve the efficiency of the culture and to provide pertinent cell growth environment. Here we report the application of Parafilm(®) M ('Parafilm') as a novel substrate for neuronal culture and patterning. Cell culture results show that elastic Parafilm had effects on cell viability, length and number of neurites, and soma spreading. Parafilm was also an effective substrate to obtain patterned neuronal cultures using a conventional micro-contract printing (μCP) technique. Polylysine micropatterns in line or grid forms were readily transferred from PDMS stamp to bare Parafilm surfaces and spatially confined neuronal cultures were successfully maintained for over three weeks. We also demonstrate that batch-processing cell culture substrates can be easily fabricated using a piece of Parafilm. The softness, plasticity, and hydrophobicity were main features that made it attractive for Parafilm to be considered as a practical cell culture platform. The results can be extended to develop an inexpensive and practical neuronal culture substrates in tissue engineering and biochip applications.

  3. Model-Free Estimation of Tuning Curves and Their Attentional Modulation, Based on Sparse and Noisy Data

    PubMed Central

    Helmer, Markus; Kozyrev, Vladislav; Stephan, Valeska; Treue, Stefan; Geisel, Theo; Battaglia, Demian

    2016-01-01

    Tuning curves are the functions that relate the responses of sensory neurons to various values within one continuous stimulus dimension (such as the orientation of a bar in the visual domain or the frequency of a tone in the auditory domain). They are commonly determined by fitting a model e.g. a Gaussian or other bell-shaped curves to the measured responses to a small subset of discrete stimuli in the relevant dimension. However, as neuronal responses are irregular and experimental measurements noisy, it is often difficult to determine reliably the appropriate model from the data. We illustrate this general problem by fitting diverse models to representative recordings from area MT in rhesus monkey visual cortex during multiple attentional tasks involving complex composite stimuli. We find that all models can be well-fitted, that the best model generally varies between neurons and that statistical comparisons between neuronal responses across different experimental conditions are affected quantitatively and qualitatively by specific model choices. As a robust alternative to an often arbitrary model selection, we introduce a model-free approach, in which features of interest are extracted directly from the measured response data without the need of fitting any model. In our attentional datasets, we demonstrate that data-driven methods provide descriptions of tuning curve features such as preferred stimulus direction or attentional gain modulations which are in agreement with fit-based approaches when a good fit exists. Furthermore, these methods naturally extend to the frequent cases of uncertain model selection. We show that model-free approaches can identify attentional modulation patterns, such as general alterations of the irregular shape of tuning curves, which cannot be captured by fitting stereotyped conventional models. Finally, by comparing datasets across different conditions, we demonstrate effects of attention that are cell- and even stimulus

  4. Growth curve prediction from optical density data.

    PubMed

    Mytilinaios, I; Salih, M; Schofield, H K; Lambert, R J W

    2012-03-15

    A fundamental aspect of predictive microbiology is the shape of the microbial growth curve and many models are used to fit microbial count data, the modified Gompertz and Baranyi equation being two of the most widely used. Rapid, automated methods such as turbidimetry have been widely used to obtain growth parameters, but do not directly give the microbial growth curve. Optical density (OD) data can be used to obtain the specific growth rate and if used in conjunction with the known initial inocula, the maximum population data and knowledge of the microbial number at a predefined OD at a known time then all the information required for the reconstruction of a standard growth curve can be obtained. Using multiple initial inocula the times to detection (TTD) at a given standard OD were obtained from which the specific growth rate was calculated. The modified logistic, modified Gompertz, 3-phase linear, Baranyi and the classical logistic model (with or without lag) were fitted to the TTD data. In all cases the modified logistic and modified Gompertz failed to reproduce the observed linear plots of the log initial inocula against TTD using the known parameters (initial inoculum, MPD and growth rate). The 3 phase linear model (3PLM), Baranyi and classical logistic models fitted the observed data and were able to reproduce elements of the OD incubation-time curves. Using a calibration curve relating OD and microbial numbers, the Baranyi equation was able to reproduce OD data obtained for Listeria monocytogenes at 37 and 30°C as well as data on the effect of pH (range 7.05 to 3.46) at 30°C. The Baranyi model was found to be the most capable primary model of those examined (in the absence of lag it defaults to the classic logistic model). The results suggested that the modified logistic and the modified Gompertz models should not be used as Primary models for TTD data as they cannot reproduce the observed data.

  5. Curved spiral antennas for underwater biological applications

    NASA Astrophysics Data System (ADS)

    Llamas, Ruben

    We developed curved spiral antennas for use in underwater (freshwater) communications. Specifically, these antennas will be integrated in so-called mussel backpacks. Backpacks are compact electronics that incorporate sensors and a small radio that operate around 300 MHz. Researchers attach these backpacks in their freshwater mussel related research. The antennas must be small, lightweight, and form-fit the mussel. Additionally, since the mussel orientation is unknown, the antennas must have broad radiation patterns. Further, the electromagnetic environment changes significantly as the mussels burrow into the river bottom. Broadband antennas, such a spiral antennas, will perform better in this instance. While spiral antennas are well established, there has been little work on their performance in freshwater. Additionally, there has been some work on curved spiral antennas, but this work focused on curving in one dimension, namely curving around a cylinder. In this thesis we develop spiral antennas that curve in two dimensions in order to conform the contour of a mussel's shell. Our research has three components, namely (a) an investigation of the relevant theoretical underpinning of spiral antennas, (b) extensive computer simulations using state-of-the art computational electromagnetics (CEM) simulation software, and (c) experimental validation. The experimental validation was performed in a large tank in a laboratory setting. We also validated some designs in a pool (~300,000 liters of water and ~410 squared-meter dive pool) with the aid of a certified diver. To use CEM software and perform successful antenna-related experiments require careful attention to many details. The mathematical description of radiation from an antenna, antenna input impedance and so on, is inherently complex. Engineers often make simplifying assumptions such as assuming no reflections, or an isotropic propagation environment, or operation in the antenna far field, and so on. This makes

  6. Variation of curve number with storm depth

    NASA Astrophysics Data System (ADS)

    Banasik, K.; Hejduk, L.

    2012-04-01

    The NRCS Curve Number (known also as SCS-CN) method is well known as a tool in predicting flood runoff depth from small ungauged catchment. The traditional way of determination the CNs, based on soil characteristics, land use and hydrological conditions, seemed to have tendency to overpredict the floods in some cases. Over 30 year rainfall-runoff data, collected in two small (A=23.4 & 82.4 km2), lowland, agricultural catchments in Center of Poland (Banasik & Woodward 2010), were used to determine runoff Curve Number and to check a tendency of changing. The observed CN declines with increasing storm size, which according recent views of Hawkins (1993) could be classified as a standard response of watershed. The analysis concluded, that using CN value according to the procedure described in USDA-SCS Handbook one receives representative value for estimating storm runoff from high rainfall depths in the analyzes catchments. This has been confirmed by applying "asymptotic approach" for estimating the watershed curve number from the rainfall-runoff data. Furthermore, the analysis indicated that CN, estimated from mean retention parameter S of recorded events with rainfall depth higher than initial abstraction, is also approaching the theoretical CN. The observed CN, ranging from 59.8 to 97.1 and from 52.3 to 95.5, in the smaller and the larger catchment respectively, declines with increasing storm size, which has been classified as a standard response of watershed. The investigation demonstrated also changeability of the CN during a year, with much lower values during the vegetation season. Banasik K. & D.E. Woodward (2010). "Empirical determination of curve number for a small agricultural watrshed in Poland". 2nd Joint Federal Interagency Conference, Las Vegas, NV, June 27 - July 1, 2010 (http://acwi.gov/sos/pubs/2ndJFIC/Contents/10E_Banasik_ 28_02_10. pdf). Hawkins R. H. (1993). "Asymptotic determination of curve numbers from data". Journal of Irrigation and Drainage

  7. Fabrication of a flexible penetrating microelectrode array for use on curved surfaces of neural tissues

    NASA Astrophysics Data System (ADS)

    Byun, Donghak; Cho, Sung Joon; Kim, Sohee

    2013-12-01

    Conventionally, invasive neural microelectrodes for recording neuronal signals or stimulating the nervous system have been fabricated based on silicon substrate mainly due to well-established manufacturing processes. However, these silicon-based microelectrode devices have an issue of mechanical stability caused by the absence of flexibility when implanted onto curved surfaces of tissues. In this paper, a flexible and penetrating microelectrode array, a hybrid structure composed of silicon and elastomer, was devised and fabricated by bulk micromachining technologies. The structure uses individual silicon needles as independent electrodes in a square array and polydimethysiloxane (PDMS) as a base to support the needles. The dimensions of the electrode array and the needles are adjustable, depending on the number of needles, the pitch between the needles and the targeted penetration depth of the neural tissue. For mechanical characterization, the adhesion between PDMS and silicon was evaluated and the flexibility and integrity of the fabricated structure were investigated through flexural test and insertion test. Also, the electrochemical impedance spectroscopy of the electrodes was measured. The results suggest that the proposed microelectrode array is promising for use in neuronal recording and stimulation over curved surfaces such as cortical surface and peripheral nerves with larger curvatures.

  8. Effect of PPAR-β/δ agonist GW0742 treatment in the acute phase response and blood-brain barrier permeability following brain injury.

    PubMed

    Chehaibi, Khouloud; le Maire, Laura; Bradoni, Sarah; Escola, Joan Carles; Blanco-Vaca, Francisco; Slimane, Mohamed Naceur

    2017-04-01

    The systemic response to ischemic stroke is associated with the hepatic acute phase response (APR) that modulates leukocytes recruitment to the injured brain. The inappropriate recruitment of leukocytes to the brain parenchyma can result in blood-brain barrier (BBB) breakdown. Emerging data suggest that peroxisome proliferator-activated receptor beta/delta (PPAR-β/δ) activation has a potential neuroprotective role in ischemic stroke. However, mechanisms of PPAR-β/δ mediated protection in ischemic insults remain unclear. In the present study, we determined for the first time, the effects of GW0742, a PPAR-β/δ agonist on the APR following brain injury and assessed the effects on BBB permeability and tight junction integrity via claudin-5, occludin, and zona occludens-1 expression. C57/BL6 mice were exposed to 1 hour of ischemia and received 10 minutes before reperfusion either a vehicle solution or GW0742. Hepatic expression of chemokines (C-X-C motif ligand: CXCL1, CXCL2, and CXCL10), serum amyloid A-1, tumor necrosis factor alpha, interleukin-1β, and interleukin-6 was measured, and the extent of brain and hepatic neutrophil infiltration was determined. The results showed that GW0742 treatment decreased infarct volume and edema, reactant production and neutrophil recruitment to the brain and liver, which is a hallmark of the APR. GW0742 significantly reduced BBB leakage and metalloproteinase 9 expression and upregulated the expression of tight junction proteins. These findings may help to guide the experimental and clinical therapeutic use of PPAR-β/δ agonists against brain injury.

  9. Adjusting for the acute phase response is essential to interpret iron status indicators among young Zanzibari children prone to chronic malaria and helminth infections.

    PubMed

    Kung'u, Jacqueline K; Wright, Victoria J; Haji, Hamad J; Ramsan, Mahdi; Goodman, David; Tielsch, James M; Bickle, Quentin D; Raynes, John G; Stoltzfus, Rebecca J

    2009-11-01

    The extent to which the acute phase response (APR) influences iron status indicators in chronic infections is not well documented. We investigated this relationship using reported recent fever and 2 acute phase proteins (APP), C-reactive protein (CRP), and alpha-1-acid glycoprotein (AGP). In a sample of 690 children matched on age and helminth infection status at baseline, we measured plasma for AGP, CRP, ferritin, transferrin receptor (TfR), and erythropoietin (EPO) and whole blood for hemoglobin (Hb) concentration, zinc protoporphyrin (ZPP), and malaria parasite density, and we obtained maternal reports of recent fever. We then examined the influence of the APR on each iron status indicator using regression analysis with Hb as the outcome variable. Ferritin was inversely related to Hb in the APR-unadjusted model. Adjusting for the APR using reported recent fever alone was not sufficient to reverse the inverse Hb-ferritin relationship. However, using CRP and/or AGP resulted in the expected positive relationship. The best fit model included reported recent fever, AGP and CRP (R(2) = 0.241; P < 0.001). The best fit Hb-ZPP, Hb-TfR, and Hb-EPO models included reported recent fever and AGP but not CRP (R(2) = 0.253, 0.310, and 0.292, respectively; P < 0.001). ZPP, TfR, and EPO were minimally influenced by the APR, whereas ferritin was immensely affected. Reported recent fever alone cannot be used as a marker for the APR. Either AGP or CRP is useful for adjusting if only 1 APP can be measured. However, AGP best predicted the APR in this population.

  10. Effects of preoperative feeding with a whey protein plus carbohydrate drink on the acute phase response and insulin resistance. A randomized trial

    PubMed Central

    2011-01-01

    Background Prolonged preoperative fasting increases insulin resistance and current evidence recommends carbohydrate (CHO) drinks 2 hours before surgery. Our hypothesis is that the addition of whey protein to a CHO-based drink not only reduces the inflammatory response but also diminish insulin resistance. Methods Seventeen patients scheduled to cholecystectomy or inguinal herniorraphy were randomized and given 474 ml and 237 ml of water (CO group) or a drink containing CHO and milk whey protein (CHO-P group) respectively, 6 and 3 hours before operation. Blood samples were collected before surgery and 24 hours afterwards for biochemical assays. The endpoints of the study were the insulin resistance (IR), the prognostic inflammatory and nutritional index (PINI) and the C-reactive protein (CRP)/albumin ratio. A 5% level for significance was established. Results There were no anesthetic or postoperative complications. The post-operative IR was lower in the CHO-P group when compared with the CO group (2.75 ± 0.72 vs 5.74 ± 1.16; p = 0.03). There was no difference between the two groups in relation to the PINI. The CHO-P group showed a decrease in the both CRP elevation and CRP/albumin ratio (p < 0.05). The proportion of patients who showed CRP/albumin ratio considered normal was significantly greater (p < 0.05) in the CHO-P group (87.5%) than in the CO group (33.3%). Conclusions Shortening the pre-operative fasting using CHO and whey protein is safe and reduces insulin resistance and postoperative acute phase response in elective moderate operations. Trial registration ClinicalTrail.gov NCT01354249 PMID:21668975

  11. Changes in cholesterol homeostasis and acute phase response link pulmonary exposure to multi-walled carbon nanotubes to risk of cardiovascular disease.

    PubMed

    Poulsen, Sarah S; Saber, Anne T; Mortensen, Alicja; Szarek, Józef; Wu, Dongmei; Williams, Andrew; Andersen, Ole; Jacobsen, Nicklas R; Yauk, Carole L; Wallin, Håkan; Halappanavar, Sabina; Vogel, Ulla

    2015-03-15

    Adverse lung effects following pulmonary exposure to multi-walled carbon nanotubes (MWCNTs) are well documented in rodents. However, systemic effects are less understood. Epidemiological studies have shown increased cardiovascular disease risk after pulmonary exposure to airborne particles, which has led to concerns that inhalation exposure to MWCNTs might pose similar risks. We analyzed parameters related to cardiovascular disease, including plasma acute phase response (APR) proteins and plasma lipids, in female C57BL/6 mice exposed to a single intratracheal instillation of 0, 18, 54 or 162μg/mouse of small, entangled (CNTSmall, 0.8±0.1μm long) or large, thick MWCNTs (CNTLarge, 4±0.4μm long). Liver tissues and plasma were harvested 1, 3 and 28days post-exposure. In addition, global hepatic gene expression, hepatic cholesterol content and liver histology were used to assess hepatic effects. The two MWCNTs induced similar systemic responses despite their different physicochemical properties. APR proteins SAA3 and haptoglobin, plasma total cholesterol and low-density/very low-density lipoprotein were significantly increased following exposure to either MWCNTs. Plasma SAA3 levels correlated strongly with pulmonary Saa3 levels. Analysis of global gene expression revealed perturbation of the same biological processes and pathways in liver, including the HMG-CoA reductase pathway. Both MWCNTs induced similar histological hepatic changes, with a tendency towards greater response following CNTLarge exposure. Overall, we show that pulmonary exposure to two different MWCNTs induces similar systemic and hepatic responses, including changes in plasma APR, lipid composition, hepatic gene expression and liver morphology. The results link pulmonary exposure to MWCNTs with risk of cardiovascular disease.

  12. Leptin role in advanced lung cancer. A mediator of the acute phase response or a marker of the status of nutrition?

    PubMed

    Alemán, María Remedios; Santolaria, Francisco; Batista, Norberto; de La Vega, María; González-Reimers, Emilio; Milena, Antonio; Llanos, Marta; Gómez-Sirvent, Juan Luis

    2002-07-07

    Leptin is an anorexia inductor peptide produced by adipocytes and related to fat mass. Leptin is also produced by fat under proinflammatory cytokine action. Our objective is to study serum leptin levels in relation to nutritional status and acute phase response in advanced-stage non-small cell lung cancer.Seventy-six patients newly diagnosed of non surgical non-small cell lung cancer before chemotherapy treatment and 30 healthy controls were included. BMI, serum leptin and cholesterol levels and lymphocyte count were decreased in lung cancer patients. Cytokine IL-6, TNF-alpha, sTNF-RII, sIL-2R, IL-12, IL-10 and IFN-gamma, and other acute phase reactants as alpha1 antitrypsin, ferritin, CRP and platelets were all raised in patients, whereas the IL-2 was decreased. We found a direct relationship between leptin and other indicators of the status of nutrition, especially total fat mass. We also found a close relationship between the status of nutrition and the performance status (Karnofsky index). However, serum leptin and nutritional status were inversely correlated with acute phase proteins and proinflammatory cytokines, suggesting a stress-type malnutrition. Although serum leptin levels, nutritional status and Karnofsky index are related to survival, at multivariate analysis they all were displaced by the acute phase reaction markers. These results suggest that cancer anorexia and cachexia are not due to a dysregulation of leptin production. Circulating leptin concentrations are not elevated in weight-losing cancer patients and are inversely related to the intensity of the inflammatory response. In advanced lung cancer patients serum leptin concentrations only depend on the total amount of fat.

  13. Phase Shifting Capacity of the Circadian Pacemaker Determined by the SCN Neuronal Network Organization

    PubMed Central

    vanderLeest, Henk Tjebbe; Rohling, Jos H. T.; Michel, Stephan; Meijer, Johanna H.

    2009-01-01

    Background In mammals, a major circadian pacemaker that drives daily rhythms is located in the suprachiasmatic nuclei (SCN), at the base of the hypothalamus. The SCN receive direct light input via the retino-hypothalamic tract. Light during the early night induces phase delays of circadian rhythms while during the late night it leads to phase advances. The effects of light on the circadian system are strongly dependent on the photoperiod to which animals are exposed. An explanation for this phenomenon is currently lacking. Methodology and Principal Findings We recorded running wheel activity in C57 mice and observed large amplitude phase shifts in short photoperiods and small shifts in long photoperiods. We investigated whether these different light responses under short and long days are expressed within the SCN by electrophysiological recordings of electrical impulse frequency in SCN slices. Application of N-methyl-D-aspartate (NMDA) induced sustained increments in electrical activity that were not significantly different in the slices from long and short photoperiods. These responses led to large phase shifts in slices from short days and small phase shifts in slices from long days. An analysis of neuronal subpopulation activity revealed that in short days the amplitude of the rhythm was larger than in long days. Conclusions The data indicate that the photoperiodic dependent phase responses are intrinsic to the SCN. In contrast to earlier predictions from limit cycle theory, we observed large phase shifting responses in high amplitude rhythms in slices from short days, and small shifts in low amplitude rhythms in slices from long days. We conclude that the photoperiodic dependent phase responses are determined by the SCN and propose that synchronization among SCN neurons enhances the phase shifting capacity of the circadian system. PMID:19305510

  14. Neuronal SUMOylation: Mechanisms, Physiology, and Roles in Neuronal Dysfunction

    PubMed Central

    Henley, Jeremy M.; Craig, Tim J.; Wilkinson, Kevin A.

    2014-01-01

    Protein SUMOylation is a critically important posttranslational protein modification that participates in nearly all aspects of cellular physiology. In the nearly 20 years since its discovery, SUMOylation has emerged as a major regulator of nuclear function, and more recently, it has become clear that SUMOylation has key roles in the regulation of protein trafficking and function outside of the nucleus. In neurons, SUMOylation participates in cellular processes ranging from neuronal differentiation and control of synapse formation to regulation of synaptic transmission and cell survival. It is a highly dynamic and usually transient modification that enhances or hinders interactions between proteins, and its consequences are extremely diverse. Hundreds of different proteins are SUMO substrates, and dysfunction of protein SUMOylation is implicated in a many different diseases. Here we briefly outline core aspects of the SUMO system and provide a detailed overview of the current understanding of the roles of SUMOylation in healthy and diseased neurons. PMID:25287864

  15. Neuronal factors determining high intelligence.

    PubMed

    Dicke, Ursula; Roth, Gerhard

    2016-01-05

    Many attempts have been made to correlate degrees of both animal and human intelligence with brain properties. With respect to mammals, a much-discussed trait concerns absolute and relative brain size, either uncorrected or corrected for body size. However, the correlation of both with degrees of intelligence yields large inconsistencies, because although they are regarded as the most intelligent mammals, monkeys and apes, including humans, have neither the absolutely nor the relatively largest brains. The best fit between brain traits and degrees of intelligence among mammals is reached by a combination of the number of cortical neurons, neuron packing density, interneuronal distance and axonal conduction velocity--factors that determine general information processing capacity (IPC), as reflected by general intelligence. The highest IPC is found in humans, followed by the great apes, Old World and New World monkeys. The IPC of cetaceans and elephants is much lower because of a thin cortex, low neuron packing density and low axonal conduction velocity. By contrast, corvid and psittacid birds have very small and densely packed pallial neurons and relatively many neurons, which, despite very small brain volumes, might explain their high intelligence. The evolution of a syntactical and grammatical language in humans most probably has served as an additional intelligence amplifier, which may have happened in songbirds and psittacids in a convergent manner.

  16. Stochastic phase-change neurons

    NASA Astrophysics Data System (ADS)

    Tuma, Tomas; Pantazi, Angeliki; Le Gallo, Manuel; Sebastian, Abu; Eleftheriou, Evangelos

    2016-08-01

    Artificial neuromorphic systems based on populations of spiking neurons are an indispensable tool in understanding the human brain and in constructing neuromimetic computational systems. To reach areal and power efficiencies comparable to those seen in biological systems, electroionics-based and phase-change-based memristive devices have been explored as nanoscale counterparts of synapses. However, progress on scalable realizations of neurons has so far been limited. Here, we show that chalcogenide-based phase-change materials can be used to create an artificial neuron in which the membrane potential is represented by the phase configuration of the nanoscale phase-change device. By exploiting the physics of reversible amorphous-to-crystal phase transitions, we show that the temporal integration of postsynaptic potentials can be achieved on a nanosecond timescale. Moreover, we show that this is inherently stochastic because of the melt-quench-induced reconfiguration of the atomic structure occurring when the neuron is reset. We demonstrate the use of these phase-change neurons, and their populations, in the detection of temporal correlations in parallel data streams and in sub-Nyquist representation of high-bandwidth signals.

  17. Stochastic phase-change neurons.

    PubMed

    Tuma, Tomas; Pantazi, Angeliki; Le Gallo, Manuel; Sebastian, Abu; Eleftheriou, Evangelos

    2016-08-01

    Artificial neuromorphic systems based on populations of spiking neurons are an indispensable tool in understanding the human brain and in constructing neuromimetic computational systems. To reach areal and power efficiencies comparable to those seen in biological systems, electroionics-based and phase-change-based memristive devices have been explored as nanoscale counterparts of synapses. However, progress on scalable realizations of neurons has so far been limited. Here, we show that chalcogenide-based phase-change materials can be used to create an artificial neuron in which the membrane potential is represented by the phase configuration of the nanoscale phase-change device. By exploiting the physics of reversible amorphous-to-crystal phase transitions, we show that the temporal integration of postsynaptic potentials can be achieved on a nanosecond timescale. Moreover, we show that this is inherently stochastic because of the melt-quench-induced reconfiguration of the atomic structure occurring when the neuron is reset. We demonstrate the use of these phase-change neurons, and their populations, in the detection of temporal correlations in parallel data streams and in sub-Nyquist representation of high-bandwidth signals.

  18. Brain Neurons as Quantum Computers:

    NASA Astrophysics Data System (ADS)

    Bershadskii, A.; Dremencov, E.; Bershadskii, J.; Yadid, G.

    The question: whether quantum coherent states can sustain decoherence, heating and dissipation over time scales comparable to the dynamical timescales of brain neurons, has been actively discussed in the last years. A positive answer on this question is crucial, in particular, for consideration of brain neurons as quantum computers. This discussion was mainly based on theoretical arguments. In the present paper nonlinear statistical properties of the Ventral Tegmental Area (VTA) of genetically depressive limbic brain are studied in vivo on the Flinders Sensitive Line of rats (FSL). VTA plays a key role in the generation of pleasure and in the development of psychological drug addiction. We found that the FSL VTA (dopaminergic) neuron signals exhibit multifractal properties for interspike frequencies on the scales where healthy VTA dopaminergic neurons exhibit bursting activity. For high moments the observed multifractal (generalized dimensions) spectrum coincides with the generalized dimensions spectrum calculated for a spectral measure of a quantum system (so-called kicked Harper model, actively used as a model of quantum chaos). This observation can be considered as a first experimental (in vivo) indication in the favor of the quantum (at least partially) nature of brain neurons activity.

  19. Neuronal Mitophagy in Neurodegenerative Diseases

    PubMed Central

    Martinez-Vicente, Marta

    2017-01-01

    Neuronal homeostasis depends on the proper functioning of different quality control systems. All intracellular components are subjected to continuous turnover through the coordinated synthesis, degradation and recycling of their constituent elements. Autophagy is the catabolic mechanism by which intracellular cytosolic components, including proteins, organelles, aggregates and any other intracellular materials, are delivered to lysosomes for degradation. Among the different types of selective autophagy described to date, the process of mitophagy involves the selective autophagic degradation of mitochondria. In this way, mitophagy is responsible for basal mitochondrial turnover, but can also be induced under certain physiological or pathogenic conditions to eliminate unwanted or damaged mitochondria. Dysfunctional cellular proteolytic systems have been linked extensively to neurodegenerative diseases (ND) like Alzheimer’s disease (AD), Parkinson’s disease (PD), or Huntington’s disease (HD), with autophagic failure being one of the main factors contributing to neuronal cell death in these diseases. Neurons are particularly vulnerable to autophagic impairment as well as to mitochondrial dysfunction, due mostly to their particular high energy dependence and to their post-mitotic nature. The accurate and proper degradation of dysfunctional mitochondria by mitophagy is essential for maintaining control over mitochondrial quality and quantity in neurons. In this report, I will review the role of mitophagy in neuronal homeostasis and the consequences of its dysfunction in ND. PMID:28337125

  20. Neuronal factors determining high intelligence

    PubMed Central

    Dicke, Ursula; Roth, Gerhard

    2016-01-01

    Many attempts have been made to correlate degrees of both animal and human intelligence with brain properties. With respect to mammals, a much-discussed trait concerns absolute and relative brain size, either uncorrected or corrected for body size. However, the correlation of both with degrees of intelligence yields large inconsistencies, because although they are regarded as the most intelligent mammals, monkeys and apes, including humans, have neither the absolutely nor the relatively largest brains. The best fit between brain traits and degrees of intelligence among mammals is reached by a combination of the number of cortical neurons, neuron packing density, interneuronal distance and axonal conduction velocity—factors that determine general information processing capacity (IPC), as reflected by general intelligence. The highest IPC is found in humans, followed by the great apes, Old World and New World monkeys. The IPC of cetaceans and elephants is much lower because of a thin cortex, low neuron packing density and low axonal conduction velocity. By contrast, corvid and psittacid birds have very small and densely packed pallial neurons and relatively many neurons, which, despite very small brain volumes, might explain their high intelligence. The evolution of a syntactical and grammatical language in humans most probably has served as an additional intelligence amplifier, which may have happened in songbirds and psittacids in a convergent manner. PMID:26598734

  1. Network synchronization in hippocampal neurons

    PubMed Central

    Penn, Yaron; Segal, Menahem; Moses, Elisha

    2016-01-01

    Oscillatory activity is widespread in dynamic neuronal networks. The main paradigm for the origin of periodicity consists of specialized pacemaking elements that synchronize and drive the rest of the network; however, other models exist. Here, we studied the spontaneous emergence of synchronized periodic bursting in a network of cultured dissociated neurons from rat hippocampus and cortex. Surprisingly, about 60% of all active neurons were self-sustained oscillators when disconnected, each with its own natural frequency. The individual neuron’s tendency to oscillate and the corresponding oscillation frequency are controlled by its excitability. The single neuron intrinsic oscillations were blocked by riluzole, and are thus dependent on persistent sodium leak currents. Upon a gradual retrieval of connectivity, the synchrony evolves: Loose synchrony appears already at weak connectivity, with the oscillators converging to one common oscillation frequency, yet shifted in phase across the population. Further strengthening of the connectivity causes a reduction in the mean phase shifts until zero-lag is achieved, manifested by synchronous periodic network bursts. Interestingly, the frequency of network bursting matches the average of the intrinsic frequencies. Overall, the network behaves like other universal systems, where order emerges spontaneously by entrainment of independent rhythmic units. Although simplified with respect to circuitry in the brain, our results attribute a basic functional role for intrinsic single neuron excitability mechanisms in driving the network’s activity and dynamics, contributing to our understanding of developing neural circuits. PMID:26961000

  2. Neuronal modelling of baroreflex response to orthostatic stress

    NASA Astrophysics Data System (ADS)

    Samin, Azfar

    The accelerations experienced in aerial combat can cause pilot loss of consciousness (GLOC) due to a critical reduction in cerebral blood circulation. The development of smart protective equipment requires understanding of how the brain processes blood pressure (BP) information in response to acceleration. We present a biologically plausible model of the Baroreflex to investigate the neural correlates of short-term BP control under acceleration or orthostatic stress. The neuronal network model, which employs an integrate-and-fire representation of a biological neuron, comprises the sensory, motor, and the central neural processing areas that form the Baroreflex. Our modelling strategy is to test hypotheses relating to the encoding mechanisms of multiple sensory inputs to the nucleus tractus solitarius (NTS), the site of central neural processing. The goal is to run simulations and reproduce model responses that are consistent with the variety of available experimental data. Model construction and connectivity are inspired by the available anatomical and neurophysiological evidence that points to a barotopic organization in the NTS, and the presence of frequency-dependent synaptic depression, which provides a mechanism for generating non-linear local responses in NTS neurons that result in quantifiable dynamic global baroreflex responses. The entire physiological range of BP and rate of change of BP variables is encoded in a palisade of NTS neurons in that the spike responses approximate Gaussian 'tuning' curves. An adapting weighted-average decoding scheme computes the motor responses and a compensatory signal regulates the heart rate (HR). Model simulations suggest that: (1) the NTS neurons can encode the hydrostatic pressure difference between two vertically separated sensory receptor regions at +Gz, and use changes in that difference for the regulation of HR; (2) even though NTS neurons do not fire with a cardiac rhythm seen in the afferents, pulse

  3. Homeostasis of intrinsic excitability in hippocampal neurones: dynamics and mechanism of the response to chronic depolarization.

    PubMed

    O'Leary, Timothy; van Rossum, Mark C W; Wyllie, David J A

    2010-01-01

    In order to maintain stable functionality in the face of continually changing input, neurones in the CNS must dynamically modulate their electrical characteristics. It has been hypothesized that in order to retain stable network function, neurones possess homeostatic mechanisms which integrate activity levels and alter network and cellular properties in such a way as to counter long-term perturbations. Here we describe a simple model system where we investigate the effects of sustained neuronal depolarization, lasting up to several days, by exposing cultures of primary hippocampal pyramidal neurones to elevated concentrations (10-30 mm) of KCl. Following exposure to KCl, neurones exhibit lower input resistances and resting potentials, and require more current to be injected to evoke action potentials. This results in a rightward shift in the frequency-input current (FI) curve which is explained by a simple linear model of the subthreshold I-V relationship. No changes are observed in action potential profiles, nor in the membrane potential at which action potentials are evoked. Furthermore, following depolarization, an increase in subthreshold potassium conductance is observed which is accounted for within a biophysical model of the subthreshold I-V characteristics of neuronal membranes. The FI curve shift was blocked by the presence of the L-type Ca(2+) channel blocker nifedipine, whilst antagonism of NMDA receptors did not interfere with the effect. Finally, changes in the intrinsic properties of neurones are reversible following removal of the depolarizing stimulus. We suggest that this experimental system provides a convenient model of homeostatic regulation of intrinsic excitability, and permits the study of temporal characteristics of homeostasis and its dependence on stimulus magnitude.

  4. Creating A Light Curve Using Gathered Data

    NASA Astrophysics Data System (ADS)

    Wiggs, Joseph; Stolarz, S. A.; DePorto, R. W.; Shake, W. J.; Piper, M.; Linder, T. R.; Holmes, R.; Conwell, J.

    2012-01-01

    Our group of students with the support of educators and astronomers carried out a program to do astrometric and photometric analysis on the asteroid 2000 SO1 with the objective of obtaining a more in depth analysis of this asteroid and publishing light curve data describing the period of the asteroid. We chose our target asteroid using the minor planet center database, choosing an object that would have an acceptable Right Ascension, Declination, magnitude, and air mass for the ARO (Astronomical Research Observatory)-30 inch telescope operated by the SKYNET program. Our journey began with using Astrometrica for the IASC/WISE Program to identify and find new asteroids in the sky and add data to the Minor Planet Center Database. We then used MPO (Minor Planet Observatory) Canopus to form a light curve and conduct a fourier analysis on an example asteroid to familiarize ourselves with the program and used the program again to conduct fourier analysis on asteroid 2000 SO1. The educational goal in mind was to (a) learn the process of collecting and analyzing data using Astrometrica, MPO Canopus, the Minor Planet Center, and SKYNET and (b) create a poster to display the steps used in the process of surveying taken images and the production of a light curve. We collected 300 images a night, while discarding all the corrupted images, until we had enough data to accurately represent the object.Our work was successful due to resources from; Eastern Illinois University's Physics Department, the Astronomical Research Observatory, the University of Chicago's Yerkes Observatory, the SKYNET network, NASA's IASC/WISE (International Astronomical Search Collaboration/ Wide-Field Infrared Survey Explorer), NITARP (NASA/IPAC Teacher Archive Research Program) and Lincoln-Way North High School.

  5. Curve of Spee - from orthodontic perspective

    PubMed Central

    Dhiman, Sushma

    2015-01-01

    The presence of a curve of Spee (COS) of variable depth is common finding in the occlusal arrangement and is sixth key of occlusion The understanding of COS in the field of orthodontics is very important as orthodontists deal with it in virtually every patient they treat. An excessive COS is a common form of malocclusion that may be addressed in many ways, including posterior extrusion, anterior intrusion, and incisor proclination. The specific approach to leveling of COS should be selected based on each patient's needs. Soft tissue, crown–gingival relations, occlusal plane, and skeletofacial concerns are among the special considerations for treatment planning for leveling of COS. PMID:26752075

  6. Calibrating Curved Crystals Used for Plasma Spectroscopy

    SciTech Connect

    Haugh, M. J., Jacoby, K. D., Ross, P. W., Rochau, G. Wu, M., Regan, S. P., Barrios, M. A.

    2012-10-29

    The throughput and resolving power of an X-ray spectrometer that uses a curved crystal as the diffraction element is determined primarily by the crystal X-ray reflectivity properties. This poster presents a measurement technique for these crystal parameters using a simple diode source to produce a narrow spectral band. The results from measurements on concave elliptical polyethylene terephthalate (PET) crystals and convex potassium acid phthalate (KAP) crystals show large variations in the key parameters compared to those from the flat crystal.

  7. Task 4 Improvised Nuclear Device Response Curves

    SciTech Connect

    Alai, Maureen; Neuscamman, Stephanie

    2016-05-31

    LLNL performed fallout and nuclear blast modeling for the 60 cities using the NARAC modeling system and predominant weather patterns determined in a previous Task 4 effort. LLNL performed model simulations and analyses to identify and provide response curves (expressed as two-dimensional contours) for radioactive fallout deposition, transport, population, and blast overpressure as a function of yield, weather, location and time. These contours can then be further combined and correlated with infrastructure and population databases to estimate city specific effects on KPFs such as impacted infrastructure and casualty rates.

  8. Template Reproduction of GRB Pulse Light Curves

    NASA Astrophysics Data System (ADS)

    Hakkila, Jon E.; Preece, R. D.; Loredo, T. J.; Wolpert, R. L.; Broadbent, M. E.

    2014-01-01

    A study of well-isolated pulses in gamma ray burst light curves indicates that simple models having smooth and monotonic pulse rises and decays are inadequate. Departures from the Norris et al. (2005) pulse shape are in the form of a wave-like pre-peak residual that is mirrored and stretched following the peak. Pulse shape departures are present in GRB pulses of all durations, but placement of the departures relative to pulse peaks correlates with asymmetry. This establishes an additional link between temporal structure and spectral evolution, as pulse asymmetry is related to initial hardness while pulse duration indicates the rate of hard-to-soft pulse evolution.

  9. Enumeration of curves with one singular point

    NASA Astrophysics Data System (ADS)

    Basu, Somnath; Mukherjee, Ritwik

    2016-06-01

    In this paper we obtain an explicit formula for the number of curves in P2, of degree d, passing through (d(d + 3) / 2 - k) generic points and having a singularity X, where X is of type Ak≤7 ,Dk≤7 or Ek≤7. Our method comprises of expressing the enumerative problem as the Euler class of an appropriate bundle and using a purely topological method to compute the degenerate contribution to the Euler class. These numbers have also been computed by M. Kazarian using the existence of universal formulas for Thom polynomials.

  10. Rapid graph layout using space filling curves.

    PubMed

    Muelder, Chris; Ma, Kwan-Liu

    2008-01-01

    Network data frequently arises in a wide variety of fields, and node-link diagrams are a very natural and intuitive representation of such data. In order for a node-link diagram to be effective, the nodes must be arranged well on the screen. While many graph layout algorithms exist for this purpose, they often have limitations such as high computational complexity or node colocation. This paper proposes a new approach to graph layout through the use of space filling curves which is very fast and guarantees that there will be no nodes that are colocated. The resulting layout is also aesthetic and satisfies several criteria for graph layout effectiveness.

  11. Cracks in Sheets Draped on Curved Surfaces

    NASA Astrophysics Data System (ADS)

    Mitchell, Noah P.; Koning, Vinzenz; Vitelli, Vincenzo; Irvine, William T. M.

    Conforming materials to surfaces with Gaussian curvature has proven a versatile tool to guide the behavior of mechanical defects such as folds, blisters, scars, and pleats. In this talk, we show how curvature can likewise be used to control material failure. In our experiments, thin elastic sheets are confined on curved geometries that stimulate or suppress the growth of cracks, and steer or arrest their propagation. By redistributing stresses in a sheet, curvature provides a geometric tool for protecting certain regions and guiding crack patterns. A simple model captures crack behavior at the onset of propagation, while a 2D phase-field model successfully captures the crack's full phenomenology.

  12. Relativistic electron in curved magnetic fields

    NASA Technical Reports Server (NTRS)

    An, S.

    1985-01-01

    Making use of the perturbation method based on the nonlinear differential equation theory, the author investigates the classical motion of a relativistic electron in a class of curved magnetic fields which may be written as B=B(O,B sub phi, O) in cylindrical coordinates (R. phi, Z). Under general astrophysical conditions the author derives the analytical expressions of the motion orbit, pitch angle, etc., of the electron in their dependence upon parameters characterizing the magnetic field and electron. The effects of non-zero curvature of magnetic field lines on the motion of electrons and applicabilities of these results to astrophysics are also discussed.

  13. Measuring Cooling Curves Following Magnetar Outbursts

    NASA Astrophysics Data System (ADS)

    Kaspi, Victoria

    2012-09-01

    Magnetars have been observed to increase their flux output by several orders of magnitude in outbursts. Following outbursts they cool on timescales of months to years. We propose to observe two magnetars, Swift J1822.3-1606 and 1E 1547.0-5408, using Chandra as they approach their quiescent state following their recent outbursts in 2011 and 2009, respectively. We will apply a newly developed crustal cooling model to these cooling curves to constrain the properties of the magnetars, such as the crust thickness and heat capacity, and of their outbursts, such as the location of energy deposition.

  14. The Bifurcating Neuron network 1.

    PubMed

    Lee, G; Farhat, N H

    2001-01-01

    The Bifurcating Neuron (BN), a chaotic integrate-and-fire neuron, is a model of a neuron augmented by coherent modulation from its environment. The BN is mathematically equivalent to the sine-circle map, and this equivalence relationship allowed us to apply the mathematics of one-dimensional maps to the design of BN networks. The study of symmetry in the BN revealed that the BN can be configured to exhibit bistability that is controlled by attractor-merging crisis. Also, the symmetry of the bistability can be controlled by the introduction of a sinusoidal fluctuation to the threshold level of the BN. These two observations led us to the design of the BN Network 1 (BNN-1), a chaotic pulse-coupled neural network exhibiting associative memory. In numerical simulations, the BNN-1 showed a better performance than the continuous-time Hopfield network, as far as the spurious-minima problem is concerned and exhibited many biologically plausible characteristics.

  15. Chimera states in bursting neurons

    NASA Astrophysics Data System (ADS)

    Bera, Bidesh K.; Ghosh, Dibakar; Lakshmanan, M.

    2016-01-01

    We study the existence of chimera states in pulse-coupled networks of bursting Hindmarsh-Rose neurons with nonlocal, global, and local (nearest neighbor) couplings. Through a linear stability analysis, we discuss the behavior of the stability function in the incoherent (i.e., disorder), coherent, chimera, and multichimera states. Surprisingly, we find that chimera and multichimera states occur even using local nearest neighbor interaction in a network of identical bursting neurons alone. This is in contrast with the existence of chimera states in populations of nonlocally or globally coupled oscillators. A chemical synaptic coupling function is used which plays a key role in the emergence of chimera states in bursting neurons. The existence of chimera, multichimera, coherent, and disordered states is confirmed by means of the recently introduced statistical measures and mean phase velocity.

  16. Towards a Neuronal Gauge Theory

    PubMed Central

    Sengupta, Biswa; Tozzi, Arturo; Cooray, Gerald K.; Douglas, Pamela K.; Friston, Karl J.

    2016-01-01

    Given the amount of knowledge and data accruing in the neurosciences, is it time to formulate a general principle for neuronal dynamics that holds at evolutionary, developmental, and perceptual timescales? In this paper, we propose that the brain (and other self-organised biological systems) can be characterised via the mathematical apparatus of a gauge theory. The picture that emerges from this approach suggests that any biological system (from a neuron to an organism) can be cast as resolving uncertainty about its external milieu, either by changing its internal states or its relationship to the environment. Using formal arguments, we show that a gauge theory for neuronal dynamics—based on approximate Bayesian inference—has the potential to shed new light on phenomena that have thus far eluded a formal description, such as attention and the link between action and perception. PMID:26953636

  17. Axon specification in hippocampal neurons.

    PubMed

    Fukata, Yuko; Kimura, Toshihide; Kaibuchi, Kozo

    2002-08-01

    Neurons are the most highly polarized cells, comprised of two structurally and functionally distinct parts, axons and dendrites. This asymmetry enables a vectorial flow of signaling within neurons. One of the most fundamental questions still to be answered in neuroscience is how these two specialized processes initially develop. The first manifestation of polarization occurs when one of the immature neurites acquires axonal characteristics. We review recent advances that have highlighted the involvement of several cellular events in the initial formation of the axon, including membrane traffic and cytoskeletal rearrangement. We then discuss the molecular mechanisms underlying axon formation, focusing on the Rho family small GTPases and an axon-inducing neuronal protein, CRMP-2.

  18. Chronaxie Measurements in Patterned Neuronal Cultures from Rat Hippocampus

    PubMed Central

    Rotem, Assaf; Moses, Elisha; Neef, Andreas

    2015-01-01

    Excitation of neurons by an externally induced electric field is a long standing question that has recently attracted attention due to its relevance in novel clinical intervention systems for the brain. Here we use patterned quasi one-dimensional neuronal cultures from rat hippocampus, exploiting the alignment of axons along the linear patterned culture to separate the contribution of dendrites to the excitation of the neuron from that of axons. Network disconnection by channel blockers, along with rotation of the electric field direction, allows the derivation of strength-duration (SD) curves that characterize the statistical ensemble of a population of cells. SD curves with the electric field aligned either parallel or perpendicular to the axons yield the chronaxie and rheobase of axons and dendrites respectively, and these differ considerably. Dendritic chronaxie is measured to be about 1 ms, while that of axons is on the order of 0.1 ms. Axons are thus more excitable at short time scales, but at longer time scales dendrites are more easily excited. We complement these studies with experiments on fully connected cultures. An explanation for the chronaxie of dendrites is found in the numerical simulations of passive, realistically structured dendritic trees under external stimulation. The much shorter chronaxie of axons is not captured in the passive model and may be related to active processes. The lower rheobase of dendrites at longer durations can improve brain stimulation protocols, since in the brain dendrites are less specifically oriented than axonal bundles, and the requirement for precise directional stimulation may be circumvented by using longer duration fields. PMID:26186201

  19. Copying and Evolution of Neuronal Topology

    PubMed Central

    Fernando, Chrisantha; Karishma, K. K.; Szathmáry, Eörs

    2008-01-01

    We propose a mechanism for copying of neuronal networks that is of considerable interest for neuroscience for it suggests a neuronal basis for causal inference, function copying, and natural selection within the human brain. To date, no model of neuronal topology copying exists. We present three increasingly sophisticated mechanisms to demonstrate how topographic map formation coupled with Spike-Time Dependent Plasticity (STDP) can copy neuronal topology motifs. Fidelity is improved by error correction and activity-reverberation limitation. The high-fidelity topology-copying operator is used to evolve neuronal topologies. Possible roles for neuronal natural selection are discussed. PMID:19020662

  20. Calcium signals in olfactory neurons.

    PubMed

    Tareilus, E; Noé, J; Breer, H

    1995-11-09

    Laser scanning confocal microscopy in combination with the fluorescent calcium indicators Fluo-3 and Fura-Red was employed to estimate the intracellular concentration of free calcium ions in individual olfactory receptor neurons and to monitor temporal and spatial changes in the Ca(2+)-level upon stimulation. The chemosensory cells responded to odorants with a significant increase in the calcium concentration, preferentially in the dendritic knob. Applying various stimulation paradigma, it was found that in a population of isolated cells, subsets of receptor neurons display distinct patterns of responsiveness.

  1. Curved Piezoelectric Actuators for Stretching Optical Fibers

    NASA Technical Reports Server (NTRS)

    Allison, Sidney G.; Shams, Qamar A.; Fox, Robert L.

    2008-01-01

    Assemblies containing curved piezoceramic fiber composite actuators have been invented as means of stretching optical fibers by amounts that depend on applied drive voltages. Piezoceramic fiber composite actuators are conventionally manufactured as sheets or ribbons that are flat and flexible, but can be made curved to obtain load-carrying ability and displacement greater than those obtainable from the flat versions. In the primary embodiment of this invention, piezoceramic fibers are oriented parallel to the direction of longitudinal displacement of the actuators so that application of drive voltage causes the actuator to flatten, producing maximum motion. Actuator motion can be transmitted to the optical fiber by use of hinges and clamp blocks. In the original application of this invention, the optical fiber contains a Bragg grating and the purpose of the controlled stretching of the fiber is to tune the grating as part of a small, lightweight, mode-hop-free, rapidly tunable laser for demodulating strain in Bragg-grating strain-measurement optical fibers attached to structures. The invention could also be used to apply controllable tensile force or displacement to an object other than an optical fiber.

  2. Vessel visualization using curved surface reformation.

    PubMed

    Auzinger, Thomas; Mistelbauer, Gabriel; Baclija, Ivan; Schernthaner, Rüdiger; Köchl, Arnold; Wimmer, Michael; Gröller, M Eduard; Bruckner, Stefan

    2013-12-01

    Visualizations of vascular structures are frequently used in radiological investigations to detect and analyze vascular diseases. Obstructions of the blood flow through a vessel are one of the main interests of physicians, and several methods have been proposed to aid the visual assessment of calcifications on vessel walls. Curved Planar Reformation (CPR) is a wide-spread method that is designed for peripheral arteries which exhibit one dominant direction. To analyze the lumen of arbitrarily oriented vessels, Centerline Reformation (CR) has been proposed. Both methods project the vascular structures into 2D image space in order to reconstruct the vessel lumen. In this paper, we propose Curved Surface Reformation (CSR), a technique that computes the vessel lumen fully in 3D. This offers high-quality interactive visualizations of vessel lumina and does not suffer from problems of earlier methods such as ambiguous visibility cues or premature discretization of centerline data. Our method maintains exact visibility information until the final query of the 3D lumina data. We also present feedback from several domain experts.

  3. Spherical nanoindentation stress–strain curves

    SciTech Connect

    Pathak, Siddhartha; Kalidindi, Surya R.

    2015-03-24

    Although indentation experiments have long been used to measure the hardness and Young's modulus, the utility of this technique in analyzing the complete elastic–plastic response of materials under contact loading has only been realized in the past few years – mostly due to recent advances in testing equipment and analysis protocols. This paper provides a timely review of the recent progress made in this respect in extracting meaningful indentation stress–strain curves from the raw datasets measured in instrumented spherical nanoindentation experiments. These indentation stress–strain curves have produced highly reliable estimates of the indentation modulus and the indentation yield strength in the sample, as well as certain aspects of their post-yield behavior, and have been critically validated through numerical simulations using finite element models as well as direct in situ scanning electron microscopy (SEM) measurements on micro-pillars. Much of this recent progress was made possible through the introduction of a new measure of indentation strain and the development of new protocols to locate the effective zero-point of initial contact between the indenter and the sample in the measured datasets. As a result, this has led to an important key advance in this field where it is now possible to reliably identify and analyze the initial loading segment in the indentation experiments.

  4. Melting curve of materials: theory versus experiments

    NASA Astrophysics Data System (ADS)

    Alfè, D.; Vocadlo, L.; Price, G. D.; Gillan, M. J.

    2004-04-01

    A number of melting curves of various materials have recently been measured experimentally and calculated theoretically, but the agreement between different groups is not always good. We discuss here some of the problems which may arise in both experiments and theory. We also report the melting curves of Fe and Al calculated recently using quantum mechanics techniques, based on density functional theory with generalized gradient approximations. For Al our results are in very good agreement with both low pressure diamond-anvil-cell experiments (Boehler and Ross 1997 Earth Planet. Sci. Lett. 153 223, Hänström and Lazor 2000 J. Alloys Compounds 305 209) and high pressure shock wave experiments (Shaner et al 1984 High Pressure in Science and Technology ed Homan et al (Amsterdam: North-Holland) p 137). For Fe our results agree with the shock wave experiments of Brown and McQueen (1986 J. Geophys. Res. 91 7485) and Nguyen and Holmes (2000 AIP Shock Compression of Condensed Matter 505 81) and the recent diamond-anvil-cell experiments of Shen et al (1998 Geophys. Res. Lett. 25 373). Our results are at variance with the recent calculations of Laio et al (2000 Science 287 1027) and, to a lesser extent, with the calculations of Belonoshko et al (2000 Phys. Rev. Lett. 84 3638). The reasons for these disagreements are discussed.

  5. Paschen Curve Observations at Liquid Nitrogen Temperatures

    NASA Astrophysics Data System (ADS)

    Dugger, Chip; Rielage, Keith; Elliott, Steven; Massarczyk, Ralph; Chu, Pinghan

    2015-10-01

    Paschen's Law states an equation giving the relationship between variables involved when forming an electrical arc between two conductive objects, otherwise known as the breakdown voltage. This equation for the breakdown voltage VB is as follows: VB =apd/ln (pd) + b where p is the pressure in Atmospheres (or Bar), d is the gap or distance between the two conductive objects, and both a and b are constants that depend on the composition of the gas. In our experiment, the Paschen curve for gases (such as nitrogen) at temperatures lower than -200 degrees Celsius will be measured. The Paschen curve for air at room temperature will also be measured in order to test and calibrate our system. The goal of this experiment is to test how accurately Paschen's Law can predict the breakdown voltage in these specific, cold conditions. This experiment is being performed to gather information for a possible future experiment, which might use high purity germanium (HPGe) detectors in a similar cold environment to search for neutrinoless double beta decay, a rare hypothesized process that may yield valuable insight into the fundamental properties of the neutrino. This work is being supported by the DOE through the LANL LDRD program. Charles ``Chip'' Dugger, Los Alamos National Laboratory and New Mexico Institute of Mining and Technology.

  6. Advances in String Theory in Curved Backgrounds

    NASA Astrophysics Data System (ADS)

    Sanchez, N. G.

    A synthetic report of the advances in the study of classical and quantum string dynamics in curved backgrounds is provided, namely : the new feature of Multistring solutions; the mass spectrum of Strings in Curved backgrounds; The effect of a Cosmological Constant and of Spacial Curvature on Classical and Quantum Strings; Classical splitting of Fundamental Strings; The General String Evolution in constant Curvature Spacetimes; The Conformal Invariance Effects; Strings on plane fronted and gravitational shock waves, string falling on spacetime singularities and its spectrum. New Developments in String Gravity and String Cosmology are reported: String driven cosmology and its Predictions; The primordial gravitational wave background; Non-singular string cosmologies from Exact Conformal Field Theories; Quantum Field Theory, String Temperature and the String Phase of de Sitter space-time Hawking Radiation in String Theory and the String Phase of Black Holes; New Dual Relation between Quantum Field Theory regime and String regime and the "QFT/String Tango" New Coherent String States and Minimal Uncertainty Principle in string theory.

  7. High speed curved position sensitive detector

    DOEpatents

    Hendricks, Robert W.; Wilson, Jack W.

    1989-01-01

    A high speed curved position sensitive porportional counter detector for use in x-ray diffraction, the detection of 5-20 keV photons and the like. The detector employs a planar anode assembly of a plurality of parallel metallic wires. This anode assembly is supported between two cathode planes, with at least one of these cathode planes having a serpentine resistive path in the form of a meander having legs generally perpendicular to the anode wires. This meander is produced by special microelectronic fabrication techniques whereby the meander "wire" fans outwardly at the cathode ends to produce the curved aspect of the detector, and the legs of the meander are small in cross-section and very closely spaced whereby a spatial resolution of about 50 .mu.m can be achieved. All of the other performance characteristics are about as good or better than conventional position sensitive proportional counter type detectors. Count rates of up to 40,000 counts per second with 0.5 .mu.s shaping time constants are achieved.

  8. Bell-Curve Based Evolutionary Optimization Algorithm

    NASA Technical Reports Server (NTRS)

    Sobieszczanski-Sobieski, J.; Laba, K.; Kincaid, R.

    1998-01-01

    The paper presents an optimization algorithm that falls in the category of genetic, or evolutionary algorithms. While the bit exchange is the basis of most of the Genetic Algorithms (GA) in research and applications in America, some alternatives, also in the category of evolutionary algorithms, but use a direct, geometrical approach have gained popularity in Europe and Asia. The Bell-Curve Based Evolutionary Algorithm (BCB) is in this alternative category and is distinguished by the use of a combination of n-dimensional geometry and the normal distribution, the bell-curve, in the generation of the offspring. The tool for creating a child is a geometrical construct comprising a line connecting two parents and a weighted point on that line. The point that defines the child deviates from the weighted point in two directions: parallel and orthogonal to the connecting line, the deviation in each direction obeying a probabilistic distribution. Tests showed satisfactory performance of BCB. The principal advantage of BCB is its controllability via the normal distribution parameters and the geometrical construct variables.

  9. Spherical nanoindentation stress–strain curves

    DOE PAGES

    Pathak, Siddhartha; Kalidindi, Surya R.

    2015-03-24

    Although indentation experiments have long been used to measure the hardness and Young's modulus, the utility of this technique in analyzing the complete elastic–plastic response of materials under contact loading has only been realized in the past few years – mostly due to recent advances in testing equipment and analysis protocols. This paper provides a timely review of the recent progress made in this respect in extracting meaningful indentation stress–strain curves from the raw datasets measured in instrumented spherical nanoindentation experiments. These indentation stress–strain curves have produced highly reliable estimates of the indentation modulus and the indentation yield strength inmore » the sample, as well as certain aspects of their post-yield behavior, and have been critically validated through numerical simulations using finite element models as well as direct in situ scanning electron microscopy (SEM) measurements on micro-pillars. Much of this recent progress was made possible through the introduction of a new measure of indentation strain and the development of new protocols to locate the effective zero-point of initial contact between the indenter and the sample in the measured datasets. As a result, this has led to an important key advance in this field where it is now possible to reliably identify and analyze the initial loading segment in the indentation experiments.« less

  10. Coexistence Curve of Perfluoromethylcyclohexane-Isopropyl Alcohol

    NASA Technical Reports Server (NTRS)

    Jacobs, D. T.; Kuhl, D. E.; Selby, C. E.

    1996-01-01

    The coexistence curve of the binary fluid mixture perfluoromethylcyclohexane-isopropyl alcohol was determined by precisely measuring the refractive index both above and below its upper critical consolute point. Sixty-seven two-phase data points were obtained over a wide range of reduced temperatures, 10(exp -5) less than t less than 2.5 x 10(exp -1), to determine the location of the critical point: critical temperature=89.901 C, and critical composition = 62.2% by volume perfluoromethylcyclohexane. These data were analyzed to determine the critical exponent 8 close to the critical point, the amplitude B, and the anomaly in the diameter. The volume-fraction coexistence curve is found to be as symmetric as any composition like variable. Correction to scaling is investigated as well as the need for a crossover theory. A model is proposed that describes the asymptotic approach to zero of the effective exponent Beta, which allows an estimation of the temperature regime free of crossover effects.

  11. Permeability and Retentivity Curves In Mountain Soils

    NASA Astrophysics Data System (ADS)

    Barontini, S.; Ranzi, R.

    The saturated conductivity, Ks, and the retentivity curves, for mountain non-mature soils have been determined after laboratory- and field-experiments carried out over about 146 soil samples in the Toce river basin (Val d'Ossola, Northern Italian Alps). Eightythree samples only have been used to measure the retentivity curves using 15 bar and 5 bar Richard's extractors. Coherently with other researches, traditional meth- ods used to derive Ks on the basis of in situ infiltration test with a single ring infiltrom- eter provided values grater than those calculated using a variable head permeameter in laboratory. So other simplified methods have been used to estimate Ks after field analysis: the traditional method based on the Darcy's law, modified in respect of soil saturation; a method based on an application of Green and Ampt infiltration model; and a method based on the Wooding's works. All these methods, in particular the Wooding (1968) solution, gave estimates of Ks closer to the laboratory ones and to the results of a finite elements numerical solution of the Richard's equation in a 3D domain with axial simmetry. As a result an updated legend for the existing surface soil saturated conductivity map for the of the Toce basin is proposed. Inhomogeneities in the vertical permeability profiles have been identified also.

  12. Effect of dietary mannanoligosaccharide and sodium chlorate on the growth performance, acute-phase response, and bacterial shedding of weaned pigs challenged with Salmonella enterica serotype Typhimurium.

    PubMed

    Burkey, T E; Dritz, S S; Nietfeld, J C; Johnson, B J; Minton, J E

    2004-02-01

    A 28-d experiment evaluated the growth, acute-phase response, and bacterial shedding patterns in pigs (n = 96; initially 6.8 +/- 1.3 kg) fed mannanoligosaccharides (MANNAN) and sodium chlorate (CHLORATE) before and after oral challenge with Salmonella enterica serotype Typhimurium (ST). The negative control diet contained no antimicrobial (CON), and the positive control contained carbadox (CARB; 55 ppm). Test diets contained (as-fed basis) MANNAN (1,500 ppm) or CHLORATE (800 ppm). Pigs were fed diets for 14 d and then given ST orally. Pigs fed CARB had greater ADG over the entire study than pigs from other treatments (P < 0.05). During wk 1 to 2, before ST challenge, feed intake (as-fed basis) was lower for pigs fed MANNAN and CHLORATE than pigs fed CARB (P < 0.05). During the final 2 wk, pigs fed CARB had greater feed intake than pigs on other treatments (P < 0.05). Gain/feed was greater for pigs fed CARB in the 2 wk before ST (P < 0.05); however, in wk 3 to 4 after ST, gain/feed was reduced for CON pigs compared to pigs on other treatments (P < 0.05). Serum IGF-I was decreased at 2 and 4 d after ST (P < 0.001), and, overall, IGF-I was greater in pigs fed CARB than CON or CHLORATE (P < 0.05). Serum haptoglobin concentrations were greater (P < 0.001) for all treatments at d 6 compared with d 13 after ST. Overall, haptoglobin was greater for MANNAN than for CARB and CHLORATE (P < 0.05) and tended to be increased (P < 0.06) relative to CON. Interleukin-6 was not affected by treatment or day post-ST challenge. Fecal shedding of salmonellae organisms was less for CHLORATE (P < 0.05) than all other treatments at 7 d after ST. Shedding scores decreased from d 7 to 14 after ST (P < 0.05) for the CON, CARB, and MANNAN treatments. We conclude that feeding MANNAN and CHLORATE before acute enteric disease challenge may support improved gut function as evidenced by improved gain/feed, and that CHLORATE may decrease bacterial shedding. But neither MANNAN nor CHLORATE enhanced

  13. [What mirror neurons have revealed: revisited].

    PubMed

    Murata, Akira; Maeda, Kazutaka

    2014-06-01

    The first paper on mirror neurons was published in 1992. In the span of over two decades since then, much knowledge about the relationship between social cognitive function and the motor control system has been accumulated. Direct matching of visual actions and their corresponding motor representations is the most important functional property of mirror neuron. Many studies have emphasized intrinsic simulation as a core concept for mirror neurons. Mirror neurons are thought to play a role in social cognitive function. However, the function of mirror neurons in the macaque remains unclear, because such cognitive functions are limited or lacking in macaque monkeys. It is therefore important to discuss these neurons in the context of motor function. Rizzolatti and colleagues have stressed that the most important function of mirror neurons in macaques is recognition of actions performed by other individuals. I suggest that mirror neurons in the Macaque inferior pariental lobule might be correlated with body schema. In the parieto-premotor network, matching of corollary discharge and actual sensory feedback is an essential neuronal operation. Recently, neurons showing mirror properties were found in some cortical areas outside the mirror neuron system. The current work would revisit the outcomes of mirror neuron studies to discuss the function of mirror neurons in the monkey.

  14. A human mirror neuron system for language: Perspectives from signed languages of the deaf.

    PubMed

    Knapp, Heather Patterson; Corina, David P

    2010-01-01

    Language is proposed to have developed atop the human analog of the macaque mirror neuron system for action perception and production [Arbib M.A. 2005. From monkey-like action recognition to human language: An evolutionary framework for neurolinguistics (with commentaries and author's response). Behavioral and Brain Sciences, 28, 105-167; Arbib M.A. (2008). From grasp to language: Embodied concepts and the challenge of abstraction. Journal de Physiologie Paris 102, 4-20]. Signed languages of the deaf are fully-expressive, natural human languages that are perceived visually and produced manually. We suggest that if a unitary mirror neuron system mediates the observation and production of both language and non-linguistic action, three prediction can be made: (1) damage to the human mirror neuron system should non-selectively disrupt both sign language and non-linguistic action processing; (2) within the domain of sign language, a given mirror neuron locus should mediate both perception and production; and (3) the action-based tuning curves of individual mirror neurons should support the highly circumscribed set of motions that form the "vocabulary of action" for signed languages. In this review we evaluate data from the sign language and mirror neuron literatures and find that these predictions are only partially upheld.

  15. Predicting the response of olfactory sensory neurons to odor mixtures from single odor response

    PubMed Central

    Marasco, Addolorata; De Paris, Alessandro; Migliore, Michele

    2016-01-01

    The response of olfactory receptor neurons to odor mixtures is not well understood. Here, using experimental constraints, we investigate the mathematical structure of the odor response space and its consequences. The analysis suggests that the odor response space is 3-dimensional, and predicts that the dose-response curve of an odor receptor can be obtained, in most cases, from three primary components with specific properties. This opens the way to an objective procedure to obtain specific olfactory receptor responses by manipulating mixtures in a mathematically predictable manner. This result is general and applies, independently of the number of odor components, to any olfactory sensory neuron type with a response curve that can be represented as a sigmoidal function of the odor concentration. PMID:27053070

  16. Predicting the response of olfactory sensory neurons to odor mixtures from single odor response

    NASA Astrophysics Data System (ADS)

    Marasco, Addolorata; de Paris, Alessandro; Migliore, Michele

    2016-04-01

    The response of olfactory receptor neurons to odor mixtures is not well understood. Here, using experimental constraints, we investigate the mathematical structure of the odor response space and its consequences. The analysis suggests that the odor response space is 3-dimensional, and predicts that the dose-response curve of an odor receptor can be obtained, in most cases, from three primary components with specific properties. This opens the way to an objective procedure to obtain specific olfactory receptor responses by manipulating mixtures in a mathematically predictable manner. This result is general and applies, independently of the number of odor components, to any olfactory sensory neuron type with a response curve that can be represented as a sigmoidal function of the odor concentration.

  17. Which Neurons Will Be the Engram - Activated Neurons and/or More Excitable Neurons?

    PubMed Central

    Kim, Ji-il; Cho, Hye-Yeon; Han, Jin-Hee

    2016-01-01

    During past decades, the formation and storage principle of memory have received much attention in the neuroscience field. Although some studies have attempted to demonstrate the nature of the engram, elucidating the memory engram allocation mechanism was not possible because of the limitations of existing methods, which cannot specifically modulate the candidate neuronal population. Recently, the development of new techniques, which offer ways to mark and control specific populations of neurons, may accelerate solving this issue. Here, we review the recent advances, which have provided substantial evidence showing that both candidates (neuronal population that is activated by learning, and that has increased CREB level/excitability at learning) satisfy the criteria of the engram, which are necessary and sufficient for memory expression. PMID:27122991

  18. The Effect of Adaptation on the Tuning Curves of Rat Auditory Cortex

    PubMed Central

    Parto Dezfouli, Mohsen; Daliri, Mohammad Reza

    2015-01-01

    Repeated stimulus causes a specific suppression of neuronal responses, which is so-called as Stimulus-Specific Adaptation (SSA). This effect can be recovered when the stimulus changes. In the auditory system SSA is a well-known phenomenon that appears at different levels of the mammalian auditory pathway. In this study, we explored the effects of adaptation to a particular stimulus on the auditory tuning curves of anesthetized rats. We used two sequences and compared the responses of each tone combination in these two conditions. First sequence consists of different pure tone combinations that were presented randomly. In the second one, the same stimuli of the first sequence were presented in the context of an adapted stimulus (adapter) that occupied 80% of sequence probability. The population results demonstrated that the adaptation factor decreased the frequency response area and made a change in the tuning curve to shift it unevenly toward the higher thresholds of tones. The local field potentials and multi-unit activity responses have indicated that the neural activities strength of the adapted frequency has been suppressed as well as with lower suppression in neighboring frequencies. This aforementioned reduction changed the characteristic frequency of the tuning curve. PMID:25719404

  19. Using Dragon Curves To Learn about Length and Area.

    ERIC Educational Resources Information Center

    Smith, Lyle R.

    1999-01-01

    Utilizes dragon curves which are made with three tiles and can be used to create fascinating patterns to help students understand the concepts of length, area, and perimeter of regions as defined by dragon curves. (ASK)

  20. Nonlinear bulging factor based on R-curve data

    NASA Technical Reports Server (NTRS)

    Jeong, David Y.; Tong, Pin

    1994-01-01

    In this paper, a nonlinear bulging factor is derived using a strain energy approach combined with dimensional analysis. The functional form of the bulging factor contains an empirical constant that is determined using R-curve data from unstiffened flat and curved panel tests. The determination of this empirical constant is based on the assumption that the R-curve is the same for both flat and curved panels.

  1. Nonlinear bulging factor based on R-curve data

    NASA Astrophysics Data System (ADS)

    Jeong, David Y.; Tong, Pin

    1994-09-01

    In this paper, a nonlinear bulging factor is derived using a strain energy approach combined with dimensional analysis. The functional form of the bulging factor contains an empirical constant that is determined using R-curve data from unstiffened flat and curved panel tests. The determination of this empirical constant is based on the assumption that the R-curve is the same for both flat and curved panels.

  2. Curved centerline air intake for a gas turbine engine

    NASA Technical Reports Server (NTRS)

    Ruehr, W. C.; Younghans, J. L.; Smith, E. B. (Inventor)

    1980-01-01

    An inlet for a gas turbine engine was disposed about a curved centerline for the purpose of accepting intake air that is flowing at an angle to engine centerline and progressively turning that intake airflow along a curved path into alignment with the engine. This curved inlet is intended for use in under the wing locations and similar regions where airflow direction is altered by aerodynamic characteristics of the airplane. By curving the inlet, aerodynamic loss and acoustic generation and emission are decreased.

  3. Neuronal circuits of fear extinction.

    PubMed

    Herry, Cyril; Ferraguti, Francesco; Singewald, Nicolas; Letzkus, Johannes J; Ehrlich, Ingrid; Lüthi, Andreas

    2010-02-01

    Fear extinction is a form of inhibitory learning that allows for the adaptive control of conditioned fear responses. Although fear extinction is an active learning process that eventually leads to the formation of a consolidated extinction memory, it is a fragile behavioural state. Fear responses can recover spontaneously or subsequent to environmental influences, such as context changes or stress. Understanding the neuronal substrates of fear extinction is of tremendous clinical relevance, as extinction is the cornerstone of psychological therapy of several anxiety disorders and because the relapse of maladaptative fear and anxiety is a major clinical problem. Recent research has begun to shed light on the molecular and cellular processes underlying fear extinction. In particular, the acquisition, consolidation and expression of extinction memories are thought to be mediated by highly specific neuronal circuits embedded in a large-scale brain network including the amygdala, prefrontal cortex, hippocampus and brain stem. Moreover, recent findings indicate that the neuronal circuitry of extinction is developmentally regulated. Here, we review emerging concepts of the neuronal circuitry of fear extinction, and highlight novel findings suggesting that the fragile phenomenon of extinction can be converted into a permanent erasure of fear memories. Finally, we discuss how research on genetic animal models of impaired extinction can further our understanding of the molecular and genetic bases of human anxiety disorders.

  4. Neuronal Inhibition under the Spotlight.

    PubMed

    Mortensen, Martin; Smart, Trevor G

    2015-12-02

    In this issue of Neuron,Lin et al. (2015) report an optical method to precisely manipulate the activity of GABAA receptors by designing a mutant receptor that binds photosensitive compounds. This allows for studying GABAA receptors in situ and represents a valuable tool to investigate how inhibition affects brain physiology.

  5. Motor neurone disease: an overview.

    PubMed

    Kent, Anna

    Motor neurone disease (MND) is a relatively rare, progressive and incurable neurological condition affecting patients' speech, mobility and respiratory function. Care of patients with MND is complex and involves various healthcare professionals and services. There is a need to discuss symptom management and promote palliative and end of life care from the point of diagnosis to ensure appropriate holistic care is provided.

  6. Bifurcating neuron: computation and learning.

    PubMed

    Lysetskiy, Mykola; Zurada, Jacek M

    2004-03-01

    The ability of bifurcating processing units and their networks to rapidly switch between different dynamic modes has been used in recent research efforts to model new computational properties of neural systems. In this spirit, we devise a bifurcating neuron based on control of chaos collapsing to a period-3 orbit in the dynamics of a quadratic logistic map (QLM). Proposed QLM3 neuron is constructed with the third iterate of QLM and uses an external input, which governs its dynamics. The input shifts the neuron's dynamics from chaos to one of the stable fixed points. This way the inputs from certain ranges (clusters) are mapped to stable fixed points, while the rest of the inputs is mapped to chaotic or periodic output dynamics. It has been shown that QLM3 neuron is able to learn a specific mapping by adaptively adjusting its bifurcation parameter, the idea of which is based on the principles of parametric control of logistic maps [Proceedings of the International Symposium on Nonlinear Theory and its Applications (NOLTA'97), Honolulu, HI, 1997; Proceedings of SPIE, 2000]. Learning algorithm for the bifurcation parameter is proposed, which employs the error gradient descent method.

  7. Biomechanics of Single Cortical Neurons

    PubMed Central

    Bernick, Kristin B.; Prevost, Thibault P.; Suresh, Subra; Socrate, Simona

    2011-01-01

    This study presents experimental results and computational analysis of the large strain dynamic behavior of single neurons in vitro with the objective of formulating a novel quantitative framework for the biomechanics of cortical neurons. Relying on the atomic force microscopy (AFM) technique, novel testing protocols are developed to enable the characterization of neural soma deformability over a range of indentation rates spanning three orders of magnitude – 10, 1, and 0.1 μm/s. Modified spherical AFM probes were utilized to compress the cell bodies of neonatal rat cortical neurons in load, unload, reload and relaxation conditions. The cell response showed marked hysteretic features, strong non-linearities, and substantial time/rate dependencies. The rheological data were complemented with geometrical measurements of cell body morphology, i.e. cross-diameter and height estimates. A constitutive model, validated by the present experiments, is proposed to quantify the mechanical behavior of cortical neurons. The model aimed to correlate empirical findings with measurable degrees of (hyper-) elastic resilience and viscosity at the cell level. The proposed formulation, predicated upon previous constitutive model developments undertaken at the cortical tissue level, was implemented into a three-dimensional finite element framework. The simulated cell response was calibrated to the experimental measurements under the selected test conditions, providing a novel single cell model that could form the basis for further refinements. PMID:20971217

  8. [The ontogeny of the mirror neuron system].

    PubMed

    Myowa-Yamakoshi, Masako

    2014-06-01

    Abstract Humans utilize the mirror neuron system to understand and predict others' actions. However, the ontogeny of the mirror neuron system remains unknown. Whether mirror neuron function is an innate trait or whether mirror neurons acquire their sensorimotor matching properties ontogenetically remains to be clarified. In this paper, I review the ontogenetic theory of the mirror neuron system. I then discuss the functioning of the mirror neuron system in the context of social cognitive abilities, which are unique to humans. Recently, some researchers argue that it is too early to interpret the function of mirror neurons as an understanding of the underlying psychological states of others. They imply that such functioning would require inferential cognitive processes that are known to involve areas outside the mirror neuron system. Filling in this missing link may be the key to elucidating the unique ability of humans to understand others' actions.

  9. Neuronal development: neighbors have to be different.

    PubMed

    Hummel, Thomas

    2007-12-18

    The assembly of neurons into functional circuits requires a multitude of cellular recognition events. Recent work on the hypervariable Drosophila Dscam gene revealed how a vast number of cell adhesion proteins contributes to neuronal patterning.

  10. Advances in applications of spiking neuron networks

    NASA Astrophysics Data System (ADS)

    Cios, Krzysztof J.; Sala, Dorel M.

    2000-03-01

    In this paper, we present new findings in constructing and applications of artificial neural networks that use a biologically inspired spiking neuron model. The used model is a point neuron with the interaction between neurons described by postsynaptic potentials. The synaptic plasticity is achieved by using a temporal correlation learning rule, specified as a function of time difference between the firings of pre- and post-synaptic neurons. Using this rule we show how certain associations between neurons in a network of spiking neurons can be implemented. As an example we analyze the dynamic properties of networks of laterally connected spiking neurons and we show their capability to self-organize into topological maps in response to external stimulation. In another application we explore the capability networks of spiking neurons to solve graph algorithms by using temporal coding of distances in a given spatial configuration. The paper underlines the importance of temporal dimension in artificial neural network information processing.

  11. Shape, connectedness and dynamics in neuronal networks.

    PubMed

    Comin, Cesar Henrique; da Fontoura Costa, Luciano

    2013-11-15

    The morphology of neurons is directly related to several aspects of the nervous system, including its connectedness, health, development, evolution, dynamics and, ultimately, behavior. Such interplays of the neuronal morphology can be understood within the more general shape-function paradigm. The current article reviews, in an introductory way, some key issues regarding the role of neuronal morphology in the nervous system, with emphasis on works developed in the authors' group. The following topics are addressed: (a) characterization of neuronal shape; (b) stochastic synthesis of neurons and neuronal systems; (c) characterization of the connectivity of neuronal networks by using complex networks concepts; and (d) investigations of influences of neuronal shape on network dynamics. The presented concepts and methods are useful also for several other multiple object systems, such as protein-protein interaction, tissues, aggregates and polymers.

  12. Network of hypothalamic neurons that control appetite.

    PubMed

    Sohn, Jong-Woo

    2015-04-01

    The central nervous system (CNS) controls food intake and energy expenditure via tight coordinations between multiple neuronal populations. Specifically, two distinct neuronal populations exist in the arcuate nucleus of hypothalamus (ARH): the anorexigenic (appetite-suppressing) pro-opiomelanocortin (POMC) neurons and the orexigenic (appetite-increasing) neuropeptide Y (NPY)/agouti-related peptide (AgRP) neurons. The coordinated regulation of neuronal circuit involving these neurons is essential in properly maintaining energy balance, and any disturbance therein may result in hyperphagia/obesity or hypophagia/starvation. Thus, adequate knowledge of the POMC and NPY/AgRP neuron physiology is mandatory to understand the pathophysiology of obesity and related metabolic diseases. This review will discuss the history and recent updates on the POMC and NPY/AgRP neuronal circuits, as well as the general anorexigenic and orexigenic circuits in the CNS.

  13. Thermonuclear supernova light curves: Progenitors and cosmology

    NASA Astrophysics Data System (ADS)

    Rodney, Steven A.

    Thermonuclear Supernovae (TN SNe) are an extremely important tool in modern astronomy. In their role as cosmological distance probes, they have revealed the accelerated expansion of the universe and have begun to constrain the nature of the dark energy that may be driving that expansion. The next decade will see a succession of wide-field surveys producing thousands of TNSN detections each year. Traditional methods of SN analysis, rooted in time-intensive spectroscopic follow-up, will become completely impractical. To realize the potential of this coming tide of massive data sets, we will need to extract cosmographic parameters (redshift and luminosity distance) from SN photometry without any spectroscopic support. In this dissertation, I present the Supernova Ontology with Fuzzy Templates (SOFT) method, an innovative new approach to the analysis of SN light curves. SOFT uses the framework of fuzzy set theory to perform direct comparisons of SN candidates against template light curves, simultaneously producing both classifications and cosmological parameter estimates. The SOFT method allows us to shed new light on two rich archival data sets. I revisit the IfA Deep Survey and HST GOODS to extract new and improved measurements of the TNSN rate from z=0.2 out to z=1.6. Our new analysis shows a steady increase in the TNSN rate out to z˜1, and adds support for a decrease in the rate at z=1.5. Comparing these rate measurements to theoretical models, I conclude that the progenitor scenario most favored by the collective observational data is a single degenerate model, regulated by a strong wind from the accreting white dwarf. Using a compilation of SN light curves from five recent surveys, I demonstrate that SOFT is able to derive useful constraints on cosmological models from a data set with no spectroscopic information at all. Looking ahead to the near future, I find that photometric analysis of data sets containing 2,000 SNe will be able to improve our constraints on

  14. Friction Stir Welding of Curved Plates

    NASA Technical Reports Server (NTRS)

    Sanchez, Nestor

    1999-01-01

    Friction stir welding (FSW) is a remarkable technology for making butt and lap joints in aluminum alloys. The process operates by passing a rotating tool between two closely butted plates. This process generates heat and the heated material is stirred from both sides of the plates to generate a high quality weld. Application of this technique has a very broad field for NASA. In particular, NASA is interested in using this welding process to manufacture tanks and curved elements. Therefore, this research has been oriented to the study the FSW of curved plates. The study has covered a number of topics that are important in the model development and to uncover the physical process involve in the welding itself. The materials used for the experimental welds were as close to each other as we could possibly find, aluminum 5454-0 and 5456-0 with properties listed at http://matweb.com. The application of FSW to curved plates needs to consider the behavior that we observed in this study. There is going to be larger force in the normal direction (Fz) as the curvature of the plate increases. A particular model needs to be derived for each material and thickness. A more complete study should also include parameters such as spin rate, tool velocity, and power used. The force in the direction of motion (Fx) needs to be reconsidered to make sure of its variability with respect to other parameters such as velocity, thickness, etc. It seems like the curvature does not play a role in this case. Variations in temperature were found with respect to the curvature. However, these changes seem to be smaller than the effect on Fz. The temperatures were all below the melting point. We understand now that the process of FSW produces a three dimensional flow of material that takes place during the weld. This flow needs to be study in a more detailed way to see in which directions the flow of material is stronger. It could be possible to model the flow using a 2-dimensional model in the

  15. Colored noise and memory effects on formal spiking neuron models

    NASA Astrophysics Data System (ADS)

    da Silva, L. A.; Vilela, R. D.

    2015-06-01

    Simplified neuronal models capture the essence of the electrical activity of a generic neuron, besides being more interesting from the computational point of view when compared to higher-dimensional models such as the Hodgkin-Huxley one. In this work, we propose a generalized resonate-and-fire model described by a generalized Langevin equation that takes into account memory effects and colored noise. We perform a comprehensive numerical analysis to study the dynamics and the point process statistics of the proposed model, highlighting interesting new features such as (i) nonmonotonic behavior (emergence of peak structures, enhanced by the choice of colored noise characteristic time scale) of the coefficient of variation (CV) as a function of memory characteristic time scale, (ii) colored noise-induced shift in the CV, and (iii) emergence and suppression of multimodality in the interspike interval (ISI) distribution due to memory-induced subthreshold oscillations. Moreover, in the noise-induced spike regime, we study how memory and colored noise affect the coherence resonance (CR) phenomenon. We found that for sufficiently long memory, not only is CR suppressed but also the minimum of the CV-versus-noise intensity curve that characterizes the presence of CR may be replaced by a maximum. The aforementioned features allow to interpret the interplay between memory and colored noise as an effective control mechanism to neuronal variability. Since both variability and nontrivial temporal patterns in the ISI distribution are ubiquitous in biological cells, we hope the present model can be useful in modeling real aspects of neurons.

  16. The actions of Pasteurella multocida toxin on neuronal cells.

    PubMed

    Surguy, Susan M; Duricki, Denise A; Reilly, Joanne M; Lax, Alistair J; Robbins, Jon

    2014-02-01

    Pasteurella multocida toxin (PMT) activates the G-proteins Gαi(₁₋₃), Gα(q), Gα₁₁, Gα₁₂ and Gα₁₃ by deamidation of specific glutamine residues. A number of these alpha subunits have signalling roles in neurones. Hence we studied the action of this toxin on rat superior cervical ganglion (SCG) neurones and NG108-15 neuronal cells. Both Gα(q) and Gα₁₁ could be identified in SCGs with immunocytochemistry. PMT had no direct action on Kv7 or Cav2 channels in SCGs. However PMT treatment enhanced muscarinic receptor mediated inhibition of M-current (Kv7.2 + 7. 3) as measured by a 19-fold leftward shift in the oxotremorine-M concentration-inhibition curve. Agonists of other receptors, such as bradykinin or angiotensin, that inhibit M-current did not produce this effect. However the amount of PIP₂ hydrolysis could be enhanced by PMT for all three agonists. In a transduction system in SCGs that is unlikely to be affected by PMT, Go mediated inhibition of calcium current, PMT was ineffective whereas the response was blocked by pertussis toxin as expected. M1 muscarinic receptor evoked calcium mobilisation in transformed NG108-15 cells was enhanced by PMT. The calcium rises evoked by uridine triphosphate acting on endogenous P2Y₂ receptors in NG108-15 cells were enhanced by PMT. The time and concentration dependence of the PMT effect was different for the resting calcium compared to the calcium rise produced by activation of P2Y₂ receptors. PMT's action on these neuronal cells would suggest that if it got into the brain, symptoms of a hyperexcitable nature would be seen, such as seizures.

  17. Colored noise and memory effects on formal spiking neuron models.

    PubMed

    da Silva, L A; Vilela, R D

    2015-06-01

    Simplified neuronal models capture the essence of the electrical activity of a generic neuron, besides being more interesting from the computational point of view when compared to higher-dimensional models such as the Hodgkin-Huxley one. In this work, we propose a generalized resonate-and-fire model described by a generalized Langevin equation that takes into account memory effects and colored noise. We perform a comprehensive numerical analysis to study the dynamics and the point process statistics of the proposed model, highlighting interesting new features such as (i) nonmonotonic behavior (emergence of peak structures, enhanced by the choice of colored noise characteristic time scale) of the coefficient of variation (CV) as a function of memory characteristic time scale, (ii) colored noise-induced shift in the CV, and (iii) emergence and suppression of multimodality in the interspike interval (ISI) distribution due to memory-induced subthreshold oscillations. Moreover, in the noise-induced spike regime, we study how memory and colored noise affect the coherence resonance (CR) phenomenon. We found that for sufficiently long memory, not only is CR suppressed but also the minimum of the CV-versus-noise intensity curve that characterizes the presence of CR may be replaced by a maximum. The aforementioned features allow to interpret the interplay between memory and colored noise as an effective control mechanism to neuronal variability. Since both variability and nontrivial temporal patterns in the ISI distribution are ubiquitous in biological cells, we hope the present model can be useful in modeling real aspects of neurons.

  18. Diversions: Hilbert and Sierpinski Space-Filling Curves, and beyond

    ERIC Educational Resources Information Center

    Gough, John

    2012-01-01

    Space-filling curves are related to fractals, in that they have self-similar patterns. Such space-filling curves were originally developed as conceptual mathematical "monsters", counter-examples to Weierstrassian and Reimannian treatments of calculus and continuity. These were curves that were everywhere-connected but…

  19. Creative Tiling: A Story of 1000-and-1 Curves

    ERIC Educational Resources Information Center

    Al-Darwish, Nasir

    2012-01-01

    We describe a procedure that utilizes symmetric curves for building artistic tiles. One particular curve was found to mesh nicely with hundreds other curves, resulting in eye-catching tiling designs. The results of our work serve as a good example of using ideas from 2-D graphics and algorithms in a practical web-based application.

  20. Retiring the Short-Run Aggregate Supply Curve

    ERIC Educational Resources Information Center

    Elwood, S. Kirk

    2010-01-01

    The author argues that the aggregate demand/aggregate supply (AD/AS) model is significantly improved--although certainly not perfected--by trimming it of the short-run aggregate supply (SRAS) curve. Problems with the SRAS curve are shown first for the AD/AS model that casts the AD curve as identifying the equilibrium level of output associated…