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Sample records for hyperpolarization-activated hcn channels

  1. Genetic variation in Hyperpolarization-activated cyclic nucleotide-gated (HCN channels and its relationship with neuroticism, cognition and risk of depression

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    Andrew Mark Mcintosh

    2012-07-01

    Full Text Available Hyperpolarization-activated cyclic nucleotide-gated (HCN channels are encoded by four genes (HCN1-4 and, through activation by cyclic AMP (cAMP, represent a point of convergence for several psychosis risk genes. On the basis of positive preliminary data, we sought to test whether genetic variation in HCN1-4 conferred risk of depression or cognitive impairment in the Generation Scotland: Scottish Family Health Study. HCN1, HCN2, HCN3 and HCN4 were genotyped for 43 haplotype-tagging SNPs and tested for association with DSM-IV depression, neuroticism and a battery of cognitive tests assessing cognitive ability, memory, verbal fluency and psychomotor performance. No association was found between any HCN channel gene SNP and risk of depression, neuroticism or on any cognitive measure. The current study does not support a genetic role for HCN channels in conferring risk of depression or cognitive impairment in human subjects within the Scottish population.

  2. Increased expression of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels in reactive astrocytes following ischemia

    Czech Academy of Sciences Publication Activity Database

    Honsa, Pavel; Pivoňková, Helena; Harantová, Lenka; Butenko, Olena; Kriška, Ján; Džamba, Dávid; Rusňáková, Vendula; Valihrach, Lukáš; Kubista, Mikael; Anděrová, Miroslava

    2014-01-01

    Roč. 62, č. 12 (2014), s. 2004-2021 ISSN 0894-1491 R&D Projects: GA ČR GA13-02154S; GA ČR(CZ) GBP304/12/G069; GA MŠk(CZ) ED1.1.00/02.0109 Grant - others:GA MŠk(CZ) CZ.1.07/2.3.00/30.0045 Institutional support: RVO:68378041 ; RVO:86652036 Keywords : Astrocytes * focal and global cerebral ischemia * HCN channels Subject RIV: FH - Neurology Impact factor: 6.031, year: 2014

  3. Dysfunctional Hyperpolarization-Activated Cyclic Nucleotide-gated Ion Channels in Cardiac Diseases

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    Xiaoqi Zhao

    Full Text Available Abstract Hyperpolarization-activated cyclic nucleotide-gated (HCN channels are reverse voltage-dependent, and their activation depends on the hyperpolarization of the membrane and may be directly or indirectly regulated by the cyclic adenosine monophosphate (cAMP or other signal-transduction cascades. The distribution, quantity and activation states of HCN channels differ in tissues throughout the body. Evidence exhibits that HCN channels play critical roles in the generation and conduction of the electrical impulse and the physiopathological process of some cardiac diseases. They may constitute promising drug targets in the treatment of these cardiac diseases. Pharmacological treatment targeting HCN channels is of benefit to these cardiac conditions.

  4. Dysfunctional HCN ion channels in neurological diseases

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    Jacopo C. DiFrancesco

    2015-03-01

    Full Text Available Hyperpolarization-activated cyclic nucleotide-gated (HCN channels are expressed as four different isoforms (HCN1-4 in the heart and in the central and peripheral nervous systems. HCN channels are activated by membrane hyperpolarization at voltages close to resting membrane potentials and carry the hyperpolarization-activated current, dubbed If (funny current in heart and Ih in neurons. HCN channels contribute in several ways to neuronal activity and are responsible for many important cellular functions, including cellular excitability, generation and modulation of rhythmic activity, dendritic integration, transmission of synaptic potentials and plasticity phenomena. Because of their role, defective HCN channels are natural candidates in the search for potential causes of neurological disorders in humans. Several data, including growing evidence that some forms of epilepsy are associated with HCN mutations, support the notion of an involvement of dysfunctional HCN channels in different experimental models of the disease. Additionally, some anti-epileptic drugs are known to modify the activity of the Ih current. HCN channels are widely expressed in the peripheral nervous system and recent evidence has highlighted the importance of the HCN2 isoform in the transmission of pain. HCN channels are also present in the midbrain system, where they finely regulate the activity of dopaminergic neurons, and a potential role of these channels in the pathogenesis of Parkinson’s disease has recently emerged. The function of HCN channels is regulated by specific accessory proteins, which control the correct expression and modulation of the neuronal Ih current. Alteration of these proteins can severely interfere with the physiological channel function, potentially predisposing to pathological conditions. In this review we address the present knowledge of the association between HCN dysfunctions and neurological diseases, including clinical, genetic and

  5. Flavonoid Regulation of HCN2 Channels*

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    Carlson, Anne E.; Rosenbaum, Joel C.; Brelidze, Tinatin I.; Klevit, Rachel E.; Zagotta, William N.

    2013-01-01

    The hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels are pacemaker channels whose currents contribute to rhythmic activity in the heart and brain. HCN channels open in response to hyperpolarizing voltages, and the binding of cAMP to their cyclic nucleotide-binding domain (CNBD) facilitates channel opening. Here, we report that, like cAMP, the flavonoid fisetin potentiates HCN2 channel gating. Fisetin sped HCN2 activation and shifted the conductance-voltage relationship to more depolarizing potentials with a half-maximal effective concentration (EC50) of 1.8 μm. When applied together, fisetin and cAMP regulated HCN2 gating in a nonadditive fashion. Fisetin did not potentiate HCN2 channels lacking their CNBD, and two independent fluorescence-based binding assays reported that fisetin bound to the purified CNBD. These data suggest that the CNBD mediates the fisetin potentiation of HCN2 channels. Moreover, binding assays suggest that fisetin and cAMP partially compete for binding to the CNBD. NMR experiments demonstrated that fisetin binds within the cAMP-binding pocket, interacting with some of the same residues as cAMP. Together, these data indicate that fisetin is a partial agonist for HCN2 channels. PMID:24085296

  6. HCN Channels Modulators: The Need for Selectivity

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    Romanelli, Maria Novella; Sartiani, Laura; Masi, Alessio; Mannaioni, Guido; Manetti, Dina; Mugelli, Alessandro; Cerbai, Elisabetta

    2016-01-01

    Hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels, the molecular correlate of the hyperpolarization-activated current (If/Ih), are membrane proteins which play an important role in several physiological processes and various pathological conditions. In the Sino Atrial Node (SAN) HCN4 is the target of ivabradine, a bradycardic agent that is, at the moment, the only drug which specifically blocks If. Nevertheless, several other pharmacological agents have been shown to modulate HCN channels, a property that may contribute to their therapeutic activity and/or to their side effects. HCN channels are considered potential targets for developing drugs to treat several important pathologies, but a major issue in this field is the discovery of isoform-selective compounds, owing to the wide distribution of these proteins into the central and peripheral nervous systems, heart and other peripheral tissues. This survey is focused on the compounds that have been shown, or have been designed, to interact with HCN channels and on their binding sites, with the aim to summarize current knowledge and possibly to unveil useful information to design new potent and selective modulators. PMID:26975509

  7. Peripheral hyperpolarization-activated cyclic nucleotide-gated channels contribute to inflammation-induced hypersensitivity of the rat temporomandibular joint.

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    Hatch, R J; Jennings, E A; Ivanusic, J J

    2013-08-01

    Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels conduct an inward cation current (Ih ) that contributes to the maintenance of neuronal membrane potential and have been implicated in a number of animal models of neuropathic and inflammatory pain. In the current study, we investigated HCN channel involvement in inflammatory pain of the temporomandibular joint (TMJ). The contribution of HCN channels to inflammation (complete Freund's adjuvant; CFA)-induced mechanical hypersensitivity of the rat TMJ was tested with injections of the HCN channel blocker ZD7288. Retrograde labelling and immunohistochemistry was used to explore HCN channel expression in sensory neurons that innervate the TMJ. Injection of CFA into the TMJ (n = 7) resulted in a significantly increased mechanical sensitivity relative to vehicle injection (n = 7) (p blocked by co-injection of ZD7288 with the CFA (n = 7). Retrograde labelling and immunohistochemistry experiments revealed expression predominantly of HCN1 and HCN2 channel subunits in trigeminal ganglion neurons that innervate the TMJ (n = 3). No change in the proportion or intensity of HCN channel expression was found in inflamed (n = 6) versus control (n = 5) animals at the time point tested. Our findings suggest a role for peripheral HCN channels in inflammation-induced pain of the TMJ. Peripheral application of a HCN channel blocker could provide therapeutic benefit for inflammatory TMJ pain and avoid side effects associated with activation of HCN channels in the central nervous system. © 2012 European Federation of International Association for the Study of Pain Chapters.

  8. Gabapentin Modulates HCN4 Channel Voltage-Dependence

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    Han-Shen Tae

    2017-08-01

    Full Text Available Gabapentin (GBP is widely used to treat epilepsy and neuropathic pain. There is evidence that GBP can act on hyperpolarization-activated cation (HCN channel-mediated Ih in brain slice experiments. However, evidence showing that GBP directly modulates HCN channels is lacking. The effect of GBP was tested using two-electrode voltage clamp recordings from human HCN1, HCN2, and HCN4 channels expressed in Xenopus oocytes. Whole-cell recordings were also made from mouse spinal cord slices targeting either parvalbumin positive (PV+ or calretinin positive (CR+ inhibitory neurons. The effect of GBP on Ih was measured in each inhibitory neuron population. HCN4 expression was assessed in the spinal cord using immunohistochemistry. When applied to HCN4 channels, GBP (100 μM caused a hyperpolarizing shift in the voltage of half activation (V1/2 thereby reducing the currents. Gabapentin had no impact on the V1/2 of HCN1 or HCN2 channels. There was a robust increase in the time to half activation for HCN4 channels with only a small increase noted for HCN1 channels. Gabapentin also caused a hyperpolarizing shift in the V1/2 of Ih measured from HCN4-expressing PV+ inhibitory neurons in the spinal dorsal horn. Gabapentin had minimal effect on Ih recorded from CR+ neurons. Consistent with this, immunohistochemical analysis revealed that the majority of CR+ inhibitory neurons do not express somatic HCN4 channels. In conclusion, GBP reduces HCN4 channel-mediated currents through a hyperpolarized shift in the V1/2. The HCN channel subtype selectivity of GBP provides a unique tool for investigating HCN4 channel function in the central nervous system. The HCN4 channel is a candidate molecular target for the acute analgesic and anticonvulsant actions of GBP.

  9. Search after new agents for hyperpolarization-activated and cyclic nucleotide-gated ion channels; Suche nach neuen Wirkstoffen fuer Hyperpolarisationsaktivierte und zyklisch Nukleotid-gesteuerte Ionenkanaele

    Energy Technology Data Exchange (ETDEWEB)

    Struenker, T.

    2005-12-01

    Rhythmic activity of single cells or cellular networks is a common feature of most organisms. Cellular rhythms govern the beating of the heart, cycles of sleep and wakefulness, breathing, and the release of hormones. The endogenous rhythmic activity of many neurons and cardiac relies on a complex interplay between several distinct ion channels. In particular, one type of ion channel plays a prominent role in the control of rhythmic electrical activity because it determines the frequency of the oscillations. The activity of the channels is thus setting the ''pace'' of the activity; therefore, these channels are often referred to as ''pacemaker'' channels. Despite their obvious physiological importance it hasn't been until a few years ago that the genes encoding pacemaker channels have been identified. Because both hyperpolarization and cyclic nucleotides are key elements that control their activity, pacemaker channels have now been designated hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels. From a scientific as well as medical point of view, HCN channels are interesting drug targets. Only a few substances are known that specifically affect HCN channels. In the present study, a microtiter plate-based high throughput screening assay for HCN1 and HCN4 channels was developed. With this assay, known drugs for HCN channels were characterized. Subsequently, venoms of snails, spiders, scorpions, and snakes were screened for toxins affecting HCN channel activity. A few venoms were identified that possibly contain drugs that act on HCN channels. (orig.)

  10. Modulation of thalamocortical oscillations by TRIP8b, an auxiliary subunit for HCN channels

    NARCIS (Netherlands)

    Zobeiri, M.; Chaudhary, R.; Datunashvili, M.; Heuermann, R.J.; Lüttjohann, A.; Narayanan, V.; Balfanz, S.; Meuth, P.; Chetkovich, D.M.; Pape, H.C.; Baumann, A.; Luijtelaar, E.L.J.M. van; Budde, T.

    2018-01-01

    Hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channels have important functions in controlling neuronal excitability and generating rhythmic oscillatory activity. The role of tetratricopeptide repeat-containing Rab8b-interacting protein (TRIP8b) in regulation of

  11. Hypoosmotic cell swelling as a novel mechanism for modulation of cloned HCN2 channels

    DEFF Research Database (Denmark)

    Calloe, Kirstine; Elmedyb, Pernille; Olesen, Søren-Peter

    2005-01-01

    This work demonstrates cell swelling as a new regulatory mechanism for the cloned hyperpolarization-activated, cyclic nucleotide-gated channel 2 (HCN2). HCN2 channels were coexpressed with aquaporin1 in Xenopus laevis oocytes and currents were monitored using a two-electrode voltage-clamp. HCN2...... channels were activated by hyperpolarization to -100 mV and the currents were measured before and during hypoosmotic cell swelling. Cell swelling increased HCN2 currents by 30% without changing the kinetics of the currents. Injection of 50 nl intracellular solution resulted in a current increase of 20......%, indicating that an increase in cell volume also under isoosmotic conditions may lead to activation of HCN2. In the absence of aquaporin1 only negligible changes in oocyte cell volume occur during exposure to hypoosmotic media and no significant change in HCN2 channel activity was observed during perfusion...

  12. HCN channels are not required for mechanotransduction in sensory hair cells of the mouse inner ear.

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    Geoffrey C Horwitz

    Full Text Available The molecular composition of the hair cell transduction channel has not been identified. Here we explore the novel hypothesis that hair cell transduction channels include HCN subunits. The HCN family of ion channels includes four members, HCN1-4. They were originally identified as the molecular correlates of the hyperpolarization-activated, cyclic nucleotide gated ion channels that carry currents known as If, IQ or Ih. However, based on recent evidence it has been suggested that HCN subunits may also be components of the elusive hair cell transduction channel. To investigate this hypothesis we examined expression of mRNA that encodes HCN1-4 in sensory epithelia of the mouse inner ear, immunolocalization of HCN subunits 1, 2 and 4, uptake of the transduction channel permeable dye, FM1-43 and electrophysiological measurement of mechanotransduction current. Dye uptake and transduction current were assayed in cochlear and vestibular hair cells of wildtype mice exposed to HCN channel blockers or a dominant-negative form of HCN2 that contained a pore mutation and in mutant mice that lacked HCN1, HCN2 or both. We found robust expression of HCNs 1, 2 and 4 but little evidence that localized HCN subunits in hair bundles, the site of mechanotransduction. Although high concentrations of the HCN antagonist, ZD7288, blocked 50-70% of the transduction current, we found no reduction of transduction current in either cochlear or vestibular hair cells of HCN1- or HCN2- deficient mice relative to wild-type mice. Furthermore, mice that lacked both HCN1 and HCN2 also had normal transduction currents. Lastly, we found that mice exposed to the dominant-negative mutant form of HCN2 had normal transduction currents as well. Taken together, the evidence suggests that HCN subunits are not required for mechanotransduction in hair cells of the mouse inner ear.

  13. Biochemical and structural analysis of the hyperpolarization-activated K(+) channel MVP.

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    Randich, Amelia M; Cuello, Luis G; Wanderling, Sherry S; Perozo, Eduardo

    2014-03-18

    In contrast to the majority of voltage-gated ion channels, hyperpolarization-activated channels remain closed at depolarizing potentials and are activated at hyperpolarizing potentials. The basis for this reverse polarity is thought to be a result of differences in the way the voltage-sensing domain (VSD) couples to the pore domain. In the absence of structural data, the molecular mechanism of this reverse polarity coupling remains poorly characterized. Here we report the characterization of the structure and local dynamics of the closed activation gate (lower S6 region) of MVP, a hyperpolarization-activated potassium channel from Methanococcus jannaschii, by electron paramagnetic resonance (EPR) spectroscopy. We show that a codon-optimized version of MVP has high expression levels in Escherichia coli, is purified as a stable tetramer, and exhibits expected voltage-dependent activity when reconstituted in liposomes. EPR analysis of the mid to lower S6 region revealed positions exhibiting strong spin-spin coupling, indicating that the activation gate of MVP is closed at 0 mV. A comparison of local environmental parameters along the activation gate for MVP and KcsA indicates that MVP adopts a different closed conformation. These structural details set the stage for future evaluations of reverse electromechanical coupling in MVP.

  14. Biochemical and Structural Analysis of the Hyperpolarization-Activated K+ Channel MVP

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    2015-01-01

    In contrast to the majority of voltage-gated ion channels, hyperpolarization-activated channels remain closed at depolarizing potentials and are activated at hyperpolarizing potentials. The basis for this reverse polarity is thought to be a result of differences in the way the voltage-sensing domain (VSD) couples to the pore domain. In the absence of structural data, the molecular mechanism of this reverse polarity coupling remains poorly characterized. Here we report the characterization of the structure and local dynamics of the closed activation gate (lower S6 region) of MVP, a hyperpolarization-activated potassium channel from Methanococcus jannaschii, by electron paramagnetic resonance (EPR) spectroscopy. We show that a codon-optimized version of MVP has high expression levels in Escherichia coli, is purified as a stable tetramer, and exhibits expected voltage-dependent activity when reconstituted in liposomes. EPR analysis of the mid to lower S6 region revealed positions exhibiting strong spin–spin coupling, indicating that the activation gate of MVP is closed at 0 mV. A comparison of local environmental parameters along the activation gate for MVP and KcsA indicates that MVP adopts a different closed conformation. These structural details set the stage for future evaluations of reverse electromechanical coupling in MVP. PMID:24490868

  15. Disturbed Processing of Contextual Information in HCN3 Channel Deficient Mice

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    Stieglitz, Marc S.; Fenske, Stefanie; Hammelmann, Verena; Becirovic, Elvir; Schöttle, Verena; Delorme, James E.; Schöll-Weidinger, Martha; Mader, Robert; Deussing, Jan; Wolfer, David P.; Seeliger, Mathias W.; Albrecht, Urs; Wotjak, Carsten T.; Biel, Martin; Michalakis, Stylianos; Wahl-Schott, Christian

    2018-01-01

    Hyperpolarization-activated cyclic nucleotide-gated channels (HCNs) in the nervous system are implicated in a variety of neuronal functions including learning and memory, regulation of vigilance states and pain. Dysfunctions or genetic loss of these channels have been shown to cause human diseases such as epilepsy, depression, schizophrenia, and Parkinson's disease. The physiological functions of HCN1 and HCN2 channels in the nervous system have been analyzed using genetic knockout mouse models. By contrast, there are no such genetic studies for HCN3 channels so far. Here, we use a HCN3-deficient (HCN3−/−) mouse line, which has been previously generated in our group to examine the expression and function of this channel in the CNS. Specifically, we investigate the role of HCN3 channels for the regulation of circadian rhythm and for the determination of behavior. Contrary to previous suggestions we find that HCN3−/− mice show normal visual, photic, and non-photic circadian function. In addition, HCN3−/− mice are impaired in processing contextual information, which is characterized by attenuated long-term extinction of contextual fear and increased fear to a neutral context upon repeated exposure. PMID:29375299

  16. Disturbed Processing of Contextual Information in HCN3 Channel Deficient Mice

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    Marc S. Stieglitz

    2018-01-01

    Full Text Available Hyperpolarization-activated cyclic nucleotide-gated channels (HCNs in the nervous system are implicated in a variety of neuronal functions including learning and memory, regulation of vigilance states and pain. Dysfunctions or genetic loss of these channels have been shown to cause human diseases such as epilepsy, depression, schizophrenia, and Parkinson's disease. The physiological functions of HCN1 and HCN2 channels in the nervous system have been analyzed using genetic knockout mouse models. By contrast, there are no such genetic studies for HCN3 channels so far. Here, we use a HCN3-deficient (HCN3−/− mouse line, which has been previously generated in our group to examine the expression and function of this channel in the CNS. Specifically, we investigate the role of HCN3 channels for the regulation of circadian rhythm and for the determination of behavior. Contrary to previous suggestions we find that HCN3−/− mice show normal visual, photic, and non-photic circadian function. In addition, HCN3−/− mice are impaired in processing contextual information, which is characterized by attenuated long-term extinction of contextual fear and increased fear to a neutral context upon repeated exposure.

  17. The role of an ancestral hyperpolarization-activated cyclic nucleotide-gated K+ channel in branchial acid-base regulation in the green crab, Carcinus maenas.

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    Fehsenfeld, Sandra; Weihrauch, Dirk

    2016-03-01

    Numerous electrophysiological studies on branchial K(+) transport in brachyuran crabs have established an important role for potassium channels in osmoregulatory ion uptake and ammonia excretion in the gill epithelium of decapod crustaceans. However, hardly anything is known of the actual nature of these channels in crustaceans. In the present study, the identification of a hyperpolarization-activated cyclic nucleotide-gated potassium channel (HCN) in the transcriptome of the green crab Carcinus maenas and subsequent performance of quantitative real-time PCR revealed the ubiquitous expression of this channel in this species. Even though mRNA expression levels in the cerebral ganglion were found to be approximately 10 times higher compared with all other tissues, posterior gills still expressed significant levels of HCN, indicating an important role for this transporter in branchial ion regulation. The relatively unspecific K(+)-channel inhibitor Ba(2+), as well as the HCN-specific blocker ZD7288, as applied in gill perfusion experiments and electrophysiological studies employing the split gill lamellae revealed the presence of at least two different K(+)/NH4(+)-transporting structures in the branchial epithelium of C. maenas. Furthermore, HCN mRNA levels in posterior gill 7 decreased significantly in response to the respiratory or metabolic acidosis that was induced by acclimation of green crabs to high environmental PCO2 and ammonia, respectively. Consequently, the present study provides first evidence that HCN-promoted NH4(+) epithelial transport is involved in both branchial acid-base and ammonia regulation in an invertebrate. © 2016. Published by The Company of Biologists Ltd.

  18. Inferior Olive HCN1 Channels Coordinate Synaptic Integration and Complex Spike Timing

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    Derek L.F. Garden

    2018-02-01

    Full Text Available Cerebellar climbing-fiber-mediated complex spikes originate from neurons in the inferior olive (IO, are critical for motor coordination, and are central to theories of cerebellar learning. Hyperpolarization-activated cyclic-nucleotide-gated (HCN channels expressed by IO neurons have been considered as pacemaker currents important for oscillatory and resonant dynamics. Here, we demonstrate that in vitro, network actions of HCN1 channels enable bidirectional glutamatergic synaptic responses, while local actions of HCN1 channels determine the timing and waveform of synaptically driven action potentials. These roles are distinct from, and may complement, proposed pacemaker functions of HCN channels. We find that in behaving animals HCN1 channels reduce variability in the timing of cerebellar complex spikes, which serve as a readout of IO spiking. Our results suggest that spatially distributed actions of HCN1 channels enable the IO to implement network-wide rules for synaptic integration that modulate the timing of cerebellar climbing fiber signals.

  19. Targeted deletion of Kcne2 impairs HCN channel function in mouse thalamocortical circuits.

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    Shui-Wang Ying

    Full Text Available Hyperpolarization-activated, cyclic nucleotide-gated (HCN channels generate the pacemaking current, I(h, which regulates neuronal excitability, burst firing activity, rhythmogenesis, and synaptic integration. The physiological consequence of HCN activation depends on regulation of channel gating by endogenous modulators and stabilization of the channel complex formed by principal and ancillary subunits. KCNE2 is a voltage-gated potassium channel ancillary subunit that also regulates heterologously expressed HCN channels; whether KCNE2 regulates neuronal HCN channel function is unknown.We investigated the effects of Kcne2 gene deletion on I(h properties and excitability in ventrobasal (VB and cortical layer 6 pyramidal neurons using brain slices prepared from Kcne2(+/+ and Kcne2(-/- mice. Kcne2 deletion shifted the voltage-dependence of I(h activation to more hyperpolarized potentials, slowed gating kinetics, and decreased I(h density. Kcne2 deletion was associated with a reduction in whole-brain expression of both HCN1 and HCN2 (but not HCN4, although co-immunoprecipitation from whole-brain lysates failed to detect interaction of KCNE2 with HCN1 or 2. Kcne2 deletion also increased input resistance and temporal summation of subthreshold voltage responses; this increased intrinsic excitability enhanced burst firing in response to 4-aminopyridine. Burst duration increased in corticothalamic, but not thalamocortical, neurons, suggesting enhanced cortical excitatory input to the thalamus; such augmented excitability did not result from changes in glutamate release machinery since miniature EPSC frequency was unaltered in Kcne2(-/- neurons.Loss of KCNE2 leads to downregulation of HCN channel function associated with increased excitability in neurons in the cortico-thalamo-cortical loop. Such findings further our understanding of the normal physiology of brain circuitry critically involved in cognition and have implications for our understanding of

  20. Contribution of large-sized primary sensory neuronal sensitization to mechanical allodynia by upregulation of hyperpolarization-activated cyclic nucleotide gated channels via cyclooxygenase 1 cascade.

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    Sun, Wei; Yang, Fei; Wang, Yan; Fu, Han; Yang, Yan; Li, Chun-Li; Wang, Xiao-Liang; Lin, Qing; Chen, Jun

    2017-02-01

    Under physiological state, small- and medium-sized dorsal root ganglia (DRG) neurons are believed to mediate nociceptive behavioral responses to painful stimuli. However, recently it has been found that a number of large-sized neurons are also involved in nociceptive transmission under neuropathic conditions. Nonetheless, the underlying mechanisms that large-sized DRG neurons mediate nociception are poorly understood. In the present study, the role of large-sized neurons in bee venom (BV)-induced mechanical allodynia and the underlying mechanisms were investigated. Behaviorally, it was found that mechanical allodynia was still evoked by BV injection in rats in which the transient receptor potential vanilloid 1-positive DRG neurons were chemically deleted. Electrophysiologically, in vitro patch clamp recordings of large-sized neurons showed hyperexcitability in these neurons. Interestingly, the firing pattern of these neurons was changed from phasic to tonic under BV-inflamed state. It has been suggested that hyperpolarization-activated cyclic nucleotide gated channels (HCN) expressed in large-sized DRG neurons contribute importantly to repeatedly firing. So we examined the roles of HCNs in BV-induced mechanical allodynia. Consistent with the overexpression of HCN1/2 detected by immunofluorescence, HCNs-mediated hyperpolarization activated cation current (I h ) was significantly increased in the BV treated samples. Pharmacological experiments demonstrated that the hyperexcitability and upregulation of I h in large-sized neurons were mediated by cyclooxygenase-1 (COX-1)-prostaglandin E2 pathway. This is evident by the fact that the COX-1 inhibitor significantly attenuated the BV-induced mechanical allodynia. These results suggest that BV can excite the large-sized DRG neurons at least in part by increasing I h through activation of COX-1. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. Distribution and function of HCN channels in the apical dendritic tuft of neocortical pyramidal neurons.

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    Harnett, Mark T; Magee, Jeffrey C; Williams, Stephen R

    2015-01-21

    The apical tuft is the most remote area of the dendritic tree of neocortical pyramidal neurons. Despite its distal location, the apical dendritic tuft of layer 5 pyramidal neurons receives substantial excitatory synaptic drive and actively processes corticocortical input during behavior. The properties of the voltage-activated ion channels that regulate synaptic integration in tuft dendrites have, however, not been thoroughly investigated. Here, we use electrophysiological and optical approaches to examine the subcellular distribution and function of hyperpolarization-activated cyclic nucleotide-gated nonselective cation (HCN) channels in rat layer 5B pyramidal neurons. Outside-out patch recordings demonstrated that the amplitude and properties of ensemble HCN channel activity were uniform in patches excised from distal apical dendritic trunk and tuft sites. Simultaneous apical dendritic tuft and trunk whole-cell current-clamp recordings revealed that the pharmacological blockade of HCN channels decreased voltage compartmentalization and enhanced the generation and spread of apical dendritic tuft and trunk regenerative activity. Furthermore, multisite two-photon glutamate uncaging demonstrated that HCN channels control the amplitude and duration of synaptically evoked regenerative activity in the distal apical dendritic tuft. In contrast, at proximal apical dendritic trunk and somatic recording sites, the blockade of HCN channels decreased excitability. Dynamic-clamp experiments revealed that these compartment-specific actions of HCN channels were heavily influenced by the local and distributed impact of the high density of HCN channels in the distal apical dendritic arbor. The properties and subcellular distribution pattern of HCN channels are therefore tuned to regulate the interaction between integration compartments in layer 5B pyramidal neurons. Copyright © 2015 the authors 0270-6474/15/351024-14$15.00/0.

  2. An N-Terminal ER Export Signal Facilitates the Plasma Membrane Targeting of HCN1 Channels in Photoreceptors.

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    Pan, Yuan; Laird, Joseph G; Yamaguchi, David M; Baker, Sheila A

    2015-06-01

    Hyperpolarization-activated cyclic nucleotide-gated 1 (HCN1) channels are widely expressed in the retina. In photoreceptors, the hyperpolarization-activated current (Ih) carried by HCN1 is important for shaping the light response. It has been shown in multiple systems that trafficking HCN1 channels to specific compartments is key to their function. The localization of HCN1 in photoreceptors is concentrated in the plasma membrane of the inner segment (IS). The mechanisms controlling this localization are not understood. We previously identified a di-arginine endoplasmic reticulum (ER) retention motif that negatively regulates the surface targeting of HCN1. In this study, we sought to identify a forward trafficking signal that could counter the function of the ER retention signal. We studied trafficking of HCN1 and several mutants by imaging their subcellular localization in transgenic X. laevis photoreceptors. Velocity sedimentation was used to assay the assembly state of HCN1 channels. We found the HCN1 N-terminus can redirect a membrane reporter from outer segments (OS) to the plasma membrane of the IS. The sequence necessary for this behavior was mapped to a 20 amino acid region containing a leucine-based ER export motif. The ER export signal is necessary for forward trafficking but not channel oligomerization. Moreover, this ER export signal alone counteracted the di-arginine ER retention signal. We identified an ER export signal in HCN1 that functions with the ER retention signal to maintain equilibrium of HCN1 between the endomembrane system and the plasma membrane.

  3. Contribution of presynaptic HCN channels to excitatory inputs of spinal substantia gelatinosa neurons.

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    Peng, S-C; Wu, J; Zhang, D-Y; Jiang, C-Y; Xie, C-N; Liu, T

    2017-09-01

    Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are pathological pain-associated voltage-gated ion channels. They are widely expressed in central nervous system including spinal lamina II (also named the substantia gelatinosa, SG). Here, we examined the distribution of HCN channels in glutamatergic synaptic terminals as well as their role in the modulation of synaptic transmission in SG neurons from SD rats and glutamic acid decarboxylase-67 (GAD67)-GFP mice. We found that the expression of the HCN channel isoforms was varied in SG. The HCN4 isoform showed the highest level of co-localization with VGLUT2 (23±3%). In 53% (n=21/40 neurons) of the SG neurons examined in SD rats, application of HCN channel blocker, ZD7288 (10μM), decreased the frequency of spontaneous (s) and miniature (m) excitatory postsynaptic currents (EPSCs) by 37±4% and 33±4%, respectively. Consistently, forskolin (FSK) (an activator of adenylate cyclase) significantly increased the frequency of mEPSCs by 225±34%, which could be partially inhibited by ZD7288. Interestingly, the effects of ZD7288 and FSK on sEPSC frequency were replicated in non-GFP-expressing neurons, but not in GFP-expressing GABAergic SG neurons, in GAD67-GFP transgenic C57/BL6 mice. In summary, our results represent a previously unknown cellular mechanism by which presynaptic HCN channels, especially HCN4, regulate the glutamate release from presynaptic terminals that target excitatory, but not inhibitory SG interneurons. Copyright © 2017 IBRO. Published by Elsevier Ltd. All rights reserved.

  4. Modulation of thalamocortical oscillations by TRIP8b, an auxiliary subunit for HCN channels.

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    Zobeiri, Mehrnoush; Chaudhary, Rahul; Datunashvili, Maia; Heuermann, Robert J; Lüttjohann, Annika; Narayanan, Venu; Balfanz, Sabine; Meuth, Patrick; Chetkovich, Dane M; Pape, Hans-Christian; Baumann, Arnd; van Luijtelaar, Gilles; Budde, Thomas

    2018-04-01

    Hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channels have important functions in controlling neuronal excitability and generating rhythmic oscillatory activity. The role of tetratricopeptide repeat-containing Rab8b-interacting protein (TRIP8b) in regulation of hyperpolarization-activated inward current, I h , in the thalamocortical system and its functional relevance for the physiological thalamocortical oscillations were investigated. A significant decrease in I h current density, in both thalamocortical relay (TC) and cortical pyramidal neurons was found in TRIP8b-deficient mice (TRIP8b -/- ). In addition basal cAMP levels in the brain were found to be decreased while the availability of the fast transient A-type K + current, I A , in TC neurons was increased. These changes were associated with alterations in intrinsic properties and firing patterns of TC neurons, as well as intrathalamic and thalamocortical network oscillations, revealing a significant increase in slow oscillations in the delta frequency range (0.5-4 Hz) during episodes of active-wakefulness. In addition, absence of TRIP8b suppresses the normal desynchronization response of the EEG during the switch from slow-wave sleep to wakefulness. It is concluded that TRIP8b is necessary for the modulation of physiological thalamocortical oscillations due to its direct effect on HCN channel expression in thalamus and cortex and that mechanisms related to reduced cAMP signaling may contribute to the present findings.

  5. De novo mutations in HCN1 cause early infantile epileptic encephalopathy

    DEFF Research Database (Denmark)

    Nava, Caroline; Dalle, Carine; Rastetter, Agnès

    2014-01-01

    Hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels contribute to cationic Ih current in neurons and regulate the excitability of neuronal networks. Studies in rat models have shown that the Hcn1 gene has a key role in epilepsy, but clinical evidence implicating HCN1 mutations in ...

  6. HCN4 ion channel function is required for early events that regulate anatomical left-right patterning in a nodal and lefty asymmetric gene expression-independent manner.

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    Pai, Vaibhav P; Willocq, Valerie; Pitcairn, Emily J; Lemire, Joan M; Paré, Jean-François; Shi, Nian-Qing; McLaughlin, Kelly A; Levin, Michael

    2017-10-15

    Laterality is a basic characteristic of all life forms, from single cell organisms to complex plants and animals. For many metazoans, consistent left-right asymmetric patterning is essential for the correct anatomy of internal organs, such as the heart, gut, and brain; disruption of left-right asymmetry patterning leads to an important class of birth defects in human patients. Laterality functions across multiple scales, where early embryonic, subcellular and chiral cytoskeletal events are coupled with asymmetric amplification mechanisms and gene regulatory networks leading to asymmetric physical forces that ultimately result in distinct left and right anatomical organ patterning. Recent studies have suggested the existence of multiple parallel pathways regulating organ asymmetry. Here, we show that an isoform of the hyperpolarization-activated cyclic nucleotide-gated (HCN) family of ion channels (hyperpolarization-activated cyclic nucleotide-gated channel 4, HCN4) is important for correct left-right patterning. HCN4 channels are present very early in Xenopus embryos. Blocking HCN channels ( I h currents) with pharmacological inhibitors leads to errors in organ situs. This effect is only seen when HCN4 channels are blocked early (pre-stage 10) and not by a later block (post-stage 10). Injections of HCN4-DN (dominant-negative) mRNA induce left-right defects only when injected in both blastomeres no later than the 2-cell stage. Analysis of key asymmetric genes' expression showed that the sidedness of Nodal , Lefty , and Pitx2 expression is largely unchanged by HCN4 blockade, despite the randomization of subsequent organ situs, although the area of Pitx2 expression was significantly reduced. Together these data identify a novel, developmental role for HCN4 channels and reveal a new Nodal-Lefty-Pitx2 asymmetric gene expression-independent mechanism upstream of organ positioning during embryonic left-right patterning. © 2017. Published by The Company of Biologists Ltd.

  7. Persistent discharges in dentate gyrus perisoma-inhibiting interneurons require hyperpolarization-activated cyclic nucleotide-gated channel activation.

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    Elgueta, Claudio; Köhler, Johannes; Bartos, Marlene

    2015-03-11

    Parvalbumin (PV)-expressing perisoma-inhibiting interneurons (PIIs) of the dentate gyrus integrate rapidly correlated synaptic inputs and generate short-duration action potentials that propagate along the axon to their output synapses, supporting fast inhibitory signaling onto their target cells. Here we show that PV-PIIs in rat and mouse dentate gyrus (DG) integrate their intrinsic activity over time and can turn into a persistent firing mode characterized by the ability to generate long-lasting trains of action potentials at ∼50 Hz in the absence of additional inputs. Persistent firing emerges in the axons remote from the axon initial segment and markedly depends on hyperpolarization-activated cyclic nucleotide-gated channel (HCNC) activation. Persistent firing properties are modulated by intracellular Ca(2+) levels and somatic membrane potential. Detailed computational single-cell PIIs models reveal that HCNC-mediated conductances can contribute to persistent firing during conditions of a shift in their voltage activation curve to more depolarized potentials. Paired recordings from PIIs and their target granule cells show that persistent firing supports strong inhibitory output signaling. Thus, persistent firing may emerge during conditions of intense activation of the network, thereby providing silencing to the circuitry and the maintenance of sparse activity in the dentate gyrus. Copyright © 2015 the authors 0270-6474/15/354131-09$15.00/0.

  8. Small functional If current in sinoatrial pacemaker cells of the brown trout (Salmo trutta fario) heart despite strong expression of HCN channel transcripts.

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    Hassinen, Minna; Haverinen, Jaakko; Vornanen, Matti

    2017-12-01

    Funny current ( I f ), formed by hyperpolarization-activated cyclic nucleotide-gated channels (HCN channels), is supposed to be crucial for the membrane clock regulating the cardiac pacemaker mechanism. We examined the presence and activity of HCN channels in the brown trout ( Salmo trutta fario ) sinoatrial (SA) pacemaker cells and their putative role in heart rate ( f H ) regulation. Six HCN transcripts (HCN1, HCN2a, HCN2ba, HCN2bb, HCN3, and HCN4) were expressed in the brown trout heart. The total HCN transcript abundance was 4.0 and 4.9 times higher in SA pacemaker tissue than in atrium and ventricle, respectively. In the SA pacemaker, HCN3 and HCN4 were the main isoforms representing 35.8 ± 2.7 and 25.0 ± 1.5%, respectively, of the total HCN transcripts. Only a small I f with a mean current density of -1.2 ± 0.37 pA/pF at -140 mV was found in 4 pacemaker cells out of 16 spontaneously beating cells examined, despite the optimization of recording conditions for I f activity. I f was not found in any of the 24 atrial myocytes and 21 ventricular myocytes examined. HCN4 coexpressed with the MinK-related peptide 1 (MiRP1) β-subunit in CHO cells generated large I f currents. In contrast, HCN3 (+MiRP1) failed to produce I f in the same expression system. Cs + (2 mM), which blocked 84 ± 12% of the native I f , reversibly reduced f H 19.2 ± 3.6% of the excised multicellular pacemaker tissue from 53 ± 5 to 44 ± 5 beats/min ( P brown trout heart is largely independent on I f . Copyright © 2017 the American Physiological Society.

  9. Novel insights into the distribution of cardiac HCN channels: an expression study in the mouse heart.

    Science.gov (United States)

    Herrmann, Stefan; Layh, Beate; Ludwig, Andreas

    2011-12-01

    HCN pacemaker channels (I(f) channels) are believed to contribute to important functions in the heart; thus these channels became an attractive target for generating transgenic mouse mutants to elucidate their role in physiological and pathophysiological cardiac conditions. A full understanding of cardiac I(f) and the interpretation of studies using HCN mouse mutants require detailed information about the expression profile of the individual HCN subunits. Here we investigate the cardiac expression pattern of the HCN isoforms at the mRNA as well as at the protein level. The specificity of antibodies used was strictly confirmed by the use of HCN1, HCN2 and HCN4 knockout animals. We find a low, but highly differential HCN expression profile outside the cardiac conduction pathway including left and right atria and ventricles. Additionally HCN distribution was investigated in tissue slices of the sinoatrial node, the atrioventricular node, the bundle of His and the bundle branches. The conduction system was marked by acetylcholine esterase staining. HCN4 was confirmed as the predominant isoform of the primary pacemaker followed by a distinct expression of HCN1. In contrast HCN2 shows only a confined expression to individual pacemaker cells. Immunolabeling of the AV-node reveals also a pronounced specificity for HCN1 and HCN4. Compared to the SN and AVN we found a low but selective expression of HCN4 as the only isoform in the atrioventricular bundle. However in the bundle branches HCN1, HCN4 and also HCN2 show a prominent and selective expression pattern. Our results display a characteristic distribution of individual HCN isoforms in several cardiac compartments and reveal that beside HCN4, HCN1 represents the isoform which is selectively expressed in most parts of the conduction system suggesting a substantial contribution of HCN1 to pacemaking. 2011 Elsevier Ltd. All rights reserved.

  10. Niflumic acid alters gating of HCN2 pacemaker channels by interaction with the outer region of S4 voltage sensing domains.

    Science.gov (United States)

    Cheng, Lan; Sanguinetti, Michael C

    2009-05-01

    Niflumic acid, 2-[[3-(trifluoromethyl)phenyl]amino]pyridine-3-carboxylic acid (NFA), is a nonsteroidal anti-inflammatory drug that also blocks or modifies the gating of many ion channels. Here, we investigated the effects of NFA on hyperpolarization-activated cyclic nucleotide-gated cation (HCN) pacemaker channels expressed in X. laevis oocytes using site-directed mutagenesis and the two-electrode voltage-clamp technique. Extracellular NFA acted rapidly and caused a slowing of activation and deactivation and a hyperpolarizing shift in the voltage dependence of HCN2 channel activation (-24.5 +/- 1.2 mV at 1 mM). Slowed channel gating and reduction of current magnitude was marked in oocytes treated with NFA, while clamped at 0 mV but minimal in oocytes clamped at -100 mV, indicating the drug preferentially interacts with channels in the closed state. NFA at 0.1 to 3 mM shifted the half-point for channel activation in a concentration-dependent manner, with an EC(50) of 0.54 +/- 0.068 mM and a predicted maximum shift of -38 mV. NFA at 1 mM also reduced maximum HCN2 conductance by approximately 20%, presumably by direct block of the pore. The rapid onset and state-dependence of NFA-induced changes in channel gating suggests an interaction with the extracellular region of the S4 transmembrane helix, the primary voltage-sensing domain of HCN2. Neutralization (by mutation to Gln) of any three of the outer four basic charged residues in S4, but not single mutations, abrogated the NFA-induced shift in channel activation. We conclude that NFA alters HCN2 gating by interacting with the extracellular end of the S4 voltage sensor domains.

  11. cAMP control of HCN2 channel Mg2+ block reveals loose coupling between the cyclic nucleotide-gating ring and the pore.

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    Alex K Lyashchenko

    Full Text Available Hyperpolarization-activated cyclic nucleotide-regulated HCN channels underlie the Na+-K+ permeable IH pacemaker current. As with other voltage-gated members of the 6-transmembrane KV channel superfamily, opening of HCN channels involves dilation of a helical bundle formed by the intracellular ends of S6 albeit this is promoted by inward, not outward, displacement of S4. Direct agonist binding to a ring of cyclic nucleotide-binding sites, one of which lies immediately distal to each S6 helix, imparts cAMP sensitivity to HCN channel opening. At depolarized potentials, HCN channels are further modulated by intracellular Mg2+ which blocks the open channel pore and blunts the inhibitory effect of outward K+ flux. Here, we show that cAMP binding to the gating ring enhances not only channel opening but also the kinetics of Mg2+ block. A combination of experimental and simulation studies demonstrates that agonist acceleration of block is mediated via acceleration of the blocking reaction itself rather than as a secondary consequence of the cAMP enhancement of channel opening. These results suggest that the activation status of the gating ring and the open state of the pore are not coupled in an obligate manner (as required by the often invoked Monod-Wyman-Changeux allosteric model but couple more loosely (as envisioned in a modular model of protein activation. Importantly, the emergence of second messenger sensitivity of open channel rectification suggests that loose coupling may have an unexpected consequence: it may endow these erstwhile "slow" channels with an ability to exert voltage and ligand-modulated control over cellular excitability on the fastest of physiologically relevant time scales.

  12. Inhibition of GluR Current in Microvilli of Sensory Neurons via Na+-Microdomain Coupling Among GluR, HCN Channel, and Na+/K+ Pump

    Directory of Open Access Journals (Sweden)

    Yasuhiro Kawasaki

    2018-04-01

    Full Text Available Glutamatergic dendritic EPSPs evoked in cortical pyramidal neurons are depressed by activation of hyperpolarization-activated cyclic nucleotide-gated (HCN channels expressed in dendritic spines. This depression has been attributed to shunting effects of HCN current (Ih on input resistance or Ih deactivation. Primary sensory neurons in the rat mesencephalic trigeminal nucleus (MTN have the somata covered by spine-like microvilli that express HCN channels. In rat MTN neurons, we demonstrated that Ih enhancement apparently diminished the glutamate receptor (GluR current (IGluR evoked by puff application of glutamate/AMPA and enhanced a transient outward current following IGluR (OT-IGluR. This suggests that some outward current opposes inward IGluR. The IGluR inhibition displayed a U-shaped voltage-dependence with a minimal inhibition around the resting membrane potential, suggesting that simple shunting effects or deactivation of Ih cannot explain the U-shaped voltage-dependence. Confocal imaging of Na+ revealed that GluR activation caused an accumulation of Na+ in the microvilli, which can cause a negative shift of the reversal potential for Ih (Eh. Taken together, it was suggested that IGluR evoked in MTN neurons is opposed by a transient decrease or increase in standing inward or outward Ih, respectively, both of which can be caused by negative shifts of Eh, as consistent with the U-shaped voltage-dependence of the IGluR inhibition and the OT-IGluR generation. An electron-microscopic immunohistochemical study revealed the colocalization of HCN channels and glutamatergic synapses in microvilli of MTN neurons, which would provide a morphological basis for the functional interaction between HCN and GluR channels. Mathematical modeling eliminated the possibilities of the involvements of Ih deactivation and/or shunting effect and supported the negative shift of Eh which causes the U-shaped voltage-dependent inhibition of IGluR.

  13. Reduced Hyperpolarization-Activated Current Contributes to Enhanced Intrinsic Excitability in Cultured Hippocampal Neurons from PrP(-/-) Mice.

    Science.gov (United States)

    Fan, Jing; Stemkowski, Patrick L; Gandini, Maria A; Black, Stefanie A; Zhang, Zizhen; Souza, Ivana A; Chen, Lina; Zamponi, Gerald W

    2016-01-01

    Genetic ablation of cellular prion protein (PrP(C)) has been linked to increased neuronal excitability and synaptic activity in the hippocampus. We have previously shown that synaptic activity in hippocampi of PrP-null mice is increased due to enhanced N-methyl-D-aspartate receptor (NMDAR) function. Here, we focused on the effect of PRNP gene knock-out (KO) on intrinsic neuronal excitability, and in particular, the underlying ionic mechanism in hippocampal neurons cultured from P0 mouse pups. We found that the absence of PrP(C) profoundly affected the firing properties of cultured hippocampal neurons in the presence of synaptic blockers. The membrane impedance was greater in PrP-null neurons, and this difference was abolished by the hyperpolarization-activated cyclic nucleotide-gated (HCN) channel blocker ZD7288 (100 μM). HCN channel activity appeared to be functionally regulated by PrP(C). The amplitude of voltage sag, a characteristic of activating HCN channel current (I h), was decreased in null mice. Moreover, I h peak current was reduced, along with a hyperpolarizing shift in activation gating and slower kinetics. However, neither HCN1 nor HCN2 formed a biochemical complex with PrP(C). These results suggest that the absence of PrP downregulates the activity of HCN channels through activation of a cell signaling pathway rather than through direct interactions. This in turn contributes to an increase in membrane impedance to potentiate neuronal excitability.

  14. I h and HCN channels in murine spiral ganglion neurons: tonotopic variation, local heterogeneity, and kinetic model.

    Science.gov (United States)

    Liu, Qing; Manis, Paul B; Davis, Robin L

    2014-08-01

    One of the major contributors to the response profile of neurons in the auditory pathways is the I h current. Its properties such as magnitude, activation, and kinetics not only vary among different types of neurons (Banks et al., J Neurophysiol 70:1420-1432, 1993; Fu et al., J Neurophysiol 78:2235-2245, 1997; Bal and Oertel, J Neurophysiol 84:806-817, 2000; Cao and Oertel, J Neurophysiol 94:821-832, 2005; Rodrigues and Oertel, J Neurophysiol 95:76-87, 2006; Yi et al., J Neurophysiol 103:2532-2543, 2010), but they also display notable diversity in a single population of spiral ganglion neurons (Mo and Davis, J Neurophysiol 78:3019-3027, 1997), the first neural element in the auditory periphery. In this study, we found from somatic recordings that part of the heterogeneity can be attributed to variation along the tonotopic axis because I h in the apical neurons have more positive half-activation voltage levels than basal neurons. Even within a single cochlear region, however, I h current properties are not uniform. To account for this heterogeneity, we provide immunocytochemical evidence for variance in the intracellular density of the hyperpolarization-activated cyclic nucleotide-gated channel α-subunit 1 (HCN1), which mediates I h current. We also observed different combinations of HCN1 and HCN4 α-subunits from cell to cell. Lastly, based on the physiological data, we performed kinetic analysis for the I h current and generated a mathematical model to better understand varied I h on spiral ganglion function. Regardless of whether I h currents are recorded at the nerve terminals (Yi et al., J Neurophysiol 103:2532-2543, 2010) or at the somata of spiral ganglion neurons, they have comparable mean half-activation voltage and induce similar resting membrane potential changes, and thus our model may also provide insights into the impact of I h on synaptic physiology.

  15. HCN Channels—Modulators of Cardiac and Neuronal Excitability

    Directory of Open Access Journals (Sweden)

    Stefan Herrmann

    2015-01-01

    Full Text Available Hyperpolarization-activated cyclic nucleotide-gated (HCN channels comprise a family of cation channels activated by hyperpolarized membrane potentials and stimulated by intracellular cyclic nucleotides. The four members of this family, HCN1–4, show distinct biophysical properties which are most evident in the kinetics of activation and deactivation, the sensitivity towards cyclic nucleotides and the modulation by tyrosine phosphorylation. The four isoforms are differentially expressed in various excitable tissues. This review will mainly focus on recent insights into the functional role of the channels apart from their classic role as pacemakers. The importance of HCN channels in the cardiac ventricle and ventricular hypertrophy will be discussed. In addition, their functional significance in the peripheral nervous system and nociception will be examined. The data, which are mainly derived from studies using transgenic mice, suggest that HCN channels contribute significantly to cellular excitability in these tissues. Remarkably, the impact of the channels is clearly more pronounced in pathophysiological states including ventricular hypertrophy as well as neural inflammation and neuropathy suggesting that HCN channels may constitute promising drug targets in the treatment of these conditions. This perspective as well as the current therapeutic use of HCN blockers will also be addressed.

  16. Cell-Type Specific Development of the Hyperpolarization-Activated Current, Ih, in Prefrontal Cortical Neurons

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    Sha-Sha Yang

    2018-05-01

    Full Text Available H-current, also known as hyperpolarization-activated current (Ih, is an inward current generated by the hyperpolarization-activated cyclic nucleotide-gated (HCN cation channels. Ih plays an essential role in regulating neuronal properties, synaptic integration and plasticity, and synchronous activity in the brain. As these biological factors change across development, the brain undergoes varying levels of vulnerability to disorders like schizophrenia that disrupt prefrontal cortex (PFC-dependent function. However, developmental changes in Ih in PFC neurons remains untested. Here, we examine Ih in pyramidal neurons vs. gamma-aminobutyric acid (GABAergic parvalbumin-expressing (PV+ interneurons in developing mouse PFC. Our findings show that the amplitudes of Ih in these cell types are identical during the juvenile period but differ at later time points. In pyramidal neurons, Ih amplitude significantly increases from juvenile to adolescence and follows a similar trend into adulthood. In contrast, the amplitude of Ih in PV+ interneurons decreases from juvenile to adolescence, and does not change from adolescence to adulthood. Moreover, the kinetics of HCN channels in pyramidal neurons is significantly slower than in PV+ interneurons, with a gradual decrease in pyramidal neurons and a gradual increase in PV+ cells across development. Our study reveals distinct developmental trajectories of Ih in pyramidal neurons and PV+ interneurons. The cell-type specific alteration of Ih during the critical period from juvenile to adolescence reflects the contribution of Ih to the maturation of the PFC and PFC-dependent function. These findings are essential for a better understanding of normal PFC function, and for elucidating Ih’s crucial role in the pathophysiology of neurodevelopmental disorders.

  17. Modulation of rod photoreceptor output by HCN1 channels is essential for regular mesopic cone vision.

    Science.gov (United States)

    Seeliger, Mathias W; Brombas, Arne; Weiler, Reto; Humphries, Peter; Knop, Gabriel; Tanimoto, Naoyuki; Müller, Frank

    2011-11-08

    Retinal photoreceptors permit visual perception over a wide range of lighting conditions. Rods work best in dim, and cones in bright environments, with considerable functional overlap at intermediate (mesopic) light levels. At many sites in the outer and inner retina where rod and cone signals interact, gap junctions, particularly those containing Connexin36, have been identified. However, little is known about the dynamic processes associated with the convergence of rod and cone system signals into ON- and OFF-pathways. Here we show that proper cone vision under mesopic conditions requires rapid adaptational feedback modulation of rod output via hyperpolarization-activated and cyclic nucleotide-gated channels 1. When these channels are absent, sustained rod responses following bright light exposure saturate the retinal network, resulting in a loss of downstream cone signalling. By specific genetic and pharmacological ablation of key signal processing components, regular cone signalling can be restored, thereby identifying the sites involved in functional rod-cone interactions.

  18. Competition between abstraction and exchange channels in H + HCN reaction: Full-dimensional quantum dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Bin; Guo, Hua, E-mail: hguo@unm.edu [Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131 (United States)

    2013-12-14

    Dynamics of the title reaction is investigated on an ab initio based potential energy surface using a full-dimensional quantum wave packet method within the centrifugal sudden approximation. It is shown that the reaction between H and HCN leads to both the hydrogen exchange and hydrogen abstraction channels. The exchange channel has a lower threshold and larger cross section than the abstraction channel. It also has more oscillations due apparently to quantum resonances. Both channels are affected by long-lived resonances supported by potential wells. Comparison with experimental cross sections indicates underestimation of the abstraction barrier height.

  19. Hyperpolarization-activated current (In is reduced in hippocampal neurons from Gabra5-/- mice.

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    Robert P Bonin

    Full Text Available Changes in the expression of γ-aminobutyric acid type A (GABAA receptors can either drive or mediate homeostatic alterations in neuronal excitability. A homeostatic relationship between α5 subunit-containing GABAA (α5GABAA receptors that generate a tonic inhibitory conductance, and HCN channels that generate a hyperpolarization-activated cation current (Ih was recently described for cortical neurons, where a reduction in Ih was accompanied by a reciprocal increase in the expression of α5GABAA receptors resulting in the preservation of dendritosomatic synaptic function. Here, we report that in mice that lack the α5 subunit gene (Gabra5-/-, cultured embryonic hippocampal pyramidal neurons and ex vivo CA1 hippocampal neurons unexpectedly exhibited a decrease in Ih current density (by 40% and 28%, respectively, compared with neurons from wild-type (WT mice. The resting membrane potential and membrane hyperpolarization induced by blockade of Ih with ZD-7288 were similar in cultured WT and Gabra5-/- neurons. In contrast, membrane hyperpolarization measured after a train of action potentials was lower in Gabra5-/- neurons than in WT neurons. Also, membrane impedance measured in response to low frequency stimulation was greater in cultured Gabra5-/- neurons. Finally, the expression of HCN1 protein that generates Ih was reduced by 41% in the hippocampus of Gabra5-/- mice. These data indicate that loss of a tonic GABAergic inhibitory conductance was followed by a compensatory reduction in Ih. The results further suggest that the maintenance of resting membrane potential is preferentially maintained in mature and immature hippocampal neurons through the homeostatic co-regulation of structurally and biophysically distinct cation and anion channels.

  20. Structural Changes and Lack of HCN1 Channels in the Binaural Auditory Brainstem of the Naked Mole-Rat (Heterocephalus glaber).

    Science.gov (United States)

    Gessele, Nikodemus; Garcia-Pino, Elisabet; Omerbašić, Damir; Park, Thomas J; Koch, Ursula

    2016-01-01

    Naked mole-rats (Heterocephalus glaber) live in large eu-social, underground colonies in narrow burrows and are exposed to a large repertoire of communication signals but negligible binaural sound localization cues, such as interaural time and intensity differences. We therefore asked whether monaural and binaural auditory brainstem nuclei in the naked mole-rat are differentially adjusted to this acoustic environment. Using antibody stainings against excitatory and inhibitory presynaptic structures, namely the vesicular glutamate transporter VGluT1 and the glycine transporter GlyT2 we identified all major auditory brainstem nuclei except the superior paraolivary nucleus in these animals. Naked mole-rats possess a well structured medial superior olive, with a similar synaptic arrangement to interaural-time-difference encoding animals. The neighboring lateral superior olive, which analyzes interaural intensity differences, is large and elongated, whereas the medial nucleus of the trapezoid body, which provides the contralateral inhibitory input to these binaural nuclei, is reduced in size. In contrast, the cochlear nucleus, the nuclei of the lateral lemniscus and the inferior colliculus are not considerably different when compared to other rodent species. Most interestingly, binaural auditory brainstem nuclei lack the membrane-bound hyperpolarization-activated channel HCN1, a voltage-gated ion channel that greatly contributes to the fast integration times in binaural nuclei of the superior olivary complex in other species. This suggests substantially lengthened membrane time constants and thus prolonged temporal integration of inputs in binaural auditory brainstem neurons and might be linked to the severely degenerated sound localization abilities in these animals.

  1. Structural Changes and Lack of HCN1 Channels in the Binaural Auditory Brainstem of the Naked Mole-Rat (Heterocephalus glaber.

    Directory of Open Access Journals (Sweden)

    Nikodemus Gessele

    Full Text Available Naked mole-rats (Heterocephalus glaber live in large eu-social, underground colonies in narrow burrows and are exposed to a large repertoire of communication signals but negligible binaural sound localization cues, such as interaural time and intensity differences. We therefore asked whether monaural and binaural auditory brainstem nuclei in the naked mole-rat are differentially adjusted to this acoustic environment. Using antibody stainings against excitatory and inhibitory presynaptic structures, namely the vesicular glutamate transporter VGluT1 and the glycine transporter GlyT2 we identified all major auditory brainstem nuclei except the superior paraolivary nucleus in these animals. Naked mole-rats possess a well structured medial superior olive, with a similar synaptic arrangement to interaural-time-difference encoding animals. The neighboring lateral superior olive, which analyzes interaural intensity differences, is large and elongated, whereas the medial nucleus of the trapezoid body, which provides the contralateral inhibitory input to these binaural nuclei, is reduced in size. In contrast, the cochlear nucleus, the nuclei of the lateral lemniscus and the inferior colliculus are not considerably different when compared to other rodent species. Most interestingly, binaural auditory brainstem nuclei lack the membrane-bound hyperpolarization-activated channel HCN1, a voltage-gated ion channel that greatly contributes to the fast integration times in binaural nuclei of the superior olivary complex in other species. This suggests substantially lengthened membrane time constants and thus prolonged temporal integration of inputs in binaural auditory brainstem neurons and might be linked to the severely degenerated sound localization abilities in these animals.

  2. De novo mutations in HCN1 cause early infantile epileptic encephalopathy.

    Science.gov (United States)

    Nava, Caroline; Dalle, Carine; Rastetter, Agnès; Striano, Pasquale; de Kovel, Carolien G F; Nabbout, Rima; Cancès, Claude; Ville, Dorothée; Brilstra, Eva H; Gobbi, Giuseppe; Raffo, Emmanuel; Bouteiller, Delphine; Marie, Yannick; Trouillard, Oriane; Robbiano, Angela; Keren, Boris; Agher, Dahbia; Roze, Emmanuel; Lesage, Suzanne; Nicolas, Aude; Brice, Alexis; Baulac, Michel; Vogt, Cornelia; El Hajj, Nady; Schneider, Eberhard; Suls, Arvid; Weckhuysen, Sarah; Gormley, Padhraig; Lehesjoki, Anna-Elina; De Jonghe, Peter; Helbig, Ingo; Baulac, Stéphanie; Zara, Federico; Koeleman, Bobby P C; Haaf, Thomas; LeGuern, Eric; Depienne, Christel

    2014-06-01

    Hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels contribute to cationic Ih current in neurons and regulate the excitability of neuronal networks. Studies in rat models have shown that the Hcn1 gene has a key role in epilepsy, but clinical evidence implicating HCN1 mutations in human epilepsy is lacking. We carried out exome sequencing for parent-offspring trios with fever-sensitive, intractable epileptic encephalopathy, leading to the discovery of two de novo missense HCN1 mutations. Screening of follow-up cohorts comprising 157 cases in total identified 4 additional amino acid substitutions. Patch-clamp recordings of Ih currents in cells expressing wild-type or mutant human HCN1 channels showed that the mutations had striking but divergent effects on homomeric channels. Individuals with mutations had clinical features resembling those of Dravet syndrome with progression toward atypical absences, intellectual disability and autistic traits. These findings provide clear evidence that de novo HCN1 point mutations cause a recognizable early-onset epileptic encephalopathy in humans.

  3. HCN channels segregate stimulation‐evoked movement responses in neocortex and allow for coordinated forelimb movements in rodents

    Science.gov (United States)

    Farrell, Jordan S.; Palmer, Laura A.; Singleton, Anna C.; Pittman, Quentin J.; Teskey, G. Campbell

    2016-01-01

    Key points The present study tested whether HCN channels contribute to the organization of motor cortex and to skilled motor behaviour during a forelimb reaching task.Experimental reductions in HCN channel signalling increase the representation of complex multiple forelimb movements in motor cortex as assessed by intracortical microstimulation.Global HCN1KO mice exhibit reduced reaching accuracy and atypical movements during a single‐pellet reaching task relative to wild‐type controls.Acute pharmacological inhibition of HCN channels in forelimb motor cortex decreases reaching accuracy and increases atypical movements during forelimb reaching. Abstract The mechanisms by which distinct movements of a forelimb are generated from the same area of motor cortex have remained elusive. Here we examined a role for HCN channels, given their ability to alter synaptic integration, in the expression of forelimb movement responses during intracortical microstimulation (ICMS) and movements of the forelimb on a skilled reaching task. We used short‐duration high‐resolution ICMS to evoke forelimb movements following pharmacological (ZD7288), experimental (electrically induced cortical seizures) or genetic approaches that we confirmed with whole‐cell patch clamp to substantially reduce I h current. We observed significant increases in the number of multiple movement responses evoked at single sites in motor maps to all three experimental manipulations in rats or mice. Global HCN1 knockout mice were less successful and exhibited atypical movements on a skilled‐motor learning task relative to wild‐type controls. Furthermore, in reaching‐proficient rats, reaching accuracy was reduced and forelimb movements were altered during infusion of ZD7288 within motor cortex. Thus, HCN channels play a critical role in the separation of overlapping movement responses and allow for successful reaching behaviours. These data provide a novel mechanism for the encoding of multiple

  4. Long-lasting spatial learning and memory impairments caused by chronic cerebral hypoperfusion associate with a dynamic change of HCN1/HCN2 expression in hippocampal CA1 region.

    Science.gov (United States)

    Luo, Pan; Lu, Yun; Li, Changjun; Zhou, Mei; Chen, Cheng; Lu, Qing; Xu, Xulin; He, Zhi; Guo, Lianjun

    2015-09-01

    Chronic cerebral hypoperfusion (CCH) causes learning and memory impairments and increases the risk of Alzheimer disease (AD) and vascular dementia (VD) through several biologically plausible pathways, yet the mechanisms underlying the disease process remained unclear particularly in a temporal manner. We performed permanent bilateral occlusion of the common carotid arteries (two-vessel occlusion, 2VO) to induce CCH. To determine whether hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are altered at different stages of cognitive impairment caused by CCH, adult male SD rats were randomly distributed into sham-operated 4, 8 and 12weeks group, 2VO 4, 8 and 12weeks group. Learning and memory performance were evaluated with Morris water maze (MWM) and long-term potentiation (LTP) was used to address the underlying synaptic mechanisms. Expression of NeuN, HCN1 and HCN2 in hippocampal CA1, DG and CA3 areas was quantified by immunohistochemistry and western blotting. Our data showed that CCH induced a remarkable spatial learning and memory deficits in rats of 2VO 4, 8, and 12weeks group although neuronal loss only occurred after 4weeks of 2VO surgery in CA1. In addition, a significant reduction of HCN1 surface expression in CA1 was observed in the group that suffered 4weeks ischemia but neither 8 nor 12weeks. However, HCN2 surface expression in CA1 increased throughout the ischemia time-scales (4, 8 and 12w). Our findings indicate spatial learning and memory deficits in the CCH model are associated with disturbed HCN1 and HCN2 surface expression in hippocampal CA1. The altered patterns of both HCN1 and HCN2 surface expression may be implicated in the early stage (4w) of spatial learning and memory impairments; and the stable and long-lasting impairments of spatial learning and memory may partially attribute to the up-regulated HCN2 surface expression. Copyright © 2015 Elsevier Inc. All rights reserved.

  5. Gain-of-function HCN2 variants in genetic epilepsy.

    Science.gov (United States)

    Li, Melody; Maljevic, Snezana; Phillips, A Marie; Petrovski, Slave; Hildebrand, Michael S; Burgess, Rosemary; Mount, Therese; Zara, Federico; Striano, Pasquale; Schubert, Julian; Thiele, Holger; Nürnberg, Peter; Wong, Michael; Weisenberg, Judith L; Thio, Liu Lin; Lerche, Holger; Scheffer, Ingrid E; Berkovic, Samuel F; Petrou, Steven; Reid, Christopher A

    2018-02-01

    Genetic generalized epilepsy (GGE) is a common epilepsy syndrome that encompasses seizure disorders characterized by spike-and-wave discharges (SWDs). Pacemaker hyperpolarization-activated cyclic nucleotide-gated channels (HCN) are considered integral to SWD genesis, making them an ideal gene candidate for GGE. We identified HCN2 missense variants from a large cohort of 585 GGE patients, recruited by the Epilepsy Phenome-Genome Project (EPGP), and performed functional analysis using two-electrode voltage clamp recordings from Xenopus oocytes. The p.S632W variant was identified in a patient with idiopathic photosensitive occipital epilepsy and segregated in the family. This variant was also independently identified in an unrelated patient with childhood absence seizures from a European cohort of 238 familial GGE cases. The p.V246M variant was identified in a patient with photo-sensitive GGE and his father diagnosed with juvenile myoclonic epilepsy. Functional studies revealed that both p.S632W and p.V246M had an identical functional impact including a depolarizing shift in the voltage dependence of activation that is consistent with a gain-of-function. In contrast, no biophysical changes resulted from the introduction of common population variants, p.E280K and p.A705T, and the p.R756C variant from EPGP that did not segregate with disease. Our data suggest that HCN2 variants can confer susceptibility to GGE via a gain-of-function mechanism. © 2017 Wiley Periodicals, Inc.

  6. Noise-induced plasticity of KCNQ2/3 and HCN channels underlies vulnerability and resilience to tinnitus

    Science.gov (United States)

    Li, Shuang; Kalappa, Bopanna I; Tzounopoulos, Thanos

    2015-01-01

    Vulnerability to noise-induced tinnitus is associated with increased spontaneous firing rate in dorsal cochlear nucleus principal neurons, fusiform cells. This hyperactivity is caused, at least in part, by decreased Kv7.2/3 (KCNQ2/3) potassium currents. However, the biophysical mechanisms underlying resilience to tinnitus, which is observed in noise-exposed mice that do not develop tinnitus (non-tinnitus mice), remain unknown. Our results show that noise exposure induces, on average, a reduction in KCNQ2/3 channel activity in fusiform cells in noise-exposed mice by 4 days after exposure. Tinnitus is developed in mice that do not compensate for this reduction within the next 3 days. Resilience to tinnitus is developed in mice that show a re-emergence of KCNQ2/3 channel activity and a reduction in HCN channel activity. Our results highlight KCNQ2/3 and HCN channels as potential targets for designing novel therapeutics that may promote resilience to tinnitus. DOI: http://dx.doi.org/10.7554/eLife.07242.001 PMID:26312501

  7. Genetic Perturbations Suggest a Role of the Resting Potential in Regulating the Expression of the Ion Channels of the KCNA and HCN families in Octopus Cells of the Ventral Cochlear Nucleus

    Science.gov (United States)

    Cao, Xiao-Jie; Oertel, Donata

    2017-01-01

    Low-voltage-activated K+ (gKL) and hyperpolarization-activated mixed cation conductances (gh) mediate currents, IKL and Ih, through channels of the Kv1 (KCNA) and HCN families respectively and give auditory neurons the temporal precision required for signaling information about the onset, fine structure, and time of arrival of sounds. Being partially activated at rest, gKL and gh contribute to the resting potential and shape responses to even small subthreshold synaptic currents. Resting gKL and gh also affect the coupling of somatic depolarization with the generation of action potentials. To learn how these important conductances are regulated we have investigated how genetic perturbations affect their expression in octopus cells of the ventral cochlear nucleus (VCN). We report five new findings: First, the magnitude of gh and gKL varied over more than two-fold between wild type strains of mice. Second, average resting potentials are not different in different strains of mice even in the face of large differences in average gKL and gh. Third, IKL has two components, one being α-dendrotoxin (α-DTX)-sensitive and partially inactivating and the other being α-DTX-insensitive, tetraethylammonium (TEA)-sensitive, and non-inactivating. Fourth, the loss of Kv1.1 results in diminution of the α-DTX-sensitive IKL, and compensatory increased expression of an α-DTX-insensitive, tetraethylammonium (TEA)-sensitive IKL. Fifth, Ih and IKL are balanced at the resting potential in all wild type and mutant octopus cells even when resting potentials vary in individual cells over nearly 10 mV, indicating that the resting potential influences the expression of gh and gKL. The independence of resting potentials on gKL and gh shows that gKL and gh do not, over days or weeks, determine the resting potential but rather that the resting potential plays a role in regulating the magnitude of either or both gKL and gh. PMID:28065805

  8. Kir2.1 channels set two levels of resting membrane potential with inward rectification.

    Science.gov (United States)

    Chen, Kuihao; Zuo, Dongchuan; Liu, Zheng; Chen, Haijun

    2018-04-01

    Strong inward rectifier K + channels (Kir2.1) mediate background K + currents primarily responsible for maintenance of resting membrane potential. Multiple types of cells exhibit two levels of resting membrane potential. Kir2.1 and K2P1 currents counterbalance, partially accounting for the phenomenon of human cardiomyocytes in subphysiological extracellular K + concentrations or pathological hypokalemic conditions. The mechanism of how Kir2.1 channels contribute to the two levels of resting membrane potential in different types of cells is not well understood. Here we test the hypothesis that Kir2.1 channels set two levels of resting membrane potential with inward rectification. Under hypokalemic conditions, Kir2.1 currents counterbalance HCN2 or HCN4 cation currents in CHO cells that heterologously express both channels, generating N-shaped current-voltage relationships that cross the voltage axis three times and reconstituting two levels of resting membrane potential. Blockade of HCN channels eliminated the phenomenon in K2P1-deficient Kir2.1-expressing human cardiomyocytes derived from induced pluripotent stem cells or CHO cells expressing both Kir2.1 and HCN2 channels. Weakly inward rectifier Kir4.1 or inward rectification-deficient Kir2.1•E224G mutant channels do not set such two levels of resting membrane potential when co-expressed with HCN2 channels in CHO cells or when overexpressed in human cardiomyocytes derived from induced pluripotent stem cells. These findings demonstrate a common mechanism that Kir2.1 channels set two levels of resting membrane potential with inward rectification by balancing inward currents through different cation channels such as hyperpolarization-activated HCN channels or hypokalemia-induced K2P1 leak channels.

  9. Targeting miR-423-5p Reverses Exercise Training-Induced HCN4 Channel Remodeling and Sinus Bradycardia

    DEFF Research Database (Denmark)

    D'Souza, Alicia; Pearman, Charles M.; Wang, Yanwen

    2017-01-01

    -generation sequencing and quantitative real-time reverse transcription polymerase chain reaction showed remodeling of miRs in the sinus node of swim-trained mice. Computational predictions highlighted a prominent role for miR-423-5p. Interaction between miR-423-5p and HCN4 was confirmed by a dose-dependent reduction...

  10. Enhancement of Spontaneous Activity by HCN4 Overexpression in Mouse Embryonic Stem Cell-Derived Cardiomyocytes - A Possible Biological Pacemaker.

    Directory of Open Access Journals (Sweden)

    Yukihiro Saito

    Full Text Available Establishment of a biological pacemaker is expected to solve the persisting problems of a mechanical pacemaker including the problems of battery life and electromagnetic interference. Enhancement of the funny current (If flowing through hyperpolarization-activated cyclic nucleotide-gated (HCN channels and attenuation of the inward rectifier K+ current (IK1 flowing through inward rectifier potassium (Kir channels are essential for generation of a biological pacemaker. Therefore, we generated HCN4-overexpressing mouse embryonic stem cells (mESCs and induced cardiomyocytes that originally show poor IK1 currents, and we investigated whether the HCN4-overexpressing mESC-derived cardiomyocytes (mESC-CMs function as a biological pacemaker in vitro.The rabbit Hcn4 gene was transfected into mESCs, and stable clones were selected. mESC-CMs were generated via embryoid bodies and purified under serum/glucose-free and lactate-supplemented conditions. Approximately 90% of the purified cells were troponin I-positive by immunostaining. In mESC-CMs, expression level of the Kcnj2 gene encoding Kir2.1, which is essential for generation of IK1 currents that are responsible for stabilizing the resting membrane potential, was lower than that in an adult mouse ventricle. HCN4-overexpressing mESC-CMs expressed about a 3-times higher level of the Hcn4 gene than did non-overexpressing mESC-CMs. Expression of the Cacna1h gene, which encodes T-type calcium channel and generates diastolic depolarization in the sinoatrial node, was also confirmed. Additionally, genes required for impulse conduction including Connexin40, Connexin43, and Connexin45 genes, which encode connexins forming gap junctions, and the Scn5a gene, which encodes sodium channels, are expressed in the cells. HCN4-overexpressing mESC-CMs showed significantly larger If currents and more rapid spontaneous beating than did non-overexpressing mESC-CMs. The beating rate of HCN4-overexpressing mESC-CMs responded

  11. Qualification of a Multi-Channel Infrared Laser Absorption Spectrometer for Monitoring CO, HCl, HCN, HF, and CO2 Aboard Manned Spacecraft

    Science.gov (United States)

    Briggs, Ryan M.; Frez, Clifford; Forouhar, Siamak; May, Randy D.; Meyer, Marit E.; Kulis, Michael J.; Berger, Gordon M.

    2015-01-01

    Monitoring of specific combustion products can provide early-warning detection of accidental fires aboard manned spacecraft and also identify the source and severity of combustion events. Furthermore, quantitative in situ measurements are important for gauging levels of exposure to hazardous gases, particularly on long-duration missions where analysis of returned samples becomes impractical. Absorption spectroscopy using tunable laser sources in the 2 to 5 micrometer wavelength range enables accurate, unambiguous detection of CO, HCl, HCN, HF, and CO2, which are produced in varying amounts through the heating of electrical components and packaging materials commonly used aboard spacecraft. Here, we report on calibration and testing of a five-channel laser absorption spectrometer designed to accurately monitor ambient gas-phase concentrations of these five compounds, with low-level detection limits based on the Spacecraft Maximum Allowable Concentrations. The instrument employs a two-pass absorption cell with a total optical pathlength of 50 cm and a dedicated infrared semiconductor laser source for each target gas. We present results from testing the five-channel sensor in the presence of trace concentrations of the target compounds that were introduced using both gas sources and oxidative pyrolysis (non-flaming combustion) of solid material mixtures.

  12. Fluoxetine ameliorates cognitive impairments induced by chronic cerebral hypoperfusion via down-regulation of HCN2 surface expression in the hippocampal CA1 area in rats.

    Science.gov (United States)

    Luo, Pan; Zhang, Xiaoxue; Lu, Yun; Chen, Cheng; Li, Changjun; Zhou, Mei; Lu, Qing; Xu, Xulin; Shen, Guanxin; Guo, Lianjun

    2016-01-01

    Chronic cerebral hypoperfusion (CCH) causes cognitive impairments and increases the risk of Alzheimer's disease (AD) and vascular dementia (VD) through several biologically plausible pathways, yet the underlying neurobiological mechanisms are still poorly understood. In this study, we investigated whether fluoxetine, a selective serotonin reuptake inhibitor (SSRI), could play a neuroprotective role against chronic cerebral hypoperfusion injury and to clarify underlying mechanisms of its efficacy. Rats were subjected to permanent bilateral occlusion of the common carotid arteries (two-vessel occlusion, 2VO). Two weeks later, rats were treated with 30 mg/kg fluoxetine (intragastric injection, i.g.) for 6 weeks. Cognitive function was evaluated by Morris water maze (MWM) and novel objects recognition (NOR) test. Long-term potentiation (LTP) was used to address the underlying synaptic mechanisms. Western blotting was used to quantify the protein levels. Our results showed that fluoxetine treatment significantly improved the cognitive impairments caused by 2VO, accompanied with a reversion of 2VO-induced inhibitory of LTP. Furthermore, 2VO caused an up-regulation of hyperpolarization-activated cyclic nucleotide-gated channel 2 (HCN2) surface expressions in the hippocampal CA1 area and fluoxetine also effectively recovered the disorder of HCN2 surface expressions, which may be a possible mechanism that fluoxetine treatment ameliorates cognitive impairments in rats with CCH. Copyright © 2015 Elsevier Inc. All rights reserved.

  13. Rates and equilibrium constants of the ligand-induced conformational transition of an HCN ion channel protein domain determined by DEER spectroscopy.

    Science.gov (United States)

    Collauto, Alberto; DeBerg, Hannah A; Kaufmann, Royi; Zagotta, William N; Stoll, Stefan; Goldfarb, Daniella

    2017-06-14

    Ligand binding can induce significant conformational changes in proteins. The mechanism of this process couples equilibria associated with the ligand binding event and the conformational change. Here we show that by combining the application of W-band double electron-electron resonance (DEER) spectroscopy with microfluidic rapid freeze quench (μRFQ) it is possible to resolve these processes and obtain both equilibrium constants and reaction rates. We studied the conformational transition of the nitroxide labeled, isolated carboxy-terminal cyclic-nucleotide binding domain (CNBD) of the HCN2 ion channel upon binding of the ligand 3',5'-cyclic adenosine monophosphate (cAMP). Using model-based global analysis, the time-resolved data of the μRFQ DEER experiments directly provide fractional populations of the open and closed conformations as a function of time. We modeled the ligand-induced conformational change in the protein using a four-state model: apo/open (AO), apo/closed (AC), bound/open (BO), bound/closed (BC). These species interconvert according to AC + L ⇌ AO + L ⇌ BO ⇌ BC. By analyzing the concentration dependence of the relative contributions of the closed and open conformations at equilibrium, we estimated the equilibrium constants for the two conformational equilibria and the open-state ligand dissociation constant. Analysis of the time-resolved μRFQ DEER data gave estimates for the intrinsic rates of ligand binding and unbinding as well as the rates of the conformational change. This demonstrates that DEER can quantitatively resolve both the thermodynamics and the kinetics of ligand binding and the associated conformational change.

  14. Biomolecules from HCN

    Science.gov (United States)

    Ferris, J. P.; Wos, J. D.; Ryan, T. J.; Lobo, A. P.; Donner, D. B.

    1974-01-01

    It has been suggested by Sanchez et al. (1967) that HCN might have been one of the more important precursors of biological molecules on the primitive earth. Studies were conducted to determine the mechanisms involved in HCN oligomerizations in dilute aqueous solutions and to identify the compounds which are produced in these oligomerization mixtures. Indirect evidence for the formation of cyanate was obtained along with direct evidence for the formation of citrulline, aspartic acid, and orotic acid.

  15. Retinal Cyclic Nucleotide-Gated Channels: From Pathophysiology to Therapy

    Directory of Open Access Journals (Sweden)

    Stylianos Michalakis

    2018-03-01

    Full Text Available The first step in vision is the absorption of photons by the photopigments in cone and rod photoreceptors. After initial amplification within the phototransduction cascade the signal is translated into an electrical signal by the action of cyclic nucleotide-gated (CNG channels. CNG channels are ligand-gated ion channels that are activated by the binding of cyclic guanosine monophosphate (cGMP or cyclic adenosine monophosphate (cAMP. Retinal CNG channels transduce changes in intracellular concentrations of cGMP into changes of the membrane potential and the Ca2+ concentration. Structurally, the CNG channels belong to the superfamily of pore-loop cation channels and share a common gross structure with hyperpolarization-activated cyclic nucleotide-gated (HCN channels and voltage-gated potassium channels (KCN. In this review, we provide an overview on the molecular properties of CNG channels and describe their physiological role in the phototransduction pathways. We also discuss insights into the pathophysiological role of CNG channel proteins that have emerged from the analysis of CNG channel-deficient animal models and human CNG channelopathies. Finally, we summarize recent gene therapy activities and provide an outlook for future clinical application.

  16. Sick sinus syndrome in HCN1-deficient mice.

    Science.gov (United States)

    Fenske, Stefanie; Krause, Stefanie C; Hassan, Sami I H; Becirovic, Elvir; Auer, Franziska; Bernard, Rebekka; Kupatt, Christian; Lange, Philipp; Ziegler, Tilman; Wotjak, Carsten T; Zhang, Henggui; Hammelmann, Verena; Paparizos, Christos; Biel, Martin; Wahl-Schott, Christian A

    2013-12-17

    Sinus node dysfunction (SND) is a major clinically relevant disease that is associated with sudden cardiac death and requires surgical implantation of electric pacemaker devices. Frequently, SND occurs in heart failure and hypertension, conditions that lead to electric instability of the heart. Although the pathologies of acquired SND have been studied extensively, little is known about the molecular and cellular mechanisms that cause congenital SND. Here, we show that the HCN1 protein is highly expressed in the sinoatrial node and is colocalized with HCN4, the main sinoatrial pacemaker channel isoform. To characterize the cardiac phenotype of HCN1-deficient mice, a detailed functional characterization of pacemaker mechanisms in single isolated sinoatrial node cells, explanted beating sinoatrial node preparation, telemetric in vivo electrocardiography, echocardiography, and in vivo electrophysiology was performed. On the basis of these experiments we demonstrate that mice lacking the pacemaker channel HCN1 display congenital SND characterized by bradycardia, sinus dysrhythmia, prolonged sinoatrial node recovery time, increased sinoatrial conduction time, and recurrent sinus pauses. As a consequence of SND, HCN1-deficient mice display a severely reduced cardiac output. We propose that HCN1 stabilizes the leading pacemaker region within the sinoatrial node and hence is crucial for stable heart rate and regular beat-to-beat variation. Furthermore, we suggest that HCN1-deficient mice may be a valuable genetic disease model for human SND.

  17. Dual Regulation of Voltage-Sensitive Ion Channels by PIP2

    Directory of Open Access Journals (Sweden)

    Aldo A Rodríguez Menchaca

    2012-09-01

    Full Text Available Over the past 16 years, there has been an impressive number of ion channels shown to be sensitive to the major phosphoinositide in the plasma membrane, phosphatidilinositol 4,5-bisphosphate (PIP2. Among them are voltage-gated channels, which are crucial for both neuronal and cardiac excitability. Voltage-gated calcium (Cav channels were shown to be regulated bidirectionally by PIP2. On one hand, PIP2 stabilized their activity by reducing current rundown but on the other hand it produced a voltage-dependent inhibition by shifting the activation curve to more positive voltages. For voltage-gated potassium (Kv channels PIP2 was first shown to prevent N-type inactivation. Careful examination of the effects of PIP2 on the activation mechanism of Kv1.2 has shown a similar bidirectional regulation as in the Cav channels. The two effects could be distinguished kinetically, in terms of their sensitivities to PIP2 and by distinct molecular determinants. The rightward shift of the Kv1.2 voltage dependence implicated basic residues in the S4-S5 linker and was consistent with stabilization of the inactive state of the voltage sensor. A third type of a voltage-gated ion channel modulated by PIP2 is the hyperpolarization-activated cyclic nucleotide-gated (HCN channel. PIP2 has been shown to enhance the opening of HCN channels by shifting their voltage-dependent activation toward depolarized potentials. The sea urchin HCN channel, SpIH, showed again a PIP2-mediated bidirectional effect but in reverse order than the depolarization-activated Cav and Kv channels: a voltage-dependent potentiation, like the mammalian HCN channels, but also an inhibition of the cGMP-induced current activation. Just like the Kv1.2 channels, distinct molecular determinants underlied the PIP2 dual effects on SpIH channels. The dual regulation of these very different ion channels, all of which are voltage dependent, points to conserved mechanisms of regulation of these channels by PIP2.

  18. The Hyperpolarization-Activated Current Determines Synaptic Excitability, Calcium Activity and Specific Viability of Substantia Nigra Dopaminergic Neurons

    Directory of Open Access Journals (Sweden)

    Carmen Carbone

    2017-06-01

    Full Text Available Differential vulnerability between Substantia Nigra pars compacta (SNpc and Ventral Tegmental Area (VTA dopaminergic (DAergic neurons is a hallmark of Parkinson’s disease (PD. Understanding the molecular bases of this key histopathological aspect would foster the development of much-needed disease-modifying therapies. Non-heterogeneous DAergic degeneration is present in both toxin-based and genetic animal models, suggesting that cellular specificity, rather than causing factors, constitutes the background for differential vulnerability. In this regard, we previously demonstrated that MPP+, a neurotoxin able to cause selective nigrostriatal degeneration in animal rodents and primates, inhibits the Hyperpolarization-activated current (Ih in SNpc DAergic neurons and that pharmacological Ih antagonism causes potentiation of evoked Excitatory post-synaptic potentials (EPSPs. Of note, the magnitude of such potentiation is greater in the SNpc subfield, consistent with higher Ih density. In the present work, we show that Ih block-induced synaptic potentiation leads to the amplification of somatic calcium responses (SCRs in vitro. This effect is specific for the SNpc subfield and largely mediated by L-Type calcium channels, as indicated by sensitivity to the CaV 1 blocker isradipine. Furthermore, Ih is downregulated by low intracellular ATP and determines the efficacy of GABAergic inhibition in SNpc DAergic neurons. Finally, we show that stereotaxic administration of Ih blockers causes SNpc-specific neurodegeneration and hemiparkinsonian motor phenotype in rats. During PD progression, Ih downregulation may result from mitochondrial dysfunction and, in concert with PD-related disinhibition of excitatory inputs, determine a SNpc-specific disease pathway.

  19. Hyperpolarization-activated current (I(h)) in vestibular calyx terminals: characterization and role in shaping postsynaptic events.

    Science.gov (United States)

    Meredith, Frances L; Benke, Tim A; Rennie, Katherine J

    2012-12-01

    Calyx afferent terminals engulf the basolateral region of type I vestibular hair cells, and synaptic transmission across the vestibular type I hair cell/calyx is not well understood. Calyces express several ionic conductances, which may shape postsynaptic potentials. These include previously described tetrodotoxin-sensitive inward Na(+) currents, voltage-dependent outward K(+) currents and a K(Ca) current. Here, we characterize an inwardly rectifying conductance in gerbil semicircular canal calyx terminals (postnatal days 3-45), sensitive to voltage and to cyclic nucleotides. Using whole-cell patch clamp, we recorded from isolated calyx terminals still attached to their type I hair cells. A slowly activating, noninactivating current (I(h)) was seen with hyperpolarizing voltage steps negative to the resting potential. External Cs(+) (1-5 mM) and ZD7288 (100 μM) blocked the inward current by 97 and 83 %, respectively, confirming that I(h) was carried by hyperpolarization-activated, cyclic nucleotide gated channels. Mean half-activation voltage of I(h) was -123 mV, which shifted to -114 mV in the presence of cAMP. Activation of I(h) was well described with a third order exponential fit to the current (mean time constant of activation, τ, was 190 ms at -139 mV). Activation speeded up significantly (τ=136 and 127 ms, respectively) when intracellular cAMP and cGMP were present, suggesting that in vivo I(h) could be subject to efferent modulation via cyclic nucleotide-dependent mechanisms. In current clamp, hyperpolarizing current steps produced a time-dependent depolarizing sag followed by either a rebound afterdepolarization or an action potential. Spontaneous excitatory postsynaptic potentials (EPSPs) became larger and wider when I(h) was blocked with ZD7288. In a three-dimensional mathematical model of the calyx terminal based on Hodgkin-Huxley type ionic conductances, removal of I(h) similarly increased the EPSP, whereas cAMP slightly decreased simulated EPSP size

  20. 5-HT modulation of hyperpolarization-activated inward current and calcium- dependent outward current in a crustacean motor neuron

    DEFF Research Database (Denmark)

    Kiehn, O.; Harris-Warrick, R. M.

    1992-01-01

    1. Serotonergic modulation of a hyperpolarization-activated inward current, I(h), and a calcium-dependent outward current, I(o(Ca)), was examined in the dorsal gastric (DG) motor neuron, with the use of intracellular recording techniques in an isolated preparation of the crab stomatogastric....... The time course of activation of I(h) was well fitted by a single exponential function and strongly voltage dependent. 5-HT increased the rate of activation of I(h). 5- HT also slowed the rate of deactivation of the I(h) tail on repolarization to -50 mV. 6. The activation curve for the conductance (G...... reduced or eliminated the 5-HT response in the depolarizing range, suggesting that 5-HT specifically reduces I(o(Ca)). 11. These results demonstrate that 5-HT has dual effects on the DG motor neuron, in the crab stomatogastric ganglion. We suggest that changes in the two conductances are responsible...

  1. Health Code Number (HCN) Development Procedure

    Energy Technology Data Exchange (ETDEWEB)

    Petrocchi, Rocky; Craig, Douglas K.; Bond, Jayne-Anne; Trott, Donna M.; Yu, Xiao-Ying

    2013-09-01

    This report provides the detailed description of health code numbers (HCNs) and the procedure of how each HCN is assigned. It contains many guidelines and rationales of HCNs. HCNs are used in the chemical mixture methodology (CMM), a method recommended by the department of energy (DOE) for assessing health effects as a result of exposures to airborne aerosols in an emergency. The procedure is a useful tool for proficient HCN code developers. Intense training and quality assurance with qualified HCN developers are required before an individual comprehends the procedure to develop HCNs for DOE.

  2. CO and HCN observations of carbon stars

    NARCIS (Netherlands)

    Baas, F; deJong, T; Loup, C

    We present CO and HCN observations of carbon stars. They consist of partly new detections in the (CO)-C-12 J = (1-0), (2-1) and HCN(1-0) lines obtained with the SEST and the IRAM telescope, and of (CO)-C-12 and (CO)-C-13 J = (1-0), (2-1) and (3-2) observations with IRAM and the JCMT of some of the

  3. Effect of Non-specific HCN1 Blocker CsCl on Spatial Learning and Memory in Mouse

    Institute of Scientific and Technical Information of China (English)

    YU Xin; GUO Lianjun; YIN Guangfu; ZONG Xiangang; AI Yongxun

    2006-01-01

    It has been suggested that HCN1 is primarily expressed in hippocampus, however little is known about its effects on spatial learning and memory. In the present study, we investigated the effects of non-specific HCN1 blocker CsCl on spatial learning and memory by using Morris water maze and in situ hybridization in mice. The results showed CsCl 160 mg/kg ip for 4 days, and the mean escape latency was 34 s longer than that of normal control (P<0.01). In hippocampal tissues, staining for the HCN1 mRNA was stronger in the DG and CA1 region of the hippocampus (P <0.05, P<0.05, when CsCl-administration group was compared with normal group). Our results suggested that CsCl could significantly affect the spatial learning and memory in mice, and HCN channel is involved in the process of learning and memory.

  4. Single Ih channels in pyramidal neuron dendrites: properties, distribution, and impact on action potential output

    NARCIS (Netherlands)

    Kole, Maarten H. P.; Hallermann, Stefan; Stuart, Greg J.

    2006-01-01

    The hyperpolarization-activated cation current (Ih) plays an important role in regulating neuronal excitability, yet its native single-channel properties in the brain are essentially unknown. Here we use variance-mean analysis to study the properties of single Ih channels in the apical dendrites of

  5. Detection of interstellar vibrationally excited HCN

    International Nuclear Information System (INIS)

    Ziurys, L.M.; Turner, B.E.

    1986-01-01

    Vibrationally excited HCN has been observed for the first time in the interstellar medium. The J = 3-2 rotational transitions of the l-doubled (0,1/sup 1d/,1c, 0) bending mode of HCN have been detected toward Orion-KL and IRC +10216. In Orion, the overall column density in the (0,1,0) mode, which exclusively samples the ''hot core,'' is 1.7-10 16 cm -2 and can be understood in terms of the ''doughnut'' model for Orion. The ground-state HCN column density implied by the excited-state observations is 2.3 x 10 18 cm -2 in the hot core, at least one order of magnitude greater than the column densities derived for HCN in its spike and plateau/doughnut components. Radiative excitation by 14 μm flux from IRc2 accounts for the (0,1,0) population provided the hot core is approx.6-7 x 10 16 cm distant from IRc2, in agreement with the ''cavity'' model for KL. Toward IRC +10216 we have detected J = 3-2 transitions of both (0,1/sup 1c/,/sup 1d/,0) and (0,2 0 ,0) excited states. The spectral profiles have been modeled to yield abundances and excitation conditions throughout the expanding envelope

  6. THE NITROGEN ISOTOPIC COMPOSITION OF METEORITIC HCN

    Energy Technology Data Exchange (ETDEWEB)

    Pizzarello, Sandra, E-mail: pizzar@asu.edu [Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85018-1604 (United States)

    2014-12-01

    HCN is ubiquitous in extraterrestrial environments and is central to current theories on the origin of early solar system organic compounds such as amino acids. These compounds, observed in carbonaceous meteorites, were likely important in the origin and/or evolution of early life. As part of our attempts to understand the origin(s) of meteoritic CN{sup –}, we have analyzed the {sup 15}N/{sup 14}N isotopic composition of HCN gas released from water extracts of the Murchison meteorite and found its value to be near those of the terrestrial atmosphere. The findings, when evaluated viz-a-viz molecular abundances and isotopic data of meteoritic organic compounds, suggest that HCN formation could have occurred during the protracted water alteration processes known to have affected the mineralogy of many asteroidal bodies during their solar residence. This was an active synthetic stage, which likely involved simple gasses, organic molecules, their presolar precursors, as well as mineral catalysts and would have lead to the formation of molecules of differing isotopic composition, including some with solar values.

  7. Characterization of a right atrial subsidiary pacemaker and acceleration of the pacing rate by HCN over-expression.

    Science.gov (United States)

    Morris, Gwilym M; D'Souza, Alicia; Dobrzynski, Halina; Lei, Ming; Choudhury, Moinuddin; Billeter, Rudi; Kryukova, Yelena; Robinson, Richard B; Kingston, Paul A; Boyett, Mark R

    2013-10-01

    Although the right atrium (RA contains subsidiary atrial pacemaker (SAP) tissue that can take over from the sinoatrial node (SAN) in sick sinus syndrome (SSS), SAP tissue is bradycardic. Little is known about SAP tissue and one aim of the study was to characterize ion channel expression to obtain insight into SAP pacemaker mechanisms. A second aim was to determine whether HCN over-expression (a 'biopacemaker'-like strategy) can accelerate the pacemaker rate producing a pacemaker that is similar in nature to the SAN. SAP tissue was isolated from the rat and the leading pacemaker site was characterized. Cell size at the leading pacemaker site in the SAP was smaller than in the RA and comparable to that in the SAN. mRNA levels showed the SAP to be similar to, but distinct from, the SAN. For example, in the SAN and SAP, expression of Tbx3 and HCN1 was higher and Nav1.5 and Cx43 lower than in the RA. Organ-cultured SAP tissue beat spontaneously, but at a slower rate than the SAN. Adenovirus-mediated gene transfer of HCN2 and the chimeric protein HCN212 significantly increased the pacemaker rate of the SAP close to that of the native SAN, but HCN4 was ineffective. SAP tissue near the inferior vena cava is bradycardic, but shares characteristics with the SAN. Pacing can be accelerated by the over-expression of HCN2 or HCN212. This provides proof of concept for the use of SAP tissue as a substrate for biopacemaking in the treatment of SSS.

  8. Genetically engineered cardiac pacemaker: Stem cells transfected with HCN2 gene and myocytes-A model

    Energy Technology Data Exchange (ETDEWEB)

    Kanani, S. [Institut Genomique Fonctionelle, 141 Rue de la Cardonille, 34396 Montpellier (France); Institut Non Lineaire de Nice, CNRS and Universite de Nice, 1361 route des Lucioles, 06560 Valbonne (France); Pumir, A. [Institut Non Lineaire de Nice, CNRS and Universite de Nice, 1361 route des Lucioles, 06560 Valbonne (France); Laboratoire J.A. Dieudonne, CNRS and Universite de Nice, Parc Valrose, 06108 Nice (France)], E-mail: alain.pumir@unice.fr; Krinsky, V. [Institut Non Lineaire de Nice, CNRS and Universite de Nice, 1361 route des Lucioles, 06560 Valbonne (France)

    2008-01-07

    One of the successfully tested methods to design genetically engineered cardiac pacemaker cells consists in transfecting a human mesenchymal stem cell (hMSC) with a HCN2 gene and connecting it to a myocyte. We develop and study a mathematical model, describing a myocyte connected to a hMSC transfected with a HCN2 gene. The cardiac action potential is described both with the simple Beeler-Reuter model, as well as with the elaborate dynamic Luo-Rudy model. The HCN2 channel is described by fitting electrophysiological records, in the spirit of Hodgkin-Huxley. The model shows that oscillations can occur in a pair myocyte-stem cell, that was not observed in the experiments yet. The model predicted that: (1) HCN pacemaker channels can induce oscillations only if the number of expressed I{sub K1} channels is low enough. At too high an expression level of I{sub K1} channels, oscillations cannot be induced, no matter how many pacemaker channels are expressed. (2) At low expression levels of I{sub K1} channels, a large domain of values in the parameter space (n, N) exists, where oscillations should be observed. We denote N the number of expressed pacemaker channels in the stem cell, and n the number of gap junction channels coupling the stem cell and the myocyte. (3) The expression levels of I{sub K1} channels observed in ventricular myocytes, both in the Beeler-Reuter and in the dynamic Luo-Rudy models are too high to allow to observe oscillations. With expression levels below {approx}1/4 of the original value, oscillations can be observed. The main consequence of this work is that in order to obtain oscillations in an experiment with a myocyte-stem cell pair, increasing the values of n, N is unlikely to be helpful, unless the expression level of I{sub K1} has been reduced enough. The model also allows us to explore levels of gene expression not yet achieved in experiments, and could be useful to plan new experiments, aimed at improving the robustness of the oscillations.

  9. Genetically engineered cardiac pacemaker: Stem cells transfected with HCN2 gene and myocytes—A model

    Science.gov (United States)

    Kanani, S.; Pumir, A.; Krinsky, V.

    2008-01-01

    One of the successfully tested methods to design genetically engineered cardiac pacemaker cells consists in transfecting a human mesenchymal stem cell (hMSC) with a HCN2 gene and connecting it to a myocyte. We develop and study a mathematical model, describing a myocyte connected to a hMSC transfected with a HCN2 gene. The cardiac action potential is described both with the simple Beeler Reuter model, as well as with the elaborate dynamic Luo Rudy model. The HCN2 channel is described by fitting electrophysiological records, in the spirit of Hodgkin Huxley. The model shows that oscillations can occur in a pair myocyte-stem cell, that was not observed in the experiments yet. The model predicted that: (1) HCN pacemaker channels can induce oscillations only if the number of expressed I channels is low enough. At too high an expression level of I channels, oscillations cannot be induced, no matter how many pacemaker channels are expressed. (2) At low expression levels of I channels, a large domain of values in the parameter space (n, N) exists, where oscillations should be observed. We denote N the number of expressed pacemaker channels in the stem cell, and n the number of gap junction channels coupling the stem cell and the myocyte. (3) The expression levels of I channels observed in ventricular myocytes, both in the Beeler Reuter and in the dynamic Luo Rudy models are too high to allow to observe oscillations. With expression levels below ˜1/4 of the original value, oscillations can be observed. The main consequence of this work is that in order to obtain oscillations in an experiment with a myocyte-stem cell pair, increasing the values of n, N is unlikely to be helpful, unless the expression level of I has been reduced enough. The model also allows us to explore levels of gene expression not yet achieved in experiments, and could be useful to plan new experiments, aimed at improving the robustness of the oscillations.

  10. The HNC/HCN ratio in star-forming regions

    International Nuclear Information System (INIS)

    Graninger, Dawn M.; Öberg, Karin I.; Herbst, Eric; Vasyunin, Anton I.

    2014-01-01

    HNC and HCN, typically used as dense gas tracers in molecular clouds, are a pair of isomers that have great potential as a temperature probe because of temperature dependent, isomer-specific formation and destruction pathways. Previous observations of the HNC/HCN abundance ratio show that the ratio decreases with increasing temperature, something that standard astrochemical models cannot reproduce. We have undertaken a detailed parameter study on which environmental characteristics and chemical reactions affect the HNC/HCN ratio and can thus contribute to the observed dependence. Using existing gas and gas-grain models updated with new reactions and reaction barriers, we find that in static models the H + HNC gas-phase reaction regulates the HNC/HCN ratio under all conditions, except for very early times. We quantitatively constrain the combinations of H abundance and H + HNC reaction barrier that can explain the observed HNC/HCN temperature dependence and discuss the implications in light of new quantum chemical calculations. In warm-up models, gas-grain chemistry contributes significantly to the predicted HNC/HCN ratio and understanding the dynamics of star formation is therefore key to model the HNC/HCN system.

  11. Simple Organics and Biomonomers Identified in HCN Polymers: An Overview

    Directory of Open Access Journals (Sweden)

    Susana Osuna-Esteban

    2013-07-01

    Full Text Available Hydrogen cyanide (HCN is a ubiquitous molecule in the Universe. It is a compound that is easily produced in significant yields in prebiotic simulation experiments using a reducing atmosphere. HCN can spontaneously polymerise under a wide set of experimental conditions. It has even been proposed that HCN polymers could be present in objects such as asteroids, moons, planets and, in particular, comets. Moreover, it has been suggested that these polymers could play an important role in the origin of life. In this review, the simple organics and biomonomers that have been detected in HCN polymers, the analytical techniques and procedures that have been used to detect and characterise these molecules and an exhaustive classification of the experimental/environmental conditions that favour the formation of HCN polymers are summarised. Nucleobases, amino acids, carboxylic acids, cofactor derivatives and other compounds have been identified in HCN polymers. The great molecular diversity found in HCN polymers encourages their placement at the central core of a plausible protobiological system.

  12. CN and HCN in the infrared spectrum of IRC + 10216

    Science.gov (United States)

    Wiedemann, G. R.; Deming, D.; Jennings, D. E.; Hinkle, Kenneth H.; Keady, John J.

    1991-01-01

    The abundance of HCN in the inner circumstellar shell of IRC + 10216 has been remeasured using the 12-micron nu2 band. The 12-micron lines are less saturated than HCN 3-micron lines previously detected in the spectrum of IRC + 10216. The observed 12-micron HCN line is formed in the circumstellar shell from about 4 to 12 R sub * in accord with a photospheric origin for HCN. The derived HCN abundance in the 4 to 12 R sub* region is 4 x 10 exp-5 and the column density is 7 x 10 exp 18/sq cm. The 5-micron CN vibration-rotation fundamental band was detected for the first time in an astronomical source. Using four CN lines, the CN column density was determined to be 2.6 x 10 exp 15/sq cm and the rotational temperature to be 8 +/-2 K. The peal radial abundance is 1 x 10 exp -5. The values for the temperature and abundance are in good agreement with microwave results and with the formation of CN from the photolysis of HCN.

  13. The Photodissociation of HCN and HNC: Effects on the HNC/HCN Abundance Ratio in the Interstellar Medium

    Energy Technology Data Exchange (ETDEWEB)

    Aguado, Alfredo [Departamento de Química Física Aplicada (UAM), Unidad Asociada a IFF-CSIC, Facultad de Ciencias Módulo 14, Universidad Autónoma de Madrid, E-28049, Madrid (Spain); Roncero, Octavio; Zanchet, Alexandre [Instituto de Física Fundamental (IFF-CSIC), C.S.I.C., Serrano 123, E-28006 Madrid (Spain); Agúndez, Marcelino; Cernicharo, José, E-mail: octavio.roncero@csic.es [Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, Cantoblanco E-28049 (Spain)

    2017-03-20

    The impact of the photodissociation of HCN and HNC isomers is analyzed in different astrophysical environments. For this purpose, the individual photodissociation cross sections of HCN and HNC isomers have been calculated in the 7–13.6 eV photon energy range for a temperature of 10 K. These calculations are based on the ab initio calculation of three-dimensional adiabatic potential energy surfaces of the 21 lower electronic states. The cross sections are then obtained using a quantum wave packet calculation of the rotational transitions needed to simulate a rotational temperature of 10 K. The cross section calculated for HCN shows significant differences with respect to the experimental one, and this is attributed to the need to consider non-adiabatic transitions. Ratios between the photodissociation rates of HCN and HNC under different ultraviolet radiation fields have been computed by renormalizing the rates to the experimental value. It is found that HNC is photodissociated faster than HCN by a factor of 2.2 for the local interstellar radiation field and 9.2 for the solar radiation field, at 1 au. We conclude that to properly describe the HNC/HCN abundance ratio in astronomical environments illuminated by an intense ultraviolet radiation field, it is necessary to use different photodissociation rates for each of the two isomers, which are obtained by integrating the product of the photodissociation cross sections and ultraviolet radiation field over the relevant wavelength range.

  14. RESOLVING THE BRIGHT HCN(1–0) EMISSION TOWARD THE SEYFERT 2 NUCLEUS OF M51: SHOCK ENHANCEMENT BY RADIO JETS AND WEAK MASING BY INFRARED PUMPING?

    International Nuclear Information System (INIS)

    Matsushita, Satoki; Trung, Dinh-V-; Boone, Frédéric; Krips, Melanie; Lim, Jeremy; Muller, Sebastien

    2015-01-01

    We present high angular resolution observations of the HCN(1-0) emission (at ∼1'' or ∼34 pc), together with CO J = 1-0, 2-1, and 3-2 observations, toward the Seyfert 2 nucleus of M51 (NGC 5194). The overall HCN(1-0) distribution and kinematics are very similar to that of the CO lines, which have been indicated as the jet-entrained molecular gas in our past observations. In addition, high HCN(1-0)/CO(1-0) brightness temperature ratio of about unity is observed along the jets, similar to that observed at the shocked molecular gas in our Galaxy. These results strongly indicate that both diffuse and dense gases are entrained by the jets and outflowing from the active galactic nucleus. The channel map of HCN(1-0) at the systemic velocity shows a strong emission right at the nucleus, where no obvious emission has been detected in the CO lines. The HCN(1-0)/CO(1-0) brightness temperature ratio at this region reaches >2, a value that cannot be explained considering standard physical/chemical conditions. Based on our calculations, we suggest infrared pumping and possibly weak HCN masing, but still requiring an enhanced HCN abundance for the cause of this high ratio. This suggests the presence of a compact dense obscuring molecular gas in front of the nucleus of M51, which remains unresolved at our ∼1'' (∼34 pc) resolution, and consistent with the Seyfert 2 classification picture

  15. RESOLVING THE BRIGHT HCN(1–0) EMISSION TOWARD THE SEYFERT 2 NUCLEUS OF M51: SHOCK ENHANCEMENT BY RADIO JETS AND WEAK MASING BY INFRARED PUMPING?

    Energy Technology Data Exchange (ETDEWEB)

    Matsushita, Satoki [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China); Trung, Dinh-V- [Institute of Physics, Vietnamese Academy of Science and Technology, 10, Daotan, BaDinh, Hanoi (Viet Nam); Boone, Frédéric [Université de Toulouse, UPS-OMP, IRAP, F-31400 Toulouse (France); Krips, Melanie [Institute de Radio Astronomie Millimétrique, 300 Rue de la Piscine, F-38406 Saint Martin d' Hères (France); Lim, Jeremy [Department of Physics, University of Hong Kong, Pokfulam Road (Hong Kong); Muller, Sebastien [Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, SE-43992 Onsala (Sweden)

    2015-01-20

    We present high angular resolution observations of the HCN(1-0) emission (at ∼1'' or ∼34 pc), together with CO J = 1-0, 2-1, and 3-2 observations, toward the Seyfert 2 nucleus of M51 (NGC 5194). The overall HCN(1-0) distribution and kinematics are very similar to that of the CO lines, which have been indicated as the jet-entrained molecular gas in our past observations. In addition, high HCN(1-0)/CO(1-0) brightness temperature ratio of about unity is observed along the jets, similar to that observed at the shocked molecular gas in our Galaxy. These results strongly indicate that both diffuse and dense gases are entrained by the jets and outflowing from the active galactic nucleus. The channel map of HCN(1-0) at the systemic velocity shows a strong emission right at the nucleus, where no obvious emission has been detected in the CO lines. The HCN(1-0)/CO(1-0) brightness temperature ratio at this region reaches >2, a value that cannot be explained considering standard physical/chemical conditions. Based on our calculations, we suggest infrared pumping and possibly weak HCN masing, but still requiring an enhanced HCN abundance for the cause of this high ratio. This suggests the presence of a compact dense obscuring molecular gas in front of the nucleus of M51, which remains unresolved at our ∼1'' (∼34 pc) resolution, and consistent with the Seyfert 2 classification picture.

  16. Differential distribution of voltage-gated channels in myelinated and unmyelinated baroreceptor afferents.

    Science.gov (United States)

    Schild, John H; Kunze, Diana L

    2012-12-24

    Voltage gated ion channels (VGC) make possible the frequency coding of arterial pressure and the neurotransmission of this information along myelinated and unmyelinated fiber pathways. Although many of the same VGC isoforms are expressed in both fiber types, it is the relative expression of each that defines the unique discharge properties of myelinated A-type and unmyelinated C-type baroreceptors. For example, the fast inward Na⁺ current is a major determinant of the action potential threshold and the regenerative transmembrane current needed to sustain repetitive discharge. In A-type baroreceptors the TTX-sensitive Na(v)1.7 VGC contributes to the whole cell Na⁺ current. Na(v)1.7 is expressed at a lower density in C-type neurons and in conjunction with TTX-insensitive Na(v)1.8 and Na(v)1.9 VGC. As a result, action potentials of A-type neurons have firing thresholds that are 15-20 mV more negative and upstroke velocities that are 5-10 times faster than unmyelinated C-type neurons. A more depolarized threshold in conjunction with a broader complement of non-inactivating K(V) VGC subtypes produces C-type action potentials that are 3-4 times longer in duration than A-type neurons and at markedly lower levels of cell excitability. Unmyelinated baroreceptors also express KCa1.1 which provides approximately 25% of the total outward K⁺ current. KCa1.1 plays a critically important role in shaping the action potential profile of C-type neurons and strongly impacts neuronal excitability. A-type neurons do not functionally express the KCa1.1 channel despite having a whole cell Ca(V) current quite similar to that of C-type neurons. As a result, A-type neurons do not have the frequency-dependent braking forces of KCa1.1. Lack of a KCa current and only a limited complement of non-inactivating K(V) VGC in addition to a hyperpolarization activated HCN1 current that is nearly 10 times larger than in C-type neurons leads to elevated levels of discharge in A-type neurons, a

  17. Hyperpolarization-activated inward leakage currents caused by deletion or mutation of carboxy-terminal tyrosines of the Na+/K+-ATPase {alpha} subunit.

    Science.gov (United States)

    Meier, Susan; Tavraz, Neslihan N; Dürr, Katharina L; Friedrich, Thomas

    2010-02-01

    The Na(+)/K(+)-ATPase mediates electrogenic transport by exporting three Na(+) ions in exchange for two K(+) ions across the cell membrane per adenosine triphosphate molecule. The location of two Rb(+) ions in the crystal structures of the Na(+)/K(+)-ATPase has defined two "common" cation binding sites, I and II, which accommodate Na(+) or K(+) ions during transport. The configuration of site III is still unknown, but the crystal structure has suggested a critical role of the carboxy-terminal KETYY motif for the formation of this "unique" Na(+) binding site. Our two-electrode voltage clamp experiments on Xenopus oocytes show that deletion of two tyrosines at the carboxy terminus of the human Na(+)/K(+)-ATPase alpha(2) subunit decreases the affinity for extracellular and intracellular Na(+), in agreement with previous biochemical studies. Apparently, the DeltaYY deletion changes Na(+) affinity at site III but leaves the common sites unaffected, whereas the more extensive DeltaKETYY deletion affects the unique site and the common sites as well. In the absence of extracellular K(+), the DeltaYY construct mediated ouabain-sensitive, hyperpolarization-activated inward currents, which were Na(+) dependent and increased with acidification. Furthermore, the voltage dependence of rate constants from transient currents under Na(+)/Na(+) exchange conditions was reversed, and the amounts of charge transported upon voltage pulses from a certain holding potential to hyperpolarizing potentials and back were unequal. These findings are incompatible with a reversible and exclusively extracellular Na(+) release/binding mechanism. In analogy to the mechanism proposed for the H(+) leak currents of the wild-type Na(+)/K(+)-ATPase, we suggest that the DeltaYY deletion lowers the energy barrier for the intracellular Na(+) occlusion reaction, thus destabilizing the Na(+)-occluded state and enabling inward leak currents. The leakage currents are prevented by aromatic amino acids at the

  18. Tonic 5nM DA stabilizes neuronal output by enabling bidirectional activity-dependent regulation of the hyperpolarization activated current via PKA and calcineurin.

    Science.gov (United States)

    Krenz, Wulf-Dieter C; Rodgers, Edmund W; Baro, Deborah J

    2015-01-01

    Volume transmission results in phasic and tonic modulatory signals. The actions of tonic dopamine (DA) at type 1 DA receptors (D1Rs) are largely undefined. Here we show that tonic 5nM DA acts at D1Rs to stabilize neuronal output over minutes by enabling activity-dependent regulation of the hyperpolarization activated current (I h). In the presence but not absence of 5nM DA, I h maximal conductance (G max) was adjusted according to changes in slow wave activity in order to maintain spike timing. Our study on the lateral pyloric neuron (LP), which undergoes rhythmic oscillations in membrane potential with depolarized plateaus, demonstrated that incremental, bi-directional changes in plateau duration produced corresponding alterations in LP I hG max when preparations were superfused with saline containing 5nM DA. However, when preparations were superfused with saline alone there was no linear correlation between LP I hGmax and duty cycle. Thus, tonic nM DA modulated the capacity for activity to modulate LP I h G max; this exemplifies metamodulation (modulation of modulation). Pretreatment with the Ca2+-chelator, BAPTA, or the specific PKA inhibitor, PKI, prevented all changes in LP I h in 5nM DA. Calcineurin inhibitors blocked activity-dependent changes enabled by DA and revealed a PKA-mediated, activity-independent enhancement of LP I hG max. These data suggested that tonic 5nM DA produced two simultaneous, PKA-dependent effects: a direct increase in LP I h G max and a priming event that permitted calcineurin regulation of LP I h. The latter produced graded reductions in LP I hG max with increasing duty cycles. We also demonstrated that this metamodulation preserved the timing of LP's first spike when network output was perturbed with bath-applied 4AP. In sum, 5nM DA permits slow wave activity to provide feedback that maintains spike timing, suggesting that one function of low-level, tonic modulation is to stabilize specific features of a dynamic output.

  19. Tonic 5nM DA stabilizes neuronal output by enabling bidirectional activity-dependent regulation of the hyperpolarization activated current via PKA and calcineurin.

    Directory of Open Access Journals (Sweden)

    Wulf-Dieter C Krenz

    Full Text Available Volume transmission results in phasic and tonic modulatory signals. The actions of tonic dopamine (DA at type 1 DA receptors (D1Rs are largely undefined. Here we show that tonic 5nM DA acts at D1Rs to stabilize neuronal output over minutes by enabling activity-dependent regulation of the hyperpolarization activated current (I h. In the presence but not absence of 5nM DA, I h maximal conductance (G max was adjusted according to changes in slow wave activity in order to maintain spike timing. Our study on the lateral pyloric neuron (LP, which undergoes rhythmic oscillations in membrane potential with depolarized plateaus, demonstrated that incremental, bi-directional changes in plateau duration produced corresponding alterations in LP I hG max when preparations were superfused with saline containing 5nM DA. However, when preparations were superfused with saline alone there was no linear correlation between LP I hGmax and duty cycle. Thus, tonic nM DA modulated the capacity for activity to modulate LP I h G max; this exemplifies metamodulation (modulation of modulation. Pretreatment with the Ca2+-chelator, BAPTA, or the specific PKA inhibitor, PKI, prevented all changes in LP I h in 5nM DA. Calcineurin inhibitors blocked activity-dependent changes enabled by DA and revealed a PKA-mediated, activity-independent enhancement of LP I hG max. These data suggested that tonic 5nM DA produced two simultaneous, PKA-dependent effects: a direct increase in LP I h G max and a priming event that permitted calcineurin regulation of LP I h. The latter produced graded reductions in LP I hG max with increasing duty cycles. We also demonstrated that this metamodulation preserved the timing of LP's first spike when network output was perturbed with bath-applied 4AP. In sum, 5nM DA permits slow wave activity to provide feedback that maintains spike timing, suggesting that one function of low-level, tonic modulation is to stabilize specific features of a dynamic output.

  20. Electric discharge synthesis of HCN in simulated Jovian atmospheres

    Science.gov (United States)

    Stribling, Roscoe; Miller, Stanley L.

    1987-01-01

    Corona discharge is presently considered as a possible source of the HCN detected in the Jovian atmosphere at 2.2 x 10 to the -7th moles/sq cm column density, for the cases of gas mixtures containing H2, CH4, and NH3, with H2/CH4 ratios from 4.4 to 1585. A 3:1 ratio of corona discharge to lightning energy similar to that of the earth is applied to Jupiter. Depending on the lightning energy available on Jupiter and the eddy diffusion coefficients in the synthesis region, HCN column densities generated by corona discharge could account for about 10 percent of the HCN observed.

  1. New CO and HCN sources associated with IRAS carbon stars

    Science.gov (United States)

    NGUYEN-Q-RIEU; Epchtein, N.; TRUONG-BACH; Cohen, M.

    1987-01-01

    Emission of CO and HCN was detected in 22 out of a sample of 53 IRAS sources classified as unidentified carbon-rich objects. The sample was selected according to the presence of the silicon carbide feature as revealed by low-resolution spectra. The molecular line widths indicate that the CO and HCN emission arises from the circumstellar envelopes of very highly evolved stars undergoing mass loss. The visible stars tend to be deficient in CO as compared with unidentified sources. Most the detected CO and HCN IRAS stars are distinct and thick-shelled objects, but their infrared and CO luminosities are similar to those of IRC + 102156 AFGL and IRC-CO evolved stars. The 12 micron flux seems to be a good indicator of the distance, hence a guide for molecular searches.

  2. Catalytic and Gas-Solid Reactions Involving HCN over Limestone

    DEFF Research Database (Denmark)

    Jensen, Anker; Johnsson, Jan Erik; Dam-Johansen, Kim

    1997-01-01

    In coal-fired combustion systems solid calcium species may be present as ash components or limestone added to the combustion chamber. In this study heterogeneous reactions involving HCN over seven different limestones were investigated in a laboratory fixed-bed quartz reactor at 873-1,173 K...

  3. HCN Polymers: Toward Structure Comprehension Using High Resolution Mass Spectrometry

    Science.gov (United States)

    Bonnet, Jean-Yves; Thissen, Roland; Frisari, Ma; Vuitton, Veronique; Quirico, Eric; Le Roy, Léna; Fray, Nicolas; Cottin, Hervé; Horst, Sarah; Yelle, Roger

    A lot of solar system materials, including cometary ices and Titan aerosols, contain dark matter that can be interpreted as complex nitrogen bearing organic matter [1]. In laboratory experi-ments, HCN polymers are thus analogs of great interest. In fact they may be present in Titan atmosphere and in comet nuclei and then reprocessed as a CN distributed source [2], when ices began to sublimate and ejects from the nucleus organic matter grains [3]. The presence of HCN polymers is suggested because HCN molecule has been directly observed in 1P/Halley comet [4] and others. HCN polymers are also of prebiotic interest [5] as it can form amino acid under hydrolysis conditions. Even if they have been studied during the last decades, their chemical composition and structure are still poorly understood, and a great analytical effort has to be continued. In this way we present a high resolution mass spectrometry (HRMS) and a high resolution tandem mass spectrometry (MS/HRMS) analysis of HCN polymers. It was shown [6] that this is a suitable technique to elucidate composition and structure of the soluble part of tholins analogs of Titan's atmosphere aerosols. HCN polymers have never been studied by HRMS, thus we used a LTQ-Orbitrap XL high resolution mass spectrometer to analyse the HCN polymers. These are produced at LISA by direct polymerisation of pure liquid HCN, catalyzed by ammonia. HCN polymers have been completely dissolved in methanol and then injected in the mass spectrometer by ElectroSpray Ionization (ESI). This atmospheric pressure ionization process produces protonated or deprotonated ions, but it does not fragment molecules. Thus HRMS, allows a direct access to the stoechiometry of all the ionizable molecules present in the samples. Fragmentation analyses (MS/MS) of selected ions have also been performed. Thess analysis provide information about the different chemical fonctionnalities present in HCN poly-mers and also about their structure. Thus we are able to

  4. Is Photolytic Production a Viable Source of HCN and HNC in Astrophysical Environments? A Laboratory-based Feasibility Study of Methyl Cyanoformate

    Science.gov (United States)

    Wilhelm, Michael J.; Martínez-Núñez, Emilio; González-Vázquez, Jesús; Vázquez, Saulo A.; Smith, Jonathan M.; Dai, Hai-Lung

    2017-11-01

    Motivated by the possibility that cyano-containing hydrocarbons may act as photolytic sources for HCN and HNC in astrophysical environments, we conducted a combined experimental and theoretical investigation of the 193 nm photolysis of the cyano-ester, methyl cyanoformate (MCF). Experimentally, nanosecond time-resolved infrared emission spectroscopy was used to detect the emission from nascent products generated in the photolysis reaction. The time-resolved spectra were analyzed using a recently developed spectral reconstruction analysis, which revealed spectral bands assignable to HCN and HNC. Fitting of the emission band shape and intensity allowed determination of the photolysis quantum yields of HCN, HNC, and {CN}({A}2{{{\\Pi }}}1) and an HNC/HCN ratio of ˜0.076 ± 0.059. Additionally, multiconfiguration self-consistent field calculations were used to characterize photoexcitation-induced reactions in the ground and four lowest singlet excited states of MCF. At 193 nm excitation, dissociation is predicted to occur predominantly on the repulsive S 2 state, with minor pathways via internal conversion from S 2 to highly excited ground state. An automated transition-state search algorithm was employed to identify the corresponding ground-state dissociation channels, and Rice-Ramsperger-Kassel-Marcus and Kinetic Monte Carlo simulations were used to calculate the associated branching ratios. The proposed mechanisms were validated using the experimentally measured and quasi-classical trajectory-deduced nascent internal energy distributions of HCN and HNC. This work, along with previous studies, illustrates the propensity for cyano-containing hydrocarbons to act as photolytic sources for astrophysical HCN and HNC and may help explain the observed overabundance of HNC in astrophysical environments.

  5. ALMA OBSERVATIONS OF HCN AND ITS ISOTOPOLOGUES ON TITAN

    Energy Technology Data Exchange (ETDEWEB)

    Molter, Edward M.; Nixon, C. A.; Cordiner, M. A.; Charnley, S. B.; Lindberg, J. E. [NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 (United States); Serigano, J. [Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD 21218 (United States); Irwin, P. G. J. [Atmospheric, Oceanic, and Planetary Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU (United Kingdom); Teanby, N. A., E-mail: edward.m.molter@nasa.gov [School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol, BS8 1RJ (United Kingdom)

    2016-08-01

    We present sub-millimeter spectra of HCN isotopologues on Titan, derived from publicly available ALMA flux calibration observations of Titan taken in early 2014. We report the detection of a new HCN isotopologue on Titan, H{sup 13}C{sup 15}N, and confirm an earlier report of detection of DCN. We model high signal-to-noise observations of HCN, H{sup 13}CN, HC{sup 15}N, DCN, and H{sup 13}C{sup 15}N to derive abundances and infer the following isotopic ratios: {sup 12}C/{sup 13}C = 89.8 ± 2.8, {sup 14}N/{sup 15}N = 72.3 ± 2.2, D/H = (2.5 ± 0.2) × 10{sup −4}, and HCN/H{sup 13}C{sup 15}N = 5800 ± 270 (1 σ errors). The carbon and nitrogen ratios are consistent with and improve on the precision of previous results, confirming a factor of ∼2.3 elevation in {sup 14}N/{sup 15}N in HCN compared to N{sub 2} and a lack of fractionation in {sup 12}C/{sup 13}C from the protosolar value. This is the first published measurement of D/H in a nitrile species on Titan, and we find evidence for a factor of ∼2 deuterium enrichment in hydrogen cyanide compared to methane. The isotopic ratios we derive may be used as constraints for future models to better understand the fractionation processes occurring in Titan’s atmosphere.

  6. Response of Si- and Al-doped graphenes toward HCN: A computational study

    International Nuclear Information System (INIS)

    Rastegar, Somayeh F.; Peyghan, Ali Ahmadi; Hadipour, Nasser L.

    2013-01-01

    Highlights: ► Sensitivity of Si- and Al-doped graphene (SiG and AlG) toward HCN is investigated. ► The electronic properties of AlG are significantly changed in the presence of HCN. ► It is established that AlG can be a good sensor for HCN molecule. - Abstract: Sensitivity of Si- and Al-doped graphenes (SiG and AlG) toward toxic HCN has been investigated using density functional theory (DFT) in terms of energetic, geometric and electronic properties. Optimized configurations corresponding to physisorption and, subsequently, chemisorption of HCN on each surface have been identified. It is found that HCN molecule can be adsorbed on impurity atoms with adsorption energies about −27.20 and −38.75 kcal/mol on the SiG and the AlG, respectively. By comparing to HCN adsorption on SiG, it can be inferred that molecular HCN adsorbed on AlG can induce significant change in AlG conductivity. On the basis of calculated changes in the HOMO/LUMO energy gap it is found that electronic properties of AlG are sensitive toward adsorption of HCN and the reverse is correct for SiG, suggesting that the AlG may be a promising sensor for HCN.

  7. Characterization of solvated electrons in hydrogen cyanide clusters: (HCN)n- (n=3, 4)

    Science.gov (United States)

    Wu, Di; Li, Ying; Li, Zhuo; Chen, Wei; Li, Zhi-Ru; Sun, Chia-Chung

    2006-02-01

    Theoretical studies of the solvated electrons (HCN)n- (n =3, 4) reveal a variety of electron trapping possibilities in the (HCN)n (n =3, 4) clusters. Two isomers for (HCN)3- and four isomers for (HCN)4- are obtained at the MP2/aug -cc-pVDZ+dBF (diffusive bond functions) level of theory. In view of vertical electron detachment energies (VDEs) at the CCSD(T) level, the excess electron always "prefers" locating in the center of the system, i.e., the isomer with higher coordination number shows larger VDE value. However, the most stable isomers of the solvated electron state (HCN)3- and (HCN)4- are found to be the linear C∞ν and D∞h structures, respectively, but not the fullyl symmetric structures which have the largest VDE values.

  8. HCN Producing Bacteria Enable Sensing Of Non-Bioavailable Hg Species by the Whole Cell Biosensor

    Science.gov (United States)

    Horvat, M.; Rijavec, T.; Koron, N.; Lapanje, A.

    2015-12-01

    Bacteria play an important role in Hg transformation reactions. The production of cyanide (HCN) and other secondary metabolites seems to be key elements involved in these transformations. Current hypotheses link the role of HCN production to growth inhibition of nonHCN producing competitor organisms (role of an antimicrobial agent). Our past investigations showed that HCN production did not correlate with antimicrobial activity and since pK value of HCN is very high (pK = 9,21), it can be expected that most of the produced HCN is removed from the microenvironment. This way, the expected inhibitory concentrations can hardly be reached. Accordingly, we proposed a new concept, where the ability of complexation of transient metals by HCN served as a regulation process for the accessibility of micro-elements. In our study, we focused on the presence of HCN producing bacteria and carried it out in the Hg contaminated environment connected to the Idrija Mercury Mine, Slovenia. We characterised the isolates according to the presence of Hg resistance (HgR), level of HCN production and genetic similarities. In laboratory setups, using our merR whole cell based biosensor, we determined the transformation of low bioavailable Hg0 and HgS forms into bioavailable Hg by these HCN producing bacteria. We observed that HgR strains producing HCN had the highest impact on increased Hg bioavailability. In the proposed ecological strategy HgR HCN producing bacteria increase their competitive edge over non-HgR competitors through the increase of Hg toxicity. Due to their activity, Hg is made available to other organisms as well and thus enters into the ecosystem. Finally, using some of the characteristics of bacteria (e.g. Hg resistance genetic elements), we developed a fully automated sensing approach, combining biosensorics and mechatronics, to measure the bioavailability of Hg in situ.

  9. Photochemistry of methane and the formation of hydrocyanic acid (HCN) in the earth's early atmosphere

    Science.gov (United States)

    Zahnle, K. J.

    1986-01-01

    A one-dimensional photochemical model is used to analyze the photochemistries of CH4 and HCN in the primitive terrestrial atmosphere. CH4, N2, and HCN photolysis are examined. The background atmosphere and boundary conditions applied in the analysis are described. The formation of HCN as a by-product of N2 and CH4 photolysis is investigated; the effects of photodissociation and rainfall on HCN is discussed. The low and high CH4 mixing ratios and radical densities are studied.

  10. Plasma density calculation based on the HCN waveform data

    International Nuclear Information System (INIS)

    Chen Liaoyuan; Pan Li; Luo Cuiwen; Zhou Yan; Deng Zhongchao

    2004-01-01

    A method to improve the plasma density calculation is introduced using the base voltage and the phase zero points obtained from the HCN interference waveform data. The method includes making the signal quality higher by putting the signal control device and the analog-to-digit converters in the same location and charging them by the same power, and excluding the noise's effect according to the possible changing rate of the signal's phase, and to make the base voltage more accurate by dynamical data processing. (authors)

  11. Widespread HCN maser emission in carbon-rich evolved stars

    Science.gov (United States)

    Menten, K. M.; Wyrowski, F.; Keller, D.; Kamiński, T.

    2018-05-01

    Context. HCN is a major constituent of the circumstellar envelopes of carbon-rich evolved stars, and rotational lines from within its vibrationally excited states probe parts of these regions closest to the stellar surface. A number of such lines are known to show maser action. Historically, in one of them, the 177 GHz J = 2 → 1 line in the l-doubled bending mode has been found to show relatively strong maser action, with results only published for a single object, the archetypical high-mass loss asymptotic giant branch (AGB) star IRC+10216. Aims: To examine how common 177 GHz HCN maser emission is, we conducted an exploratory survey for this line toward a select sample of carbon-rich asymptotic giant branch stars that are observable from the southern hemisphere. Methods: We used the Atacama Pathfinder Experiment 12 meter submillimeter Telescope (APEX) equipped with a new receiver to simultaneously observe three J = 2 → 1 HCN rotational transitions, the (0, 11c, 0) and (0, 11d, 0) l-doublet components, and the line from the (0,0,0) ground state. Results: The (0, 11c, 0) maser line is detected toward 11 of 13 observed sources, which all show emission in the (0,0,0) transition. In most of the sources, the peak intensity of the (0, 11c, 0) line rivals that of the (0,0,0) line; in two sources, it is even stronger. Except for the object with the highest mass-loss rate, IRC+10216, the (0, 11c, 0) line covers a smaller velocity range than the (0,0,0) line. The (0, 11d, 0) line, which is detected in four of the sources, is much weaker than the other two lines and covers a velocity range that is smaller yet, again except for IRC+10216. Compared to its first detection in 1989, the profile of the (0, 11c, 0) line observed toward IRC+10216 looks very different, and we also appear to see variability in the (0,0,0) line profile (at a much lower degree). Our limited information on temporal variabilitydisfavors a strong correlation of maser and stellar continuum flux

  12. A TENTATIVE IDENTIFICATION OF HCN ICE ON TRITON

    International Nuclear Information System (INIS)

    Burgdorf, M.; Cruikshank, D. P.; Dalle Ore, C. M.; Sekiguchi, T.; Nakamura, R.; Orton, G.; Quirico, E.; Schmitt, B.

    2010-01-01

    Spectra of Triton between 1.8 and 5.5 μm, obtained in 2007 May and 2009 November, have been analyzed to determine the global surface composition. The spectra were acquired with the grism and the prism of the Infrared Camera on board AKARI with spectral resolutions of 135 and 22, respectively. The data from 4 to 5 μm are shown in this Letter and compared to the spectra of N 2 , CO, and CO 2 , i.e., all the known ices on this moon that have distinct bands in this previously unexplored wavelength range. We report the detection of a 4σ absorption band at 4.76 μm (2101 cm -1 ), which we attribute tentatively to the presence of solid HCN. This is the sixth ice to be identified on Triton and an expected component of its surface because it is a precipitating photochemical product of Triton's thin N 2 and CH 4 atmosphere. It is also formed directly by irradiation of mixtures of N 2 and CH 4 ices. Here we consider only pure HCN, although it might be dissolved in N 2 on the surface of Triton because of the evaporation and recondensation of N 2 over its seasonal cycle. The AKARI spectrum of Triton also covers the wavelengths of the fundamental (1-0) band of β-phase N 2 ice (4.296 μm, 2328 cm -1 ), which has never been detected in an astronomical body before, and whose presence is consistent with the overtone (2-0) band previously reported. Fundamental bands of CO and CO 2 ices are also present.

  13. SPATIALLY RESOLVED HCN ABSORPTION FEATURES IN THE CIRCUMNUCLEAR REGION OF NGC 1052

    Energy Technology Data Exchange (ETDEWEB)

    Sawada-Satoh, Satoko [Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-12 Hoshigaoka-cho, Mizusawa-ku, Oshu, Iwate 023-0861 (Japan); Roh, Duk-Gyoo; Oh, Se-Jin; Lee, Sang-Sung; Byun, Do-Young; Yeom, Jae-Hwan; Jung, Dong-Kyu; Kim, Hyo-Ryoung; Hwang, Ju-Yeon [Korea Astronomy and Space Science Institute, 776 Daedeok-daero, Yuseong, Daejeon 34055 (Korea, Republic of); Kameno, Seiji, E-mail: satoko.ss@nao.ac.jp, E-mail: sss@mx.ibaraki.ac.jp [Joint ALMA Observatory, Alonso de Cordova 3107 Vitacura, Santiago 763 0355 (Chile)

    2016-10-10

    We present the first VLBI detection of HCN molecular absorption in the nearby active galactic nucleus NGC 1052. Utilizing the 1 mas resolution achieved by the Korean VLBI Network, we have spatially resolved the HCN absorption against a double-sided nuclear jet structure. Two velocity features of HCN absorption are detected significantly at the radial velocity of 1656 and 1719 km s{sup −1}, redshifted by 149 and 212 km s{sup −1} with respect to the systemic velocity of the galaxy. The column density of the HCN molecule is estimated to be 10{sup 15}–10{sup 16} cm{sup −2}, assuming an excitation temperature of 100–230 K. The absorption features show high optical depth localized on the receding jet side, where the free–free absorption occurred due to the circumnuclear torus. The size of the foreground absorbing molecular gas is estimated to be on approximately one-parsec scales, which agrees well with the approximate size of the circumnuclear torus. HCN absorbing gas is likely to be several clumps smaller than 0.1 pc inside the circumnuclear torus. The redshifted velocities of the HCN absorption features imply that HCN absorbing gas traces ongoing infall motion inside the circumnuclear torus onto the central engine.

  14. An Ab Initio MP2 Study of HCN-HX Hydrogen Bonded Complexes

    Directory of Open Access Journals (Sweden)

    Araújo Regiane C.M.U.

    1998-01-01

    Full Text Available An ab initio MP2/6-311++G** study has been performed to obtain geometries, binding energies and vibrational properties of HCN-HX H-bonded complexes with X = F, Cl, NC, CN and CCH. These MP2/6-311++G** results have revealed that: (i the calculated H-bond lengths are in very good agreement with the experimental ones; (ii the H-bond strength is associated with the intermolecular charge transfer and follows the order: HCN-HNC ~ HCN-HF > HCN-HCl ~ HCN-HCN > HCN-HCCH; (iii BSSE correction introduces an average reduction of 2.4 kJ/mol on the MP2/6-311++G** binding energies, i.e. 11% of the uncorrected binding energy; (iv the calculated zero-point energies reduce the stability of these complexes and show a good agreement with the available experimental values; (v the H-X stretching frequency is shifted downward upon H-bond formation. This displacement is associated with the H-bond length; (vi The more pronounced effect on the infrared intensities occurs with the H-X stretching intensity. It is much enhanced after complexation due to the charge-flux term; (vii the calculated intermolecular stretching frequencies are in very good agreement with the experimental ones; and, finally, (viii the results obtained for the HCN-HX complexes follow the same profile as those found for the acetylene-HX series but, in the latter case, the effects on the properties of the free molecules due to complexation are less pronounced than those in HCN-HX.

  15. The Puzzle of HCN in Comets: Is it both a Product and a Primary Species?

    Science.gov (United States)

    Mumma, Michael J.; Bonev, Boncho P.; Charnley, Steven B.; Cordiner, Martin A.; DiSanti, Michael A.; Gibb, Erika L.; Magee-Sauer, Karen; Paganini, Lucas; Villanueva, Geronimo L.

    2014-11-01

    Hydrogen cyanide has long been regarded as a primary volatile in comets, stemming from its presence in dense molecular cloud cores and its supposed storage in the cometary nucleus. Here, we examine the observational evidence for and against that hypothesis, and argue that HCN may also result from near-nucleus chemical reactions in the coma. The distinction (product vs. primary species) is important for multiple reasons: 1. HCN is often used as a proxy for water when the dominant species (H2O) is not available for simultaneous measurement, as at radio wavelengths. 2. HCN is one of the few volatile carriers of nitrogen accessible to remote sensing. If HCN is mainly a product species, its precursor becomes the more important metric for compiling a taxonomic classification based on nitrogen chemistry. 3. The stereoisomer HNC is now confirmed as a product species. Could reaction of a primary precursor (X-CN) with a hydrocarbon co-produce both HNC and HCN? 4. The production rate for CN greatly exceeds that of HCN in some comets, demonstrating the presence of another (more important) precursor of CN. Several puzzling lines of evidence raise issues about the origin of HCN: a. The production rates of HCN measured through rotational (radio) and vibrational (infrared) spectroscopy agree in some comets - in others the infrared rate exceeds the radio rate substantially. b. With its strong dipole moment and H-bonding character, HCN should be linked more strongly in the nuclear ice to other molecules with similar properties (H2O, CH3OH), but instead its spatial release in some comets seems strongly coupled to volatiles that lack a dipole moment and thus do not form H-bonds (methane, ethane). c. The nucleus-centered rotational temperatures measured for H2O and other species (C2H6, CH3OH) usually agree within error, but those for HCN are often slightly smaller. d. In comet ISON, ALMA maps of HCN and the dust continuum show a slight displacement 80 km) in the centroids. We will

  16. MLS/Aura L2 Hydrogen Cyanide (HCN) Mixing Ratio V003

    Data.gov (United States)

    National Aeronautics and Space Administration — ML2HCN is the EOS Aura Microwave Limb Sounder (MLS) standard product for hydrogen cyanide derived from radiances measured primarily by the 190 GHz radiometer. The...

  17. MLS/Aura L2 Hydrogen Cyanide (HCN) Mixing Ratio V002

    Data.gov (United States)

    National Aeronautics and Space Administration — ML2HCN is the EOS Aura Microwave Limb Sounder (MLS) standard product for hydrogen cyanide derived from radiances measured primarily by the 190 GHz radiometer. The...

  18. A 1D coordination polymer of UF{sub 5} with HCN as a ligand

    Energy Technology Data Exchange (ETDEWEB)

    Scheibe, Benjamin; Rudel, Stefan S.; Buchner, Magnus R.; Kraus, Florian [Fachbereich Chemie, Philipps-Universitaet Marburg (Germany); Karttunen, Antti J. [Department of Chemistry, Aalto University (Finland)

    2017-01-05

    β-Uranium(V) fluoride was reacted with liquid anhydrous hydrogen cyanide to obtain a 1D coordination polymer with the composition {sup 1}{sub ∞}[UF{sub 5}(HCN){sub 2}], {sup 1}{sub ∞}[UF{sub 4/1}F{sub 2/2}-(HCN){sub 2/1}], revealed by single-crystal X-ray structure determination. The reaction system was furthermore studied by means of vibrational and NMR spectroscopy, as well as by quantum chemical calculations. The compound presents the first described polymeric HCN Lewis adduct and the first HCN adduct of a uranium fluoride. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. WARM HCN IN THE PLANET FORMATION ZONE OF GV TAU N

    Energy Technology Data Exchange (ETDEWEB)

    Fuente, Asuncion [Observatorio Astronomico Nacional (OAN,IGN), Apdo 112, E-28803 Alcala de Henares (Spain); Cernicharo, Jose; Agundez, Marcelino, E-mail: a.fuente@oan.es [Centro de Astrobiologia (CSIC/INTA), Laboratory of Molecular Astrophysics, Ctra. Ajalvir km. 4, E-28850 Torrejon de Ardoz (Spain)

    2012-07-20

    The Plateau de Bure Interferometer has been used to map the continuum emission at 3.4 mm and 1.1 mm together with the J = 1{yields}0 and J = 3{yields}2 lines of HCN and HCO{sup +} toward the binary star GV Tau. The 3.4 mm observations did not resolve the binary components, and the HCN J = 1{yields}0 and HCO{sup +} J 1{yields}0 line emissions trace the circumbinary disk and the flattened envelope. However, the 1.1 mm observations resolved the individual disks of GV Tau N and GV Tau S and allowed us to study their chemistry. We detected the HCN 3{yields}2 line only toward the individual disk of GV Tau N, and the emission of the HCO{sup +} 3{yields}2 line toward GV Tau S. Simple calculations indicate that the 3{yields}2 line of HCN is formed in the inner R < 12 AU of the disk around GV Tau N where the HCN/HCO{sup +} abundance ratio is >300. On the contrary, this ratio is <1.6 in the disk around GV Tau S. The high HCN abundance measured in GV Tau N is well explained by photochemical processes in the warm (>400 K) and dense (n > 10{sup 7} cm{sup -3}) disk surface.

  20. Hyperfine anomalies of HCN in cold dark clouds

    International Nuclear Information System (INIS)

    Walmsley, C.M.; Churchwell, E.; Nash, A.; Fitzpatrick, E.; and Physics Department, University of Illinois at Urbana-Champaign)

    1982-01-01

    We report observations of the J = 1→0 line of HCN measured toward six positions in nearby low-temperature dark clouds. The measured relative intensities of the hyperfine components of the J = 1→0 line are anomalous in that the F = 0→1 transition is stronger than would be expected if all three components (F = 2→1, F = 1→1, F = 0→1) had equal excitation temperatures. Differences of approximately 20% in the populations per sublevel of J = 1 could account for the observations. The results are in contrast to the situation observed in warmer molecular clouds associated with H II regions where the F = 1→1 line is anomalously weak. The apparent overpopulation of J = 1, F = 0 in dark clouds may be related to the phenomenon observed in the J = 1→0 transitions of HCO + and HNC in the same objects where 13 C substituted version of these species is found to be stronger than the 12 C species

  1. Rotational excitation of HCN by para- and ortho-H{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Vera, Mario Hernández, E-mail: marhvera@gmail.com [LOMC - UMR 6294, CNRS-Université du Havre, 25 rue Philippe Lebon, BP 1123, 76 063 Le Havre cedex (France); InSTEC, Quinta de Los Molinos, Plaza, La Habana 10600 (Cuba); Kalugina, Yulia [LOMC - UMR 6294, CNRS-Université du Havre, 25 rue Philippe Lebon, BP 1123, 76 063 Le Havre cedex (France); Tomsk State University, 36 Lenin av., Tomsk 634050 (Russian Federation); Denis-Alpizar, Otoniel [Université de Bordeaux, ISM, CNRS UMR 5255, 33405 Talence Cedex (France); Departamento de Física, Universidad de Matanzas, Matanzas 40100 (Cuba); Stoecklin, Thierry [Université de Bordeaux, ISM, CNRS UMR 5255, 33405 Talence Cedex (France); Lique, François, E-mail: francois.lique@univ-lehavre.fr [LOMC - UMR 6294, CNRS-Université du Havre, 25 rue Philippe Lebon, BP 1123, 76 063 Le Havre cedex (France)

    2014-06-14

    Rotational excitation of the hydrogen cyanide (HCN) molecule by collisions with para-H{sub 2}( j = 0, 2) and ortho-H{sub 2}( j = 1) is investigated at low temperatures using a quantum time independent approach. Both molecules are treated as rigid rotors. The scattering calculations are based on a highly correlated ab initio 4-dimensional (4D) potential energy surface recently published. Rotationally inelastic cross sections among the 13 first rotational levels of HCN were obtained using a pure quantum close coupling approach for total energies up to 1200 cm{sup −1}. The corresponding thermal rate coefficients were computed for temperatures ranging from 5 to 100 K. The HCN rate coefficients are strongly dependent on the rotational level of the H{sub 2} molecule. In particular, the rate coefficients for collisions with para-H{sub 2}( j = 0) are significantly lower than those for collisions with ortho-H{sub 2}( j = 1) and para-H{sub 2}( j = 2). Propensity rules in favor of even Δj transitions were found for HCN in collisions with para-H{sub 2}( j = 0) whereas propensity rules in favor of odd Δj transitions were found for HCN in collisions with H{sub 2}( j ⩾ 1). The new rate coefficients were compared with previously published HCN-para-H{sub 2}( j = 0) rate coefficients. Significant differences were found due the inclusion of the H{sub 2} rotational structure in the scattering calculations. These new rate coefficients will be crucial to improve the estimation of the HCN abundance in the interstellar medium.

  2. Development of a high power HCN waveguide laser for plasma diagnostic

    International Nuclear Information System (INIS)

    Deng Zhongchao; Zhou Yan; Tang Yiwu; Yi Jiang; Gao Bingyi; Tian Chongli

    2007-06-01

    Both design and development of a high power cw HCN waveguide laser is described for multichannel FIR laser interferometer on the HL-2A divertor tokamak. The geometry parameters of stracture of the HCN laser are calculated according to scaling laws for cw 337 μm HCN waveguide laser offered by P. Belland et al. The designed value of output power of the laser that is more than 400 mW with discharge length of 5.6 m and 6.3 cm inner diameter of tube have been chosen in case of external loss of the cavity of 2%. At the same time, in order to get a laser system of stable output both of configuration and operating condition is discussed. In developed laser a hot LaB 6 cathode is employed to en- sure a stable discharge, the cavity mirrors are spaced using four invar rod of φ25 mm in diameter and an structure of adjusting machine for axially movable flat mirror in cavity has been also designed, and that it can be taken down many times without badly destroying alignment of the cavity etc.. A suit of pipes sys- tem of cw HCN laser is schemed out so that some experiments of operating parameter optimization can be done. The results of primary test of operating waveguide HCN laser are briefly showed. (authors)

  3. ORIGINS OF SCATTER IN THE RELATIONSHIP BETWEEN HCN 1-0 AND DENSE GAS MASS IN THE GALACTIC CENTER

    Energy Technology Data Exchange (ETDEWEB)

    Mills, Elisabeth A. C. [San Jose State University, 1 Washington Square, San Jose, CA 95192 (United States); Battersby, Cara, E-mail: elisabeth.mills@sjsu.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2017-01-20

    We investigate the correlation of HCN 1-0 with gas mass in the central 300 pc of the Galaxy. We find that on the ∼10 pc size scale of individual cloud cores, HCN 1-0 is well correlated with dense gas mass when plotted as a log–log relationship. There is ∼0.75 dex of scatter in this relationship from clouds like Sgr B2, which has an integrated HCN 1-0 intensity of a cloud less than half its mass, and others that have HCN 1-0 enhanced by a factor of 2–3 relative to clouds of comparable mass. We identify the two primary sources of scatter to be self-absorption and variations in HCN abundance. We also find that the extended HCN 1-0 emission is more intense per unit mass than in individual cloud cores. In fact the majority (80%) of HCN 1-0 emission comes from extended gas with column densities below 7 × 10{sup 22} cm{sup −2}, accounting for 68% of the total mass. We find variations in the brightness of HCN 1-0 would only yield a ∼10% error in the dense gas mass inferred from this line in the Galactic center. However, the observed order of magnitude HCN abundance variations, and the systematic nature of these variations, warn of potential biases in the use of HCN as dense gas mass tracer in more extreme environments such as an active galactic nucleus and shock-dominated regions. We also investigate other 3 mm tracers, finding that HNCO is better correlated with mass than HCN, and might be a better tracer of cloud mass in this environment.

  4. Ab initio study of low-energy electrons interacting with HCN molecules

    International Nuclear Information System (INIS)

    Jain, A.; Norcross, D.W.

    1984-01-01

    Our earlier study of low-energy electron scattering with HCN molecules is further improved by treating exchange exactly (in a separable exchange approximation 2 ) in Σ, π and Δ symmetries: the 3.8 eV π resonance is shifted towards lower energy (2.56 eV, the experimental position is around 2.26 eV 3 ), while in Σ and the Δ symmetries the difference is within 15%. We also study possible negative ion states of HCN by calculating potential energy curves with respect to C-H and C-N stretches. For example, there is evidence of an avoiding crossing between a 1Σ + and a 2Σ + state (C-H stretch) of HCN -

  5. HCN Production via Impact Ejecta Reentry During the Late Heavy Bombardment

    Science.gov (United States)

    Parkos, Devon; Pikus, Aaron; Alexeenko, Alina; Melosh, H. Jay

    2018-04-01

    Major impact events have shaped the Earth as we know it. The Late Heavy Bombardment is of particular interest because it immediately precedes the first evidence of life. The reentry of impact ejecta creates numerous chemical by-products, including biotic precursors such as HCN. This work examines the production of HCN during the Late Heavy Bombardment in more detail. We stochastically simulate the range of impacts on the early Earth and use models developed from existing studies to predict the corresponding ejecta properties. Using multiphase flow methods and finite-rate equilibrium chemistry, we then find the HCN production due to the resulting atmospheric heating. We use Direct Simulation Monte Carlo to develop a correction factor to account for increased yields due to thermochemical nonequilibrium. We then model 1-D atmospheric turbulent diffusion to find the time accurate transport of HCN to lower altitudes and ultimately surface water. Existing works estimate the necessary HCN molarity threshold to promote polymerization that is 0.01 M. For a mixing depth of 100 m, we find that the Late Heavy Bombardment will produce at least one impact event above this threshold with probability 24.1% for an oxidized atmosphere and 56.3% for a partially reduced atmosphere. For a mixing depth of 10 m, the probability is 79.5% for an oxidized atmosphere and 96.9% for a partially reduced atmosphere. Therefore, Late Heavy Bombardment impact ejecta is likely an HCN source sufficient for polymerization in shallow bodies of water, particularly if the atmosphere were in a partially reduced state.

  6. Experimental conditions affecting the kinetics of aqueous HCN polymerization as revealed by UV-vis spectroscopy.

    Science.gov (United States)

    Marín-Yaseli, Margarita R; Moreno, Miguel; de la Fuente, José L; Briones, Carlos; Ruiz-Bermejo, Marta

    2018-02-15

    HCN polymerization is one of the most important and fascinating reactions in prebiotic chemistry, and interest in HCN polymers in the field of materials science is growing. However, little is known about the kinetics of the HCN polymerization process. In the present study, a first approach to the kinetics of two sets of aqueous HCN polymerizations, from NH 4 CN and NaCN, at middle temperatures between 4 and 38°C, has been carried out. For each series, the presence of air and salts in the reaction medium has been systematically explored. A previous kinetic analysis was conducted during the conversion of the insoluble black HCN polymers obtained as gel fractions in these precipitation polymerizations for a reaction of one month, where a limit conversion was achieved at the highest polymerization temperature. The kinetic description of the gravimetric data for this complex system shows a clear change in the linear dependence with the polymerization temperature for the reaction from NH 4 CN, besides a relevant catalytic effect of ammonium, in comparison with those data obtained from the NaCN series. These results also demonstrated the notable influence of air, oxygen, and the saline medium in HCN polymer formation. Similar conclusions were reached when the sol fractions were monitored by UV-vis spectroscopy, and a Hill type correlation was used to describe the polymerization profiles obtained. This technique was chosen because it provides an easy, prompt and fast method to follow the evolution of the liquid or continuous phase of the process under study. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. The excitation of HCN and HCO{sup +} in the galactic center circumnuclear disk

    Energy Technology Data Exchange (ETDEWEB)

    Mills, E. A. C. [National Radio Astronomy Observatory, P.O. Box O 1009, Lopezville Drive, Socorro, NM 87801 (United States); Güsten, R.; Requena-Torres, M. A. [Max Planck Institut für Radioastronomie, Auf Dem Huegel 69, D-53121 Bonn (Germany); Morris, M. R., E-mail: millsb@astro.ucla.edu [Department of Physics and Astronomy, University of California, Physics and Astronomy Building, 430 Portola Plaza, Box 951547 Los Angeles, CA 90095-1547 (United States)

    2013-12-10

    We present new observations of HCN and HCO{sup +} in the circumnuclear disk (CND) of the Galaxy, which we obtained with the Atacama Pathfinder Experiment telescope. We mapped emission in rotational lines of HCN J = 3-2, 4-3, and 8-7, as well as of HCO{sup +} J = 3-2, 4-3, and 9-8. We also present spectra of H{sup 13}CN J = 3-2 and 4-3 as well as H{sup 13}CO{sup +} J = 3-2 and 4-3 toward four positions in the CND. Using the intensities of all of these lines, we present an excitation analysis for each molecule using the non-LTE radiative transfer code RADEX. The HCN line intensities toward the northern emission peak of the CND yield log densities (cm{sup –3}) of 5.6{sub −0.6}{sup +0.6}, consistent with those measured with HCO{sup +} as well as with densities recently reported for this region from an excitation analysis of highly excited lines of CO. These densities are too low for the gas to be tidally stable. The HCN line intensities toward the CND's southern emission peak yield log densities of 6.5{sub −0.7}{sup +0.5}, higher than densities determined for this part of the CND with CO (although the densities measured with HCO{sup +}, log [n] = 5.6{sub −0.2}{sup +0.2}, are more consistent with the CO-derived densities). We investigate whether the higher densities we infer from HCN are affected by midinfrared radiative excitation of this molecule through its 14 μm rovibrational transitions. We find that radiative excitation is important for at least one clump in the CND, where we additionally detect the J = 4-3, v {sub 2} = 1 vibrationally excited transition of HCN, which is excited by dust temperatures of ≳125-150 K. If this hot dust is present elsewhere in the CND, it could lower our inferred densities, potentially bringing the HCN-derived densities for the southern part of the CND into agreement with those measured using HCO{sup +} and CO. Additional sensitive, high-resolution submillimeter observations, as well as midinfrared observations, would be

  8. First-principles insights into interaction of CO, NO, and HCN with Ag{sub 8}

    Energy Technology Data Exchange (ETDEWEB)

    Torbatian, Zahra; Hashemifar, S. Javad, E-mail: hashemifar@cc.iut.ac.ir; Akbarzadeh, Hadi [Department of Physics, Isfahan University of Technology, 84156-83111 Isfahan (Iran, Islamic Republic of)

    2014-02-28

    We use static as well as time-dependent first-principles computations to study interaction of the CO, NO, and HCN molecules with the Ag{sub 8} nanocluster. The many-body based GW correction is applied for accurate description of the highest occupied (HOMO) and the lowest unoccupied (LUMO) molecular orbital levels. It is argued that the adsorption of these molecules changes the stable structure of Ag{sub 8} from Td to the more chemically active D{sub 2d} symmetry. We discuss that the CO, NO, and HCN molecules prefer to adsorb on the atom of the cluster with significant contribution to both HOMO and LUMO, for the accomplishment of the required charge transfers in the systems. The charge back donation is found to leave an excess energy of about 110 meV on the NO molecular bond, evidencing potential application of silver clusters for NO reduction. It is argued that CO and specially NO exhibit strong physical interaction with the silver cluster and hence significantly modify the electronic and optical properties of the system, while HCN makes very week physical bonds with the cluster. The optical absorption spectra of the Ag{sub 8} cluster before and after molecule adsorption are computed and a nontrivial red shift is observed in the NO and HCN adsorbed clusters.

  9. The HCN-Water Ratio in the Planet Formation Region of Disks

    NARCIS (Netherlands)

    Najita, J.; Carr, J.; Pontoppidan, K.; Salyk, C.; Dishoeck, van E.F.; Blake, G.

    2013-01-01

    We find a trend between the mid-infrared HCN/H$_{2}$O flux ratio and submillimeter disk mass among T Tauri stars in Taurus. While it may seem puzzling that the molecular emission properties of the inner disk ({lt}few AU) are related to the properties of the outer disk (beyond ~{}20 AU) probed by the

  10. WARM HCN IN THE PLANET FORMATION ZONE OF GV TAU N

    International Nuclear Information System (INIS)

    Fuente, Asunción; Cernicharo, José; Agúndez, Marcelino

    2012-01-01

    The Plateau de Bure Interferometer has been used to map the continuum emission at 3.4 mm and 1.1 mm together with the J = 1→0 and J = 3→2 lines of HCN and HCO + toward the binary star GV Tau. The 3.4 mm observations did not resolve the binary components, and the HCN J = 1→0 and HCO + J 1→0 line emissions trace the circumbinary disk and the flattened envelope. However, the 1.1 mm observations resolved the individual disks of GV Tau N and GV Tau S and allowed us to study their chemistry. We detected the HCN 3→2 line only toward the individual disk of GV Tau N, and the emission of the HCO + 3→2 line toward GV Tau S. Simple calculations indicate that the 3→2 line of HCN is formed in the inner R + abundance ratio is >300. On the contrary, this ratio is 400 K) and dense (n > 10 7 cm –3 ) disk surface.

  11. Millimeterwave spectroscopy of active laser plasmas; the excited vibrational states of HCN

    International Nuclear Information System (INIS)

    De Lucia, F.C.; Helminger, P.A.

    1977-01-01

    Millimeter and submillimeter microwave techniques have been used for the spectroscopic study of an HCN laser plasma. Forty-seven rotational transitions in 12 excited vibrational states have been observed. Numerous rotational, vibrational, and perturbation parameters have been calculated from these data. A discussion of experimental techniques is included

  12. THE HCN/HNC ABUNDANCE RATIO TOWARD DIFFERENT EVOLUTIONARY PHASES OF MASSIVE STAR FORMATION

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Mihwa; Lee, Jeong-Eun [School of Space Research, Kyung Hee University, Yongin-Si, Gyeonggi-Do 446-701 (Korea, Republic of); Kim, Kee-Tae, E-mail: mihwajin.sf@gmail.com, E-mail: jeongeun.lee@khu.ac.kr, E-mail: ktkim@kasi.re.kr [Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 305-348 (Korea, Republic of)

    2015-07-20

    Using the H{sup 13}CN and HN{sup 13}C J = 1–0 line observations, the abundance ratio of HCN/HNC has been estimated for different evolutionary stages of massive star formation: infrared dark clouds (IRDCs), high-mass protostellar objects (HMPOs), and ultracompact H ii regions (UCH iis). IRDCs were divided into “quiescent IRDC cores (qIRDCc)” and “active IRDC cores (aIRDCc),” depending on star formation activity. The HCN/HNC ratio is known to be higher at active and high temperature regions related to ongoing star formation, compared to cold and quiescent regions. Our observations toward 8 qIRDCc, 16 aIRDCc, 23 HMPOs, and 31 UCH iis show consistent results; the ratio is 0.97 (±0.10), 2.65 (±0.88), 4.17 (±1.03), and 8.96 (±3.32) in these respective evolutionary stages, increasing from qIRDCc to UCH iis. The change of the HCN/HNC abundance ratio, therefore, seems directly associated with the evolutionary stages of star formation, which have different temperatures. One suggested explanation for this trend is the conversion of HNC to HCN, which occurs effectively at higher temperatures. To test the explanation, we performed a simple chemical model calculation. In order to fit the observed results, the energy barrier of the conversion must be much lower than the value provided by theoretical calculations.

  13. Photodissociation of HCN and HNC isomers in the 7-10 eV energy range

    Energy Technology Data Exchange (ETDEWEB)

    Chenel, Aurelie; Roncero, Octavio, E-mail: octavio.roncero@csic.es [Instituto de Física Fundamental (IFF-CSIC), C.S.I.C., Serrano 123, 28006 Madrid (Spain); Aguado, Alfredo [Departamento de Química Física Aplicada (UAM), Unidad Asociada a IFF-CSIC, Facultad de Ciencias Módulo 14, Universidad Autónoma de Madrid, 28049 Madrid (Spain); Agúndez, Marcelino; Cernicharo, José [Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco (Spain)

    2016-04-14

    The ultraviolet photoabsorption spectra of the HCN and HNC isomers have been simulated in the 7-10 eV photon energy range. For this purpose, the three-dimensional adiabatic potential energy surfaces of the 7 lowest electronic states, and the corresponding transition dipole moments, have been calculated, at multireference configuration interaction level. The spectra are calculated with a quantum wave packet method on these adiabatic potential energy surfaces. The spectra for the 3 lower excited states, the dissociative electronic states, correspond essentially to predissociation peaks, most of them through tunneling on the same adiabatic state. The 3 higher electronic states are bound, hereafter electronic bound states, and their spectra consist of delta lines, in the adiabatic approximation. The radiative lifetime towards the ground electronic states of these bound states has been calculated, being longer than 10 ns in all cases, much longer that the characteristic predissociation lifetimes. The spectra of HCN is compared with the available experimental and previous theoretical simulations, while in the case of HNC there are no previous studies to our knowledge. The spectrum for HNC is considerably more intense than that of HCN in the 7-10 eV photon energy range, which points to a higher photodissociation rate for HNC, compared to HCN, in astrophysical environments illuminated by ultraviolet radiation.

  14. Probing highly obscured, self-absorbed galaxy nuclei with vibrationally excited HCN

    Science.gov (United States)

    Aalto, S.; Martín, S.; Costagliola, F.; González-Alfonso, E.; Muller, S.; Sakamoto, K.; Fuller, G. A.; García-Burillo, S.; van der Werf, P.; Neri, R.; Spaans, M.; Combes, F.; Viti, S.; Mühle, S.; Armus, L.; Evans, A.; Sturm, E.; Cernicharo, J.; Henkel, C.; Greve, T. R.

    2015-12-01

    We present high resolution (0.̋4) IRAM PdBI and ALMA mm and submm observations of the (ultra) luminous infrared galaxies ((U)LIRGs) IRAS 17208-0014, Arp220, IC 860 and Zw049.057 that reveal intense line emission from vibrationally excited (ν2 = 1) J = 3-2 and 4-3 HCN. The emission is emerging from buried, compact (r 5 × 1013 L⊙ kpc-2. These nuclei are likely powered by accreting supermassive black holes (SMBHs) and/or hot (>200 K) extreme starbursts. Vibrational, ν2 = 1, lines of HCN are excited by intense 14 μm mid-infrared emission and are excellent probes of the dynamics, masses, and physical conditions of (U)LIRG nuclei when H2 column densities exceed 1024 cm-2. It is clear that these lines open up a new interesting avenue to gain access to the most obscured AGNs and starbursts. Vibrationally excited HCN acts as a proxy for the absorbed mid-infrared emission from the embedded nuclei, which allows for reconstruction of the intrinsic, hotter dust SED. In contrast, we show strong evidence that the ground vibrational state (ν = 0), J = 3-2and 4-3 rotational lines of HCN and HCO+ fail to probe the highly enshrouded, compact nuclear regions owing to strong self- and continuum absorption. The HCN and HCO+ line profiles are double-peaked because of the absorption and show evidence of non-circular motions - possibly in the form of in- or outflows. Detections of vibrationally excited HCN in external galaxies are so far limited to ULIRGs and early-type spiral LIRGs, and we discuss possible causes for this. We tentatively suggest that the peak of vibrationally excited HCN emission is connected to a rapid stage of nuclear growth, before the phase of strong feedback. Based on observations carried out with the IRAM Plateau de Bure and ALMA Interferometers. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada) and NSC and ASIAA

  15. Synthesis of HCN and HNC in Ion-Irradiated N2-Rich Ices

    Science.gov (United States)

    Moore, M. H.; Hudson, R. L.; Ferrante, R. F.

    2002-11-01

    Near-IR observations reveal that nitrogen-rich ice containing small amounts of methane, CH4, and carbon monoxide, CO, is abundant on the surfaces of Triton, a moon of Neptune, and Pluto (Cruikshank et al.. 1993; Owen et al., 1993). N2-rich apolar ices are also possible in some interstellar environments (Ehrenfreund et al., 1998). To investigate the radiation chemical behavior of N2-dominated ices we performed a systematic IR study of ion-irradiated N2-rich ices containing CH4 and CO. Experiments at 18 K, showed that HCN, HNC, and the reactive molecule diazomethane, CH2N2, formed along with several radicals. NH3 was also identified in irradiated N2 + CH4. Comparing results from similarly photolyzed ices (Bohn et al., 1994) shows that the significant difference between radiolysis and photolysis of these N2-dominated ices is that photolyzed ices do not form detectable HCN and HNC. Our experiments examined different N2/CH4 ratios, the half-life of CH4, possible HCN and HNC formation routes, and competing pathways in the presence of CO. Intrinsic band strengths (A(HCN) and A(HNC)) were measured and used to calculate nearly equal values of HCN and HNC yields in N2+CH4 irradiated ices. Low temperature results apply to interstellar ices. Reaction products that appear at 30-35 K are also expected to form and survive on the surfaces of Triton and Pluto and interstellar grains. We examined the evolution of ice features as species undergo acid-base (acids such as HCN, HNC, HNCO and a base NH3) reactions triggered by warming from 18 K to 30-35 K. We identified anions (OCN-, CN- and N3-) attributed to relatively stable salts in ices where NH4+ is the likely cation. These results also have an astrobiology implication since many of these products (HCN, HNC, HNCO, NH3, NH4OCN, and NH4CN) are reactants used in synthesis studies of bio- molecules such as amino acids and peptides.

  16. Structural Insight into the Gene Expression Profiling of the hcn Operon in Pseudomonas aeruginosa.

    Science.gov (United States)

    Chowdhury, Nilkanta; Bagchi, Angshuman

    2017-07-01

    Pseudomonas aeruginosa is a common opportunistic human pathogen. It generally attacks immunosuppressed patients like AIDS, cancer, cystic fibrosis, etc. The virulence of P. aeruginosa is mediated by various virulence factors. One of such potential virulence factors is HCN synthesized by HCN synthase enzyme, which is encoded by the hcnABC operon. The expressions of the genes of this operon are regulated by three transcriptional regulators, viz., LasR, ANR, and RhlR. In our previous work, we analyzed the molecular details of the functionalities of LasR. In this work, we focused on ANR. ANR is a regulatory protein which belongs to the FNR family and works in anaerobic condition. ANR binds to the promoter DNA, named ANR box, as a dimer. The dimerization of this ANR protein is regulated by Fe 4 S 4 , an iron-sulfur cluster. This dimer of ANR (ANR-Fe 4 S 4 /ANR-Fe 4 S 4 ) recognizes and binds the promoter DNA sequence and regulates the transcription of this hcnABC operon. Till date, the biomolecular details of the interactions of ANR dimer with the promoter DNA are not fully understood. Thus, we built the molecular model of ANR-Fe 4 S 4 /ANR-Fe 4 S 4 . We docked the complex with the corresponding promoter DNA region. We analyzed the mode of interactions with the promoter DNA under different conditions. Thus, we tried to analyze the functionality of the ANR protein during the expressions of the genes of the hcnABC operon. So far, this is the first report to detail the molecular mechanism of the gene expression in P. aeruginosa.

  17. HCN(1-0) enhancement in the bar of NGC 2903

    Science.gov (United States)

    Leon, S.; Jeyakumar, S.; Pérez-Ramírez, D.; Verdes-Montenegro, L.; Lee, S. W.; Ocaña Flaquer, B.

    2008-12-01

    We have mapped the HCN(1-0) emission from two spiral galaxies, NGC 2903 and NGC 3504 to study the gas properties in the bars. The HCN(1-0) emission is detected in the center and along the bar of NGC 2903. The line ratio HCN(1-0)/ 12CO(1-0) ranges from 0.07 to 0.12 with the lowest value in the center. The enhancement of HCN(1-0) emission along the bar indicates a higher fraction of dense molecular gas in the bar than at the center. The mass of dense molecular gas in the center (2.2 × 107 M⊙) is about 6 times lower than that in the bar (1.2 × 108 M⊙). The total star formation rate (SFR) is estimated to be 1.4 M⊙ yr-1, where the SFR at the center is 1.9 times higher than that in the bar. The time scale of consumption of the dense molecular gas in the center is about ~ 3 × 107 yr which is much shorter than that in the bar of about 2 to 10 × 108 yr. The dynamical time scale of inflow of the gas from the bar to the center is shorter than the consumption time scale in the bar, which suggests that the star formation (SF) activity at the center is not deprived of fuel. In the bar, the fraction of dense molecular gas mass relative to the total molecular gas mass is twice as high along the leading edge than along the central axis of the bar. The HCN(1-0) emission has a large velocity dispersion in the bar, which can be attributed partially to the streaming motions indicative of shocks along the bar. In NGC 3504, the HCN(1-0) emission is detected only at the center. The fraction of dense molecular gas mass in the center is about 15%. Comparison of the SFR with the predictions from numerical simulations suggest that NGC 2903 harbors a young type B bar with a strong inflow of gas toward the center whereas NGC 3504 has an older bar and has already passed the phase of inflow of gas toward the center.

  18. Expression and distribution of voltage-gated ion channels in ferret sinoatrial node.

    Science.gov (United States)

    Brahmajothi, Mulugu V; Morales, Michael J; Campbell, Donald L; Steenbergen, Charles; Strauss, Harold C

    2010-10-01

    Spontaneous diastolic depolarization in the sinoatrial (SA) node enables it to serve as pacemaker of the heart. The variable cell morphology within the SA node predicts that ion channel expression would be heterogeneous and different from that in the atrium. To evaluate ion channel heterogeneity within the SA node, we used fluorescent in situ hybridization to examine ion channel expression in the ferret SA node region and atrial appendage. SA nodal cells were distinguished from surrounding cardiac myocytes by expression of the slow (SA node) and cardiac (surrounding tissue) forms of troponin I. Nerve cells in the sections were identified by detection of GAP-43 and cytoskeletal middle neurofilament. Transcript expression was characterized for the 4 hyperpolarization-activated cation channels, 6 voltage-gated Na(+) channels, 3 voltage-gated Ca(2+) channels, 24 voltage-gated K(+) channel α-subunits, and 3 ancillary subunits. To ensure that transcript expression was representative of protein expression, immunofluorescence was used to verify localization patterns of voltage-dependent K(+) channels. Colocalizations were performed to observe any preferential patterns. Some overlapping and nonoverlapping binding patterns were observed. Measurement of different cation channel transcripts showed heterogeneous expression with many different patterns of expression, attesting to the complexity of electrical activity in the SA node. This study provides insight into the possible role ion channel heterogeneity plays in SA node pacemaker activity.

  19. A search for the millimetre lines of HCN in Comets Wilson 1987 VII and Machholz 1988 XV

    Science.gov (United States)

    Crouvisier, J.; Despois, D.; Bockelee-Morvan, D.; Gerard, E.; Paubert, G.; Johansson, L. E. B.; Ekelund, L.; Winnberg, A.; Ge, W.; Irvine, W. M.; Kinzel, W. M.; Schloerb, F. P.

    1990-08-01

    The J(1-0) lines of HCN at 89 GHz were searched for in Comet Wilson 1987 VII, with the FCRAO, the SEST and the IRAM radio telescopes between February and June 1987. There was no firm detection, but significant upper limits were obtained, which put severe constraints on the HCN production rate in that comet. A direct comparison with the observations of P/Halley suggests that the HCN abundance relative to water might be smaller in Comet Wilson by at least a factor of two. The J(1-0) and J(3-2) lines of HCN at 89 and 266 GHz were searched for in Comet Machholz 1988 XV when it was close to perihelion at 0.17 AU from the sun. There was no detection. At that moment, the comet was probably no longer active.

  20. Substitutional HCN- molecular ions in KCN crystal: a paramagnetic probe in a ferroelastic material

    International Nuclear Information System (INIS)

    Weid, J.P. von der; Carmo, L.C.S. do; Ribeiro, S.C.

    1978-01-01

    The HCN - molecular ion was produced in single crystals of KCN: 10 -2 OH - irradiated by UV light at 77 K. The spin Hamiltonian parameters were measured at 60 K and the temperature dependence of the spectrum was investigated between 60 K and 170 K. This temperature dependence is explained by the rapid motion of the molecule with the increasing temperature and the elastic interaction of the molecule with the surrounding ions. Using the similarity between the paramagnetic HCN - molecule and the CN - ions of the host lattice a qualitative picture of the local phenomena occuring in the ferroelastic phase of KCN could be made and the energy of the elastic interaction between CN - was estimated of the order of 7 meV [pt

  1. Detection of HCN and C2H2 in ISO Spectra of Oxygen-Rich AGB Stars

    Science.gov (United States)

    Carbon, Duane F.; Chiar, Jean; Goorvitch, David; Kwak, Dochan (Technical Monitor)

    2002-01-01

    Cool oxygen-rich AGB stars were not expected to have organic molecules like HCN in either their photospheres or circumstellar envelopes (CSEs). The discovery of HCN and CS microwave emission from the shallowest CSE layers of these stars was a considerable surprise and much theoretical effort has been expended in explaining the presence of such organics. To further explore this problem, we have undertaken a systematic search of oxygen-rich AGB stellar spectra in the Infrared Space Observatory (ISO) data archive. Our purposes are to find evidence regarding critical molecular species that could be of value in choosing among the proposed theoretical models, to locate spectral features which might give clues to conditions deeper in the CSEs, and to lay the groundwork for future SIRTF (Space Infrared Telescope Facility) and SOFIA (Stratospheric Observatory for Infrared Astronomy) observations. Using carefully reduced observations, we have detected weak absorption features arising from HCN and possibly C2H2 in a small number of oxygen-rich AGB stars. The most compelling case is NML Cyg which shows both HCN (14 microns) and CO2 (15 microns). VY CMa, a similar star, shows evidence for HCN, but not CO2. Two S-type stars show evidence for the C-H bending transitions: W Aql at 14 microns (HCN) and both W Aql and S Cas at 13.7 microns (C2H2). Both W Aql and S Cas as well as S Lyr, a SC-type star, show 3 micron absorption which may arise from the C-H stretch of HCN and C2H2. In the case of NML Cyg, we show that the HCN and CO2 spectral features are formed in the CSE at temperatures well above those of the outermost CSE layers and derive approximate column densities. In the case of the S-stars, we discuss the evidence for the organic features and their photospheric origin.

  2. Chemical evolution. XXI - The amino acids released on hydrolysis of HCN oligomers

    Science.gov (United States)

    Ferris, J. P.; Wos, J. D.; Nooner, D. W.; Oro, J.

    1974-01-01

    Major amino acids released by hydrolysis of acidic and basic HCN oligomers are identified by chromatography as Gly, Asp, and diaminosuccinic acid. Smaller amounts of Ala, Ile and alpha-aminoisobutyric acid are also detected. The amino acids released did not change appreciably when the hydrolysis medium was changed from neutral to acidic or basic. The presence of both meso and d, l-diaminosuccinic acids was established by paper chromatography and on an amino acid analyzer.

  3. Investigating the Spatial Structure of HCN Emission in Comet C/2012 F6 (Lemmon)

    Science.gov (United States)

    Booth, Shawn; Burkhardt, Andrew; Corby, Joanna; Dollhopf, Niklaus; Rawlings, Mark; Remijan, Anthony

    2015-11-01

    Comets are of particular interest in the field of Astrochemistry as they can be used as a direct probe of formation chemistry of the Solar System. Originating in the Oort Cloud reservoir, these long period objects experience relatively limited solar influence. The majority of cometary material (water, methane and ammonia ices) has remained in the same state as when it formed. These ices are precursors to more complex molecules which have been shown to form amino acids that are crucial for the development of life. HCN, or hydrogen cyanide, is of particular interest because it can form the nucleobase adenine (C5H5N5). The goals of this project are to map the HCN distribution of Comet C/2012 F6 (Lemmon) and to show the simultaneous observation capabilities of the Atacama Large Millimeter/Submillimeter Array (ALMA), which allows the extraction of 7-m array, 12-m array and single dish observation data. On UT 2013 May 11, Comet Lemmon was observed using ALMA. The Cycle 1 configuration was used with the Band 6 receivers, with a 1.5 GHz range centered on the HCN transition at 265.86 GHz, which gave a spectral resolution of 0.07 km/s. We show that Comet Lemmon has both a compact HCN region (found with the 12-m array) and also an extended component, forming a tail-like structure in the anti-motion direction (found with the 7-m array). We were also able to extract the autocorrelation data (single dish) and show that it is viable. This project was supported and funded by NRAO in conjunction with the National Science Foundation (NSF), with special thanks to the Astronomy Department at University of Virginia.

  4. Lamellar γ-AlOOH architectures: Synthesis and application for the removal of HCN

    International Nuclear Information System (INIS)

    Hou Hongwei; Zhu You; Tang Gangling; Hu Qingyuan

    2012-01-01

    Using hexadecyl trimethyl ammonium bromide (CTAB) as a structure-directing agent and precipitator, the complete synthesis of lamellar γ-AlOOH architectures was successfully accomplished via a hydrothermal route. Different product structures were obtained by varying the molar ratio of aluminum nitrate and CTAB. Several techniques, including X-ray powder diffraction, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, and differential scanning calorimetry thermal analysis, were used to characterize the products. The effects of CTAB concentration, reaction temperature and time, and the molar ratio of Al 3+ /CTAB on the product morphologies were investigated. The nitrogen adsorption and desorption measurements indicated that the γ-AlOOH architectures possess a Brunauer–Emmett–Teller surface area of approximately 75.02 m 2 /g. It was also demonstrated that 10 mg γ-AlOOH architectures can remove 45.3% of the HCN (1.68 μg/mL) from model wastewater. When 0.03 mg/cig γ-AlOOH architectures were combined with cigarette paper, 8.12% of the present HCN was adsorbed. These results indicate that lamellar γ-AlOOH architectures may be a potential adsorbent for removing HCN from highly toxic pollutant solutions and harmful cigarette smoke. Highlights: ► Hexadecyl trimethyl ammonium bromide (CTAB) was used as a structure-directing agent and precipitator. ► Hydrothermal treatment enables growth of lamellar γ-AlOOH architectures. ► Lamellar γ-AlOOH architectures were demonstrated to exhibit high BET surface area and excellent adsorptive capacity. ► HCN in contaminated water and cigarette smoke can be effectively removed by the prepared lamellar γ-AlOOH superstructures.

  5. EXTENDED HCN AND HCO{sup +} EMISSION IN THE STARBURST GALAXY M82

    Energy Technology Data Exchange (ETDEWEB)

    Salas, P.; Galaz, G. [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicua Mackenna 4860, 782-0436 Macul, Santiago (Chile); Salter, D.; Herrera-Camus, R.; Bolatto, A. D. [Department of Astronomy and Laboratory for Millimeter-Wave Astronomy, University of Maryland, College Park, MD 20742 (United States); Kepley, A. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475 (United States)

    2014-12-20

    We mapped 3 mm continuum and line emission from the starburst galaxy M82 using the Combined Array for Research in Millimeter-wave Astronomy. We targeted the HCN, HCO{sup +}, HNC, CS, and HC{sub 3}N lines, but here we focus on the HCN and HCO{sup +} emission. The map covers a field of 1.'2 with an ≈5'' resolution. The HCN and HCO{sup +} observations are short spacings corrected. The molecular gas in M82 had been previously found to be distributed in a molecular disk, coincident with the central starburst, and a galactic scale outflow which originates in the central starburst. With the new short spacings-corrected maps we derive some of the properties of the dense molecular gas in the base of the outflow. From the HCN and HCO{sup +} J = (1-0) line emission, and under the assumptions of the gas being optically thin and in local thermodynamic equilibrium, we place lower limits on the amount of dense molecular gas in the base of the outflow. The lower limits are 7 × 10{sup 6} M {sub ☉} and 21 × 10{sup 6} M {sub ☉}, or ≳ 2% of the total molecular mass in the outflow. The kinematics and spatial distribution of the dense gas outside the central starburst suggests that it is being expelled through chimneys. Assuming a constant outflow velocity, the derived outflow rate of dense molecular gas is ≥0.3 M {sub ☉} yr{sup –1}, which would lower the starburst lifetime by ≥5%. The energy required to expel this mass of dense gas is (1-10) × 10{sup 52} erg.

  6. Adsorption of HCN molecules on Ni, Pd and Pt-doped (7, 0) boron nitride nanotube: a DFT study

    Science.gov (United States)

    Habibi-Yangjeh, Aziz; Basharnavaz, Hadi

    2018-05-01

    We studied affinity of pure and Ni, Pd and Pt-doped (7, 0) boron nitride nanotubes (BNNTs) to toxic HCN molecules using density functional theory calculations. The results indicated that the pure (7, 0) BNNTs can weakly adsorb HCN molecules with adsorption energy of -0.2474 eV. Upon adsorption of HCN molecules on this nanotube, the band gap energy was decreased from 3.320 to 2.960 eV. The more negative adsorption energy between these transition metal-doped (7, 0) BNNTs and HCN molecules indicated that doping of (7, 0) BNNTs with Ni, Pd and Pt elements can significantly improve the affinity of BNNTs toward this gas. Additionally, it was found that the interaction energy between HCN molecules and Pt-doped BNNTs is more negative than those of the Ni and Pd-doped BNNTs. These observations suggested that the Pt-doped (7, 0) BNNTs are strongly sensitive to HCN molecules and therefore it may be used in gas sensor devices for detecting this toxic gas.

  7. United States Historical Climatology Network (US HCN) monthly temperature and precipitation data

    Energy Technology Data Exchange (ETDEWEB)

    Daniels, R.C. [ed.] [Univ. of Tennessee, Knoxville, TN (United States). Energy, Environment and Resources Center; Boden, T.A. [ed.] [Oak Ridge National Lab., TN (United States); Easterling, D.R.; Karl, T.R.; Mason, E.H.; Hughes, P.Y.; Bowman, D.P. [National Climatic Data Center, Asheville, NC (United States)

    1996-01-11

    This document describes a database containing monthly temperature and precipitation data for 1221 stations in the contiguous United States. This network of stations, known as the United States Historical Climatology Network (US HCN), and the resulting database were compiled by the National Climatic Data Center, Asheville, North Carolina. These data represent the best available data from the United States for analyzing long-term climate trends on a regional scale. The data for most stations extend through December 31, 1994, and a majority of the station records are serially complete for at least 80 years. Unlike many data sets that have been used in past climate studies, these data have been adjusted to remove biases introduced by station moves, instrument changes, time-of-observation differences, and urbanization effects. These monthly data are available free of charge as a numeric data package (NDP) from the Carbon Dioxide Information Analysis Center. The NDP includes this document and 27 machine-readable data files consisting of supporting data files, a descriptive file, and computer access codes. This document describes how the stations in the US HCN were selected and how the data were processed, defines limitations and restrictions of the data, describes the format and contents of the magnetic media, and provides reprints of literature that discuss the editing and adjustment techniques used in the US HCN.

  8. Outward Rectification of Voltage-Gated K+ Channels Evolved at Least Twice in Life History.

    Directory of Open Access Journals (Sweden)

    Janin Riedelsberger

    Full Text Available Voltage-gated potassium (K+ channels are present in all living systems. Despite high structural similarities in the transmembrane domains (TMD, this K+ channel type segregates into at least two main functional categories-hyperpolarization-activated, inward-rectifying (Kin and depolarization-activated, outward-rectifying (Kout channels. Voltage-gated K+ channels sense the membrane voltage via a voltage-sensing domain that is connected to the conduction pathway of the channel. It has been shown that the voltage-sensing mechanism is the same in Kin and Kout channels, but its performance results in opposite pore conformations. It is not known how the different coupling of voltage-sensor and pore is implemented. Here, we studied sequence and structural data of voltage-gated K+ channels from animals and plants with emphasis on the property of opposite rectification. We identified structural hotspots that alone allow already the distinction between Kin and Kout channels. Among them is a loop between TMD S5 and the pore that is very short in animal Kout, longer in plant and animal Kin and the longest in plant Kout channels. In combination with further structural and phylogenetic analyses this finding suggests that outward-rectification evolved twice and independently in the animal and plant kingdom.

  9. THE VARIABILITY OF HCN IN TITAN’S UPPER ATMOSPHERE AS IMPLIED BY THE CASSINI ION-NEUTRAL MASS SPECTROMETER MEASUREMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Cui, J.; Cao, Y.-T. [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Lavvas, P. P. [Groupe de Spectroscopie Moleculaire et Atmospherique, Universite de Reims, Champagne-Ardenne, CNRS UMR F-7331 (France); Koskinen, T. T. [Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721 (United States)

    2016-07-20

    HCN is an important constituent in Titan’s upper atmosphere, serving as the main coolant in the local energy budget. In this study, we derive the HCN abundance at the altitude range of 960–1400 km, combining the Ion-Neutral Mass Spectrometer data acquired during a large number of Cassini flybys with Titan. Typically, the HCN abundance declines modestly with increasing altitude and flattens to a near constant level above 1200 km. The data reveal a tendency for dayside depletion of HCN, which is clearly visible below 1000 km but weakens with increasing altitude. Despite the absence of convincing anti-correlation between HCN volume mixing ratio and neutral temperature, we argue that the variability in HCN abundance makes an important contribution to the large temperature variability observed in Titan’s upper atmosphere.

  10. ALMA INVESTIGATION OF VIBRATIONALLY EXCITED HCN/HCO{sup +}/HNC EMISSION LINES IN THE AGN-HOSTING ULTRALUMINOUS INFRARED GALAXY IRAS 20551−4250

    Energy Technology Data Exchange (ETDEWEB)

    Imanishi, Masatoshi [Subaru Telescope, 650 North A’ohoku Place, Hilo, HI 96720 (United States); Nakanishi, Kouichiro [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Izumi, Takuma, E-mail: masa.imanishi@nao.ac.jp [Institute of Astronomy, School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan)

    2016-07-01

    We present the results of ALMA Cycle 2 observations of the ultraluminous infrared galaxy IRAS 20551−4250 at HCN/HCO{sup +}/HNC J = 3–2 lines at both vibrational ground ( v = 0) and vibrationally excited ( v {sub 2} = 1) levels. This galaxy contains a luminous buried active galactic nucleus (AGN), in addition to starburst activity, and our ALMA Cycle 0 data revealed a tentatively detected vibrationally excited HCN v {sub 2} = 1f J = 4–3 emission line. In our ALMA Cycle 2 data, the HCN/HCO{sup +}/HNC J = 3–2 emission lines at v = 0 are clearly detected. The HCN and HNC v {sub 2} = 1f J = 3–2 emission lines are also detected, but the HCO{sup +} v {sub 2} = 1f J = 3–2 emission line is not. Given the high energy level of v {sub 2} = 1 and the resulting difficulty of collisional excitation, we compared these results with those of the calculation of infrared radiative pumping, using the available infrared 5–35 μ m spectrum. We found that all of the observational results were reproduced if the HCN abundance was significantly higher than that of HCO{sup +} and HNC. The flux ratio and excitation temperature between v {sub 2} = 1f and v = 0, after correction for possible line opacity, suggests that infrared radiative pumping affects rotational ( J -level) excitation at v = 0 at least for HCN and HNC. The HCN-to-HCO{sup +} v = 0 flux ratio is higher than those of starburst-dominated regions, and will increase even more when the derived high HCN opacity is corrected. The enhanced HCN-to-HCO{sup +} flux ratio in this AGN-hosting galaxy can be explained by the high HCN-to-HCO{sup +} abundance ratio and sufficient HCN excitation at up to J = 4, rather than the significantly higher efficiency of infrared radiative pumping for HCN than HCO{sup +}.

  11. In situ measurements of HCN and CH3CN over the Pacific Ocean: Sources, sinks, and budgets

    Science.gov (United States)

    Singh, H. B.; Salas, L.; Herlth, D.; Kolyer, R.; Czech, E.; Viezee, W.; Li, Q.; Jacob, D. J.; Blake, D.; Sachse, G.; Harward, C. N.; Fuelberg, H.; Kiley, C. M.; Zhao, Y.; Kondo, Y.

    2003-10-01

    We report the first in situ measurements of hydrogen cyanide (HCN) and methyl cyanide (CH3CN, acetonitrile) from the Pacific troposphere (0-12 km) obtained during the NASA Transport and Chemical Evolution over the Pacific (TRACE-P) airborne mission (February-April 2001). Mean HCN and CH3CN mixing ratios of 243 ± 118 (median 218) ppt and 149 ± 56 (median 138) ppt, respectively, were measured. These in situ observations correspond to a mean tropospheric HCN column of 4.2 × 1015 molecules cm-2 and a CH3CN column of 2.5 × 1015 molecules cm-2. This is in good agreement with the 0-12 km HCN column of 4.4 (±0.6) × 1015 molecules cm-2 derived from infrared solar spectroscopic observations over Japan. Mixing ratios of HCN and CH3CN were greatly enhanced in pollution outflow from Asia and were well correlated with each other as well as with known tracers of biomass combustion (e.g., CH3Cl, CO). Volumetric enhancement (or emission) ratios (ERs) relative to CO in free tropospheric plumes, likely originating from fires, were 0.34% for HCN and 0.17% for CH3CN. ERs with respect to CH3Cl and CO in selected biomass burning (BB) plumes in the free troposphere and in boundary layer pollution episodes are used to estimate a global BB source of 0.8 ± 0.4 Tg (N) yr-1 for HCN and 0.4 ± 0.1 Tg (N) yr-1 for CH3CN. In comparison, emissions from industry and fossil fuel combustion are quite small (atmospheric residence time of 5.0 months for HCN and 6.6 months for CH3CN is calculated. A global budget analysis shows that the sources and sinks of HCN and CH3CN are roughly in balance but large uncertainties remain in part due to a lack of observational data from the atmosphere and the oceans. Pathways leading to the oceanic (and soil) degradation of these cyanides are poorly known but are expected to be biological in nature.

  12. The correlation between HCN/H2O flux ratios and disk mass: evidence for protoplanet formation

    Science.gov (United States)

    Rose, Caitlin; Salyk, Colette

    2017-01-01

    We analyze hydrogen cyanide (HCN) and water vapor flux ratios in protoplanetary disks as a way to trace planet formation. Analyzing only disks in the Taurus molecular cloud, Najita et al. (2013) found a tentative correlation between protoplanetary disk mass and the HCN/H2O line flux ratio in Spitzer-IRS emission spectra. They interpret this correlation to be a consequence of more massive disks forming planetesimals more efficiently than smaller disks, as the formation of large planetesimals may lock up water ice in the cool outer disk region and prevent it from migrating, drying out the inner disk. The sequestering of water (and therefore oxygen) in the outer disk may also increase the carbon-to- oxygen ratio in the inner disk, leading to enhanced organic molecule (e.g. HCN) emission. To confirm this trend, we expand the Najita et al. sample by calculating HCN/H2O line flux ratios for 8 more sources with known disk masses from clusters besides Taurus. We find agreement with the Najita et al. trend, suggesting that this is a widespread phenomenon. In addition, we find HCN/H2O line flux ratios for 17 more sources that await disk mass measurements, which should become commonplace in the ALMA era. Finally, we investigate linear fits and outliers to this trend, and discuss possible causes.

  13. A widely tunable, near-infrared laser-based trace gas sensor for hydrogen cyanide (HCN) detection in exhaled breath

    Science.gov (United States)

    Azhar, M.; Mandon, J.; Neerincx, A. H.; Liu, Z.; Mink, J.; Merkus, P. J. F. M.; Cristescu, S. M.; Harren, F. J. M.

    2017-11-01

    A compact, cost-effective sensor is developed for detection of hydrogen cyanide (HCN) in exhaled breath within seconds. For this, an off-axis integrated cavity output spectroscopy setup is combined with a widely tunable compact near-infrared laser (tunability 1527-1564 nm). For HCN a detection sensitivity has been obtained of 8 ppbv in nitrogen (within 1 s), equal to a noise equivalent absorption sensitivity of 1.9 × 10-9 cm-1 Hz-1/2. With this sensor we demonstrated the presence of HCN in exhaled breath; its detection could be a good indicator for bacterial lung infection. Due to its compact, cost-effective and user-friendly design, this laser-based sensor has the potential to be implemented in future clinical applications.

  14. Signal detection circuit design of HCN measurement system based on TDLAS

    Science.gov (United States)

    He, Chungui; Zhang, Yujun; Chen, Chen; Lu, Yibing; Liu, Guohua; Gao, Yanwei; You, Kun; He, Ying; Zhang, Kai; Liu, Wenqing

    2016-10-01

    Hydrogen cyanide gas leakage may exist in the petrochemical industry, smelting plant, and other industrial processes, causing serious harm to the environment, and even threatening the safety of personnel. So the continuous detection of HCN gas plays an important role in the prevention of risk in production process and storage environment that existing hydrogen cyanide gas. The Tunable Diode Laser Technology (TDLAS) has advantages of non-contact, high sensitivity, high selectivity, and fast response time, etc., which is one of the ideal method of gas detection technologies and can be used to measure the hydrogen cyanide concentration. This paper studies the HCN detection system based on TDLAS technology, selects the absorption lines of hydrogen cyanide in 6539.12cm-1, and utilizes the center wavelength of 1.529μm distributed feedback (DFB) laser as a light source. It is discussed in detail on technical requirements of a high frequency modulated laser signal detection circuit, including noise level, gain, and bandwidth. Based on the above theory, the high frequency modulation preamplifier circuit and main amplifier circuit are designed for InGaAs photoelectric detector. The designed circuits are calculation analyzed with corresponding formula and simulation analyzed based on the Multisim software.

  15. DFT coupled with NEGF study of ultra-sensitive HCN and HNC gases detection and distinct I-V response based on phosphorene.

    Science.gov (United States)

    Pang, Jiu; Yang, Qun; Ma, Xiaosong; Wang, Liming; Tan, Chunjian; Xiong, Daxi; Ye, Huaiyu; Chen, Xianping

    2017-11-22

    The sensing performances of pristine and X-doped phosphorene substrates (X = Al, Si, and S atoms) toward the adsorption of the toxic gases HCN and HNC were systematically investigated by first-principles simulations. The numerical results show that the pristine phosphorene is sensitive to HCN and HNC molecules with moderate adsorption energy, excellent charge transfer, high sensitivity and selectivity, implying its potential applications as excellent HCN and HNC sensors. In addition, the Al-doped phosphorene exhibits extremely high reactive activity toward HCN and HNC gases; thus, it has potential for use as a metal-free catalyst for activating or catalyzing HCN or HNC adsorbates. Moreover, the transport properties, i.e., current-voltage (I-V) characteristics, were calculated by the non-equilibrium Green's function (NEGF) method within the framework of the density functional theory (DFT). The obtained results reveal that the adsorbed HCN or HNC gas molecules have a remarkable impact on the electronic conductivity of phosphorene, and the zigzag direction of phosphorene is more sensitive to gas molecules than the armchair direction. The combination of the high sensitivity, superior selectivity, and moderate adsorption energy of pristine phosphorene toward HCN or HNC gas molecules adsorption, makes phosphorene an excellent candidate for HCN and HNC sensors.

  16. ALMA HCN AND HCO{sup +} J  = 3 − 2 OBSERVATIONS OF OPTICAL SEYFERT AND LUMINOUS INFRARED GALAXIES: CONFIRMATION OF ELEVATED HCN-TO-HCO{sup +} FLUX RATIOS IN AGNS

    Energy Technology Data Exchange (ETDEWEB)

    Imanishi, Masatoshi; Nakanishi, Kouichiro [National Astronomical Observatory of Japan, National Institutes of Natural Sciences (NINS), 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Izumi, Takuma, E-mail: masa.imanishi@nao.ac.jp [Institute of Astronomy, School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan)

    2016-12-01

    We present the results of our ALMA observations of three active galactic nucleus (AGN)-dominated nuclei in optical Seyfert 1 galaxies (NGC 7469, I Zw 1, and IC 4329 A) and eleven luminous infrared galaxies (LIRGs) with various levels of infrared estimated energetic contributions by AGNs at the HCN and HCO{sup +} J  = 3 − 2 emission lines. The HCN and HCO{sup +} J  = 3 − 2 emission lines are clearly detected at the main nuclei of all sources, except for IC 4329 A. The vibrationally excited ( v {sub 2} = 1f) HCN J  = 3 − 2 and HCO{sup +} J  = 3 − 2 emission lines are simultaneously covered, and HCN v {sub 2} = 1f J  = 3 − 2 emission line signatures are seen in the main nuclei of two LIRGs, IRAS 12112+0305 and IRAS 22491–1808, neither of which shows clear buried AGN signatures in the infrared. If the vibrational excitation is dominated by infrared radiative pumping, through the absorption of infrared 14 μ m photons, primarily originating from AGN-heated hot dust emission, then these two LIRGs may contain infrared-elusive, but (sub)millimeter-detectable, extremely deeply buried AGNs. These vibrationally excited emission lines are not detected in the three AGN-dominated optical Seyfert 1 nuclei. However, the observed HCN v {sub 2} = 1f to v  = 0 flux ratios in these optical Seyferts are still consistent with the intrinsic flux ratios in LIRGs with detectable HCN v {sub 2} = 1f emission lines. The observed HCN-to-HCO{sup +} J  = 3 − 2 flux ratios tend to be higher in galactic nuclei with luminous AGN signatures compared with starburst-dominated regions, as previously seen at J  = 1 − 0 and J  = 4 − 3.

  17. Coupling catalytic hydrolysis and oxidation on Mn/TiO2-Al2O3 for HCN removal

    Science.gov (United States)

    Wang, Langlang; Wang, Xueqian; Cheng, Jinhuan; Ning, Ping; Lin, Yilong

    2018-05-01

    The manganese-modified titania-alumina (Mn/TiO2-Al2O3) catalyst synthesized by sol-gol method was used to remove hydrogen cyanide (HCN) from simulated flue gas. Further, effects of the mass ratios of Ti/Al, Mn loading, calcination temperature, and relative humidity on HCN conversion efficiency and catalytic activity were systematically investigated. The results indicated that the Mn/TiO2-Al2O3 catalyst exhibited significantly enhanced HCN removal efficiency, and the maximum yield of N2 increased to 68.02% without the participation of water vapor. When water vapor was added into the flue gas, the yield of N2 decreased and the formation of NOx was also inhibited. The XRD and XPS results indicated that Mn was mainly present in the form of Mn2+, Mn3+, and Mn4+ on the surface of catalyst and chemisorbed oxygen played a major role in the HCN catalytic oxidation process. The results of DSC-TGA analysis and H2-TPR indicated that the catalyst also exhibited a good thermal and chemical stability. NH3-TPD and CO2-TPD indicated that the surface of the catalyst mainly contained acidic sites. During the reaction, part of NH3 was adsorbed by Brönsted and Lewis acid sites. NH3 adsorbed on Lewis acid sites participated in NH3-SCR, which reduced the amount of NOx produced and resulted in a high N2 yield.

  18. Electron density profile reconstruction by maximum entropy method with multichannel HCN laser interferometer system on SPAC VII

    International Nuclear Information System (INIS)

    Kubo, S.; Narihara, K.; Tomita, Y.; Hasegawa, M.; Tsuzuki, T.; Mohri, A.

    1988-01-01

    A multichannel HCN laser interferometer system has been developed to investigate the plasma electron confinement properties in SPAC VII device. Maximum entropy method is applied to reconstruct the electron density profile from measured line integrated data. Particle diffusion coefficient in the peripheral region of the REB ring core spherator was obtained from the evolution of the density profile. (author)

  19. A size upper limit and position for the HCN maser in CIT 6

    International Nuclear Information System (INIS)

    Carlstrom, J.E.; Welch, W.J.; Goldsmith, P.F.; Lis, D.C.

    1990-01-01

    A size upper limit and position for the HCN maser in CIT 6 were determined from interferometric observations with the Hat Creek millimeter array. The maser is located at alpha(1950) = 10 h 13 m 10.942 + or - 0.012 s and delta(1950) = + 30 deg 49 arcmin 16.75 arcsec + or - 0.15, coincident with the optical image taken from the Palomar plates, within the 3 arcsec uncertainty of the latter. The size of the maser emission region is less than 0.45 arcsec, approximately 180 AU at the distance estimated for CIT 6. The small size and strong emission (40 Jy) set a lower limit to the brightness temperature of 44,000 K, further strengthening the maser interpretation. 14 refs

  20. Diagnostics of a stationary MPD-type plasma jet with a HCN laser interferometer

    International Nuclear Information System (INIS)

    Graser, W.; Hoffmann, P.

    1975-01-01

    A HCN laser interferometer of the Ashby-Jephcott type operating at a wavelength of 337 μm was used to measure spatially resolved electron densities in a stationary MPD-type plasma jet with non-LTE behavior. Experiments were performed with and without superimposed magnetic fields up to 0.1 T at the exit of the plasma accelerator. Electron densities were obtained within the limits of 5times10 12 and 10 15 cm -3 with an accuracy better than 10%. Within the axially symmetric expanding plasma of about 15-cm average diameter and 50-cm length the radial resolving power came to less than 1 cm. So this technique has proved to be suitable to fill a gap in the diagnostics of stationary magnetized plasmas in the mean range of electron densities. (auth)

  1. PENGARUH LAMA PERENDAMAN KORO BENGU (Mucuna pruriens DALAM AIR KAPUR (Ca(OH2 TERHADAP KADAR ASAM SIANIDA (HCN

    Directory of Open Access Journals (Sweden)

    Arif Nurmawan Toro

    2014-03-01

    Full Text Available Latar belakang: Masyarakat Indonesia masih menitikberatkan pada komoditas kacang kedelai sebagai sumber utama protein, sedangkan pemanfaatan komoditas lain seperti koro benguk masih sangat minim. Minimnya pemanfaatan koro benguk ini karena di dalamnya terkandung senyawa alami berupa glokusida sianogenik yang dapat mengalami hidrolisis enzimatis menjadi asam sianida (HCN yang bersifat racun. Karena asam sianida bersifat asam yang sangat mudah larut dalam air, maka dilakukan perendaman menggunakan air kapur (Ca(OH2 bersifat basa yang dirasa cukup efektif menetralkan HCN dalam koro benguk.   Tujuan Penelitian: Mengetahui pengaruh lama perendaman koro benguk dalam air kapur terhadap kadar asam sianida dan mengetahui apakah air kapur lebih efektif dibandingkan air biasa dalam menetralkan HCN koro benguk.   Metode Penelitian: Penelitian dengan desain post test with control group. Obyek penelitian ini adalah koro benguk varietas benguk putih berumur 4-6 bulan yang diperoleh di Dusun Nogosari, Desa Purwosari, Kecamatan Girimulyo, Kabupaten Kulon Progo, DIY yang dilakukan perendaman dalam air sebagai kelompok kontrol dan air kapur 100 mg/L sebagai kelompok perlakuan selama 12, 24 dan 36 jam kemudian dilakukan destilasi. Destilat direaksikan dengan asam pikrat 1% kemudia diukur kadar HCN secara spektrofotometri.   Hasil: Kadar HCN  koro benguk pada perendaman dalam air selama 12 jam adalah 20,736 mg/kg, selama 24 jam adalah 19,348 mg/kg dan selama 36 jam adalah 16,786 mg/kg. Sedangkan kadar HCN pada perendaman air kapur 100 mg/L selama 12 jam adalah 19,020 mg/kg, selama 24 jam adalah 1,635 mg/kg dan selama 36 jam adalah 9,307 mg/kg. Hasil Uji ANOVA satu jalan pada kelompok perlakuan didapatkan nilai signifikansi 0.000 (p< 0.05.   Kesimpulan: Ada pengaruh bermakna lama perendaman koro benguk dalam air kapur terhadap kadar asam sianida. Perendaman dalam air kapur terbukti lebih efektif menetralkan asam sianida koro benguk dibandingkan perendaman dalam

  2. Dormancy alleviation by NO or HCN leading to decline of protein carbonylation levels in apple (Malus domestica Borkh.) embryos.

    Science.gov (United States)

    Krasuska, Urszula; Ciacka, Katarzyna; Dębska, Karolina; Bogatek, Renata; Gniazdowska, Agnieszka

    2014-08-15

    Deep dormancy of apple (Malus domestica Borkh.) embryos can be overcome by short-term pre-treatment with nitric oxide (NO) or hydrogen cyanide (HCN). Dormancy alleviation of embryos modulated by NO or HCN and the first step of germination depend on temporary increased production of reactive oxygen species (ROS). Direct oxidative attack on some amino acid residues or secondary reactions via reactive carbohydrates and lipids can lead to the formation of protein carbonyl derivatives. Protein carbonylation is a widely accepted covalent and irreversible modification resulting in inhibition or alteration of enzyme/protein activities. It also increases the susceptibility of proteins to proteolytic degradation. The aim of this work was to investigate protein carbonylation in germinating apple embryos, the dormancy of which was removed by pre-treatment with NO or HCN donors. It was performed using a quantitative spectrophotometric method, while patterns of carbonylated protein in embryo axes were analyzed by immunochemical techniques. The highest concentration of protein carbonyl groups was observed in dormant embryos. It declined in germinating embryos pre-treated with NO or HCN, suggesting elevated degradation of modified proteins during seedling formation. A decrease in the concentration of carbonylated proteins was accompanied by modification in proteolytic activity in germinating apple embryos. A strict correlation between the level of protein carbonyl groups and cotyledon growth and greening was detected. Moreover, direct in vitro carbonylation of BSA treated with NO or HCN donors was analyzed, showing action of both signaling molecules as protein oxidation agents. Copyright © 2014 Elsevier GmbH. All rights reserved.

  3. SUBMILLIMETER-HCN DIAGRAM FOR ENERGY DIAGNOSTICS IN THE CENTERS OF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Izumi, Takuma; Kohno, Kotaro [Institute of Astronomy, School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan); Aalto, Susanne [Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Observatory, SE-439 94 Onsala (Sweden); Espada, Daniel; Martín, Sergio; Nakanishi, Kouichiro [Joint ALMA Observatory, Alonso de Córdova, 3107, Vitacura, Santiago 763-0355 (Chile); Fathi, Kambiz [Stockholm Observatory, Department of Astronomy, Stockholm University, AlbaNova Centre, SE-106 91 Stockholm (Sweden); Harada, Nanase; Hsieh, Pei-Ying; Matsushita, Satoki [Academia Sinica, Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China); Hatsukade, Bunyo; Imanishi, Masatoshi [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Krips, Melanie [Institut de Radio Astronomie Millimétrique, 300 rue de la Piscine, Domaine Universitaire, F-38406 St. Martin d’Hères (France); Meier, David S. [Department of Physics, New Mexico Institute of Mining and Technology, 801 Leroy Place, Soccoro, NM 87801 (United States); Nakai, Naomasa [Department of Physics, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Ten-nodai, Tsukuba, Ibaraki 305-8571 (Japan); Schinnerer, Eva [Max Planck Institute for Astronomy, Königstuhl 17, Heidelberg D-69117 (Germany); Sheth, Kartik [NASA, 300 E Street SW, Washington, DC 20546 (United States); Terashima, Yuichi [Department of Physics, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime 790-8577 (Japan); Turner, Jean L., E-mail: takumaizumi@ioa.s.u-tokyo.ac.jp [Department of Physics and Astronomy, UCLA, 430 Portola Plaza, Los Angeles, CA 90095-1547 (United States)

    2016-02-10

    Compiling data from literature and the Atacama Large Millimeter/submillimeter Array archive, we show enhanced HCN(4–3)/HCO{sup +}(4–3) and/or HCN(4–3)/CS(7–6) integrated intensity ratios in circumnuclear molecular gas around active galactic nuclei (AGNs) compared to those in starburst (SB) galaxies (submillimeter HCN enhancement). The number of sample galaxies is significantly increased from our previous work. We expect that this feature could potentially be an extinction-free energy diagnostic tool of nuclear regions of galaxies. Non-LTE radiative transfer modelings of the above molecular emission lines involving both collisional and radiative excitation, as well as a photon trapping effect, were conducted to investigate the cause of the high line ratios in AGNs. As a result, we found that enhanced abundance ratios of HCN to HCO{sup +} and HCN to CS in AGNs as compared to SB galaxies by a factor of a few to even ≳10 are a plausible explanation for the submillimeter HCN enhancement. However, a counterargument of a systematically higher gas density in AGNs than in SB galaxies can also be a plausible scenario. Although we cannot fully distinguish these two scenarios at this moment owing to an insufficient amount of multi-transition, multi-species data, the former scenario is indicative of abnormal chemical composition in AGNs. Regarding the actual mechanism to realize the composition, we suggest that it is difficult with conventional gas-phase X-ray-dominated region ionization models to reproduce the observed high line ratios. We might have to take into account other mechanisms such as neutral–neutral reactions that are efficiently activated in high-temperature environments and/or mechanically heated regions to further understand the high line ratios in AGNs.

  4. ALMA IMAGING OF HCN, CS, AND DUST IN ARP 220 AND NGC 6240

    Energy Technology Data Exchange (ETDEWEB)

    Scoville, Nick; Manohar, Swarnima; Murchikova, Lena [California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Sheth, Kartik [North American ALMA Science Center, National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22901 (United States); Walter, Fabian; Zschaechner, Laura [Max-Planck-Institut fur Astronomie, Konigstuhl 17, D-69117 Heidelberg (Germany); Yun, Min [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Koda, Jin [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794 (United States); Sanders, David; Barnes, Joshua [Institute for Astronomy, 2680 Woodlawn Drive, University of Hawaii, Honolulu, Hawaii, HI 96822 (United States); Thompson, Todd [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Robertson, Brant; Tacconi, Linda; Narayanan, Desika [Department of Astronomy and Steward Observatory, University of Arizona, Tucson AZ 85721 (United States); Genzel, Reinhard; Davies, Richard [Max-Planck-Institut fur extraterrestrische Physik (MPE), Giessenbachstrasse, D-85748 Garching (Germany); Hernquist, Lars [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Brown, Robert [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22901 (United States); Hayward, Christopher C. [TAPIR 350-17, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Kartaltepe, Jeyhan [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); and others

    2015-02-10

    We report ALMA Band 7 (350 GHz) imaging at 0.''4-0.''6 resolution and Band 9 (696 GHz) at ∼0.''25 resolution of the luminous IR galaxies Arp 220 and NGC 6240. The long wavelength dust continuum is used to estimate interstellar medium masses for Arp 220 east and west and NGC 6240 of 1.9, 4.2, and 1.6 × 10{sup 9} M {sub ☉}within radii of 69, 65, and 190 pc. The HCN emission was modeled to derive the emissivity distribution as a function of radius and the kinematics of each nuclear disk, yielding dynamical masses consistent with the masses and sizes derived from the dust emission. In Arp 220, the major dust and gas concentrations are at radii less than 50 pc in both counter-rotating nuclear disks. The thickness of the disks in Arp 220 estimated from the velocity dispersion and rotation velocities are 10-20 pc and the mean gas densities are n{sub H{sub 2}}∼10{sup 5} cm{sup –3} at R <50 pc. We develop an analytic treatment for the molecular excitation (including photon trapping), yielding volume densities for both the HCN and CS emission with n {sub H2} ∼ 2 × 10{sup 5} cm{sup –3}. The agreement of the mean density from the total mass and size with that required for excitation suggests that the volume is essentially filled with dense gas, i.e., it is not cloudy or like swiss cheese.

  5. ALMA IMAGING OF HCN, CS, AND DUST IN ARP 220 AND NGC 6240

    International Nuclear Information System (INIS)

    Scoville, Nick; Manohar, Swarnima; Murchikova, Lena; Sheth, Kartik; Walter, Fabian; Zschaechner, Laura; Yun, Min; Koda, Jin; Sanders, David; Barnes, Joshua; Thompson, Todd; Robertson, Brant; Tacconi, Linda; Narayanan, Desika; Genzel, Reinhard; Davies, Richard; Hernquist, Lars; Brown, Robert; Hayward, Christopher C.; Kartaltepe, Jeyhan

    2015-01-01

    We report ALMA Band 7 (350 GHz) imaging at 0.''4-0.''6 resolution and Band 9 (696 GHz) at ∼0.''25 resolution of the luminous IR galaxies Arp 220 and NGC 6240. The long wavelength dust continuum is used to estimate interstellar medium masses for Arp 220 east and west and NGC 6240 of 1.9, 4.2, and 1.6 × 10 9 M ☉ within radii of 69, 65, and 190 pc. The HCN emission was modeled to derive the emissivity distribution as a function of radius and the kinematics of each nuclear disk, yielding dynamical masses consistent with the masses and sizes derived from the dust emission. In Arp 220, the major dust and gas concentrations are at radii less than 50 pc in both counter-rotating nuclear disks. The thickness of the disks in Arp 220 estimated from the velocity dispersion and rotation velocities are 10-20 pc and the mean gas densities are n H 2 ∼10 5  cm –3 at R <50 pc. We develop an analytic treatment for the molecular excitation (including photon trapping), yielding volume densities for both the HCN and CS emission with n H2 ∼ 2 × 10 5  cm –3 . The agreement of the mean density from the total mass and size with that required for excitation suggests that the volume is essentially filled with dense gas, i.e., it is not cloudy or like swiss cheese

  6. Large-scale upper tropospheric pollution observed by MIPAS HCN and C2H6 global distributions

    Science.gov (United States)

    Glatthor, N.; von Clarmann, T.; Stiller, G. P.; Funke, B.; Koukouli, M. E.; Fischer, H.; Grabowski, U.; Höpfner, M.; Kellmann, S.; Linden, A.

    2009-12-01

    We present global upper tropospheric HCN and C2H6 amounts derived from MIPAS/ENVISAT limb emission spectra. HCN and C2H6 are retrieved in the spectral regions 715.5-782.7 cm-1 and 811.5-835.7 cm-1, respectively. The datasets consist of 54 days between September 2003 and March 2004. This period covers the peak and decline of the southern hemispheric biomass burning period and some months thereafter. HCN is a nearly unambiguous tracer of biomass burning with an assumed tropospheric lifetime of several months. Indeed, the most significant feature in the MIPAS HCN dataset is an upper tropospheric plume of enhanced values caused by southern hemispheric biomass burning, which in September and October 2003 extended from tropical South America over Africa, Australia to the Southern Pacific. The spatial extent of this plume agrees well with the MOPITT CO distribution of September 2003. Further there is good agreement with the shapes and mixing ratios of the southern hemispheric HCN and C2H6 fields measured by the ACE experiment between September and November 2005. The MIPAS HCN plume extended from the lowermost observation height of 8 km up to about 16 km altitude, with maximum values of 500-600 pptv in October 2003. It was still clearly visible in December 2003, but had strongly decreased by March 2004, confirming the assumed tropospheric lifetime. The main sources of C2H6 are production and transmission of fossil fuels, followed by biofuel use and biomass burning. The C2H6 distribution also clearly reflected the southern hemispheric biomass burning plume and its seasonal variation, with maximum amounts of 600-700 pptv. Generally there was good spatial overlap between the southern hemispheric distributions of both pollution tracers, except for the region between Peru and the mid-Pacific. Here C2H6was considerably enhanced, whereas the HCN amounts were low. Backward trajectory calculations suggested that industrial pollution was responsible for the elevated C2H6

  7. Large-scale upper tropospheric pollution observed by MIPAS HCN and C2H6 global distributions

    Directory of Open Access Journals (Sweden)

    A. Linden

    2009-12-01

    Full Text Available We present global upper tropospheric HCN and C2H6 amounts derived from MIPAS/ENVISAT limb emission spectra. HCN and C2H6 are retrieved in the spectral regions 715.5–782.7 cm−1 and 811.5–835.7 cm−1, respectively. The datasets consist of 54 days between September 2003 and March 2004. This period covers the peak and decline of the southern hemispheric biomass burning period and some months thereafter. HCN is a nearly unambiguous tracer of biomass burning with an assumed tropospheric lifetime of several months. Indeed, the most significant feature in the MIPAS HCN dataset is an upper tropospheric plume of enhanced values caused by southern hemispheric biomass burning, which in September and October 2003 extended from tropical South America over Africa, Australia to the Southern Pacific. The spatial extent of this plume agrees well with the MOPITT CO distribution of September 2003. Further there is good agreement with the shapes and mixing ratios of the southern hemispheric HCN and C2H6 fields measured by the ACE experiment between September and November 2005. The MIPAS HCN plume extended from the lowermost observation height of 8 km up to about 16 km altitude, with maximum values of 500–600 pptv in October 2003. It was still clearly visible in December 2003, but had strongly decreased by March 2004, confirming the assumed tropospheric lifetime. The main sources of C2H6 are production and transmission of fossil fuels, followed by biofuel use and biomass burning. The C2H6 distribution also clearly reflected the southern hemispheric biomass burning plume and its seasonal variation, with maximum amounts of 600–700 pptv. Generally there was good spatial overlap between the southern hemispheric distributions of both pollution tracers, except for the region between Peru and the mid-Pacific. Here C2H6was considerably enhanced, whereas the HCN amounts were low. Backward trajectory calculations suggested that industrial pollution was responsible

  8. Airborne measurements of CO2, CH4 and HCN in boreal biomass burning plumes

    Science.gov (United States)

    O'Shea, Sebastian J.; Bauguitte, Stephane; Muller, Jennifer B. A.; Le Breton, Michael; Archibald, Alex; Gallagher, Martin W.; Allen, Grant; Percival, Carl J.

    2013-04-01

    Biomass burning plays an important role in the budgets of a variety of atmospheric trace gases and particles. For example, fires in boreal Russia have been linked with large growths in the global concentrations of trace gases such as CO2, CH4 and CO (Langenfelds et al., 2002; Simpson et al., 2006). High resolution airborne measurements of CO2, CH4 and HCN were made over Eastern Canada onboard the UK Atmospheric Research Aircraft FAAM BAe-146 from 12 July to 4 August 2011. These observations were made as part of the BORTAS project (Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites). Flights were aimed at transecting and sampling the outflow from the commonly occurring North American boreal forest fires during the summer months and to investigate and identify the chemical composition and evolution of these plumes. CO2 and CH4 dry air mole fractions were determined using an adapted system based on a Fast Greenhouse Gas Analyser (FGGA, Model RMT-200) from Los Gatos Research Inc, which uses the cavity enhanced absorption spectroscopy technique. In-flight calibrations revealed a mean accuracy of 0.57 ppmv and 2.31 ppbv for 1 Hz observations of CO2 and CH4, respectively, during the BORTAS project. During these flights a number of fresh and photochemically-aged plumes were identified using simultaneous HCN measurements. HCN is a distinctive and useful marker for forest fire emissions and it was detected using chemical ionisation mass spectrometry (CIMS). In the freshest plumes, strong relationships were found between CH4, CO2 and other tracers for biomass burning. From this we were able to estimate that 8.5 ± 0.9 g of CH4 and 1512 ± 185 g of CO2 were released into the atmosphere per kg of dry matter burnt. These emission factors are in good agreement with estimates from previous studies and can be used to calculate budgets for the region. However for aged plumes the correlations between CH4 and other

  9. Ab initio calculation of a global potential, vibrational energies, and wave functions for HCN/HNC, and a simulation of the (A-tilde)-(X-tilde) emission spectrum

    Science.gov (United States)

    Bowman, Joel M.; Gazdy, Bela; Bentley, Joseph A.; Lee, Timothy J.; Dateo, Christopher E.

    1993-01-01

    A potential energy surface for the HCN/HNC system which is a fit to extensive, high-quality ab initio, coupled-cluster calculations is presented. All HCN and HNC states with energies below the energy of the first delocalized state are reported and characterized. Vibrational transition energies are compared with all available experimental data on HCN and HNC, including high CH-overtone states up to 23,063/cm. A simulation of the (A-tilde)-(X-tilde) stimulated emission pumping (SEP) spectrum is also reported, and the results are compared to experiment. Franck-Condon factors are reported for odd bending states of HCN, with one quantum of vibrational angular momentum, in order to compare with the recent assignment by Jonas et al. (1992), on the basis of axis-switching arguments of a number of previously unassigned states in the SEP spectrum.

  10. Retrieving molecular structural information and tracking HNC/HCN isomerization process with high harmonic generation by ultrashort laser pulses

    International Nuclear Information System (INIS)

    Nguyen Ngoc Ty; Le Van Hoang; Vu Ngoc Tuoc; Le Anh Thu

    2010-01-01

    We investigate the possibility of applying the iterative method, suggested in our previous work, for HCN molecule and its HNC isomer. We found that the high-order harmonic generation (HHG) spectra are quite insensitive to the change of H-C (or H-N) bond length so that only the inter-nuclear C-N distance can be retrieved from the high-order harmonic spectra using ultrashort intense lasers. Furthermore, by analyzing the HHG spectra emitted by HCN during the chemical reaction path of isomerization we identify the intensity peaks nearby the stable, metastable and transition states. this finding can be useful for tracking the HNC/HNC isomerization process. (author)

  11. Ion Channels of Pituitary Gonadotrophs and Their Roles in Signaling and Secretion

    Directory of Open Access Journals (Sweden)

    Stanko S. Stojilkovic

    2017-06-01

    Full Text Available Gonadotrophs are basophilic cells of the anterior pituitary gland specialized to secrete gonadotropins in response to elevation in intracellular calcium concentration. These cells fire action potentials (APs spontaneously, coupled with voltage-gated calcium influx of insufficient amplitude to trigger gonadotropin release. The spontaneous excitability of gonadotrophs reflects the expression of voltage-gated sodium, calcium, potassium, non-selective cation-conducting, and chloride channels at their plasma membrane (PM. These cells also express the hyperpolarization-activated and cyclic nucleotide-gated cation channels at the PM, as well as GABAA, nicotinic, and purinergic P2X channels gated by γ-aminobutyric acid (GABA, acetylcholine (ACh, and ATP, respectively. Activation of these channels leads to initiation or amplification of the pacemaking activity, facilitation of calcium influx, and activation of the exocytic pathway. Gonadotrophs also express calcium-conducting channels at the endoplasmic reticulum membranes gated by inositol trisphosphate and intracellular calcium. These channels are activated potently by hypothalamic gonadotropin-releasing hormone (GnRH and less potently by several paracrine calcium-mobilizing agonists, including pituitary adenylate cyclase-activating peptides, endothelins, ACh, vasopressin, and oxytocin. Activation of these channels causes oscillatory calcium release and a rapid gonadotropin release, accompanied with a shift from tonic firing of single APs to periodic bursting type of electrical activity, which accounts for a sustained calcium signaling and gonadotropin secretion. This review summarizes our current understanding of ion channels as signaling molecules in gonadotrophs, the role of GnRH and paracrine agonists in their gating, and the cross talk among channels.

  12. First-principle study of structural, electronic, vibrational and magnetic properties of HCN adsorbed graphene doped with Cr, Mn and Fe

    International Nuclear Information System (INIS)

    Shi, Li Bin; Wang, Yong Ping; Dong, Hai Kuan

    2015-01-01

    Graphical abstract: - Highlights: • Cr, Mn and Fe doped graphene is more active to adsorb HCN molecule than pristine graphene. • The conductivity of Fe and Mn doped graphene hardly changes after adsorption HCN molecule. • The conductivity of Cr doped graphene can be affected significantly due to HCN adsorption. • The Cr, Mn and Fe may destroy the long range order in graphene. • Phonon density of states suggests that Cr doped graphene is stable. - Abstract: The adsorption energy, electronic structure, lattice vibration and magnetic properties of Cr, Mn and Fe doped graphene with and without HCN adsorption are investigated by the first principles based on density functional theory. The physisorption and chemisorption have been identified. In the paper, Cr-NG, Mn-NG and Fe-NG denote HCN adsorption on Cr, Mn and Fe doped graphene with N atom toward the adsorption site. It is found that the adsorption energy is −1.36 eV for Fe-NG, −0.60 eV for Mn-NG and −0.86 eV for Cr-NG. The Cr-NG will convert from half-metallic behavior to semiconductor after adsorbing HCN molecule, which indicates that the conductivity changes significantly. Phonon density of states (PDOS) shows that the long range order in graphene can be destroyed by doping Fe, Mn and Cr. The imaginary frequency mode in PDOS suggests that Fe and Mn doped graphene is unstable, while Cr doped graphene is stable. The electronic properties are sensitive toward adsorbing HCN, indicating that Cr doped graphene is a promising sensor for detecting HCN molecule. This study provides a useful basis for understanding of a wide variety of physical properties on graphene

  13. ALMA DETECTION OF THE VIBRATIONALLY EXCITED HCN J = 4-3 EMISSION LINE IN THE AGN-HOSTING LUMINOUS INFRARED GALAXY IRAS 20551–4250

    Energy Technology Data Exchange (ETDEWEB)

    Imanishi, Masatoshi [Subaru Telescope, 650 North A' ohoku Place, Hilo, Hawaii, 96720 (United States); Nakanishi, Kouichiro, E-mail: masa.imanishi@nao.ac.jp [Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura 763-0355, Santiago de Chile (Chile)

    2013-10-01

    We present results from our ALMA Cycle 0 observations, at the frequencies around the HCN, HCO{sup +}, and HNC J = 4-3 transition lines, of the luminous infrared galaxy IRAS 20551–4250 at z = 0.043, which is known to host an energetically important obscured active galactic nucleus (AGN). In addition to the targeted HCN, HCO{sup +}, and HNC J = 4-3 emission lines, two additional strong emission lines are seen, which we attribute to H{sub 2}S and CH{sub 3}CN(+CCH). The HCN-to-HCO{sup +} J = 4-3 flux ratio (∼0.7) is higher than in the other starburst-dominated galaxy (∼0.2) observed in our ALMA Cycle 0 program. We tentatively (∼5σ) detected the vibrationally excited (v {sub 2} = 1) HCN J = 4-3 (l = 1f) emission line, which is important for testing an infrared radiative pumping scenario for HCN. This is the second detection of this molecular transition in external galaxies. The most likely reason for this detection is not only the high flux of this emission line, but also the small molecular line widths observed in this galaxy, suggesting that vibrational excitation of HCN may be relatively common in AGN-hosting galaxies.

  14. CO, CS, and HCN in a clustering of reflection nebulae in Monoceros

    International Nuclear Information System (INIS)

    Kutner, M.L.; Tucker, K.D.

    1975-01-01

    Carbon monoxide line emission at lambda=2.6 mm has been observed over an area of approx.3 1/2degreetimes3 1/2degree in L1646, a diffuse dust cloud containing a grouping of reflection nebulae. The H 2 mass is estimated from the CO observations to be >3.2times10 4 M/sub sun/. Five CO emission peaks are observed, each apparently associated with at least one reflection nebula, with the strongest peak at α (1950) =6)05)20), delta (1950) =-6degree22'30''. Around this position, extended (10'times10') emission is observed from HCN and CS, suggesting a core with H 2 density approximately-less-than8times10 4 cm -3 . This core appears to be rotating with Ωgreater than or equal to7.4times10 -14 s -1 . There is also evidence for self-absorption in the CO line in this direction, suggestive of a collapsing cloud. (auth)

  15. Data processing with PC-9801 micro-computer for HCN laser scattering experiments

    International Nuclear Information System (INIS)

    Iwasaki, T.; Okajima, S.; Kawahata, K.; Tetsuka, T.; Fujita, J.

    1986-09-01

    In order to process the data of HCN laser scattering experiments, a micro-computer software has been developed and applied to the measurements of density fluctuations in the JIPP T-IIU tokamak plasma. The data processing system consists of a spectrum analyzer, SM-2100A Signal Analyzer (IWATSU ELECTRIC CO., LTD.), PC-9801m3 micro-computer, a CRT-display and a dot-printer. The output signals from the spectrum analyzer are A/D converted, and stored on a mini-floppy-disk equipped to the signal analyzer. The software to process the data is composed of system-programs and several user-programs. The real time data processing is carried out for every shot of plasma at 4 minutes interval by the micro-computer connected with the signal analyzer through a GP-IB interface. The time evolutions of the frequency spectrum of the density fluctuations are displayed on the CRT attached to the micro-computer and printed out on a printer-sheet. In the case of the data processing after experiments, the data stored on the floppy-disk of the signal analyzer are read out by using a floppy-disk unit attached to the micro-computer. After computation with the user-programs, the results, such as monitored signal, frequency spectra, wave number spectra and the time evolutions of the spectrum, are displayed and printed out. In this technical report, the system, the software and the directions for use are described. (author)

  16. MEG3, HCN3 and linc01105 influence the proliferation and apoptosis of neuroblastoma cells via the HIF-1α and p53 pathways.

    Science.gov (United States)

    Tang, Weitao; Dong, Kuiran; Li, Kai; Dong, Rui; Zheng, Shan

    2016-11-08

    The purpose of this study was to investigate the differential expression and functional roles of long non-coding RNAs (lncRNAs) in neuroblastoma tissue. LncRNA microarrays were used to identify differentially expressed lncRNAs between tumor and para-tumor tissues. In total, in tumor tissues, 3,098 and 1,704 lncRNAs were upregulated and downregulated, respectively. HCN3 and linc01105 exhibited the higher expression (P INSS) stage were -0.48, -0.58 and -0.55, respectively. In conclusion, we have identified lncRNAs that are differentially expressed in neuroblastoma tissues. The lncRNAs HCN3, linc01105, and MEG3 may be important in biological behaviors of neuroblastoma through mechanisms involving p53 pathway members such as HIF-1α, Noxa, and Bid. The expressions of MEG3, HCN3 and linc01105 are all negatively correlated with the INSS stage.

  17. Reduction of nitrogen compounds in oceanic basement and its implications for HCN formation and abiotic organic synthesis.

    Science.gov (United States)

    Holm, Nils G; Neubeck, Anna

    2009-10-22

    Hydrogen cyanide is an excellent organic reagent and is central to most of the reaction pathways leading to abiotic formation of simple organic compounds containing nitrogen, such as amino acids, purines and pyrimidines. Reduced carbon and nitrogen precursor compounds for the synthesis of HCN may be formed under off-axis hydrothermal conditions in oceanic lithosphere in the presence of native Fe and Ni and are adsorbed on authigenic layer silicates and zeolites. The native metals as well as the molecular hydrogen reducing CO2 to CO/CH4 and NO3-/NO2- to NH3/NH4+ are a result of serpentinization of mafic rocks. Oceanic plates are conveyor belts of reduced carbon and nitrogen compounds from the off-axis hydrothermal environments to the subduction zones, where compaction, dehydration, desiccation and diagenetic reactions affect the organic precursors. CO/CH4 and NH3/NH4+ in fluids distilled out of layer silicates and zeolites in the subducting plate at an early stage of subduction will react upon heating and form HCN, which is then available for further organic reactions to, for instance, carbohydrates, nucleosides or even nucleotides, under alkaline conditions in hydrated mantle rocks of the overriding plate. Convergent margins in the initial phase of subduction must, therefore, be considered the most potent sites for prebiotic reactions on Earth. This means that origin of life processes are, perhaps, only possible on planets where some kind of plate tectonics occur.

  18. Reduction of nitrogen compounds in oceanic basement and its implications for HCN formation and abiotic organic synthesis

    Directory of Open Access Journals (Sweden)

    Neubeck Anna

    2009-10-01

    Full Text Available Abstract Hydrogen cyanide is an excellent organic reagent and is central to most of the reaction pathways leading to abiotic formation of simple organic compounds containing nitrogen, such as amino acids, purines and pyrimidines. Reduced carbon and nitrogen precursor compounds for the synthesis of HCN may be formed under off-axis hydrothermal conditions in oceanic lithosphere in the presence of native Fe and Ni and are adsorbed on authigenic layer silicates and zeolites. The native metals as well as the molecular hydrogen reducing CO2 to CO/CH4 and NO3-/NO2- to NH3/NH4+ are a result of serpentinization of mafic rocks. Oceanic plates are conveyor belts of reduced carbon and nitrogen compounds from the off-axis hydrothermal environments to the subduction zones, where compaction, dehydration, desiccation and diagenetic reactions affect the organic precursors. CO/CH4 and NH3/NH4+ in fluids distilled out of layer silicates and zeolites in the subducting plate at an early stage of subduction will react upon heating and form HCN, which is then available for further organic reactions to, for instance, carbohydrates, nucleosides or even nucleotides, under alkaline conditions in hydrated mantle rocks of the overriding plate. Convergent margins in the initial phase of subduction must, therefore, be considered the most potent sites for prebiotic reactions on Earth. This means that origin of life processes are, perhaps, only possible on planets where some kind of plate tectonics occur.

  19. Molecular Line Emission as a Tool for Galaxy Observations (LEGO). I. HCN as a tracer of moderate gas densities in molecular clouds and galaxies

    Science.gov (United States)

    Kauffmann, Jens; Goldsmith, Paul F.; Melnick, Gary; Tolls, Volker; Guzman, Andres; Menten, Karl M.

    2017-09-01

    Trends observed in galaxies, such as the Gao & Solomon relation, suggest a linear relationship between the star formation rate and the mass of dense gas available for star formation. Validation of such trends requires the establishment of reliable methods to trace the dense gas in galaxies. One frequent assumption is that the HCN (J = 1-0) transition is unambiguously associated with gas at H2 densities ≫ 104 cm-3. If so, the mass of gas at densities ≫ 104 cm-3 could be inferred from the luminosity of this emission line, LHCN (1-0). Here we use observations of the Orion A molecular cloud to show that the HCN (J = 1-0) line traces much lower densities 103 cm-3 in cold sections of this molecular cloud, corresponding to visual extinctions AV ≈ 6 mag. We also find that cold and dense gas in a cloud like Orion produces too little HCN emission to explain LHCN (1-0) in star forming galaxies, suggesting that galaxies might contain a hitherto unknown source of HCN emission. In our sample of molecules observed at frequencies near 100 GHz (also including 12CO, 13CO, C18O, CN, and CCH), N2H+ is the only species clearly associated with relatively dense gas.

  20. Ion channeling

    International Nuclear Information System (INIS)

    Erramli, H.; Blondiaux, G.

    1994-01-01

    Channeling phenomenon was predicted, many years ago, by stark. The first channeling experiments were performed in 1963 by Davies and his coworkers. Parallely Robinson and Oen have investigated this process by simulating trajectories of ions in monocrystals. This technique has been combined with many methods like Rutherford Backscattering Spectrometry (R.B.S.), Particles Induced X-rays Emission (P.I.X.E) and online Nuclear Reaction (N.R.A.) to localize trace elements in the crystal or to determine crystalline quality. To use channeling for material characterization we need data about the stopping power of the incident particle in the channeled direction. The ratios of channeled to random stopping powers of silicon for irradiation in the direction have been investigated and compared to the available theoretical results. We describe few applications of ion channeling in the field of materials characterization. Special attention is given to ion channeling combined with Charged Particle Activation Analysis (C.P.A.A.) for studying the behaviour of oxygen atoms in Czochralski silicon lattices under the influence of internal gettering and in different gaseous atmospheres. Association between ion channeling and C.P.A.A was also utilised for studying the influence of the growing conditions on concentration and position of carbon atoms at trace levels in the MOVPE Ga sub (1-x) Al sub x lattice. 6 figs., 1 tab., 32 refs. (author)

  1. Searching for Faint Traces of CO(2-1) and HCN(4-3) Gas In Debris Disks

    Science.gov (United States)

    Stafford Lambros, Zachary; Hughes, A. Meredith

    2018-01-01

    The surprising presence of molecular gas in the debris disks around main sequence stars provides an opportunity to study the dissipation of primordial gas and, potentially, the composition of gas in other solar systems. Molecular gas is not expected to survive beyond the pre-main sequence phase, and it is not yet clear whether the gas is a remnant of the primordial protoplanetary material or whether the gas, like the dust, is second-generation material produced by collisional or photodesorption from planetesimals, exocomets, or the icy mantles of dust grains. Here we present two related efforts to characterize the prevalence and properties of gas in debris disks. First, we place the lowest limits to date on the CO emission from an M star debris disk, using 0.3" resolution observations of CO(2-1) emission from the AU Mic system with the Atacama Large Millimeter/submillimeter Array (ALMA). We place a 3-sigma upper limit on the integrated flux of 0.39 Jy km/s, corresponding to a maximum CO mass of 5e10-6 (Earth Masses) if the gas is in LTE. We also present the results of an ALMA search for HCN(4-3) emission from the prototypical gas-rich debris disk around 49 Ceti at a spatial resolution of 0.3". Despite hosting one of the brightest CO-rich debris disks yet discovered, our observations of 49 Ceti also yield a low upper limit of 0.057 Jy km/s in the HCN line, leaving CO as the only molecule clearly detected in emission from a debris disk. We employ several methods of detecting faint line emission from debris disks, including a model based on Keplerian kinematics as well as a spectral shifting method previously used to detect faint CO emission from the Fomalhaut debris disk, and compare our results.

  2. Submillimeter Monitoring of the HCN Molecule in Fragment C of the Split Comet 73P/Schwassmann-Wachmann 3

    Science.gov (United States)

    Drahus, Michal; Kueppers, M.; Jarchow, C.; Paganini, L.; Hartogh, P.; Villanueva, G. L.

    2007-10-01

    Comet 73P/Schwassmann-Wachmann 3 is a member of the Jupiter family which broke up into several fragments in 1995. After the unfavourable return in 2000/2001, the comet passed very close to the Earth in 2006, with the perigee distance below 0.1 AU. Simultaneously, it was well situated on the sky, which resulted in several observing campaigns. We observed this comet using the SMT facility at the Mt. Graham International Observatory in Arizona. In particular, on 5 nights between 10 and 22 May 2006 the HCN molecule in fragment C was spectroscopically monitored, through the J(3-2) and J(4-3) transitions. Using a simplified model, we found the expansion velocity of the HCN coma to be equal to 0.8 ± 0.1 km/s, what is a typical value for a comet at heliocentric distance r = 1 AU. We also reconstructed the production rates Q of this molecule, finding Q(r=1AU) = 2.7 ± 0.1 × 1025 molec/s. Our result is consistent with most of the other estimates, including the CN production rate. Furthermore, taking advantage of the fairly small beam sizes during our campaign (ranging from 600 km to 1200 km in radius), we detected short-term variability of the production rate, presumably stimulated by the nucleus rotation. Although our analysis did not yield a unique rotation period, we found a limited number of possible solutions. We will discuss them in detail along with a comparison with other period claims, and propose a possible scenario that links most of the periodicities reported so far for this comet. The SMT is operated by the Arizona Radio Observatory (ARO), Steward Observatory, University of Arizona.

  3. Product channels in the 193-nm photodissociation of HCNO (fulminic acid)

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Wenhui; Hershberger, John F., E-mail: john.hershberger@ndsu.edu

    2016-06-15

    IR diode laser spectroscopy was used to detect the products of HCNO (fulminic acid) photolysis at 193 nm. Six product channels are energetically possible at this photolysis wavelength: O + HCN, H + NCO/CNO, CN + OH, CO + NH, NO + CH and HNCO. In some experiments, isotopically labeled {sup 15}N{sup 18}O, C{sub 2}D{sub 6} or C{sub 6}H{sub 12} reagents were included into the photolysis mixture in order to suppress and/or redirect possible secondary reactions. HCN, OC{sup 18}O, {sup 15}N{sup 15}NO, CO, DCN and HNCO molecules were detected upon laser photolysis of HCNO/reagents/buffer gas mixtures. Analysis of the yields of product molecules leads to the following photolysis quantum yields: ϕ{sub 1a} (O + HCN) = 0.38 ± 0.04, ϕ{sub 1b} (H + (NCO)) = 0.07 ± 0.02, ϕ{sub 1c} (CN + OH) = 0.24 ± 0.03, ϕ{sub 1d} (CO + NH(a{sup 1}Δ)) < 0.22 ± 0.1, ϕ{sub 1e} (HNCO) = 0.02 ± 0.01 and ϕ{sub 1f} (CH + NO) = 0.21 ± 0.1, respectively.

  4. Channel box

    International Nuclear Information System (INIS)

    Tanabe, Akira.

    1993-01-01

    In a channel box of a BWR type reactor, protruding pads are disposed in axial position on the lateral side of a channel box opposing to a control rod and facing the outer side portion of the control rod in a reactor core loaded state. In the initial loading stage of fuel assemblies, channel fasteners and spacer pads are abutted against each other in the upper portion between the channel boxes sandwiching the control rod therebetween. Further, in the lower portion, a gap as a channel for the movement of the control rod is ensured by the support of fuel support metals. If the channel box is bent toward the control rod along with reactor operation, the pads are abutted against each other to always ensure the gap through which the control rod can move easily. Further, when the pads are brought into contact with each other, the bending deformation of the channel box is corrected by urging to each other. Thus, the control rod can always be moved smoothly to attain reactor safety operation. (N.H.)

  5. Surface channeling

    International Nuclear Information System (INIS)

    Sizmann, R.; Varelas, C.

    1976-01-01

    There is experimental evidence that swift light ions incident at small angles towards single crystalline surfaces can lose an appreciable fraction of their kinetic energy during reflection. It is shown that these projectiles penetrate into the bulk surface region of the crystal. They can travel as channeled particles along long paths through the solid (surface channeling). The angular distribution and the depth history of the re-emerged projectiles are investigated by computer simulations. A considerable fraction of the penetrating projectiles re-emerges from the crystal with constant transverse energy if the angle of incidence is smaller than the critical angle for axial channeling. Analytical formulae are derived based on a diffusion model for surface channeling. A comparison with experimental data exhibits the relevance of the analytical solutions. (Auth.)

  6. High-pass filtering of input signals by the Ih current in a non-spiking neuron, the retinal rod bipolar cell.

    Directory of Open Access Journals (Sweden)

    Lorenzo Cangiano

    Full Text Available Hyperpolarization-activated cyclic nucleotide-sensitive (HCN channels mediate the I(f current in heart and I(h throughout the nervous system. In spiking neurons I(h participates primarily in different forms of rhythmic activity. Little is known, however, about its role in neurons operating with graded potentials as in the retina, where all four channel isoforms are expressed. Intriguing evidence for an involvement of I(h in early visual processing are the side effects reported, in dim light or darkness, by cardiac patients treated with HCN inhibitors. Moreover, electroretinographic recordings indicate that these drugs affect temporal processing in the outer retina. Here we analyzed the functional role of HCN channels in rod bipolar cells (RBCs of the mouse. Perforated-patch recordings in the dark-adapted slice found that RBCs exhibit I(h, and that this is sensitive to the specific blocker ZD7288. RBC input impedance, explored by sinusoidal frequency-modulated current stimuli (0.1-30 Hz, displays band-pass behavior in the range of I(h activation. Theoretical modeling and pharmacological blockade demonstrate that high-pass filtering of input signals by I(h, in combination with low-pass filtering by passive properties, fully accounts for this frequency-tuning. Correcting for the depolarization introduced by shunting through the pipette-membrane seal, leads to predict that in darkness I(h is tonically active in RBCs and quickens their responses to dim light stimuli. Immunohistochemistry targeting candidate subunit isoforms HCN1-2, in combination with markers of RBCs (PKC and rod-RBC synaptic contacts (bassoon, mGluR6, Kv1.3, suggests that RBCs express HCN2 on the tip of their dendrites. The functional properties conferred by I(h onto RBCs may contribute to shape the retina's light response and explain the visual side effects of HCN inhibitors.

  7. Spark Channels

    Energy Technology Data Exchange (ETDEWEB)

    Haydon, S. C. [Department of Physics, University of New England, Armidale, NSW (Australia)

    1968-04-15

    A brief summary is given of the principal methods used for initiating spark channels and the various highly time-resolved techniques developed recently for studies with nanosecond resolution. The importance of the percentage overvoltage in determining the early history and subsequent development of the various phases of the growth of the spark channel is discussed. An account is then given of the recent photographic, oscillographic and spectroscopic investigations of spark channels initiated by co-axial cable discharges of spark gaps at low [{approx} 1%] overvoltages. The phenomena observed in the development of the immediate post-breakdown phase, the diffuse glow structure, the growth of the luminous filament and the final formation of the spark channel in hydrogen are described. A brief account is also given of the salient features emerging from corresponding studies of highly overvolted spark gaps in which the spark channel develops from single avalanche conditions. The essential differences between the two types of channel formation are summarized and possible explanations of the general features are indicated. (author)

  8. Lewis acid-base interactions in weakly bound formaldehyde complexes with CO2, HCN, and FCN: considerations on the cooperative H-bonding effects.

    Science.gov (United States)

    Rivelino, Roberto

    2008-01-17

    Ab initio quantum chemistry calculations reveal that HCN and mainly FCN can form Lewis acid-base complexes with formaldehyde associated with cooperative H bonds, as first noticed by Wallen et al. (Blatchford, M. A.; Raveendran, P.; Wallen, S. L. J. Am. Chem. Soc. 2002, 124, 14818-14819) for CO2-philic materials under supercritical conditions. The present results, obtained with MP2(Full)/aug-cc-pVDZ calculations, show that the degeneracy of the nu(2) mode in free HCN or FCN is removed upon complexation in the same fashion as that of CO2. The splitting of these bands along with the electron structure analysis provides substantial evidence of the interaction of electron lone pairs of the carbonyl oxygen with the electron-deficient carbon atom of the cyanides. Also, this work investigates the role of H bonds acting as additional stabilizing interactions in the complexes by performing the energetic and geometric characterization.

  9. Hydrogen constituents of the mesosphere inferred from positive ions - H2O, CH4, H2CO, H2O2, and HCN

    Science.gov (United States)

    Kopp, E.

    1990-01-01

    The concentrations in the mesosphere of H2O, CH4, H2CO, H2O2, and HCN were inferred from data on positive ion compositions, obtained from one mid-latitude and four high-latitude rocket flights. The inferred concentrations were found to agree only partially with the ground-based microwave measurements and/or model prediction by Garcia and Solomon (1985). The CH4 concentration was found to vary between 70 and 4 ppb in daytime and 900 and 100 ppbv at night, respectively. Unexpectedly high H2CO concentrations were obtained, with H2CO/H2O ratios between 0.0006 and 0.1, and a mean HCN volume mixing ratio of 6 x 10 to the -10th was inferred.

  10. MARKETING CHANNELS

    Directory of Open Access Journals (Sweden)

    Ljiljana Stošić Mihajlović

    2014-07-01

    Full Text Available Marketing channel is a set of entities and institutions, completion of distribution and marketing activities, attend the efficient and effective networking of producers and consumers. Marketing channels include the total flows of goods, money and information taking place between the institutions in the system of marketing, establishing a connection between them. The functions of the exchange, the physical supply and service activities, inherent in the system of marketing and trade. They represent paths which products and services are moving after the production, which will ultimately end up buying and eating by the user.

  11. Rate Coefficients for Reactions of Ethynyl Radical (C2H) With HCN and CH3CN: Implications for the Formation of Comples Nitriles on Titan

    Science.gov (United States)

    Hoobler, Ray J.; Leone, Stephen R.

    1997-01-01

    Rate coefficients for the reactions of C2H + HCN yields products and C2H + CH3CN yields products have been measured over the temperature range 262-360 K. These experiments represent an ongoing effort to accurately measure reaction rate coefficients of the ethynyl radical, C2H, relevant to planetary atmospheres such as those of Jupiter and Saturn and its satellite Titan. Laser photolysis of C2H2 is used to produce C2H, and transient infrared laser absorption is employed to measure the decay of C2H to obtain the subsequent reaction rates in a transverse flow cell. Rate constants for the reaction C2H + HCN yields products are found to increase significantly with increasing temperature and are measured to be (3.9-6.2) x 10(exp 13) cm(exp 3) molecules(exp -1) s(exp -1) over the temperature range of 297-360 K. The rate constants for the reaction C2H + CH3CN yields products are also found to increase substantially with increasing temperature and are measured to be (1.0-2.1) x 10(exp -12) cm(exp 3) molecules(exp -1) s(exp -1) over the temperature range of 262-360 K. For the reaction C2H + HCN yields products, ab initio calculations of transition state structures are used to infer that the major products form via an addition/elimination pathway. The measured rate constants for the reaction of C2H + HCN yields products are significantly smaller than values currently employed in photochemical models of Titan, which will affect the HC3N distribution.

  12. Sugar-to-base correlation in nucleic acids with a 5D APSY-HCNCH or two 3D APSY-HCN experiments

    Energy Technology Data Exchange (ETDEWEB)

    Kraehenbuehl, Barbara; Hofmann, Daniela; Maris, Christophe; Wider, Gerhard, E-mail: gsw@mol.biol.ethz.ch [Institute of Molecular Biology and Biophysics (Switzerland)

    2012-02-15

    A five-dimensional (5D) APSY (automated projection spectroscopy) HCNCH experiment is presented, which allows unambiguous correlation of sugar to base nuclei in nucleic acids. The pulse sequence uses multiple quantum (MQ) evolution which enables long constant-time evolution periods in all dimensions, an improvement that can also benefit non-APSY applications. Applied with an RNA with 23 nucleotides the 5D APSY-HCNCH experiment produced a complete and highly precise 5D chemical shift list within 1.5 h. Alternatively, and for molecules where the out-and-stay 5D experiment sensitivity is not sufficient, a set of out-and-back 3D APSY-HCN experiments is proposed: an intra-base (3D APSY-b-HCN) experiment in an MQ or in a TROSY version, and an MQ sugar-to-base (3D APSY-s-HCN) experiment. The two 3D peak lists require subsequent matching via the N1/9 chemical shift values to one 5D peak list. Optimization of the 3D APSY experiments for maximal precision in the N1/9 dimension allowed matching of all {sup 15}N chemical shift values contained in both 3D peak lists. The precise 5D chemical shift correlation lists resulting from the 5D experiment or a pair of 3D experiments also provide a valuable basis for subsequent connection to chemical shifts derived with other experiments.

  13. Sugar-to-base correlation in nucleic acids with a 5D APSY-HCNCH or two 3D APSY-HCN experiments

    International Nuclear Information System (INIS)

    Krähenbühl, Barbara; Hofmann, Daniela; Maris, Christophe; Wider, Gerhard

    2012-01-01

    A five-dimensional (5D) APSY (automated projection spectroscopy) HCNCH experiment is presented, which allows unambiguous correlation of sugar to base nuclei in nucleic acids. The pulse sequence uses multiple quantum (MQ) evolution which enables long constant-time evolution periods in all dimensions, an improvement that can also benefit non-APSY applications. Applied with an RNA with 23 nucleotides the 5D APSY-HCNCH experiment produced a complete and highly precise 5D chemical shift list within 1.5 h. Alternatively, and for molecules where the out-and-stay 5D experiment sensitivity is not sufficient, a set of out-and-back 3D APSY-HCN experiments is proposed: an intra-base (3D APSY-b-HCN) experiment in an MQ or in a TROSY version, and an MQ sugar-to-base (3D APSY-s-HCN) experiment. The two 3D peak lists require subsequent matching via the N1/9 chemical shift values to one 5D peak list. Optimization of the 3D APSY experiments for maximal precision in the N1/9 dimension allowed matching of all 15 N chemical shift values contained in both 3D peak lists. The precise 5D chemical shift correlation lists resulting from the 5D experiment or a pair of 3D experiments also provide a valuable basis for subsequent connection to chemical shifts derived with other experiments.

  14. Channel Power in Multi-Channel Environments

    NARCIS (Netherlands)

    M.G. Dekimpe (Marnik); B. Skiera (Bernd)

    2004-01-01

    textabstractIn the literature, little attention has been paid to instances where companies add an Internet channel to their direct channel portfolio. However, actively managing multiple sales channels requires knowing the customers’ channel preferences and the resulting channel power. Two key

  15. Chemical content of the circumstellar envelope of the oxygen-rich AGB star R Doradus. Non-LTE abundance analysis of CO, SiO, and HCN

    Science.gov (United States)

    Van de Sande, M.; Decin, L.; Lombaert, R.; Khouri, T.; de Koter, A.; Wyrowski, F.; De Nutte, R.; Homan, W.

    2018-01-01

    Context. The stellar outflows of low- to intermediate-mass stars are characterised by a rich chemistry. Condensation of molecular gas species into dust grains is a key component in a chain of physical processes that leads to the onset of a stellar wind. In order to improve our understanding of the coupling between the micro-scale chemistry and macro-scale dynamics, we need to retrieve the abundance of molecules throughout the outflow. Aims: Our aim is to determine the radial abundance profile of SiO and HCN throughout the stellar outflow of R Dor, an oxygen-rich AGB star with a low mass-loss rate. SiO is thought to play an essential role in the dust-formation process of oxygen-rich AGB stars. The presence of HCN in an oxygen-rich environment is thought to be due to non-equilibrium chemistry in the inner wind. Methods: We analysed molecular transitions of CO, SiO, and HCN measured with the APEX telescope and all three instruments on the Herschel Space Observatory, together with data available in the literature. Photometric data and the infrared spectrum measured by ISO-SWS were used to constrain the dust component of the outflow. Using both continuum and line radiative transfer methods, a physical envelope model of both gas and dust was established. We performed an analysis of the SiO and HCN molecular transitions in order to calculate their abundances. Results: We have obtained an envelope model that describes the dust and the gas in the outflow, and determined the abundance of SiO and HCN throughout the region of the stellar outflow probed by our molecular data. For SiO, we find that the initial abundance lies between 5.5 × 10-5 and 6.0 × 10-5 with respect to H2. The abundance profile is constant up to 60 ± 10 R∗, after which it declines following a Gaussian profile with an e-folding radius of 3.5 ± 0.5 × 1013 cm or 1.4 ± 0.2 R∗. For HCN, we find an initial abundance of 5.0 × 10-7 with respect to H2. The Gaussian profile that describes the decline

  16. Development of selective catalytic oxidation (SCO) for NH{sub 3} and HCN removal from gasification gas; Selektiivisen katalyyttisen hapetusprosessin (SCO) kehittaeminen kaasutuskaasun NH{sub 3}:n ja HCN:n poistoon

    Energy Technology Data Exchange (ETDEWEB)

    Leppaelahti, J.; Koljonen, T.; Heiskanen, K. [VTT Energy, Espoo (Finland)

    1997-10-01

    In gasification, reactive nitrogen compounds (mainly NH{sub 3} and HCN) are formed from fuel nitrogen. If the gas containing NH{sub 3} is burned, a high NO{sub x} emission may be formed. The content of nitrogen compounds of the hot gasification gas could be reduced in Selective Catalytic Oxidation (SCO) process. In this process small amounts of reactive oxidisers are injected into the gas in order to convert NH{sub 3} to N{sub 2}. The utilization of SCO process together with low NO{sub x} burners in advanced gasification power stations might offer an alternative for flue gas treatment technologies like SCR (Selective Catalytic Reduction). In the earlier research, conditions were found, where oxidizers reacted selectively with ammonia in the gasification gas. Highest ammonia reduction took place in the aluminium oxide bed in the presence of NO and O{sub 2}. The aim of this study is to examine the reaction mechanism in order to be able to further evaluate the development possibilities of this kind process. The effect of composition and the amount of added oxidizer, the content of combustible gas components, space velocity, pressure and temperature will be studied. The experiments are carried out with the laboratory scale high pressure flow reactor of VTT Energy. Kinetic modelling of the experimental results is carried out in co-operation with the combustion chemistry group of Aabo Akademi. The aim of the modelling work is to bring insight to the gas-phase reactions that are important for the SCO-process. (orig.)

  17. Adsorption behavior of Co anchored on graphene sheets toward NO, SO2, NH3, CO and HCN molecules

    International Nuclear Information System (INIS)

    Tang, Yanan; Chen, Weiguang; Li, Chenggang; Pan, Lijun; Dai, Xianqi; Ma, Dongwei

    2015-01-01

    Graphical abstract: - Highlights: • In contrast to the pristine graphene, a vacancy defect in graphene strongly stabilizes the Co atom. • The positively charged of Co atom on graphene can regulate the stability of gas molecules. • Different gas molecules can modulate the electronic structure of Co–graphene systems. • The adsorbed NO on Co–graphene can effectively regulate the magnetic properties of systems. - Abstract: Based on the first-principles of density-functional theory (DFT), the effects of gas adsorption on the change in geometric stability, electronic structure and magnetic properties of graphene with anchored Co (Co–graphene) systems were investigated. A single Co adatom interacts much weaker with pristine graphene (Co/pri–graphene) than with the graphene containing a single vacancy (Co/SV–graphene). The Co dopant provides more electrons to the dangling bonds of carbon atom at defective site and exhibits more positive charges, which makes Co/SV–graphene less prone to be adsorbed by gas molecules in comparison to Co/pri–graphene. It is found that the electronic structure and magnetic properties of Co–graphene systems can be modulated by adsorbing gas molecules. Except the NH 3 molecule, the adsorbed NO, SO 2 , CO or HCN as electron acceptors on the Co/pri–graphene can exhibit semiconducting properties. Among the gas molecules, the strong adsorption of NO molecule can effectively regulate the magnetic properties of Co–graphene systems. Moreover, the stable configuration of Co/SV–graphene is more likely to be the gas sensor for detecting NO and SO 2 . The results validate that the reactivity of atomic-scale catalyst is supported on graphene sheets, which is expected to be potentially efficient in the gas sensors and electronic device

  18. Channelling and electromagnetic radiation of channelling particles

    International Nuclear Information System (INIS)

    Kalashnikov, N.

    1983-01-01

    A brief description is presented of the channelling of charged particles between atoms in the crystal lattice. The specificities are discussed of the transverse motion of channelling particles as are the origin and properties of quasi-characteristic radiation of channelling particles which accompany transfers from one band of permissible energies of the transverse motion of channelling particles to the other. (B.S.)

  19. The influence of zinc hydroxystannate on reducing toxic gases (CO, NO{sub x} and HCN) generation and fire hazards of thermoplastic polyurethane composites

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Bibo; Sheng, Haibo [State Key Laboratory of Fire Science, University of Science and Technology of China, Anhui 230026 (China); Shi, Yongqian [State Key Laboratory of Fire Science, University of Science and Technology of China, Anhui 230026 (China); Suzhou Key Laboratory of Urban Public Safety, Suzhou Institute for Advanced Study, University of Science and Technology of China, Jiangsu, Suzhou 215123 (China); Song, Lei [State Key Laboratory of Fire Science, University of Science and Technology of China, Anhui 230026 (China); Zhang, Yan [State Key Laboratory of Fire Science, University of Science and Technology of China, Anhui 230026 (China); Suzhou Key Laboratory of Urban Public Safety, Suzhou Institute for Advanced Study, University of Science and Technology of China, Jiangsu, Suzhou 215123 (China); Hu, Yuan, E-mail: yuanhu@ustc.edu.cn [State Key Laboratory of Fire Science, University of Science and Technology of China, Anhui 230026 (China); Suzhou Key Laboratory of Urban Public Safety, Suzhou Institute for Advanced Study, University of Science and Technology of China, Jiangsu, Suzhou 215123 (China); Hu, Weizhao, E-mail: hwz1988@ustc.edu.cn [State Key Laboratory of Fire Science, University of Science and Technology of China, Anhui 230026 (China)

    2016-08-15

    Highlights: • The ZnHS could significantly enhance the mechanical properties of the TPU composites. • ZnHS has excellent smoke suppression and reduction the HRR for TPU composites. • ZnHS shows significant decrease in CO, HCN, NO{sub x} for TPU composites. • These improvements are due to charring and catalytic degradation the toxic gases. - Abstract: A uniform zinc hydroxystannate (ZnHS) microcube was synthesized to reduce toxicity and fire hazards of thermoplastic polyurethane (TPU) composites using ammonium polyphosphate as a flame retardant agent. The structure, morphology and thermal properties of ZnHS were characterized by X-ray diffraction, transmission electron microscopy and thermogravimetric analysis, respectively. Smoke suppression properties and synergistic flame retardant effect of ZnHS on flame retardant TPU composites were intensively investigated by smoke density test, cone calorimeter test, and thermalgravimetric analysis. Thermogravimetric analysis/infrared spectrometry and tube furnace were employed to evaluate the toxic gases (CO, NO{sub x} and HCN) of TPU composites. The incorporation of ZnHS into TPU matrix effectively improved the fire safety and restrained the smoke density, which is attributed to that the char residue catalyzed by ZnHS enhanced barrier effect that reduced peak heat release rate, total heat release, smoke particles and organic volatiles during combustion. Furthermore, the ZnHS synergist demonstrated high efficiency in catalytic degradation of the toxic gases, which obviously decreased total volatiled product and toxic volatiles evolved, such as the CO, HCN and NO{sub x}, indicating suppressed toxicity of the TPU composites.

  20. Channel Modeling

    Science.gov (United States)

    Schmitz, Arne; Schinnenburg, Marc; Gross, James; Aguiar, Ana

    For any communication system the Signal-to-Interference-plus-Noise-Ratio of the link is a fundamental metric. Recall (cf. Chapter 9) that the SINR is defined as the ratio between the received power of the signal of interest and the sum of all "disturbing" power sources (i.e. interference and noise). From information theory it is known that a higher SINR increases the maximum possible error-free transmission rate (referred to as Shannon capacity [417] of any communication system and vice versa). Conversely, the higher the SINR, the lower will be the bit error rate in practical systems. While one aspect of the SINR is the sum of all distracting power sources, another issue is the received power. This depends on the transmitted power, the used antennas, possibly on signal processing techniques and ultimately on the channel gain between transmitter and receiver.

  1. Channeling experiment

    International Nuclear Information System (INIS)

    Abelin, H.; Birgersson, L.; Widen, H.; Aagren, T.; Moreno, L.; Neretnieks, I.

    1990-07-01

    Channeling of water flow and tracer transport in real fractures in a granite body at Stripa have been investigated experimentally. The experimental site was located 360 m below the ground level. Two kinds of experiments were performed. In the single hole experiments, 20 cm diameter holes were drilled about 2.5 m into the rock in the plane of the fracture. Specially designed packers were used to inject water into the fracture in 5 cm intervals all along the fracture trace in the hole. The variation of the injection flowrates along the fracture were used to determine the transmissivity variations in the fracture plane. Detailed photographs were taken from inside the hole and the visual fracture aperture was compared with the injection flowrates in the same locations. Geostatistical methods were used to evaluate the results. Five holes were measured in great detail. In addition 7 holes were drilled and scanned by simpler packer systems. A double hole experiment was performed where two parallel holes were drilled in the same fracture plane at nearly 2 m distance. Pressure pulse tests were made between the holes in both directions. Tracers were injected in 5 locations in one hole and monitored for in many locations in the other hole. The single hole experiment and the double hole experiment show that most of the fracture planes are tight but that there are open sections which form connected channels over distances of at least 2 meters. It was also found in the double hole experiment that the investigated fracture was intersected by at least one fracture between the two holes which diverted a large amount of the injected tracers to several distant locations at the tunnel wall. (authours)

  2. Voltage-gated sodium channels in taste bud cells.

    Science.gov (United States)

    Gao, Na; Lu, Min; Echeverri, Fernando; Laita, Bianca; Kalabat, Dalia; Williams, Mark E; Hevezi, Peter; Zlotnik, Albert; Moyer, Bryan D

    2009-03-12

    Taste bud cells transmit information regarding the contents of food from taste receptors embedded in apical microvilli to gustatory nerve fibers innervating basolateral membranes. In particular, taste cells depolarize, activate voltage-gated sodium channels, and fire action potentials in response to tastants. Initial cell depolarization is attributable to sodium influx through TRPM5 in sweet, bitter, and umami cells and an undetermined cation influx through an ion channel in sour cells expressing PKD2L1, a candidate sour taste receptor. The molecular identity of the voltage-gated sodium channels that sense depolarizing signals and subsequently initiate action potentials coding taste information to gustatory nerve fibers is unknown. We describe the molecular and histological expression profiles of cation channels involved in electrical signal transmission from apical to basolateral membrane domains. TRPM5 was positioned immediately beneath tight junctions to receive calcium signals originating from sweet, bitter, and umami receptor activation, while PKD2L1 was positioned at the taste pore. Using mouse taste bud and lingual epithelial cells collected by laser capture microdissection, SCN2A, SCN3A, and SCN9A voltage-gated sodium channel transcripts were expressed in taste tissue. SCN2A, SCN3A, and SCN9A were expressed beneath tight junctions in subsets of taste cells. SCN3A and SCN9A were expressed in TRPM5 cells, while SCN2A was expressed in TRPM5 and PKD2L1 cells. HCN4, a gene previously implicated in sour taste, was expressed in PKD2L1 cells and localized to cell processes beneath the taste pore. SCN2A, SCN3A and SCN9A voltage-gated sodium channels are positioned to sense initial depolarizing signals stemming from taste receptor activation and initiate taste cell action potentials. SCN2A, SCN3A and SCN9A gene products likely account for the tetrodotoxin-sensitive sodium currents in taste receptor cells.

  3. Opposite effects of the S4-S5 linker and PIP2 on voltage-gated channel function: KCNQ1/KCNE1 and other channels

    Directory of Open Access Journals (Sweden)

    Frank S Choveau

    2012-07-01

    Full Text Available Voltage-gated potassium (Kv channels are tetramers, each subunit presenting six transmembrane segments (S1-S6, with each S1-S4 segments forming a voltage-sensing domain (VSD and the four S5-S6 forming both the conduction pathway and its gate. S4 segments control the opening of the intracellular activation gate in response to changes in membrane potential. Crystal structures of several voltage-gated ion channels in combination with biophysical and mutagenesis studies highlighted the critical role of the S4-S5 linker (S4S5L and of the S6 C-terminal part (S6T in the coupling between the VSD and the activation gate. Several mechanisms have been proposed to describe the coupling at a molecular scale. This review summarizes the mechanisms suggested for various voltage-gated ion channels, including a mechanism that we described for KCNQ1, in which S4S5L is acting like a ligand binding to S6T to stabilize the channel in a closed state. As discussed in this review, this mechanism may explain the reverse response to depolarization in HCN-like channels. As opposed to S4S5L, the phosphoinositide, phosphatidylinositol 4,5-bisphosphate (PIP2, stabilizes KCNQ1 channel in an open state. Many other ion channels (not only voltage-gated require PIP2 to function properly, confirming its crucial importance as an ion channel co-factor. This is highlighted in cases in which an altered regulation of ion channels by PIP2 leads to channelopathies, as observed for KCNQ1. This review summarizes the state of the art on the two regulatory mechanisms that are critical for KCNQ1 and other voltage-gated channels function (PIP2 and S4-S5L, and assesses their potential physiological and pathophysiological roles.

  4. IRRADIATION OF ETHYLENE DILUTED IN SOLID NITROGEN WITH VACUUM ULTRAVIOLET LIGHT AND ELECTRONS: ITS IMPLICATIONS FOR THE FORMATION OF HCN AND HNC

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hui-Fen [Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, 100, Shih-Chuan 1st Road, Kaohsiung 80708, Taiwan (China); Liu, Meng-Chen; Chen, Sian-Cong; Huang, Tzu-Ping; Wu, Yu-Jong, E-mail: yjwu@nsrrc.org.tw [National Synchrotron Radiation Research Center, No. 101, Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan (China)

    2015-05-01

    Chemical reactions of C{sub 2}H{sub 4} dispersed in solid nitrogen at 10 K that occur upon irradiation with Lyα light at a wavelength of 121.6 nm and 500 eV electrons were investigated by measuring the infrared absorption spectra. Photolysis of the matrix samples with 121.6 nm light yielded products, including C{sub 2}H{sub 2}, CN, and isomers of C{sub 2}N{sub 2}, as well as a pair of HCN and HNC. In contrast, electron bombardment of similar matrix samples mainly resulted in the generation of N{sub 3}, C{sub 2}H{sub 2}, C{sub 2}H{sub 3}, C{sub 3}H{sub 2}, and C{sub 3}N{sup −}. Mechanisms of the reactions that occur during the photolysis and electron-radiation of the matrix samples are discussed. The results of the study provide insights into the formation of HNC and HCN, as well as nitriles, in N{sub 2}-rich ice samples containing a small proportion of C{sub 2}H{sub 4}.

  5. A new ab initio potential energy surface for the collisional excitation of HCN by para- and ortho-H{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Denis-Alpizar, Otoniel, E-mail: otonieldenisalpizar@gmail.com [Université de Bordeaux, ISM, CNRS UMR 5255, 33405 Talence Cedex (France); Departamento de Física, Universidad de Matanzas, Matanzas 40100 (Cuba); Kalugina, Yulia [LOMC - UMR 6294, CNRS-Université du Havre, 25 rue Philippe Lebon, BP 540, 76058, Le Havre (France); Department of Optics and Spectroscopy, Tomsk State University, 36 Lenin av., Tomsk 634050 (Russian Federation); Stoecklin, Thierry [Université de Bordeaux, ISM, CNRS UMR 5255, 33405 Talence Cedex (France); Vera, Mario Hernández [LOMC - UMR 6294, CNRS-Université du Havre, 25 rue Philippe Lebon, BP 540, 76058, Le Havre (France); Instituto Superior de Tecnologías y Ciencias Aplicadas, Quinta de Los Molinos, Plaza, La Habana 10600 (Cuba); Lique, François, E-mail: francois.lique@univ-lehavre.fr [Departamento de Física, Universidad de Matanzas, Matanzas 40100 (Cuba)

    2013-12-14

    We present a new four-dimensional potential energy surface for the collisional excitation of HCN by H{sub 2}. Ab initio calculations of the HCN–H{sub 2} van der Waals complex, considering both molecules as rigid rotors, were carried out at the explicitly correlated coupled cluster with single, double, and perturbative triple excitations [CCSD(T)-F12a] level of theory using an augmented correlation-consistent triple zeta (aVTZ) basis set. The equilibrium structure is linear HCN–H{sub 2} with the nitrogen pointing towards H{sub 2} at an intermolecular separation of 7.20 a{sub 0}. The corresponding well depth is −195.20 cm{sup −1}. A secondary minimum of −183.59 cm{sup −1} was found for a T-shape configuration with the H of HCN pointing to the center of mass of H{sub 2}. We also determine the rovibrational energy levels of the HCN–para-H{sub 2} and HCN–ortho-H{sub 2} complexes. The calculated dissociation energies for the para and ortho complexes are 37.79 cm{sup −1} and 60.26 cm{sup −1}, respectively. The calculated ro-vibrational transitions in the HCN–H{sub 2} complex are found to agree by more than 0.5% with the available experimental data, confirming the accuracy of the potential energy surface.

  6. Convergent and reciprocal modulation of a leak K+ current and Ih by an inhalational anaesthetic and neurotransmitters in rat brainstem motoneurones

    Science.gov (United States)

    Sirois, Jay E; Lynch, Carl; Bayliss, Douglas A

    2002-01-01

    anaesthetic actions resulting from effects on either TASK or hyperpolarization-activated cyclic nucleotide-gated (HCN) channels in motoneurones, and perhaps at other CNS sites, can be modulated by prevailing neurotransmitter tone. PMID:12068035

  7. Citizens and service channels: channel choice and channel management implications

    NARCIS (Netherlands)

    Pieterson, Willem Jan

    2010-01-01

    The arrival of electronic channels in the 1990s has had a huge impact on governmental service delivery. The new channels have led to many new opportunities to improve public service delivery, not only in terms of citizen satisfaction, but also in cost reduction for governmental agencies. However,

  8. USACE Navigation Channels 2012

    Data.gov (United States)

    California Natural Resource Agency — This dataset represents both San Francisco and Los Angeles District navigation channel lines. All San Francisco District channel lines were digitized from CAD files...

  9. Calcium channel blocker overdose

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/002580.htm Calcium-channel blocker overdose To use the sharing features on this page, please enable JavaScript. Calcium-channel blockers are a type of medicine used ...

  10. Quantum Channels With Memory

    International Nuclear Information System (INIS)

    Rybar, T.

    2012-01-01

    Quantum memory channels represent a very general, yet simple and comprehensible model for causal processes. As such they have attracted considerable research interest, mostly aimed on their transfer capabilities and structure properties. Most notably it was shown that memory channels can be implemented via physically naturally motivated collision models. We also define the concept of repeatable channels and show that only unital channels can be implemented repeat ably with pure memory channels. In the special case of qubit channels we also show that every unital qubit channel has a repeatable implementation. We also briefly explore the possibilities of stroboscopical simulation of channels and show that all random unitary channels can be stroboscopically simulated. Particularly in qubit case, all indivisible qubit channels are also random unitary, hence for qubit all indivisible channels can be stroboscopically simulated. Memory channels also naturally capture the framework of correlated experiments. We develop methods to gather and interpret data obtained in such setting and in detail examine the two qubit case. We also show that for control unitary interactions the measured data will never contradict a simple unitary evolution. Thus no memory effects can be spotted then. (author)

  11. Eight channel fast scalar

    Energy Technology Data Exchange (ETDEWEB)

    Waddoup, W D; Stubbs, R J [Durham Univ. (UK)

    1977-11-01

    An eight channel 64-bit scaler has been constructed with a static CMOS memory. Scaling frequencies are independently variable, at each channel, as are the number of bits/channel. The scaler, when used in conjunction with a multichannel charge to time converter results in a very flexible, gated multichannel ADC.

  12. KV7 potassium channels

    DEFF Research Database (Denmark)

    Stott, Jennifer B; Jepps, Thomas Andrew; Greenwood, Iain A

    2014-01-01

    Potassium channels are key regulators of smooth muscle tone, with increases in activity resulting in hyperpolarisation of the cell membrane, which acts to oppose vasoconstriction. Several potassium channels exist within smooth muscle, but the KV7 family of voltage-gated potassium channels have been...

  13. Modulation of leak K(+) channel in hypoglossal motoneurons of rats by serotonin and/or variation of pH value.

    Science.gov (United States)

    Xu, Xue-Feng; Tsai, Hao-Jan; Li, Lin; Chen, Yi-Fan; Zhang, Cheng; Wang, Guang-Fa

    2009-08-25

    The cloned TWIK-related acid-sensitive K(+) channel (TASK-1) is sensitive to the pH changes within physiological pH range (pK~7.4). Recently, the native TASK-1-like channel was suggested to be the main contributor to the background (or leak) K(+) conductance in the motoneurons of the brain stem. Serotonin (5-HT) and variation of pH value in perfused solution could modulate these currents. Here we aimed to examine the properties and modulation of the currents by serotonin or variation of pH value in hypoglossal motoneurons of rats. Transverse slices were prepared from the brainstem of neonatal Sprague-Dawley rats (postnatal days 7-8). Hypoglossal motoneurons were used for the study. The leak K(+) current (TASK-1-like current) and hyperpolarization-activated cationic current (I(h)) were recorded with the whole-cell patch-clamp technique. The results showed that these currents were inhibited by acidified artificial cerebrospinal fluid (ACSF, pH 6.0) and activated by alkalized ACSF (pH 8.5). 5-HT (10 mumol/L) significantly inhibited both leak K(+) current and I(h) with depolarization of membrane potential and the occurrence of oscillation and/or spikes. Bath application of Ketanserine, an antagonist of 5-HT₂ receptor, reversed or reduced the inhibitory effect of acidified solution on leak K(+) current and I(h). The results suggest that 5-HT₂ receptors mediate the effects of acidified media on leak K(+) current and I(h) in hypoglossal motoneurons.

  14. Fine Channel Networks

    Science.gov (United States)

    1997-01-01

    A color image of fine channel networks on Mars; north toward top. The scene shows heavily cratered highlands dissected by dendritic open channel networks that dissect steep slopes of impact crater walls. This image is a composite of Viking high-resolution images in black and white and low-resolution images in color. The image extends from latitude 9 degrees S. to 5 degrees S. and from longitude 312 degrees to 320 degrees; Mercator projection. The dendritic pattern of the fine channels and their location on steep slopes leads to the interpretation that these are runoff channels. The restriction of these types of channels to ancient highland rocks suggests that these channels are old and date from a time on Mars when conditions existed for precipitation to actively erode rocks. After the channels reach a low plain, they appear to end. Termination may have resulted from burial by younger deposits or perhaps the flows percolated into the surface materials and continued underground.

  15. Voltage-gated sodium channels in taste bud cells

    Directory of Open Access Journals (Sweden)

    Williams Mark E

    2009-03-01

    Full Text Available Abstract Background Taste bud cells transmit information regarding the contents of food from taste receptors embedded in apical microvilli to gustatory nerve fibers innervating basolateral membranes. In particular, taste cells depolarize, activate voltage-gated sodium channels, and fire action potentials in response to tastants. Initial cell depolarization is attributable to sodium influx through TRPM5 in sweet, bitter, and umami cells and an undetermined cation influx through an ion channel in sour cells expressing PKD2L1, a candidate sour taste receptor. The molecular identity of the voltage-gated sodium channels that sense depolarizing signals and subsequently initiate action potentials coding taste information to gustatory nerve fibers is unknown. Results We describe the molecular and histological expression profiles of cation channels involved in electrical signal transmission from apical to basolateral membrane domains. TRPM5 was positioned immediately beneath tight junctions to receive calcium signals originating from sweet, bitter, and umami receptor activation, while PKD2L1 was positioned at the taste pore. Using mouse taste bud and lingual epithelial cells collected by laser capture microdissection, SCN2A, SCN3A, and SCN9A voltage-gated sodium channel transcripts were expressed in taste tissue. SCN2A, SCN3A, and SCN9A were expressed beneath tight junctions in subsets of taste cells. SCN3A and SCN9A were expressed in TRPM5 cells, while SCN2A was expressed in TRPM5 and PKD2L1 cells. HCN4, a gene previously implicated in sour taste, was expressed in PKD2L1 cells and localized to cell processes beneath the taste pore. Conclusion SCN2A, SCN3A and SCN9A voltage-gated sodium channels are positioned to sense initial depolarizing signals stemming from taste receptor activation and initiate taste cell action potentials. SCN2A, SCN3A and SCN9A gene products likely account for the tetrodotoxin-sensitive sodium currents in taste receptor cells.

  16. Infrared Solar Spectroscopic Measurements of Free Tropospheric CO, C2H6, and HCN above Mauna Loa, Hawaii: Seasonal Variations and Evidence for Enhanced Emissions from the Southeast Asian Tropical Fires of 1997-1998

    Science.gov (United States)

    Rinsland, C. P.; Goldman, A.; Murcray, F. J.; Stephen, T. M.; Pougatchev, N. S.; Fishman, J.; David, S. J.; Blatherwick, R. D.; Novelli, P. C.; Jones, N. B.

    1999-01-01

    High spectral resolution (0.003 per cm) infrared solar absorption measurements of CO, C2H6, and HCN have been recorded at the Network for the Detection of Stratospheric Change station on Mauna Loa, Hawaii, (19.5N, 155.6W, altitude 3.4 km). The observations were obtained on over 250 days between August 1995 and February 1998. Column measurements are reported for the 3.4-16 km altitude region, which corresponds approximately to the free troposphere above the station. Average CO mixing ratios computed for this layer have been compared with flask sampling CO measurements obtained in situ at the station during the same time period. Both show asymmetrical seasonal cycles superimposed on significant variability. The first 2 years of observations exhibit a broad January-April maximum and a sharper CO minimum during late summer. The C2H6 and CO 3.4-16 km columns were highly correlated throughout the observing period with the C2H6/CO slope intermediate between higher and lower values derived from similar infrared spectroscopic measurements at 32'N and 45'S latitude, respectively. Variable enhancements in CO, C2H6, and particularly HCN were observed beginning in about September 1997. The maximum HCN free tropospheric monthly mean column observed in November 1997 corresponds to an average 3.4-16 km mixing ratio of 0.7 ppbv (1 ppbv = 10(exp -9) per unit volume), more than a factor of 3 above the background level. The HCN enhancements continued through the end of the observational series. Back-trajectory calculations suggest that the emissions originated at low northern latitudes in southeast Asia. Surface CO mixing ratios and the C2H6 tropospheric columns measured during the same time also showed anomalous autumn 1997 maxima. The intense and widespread tropical wild fires that burned during the strong El Nino warm phase of 1997- 1998 are the likely source of the elevated emission products.

  17. Ion channels in plants.

    Science.gov (United States)

    Hedrich, Rainer

    2012-10-01

    Since the first recordings of single potassium channel activities in the plasma membrane of guard cells more than 25 years ago, patch-clamp studies discovered a variety of ion channels in all cell types and plant species under inspection. Their properties differed in a cell type- and cell membrane-dependent manner. Guard cells, for which the existence of plant potassium channels was initially documented, advanced to a versatile model system for studying plant ion channel structure, function, and physiology. Interestingly, one of the first identified potassium-channel genes encoding the Shaker-type channel KAT1 was shown to be highly expressed in guard cells. KAT1-type channels from Arabidopsis thaliana and its homologs from other species were found to encode the K(+)-selective inward rectifiers that had already been recorded in early patch-clamp studies with guard cells. Within the genome era, additional Arabidopsis Shaker-type channels appeared. All nine members of the Arabidopsis Shaker family are localized at the plasma membrane, where they either operate as inward rectifiers, outward rectifiers, weak voltage-dependent channels, or electrically silent, but modulatory subunits. The vacuole membrane, in contrast, harbors a set of two-pore K(+) channels. Just very recently, two plant anion channel families of the SLAC/SLAH and ALMT/QUAC type were identified. SLAC1/SLAH3 and QUAC1 are expressed in guard cells and mediate Slow- and Rapid-type anion currents, respectively, that are involved in volume and turgor regulation. Anion channels in guard cells and other plant cells are key targets within often complex signaling networks. Here, the present knowledge is reviewed for the plant ion channel biology. Special emphasis is drawn to the molecular mechanisms of channel regulation, in the context of model systems and in the light of evolution.

  18. FORMATION OF N{sub 3}, CH{sub 3}, HCN, AND HNC FROM THE FAR-UV PHOTOLYSIS OF CH{sub 4} IN NITROGEN ICE

    Energy Technology Data Exchange (ETDEWEB)

    Lo, Jen-Iu; Chou, Sheng-Lung; Peng, Yu-Chain; Lin, Meng-Yeh; Lu, Hsiao-Chi; Cheng, Bing-Ming, E-mail: bmcheng@nsrrc.org.tw [National Synchrotron Radiation Research Center, No. 101, Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan (China)

    2015-11-15

    The irradiation of pure solid N{sub 2} at 3 K with far-ultraviolet light from a synchrotron produced infrared absorption lines at 1657.7, 1655.6, and 1652.4 cm{sup −1} and an ultraviolet absorption line at 272.0 nm, which are characteristic of the product N{sub 3}. The threshold wavelength at which N{sub 3} was generated was 145.6 ± 2.9 nm, corresponding to an energy of 8.52 ± 0.17 eV. The photolysis of isotopically labeled {sup 15}N{sub 2} at 3 K consistently led to the formation of {sup 15}N{sub 3} with the same threshold wavelength of 145.6 ± 2.9 nm for its formation. The photolysis of CH{sub 4} in nitrogen ice in low concentrations also led to the formation of N{sub 3}, together with CH{sub 3}, HCN, and HNC, with the same threshold wavelength of 145.6 ± 2.9 nm. These results indicate that N{sub 3} radicals may play an important role in the photochemistry of nitrogen ices in astronomical environments.

  19. Compound Wiretap Channels

    Directory of Open Access Journals (Sweden)

    Shlomo Shamai (Shitz

    2009-01-01

    Full Text Available This paper considers the compound wiretap channel, which generalizes Wyner's wiretap model to allow the channels to the (legitimate receiver and to the eavesdropper to take a number of possible states. No matter which states occur, the transmitter guarantees that the receiver decodes its message and that the eavesdropper is kept in full ignorance about the message. The compound wiretap channel can also be viewed as a multicast channel with multiple eavesdroppers, in which the transmitter sends information to all receivers and keeps the information secret from all eavesdroppers. For the discrete memoryless channel, lower and upper bounds on the secrecy capacity are derived. The secrecy capacity is established for the degraded channel and the semideterministic channel with one receiver. The parallel Gaussian channel is further studied. The secrecy capacity and the secrecy degree of freedom (s.d.o.f. are derived for the degraded case with one receiver. Schemes to achieve the s.d.o.f. for the case with two receivers and two eavesdroppers are constructed to demonstrate the necessity of a prefix channel in encoder design. Finally, the multi-antenna (i.e., MIMO compound wiretap channel is studied. The secrecy capacity is established for the degraded case and an achievable s.d.o.f. is given for the general case.

  20. Compound Wiretap Channels

    Directory of Open Access Journals (Sweden)

    Kramer Gerhard

    2009-01-01

    Full Text Available Abstract This paper considers the compound wiretap channel, which generalizes Wyner's wiretap model to allow the channels to the (legitimate receiver and to the eavesdropper to take a number of possible states. No matter which states occur, the transmitter guarantees that the receiver decodes its message and that the eavesdropper is kept in full ignorance about the message. The compound wiretap channel can also be viewed as a multicast channel with multiple eavesdroppers, in which the transmitter sends information to all receivers and keeps the information secret from all eavesdroppers. For the discrete memoryless channel, lower and upper bounds on the secrecy capacity are derived. The secrecy capacity is established for the degraded channel and the semideterministic channel with one receiver. The parallel Gaussian channel is further studied. The secrecy capacity and the secrecy degree of freedom ( are derived for the degraded case with one receiver. Schemes to achieve the for the case with two receivers and two eavesdroppers are constructed to demonstrate the necessity of a prefix channel in encoder design. Finally, the multi-antenna (i.e., MIMO compound wiretap channel is studied. The secrecy capacity is established for the degraded case and an achievable is given for the general case.

  1. ATP Release Channels

    Directory of Open Access Journals (Sweden)

    Akiyuki Taruno

    2018-03-01

    Full Text Available Adenosine triphosphate (ATP has been well established as an important extracellular ligand of autocrine signaling, intercellular communication, and neurotransmission with numerous physiological and pathophysiological roles. In addition to the classical exocytosis, non-vesicular mechanisms of cellular ATP release have been demonstrated in many cell types. Although large and negatively charged ATP molecules cannot diffuse across the lipid bilayer of the plasma membrane, conductive ATP release from the cytosol into the extracellular space is possible through ATP-permeable channels. Such channels must possess two minimum qualifications for ATP permeation: anion permeability and a large ion-conducting pore. Currently, five groups of channels are acknowledged as ATP-release channels: connexin hemichannels, pannexin 1, calcium homeostasis modulator 1 (CALHM1, volume-regulated anion channels (VRACs, also known as volume-sensitive outwardly rectifying (VSOR anion channels, and maxi-anion channels (MACs. Recently, major breakthroughs have been made in the field by molecular identification of CALHM1 as the action potential-dependent ATP-release channel in taste bud cells, LRRC8s as components of VRACs, and SLCO2A1 as a core subunit of MACs. Here, the function and physiological roles of these five groups of ATP-release channels are summarized, along with a discussion on the future implications of understanding these channels.

  2. Volume Regulated Channels

    DEFF Research Database (Denmark)

    Klausen, Thomas Kjær

    of volume perturbations evolution have developed system of channels and transporters to tightly control volume homeostasis. In the past decades evidence has been mounting, that the importance of these volume regulated channels and transporters are not restricted to the defense of cellular volume...... but are also essential for a number of physiological processes such as proliferation, controlled cell death, migration and endocrinology. The thesis have been focusing on two Channels, namely the swelling activated Cl- channel (ICl, swell) and the transient receptor potential Vanilloid (TRPV4) channel. I: Cl......- serves a multitude of functions in the mammalian cell, regulating the membrane potential (Em), cell volume, protein activity and the driving force for facilitated transporters giving Cl- and Cl- channels a major potential of regulating cellular function. These functions include control of the cell cycle...

  3. HIPPI and Fibre Channel

    International Nuclear Information System (INIS)

    Tolmie, D.E.

    1992-01-01

    The High-Performance Parallel Interface (HIPPI) and Fibre Channel are near-gigabit per second data communications interfaces being developed in ANSI standards Task Group X3T9.3. HIPPI is the current interface of choice in the high-end and supercomputer arena, and Fibre Channel is a follow-on effort. HIPPI came from a local area network background, and Fibre Channel came from a mainframe to peripheral interface background

  4. Nuclear reactor coolant channels

    International Nuclear Information System (INIS)

    Macbeth, R.V.

    1978-01-01

    Reference is made to coolant channels for pressurised water and boiling water reactors and the arrangement described aims to improve heat transfer between the fuel rods and the coolant. Baffle means extending axially within the channel are provided and disposed relative to the fuel rods so as to restrict flow oscillations occurring within the coolant from being propagated transversely to the axis of the channel. (UK)

  5. New Channels, New Possibilities

    DEFF Research Database (Denmark)

    Pieterson, Willem; Ebbers, Wolfgang; Østergaard Madsen, Christian

    2017-01-01

    In this contribution we discuss the characteristics of what we call the fourth generation of public sector service channels: social robots. Based on a review of relevant literature we discuss their characteristics and place into multi-channel models of service delivery. We argue that social robots......-channel models of service delivery. This is especially relevant given the current lack of evaluations of such models, the broad range of channels available, and their different stages of deployment at governments around the world. Nevertheless, social robots offer an potentially very relevant addition...

  6. Calcium Channel Blockers

    Science.gov (United States)

    ... Certain calcium channel blockers interact with grapefruit products. Kaplan NM, et al. Treatment of hypertension: Drug therapy. In: Kaplan's Clinical Hypertension. 11th ed. Philadelphia, Pa.: Wolters Kluwer ...

  7. A channel profile analyser

    International Nuclear Information System (INIS)

    Gobbur, S.G.

    1983-01-01

    It is well understood that due to the wide band noise present in a nuclear analog-to-digital converter, events at the boundaries of adjacent channels are shared. It is a difficult and laborious process to exactly find out the shape of the channels at the boundaries. A simple scheme has been developed for the direct display of channel shape of any type of ADC on a cathode ray oscilliscope display. This has been accomplished by sequentially incrementing the reference voltage of a precision pulse generator by a fraction of a channel and storing ADC data in alternative memory locations of a multichannel pulse height analyser. Alternative channels are needed due to the sharing at the boundaries of channels. In the flat region of the profile alternate memory locations are channels with zero counts and channels with the full scale counts. At the boundaries all memory locations will have counts. The shape of this is a direct display of the channel boundaries. (orig.)

  8. Ammonothermal synthesis of alkali-alkaline earth metal and alkali-rare earth metal carbodiimides. K{sub 5-x}M{sub x}(CN{sub 2}){sub 2+x}(HCN{sub 2}){sub 1-x} (M = Sr, Eu) and Na{sub 4.32}Sr{sub 0.68}(CN{sub 2}){sub 2.68}(HCN{sub 2}){sub 0.32}

    Energy Technology Data Exchange (ETDEWEB)

    Mallmann, Mathias; Haeusler, Jonas; Cordes, Niklas; Schnick, Wolfgang [Department of Chemistry, University of Munich (LMU) (Germany)

    2017-12-13

    Alkali-alkaline earth metal and alkali-rare earth metal carbodiimides, namely K{sub 5-x}M{sub x}(CN{sub 2}){sub 2+x}(HCN{sub 2}){sub 1-x} (x = 0 - 1) (M = Sr, Eu) and Na{sub 4.32}Sr{sub 0.68}(CN{sub 2}){sub 2.68}(HCN{sub 2}){sub 0.32}, were synthesized under ammonothermal conditions in high-pressure autoclaves. The structures of the three compounds can be derived from homeotypic K{sub 5}H(CN{sub 2}){sub 3} and Na{sub 5}H(CN{sub 2}){sub 3} by partial substitution of K{sup +} or Na{sup +}by Sr{sup 2+} or Eu{sup 2+}. The reactions were carried out in two step syntheses (T{sub 1} = 673 K, T{sub 2} = 823 K) starting from sodium or potassium azide, dicyandiamide and strontium or Eu(NH{sub 2}){sub 2}, respectively. The crystal structures were solved and refined from single-crystal X-ray diffraction data [K{sub 4.16}Sr{sub 0.84}(CN{sub 2}){sub 2.84}(HCN{sub 2}){sub 0.16}: space group Im3m (no. 229), a = 7.8304(5) Aa, Z = 2, R{sub 1} = 0.024, wR{sub 2} = 0.052; K{sub 4.40}Eu{sub 0.60}(CN{sub 2}){sub 2.60}(HCN{sub 2}){sub 0.40}: space group Im anti 3m (no. 229), a = 7.8502(6) Aa, Z = 2, R{sub 1} = 0.022, wR{sub 2} = 0.049]. In contrast to the potassium carbodiimides, the sodium-strontium carbodiimide was only synthesized as microcrystalline powder. The crystal structure was determined by powder X-ray diffraction and refined by the Rietveld method [Na{sub 4.32}Sr{sub 0.68}(CN{sub 2}){sub 2.68}(HCN{sub 2}){sub 0.32}: space group Im3m (no. 229), a = 7.2412(1) Aa, Z = 2, R{sub wp} = 0.050]. The presence of hydrogencyanamide units ([HNCN]{sup -}) next to carbodiimide units ([CN{sub 2}]{sup 2-}) in all compounds was confirmed by FT-IR spectroscopy. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. A linearization of quantum channels

    Science.gov (United States)

    Crowder, Tanner

    2015-06-01

    Because the quantum channels form a compact, convex set, we can express any quantum channel as a convex combination of extremal channels. We give a Euclidean representation for the channels whose inverses are also valid channels; these are a subset of the extreme points. They form a compact, connected Lie group, and we calculate its Lie algebra. Lastly, we calculate a maximal torus for the group and provide a constructive approach to decomposing any invertible channel into a product of elementary channels.

  10. Omni channel fashion shopping

    NARCIS (Netherlands)

    Kemperman, A.D.A.M.; van Delft, L.; Borgers, A.W.J.; Pantano, E.

    2015-01-01

    This chapter gives insight into consumers' online and offline fashion shopping behavior, consumers' omni-channel usage during the shopping process, and consumer fashion shopper segments. Based on a literature review, omni-channel shopping behavior during the shopping process was operationalized.

  11. Channel electron multipliers

    International Nuclear Information System (INIS)

    Seidman, A.; Avrahami, Z.; Sheinfux, B.; Grinberg, J.

    1976-01-01

    A channel electron multiplier is described having a tubular wall coated with a secondary-electron emitting material and including an electric field for accelerating the electrons, the electric field comprising a plurality of low-resistive conductive rings each alternating with a high-resistive insulating ring. The thickness of the low-resistive rings is many times larger than that of the high-resistive rings, being in the order of tens of microns for the low-resistive rings and at least one order of magnitude lower for the high-resistive rings; and the diameter of the channel tubular walls is also many times larger than the thickness of the high-resistive rings. Both single-channel and multiple-channel electron multipliers are described. A very important advantage, particularly in making multiple-channel multipliers, is the simplicity of the procedure that may be used in constructing such multipliers. Other operational advantages are described

  12. Cardiac potassium channel subtypes

    DEFF Research Database (Denmark)

    Schmitt, Nicole; Grunnet, Morten; Olesen, Søren-Peter

    2014-01-01

    About 10 distinct potassium channels in the heart are involved in shaping the action potential. Some of the K(+) channels are primarily responsible for early repolarization, whereas others drive late repolarization and still others are open throughout the cardiac cycle. Three main K(+) channels...... drive the late repolarization of the ventricle with some redundancy, and in atria this repolarization reserve is supplemented by the fairly atrial-specific KV1.5, Kir3, KCa, and K2P channels. The role of the latter two subtypes in atria is currently being clarified, and several findings indicate...... that they could constitute targets for new pharmacological treatment of atrial fibrillation. The interplay between the different K(+) channel subtypes in both atria and ventricle is dynamic, and a significant up- and downregulation occurs in disease states such as atrial fibrillation or heart failure...

  13. Cl- channels in apoptosis

    DEFF Research Database (Denmark)

    Wanitchakool, Podchanart; Ousingsawat, Jiraporn; Sirianant, Lalida

    2016-01-01

    A remarkable feature of apoptosis is the initial massive cell shrinkage, which requires opening of ion channels to allow release of K(+), Cl(-), and organic osmolytes to drive osmotic water movement and cell shrinkage. This article focuses on the role of the Cl(-) channels LRRC8, TMEM16/anoctamin......, and cystic fibrosis transmembrane conductance regulator (CFTR) in cellular apoptosis. LRRC8A-E has been identified as a volume-regulated anion channel expressed in many cell types. It was shown to be required for regulatory and apoptotic volume decrease (RVD, AVD) in cultured cell lines. Its presence also......(-) channels or as regulators of other apoptotic Cl(-) channels, such as LRRC8. CFTR has been known for its proapoptotic effects for some time, and this effect may be based on glutathione release from the cell and increase in cytosolic reactive oxygen species (ROS). Although we find that CFTR is activated...

  14. CHANNEL ESTIMATION TECHNIQUE

    DEFF Research Database (Denmark)

    2015-01-01

    A method includes determining a sequence of first coefficient estimates of a communication channel based on a sequence of pilots arranged according to a known pilot pattern and based on a receive signal, wherein the receive signal is based on the sequence of pilots transmitted over the communicat......A method includes determining a sequence of first coefficient estimates of a communication channel based on a sequence of pilots arranged according to a known pilot pattern and based on a receive signal, wherein the receive signal is based on the sequence of pilots transmitted over...... the communication channel. The method further includes determining a sequence of second coefficient estimates of the communication channel based on a decomposition of the first coefficient estimates in a dictionary matrix and a sparse vector of the second coefficient estimates, the dictionary matrix including...... filter characteristics of at least one known transceiver filter arranged in the communication channel....

  15. Experimental investigation of aminoacetonitrile formation through the Strecker synthesis in astrophysical-like conditions: reactivity of methanimine (CH2NH), ammonia (NH3), and hydrogen cyanide (HCN)

    Science.gov (United States)

    Danger, G.; Borget, F.; Chomat, M.; Duvernay, F.; Theulé, P.; Guillemin, J.-C.; Le Sergeant D'Hendecourt, L.; Chiavassa, T.

    2011-11-01

    Context. Studing chemical reactivity in astrophysical environments is an important means for improving our understanding of the origin of the organic matter in molecular clouds, in protoplanetary disks, and possibly, as a final destination, in our solar system. Laboratory simulations of the reactivity of ice analogs provide important insight into the reactivity in these environments. Here, we use these experimental simulations to investigate the Strecker synthesis leading to the formation of aminoacetonitrile in astrophysical-like conditions. The aminoacetonitrile is an interesting compound because it was detected in SgrB2, hence could be a precursor of the smallest amino acid molecule, glycine, in astrophysical environments. Aims: We present the first experimental investigation of the formation of aminoacetonitrile NH2CH2CN from the thermal processing of ices including methanimine (CH2NH), ammonia (NH3), and hydrogen cyanide (HCN) in interstellar-like conditions without VUV photons or particules. Methods: We use Fourier Transform InfraRed (FTIR) spectroscopy to monitor the ice evolution during its warming. Infrared spectroscopy and mass spectroscopy are then used to identify the aminoacetonitrile formation. Results: We demonstrate that methanimine can react with -CN during the warming of ice analogs containing at 20 K methanimine, ammonia, and [NH4+ -CN] salt. During the ice warming, this reaction leads to the formation of poly(methylene-imine) polymers. The polymer length depend on the initial ratio of mass contained in methanimine to that in the [NH4+ -CN] salt. In a methanimine excess, long polymers are formed. As the methanimine is progressively diluted in the [NH4+ -CN] salt, the polymer length decreases until the aminoacetonitrile formation at 135 K. Therefore, these results demonstrate that aminoacetonitrile can be formed through the second step of the Strecker synthesis in astrophysical-like conditions.

  16. Adsorption behavior of Co anchored on graphene sheets toward NO, SO{sub 2}, NH{sub 3}, CO and HCN molecules

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Yanan, E-mail: yntang2010@hotmail.com [College of Physics and Electronic Engineering, Zhengzhou Normal University, Zhengzhou, Henan 450044 (China); Quantum Materials Research Center, Zhengzhou Normal University, Henan 450044 (China); Chen, Weiguang; Li, Chenggang; Pan, Lijun [College of Physics and Electronic Engineering, Zhengzhou Normal University, Zhengzhou, Henan 450044 (China); Quantum Materials Research Center, Zhengzhou Normal University, Henan 450044 (China); Dai, Xianqi, E-mail: xqdai@henannu.edu.cn [College of Physics and Electronic Engineering, Zhengzhou Normal University, Zhengzhou, Henan 450044 (China); Quantum Materials Research Center, Zhengzhou Normal University, Henan 450044 (China); Ma, Dongwei [College of Physics and Electrical Engineering, Anyang Normal University, Anyang, Henan 455000 (China)

    2015-07-01

    Graphical abstract: - Highlights: • In contrast to the pristine graphene, a vacancy defect in graphene strongly stabilizes the Co atom. • The positively charged of Co atom on graphene can regulate the stability of gas molecules. • Different gas molecules can modulate the electronic structure of Co–graphene systems. • The adsorbed NO on Co–graphene can effectively regulate the magnetic properties of systems. - Abstract: Based on the first-principles of density-functional theory (DFT), the effects of gas adsorption on the change in geometric stability, electronic structure and magnetic properties of graphene with anchored Co (Co–graphene) systems were investigated. A single Co adatom interacts much weaker with pristine graphene (Co/pri–graphene) than with the graphene containing a single vacancy (Co/SV–graphene). The Co dopant provides more electrons to the dangling bonds of carbon atom at defective site and exhibits more positive charges, which makes Co/SV–graphene less prone to be adsorbed by gas molecules in comparison to Co/pri–graphene. It is found that the electronic structure and magnetic properties of Co–graphene systems can be modulated by adsorbing gas molecules. Except the NH{sub 3} molecule, the adsorbed NO, SO{sub 2}, CO or HCN as electron acceptors on the Co/pri–graphene can exhibit semiconducting properties. Among the gas molecules, the strong adsorption of NO molecule can effectively regulate the magnetic properties of Co–graphene systems. Moreover, the stable configuration of Co/SV–graphene is more likely to be the gas sensor for detecting NO and SO{sub 2}. The results validate that the reactivity of atomic-scale catalyst is supported on graphene sheets, which is expected to be potentially efficient in the gas sensors and electronic device.

  17. Coherifying quantum channels

    Science.gov (United States)

    Korzekwa, Kamil; Czachórski, Stanisław; Puchała, Zbigniew; Życzkowski, Karol

    2018-04-01

    Is it always possible to explain random stochastic transitions between states of a finite-dimensional system as arising from the deterministic quantum evolution of the system? If not, then what is the minimal amount of randomness required by quantum theory to explain a given stochastic process? Here, we address this problem by studying possible coherifications of a quantum channel Φ, i.e., we look for channels {{{Φ }}}{ \\mathcal C } that induce the same classical transitions T, but are ‘more coherent’. To quantify the coherence of a channel Φ we measure the coherence of the corresponding Jamiołkowski state J Φ. We show that the classical transition matrix T can be coherified to reversible unitary dynamics if and only if T is unistochastic. Otherwise the Jamiołkowski state {J}{{Φ }}{ \\mathcal C } of the optimally coherified channel is mixed, and the dynamics must necessarily be irreversible. To assess the extent to which an optimal process {{{Φ }}}{ \\mathcal C } is indeterministic we find explicit bounds on the entropy and purity of {J}{{Φ }}{ \\mathcal C }, and relate the latter to the unitarity of {{{Φ }}}{ \\mathcal C }. We also find optimal coherifications for several classes of channels, including all one-qubit channels. Finally, we provide a non-optimal coherification procedure that works for an arbitrary channel Φ and reduces its rank (the minimal number of required Kraus operators) from {d}2 to d.

  18. CANDU channel flow verification

    International Nuclear Information System (INIS)

    Mazalu, N.; Negut, Gh.

    1997-01-01

    The purpose of this evaluation was to obtain accurate information on each channel flow that enables us to assess precisely the level of reactor thermal power and, for reasons of safety, to establish which channel is boiling. In order to assess the channel flow parameters, computer simulations were done with the NUCIRC code and the results were checked by measurements. The complete channel flow measurements were made in the zero power cold condition. In hot conditions there were made flow measurements using the Shut Down System 1 (SDS 1) flow devices from 0.1 % F.P. up to 100 % F.P. The NUCIRC prediction for CANDU channel flows and the measurements by Ultrasonic Flow Meter at zero power cold conditions and SDS 1 flow channel measurements at different reactor power levels showed an acceptable agreement. The 100 % F.P. average errors for channel flow of R, shows that suitable NUCIRC flow assessment can be made. So, it can be done a fair prediction of the reactor power distribution. NUCIRC can predict accurately the onset of boiling and helps to warn at the possible power instabilities at high powers or it can detect the flow blockages. The thermal hydraulic analyst has in NUCIRC a suitable tool to do accurate predictions for the thermal hydraulic parameters for different steady state power levels which subsequently leads to an optimal CANDU reactor operation. (authors)

  19. Reconfigurable virtual electrowetting channels.

    Science.gov (United States)

    Banerjee, Ananda; Kreit, Eric; Liu, Yuguang; Heikenfeld, Jason; Papautsky, Ian

    2012-02-21

    Lab-on-a-chip systems rely on several microfluidic paradigms. The first uses a fixed layout of continuous microfluidic channels. Such lab-on-a-chip systems are almost always application specific and far from a true "laboratory." The second involves electrowetting droplet movement (digital microfluidics), and allows two-dimensional computer control of fluidic transport and mixing. The merging of the two paradigms in the form of programmable electrowetting channels takes advantage of both the "continuous" functionality of rigid channels based on which a large number of applications have been developed to date and the "programmable" functionality of digital microfluidics that permits electrical control of on-chip functions. In this work, we demonstrate for the first time programmable formation of virtual microfluidic channels and their continuous operation with pressure driven flows using an electrowetting platform. Experimental, theoretical, and numerical analyses of virtual channel formation with biologically relevant electrolyte solutions and electrically-programmable reconfiguration are presented. We demonstrate that the "wall-less" virtual channels can be formed reliably and rapidly, with propagation rates of 3.5-3.8 mm s(-1). Pressure driven transport in these virtual channels at flow rates up to 100 μL min(-1) is achievable without distortion of the channel shape. We further demonstrate that these virtual channels can be switched on-demand between multiple inputs and outputs. Ultimately, we envision a platform that would provide rapid prototyping of microfluidic concepts and would be capable of a vast library of functions and benefitting applications from clinical diagnostics in resource-limited environments to rapid system prototyping to high throughput pharmaceutical applications.

  20. Evaluation channel performance in multichannel environments

    NARCIS (Netherlands)

    Gensler, S.; Dekimpe, M.; Skiera, B.

    2007-01-01

    Evaluating channel performance is crucial for actively managing multiple sales channels, and requires understanding the customers' channel preferences. Two key components of channel performance are (i) the existing customers' intrinsic loyalty to a particular channel and (ii) the channel's ability

  1. Channel follower leakage restrictor

    International Nuclear Information System (INIS)

    Williamson, H.E.; Smith, B.A.

    1977-01-01

    An improved means is provided to control coolant leakage between the flow channel and the lower tie plate of a nuclear fuel assembly. The means includes an opening in the lower tie plate and a movable element adjacent thereto. The coolant pressure within the tie plate biases the movable means toward the inner surface of the surrounding flow channel to compensate for any movement of the flow channel away from the lower tie plate to thereby control the leakage of coolant flow from the fuel assemblies to the spaces among the fuel assemblies of the core. 9 figures

  2. Free-energy relationships in ion channels activated by voltage and ligand

    Science.gov (United States)

    Chowdhury, Sandipan

    2013-01-01

    Many ion channels are modulated by multiple stimuli, which allow them to integrate a variety of cellular signals and precisely respond to physiological needs. Understanding how these different signaling pathways interact has been a challenge in part because of the complexity of underlying models. In this study, we analyzed the energetic relationships in polymodal ion channels using linkage principles. We first show that in proteins dually modulated by voltage and ligand, the net free-energy change can be obtained by measuring the charge-voltage (Q-V) relationship in zero ligand condition and the ligand binding curve at highly depolarizing membrane voltages. Next, we show that the voltage-dependent changes in ligand occupancy of the protein can be directly obtained by measuring the Q-V curves at multiple ligand concentrations. When a single reference ligand binding curve is available, this relationship allows us to reconstruct ligand binding curves at different voltages. More significantly, we establish that the shift of the Q-V curve between zero and saturating ligand concentration is a direct estimate of the interaction energy between the ligand- and voltage-dependent pathway. These free-energy relationships were tested by numerical simulations of a detailed gating model of the BK channel. Furthermore, as a proof of principle, we estimate the interaction energy between the ligand binding and voltage-dependent pathways for HCN2 channels whose ligand binding curves at various voltages are available. These emerging principles will be useful for high-throughput mutagenesis studies aimed at identifying interaction pathways between various regulatory domains in a polymodal ion channel. PMID:23250866

  3. Direct channel problems and phenomena

    International Nuclear Information System (INIS)

    Cutkosky, R.E.

    1975-01-01

    Direct channel problems and phenomena are considered covering the need for precision hadron spectroscopy, the data base for precision hadron spectroscopy, some relations between direct-channel and cross-channel effects, and spin rotation phenomena

  4. Many channel spectrum unfolding

    International Nuclear Information System (INIS)

    Najzer, M.; Glumac, B.; Pauko, M.

    1980-01-01

    The principle of the ITER unfolding code as used for the many channel spectrum unfolding is described. Its unfolding ability is tested on seven typical neutron spectra. The effect of the initial spectrum approximation upon the solution is discussed

  5. Channelized Streams in Iowa

    Data.gov (United States)

    Iowa State University GIS Support and Research Facility — This draft dataset consists of all ditches or channelized pieces of stream that could be identified using three input datasets; namely the1:24,000 National...

  6. Coding for optical channels

    CERN Document Server

    Djordjevic, Ivan; Vasic, Bane

    2010-01-01

    This unique book provides a coherent and comprehensive introduction to the fundamentals of optical communications, signal processing and coding for optical channels. It is the first to integrate the fundamentals of coding theory and optical communication.

  7. Sensing with Ion Channels

    CERN Document Server

    Martinac, Boris

    2008-01-01

    All living cells are able to detect and translate environmental stimuli into biologically meaningful signals. Sensations of touch, hearing, sight, taste, smell or pain are essential to the survival of all living organisms. The importance of sensory input for the existence of life thus justifies the effort made to understand its molecular origins. Sensing with Ion Channels focuses on ion channels as key molecules enabling biological systems to sense and process the physical and chemical stimuli that act upon cells in their living environment. Its aim is to serve as a reference to ion channel specialists and as a source of new information to non specialists who want to learn about the structural and functional diversity of ion channels and their role in sensory physiology.

  8. Calcium channel blocker poisoning

    Directory of Open Access Journals (Sweden)

    Miran Brvar

    2005-04-01

    Full Text Available Background: Calcium channel blockers act at L-type calcium channels in cardiac and vascular smooth muscles by preventing calcium influx into cells with resultant decrease in vascular tone and cardiac inotropy, chronotropy and dromotropy. Poisoning with calcium channel blockers results in reduced cardiac output, bradycardia, atrioventricular block, hypotension and shock. The findings of hypotension and bradycardia should suggest poisoning with calcium channel blockers.Conclusions: Treatment includes immediate gastric lavage and whole-bowel irrigation in case of ingestion of sustainedrelease products. All patients should receive an activated charcoal orally. Specific treatment includes calcium, glucagone and insulin, which proved especially useful in shocked patients. Supportive care including the use of catecholamines is not always effective. In the setting of failure of pharmacological therapy transvenous pacing, balloon pump and cardiopulmonary by-pass may be necessary.

  9. TRP channels: an overview

    DEFF Research Database (Denmark)

    Pedersen, Stine Falsig; Owsianik, Grzegorz; Nilius, Bernd

    2005-01-01

    The TRP ("transient receptor potential") family of ion channels now comprises more than 30 cation channels, most of which are permeable for Ca2+, and some also for Mg2+. On the basis of sequence homology, the TRP family can be divided in seven main subfamilies: the TRPC ('Canonical') family......, the TRPV ('Vanilloid') family, the TRPM ('Melastatin') family, the TRPP ('Polycystin') family, the TRPML ('Mucolipin') family, the TRPA ('Ankyrin') family, and the TRPN ('NOMPC') family. The cloning and characterization of members of this cation channel family has exploded during recent years, leading...... to a plethora of data on the roles of TRPs in a variety of tissues and species, including mammals, insects, and yeast. The present review summarizes the most pertinent recent evidence regarding the structural and functional properties of TRP channels, focusing on the regulation and physiology of mammalian TRPs....

  10. Authentication over Noisy Channels

    OpenAIRE

    Lai, Lifeng; Gamal, Hesham El; Poor, H. Vincent

    2008-01-01

    In this work, message authentication over noisy channels is studied. The model developed in this paper is the authentication theory counterpart of Wyner's wiretap channel model. Two types of opponent attacks, namely impersonation attacks and substitution attacks, are investigated for both single message and multiple message authentication scenarios. For each scenario, information theoretic lower and upper bounds on the opponent's success probability are derived. Remarkably, in both scenarios,...

  11. Channelling versus inversion

    DEFF Research Database (Denmark)

    Gale, A.S.; Surlyk, Finn; Anderskouv, Kresten

    2013-01-01

    Evidence from regional stratigraphical patterns in Santonian−Campanian chalk is used to infer the presence of a very broad channel system (5 km across) with a depth of at least 50 m, running NNW−SSE across the eastern Isle of Wight; only the western part of the channel wall and fill is exposed. W......−Campanian chalks in the eastern Isle of Wight, involving penecontemporaneous tectonic inversion of the underlying basement structure, are rejected....

  12. Stream Channel Stability.

    Science.gov (United States)

    1981-04-01

    Cycles of wetting and drying are also t ,v itiue swelling and shrinkage of the soil. S 11ied blocks or peds of soil fabric ,,ks. id downslope soil creep ...hydrographs of water and sediment at the point in question. By feeding the output from the hydrology-transport model into the finite element model...the banks as undercut banks fail. Channel irregularities such as seepage zones, cattle crossings, overbank drainage, buried channels, organic deposits

  13. Channeling and dynamic chaos

    Energy Technology Data Exchange (ETDEWEB)

    Bolotin, IU L; Gonchar, V IU; Truten, V I; Shulga, N F

    1986-01-01

    It is shown that axial channeling of relativistic electrons can give rise to the effect of dynamic chaos which involves essentially chaotic motion of a particle in the channel. The conditions leading to the effect of dynamic chaos and the manifestations of this effect in physical processes associated with the passage of particles through a crystal are examined using a silicon crystal as an example. 7 references.

  14. Course on Ionic Channels

    CERN Document Server

    1986-01-01

    This book is based on a series of lectures for a course on ionic channels held in Santiago, Chile, on November 17-20, 1984. It is intended as a tutorial guide on the properties, function, modulation, and reconstitution of ionic channels, and it should be accessible to graduate students taking their first steps in this field. In the presentation there has been a deliberate emphasis on the spe­ cific methodologies used toward the understanding of the workings and function of channels. Thus, in the first section, we learn to "read" single­ channel records: how to interpret them in the theoretical frame of kinetic models, which information can be extracted from gating currents in re­ lation to the closing and opening processes, and how ion transport through an open channel can be explained in terms of fluctuating energy barriers. The importance of assessing unequivocally the origin and purity of mem­ brane preparations and the use of membrane vesicles and optical tech­ niques in the stUGY of ionic channels a...

  15. Ion channelling in diamond

    International Nuclear Information System (INIS)

    Derry, T.E.

    1978-06-01

    Diamond is one of the most extreme cases from a channelling point of view, having the smallest thermal vibration amplitude and the lowest atomic number of commonly-encountered crystals. These are the two parameters most important for determining channelling behaviour. It is of consiberable interest therefore to see how well the theories explaining and predicting the channeling properties of other substance, succeed with diamond. Natural diamond, although the best available form for these experiments, is rather variable in its physical properties. Part of the project was devoted to considering and solving the problem of obtaining reproducible results representative of the ideal crystal. Channelling studies were performed on several good crystals, using the Rutherford backscattering method. Critical angles for proton channelling were measured for incident energies from 0.6 to 4.5 MeV, in the three most open axes and three most open planes of the diamond structure, and for α-particle channelling at 0.7 and 1.0 MeV (He + ) in the same axes and planes. For 1.0 MeV protons, the crystal temperature was varied from 20 degrees Celsius to 700 degrees Celsius. The results are presented as curves of backscattered yield versus angle in the region of each axis or plane, and summarised in the form of tables and graphs. Generally the critical angles, axial minimum yields, and temperature dependence are well predicted by the accepted theories. The most valuable overall conclusion is that the mean thermal vibration amplitude of the atoms in a crytical determines the critical approach distance to the channel walls at which an ion can remain channelled, even when this distance is much smaller than the Thomas-Fermi screening distance of the atomic potential, as is the case in diamond. A brief study was made of the radiation damage caused by α-particle bombardment, via its effect on the channelling phenomenon. It was possible to hold damage down to negligible levels during the

  16. Optical Communications Channel Combiner

    Science.gov (United States)

    Quirk, Kevin J.; Quirk, Kevin J.; Nguyen, Danh H.; Nguyen, Huy

    2012-01-01

    NASA has identified deep-space optical communications links as an integral part of a unified space communication network in order to provide data rates in excess of 100 Mb/s. The distances and limited power inherent in a deep-space optical downlink necessitate the use of photon-counting detectors and a power-efficient modulation such as pulse position modulation (PPM). For the output of each photodetector, whether from a separate telescope or a portion of the detection area, a communication receiver estimates a log-likelihood ratio for each PPM slot. To realize the full effective aperture of these receivers, their outputs must be combined prior to information decoding. A channel combiner was developed to synchronize the log-likelihood ratio (LLR) sequences of multiple receivers, and then combines these into a single LLR sequence for information decoding. The channel combiner synchronizes the LLR sequences of up to three receivers and then combines these into a single LLR sequence for output. The channel combiner has three channel inputs, each of which takes as input a sequence of four-bit LLRs for each PPM slot in a codeword via a XAUI 10 Gb/s quad optical fiber interface. The cross-correlation between the channels LLR time series are calculated and used to synchronize the sequences prior to combining. The output of the channel combiner is a sequence of four-bit LLRs for each PPM slot in a codeword via a XAUI 10 Gb/s quad optical fiber interface. The unit is controlled through a 1 Gb/s Ethernet UDP/IP interface. A deep-space optical communication link has not yet been demonstrated. This ground-station channel combiner was developed to demonstrate this capability and is unique in its ability to process such a signal.

  17. Channel Choice: A Literature Review

    DEFF Research Database (Denmark)

    Østergaard Madsen, Christian; Kræmmergaard, Pernille

    2015-01-01

    The channel choice branch of e-government studies citizens’ and businesses’ choice of channels for interacting with government, and how government organizations can integrate channels and migrate users towards the most cost-efficient channels. In spite of the valuable contributions offered...

  18. Channel Identification Machines

    Directory of Open Access Journals (Sweden)

    Aurel A. Lazar

    2012-01-01

    Full Text Available We present a formal methodology for identifying a channel in a system consisting of a communication channel in cascade with an asynchronous sampler. The channel is modeled as a multidimensional filter, while models of asynchronous samplers are taken from neuroscience and communications and include integrate-and-fire neurons, asynchronous sigma/delta modulators and general oscillators in cascade with zero-crossing detectors. We devise channel identification algorithms that recover a projection of the filter(s onto a space of input signals loss-free for both scalar and vector-valued test signals. The test signals are modeled as elements of a reproducing kernel Hilbert space (RKHS with a Dirichlet kernel. Under appropriate limiting conditions on the bandwidth and the order of the test signal space, the filter projection converges to the impulse response of the filter. We show that our results hold for a wide class of RKHSs, including the space of finite-energy bandlimited signals. We also extend our channel identification results to noisy circuits.

  19. Channel identification machines.

    Science.gov (United States)

    Lazar, Aurel A; Slutskiy, Yevgeniy B

    2012-01-01

    We present a formal methodology for identifying a channel in a system consisting of a communication channel in cascade with an asynchronous sampler. The channel is modeled as a multidimensional filter, while models of asynchronous samplers are taken from neuroscience and communications and include integrate-and-fire neurons, asynchronous sigma/delta modulators and general oscillators in cascade with zero-crossing detectors. We devise channel identification algorithms that recover a projection of the filter(s) onto a space of input signals loss-free for both scalar and vector-valued test signals. The test signals are modeled as elements of a reproducing kernel Hilbert space (RKHS) with a Dirichlet kernel. Under appropriate limiting conditions on the bandwidth and the order of the test signal space, the filter projection converges to the impulse response of the filter. We show that our results hold for a wide class of RKHSs, including the space of finite-energy bandlimited signals. We also extend our channel identification results to noisy circuits.

  20. Cryogenic microwave channelized receiver

    International Nuclear Information System (INIS)

    Rauscher, C.; Pond, J.M.; Tait, G.B.

    1996-01-01

    The channelized receiver being presented demonstrates the use of high temperature superconductor technology in a microwave system setting where superconductor, microwave-monolithic-integrated-circuit, and hybrid-integrated-circuit components are united in one package and cooled to liquid-nitrogen temperatures. The receiver consists of a superconducting X-band four-channel demultiplexer with 100-MHz-wide channels, four commercial monolithically integrated mixers, and four custom-designed hybrid-circuit detectors containing heterostructure ramp diodes. The composite receiver unit has been integrated into the payload of the second-phase NRL high temperature superconductor space experiment (HTSSE-II). Prior to payload assembly, the response characteristics of the receiver were measured as functions of frequency, temperature, and drive levels. The article describes the circuitry, discusses the key issues related to design and implementation, and summarizes the experimental results

  1. Chaos in quantum channels

    Energy Technology Data Exchange (ETDEWEB)

    Hosur, Pavan; Qi, Xiao-Liang [Department of Physics, Stanford University,476 Lomita Mall, Stanford, California 94305 (United States); Roberts, Daniel A. [Center for Theoretical Physics and Department of Physics, Massachusetts Institute of Technology,77 Massachusetts Ave, Cambridge, Massachusetts 02139 (United States); Yoshida, Beni [Perimeter Institute for Theoretical Physics,31 Caroline Street North, Waterloo, Ontario N2L 2Y5 (Canada); Walter Burke Institute for Theoretical Physics, California Institute of Technology,1200 E California Blvd, Pasadena CA 91125 (United States)

    2016-02-01

    We study chaos and scrambling in unitary channels by considering their entanglement properties as states. Using out-of-time-order correlation functions to diagnose chaos, we characterize the ability of a channel to process quantum information. We show that the generic decay of such correlators implies that any input subsystem must have near vanishing mutual information with almost all partitions of the output. Additionally, we propose the negativity of the tripartite information of the channel as a general diagnostic of scrambling. This measures the delocalization of information and is closely related to the decay of out-of-time-order correlators. We back up our results with numerics in two non-integrable models and analytic results in a perfect tensor network model of chaotic time evolution. These results show that the butterfly effect in quantum systems implies the information-theoretic definition of scrambling.

  2. Distribution Channels Conflict and Management

    OpenAIRE

    Kiran, Dr Vasanth; Majumdar, Dr Mousumi; Kishore, Dr Krishna

    2012-01-01

    Relationships in distribution channels tend to be long-term oriented and members of the channel rely on each other to jointly realize their goals by serving buyers. Despite the channels focus on serving buyers, conflicts often arise between channel members because of each members self-interest. When conflicts arise, the perceptions of a channel member based on normative, rational/instrumental, or emotional reasoning will influence relational norms like trust and commitment that characterize t...

  3. FTIR time-series of biomass burning products (HCN, C2H6, C2H2, CH3OH, and HCOOH at Reunion Island (21° S, 55° E and comparisons with model data

    Directory of Open Access Journals (Sweden)

    D. B. A. Jones

    2012-11-01

    Full Text Available Reunion Island (21° S, 55° E, situated in the Indian Ocean at about 800 km east of Madagascar, is appropriately located to monitor the outflow of biomass burning pollution from Southern Africa and Madagascar, in the case of short-lived compounds, and from other Southern Hemispheric landmasses such as South America, in the case of longer-lived species. Ground-based Fourier transform infrared (FTIR solar absorption observations are sensitive to a large number of biomass burning products. We present in this work the FTIR retrieval strategies, suitable for very humid sites such as Reunion Island, for hydrogen cyanide (HCN, ethane (C2H6, acetylene (C2H2, methanol (CH3OH, and formic acid (HCOOH. We provide their total columns time-series obtained from the measurements during August–October 2004, May–October 2007, and May 2009–December 2010. We show that biomass burning explains a large part of the observed seasonal and interannual variability of the chemical species. The correlations between the daily mean total columns of each of the species and those of CO, also measured with our FTIR spectrometer at Reunion Island, are very good from August to November (R ≥ 0.86. This allows us to derive, for that period, the following enhancement ratios with respect to CO: 0.0047, 0.0078, 0.0020, 0.012, and 0.0046 for HCN, C2H6, C2H2, CH3OH, and HCOOH, respectively. The HCN ground-based data are compared to the chemical transport model GEOS-Chem, while the data for the other species are compared to the IMAGESv2 model. We show that using the HCN/CO ratio derived from our measurements (0.0047 in GEOS-Chem reduces the underestimation of the modeled HCN columns compared with the FTIR measurements. The comparisons between IMAGESv2 and the long-lived species C2H6 and C2H2 indicate that the biomass burning emissions used in the model (from the GFED3 inventory are probably underestimated in the late September–October period for all years of measurements, and

  4. Fuel channel refilling

    International Nuclear Information System (INIS)

    Shoukri, M.; Abdul-Razzak, A.

    1992-11-01

    This report extends the work reported in document INFO-0370 on fuel channel refilling by providing analysis of the refilling tests conducted using the RD-14 and RD-14M test facilities. The analysis focuses on the general thermal-hydraulic characteristics of the facilities following various small and large inlet and outlet header breaks with emergency coolant injection. The two-fluid model thermal-hydraulic computer code CATHENA was tested against results obtained from selected experiments carried out in the two facilities. Conclusions related to the effect of break size, mode of emergency core injection, primary pump operation and parallel channels are presented. (Author) (116 figs., 17 tabs., 53 refs.)

  5. Ion channels in glioblastoma.

    Science.gov (United States)

    Molenaar, Remco J

    2011-01-01

    Glioblastoma is the most common primary brain tumor with the most dismal prognosis. It is characterized by extensive invasion, migration, and angiogenesis. Median survival is only 15 months due to this behavior, rendering focal surgical resection ineffective and adequate radiotherapy impossible. At this moment, several ion channels have been implicated in glioblastoma proliferation, migration, and invasion. This paper summarizes studies on potassium, sodium, chloride, and calcium channels of glioblastoma. It provides an up-to-date overview of the literature that could ultimately lead to new therapeutic targets.

  6. Fuel channel refilling

    International Nuclear Information System (INIS)

    Shoukri, M.; Abdul-Razzak, A.

    1990-04-01

    Analysis of existing data on fuel channel refilling is presented. The analysis focuses on the data obtained using the Stern Laboratories Cold Water Injection Test (CWIT) Facility. The two-fluid model thermal-hydraulics computer code CATHENA is also used to simulate experimental results on fuel channel refilling from both the CWIT and RD-14 facilities. Conclusions related to single and double break tests, including the effect of non-condensible gases, are presented. A set of recommendations is given for further analysis and separate effect experiments. (67 figs., 5 tabs., 24 refs.)

  7. Potassium channels in brain mitochondria.

    Science.gov (United States)

    Bednarczyk, Piotr

    2009-01-01

    Potassium channels are the most widely distributed class of ion channels. These channels are transmembrane proteins known to play important roles in both normal and pathophysiological functions in all cell types. Various potassium channels are recognised as potential therapeutic targets in the treatment of Parkinson's disease, Alzheimer's disease, brain/spinal cord ischaemia and sepsis. In addition to their importance as therapeutic targets, certain potassium channels are known for their beneficial roles in anaesthesia, cardioprotection and neuroprotection. Some types of potassium channels present in the plasma membrane of various cells have been found in the inner mitochondrial membrane as well. Potassium channels have been proposed to regulate mitochondrial membrane potential, respiration, matrix volume and Ca(+) ion homeostasis. It has been proposed that mitochondrial potassium channels mediate ischaemic preconditioning in various tissues. However, the specificity of a pharmacological agents and the mechanisms underlying their effects on ischaemic preconditioning remain controversial. The following potassium channels from various tissues have been identified in the inner mitochondrial membrane: ATP-regulated (mitoK(ATP)) channel, large conductance Ca(2+)-regulated (mitoBK(Ca)) channel, intermediate conductance Ca(2+)-regulated (mitoIK(Ca)) channel, voltage-gated (mitoKv1.3 type) channel, and twin-pore domain (mitoTASK-3) channel. It has been shown that increased potassium flux into brain mitochondria induced by either the mitoK(ATP) channel or mitoBK(Ca) channel affects the beneficial effects on neuronal cell survival under pathological conditions. Recently, differential distribution of mitoBK(Ca) channels has been observed in neuronal mitochondria. These findings may suggest a neuroprotective role for the mitoBK(Ca) channel in specific brain structures. This minireview summarises current data on brain mitochondrial potassium channels and the efforts to identify

  8. MITOCHONDRIAL BKCa CHANNEL

    Directory of Open Access Journals (Sweden)

    Enrique eBalderas

    2015-03-01

    Full Text Available Since its discovery in a glioma cell line 15 years ago, mitochondrial BKCa channel (mitoBKCa has been studied in brain cells and cardiomyocytes sharing general biophysical properties such as high K+ conductance (~300 pS, voltage-dependency and Ca2+-sensitivity. Main advances in deciphering the molecular composition of mitoBKCa have included establishing that it is encoded by the Kcnma1 gene, that a C-terminal splice insert confers mitoBKCa ability to be targeted to cardiac mitochondria, and evidence for its potential coassembly with β subunits. Notoriously, β1 subunit directly interacts with cytochrome c oxidase and mitoBKCa can be modulated by substrates of the respiratory chain. mitoBKCa channel has a central role in protecting the heart from ischemia, where pharmacological activation of the channel impacts the generation of reactive oxygen species and mitochondrial Ca2+ preventing cell death likely by impeding uncontrolled opening of the mitochondrial transition pore. Supporting this view, inhibition of mitoBKCa with Iberiotoxin, enhances cytochrome c release from glioma mitochondria. Many tantalizing questions remain. Some of them are: how is mitoBKCa coupled to the respiratory chain? Does mitoBKCa play non-conduction roles in mitochondria physiology? Which are the functional partners of mitoBKCa? What are the roles of mitoBKCa in other cell types? Answers to these questions are essential to define the impact of mitoBKCa channel in mitochondria biology and disease.

  9. Chemistry in Microfluidic Channels

    Science.gov (United States)

    Chia, Matthew C.; Sweeney, Christina M.; Odom, Teri W.

    2011-01-01

    General chemistry introduces principles such as acid-base chemistry, mixing, and precipitation that are usually demonstrated in bulk solutions. In this laboratory experiment, we describe how chemical reactions can be performed in a microfluidic channel to show advanced concepts such as laminar fluid flow and controlled precipitation. Three sets of…

  10. Workshop on Gas Channels

    Science.gov (United States)

    2013-02-07

    Effect of pressure on gas permeability. In Fish … Different channels or splice variants at different depth.  HRE (hypoxia-response elements): which...proteins unexpectedly have HREs . HIF-1.  Shear stress:  expression of NOS  Are different splice variants used under different conditions?  Size

  11. Quantum communication under channel uncertainty

    International Nuclear Information System (INIS)

    Noetzel, Janis Christian Gregor

    2012-01-01

    This work contains results concerning transmission of entanglement and subspaces as well as generation of entanglement in the limit of arbitrary many uses of compound- and arbitrarily varying quantum channels (CQC, AVQC). In both cases, the channel is described by a set of memoryless channels. Only forward communication between one sender and one receiver is allowed. A code is said to be ''good'' only, if it is ''good'' for every channel out of the set. Both settings describe a scenario, in which sender and receiver have only limited channel knowledge. For different amounts of information about the channel available to sender or receiver, coding theorems are proven for the CQC. For the AVQC, both deterministic and randomised coding schemes are considered. Coding theorems are proven, as well as a quantum analogue of the Ahlswede-dichotomy. The connection to zero-error capacities of stationary memoryless quantum channels is investigated. The notion of symmetrisability is defined and used for both classes of channels.

  12. VAX CAMAC channel

    International Nuclear Information System (INIS)

    Nelson, D.J.; Breidenbach, M.; Granieri, C.D.; Grund, J.E.; Patrick, J.F.; Weaver, L.J.

    1980-10-01

    A new generation CAMAC System has been developed for the Mark II Detector at SLAC's PEP storage ring. This flexible system can efficiently transfer data between a host computer and a very large set of CAMAC data acquisition and control modules. A bipolar microprocessor operates as a Channel interface by supervising the CAMAC system and minimizing the host computer's work. This programmable channel couples the host to a set of System Crates; each System Crate houses Branch Drivers that can directly control a set of crates or communicate over differential parallel highways to Branch Receivers for control of distant crates. A coherent software package integrates the high level programs, system driver level programs, and microcode control of the system

  13. Geysering in boiling channels

    Energy Technology Data Exchange (ETDEWEB)

    Aritomi, Masanori; Takemoto, Takatoshi [Tokyo Institute of Technology, Tokyo (Japan); Chiang, Jing-Hsien [Japan NUS Corp. Ltd., Toyko (Japan)] [and others

    1995-09-01

    A concept of natural circulation BWRs such as the SBWR has been proposed and seems to be promising in that the primary cooling system can be simplified. The authors have been investigating thermo-hydraulic instabilities which may appear during the start-up in natural circulation BWRs. In our previous works, geysering was investigated in parallel boiling channels for both natural and forced circulations, and its driving mechanism and the effect of system pressure on geysering occurrence were made clear. In this paper, geysering is investigated in a vertical column and a U-shaped vertical column heated in the lower parts. It is clarified from the results that the occurrence mechanism of geysering and the dependence of system pressure on geysering occurrence coincide between parallel boiling channels in circulation systems and vertical columns in non-circulation systems.

  14. Coolant channel module CCM

    International Nuclear Information System (INIS)

    Hoeld, Alois

    2007-01-01

    A complete and detailed description of the theoretical background of an '(1D) thermal-hydraulic drift-flux based mixture-fluid' coolant channel model and its resulting module CCM will be presented. The objective of this module is to simulate as universally as possible the steady state and transient behaviour of the key characteristic parameters of a single- or two-phase fluid flowing within any type of heated or non-heated coolant channel. Due to the possibility that different flow regimes can appear along any channel, such a 'basic (BC)' 1D channel is assumed to be subdivided into a number of corresponding sub-channels (SC-s). Each SC can belong to only two types of flow regime, an SC with just a single-phase fluid, containing exclusively either sub-cooled water or superheated steam, or an SC with a two-phase mixture flow. After an appropriate nodalisation of such a BC (and therefore also its SC-s) a 'modified finite volume method' has been applied for the spatial discretisation of the partial differential equations (PDE-s) which represent the basic conservation equations of thermal-hydraulics. Special attention had to be given to the possibility of variable SC entrance or outlet positions (which describe boiling boundaries or mixture levels) and thus the fact that an SC can even disappear or be created anew. The procedure yields for each SC type (and thus the entire BC), a set of non-linear ordinary 1st order differential equations (ODE-s). To link the resulting mean nodal with the nodal boundary function values, both of which are present in the discretised differential equations, a special quadratic polygon approximation procedure (PAX) had to be constructed. Together with the very thoroughly tested packages for drift-flux, heat transfer and single- and two-phase friction factors this procedure represents the central part of the here presented 'Separate-Region' approach, a theoretical model which provides the basis to the very effective working code package CCM

  15. Tourism distribution channels

    OpenAIRE

    Camilleri, Mark Anthony

    2017-01-01

    The distribution channels link the customers with the businesses. For many years, the tourism businesses may have distributed their products and services through intermediaries. However, the latest advances in technology have brought significant changes in this regard. More individuals and corporate customers are increasingly benefiting of ubiquitous technologies, including digital media. The development of mobile devices and their applications, are offering a wide range of possibilities to t...

  16. Athermal channeled spectropolarimeter

    Science.gov (United States)

    Jones, Julia Craven

    2015-12-08

    A temperature insensitive (athermal) channeled spectropolarimeter (CSP) is described. The athermal CSP includes a crystal retarder formed of a biaxial crystal. The crystal retarder has three crystal axes, wherein each axis has its own distinct index of refraction. The axes are oriented in a particular manner, causing an amplitude modulating carrier frequency induced by the crystal retarder to be thermally invariant. Accordingly, a calibration beam technique can be used over a relatively wide range of ambient temperatures, with a common calibration data set.

  17. Nuclear reactor coolant channels

    International Nuclear Information System (INIS)

    Macbeth, R.V.

    1978-01-01

    A nuclear reactor coolant channel is described that is suitable for sub-cooled reactors as in pressurised water reactors as well as for bulk boiling, as in boiling water reactors and steam generating nuclear reactors. The arrangement aims to improve heat transfer between the fuel elements and the coolant. Full constructional details are given. See also other similar patents by the author. (U.K.)

  18. The M2 Channel

    DEFF Research Database (Denmark)

    Santner, Paul

    Drug resistance of Influenza A against antivirals is an increasing problem. No effective Influenza A drugs targeting the crucial viral protein, the proton transporter M2 are available anymore due to widespread resistance. Thanks to research efforts elucidating M2 protein structure, function and i...... resistance escape routes from drug inhibition. We thereby were hopefully able to provide a platform for the large-scale evaluation of M2 channel activity, inhibitors and resistance....

  19. Aquaglyceroporins: generalized metalloid channels

    Science.gov (United States)

    Mukhopadhyay, Rita; Bhattacharjee, Hiranmoy; Rosen, Barry P.

    2014-01-01

    Background: Aquaporins (AQPs), members of a superfamily of transmembrane channel proteins, are ubiquitous in all domains of life. They fall into a number of branches that can be functionally categorized into two major sub-groups: i) orthodox aquaporins, which are water-specific channels, and ii) aquaglyceroporins, which allow the transport of water, non-polar solutes, such as urea or glycerol, the reactive oxygen species hydrogen peroxide, and gases such as ammonia, carbon dioxide and nitric oxide and, as described in this review, metalloids. Scope of Review: This review summarizes the key findings that AQP channels conduct bidirectional movement of metalloids into and out of cells. Major Conclusions: As(OH)3 and Sb(OH)3 behave as inorganic molecular mimics of glycerol, a property that allows their passage through AQP channels. Plant AQPs also allow the passage of boron and silicon as their hydroxyacids, boric acid (B(OH)3) and orthosilicic acid (Si(OH)4), respectively. Genetic analysis suggests that germanic acid (GeO2) is also a substrate. While As(III), Sb(III) and Ge(IV) are toxic metalloids, borate (B(III)) and silicate (Si(IV)) are essential elements in higher plants. General Significance: The uptake of environmental metalloids by aquaporins provides an understanding of (i) how toxic elements such as arsenic enter the food chain; (ii) the delivery of arsenic and antimony containing drugs in the treatment of certain forms of leukemia and chemotherapy of diseases caused by pathogenic protozoa; and (iii) the possibility that food plants such as rice could be made safer by genetically modifying them to exclude arsenic while still accumulating boron and silicon. PMID:24291688

  20. Congestive Heart Failure Leads to Prolongation of the PR Interval and Atrioventricular Junction Enlargement and Ion Channel Remodelling in the Rabbit

    Science.gov (United States)

    Nikolaidou, Theodora; Cai, Xue J.; Stephenson, Robert S.; Yanni, Joseph; Lowe, Tristan; Atkinson, Andrew J.; Jones, Caroline B.; Sardar, Rida; Corno, Antonio F.; Dobrzynski, Halina; Withers, Philip J.; Jarvis, Jonathan C.; Hart, George; Boyett, Mark R.

    2015-01-01

    Heart failure is a major killer worldwide. Atrioventricular conduction block is common in heart failure; it is associated with worse outcomes and can lead to syncope and bradycardic death. We examine the effect of heart failure on anatomical and ion channel remodelling in the rabbit atrioventricular junction (AVJ). Heart failure was induced in New Zealand rabbits by disruption of the aortic valve and banding of the abdominal aorta resulting in volume and pressure overload. Laser micro-dissection and real-time polymerase chain reaction (RT-PCR) were employed to investigate the effects of heart failure on ion channel remodelling in four regions of the rabbit AVJ and in septal tissues. Investigation of the AVJ anatomy was performed using micro-computed tomography (micro-CT). Heart failure animals developed first degree heart block. Heart failure caused ventricular myocardial volume increase with a 35% elongation of the AVJ. There was downregulation of HCN1 and Cx43 mRNA transcripts across all regions and downregulation of Cav1.3 in the transitional tissue. Cx40 mRNA was significantly downregulated in the atrial septum and AVJ tissues but not in the ventricular septum. mRNA abundance for ANP, CLCN2 and Navβ1 was increased with heart failure; Nav1.1 was increased in the inferior nodal extension/compact node area. Heart failure in the rabbit leads to prolongation of the PR interval and this is accompanied by downregulation of HCN1, Cav1.3, Cx40 and Cx43 mRNAs and anatomical enlargement of the entire heart and AVJ. PMID:26509807

  1. Congestive Heart Failure Leads to Prolongation of the PR Interval and Atrioventricular Junction Enlargement and Ion Channel Remodelling in the Rabbit.

    Directory of Open Access Journals (Sweden)

    Theodora Nikolaidou

    Full Text Available Heart failure is a major killer worldwide. Atrioventricular conduction block is common in heart failure; it is associated with worse outcomes and can lead to syncope and bradycardic death. We examine the effect of heart failure on anatomical and ion channel remodelling in the rabbit atrioventricular junction (AVJ. Heart failure was induced in New Zealand rabbits by disruption of the aortic valve and banding of the abdominal aorta resulting in volume and pressure overload. Laser micro-dissection and real-time polymerase chain reaction (RT-PCR were employed to investigate the effects of heart failure on ion channel remodelling in four regions of the rabbit AVJ and in septal tissues. Investigation of the AVJ anatomy was performed using micro-computed tomography (micro-CT. Heart failure animals developed first degree heart block. Heart failure caused ventricular myocardial volume increase with a 35% elongation of the AVJ. There was downregulation of HCN1 and Cx43 mRNA transcripts across all regions and downregulation of Cav1.3 in the transitional tissue. Cx40 mRNA was significantly downregulated in the atrial septum and AVJ tissues but not in the ventricular septum. mRNA abundance for ANP, CLCN2 and Navβ1 was increased with heart failure; Nav1.1 was increased in the inferior nodal extension/compact node area. Heart failure in the rabbit leads to prolongation of the PR interval and this is accompanied by downregulation of HCN1, Cav1.3, Cx40 and Cx43 mRNAs and anatomical enlargement of the entire heart and AVJ.

  2. Matching Dyadic Distributions to Channels

    OpenAIRE

    Böcherer, Georg; Mathar, Rudolf

    2010-01-01

    Many communication channels with discrete input have non-uniform capacity achieving probability mass functions (PMF). By parsing a stream of independent and equiprobable bits according to a full prefix-free code, a modu-lator can generate dyadic PMFs at the channel input. In this work, we show that for discrete memoryless channels and for memoryless discrete noiseless channels, searching for good dyadic input PMFs is equivalent to minimizing the Kullback-Leibler distance between a dyadic PMF ...

  3. Radar channel balancing with commutation

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin Walter

    2014-02-01

    When multiple channels are employed in a pulse-Doppler radar, achieving and maintaining balance between the channels is problematic. In some circumstances the channels may be commutated to achieve adequate balance. Commutation is the switching, trading, toggling, or multiplexing of the channels between signal paths. Commutation allows modulating the imbalance energy away from the balanced energy in Doppler, where it can be mitigated with filtering.

  4. Microstructural information from channeling measurements

    International Nuclear Information System (INIS)

    Quere, Y.

    1984-09-01

    Channeling is sensitive to nearly all structural changes in solids. One briefly recalls how particles are dechanneled by lattice defects and describes the main applications of channeling to materials science: detection of radiation damage, location of impurity atoms, precipitations in alloys... Channeling being a phenomenon characteristic of perfect crystals, any type of lattice imperfection (phonons, crystal defects, precipitation etc.) is expected to produce dechanneling. Consequently channeling and its opposite, dechanneling, have both been used to study structure and structural changes of materials

  5. Ion channeling revisited

    Energy Technology Data Exchange (ETDEWEB)

    Doyle, Barney Lee [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Corona, Aldo [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Nguyen, Anh [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-09-01

    A MS Excel program has been written that calculates accidental, or unintentional, ion channeling in cubic bcc, fcc and diamond lattice crystals or polycrystalline materials. This becomes an important issue when simulating the creation by energetic neutrons of point displacement damage and extended defects using beams of ions. All of the tables and graphs in the three Ion Beam Analysis Handbooks that previously had to be manually looked up and read from were programed into Excel in handy lookup tables, or parameterized, for the case of the graphs, using rather simple exponential functions with different powers of the argument. The program then offers an extremely convenient way to calculate axial and planar half-angles and minimum yield or dechanneling probabilities, effects on half-angles of amorphous overlayers, accidental channeling probabilities for randomly oriented crystals or crystallites, and finally a way to automatically generate stereographic projections of axial and planar channeling half-angles. The program can generate these projections and calculate these probabilities for axes and [hkl] planes up to (555).

  6. The alpha channeling effect

    Science.gov (United States)

    Fisch, N. J.

    2015-12-01

    Alpha particles born through fusion reactions in a tokamak reactor tend to slow down on electrons, but that could take up to hundreds of milliseconds. Before that happens, the energy in these alpha particles can destabilize on collisionless timescales toroidal Alfven modes and other waves, in a way deleterious to energy confinement. However, it has been speculated that this energy might be instead be channeled into useful energy, so as to heat fuel ions or to drive current. Such a channeling needs to be catalyzed by waves Waves can produce diffusion in energy of the alpha particles in a way that is strictly coupled to diffusion in space. If these diffusion paths in energy-position space point from high energy in the center to low energy on the periphery, then alpha particles will be cooled while forced to the periphery. The energy from the alpha particles is absorbed by the wave. The amplified wave can then heat ions or drive current. This process or paradigm for extracting alpha particle energy collisionlessly has been called alpha channeling. While the effect is speculative, the upside potential for economical fusion is immense. The paradigm also operates more generally in other contexts of magnetically confined plasma.

  7. TRP channels in kidney disease.

    NARCIS (Netherlands)

    Hsu, Y.J.; Hoenderop, J.G.J.; Bindels, R.J.M.

    2007-01-01

    Mammalian TRP channel proteins form six-transmembrane cation-permeable channels that may be grouped into six subfamilies on the basis of amino acid sequence homology (TRPC, TRPV, TRPM, TRPA, TRPP, and TRPML). Recent studies of TRP channels indicate that they are involved in numerous fundamental cell

  8. Parallel inter channel interaction mechanisms

    International Nuclear Information System (INIS)

    Jovic, V.; Afgan, N.; Jovic, L.

    1995-01-01

    Parallel channels interactions are examined. For experimental researches of nonstationary regimes flow in three parallel vertical channels results of phenomenon analysis and mechanisms of parallel channel interaction for adiabatic condition of one-phase fluid and two-phase mixture flow are shown. (author)

  9. Voltage-Gated Calcium Channels

    Science.gov (United States)

    Zamponi, Gerald Werner

    Voltage Gated Calcium Channels is the first comprehensive book in the calcium channel field, encompassing over thirty years of progress towards our understanding of calcium channel structure, function, regulation, physiology, pharmacology, and genetics. This book balances contributions from many of the leading authorities in the calcium channel field with fresh perspectives from risings stars in the area, taking into account the most recent literature and concepts. This is the only all-encompassing calcium channel book currently available, and is an essential resource for academic researchers at all levels in the areas neuroscience, biophysics, and cardiovascular sciences, as well as to researchers in the drug discovery area.

  10. Beyond the Manual Channel

    DEFF Research Database (Denmark)

    , the main focus there is on spoken languages in their written and spoken forms. This series of workshops, however, offers a forum for researchers focussing on sign languages. For the fourth time, the workshop had sign language corpora as its main topic. This time, the focus was on any aspect beyond...... the manual channel. Not surprisingly, most papers deal with non-manuals on the face. Once again, the papers at this workshop clearly identify the potentials of even closer cooperation between sign linguists and sign language engineers, and we think it is events like this that contribute a lot to a better...

  11. Ion Channels in Leukocytes

    Science.gov (United States)

    1991-07-01

    muscle k142), heart muscle (80), bo- are released. In recent years much has been learned vine pulmonar arter endothelial cells (251), and rat about the...b3 Zn or cytes from cystic fibrosis patients lack a Cl current that Ni (1 mM)-added to the cytoplasmic side of the mem- can be acti% ated b3 the...that at37’C hu- to be defectiv.- in cystic fibrosis (55, 277), and Chen et al. man T-cell CiL channels are active at rest, implies that (25) have shown

  12. A Micromechanical RF Channelizer

    Science.gov (United States)

    Akgul, Mehmet

    The power consumption of a radio generally goes as the number and strength of the RF signals it must process. In particular, a radio receiver would consume much less power if the signal presented to its electronics contained only the desired signal in a tiny percent bandwidth frequency channel, rather than the typical mix of signals containing unwanted energy outside the desired channel. Unfortunately, a lack of filters capable of selecting single channel bandwidths at RF forces the front-ends of contemporary receivers to accept unwanted signals, and thus, to operate with sub-optimal efficiency. This dissertation focuses on the degree to which capacitive-gap transduced micromechanical resonators can achieve the aforementioned RF channel-selecting filters. It aims to first show theoretically that with appropriate scaling capacitive-gap transducers are strong enough to meet the needed coupling requirements; and second, to fully detail an architecture and design procedure needed to realize said filters. Finally, this dissertation provides an actual experimentally demonstrated RF channel-select filter designed using the developed procedures and confirming theoretical predictions. Specifically, this dissertation introduces four methods that make possible the design and fabrication of RF channel-select filters. The first of these introduces a small-signal equivalent circuit for parallel-plate capacitive-gap transduced micromechanical resonators that employs negative capacitance to model the dependence of resonance frequency on electrical stiffness in a way that facilitates the analysis of micromechanical circuits loaded with arbitrary electrical impedances. The new circuit model not only correctly predicts the dependence of electrical stiffness on the impedances loading the input and output electrodes of parallel-plate capacitive-gap transduced micromechanical device, but does so in a visually intuitive way that identifies current drive as most appropriate for

  13. TRPV6 channels.

    Science.gov (United States)

    Fecher-Trost, Claudia; Weissgerber, Petra; Wissenbach, Ulrich

    2014-01-01

    TRPV6 (former synonyms ECAC2, CaT1, CaT-like) displays several specific features which makes it unique among the members of the mammalian Trp gene family (1) TRPV6 (and its closest relative, TRPV5) are the only highly Ca(2+)-selective channels of the entire TRP superfamily (Peng et al. 1999; Wissenbach et al. 2001; Voets et al. 2004). (2) Translation of Trpv6 initiates at a non-AUG codon, at ACG, located upstream of the annotated AUG, which is not used for initiation (Fecher-Trost et al. 2013). The ACG codon is nevertheless decoded by methionine. Not only a very rare event in eukaryotic biology, the full-length TRPV6 protein existing in vivo comprises an amino terminus extended by 40 amino acid residues compared to the annotated truncated TRPV6 protein which has been used in most studies on TRPV6 channel activity so far. (In the following numbering occurs according to this full-length protein, with the numbers of the so far annotated truncated protein in brackets). (3) Only in humans a coupled polymorphism of Trpv6 exists causing three amino acid exchanges and resulting in an ancestral Trpv6 haplotype and a so-called derived Trpv6 haplotype (Wissenbach et al. 2001). The ancestral allele encodes the amino acid residues C197(157), M418(378) and M721(681) and the derived alleles R197(157), V418(378) and T721(681). The ancestral haplotype is found in all species, the derived Trpv6 haplotype has only been identified in humans, and its frequency increases with the distance to the African continent. Apparently the Trpv6 gene has been a strong target for selection in humans, and its derived variant is one of the few examples showing consistently differences to the orthologues genes of other primates (Akey et al. 2004, 2006; Stajich and Hahn 2005; Hughes et al. 2008). (4) The Trpv6 gene expression is significantly upregulated in several human malignancies including the most common cancers, prostate and breast cancer (Wissenbach et al. 2001; Zhuang et al. 2002; Fixemer et al

  14. Chemical Selectivity and Sensitivity of a 16-Channel Electronic Nose for Trace Vapour Detection

    Directory of Open Access Journals (Sweden)

    Drago Strle

    2017-12-01

    Full Text Available Good chemical selectivity of sensors for detecting vapour traces of targeted molecules is vital to reliable detection systems for explosives and other harmful materials. We present the design, construction and measurements of the electronic response of a 16 channel electronic nose based on 16 differential microcapacitors, which were surface-functionalized by different silanes. The e-nose detects less than 1 molecule of TNT out of 10+12 N2 molecules in a carrier gas in 1 s. Differently silanized sensors give different responses to different molecules. Electronic responses are presented for TNT, RDX, DNT, H2S, HCN, FeS, NH3, propane, methanol, acetone, ethanol, methane, toluene and water. We consider the number density of these molecules and find that silane surfaces show extreme affinity for attracting molecules of TNT, DNT and RDX. The probability to bind these molecules and form a surface-adsorbate is typically 10+7 times larger than the probability to bind water molecules, for example. We present a matrix of responses of differently functionalized microcapacitors and we propose that chemical selectivity of multichannel e-nose could be enhanced by using artificial intelligence deep learning methods.

  15. Mimicking multi-channel scattering with single-channel approaches

    OpenAIRE

    Grishkevich, Sergey; Schneider, Philipp-Immanuel; Vanne, Yulian V.; Saenz, Alejandro

    2009-01-01

    The collision of two atoms is an intrinsic multi-channel (MC) problem as becomes especially obvious in the presence of Feshbach resonances. Due to its complexity, however, single-channel (SC) approximations, which reproduce the long-range behavior of the open channel, are often applied in calculations. In this work the complete MC problem is solved numerically for the magnetic Feshbach resonances (MFRs) in collisions between generic ultracold 6Li and 87Rb atoms in the ground state and in the ...

  16. Multiplicative properties of quantum channels

    Science.gov (United States)

    Rahaman, Mizanur

    2017-08-01

    In this paper, we study the multiplicative behaviour of quantum channels, mathematically described by trace preserving, completely positive maps on matrix algebras. It turns out that the multiplicative domain of a unital quantum channel has a close connection to its spectral properties. A structure theorem (theorem 2.5), which reveals the automorphic property of an arbitrary unital quantum channel on a subalgebra, is presented. Various classes of quantum channels (irreducible, primitive, etc) are then analysed in terms of this stabilising subalgebra. The notion of the multiplicative index of a unital quantum channel is introduced, which measures the number of times a unital channel needs to be composed with itself for the multiplicative algebra to stabilise. We show that the maps that have trivial multiplicative domains are dense in completely bounded norm topology in the set of all unital completely positive maps. Some applications in quantum information theory are discussed.

  17. Upgrading a marketing channels role

    Directory of Open Access Journals (Sweden)

    Tišma-Borota Ankica

    2002-01-01

    Full Text Available As one of the marketing mix instruments, marketing channels were usually behind other instruments (product, price and promotion. Many companies regarded marketing channels as something that was 'left' after more important strategies of price, product and promotion were created. In recent past, things have changed and marketing channels became more interesting for research. This change came as a result of change in global market functioning especially in competitive advantage, distributors' strength and increasing technology.

  18. Single-channel kinetics of BK (Slo1 channels

    Directory of Open Access Journals (Sweden)

    Yanyan eGeng

    2015-01-01

    Full Text Available Single-channel kinetics has proven a powerful tool to reveal information about the gating mechanisms that control the opening and closing of ion channels. This introductory review focuses on the gating of large conductance Ca2+- and voltage-activated K+ (BK or Slo1 channels at the single-channel level. It starts with single-channel current records and progresses to presentation and analysis of single-channel data and the development of gating mechanisms in terms of discrete state Markov (DSM models. The DSM models are formulated in terms of the tetrameric modular structure of BK channels, consisting of a central transmembrane pore-gate domain (PGD attached to four surrounding transmembrane voltage sensing domains (VSD and a large intracellular cytosolic domain (CTD, also referred to as the gating ring. The modular structure and data analysis shows that the Ca2+ and voltage dependent gating considered separately can each be approximated by 10-state two-tiered models with 5 closed states on the upper tier and 5 open states on the lower tier. The modular structure and joint Ca2+ and voltage dependent gating are consistent with a 50 state two-tiered model with 25 closed states on the upper tier and 25 open states on the lower tier. Adding an additional tier of brief closed (flicker states to the 10-state or 50-state models improved the description of the gating. For fixed experimental conditions a channel would gate in only a subset of the potential number of states. The detected number of states and the correlations between adjacent interval durations are consistent with the tiered models. The examined models can account for the single-channel kinetics and the bursting behavior of gating. Ca2+ and voltage activate BK channels by predominantly increasing the effective opening rate of the channel with a smaller decrease in the effective closing rate. Ca2+ and depolarization thus activate by mainly destabilizing the closed states.

  19. Hydroxychloroquine reduces heart rate by modulating the hyperpolarization-activated current If: Novel electrophysiological insights and therapeutic potential

    Science.gov (United States)

    Capel, Rebecca A.; Herring, Neil; Kalla, Manish; Yavari, Arash; Mirams, Gary R.; Douglas, Gillian; Bub, Gil; Channon, Keith; Paterson, David J.; Terrar, Derek A.; Burton, Rebecca-Ann B.

    2015-01-01

    Background Bradycardic agents are of interest for the treatment of ischemic heart disease and heart failure, as heart rate is an important determinant of myocardial oxygen consumption. Objectives The purpose of this study was to investigate the propensity of hydroxychloroquine (HCQ) to cause bradycardia. Methods We assessed the effects of HCQ on (1) cardiac beating rate in vitro (mice); (2) the “funny” current (If) in isolated guinea pig sinoatrial node (SAN) myocytes (1, 3, 10 µM); (3) heart rate and blood pressure in vivo by acute bolus injection (rat, dose range 1–30 mg/kg), (4) blood pressure and ventricular function during feeding (mouse, 100 mg/kg/d for 2 wk, tail cuff plethysmography, anesthetized echocardiography). Results In mouse atria, spontaneous beating rate was significantly (P < .05) reduced (by 9% ± 3% and 15% ± 2% at 3 and 10 µM HCQ, n = 7). In guinea pig isolated SAN cells, HCQ conferred a significant reduction in spontaneous action potential firing rate (17% ± 6%, 1 μM dose) and a dose-dependent reduction in If (13% ± 3% at 1 µM; 19% ± 2% at 3 µM). Effects were also observed on L-type calcium ion current (ICaL) (12% ± 4% reduction) and rapid delayed rectifier potassium current (IKr) (35% ± 4%) at 3 µM. Intravenous HCQ decreased heart rate in anesthetized rats (14.3% ± 1.1% at 15mg/kg; n = 6) without significantly reducing mean arterial blood pressure. In vivo feeding studies in mice showed no significant change in systolic blood pressure nor left ventricular function. Conclusions We have shown that HCQ acts as a bradycardic agent in SAN cells, in atrial preparations, and in vivo. HCQ slows the rate of spontaneous action potential firing in the SAN through multichannel inhibition, including that of If. PMID:26025323

  20. UMTS Common Channel Sensitivity Analysis

    DEFF Research Database (Denmark)

    Pratas, Nuno; Rodrigues, António; Santos, Frederico

    2006-01-01

    and as such it is necessary that both channels be available across the cell radius. This requirement makes the choice of the transmission parameters a fundamental one. This paper presents a sensitivity analysis regarding the transmission parameters of two UMTS common channels: RACH and FACH. Optimization of these channels...... is performed and values for the key transmission parameters in both common channels are obtained. On RACH these parameters are the message to preamble offset, the initial SIR target and the preamble power step while on FACH it is the transmission power offset....

  1. Demystifying Mechanosensitive Piezo Ion Channels.

    Science.gov (United States)

    Xu, X Z Shawn

    2016-06-01

    Mechanosensitive channels mediate touch, hearing, proprioception, and blood pressure regulation. Piezo proteins, including Piezo1 and Piezo2, represent a new class of mechanosensitive channels that have been reported to play key roles in most, if not all, of these modalities. The structural architecture and molecular mechanisms by which Piezos act as mechanosensitive channels, however, remain mysterious. Two new studies have now provided critical insights into the atomic structure and molecular basis of the ion permeation and mechano-gating properties of the Piezo1 channel.

  2. Defect Distributions in Channeling Experiments

    DEFF Research Database (Denmark)

    Andersen, Hans Henrik; Sigmund, P.

    1965-01-01

    A simple collision model allows to calculate energy losses of perfectly channeled particles. The maximum energy loss is related in a simple way to the displacement energy of lattice atoms perpendicular to the channel. From that, one obtains rather definite predictions on the possibility...... of radiation damage by channeled particles. As an application, one gets a necessary criterion for the occurence of super tails in channeling experiments. The theory involves some assumptions on the behaviour of Born-Mayer potentials which are verified by comparison to experimental displacement energies....

  3. Preservation of meandering river channels in uniformly aggrading channel belts

    NARCIS (Netherlands)

    Lageweg, W.I. van de; Schuurman, F.; Cohen, K.M.; Dijk, W.M. van; Shimizu, Y.; Kleinhans, M.G.

    2016-01-01

    Channel belt deposits from meandering river systems commonly display an internal architecture of stacked depositional features with scoured basal contacts due to channel and bedform migration across a range of scales. Recognition and correct interpretation of these bounding surfaces is essential to

  4. MONETARY TRANSMISSION CHANNELS IN ROMANIA – THE CREDIT CHANNEL

    Directory of Open Access Journals (Sweden)

    Magdalena RĂDULESCU

    2009-12-01

    Full Text Available The theoretical – intuitive analysis applied to the segment of monetary transmission evidences the fact that forming the traditional monetary impulses transmission channels are in a starting phase due to the long financial non – intermediary process which Romanian economy had known. In these conditions, the exchange rate channel, and also NBR currency purchases was, for a long time, an important way through which monetary authorities actions influenced macro economical behaviors. But starting with 2000, it is observed a credit channel reactivation and, especially, interest rate channel. Anyhow, the credit channel continues to be undermined by the existence of liquidity surplus within the system, by the phenomena of substitution of national currency credit with currency credits, and also moral hazardous displays. Albeit some of these phenomena also affect the interest rate channel, its role in sending monetary policy impulses is in a continuous progress. Apparently, it acts by way of nominal interest rates, their real level seeming less relevant. Once with remaking the two traditional channels, the companies and households balance is configured and consolidated, which shall potentate in the future the efficiency of the monetary policy. This paper analyses the credit channel in Romania, through an unrestricted VAR analysis.. It shows the responses of exchange rate, inflation rate, GDP, interest rate, imports and exports to a shock on non-governmental credit

  5. The emergence of two anti-phase oscillatory neural populations in a computational model of the Parkinsonian globus pallidus

    Directory of Open Access Journals (Sweden)

    Robert John Merrison-Hort

    2013-12-01

    Full Text Available Experiments in rodent models of Parkinson's Disease have demonstrated a prominent increase of oscillatory firing patterns in neurons within the Parkinsonian globus pallidus (GP which may underlie some of the motor symptoms of the disease. There are two main pathways from the cortex to GP: via the striatum and via the subthalamic nucleus (STN, but it is not known how these inputs sculpt the pathological pallidal firing patterns. To study this we developed a novel neural network model of conductance-based spiking pallidal neurons with cortex-modulated input from STN neurons. Our results support the hypothesis that entrainment occurs primarily via the subthalamic pathway. We find that as a result of the interplay between excitatory input from the STN and mutual inhibitory coupling between GP neurons, a homogeneous population of GP neurons demonstrates a self-organising dynamical behaviour where two groups of neurons emerge: one spiking in-phase with the cortical rhythm and the other in anti-phase. This finding mirrors what is seen in recordings from the GP of rodents that have had Parkinsonism induced via brain lesions. Our model also includes downregulation of Hyperpolarization-activated Cyclic Nucleotide-gated (HCN channels in response to burst firing of GP neurons, since this has been suggested as a possible mechanism for the emergence of Parkinsonian activity. We found that the downregulation of HCN channels provides even better correspondence with experimental data but that it is not essential in order for the two groups of oscillatory neurons to appear. We discuss how the influence of inhibitory striatal input will strengthen our results.

  6. ZnO-channel thin-film transistors: Channel mobility

    International Nuclear Information System (INIS)

    Hoffman, R.L.

    2004-01-01

    ZnO-channel thin-film transistor (TFT) test structures are fabricated using a bottom-gate structure on thermally oxidized Si; ZnO is deposited via RF sputtering from an oxide target, with an unheated substrate. Electrical characteristics are evaluated, with particular attention given to the extraction and interpretation of transistor channel mobility. ZnO-channel TFT mobility exhibits severe deviation from that assumed by ideal TFT models; mobility extraction methodology must accordingly be recast so as to provide useful insight into device operation. Two mobility metrics, μ avg and μ inc , are developed and proposed as relevant tools in the characterization of nonideal TFTs. These mobility metrics are employed to characterize the ZnO-channel TFTs reported herein; values for μ inc as high as 25 cm2/V s are measured, comprising a substantial increase in ZnO-channel TFT mobility as compared to previously reported performance for such devices

  7. An improved channel assessment scheme

    KAUST Repository

    Bader, Ahmed

    2014-01-01

    A source node in a multihop network determines whether to transmit in a channel based on whether the channel is occupied by a packet transmission with a large number of relays; whether the source node is in the data tones back-off zone; and the source node is in the busy tone back-off zone.

  8. Quantum communication under channel uncertainty

    Energy Technology Data Exchange (ETDEWEB)

    Noetzel, Janis Christian Gregor

    2012-09-06

    This work contains results concerning transmission of entanglement and subspaces as well as generation of entanglement in the limit of arbitrary many uses of compound- and arbitrarily varying quantum channels (CQC, AVQC). In both cases, the channel is described by a set of memoryless channels. Only forward communication between one sender and one receiver is allowed. A code is said to be ''good'' only, if it is ''good'' for every channel out of the set. Both settings describe a scenario, in which sender and receiver have only limited channel knowledge. For different amounts of information about the channel available to sender or receiver, coding theorems are proven for the CQC. For the AVQC, both deterministic and randomised coding schemes are considered. Coding theorems are proven, as well as a quantum analogue of the Ahlswede-dichotomy. The connection to zero-error capacities of stationary memoryless quantum channels is investigated. The notion of symmetrisability is defined and used for both classes of channels.

  9. Perceived quality of channel zapping

    NARCIS (Netherlands)

    Kooij, R.E.; Ahmed, K.; Brunnström, K.

    2006-01-01

    The end user experience of service quality is critical to the success of a service provider's IPTV deployment program. A key element involved in validating IPTV quality of experience (QoE) is how quickly and reliably users can change TV channels, often referred to as channel zapping. Currently there

  10. Channel's Concurrence and Quantum Teleportation

    Institute of Scientific and Technical Information of China (English)

    LING Yin-Sheng

    2005-01-01

    Concurrence can measure the entanglement property of a system. If the channel is a pure state, positive concurrence state can afford the good performance in the teleportation process. If the channel ia a mixed state, positive concurrence state cannot assure the good performance in the teleportation. The conditions of the positive concurrence and the quantum teleportation in the Heisenberg spin ring is derived.

  11. An improved channel assessment scheme

    KAUST Repository

    Bader, Ahmed

    2014-05-01

    A source node in a multihop network determines whether to transmit in a channel based on whether the channel is occupied by a packet transmission with a large number of relays; whether the source node is in the data tones back-off zone; and the source node is in the busy tone back-off zone.

  12. Decreasing vortex flux in channels

    International Nuclear Information System (INIS)

    Migaj, V.K.; Nosova, I.S.

    1979-01-01

    A new method for reducing vortex flow losses in power plant channels is suggested. The method is based on vortex splitting in vortex flow areas with transverse barriers placed on the channel walls. The upper barrier ends are at the level of the upper boundary of the vortex area and don't protrude to the active flow beyond this boundary. The effectiveness of the method suggested is illustrated taking as an example the investigation of square and flat channels with abrupt widening in one plane, diffusers with widening in one plane, or a rectangualr bend. It is shown that splitting the vortex areas with transverse barriers in the channels results in reduction of hydraulic losses by 10-25%. The above method is characteristic of an extreme simplicity, its application doesn't require changes in the channel shape nor installation of any devices in the flow

  13. Channel box dimension measuring method

    International Nuclear Information System (INIS)

    Oshima, Hirotake; Jo, Hiroto.

    1994-01-01

    The present invention provides a method for measuring the entire length of a channel box of a fuel assembly of a BWR type reactor. Namely, four sensors are used as one set that generate ultrasonic waves from oblique upper portion, oblique lower portion, upper portion and lower portion of the channel box respectively. The distances between the four sensors and each of the portions of the channel box are measured respectively for both of a reference member and a member to be measured. The entire length of the channel box is measured by calculating the measured values and the angles of the obliquely disposed sensors according to a predetermined formula. According to the method of the present invention, the inclination of the channel box to be measured can be corrected. In addition, accuracy of the measurement is improved and the measuring time is saved as well as the measuring device and operation can be simplified. (I.S.)

  14. Marketing channels and competitive advantage

    Directory of Open Access Journals (Sweden)

    Jovičić Dragoljub

    2005-01-01

    Full Text Available Issue that can already be seen and will be very clear in the future is that the central problem in the market of tube caps will not be the product or the price or promotion, but marketing channels. Therefore, the competitive advantage will most probably be built on marketing channels and not the production - as it has been so far, so, the questions of choice functioning and modification of marketing channels, as well as selection of the most appropriate members of channels will become more and more important. Accordingly, it may freely be said that the choice, i.e. the movement of marketing channels represents one of the strategic decisions which has to be made by a company management and which will subsequently very significantly influence the functioning and efficacy of not only the system of distribution, but also the entire business transactions.

  15. Ex situ generation of stoichiometric HCN and its application in the Pd-catalysed cyanation of aryl bromides: evidence for a transmetallation step between two oxidative addition Pd-complexes.

    Science.gov (United States)

    Kristensen, Steffan K; Eikeland, Espen Z; Taarning, Esben; Lindhardt, Anders T; Skrydstrup, Troels

    2017-12-01

    A protocol for the Pd-catalysed cyanation of aryl bromides using near stoichiometric and gaseous hydrogen cyanide is reported for the first time. A two-chamber reactor was adopted for the safe liberation of ex situ generated HCN in a closed environment, which proved highly efficient in the Ni-catalysed hydrocyanation as the test reaction. Subsequently, this setup was exploited for converting a range of aryl and heteroaryl bromides (28 examples) directly into the corresponding benzonitriles in high yields, without the need for cyanide salts. Cyanation was achieved employing the Pd(0) precatalyst, P( t Bu) 3 -Pd-G3 and a weak base, potassium acetate, in a dioxane-water solvent mixture. The methodology was also suitable for the synthesis of 13 C-labelled benzonitriles with ex situ generated 13 C-hydrogen cyanide. Stoichiometric studies with the metal complexes were undertaken to delineate the mechanism for this catalytic transformation. Treatment of Pd(P( t Bu) 3 ) 2 with H 13 CN in THF provided two Pd-hydride complexes, (P( t Bu) 3 ) 2 Pd(H)( 13 CN), and [(P( t Bu) 3 )Pd(H)] 2 Pd( 13 CN) 4 , both of which were isolated and characterised by NMR spectroscopy and X-ray crystal structure analysis. When the same reaction was performed in a THF : water mixture in the presence of KOAc, only (P( t Bu) 3 ) 2 Pd(H)( 13 CN) was formed. Subjection of this cyano hydride metal complex with the oxidative addition complex (P( t Bu) 3 )Pd(Ph)(Br) in a 1 : 1 ratio in THF led to a transmetallation step with the formation of (P( t Bu) 3 ) 2 Pd(H)(Br) and 13 C-benzonitrile from a reductive elimination step. These experiments suggest the possibility of a catalytic cycle involving initially the formation of two Pd(ii)-species from the oxidative addition of L n Pd(0) into HCN and an aryl bromide followed by a transmetallation step to L n Pd(Ar)(CN) and L n Pd(H)(Br), which both reductively eliminate, the latter in the presence of KOAc, to generate the benzonitrile and L n Pd(0).

  16. Methods of channeling simulation

    International Nuclear Information System (INIS)

    Barrett, J.H.

    1989-06-01

    Many computer simulation programs have been used to interpret experiments almost since the first channeling measurements were made. Certain aspects of these programs are important in how accurately they simulate ions in crystals; among these are the manner in which the structure of the crystal is incorporated, how any quantity of interest is computed, what ion-atom potential is used, how deflections are computed from the potential, incorporation of thermal vibrations of the lattice atoms, correlations of thermal vibrations, and form of stopping power. Other aspects of the programs are included to improve the speed; among these are table lookup, importance sampling, and the multiparameter method. It is desirable for programs to facilitate incorporation of special features of interest in special situations; examples are relaxations and enhanced vibrations of surface atoms, easy substitution of an alternate potential for comparison, change of row directions from layer to layer in strained-layer lattices, and different vibration amplitudes for substitutional solute or impurity atoms. Ways of implementing all of these aspects and features and the consequences of them will be discussed. 30 refs., 3 figs

  17. Based on Channel Characteristics

    Directory of Open Access Journals (Sweden)

    Zhuo Hao

    2013-01-01

    Full Text Available A number of key agreement schemes based on wireless channel characteristics have been proposed recently. However, previous key agreement schemes require that two nodes which need to agree on a key are within the communication range of each other. Hence, they are not suitable for multihop wireless networks, in which nodes do not always have direct connections with each other. In this paper, we first propose a basic multihop key agreement scheme for wireless ad hoc networks. The proposed basic scheme is resistant to external eavesdroppers. Nevertheless, this basic scheme is not secure when there exist internal eavesdroppers or Man-in-the-Middle (MITM adversaries. In order to cope with these adversaries, we propose an improved multihop key agreement scheme. We show that the improved scheme is secure against internal eavesdroppers and MITM adversaries in a single path. Both performance analysis and simulation results demonstrate that the improved scheme is efficient. Consequently, the improved key agreement scheme is suitable for multihop wireless ad hoc networks.

  18. Information geometry of Gaussian channels

    International Nuclear Information System (INIS)

    Monras, Alex; Illuminati, Fabrizio

    2010-01-01

    We define a local Riemannian metric tensor in the manifold of Gaussian channels and the distance that it induces. We adopt an information-geometric approach and define a metric derived from the Bures-Fisher metric for quantum states. The resulting metric inherits several desirable properties from the Bures-Fisher metric and is operationally motivated by distinguishability considerations: It serves as an upper bound to the attainable quantum Fisher information for the channel parameters using Gaussian states, under generic constraints on the physically available resources. Our approach naturally includes the use of entangled Gaussian probe states. We prove that the metric enjoys some desirable properties like stability and covariance. As a by-product, we also obtain some general results in Gaussian channel estimation that are the continuous-variable analogs of previously known results in finite dimensions. We prove that optimal probe states are always pure and bounded in the number of ancillary modes, even in the presence of constraints on the reduced state input in the channel. This has experimental and computational implications. It limits the complexity of optimal experimental setups for channel estimation and reduces the computational requirements for the evaluation of the metric: Indeed, we construct a converging algorithm for its computation. We provide explicit formulas for computing the multiparametric quantum Fisher information for dissipative channels probed with arbitrary Gaussian states and provide the optimal observables for the estimation of the channel parameters (e.g., bath couplings, squeezing, and temperature).

  19. Channel Simulation in Quantum Metrology

    Directory of Open Access Journals (Sweden)

    Laurenza Riccardo

    2018-04-01

    Full Text Available In this review we discuss how channel simulation can be used to simplify the most general protocols of quantum parameter estimation, where unlimited entanglement and adaptive joint operations may be employed. Whenever the unknown parameter encoded in a quantum channel is completely transferred in an environmental program state simulating the channel, the optimal adaptive estimation cannot beat the standard quantum limit. In this setting, we elucidate the crucial role of quantum teleportation as a primitive operation which allows one to completely reduce adaptive protocols over suitable teleportation-covariant channels and derive matching upper and lower bounds for parameter estimation. For these channels,wemay express the quantum Cramér Rao bound directly in terms of their Choi matrices. Our review considers both discrete- and continuous-variable systems, also presenting some new results for bosonic Gaussian channels using an alternative sub-optimal simulation. It is an open problem to design simulations for quantum channels that achieve the Heisenberg limit.

  20. Skeletal Muscle Na+ Channel Disorders

    Directory of Open Access Journals (Sweden)

    Dina eSimkin

    2011-10-01

    Full Text Available Five inherited human disorders affecting skeletal muscle contraction have been traced to mutations in the gene encoding the voltage-gated sodium channel Nav1.4. The main symptoms of these disorders are myotonia or periodic paralysis caused by changes in skeletal muscle fiber excitability. Symptoms of these disorders vary from mild or latent disease to incapacitating or even death in severe cases. As new human sodium channel mutations corresponding to disease states become discovered, the importance of understanding the role of the sodium channel in skeletal muscle function and disease state grows.

  1. Formation of doubly and triply bonded unsaturated compounds HCN, HNC, and CH2NH via N + CH4 low-temperature solid state reaction: from molecular clouds to solar system objects

    Science.gov (United States)

    Mencos, Alejandro; Krim, Lahouari

    2018-06-01

    We show in the current study carried out in solid phase at cryogenic temperatures that methane (CH4) ice exposed to nitrogen atoms is a source of two acids HCN, HNC, and their corresponding hydrogenated unsaturated species CH2NH, in addition to CH3, C2H6, CN-, and three nitrogen hydrides NH, NH2, and NH3. The solid state N + CH4 reaction taken in the ground state seems to be strongly temperature dependent. While at temperatures lower than 10 K only CH3, NH, NH2, and NH3 species formation is promoted due to CH bond dissociation and NH bond formation, stable compounds with CN bonds are formed at temperatures ranged between 10 and 40 K. Many of these reaction products, resulting from CH4 + N reaction, have already been observed in N2-rich regions such as the atmospheres of Titan, Kuiper belt objects, and molecular clouds of the interstellar medium. Our results show the power of the solid state N-atom chemistry in the transformation of simple astrochemical relevant species, such as CH4 molecules and N atoms into complex organic molecules which are also potentially prebiotic species.

  2. Hydraulic jumps in a channel

    DEFF Research Database (Denmark)

    Bonn, D.; Andersen, Anders Peter; Bohr, Tomas

    2009-01-01

    We present a study of hydraulic jumps with flow predominantly in one direction, created either by confining the flow to a narrow channel with parallel walls or by providing an inflow in the form of a narrow sheet. In the channel flow, we find a linear height profile upstream of the jump as expected......'s mixing-length theory with a mixing length that is proportional to the height of the fluid layer. Using averaged boundary-layer equations, taking into account the friction with the channel walls and the eddy viscosity, the flow both upstream and downstream of the jump can be understood. For the downstream...... subcritical flow, we assume that the critical height is attained close to the channel outlet. We use mass and momentum conservation to determine the position of the jump and obtain an estimate which is in rough agreement with our experiment. We show that the averaging method with a varying velocity profile...

  3. Green channel cargo inspection system

    International Nuclear Information System (INIS)

    Shi Yuanping; Yu Jingsheng; Sun Hongqiang; Hao Pu; Cai Wenxia

    2011-01-01

    A radiation detection device was installed in the lanes of a highway toll station, radioactive rays which was collimated emitted through the measured, and arrived the detector. The average density of the fresh agricultural products belonged to Green channel and other prohibited items vary greatly, the absorption of radiation are different between the Green Channel Cargo and other substances. Prior to the experimental group, different standard samples which represent different models and goods were measured, the different standard samples were stored in a computer database. When the trucks get through the Green Channel, the detector will detect the radiation signal and bring to the computer, the computer will process the measured data, and make a conclusion whether the goods are Green Channel cargo. (authors)

  4. Flooding correlations in narrow channel

    International Nuclear Information System (INIS)

    Kim, S. H.; Baek, W. P.; Chang, S. H.

    1999-01-01

    Heat transfer in narrow gap is considered as important phenomena in severe accidents in nuclear power plants. Also in heat removal of electric chip. Critical heat flux(CHF) in narrow gap limits the maximum heat transfer rate in narrow channel. In case of closed bottom channel, flooding limited CHF occurrence is observed. Flooding correlations will be helpful to predict the CHF in closed bottom channel. In present study, flooding data for narrow channel geometry were collected and the work to recognize the effect of the span, w and gap size, s were performed. And new flooding correlations were suggested for high-aspect-ratio geometry. Also, flooding correlation was applied to flooding limited CHF data

  5. Multi-channel Kondo necklace

    International Nuclear Information System (INIS)

    Fazekas, P.; Kee Haeyoung.

    1993-06-01

    A multi-channel generalization of Doniach's Kondo necklace model is formulated, and its phase diagram studied in the mean-field approximation. Our intention is to introduce the possible simplest model which displays some of the features expected from the overscreened Kondo lattice. The N conduction electron channels are represented by N sets of pseudospins τ J , j = 1 1,..., N which are all antiferromagnetically coupled to a periodic array of modul S = 1/2 spins. Exploiting permutation symmetry in the channel index j allows us to write down the self-consistency equation for general N. For N > 2, we find that the critical temperature is rising with increasing Kondo interaction; we interpret this effect by pointing out that the Kondo coupling creates the composite pseudospin objects which undergo an ordering transition. The relevance of our findings to the underlying fermionic multi-channel problem is discussed. (author). 33 refs, 1 fig

  6. Experimentation with PEC channel prototype

    International Nuclear Information System (INIS)

    Caponetti, R.; Iacovelli, M.

    1984-01-01

    Experimentation on prototypes of PEC components is presently being carried out at Casaccia CRE. This report shows the results of the first cycle of experimentation of the central channel, concerning the aspects of sodium removal after experimentation

  7. Multi-channel Kondo necklace

    Energy Technology Data Exchange (ETDEWEB)

    Fazekas, P; Haeyoung, Kee

    1993-06-01

    A multi-channel generalization of Doniach`s Kondo necklace model is formulated, and its phase diagram studied in the mean-field approximation. Our intention is to introduce the possible simplest model which displays some of the features expected from the overscreened Kondo lattice. The N conduction electron channels are represented by N sets of pseudospins {tau}{sub J}, j = 1 1,..., N which are all antiferromagnetically coupled to a periodic array of modul S = 1/2 spins. Exploiting permutation symmetry in the channel index j allows us to write down the self-consistency equation for general N. For N > 2, we find that the critical temperature is rising with increasing Kondo interaction; we interpret this effect by pointing out that the Kondo coupling creates the composite pseudospin objects which undergo an ordering transition. The relevance of our findings to the underlying fermionic multi-channel problem is discussed. (author). 33 refs, 1 fig.

  8. FMCG companies specific distribution channels

    Directory of Open Access Journals (Sweden)

    Ioana Barin

    2009-12-01

    Full Text Available Distribution includes all activities undertaken by the producer, alone or in cooperation, since the end of the final finished products or services until they are in possession of consumers. The distribution consists of the following major components: distribution channels or marketing channels, which together form a distribution network; logistics o rphysical distribution. In order to effective achieve, distribution of goods requires an amount of activities and operational processes related to transit of goods from producer to consumer, the best conditions, using existing distribution channels and logistics system. One of the essential functions of a distribution is performing acts of sale, through which, with the actual movement of goods, their change of ownership takes place, that the successive transfer of ownership from producer to consumer. This is an itinerary in the economic cycle of goods, called the distribution channel.

  9. Marketing channel behaviour and performance

    OpenAIRE

    Duarte, Margarida

    2000-01-01

    Thesis submitted to University of Manchester for the degree of Doctor of Philosophy in the Faculty of Business Administration. A major aim of this study is to offer a relatively comprehensive picture of marketing channel behaviour and performance. Given the statistical difficulties in testing a very large, comprehensive model to achieve this aim, two separate but overlapping models are proposed. One model specifically addresses behaviour in marketing channels, while the other integrates k...

  10. Channel coincidence counter: version 1

    International Nuclear Information System (INIS)

    Krick, M.S.; Menlove, H.O.

    1980-06-01

    A thermal neutron coincidence counter has been designed for the assay of fast critical assembly fuel drawers and plutonium-bearing fuel rods. The principal feature of the detector is a 7-cm by 7-cm by 97-cm detector channel, which provides a uniform neutron detection efficiency of 16% along the central 40 cm of the channel. The electronics system is identical to that used for the High-Level Neutron Coincidence Counter

  11. TRP Channels in Human Prostate

    Directory of Open Access Journals (Sweden)

    Carl Van Haute

    2010-01-01

    Full Text Available This review gives an overview of morphological and functional characteristics in the human prostate. It will focus on the current knowledge about transient receptor potential (TRP channels expressed in the human prostate, and their putative role in normal physiology and prostate carcinogenesis. Controversial data regarding the expression pattern and the potential impact of TRP channels in prostate function, and their involvement in prostate cancer and other prostate diseases, will be discussed.

  12. Electrophysiological characterisation of KCNQ channel modulators

    DEFF Research Database (Denmark)

    Schrøder, R.L

    Potassium (K+) ion channels are ubiquitously expressed in mammalian cells, and each channel serves a precise physiological role due to its specific biophysical characteristics and expression pattern. A few K+ channels are targets for certain drugs, and in this thesis it is suggested that the KCNQ K......+ channels may be targets for neuroprotective, anti-epileptic and anti-nociceptive compounds. The importance of these channels is underscored by the fact that four out of five KCNQ channel subtypes are involved in severe human diseases. However, the pharmacology of the KCNQ channels is yet poorly understood...... as these channels were identified only recently. Therefore, there is a need for understanding the biophysical behavior and pharmacology of these ion channels. KCNQ channels belong to the group of voltage-activated K+ channels. The subfamily consists of KCNQ1-5, which is primarily expressed in the CNS, heart, ear...

  13. Uncertainty analysis for hot channel

    International Nuclear Information System (INIS)

    Panka, I.; Kereszturi, A.

    2006-01-01

    The fulfillment of the safety analysis acceptance criteria is usually evaluated by separate hot channel calculations using the results of neutronic or/and thermo hydraulic system calculations. In case of an ATWS event (inadvertent withdrawal of control assembly), according to the analysis, a number of fuel rods are experiencing DNB for a longer time and must be regarded as failed. Their number must be determined for a further evaluation of the radiological consequences. In the deterministic approach, the global power history must be multiplied by different hot channel factors (kx) taking into account the radial power peaking factors for each fuel pin. If DNB occurs it is necessary to perform a few number of hot channel calculations to determine the limiting kx leading just to DNB and fuel failure (the conservative DNBR limit is 1.33). Knowing the pin power distribution from the core design calculation, the number of failed fuel pins can be calculated. The above procedure can be performed by conservative assumptions (e.g. conservative input parameters in the hot channel calculations), as well. In case of hot channel uncertainty analysis, the relevant input parameters (k x, mass flow, inlet temperature of the coolant, pin average burnup, initial gap size, selection of power history influencing the gap conductance value) of hot channel calculations and the DNBR limit are varied considering the respective uncertainties. An uncertainty analysis methodology was elaborated combining the response surface method with the one sided tolerance limit method of Wilks. The results of deterministic and uncertainty hot channel calculations are compared regarding to the number of failed fuel rods, max. temperature of the clad surface and max. temperature of the fuel (Authors)

  14. Planar channeling in superlattices: Theory

    International Nuclear Information System (INIS)

    Ellison, J.A.; Picraux, S.T.; Allen, W.R.; Chu, W.K.

    1988-01-01

    The well-known continuum model theory for planar channeled energetic particles in perfect crystals is extended to layered crystalline structures and applied to superlattices. In a strained-layer structure, the planar channels with normals which are not perpendicular to the growth direction change their direction at each interface, and this dramatically influences the channeling behavior. The governing equation of motion for a planar channeled ion in a strained-layer superlattice with equal layer thicknesses is a one degree of freedom nonlinear oscillator which is periodically forced with a sequence of δ functions. These δ functions, which are of equal spacing and amplitude with alternating sign, represent the tilts at each of the interfaces. Thus upon matching an effective channeled particle wavelength, corresponding to a natural period of the nonlinear oscillator, to the period of the strained-layer superlattice, corresponding to the periodic forcing, strong resonance effects are expected. The condition of one effective wavelength per period corresponds to a rapid dechanneling at a well-defined depth (catastrophic dechanneling), whereas two wavelengths per period corresponds to no enhanced dechanneling after the first one or two layers (resonance channeling). A phase plane analysis is used to characterize the channeled particle motion. Detailed calculations using the Moliere continuum potential are compared with our previously described modified harmonic model, and new results are presented for the phase plane evolution, as well as the dechanneling as a function of depth, incident angle, energy, and layer thickness. General scaling laws are developed and nearly universal curves are obtained for the dechanneling versus depth under catastrophic dechanneling

  15. Volume of the space of qubit-qubit channels and state transformations under random quantum channels

    OpenAIRE

    Lovas, Attila; Andai, Attila

    2017-01-01

    The simplest building blocks for quantum computations are the qubit-qubit quantum channels. In this paper, we analyze the structure of these channels via their Choi representation. The restriction of a quantum channel to the space of classical states (i.e. probability distributions) is called the underlying classical channel. The structure of quantum channels over a fixed classical channel is studied, the volume of general and unital qubit channels with respect to the Lebesgue measure is comp...

  16. Information transfer through quantum channels

    International Nuclear Information System (INIS)

    Kretschmann, D.

    2007-01-01

    This PhD thesis represents work done between Aug. 2003 and Dec. 2006 in Reinhard F. Werner's quantum information theory group at Technische Universitaet Braunschweig, and Artur Ekert's Centre for Quantum Computation at the University of Cambridge. My thesis falls into the field of abstract quantum information theory. This work investigates both fundamental properties of quantum channels and their asymptotic capacities for classical as well as quantum information transfer. Stinespring's theorem is the basic structure theorem for quantum channels. It implies that every quantum channel can be represented as a unitary evolution on an enlarged system. In Ch. 3 we present a continuity theorem for Stinespring's representation: two quantum channels are similar if and only if it is possible to find unitary implementations that are likewise similar, with dimension-independent norm bounds. The continuity theorem allows to derive a formulation of the information-disturbance tradeoff in terms of quantum channels, and a continuity estimate for the no-broadcasting principle. In Ch. 4 we then apply the continuity theorem to give a strengthened no-go proof for quantum bit commitment, an important cryptographic primitive. This result also provides a natural characterization of those protocols that fall outside the standard setting of unconditional security, and thus may allow secure bit commitment. We present a new such protocol whose security relies on decoherence in the receiver's lab. Ch. 5 reviews the capacities of quantum channels for the transfer of both classical and quantum information, and investigates several variations in the notion of channel capacity. Memory effects are then investigated in detail in Ch. 6. We advertise a model which is sufficiently general to encompass all causal automata: every quantum process in which the outputs up to any given time t do not depend on the inputs at times t'>t can be represented as a concatenated memory channel. We then explain how

  17. Information transfer through quantum channels

    Energy Technology Data Exchange (ETDEWEB)

    Kretschmann, D.

    2007-03-12

    This PhD thesis represents work done between Aug. 2003 and Dec. 2006 in Reinhard F. Werner's quantum information theory group at Technische Universitaet Braunschweig, and Artur Ekert's Centre for Quantum Computation at the University of Cambridge. My thesis falls into the field of abstract quantum information theory. This work investigates both fundamental properties of quantum channels and their asymptotic capacities for classical as well as quantum information transfer. Stinespring's theorem is the basic structure theorem for quantum channels. It implies that every quantum channel can be represented as a unitary evolution on an enlarged system. In Ch. 3 we present a continuity theorem for Stinespring's representation: two quantum channels are similar if and only if it is possible to find unitary implementations that are likewise similar, with dimension-independent norm bounds. The continuity theorem allows to derive a formulation of the information-disturbance tradeoff in terms of quantum channels, and a continuity estimate for the no-broadcasting principle. In Ch. 4 we then apply the continuity theorem to give a strengthened no-go proof for quantum bit commitment, an important cryptographic primitive. This result also provides a natural characterization of those protocols that fall outside the standard setting of unconditional security, and thus may allow secure bit commitment. We present a new such protocol whose security relies on decoherence in the receiver's lab. Ch. 5 reviews the capacities of quantum channels for the transfer of both classical and quantum information, and investigates several variations in the notion of channel capacity. Memory effects are then investigated in detail in Ch. 6. We advertise a model which is sufficiently general to encompass all causal automata: every quantum process in which the outputs up to any given time t do not depend on the inputs at times t'>t can be represented as a concatenated memory

  18. A Crash Course in Calcium Channels.

    Science.gov (United States)

    Zamponi, Gerald W

    2017-12-20

    Much progress has been made in understanding the molecular physiology and pharmacology of calcium channels. Recently, there have been tremendous advances in learning about calcium channel structure and function through crystallography and cryo-electron microscopy studies. Here, I will give an overview of our knowledge about calcium channels, and highlight two recent studies that give important insights into calcium channel structure.

  19. Transient receptor potential channels in essential hypertension

    DEFF Research Database (Denmark)

    Liu, Daoyan; Scholze, Alexandra; Zhu, Zhiming

    2006-01-01

    The role of nonselective cation channels of the transient receptor potential channel (TRPC) family in essential hypertension has not yet been investigated.......The role of nonselective cation channels of the transient receptor potential channel (TRPC) family in essential hypertension has not yet been investigated....

  20. The minimum yield in channeling

    International Nuclear Information System (INIS)

    Uguzzoni, A.; Gaertner, K.; Lulli, G.; Andersen, J.U.

    2000-01-01

    A first estimate of the minimum yield was obtained from Lindhard's theory, with the assumption of a statistical equilibrium in the transverse phase-space of channeled particles guided by a continuum axial potential. However, computer simulations have shown that this estimate should be corrected by a fairly large factor, C (approximately equal to 2.5), called the Barrett factor. We have shown earlier that the concept of a statistical equilibrium can be applied to understand this result, with the introduction of a constraint in phase-space due to planar channeling of axially channeled particles. Here we present an extended test of these ideas on the basis of computer simulation of the trajectories of 2 MeV α particles in Si. In particular, the gradual trend towards a full statistical equilibrium is studied. We also discuss the introduction of this modification of standard channeling theory into descriptions of the multiple scattering of channeled particles (dechanneling) by a master equation and show that the calculated minimum yields are in very good agreement with the results of a full computer simulation

  1. Generic theory for channel sinuosity.

    Science.gov (United States)

    Lazarus, Eli D; Constantine, José Antonio

    2013-05-21

    Sinuous patterns traced by fluid flows are a ubiquitous feature of physical landscapes on Earth, Mars, the volcanic floodplains of the Moon and Venus, and other planetary bodies. Typically discussed as a consequence of migration processes in meandering rivers, sinuosity is also expressed in channel types that show little or no indication of meandering. Sinuosity is sometimes described as "inherited" from a preexisting morphology, which still does not explain where the inherited sinuosity came from. For a phenomenon so universal as sinuosity, existing models of channelized flows do not explain the occurrence of sinuosity in the full variety of settings in which it manifests, or how sinuosity may originate. Here we present a generic theory for sinuous flow patterns in landscapes. Using observations from nature and a numerical model of flow routing, we propose that flow resistance (representing landscape roughness attributable to topography or vegetation density) relative to surface slope exerts a fundamental control on channel sinuosity that is effectively independent of internal flow dynamics. Resistance-dominated surfaces produce channels with higher sinuosity than those of slope-dominated surfaces because increased resistance impedes downslope flow. Not limited to rivers, the hypothesis we explore pertains to sinuosity as a geomorphic pattern. The explanation we propose is inclusive enough to account for a wide variety of sinuous channel types in nature, and can serve as an analytical tool for determining the sinuosity a landscape might support.

  2. Charged and Neutral Particles Channeling Phenomena Channeling 2008

    Science.gov (United States)

    Dabagov, Sultan B.; Palumbo, Luigi

    2010-04-01

    On the discovery of coherent Bremsstrahlung in a single crystal at the Frascati National Laboratories / C. Barbiellini, G. P. Murtas and S. B. Dabagov -- Advances in coherent Bremsstrahlung and LPM-effect studies (to the lOOth anniversary from the birth of L. D. Landau) / N. F. Shul'ga -- Spectra of radiation and created particles at intermediate energy in oriented crystal taking into account energy loss / V. N. Baier and V. M. Katkov -- The coherent Bremsstrahlung beam at MAX-lab facility / K. Fissum ... [et al.] -- Radiation from thin, structured targets (CERN NA63) / A. Dizdar -- Hard incoherent radiation in thick crystals / N. F. Shul'ga, V. V. Syshchenko and A. I. Tarnovsky -- Coherent Bremsstrahlung in periodically deformed crystals with a complex base / A. R. Mkrtchyan, A. A. Saharian and V. V. Parazian -- Induction of coherent x-ray Bremsstrahlung in crystals under the influence of acoustic waves / A. R. Mkrtchyan and V. V. Parazian -- Coherent processes in bent single crystals / V. A. Maisheev -- Experimental and theoretical investigation of complete transfer phenomenon for media with various heat exchange coefficients / A. R. Mkrtchyan, A. E. Movsisyan and V. R. Kocharyan -- Coherent pair production in crystals / A. R. Mkrtchyan, A. A. Saharian and V. V. Parazian -- Negative particle planar and axial channeling and channeling collimation / R. A. Carrigan, Jr. -- CERN crystal-based collimation in modern hadron colliders / W. Scandale -- Studies and application of bent crystals for beam steering at 70 GeV IHEP accelerator / A. G. Afonin ... [et al.] -- Crystal collimation studies at the Tevatron (T-980) / N. V. Mokhov ... [et al.] -- Fabrication of crystals for channeling of particles in accellerators / A. Mazzolari ... [et al.] -- New possibilities to facilitate collimation of both positively and negatively charged particle beams by crystals / V. Guidi, A. Mazzolari and V. V. Tikhomirov -- Increase of probability of particle capture into the channeling

  3. Pannexin-1 channels in epilepsy.

    Science.gov (United States)

    Aquilino, Mark S; Whyte-Fagundes, Paige; Zoidl, Georg; Carlen, Peter L

    2017-09-05

    Pannexin-1 (Panx1) expression is raised in several animal seizure models and in resected human epileptic brain tissue, suggesting relevance to epilepsy. Multiple factors that are characteristic of seizures are thought to regulate Panx1 channel opening, including elevated levels of extracellular K + . Panx1, when open, 1) releases ATP, glutamate, and other metabolites into the extracellular medium, and 2) may depolarize the membrane due to a channel reversal potential around 0mV. Resultant ATP release from stimulated Panx1 can activate purinergic receptors, including P2X7 receptors. Glutamate and other signaling molecules released by Panx1 opening may have both excitatory and inhibitory actions on seizure generation. This review examines the critical and complex roles of Panx1 channels in epilepsy, which could provide a basis for future therapeutics. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Axial channeling of uttrarelativistic electrons

    Energy Technology Data Exchange (ETDEWEB)

    Telegin, V.I.; Khokonov, M.Kh. (Moskovskij Gosudarstvennyj Univ. (USSR). Nauchno-Issledovatel' skij Inst. Yadernoj Fiziki)

    1982-07-01

    The dynamics of motion of ultrarelativistic electrons under axial channeling conditions is investigated. The analysis is based on the solution of the kinetic equation obtained recently by Beloshitsky and Kumakhov. The particle dechanneling function is investigated as depending on the type of a crystal, particle energy and angle of entrance into the single crystal. It is found that for most of the beam the major diffusion mechanism is scattering by electrons. It is shown that an optimal depth range exists for which the fraction of channeled particles sharply increases at the expense of the quasi-channeled particles. In a number of cases the dechanneling length for crystals with high atomic numbers may be greater than that of light elements.

  5. Axial channeling of uttrarelativistic electrons

    International Nuclear Information System (INIS)

    Telegin, V.I.; Khokonov, M.Kh.

    1982-01-01

    The dynamics of motion of ultrarelativistic electrons under axial channeling conditions is investigated. The analysis is based on the solution of the kinetic equation obtained recently by Beloshitsky and Kumakhov. The particle dechanneling function is investigated as depending on the type of a crystal, particle energy and angle of entrance into the single crystal. It is found that for most of the beam the major diffusion mechanism is scattering by electrons. It is shown that an optimal depth range exists for which the fraction of channeled particles sharply increases at the expense of the quasi-channeled particles. In a number of cases the dechanneling length for crystals with high atomic numbers may be greater than that of light elements

  6. Pharmacological modulation of SK3 channels

    DEFF Research Database (Denmark)

    Grunnet, M; Jespersen, Thomas; Angelo, K

    2001-01-01

    Small-conductance, calcium-activated K+ channels (SK channels) are voltage-insensitive channels that have been identified molecularly within the last few years. As SK channels play a fundamental role in most excitable cells and participate in afterhyperpolarization (AHP) and spike-frequency adapt...... at concentrations of 3 microM and above. Amitriptyline, a tricyclic antidepressive widely used clinically, inhibits SK3 channels with an IC50 of 39.1 +/- 10 microM (n=6)....

  7. Local quantum channels preserving classical correlations

    International Nuclear Information System (INIS)

    Guo Zhihua; Cao Huaixin

    2013-01-01

    The aim of this paper is to discuss local quantum channels that preserve classical correlations. First, we give two equivalent characterizations of classical correlated states. Then we obtain the relationships among classical correlation-preserving local quantum channels, commutativity-preserving local quantum channels and commutativity-preserving quantum channels on each subsystem. Furthermore, for a two-qubit system, we show the general form of classical correlation-preserving local quantum channels. (paper)

  8. The ion-channel laser

    International Nuclear Information System (INIS)

    Whittum, D.H.; Sessler, A.M.; Dawson, J.M.

    1990-01-01

    A relativistic electron beam propagating through a plasma in the ion-focused regime exhibits an electromagnetic instability at a resonant frequency ω ∼ 2γ 2 ω β . Growth is enhanced by optical guiding in the ion channel, which acts as dielectric waveguide, with fiber parameter V ∼ 2 (I/I A ) 1/2 . A 1-D theory for such an ''ion-channel laser'' is formulated, scaling laws are derived and numerical examples are given. Possible experimental evidence is noted. 23 refs., 1 fig., 1 tab

  9. Electron angular distribution axial channeling

    International Nuclear Information System (INIS)

    Khokonov, A.Kh.; Khokonov, M.Kh.

    1989-01-01

    Angular distributions of ultra-relativistic electrons are calculated in the assumption about presence of statistical equilibrium. Analysis is based on numerical solution of Fokker-Planck type kinetic equation. It is shown that in contrast to case of amorphous medium, the multiple scattering at axial channeling of negative particles results in self-focusing of the initial beam particles and due to it number of electrons moving at an angles to the chain, which are smaller, than critical angle of channeling, may increase by several times as compared to the initial one

  10. Antenna for Ultrawideband Channel Sounding

    DEFF Research Database (Denmark)

    Zhekov, Stanislav Stefanov; Tatomirescu, Alexandru; Pedersen, Gert F.

    2016-01-01

    A novel compact antenna for ultrawideband channel sounding is presented. The antenna is composed of a symmetrical biconical antenna modified by adding a cylinder and a ring to each cone. A feeding coaxial cable is employed during the simulations in order to evaluate and reduce its impact on the a......A novel compact antenna for ultrawideband channel sounding is presented. The antenna is composed of a symmetrical biconical antenna modified by adding a cylinder and a ring to each cone. A feeding coaxial cable is employed during the simulations in order to evaluate and reduce its impact...

  11. EPICS: Channel Access security design

    International Nuclear Information System (INIS)

    Kraimer, M.; Hill, J.

    1994-05-01

    This document presents the design for implementing the requirements specified in: EPICS -- Channel Access Security -- functional requirements, Ned. D. Arnold, 03/09/92. Use of the access security system is described along with a summary of the functional requirements. The programmer's interface is given. Security protocol is described and finally aids for reading the access security code are provided

  12. Improved Ion-Channel Biosensors

    Science.gov (United States)

    Nadeau, Jay; White, Victor; Dougherty, Dennis; Maurer, Joshua

    2004-01-01

    An effort is underway to develop improved biosensors of a type based on ion channels in biomimetic membranes. These sensors are microfabricated from silicon and other materials compatible with silicon. As described, these sensors offer a number of advantages over prior sensors of this type.

  13. Single top t-channel

    CERN Document Server

    Faltermann, Nils

    2017-01-01

    The production of single top quarks allows to study the interplay of top quark physics and the electroweak sector of the standard model. Deviations from predictions can be a hint for physics beyond the standard model. The t-channel is the dominant production mode for single top quarks at the LHC. This talk presents the latest measurements from the ATLAS and CMS collaborations.

  14. Visualizing multi-channel networks

    DEFF Research Database (Denmark)

    Antemijczuk, Paweł; Magiera, Marta; Jørgensen, Sune Lehmann

    2014-01-01

    In this paper, we propose a visualization to illustrate social interactions, built from multiple distinct channels of communication. The visualization displays a summary of dense personal information in a compact graphical notation. The starting point is an abstract drawing of a spider’s web. Below...

  15. CHANNELING IN QUASI-CRYSTALS

    NARCIS (Netherlands)

    VANVOORTHUYSEN, EHD; SMULDERS, PJM; WERKMAN, RD; DEBOER, JL; VANSMAALEN, S

    Ion-beam channeling has been observed in quasicrystals. For 1 MeV He-4+ ions in icosahedral AlCuFe the maximum effect found is 36%. The full width at half maximum of the observed dips is 1.3-degrees. The effect persists up to great depths (> 200 nm), thus showing a high degree of ordering in this

  16. Sorting out river channel patterns

    NARCIS (Netherlands)

    Kleinhans, M.G.

    2010-01-01

    Rivers self-organize their pattern/planform through feedbacks between bars, channels, floodplain and vegetation, which emerge as a result of the basic spatial sorting process of wash load sediment and bed sediment. The balance between floodplain formation and destruction determines the width and

  17. Aquaglyceroporins: ancient channels for metalloids

    Science.gov (United States)

    Bhattacharjee, Hiranmoy; Mukhopadhyay, Rita; Thiyagarajan, Saravanamuthu; Rosen, Barry P

    2008-01-01

    The identification of aquaglyceroporins as uptake channels for arsenic and antimony shows how these toxic elements can enter the food chain, and suggests that food plants could be genetically modified to exclude arsenic while still accumulating boron and silicon. PMID:19014407

  18. Sales promotions and channel coordination

    NARCIS (Netherlands)

    B. Wierenga (Berend); H. Soethoudt (Han)

    2009-01-01

    textabstractConsumer sales promotions are usually the result of the decisions of two marketing channel parties, the manufacturer and the retailer. In making these decisions, each party normally follows its own interest: i.e. maximizes its own profit. Unfortunately, this results in a suboptimal

  19. Sales promotion and channel coordination

    NARCIS (Netherlands)

    Wierenga, B.; Soethoudt, J.M.

    2010-01-01

    Consumer sales promotions are usually the result of the decisions of two marketing channel parties, the manufacturer and the retailer. In making these decisions, each party normally follows its own interest: i.e. maximizes its own profit. Unfortunately, this results in a suboptimal outcome for the

  20. CONDUCTIVE CHANNEL FOR ENERGY TRANSMISSION

    Directory of Open Access Journals (Sweden)

    V. V. Apollonov

    2014-01-01

    Full Text Available Laser spark obtained by using a conical optics is much more appropriate to form conducting channels in atmosphere. Only two types of lasers are actively considered to be used in forming high-conductivity channels in atmosphere, controlled by laser spark: pulsed sub-microsecond gas and chemical lasers (CO2, DF and short pulse solid-state and UV lasers. Main advantage of short pulse lasers is their ability in forming of super long ionized channels with a characteristic diameter of ~100  µ  in atmosphere along the  beam propagation direction. At estimated electron densities below  10 ⋅ 16 cm–3 in these filaments and laser wavelengths in the range of 0,5–1,0 mm, the plasma barely absorbs laser radiation.  In this case, the length of the track composed of many filaments is determined by the laser intensity and may reach many kilometers at a femtosecond pulse energy of ~100 mJ. However, these lasers could not be used to form high-conductivity long channels in atmosphere. The ohmic resistance of this type a conducting channels turned out to be very high, and the gas in the channels could not be strongly heated (< 1 J. An electric breakdown controlled by radiation of femtosecond solid-state laser was implemented in only at a length of 3 m with a voltage of 2 MV across the discharge gap (670 kV/m.Not so long ago scientific group from P. N. Lebedev has improved that result, the discharge gap – 1 m had been broken under KrF laser irradiation when switching high-voltage (up to 390 kV/m electric discharge by 100-ns UV pulses. Our previous result  –  16 m long conducting channel controlled by a  laser spark at the voltage  –  3 MV  – was obtained more than 20 years ago in Russia and Japan by using pulsed CO2  laser with energy  –  0,5 kJ. An average electric field strength  was < 190 kV/m. It is still too much for efficient applications.

  1. Interior point decoding for linear vector channels

    International Nuclear Information System (INIS)

    Wadayama, T

    2008-01-01

    In this paper, a novel decoding algorithm for low-density parity-check (LDPC) codes based on convex optimization is presented. The decoding algorithm, called interior point decoding, is designed for linear vector channels. The linear vector channels include many practically important channels such as inter-symbol interference channels and partial response channels. It is shown that the maximum likelihood decoding (MLD) rule for a linear vector channel can be relaxed to a convex optimization problem, which is called a relaxed MLD problem

  2. Interior point decoding for linear vector channels

    Energy Technology Data Exchange (ETDEWEB)

    Wadayama, T [Nagoya Institute of Technology, Gokiso, Showa-ku, Nagoya, Aichi, 466-8555 (Japan)], E-mail: wadayama@nitech.ac.jp

    2008-01-15

    In this paper, a novel decoding algorithm for low-density parity-check (LDPC) codes based on convex optimization is presented. The decoding algorithm, called interior point decoding, is designed for linear vector channels. The linear vector channels include many practically important channels such as inter-symbol interference channels and partial response channels. It is shown that the maximum likelihood decoding (MLD) rule for a linear vector channel can be relaxed to a convex optimization problem, which is called a relaxed MLD problem.

  3. The MISO wiretap channel with channel uncertainty: Asymptotic perspectives

    KAUST Repository

    Chaaban, Anas; Rezki, Zouheir; Alomair, Basel; Alouini, Mohamed-Slim

    2017-01-01

    The N-antenna MISO Gaussian wiretap channel with imperfect channel-state information at the transmitter (CSIT) is studied in terms of secrecy rate scaling versus the signal-to-noise ratio (SNR) and N. Two schemes are considered, beamforming (BF) and artificial noise injection (AN). It is shown that if the CSIT error is independent of SNR, then both schemes do not achieve scaling versus SNR. However, if this error vanishes as SNR increases, then AN achieves the optimal scaling versus SNR, contrary to BF. Scaling can be achieved in BF by increasing N. In fact, BF achieves the optimal scaling versus N. In the AN scheme however, injecting noise in multiple direction deteriorates its scaling versus N. Nevertheless, AN can achieve the optimal scaling if noise is sent in only one direction. This leads to better performance than BF if the CSIT error is smaller than a threshold which is also derived.

  4. The MISO wiretap channel with channel uncertainty: Asymptotic perspectives

    KAUST Repository

    Chaaban, Anas

    2017-05-12

    The N-antenna MISO Gaussian wiretap channel with imperfect channel-state information at the transmitter (CSIT) is studied in terms of secrecy rate scaling versus the signal-to-noise ratio (SNR) and N. Two schemes are considered, beamforming (BF) and artificial noise injection (AN). It is shown that if the CSIT error is independent of SNR, then both schemes do not achieve scaling versus SNR. However, if this error vanishes as SNR increases, then AN achieves the optimal scaling versus SNR, contrary to BF. Scaling can be achieved in BF by increasing N. In fact, BF achieves the optimal scaling versus N. In the AN scheme however, injecting noise in multiple direction deteriorates its scaling versus N. Nevertheless, AN can achieve the optimal scaling if noise is sent in only one direction. This leads to better performance than BF if the CSIT error is smaller than a threshold which is also derived.

  5. An Effective Channel Allocation Scheme to Reduce Co-Channel and Adjacent Channel Interference for WMN Backhaul

    International Nuclear Information System (INIS)

    Abbasi, S.; Ismaili, I.A.; Khuhawar, F.Y.

    2016-01-01

    Two folded work presents channel allocation scheme sustaining channel orthogonality and channel spacing to reduce CCI (Co-Channel Interference) and ACI (Adjacent Channel Interference) for inter flow of an intra-flow link. Proposed scheme as a part of radio resource allocation is applied on infrastructure based backhaul of wireless mesh network using directional antennas. The proposed approach is applied separately on 2.4 and 5GHz bands. Interference of connectivity graph is modelled by strongly connected directed graph and greedy algorithms are used for channel allocation. We have used OPNET Modeller suite to simulate network models for this research. The proposed arrangement reduces the channel interference and increases system throughput. In this research, the influence of channel is computed in terms of network throughput and delay. (author)

  6. Clofilium inhibits Slick and Slack potassium channels.

    Science.gov (United States)

    de Los Angeles Tejada, Maria; Stolpe, Kathleen; Meinild, Anne-Kristine; Klaerke, Dan A

    2012-01-01

    Slick and Slack high-conductance potassium channels have been recently discovered, and are found in the central nervous system and in the heart. Both channels are activated by Na(+) and Cl(-), and Slick channels are also inhibited by adenosine triphospate (ATP). An important role of setting the resting membrane potential and controlling the basal excitability of neurons has been suggested for these channels. In addition, no specific blockers for these channels are known up to the present. With the purpose of studying the pharmacological characteristics of Slick and Slack channels, the effects of exposure to the antiarrhythmic compound clofilium were evaluated. Clofilium was able to modulate the activity of Slick and Slack channels effectively, with a stronger effect on Slack than Slick channels. In order to evaluate the pharmacological behavior of Slick and Slack channels further, 38 commonly used potassium channel blockers were tested. Screening of these compounds did not reveal any modulators of Slick and Slack channels, except for clofilium. The present study provides a first approach towards elucidating the pharmacological characteristics of Slick and Slack channels and could be the basis for future studies aimed at developing potent and specific blockers and activators for these channels.

  7. Broadening of spectral lines of CO2, N2O , H2CO, HCN, and H2S by pressure of gases dominant in planetary atmospheres (H2, He and CO2)

    Science.gov (United States)

    Samuels, Shanelle; Gordon, Iouli; Tan, Yan

    2018-01-01

    HITRAN1,2 is a compilation of spectroscopic parameters that a variety of computer codes use to predict and simulate the transmission and emission of light in planetary atmospheres. The goal of this project is to add to the potential of the HITRAN database towards the exploration of the planetary atmospheres by including parameters describing broadening of spectral lines by H2, CO2, and He. These spectroscopic data are very important for the study of the hydrogen and helium-rich atmospheres of gas giants as well as rocky planets with volcanic activities, including Venus and Mars, since their atmospheres are dominated by CO2. First step in this direction was accomplished by Wilzewski et al.3 where this was done for SO2, NH3, HF, HCl, OCS and C2H2. The molecules investigated in this work were CO2, N2O, H2CO, HCN and H2S. Line-broadening coefficients, line shifts and temperature-dependence exponents for transitions of these molecules perturbed by H2, CO2 and He have been assembled from available peer-reviewed experimental and theoretical sources. The data was evaluated and the database was populated with these data and their extrapolations/interpolations using semi-empirical models that were developed to this end.Acknowledgements: Financial support from NASA PDART grant NNX16AG51G and the Smithsonian Astrophysical Observatory Latino Initiative Program from the Latino Initiatives Pool, administered by the Smithsonian Latino Center is gratefully acknowledged.References: 1. HITRAN online http://hitran.org/2. Gordon, I.E., Rothman, L.S., Hill, C., Kochanov, R.V., Tan, Y., et al., 2017. The HITRAN2016 Molecular Spectroscopic Database. J. Quant. Spectrosc. Radiat. Transf. doi:10.1016/j.jqsrt.2017.06.0383. Wilzewski, J.S., Gordon, I.E., Kochanov, R. V., Hill, C., Rothman, L.S., 2016. H2, He, and CO2 line-broadening coefficients, pressure shifts and temperature-dependence exponents for the HITRAN database. Part 1: SO2, NH3, HF, HCl, OCS and C2H2. J. Quant. Spectrosc. Radiat

  8. Targeting sodium channels in cardiac arrhythmia

    NARCIS (Netherlands)

    Remme, Carol Ann; Wilde, Arthur A. M.

    2014-01-01

    Cardiac voltage-gated sodium channels are responsible for proper electrical conduction in the heart. During acquired pathological conditions and inherited sodium channelopathies, altered sodium channel function causes conduction disturbances and ventricular arrhythmias. Although the clinical,

  9. Matagorda Ship Channel, Texas: Jetty Stability Study

    National Research Council Canada - National Science Library

    Kraus, Nicholas C; Lin, Lihwa; Batten, Brian K; Brown, Gary L

    2006-01-01

    .... The current has produced a large area of scour on the bay side of the inlet adjacent to the west jetty, and vessels encountering a strong along-channel and cross-channel current at the entrance...

  10. Quantum Correlations Evolution Asymmetry in Quantum Channels

    International Nuclear Information System (INIS)

    Li Meng; Huang Yun-Feng; Guo Guang-Can

    2017-01-01

    It was demonstrated that the entanglement evolution of a specially designed quantum state in the bistochastic channel is asymmetric. In this work, we generalize the study of the quantum correlations, including entanglement and quantum discord, evolution asymmetry to various quantum channels. We found that the asymmetry of entanglement and quantum discord only occurs in some special quantum channels, and the behavior of the entanglement evolution may be quite different from the behavior of the quantum discord evolution. To quantum entanglement, in some channels it decreases monotonously with the increase of the quantum channel intensity. In some other channels, when we increase the intensity of the quantum channel, it decreases at first, then keeps zero for some time, and then rises up. To quantum discord, the evolution becomes more complex and you may find that it evolutes unsmoothly at some points. These results illustrate the strong dependence of the quantum correlations evolution on the property of the quantum channels. (paper)

  11. Coastal Maintained Channels in US waters

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This layer shows coastal channels and waterways that are maintained and surveyed by the U.S. Army Corps of Engineers (USACE). These channels are necessary...

  12. Channel Estimation in DCT-Based OFDM

    Science.gov (United States)

    Wang, Yulin; Zhang, Gengxin; Xie, Zhidong; Hu, Jing

    2014-01-01

    This paper derives the channel estimation of a discrete cosine transform- (DCT-) based orthogonal frequency-division multiplexing (OFDM) system over a frequency-selective multipath fading channel. Channel estimation has been proved to improve system throughput and performance by allowing for coherent demodulation. Pilot-aided methods are traditionally used to learn the channel response. Least square (LS) and mean square error estimators (MMSE) are investigated. We also study a compressed sensing (CS) based channel estimation, which takes the sparse property of wireless channel into account. Simulation results have shown that the CS based channel estimation is expected to have better performance than LS. However MMSE can achieve optimal performance because of prior knowledge of the channel statistic. PMID:24757439

  13. Channel CAT: A Tactical Link Analysis Tool

    National Research Council Canada - National Science Library

    Coleman, Michael

    1997-01-01

    .... This thesis produced an analysis tool, the Channel Capacity Analysis Tool (Channel CAT), designed to provide an automated tool for the analysis of design decisions in developing client-server software...

  14. Investigation Of Information Sources And Communication Channels ...

    African Journals Online (AJOL)

    Investigation Of Information Sources And Communication Channels In Ipm Rice ... the information accessibility of farmer groups seems as empowerment strategy. ... information sources and communication channels, in order of importance, ...

  15. The KATP channel in migraine pathophysiology

    DEFF Research Database (Denmark)

    Al-Karagholi, Mohammad Al-Mahdi; Hansen, Jakob Møller; Severinsen, Johanne

    2017-01-01

    BACKGROUND: To review the distribution and function of KATP channels, describe the use of KATP channels openers in clinical trials and make the case that these channels may play a role in headache and migraine. DISCUSSION: KATP channels are widely present in the trigeminovascular system and play...... an important role in the regulation of tone in cerebral and meningeal arteries. Clinical trials using synthetic KATP channel openers report headache as a prevalent-side effect in non-migraine sufferers, indicating that KATP channel opening may cause headache, possibly due to vascular mechanisms. Whether KATP...... channel openers can provoke migraine in migraine sufferers is not known. CONCLUSION: We suggest that KATP channels may play an important role in migraine pathogenesis and could be a potential novel therapeutic anti-migraine target....

  16. Optimization of Communication in Noisy Quantum Channels

    National Research Council Canada - National Science Library

    Ruskai, Mary

    2002-01-01

    .... This project has been concerned with the analysis of mathematical models of noise for qubit channels, with the capacity of qubit channels used to transmit classical information, and with exchange...

  17. Four-channel delay generator model 5740

    International Nuclear Information System (INIS)

    Baumatz, D.; Milner, M.

    1978-01-01

    The 4-channel delay generator model 5740 generates 4-pulse groups in independent channels. The device offers the possibility of controlling both the time intervals between the pulses of a group and the rate of generation of groups

  18. Channelling of flow through fractures in rock

    International Nuclear Information System (INIS)

    Bourke, P.J.

    1987-05-01

    A method of mapping the channelling of flow in rock fractures formed by contacts between rock faces and of measuring the effective apertures of channels has been developed. Some typical results are given. (author)

  19. Consolidation equipment for irradiated nuclear fuel channels

    International Nuclear Information System (INIS)

    Taguchi, M.; Komatsu, Y.; Ose, T.

    1989-01-01

    The authors have developed and put into use a new type of mechanical consolidation equipment for irradiated nuclear fuel channels. This includes round-slice cutting of the top 100mm of the fuel channel with a guillotine cutter, and press cutting of the two corners of the remaining length of the fuel channel. Four guillotine blades work in combination with receiving blades arranged inside the fuel channel to cut the top 100mm, including the clips and spacers, of the fuel channel into a round slice. A press assembled in the consolidation equipment then presses the slice to achieve volume reduction. The press cutting operation uses two press cutting blades arranged inside the fuel channel and the receiving blades outside the fuel channel. The remaining length of fuel channel is cut off into L-shaped pieces by press cutting. This consolidation equipment is highly efficient because the round-slice cutting, pressing, and press cutting are all achieved by one unit

  20. Channeling experiments at IPNE Cyclotron

    Energy Technology Data Exchange (ETDEWEB)

    Constantin, F; Dumitru, M; Ivan, A [Cyclotron Laboratory, Institute of Atomic Physics, Institute of Physics and Nuclear Engineering, R-76900 Bucharest, P.O.Box MG-6, (Romania)

    1992-01-01

    Channeling experiments have been performed at the I.P.N.E Cyclotron using a 3 MeV alpha beam. A slide system cut the beam up to 5 minutes spatial resolution with a maximum 60 nA beam current on the target. The two-axis goniometer, fully computer-controlled, moves the target, a silicon wafer, with 2.5 minute resolution, while an alpha particle sensitive solid state detector, monitors the backscattered particle fluence. In the first stage, channeling appears to be a simple, fast and reliable method for precise monocrystal orientation. A reduction of the host yield by a factor of two allowed impurities and defects to be studied. (Author).

  1. Thermoelectricity in Heterogeneous Nanofluidic Channels.

    Science.gov (United States)

    Li, Long; Wang, Qinggong

    2018-05-01

    Ionic fluids are essential to energy conversion, water desalination, drug delivery, and lab-on-a-chip devices. Ionic transport in nanoscale confinements and complex physical fields still remain elusive. Here, a nanofluidic system is developed using nanochannels of heterogeneous surface properties to investigate transport properties of ions under different temperatures. Steady ionic currents are observed under symmetric temperature gradients, which is equivalent to generating electricity using waste heat (e.g., electronic chips and solar panels). The currents increase linearly with temperature gradient and nonlinearly with channel size. Contributions to ion motion from temperatures and channel properties are evaluated for this phenomenon. The findings provide insights into the study of confined ionic fluids in multiphysical fields, and suggest applications in thermal energy conversion, temperature sensors, and chip-level thermal management. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Improving Channel Coordination Through Franchising

    OpenAIRE

    Rajiv Lal

    1990-01-01

    In this paper, we explore the role of franchising arrangements in improving coordination between channel members. In particular we focus on two elements of the franchising contract, namely, the royalty structure and the monitoring technology. We begin with a simple analysis where a manufacturer distributes its product through a retailer and the retail demand is affected by the retail price and the service provided by the retailer. In this context we show that neither royalty payments nor moni...

  3. Digital Multi Channel Analyzer Enhancement

    International Nuclear Information System (INIS)

    Gonen, E.; Marcus, E.; Wengrowicz, U.; Beck, A.; Nir, J.; Sheinfeld, M.; Broide, A.; Tirosh, D.

    2002-01-01

    A cement analyzing system based on radiation spectroscopy had been developed [1], using novel digital approach for real-time, high-throughput and low-cost Multi Channel Analyzer. The performance of the developed system had a severe problem: the resulted spectrum suffered from lack of smoothness, it was very noisy and full of spikes and surges, therefore it was impossible to use this spectrum for analyzing the cement substance. This paper describes the work carried out to improve the system performance

  4. Trafficking of neuronal calcium channels

    Czech Academy of Sciences Publication Activity Database

    Weiss, Norbert; Zamponi, G. W.

    2017-01-01

    Roč. 1, č. 1 (2017), č. článku NS20160003. ISSN 2059-6553 R&D Projects: GA ČR GA15-13556S; GA MŠk 7AMB15FR015 Institutional support: RVO:61388963 Keywords : calcium channel * neuron * trafficing Subject RIV: ED - Physiology OBOR OECD: Physiology (including cytology) http://www.neuronalsignaling.org/content/1/1/NS20160003

  5. Spark channel propagation in a microbubble liquid

    Energy Technology Data Exchange (ETDEWEB)

    Panov, V. A.; Vasilyak, L. M., E-mail: vasilyak@ihed.ras.ru; Vetchinin, S. P.; Pecherkin, V. Ya.; Son, E. E. [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)

    2016-11-15

    Experimental study on the development of the spark channel from the anode needle under pulsed electrical breakdown of isopropyl alcohol solution in water with air microbubbles has been performed. The presence of the microbubbles increases the velocity of the spark channel propagation and increases the current in the discharge gap circuit. The observed rate of spark channel propagation in microbubble liquid ranges from 4 to 12 m/s, indicating the thermal mechanism of the spark channel development in a microbubble liquid.

  6. Assessing the Consequences of a Channel Switch

    OpenAIRE

    Xinlei (Jack) Chen; George John; Om Narasimhan

    2008-01-01

    Switching marketing channels is an expensive and sticky decision. While a number of theories suggest efficiency and strategic differences between channels, there is virtually no work on combining these ideas into an empirically workable methodology to assess the impact of a channel switch. In this study, we undertake to close this gap with an empirical study of the sports drink market, featuring competing producers and heterogeneous channels. We estimate demand and cost parameters for a numbe...

  7. Degenerate RFID Channel Modeling for Positioning Applications

    Directory of Open Access Journals (Sweden)

    A. Povalac

    2012-12-01

    Full Text Available This paper introduces the theory of channel modeling for positioning applications in UHF RFID. It explains basic parameters for channel characterization from both the narrowband and wideband point of view. More details are given about ranging and direction finding. Finally, several positioning scenarios are analyzed with developed channel models. All the described models use a degenerate channel, i.e. combined signal propagation from the transmitter to the tag and from the tag to the receiver.

  8. Channel CAT: A Tactical Link Analysis Tool

    Science.gov (United States)

    1997-09-01

    NAVAL POSTGRADUATE SCHOOL Monterey, California THESIS CHANNEL CAT : A TACTICAL LINK ANALYSIS TOOL by Michael Glenn Coleman September 1997 Thesis...REPORT TYPE AND DATES COVERED September 1997 Master’s Thesis 4. TITLE AND SUBTITLE CHANNEL CAT : A TACTICAL LINK ANALYSIS TOOL 5. FUNDING NUMBERS 6...tool, the Channel Capacity Analysis Tool (Channel CAT ), designed to provide an automated tool for the anlysis of design decisions in developing client

  9. Optimal super dense coding over memory channels

    OpenAIRE

    Shadman, Zahra; Kampermann, Hermann; Macchiavello, Chiara; Bruß, Dagmar

    2011-01-01

    We study the super dense coding capacity in the presence of quantum channels with correlated noise. We investigate both the cases of unitary and non-unitary encoding. Pauli channels for arbitrary dimensions are treated explicitly. The super dense coding capacity for some special channels and resource states is derived for unitary encoding. We also provide an example of a memory channel where non-unitary encoding leads to an improvement in the super dense coding capacity.

  10. Radio propagation measurement and channel modelling

    CERN Document Server

    Salous, Sana

    2013-01-01

    While there are numerous books describing modern wireless communication systems that contain overviews of radio propagation and radio channel modelling, there are none that contain detailed information on the design, implementation and calibration of radio channel measurement equipment, the planning of experiments and the in depth analysis of measured data. The book would begin with an explanation of the fundamentals of radio wave propagation and progress through a series of topics, including the measurement of radio channel characteristics, radio channel sounders, measurement strategies

  11. Spin chain model for correlated quantum channels

    Energy Technology Data Exchange (ETDEWEB)

    Rossini, Davide [International School for Advanced Studies SISSA/ISAS, via Beirut 2-4, I-34014 Trieste (Italy); Giovannetti, Vittorio; Montangero, Simone [NEST-CNR-INFM and Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa (Italy)], E-mail: monta@sns.it

    2008-11-15

    We analyze the quality of the quantum information transmission along a correlated quantum channel by studying the average fidelity between input and output states and the average output purity, giving bounds for the entropy of the channel. Noise correlations in the channel are modeled by the coupling of each channel use with an element of a one-dimensional interacting quantum spin chain. Criticality of the environment chain is seen to emerge in the changes of the fidelity and of the purity.

  12. Subunit Stoichiometry of Human Muscle Chloride Channels

    OpenAIRE

    Fahlke, Christoph; Knittle, Timothy; Gurnett, Christina A.; Campbell, Kevin P.; George, Alfred L.

    1997-01-01

    Voltage-gated Cl? channels belonging to the ClC family appear to function as homomultimers, but the number of subunits needed to form a functional channel is controversial. To determine subunit stoichiometry, we constructed dimeric human skeletal muscle Cl? channels in which one subunit was tagged by a mutation (D136G) that causes profound changes in voltage-dependent gating. Sucrose-density gradient centrifugation experiments indicate that both monomeric and dimeric hClC-1 channels in their ...

  13. Hollow core plasma channel generation

    International Nuclear Information System (INIS)

    Quast, Heinrich Martin

    2018-03-01

    The use of a hollow plasma channel in plasma-based acceleration has beneficial properties for the acceleration of electron and positron bunches. In the scope of the FLASHForward facility at DESY, the generation of such a plasma structure is examined. Therefore, the generation of a ring-shaped laser intensity profile with different techniques is analyzed. From the obtained intensity profiles the electron density of a hollow plasma channel is simulated in the focal region. Different parameters are scanned to understand their influence on the electron density distribution - an important parameter being, for example, the radius of the central region of the channel. In addition to the simulations, experiments are presented, during which a laser pulse is transformed into a hollow beam with a spiral phase plate. Subsequently, it forms a plasma during the interaction with hydrogen, where the plasma is imaged with interferometry. For energies above 0.9 mJ a hollow plasma structure can be observed at the location of first plasma formation.

  14. Local Transfer Coefficient, Smooth Channel

    Directory of Open Access Journals (Sweden)

    R. T. Kukreja

    1998-01-01

    Full Text Available Naphthalene sublimation technique and the heat/mass transfer analogy are used to determine the detailed local heat/mass transfer distributions on the leading and trailing walls of a twopass square channel with smooth walls that rotates about a perpendicular axis. Since the variation of density is small in the flow through the channel, buoyancy effect is negligible. Results show that, in both the stationary and rotating channel cases, very large spanwise variations of the mass transfer exist in he turn and in the region immediately downstream of the turn in the second straight pass. In the first straight pass, the rotation-induced Coriolis forces reduce the mass transfer on the leading wall and increase the mass transfer on the trailing wall. In the turn, rotation significantly increases the mass transfer on the leading wall, especially in the upstream half of the turn. Rotation also increases the mass transfer on the trailing wall, more in the downstream half of the turn than in the upstream half of the turn. Immediately downstream of the turn, rotation causes the mass transfer to be much higher on the trailing wall near the downstream corner of the tip of the inner wall than on the opposite leading wall. The mass transfer in the second pass is higher on the leading wall than on the trailing wall. A slower flow causes higher mass transfer enhancement in the turn on both the leading and trailing walls.

  15. Study of material properties using channeling radiation

    International Nuclear Information System (INIS)

    Pantell, R.H.; Kephart, J.O.; Klein, R.K.; Park, H.; Berman, B.L.; Datz, S.

    1986-01-01

    A possible application for channeling radiation is for investigating the properties of crystals in which the channeling occurs. In this paper we present some general considerations concerning channeling radiation as a measurement technique, and then we proceed to describe several specific examples

  16. Square root approximation to the poisson channel

    NARCIS (Netherlands)

    Tsiatmas, A.; Willems, F.M.J.; Baggen, C.P.M.J.

    2013-01-01

    Starting from the Poisson model we present a channel model for optical communications, called the Square Root (SR) Channel, in which the noise is additive Gaussian with constant variance. Initially, we prove that for large peak or average power, the transmission rate of a Poisson Channel when coding

  17. The Marketing Channels of China Auto Industry

    Institute of Scientific and Technical Information of China (English)

    our reporter

    2001-01-01

    <正> After the 1990’s, the multi-channel structure of sales has still existed although the market mechanism is playing a main role in Chinese auto marketing circulation. Now, the channels of automobile marketing in China are as follows: 1. Manufacturer-established marketing channels

  18. Molecular determinants in TRPV5 channel assembly.

    NARCIS (Netherlands)

    Chang, Q.; Gyftogianni, E.; Graaf, K.F.J. van de; Hoefs, S.J.G.; Weidema, A.F.; Bindels, R.J.M.; Hoenderop, J.G.J.

    2004-01-01

    The epithelial Ca(2+) channels TRPV5 and TRPV6 mediate the Ca(2+) influx in 1,25-dihydroxyvitamin D(3)-responsive epithelia and are therefore essential in the maintenance of the body Ca(2+) balance. These Ca(2+) channels assemble in (hetero)tetrameric channel complexes with different functional

  19. Molecular determinants in TRPV5 channel assembly

    NARCIS (Netherlands)

    Chang, Qing; Gyftogianni, Emmanouela; van de Graaf, Stan F. J.; Hoefs, Susan; Weidema, Freek A.; Bindels, René J. M.; Hoenderop, Joost G. J.

    2004-01-01

    The epithelial Ca(2+) channels TRPV5 and TRPV6 mediate the Ca(2+) influx in 1,25-dihydroxyvitamin D(3)-responsive epithelia and are therefore essential in the maintenance of the body Ca(2+) balance. These Ca(2+) channels assemble in (hetero)tetrameric channel complexes with different functional

  20. Electronic Commerce and Retail Channel Substitution

    NARCIS (Netherlands)

    M.C.W. Janssen (Maarten); R. van der Noll

    2002-01-01

    textabstractWe analyze a market where firms compete in a conventional and an electronic retail channel. Consumers easily compare prices online, but some incur purchase uncertainties on the online channel. We investigate the market shares of the two retail channels and the prices that are charged. We

  1. 47 CFR 95.29 - Channels available.

    Science.gov (United States)

    2010-10-01

    ... with no more than 5 watts ERP. (g) Fixed stations in GMRS systems authorized before March 18, 1968... transmission of another GMRS station on a different channel or channels), the licensee of the GMRS system must... GMRS system from the following 462 MHz channels: 462.5500, 462.5750, 462.6000, 462.6250, 462.6500, 462...

  2. Mechanosensitive Channels: In Touch with Piezo

    OpenAIRE

    Xiao, Rui; Xu, X.Z. Shawn

    2010-01-01

    Mechanosensory transduction underlies touch, hearing and proprioception and requires mechanosensitive channels that are directly gated by forces; however, the molecular identities of these channels remain largely elusive. A new study has identified Piezo1 and Piezo2 as a novel class of mechanosensitive channels.

  3. Language Planning, Channel Management, and ESP.

    Science.gov (United States)

    Kennedy, Chris

    Channel management, a concept developed in marketing to refer to the process by which a product is moved from production to consumption, uses a channel of distribution operating at several levels, each responsible for one or more of the activities of moving the product forward to the consumer. The function of channel management is to select the…

  4. Animal Model Selection for Inhalational HCN Exposure

    Science.gov (United States)

    2016-08-01

    effects. Following acute inhalation exposure in humans and animals, cyanide is found in the lung, heart, blood , kidneys, and brain (Ballantyne, 1983...Pritchard, 2007). Other direct or secondary effects associated with CN are reacting with the ferric and carbonyl group of enzymes (e.g. catalase...mechanisms occurs before myocardial depression. Clinically, an initial period of bradycardia and hypertension may occur, followed by hypotension with reflex

  5. Separation of Particles in Channels Rotary Engine

    Directory of Open Access Journals (Sweden)

    Zyatikov Pavel

    2015-01-01

    Full Text Available The article considers the separation of particles in channels with different relative length. It is shown that the intensity of turbulence at the inlet section of the channel varies considerably in its length. The dependence of the turbulence damping along the channel expressing by fraction of the distance is shown. The ratio of the particle separation efficiency out the gas flow in the rotor channel is defined. The values of particle separation efficiency in the channel for the angle α=π/4 in turbulent aerosol flow is shows, including without mixing the particles.

  6. CHANNEL EVOLUTION IN MODIFIED ALLUVIAL STREAMS.

    Science.gov (United States)

    Simon, Andrew; Hupp, Cliff R.

    1987-01-01

    This study (a) assesses the channel changes and network trends of bed level response after modifications between 1959 and 1972 of alluvial channels in western Tennessee and (b) develops a conceptual model of bank slope development to qualitatively assess bank stability and potential channel widening. A six-step, semiquantitative model of channel evolution in disturbed channels was developed by quantifying bed level trends and recognizing qualitative stages of bank slope development. Development of the bank profile is defined in terms of three dynamic and observable surfaces: (a) vertical face (70 to 90 degrees), (b) upper bank (25 to 50 degrees), and (c) slough line (20 to 25 degrees).

  7. Modulation of ERG channels by XE991

    DEFF Research Database (Denmark)

    Elmedyb, Pernille; Calloe, Kirstine; Schmitt, Nicole

    2007-01-01

    In neuronal tissue, KCNQ2-5 channels conduct the physiologically important M-current. In some neurones, the M-current may in addition be conducted partly by ERG potassium channels, which have widely overlapping expression with the KCNQ channel subunits. XE991 and linopiridine are known to be stan......In neuronal tissue, KCNQ2-5 channels conduct the physiologically important M-current. In some neurones, the M-current may in addition be conducted partly by ERG potassium channels, which have widely overlapping expression with the KCNQ channel subunits. XE991 and linopiridine are known...... to be standard KCNQ potassium channel blockers. These compounds have been used in many different tissues as specific pharmacological tools to discern native currents conducted by KCNQ channels from other potassium currents. In this article, we demonstrate that ERG1-2 channels are also reversibly inhibited by XE......991 in the micromolar range (EC(50) 107 microM for ERG1). The effect has been characterized in Xenopus laevis oocytes expressing ERG1-2 and in the mammalian HEK293 cell line stably expressing ERG1 channels. The IC(50) values for block of KCNQ channels by XE991 range 1-65 microM. In conclusion, great...

  8. Plasma channels for electron beam transport

    International Nuclear Information System (INIS)

    Schneider, R.F.; Smith, J.R.; Moffatt, M.E.; Nguyen, K.T.; Uhm, H.S.

    1988-01-01

    In recent years, there has been much interest in transport of intense relativistic electron beams using plasma channels. These channels are formed by either: ionization of an organic gas by UV photoionization or electron impact ionization of a low pressure gas utilizing a low energy (typically several hundred volts) electron gun. The second method is discussed here. As their electron gun, the authors used a 12 volt lightbulb filament which is biased to -400 volts with respect to the grounded 15 cm diameter drift tube. The electrons emitted from the filament are confined by an axial magnetic field of --100 Gauss to create a plasma channel which is less than 1 cm in radius. The channel density has been determined with Langmuir probes and the resulting line densities were found to be 10 11 to 10 12 per cm. When a multi-kiloamp electron beam is injected onto this channel, the beam space charge will eject the plasma electrons leaving the ions behind to charge neutralize the electron beam, hence allowing the beam to propagate. In this work, the authors performed experimental studies on the dynamics of the plasma channel. These include Langmuir probe measurements of a steady state (DC) channel, as well as time-resolved Langmuir probe studies of pulsed channels. In addition they performed experimental studies of beam propagation in these plasma channels. Specifically, they observed the behavior of current transport in these channels. Detailed results of beam transport and channel studies are presented

  9. Post-Translational Modifications of TRP Channels

    Directory of Open Access Journals (Sweden)

    Olaf Voolstra

    2014-04-01

    Full Text Available Transient receptor potential (TRP channels constitute an ancient family of cation channels that have been found in many eukaryotic organisms from yeast to human. TRP channels exert a multitude of physiological functions ranging from Ca2+ homeostasis in the kidney to pain reception and vision. These channels are activated by a wide range of stimuli and undergo covalent post-translational modifications that affect and modulate their subcellular targeting, their biophysical properties, or channel gating. These modifications include N-linked glycosylation, protein phosphorylation, and covalent attachment of chemicals that reversibly bind to specific cysteine residues. The latter modification represents an unusual activation mechanism of ligand-gated ion channels that is in contrast to the lock-and-key paradigm of receptor activation by its agonists. In this review, we summarize the post-translational modifications identified on TRP channels and, when available, explain their physiological role.

  10. Quantum capacity of Pauli channels with memory

    International Nuclear Information System (INIS)

    Huang Peng; He Guangqiang; Lu Yuan; Zeng Guihua

    2011-01-01

    The amount of coherent quantum information that can be reliably transmitted down the memory Pauli channels with Markovian correlated noise is investigated. Two methods for evaluating the quantum capacity of the memory Pauli channels are proposed to try to trace the memory effect on the transmissions of quantum information. We show that the evaluation of quantum capacity can be reduced to the calculation of the initial memory state of each successive transmission. Furthermore, we derive quantum capacities of the memory phase flip channel, bit flip channel and bit-phase flip channel. Also, a lower bound of the quantum capacity of the memory depolarizing channel is obtained. An increase of the degree of memory of the channels has a positive effect on the increase of their quantum capacities.

  11. Effects of dislocations on electron channeling

    International Nuclear Information System (INIS)

    George, Juby; Pathak, A P

    2009-01-01

    The phenomenon of electron channeling in a crystal affected by dislocations is considered. Earlier we had considered the quantum aspects of the positron channeling in a crystal bent by dislocations where the effects of longitudinal motion of the particle were also considered along with the transverse motion. In this paper, the effective potential for the electron case is found for the two regions of dislocation-affected channel. There is considerable shift in the potential minima due to dislocations. The frequency and the corresponding spectrum of the channeling radiation due to electrons channeling through the perfect channel and the two regions of dislocation-affected channels are calculated. The spectral distribution of radiation intensity changes with the parameters of dislocation. The continuity of wavefunctions and their derivatives is used at the three boundaries and the reflection and transmission coefficients are found using these boundary conditions in the same way as in the positron case.

  12. Channel selection for automatic seizure detection

    DEFF Research Database (Denmark)

    Duun-Henriksen, Jonas; Kjaer, Troels Wesenberg; Madsen, Rasmus Elsborg

    2012-01-01

    Objective: To investigate the performance of epileptic seizure detection using only a few of the recorded EEG channels and the ability of software to select these channels compared with a neurophysiologist. Methods: Fifty-nine seizures and 1419 h of interictal EEG are used for training and testing...... of an automatic channel selection method. The characteristics of the seizures are extracted by the use of a wavelet analysis and classified by a support vector machine. The best channel selection method is based upon maximum variance during the seizure. Results: Using only three channels, a seizure detection...... sensitivity of 96% and a false detection rate of 0.14/h were obtained. This corresponds to the performance obtained when channels are selected through visual inspection by a clinical neurophysiologist, and constitutes a 4% improvement in sensitivity compared to seizure detection using channels recorded...

  13. On luminescence bleaching of tidal channel sediments

    DEFF Research Database (Denmark)

    Fruergaard, Mikkel; Pejrup, Morten; Murray, Andrew S.

    2015-01-01

    We investigate the processes responsible for bleaching of the quartz OSL signal from tidal channel sediment. Tidal dynamics are expected to play an important role for complete bleaching of tidal sediments. However, no studies have examined the amount of reworking occurring in tidal channels...... and on tidal flats due to the mixing caused by currents and waves. We apply bed level data to evaluate the amount of vertical sediment reworking in modern tidal channels and at a tidal flat. Cycles of deposition and erosion are measured with a bed level sensor, and the results show that gross sedimentation...... was several times higher than net sedimentation. We propose that tidal channel sediment is bleached either on the tidal flat before it is transported to the tidal channels and incorporated in channel-fill successions or, alternatively, on the shallow intertidal part of the channel banks. Based...

  14. Anion channels: master switches of stress responses.

    Science.gov (United States)

    Roelfsema, M Rob G; Hedrich, Rainer; Geiger, Dietmar

    2012-04-01

    During stress, plant cells activate anion channels and trigger the release of anions across the plasma membrane. Recently, two new gene families have been identified that encode major groups of anion channels. The SLAC/SLAH channels are characterized by slow voltage-dependent activation (S-type), whereas ALMT genes encode rapid-activating channels (R-type). Both S- and R-type channels are stimulated in guard cells by the stress hormone ABA, which leads to stomatal closure. Besides their role in ABA-dependent stomatal movement, anion channels are also activated by biotic stress factors such as microbe-associated molecular patterns (MAMPs). Given that anion channels occur throughout the plant kingdom, they are likely to serve a general function as master switches of stress responses. Copyright © 2012 Elsevier Ltd. All rights reserved.

  15. Quantum channels with a finite memory

    International Nuclear Information System (INIS)

    Bowen, Garry; Mancini, Stefano

    2004-01-01

    In this paper we study quantum communication channels with correlated noise effects, i.e., quantum channels with memory. We derive a model for correlated noise channels that includes a channel memory state. We examine the case where the memory is finite, and derive bounds on the classical and quantum capacities. For the entanglement-assisted and unassisted classical capacities it is shown that these bounds are attainable for certain classes of channel. Also, we show that the structure of any finite-memory state is unimportant in the asymptotic limit, and specifically, for a perfect finite-memory channel where no information is lost to the environment, achieving the upper bound implies that the channel is asymptotically noiseless

  16. Multicarrier chaotic communications in multipath fading channels without channel estimation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Shilian, E-mail: wangsl@nudt.edu.cn; Zhang, Zhili [College of Electrical Science and Engineering, National University of Defense Technology, Changsha, 410073, P R China (China)

    2015-01-15

    A multi-carrier chaotic shift keying(MC-CSK) communication scheme with low probability of interception(LPI) is proposed in this article. We apply chaotic spreading sequences in the frequency domain, mapping a different chip of a chaotic sequence to an individual orthogonal frequency division multiplexing(OFDM) subcarrier. In each block size of $M$ OFDM symbols, we use one pilot OFDM symbol inserted time-spaced in all-frequency to transmit the reference chaotic signal and use the other M-1 OFDM symbols to transmit the information-bearing signals each spreaded by the reference chaotic signal. At the receiver, we construct a differential detector after DFT and recover the information bits from the correlations between the pilot OFDM symbol and the other M-1 OFDM symbols in each block size of M. Performance analysis and computer simulations show that the MC-CSK outperforms differential chaos shift keying(DCSK) in AWGN channels with high bandwidth efficiency for the block size of M=2 and that the MC-CSK exploits effectively the frequent diversity of the multipath channel.

  17. Multicarrier chaotic communications in multipath fading channels without channel estimation

    Directory of Open Access Journals (Sweden)

    Shilian Wang

    2015-01-01

    Full Text Available A multi-carrier chaotic shift keying(MC-CSK communication scheme with low probability of interception(LPI is proposed in this article. We apply chaotic spreading sequences in the frequency domain, mapping a different chip of a chaotic sequence to an individual orthogonal frequency division multiplexing(OFDM subcarrier. In each block size of $M$ OFDM symbols, we use one pilot OFDM symbol inserted time-spaced in all-frequency to transmit the reference chaotic signal and use the other M-1 OFDM symbols to transmit the information-bearing signals each spreaded by the reference chaotic signal. At the receiver, we construct a differential detector after DFT and recover the information bits from the correlations between the pilot OFDM symbol and the other M-1 OFDM symbols in each block size of M. Performance analysis and computer simulations show that the MC-CSK outperforms differential chaos shift keying(DCSK in AWGN channels with high bandwidth efficiency for the block size of M=2 and that the MC-CSK exploits effectively the frequent diversity of the multipath channel.

  18. Precipitation patterns during channel flow

    Science.gov (United States)

    Jamtveit, B.; Hawkins, C.; Benning, L. G.; Meier, D.; Hammer, O.; Angheluta, L.

    2013-12-01

    Mineral precipitation during channelized fluid flow is widespread in a wide variety of geological systems. It is also a common and costly phenomenon in many industrial processes that involve fluid flow in pipelines. It is often referred to as scale formation and encountered in a large number of industries, including paper production, chemical manufacturing, cement operations, food processing, as well as non-renewable (i.e. oil and gas) and renewable (i.e. geothermal) energy production. We have studied the incipient stages of growth of amorphous silica on steel plates emplaced into the central areas of the ca. 1 meter in diameter sized pipelines used at the hydrothermal power plant at Hellisheidi, Iceland (with a capacity of ca 300 MW electricity and 100 MW hot water). Silica precipitation takes place over a period of ca. 2 months at approximately 120°C and a flow rate around 1 m/s. The growth produces asymmetric ca. 1mm high dendritic structures ';leaning' towards the incoming fluid flow. A novel phase-field model combined with the lattice Boltzmann method is introduced to study how the growth morphologies vary under different hydrodynamic conditions, including non-laminar systems with turbulent mixing. The model accurately predicts the observed morphologies and is directly relevant for understanding the more general problem of precipitation influenced by turbulent mixing during flow in channels with rough walls and even for porous flow. Reference: Hawkins, C., Angheluta, L., Hammer, Ø., and Jamtveit, B., Precipitation dendrites in channel flow. Europhysics Letters, 102, 54001

  19. Multiple channel programmable coincidence counter

    Science.gov (United States)

    Arnone, Gaetano J.

    1990-01-01

    A programmable digital coincidence counter having multiple channels and featuring minimal dead time. Neutron detectors supply electrical pulses to a synchronizing circuit which in turn inputs derandomized pulses to an adding circuit. A random access memory circuit connected as a programmable length shift register receives and shifts the sum of the pulses, and outputs to a serializer. A counter is input by the adding circuit and downcounted by the seralizer, one pulse at a time. The decoded contents of the counter after each decrement is output to scalers.

  20. Mechanosensitive gating of Kv channels.

    Directory of Open Access Journals (Sweden)

    Catherine E Morris

    Full Text Available K-selective voltage-gated channels (Kv are multi-conformation bilayer-embedded proteins whose mechanosensitive (MS Popen(V implies that at least one conformational transition requires the restructuring of the channel-bilayer interface. Unlike Morris and colleagues, who attributed MS-Kv responses to a cooperative V-dependent closed-closed expansion↔compaction transition near the open state, Mackinnon and colleagues invoke expansion during a V-independent closed↔open transition. With increasing membrane tension, they suggest, the closed↔open equilibrium constant, L, can increase >100-fold, thereby taking steady-state Popen from 0→1; "exquisite sensitivity to small…mechanical perturbations", they state, makes a Kv "as much a mechanosensitive…as…a voltage-dependent channel". Devised to explain successive gK(V curves in excised patches where tension spontaneously increased until lysis, their L-based model falters in part because of an overlooked IK feature; with recovery from slow inactivation factored in, their g(V datasets are fully explained by the earlier model (a MS V-dependent closed-closed transition, invariant L≥4. An L-based MS-Kv predicts neither known Kv time courses nor the distinctive MS responses of Kv-ILT. It predicts Kv densities (hence gating charge per V-sensor several-fold different from established values. If opening depended on elevated tension (L-based model, standard gK(V operation would be compromised by animal cells' membrane flaccidity. A MS V-dependent transition is, by contrast, unproblematic on all counts. Since these issues bear directly on recent findings that mechanically-modulated Kv channels subtly tune pain-related excitability in peripheral mechanoreceptor neurons we undertook excitability modeling (evoked action potentials. Kvs with MS V-dependent closed-closed transitions produce nuanced mechanically-modulated excitability whereas an L-based MS-Kv yields extreme, possibly excessive

  1. Use of navigation channels by Lake Sturgeon: Does channelization increase vulnerability of fish to ship strikes?

    Directory of Open Access Journals (Sweden)

    Darryl W Hondorp

    Full Text Available Channelization for navigation and flood control has altered the hydrology and bathymetry of many large rivers with unknown consequences for fish species that undergo riverine migrations. In this study, we investigated whether altered flow distributions and bathymetry associated with channelization attracted migrating Lake Sturgeon (Acipenser fulvescens into commercial navigation channels, potentially increasing their exposure to ship strikes. To address this question, we quantified and compared Lake Sturgeon selection for navigation channels vs. alternative pathways in two multi-channel rivers differentially affected by channelization, but free of barriers to sturgeon movement. Acoustic telemetry was used to quantify Lake Sturgeon movements. Under the assumption that Lake Sturgeon navigate by following primary flow paths, acoustic-tagged Lake Sturgeon in the more-channelized lower Detroit River were expected to choose navigation channels over alternative pathways and to exhibit greater selection for navigation channels than conspecifics in the less-channelized lower St. Clair River. Consistent with these predictions, acoustic-tagged Lake Sturgeon in the more-channelized lower Detroit River selected the higher-flow and deeper navigation channels over alternative migration pathways, whereas in the less-channelized lower St. Clair River, individuals primarily used pathways alternative to navigation channels. Lake Sturgeon selection for navigation channels as migratory pathways also was significantly higher in the more-channelized lower Detroit River than in the less-channelized lower St. Clair River. We speculated that use of navigation channels over alternative pathways would increase the spatial overlap of commercial vessels and migrating Lake Sturgeon, potentially enhancing their vulnerability to ship strikes. Results of our study thus demonstrated an association between channelization and the path use of migrating Lake Sturgeon that could prove

  2. ASIC3 channels in multimodal sensory perception.

    Science.gov (United States)

    Li, Wei-Guang; Xu, Tian-Le

    2011-01-19

    Acid-sensing ion channels (ASICs), which are members of the sodium-selective cation channels belonging to the epithelial sodium channel/degenerin (ENaC/DEG) family, act as membrane-bound receptors for extracellular protons as well as nonproton ligands. At least five ASIC subunits have been identified in mammalian neurons, which form both homotrimeric and heterotrimeric channels. The highly proton sensitive ASIC3 channels are predominantly distributed in peripheral sensory neurons, correlating with their roles in multimodal sensory perception, including nociception, mechanosensation, and chemosensation. Different from other ASIC subunit composing ion channels, ASIC3 channels can mediate a sustained window current in response to mild extracellular acidosis (pH 7.3-6.7), which often occurs accompanied by many sensory stimuli. Furthermore, recent evidence indicates that the sustained component of ASIC3 currents can be enhanced by nonproton ligands including the endogenous metabolite agmatine. In this review, we first summarize the growing body of evidence for the involvement of ASIC3 channels in multimodal sensory perception and then discuss the potential mechanisms underlying ASIC3 activation and mediation of sensory perception, with a special emphasis on its role in nociception. We conclude that ASIC3 activation and modulation by diverse sensory stimuli represent a new avenue for understanding the role of ASIC3 channels in sensory perception. Furthermore, the emerging implications of ASIC3 channels in multiple sensory dysfunctions including nociception allow the development of new pharmacotherapy.

  3. A Perspective on the MIMO Wiretap Channel

    KAUST Repository

    Oggier, Frederique; Hassibi, Babak

    2015-01-01

    A wiretap channel is a communication channel between a transmitter Alice and a legitimate receiver Bob, in the presence of an eavesdropper Eve. The goal of communication is to achieve reliability between Alice and Bob, but also confidentiality despite Eve’s presence. Wiretap channels are declined in all kinds of flavors, depending on the underlying channels used by the three players: discrete memoryless channels, additive Gaussian noise channels, or fading channels, to name a few. In this survey, we focus on the case where the three players use multiple-antenna channels with Gaussian noise to communicate. After summarizing known results for multiple-input–multiple-output (MIMO) channels, both in terms of achievable reliable data rate (capacity) and code design, we introduce the MIMO wiretap channel. We then state the MIMO wiretap capacity, summarize the idea of the proof(s) behind this result, and comment on the insights given by the proofs on the physical meaning of the secrecy capacity. We finally discuss design criteria for MIMO wiretap codes.

  4. VKCDB: Voltage-gated potassium channel database

    Directory of Open Access Journals (Sweden)

    Gallin Warren J

    2004-01-01

    Full Text Available Abstract Background The family of voltage-gated potassium channels comprises a functionally diverse group of membrane proteins. They help maintain and regulate the potassium ion-based component of the membrane potential and are thus central to many critical physiological processes. VKCDB (Voltage-gated potassium [K] Channel DataBase is a database of structural and functional data on these channels. It is designed as a resource for research on the molecular basis of voltage-gated potassium channel function. Description Voltage-gated potassium channel sequences were identified by using BLASTP to search GENBANK and SWISSPROT. Annotations for all voltage-gated potassium channels were selectively parsed and integrated into VKCDB. Electrophysiological and pharmacological data for the channels were collected from published journal articles. Transmembrane domain predictions by TMHMM and PHD are included for each VKCDB entry. Multiple sequence alignments of conserved domains of channels of the four Kv families and the KCNQ family are also included. Currently VKCDB contains 346 channel entries. It can be browsed and searched using a set of functionally relevant categories. Protein sequences can also be searched using a local BLAST engine. Conclusions VKCDB is a resource for comparative studies of voltage-gated potassium channels. The methods used to construct VKCDB are general; they can be used to create specialized databases for other protein families. VKCDB is accessible at http://vkcdb.biology.ualberta.ca.

  5. Mechanosensitive Piezo Channels in the Gastrointestinal Tract.

    Science.gov (United States)

    Alcaino, C; Farrugia, G; Beyder, A

    2017-01-01

    Sensation of mechanical forces is critical for normal function of the gastrointestinal (GI) tract and abnormalities in mechanosensation are linked to GI pathologies. In the GI tract there are several mechanosensitive cell types-epithelial enterochromaffin cells, intrinsic and extrinsic enteric neurons, smooth muscle cells and interstitial cells of Cajal. These cells use mechanosensitive ion channels that respond to mechanical forces by altering transmembrane ionic currents in a process called mechanoelectrical coupling. Several mechanosensitive ionic conductances have been identified in the mechanosensory GI cells, ranging from mechanosensitive voltage-gated sodium and calcium channels to the mechanogated ion channels, such as the two-pore domain potassium channels K2P (TREK-1) and nonselective cation channels from the transient receptor potential family. The recently discovered Piezo channels are increasingly recognized as significant contributors to cellular mechanosensitivity. Piezo1 and Piezo2 are nonselective cationic ion channels that are directly activated by mechanical forces and have well-defined biophysical and pharmacologic properties. The role of Piezo channels in the GI epithelium is currently under investigation and their role in the smooth muscle syncytium and enteric neurons is still not known. In this review, we outline the current state of knowledge on mechanosensitive ion channels in the GI tract, with a focus on the known and potential functions of the Piezo channels. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. A Perspective on the MIMO Wiretap Channel

    KAUST Repository

    Oggier, Frederique

    2015-10-01

    A wiretap channel is a communication channel between a transmitter Alice and a legitimate receiver Bob, in the presence of an eavesdropper Eve. The goal of communication is to achieve reliability between Alice and Bob, but also confidentiality despite Eve’s presence. Wiretap channels are declined in all kinds of flavors, depending on the underlying channels used by the three players: discrete memoryless channels, additive Gaussian noise channels, or fading channels, to name a few. In this survey, we focus on the case where the three players use multiple-antenna channels with Gaussian noise to communicate. After summarizing known results for multiple-input–multiple-output (MIMO) channels, both in terms of achievable reliable data rate (capacity) and code design, we introduce the MIMO wiretap channel. We then state the MIMO wiretap capacity, summarize the idea of the proof(s) behind this result, and comment on the insights given by the proofs on the physical meaning of the secrecy capacity. We finally discuss design criteria for MIMO wiretap codes.

  7. Sediment sorting at a side channel bifurcation

    Science.gov (United States)

    van Denderen, Pepijn; Schielen, Ralph; Hulscher, Suzanne

    2017-04-01

    Side channels have been constructed to reduce the flood risk and to increase the ecological value of the river. In various Dutch side channels large aggradation in these channels occurred after construction. Measurements show that the grain size of the deposited sediment in the side channel is smaller than the grain size found on the bed of the main channel. This suggest that sorting occurs at the bifurcation of the side channel. The objective is to reproduce with a 2D morphological model the fining of the bed in the side channel and to study the effect of the sediment sorting on morphodynamic development of the side channel. We use a 2D Delft3D model with two sediment fractions. The first fraction corresponds with the grain size that can be found on the bed of the main channel and the second fraction corresponds with the grain size found in the side channel. With the numerical model we compute several side channel configurations in which we vary the length and the width of the side channel, and the curvature of the upstream channel. From these computations we can derive the equilibrium state and the time scale of the morphodynamic development of the side channel. Preliminary results show that even when a simple sediment transport relation is used, like Engelund & Hansen, more fine sediment enters the side channel than coarse sediment. This is as expected, and is probably related to the bed slope effects which are a function of the Shields parameter. It is expected that by adding a sill at the entrance of the side channel the slope effect increases. This might reduce the amount of coarse sediment which enters the side channel even more. It is unclear whether the model used is able to reproduce the effect of such a sill correctly as modelling a sill and reproducing the correct hydrodynamic and morphodynamic behaviour is not straightforward in a 2D model. Acknowledgements: This research is funded by STW, part of the Dutch Organization for Scientific Research under

  8. Performance Analysis of Iterative Channel Estimation and Multiuser Detection in Multipath DS-CDMA Channels

    Science.gov (United States)

    Li, Husheng; Betz, Sharon M.; Poor, H. Vincent

    2007-05-01

    This paper examines the performance of decision feedback based iterative channel estimation and multiuser detection in channel coded aperiodic DS-CDMA systems operating over multipath fading channels. First, explicit expressions describing the performance of channel estimation and parallel interference cancellation based multiuser detection are developed. These results are then combined to characterize the evolution of the performance of a system that iterates among channel estimation, multiuser detection and channel decoding. Sufficient conditions for convergence of this system to a unique fixed point are developed.

  9. Roughness coefficients for stream channels in Arizona

    Science.gov (United States)

    Aldridge, B.N.; Garrett, J.M.

    1973-01-01

    When water flows in an open channel, energy is lost through friction along the banks and bed of the channel and through turbulence within the channel. The amount of energy lost is governed by channel roughness, which is expressed in terms of a roughness coefficient. An evaluation of the roughness coefficient is necessary in many hydraulic computations that involve flow in an open channel. Owing to the lack of satisfactory quantitative procedure, the ability of evaluate roughness coefficients can be developed only through experience; however, a basic knowledge of the methods used to assign the coefficients and the factors affecting them will be a great help. One of the most commonly used equations in open-channel hydraulics is that of Manning. The Manning equation is       1.486

  10. KATP Channels in the Cardiovascular System.

    Science.gov (United States)

    Foster, Monique N; Coetzee, William A

    2016-01-01

    KATP channels are integral to the functions of many cells and tissues. The use of electrophysiological methods has allowed for a detailed characterization of KATP channels in terms of their biophysical properties, nucleotide sensitivities, and modification by pharmacological compounds. However, even though they were first described almost 25 years ago (Noma 1983, Trube and Hescheler 1984), the physiological and pathophysiological roles of these channels, and their regulation by complex biological systems, are only now emerging for many tissues. Even in tissues where their roles have been best defined, there are still many unanswered questions. This review aims to summarize the properties, molecular composition, and pharmacology of KATP channels in various cardiovascular components (atria, specialized conduction system, ventricles, smooth muscle, endothelium, and mitochondria). We will summarize the lessons learned from available genetic mouse models and address the known roles of KATP channels in cardiovascular pathologies and how genetic variation in KATP channel genes contribute to human disease. Copyright © 2016 the American Physiological Society.

  11. Pore size matters for potassium channel conductance

    Science.gov (United States)

    Moldenhauer, Hans; Pincuntureo, Matías

    2016-01-01

    Ion channels are membrane proteins that mediate efficient ion transport across the hydrophobic core of cell membranes, an unlikely process in their absence. K+ channels discriminate K+ over cations with similar radii with extraordinary selectivity and display a wide diversity of ion transport rates, covering differences of two orders of magnitude in unitary conductance. The pore domains of large- and small-conductance K+ channels share a general architectural design comprising a conserved narrow selectivity filter, which forms intimate interactions with permeant ions, flanked by two wider vestibules toward the internal and external openings. In large-conductance K+ channels, the inner vestibule is wide, whereas in small-conductance channels it is narrow. Here we raise the idea that the physical dimensions of the hydrophobic internal vestibule limit ion transport in K+ channels, accounting for their diversity in unitary conductance. PMID:27619418

  12. Structure of conducting channel of lightning

    International Nuclear Information System (INIS)

    Alanakyan, Yu. R.

    2013-01-01

    The spatial distribution of the plasma density in a lightning channel is studied theoretically. It is shown that the electric-field double layer is formed at the channel boundary. In this case, the electron temperature changes abruptly and ions are accelerated by the electric field of the double layer. The ion momentum flux density is close to the surrounding gas pressure. Cleaning of the channel from heavy particles occurs in particle-exchange processes between the plasma channel and the surrounding air. Hydrogen ions are accumulated inside the expanding channel from the surrounding air, which is enriched by hydrogen-contained molecules. In this case, the plasma channel is unstable and splits to a chain of equidistant bunches of plasma. The hydrogen-enrich bunches burn diffusely after recombination exhibiting the bead lightning behavior

  13. Bywalled plasma formation in vacuum prolonged channels

    International Nuclear Information System (INIS)

    Korenev, S.A.; Rubin, N.B.

    1982-01-01

    To produce homogeneous along the channel length plasma the application of incomplete rate-in surface dielectric discharge for generating the bywalled plasma in prolonged cylindrical channels at a pressure of the residual gas of P approximately 10 -5 Torr is proposed. Experimental set-up consisted of a pulse voltage generator and a plasma channel. The plasma channel was a coaxial system of three tubes inserted into each other. The first outer tube is made of a stainless steel, the second - of a dielectric material, the third - of smallsized stainless steel greed. It is demonstrated that the plasma being formed in the process is sufficiently homogeneous by concentration of the components, by the channel length and azimuth. The length of the experimental channel under investigation was 1.6 m, its diameter amounted 0.05 m. The maximum concentration of electron component was 10 17 m -3

  14. Analytical admittance characterization of high mobility channel

    Energy Technology Data Exchange (ETDEWEB)

    Mammeri, A. M.; Mahi, F. Z., E-mail: fati-zo-mahi2002@yahoo.fr [Institute of Science and Technology, University of Bechar (Algeria); Varani, L. [Institute of Electronics of the South (IES - CNRS UMR 5214), University of Montpellier (France)

    2015-03-30

    In this contribution, we investigate the small-signal admittance of the high electron mobility transistors field-effect channels under a continuation branching of the current between channel and gate by using an analytical model. The analytical approach takes into account the linearization of the 2D Poisson equation and the drift current along the channel. The analytical equations discuss the frequency dependence of the admittance at source and drain terminals on the geometrical transistor parameters.

  15. Control system design for concrete irrigation channels

    OpenAIRE

    Strecker, Timm; Aamo, Ole Morten; Cantoni, Michael

    2017-01-01

    Concrete channels find use at the periphery of irrigation networks, for expansion and to replace small earthen channels given the relative ease of maintenance and elimination of seepage losses. In design, it is important to account for control system performance when dimensioning the channel infrastructure. In this paper, the design of a distributed controller is investigated in terms managing water-levels, and thereby the depth profile (i.e., amount of concrete) needed to support peak flow l...

  16. Electronic trade effect of marketing channels

    OpenAIRE

    Lovreta Stipe; Stojković Dragan

    2009-01-01

    E-commerce has caused many significant changes in marketing channels. Consumers had obtained multiple benefits from e-commerce. In addition, it has increased the level of competition in marketing channels. However, the focus of this paper is multichannel strategy and integration of physical (store) and electronic marketing channels. E-commerce has induced dynamic development of multichannel strategy. This strategy has evolved as a consequence of multichannel consumer orientation. In developed...

  17. Universal communication part II: channels with memory

    OpenAIRE

    Lomnitz, Yuval; Feder, Meir

    2012-01-01

    Consider communication over a channel whose probabilistic model is completely unknown vector-wise and is not assumed to be stationary. Communication over such channels is challenging because knowing the past does not indicate anything about the future. The existence of reliable feedback and common randomness is assumed. In a previous paper it was shown that the Shannon capacity cannot be attained, in general, if the channel is not known. An alternative notion of "capacity" was defined, as the...

  18. Stability analysis for downflow in heated channels

    International Nuclear Information System (INIS)

    Sampaio, P.A.B. de.

    1985-01-01

    Stability and flow distribution are analysed for downflow in heated channels. It is shown that at low flow rates instabilities associated with the buoyancy forces may appear. A computer code in FORTRAN language to determine downflow distribution among n heated channels is presented. The model used to calculate downflow distribution and the onset of instability is compared with experiments performed in a test section with two parallel channels. (Author) [pt

  19. Export channel pricing management for integrated solutions

    OpenAIRE

    Roine, Henna; Sainio, Liisa-Maija; Saarenketo, Sami

    2012-01-01

    This article studies systems integrators' export channel pricing management for integrated solutions. We find support from our empirical case study for the notion that a systems integrator's export channel pricing strategy is multidimensional and dependent on international pricing environment and partner characteristics and that export partnerships have unique implications on a systems integrator's pricing process. The results show that giving up pricing control in export channel context may ...

  20. Pharmaceutical Distribution Market Channels in Poland

    Directory of Open Access Journals (Sweden)

    Agnieszka Woś

    2009-09-01

    Full Text Available Distribution on the pharmaceutical market in Poland is interesting and the most difficult sphere to manage. Numerous varied and specialized companies operating on the market cause that the processes of choosing middlemen in distribution channels are very complex. The hereby article presents the role and location of the companies operating within distribution channels on the pharmaceutical market. It draws attention to the development of non-pharmacy and non-wholesale sales channels.

  1. Quantum privacy and Schur product channels

    Science.gov (United States)

    Levick, Jeremy; Kribs, David W.; Pereira, Rajesh

    2017-12-01

    We investigate the quantum privacy properties of an important class of quantum channels, by making use of a connection with Schur product matrix operations and associated correlation matrix structures. For channels implemented by mutually commuting unitaries, which cannot privatise qubits encoded directly into subspaces, we nevertheless identify private algebras and subsystems that can be privatised by the channels. We also obtain further results by combining our analysis with tools from the theory of quasi-orthogonal operator algebras and graph theory.

  2. Channeling crystals for positron production

    International Nuclear Information System (INIS)

    Decker, F.J.

    1991-05-01

    Particles traversing at small angles along a single crystal axis experience a collective scattering force of many crystal atoms. The enormous fields can trap the particles along an axis or plane, called channeling. High energy electrons are attracted by the positive nuclei and therefore produce strongly enhanced so called coherent bremsstrahlung and pair production. These effects could be used in a positron production target: A single tungsten crystal is oriented to the incident electron beam within 1 mrad. At 28 GeV/c the effective radiation length is with 0.9 mm about one quarter of the amorphous material. So the target length can be shorter, which yields a higher conversion coefficient and a lower emittance of the positron beam. This makes single crystals very interesting for positron production targets. 18 refs., 2 figs

  3. Fuel channel closure and adapter

    International Nuclear Information System (INIS)

    Cashen, W.S.

    1985-01-01

    This invention provides a mechanical closure/actuating ram combination particularly suited for use in sealing the ends of the pressure tubes when a CANDU-type reactor is refueled. It provides a cluster that may be inserted into a fuel channel end fitting to provide at least partial closing off of a pressure tube while permitting the disengagement of the fueling machine and its withdrawal from the closure for other purposes. The invention also provides a ram/closure combination wherein the application of loading force to a deformable sealing disk is regulated by a massive load bar component forming part of the fueling machine and being therefore accessible for maintenance or replacement

  4. Axial channeling in electron diffraction

    International Nuclear Information System (INIS)

    Ichimiya, A.; Lehmpfuhl, G.

    1978-01-01

    Kossel patterns from Silicon and Niobium were obtained with a convergent electron beam. An intensity maximum in the direction of the zone axes [001] and [111] of Nb was interpreted as axial channeling. The intensity distribution in Kossel patterns was calculated by means of the Bloch wave picture of the dynamical theory of electron diffraction. Particularly zone axis patterns were calculated for different substance-energy combinations and they were compared with experimental observations. The intensity distribution in the calculated Kossel patterns was very sensitive to the model of absorption and it was found that a treatment of the absorption close to the model of Humphreys and Hirsch [Phil. Mag. 18, 115 (1968)] gave the best agreement with the experimental observations. Furthermore it is shown which Bloch waves are important for the intensity distribution in the Kossel patterns, how they are absorbed and how they change with energy. (orig.) [de

  5. [Synopsis about the hypothesis of "information channel" of channel-collateral system].

    Science.gov (United States)

    Chang, Xi-Lang

    2008-10-01

    The author of the present paper founded a theorem about the "incompleteness of single channel structure" (nerve, blood vessel, lymphatic, interspace, aperture, etc.) through quantitative and qualitative analysis about the economic information channel in the human body, which eliminates the probability of single channel structure in the information channel of channel (meridian)-collateral system. After comprehensive analysis on the current researches, the author puts forward a neodoxy, i.e., the body "information channel" structure of the channel-collateral system, mainly follows the distribution regularity of systemic statistics, and is not a single specific entity; various layers of the information channel in the main stems of the channel-collaterals are composed of optimized structure tissues. Hence, the structure of this information channel of channel-collateral system is an overall-optimized, sequential and compatible systemic structure. From this neodoxy, the author brings forward a working principle of channel-collaterals, which is supported theoretically by bio-auxology. The longitudinal distribution of the main stems of meridian-collaterals is considered to result from that in the process of the animal evolution, in the animals moving forward, the microscopic complicated movement of intracorporeal information and energy molecules is related to the forward macroscopic and non-uniform movement of organism in trans-measure. Its impulse and kinetic momentum forms a main vector in the longitudinal direction of the body (the direction of the main stem of channel-collaterals). In order to adapt to and utilize natural regularities, the main stems of the channel-collaterals gradually differentiate and evolve in the living organism, forming a whole system. The "hypothesis of biological origin of channel-collateral system" and "that of information channel of the channel-collaterals in the body" constitute a relatively complete theoretical system framework.

  6. Customer Engagement Tool (Multi Channel Communication)

    Data.gov (United States)

    Social Security Administration — Add new infrastructure within SSA's Enterprise Architecture to allow interactions over multiple, yet to be defined, channels. Possibilities include: Provide a portal...

  7. Channeling ion implantation through palladium films

    International Nuclear Information System (INIS)

    Ishiwara, H.; Furukawa, S.

    1975-01-01

    The possibility of channeling ion implantation into semiconductors through polycrystalline metallic layers is studied. Minimum values and standard deviations of channeling angular yield in polycrystalline Pd 2 Si layers formed on Si have been measured by protons and 4 He, and 14 N ion backscattering and channeling measurements. Depth distributions of the spread of crystallite orientations and scattering centers such as lattice defects have been separately derived by using the above two quantities. It has been concluded that the channeling-ion-implantation technique will become a practical one by using the parallel scanning system

  8. Indoor MIMO Channel Measurement and Modeling

    DEFF Research Database (Denmark)

    Nielsen, Jesper Ødum; Andersen, Jørgen Bach

    2005-01-01

    Forming accurate models of the multiple input multiple output (MIMO) channel is essential both for simulation as well as understanding of the basic properties of the channel. This paper investigates different known models using measurements obtained with a 16x32 MIMO channel sounder for the 5.8GHz...... band. The measurements were carried out in various indoor scenarios including both temporal and spatial aspects of channel changes. The models considered include the so-called Kronecker model, a model proposed by Weichselberger et. al., and a model involving the full covariance matrix, the most...

  9. Achromatic Cooling Channel with Li Lenses

    Energy Technology Data Exchange (ETDEWEB)

    Balbekov, V. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

    2002-04-29

    A linear cooling channel with Li lenses, solenoids, and 201 MHz RF cavities is considered. A special lattice design is used to minimize chromatic aberrations by suppression of several betatron resonances. Transverse emittance of muon beam decreases from 2 mm to 0.5 mm at the channel of about 110 m length. Longitudinal heating is modest, therefore transmission of the channel is rather high: 96% without decay and 90% with decay. Minimal beam emittance achievable by similar channel estimated as about 0.25 mm at surface field of Li lenses 10 T.

  10. Optimal processing of reversible quantum channels

    Energy Technology Data Exchange (ETDEWEB)

    Bisio, Alessandro, E-mail: alessandro.bisio@unipv.it [QUIT Group, Dipartimento di Fisica, INFN Sezione di Pavia, via Bassi 6, 27100 Pavia (Italy); D' Ariano, Giacomo Mauro; Perinotti, Paolo [QUIT Group, Dipartimento di Fisica, INFN Sezione di Pavia, via Bassi 6, 27100 Pavia (Italy); Sedlák, Michal [Department of Optics, Palacký University, 17. Listopadu 1192/12, CZ-771 46 Olomouc (Czech Republic); Institute of Physics, Slovak Academy of Sciences, Dúbravská Cesta 9, 845 11 Bratislava (Slovakia)

    2014-05-01

    We consider the general problem of the optimal transformation of N uses of (possibly different) unitary channels to a single use of another unitary channel in any finite dimension. We show how the optimal transformation can be fully parallelized, consisting in a preprocessing channel followed by a parallel action of all the N unitaries and a final postprocessing channel. Our techniques allow to achieve an exponential reduction in the number of the free parameters of the optimization problem making it amenable to an efficient numerical treatment. Finally, we apply our general results to find the analytical solution for special cases of interest like the cloning of qubit phase gates.

  11. Almost all quantum channels are equidistant

    Science.gov (United States)

    Nechita, Ion; Puchała, Zbigniew; Pawela, Łukasz; Życzkowski, Karol

    2018-05-01

    In this work, we analyze properties of generic quantum channels in the case of large system size. We use random matrix theory and free probability to show that the distance between two independent random channels converges to a constant value as the dimension of the system grows larger. As a measure of the distance we use the diamond norm. In the case of a flat Hilbert-Schmidt distribution on quantum channels, we obtain that the distance converges to 1/2 +2/π , giving also an estimate for the maximum success probability for distinguishing the channels. We also consider the problem of distinguishing two random unitary rotations.

  12. Secure Broadcasting with Uncertain Channel State Information

    KAUST Repository

    Hyadi, Amal; Rezki, Zouheir; Khisti, Ashish; Alouini, Mohamed-Slim

    2017-01-01

    -main CSI are also analyzed. Analytical derivations and numerical results are presented to illustrate the obtained expressions for the case of independent and identically distributed Rayleigh fading channels.

  13. Secure Broadcasting with Uncertain Channel State Information

    KAUST Repository

    Hyadi, Amal; Rezki, Zouheir; Khisti, Ashish; Alouini, Mohamed-Slim

    2016-01-01

    -main CSI are also analyzed. Analytical derivations and numerical results are presented to illustrate the obtained expressions for the case of independent and identically distributed Rayleigh fading channels.

  14. Channel Responses and Hydromodification in Southern California

    Science.gov (United States)

    Hawley, R. J.; Dust, D. W.; Bledsoe, B. P.

    2007-12-01

    Hydromodification (changes in watershed hydrologic characteristics, and the resulting hydraulics and channel forms due to urbanization) is ubiquitous in Southern California. In this region, the effects of hydromodification are driven and compounded by the arid/semiarid climate, high relief, erodible soils, high urbanization rates, and relatively low frequency of retention/detention. We conducted a preliminary survey of over 50 stream reaches along a gradient from least disturbed to fully urbanized. All stages of the Channel Evolution Model (CEM) of Schumm et al. (1984) were observed, from stable to degrading, widening, aggrading, and quasi-equilibrium channels. Several sites have CEM stages II through V in close proximity due to headcutting, hardpoints, and infrastructure. We also observed channels in undeveloped watersheds impacted by downstream urbanization via headcutting. A range of intervention measures was observed, with the frequent evolutionary endpoint as a concrete engineered flood control channel. We also observed multiple channel evolution sequences that deviate from the CEM for single-thread, incising channels. An alternative channel response, particularly on smaller urbanized streams is a stabilized, vegetation encroached low-flow channel with regular baseflow supplied by residential irrigation runoff. The limited cases of unimpacted streams that remain tend to be high gradient, high energy systems that are naturally proximate to the transition between braided and meandering form for a given sediment size.

  15. Flow and sediment transport across oblique channels

    DEFF Research Database (Denmark)

    Hjelmager Jensen, Jacob; Madsen, Erik Østergaard; Fredsøe, Jørgen

    1998-01-01

    A 3D numerical investigation of flow across channels aligned obliquely to the main flow direction has been conducted. The applied numerical model solves the Reynolds-averaged Navier-Stokes equations using the k-ε model for turbulence closure on a curvilinear grid. Three momentum equations...... are solved, but the computational domain is 2D due to a uniformity along the channel alignment. Two important flow features arise when the flow crosses the channel: (i) the flow will be refracted in the direction of the channel alignment. This may be described by a depth-averaged model. (ii) due to shear...

  16. On the domestic fuel channel for BWR

    International Nuclear Information System (INIS)

    Fukada, Hiroshi

    1979-01-01

    Kobe Steel Ltd. started the domestic manufacture of fuel channel boxes for BWRs in 1967, and entered the actual production stage four years after that. Since 1976, the mass production system was adopted with the increase of the demand. The requirements about the surface contamination and the dimensional accuracy over whole length are very strict in the fuel channel boxes, moreover, special consideration must be given so as to prevent the deformation in use. The unique working methods such as electron beam welding, high temperature press forming and so on are employed in Kobe Steel Ltd. to satisfy such strict requirements, therefore the quality of the produced fuel channel boxes is superior to imported ones. At present, the fuel channel boxes domestically made by Kobe Steel Ltd. are used for almost all BWRs in Japan. The functions of fuel channel boxes are to flow boiling coolant uniformly upward, to guide control rods, and to increase the rigidity of fuel assembly. The fuel channel boxes are the square tubes of zircaloy 4 of 134.06 mm inside width, 2.03 mm thickness, and 4118 or 4239 mm length. The progress of the development and the features of the fuel channel boxes and the manufacturing processes are described. Zircaloy plates are formed into channels, and two channels are electron beam-welded after the edge preparation, to make a box. Ultrasonic examination and stress relief treatment are applied, and clips and spacers are welded. (Kako, I.)

  17. Dimension measuring method for channel box

    International Nuclear Information System (INIS)

    Jo, Hiroto.

    1995-01-01

    The device of the present invention concerns detection of a channel box for spent fuel assemblies of a BWR type reactor, which measures a cross sectional shape and dimension of the channel box to check deformation amount such as expansion. That is, a customary fuel exchanger and a dimension measuring device are used. The lower end of the channel box is measured by a distance sensor of the dimension measuring device when it is aligned with a position of the distance sensor. The channel box is lowered at the same time while detecting axial position data of the fuel exchanger. The position of the channel box in an axial direction is detected based on axial position data of the fuel exchanger. The lower end of the channel box can accurately be recognized by the detection of both of them. Subsequent deformation measurement for the channel box at accurate axial positions is enabled. In addition, since the axial position data of the fuel exchanger per se are detected, an axial profile of the channel box can be measured even if a lifting speed of the channel box is varied on every region. (I.S.)

  18. Measuring Balance Across Multiple Radar Receiver Channels.

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin W.; Bickel, Douglas L.

    2018-03-01

    When radar receivers employ multiple channels, the general intent is for the receive channels to be as alike as possible, if not as ideal as possible. This is usually done via prudent hardware design, supplemented by system calibration. Towards this end, we require a quality metric for ascertaining the goodness of a radar channel, and the degree of match to sibling channels. We propose a relevant and useable metric to do just that. Acknowledgements This report was the result of an unfunded research and development activity.

  19. Channeling and related crystal effects

    International Nuclear Information System (INIS)

    Uggerhoj, Erik

    1995-01-01

    Channeling, the interaction of particles with oriented crystals, has been applied in a wide variety of scientific and technological areas. A workshop at Aarhus, Denmark, this summer highlighted progress and future directions. Radiation emission has been explored and linked to coherent bremsstrahlung and other oriented crystal radiations. Dramatic effects have been found for ultra-relativistic electrons with Lorentz factors of 105 6. Single crystals are unique for investigations of quantum electrodynamics in strong external fields because probabilities for processes in axial/ planar fields are determined by the magnitude of these fields in the particle rest frame. Erik Uggerhoj of Aarhus reported on an extensive series of experiments concerning radiation emission, pair production, and shower formation carried out at CERN by the NA43 collaboration. As Vladimir Baier of Novosibirsk and Yuri Kononets of Kurchatov noted, theoretical treatment of these interconnected radiation distributions is challenging and much work needs to be done. In general, the agreement with the CERN experiments is good, but many areas like polarization phenomena and particle production need investigation. Prominent among high energy applications is extraction from accelerators. At the workshop, Alexei Asseev reported on beam extraction using a bent crystal at Serpukhov. Konrad Elsener and Jukka Klem reviewed recent CERN SPS studies driven by the possibility of using crystals for extraction of LHC beams. Thornton Murphy of Fermilab announced a step in that direction, with a demonstration this summer of extraction from the Tevatron at 900 GeV. Bent crystal channeling is also used for handling extracted high energy beams. Niels Doble presented a beautiful example of a beam for the CERN NA48 CP-violation experiment. Yuri Chesnokov reported that beams had been deflected through angles up to 150 milliradians at Serpukhov

  20. EPICS channel access using websocket

    International Nuclear Information System (INIS)

    Uchiyama, A.; Furukawa, K.; Higurashi, Y.

    2012-01-01

    Web technology is useful as a means of widely disseminating accelerator and beam status information. For this purpose, WebOPI was implemented by SNS as a web-based system using Ajax (asynchronous JavaScript and XML) with EPICS. On the other hand, it is often necessary to control the accelerator from different locations as well as the central control room during beam operation and maintenance. However, it is not realistic to replace the GUI-based operator interface (OPI) with a Web-based system using Ajax technology because of interactive performance issue. Therefore, as a next generation OPI over the web using EPICS Channel Access (CA), we developed a client system based on WebSocket, which is a new protocol provided by the Internet Engineering Task Force (IETF) for Web-based systems. WebSocket is a web technology that provides bidirectional, full-duplex communication channels over a single TCP connection. By utilizing Node.js and the WebSocket access library called Socket.IO, a WebSocket server was implemented. Node.js is a server-side JavaScript language built on the Google V8 JavaScript Engine. In order to construct the WebSocket server as an EPICS CA client, an add-on for Node.js was developed in C/C++ using the EPICS CA library, which is included in the EPICS base. As a result, for accelerator operation, Web-based client systems became available not only in the central control room but also with various types of equipment. (author)

  1. Improvement of Metroliner Telephone Channel Capacity and Modeling of Telephone Channel Demands

    Science.gov (United States)

    1972-03-01

    The channel capacity of the present Metroliner telephone system is analyzed and methods are proposed to increase that capacity without increasing the overall bandwidth. To determine the number of channels required, calculations have been carried out ...

  2. An information-guided channel-hopping scheme for block-fading channels with estimation errors

    KAUST Repository

    Yang, Yuli

    2010-12-01

    Information-guided channel-hopping technique employing multiple transmit antennas was previously proposed for supporting high data rate transmission over fading channels. This scheme achieves higher data rates than some mature schemes, such as the well-known cyclic transmit antenna selection and space-time block coding, by exploiting the independence character of multiple channels, which effectively results in having an additional information transmitting channel. Moreover, maximum likelihood decoding may be performed by simply decoupling the signals conveyed by the different mapping methods. In this paper, we investigate the achievable spectral efficiency of this scheme in the case of having channel estimation errors, with optimum pilot overhead for minimum meansquare error channel estimation, when transmitting over blockfading channels. Our numerical results further substantiate the robustness of the presented scheme, even with imperfect channel state information. ©2010 IEEE.

  3. Channel characteristics and coordination in three-echelon dual-channel supply chain

    Science.gov (United States)

    Saha, Subrata

    2016-02-01

    We explore the impact of channel structure on the manufacturer, the distributer, the retailer and the entire supply chain by considering three different channel structures in radiance of with and without coordination. These structures include a traditional retail channel and two manufacturer direct channels with and without consistent pricing. By comparing the performance of the manufacturer, the distributer and the retailer, and the entire supply chain in three different supply chain structures, it is established analytically that, under some conditions, a dual channel can outperform a single retail channel; as a consequence, a coordination mechanism is developed that not only coordinates the dual channel but also outperforms the non-cooperative single retail channel. All the analytical results are further analysed through numerical examples.

  4. An approach to implement virtual channels for flowing magnetic beads

    International Nuclear Information System (INIS)

    Tang, Shih-Hao; Chiang, Hung-Wei; Hsieh, Min-Chien; Chang, Yen-Di; Yeh, Po-Fan; Tsai, Jui-che; Shieh, Wung-Yang

    2014-01-01

    This work demonstrates the feasibility of a novel microfluidic system with virtual channels formed by ‘walls’ of magnetic fields, including collecting channels, transporting channels and function channels. The channels are defined by the nickel patterns. With its own ferromagnetism, nickel can be magnetized using an external magnetic field; the nickel structures then generate magnetic fields that can either guide or trap magnetic beads. A glass substrate is sandwiched between the liquid containing magnetic beads and the chip with nickel structures, preventing the liquid from directly contacting the nickel. In this work, collecting channels, transporting channels and function channels are displayed sequentially. In the collecting channel portion, channels with different shapes are compared. Next, in the transporting channel portion we demonstrate I-, S- and Y-shaped channels can steer magnetic beads smoothly. Finally, in the function channel portion, a switchable trapping channel implemented with a bistable mechanism performs the passing and blocking of a magnetic bead. (paper)

  5. Differential Effects of TRPA and TRPV Channels on Behaviors of

    Directory of Open Access Journals (Sweden)

    Jennifer Thies

    2016-01-01

    Full Text Available TRPA and TRPV ion channels are members of the transient receptor potential (TRP cation channel superfamily, which mediates various sensory transductions. In Caenorhabditis elegans , the TRPV channels are known to affect chemosensation, while the TRPA-1 channel is associated with thermosensation and mechanosensation. We examined thermosensation, chemosensation, and osmosensation in strains lacking TRPA-1 or TRPV channels. We found that TRPV channel knockout worms exhibited similar behavioral deficits associated with thermotaxis as the TRPA-1 channel knockout, suggesting a dual role for TRPV channels. In contrast, chemosensation responses, assessed by both avoidance reversal behavior and NaCl osmosensation, were dependent on TRPV channels but seemed independent of TRPA-1 channel. Our findings suggest that, in addition to TRPA-1 channel, TRPV channels are necessary for thermotaxis and may activate, or modulate, the function of TRPA-1 channels. In contrast, TRPA-1 channels do not have a dual responsibility, as they have no functional role in odorant avoidance or osmosensation.

  6. XPM-induced degradation of multilevel phase modulated channel caused by neighboring NRZ modulated channels

    DEFF Research Database (Denmark)

    Jensen, Jesper Bevensee; Schiellerup, G.; Peucheret, Christophe

    2008-01-01

    The impact of XPM from NRZ modulated channels on an 8-level phase modulated channel in a WDM system was investigated. Requirements on launch power are found. 400 km transmission was achieved with negligible penalty.......The impact of XPM from NRZ modulated channels on an 8-level phase modulated channel in a WDM system was investigated. Requirements on launch power are found. 400 km transmission was achieved with negligible penalty....

  7. On the Capacity of the Dirty Paper Channel with Fast Fading and Discrete Channel States

    OpenAIRE

    Rini, Stefano; Shitz, Shlomo Shamai

    2016-01-01

    The "writing dirty paper" capacity result crucially dependents on the perfect channel knowledge at the transmitter as the presence of even a small uncertainty in the channel realization gravely hampers the ability of the transmitter to pre-code its transmission against the channel state. This is particularly disappointing as it implies that interference pre-coding in practical systems is effective only when the channel estimates at the users have very high precision, a condition which is gene...

  8. A new simple model for composite fading channels: Second order statistics and channel capacity

    KAUST Repository

    Yilmaz, Ferkan; Alouini, Mohamed-Slim

    2010-01-01

    In this paper, we introduce the most general composite fading distribution to model the envelope and the power of the received signal in such fading channels as millimeter wave (60 GHz or above) fading channels and free-space optical channels, which

  9. Multi-channel service retailing: The effects of channel performance satisfaction on behavioral intentions.

    NARCIS (Netherlands)

    Birgelen, van M.; Jong, de A.; Ruyter, de J.C.

    2006-01-01

    Abstract The number of channels that retailers can use interchangeably to provide customer service has increased. We report on a study of clients of a large retail bank that investigates the channel performance satisfaction–behavioral intentions relationship when the traditional service channel

  10. Optimising the Quality of Experience during Channel Zapping : The Impact of Advertisements during Channel Zapping

    NARCIS (Netherlands)

    Kooij, R.E.; Klos, V.B.; Godana, B.E.; Nicolai, F.P.; Ahmed, O.K.

    2009-01-01

    Nowadays various digital television services are available. However, the user of these services experiences longer delays than the traditional analog TV while switching from channel to channel. The digital TV operator usually displays a black screen with the channel number during zapping. However,

  11. The sedimentary record of submarine channel morphodynamics

    NARCIS (Netherlands)

    de Leeuw, J.

    2017-01-01

    Submarine channels are ubiquitous on the ocean floor and are considered to be the equivalent of rivers on land. These channels are created by turbidity currents, which originate from the continental margins and which can transport sediment for thousands of kilometres into the oceans. The aim of this

  12. Steady turbulent flow in curved rectangular channels

    NARCIS (Netherlands)

    De Vriend, H.J.

    1979-01-01

    After the study of fully developed and developing steady laminar flow in curved channels of shallow rectangular wet cross-section (see earlier reports in this series), steady turbulent flow in such channels is investigated as a next step towards a mathematical model of the flow in shallow river

  13. 47 CFR 101.1405 - Channeling plan.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Channeling plan. 101.1405 Section 101.1405 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES FIXED MICROWAVE... Channeling plan. Each license shall have one spectrum block of 500 megahertz per geographic area that can be...

  14. Privacy of a lossy bosonic memory channel

    Energy Technology Data Exchange (ETDEWEB)

    Ruggeri, Giovanna [Dipartimento di Fisica, Universita di Lecce, I-73100 Lecce (Italy)]. E-mail: ruggeri@le.infn.it; Mancini, Stefano [Dipartimento di Fisica, Universita di Camerino, I-62032 Camerino (Italy)]. E-mail: stefano.mancini@unicam.it

    2007-03-12

    We study the security of the information transmission between two honest parties realized through a lossy bosonic memory channel when losses are captured by a dishonest party. We then show that entangled inputs can enhance the private information of such a channel, which however does never overcome that of unentangled inputs in absence of memory.

  15. Forbidden Channels and SIMP Dark Matter

    OpenAIRE

    Choi Soo-Min; Kang Yoo-Jin; Lee Hyun Min

    2018-01-01

    In this review, we focus on dark matter production from thermal freeze-out with forbidden channels and SIMP processes. We show that forbidden channels can be dominant to produce dark matter depending on the dark photon and / or dark Higgs mass compared to SIMP.

  16. Hydrodynamic blood plasma separation in microfluidic channels

    DEFF Research Database (Denmark)

    Jouvet, Lionel

    2010-01-01

    The separation of red blood cells from plasma flowing in microchannels is possible by biophysical effects such as the Zweifach–Fung bifurcation law. In the present study, daughter channels are placed alongside a main channel such that cells and plasma are collected separately. The device is aimed...

  17. Measuring vibrations in fuel channels CNE

    International Nuclear Information System (INIS)

    Martín Ghiselli, A.; Fiori, J.; Sacchi, M.; Villabrille, G.

    2013-01-01

    This paper present a description of implementation and execution of vibration measurements made at the request of NUCLEOELECTRICA ARGENTINA S.A. on the ends of the reactor fuel channels of Embalse Nuclear Power Plant to explore possible differences between the dynamic behavior of empty fuel channel and with full charge of fuel elements inside. (author)

  18. Additivity properties of a Gaussian channel

    International Nuclear Information System (INIS)

    Giovannetti, Vittorio; Lloyd, Seth

    2004-01-01

    The Amosov-Holevo-Werner conjecture implies the additivity of the minimum Renyi entropies at the output of a channel. The conjecture is proven true for all Renyi entropies of integer order greater than two in a class of Gaussian bosonic channel where the input signal is randomly displaced or where it is coupled linearly to an external environment

  19. Transportation channels calculation method in MATLAB

    International Nuclear Information System (INIS)

    Averyanov, G.P.; Budkin, V.A.; Dmitrieva, V.V.; Osadchuk, I.O.; Bashmakov, Yu.A.

    2014-01-01

    Output devices and charged particles transport channels are necessary components of any modern particle accelerator. They differ both in sizes and in terms of focusing elements depending on particle accelerator type and its destination. A package of transport line designing codes for magnet optical channels in MATLAB environment is presented in this report. Charged particles dynamics in a focusing channel can be studied easily by means of the matrix technique. MATLAB usage is convenient because its information objects are matrixes. MATLAB allows the use the modular principle to build the software package. Program blocks are small in size and easy to use. They can be executed separately or commonly. A set of codes has a user-friendly interface. Transport channel construction consists of focusing lenses (doublets and triplets). The main of the magneto-optical channel parameters are total length and lens position and parameters of the output beam in the phase space (channel acceptance, beam emittance - beam transverse dimensions, particles divergence and image stigmaticity). Choice of the channel operation parameters is based on the conditions for satisfying mutually competing demands. And therefore the channel parameters calculation is carried out by using the search engine optimization techniques.

  20. Adaptive RAC codes employing statistical channel evaluation ...

    African Journals Online (AJOL)

    An adaptive encoding technique using row and column array (RAC) codes employing a different number of parity columns that depends on the channel state is proposed in this paper. The trellises of the proposed adaptive codes and a statistical channel evaluation technique employing these trellises are designed and ...

  1. Channel One Online: Advertising Not Educating.

    Science.gov (United States)

    Pasnik, Shelley

    Rather than viewing Channel One's World Wide Web site as an authentic news bureau, as the organization claims, it is better understood as an advertising delivery system. The web site is an attempt to expand Channel One's reach into schools, taking advantage of unsuspecting teachers and students who might fall prey to spurious claims. This paper…

  2. Open channel steam generator feedwater system

    International Nuclear Information System (INIS)

    Kim, R.F.; Min-Hsiung Hu.

    1985-01-01

    A steam generator which utilizes a primary fluid to vaporize a secondary fluid is provided with an open flow channel and elevated discharge nozzle for the introduction of secondary fluid. The discharge nozzle is positioned above a portion of the inlet line such that the secondary fluid passes through a vertical section of inlet line prior to its discharge into the open channel. (author)

  3. Laboratory Experiments on Meandering Meltwater Channels

    Science.gov (United States)

    Fernandez, R.; Berens, J.; Parker, G.; Stark, C. P.

    2017-12-01

    Meandering channels of all scales and flowing over a wide variety of media have common planform patterns. Although the analogy in planform suggests there is a common underlying framework, the constitutive relations driving planform evolution through vertical incision/deposition and lateral migration differ from medium to medium. The driving processes in alluvial and mixed bedrock-alluvial meandering channels have been studied substantially over the last decades. However, this is not the case for meandering channels in other media such as ice or soluble rock. Here we present results from experiments conducted at the Ven Te Chow Hydrosystems Laboratory of the University of Illinois at Urbana-Champaign on meltwater meandering channels. A rivulet is carved into an ice block and water is allowed to flow at a constant discharge. Planform evolution is analyzed with time lapse imaging and complemented with rubber molds of the channel once the experiment is over. These molds give us the full 3D structure of the meandering, including incisional overhang. Vertical incision rates are measured throughout the run by taking elevations along the channel, and these measurements are complemented with analysis from the molds. We show examples of meandering of intense amplitude with deep overhangs. Features resembling scroll bars document cyclically punctuated melting. We report on lateral migration rates, incision rates, sinuosity, channel depths, channel widths, reach averaged velocities, bend wavelengths and amplitudes and compare them to values reported in the literature for alluvial rivers.

  4. Dental enamel cells express functional SOCE channels.

    Science.gov (United States)

    Nurbaeva, Meerim K; Eckstein, Miriam; Concepcion, Axel R; Smith, Charles E; Srikanth, Sonal; Paine, Michael L; Gwack, Yousang; Hubbard, Michael J; Feske, Stefan; Lacruz, Rodrigo S

    2015-10-30

    Dental enamel formation requires large quantities of Ca(2+) yet the mechanisms mediating Ca(2+) dynamics in enamel cells are unclear. Store-operated Ca(2+) entry (SOCE) channels are important Ca(2+) influx mechanisms in many cells. SOCE involves release of Ca(2+) from intracellular pools followed by Ca(2+) entry. The best-characterized SOCE channels are the Ca(2+) release-activated Ca(2+) (CRAC) channels. As patients with mutations in the CRAC channel genes STIM1 and ORAI1 show abnormal enamel mineralization, we hypothesized that CRAC channels might be an important Ca(2+) uptake mechanism in enamel cells. Investigating primary murine enamel cells, we found that key components of CRAC channels (ORAI1, ORAI2, ORAI3, STIM1, STIM2) were expressed and most abundant during the maturation stage of enamel development. Furthermore, inositol 1,4,5-trisphosphate receptor (IP3R) but not ryanodine receptor (RyR) expression was high in enamel cells suggesting that IP3Rs are the main ER Ca(2+) release mechanism. Passive depletion of ER Ca(2+) stores with thapsigargin resulted in a significant raise in [Ca(2+)]i consistent with SOCE. In cells pre-treated with the CRAC channel blocker Synta-66 Ca(2+) entry was significantly inhibited. These data demonstrate that enamel cells have SOCE mediated by CRAC channels and implicate them as a mechanism for Ca(2+) uptake in enamel formation.

  5. Visualizing individual sodium channels on the move.

    Science.gov (United States)

    Heinemann, Stefan H

    2012-07-27

    Visualization of voltage-gated sodium channels at work is an important requirement for the understanding of rapid electrical signaling in nerve cells. In this issue of Chemistry & Biology, Ondrus and colleagues have mastered this challenge by chemical synthesis of a fluorescent antagonist and by monitoring single sodium channels in living cells with unprecedented optical resolution. Copyright © 2012 Elsevier Ltd. All rights reserved.

  6. CHANNELING OF B-IONS IN SILICON

    NARCIS (Netherlands)

    VOS, M; MITCHELL, [No Value; SMULDERS, PJM

    We present new results on the channeling of B ions in Si crystals. Standard surface barrier detectors have been used to record energy spectra for B ions backscattered from the near surface (approximately 1500 angstrom) of a silicon crystal, under perfect, and near axial and planar channeling

  7. TRANSMISSION ION CHANNELING IMAGES OF CRYSTAL DEFECTS

    NARCIS (Netherlands)

    KING, PJC; BREESE, MBH; WILSHAW, PR; SMULDERS, PJM; GRIME, GW

    This paper demonstrates how images of crystal defects can be produced using ion channeling. A focused, scanned beam of MeV protons from the University of Oxford Nuclear Microprobe has been used. With the beam aligned with a channeling direction of the crystal, protons transmitted through the thinned

  8. Privacy of a lossy bosonic memory channel

    International Nuclear Information System (INIS)

    Ruggeri, Giovanna; Mancini, Stefano

    2007-01-01

    We study the security of the information transmission between two honest parties realized through a lossy bosonic memory channel when losses are captured by a dishonest party. We then show that entangled inputs can enhance the private information of such a channel, which however does never overcome that of unentangled inputs in absence of memory

  9. BK channel modulators: a comprehensive overview

    DEFF Research Database (Denmark)

    Nardi, Antonio; Olesen, Søren-Peter

    2008-01-01

    channels as a potentially attractive target, the design and synthesis of potent and selective BK modulators continue based on novel chemical ideas. A comprehensive overview of BK channel modulators is therefore timely and important to the current medicinal chemist for review, summary, and classification...

  10. Micromachining of buried micro channels in silicon

    NARCIS (Netherlands)

    de Boer, Meint J.; Tjerkstra, R.W.; Berenschot, Johan W.; Jansen, Henricus V.; Burger, G.J.; Burger, G.J.; Gardeniers, Johannes G.E.; Elwenspoek, Michael Curt; van den Berg, Albert

    A new method for the fabrication of micro structures for fluidic applications, such as channels, cavities, and connector holes in the bulk of silicon wafers, called buried channel technology (BCT), is presented in this paper. The micro structures are constructed by trench etching, coating of the

  11. Remarks to the hot channel power characteristics

    International Nuclear Information System (INIS)

    Tinka, I.; Tinkova, E.

    2002-01-01

    In connection with methodological improvements of safety analyses, some effects of detail power distributions, that should be taken into account for the hot channel characteristics determination, have been studied. This determination concerns the whole channel power (power of the fuel rod) and its axial (along the channel) and radial (across the fuel pellet radius) distribution. The total power of the channel is studied from the point of possible restrictions for different numbers of main cooling loops in operation. For radial power distribution the effect of burnup has been studied and for axial distribution the effect of the control rod vicinity (its coupler part) has been evaluated. The DNBR and fuel temperatures have been the key safety parameters influenced by these hot channel characteristics and have been evaluated in this study (Authors)

  12. Spiking neural P systems with multiple channels.

    Science.gov (United States)

    Peng, Hong; Yang, Jinyu; Wang, Jun; Wang, Tao; Sun, Zhang; Song, Xiaoxiao; Luo, Xiaohui; Huang, Xiangnian

    2017-11-01

    Spiking neural P systems (SNP systems, in short) are a class of distributed parallel computing systems inspired from the neurophysiological behavior of biological spiking neurons. In this paper, we investigate a new variant of SNP systems in which each neuron has one or more synaptic channels, called spiking neural P systems with multiple channels (SNP-MC systems, in short). The spiking rules with channel label are introduced to handle the firing mechanism of neurons, where the channel labels indicate synaptic channels of transmitting the generated spikes. The computation power of SNP-MC systems is investigated. Specifically, we prove that SNP-MC systems are Turing universal as both number generating and number accepting devices. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Ergodic Capacity for the SIMO Nakagami- Channel

    Directory of Open Access Journals (Sweden)

    Vagenas EfstathiosD

    2009-01-01

    Full Text Available This paper presents closed-form expressions for the ergodic channel capacity of SIMO (single-input and multiple output wireless systems operating in a Nakagami- fading channel. As the performance of SIMO channel is closely related to the diversity combining techniques, we present closed-form expressions for the capacity of maximal ratio combining (MRC, equal gain combining (EGC, selection combining (SC, and switch and stay (SSC diversity systems operating in Nakagami- fading channels. Also, the ergodic capacity of a SIMO system in a Nakagami- fading channel without any diversity technique is derived. The latter scenario is further investigated for a large amount of receive antennas. Finally, numerical results are presented for illustration.

  14. [Channels: a new way to revisit pathology].

    Science.gov (United States)

    Fournier, Emmanuel

    2014-02-01

    Many "essential" diseases that manifest themselves in the form of crises or fits (epilepsies, episodic ataxia, periodic paralyses, myotonia, heart rhythm disorders, etc.) are due to ionic channel dysfunction and are thus referred to as "channelopathies". Some of these disorders are congenital, due to mutations of genes encoding channel subunits, while others result from toxic, immune or hormonal disturbances affecting channelfunction. Channelopathies take on a wide variety of clinical forms, depending on the type of channel (sodium, potassium, calcium, chloride...) and the type of dysfunction (loss or gain of function). Some apparently unrelated diseases affecting distinct organs are due to a similar dysfunction of the same channel, revealing unsuspected relationships between organs and between medical specialties. In addition, a given syndrome can be caused by distinct channel dysfunctions. This provides new opportunities for diferential diagnosis and specific correction of the causal defects, although some treatments find applications across multiple medical specialties.

  15. Customers’ Perception regarding Assurance of Bancassurance Channel

    Directory of Open Access Journals (Sweden)

    Choudhury Mousumi

    2016-12-01

    Full Text Available Bancassurance has evolved as a strong distribution channel in India. Bancassurance means that the insurance company and the bank come together to offer insurance products from the counter of the banks to the bank’s customer. The present study attempts to analyse customers’ perception regarding assurance of bancassurance channel in providing insurance-related services. The study also tries to find out the impact of various demographic variables on customers’ perception regarding assurance of bancassurance channel. The study finds that customers consider bancassurance channel having high assurance in providing insurance services. It is also found in the study that there is no significant association between the demographic variables considered in the study and customers’ perception regarding assurance of bancassurance channel.

  16. Coupling of laser energy into plasma channels

    International Nuclear Information System (INIS)

    Dimitrov, D. A.; Giacone, R. E.; Bruhwiler, D. L.; Busby, R.; Cary, J. R.; Geddes, C. G. R.; Esarey, E.; Leemans, W. P.

    2007-01-01

    Diffractive spreading of a laser pulse imposes severe limitations on the acceleration length and maximum electron energy in the laser wake field accelerator (LWFA). Optical guiding of a laser pulse via plasma channels can extend the laser-plasma interaction distance over many Rayleigh lengths. Energy efficient coupling of laser pulses into and through plasma channels is very important for optimal LWFA performance. Results from simulation parameter studies on channel guiding using the particle-in-cell (PIC) code VORPAL [C. Nieter and J. R. Cary, J. Comput. Phys. 196, 448 (2004)] are presented and discussed. The effects that density ramp length and the position of the laser pulse focus have on coupling into channels are considered. Moreover, the effect of laser energy leakage out of the channel domain and the effects of tunneling ionization of a neutral gas on the guided laser pulse are also investigated. Power spectral diagnostics were developed and used to separate pump depletion from energy leakage. The results of these simulations show that increasing the density ramp length decreases the efficiency of coupling a laser pulse to a channel and increases the energy loss when the pulse is vacuum focused at the channel entrance. Then, large spot size oscillations result in increased energy leakage. To further analyze the coupling, a differential equation is derived for the laser spot size evolution in the plasma density ramp and channel profiles are simulated. From the numerical solution of this equation, the optimal spot size and location for coupling into a plasma channel with a density ramp are determined. This result is confirmed by the PIC simulations. They show that specifying a vacuum focus location of the pulse in front of the top of the density ramp leads to an actual focus at the top of the ramp due to plasma focusing, resulting in reduced spot size oscillations. In this case, the leakage is significantly reduced and is negligibly affected by ramp length

  17. Assesment of strength and integrity of fuel channels

    International Nuclear Information System (INIS)

    2000-01-01

    Detailed analysis to base strength and integrity of fuel channels was necessary for the licensing process. Description of tasks performed in this direction in 1999 is presented: fuel channel independent strength calculations, assessment of present fuel channels state, analysis of dynamic processes during partial group distribution header rupture, structural integrity analysis of fuel channels located next to broke channel

  18. Channel and Timeslot Co-Scheduling with Minimal Channel Switching for Data Aggregation in MWSNs

    Directory of Open Access Journals (Sweden)

    Sanggil Yeoum

    2017-05-01

    Full Text Available Collision-free transmission and efficient data transfer between nodes can be achieved through a set of channels in multichannel wireless sensor networks (MWSNs. While using multiple channels, we have to carefully consider channel interference, channel and time slot (resources optimization, channel switching delay, and energy consumption. Since sensor nodes operate on low battery power, the energy consumed in channel switching becomes an important challenge. In this paper, we propose channel and time slot scheduling for minimal channel switching in MWSNs, while achieving efficient and collision-free transmission between nodes. The proposed scheme constructs a duty-cycled tree while reducing the amount of channel switching. As a next step, collision-free time slots are assigned to every node based on the minimal data collection delay. The experimental results demonstrate that the validity of our scheme reduces the amount of channel switching by 17.5%, reduces energy consumption for channel switching by 28%, and reduces the schedule length by 46%, as compared to the existing schemes.

  19. Disguising quantum channels by mixing and channel distance trade-off

    International Nuclear Information System (INIS)

    Fung, Chi-Hang Fred; Chau, H F

    2014-01-01

    We consider the reverse problem of the distinguishability of two quantum channels, which we call the disguising problem. Given two quantum channels, the goal here is to make the two channels identical by mixing with some other channels with minimal mixing probabilities. This quantifies how much one channel can disguise as the other. In addition, the possibility to trade-off between the two mixing probabilities allows one channel to be more preserved (less mixed) at the expense of the other. We derive lower- and upper-bounds of the trade-off curve and apply them to a few example channels. Optimal trade-off is obtained in one example. We relate the disguising problem and the distinguishability problem by showing that the former can lower and upper bound the diamond norm. We also show that the disguising problem gives an upper-bound on the key generation rate in quantum cryptography. (paper)

  20. Evolutionary origins of mechanosensitive ion channels.

    Science.gov (United States)

    Martinac, Boris; Kloda, Anna

    2003-01-01

    According to the recent revision, the universal phylogenetic tree is composed of three domains: Eukarya (eukaryotes), Bacteria (eubacteria) and Archaea (archaebacteria). Mechanosensitive (MS) ion channels have been documented in cells belonging to all three domains suggesting their very early appearance during evolution of life on Earth. The channels show great diversity in conductance, selectivity and voltage dependence, while sharing the property of being gated by mechanical stimuli exerted on cell membranes. In prokaryotes, MS channels were first documented in Bacteria followed by their discovery in Archaea. The finding of MS channels in archaeal cells helped to recognize and establish the evolutionary relationship between bacterial and archaeal MS channels and to show that this relationship extends to eukaryotic Fungi (Schizosaccharomyces pombe) and Plants (Arabidopsis thaliana). Similar to their bacterial and archaeal homologues, MS channels in eukaryotic cell-walled Fungi and Plants may serve in protecting the cellular plasma membrane from excessive dilation and rupture that may occur during osmotic stress. This review summarizes briefly some of the recent developments in the MS channel research field that may ultimately lead to elucidation of the biophysical and evolutionary principles underlying the mechanosensory transduction in living cells.

  1. Calcium homeostasis modulator (CALHM) ion channels.

    Science.gov (United States)

    Ma, Zhongming; Tanis, Jessica E; Taruno, Akiyuki; Foskett, J Kevin

    2016-03-01

    Calcium homeostasis modulator 1 (CALHM1), formerly known as FAM26C, was recently identified as a physiologically important plasma membrane ion channel. CALHM1 and its Caenorhabditis elegans homolog, CLHM-1, are regulated by membrane voltage and extracellular Ca(2+) concentration ([Ca(2+)]o). In the presence of physiological [Ca(2+)]o (∼1.5 mM), CALHM1 and CLHM-1 are closed at resting membrane potentials but can be opened by strong depolarizations. Reducing [Ca(2+)]o increases channel open probability, enabling channel activation at negative membrane potentials. Together, voltage and Ca(2+) o allosterically regulate CALHM channel gating. Through convergent evolution, CALHM has structural features that are reminiscent of connexins and pannexins/innexins/LRRC8 (volume-regulated anion channel (VRAC)) gene families, including four transmembrane helices with cytoplasmic amino and carboxyl termini. A CALHM1 channel is a hexamer of CALHM1 monomers with a functional pore diameter of ∼14 Å. CALHM channels discriminate poorly among cations and anions, with signaling molecules including Ca(2+) and ATP able to permeate through its pore. CALHM1 is expressed in the brain where it plays an important role in cortical neuron excitability induced by low [Ca(2+)]o and in type II taste bud cells in the tongue that sense sweet, bitter, and umami tastes where it functions as an essential ATP release channel to mediate nonsynaptic neurotransmitter release. CLHM-1 is expressed in C. elegans sensory neurons and body wall muscles, and its genetic deletion causes locomotion defects. Thus, CALHM is a voltage- and Ca(2+) o-gated ion channel, permeable to large cations and anions, that plays important roles in physiology.

  2. Sodium channels as targets for volatile anesthetics

    Directory of Open Access Journals (Sweden)

    Karl F. Herold

    2012-03-01

    Full Text Available The molecular mechanisms of modern inhaled anesthetics although widely used in clinical settings are still poorly understood. Considerable evidence supports effects on membrane proteins such as ligand- and voltage-gated ion channels of excitable cells. Na+ channels are crucial to action potential initiation and propagation, and represent potential targets for volatile anesthetics. Inhibition of presynaptic Na+ channels leads to reduced neurotransmitter release at the synapse and could therefore contribute to the mechanisms by which volatile anesthetics produce their characteristic effects: amnesia, unconsciousness, and immobility. Early studies on crayfish and squid giant axon showed inhibition of Na+ currents by volatile anesthetics. Subsequent studies using native neuronal preparations and heterologous expression systems with various mammalian Na+ channel isoforms implicated inhibition of presynaptic Na+ channels in anesthetic actions. Volatile anesthetics reduce peak Na+ current and shift the voltage of half-maximal steady-state inactivation towards more negative potentials, thus stabilizing the fast-inactivated state. Furthermore recovery from fast-inactivation is slowed together with an enhanced use-dependent block during pulse train protocols. These effects can reduce neurotransmitter release by depressing presynaptic excitability, depolarization and Ca entry, and ultimately transmitter release. This reduction in transmitter release is more portent for glutamatergic vs. GABAergic terminals. Involvement of Na+ channel inhibition in mediating the immobility caused by volatile anesthetics has been demonstrated in animal studies, in which intrathecal infusion of the Na+ channel blocker tetrodotoxin increases volatile anesthetic potency, whereas infusion of the Na+ channels agonist veratridine reduces anesthetic potency. These studies indicate that inhibition of presynaptic Na+ channels by volatile anesthetics is involved in mediating some of

  3. Performance of Machine Learning Algorithms for Qualitative and Quantitative Prediction Drug Blockade of hERG1 channel.

    Science.gov (United States)

    Wacker, Soren; Noskov, Sergei Yu

    2018-05-01

    Drug-induced abnormal heart rhythm known as Torsades de Pointes (TdP) is a potential lethal ventricular tachycardia found in many patients. Even newly released anti-arrhythmic drugs, like ivabradine with HCN channel as a primary target, block the hERG potassium current in overlapping concentration interval. Promiscuous drug block to hERG channel may potentially lead to perturbation of the action potential duration (APD) and TdP, especially when with combined with polypharmacy and/or electrolyte disturbances. The example of novel anti-arrhythmic ivabradine illustrates clinically important and ongoing deficit in drug design and warrants for better screening methods. There is an urgent need to develop new approaches for rapid and accurate assessment of how drugs with complex interactions and multiple subcellular targets can predispose or protect from drug-induced TdP. One of the unexpected outcomes of compulsory hERG screening implemented in USA and European Union resulted in large datasets of IC 50 values for various molecules entering the market. The abundant data allows now to construct predictive machine-learning (ML) models. Novel ML algorithms and techniques promise better accuracy in determining IC 50 values of hERG blockade that is comparable or surpassing that of the earlier QSAR or molecular modeling technique. To test the performance of modern ML techniques, we have developed a computational platform integrating various workflows for quantitative structure activity relationship (QSAR) models using data from the ChEMBL database. To establish predictive powers of ML-based algorithms we computed IC 50 values for large dataset of molecules and compared it to automated patch clamp system for a large dataset of hERG blocking and non-blocking drugs, an industry gold standard in studies of cardiotoxicity. The optimal protocol with high sensitivity and predictive power is based on the novel eXtreme gradient boosting (XGBoost) algorithm. The ML-platform with XGBoost

  4. Omni-channel Retail Information Systems

    DEFF Research Database (Denmark)

    Tambo, Torben

    2014-01-01

    key players in the industry of retailing (Wilson, 2012; Verizon, 2012) and covers the idea that anything can be sold anywhere with consistent marketing, reasonable efficiency of the supply chain channels and responsible customer service. This article aims at contributing to a characterisation...... and definition of omni-channel retail information systems (OCRIS) by using the information systems research tradition as a distinctive starting point (Treiblmaier and Strebinger, 2008; Avgerou, 2001; Parboteah et al., 2009). Omni-channel retailing has evolved since 2010 with the ultimate aim of aligning physical...

  5. Multi-channel polarized thermal emitter

    Science.gov (United States)

    Lee, Jae-Hwang; Ho, Kai-Ming; Constant, Kristen P

    2013-07-16

    A multi-channel polarized thermal emitter (PTE) is presented. The multi-channel PTE can emit polarized thermal radiation without using a polarizer at normal emergence. The multi-channel PTE consists of two layers of metallic gratings on a monolithic and homogeneous metallic plate. It can be fabricated by a low-cost soft lithography technique called two-polymer microtransfer molding. The spectral positions of the mid-infrared (MIR) radiation peaks can be tuned by changing the periodicity of the gratings and the spectral separation between peaks are tuned by changing the mutual angle between the orientations of the two gratings.

  6. Channel uranium-graphite reactor mounting

    International Nuclear Information System (INIS)

    Polushkin, K.K.; Kuznetsov, A.G.; Zheleznyakov, B.N.

    1981-01-01

    According to theoretical principles of general engineering technology the engineering experience of construction-mounting works at the NPP with channel uranium-graphite reactors is systematized. Main parameters and structural features of the 1000 MW channel uranium-graphite reactors are considered. The succession of mounting operations, premounting equipment and pipelines preparation and mounting works technique are described. The most efficient methods of fitting, welding and machining of reactor elements are recommended. Main problems of technical control service are discussed. A typical netted diagram of main equipment of channel uranium-graphite reactors mounting is given

  7. Quantum Stackelberg Duopoly Game in Depolarizing Channel

    International Nuclear Information System (INIS)

    Zhu Xia; Kuang Leman

    2008-01-01

    In this paper, we investigate the quantum Stackelberg duopoly (QSD) game in the noise environment with the depolarizing channel expressed by the Kraus-operator representation. It is found that the presence of the damping in the depolarizing channel always leads to the decrease of the quantities of the moves and payoffs of the two players in the QSD game. It is indicated that under certain conditions the first-mover advantage in the QSD game can be weakened due to the presence of the damping in the depolarizing channel.

  8. Tema con variazioni: quantum channel capacity

    Science.gov (United States)

    Kretschmann, Dennis; Werner, Reinhard F.

    2004-02-01

    Channel capacity describes the size of the nearly ideal channels, which can be obtained from many uses of a given channel, using an optimal error correcting code. In this paper we collect and compare minor and major variations in the mathematically precise statements of this idea which have been put forward in the literature. We show that all the variations considered lead to equivalent capacity definitions. In particular, it makes no difference whether one requires mean or maximal errors to go to zero, and it makes no difference whether errors are required to vanish for any sequence of block sizes compatible with the rate, or only for one infinite sequence.

  9. Electronic trade effect of marketing channels

    Directory of Open Access Journals (Sweden)

    Lovreta Stipe

    2009-01-01

    Full Text Available E-commerce has caused many significant changes in marketing channels. Consumers had obtained multiple benefits from e-commerce. In addition, it has increased the level of competition in marketing channels. However, the focus of this paper is multichannel strategy and integration of physical (store and electronic marketing channels. E-commerce has induced dynamic development of multichannel strategy. This strategy has evolved as a consequence of multichannel consumer orientation. In developed economies, consumers are multichannel entities and active marketers aim to meet their requirements by creating multichannel offer.

  10. Multi-Channel Maximum Likelihood Pitch Estimation

    DEFF Research Database (Denmark)

    Christensen, Mads Græsbøll

    2012-01-01

    In this paper, a method for multi-channel pitch estimation is proposed. The method is a maximum likelihood estimator and is based on a parametric model where the signals in the various channels share the same fundamental frequency but can have different amplitudes, phases, and noise characteristics....... This essentially means that the model allows for different conditions in the various channels, like different signal-to-noise ratios, microphone characteristics and reverberation. Moreover, the method does not assume that a certain array structure is used but rather relies on a more general model and is hence...

  11. Decoding LDPC Convolutional Codes on Markov Channels

    Directory of Open Access Journals (Sweden)

    Kashyap Manohar

    2008-01-01

    Full Text Available Abstract This paper describes a pipelined iterative technique for joint decoding and channel state estimation of LDPC convolutional codes over Markov channels. Example designs are presented for the Gilbert-Elliott discrete channel model. We also compare the performance and complexity of our algorithm against joint decoding and state estimation of conventional LDPC block codes. Complexity analysis reveals that our pipelined algorithm reduces the number of operations per time step compared to LDPC block codes, at the expense of increased memory and latency. This tradeoff is favorable for low-power applications.

  12. Decoding LDPC Convolutional Codes on Markov Channels

    Directory of Open Access Journals (Sweden)

    Chris Winstead

    2008-04-01

    Full Text Available This paper describes a pipelined iterative technique for joint decoding and channel state estimation of LDPC convolutional codes over Markov channels. Example designs are presented for the Gilbert-Elliott discrete channel model. We also compare the performance and complexity of our algorithm against joint decoding and state estimation of conventional LDPC block codes. Complexity analysis reveals that our pipelined algorithm reduces the number of operations per time step compared to LDPC block codes, at the expense of increased memory and latency. This tradeoff is favorable for low-power applications.

  13. Two-Channel Dielectric Wake Field Accelerator

    International Nuclear Information System (INIS)

    Hirshfield, Jay L.

    2012-01-01

    Experimental results are reported for test beam acceleration and deflection in a two-channel, cm-scale, rectangular dielectric-lined wakefield accelerator structure energized by a 14-MeV drive beam. The dominant waveguide mode of the structure is at ∼30 GHz, and the structure is configured to exhibit a high transformer ratio (∼12:1). Accelerated bunches in the narrow secondary channel of the structure are continuously energized via Cherenkov radiation that is emitted by a drive bunch moving in the wider primary channel. Observed energy gains and losses, transverse deflections, and changes in the test bunch charge distribution compare favorably with predictions of theory.

  14. Fluvial processes and channel morphometry of the upper Orashi ...

    African Journals Online (AJOL)

    Fluvial processes and channel morphometry of the upper Orashi basin in ... of channel equilibrium between morphology and hydrology, the Orashi channel is not well ... Drainage basins, watershed morphology, morphometric analysis, Nigeria ...

  15. Multi-channel software defined radio experimental evaluation and analysis

    CSIR Research Space (South Africa)

    Van der Merwe, JR

    2014-09-01

    Full Text Available Multi-channel software-defined radios (SDRs) can be utilised as inexpensive prototyping platforms for transceiver arrays. The application for multi-channel prototyping is discussed and measured results of coherent channels for both receiver...

  16. Bidirectional Fano Algorithm for Lattice Coded MIMO Channels

    KAUST Repository

    Al-Quwaiee, Hessa

    2013-01-01

    channel model. Channel codes based on lattices are preferred due to three facts: lattice codes have simple structure, the code can achieve the limits of the channel, and they can be decoded efficiently using lattice decoders which can be considered

  17. Efficient channel estimation in massive MIMO systems - a distributed approach

    KAUST Repository

    Al-Naffouri, Tareq Y.

    2016-01-01

    We present two efficient algorithms for distributed estimation of channels in massive MIMO systems. The two cases of 1) generic, and 2) sparse channels is considered. The algorithms estimate the impulse response for each channel observed

  18. Research on Cost Information Sharing and Channel Choice in a Dual-Channel Supply Chain

    Directory of Open Access Journals (Sweden)

    Huihui Liu

    2016-01-01

    Full Text Available Many studies examine information sharing in an uncertain demand environment in a supply chain. However there is little literature on cost information sharing in a dual-channel structure consisting of a retail channel and a direct sales channel. Assuming that the retail sale cost and direct sale cost are random variables with a general distribution, the paper investigates the retailer’s choice on cost information sharing in a Bertrand competition model. Based on the equilibrium outcome of information sharing, the manufacturer’s channel choice is discussed in detail. Our paper provides several interesting conclusions. In both single- and dual-channel structures, the retailer has little motivation to share its private cost information which is verified to be valuable for the manufacturer. When the cost correlation between the two channels increases, our analyses show that the manufacturer’s profit improves. However, when channel choice is involved, the value of information could play a different role. The paper finds that a dual-channel structure can benefit the manufacturer only when the cost correlation is sufficiently low. In addition, if the cost correlation is weak, the cost fluctuation will bring out the advantage of a dual-channel structure and adding a new direct channel will help in risk pooling.

  19. Channel Planform Dynamics Monitoring and Channel Stability Assessment in Two Sediment-Rich Rivers in Taiwan

    Directory of Open Access Journals (Sweden)

    Cheng-Wei Kuo

    2017-01-01

    Full Text Available Recurrent flood events induced by typhoons are powerful agents to modify channel morphology in Taiwan’s rivers. Frequent channel migrations reflect highly sensitive valley floors and increase the risk to infrastructure and residents along rivers. Therefore, monitoring channel planforms is essential for analyzing channel stability as well as improving river management. This study analyzed annual channel changes along two sediment-rich rivers, the Zhuoshui River and the Gaoping River, from 2008 to 2015 based on satellite images of FORMOSAT-2. Channel areas were digitized from mid-catchment to river mouth (~90 km. Channel stability for reaches was assessed through analyzing the changes of river indices including braid index, active channel width, and channel activity. In general, the valley width plays a key role in braided degree, active channel width, and channel activity. These indices increase as the valley width expands whereas the braid index decreases slightly close to the river mouth due to the change of river types. This downstream pattern in the Zhuoshui River was interrupted by hydraulic construction which resulted in limited changes downstream from the weir, due to the lack of water and sediment supply. A 200-year flood, Typhoon Morakot in 2009, induced significant changes in the two rivers. The highly active landscape in Taiwan results in very sensitive channels compared to other regions. An integrated Sensitivity Index was proposed for identifying unstable reaches, which could be a useful reference for river authorities when making priorities in river regulation strategy. This study shows that satellite image monitoring coupled with river indices analysis could be an effective tool to evaluate spatial and temporal changes in channel stability in highly dynamic river systems.

  20. Quantum capacity under adversarial quantum noise: arbitrarily varying quantum channels

    OpenAIRE

    Ahlswede, Rudolf; Bjelakovic, Igor; Boche, Holger; Noetzel, Janis

    2010-01-01

    We investigate entanglement transmission over an unknown channel in the presence of a third party (called the adversary), which is enabled to choose the channel from a given set of memoryless but non-stationary channels without informing the legitimate sender and receiver about the particular choice that he made. This channel model is called arbitrarily varying quantum channel (AVQC). We derive a quantum version of Ahlswede's dichotomy for classical arbitrarily varying channels. This includes...