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Sample records for networks suppresses selection

  1. Attentional selection by distractor suppression.

    PubMed

    Caputo, G; Guerra, S

    1998-03-01

    Selective attention was studied in displays containing singletons popping out for their odd form or color. The target was defined as the form-singleton, the distractor as the color-singleton. The task was to discriminate the length of a longer line inside the target. Target-distractor similarity was controlled using a threshold measurement as dependent variable in experiments in which distractor presence vs absence, bottom-up vs top-down selection (through knowledge of target features), and target-distractor distance were manipulated. The results in the bottom-up condition showed that length threshold was elevated when a distractor was present and that this elevation progressively increased as the number of distractors was increased from one to two. This set-size effect was not accounted by the hypothesis that selective attention intervenes only at the stage of decision before response. Selective attention produced a suppressive surround in which discriminability of neighboring objects was strongly reduced, and a larger surround in which discriminability was reduced by an approximately constant amount. Different results were found in the top-down condition in which target discriminability was unaffected by distractor presence and no effect of target-distractor distance was found. On the other hand, response times in both bottom-up and top-down conditions were slower the shorter the target-distractor distance was. On the basis of the experimental results, selective attention is a parallel process of spatial filtering at an intermediate processing level operating after objects have been segmented. This filtering stage explores high level interactions between objects taking control on combinatorial explosion by operating over only a limited spatial extent: it picks out a selected object and inhibits the neighboring objects; then, non-selected objects are suppressed across the overall image. When no feature-based selection is available in the current behavior, this

  2. Suppressed epidemics in multirelational networks

    NASA Astrophysics Data System (ADS)

    Xu, Elvis H. W.; Wang, Wei; Xu, C.; Tang, Ming; Do, Younghae; Hui, P. M.

    2015-08-01

    A two-state epidemic model in networks with links mimicking two kinds of relationships between connected nodes is introduced. Links of weights w1 and w0 occur with probabilities p and 1 -p , respectively. The fraction of infected nodes ρ (p ) shows a nonmonotonic behavior, with ρ drops with p for small p and increases for large p . For small to moderate w1/w0 ratios, ρ (p ) exhibits a minimum that signifies an optimal suppression. For large w1/w0 ratios, the suppression leads to an absorbing phase consisting only of healthy nodes within a range pL≤p ≤pR , and an active phase with mixed infected and healthy nodes for p pR . A mean field theory that ignores spatial correlation is shown to give qualitative agreement and capture all the key features. A physical picture that emphasizes the intricate interplay between infections via w0 links and within clusters formed by nodes carrying the w1 links is presented. The absorbing state at large w1/w0 ratios results when the clusters are big enough to disrupt the spread via w0 links and yet small enough to avoid an epidemic within the clusters. A theory that uses the possible local environments of a node as variables is formulated. The theory gives results in good agreement with simulation results, thereby showing the necessity of including longer spatial correlations.

  3. Broadband network selection issues

    NASA Astrophysics Data System (ADS)

    Leimer, Michael E.

    1996-01-01

    Selecting the best network for a given cable or telephone company provider is not as obvious as it appears. The cost and performance trades between Hybrid Fiber Coax (HFC), Fiber to the Curb (FTTC) and Asymmetric Digital Subscriber Line networks lead to very different choices based on the existing plant and the expected interactive subscriber usage model. This paper presents some of the issues and trades that drive network selection. The majority of the Interactive Television trials currently underway or planned are based on HFC networks. As a throw away market trial or a short term strategic incursion into a cable market, HFC may make sense. In the long run, if interactive services see high demand, HFC costs per node and an ever shrinking neighborhood node size to service large numbers of subscribers make FTTC appear attractive. For example, thirty-three 64-QAM modulators are required to fill the 550 MHz to 750 MHz spectrum with compressed video streams in 6 MHz channels. This large amount of hardware at each node drives not only initial build-out costs, but operations and maintenance costs as well. FTTC, with its potential for digitally switching large amounts of bandwidth to an given home, offers the potential to grow with the interactive subscriber base with less downstream cost. Integrated telephony on these networks is an issue that appears to be an afterthought for most of the networks being selected at the present time. The major players seem to be videocentric and include telephony as a simple add-on later. This may be a reasonable view point for the telephone companies that plan to leave their existing phone networks untouched. However, a phone company planning a network upgrade or a cable company jumping into the telephony business needs to carefully weigh the cost and performance issues of the various network choices. Each network type provides varying capability in both upstream and downstream bandwidth for voice channels. The noise characteristics

  4. Selective Memories: Infants’ Encoding is Enhanced in Selection Via Suppression

    PubMed Central

    Markant, Julie; Amso, Dima

    2013-01-01

    The present study examined the hypothesis that inhibitory visual selection mechanisms play a vital role in memory by limiting distractor interference during item encoding. In Experiment 1a we used a modified spatial cueing task in which 9-month-old infants encoded multiple category exemplars in the contexts of an attention orienting mechanism involving suppression (i.e., inhibition of return, IOR) versus one that does not (i.e., facilitation). At test, infants in the IOR condition showed both item specific learning as well as abstraction of broader category information. In contrast, infants in the facilitation condition did not discriminate across novel and familiar test items. Experiment 1b confirmed that the learning observed in the IOR condition was specific to spatial cueing of attention and was not due to timing differences across the IOR and facilitation conditions. In Experiment 2, we replicated the results of Experiment 1, using a within-subjects design to explicitly examine learning and memory encoding in the context of concurrent suppression. These data show that developing inhibitory selective attention enhances efficacy of memory encoding for subsequent retrieval. Furthermore, these results highlight the importance of considering interactions between developing attention and memory systems. PMID:24118717

  5. Selective memories: infants' encoding is enhanced in selection via suppression.

    PubMed

    Markant, Julie; Amso, Dima

    2013-11-01

    The present study examined the hypothesis that inhibitory visual selection mechanisms play a vital role in memory by limiting distractor interference during item encoding. In Experiment 1a we used a modified spatial cueing task in which 9-month-old infants encoded multiple category exemplars in the contexts of an attention orienting mechanism involving suppression (i.e. inhibition of return, IOR) versus one that does not (i.e. facilitation). At test, infants in the IOR condition showed both item-specific learning and abstraction of broader category information. In contrast, infants in the facilitation condition did not discriminate across novel and familiar test items. Experiment 1b confirmed that the learning observed in the IOR condition was specific to spatial cueing of attention and was not due to timing differences across the IOR and facilitation conditions. In Experiment 2, we replicated the results of Experiment 1, using a within-subjects design to explicitly examine learning and memory encoding in the context of concurrent suppression. These data show that developing inhibitory selective attention enhances efficacy of memory encoding for subsequent retrieval. Furthermore, these results highlight the importance of considering interactions between developing attention and memory systems.

  6. Neural Networks for Mindfulness and Emotion Suppression.

    PubMed

    Murakami, Hiroki; Katsunuma, Ruri; Oba, Kentaro; Terasawa, Yuri; Motomura, Yuki; Mishima, Kazuo; Moriguchi, Yoshiya

    2015-01-01

    Mindfulness, an attentive non-judgmental focus on "here and now" experiences, has been incorporated into various cognitive behavioral therapy approaches and beneficial effects have been demonstrated. Recently, mindfulness has also been identified as a potentially effective emotion regulation strategy. On the other hand, emotion suppression, which refers to trying to avoid or escape from experiencing and being aware of one's own emotions, has been identified as a potentially maladaptive strategy. Previous studies suggest that both strategies can decrease affective responses to emotional stimuli. They would, however, be expected to provide regulation through different top-down modulation systems. The present study was aimed at elucidating the different neural systems underlying emotion regulation via mindfulness and emotion suppression approaches. Twenty-one healthy participants used the two types of strategy in response to emotional visual stimuli while functional magnetic resonance imaging was conducted. Both strategies attenuated amygdala responses to emotional triggers, but the pathways to regulation differed across the two. A mindful approach appears to regulate amygdala functioning via functional connectivity from the medial prefrontal cortex, while suppression uses connectivity with other regions, including the dorsolateral prefrontal cortex. Thus, the two types of emotion regulation recruit different top-down modulation processes localized at prefrontal areas. These different pathways are discussed.

  7. Transient amplification limits noise suppression in biochemical networks

    NASA Astrophysics Data System (ADS)

    Dixon, John; Lindemann, Anika; McCoy, Jonathan H.

    2016-01-01

    Cell physiology is orchestrated, on a molecular level, through complex networks of biochemical reactions. The propagation of random fluctuations through these networks can significantly impact cell behavior, raising challenging questions about how network design shapes the cell's ability to suppress or exploit these fluctuations. Here, drawing on insights from statistical physics, fluid dynamics, and systems biology, we explore how transient amplification phenomena arising from network connectivity naturally limit a biochemical system's ability to suppress small fluctuations around steady-state behaviors. We find that even a simple system consisting of two variables linked by a single interaction is capable of amplifying small fluctuations orders of magnitude beyond the levels predicted by linear stability theory. We also find that adding additional interactions can promote further amplification, even when these interactions implement classic design strategies known to suppress fluctuations. These results establish that transient amplification is an essential factor determining baseline noise levels in stable intracellular networks. Significantly, our analysis is not bound to specific systems or interaction mechanisms: we find that noise amplification is an emergent phenomenon found near steady states in any network containing sufficiently strong interactions, regardless of its form or function.

  8. Optical frequency tripling with improved suppression and sideband selection.

    PubMed

    Thakur, Manoj P; Medeiros, Maria C R; Laurêncio, Paula; Mitchell, John E

    2011-12-12

    A novel optical dispersion tolerant millimetre-wave radio-over-fibre system using optical frequency tripling technique with enhanced and selectable sideband suppression is demonstrated. The implementation utilises cascaded optical modulators to achieve either an optical single sideband (OSSB) or double sideband-suppressed carrier (DSB-SC) signal with high sideband suppression. Our analysis and simulation results indicate that the achievable suppression ratio of this configuration is only limited by other system factors such as optical noise and drifting of the operational conditions. The OSSB transmission system performance is assessed experimentally by the transport of 4 WiMax channels modulating a 10 GHz optical upconverted RF carrier as well as for optical frequency doubling and tripling. The 10 GHz and tripled carrier at 30 GHz are dispersion tolerant resulting both in an average relative constellation error (RCE) of -28.7 dB after 40 km of fibre.

  9. Stimulus-dependent suppression of chaos in recurrent neural networks

    SciTech Connect

    Rajan, Kanaka; Abbott, L. F.; Sompolinsky, Haim

    2010-07-15

    Neuronal activity arises from an interaction between ongoing firing generated spontaneously by neural circuits and responses driven by external stimuli. Using mean-field analysis, we ask how a neural network that intrinsically generates chaotic patterns of activity can remain sensitive to extrinsic input. We find that inputs not only drive network responses, but they also actively suppress ongoing activity, ultimately leading to a phase transition in which chaos is completely eliminated. The critical input intensity at the phase transition is a nonmonotonic function of stimulus frequency, revealing a 'resonant' frequency at which the input is most effective at suppressing chaos even though the power spectrum of the spontaneous activity peaks at zero and falls exponentially. A prediction of our analysis is that the variance of neural responses should be most strongly suppressed at frequencies matching the range over which many sensory systems operate.

  10. Signal enhancement and suppression during visual-spatial selective attention.

    PubMed

    Couperus, J W; Mangun, G R

    2010-11-04

    Selective attention involves the relative enhancement of relevant versus irrelevant stimuli. However, whether this relative enhancement involves primarily enhancement of attended stimuli, or suppression of irrelevant stimuli, remains controversial. Moreover, if both enhancement and suppression are involved, whether they result from a single mechanism or separate mechanisms during attentional control or selection is not known. In two experiments using a spatial cuing paradigm with task-relevant targets and irrelevant distractors, target, and distractor processing was examined as a function of distractor expectancy. Additionally, in the second study the interaction of perceptual load and distractor expectancy was explored. In both experiments, distractors were either validly cued (70%) or invalidly cued (30%) in order to examine the effects of distractor expectancy on attentional control as well as target and distractor processing. The effects of distractor expectancy were assessed using event-related potentials recorded during the cue-to-target period (preparatory attention) and in response to the task-relevant target stimuli (selective stimulus processing). Analyses of distractor-present displays (anticipated versus unanticipated), showed modulations in brain activity during both the preparatory period and during target processing. The pattern of brain responses suggest both facilitation of attended targets and suppression of unattended distractors. These findings provide evidence for a two-process model of visual-spatial selective attention, where one mechanism (facilitation) influences relevant stimuli and another (suppression) acts to filter distracting stimuli.

  11. Selective networks and recognition automata.

    PubMed

    Reeke, G N; Edelman, G M

    1984-01-01

    The results we have presented demonstrate that a network based on a selective principle can function in the absence of forced learning or an a priori program to give recognition, classification, generalization, and association. While Darwin II is not a model of any actual nervous system, it does set out to solve one of the same problems that evolution had to solve--the need to form categories in a bottom-up manner from information in the environment, without incorporating the assumptions of any particular observer. The key features of the model that make this possible are (1) Darwin II incorporates selective networks whose initial specificities enable them to respond without instruction to unfamiliar stimuli; (2) degeneracy provides multiple possibilities of response to any one stimulus, at the same time providing functional redundancy against component failure; (3) the output of Darwin II is a pattern of response, making use of the simultaneous responses of multiple degenerate groups to avoid the need for very high specificity and the combinatorial disaster that would imply; (4) reentry within individual networks vitiates the limitations described by Minsky and Papert for a class of perceptual automata lacking such connections; and (5) reentry between intercommunicating networks with different functions gives rise to new functions, such as association, that either one alone could not display. The two kinds of network are roughly analogous to the two kinds of category formation that people use: Darwin, corresponding to the exemplar description of categories, and Wallace, corresponding to the probabilistic matching description of categories. These principles lead to a new class of pattern-recognizing machine of which Darwin II is just an example. There are a number of obvious extensions to this work that we are pursuing. These include giving Darwin II the capability to deal with stimuli that are in motion, an ability that probably precedes the ability of biological

  12. Neuronal Networks during Burst Suppression as Revealed by Source Analysis

    PubMed Central

    Reinicke, Christine; Moeller, Friederike; Anwar, Abdul Rauf; Mideksa, Kidist Gebremariam; Pressler, Ronit; Deuschl, Günther; Stephani, Ulrich; Siniatchkin, Michael

    2015-01-01

    Introduction Burst-suppression (BS) is an electroencephalography (EEG) pattern consisting of alternant periods of slow waves of high amplitude (burst) and periods of so called flat EEG (suppression). It is generally associated with coma of various etiologies (hypoxia, drug-related intoxication, hypothermia, and childhood encephalopathies, but also anesthesia). Animal studies suggest that both the cortex and the thalamus are involved in the generation of BS. However, very little is known about mechanisms of BS in humans. The aim of this study was to identify the neuronal network underlying both burst and suppression phases using source reconstruction and analysis of functional and effective connectivity in EEG. Material/Methods Dynamic imaging of coherent sources (DICS) was applied to EEG segments of 13 neonates and infants with burst and suppression EEG pattern. The brain area with the strongest power in the analyzed frequency (1–4 Hz) range was defined as the reference region. DICS was used to compute the coherence between this reference region and the entire brain. The renormalized partial directed coherence (RPDC) was used to describe the informational flow between the identified sources. Results/Conclusion Delta activity during the burst phases was associated with coherent sources in the thalamus and brainstem as well as bilateral sources in cortical regions mainly frontal and parietal, whereas suppression phases were associated with coherent sources only in cortical regions. Results of the RPDC analyses showed an upwards informational flow from the brainstem towards the thalamus and from the thalamus to cortical regions, which was absent during the suppression phases. These findings may support the theory that a “cortical deafferentiation” between the cortex and sub-cortical structures exists especially in suppression phases compared to burst phases in burst suppression EEGs. Such a deafferentiation may play a role in the poor neurological outcome of

  13. Attention selection, distractor suppression and N2pc.

    PubMed

    Mazza, Veronica; Turatto, Massimo; Caramazza, Alfonso

    2009-01-01

    N2pc is generally interpreted as the electrocortical correlate of the distractor-suppression mechanisms through which attention selection takes place in humans. Here, we present data that challenge this common N2pc interpretation. In Experiment 1, multiple distractors induced greater N2pc amplitudes even when they facilitated target identification, despite the suppression account of the N2pc predicted the contrary; in Experiment 2, spatial proximity between target and distractors did not affect the N2pc amplitude, despite resulting in more interference in response times; in Experiment 3, heterogeneous distractors delayed response times but did not elicit a greater N2pc relative to homogeneous distractors again in contrast with what would have predicted the suppression hypothesis. These results do not support the notion that the N2pc unequivocally mirrors distractor-suppression processes. We propose that the N2pc indexes mechanisms involved in identifying and localizing relevant stimuli in the scene through enhancement of their features and not suppression of distractors.

  14. Deconstructing p53 transcriptional networks in tumor suppression.

    PubMed

    Bieging, Kathryn T; Attardi, Laura D

    2012-02-01

    p53 is a pivotal tumor suppressor that induces apoptosis, cell-cycle arrest and senescence in response to stress signals. Although p53 transcriptional activation is important for these responses, the mechanisms underlying tumor suppression have been elusive. To date, no single or compound mouse knockout of specific p53 target genes has recapitulated the dramatic tumor predisposition that characterizes p53-null mice. Recently, however, analysis of knock-in mice expressing p53 transactivation domain mutants has revealed a group of primarily novel direct p53 target genes that may mediate tumor suppression in vivo. We present here an overview of well-known p53 target genes and the tumor phenotypes of the cognate knockout mice, and address the recent identification of new p53 transcriptional targets and how they enhance our understanding of p53 transcriptional networks central for tumor suppression.

  15. Selective Suppression of Local Circuits during Movement Preparation in the Mouse Motor Cortex.

    PubMed

    Hasegawa, Masashi; Majima, Kei; Itokazu, Takahide; Maki, Takakuni; Albrecht, Urban-Raphael; Castner, Nora; Izumo, Mariko; Sohya, Kazuhiro; Sato, Tatsuo K; Kamitani, Yukiyasu; Sato, Takashi R

    2017-03-14

    Prepared movements are more efficient than those that are not prepared for. Although changes in cortical activity have been observed prior to a forthcoming action, the circuits involved in motor preparation remain unclear. Here, we use in vivo two-photon calcium imaging to uncover changes in the motor cortex during variable waiting periods prior to a forepaw reaching task in mice. Consistent with previous reports, we observed a subset of neurons with increased activity during the waiting period; however, these neurons did not account for the degree of preparation as defined by reaction time (RT). Instead, the suppression of activity of distinct neurons in the same cortical area better accounts for RT. This suppression of neural activity resulted in a distinct and reproducible pattern when mice were well prepared. Thus, the selective suppression of network activity in the motor cortex may be a key feature of prepared movements.

  16. Transient and selective suppression of neural activity with infrared light

    PubMed Central

    Duke, Austin R.; Jenkins, Michael W.; Lu, Hui; McManus, Jeffrey M.; Chiel, Hillel J.; Jansen, E. Duco

    2013-01-01

    Analysis and control of neural circuitry requires the ability to selectively activate or inhibit neurons. Previous work showed that infrared laser light selectively excited neural activity in endogenous unmyelinated and myelinated axons. However, inhibition of neuronal firing with infrared light was only observed in limited cases, is not well understood and was not precisely controlled. Using an experimentally tractable unmyelinated preparation for detailed investigation and a myelinated preparation for validation, we report that it is possible to selectively and transiently inhibit electrically-initiated axonal activation, as well as to both block or enhance the propagation of action potentials of specific motor neurons. Thus, in addition to previously shown excitation, we demonstrate an optical method of suppressing components of the nervous system with functional spatiotemporal precision. We believe this technique is well-suited for non-invasive investigations of diverse excitable tissues and may ultimately be applied for treating neurological disorders. PMID:24009039

  17. Appetite suppression based on selective inhibition of NPY receptors.

    PubMed

    Chamorro, S; Della-Zuana, O; Fauchère, J-L; Félétou, M; Galizzi, J-P; Levens, N

    2002-03-01

    The aim of this review is to critically assess available evidence that blockade of the actions of NPY at one of the five NPY receptor subtypes represents an attractive new drug discovery target for the development of an appetite suppressant drug. Blockade of the central actions of NPY using anti-NPY antibodies, antisense oligodeoxynucleotides against NPY and NPY receptor antagonists results in a decrease in food intake in energy-deprived animals. These results appear to show that endogenous NPY plays a role in the control of appetite. The fact that NPY receptors exist as at least five different subtypes raises the possibility that the actions of endogenous NPY on food intake can be adequately dissociated from other effects of the peptide. Current drug discovery has produced a number of highly selective NPY receptor antagonists which have been used to establish the NPY Y(1) receptor subtype as the most critical in regulating short-term food intake. However, additional studies are now needed to more clearly define the relative contribution of NPY acting through the NPY Y2 and NPY Y5 receptors in the complex sequence of physiological and behavioral events that underlie the long-term control of appetite. Blockade of the NPY receptor may produce appetite-suppressing drugs. However, it is too early to state with certainty whether a single subtype selective drug used alone or a combination of NPY receptor selective antagonists used in combination will be necessary to adequately influence appetite regulation.

  18. Small molecule selectively suppresses MYC transcription in cancer cells.

    PubMed

    Bouvard, Claire; Lim, Sang Min; Ludka, John; Yazdani, Nahid; Woods, Ashley K; Chatterjee, Arnab K; Schultz, Peter G; Zhu, Shoutian

    2017-03-28

    Stauprimide is a staurosporine analog that promotes embryonic stem cell (ESC) differentiation by inhibiting nuclear localization of the MYC transcription factor NME2, which in turn results in down-regulation of MYC transcription. Given the critical role the oncogene MYC plays in tumor initiation and maintenance, we explored the potential of stauprimide as an anticancer agent. Here we report that stauprimide suppresses MYC transcription in cancer cell lines derived from distinct tissues. Using renal cancer cells, we confirmed that stauprimide inhibits NME2 nuclear localization. Gene expression analysis also confirmed the selective down-regulation of MYC target genes by stauprimide. Consistent with this activity, administration of stauprimide inhibited tumor growth in rodent xenograft models. Our study provides a unique strategy for selectively targeting MYC transcription by pharmacological means as a potential treatment for MYC-dependent tumors.

  19. Suppression of eukaryotic translation termination by selected RNAs.

    PubMed Central

    Carnes, J; Frolova, L; Zinnen, S; Drugeon, G; Phillippe, M; Justesen, J; Haenni, A L; Leinwand, L; Kisselev, L L; Yarus, M

    2000-01-01

    Using selection-amplification, we have isolated RNAs with affinity for translation termination factors eRF1 and eRF1.eRF3 complex. Individual RNAs not only bind, but inhibit eRF1-mediated release of a model nascent chain from eukaryotic ribosomes. There is also significant but weaker inhibition of eRF1-stimulated eRF3 GTPase and eRF3 stimulation of eRF1 release activity. These latter selected RNAs therefore hinder eRF1.eRF3 interactions. Finally, four RNA inhibitors of release suppress a UAG stop codon in mammalian extracts dependent for termination on eRF1 from several metazoan species. These RNAs are therefore new specific inhibitors for the analysis of eukaryotic termination, and potentially a new class of omnipotent termination suppressors with possible therapeutic significance. PMID:11073222

  20. Optimal Feedback Strength for Noise Suppression in Autoregulatory Gene Networks

    PubMed Central

    Singh, Abhyudai; Hespanha, Joao P.

    2009-01-01

    Autoregulatory feedback loops, where the protein expressed from a gene inhibits or activates its own expression are common gene network motifs within cells. In these networks, stochastic fluctuations in protein levels are attributed to two factors: intrinsic noise (i.e., the randomness associated with mRNA/protein expression and degradation) and extrinsic noise (i.e., the noise caused by fluctuations in cellular components such as enzyme levels and gene-copy numbers). We present results that predict the level of both intrinsic and extrinsic noise in protein numbers as a function of quantities that can be experimentally determined and/or manipulated, such as the response time of the protein and the level of feedback strength. In particular, we show that for a fixed average number of protein molecules, decreasing response times leads to attenuation of both protein intrinsic and extrinsic noise, with the extrinsic noise being more sensitive to changes in the response time. We further show that for autoregulatory networks with negative feedback, the protein noise levels can be minimal at an optimal level of feedback strength. For such cases, we provide an analytical expression for the highest level of noise suppression and the amount of feedback that achieves this minimal noise. These theoretical results are shown to be consistent and explain recent experimental observations. Finally, we illustrate how measuring changes in the protein noise levels as the feedback strength is manipulated can be used to determine the level of extrinsic noise in these gene networks. PMID:19450473

  1. Targeting prion-like protein doppel selectively suppresses tumor angiogenesis

    PubMed Central

    Al-Hilal, Taslim A.; Chung, Seung Woo; Choi, Jeong Uk; Kim, Seong Who; Kim, Sang Yoon; Ahsan, Fakhrul; Kim, In-San

    2016-01-01

    Controlled and site-specific regulation of growth factor signaling remains a major challenge for current antiangiogenic therapies, as these antiangiogenic agents target normal vasculature as well tumor vasculature. In this article, we identified the prion-like protein doppel as a potential therapeutic target for tumor angiogenesis. We investigated the interactions between doppel and VEGFR2 and evaluated whether blocking the doppel/VEGFR2 axis suppresses the process of angiogenesis. We discovered that tumor endothelial cells (TECs), but not normal ECs, express doppel; tumors from patients and mouse xenografts expressed doppel in their vasculatures. Induced doppel overexpression in ECs enhanced vascularization, whereas doppel constitutively colocalized and complexed with VEGFR2 in TECs. Doppel inhibition depleted VEGFR2 from the cell membrane, subsequently inducing the internalization and degradation of VEGFR2 and thereby attenuating VEGFR2 signaling. We also synthesized an orally active glycosaminoglycan (LHbisD4) that specifically binds with doppel. We determined that LHbisD4 concentrates over the tumor site and that genetic loss of doppel in TECs decreases LHbisD4 binding and targeting both in vitro and in vivo. Moreover, LHbisD4 eliminated VEGFR2 from the cell membrane, prevented VEGF binding in TECs, and suppressed tumor growth. Together, our results demonstrate that blocking doppel can control VEGF signaling in TECs and selectively inhibit tumor angiogenesis. PMID:26950422

  2. Suppressing disease spreading by using information diffusion on multiplex networks

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Liu, Quan-Hui; Cai, Shi-Min; Tang, Ming; Braunstein, Lidia A.; Stanley, H. Eugene

    2016-07-01

    Although there is always an interplay between the dynamics of information diffusion and disease spreading, the empirical research on the systemic coevolution mechanisms connecting these two spreading dynamics is still lacking. Here we investigate the coevolution mechanisms and dynamics between information and disease spreading by utilizing real data and a proposed spreading model on multiplex network. Our empirical analysis finds asymmetrical interactions between the information and disease spreading dynamics. Our results obtained from both the theoretical framework and extensive stochastic numerical simulations suggest that an information outbreak can be triggered in a communication network by its own spreading dynamics or by a disease outbreak on a contact network, but that the disease threshold is not affected by information spreading. Our key finding is that there is an optimal information transmission rate that markedly suppresses the disease spreading. We find that the time evolution of the dynamics in the proposed model qualitatively agrees with the real-world spreading processes at the optimal information transmission rate.

  3. Selective adaptation in networks of cortical neurons.

    PubMed

    Eytan, Danny; Brenner, Naama; Marom, Shimon

    2003-10-15

    A key property of neural systems is their ability to adapt selectively to stimuli with different features. Using multisite electrical recordings from networks of cortical neurons developing ex vivo, we show that neurons adapt selectively to different stimuli invading the network. We focus on selective adaptation to frequent and rare stimuli; networks were stimulated at two sites with two different stimulus frequencies. When both stimuli were presented within the same period, neurons in the network attenuated their responsiveness to the more frequent input, whereas their responsiveness to the rarely delivered stimuli showed a marked average increase. The amplification of the response to rare stimuli required the presence of the other, more frequent stimulation source. By contrast, the decreased response to the frequent stimuli occurred regardless of the presence of the rare stimuli. Analysis of the response of single units suggests that both of these effects are caused by changes in synaptic transmission. By using synaptic blockers, we find that the increased responsiveness to the rarely stimulated site depends specifically on fast GABAergic transmission. Thus, excitatory synaptic depression, the inhibitory sub-network, and their balance play an active role in generating selective gain control. The observation that selective adaptation arises naturally in a network of cortical neurons developing ex vivo indicates that this is an inherent feature of spontaneously organizing cortical networks.

  4. Selective Serotonin Reuptake Inhibitor Suppression of HIV Infectivity and Replication

    PubMed Central

    Benton, Tami; Lynch, Kevin; Dubé, Benoit; Gettes, David R.; Tustin, Nancy B.; Lai, Jian Ping; Metzger, David S.; Blume, Joshua; Douglas, Steven D.; Evans, Dwight L.

    2010-01-01

    Objective To test the hypothesis that the selective serotonin reuptake inhibitor (SSRI) citalopram would down regulate HIV infectivity and that the greatest effects would be seen in people with depression. Depression is a risk factor for morbidity and mortality in HIV/AIDS. Serotonin (5-HT) neurotransmission has been implicated in the pathobiology of depression, and pharmacologic therapies for depression target this system. The 5-HT transporter and 5-HT receptors are widely distributed throughout the central nervous and immune systems. Depression has been associated with suppression of natural killer cells (NK) cells and CD8+ lymphocytes, key regulators of HIV infection. Methods Ex-vivo models for acute and chronic HIV infection were used to study the effects of citalopram on HIV viral infection and replication, in 48 depressed and non-depressed women. For both the acute and chronic infection models, HIV reverse transcriptase (RT) activity was measured in the citalopram treatment condition and the control condition. Results The SSRI significantly downregulated the RT response in both the acute and chronic infection models. Specifically, citalopram significantly decreased the acute HIV infectivity of macrophages. Citalopram also significantly decreased HIV viral replication in the latently infected T-cell line and in the latently infected macrophage cell line. There was no difference in down-regulation by depression status. Conclusions These studies suggest that an SSRI enhances NK/CD8 non-cytolytic HIV suppression in HIV/AIDS and decreases HIV viral infectivity of macrophages, ex vivo, suggesting the need for in vivo studies to determine a potential role for agents targeting serotonin in the host defense against HIV. PMID:20947783

  5. Leader selection for fast consensus in networks

    NASA Astrophysics Data System (ADS)

    Wang, Ying; Yang, Wen; Wang, Lin; Wang, Xiaofan

    2015-12-01

    This paper considers a leader-follower system with the aim to select an optimal leader so as to drive the remaining nodes to reach the desired consensus with the fastest convergence speed. An index called consensus centrality (CC) is proposed to quantify how fast a leader could guide the network to achieve the desired consensus. The experiment results explored the big similarities between the distributions of CC and degree in the network, which suggest that the suboptimal leader selected by the maximum degree can approximately approach the optimal leader in heterogeneous networks. Combining the degree-based k-shell decomposition with consensus centrality, a leader selection algorithm is proposed to reduce the computational complexity in large-scale networks. Finally, the convergence time of an equivalent discrete-time model is given to illustrate the properties of the suboptimal solutions.

  6. Stochastic cycle selection in active flow networks

    PubMed Central

    Woodhouse, Francis G.; Forrow, Aden; Fawcett, Joanna B.; Dunkel, Jörn

    2016-01-01

    Active biological flow networks pervade nature and span a wide range of scales, from arterial blood vessels and bronchial mucus transport in humans to bacterial flow through porous media or plasmodial shuttle streaming in slime molds. Despite their ubiquity, little is known about the self-organization principles that govern flow statistics in such nonequilibrium networks. Here we connect concepts from lattice field theory, graph theory, and transition rate theory to understand how topology controls dynamics in a generic model for actively driven flow on a network. Our combined theoretical and numerical analysis identifies symmetry-based rules that make it possible to classify and predict the selection statistics of complex flow cycles from the network topology. The conceptual framework developed here is applicable to a broad class of biological and nonbiological far-from-equilibrium networks, including actively controlled information flows, and establishes a correspondence between active flow networks and generalized ice-type models. PMID:27382186

  7. Stochastic cycle selection in active flow networks

    NASA Astrophysics Data System (ADS)

    Woodhouse, Francis; Forrow, Aden; Fawcett, Joanna; Dunkel, Jorn

    2016-11-01

    Active biological flow networks pervade nature and span a wide range of scales, from arterial blood vessels and bronchial mucus transport in humans to bacterial flow through porous media or plasmodial shuttle streaming in slime molds. Despite their ubiquity, little is known about the self-organization principles that govern flow statistics in such non-equilibrium networks. By connecting concepts from lattice field theory, graph theory and transition rate theory, we show how topology controls dynamics in a generic model for actively driven flow on a network. Through theoretical and numerical analysis we identify symmetry-based rules to classify and predict the selection statistics of complex flow cycles from the network topology. Our conceptual framework is applicable to a broad class of biological and non-biological far-from-equilibrium networks, including actively controlled information flows, and establishes a new correspondence between active flow networks and generalized ice-type models.

  8. Competitive seeds-selection in complex networks

    NASA Astrophysics Data System (ADS)

    Zhao, Jiuhua; Liu, Qipeng; Wang, Lin; Wang, Xiaofan

    2017-02-01

    This paper investigates a competitive diffusion model where two competitors simultaneously select a set of nodes (seeds) in the network to influence. We focus on the problem of how to select these seeds such that, when the diffusion process terminates, a competitor can obtain more supports than its opponent. Instead of studying this problem in the game-theoretic framework as in the existing work, in this paper we design several heuristic seed-selection strategies inspired by commonly used centrality measures-Betweenness Centrality (BC), Closeness Centrality (CC), Degree Centrality (DC), Eigenvector Centrality (EC), and K-shell Centrality (KS). We mainly compare three centrality-based strategies, which have better performances in competing with the random selection strategy, through simulations on both real and artificial networks. Even though network structure varies across different networks, we find certain common trend appearing in all of these networks. Roughly speaking, BC-based strategy and DC-based strategy are better than CC-based strategy. Moreover, if a competitor adopts CC-based strategy, then BC-based strategy is a better strategy than DC-based strategy for his opponent, and the superiority of BC-based strategy decreases as the heterogeneity of the network decreases.

  9. Mode Selection in Compressible Active Flow Networks

    NASA Astrophysics Data System (ADS)

    Forrow, Aden; Woodhouse, Francis G.; Dunkel, Jörn

    2017-07-01

    Coherent, large-scale dynamics in many nonequilibrium physical, biological, or information transport networks are driven by small-scale local energy input. Here, we introduce and explore an analytically tractable nonlinear model for compressible active flow networks. In contrast to thermally driven systems, we find that active friction selects discrete states with a limited number of oscillation modes activated at distinct fixed amplitudes. Using perturbation theory, we systematically predict the stationary states of noisy networks and find good agreement with a Bayesian state estimation based on a hidden Markov model applied to simulated time series data. Our results suggest that the macroscopic response of active network structures, from actomyosin force networks to cytoplasmic flows, can be dominated by a significantly reduced number of modes, in contrast to energy equipartition in thermal equilibrium. The model is also well suited to study topological sound modes and spectral band gaps in active matter.

  10. Pattern Selection in Network of Coupled Multi-Scroll Attractors.

    PubMed

    Li, Fan; Ma, Jun

    2016-01-01

    Multi-scroll chaotic attractor makes the oscillator become more complex in dynamic behaviors. The collective behaviors of coupled oscillators with multi-scroll attractors are investigated in the regular network in two-dimensional array, which the local kinetics is described by an improved Chua circuit. A feasible scheme of negative feedback with diversity is imposed on the network to stabilize the spatial patterns. Firstly, the Chua circuit is improved by replacing the nonlinear term with Sine function to generate infinite aquariums so that multi-scroll chaotic attractors could be generated under appropriate parameters, which could be detected by calculating the Lyapunov exponent in the parameter region. Furthermore, negative feedback with different gains (D1, D2) is imposed on the local square center area A2 and outer area A1 of the network, it is found that spiral wave, target wave could be developed in the network under appropriate feedback gain with diversity and size of controlled area. Particularly, homogeneous state could be reached after synchronization by selecting appropriate feedback gain and controlled size in the network. Finally, the distribution for statistical factors of synchronization is calculated in the two-parameter space to understand the transition of pattern region. It is found that developed spiral waves, target waves often are associated with smaller factor of synchronization. These results show that emergence of sustained spiral wave and continuous target wave could be effective for further suppression of spatiotemporal chaos in network by generating stable pacemaker completely.

  11. Pattern Selection in Network of Coupled Multi-Scroll Attractors

    PubMed Central

    Li, Fan

    2016-01-01

    Multi-scroll chaotic attractor makes the oscillator become more complex in dynamic behaviors. The collective behaviors of coupled oscillators with multi-scroll attractors are investigated in the regular network in two-dimensional array, which the local kinetics is described by an improved Chua circuit. A feasible scheme of negative feedback with diversity is imposed on the network to stabilize the spatial patterns. Firstly, the Chua circuit is improved by replacing the nonlinear term with Sine function to generate infinite aquariums so that multi-scroll chaotic attractors could be generated under appropriate parameters, which could be detected by calculating the Lyapunov exponent in the parameter region. Furthermore, negative feedback with different gains (D1, D2) is imposed on the local square center area A2 and outer area A1 of the network, it is found that spiral wave, target wave could be developed in the network under appropriate feedback gain with diversity and size of controlled area. Particularly, homogeneous state could be reached after synchronization by selecting appropriate feedback gain and controlled size in the network. Finally, the distribution for statistical factors of synchronization is calculated in the two-parameter space to understand the transition of pattern region. It is found that developed spiral waves, target waves often are associated with smaller factor of synchronization. These results show that emergence of sustained spiral wave and continuous target wave could be effective for further suppression of spatiotemporal chaos in network by generating stable pacemaker completely. PMID:27119986

  12. Network selection: a method for ranked lists selection.

    PubMed

    Cutillo, Luisa; Carissimo, Annamaria; Figini, Silvia

    2012-01-01

    We consider the problem of finding the set of rankings that best represents a given group of orderings on the same collection of elements (preference lists). This problem arises from social choice and voting theory, in which each voter gives a preference on a set of alternatives, and a system outputs a single preference order based on the observed voters' preferences. In this paper, we observe that, if the given set of preference lists is not homogeneous, a unique true underling ranking might not exist. Moreover only the lists that share the highest amount of information should be aggregated, and thus multiple rankings might provide a more feasible solution to the problem. In this light, we propose Network Selection, an algorithm that, given a heterogeneous group of rankings, first discovers the different communities of homogeneous rankings and then combines only the rank orderings belonging to the same community into a single final ordering. Our novel approach is inspired by graph theory; indeed our set of lists can be loosely read as the nodes of a network. As a consequence, only the lists populating the same community in the network would then be aggregated. In order to highlight the strength of our proposal, we show an application both on simulated and on two real datasets, namely a financial and a biological dataset. Experimental results on simulated data show that Network Selection can significantly outperform existing related methods. The other way around, the empirical evidence achieved on real financial data reveals that Network Selection is also able to select the most relevant variables in data mining predictive models, providing a clear superiority in terms of predictive power of the models built. Furthermore, we show the potentiality of our proposal in the bioinformatics field, providing an application to a biological microarray dataset.

  13. Network Selection: A Method for Ranked Lists Selection

    PubMed Central

    Figini, Silvia

    2012-01-01

    We consider the problem of finding the set of rankings that best represents a given group of orderings on the same collection of elements (preference lists). This problem arises from social choice and voting theory, in which each voter gives a preference on a set of alternatives, and a system outputs a single preference order based on the observed voters’ preferences. In this paper, we observe that, if the given set of preference lists is not homogeneous, a unique true underling ranking might not exist. Moreover only the lists that share the highest amount of information should be aggregated, and thus multiple rankings might provide a more feasible solution to the problem. In this light, we propose Network Selection, an algorithm that, given a heterogeneous group of rankings, first discovers the different communities of homogeneous rankings and then combines only the rank orderings belonging to the same community into a single final ordering. Our novel approach is inspired by graph theory; indeed our set of lists can be loosely read as the nodes of a network. As a consequence, only the lists populating the same community in the network would then be aggregated. In order to highlight the strength of our proposal, we show an application both on simulated and on two real datasets, namely a financial and a biological dataset. Experimental results on simulated data show that Network Selection can significantly outperform existing related methods. The other way around, the empirical evidence achieved on real financial data reveals that Network Selection is also able to select the most relevant variables in data mining predictive models, providing a clear superiority in terms of predictive power of the models built. Furthermore, we show the potentiality of our proposal in the bioinformatics field, providing an application to a biological microarray dataset. PMID:22937075

  14. 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

  15. 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

  16. Resting in peace or noise: scanner background noise suppresses default-mode network.

    PubMed

    Gaab, Nadine; Gabrieli, John D E; Glover, Gary H

    2008-07-01

    Studies have identified specific brain regions that increase activation during rest relative to attention-demanding tasks; these regions subserve the "default mode of brain function". Most of these studies have been conducted in the presence of scanner background noise (SBN). This noise has been shown to lead to altered attentional demands, and thus may modulate the default-mode network. Twelve subjects were examined during a rest condition that was contrasted with an auditory task. Words were presented either with SBN employing a conventional acquisition or without SBN using a sparse sampling approach. The number of experimental and resting trials was equated between the designs. Selecting the images in the condition with SBN that corresponded in time with the images in the condition without SBN made a direct comparison of the default-mode network (rest contrasted with active task) possible. There was typical activation of the default-mode network during rest versus task for both designs. However, SBN suppressed major components of the default-mode network, including medial prefrontal cortex, posterior cingulate, and precuneus. Our results suggest that the default mode of brain function differs when assessed in the presence compared to the absence of scanner noise, with the presence of scanner noise perhaps adding attentional demands that diminish activation changes between rest and task in a nonlinear way within the default network. Further studies are needed to clarify whether the use of a sparse sampling technique might enhance clinical utilities that have been proposed for analysis of the default-mode network.

  17. Modality-specificity of Selective Attention Networks

    PubMed Central

    Stewart, Hannah J.; Amitay, Sygal

    2015-01-01

    Objective: To establish the modality specificity and generality of selective attention networks. Method: Forty-eight young adults completed a battery of four auditory and visual selective attention tests based upon the Attention Network framework: the visual and auditory Attention Network Tests (vANT, aANT), the Test of Everyday Attention (TEA), and the Test of Attention in Listening (TAiL). These provided independent measures for auditory and visual alerting, orienting, and conflict resolution networks. The measures were subjected to an exploratory factor analysis to assess underlying attention constructs. Results: The analysis yielded a four-component solution. The first component comprised of a range of measures from the TEA and was labeled “general attention.” The third component was labeled “auditory attention,” as it only contained measures from the TAiL using pitch as the attended stimulus feature. The second and fourth components were labeled as “spatial orienting” and “spatial conflict,” respectively—they were comprised of orienting and conflict resolution measures from the vANT, aANT, and TAiL attend-location task—all tasks based upon spatial judgments (e.g., the direction of a target arrow or sound location). Conclusions: These results do not support our a-priori hypothesis that attention networks are either modality specific or supramodal. Auditory attention separated into selectively attending to spatial and non-spatial features, with the auditory spatial attention loading onto the same factor as visual spatial attention, suggesting spatial attention is supramodal. However, since our study did not include a non-spatial measure of visual attention, further research will be required to ascertain whether non-spatial attention is modality-specific. PMID:26635709

  18. Selective suppression of interleukin-12 induction after macrophage receptor ligation.

    PubMed

    Sutterwala, F S; Noel, G J; Clynes, R; Mosser, D M

    1997-06-02

    Interleukin (IL)-12 is a monocyte- and macrophage-derived cytokine that plays a crucial role in both the innate and the acquired immune response. In this study, we examined the effects that ligating specific macrophage receptors had on the induction of IL-12 by lipopolysaccharide (LPS). We report that ligation of the macrophage Fcgamma, complement, or scavenger receptors inhibited the induction of IL-12 by LPS. Both mRNA synthesis and protein secretion were diminished to near-undetectable levels following receptor ligation. Suppression was specific to IL-12 since IL-10 and tumor necrosis factor-alpha (TNF-alpha) production were not inhibited by ligating macrophage receptors. The results of several different experimental approaches suggest that IL-12 downregulation was due to extracellular calcium influxes that resulted from receptor ligation. First, preventing extracellular calcium influxes, by performing the assays in EGTA, abrogated FcgammaR-mediated IL-12(p40) mRNA suppression. Second, exposure of macrophages to the calcium ionophores, ionomycin or A23187, mimicked receptor ligation and inhibited IL-12(p40) mRNA induction by LPS. Finally, bone marrow-derived macrophages from FcR gamma chain-deficient mice, which fail to flux calcium after receptor ligation, failed to inhibit IL-12(p40) mRNA induction. These results indicate that the calcium influxes that occur as a result of receptor ligation are responsible for inhibiting the induction of IL-12 by LPS. Hence, the ligation of phagocytic receptors on macrophages can lead to a dramatic decrease in IL-12 induction. This downregulation may be a way of limiting proinflammatory responses of macrophages to extracellular pathogens, or suppressing the development of cell-mediated immunity to intracellular pathogens.

  19. Cotton genotypes selection through artificial neural networks.

    PubMed

    Júnior, E G Silva; Cardoso, D B O; Reis, M C; Nascimento, A F O; Bortolin, D I; Martins, M R; Sousa, L B

    2017-09-27

    Breeding programs currently use statistical analysis to assist in the identification of superior genotypes at various stages of a cultivar's development. Differently from these analyses, the computational intelligence approach has been little explored in genetic improvement of cotton. Thus, this study was carried out with the objective of presenting the use of artificial neural networks as auxiliary tools in the improvement of the cotton to improve fiber quality. To demonstrate the applicability of this approach, this research was carried out using the evaluation data of 40 genotypes. In order to classify the genotypes for fiber quality, the artificial neural networks were trained with replicate data of 20 genotypes of cotton evaluated in the harvests of 2013/14 and 2014/15, regarding fiber length, uniformity of length, fiber strength, micronaire index, elongation, short fiber index, maturity index, reflectance degree, and fiber quality index. This quality index was estimated by means of a weighted average on the determined score (1 to 5) of each characteristic of the HVI evaluated, according to its industry standards. The artificial neural networks presented a high capacity of correct classification of the 20 selected genotypes based on the fiber quality index, so that when using fiber length associated with the short fiber index, fiber maturation, and micronaire index, the artificial neural networks presented better results than using only fiber length and previous associations. It was also observed that to submit data of means of new genotypes to the neural networks trained with data of repetition, provides better results of classification of the genotypes. When observing the results obtained in the present study, it was verified that the artificial neural networks present great potential to be used in the different stages of a genetic improvement program of the cotton, aiming at the improvement of the fiber quality of the future cultivars.

  20. Genetic suppression of transgenic APP rescues Hypersynchronous network activity in a mouse model of Alzeimer's disease.

    PubMed

    Born, Heather A; Kim, Ji-Yoen; Savjani, Ricky R; Das, Pritam; Dabaghian, Yuri A; Guo, Qinxi; Yoo, Jong W; Schuler, Dorothy R; Cirrito, John R; Zheng, Hui; Golde, Todd E; Noebels, Jeffrey L; Jankowsky, Joanna L

    2014-03-12

    Alzheimer's disease (AD) is associated with an elevated risk for seizures that may be fundamentally connected to cognitive dysfunction. Supporting this link, many mouse models for AD exhibit abnormal electroencephalogram (EEG) activity in addition to the expected neuropathology and cognitive deficits. Here, we used a controllable transgenic system to investigate how network changes develop and are maintained in a model characterized by amyloid β (Aβ) overproduction and progressive amyloid pathology. EEG recordings in tet-off mice overexpressing amyloid precursor protein (APP) from birth display frequent sharp wave discharges (SWDs). Unexpectedly, we found that withholding APP overexpression until adulthood substantially delayed the appearance of epileptiform activity. Together, these findings suggest that juvenile APP overexpression altered cortical development to favor synchronized firing. Regardless of the age at which EEG abnormalities appeared, the phenotype was dependent on continued APP overexpression and abated over several weeks once transgene expression was suppressed. Abnormal EEG discharges were independent of plaque load and could be extinguished without altering deposited amyloid. Selective reduction of Aβ with a γ-secretase inhibitor has no effect on the frequency of SWDs, indicating that another APP fragment or the full-length protein was likely responsible for maintaining EEG abnormalities. Moreover, transgene suppression normalized the ratio of excitatory to inhibitory innervation in the cortex, whereas secretase inhibition did not. Our results suggest that APP overexpression, and not Aβ overproduction, is responsible for EEG abnormalities in our transgenic mice and can be rescued independently of pathology.

  1. Effects of search efficiency on surround suppression during visual selection in frontal eye field.

    PubMed

    Schall, Jeffrey D; Sato, Takashi R; Thompson, Kirk G; Vaughn, Amanda A; Juan, Chi-Hung

    2004-06-01

    Previous research has shown that visually responsive neurons in the frontal eye field of macaque monkeys select the target for a saccade during efficient, pop-out visual search through suppression of the representation of the nontarget distractors. For a fraction of these neurons, the magnitude of this distractor suppression varied with the proximity of the target to the receptive field, exhibiting more suppression of the distractor representation when the target was nearby than when the target was distant. The purpose of this study was to determine whether the variation of distractor suppression related to target proximity varied with target-distractor feature similarity. The effect of target proximity on distractor suppression did not vary with target-distractor similarity and therefore may be an endogenous property of the selection process.

  2. Targeting Immune Regulatory Networks to Counteract Immune Suppression in Cancer.

    PubMed

    Camisaschi, Chiara; Vallacchi, Viviana; Vergani, Elisabetta; Tazzari, Marcella; Ferro, Simona; Tuccitto, Alessandra; Kuchuk, Olga; Shahaj, Eriomina; Sulsenti, Roberta; Castelli, Chiara; Rodolfo, Monica; Rivoltini, Licia; Huber, Veronica

    2016-11-04

    The onset of cancer is unavoidably accompanied by suppression of antitumor immunity. This occurs through mechanisms ranging from the progressive accumulation of regulatory immune cells associated with chronic immune stimulation and inflammation, to the expression of immunosuppressive molecules. Some of them are being successfully exploited as therapeutic targets, with impressive clinical results achieved in patients, as in the case of immune checkpoint inhibitors. To limit immune attack, tumor cells exploit specific pathways to render the tumor microenvironment hostile for antitumor effector cells. Local acidification might, in fact, anergize activated T cells and facilitate the accumulation of immune suppressive cells. Moreover, the release of extracellular vesicles by tumor cells can condition distant immune sites contributing to the onset of systemic immune suppression. Understanding which mechanisms may be prevalent in specific cancers or disease stages, and identifying possible strategies to counterbalance would majorly contribute to improving clinical efficacy of cancer immunotherapy. Here, we intend to highlight these mechanisms, how they could be targeted and the tools that might be available in the near future to achieve this goal.

  3. Targeting Immune Regulatory Networks to Counteract Immune Suppression in Cancer

    PubMed Central

    Camisaschi, Chiara; Vallacchi, Viviana; Vergani, Elisabetta; Tazzari, Marcella; Ferro, Simona; Tuccitto, Alessandra; Kuchuk, Olga; Shahaj, Eriomina; Sulsenti, Roberta; Castelli, Chiara; Rodolfo, Monica; Rivoltini, Licia; Huber, Veronica

    2016-01-01

    The onset of cancer is unavoidably accompanied by suppression of antitumor immunity. This occurs through mechanisms ranging from the progressive accumulation of regulatory immune cells associated with chronic immune stimulation and inflammation, to the expression of immunosuppressive molecules. Some of them are being successfully exploited as therapeutic targets, with impressive clinical results achieved in patients, as in the case of immune checkpoint inhibitors. To limit immune attack, tumor cells exploit specific pathways to render the tumor microenvironment hostile for antitumor effector cells. Local acidification might, in fact, anergize activated T cells and facilitate the accumulation of immune suppressive cells. Moreover, the release of extracellular vesicles by tumor cells can condition distant immune sites contributing to the onset of systemic immune suppression. Understanding which mechanisms may be prevalent in specific cancers or disease stages, and identifying possible strategies to counterbalance would majorly contribute to improving clinical efficacy of cancer immunotherapy. Here, we intend to highlight these mechanisms, how they could be targeted and the tools that might be available in the near future to achieve this goal. PMID:27827921

  4. Riboflavin-binding protein exhibits selective sweet suppression toward protein sweeteners.

    PubMed

    Maehashi, Kenji; Matano, Mami; Kondo, Azusa; Yamamoto, Yasushi; Udaka, Shigezo

    2007-02-01

    Riboflavin-binding protein (RBP) is well known as a riboflavin carrier protein in chicken egg and serum. A novel function of RBP was found as a sweet-suppressing protein. RBP, purified from hen egg white, suppressed the sweetness of protein sweeteners such as thaumatin, monellin, and lysozyme, whereas it did not suppress the sweetness of low molecular weight sweeteners such as sucrose, glycine, D-phenylalanine, saccharin, cyclamate, aspartame, and stevioside. Therefore, the sweet-suppressing activity of RBP was apparently selective to protein sweeteners. The sweet suppression by RBP was independent of binding of riboflavin with its molecule. Yolk RBP, with minor structural differences compared with egg white RBP, also elicited a weaker sweet suppression. However, other commercially available proteins including ovalbumin, ovomucoid, beta-lactogloblin, myoglobin, and albumin did not substantially alter the sweetness of protein sweeteners. Because a prerinse with RBP reduced the subsequent sweetness of protein sweeteners, whereas the enzymatic activity of lysozyme and the elution profile of lysozyme on gel permeation chromatography were not affected by RBP, it is suggested that the sweet suppression is caused by an interaction of RBP with a sweet taste receptor rather than with the protein sweeteners themselves. The selectivity in the sweet suppression by RBP is consistent with the existence of multiple interaction sites within a single sweet taste receptor.

  5. Pseudomonas fluorescens strains selectively suppress annual bluegrass (Poa annua L.)

    USDA-ARS?s Scientific Manuscript database

    Annual bluegrass (Poa annua L.) is a cool-season annual grass that is a major weed species in turf, turfgrass-seed production, sod production, and golf courses of the western United States. There are few selective herbicides available for the management of annual bluegrass. While the life cycles o...

  6. Selective two-photon fluorescence suppression by ultrafast pulse-pair excitation: control by selective one-color stimulated emission.

    PubMed

    Kumar De, Arijit; Roy, Debjit; Goswami, Debabrata

    2011-10-01

    Controlling two-photon molecular fluorescence leading to selective fluorophore excitation has been a long sought after goal in fluorescence microscopy. In this letter, we thoroughly explore selective fluorescence suppression through simultaneous two-photon absorption by two different fluorophores followed by selective one-photon stimulated emission for one particular fluorophore. We achieve this by precisely controlling the time delay between two identical ultrafast near infrared laser pulses.

  7. Human behavior in Prisoner's Dilemma experiments suppresses network reciprocity.

    PubMed

    Gracia-Lázaro, Carlos; Cuesta, José A; Sánchez, Angel; Moreno, Yamir

    2012-01-01

    During the last few years, much research has been devoted to strategic interactions on complex networks. In this context, the Prisoner's Dilemma has become a paradigmatic model, and it has been established that imitative evolutionary dynamics lead to very different outcomes depending on the details of the network. We here report that when one takes into account the real behavior of people observed in the experiments, both at the mean-field level and on utterly different networks, the observed level of cooperation is the same. We thus show that when human subjects interact in a heterogeneous mix including cooperators, defectors and moody conditional cooperators, the structure of the population does not promote or inhibit cooperation with respect to a well mixed population.

  8. Human behavior in Prisoner's Dilemma experiments suppresses network reciprocity

    PubMed Central

    Gracia-Lázaro, Carlos; Cuesta, José A.; Sánchez, Angel; Moreno, Yamir

    2012-01-01

    During the last few years, much research has been devoted to strategic interactions on complex networks. In this context, the Prisoner's Dilemma has become a paradigmatic model, and it has been established that imitative evolutionary dynamics lead to very different outcomes depending on the details of the network. We here report that when one takes into account the real behavior of people observed in the experiments, both at the mean-field level and on utterly different networks, the observed level of cooperation is the same. We thus show that when human subjects interact in a heterogeneous mix including cooperators, defectors and moody conditional cooperators, the structure of the population does not promote or inhibit cooperation with respect to a well mixed population. PMID:22439103

  9. Caregivers' Support Network Characteristics Associated with Viral Suppression among HIV Care Recipients.

    PubMed

    Denison, Julie A; Mitchell, Mary M; Maragh-Bass, Allysha C; Knowlton, Amy R

    2017-03-17

    Informal care receipt is associated with health outcomes among people living with HIV. Less is known about how caregivers' own social support may affect their care recipient's health. We examined associations between network characteristics of informal caregivers and HIV viral suppression among former or current drug using care recipients. We analyzed data from 258 caregiver-recipient dyads from the Beacon study, of whom 89% of caregivers were African American and 59% were female. In adjusted logistic regression analysis, care recipients had lower odds of being virally suppressed if their caregiver was female, was caring for youth involved in the criminal justice system, and had network members who used illicit drugs. Caregivers' greater numbers of non-kin in their support network was positively associated with viral suppression among care recipients. The findings reveal contextual factors affecting ART outcomes and the need for interventions to support caregivers, especially HIV caregiving women with high-risk youth.

  10. Frequency selectivity of the human cochlea: Suppression tuning of spontaneous otoacoustic emissions.

    PubMed

    Manley, Geoffrey A; van Dijk, Pim

    2016-06-01

    Frequency selectivity is a key functional property of the inner ear and since hearing research began, the frequency resolution of the human ear has been a central question. In contrast to animal studies, which permit invasive recording of neural activity, human studies must rely on indirect methods to determine hearing selectivity. Psychophysical studies, which used masking of a tone by other sounds, indicate a modest frequency selectivity in humans. By contrast, estimates using the phase delays of stimulus-frequency otoacoustic emissions (SFOAE) predict a remarkably high selectivity, unique among mammals. An alternative measure of cochlear frequency selectivity are suppression tuning curves of spontaneous otoacoustic emissions (SOAE). Several animal studies show that these measures are in excellent agreement with neural frequency selectivity. Here we contribute a large data set from normal-hearing young humans on suppression tuning curves (STC) of spontaneous otoacoustic emissions (SOAE). The frequency selectivities of human STC measured near threshold levels agree with the earlier, much lower, psychophysical estimates. They differ, however, from the typical patterns seen in animal auditory nerve data in that the selectivity is remarkably independent of frequency. In addition, SOAE are suppressed by higher-level tones in narrow frequency bands clearly above the main suppression frequencies. These narrow suppression bands suggest interactions between the suppressor tone and a cochlear standing wave corresponding to the SOAE frequency being suppressed. The data show that the relationship between pre-neural mechanical processing in the cochlea and neural coding at the hair-cell/auditory nerve synapse needs to be reconsidered.

  11. Lipid and water suppression by selective 1H homonuclear polarization transfer.

    PubMed

    Hardy, C J; Dumoulin, C L

    1987-07-01

    A pulse sequence is presented which uses Polarization Transfer by a Selective Homonuclear Technique (POTSHOT) to retain all resonances, in phase, from a selected coupled spin system while suppressing all other peaks, from both coupled and noncoupled spins. This technique, which is a selective form of Homonuclear Polarization Transfer (HPT), has been used in a 1.5-T whole-body system to generate edited 1H lactate spectra from lactate/oil phantoms and from excised dog hearts.

  12. Inclusive fitness effects can select for cancer suppression into old age

    PubMed Central

    Brown, Joel S.; Aktipis, C. Athena

    2015-01-01

    Natural selection can favour health at youth or middle age (high reproductive value) over health at old age (low reproductive value). This means, all else being equal, selection for cancer suppression should dramatically drop after reproductive age. However, in species with significant parental investment, the capacity to enhance inclusive fitness may increase the reproductive value of older individuals or even those past reproductive age. Variation in parental investment levels could therefore contribute to variation in cancer susceptibility across species. In this article, we describe a simple model and framework for the evolution of cancer suppression with varying levels of parental investment and use this model to make testable predictions about variation in cancer suppression across species. This model can be extended to show that selection for cancer suppression is stronger in species with cooperative breeding systems and intergenerational transfers. We consider three cases that can select for cancer suppression into old age: (i) extended parental care that increases the survivorship of their offspring, (ii) grandparents contributing to higher fecundity of their children and (iii) cooperative breeding where helpers forgo reproduction or even survivorship to assist parents in having higher fecundity. PMID:26056358

  13. On the properties of artificial neural network filters for bone-suppressed digital radiography

    NASA Astrophysics Data System (ADS)

    Park, Eunpyeong; Park, Junbeom; Kim, Daecheon; Youn, Hanbean; Jeon, Hosang; Kim, Jin Sung; Kang, Dong-Joong; Kim, Ho Kyung

    2016-04-01

    Dual-energy imaging can enhance lesion conspicuity. However, the conventional (fast kilovoltage switching) dual-shot dual-energy imaging is vulnerable to patient motion. The single-shot method requires a special design of detector system. Alternatively, single-shot bone-suppressed imaging is possible using post-image processing combined with a filter obtained from training an artificial neural network. In this study, the authors investigate the general properties of artificial neural network filters for bone-suppressed digital radiography. The filter properties are characterized in terms of various parameters such as the size of input vector, the number of hidden units, the learning rate, and so on. The preliminary result shows that the bone-suppressed image obtained from the filter, which is designed with 5,000 teaching images from a single radiograph, results in about 95% similarity with a commercial bone-enhanced image.

  14. A fuzzy neural network sliding mode controller for vibration suppression in robotically assisted minimally invasive surgery.

    PubMed

    Sang, Hongqiang; Yang, Chenghao; Liu, Fen; Yun, Jintian; Jin, Guoguang

    2016-12-01

    It is very important for robotically assisted minimally invasive surgery to achieve a high-precision and smooth motion control. However, the surgical instrument tip will exhibit vibration caused by nonlinear friction and unmodeled dynamics, especially when the surgical robot system is attempting low-speed, fine motion. A fuzzy neural network sliding mode controller (FNNSMC) is proposed to suppress vibration of the surgical robotic system. Nonlinear friction and modeling uncertainties are compensated by a Stribeck model, a radial basis function (RBF) neural network and a fuzzy system, respectively. Simulations and experiments were performed on a 3 degree-of-freedom (DOF) minimally invasive surgical robot. The results demonstrate that the FNNSMC is effective and can suppress vibrations at the surgical instrument tip. The proposed FNNSMC can provide a robust performance and suppress the vibrations at the surgical instrument tip, which can enhance the quality and security of surgical procedures. Copyright © 2016 John Wiley & Sons, Ltd.

  15. Glucocorticoids Suppress Selected Components of the Senescence-Associated Secretory Phenotype

    PubMed Central

    Laberge, Remi-Martin; Zhou, Lili; Sarantos, Melissa R.; Rodier, Francis; Freund, Adam; de Keizer, Peter L.J.; Liu, Su; Demaria, Marco; Cong, Yu-Sheng; Kapahi, Pankaj; Desprez, Pierre-Yves; Hughes, Robert E.; Campisi, Judith

    2012-01-01

    SUMMARY Cellular senescence suppresses cancer by arresting the proliferation of cells at risk for malignant transformation. Recently, senescent cells were shown to secrete numerous cytokines, growth factors and proteases that can alter the tissue microenvironment and may promote age-related pathology. To identify small molecules that suppress the senescence-associated secretory phenotype (SASP), we developed a screening protocol using normal human fibroblasts and a library of compounds that are approved for human use. Among the promising library constituents was the glucocorticoid corticosterone. Both corticosterone and the related glucocorticoid cortisol decreased the production and secretion of selected SASP components, including several pro-inflammatory cytokines. Importantly, the glucocorticoids suppressed the SASP without reverting the tumor suppressive growth arrest, and were efficacious whether cells were induced to senesce by ionizing radiation or strong mitogenic signals delivered by oncogenic RAS or MAP kinase kinase 6 overexpression. Suppression of the prototypical SASP component IL-6 required the glucocorticoid receptor, which, in the presence of ligand, inhibited IL-1α signaling and NF-κB transactivation activity. Accordingly, co-treatments combining glucocorticoids with the glucocorticoid antagonist RU-486 or recombinant IL-1α efficiently reestablished NF-κB transcriptional activity and IL-6 secretion. Our findings demonstrate feasibility of screening for compounds that inhibit the effects of senescent cells. They further show that glucocorticoids inhibit selected components of the SASP, and suggest that corticosterone and cortisol, two FDA-approved drugs, might exert their effects in part by suppressing senescence-associated inflammation. PMID:22404905

  16. Glucocorticoids suppress selected components of the senescence-associated secretory phenotype.

    PubMed

    Laberge, Remi-Martin; Zhou, Lili; Sarantos, Melissa R; Rodier, Francis; Freund, Adam; de Keizer, Peter L J; Liu, Su; Demaria, Marco; Cong, Yu-Sheng; Kapahi, Pankaj; Desprez, Pierre-Yves; Hughes, Robert E; Campisi, Judith

    2012-08-01

    Cellular senescence suppresses cancer by arresting the proliferation of cells at risk for malignant transformation. Recently, senescent cells were shown to secrete numerous cytokines, growth factors, and proteases that can alter the tissue microenvironment and may promote age-related pathology. To identify small molecules that suppress the senescence-associated secretory phenotype (SASP), we developed a screening protocol using normal human fibroblasts and a library of compounds that are approved for human use. Among the promising library constituents was the glucocorticoid corticosterone. Both corticosterone and the related glucocorticoid cortisol decreased the production and secretion of selected SASP components, including several pro-inflammatory cytokines. Importantly, the glucocorticoids suppressed the SASP without reverting the tumor suppressive growth arrest and were efficacious whether cells were induced to senesce by ionizing radiation or strong mitogenic signals delivered by oncogenic RAS or MAP kinase kinase 6 overexpression. Suppression of the prototypical SASP component IL-6 required the glucocorticoid receptor, which, in the presence of ligand, inhibited IL-1α signaling and NF-κB transactivation activity. Accordingly, co-treatments combining glucocorticoids with the glucocorticoid antagonist RU-486 or recombinant IL-1α efficiently reestablished NF-κB transcriptional activity and IL-6 secretion. Our findings demonstrate feasibility of screening for compounds that inhibit the effects of senescent cells. They further show that glucocorticoids inhibit selected components of the SASP and suggest that corticosterone and cortisol, two FDA-approved drugs, might exert their effects in part by suppressing senescence-associated inflammation.

  17. Delayed resonator concept for vibration suppression using piezoelectric networks

    NASA Astrophysics Data System (ADS)

    Kammer, Ayhan S.; Olgac, Nejat

    2016-11-01

    Delayed resonators (DR) are a class of active vibration absorbers, where resonance in the absorber is achieved through a delayed feedback control. Studies on DR theory so far, have focused on traditional mechanical absorber structures with proof masses. Both in linear and rotational vibration applications, a mechanical substructure is brought to resonance; which, in turn, absorbs vibration from the primary structure. This study is a departure from the existing literature in the sense that the mechanical absorber structure is replaced by an electrical circuit that resonates. The tuning is achieved by the use of piezoelectric elements, which introduce a coupling between the mechanical and electrical components in the system. The resonance and desired vibration absorption are still the objectives but with a distinct feature, ‘without a proof mass’. This work unites the two fronts of research from this interesting angle, namely DR theory and piezoelectric networks, to benefit from their individual strengths.

  18. Supplier Selection in Virtual Enterprise Model of Manufacturing Supply Network

    NASA Astrophysics Data System (ADS)

    Kaihara, Toshiya; Opadiji, Jayeola F.

    The market-based approach to manufacturing supply network planning focuses on the competitive attitudes of various enterprises in the network to generate plans that seek to maximize the throughput of the network. It is this competitive behaviour of the member units that we explore in proposing a solution model for a supplier selection problem in convergent manufacturing supply networks. We present a formulation of autonomous units of the network as trading agents in a virtual enterprise network interacting to deliver value to market consumers and discuss the effect of internal and external trading parameters on the selection of suppliers by enterprise units.

  19. Depolarization Induced Suppression of Excitation and the Emergence of Ultraslow Rhythms in Neural Networks

    NASA Astrophysics Data System (ADS)

    Hlinka, J.; Coombes, S.

    2010-02-01

    Ultraslow fluctuations (0.01-0.1 Hz) are a feature of intrinsic brain activity of as yet unclear origin. We propose a candidate mechanism based on retrograde endocannabinoid signaling in a synaptically coupled network of excitatory neurons. This is known to cause depolarization-induced suppression of excitation (DISE), which we model phenomenologically. We construct emergent network oscillations in a globally coupled network and show that for strong synaptic coupling DISE can lead to a synchronized population burst at the frequencies of resting brain rhythms.

  20. Computer-Based Information Networks: Selected Examples.

    ERIC Educational Resources Information Center

    Hardesty, Larry

    The history, purpose, and operation of six computer-based information networks are described in general and nontechnical terms. In the introduction the many definitions of an information network are explored. Ohio College Library Center's network (OCLC) is the first example. OCLC began in 1963, and since early 1973 has been extending its services…

  1. Computer-Based Information Networks: Selected Examples.

    ERIC Educational Resources Information Center

    Hardesty, Larry

    The history, purpose, and operation of six computer-based information networks are described in general and nontechnical terms. In the introduction the many definitions of an information network are explored. Ohio College Library Center's network (OCLC) is the first example. OCLC began in 1963, and since early 1973 has been extending its services…

  2. Transient selection in multicellular immune networks

    NASA Astrophysics Data System (ADS)

    Ivanchenko, M. V.

    2011-03-01

    We analyze the dynamics of a multi-clonotype naive T-cell population competing for survival signals from antigen-presenting cells. We find that this competition provides with an efficacious selection of clonotypes, making the less able and more repetitive get extinct. We uncover the scaling principles for large systems the extinction rate obeys and calibrate the model parameters to their experimental counterparts. For the first time, we estimate the physiological values of the T-cell receptor-antigen presentation profile recognition probability and T-cell clonotypes niche overlap. We demonstrate that, while the ultimate state is a stable fixed point, sequential transients dominate the dynamics over large timescales that may span over years, if not decades, in real time. We argue that what is currently viewed as "homeostasis" is a complex sequential transient process, while being quasi-stationary in the total number of T-cells only. The discovered type of sequential transient dynamics in large random networks is a novel alternative to the stable heteroclinic channel mechanism.

  3. Selecting Microcomputer Network Configurations: A Model for Technological Endurance.

    ERIC Educational Resources Information Center

    Drummond, Marshall; And Others

    A model approach is suggested for the selection of a microcomputer network that will identify specific needs and arrive at solutions with maximum flexibility to avoid technological obsolescence. Chapter 1 specifies functional needs for a network design. This chapter discusses the process of evaluating whether a network is appropriate; examines and…

  4. Viral microRNAs Target a Gene Network, Inhibit STAT Activation, and Suppress Interferon Responses

    PubMed Central

    Ramalingam, Dhivya; Ziegelbauer, Joseph M.

    2017-01-01

    Kaposi’s sarcoma-associated herpesvirus (KSHV) encodes 12 pre-microRNAs during latency that are processed to yield ~25 mature microRNAs (miRNAs). We were interested in identifying cellular networks that were targeted by KSHV-miRNAs and employed network building strategies using validated KSHV miRNA targets. Here, we report the identification of a gene network centering on the transcription factor- signal transducer and activator of transcription 3 (STAT3) that is targeted by KSHV miRNAs. KSHV miRNAs suppressed STAT3 and STAT5 activation and inhibited STAT3-dependent reporter activation upon IL6-treatment. KSHV miRNAs also repressed the induction of antiviral interferon-stimulated genes upon IFNα- treatment. Finally, we observed increased lytic reactivation of KSHV from latently infected cells upon STAT3 repression with siRNAs or a small molecule inhibitor. Our data suggest that treatment of infected cells with a STAT3 inhibitor and a viral replication inhibitor, ganciclovir, represents a possible strategy to eliminate latently infected cells without increasing virion production. Together, we show that KSHV miRNAs suppress a network of targets associated with STAT3, deregulate cytokine-mediated gene activation, suppress an interferon response, and influence the transition into the lytic phase of viral replication. PMID:28102325

  5. A Network Selection Algorithm Considering Power Consumption in Hybrid Wireless Networks

    NASA Astrophysics Data System (ADS)

    Joe, Inwhee; Kim, Won-Tae; Hong, Seokjoon

    In this paper, we propose a novel network selection algorithm considering power consumption in hybrid wireless networks for vertical handover. CDMA, WiBro, WLAN networks are candidate networks for this selection algorithm. This algorithm is composed of the power consumption prediction algorithm and the final network selection algorithm. The power consumption prediction algorithm estimates the expected lifetime of the mobile station based on the current battery level, traffic class and power consumption for each network interface card of the mobile station. If the expected lifetime of the mobile station in a certain network is not long enough compared the handover delay, this particular network will be removed from the candidate network list, thereby preventing unnecessary handovers in the preprocessing procedure. On the other hand, the final network selection algorithm consists of AHP (Analytic Hierarchical Process) and GRA (Grey Relational Analysis). The global factors of the network selection structure are QoS, cost and lifetime. If user preference is lifetime, our selection algorithm selects the network that offers longest service duration due to low power consumption. Also, we conduct some simulations using the OPNET simulation tool. The simulation results show that the proposed algorithm provides longer lifetime in the hybrid wireless network environment.

  6. Improved frequency selective fat suppression in the posterior neck with tissue susceptibility matched pyrolytic graphite foam.

    PubMed

    Lee, Gary; Jordan, Caroline; Tiet, Pamela; Ruiz, Carlos; McCormick, Jeff; Phuong, Kevin; Hargreaves, Brian; Conolly, Steven

    2015-03-01

    To demonstrate improved frequency selective fat suppression in MRI using a magnetic susceptibility matching foam by reducing B0 inhomogeneities induced within the body by air-tissue interfaces. Flexible pyrolytic graphite (PG) composite foam was tailored to match the magnetic susceptibility of human tissue and was shaped to surround the cervical spine region. Field maps and frequency selective fat suppressed T1 -weighted FLASH images were acquired at 3 Tesla in both phantoms and six healthy necks. B0 field uniformity was shimmed to a target critical threshold of 1 ppm for fat suppression. The percentage of voxels in the phantom that did not achieve the critical threshold was reduced from 64% without the PG foam to only 1% with the foam. A similar decrease from 16% to 2% was observed in the in vivo region of interest. PG foam improved B0 field uniformity by moving air-tissue field gradients outside of the neck where they cannot cause MRI artifacts. The PG foams consistently mitigated signal dropout, improved overall SNR, and enabled more robust frequency selective fat suppression. © 2014 Wiley Periodicals, Inc.

  7. Induction of selective Bayesian networks from data

    SciTech Connect

    Singh, M.

    1996-12-31

    Bayesian networks, which provide a compact graphical way to express complex probabilistic relationships among several random variables, are rapidly becoming the tool of choice for dealing with uncertainty in knowledge based systems. Amongst the many advantages offered by Bayesian networks over other representations such as decision trees and neural networks are the ease of comprehensibility to humans, effectiveness as complex decision making models and elicitability of informative prior distributions.

  8. Selective Modulation of Orbitofrontal Network Activity during Negative Occasion Setting.

    PubMed

    Shobe, Justin L; Bakhurin, Konstantin I; Claar, Leslie D; Masmanidis, Sotiris C

    2017-09-27

    Discrete cues can gain powerful control over behavior to help an animal anticipate and cope with upcoming events. This is important in conditions where understanding the relationship between complex stimuli provides a means to resolving situational ambiguity. However, it is unclear how cortical circuits generate and maintain these signals that conditionally regulate behavior. To address this, we established a Pavlovian serial feature-negative conditioning paradigm, where male mice are trained on a trial in which a conditioned stimulus (CS) is presented alone and followed by reward, or a feature-negative trial in which the CS is preceded by a feature cue indicating there is no reward. Mice learn to respond with anticipatory licking to a solitary CS, but significantly suppress their responding to the same cue during feature-negative trials. We show that the feature cue forms a selective association with its paired CS, because the ability of the feature to transfer its suppressive properties to a separately rewarded cue is limited. Next, to examine the underlying neural dynamics, we conduct recordings in the orbitofrontal cortex (OFC). We find that the feature cue significantly and selectively inhibits CS-evoked activity. Finally, we find that the feature triggers a distinct OFC network state during the delay period between the feature and CS, establishing a potential link between the feature and future events. Together, our findings suggest that OFC dynamics are modulated by the feature cue and its associated conditioned stimulus in a manner consistent with an occasion setting model.SIGNIFICANCE STATEMENT The ability of patterned cues to form an inhibitory relationship with ambiguously rewarded outcomes has been appreciated since early studies on learning and memory. However, it was often assumed that these cues, despite their hierarchical nature, still made direct associative links with neural rewarding events. This model was significantly challenged, largely by the

  9. Heuristic Strategies for Persuader Selection in Contagions on Complex Networks

    PubMed Central

    Wang, Peng; Zhang, Li-Jie; Xiao, Gaoxi

    2017-01-01

    Individual decision to accept a new idea or product is often driven by both self-adoption and others’ persuasion, which has been simulated using a double threshold model [Huang et al., Scientific Reports 6, 23766 (2016)]. We extend the study to consider the case with limited persuasion. That is, a set of individuals is chosen from the population to be equipped with persuasion capabilities, who may succeed in persuading their friends to take the new entity when certain conditions are satisfied. Network node centrality is adopted to characterize each node’s influence, based on which three heuristic strategies are applied to pick out persuaders. We compare these strategies for persuader selection on both homogeneous and heterogeneous networks. Two regimes of the underline networks are identified in which the system exhibits distinct behaviors: when networks are sufficiently sparse, selecting persuader nodes in descending order of node centrality achieves the best performance; when networks are sufficiently dense, however, selecting nodes with medium centralities to serve as the persuaders performs the best. Under respective optimal strategies for different types of networks, we further probe which centrality measure is most suitable for persuader selection. It turns out that for the first regime, degree centrality offers the best measure for picking out persuaders from homogeneous networks; while in heterogeneous networks, betweenness centrality takes its place. In the second regime, there is no significant difference caused by centrality measures in persuader selection for homogeneous network; while for heterogeneous networks, closeness centrality offers the best measure. PMID:28072847

  10. Heuristic Strategies for Persuader Selection in Contagions on Complex Networks.

    PubMed

    Wang, Peng; Zhang, Li-Jie; Xu, Xin-Jian; Xiao, Gaoxi

    2017-01-01

    Individual decision to accept a new idea or product is often driven by both self-adoption and others' persuasion, which has been simulated using a double threshold model [Huang et al., Scientific Reports 6, 23766 (2016)]. We extend the study to consider the case with limited persuasion. That is, a set of individuals is chosen from the population to be equipped with persuasion capabilities, who may succeed in persuading their friends to take the new entity when certain conditions are satisfied. Network node centrality is adopted to characterize each node's influence, based on which three heuristic strategies are applied to pick out persuaders. We compare these strategies for persuader selection on both homogeneous and heterogeneous networks. Two regimes of the underline networks are identified in which the system exhibits distinct behaviors: when networks are sufficiently sparse, selecting persuader nodes in descending order of node centrality achieves the best performance; when networks are sufficiently dense, however, selecting nodes with medium centralities to serve as the persuaders performs the best. Under respective optimal strategies for different types of networks, we further probe which centrality measure is most suitable for persuader selection. It turns out that for the first regime, degree centrality offers the best measure for picking out persuaders from homogeneous networks; while in heterogeneous networks, betweenness centrality takes its place. In the second regime, there is no significant difference caused by centrality measures in persuader selection for homogeneous network; while for heterogeneous networks, closeness centrality offers the best measure.

  11. Selective suppression of high-order harmonics within phase-matched spectral regions.

    PubMed

    Lerner, Gavriel; Diskin, Tzvi; Neufeld, Ofer; Kfir, Ofer; Cohen, Oren

    2017-04-01

    Phase matching in high-harmonic generation leads to enhancement of multiple harmonics. It is sometimes desired to control the spectral structure within the phase-matched spectral region. We propose a scheme for selective suppression of high-order harmonics within the phase-matched spectral region while weakly influencing the other harmonics. The method is based on addition of phase-mismatched segments within a phase-matched medium. We demonstrate the method numerically in two examples. First, we show that one phase-mismatched segment can significantly suppress harmonic orders 9, 15, and 21. Second, we show that two phase-mismatched segments can efficiently suppress circularly polarized harmonics with one helicity over the other when driven by a bi-circular field. The new method may be useful for various applications, including the generation of highly helical bright attosecond pulses.

  12. Optogenetic activation of superior colliculus neurons suppresses seizures originating in diverse brain networks

    PubMed Central

    Soper, Colin; Wicker, Evan; Kulick, Catherine V.; N’Gouemo, Prosper; Forcelli, Patrick A.

    2016-01-01

    Because sites of seizure origin may be unknown or multifocal, identifying targets from which activation can suppress seizures originating in diverse networks is essential. We evaluated the ability of optogenetic activation of the deep/intermediate layers of the superior colliculus (DLSC) to fill this role. Optogenetic activation of DLSC suppressed behavioral and electrographic seizures in the pentylenetetrazole (forebrain+brainstem seizures) and Area Tempestas (forebrain/complex partial seizures) models; this effect was specific to activation of DLSC, and not neighboring structures. DLSC activation likewise attenuated seizures evoked by gamma butyrolactone (thalamocortical/absence seizures), or acoustic stimulation of genetically epilepsy prone rates (brainstem seizures). Anticonvulsant effects were seen with stimulation frequencies as low as 5 Hz. Unlike previous applications of optogenetics for the control of seizures, activation of DLSC exerted broad-spectrum anticonvulsant actions, attenuating seizures originating in diverse and distal brain networks. These data indicate that DLSC is a promising target for optogenetic control of epilepsy. PMID:26721319

  13. Effective Suppression of Pathological Synchronization in Cortical Networks by Highly Heterogeneous Distribution of Inhibitory Connections

    PubMed Central

    Kada, Hisashi; Teramae, Jun-Nosuke; Tokuda, Isao T.

    2016-01-01

    Even without external random input, cortical networks in vivo sustain asynchronous irregular firing with low firing rate. In addition to detailed balance between excitatory and inhibitory activities, recent theoretical studies have revealed that another feature commonly observed in cortical networks, i.e., long-tailed distribution of excitatory synapses implying coexistence of many weak and a few extremely strong excitatory synapses, plays an essential role in realizing the self-sustained activity in recurrent networks of biologically plausible spiking neurons. The previous studies, however, have not considered highly non-random features of the synaptic connectivity, namely, bidirectional connections between cortical neurons are more common than expected by chance and strengths of synapses are positively correlated between pre- and postsynaptic neurons. The positive correlation of synaptic connections may destabilize asynchronous activity of networks with the long-tailed synaptic distribution and induce pathological synchronized firing among neurons. It remains unclear how the cortical network avoids such pathological synchronization. Here, we demonstrate that introduction of the correlated connections indeed gives rise to synchronized firings in a cortical network model with the long-tailed distribution. By using a simplified feed-forward network model of spiking neurons, we clarify the underlying mechanism of the synchronization. We then show that the synchronization can be efficiently suppressed by highly heterogeneous distribution, typically a lognormal distribution, of inhibitory-to-excitatory connection strengths in a recurrent network model of cortical neurons. PMID:27803659

  14. Dissociating the influence of response selection and task anticipation on corticospinal suppression during response preparation.

    PubMed

    Duque, Julie; Labruna, Ludovica; Cazares, Christian; Ivry, Richard B

    2014-12-01

    Motor behavior requires selecting between potential actions. The role of inhibition in response selection has frequently been examined in tasks in which participants are engaged in some advance preparation prior to the presentation of an imperative signal. Under such conditions, inhibition could be related to processes associated with response selection, or to more general inhibitory processes that are engaged in high states of anticipation. In Experiment 1, we manipulated the degree of anticipatory preparation. Participants performed a choice reaction time task that required choosing between a movement of the left or right index finger, and used transcranial magnetic stimulation (TMS) to elicit motor evoked potentials (MEPs) in the left hand agonist. In high anticipation blocks, a non-informative cue (e.g., fixation marker) preceded the imperative; in low anticipation blocks, there was no cue and participants were required to divide their attention between two tasks to further reduce anticipation. MEPs were substantially reduced before the imperative signal in high anticipation blocks. In contrast, in low anticipation blocks, MEPs remained unchanged before the imperative signal but showed a marked suppression right after the onset of the imperative. This effect occurred regardless of whether the imperative had signalled a left or right hand response. After this initial inhibition, left MEPs increased when the left hand was selected and remained suppressed when the right hand was selected. We obtained similar results in Experiment 2 except that the persistent left MEP suppression when the left hand was not selected was attenuated when the alternative response involved a non-homologous effector (right foot). These results indicate that, even in the absence of an anticipatory period, inhibitory mechanisms are engaged during response selection, possibly to prevent the occurrence of premature and inappropriate responses during a competitive selection process. Copyright

  15. Dissociating the Influence of Response Selection and Task Anticipation on Corticospinal Suppression During Response Preparation

    PubMed Central

    Duque, Julie; Labruna, Ludovica; Cazares, Christian; Ivry, Richard B.

    2014-01-01

    Motor behavior requires selecting between potential actions. The role of inhibition in response selection has frequently been examined in tasks in which participants are engaged in some advance preparation prior to the presentation of an imperative signal. Under such conditions, inhibition could be related to processes associated with response selection, or to more general inhibitory processes that are engaged in high states of anticipation. In Experiment 1, we manipulated the degree of anticipatory preparation. Participants performed a choice reaction time task that required choosing between a movement of the left or right index finger, and used transcranial magnetic stimulation (TMS) to elicit motor evoked potentials (MEPs) in the left hand agonist. In high anticipation blocks, a non-informative cue (e.g., fixation marker) preceded the imperative; in low anticipation blocks, there was no cue and participants were required to divide their attention between two tasks to further reduce anticipation. MEPs were substantially reduced before the imperative signal in high anticipation blocks. In contrast, in low anticipation blocks, MEPs remained unchanged before the imperative signal but showed a marked suppression right after the onset of the imperative. This effect occurred regardless of whether the imperative had signaled a left or right hand response. After this initial inhibition, left MEPs increased when the left hand was selected and remained suppressed when the right hand was selected. We obtained similar results in Experiment 2 except that the persistent left MEP suppression when the left hand was not selected was attenuated when the alternative response involved a non-homologous effector (right foot). These results indicate that, even in the absence of an anticipatory period, inhibitory mechanisms are engaged during response selection, possibly to prevent the occurrence of premature and inappropriate responses during a competitive selection process. PMID

  16. Volume-selective multi-pulse spin-echo spectroscopy and selective suppression of spectral lines.

    PubMed

    Kimmich, R; Schnur, G; Hoepfel, D; Ratzel, D

    1987-10-01

    A method is described allowing the recording of in vivo NMR spectra in sharply bound volume elements preselected on the basis of slice images. Experiments with phantom samples, as well as with a test person in a whole-body instrument, have been carried out to demonstrate the applicability of the technique. In the case of proton spectroscopy, suppression of the water and/or or of the lipid line is often desirable. A corresponding pulse sequence has been implemented and successfully tested with a phantom sample.

  17. Bidirectional selection between two classes in complex social networks.

    PubMed

    Zhou, Bin; He, Zhe; Jiang, Luo-Luo; Wang, Nian-Xin; Wang, Bing-Hong

    2014-12-19

    The bidirectional selection between two classes widely emerges in various social lives, such as commercial trading and mate choosing. Until now, the discussions on bidirectional selection in structured human society are quite limited. We demonstrated theoretically that the rate of successfully matching is affected greatly by individuals' neighborhoods in social networks, regardless of the type of networks. Furthermore, it is found that the high average degree of networks contributes to increasing rates of successful matches. The matching performance in different types of networks has been quantitatively investigated, revealing that the small-world networks reinforces the matching rate more than scale-free networks at given average degree. In addition, our analysis is consistent with the modeling result, which provides the theoretical understanding of underlying mechanisms of matching in complex networks.

  18. Network selection, Information filtering and Scalable computation

    NASA Astrophysics Data System (ADS)

    Ye, Changqing

    This dissertation explores two application scenarios of sparsity pursuit method on large scale data sets. The first scenario is classification and regression in analyzing high dimensional structured data, where predictors corresponds to nodes of a given directed graph. This arises in, for instance, identification of disease genes for the Parkinson's diseases from a network of candidate genes. In such a situation, directed graph describes dependencies among the genes, where direction of edges represent certain causal effects. Key to high-dimensional structured classification and regression is how to utilize dependencies among predictors as specified by directions of the graph. In this dissertation, we develop a novel method that fully takes into account such dependencies formulated through certain nonlinear constraints. We apply the proposed method to two applications, feature selection in large margin binary classification and in linear regression. We implement the proposed method through difference convex programming for the cost function and constraints. Finally, theoretical and numerical analyses suggest that the proposed method achieves the desired objectives. An application to disease gene identification is presented. The second application scenario is personalized information filtering which extracts the information specifically relevant to a user, predicting his/her preference over a large number of items, based on the opinions of users who think alike or its content. This problem is cast into the framework of regression and classification, where we introduce novel partial latent models to integrate additional user-specific and content-specific predictors, for higher predictive accuracy. In particular, we factorize a user-over-item preference matrix into a product of two matrices, each representing a user's preference and an item preference by users. Then we propose a likelihood method to seek a sparsest latent factorization, from a class of over

  19. Temporal selection is suppressed, delayed, and diffused during the attentional blink.

    PubMed

    Vul, Edward; Nieuwenstein, Mark; Kanwisher, Nancy

    2008-01-01

    How does temporal selection work, and along what dimensions does it vary from one instance to the next? We explored these questions using a phenomenon in which temporal selection goes awry. In the attentional blink, subjects fail to report the second of a pair of targets (T1 and T2) when they are presented at stimulus onset asynchronies (SOAs) of roughly 200 to 500 ms. We directly tested the properties of temporal selection during the blink by analyzing distractor intrusions at a fast rate of item presentation. Our analysis shows that attentional selection is (a) suppressed, (b) delayed, and (c) diffused in time during the attentional blink. These effects are dissociated by their time course: The measure of each effect returns to the baseline value at a different SOA. Our results constrain theories of the attentional blink and indicate that temporal selection varies along at least three dissociable dimensions: efficacy, latency, and precision.

  20. Incorporating spatial criteria in optimum reserve network selection.

    PubMed Central

    Onal, Hayri; Briers, Robert A

    2002-01-01

    Considering the spatial location of sites that are to be selected for inclusion in a protected reserve network may be necessary to facilitate dispersal and long-term persistence of species in the selected sites. This paper presents an integer programming (IP) approach to the reserve network selection problem where spatial considerations based on intersite distances are taken into account when selecting reserve sites. The objective is to reduce the fragmentation of preserved sites and design a compact reserve network. Two IP formulations are developed which minimize the sum of pairwise distances and the maximum intersite distance between all sites in the reserve network, respectively, while representing all species under consideration. This approach is applied to a pond invertebrate dataset consisting of 131 sites containing 256 species in Oxfordshire, UK. The results show that significant reductions in reserve fragmentation can be achieved, compared with spatially unrestricted optimum reserve selection, at the expense of a small loss in reserve efficiency. PMID:12495486

  1. Noise-suppressed image enhancement using multiscale top-hat selection transform through region extraction.

    PubMed

    Bai, Xiangzhi; Zhou, Fugen; Xue, Bindang

    2012-01-20

    Enhancing an image through increasing the contrast of the image is one effective way of image enhancement. To well enhance an image and suppress the produced noises in the resulting image, a multiscale top-hat selection transform-based algorithm through extracting bright and dark image regions and increasing the contrast between them is proposed. First, the multiscale top-hat selection transform is discussed and then is used to extract the bright and dark image regions of each scale. Second, the final extracted bright and dark image regions are obtained through a maximum operation on all the extracted multiscale bright and dark image regions at all scales. Finally, by using a weight strategy, the image is enhanced through increasing the contrast of the image by adding the final bright regions on and subtracting the final dark regions from the original image. The weight parameters are used to adjust the effect of image enhancement. Because the multiscale top-hat selection transform is used to effectively extract the final image regions and discriminate the possible noise regions, the image is well enhanced and some noises are suppressed. Experimental results on different types of images show that our algorithm performs well for noise-suppressed image enhancement and is useful for different applications. © 2012 Optical Society of America

  2. Amplification or suppression: Social networks and the climate change—migration association in rural Mexico

    PubMed Central

    Riosmena, Fernando; Hunter, Lori M.; Runfola, Daniel M.

    2015-01-01

    Increasing rates of climate migration may be of economic and national concern to sending and destination countries. It has been argued that social networks – the ties connecting an origin and destination – may operate as “migration corridors” with the potential to strongly facilitate climate change-related migration. This study investigates whether social networks at the household and community levels amplify or suppress the impact of climate change on international migration from rural Mexico. A novel set of 15 climate change indices was generated based on daily temperature and precipitation data for 214 weather stations across Mexico. Employing geostatistical interpolation techniques, the climate change values were linked to 68 rural municipalities for which sociodemographic data and detailed migration histories were available from the Mexican Migration Project. Multi-level discrete-time event-history models were used to investigate the effect of climate change on international migration between 1986 and 1999. At the household level, the effect of social networks was approximated by comparing the first to the last move, assuming that through the first move a household establishes internal social capital. At the community level, the impact of social capital was explored through interactions with a measure of the proportion of adults with migration experience. The results show that rather than amplifying, social capital may suppress the sensitivity of migration to climate triggers, suggesting that social networks could facilitate climate change adaptation in place. PMID:26692656

  3. Amplification or suppression: Social networks and the climate change-migration association in rural Mexico.

    PubMed

    Nawrotzki, Raphael J; Riosmena, Fernando; Hunter, Lori M; Runfola, Daniel M

    2015-11-01

    Increasing rates of climate migration may be of economic and national concern to sending and destination countries. It has been argued that social networks - the ties connecting an origin and destination - may operate as "migration corridors" with the potential to strongly facilitate climate change-related migration. This study investigates whether social networks at the household and community levels amplify or suppress the impact of climate change on international migration from rural Mexico. A novel set of 15 climate change indices was generated based on daily temperature and precipitation data for 214 weather stations across Mexico. Employing geostatistical interpolation techniques, the climate change values were linked to 68 rural municipalities for which sociodemographic data and detailed migration histories were available from the Mexican Migration Project. Multi-level discrete-time event-history models were used to investigate the effect of climate change on international migration between 1986 and 1999. At the household level, the effect of social networks was approximated by comparing the first to the last move, assuming that through the first move a household establishes internal social capital. At the community level, the impact of social capital was explored through interactions with a measure of the proportion of adults with migration experience. The results show that rather than amplifying, social capital may suppress the sensitivity of migration to climate triggers, suggesting that social networks could facilitate climate change adaptation in place.

  4. Development of Haemonchus contortus resistance in sheep under suppressive or targeted selective treatment with monepantel.

    PubMed

    de Albuquerque, Ana Cláudia Alexandre; Bassetto, Cesar Cristiano; de Almeida, Fabiana Alves; Amarante, Alessandro F T

    2017-11-15

    This study examined the development of resistance to anthelmintics in Haemonchus contortus in lambs under suppressive or selective treatment regimens that included monepantel. Twenty Ile de France and 20 Santa Ines lambs were allocated to two anthelmintic treatment regimens, based on body weight and nematode faecal egg counts (FEC): targeted selective treatment (TST) or suppressive treatment, both with monepantel. Lambs of the TST group were treated individually when they presented with a packed cell volume (PCV) ≤20%. On 7 October 2016, the lambs were allocated to clean pastures, where they grazed in separated paddocks by group until late February 2017. The experimental area was contaminated with nematodes that were introduced with the experimental Ile de France and Santa Ines lambs, naturally infected with gastrointestinal nematodes. To maintain the grazing lambs in the suppressive treatment group and their pasture as free of worms as possible, these lambs were treated with anthelmintics before being allocated to their paddock and then were periodically treated with monepantel. However, the use of a suppressive treatment regimen that included monepantel over a period of 3 months resulted in the emergence of a population of resistant H. contortus. In the TST group, there was a rapid and progressive reduction in the efficacy of monepantel, which at the end of the experiment was only 76%. The Ile de France lambs were all treated one or more times during the experiment, whereas only two Santa Ines lambs in the TST required treatment. In conclusion, a population of H. contortus resistant to monepantel emerged quickly during the rainy season, even when sheep were submitted to selective treatment. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Convergent recombination suppression suggests role of sexual selection in guppy sex chromosome formation

    PubMed Central

    Wright, Alison E.; Darolti, Iulia; Bloch, Natasha I.; Oostra, Vicencio; Sandkam, Ben; Buechel, Severine D.; Kolm, Niclas; Breden, Felix; Vicoso, Beatriz; Mank, Judith E.

    2017-01-01

    Sex chromosomes evolve once recombination is halted between a homologous pair of chromosomes. The dominant model of sex chromosome evolution posits that recombination is suppressed between emerging X and Y chromosomes in order to resolve sexual conflict. Here we test this model using whole genome and transcriptome resequencing data in the guppy, a model for sexual selection with many Y-linked colour traits. We show that although the nascent Y chromosome encompasses nearly half of the linkage group, there has been no perceptible degradation of Y chromosome gene content or activity. Using replicate wild populations with differing levels of sexually antagonistic selection for colour, we also show that sexual selection leads to greater expansion of the non-recombining region and increased Y chromosome divergence. These results provide empirical support for longstanding models of sex chromosome catalysis, and suggest an important role for sexual selection and sexual conflict in genome evolution. PMID:28139647

  6. Voluntary strategy suppresses the positive impact of preferential selection in prisoner’s dilemma

    NASA Astrophysics Data System (ADS)

    Sun, Lei; Lin, Pei-jie; Chen, Ya-shan

    2014-11-01

    Impact of aspiration is ubiquitous in social and biological disciplines. In this work, we try to explore the impact of such a trait on voluntary prisoners’ dilemma game via a selection parameter w. w=0 returns the traditional version of random selection. For positive w, the opponent of high payoff will be selected; while negative w means that the partner of low payoff will be chosen. We find that for positive w, cooperation will be greatly promoted in the interval of small b, at variance cooperation is inhibited with large b. For negative w, cooperation is fully restrained, irrespective of b value. It is found that the positive impact of preferential selection is suppressed by the voluntary strategy in prisoner’s dilemma. These observations can be supported by the spatial patterns. Our work may shed light on the emergence and persistence of cooperation with voluntary participation in social dilemma.

  7. [Lateralized brain language semantic network demonstrated by word repetition suppression effect in MEG].

    PubMed

    Nikolaeva, A Yu; Butorina, A V; Prokofyev, A O; Stroganova, T A

    2015-01-01

    We studied auditory word repetition suppression effect using magnetoencephalography while subjects listened to "new" and "old" words whose familiarity they had to judge upon presentation. The lateralization of brain magnetic activity during processing of "new" and "old" words were estimated by computing RMS measure of whole-brain magnetic response within time window of semantic N400 (350-450 ms). A magnetic N400 was significantly stronger in the left than in the right hemisphere for the "new" words only. Repetition of "new" words led to sharp decrease of N400 response RMS in the left hemisphere but did not change right-hemispheric N400 RMS. The asymmetry index of this repetition suppression effect was lateralized to the left hemisphere for the majority of the participants and its magnitude was related to memory task performance. The findings point to a strong left-hemispheric dominance of word repetition suppression effect within the brain semantic networks at the level of whole-network response.

  8. Selective Memories: Infants' Encoding Is Enhanced in Selection via Suppression

    ERIC Educational Resources Information Center

    Markant, Julie; Amso, Dima

    2013-01-01

    The present study examined the hypothesis that inhibitory visual selection mechanisms play a vital role in memory by limiting distractor interference during item encoding. In Experiment 1a we used a modified spatial cueing task in which 9-month-old infants encoded multiple category exemplars in the contexts of an attention orienting mechanism…

  9. Selective Memories: Infants' Encoding Is Enhanced in Selection via Suppression

    ERIC Educational Resources Information Center

    Markant, Julie; Amso, Dima

    2013-01-01

    The present study examined the hypothesis that inhibitory visual selection mechanisms play a vital role in memory by limiting distractor interference during item encoding. In Experiment 1a we used a modified spatial cueing task in which 9-month-old infants encoded multiple category exemplars in the contexts of an attention orienting mechanism…

  10. Networks in Education: An Analysis of Selected Discourses

    ERIC Educational Resources Information Center

    Sousa, Sofia Branco; Doroftei, Alexandra Oliveira; Araújo, Helena Costa

    2013-01-01

    "Network" is a fashionable and current term in every field of contemporary society and education is no exception. In this paper, the concept of network (and other associated concepts, such as partnership and collaboration) is reviewed. Such revision regards selected theoretical contributions and is explored in terms of the use of the…

  11. Networks in Education: An Analysis of Selected Discourses

    ERIC Educational Resources Information Center

    Sousa, Sofia Branco; Doroftei, Alexandra Oliveira; Araújo, Helena Costa

    2013-01-01

    "Network" is a fashionable and current term in every field of contemporary society and education is no exception. In this paper, the concept of network (and other associated concepts, such as partnership and collaboration) is reviewed. Such revision regards selected theoretical contributions and is explored in terms of the use of the…

  12. Popularity and Adolescent Friendship Networks: Selection and Influence Dynamics

    ERIC Educational Resources Information Center

    Dijkstra, Jan Kornelis; Cillessen, Antonius H. N.; Borch, Casey

    2013-01-01

    This study examined the dynamics of popularity in adolescent friendship networks across 3 years in middle school. Longitudinal social network modeling was used to identify selection and influence in the similarity of popularity among friends. It was argued that lower status adolescents strive to enhance their status through befriending higher…

  13. Popularity and Adolescent Friendship Networks: Selection and Influence Dynamics

    ERIC Educational Resources Information Center

    Dijkstra, Jan Kornelis; Cillessen, Antonius H. N.; Borch, Casey

    2013-01-01

    This study examined the dynamics of popularity in adolescent friendship networks across 3 years in middle school. Longitudinal social network modeling was used to identify selection and influence in the similarity of popularity among friends. It was argued that lower status adolescents strive to enhance their status through befriending higher…

  14. Selective Estrogen Receptor Modulators Suppress Hif1α Protein Accumulation in Mouse Osteoclasts

    PubMed Central

    Iwasaki, Ryotaro; Kobayashi, Tami; Watanabe, Ryuichi; Oike, Takatsugu; Toyama, Yoshiaki; Matsumoto, Morio; Nakamura, Masaya; Kawana, Hiromasa; Nakagawa, Taneaki; Miyamoto, Takeshi

    2016-01-01

    Anti-bone resorptive drugs such as bisphosphonates, the anti-RANKL antibody (denosumab), or selective estrogen receptor modulators (SERMs) have been developed to treat osteoporosis. Mechanisms underlying activity of bisphosphonates or denosumab in this context are understood, while it is less clear how SERMs like tamoxifen, raloxifene, or bazedoxifene inhibit bone resorption. Recently, accumulation of hypoxia inducible factor 1 alpha (Hif1α) in osteoclasts was shown to be suppressed by estrogen in normal cells. In addition, osteoclast activation and decreased bone mass seen in estrogen-deficient conditions was found to require Hif1α. Here, we used western blot analysis of cultured osteoclast precursor cells to show that tamoxifen, raloxifene, or bazedoxifene all suppress Hif1α protein accumulation. The effects of each SERM on osteoclast differentiation differed in vitro. Our results suggest that interventions such as the SERMs evaluated here could be useful to inhibit Hif1α and osteoclast activity under estrogen-deficient conditions. PMID:27802325

  15. Selection Shapes Transcriptional Logic and Regulatory Specialization in Genetic Networks.

    PubMed

    Fogelmark, Karl; Peterson, Carsten; Troein, Carl

    2016-01-01

    Living organisms need to regulate their gene expression in response to environmental signals and internal cues. This is a computational task where genes act as logic gates that connect to form transcriptional networks, which are shaped at all scales by evolution. Large-scale mutations such as gene duplications and deletions add and remove network components, whereas smaller mutations alter the connections between them. Selection determines what mutations are accepted, but its importance for shaping the resulting networks has been debated. To investigate the effects of selection in the shaping of transcriptional networks, we derive transcriptional logic from a combinatorially powerful yet tractable model of the binding between DNA and transcription factors. By evolving the resulting networks based on their ability to function as either a simple decision system or a circadian clock, we obtain information on the regulation and logic rules encoded in functional transcriptional networks. Comparisons are made between networks evolved for different functions, as well as with structurally equivalent but non-functional (neutrally evolved) networks, and predictions are validated against the transcriptional network of E. coli. We find that the logic rules governing gene expression depend on the function performed by the network. Unlike the decision systems, the circadian clocks show strong cooperative binding and negative regulation, which achieves tight temporal control of gene expression. Furthermore, we find that transcription factors act preferentially as either activators or repressors, both when binding multiple sites for a single target gene and globally in the transcriptional networks. This separation into positive and negative regulators requires gene duplications, which highlights the interplay between mutation and selection in shaping the transcriptional networks.

  16. Selection Shapes Transcriptional Logic and Regulatory Specialization in Genetic Networks

    PubMed Central

    Fogelmark, Karl; Peterson, Carsten; Troein, Carl

    2016-01-01

    Background Living organisms need to regulate their gene expression in response to environmental signals and internal cues. This is a computational task where genes act as logic gates that connect to form transcriptional networks, which are shaped at all scales by evolution. Large-scale mutations such as gene duplications and deletions add and remove network components, whereas smaller mutations alter the connections between them. Selection determines what mutations are accepted, but its importance for shaping the resulting networks has been debated. Methodology To investigate the effects of selection in the shaping of transcriptional networks, we derive transcriptional logic from a combinatorially powerful yet tractable model of the binding between DNA and transcription factors. By evolving the resulting networks based on their ability to function as either a simple decision system or a circadian clock, we obtain information on the regulation and logic rules encoded in functional transcriptional networks. Comparisons are made between networks evolved for different functions, as well as with structurally equivalent but non-functional (neutrally evolved) networks, and predictions are validated against the transcriptional network of E. coli. Principal Findings We find that the logic rules governing gene expression depend on the function performed by the network. Unlike the decision systems, the circadian clocks show strong cooperative binding and negative regulation, which achieves tight temporal control of gene expression. Furthermore, we find that transcription factors act preferentially as either activators or repressors, both when binding multiple sites for a single target gene and globally in the transcriptional networks. This separation into positive and negative regulators requires gene duplications, which highlights the interplay between mutation and selection in shaping the transcriptional networks. PMID:26927540

  17. The mechanism of selective molecular capture in carbon nanotube networks.

    PubMed

    Wan, Yu; Guan, Jun; Yang, Xudong; Zheng, Quanshui; Xu, Zhiping

    2014-07-28

    Recently, air pollution issues have drawn significant attention to the development of efficient air filters, and one of the most promising materials for this purpose is nanofibers. We explore here the mechanism of selective molecular capture of volatile organic compounds in carbon nanotube networks by performing atomistic simulations. The results are discussed with respect to the two key parameters that define the performance of nanofiltration, i.e. the capture efficiency and flow resistance, which demonstrate the advantages of carbon nanotube networks with high surface-to-volume ratio and atomistically smooth surfaces. We also reveal the important roles of interfacial adhesion and diffusion that govern selective gas transport through the network.

  18. Artificial neural network for suppression of banding artifacts in balanced steady-state free precession MRI.

    PubMed

    Kim, Ki Hwan; Park, Sung-Hong

    2017-04-01

    The balanced steady-state free precession (bSSFP) MR sequence is frequently used in clinics, but is sensitive to off-resonance effects, which can cause banding artifacts. Often multiple bSSFP datasets are acquired at different phase cycling (PC) angles and then combined in a special way for banding artifact suppression. Many strategies of combining the datasets have been suggested for banding artifact suppression, but there are still limitations in their performance, especially when the number of phase-cycled bSSFP datasets is small. The purpose of this study is to develop a learning-based model to combine the multiple phase-cycled bSSFP datasets for better banding artifact suppression. Multilayer perceptron (MLP) is a feedforward artificial neural network consisting of three layers of input, hidden, and output layers. MLP models were trained by input bSSFP datasets acquired from human brain and knee at 3T, which were separately performed for two and four PC angles. Banding-free bSSFP images were generated by maximum-intensity projection (MIP) of 8 or 12 phase-cycled datasets and were used as targets for training the output layer. The trained MLP models were applied to another brain and knee datasets acquired with different scan parameters and also to multiple phase-cycled bSSFP functional MRI datasets acquired on rat brain at 9.4T, in comparison with the conventional MIP method. Simulations were also performed to validate the MLP approach. Both the simulations and human experiments demonstrated that MLP suppressed banding artifacts significantly, superior to MIP in both banding artifact suppression and SNR efficiency. MLP demonstrated superior performance over MIP for the 9.4T fMRI data as well, which was not used for training the models, while visually preserving the fMRI maps very well. Artificial neural network is a promising technique for combining multiple phase-cycled bSSFP datasets for banding artifact suppression. Copyright © 2016 Elsevier Inc. All

  19. Perceptual Competition Promotes Suppression of Reward Salience in Behavioral Selection and Neural Representation.

    PubMed

    Gong, Mengyuan; Jia, Ke; Li, Sheng

    2017-06-28

    Visual attentional selection is influenced by the value of objects. Previous studies have demonstrated that reward-associated items lead to rapid distraction and associated behavioral costs, which are difficult to override with top-down control. However, it has not been determined whether a perceptually competitive environment could render the reward-driven distraction more susceptible to top-down suppression. Here, we trained both genders of human subjects to associate two orientations with high and low magnitudes of reward. After training, we collected fMRI data while the subjects performed a categorical visual search task. The item in the reward-associated orientation served as the distractor, and the relative physical salience between the target and distractor was carefully controlled to modulate the degree of perceptual competition. The behavioral results showed faster searches in the presence of high, relative to low, reward-associated distractors. However, this effect was evident only if the physical salience of the distractor was higher than that of the target, indicating a context-dependent suppression effect of reward salience that relied on high perceptual competition. By analyzing the fMRI data in primary visual cortex, we found that the behavioral pattern of results could be predicted by the suppressed channel responses tuned to the reward-associated orientation in the distractor location, accompanied by increased responses in the midbrain dopaminergic region. Our results suggest that the learned salience of a reward plays a flexible role in solving perceptual competition, enabling the neural system to adaptively modulate the perceptual representation for behavioral optimization.SIGNIFICANCE STATEMENT The predictiveness principle in learning theory suggests that the stimulus with high predictability of reward receives priority in attentional selection. This selection bias leads to difficulties in changing approach behaviors, and thus becomes an

  20. Spontaneous Local Gamma Oscillation Selectively Enhances Neural Network Responsiveness

    PubMed Central

    Paik, Se-Bum; Kumar, Tribhawan; Glaser, Donald A.

    2009-01-01

    Synchronized oscillation is very commonly observed in many neuronal systems and might play an important role in the response properties of the system. We have studied how the spontaneous oscillatory activity affects the responsiveness of a neuronal network, using a neural network model of the visual cortex built from Hodgkin-Huxley type excitatory (E-) and inhibitory (I-) neurons. When the isotropic local E-I and I-E synaptic connections were sufficiently strong, the network commonly generated gamma frequency oscillatory firing patterns in response to random feed-forward (FF) input spikes. This spontaneous oscillatory network activity injects a periodic local current that could amplify a weak synaptic input and enhance the network's responsiveness. When E-E connections were added, we found that the strength of oscillation can be modulated by varying the FF input strength without any changes in single neuron properties or interneuron connectivity. The response modulation is proportional to the oscillation strength, which leads to self-regulation such that the cortical network selectively amplifies various FF inputs according to its strength, without requiring any adaptation mechanism. We show that this selective cortical amplification is controlled by E-E cell interactions. We also found that this response amplification is spatially localized, which suggests that the responsiveness modulation may also be spatially selective. This suggests a generalized mechanism by which neural oscillatory activity can enhance the selectivity of a neural network to FF inputs. PMID:19343222

  1. Reverberation suppression in cochlear implants using a blind channel-selection strategy

    PubMed Central

    Hazrati, Oldooz; Loizou, Philipos C.

    2013-01-01

    Reverberation severely degrades speech intelligibility for cochlear implant (CI) users. The ideal reverberant mask (IRM), a binary mask for reverberation suppression which is computed using signal-to-reverberant ratio, was found to yield substantial intelligibility gains for CI users even in highly reverberant environments (e.g., T60 = 1.0 s). Motivated by the intelligibility improvements obtained from IRM, a monaural blind channel-selection criterion for reverberation suppression is proposed. The proposed channel-selection strategy is blind, meaning that prior knowledge of neither the room impulse response nor the anechoic signal is required. By the use of a residual signal obtained from linear prediction analysis of the reverberant signal, the residual-to-reverberant ratio (RRR) of individual frequency channels was employed as the channel-selection criterion. In each frame, the channels with RRR less than an adaptive threshold were retained while the rest were zeroed out. Performance of the proposed strategy was evaluated via intelligibility listening tests conducted with CI users in simulated rooms with two reverberation times of 0.6 and 0.8 s. The results indicate significant intelligibility improvements in both reverberant conditions (over 30 and 40 percentage points in T60 = 0.6 and 0.8 s, respectively). The improvement is comparable to that obtained with the IRM strategy. PMID:23742370

  2. The Medieval inquisition: scale-free networks and the suppression of heresy

    NASA Astrophysics Data System (ADS)

    Ormerod, Paul; Roach, Andrew P.

    2004-08-01

    Qualitative evidence suggests that heresy within the medieval Church had many of the characteristics of a scale-free network. From the perspective of the Church, heresy can be seen as an infectious disease. The disease persisted for long periods of time, breaking out again even when the Church believed it to have been eradicated. A principal mechanism of heresy was through a small number of individuals with very large numbers of social contacts. Initial attempts by the inquisition to suppress heresy by general persecution, or even mass slaughter, of populations thought to harbour the ‘disease’ failed. Gradually, however, inquisitors learned about the nature of the social networks by which heresy both spread and persisted. Eventually, a policy of targeting key individuals was implemented, which proved to be much more successful.

  3. ERK Signal Suppression and Sensitivity to CH5183284/Debio 1347, a Selective FGFR Inhibitor.

    PubMed

    Nakanishi, Yoshito; Mizuno, Hideaki; Sase, Hitoshi; Fujii, Toshihiko; Sakata, Kiyoaki; Akiyama, Nukinori; Aoki, Yuko; Aoki, Masahiro; Ishii, Nobuya

    2015-12-01

    Drugs that target specific gene alterations have proven beneficial in the treatment of cancer. Because cancer cells have multiple resistance mechanisms, it is important to understand the downstream pathways of the target genes and monitor the pharmacodynamic markers associated with therapeutic efficacy. We performed a transcriptome analysis to characterize the response of various cancer cell lines to a selective fibroblast growth factor receptor (FGFR) inhibitor (CH5183284/Debio 1347), a mitogen-activated protein kinase kinase (MEK) inhibitor, or a phosphoinositide 3-kinase (PI3K) inhibitor. FGFR and MEK inhibition produced similar expression patterns, and the extracellular signal-regulated kinase (ERK) gene signature was altered in several FGFR inhibitor-sensitive cell lines. Consistent with these findings, CH5183284/Debio 1347 suppressed phospho-ERK in every tested FGFR inhibitor-sensitive cell line. Because the mitogen-activated protein kinase (MAPK) pathway functions downstream of FGFR, we searched for a pharmacodynamic marker of FGFR inhibitor efficacy in a collection of cell lines with the ERK signature and identified dual-specificity phosphatase 6 (DUSP6) as a candidate marker. Although a MEK inhibitor suppressed the MAPK pathway, most FGFR inhibitor-sensitive cell lines are insensitive to MEK inhibitors and we found potent feedback activation of several pathways via FGFR. We therefore suggest that FGFR inhibitors exert their effect by suppressing ERK signaling without feedback activation. In addition, DUSP6 may be a pharmacodynamic marker of FGFR inhibitor efficacy in FGFR-addicted cancers.

  4. Intercellular Redistribution of cAMP Underlies Selective Suppression of Cancer Cell Growth by Connexin26

    PubMed Central

    Polusani, Srikanth R.; Mathis, Sandra A.; Zucker, Shoshanna N.; Nicholson, Bruce J.

    2013-01-01

    Connexins (Cx), which constitute gap junction intercellular channels in vertebrates, have been shown to suppress transformed cell growth and tumorigenesis, but the mechanism(s) still remain largely speculative. Here, we define the molecular basis by which Cx26, but less frequently Cx43 or Cx32, selectively confer growth suppression on cancer cells. Functional intercellular coupling is shown to be required, producing partial blocks of the cell cycle due to prolonged activation of several mitogenic kinases. PKA is both necessary and sufficient for the Cx26 induced growth inhibition in low serum and the absence of anchorage. Activation of PKA was not associated with elevated cAMP levels, but appeared to result from a redistribution of cAMP throughout the cell population, eliminating the cell cycle oscillations in cAMP required for efficient cell cycle progression. Cx43 and Cx32 fail to mediate this redistribution as, unlike Cx26, these channels are closed during the G2/M phase of the cell cycle when cAMP levels peak. Comparisons of tumor cell lines indicate that this is a general pattern, with growth suppression by connexins occurring whenever cAMP oscillates with the cell cycle, and the gap junction remain open throughout the cell cycle. Thus, gap junctional coupling, in the absence of any external signals, provides a general means to limit the mitotic rate of cell populations. PMID:24312655

  5. Selective Killing Of Malignant Cancer Cells By Suppression Of Geminin Activity

    PubMed Central

    Zhu, Wenge; DePamphilis, Melvin L.

    2009-01-01

    Eukaryotic cells normally restrict genome duplication to once per cell division. In metazoa, re-replication of DNA during a single S-phase appears to be prevented solely by suppressing CDT1 activity, a protein required for loading the replicative MCM DNA helicase. However, siRNA suppression of geminin (a specific inhibitor of CDT1) arrested proliferation only of cells derived from malignant cancers by inducing DNA re-replication and DNA damage that spontaneously triggered apoptosis. None of these effects were detected either in cells derived from normal human tissues, or in cells immortalized by a viral oncogene. To induce these effects in non-cancer cells required suppression of both geminin and cyclin A, another cell cycle regulator. Therefore, initiating DNA replication in some cancer cells is limited solely by regulating the level of CDT1 activity with geminin, whereas non-cancer cells contain additional safeguards that prevent DNA re-replication. These results demonstrate that inhibition of geminin activity could be used to selectively kill cancer cells without harming other cells. PMID:19487297

  6. Top-down suppression of incompatible motor activations during response selection under conflict.

    PubMed

    Klein, Pierre-Alexandre; Petitjean, Charlotte; Olivier, Etienne; Duque, Julie

    2014-02-01

    Top-down control is critical to select goal-directed actions in changeable environments, particularly when several options compete for selection. This control system is thought to involve a mechanism that suppresses activation of unwanted response representations. We tested this hypothesis, in humans, by measuring motor-evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) in a left finger muscle during motor preparation in an adapted Eriksen flanker task. Subjects reported, by a left or right button-press, the orientation of a left- or right-facing central arrow, flanked by two distractor arrows on each side. Central and peripheral arrows either pointed in the same (congruent trial) or in the opposite direction (incongruent trial). Top-down control was manipulated by changing the probability of congruent and incongruent trials in a given block. In the "mostly incongruent" (MI) blocks, 80% of trials were incongruent, producing a context in which subjects strongly anticipated that they would have to face conflict. In the "mostly congruent" (MC) blocks, 80% of trials were congruent and thus subjects barely anticipated conflict in that context. Thus, we assume that top-down control was stronger in the MI than in the MC condition. Accordingly, subjects displayed a lower error rate and shorter reaction times for the incongruent trials in the MI context than for similar trials in the MC context. More interestingly, we found that top-down control specifically reduced activation of the incompatible motor representation during response selection under high conflict. That is, when the central arrow specified a right hand response, left (non-selected) MEPs became smaller in the MI than in the MC condition, but only for incongruent trials, and this measure was positively correlated with performance. In contrast, MEPs elicited in the non-selected hand during congruent trials, or during all trials in which the left hand was selected, tended to increase

  7. Causal Networks with Selectively Influenced Components

    DTIC Science & Technology

    2012-02-29

    The sorites paradox: A behavioral approach . In J. Valsiner and L. Rudolph (Eds). Mathematical Models for Research on Cultural Dynamics: Qualitative...tests it through goodness of fit. A portion of the work on the grant is on developing further another approach , Tree Inference (Schweickert & Chen...of a given stimulus property selectively influenced by this property alone? in medical research , does the presence or absence of a given symptom

  8. Suppression of epidemic spreading in complex networks by local information based behavioral responses.

    PubMed

    Zhang, Hai-Feng; Xie, Jia-Rong; Tang, Ming; Lai, Ying-Cheng

    2014-12-01

    The interplay between individual behaviors and epidemic dynamics in complex networks is a topic of recent interest. In particular, individuals can obtain different types of information about the disease and respond by altering their behaviors, and this can affect the spreading dynamics, possibly in a significant way. We propose a model where individuals' behavioral response is based on a generic type of local information, i.e., the number of neighbors that has been infected with the disease. Mathematically, the response can be characterized by a reduction in the transmission rate by a factor that depends on the number of infected neighbors. Utilizing the standard susceptible-infected-susceptible and susceptible-infected-recovery dynamical models for epidemic spreading, we derive a theoretical formula for the epidemic threshold and provide numerical verification. Our analysis lays on a solid quantitative footing the intuition that individual behavioral response can in general suppress epidemic spreading. Furthermore, we find that the hub nodes play the role of "double-edged sword" in that they can either suppress or promote outbreak, depending on their responses to the epidemic, providing additional support for the idea that these nodes are key to controlling epidemic spreading in complex networks.

  9. Reduced default mode network suppression during a working memory task in remitted major depression

    PubMed Central

    Bartova, Lucie; Meyer, Bernhard M.; Diers, Kersten; Rabl, Ulrich; Scharinger, Christian; Popovic, Ana; Pail, Gerald; Kalcher, Klaudius; Boubela, Roland N.; Huemer, Julia; Mandorfer, Dominik; Windischberger, Christian; Sitte, Harald H.; Kasper, Siegfried; Praschak-Rieder, Nicole; Moser, Ewald; Brocke, Burkhard; Pezawas, Lukas

    2015-01-01

    Insufficient default mode network (DMN) suppression was linked to increased rumination in symptomatic Major Depressive Disorder (MDD). Since rumination is known to predict relapse and a more severe course of MDD, we hypothesized that similar DMN alterations might also exist during full remission of MDD (rMDD), a condition known to be associated with increased relapse rates specifically in patients with adolescent onset. Within a cross-sectional functional magnetic resonance imaging study activation and functional connectivity (FC) were investigated in 120 adults comprising 78 drug-free rMDD patients with adolescent- (n = 42) and adult-onset (n = 36) as well as 42 healthy controls (HC), while performing the n-back task. Compared to HC, rMDD patients showed diminished DMN deactivation with strongest differences in the anterior-medial prefrontal cortex (amPFC), which was further linked to increased rumination response style. On a brain systems level, rMDD patients showed an increased FC between the amPFC and the dorsolateral prefrontal cortex, which constitutes a key region of the antagonistic working-memory network. Both whole-brain analyses revealed significant differences between adolescent-onset rMDD patients and HC, while adult-onset rMDD patients showed no significant effects. Results of this study demonstrate that reduced DMN suppression exists even after full recovery of depressive symptoms, which appears to be specifically pronounced in adolescent-onset MDD patients. Our results encourage the investigation of DMN suppression as a putative predictor of relapse in clinical trials, which might eventually lead to important implications for antidepressant maintenance treatment. PMID:25801734

  10. Selection of motor programs for suppressing food intake and inducing locomotion in the Drosophila brain.

    PubMed

    Schoofs, Andreas; Hückesfeld, Sebastian; Schlegel, Philipp; Miroschnikow, Anton; Peters, Marc; Zeymer, Malou; Spieß, Roland; Chiang, Ann-Shyn; Pankratz, Michael J

    2014-06-01

    Central mechanisms by which specific motor programs are selected to achieve meaningful behaviors are not well understood. Using electrophysiological recordings from pharyngeal nerves upon central activation of neurotransmitter-expressing cells, we show that distinct neuronal ensembles can regulate different feeding motor programs. In behavioral and electrophysiological experiments, activation of 20 neurons in the brain expressing the neuropeptide hugin, a homolog of mammalian neuromedin U, simultaneously suppressed the motor program for food intake while inducing the motor program for locomotion. Decreasing hugin neuropeptide levels in the neurons by RNAi prevented this action. Reducing the level of hugin neuronal activity alone did not have any effect on feeding or locomotion motor programs. Furthermore, use of promoter-specific constructs that labeled subsets of hugin neurons demonstrated that initiation of locomotion can be separated from modulation of its motor pattern. These results provide insights into a neural mechanism of how opposing motor programs can be selected in order to coordinate feeding and locomotive behaviors.

  11. Selective suppression of the incorrect response implementation in choice behavior assessed by transcranial magnetic stimulation.

    PubMed

    Tandonnet, Christophe; Garry, Michael I; Summers, Jeffery J

    2011-04-01

    Selecting the adequate alternative in choice situations may involve an inhibition process. Here we assessed response implementation during the reaction time of a between-hand choice task with single- or paired-pulse (3 or 15 ms interstimulus intervals [ISIs]) transcranial magnetic stimulation of the motor cortex. The amplitude of the single-pulse motor evoked potential (MEP) initially increased for both hands. At around 130 ms, the single-pulse MEP kept increasing for the responding hand and decreased for the nonresponding hand. The paired-pulse MEP revealed a similar pattern for both ISIs with no effect on short intracortical inhibition and intracortical facilitation measures. The results suggest that the incorrect response implementation was selectively suppressed before execution of the correct response, preventing errors in choice context. The results favor models assuming that decision making involves an inhibition process.

  12. Sexual networks: measuring sexual selection in structured, polyandrous populations

    PubMed Central

    McDonald, Grant C.; James, Richard; Krause, Jens; Pizzari, Tommaso

    2013-01-01

    Sexual selection is traditionally measured at the population level, assuming that populations lack structure. However, increasing evidence undermines this approach, indicating that intrasexual competition in natural populations often displays complex patterns of spatial and temporal structure. This complexity is due in part to the degree and mechanisms of polyandry within a population, which can influence the intensity and scale of both pre- and post-copulatory sexual competition. Attempts to measure selection at the local and global scale have been made through multi-level selection approaches. However, definitions of local scale are often based on physical proximity, providing a rather coarse measure of local competition, particularly in polyandrous populations where the local scale of pre- and post-copulatory competition may differ drastically from each other. These limitations can be solved by social network analysis, which allows us to define a unique sexual environment for each member of a population: ‘local scale’ competition, therefore, becomes an emergent property of a sexual network. Here, we first propose a novel quantitative approach to measure pre- and post-copulatory sexual selection, which integrates multi-level selection with information on local scale competition derived as an emergent property of networks of sexual interactions. We then use simple simulations to illustrate the ways in which polyandry can impact estimates of sexual selection. We show that for intermediate levels of polyandry, the proposed network-based approach provides substantially more accurate measures of sexual selection than the more traditional population-level approach. We argue that the increasing availability of fine-grained behavioural datasets provides exciting new opportunities to develop network approaches to study sexual selection in complex societies. PMID:23339246

  13. Popularity and adolescent friendship networks: selection and influence dynamics.

    PubMed

    Dijkstra, Jan Kornelis; Cillessen, Antonius H N; Borch, Casey

    2013-07-01

    This study examined the dynamics of popularity in adolescent friendship networks across 3 years in middle school. Longitudinal social network modeling was used to identify selection and influence in the similarity of popularity among friends. It was argued that lower status adolescents strive to enhance their status through befriending higher status adolescents, whereas higher status adolescents strive to maintain their status by keeping lower status adolescents at a distance. The results largely supported these expectations. Selection partially accounted for similarity in popularity among friends; adolescents preferred to affiliate with similar-status or higher status peers, reinforcing the attractiveness of popular adolescents and explaining stability of popularity at the individual level. Influence processes also accounted for similarity in popularity over time, showing that peers increase in popularity and become more similar to their friends. The results showed how selection and influence processes account for popularity dynamics in adolescent networks over time.

  14. Valproic acid suppresses collagen by selective regulation of Smads in conjunctival fibrosis.

    PubMed

    Seet, Li-Fong; Toh, Li Zhen; Finger, Sharon N; Chu, Stephanie W L; Stefanovic, Branko; Wong, Tina T

    2016-03-01

    Overproduction of type I collagen is associated with a wide range of fibrotic diseases as well as surgical failure such as in glaucoma filtration surgery (GFS). Its modulation is therefore of clinical importance. Valproic acid (VPA) is known to reduce collagen in a variety of tissues with unclear mechanism of action. In this report, we demonstrate that VPA inhibited collagen production in both conjunctival fibroblasts and the mouse model of GFS. In fibroblasts, VPA decreased type I collagen expression which intensified with longer drug exposure and suppressed steady-state type I collagen promoter activity. Moreover, VPA decreased Smad2, Smad3 and Smad4 but increased Smad6 expression with a similar intensity-exposure profile. Reduction of Smad3 using small hairpin RNA and/or overexpression of Smad6 resulted in decreased collagen expression which was exacerbated when VPA was simultaneously present. Furthermore, fibrogenic TGF-β2 failed to induce collagen when VPA was present, as opposed to the myofibroblast markers, beta-actin, alpha-smooth muscle actin and tenascin-C, which were elevated by TGF-β2. VPA suppressed p3TP-Lux luciferase activity and selectively rescued Smad6 expression from suppression by TGF-β2. Notably, SMAD6 overexpression reduced the effectiveness of TGF-β2 in inducing collagen expression. In corroboration, VPA inhibited type I collagen but increased Smad6 expression in the late phase of wound healing in the mouse model of GFS. Taken together, our data indicate that VPA has the capacity to effectively suppress both steady-state and fibrogenic activation of type I collagen expression by modulating Smad expression. Hence, VPA is potentially applicable as an anti-fibrotic therapeutic by targeting collagen. Key message: • VPA modulates type I collagen expression via members of the Smad family. • VPA suppresses Smad2, Smad3 and Smad4 but upregulates Smad6. • Smad3 and Smad6 are involved in VPA regulation of steady-state collagen expression.

  15. Social networks predict selective observation and information spread in ravens

    PubMed Central

    Rubenstein, Daniel I.; Bugnyar, Thomas; Hoppitt, William; Mikus, Nace; Schwab, Christine

    2016-01-01

    Animals are predicted to selectively observe and learn from the conspecifics with whom they share social connections. Yet, hardly anything is known about the role of different connections in observation and learning. To address the relationships between social connections, observation and learning, we investigated transmission of information in two raven (Corvus corax) groups. First, we quantified social connections in each group by constructing networks on affiliative interactions, aggressive interactions and proximity. We then seeded novel information by training one group member on a novel task and allowing others to observe. In each group, an observation network based on who observed whose task-solving behaviour was strongly correlated with networks based on affiliative interactions and proximity. Ravens with high social centrality (strength, eigenvector, information centrality) in the affiliative interaction network were also central in the observation network, possibly as a result of solving the task sooner. Network-based diffusion analysis revealed that the order that ravens first solved the task was best predicted by connections in the affiliative interaction network in a group of subadult ravens, and by social rank and kinship (which influenced affiliative interactions) in a group of juvenile ravens. Our results demonstrate that not all social connections are equally effective at predicting the patterns of selective observation and information transmission. PMID:27493780

  16. Social networks predict selective observation and information spread in ravens.

    PubMed

    Kulahci, Ipek G; Rubenstein, Daniel I; Bugnyar, Thomas; Hoppitt, William; Mikus, Nace; Schwab, Christine

    2016-07-01

    Animals are predicted to selectively observe and learn from the conspecifics with whom they share social connections. Yet, hardly anything is known about the role of different connections in observation and learning. To address the relationships between social connections, observation and learning, we investigated transmission of information in two raven (Corvus corax) groups. First, we quantified social connections in each group by constructing networks on affiliative interactions, aggressive interactions and proximity. We then seeded novel information by training one group member on a novel task and allowing others to observe. In each group, an observation network based on who observed whose task-solving behaviour was strongly correlated with networks based on affiliative interactions and proximity. Ravens with high social centrality (strength, eigenvector, information centrality) in the affiliative interaction network were also central in the observation network, possibly as a result of solving the task sooner. Network-based diffusion analysis revealed that the order that ravens first solved the task was best predicted by connections in the affiliative interaction network in a group of subadult ravens, and by social rank and kinship (which influenced affiliative interactions) in a group of juvenile ravens. Our results demonstrate that not all social connections are equally effective at predicting the patterns of selective observation and information transmission.

  17. Suppression of heavy drinking and alcohol seeking by a selective ALDH-2 inhibitor.

    PubMed

    Arolfo, Maria P; Overstreet, David H; Yao, Lina; Fan, Peidong; Lawrence, Andrew J; Tao, Guoxin; Keung, Wing-Ming; Vallee, Bert L; Olive, M Foster; Gass, Justin T; Rubin, Emanuel; Anni, Helen; Hodge, Clyde W; Besheer, Joyce; Zablocki, Jeff; Leung, Kwan; Blackburn, Brent K; Lange, Louis G; Diamond, Ivan

    2009-11-01

    Inherited human aldehyde dehydrogenase 2 (ALDH-2) deficiency reduces the risk for alcoholism. Kudzu plants and extracts have been used for 1,000 years in traditional Chinese medicine to treat alcoholism. Kudzu contains daidzin, which inhibits ALDH-2 and suppresses heavy drinking in rodents. Decreased drinking due to ALDH-2 inhibition is attributed to aversive properties of acetaldehyde accumulated during alcohol consumption. However, daidzin can reduce drinking in some rodents without necessarily increasing acetaldehyde. Therefore, a selective ALDH-2 inhibitor might affect other metabolic factors involved in regulating drinking. Aldehyde dehydrogenase 2 inhibitors were synthesized based on the co-crystal structure of ALDH-2 and daidzin. We tested the efficacy of a highly selective reversible ALDH-2 inhibitor, CVT-10216, in models of moderate and high alcohol drinking rats. We studied 2-bottle choice and deprivation-induced drinking paradigms in Fawn Hooded (FH) rats, operant self-administration in Long Evans (LE), FH, and inbred P (iP) rats and in cue-induced reinstatement in iP rats. We also assayed blood acetaldehyde levels as well as dopamine (DA) release in the nucleus accumbens (NAc) and tested possible rewarding/aversive effects of the inhibitor in a conditioned place preference (CPP) paradigm. CVT-10216 increases acetaldehyde after alcohol gavage and inhibits 2-bottle choice alcohol intake in heavy drinking rodents, including deprivation-induced drinking. Moreover, CVT-10216 also prevents operant self-administration and eliminates cue-induced reinstatement of alcohol seeking even when alcohol is not available (i.e., no acetaldehyde). Alcohol stimulates DA release in the NAc, which is thought to contribute to increased drinking and relapse in alcoholism. CVT-10216 prevents alcohol-induced increases in NAc DA without changing basal levels. CVT-10216 does not show rewarding or aversive properties in the CPP paradigm at therapeutic doses. Our findings suggest

  18. Selecting public relations personnel of hospitals by analytic network process.

    PubMed

    Liao, Sen-Kuei; Chang, Kuei-Lun

    2009-01-01

    This study describes the use of analytic network process (ANP) in the Taiwanese hospital public relations personnel selection process. Starting with interviewing 48 practitioners and executives in north Taiwan, we collected selection criteria. Then, we retained the 12 critical criteria that were mentioned above 40 times by theses respondents, including: interpersonal skill, experience, negotiation, language, ability to follow orders, cognitive ability, adaptation to environment, adaptation to company, emotion, loyalty, attitude, and Response. Finally, we discussed with the 20 executives to take these important criteria into three perspectives to structure the hierarchy for hospital public relations personnel selection. After discussing with practitioners and executives, we find that selecting criteria are interrelated. The ANP, which incorporates interdependence relationships, is a new approach for multi-criteria decision-making. Thus, we apply ANP to select the most optimal public relations personnel of hospitals. An empirical study of public relations personnel selection problems in Taiwan hospitals is conducted to illustrate how the selection procedure works.

  19. Open Peer Review by a Selected-Papers Network

    PubMed Central

    Lee, Christopher

    2011-01-01

    A selected-papers (SP) network is a network in which researchers who read, write, and review articles subscribe to each other based on common interests. Instead of reviewing a manuscript in secret for the Editor of a journal, each reviewer simply publishes his review (typically of a paper he wishes to recommend) to his SP network subscribers. Once the SP network reviewers complete their review decisions, the authors can invite any journal editor they want to consider these reviews and initial audience size, and make a publication decision. Since all impact assessment, reviews, and revisions are complete, this decision process should be short. I show how the SP network can provide a new way of measuring impact, catalyze the emergence of new subfields, and accelerate discovery in existing fields, by providing each reader a fine-grained filter for high-impact. I present a three phase plan for building a basic SP network, and making it an effective peer review platform that can be used by journals, conferences, users of repositories such as arXiv, and users of search engines such as PubMed. I show how the SP network can greatly improve review and dissemination of research articles in areas that are not well-supported by existing journals. Finally, I illustrate how the SP network concept can work well with existing publication services such as journals, conferences, arXiv, PubMed, and online citation management sites. PMID:22291635

  20. Strategy selection in evolutionary game dynamics on group interaction networks.

    PubMed

    Tan, Shaolin; Feng, Shasha; Wang, Pei; Chen, Yao

    2014-11-01

    Evolutionary game theory provides an appropriate tool for investigating the competition and diffusion of behavioral traits in biological or social populations. A core challenge in evolutionary game theory is the strategy selection problem: Given two strategies, which one is favored by the population? Recent studies suggest that the answer depends not only on the payoff functions of strategies but also on the interaction structure of the population. Group interactions are one of the fundamental interactive modes within populations. This work aims to investigate the strategy selection problem in evolutionary game dynamics on group interaction networks. In detail, the strategy selection conditions are obtained for some typical networks with group interactions. Furthermore, the obtained conditions are applied to investigate selection between cooperation and defection in populations. The conditions for evolution of cooperation are derived for both the public goods game and volunteer's dilemma game. Numerical experiments validate the above analytical results.

  1. Direction Selectivity in Drosophila Emerges from Preferred-Direction Enhancement and Null-Direction Suppression.

    PubMed

    Leong, Jonathan Chit Sing; Esch, Jennifer Judson; Poole, Ben; Ganguli, Surya; Clandinin, Thomas Robert

    2016-08-03

    Across animal phyla, motion vision relies on neurons that respond preferentially to stimuli moving in one, preferred direction over the opposite, null direction. In the elementary motion detector of Drosophila, direction selectivity emerges in two neuron types, T4 and T5, but the computational algorithm underlying this selectivity remains unknown. We find that the receptive fields of both T4 and T5 exhibit spatiotemporally offset light-preferring and dark-preferring subfields, each obliquely oriented in spacetime. In a linear-nonlinear modeling framework, the spatiotemporal organization of the T5 receptive field predicts the activity of T5 in response to motion stimuli. These findings demonstrate that direction selectivity emerges from the enhancement of responses to motion in the preferred direction, as well as the suppression of responses to motion in the null direction. Thus, remarkably, T5 incorporates the essential algorithmic strategies used by the Hassenstein-Reichardt correlator and the Barlow-Levick detector. Our model for T5 also provides an algorithmic explanation for the selectivity of T5 for moving dark edges: our model captures all two- and three-point spacetime correlations relevant to motion in this stimulus class. More broadly, our findings reveal the contribution of input pathway visual processing, specifically center-surround, temporally biphasic receptive fields, to the generation of direction selectivity in T5. As the spatiotemporal receptive field of T5 in Drosophila is common to the simple cell in vertebrate visual cortex, our stimulus-response model of T5 will inform efforts in an experimentally tractable context to identify more detailed, mechanistic models of a prevalent computation. Feature selective neurons respond preferentially to astonishingly specific stimuli, providing the neurobiological basis for perception. Direction selectivity serves as a paradigmatic model of feature selectivity that has been examined in many species. While

  2. Direction Selectivity in Drosophila Emerges from Preferred-Direction Enhancement and Null-Direction Suppression

    PubMed Central

    Leong, Jonathan Chit Sing; Esch, Jennifer Judson; Poole, Ben; Ganguli, Surya

    2016-01-01

    Across animal phyla, motion vision relies on neurons that respond preferentially to stimuli moving in one, preferred direction over the opposite, null direction. In the elementary motion detector of Drosophila, direction selectivity emerges in two neuron types, T4 and T5, but the computational algorithm underlying this selectivity remains unknown. We find that the receptive fields of both T4 and T5 exhibit spatiotemporally offset light-preferring and dark-preferring subfields, each obliquely oriented in spacetime. In a linear-nonlinear modeling framework, the spatiotemporal organization of the T5 receptive field predicts the activity of T5 in response to motion stimuli. These findings demonstrate that direction selectivity emerges from the enhancement of responses to motion in the preferred direction, as well as the suppression of responses to motion in the null direction. Thus, remarkably, T5 incorporates the essential algorithmic strategies used by the Hassenstein–Reichardt correlator and the Barlow–Levick detector. Our model for T5 also provides an algorithmic explanation for the selectivity of T5 for moving dark edges: our model captures all two- and three-point spacetime correlations relevant to motion in this stimulus class. More broadly, our findings reveal the contribution of input pathway visual processing, specifically center-surround, temporally biphasic receptive fields, to the generation of direction selectivity in T5. As the spatiotemporal receptive field of T5 in Drosophila is common to the simple cell in vertebrate visual cortex, our stimulus-response model of T5 will inform efforts in an experimentally tractable context to identify more detailed, mechanistic models of a prevalent computation. SIGNIFICANCE STATEMENT Feature selective neurons respond preferentially to astonishingly specific stimuli, providing the neurobiological basis for perception. Direction selectivity serves as a paradigmatic model of feature selectivity that has been

  3. Empirical evaluation of scoring functions for Bayesian network model selection.

    PubMed

    Liu, Zhifa; Malone, Brandon; Yuan, Changhe

    2012-01-01

    In this work, we empirically evaluate the capability of various scoring functions of Bayesian networks for recovering true underlying structures. Similar investigations have been carried out before, but they typically relied on approximate learning algorithms to learn the network structures. The suboptimal structures found by the approximation methods have unknown quality and may affect the reliability of their conclusions. Our study uses an optimal algorithm to learn Bayesian network structures from datasets generated from a set of gold standard Bayesian networks. Because all optimal algorithms always learn equivalent networks, this ensures that only the choice of scoring function affects the learned networks. Another shortcoming of the previous studies stems from their use of random synthetic networks as test cases. There is no guarantee that these networks reflect real-world data. We use real-world data to generate our gold-standard structures, so our experimental design more closely approximates real-world situations. A major finding of our study suggests that, in contrast to results reported by several prior works, the Minimum Description Length (MDL) (or equivalently, Bayesian information criterion (BIC)) consistently outperforms other scoring functions such as Akaike's information criterion (AIC), Bayesian Dirichlet equivalence score (BDeu), and factorized normalized maximum likelihood (fNML) in recovering the underlying Bayesian network structures. We believe this finding is a result of using both datasets generated from real-world applications rather than from random processes used in previous studies and learning algorithms to select high-scoring structures rather than selecting random models. Other findings of our study support existing work, e.g., large sample sizes result in learning structures closer to the true underlying structure; the BDeu score is sensitive to the parameter settings; and the fNML performs pretty well on small datasets. We also

  4. Empirical evaluation of scoring functions for Bayesian network model selection

    PubMed Central

    2012-01-01

    In this work, we empirically evaluate the capability of various scoring functions of Bayesian networks for recovering true underlying structures. Similar investigations have been carried out before, but they typically relied on approximate learning algorithms to learn the network structures. The suboptimal structures found by the approximation methods have unknown quality and may affect the reliability of their conclusions. Our study uses an optimal algorithm to learn Bayesian network structures from datasets generated from a set of gold standard Bayesian networks. Because all optimal algorithms always learn equivalent networks, this ensures that only the choice of scoring function affects the learned networks. Another shortcoming of the previous studies stems from their use of random synthetic networks as test cases. There is no guarantee that these networks reflect real-world data. We use real-world data to generate our gold-standard structures, so our experimental design more closely approximates real-world situations. A major finding of our study suggests that, in contrast to results reported by several prior works, the Minimum Description Length (MDL) (or equivalently, Bayesian information criterion (BIC)) consistently outperforms other scoring functions such as Akaike's information criterion (AIC), Bayesian Dirichlet equivalence score (BDeu), and factorized normalized maximum likelihood (fNML) in recovering the underlying Bayesian network structures. We believe this finding is a result of using both datasets generated from real-world applications rather than from random processes used in previous studies and learning algorithms to select high-scoring structures rather than selecting random models. Other findings of our study support existing work, e.g., large sample sizes result in learning structures closer to the true underlying structure; the BDeu score is sensitive to the parameter settings; and the fNML performs pretty well on small datasets. We also

  5. Modulation of behavioral networks by selective interneuronal inactivation

    PubMed Central

    Schmidt, MJ; Horvath, S; Ebert, P; Norris, JL; Seeley, EH; Brown, J; Gellert, L; Everheart, M; Garbett, KA; Grice, TW; Caprioli, RM; Mirnics, K

    2014-01-01

    Gamma-aminobutyric acid (GABA)-ergic disturbances are hallmark features of schizophrenia and other neuropsychiatric disorders and encompass multiple interneuronal cell types. Using bacterial artificial chromosome-driven, miRNA silencing technology we generated transgenic mouse lines that suppress glutamic acid decarboxylase 1 (GAD1) in either cholecystokinin (CCK)- or neuropeptide Y (NPY)-expressing interneurons. In situ lipidomic and proteomic analyses on brain tissue sections revealed distinct, brain region-specific profiles in each transgenic line. Behavioral analyses revealed that suppression of GAD1 in CCK+ interneurons resulted in locomotor and olfactory sensory changes, whereas suppression in NPY+ interneurons affected anxiety-related behaviors and social interaction. Both transgenic mouse lines had altered sensitivity to amphetamine albeit in opposite directions. Together, these data argue that reduced GAD1 expression leads to altered molecular and behavioral profiles in a cell type-dependent manner, and that these subpopulations of interneurons are strong and opposing modulators of dopamine system function. Furthermore, our findings also support the hypothesis that neuronal networks are differentially controlled by diverse inhibitory subnetworks. PMID:24322205

  6. A channel-selection criterion for suppressing reverberation in cochlear implants

    PubMed Central

    Kokkinakis, Kostas; Hazrati, Oldooz; Loizou, Philipos C.

    2011-01-01

    Little is known about the extent to which reverberation affects speech intelligibility by cochlear implant (CI) listeners. Experiment 1 assessed CI users’ performance using Institute of Electrical and Electronics Engineers (IEEE) sentences corrupted with varying degrees of reverberation. Reverberation times of 0.30, 0.60, 0.80, and 1.0 s were used. Results indicated that for all subjects tested, speech intelligibility decreased exponentially with an increase in reverberation time. A decaying-exponential model provided an excellent fit to the data. Experiment 2 evaluated (offline) a speech coding strategy for reverberation suppression using a channel-selection criterion based on the signal-to-reverberant ratio (SRR) of individual frequency channels. The SRR reflects implicitly the ratio of the energies of the signal originating from the early (and direct) reflections and the signal originating from the late reflections. Channels with SRR larger than a preset threshold were selected, while channels with SRR smaller than the threshold were zeroed out. Results in a highly reverberant scenario indicated that the proposed strategy led to substantial gains (over 60 percentage points) in speech intelligibility over the subjects’ daily strategy. Further analysis indicated that the proposed channel-selection criterion reduces the temporal envelope smearing effects introduced by reverberation and also diminishes the self-masking effects responsible for flattened formants. PMID:21568424

  7. Selecting a Local Area Network for an Academic Environment.

    ERIC Educational Resources Information Center

    Aman, Mohammed M.; And Others

    1990-01-01

    Describes the process used to select a local area network (LAN) for the University of Wisconsin-Milwaukee School of Library and Information Science. The use of computers at the library school by staff, faculty, and students is described, technical aspects of a LAN are explained, and the future of LANs is discussed. (LRW)

  8. Database Software Selection for the Egyptian National STI Network.

    ERIC Educational Resources Information Center

    Slamecka, Vladimir

    The evaluation and selection of information/data management system software for the Egyptian National Scientific and Technical (STI) Network are described. An overview of the state-of-the-art of database technology elaborates on the differences between information retrieval and database management systems (DBMS). The desirable characteristics of…

  9. PRMT5-Selective Inhibitors Suppress Inflammatory T Cell Responses and Experimental Autoimmune Encephalomyelitis.

    PubMed

    Webb, Lindsay M; Amici, Stephanie A; Jablonski, Kyle A; Savardekar, Himanshu; Panfil, Amanda R; Li, Linsen; Zhou, Wei; Peine, Kevin; Karkhanis, Vrajesh; Bachelder, Eric M; Ainslie, Kristy M; Green, Patrick L; Li, Chenglong; Baiocchi, Robert A; Guerau-de-Arellano, Mireia

    2017-02-15

    In the autoimmune disease multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE), expansion of pathogenic, myelin-specific Th1 cell populations drives active disease; selectively targeting this process may be the basis for a new therapeutic approach. Previous studies have hinted at a role for protein arginine methylation in immune responses, including T cell-mediated autoimmunity and EAE. However, a conclusive role for the protein arginine methyltransferase (PRMT) enzymes that catalyze these reactions has been lacking. PRMT5 is the main PRMT responsible for symmetric dimethylation of arginine residues of histones and other proteins. PRMT5 drives embryonic development and cancer, but its role in T cells, if any, has not been investigated. In this article, we show that PRMT5 is an important modulator of CD4(+) T cell expansion. PRMT5 was transiently upregulated during maximal proliferation of mouse and human memory Th cells. PRMT5 expression was regulated upstream by the NF-κB pathway, and it promoted IL-2 production and proliferation. Blocking PRMT5 with novel, highly selective small molecule PRMT5 inhibitors severely blunted memory Th expansion, with preferential suppression of Th1 cells over Th2 cells. In vivo, PRMT5 blockade efficiently suppressed recall T cell responses and reduced inflammation in delayed-type hypersensitivity and clinical disease in EAE mouse models. These data implicate PRMT5 in the regulation of adaptive memory Th cell responses and suggest that PRMT5 inhibitors may be a novel therapeutic approach for T cell-mediated inflammatory disease. Copyright © 2017 by The American Association of Immunologists, Inc.

  10. PRMT5-Selective Inhibitors Suppress Inflammatory T Cell Responses and Experimental Autoimmune Encephalomyelitis

    PubMed Central

    Webb, Lindsay M.; Amici, Stephanie A.; Jablonski, Kyle A.; Savardekar, Himanshu; Panfil, Amanda R.; Li, Linsen; Zhou, Wei; Peine, Kevin; Karkhanis, Vrajesh; Bachelder, Eric M.; Ainslie, Kristy M.; Green, Patrick L.; Li, Chenglong; Baiocchi, Robert A.

    2017-01-01

    In the autoimmune disease multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE), expansion of pathogenic, myelin-specific Th1 cell populations drives active disease; selectively targeting this process may be the basis for a new therapeutic approach. Previous studies have hinted at a role for protein arginine methylation in immune responses, including T cell–mediated autoimmunity and EAE. However, a conclusive role for the protein arginine methyltransferase (PRMT) enzymes that catalyze these reactions has been lacking. PRMT5 is the main PRMT responsible for symmetric dimethylation of arginine residues of histones and other proteins. PRMT5 drives embryonic development and cancer, but its role in T cells, if any, has not been investigated. In this article, we show that PRMT5 is an important modulator of CD4+ T cell expansion. PRMT5 was transiently upregulated during maximal proliferation of mouse and human memory Th cells. PRMT5 expression was regulated upstream by the NF-κB pathway, and it promoted IL-2 production and proliferation. Blocking PRMT5 with novel, highly selective small molecule PRMT5 inhibitors severely blunted memory Th expansion, with preferential suppression of Th1 cells over Th2 cells. In vivo, PRMT5 blockade efficiently suppressed recall T cell responses and reduced inflammation in delayed-type hypersensitivity and clinical disease in EAE mouse models. These data implicate PRMT5 in the regulation of adaptive memory Th cell responses and suggest that PRMT5 inhibitors may be a novel therapeutic approach for T cell–mediated inflammatory disease. PMID:28087667

  11. Optimal selection of nodes to propagate influence on networks

    NASA Astrophysics Data System (ADS)

    Sun, Yifan

    2016-11-01

    How to optimize the spreading process on networks has been a hot issue in complex networks, marketing, epidemiology, finance, etc. In this paper, we investigate a problem of optimizing locally the spreading: identifying a fixed number of nodes as seeds which would maximize the propagation of influence to their direct neighbors. All the nodes except the selected seeds are assumed not to spread their influence to their neighbors. This problem can be mapped onto a spin glass model with a fixed magnetization. We provide a message-passing algorithm based on replica symmetrical mean-field theory in statistical physics, which can find the nearly optimal set of seeds. Extensive numerical results on computer-generated random networks and real-world networks demonstrate that this algorithm has a better performance than several other optimization algorithms.

  12. Nitric oxide selectively suppresses IH currents mediated by HCN1-containing channels

    PubMed Central

    Kopp-Scheinpflug, Cornelia; Pigott, Beatrice M; Forsythe, Ian D

    2015-01-01

    Key points The superior olivary complex (SOC) exhibits a spectrum of HCN1 and HCN2 subunit expression, which generate IH currents with fast and slow kinetics, respectively. Neuronal nitric oxide synthase (nNOS) was broadly distributed across the SOC. NO hyperpolarizes the half-activation voltage of HCN1-mediated currents and caused a slowing of the IH current kinetics in the respective nuclei (medial and lateral superior olives and superior paraolivary nucleus). This signalling was independent of cGMP. NO also caused a depolarizing shift in the half-activation voltage of HCN2-mediated IH currents, increasing activation at resting potentials; this was cGMP-dependent. Thus, NO signalling suppressed fast HCN1-mediated currents and potentiated slow HCN2-mediated currents, modulating the overall kinetics and magnitude of the endogenous IH. Abstract Hyperpolarization-activated non-specific cation-permeable channels (HCN) mediate IH currents, which are modulated by cGMP and cAMP and by nitric oxide (NO) signalling. Channel properties depend upon subunit composition (HCN1–4 and accessory subunits) as demonstrated in expression systems, but physiological relevance requires investigation in native neurons with intact intracellular signalling. Here we use the superior olivary complex (SOC), which exhibits a distinctive pattern of HCN1 and HCN2 expression, to investigate NO modulation of the respective IH currents, and compare properties in wild-type and HCN1 knockout mice. The medial nucleus of the trapezoid body (MNTB) expresses HCN2 subunits exclusively, and sends inhibitory projections to the medial and lateral superior olives (MSO, LSO) and the superior paraolivary nucleus (SPN). In contrast to the MNTB, these target nuclei possess an IH with fast kinetics, and they express HCN1 subunits. NO is generated in the SOC following synaptic activity and here we show that NO selectively suppresses HCN1, while enhancing IH mediated by HCN2 subunits. NO hyperpolarizes the half

  13. Selective randomized load balancing and mesh networks with changing demands

    NASA Astrophysics Data System (ADS)

    Shepherd, F. B.; Winzer, P. J.

    2006-05-01

    We consider the problem of building cost-effective networks that are robust to dynamic changes in demand patterns. We compare several architectures using demand-oblivious routing strategies. Traditional approaches include single-hop architectures based on a (static or dynamic) circuit-switched core infrastructure and multihop (packet-switched) architectures based on point-to-point circuits in the core. To address demand uncertainty, we seek minimum cost networks that can carry the class of hose demand matrices. Apart from shortest-path routing, Valiant's randomized load balancing (RLB), and virtual private network (VPN) tree routing, we propose a third, highly attractive approach: selective randomized load balancing (SRLB). This is a blend of dual-hop hub routing and randomized load balancing that combines the advantages of both architectures in terms of network cost, delay, and delay jitter. In particular, we give empirical analyses for the cost (in terms of transport and switching equipment) for the discussed architectures, based on three representative carrier networks. Of these three networks, SRLB maintains the resilience properties of RLB while achieving significant cost reduction over all other architectures, including RLB and multihop Internet protocol/multiprotocol label switching (IP/MPLS) networks using VPN-tree routing.

  14. Frequency selective tunable spin wave channeling in the magnonic network

    SciTech Connect

    Sadovnikov, A. V. Nikitov, S. A.; Beginin, E. N.; Odincov, S. A.; Sheshukova, S. E.; Sharaevskii, Yu. P.; Stognij, A. I.

    2016-04-25

    Using the space-resolved Brillouin light scattering spectroscopy, we study the frequency and wavenumber selective spin-wave channeling. We demonstrate the frequency selective collimation of spin-wave in an array of magnonic waveguides, formed between the adjacent magnonic crystals on the surface of yttrium iron garnet film. We show the control over spin-wave propagation length by the orientation of an in-plane bias magnetic field. Fabricated array of magnonic crystal can be used as a magnonic platform for multidirectional frequency selective signal processing applications in magnonic networks.

  15. Dopamine suppresses persistent network activity via D1-like dopamine receptors in rat medial entorhinal cortex

    PubMed Central

    Mayne, Elizabeth W; Craig, Michael T; McBain, Chris J; Paulsen, Ole

    2013-01-01

    Cortical networks display persistent activity in the form of periods of sustained synchronous depolarizations (‘UP states’) punctuated by periods of relative hyperpolarization (‘DOWN states’), which together form the slow oscillation. UP states are known to be synaptically generated and are sustained by a dynamic balance of excitation and inhibition, with fast ionotropic glutamatergic excitatory and GABAergic inhibitory conductances increasing during the UP state. Previously, work from our group demonstrated that slow metabotropic GABA receptors also play an important role in terminating the UP state, but the effects of other neuromodulators on this network phenomenon have received little attention. Given that persistent activity is a neural correlate of working memory and that signalling through dopamine receptors has been shown to be critical for working memory tasks, we examined whether dopaminergic neurotransmission affected the slow oscillation. Here, using an in vitro model of the slow oscillation in rat medial entorhinal cortex, we showed that dopamine strongly and reversibly suppressed cortical UP states. We showed that this effect was mediated through D1-like and not D2-like dopamine receptors, and we found no evidence that tonic dopaminergic transmission affected UP states in our model. PMID:23336973

  16. Using principal component analysis for selecting network behavioral anomaly metrics

    NASA Astrophysics Data System (ADS)

    Gregorio-de Souza, Ian; Berk, Vincent; Barsamian, Alex

    2010-04-01

    This work addresses new approaches to behavioral analysis of networks and hosts for the purposes of security monitoring and anomaly detection. Most commonly used approaches simply implement anomaly detectors for one, or a few, simple metrics and those metrics can exhibit unacceptable false alarm rates. For instance, the anomaly score of network communication is defined as the reciprocal of the likelihood that a given host uses a particular protocol (or destination);this definition may result in an unrealistically high threshold for alerting to avoid being flooded by false positives. We demonstrate that selecting and adapting the metrics and thresholds, on a host-by-host or protocol-by-protocol basis can be done by established multivariate analyses such as PCA. We will show how to determine one or more metrics, for each network host, that records the highest available amount of information regarding the baseline behavior, and shows relevant deviances reliably. We describe the methodology used to pick from a large selection of available metrics, and illustrate a method for comparing the resulting classifiers. Using our approach we are able to reduce the resources required to properly identify misbehaving hosts, protocols, or networks, by dedicating system resources to only those metrics that actually matter in detecting network deviations.

  17. Processing of Feature Selectivity in Cortical Networks with Specific Connectivity

    PubMed Central

    Sadeh, Sadra; Clopath, Claudia; Rotter, Stefan

    2015-01-01

    Although non-specific at the onset of eye opening, networks in rodent visual cortex attain a non-random structure after eye opening, with a specific bias for connections between neurons of similar preferred orientations. As orientation selectivity is already present at eye opening, it remains unclear how this specificity in network wiring contributes to feature selectivity. Using large-scale inhibition-dominated spiking networks as a model, we show that feature-specific connectivity leads to a linear amplification of feedforward tuning, consistent with recent electrophysiological single-neuron recordings in rodent neocortex. Our results show that optimal amplification is achieved at an intermediate regime of specific connectivity. In this configuration a moderate increase of pairwise correlations is observed, consistent with recent experimental findings. Furthermore, we observed that feature-specific connectivity leads to the emergence of orientation-selective reverberating activity, and entails pattern completion in network responses. Our theoretical analysis provides a mechanistic understanding of subnetworks’ responses to visual stimuli, and casts light on the regime of operation of sensory cortices in the presence of specific connectivity. PMID:26083363

  18. Hadoop neural network for parallel and distributed feature selection.

    PubMed

    Hodge, Victoria J; O'Keefe, Simon; Austin, Jim

    2016-06-01

    In this paper, we introduce a theoretical basis for a Hadoop-based neural network for parallel and distributed feature selection in Big Data sets. It is underpinned by an associative memory (binary) neural network which is highly amenable to parallel and distributed processing and fits with the Hadoop paradigm. There are many feature selectors described in the literature which all have various strengths and weaknesses. We present the implementation details of five feature selection algorithms constructed using our artificial neural network framework embedded in Hadoop YARN. Hadoop allows parallel and distributed processing. Each feature selector can be divided into subtasks and the subtasks can then be processed in parallel. Multiple feature selectors can also be processed simultaneously (in parallel) allowing multiple feature selectors to be compared. We identify commonalities among the five features selectors. All can be processed in the framework using a single representation and the overall processing can also be greatly reduced by only processing the common aspects of the feature selectors once and propagating these aspects across all five feature selectors as necessary. This allows the best feature selector and the actual features to select to be identified for large and high dimensional data sets through exploiting the efficiency and flexibility of embedding the binary associative-memory neural network in Hadoop.

  19. Selection of Motor Programs for Suppressing Food Intake and Inducing Locomotion in the Drosophila Brain

    PubMed Central

    Schoofs, Andreas; Hückesfeld, Sebastian; Schlegel, Philipp; Miroschnikow, Anton; Peters, Marc; Zeymer, Malou; Spieß, Roland; Chiang, Ann-Shyn; Pankratz, Michael J.

    2014-01-01

    Central mechanisms by which specific motor programs are selected to achieve meaningful behaviors are not well understood. Using electrophysiological recordings from pharyngeal nerves upon central activation of neurotransmitter-expressing cells, we show that distinct neuronal ensembles can regulate different feeding motor programs. In behavioral and electrophysiological experiments, activation of 20 neurons in the brain expressing the neuropeptide hugin, a homolog of mammalian neuromedin U, simultaneously suppressed the motor program for food intake while inducing the motor program for locomotion. Decreasing hugin neuropeptide levels in the neurons by RNAi prevented this action. Reducing the level of hugin neuronal activity alone did not have any effect on feeding or locomotion motor programs. Furthermore, use of promoter-specific constructs that labeled subsets of hugin neurons demonstrated that initiation of locomotion can be separated from modulation of its motor pattern. These results provide insights into a neural mechanism of how opposing motor programs can be selected in order to coordinate feeding and locomotive behaviors. PMID:24960360

  20. SB223412, a neurokinin-3 receptor-selective antagonist, suppresses testosterone secretion in male guinea pigs.

    PubMed

    Nakamura, Sho; Ito, Yoshiko; Yamamoto, Koki; Takahashi, Chudai; Dai, Mingdao; Tanahashi, Miyu; Uenoyama, Yoshihisa; Tsukamura, Hiroko; Oishi, Shinya; Maeda, Kei-Ichiro; Matsuda, Fuko

    2017-10-15

    Guinea pigs are important zoo animals and have been recommended for animal-assisted activities or therapy, however there are problems concerning testosterone inducing aggressive or sexual behaviors in male guinea pigs. Testicular testosterone secretion is regulated by pulsatile gonadotropin releasing hormone (GnRH)/luteinizing hormone (LH) release in mammals. The mechanism generating GnRH/LH pulses is thought to be governed by kisspeptin neurons, which coexpress neurokinin B (NKB) and dynorphin A (Dyn), in the arcuate nucleus (ARC). Kisspeptin neurons in the ARC are frequently referred to as KNDy neurons. The purpose of this study was to examine whether the antagonization of NKB-neurokinin-3 receptor (NK3R) signaling can manipulate testosterone secretion in male guinea pigs. A single subcutaneous administration or 7 days of oral administration of an NK3R-selective antagonist, SB223412 (50 mg/body), significantly decreased plasma testosterone levels in male guinea pigs. In vitro binding assays confirmed that SB223412 has a high affinity to guinea pig NK3R. These results suggest that SB223412 could be used as an orally-available compound to suppress testosterone levels in male guinea pigs. Double labeling in situ hybridization of kisspeptin and either NKB or Dyn showed that kisspeptin-expressing neurons contained NKB (77.9%) or Dyn (62.3%) in the ARC, suggesting the presence of KNDy neurons in the ARC of guinea pigs. In conclusion, the present study shows that SB223412 could be a candidate compound to suppress testosterone secretion in male guinea pigs for controlling sexual and aggressive behaviors in the species. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. Improved water and lipid suppression for 3D PRESS CSI using RF band selective inversion with gradient dephasing (BASING).

    PubMed

    Star-Lack, J; Nelson, S J; Kurhanewicz, J; Huang, L R; Vigneron, D B

    1997-08-01

    A T1 insensitive solvent suppression technique-band selective inversion with gradient dephasing (BASING)-was developed to suppress water and lipids for 1H magnetic resonance spectroscopy (MRS). BASING, which consists of a frequency selective RF inversion pulse surrounded by spoiler gradient pulses of opposite signs, was used to dephase stopband resonances and minimally impact passband metabolites. Passband phase linearity was achieved with a dual BASING scheme. Using the Shinnar-Le Roux algorithm, a highpass filter was designed to suppress water and rephase the lactate methyl doublet independently of TE, and water/lipid bandstop filters were designed for the brain and prostate. Phantom and in vivo experimental 3D PRESS CSI data were acquired at 1.5 T to compare BASING with CHESS and STIR suppression. With BASING, the measured suppression factor was over 100 times higher than with CHESS or STIR causing baseline distortions to be removed. It was shown that BASING can be incorporated into a variety of sequences to offer improved suppression in the presence of B1 and T1 inhomogeneites.

  2. Supplemental feedings increase self-selected work output during wildfire suppression.

    PubMed

    Cuddy, John S; Gaskill, Steven E; Sharkey, Brian J; Harger, Stephanie G; Ruby, Brent C

    2007-06-01

    The purpose of this study was to determine the impact of supplemental feeding strategies on self-selected activity during wildland fire suppression. Seventy-six wildland firefighters were studied in three experiments for three fire seasons. During the first two seasons, subjects consumed, in addition to their sack lunch, 1) liquid carbohydrate (CHO) (200 mL.h, 20% CHO (40 g.h, 160 kcal.h)) or placebo (PLA) every hour, or 2) liquid CHO (200 mL.h, 20% CHO (40 g.h, 160 kcal.h) every even hour and solid CHO (25 g of CHO, 10 g of protein, 2 g of fat, and 160 kcal.h) every odd hour, or PLA, using counterbalanced crossover designs. During the third season, subjects consumed their sack lunch halfway through their workday, or shift food items of approximately 150-400 kcal at 90-min intervals after breakfast in a randomized crossover design (isocaloric intake, 1534+/-265 kcal per workday). Work output was monitored using CSA and MiniMitter actigraphy units. During the liquid CHO trials, subjects consuming CHO demonstrated significantly higher average activity counts throughout the day compared with PLA (50,262+/-36,560 and 40,159+/-35,969 counts per hour for 12 h for the CHO and PLA trials, respectively; P<0.05). For the liquid+solid CHO trials, subjects consuming CHO demonstrated higher average activity counts per minute 2 h before lunch and the last 4 h of the workday compared with PLA (P<0.05). For the sack lunch and shift food trials, subjects consuming shift foods demonstrated higher average counts per minute during the final 2 h compared with those consuming sack lunch (521+/-421 vs 366+/-249 counts per minute during 2 h; P<0.05). Liquid and/or solid supplemental CHO and regular feedings increased self-selected work rates during wildland fire suppression, particularly during the latter hours of the workday.

  3. Feature Selection for Neural Network Based Stock Prediction

    NASA Astrophysics Data System (ADS)

    Sugunnasil, Prompong; Somhom, Samerkae

    We propose a new methodology of feature selection for stock movement prediction. The methodology is based upon finding those features which minimize the correlation relation function. We first produce all the combination of feature and evaluate each of them by using our evaluate function. We search through the generated set with hill climbing approach. The self-organizing map based stock prediction model is utilized as the prediction method. We conduct the experiment on data sets of the Microsoft Corporation, General Electric Co. and Ford Motor Co. The results show that our feature selection method can improve the efficiency of the neural network based stock prediction.

  4. Network Marker Selection for Untargeted LC-MS Metabolomics Data.

    PubMed

    Cai, Qingpo; Alvarez, Jessica A; Kang, Jian; Yu, Tianwei

    2017-02-17

    Untargeted metabolomics using high-resolution liquid chromatography-mass spectrometry (LC-MS) is becoming one of the major areas of high-throughput biology. Functional analysis, that is, analyzing the data based on metabolic pathways or the genome-scale metabolic network, is critical in feature selection and interpretation of metabolomics data. One of the main challenges in the functional analyses is the lack of the feature identity in the LC-MS data itself. By matching mass-to-charge ratio (m/z) values of the features to theoretical values derived from known metabolites, some features can be matched to one or more known metabolites. When multiple matchings occur, in most cases only one of the matchings can be true. At the same time, some known metabolites are missing in the measurements. Current network/pathway analysis methods ignore the uncertainty in metabolite identification and the missing observations, which could lead to errors in the selection of significant subnetworks/pathways. In this paper, we propose a flexible network feature selection framework that combines metabolomics data with the genome-scale metabolic network. The method adopts a sequential feature screening procedure and machine learning-based criteria to select important subnetworks and identify the optimal feature matching simultaneously. Simulation studies show that the proposed method has a much higher sensitivity than the commonly used maximal matching approach. For demonstration, we apply the method on a cohort of healthy subjects to detect subnetworks associated with the body mass index (BMI). The method identifies several subnetworks that are supported by the current literature, as well as detects some subnetworks with plausible new functional implications. The R code is available at http://web1.sph.emory.edu/users/tyu8/MSS.

  5. A Cytosolic Network Suppressing Mitochondria-Mediated Proteostatic Stress and Cell Death

    PubMed Central

    Wang, Xiaowen; Chen, Xin Jie

    2015-01-01

    Mitochondria are multifunctional organelles whose dysfunction leads to neuromuscular degeneration and ageing. The multi-functionality poses a great challenge for understanding the mechanisms by which mitochondrial dysfunction causes specific pathologies. Among the leading mitochondrial mediators of cell death are energy depletion, free radical production, defect in iron-sulfur cluster biosynthesis, the release of pro-apoptotic and non-cell-autonomous signaling molecules, and altered stress signaling 1–5. Here, we identified a novel pathway of mitochondria-mediated cell death. This pathway was named mitochondrial Precursor Over-accumulation Stress (mPOS), characterized by aberrant accumulation of mitochondrial precursors in the cytosol. mPOS can be triggered by clinically relevant mitochondrial damage which is not limited to the core machineries of protein import. We also identified a large network of genes that suppress mPOS, by modulating ribosomal biogenesis, mRNA decapping, transcript-specific translation, protein chaperoning and turnover. In response to mPOS, several ribosome-associated proteins were up-regulated including Gis2 and Nog2, which promote cap-independent translation and inhibit the nuclear export of the 60S ribosomal subunit respectively 6, 7. Gis2 and Nog2 up-regulation promotes cell survival, which may be part of a feedback loop that attenuates mPOS. Our data indicate that mitochondrial dysfunction contributes directly to cytosolic proteostatic stress, and provide an explanation for the enigmatic association between these two hallmarks of degenerative diseases and ageing. The results are relevant to understanding diseases (e.g., spinocerebellar ataxia, amyotrophic lateral sclerosis and myotonic dystrophy) that involve mutations within the anti-degenerative network. PMID:26192197

  6. Selective suppression of cytokine secretion in whole blood cell cultures of patients with colorectal cancer.

    PubMed Central

    Lahm, H.; Schindel, M.; Frikart, L.; Cerottini, J. P.; Yilmaz, A.; Givel, J. C.; Fischer, J. R.

    1998-01-01

    We have investigated the secretion of interferon alpha (IFN-alpha), IFN-gamma, interleukin-1alpha (IL-1alpha), IL-1beta, IL-2 and tumour necrosis factor alpha (TNF-alpha) in whole blood cell cultures (WBCCs) of colorectal cancer patients upon mitogen stimulation. Whereas the values for IL-1beta and TNF-alpha remained virtually unchanged in comparison with healthy control subjects, WBCCs of colorectal cancer patients secreted significantly lower amounts of IFN-alpha (P < 0.005), IFN-gamma (P < 0.0001), IL-1alpha (P < 0.0001) and IL-2 (P < 0.05). This reduction correlated with the progression of the disease. The total leucocyte and monocyte population were almost identical in both groups. In contrast, a dramatic depletion of lymphocytes was observed in colorectal cancer patients, which affected both lymphocyte counts (P < 0.0005) and their distribution (P < 0.0001). Our results suggest a selective suppression of cytokines in colorectal cancer patients that is related to tumour burden. Several mechanisms might account for this phenomenon, one of which might be lymphocyte depletion. PMID:9792144

  7. Planar avalanche photodiodes with edge breakdown suppression using a novel selective area growth based process

    NASA Astrophysics Data System (ADS)

    Pitts, O. J.; Hisko, M.; Benyon, W.; Bonneville, G.; Storey, C.; SpringThorpe, A. J.

    2017-07-01

    We propose and demonstrate a novel process to fabricate planar avalanche photodiodes using selective area growth (SAG) followed by a single Zn diffusion through the SAG material using the same dielectric mask. The tapered surface profile of the SAG epitaxy due to the enhancement of the growth rate in the vicinity of the mask edge modifies the diffusion profile, resulting in a gradual reduction of the diffusion depth towards the outer edge of the active area. The associated reduction of the electric field counteracts the edge curvature effect sufficiently to suppress edge breakdown. For undoped InP SAG epitaxy, small areas of higher electric field occur where the mask edge is along the [1 0 0] or [0 1 0] directions, associated with the formation of enhanced ridges in the SAG material in these locations. Similar ridges are observed for Si-doped InP and InP/InGaAs/InP SAG structures, but the enhancement of the electric field in these locations is significantly lower.

  8. An exotic invasive plant selects for increased competitive tolerance, but not competitive suppression, in a native grass.

    PubMed

    Fletcher, Rebecca A; Callaway, Ragan M; Atwater, Daniel Z

    2016-06-01

    Exotic invasive plants can exert strong selective pressure for increased competitive ability in native plants. There are two fundamental components of competitive ability: suppression and tolerance, and the current paradigm that these components have equal influences on a species' overall competitive ability has been recently questioned. If these components do not have equal influences on overall ability, then selection on competitive tolerance and suppression may be disproportionate. We used naturally invaded communities to study the effects of selection caused by an invasive forb, Centaurea stoebe, on a native grass, Pseudoroegneria spicata. P. spicata plants were harvested from within dense C. stoebe patches and from nearby uninvaded areas, divided clonally into replicates, then transplanted into a common garden where they grew alone or competed with C. stoebe. We found that P. spicata plants collected from within C. stoebe patches were significantly more tolerant of competition with C. stoebe than P. spicata plants collected from uninvaded areas, but plants from inside invaded patches were not superior at suppressing C. stoebe. These results are consistent with the hypothesis that strong competitors may select for tolerance to competition more than for the ability to suppress neighbors. This has important implications for how native plant communities may respond to invasion over time, and how invasive and native species may ultimately coexist.

  9. Selective suppression of harmful cyanobacteria in an entire lake with hydrogen peroxide.

    PubMed

    Matthijs, Hans C P; Visser, Petra M; Reeze, Bart; Meeuse, Jeroen; Slot, Pieter C; Wijn, Geert; Talens, Renée; Huisman, Jef

    2012-04-01

    Although harmful cyanobacteria form a major threat to water quality, few methods exist for the rapid suppression of cyanobacterial blooms. Since laboratory studies indicated that cyanobacteria are more sensitive to hydrogen peroxide (H(2)O(2)) than eukaryotic phytoplankton, we tested the application of H(2)O(2) in natural waters. First, we exposed water samples from a recreational lake dominated by the toxic cyanobacterium Planktothrix agardhii to dilute H(2)O(2). This reduced the photosynthetic vitality by more than 70% within a few hours. Next, we installed experimental enclosures in the lake, which revealed that H(2)O(2) selectively killed the cyanobacteria without major impacts on eukaryotic phytoplankton, zooplankton, or macrofauna. Based on these tests, we introduced 2 mg L(-1) (60 μM) of H(2)O(2) homogeneously into the entire water volume of the lake with a special dispersal device, called the water harrow. The cyanobacterial population as well as the microcystin concentration collapsed by 99% within a few days. Eukaryotic phytoplankton (including green algae, cryptophytes, chrysophytes and diatoms), zooplankton and macrofauna remained largely unaffected. Following the treatment, cyanobacterial abundances remained low for 7 weeks. Based on these results, we propose the use of dilute H(2)O(2) for the selective elimination of harmful cyanobacteria from recreational lakes and drinking water reservoirs, especially when immediate action is urgent and/or cyanobacterial control by reduction of eutrophication is currently not feasible. A key advantage of this method is that the added H(2)O(2) degrades to water and oxygen within a few days, and thus leaves no long-term chemical traces in the environment.

  10. Suppression of PKR Promotes Network Excitability and Enhanced Cognition by Interferon-γ-Mediated Disinhibition

    PubMed Central

    Zhu, Ping Jun; Huang, Wei; Kalikulov, Djanenkhodja; Yoo, Jong W.; Placzek, Andon N.; Stoica, Loredana; Zhou, Hongyi; Bell, John C.; Friedlander, Michael J.; Krnjević, Krešimir; Noebels, Jeffrey L.; Costa-Mattioli, Mauro

    2013-01-01

    SUMMARY The double-stranded RNA-activated protein kinase (PKR) was originally identified as a sensor of virus infection, but its function in the brain remains unknown. Here, we report that the lack of PKR enhances learning and memory in several behavioral tasks while increasing network excitability. In addition, loss of PKR increases the late phase of long-lasting synaptic potentiation (L-LTP) in hippocampal slices. These effects are caused by an interferon-γ (IFN-γ)-mediated selective reduction in GABAergic synaptic action. Together, our results reveal that PKR finely tunes the network activity that must be maintained while storing a given episode during learning. Because PKR activity is altered in several neurological disorders, this kinase presents a promising new target for the treatment of cognitive dysfunction. As a first step in this direction, we show that a selective PKR inhibitor replicates the Pkr−/− phenotype in WT mice, enhancing long-term memory storage and L-LTP. PMID:22153080

  11. It takes three: selection, influence, and de-selection processes of depression in adolescent friendship networks.

    PubMed

    Van Zalk, Maarten Herman Walter; Kerr, Margaret; Branje, Susan J T; Stattin, Håkan; Meeus, Wim H J

    2010-07-01

    The authors of this study tested a selection-influence-de-selection model of depression. This model explains friendship influence processes (i.e., friends' depressive symptoms increase adolescents' depressive symptoms) while controlling for two processes: friendship selection (i.e., selection of friends with similar levels of depressive symptoms) and friendship de-selection (i.e., de-selection of friends with dissimilar levels of depressive symptoms). Further, this study is unique in that these processes were studied both inside and outside the school context. The authors used a social network approach to examine 5 annual measurements of data in a large (N =847) community-based network of adolescents and their friends (M = 14.3 years old at first measurement). Results supported the proposed model: adolescents tend to select friends with similar levels of depression, and friends may increase each other's depressive symptoms as relationships endure. These two processes were most salient outside the school context. At the same time, friendships seemed to be ended more frequently if adolescents' level of depressive symptoms was dissimilar to that of their friends.

  12. Selection of genetically diverse Trichoderma spp. isolates for suppression of Phytophthora capsici on bell pepper.

    PubMed

    Roberts, Daniel P; Maul, Jude E; McKenna, Laurie F; Emche, Sarah E; Meyer, Susan L F; Collins, Ronald T; Bowers, John H

    2010-10-01

    Environmentally compatible control measures are needed for suppression of Phytophthora capsici on pepper. Twenty-three isolates of Trichoderma were screened for suppression of a mixture of 4 genetically distinct isolates of this pathogen on bell pepper (Capsicum anuum) in greenhouse pot assays. Of these 23 isolates, GL12, GL13, and Th23 provided significant suppression of P. capsici in at least 2 assays. These isolates were then compared with Trichoderma virens isolates GL3 and GL21 for suppression of this disease in the presence and absence of the harpin-based natural product Messenger. Isolates GL3 and Th23 provided significant disease suppression (P ≤ 0.05) in 3 of 4 assays, while GL12, GL13, and GL21 provided significant suppression in 2 of 4 assays. There was no apparent benefit from the application of Messenger. Phylogenetic analysis of these 5 isolates (based on the ITS1 region of the nuclear rDNA cluster and tef1), and an additional 9 isolates that suppressed P. capsici in at least 1 assay, separated isolates into 2 clades, with 1 clade containing GL3, GL12, GL13, and GL21. There were also 2 more distantly related isolates, one of which was Th23. We report here the identification of genetically distinct Trichoderma isolates for potential use in disease management strategies employing isolate combinations directed at suppression of P. capsici on pepper.

  13. Selection of genetically diverse trichoderma spp. isolates for suppression of phytophthora capsici on bell pepper

    USDA-ARS?s Scientific Manuscript database

    Environmentally compatible control measures are needed for suppression of Phytophthora capsici on pepper. Twenty-four isolates of Trichoderma were screened for suppression of this pathogen on bell pepper in greenhouse pot assays. Of these twenty-four isolates, GL12, GL13, and Th23 provided signifi...

  14. A neural network model for visual selection and shifting.

    PubMed

    Qiao, Yuanhua; Liu, Xiaojie; Miao, Jun; Duan, Lijuan

    2016-09-01

    In this paper, a two-layer network is built to simulate the mechanism of visual selection and shifting based on the mapping dynamic model for instantaneous frequency. Unlike the differential equation model using limit cycle to simulate neuron oscillation, we build an instantaneous frequency mapping dynamic model to describe the change of the neuron frequency to avoid the difficulty of generating limit cycle. The activity of the neuron is rebuilt based on the instantaneous frequency and in this work, we use the first layer of neurons to implement image segmentation and the second layer of neurons to act as visual selector. The frequency of the second neuron (central neuron) is always changing, while central neuron resonates with the neurons corresponding to an object, the object is selected, then with the central neuron frequency changing, the selected object loses attention, the process goes on.

  15. Distributed estimation for adaptive sensor selection in wireless sensor networks

    NASA Astrophysics Data System (ADS)

    Mahmoud, Magdi S.; Hassan Hamid, Matasm M.

    2014-05-01

    Wireless sensor networks (WSNs) are usually deployed for monitoring systems with the distributed detection and estimation of sensors. Sensor selection in WSNs is considered for target tracking. A distributed estimation scenario is considered based on the extended information filter. A cost function using the geometrical dilution of precision measure is derived for active sensor selection. A consensus-based estimation method is proposed in this paper for heterogeneous WSNs with two types of sensors. The convergence properties of the proposed estimators are analyzed under time-varying inputs. Accordingly, a new adaptive sensor selection (ASS) algorithm is presented in which the number of active sensors is adaptively determined based on the absolute local innovations vector. Simulation results show that the tracking accuracy of the ASS is comparable to that of the other algorithms.

  16. Targeting tumor-associated immune suppression with selective protein kinase A type I (PKAI) inhibitors may enhance cancer immunotherapy.

    PubMed

    Hussain, Muzammal; Shah, Zahir; Abbas, Nasir; Javeed, Aqeel; Mukhtar, Muhammad Mahmood; Zhang, Jiancun

    2016-01-01

    Despite the tremendous progress in last few years, the cancer immunotherapy has not yet improved disease-free because of the tumor-associated immune suppression being a major barrier. Novel trends to enhance cancer immunotherapy aims at harnessing the therapeutic manipulation of signaling pathways mediating the tumor-associated immune suppression, with the general aims of: (a) reversing the tumor immune suppression; (b) enhancing the innate and adaptive components of anti-tumor immunosurveillance, and (c) protecting immune cells from the suppressive effects of T regulatory cells (Tregs) and the tumor-derived immunoinhibitory mediators. A particular striking example in this context is the cyclic adenosine monophosphate (cAMP)-dependent protein kinase A type I (PKAI) pathway. Oncogenic cAMP/PKAI signaling has long been implicated in the initiation and progression of several human cancers. Emerging data indicate that cAMP/PKAI signaling also contributes to tumor- and Tregs-derived suppression of innate and adaptive arms of anti-tumor immunosurveillance. Therapeutically, selective PKAI inhibitors have been developed which have shown promising anti-cancer activity in pre-clinical and clinical settings. Rp-8-Br-cAMPS is a selective PKAI antagonist that is widely used as a biochemical tool in signal transduction research. Collateral data indicate that Rp-8-Br-cAMPS has shown immune-rescuing potential in terms of enhancing the innate and adaptive anti-tumor immunity, as well as protecting adaptive T cells from the suppressive effects of Tregs. Therefore, this proposal specifically implicates that combining selective PKAI antagonists/inhibitors with cancer immunotherapy may have multifaceted benefits, such as rescuing the endogenous anti-tumor immunity, enhancing the efficacy of cancer immunotherapy, and direct anti-cancer effects.

  17. Inhibition of eukaryotic initiation factor 4E phosphorylation by cercosporamide selectively suppresses angiogenesis, growth and survival of human hepatocellular carcinoma.

    PubMed

    Liu, Yongdong; Sun, Liling; Su, Xingwang; Guo, Sien

    2016-12-01

    Mnk kinase is required for the phosphorylation and activation of the eukaryotic initiation factor 4E (eIF4E), which regulates translation of proteins involve in important aspects of hepatocellular carcinoma (HCC). Here we investigated whether an antifungal agent, cercosporamide, which had been recently identified as a potent Mnk inhibitor, is active against HCC and angiogenesis. We showed that cercosporamide significantly inhibited growth and induced caspase-dependent apoptosis on numerous HCC cell lines, while sparing normal liver cells. In addition, cercosporamide impaired HCC angiogenesis via inhibiting HCC-endothelial cells (HCC-EC) capillary network formation, migration, proliferation and survival. Importantly, cercosporamide sensitized HCC cells to cisplatin in in vitro cell culture and in vivo HCC xenograft mouse model. Cercosporamide blocked the phosphorylation of eIF4E but not Erk or p38 in a dose- and time-dependent manner in HCC and HCC-EC cells, suggesting that suppression of eIF4E phosphorylation was the result of inhibition of Mnk but not Mnk upstream pathways. Overexpression of constitutively active eIF4E (S209D) but not the nonphosphorylatable eIF4E (S209A) abolished the inhibitory effects of cercosporamide in HepG2 cells. Altogether, our work demonstrates that cercosporamide acts as a Mnk inhibitor through blockage of eIF4E phosphorylation and selectively exhibits anti-HCC activities. Our work suggests that targeting MNK-eIF4E pathway represents a therapeutic strategy to overcome chemo-resistance for HCC treatment. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  18. Smartphone technologies and Bayesian networks to assess shorebird habitat selection

    USGS Publications Warehouse

    Zeigler, Sara; Thieler, E. Robert; Gutierrez, Ben; Plant, Nathaniel G.; Hines, Megan K.; Fraser, James D.; Catlin, Daniel H.; Karpanty, Sarah M.

    2017-01-01

    Understanding patterns of habitat selection across a species’ geographic distribution can be critical for adequately managing populations and planning for habitat loss and related threats. However, studies of habitat selection can be time consuming and expensive over broad spatial scales, and a lack of standardized monitoring targets or methods can impede the generalization of site-based studies. Our objective was to collaborate with natural resource managers to define available nesting habitat for piping plovers (Charadrius melodus) throughout their U.S. Atlantic coast distribution from Maine to North Carolina, with a goal of providing science that could inform habitat management in response to sea-level rise. We characterized a data collection and analysis approach as being effective if it provided low-cost collection of standardized habitat-selection data across the species’ breeding range within 1–2 nesting seasons and accurate nesting location predictions. In the method developed, >30 managers and conservation practitioners from government agencies and private organizations used a smartphone application, “iPlover,” to collect data on landcover characteristics at piping plover nest locations and random points on 83 beaches and barrier islands in 2014 and 2015. We analyzed these data with a Bayesian network that predicted the probability a specific combination of landcover variables would be associated with a nesting site. Although we focused on a shorebird, our approach can be modified for other taxa. Results showed that the Bayesian network performed well in predicting habitat availability and confirmed predicted habitat preferences across the Atlantic coast breeding range of the piping plover. We used the Bayesian network to map areas with a high probability of containing nesting habitat on the Rockaway Peninsula in New York, USA, as an example application. Our approach facilitated the collation of evidence-based information on habitat selection

  19. Evolution and selection of river networks: statics, dynamics, and complexity.

    PubMed

    Rinaldo, Andrea; Rigon, Riccardo; Banavar, Jayanth R; Maritan, Amos; Rodriguez-Iturbe, Ignacio

    2014-02-18

    Moving from the exact result that drainage network configurations minimizing total energy dissipation are stationary solutions of the general equation describing landscape evolution, we review the static properties and the dynamic origins of the scale-invariant structure of optimal river patterns. Optimal channel networks (OCNs) are feasible optimal configurations of a spanning network mimicking landscape evolution and network selection through imperfect searches for dynamically accessible states. OCNs are spanning loopless configurations, however, only under precise physical requirements that arise under the constraints imposed by river dynamics--every spanning tree is exactly a local minimum of total energy dissipation. It is remarkable that dynamically accessible configurations, the local optima, stabilize into diverse metastable forms that are nevertheless characterized by universal statistical features. Such universal features explain very well the statistics of, and the linkages among, the scaling features measured for fluvial landforms across a broad range of scales regardless of geology, exposed lithology, vegetation, or climate, and differ significantly from those of the ground state, known exactly. Results are provided on the emergence of criticality through adaptative evolution and on the yet-unexplored range of applications of the OCN concept.

  20. Evolution and selection of river networks: Statics, dynamics, and complexity

    PubMed Central

    Rinaldo, Andrea; Rigon, Riccardo; Banavar, Jayanth R.; Maritan, Amos; Rodriguez-Iturbe, Ignacio

    2014-01-01

    Moving from the exact result that drainage network configurations minimizing total energy dissipation are stationary solutions of the general equation describing landscape evolution, we review the static properties and the dynamic origins of the scale-invariant structure of optimal river patterns. Optimal channel networks (OCNs) are feasible optimal configurations of a spanning network mimicking landscape evolution and network selection through imperfect searches for dynamically accessible states. OCNs are spanning loopless configurations, however, only under precise physical requirements that arise under the constraints imposed by river dynamics—every spanning tree is exactly a local minimum of total energy dissipation. It is remarkable that dynamically accessible configurations, the local optima, stabilize into diverse metastable forms that are nevertheless characterized by universal statistical features. Such universal features explain very well the statistics of, and the linkages among, the scaling features measured for fluvial landforms across a broad range of scales regardless of geology, exposed lithology, vegetation, or climate, and differ significantly from those of the ground state, known exactly. Results are provided on the emergence of criticality through adaptative evolution and on the yet-unexplored range of applications of the OCN concept. PMID:24550264

  1. Application of Fuzzy AHP and ELECTRE to Network Selection

    NASA Astrophysics Data System (ADS)

    Charilas, Dimitris E.; Markaki, Ourania I.; Psarras, John; Constantinou, Philip

    In a heterogeneous wireless network environment services are ubiquitously delivered over multiple wireless access technologies. Ranking of the alternatives and selection of the most efficient and suitable access network to meet the QoS requirements of a specific service, as these are defined by the user, constitutes thus an important issue. Decisions on which network to connect to are however difficult to be reached, since multiple factors of different relative importance have to be taken into consideration. This paper addresses this difficulty by adopting Multi Attribute Decision Making (MADM) methods. Fuzzy AHP, a MADM method, is initially applied to determine the weights of certain Quality of Service indicators that act as the criteria impacting the decision process. The fuzzy extension of the method, and consequently the use of fuzzy numbers, is adopted in order to incorporate the existence of fuzziness as a result of subjective evaluations. Afterwards, ELECTRE, a ranking MADM method, is applied to rank the alternatives, in this case wireless networks, based on their overall performance.

  2. Robust nonlinear variable selective control for networked systems

    NASA Astrophysics Data System (ADS)

    Rahmani, Behrooz

    2016-10-01

    This paper is concerned with the networked control of a class of uncertain nonlinear systems. In this way, Takagi-Sugeno (T-S) fuzzy modelling is used to extend the previously proposed variable selective control (VSC) methodology to nonlinear systems. This extension is based upon the decomposition of the nonlinear system to a set of fuzzy-blended locally linearised subsystems and further application of the VSC methodology to each subsystem. To increase the applicability of the T-S approach for uncertain nonlinear networked control systems, this study considers the asynchronous premise variables in the plant and the controller, and then introduces a robust stability analysis and control synthesis. The resulting optimal switching-fuzzy controller provides a minimum guaranteed cost on an H2 performance index. Simulation studies on three nonlinear benchmark problems demonstrate the effectiveness of the proposed method.

  3. Network characteristics for server selection in online games

    NASA Astrophysics Data System (ADS)

    Claypool, Mark

    2008-01-01

    Online gameplay is impacted by the network characteristics of players connected to the same server. Unfortunately, the network characteristics of online game servers are not well-understood, particularly for groups that wish to play together on the same server. As a step towards a remedy, this paper presents analysis of an extensive set of measurements of game servers on the Internet. Over the course of many months, actual Internet game servers were queried simultaneously by twenty-five emulated game clients, with both servers and clients spread out on the Internet. The data provides statistics on the uptime and populations of game servers over a month long period an an in-depth look at the suitability for game servers for multi-player server selection, concentrating on characteristics critical to playability--latency and fairness. Analysis finds most game servers have latencies suitable for third-person and omnipresent games, such as real-time strategy, sports and role-playing games, providing numerous server choices for game players. However, far fewer game servers have the low latencies required for first-person games, such as shooters or race games. In all cases, groups that wish to play together have a greatly reduced set of servers from which to choose because of inherent unfairness in server latencies and server selection is particularly limited as the group size increases. These results hold across different game types and even across different generations of games. The data should be useful for game developers and network researchers that seek to improve game server selection, whether for single or multiple players.

  4. A Predictive Based Regression Algorithm for Gene Network Selection

    PubMed Central

    Guerrier, Stéphane; Mili, Nabil; Molinari, Roberto; Orso, Samuel; Avella-Medina, Marco; Ma, Yanyuan

    2016-01-01

    Gene selection has become a common task in most gene expression studies. The objective of such research is often to identify the smallest possible set of genes that can still achieve good predictive performance. To do so, many of the recently proposed classification methods require some form of dimension-reduction of the problem which finally provide a single model as an output and, in most cases, rely on the likelihood function in order to achieve variable selection. We propose a new prediction-based objective function that can be tailored to the requirements of practitioners and can be used to assess and interpret a given problem. Based on cross-validation techniques and the idea of importance sampling, our proposal scans low-dimensional models under the assumption of sparsity and, for each of them, estimates their objective function to assess their predictive power in order to select. Two applications on cancer data sets and a simulation study show that the proposal compares favorably with competing alternatives such as, for example, Elastic Net and Support Vector Machine. Indeed, the proposed method not only selects smaller models for better, or at least comparable, classification errors but also provides a set of selected models instead of a single one, allowing to construct a network of possible models for a target prediction accuracy level. PMID:27379155

  5. The production route selection algorithm in virtual manufacturing networks

    NASA Astrophysics Data System (ADS)

    Krenczyk, D.; Skolud, B.; Olender, M.

    2017-08-01

    The increasing requirements and competition in the global market are challenges for the companies profitability in production and supply chain management. This situation became the basis for construction of virtual organizations, which are created in response to temporary needs. The problem of the production flow planning in virtual manufacturing networks is considered. In the paper the algorithm of the production route selection from the set of admissible routes, which meets the technology and resource requirements and in the context of the criterion of minimum cost is proposed.

  6. Long-range recruitment of Martinotti cells causes surround suppression and promotes saliency in an attractor network model

    PubMed Central

    Krishnamurthy, Pradeep; Silberberg, Gilad; Lansner, Anders

    2015-01-01

    Although the importance of long-range connections for cortical information processing has been acknowledged for a long time, most studies focused on the long-range interactions between excitatory cortical neurons. Inhibitory interneurons play an important role in cortical computation and have thus far been studied mainly with respect to their local synaptic interactions within the cortical microcircuitry. A recent study showed that long-range excitatory connections onto Martinotti cells (MC) mediate surround suppression. Here we have extended our previously reported attractor network of pyramidal cells (PC) and MC by introducing long-range connections targeting MC. We have demonstrated how the network with Martinotti cell-mediated long-range inhibition gives rise to surround suppression and also promotes saliency of locations at which simple non-uniformities in the stimulus field are introduced. Furthermore, our analysis suggests that the presynaptic dynamics of MC is only ancillary to its orientation tuning property in enabling the network with saliency detection. Lastly, we have also implemented a disinhibitory pathway mediated by another interneuron type (VIP interneurons), which inhibits MC and abolishes surround suppression. PMID:26528143

  7. Contrast-Dependence of Surround Suppression in Macaque V1: Experimental Testing of a Recurrent Network Model

    PubMed Central

    Schwabe, Lars; Ichida, Jennifer M.; Shushruth, S.; Mangapathy, Pradeep; Angelucci, Alessandra

    2010-01-01

    Neuronal responses in primary visual cortex (V1) to optimally oriented high-contrast stimuli in the receptive field (RF) center are suppressed by stimuli in the RF surround, but can be facilitated when the RF center is stimulated at low contrast. The neural circuits and mechanisms for surround modulation are still unknown. We previously proposed that topdown feedback connections mediate suppression from the “far” surround, while “near” surround suppression is mediated primarily by horizontal connections. We implemented this idea in a recurrent network model of V1. A model assumption needed to account for the contrast-dependent sign of surround modulation is a response asymmetry between excitation and inhibition; accordingly, inhibition, but not excitation, is silent for weak visual inputs to the RF center, and surround stimulation can evoke facilitation. A prediction stemming from this same assumption is that surround suppression is weaker for low than for high contrast stimuli in the RF center. Previous studies are inconsistent with this prediction. Using single unit recordings in macaque V1, we confirm this model's prediction. Model simulations demonstrate that our results can be reconciled with those from previous studies. We also performed a systematic comparison of the experimentally-measured surround suppression strength with predictions of the model operated in different parameter regimes. We find that the original model, with strong horizontal and no feedback excitation of local inhibitory neurons, can only partially account quantitatively for the experimentally-measured suppression. Strong direct feedback excitation of V1 inhibitory neurons is necessary to account for the experimentally-measured surround suppression strength. PMID:20079853

  8. Coevolution of cooperation and network structure under natural selection

    NASA Astrophysics Data System (ADS)

    Yang, D.-P.; Lin, H.; Shuai, J. W.

    2011-02-01

    A coevolution model by coupling mortality and fertility selection is introduced to investigate the evolution of cooperation and network structure in the prisoner's dilemma game. The cooperation level goes through a continuous phase transition vs. defection temptation b for low mortality selection intensity β and through a discontinuous one for infinite β. The cooperation level is enhanced most at β≈1 for any b. The local and global properties of the network structure, such as cluster and cooperating k-core, are investigated for the understanding of cooperation evolution. Cooperation is promoted by forming a tight cooperating k-core at moderate β, but too large β will destroy the cooperating k-core rapidly resulting in a rapid drop of the cooperation level. Importantly, the infinite β changes the normalized sucker's payoff S from 0 to 1-b and its dynamics of the cooperation level undergoes a very slow power-law decay, which leads the evolution into the regime of neutral evolution.

  9. Caenorhabditis elegans neuron degeneration and mitochondrial suppression caused by selected environmental chemicals.

    PubMed

    Zhou, Shaoyu; Wang, Zemin; Klaunig, James E

    2013-01-01

    Mitochondrial alterations have been documented for many years in the brains of Parkinson's disease (PD), a disorder that is characterized by the selective loss of dopamine neurons. Recent studies have demonstrated that Parkinson's disease-associated proteins are either present in mitochondria or translocated into mitochondria in response to stress, further reinforcing the importance of the mitochondrial function in the pathogenesis of Parkinson's disease. Exposure to environmental chemicals such as pesticides and heavy metals has been suggested as risk factors in the development of Parkinson's disease. It has been reported that a number of environmental agents including tobacco smoke and perfluorinated compounds, pesticides, as well as metals (Mn(2+) and Pb(2+)) modulate mitochondrial function. However the exact mechanism of mitochondrial alteration has not been defined in the context of the development and progression of Parkinson's disease. The complexity of the mammalian system has made it difficult to dissect the molecular components involved in the pathogenesis of Parkinson's disease. In the present study we used the nematode Caenorhabditis elegans (C. elegans) model of neuron degeneration and investigated the effect of environmental chemicals on mitochondrial biogenesis and mitochondrial gene regulation. Chronic exposure to low concentration (2 or 4 μM) of pesticide rotenone, resulted in significant loss of dopamine neuron in C. elegans, a classic feature of Parkinson's disease. We then determined if the rotenone-induced neuron degeneration is accompanied by a change in mitochondria biogenesis. Analysis of mitochondrial genomic replication by quantitative PCR showed a dramatic decrease in mitochondrial DNA (mtDNA) copies of rotenone-treated C. elegans compared to control. This decreased mitochondrial biogenesis occurred prior to the development of loss of dopamine neurons, and was persistent. The inhibition of mtDNA replication was also found in C. elegans

  10. Joint Network Selection and Discrete Power Control in Heterogeneous MIMO Networks: A Game Theoretical Approach

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Tian, Hua; Xie, Wei; Zhong, Wei

    2013-09-01

    Next-generation wireless networks will integrate multiple wireless access technologies and the users will access the network using one of several available radio access technologies. In this paper, we study the spectrum access problem in heterogeneous multipleinput multiple-output (MIMO) networks through a game theoretic approach. The spectrum access problem in the considered system model is defined as joint network selection and discrete power control. We formulate the problem as a noncooperative game where the players are the multi-mode terminals and. The proposed common utility function takes both transmission rate and the power consumption into account. This game is shown to be a potential game which possess at least one pure strategy Nash equilibrium (NE) and the optimal strategy profile which maximizes the total energy efficiency of the heterogeneous MIMO network constitutes a pure strategy NE of our proposed game. Furthermore, we prove that the price of anarchy of the proposed game is equal to 1. In order to achieve the pure strategy NE, we design an iterative spectrum access algorithm. The convergence and the complexity of our designed algorithm is discussed. It is shown that the designed algorithm can achieve optimal performance with low complexity.

  11. Escherichia coli persister cells suppress translation by selectively disassembling and degrading their ribosomes.

    PubMed

    Cho, Junho; Rogers, Janet; Kearns, Mark; Leslie, Macall; Hartson, Steven D; Wilson, Kevin S

    2015-01-01

    Bacterial persisters are rare, phenotypically distinct cells that survive exposure to multiple antibiotics. Previous studies indicated that formation and maintenance of the persister phenotype are regulated by suppressing translation. To examine the mechanism of this translational suppression, we developed novel methodology to rapidly purify ribosome complexes from persister cells. We purified His-tagged ribosomes from Escherichia coli cells that over-expressed HipA protein, which induces persister formation, and were treated with ampicillin to remove antibiotic-sensitive cells. We profiled ribosome complexes and analyzed the ribosomal RNA and protein components from these persister cells. Our results show that (i) ribosomes in persisters exist largely as inactive ribosomal subunits, (ii) rRNAs and tRNAs are mostly degraded and (iii) a small fraction of the ribosomes remain mostly intact, except for reduced amounts of seven ribosomal proteins. Our findings explain the basis for translational suppression in persisters and suggest how persisters survive exposure to multiple antibiotics.

  12. Effect of selective suppression of spatial frequency domain noise on visual detection of a sample object in an inhomogeneous background

    NASA Astrophysics Data System (ADS)

    Pietrzyk, Mariusz W.; McDonald, J. Scott; Brennan, Patrick C.; Bourne, Roger M.

    2012-02-01

    This study aims to investigate the effect of selective suppression of spatial frequency (SF) domain Gaussian white noise on visibility of a sample object in inhomogeneous backgrounds. SF-specific variation in signal-to-noise ratio due to selective signal averaging in the SF domain is a consequence of some of MRI acquisition methods. This study models the potential effect on visibility of an object in a complex image. A single disc was randomly positioned in 25 of 50 synthetic clustered lumpy background images. Neutral, low mid and high frequency suppressed Gaussian white noise was added in the frequency domain to simulate SF-weighted MRI signal averaging. Twelve readers performed visual searching and localization tasks on ordered sets. Subjects were asked to detect and locate discs and to rank confidence level. Sensitivity, specificity and ROC analyses were performed. Readers achieved significantly higher ROC AUC - Azscores - (p<0.001) and case-based sensitivity (p<0.001) and target-based sensitivity (p<0.001) with images in which low SF noise was suppressed. Also, significant higher cased-based sensitivity (p=0.005), target-based sensitivity (p=0.022) and Az-values (p=0.01) were scored under mid SF noise filtration. No significant differences were observed when images with SF-neutral noise suppression were compared with high SF noise suppression. In conclusion, increase of low and also mid SF signal signal-to-noise ratio significantly improves human performance in visual detection of simple targets in inhomogeneous backgrounds and suggests that a low SF bias in MRI signal averaging may enhance diagnostic quality.

  13. A new bio-inspired stimulator to suppress hyper-synchronized neural firing in a cortical network.

    PubMed

    Amiri, Masoud; Amiri, Mahmood; Nazari, Soheila; Faez, Karim

    2016-12-07

    Hyper-synchronous neural oscillations are the character of several neurological diseases such as epilepsy. On the other hand, glial cells and particularly astrocytes can influence neural synchronization. Therefore, based on the recent researches, a new bio-inspired stimulator is proposed which basically is a dynamical model of the astrocyte biophysical model. The performance of the new stimulator is investigated on a large-scale, cortical network. Both excitatory and inhibitory synapses are also considered in the simulated spiking neural network. The simulation results show that the new stimulator has a good performance and is able to reduce recurrent abnormal excitability which in turn avoids the hyper-synchronous neural firing in the spiking neural network. In this way, the proposed stimulator has a demand controlled characteristic and is a good candidate for deep brain stimulation (DBS) technique to successfully suppress the neural hyper-synchronization.

  14. Reflexive and preparatory selection and suppression of salient information in the right and left posterior parietal cortex.

    PubMed

    Mevorach, Carmel; Humphreys, Glyn W; Shalev, Lilach

    2009-06-01

    Attentional cues can trigger activity in the parietal cortex in anticipation of visual displays, and this activity may, in turn, induce changes in other areas of the visual cortex, hence, implementing attentional selection. In a recent TMS study [Mevorach, C., Humphreys, G. W., & Shalev, L. Opposite biases in salience-based selection for the left and right posterior parietal cortex. Nature Neuroscience, 9, 740-742, 2006b], it was shown that the posterior parietal cortex (PPC) can utilize the relative saliency (a nonspatial property) of a target and a distractor to bias visual selection. Furthermore, selection was lateralized so that the right PPC is engaged when salient information must be selected and the left PPC when the salient information must be ignored. However, it is not clear how the PPC implements these complementary forms of selection. Here we used on-line triple-pulse TMS over the right or left PPC prior to or after the onset of global/local displays. When delivered after the onset of the display, TMS to the right PPC disrupted the selection of the more salient aspect of the hierarchical letter. In contrast, left PPC TMS delivered prior to the onset of the stimulus disrupted responses to the lower saliency stimulus. These findings suggest that selection and suppression of saliency, rather than being "two sides of the same coin," are fundamentally different processes. Selection of saliency seems to operate reflexively, whereas suppression of saliency relies on a preparatory phase that "sets up" the system in order to effectively ignore saliency.

  15. Optimal experiment design for model selection in biochemical networks

    PubMed Central

    2014-01-01

    Background Mathematical modeling is often used to formalize hypotheses on how a biochemical network operates by discriminating between competing models. Bayesian model selection offers a way to determine the amount of evidence that data provides to support one model over the other while favoring simple models. In practice, the amount of experimental data is often insufficient to make a clear distinction between competing models. Often one would like to perform a new experiment which would discriminate between competing hypotheses. Results We developed a novel method to perform Optimal Experiment Design to predict which experiments would most effectively allow model selection. A Bayesian approach is applied to infer model parameter distributions. These distributions are sampled and used to simulate from multivariate predictive densities. The method is based on a k-Nearest Neighbor estimate of the Jensen Shannon divergence between the multivariate predictive densities of competing models. Conclusions We show that the method successfully uses predictive differences to enable model selection by applying it to several test cases. Because the design criterion is based on predictive distributions, which can be computed for a wide range of model quantities, the approach is very flexible. The method reveals specific combinations of experiments which improve discriminability even in cases where data is scarce. The proposed approach can be used in conjunction with existing Bayesian methodologies where (approximate) posteriors have been determined, making use of relations that exist within the inferred posteriors. PMID:24555498

  16. Brain networks supporting perceptual grouping and contour selection.

    PubMed

    Volberg, Gregor; Greenlee, Mark W

    2014-01-01

    The human visual system groups local elements into global objects seemingly without effort. Using a contour integration task and EEG source level analyses, we tested the hypothesis that perceptual grouping requires a top-down selection, rather than a passive pooling, of neural information that codes local elements in the visual image. The participants were presented visual displays with or without a hidden contour. Two tasks were performed: a central luminance-change detection task and a peripheral contour detection task. Only in the contour-detection task could we find differential brain activity between contour and non-contour conditions, within a distributed brain network including parietal, lateral occipital and primary visual areas. Contour processing was associated with an inflow of information from lateral occipital into primary visual regions, as revealed from the slope of phase differences between source level oscillations within these areas. The findings suggest that contour integration results from a selection of neural information from lower visual areas, and that this selection is driven by the lateral occipital cortex.

  17. Neural network feature selection for breast cancer diagnosis

    NASA Astrophysics Data System (ADS)

    Kocur, Catherine M.; Rogers, Steven K.; Bauer, Kenneth W., Jr.; Steppe, Jean M.; Hoffmeister, Jeffrey W.

    1995-04-01

    More than 50 million women over the age of 40 are currently at risk for breast cancer in the United States. Computer-aided diagnosis, as a second opinion to radiologists, will aid in decreasing the number of false readings of mammograms. Neural network benefits are exploited at both the classification and feature selection stages in the development of a computer-aided breast cancer diagnostic system. The multilayer perceptron is used to classify and contrast three features (angular second moment, eigenmasses, and wavelets) developed to distinguish benign from malignant lesion in a database of 94 difficult-to-diagnose digitized microcalcification cases. System performance of 74 percent correct classifications is achieved. Feature selection techniques are presented which further improve performance. Neural and decision boundary-based methods are implemented, compared, and validated to isolate and remove useless features. The contribution from this analysis is an increase to 88 percent correct classification in system performance. These feature selection techniques can also process risk factor data.

  18. Orientation selective neural network for cosmic muon identification

    NASA Astrophysics Data System (ADS)

    Abramowicz, Halina; Horn, David; Naftaly, Ury; Sahar-Pikielny, Carmit

    1997-02-01

    We discuss a novel method for identification of a linear pattern of pixels on a two-dimensional grid. Motivated by principles employed by the visual cortex, we construct orientation selective neurons in a neural network that performs this task. The method is then applied to a sample of data collected with the ZEUS detector at HERA in order to identify cosmic muons that leave a linear pattern of signals in the segmented uranium-scintillator calorimeter. A two dimensional representation of the relevant part of the detector is used. The algorithm performs well in the presence of noise and pixels with limited efficiency. Given its architecture, this system becomes a good candidate for fast pattern recognition in parallel processing devices.

  19. Social selection and peer influence in an online social network

    PubMed Central

    Lewis, Kevin; Gonzalez, Marco; Kaufman, Jason

    2012-01-01

    Disentangling the effects of selection and influence is one of social science's greatest unsolved puzzles: Do people befriend others who are similar to them, or do they become more similar to their friends over time? Recent advances in stochastic actor-based modeling, combined with self-reported data on a popular online social network site, allow us to address this question with a greater degree of precision than has heretofore been possible. Using data on the Facebook activity of a cohort of college students over 4 years, we find that students who share certain tastes in music and in movies, but not in books, are significantly likely to befriend one another. Meanwhile, we find little evidence for the diffusion of tastes among Facebook friends—except for tastes in classical/jazz music. These findings shed light on the mechanisms responsible for observed network homogeneity; provide a statistically rigorous assessment of the coevolution of cultural tastes and social relationships; and suggest important qualifications to our understanding of both homophily and contagion as generic social processes. PMID:22184242

  20. Social selection and peer influence in an online social network.

    PubMed

    Lewis, Kevin; Gonzalez, Marco; Kaufman, Jason

    2012-01-03

    Disentangling the effects of selection and influence is one of social science's greatest unsolved puzzles: Do people befriend others who are similar to them, or do they become more similar to their friends over time? Recent advances in stochastic actor-based modeling, combined with self-reported data on a popular online social network site, allow us to address this question with a greater degree of precision than has heretofore been possible. Using data on the Facebook activity of a cohort of college students over 4 years, we find that students who share certain tastes in music and in movies, but not in books, are significantly likely to befriend one another. Meanwhile, we find little evidence for the diffusion of tastes among Facebook friends-except for tastes in classical/jazz music. These findings shed light on the mechanisms responsible for observed network homogeneity; provide a statistically rigorous assessment of the coevolution of cultural tastes and social relationships; and suggest important qualifications to our understanding of both homophily and contagion as generic social processes.

  1. Selective suppression of adipose tissue apoE expression impacts systemic metabolic phenotype and adipose tissue inflammation.

    PubMed

    Huang, Zhi H; Reardon, Catherine A; Getz, Godfrey S; Maeda, Nobuyo; Mazzone, Theodore

    2015-02-01

    apoE is a multi-functional protein expressed in several cell types and in several organs. It is highly expressed in adipose tissue, where it is important for modulating adipocyte lipid flux and gene expression in isolated adipocytes. In order to investigate a potential systemic role for apoE that is produced in adipose tissue, mice were generated with selective suppression of adipose tissue apoE expression and normal circulating apoE levels. These mice had less adipose tissue with smaller adipocytes containing fewer lipids, but no change in adipocyte number compared with control mice. Adipocyte TG synthesis in the presence of apoE-containing VLDL was markedly impaired. Adipocyte caveolin and leptin gene expression were reduced, but adiponectin, PGC-1, and CPT-1 gene expression were increased. Mice with selective suppression of adipose tissue apoE had lower fasting lipid, insulin, and glucose levels, and glucose and insulin tolerance tests were consistent with increased insulin sensitivity. Lipid storage in muscle, heart, and liver was significantly reduced. Adipose tissue macrophage inflammatory activation was markedly diminished with suppression of adipose tissue apoE expression. Our results establish a novel effect of adipose tissue apoE expression, distinct from circulating apoE, on systemic substrate metabolism and adipose tissue inflammatory state. Copyright © 2015 by the American Society for Biochemistry and Molecular Biology, Inc.

  2. Proton echo-planar spectroscopic imaging with highly effective outer volume suppression using combined presaturation and spatially selective echo dephasing.

    PubMed

    Chu, Archie; Alger, Jeffry R; Moore, Gregory J; Posse, Stefan

    2003-05-01

    A highly effective outer volume suppression (OVS) technique, termed spatially selective echo dephasing (SSED), which employs gradient dephasing of spatially selective spin echoes, is introduced. SSED, which is relatively insensitive to T(1) dispersion among lipid signals and B(1) inhomogeneity, was integrated with very high spatial resolution 2D proton echo-planar spectroscopic imaging (PEPSI) to assess residual lipid bleeding into cortical regions in the human brain. The method was optimized to minimize signal refocusing of secondary spin-echoes in areas of overlapping suppression slices. A comparison of spatial presaturation with single or double SSED, and with combined presaturation and SSED shows that the latter method has superior performance with spatially uniform lipid suppression factors in excess of 70. Metabolite mapping (choline, creatine, and NAA) with a 64 x 64 spatial matrix and 0.3 cm(3) voxels in close proximity to peripheral lipid regions was demonstrated at 1.5 T with a scan time of 32 min using the standard head coil.

  3. Selective slow wave sleep but not rapid eye movement sleep suppression impairs morning glucose tolerance in healthy men.

    PubMed

    Herzog, Nina; Jauch-Chara, Kamila; Hyzy, Franziska; Richter, Annekatrin; Friedrich, Alexia; Benedict, Christian; Oltmanns, Kerstin M

    2013-10-01

    Shortened nocturnal sleep impairs morning glucose tolerance. The underlying mechanism of this effect is supposed to involve a reduced fraction of slow wave sleep (SWS). However, it remains unanswered if impaired glucose tolerance occurs due to specific SWS reduction or a general disturbance of sleep. Sixteen healthy men participated in three experimental conditions in a crossover design: SWS suppression, rapid eye movement (REM)-sleep disturbance, and regular sleep. Selective sleep stage disturbance was performed by means of an acoustic tone (532Hz) with gradually rising sound intensity. Blood concentrations of glucoregulatory parameters were measured upon an oral glucose tolerance test the next morning. Our data show that morning plasma glucose and serum insulin responses were significantly increased after selective SWS suppression. Moreover, SWS suppression reduced postprandial insulin sensitivity up to 20%, as determined by Matsuda Index. Contrastingly, disturbed REM-sleep did not affect glucose homeostasis. We conclude that specifically SWS reduction is critically involved in the impairment of glucose tolerance associated with disturbed sleep. Therefore, glucose metabolism in subjects predisposed to reduced SWS (e.g. depression, aging, obstructive sleep apnea, pharmacological treatment) should be thoroughly monitored.

  4. Suppression of Hydroxycinnamate Network Formation in Cell Walls of Rice Shoots Grown under Microgravity Conditions in Space.

    PubMed

    Wakabayashi, Kazuyuki; Soga, Kouichi; Hoson, Takayuki; Kotake, Toshihisa; Yamazaki, Takashi; Higashibata, Akira; Ishioka, Noriaki; Shimazu, Toru; Fukui, Keiji; Osada, Ikuko; Kasahara, Haruo; Kamada, Motoshi

    2015-01-01

    Network structures created by hydroxycinnamate cross-links within the cell wall architecture of gramineous plants make the cell wall resistant to the gravitational force of the earth. In this study, the effects of microgravity on the formation of cell wall-bound hydroxycinnamates were examined using etiolated rice shoots simultaneously grown under artificial 1 g and microgravity conditions in the Cell Biology Experiment Facility on the International Space Station. Measurement of the mechanical properties of cell walls showed that shoot cell walls became stiff during the growth period and that microgravity suppressed this stiffening. Amounts of cell wall polysaccharides, cell wall-bound phenolic acids, and lignin in rice shoots increased as the shoot grew. Microgravity did not influence changes in the amounts of cell wall polysaccharides or phenolic acid monomers such as ferulic acid (FA) and p-coumaric acid, but it suppressed increases in diferulic acid (DFA) isomers and lignin. Activities of the enzymes phenylalanine ammonia-lyase (PAL) and cell wall-bound peroxidase (CW-PRX) in shoots also increased as the shoot grew. PAL activity in microgravity-grown shoots was almost comparable to that in artificial 1 g-grown shoots, while CW-PRX activity increased less in microgravity-grown shoots than in artificial 1 g-grown shoots. Furthermore, the increases in expression levels of some class III peroxidase genes were reduced under microgravity conditions. These results suggest that a microgravity environment modifies the expression levels of certain class III peroxidase genes in rice shoots, that the resultant reduction of CW-PRX activity may be involved in suppressing DFA formation and lignin polymerization, and that this suppression may cause a decrease in cross-linkages within the cell wall architecture. The reduction in intra-network structures may contribute to keeping the cell wall loose under microgravity conditions.

  5. Suppression of Hydroxycinnamate Network Formation in Cell Walls of Rice Shoots Grown under Microgravity Conditions in Space

    PubMed Central

    Wakabayashi, Kazuyuki; Soga, Kouichi; Hoson, Takayuki; Kotake, Toshihisa; Yamazaki, Takashi; Higashibata, Akira; Ishioka, Noriaki; Shimazu, Toru; Fukui, Keiji; Osada, Ikuko; Kasahara, Haruo; Kamada, Motoshi

    2015-01-01

    Network structures created by hydroxycinnamate cross-links within the cell wall architecture of gramineous plants make the cell wall resistant to the gravitational force of the earth. In this study, the effects of microgravity on the formation of cell wall-bound hydroxycinnamates were examined using etiolated rice shoots simultaneously grown under artificial 1 g and microgravity conditions in the Cell Biology Experiment Facility on the International Space Station. Measurement of the mechanical properties of cell walls showed that shoot cell walls became stiff during the growth period and that microgravity suppressed this stiffening. Amounts of cell wall polysaccharides, cell wall-bound phenolic acids, and lignin in rice shoots increased as the shoot grew. Microgravity did not influence changes in the amounts of cell wall polysaccharides or phenolic acid monomers such as ferulic acid (FA) and p-coumaric acid, but it suppressed increases in diferulic acid (DFA) isomers and lignin. Activities of the enzymes phenylalanine ammonia-lyase (PAL) and cell wall-bound peroxidase (CW-PRX) in shoots also increased as the shoot grew. PAL activity in microgravity-grown shoots was almost comparable to that in artificial 1 g-grown shoots, while CW-PRX activity increased less in microgravity-grown shoots than in artificial 1 g-grown shoots. Furthermore, the increases in expression levels of some class III peroxidase genes were reduced under microgravity conditions. These results suggest that a microgravity environment modifies the expression levels of certain class III peroxidase genes in rice shoots, that the resultant reduction of CW-PRX activity may be involved in suppressing DFA formation and lignin polymerization, and that this suppression may cause a decrease in cross-linkages within the cell wall architecture. The reduction in intra-network structures may contribute to keeping the cell wall loose under microgravity conditions. PMID:26378793

  6. Insect herbivores selectively suppress the HPL branch of the oxylipin pathway in host plants.

    PubMed

    Savchenko, Tatyana; Pearse, Ian S; Ignatia, Laura; Karban, Richard; Dehesh, Katayoon

    2013-02-01

    Insect herbivores have developed a myriad of strategies to manipulate the defense responses of their host plants. Here we provide evidence that chewing insects differentially alter the oxylipin profiles produced by the two main and competing branches of the plant defensive response pathway, the allene oxide synthase (AOS) and hydroperoxide lyase (HPL) branches, which are responsible for wound-inducible production of jasmonates (JAs), and green leafy volatiles (GLVs) respectively. Specifically, we used three Arabidopsis genotypes that were damaged by mechanical wounding or by insects of various feeding guilds (piercing aphids, generalist chewing caterpillars and specialist chewing caterpillars). We established that emission of GLVs is stimulated by wounding incurred mechanically or by aphids, but release of these volatiles is constitutively impaired by both generalist and specialist chewing insects. Simultaneously, however, these chewing herbivores stimulated JA production, demonstrating targeted insect suppression of the HPL branch of the oxylipin pathway. Use of lines engineered to express HPL constitutively, in conjunction with quantitative RT-PCR-based expression analyses, established a combination of transcriptional and post-transcriptional reprogramming of the HPL pathway genes as the mechanistic basis of insect-mediated suppression of the corresponding metabolites. Feeding studies suggested a potential evolutionary advantage of suppressing GLV production, as caterpillars preferably consumed leaf tissue from plants that had not been primed by these volatile cues.

  7. Enabling Interoperable and Selective Data Sharing among Social Networking Sites

    NASA Astrophysics Data System (ADS)

    Shin, Dongwan; Lopes, Rodrigo

    With the widespread use of social networking (SN) sites and even introduction of a social component in non-social oriented services, there is a growing concern over user privacy in general, how to handle and share user profiles across SN sites in particular. Although there have been several proprietary or open source-based approaches to unifying the creation of third party applications, the availability and retrieval of user profile information are still limited to the site where the third party application is run, mostly devoid of the support for data interoperability. In this paper we propose an approach to enabling interopearable and selective data sharing among SN sites. To support selective data sharing, we discuss an authenticated dictionary (ADT)-based credential which enables a user to share only a subset of her information certified by external SN sites with applications running on an SN site. For interoperable data sharing, we propose an extension to the OpenSocial API so that it can provide an open source-based framework for allowing the ADT-based credential to be used seamlessly among different SN sites.

  8. Image-processing technique for suppressing ribs in chest radiographs by means of massive training artificial neural network (MTANN).

    PubMed

    Suzuki, Kenji; Abe, Hiroyuki; MacMahon, Heber; Doi, Kunio

    2006-04-01

    When lung nodules overlap with ribs or clavicles in chest radiographs, it can be difficult for radiologists as well as computer-aided diagnostic (CAD) schemes to detect these nodules. In this paper, we developed an image-processing technique for suppressing the contrast of ribs and clavicles in chest radiographs by means of a multiresolution massive training artificial neural network (MTANN). An MTANN is a highly nonlinear filter that can be trained by use of input chest radiographs and the corresponding "teaching" images. We employed "bone" images obtained by use of a dual-energy subtraction technique as the teaching images. For effective suppression of ribs having various spatial frequencies, we developed a multiresolution MTANN consisting of multiresolution decomposition/composition techniques and three MTANNs for three different-resolution images. After training with input chest radiographs and the corresponding dual-energy bone images, the multiresolution MTANN was able to provide "bone-image-like" images which were similar to the teaching bone images. By subtracting the bone-image-like images from the corresponding chest radiographs, we were able to produce "soft-tissue-image-like" images where ribs and clavicles were substantially suppressed. We used a validation test database consisting of 118 chest radiographs with pulmonary nodules and an independent test database consisting of 136 digitized screen-film chest radiographs with 136 solitary pulmonary nodules collected from 14 medical institutions in this study. When our technique was applied to nontraining chest radiographs, ribs and clavicles in the chest radiographs were suppressed substantially, while the visibility of nodules and lung vessels was maintained. Thus, our image-processing technique for rib suppression by means of a multiresolution MTANN would be potentially useful for radiologists as well as for CAD schemes in detection of lung nodules on chest radiographs.

  9. A genetic network that suppresses genome rearrangements in Saccharomyces cerevisiae and contains defects in cancers

    PubMed Central

    Putnam, Christopher D.; Srivatsan, Anjana; Nene, Rahul V.; Martinez, Sandra L.; Clotfelter, Sarah P.; Bell, Sara N.; Somach, Steven B.; E.S. de Souza, Jorge; Fonseca, André F.; de Souza, Sandro J.; Kolodner, Richard D.

    2016-01-01

    Gross chromosomal rearrangements (GCRs) play an important role in human diseases, including cancer. The identity of all Genome Instability Suppressing (GIS) genes is not currently known. Here multiple Saccharomyces cerevisiae GCR assays and query mutations were crossed into arrays of mutants to identify progeny with increased GCR rates. One hundred eighty two GIS genes were identified that suppressed GCR formation. Another 438 cooperatively acting GIS genes were identified that were not GIS genes, but suppressed the increased genome instability caused by individual query mutations. Analysis of TCGA data using the human genes predicted to act in GIS pathways revealed that a minimum of 93% of ovarian and 66% of colorectal cancer cases had defects affecting one or more predicted GIS gene. These defects included loss-of-function mutations, copy-number changes associated with reduced expression, and silencing. In contrast, acute myeloid leukaemia cases did not appear to have defects affecting the predicted GIS genes. PMID:27071721

  10. Narrow-band injection seeding of a terahertz frequency quantum cascade laser: Selection and suppression of longitudinal modes

    SciTech Connect

    Nong, Hanond Markmann, Sergej; Hekmat, Negar; Jukam, Nathan; Pal, Shovon; Mohandas, Reshma A.; Dean, Paul; Li, Lianhe; Linfield, Edmund H.; Giles Davies, A.; Wieck, Andreas D.

    2014-09-15

    A periodically poled lithium niobate (PPLN) crystal with multiple poling periods is used to generate tunable narrow-bandwidth THz pulses for injection seeding a quantum cascade laser (QCL). We demonstrate that longitudinal modes of the quantum cascade laser close to the gain maximum can be selected or suppressed according to the seed spectrum. The QCL emission spectra obtained by electro-optic sampling from the quantum cascade laser, in the most favorable case, shows high selectivity and amplification of the longitudinal modes that overlap the frequency of the narrow-band seed. Proper selection of the narrow-band THz seed from the PPLN crystal discretely tunes the longitudinal mode emission of the quantum cascade laser. Moreover, the THz wave build-up within the laser cavity is studied as a function of the round-trip time. When the seed frequency is outside the maximum of the gain spectrum the laser emission shifts to the preferential longitudinal mode.

  11. Optimal weighting scheme for suppressing cascades and traffic congestion in complex networks.

    PubMed

    Yang, Rui; Wang, Wen-Xu; Lai, Ying-Cheng; Chen, Guanrong

    2009-02-01

    This paper is motivated by the following two related problems in complex networks: (i) control of cascading failures and (ii) mitigation of traffic congestion. Both problems are of significant recent interest as they address, respectively, the security of and efficient information transmission on complex networks. Taking into account typical features of load distribution and weights in real-world networks, we have discovered an optimal solution to both problems. In particular, we shall provide numerical evidence and theoretical analysis that, by choosing a proper weighting parameter, a maximum level of robustness against cascades and traffic congestion can be achieved, which practically rids the network of occurrences of the catastrophic dynamics.

  12. Suppression of the contrast of ribs in chest radiographs by means of massive training artificial neural network

    NASA Astrophysics Data System (ADS)

    Suzuki, Kenji; Abe, Hiroyuki; Li, Feng; Doi, Kunio

    2004-05-01

    We developed a method for suppression of the contrast of ribs in chest radiographs by means of a massive training artificial neural network (MTANN). The MTANN is a trainable highly nonlinear filter that can be trained by using input chest radiographs and the corresponding teacher images. We used either the soft-tissue image or the bone image obtained by use of a dual-energy subtraction technique as the teacher image for suppression of ribs in chest radiographs. When the soft-tissue images were used as the teacher images, the MTANN directly produced a "soft-tissue-image-like" image where the contrast of ribs was suppressed. When the bone images were used as the teacher images, the MTANN was able to produce a "bone-image-like" image, and then was subtracted from the corresponding chest radiograph to produce a bone-subtracted image where ribs are suppressed. Thus, the two kinds of rib-suppressed images, i.e., the soft-tissue-image-like image and the bone-subtracted image, could be produced by use of the MTANNs trained with two different teacher images. We applied each of the two trained MTANNs to non-training chest radiographs to investigate the difference between the processed images. The results showed that the contrast of ribs in chest radiographs almost disappeared, and was reduced to less than 10% in both processed images. The contrast of ribs was reduced slightly better in the soft-tissue-image-like images than in the bone-subtracted images, whereas soft-tissue opacities such as lung vessels and nodules were maintained better in the bone-subtracted images. Therefore, the use of the bone images as the teacher images for training the MTANN has produced better rib-suppressed images where soft-tissue opacities were substantially maintained. A method for rib suppression using the MTANN would be useful for radiologists as well as CAD schemes in detection of lung diseases such as nodules in chest radiographs.

  13. Centrally controlled self-healing wavelength division multiplexing passive optical network based on optical carrier suppression technique

    NASA Astrophysics Data System (ADS)

    Zhu, Min; Zhang, Jiao; Sun, Xiaohan

    2015-12-01

    We proposed and demonstrated a centrally controlled and self-healing wavelength division multiplexing passive optical network with colorless optical network units (ONUs) based on optical carrier suppression technique. By switching the affected data in the OCS signal sideband to an alternate protection path, only one optical switch is provisioned at the optical line terminal, which is controlled by a logic control circuit upon monitoring of power outage on the working path. The proposed scheme can reliably protect against both distribution and feeder fiber failures. Moreover, gain-saturated reflective semiconductor optical amplifiers are used as colorless transmitters in ONUs. The protection scheme feasibility and system performances are experimentally verified with 10 Gb/s downstream and 1.25 Gb/s upstream data in both working and protection modes. The protection switching time was measured to be around 1 ms.

  14. Selective enhancement and suppression of frog gustatory responses to amino acids

    PubMed Central

    1981-01-01

    Properties of the receptor sites for L-amino acids in taste cells of the bullfrog (Rana catesbeiana) were examined by measuring the neural activities of the glossopharyngeal nerve under various conditions. (a) The frogs responded to 12 amino acids, but the responses to the amino acids varied with individual frogs under natural conditions. The frog tongues, however, exhibited similar responses after an alkaline treatment that removes Ca2+ from the tissue. The variation in the responses under natural conditions was apparently due to the variation in the amount of Ca2+ bound to the receptor membrane. (b) The responses to hydrophilic L-amino acids (glycine, L-alanine, L-serine, L- threonine, L-cysteine, and L-proline) were of a tonic type, but those to hydrophobic L-amino acids (L-valine, L-leucine, L-isoleucine, L- methionine, L-phenylalanine, and L-tyrptophan) were usually composed of both phasic and tonic components. (c) The properties of the tonic component were quite different from those of the phasic component: the tonic component was largely enhanced by the alkaline treatment and suppressed by the acidic treatment that increases binding of Ca2+ to the tissue. Also, the tonic component was suppressed by the presence of low concentrations of salts, or the action of pronase E, whereas the phasic component was unchanged under these conditions. These properties of the phasic component were quite similar to those of the response to hydrophobic substances such as quinine. These results suggest that the hydrophilic L-amino acids stimulate receptor protein(s) and that the hydrophobic L-amino acids stimulate both the receptor protein and a receptor site similar to that for quinine. (d) On the basis of the suppression of the responses to amino acids by salts, the mechanism of generation of the receptor potential is discussed. PMID:6972437

  15. Alpha 1-adrenergic agonists selectively suppress voltage-dependent K+ current in rat ventricular myocytes.

    PubMed Central

    Apkon, M; Nerbonne, J M

    1988-01-01

    The effects of alpha 1-adrenergic agonists on the waveforms of action potentials and voltage-gated ionic currents were examined in isolated adult rat ventricular myocytes by the whole-cell patch-clamp recording technique. After "puffer" applications of either of two alpha 1 agonists, phenylephrine and methoxamine, action-potential durations were increased. In voltage-clamped cells, phenylephrine (5-20 microM) or methoxamine (5-10 microM) reduced the amplitudes of Ca2+-independent voltage-activated outward K+ currents (Iout); neither the kinetics nor the voltage-dependent properties of Iout were significantly affected. The effects of phenylephrine or methoxamine on Iout were larger and longer-lasting at higher concentrations and after prolonged or repeated exposures; in all experiments, however, Iout recovered completely when puffer applications were discontinued. The suppression of Iout is attributed to the activation of alpha 1-adrenergic receptors, as neither beta- nor alpha 2-adrenergic agonists had measurable effects on Iout; in addition, the effect of phenylephrine was attenuated in the presence of the alpha antagonist phentolamine (10 microM), but not in the presence of the beta antagonist propranolol (10 microM). Voltage-gated Ca2+ currents, in contrast, were not altered measurably by phenylephrine or methoxamine and no currents were activated directly by these agents. Suppression of Iout was also observed during puffer applications of either of two protein kinase C activators, phorbol 12-myristate 13-acetate (10 nM-1 microM) and 1-oleoyl-2-acetylglycerol (60 microM). We conclude that the activation of alpha 1-adrenergic receptors in adult rat ventricular myocytes leads to action-potential prolongation as a result of the specific suppression of Iout and that this effect may be mediated by activation of protein kinase C. PMID:2903506

  16. Thiol-Based Potent and Selective HDAC6 Inhibitors Promote Tubulin Acetylation and T-Regulatory Cell Suppressive Function.

    PubMed

    Segretti, Mariana C F; Vallerini, Gian Paolo; Brochier, Camille; Langley, Brett; Wang, Liqing; Hancock, Wayne W; Kozikowski, Alan P

    2015-11-12

    Several new mercaptoacetamides were synthesized and studied as HDAC6 inhibitors. One compound, 2b, bearing an aminoquinoline cap group, was found to show 1.3 nM potency at HDAC6, with >3000-fold selectivity over HDAC1. 2b also showed excellent efficacy at increasing tubulin acetylation in rat primary cortical cultures, inducing a 10-fold increase in acetylated tubulin at 1 μM. To assess possible therapeutic effects, compounds were assayed for their ability to increase T-regulatory (Treg) suppressive function. Some but not all of the compounds increased Treg function, and thereby decreased conventional T cell activation and proliferation in vitro.

  17. Thiol-Based Potent and Selective HDAC6 Inhibitors Promote Tubulin Acetylation and T-Regulatory Cell Suppressive Function

    PubMed Central

    2015-01-01

    Several new mercaptoacetamides were synthesized and studied as HDAC6 inhibitors. One compound, 2b, bearing an aminoquinoline cap group, was found to show 1.3 nM potency at HDAC6, with >3000-fold selectivity over HDAC1. 2b also showed excellent efficacy at increasing tubulin acetylation in rat primary cortical cultures, inducing a 10-fold increase in acetylated tubulin at 1 μM. To assess possible therapeutic effects, compounds were assayed for their ability to increase T-regulatory (Treg) suppressive function. Some but not all of the compounds increased Treg function, and thereby decreased conventional T cell activation and proliferation in vitro. PMID:26617971

  18. Large-Scale Identification and Analysis of Suppressive Drug Interactions

    PubMed Central

    Cokol, Murat; Weinstein, Zohar B.; Yilancioglu, Kaan; Tasan, Murat; Doak, Allison; Cansever, Dilay; Mutlu, Beste; Li, Siyang; Rodriguez-Esteban, Raul; Akhmedov, Murodzhon; Guvenek, Aysegul; Cokol, Melike; Cetiner, Selim; Giaever, Guri; Iossifov, Ivan; Nislow, Corey; Shoichet, Brian; Roth, Frederick P.

    2014-01-01

    SUMMARY One drug may suppress the effects of another. Although knowledge of drug suppression is vital to avoid efficacy-reducing drug interactions or discover countermeasures for chemical toxins, drug-drug suppression relationships have not been systematically mapped. Here, we analyze the growth response of Saccharomyces cerevisiae to anti-fungal compound (“drug”) pairs. Among 440 ordered drug pairs, we identified 94 suppressive drug interactions. Using only pairs not selected on the basis of their suppression behavior, we provide an estimate of the prevalence of suppressive interactions between anti-fungal compounds as 17%. Analysis of the drug suppression network suggested that Bromopyruvate is a frequently suppressive drug and Staurosporine is a frequently suppressed drug. We investigated potential explanations for suppressive drug interactions, including chemogenomic analysis, coaggregation, and pH effects, allowing us to explain the interaction tendencies of Bromopyruvate. PMID:24704506

  19. Social networks and college drinking: probing processes of social influence and selection.

    PubMed

    Reifman, Alan; Watson, Wendy K; McCourt, Andrea

    2006-06-01

    This study used a three-wave panel design (N = 119 complete cases for all waves) to test for social influence and selection in the relation of college students' heavy drinking and that of their social networks. Evidence emerged for both social influence and selection, leading the authors to probe more specialized issues related to each. Results regarding social influence revealed, further, that greater presence in the network of individuals that the focal respondent considered "drinking buddies" was predictive of one's own later drinking, controlling for potential confounds. Network demographic characteristics associated with a "risky" (i.e., heavy-drinking) network also were documented. An additional finding, important for selection, was that wave-to-wave change in average network drinking appeared to result primarily from network members with different drinking levels being added to and dropped from the network. Findings are discussed in the context of the recent renaissance in social-network research.

  20. Selective Suppression of Endothelial Cell Apoptosis by the High Molecular Weight Form of Adiponectin

    PubMed Central

    Kobayashi, Hideki; Ouchi, Noriyuki; Kihara, Shinji; Walsh, Kenneth; Kumada, Masahiro; Abe, Yuki; Funahashi, Tohru; Matsuzawa, Yuji

    2015-01-01

    Adiponectin is an adipocyte-derived, antiatherogenic protein that is present in serum as three isoforms. Total adiponectin levels are decreased in obese or diabetic humans or animal models. This study was designed to elucidate the relative isoform distribution of adiponectin in human disease states and identify the active form of adiponectin toward vascular endothelial cells. The percentage of high molecular weight form (HMW) per total adiponectin was significantly lower in patients with coronary artery disease than control subjects, whereas the hexamer form was similar and the trimer form was significantly higher. During weight reduction in obese subjects, the HMW form increased and the trimer and hexamer forms decreased. Recombinant adiponectin dose-dependently suppressed apoptosis and caspase-3 activity in human umbilical vein endothelial cells (HUVECs). Transduction with dominant-negative AMP-activated protein kinase (AMPK) abolished the suppressive effect of adiponectin on HUVECs. Gel filtration chromatography was used to separate the adiponectin isoforms, and the antiapoptotic effect toward HUVECs was only observed with the HMW form. These data suggest that HMW adiponectin specifically confers the vascular-protective activities of this adipocytokine. PMID:14752031

  1. Anti-coreceptor therapy drives selective T cell egress by suppressing inflammation-dependent chemotactic cues

    PubMed Central

    Martin, Aaron J.; Clark, Matthew; Gojanovich, Gregory; Manzoor, Fatima; Miller, Keith; Kline, Douglas E.; Morillon, Y. Maurice; Wang, Bo

    2016-01-01

    There continues to be a need for immunotherapies to treat type 1 diabetes in the clinic. We previously reported that nondepleting anti-CD4 and -CD8 Ab treatment effectively reverses diabetes in new-onset NOD mice. A key feature of the induction of remission is the egress of the majority of islet-resident T cells. How this occurs is undefined. Herein, the effects of coreceptor therapy on islet T cell retention were investigated. Bivalent Ab binding to CD4 and CD8 blocked TCR signaling and T cell cytokine production, while indirectly downregulating islet chemokine expression. These processes were required for T cell retention, as ectopic IFN-γ or CXCL10 inhibited Ab-mediated T cell purging. Importantly, treatment of humanized mice with nondepleting anti–human CD4 and CD8 Ab similarly reduced tissue-infiltrating human CD4+ and CD8+ T cells. These findings demonstrate that Ab binding of CD4 and CD8 interrupts a feed-forward circuit by suppressing T cell–produced cytokines needed for expression of chemotactic cues, leading to rapid T cell egress from the islets. Coreceptor therapy therefore offers a robust approach to suppress T cell–mediated pathology by purging T cells in an inflammation-dependent manner. PMID:27777971

  2. Limitations of short range Mexican hat connection for driving target selection in a 2D neural field: activity suppression and deviation from input stimuli

    PubMed Central

    Mégardon, Geoffrey; Tandonnet, Christophe; Sumner, Petroc; Guillaume, Alain

    2015-01-01

    Dynamic Neural Field models (DNF) often use a kernel of connection with short range excitation and long range inhibition. This organization has been suggested as a model for brain structures or for artificial systems involved in winner-take-all processes such as saliency localization, perceptual decision or target/action selection. A good example of such a DNF is the superior colliculus (SC), a key structure for eye movements. Recent results suggest that the superficial layers of the SC (SCs) exhibit relatively short range inhibition with a longer time constant than excitation. The aim of the present study was to further examine the properties of a DNF with such an inhibition pattern in the context of target selection. First we tested the effects of stimulus size and shape on when and where self-maintained clusters of firing neurons appeared, using three variants of the model. In each model variant, small stimuli led to rapid formation of a spiking cluster, a range of medium sizes led to the suppression of any activity on the network and hence to no target selection, while larger sizes led to delayed selection of multiple loci. Second, we tested the model with two stimuli separated by a varying distance. Again single, none, or multiple spiking clusters could occur, depending on distance and relative stimulus strength. For short distances, activity attracted toward the strongest stimulus, reminiscent of well-known behavioral data for saccadic eye movements, while for larger distances repulsion away from the second stimulus occurred. All these properties predicted by the model suggest that the SCs, or any other neural structure thought to implement a short range MH, is an imperfect winner-take-all system. Although, those properties call for systematic testing, the discussion gathers neurophysiological and behavioral data suggesting that such properties are indeed present in target selection for saccadic eye movements. PMID:26539103

  3. Selective Mitochondrial Uptake of MKT-077 Can Suppress Medullary Thyroid Carcinoma Cell Survival In Vitro and In Vivo

    PubMed Central

    Starenki, Dmytro

    2015-01-01

    Background Medullary thyroid carcinoma (MTC) is a neuroendocrine tumor mainly caused by mutations in the rearranged during transfection (RET) proto-oncogene. Not all patients with progressive MTC respond to current therapy inhibiting RET, demanding additional therapeutic strategies. We recently demonstrated that disrupting mitochondrial metabolism using a mitochondria-targeted agent or by depleting a mitochondrial chaperone effectively suppressed human MTC cells in culture and in mouse xenografts by inducing apoptosis and RET downregulation. These observations led us to hypothesize that mitochondria are potential therapeutic targets for MTC. This study further tests this hypothesis using1-ethyl-2-[[3-ethyl-5-(3-methylbenzothiazolin-2-yliden)]-4-oxothiazolidin-2-ylidenemethyl] pyridinium chloride (MKT-077), a water-soluble rhodocyanine dye analogue, which can selectively accumulate in mitochondria. Methods The effects of MKT-077 on cell proliferation, survival, expression of RET and tumor protein 53 (TP53), and mitochondrial activity were determined in the human MTC lines in culture and in mouse xenografts. Results MKT-077 induced cell cycle arrest in TT and MZ-CRC-1. Intriguingly, MKT-077 also induced RET downregulation and strong cell death responses in TT cells, but not in MZ-CRC-1 cells. This discrepancy was mainly due to the difference between the capacities of these cell lines to retain MKT-077 in mitochondria. The cytotoxicity of MKT-077 in TT cells was mainly attributed to oxidative stress while being independent of TP53. MKT-077 also effectively suppressed tumor growth of TT xenografts. Conclusion MKT-077 can suppress cell survival of certain MTC subtypes by accumulating in mitochondria and interfering with mitochondrial activity although it can also suppress cell proliferation via other mechanisms. These results consistently support the hypothesis that mitochondrial targeting has therapeutic potential for MTC. PMID:26485469

  4. A Neuronal Network Model for Pitch Selectivity and Representation

    PubMed Central

    Huang, Chengcheng; Rinzel, John

    2016-01-01

    Pitch is a perceptual correlate of periodicity. Sounds with distinct spectra can elicit the same pitch. Despite the importance of pitch perception, understanding the cellular mechanism of pitch perception is still a major challenge and a mechanistic model of pitch is lacking. A multi-stage neuronal network model is developed for pitch frequency estimation using biophysically-based, high-resolution coincidence detector neurons. The neuronal units respond only to highly coincident input among convergent auditory nerve fibers across frequency channels. Their selectivity for only very fast rising slopes of convergent input enables these slope-detectors to distinguish the most prominent coincidences in multi-peaked input time courses. Pitch can then be estimated from the first-order interspike intervals of the slope-detectors. The regular firing pattern of the slope-detector neurons are similar for sounds sharing the same pitch despite the distinct timbres. The decoded pitch strengths also correlate well with the salience of pitch perception as reported by human listeners. Therefore, our model can serve as a neural representation for pitch. Our model performs successfully in estimating the pitch of missing fundamental complexes and reproducing the pitch variation with respect to the frequency shift of inharmonic complexes. It also accounts for the phase sensitivity of pitch perception in the cases of Schroeder phase, alternating phase and random phase relationships. Moreover, our model can also be applied to stochastic sound stimuli, iterated-ripple-noise, and account for their multiple pitch perceptions. PMID:27378900

  5. Bayesian Model Selection with Network Based Diffusion Analysis

    PubMed Central

    Whalen, Andrew; Hoppitt, William J. E.

    2016-01-01

    A number of recent studies have used Network Based Diffusion Analysis (NBDA) to detect the role of social transmission in the spread of a novel behavior through a population. In this paper we present a unified framework for performing NBDA in a Bayesian setting, and demonstrate how the Watanabe Akaike Information Criteria (WAIC) can be used for model selection. We present a specific example of applying this method to Time to Acquisition Diffusion Analysis (TADA). To examine the robustness of this technique, we performed a large scale simulation study and found that NBDA using WAIC could recover the correct model of social transmission under a wide range of cases, including under the presence of random effects, individual level variables, and alternative models of social transmission. This work suggests that NBDA is an effective and widely applicable tool for uncovering whether social transmission underpins the spread of a novel behavior, and may still provide accurate results even when key model assumptions are relaxed. PMID:27092089

  6. Oroxin B selectively induces tumor-suppressive ER stress and concurrently inhibits tumor-adaptive ER stress in B-lymphoma cells for effective anti-lymphoma therapy.

    PubMed

    Yang, Ping; Fu, Shilong; Cao, Zhifei; Liao, Huaidong; Huo, Zihe; Pan, Yanyan; Zhang, Gaochuan; Gao, Aidi; Zhou, Quansheng

    2015-10-15

    Cancer cells have both tumor-adaptive and -suppressive endoplasmic reticulum (ER) stress machineries that determine cell fate. In malignant tumors including lymphoma, constant activation of tumor-adaptive ER stress and concurrent reduction of tumor-suppressive ER stress favors cancer cell proliferation and tumor growth. Current ER stress-based anti-tumor drugs typically activate both tumor-adaptive and -suppressive ER stresses, resulting in low anti-cancer efficacy; hence, selective induction of tumor-suppressive ER stress and inhibition of tumor-adaptive ER stress are new strategies for novel anti-cancer drug discovery. Thus far, specific tumor-suppressive ER stress therapeutics have remained absent in clinical settings. In this study, we explored unique tumor-suppressive ER stress agents from the traditional Chinese medicinal herb Oroxylum indicum, and found that a small molecule oroxin B selectively induced tumor-suppressive ER stress in malignant lymphoma cells, but not in normal cells, effectively inhibited lymphoma growth in vivo, and significantly prolonged overall survival of lymphoma-xenografted mice without obvious toxicity. Mechanistic studies have revealed that the expression of key tumor-adaptive ER-stress gene GRP78 was notably suppressed by oroxin B via down-regulation of up-stream key signaling protein ATF6, while tumor-suppressive ER stress master gene DDIT3 was strikingly activated through activating the MKK3-p38 signaling pathway, correcting the imbalance between tumor-suppressive DDIT3 and tumor-adaptive GRP78 in lymphoma. Together, selective induction of unique tumor-suppressive ER stress and concurrent inhibition of tumor-adaptive ER stress in malignant lymphoma are new and feasible approaches for novel anti-lymphoma drug discovery and anti-lymphoma therapy.

  7. Innate-like CD4 T cells selected by thymocytes suppress adaptive immune responses against bacterial infections

    PubMed Central

    Qiao, Yu; Gray, Brian M.; Sofi, Mohammed H.; Bauler, Laura D.; Eaton, Kathryn A.; O'Riordan, Mary X. D.; Chang, Cheong-Hee

    2012-01-01

    We have reported a new innate-like CD4 T cell population that expresses cell surface makers of effector/memory cells and produce Th1 and Th2 cytokines immediately upon activation. Unlike conventional CD4 T cells that are selected by thymic epithelial cells, these CD4 T cells, named T-CD4 T cells, are selected by MHC class II expressing thymocytes. Previously, we showed that the presence of T-CD4 T cells protected mice from airway inflammation suggesting an immune regulatory role of T-CD4 T cells. To further understand the function of T-CD4 T cells, we investigated immune responses mediated by T-CD4 T cells during bacterial infection because the generation of antigen specific CD4 T cells contributes to clearance of infection and for the development of immune memory. The current study shows a suppressive effect of T-CD4 T cells on both CD8 and CD4 T cell-mediated immune responses during Listeria and Helicobacter infections. In the mouse model of Listeria monocytogenes infection, T-CD4 T cells resulted in decreasedfrequency of Listeria-specific CD8 T cells and the killing activity of them. Furthermore, mice with T-CD4 T cells developed poor immune memory, demonstrated by reduced expansion of antigen-specific T cells and high bacterial burden upon re-infection. Similarly, the presence of T-CD4 T cells suppressed the generation of antigen-specific CD4 T cells in Helicobacter pylori infected mice. Thus, our studies reveal a novel function of T-CD4 T cells in suppressing anti-bacterial immunity. PMID:23264931

  8. Inhibition of glutaminase selectively suppresses the growth of primary acute myeloid leukemia cells with IDH mutations.

    PubMed

    Emadi, Ashkan; Jun, Sung Ah; Tsukamoto, Takashi; Fathi, Amir T; Minden, Mark D; Dang, Chi V

    2014-04-01

    The incidence of mutations in isocitrate dehydrogenase 1 and 2 (IDH1/2) in de novo acute myeloid leukemia (AML) is approximately 20%. These mutations result in distinct metabolic characteristics including dependency of cancer cells on glutamine as the main source for α-ketoglutarate, which is consumed by leukemia cells to produce a cancer-derived metabolite, 2-hydroxyglutarate. We sought to exploit this glutamine addiction therapeutically in mutant IDH primary AML cells from patients by measuring cell growth after exposure to a small molecule glutaminase inhibitor, BPTES. We found that BPTES only suppressed the growth of AML cells expressing mutant IDH compared with those expressing wild type IDH. This study lays the groundwork for strategies to target a specific subtype of AML metabolically with IDH mutations with a unique reprogramming of intermediary metabolism that culminates in glutamine dependency of cancer cells for survival.

  9. A theory of the transition to critical period plasticity: inhibition selectively suppresses spontaneous activity.

    PubMed

    Toyoizumi, Taro; Miyamoto, Hiroyuki; Yazaki-Sugiyama, Yoko; Atapour, Nafiseh; Hensch, Takao K; Miller, Kenneth D

    2013-10-02

    What causes critical periods (CPs) to open? For the best-studied case, ocular dominance plasticity in primary visual cortex in response to monocular deprivation (MD), the maturation of inhibition is necessary and sufficient. How does inhibition open the CP? We present a theory: the transition from pre-CP to CP plasticity arises because inhibition preferentially suppresses responses to spontaneous relative to visually driven input activity, switching learning cues from internal to external sources. This differs from previous proposals in (1) arguing that the CP can open without changes in plasticity mechanisms when activity patterns become more sensitive to sensory experience through circuit development, and (2) explaining not simply a transition from no plasticity to plasticity, but a change in outcome of MD-induced plasticity from pre-CP to CP. More broadly, hierarchical organization of sensory-motor pathways may develop through a cascade of CPs induced as circuit maturation progresses from "lower" to "higher" cortical areas.

  10. Ataluren stimulates ribosomal selection of near-cognate tRNAs to promote nonsense suppression

    PubMed Central

    Roy, Bijoyita; Friesen, Westley J.; Tomizawa, Yuki; Leszyk, John D.; Zhuo, Jin; Johnson, Briana; Dakka, Jumana; Trotta, Christopher R.; Xue, Xiaojiao; Mutyam, Venkateshwar; Keeling, Kim M.; Mobley, James A.; Rowe, Steven M.; Bedwell, David M.; Welch, Ellen M.; Jacobson, Allan

    2016-01-01

    A premature termination codon (PTC) in the ORF of an mRNA generally leads to production of a truncated polypeptide, accelerated degradation of the mRNA, and depression of overall mRNA expression. Accordingly, nonsense mutations cause some of the most severe forms of inherited disorders. The small-molecule drug ataluren promotes therapeutic nonsense suppression and has been thought to mediate the insertion of near-cognate tRNAs at PTCs. However, direct evidence for this activity has been lacking. Here, we expressed multiple nonsense mutation reporters in human cells and yeast and identified the amino acids inserted when a PTC occupies the ribosomal A site in control, ataluren-treated, and aminoglycoside-treated cells. We find that ataluren’s likely target is the ribosome and that it produces full-length protein by promoting insertion of near-cognate tRNAs at the site of the nonsense codon without apparent effects on transcription, mRNA processing, mRNA stability, or protein stability. The resulting readthrough proteins retain function and contain amino acid replacements similar to those derived from endogenous readthrough, namely Gln, Lys, or Tyr at UAA or UAG PTCs and Trp, Arg, or Cys at UGA PTCs. These insertion biases arise primarily from mRNA:tRNA mispairing at codon positions 1 and 3 and reflect, in part, the preferred use of certain nonstandard base pairs, e.g., U-G. Ataluren’s retention of similar specificity of near-cognate tRNA insertion as occurs endogenously has important implications for its general use in therapeutic nonsense suppression. PMID:27702906

  11. Piperlongumine selectively suppresses ABC-DLBCL through inhibition of NF-κB p65 subunit nuclear import

    SciTech Connect

    Niu, Mingshan; Shen, Yangling; Xu, Xiaoyu; Yao, Yao; Fu, Chunling; Yan, Zhiling; Wu, Qingyun; Cao, Jiang; Sang, Wei; Zeng, Lingyu; Li, Zhenyu; Liu, Xuejiao; and others

    2015-07-10

    Constitutive NF-κB activation is required for survival of activated B cell-like subtype of diffuse large B cell lymphoma (ABC-DLBCL). However, current NF-κB targeting strategies lack cancer cell specificity. Here, we identified a novel inhibitor, piperlongumine, features direct binding to NF-κB p65 subunit and suppression of p65 nuclear import. This was accompanied by NF-κB reporter activity suppression and NF-κB target gene downregulation. Moreover, mutation of Cys{sup 38} to Ser in p65 abolished this effect of piperlongumine on inhibition of p65 nuclear import. Furthermore, we show that piperlongumine selectively inhibited proliferation and induced apoptosis of ABC-DLBCL cells. Most notably, it has been reported that piperlongumine did not affect normal cells even at high doses and was nontoxic to animals. Hence, our current study provides new insight into piperlongumine's mechanism of action and novel approach to ABC-DLBCL target therapy. - Highlights: • Current NF-κB targeting strategies lack cancer cell specificity. • Piperlongumine inhibits NF-κB p65 subunit nuclear import via directly binding to p65. • Piperlongumine selectively inhibits proliferation of ABC-DLBCL cells. • This study provides a novel approach to ABC-DLBCL target therapy.

  12. Selective Narrowing of Social Networks across Adulthood is Associated with Improved Emotional Experience in Daily Life

    ERIC Educational Resources Information Center

    English, Tammy; Carstensen, Laura L.

    2014-01-01

    Past research has documented age differences in the size and composition of social networks that suggest that networks grow smaller with age and include an increasingly greater proportion of well-known social partners. According to socioemotional selectivity theory, such changes in social network composition serve an antecedent emotion regulatory…

  13. Selective Narrowing of Social Networks across Adulthood is Associated with Improved Emotional Experience in Daily Life

    ERIC Educational Resources Information Center

    English, Tammy; Carstensen, Laura L.

    2014-01-01

    Past research has documented age differences in the size and composition of social networks that suggest that networks grow smaller with age and include an increasingly greater proportion of well-known social partners. According to socioemotional selectivity theory, such changes in social network composition serve an antecedent emotion regulatory…

  14. A failure of suppression within the default mode network in depressed adolescents with compulsive internet game play.

    PubMed

    Han, Doug Hyun; Kim, Sun Mi; Bae, Sujin; Renshaw, Perry F; Anderson, Jeffrey S

    2016-04-01

    Individuals who are chronic, compulsive video game players experience an elevated incidence of major depression. Excessive or problematic game play can interact with depression clinically, and may magnify impulsive behavior associated with video gaming. Functional brain imaging was performed during a Wisconsin Card Sorting Test (WCST) task in 42 healthy control and 95 volunteers seeking treatment for compulsive video game playing, including 60 participants without major depression (pure internet gaming disorder, pure IGD) and 35 participants comorbid with major depression (IGD+MDD). In response to the WCST in contrast to fixation, activation was observed in canonical brain attentional networks including bilateral intraparietal sulcus, frontal eye fields, and middle temporal cortical regions as well as dorsolateral prefrontal, inferior parietal and anterior insula, anterior cingulate cortex in all participants. For WCST>Fixation contrasts, the IGD+MDD group exhibited greater relative activation within the left hippocampus, compared to healthy control participants. For WCST>Fixation contrasts, the IGD+MDD group exhibited greater relative activation within the left hippocampus and the right parahippocampal gyrus immediately posterior to the hippocampus, compared to the pure IGD group. In cohorts of individuals with a history of compulsive internet game play, individuals with depression showed failure to suppress default mode network activity during an attentionally demanding task, compared to individuals without depression, including comparison groups with and without a history of compulsive video gaming. This reduced suppression of the brain regions within the default mode network may be a consequence of depressive neurophysiology or represent a predisposition for depression within compulsive game players. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Generative model selection using a scalable and size-independent complex network classifier

    NASA Astrophysics Data System (ADS)

    Motallebi, Sadegh; Aliakbary, Sadegh; Habibi, Jafar

    2013-12-01

    Real networks exhibit nontrivial topological features, such as heavy-tailed degree distribution, high clustering, and small-worldness. Researchers have developed several generative models for synthesizing artificial networks that are structurally similar to real networks. An important research problem is to identify the generative model that best fits to a target network. In this paper, we investigate this problem and our goal is to select the model that is able to generate graphs similar to a given network instance. By the means of generating synthetic networks with seven outstanding generative models, we have utilized machine learning methods to develop a decision tree for model selection. Our proposed method, which is named "Generative Model Selection for Complex Networks," outperforms existing methods with respect to accuracy, scalability, and size-independence.

  16. Generative model selection using a scalable and size-independent complex network classifier.

    PubMed

    Motallebi, Sadegh; Aliakbary, Sadegh; Habibi, Jafar

    2013-12-01

    Real networks exhibit nontrivial topological features, such as heavy-tailed degree distribution, high clustering, and small-worldness. Researchers have developed several generative models for synthesizing artificial networks that are structurally similar to real networks. An important research problem is to identify the generative model that best fits to a target network. In this paper, we investigate this problem and our goal is to select the model that is able to generate graphs similar to a given network instance. By the means of generating synthetic networks with seven outstanding generative models, we have utilized machine learning methods to develop a decision tree for model selection. Our proposed method, which is named "Generative Model Selection for Complex Networks," outperforms existing methods with respect to accuracy, scalability, and size-independence.

  17. Generative model selection using a scalable and size-independent complex network classifier

    SciTech Connect

    Motallebi, Sadegh Aliakbary, Sadegh Habibi, Jafar

    2013-12-15

    Real networks exhibit nontrivial topological features, such as heavy-tailed degree distribution, high clustering, and small-worldness. Researchers have developed several generative models for synthesizing artificial networks that are structurally similar to real networks. An important research problem is to identify the generative model that best fits to a target network. In this paper, we investigate this problem and our goal is to select the model that is able to generate graphs similar to a given network instance. By the means of generating synthetic networks with seven outstanding generative models, we have utilized machine learning methods to develop a decision tree for model selection. Our proposed method, which is named “Generative Model Selection for Complex Networks,” outperforms existing methods with respect to accuracy, scalability, and size-independence.

  18. Social Capital for College: Network Composition and Access to Selective Institutions among Urban High School Students

    ERIC Educational Resources Information Center

    Hill, Lori Diane; Bregman, Allyson; Andrade, Fernando

    2015-01-01

    This study examines the relationship between networks that provide high school students with "social capital for college" (SCFC) and their access to selective institutions. It also explores the link between racial disparities in access to selective colleges and the composition of students' SCFC networks. Findings indicate that while…

  19. Selective strong-field enhancement and suppression of ionization with short laser pulses

    NASA Astrophysics Data System (ADS)

    Hart, N. A.; Strohaber, J.; Kolomenskii, A. A.; Paulus, G. G.; Bauer, D.; Schuessler, H. A.

    2016-06-01

    We experimentally demonstrate robust selective excitation and attenuation of atomic Rydberg level populations in sodium vapor (Na i) using intense laser pulses in the strong-field limit (>1012W /c m2 ). Coherent control of the atomic population and related ionization channels is realized for intensities above the over-the-barrier ionization intensity. Moreover, atomic excitation selectivity and high ionization yield are simultaneously achieved without the need to tailor the spectral phase of the laser. A qualitative model confirms that this strong-field coherent control arises through the manifestation of a Freeman resonance.

  20. Some scale-free networks could be robust under selective node attacks

    NASA Astrophysics Data System (ADS)

    Zheng, Bojin; Huang, Dan; Li, Deyi; Chen, Guisheng; Lan, Wenfei

    2011-04-01

    It is a mainstream idea that scale-free network would be fragile under the selective attacks. Internet is a typical scale-free network in the real world, but it never collapses under the selective attacks of computer viruses and hackers. This phenomenon is different from the deduction of the idea above because this idea assumes the same cost to delete an arbitrary node. Hence this paper discusses the behaviors of the scale-free network under the selective node attack with different cost. Through the experiments on five complex networks, we show that the scale-free network is possibly robust under the selective node attacks; furthermore, the more compact the network is, and the larger the average degree is, then the more robust the network is; with the same average degrees, the more compact the network is, the more robust the network is. This result would enrich the theory of the invulnerability of the network, and can be used to build robust social, technological and biological networks, and also has the potential to find the target of drugs.

  1. Selective Disruption of Respiratory Supercomplexes as a New Strategy to Suppress Her2high Breast Cancer

    PubMed Central

    Sachaphibulkij, Karishma; Stursa, Jan; Bezawork-Geleta, Ayenachew; Blecha, Jan; Endaya, Berwini; Werner, Lukas; Cerny, Jiri; Zobalova, Renata; Goodwin, Jacob; Spacek, Tomas; Alizadeh Pesdar, Elham; Yan, Bing; Nguyen, Maria Nga; Vondrusova, Magdalena; Sobol, Margaryta; Jezek, Petr; Hozak, Pavel; Truksa, Jaroslav; Dong, Lan-Feng

    2017-01-01

    Abstract Aims: Expression of the HER2 oncogene in breast cancer is associated with resistance to treatment, and Her2 may regulate bioenergetics. Therefore, we investigated whether disruption of the electron transport chain (ETC) is a viable strategy to eliminate Her2high disease. Results: We demonstrate that Her2high cells and tumors have increased assembly of respiratory supercomplexes (SCs) and increased complex I-driven respiration in vitro and in vivo. They are also highly sensitive to MitoTam, a novel mitochondrial-targeted derivative of tamoxifen. Unlike tamoxifen, MitoTam efficiently suppresses experimental Her2high tumors without systemic toxicity. Mechanistically, MitoTam inhibits complex I-driven respiration and disrupts respiratory SCs in Her2high background in vitro and in vivo, leading to elevated reactive oxygen species production and cell death. Intriguingly, higher sensitivity of Her2high cells to MitoTam is dependent on the mitochondrial fraction of Her2. Innovation: Oncogenes such as HER2 can restructure ETC, creating a previously unrecognized therapeutic vulnerability exploitable by SC-disrupting agents such as MitoTam. Conclusion: We propose that the ETC is a suitable therapeutic target in Her2high disease. Antioxid. Redox Signal. 26, 84–103. PMID:27392540

  2. Selective suppression of antisense transcription by Set2-mediated H3K36 methylation

    PubMed Central

    Venkatesh, Swaminathan; Li, Hua; Gogol, Madelaine M.; Workman, Jerry L.

    2016-01-01

    Maintenance of a regular chromatin structure over the coding regions of genes occurs co-transcriptionally via the ‘chromatin resetting' pathway. One of the central players in this pathway is the histone methyltransferase Set2. Here we show that the loss of Set2 in yeast, Saccharomyces cerevisiae, results in transcription initiation of antisense RNAs embedded within body of protein-coding genes. These RNAs are distinct from the previously identified non-coding RNAs and cover 11% of the yeast genome. These RNA species have been named Set2-repressed antisense transcripts (SRATs) since the co-transcriptional addition of the H3K36 methyl mark by Set2 over their start sites results in their suppression. Interestingly, loss of chromatin resetting factor Set2 or the subsequent production of SRATs does not affect the abundance of the sense transcripts. This difference in transcriptional outcomes of overlapping transcripts due to a strand-independent addition of H3K36 methylation is a key regulatory feature of interleaved transcriptomes. PMID:27892455

  3. Selective Disruption of Respiratory Supercomplexes as a New Strategy to Suppress Her2(high) Breast Cancer.

    PubMed

    Rohlenova, Katerina; Sachaphibulkij, Karishma; Stursa, Jan; Bezawork-Geleta, Ayenachew; Blecha, Jan; Endaya, Berwini; Werner, Lukas; Cerny, Jiri; Zobalova, Renata; Goodwin, Jacob; Spacek, Tomas; Alizadeh Pesdar, Elham; Yan, Bing; Nguyen, Maria Nga; Vondrusova, Magdalena; Sobol, Margaryta; Jezek, Petr; Hozak, Pavel; Truksa, Jaroslav; Rohlena, Jakub; Dong, Lan-Feng; Neuzil, Jiri

    2017-01-10

    Expression of the HER2 oncogene in breast cancer is associated with resistance to treatment, and Her2 may regulate bioenergetics. Therefore, we investigated whether disruption of the electron transport chain (ETC) is a viable strategy to eliminate Her2(high) disease. We demonstrate that Her2(high) cells and tumors have increased assembly of respiratory supercomplexes (SCs) and increased complex I-driven respiration in vitro and in vivo. They are also highly sensitive to MitoTam, a novel mitochondrial-targeted derivative of tamoxifen. Unlike tamoxifen, MitoTam efficiently suppresses experimental Her2(high) tumors without systemic toxicity. Mechanistically, MitoTam inhibits complex I-driven respiration and disrupts respiratory SCs in Her2(high) background in vitro and in vivo, leading to elevated reactive oxygen species production and cell death. Intriguingly, higher sensitivity of Her2(high) cells to MitoTam is dependent on the mitochondrial fraction of Her2. Oncogenes such as HER2 can restructure ETC, creating a previously unrecognized therapeutic vulnerability exploitable by SC-disrupting agents such as MitoTam. We propose that the ETC is a suitable therapeutic target in Her2(high) disease. Antioxid. Redox Signal. 26, 84-103.

  4. Salinomycin inhibits the tumor growth of glioma stem cells by selectively suppressing glioma-initiating cells.

    PubMed

    Chen, Tunan; Yi, Liang; Li, Fei; Hu, Rong; Hu, Shengli; Yin, Yi; Lan, Chuan; Li, Zhao; Fu, Chuhua; Cao, Liu; Chen, Zhi; Xian, Jishu; Feng, Hua

    2015-04-01

    Glioma‑initiating cells are a small population of cells that have the ability to undergo self‑renewal and initiate tumorigenesis. In the present study, the potential role of salinomycin, a polyether antibiotic, on the suppression of glioma cell growth was investigated. GL261 glioma cells were maintained in a stem‑cell‑like status [GL261 neurospheres (GL261‑NS)] or induced for differentiation [GL261 adherent cells (GL261‑AC)]. It was demonstrated that salinomycin significantly reduced the cell viability of GL261‑NS and GL261‑AC cells in a dose‑dependent manner, with a more substantial inhibition of GL261‑NS proliferation (P<0.05). The inhibitory effect of salinomycin on cell growth was more effective than that of 1‑(4‑amino‑2‑methyl‑5‑pyrimid l)‑methyl‑3‑(2‑chloroethyl)‑3‑nitrosourea hydrochloride and vincristine (P<0.05). Salinomycin depleted GL261‑NS from tumorspheres and induced cell apoptosis. In addition, salinomycin prolonged the median survival time of glioma‑bearing mice (P<0.05). Therefore, the present study indicated that salinomycin may preferentially inhibit glioma‑initiated cell growth by inducing apoptosis, suggesting that salinomycin may provide a valuable therapeutic strategy for the treatment of malignant glioma.

  5. Selective suppression of antisense transcription by Set2-mediated H3K36 methylation.

    PubMed

    Venkatesh, Swaminathan; Li, Hua; Gogol, Madelaine M; Workman, Jerry L

    2016-11-28

    Maintenance of a regular chromatin structure over the coding regions of genes occurs co-transcriptionally via the 'chromatin resetting' pathway. One of the central players in this pathway is the histone methyltransferase Set2. Here we show that the loss of Set2 in yeast, Saccharomyces cerevisiae, results in transcription initiation of antisense RNAs embedded within body of protein-coding genes. These RNAs are distinct from the previously identified non-coding RNAs and cover 11% of the yeast genome. These RNA species have been named Set2-repressed antisense transcripts (SRATs) since the co-transcriptional addition of the H3K36 methyl mark by Set2 over their start sites results in their suppression. Interestingly, loss of chromatin resetting factor Set2 or the subsequent production of SRATs does not affect the abundance of the sense transcripts. This difference in transcriptional outcomes of overlapping transcripts due to a strand-independent addition of H3K36 methylation is a key regulatory feature of interleaved transcriptomes.

  6. P50 Suppression in Children with Selective Mutism: A Preliminary Report

    ERIC Educational Resources Information Center

    Henkin, Yael; Feinholz, Maya; Arie, Miri; Bar-Haim, Yair

    2010-01-01

    Evidence suggests that children with selective mutism (SM) display significant aberrations in auditory efferent activity at the brainstem level that may underlie inefficient auditory processing during vocalization, and lead to speech avoidance. The objective of the present study was to explore auditory filtering processes at the cortical level in…

  7. P50 Suppression in Children with Selective Mutism: A Preliminary Report

    ERIC Educational Resources Information Center

    Henkin, Yael; Feinholz, Maya; Arie, Miri; Bar-Haim, Yair

    2010-01-01

    Evidence suggests that children with selective mutism (SM) display significant aberrations in auditory efferent activity at the brainstem level that may underlie inefficient auditory processing during vocalization, and lead to speech avoidance. The objective of the present study was to explore auditory filtering processes at the cortical level in…

  8. A scheme for noise suppression and spectral enhancement of speech to alleviate speech reception problems from loss of frequency selectivity

    NASA Astrophysics Data System (ADS)

    Lyzenga, Johannes; Festen, Joost M.; Houtgast, Tammo

    2002-05-01

    Even after sufficient amplification, hearing-impaired listeners often experience problems in understanding speech under noisy conditions. This may be caused by suprathreshold deficits such as loss of compression and reduced frequency selectivity. In this project we investigate a scheme in which speech and noise are processed before presentation to try and alleviate intelligibility problems caused by reduced frequency selectivity. The scheme contains three strategies, one in which the peak-to-valley ratios of selected modulations in the speech spectrum are enlarged, a second in which the overall speech spectrum is modified, and a third in which noise is suppressed before the two enhancement steps. An overlap-and-add (OLA) algorithm is used in the implementation. The effect of the speech processing is evaluated by measuring speech-reception thresholds (SRT) for sentences in speech noise, estimating the signal-to-noise ratio at which listeners can correctly reproduce 50% of presented sentences. Hearing-impaired and normal-hearing listeners were used. To simulate the hearing impairment resulting from a loss of frequency selectivity, we spectrally smeared the stimuli presented to the normal-hearing listeners. We found that the preprocessing scheme achieved a modest improvement of nearly 2 dB in the SRT for normal-hearing listeners. Data for hearing-impaired listeners are presently being collected.

  9. Dihydroartemisinin suppresses pancreatic cancer cells via a microRNA-mRNA regulatory network

    PubMed Central

    Li, Yilong; Wang, Yongwei; Kong, Rui; Xue, Dongbo; Pan, Shangha; Chen, Hua; Sun, Bei

    2016-01-01

    Despite improvements in surgical procedures and chemotherapy, pancreatic cancer remains one of the most aggressive and fatal human malignancies, with a low 5-year survival rate of only 8%. Therefore, novel strategies for prevention and treatment are urgently needed. Here, we investigated the mechanisms underlying the anti-pancreatic cancer effects dihydroartemisinin (DHA). Microarray and systematic analysis showed that DHA suppressed proliferation, inhibited angiogenesis and promoted apoptosis in two different human pancreatic cancer cell lines, and that 5 DHA-regulated microRNAs and 11 of their target mRNAs were involved in these effects via 19 microRNA-mRNA interactions. Four of these microRNAs, 9 of the mRNAs and 17 of the interactions were experimentally verified. Furthermore, we found that the anti-pancreatic caner effects of DHA in vivo involved 4 microRNAs, 9 mRNAs and 17 microRNA-mRNA interactions. These results improve the understanding of the mechanisms by which DHA suppresses proliferation and angiogenesis and promotes apoptosis in pancreatic cancer cells and indicate that DHA, an effective antimalarial drug, might improve pancreatic cancer treatments. PMID:27613829

  10. Network Analysis: A Selected Bibliography. Exchange Bibliography No. 165.

    ERIC Educational Resources Information Center

    Hebert, Budd H.; Murphy, Elaine

    This bibliography presents a series of studies that focus on the topic of networks and on the manner in which they have been considered in the literature. Each section of the bibliography provides a working set of references for one of the five major areas of research in which network analysis has been used. The first section deals primarily with…

  11. Guidelines for Selection of Electronic Networking Software and Hardware.

    ERIC Educational Resources Information Center

    Rieck, Donald A.

    This article discusses the issues that confront network users and systems operators when they explore and adapt their professional communications activities to electronic communication. (Electronic networking here refers to the use of the telephone and the computer to facilitate communication between or among professional groups in a variety of…

  12. CD-ROM Selection and Acquisition in a Network Environment: A Guide to Finding, Acquiring, and Networking CD-ROMs.

    ERIC Educational Resources Information Center

    Johnson, Denise

    1991-01-01

    Discussion of concerns of librarians who are involved in CD-ROM selection and acquisition focuses on three main areas: (1) sources for discovering and investigating CD-ROM products, including an annotated bibliography of journals, publisher's catalogs, books, network conferences, and online indexes; (2) criteria for selection; and (3) vendor…

  13. Selection of BW 5147 subclones devoid of non-specific suppressive activity for use in cell hybridization.

    PubMed Central

    Chaouat, G; Liacopoulos-Briot, M; Couderc, J; Parlebas, J; Perrodon, Y; Briffaut, O; Liacopoulos, P

    1985-01-01

    Culture supernatants of BW 5147 cells widely used for T-cell hybridization often manifest non-MHC-restricted, non-antigen-specific regulatory activities on the mixed lymphocyte reaction (MLR) of mouse cells. This report demonstrates that, whereas supernatants of BW 5147 cells grown at low concentrations (2 X 10(5)/ml) enhanced MLR, high cell concentration (2 X 10(6)/ml) supernatants markedly inhibited this reaction. BW 5147 cell-free extracts significantly inhibited MLR and in vitro antibody production (PFC), as well as the mitogenic response to lipopolysaccharide E. coli (LPS) of mouse spleen cells, but did not affect the response to an optimal dose of phytohaemagglutinin (PHA). Both supernatant and cell-free extract inhibitory activities were located in 60,000 MW fraction. Inhibitory material of low MW (less than 12,000) was also found in high cell concentration supernatants. A similar suppressive activity was exerted by cell-free extracts of P3 X 63 NS cells used for B-cell hybridization. The suppressive activity seemed to stem from some kind of interaction between BW 5147 cells and the fetal calf serum (FCS) of the culture medium. Supernatants from subclones of BW 5147 cells obtained in selected batches of FCS and maintained in the same serum, even at high cell concentrations, did not affect MLR, whereas the supernatants from the same subclones maintained in other batches definitely suppressed this reaction. Thus, provided that culture conditions are chosen carefully, subclones of BW 5147 devoid of effect on in vitro immune reactions can be obtained. PMID:3155706

  14. Selection of BW 5147 subclones devoid of non-specific suppressive activity for use in cell hybridization.

    PubMed

    Chaouat, G; Liacopoulos-Briot, M; Couderc, J; Parlebas, J; Perrodon, Y; Briffaut, O; Liacopoulos, P

    1985-02-01

    Culture supernatants of BW 5147 cells widely used for T-cell hybridization often manifest non-MHC-restricted, non-antigen-specific regulatory activities on the mixed lymphocyte reaction (MLR) of mouse cells. This report demonstrates that, whereas supernatants of BW 5147 cells grown at low concentrations (2 X 10(5)/ml) enhanced MLR, high cell concentration (2 X 10(6)/ml) supernatants markedly inhibited this reaction. BW 5147 cell-free extracts significantly inhibited MLR and in vitro antibody production (PFC), as well as the mitogenic response to lipopolysaccharide E. coli (LPS) of mouse spleen cells, but did not affect the response to an optimal dose of phytohaemagglutinin (PHA). Both supernatant and cell-free extract inhibitory activities were located in 60,000 MW fraction. Inhibitory material of low MW (less than 12,000) was also found in high cell concentration supernatants. A similar suppressive activity was exerted by cell-free extracts of P3 X 63 NS cells used for B-cell hybridization. The suppressive activity seemed to stem from some kind of interaction between BW 5147 cells and the fetal calf serum (FCS) of the culture medium. Supernatants from subclones of BW 5147 cells obtained in selected batches of FCS and maintained in the same serum, even at high cell concentrations, did not affect MLR, whereas the supernatants from the same subclones maintained in other batches definitely suppressed this reaction. Thus, provided that culture conditions are chosen carefully, subclones of BW 5147 devoid of effect on in vitro immune reactions can be obtained.

  15. A selective inhibitor of intestinal ACAT, EAB309 suppresses both intestinal and hepatic cholesterol output and stimulates chylomicron removal.

    PubMed

    Umeda, Y; Hirano, T; Kako, Y; Kamagata, K; Okuyama, K; Suzuki, K

    1998-01-01

    The effect of a novel inhibitor of acylcoenzyme A:cholesterol acyltransferase (EC 2.3.1.26, ACAT), EAB309 (EAB) on plasma lipid metabolism was studied in cholesterol-fed rats. Orally administered EAB was not detected in the portal vein or the liver but distributed exclusively in the intestine, suggesting that this agent selectively inhibits intestinal ACAT. The rats were fed with either a cholesterol-diet or a cholesterol-diet containing 0.005% EAB (w/w) ad. libium for three weeks. ACAT activity in intestinal microsomes was significantly inhibited in EAB-treated rats. Hepatic ACAT activity was also decreased in EAB-treated rats, however, this was attenuated by the addition of excess cholesterol to the liver microsome, indicating that substrate availability is tightly associated with this enzyme's activity and the inhibition of hepatic ACAT by EAB is not direct. Incorporation of [3H]-cholesterol to cholesteryl ester (CE) in mesenteric lymph were markedly suppressed by EAB treatment. Chylomicrons (CMs) were doubly labeled with [3H]-vitamin A and [14C]-triglyceride (TG) in EAB-treated or non-treated rats and injected into normal chow-fed rats. The CMs from EAB-treated rats were cleared faster from the plasma and taken up more by the liver compared with the CMs from non-treated rats. The content of CE in newly secreted VLDL was remarkably decreased by EAB treatment without affecting TG output. These results demonstrate that EAB, a novel inhibitor of intestinal ACAT, significantly suppresses both intestinal and hepatic CE output and stimulates CM removal. This suggests that the inhibition of intestinal ACAT can subsequently suppress hepatic ACAT by decreased CE delivery from the intestine to the liver.

  16. Model selection for athermal cross-linked fiber networks.

    PubMed

    Shahsavari, A; Picu, R C

    2012-07-01

    Athermal random fiber networks are usually modeled by representing each fiber as a truss, a Euler-Bernoulli or a Timoshenko beam, and, in the case of cross-linked networks, each cross-link as a pinned, rotating, or welded joint. In this work we study the effect of these various modeling options on the dependence of the overall network stiffness on system parameters. We conclude that Timoshenko beams can be used for the entire range of density and beam stiffness parameters, while the Euler-Bernoulli model can be used only at relatively low network densities. In the high density-high bending stiffness range, strain energy is stored predominantly in the axial and shear deformation modes, while in the other extreme range of parameters, the energy is stored in the bending mode. The effect of the model size on the network stiffness is also discussed.

  17. Noise-tolerant model selection and parameter estimation for complex networks

    NASA Astrophysics Data System (ADS)

    Aliakbary, Sadegh; Motallebi, Sadegh; Rashidian, Sina; Habibi, Jafar; Movaghar, Ali

    2015-06-01

    Real networks often exhibit nontrivial topological features that do not occur in random graphs. The need for synthesizing realistic networks has resulted in development of various network models. In this paper, we address the problem of selecting and calibrating the model that best fits a given target network. The existing model fitting approaches mostly suffer from sensitivity to network perturbations, lack of the parameter estimation component, dependency on the size of the networks, and low accuracy. To overcome these limitations, we considered a broad range of network features and employed machine learning techniques such as genetic algorithms, distance metric learning, nearest neighbor classification, and artificial neural networks. Our proposed method, which is named ModelFit, outperforms the state-of-the-art baselines with respect to accuracy and noise tolerance in different network datasets.

  18. Suppressed N2O formation during NH3 selective catalytic reduction using vanadium on zeolitic microporous TiO2

    PubMed Central

    Lee, Seung Gwan; Lee, Hyun Jeong; Song, Inhak; Youn, Seunghee; Kim, Do Heui; Cho, Sung June

    2015-01-01

    Emission of N2O from mobile and off-road engine is now being currently regulated because of its high impact compared to that of CO2, thereby implying that N2O formation from the exhaust gas after-treatment system should be suppressed. Selective catalytic reduction using vanadium supported TiO2 catalyst in mobile and off-road engine has been considered to be major source for N2O emission in the system. Here we have demonstrated that vanadium catalyst supported on zeolitic microporous TiO2 obtained from the hydrothermal reaction of bulk TiO2 at 400 K in the presence of LiOH suppresses significantly the N2O emission compared to conventional VOx/TiO2 catalyst, while maintaining the excellent NOx reduction, which was ascribed to the location of VOx domain in the micropore of TiO2, resulting in the strong metal support interaction. The use of zeolitic microporous TiO2 provides a new way of preparing SCR catalyst with a high thermal stability and superior catalytic performance. It can be also extended further to the other catalytic system employing TiO2-based substrate. PMID:26235671

  19. Ramelteon, a selective MT1/MT2 receptor agonist, suppresses the proliferation and invasiveness of endometrial cancer cells.

    PubMed

    Osanai, Kiyono; Kobayashi, Yoichi; Otsu, Masahiro; Izawa, Tomoko; Sakai, Keiji; Iwashita, Mitsutoshi

    2017-07-01

    The incidence of endometrial cancer is increasing, making it the fifth most common cancer worldwide. To date, however, there is no standard therapy for patients with recurrent endometrial cancer. Melatonin, a hormone secreted by the pineal gland, has been shown to have anti-tumor effects in various tumor types. Although melatonin is available as a supplement, it has not been approved for cancer treatment. Ramelteon, a selective melatonin receptor type 1 and 2 (MT1/MT2) receptor agonist, has been approved to treat sleep disorders, suggesting that ramelteon may be effective in the treatment of endometrial cancer. To determine whether this agent may be effective in the treatment of endometrial cancer, this study investigated the ability of ramelteon to suppress the proliferation and invasiveness of HHUA cells, an estrogen receptor-positive endometrial cancer cell line. Ramelteon at 10(-8) M maximally suppressed the proliferation of HHUA cells, reducing the percentage of Ki-67 positive proliferating cells. This effect was completely blocked by luzindole, a MT1/MT2 receptor antagonist. Furthermore, ramelteon inhibited HHUA cell invasion and reduced the expression of the MMP-2 and MMP-9 genes. These results suggested that ramelteon may be a candidate for the treatment of recurrent endometrial cancer, with activity similar to that of melatonin.

  20. Suppressed N2O formation during NH3 selective catalytic reduction using vanadium on zeolitic microporous TiO2.

    PubMed

    Lee, Seung Gwan; Lee, Hyun Jeong; Song, Inhak; Youn, Seunghee; Kim, Do Heui; Cho, Sung June

    2015-08-03

    Emission of N2O from mobile and off-road engine is now being currently regulated because of its high impact compared to that of CO2, thereby implying that N2O formation from the exhaust gas after-treatment system should be suppressed. Selective catalytic reduction using vanadium supported TiO2 catalyst in mobile and off-road engine has been considered to be major source for N2O emission in the system. Here we have demonstrated that vanadium catalyst supported on zeolitic microporous TiO2 obtained from the hydrothermal reaction of bulk TiO2 at 400 K in the presence of LiOH suppresses significantly the N2O emission compared to conventional VOx/TiO2 catalyst, while maintaining the excellent NOx reduction, which was ascribed to the location of VOx domain in the micropore of TiO2, resulting in the strong metal support interaction. The use of zeolitic microporous TiO2 provides a new way of preparing SCR catalyst with a high thermal stability and superior catalytic performance. It can be also extended further to the other catalytic system employing TiO2-based substrate.

  1. Suppressed N2O formation during NH3 selective catalytic reduction using vanadium on zeolitic microporous TiO2

    NASA Astrophysics Data System (ADS)

    Lee, Seung Gwan; Lee, Hyun Jeong; Song, Inhak; Youn, Seunghee; Kim, Do Heui; Cho, Sung June

    2015-08-01

    Emission of N2O from mobile and off-road engine is now being currently regulated because of its high impact compared to that of CO2, thereby implying that N2O formation from the exhaust gas after-treatment system should be suppressed. Selective catalytic reduction using vanadium supported TiO2 catalyst in mobile and off-road engine has been considered to be major source for N2O emission in the system. Here we have demonstrated that vanadium catalyst supported on zeolitic microporous TiO2 obtained from the hydrothermal reaction of bulk TiO2 at 400 K in the presence of LiOH suppresses significantly the N2O emission compared to conventional VOx/TiO2 catalyst, while maintaining the excellent NOx reduction, which was ascribed to the location of VOx domain in the micropore of TiO2, resulting in the strong metal support interaction. The use of zeolitic microporous TiO2 provides a new way of preparing SCR catalyst with a high thermal stability and superior catalytic performance. It can be also extended further to the other catalytic system employing TiO2-based substrate.

  2. Evaluation of Fat Suppression of Diffusion-weighted Imaging Using Section Select Gradient Reversal Technique on 3 T Breast MRI.

    PubMed

    Takemori, Daichi; Kimura, Daisuke; Yamada, Eiji; Higashida, Mitsuji

    2016-07-01

    This study evaluates fat suppression of diffusion-weighted imaging (DWI) using section select gradient reversal (SSGR) technique in clinical images on 3 T breast MRI. A total of 20 patients with breast cancer were examined at a Philips Ingenia 3 T MRI. We acquired DWI with SPAIR, SSGR-SPAIR, STIR, and SSGR-STIR. We evaluated contrast between the fat region and lesion, the coefficient of variance (CV) of the fat region and the apparent diffusion coefficient (ADC) of normal breast tissue and lesion. The contrast between the fat region and lesion was improved with SSGR technique. The CV of the fattest region did not have any significant difference in SPAIR technique (p>0.05), but it was significantly decreased in the STIR technique using SSGR technique (p<0.05). Positive correlation was observed in ADC value between SPAIR and other fat suppression techniques (SSGR-SPAIR, STIR, SSGR-STIR). DWI using SSGR technique was suggested to be effective on 3 T breast MRI.

  3. Real-time multi-channel monitoring of burst-suppression using neural network technology during pediatric status epilepticus treatment.

    PubMed

    Papadelis, Christos; Ashkezari, Seyedeh Fatemeh Salimi; Doshi, Chiran; Thome-Souza, Sigride; Pearl, Phillip L; Grant, P Ellen; Tasker, Robert C; Loddenkemper, Tobias

    2016-08-01

    To develop a real-time monitoring system that has the potential to guide the titration of anesthetic agents in the treatment of pediatric status epilepticus (SE). We analyzed stored multichannel electroencephalographic (EEG) data collected from 12 pediatric patients with generalized SE. EEG recordings were initially segmented in 500ms time-windows. Features characterizing the power, frequency, and entropy of the signal were extracted from each segment. The segments were annotated as bursts (B), suppressions (S), or artifacts (A) by two electroencephalographers. The EEG features together with the annotations were inputted in a three-layer feed forward neural network (NN). The sensitivity and specificity of NNs with different architectures and training algorithms to classify segments into B, S, or A were estimated. The maximum sensitivity (95.96% for B, 89.25% for S, and 75% for A) and specificity (89.36 for B, 96.26% for S, and 99.8% for A) was observed for the NN with 10 nodes in the hidden layer. By using this NN, we designed a real-time system that estimates the burst-suppression index (BSI). Our system provides a reliable real-time estimate of multichannel BSI requiring minimal memory and computation time. The system has the potential to assist intensive care unit attendants in the continuous EEG monitoring. Copyright © 2016 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

  4. Absence of positive selection on CenH3 in Luzula suggests that holokinetic chromosomes may suppress centromere drive.

    PubMed

    Zedek, František; Bureš, Petr

    2016-12-01

    The centromere drive theory explains diversity of eukaryotic centromeres as a consequence of the recurrent conflict between centromeric repeats and centromeric histone H3 (CenH3), in which selfish centromeres exploit meiotic asymmetry and CenH3 evolves adaptively to counterbalance deleterious consequences of driving centromeres. Accordingly, adaptively evolving CenH3 has so far been observed only in eukaryotes with asymmetric meiosis. However, if such evolution is a consequence of centromere drive, it should depend not only on meiotic asymmetry but also on monocentric or holokinetic chromosomal structure. Selective pressures acting on CenH3 have never been investigated in organisms with holokinetic meiosis despite the fact that holokinetic chromosomes have been hypothesized to suppress centromere drive. Therefore, the present study evaluates selective pressures acting on the CenH3 gene in holokinetic organisms for the first time, specifically in the representatives of the plant genus Luzula (Juncaceae), in which the kinetochore formation is not co-localized with any type of centromeric repeat. PCR, cloning and sequencing, and database searches were used to obtain coding CenH3 sequences from Luzula species. Codon substitution models were employed to infer selective regimes acting on CenH3 in Luzula KEY RESULTS: In addition to the two previously published CenH3 sequences from L. nivea, 16 new CenH3 sequences have been isolated from 12 Luzula species. Two CenH3 isoforms in Luzula that originated by a duplication event prior to the divergence of analysed species were found. No signs of positive selection acting on CenH3 in Luzula were detected. Instead, evidence was found that selection on CenH3 of Luzula might have been relaxed. The results indicate that holokinetism itself may suppress centromere drive and, therefore, holokinetic chromosomes might have evolved as a defence against centromere drive. © The Author 2016. Published by Oxford University Press on behalf of

  5. ICA model order selection of task co-activation networks.

    PubMed

    Ray, Kimberly L; McKay, D Reese; Fox, Peter M; Riedel, Michael C; Uecker, Angela M; Beckmann, Christian F; Smith, Stephen M; Fox, Peter T; Laird, Angela R

    2013-01-01

    Independent component analysis (ICA) has become a widely used method for extracting functional networks in the brain during rest and task. Historically, preferred ICA dimensionality has widely varied within the neuroimaging community, but typically varies between 20 and 100 components. This can be problematic when comparing results across multiple studies because of the impact ICA dimensionality has on the topology of its resultant components. Recent studies have demonstrated that ICA can be applied to peak activation coordinates archived in a large neuroimaging database (i.e., BrainMap Database) to yield whole-brain task-based co-activation networks. A strength of applying ICA to BrainMap data is that the vast amount of metadata in BrainMap can be used to quantitatively assess tasks and cognitive processes contributing to each component. In this study, we investigated the effect of model order on the distribution of functional properties across networks as a method for identifying the most informative decompositions of BrainMap-based ICA components. Our findings suggest dimensionality of 20 for low model order ICA to examine large-scale brain networks, and dimensionality of 70 to provide insight into how large-scale networks fractionate into sub-networks. We also provide a functional and organizational assessment of visual, motor, emotion, and interoceptive task co-activation networks as they fractionate from low to high model-orders.

  6. ICA model order selection of task co-activation networks

    PubMed Central

    Ray, Kimberly L.; McKay, D. Reese; Fox, Peter M.; Riedel, Michael C.; Uecker, Angela M.; Beckmann, Christian F.; Smith, Stephen M.; Fox, Peter T.; Laird, Angela R.

    2013-01-01

    Independent component analysis (ICA) has become a widely used method for extracting functional networks in the brain during rest and task. Historically, preferred ICA dimensionality has widely varied within the neuroimaging community, but typically varies between 20 and 100 components. This can be problematic when comparing results across multiple studies because of the impact ICA dimensionality has on the topology of its resultant components. Recent studies have demonstrated that ICA can be applied to peak activation coordinates archived in a large neuroimaging database (i.e., BrainMap Database) to yield whole-brain task-based co-activation networks. A strength of applying ICA to BrainMap data is that the vast amount of metadata in BrainMap can be used to quantitatively assess tasks and cognitive processes contributing to each component. In this study, we investigated the effect of model order on the distribution of functional properties across networks as a method for identifying the most informative decompositions of BrainMap-based ICA components. Our findings suggest dimensionality of 20 for low model order ICA to examine large-scale brain networks, and dimensionality of 70 to provide insight into how large-scale networks fractionate into sub-networks. We also provide a functional and organizational assessment of visual, motor, emotion, and interoceptive task co-activation networks as they fractionate from low to high model-orders. PMID:24339802

  7. The role of selected f ions in the suppression of high-Tc superconductivity.

    SciTech Connect

    Soderholm, L.

    1998-09-25

    The initial observations of superconductivity at temperatures above 77 K in copper-oxide based materials was surprising from a variety of different perspectives. Among the unexpected findings were reports of superconductivity for the series RBa{sub 2}Cu{sub 3}O{sub 7} where R is a rare earth (Y, Nd-Tm), which may carry a large, local magnetic moment. Superconductivity was subsequently demonstrated for all 4f analogs in this series except Ce, Pr, and Tb. In addition to the RBa{sub 2}Cu{sub 3}O{sub 7} series, there are several other CuO based series of superconductors that are formed by substituting R ions. The most studied of these are listed in Table 1, together with the f ions that form isostructural compounds and their superconducting critical temperatures (T{sub c}). The presence of an R ion with a large magnetic moment does not significantly influence the superconductivity. In contrast, even the presence of small concentrations of magnetic impurity ions in a conventional superconductor inhibits superconductivity by interfering with the formation of Cooper pairs. Most R ions substitute into an isostructural series with no observable effect on the superconducting properties of the material. As can be seen from Table 1, there are notable exceptions to this observation. In particular, the rare-earth ions Ce, Pr, and Tb, together with the 5f-actinide ions Am and Cm, sometimes behave anomalously. These ions either do not form an isostructural phase, or if the phase forms it may not be superconducting. The fact that an f-ion can suppress superconductivity is clearly demonstrated in the isostructural series Y{sub 1{minus}x}Pr{sub x}Ba{sub 2}Cu{sub 3}O{sub 7} (0 < x < 1){sup 3}, in which the critical temperature decreases with increasing x, such that for concentrations of Pr greater than x {approx} 0.5, the samples no longer superconduct.

  8. Bismuth as a modifier of Au Pd catalyst: Enhancing selectivity in alcohol oxidation by suppressing parallel reaction

    SciTech Connect

    Villa, Alberto; Wang, Di; Veith, Gabriel M; Prati, Laura

    2012-01-01

    Bi has been widely employed as a modifier for Pd and Pt based catalyst mainly in order to improve selectivity. We found that when Bi was added to the bimetallic system AuPd, the effect on activity in alcohol oxidation mainly depends on the amount of Bi regardless its position, being negligible when Bi was 0.1 wt% and detectably negative when the amount was increased to 3 wt%. However, the selectivity of the reactions notably varied only when Bi was deposited on the surface of metal nanoparticles suppressing parallel reaction in both benzyl alcohol and glycerol oxidation. After a careful characterization of all the catalysts and additional catalytic tests, we concluded that the Bi influence on the activity of the catalysts could be ascribed to electronic effect whereas the one on selectivity mainly to a geometric modification. Moreover, the Bi-modified AuPd/AC catalyst showed possible application in the production of tartronic acid, a useful intermediate, from glycerol.

  9. Cellular Signaling Networks Function as Generalized Wiener-Kolmogorov Filters to Suppress Noise

    NASA Astrophysics Data System (ADS)

    Hinczewski, Michael; Thirumalai, D.

    2014-10-01

    Cellular signaling involves the transmission of environmental information through cascades of stochastic biochemical reactions, inevitably introducing noise that compromises signal fidelity. Each stage of the cascade often takes the form of a kinase-phosphatase push-pull network, a basic unit of signaling pathways whose malfunction is linked with a host of cancers. We show that this ubiquitous enzymatic network motif effectively behaves as a Wiener-Kolmogorov optimal noise filter. Using concepts from umbral calculus, we generalize the linear Wiener-Kolmogorov theory, originally introduced in the context of communication and control engineering, to take nonlinear signal transduction and discrete molecule populations into account. This allows us to derive rigorous constraints for efficient noise reduction in this biochemical system. Our mathematical formalism yields bounds on filter performance in cases important to cellular function—such as ultrasensitive response to stimuli. We highlight features of the system relevant for optimizing filter efficiency, encoded in a single, measurable, dimensionless parameter. Our theory, which describes noise control in a large class of signal transduction networks, is also useful both for the design of synthetic biochemical signaling pathways and the manipulation of pathways through experimental probes such as oscillatory input.

  10. Selecting and Weighting Data for Building Consensus Gene Regulatory Networks

    NASA Astrophysics Data System (ADS)

    Steele, Emma; Tucker, Allan

    Microarrays are the major source of data for gene expression activity, allowing the expression of thousands of genes to be measured simultaneously. Gene regulatory networks (GRNs) describe how the expression level of genes affect the expression of the other genes. Modelling GRNs from expression data is a topic of great interest in current bioinformatics research. Previously, we took advantage of publicly available gene expression datasets generated by similar biological studies by drawing together a richer and/or broader collection of data in order to produce GRN models that are more robust, have greater confidence and place less reliance on a single dataset. In this paper a new approach, Weighted Consensus Bayesian Networks, introduces the use of weights in order to place more influence on certain input networks or remove the least reliable networks from the input with encouraging results on both synthetic data and real world yeast microarray datasets.

  11. Active suppression of nonlinear composite beam vibrations by selected control algorithms

    NASA Astrophysics Data System (ADS)

    Warminski, Jerzy; Bochenski, Marcin; Jarzyna, Wojciech; Filipek, Piotr; Augustyniak, Michal

    2011-05-01

    This paper is focused on application of different control algorithms for a flexible, geometrically nonlinear beam-like structure with Macro Fiber Composite (MFC) actuator. Based on the mathematical model of a geometrically nonlinear beam, analytical solutions for Nonlinear Saturation Controller (NSC) are obtained using Multiple Scale Method. Effectiveness of different control strategies is evaluated by numerical simulations in Matlab-Simulink software. Then, the Digital Signal Processing (DSP) controller and selected control algorithms are implemented to the physical system to compare numerical and experimental results. Detailed analysis for the NSC system is carried out, especially for high level of amplitude and wide range of frequencies of excitation. Finally, the efficiency of the considered controllers is tested experimentally for a more complex autoparametric " L-shape" beam system.

  12. Gene replacement without selection: regulated suppression of amber mutations in Escherichia coli.

    PubMed

    Herring, Christopher D; Glasner, Jeremy D; Blattner, Frederick R

    2003-06-05

    We have developed a method called "gene gorging" to make precise mutations in the Escherichia coli genome at frequencies high enough (1-15%) to allow direct identification of mutants by PCR or other screen rather than by selection. Gene gorging begins by establishing a donor plasmid carrying the desired mutation in the target cell. This plasmid is linearized by in vivo expression of the meganuclease I-SceI, providing a DNA substrate for lambda Red mediated recombination. This results in efficient replacement of the wild type allele on the chromosome with the modified sequence. We demonstrate gene gorging by introducing amber stop codons into the genes xylA, melA, galK, fucI, citA, ybdO, and lacZ. To compliment this approach we developed an arabinose inducible amber suppressor tRNA. Controlled expression mediated by the suppressor was demonstrated for the lacZ and xylA amber mutants.

  13. A network-based feature selection approach to identify metabolic signatures in disease.

    PubMed

    Netzer, Michael; Kugler, Karl G; Müller, Laurin A J; Weinberger, Klaus M; Graber, Armin; Baumgartner, Christian; Dehmer, Matthias

    2012-10-07

    The identification and interpretation of metabolic biomarkers is a challenging task. In this context, network-based approaches have become increasingly a key technology in systems biology allowing to capture complex interactions in biological systems. In this work, we introduce a novel network-based method to identify highly predictive biomarker candidates for disease. First, we infer two different types of networks: (i) correlation networks, and (ii) a new type of network called ratio networks. Based on these networks, we introduce scores to prioritize features using topological descriptors of the vertices. To evaluate our method we use an example dataset where quantitative targeted MS/MS analysis was applied to a total of 52 blood samples from 22 persons with obesity (BMI >30) and 30 healthy controls. Using our network-based feature selection approach we identified highly discriminating metabolites for obesity (F-score >0.85, accuracy >85%), some of which could be verified by the literature.

  14. Lateral and feedforward inhibition suppress asynchronous activity in a large, biophysically-detailed computational model of the striatal network

    PubMed Central

    Moyer, Jason T.; Halterman, Benjamin L.; Finkel, Leif H.; Wolf, John A.

    2014-01-01

    Striatal medium spiny neurons (MSNs) receive lateral inhibitory projections from other MSNs and feedforward inhibitory projections from fast-spiking, parvalbumin-containing striatal interneurons (FSIs). The functional roles of these connections are unknown, and difficult to study in an experimental preparation. We therefore investigated the functionality of both lateral (MSN-MSN) and feedforward (FSI-MSN) inhibition using a large-scale computational model of the striatal network. The model consists of 2744 MSNs comprised of 189 compartments each and 121 FSIs comprised of 148 compartments each, with dendrites explicitly represented and almost all known ionic currents included and strictly constrained by biological data as appropriate. Our analysis of the model indicates that both lateral inhibition and feedforward inhibition function at the population level to limit non-ensemble MSN spiking while preserving ensemble MSN spiking. Specifically, lateral inhibition enables large ensembles of MSNs firing synchronously to strongly suppress non-ensemble MSNs over a short time-scale (10–30 ms). Feedforward inhibition enables FSIs to strongly inhibit weakly activated, non-ensemble MSNs while moderately inhibiting activated ensemble MSNs. Importantly, FSIs appear to more effectively inhibit MSNs when FSIs fire asynchronously. Both types of inhibition would increase the signal-to-noise ratio of responding MSN ensembles and contribute to the formation and dissolution of MSN ensembles in the striatal network. PMID:25505406

  15. Selective blockade of T-type Ca2+ channels suppresses human breast cancer cell proliferation.

    PubMed

    Taylor, James T; Huang, Luping; Pottle, Jonathan E; Liu, Kai; Yang, Yali; Zeng, Xiangbin; Keyser, Brian M; Agrawal, Krishna C; Hansen, J Bondo; Li, Ming

    2008-08-18

    We have measured the expression of T-type Ca2+ channel mRNA in breast cancer cell lines (MCF-7 (ERalpha+) using Western blot and quantitative real-time PCR (Q-RT-PCR). These results revealed that the MCF-7 cells express both alpha1G and alpha1H isoforms of T-type Ca2+ channels. In order to further clarify the role of T-type Ca2+ channels in proliferation, we tested the effects of a selective T-type Ca2+ channel inhibitor NNC-55-0396 on cellular proliferation. MCF-7 (ERalpha+) cellular proliferation was inhibited by the compound. In contrast, NNC-55-0396 at same concentration had no effect on the proliferation of MCF-10A cells, a non-cancer breast epithelial cell line. We also found that message expression of the T-type Ca2+ channels were only expressed in rapidly growing non-confluent cells but not in the cytostatic confluent cells. Knocking down the expression of T-type Ca2+ channels with siRNA targeting both alpha1G and alpha1H resulted in growth inhibition as much as 45%+/-5.0 in MCF-7 cells as compared to controls. In conclusion, our results suggest that T-type Ca2+ channel antagonism/silencing may reduce cellular proliferation in mitogenic breast cells.

  16. Selective suppression of excitatory synapses on GABAergic interneurons by norepinephrine in juvenile rat prefrontal cortical microcircuitry.

    PubMed

    Wang, H-X; Waterhouse, B D; Gao, W-J

    2013-08-29

    The noradrenergic system of the brain is thought to facilitate neuronal processes that promote behavioral activation, alertness, and attention. It is known that norepinephrine (NE) can be significantly elevated in the prefrontal cortex under normal conditions such as arousal and attention, and following the administration of psychostimulants and various other drugs prescribed for psychiatric disorders. However, how NE modulates neuronal activity and synapses in the local prefrontal circuitry remains elusive. In this study, we characterized the actions of NE on individual monosynaptic connections among layer V pyramidal neurons (P) and fast-spiking (FS) GABAergic interneurons in the juvenile (postnatal days 20-23) rat prefrontal local circuitry. We found that NE selectively depresses excitatory synaptic transmission in P-FS connections but has no detectable effect on the excitatory synapses in P-P connections and the inhibitory synapses in FS-P connections. NE apparently exerts distinctly different modulatory actions on identified synapses that target GABAergic interneurons but has no effect on those in the pyramidal neurons in this specific developmental period. These results indicate that, depending on the postsynaptic targets, the effects of NE in prefrontal cortex are synapse-specific, at least in the juvenile animals.

  17. Distractor suppression when attention fails: behavioral evidence for a flexible selective attention mechanism.

    PubMed

    Elliott, James C; Giesbrecht, Barry

    2015-01-01

    Despite consistent evidence showing that attention is a multifaceted mechanism that can operate at multiple levels of processing depending on the structure and demands of the task, investigations of the attentional blink phenomenon have consistently shown that the impairment in reporting the second of two targets typically occurs at a late, or post-perceptual, stage of processing. This suggests that the attentional blink phenomenon may represent the operation of a unique attentional mechanism that is not as flexible as other attentional mechanisms. To test whether the attentional blink is a fixed or flexible phenomenon, we manipulated first target task demands (i.e., difficulty) and measured the influence this had on processing a subsequently presented distractor and the second target. If the attentional blink represents a mechanism that is fixed and consistently fails at a single stage of processing, then manipulations of task difficulty should not affect distractor processing. However, if the attentional blink represents a more multifaceted and flexible mechanism, then task difficulty should modulate distractor processing. The results revealed that distractor processing during the AB was attenuated under high task difficulty. In addition, unlike previous studies, we failed to find a correlation between distractor processing and the severity of the attentional blink. Using a simulation, we demonstrate that the previously reported correlations may have been spurious and due to using variables that were not independent. Overall, the present results support the conclusion that the selectivity of attention during the AB is flexible and depends on the structure and demands of the task.

  18. Histone acetylation in astrocytes suppresses GFAP and stimulates a reorganization of the intermediate filament network.

    PubMed

    Kanski, Regina; Sneeboer, Marjolein A M; van Bodegraven, Emma J; Sluijs, Jacqueline A; Kropff, Wietske; Vermunt, Marit W; Creyghton, Menno P; De Filippis, Lidia; Vescovi, Angelo; Aronica, Eleonora; van Tijn, Paula; van Strien, Miriam E; Hol, Elly M

    2014-10-15

    Glial fibrillary acidic protein (GFAP) is the main intermediate filament in astrocytes and is regulated by epigenetic mechanisms during development. We demonstrate that histone acetylation also controls GFAP expression in mature astrocytes. Inhibition of histone deacetylases (HDACs) with trichostatin A or sodium butyrate reduced GFAP expression in primary human astrocytes and astrocytoma cells. Because splicing occurs co-transcriptionally, we investigated whether histone acetylation changes the ratio between the canonical isoform GFAPα and the alternative GFAPδ splice variant. We observed that decreased transcription of GFAP enhanced alternative isoform expression, as HDAC inhibition increased the GFAPδ∶GFAPα ratio. Expression of GFAPδ was dependent on the presence and binding of splicing factors of the SR protein family. Inhibition of HDAC activity also resulted in aggregation of the GFAP network, reminiscent of our previous findings of a GFAPδ-induced network collapse. Taken together, our data demonstrate that HDAC inhibition results in changes in transcription, splicing and organization of GFAP. These data imply that a tight regulation of histone acetylation in astrocytes is essential, because dysregulation of gene expression causes the aggregation of GFAP, a hallmark of human diseases like Alexander's disease. © 2014. Published by The Company of Biologists Ltd.

  19. Fluvoxamine, a selective serotonin reuptake inhibitor, and 5-HT2C receptor inactivation induce appetite-suppressing effects in mice via 5-HT1B receptors.

    PubMed

    Nonogaki, Katsunori; Nozue, Kana; Takahashi, Yukiko; Yamashita, Nobuyuki; Hiraoka, Shuichi; Kumano, Hiroaki; Kuboki, Tomifusa; Oka, Yohsitomo

    2007-10-01

    Serotonin (5-hydroxytryptamine; 5-HT) 2C receptors and the downstream melanocortin pathway are suggested to mediate the appetite-suppressing effects of 5-HT drugs such as m-chlorophenylpiperazine (mCPP) and fenfluramine. Here, we report that fluvoxamine (3-30 mg/kg), a selective serotonin reuptake inhibitor (SSRI), in the presence of SB 242084 (1-2 mg/kg), a selective 5-HT2C receptor antagonist, exerts appetite-suppressing effects while fluvoxamine or SB 242084 alone has no effect. The appetite-suppressing effects were attenuated in the presence of SB 224289 (5 mg/kg), a selective 5-HT1B receptor antagonist. Moreover, CP 94253 (5-10 mg/kg), a selective 5-HT1B receptor agonist, exerted appetite-suppressing effects and significantly increased hypothalamic pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART) gene expression and decreased hypothalamic orexin gene expression. These results suggest that fluvoxamine and inactivation of 5-HT2C receptors exert feeding suppression through activation of 5-HT1B receptors, and that 5-HT1B receptors up-regulate hypothalamic POMC and CART gene expression and down-regulate hypothalamic orexin gene expression in mice.

  20. Smoking-based selection and influence in gender-segregated friendship networks: a social network analysis of adolescent smoking.

    PubMed

    Mercken, Liesbeth; Snijders, Tom A B; Steglich, Christian; Vertiainen, Erkki; de Vries, Hein

    2010-07-01

    The main goal of this study was to examine differences between adolescent male and female friendship networks regarding smoking-based selection and influence processes using newly developed social network analysis methods that allow the current state of continuously changing friendship networks to act as a dynamic constraint for changes in smoking behaviour, while allowing current smoking behaviour to be simultaneously a dynamic constraint for changes in friendship networks. Longitudinal design with four measurements. Nine junior high schools in Finland. A total of 1163 adolescents (mean age = 13.6 years) who participated in the control group of the ESFA (European Smoking prevention Framework Approach) study, including 605 males and 558 females. Smoking behaviour of adolescents, parents, siblings and friendship ties. Smoking-based selection of friends was found in male as well as female networks. However, support for influence among friends was found only in female networks. Furthermore, females and males were both influenced by parental smoking behaviour. In Finnish adolescents, both male and female smokers tend to select other smokers as friends but it appears that only females are influenced to smoke by their peer group. This suggests that prevention campaigns targeting resisting peer pressure may be more effective in adolescent girls than boys.

  1. Selective suppression of the slow-inactivating potassium currents by nootropics in molluscan neurons.

    PubMed

    Bukanova, Julia V; Solntseva, Elena I; Skrebitsky, Vladimir G

    2002-09-01

    The role of the voltage-gated K+ channels in the effect of some nootropics was investigated. Earlier, the multiple effect of high concentrations of two nootropics, piracetam and its peptide analogue GVS-111 [Seredenin et al. (1995), US Patent No. 5,439,930], on Ca2+ and K+ currents of molluscan neurons was shown [Solntseva et al. (1997), General Pharmacology 29, 85-89]. In the present work, we describe the selective effect of low concentrations of these nootropics as well as vinpocetine on certain types of K+ current. The experiments were performed on isolated neurons of the land snail Helix pomatia using a two-microelectrode voltage-clamp method. The inward voltage-gated Ca2+ current (ICa) and three subtypes of the outward voltage-gated K+ current were recorded: Ca2+-dependent K+ current (IK(Ca)), delayed rectifying current (IKD), and fast-inactivating K+ current (IA). It has been found that I Ca was not changed in the presence of 30 microM vinpocetine, 100 microM piracetam or 10 nM GVS-111, while slow-inactivating, TEA-sensitive IK(Ca) and IKD were inhibited (IK(Ca) more strongly than IKD). In contrast, the fast-inactivating, 4-AP-sensitive K+ current (IA) was not diminished by low concentrations of piracetam and GVS-111, while vinpocetine even augmented it. A possible role of slow-inactivating subtypes of the K+ channels in the development of different forms of dementia is discussed.

  2. Selective pinning control of the average disease transmissibility in an HIV contact network

    NASA Astrophysics Data System (ADS)

    du Toit, E. F.; Craig, I. K.

    2015-07-01

    Medication is applied to the HIV-infected nodes of high-risk contact networks with the aim of controlling the spread of disease to a predetermined maximum level. This intervention, known as pinning control, is performed both selectively and randomly in the network. These strategies are applied to 300 independent realizations per reference level of incidence on connected undirectional networks without isolated components and varying in size from 100 to 10 000 nodes per network. It is shown that a selective on-off pinning control strategy can control the networks studied with limited steady-state error and, comparing the medians of the doses from both strategies, uses 51.3% less medication than random pinning of all infected nodes. Selective pinning could possibly be used by public health specialists to identify the maximum level of HIV incidence in a population that can be achieved in a constrained funding environment.

  3. Selective suppression of Th2-mediated airway eosinophil infiltration by low-molecular weight CCR3 antagonists.

    PubMed

    Mori, Akio; Ogawa, Koji; Someya, Koichiro; Kunori, Yuichi; Nagakubo, Daisuke; Yoshie, Osamu; Kitamura, Fujiko; Hiroi, Takachika; Kaminuma, Osamu

    2007-08-01

    The effects of selective CC chemokine receptor (CCR)-3 antagonists on antigen-induced leukocyte accumulation in the lungs of mice adoptively transferred with in vitro-differentiated T(h)1 and T(h)2 were investigated. Inhalation of antigen by mice injected with T(h)1 and T(h)2 initiated the migration of T cells themselves into the lungs. Subsequently, neutrophils massively accumulated in T(h)1-transferred mice, whereas eosinophil infiltration was specifically induced by T(h)2. CCR3 antagonists, SB-297006 and/or SB-328437, suppressed antigen-induced accumulation of T(h)2 as well as eosinophils in the lungs, whereas they failed to affect T(h)1-mediated airway inflammation. Not only T(h)2 and eosinophil infiltration but also cellular mobilization in T(h)1-transferred mice was attenuated by an anti-CC chemokine ligand-11 antibody. CCR3 antagonists reduced chemokine production in the lungs of mice transferred with T(h)2 but not T(h)1, suggesting that down-regulation of chemokine synthesis is involved in the selective inhibition of T(h)2-mediated eosinophil infiltration by CCR3 antagonists.

  4. Psychiatric neural networks and neuropharmacology: Selected advances and novel implications

    PubMed Central

    Ghanemi, Abdelaziz

    2013-01-01

    Psychiatric disorders are often considered as simple imbalances between a limited number of cerebral neurotransmitters. In fact, it is more complicated than this “simple approach” and each psychiatric disorder constitutes network dysfunction within which several agents and factors are implicated. Thus, the therapeutical perspectives and implications are as vast and as numerous as the diversity of those network dysfunctions. Furthermore, the description of factors influencing diseases prognoses and treatment efficacy indicates new elements to consider both in therapies and drug researches. PMID:24648819

  5. Search-Related Suppression of Hippocampus and Default Network Activity during Associative Memory Retrieval

    PubMed Central

    Reas, Emilie T.; Gimbel, Sarah I.; Hales, Jena B.; Brewer, James B.

    2011-01-01

    Episodic memory retrieval involves the coordinated interaction of several cognitive processing stages such as mental search, access to a memory store, associative re-encoding, and post-retrieval monitoring. The neural response during memory retrieval is an integration of signals from multiple regions that may subserve supportive cognitive control, attention, sensory association, encoding, or working memory functions. It is particularly challenging to dissociate contributions of these distinct components to brain responses in regions such as the hippocampus, which lies at the interface between overlapping memory encoding and retrieval, and “default” networks. In the present study, event-related functional magnetic resonance imaging (fMRI) and measures of memory performance were used to differentiate brain responses to memory search from subcomponents of episodic memory retrieval associated with successful recall. During the attempted retrieval of both poorly and strongly remembered word pair associates, the hemodynamic response was negatively deflected below baseline in anterior hippocampus and regions of the default network. Activations in anterior hippocampus were functionally distinct from those in posterior hippocampus and negatively correlated with response times. Thus, relative to the pre-stimulus period, the hippocampus shows reduced activity during intensive engagement in episodic memory search. Such deactivation was most salient during trials that engaged only pre-retrieval search processes in the absence of successful recollection or post-retrieval processing. Implications for interpretation of hippocampal fMRI responses during retrieval are discussed. A model is presented to interpret such activations as representing modulation of encoding-related activity, rather than retrieval-related activity. Engagement in intensive mental search may reduce neural and attentional resources that are otherwise tonically devoted to encoding an individual’s stream

  6. Astrocytic gap junctional networks suppress cellular damage in an in vitro model of ischemia

    SciTech Connect

    Shinotsuka, Takanori; Yasui, Masato; Nuriya, Mutsuo

    2014-02-07

    Highlights: • Astrocytes exhibit characteristic changes in [Ca{sup 2+}]{sub i} under OGD. • Astrocytic [Ca{sup 2+}]{sub i} increase is synchronized with a neuronal anoxic depolarization. • Gap junctional couplings protect neurons as well as astrocytes during OGD. - Abstract: Astrocytes play pivotal roles in both the physiology and the pathophysiology of the brain. They communicate with each other via extracellular messengers as well as through gap junctions, which may exacerbate or protect against pathological processes in the brain. However, their roles during the acute phase of ischemia and the underlying cellular mechanisms remain largely unknown. To address this issue, we imaged changes in the intracellular calcium concentration ([Ca{sup 2+}]{sub i}) in astrocytes in mouse cortical slices under oxygen/glucose deprivation (OGD) condition using two-photon microscopy. Under OGD, astrocytes showed [Ca{sup 2+}]{sub i} oscillations followed by larger and sustained [Ca{sup 2+}]{sub i} increases. While the pharmacological blockades of astrocytic receptors for glutamate and ATP had no effect, the inhibitions of gap junctional intercellular coupling between astrocytes significantly advanced the onset of the sustained [Ca{sup 2+}]{sub i} increase after OGD exposure. Interestingly, the simultaneous recording of the neuronal membrane potential revealed that the onset of the sustained [Ca{sup 2+}]{sub i} increase in astrocytes was synchronized with the appearance of neuronal anoxic depolarization. Furthermore, the blockade of gap junctional coupling resulted in a concurrent faster appearance of neuronal depolarizations, which remain synchronized with the sustained [Ca{sup 2+}]{sub i} increase in astrocytes. These results indicate that astrocytes delay the appearance of the pathological responses of astrocytes and neurons through their gap junction-mediated intercellular network under OGD. Thus, astrocytic gap junctional networks provide protection against tissue damage

  7. Wavelength selective polymer network formation of end-functional star polymers.

    PubMed

    Kaupp, Michael; Hiltebrandt, Kai; Trouillet, Vanessa; Mueller, Patrick; Quick, Alexander S; Wegener, Martin; Barner-Kowollik, Christopher

    2016-01-31

    A wavelength selective technique for light-induced network formation based on two photo-active moieties, namely ortho-methylbenzaldehyde and tetrazole is introduced. The network forming species are photo-reactive star polymers generated via reversible activation fragmentation chain transfer (RAFT) polymerization, allowing the network to be based on almost any vinylic monomer. Direct laser writing (DLW) allows to form any complex three-dimensional structure based on the photo-reactive star polymers.

  8. Universal Service in a Global Networked Environment: Selected Issues and Possible Approaches.

    ERIC Educational Resources Information Center

    Bertot, John Carlo; McClure, Charles R.; Owens, Kimberly A.

    1999-01-01

    Presents selected issues related to the development of universal service to networked information resources and services in a global networked environment. Defines universal service as a set of telecommunications services to which users should have access, including appropriate funding and interconnected public telecommunications infrastructure…

  9. An Integrated Architecture and Feature Selection Algorithm for Radial Basis Neural Networks

    DTIC Science & Technology

    2002-03-01

    The research contribution of this thesis is the first known integrated architecture and feature selection algorithm for Radial Basis Neural Networks (RBNNs...Additionally, this thesis compares three different classification techniques, Discriminant Analysis (DA), Feed-Forward Neural Networks (FFN) and RBNNs against

  10. A Novel Complex-Coefficient In-Band Interference Suppression Algorithm for Cognitive Ultra-Wide Band Wireless Sensors Networks

    PubMed Central

    Xiong, Hailiang; Zhang, Wensheng; Xu, Hongji; Du, Zhengfeng; Tang, Huaibin; Li, Jing

    2017-01-01

    With the rapid development of wireless communication systems and electronic techniques, the limited frequency spectrum resources are shared with various wireless devices, leading to a crowded and challenging coexistence circumstance. Cognitive radio (CR) and ultra-wide band (UWB), as sophisticated wireless techniques, have been considered as significant solutions to solve the harmonious coexistence issues. UWB wireless sensors can share the spectrum with primary user (PU) systems without harmful interference. The in-band interference of UWB systems should be considered because such interference can severely affect the transmissions of UWB wireless systems. In order to solve the in-band interference issues for UWB wireless sensor networks (WSN), a novel in-band narrow band interferences (NBIs) elimination scheme is proposed in this paper. The proposed narrow band interferences suppression scheme is based on a novel complex-coefficient adaptive notch filter unit with a single constrained zero-pole pair. Moreover, in order to reduce the computation complexity of the proposed scheme, an adaptive complex-coefficient iterative method based on two-order Taylor series is designed. To cope with multiple narrow band interferences, a linear cascaded high order adaptive filter and a cyclic cascaded high order matrix adaptive filter (CCHOMAF) interference suppression algorithm based on the basic adaptive notch filter unit are also presented. The theoretical analysis and numerical simulation results indicate that the proposed CCHOMAF algorithm can achieve better performance in terms of average bit error rate for UWB WSNs. The proposed in-band NBIs elimination scheme can significantly improve the reception performance of low-cost and low-power UWB wireless systems. PMID:28587085

  11. Selective siRNA-mediated suppression of 5-HT1A autoreceptors evokes strong anti-depressant-like effects.

    PubMed

    Bortolozzi, A; Castañé, A; Semakova, J; Santana, N; Alvarado, G; Cortés, R; Ferrés-Coy, A; Fernández, G; Carmona, M C; Toth, M; Perales, J C; Montefeltro, A; Artigas, F

    2012-06-01

    Depression is a major health problem worldwide. Most prescribed anti-depressants, the selective serotonin reuptake inhibitors (SSRI) show limited efficacy and delayed onset of action, partly due to the activation of somatodendritic 5-HT(1A)-autoreceptors by the excess extracellular serotonin (5-HT) produced by SSRI in the raphe nuclei. Likewise, 5-HT(1A) receptor (5-HT(1A)R) gene polymorphisms leading to high 5-HT(1A)-autoreceptor expression increase depression susceptibility and decrease treatment response. In this study, we report on a new treatment strategy based on the administration of small-interfering RNA (siRNA) to acutely suppress 5-HT(1A)-autoreceptor-mediated negative feedback mechanisms. We developed a conjugated siRNA (C-1A-siRNA) by covalently binding siRNA targeting 5-HT(1A) receptor mRNA with the SSRI sertraline in order to concentrate it in serotonin axons, rich in serotonin transporter (SERT) sites. The intracerebroventricular (i.c.v.) infusion of C-1A-siRNA to mice resulted in its selective accumulation in serotonin neurons. This evoked marked anti-depressant-like effects in the forced swim and tail suspension tests, but did not affect anxiety-like behaviors in the elevated plus-maze. In parallel, C-1A-siRNA administration markedly decreased 5-HT(1A)-autoreceptor expression and suppressed 8-OH-DPAT-induced hypothermia (a pre-synaptic 5-HT(1A)R effect in mice) without affecting post-synaptic 5-HT(1A)R expression in hippocampus and prefrontal cortex. Moreover, i.c.v. C-1A-siRNA infusion augmented the increase in extracellular serotonin evoked by fluoxetine in prefrontal cortex to the level seen in 5-HT(1A)R knockout mice. Interestingly, intranasal C-1A-siRNA administration produced the same effects, thus opening the way to the therapeutic use of C-1A-siRNA. Hence, C-1A-siRNA represents a new approach to treat mood disorders as monotherapy or in combination with SSRI.

  12. Feature and Model Selection in Feedforward Neural Networks

    DTIC Science & Technology

    1994-06-01

    and Urig studied a neural network model of nuclear power plant thermal performance data to identify the variables which strongly affect the heat rate...to determine which efforts will be most effective in improving nuclear power plant efficiency [21]. Klimasauskas investigates the impact of small...approximating A, is defined by sampling only the known data. Guo and Urig suggested a similar metric for sensitivity analysis of nuclear power plant thermal

  13. Size and shape selectivity of host networks built based on tunable secondary building units.

    PubMed

    Moon, Dohyun; Lah, Myoung Soo

    2005-03-21

    By modulating the secondary building units derived from the primary building units, N-acylsalicylhydrazides (H3 xshz), we have been able to construct isostructural but tunable host networks, [Mn6(xshz)6(dmf)2(bpea)2], with different cavity sizes and shapes where the secondary building units, [Mn6(xshz)6], were linked through exo-bidentate bridging ligand, 1,2-bis(pyridyl)ethane (bpea) to form 3-D networks. With a short length linear N-acyl side chain at the primary building unit, the host networks have a 3-D network with three-dimensional cavities. With an appropriate length linear N-acyl side chain at the primary building unit, the host network keeps the isostructural 3-D network but with two types of one-dimensional channels of reduced cavity volume. The tuned host networks showed not only size selectivity for the guest molecules but also shape selectivity. While the three-dimensional channeled host showed selectivity depending on the length of the podal guests, the one-dimensional channeled host showed selectivity depending on both the length and/or the podality of the guest molecules.

  14. Selective Narrowing of Social Networks Across Adulthood is Associated With Improved Emotional Experience in Daily Life.

    PubMed

    English, Tammy; Carstensen, Laura L

    2014-03-01

    Past research has documented age differences in the size and composition of social networks that suggest that networks grow smaller with age and include an increasingly greater proportion of well-known social partners. According to socioemotional selectivity theory, such changes in social network composition serve an antecedent emotion regulatory function that supports an age-related increase in the priority that people place on emotional well-being. The present study employed a longitudinal design with a sample that spanned the full adult age range to examine whether there is evidence of within-individual (developmental) change in social networks and whether the characteristics of relationships predict emotional experiences in daily life. Using growth curve analyses, social networks were found to increase in size in young adulthood and then decline steadily throughout later life. As postulated by socioemotional selectivity theory, reductions were observed primarily in the number of peripheral partners; the number of close partners was relatively stable over time. In addition, cross-sectional analyses revealed that older adults reported that social network members elicited less negative emotion and more positive emotion. The emotional tone of social networks, particularly when negative emotions were associated with network members, also predicted experienced emotion of participants. Overall, findings were robust after taking into account demographic variables and physical health. The implications of these findings are discussed in the context of socioemotional selectivity theory and related theoretical models.

  15. Selective Narrowing of Social Networks Across Adulthood is Associated With Improved Emotional Experience in Daily Life

    PubMed Central

    English, Tammy; Carstensen, Laura L.

    2014-01-01

    Past research has documented age differences in the size and composition of social networks that suggest that networks grow smaller with age and include an increasingly greater proportion of well-known social partners. According to socioemotional selectivity theory, such changes in social network composition serve an antecedent emotion regulatory function that supports an age-related increase in the priority that people place on emotional well-being. The present study employed a longitudinal design with a sample that spanned the full adult age range to examine whether there is evidence of within-individual (developmental) change in social networks and whether the characteristics of relationships predict emotional experiences in daily life. Using growth curve analyses, social networks were found to increase in size in young adulthood and then decline steadily throughout later life. As postulated by socioemotional selectivity theory, reductions were observed primarily in the number of peripheral partners; the number of close partners was relatively stable over time. In addition, cross-sectional analyses revealed that older adults reported that social network members elicited less negative emotion and more positive emotion. The emotional tone of social networks, particularly when negative emotions were associated with network members, also predicted experienced emotion of participants. Overall, findings were robust after taking into account demographic variables and physical health. The implications of these findings are discussed in the context of socioemotional selectivity theory and related theoretical models. PMID:24910483

  16. Joint Bayesian variable and graph selection for regression models with network-structured predictors.

    PubMed

    Peterson, Christine B; Stingo, Francesco C; Vannucci, Marina

    2016-03-30

    In this work, we develop a Bayesian approach to perform selection of predictors that are linked within a network. We achieve this by combining a sparse regression model relating the predictors to a response variable with a graphical model describing conditional dependencies among the predictors. The proposed method is well-suited for genomic applications because it allows the identification of pathways of functionally related genes or proteins that impact an outcome of interest. In contrast to previous approaches for network-guided variable selection, we infer the network among predictors using a Gaussian graphical model and do not assume that network information is available a priori. We demonstrate that our method outperforms existing methods in identifying network-structured predictors in simulation settings and illustrate our proposed model with an application to inference of proteins relevant to glioblastoma survival.

  17. Joint Bayesian variable and graph selection for regression models with network-structured predictors

    PubMed Central

    Peterson, C. B.; Stingo, F. C.; Vannucci, M.

    2015-01-01

    In this work, we develop a Bayesian approach to perform selection of predictors that are linked within a network. We achieve this by combining a sparse regression model relating the predictors to a response variable with a graphical model describing conditional dependencies among the predictors. The proposed method is well-suited for genomic applications since it allows the identification of pathways of functionally related genes or proteins which impact an outcome of interest. In contrast to previous approaches for network-guided variable selection, we infer the network among predictors using a Gaussian graphical model and do not assume that network information is available a priori. We demonstrate that our method outperforms existing methods in identifying network-structured predictors in simulation settings, and illustrate our proposed model with an application to inference of proteins relevant to glioblastoma survival. PMID:26514925

  18. Selective inhibition of cyclooxygenase-2 suppresses metastatic disease without affecting primary tumor growth in a murine model of Ewing sarcoma.

    PubMed

    Gendy, Amir S; Lipskar, Aaron; Glick, Richard D; Steinberg, Bettie M; Edelman, Morris; Soffer, Samuel Z

    2011-01-01

    Mammalian target of rapamycin suppression by rapamycin inhibits tumor growth and neovascularization via cyclooxygenase-2 (COX-2) downregulation with no effect on lung metastases. We hypothesize that combining a selective COX-2 antagonist (celecoxib) with rapamycin would decrease lung metastases. Ewing sarcoma cells (SK-NEP-1) were surgically implanted into the left kidney of athymic mice (n = 40). The mice were divided into 4 treatment groups (control, rapamycin only, celecoxib only, and combination) and then killed at 6 weeks. Primary tumors were weighed. Vasculature was examined using lectin angiography and immunohistochemistry, and lung metastases were examined using H&E and CD99 immunostaining. Tumor weight and lung metastases were analyzed. Mean primary tumor weights were significantly reduced in the rapamycin-treated groups but not in the celecoxib-only group. Lectin angiography and endothelial markers immunostaining showed markedly decreased vascularity in the rapamycin-treated groups but not in the celecoxib-only group. Celecoxib-treated groups showed significantly fewer mice with lung metastases than non-celecoxib-treated groups. Celecoxib prevents lung metastasis in a murine model of Ewing sarcoma with no effect on tumor size or neovascularization. Cyclooxygenase-2 may represent a future potential target for metastatic disease prevention. Copyright © 2011 Elsevier Inc. All rights reserved.

  19. Selection of genes associated with variations in the Circle of Willis in gerbils using suppression subtractive hybridization.

    PubMed

    Li, Zhenkun; Huo, Xueyun; Zhang, Shuangyue; Lu, Jing; Li, Changlong; Guo, Meng; Fu, Rui; He, Zhengming; Du, Xiaoyan; Chen, Zhenwen

    2015-01-01

    Deformities in the Circle of Willis (CoW) can significantly increase the risk of cerebrovascular disease in humans. However, the molecular mechanisms underlying these deformities have not been understood. Based on our previous studies, variations in the CoW of gerbils are hereditary. A normal CoW is observed in approximately 60% of gerbils, a percentage that also applies to humans. Thus, gerbil is an ideal experimental model for studying variations in the CoW. To study the mechanisms underlying these variations, we selected genes associated with different types of the CoW using suppression subtractive hybridization (SSH). After evaluating the efficiency of SSH using quantitative real-time polymerase chain reaction (qPCR) on subtracted and unsubtracted cDNA and Southern blotting on SSH PCR products, 12 SSH libraries were established. We identified 4 genes (CST3, GNAS, GPx4 and PFN2) associated with variations in the CoW. These genes were identified with qPCR and Western blotting using 70 expressed sequence tags from the SSH libraries. Cloning and sequencing allowed us to demonstrate that the 4 genes were closely related to mouse genes. We may assume that these 4 genes play an important role in the development of variations in the CoW. This study provides a foundation for further research of genes related to development of variations in the CoW and the mechanisms of dysmorphosis of cerebral vessels.

  20. BIOLOGICAL CONTROL OF WHEAT TAKE-ALL DISEASE: II – RAPID SELECTION OF BACTERIA SUPPRESSIVE TO GAEUMANNOMYCES GRAMINIS VAR. TRITICI IN LABORATORY WITH GREENHOUSE AND FIELD CONFIRMATION TRIALS

    USDA-ARS?s Scientific Manuscript database

    Screening large collections of bacteria for potential biological control activity on economically important diseases is often difficult. A quick test tube assay was developed to rapidly screen selected bacterial isolates for their ability to suppress take-all disease of wheat, caused by Gaeumannomyc...

  1. Tigecycline-Amikacin Combination Effectively Suppresses the Selection of Resistance in Clinical Isolates of KPC-Producing Klebsiella pneumoniae

    PubMed Central

    Ni, Wentao; Wei, Chuanqi; Zhou, Chufei; Zhao, Jin; Liang, Beibei; Cui, Junchang; Wang, Rui; Liu, Youning

    2016-01-01

    By far, only tigecycline, colistin, and some aminoglycosides still show favorable in vitro activities against carbapenem-resistant Enterobacteriaceae. However, rapid emergence of resistance often occurs during long-term treatment in clinic, challenging these last resort antimicrobials. In this study, we measured mutant prevention concentration (MPC) and mutant selection window (MSW) of tigecycline, colistin and amikacin alone and in combination for clinical isolates of KPC-producing K. pneumoniae, and characterized the resistant mutants recovered. The MPC90 of 30 tested isolates for tigecycline, colistin, and amikacin were 16, >128, and 128 mg/L, respectively. The average MSW of tigecycline-amikacin, tigecycline-colistin, and amikacin-colistin combinations for four representative strains were 11.99, 200.13, and 372.38, respectively. A strong correlation was found between the MSWcombination and the product of MSW of each single drug. Combinations of 1 minimal inhibitory concentration (MIC) multiple tigecycline and 1 MIC multiple amikacin could result in 1000- to 10000-fold reduction in mutational frequency relative to their individual mutational frequencies, and combinations of 1 MIC multiple amikacin and 1.5–2 MIC multiple tigecycline could successfully restrict the recovery of resistant mutants on agar plates. However, 2 MIC multiple colistin in combination with 2 MIC multiple tigecycline or amikacin merely resulted in approximately 10-fold decrease in the mutational frequency. In conclusion, this study showed tigecycline-amikacin combination could effectively suppress the selection of resistance at low concentrations compared with the colistin-tigecycline and colistin-amikacin combinations, suggesting that this combination may be useful in clinical therapy. PMID:27594855

  2. Tigecycline-Amikacin Combination Effectively Suppresses the Selection of Resistance in Clinical Isolates of KPC-Producing Klebsiella pneumoniae.

    PubMed

    Ni, Wentao; Wei, Chuanqi; Zhou, Chufei; Zhao, Jin; Liang, Beibei; Cui, Junchang; Wang, Rui; Liu, Youning

    2016-01-01

    By far, only tigecycline, colistin, and some aminoglycosides still show favorable in vitro activities against carbapenem-resistant Enterobacteriaceae. However, rapid emergence of resistance often occurs during long-term treatment in clinic, challenging these last resort antimicrobials. In this study, we measured mutant prevention concentration (MPC) and mutant selection window (MSW) of tigecycline, colistin and amikacin alone and in combination for clinical isolates of KPC-producing K. pneumoniae, and characterized the resistant mutants recovered. The MPC90 of 30 tested isolates for tigecycline, colistin, and amikacin were 16, >128, and 128 mg/L, respectively. The average MSW of tigecycline-amikacin, tigecycline-colistin, and amikacin-colistin combinations for four representative strains were 11.99, 200.13, and 372.38, respectively. A strong correlation was found between the MSW combination and the product of MSW of each single drug. Combinations of 1 minimal inhibitory concentration (MIC) multiple tigecycline and 1 MIC multiple amikacin could result in 1000- to 10000-fold reduction in mutational frequency relative to their individual mutational frequencies, and combinations of 1 MIC multiple amikacin and 1.5-2 MIC multiple tigecycline could successfully restrict the recovery of resistant mutants on agar plates. However, 2 MIC multiple colistin in combination with 2 MIC multiple tigecycline or amikacin merely resulted in approximately 10-fold decrease in the mutational frequency. In conclusion, this study showed tigecycline-amikacin combination could effectively suppress the selection of resistance at low concentrations compared with the colistin-tigecycline and colistin-amikacin combinations, suggesting that this combination may be useful in clinical therapy.

  3. Atrial-selective Inhibition of Sodium Channel Current by Wenxin Keli is Effective in Suppressing Atrial Fibrillation

    PubMed Central

    Burashnikov, Alexander; Petroski, Alyssa; Hu, Dan; Barajas-Martinez, Hector; Antzelevitch, Charles

    2011-01-01

    BACKGROUND Wenxin Keli is a Chinese herb extract reported to be of benefit in the treatment of cardiac arrhythmias, cardiac inflammation and heart failure. METHODS AND RESULTS We evaluated the electrophysiologic effects of Wenxin Keli in isolated canine arterially-perfused right atrial preparations with a rim of right ventricular tissue (n=11). Transmembrane action potentials and a pseudo-electrocardiogram were simultaneously recorded. Acetylcholine (ACh, 1 μM) was used to induce atrial fibrillation (AF) and to test the anti-AF potential of Wenxin Keli (5 g/L). Wenxin Keli produced preferential abbreviation of action potential duration (APD90) in atria, but caused atrial-selective prolongation of effective refractory period, due to development of post-repolarization refractoriness. The maximum rate of rise of the action potential upstroke (Vmax) was preferentially reduced in atria. Diastolic threshold of excitation increased in both atria and ventricles, but much more in atria. The duration of the “P wave” (index of atrial conduction time) was prolonged to a much greater extent than the duration of the “QRS complex” (index of ventricular conduction time). Wenxin Keli significantly reduced INa and shifted steady-state inactivation to more negative potentials in HEK293 cells stably expressing SCN5A. Wenxin Keli prevented induction of persistent AF in 100% atria (6/6) and, in another experimental series was found to terminate persistent ACh-mediated AF in 100% of atria (3/3). CONCLUSION Wenxin Keli produces atrial-selective depression of INa-dependent parameters in canine isolated coronary perfused preparations via a unique mechanism and is effective in suppressing AF and preventing its induction, with minimal effects on ventricular electrophysiology. PMID:21884675

  4. Network Structure and Selection Asymmetry Drive Coevolution in Species-Rich Antagonistic Interactions.

    PubMed

    Andreazzi, Cecilia S; Thompson, John N; Guimarães, Paulo R

    2017-07-01

    Ecological interactions shape and are shaped by the evolution of interacting species. Mathematical models and empirical work have explored the multiple ways coevolution could occur in small sets of species, revealing that the addition of even one species can change the coevolutionary dynamics of a pairwise interaction. As a consequence, one of the current challenges in evolutionary biology is to understand how species-rich assemblages evolve and coevolve as networks of interacting species. We combined an adaptive network framework, a trait evolutionary model, and data on network structure to study how network organization affects and is affected by selection in antagonistic interactions such as parasitism, predation, and herbivory. We explored how selection imposed by interactions shapes the evolution of attack and defense traits, parameterizing our models with structural information from 31 empirical assemblages of antagonistic species. In the simulations, the form of coevolution in antagonistic interactions is affected by the intensity and asymmetry of the selection imposed by the interacting partners. Transient escalation in attack and defensive traits was the most prevalent form of coevolutionary dynamics, especially in networks formed by modules of highly interacting species. Fluctuating evolution of traits was observed when the intensity of selection was higher in exploiters than in victims and was especially favored in nested networks. At the species level, highly connected species experienced higher temporal variation in selection regardless of the network structure, resulting in high trait mismatching with their partners. The mismatched patterns of highly connected species, in turn, may explain the emergence of modularity in antagonistic interactions in which selection is stronger on exploiters than on their victims. Our results highlight the roles of different aspects of network structure on antagonistic coevolution: nestedness shapes coevolutionary

  5. The Stochastic Evolutionary Game for a Population of Biological Networks Under Natural Selection

    PubMed Central

    Chen, Bor-Sen; Ho, Shih-Ju

    2014-01-01

    In this study, a population of evolutionary biological networks is described by a stochastic dynamic system with intrinsic random parameter fluctuations due to genetic variations and external disturbances caused by environmental changes in the evolutionary process. Since information on environmental changes is unavailable and their occurrence is unpredictable, they can be considered as a game player with the potential to destroy phenotypic stability. The biological network needs to develop an evolutionary strategy to improve phenotypic stability as much as possible, so it can be considered as another game player in the evolutionary process, ie, a stochastic Nash game of minimizing the maximum network evolution level caused by the worst environmental disturbances. Based on the nonlinear stochastic evolutionary game strategy, we find that some genetic variations can be used in natural selection to construct negative feedback loops, efficiently improving network robustness. This provides larger genetic robustness as a buffer against neutral genetic variations, as well as larger environmental robustness to resist environmental disturbances and maintain a network phenotypic traits in the evolutionary process. In this situation, the robust phenotypic traits of stochastic biological networks can be more frequently selected by natural selection in evolution. However, if the harbored neutral genetic variations are accumulated to a sufficiently large degree, and environmental disturbances are strong enough that the network robustness can no longer confer enough genetic robustness and environmental robustness, then the phenotype robustness might break down. In this case, a network phenotypic trait may be pushed from one equilibrium point to another, changing the phenotypic trait and starting a new phase of network evolution through the hidden neutral genetic variations harbored in network robustness by adaptive evolution. Further, the proposed evolutionary game is extended to

  6. Selective enhancement of attentional networks in college table tennis athletes: a preliminary investigation.

    PubMed

    Wang, Biye; Guo, Wei; Zhou, Chenglin

    2016-01-01

    The purpose of the study was to investigate the characteristics of the attentional network in college table tennis athletes. A total of 65 college students categorized as table tennis athlete group or non-athlete group participated in the study. All participants completed the attentional network test (ANT) which measured the alerting, orienting and executive control networks. The results showed a significant difference between the athlete and non-athlete group for executive control network (p < 0.01), while no differences were observed for alerting (p > 0.05) or orienting (p > 0.05) networks. These results combined suggest that college table tennis athletes exhibited selectively enhanced executive control of attentional networks.

  7. Selective enhancement of attentional networks in college table tennis athletes: a preliminary investigation

    PubMed Central

    Wang, Biye; Guo, Wei

    2016-01-01

    The purpose of the study was to investigate the characteristics of the attentional network in college table tennis athletes. A total of 65 college students categorized as table tennis athlete group or non-athlete group participated in the study. All participants completed the attentional network test (ANT) which measured the alerting, orienting and executive control networks. The results showed a significant difference between the athlete and non-athlete group for executive control network (p < 0.01), while no differences were observed for alerting (p > 0.05) or orienting (p > 0.05) networks. These results combined suggest that college table tennis athletes exhibited selectively enhanced executive control of attentional networks. PMID:27957396

  8. Selective frontal, parietal, and temporal networks in generalized seizures.

    PubMed

    Blumenfeld, Hal; Westerveld, Michael; Ostroff, Robert B; Vanderhill, Susan D; Freeman, Jason; Necochea, Alexandro; Uranga, Paula; Tanhehco, Tasha; Smith, Arien; Seibyl, John P; Stokking, Rik; Studholme, Colin; Spencer, Susan S; Zubal, I George

    2003-08-01

    Are "generalized" seizures truly generalized? Generalized tonic-clonic seizures are classified as either secondarily generalized with local onset or primarily generalized, without known focal onset. In both types of generalized seizures widespread regions of the nervous system engage in abnormally synchronous and high-frequency neuronal firing. However, emerging evidence suggests that all neurons are not homogeneously involved; specific nodes within the network may be crucial for the propagation and behavioral manifestations of generalized tonic-clonic seizures. Study of human tonic-clonic seizures has been limited by problems with patient movement and variable seizure types. To circumvent these problems, we imaged generalized tonic-clonic seizures during electroconvulsive therapy, in which seizure type and timing are well controlled. (99m)Tc-hexamethylpropylene amine oxime injections during seizures provide a "snapshot" of cerebral blood flow that can be imaged by single photon emission computed tomography (SPECT) after seizure termination. Here we show that focal regions of frontal and parietal association cortex show the greatest relative signal increases. Involvement of the higher-order association cortex may explain the profound impairment of consciousness seen in generalized seizures. In addition, focal involvement of the dominant temporal lobe was associated with impaired retrograde verbal memory. Similar focal increases were also seen in imaging of spontaneous secondarily generalized tonic-clonic seizures. Relative sparing of many brain regions during both spontaneous and induced seizures suggests that specific networks may be more important than others in so-called generalized seizures.

  9. Selection of a minimum-boundary reserve network using integer programming.

    PubMed Central

    Onal, Hayri; Briers, Robert A

    2003-01-01

    In the conservation literature, heuristic procedures have been employed to incorporate spatial considerations in reserve network selection with the presumption that computationally convenient optimization models would be too difficult or impossible to formulate. This paper extends the standard set-covering formulation to incorporate a particular spatial selection criterion, namely reducing the reserve boundary to the extent possible, when selecting a reserve network that represents a set of target species at least once. Applying the model to a dataset on the occurrence of breeding birds in Berkshire, UK, demonstrated that the technique resulted in significant reductions in reserve boundary length relative to solutions produced by the standard set-covering formulation. Computational results showed that moderately large reserve network selection problems could be solved without issue. Alternative solutions may be produced to explore trade-offs between boundary length, number of sites required or alternative criteria. PMID:12965014

  10. Spatially reciprocal inhibition of inhibition within a stimulus selection network in the avian midbrain.

    PubMed

    Goddard, C Alex; Mysore, Shreesh P; Bryant, Astra S; Huguenard, John R; Knudsen, Eric I

    2014-01-01

    Reciprocal inhibition between inhibitory projection neurons has been proposed as the most efficient circuit motif to achieve the flexible selection of one stimulus among competing alternatives. However, whether such a motif exists in networks that mediate selection is unclear. Here, we study the connectivity within the nucleus isthmi pars magnocellularis (Imc), a GABAergic nucleus that mediates competitive selection in the midbrain stimulus selection network. Using laser photostimulation of caged glutamate, we find that feedback inhibitory connectivity is global within the Imc. Unlike typical lateral inhibition in other circuits, intra-Imc inhibition remains functionally powerful over long distances. Anatomically, we observed long-range axonal projections and retrograde somatic labeling from focal injections of bi-directional tracers in the Imc, consistent with spatial reciprocity of intra-Imc inhibition. Together, the data indicate that spatially reciprocal inhibition of inhibition occurs throughout the Imc. Thus, the midbrain selection circuit possesses the most efficient circuit motif possible for fast, reliable, and flexible selection.

  11. Sensor Selection for Target Tracking in Wireless Sensor Networks With Uncertainty

    NASA Astrophysics Data System (ADS)

    Cao, Nianxia; Choi, Sora; Masazade, Engin; Varshney, Pramod K.

    2016-10-01

    In this paper, we propose a multiobjective optimization framework for the sensor selection problem in uncertain Wireless Sensor Networks (WSNs). The uncertainties of the WSNs result in a set of sensor observations with insufficient information about the target. We propose a novel mutual information upper bound (MIUB) based sensor selection scheme, which has low computational complexity, same as the Fisher information (FI) based sensor selection scheme, and gives estimation performance similar to the mutual information (MI) based sensor selection scheme. Without knowing the number of sensors to be selected a priori, the multiobjective optimization problem (MOP) gives a set of sensor selection strategies that reveal different trade-offs between two conflicting objectives: minimization of the number of selected sensors and minimization of the gap between the performance metric (MIUB and FI) when all the sensors transmit measurements and when only the selected sensors transmit their measurements based on the sensor selection strategy. Illustrative numerical results that provide valuable insights are presented.

  12. Functional brain networks for sensory maintenance in top-down selective attention to audiovisual inputs.

    PubMed

    Hong, Xiangfei; Sun, Junfeng; Tong, Shanbao

    2013-09-01

    Sensory maintenance in top-down selective attention to audiovisual inputs involves distributed cortical activations, while the connectivity between the widespread cortical regions has not been well understood. Graph theory has been demonstrated to be a useful tool in the analysis of brain networks. In this study, we used graph theoretical analysis to investigate the functional brain networks for sensory maintenance in top-down selective attention to audiovisual inputs. Electroencephalograms (EEGs) of 30 channels were recorded from 13 young healthy subjects during a passive view task and a top-down intersensory selective attention task. Phase synchronization indices of EEG signals in pair were computed to construct weighted brain networks. We found small-world properties of the brain networks during both passive view state and top-down selective attentional state in α, β, and γ bands. In addition, the significantly increased clustering coefficient and decreased characteristic path length were observed for brain networks during attentional state compared with passive view state in both β band and γ band. Our results suggest that functional brain networks in higher frequency bands, i.e., β band and γ band, are integrated in different ways during attentional state compared with passive view state.

  13. Gene Expression Network Reconstruction by Convex Feature Selection when Incorporating Genetic Perturbations

    PubMed Central

    Logsdon, Benjamin A.; Mezey, Jason

    2010-01-01

    Cellular gene expression measurements contain regulatory information that can be used to discover novel network relationships. Here, we present a new algorithm for network reconstruction powered by the adaptive lasso, a theoretically and empirically well-behaved method for selecting the regulatory features of a network. Any algorithms designed for network discovery that make use of directed probabilistic graphs require perturbations, produced by either experiments or naturally occurring genetic variation, to successfully infer unique regulatory relationships from gene expression data. Our approach makes use of appropriately selected cis-expression Quantitative Trait Loci (cis-eQTL), which provide a sufficient set of independent perturbations for maximum network resolution. We compare the performance of our network reconstruction algorithm to four other approaches: the PC-algorithm, QTLnet, the QDG algorithm, and the NEO algorithm, all of which have been used to reconstruct directed networks among phenotypes leveraging QTL. We show that the adaptive lasso can outperform these algorithms for networks of ten genes and ten cis-eQTL, and is competitive with the QDG algorithm for networks with thirty genes and thirty cis-eQTL, with rich topologies and hundreds of samples. Using this novel approach, we identify unique sets of directed relationships in Saccharomyces cerevisiae when analyzing genome-wide gene expression data for an intercross between a wild strain and a lab strain. We recover novel putative network relationships between a tyrosine biosynthesis gene (TYR1), and genes involved in endocytosis (RCY1), the spindle checkpoint (BUB2), sulfonate catabolism (JLP1), and cell-cell communication (PRM7). Our algorithm provides a synthesis of feature selection methods and graphical model theory that has the potential to reveal new directed regulatory relationships from the analysis of population level genetic and gene expression data. PMID:21152011

  14. Selection for territory acquisition is modulated by social network structure in a wild songbird.

    PubMed

    Farine, D R; Sheldon, B C

    2015-03-01

    The social environment may be a key mediator of selection that operates on animals. In many cases, individuals may experience selection not only as a function of their phenotype, but also as a function of the interaction between their phenotype and the phenotypes of the conspecifics they associate with. For example, when animals settle after dispersal, individuals may benefit from arriving early, but, in many cases, these benefits will be affected by the arrival times of other individuals in their local environment. We integrated a recently described method for calculating assortativity on weighted networks, which is the correlation between an individual's phenotype and that of its associates, into an existing framework for measuring the magnitude of social selection operating on phenotypes. We applied this approach to large-scale data on social network structure and the timing of arrival into the breeding area over three years. We found that late-arriving individuals had a reduced probability of breeding. However, the probability of breeding was also influenced by individuals' social networks. Associating with late-arriving conspecifics increased the probability of successfully acquiring a breeding territory. Hence, social selection could offset the effects of nonsocial selection. Given parallel theoretical developments of the importance of local network structure on population processes, and increasing data being collected on social networks in free-living populations, the integration of these concepts could yield significant insights into social evolution.

  15. Selection for territory acquisition is modulated by social network structure in a wild songbird

    PubMed Central

    Farine, D R; Sheldon, B C

    2015-01-01

    The social environment may be a key mediator of selection that operates on animals. In many cases, individuals may experience selection not only as a function of their phenotype, but also as a function of the interaction between their phenotype and the phenotypes of the conspecifics they associate with. For example, when animals settle after dispersal, individuals may benefit from arriving early, but, in many cases, these benefits will be affected by the arrival times of other individuals in their local environment. We integrated a recently described method for calculating assortativity on weighted networks, which is the correlation between an individual's phenotype and that of its associates, into an existing framework for measuring the magnitude of social selection operating on phenotypes. We applied this approach to large-scale data on social network structure and the timing of arrival into the breeding area over three years. We found that late-arriving individuals had a reduced probability of breeding. However, the probability of breeding was also influenced by individuals’ social networks. Associating with late-arriving conspecifics increased the probability of successfully acquiring a breeding territory. Hence, social selection could offset the effects of nonsocial selection. Given parallel theoretical developments of the importance of local network structure on population processes, and increasing data being collected on social networks in free-living populations, the integration of these concepts could yield significant insights into social evolution. PMID:25611344

  16. The role of verbal short-term memory in task selection: how articulatory suppression influences task choice in voluntary task switching.

    PubMed

    Weywadt, Christina R B; Butler, Karin M

    2013-04-01

    The roles of verbal short-term memory (vSTM) in task selection and task performance processes were examined when individuals were asked to voluntarily choose which of two tasks to perform on each trial randomly. Consistent with previous voluntary task-switching (VTS) research, we hypothesized that vSTM would support random task selection by maintaining a sequence of previously executed tasks that would be used by a representativeness heuristic. Furthermore, because using a representativeness heuristic requires sufficient time for updating and comparison processes, we expected that vSTM would have a greater effect on task selection when more time was available. Participants completed VTS under concurrent articulatory suppression and foot tapping at short and long response-to-stimulus intervals (RSIs). Task selection in VTS was more repetitive under suppression than under foot tapping, but this effect did not vary with RSI, suggesting that vSTM does not maintain the sequence of executed tasks to guide task selection. Instead, vSTM is critical for maintaining the intended task and ensuring that it is carried out. In contrast to the finding that a working memory load impairs task performance, we found no difference in reaction times and no switch costs between suppression and foot-tapping conditions, suggesting that vSTM is not critical for task performance.

  17. Patterns of Population Differentiation and Natural Selection on the Celiac Disease Background Risk Network

    PubMed Central

    Sams, Aaron; Hawks, John

    2013-01-01

    Celiac disease is a common small intestinal inflammatory condition induced by wheat gluten and related proteins from rye and barley. Left untreated, the clinical presentation of CD can include failure to thrive, malnutrition, and distension in juveniles. The disease can additionally lead to vitamin deficiencies, anemia, and osteoporosis. Therefore, CD potentially negatively affected fitness in past populations utilizing wheat, barley, and rye. Previous analyses of CD risk variants have uncovered evidence for positive selection on some of these loci. These studies also suggest the possibility that risk for common autoimmune conditions such as CD may be the result of positive selection on immune related loci in the genome to fight infection. Under this evolutionary scenario, disease phenotypes may be a trade-off from positive selection on immunity. If this hypothesis is generally true, we can expect to find a signal of natural selection when we survey across the network of loci known to influence CD risk. This study examines the non-HLA autosomal network of gene loci associated with CD risk in Europe. We reject the null hypothesis of neutrality on this network of CD risk loci. Additionally, we can localize evidence of selection in time and space by adding information from the genome of the Tyrolean Iceman. While we can show significant differentiation between continental regions across the CD network, the pattern of evidence is not consistent with primarily recent (Holocene) selection across this network in Europe. Further localization of ancient selection on this network may illuminate the ecological pressures acting on the immune system during this critically interesting phase of our evolution. PMID:23936230

  18. Patterns of population differentiation and natural selection on the celiac disease background risk network.

    PubMed

    Sams, Aaron; Hawks, John

    2013-01-01

    Celiac disease is a common small intestinal inflammatory condition induced by wheat gluten and related proteins from rye and barley. Left untreated, the clinical presentation of CD can include failure to thrive, malnutrition, and distension in juveniles. The disease can additionally lead to vitamin deficiencies, anemia, and osteoporosis. Therefore, CD potentially negatively affected fitness in past populations utilizing wheat, barley, and rye. Previous analyses of CD risk variants have uncovered evidence for positive selection on some of these loci. These studies also suggest the possibility that risk for common autoimmune conditions such as CD may be the result of positive selection on immune related loci in the genome to fight infection. Under this evolutionary scenario, disease phenotypes may be a trade-off from positive selection on immunity. If this hypothesis is generally true, we can expect to find a signal of natural selection when we survey across the network of loci known to influence CD risk. This study examines the non-HLA autosomal network of gene loci associated with CD risk in Europe. We reject the null hypothesis of neutrality on this network of CD risk loci. Additionally, we can localize evidence of selection in time and space by adding information from the genome of the Tyrolean Iceman. While we can show significant differentiation between continental regions across the CD network, the pattern of evidence is not consistent with primarily recent (Holocene) selection across this network in Europe. Further localization of ancient selection on this network may illuminate the ecological pressures acting on the immune system during this critically interesting phase of our evolution.

  19. A neural network based reputation bootstrapping approach for service selection

    NASA Astrophysics Data System (ADS)

    Wu, Quanwang; Zhu, Qingsheng; Li, Peng

    2015-10-01

    With the concept of service-oriented computing becoming widely accepted in enterprise application integration, more and more computing resources are encapsulated as services and published online. Reputation mechanism has been studied to establish trust on prior unknown services. One of the limitations of current reputation mechanisms is that they cannot assess the reputation of newly deployed services as no record of their previous behaviours exists. Most of the current bootstrapping approaches merely assign default reputation values to newcomers. However, by this kind of methods, either newcomers or existing services will be favoured. In this paper, we present a novel reputation bootstrapping approach, where correlations between features and performance of existing services are learned through an artificial neural network (ANN) and they are then generalised to establish a tentative reputation when evaluating new and unknown services. Reputations of services published previously by the same provider are also incorporated for reputation bootstrapping if available. The proposed reputation bootstrapping approach is seamlessly embedded into an existing reputation model and implemented in the extended service-oriented architecture. Empirical studies of the proposed approach are shown at last.

  20. Early-Onset Network Hyperexcitability in Presymptomatic Alzheimer's Disease Transgenic Mice Is Suppressed by Passive Immunization with Anti-Human APP/Aβ Antibody and by mGluR5 Blockade.

    PubMed

    Kazim, Syed F; Chuang, Shih-Chieh; Zhao, Wangfa; Wong, Robert K S; Bianchi, Riccardo; Iqbal, Khalid

    2017-01-01

    Cortical and hippocampal network hyperexcitability appears to be an early event in Alzheimer's disease (AD) pathogenesis, and may contribute to memory impairment. It remains unclear if network hyperexcitability precedes memory impairment in mouse models of AD and what are the underlying cellular mechanisms. We thus evaluated seizure susceptibility and hippocampal network hyperexcitability at ~3 weeks of age [prior to amyloid beta (Aβ) plaque deposition, neurofibrillary pathology, and cognitive impairment] in a triple transgenic mouse model of familial AD (3xTg-AD mouse) that harbors mutated human Aβ precursor protein (APP), tau and presenilin 1 (PS1) genes. Audiogenic seizures were elicited in a higher proportion of 3xTg-AD mice compared with wild type (WT) controls. Seizure susceptibility in 3xTg-AD mice was attenuated either by passive immunization with anti-human APP/Aβ antibody (6E10) or by blockade of metabotropic glutamate receptor 5 (mGluR5) with the selective antagonist, 2-methyl-6-(phenylethynyl)pyridine hydrochloride (MPEP). In in vitro hippocampal slices, suppression of synaptic inhibition with the GABAA receptor antagonist, bicuculline, induced prolonged epileptiform (>1.5 s in duration) ictal-like discharges in the CA3 neuronal network in the majority of the slices from 3xTg-AD mice. In contrast, only short epileptiform (<1.5 s in duration) interictal-like discharges were observed following bicuculline application in the CA3 region of WT slices. The ictal-like activity in CA3 region of the hippocampus was significantly reduced in the 6E10-immunized compared to the saline-treated 3xTg-AD mice. MPEP acutely suppressed the ictal-like discharges in 3xTg-AD slices. Remarkably, epileptiform discharge duration positively correlated with intraneuronal human (transgenic) APP/Aβ expression in the CA3 region of the hippocampus. Our data suggest that in a mouse model of familial AD, hypersynchronous network activity underlying seizure susceptibility precedes

  1. Early-Onset Network Hyperexcitability in Presymptomatic Alzheimer’s Disease Transgenic Mice Is Suppressed by Passive Immunization with Anti-Human APP/Aβ Antibody and by mGluR5 Blockade

    PubMed Central

    Kazim, Syed F.; Chuang, Shih-Chieh; Zhao, Wangfa; Wong, Robert K. S.; Bianchi, Riccardo; Iqbal, Khalid

    2017-01-01

    Cortical and hippocampal network hyperexcitability appears to be an early event in Alzheimer’s disease (AD) pathogenesis, and may contribute to memory impairment. It remains unclear if network hyperexcitability precedes memory impairment in mouse models of AD and what are the underlying cellular mechanisms. We thus evaluated seizure susceptibility and hippocampal network hyperexcitability at ~3 weeks of age [prior to amyloid beta (Aβ) plaque deposition, neurofibrillary pathology, and cognitive impairment] in a triple transgenic mouse model of familial AD (3xTg-AD mouse) that harbors mutated human Aβ precursor protein (APP), tau and presenilin 1 (PS1) genes. Audiogenic seizures were elicited in a higher proportion of 3xTg-AD mice compared with wild type (WT) controls. Seizure susceptibility in 3xTg-AD mice was attenuated either by passive immunization with anti-human APP/Aβ antibody (6E10) or by blockade of metabotropic glutamate receptor 5 (mGluR5) with the selective antagonist, 2-methyl-6-(phenylethynyl)pyridine hydrochloride (MPEP). In in vitro hippocampal slices, suppression of synaptic inhibition with the GABAA receptor antagonist, bicuculline, induced prolonged epileptiform (>1.5 s in duration) ictal-like discharges in the CA3 neuronal network in the majority of the slices from 3xTg-AD mice. In contrast, only short epileptiform (<1.5 s in duration) interictal-like discharges were observed following bicuculline application in the CA3 region of WT slices. The ictal-like activity in CA3 region of the hippocampus was significantly reduced in the 6E10-immunized compared to the saline-treated 3xTg-AD mice. MPEP acutely suppressed the ictal-like discharges in 3xTg-AD slices. Remarkably, epileptiform discharge duration positively correlated with intraneuronal human (transgenic) APP/Aβ expression in the CA3 region of the hippocampus. Our data suggest that in a mouse model of familial AD, hypersynchronous network activity underlying seizure susceptibility precedes

  2. Performance analysis of relay subset selection for amplify-and-forward cognitive relay networks.

    PubMed

    Sultan, Kiran; Qureshi, Ijaz Mansoor; Malik, Aqdas Naveed; Zubair, Muhammad

    2014-01-01

    Cooperative communication is regarded as a key technology in wireless networks, including cognitive radio networks (CRNs), which increases the diversity order of the signal to combat the unfavorable effects of the fading channels, by allowing distributed terminals to collaborate through sophisticated signal processing. Underlay CRNs have strict interference constraints towards the secondary users (SUs) active in the frequency band of the primary users (PUs), which limits their transmit power and their coverage area. Relay selection offers a potential solution to the challenges faced by underlay networks, by selecting either single best relay or a subset of potential relay set under different design requirements and assumptions. The best relay selection schemes proposed in the literature for amplify-and-forward (AF) based underlay cognitive relay networks have been very well studied in terms of outage probability (OP) and bit error rate (BER), which is deficient in multiple relay selection schemes. The novelty of this work is to study the outage behavior of multiple relay selection in the underlay CRN and derive the closed-form expressions for the OP and BER through cumulative distribution function (CDF) of the SNR received at the destination. The effectiveness of relay subset selection is shown through simulation results.

  3. Selecting networks of nature reserves: methods do affect the long-term outcome

    PubMed Central

    Virolainen, K. M.; Virola, T.; Suhonen, J.; Kuitunen, M.; Lammi, A.; ki, P. Siikam

    1999-01-01

    Data on vascular plants of boreal lakes in Finland were used to compare the efficiency of reserve selection methods in representing four aspects of biodiversity over a 63 year period. These aspects included species richness, phylogenetic diversity, restricted range diversity and threatened species. Our results show that the efficiency of reserve selection methods depends on the selection criteria used and on the aspect of biodiversity under consideration. Heuristic methods and optimizing algorithms were nearly equally efficient in selecting lake networks over a small geographical range. In addition, a scoring procedure was observed to be efficient in maintaining different aspects of biodiversity over time. However, the random selection of lakes seems to be the most inefficient option for a reserve network. In general, reserve selection methods seem to favour lakes that maximize one aspect of diversity at the time of selection, but the network may not be the best option for maintaining the maximum diversity over time. The reserve selection methods do affect the long-term outcome but it is impossible to recommend one method over the others unequivocally.

  4. Using attribute grammars for the genetic selection of back-propagation networks for character recognition

    NASA Astrophysics Data System (ADS)

    Browse, Roger A.; Hussain, Talib S.; Smillie, Matthew B.

    1999-03-01

    Determining exactly which neural network architecture, with which parameters, will provide the best solution to a classification task is often based upon the intuitions and experience of the implementers of neural network solutions. The research presented in this paper is centered on the development of automated methods for the selection of appropriate networks, as applied to character recognition. The Network Generating Attribute Grammar Encoding system is a compact and general method for the specification of commonly accepted network architectures that can be easily expanded to include novel architectures, or that can be easily restricted to a small subset of some known architecture. Within this system, the context-free component of the attribute grammar specifies a class of basic architectures by using the non-terminals to represent network, layers and component structures. The inherited and synthesized attributes indicate the connections necessary to develop a functioning network from any parse tree that is generated from the grammar. The attribute grammar encoding is particularly conducive to the use of genetic algorithms as a strategy for searching the space of possible networks. The resultant parse trees are used as the genetic code, permitting a variety of different genetic manipulations. We apply this approach in the generation of backpropagation networks for recognition of characters from a set consisting of 20,000 examples of 26 letters.

  5. Differential Selection within the Drosophila Retinal Determination Network and Evidence for Functional Divergence between Paralog Pairs

    PubMed Central

    Datta, Rhea R.; Cruickshank, Tami; Kumar, Justin P.

    2011-01-01

    The retinal determination (RD) network in Drosophila comprises fourteen known nuclear proteins that include DNA binding proteins, transcriptional co-activators, kinases and phosphatases. The composition of the network varies considerably throughout the animal kingdom, with the network in several basal insects having fewer members and with vertebrates having potentially significantly higher numbers of retinal determination genes. One important contributing factor for the variation in gene number within the network is gene duplication. For example, ten members of the RD network in Drosophila are derived from duplication events. Here we present an analysis of the coding regions of the five pairs of duplicate genes from within the retinal determination network of several different Drosophila species. We demonstrate that there is differential selection across the coding regions of all RD genes. Additionally, some of the most significant differences in ratios of non-silent to silent site substitutions (dN/dS) between paralog pairs are found within regions that have no ascribed function. Previous structure/function analyses of several duplicate genes have identified areas within one gene that contain novel activities when compared to its paralog. The evolutionary analysis presented here identifies these same areas in the paralogs as being under high levels of relaxed selection. We suggest that sequence divergence between paralogs and selection signatures can be used as a reasonable predictor of functional changes in rapidly evolving motifs. PMID:21210943

  6. On cooperative and efficient overlay network evolution based on a group selection pattern.

    PubMed

    Nakao, Akihiro; Wang, Yufeng

    2010-04-01

    In overlay networks, the interplay between network structure and dynamics remains largely unexplored. In this paper, we study dynamic coevolution between individual rational strategies (cooperative or defect) and the overlay network structure, that is, the interaction between peer's local rational behaviors and the emergence of the whole network structure. We propose an evolutionary game theory (EGT)-based overlay topology evolution scheme to drive a given overlay into the small-world structure (high global network efficiency and average clustering coefficient). Our contributions are the following threefold: From the viewpoint of peers' local interactions, we explicitly consider the peer's rational behavior and introduce a link-formation game to characterize the social dilemma of forming links in an overlay network. Furthermore, in the evolutionary link-formation phase, we adopt a simple economic process: Each peer keeps one link to a cooperative neighbor in its neighborhood, which can slightly speed up the convergence of cooperation and increase network efficiency; from the viewpoint of the whole network structure, our simulation results show that the EGT-based scheme can drive an arbitrary overlay network into a fully cooperative and efficient small-world structure. Moreover, we compare our scheme with a search-based economic model of network formation and illustrate that our scheme can achieve the experimental and analytical results in the latter model. In addition, we also graphically illustrate the final overlay network structure; finally, based on the group selection model and evolutionary set theory, we theoretically obtain the approximate threshold of cost and draw the conclusion that the small value of the average degree and the large number of the total peers in an overlay network facilitate the evolution of cooperation.

  7. Distribution of Orientation Selectivity in Recurrent Networks of Spiking Neurons with Different Random Topologies

    PubMed Central

    Sadeh, Sadra; Rotter, Stefan

    2014-01-01

    Neurons in the primary visual cortex are more or less selective for the orientation of a light bar used for stimulation. A broad distribution of individual grades of orientation selectivity has in fact been reported in all species. A possible reason for emergence of broad distributions is the recurrent network within which the stimulus is being processed. Here we compute the distribution of orientation selectivity in randomly connected model networks that are equipped with different spatial patterns of connectivity. We show that, for a wide variety of connectivity patterns, a linear theory based on firing rates accurately approximates the outcome of direct numerical simulations of networks of spiking neurons. Distance dependent connectivity in networks with a more biologically realistic structure does not compromise our linear analysis, as long as the linearized dynamics, and hence the uniform asynchronous irregular activity state, remain stable. We conclude that linear mechanisms of stimulus processing are indeed responsible for the emergence of orientation selectivity and its distribution in recurrent networks with functionally heterogeneous synaptic connectivity. PMID:25469704

  8. Selective Laser Direct Patterning of Silver Nanowire Percolation Network Transparent Conductor for Capacitive Touch Panel.

    PubMed

    Hong, Sukjoon; Yeo, Junyeob; Lee, Jinhwan; Lee, Habeom; Lee, Phillip; Lee, Seung S; Ko, Seung Hwan

    2015-03-01

    We introduce a facile method to enhance the functionality of a patterned metallic transparent conductor through selective laser ablation of metal nanowire percolation network. By scanning focused nanosecond pulsed laser on silver nanowire percolation network, silver nanowires are selectively ablated and patterned without using any conventional chemical etching or photolithography steps. Various arbitrary patterns of silver nanowire transparent conductors are readily created on the percolation network by changing various laser parameters such as repetition rate and power. The macroscopic optical and electrical properties of the percolation network transparent conductor can be easily tuned by changing the conductor pattern design via digital selective laser ablation. Further investigation on the silver nanowire based electrode line prepared by the ablation process substantiates that the general relation for a conducting thin film fails at a narrow width, which should be considered for the applications that requires a high resolution patterns. Finally, as a proof of concept, a capacitive touch sensor with diamond patterns has been demonstrated by selective laser ablation of metal nanowire percolation network.

  9. Teen Alcohol Use and Social Networks: The Contributions of Friend Influence and Friendship Selection.

    PubMed

    Cheadle, Jacob E; Walsemann, Katrina M; Goosby, Bridget J

    2015-10-01

    We evaluated the contributions of teen alcohol use to the formation and continuation of new and existing friendships while in turn estimating the influence of friend drinking on individuals' regular use and heavy drinking. Longitudinal network analysis was used to assess the mutual influences between teen drinking and social networks among adolescents in two large Add Health schools where full network data was collected three times. Friendship processes were disaggregated into the formation of new friendships and the continuation of existing friendships in a joint model isolating friendship selection and friend influences. Friends have a modest influence on one another when selection is controlled. Selection is more complicated than prior studies suggest, and is only related to new friendships and not their duration in the largest school. Alcohol use predicts decreasing popularity in some cases, and popularity does not predict alcohol consumption. Intervention efforts should continue pursuing strategies that mitigate negative peer influences. The development of socializing opportunities that facilitate relationship opportunities to select on healthy behaviors also appears promising. Future work preventing teen substance use should incorporate longitudinal network assessments to determine whether programs promote protective peer relationships in addition to how treatment effects diffuse through social networks.

  10. Teen Alcohol Use and Social Networks: The Contributions of Friend Influence and Friendship Selection

    PubMed Central

    Cheadle, Jacob E; Walsemann, Katrina M; Goosby, Bridget J

    2015-01-01

    Background We evaluated the contributions of teen alcohol use to the formation and continuation of new and existing friendships while in turn estimating the influence of friend drinking on individuals’ regular use and heavy drinking. Method Longitudinal network analysis was used to assess the mutual influences between teen drinking and social networks among adolescents in two large Add Health schools where full network data was collected three times. Friendship processes were disaggregated into the formation of new friendships and the continuation of existing friendships in a joint model isolating friendship selection and friend influences. Results Friends have a modest influence on one another when selection is controlled. Selection is more complicated than prior studies suggest, and is only related to new friendships and not their duration in the largest school. Alcohol use predicts decreasing popularity in some cases, and popularity does not predict alcohol consumption. Conclusion Intervention efforts should continue pursuing strategies that mitigate negative peer influences. The development of socializing opportunities that facilitate relationship opportunities to select on healthy behaviors also appears promising. Future work preventing teen substance use should incorporate longitudinal network assessments to determine whether programs promote protective peer relationships in addition to how treatment effects diffuse through social networks. PMID:26692436

  11. A Reinforcement Routing Algorithm with Access Selection in the Multi-Hop Multi-Interface Networks

    NASA Astrophysics Data System (ADS)

    Jafari, Amir Hosein; Shahhoseini, Hadi Shahriar

    2015-03-01

    In this paper, a routing algorithm is proposed for access selection in a network to find the optimal paths among intermediate nodes with multiple interfaces. Markov Decision Process is applied in each node to find optimal policy and select proper paths to the best access point in a dynamic environment. A reward function is defined as environment feedback to optimize and adapt routing behavior of nodes based on the local information. Selection metrics in each node are interface load, link quality and destination condition. It is shown, by using the proposed algorithm, there are better management in the node which decreases interference and collision and selects links with better quality toward the best possible destination. The performance of the method is exemplified and it is shown how the throughput and average delay of the network with more interface in its nodes, improved while packet loss degrades. As an example a two-interface and a one-interface network are studied. It is shown when network load is increased, interface management will improve the throughput, in the network with two-interface nodes. Also, by considering the link quality factor in the reward function, packet dropping becomes less but average delay increases.

  12. NetDiff – Bayesian model selection for differential gene regulatory network inference

    PubMed Central

    Thorne, Thomas

    2016-01-01

    Differential networks allow us to better understand the changes in cellular processes that are exhibited in conditions of interest, identifying variations in gene regulation or protein interaction between, for example, cases and controls, or in response to external stimuli. Here we present a novel methodology for the inference of differential gene regulatory networks from gene expression microarray data. Specifically we apply a Bayesian model selection approach to compare models of conserved and varying network structure, and use Gaussian graphical models to represent the network structures. We apply a variational inference approach to the learning of Gaussian graphical models of gene regulatory networks, that enables us to perform Bayesian model selection that is significantly more computationally efficient than Markov Chain Monte Carlo approaches. Our method is demonstrated to be more robust than independent analysis of data from multiple conditions when applied to synthetic network data, generating fewer false positive predictions of differential edges. We demonstrate the utility of our approach on real world gene expression microarray data by applying it to existing data from amyotrophic lateral sclerosis cases with and without mutations in C9orf72, and controls, where we are able to identify differential network interactions for further investigation. PMID:27982083

  13. NetDiff - Bayesian model selection for differential gene regulatory network inference.

    PubMed

    Thorne, Thomas

    2016-12-16

    Differential networks allow us to better understand the changes in cellular processes that are exhibited in conditions of interest, identifying variations in gene regulation or protein interaction between, for example, cases and controls, or in response to external stimuli. Here we present a novel methodology for the inference of differential gene regulatory networks from gene expression microarray data. Specifically we apply a Bayesian model selection approach to compare models of conserved and varying network structure, and use Gaussian graphical models to represent the network structures. We apply a variational inference approach to the learning of Gaussian graphical models of gene regulatory networks, that enables us to perform Bayesian model selection that is significantly more computationally efficient than Markov Chain Monte Carlo approaches. Our method is demonstrated to be more robust than independent analysis of data from multiple conditions when applied to synthetic network data, generating fewer false positive predictions of differential edges. We demonstrate the utility of our approach on real world gene expression microarray data by applying it to existing data from amyotrophic lateral sclerosis cases with and without mutations in C9orf72, and controls, where we are able to identify differential network interactions for further investigation.

  14. Chain-Wise Generalization of Road Networks Using Model Selection

    NASA Astrophysics Data System (ADS)

    Bulatov, D.; Wenzel, S.; Häufel, G.; Meidow, J.

    2017-05-01

    Streets are essential entities of urban terrain and their automatized extraction from airborne sensor data is cumbersome because of a complex interplay of geometric, topological and semantic aspects. Given a binary image, representing the road class, centerlines of road segments are extracted by means of skeletonization. The focus of this paper lies in a well-reasoned representation of these segments by means of geometric primitives, such as straight line segments as well as circle and ellipse arcs. We propose the fusion of raw segments based on similarity criteria; the output of this process are the so-called chains which better match to the intuitive perception of what a street is. Further, we propose a two-step approach for chain-wise generalization. First, the chain is pre-segmented using circlePeucker and finally, model selection is used to decide whether two neighboring segments should be fused to a new geometric entity. Thereby, we consider both variance-covariance analysis of residuals and model complexity. The results on a complex data-set with many traffic roundabouts indicate the benefits of the proposed procedure.

  15. Determine the optimal carrier selection for a logistics network based on multi-commodity reliability criterion

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Kuei; Yeh, Cheng-Ta

    2013-05-01

    From the perspective of supply chain management, the selected carrier plays an important role in freight delivery. This article proposes a new criterion of multi-commodity reliability and optimises the carrier selection based on such a criterion for logistics networks with routes and nodes, over which multiple commodities are delivered. Carrier selection concerns the selection of exactly one carrier to deliver freight on each route. The capacity of each carrier has several available values associated with a probability distribution, since some of a carrier's capacity may be reserved for various orders. Therefore, the logistics network, given any carrier selection, is a multi-commodity multi-state logistics network. Multi-commodity reliability is defined as a probability that the logistics network can satisfy a customer's demand for various commodities, and is a performance indicator for freight delivery. To solve this problem, this study proposes an optimisation algorithm that integrates genetic algorithm, minimal paths and Recursive Sum of Disjoint Products. A practical example in which multi-sized LCD monitors are delivered from China to Germany is considered to illustrate the solution procedure.

  16. Emergence of Selectivity to Looming Stimuli in a Spiking Network Model of the Optic Tectum

    PubMed Central

    Jang, Eric V.; Ramirez-Vizcarrondo, Carolina; Aizenman, Carlos D.; Khakhalin, Arseny S.

    2016-01-01

    The neural circuits in the optic tectum of Xenopus tadpoles are selectively responsive to looming visual stimuli that resemble objects approaching the animal at a collision trajectory. This selectivity is required for adaptive collision avoidance behavior in this species, but its underlying mechanisms are not known. In particular, it is still unclear how the balance between the recurrent spontaneous network activity and the newly arriving sensory flow is set in this structure, and to what degree this balance is important for collision detection. Also, despite the clear indication for the presence of strong recurrent excitation and spontaneous activity, the exact topology of recurrent feedback circuits in the tectum remains elusive. In this study we take advantage of recently published detailed cell-level data from tadpole tectum to build an informed computational model of it, and investigate whether dynamic activation in excitatory recurrent retinotopic networks may on its own underlie collision detection. We consider several possible recurrent connectivity configurations and compare their performance for collision detection under different levels of spontaneous neural activity. We show that even in the absence of inhibition, a retinotopic network of quickly inactivating spiking neurons is naturally selective for looming stimuli, but this selectivity is not robust to neuronal noise, and is sensitive to the balance between direct and recurrent inputs. We also describe how homeostatic modulation of intrinsic properties of individual tectal cells can change selectivity thresholds in this network, and qualitatively verify our predictions in a behavioral experiment in freely swimming tadpoles. PMID:27932957

  17. Markov Chain Model-Based Optimal Cluster Heads Selection for Wireless Sensor Networks.

    PubMed

    Ahmed, Gulnaz; Zou, Jianhua; Zhao, Xi; Sadiq Fareed, Mian Muhammad

    2017-02-23

    The longer network lifetime of Wireless Sensor Networks (WSNs) is a goal which is directly related to energy consumption. This energy consumption issue becomes more challenging when the energy load is not properly distributed in the sensing area. The hierarchal clustering architecture is the best choice for these kind of issues. In this paper, we introduce a novel clustering protocol called Markov chain model-based optimal cluster heads (MOCHs) selection for WSNs. In our proposed model, we introduce a simple strategy for the optimal number of cluster heads selection to overcome the problem of uneven energy distribution in the network. The attractiveness of our model is that the BS controls the number of cluster heads while the cluster heads control the cluster members in each cluster in such a restricted manner that a uniform and even load is ensured in each cluster. We perform an extensive range of simulation using five quality measures, namely: the lifetime of the network, stable and unstable region in the lifetime of the network, throughput of the network, the number of cluster heads in the network, and the transmission time of the network to analyze the proposed model. We compare MOCHs against Sleep-awake Energy Efficient Distributed (SEED) clustering, Artificial Bee Colony (ABC), Zone Based Routing (ZBR), and Centralized Energy Efficient Clustering (CEEC) using the above-discussed quality metrics and found that the lifetime of the proposed model is almost 1095, 2630, 3599, and 2045 rounds (time steps) greater than SEED, ABC, ZBR, and CEEC, respectively. The obtained results demonstrate that the MOCHs is better than SEED, ABC, ZBR, and CEEC in terms of energy efficiency and the network throughput.

  18. Markov Chain Model-Based Optimal Cluster Heads Selection for Wireless Sensor Networks

    PubMed Central

    Ahmed, Gulnaz; Zou, Jianhua; Zhao, Xi; Sadiq Fareed, Mian Muhammad

    2017-01-01

    The longer network lifetime of Wireless Sensor Networks (WSNs) is a goal which is directly related to energy consumption. This energy consumption issue becomes more challenging when the energy load is not properly distributed in the sensing area. The hierarchal clustering architecture is the best choice for these kind of issues. In this paper, we introduce a novel clustering protocol called Markov chain model-based optimal cluster heads (MOCHs) selection for WSNs. In our proposed model, we introduce a simple strategy for the optimal number of cluster heads selection to overcome the problem of uneven energy distribution in the network. The attractiveness of our model is that the BS controls the number of cluster heads while the cluster heads control the cluster members in each cluster in such a restricted manner that a uniform and even load is ensured in each cluster. We perform an extensive range of simulation using five quality measures, namely: the lifetime of the network, stable and unstable region in the lifetime of the network, throughput of the network, the number of cluster heads in the network, and the transmission time of the network to analyze the proposed model. We compare MOCHs against Sleep-awake Energy Efficient Distributed (SEED) clustering, Artificial Bee Colony (ABC), Zone Based Routing (ZBR), and Centralized Energy Efficient Clustering (CEEC) using the above-discussed quality metrics and found that the lifetime of the proposed model is almost 1095, 2630, 3599, and 2045 rounds (time steps) greater than SEED, ABC, ZBR, and CEEC, respectively. The obtained results demonstrate that the MOCHs is better than SEED, ABC, ZBR, and CEEC in terms of energy efficiency and the network throughput. PMID:28241492

  19. A sensitive dual-fluorescence reporter system enables positive selection of ras suppressors by suppression of ras-induced apoptosis.

    PubMed

    Dolnikov, Alla; Shen, Sylvie; Millington, Michelle; Passioura, Toby; Pedler, Michelle; Rasko, John Edward Joshua; Symonds, Geoff

    2003-10-01

    We have developed a novel dual-fluorescence reporter system incorporating green (GFP) and red (RFP) fluorescent proteins to monitor expression of the N-ras(m) gene and an N-ras(m) suppressor, respectively. Retroviral vectors were produced in which human N-ras(m) (codon 13 mutation) was coexpressed with GFP, and a ribozyme specifically targeting N-ras(m) was coexpressed with RFP. N-Ras(m) suppression was monitored by measurement of GFP fluorescence in dual-fluorescent (GFP and RFP) cells. We demonstrated that the degree of N-ras(m) suppression was dependent on the ribozyme dose, proportional to red fluorescence, in dual-fluorescent cells. We further showed that ribozyme-mediated N-ras(m)suppression inhibited growth of NIH3T3 and CD34-positive TF-1 cells. In these cultures, ras suppressor activity resulted in the depletion of suppressor-positive cells due to inhibition of cell growth. In contrast, N-ras(m) suppression produced a growth advantage to human leukemic K562 cells, presumably by inhibiting N-ras(m)-induced apoptosis. In K562 cells, ras suppression resulted in the outgrowth of suppressor-positive cells. This provides a platform to identify suppressors of ras that is based on function.

  20. A Framework to Implement IoT Network Performance Modelling Techniques for Network Solution Selection.

    PubMed

    Delaney, Declan T; O'Hare, Gregory M P

    2016-12-01

    No single network solution for Internet of Things (IoT) networks can provide the required level of Quality of Service (QoS) for all applications in all environments. This leads to an increasing number of solutions created to fit particular scenarios. Given the increasing number and complexity of solutions available, it becomes difficult for an application developer to choose the solution which is best suited for an application. This article introduces a framework which autonomously chooses the best solution for the application given the current deployed environment. The framework utilises a performance model to predict the expected performance of a particular solution in a given environment. The framework can then choose an apt solution for the application from a set of available solutions. This article presents the framework with a set of models built using data collected from simulation. The modelling technique can determine with up to 85% accuracy the solution which performs the best for a particular performance metric given a set of solutions. The article highlights the fractured and disjointed practice currently in place for examining and comparing communication solutions and aims to open a discussion on harmonising testing procedures so that different solutions can be directly compared and offers a framework to achieve this within IoT networks.

  1. A Framework to Implement IoT Network Performance Modelling Techniques for Network Solution Selection

    PubMed Central

    Delaney, Declan T.; O’Hare, Gregory M. P.

    2016-01-01

    No single network solution for Internet of Things (IoT) networks can provide the required level of Quality of Service (QoS) for all applications in all environments. This leads to an increasing number of solutions created to fit particular scenarios. Given the increasing number and complexity of solutions available, it becomes difficult for an application developer to choose the solution which is best suited for an application. This article introduces a framework which autonomously chooses the best solution for the application given the current deployed environment. The framework utilises a performance model to predict the expected performance of a particular solution in a given environment. The framework can then choose an apt solution for the application from a set of available solutions. This article presents the framework with a set of models built using data collected from simulation. The modelling technique can determine with up to 85% accuracy the solution which performs the best for a particular performance metric given a set of solutions. The article highlights the fractured and disjointed practice currently in place for examining and comparing communication solutions and aims to open a discussion on harmonising testing procedures so that different solutions can be directly compared and offers a framework to achieve this within IoT networks. PMID:27916929

  2. Model selection for factorial Gaussian graphical models with an application to dynamic regulatory networks.

    PubMed

    Vinciotti, Veronica; Augugliaro, Luigi; Abbruzzo, Antonino; Wit, Ernst C

    2016-06-01

    Factorial Gaussian graphical Models (fGGMs) have recently been proposed for inferring dynamic gene regulatory networks from genomic high-throughput data. In the search for true regulatory relationships amongst the vast space of possible networks, these models allow the imposition of certain restrictions on the dynamic nature of these relationships, such as Markov dependencies of low order - some entries of the precision matrix are a priori zeros - or equal dependency strengths across time lags - some entries of the precision matrix are assumed to be equal. The precision matrix is then estimated by l1-penalized maximum likelihood, imposing a further constraint on the absolute value of its entries, which results in sparse networks. Selecting the optimal sparsity level is a major challenge for this type of approaches. In this paper, we evaluate the performance of a number of model selection criteria for fGGMs by means of two simulated regulatory networks from realistic biological processes. The analysis reveals a good performance of fGGMs in comparison with other methods for inferring dynamic networks and of the KLCV criterion in particular for model selection. Finally, we present an application on a high-resolution time-course microarray data from the Neisseria meningitidis bacterium, a causative agent of life-threatening infections such as meningitis. The methodology described in this paper is implemented in the R package sglasso, freely available at CRAN, http://CRAN.R-project.org/package=sglasso.

  3. Selection for distinct gene expression properties favours the evolution of mutational robustness in gene regulatory networks.

    PubMed

    Espinosa-Soto, C

    2016-11-01

    Mutational robustness is a genotype's tendency to keep a phenotypic trait with little and few changes in the face of mutations. Mutational robustness is both ubiquitous and evolutionarily important as it affects in different ways the probability that new phenotypic variation arises. Understanding the origins of robustness is specially relevant for systems of development that are phylogenetically widespread and that construct phenotypic traits with a strong impact on fitness. Gene regulatory networks are examples of this class of systems. They comprise sets of genes that, through cross-regulation, build the gene activity patterns that define cellular responses, different tissues or distinct cell types. Several empirical observations, such as a greater robustness of wild-type phenotypes, suggest that stabilizing selection underlies the evolution of mutational robustness. However, the role of selection in the evolution of robustness is still under debate. Computer simulations of the dynamics and evolution of gene regulatory networks have shown that selection for any gene activity pattern that is steady and self-sustaining is sufficient to promote the evolution of mutational robustness. Here, I generalize this scenario using a computational model to show that selection for different aspects of a gene activity phenotype increases mutational robustness. Mutational robustness evolves even when selection favours properties that conflict with the stationarity of a gene activity pattern. The results that I present support an important role for stabilizing selection in the evolution of robustness in gene regulatory networks.

  4. Bully Victimization: Selection and Influence Within Adolescent Friendship Networks and Cliques.

    PubMed

    Lodder, Gerine M A; Scholte, Ron H J; Cillessen, Antonius H N; Giletta, Matteo

    2016-01-01

    Adolescents tend to form friendships with similar peers and, in turn, their friends further influence adolescents' behaviors and attitudes. Emerging work has shown that these selection and influence processes also might extend to bully victimization. However, no prior work has examined selection and influence effects involved in bully victimization within cliques, despite theoretical account emphasizing the importance of cliques in this regard. This study examined selection and influence processes in adolescence regarding bully victimization both at the level of the entire friendship network and the level of cliques. We used a two-wave design (5-month interval). Participants were 543 adolescents (50.1% male, Mage = 15.8) in secondary education. Stochastic actor-based models indicated that at the level of the larger friendship network, adolescents tended to select friends with similar levels of bully victimization as they themselves. In addition, adolescent friends influenced each other in terms of bully victimization over time. Actor Parter Interdependence models showed that similarities in bully victimization between clique members were not due to selection of clique members. For boys, average clique bully victimization predicted individual bully victimization over time (influence), but not vice versa. No influence was found for girls, indicating that different mechanisms may underlie friend influence on bully victimization for girls and boys. The differences in results at the level of the larger friendship network versus the clique emphasize the importance of taking the type of friendship ties into account in research on selection and influence processes involved in bully victimization.

  5. Secure and fair cluster head selection protocol for enhancing security in mobile ad hoc networks.

    PubMed

    Paramasivan, B; Kaliappan, M

    2014-01-01

    Mobile ad hoc networks (MANETs) are wireless networks consisting of number of autonomous mobile devices temporarily interconnected into a network by wireless media. MANETs become one of the most prevalent areas of research in the recent years. Resource limitations, energy efficiency, scalability, and security are the great challenging issues in MANETs. Due to its deployment nature, MANETs are more vulnerable to malicious attack. The secure routing protocols perform very basic security related functions which are not sufficient to protect the network. In this paper, a secure and fair cluster head selection protocol (SFCP) is proposed which integrates security factors into the clustering approach for achieving attacker identification and classification. Byzantine agreement based cooperative technique is used for attacker identification and classification to make the network more attack resistant. SFCP used to solve this issue by making the nodes that are totally surrounded by malicious neighbors adjust dynamically their belief and disbelief thresholds. The proposed protocol selects the secure and energy efficient cluster head which acts as a local detector without imposing overhead to the clustering performance. SFCP is simulated in network simulator 2 and compared with two protocols including AODV and CBRP.

  6. Using a two-phase evolutionary framework to select multiple network spreaders based on community structure

    NASA Astrophysics Data System (ADS)

    Fu, Yu-Hsiang; Huang, Chung-Yuan; Sun, Chuen-Tsai

    2016-11-01

    Using network community structures to identify multiple influential spreaders is an appropriate method for analyzing the dissemination of information, ideas and infectious diseases. For example, data on spreaders selected from groups of customers who make similar purchases may be used to advertise products and to optimize limited resource allocation. Other examples include community detection approaches aimed at identifying structures and groups in social or complex networks. However, determining the number of communities in a network remains a challenge. In this paper we describe our proposal for a two-phase evolutionary framework (TPEF) for determining community numbers and maximizing community modularity. Lancichinetti-Fortunato-Radicchi benchmark networks were used to test our proposed method and to analyze execution time, community structure quality, convergence, and the network spreading effect. Results indicate that our proposed TPEF generates satisfactory levels of community quality and convergence. They also suggest a need for an index, mechanism or sampling technique to determine whether a community detection approach should be used for selecting multiple network spreaders.

  7. Formation of nanoscale networks: selectively swelling amphiphilic block copolymers with CO2-expanded liquids.

    PubMed

    Gong, Jianliang; Zhang, Aijuan; Bai, Hua; Zhang, Qingkun; Du, Can; Li, Lei; Hong, Yanzhen; Li, Jun

    2013-02-07

    Polymeric films with nanoscale networks were prepared by selectively swelling an amphiphilic diblock copolymer, polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP), with the CO(2)-expanded liquid (CXL), CO(2)-methanol. The phase behavior of the CO(2)-methanol system was investigated by both theoretical calculation and experiments, revealing that methanol can be expanded by CO(2), forming homogeneous CXL under the experimental conditions. When treated with the CO(2)-methanol system, the spin cast compact PS-b-P4VP film was transformed into a network with interconnected pores, in a pressure range of 12-20 MPa and a temperature range of 45-60 °C. The formation mechanism of the network, involving plasticization of PS and selective swelling of P4VP, was proposed. Because the diblock copolymer diffusion process is controlled by the activated hopping of individual block copolymer chains with the thermodynamic barrier for moving PVP segments from one to another, the formation of the network structures is achieved in a short time scale and shows "thermodynamically restricted" character. Furthermore, the resulting polymer networks were employed as templates, for the preparation of polypyrrole networks, by an electrochemical polymerization process. The prepared porous polypyrrole film was used to fabricate a chemoresistor-type gas sensor which showed high sensitivity towards ammonia.

  8. Secure and Fair Cluster Head Selection Protocol for Enhancing Security in Mobile Ad Hoc Networks

    PubMed Central

    Paramasivan, B.; Kaliappan, M.

    2014-01-01

    Mobile ad hoc networks (MANETs) are wireless networks consisting of number of autonomous mobile devices temporarily interconnected into a network by wireless media. MANETs become one of the most prevalent areas of research in the recent years. Resource limitations, energy efficiency, scalability, and security are the great challenging issues in MANETs. Due to its deployment nature, MANETs are more vulnerable to malicious attack. The secure routing protocols perform very basic security related functions which are not sufficient to protect the network. In this paper, a secure and fair cluster head selection protocol (SFCP) is proposed which integrates security factors into the clustering approach for achieving attacker identification and classification. Byzantine agreement based cooperative technique is used for attacker identification and classification to make the network more attack resistant. SFCP used to solve this issue by making the nodes that are totally surrounded by malicious neighbors adjust dynamically their belief and disbelief thresholds. The proposed protocol selects the secure and energy efficient cluster head which acts as a local detector without imposing overhead to the clustering performance. SFCP is simulated in network simulator 2 and compared with two protocols including AODV and CBRP. PMID:25143986

  9. Exact probability distributions of selected species in stochastic chemical reaction networks.

    PubMed

    López-Caamal, Fernando; Marquez-Lago, Tatiana T

    2014-09-01

    Chemical reactions are discrete, stochastic events. As such, the species' molecular numbers can be described by an associated master equation. However, handling such an equation may become difficult due to the large size of reaction networks. A commonly used approach to forecast the behaviour of reaction networks is to perform computational simulations of such systems and analyse their outcome statistically. This approach, however, might require high computational costs to provide accurate results. In this paper we opt for an analytical approach to obtain the time-dependent solution of the Chemical Master Equation for selected species in a general reaction network. When the reaction networks are composed exclusively of zeroth and first-order reactions, this analytical approach significantly alleviates the computational burden required by simulation-based methods. By building upon these analytical solutions, we analyse a general monomolecular reaction network with an arbitrary number of species to obtain the exact marginal probability distribution for selected species. Additionally, we study two particular topologies of monomolecular reaction networks, namely (i) an unbranched chain of monomolecular reactions with and without synthesis and degradation reactions and (ii) a circular chain of monomolecular reactions. We illustrate our methodology and alternative ways to use it for non-linear systems by analysing a protein autoactivation mechanism. Later, we compare the computational load required for the implementation of our results and a pure computational approach to analyse an unbranched chain of monomolecular reactions. Finally, we study calcium ions gates in the sarco/endoplasmic reticulum mediated by ryanodine receptors.

  10. From Cellular Attractor Selection to Adaptive Signal Control for Traffic Networks.

    PubMed

    Tian, Daxin; Zhou, Jianshan; Sheng, Zhengguo; Wang, Yunpeng; Ma, Jianming

    2016-03-14

    The management of varying traffic flows essentially depends on signal controls at intersections. However, design an optimal control that considers the dynamic nature of a traffic network and coordinates all intersections simultaneously in a centralized manner is computationally challenging. Inspired by the stable gene expressions of Escherichia coli in response to environmental changes, we explore the robustness and adaptability performance of signalized intersections by incorporating a biological mechanism in their control policies, specifically, the evolution of each intersection is induced by the dynamics governing an adaptive attractor selection in cells. We employ a mathematical model to capture such biological attractor selection and derive a generic, adaptive and distributed control algorithm which is capable of dynamically adapting signal operations for the entire dynamical traffic network. We show that the proposed scheme based on attractor selection can not only promote the balance of traffic loads on each link of the network but also allows the global network to accommodate dynamical traffic demands. Our work demonstrates the potential of bio-inspired intelligence emerging from cells and provides a deep understanding of adaptive attractor selection-based control formation that is useful to support the designs of adaptive optimization and control in other domains.

  11. From Cellular Attractor Selection to Adaptive Signal Control for Traffic Networks

    NASA Astrophysics Data System (ADS)

    Tian, Daxin; Zhou, Jianshan; Sheng, Zhengguo; Wang, Yunpeng; Ma, Jianming

    2016-03-01

    The management of varying traffic flows essentially depends on signal controls at intersections. However, design an optimal control that considers the dynamic nature of a traffic network and coordinates all intersections simultaneously in a centralized manner is computationally challenging. Inspired by the stable gene expressions of Escherichia coli in response to environmental changes, we explore the robustness and adaptability performance of signalized intersections by incorporating a biological mechanism in their control policies, specifically, the evolution of each intersection is induced by the dynamics governing an adaptive attractor selection in cells. We employ a mathematical model to capture such biological attractor selection and derive a generic, adaptive and distributed control algorithm which is capable of dynamically adapting signal operations for the entire dynamical traffic network. We show that the proposed scheme based on attractor selection can not only promote the balance of traffic loads on each link of the network but also allows the global network to accommodate dynamical traffic demands. Our work demonstrates the potential of bio-inspired intelligence emerging from cells and provides a deep understanding of adaptive attractor selection-based control formation that is useful to support the designs of adaptive optimization and control in other domains.

  12. From Cellular Attractor Selection to Adaptive Signal Control for Traffic Networks

    PubMed Central

    Tian, Daxin; Zhou, Jianshan; Sheng, Zhengguo; Wang, Yunpeng; Ma, Jianming

    2016-01-01

    The management of varying traffic flows essentially depends on signal controls at intersections. However, design an optimal control that considers the dynamic nature of a traffic network and coordinates all intersections simultaneously in a centralized manner is computationally challenging. Inspired by the stable gene expressions of Escherichia coli in response to environmental changes, we explore the robustness and adaptability performance of signalized intersections by incorporating a biological mechanism in their control policies, specifically, the evolution of each intersection is induced by the dynamics governing an adaptive attractor selection in cells. We employ a mathematical model to capture such biological attractor selection and derive a generic, adaptive and distributed control algorithm which is capable of dynamically adapting signal operations for the entire dynamical traffic network. We show that the proposed scheme based on attractor selection can not only promote the balance of traffic loads on each link of the network but also allows the global network to accommodate dynamical traffic demands. Our work demonstrates the potential of bio-inspired intelligence emerging from cells and provides a deep understanding of adaptive attractor selection-based control formation that is useful to support the designs of adaptive optimization and control in other domains. PMID:26972968

  13. An Examination of Native and Immigrant Students' Social Networking Using the College Search and Selection Process

    ERIC Educational Resources Information Center

    Neimeyer, Bruce Carlton

    2009-01-01

    This dissertation explores the use of formal and informal networks through cyber- and traditional communication methods in the college search and selection process by native and immigrant students to examine various postulates and propositions of social capital theory. In addition, the analysis of cybernetworks used by disadvantaged, college bound…

  14. An Examination of Native and Immigrant Students' Social Networking Using the College Search and Selection Process

    ERIC Educational Resources Information Center

    Neimeyer, Bruce Carlton

    2009-01-01

    This dissertation explores the use of formal and informal networks through cyber- and traditional communication methods in the college search and selection process by native and immigrant students to examine various postulates and propositions of social capital theory. In addition, the analysis of cybernetworks used by disadvantaged, college bound…

  15. Using claims data to select primary care physicians for a managed care network.

    PubMed

    Nathanson, P; Noether, M; Ozminkowski, R J; Smith, K M; Raney, B E; Mickey, D; Hawley, P M

    1994-01-01

    An insurance claims databased profiling system was developed to help select new primary care physicians (PCPs) for a managed care network. PCPs (family practitioners, internists, and pediatricians) were ranked based on how closely their actual use of outpatient services conformed to the predictions of a mathematical model that adjusted for differences in age, sex, and case mix.

  16. Characterizing selection in black-throated blue warblers using a sexual network approach.

    PubMed

    Cramer, Emily Ra; Kaiser, Sara A; Webster, Michael S; Sillett, T Scott; Ryder, T Brandt

    2017-10-06

    Our understanding of trait evolution is built upon studies that examine the correlation between traits and fitness, most of which implicitly assume all individuals experience similar selective environments. However, accounting for differences in selective pressures, such as variation in the social environment, can advance our understanding of how selection shapes individual traits and subsequent fitness. In this study, we test whether variation in the social environment affects selection on individual phenotype. We apply a new sexual network framework to quantify each male's social environment as the mean body size of his primary competitors. We test for direct and social selection on male body size using a 10-year dataset on black-throated blue warblers (Setophaga caerulescens), a territorial species for which body size is hypothesized to mediate competition for mates. We found that direct selection on body size was weak and non-significant, as was social selection via the body size of the males' competitors. Analyzing both types of selection simultaneously allows us to firmly reject a role for body size in competitive interactions between males and subsequent male fitness in this population. We evaluate the application of the sexual network approach to empirical data, and suggest that other phenotypic traits such as song characteristics and plumage may be more relevant than body size for male-male competition in this small passerine bird. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  17. Adaptive Path Selection for Link Loss Inference in Network Tomography Applications

    PubMed Central

    Qiao, Yan; Jiao, Jun; Rao, Yuan; Ma, Huimin

    2016-01-01

    In this study, we address the problem of selecting the optimal end-to-end paths for link loss inference in order to improve the performance of network tomography applications, which infer the link loss rates from the path loss rates. Measuring the path loss rates using end-to-end probing packets may incur additional traffic overheads for networks, so it is important to select the minimum path set carefully while maximizing their performance. The usual approach is to select the maximum independent paths from the candidates simultaneously, while the other paths can be replaced by linear combinations of them. However, this approach ignores the fact that many paths always exist that do not lose any packets, and thus it is easy to determine that all of the links of these paths also have 0 loss rates. Not considering these good paths will inevitably lead to inefficiency and high probing costs. Thus, we propose an adaptive path selection method that selects paths sequentially based on the loss rates of previously selected paths. We also propose a theorem as well as a graph construction and decomposition approach to efficiently find the most valuable path during each round of selection. Our new method significantly outperforms the classical path selection method based on simulations in terms of the probing cost, number of accurate links determined, and the running speed. PMID:27701447

  18. Adolescent smoking networks: the effects of influence and selection on future smoking.

    PubMed

    Hall, Jeffrey A; Valente, Thomas W

    2007-12-01

    Peer influence and peer selection have both been linked to the smoking behavior of adolescents. The present investigation uses social network analysis methodology to explore the simultaneous effects of both processes on adolescent smoking and smoking susceptibility over two time periods. Results suggest the effects of friendship selection in 6th grade on smoking behavior in 7th grade were primarily direct. Selecting smokers as friends in 6th grade predicted both smoking and smoking susceptibility in 7th grade, and selecting susceptibles predicted future friendship selection and peer influence. Influence processes were indirectly related to smoking. Smokers' influence in 6th grade predicts the selection of smokers as friends in 7th grade. Smokers' influence also demonstrated a protective effect when ties were not reciprocated.

  19. Common and differential neural networks of emotion regulation by Detachment, Reinterpretation, Distraction, and Expressive Suppression: a comparative fMRI investigation.

    PubMed

    Dörfel, Denise; Lamke, Jan-Peter; Hummel, Falk; Wagner, Ullrich; Erk, Susanne; Walter, Henrik

    2014-11-01

    Emotions are an indispensable part of our mental life. The term emotion regulation refers to those processes that influence the generation, the experience and the expression of emotions. There is a great variety of strategies to regulate emotions efficiently, which are used in daily life and that have been investigated by cognitive neuroscience. Distraction guides attention to a secondary task. Reinterpretation, a variant of cognitive reappraisal, works by changing the meaning of an emotional stimulus. Detachment, another reappraisal strategy, refers to distancing oneself from an emotional stimulus, thereby reducing its personal relevance. Expressive Suppression modifies the behavioral or physiological response to an emotional stimulus. These four strategies are not equally effective in terms of emotion regulation success and have been shown to partly rely on different neuronal systems. Here, we compare for the first time the neural mechanisms of these typical strategies directly in a common functional magnetic resonance imaging (fMRI) paradigm of downregulation of negative emotions. Our results indicate that three of those strategies (Detachment, Expressive Suppression and Distraction) conjointly increase brain activation in a right prefronto-parietal regulation network and significantly reduce activation of the left amygdala. Compared to the other regulation strategies, Reinterpretation specifically recruited a different control network comprising left ventrolateral prefrontal cortex and orbitofrontal gyrus and was not effective in downregulation of the amygdala. We conclude that Detachment, Distraction and Expressive Suppression recruit very similar emotion regulation networks, whereas Reinterpretation is associated with activation of a qualitatively different network, making this regulation strategy a special one. Notably, Reinterpretation also proved to be the least effective strategy in neural terms, as measured by downregulation of amygdala activation.

  20. Data from selected U.S. Geological Survey National Stream Water-Quality Networks (WQN)

    USGS Publications Warehouse

    Alexander, Richard B.; Slack, J.R.; Ludtke, A.S.; Fitzgerald, K.K.; Schertz, T.L.; Briel, L.I.; Buttleman, K.P.

    1996-01-01

    This CD-ROM set contains data from two USGS national stream water-quality networks, the Hydrologic Benchmark Network (HBN) and the National Stream Quality Accounting Network (NASQAN), operated during the past 30 years. These networks were established to provide national and regional descriptions of stream water-quality conditions and trends, based on uniform monitoring of selected watersheds throughout the United States, and to improve our understanding of the effects of the natural environment and human activities on water quality. The HBN, consisting of 63 relatively small, minimally disturbed watersheds, provides data for investigating naturally induced changes in streamflow and water quality and the effects of airborne substances on water quality. NASQAN, consisting of 618 larger, more culturally influenced watersheds, provides information for tracking water-quality conditions in major U.S. rivers and streams.

  1. Joint Mode Selection and Resource Allocation for Cellular Controlled Short-Range Communication in OFDMA Networks

    NASA Astrophysics Data System (ADS)

    Deng, Hui; Tao, Xiaoming; Ge, Ning; Lu, Jianhua

    This letter studies cellular controlled short-range communication in OFDMA networks. The network needs to decide when to allow direct communication between a closely located device-to-device (D2D) pair instead of conveying data from one device to the other via the base station and when not to, in addition to subchannel and power allocation. Our goal is to maximize the total network throughput while guaranteeing the rate requirements of all users. For that purpose, we formulate an optimization problem subject to subchannel and power constraints. A scheme which combines a joint mode selection and subchannel allocation algorithm based on equal power allocation with a power reallocation scheme is proposed. Simulation results show that our proposed scheme can improve the network throughput and outage probability compared with other schemes.

  2. A New HIV Prevention Network Approach: Sociometric Peer Change Agent Selection

    PubMed Central

    Schneider, John A.; Zhou, A. Ning; Laumann, Edward O.

    2014-01-01

    Internationally, the Peer Change Agent (PCA) model is the most frequently used conceptual framework for HIV prevention. Change agents themselves can be more important than the messages they convey. PCA selection is operationalized via heterogeneous methods based upon individual-level attributes. A sociometric position selection strategy, however, could increase peer influence potency and halt transmission at key network locations. In this study, we selected candidate PCAs based upon relative sociometric bridging and centrality scores and assessed their attributes in comparison to one another and to existing peer educators. We focused upon an emerging HIV epidemic among men who have sex with men in Southern India in 2011. PCAs selected based on their bridging score were more likely to be innovators when compared to other centrally-located PCAs, to PCAs located on the periphery, and to existing peer educators. We also found that sociodemographic attributes and risk behaviors were similar across all candidate PCAs, but risk behaviors of existing peer educators differed. Existing peer educators were more likely to engage in higher risk behavior such as receiving money for sex when compared to sociometrically selected peer changes agents. These existing peer educators were also more likely to exhibit leadership qualities within the overall network; they were, however, just as likely as other non-trained candidate peer change agents to report important HIV intravention behavior (encouraging condoms within their network). The importance of identifying bridges who may be able to diffuse innovation more effectively within high risk HIV networks is especially critical given recent efficacy data from novel HIV prevention interventions such as pre-exposure prophylaxis. Moreover, while existing peer educators were more likely to be leaders in our analysis, using peer educators with high risk behavior may have limited utility in enacting behavior change among sex worker peers or

  3. A cooperative MAC protocol with error-aware relay selection for wireless ad hoc networks

    NASA Astrophysics Data System (ADS)

    Liu, Shanzhi; Liu, Kai; Wang, Rui; Fang, Ruochen; Liu, Feng

    2017-01-01

    To solve performance degradation caused by channel fading, we propose a cooperative MAC protocol with error-aware relay selection for wireless ad hoc networks in this paper. In the protocol, the transmission error of data packet caused by channel fading are considered in order to achieve the best cooperative gain in the poor quality channel. In the relay selection process, potential relay nodes satisfying corresponding requirement can compete to sever as final relay node by means of priority selection and collision resolution process. Finally, simulation results show that the proposed protocol outperforms other protocol in terms of packet error rate and the saturation throughput.

  4. Selective suppression of the human aryl hydrocarbon receptor function can be mediated through binding interference at the C-terminal half of the receptor.

    PubMed

    Ren, Lina; Thompson, John D; Cheung, Michael; Ngo, Katherine; Sung, Sarah; Leong, Scott; Chan, William K

    2016-05-01

    The human aryl hydrocarbon receptor is a cytosolic signaling molecule which affects immune response and aberrant cell growth. Canonical signaling of the receptor requires the recruitment of coactivators to the promoter region to remodel local chromatin structure. We predicted that interference of this recruitment would block the aryl hydrocarbon receptor function. To prove that, we employed phage display to identify nine peptides of twelve-amino-acid in length which target the C-terminal half of the human aryl hydrocarbon receptor, including the region where coactivators bind. Eight 12mer peptides, in the form of GFP fusion, suppressed the ligand-dependent transcription of six AHR target genes (cyp1a1, cyp1a2, cyp1b1, ugt1a1, nqo1, and ahrr) in different patterns in Hep3B cells, whereas the AHR antagonist CH-223191 suppressed all these target genes similarly. Three of the 12mer peptides (namely 11-3, 1-7, and 7-3) suppressed the 3MC-induced, CYP1A1-dependent EROD activity and the ROS production caused by benzo[a]pyrene. These 12mer peptides suppressed the AHR function synergistically with CH-223191. In conclusion, we provide evidence that targeting the C-terminal half of the human aryl hydrocarbon receptor is a viable, new approach to selectively block the receptor function.

  5. Green supply chain management strategy selection using analytic network process: case study at PT XYZ

    NASA Astrophysics Data System (ADS)

    Adelina, W.; Kusumastuti, R. D.

    2017-01-01

    This study is about business strategy selection for green supply chain management (GSCM) for PT XYZ by using Analytic Network Process (ANP). GSCM is initiated as a response to reduce environmental impacts from industrial activities. The purposes of this study are identifying criteria and sub criteria in selecting GSCM Strategy, and analysing a suitable GSCM strategy for PT XYZ. This study proposes ANP network with 6 criteria and 29 sub criteria, which are obtained from the literature and experts’ judgements. One of the six criteria contains GSCM strategy options, namely risk-based strategy, efficiency-based strategy, innovation-based strategy, and closed loop strategy. ANP solves complex GSCM strategy-selection by using a more structured process and considering green perspectives from experts. The result indicates that innovation-based strategy is the most suitable green supply chain management strategy for PT XYZ.

  6. Adolescent Friendships, BMI, and Physical Activity: Untangling Selection and Influence Through Longitudinal Social Network Analysis.

    PubMed

    Simpkins, Sandra D; Schaefer, David R; Price, Chara D; Vest, Andrea E

    2013-09-01

    Bioecological theory suggests that adolescents' health is a result of selection and socialization processes occurring between adolescents and their microsettings. This study examines the association between adolescents' friends and health using a social network model and data from the National Longitudinal Study of Adolescent Health (N = 1,896, mean age = 15.97 years). Results indicated evidence of friend influence on BMI and physical activity. Friendships were more likely among adolescents who engaged in greater physical activity and who were similar to one another in BMI and physical activity. These effects emerged after controlling for alternative friend selection factors, such as endogenous social network processes and propinquity through courses and activities. Some selection effects were moderated by gender, popularity, and reciprocity.

  7. Supplier selection based on a neural network model using genetic algorithm.

    PubMed

    Golmohammadi, Davood; Creese, Robert C; Valian, Haleh; Kolassa, John

    2009-09-01

    In this paper, a decision-making model was developed to select suppliers using neural networks (NNs). This model used historical supplier performance data for selection of vendor suppliers. Input and output were designed in a unique manner for training purposes. The managers' judgments about suppliers were simulated by using a pairwise comparisons matrix for output estimation in the NN. To obtain the benefit of a search technique for model structure and training, genetic algorithm (GA) was applied for the initial weights and architecture of the network. The suppliers' database information (input) can be updated over time to change the suppliers' score estimation based on their performance. The case study illustrated shows how the model can be applied for suppliers' selection.

  8. High performances CNTFETs achieved using CNT networks for selective gas sensing

    NASA Astrophysics Data System (ADS)

    Gorintin, Louis; Bondavalli, Paolo; Legagneux, Pierre; Pribat, Didier

    2009-08-01

    Our study deals with the utilization of carbon nanotubes networks based transistors with different metal electrodes for highly selective gas sensing. Indeed, carbon nanotubes networks can be used as semi conducting materials to achieve good performances transistors. These devices are extremely sensitive to the change of the Schottky barrier heights between Single Wall Carbon Nanotubes (SWCNTs) and drain/source metal electrodes: the gas adsorption creates an interfacial dipole that modifies the metal work function and so the bending and the height of the Schottky barrier at the contacts. Moreover each gas interacts specifically with each metal identifying a sort of electronic fingerprinting. Using airbrush technique for deposition, we have been able to achieve uniform random networks of carbon nanotubes suitable for large area applications and mass production such as fabrication of CNT based gas sensors. These networks enable us to achieve transistors with on/off ratio of more than 5 orders of magnitude. To reach these characteristics, the density of the CNT network has been adjusted in order to reach the percolation threshold only for semi-conducting nanotubes. These optimized devices have allowed us to tune the sensitivity (improving it) of our sensors for highly selective detection of DiMethyl-Methyl-Phosphonate (DMMP, a sarin stimulant), and even volatile drug precursors using Pd, Au and Mo electrodes.

  9. A Lifetime Maximization Relay Selection Scheme in Wireless Body Area Networks

    PubMed Central

    Zhang, Yu; Zhang, Bing; Zhang, Shi

    2017-01-01

    Network Lifetime is one of the most important metrics in Wireless Body Area Networks (WBANs). In this paper, a relay selection scheme is proposed under the topology constrains specified in the IEEE 802.15.6 standard to maximize the lifetime of WBANs through formulating and solving an optimization problem where relay selection of each node acts as optimization variable. Considering the diversity of the sensor nodes in WBANs, the optimization problem takes not only energy consumption rate but also energy difference among sensor nodes into account to improve the network lifetime performance. Since it is Non-deterministic Polynomial-hard (NP-hard) and intractable, a heuristic solution is then designed to rapidly address the optimization. The simulation results indicate that the proposed relay selection scheme has better performance in network lifetime compared with existing algorithms and that the heuristic solution has low time complexity with only a negligible performance degradation gap from optimal value. Furthermore, we also conduct simulations based on a general WBAN model to comprehensively illustrate the advantages of the proposed algorithm. At the end of the evaluation, we validate the feasibility of our proposed scheme via an implementation discussion. PMID:28574455

  10. Network-selective vulnerability of the human cerebellum to Alzheimer's disease and frontotemporal dementia.

    PubMed

    Guo, Christine C; Tan, Rachel; Hodges, John R; Hu, Xintao; Sami, Saber; Hornberger, Michael

    2016-05-01

    SEE SCHMAHMANN DOI101093/BRAIN/AWW064 FOR A SCIENTIFIC COMMENTARY ON THIS ARTICLE: Neurodegenerative diseases are associated with distinct and distributed patterns of atrophy in the cerebral cortex. Emerging evidence suggests that these atrophy patterns resemble intrinsic connectivity networks in the healthy brain, supporting the network-based degeneration framework where neuropathology spreads across connectivity networks. An intriguing yet untested possibility is that the cerebellar circuits, which share extensive connections with the cerebral cortex, could be selectively targeted by major neurodegenerative diseases. Here we examined the structural atrophy in the cerebellum across common types of neurodegenerative diseases, and characterized the functional connectivity patterns of these cerebellar atrophy regions. Our results showed that Alzheimer's disease and frontotemporal dementia are associated with distinct and circumscribed atrophy in the cerebellum. These cerebellar atrophied regions share robust and selective intrinsic connectivity with the atrophied regions in the cerebral cortex. These findings for the first time demonstrated the selective vulnerability of the cerebellum to common neurodegenerative disease, extending the network-based degeneration framework to the cerebellum. Our work also has direct implications on the cerebellar contribution to the cognitive and affective processes that are compromised in neurodegeneration as well as the practice of using the cerebellum as reference region for ligand neuroimaging studies. © The Author (2016). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  11. Genetic Algorithm Sampling the Solution Space Selectively Depending on Difficulty of Power Distribution Network Restoration

    NASA Astrophysics Data System (ADS)

    Kato, Yoshifumi; Hamagami, Tomoki

    A new genetic algorithm for multi agent based autonomous power distribution network restoration system is proposed. The state of the art of this study is to realize a new genetic algorithm using selective sampling for improving the restoration performance. A proposed method realizes the selective sampling by a virtual accident selecting algorithm that changes probability of selecting virtual accident area. The virtual accident selecting algorithm consists of weight table and area-value list. The weight table represents a difficulty of restoration in each accident area. The area-value list represents a difficulty of restoration in latest generation, and effects on weight table in next generation. This architecture enables the system to change the probability of changing each virtual accident area autonomously from restoration simulation. The simulation results show the proposed method achieves to improve the performance.

  12. The use of a selective saturation pulse to suppress t1 noise in two-dimensional 1H fast magic angle spinning solid-state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Robertson, Aiden J.; Pandey, Manoj Kumar; Marsh, Andrew; Nishiyama, Yusuke; Brown, Steven P.

    2015-11-01

    A selective saturation pulse at fast magic angle spinning (MAS) frequencies (60+ kHz) suppresses t1 noise in the indirect dimension of two-dimensional 1H MAS NMR spectra. The method is applied to a synthetic nucleoside with an intense methyl 1H signal due to triisopropylsilyl (TIPS) protecting groups. Enhanced performance in terms of suppressing the methyl signal while minimising the loss of signal intensity of nearby resonances of interest relies on reducing spin diffusion - this is quantified by comparing two-dimensional 1H NOESY-like spin diffusion spectra recorded at 30-70 kHz MAS. For a saturation pulse centred at the methyl resonance, the effect of changing the nutation frequency at different MAS frequencies as well as the effect of changing the pulse duration is investigated. By applying a pulse of duration 30 ms and nutation frequency 725 Hz at 70 kHz MAS, a good compromise of significant suppression of the methyl resonance combined with the signal intensity of resonances greater than 5 ppm away from the methyl resonance being largely unaffected is achieved. The effectiveness of using a selective saturation pulse is demonstrated for both homonuclear 1H-1H double quantum (DQ)/single quantum (SQ) MAS and 14N-1H heteronuclear multiple quantum coherence (HMQC) two-dimensional solid-state NMR experiments.

  13. The use of a selective saturation pulse to suppress t1 noise in two-dimensional (1)H fast magic angle spinning solid-state NMR spectroscopy.

    PubMed

    Robertson, Aiden J; Pandey, Manoj Kumar; Marsh, Andrew; Nishiyama, Yusuke; Brown, Steven P

    2015-11-01

    A selective saturation pulse at fast magic angle spinning (MAS) frequencies (60+kHz) suppresses t1 noise in the indirect dimension of two-dimensional (1)H MAS NMR spectra. The method is applied to a synthetic nucleoside with an intense methyl (1)H signal due to triisopropylsilyl (TIPS) protecting groups. Enhanced performance in terms of suppressing the methyl signal while minimising the loss of signal intensity of nearby resonances of interest relies on reducing spin diffusion--this is quantified by comparing two-dimensional (1)H NOESY-like spin diffusion spectra recorded at 30-70 kHz MAS. For a saturation pulse centred at the methyl resonance, the effect of changing the nutation frequency at different MAS frequencies as well as the effect of changing the pulse duration is investigated. By applying a pulse of duration 30 ms and nutation frequency 725 Hz at 70 kHz MAS, a good compromise of significant suppression of the methyl resonance combined with the signal intensity of resonances greater than 5 ppm away from the methyl resonance being largely unaffected is achieved. The effectiveness of using a selective saturation pulse is demonstrated for both homonuclear (1)H-(1)H double quantum (DQ)/single quantum (SQ) MAS and (14)N-(1)H heteronuclear multiple quantum coherence (HMQC) two-dimensional solid-state NMR experiments.

  14. Selection of Multiarmed Spiral Waves in a Regular Network of Neurons

    PubMed Central

    Hu, Bolin; Ma, Jun; Tang, Jun

    2013-01-01

    Formation and selection of multiarmed spiral wave due to spontaneous symmetry breaking are investigated in a regular network of Hodgkin-Huxley neuron by changing the excitability and imposing spatial forcing currents on the neurons in the network. The arm number of the multiarmed spiral wave is dependent on the distribution of spatial forcing currents and excitability diversity in the network, and the selection criterion for supporting multiarmed spiral waves is discussed. A broken spiral segment is measured by a short polygonal line connected by three adjacent points (controlled nodes), and a double-spiral wave can be developed from the spiral segment. Multiarmed spiral wave is formed when a group of double-spiral waves rotate in the same direction in the network. In the numerical studies, a group of controlled nodes are selected and spatial forcing currents are imposed on these nodes, and our results show that l-arm stable spiral wave (l = 2, 3, 4,...8) can be induced to occupy the network completely. It is also confirmed that low excitability is critical to induce multiarmed spiral waves while high excitability is important to propagate the multiarmed spiral wave outside so that distinct multiarmed spiral wave can occupy the network completely. Our results confirm that symmetry breaking of target wave in the media accounts for emergence of multiarmed spiral wave, which can be developed from a group of spiral waves with single arm under appropriate condition, thus the potential formation mechanism of multiarmed spiral wave in the media is explained. PMID:23935966

  15. Selection of multiarmed spiral waves in a regular network of neurons.

    PubMed

    Hu, Bolin; Ma, Jun; Tang, Jun

    2013-01-01

    Formation and selection of multiarmed spiral wave due to spontaneous symmetry breaking are investigated in a regular network of Hodgkin-Huxley neuron by changing the excitability and imposing spatial forcing currents on the neurons in the network. The arm number of the multiarmed spiral wave is dependent on the distribution of spatial forcing currents and excitability diversity in the network, and the selection criterion for supporting multiarmed spiral waves is discussed. A broken spiral segment is measured by a short polygonal line connected by three adjacent points (controlled nodes), and a double-spiral wave can be developed from the spiral segment. Multiarmed spiral wave is formed when a group of double-spiral waves rotate in the same direction in the network. In the numerical studies, a group of controlled nodes are selected and spatial forcing currents are imposed on these nodes, and our results show that l-arm stable spiral wave (l = 2, 3, 4,...8) can be induced to occupy the network completely. It is also confirmed that low excitability is critical to induce multiarmed spiral waves while high excitability is important to propagate the multiarmed spiral wave outside so that distinct multiarmed spiral wave can occupy the network completely. Our results confirm that symmetry breaking of target wave in the media accounts for emergence of multiarmed spiral wave, which can be developed from a group of spiral waves with single arm under appropriate condition, thus the potential formation mechanism of multiarmed spiral wave in the media is explained.

  16. Default network activation during episodic and semantic memory retrieval: A selective meta-analytic comparison.

    PubMed

    Kim, Hongkeun

    2016-01-08

    It remains unclear whether and to what extent the default network subregions involved in episodic memory (EM) and semantic memory (SM) processes overlap or are separated from one another. This study addresses this issue through a controlled meta-analysis of functional neuroimaging studies involving healthy participants. Various EM and SM task paradigms differ widely in the extent of default network involvement. Therefore, the issue at hand cannot be properly addressed without some control for this factor. In this regard, this study employs a two-stage analysis: a preliminary meta-analysis to select EM and SM task paradigms that recruit relatively extensive default network regions and a main analysis to compare the selected task paradigms. Based on a within-EM comparison, the default network contributed more to recollection/familiarity effects than to old/new effects, and based on a within-SM comparison, it contributed more to word/pseudoword effects than to semantic/phonological effects. According to a direct comparison of recollection/familiarity and word/pseudoword effects, each involving a range of default network regions, there were more overlaps than separations in default network subregions involved in these two effects. More specifically, overlaps included the bilateral posterior cingulate/retrosplenial cortex, left inferior parietal lobule, and left anteromedial prefrontal regions, whereas separations included only the hippocampal formation and the parahippocampal cortex region, which was unique to recollection/familiarity effects. These results indicate that EM and SM retrieval processes involving strong memory signals recruit extensive and largely overlapping default network regions and differ mainly in distinct contributions of hippocampus and parahippocampal regions to EM retrieval.

  17. Optimizing Network-Coded Cooperative Communications via Joint Session Grouping and Relay Node Selection

    DTIC Science & Technology

    2011-01-01

    Optimizing Network-Coded Cooperative Communications via Joint Session Grouping and Relay Node Selection Sushant Sharma Yi Shi Y. Thomas Hou Hanif...that for a single relay node, we can group as many sessions as we want. But, in a recent study [20], Sharma et al. showed that there exists a so-called...destination wireless network. In [20], Sharma et al. considered NC-CC with only one relay node. Their analysis showed that NC is not always good for CC, and

  18. Elaboration versus suppression of cued memories: influence of memory recall instruction and success on parietal lobe, default network, and hippocampal activity.

    PubMed

    Gimbel, Sarah I; Brewer, James B

    2014-01-01

    Functional imaging studies of episodic memory retrieval consistently report task-evoked and memory-related activity in the medial temporal lobe, default network and parietal lobe subregions. Associated components of memory retrieval, such as attention-shifts, search, retrieval success, and post-retrieval processing also influence regional activity, but these influences remain ill-defined. To better understand how top-down control affects the neural bases of memory retrieval, we examined how regional activity responses were modulated by task goals during recall success or failure. Specifically, activity was examined during memory suppression, recall, and elaborative recall of paired-associates. Parietal lobe was subdivided into dorsal (BA 7), posterior ventral (BA 39), and anterior ventral (BA 40) regions, which were investigated separately to examine hypothesized distinctions in sub-regional functional responses related to differential attention-to-memory and memory strength. Top-down suppression of recall abolished memory strength effects in BA 39, which showed a task-negative response, and BA 40, which showed a task-positive response. The task-negative response in default network showed greater negatively-deflected signal for forgotten pairs when task goals required recall. Hippocampal activity was task-positive and was influenced by memory strength only when task goals required recall. As in previous studies, we show a memory strength effect in parietal lobe and hippocampus, but we show that this effect is top-down controlled and sensitive to whether the subject is trying to suppress or retrieve a memory. These regions are all implicated in memory recall, but their individual activity patterns show distinct memory-strength-related responses when task goals are varied. In parietal lobe, default network, and hippocampus, top-down control can override the commonly identified effects of memory strength.

  19. Elaboration versus Suppression of Cued Memories: Influence of Memory Recall Instruction and Success on Parietal Lobe, Default Network, and Hippocampal Activity

    PubMed Central

    Gimbel, Sarah I.; Brewer, James B.

    2014-01-01

    Functional imaging studies of episodic memory retrieval consistently report task-evoked and memory-related activity in the medial temporal lobe, default network and parietal lobe subregions. Associated components of memory retrieval, such as attention-shifts, search, retrieval success, and post-retrieval processing also influence regional activity, but these influences remain ill-defined. To better understand how top-down control affects the neural bases of memory retrieval, we examined how regional activity responses were modulated by task goals during recall success or failure. Specifically, activity was examined during memory suppression, recall, and elaborative recall of paired-associates. Parietal lobe was subdivided into dorsal (BA 7), posterior ventral (BA 39), and anterior ventral (BA 40) regions, which were investigated separately to examine hypothesized distinctions in sub-regional functional responses related to differential attention-to-memory and memory strength. Top-down suppression of recall abolished memory strength effects in BA 39, which showed a task-negative response, and BA 40, which showed a task-positive response. The task-negative response in default network showed greater negatively-deflected signal for forgotten pairs when task goals required recall. Hippocampal activity was task-positive and was influenced by memory strength only when task goals required recall. As in previous studies, we show a memory strength effect in parietal lobe and hippocampus, but we show that this effect is top-down controlled and sensitive to whether the subject is trying to suppress or retrieve a memory. These regions are all implicated in memory recall, but their individual activity patterns show distinct memory-strength-related responses when task goals are varied. In parietal lobe, default network, and hippocampus, top-down control can override the commonly identified effects of memory strength. PMID:24586492

  20. Resource constrained flux balance analysis predicts selective pressure on the global structure of metabolic networks.

    PubMed

    Abedpour, Nima; Kollmann, Markus

    2015-11-23

    A universal feature of metabolic networks is their hourglass or bow-tie structure on cellular level. This architecture reflects the conversion of multiple input nutrients into multiple biomass components via a small set of precursor metabolites. However, it is yet unclear to what extent this structural feature is the result of natural selection. We extend flux balance analysis to account for limited cellular resources. Using this model, optimal structure of metabolic networks can be calculated for different environmental conditions. We observe a significant structural reshaping of metabolic networks for a toy-network and E. coli core metabolism if we increase the share of invested resources for switching between different nutrient conditions. Here, hub nodes emerge and the optimal network structure becomes bow-tie-like as a consequence of limited cellular resource constraint. We confirm this theoretical finding by comparing the reconstructed metabolic networks of bacterial species with respect to their lifestyle. We show that bow-tie structure can give a system-level fitness advantage to organisms that live in highly competitive and fluctuating environments. Here, limitation of cellular resources can lead to an efficiency-flexibility tradeoff where it pays off for the organism to shorten catabolic pathways if they are frequently activated and deactivated. As a consequence, generalists that shuttle between diverse environmental conditions should have a more predominant bow-tie structure than specialists that visit just a few isomorphic habitats during their life cycle.

  1. Spatially Reciprocal Inhibition of Inhibition within a Stimulus Selection Network in the Avian Midbrain

    PubMed Central

    Goddard, C. Alex; Mysore, Shreesh P.; Bryant, Astra S.; Huguenard, John R.; Knudsen, Eric I.

    2014-01-01

    Reciprocal inhibition between inhibitory projection neurons has been proposed as the most efficient circuit motif to achieve the flexible selection of one stimulus among competing alternatives. However, whether such a motif exists in networks that mediate selection is unclear. Here, we study the connectivity within the nucleus isthmi pars magnocellularis (Imc), a GABAergic nucleus that mediates competitive selection in the midbrain stimulus selection network. Using laser photostimulation of caged glutamate, we find that feedback inhibitory connectivity is global within the Imc. Unlike typical lateral inhibition in other circuits, intra-Imc inhibition remains functionally powerful over long distances. Anatomically, we observed long-range axonal projections and retrograde somatic labeling from focal injections of bi-directional tracers in the Imc, consistent with spatial reciprocity of intra-Imc inhibition. Together, the data indicate that spatially reciprocal inhibition of inhibition occurs throughout the Imc. Thus, the midbrain selection circuit possesses the most efficient circuit motif possible for fast, reliable, and flexible selection. PMID:24465755

  2. Environmentally induced changes in correlated responses to selection reveal variable pleiotropy across a complex genetic network.

    PubMed

    Sikkink, Kristin L; Reynolds, Rose M; Cresko, William A; Phillips, Patrick C

    2015-05-01

    Selection in novel environments can lead to a coordinated evolutionary response across a suite of characters. Environmental conditions can also potentially induce changes in the genetic architecture of complex traits, which in turn could alter the pattern of the multivariate response to selection. We describe a factorial selection experiment using the nematode Caenorhabditis remanei in which two different stress-related phenotypes (heat and oxidative stress resistance) were selected under three different environmental conditions. The pattern of covariation in the evolutionary response between phenotypes or across environments differed depending on the environment in which selection occurred, including asymmetrical responses to selection in some cases. These results indicate that variation in pleiotropy across the stress response network is highly sensitive to the external environment. Our findings highlight the complexity of the interaction between genes and environment that influences the ability of organisms to acclimate to novel environments. They also make clear the need to identify the underlying genetic basis of genetic correlations in order understand how patterns of pleiotropy are distributed across complex genetic networks.

  3. The relationship between selection, network connectivity, and regulatory variation within a population of Capsella grandiora.

    PubMed

    Josephs, Emily B; Wright, Stephen I; Stinchcombe, John R; Schoen, Daniel J

    2017-04-08

    Interactions between genes can have important consequences for how selection shapes sequence variation at these genes. Specifically, genes that have pleiotropic effects by affecting the expression level of many other genes may be under stronger selective constraint. We used coexpression networks to measure connectivity between genes and investigated the relationship between gene connectivity and selection in a natural population of the plant Capsella grandiora. We observed that network connectivity was negatively correlated with genetic divergence due to stronger negative selection on highly-connected genes even when controlling for variation in gene expression level. However, the presence of local regulatory variation for a gene's expression level was also associated with reduced negative selection and lower gene connectivity. While it is difficult to disentangle the causal relationships between these factors, our results show that both connectivity and local regulatory variation are important factors for explaining variation in selection between genes. © The Author(s) 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

  4. ADMM-Based Algorithm for Training Fault Tolerant RBF Networks and Selecting Centers.

    PubMed

    Wang, Hao; Feng, Ruibin; Han, Zi-Fa; Leung, Chi-Sing

    2017-08-15

    In the training stage of radial basis function (RBF) networks, we need to select some suitable RBF centers first. However, many existing center selection algorithms were designed for the fault-free situation. This brief develops a fault tolerant algorithm that trains an RBF network and selects the RBF centers simultaneously. We first select all the input vectors from the training set as the RBF centers. Afterward, we define the corresponding fault tolerant objective function. We then add an ℓ₁-norm term into the objective function. As the ℓ₁-norm term is able to force some unimportant weights to zero, center selection can be achieved at the training stage. Since the ℓ₁-norm term is nondifferentiable, we formulate the original problem as a constrained optimization problem. Based on the alternating direction method of multipliers framework, we then develop an algorithm to solve the constrained optimization problem. The convergence proof of the proposed algorithm is provided. Simulation results show that the proposed algorithm is superior to many existing center selection algorithms.

  5. ENVIRONMENTALLY INDUCED CHANGES IN CORRELATED RESPONSES TO SELECTION REVEAL VARIABLE PLEIOTROPY ACROSS A COMPLEX GENETIC NETWORK

    PubMed Central

    Sikkink, Kristin L.; Reynolds, Rose M.; Cresko, William A.; Phillips, Patrick C.

    2017-01-01

    Selection in novel environments can lead to a coordinated evolutionary response across a suite of characters. Environmental conditions can also potentially induce changes in the genetic architecture of complex traits, which in turn could alter the pattern of the multivariate response to selection. We describe a factorial selection experiment using the nematode Caenorhabditis remanei in which two different stress-related phenotypes (heat and oxidative stress resistance) were selected under three different environmental conditions. The pattern of covariation in the evolutionary response between phenotypes or across environments differed depending on the environment in which selection occurred, including asymmetrical responses to selection in some cases. These results indicate that variation in pleiotropy across the stress response network is highly sensitive to the external environment. Our findings highlight the complexity of the interaction between genes and environment that influences the ability of organisms to acclimate to novel environments. They also make clear the need to identify the underlying genetic basis of genetic correlations in order understand how patterns of pleiotropy are distributed across complex genetic networks. PMID:25809411

  6. Efficient File Sharing by Multicast - P2P Protocol Using Network Coding and Rank Based Peer Selection

    NASA Technical Reports Server (NTRS)

    Stoenescu, Tudor M.; Woo, Simon S.

    2009-01-01

    In this work, we consider information dissemination and sharing in a distributed peer-to-peer (P2P highly dynamic communication network. In particular, we explore a network coding technique for transmission and a rank based peer selection method for network formation. The combined approach has been shown to improve information sharing and delivery to all users when considering the challenges imposed by the space network environments.

  7. Efficient File Sharing by Multicast - P2P Protocol Using Network Coding and Rank Based Peer Selection

    NASA Technical Reports Server (NTRS)

    Stoenescu, Tudor M.; Woo, Simon S.

    2009-01-01

    In this work, we consider information dissemination and sharing in a distributed peer-to-peer (P2P highly dynamic communication network. In particular, we explore a network coding technique for transmission and a rank based peer selection method for network formation. The combined approach has been shown to improve information sharing and delivery to all users when considering the challenges imposed by the space network environments.

  8. Techniques for selecting topology and implementing the distributed control system network

    NASA Astrophysics Data System (ADS)

    Chernyi, S.

    2016-04-01

    On grounds of reviews devoted to flows analysis methods in the data processing networks within the automated control systems for the technological process and assessment of these methods by the selected set of requirements, one may make conclusion about expediency of using the combination of graph flow algorithms and the queuing theory. The outputs of the research concerning the impact of network dynamics on the drilling platform distributed system control quality prove the fact that the quality of the transient depends upon the frequency of discretization and intensity of flows. With increasing the intensity of flows, the static error of the control enlarges. It was concluded that in order to control the automation objects in the real-time mode it is required to minimize the delays in transmitting packets in the network.

  9. Formation of nanoscale networks: selectively swelling amphiphilic block copolymers with CO2-expanded liquids

    NASA Astrophysics Data System (ADS)

    Gong, Jianliang; Zhang, Aijuan; Bai, Hua; Zhang, Qingkun; Du, Can; Li, Lei; Hong, Yanzhen; Li, Jun

    2013-01-01

    Polymeric films with nanoscale networks were prepared by selectively swelling an amphiphilic diblock copolymer, polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP), with the CO2-expanded liquid (CXL), CO2-methanol. The phase behavior of the CO2-methanol system was investigated by both theoretical calculation and experiments, revealing that methanol can be expanded by CO2, forming homogeneous CXL under the experimental conditions. When treated with the CO2-methanol system, the spin cast compact PS-b-P4VP film was transformed into a network with interconnected pores, in a pressure range of 12-20 MPa and a temperature range of 45-60 °C. The formation mechanism of the network, involving plasticization of PS and selective swelling of P4VP, was proposed. Because the diblock copolymer diffusion process is controlled by the activated hopping of individual block copolymer chains with the thermodynamic barrier for moving PVP segments from one to another, the formation of the network structures is achieved in a short time scale and shows ``thermodynamically restricted'' character. Furthermore, the resulting polymer networks were employed as templates, for the preparation of polypyrrole networks, by an electrochemical polymerization process. The prepared porous polypyrrole film was used to fabricate a chemoresistor-type gas sensor which showed high sensitivity towards ammonia.Polymeric films with nanoscale networks were prepared by selectively swelling an amphiphilic diblock copolymer, polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP), with the CO2-expanded liquid (CXL), CO2-methanol. The phase behavior of the CO2-methanol system was investigated by both theoretical calculation and experiments, revealing that methanol can be expanded by CO2, forming homogeneous CXL under the experimental conditions. When treated with the CO2-methanol system, the spin cast compact PS-b-P4VP film was transformed into a network with interconnected pores, in a pressure range of 12-20 MPa and a

  10. Selective Self-Presentation and Social Comparison Through Photographs on Social Networking Sites.

    PubMed

    Fox, Jesse; Vendemia, Megan A

    2016-10-01

    Through social media and camera phones, users enact selective self-presentation as they choose, edit, and post photographs of themselves (such as selfies) to social networking sites for an imagined audience. Photos typically focus on users' physical appearance, which may compound existing sociocultural pressures about body image. We identified users of social networking sites among a nationally representative U.S. sample (N = 1,686) and examined women's and men's photo-related behavior, including posting photos, editing photos, and feelings after engaging in upward and downward social comparison with others' photos on social networking sites. We identified some sex differences: women edited photos more frequently and felt worse after upward social comparison than men. Body image and body comparison tendency mediated these effects.

  11. Effects of amount of Food on Path Selection in the Transport Network of AN Amoeboid Organism

    NASA Astrophysics Data System (ADS)

    Nakagaki, T.; Saigusa, T.; Tero, A.; Kobayashi, R.

    2007-07-01

    We studied the effect of the size of food sources (FSs) presented to the true slime mould Physarum polycephalum on the tubular networks formed by the organism to absorb nutrient. The amount of plasmodium gathering at an FS was shown to be proportional to both the concentration of nutrient and the surface area of the FS. We presented two FSs to test which connection the organism selected in response to varying amounts of food and derived a simple rule for connection persistence: the longer connection collapses earlier. A mathematical model for tube selection in response to amount of food was derived and predicted our experimental findings regarding the choice of connection. When three FSs were presented to the organism, the longer tubes were also the first to collapse, explained by the relative probability of disconnection. The size of the FS is thus a key parameter determining network formation.

  12. Reversible Assembly of Graphitic Carbon Nitride 3D Network for Highly Selective Dyes Absorption and Regeneration.

    PubMed

    Zhang, Yuye; Zhou, Zhixin; Shen, Yanfei; Zhou, Qing; Wang, Jianhai; Liu, Anran; Liu, Songqin; Zhang, Yuanjian

    2016-09-27

    Responsive assembly of 2D materials is of great interest for a range of applications. In this work, interfacial functionalized carbon nitride (CN) nanofibers were synthesized by hydrolyzing bulk CN in sodium hydroxide solution. The reversible assemble and disassemble behavior of the as-prepared CN nanofibers was investigated by using CO2 as a trigger to form a hydrogel network at first. Compared to the most widespread absorbent materials such as active carbon, graphene and previously reported supramolecular gel, the proposed CN hydrogel not only exhibited a competitive absorbing capacity (maximum absorbing capacity of methylene blue up to 402 mg/g) but also overcame the typical deficiencies such as poor selectivity and high energy-consuming regeneration. This work would provide a strategy to construct a 3D CN network and open an avenue for developing smart assembly for potential applications ranging from environment to selective extraction.

  13. Corticostriatal response selection in sentence production: Insights from neural network simulation with reservoir computing.

    PubMed

    Hinaut, Xavier; Lance, Florian; Droin, Colas; Petit, Maxime; Pointeau, Gregoire; Dominey, Peter Ford

    2015-11-01

    Language production requires selection of the appropriate sentence structure to accommodate the communication goal of the speaker - the transmission of a particular meaning. Here we consider event meanings, in terms of predicates and thematic roles, and we address the problem that a given event can be described from multiple perspectives, which poses a problem of response selection. We present a model of response selection in sentence production that is inspired by the primate corticostriatal system. The model is implemented in the context of reservoir computing where the reservoir - a recurrent neural network with fixed connections - corresponds to cortex, and the readout corresponds to the striatum. We demonstrate robust learning, and generalization properties of the model, and demonstrate its cross linguistic capabilities in English and Japanese. The results contribute to the argument that the corticostriatal system plays a role in response selection in language production, and to the stance that reservoir computing is a valid potential model of corticostriatal processing.

  14. Characterization of computer network events through simultaneous feature selection and clustering of intrusion alerts

    NASA Astrophysics Data System (ADS)

    Chen, Siyue; Leung, Henry; Dondo, Maxwell

    2014-05-01

    As computer network security threats increase, many organizations implement multiple Network Intrusion Detection Systems (NIDS) to maximize the likelihood of intrusion detection and provide a comprehensive understanding of intrusion activities. However, NIDS trigger a massive number of alerts on a daily basis. This can be overwhelming for computer network security analysts since it is a slow and tedious process to manually analyse each alert produced. Thus, automated and intelligent clustering of alerts is important to reveal the structural correlation of events by grouping alerts with common features. As the nature of computer network attacks, and therefore alerts, is not known in advance, unsupervised alert clustering is a promising approach to achieve this goal. We propose a joint optimization technique for feature selection and clustering to aggregate similar alerts and to reduce the number of alerts that analysts have to handle individually. More precisely, each identified feature is assigned a binary value, which reflects the feature's saliency. This value is treated as a hidden variable and incorporated into a likelihood function for clustering. Since computing the optimal solution of the likelihood function directly is analytically intractable, we use the Expectation-Maximisation (EM) algorithm to iteratively update the hidden variable and use it to maximize the expected likelihood. Our empirical results, using a labelled Defense Advanced Research Projects Agency (DARPA) 2000 reference dataset, show that the proposed method gives better results than the EM clustering without feature selection in terms of the clustering accuracy.

  15. Mechanisms of Winner-Take-All and Group Selection in Neuronal Spiking Networks

    PubMed Central

    Chen, Yanqing

    2017-01-01

    A major function of central nervous systems is to discriminate different categories or types of sensory input. Neuronal networks accomplish such tasks by learning different sensory maps at several stages of neural hierarchy, such that different neurons fire selectively to reflect different internal or external patterns and states. The exact mechanisms of such map formation processes in the brain are not completely understood. Here we study the mechanism by which a simple recurrent/reentrant neuronal network accomplish group selection and discrimination to different inputs in order to generate sensory maps. We describe the conditions and mechanism of transition from a rhythmic epileptic state (in which all neurons fire synchronized and indiscriminately to any input) to a winner-take-all state in which only a subset of neurons fire for a specific input. We prove an analytic condition under which a stable bump solution and a winner-take-all state can emerge from the local recurrent excitation-inhibition interactions in a three-layer spiking network with distinct excitatory and inhibitory populations, and demonstrate the importance of surround inhibitory connection topology on the stability of dynamic patterns in spiking neural network. PMID:28484384

  16. Fuzzy C-Means Clustering and Energy Efficient Cluster Head Selection for Cooperative Sensor Network.

    PubMed

    Bhatti, Dost Muhammad Saqib; Saeed, Nasir; Nam, Haewoon

    2016-09-09

    We propose a novel cluster based cooperative spectrum sensing algorithm to save the wastage of energy, in which clusters are formed using fuzzy c-means (FCM) clustering and a cluster head (CH) is selected based on a sensor's location within each cluster, its location with respect to fusion center (FC), its signal-to-noise ratio (SNR) and its residual energy. The sensing information of a single sensor is not reliable enough due to shadowing and fading. To overcome these issues, cooperative spectrum sensing schemes were proposed to take advantage of spatial diversity. For cooperative spectrum sensing, all sensors sense the spectrum and report the sensed energy to FC for the final decision. However, it increases the energy consumption of the network when a large number of sensors need to cooperate; in addition to that, the efficiency of the network is also reduced. The proposed algorithm makes the cluster and selects the CHs such that very little amount of network energy is consumed and the highest efficiency of the network is achieved. Using the proposed algorithm maximum probability of detection under an imperfect channel is accomplished with minimum energy consumption as compared to conventional clustering schemes.

  17. Fuzzy C-Means Clustering and Energy Efficient Cluster Head Selection for Cooperative Sensor Network

    PubMed Central

    Bhatti, Dost Muhammad Saqib; Saeed, Nasir; Nam, Haewoon

    2016-01-01

    We propose a novel cluster based cooperative spectrum sensing algorithm to save the wastage of energy, in which clusters are formed using fuzzy c-means (FCM) clustering and a cluster head (CH) is selected based on a sensor’s location within each cluster, its location with respect to fusion center (FC), its signal-to-noise ratio (SNR) and its residual energy. The sensing information of a single sensor is not reliable enough due to shadowing and fading. To overcome these issues, cooperative spectrum sensing schemes were proposed to take advantage of spatial diversity. For cooperative spectrum sensing, all sensors sense the spectrum and report the sensed energy to FC for the final decision. However, it increases the energy consumption of the network when a large number of sensors need to cooperate; in addition to that, the efficiency of the network is also reduced. The proposed algorithm makes the cluster and selects the CHs such that very little amount of network energy is consumed and the highest efficiency of the network is achieved. Using the proposed algorithm maximum probability of detection under an imperfect channel is accomplished with minimum energy consumption as compared to conventional clustering schemes. PMID:27618061

  18. Interference Mitigation Based on Intelligent Location Selection in a Canonical Communication Network

    NASA Astrophysics Data System (ADS)

    Qu, Junyue; Cai, Yueming; Zheng, Jianchao; Yang, Wendong; Yang, Weiwei; Hu, Yajie

    2016-01-01

    In this letter, the interference mitigation in a canonical communication network is discussed from the perspective of intelligent location selection. A potential game model is constructed and a location-selection algorithm is designed combining no-regret procedure. With the proposed algorithm, all nodes can update their strategies with limited information exchange. Specifically, our proposed algorithm can converge to a set of correlated equilibria which are the globally or locally optimal solution to the problem of interference minimization. Moreover, our proposed algorithm can achieve distributed implementation without a central node. Simulation results demonstrate that the total interference can be mitigated efficiently with our proposed algorithm. And the proposed algorithm can converge fast.

  19. Topology-selective jamming of fully-connected, code-division random-access networks

    NASA Technical Reports Server (NTRS)

    Polydoros, Andreas; Cheng, Unjeng

    1990-01-01

    The purpose is to introduce certain models of topology selective stochastic jamming and examine its impact on a class of fully-connected, spread-spectrum, slotted ALOHA-type random access networks. The theory covers dedicated as well as half-duplex units. The dominant role of the spatial duty factor is established, and connections with the dual concept of time selective jamming are discussed. The optimal choices of coding rate and link access parameters (from the users' side) and the jamming spatial fraction are numerically established for DS and FH spreading.

  20. Network intrusion detection by the coevolutionary immune algorithm of artificial immune systems with clonal selection

    NASA Astrophysics Data System (ADS)

    Salamatova, T.; Zhukov, V.

    2017-02-01

    The paper presents the application of the artificial immune systems apparatus as a heuristic method of network intrusion detection for algorithmic provision of intrusion detection systems. The coevolutionary immune algorithm of artificial immune systems with clonal selection was elaborated. In testing different datasets the empirical results of evaluation of the algorithm effectiveness were achieved. To identify the degree of efficiency the algorithm was compared with analogs. The fundamental rules based of solutions generated by this algorithm are described in the article.

  1. Tumor-selective mitochondrial network collapse induced by atmospheric gas plasma-activated medium.

    PubMed

    Saito, Kosuke; Asai, Tomohiko; Fujiwara, Kyoko; Sahara, Junki; Koguchi, Haruhisa; Fukuda, Noboru; Suzuki-Karasaki, Miki; Soma, Masayoshi; Suzuki-Karasaki, Yoshihiro

    2016-04-12

    Non-thermal atmospheric gas plasma (AGP) exhibits cytotoxicity against malignant cells with minimal cytotoxicity toward normal cells. However, the mechanisms of its tumor-selective cytotoxicity remain unclear. Here we report that AGP-activated medium increases caspase-independent cell death and mitochondrial network collapse in a panel of human cancer cells, but not in non-transformed cells. AGP irradiation stimulated reactive oxygen species (ROS) generation in AGP-activated medium, and in turn the resulting stable ROS, most likely hydrogen peroxide (H2O2), activated intracellular ROS generation and mitochondrial ROS (mROS) accumulation. Culture in AGP-activated medium resulted in cell death and excessive mitochondrial fragmentation and clustering, and these responses were inhibited by ROS scavengers. AGP-activated medium also increased dynamin-related protein 1-dependent mitochondrial fission in a tumor-specific manner, and H2O2 administration showed similar effects. Moreover, the vulnerability of tumor cells to mitochondrial network collapse appeared to result from their higher sensitivity to mROS accumulation induced by AGP-activated medium or H2O2. The present findings expand our previous observations on death receptor-mediated tumor-selective cell killing and reinforce the importance of mitochondrial network remodeling as a powerful target for tumor-selective cancer treatment.

  2. Tumor-selective mitochondrial network collapse induced by atmospheric gas plasma-activated medium

    PubMed Central

    Saito, Kosuke; Asai, Tomohiko; Fujiwara, Kyoko; Sahara, Junki; Koguchi, Haruhisa; Fukuda, Noboru; Suzuki-Karasaki, Miki; Soma, Masayoshi; Suzuki-Karasaki, Yoshihiro

    2016-01-01

    Non-thermal atmospheric gas plasma (AGP) exhibits cytotoxicity against malignant cells with minimal cytotoxicity toward normal cells. However, the mechanisms of its tumor-selective cytotoxicity remain unclear. Here we report that AGP-activated medium increases caspase-independent cell death and mitochondrial network collapse in a panel of human cancer cells, but not in non-transformed cells. AGP irradiation stimulated reactive oxygen species (ROS) generation in AGP-activated medium, and in turn the resulting stable ROS, most likely hydrogen peroxide (H2O2), activated intracellular ROS generation and mitochondrial ROS (mROS) accumulation. Culture in AGP-activated medium resulted in cell death and excessive mitochondrial fragmentation and clustering, and these responses were inhibited by ROS scavengers. AGP-activated medium also increased dynamin-related protein 1-dependent mitochondrial fission in a tumor-specific manner, and H2O2 administration showed similar effects. Moreover, the vulnerability of tumor cells to mitochondrial network collapse appeared to result from their higher sensitivity to mROS accumulation induced by AGP-activated medium or H2O2. The present findings expand our previous observations on death receptor-mediated tumor-selective cell killing and reinforce the importance of mitochondrial network remodeling as a powerful target for tumor-selective cancer treatment. PMID:26942565

  3. Stochastic noncooperative and cooperative evolutionary game strategies of a population of biological networks under natural selection.

    PubMed

    Chen, Bor-Sen; Yeh, Chin-Hsun

    2017-09-05

    We review current static and dynamic evolutionary game strategies of biological networks and discuss the lack of random genetic variations and stochastic environmental disturbances in these models. To include these factors, a population of evolving biological networks is modeled as a nonlinear stochastic biological system with Poisson-driven genetic variations and random environmental fluctuations (stimuli). To gain insight into the evolutionary game theory of stochastic biological networks under natural selection, the phenotypic robustness and network evolvability of noncooperative and cooperative evolutionary game strategies are discussed from a stochastic Nash game perspective. The noncooperative strategy can be transformed into an equivalent multi-objective optimization problem and is shown to display significantly improved network robustness to tolerate genetic variations and buffer environmental disturbances, maintaining phenotypic traits for longer than the cooperative strategy. However, the noncooperative case requires greater effort and more compromises between partly conflicting players. Global linearization is used to simplify the problem of solving nonlinear stochastic evolutionary games. Finally, a simple stochastic evolutionary model of a metabolic pathway is simulated to illustrate the procedure of solving for two evolutionary game strategies and to confirm and compare their respective characteristics in the evolutionary process. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Targets of selection in a disease resistance network in wild tomatoes.

    PubMed

    Rose, Laura E; Grzeskowiak, Lukasz; Hörger, Anja C; Groth, Martin; Stephan, Wolfgang

    2011-12-01

    Studies combining comparative genomics and information on biochemical pathways have revealed that protein evolution can be affected by the amount of pleiotropy associated with a particular gene. The amount of pleiotropy, in turn, can be a function of the position at which a gene operates in a pathway and the pathway structure. Genes that serve as convergence points and have several partners (so-called hubs) often show the greatest constraint and hence the slowest rate of protein evolution. In this article, we have studied five genes (Pto, Fen, Rin4, Prf and Pfi) in a defence signalling network in a wild tomato species, Solanum peruvianum. These proteins operate together and contribute to bacterial resistance in tomato. We predicted that Prf (and possibly Pfi), which serves as a convergence point for upstream signals, should show greater evolutionary constraint. However, we found instead that two of the genes which potentially interact with pathogen ligands, Rin4 and Fen, have evolved under strong evolutionary constraint, whereas Prf and Pfi, which probably function further downstream in the network, show evidence of balancing selection. This counterintuitive observation may be probable in pathogen defence networks, because pathogens may target positions throughout resistance networks to manipulate or nullify host resistance, thereby leaving a molecular signature of host-parasite co-evolution throughout a single network. © 2011 The Authors. Molecular Plant Pathology © 2011 BSPP and Blackwell Publishing Ltd.

  5. Fuzzy rough sets, and a granular neural network for unsupervised feature selection.

    PubMed

    Ganivada, Avatharam; Ray, Shubhra Sankar; Pal, Sankar K

    2013-12-01

    A granular neural network for identifying salient features of data, based on the concepts of fuzzy set and a newly defined fuzzy rough set, is proposed. The formation of the network mainly involves an input vector, initial connection weights and a target value. Each feature of the data is normalized between 0 and 1 and used to develop granulation structures by a user defined α-value. The input vector and the target value of the network are defined using granulation structures, based on the concept of fuzzy sets. The same granulation structures are also presented to a decision system. The decision system helps in extracting the domain knowledge about data in the form of dependency factors, using the notion of new fuzzy rough set. These dependency factors are assigned as the initial connection weights of the proposed network. It is then trained using minimization of a novel feature evaluation index in an unsupervised manner. The effectiveness of the proposed network, in evaluating selected features, is demonstrated on several real-life datasets. The results of FRGNN are found to be statistically more significant than related methods in 28 instances of 40 instances, i.e., 70% of instances, using the paired t-test.

  6. On Proper Selection of Multihop Relays for Future Enhancement of AeroMACS Networks

    NASA Technical Reports Server (NTRS)

    Kamali, Behnam; Kerczewski, Robert J.; Apaza, Rafael D.

    2015-01-01

    As the Aeronautical Mobile Airport Communications System (AeroMACS) has evolved from a technology concept to a deployed communications network over major US airports, it is now time to contemplate whether the existing capacity of AeroMACS is sufficient to meet the demands set forth by all fixed and mobile applications over the airport surface given the AeroMACS constraints regarding bandwidth and transmit power. The underlying idea in this article is to present IEEE 802.16j-based WiMAX as a technology that can address future capacity enhancements and therefore is most feasible for AeroMACS applications. The principal argument in favor IEEE 802.16j technology is the flexible and cost effective extension of radio coverage that is afforded by relay fortified networks, with virtually no increase in the power requirements and virtually no rise in interference levels to co-allocated applications. The IEEE 802.16j-based multihop relay systems are briefly described. The focus is on key features of this technology, frame structure, and its architecture. Next, AeroMACS is described as a WiMAX-based wireless network. The two major relay modes supported by IEEE 802.16j amendment, i.e., transparent and non-transparent are described. The benefits of employing multihop relays are listed. Some key challenges related to incorporating relays into AeroMACS networks are discussed. The selection of relay type in a broadband wireless network affects a number of network parameters such as latency, signal overhead, PHY (Scalable Physical Layer) and MAC (Media Access Layer) layer protocols, consequently it can alter key network quantities of throughput and QoS (Quality of Service).

  7. Network Receptive Field Modeling Reveals Extensive Integration and Multi-feature Selectivity in Auditory Cortical Neurons.

    PubMed

    Harper, Nicol S; Schoppe, Oliver; Willmore, Ben D B; Cui, Zhanfeng; Schnupp, Jan W H; King, Andrew J

    2016-11-01

    Cortical sensory neurons are commonly characterized using the receptive field, the linear dependence of their response on the stimulus. In primary auditory cortex neurons can be characterized by their spectrotemporal receptive fields, the spectral and temporal features of a sound that linearly drive a neuron. However, receptive fields do not capture the fact that the response of a cortical neuron results from the complex nonlinear network in which it is embedded. By fitting a nonlinear feedforward network model (a network receptive field) to cortical responses to natural sounds, we reveal that primary auditory cortical neurons are sensitive over a substantially larger spectrotemporal domain than is seen in their standard spectrotemporal receptive fields. Furthermore, the network receptive field, a parsimonious network consisting of 1-7 sub-receptive fields that interact nonlinearly, consistently better predicts neural responses to auditory stimuli than the standard receptive fields. The network receptive field reveals separate excitatory and inhibitory sub-fields with different nonlinear properties, and interaction of the sub-fields gives rise to important operations such as gain control and conjunctive feature detection. The conjunctive effects, where neurons respond only if several specific features are present together, enable increased selectivity for particular complex spectrotemporal structures, and may constitute an important stage in sound recognition. In conclusion, we demonstrate that fitting auditory cortical neural responses with feedforward network models expands on simple linear receptive field models in a manner that yields substantially improved predictive power and reveals key nonlinear aspects of cortical processing, while remaining easy to interpret in a physiological context.

  8. Network Receptive Field Modeling Reveals Extensive Integration and Multi-feature Selectivity in Auditory Cortical Neurons

    PubMed Central

    Willmore, Ben D. B.; Cui, Zhanfeng; Schnupp, Jan W. H.; King, Andrew J.

    2016-01-01

    Cortical sensory neurons are commonly characterized using the receptive field, the linear dependence of their response on the stimulus. In primary auditory cortex neurons can be characterized by their spectrotemporal receptive fields, the spectral and temporal features of a sound that linearly drive a neuron. However, receptive fields do not capture the fact that the response of a cortical neuron results from the complex nonlinear network in which it is embedded. By fitting a nonlinear feedforward network model (a network receptive field) to cortical responses to natural sounds, we reveal that primary auditory cortical neurons are sensitive over a substantially larger spectrotemporal domain than is seen in their standard spectrotemporal receptive fields. Furthermore, the network receptive field, a parsimonious network consisting of 1–7 sub-receptive fields that interact nonlinearly, consistently better predicts neural responses to auditory stimuli than the standard receptive fields. The network receptive field reveals separate excitatory and inhibitory sub-fields with different nonlinear properties, and interaction of the sub-fields gives rise to important operations such as gain control and conjunctive feature detection. The conjunctive effects, where neurons respond only if several specific features are present together, enable increased selectivity for particular complex spectrotemporal structures, and may constitute an important stage in sound recognition. In conclusion, we demonstrate that fitting auditory cortical neural responses with feedforward network models expands on simple linear receptive field models in a manner that yields substantially improved predictive power and reveals key nonlinear aspects of cortical processing, while remaining easy to interpret in a physiological context. PMID:27835647

  9. Artepillin C (ARC) in Brazilian green propolis selectively blocks oncogenic PAK1 signaling and suppresses the growth of NF tumors in mice.

    PubMed

    Messerli, Shanta M; Ahn, Mok-Ryeon; Kunimasa, Kazuhiro; Yanagihara, Miyako; Tatefuji, Tomoki; Hashimoto, Ken; Mautner, Victor; Uto, Yoshihiro; Hori, Hitoshi; Kumazawa, Shigenori; Kaji, Kazuhiko; Ohta, Toshiro; Maruta, Hiroshi

    2009-03-01

    There are mainly three types of propolis whose major anticancer ingredients are entirely different: (1) CAPE (caffeic acid phenethyl ester)-based propolis in Europe, Far East and New Zealand, (2) artepillin C (ARC)-based Brazilian green propolis and (3) Brazilian red propolis. It was shown previously that NF (neurofibromatosis)-associated tumors require the kinase PAK1 for their growth, and CAPE-based propolis extracts such as Bio 30 suppress completely the growth of NF tumors in vivo by blocking PAK1 signaling. Also it was demonstrated that ARC suppresses angiogenesis, suggesting the possibility that ARC also blocks oncogenic PAK1 signaling. Here it is shown for the first time that both ARC and green propolis extract (GPE) indeed block the PAK1 signaling selectively, without affecting another kinase known as AKT. Furthermore, it was confirmed that ARC as well as GPE suppress almost completely the growth of human NF tumor xenografts in mice, as does Bio 30. These results suggest that both CAPE-based and ARC-based propolis extracts are natural anti-PAK1 remedies and could be among the first effective NF therapeutics available on the market. Since more than 70% of human cancers such as breast and prostate cancers require the kinase PAK1 for their growth, it is quite possible that GPE could be potentially useful for the treatment of these cancers, as is Bio 30. (c) 2008 John Wiley & Sons, Ltd.

  10. Integrated network-diversity analyses suggest suppressive effect of Hodgkin’s lymphoma and slightly relieving effect of chemotherapy on human milk microbiome

    PubMed Central

    Ma, Zhanshan (Sam); Li, Lianwei; Li, Wendy; Li, Jie; Chen, Hongju

    2016-01-01

    We aim to investigate the effects of Hodgkin’s lymphoma and the chemotherapy for treating the disease on the human milk microbiome through integrated network and community diversity analyses. Our analyses suggest that Hodgkin’s lymphoma seems to have a suppressing effect on the milk microbiome by lowering the milk microbial community diversity, as measured by the Hill numbers profiles. Although the diversity analysis did not reveal an effect of chemotherapy on community diversity, bacterial species interaction network analysis shows that chemotherapy may help to slightly restore the milk microbiome impacted by Hodgkin’s lymphoma through its influence on the interactions among species (or OTUs). We further constructed diversity-metabolites network, which suggests that the milk microbial diversity is positively correlated with some beneficial milk metabolites such as DHA (DocosaHexaenoic Acid), and that the diversity is negatively correlated with some potentially harmful metabolites such as Butanal. We hence postulate that higher milk microbial diversity should be a signature of healthy mothers and beneficial to infants. Finally, we constructed metabolites OTU correlation networks, from which we identified some special OTUs. These OTUs deserve further investigations given their apparent involvements in regulating the levels of critical milk metabolites such as DHA, Inositol and Butanal. PMID:27386954

  11. Orbital-selective singlet dimer formation and suppression of double exchange in 4d and 5d systems

    NASA Astrophysics Data System (ADS)

    Streltsov, Sergey; Cao, Gang; Khomskii, Daniel

    One of the main mechanisms of ferromagnetic ordering in conducting materials is the double exchange (DE). It is usually supposed in DE model that the Hund's coupling JH is much larger than electron hopping t; in this case one stabilizes the state with maximum spin per pair of ions, which finally leads to ferromagnetism in bulk systems. We show that in the dimerized 4 d / 5 d transition metal oxides for which JH is reduced and t is in contrast enhanced, another situation is possible, when formation of the spin-singlets on delocalized orbitals is more favorable. This leads to suppression of the DE and to a strong decrease of the total spin. The model calculations using the dynamical mean-field theory show that this effect survives even in the extended systems, not only for dimers. Such a situation is realized, e.g., in Y5Mo2O12, CrO2 under pressure and in many other 4 d / 5 d based materials. Another mechanism, which may suppress DE and which is also typical for 4 d / 5 d compounds is the spin-orbit coupling (SOC). We show on the example of Ba5AlIr2O11, that in this system it is the combination of molecular-orbital formation and SOC that strongly decreases magnetic moment on Ir. Civil Research and Development Foundation via FSCX-14-61025-0.

  12. A selection model for accounting for publication bias in a full network meta-analysis.

    PubMed

    Mavridis, Dimitris; Welton, Nicky J; Sutton, Alex; Salanti, Georgia

    2014-12-30

    Copas and Shi suggested a selection model to explore the potential impact of publication bias via sensitivity analysis based on assumptions for the probability of publication of trials conditional on the precision of their results. Chootrakool et al. extended this model to three-arm trials but did not fully account for the implications of the consistency assumption, and their model is difficult to generalize for complex network structures with more than three treatments. Fitting these selection models within a frequentist setting requires maximization of a complex likelihood function, and identification problems are common. We have previously presented a Bayesian implementation of the selection model when multiple treatments are compared with a common reference treatment. We now present a general model suitable for complex, full network meta-analysis that accounts for consistency when adjusting results for publication bias. We developed a design-by-treatment selection model to describe the mechanism by which studies with different designs (sets of treatments compared in a trial) and precision may be selected for publication. We fit the model in a Bayesian setting because it avoids the numerical problems encountered in the frequentist setting, it is generalizable with respect to the number of treatments and study arms, and it provides a flexible framework for sensitivity analysis using external knowledge. Our model accounts for the additional uncertainty arising from publication bias more successfully compared to the standard Copas model or its previous extensions. We illustrate the methodology using a published triangular network for the failure of vascular graft or arterial patency.

  13. Analyzing heterogeneity in the effects of physical activity in children on social network structure and peer selection dynamics

    PubMed Central

    Henry, Teague; Gesell, Sabina B.; Ip, Edward H.

    2016-01-01

    Background Social networks influence children and adolescents’ physical activity. The focus of this paper is to examine the differences in the effects of physical activity on friendship selection, with eye to the implications on physical activity interventions for young children. Network interventions to increase physical activity are warranted but have not been conducted. Prior to implementing a network intervention in the field, it is important to understand potential heterogeneities in the effects that activity level have on network structure. In this study, the associations between activity level and cross sectional network structure, and activity level and change in network structure are assessed. Methods We studied a real-world friendship network among 81 children (average age 7.96 years) who lived in low SES neighborhoods, attended public schools, and attended one of two structured aftercare programs, of which one has existed and the other was new. We used the exponential random graph model (ERGMs) and its longitudinal extension to evaluate the association between activity level and various demographic factors in having, forming, and dissolving friendship. Due to heterogeneity between the friendship networks within the aftercare programs, separate analyses were conducted for each network. Results There was heterogeneity in the effect of physical activity on both cross sectional network structure and the formation and dissolution processes, both across time and between networks. Conclusions Network analysis could be used to assess the unique structure and dynamics of a social network before an intervention is implemented, so as to optimize the effects of the network intervention for increasing childhood physical activity. Additionally, if peer selection processes are changing within a network, a static network intervention strategy for childhood physical activity could become inefficient as the network evolves. PMID:27867518

  14. Alzheimer disease susceptibility loci: evidence for a protein network under natural selection.

    PubMed

    Raj, Towfique; Shulman, Joshua M; Keenan, Brendan T; Chibnik, Lori B; Evans, Denis A; Bennett, David A; Stranger, Barbara E; De Jager, Philip L

    2012-04-06

    Recent genome-wide association studies have identified a number of susceptibility loci for Alzheimer disease (AD). To understand the functional consequences and potential interactions of the associated loci, we explored large-scale data sets interrogating the human genome for evidence of positive natural selection. Our findings provide significant evidence for signatures of recent positive selection acting on several haplotypes carrying AD susceptibility alleles; interestingly, the genes found in these selected haplotypes can be assembled, independently, into a molecular complex via a protein-protein interaction (PPI) network approach. These results suggest a possible coevolution of genes encoding physically-interacting proteins that underlie AD susceptibility and are coexpressed in different tissues. In particular, PICALM, BIN1, CD2AP, and EPHA1 are interconnected through multiple interacting proteins and appear to have coordinated evidence of selection in the same human population, suggesting that they may be involved in the execution of a shared molecular function. This observation may be AD-specific, as the 12 loci associated with Parkinson disease do not demonstrate excess evidence of natural selection. The context for selection is probably unrelated to AD itself; it is likely that these genes interact in another context, such as in immune cells, where we observe cis-regulatory effects at several of the selected AD loci. Copyright © 2012 The American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.

  15. Social network theory applied to resting-state fMRI connectivity data in the identification of epilepsy networks with iterative feature selection.

    PubMed

    Zhang, Xiaohui; Tokoglu, Fuyuze; Negishi, Michiro; Arora, Jagriti; Winstanley, Scott; Spencer, Dennis D; Constable, R Todd

    2011-07-15

    Epilepsy is a brain disorder usually associated with abnormal cortical and/or subcortical functional networks. Exploration of the abnormal network properties and localization of the brain regions involved in human epilepsy networks are critical for both the understanding of the epilepsy networks and planning therapeutic strategies. Currently, most localization of seizure networks come from ictal EEG observations. Functional MRI provides high spatial resolution together with more complete anatomical coverage compared with EEG and may have advantages if it can be used to identify the network(s) associated with seizure onset and propagation. Epilepsy networks are believed to be present with detectable abnormal signatures even during the interictal state. In this study, epilepsy networks were investigated using resting-state fMRI acquired with the subjects in the interictal state. We tested the hypothesis that social network theory applied to resting-state fMRI data could reveal abnormal network properties at the group level. Using network data as input to a classification algorithm allowed separation of medial temporal lobe epilepsy (MTLE) patients from normal control subjects indicating the potential value of such network analyses in epilepsy. Five local network properties obtained from 36 anatomically defined ROIs were input as features to the classifier. An iterative feature selection strategy based on the classification efficiency that can avoid 'over-fitting' is proposed to further improve the classification accuracy. An average sensitivity of 77.2% and specificity of 83.86% were achieved via 'leave one out' cross validation. This finding of significantly abnormal network properties in group level data confirmed our initial hypothesis and provides motivation for further investigation of the epilepsy process at the network level.

  16. Application of ecological criteria in selecting marine reserves and developing reserve networks

    USGS Publications Warehouse

    Roberts, Callum M.; Branch, George; Bustamante, Rodrigo H.; Castilla, Juan Carlos; Dugan, Jenifer; Halpern, Benjamin S.; Lafferty, Kevin D.; Leslie, Heather; McArdle, Deborah; Ruckelshaus, Mary; Warner, Robert R.

    2003-01-01

    Marine reserves are being established worldwide in response to a growing recognition of the conservation crisis that is building in the oceans. However, designation of reserves has been largely opportunistic, or protective measures have been implemented (often overlapping and sometimes in conflict) by different entities seeking to achieve different ends. This has created confusion among both users and enforcers, and the proliferation of different measures provides a false sense of protection where little is offered. This paper sets out a procedure grounded in current understanding of ecological processes, that allows the evaluation and selection of reserve sites in order to develop functional, interconnected networks of fully protected reserves that will fulfill multiple objectives. By fully protected we mean permanently closed to fishing and other resource extraction. We provide a framework that unifies the central aims of conservation and fishery management, while also meeting other human needs such as the provision of ecosystem services (e.g., maintenance of coastal water quality, shoreline protection, and recreational opportunities). In our scheme, candidate sites for reserves are evaluated against 12 criteria focused toward sustaining the biological integrity and productivity of marine systems at both local and regional scales. While a limited number of sites will be indispensable in a network, many will be of similar value as reserves, allowing the design of numerous alternative, biologically adequate networks. Devising multiple network designs will help ensure that ecological functionality is preserved throughout the socioeconomic evaluation process. Too often, socioeconomic criteria have dominated the process of reserve selection, potentially undermining their efficacy. We argue that application of biological criteria must precede and inform socioeconomic evaluation, since maintenance of ecosystem functioning is essential for meeting all of the goals for

  17. Frequency-selective control of cortical and subcortical networks by central thalamus

    PubMed Central

    Liu, Jia; Lee, Hyun Joo; Weitz, Andrew J; Fang, Zhongnan; Lin, Peter; Choy, ManKin; Fisher, Robert; Pinskiy, Vadim; Tolpygo, Alexander; Mitra, Partha; Schiff, Nicholas; Lee, Jin Hyung

    2015-01-01

    Central thalamus plays a critical role in forebrain arousal and organized behavior. However, network-level mechanisms that link its activity to brain state remain enigmatic. Here, we combined optogenetics, fMRI, electrophysiology, and video-EEG monitoring to characterize the central thalamus-driven global brain networks responsible for switching brain state. 40 and 100 Hz stimulations of central thalamus caused widespread activation of forebrain, including frontal cortex, sensorimotor cortex, and striatum, and transitioned the brain to a state of arousal in asleep rats. In contrast, 10 Hz stimulation evoked significantly less activation of forebrain, inhibition of sensory cortex, and behavioral arrest. To investigate possible mechanisms underlying the frequency-dependent cortical inhibition, we performed recordings in zona incerta, where 10, but not 40, Hz stimulation evoked spindle-like oscillations. Importantly, suppressing incertal activity during 10 Hz central thalamus stimulation reduced the evoked cortical inhibition. These findings identify key brain-wide dynamics underlying central thalamus arousal regulation. DOI: http://dx.doi.org/10.7554/eLife.09215.001 PMID:26652162

  18. Activation of NPY receptors suppresses excitatory synaptic transmission in a taste-feeding network in the lower brain stem.

    PubMed

    Chen, Zhixiong; Travers, Susan P; Travers, Joseph B

    2012-06-15

    Consummatory responses to taste stimuli are modulated by visceral signals processed in the caudal nucleus of the solitary tract (cNST) and ventrolateral medulla. On the basis of decerebrate preparations, this modulation can occur through local brain stem pathways. Among the large number of neuropeptides and neuromodulators implicated in these visceral pathways is neuropeptide Y (NPY), which is oftentimes colocalized in catecholaminergic neurons themselves implicated in glucoprivic-induced feeding and satiety. In addition to the cNST and ventrolateral medulla, noradrenergic and NPY receptors are found in circumscribed regions of the medullary reticular formation rich in preoromotor neurons. To test the hypothesis that NPY may act as a neuromodulator on preoromotor neurons, we recorded the effects of bath application of NPY and specific Y1 and Y2 agonists on currents elicited from electrical stimulation of the rostral (taste) NST in prehypoglossal neurons in a brain stem slice preparation. A high proportion of NST-driven responses were suppressed by NPY, as well as Y1 and Y2 agonists. On the basis of paired pulse ratios and changes in membrane resistance, we concluded that Y1 receptors influence these neurons both presynaptically and postsynaptically and that Y2 receptors have a presynaptic locus. To test the hypothesis that NPY may act in concert with norepinephrine (NE), we examined neurons showing suppressed responses in the presence of a Y2 agonist and demonstrated a greater degree of suppression to a Y2 agonist/NE cocktail. These suppressive effects on preoromotoneurons may reflect a satiety pathway originating from A2 neurons in the caudal brain stem.

  19. Tofogliflozin, A Highly Selective Inhibitor of SGLT2 Blocks Proinflammatory and Proapoptotic Effects of Glucose Overload on Proximal Tubular Cells Partly by Suppressing Oxidative Stress Generation.

    PubMed

    Ishibashi, Y; Matsui, T; Yamagishi, S

    2016-03-01

    Ninety percent of glucose filtered by the glomerulus is reabsorbed by a sodium-glucose cotransporter 2 (SGLT2), which is mainly expressed on S1 and S2 segment of renal proximal tubules. Since SGLT-2-mediated glucose reabsorption is increased under diabetic conditions, selective inhibition of SGLT2 is a potential therapeutic target for the treatment of diabetes. We have recently shown that an inhibitor of SGLT2 has anti-inflammatory and antifibrotic effects on experimental diabetic nephropathy partly by suppressing advanced glycation end products formation and oxidative stress generation in the kidney. However, the direct effects of SGLT2 inhibitor on tubular cell damage remain unclear. In this study, we investigated the effects of tofogliflozin, a highly selective inhibitor of SGLT2 on oxidative stress generation, inflammatory and proapoptotic reactions in cultured human proximal tubular cells exposed to high glucose. Tofogliflozin dose-dependently suppressed glucose entry into tubular cells. High glucose exposure (30 mM) for 4 and 24 h significantly increased oxidative stress generation in tubular cells, which were suppressed by the treatment of tofogliflozin or an antioxidant N-acetylcysteine (NAC). Monocyte chemoattractant protein-1 (MCP-1) gene expression and apoptotic cell death were induced by 4 h- and 8 day-exposure to high glucose, respectively, both of which were also blocked by tofogliflozin or NAC. The present study suggests that SGLT2-mediated glucose entry into tubular cells could stimulate oxidative stress and evoke inflammatory and proapoptotic reactions in this cell type. Blockade of glucose reabsorption in tubular cells by SGLT2 inhibitor might exert beneficial effects on tubulointerstitial damage in diabetic nephropathy.

  20. A frequency-selective feedback model of auditory efferent suppression and its implications for the recognition of speech in noise.

    PubMed

    Clark, Nicholas R; Brown, Guy J; Jürgens, Tim; Meddis, Ray

    2012-09-01

    The potential contribution of the peripheral auditory efferent system to our understanding of speech in a background of competing noise was studied using a computer model of the auditory periphery and assessed using an automatic speech recognition system. A previous study had shown that a fixed efferent attenuation applied to all channels of a multi-channel model could improve the recognition of connected digit triplets in noise [G. J. Brown, R. T. Ferry, and R. Meddis, J. Acoust. Soc. Am. 127, 943-954 (2010)]. In the current study an anatomically justified feedback loop was used to automatically regulate separate attenuation values for each auditory channel. This arrangement resulted in a further enhancement of speech recognition over fixed-attenuation conditions. Comparisons between multi-talker babble and pink noise interference conditions suggest that the benefit originates from the model's ability to modify the amount of suppression in each channel separately according to the spectral shape of the interfering sounds.

  1. Feature selection for MLP neural network: the use of random permutation of probabilistic outputs.

    PubMed

    Yang, Jian-Bo; Shen, Kai-Quan; Ong, Chong-Jin; Li, Xiao-Ping

    2009-12-01

    This paper presents a new wrapper-based feature selection method for multilayer perceptron (MLP) neural networks. It uses a feature ranking criterion to measure the importance of a feature by computing the aggregate difference, over the feature space, of the probabilistic outputs of the MLP with and without the feature. Thus, a score of importance with respect to every feature can be provided using this criterion. Based on the numerical experiments on several artificial and real-world data sets, the proposed method performs, in general, better than several selected feature selection methods for MLP, particularly when the data set is sparse or has many redundant features. In addition, as a wrapper-based approach, the computational cost for the proposed method is modest.

  2. Selective-pulse-network compilation on a liquid-state nuclear-magnetic-resonance system

    NASA Astrophysics Data System (ADS)

    Li, Jun; Cui, Jiangyu; Laflamme, Raymond; Peng, Xinhua

    2016-09-01

    In creating a large-scale quantum information processor, the ability to construct control pulses for implementing an arbitrary quantum circuit in a scalable manner is an important requirement. For liquid-state nuclear-magnetic-resonance quantum computing, a circuit is generally realized through a sequence of selective soft pulses, in which various control imperfections exist and are to be corrected. In this work, we present a comprehensive analysis of the errors arisen in a selective pulse network by using the zeroth- and first-order average Hamiltonian theory. Effective correction rules are derived for adjusting important pulse parameters such as irradiation frequencies, rotational angles, and transmission phases of the selective pulses to increase the control fidelity. Simulations show that applying our compilation procedure for a given circuit is efficient and can greatly reduce the error accumulation.

  3. Epitaxial Growth of Oriented Metalloporphyrin Network Thin Film for Improved Selectivity of Volatile Organic Compounds.

    PubMed

    Li, De-Jing; Gu, Zhi-Gang; Vohra, Ismail; Kang, Yao; Zhu, Yong-Sheng; Zhang, Jian

    2017-03-03

    This study reports an oriented and homogenous cobalt-metalloporphyrin network (PIZA-1) thin film prepared by liquid phase epitaxial (LPE) method. The thickness of the obtained thin films can be well controlled, and their photocurrent properties can also be tuned by LPE cycles or the introduction of conductive guest molecules (tetracyanoquinodimethane and C60 ) into the PIZA-1 pores. The study of quartz crystal microbalance adsorption confirms that the PIZA-1 thin film with [110]-orientation presents much higher selectivity of benzene over toluene and p-xylene than that of the PIZA-1 powder with mixed orientations. These results reveal that the selective adsorption of volatile organic compounds highly depends on the growth orientations of porphyrin-based metal-organic framework thin films. Furthermore, the work will provide a new perspective for developing important semiconductive sensing materials with improved selectivity of guest compounds.

  4. Selection and Influence Mechanisms Associated With Marijuana Initiation and Use in Adolescent Friendship Networks.

    PubMed

    de la Haye, Kayla; Green, Harold D; Kennedy, David P; Pollard, Michael S; Tucker, Joan S

    2013-09-01

    Friends are thought to influence adolescent drug use. However, few studies have examined the role of drugs in friendship selection, which is necessary to draw sound conclusions about influence. This study applied statistical models for social networks to test the contribution of selection and influence to associations in marijuana use among friends in two large high schools (N = 1,612; M age = 16.4). There was evidence for friend selection based on similar lifetime and current marijuana use at both schools, but friends were found to influence the initiation and frequency of adolescent marijuana use in just one of these schools. There was minimal evidence that peer effects were moderated by personal, school, or family risk factors.

  5. Selection and Influence Mechanisms Associated With Marijuana Initiation and Use in Adolescent Friendship Networks

    PubMed Central

    de la Haye, Kayla; Green, Harold D.; Kennedy, David P.; Pollard, Michael S.; Tucker, Joan S.

    2013-01-01

    Friends are thought to influence adolescent drug use. However, few studies have examined the role of drugs in friendship selection, which is necessary to draw sound conclusions about influence. This study applied statistical models for social networks to test the contribution of selection and influence to associations in marijuana use among friends in two large high schools (N = 1,612; M age = 16.4). There was evidence for friend selection based on similar lifetime and current marijuana use at both schools, but friends were found to influence the initiation and frequency of adolescent marijuana use in just one of these schools. There was minimal evidence that peer effects were moderated by personal, school, or family risk factors. PMID:24187477

  6. Selective β2-AR Blockage Suppresses Colorectal Cancer Growth Through Regulation of EGFR-Akt/ERK1/2 Signaling, G1-Phase Arrest, and Apoptosis.

    PubMed

    Chin, Chih-Chien; Li, Jhy-Ming; Lee, Kam-Fai; Huang, Yun-Ching; Wang, Kuan-Chieh; Lai, Hsiao-Ching; Cheng, Chih-Chung; Kuo, Yi-Hung; Shi, Chung-Sheng

    2016-02-01

    The stress-upregulated catecholamines-activated β1- and β2-adrenergic receptors (β1/2-ARs) have been shown to accelerate the progression of cancers such as colorectal cancer (CRC). We investigated the underlying mechanism of the inhibition of β1/2-ARs signaling for the treatment of CRC and elucidated the significance of β2-AR expression in CRC in vitro and in clinical samples. The impacts of β1/2-AR antagonists in CRC in vitro and CRC-xenograft in vivo were examined. We found that repression of β2-AR but not β1-AR signaling selectively suppressed cell viability, induced G1-phase cell cycle arrest, caused both intrinsic and extrinsic pathways-mediated apoptosis of specific CRC cells and inhibited CRC-xenograft growth in vivo. Moreover, the expression of β2-AR was not consistent with the progression of CRC in vitro or in clinical samples. Our data evidence that the expression profiles, signaling, and blockage of β2-AR have a unique pattern in CRC comparing to other cancers. β2-AR antagonism selectively suppresses the growth of CRC accompanying active β2-AR signaling, which potentially carries wild-type KRAS, in vitro and in vivo via the inhibition of β2-AR transactivated EFGR-Akt/ERK1/2 signaling pathway. Thus, β2-AR blockage might be a potential therapeutic strategy for combating the progressions of β2-AR-dependent CRC.

  7. A Selective Insular Perfusion Deficit Contributes to Compromised Salience Network Connectivity in Recovering Alcoholic Men

    PubMed Central

    Sullivan, Edith V.; Müller-Oehring, Eva; Pitel, Anne-Lise; Chanraud, Sandra; Shankaranarayanan, Ajit; Alsop, David C.; Rohlfing, Torsten; Pfefferbaum, Adolf

    2013-01-01

    Background Alcoholism can disrupt neural synchrony between nodes of intrinsic functional networks that are maximally active when resting relative to engaging in a task, the default mode network (DMN) pattern. Untested, however, are whether the DMN in alcoholics can rebound normally from the relatively depressed task-state to the active resting-state and whether local perfusion deficits could disrupt network synchrony when switching from conditions of rest to task to rest, thereby indicating a physiological mechanism of neural network adaptation capability. Methods Whole-brain, 3D pulsed-continuous arterial spin labeling (PCASL) provided measurements of regional cerebral blood flow (rCBF) in 12 alcoholics and 12 controls under three conditions: pre-task rest, spatial working-memory task, post-task rest. Results With practice, alcoholics and controls achieved similar task accuracy and reaction times. Both groups exhibited a high-low-high pattern of perfusion levels in DMN regions during the rest-task-rest runs and the opposite pattern in posterior and cerebellar regions known to be associated with spatial working memory. Alcoholics showed selective differences from controls in the rest-task-rest CBF pattern in the anterior precuneus and CBF level in the insula, a hub of the salience network. Connectivity analysis identified activation synchrony from an insula seed to salience nodes (parietal, medial frontal, anterior cingulate cortices) in controls only. Conclusions We propose that attenuated insular CBF is a mechanism underlying compromised connectivity among salience network nodes. This local perfusion deficit in alcoholics has the potential to impair ability to switch from cognitive states of interoceptive cravings to cognitive control for curbing internal urges. PMID:23587427

  8. Selective attention modulates high-frequency activity in the face-processing network.

    PubMed

    Müsch, Kathrin; Hamamé, Carlos M; Perrone-Bertolotti, Marcela; Minotti, Lorella; Kahane, Philippe; Engel, Andreas K; Lachaux, Jean-Philippe; Schneider, Till R

    2014-11-01

    Face processing depends on the orchestrated activity of a large-scale neuronal network. Its activity can be modulated by attention as a function of task demands. However, it remains largely unknown whether voluntary, endogenous attention and reflexive, exogenous attention to facial expressions equally affect all regions of the face-processing network, and whether such effects primarily modify the strength of the neuronal response, the latency, the duration, or the spectral characteristics. We exploited the good temporal and spatial resolution of intracranial electroencephalography (iEEG) and recorded from depth electrodes to uncover the fast dynamics of emotional face processing. We investigated frequency-specific responses and event-related potentials (ERP) in the ventral occipito-temporal cortex (VOTC), ventral temporal cortex (VTC), anterior insula, orbitofrontal cortex (OFC), and amygdala when facial expressions were task-relevant or task-irrelevant. All investigated regions of interest (ROI) were clearly modulated by task demands and exhibited stronger changes in stimulus-induced gamma band activity (50-150 Hz) when facial expressions were task-relevant. Observed latencies demonstrate that the activation is temporally coordinated across the network, rather than serially proceeding along a processing hierarchy. Early and sustained responses to task-relevant faces in VOTC and VTC corroborate their role for the core system of face processing, but they also occurred in the anterior insula. Strong attentional modulation in the OFC and amygdala (300 msec) suggests that the extended system of the face-processing network is only recruited if the task demands active face processing. Contrary to our expectation, we rarely observed differences between fearful and neutral faces. Our results demonstrate that activity in the face-processing network is susceptible to the deployment of selective attention. Moreover, we show that endogenous attention operates along the whole

  9. A lateralized functional auditory network is involved in anuran sexual selection.

    PubMed

    Xue, Fei; Fang, Guangzhan; Yue, Xizi; Zhao, Ermi; Brauth, Steven E; Tang, Yezhong

    2016-12-01

    Right ear advantage (REA) exists in many land vertebrates in which the right ear and left hemisphere preferentially process conspecific acoustic stimuli such as those related to sexual selection. Although ecological and neural mechanisms for sexual selection have been widely studied, the brain networks involved are still poorly understood. In this study we used multi-channel electroencephalographic data in combination with Granger causal connectivity analysis to demonstrate, for the first time, that auditory neural network interconnecting the left and right midbrain and forebrain function asymmetrically in the Emei music frog (Babina daunchina), an anuran species which exhibits REA. The results showed the network was lateralized. Ascending connections between the mesencephalon and telencephalon were stronger in the left side while descending ones were stronger in the right, which matched with the REA in this species and implied that inhibition from the forebrainmay induce REA partly. Connections from the telencephalon to ipsilateral mesencephalon in response to white noise were the highest in the non-reproductive stage while those to advertisement calls were the highest in reproductive stage, implying the attention resources and living strategy shift when entered the reproductive season. Finally, these connection changes were sexually dimorphic, revealing sex differences in reproductive roles.

  10. Using maximum entropy modeling for optimal selection of sampling sites for monitoring networks

    USGS Publications Warehouse

    Stohlgren, Thomas J.; Kumar, Sunil; Barnett, David T.; Evangelista, Paul H.

    2011-01-01

    Environmental monitoring programs must efficiently describe state shifts. We propose using maximum entropy modeling to select dissimilar sampling sites to capture environmental variability at low cost, and demonstrate a specific application: sample site selection for the Central Plains domain (453,490 km2) of the National Ecological Observatory Network (NEON). We relied on four environmental factors: mean annual temperature and precipitation, elevation, and vegetation type. A “sample site” was defined as a 20 km × 20 km area (equal to NEON’s airborne observation platform [AOP] footprint), within which each 1 km2 cell was evaluated for each environmental factor. After each model run, the most environmentally dissimilar site was selected from all potential sample sites. The iterative selection of eight sites captured approximately 80% of the environmental envelope of the domain, an improvement over stratified random sampling and simple random designs for sample site selection. This approach can be widely used for cost-efficient selection of survey and monitoring sites.

  11. Using Social Network Analysis to Clarify the Role of Obesity in Selection of Adolescent Friends

    PubMed Central

    Simpkins, Sandra D.

    2014-01-01

    Objectives. We used social network analysis to examine how weight status affects friend selection, with an emphasis on homophily and the social marginalization of overweight youths. Methods. We used an exponential random graph model to assess the effects of body mass index (BMI) on friend selection while controlling for several alternative selection processes. Data were derived from 58 987 students in 88 US middle and high schools who took part in the 1994 to 1996 National Longitudinal Study of Adolescent Health. Results. On average, overweight youths were less likely than nonoverweight youths to be selected as a friend; however, this effect differed according to the BMI of the person initiating the friendship. Nonoverweight youths were 30% more likely to select a nonoverweight friend than an overweight friend, whereas overweight youths were largely indifferent to the weight status of their friends. Friendship ties from overweight youths to nonoverweight peers were more likely than ties in the reverse direction. Conclusions. We found evidence consistent with homophily and social marginalization but only for the selection behavior of nonoverweight youths. We conclude that avoidance of overweight friends is the primary determinant of friendship patterns related to BMI. PMID:24832139

  12. Bayesian model selection applied to artificial neural networks used for water resources modeling

    NASA Astrophysics Data System (ADS)

    Kingston, Greer B.; Maier, Holger R.; Lambert, Martin F.

    2008-04-01

    Artificial neural networks (ANNs) have proven to be extremely valuable tools in the field of water resources engineering. However, one of the most difficult tasks in developing an ANN is determining the optimum level of complexity required to model a given problem, as there is no formal systematic model selection method. This paper presents a Bayesian model selection (BMS) method for ANNs that provides an objective approach for comparing models of varying complexity in order to select the most appropriate ANN structure. The approach uses Markov Chain Monte Carlo posterior simulations to estimate the evidence in favor of competing models and, in this study, three known methods for doing this are compared in terms of their suitability for being incorporated into the proposed BMS framework for ANNs. However, it is acknowledged that it can be particularly difficult to accurately estimate the evidence of ANN models. Therefore, the proposed BMS approach for ANNs incorporates a further check of the evidence results by inspecting the marginal posterior distributions of the hidden-to-output layer weights, which unambiguously indicate any redundancies in the hidden layer nodes. The fact that this check is available is one of the greatest advantages of the proposed approach over conventional model selection methods, which do not provide such a test and instead rely on the modeler's subjective choice of selection criterion. The advantages of a total Bayesian approach to ANN development, including training and model selection, are demonstrated on two synthetic and one real world water resources case study.

  13. Water on Mars - Analyses on fluvial activity of selected valley networks

    NASA Astrophysics Data System (ADS)

    Al-Samir, M.; Tirsch, D.; Musiol, S.; Trauthan, F.; Jaumann, R.

    2010-05-01

    Water on Mars is a precondition for a possible habitability as a requirement for the evolution of life on planet Mars. Water is also responsible for erosion, transport and is a trigger for climate and climate changes in Martian history. Therefore, a possible habitability on Mars is one of the main objectives of the HGF Alliance Program "Planetary Evolution and Life". Valley networks and outflow channels in conjunction with local climate changes on Mars are not yet sufficiently explored. Mapping of selected valley networks as global representatives is necessary to correlate controls on habitability in their chronological relationship. Within this study we are focussing on dendritic and longitudinal valley networks over time and space by using the crater-size frequency distribution (CSFD) in order to date the planetary surfaces of the valley networks most accurately on high resolution imagery from the High Resolution Stereo Camera (HRSC) on board of the ESA Mars Express Orbiter. Morphometric parameters of the channels, as measured from digital terrain models (DTM), will be used to clarify the water and sediment discharge. The correlation of this information, combined with the results of the CSFD, allow us to interpret the development and the timing of the flooding events. The resulting data set might give us clues to ancient climatic conditions and its influence on the morphology and the discharge rates of the channel systems. The calculations of the bulk fluxes of water and sediment, based on the dimensions of channels and valleys, will be the topic of our future work.

  14. Elucidation of Genetic Interactions in the Yeast GATA-Factor Network Using Bayesian Model Selection

    PubMed Central

    Milias-Argeitis, Andreas; Oliveira, Ana Paula; Gerosa, Luca; Falter, Laura; Sauer, Uwe; Lygeros, John

    2016-01-01

    Understanding the structure and function of complex gene regulatory networks using classical genetic assays is an error-prone procedure that frequently generates ambiguous outcomes. Even some of the best-characterized gene networks contain interactions whose validity is not conclusively proven. Founded on dynamic experimental data, mechanistic mathematical models are able to offer detailed insights that would otherwise require prohibitively large numbers of genetic experiments. Here we attempt mechanistic modeling of the transcriptional network formed by the four GATA-factor proteins, a well-studied system of central importance for nitrogen-source regulation of transcription in the yeast Saccharomyces cerevisiae. To resolve ambiguities in the network organization, we encoded a set of five interactions hypothesized in the literature into a set of 32 mathematical models, and employed Bayesian model selection to identify the most plausible set of interactions based on dynamic gene expression data. The top-ranking model was validated on newly generated GFP reporter dynamic data and was subsequently used to gain a better understanding of how yeast cells organize their transcriptional response to dynamic changes of nitrogen sources. Our work constitutes a necessary and important step towards obtaining a holistic view of the yeast nitrogen regulation mechanisms; on the computational side, it provides a demonstration of how powerful Monte Carlo techniques can be creatively combined and used to address the great challenges of large-scale dynamical system inference. PMID:26967983

  15. A new hyperbox selection rule and a pruning strategy for the enhanced fuzzy min-max neural network.

    PubMed

    Mohammed, Mohammed Falah; Lim, Chee Peng

    2017-02-01

    In this paper, we extend our previous work on the Enhanced Fuzzy Min-Max (EFMM) neural network by introducing a new hyperbox selection rule and a pruning strategy to reduce network complexity and improve classification performance. Specifically, a new k-nearest hyperbox expansion rule (for selection of a new winning hyperbox) is first introduced to reduce the network complexity by avoiding the creation of too many small hyperboxes within the vicinity of the winning hyperbox. A pruning strategy is then deployed to further reduce the network complexity in the presence of noisy data. The effectiveness of the proposed network is evaluated using a number of benchmark data sets. The results compare favorably with those from other related models. The findings indicate that the newly introduced hyperbox winner selection rule coupled with the pruning strategy are useful for undertaking pattern classification problems.

  16. A model selection algorithm for a posteriori probability estimation with neural networks.

    PubMed

    Arribas, Juan Ignacio; Cid-Sueiro, Jesús

    2005-07-01

    This paper proposes a novel algorithm to jointly determine the structure and the parameters of a posteriori probability model based on neural networks (NNs). It makes use of well-known ideas of pruning, splitting, and merging neural components and takes advantage of the probabilistic interpretation of these components. The algorithm, so called a posteriori probability model selection (PPMS), is applied to an NN architecture called the generalized softmax perceptron (GSP) whose outputs can be understood as probabilities although results shown can be extended to more general network architectures. Learning rules are derived from the application of the expectation-maximization algorithm to the GSP-PPMS structure. Simulation results show the advantages of the proposed algorithm with respect to other schemes.

  17. Selection of influential spreaders in complex networks using Pareto Shell decomposition

    NASA Astrophysics Data System (ADS)

    Yeruva, Sujatha; Devi, T.; Reddy, Y. Samtha

    2016-06-01

    The selection of prominent nodes in order to maximize the ability of spreading is very crucial in complex networks. The well known K-Shell method, which comprises nodes located at the core of a network, is better than the degree centrality and betweenness centrality, in capturing the spreading ability for a single origin spreader. As per the multiple origin spreaders, the K-Shell method fails to yield similar results when compared to the degree centrality. Current research proposes a Pareto-Shell Decomposition. It employs Pareto front function. It's Pareto optimal set comprises non-dominated spreads, with the ratio of high out-degree to in-degree and high in-degree. Pareto-Shell decomposition outperforms the K-Shell and the degree centrality for multiple origin spreaders, with the simulation of epidemic spreading process.

  18. A Scheme to Optimize Flow Routing and Polling Switch Selection of Software Defined Networks.

    PubMed

    Chen, Huan; Li, Lemin; Ren, Jing; Wang, Yang; Zhao, Yangming; Wang, Xiong; Wang, Sheng; Xu, Shizhong

    2015-01-01

    This paper aims at minimizing the communication cost for collecting flow information in Software Defined Networks (SDN). Since flow-based information collecting method requires too much communication cost, and switch-based method proposed recently cannot benefit from controlling flow routing, jointly optimize flow routing and polling switch selection is proposed to reduce the communication cost. To this end, joint optimization problem is formulated as an Integer Linear Programming (ILP) model firstly. Since the ILP model is intractable in large size network, we also design an optimal algorithm for the multi-rooted tree topology and an efficient heuristic algorithm for general topology. According to extensive simulations, it is found that our method can save up to 55.76% communication cost compared with the state-of-the-art switch-based scheme.

  19. A Scheme to Optimize Flow Routing and Polling Switch Selection of Software Defined Networks

    PubMed Central

    Chen, Huan; Li, Lemin; Ren, Jing; Wang, Yang; Zhao, Yangming; Wang, Xiong; Wang, Sheng; Xu, Shizhong

    2015-01-01

    This paper aims at minimizing the communication cost for collecting flow information in Software Defined Networks (SDN). Since flow-based information collecting method requires too much communication cost, and switch-based method proposed recently cannot benefit from controlling flow routing, jointly optimize flow routing and polling switch selection is proposed to reduce the communication cost. To this end, joint optimization problem is formulated as an Integer Linear Programming (ILP) model firstly. Since the ILP model is intractable in large size network, we also design an optimal algorithm for the multi-rooted tree topology and an efficient heuristic algorithm for general topology. According to extensive simulations, it is found that our method can save up to 55.76% communication cost compared with the state-of-the-art switch-based scheme. PMID:26690571

  20. Selective assembly and guiding of actomyosin using carbon nanotube network monolayer patterns.

    PubMed

    Byun, Kyung-Eun; Kim, Min-Gon; Chase, P Bryant; Hong, Seunghun

    2007-09-11

    We report a new method for the selective assembly and guiding of actomyosin using carbon nanotube patterns. In this method, monolayer patterns of the single-walled carbon nanotube (swCNT) network were prepared via the self-limiting mechanism during the directed assembly process, and they were used to block the adsorption of both myosin and actin filaments on specific substrate regions. The swCNT network patterns were also used as an efficient barrier for the guiding experiments of actomyosin. This is the first result showing that inorganic nanostructures such as carbon nanotubes can be used to control the adsorption and activity of actomyosin. This strategy is advantageous over previous methods because it does not require complicated biomolecular linking processes and nonbiological nanostructures are usually more stable than biomolecular linkers.

  1. Molecular template-directed synthesis of microporous polymer networks for highly selective CO2 capture.

    PubMed

    Shi, Yao-Qi; Zhu, Jing; Liu, Xiao-Qin; Geng, Jian-Cheng; Sun, Lin-Bing

    2014-11-26

    Porous polymer networks have great potential in various applications including carbon capture. However, complex monomers and/or expensive catalysts are commonly used for their synthesis, which makes the process complicated, costly, and hard to scale up. Herein, we develop a molecular template strategy to fabricate new porous polymer networks by a simple nucleophilic substitution reaction of two low-cost monomers (i.e., chloromethylbenzene and ethylene diamine). The polymerization reactions can take place under mild conditions in the absence of any catalysts. The resultant materials are interconnected with secondary amines and show well-defined micropores due to the structure-directing role of solvent molecules. These properties make our materials highly efficient for selective CO2 capture, and unusually high CO2/N2 and CO2/CH4 selectivities are obtained. Furthermore, the adsorbents can be completely regenerated under mild conditions. Our materials may provide promising candidates for selective capture of CO2 from mixtures such as flue gas and natural gas.

  2. Select and Cluster: A Method for Finding Functional Networks of Clustered Voxels in fMRI

    PubMed Central

    DonGiovanni, Danilo

    2016-01-01

    Extracting functional connectivity patterns among cortical regions in fMRI datasets is a challenge stimulating the development of effective data-driven or model based techniques. Here, we present a novel data-driven method for the extraction of significantly connected functional ROIs directly from the preprocessed fMRI data without relying on a priori knowledge of the expected activations. This method finds spatially compact groups of voxels which show a homogeneous pattern of significant connectivity with other regions in the brain. The method, called Select and Cluster (S&C), consists of two steps: first, a dimensionality reduction step based on a blind multiresolution pairwise correlation by which the subset of all cortical voxels with significant mutual correlation is selected and the second step in which the selected voxels are grouped into spatially compact and functionally homogeneous ROIs by means of a Support Vector Clustering (SVC) algorithm. The S&C method is described in detail. Its performance assessed on simulated and experimental fMRI data is compared to other methods commonly used in functional connectivity analyses, such as Independent Component Analysis (ICA) or clustering. S&C method simplifies the extraction of functional networks in fMRI by identifying automatically spatially compact groups of voxels (ROIs) involved in whole brain scale activation networks. PMID:27656202

  3. Leader selection problem for stochastically forced consensus networks based on matrix differentiation

    NASA Astrophysics Data System (ADS)

    Gao, Leitao; Zhao, Guangshe; Li, Guoqi; Yang, Zhaoxu

    2017-03-01

    The leader selection problem refers to determining a predefined number of agents as leaders in order to minimize the mean-square deviation from consensus in stochastically forced networks. The original leader selection problem is formulated as a non-convex optimization problem where matrix variables are involved. By relaxing the constraints, a convex optimization model can be obtained. By introducing a chain rule of matrix differentiation, we can obtain the gradient of the cost function which consists matrix variables. We develop a "revisited projected gradient method" (RPGM) and a "probabilistic projected gradient method" (PPGM) to solve the two formulated convex and non-convex optimization problems, respectively. The convergence property of both methods is established. For convex optimization model, the global optimal solution can be achieved by RPGM, while for the original non-convex optimization model, a suboptimal solution is achieved by PPGM. Simulation results ranging from the synthetic to real-life networks are provided to show the effectiveness of RPGM and PPGM. This works will deepen the understanding of leader selection problems and enable applications in various real-life distributed control problems.

  4. Capacity Analysis of Cooperative Relaying Networks with Adaptive Relaying Scheme Selection

    NASA Astrophysics Data System (ADS)

    Teshima, Kunihiko; Yamamoto, Koji; Murata, Hidekazu; Yoshida, Susumu

    In the present paper, the performance of cooperative relaying networks with adaptive relaying scheme selection is analyzed. Cooperative relaying is a new technique to achieve spatial diversity gain by using neighboring stations. However, when multiple stations transmit simultaneously, the number of interference signals increases. Therefore, the introduction of cooperative relaying in radio communication systems does not always increase the network capacity due to the co-channel interference. Therefore, in order to achieve high spectral efficiency, it is necessary to select cooperative relaying or non-cooperative relaying adaptively. Assuming both centralized and decentralized adaptive controls, the spectrum efficiency is evaluated. The performance under decentralized control is evaluated using a game-theoretic approach. Simulation results show that the introduction of cooperative relaying with centralized control always increases the spectral efficiency. On the other hand, Simulation results also show that, when each source selects a relaying scheme independently and selfishly to maximize its own spectral efficiency, the introduction of the cooperative relaying may reduce the spectral efficiency due to the increase in the number of interference signals.

  5. Selecting Local Area Networks and CD-ROM/Computer Workstations for the High School Library: An Update.

    ERIC Educational Resources Information Center

    Behn, John; Kirsch, Robert

    1992-01-01

    Provides guidelines for selection of a local area network for a high school library and discusses network and equipment costs and computer requirements, including recommendations regarding monitors, printers, compact disk players, mouse devices, and computer architecture. A second article reviews new technology exhibited at a recent computer…

  6. A Study for the Feature Selection to Identify GIEMSA-Stained Human Chromosomes Based on Artificial Neural Network

    DTIC Science & Technology

    2007-11-02

    neural network (ANN) has been adopted for the human chromosome classification. It is important to select optimum features for training neural network...Many studies for computer-based chromosome analysis have shown that it is possible to classify chromosomes into 24 subgroups. In addition, artificial

  7. Effects on Learners' Performance of Using Selected and Open Network Resources in a Problem-Based Learning Activity

    ERIC Educational Resources Information Center

    Hsu, Ching-Kun; Hwang, Gwo-Jen; Chuang, Chien-Wen; Chang, Chih-Kai

    2012-01-01

    Owing to the popularity of computers and computer networks, fostering the web-based problem-solving ability of students has become an important educational objective in recent years. This study attempted to compare the effects of using selected and open network resources on students' intentions with regard to their information system usage by…

  8. Effects on Learners' Performance of Using Selected and Open Network Resources in a Problem-Based Learning Activity

    ERIC Educational Resources Information Center

    Hsu, Ching-Kun; Hwang, Gwo-Jen; Chuang, Chien-Wen; Chang, Chih-Kai

    2012-01-01

    Owing to the popularity of computers and computer networks, fostering the web-based problem-solving ability of students has become an important educational objective in recent years. This study attempted to compare the effects of using selected and open network resources on students' intentions with regard to their information system usage by…

  9. IL-32-induced Inflammatory Cytokines Are Selectively Suppressed by α1-antitrypsin in Mouse Bone Marrow Cells.

    PubMed

    Lee, Siyoung; Choi, Dong-Ki; Kwak, Areum; Kim, Sinae; Nguyen, Tam Thanh; Gil, Gaae; Kim, Eunhye; Yoo, Kwang Ha; Kim, In Ae; Lee, Youngmin; Jhun, Hyunjhung; Chan, Edward D; Bai, Xiyuan; Kim, Hyunwoo; Kim, Yong-Sung; Kim, Soohyun

    2017-04-01

    The induction of interleukin (IL)-32 in bone marrow (BM) inflammation is crucial in graft versus host disease (GvHD) that is a common side effect of allogeneic BM transplantation. Clinical trials on α-1 antitrypsin (AAT) in patients with GvHD are based on the preliminary human and mouse studies on AAT reducing the severity of GvHD. Proteinase 3 (PR3) is an IL-32-binding protein that was isolated from human urine. IL-32 primarily induces inflammatory cytokines in myeloid cells, probably due to PR3 expression on the membrane of the myeloid lineage cells. The inhibitory activity of AAT on serine proteinases may explain the anti-inflammatory effect of AAT on GvHD. However, the anti-inflammatory activity of AAT on BM cells remains unclear. Mouse BM cells were treated with IL-32γ and different inflammatory stimuli to investigate the anti-inflammatory activity of AAT. Recombinant AAT-Fc fusion protein inhibited IL-32γ-induced IL-6 expression in BM cells, but failed to suppress that induced by other stimuli. In addition, the binding of IL-32γ to PR3 was abrogated by AAT-Fc. The data suggest that the specific anti-inflammatory effect of AAT in mouse BM cells is due to the blocking of IL-32 binding to membrane PR3.

  10. Selective suppression of cocaine- versus food-maintained responding by monoamine releasers in rhesus monkeys: benzylpiperazine, (+)phenmetrazine, and 4-benzylpiperidine.

    PubMed

    Negus, S S; Baumann, M H; Rothman, R B; Mello, N K; Blough, B E

    2009-04-01

    Monoamine releasers constitute one class of drugs currently under investigation as potential agonist medications for the treatment of cocaine dependence. The efficacy and safety of monoamine releasers as candidate medications may be influenced in part by their relative potency to release dopamine and serotonin, and we reported previously that releasers with approximately 30-fold selectivity for dopamine versus serotonin release may be especially promising. The present study examined the effects of the releasers benzylpiperazine, (+)phenmetrazine, and 4-benzylpiperidine, which have 20- to 48-fold selectivity in vitro for releasing dopamine versus serotonin. In an assay of cocaine discrimination, rhesus monkeys were trained to discriminate 0.4 mg/kg i.m. cocaine from saline in a two-key, food-reinforced procedure. Each of the releasers produced a dose- and time-dependent substitution for cocaine. 4-Benzylpiperidine had the most rapid onset and shortest duration of action. Phenmetrazine and benzylpiperazine had slower onsets and longer durations of action. In an assay of cocaine self-administration, rhesus monkeys were trained to respond for cocaine injections and food pellets under a second order schedule. Treatment for 7 days with each of the releasers produced a dose-dependent and selective reduction in self-administration of cocaine (0.01 mg/kg/injection). The most selective effects were produced by phenmetrazine. Phenmetrazine also produced a downward shift in the cocaine self-administration dose effect curve, virtually eliminating responding maintained by a 30-fold range of cocaine doses (0.0032-0.1 mg/kg/injection) while having only small and transient effects on food-maintained responding. These findings support the potential utility of dopamine-selective releasers as candidate treatments for cocaine dependence.

  11. Neural network cascade optimizes microRNA biomarker selection for nasopharyngeal cancer prognosis.

    PubMed

    Zhu, Wenliang; Kan, Xuan

    2014-01-01

    MicroRNAs (miRNAs) have been shown to be promising biomarkers in predicting cancer prognosis. However, inappropriate or poorly optimized processing and modeling of miRNA expression data can negatively affect prediction performance. Here, we propose a holistic solution for miRNA biomarker selection and prediction model building. This work introduces the use of a neural network cascade, a cascaded constitution of small artificial neural network units, for evaluating miRNA expression and patient outcome. A miRNA microarray dataset of nasopharyngeal carcinoma was retrieved from Gene Expression Omnibus to illustrate the methodology. Results indicated a nonlinear relationship between miRNA expression and patient death risk, implying that direct comparison of expression values is inappropriate. However, this method performs transformation of miRNA expression values into a miRNA score, which linearly measures death risk. Spearman correlation was calculated between miRNA scores and survival status for each miRNA. Finally, a nine-miRNA signature was optimized to predict death risk after nasopharyngeal carcinoma by establishing a neural network cascade consisting of 13 artificial neural network units. Area under the ROC was 0.951 for the internal validation set and had a prediction accuracy of 83% for the external validation set. In particular, the established neural network cascade was found to have strong immunity against noise interference that disturbs miRNA expression values. This study provides an efficient and easy-to-use method that aims to maximize clinical application of miRNAs in prognostic risk assessment of patients with cancer.

  12. Cognitive Science Program. Hierarchical Distributed Networks in the Neuropsychology of Selective Attention.

    DTIC Science & Technology

    2014-09-26

    ID-fi57 540 COGNITIVE SCIENCE PROGRAM HIERARCHICAL DISTRIBUTED I/i NETWORKS IN THE NEUROP..(U) OREGON UNIV EUGENE DEPT OF PSYCHOLOGY M I POSNER 15...NEUROPSYCIIOLOGY OF SELECTIVE ATTENTION by Michael f. Posner Technical Report 85-1 University of Oregon JULI 7 ?9 Research Sponsored by: i-- L.n Personnel...WORK UNIT NUMBERS Department of Psychology University of Oregon NR 667-523 II. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE May 15, 1985 1I

  13. Neural network models for spatial data mining, map production, and cortical direction selectivity

    NASA Astrophysics Data System (ADS)

    Parsons, Olga

    A family of ARTMAP neural networks for incremental supervised learning has been developed over the last decade. The Sensor Exploitation Group of MIT Lincoln Laboratory (LL) has incorporated an early version of this network as the recognition engine of a hierarchical system for fusion and data mining of multiple registered geospatial images. The LL system has been successfully fielded, but it is limited to target vs. non-target identifications and does not produce whole maps. This dissertation expands the capabilities of the LL system so that it learns to identify arbitrarily many target classes at once and can thus produce a whole map. This new spatial data mining system is designed particularly to cope with the highly skewed class distributions of typical mapping problems. Specification of a consistent procedure and a benchmark testbed has permitted the evaluation of candidate recognition networks as well as pre- and post-processing and feature extraction options. The resulting default ARTMAP network and mapping methodology set a standard for a variety of related mapping problems and application domains. The second part of the dissertation investigates the development of cortical direction selectivity. The possible role of visual experience and oculomotor behavior in the maturation of cells in the primary visual cortex is studied. The responses of neurons in the thalamus and cortex of the cat are modeled when natural scenes are scanned by several types of eye movements. Inspired by the Hebbian-like synaptic plasticity, which is based upon correlations between cell activations, the second-order statistical structure of thalamo-cortical activity is examined. In the simulations, patterns of neural activity that lead to a correct refinement of cell responses are observed during visual fixation, when small ocular movements occur, but are not observed in the presence of large saccades. Simulations also replicate experiments in which kittens are reared under stroboscopic

  14. Wavelength-selective 4 × 4 nonblocking silicon optical router for networks-on-chip.

    PubMed

    Hu, Ting; Qiu, Huiye; Yu, Ping; Qiu, Chen; Wang, Wanjun; Jiang, Xiaoqing; Yang, Mei; Yang, Jianyi

    2011-12-01

    We design and fabricate a wavelength-selective nonblocking 4 × 4 silicon optical router based on microring resonator for use in future integrated photonic interconnection networks. We successfully demonstrate 12 possible I/O routing paths and present 13 nonblocking operating states, including four broadcasting states, with worst-case extinction ratio and cross talk of 21.05 and -21.56 dB, respectively. Thermal tuning is employed to compensate the resonance shift of microring resonators caused by fabrication errors and adjust the resonance to match the International Telecommunication Unit grid with the channel spacing of 100 GHz. © 2011 Optical Society of America

  15. Your Health Buddies Matter: Preferential Selection and Social Influence on Weight Management in an Online Health Social Network.

    PubMed

    Meng, Jingbo

    2016-12-01

    A growing number of online social networks are designed with the intention to promote health by providing virtual space wherein individuals can seek and share information and support with similar others. Research has shown that real-world social networks have a significant influence on one's health behavior and outcomes. However, there is a dearth of studies on how individuals form social networks in virtual space and whether such online social networks exert any impact on individuals' health outcomes. Built on the Multi-Theoretical Multilevel (MTML) framework and drawing from literature on social influence, this study examined the mechanisms underlying the formation of an online health social network and empirically tested social influence on individual health outcomes through the network. Situated in a weight management social networking site, the study tracked a health buddy network of 709 users and their weight management activities and outcomes for 4 months. Actor-based modeling was used to test the joint dynamics of preferential selection and social influence among health buddies. The results showed that baseline, inbreeding, and health status homophily significantly predicted preferential selection of health buddies in the weight management social networking site, whereas self-interest in seeking experiential health information did not. The study also found peer influence of online health buddy networks on individual weight outcomes, such that an individual's odds of losing weight increased if, on average, the individual's health buddies were losing weight.

  16. Interleukin-10-induced gene expression and suppressive function are selectively modulated by the PI3K-Akt-GSK3 pathway

    PubMed Central

    Antoniv, Taras T; Ivashkiv, Lionel B

    2011-01-01

    Interleukin-10 (IL-10) is an immunosuppressive cytokine that inhibits inflammatory gene expression. Phosphatidylinositol 3-kinase (PI3K) -mediated signalling regulates inflammatory responses and can induce IL-10 production, but a role for PI3K signalling in cellular responses to IL-10 is not known. In this study we investigated the involvement of the PI3K-Akt-GSK3 signalling pathway in IL-10-induced gene expression and IL-10-mediated suppression of Toll-like receptor-induced gene expression in primary human macrophages. A combination of loss and gain of function approaches using kinase inhibitors, expression of constitutively active Akt, and RNA interference in primary human macrophages showed that expression of a subset of IL-10-inducible genes was dependent on PI3K-Akt signalling. The effects of PI3K-Akt signalling on IL-10 responses were mediated at least in part by glycogen synthase kinase 3 (GSK3). In accordance with a functional role for PI3K pathways in contributing to the suppressive actions of IL-10, PI3K signalling augmented IL-10-mediated inhibition of lipopolysaccharide-induced IL-1, IL-8 and cyclo-oxygenase-2 expression. The PI3K signalling selectively modulated IL-10 responses, as it was not required for inhibition of tumour necrosis factor expression or for induction of certain IL-10-inducible genes such as SOCS3. These findings identify a new mechanism by which PI3K-mediated signalling can suppress inflammation by regulating IL-10-mediated gene induction and anti-inflammatory function. PMID:21255011

  17. Lung tumorigenesis suppressing effects of a commercial kava extract and its selected compounds in A/J mice.

    PubMed

    Johnson, Thomas E; Hermanson, David; Wang, Lei; Kassie, Fekadu; Upadhyaya, Pramod; O'Sullivan, Michael G; Hecht, Stephen S; Lu, Junxuan; Xing, Chengguo

    2011-01-01

    Lung cancer is the most deadly malignancy in the US. Chemoprevention is potentially a complementary approach to smoking cessation for lung cancer control. Recently, we reported that a commercially available form of kava extract significantly inhibits 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and benzo(a)pyrene (BaP)-induced lung tumorigenesis in A/J mice at a dose of 10 mg per gram diet. In the present study, we examined the dose-dependent lung tumor inhibitory activities of kava and investigated potential active constituent(s). Mice treated with carcinogen alone contained 12.1±5.8 lung adenomas per mouse 22 weeks after final carcinogen administration. Mice that were fed diets containing kava at dosages of 1.25, 2.5, 5, and 10 mg/g of diet had 8.4±3.5, 6.6±3.5, 4.3±2.4, and 3.8±2.3 lung adenomas per mouse, respectively. This corresponds to a reduction of 31%, 46%, 65% and 69% in tumor multiplicity, which were all statistically significant (p < 0.05). Analyses of lung adenoma tissues derived from kava-treated animals revealed that kava significantly inhibited adenoma cell proliferation while it had no detectable effect on cell death, indicating that kava primarily suppressed lung tumorigenesis in A/J mice via inhibition of cell proliferation. Flavokawains A, B, and C, three chalcone-based components from kava, demonstrated greatly reduced chemopreventive efficacies even at concentrations much higher than their natural abundance, suggesting that they alone were unlikely to be responsible for kava's chemopreventive activity. Kava at all dosages and treatment regimens did not induce detectable adverse effects, particularly with respect to liver. Specifically, kava treatment showed no effect on liver integrity indicator enzymes or liver weight, indicating that kava may be potentially safe for long-term chemopreventive application.

  18. Selection of dinB Alleles Suppressing Survival Loss upon dinB Overexpression in Escherichia coli

    PubMed Central

    Benson, Ryan W.; Cafarelli, Tiziana M.; Rands, Thomas J.; Lin, Ida

    2014-01-01

    Escherichia coli strains overproducing DinB undergo survival loss; however, the mechanisms regulating this phenotype are poorly understood. Here we report a genetic selection revealing DinB residues essential to effect this loss-of-survival phenotype. The selection uses strains carrying both an antimutator allele of DNA polymerase III (Pol III) α-subunit (dnaE915) and either chromosomal or plasmid-borne dinB alleles. We hypothesized that dnaE915 cells would respond to DinB overproduction differently from dnaE+ cells because the dnaE915 allele is known to have an altered genetic interaction with dinB+ compared to its interaction with dnaE+. Notably, we observe a loss-of-survival phenotype in dnaE915 strains with either a chromosomal catalytically inactive dinB(D103N) allele or a low-copy-number plasmid-borne dinB+ upon DNA damage treatment. Furthermore, we find that the loss-of-survival phenotype occurs independently of DNA damage treatment in a dnaE915 strain expressing the catalytically inactive dinB(D103N) allele from a low-copy-number plasmid. The selective pressure imposed resulted in suppressor mutations that eliminated growth defects. The dinB intragenic mutations examined were either base pair substitutions or those that we inferred to be loss of function (i.e., deletions and insertions). Further analyses of selected novel dinB alleles, generated by single-base-pair substitutions in the dnaE915 strain, indicated that these no longer effect loss of survival upon overproduction in dnaE+ strains. These mutations are mapped to specific areas of DinB; this permits us to gain insights into the mechanisms underlying the DinB-mediated overproduction loss-of-survival phenotype. PMID:24914188

  19. Selective suppression of two-photon fluorescence in laser scanning microscopy by ultrafast pulse-train excitation.

    PubMed

    De, Arijit Kumar; Roy, Debjit; Goswami, Debabrata

    2010-01-01

    Selective excitation of a particular fluorophore in the presence of others demands clever design of the optical field interacting with the molecules. We describe the use of 20- to 50-GHz pulse-train excitation leading to two-photon absorption, followed by successive one-photon stimulated emission as a potential technique in the context of controlling two-photon molecular fluorescence, with applications in microscopy.

  20. Suppressing the Skin-Core Structure of Injection-Molded Isotactic Polypropylene via Combination of an in situ Microfibrillar Network and an Interfacial Compatibilizer

    SciTech Connect

    X Yi; C Chen; G Zhong; L Xu; J Tang; X Ji; B Hsiao; Z Li

    2011-12-31

    Injection-molded semicrystalline polymer parts generally exhibited a so-called skin-core structure basically as a result of the large gradients of temperature, shear rate, stress, and pressure fields created by the boundary conditions of injection molding. Suppression of the skin-core structure is a long-term practical challenge. In the current work, the skin-core structure of the conventional injection-molded isotactic polypropylene (iPP) was largely relieved by the cooperative effects of an in situ microfibrillar network and interfacial compatibilizer. The in situ poly(ethylene terephthalate) microfibrils of 1-8 {micro}m in diameter and large aspect ratios of above 40 tended to entangle with each other to generate a microfibrillar network in the iPP melt. During injection molding, the iPP molecules experienced confined flow in the microchannels or pores formed by the microfibrillar network, which could redistribute and homogenize the flow field of polymer melt. Addition of the compatibilizer, glycidyl methacrylate-grafted iPP, restrained the molecular orientation but facilitated preservation of oriented molecules due to the chemical bonds at the interface between PET microfibrils and iPP. The cooperative effects of in situ microfibrillar network and interfacial compatibilizer led to almost the same molecular orientation across the whole thickness of the injection-molded parts. Additionally, the content of {beta} crystals in different layers of injection-molded iPP parts depended on the combined effects of the molecular orientation, the amount of oriented crystals, and the crystallization time between 105 and 140 C. The presence of the interfacial compatibilizer facilitated formation of the {beta} crystals because of preservation of the oriented molecules.

  1. Microglia protect against brain injury and their selective elimination dysregulates neuronal network activity after stroke

    PubMed Central

    Szalay, Gergely; Martinecz, Bernadett; Lénárt, Nikolett; Környei, Zsuzsanna; Orsolits, Barbara; Judák, Linda; Császár, Eszter; Fekete, Rebeka; West, Brian L.; Katona, Gergely; Rózsa, Balázs; Dénes, Ádám

    2016-01-01

    Microglia are the main immune cells of the brain and contribute to common brain diseases. However, it is unclear how microglia influence neuronal activity and survival in the injured brain in vivo. Here we develop a precisely controlled model of brain injury induced by cerebral ischaemia combined with fast in vivo two-photon calcium imaging and selective microglial manipulation. We show that selective elimination of microglia leads to a striking, 60% increase in infarct size, which is reversed by microglial repopulation. Microglia-mediated protection includes reduction of excitotoxic injury, since an absence of microglia leads to dysregulated neuronal calcium responses, calcium overload and increased neuronal death. Furthermore, the incidence of spreading depolarization (SD) is markedly reduced in the absence of microglia. Thus, microglia are involved in changes in neuronal network activity and SD after brain injury in vivo that could have important implications for common brain diseases. PMID:27139776

  2. Joint Transmit Antenna Selection and Power Allocation for ISDF Relaying Mobile-to-Mobile Sensor Networks

    PubMed Central

    Xu, Lingwei; Zhang, Hao; Gulliver, T. Aaron

    2016-01-01

    The outage probability (OP) performance of multiple-relay incremental-selective decode-and-forward (ISDF) relaying mobile-to-mobile (M2M) sensor networks with transmit antenna selection (TAS) over N-Nakagami fading channels is investigated. Exact closed-form OP expressions for both optimal and suboptimal TAS schemes are derived. The power allocation problem is formulated to determine the optimal division of transmit power between the broadcast and relay phases. The OP performance under different conditions is evaluated via numerical simulation to verify the analysis. These results show that the optimal TAS scheme has better OP performance than the suboptimal scheme. Further, the power allocation parameter has a significant influence on the OP performance. PMID:26907282

  3. A Multi-Step Assessment Scheme for Seismic Network Site Selection in Densely Populated Areas

    NASA Astrophysics Data System (ADS)

    Plenkers, Katrin; Husen, Stephan; Kraft, Toni

    2015-10-01

    We developed a multi-step assessment scheme for improved site selection during seismic network installation in densely populated areas. Site selection is a complex process where different aspects (seismic background noise, geology, and financing) have to be taken into account. In order to improve this process, we developed a step-wise approach that allows quantifying the quality of a site by using, in addition to expert judgement and test measurements, two weighting functions as well as reference stations. Our approach ensures that the recording quality aimed for is reached and makes different sites quantitatively comparable to each other. Last but not least, it is an easy way to document the decision process, because all relevant parameters are listed, quantified, and weighted.

  4. A Comparison of Techniques for Camera Selection and Hand-Off in a Video Network

    NASA Astrophysics Data System (ADS)

    Li, Yiming; Bhanu, Bir

    Video networks are becoming increasingly important for solving many real-world problems. Multiple video sensors require collaboration when performing various tasks. One of the most basic tasks is the tracking of objects, which requires mechanisms to select a camera for a certain object and hand-off this object from one camera to another so as to accomplish seamless tracking. In this chapter, we provide a comprehensive comparison of current and emerging camera selection and hand-off techniques. We consider geometry-, statistics-, and game theory-based approaches and provide both theoretical and experimental comparison using centralized and distributed computational models. We provide simulation and experimental results using real data for various scenarios of a large number of cameras and objects for in-depth understanding of strengths and weaknesses of these techniques.

  5. Artificial neural network approach to assess selective flocculation on hematite and kaolinite

    NASA Astrophysics Data System (ADS)

    Panda, Lopamudra; Banerjee, P. K.; Biswal, Surendra Kumar; Venugopal, R.; Mandre, N. R.

    2014-07-01

    Because of the current depletion of high grade reserves, beneficiation of low grade ore, tailings produced and tailings stored in tailing ponds is needed to fulfill the market demand. Selective flocculation is one alternative process that could be used for the beneficiation of ultra-fine material. This process has not been extensively used commercially because of its complex dependency on process parameters. In this paper, a selective flocculation process, using synthetic mixtures of hematite and kaolinite in different ratios, was attempted, and the adsorption mechanism was investigated by Fourier transform infrared (FTIR) spectroscopy. A three-layer artificial neural network (ANN) model (4-4-3) was used to predict the separation performance of the process in terms of grade, Fe recovery, and separation efficiency. The model values were in good agreement with experimental values.

  6. Integrative network analysis of nineteen brain regions identifies molecular signatures and networks underlying selective regional vulnerability to Alzheimer's disease.

    PubMed

    Wang, Minghui; Roussos, Panos; McKenzie, Andrew; Zhou, Xianxiao; Kajiwara, Yuji; Brennand, Kristen J; De Luca, Gabriele C; Crary, John F; Casaccia, Patrizia; Buxbaum, Joseph D; Ehrlich, Michelle; Gandy, Sam; Goate, Alison; Katsel, Pavel; Schadt, Eric; Haroutunian, Vahram; Zhang, Bin

    2016-11-01

    sites associated with the greatest and earliest gene expression abnormalities. This transcriptomic network analysis of 19 brain regions provides a comprehensive assessment of the critical molecular pathways associated with AD pathology and offers new insights into molecular mechanisms underlying selective regional vulnerability to AD at different stages of the progression of cognitive compromise and development of the canonical neuropathological lesions of AD.

  7. SacB-SacR Gene Cassette As the Negative Selection Marker to Suppress Agrobacterium Overgrowth in Agrobacterium-Mediated Plant Transformation.

    PubMed

    Liu, Yiming; Miao, Jiamin; Traore, Sy; Kong, Danyu; Liu, Yi; Zhang, Xunzhong; Nimchuk, Zachary L; Liu, Zongrang; Zhao, Bingyu

    2016-01-01

    Agrobacterium overgrowth is a common problem in Agrobacterium-mediated plant transformation. To suppress the Agrobacterium overgrowth, various antibiotics have been used during plant tissue culture steps. The antibiotics are expensive and may adversely affect plant cell differentiation and reduce plant transformation efficiency. The SacB-SacR proteins are toxic to most Agrobacterium tumefaciens strains when they are grown on culture medium supplemented with sucrose. Therefore, SacB-SacR genes can be used as negative selection markers to suppress the overgrowth of A. tumefaciens in the plant tissue culture process. We generated a mutant A. tumefaciens strain GV2260 (recA-SacB/R) that has the SacB-SacR cassette inserted into the bacterial genome at the recA gene locus. The mutant Agrobacterium strain is sensitive to sucrose but maintains its ability to transform plant cells in both transient and stable transformation assays. We demonstrated that the mutant strain GV2260 (recA-SacB/R) can be inhibited by sucrose that reduces the overgrowth of Agrobacterium and therefore improves the plant transformation efficiency. We employed GV2260 (recA-SacB/R) to generate stable transgenic N. benthamiana plants expressing a CRISPR-Cas9 for knocking out a WRKY transcription factor.

  8. Triple negative breast cancer development can be selectively suppressed by sustaining an elevated level of cellular cyclic AMP through simultaneously blocking its efflux and decomposition.

    PubMed

    Wang, Wei; Li, Yue; Zhu, Jessica Y; Fang, Dongdong; Ding, Han-Fei; Dong, Zheng; Jing, Qing; Su, Shi-Bing; Huang, Shuang

    2016-12-27

    Triple negative breast cancer (TNBC) has the highest mortality among all breast cancer types and lack of targeted therapy is a key factor contributing to its high mortality rate. In this study, we show that 8-bromo-cAMP, a cyclic adenosine monophosphate (cAMP) analog at high concentration (> 1 mM) selectively suppresses TNBC cell growth. However, commonly-used cAMP-elevating agents such as adenylyl cyclase activator forskolin and pan phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) are ineffective. Inability of cAMP elevating agents to inhibit TNBC cell growth is due to rapid diminution of cellular cAMP through efflux and decomposition. By performing bioinformatics analyses with publically available gene expression datasets from breast cancer patients/established breast cancer cell lines and further validating using specific inhibitors/siRNAs, we reveal that multidrug resistance-associated protein 1/4 (MRP1/4) mediate rapid cAMP efflux while members PDE4 subfamily facilitate cAMP decomposition. When cAMP clearance is prevented by specific inhibitors, forskolin blocks TNBC's in vitro cell growth by arresting cell cycle at G1/S phase. Importantly, cocktail of forskolin, MRP inhibitor probenecid and PDE4 inhibitor rolipram suppresses TNBC in vivo tumor development. This study suggests that a TNBC-targeted therapeutic strategy can be developed by sustaining an elevated level of cAMP through simultaneously blocking its efflux and decomposition.

  9. Triple negative breast cancer development can be selectively suppressed by sustaining an elevated level of cellular cyclic AMP through simultaneously blocking its efflux and decomposition

    PubMed Central

    Wang, Wei; Li, Yue; Zhu, Jessica Y.; Fang, Dongdong; Ding, Han-Fei; Dong, Zheng; Jing, Qing; Su, Shi-Bing; Huang, Shuang

    2016-01-01

    Triple negative breast cancer (TNBC) has the highest mortality among all breast cancer types and lack of targeted therapy is a key factor contributing to its high mortality rate. In this study, we show that 8-bromo-cAMP, a cyclic adenosine monophosphate (cAMP) analog at high concentration (> 1 mM) selectively suppresses TNBC cell growth. However, commonly-used cAMP-elevating agents such as adenylyl cyclase activator forskolin and pan phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) are ineffective. Inability of cAMP elevating agents to inhibit TNBC cell growth is due to rapid diminution of cellular cAMP through efflux and decomposition. By performing bioinformatics analyses with publically available gene expression datasets from breast cancer patients/established breast cancer cell lines and further validating using specific inhibitors/siRNAs, we reveal that multidrug resistance-associated protein 1/4 (MRP1/4) mediate rapid cAMP efflux while members PDE4 subfamily facilitate cAMP decomposition. When cAMP clearance is prevented by specific inhibitors, forskolin blocks TNBC's in vitro cell growth by arresting cell cycle at G1/S phase. Importantly, cocktail of forskolin, MRP inhibitor probenecid and PDE4 inhibitor rolipram suppresses TNBC in vivo tumor development. This study suggests that a TNBC-targeted therapeutic strategy can be developed by sustaining an elevated level of cAMP through simultaneously blocking its efflux and decomposition. PMID:27901486

  10. SacB-SacR Gene Cassette As the Negative Selection Marker to Suppress Agrobacterium Overgrowth in Agrobacterium-Mediated Plant Transformation

    PubMed Central

    Liu, Yiming; Miao, Jiamin; Traore, Sy; Kong, Danyu; Liu, Yi; Zhang, Xunzhong; Nimchuk, Zachary L.; Liu, Zongrang; Zhao, Bingyu

    2016-01-01

    Agrobacterium overgrowth is a common problem in Agrobacterium-mediated plant transformation. To suppress the Agrobacterium overgrowth, various antibiotics have been used during plant tissue culture steps. The antibiotics are expensive and may adversely affect plant cell differentiation and reduce plant transformation efficiency. The SacB-SacR proteins are toxic to most Agrobacterium tumefaciens strains when they are grown on culture medium supplemented with sucrose. Therefore, SacB-SacR genes can be used as negative selection markers to suppress the overgrowth of A. tumefaciens in the plant tissue culture process. We generated a mutant A. tumefaciens strain GV2260 (recA-SacB/R) that has the SacB-SacR cassette inserted into the bacterial genome at the recA gene locus. The mutant Agrobacterium strain is sensitive to sucrose but maintains its ability to transform plant cells in both transient and stable transformation assays. We demonstrated that the mutant strain GV2260 (recA-SacB/R) can be inhibited by sucrose that reduces the overgrowth of Agrobacterium and therefore improves the plant transformation efficiency. We employed GV2260 (recA-SacB/R) to generate stable transgenic N. benthamiana plants expressing a CRISPR-Cas9 for knocking out a WRKY transcription factor. PMID:27833912

  11. Selective class I histone deacetylase inhibitors suppress persistent spontaneous nociception and thermal hypersensitivity in a rat model of bee venom-induced inflammatory pain.

    PubMed

    Yang, Fan; Yang, Yan; Wang, Yan; Yang, Fei; Li, Chun-Li; Wang, Xiao-Liang; Li, Zhen; Chen, Jun

    2015-10-25

    To confirm whether class I histone deacetylase inhibitors (HDACIs) are effective in relief of peripheral inflammatory pain, the effects of two selective inhibitors, MS-275 and MGCD0103, were studied in rats inflamed by subcutaneous (s.c.) injection of bee venom (BV). The BV test is characterized by displaying both persistent spontaneous nociception (PSN) and primary hypersensitivity. Intrathecal (i.t.) pre-treatment of either MS-275 or MGCD0103 with a single dose of 60 nmol/20 μL resulted in profound suppression of both PSN and primary thermal hypersensitivity but without significant influence upon the primary mechanical hypersensitivity and mirror-image thermal hypersensitivity. Moreover, the up-regulation of both HDAC1 and HDAC2 induced by s.c. BV injection was completely suppressed by i.t. pre-treatment of MS-275. The present results provide with another new line of evidence showing involvement of epigenetic regulation of chromatin structure by HDAC1/2-mediated histone hypoacetylation in the BV-induced PSN and thermal hypersensitivity and demonstrate the beneficial effects of class I HDACIs in prevention of peripheral inflammatory pain from occurring.

  12. Suppression of acetylpolyamine oxidase by selected AP-1 members regulates DNp73 abundance: mechanistic insights for overcoming DNp73-mediated resistance to chemotherapeutic drugs

    PubMed Central

    Bunjobpol, W; Dulloo, I; Igarashi, K; Concin, N; Matsuo, K; Sabapathy, K

    2014-01-01

    Enhanced resistance to chemotherapy has been correlated with high levels of Delta-Np73 (DNp73), an anti-apoptotic protein of the p53 tumor-suppressor family which inhibits the pro-apoptotic members such as p53 and TAp73. Although genotoxic drugs have been shown to induce DNp73 degradation, lack of mechanistic understanding of this process precludes strategies to enhance the targeting of DNp73 and improve treatment outcomes. Antizyme (Az) is a mediator of ubiquitin-independent protein degradation regulated by the polyamine biosynthesis pathway. We show here that acetylpolyamine oxidase (PAOX), a catabolic enzyme of this pathway, upregulates DNp73 levels by suppressing its degradation via the Az pathway. Conversely, downregulation of PAOX activity by siRNA-mediated knockdown or chemical inhibition leads to DNp73 degradation in an Az-dependent manner. PAOX expression is suppressed by several genotoxic drugs, via selected members of the activator protein-1 (AP-1) transcription factors, namely c-Jun, JunB and FosB, which are required for stress-mediated DNp73 degradation. Finally, chemical- and siRNA-mediated inhibition of PAOX significantly reversed the resistant phenotype of DNp73-overexpressing cancer cells to genotoxic drugs. Together, these data define a critical mechanism for the regulation of DNp73 abundance, and reveal that inhibition of PAOX could widen the therapeutic index of cytotoxic drugs and overcome DNp73-mediated chemoresistance in tumors. PMID:24722210

  13. Evolutionary dynamics of continuous strategy games on graphs and social networks under weak selection.

    PubMed

    Zhong, Weicai; Liu, Jing; Zhang, Li

    2013-02-01

    Understanding the emergence of cooperation among selfish individuals has been a long-standing puzzle, which has been studied by a variety of game models. Most previous studies presumed that interactions between individuals are discrete, but it seems unrealistic in real systems. Recently, there are increasing interests in studying game models with a continuous strategy space. Existing research work on continuous strategy games mainly focuses on well-mixed populations. Especially, little theoretical work has been conducted on their evolutionary dynamics in a structured population. In the previous work (Zhong et al., BioSystems, 2012), we showed that under strong selection, continuous and discrete strategies have significantly different equilibrium and game dynamics in spatially structured populations. In this paper, we further study evolutionary dynamics of continuous strategy games under weak selection in structured populations. By using the fixation probability based stochastic dynamics, we derive exact conditions of natural selection favoring cooperation for the death-birth updating scheme. We also present a network gain decomposition of the game equilibrium, which might provide a new view of the network reciprocity in a quantitative way. Finally, we make a detailed comparison between games using discrete and continuous strategies. As compared to the former, we find that for the latter (i) the same selection conditions are derived for the general 2×2 game; especially, the rule b/c>k in a simplified Prisoner's Dilemma is valid as well; however, (ii) for a coordination game, interestingly, the risk-dominant strategy is disfavored. Numerical simulations have also been conducted to validate our results.

  14. Parameter Selection and Performance Comparison of Particle Swarm Optimization in Sensor Networks Localization.

    PubMed

    Cui, Huanqing; Shu, Minglei; Song, Min; Wang, Yinglong

    2017-03-01

    Localization is a key technology in wireless sensor networks. Faced with the challenges of the sensors' memory, computational constraints, and limited energy, particle swarm optimization has been widely applied in the localization of wireless sensor networks, demonstrating better performance than other optimization methods. In particle swarm optimization-based localization algorithms, the variants and parameters should be chosen elaborately to achieve the best performance. However, there is a lack of guidance on how to choose these variants and parameters. Further, there is no comprehensive performance comparison among particle swarm optimization algorithms. The main contribution of this paper is three-fold. First, it surveys the popular particle swarm optimization variants and particle swarm optimization-based localization algorithms for wireless sensor networks. Secondly, it presents parameter selection of nine particle swarm optimization variants and six types of swarm topologies by extensive simulations. Thirdly, it comprehensively compares the performance of these algorithms. The results show that the particle swarm optimization with constriction coefficient using ring topology outperforms other variants and swarm topologies, and it performs better than the second-order cone programming algorithm.

  15. Energy-aware Gateway Selection for increasing the lifetime of Wireless Body Area Sensor Networks.

    PubMed

    Bayilmis, Cuneyt; Younis, Mohamed

    2012-06-01

    A Wireless Body Area Sensor Network (WBASN) is composed of a set of sensor nodes, placed on, near or within a human body. WBASNs opt to continuously monitor the health conditions of individuals under medical risk, e.g., elders and chronically ill people, without keeping them in a hospital or restraining their motion. A WBASN needs to stay connected to local or wide area networks using wireless technologies in order to send sensor readings to a medical center. The WBASN nodes are implanted within the human body and would thus have limited energy supply. Since the mission of the WBASN is very critical, increasing the lifetime of nodes is essential in order to maintain both practicality and effectiveness. This paper presents a new Gateway Selection Algorithm (GSA) that factors in the use of energy harvesting technologies and dynamically picks the most suitable WBASN node that serves as a gateway to other wireless networks. The goal of GSA is to balance the load among the nodes by adaptively changing the gateway node in WBASN depending on the energy reserve of nodes. Computer modeling and simulations of the proposed GSA are carried out using OPNET. The simulation results demonstrate the effectiveness of the proposed GSA approach.

  16. Parameter Selection and Performance Comparison of Particle Swarm Optimization in Sensor Networks Localization

    PubMed Central

    Cui, Huanqing; Shu, Minglei; Song, Min; Wang, Yinglong

    2017-01-01

    Localization is a key technology in wireless sensor networks. Faced with the challenges of the sensors’ memory, computational constraints, and limited energy, particle swarm optimization has been widely applied in the localization of wireless sensor networks, demonstrating better performance than other optimization methods. In particle swarm optimization-based localization algorithms, the variants and parameters should be chosen elaborately to achieve the best performance. However, there is a lack of guidance on how to choose these variants and parameters. Further, there is no comprehensive performance comparison among particle swarm optimization algorithms. The main contribution of this paper is three-fold. First, it surveys the popular particle swarm optimization variants and particle swarm optimization-based localization algorithms for wireless sensor networks. Secondly, it presents parameter selection of nine particle swarm optimization variants and six types of swarm topologies by extensive simulations. Thirdly, it comprehensively compares the performance of these algorithms. The results show that the particle swarm optimization with constriction coefficient using ring topology outperforms other variants and swarm topologies, and it performs better than the second-order cone programming algorithm. PMID:28257060

  17. Selective modulation of chemical and electrical synapses of Helix neuronal networks during in vitro development

    PubMed Central

    2013-01-01

    Background A large number of invertebrate models, including the snail Helix, emerged as particularly suitable tools for investigating the formation of synapses and the specificity of neuronal connectivity. Helix neurons can be individually identified and isolated in cell culture, showing well-conserved size, position, biophysical properties, synaptic connections, and physiological functions. Although we previously showed the potential usefulness of Helix polysynaptic circuits, a full characterization of synaptic connectivity and its dynamics during network development has not been performed. Results In this paper, we systematically investigated the in vitro formation of polysynaptic circuits, among Helix B2 and the serotonergic C1 neurons, from a morphological and functional point of view. Since these cells are generally silent in culture, networks were chemically stimulated with either high extracellular potassium concentrations or, alternatively, serotonin. Potassium induced a transient depolarization of all neurons. On the other hand, we found prolonged firing activity, selectively maintained following the first serotonin application. Statistical analysis revealed no significant changes in neuronal dynamics during network development. Moreover, we demonstrated that the cell-selective effect of serotonin was also responsible for short-lasting alterations in C1 excitability, without long-term rebounds. Estimation of the functional connections by means of cross-correlation analysis revealed that networks under elevated KCl concentrations exhibited strongly correlated signals with short latencies (about 5 ms), typical of electrically coupled cells. Conversely, neurons treated with serotonin were weakly connected with longer latencies (exceeding 20 ms) between the interacting neurons. Finally, we clearly demonstrated that these two types of correlations (in terms of strength/latency) were effectively related to the presence of electrical or chemical connections, by

  18. Glycogen synthase kinase-3 inhibitors suppress the AR-V7-mediated transcription and selectively inhibit cell growth in AR-V7-positive prostate cancer cells.

    PubMed

    Nakata, Daisuke; Koyama, Ryokichi; Nakayama, Kazuhide; Kitazawa, Satoshi; Watanabe, Tatsuya; Hara, Takahito

    2017-06-01

    Recent evidence suggests that androgen receptor (AR) splice variants, including AR-V7, play a pivotal role in resistance to androgen blockade in prostate cancer treatment. The development of new therapeutic agents that can suppress the transcriptional activities of AR splice variants has been anticipated as the next generation treatment of castration-resistant prostate cancer. High-throughput screening of AR-V7 signaling inhibitors was performed using an AR-V7 reporter system. The effects of a glycogen synthase kinase-3 (GSK3) inhibitor, LY-2090314, on endogenous AR-V7 signaling were evaluated in an AR-V7-positive cell line, JDCaP-hr, by quantitative reverse transcription polymerase chain reaction. The relationship between AR-V7 signaling and β-catenin signaling was assessed using RNA interference. The effect of LY-2090314 on cell growth in various prostate cancer cell lines was also evaluated. We identified GSK3 inhibitors as transcriptional suppressors of AR-V7 using a high-throughput screen with an AR-V7 reporter system. LY-2090314 suppressed the reporter activity and endogenous AR-V7 activity in JDCaP-hr cells. Because silencing of β-catenin partly rescued the suppression, it was evident that the suppression was mediated, at least partially, via the activation of β-catenin signaling. AR-V7 signaling and β-catenin signaling reciprocally regulate each other in JDCaP-hr cells, and therefore, GSK3 inhibition can repress AR-V7 transcriptional activity by accumulating intracellular β-catenin. Notably, LY-2090314 selectively inhibited the growth of AR-V7-positive prostate cancer cells in vitro. Our findings demonstrate the potential of GSK3 inhibitors in treating advanced prostate cancer driven by AR splice variants. In vivo evaluation of AR splice variant-positive prostate cancer models will help illustrate the overall significance of GSK3 inhibitors in treating prostate cancer. © 2017 Wiley Periodicals, Inc.

  19. 2-[(Carboxymethyl)sulfanyl]-4-oxo-4-arylbutanoic acids selectively suppressed proliferation of neoplastic human HeLa cells. A SAR/QSAR study.

    PubMed

    Drakulić, Branko J; Juranić, Zorica D; Stanojković, Tatjana P; Juranić, Ivan O

    2005-08-25

    A series of twenty alkyl-, halo-, and methoxy-aryl-substituted 2-[(carboxymethyl)sulfanyl]-4-oxo-4-arylbutanoic acids were synthesized. The new compounds, called CSAB, suppressed proliferation of human cervix carcinoma, HeLa cells, in vitro in a concentration range of 0.644 to 29.48 microM/L. Two compounds exhibit antiproliferative activity in sub-micromolar concentrations. Five compounds act in low micromolar concentrations (<2 microM/L). The most active compounds exert lower cytotoxicity toward healthy human peripheral blood mononuclear cells (PBMC and PBMC+PHA) (selectivity indexes > 10). A strong structure-activity relationship, using estimated log P values and BCUT descriptors, was observed.

  20. Honeybee social regulatory networks are shaped by colony-level selection.

    PubMed

    Linksvayer, Timothy A; Fondrk, Michael K; Page, Robert E

    2009-03-01

    Social interactions pervade all aspects of life in the social insects. Networks of interacting nestmates enable the maintenance of colony homeostasis and regulation of brood development. Artificial colony-level selection on the amount of pollen stored in honeybee colonies has produced high- and low-pollen-hoarding strains that have been used as a model system to study the genetic and physiological basis of differences in forager behavior that contribute to colony-level differences in pollen hoarding. Here we extend this model system using an interacting-phenotypes approach that explicitly studies genetic components arising from social interactions. High- and low-pollen-hoarding-strain larvae were reared in hives with high- or low-strain older larvae and high- or low-strain adult workers. The ovariole number and dry mass of focal individuals depended on interactions between the genotypes of the focal individuals and their brood and adult worker nestmates. These results show that trait expression by individual honeybee workers is modulated by the genotypic composition of the colony, indicating that individual-level phenotypes are properties of the composite "sociogenome." Thus, colony-level selection has produced strains with distinct combinations of socially interacting genes, which make up the social networks that regulate development and expressed phenotypes.

  1. Wireless Relay Selection in Pocket Switched Networks Based on Spatial Regularity of Human Mobility †

    PubMed Central

    Huang, Jianhui; Cheng, Xiuzhen; Bi, Jingping; Chen, Biao

    2016-01-01

    Pocket switched networks (PSNs) take advantage of human mobility to deliver data. Investigations on real-world trace data indicate that human mobility shows an obvious spatial regularity: a human being usually visits a few places at high frequencies. These most frequently visited places form the home of a node, which is exploited in this paper to design two HomE based Relay selectiOn (HERO) algorithms. Both algorithms input single data copy into the network at any time. In the basic HERO, only the first node encountered by the source and whose home overlaps a destination’s home is selected as a relay while the enhanced HERO keeps finding more optimal relay that visits the destination’s home with higher probability. The two proposed algorithms only require the relays to exchange the information of their home and/or the visiting frequencies to their home when two nodes meet. As a result, the information update is reduced and there is no global status information that needs to be maintained. This causes light loads on relays because of the low communication cost and storage requirements. Additionally, only simple operations are needed in the two proposed algorithms, resulting in little computation overhead at relays. At last, a theoretical analysis is performed on some key metrics and then the real-world based simulations indicate that the two HERO algorithms are efficient and effective through employing only one or a few relays. PMID:26797609

  2. Site selectivity for protein tyrosine nitration: insights from features of structure and topological network.

    PubMed

    Cheng, Shangli; Lian, Baofeng; Liang, Juan; Shi, Ting; Xie, Lu; Zhao, Yi-Lei

    2013-11-01

    Tyrosine nitration is a covalent post-translational modification, which regulates protein functions such as hindering tyrosine phosphorylation and affecting essential signal transductions in cells. Based on up-to-date proteomics data, tyrosine nitration appears to be a highly selective process since not all tyrosine residues in proteins or all proteins are nitrated in vivo. Quite a few investigations included the protein structural information from the RCSB PDB database, where near 100,000 high-quality three-dimensional structures are available. In this work, we analyzed the local protein structures and amino acid topological networks of the nitrated and non-nitrated tyrosine sites in nitrated proteins, including neighboring atomic distribution, amino acid pair (AAP) and amino acid triangle (AAT). It has been found that aromatic and aliphatic residues, particularly with large volume, aromatic, aliphatic, or acidic side chains, are disfavored for the nitration. After integrating these structural features and topological network features with traditional sequence features, the predictive model achieves a sensitivity of 63.30% and a specificity of 92.24%, resulting in a much better accuracy compared to the previous models with only protein sequence information. Our investigation implies that the site selectivity may stem from a more open, hydrophilic and high-pH chemical environment around the tyrosine residue.

  3. Graphene networks with low percolation threshold in ABS nanocomposites: selective localization and electrical and rheological properties.

    PubMed

    Gao, Chong; Zhang, Shimin; Wang, Feng; Wen, Bin; Han, Chunchun; Ding, Yanfen; Yang, Mingshu

    2014-08-13

    Acrylonitrile-butadiene-styrene resin (ABS)/graphene nanocomposites were prepared through a facile coagulation method. Because the chemical reduction of graphene oxide was in situ conducted in the presence of ABS at the dispersion stage, the aggregation of the graphene nanosheets was avoided. It was shown by transmission electron microscopy that the graphene nanosheets were selectively located and homogeneously dispersed in the styrene-acrylonitrile (SAN) phase. The electrical conductivity and linear viscoelastic behavior of the nanocomposites were systematically studied. With increasing filler content, graphene networks were established in the SAN phase. Consequently, the nanocomposites underwent a transition from electrical insulator to conductor at a percolation threshold of 0.13 vol %, which is smaller than that of other ABS composites. Such a low percolation threshold results from extreme geometry, selective localization, and homogeneous dispersion of the graphene nanosheets in SAN phase. Similarly, the rheological response of the nanocomposites also showed a transition to solid-like behavior. Due to the thermal reduction of graphene nanosheets and structure improvement of graphene networks, enhanced electrical conductivity of the nanocomposites was obtained after annealing.

  4. Wireless Relay Selection in Pocket Switched Networks Based on Spatial Regularity of Human Mobility.

    PubMed

    Huang, Jianhui; Cheng, Xiuzhen; Bi, Jingping; Chen, Biao

    2016-01-18

    Pocket switched networks (PSNs) take advantage of human mobility to deliver data. Investigations on real-world trace data indicate that human mobility shows an obvious spatial regularity: a human being usually visits a few places at high frequencies. These most frequently visited places form the home of a node, which is exploited in this paper to design two HomE based Relay selectiOn (HERO) algorithms. Both algorithms input single data copy into the network at any time. In the basic HERO, only the first node encountered by the source and whose home overlaps a destination's home is selected as a relay while the enhanced HERO keeps finding more optimal relay that visits the destination's home with higher probability. The two proposed algorithms only require the relays to exchange the information of their home and/or the visiting frequencies to their home when two nodes meet. As a result, the information update is reduced and there is no global status information that needs to be maintained. This causes light loads on relays because of the low communication cost and storage requirements. Additionally, only simple operations are needed in the two proposed algorithms, resulting in little computation overhead at relays. At last, a theoretical analysis is performed on some key metrics and then the real-world based simulations indicate that the two HERO algorithms are efficient and effective through employing only one or a few relays.

  5. Friendship networks and achievement goals: an examination of selection and influence processes and variations by gender.

    PubMed

    Shin, Huiyoung; Ryan, Allison M

    2014-09-01

    Interactions with friends are a salient part of students' experience at school. Thus, friends are likely to be an important source of influence on achievement goals. This study investigated processes within early adolescent friendships (selection and influence) with regard to achievement goals (mastery, performance-approach, and performance-avoidance goals) among sixth graders (N = 587, 50% girls at wave 1, N = 576, 52% girls at wave 2) followed from fall to spring within one academic year. Students' gender was examined as a moderator in these processes. Longitudinal social network analysis found that friends were similar to each other in mastery goals and that this similarity was due to both selection and influence effects. Influence but not selection effects were found for performance-approach goals. Influence effects for performance-approach goals were stronger for boys compared to girls in the classroom. Neither selection, nor influence, effects were found in relation to performance-avoidance goals. However, the higher a student was in performance-avoidance goals, the less likely they were to be named as a friend by classmates. Implications for early adolescents' classroom adjustment are discussed.

  6. Adolescent girls' friendship networks, body dissatisfaction, and disordered eating: examining