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Sample records for agonist-activated trpc5 channels

  1. Corticolimbic expression of TRPC4 and TRPC5 channels in the rodent brain.

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    Melissa A Fowler

    Full Text Available The canonical transient receptor potential (TRPC channels are a family of non-selective cation channels that are activated by increases in intracellular Ca(2+ and G(q/phospholipase C-coupled receptors. We used quantitative real-time PCR, in situ hybridization, immunoblots and patch-clamp recording from several brain regions to examine the expression of the predominant TRPC channels in the rodent brain. Quantitative real-time PCR of the seven TRPC channels in the rodent brain revealed that TRPC4 and TRPC5 channels were the predominant TRPC subtypes in the adult rat brain. In situ hybridization histochemistry and immunoblotting further resolved a dense corticolimbic expression of the TRPC4 and TRPC5 channels. Total protein expression of HIP TRPC4 and 5 proteins increased throughout development and peaked late in adulthood (6-9 weeks. In adults, TRPC4 expression was high throughout the frontal cortex, lateral septum (LS, pyramidal cell layer of the hippocampus (HIP, dentate gyrus (DG, and ventral subiculum (vSUB. TRPC5 was highly expressed in the frontal cortex, pyramidal cell layer of the HIP, DG, and hypothalamus. Detailed examination of frontal cortical layer mRNA expression indicated TRPC4 mRNA is distributed throughout layers 2-6 of the prefrontal cortex (PFC, motor cortex (MCx, and somatosensory cortex (SCx. TRPC5 mRNA expression was concentrated specifically in the deep layers 5/6 and superficial layers 2/3 of the PFC and anterior cingulate. Patch-clamp recording indicated a strong metabotropic glutamate-activated cation current-mediated depolarization that was dependent on intracellular Ca(2+and inhibited by protein kinase C in brain regions associated with dense TRPC4 or 5 expression and absent in regions lacking TRPC4 and 5 expression. Overall, the dense corticolimbic expression pattern suggests that these Gq/PLC coupled nonselective cation channels may be involved in learning, memory, and goal-directed behaviors.

  2. Calmodulin and calcium interplay in the modulation of TRPC5 channel activity. Identification of a novel C-terminal domain for calcium/calmodulin-mediated facilitation.

    Science.gov (United States)

    Ordaz, Benito; Tang, Jisen; Xiao, Rui; Salgado, Alfonso; Sampieri, Alicia; Zhu, Michael X; Vaca, Luis

    2005-09-01

    TRPC5 forms Ca2+-permeable nonselective cation channels important for neurite outgrowth and growth cone morphology of hippocampal neurons. Here we studied the activation of mouse TRPC5 expressed in Chinese hamster ovary and human embryonic kidney 293 cells by agonist stimulation of several receptors that couple to the phosphoinositide signaling cascade and the role of calmodulin (CaM) on the activation. We showed that exogenous application of 10 microM CaM through patch pipette accelerated the agonist-induced channel activation by 2.8-fold, with the time constant for half-activation reduced from 4.25 +/- 0.4 to 1.56 +/- 0.85 min. We identified a novel CaM-binding site located at the C terminus of TRPC5, 95 amino acids downstream from the previously determined common CaM/IP3R-binding (CIRB) domain for all TRPC proteins. Deletion of the novel CaM-binding site attenuated the acceleration in channel activation induced by CaM. However, disruption of the CIRB domain from TRPC5 rendered the channel irresponsive to agonist stimulation without affecting the cell surface expression of the channel protein. Furthermore, we showed that high (>5 microM) intracellular free Ca2+ inhibited the current density without affecting the time course of TRPC5 activation by receptor agonists. These results demonstrated that intracellular Ca2+ has dual and opposite effects on the activation of TRPC5. The novel CaM-binding site is important for the Ca2+/CaM-mediated facilitation, whereas the CIRB domain is critical for the overall response of receptor-induced TRPC5 channel activation.

  3. The Phospholipid-binding Protein SESTD1 Is a Novel Regulator of the Transient Receptor Potential Channels TRPC4 and TRPC5

    Science.gov (United States)

    Miehe, Susanne; Bieberstein, Andrea; Arnould, Isabelle; Ihdene, Orhia; Rütten, Hartmut; Strübing, Carsten

    2010-01-01

    TRPC4 and TRPC5 are two closely related members of the mammalian transient receptor potential cation channel family that have been implicated in important physiological functions, such as growth cone guidance and smooth muscle contraction. To further unravel the role of TRPC4 and TRPC5 in these processes in vivo, detailed information about the molecular composition of native channel complexes and their association with cellular signaling networks is needed. We therefore searched a human aortic cDNA library for novel TRPC4-interacting proteins using a modified yeast two-hybrid assay. This screen identified SESTD1, a previously uncharacterized protein containing a lipid-binding SEC14-like domain as well as spectrin-type cytoskeleton interaction domains. SESTD1 was found to associate with TRPC4 and TRPC5 via the channel's calmodulin- and inositol 1,4,5-trisphosphate receptor-binding domain. In functional studies, we demonstrate that SESTD1 binds several phospholipid species in vitro and is essential for efficient receptor-mediated activation of TRPC5. Notably, phospholipid binding to SESTD1 was Ca2+-dependent. Because TRPC4 and -5 conduct Ca2+, SESTD1-channel signaling may be bidirectional and also couple TRPC activity to lipid signaling through SESTD1. The modulation of TRPC channel function by specific lipid-binding proteins, such as SESTD1, adds another facet to the complex regulation of these channels complementary to the previously described effects of direct channel-phospholipid interaction. PMID:20164195

  4. Cocaine self-administration in mice with forebrain knock-down of trpc5 ion channels [v1; ref status: indexed, http://f1000r.es/pb

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    Matthew B Pomrenze

    2013-02-01

    Full Text Available Canonical transient receptor potential (TRPC channels are a family of non-selective cation channels that play a crucial role in modulating neuronal excitability due to their involvement in intracellular Ca2+ regulation and dendritic growth. TRPC5 channels a are one of the two most prevalent TRPC channels in the adult rodent brain; b are densely expressed in deep layer pyramidal neurons of the prefrontal cortex (PFC; and c modulate neuronal persistent activity necessary for working memory and attention. In order to evaluate the causal role of TRPC5 in motivation/reward-related behaviors, conditional forebrain TRPC5 knock-down (trpc5-KD mice were generated and trained to nose-poke for intravenous cocaine. Here we present a data set containing the first 6 days of saline or cocaine self-administration in wild type (WT and trpc5-KD mice. In addition, we also present a data set showing the dose-response to cocaine after both groups had achieved similar levels of cocaine self-administration. Compared to WT mice, trpc5-KD mice exhibited an apparent increase in self-administration on the first day of cocaine testing without prior operant training. There were no apparent differences between WT and trpc5-KD mice for saline responding on the first day of training. Both groups showed similar dose-response sensitivity to cocaine after several days of achieving similar levels of cocaine intake.

  5. Calcium-mediated agonists activate an inwardly rectified K+ channel in colonic secretory cells.

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    Devor, D C; Frizzell, R A

    1993-11-01

    Single-channel recording techniques were used to identify and characterize the K+ channel activated by Ca(2+)-mediated secretory agonists in T84 cells. Carbachol (CCh; 100 microM) and taurodeoxycholate (TDC; 0.75 mM) stimulated oscillatory outward K+ currents. With K gluconate in bath and pipette, cell-attached single-channel K+ currents stimulated by CCh and ionomycin (2 microM) were inwardly rectified and reversed at 0 mV. The single-channel chord conductance was 32 pS at -90 mV and 14 pS at +90 mV. Similar properties were observed in excised inside-out patches in symmetric K+, permitting further characterization of channel properties. Partial substitution of bath or pipette K+ with Na+ gave a K(+)-to-Na+ selectivity ratio of 5.5:1. Channel activity increased with increasing bath Ca2+ concentration in the physiological range of 50-800 nM. Maximal channel activity occurred at intracellular pH 7.2 and decreased at more acidic or alkaline pH values. Extracellular charybdotoxin (CTX; 50 nM) blocked inward but not outward currents. Extracellular tetraethylammonium (TEA; 10 mM) reduced single-channel amplitude at all voltages. No apparent block of the channel was observed with extracellular Ba2+ (1 mM), apamin (1 microM), 4-aminopyridine (4-AP; 4 mM), quinine (500 microM), or glyburide (10 microM). Cytosolic quinine and 4-AP blocked both inward and outward currents, whereas Ba2+ blocked only outward currents. Apamin, CTX, TEA, and glyburide did not affect channel activity. The agonist activation and pharmacological profile of this inwardly rectified K+ channel indicate that it is responsible for the increase in basolateral K+ conductance stimulated by Ca(2+)-mediated agonists in T84 cells. PMID:7694492

  6. Tumor endothelial expression of P-glycoprotein upon microvesicular transfer of TrpC5 derived from adriamycin-resistant breast cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Dong, YePing; Pan, QiongXi; Jiang, Li; Chen, Zhen; Zhang, FangFang; Liu, YanJun; Xing, Hui; Shi, Mei; Li, Jiao; Li, XiYuan; Zhu, YaoDan; Chen, Yun; Bruce, Iain C.; Jin, Jian, E-mail: jinjian31@126.com; Ma, Xin, E-mail: maxin@jiangnan.edu.cn

    2014-03-28

    Highlights: • TrpC5 was mainly accumulated in microvesicles of drug-resistant MCF-7/ADM cells. • Microvesicles from MCF-7/ADM transferred TrpC5 to endothelial cells. • TrpC5 inhibition reduced P-glycoprotein accumulation on tumor blood vessels in vivo. - Abstract: Treatment of carcinoma commonly fails due to chemoresistance. Studies have shown that endothelial cells acquire resistance via the tumor microenvironment. Microvesicle (MV) shedding from the cell membrane to the microenvironment plays an important role in communication between cells. The aim of the present study was to determine whether MCF-7 adriamycin-resistant cells (MCF-7/ADM) shed MVs that alter the characteristics of human microvessel endothelial cells (HMECs). MVs from tumor cells transferred a Ca{sup 2+}-permeable channel TrpC5 to HMECs, inducing the expression of P-glycoprotein (P-gp) by activation of the transcription factor NFATc3 (nuclear factor of activated T cells isoform c3). Expression of the mdr1 gene was blocked by the TrpC5-blocking antibody T5E3, and the production of P-gp in HMECs was reduced by blockade of TrpC5. Thus, we postulate that endothelial cells acquire the resistant protein upon exposure to TrpC5-containg MVs in the microenvironment, and express P-gp in the TrpC5–NFATc3 signal pathway.

  7. Partial Agonists Activate PPARgamma Using a Helix 12 Independent Mechanism

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    Bruning, J.B.; Chalmers, M.J.; Prasad, S.; Bushby, S.A.; Kamenecka, T.A.; He, Y.; Nettles, K.W.; Griffin, P.R.

    2009-05-28

    Binding to helix 12 of the ligand-binding domain of PPAR{gamma} is required for full agonist activity. Previously, the degree of stabilization of the activation function 2 (AF-2) surface was thought to correlate with the degree of agonism and transactivation. To examine this mechanism, we probed structural dynamics of PPAR{gamma} with agonists that induced graded transcriptional responses. Here we present crystal structures and amide H/D exchange (HDX) kinetics for six of these complexes. Amide HDX revealed each ligand induced unique changes to the dynamics of the ligand-binding domain (LBD). Full agonists stabilized helix 12, whereas intermediate and partial agonists did not at all, and rather differentially stabilized other regions of the binding pocket. The gradient of PPAR{gamma} transactivation cannot be accounted for solely through changes to the dynamics of AF-2. Thus, our understanding of allosteric signaling must be extended beyond the idea of a dynamic helix 12 acting as a molecular switch.

  8. 2-aminoethoxydiphenyl borate or lanthanum potentiates transient receptor potential-like channels in rat CA1 hippocampal neurons

    Institute of Scientific and Technical Information of China (English)

    Fengpeng Sun; Tian-ming Gao

    2010-01-01

    Expression of transient receptor potential(TRP)channels is widespread with transcripts distributed throughout the brain.All TRP channel subunits are activated following phospholipase C activation and form cation-selective ion channels.Previous studies examining the existence of TRP channels in hippocampal CA1 pyramidal neurons were based on cultured neurons.Therefore,their relevance for living tissue remains unclear.In the present study,patch-clamp recordings were conducted from CA1 pyramidal neurons in hippocampal slices from 7-day-old rats.Whole-cell currents were obtained from CA1 hippocampal neurons with potentiation effects of 2-aminoethoxydiphenyl borate and lanthanum,revealing that recorded experimental currents were characteristic TRP-like channel currents.Identification of rat hippocampal mRNA transcripts of TRPC4,TRPC5,TRPV1,TRPV2,and TRPV3 channels further verified the expression of characteristic TRP-like channels on rat CA1hippocampal neurons.

  9. Pharmacological properties of novel cyclic pentapeptides with µ-opioid receptor agonist activity.

    Science.gov (United States)

    Perlikowska, Renata; Piekielna, Justyna; Fichna, Jakub; do-Rego, Jean Claude; Toth, Geza; Janecki, Tomasz; Janecka, Anna

    2014-03-01

    In our previous paper we have reported the synthesis and biological activity of a cyclic analog, Tyr-c(D-Lys- Phe-Phe-Asp)-NH2, based on endomorphin-2 (EM-2) structure. This analog displayed high affinity for the µ-opioid receptor, was much more stable than EM-2 in rat brain homogenate and showed remarkable antinociceptive activity after intracerebroventricular (i.c.v.) injection. Even more importantly, the cyclic analog elicited weak analgesia also after peripheral administration, giving evidence that it was able to cross, at least to some extent, the blood-brain barrier (BBB). Here we describe further modifications of this analog aimed at enhancing brain delivery by increasing lipophilicity. Two new cyclic pentapeptides, Tyr-c(D-Lys-D-1-Nal-Phe-Asp)-NH2 and Tyr-c(D-Lys-D-2-Nal-Phe-Asp)-NH2 (where 1-Nal=1- naphthyl-3-alanine, 2-Nal=2-naphthyl-3-alanine) were synthesized and evaluated in biological assays. Both analogs showed high µ-opioid receptor affinity and agonist activity and were stable in the rat brain homogenates. Unfortunately, the increase of lipophilicity was achieved at the expense of water solubility. The analog with D-2-Nal residue showed strong analgesic effect when given i.c.v. but could not be tested after intravenous (i.v.) administration where higher concentrations of the compound are required. However, this analog showed inhibitory effect on gastrointestinal (GI) motility in vivo, providing an interesting approach to the development of peripherally restricted agents that could be useful for studying gastrointestinal disorders in animal models. PMID:23628088

  10. Comparative study of human and mouse pregnane X receptor agonistic activity in 200 pesticides using in vitro reporter gene assays

    International Nuclear Information System (INIS)

    The nuclear receptor, pregnane X receptor (PXR), is a ligand-dependent transcription factor that regulates genes involved in xenobiotic metabolism. Recent studies have shown that PXR activation may affect energy metabolism as well as the endocrine and immune systems. In this study, we characterized and compared the agonistic activities of a variety of pesticides against human PXR (hPXR) and mouse PXR (mPXR). We tested the hPXR and mPXR agonistic activity of 200 pesticides (29 organochlorines, 11 diphenyl ethers, 56 organophosphorus pesticides, 12 pyrethroids, 22 carbamates, 12 acid amides, 7 triazines, 7 ureas, and 44 others) by reporter gene assays using COS-7 simian kidney cells. Of the 200 pesticides tested, 106 and 93 activated hPXR and mPXR, respectively, and a total of 111 had hPXR and/or mPXR agonistic activity with greater or lesser inter-species differences. Although all of the pyrethroids and most of the organochlorines and acid amides acted as PXR agonists, a wide range of pesticides with diverse structures also showed hPXR and/or mPXR agonistic activity. Among the 200 pesticides, pyributicarb, pretilachlor, piperophos and butamifos for hPXR, and phosalone, prochloraz, pendimethalin, and butamifos for mPXR, acted as particularly potent activators at low concentrations in the order of 10-8-10-7 M. In addition, we found that several organophosphorus oxon- and pyributicarb oxon-metabolites decreased PXR activation potency compared to their parent compounds. These results suggest that a large number of structurally diverse pesticides and their metabolites possess PXR-mediated transcriptional activity, and their ability to do so varies in a species-dependent manner in humans and mice.

  11. Swietenia mahagony extract shows agonistic activity to PPARγ and gives ameliorative effects on diabetic db/db mice

    Institute of Scientific and Technical Information of China (English)

    Dan-dan LI; Xu SHEN; Hua-liang JIANG; Jun-hua CHEN; Qing CHEN; Guo-wei LI; Jing CHEN; Jian-min YUE; Min-li CHEN; Xiao-ping WANG; Jian-hua SHEN

    2005-01-01

    Aim: To search the peroxisome proliferator-activated receptor γ (PPARγ) agonists from Swietenia mahagony extract (SmE) and observe the possible ameliorative effects of SmE on diabetic db/db mice. Methods: The PPARγ agonistic activity of SmE was screened by yeast-two hybrid system. The blood glucose levels of diabetic db/db mice were measured using a blood glucose level monitor and the data were statistically analyzed by NDST8.8W software. Results: By using the clinical drug rosiglitazone as a positive control, it was found that the PPARγ agonistic activity of SmE at a concentration of 50 μg/L was approximately half that of 35.7 μg/L (0.1 μmol/L) of rosiglitazone. At the dose of 1000 mg/kg, SmE remark ably decreased the blood glucose concentration of db/db mice from (15.26±2.98) to (7.58±2.20) mmol/L, and reduced the blood glucose levels by 55.49% compared with the control group (P<0.01). Conclusion: SmE shows agonistic activity to PPARγ and can ameliorate the blood glucose levels of diabetic db/db mice. SmE may be thus used as a potential agent for diabetes therapy.

  12. Evaluation of in vivo partial beta 1/beta 2-agonist activity: a dose-ranging study with carteolol.

    OpenAIRE

    Wheeldon, N M; McDevitt, D G; Lipworth, B J

    1992-01-01

    1. The aims of this study were to investigate the partial agonist profile of carteolol and evaluate methodology for differentiating relative beta 1 and beta 2 partial agonist activity (PAA) in vivo. 2. Eight normal subjects received single oral doses of carteolol 10 mg, 30 mg and 60 mg; nadolol 40 mg; pindolol 30 mg and placebo, given in a single-blind, randomised crossover design. 3. beta 1-PAA was demonstrated with carteolol by dose-related increases in resting heart rate and systolic blood...

  13. Direct assessment of cumulative aryl hydrocarbon receptor agonist activity in sera from experimentally exposed mice and environmentally exposed humans

    DEFF Research Database (Denmark)

    Schlezinger, Jennifer J; Bernard, Pamela L; Haas, Amelia;

    2010-01-01

    readouts to provide a broader context for estimating human risk than that obtained with serum extraction and gas chromatography/mass spectroscopy (GC/MS)-based assays alone. METHODS: AhR agonist activity was quantified in sera from dioxin-treated mice, commercial human sources, and polychlorinated biphenyl......BACKGROUND: Aryl hydrocarbon receptor (AhR) ligands adversely affect many biological processes. However, assessment of the significance of human exposures is hampered by an incomplete understanding of how complex mixtures affect AhR activation/inactivation. OBJECTIVES: These studies used biological...

  14. Hair-Cell Mechanotransduction Persists in TRP Channel Knockout Mice.

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    Wu, Xudong; Indzhykulian, Artur A; Niksch, Paul D; Webber, Roxanna M; Garcia-Gonzalez, Miguel; Watnick, Terry; Zhou, Jing; Vollrath, Melissa A; Corey, David P

    2016-01-01

    Members of the TRP superfamily of ion channels mediate mechanosensation in some organisms, and have been suggested as candidates for the mechanotransduction channel in vertebrate hair cells. Some TRP channels can be ruled out based on lack of an inner ear phenotype in knockout animals or pore properties not similar to the hair-cell channel. Such studies have excluded Trpv4, Trpa1, Trpml3, Trpm1, Trpm3, Trpc1, Trpc3, Trpc5, and Trpc6. However, others remain reasonable candidates. We used data from an RNA-seq analysis of gene expression in hair cells as well as data on TRP channel conductance to narrow the candidate group. We then characterized mice lacking functional Trpm2, Pkd2, Pkd2l1, Pkd2l2 and Pkd1l3, using scanning electron microscopy, auditory brainstem response, permeant dye accumulation, and single-cell electrophysiology. In all of these TRP-deficient mice, and in double and triple knockouts, mechanotransduction persisted. Together with published studies, these results argue against the participation of any of the 33 mouse TRP channels in hair cell transduction. PMID:27196058

  15. Hair-Cell Mechanotransduction Persists in TRP Channel Knockout Mice.

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    Xudong Wu

    Full Text Available Members of the TRP superfamily of ion channels mediate mechanosensation in some organisms, and have been suggested as candidates for the mechanotransduction channel in vertebrate hair cells. Some TRP channels can be ruled out based on lack of an inner ear phenotype in knockout animals or pore properties not similar to the hair-cell channel. Such studies have excluded Trpv4, Trpa1, Trpml3, Trpm1, Trpm3, Trpc1, Trpc3, Trpc5, and Trpc6. However, others remain reasonable candidates. We used data from an RNA-seq analysis of gene expression in hair cells as well as data on TRP channel conductance to narrow the candidate group. We then characterized mice lacking functional Trpm2, Pkd2, Pkd2l1, Pkd2l2 and Pkd1l3, using scanning electron microscopy, auditory brainstem response, permeant dye accumulation, and single-cell electrophysiology. In all of these TRP-deficient mice, and in double and triple knockouts, mechanotransduction persisted. Together with published studies, these results argue against the participation of any of the 33 mouse TRP channels in hair cell transduction.

  16. Screening of agonistic activities against four nuclear receptors in wastewater treatment plants in Japan using a yeast two-hybrid assay

    Institute of Scientific and Technical Information of China (English)

    Daisuke Inoue; Koki Nakama; Kazuko Sawada; Taro Watanabe; Hisae Matsui; Kazunari Sei; Tsuyoshi Nakanishi; Michihiko Ike

    2011-01-01

    To assess the potential endocrine disruptive effects through multiple nuclear receptors (NRs), especially non-steroidal NRs, in municipal wastewater, we examined the agonistic activities on four NRs (estrogen receptor c, thyroid hormone receptor α, retinoic acid receptor α and retinoid X receptor α) of untreated and treated wastewater from municipal wastewater treatment plants (WWTPs) in Japan using a yeast two-hybrid assay.Investigation of the infiuent and effluent of seven WWTPs revealed that agonistic activities against steroidal and non-steroidal NRs were always detected in the infiuents and partially remained in the effluents.Further investigation of four WWTPs employing conventional activated sludge, pseudo-anoxic-oxic, anoxic-oxic and anaerobic-anoxic-oxic processes revealed that the ability to reduce the agonistic activity against each of the four NRs varies depending on the treatment process.These results indicated that municipal wastewater in Japan commonly contains endocrine disrupting chemicals that exert agonistic activities on steroidal and non-steroidal NRs, and that some of these chemicals are released into the natural aquatic environment.Although the results obtained in yeast assays suggested that measured levels of non-steroidal NR agonists in the effluent of WWTPs were not likely to cause any biological effect, further study is required to assess their possible risks in detail.

  17. The Role of Canonical Transient Receptor Potential Channels in Seizure and Excitotoxicity

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    Fang Zheng

    2014-04-01

    Full Text Available Canonical transient receptor potential (TRPC channels are a family of polymodal cation channels with some degree of Ca2+ permeability. Although initially thought to be channels mediating store-operated Ca2+ influx, TRPC channels can be activated by stimulation of Gq-coupled G-protein coupled receptors, or by an increase in intracellular free Ca2+ concentration. Thus, activation of TRPC channels could be a common downstream event of many signaling pathways that contribute to seizure and excitotoxicity, such as N-methyl-D-aspartate (NMDA receptor-mediated Ca2+ influx, or metabotropic glutamate receptor activation. Recent studies with genetic ablation of various TRPC family members have demonstrated that TRPC channels, in particular heteromeric TRPC1/4 channels and homomeric TRPC5 channels, play a critical role in both pilocarpine-induced acute seizures and neuronal cell death. However, exact underlying mechanisms remain to be fully elucidated, and selective TRPC modulators and antibodies with better specificity are urgently needed for future research.

  18. Conicasterol E, a Small Heterodimer Partner Sparing Farnesoid X Receptor Modulator Endowed with a Pregnane X Receptor Agonistic Activity, from the Marine Sponge Theonella swinhoei

    OpenAIRE

    V. Sepe; Ummarino, R.; D'Auria, M.V.; Chini, M.G.; G. Bifulco; Renga, B.; D' Amore, C.; Debitus, Cécile; Fiorucci, S.; Zampella, A.

    2012-01-01

    We report the isolation and pharmacological characterization of conicasterol E isolated from the marine sponge Theonella swinhoei. Pharmacological characterization of this steroid in comparison to CDCA, a natural FXR ligand, and 6-ECDCA, a synthetic FXR agonist generated by an improved synthetic strategy, and rifaximin, a potent PXR agonist, demonstrated that conicasterol E is an FXR modulator endowed with PXR agonistic activity. Conicasterol E induces the expression of genes involved in bile...

  19. In silico investigation of agonist activity of a structurally diverse set of drugs to hPXR using HM-BSM and HM-PNN.

    Science.gov (United States)

    Zhang, Yi-Ming; Chang, Mei-Jia; Yang, Xu-Shu; Han, Xiao

    2016-06-01

    The human pregnane X receptor (hPXR) plays a critical role in the metabolism, transport and clearance of xenobiotics in the liver and intestine. The hPXR can be activated by a structurally diverse of drugs to initiate clinically relevant drug-drug interactions. In this article, in silico investigation was performed on a structurally diverse set of drugs to identify critical structural features greatly related to their agonist activity towards hPXR. Heuristic method (HM)-Best Subset Modeling (BSM) and HM-Polynomial Neural Networks (PNN) were utilized to develop the linear and non-linear quantitative structure-activity relationship models. The applicability domain (AD) of the models was assessed by Williams plot. Statistically reliable models with good predictive power and explain were achieved (for HM-BSM, r (2)=0.881, q LOO (2) =0.797, q EXT (2) =0.674; for HM-PNN, r (2)=0.882, q LOO (2) =0.856, q EXT (2) =0.655). The developed models indicated that molecular aromatic and electric property, molecular weight and complexity may govern agonist activity of a structurally diverse set of drugs to hPXR. PMID:27376821

  20. Detection and measurement of the agonistic activities of PCBs and mono-hydroxylated PCBs to the constitutive androstane receptor using a recombinant yeast assay.

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    Kamata, Ryo; Shiraishi, Fujio; Kageyama, Shiho; Nakajima, Daisuke

    2015-10-01

    Polychlorinated biphenyls (PCBs) are thought to exert their toxicities mainly by binding to the aryl hydrocarbon receptor and by stimulating transcription of various genes, notably metabolizing enzymes including the cytochrome P450 (CYP) 1 family. However, PCBs and their metabolites could have potential to activate other nuclear receptors and subsequent events. We focused on the constitutive androstane receptor (CAR) inducing CYP2B and measured the agonistic activity of PCBs and mono-hydroxylated PCBs (OH-PCBs) to the CAR using yeast cells transduced with the human CAR and its response pathway. Twenty-nine of 34 tested PCBs and 72 of 91 OH-PCBs exhibited CAR agonistic effects. Of 41 OH-PCBs that had the same chlorination patterns as the tested PCBs, 9 had activities more than twice those of their non-hydroxylated analogs. In particular, 2',4',6'-trichlorobiphenyl-4-ol and 2,2',4',6'-tetrachlorobiphenyl-4-ol were 332- and 22-fold more potent than their analogs and were 15 times and 2.8 times, respectively, as active as a reference substance, 4-tert-octylphenol. The activities of 17 of the OH-PCBs were reduced to less than half those of their non-hydroxylated analogs. Four OH-PCBs derived from 3 active PCBs were inactive. However, a consistent relationship between hydroxyl substituent position and activity could not be discerned. Comprehensive evaluation of the toxic potential of PCBs and their hydroxylated metabolites and their concentrations in the environment are required. PMID:26231822

  1. Α-galactosylceramide analogs with weak agonist activity for human iNKT cells define new candidate anti-inflammatory agents.

    Science.gov (United States)

    Bricard, Gabriel; Venkataswamy, Manjunatha M; Yu, Karl O A; Im, Jin S; Ndonye, Rachel M; Howell, Amy R; Veerapen, Natacha; Illarionov, Petr A; Besra, Gurdyal S; Li, Qian; Chang, Young-Tae; Porcelli, Steven A

    2010-12-17

    CD1d-restricted natural killer T cells with invariant T cell receptor α chains (iNKT cells) are a unique lymphocyte subset that responds to recognition of specific lipid and glycolipid antigens. They are conserved between mice and humans and exert various immunoregulatory functions through their rapid secretion of a variety of cytokines and secondary activation of dendritic cells, B cells and NK cells. In the current study, we analyzed the range of functional activation states of human iNKT cells using a library of novel analogs of α-galactosylceramide (αGalCer), the prototypical iNKT cell antigen. Measurement of cytokines secreted by human iNKT cell clones over a wide range of glycolipid concentrations revealed that iNKT cell ligands could be classified into functional groups, correlating with weak versus strong agonistic activity. The findings established a hierarchy for induction of different cytokines, with thresholds for secretion being consistently lowest for IL-13, higher for interferon-γ (IFNγ), and even higher for IL-4. These findings suggested that human iNKT cells can be intrinsically polarized to selective production of IL-13 by maintaining a low level of activation using weak agonists, whereas selective polarization to IL-4 production cannot be achieved through modulating the strength of the activating ligand. In addition, using a newly designed in vitro system to assess the ability of human iNKT cells to transactivate NK cells, we found that robust secondary induction of interferon-γ secretion by NK cells was associated with strong but not weak agonist ligands of iNKT cells. These results indicate that polarization of human iNKT cell responses to Th2-like or anti-inflammatory effects may best be achieved through selective induction of IL-13 and suggest potential discrepancies with findings from mouse models that may be important in designing iNKT cell-based therapies in humans.

  2. Α-galactosylceramide analogs with weak agonist activity for human iNKT cells define new candidate anti-inflammatory agents.

    Directory of Open Access Journals (Sweden)

    Gabriel Bricard

    Full Text Available CD1d-restricted natural killer T cells with invariant T cell receptor α chains (iNKT cells are a unique lymphocyte subset that responds to recognition of specific lipid and glycolipid antigens. They are conserved between mice and humans and exert various immunoregulatory functions through their rapid secretion of a variety of cytokines and secondary activation of dendritic cells, B cells and NK cells. In the current study, we analyzed the range of functional activation states of human iNKT cells using a library of novel analogs of α-galactosylceramide (αGalCer, the prototypical iNKT cell antigen. Measurement of cytokines secreted by human iNKT cell clones over a wide range of glycolipid concentrations revealed that iNKT cell ligands could be classified into functional groups, correlating with weak versus strong agonistic activity. The findings established a hierarchy for induction of different cytokines, with thresholds for secretion being consistently lowest for IL-13, higher for interferon-γ (IFNγ, and even higher for IL-4. These findings suggested that human iNKT cells can be intrinsically polarized to selective production of IL-13 by maintaining a low level of activation using weak agonists, whereas selective polarization to IL-4 production cannot be achieved through modulating the strength of the activating ligand. In addition, using a newly designed in vitro system to assess the ability of human iNKT cells to transactivate NK cells, we found that robust secondary induction of interferon-γ secretion by NK cells was associated with strong but not weak agonist ligands of iNKT cells. These results indicate that polarization of human iNKT cell responses to Th2-like or anti-inflammatory effects may best be achieved through selective induction of IL-13 and suggest potential discrepancies with findings from mouse models that may be important in designing iNKT cell-based therapies in humans.

  3. Distinct properties of telmisartan on agonistic activities for peroxisome proliferator-activated receptor γ among clinically used angiotensin II receptor blockers: drug-target interaction analyses.

    Science.gov (United States)

    Kakuta, Hirotoshi; Kurosaki, Eiji; Niimi, Tatsuya; Gato, Katsuhiko; Kawasaki, Yuko; Suwa, Akira; Honbou, Kazuya; Yamaguchi, Tomohiko; Okumura, Hiroyuki; Sanagi, Masanao; Tomura, Yuichi; Orita, Masaya; Yonemoto, Takako; Masuzaki, Hiroaki

    2014-04-01

    A proportion of angiotensin II type 1 receptor blockers (ARBs) improves glucose dyshomeostasis and insulin resistance in a clinical setting. Of these ARBs, telmisartan has the unique property of being a partial agonist for peroxisome proliferator-activated receptor γ (PPARγ). However, the detailed mechanism of how telmisartan acts on PPARγ and exerts its insulin-sensitizing effect is poorly understood. In this context, we investigated the agonistic activity of a variety of clinically available ARBs on PPARγ using isothermal titration calorimetry (ITC) and surface plasmon resonance (SPR) system. Based on physicochemical data, we then reevaluated the metabolically beneficial effects of telmisartan in cultured murine adipocytes. ITC and SPR assays demonstrated that telmisartan exhibited the highest affinity of the ARBs tested. Distribution coefficient and parallel artificial membrane permeability assays were used to assess lipophilicity and cell permeability, for which telmisartan exhibited the highest levels of both. We next examined the effect of each ARB on insulin-mediated glucose metabolism in 3T3-L1 preadipocytes. To investigate the impact on adipogenesis, 3T3-L1 preadipocytes were differentiated with each ARB in addition to standard inducers of differentiation for adipogenesis. Telmisartan dose-dependently facilitated adipogenesis and markedly augmented the mRNA expression of adipocyte fatty acid-binding protein (aP2), accompanied by an increase in the uptake of 2-deoxyglucose and protein expression of glucose transporter 4 (GLUT4). In contrast, other ARBs showed only marginal effects in these experiments. In accordance with its highest affinity of binding for PPARγ as well as the highest cell permeability, telmisartan superbly activates PPARγ among the ARBs tested, thereby providing a fresh avenue for treating hypertensive patients with metabolic derangement. PMID:24424487

  4. Englerin A Agonizes the TRPC4/C5 Cation Channels to Inhibit Tumor Cell Line Proliferation.

    Directory of Open Access Journals (Sweden)

    Cheryl Carson

    Full Text Available Englerin A is a structurally unique natural product reported to selectively inhibit growth of renal cell carcinoma cell lines. A large scale phenotypic cell profiling experiment (CLiP of englerin A on ¬over 500 well characterized cancer cell lines showed that englerin A inhibits growth of a subset of tumor cell lines from many lineages, not just renal cell carcinomas. Expression of the TRPC4 cation channel was the cell line feature that best correlated with sensitivity to englerin A, suggesting the hypothesis that TRPC4 is the efficacy target for englerin A. Genetic experiments demonstrate that TRPC4 expression is both necessary and sufficient for englerin A induced growth inhibition. Englerin A induces calcium influx and membrane depolarization in cells expressing high levels of TRPC4 or its close ortholog TRPC5. Electrophysiology experiments confirmed that englerin A is a TRPC4 agonist. Both the englerin A induced current and the englerin A induced growth inhibition can be blocked by the TRPC4/C5 inhibitor ML204. These experiments confirm that activation of TRPC4/C5 channels inhibits tumor cell line proliferation and confirms the TRPC4 target hypothesis generated by the cell line profiling. In selectivity assays englerin A weakly inhibits TRPA1, TRPV3/V4, and TRPM8 which suggests that englerin A may bind a common feature of TRP ion channels. In vivo experiments show that englerin A is lethal in rodents near doses needed to activate the TRPC4 channel. This toxicity suggests that englerin A itself is probably unsuitable for further drug development. However, since englerin A can be synthesized in the laboratory, it may be a useful chemical starting point to identify novel modulators of other TRP family channels.

  5. Acute Treatment with a Novel TRPC4/C5 Channel Inhibitor Produces Antidepressant and Anxiolytic-Like Effects in Mice.

    Directory of Open Access Journals (Sweden)

    Li-Ping Yang

    Full Text Available Transient receptor potential canonical (TRPC channels are widely expressed in brain and involved in various aspects of brain function. Both TRPC4 and TRPC5 have been implicated in innate fear function, which represents a key response to environmental stress. However, to what extent the TRPC4/C5 channels are involved in psychiatric disorders remains unexplored. Here, we tested the antidepressant and anxiolytic-like effects of a newly identified TRPC4/C5 inhibitor, M084. We show that a single intraperitoneal administration of M084 at 10 mg/kg body weight to C57BL/6 male mice significantly shortened the immobility time in forced swim test and tail suspension test within as short as 2 hours. The M084-treated mice spent more time exploring in illuminated and open areas in light/dark transition test and elevated plus maze test. In mice subjected to chronic unpredictable stress, M084 treatment reversed the enhanced immobility time in forced swim test and decreased the latency to feed in novelty suppressed feeding test. The treatment of M084 increased BDNF expression in both mRNA and protein levels, as well as phosphorylation levels of AKT and ERK, in prefrontal cortex. Our results indicate that M084 exerts rapid antidepressant and anxiolytic-like effects at least in part by acting on BDNF and its downstream signaling. We propose M084 as a lead compound for further druggability research.

  6. Discovery of a Series of 2-phenyl-N-(2-(pyrrolidin-1-yl)phenyl)acetamides as Novel Molecular Switches that Modulate Modes of Kv7.2 (KCNQ2) Channel Pharmacology: Identification of (S)-2-phenyl-N-(2-(pyrrolidin-1-yl)phenyl)butanamide (ML252) as a Potent, Brain Penetrant Kv7.2 Channel Inhibitor

    Science.gov (United States)

    Cheung, Yiu-Yin; Yu, Haibo; Xu, Kaiping; Zou, Beiyan; Wu, Meng; McManus, Owen B.; Li, Min; Lindsley, Craig W.; Hopkins, Corey R.

    2012-01-01

    A potent and selective inhibitor of KCNQ2, (S)-5 (ML252, IC50 = 69 nM), was discovered after a high-throughput screen of the MLPCN library was performed. SAR studies revealed a small structural change (ethyl group to hydrogen) caused a functional shift from antagonist to agonist activity (37, EC50 = 170 nM), suggesting an interaction at a critical site for controlling gating of KCNQ2 channels. PMID:22793372

  7. RFI channels

    Science.gov (United States)

    Mceliece, R. J.

    1980-01-01

    A class of channel models is presented which exhibit varying burst error severity much like channels encountered in practice. An information-theoretic analysis of these channel models is made, and conclusions are drawn that may aid in the design of coded communication systems for realistic noisy channels.

  8. Structural requirements for activation of the 5-oxo-6E,8Z, 11Z,14Z-eicosatetraenoic acid (5-oxo-ETE) receptor: identification of a mead acid metabolite with potent agonist activity.

    Science.gov (United States)

    Patel, Pranav; Cossette, Chantal; Anumolu, Jaganmohan R; Gravel, Sylvie; Lesimple, Alain; Mamer, Orval A; Rokach, Joshua; Powell, William S

    2008-05-01

    The 5-lipoxygenase product 5-oxo-6E,8Z,11Z,14Z-eicosatetraenoic acid (5-oxo-ETE) is a potent chemoattractant for neutrophils and eosinophils, and its actions are mediated by the oxoeicosanoid (OXE) receptor, a member of the G protein-coupled receptor family. To define the requirements for activation of the OXE receptor, we have synthesized a series of 5-oxo-6E,8Z-dienoic acids with chain lengths between 12 and 20 carbons, as well as a series of 20-carbon 5-oxo fatty acids, either fully saturated or containing between one and five double bonds. The effects of these compounds on neutrophils (calcium mobilization, CD11b expression, and cell migration) and eosinophils (actin polymerization) were compared with those of 5-oxo-ETE. The C12 and C14 analogs were without appreciable activity, whereas the C16 5-oxo-dienoic acid was a weak partial agonist. In contrast, the corresponding C18 analog (5-oxo-18:2) was nearly as potent as 5-oxo-ETE. Among the C20 analogs, the fully saturated compound had virtually no activity, whereas 5-oxo-6E-eicosenoic acid had only weak agonist activity. In contrast, 5-oxo-6E,8Z,11Z-eicosatrienoic acid (5-oxo-20:3) and its 8-trans isomer were approximately equipotent with 5-oxo-ETE in activating granulocytes. Because of the potent effects of 5-oxo-20:3, we investigated its formation from Mead acid (5Z,8Z,11Z-eicosatrienoic acid), which accumulates in dietary essential fatty acid deficiency, by neutrophils. The main Mead acid metabolite identified was 5-hydroxy-6,8,11-eicosatrienoic acid, followed by 5-oxo-20:3 and two 6-trans isomers of leukotriene B(3). We conclude that optimal activation of the OXE receptor is achieved with 5-oxo-ETE, 5-oxo-18:2, and 5-oxo-20:3, and that the latter compound could potentially be formed under conditions of essential fatty acid deficiency. PMID:18292294

  9. Brands & Channels

    Institute of Scientific and Technical Information of China (English)

    Alice Yang

    2009-01-01

    @@ "Brands" and "Channels" are the two most important things in Ku-Hai Chen's eyes when doing business with Main-land China. Ku-Hai Chen, Executive Director of the International Trade Institute of Taiwan External Trade Development Council (TAITRA), flies frequently between Chinese Taipei and Mainland China, and was in Beijing earlier this month for his seminar.

  10. 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 compon

  11. Channel Networks

    Science.gov (United States)

    Rinaldo, Andrea; Rodriguez-Iturbe, Ignacio; Rigon, Riccardo

    This review proceeds from Luna Leopold's and Ronald Shreve's lasting accomplishments dealing with the study of random-walk and topologically random channel networks. According to the random perspective, which has had a profound influence on the interpretation of natural landforms, nature's resiliency in producing recurrent networks and landforms was interpreted to be the consequence of chance. In fact, central to models of topologically random networks is the assumption of equal likelihood of any tree-like configuration. However, a general framework of analysis exists that argues that all possible network configurations draining a fixed area are not necessarily equally likely. Rather, a probability P(s) is assigned to a particular spanning tree configuration, say s, which can be generally assumed to obey a Boltzmann distribution: P(s) % e^-H(s)/T, where T is a parameter and H(s) is a global property of the network configuration s related to energetic characters, i.e. its Hamiltonian. One extreme case is the random topology model where all trees are equally likely, i.e. the limit case for T6 4 . The other extreme case is T 6 0, and this corresponds to network configurations that tend to minimize their total energy dissipation to improve their likelihood. Networks obtained in this manner are termed optimal channel networks (OCNs). Observational evidence suggests that the characters of real river networks are reproduced extremely well by OCNs. Scaling properties of energy and entropy of OCNs suggest that large network development is likely to effectively occur at zero temperature (i.e. minimizing its Hamiltonian). We suggest a corollary of dynamic accessibility of a network configuration and speculate towards a thermodynamics of critical self-organization. We thus conclude that both chance and necessity are equally important ingredients for the dynamic origin of channel networks---and perhaps of the geometry of nature.

  12. Channeling experiment

    International Nuclear Information System (INIS)

    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)

  13. Channel strategy adaptation

    OpenAIRE

    Rangan, V. Kasturi; Nueno, Jose L

    1999-01-01

    Using transaction cost theory, considerable research in marketing has focused on the conditions under which firms would use direct or vertically integrated versus indirect or arms length channels of distribution. Data from the field, however, indicate that channel configurations are more varied and complex, with multiple channels and composite channels being just as common as direct and indirect channels. In an attempt to explain this variety, this paper revisits the influence on channel stru...

  14. Mobile radio channels

    CERN Document Server

    Pätzold, Matthias

    2011-01-01

    Providing a comprehensive overview of the modelling, analysis and simulation of mobile radio channels, this book gives a detailed understanding of fundamental issues and examines state-of-the-art techniques in mobile radio channel modelling. It analyses several mobile fading channels, including terrestrial and satellite flat-fading channels, various types of wideband channels and advanced MIMO channels, providing a fundamental understanding of the issues currently being investigated in the field. Important classes of narrowband, wideband, and space-time wireless channels are explored in deta

  15. Channel nut tool

    Energy Technology Data Exchange (ETDEWEB)

    Olson, Marvin

    2016-01-12

    A method, system, and apparatus for installing channel nuts includes a shank, a handle formed on a first end of a shank, and an end piece with a threaded shaft configured to receive a channel nut formed on the second end of the shaft. The tool can be used to insert or remove a channel nut in a channel framing system and then removed from the channel nut.

  16. The Earliest Ion Channels

    Science.gov (United States)

    Pohorille, A.; Wilson, M. A.; Wei, C.

    2009-12-01

    Supplying protocells with ions required assistance from channels spanning their membrane walls. The earliest channels were most likely short proteins that formed transmembrane helical bundles surrounding a water-filled pore. These simple aggregates were capable of transporting ions with efficiencies comparable to those of complex, contemporary ion channels. Channels with wide pores exhibited little ion selectivity but also imposed only modest constraints on amino acid sequences of channel-forming proteins. Channels with small pores could have been selective but also might have required a more precisely defined sequence of amino acids. In contrast to modern channels, their protocellular ancestors had only limited capabilities to regulate ion flux. It is postulated that subsequent evolution of ion channels progressed primarily to acquire precise regulation, and not high efficiency or selectivity. It is further proposed that channels and the surrounding membranes co-evolved.

  17. Gramicidin Channels: Versatile Tools

    Science.gov (United States)

    Andersen, Olaf S.; Koeppe, Roger E., II; Roux, Benoît

    Gramicidin channels are miniproteins in which two tryptophan-rich subunits associate by means of transbilayer dimerization to form the conducting channels. That is, in contrast to other ion channels, gramicidin channels do not open and close; they appear and disappear. Each subunit in the bilayer-spanning channel is tied to the bilayer/solution interface through hydrogen bonds that involve the indole NH groups as donors andwater or the phospholipid backbone as acceptors. The channel's permeability characteristics are well-defined: gramicidin channels are selective for monovalent cations, with no measurable permeability to anions or polyvalent cations; ions and water move through a pore whose wall is formed by the peptide backbone; and the single-channel conductance and cation selectivity vary when the amino acid sequence is varied, even though the permeating ions make no contact with the amino acid side chains. Given the plethora of available experimental information—for not only the wild-type channels but also for channels formed by amino acid-substituted gramicidin analogues—gramicidin channels continue to provide important insights into the microphysics of ion permeation through bilayer-spanning channels. For similar reasons, gramicidin channels constitute a system of choice for evaluating computational strategies for obtaining mechanistic insights into ion permeation through the more complex channels formed by integral membrane proteins.

  18. Multi-Channel Retailing

    Directory of Open Access Journals (Sweden)

    Dirk Morschett, Dr.,

    2005-01-01

    Full Text Available Multi-channel retailing entails the parallel use by retailing enterprises of several sales channels. The results of an online buyer survey which has been conducted to investigate the impact of multi-channel retailing (i.e. the use of several retail channels by one retail company on consumer behaviour show that the frequently expressed concern that the application of multi-channel systems in retailing would be associated with cannibalization effects, has proven unfounded. Indeed, the appropriate degree of similarity, consistency, integration and agreement achieves the exact opposite. Different channels create different advantages for consumers. Therefore the total benefit an enterprise which has a multi-channel system can offer to its consumers is larger, the greater the number of available channels. The use of multi-channel systems is associated with additional purchases in the different channels. Such systems are thus superior to those offering only one sales channel to their customers. Furthermore, multi-channel systems with integrated channels are superior to those in which the channels are essentially autonomous and independent of one another. In integrated systems, consumers can achieve synergy effects in the use of sales-channel systems. Accordingly, when appropriately formulated, multi-channel systems in retailing impact positively on consumers. They use the channels more frequently, buy more from them and there is a positive customer-loyalty impact. Multi-channel systems are strategic options for achieving customer loyalty, exploiting customer potential and for winning new customers. They are thus well suited for approaching differing and varied target groups.

  19. 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 ...

  20. Dynamic channel allocation

    OpenAIRE

    Kaminsky, Andrew D.

    2003-01-01

    Approved for public release; distribution in unlimited. Dynamic Channel Allocation (DCA) offers the possibility of capturing unused channel capacity by allocating unused resources between competing network nodes. This can reduce or possibly eliminate channels sitting idle while information awaits transmission. This holds potential for increasing throughput on bandwidth constrained networks. The purpose of this thesis is to examine the techniques used to allocate channels on demand and acc...

  1. Desynched channels on IRCnet

    CERN Document Server

    Hansen, Michael

    2008-01-01

    In this paper we describe what a desynchronised channel on IRC is. We give procedures on how to create such a channel and how to remove desynchronisation. We explain which types of desynchronisation there are, what properties desynchronised channels have, and which properties can be exploited.

  2. Quantum Binary Symmetric Channels

    Institute of Scientific and Technical Information of China (English)

    陈小余; 仇佩亮

    2001-01-01

    Quantum binary symmetric channels are defined via the invariance of fidelity under unitary transformations ofthe input density operators. In this definition, they not only include the most studied case of the depolarizingchannel but also other channels. We investigate the character of the latter and find the maximum of the coherentinformation to estimate the capacities of the channels.

  3. Quantum Multiple Access Channel

    Institute of Scientific and Technical Information of China (English)

    侯广; 黄民信; 张永德

    2002-01-01

    We consider the transmission of classical information over a quantum channel by many senders, which is a generalization of the two-sender case. The channel capacity region is shown to be a convex hull bound by the yon Neumann entropy and the conditional yon Neumann entropies. The result allows a reasonable distribution of channel capacity over the senders.

  4. 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...

  5. 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...

  6. On 1-qubit channels

    OpenAIRE

    Uhlmann, Armin

    2000-01-01

    The entropy H_T(rho) of a state rho with respect to a channel T and the Holevo capacity of the channel require the solution of difficult variational problems. For a class of 1-qubit channels, which contains all the extremal ones, the problem can be significantly simplified by associating an Hermitian antilinear operator theta to every channel of the considered class. The concurrence of the channel can be expressed by theta and turns out to be a flat roof. This allows to write down an explicit...

  7. On 1-qubit channels

    CERN Document Server

    Uhlmann, A

    2001-01-01

    The entropy H_T(rho) of a state rho with respect to a channel T and the Holevo capacity of the channel require the solution of difficult variational problems. For a class of 1-qubit channels, which contains all the extremal ones, the problem can be significantly simplified by associating an Hermitian antilinear operator theta to every channel of the considered class. The concurrence of the channel can be expressed by theta and turns out to be a flat roof. This allows to write down an explicit expression for H_T. Its maximum would give the Holevo (1-shot) capacity.

  8. Source and Channel Coding for Correlated Sources Over Multiuser Channels

    OpenAIRE

    Gunduz, Deniz; Erkip, Elza; Goldsmith, Andrea; Poor, H. Vincent

    2008-01-01

    Source and channel coding over multiuser channels in which receivers have access to correlated source side information is considered. For several multiuser channel models necessary and sufficient conditions for optimal separation of the source and channel codes are obtained. In particular, the multiple access channel, the compound multiple access channel, the interference channel and the two-way channel with correlated sources and correlated receiver side information are considered, and the o...

  9. C. elegans TRP channels.

    Science.gov (United States)

    Xiao, Rui; Xu, X Z Shawn

    2011-01-01

    Transient receptor potential (TRP) channels represent a superfamily of cation channels found in all eukaryotes. The C. elegans genome encodes seventeen TRP channels covering all of the seven TRP subfamilies. Genetic analyses in C. elegans have implicated TRP channels in a wide spectrum of behavioral and physiological processes, ranging from sensory transduction (e.g. chemosensation, touch sensation, proprioception and osmosensation) to fertilization, drug dependence, organelle biogenesis, apoptosis, gene expression, and neurotransmitter/hormone release. Many C. elegans TRP channels share similar activation and regulatory mechanisms with their vertebrate counterparts. Studies in C. elegans have also revealed some previously unrecognized functions and regulatory mechanisms of TRP channels. C. elegans represents an excellent genetic model organism for the study of function and regulation of TRP channels in vivo. PMID:21290304

  10. 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.

  11. 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.

  12. Channel capacity and error exponents of variable rate adaptive channel coding for Rayleigh fading channels

    OpenAIRE

    Lau, KN

    1999-01-01

    We have evaluated the information theoretical performance of variable rate adaptive channel coding for Rayleigh fading channels. The channel states are detected at the receiver and fed back to the transmitter by means of a noiseless feedback link. Based on the channel state informations, the transmitter can adjust the channel coding scheme accordingly. Coherent channel and arbitrary channel symbols with a fixed average transmitted power constraint are assumed. The channel capacity and the err...

  13. Quantum broadcast channels

    CERN Document Server

    Yard, J; Devetak, I; Yard, Jon; Hayden, Patrick; Devetak, Igor

    2006-01-01

    We analyze quantum broadcast channels, which are quantum channels with a single sender and many receivers. Focusing on channels with two receivers for simplicity, we generalize a number of results from the network Shannon theory literature which give the rates at which two senders can receive a common message, while a personalized one is sent to one of them. Our first collection of results applies to channels with a classical input and quantum outputs. The second class of theorems we prove concern sending a common classical message over a quantum broadcast channel, while sending quantum information to one of the receivers. The third group of results we obtain concern communication over an isometry, giving the rates at quantum information can be sent to one receiver, while common quantum information is sent to both, in the sense that tripartite GHZ entanglement is established. For each scenario, we provide an additivity proof for an appropriate class of channels, yielding single-letter characterizations of the...

  14. HIPPI and Fibre Channel

    International Nuclear Information System (INIS)

    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

  15. Decreased expression of transient receptor potential channels in cerebral vascular tissue from patients after hypertensive intracerebral hemorrhage

    DEFF Research Database (Denmark)

    Thilo, Florian; Suess, Olaf; Liu, Ying;

    2011-01-01

    the expression of TRP expression and hypoxic conditions caused by the intracerebral bleeding, we examined the expression of hypoxia inducible factor 1a (HIF1a). Transcripts of TRPC3, TRPC5, TRPM6, and HIF1a were significantly reduced in cerebral vascular tissue from patients after hypertensive intracerebral...... hemorrhage compared to controls. TRPC3 mRNA correlated well with the expression of HIF1a mRNA (r(2) = 0.59; p = 0.01). TRPC3 expression is associated with hypertension and hypoxic conditions in human cerebral vascular tissue....

  16. FXR agonist activity of conformationally constrained analogs of GW 4064

    Energy Technology Data Exchange (ETDEWEB)

    Akwabi-Ameyaw, Adwoa; Bass, Jonathan Y.; Caldwell, Richard D.; Caravella, Justin A.; Chen, Lihong; Creech, Katrina L.; Deaton, David N.; Madauss, Kevin P.; Marr, Harry B.; McFadyen, Robert B.; Miller, Aaron B.; Navas, III, Frank; Parks, Derek J.; Spearing, Paul K.; Todd, Dan; Williams, Shawn P.; Wisely, G. Bruce; (GSKNC)

    2010-09-27

    Two series of conformationally constrained analogs of the FXR agonist GW 4064 1 were prepared. Replacement of the metabolically labile stilbene with either benzothiophene or naphthalene rings led to the identification of potent full agonists 2a and 2g.

  17. Dopamine agonist activity of EMD 23,448

    Energy Technology Data Exchange (ETDEWEB)

    Martin, G.E.; Pettibone, D.J. (Merck Sharp and Dohme Research Laboratories, West Point, Pennsylvania (USA). Dept. of Pharmacology)

    1985-01-01

    EMD 23,448 was examined in tests of dopaminergic function and was found to be an atypical dopamine (DA) agonist. EMD 23,448 was a weak or inactive DA agonist when examined in tests of normal postsynaptic DA receptor function: production of stereotypy in the rat (ED/sub 50/ greater than sign 5.0 mg/kg.i.p.); production of emesis in beagles (minimum effective dose = 81..mu..g/kg i.v.); and, enhanced locomotor activity of the mouse (no excitation in doses <=50 mg/i.p.). Moreover, EMD 23,448 was relatively weak in competing for (/sup 3/H)-apomorphine binding to rat striatal membranes (Ki, 205 nM). On the other hand, this indolyl-3-butylamine did activate supersensitive postsynaptic DA receptors. Specifically, it elicited contralateral turning in rats with a unilateral 6-hydroxydopamine lesion of the substantia nigra (ED/sub 50/ value = 0.9 mg/kg) and did elicit stereotypy in rats given chronic daily haloperidol treatments. EMD 23,448 also exerted pharmacological effects in tests designed to measure activation of dopamine autoreceptors. It inhibited the ..gamma..-butyrolactone-induced increase in striatal dopa levels (ED/sub 50/ = 1 mg/kg i.p.) and produced a dose-related fall in the locomotor activity of the mouse. The results are discussed and contrasted with data derived for apomorphine and the putatively selective autoreceptor agonist (+-)-3-PPP.

  18. Ah receptor agonist activity in frequently consumed food items

    NARCIS (Netherlands)

    Waard, de W.J.; Aarts, J.M.M.J.G.; Peijnenburg, A.A.C.M.; Kok, de T.M.C.M.; Schooten, van F.J.; Hoogenboom, L.A.P.

    2008-01-01

    The aryl hydrocarbon receptor (AhR) receives much attention for its role in the toxicity of dioxins and dioxin-like polychlorinated biphenyls. However, many other compounds have also been reported to bind and activate AhR, of which natural food components are of special interest from a human health

  19. 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.

  20. RFI channels, 2

    Science.gov (United States)

    Mceliece, R. J.

    1981-01-01

    The cutoff parameters for a class of channel models exhibiting burst noise behavior were calculated and the performance of interleaved coding strategies was evaluated. It is concluded that, provided the channel memory is large enough and is properly exploited, interleaved coding is nearly optimal.

  1. Athermalized channeled spectropolarimeter enhancement.

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Julia Craven; Way, Brandyn Michael; Mercier, Jeffrey Alan; Hunt, Jeffery P.

    2013-09-01

    Channeled spectropolarimetry can measure the complete polarization state of light as a function of wavelength. Typically, a channeled spectropolarimeter uses high order retarders made of uniaxial crystal to amplitude modulate the measured spectrum with the spectrally-dependent Stokes polarization information. A primary limitation of conventional channeled spectropolarimeters is related to the thermal variability of the retarders. Thermal variation often forces frequent system recalibration, particularly for field deployed systems. However, implementing thermally stable retarders, made of biaxial crystal, results in an athermal channeled spectropolarimeter that relieves the need for frequent recalibration. This report presents experimental results for an anthermalized channeled spectropolarimeter prototype produced using potassium titanyl phosphate. The results of this prototype are compared to the current thermal stabilization state of the art. Finally, the application of the technique to the thermal infrared is studied, and the athermalization concept is applied to an infrared imaging spectropolarimeter design.

  2. Channelling versus inversion

    DEFF Research Database (Denmark)

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

    2013-01-01

    . Within this channel were smaller erosional structures (<10 m deep) that truncate originally horizontal bedding, are floored by hardgrounds, and locally have a basal fill of granular phosphorite. The entire channel system was progressively infilled by chalk, as demonstrated by the expanded succession of...... the lower Campanian Culver Chalk Formation. The beds of the channel fill are cut by small step faults, resulting from gravitational collapse. Complete burial had taken place by the base of the upper Campanian Portsdown Chalk Formation, which is of even thickness across the region. The structures are......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...

  3. 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 no sys...... no systematic overview exist of channel choice. We present a literature review of channel choice studies in government to citizen context identifying authors, countries, methods, concepts, units of analysis, and theories, and offer suggestionsfor future studies....

  4. A Simple Water Channel

    Science.gov (United States)

    White, A. S.

    1976-01-01

    Describes a simple water channel, for use with an overhead projector. It is run from a water tap and may be used for flow visualization experiments, including the effect of streamlining and elementary building aerodynamics. (MLH)

  5. 28-Channel rotary transformer

    Science.gov (United States)

    Mclyman, W. T.

    1981-01-01

    Transformer transmits power and digital data across rotating interface. Array has many parallel data channels, each with potential l megabaud data rate. Ferrite-cored transformers are spaced along rotor; airgap between them reduces crosstalk.

  6. 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...

  7. 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...

  8. 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.

  9. TRP channels in disease.

    Science.gov (United States)

    Jordt, S E; Ehrlich, B E

    2007-01-01

    The transient receptor potential (TRP) channels are a large family of proteins with six main subfamilies termed the TRPC (canonical), TRPV (vanilloid), TRPM (melastatin), TRPP (polycystin), TRPML (mucolipin), and TRPA (ankyrin) groups. The sheer number of different TRPs with distinct functions supports the statement that these channels are involved in a wide range of processes ranging from sensing of thermal and chemical signals to reloading intracellular stores after responding to an extracellular stimulus. Mutations in TRPs are linked to pathophysiology and specific diseases. An understanding of the role of TRPs in normal physiology is just beginning; the progression from mutations in TRPs to pathophysiology and disease will follow. In this review, we focus on two distinct aspects of TRP channel physiology, the role of TRP channels in intracellular Ca2+ homeostasis, and their role in the transduction of painful stimuli in sensory neurons. PMID:18193640

  10. Chloride channels in stroke

    Institute of Scientific and Technical Information of China (English)

    Ya-ping ZHANG; Hao ZHANG; Dayue Darrel DUAN

    2013-01-01

    Vascular remodeling of cerebral arterioles,including proliferation,migration,and apoptosis of vascular smooth muscle cells (VSMCs),is the major cause of changes in the cross-sectional area and diameter of the arteries and sudden interruption of blood flow or hemorrhage in the brain,ie,stroke.Accumulating evidence strongly supports an important role for chloride (Clˉ) channels in vascular remodeling and stroke.At least three Clˉ channel genes are expressed in VSMCs:1) the TMEM16A (or Ano1),which may encode the calcium-activated Clˉ channels (CACCs); 2) the CLC-3 Clˉ channel and Clˉ/H+ antiporter,which is closely related to the volume-regulated Clˉ channels (VRCCs); and 3) the cystic fibrosis transmembrane conductance regulator (CFTR),which encodes the PKA-and PKC-activated Clˉ channels.Activation of the CACCs by agonist-induced increase in intracellular Ca2+ causes membrane depolarization,vasoconstriction,and inhibition of VSMC proliferation.Activation of VRCCs by cell volume increase or membrane stretch promotes the production of reactive oxygen species,induces proliferation and inhibits apoptosis of VSMCs.Activation of CFTR inhibits oxidative stress and may prevent the development of hypertension.In addition,Clˉ current mediated by gammaaminobutyric acid (GABA) receptor has also been implicated a role in ischemic neuron death.This review focuses on the functional roles of Clˉ channels in the development of stroke and provides a perspective on the future directions for research and the potential to develop Clˉ channels as new targets for the prevention and treatment of stroke.

  11. Physics of Ion Channels

    OpenAIRE

    Kuyucak, Serdar; Bastug, Turgut

    2003-01-01

    We review the basic physics involved in transport of ions across membrane channels in cells. Electrochemical forces that control the diffusion of ions are discussed both from microscopic and macroscopic perspectives. A case is made for use of Brownian dynamics as the minimal phenomenological model that provides a bridge between experiments and more fundamental theoretical approaches. Application of Brownian and molecular dynamics methods to channels with known molecular structures is discussed.

  12. Identification Via Quantum Channels

    OpenAIRE

    Winter, Andreas

    2012-01-01

    We review the development of the quantum version of Ahlswede and Dueck's theory of identification via channels. As is often the case in quantum probability, there is not just one but several quantizations: we know at least two different concepts of identification of classical information via quantum channels, and three different identification capacities for quantum information. In the present summary overview we concentrate on conceptual points and open problems, referring the reader to the ...

  13. Quantum Feedback Channels

    OpenAIRE

    Bowen, Garry

    2002-01-01

    In Shannon information theory the capacity of a memoryless communication channel cannot be increased by the use of feedback. In quantum information theory the no-cloning theorem means that noiseless copying and feedback of quantum information cannot be achieved. In this paper, quantum feedback is defined as the unlimited use of a noiseless quantum channel from receiver to sender. Given such quantum feedback, it is shown to provide no increase in the entanglement--assisted capacities of a memo...

  14. Chaos in quantum channels

    OpenAIRE

    Hosur, Pavan; Qi, Xiao-Liang; Roberts, Daniel; Yoshida, Beni(Institute for Quantum Information & Matter and Walter Burke Institute for Theoretical Physics, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA, 91125, U.S.A.)

    2016-01-01

    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 channe...

  15. 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...

  16. Morphodynamics of Floodplain Chute Channels

    Science.gov (United States)

    David, S. R.; Edmonds, D. A.

    2015-12-01

    Floodplain chute channel formation is a key process that can enable rivers to transition from single-thread to multi-thread planform geometries. Floodplain chute channels are usually incisional channels connecting topographic lows across point bars and in the floodplain. Surprisingly, it is still not clear what conditions promote chute channel formation and what governs their morphodynamic behavior. Towards this end we have initiated an empirical and theoretical study of floodplain chute channels in Indiana, USA. Using elevation models and satellite imagery we mapped 3064 km2 of floodplain in Indiana, and find that 37.3% of mapped floodplains in Indiana have extensive chute channel networks. These chute channel networks consist of two types of channel segments: meander cutoffs of the main channel and chute channels linking the cutoffs together. To understand how these chute channels link meander cutoffs together and eventually create floodplain channel networks we use Delft3D to explore floodplain morphodynamics. Our first modeling experiment starts from a generic floodplain prepopulated with meander cutoffs to test under what conditions chute channels form.We find that chute channel formation is optimized at an intermediate flood discharge. If the flood discharge is too large the meander cutoffs erosively diffuse, whereas if the floodwave is too small the cutoffs fill with sediment. A moderately sized floodwave reworks the sediment surrounding the topographic lows, enhancing the development of floodplain chute channels. Our second modeling experiments explore how floodplain chute channels evolve on the West Fork of the White River, Indiana, USA. We find that the floodplain chute channels are capable of conveying the entire 10 yr floodwave (Q=1330m3/s) leaving the inter-channel areas dry. Moreover, the chute channels can incise into the floodplain while the margins of channels are aggrading, creating levees. Our results suggest that under the right conditions

  17. MEMS in microfluidic channels.

    Energy Technology Data Exchange (ETDEWEB)

    Ashby, Carol Iris Hill; Okandan, Murat; Michalske, Terry A.; Sounart, Thomas L.; Matzke, Carolyn M.

    2004-03-01

    Microelectromechanical systems (MEMS) comprise a new class of devices that include various forms of sensors and actuators. Recent studies have shown that microscale cantilever structures are able to detect a wide range of chemicals, biomolecules or even single bacterial cells. In this approach, cantilever deflection replaces optical fluorescence detection thereby eliminating complex chemical tagging steps that are difficult to achieve with chip-based architectures. A key challenge to utilizing this new detection scheme is the incorporation of functionalized MEMS structures within complex microfluidic channel architectures. The ability to accomplish this integration is currently limited by the processing approaches used to seal lids on pre-etched microfluidic channels. This report describes Sandia's first construction of MEMS instrumented microfluidic chips, which were fabricated by combining our leading capabilities in MEMS processing with our low-temperature photolithographic method for fabricating microfluidic channels. We have explored in-situ cantilevers and other similar passive MEMS devices as a new approach to directly sense fluid transport, and have successfully monitored local flow rates and viscosities within microfluidic channels. Actuated MEMS structures have also been incorporated into microfluidic channels, and the electrical requirements for actuation in liquids have been quantified with an elegant theory. Electrostatic actuation in water has been accomplished, and a novel technique for monitoring local electrical conductivities has been invented.

  18. Mitochondrial Ion Channels

    Science.gov (United States)

    O’Rourke, Brian

    2009-01-01

    In work spanning more than a century, mitochondria have been recognized for their multifunctional roles in metabolism, energy transduction, ion transport, inheritance, signaling, and cell death. Foremost among these tasks is the continuous production of ATP through oxidative phosphorylation, which requires a large electrochemical driving force for protons across the mitochondrial inner membrane. This process requires a membrane with relatively low permeability to ions to minimize energy dissipation. However, a wealth of evidence now indicates that both selective and nonselective ion channels are present in the mitochondrial inner membrane, along with several known channels on the outer membrane. Some of these channels are active under physiological conditions, and others may be activated under pathophysiological conditions to act as the major determinants of cell life and death. This review summarizes research on mitochondrial ion channels and efforts to identify their molecular correlates. Except in a few cases, our understanding of the structure of mitochondrial ion channels is limited, indicating the need for focused discovery in this area. PMID:17059356

  19. 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.

  20. QKD Quantum Channel Authentication

    CERN Document Server

    Kosloski, J T

    2006-01-01

    Several simple yet secure protocols to authenticate the quantum channel of various QKD schemes, by coupling the photon sender's knowledge of a shared secret and the QBER Bob observes, are presented. It is shown that Alice can encrypt certain portions of the information needed for the QKD protocols, using a sequence whose security is based on computational-complexity, without compromising all of the sequence's entropy. It is then shown that after a Man-in-the-Middle attack on the quantum and classical channels, there is still enough entropy left in the sequence for Bob to detect the presence of Eve by monitoring the QBER. Finally, it is shown that the principles presented can be implemented to authenticate the quantum channel associated with any type of QKD scheme, and they can also be used for Alice to authenticate Bob.

  1. Dequantization Via Quantum Channels

    Science.gov (United States)

    Andersson, Andreas

    2016-10-01

    For a unital completely positive map {Φ} ("quantum channel") governing the time propagation of a quantum system, the Stinespring representation gives an enlarged system evolving unitarily. We argue that the Stinespring representations of each power {Φ^m} of the single map together encode the structure of the original quantum channel and provide an interaction-dependent model for the bath. The same bath model gives a "classical limit" at infinite time {mto∞} in the form of a noncommutative "manifold" determined by the channel. In this way, a simplified analysis of the system can be performed by making the large- m approximation. These constructions are based on a noncommutative generalization of Berezin quantization. The latter is shown to involve very fundamental aspects of quantum-information theory, which are thereby put in a completely new light.

  2. Dequantization Via Quantum Channels

    Science.gov (United States)

    Andersson, Andreas

    2016-08-01

    For a unital completely positive map {Φ} ("quantum channel") governing the time propagation of a quantum system, the Stinespring representation gives an enlarged system evolving unitarily. We argue that the Stinespring representations of each power {Φ^m} of the single map together encode the structure of the original quantum channel and provide an interaction-dependent model for the bath. The same bath model gives a "classical limit" at infinite time {mto∞} in the form of a noncommutative "manifold" determined by the channel. In this way, a simplified analysis of the system can be performed by making the large-m approximation. These constructions are based on a noncommutative generalization of Berezin quantization. The latter is shown to involve very fundamental aspects of quantum-information theory, which are thereby put in a completely new light.

  3. Entanglement-saving channels

    Science.gov (United States)

    Lami, L.; Giovannetti, V.

    2016-03-01

    The set of Entanglement Saving (ES) quantum channels is introduced and characterized. These are completely positive, trace preserving transformations which when acting locally on a bipartite quantum system initially prepared into a maximally entangled configuration, preserve its entanglement even when applied an arbitrary number of times. In other words, a quantum channel ψ is said to be ES if its powers ψn are not entanglement-breaking for all integers n. We also characterize the properties of the Asymptotic Entanglement Saving (AES) maps. These form a proper subset of the ES channels that is constituted by those maps that not only preserve entanglement for all finite n but which also sustain an explicitly not null level of entanglement in the asymptotic limit n → ∞. Structure theorems are provided for ES and for AES maps which yield an almost complete characterization of the former and a full characterization of the latter.

  4. Chaos in quantum channels

    CERN Document Server

    Hosur, Pavan; Roberts, Daniel A; Yoshida, Beni

    2015-01-01

    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.

  5. Voltage-Gated Proton Channels

    OpenAIRE

    DeCoursey, Thomas E.

    2008-01-01

    Voltage-gated proton channels, HV1, have vaulted from the realm of the esoteric into the forefront of a central question facing ion channel biophysicists, namely the mechanism by which voltage-dependent gating occurs. This transformation is the result of several factors. Identification of the gene in 2006 revealed that proton channels are homologues of the voltage-sensing domain of most other voltage-gated ion channels. Unique, or at least eccentric, properties of proton channels include dime...

  6. The neutron channeling phenomenon.

    Science.gov (United States)

    Khanouchi, A; Sabir, A; Boulkheir, M; Ichaoui, R; Ghassoun, J; Jehouani, A

    1997-01-01

    Shields, used for protection against radiation, are often pierced with vacuum channels for passing cables and other instruments for measurements. The neutron transmission through these shields is an unavoidable phenomenon. In this work we study and discuss the effect of channels on neutron transmission through shields. We consider an infinite homogeneous slab, with a fixed thickness (20 lambda, with lambda the mean free path of the neutron in the slab), which contains a vacuum channel. This slab is irradiated with an infinite source of neutrons on the left side and on the other side (right side) many detectors with windows equal to 2 lambda are placed in order to evaluate the neutron transmission probabilities (Khanouchi, A., Aboubekr, A., Ghassoun, J. and Jehouani, A. (1994) Rencontre Nationale des Jeunes Chercheurs en Physique. Casa Blanca Maroc; Khanouchi, A., Sabir, A., Ghassoun, J. and Jehouani, A. (1995) Premier Congré International des Intéractions Rayonnements Matière. Eljadida Maroc). The neutron history within the slab is simulated by the Monte Carlo method (Booth, T. E. and Hendricks, J. S. (1994) Nuclear Technology 5) and using the exponential biasing technique in order to improve the Monte Carlo calculation (Levitt, L. B. (1968) Nuclear Science and Engineering 31, 500-504; Jehouani, A., Ghassoun, J. and Aboubker, A. (1994) In Proceedings of the 6th International Symposium on Radiation Physics, Rabat, Morocco). Then different geometries of the vacuum channel have been studied. For each geometry we have determined the detector response and calculated the neutron transmission probability for different detector positions. This neutron transmission probability presents a peak for the detectors placed in front of the vacuum channel. This study allowed us to clearly identify the neutron channeling phenomenon. One application of our study is to detect vacuum defects in materials. PMID:9463884

  7. BLIND CHANNEL ESTIMATION IN DELAY DIVERSITY FOR FREQUENCY SELECTIVE CHANNELS

    Institute of Scientific and Technical Information of China (English)

    Zhao Zheng; Jia Ying; Yin Qinye

    2003-01-01

    Delay diversity is an effective transmit diversity technique to combat adverse ef-fects of fading. Thus far, previous work in delay diversity assumed that perfect estimates ofcurrent channel fading conditions are available at the receiver and training symbols are requiredto estimate the channel from the transmitter to the receiver. However, increasing the number ofthe antennas increases the required training interval and reduces the available time within whichdata may be transmitted. Learning the channel coefficients becomes increasingly difficult for thefrequency selective channels. In this paper, with the subspace method and the delay character ofdelay diversity, a channel estimation method is proposed, which does not use training symbols. Itaddresses the transmit diversity for a frequency selective channel from a single carrier perspectivein the form of a simple equivalent fiat fading model. Monte Carlo simulations give the perfor-mance of channel estimation and the performance comparison of our channel-estimation-baseddetector with decision feedback equalization, which uses the perfect channel information.

  8. K(v)7 channels: function, pharmacology and channel modulators.

    Science.gov (United States)

    Dalby-Brown, William; Hansen, Henrik H; Korsgaard, Mads P G; Mirza, Naheed; Olesen, Søren-P

    2006-01-01

    K(v)7 channels are unique among K(+) channels, since four out of the five channel subtypes have well-documented roles in the development of human diseases. They have distinct physiological functions in the heart and in the nervous system, which can be ascribed to their voltage-gating properties. The K(v)7 channels also lend themselves to pharmacological modulation, and synthetic openers as well as blockers of the channels, regulating neuronal excitability, have existed even before the K(v)7 channels were identified by cloning. In the present review we give an account on the focused efforts to develop selective modulators, openers as well as blockers, of the K(v)7 channel subtypes, which have been undertaken during recent years, along with a discussion of the K(v)7 ion channel physiology and therapeutic indications for modulators of the neuronal K(v)7 channels.

  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. Beyond the Manual Channel

    DEFF Research Database (Denmark)

    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. TRP channels: an overview

    DEFF Research Database (Denmark)

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

    2005-01-01

    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....

  12. All channels open

    NARCIS (Netherlands)

    Frank Huysmans; Jos de Haan

    2010-01-01

    Original title: Alle kanalen staan open. The rapid changes taking place in the media landscape in the Netherlands - characterised by digitisation and convergence of media technologies - raise the question of how the Dutch are dealing with the many new opportunities that have opened up. All channels

  13. Channeling through Bent Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Mack, Stephanie; /Ottawa U. /SLAC

    2012-09-07

    Bent crystals have demonstrated potential for use in beam collimation. A process called channeling is when accelerated particle beams are trapped by the nuclear potentials in the atomic planes within a crystal lattice. If the crystal is bent then the particles can follow the bending angle of the crystal. There are several different effects that are observed when particles travel through a bent crystal including dechanneling, volume capture, volume reflection and channeling. With a crystal placed at the edge of a particle beam, part of the fringe of the beam can be deflected away towards a detector or beam dump, thus helping collimate the beam. There is currently FORTRAN code by Igor Yazynin that has been used to model the passage of particles through a bent crystal. Using this code, the effects mentioned were explored for beam energy that would be seen at the Facility for Advanced Accelerator Experimental Tests (FACET) at a range of crystal orientations with respect to the incoming beam. After propagating 5 meters in vacuum space past the crystal the channeled particles were observed to separate from most of the beam with some noise due to dechanneled particles. Progressively smaller bending radii, with corresponding shorter crystal lengths, were compared and it was seen that multiple scattering decreases with the length of the crystal therefore allowing for cleaner detection of the channeled particles. The input beam was then modified and only a portion of the beam sent through the crystal. With the majority of the beam not affected by the crystal, most particles were not deflected and after propagation the channeled particles were seen to be deflected approximately 5mm. After a portion of the beam travels through the crystal, the entire beam was then sent through a quadrupole magnet, which increased the separation of the channeled particles from the remainder of the beam to a distance of around 20mm. A different code, which was developed at SLAC, was used to

  14. Improving Virtual Channel Discrimination in a Multi-Channel Context

    OpenAIRE

    Srinivasan, Arthi G.; Shannon, Robert V.; Landsberger, David M.

    2012-01-01

    Improving spectral resolution in cochlear implants is key to improving performance in difficult listening conditions (e.g. speech in noise, music, etc.). Current focusing might reduce channel interaction, thereby increasing spectral resolution. Previous studies have shown that combining current steering and current focusing reduces spread of excitation and improves virtual channel discrimination in a single-channel context. It is unclear whether the single-channel benefits from current focusi...

  15. 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.

  16. Lipid Ion Channels

    CERN Document Server

    Heimburg, Thomas

    2010-01-01

    The interpretation electrical phenomena in biomembranes is usually based on the assumption that the experimentally found discrete ion conduction events are due to a particular class of proteins called ion channels while the lipid membrane is considered being an inert electrical insulator. The particular protein structure is thought to be related to ion specificity, specific recognition of drugs by receptors and to macroscopic phenomena as nerve pulse propagation. However, lipid membranes in their chain melting regime are known to be highly permeable to ions, water and small molecules, and are therefore not always inert. In voltage-clamp experiments one finds quantized conduction events through protein-free membranes in their melting regime similar to or even undistinguishable from those attributed to proteins. This constitutes a conceptual problem for the interpretation of electrophysiological data obtained from biological membrane preparations. Here, we review the experimental evidence for lipid ion channels...

  17. Ion Channels, Natural Nanovalves

    OpenAIRE

    Eisenberg, Bob

    2012-01-01

    Ion channels are proteins with holes down their middle that control the flow of ions and electric current across otherwise impermeable biological membranes. The flow of sodium, potassium, calcium (divalent), and chloride ions have been central issues in biology for more than a century. The flow of current is responsible for the signals of the nervous system that propagate over long distances (meters). The concentration of divalent calcium ions is a 'universal' signal that controls many differ...

  18. Proton channel models

    OpenAIRE

    Pupo, Amaury; Baez-Nieto, David; Martínez, Agustín; Latorre, Ramón; González, Carlos

    2014-01-01

    Voltage-gated proton channels are integral membrane proteins with the capacity to permeate elementary particles in a voltage and pH dependent manner. These proteins have been found in several species and are involved in various physiological processes. Although their primary topology is known, lack of details regarding their structures in the open conformation has limited analyses toward a deeper understanding of the molecular determinants of their function and regulation. Consequently, the f...

  19. Athermal channeled spectropolarimeter

    Energy Technology Data Exchange (ETDEWEB)

    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.

  20. 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.

  1. 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).

  2. The alpha channeling effect

    Energy Technology Data Exchange (ETDEWEB)

    Fisch, N. J.

    2015-12-10

    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.

  3. DMT of weighted Parallel Channels: Application to Broadcast Channel

    CERN Document Server

    Mroueh, Lina; Othman, Ghaya Rekaya-Ben; Belfiore, Jean-Claude

    2008-01-01

    In a broadcast channel with random packet arrival and transmission queues, the stability of the system is achieved by maximizing a weighted sum rate capacity with suitable weights that depend on the queue size. The weighted sum rate capacity using Dirty Paper Coding (DPC) and Zero Forcing (ZF) is asymptotically equivalent to the weighted sum capacity over parallel single-channels. In this paper, we study the Diversity Multiplexing Tradeoff (DMT) of the fading broadcast channel under a fixed weighted sum rate capacity constraint. The DMT of both identical and different parallel weighted MISO channels is first derived. Finally, we deduce the DMT of a broadcast channel using DPC and ZF precoders.

  4. Cascading blockages in channel bundles.

    Science.gov (United States)

    Barré, C; Talbot, J

    2015-11-01

    Flow in channel networks may involve a redistribution of flux following the blockage or failure of an individual link. Here we consider a simplified model consisting of N(c) parallel channels conveying a particulate flux. Particles enter these channels according to a homogeneous Poisson process and an individual channel blocks if more than N particles are simultaneously present. The behavior of the composite system depends strongly on how the flux of entering particles is redistributed following a blockage. We consider two cases. In the first, the intensity on each open channel remains constant while in the second the total intensity is evenly redistributed over the open channels. We obtain exact results for arbitrary N(c) and N for a system of independent channels and for arbitrary N(c) and N=1 for coupled channels. For N>1 we present approximate analytical as well as numerical results. Independent channels block at a decreasing rate due to a simple combinatorial effect, while for coupled channels the interval between successive blockages remains constant for N=1 but decreases for N>1. This accelerating cascade is due to the nonlinear dependence of the mean blocking time of a single channel on the entering particle flux that more than compensates for the decrease in the number of active channels.

  5. Micro-channel plate detector

    Energy Technology Data Exchange (ETDEWEB)

    Elam, Jeffrey W.; Lee, Seon W.; Wang, Hsien -Hau; Pellin, Michael J.; Byrum, Karen; Frisch, Henry J.

    2015-09-22

    A method and system for providing a micro-channel plate detector. An anodized aluminum oxide membrane is provided and includes a plurality of nanopores which have an Al coating and a thin layer of an emissive oxide material responsive to incident radiation, thereby providing a plurality of radiation sensitive channels for the micro-channel plate detector.

  6. Nomenclature for Ion channel Subunits

    OpenAIRE

    Bradley, Jonathan; Frings, Stephan; Yau, King-Wai; Reed, Randall

    2001-01-01

    Presents the nomenclature for ion channel subunits. Role of ion channels in the mediation of visual and olfactory signal transduction; Expression of ion channels in cell types and tissues; Assessment on the nucleotide sensitivity, ion conductance and calcium modulation in heteromers.

  7. QKD Quantum Channel Authentication

    OpenAIRE

    Kosloski, J. T.

    2006-01-01

    Several simple yet secure protocols to authenticate the quantum channel of various QKD schemes, by coupling the photon sender's knowledge of a shared secret and the QBER Bob observes, are presented. It is shown that Alice can encrypt certain portions of the information needed for the QKD protocols, using a sequence whose security is based on computational-complexity, without compromising all of the sequence's entropy. It is then shown that after a Man-in-the-Middle attack on the quantum and c...

  8. Improving virtual channel discrimination in a multi-channel context.

    Science.gov (United States)

    Srinivasan, Arthi G; Shannon, Robert V; Landsberger, David M

    2012-04-01

    Improving spectral resolution in cochlear implants is key to improving performance in difficult listening conditions (e.g. speech in noise, music, etc.). Current focusing might reduce channel interaction, thereby increasing spectral resolution. Previous studies have shown that combining current steering and current focusing reduces spread of excitation and improves virtual channel discrimination in a single-channel context. It is unclear whether the single-channel benefits from current focusing extend to a multi-channel context, in which the physical and perceptual interference of multiple stimulated channels might overwhelm the benefits of improved spectral resolution. In this study, signal discrimination was measured with and without current focusing, in the presence of competing stimuli on nearby electrodes. Results showed that signal discrimination was consistently better with current focusing than without, regardless of the amplitude of the competing stimuli. Therefore, combining current steering and current focusing may provide more effective spectral cues than are currently available. PMID:22616092

  9. EFFICIENT UTILIZATION OF CHANNELS USING DYNAMIC GUARD CHANNEL ALLOCATION WITH CHANNEL BORROWING STRATEGY IN HANDOFFS

    Directory of Open Access Journals (Sweden)

    Alagu S

    2012-05-01

    Full Text Available User mobility in wireless data networks is increasing because of technological advances and the desire for voice and multimedia applications. These applications, however, require fast handoffs between base stations to maintain the quality of the connections. In this paper, the authors describe the use of novel and efficient data structure which dynamically allocates guard channel for handoffs and introduces the concept of channel borrowing strategy. The proposed scheme allocates the guard channels for handoff requests dynamically, based on the traffic load for certain time period. A new originating call in the cell coverage area also uses these guard channels if they are unused. Our basic idea is to allow Guard channels to be shared between new calls and handoff calls. This approach maximizes the channel utilization. The simulation results prove that the channel borrowing scheme improves the overall throughput.

  10. Multiuser MIMO Channel Estimation

    Directory of Open Access Journals (Sweden)

    G.Indumathi

    2016-05-01

    Full Text Available In this paper, three beamforming design are considered for multi user MIMO system. First, transmit beamformers are fixed and the receive (RX beamformers are calculated. Transmit beamformer (TX-BFis projectedas a null space of appropriate channels. It reduces the interference for each user. Then the receiver beamformer is determined which maximize the SNR. This beamforming design provides less computation time. The second case is joint TX and RX beamformer for SNR maximization. In this transmitter and receiver beamformer are calculated using extended alternating optimization (EAO algorithm. The third one is joint transmitter and receiver beamforming for SNR and SINR maximization using EAO algorithm. This algorithm provides better error performance and sum rate performance. All the design cases are simulated by using standard multipath channel model. Our simulation results illustrate that compared to the least square design and zero forcing design, the joint TX and RX beamforming design using EAO algorithm provides faster beamforming and improved error performance and sum rate.

  11. DMT of weighted Parallel Channels: Application to Broadcast Channel

    OpenAIRE

    Mroueh, Lina; Rouquette-Léveil, Stéphanie; Othman, Ghaya Rekaya-Ben; Belfiore, Jean-Claude

    2008-01-01

    In a broadcast channel with random packet arrival and transmission queues, the stability of the system is achieved by maximizing a weighted sum rate capacity with suitable weights that depend on the queue size. The weighted sum rate capacity using Dirty Paper Coding (DPC) and Zero Forcing (ZF) is asymptotically equivalent to the weighted sum capacity over parallel single-channels. In this paper, we study the Diversity Multiplexing Tradeoff (DMT) of the fading broadcast channel under a fixed w...

  12. Ca2+Entry Through TRPC1 Channels Contributes to Intraceilular Ca2+ Dynamics and Consequent Glutamate Release from Rat Astrocytes

    Institute of Scientific and Technical Information of China (English)

    ERIK B. MALARKEY; YINGCHUN NI; VLADIMIR PARPURA

    2008-01-01

    钙池操纵Ca2+的内流.本文发现培养的星形胶质细胞以及从视皮质中新分离的星形胶质细胞表达TRPC1,TRPC4,和TRPC5.间接免疫组化显示这些蛋白存在于整个细胞中.然而机能检测TRPC1主要表达在质膜上.在新分离的星形胶质细胞中做标记,显示了在细胞发育过程中TRPC表达的改变.应用抗TRPC1的抗体.可以阻断TRPC1通道并且可以测定它们在培养的星形细胞的机械性和激动剂触发的钙离子内流过程中的作用.阻断TRPC1可以减少机械诱导的钙离子依赖性的谷氨酸盐的释放.这些实验数据表明.钙离子通过TRPC1通道的内流有助于钙离子在星形细胞中的信号传导以及由此引起的谷氨酸盐的释放.

  13. 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

  14. Calcium ion channel and epilepsy

    Institute of Scientific and Technical Information of China (English)

    Yudan Lü; Weihong Lin; Dihui Ma

    2006-01-01

    OBJECTIVE: To review the relationship between calcium ion channel and epilepsy for well investigating the pathogenesis of epilepsy and probing into the new therapeutic pathway of epilepsy.DATA SOURCES: A computer-based online research Calcium ion channel and epilepsy related articles published between January 1994 and December 2006 in the CKNI and Wanfang database with the key words of "calcium influxion, epilepsy, calcium-channel blocker". The language was limited to Chinese. At the same time,related articles published between January 1993 and December 2006 in Pubmed were searched for on online with the key words of "calcium influxion, epilepsy" in English.STUDY SELECTION: The materials were selected firstly. Inclusive criteria: ① Studies related to calcium ion channel and the pat1hogenesis of epilepsy. ② Studies on the application of calcium ion channel blocker in the treatment of epilepsy. Exclusive criteria: repetitive or irrelated studies.DATA EXTRACTION: According to the criteria, 123 articles were retrieved and 93 were excluded due to repetitive or irrelated studies. Altogether 30 articles met the inclusive criteria, 11 of them were about the structure and characters of calcium ion channel, 10 about calcium ion channel and the pathogenesis of epilepsy and 9 about calcium blocker and the treatment of epilepsy.DATA SYNTHESIS: Calcium ion channels mainly consist of voltage dependent calcium channel and receptor operated calcium channel. Depolarization caused by voltage gating channel-induced influxion is the pathological basis of epileptic attack, and it is found in many studies that many anti-epileptic drugs have potential and direct effect to rivalizing voltage-dependent calcium ion channel.CONCLUSION: Calcium influxion plays an important role in the seizure of epilepsy. Some calcium antagonists seen commonly are being tried in the clinical therapy of epilepsy that is being explored, not applied in clinical practice. If there are enough evidences to

  15. Secure refinements of communication channels

    OpenAIRE

    Cheval, Vincent; Cortier, Véronique; Le Morvan, Eric

    2015-01-01

    International audience It is a common practice to design a protocol (say Q) assuming some secure channels. Then the secure channels are implemented using any standard protocol, e.g. TLS. In this paper, we study when such a practice is indeed secure. We provide a characterization of both confidential and authenticated channels. As an application, we study several protocols of the literature including TLS and BAC protocols. Thanks to our result, we can consider a larger number of sessions wh...

  16. Determining nitrogen laser channel parameters

    International Nuclear Information System (INIS)

    This paper reports the measurement of the nitrogen laser channel current using a magnetic probe. For a 46 cm laser channel of gap 16 mm operated at 10 kV, 60 torr with foil capacitors of 58 and 28 nF, the channel current, inductance and resistance are found to be 42 kA, l.6 nH and 0.1 Ω respectively. (author)

  17. 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.

  18. Geometric pumping in autophoretic channels

    CERN Document Server

    Michelin, Sebastien; De Canio, Gabriele; Lobato-Dauzier, Nicolas; Lauga, Eric

    2015-01-01

    Many microfluidic devices use macroscopic pressure differentials to overcome viscous friction and generate flows in microchannels. In this work, we investigate how the chemical and geometric properties of the channel walls can drive a net flow by exploiting the autophoretic slip flows induced along active walls by local concentration gradients of a solute species. We show that chemical patterning of the wall is not required to generate and control a net flux within the channel, rather channel geometry alone is sufficient. Using numerical simulations, we determine how geometric characteristics of the wall influence channel flow rate, and confirm our results analytically in the asymptotic limit of lubrication theory.

  19. Flag flapping in a channel

    Science.gov (United States)

    Alben, Silas; Shoele, Kourosh; Mittal, Rajat; Jha, Sourabh; Glezer, Ari

    2015-11-01

    We study the flapping of a flag in an inviscid channel flow. We focus especially on how quantities vary with channel spacing. As the channel walls move inwards towards the flag, heavier flags become more unstable, while light flags' stability is less affected. We use a vortex sheet model to compute large-amplitude flapping, and find that the flag undergoes a series of jumps to higher flapping modes as the channel walls are moved towards the flag. Meanwhile, the drag on the flag and the energy lost to the wake first rise as the walls become closer, then drop sharply as the flag moves to a higher flapping mode.

  20. 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. PMID:27164907

  1. 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

  2. CHANNEL ESTIMATION FOR ITERATIVE DECODING OVER FADING CHANNELS

    Institute of Scientific and Technical Information of China (English)

    K. H. Sayhood; Wu Lenan

    2002-01-01

    A method of coherent detection and channel estimation for punctured convolutional coded binary Quadrature Amplitude Modulation (QAM) signals transmitted over a frequency-flat Rayleigh fading channels used for a digital radio broadcasting transmission is presented. Some known symbols are inserted in the encoded data stream to enhance the channel estimation process.The pilot symbols are used to replace the existing parity symbols so no bandwidth expansion is required. An iterative algorithm that uses decoding information as well as the information contained in the known symbols is used to improve the channel parameter estimate. The scheme complexity grows exponentially with the channel estimation filter length. The performance of the system is compared for a normalized fading rate with both perfect coherent detection (corresponding to a perfect knowledge of the fading process and noise variance) and differential detection of Differential Amplitude Phase Shift Keying (DAPSK). The tradeoff between simplicity of implementation and bit-error-rate performance of different techniques is also compared.

  3. 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.

  4. Channel's Concurrence and Quantum Teleportation

    International Nuclear Information System (INIS)

    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.

  5. 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.

  6. Defect Distributions in Channeling Experiments

    DEFF Research Database (Denmark)

    Andersen, Hans Henrik; Sigmund, P.

    1965-01-01

    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....

  7. Synchronization strategies for RFI channels

    Science.gov (United States)

    Mceliece, R. J.; Vantilborg, H.; Tung, S.

    1977-01-01

    An RFI channel to be a multiple-access channel is defined in which no sender can know when any other starts, and the problem of determining the relative phases of the senders at the receiver is studied. A new result is proved about binary DEBruijn sequences.

  8. 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...

  9. Lipid Regulation of Sodium Channels.

    Science.gov (United States)

    D'Avanzo, N

    2016-01-01

    The lipid landscapes of cellular membranes are complex and dynamic, are tissue dependent, and can change with the age and the development of a variety of diseases. Researchers are now gaining new appreciation for the regulation of ion channel proteins by the membrane lipids in which they are embedded. Thus, as membrane lipids change, for example, during the development of disease, it is likely that the ionic currents that conduct through the ion channels embedded in these membranes will also be altered. This chapter provides an overview of the complex regulation of prokaryotic and eukaryotic voltage-dependent sodium (Nav) channels by fatty acids, sterols, glycerophospholipids, sphingolipids, and cannabinoids. The impact of lipid regulation on channel gating kinetics, voltage-dependence, trafficking, toxin binding, and structure are explored for Nav channels that have been examined in heterologous expression systems, native tissue, and reconstituted into artificial membranes. Putative mechanisms for Nav regulation by lipids are also discussed. PMID:27586290

  10. Quantum channel capacities - multiparty communication

    CERN Document Server

    Demianowicz, M; Demianowicz, Maciej; Horodecki, Pawel

    2006-01-01

    We analyze different aspects of multiparty communication over quantum memoryless channels and generalize some of key results known from bipartite channels to that of multiparty scenario. In particular, we introduce multiparty versions of minimal subspace transmission fidelity and entanglement transmission fidelity. We also provide alternative, local, versions of fidelities and show their equivalence to the global ones in context of capacity regions defined. The equivalence of two different capacity notions with respect to two types of the fidelities is proven. In analogy to bipartite case it is shown, via sufficiency of isometric encoding theorem, that additional classical forward side channel does not increase capacity region of any quantum channel with $k$ senders and $m$ receivers which represents a compact unit of general quantum networks theory. The result proves that recently provided capacity region of multiple access channel ([M. Horodecki et al, Nature {\\bf 436} 673 (2005)], [J.Yard et al, quant-ph/0...

  11. Voltage-gated proton channels.

    Science.gov (United States)

    Decoursey, Thomas E

    2012-04-01

    Voltage-gated proton channels, HV1, have vaulted from the realm of the esoteric into the forefront of a central question facing ion channel biophysicists, namely, the mechanism by which voltage-dependent gating occurs. This transformation is the result of several factors. Identification of the gene in 2006 revealed that proton channels are homologues of the voltage-sensing domain of most other voltage-gated ion channels. Unique, or at least eccentric, properties of proton channels include dimeric architecture with dual conduction pathways, perfect proton selectivity, a single-channel conductance approximately 10(3) times smaller than most ion channels, voltage-dependent gating that is strongly modulated by the pH gradient, ΔpH, and potent inhibition by Zn(2+) (in many species) but an absence of other potent inhibitors. The recent identification of HV1 in three unicellular marine plankton species has dramatically expanded the phylogenetic family tree. Interest in proton channels in their own right has increased as important physiological roles have been identified in many cells. Proton channels trigger the bioluminescent flash of dinoflagellates, facilitate calcification by coccolithophores, regulate pH-dependent processes in eggs and sperm during fertilization, secrete acid to control the pH of airway fluids, facilitate histamine secretion by basophils, and play a signaling role in facilitating B-cell receptor mediated responses in B-lymphocytes. The most elaborate and best-established functions occur in phagocytes, where proton channels optimize the activity of NADPH oxidase, an important producer of reactive oxygen species. Proton efflux mediated by HV1 balances the charge translocated across the membrane by electrons through NADPH oxidase, minimizes changes in cytoplasmic and phagosomal pH, limits osmotic swelling of the phagosome, and provides substrate H(+) for the production of H2O2 and HOCl, reactive oxygen species crucial to killing pathogens.

  12. Opening Channels of Communication

    Directory of Open Access Journals (Sweden)

    Clarice Moura Costa

    2009-03-01

    Full Text Available Psychosis, as described through a psychodynamic perspective, is conceptualized as an attempt to deny the enveloping reality to avoid contact with the other. Music therapy is a way to break this barrier of non-communication raised by the patients. The music therapy process is configured as a trinomial – action (making music/ relationship (action with the other/communication (musical or verbal voluntary expression of feelings and conflicts, which, although intrinsically connected, is perceived in a sequential process. Aulagnier asserts that psychic activity represents the conjunction of three modes of functioning: the original process, the primary process and the secondary process. The perception of sound passes through three phases, corresponding to each manner of functioning of the psychic system – the pleasure of hearing, the desire to listen (to the other and the imperative of meaning. The music therapy process offers a significant similarity with the theory proposed by Aulagnier. We propose the hypothesis that in music therapy, there is an opportunity to (reexperience very archaic phases in the constitution of the ego, but in a new manner, so helping to open communication channels. This theoretical hypothesis is illustrated by real examples of patients.

  13. Single-Channel Recording of Ligand-Gated Ion Channels.

    Science.gov (United States)

    Plested, Andrew J R

    2016-01-01

    Single-channel recordings reveal the microscopic properties of individual ligand-gated ion channels. Such recordings contain much more information than measurements of ensemble behavior and can yield structural and functional information about the receptors that participate in fast synaptic transmission in the brain. With a little care, a standard patch-clamp electrophysiology setup can be adapted for single-channel recording in a matter of hours. Thenceforth, it is a realistic aim to record single-molecule activity with microsecond resolution from arbitrary cell types, including cell lines and neurons. PMID:27480725

  14. M channel enhancers and physiological M channel block.

    Science.gov (United States)

    Linley, John E; Pettinger, Louisa; Huang, Dongyang; Gamper, Nikita

    2012-02-15

    M-type (Kv7, KCNQ) K(+) channels control the resting membrane potential of many neurons, including peripheral nociceptive sensory neurons. Several M channel enhancers were suggested as prospective analgesics, and targeting M channels specifically in peripheral nociceptors is a plausible strategy for peripheral analgesia. However, receptor-induced inhibition of M channels in nociceptors is often observed in inflammation and may contribute to inflammatory pain. Such inhibition is predominantly mediated by phospholipase C. We investigated four M channel enhancers (retigabine, flupirtine, zinc pyrithione and H(2)O(2)) for their ability to overcome M channel inhibition via two phospholipase C-mediated mechanisms, namely depletion of membrane phosphatidylinositol 4,5-bisphosphate (PIP(2)) and a rise in intracellular Ca(2+) (an action mediated by calmodulin). Data from overexpressed Kv7.2/Kv7.3 heteromers and native M currents in dorsal root ganglion neurons suggest the following conclusions. (i) All enhancers had a dual effect on M channel activity, a negative shift in voltage dependence and an increase of the maximal current at saturating voltages. The enhancers differed in their efficacy to produce these effects. (ii) Both PIP(2) depletion and Ca(2+)/calmodulin strongly reduced the M current amplitude; however, at voltages near the threshold for M channel activation (-60 mV) all enhancers were able to restore M channel activity to a control level or above, while at saturating voltages the effects were more variable. (iii) Receptor-mediated inhibition of M current in nociceptive dorsal root ganglion neurons did not reduce the efficacy of retigabine or flupirtine to hyperpolarize the resting membrane potential. In conclusion, we show that all four M channel enhancers tested could overcome both PIP(2) and Ca(2+)-calmodulin-induced inhibition of Kv7.2/7.3 at voltages close to the threshold for action potential firing (-60 mV) but generally had reduced efficacy at a

  15. Ion Channels in Brain Metastasis.

    Science.gov (United States)

    Klumpp, Lukas; Sezgin, Efe C; Eckert, Franziska; Huber, Stephan M

    2016-01-01

    Breast cancer, lung cancer and melanoma exhibit a high metastatic tropism to the brain. Development of brain metastases severely worsens the prognosis of cancer patients and constrains curative treatment options. Metastasizing to the brain by cancer cells can be dissected in consecutive processes including epithelial-mesenchymal transition, evasion from the primary tumor, intravasation and circulation in the blood, extravasation across the blood-brain barrier, formation of metastatic niches, and colonization in the brain. Ion channels have been demonstrated to be aberrantly expressed in tumor cells where they regulate neoplastic transformation, malignant progression or therapy resistance. Moreover, many ion channel modulators are FDA-approved drugs and in clinical use proposing ion channels as druggable targets for future anti-cancer therapy. The present review article aims to summarize the current knowledge on the function of ion channels in the different processes of brain metastasis. The data suggest that certain channel types involving voltage-gated sodium channels, ATP-release channels, ionotropic neurotransmitter receptors and gap junction-generating connexins interfere with distinct processes of brain metastazation. PMID:27618016

  16. Information geometry of Gaussian channels

    International Nuclear Information System (INIS)

    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).

  17. Entanglement Cost of Quantum Channels

    CERN Document Server

    Berta, Mario; Christandl, Matthias; Wehner, Stephanie

    2011-01-01

    A natural question in characterizing the information theoretic power of quantum channels is to ask at what rate entanglement is needed in order to asymptotically simulate a quantum channel in the presence of free classical communication. We call this the entanglement cost of a channel, and prove a formula describing it for all channels. We discuss two applications. Firstly, our result has consequences for the study of the strong converse property of the quantum capacity. More precisely, we show that any coding scheme sending quantum information through a quantum channel at a rate larger than the entanglement cost of the channel is exponentially 'bad' in the number of channel uses. Secondly, and independently of the first application, we are able to link the security in the noisy-storage model to a problem of sending quantum rather than classical information through the adversary's storage device. This not only greatly improves the range of parameters where security could be shown previously, but allows us to ...

  18. Channel Coding in Random Access Communication over Compound Channels

    CERN Document Server

    Wang, Zheng

    2011-01-01

    Due to the short and bursty incoming messages, channel access activities in a wireless random access system are often fractional. The lack of frequent data support consequently makes it difficult for the receiver to estimate and track the time varying channel states with high precision. This paper investigates random multiple access communication over a compound wireless channel where channel realization is known neither at the transmitters nor at the receiver. An achievable rate and error probability tradeoff bound is derived under the non-asymptotic assumption of a finite codeword length. The results are then extended to the random multiple access system where the receiver is only interested in decoding messages from a user subset.

  19. Channel estimation in TDD mode

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yi; GU Jian; YANG Da-cheng

    2006-01-01

    An efficient solution is proposed in this article for the channel estimation in time division duplex (TDD) mode wireless communication systems. In the proposed solution, the characteristics of fading channels in TDD mode systems are fully exploited to estimate the path delay of the fading channel.The corresponding amplitude is estimated using the minimum mean square error (MMSE) criterion. As a result, it is shown that the proposed novel solution is more accurate and efficient than the traditional solution, and the improvement is beneficial to the performance of Joint Detection.

  20. Marine Toxins Targeting Ion Channels

    Directory of Open Access Journals (Sweden)

    Hugo R. Arias

    2006-04-01

    Full Text Available Abstract: This introductory minireview points out the importance of ion channels for cell communication. The basic concepts on the structure and function of ion channels triggered by membrane voltage changes, the so-called voltage-gated ion channels (VGICs, as well as those activated by neurotransmitters, the so-called ligand-gated ion channel (LGICs, are introduced. Among the most important VGIC superfamiles, we can name the voltage-gated Na+ (NaV, Ca2+ (CaV, and K+ (KV channels. Among the most important LGIC super families, we can include the Cys-loop or nicotinicoid, the glutamate-activated (GluR, and the ATP-activated (P2XnR receptor superfamilies. Ion channels are transmembrane proteins that allow the passage of different ions in a specific or unspecific manner. For instance, the activation of NaV, CaV, or KV channels opens a pore that is specific for Na+, Ca2+, or K+, respectively. On the other hand, the activation of certain LGICs such as nicotinic acetylcholine receptors, GluRs, and P2XnRs allows the passage of cations (e.g., Na+, K+, and/or Ca2+, whereas the activation of other LGICs such as type A γ-butyric acid and glycine receptors allows the passage of anions (e.g., Cl− and/or HCO3−. In this regard, the activation of NaV and CaV as well as ligand-gated cation channels produce membrane depolarization, which finally leads to stimulatory effects in the cell, whereas the activation of KV as well as ligand-gated anion channels induce membrane hyperpolarization that finally leads to inhibitory effects in the cell. The importance of these ion channel superfamilies is emphasized by considering their physiological functions throughout the body as well as their pathophysiological implicance in several neuronal diseases. In this regard, natural molecules, and especially marine toxins, can be potentially used as modulators (e.g., inhibitors or prolongers of ion channel functions to treat or to alleviate a specific

  1. Neural KCNQ (Kv7) channels

    OpenAIRE

    Brown, David A.; Passmore, Gayle M.

    2009-01-01

    KCNQ genes encode five Kv7 K+ channel subunits (Kv7.1–Kv7.5). Four of these (Kv7.2–Kv7.5) are expressed in the nervous system. Kv7.2 and Kv7.3 are the principal molecular components of the slow voltage-gated M-channel, which widely regulates neuronal excitability, although other subunits may contribute to M-like currents in some locations. M-channels are closed by receptors coupled to Gq such as M1 and M3 muscarinic receptors; this increases neuronal excitability and underlies some forms of c...

  2. The Degraded Poisson Wiretap Channel

    CERN Document Server

    Laourine, Amine

    2010-01-01

    Providing security guarantees for wireless communication is critically important for today's applications. While previous work in this area has concentrated on radio frequency (RF) channels, providing security guarantees for RF channels is inherently difficult because they are prone to rapid variations due small scale fading. Wireless optical communication, on the other hand, is inherently more secure than RF communication due to the intrinsic aspects of the signal propagation in the optical and near-optical frequency range. In this paper, secure communication over wireless optical links is examined by studying the secrecy capacity of a direct detection system. For the degraded Poisson wiretap channel, a closed-form expression of the secrecy capacity is given. A complete characterization of the general rate-equivocation region is also presented. For achievability, an optimal code is explicitly constructed by using the structured code designed by Wyner for the Poisson channel. The converse is proved in two dif...

  3. 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.

  4. Message Authentication over Noisy Channels

    Directory of Open Access Journals (Sweden)

    Fanfan Zheng

    2015-01-01

    Full Text Available The essence of authentication is the transmission of unique and irreproducible information. In this paper, the authentication becomes a problem of the secure transmission of the secret key over noisy channels. A general analysis and design framework for message authentication is presented based on the results of Wyner’s wiretap channel. Impersonation and substitution attacks are primarily investigated. Information-theoretic lower and upper bounds on the opponent’s success probability are derived, and the lower bound and the upper bound are shown to match. In general, the fundamental limits on message authentication over noisy channels are fully characterized. Analysis results demonstrate that introducing noisy channels is a reliable way to enhance the security of authentication.

  5. Aquaglyceroporins: ancient channels for metalloids

    OpenAIRE

    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.

  6. Thermosyphon boiling in vertical channels

    Science.gov (United States)

    Bar-Cohen, A.; Schweitzer, H.

    The thermal characteristics of ebullient cooling systems for VHSIC and VLSI microelectronic component thermal control are studied by experimentally and analytically investigating boiling heat transfer from a pair of flat, closely spaced, isoflux plates immersed in saturated water. A theoretical model for liquid flow rate through the channel is developed and used as a basis for correlating the rate of heat transfer from the channel walls. Experimental results for wall temperature as a function of axial location, heat flux, and plate spacing are presented. The finding that the wall superheat at constant imposed heat flux decreases as the channel is narrowed is explained with the aid of a boiling thermosiphon analysis which yields the mass flux through the channel.

  7. Catalytic reaction in confined flow channel

    Energy Technology Data Exchange (ETDEWEB)

    Van Hassel, Bart A.

    2016-03-29

    A chemical reactor comprises a flow channel, a source, and a destination. The flow channel is configured to house at least one catalytic reaction converting at least a portion of a first nanofluid entering the channel into a second nanofluid exiting the channel. The flow channel includes at least one turbulating flow channel element disposed axially along at least a portion of the flow channel. A plurality of catalytic nanoparticles is dispersed in the first nanofluid and configured to catalytically react the at least one first chemical reactant into the at least one second chemical reaction product in the flow channel.

  8. 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......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...

  9. FMCG companies specific distribution channels

    OpenAIRE

    Ioana Barin

    2009-01-01

    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 t...

  10. CHANNEL ESTIMATION FOR ITERATIVE DECODING OVER FADING CHANNELS

    Institute of Scientific and Technical Information of China (English)

    K.H.Sayhood; WuLenan

    2002-01-01

    A method of coherent detection and channel estimation for punctured convolutional coded binary Quadrature Amplitude Modulation (QAM) signals transmitted over a frequency-flat Rayleigh fading channels used for a digital radio broadcasting transmission is presented.Some known symbols are inserted in the encoded data stream to enhance the channel estimation process.The puilot symbols are used to replace the existing parity symbols so no bandwidth expansion is required.An iterative algorithm that uses decoding information as well as the information contained in the known symbols is used to improve the channel parameter estimate.The scheme complexity grows exponentially with the channel estimation filter length,The performance of the system is compared for a normalized fading rate with both perfect coherent detection(Corresponding to a perfect knowledge of the fading process and noise variance)and differential detection of Differential Amplitude Phase Shift Keying (DAPSK).The tradeoff between simplicity of implementation and bit-error-rate performance of different techniques is also compared.

  11. Information transfer through quantum channels

    International Nuclear Information System (INIS)

    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

  12. 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

  13. Memory effects in quantum channel discrimination

    OpenAIRE

    Chiribella G.; D'Ariano G.M.; Perinotti P.

    2008-01-01

    We consider quantum-memory assisted protocols for discriminating quantum channels. We show that for optimal discrimination of memory channels, memory assisted protocols are needed. This leads to a new notion of distance for channels with memory. For optimal discrimination and estimation of sets of unitary channels memory-assisted protocols are not required.

  14. 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....

  15. Continuous Time Channels with Interference

    CERN Document Server

    Ivan, Ioana; Thaler, Justin; Yuen, Henry

    2012-01-01

    Khanna and Sudan studied a natural model of continuous time channels where signals are corrupted by the effects of both noise and delay, and showed that, surprisingly, in some cases both are not enough to prevent such channels from achieving unbounded capacity. Inspired by their work, we consider channels that model continuous time communication with adversarial delay errors. The sender is allowed to subdivide time into arbitrarily large number $M$ of micro-units in which binary symbols may be sent, but the symbols are subject to unpredictable delays and may interfere with each other. We model interference by having symbols that land in the same micro-unit of time be summed, and a $k$-interference channels allows receivers to distinguish sums up to the value $k$. We consider both a channel adversary that has a limit on the maximum number of steps it can delay each symbol, and a more powerful adversary that only has a bound on the average delay. We give precise characterizations of the threshold between finite...

  16. 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

  17. Quantum channels with a finite memory

    CERN Document Server

    Bowen, G; 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, the channel is asymptotically noiseless.

  18. Researches toward potassium channels on tumor progressions.

    Science.gov (United States)

    Shen, Zheng; Yang, Qian; You, Qidong

    2009-01-01

    As trans-membrane proteins located in cytoplasm and organelle membrane, potassium (K(+)) channels are generally divided into four super-families: voltage-gated K(+) channels (K(v)), Ca(2+)-activated K(+) channels (K(Ca)), inwardly rectifying K(+) channels (K(ir)) and two-pore domain K(+) channels (K(2P)). Since dysfunctions of K(+) channels would induce many diseases, various studies toward their functions in physiologic and pathologic process have been extensively launched. This review focuses on the recent advances of K(+) channels in tumor progression, including the brief introduction of K(+) channels, the role of K(+) channels in tumor cells, the possible mechanism of action at cellular level, and the possible application of K(+) channel modulators in cancer chemotherapy.

  19. Sodium Channel Inhibiting Marine Toxins

    Science.gov (United States)

    Llewellyn, Lyndon E.

    Saxitoxin (STX), tetrodotoxin (TTX) and their many chemical relatives are part of our daily lives. From killing people who eat seafood containing these toxins, to being valuable research tools unveiling the invisible structures of their pharmacological receptor, their global impact is beyond measure. The pharmacological receptor for these toxins is the voltage-gated sodium channel which transports Na ions between the exterior to the interior of cells. The two structurally divergent families of STX and TTX analogues bind at the same location on these Na channels to stop the flow of ions. This can affect nerves, muscles and biological senses of most animals. It is through these and other toxins that we have developed much of our fundamental understanding of the Na channel and its part in generating action potentials in excitable cells.

  20. Information geometry of Gaussian channels

    CERN Document Server

    Monras, Alex

    2009-01-01

    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 from distinguishability considerations: It serves as an upper bound to the attainable quantum Fisher information for the channel parameters using Gaussian states, under some restriction on the available resources. We prove that optimal states are always pure and bounded in the number of ancillary modes that are needed. This has experimental and computational advantages: 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 computing the metric. We provide explicit formulae for computing the multiparametric quantum F...

  1. Resolvability of positron decay channels

    International Nuclear Information System (INIS)

    Many data analysis treatments of positron experiments attempt to resolve two or more positron decay or exist channels which may be open simultaneously. Examples of the need to employ such treatments of the experimental results can be found in the resolution of the constituents of a defect ensemble, or in the analysis of the complex spectra which arise from the interaction of slow positrons at or near the surfaces of solids. Experimental one- and two-dimensional angular correlation of annihilation radiation experiments in Al single crystals have shown that two defect species (mono- and divacancies) can be resolved under suitable conditions. Recent experiments at LLNL indicate that there are a variety of complex exit channels open to positrons interacting at surfaces, and ultimely these decay channels must also be suitably resolved from one another. 6 refs., 4 figs

  2. Quantum channels with a finite memory

    OpenAIRE

    Bowen, Garry; Mancini, Stefano

    2003-01-01

    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 ...

  3. Insect sodium channels and insecticide resistance

    OpenAIRE

    Dong, Ke

    2007-01-01

    Voltage-gated sodium channels are essential for the generation and propagation of action potentials (i.e., electrical impulses) in excitable cells. Although most of our knowledge about sodium channels is derived from decades of studies of mammalian isoforms, research on insect sodium channels is revealing both common and unique aspects of sodium channel biology. In particular, our understanding of the molecular dynamics and pharmacology of insect sodium channels has advanced greatly in recent...

  4. Mobile Radio Channels Modeling in MATLAB

    OpenAIRE

    N. Kostov

    2003-01-01

    In this paper, a MATLAB based approach for mobile radio channels modeling is presented. Specifically, the paper introduces the basic concepts for modeling flat fading channels in MATLAB by means of user-defined m-files. Typical small-scale fading channel models are derived such as uncorrelated Rician fading channel and Rayleigh fading channel with Doppler shift. Further, simple and useful MATLAB constructions for approximation of cumulative distribution functions (CDFs) and probability densit...

  5. Channel incision and water quality

    Science.gov (United States)

    Shields, F. D.

    2009-12-01

    Watershed development often triggers channel incision that leads to radical changes in channel morphology. Although morphologic evolution due to channel incision has been documented and modeled by others, ecological effects, particularly water quality effects, are less well understood. Furthermore, environmental regulatory frameworks for streams frequently focus on stream water quality and underemphasize hydrologic and geomorphic issues. Discharge, basic physical parameters, solids, nutrients (nitrogen and phosphorus), chlorophyll and bacteria were monitored for five years at two sites along a stream in a mixed cover watershed characterized by rapid incision of the entire channel network. Concurrent data were collected from two sites on a nearby stream draining a watershed of similar size and cultivation intensity, but without widespread incision. Data sets describing physical aquatic habitat and fish fauna of each stream were available from other studies. The second stream was impacted by watershed urbanization, but was not incised, so normal channel-floodplain interaction maintained a buffer zone of floodplain wetlands between the study reach and the urban development upstream. The incised stream had mean channel depth and width that were 1.8 and 3.5 times as large as for the nonincised stream, and was characterized by flashier hydrology. The median rise rate for the incised stream was 6.4 times as great as for the nonincised stream. Correlation analyses showed that hydrologic perturbations were associated with water quality degradation, and the incised stream had levels of turbidity and solids that were two to three times higher than the nonincised, urbanizing stream. Total phosphorus, total Kjeldahl N, and chlorophyll a concentrations were significantly higher in the incised stream, while nitrate was significantly greater in the nonincised, urbanizing stream (p urbanizing stream were superior, as it supported almost twice as many species and yielded more than

  6. Vascular potassium channels in NVC.

    Science.gov (United States)

    Yamada, K

    2016-01-01

    It has long been proposed that the external potassium ion ([K(+)]0) works as a potent vasodilator in the dynamic regulation of local cerebral blood flow. Astrocytes may play a central role for producing K(+) outflow possibly through calcium-activated potassium channels on the end feet, responding to a rise in the intracellular Ca(2+) concentration, which might well reflect local neuronal activity. A mild elevation of [K(+)]0 in the end feet/vascular smooth muscle space could activate Na(+)/K(+)-ATPase concomitant with inwardly rectifying potassium (Kir) channels in vascular smooth muscle cells, leading to a hyperpolarization of vascular smooth muscle and relaxation of smooth muscle actin-positive vessels. Also proposed notion is endothelial calcium-activated potassium channels and/or inwardly rectifying potassium channel-mediated hyperpolarization of vascular smooth muscle. A larger elevation of [K(+)]0, which may occur pathophysiologically in such as spreading depression or stroke, can trigger a depolarization of vascular smooth muscle cells and vasoconstriction instead. PMID:27130411

  7. Multi channel beam profile digitizer

    International Nuclear Information System (INIS)

    Beam of ions in an accelerator are focussed with the help of focussing magnets to achieve very narrow circular beam. To verify the beam profile along its length, Beam Profile Monitors (BPM) are installed at number of points. The signal generated from these units convey information about the shape and axial error of the beam. Presently BPM signals are monitored on oscilloscope. One oscilloscope is required per BPM channel to be monitored and normally 2 oscilloscopes are kept for viewing beam at two successive points along with one channel selector to select the channel to be monitored. The 8 channel beam profile digitizer being developed is a low cost intelligent PC-add on card, built around Intel's 8751 microcontroller, which can be easily integrated with PC based data acquisition and control system for accelerators. Microcontroller digitizes the signal and stores information on FIFO for PC to read and graphically display the profile. User can select up to 8 profiles to view simultaneously on the screen. (author). 1 ref., 2 figs

  8. 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 c

  9. 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 outco

  10. Wireless Communication over Dispersive Channels

    NARCIS (Netherlands)

    Fang, K.

    2010-01-01

    Broadband wireless communication systems require high transmission rates, where the bandwidth of the transmitted signal is larger than the channel coherence bandwidth. This gives rise to time dispersion of the transmitted symbols or frequency-selectivity with different frequency components exhibitin

  11. 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. Bel...

  12. Potential flow through channel constriction.

    Science.gov (United States)

    Lee, J.K.

    1984-01-01

    Potential flow through an eccentric, normal constriction of zero thickness in an infinitely long, straight channel of constant width and unit depth is studied by use of a Schwarz-Christoffel transformation. The transformation is integrated by a direct approach. Parametric equations for streamlines are obtained and used to compute an average streamline length for a potential-flow field. -from ASCE Publications Information

  13. Hidden systematics of fission channels

    Directory of Open Access Journals (Sweden)

    Schmidt Karl-Heinz

    2013-12-01

    Full Text Available It is a common procedure to describe the fission-fragment mass distributions of fissioning systems in the actinide region by a sum of at least 5 Gaussian curves, one for the symmetric component and a few additional ones, together with their complementary parts, for the asymmetric components. These components have been attributed to the influence of fragment shells, e.g. in the statistical scission-point model of Wilkins, Steinberg and Chasman. They have also been associated with valleys in the potential-energy landscape between the outer saddle and the scission configuration in the multi-channel fission model of Brosa. When the relative yields, the widths and the mean mass-asymmetry values of these components are fitted to experimental data, the mass distributions can be very well reproduced. Moreover, these fission channels are characterised by specific values of charge polarisation, total kinetic energy and prompt-neutron yields. The present contribution investigates the systematic variation of the characteristic fission-channel properties as a function of the composition and the excitation energy of the fissioning system. The mean position of the asymmetric fission channels in the heavy fragment is almost constant in atomic number. The deformation of the nascent fragments at scission, which is the main source of excitation energy of the separated fission fragments ending up in prompt-neutron emission, is found to be a unique function of Z for the light and the heavy fragment of the asymmetric fission channels. A variation of the initial excitation energy of the fissioning system above the fission saddle is only seen in the neutron yield of the heavy fragment. The charge polarisation in the two most important asymmetric fission channels is found to be constant and to appreciably exceed the macroscopic value. The variation of the relative yields and of the positions of the fission channels as a function of the composition and excitation energy

  14. 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.

  15. Integrated criteria for covert channel auditing

    Institute of Scientific and Technical Information of China (English)

    Chang-da WANG; Shi-guang JU

    2008-01-01

    A new concept, the security level difference of a covert channel, is presented, which means the security level span from the sender to the receiver of the covert channel. Based on this, the integrated criteria for covert channel auditing are given. Whereas TCSEC (Trusted Computer System Evaluation Criteria) or CC (Common Criteria for Information Technology Security Evaluation) only use the bandwidth to evaluate the threat of covert channels, our new criteria integrate the security level difference, the bandwidth sensitive parameter, bandwidth, duration and instantaneous time of covert channels, so as to give a comprehensive evaluation of the threat of covert channels in a multilevel security system.

  16. Electromagnetic channel capacity for practical purposes

    CERN Document Server

    Giovannetti, Vittorio; Maccone, Lorenzo; Shapiro, Jeffrey H

    2012-01-01

    We give analytic upper bounds to the channel capacity C for transmission of classical information in electromagnetic channels (bosonic channels with thermal noise). In the practically relevant regimes of high noise and low transmissivity, by comparison with know lower bounds on C, our inequalities determine the value of the capacity up to corrections which are irrelevant for all practical purposes. Examples of such channels are radio communication, infrared or visible-wavelength free space channels. We also provide bounds to active channels that include amplification.

  17. 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.

  18. 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...... 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...

  19. Chloride Channels: Often enigmatic, rarely predictable

    Science.gov (United States)

    Duran, Charity; Thompson, Christopher H.; Xiao, Qinghuan; Hartzell, Criss

    2010-01-01

    Until recently, anion (Cl−) channels have received considerably less attention than cation channels. One reason for this may be that many Cl− channels perform functions that might be considered cell biological, like fluid secretion and cell volume regulation, whereas cation channels have historically been associated with cellular excitability that typically happens more rapidly. In this review, we discuss the recent explosion of interest in Cl− channels with special emphasis on new and often surprising developments over the last 5 years. This is exemplified by the findings that more than half of the ClC family members are antiporters, and not channels as was previously thought, and that bestrophins, previously prime candidates for Ca2+-activated Cl− channels, have been supplanted by the newly discovered anoctamins and now hold a tenuous position in the Cl− channel world. PMID:19827947

  20. The quantum capacity with symmetric side channels

    CERN Document Server

    Smith, G; Winter, A; Smith, Graeme; Smolin, John A.; Winter, Andreas

    2006-01-01

    We present an upper bound for the quantum channel capacity that is both additive and convex. Our bound can be interpreted as the capacity of a channel for high-fidelity communication when assisted by the family of all channels mapping symmetrically to their output and environment. The bound seems to be quite tight, and for degradable quantum channels it coincides with the unassisted channel capacity. Using this symmetric side channel capacity, we find new upper bounds on the capacity of the depolarizing channel. We also briefly indicate an analogous notion for distilling entanglement using the same class of (one-way) channels, yielding one of the few genuinely 1-LOCC monotonic entanglement measures.

  1. 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...

  2. BK channel modulators: a comprehensive overview

    DEFF Research Database (Denmark)

    Nardi, Antonio; Olesen, Søren-Peter

    2008-01-01

    and blockers 4) Marketed and/or investigational drugs with BK-modulating side properties and structural analogues 5) Naturally-occurring BK channel openers and structural analogues 6) Synthetic BK channel openers. This review is intended to provide readers with current opinion on the BK channel as a drug......The large Ca(2+)-activated K(+) channel (BK channel) reflects per excellence the dilemma of the molecular target driven drug discovery process. Significant experimental evidence suggests that the BK channels play a pivotal and specific role in many pathophysiological conditions supporting...... the notion that the channel represents an innovative and promising drug target. However, after more than ten years of intense research effort both in academia and industry, scientists have yet to witness the approval of a single BK channel modulator for clinical use. On the contrary, three BK openers...

  3. Membrane lipid modulations remove divalent open channel block from TRP-like and NMDA channels.

    Science.gov (United States)

    Parnas, Moshe; Katz, Ben; Lev, Shaya; Tzarfaty, Vered; Dadon, Daniela; Gordon-Shaag, Ariela; Metzner, Henry; Yaka, Rami; Minke, Baruch

    2009-02-25

    Open channel block is a process in which ions bound to the inside of a channel pore block the flow of ions through that channel. Repulsion of the blocking ions by depolarization is a known mechanism of open channel block removal. For the NMDA channel, this mechanism is necessary for channel activation and is involved in neuronal plasticity. Several types of transient receptor potential (TRP) channels, including the Drosophila TRP and TRP-like (TRPL) channels, also exhibit open channel block. Therefore, removal of open channel block is necessary for the production of the physiological response to light. Because there is no membrane depolarization before the light response develops, it is not clear how the open channel block is removed, an essential step for the production of a robust light response under physiological conditions. Here we present a novel mechanism to alleviate open channel block in the absence of depolarization by membrane lipid modulations. The results of this study show open channel block removal by membrane lipid modulations in both TRPL and NMDA channels of the photoreceptor cells and CA1 hippocampal neurons, respectively. Removal of open channel block is characterized by an increase in the passage-rate of the blocking cations through the channel pore. We propose that the profound effect of membrane lipid modulations on open channel block alleviation, allows the productions of a robust current in response to light in the absence of depolarization.

  4. GMSK co-channel demodulation

    Science.gov (United States)

    Nelson, D. J.; Hopkins, J. R.

    2009-08-01

    Gaussian Minimum Shift Keying (GMSK) is a modulation method used by GSM phone networks and the Automatic Identification System (AIS) used by commercial ships. Typically these systems transmit data in short bursts and accomodate a large number of users by time, frequency and power management. Co-channel interference is not a problem unless the system is heavily loaded. This system load is a function of the density of users and the footprint of the receiver. We consider the problem of demodulation of burst GMSK signals in the presence of severe noise and co-channel interference. We further examine the problem of signal detection and blind estimation and tracking of all of the parameters required in the demodulation process. These parameters include carrier frequency, carrier phase, baud rate, baud phase, modulation index and the start and duration of the signal.

  5. Gramicidin channel kinetics under tension.

    OpenAIRE

    Goulian, M; Mesquita, O. N.; Fygenson, D K; Nielsen, C; Andersen, O S; Libchaber, A.

    1998-01-01

    We have measured the effect of tension on dimerization kinetics of the channel-forming peptide gramicidin A. By aspirating large unilamellar vesicles into a micropipette electrode, we are able to simultaneously monitor membrane tension and electrical activity. We find that the dimer formation rate increases by a factor of 5 as tension ranges from 0 to 4 dyn/cm. The dimer lifetime also increases with tension. This behavior is well described by a phenomenological model of membrane elasticity in...

  6. Wireless Channel Propagation Models Evaluation

    OpenAIRE

    Raikel Bordón López; Reinier Alonso Quintana; Samuel Montejo Sánchez

    2012-01-01

    In the design of wireless communications systems, channel modelling is an efficient alternative to predict the path loss. In this paper we present a comparative study between Okumura, Hata, Walfisch-Bertoni and Walfisch-Ikegami propagation models. We present a developed software tool, which is useful to evaluate these models from a graphical user interface. The main objective is to analyze and compare path loss predictions, taking into account different environment conditions and a common val...

  7. SOCIAL NETWORKS AS MARKETING CHANNELS

    OpenAIRE

    Sonja Petrov, Vesna Zubac, Miroslav Milojeviæ

    2015-01-01

    Fast technological development in social media offers many opportunities for companies in order to have better connection with their customers. Traditional tools become less effective and companies are working intensively to be present on the web. This paper will try to answer the question what are the advantages of social media as a marketing channels compared to conventional way of advertising. The authors will specially pay attention to how can companies improve and increase their presence...

  8. 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.

  9. Interference Channels with Correlated Receiver Side Information

    OpenAIRE

    Liu, Nan; Gunduz, Deniz; Goldsmith, Andrea J.; Poor, H. Vincent

    2008-01-01

    The problem of joint source-channel coding in transmitting independent sources over interference channels with correlated receiver side information is studied. When each receiver has side information correlated with its own desired source, it is shown that source-channel code separation is optimal. When each receiver has side information correlated with the interfering source, sufficient conditions for reliable transmission are provided based on a joint source-channel coding scheme using the ...

  10. Southern California Channel Islands Bibliography, through 1992

    OpenAIRE

    Channel Islands National Marine Sanctuary

    1992-01-01

    The Southern California Channel Islands Bibliography, through 1992, comprises 4035 references to the scientific literature on Southern California's Channel Islands. The Bibliography was compiled by the Channel Islands National Marine Sanctuary and is presented here in a February 1993 version. The Santa Barbara Museum of Natural History presents a California Channel Islands Bibliography on its website. It has more recent references and overlaps considerably with this bibliography. How...

  11. Ions in Fluctuating Channels: Transistors Alive

    OpenAIRE

    Eisenberg, Bob

    2005-01-01

    Ion channels are proteins with a hole down the middle embedded in cell membranes. Membranes form insulating structures and the channels through them allow and control the movement of charged particles, spherical ions, mostly Na+, K+, Ca++, and Cl-. Membranes contain hundreds or thousands of types of channels, fluctuating between open conducting, and closed insulating states. Channels control an enormous range of biological function by opening and closing in response to specific stimuli using ...

  12. Artificial water channels--incipient innovative developments.

    Science.gov (United States)

    Barboiu, Mihail

    2016-04-28

    Aquaporins (AQPs) are biological water channels known for fast water transport (∼10(8)-10(9) water molecules per s per channel), with complete proton/ion exclusion. Few synthetic channels have been designed to mimic this high water permeability and to reject ions at a significant level. This Feature Article will discuss the incipient developments of the first artificial water channel systems. PMID:27046217

  13. Customer Evolution in Sales Channel Migration

    OpenAIRE

    Valentini, Sara

    2008-01-01

    This research has been triggered by an emergent trend in customer behavior: customers have rapidly expanded their channel experiences and preferences beyond traditional channels (such as stores) and they expect the company with which they do business to have a presence on all these channels. This evidence has produced an increasing interest in multichannel customer behavior and it has motivated several researchers to study the customers’ channel choices dynamics in multichannel environment. W...

  14. 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

  15. Interference Channels with Strong Secrecy

    CERN Document Server

    He, Xiang

    2009-01-01

    It is known that given the real sum of two independent uniformly distributed lattice points from the same nested lattice codebook, the eavesdropper can obtain at most 1 bit of information per channel regarding the value of one of the lattice points. In this work, we study the effect of this 1 bit information on the equivocation expressed in three commonly used information theoretic measures, i.e., the Shannon entropy, the Renyi entropy and the min entropy. We then demonstrate its applications in an interference channel with a confidential message. In our previous work, we showed that nested lattice codes can outperform Gaussian codes for this channel when the achieved rate is measured with the weak secrecy notion. Here, with the Renyi entropy and the min entropy measure, we prove that the same secure degree of freedom is achievable with the strong secrecy notion as well. A major benefit of the new coding scheme is that the strong secrecy is generated from a single lattice point instead of a sequence of lattic...

  16. Water channels in peritoneal dialysis.

    Science.gov (United States)

    Devuyst, Olivier

    2010-01-01

    Peritoneal dialysis involves diffusive and convective transports and osmosis through the highly vascularized peritoneal membrane. Several lines of evidence have demonstrated that the water channel aquaporin-1 (AQP1) corresponds to the ultrasmall pore predicted by the modelization of peritoneal transport. Proof-of-principle studies have shown that up-regulation of the expression of AQP1 in peritoneal capillaries is reflected by increased water permeability and ultrafiltration, without affecting the osmotic gradient and the permeability for small solutes. Inversely, studies in Aqp1 mice have shown that haploinsufficiency in AQP1 is reflected by significant attenuation of water transport. Recent studies have identified lead compounds that could act as agonists of aquaporins, as well as putative binding sites and potential mechanisms of gating the water channel. By modulating water transport, these pharmacological agents could have clinically relevant effects in targeting specific tissues or disease states. These studies on the peritoneal membrane also provide an experimental framework to investigate the role of water channels in the endothelium and various cell types.

  17. 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.

  18. Channel One: But What about the Advertising?

    Science.gov (United States)

    Greenberg, Bradley S.; Brand, Jeffrey E.

    1994-01-01

    A survey of students in Channel One and control schools showed that regular viewing of Channel One reinforces materialistic attitudes. Youngsters are bombarded daily with advertising from adolescent-oriented radio stations, magazines, and TV programs outside school. Channel One does provide educators with a excellent opportunity to educate youth…

  19. One-mode quantum Gaussian channels

    OpenAIRE

    Holevo, A. S.

    2006-01-01

    A classification of one-mode Gaussian channels is given up to canonical unitary equivalence. A complementary to the quantum channel with additive classical Gaussian noise is described providing an example of one-mode Gaussian channel which is neither degradable nor anti-degradable.

  20. 47 CFR 95.29 - Channels available.

    Science.gov (United States)

    2010-10-01

    ... 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,...

  1. 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…

  2. Na+ channel β subunits: Overachievers of the ion channel family

    OpenAIRE

    LoriLIsom; WilliamJBrackenbury

    2011-01-01

    Voltage gated Na+ channels (VGSCs) in mammals contain a pore-forming α subunit and one or more β subunits. There are five mammalian β subunits in total: β1, β1B, β2, β3, and β4, encoded by four genes: SCN1B-SCN4B. With the exception of the SCN1B splice variant, β1B, the β subunits are type I topology transmembrane proteins. In contrast, β1B lacks a transmembrane domain and is a secreted protein. A growing body of work shows that VGSC β subunits are multifunctional. While they do not form the...

  3. A simple channel estimator for space-time coded OFDM systems in rapid fading channels

    Institute of Scientific and Technical Information of China (English)

    单淑伟; 罗汉文; 宋文涛

    2004-01-01

    A simple channel estimator for space-time coded orthogonal frequency division multiplexing (OFDM) systems in rapid fading channels is proposed. The channels at the training bauds are estimated using the EM (expectation-maximization) algorithm, while the channels at the data bauds are estimated based on the method for modelling the time-varying channel as the linear combination of several time-invariant " Doppler channels". Computer simulations showed that this estimator outperforms the decision-directed tracking in rapid fading channels and that the performance of this method can be improved by iteration.

  4. A simple channel estimator for space-time coded OFDM systems in rapid fading channels

    Institute of Scientific and Technical Information of China (English)

    SHAN Shu-wei(单淑伟); LUO Han-wen(罗汉文); SONG Wen-tao(宋文涛)

    2004-01-01

    A simple channel estimator for space-time coded orthogonal frequency division multiplexing (OFDM) systems in rapid fading channels is proposed. The channels at the training bauds are estimated using the EM (expectation-maximization) algorithm, while the channels at the data bauds are estimated based on the method for modelling the time-varying channel as the linear combination of several time-invariant "Doppler channels". Computer simulations showed that this estimator outperforms the decision-directed tracking in rapid fading channels and that the performance of this method can be improved by iteration.

  5. HYDRAULICS OF COMPOUND CHANNEL WITH VEGETATED FLOODPLAINS

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Experimental researches were conducted on flood carrying capacity of compound open channels with wide and narrow floodplains as well as hydrodynamic behavior of overbank flow across vegetated floodplains. Results show that hydrodynamic behavior of compound channels with narrow floodplains is different from that of the wide floodplains. In such compound channels with narrow vegetated floodplains as in the Pearl River delta nework, it has been found that vegetated domains become really impenetrable when the length of vegetated domain is larger than Lm, the length of flow in floodplain coming into the main channel, and that the influence of vegetated floodplains upon flood stages of a channel is not very significant.

  6. Generation of single plasma channel in air

    International Nuclear Information System (INIS)

    The conditions of generating a single plasma channel in air are studied by using picosecond and femtosecond laser pulse. A stable and single plasma channel can be generated by a picosecond laser pulse with energy of 8-12 mJ and focusing length of 15 cm. The self-generated light emission is observed to be confined in the plasma channel and propagates in the channel. When using short focal length lenses it is easy to generate a single plasma channel in air with femtosecond laser with energy less than 10 mJ. (authors)

  7. CHANNEL WIDENING DURING DEGRADATION OF ALLUVIAL RIVERS

    Institute of Scientific and Technical Information of China (English)

    Guangqian WANG; Junqiang XIA

    2001-01-01

    This paper first describes the phenomenon of channel widening during degradation of alluvial rivers,explains the mechanisms of channel widening, and analyzes the stability of cohesive riverbank. Then a one-dimensional mathematical model is developed to simulate the transport of non-uniform suspended sediments, with a sub-model for the simulation of channel widening, and is used to study the process of channel widening during degradation. The effects of different incident flow and sediment conditions and different riverbank material characteristics on channel widening and bed degradation are compared.Finally, main factors that control the deformation processes are identified.

  8. Box model for channels of human migration

    CERN Document Server

    Vitanov, Nikolay K

    2016-01-01

    We discuss a mathematical model of migration channel based on the truncated Waring distribution. The truncated Waring distribution is obtained for a more general model of motion of substance through a channel containing finite number of boxes. The model is applied then for case of migrants moving through a channel consisting of finite number of countries or cities. The number of migrants in the channel strongly depends on the number of migrants that enter the channel through the country of entrance. It is shown that if the final destination country is very popular then large percentage of migrants may concentrate there.

  9. Dynamic Channel Allocation in Sectored Cellular Systems

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    It is known that dynamic channel assignment(DCA) strategy outperforms the fixed channel assignment(FCA) strategy in omni-directional antenna cellular systems. One of the most important methods used in DCA was channel borrowing. But with the emergence of cell sectorization and spatial division multiple access(SDMA) which are used to increase the capacity of cellular systems, the channel assignment faces a series of new problems. In this paper, a dynamic channel allocation scheme based on sectored cellular systems is proposed. By introducing intra-cell channel borrowing (borrowing channels from neighboring sectors) and inter-cell channel borrowing (borrowing channels from neighboring cells) methods, previous DCA strategies, including compact pattern based channel borrowing(CPCB) and greedy based dynamic channel assignment(GDCA) schemes proposed by the author, are improved significantly. The computer simulation shows that either intra-cell borrowing scheme or inter-cell borrowing scheme is efficient enough to uniform and non-uniform traffic service distributions.

  10. The Holevo-Schumacher-Westmoreland Channel Capacity for a Class of Qudit Unital Channels

    OpenAIRE

    Cortese, John A.

    2002-01-01

    The Holevo-Schumacher-Westmoreland (HSW) classical (entanglement-unassisted) channel capacity for a class of qudit unital channels is shown to be C = log2(d) - Smin, where d is the dimension of the qudit, and Smin is the minimum possible von Neumann entropy at the channel output. The HSW channel capacity for tensor products of this class of unital qudit channels is shown to obey the same formula.

  11. VARIABLE-RATE MULTIUSER DIVERSITY IN CORRELATED MIMO CHANNEL VIA VIRTUAL CHANNEL REPRESENTATION

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper studies the multiuser diversity with constellation selection based on a virtual representation of realistic Multiple Input Multiple Output (MIMO) correlated channels. To realize multiuser diversity in slow fading channels, random beamforming is adopted. Random beamforming matrix exploiting virtual channel representation is constructed, which can match the channel matrix of the desired user better. Simultaneously, adaptive coded modulation is applied to each sub-channel of the selected user to improve the system performance further.

  12. The Holevo-Schumacher-Westmoreland Channel Capacity for a Class of Qudit Unital Channels

    CERN Document Server

    Cortese, J A

    2004-01-01

    The Holevo-Schumacher-Westmoreland (HSW) classical (entanglement-unassisted) channel capacity for a class of qudit unital channels is shown to be C = log2(d) - Smin, where d is the dimension of the qudit, and Smin is the minimum possible von Neumann entropy at the channel output. The HSW channel capacity for tensor products of this class of unital qudit channels is shown to obey the same formula.

  13. Joint design of fixed-rate source codes and UEP channel codes for fading channels

    OpenAIRE

    Tie, Hai-Xin; Goldsmith, Andrea; Effros, Michelle

    1998-01-01

    We study an iterative design algorithm that jointly optimizes source and channel codes for image transmission over Rayleigh fading channels. The joint design combines channel-optimized vector quantization (COVQ) for the source code with a family of rate-compatible punctured convolutional codes for the unequal-error-protection (UEP) channel code. We consider both hard-decision and soft-decision decoding for these channel codes. Our objective is to minimize the average end-to-end distortion, av...

  14. Analytical Expression for the MIMO Channel Capacity

    Institute of Scientific and Technical Information of China (English)

    ZHAO Yifei; ZHAO Ming; XIAO Limin; WANG Jing

    2006-01-01

    This paper presents analytical expressions for the multiple-input multiple-output (MIMO) channel capacity in frequency-flat Rayleigh fading environments. An exact analytical expression is given for the ergodic capacity for single-input multiple-output (SIMO) channels. The analysis shows that the SIMO channel capacity can be approximated by a Gaussian random variable and that the MIMO channel capacity can be approximated as the sum of multiple SIMO capacities. The SIMO channel results are used to derive approximate closed-form expressions for the MIMO channel ergodic capacity and the complementary cumulative distribution function (CCDF) of the MIMO channel capacity (outage capacity). Simulations show that these theoretical results are good approximations for MIMO systems with an arbitrary number of transmit or receive antennas. Moreover, these analytical expressions are relatively simple which makes them very useful for practical computations.

  15. Quartz Channel Fabrication for Electrokinetically Driven Separations

    Energy Technology Data Exchange (ETDEWEB)

    Arnold, D.W.; Ashby, C.I.H.; Bailey, C.G.; Kravitz, S.H., Warren, M.E.; Matzke, C.M.

    1998-12-01

    For well resolved electrokinetic separation, we L tilize crystalline quartz to micromachine a uniformly packe Q&iKLmnel. Packing features are posts 5 Vm on a side with:} pm spacing and etched 42 Vm deep. In addition to anisotropic wet etch characteristics for micromachining, quartz propmties are compatible with chemical soiutioits, ekctrokinetic high voltage operation, and stationary phase film depositions. To seal these channels, we employ a room temperature silicon-oxynhride deposition to forma membrane, that is subsequently coated for mechanical stability. Using this technique, particulate issues and global warp, that make large area wafer bon ding methods difficult, are avoided, and a room temperature process, in contrast to high temperature bonding techniques, accommodate preprocessing of metal films for electrical interconnect. After sealing channels, a number of macro-assembly steps are required to attach a micro-optical detection system and fluid interconnects. Keywords: microcharmel, integrated channel, micromachined channel, packed channel, electrokinetic channel, eleetrophoretic channel

  16. Quantum channels with a finite memory

    International Nuclear Information System (INIS)

    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

  17. Quantum channels with a finite memory

    Science.gov (United States)

    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.

  18. 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.

  19. Fundamental channeling questions at ultra relativistic energies

    Energy Technology Data Exchange (ETDEWEB)

    Carrigan, Richard A., Jr.; /Fermilab

    2006-08-01

    TeV-range bent crystal channeling has interesting advantages for several applications at high energy accelerators. Observations of enhanced deflection over the whole arc of a bent crystal at RHIC and recently at the Tevatron may be due to a process called ''volume reflection''. More investigations of volume reflection and of the complimentary process, volume capture, are needed. So-called quasimosaic bending processes also deserve additional study. Negative particle channeling may be relevant to channeling collimation for electron machines. Electron and positron channeling and channeling radiation are interwoven so that the impact of channeling radiation on applications needs to be better understood. Beams in the 0.1 to 1 GeV range may be useful for some of these investigations. Finally there has been little or no study of positive and negative muon channeling. The current understanding of these topics and the desirability of further work is reviewed.

  20. 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.

  1. 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.

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

    International Nuclear Information System (INIS)

    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

  3. Nav Channels in Damaged Membranes.

    Science.gov (United States)

    Morris, C E; Joos, B

    2016-01-01

    Sick excitable cells (ie, Nav channel-expressing cells injured by trauma, ischemia, inflammatory, and other conditions) typically exhibit "acquired sodium channelopathies" which, we argue, reflect bleb-damaged membranes rendering their Nav channels "leaky." The situation is excitotoxic because untreated Nav leak exacerbates bleb damage. Fast Nav inactivation (a voltage-independent process) is so tightly coupled, kinetically speaking, to the inherently voltage-dependent process of fast activation that when bleb damage accelerates and thus left-shifts macroscopic fast activation, fast inactivation accelerates to the same extent. The coupled g(V) and availability(V) processes and their window conductance regions consequently left-shift by the same number of millivolts. These damage-induced hyperpolarizing shifts, whose magnitude increases with damage intensity, are called coupled left shift (CLS). Based on past work and modeling, we discuss how to test for Nav-CLS, emphasizing the virtue of sawtooth ramp clamp. We explain that it is the inherent mechanosensitivity of Nav activation that underlies Nav-CLS. Using modeling of excitability, we show the known process of Nav-CLS is sufficient to predict a wide variety of "sick excitable cell" phenomena, from hyperexcitability through to depolarizing block. When living cells are mimicked by inclusion of pumps, mild Nav-CLS produces a wide array of burst phenomena and subthreshold oscillations. Dynamical analysis of mild damage scenarios shows how these phenomena reflect changes in spike thresholds as the pumps try to counteract the leaky Nav channels. Smart Nav inhibitors designed for sick excitable cells would target bleb-damaged membrane, buying time for cell-mediated removal or repair of Nav-bearing membrane that has become bleb-damaged (ie, detached from the cytoskeleton). PMID:27586295

  4. 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

  5. TRANSITIONAL FLOW IN CHANNEL JUNCTIONS

    Institute of Scientific and Technical Information of China (English)

    NI Han-gen; LIU Ya-kun

    2004-01-01

    On the basis of energy and continuity equations a simple one-dimensional formulation was proposed to predict the transitional flow at an open-channel junction. An empilical relation between the junction losses, the junction angle, and the discharge ratio was suggested which agrees well with the experimental results. The results calculated by the present formulation for the depth ratio were compared with the results of earlier one-dimensional formulations and experiments. It is found that the present results coincide better with experiments than those of others.

  6. Magnetohydrodynamic (MHD) channel corner seal

    Science.gov (United States)

    Spurrier, Francis R.

    1980-01-01

    A corner seal for an MHD duct includes a compressible portion which contacts the duct walls and an insulating portion which contacts the electrodes, sidewall bars and insulators. The compressible portion may be a pneumatic or hydraulic gasket or an open-cell foam rubber. The insulating portion is segmented into a plurality of pieces of the same thickness as the electrodes, insulators and sidewall bars and aligned therewith, the pieces aligned with the insulator being of a different size from the pieces aligned with the electrodes and sidewall bars to create a stepped configuration along the corners of the MHD channel.

  7. Channel guiding for advanced accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Milchberg, H.M. [Institute for Physical Science and Technology (United States); Durfee, C.G. III [Institute for Physical Science and Technology (United States); Antonsen, T.M. [Institute for Plasma Research, University of Maryland, College Park, Maryland, (United States) 20742; Mora, P. [Centre de Physique Theorique, Ecole Polytechnique, 91128 Palaiseau (France)

    1996-02-01

    The recent demonstration of optical guiding of high intensity laser pulses in plasma waveguides [C. G. Durfee III and H. M. Milchberg, Phys. Rev. Lett 71, 2409 (1993)] has opened the way to new advances in the development of compact laser-driven electron particle accelerators. We review plasma waveguide properties relevant to intense pulse guiding and electron acceleration and show that the shock driven channels described here are well suited for stabilization of a large class of laser-plasma instabilities deleterious to high intensity guiding over long distances. {copyright} {ital 1996 American Institute of Physics.}

  8. Geometric pumping in autophoretic channels

    Science.gov (United States)

    Michelin, Sebastien; Montenegro Johnson, Thomas; de Canio, Gabriele; Lobatto-Dauzier, Nicolas; Lauga, Eric

    2015-11-01

    Pumping at the microscale has important applications from biological fluid handling to lab-on-a-chip systems. It can be achieved either from a global (e.g. imposed pressure gradient) or local forcing (e.g. ciliary pumping). Phoretic slip flows generated from concentration or temperature gradients are examples of such local flow forcing. Autophoresis is currently receiving much attention for the design of self-propelled particles achieving force- and torque-free locomotion by combining two essential surface properties: (i) an activity that modifies the solute content of the particle's environment (e.g. catalytic reaction or solute release), and (ii) a mobility that generates a slip flow from the resulting local concentration gradients. Recent work showed that geometric asymmetry is sufficient for a chemically-homogeneous particle to self-propel. Here we extend this idea to micro-pumping in active channels whose walls possess both chemical activity and phoretic mobility. Using a combination of theoretical analysis and numerical simulations, we show that geometrically-asymmetric but chemically-homogeneous channels can generate pumping and analyze the resulting flow patterns.

  9. Channel simulation via interactive communications

    CERN Document Server

    Yassaee, Mohammad Hossein; Aref, Mohammad Reza

    2012-01-01

    In this paper, we study the problem of channel simulation via interactive communication, known as the coordination capacity, in a two-terminal network. We assume that two terminals observe i.i.d.\\ copies of two random variables and would like to generate i.i.d.\\ copies of two other random variables jointly distributed with the observed random variables. The terminals are provided with two-way communication links, and shared common randomness, all at limited rates. Two special cases of this problem are the interactive function computation studied by Ma and Ishwar, and the tradeoff curve between one-way communication and shared randomness studied by Cuff. The latter work had inspired Gohari and Anantharam to study the general problem of channel simulation via interactive communication stated above. However only inner and outer bounds for the special case of no shared randomness were obtained in their work. In this paper we settle this problem by providing an exact computable characterization of the multi-round ...

  10. The molecular physiology of CRAC channels

    Science.gov (United States)

    Prakriya, Murali

    2011-01-01

    Summary The Ca2+release-activated Ca2+ (CRAC) channel is a highly Ca2+-selective store-operated channel expressed in T cells, mast cells, and various other tissues. CRAC channels regulate critical cellular processes such as gene expression, motility, and the secretion of inflammatory mediators. The identification of Orai1, a key subunit of the CRAC channel pore, and STIM1, the endoplasmic reticulum (ER) Ca2+ sensor, have provided the tools to illuminate the mechanisms of regulation and the pore properties of CRAC channels. Recent evidence indicates that the activation of CRAC channels by store depletion involves a coordinated series of steps, which include the redistributions of STIM1 and Orai1, direct physical interactions between these proteins, and conformational changes in Orai1, culminating in channel activation. Additional studies have revealed that the high Ca2+ selectivity of CRAC channels arises from the presence of an intrapore Ca2+ binding site, the properties of which are finely honed to occlude the permeation of the much more prevalent Na+. Structure-function studies have led to the identification of the potential pore-binding sites for Ca2+, providing a firm framework for understanding the mechanisms of selectivity and gating of the CRAC channel. This review summarizes recent progress in understanding the mechanisms of CRAC channel activation, pore properties, and modulation. PMID:19754891

  11. 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.

  12. 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.

  13. 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. PMID:22778854

  14. Inertial (non-Darcian) channeled seepage flow

    Science.gov (United States)

    Foda, Mostafa A.

    1994-10-01

    A slow wave solution is identified for an infinite elastic medium intersected by a two-dimensional fluid channel. Because the wave speed is much slower than the medium's elastic shear wave, the response in the elastic medium is governed by elastostatics. The inertia of the wave is essentially focused in the fluid channel. Furthermore, wave damping is caused by fluid viscous friction on the channel in an elastic solid. It is proposed that these solutions may also be used in the case of a granular porous medium. The seepage channels would then represent a network of preferential flow paths. Therefore we would allow, in this case, the channel porosity to be different from the average granular porosity. For a strongly channel seepage flow or for a low channel porosity the solution is shown to approach that of a single-channel solution, giving rise to a slow propagating wave mode. On the other hand, for weak channeling or nearly `homogeneous' seepage flow the solution is shown to reproduce Biot's (1956) critically damped wave of the second kind. It is proposed that the resonance observed by Foda and Tzang (1994) are in the form of these strongly channeled wave modes.

  15. Decoding with approximate channel statistics for band-limited nonlinear satellite channels

    Science.gov (United States)

    Biederman, L.; Omura, J. K.; Jain, P. C.

    1981-11-01

    Expressions for the cutoff rate of memoryless channels and certain channels with memory are derived assuming decoding with approximate channel statistics. For channels with memory, two different decoding techniques are examined: conventional decoders in conjunction with ideal interleaving/deinterleaving, and maximum likelihood decoders that take advantage of the channel memory. As a practical case of interest, the cutoff rate for the band-limited nonlinear satellite channel is evaluated where the modulation is assumed to be M-ary phase shift keying (MPSK). The channel nonlinearity is introduced by a limiter in cascade with a traveling wave tube amplifier (TWTA) at the satellite repeater while the channel memory is created by channel filters in the transmission path.

  16. The CYP17A1 inhibitor abiraterone exhibits estrogen receptor agonist activity in breast cancer.

    Science.gov (United States)

    Capper, Cameron P; Larios, José M; Sikora, Matthew J; Johnson, Michael D; Rae, James M

    2016-05-01

    Cytochrome P450 17A1 (CYP17A1) is the requisite enzyme for synthesis of sex steroids, including estrogens and androgens. As such, inhibition of CYP17A1 is a target for inhibiting the growth of hormone-dependent cancers including prostate and breast cancer. Abiraterone, is a first in class potent and selective CYP17A1 inhibitor that has been approved for the treatment of castration-resistant prostate cancer. Given that, androgens are the precursors for estrogen production, it has been proposed that abiraterone could be an effective form of treatment for estrogen receptor (ER)-positive breast cancer, though its utility in this context has yet to be established. Abiraterone has a core steroid-like chemical structure, and so we hypothesized that it may bind to nuclear steroid receptors including ER and have estrogenic activity. We tested this hypothesis by investigating abiraterone's ability to directly modulate ER signaling in breast cancer cell line models. We show that abiraterone directly activates ER, induces ER-target gene expression, and elicits estrogen-response-element reporter activity in the ER-positive cell lines MCF-7 and T47D. Abiraterone also induced cell proliferation by ~2.5-fold over vehicle in both MCF-7 and T47D cells. Importantly, abiraterone-induced cell proliferation and ER-activity was blocked by the selective estrogen receptor downregulator (SERD) fulvestrant, confirming that abiraterone directly acts at the ER. These data suggest that abiraterone should be combined with other ER antagonists when used for the clinical management of ER-positive breast cancer. PMID:27083183

  17. β2-Adrenergic receptor agonists activate CFTR in intestinal organoids and subjects with cystic fibrosis.

    Science.gov (United States)

    Vijftigschild, Lodewijk A W; Berkers, Gitte; Dekkers, Johanna F; Zomer-van Ommen, Domenique D; Matthes, Elizabeth; Kruisselbrink, Evelien; Vonk, Annelotte; Hensen, Chantal E; Heida-Michel, Sabine; Geerdink, Margot; Janssens, Hettie M; van de Graaf, Eduard A; Bronsveld, Inez; de Winter-de Groot, Karin M; Majoor, Christof J; Heijerman, Harry G M; de Jonge, Hugo R; Hanrahan, John W; van der Ent, Cornelis K; Beekman, Jeffrey M

    2016-09-01

    We hypothesized that people with cystic fibrosis (CF) who express CFTR (cystic fibrosis transmembrane conductance regulator) gene mutations associated with residual function may benefit from G-protein coupled receptor (GPCR)-targeting drugs that can activate and enhance CFTR function.We used intestinal organoids to screen a GPCR-modulating compound library and identified β2-adrenergic receptor agonists as the most potent inducers of CFTR function.β2-Agonist-induced organoid swelling correlated with the CFTR genotype, and could be induced in homozygous CFTR-F508del organoids and highly differentiated primary CF airway epithelial cells after rescue of CFTR trafficking by small molecules. The in vivo response to treatment with an oral or inhaled β2-agonist (salbutamol) in CF patients with residual CFTR function was evaluated in a pilot study. 10 subjects with a R117H or A455E mutation were included and showed changes in the nasal potential difference measurement after treatment with oral salbutamol, including a significant improvement of the baseline potential difference of the nasal mucosa (+6.35 mV, pCFTR activation when administered ex vivo to organoids.This proof-of-concept study suggests that organoids can be used to identify drugs that activate CFTR function in vivo and to select route of administration. PMID:27471203

  18. Cyclic AMP-and beta-agonist-activated chloride conductance of a toad skin epithelium.

    Science.gov (United States)

    Willumsen, N J; Vestergaard, L; Larsen, E H

    1992-04-01

    1. The control by intracellular cyclic AMP and beta-adrenergic stimulation of chloride conductance was studied in toad skin epithelium mounted in a chamber on the stage of an upright microscope. Impalement of identified principal cells from the serosal side with single-barrelled conventional or double-barrelled Cl(-)-sensitive microelectrodes was performed at x500 magnification. For blocking the active sodium current 50 microM-amiloride was present in the mucosal bath. 2. When clamped at transepithelial potential difference V = 0 mV, the preparations generated clamping currents of 0.9 +/- 1 microA/cm2 (mean +/- S.E.M.; number of observations n = 55). The intracellular potential of principal cells (Vb) was -96 +/- 2 mV with a fractional resistance of the basolateral membrane (fRb) of 0.016 +/- 0.003 (n = 54), and an intracellular Cl- activity of 40 +/- 2 mM (n = 24). 3. At V = 0 mV, serosal application of a cyclic AMP analogue, dibutyryl cyclic AMP (500 microM) or a beta-adrenergic agonist, isoprenaline (5 microM) resulted in a sixfold increase in transepithelial Cl- conductance identified by standard 36Cl- tracer technique. 4. The clamping current at V = 0 mV was unaffected by cyclic AMP (short-circuit current Isc = 0.1 +/- 0.3 microA/cm2, n = 16) indicating that subepidermal Cl(-)-secreting glands are not functioning in our preparations obtained by collagenase treatment. 5. Cyclic AMP- or isoprenaline-induced chloride conductance (Gcl) activation (V = 0 mV) was not reflected in membrane potential and intracellular Cl- activity in principal cells. Intracellular chloride activity was constant at approximately 40 mM at membrane potentials between -90 and -100 mV. Therefore, it can be concluded that the principal cells are not contributing to activated Cl- currents. 6. At V = -100 mV where the voltage-dependent chloride conductance of mitochondria-rich (MR) cells was already fully activated, GCl was unaffected by cyclic AMP or isoprenaline. The major effect of these treatments was a rightward displacement of the MR cell-generated GCl-V relationship along the V axis. 7. Our results indicate that the beta-adrenergically controlled cyclic AMP-mediated chloride conductance is localized to the mitochondria-rich cells. PMID:1326049

  19. Statistical-mechanical analysis of multiuser channel capacity with imperfect channel state information

    Institute of Scientific and Technical Information of China (English)

    Wang Hui-Song; Zeng Gui-Hua

    2008-01-01

    In this paper,the effect of imperfect channel state information at the receiver, which is caused by noise and other interference, on the multi-access channel capacity is analysed through a statistical-mechanical approach. Replica analyses focus on analytically studying how the minimum mean square error (MMSE) channel estimation error appears in a multiuser channel capacity formula. And the relevant mathematical expressions are derived. At the same time,numerical simulation results are demonstrated to validate the Replica analyses. The simulation results show how the system parameters, such as channel estimation error, system load and signal-to-noise ratio, affect the channel capacity.

  20. K-user Interference Channels: General Outer Bound and Sum-capacity for Certain Gaussian Channels

    CERN Document Server

    Tuninetti, Daniela

    2011-01-01

    This paper derives an outer bound on the capacity region of a general memoryless interference channel with an arbitrary number of users. The derivation follows from a generalization of the techniques developed by Kramer and by Etkin et al for the Gaussian two-user channel. The derived bound is the first known outer bound valid for any memoryless channel. In Gaussian noise, classes of channels for which the proposed bound gives the sum-rate capacity are identified, including degraded channels and a class of Z-channels.

  1. Parameter estimation in channel network flow simulation

    Institute of Scientific and Technical Information of China (English)

    Han Longxi

    2008-01-01

    Simulations of water flow in channel networks require estimated values of roughness for all the individual channel segments that make up a network. When the number of individual channel segments is large, the parameter calibration workload is substantial and a high level of uncertainty in estimated roughness cannot be avoided. In this study, all the individual channel segments are graded according to the factors determining the value of roughness. It is assumed that channel segments with the same grade have the same value of roughness. Based on observed hydrological data, an optimal model for roughness estimation is built. The procedure of solving the optimal problem using the optimal model is described. In a test of its efficacy, this estimation method was applied successfully in the simulation of tidal water flow in a large complicated channel network in the lower reach of the Yangtze River in China.

  2. Interference Channels with One Cognitive Transmitter

    CERN Document Server

    Cao, Yi

    2009-01-01

    This paper studies the problem of interference channels with one cognitive transmitter (ICOCT) where "cognitive" is defined from both the noncausal and causal perspectives. For the noncausal ICOCT, referred to as interference channels with degraded message sets (IC-DMS), we propose a new achievable rate region that generalizes existing achievable rate regions for IC-DMS. In the absence of the noncognitive transmitter, the proposed region coincides with Marton's region for the broadcast channel. Based on this result, the capacity region of a class of semi-deterministic IC-DMS is established. For the causal ICOCT, due to the complexity of the channel model, we focus primarily on the cognitive Z interference channel (ZIC), where the interference link from the cognitive transmitter to the primary receiver is assumed to be absent due to practical design considerations. Capacity bounds for such channels in different parameter regimes are obtained and the impact of such causal cognitive ability is carefully studied....

  3. Rateless Coding for MIMO Block Fading Channels

    CERN Document Server

    Fan, Yijia; Erkip, Elza; Poor, H Vincent

    2008-01-01

    In this paper the performance limits and design principles of rateless codes over fading channels are studied. The diversity-multiplexing tradeoff (DMT) is used to analyze the system performance for all possible transmission rates. It is revealed from the analysis that the design of such rateless codes follows the design principle of approximately universal codes for parallel multiple-input multiple-output (MIMO) channels, in which each sub-channel is a MIMO channel. More specifically, it is shown that for a single-input single-output (SISO) channel, the previously developed permutation codes of unit length for parallel channels having rate LR can be transformed directly into rateless codes of length L having multiple rate levels (R, 2R, . . ., LR), to achieve the DMT performance limit.

  4. Parameter estimation in channel network flow simulation

    Directory of Open Access Journals (Sweden)

    Han Longxi

    2008-03-01

    Full Text Available Simulations of water flow in channel networks require estimated values of roughness for all the individual channel segments that make up a network. When the number of individual channel segments is large, the parameter calibration workload is substantial and a high level of uncertainty in estimated roughness cannot be avoided. In this study, all the individual channel segments are graded according to the factors determining the value of roughness. It is assumed that channel segments with the same grade have the same value of roughness. Based on observed hydrological data, an optimal model for roughness estimation is built. The procedure of solving the optimal problem using the optimal model is described. In a test of its efficacy, this estimation method was applied successfully in the simulation of tidal water flow in a large complicated channel network in the lower reach of the Yangtze River in China.

  5. Electrical conductivity channel for a shock tube

    Science.gov (United States)

    Lu, Frank K.; Liu, Hsuan-Cheng; Wilson, Donald R.

    2005-09-01

    The design of an electrical conductivity measurement channel for a shock tube is described. This measurement channel is used for the study of weakly ionized, high-enthalpy flows of gases seeded with alkali salts. The theory for determining the dimensions of the measurement channel and the electrical power supply for the channel is based on Ohm's law. Data are shown which demonstrate that the channel performs well. However, the measured electrical conductivity was one or two orders less than theoretical values. The current traces for each case show that the peak current occurred behind the contact surface, which indicates that some of the seed was entrained behind the test gas originally in the driven tube. An analysis of the effect of Joule heating on the measured conductivity was conducted. The result of increased temperature due to Joule heating in the measurement channel is believed to be minimal. Reasons for the discrepancy are given.

  6. Optimum performance characteristics of a conduction channel

    Energy Technology Data Exchange (ETDEWEB)

    Okulov, N.A.

    1978-01-01

    Steady laminar flow of an incompressible viscous and electrically conducting fluid is considered in an infinitely long cylindrical conduction channel. A set of permanent magnets outside produces a transverse magnetic field which does not vary over the channel length. An external electric dc generator or load maintains on the channel-fluid boundary a distribution of electric potential which also does not vary over the channel length. The power efficiency of such a channel is calculated and the distribution of electric potential is then optimized to yield the maximum efficiency for a given pressure head and flow rate, with a given scalar magnetic potential. Two mathematical theorems are proved for solving the optimization problem, i.e., the problem of minimizing a functional. An upper estimate of the efficiency is made on the basis of a third theorem. An estimate is also made of the flow rate in a conduction channel with a passive electrical system (load without generator). 3 references.

  7. A father protocol for quantum broadcast channels

    OpenAIRE

    Dupuis, Frédéric; Hayden, Patrick; Li, Ke

    2006-01-01

    A new protocol for quantum broadcast channels based on the fully quantum Slepian-Wolf protocol is presented. The protocol yields an achievable rate region for entanglement-assisted transmission of quantum information through a quantum broadcast channel that can be considered the quantum analogue of Marton's region for classical broadcast channels. The protocol can be adapted to yield achievable rate regions for unassisted quantum communication and for entanglement-assisted classical communica...

  8. Chromatic effects in long periodic transport channels

    Energy Technology Data Exchange (ETDEWEB)

    Litvinenko V. N.; Hao, Y.; Jing, Y.

    2015-05-03

    Long periodic transport channels are frequently used in accelerator complexes and suggested for using in high-energy ERLs for electron-hadron colliders. Without proper chromaticity compensation, such transport channels exhibit high sensitivity to the random orbit errors causing significant emittance growth. Such emittance growth can come from both the correlated and the uncorrelated energy spread. In this paper we present results of our theoretical and numerical studies of such effects and develop a criteria for acceptable chromaticity in such channels.

  9. Two-channel Optimal Quantum Teleportation

    OpenAIRE

    Quan, Quan; Fei, Shao-Ming; Fan, Heng; Yang, Wen-Li(Institute of Modern Physics, Northwest University, Xian, 710069, China)

    2015-01-01

    We investigate two-channel scenarios of optimal quantum teleportation based on Bell measurements and GHZ measurements. The detailed protocols are presented and the general expressions of the optimal teleportation fidelities are derived, which turn out to be functions of two-channel fully entangled fractions -- invariants under local unitary transformations. We prove that the set of states which are useful for two-channel teleportation is convex and compact. Hence witness operators exist to se...

  10. Natural Products and Ion Channel Pharmacology

    OpenAIRE

    Teichert, Russell W.; Olivera, Baldomero M.

    2010-01-01

    An accelerated rate of natural-product discovery is critical for the future of ion channel pharmacology. For the full potential of natural products to be realized, an interdisciplinary initiative is required that combines chemical ecology and ion channel physiology. A prime source of future drug leads targeted to ion channels is the vast assortment of compounds that mediate biotic interactions in the marine environment. Many animals have evolved a chemical strategy to change the behavior of t...

  11. Efficient communication channels towards the researchers

    OpenAIRE

    Mammadova, Zaira

    2012-01-01

    Aalto University has over 4000 researchers. While reaching out and informing them about Aalto Center for Entrepreneurship (ACE) and its services is one of the tasks of ACE, maintaining a relationship via various channels with the researchers who are aware of ACE is equally important. Project is part of the development of communication channels towards the stakeholders of ACE. The purpose of the given project was to identify the best communications channels. ACE aims to use these chann...

  12. Value Assessment of Enterprise Marketing Channels

    OpenAIRE

    Lixia Yan

    2010-01-01

    The factors that impose influence on the value assessment of enterprise’s marketing channels are numerous, and complex in relations with each other. Whether the value of enterprise’s marketing channels is good or not can finally be determined by using principal component analysis to eliminate the related effects among the assessment indicators and reduce the workload of selecting indicators, and expert evaluating and assessing the value of enterprise’s marketing channel by relevant indicators...

  13. Camouflaging Timing Channels in Web Traffic

    OpenAIRE

    Sellke, Sarah H; Wang, Chih-Chun; Bagchi, Saurabh; Shroff, Ness B.

    2009-01-01

    Web traffic accounts for more than half of Internet traffic today. Camouflaging covert timing channels in Web traffic would be advantageous for concealment. In this paper, we investigate the possibility of disguising network covert timing channels as HTTP traffic to avoid detection. Extensive research has shown that Internet traffic, including HTTP traffic, exhibits self-similarity and long range persistence. Existing covert timing channels that mimic i.i.d. legitimate traffic cannot imitate ...

  14. 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 ...

  15. A father protocol for quantum broadcast channels

    CERN Document Server

    Dupuis, F; Dupuis, Fr\\'ed\\'eric; Hayden, Patrick

    2006-01-01

    We present a new protocol for quantum broadcast channels based on the fully quantum Slepian-Wolf protocol. The protocol yields an achievable rate region for entanglement-assisted transmission of quantum information through a quantum broadcast channel that can be considered the quantum analogue of Marton's region for classical broadcast channels. The protocol can be adapted to yield achievable rate regions for unassisted quantum communication and for entanglement-assisted classical communication. Regularized versions of all three rate regions are provably optimal.

  16. [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.

  17. [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. PMID

  18. Study of Dispersion Coefficient Channel

    Science.gov (United States)

    Akiyama, K. R.; Bressan, C. K.; Pires, M. S. G.; Canno, L. M.; Ribeiro, L. C. L. J.

    2016-08-01

    The issue of water pollution has worsened in recent times due to releases, intentional or not, of pollutants in natural water bodies. This causes several studies about the distribution of pollutants are carried out. The water quality models have been developed and widely used today as a preventative tool, ie to try to predict what will be the concentration distribution of constituent along a body of water in spatial and temporal scale. To understand and use such models, it is necessary to know some concepts of hydraulic high on their application, including the longitudinal dispersion coefficient. This study aims to conduct a theoretical and experimental study of the channel dispersion coefficient, yielding more information about their direct determination in the literature.

  19. Dynamic random channel reservation protocol

    Institute of Scientific and Technical Information of China (English)

    Ren Yanying; Zhang Wenjun; Yu Songyu

    2005-01-01

    Demand assignment MAC protocols have been used widely in wireless networks. It can effectively utilize wireless bandwidth. Some strategies can be used by demand assignment MAC protocols to further improve their efficiency. The concept of transmit probability is introduced. This concept allows a request slot to be assigned to many different traffic classes at the same time. Based on it, the dynamic random channel reservation (DRCR) protocol is proposed. The DRCR protocol operates dynamically by observing the traffic conditions. It uses information about the recent traffic conditions to assign transmit probability with which an mobile station can select request slots with lower traffic. The performance of DRCR is evaluated and compared with RSCA. The results show that DRCR is more stable than RSCA, it offers shorter delays of requests than RSCA and can relieve heavily stressed traffic classes faster than RSCA.

  20. Amoeboid swimming in a channel

    CERN Document Server

    Wu, Hao; Hu, W -F; Thiébaud, M; Rafaï, S; Peyla, P; Lai, M -C; Misbah, C

    2016-01-01

    Several micro-organisms, such as bacteria, algae, or spermatozoa, use flagellum or cilium activity to swim in a fluid. Many other organisms use rather ample shape deformation, described as amoeboid, to propel themselves, either crawling on a substrate or swimming. Many eukaryotic cells were believed to require an underlying substratum to migrate (crawl) by using ample membrane deformation (like blebbing). There is now an increasing evidence that a large variety of cells (including those of the immune system) can migrate without the assistance of focal adhesion, and can perform swimming as efficiently as crawling. This paper deals with a detailed analysis of amoeboid swimming in a confined fluid, by modeling the swimmer as an inextensible membrane deploying local active forces. The swimmer exhibits a rich behavior: it can settle into a straight trajectory in the channel, or can navigate from one wall to the other, depending on confinement. Furthermore, the nature of the swimmer is found to be affected by the c...

  1. Pyridoxine requirements of channel catfish.

    Science.gov (United States)

    Andrews, J W; Murai, T

    1979-04-01

    In 20 and 12 week feeding trials, channel catfish fingerlings were fed purified diets containing five levels (0, 5, 10, 20, and 30 mg/kg) and six levels (0, 1, 2, 5, 10, and 20 mg/kg) of supplemental pyridoxine hydrochloride. Fish fed unsupplemented diets (pyridoxine content of 1.2 mg/kg) were characterized by anoxeria, nervous disorders, tetany, greenish-blue body coloration, and eventual mortality. Anemia, which has been reported in pyridoxine deficient salmonids, was not observed in pyridoxine deficient catfish. However, a microcytic, normochromic anemia was observed in groups fed high dietary levels of pyridoxine (20 mg/kg or greater). The dietary pyridoxine level required for maximal growth was approximately 3 mg/kg of diet. All other deficiency signs were prevented by 2.2 mg/kg of diet. PMID:430257

  2. Secrecy Capacity over Correlated Ergodic Fading Channel

    CERN Document Server

    Jeon, Hyoungsuk; Kim, Minki; Lee, Hyuckjae; Ha, Jeongseok

    2008-01-01

    We investigate the secrecy capacity of an ergodic fading wiretap channel in which the main channel is correlated with the eavesdropper channel. In this study, the full Channel State Information (CSI) is assumed, and thus the transmitter knows the channel gains of the legitimate receiver and the eavesdropper. By analyzing the resulting secrecy capacity we quantify the loss of the secrecy capacity due to the correlation. In addition, we study the asymptotic behavior of the secrecy capacity as Signal-to-Noise Ratio (SNR) tends to infinity. The capacity of an ordinary fading channel logarithmically increases with SNR. On the contrary, the secrecy capacity converges into a limit which can be an upper bound on the secrecy capacity over the fading wiretap channel. We find a closed form of the upper bound for the correlated Rayleigh wiretap channel which also includes the independent case as a special one. Our work shows that the upper bound is determined by only two channel parameters; the correlation coefficient an...

  3. Optimized teleportation in Gaussian noisy channels

    International Nuclear Information System (INIS)

    We address continuous variable quantum teleportation in Gaussian quantum noisy channels, either thermal or squeezed-thermal. We first study the propagation of twin-beam and evaluate a threshold for its separability. We find that the threshold for purely thermal channels is always larger than for squeezed-thermal ones. On the other hand, we show that squeezing the channel improves teleportation of squeezed states and, in particular, we find the class of squeezed states that are better teleported in a given noisy channel. Finally, we find regimes where optimized teleportation of squeezed states improves amplitude-modulated communication in comparison with direct transmission

  4. ICEPO: the ion channel electrophysiology ontology.

    Science.gov (United States)

    Hinard, V; Britan, A; Rougier, J S; Bairoch, A; Abriel, H; Gaudet, P

    2016-01-01

    Ion channels are transmembrane proteins that selectively allow ions to flow across the plasma membrane and play key roles in diverse biological processes. A multitude of diseases, called channelopathies, such as epilepsies, muscle paralysis, pain syndromes, cardiac arrhythmias or hypoglycemia are due to ion channel mutations. A wide corpus of literature is available on ion channels, covering both their functions and their roles in disease. The research community needs to access this data in a user-friendly, yet systematic manner. However, extraction and integration of this increasing amount of data have been proven to be difficult because of the lack of a standardized vocabulary that describes the properties of ion channels at the molecular level. To address this, we have developed Ion Channel ElectroPhysiology Ontology (ICEPO), an ontology that allows one to annotate the electrophysiological parameters of the voltage-gated class of ion channels. This ontology is based on a three-state model of ion channel gating describing the three conformations/states that an ion channel can adopt: closed, open and inactivated. This ontology supports the capture of voltage-gated ion channel electrophysiological data from the literature in a structured manner and thus enables other applications such as querying and reasoning tools. Here, we present ICEPO (ICEPO ftp site:ftp://ftp.nextprot.org/pub/current_release/controlled_vocabularies/), as well as examples of its use.

  5. The Origins of Transmembrane Ion Channels

    Science.gov (United States)

    Pohorille, Andrew; Wilson, Michael A.

    2012-01-01

    Even though membrane proteins that mediate transport of ions and small molecules across cell walls are among the largest and least understood biopolymers in contemporary cells, it is still possible to shed light on their origins and early evolution. The central observation is that transmembrane portions of most ion channels are simply bundles of -helices. By combining results of experimental and computer simulation studies on synthetic models and natural channels, mostly of non-genomic origin, we show that the emergence of -helical channels was protobiologically plausible, and did not require highly specific amino acid sequences. Despite their simple structure, such channels could possess properties that, at the first sight, appear to require markedly larger complexity. Specifically, we explain how the antiamoebin channels, which are made of identical helices, 16 amino acids in length, achieve efficiency comparable to that of highly evolved channels. We further show that antiamoebin channels are extremely flexible, compared to modern, genetically coded channels. On the basis of our results, we propose that channels evolved further towards high structural complexity because they needed to acquire stable rigid structures and mechanisms for precise regulation rather than improve efficiency. In general, even though architectures of membrane proteins are not nearly as diverse as those of water-soluble proteins, they are sufficiently flexible to adapt readily to the functional demands arising during evolution.

  6. The molecular physiology of CRAC channels

    OpenAIRE

    Prakriya, Murali

    2009-01-01

    The Ca2+release-activated Ca2+ (CRAC) channel is a highly Ca2+-selective store-operated channel expressed in T cells, mast cells, and various other tissues. CRAC channels regulate critical cellular processes such as gene expression, motility, and the secretion of inflammatory mediators. The identification of Orai1, a key subunit of the CRAC channel pore, and STIM1, the endoplasmic reticulum (ER) Ca2+ sensor, have provided the tools to illuminate the mechanisms of regulation and the pore prope...

  7. Potassium channels in prostate and colonic cancer

    OpenAIRE

    Ousingsawat, Jiraporn

    2007-01-01

    Large conductance Ca2+-activated K+ channels in human prostate cancer The KCNMA1 gene encoding the alpha-subunit of BK channels is amplified and BK channel expression is enhanced in late-stage, metastatic and hormone-refractory human prostate cancer tissues, whereas benign prostate tissues show only a weak expression of BK channels. PC-3 hormone-insensitive prostate cancer cells, but not hormone-sensitive prostate cancer cells (LNCaP) and benign prostate hyperplasia cells (BPH-1), show an ...

  8. On the domestic fuel channel for BWR

    International Nuclear Information System (INIS)

    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.)

  9. Classical codes for quantum broadcast channels

    CERN Document Server

    Savov, Ivan

    2011-01-01

    We discuss two techniques for transmitting classical information over quantum broadcast channels. The first technique is a quantum generalization of the superposition coding scheme for the classical broadcast channel. We use a quantum simultaneous nonunique decoder and obtain a simpler proof of the rate region recently published by Yard et al. in independent work. Our second result is a quantum Marton coding scheme, which gives the best known achievable rate region for quantum broadcast channels. Both results exploit recent advances in quantum simultaneous decoding developed in the context of quantum interference channels.

  10. 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...... accurate model for Gaussian channels. For each of the environments different sizes of both the transmitter and receiver antenna arrays are investigated, 2x2 up to 16x32. Generally it was found that in terms of capacity cumulative distribution functions (CDFs) all models fit well for small array sizes, but...

  11. Anisotropic flow in striped superhydrophobic channels

    CERN Document Server

    Zhou, Jiajia; Schmid, Friederike; Vinogradova, Olga I

    2012-01-01

    We report results of dissipative particle dynamics simulations and develop a semi-analytical theory and of an anisotropic flow in a parallel-plate channel with two superhydrophobic striped walls. Our approach is valid for any local slip at the gas sectors and an arbitrary distance between the plates, ranging from a thick to a thin channel. It allows us to optimize area fractions, slip lengths, channel thickness and texture orientation to maximize a transverse flow. Our results may be useful for extracting effective slip tensors from global measurements, such as the permeability of a channel, in experiments or simulations, and may also find applications in passive microfluidic mixing.

  12. 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.

  13. 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...

  14. Mobile Radio Channels Modeling in MATLAB

    Directory of Open Access Journals (Sweden)

    N. Kostov

    2003-12-01

    Full Text Available In this paper, a MATLAB based approach for mobile radio channelsmodeling is presented. Specifically, the paper introduces the basicconcepts for modeling flat fading channels in MATLAB by means ofuser-defined m-files. Typical small-scale fading channel models arederived such as uncorrelated Rician fading channel and Rayleigh fadingchannel with Doppler shift. Further, simple and useful MATLABconstructions for approximation of cumulative distribution functions(CDFs and probability density functions (PDFs are also given.Finally, a MATLAB based Monte Carlo simulation example is presented,which comprises performance estimation of phase shift keying (PSKsignaling over a Rician fading channel.

  15. Opening the Shaker K+ channel with hanatoxin

    OpenAIRE

    Milescu, Mirela; Lee, Hwa C.; Bae, Chan Hyung; Kim, Jae Il; Swartz, Kenton J.

    2013-01-01

    Voltage-activated ion channels open and close in response to changes in membrane voltage, a property that is fundamental to the roles of these channels in electrical signaling. Protein toxins from venomous organisms commonly target the S1–S4 voltage-sensing domains in these channels and modify their gating properties. Studies on the interaction of hanatoxin with the Kv2.1 channel show that this tarantula toxin interacts with the S1–S4 domain and inhibits opening by stabilizing a closed state....

  16. OFDM System Channel Estimation with Hidden Pilot

    Institute of Scientific and Technical Information of China (English)

    YANG Feng; LIN Cheng-yu; ZHANG Wen-jun

    2007-01-01

    Channel estimation using pilot is common used in OFDM system. The pilot is usually time division multiplexed with the informative sequence. One of the main drawbacks is bandwidth losing. In this paper, a new method was proposed to perform channel estimation in OFDM system. The pilot is arithmetically added to the output of OFDM modulator. Receiver uses the hidden pilot to get an accurate estimation of the channel. Then pilot is removed after channel estimation. The Cramer-Rao lower bound for this method was deprived. The performance of the algorithm is then shown. Compared with traditional methods, the proposed algorithm increases the bandwidth efficiency dramatically.

  17. EPICS channel access using websocket

    International Nuclear Information System (INIS)

    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)

  18. 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.

  19. 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.

  20. Distributed Joint Source-Channel Coding on a Multiple Access Channel with Side Information

    OpenAIRE

    R. Rajesh; Sharma, Vinod

    2008-01-01

    We consider the problem of transmission of several distributed sources over a multiple access channel (MAC) with side information at the sources and the decoder. Source-channel separation does not hold for this channel. Sufficient conditions are provided for transmission of sources with a given distortion. The source and/or the channel could have continuous alphabets (thus Gaussian sources and Gaussian MACs are special cases). Various previous results are obtained as special cases. We also pr...

  1. Understanding consumers' channel choice in omni-channel retail environments - case Tokmanni

    OpenAIRE

    Lehikoinen, Iida-Maria

    2015-01-01

    Objectives: The retailing landscape has been evolving drastically over the past years due to technological developments and changes in consumer behavior. As a result, many retailers have increased the number of retail channels as they seek to reach consumers through, for example, online and mobile channels in addition to the traditional brick-and-mortar stores. The current theoretical paradigm of omni-channel retailing is based on seamless, perfectly integrated channel mixes where the bou...

  2. Pilot study on navigation channel regulation works in the North Channel, Yangtze estuary

    NARCIS (Netherlands)

    Gao, M.; Roelvink, J.A.

    2011-01-01

    It is estimated that the waterway in North Passage would not be able to meet the demand of shipping development soon and it is necessary to open a new deep navigation channel with a depth of 10 m in North Channel in the near future. A pilot study on the regulation of North Channel was proposed by Ya

  3. 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, i

  4. 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…

  5. 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.

  6. Channeling Sealing Technique with QN-70 Agent

    Institute of Scientific and Technical Information of China (English)

    Zhang Xiuyun

    1997-01-01

    @@ Sealing channels with QN-70 agent is a new technique developed by Institute of Oil Production Technology of Daqing Petroleum Administration, suitable to sealing channels between layers and high water-cut intervals of oil wells, as well as leakage zones.

  7. 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...

  8. Pathogenicity of Streptococcus ictaluri to Channel Catfish

    Science.gov (United States)

    The infectivity of a Streptococcus ictaluri isolate for fry (0.5 g), fingerling (15 g), and juvenile (55 g) channel catfish (Ictalurus punctatus) was determined by bath immersion and injection infectivity experiments. Channel catfish exposed by immersion were exposed to baths containing 1012, 1011,...

  9. BK channel activators and their therapeutic perspectives

    DEFF Research Database (Denmark)

    Bentzen, Bo Hjorth; Olesen, Søren-Peter; Rønn, Lars C B;

    2014-01-01

    The large conductance calcium- and voltage-activated K(+) channel (KCa1.1, BK, MaxiK) is ubiquitously expressed in the body, and holds the ability to integrate changes in intracellular calcium and membrane potential. This makes the BK channel an important negative feedback system linking increase...... years. After a short introduction to the structure, function and regulation of BK channels, we review the small organic molecules activating BK channels and how these tool compounds have helped delineate the roles of BK channels in health and disease.......The large conductance calcium- and voltage-activated K(+) channel (KCa1.1, BK, MaxiK) is ubiquitously expressed in the body, and holds the ability to integrate changes in intracellular calcium and membrane potential. This makes the BK channel an important negative feedback system linking increases...... in intracellular calcium to outward hyperpolarizing potassium currents. Consequently, the channel has many important physiological roles including regulation of smooth muscle tone, neurotransmitter release and neuronal excitability. Additionally, cardioprotective roles have been revealed in recent...

  10. Study of turbine with side channel runner

    OpenAIRE

    Jandourek, Pavel

    2012-01-01

    This thesis deals with proposal of constructional solving turbine with side channel. Basis for the design is lossy characteristics of the valve. The intention is to replace hydraulic closures by turbine with side channel runner. Hydraulic losses in the flow restriction in turn replaced by the electricity generation in the comparable characteristics of valve and turbine.

  11. Calmodulin modulation of ion channels and receptors

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Ion channels and receptors are the structural basis for neural signaling and transmission. Recently, the function of ion channels and receptors has been demonstrated to be modulated by many intracellular and extracellular chemicals and signaling molecules. Increasing evidence indicates that the complexity and plasticity of the function of central nervous system is determined by the modulation of ion channels and receptors. Among various mechanisms, Ca 2+ signaling pathways play important roles in neuronal activity and some pathological changes. Ca 2+ influx through ion channels and receptors can modulate its further influx in a feedback way or modulate other ion channels and receptors. The common feature of the modulation is that Ca 2+ /calmodulin (CaM) is the universal mediator. CaM maintains the coordination among ion channels/receptors and intracellular Ca 2+ homeostasis by feedback modulation of ion channels/receptors activity. This review focuses on the modulating processes of ion channels and receptors mediated by CaM, and further elucidates the mechanisms of Ca 2+ signaling.

  12. Transportation channels calculation method in MATLAB

    International Nuclear Information System (INIS)

    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.

  13. Channels that do not generate coherence

    Science.gov (United States)

    Hu, Xueyuan

    2016-07-01

    We define the non-coherence-generating channel as the completely positive trace-preserving map which does not generate quantum coherence from an incoherent state. The incoherent operations are the strict subset of the non-coherence-generating channels. Although the relative entropy of coherence is monotonically decreasing under the non-coherence-generating channels, we prove that the coherence of formation may increase under such channels. Interestingly, by building a mathematical relation between the coherence of formation and the entanglement of formation, we show that the coherence of formation of a single-qubit state is never increased by a non-coherence-generating channel. This leads to the superadditivity property for the coherence increasing power of quantum channels, namely, while two channels cannot increase coherence individually, they may increase the quantum coherence of a composed system. Further, we derive the general form of the rank-2 non-coherence-generating qubit channels. Our results contribute to the resource theory of quantum coherence.

  14. Energy loss spectra in planar channeling

    International Nuclear Information System (INIS)

    Using simple models for the motion of particles in planar channels and for the energy loss and its dependence on the path, energy loss spectra of particles transmitted through thin foils in planar channels are calculated. A comparison with measurements is made. (Auth.)

  15. Decay channels and charmonium mass-shifts

    CERN Document Server

    Pennington, Michael R

    2007-01-01

    The discovery in the last few years of the $X, Y$ and $Z$ states of the extended charmonium family has highlighted the importance of the closeness of decay channels to an understanding of these mesons. We aid this debate by illustrating a simple calculational procedure for including the effect of open and nearby closed channels.

  16. Voltage-gated lipid ion channels

    DEFF Research Database (Denmark)

    Blicher, Andreas; Heimburg, Thomas Rainer

    2013-01-01

    Synthetic lipid membranes can display channel-like ion conduction events even in the absence of proteins. We show here that these events are voltage-gated with a quadratic voltage dependence as expected from electrostatic theory of capacitors. To this end, we recorded channel traces and current...

  17. Ion Channels Involved in Cell Volume Regulation

    DEFF Research Database (Denmark)

    Hoffmann, Else Kay

    2011-01-01

    regulatory ion channels involved, and the mechanisms (cellular signalling pathways) that regulate these channels. Finally, I shall also briefly review current investigations in these two cell lines that focuses on how changes in cell volume can regulate cell functions such as cell migration, proliferation...

  18. Crystal assisted processes in ion channeling

    Science.gov (United States)

    Datz, S.; Krause, H. F.; Vane, C. R.

    1996-07-01

    Channeled ions experience a restoring force from adjacent atomic rows or planes that govern their trajectories and hence limit their interactions to those with valence or conduction electrons. Trajectory information can be gained from emergence patterns and studies of radiative electron capture (REC) can give information on the electron momentum distributions and densities in the channel. With this knowledge, one can study ion-electron collisions in dense media; in particular, dielectronic excitation and recombination. The states of the energetic channeled ions can be influenced by the crystal field and by the wake field that follows them. They can also be perturbed by the periodic electromagnetic force with a frequency depending on their velocity and the periodicity of the lattice. When the frequency of the perturbation v caused by passing along a given crystal direction with atomic spacing d at velocity v reaches a resonance, v res = ( {v}/{d})K , where K = 1, 2, 3, …, resonant coherent excitation (RCE) can occur to non-degenerate eigenstates of the ion. Ions in these excited states can then be ionized by the channel electrons or, if not ionized, can escape from the crystal and radiate. RCE has been studied in both axial and planar channeling by varying the ion velocity or, in the case of planar channeling, by varying the apparent interatomic spacing by changing the angle with respect to an axis. In both cases, information can be gained concerning the states of channeled ions and the nature of the crystal channel.

  19. Structure of conducting channel of lightning

    NARCIS (Netherlands)

    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 lay

  20. Regulated trafficking of the CFTR chloride channel

    NARCIS (Netherlands)

    Braakman, L.J.; Kleizen, B.; Jonge, H.R. de

    2000-01-01

    The cystic fibrosis transmembrane conductance regulator (CFTR), the ABC transporter encoded by the cystic fibrosis gene, is localized in the apical membrane of epithelial cells where it functions as a cyclic AMP-regulated chloride channel and as a regulator of other ion channels and transporters. Wh

  1. Theory of small-depth channeling

    International Nuclear Information System (INIS)

    Ion channeling at small depths is studied on the basis of the Fokker-Planck equation solved for the distribution function of ions in the channel. The expressions for the flux and oscillation peak width as functions of depth are obtained which are valid for whatever small depths of penetration

  2. Sodium channels, inherited epilepsy, and antiepileptic drugs.

    Science.gov (United States)

    Catterall, William A

    2014-01-01

    Voltage-gated sodium channels initiate action potentials in brain neurons, mutations in sodium channels cause inherited forms of epilepsy, and sodium channel blockers-along with other classes of drugs-are used in therapy of epilepsy. A mammalian voltage-gated sodium channel is a complex containing a large, pore-forming α subunit and one or two smaller β subunits. Extensive structure-function studies have revealed many aspects of the molecular basis for sodium channel structure, and X-ray crystallography of ancestral bacterial sodium channels has given insight into their three-dimensional structure. Mutations in sodium channel α and β subunits are responsible for genetic epilepsy syndromes with a wide range of severity, including generalized epilepsy with febrile seizures plus (GEFS+), Dravet syndrome, and benign familial neonatal-infantile seizures. These seizure syndromes are treated with antiepileptic drugs that offer differing degrees of success. The recent advances in understanding of disease mechanisms and sodium channel structure promise to yield improved therapeutic approaches. PMID:24392695

  3. 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 o...

  4. Variability of the Mozambique Channel Throughflow

    NARCIS (Netherlands)

    van der Werf, P.M.

    2010-01-01

    The Mozambique Channel is an important link in the thermohaline circulation, as the variability in its throughflow affects the exchange between the Indian and South Atlantic Ocean south of Africa. In this dissertation, we study the variability of the Mozambique Channel throughflow in the range from

  5. Channel Capacity Estimation using Free Probability Theory

    CERN Document Server

    Ryan, Øyvind

    2007-01-01

    In many channel measurement applications, one needs to estimate some characteristics of the channels based on a limited set of measurements. This is mainly due to the highly time varying characteristics of the channel. In this contribution, it will be shown how free probability can be used for channel capacity estimation in MIMO systems. Free probability has already been applied in various application fields such as digital communications, nuclear physics and mathematical finance, and has been shown to be an invaluable tool for describing the asymptotic behaviour of many systems when the dimensions of the system get large (i.e. the number of antennas). In particular, introducing the notion of free deconvolution, we provide hereafter an asymptotically (in the number of antennas) unbiased capacity estimator (w.r.t. the number of observations) for MIMO channels impaired with noise. Another unbiased estimator (for any number of observations) is also constructed by slightly modifying the free probability based est...

  6. 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.

  7. Stability of flowing open fluidic channels

    Directory of Open Access Journals (Sweden)

    Jue Nee Tan

    2013-02-01

    Full Text Available Open fluidic systems have a distinct advantage over enclosed channels in that the fluids exposed nature makes for easy external interaction, this finds uses in introduction of samples by adding liquid droplets or from the surrounding gaseous medium. This work investigates flowing open channels and films, which can potentially make use of the open section of the system as an external interface, before bringing the sample into an enclosed channel. Clearly, in this scenario a key factor is the stability of the flowing open fluid. The open channels investigated include a straight open channel defined by a narrow strip of solid surface, the edges of which allow large contact angle hysteresis, and a wider structure allowing for multiple inputs and outputs. A model is developed for fluid flow, and the findings used to describe the process of failure in both cases.

  8. Perfect Multi-Channel Flat Reflectors

    CERN Document Server

    Asadchy, V S; Elsakka, A; Albooyeh, M; Tretyakov, S A

    2016-01-01

    Recent advances in engineered gradient metasurfaces have enabled unprecedented opportunities for light manipulation using optically thin sheets, such as anomalous refraction, reflection, or focusing of an incident beam. Here we introduce a concept of multi-channel functional metasurfaces, which are able to control incoming and outgoing waves in a number of propagation directions or polarization states simultaneously and independently. In particular, we reveal a possibility to create perfect multi-channel reflectors. Under the assumption of reciprocity and energy conservation, we find that there exist three fundamental classes of multi-channel mirrors. Together they form a basis of all possible reflection functionalities achievable with flat periodically modulated reflectors. To demonstrate the potential of the introduced concept, we design and experimentally test one of the basis multi-channel reflectors, confirming the desired multi-channel response. Furthermore, by extending the concept to reflectors suppor...

  9. Entanglement cannot make imperfect quantum channels perfect

    CERN Document Server

    Brandao, F G S L; Horodecki, M; Yang, D

    2010-01-01

    Entangled inputs can enhance the capacity of quantum channels, this being one of the consequences of the celebrated result showing the non-additivity of several quantities relevant for quantum information science. In this work, we answer the converse question - whether entangled inputs can ever render noisy quantum channels have maximum capacity - to the negative: No sophisticated entangled input of any quantum channel can ever enhance the capacity to the maximum possible value; a result that holds true for all channels both for the classical as well as the quantum capacity. This result can hence be seen as a bound as to how "non-additive quantum information can be". We find several practical and remarkably simple computable single-shot bounds to capacities, related to entanglement measures. As examples, we discuss the qubit amplitude damping and an anti-symmetric channel and identify the first meaningful bound for their classical capacities.

  10. Serial data transmission between redundant channels

    Science.gov (United States)

    Tulpule, Bhalchandra R. (Inventor); Binnall, Daniel G. (Inventor)

    1992-01-01

    Data is communicated between redundant channels formatted in blocks having an initial command word followed by a destination code, starting address and a variable number of data words including a word count. The blocks are transmitted between each channel and all of the channels over cross-channel data links, each channel receiving the data blocks and determining the validity thereof by counting the number of data words received and comparing that number to the word count transmitted for that block. An interrupt signal indicative of invalidity of a block is provided in the event of a miscompare. A stop address is generated for each block received for storage at the start address. A memory address is generated for each valid word received for storage in sequence starting immediately after the start address. The next block received has its start address placed immediately at the end of the previously received block.

  11. Understanding autoimmunity: The ion channel perspective.

    Science.gov (United States)

    RamaKrishnan, Anantha Maharasi; Sankaranarayanan, Kavitha

    2016-07-01

    Ion channels are integral membrane proteins that orchestrate the passage of ions across the cell membrane and thus regulate various key physiological processes of the living system. The stringently regulated expression and function of these channels hold a pivotal role in the development and execution of various cellular functions. Malfunction of these channels results in debilitating diseases collectively termed channelopathies. In this review, we highlight the role of these proteins in the immune system with special emphasis on the development of autoimmunity. The role of ion channels in various autoimmune diseases is also listed out. This comprehensive review summarizes the ion channels that could be used as molecular targets in the development of new therapeutics against autoimmune disorders.

  12. A Compressed Sensing Wire-Tap Channel

    CERN Document Server

    Reeves, Galen; Milosavljevic, Nebojsa; Gastpar, Michael

    2011-01-01

    A multiplicative Gaussian wire-tap channel inspired by compressed sensing is studied. Lower and upper bounds on the secrecy capacity are derived, and shown to be relatively tight in the large system limit for a large class of compressed sensing matrices. Surprisingly, it is shown that the secrecy capacity of this channel is nearly equal to the capacity without any secrecy constraint provided that the channel of the eavesdropper is strictly worse than the channel of the intended receiver. In other words, the eavesdropper can see almost everything and yet learn almost nothing. This behavior, which contrasts sharply with that of many commonly studied wiretap channels, is made possible by the fact that a small number of linear projections can make a crucial difference in the ability to estimate sparse vectors.

  13. Slow flow in channels with porous walls

    CERN Document Server

    Jensen, Kaare H

    2012-01-01

    We consider the slow flow of a viscous incompressible liquid in a channel of constant but arbitrary cross section shape, driven by non-uniform suction or injection through the porous channel walls. A similarity transformation reduces the Navier-Stokes equations to a set of coupled equations for the velocity potential in two dimensions. When the channel aspect ratio and Reynolds number are both small, the problem reduces to solving the biharmonic equation with constant forcing in two dimensions. With the relevant boundary conditions, determining the velocity field in a porous channels is thus equivalent to solving for the vertical displacement of a simply suspended thin plate under uniform load. This allows us to provide analytic solutions for flow in porous channels whose cross-section is e.g. a rectangle or an equilateral triangle, and provides a general framework for the extension of Berman flow (Journal of Applied Physics 24(9), p. 1232, 1953) to three dimensions.

  14. How do mechanosensitive channels sense membrane tension?

    Science.gov (United States)

    Rasmussen, Tim

    2016-08-15

    Mechanosensitive (MS) channels provide protection against hypo-osmotic shock in bacteria whereas eukaryotic MS channels fulfil a multitude of important functions beside osmoregulation. Interactions with the membrane lipids are responsible for the sensing of mechanical force for most known MS channels. It emerged recently that not only prokaryotic, but also eukaryotic, MS channels are able to directly sense the tension in the membrane bilayer without any additional cofactor. If the membrane is solely viewed as a continuous medium with specific anisotropic physical properties, the sensitivity towards tension changes can be explained as result of the hydrophobic coupling between membrane and transmembrane (TM) regions of the channel. The increased cross-sectional area of the MS channel in the active conformation and elastic deformations of the membrane close to the channel have been described as important factors. However, recent studies suggest that molecular interactions of lipids with the channels could play an important role in mechanosensation. Pockets in between TM helices were identified in the MS channel of small conductance (MscS) and YnaI that are filled with lipids. Less lipids are present in the open state of MscS than the closed according to MD simulations. Thus it was suggested that exclusion of lipid fatty acyl chains from these pockets, as a consequence of increased tension, would trigger gating. Similarly, in the eukaryotic MS channel TRAAK it was found that a lipid chain blocks the conducting path in the closed state. The role of these specific lipid interactions in mechanosensation are highlighted in this review. PMID:27528747

  15. A computer program for analyzing channel geometry

    Science.gov (United States)

    Regan, R.S.; Schaffranek, R.W.

    1985-01-01

    The Channel Geometry Analysis Program (CGAP) provides the capability to process, analyze, and format cross-sectional data for input to flow/transport simulation models or other computational programs. CGAP allows for a variety of cross-sectional data input formats through use of variable format specification. The program accepts data from various computer media and provides for modification of machine-stored parameter values. CGAP has been devised to provide a rapid and efficient means of computing and analyzing the physical properties of an open-channel reach defined by a sequence of cross sections. CGAP 's 16 options provide a wide range of methods by which to analyze and depict a channel reach and its individual cross-sectional properties. The primary function of the program is to compute the area, width, wetted perimeter, and hydraulic radius of cross sections at successive increments of water surface elevation (stage) from data that consist of coordinate pairs of cross-channel distances and land surface or channel bottom elevations. Longitudinal rates-of-change of cross-sectional properties are also computed, as are the mean properties of a channel reach. Output products include tabular lists of cross-sectional area, channel width, wetted perimeter, hydraulic radius, average depth, and cross-sectional symmetry computed as functions of stage; plots of cross sections; plots of cross-sectional area and (or) channel width as functions of stage; tabular lists of cross-sectional area and channel width computed as functions of stage for subdivisions of a cross section; plots of cross sections in isometric projection; and plots of cross-sectional area at a fixed stage as a function of longitudinal distance along an open-channel reach. A Command Procedure Language program and Job Control Language procedure exist to facilitate program execution on the U.S. Geological Survey Prime and Amdahl computer systems respectively. (Lantz-PTT)

  16. Convection in a vertical channel

    Energy Technology Data Exchange (ETDEWEB)

    Tisserand, J-C; Creyssels, M; Gibert, M; Castaing, B; Chilla, F, E-mail: Francesca.Chilla@ens-lyon.f [Universite de Lyon, ENS Lyon, UMR 5672 CNRS, 46 Allee d' Italie, 69364 Lyon Cedex 7 (France)

    2010-07-15

    The flow generated by heat convection in a long, vertical channel is studied by means of particle imagery velocimetry techniques, with the help of the thermal measurements from a previous paper (Gibert et al 2009 Phys. Fluids 21 035109). We analyse the mean velocity profiles and the Reynolds stresses, and compare the present results with the previous ones obtained in a larger cell and at a larger Reynolds number. We calculate the horizontal temperature profile and the related horizontal heat flux. The pertinence of effective turbulent diffusivity and viscosity is confirmed by the low value of the associated mixing length. We study the one-point and two-point statistics of both velocity components. We show how the concept of turbulent viscosity explains the relations between the local probability density functions (pdf) of fluctuations for temperature, vertical and horizontal velocity components. Despite the low Reynolds number values explored, some conclusions can be drawn about the small scale velocity differences and the related energy cascade.

  17. The lifting scheme of 4-channel orthogonal wavelet transforms

    Institute of Scientific and Technical Information of China (English)

    PENG Lizhong; CHU Xiaoyong

    2006-01-01

    The 4-channel smooth wavelets with linear phase and orthogonality are designed from the 2-channel orthogonal wavelets with high transfer vanishing moments. Reversely, for simple lifting scheme of such 4-channel orthogonal wavelet transforms, a new 2-channel orthogonal wavelet associated with this 4-channel wavelet is constructed. The new 2-channel wavelet has at least the same number of vanishing moments as the associated 4-channel one. Finally, by combining the two such 2-channel wavelet systems, the lifting scheme of 4-channel orthogonal wavelet transform, which has simple structure and is easy to apply, is presented.

  18. Study about the Asymmetry Competing Channel Structure under Bargaining Power

    Institute of Scientific and Technical Information of China (English)

    ZHOU Lan; AI Xing-zheng

    2005-01-01

    On the problem of competing channel structure, we present asymmetry competing channel structure models under bargaining power, analyze the evolving process of channel structure under different bargaining power and product nature, find different bargaining power and product nature important role for channel structure, and also present equilibrium result. Furthermore, the academic proof for channel structure choice is presented.

  19. River channel adjustments in Southern Italy over the past 150 years and implications for channel recovery

    Science.gov (United States)

    Scorpio, Vittoria; Aucelli, Pietro P. C.; Giano, Salvatore I.; Pisano, Luca; Robustelli, Gaetano; Rosskopf, Carmen M.; Schiattarella, Marcello

    2015-12-01

    Multi-temporal GIS analysis of topographic maps and aerial photographs along with topographic and geomorphological surveys are used to assess evolutionary trends and key control factors of channel adjustments for five major rivers in southern Italy (the Trigno, Biferno, Volturno, Sinni and Crati rivers) to support assessment of channel recovery and river restoration. Three distinct phases of channel adjustment are identified over the past 150 years primarily driven by human disturbances. Firstly, slight channel widening dominated from the last decades of the nineteenth century to the 1950s. Secondly, from the 1950s to the end of the 1990s, altered sediment fluxes induced by in-channel mining and channel works brought about moderate to very intense incision (up to 6-7 m) accompanied by strong channel narrowing (up to 96%) and changes in channel configuration from multi-threaded to single-threaded patterns. Thirdly, the period from around 2000 to 2015 has been characterized by channel stabilization and local widening. Evolutionary trajectories of the rivers studied are quite similar to those reconstructed for other Italian rivers, particularly regarding the second phase of channel adjustments and ongoing transitions towards channel recovery in some reaches. Analyses of river dynamics, recovery potential and connectivity with sediment sources of the study reaches, framed in their catchment context, can be used as part of a wider interdisciplinary approach that views effective river restoration alongside sustainable and risk-reduced river management.

  20. Epilepsy-Related Slack Channel Mutants Lead to Channel Over-Activity by Two Different Mechanisms.

    Science.gov (United States)

    Tang, Qiong-Yao; Zhang, Fei-Fei; Xu, Jie; Wang, Ran; Chen, Jian; Logothetis, Diomedes E; Zhang, Zhe

    2016-01-01

    Twelve sodium-activated potassium channel (KCNT1, Slack) genetic mutants have been identified from severe early-onset epilepsy patients. The changes in biophysical properties of these mutants and the underlying mechanisms causing disease remain elusive. Here, we report that seven of the 12 mutations increase, whereas one mutation decreases, the channel's sodium sensitivity. Two of the mutants exhibit channel over-activity only when the intracellular Na(+) ([Na(+)]i) concentration is ∼80 mM. In contrast, single-channel data reveal that all 12 mutants increase the maximal open probability (Po). We conclude that these mutant channels lead to channel over-activity predominantly by increasing the ability of sodium binding to activate the channel, which is indicated by its maximal Po. The sodium sensitivity of these epilepsy causing mutants probably determines the [Na(+)]i concentration at which these mutants exert their pathological effects. PMID:26725113

  1. Scaling Vegetation on Experimental Channel Patterns

    Science.gov (United States)

    van Breemen, D. M.; van de Lageweg, W. I.; van Dijk, W. M.; Kleinhans, M. G.

    2010-12-01

    There are strong feedbacks between river channels, floodplains and riparian and floodplain vegetation. We study the effect of experimental vegetation on channel pattern. Through linear bar theory it is known that channel width-depth ratio affects bar pattern and relatively narrow channels with strong banks are required for meandering. Riparian vegetation is able to alter the channel width-depth ratio and therefore the channel pattern through strengthening of the banks. Floodplain vegetation adds hydraulic resistance so the flow is more focused into the channels. However, determination of the underlying mechanisms and processes has remained scarce and qualitative and hence these effects are not yet fully understood. The objectives of this study are 1) to develop a controllable and scalable method to reproduce vegetation effect in experimental self-formed channels, and 2) to experimentally determine the effects of riparian vegetation on bank strength, channel pattern and meandering dynamics. Sprouts of three plant species were systematically subjected to different seeding densities and to various growing conditions, including light intensity, submergence and nutrient starvation. Denser seeding reduced sprout growth after about a week. Stronger light increased plant growth and plant strength. Nutrient starvation caused different branching intensity of the root system. Tens of small-scale bank erosion experiments and bank failure experiments (see Kleinhans et al., this conference) were performed to quantify the strength of banks reinforced by plant roots at the experimental scale, demonstrating that bank strength is strongly determined by seeding density, rooting density and depth relative to channel depth. To study pattern evolution and morphodynamics we used a 1.25x7.5 m flume with a constant discharge and sediment feed. The introduction of vegetation in experiments results in narrower and deeper channels. Higher vegetation density leads to static channels with

  2. Pharmacology of the human red cell voltage-dependent cation channel Part I. Activation by clotrimazole and analogues

    DEFF Research Database (Denmark)

    Barksmann, Trine Lyberth; Kristensen, Berit I.; Christophersen, Palle.;

    2004-01-01

    Human red cells, Nonselective voltage dependent cation channel, NSVDC channel, Gárdos channel blockers, NSVDC channel activators......Human red cells, Nonselective voltage dependent cation channel, NSVDC channel, Gárdos channel blockers, NSVDC channel activators...

  3. Piezo channels: from structure to function.

    Science.gov (United States)

    Volkers, Linda; Mechioukhi, Yasmine; Coste, Bertrand

    2015-01-01

    Mechanotransduction is the conversion of mechanical stimuli into biological signals. It is involved in the modulation of diverse cellular functions such as migration, proliferation, differentiation, and apoptosis as well as in the detection of sensory stimuli such as air vibration and mechanical contact. Therefore, mechanotransduction is crucial for organ development and homeostasis and plays a direct role in hearing, touch, proprioception, and pain. Multiple molecular players involved in mechanotransduction have been identified in the past, among them ion channels directly activated by cell membrane deformation. Most of these channels have well-established roles in lower organisms but are not conserved in mammals or fail to encode mechanically activated channels in mammals due to non-conservation of mechanotransduction property. A family of mechanically activated channels that counts only two members in human, piezo1 and 2, has emerged recently. Given the lack of valid mechanically activated channel candidates in mammals in the past decades, particular attention is given to piezo channels and their potential roles in various biological functions. This review summarizes our current knowledge on these ion channels.

  4. Channel blocking of MspA revisited.

    Science.gov (United States)

    Perera, Ayomi S; Wang, Hongwang; Basel, Matthew T; Pokhrel, Megh Raj; Gamage, Pubudu Siyambalagoda; Kalita, Mausam; Wendel, Sebastian; Sears, Bryan; Welideniya, Dhanushi; Liu, Yao; Turro, Claudia; Troyer, Deryl L; Bossmann, Stefan H

    2013-01-01

    Porin A from Mycobacterium smegmatis (MspA) is a highly stable, octameric channel protein, which acts as the main transporter of electrolytes across the cell membrane. MspA features a narrow, negatively charged constriction zone, allowing stable binding of various analytes thereby blocking the channel. Investigation of channel blocking of mycobacterial porins is of significance in developing alternate treatment methods for tuberculosis. The concept that ruthenium(II)quaterpyridinium complexes have the capability to act as efficient channel blockers for MspA and related porins, emerged after very high binding constants were measured by high-performance liquid chromatography and steady-state luminescence studies. Consequently, the interactions between the ruthenium(II) complex RuC2 molecules and MspA, leading to RuC2@MspA assemblies, have been studied utilizing time-resolved absorption/emission, atomic force microscopy, dynamic light scattering, ζ potential measurements, and isothermal titration calorimetry. The results obtained provide evidence for the formation of clusters/large aggregates of RuC2 and MspA. The results are of interest with respect to utilizing prospective channel blockers in porins. The combination of results from conceptually different techniques shed some light onto the chemical nature of MspA-channel blocker interactions thus contributing to the development of a paradigm for channel blocking. PMID:23214433

  5. Kinetic ELISA in Microfluidic Channels

    Directory of Open Access Journals (Sweden)

    Debashis Dutta

    2011-06-01

    Full Text Available In this article, we describe the kinetic ELISA of Blue Tongue and Epizootic Hemorrhagic Disease viral antibodies in microfluidic channels by monitoring the rate of generation of the enzyme reaction product under static conditions. It has been shown that this format of the immunoassay allows very reliable quantitation of the target species using inexpensive glass microchips and a standard epifluorescence microscope system coupled to a CCD camera. For the viral antibodies assayed here, the limit of detection (LOD for the analyte concentration in our microchips was established to be 3–5 times lower than that obtained on commercial microwell plates using a fiftieth of the sample volume and less than a third of the incubation time. Our analyses further show that when compared to the end-point ELISA format, the kinetic mode of this assay yields an improvement in the LOD by over an order of magnitude in microfluidic devices. This benefit is primarily realized as the observed variation in the background fluorescence (signal at the start of the enzyme reaction period was significantly larger than that in the rate of signal generation upon repeating these assays in different microchannels/microchips. Because the kinetic ELISA results depend only on the latter quantity, the noise level in them was substantially lower compared to that in its end-point counterpart in which the absolute fluorescence measurements are of greater significance. While a similar benefit was also recorded through implementation of kinetic ELISAs on the microwell platform, the improvement in LOD registered in that system was not as significant as was observed in the case of microfluidic assays.

  6. 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. PMID:26603282

  7. Morphological dynamics of an englacial channel

    Directory of Open Access Journals (Sweden)

    G. Vatne

    2015-08-01

    Full Text Available Despite an interest in the hydraulic functioning of supraglacial and englacial channels over the last four decades, the processes and forms of such ice-bounded streams have remained poorly documented. Recent glaciological research has demonstrated the potential significance of so-called "cut and closure" streams, where englacial or subglacial flowpaths are created from the long-term incision of supraglacial channels. These flowpaths are reported to exhibit step-pool morphology, comprising knickpoints and/or knickzones, albeit exaggerated in dimensions in comparison to their supraglacial channel counterparts. However, little is known of the development of such channels' morphology. Here, we examine the spatial organization of step-pools and the upstream migration of steps, many of which form knickzones, with repeated surveys over a 10 year period in an englacial conduit in cold-based Austre Brøggerbreen, Svalbard. The observations show upstream knickpoint recession to be the dominant process for channel evolution. This is paralleled by an increase in average step height and conduit gradient over time. Characteristic channel reach types and step-riser forms are consistently observed in each of the morphological surveys reported. We suggest that the formation of steps has a hydrodynamic origin, where step-pool geometry is more efficient for energy dissipation than meanders, and that the englacial channel system is one in rapid transition rather than in dynamic equilibrium. The evolution and recession of knickzones reported here result in the formation of a 37 m moulin, suggesting over time the englacial channel may evolve towards a stable end-point characterised by a singular vertical descent to the local hydraulic base level. In light of this, our observations highlight the need to further examine the adjustment processes in cut-and-closure channels to better understand their coupling to supraglacial meltwater sources and role and potential

  8. Quantum Biological Channel Modeling and Capacity Calculation

    Directory of Open Access Journals (Sweden)

    Ivan B. Djordjevic

    2012-12-01

    Full Text Available Quantum mechanics has an important role in photosynthesis, magnetoreception, and evolution. There were many attempts in an effort to explain the structure of genetic code and transfer of information from DNA to protein by using the concepts of quantum mechanics. The existing biological quantum channel models are not sufficiently general to incorporate all relevant contributions responsible for imperfect protein synthesis. Moreover, the problem of determination of quantum biological channel capacity is still an open problem. To solve these problems, we construct the operator-sum representation of biological channel based on codon basekets (basis vectors, and determine the quantum channel model suitable for study of the quantum biological channel capacity and beyond. The transcription process, DNA point mutations, insertions, deletions, and translation are interpreted as the quantum noise processes. The various types of quantum errors are classified into several broad categories: (i storage errors that occur in DNA itself as it represents an imperfect storage of genetic information, (ii replication errors introduced during DNA replication process, (iii transcription errors introduced during DNA to mRNA transcription, and (iv translation errors introduced during the translation process. By using this model, we determine the biological quantum channel capacity and compare it against corresponding classical biological channel capacity. We demonstrate that the quantum biological channel capacity is higher than the classical one, for a coherent quantum channel model, suggesting that quantum effects have an important role in biological systems. The proposed model is of crucial importance towards future study of quantum DNA error correction, developing quantum mechanical model of aging, developing the quantum mechanical models for tumors/cancer, and study of intracellular dynamics in general.

  9. BK Channels in the Vascular System.

    Science.gov (United States)

    Krishnamoorthy-Natarajan, G; Koide, M

    2016-01-01

    Autoregulation of blood flow is essential for the preservation of organ function to ensure continuous supply of oxygen and essential nutrients and removal of metabolic waste. This is achieved by controlling the diameter of muscular arteries and arterioles that exhibit a myogenic response to changes in arterial blood pressure, nerve activity and tissue metabolism. Large-conductance voltage and Ca(2+)-dependent K(+) channels (BK channels), expressed exclusively in smooth muscle cells (SMCs) in the vascular wall of healthy arteries, play a critical role in regulating the myogenic response. Activation of BK channels by intracellular, local, and transient ryanodine receptor-mediated "Ca(2+) sparks," provides a hyperpolarizing influence on the SMC membrane potential thereby decreasing the activity of voltage-dependent Ca(2+) channels and limiting Ca(2+) influx to promote SMC relaxation and vasodilation. The BK channel α subunit, a large tetrameric protein with each monomer consisting of seven-transmembrane domains, a long intracellular C-terminal tail and an extracellular N-terminus, associates with the β1 and γ subunits in vascular SMCs. The BK channel is regulated by factors originating within the SMC or from the endothelium, perivascular nerves and circulating blood, that significantly alter channel gating properties, Ca(2+) sensitivity and expression of the α and/or β1 subunit. The BK channel thus serves as a central receiving dock that relays the effects of the changes in several such concomitant autocrine and paracrine factors and influences cardiovascular health. This chapter describes the primary mechanism of regulation of myogenic response by BK channels and the alterations to this mechanism wrought by different vasoactive mediators. PMID:27238270

  10. Pannexin 1 channels in skeletal muscles

    Science.gov (United States)

    Cea, Luis A.; Riquelme, Manuel A.; Vargas, Anibal A.; Urrutia, Carolina; Sáez, Juan C.

    2014-01-01

    Normal myotubes and adult innervated skeletal myofibers express the glycoprotein pannexin1 (Panx1). Six of them form a “gap junction hemichannel-like” structure that connects the cytoplasm with the extracellular space; here they will be called Panx1 channels. These are poorly selective channels permeable to ions, small metabolic substrate, and signaling molecules. So far little is known about the role of Panx1 channels in muscles but skeletal muscles of Panx1−/− mice do not show an evident phenotype. Innervated adult fast and slow skeletal myofibers show Panx1 reactivity in close proximity to dihydropyridine receptors in the sarcolemma of T-tubules. These Panx1 channels are activated by electrical stimulation and extracellular ATP. Panx1 channels play a relevant role in potentiation of muscle contraction because they allow release of ATP and uptake of glucose, two molecules required for this response. In support of this notion, the absence of Panx1 abrogates the potentiation of muscle contraction elicited by repetitive electrical stimulation, which is reversed by exogenously applied ATP. Phosphorylation of Panx1 Thr and Ser residues might be involved in Panx1 channel activation since it is enhanced during potentiation of muscle contraction. Under denervation, Panx1 levels are upregulated and this partially explains the reduction in electrochemical gradient, however its absence does not prevent denervation-induced atrophy but prevents the higher oxidative state. Panx1 also forms functional channels at the cell surface of myotubes and their functional state has been associated with intracellular Ca2+ signals and regulation of myotube plasticity evoked by electrical stimulation. We proposed that Panx1 channels participate as ATP channels and help to keep a normal oxidative state in skeletal muscles. PMID:24782784

  11. General teleportation as a quantum channel

    International Nuclear Information System (INIS)

    Teleportation is viewed as a quantum channel. We present an explicit expression for the general teleportation channel in the Kraus decomposition form. We then analyse optimal teleportation procedures for a noisy entangled resource, Bell measurement by the sender and arbitrary operations by the receiver. Our general result allows us to derive the corresponding quantum channel and fidelity, thereby enabling us to formulate the fidelity-based optimization problem and to conclude that this is a problem of semidefinite programming. We offer an alternative viewpoint on optimal teleportation, namely one can perform corrective operations at the receiver's side instead of first manipulating entanglement, and we give an optimal teleportation strategy

  12. Information capacities of quantum measurement channels

    Science.gov (United States)

    Holevo, A. S.

    2013-03-01

    We study the relation between the unassisted and entanglement-assisted classical capacities C and Cea of entanglement-breaking channels. We argue that the gain of entanglement assistance Cea/C > 1 generically for measurement channels with unsharp observables; in particular for the measurements with pure posterior states the information loss in the entanglement-assisted protocol is zero, resulting in an arbitrarily large gain for very noisy or weak signal channels. This is illustrated by examples of continuous observables corresponding to state tomography in finite dimensions and heterodyne measurement. In contrast, state preparations are characterized by the property of having no gain of entanglement assistance, Cea/C = 1.

  13. Covert Communication over Classical-Quantum Channels

    OpenAIRE

    Sheikholeslami, Azadeh; Bash, Boulat A.; Towsley, Donald; Goeckel, Dennis; Guha, Saikat

    2016-01-01

    Recently, the fundamental limits of covert, i.e., reliable-yet-undetectable, communication have been established for general memoryless channels and for lossy-noisy bosonic (quantum) channels with a quantum-limited adversary. The key import of these results was the square-root law (SRL) for covert communication, which states that $O(\\sqrt{n})$ covert bits, but no more, can be reliably transmitted over $n$ channel uses with $O(\\sqrt{n})$ bits of secret pre-shared between communicating parties....

  14. Information capacities of quantum measurement channels

    International Nuclear Information System (INIS)

    We study the relation between the unassisted and entanglement-assisted classical capacities C and Cea of entanglement-breaking channels. We argue that the gain of entanglement assistance Cea/C > 1 generically for measurement channels with unsharp observables; in particular for the measurements with pure posterior states the information loss in the entanglement-assisted protocol is zero, resulting in an arbitrarily large gain for very noisy or weak signal channels. This is illustrated by examples of continuous observables corresponding to state tomography in finite dimensions and heterodyne measurement. In contrast, state preparations are characterized by the property of having no gain of entanglement assistance, Cea/C = 1. (paper)

  15. Connexin channels and phospholipids: association and modulation

    Directory of Open Access Journals (Sweden)

    Harris Andrew L

    2009-08-01

    Full Text Available Abstract Background For membrane proteins, lipids provide a structural framework and means to modulate function. Paired connexin hemichannels form the intercellular channels that compose gap junction plaques while unpaired hemichannels have regulated functions in non-junctional plasma membrane. The importance of interactions between connexin channels and phospholipids is poorly understood. Results Endogenous phospholipids most tightly associated with purified connexin26 or connexin32 hemichannels or with junctional plaques in cell membranes, those likely to have structural and/or modulatory effects, were identified by tandem electrospray ionization-mass spectrometry using class-specific interpretative methods. Phospholipids were characterized by headgroup class, charge, glycerol-alkyl chain linkage and by acyl chain length and saturation. The results indicate that specific endogenous phospholipids are uniquely associated with either connexin26 or connexin32 channels, and some phospholipids are associated with both. Functional effects of the major phospholipid classes on connexin channel activity were assessed by molecular permeability of hemichannels reconstituted into liposomes. Changes to phospholipid composition(s of the liposome membrane altered the activity of connexin channels in a manner reflecting changes to the surface charge/potential of the membrane and, secondarily, to cholesterol content. Together, the data show that connexin26 and connexin32 channels have a preference for tight association with unique anionic phospholipids, and that these, independent of headgroup, have a positive effect on the activity of both connexin26 and connexin32 channels. Additionally, the data suggest that the likely in vivo phospholipid modulators of connexin channel structure-function that are connexin isoform-specific are found in the cytoplasmic leaflet. A modulatory role for phospholipids that promote negative curvature is also inferred. Conclusion

  16. 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 digital sales channels by the use of technology, thus providing uniform customer experience and operational effectiveness across the channels (Hansen and Tambo, 2011). The vision of OCRIS remains largely at a conceptual level. Selected point-of-sale (“cash registers”) products and retail management...

  17. INTERFERENCE CANCELLATION FOR MOBILE DISPERSIVE CHANNELS

    Institute of Scientific and Technical Information of China (English)

    Kazi Takpaya

    2003-01-01

    A robust interference canceller for Multi-Carrier Code Division Multiple Access(MC-CDMA) using Orthogonal Frequency Division Multiplexing (OFDM) in Rayleigh fading isproposed. This interference canceller is robust in the sense that it cancels Inter-Carriers Inter-ference (ICI) and is suitable for use in dispersive channels. To come up the effects of the signaldispersion, Doppler shifts and delay spreads on the performance of MC-CDMA systems over mo-bile fading channels, this interference canceller exploits the merit of the orthogonal signaling andpilot signals to evaluate the channel parameters. This interface canceller is well suited to work initerative turbo interference cancellation.

  18. Multi-Channel Maximum Likelihood Pitch Estimation

    DEFF Research Database (Denmark)

    Christensen, Mads Græsbøll

    2012-01-01

    . 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......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...

  19. Pannexin 1 channels in skeletal muscles

    OpenAIRE

    Cea, Luis A.; Riquelme, Manuel A.; Vargas, Anibal A.; Urrutia, Carolina; Sáez, Juan C.

    2014-01-01

    Normal myotubes and adult innervated skeletal myofibers express the glycoprotein pannexin1 (Panx1). Six of them form a “gap junction hemichannel-like” structure that connects the cytoplasm with the extracellular space; here they will be called Panx1 channels. These are poorly selective channels permeable to ions, small metabolic substrate, and signaling molecules. So far little is known about the role of Panx1 channels in muscles but skeletal muscles of Panx1−/− mice do not show an evident ph...

  20. COMPETITIVE PARALLEL DISTRIBUTION CHANNELS WITH MOVE SEQUENCE

    Institute of Scientific and Technical Information of China (English)

    Yu QIAN

    2006-01-01

    In this paper, we consider two competitive parallel distribution channels (PDCs) each of them consisting of a manufacturer and a retailer. In every PDC, the manufacturer sells differentiated products to the retailer and the retailer chooses the retail price (margin). We explore the effects of the move sequence on the system performance not only in each distribution channel, but also in the inter-parallel distribution channels subject to the deterministic demand. Under some assumptions, we show that the PDC has the second-mover advantage in this scenario. The system performance will be improved in our model when the parameters satisfy certain conditions. Furthermore, we discuss the results and find some implications.

  1. Quantum Capacity Approaching Codes for the Detected-Jump Channel

    CERN Document Server

    Grassl, Markus; Wei, Zhaohui; Zeng, Bei

    2010-01-01

    The quantum channel capacity gives the ultimate limit for the rate at which quantum data can be reliably transmitted through a noisy quantum channel. Degradable quantum channels are among the few channels whose quantum capacities are known. Given the quantum capacity of a degradable channel, it remains challenging to find a practical coding scheme which approaches capacity. Here we discuss code designs for the detected-jump channel, a degradable channel with practical relevance describing the physics of spontaneous decay of atoms with detected photon emission. We show that this channel can be used to simulate a binary classical channel with both erasures and bit-flips. The capacity of the simulated classical channel gives a lower bound on the quantum capacity of the detected-jump channel. When the jump probability is small, it almost equals the quantum capacity. Hence using a classical capacity approaching code for the simulated classical channel yields a quantum code which approaches the quantum capacity of ...

  2. Molecular basis of potassium channels in pancreatic duct epithelial cells

    DEFF Research Database (Denmark)

    Hayashi, M.; Novak, Ivana

    2013-01-01

    Potassium channels regulate excitability, epithelial ion transport, proliferation, and apoptosis. In pancreatic ducts, K channels hyperpolarize the membrane potential and provide the driving force for anion secretion. This review focuses on the molecular candidates of functional K channels...

  3. 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.

  4. Monolithic DWDM Multi-channel planar waveguide laser

    DEFF Research Database (Denmark)

    Sckerl, Mads W.; Guldberg-Kjær, Søren Andreas; Laurent-Lund, Christian

    1999-01-01

    silica -on-silicon-based multi-channel waveguide laser with four outputs channel with ~ 50 GHz spacing is presented. Excellent control over channel positions and spacings is obtained by the method presented here. Remarkable temperature tuning properties have been obtained.......silica -on-silicon-based multi-channel waveguide laser with four outputs channel with ~ 50 GHz spacing is presented. Excellent control over channel positions and spacings is obtained by the method presented here. Remarkable temperature tuning properties have been obtained....

  5. Dual-recycling channel management for WEEE with stochastic demand

    OpenAIRE

    Li, Chuanfa; Feng, Lipan; Wang, Xuehong

    2014-01-01

    More and more enterprises collecting e-wastes through the online recycling channel as the rapidly improving of the customer acceptance of the online recycling channel. And they are facing a problem, however, that they have to offer a higher price in the online recycling channel than the traditional recycling channel as well as reducing the searching cost by using the online recycling channel. Base on that, we incorporate a detailed consumer recycling channel choice model where the collection ...

  6. GEOMORPHIC THRESHOLDS FOR CHANNEL EVOLUTION IN THE LOWER YELLOW RIVER

    Institute of Scientific and Technical Information of China (English)

    Zhongyan LI; Zhongchen LU

    2004-01-01

    Channel evolution refers to boundary changes of rivers affected by fluvial actions. This paper provides an analysis of the development and formation of stream patterns in the lower Yellow River and presents intensive studies of several critical problems relating to channel evolution, including thresholds of channel gradient and longitudinal profile adjustment, channel surface morphology, response of channel pattern to boundary conditions, critical discrimination of cross sections and the discrimination of channel pattern changes using hydrologic parameters.

  7. Role of the membrane for mechanosensing by tethered channels

    CERN Document Server

    Sabass, Benedikt

    2016-01-01

    Biologically important membrane channels are gated by force at attached tethers. Here, we generically characterize the non-trivial interplay of force, membrane tension, and channel deformations that can affect gating. A central finding is that minute conical channel deformation under force leads to significant energy release during opening. We also calculate channel-channel interactions and show that they can amplify force sensitivity of tethered channels.

  8. Optimization of bandwidth of communication channels of corporate networks

    OpenAIRE

    G. I. Bondarenko; P. M. Korobenkov

    2014-01-01

    Introduction. This article contains overview of the organization of communication between applications on the corporate network. It is stated that the main digital channel (channel B - 64 kbit/s) and the primary digital channel (channel E1 the digital stream - 2048 kbit/s) are used as the main channels in corporate networks. Problem areas of the functioning of the corporate network are identified. There are the rent of communication channels, which is growing rapidly with increasing the quali...

  9. Uplink Channel Dependent Scheduling for Future Cellular Systems

    OpenAIRE

    Jersenius, Kristina

    2007-01-01

    One goal in the development of future cellular systems is to increase performance. Channel dependent scheduling can possibly contribute to a performance enhancement. It requires channel qualityinformation and uplink channel knowledge is often incomplete. This master thesis work compares channel dependent scheduling and channel independent scheduling for a Single Carrier Frequency Division Multiple Access-based uplink in time domain and time and frequencydomain assuming continuous channel qual...

  10. Secrecy Outage Capacity of Fading Channels

    CERN Document Server

    Gungor, Onur; Koksal, C Emre; Gamal, Hesham El; Shroff, Ness B

    2011-01-01

    This paper considers point to point secure communication over flat fading channels under an outage constraint. More specifically, we extend the definition of outage capacity to account for the secrecy constraint and obtain sharp characterizations of the corresponding fundamental limits under two different assumptions on the transmitter CSI (Channel state information). First, we find the outage secrecy capacity assuming that the transmitter has perfect knowledge of the legitimate and eavesdropper channel gains. In this scenario, the capacity achieving scheme relies on opportunistically exchanging private keys between the legitimate nodes. These keys are stored in a key buffer and later used to secure delay sensitive data using the Vernam's one time pad technique. We then extend our results to the more practical scenario where the transmitter is assumed to know only the legitimate channel gain. Here, our achievability arguments rely on privacy amplification techniques to generate secret key bits. In the two cas...

  11. VEGF regulates TRPC6 channels in podocytes

    DEFF Research Database (Denmark)

    Thilo, Florian; Liu, Ying; Loddenkemper, Christoph;

    2012-01-01

    BACKGROUND: Both, increased plasma concentrations of vascular endothelial growth factor (VEGF) and increased expression of transient receptor potential canonical type 6 (TRPC6) channels in podocytes have been associated with proteinuric kidney diseases. Now, we investigated the hypothesis that VE...

  12. Manufacturing Advanced Channel Wall Rocket Liners Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR will adapt and demonstrate a low cost flexible method of manufacturing channel wall liquid rocket nozzles and combustors, while providing developers a...

  13. Modified MIMO Cube for Enhanced Channel Capacity

    Directory of Open Access Journals (Sweden)

    Lajos Nagy

    2012-01-01

    Full Text Available This paper deals with the optimization of MIMO antenna elements' position in modified MIMO cube for getting maximal channel capacity in indoor environment. The dependence of the channel capacity on the antenna orientation was analyzed by simulations. We have also examined the effect of the frequency dependence of the antenna system (in case of conjugate matching and nonconjugate matching for the channel capacity. Based on the simulation results in the created and measured antenna system, the antennas were at a right angle to each other. At the two chosen different structures, we measured the antenna parameters and the channel capacity. In this paper, we present the results of the measurements which clearly confirm our simulations. We will point out the differences between the two antenna structures.

  14. Nonperturbative approach to relativistic quantum communication channels

    Science.gov (United States)

    Landulfo, André G. S.

    2016-05-01

    We investigate the transmission of both classical and quantum information between two arbitrary observers in globally hyperbolic spacetimes using a quantum field as a communication channel. The field is supposed to be in some arbitrary quasifree state and no choice of representation of its canonical commutation relations is made. Both sender and receiver possess some localized two-level quantum system with which they can interact with the quantum field to prepare the input and receive the output of the channel, respectively. The interaction between the two-level systems and the quantum field is such that one can trace out the field degrees of freedom exactly and thus obtain the quantum channel in a nonperturbative way. We end the paper determining the unassisted as well as the entanglement-assisted classical and quantum channel capacities.

  15. Dean Instability in Double-Curved Channels

    CERN Document Server

    Debus, J -D; Herrmann, H J

    2014-01-01

    We study the Dean instability in curved channels using the lattice Boltzmann model for generalized metrics. For this purpose, we first improve and validate the method by measuring the critical Dean number at the transition from laminar to vortex flow for a streamwise curved rectangular channel, obtaining very good agreement with the literature values. Taking advantage of the easy implementation of arbitrary metrics within our model, we study the fluid flow through a double-curved channel, using ellipsoidal coordinates, and study the transition to vortex flow in dependence of the two perpendicular curvature radii of the channel. We observe not only transitions to 2-cell vortex flow, but also to 4-cell and even 6-cell vortex flow, and we find that the critical Dean number at the transition to 2-cell vortex flow exhibits a minimum when the two curvature radii are approximately equal.

  16. Natural products and ion channel pharmacology.

    Science.gov (United States)

    Teichert, Russell W; Olivera, Baldomero M

    2010-05-01

    An accelerated rate of natural-product discovery is critical for the future of ion channel pharmacology. For the full potential of natural products to be realized, an interdisciplinary initiative is required that combines chemical ecology and ion channel physiology. A prime source of future drug leads targeted to ion channels is the vast assortment of compounds that mediate biotic interactions in the marine environment. Many animals have evolved a chemical strategy to change the behavior of their prey, predators or competitors, which appears to require a large set of ion channel-targeted compounds acting in concert. Some of these compounds (e.g., ziconotide [Prialt(®)]) have already found important biomedical applications. The elucidation of molecular mechanisms mediating biotic interactions should yield a rich stream of potent and selective natural products for the drug pipeline. PMID:21426200

  17. The complex channel networks of bone structure

    CERN Document Server

    Costa, Luciano da Fontoura; Beletti, Marcelo E

    2006-01-01

    Bone structure in mammals involves a complex network of channels (Havers and Volkmann channels) required to nourish the bone marrow cells. This work describes how three-dimensional reconstructions of such systems can be obtained and represented in terms of complex networks. Three important findings are reported: (i) the fact that the channel branching density resembles a power law implies the existence of distribution hubs; (ii) the conditional node degree density indicates a clear tendency of connection between nodes with degrees 2 and 4; and (iii) the application of the recently introduced concept of hierarchical clustering coefficient allows the identification of typical scales of channel redistribution. A series of important biological insights is drawn and discussed

  18. Measuring Method for Lightning Channel Temperature

    Science.gov (United States)

    Li, X.; Zhang, J.; Chen, L.; Xue, Q.; Zhu, R.

    2016-01-01

    In this paper, we demonstrate the temperature of lightning channel utilizing the theory of lightning spectra and the model of local thermodynamic equilibrium (LTE). The impulse current generator platform (ICGS) was used to simulate the lightning discharge channel, and the spectral energy of infrared spectroscopy (930 nm) and the visible spectroscopy (648.2 nm) of the simulated lightning has been calculated. Results indicate that the peaks of luminous intensity of both infrared and visible spectra increase with the lightning current intensity in range of 5–50 kA. Based on the results, the temperature of the lightning channel is derived to be 6140.8–10424 K. Moreover, the temperature of the channel is approximately exponential to the lightning current intensity, which shows good agreement with that of the natural lightning cases. PMID:27665937

  19. Discrete stochastic modeling of calcium channel dynamics

    CERN Document Server

    Baer, M E; Levine, H; Tsimring, L S; Baer, Markus; Falcke, Martin; Levine, Herbert; Tsimring, Lev S.

    1999-01-01

    We propose a simple discrete stochastic model for calcium dynamics in living cells. Specifically, the calcium concentration distribution is assumed to give rise to a set of probabilities for the opening/closing of channels which release calcium thereby changing those probabilities. We study this model in one dimension, analytically in the mean-field limit of large number of channels per site N, and numerically for small N. As the number of channels per site is increased, the transition from a non-propagating region of activity to a propagating one changes in nature from one described by directed percolation to that of deterministic depinning in a spatially discrete system. Also, for a small number of channels a propagating calcium wave can leave behind a novel fluctuation-driven state, in a parameter range where the limiting deterministic model exhibits only single pulse propagation.

  20. Discrete Stochastic Modeling of Calcium Channel Dynamics

    International Nuclear Information System (INIS)

    We propose a discrete stochastic model for calcium dynamics in living cells. A set of probabilities for the opening/closing of calcium channels is assumed to depend on the calcium concentration. We study this model in one dimension, analytically in the limit of a large number of channels per site N , and numerically for small N . As the number of channels per site is increased, the transition from a nonpropagating region of activity to a propagating one changes from one described by directed percolation to that of deterministic depinning in a spatially discrete system. Also, for a small number of channels a propagating calcium wave can leave behind a novel fluctuation-driven state. (c) 2000 The American Physical Society

  1. Inspection of Candu Nuclear Reactor Fuel Channels

    International Nuclear Information System (INIS)

    The Channel Inspection and Gauging Apparatus of Reactors (CIGAR) is a fully atomated, remotely operated inspection system designed to perform multi-channel, multi-task inspection of CANDU reactor fuel channels. Ultrasonic techniques are used for flaw detection, (with a sensitivity capable of detecting a 0.075 mm deep notch with a signal to noise ratio of 10 dB) and pressure tube wall thickness and diameter measurements. Eddy currrent systems are used to detect the presence of spacers between the coaxial pressure tube and calandria tube, as well as to measure their relative spacing. A servo-accelerometer is used to estimate the sag of the fuel channels. This advanced inspection system was commissioned and declared in service in September 1985. The paper describes the inspection systems themselves and discussed the results achieved to-date. (author)

  2. Layered MAP algorithm for MIMO ISI channels

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The layered maximum a posteriori (L-MAP) algorithm has been proposed to detect signals under frequency selective fading multiple input multiple output (MIMO) channels. Compared to the optimum MAP detector, the L-MAP algorithm can efficiently identify signal bits, and the complexity grows linearly with the number of input antennas. The basic idea of L-MAP is to operate on each input sub-stream with an optimum MAP sequential detector separately by assuming the other streams are Gaussian noise. The soft output can also be forwarded to outer channel decoder for iterative decoding. Simulation results show that the proposed method can converge with a small number of iterations under different channel conditions and outperforms other sub-optimum detectors for rank-deficient channels.

  3. Stage- vs. Channel-strip Metaphor

    DEFF Research Database (Denmark)

    Gelineck, Steven; Korsgaard, Dannie Michael; Büchert, Morten

    2015-01-01

    This study compares the stage metaphor and the channel strip metaphor in terms of performance. Traditionally, music mixing consoles employ a channels strip control metaphor for adjusting parameters such as volume and panning of each track. An alternative control metaphor, the so-called stage...... metaphor lets the user adjust volume and panning by positioning tracks relative to a virtual listening position. In this study test participants are given the task to adjust volume and panning of one channel (in mixes consisting of three channels) in order to replicate a series of simple pre-rendered mixes....... They do this using (1) a small physical mixing controller and (2) using an iPad app, which implements a simple stage metaphor interface. We measure how accurately they are able to replicate mixes in terms of volume and panning and how fast they are at doing so. Results reveal that performance...

  4. Computer simulation of proton channelling in silicon

    Indian Academy of Sciences (India)

    N K Deepak; K Rajasekharan; K Neelakandan

    2000-06-01

    The channelling of 3 MeV protons in the $\\langle 110\\rangle$ direction of silicon has been simulated using Vineyard model taking into account thermally vibrating nuclei and energy loss due to ionelectron interactions. A beam made up of constant energy particles but with spatial divergence has been simulated for the purpose. The values of the minimum scattering yield and half width of the channelling dip are shown to be depth sensitive and agree well with the measured values. The dependence of yield on the angle of incidence has been found to give information of all three types of channelling. The critical angles for the three types of channelling and wavelength of planar oscillations are consistent with the previous calculations.

  5. Proton implanted sapphire planar and channel waveguides

    NARCIS (Netherlands)

    Laversenne, L.; Crunteanu, A.; Hoffmann, P.; Pollnau, M.; Moretti, P.; Mugnier, J.

    2003-01-01

    We report low-order transverse-mode planar waveguides in sapphire fabricated for the first time by proton implantation. The waveguides show good guiding properties without post-implantation annealing. Channel waveguiding was achieved by polyimide strip-loading.

  6. Hydraulics of free overfall in -shaped channels

    Indian Academy of Sciences (India)

    Subhasish Dey; B Ravi Kumar

    2002-06-01

    In this paper, two methods are presented to analyse the free overfall in -shaped (equilateral triangle-shaped) channels. First, the flow upstream of a free overfall from smooth horizontal or mildly sloping -shaped channels is analysed theoretically to determine the end-depth-ratio (EDR), applying the momentum equation based on the Boussinesq approximation. Second, an alternate method for analysing free overfall in -shaped channels is also presented where the flow over a free overfall in a -shaped channel is simulated by that over a sharp-crested weir to calculate the EDR. The method of estimation of discharge from the known end depth is also presented for both the methods. These approaches eliminate the need of an experimentally determined pressure coefficient. Experiments are conducted to verify the results obtained from the present methods. Comparisons of the computed and experimental results are satisfactory.

  7. Flag flutter in inviscid channel flow

    CERN Document Server

    Alben, Silas

    2014-01-01

    Using nonlinear vortex-sheet simulations, we determine the region in parameter space in which a straight flag in a channel-bounded inviscid flow is unstable to flapping motions. We find that for heavier flags, greater confinement increases the size of the region of instability. For lighter flags, confinement has little influence. We then compute the stability boundaries analytically for an infinite flag, and find similar results. For the finite flag we also consider the effect of channel walls on the large-amplitude periodic flapping dynamics. We find that multiple flapping states are possible but rare at a given set of parameters, when periodic flapping occurs. As the channel walls approach the flag, its flapping amplitude decreases roughly in proportion to the near-wall distance, for both symmetric and asymmetric channels. Meanwhile, its dominant flapping frequency and mean number of deflection extrema (or "wavenumber") increase in a nearly stepwise fashion. That is, they remain nearly unchanged over a wide...

  8. Two-way quantum communication channels

    CERN Document Server

    Childs, A M; Lo, H K; Childs, Andrew M.; Leung, Debbie W.; Lo, Hoi-Kwong

    2005-01-01

    We consider communication between two parties using a bipartite quantum operation, which constitutes the most general quantum mechanical model of two-party communication. We primarily focus on the simultaneous forward and backward communication of classical messages. For the case in which the two parties share unlimited prior entanglement, we give inner and outer bounds on the achievable rate region that generalize classical results due to Shannon. In particular, using a protocol of Bennett, Harrow, Leung, and Smolin, we give a one-shot expression in terms of the Holevo information for the entanglement-assisted one-way capacity of a two-way quantum channel. As applications, we rederive two known additivity results for one-way channel capacities: the entanglement-assisted capacity of a general one-way channel, and the unassisted capacity of an entanglement-breaking one-way channel.

  9. Multi-channel gas-delivery system

    Energy Technology Data Exchange (ETDEWEB)

    Rozenzon, Yan; Trujillo, Robert T.; Beese, Steven C.

    2016-09-13

    One embodiment of the present invention provides a gas-delivery system for delivering reaction gas to a reactor chamber. The gas-delivery system includes a main gas-inlet port for receiving reaction gases and a gas-delivery plate that includes a plurality of gas channels. A gas channel includes a plurality of gas holes for allowing the reaction gases to enter the reactor chamber from the gas channel. The gas-delivery system further includes a plurality of sub-gas lines coupling together the main gas-inlet port and the gas-delivery plate, and a respective sub-gas line is configured to deliver a portion of the received reaction gases to a corresponding gas channel.

  10. Contraction coefficients for noisy quantum channels

    Energy Technology Data Exchange (ETDEWEB)

    Hiai, Fumio, E-mail: hiai.fumio@gmail.com [Tohoku University, Hakusan 3-8-16-303, Abiko 270-1154 (Japan); Ruskai, Mary Beth, E-mail: ruskai@member.ams.org [Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada)

    2016-01-15

    Generalized relative entropy, monotone Riemannian metrics, geodesic distance, and trace distance are all known to decrease under the action of quantum channels. We give some new bounds on, and relationships between, the maximal contraction for these quantities.

  11. Channel Islands, Kelp Forest Monitoring, Sea Temperature

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset from the Channel Islands National Park's Kelp Forest Monitoring Program has subtidal temperature data taken at permanent monitoring sites. Since 1993,...

  12. Finite blocklength converse bounds for quantum channels

    OpenAIRE

    Matthews, William; Wehner, Stephanie

    2012-01-01

    We derive upper bounds on the rate of transmission of classical information over quantum channels by block codes with a given blocklength and error probability, for both entanglement-assisted and unassisted codes, in terms of a unifying framework of quantum hypothesis testing with restricted measurements. Our bounds do not depend on any special property of the channel (such as memorylessness) and generalise both a classical converse of Polyanskiy, Poor, and Verd\\'{u} as well as a quantum conv...

  13. Web services interface to EPICS channel access

    Institute of Scientific and Technical Information of China (English)

    DUAN Lei; SHEN Liren

    2008-01-01

    Web services is used in Experimental Physics and Industrial Control System (EPICS). Combined with EPICS Channel Access protocol, Web services' high usability, platform independence and language independence can be used to design a fully transparent and uniform software interface layer, which helps us complete channel data acquisition, modification and monitoring functions. This software interface layer, a cross-platform of cross-language,has good interopcrability and reusability.

  14. In-Store Media and Channel Management

    OpenAIRE

    Anthony Dukes; Yunchuan Liu

    2007-01-01

    In this paper, we study the interesting and complicated effects of retailer in-store media on distribution channel relationships. With the help of advanced technology, retailers can open in-store media in their stores and allow manufacturers to advertise through the instore media. We show that opening in-store media is a strategic decision for a retailer, and a retailer may strategically subsidize manufacturers on their advertising through instore media to better coordinate the channel. Even ...

  15. Characterization of dihydropyridine-sensitive calcium channels

    International Nuclear Information System (INIS)

    The structural and regulatory properties of the dihydropyridine-sensitive calcium channel were studied by isolating protein components of the channel complex from both cardiac and skeletal muscle. Hydrodynamic characterization of the (+)-(3H)PN200-110-labeled cardiac calcium channel revealed that the protein components of the complex had a total molecular mass of 370,000 daltons, a Stokes radius of 86 angstrom, and a frictional ratio of 1.3. A technique is described for the rapid incorporation of the CHAPS solubilized skeletal muscle calcium channel complex into phospholipid vesicles. 45Ca2+ uptake into phospholipid vesicles containing calcium channels was inhibited by phenylalkalamine calcium antagonists. Wheat germ lectin followed by DEAE chromatography of the CHAPS solubilized complex resulted in the dissociation of regulatory components of the complex from channel components. The DEAE preparation gave rise to 45Ca2+ uptake that was not inhibited by verapamil but was inhibited by GTPgS activated G0. The inhibition of 45Ca2+ uptake by verapamil was restored by co-reconstitution of wash fractions from wheat germ lectin chromatography. Phosphorylation of polypeptides in this fraction by polypeptide-dependent protein kinase prevented the restoration of verapamil sensitivity. The partial purification of an endogenous skeletal muscle ADP-ribosyltransferase is also described. ADP-ribosylation of the α2 subunit of the calcium channel complex is enhanced by polylysine and inhibited by GTPγS, suggesting that regulation of this enzyme is under the control of GTP binding proteins. These results suggest a complex model, involving a number of different protein components, for calcium channel regulation in skeletal muscle

  16. Calcium channel blockers and Alzheimer's disease

    Institute of Scientific and Technical Information of China (English)

    Yi Tan; Yulin Deng; Hong Qing

    2012-01-01

    Alzheimer's disease is characterized by two pathological hallmarks: amyloid plaques and neurofi-brillary tangles. In addition, calcium homeostasis is disrupted in the course of human aging. Recent research shows that dense plaques can cause functional alteration of calcium signals in mice with Alzheimer's disease. Calcium channel blockers are effective therapeutics for treating Alzheimer's disease. This review provides an overview of the current research of calcium channel blockers in-volved in Alzheimer's disease therapy.

  17. Joint Pose and Radio Channel Estimation

    OpenAIRE

    Mannesson, Anders

    2013-01-01

    This thesis investigates the combination of pose and radio channel estimation. Pose is the knowledge of the position and orientation of a device whereas the radio channel describes the transmission medium between radio transmitters and receivers. The two subjects are both active research topics with a long history of applications but there has to the author's knowledge been very little work published about combining the two areas using a sensor fusion framework. A well established...

  18. Channel capacities via $p$-summing norms

    OpenAIRE

    Junge, Marius; Palazuelos Cabezón, Carlos

    2013-01-01

    In this paper we show how the metric theory of tensor products developed by Grothendieck perfectly fits in the study of channel capacities, a central topic in Shannon’s information theory. Furthermore, in the last years Shannon’s theory has been fully generalized to the quantum setting, and revealed qualitatively new phenomena in comparison. In this paper we consider the classical capacity of quantum channels with restricted assisted entanglement. These capacities include the classical capaci...

  19. Information transmission through a noisy quantum channel

    OpenAIRE

    Barnum, Howard; Nielsen, M. A.; Schumacher, Benjamin

    1998-01-01

    Noisy quantum channels may be used in many information carrying applications. We show that different applications may result in different channel capacities. Upper bounds on several of these capacities are proved. These bounds are based on the coherent information, which plays a role in quantum information theory analogous to that played by the mutual information in classical information theory. Many new properties of the coherent information and entanglement fidelity are proved. Two non-clas...

  20. Robust Monetary Policy with the Cost Channel

    OpenAIRE

    Peter Tillmann

    2007-01-01

    Recent research argues that model uncertainty leads the central bank to adjust interest rates stronger to exogenous disturbances than under certainty. This paper investigates whether the introduction of a cost channel of monetary transmission, whose presence is empirically supported, changes the impact of model uncertainty on interest rate setting. The basic model is simple enough to facilitate an analytical closed form solution. We find that the presence of the cost channel dampens the effec...

  1. Retail distribution channel barriers to international trade

    OpenAIRE

    Scherer, Frederic Michael

    1996-01-01

    With the referral of the Kodak - Fuji market access dispute to the World Trade Organization, the role of retail distribution channel control by incumbent firms as a barrier to imports has drawn much interest. This paper reviews the issues from an historical perspective and analyzes the difficulties facing firms attempting to sell their products in other nations' automobile and photo supplies markets. There has been a natural evolution of retail distribution channels from mom and pop stores to...

  2. Trade Credit and the Bank Lending Channel

    OpenAIRE

    Nilsen, Jeffrey H.

    1999-01-01

    The bank lending channel theory posits that during monetary contractions banks restrict some firms’ loans, thus reducing their desired investment independently of interest rates. Previous research finds small firms reduce, while large firms accelerate, loan growth. We find that small firms increase trade credit, a substitute credit, indicating a strong loan demand. It supports the bank lending channel: they do not voluntarily cut bank loans since they increase a less-desirable alternative. Us...

  3. Voltage-gated lipid ion channels

    CERN Document Server

    Blicher, Andreas

    2012-01-01

    Lipid membranes can display channel-like ion conduction events even in the absence of proteins. We show here that these events are voltage-gated with a quadratic voltage dependence as expected from electrostatic theory. To this end, we recorded channel traces and open current histograms. We determined the equilibrium constant between closed and open state and the open probability as a function of voltage

  4. Channeling of fast particles in fullerenes

    CERN Document Server

    Zhevago, N K

    2002-01-01

    The theory on channeling the relativistic electrons and positrons as well as positively and negatively charged ions in the fullerenes molecular crystals (fullerites) is developed. The calculation of the crystalline potentials is carried out and spatial and angular distribution of the particles beams, propagating along the main crystallographic directions is studied. The method making it possible to account for the effect of the incoherent scattering on the channeling process is developed

  5. The Business Cluster's Distribution e-Channels

    OpenAIRE

    Milan Davidovic

    2011-01-01

    The business cluster cooperative potential and business capability improvement are dependent on e-business implementation and business model change dynamics in cluster and his members based in new and existing distribution channels, customer relationships management and supplychain integration. In this work analyse cluster’s e-business models, e-commerce forms and distribution e-channels for three business cases: when cluster members are oriented on own business, on cooperative’s project or c...

  6. Cooperative communications hardware, channel and PHY

    CERN Document Server

    Dohler, Mischa

    2010-01-01

    Facilitating Cooperation for Wireless Systems Cooperative Communications: Hardware, Channel & PHY focuses on issues pertaining to the PHY layer of wireless communication networks, offering a rigorous taxonomy of this dispersed field, along with a range of application scenarios for cooperative and distributed schemes, demonstrating how these techniques can be employed. The authors discuss hardware, complexity and power consumption issues, which are vital for understanding what can be realized at the PHY layer, showing how wireless channel models differ from more traditional

  7. Progressive Source Channel Embedded Coding of Image Over Static (Memory Less Channel

    Directory of Open Access Journals (Sweden)

    Anil L.Wanare

    2009-06-01

    Full Text Available In this paper, we proposed a progressive time varying source channel coding system for transmitting image over wireless channels. Transmission of compressed image data over noisy channel is an important problem and has been investigated in a variety of scenarios. the core results obtained by a systematic method of instantaneous rate allocation between the progressive source coder and progressive channel coder .It is developed by closed form ofexpression for end-to-end distortion , rate allocation respectively in static channels. It is extended the static result to an algorithm for fading channels. It is introduced set DCT (blocks approach is adapted to perform sub band decomposition followed by SPIHT (Setpartitioning in Hierarchical tree

  8. Dual Turbo MIMO-OFDM Channel Estimation Based on Puncher Technique via UWA Channels

    Directory of Open Access Journals (Sweden)

    Gang Qiao

    2013-02-01

    Full Text Available In this study, various techniques of UWA (Underwater Acoustic, UWA channel estimation for underwater MIMO-OFDM system are studied. Dual turbo channel estimation algorithm based on channel puncture technique is proposed. In order to judge the criteria of channel compensation, difference between the raw received signal and the re-coded information signal is carried out. The uncertain sub-channels are punched by using channel puncture technique and replaced by the responses estimated by MMSE (Minimum Mean Square Error, MMSE or OMP (Orthogonal Matching Pursuit, OMP algorithms. Compared with the conventional existing algorithms, the proposed algorithm can effectively reduce the occupancy of pilots, offer confined error propagation and significantly increase the stability of the system with Monte Caro simulation. The results of in-tank-experiment further indorse the reliable performance with improved efficiency of 1.51 bits/s/Hz.

  9. A novel potassium channel in photosynthetic cyanobacteria.

    Directory of Open Access Journals (Sweden)

    Manuela Zanetti

    Full Text Available Elucidation of the structure-function relationship of a small number of prokaryotic ion channels characterized so far greatly contributed to our knowledge on basic mechanisms of ion conduction. We identified a new potassium channel (SynK in the genome of the cyanobacterium Synechocystis sp. PCC6803, a photosynthetic model organism. SynK, when expressed in a K(+-uptake-system deficient E. coli strain, was able to recover growth of these organisms. The protein functions as a potassium selective ion channel when expressed in Chinese hamster ovary cells. The location of SynK in cyanobacteria in both thylakoid and plasmamembranes was revealed by immunogold electron microscopy and Western blotting of isolated membrane fractions. SynK seems to be conserved during evolution, giving rise to a TPK (two-pore K(+ channel family member which is shown here to be located in the thylakoid membrane of Arabidopsis. Our work characterizes a novel cyanobacterial potassium channel and indicates the molecular nature of the first higher plant thylakoid cation channel, opening the way to functional studies.

  10. TPC1 - SV Channels Gain Shape

    Institute of Scientific and Technical Information of China (English)

    Rainer Hedrich; Irene Marten

    2011-01-01

    T The most prominent ion channel localized in plant vacuoles is the slow activating SV type. Slow vacuolar (SV)channels were discovered by patch clamp studies as early as 1986. In the following two decades, numerous studies revealed that these calcium- and voltage-activated, nonselective cation channels are expressed in the vacuoles of all plants and every plant tissue. The voltage-dependent properties of the SV channel are susceptible to modulation by calcium, pH, redox state, as well as regulatory proteins. In Arabidopsis, the SV channel is encoded by the AtTPC1 gene, and even though its gene product represents the by far largest conductance of the vacuolar membrane, tpc1-loss-of-function mutants appeared not to be impaired in major physiological functions such as growth, development, and reproduction. In contrast, the fou2 gain-of-function point mutation D454N within TPC1 leads to a pronounced growth phenotype and increased synthesis of the stress hormone jasmonate. Since the TPC1 gene is present in all land plants, it likely encodes a very general function. In this review, we will discuss major SV channel properties and their impact on plant cell physiology.

  11. On conduction in a bacterial sodium channel.

    Directory of Open Access Journals (Sweden)

    Simone Furini

    Full Text Available Voltage-gated Na⁺-channels are transmembrane proteins that are responsible for the fast depolarizing phase of the action potential in nerve and muscular cells. Selective permeability of Na⁺ over Ca²⁺ or K⁺ ions is essential for the biological function of Na⁺-channels. After the emergence of the first high-resolution structure of a Na⁺-channel, an anionic coordination site was proposed to confer Na⁺ selectivity through partial dehydration of Na⁺ via its direct interaction with conserved glutamate side chains. By combining molecular dynamics simulations and free-energy calculations, a low-energy permeation pathway for Na⁺ ion translocation through the selectivity filter of the recently determined crystal structure of a prokaryotic sodium channel from Arcobacter butzleri is characterised. The picture that emerges is that of a pore preferentially occupied by two ions, which can switch between different configurations by crossing low free-energy barriers. In contrast to K⁺-channels, the movements of the ions appear to be weakly coupled in Na⁺-channels. When the free-energy maps for Na⁺ and K⁺ ions are compared, a selective site is characterised in the narrowest region of the filter, where a hydrated Na⁺ ion, and not a hydrated K⁺ ion, is energetically stable.

  12. Diversity of MIMO Multihop Relay Channels

    CERN Document Server

    Yang, Sheng

    2007-01-01

    We consider slow fading relay channels with a single multi-antenna source-destination terminal pair. The source signal arrives at the destination via N hops through N-1 layers of relays. We analyze the diversity of such channels with fixed network size at high SNR. In the clustered case where the relays within the same layer can have full cooperation, the cooperative decode-and-forward (DF) scheme is shown to be optimal in terms of the diversity-multiplexing tradeoff (DMT). The upper bound on the DMT, the cut-set bound, is attained. In the non-clustered case, we show that the naive amplify-and-forward (AF) scheme has the maximum multiplexing gain of the channel but is suboptimal in diversity, as compared to the cut-set bound. To improve the diversity, space-time relay processing is introduced through the parallel partition of the multihop channel. The idea is to let the source signal go through K different "AF paths" in the multihop channel. This parallel AF scheme creates a parallel channel in the time domai...

  13. Optimal Design of Round Bottomed Triangle Channels

    Directory of Open Access Journals (Sweden)

    Ayman T. Hameed

    2013-05-01

    Full Text Available     In optimal design concept, the geometric dimensions of a channel cross-section are determined in a manner to minimize the total construction costs. The Direct search optimization method by using MATALAB is used to solve the resulting channel optimization models for a specified flow rate, roughness coefficient and longitudinal slope. The developed optimization models are applied to design the round bottomed triangle channel and trapezoidal channels to convey a given design flow considering various design scenarios However, it also can be extended to other shapes of channels. This method optimizes the total construction cost by minimizing the cross-sectional area and wetted perimeter per unit length of the channel. In the present study, it is shown that for all values of side slope, the total construction cost in the round bottomed triangle cross-section are less than those of trapezoidal cross-section for the same values of discharge. This indicates that less excavation and a lining are involved and therefore implies that the round bottomed triangle cross-section is more economical than trapezoidal cross-section.

  14. Experimental Channel Response to Tectonic Uplift

    Science.gov (United States)

    Turowski, J. M.; Lague, D.; Crave, A.; Hovius, N.

    2004-12-01

    We performed a series of experiments to investigate the relationship between channel geometry and tectonic forcing in steady state landscapes at various uplift rates. The experiment consists of uniformly uplifted silica paste eroded by artificial rainfall. The landscape evolves by growth and amalgamation of incisions and organises into a drainage network. High precision (0.5mm pixel size) digital elevation models were taken by a stereometric camera system. Channel bed slope is found to be independent of discharge and position on the experimental surface and increases linearly with uplift rate. This suggests it is controlled by global conditions rather than local channel processes. Using hydraulic assumptions the channel parameters width, depth, cross-sectional area, wetted perimeter and hydraulic radius were derived. We find that the channel width, cross-sectional area and wetted perimeter decay exponentially with uplift rate. The hydraulic radius is approximately constant and the channel depth rises linearly with uplift rate. These results are qualitatively consistent with recent field surveys.

  15. Targeting TRP channels for novel migraine therapeutics.

    Science.gov (United States)

    Dussor, Gregory; Yan, J; Xie, Jennifer Y; Ossipov, Michael H; Dodick, David W; Porreca, Frank

    2014-11-19

    Migraine is increasingly understood to be a disorder of the brain. In susceptible individuals, a variety of "triggers" may influence altered central excitability, resulting in the activation and sensitization of trigeminal nociceptive afferents surrounding blood vessels (i.e., the trigeminovascular system), leading to migraine pain. Transient receptor potential (TRP) channels are expressed in a subset of dural afferents, including those containing calcitonin gene related peptide (CGRP). Activation of TRP channels promotes excitation of nociceptive afferent fibers and potentially lead to pain. In addition to pain, allodynia to mechanical and cold stimuli can result from sensitization of both peripheral afferents and of central pain pathways. TRP channels respond to a variety of endogenous conditions including chemical mediators and low pH. These channels can be activated by exogenous stimuli including a wide range of chemical and environmental irritants, some of which have been demonstrated to trigger migraine in humans. Activation of TRP channels can elicit CGRP release, and blocking the effects of CGRP through receptor antagonism or antibody strategies has been demonstrated to be effective in the treatment of migraine. Identification of approaches that can prevent activation of TRP channels provides an additional novel strategy for discovery of migraine therapeutics.

  16. Temperature dependence of gramicidin channel conductance

    Science.gov (United States)

    Song, Hyundeok; Beck, Thomas

    2010-03-01

    The gramicidin channel is the smallest known biological ion channel, and it exhibits cation selectivity. Recently, Dr. John Cuppoletti's group at the University of Cincinnati has shown that the gramicidin channel can function at high temperatures with significant currents. This finding may have implications for fuel cell technologies. In order to explore the effect of temperature on channel conductance, we examined the gramicidin system at 300K, 330K, and 360K by computer simulation. Two forms of gramicidin, the head-to-head helical dimer and the intertwined double helix, were examined. Both the decrease of the free energy barrier and the increase of the diffusion of potassium ions inside the gramicidin channel at high temperatures imply an increase of current. We found that higher temperatures also affect the lifetime of hydrogen bonds, the distribution of the bending angle, the distribution of the distance between dimers, and the size of the pore radius for the helical dimer structure. These finding may be related to the gating of the gramicidin channel.

  17. The Analysis on the Factors Which Affecting Price Dispersion between Traditional Retail Channel and Internet Retail Channel

    OpenAIRE

    Xujin Pu

    2009-01-01

    With network economy springing up and communication technology expanding fast, the retailing channels composed of Internet retail channel become the choice of many traditional retailers. Price dispersion always exists between traditional retail channel and Internet retail channel. In this text, we bring forward the model about traditional retail channel and internet retail channel based on classical hotelling linear city model. We find the price dispersion will be different when the parameter...

  18. Optimising the Quality of Experience during Channel Zapping: The Impact of Advertisements during Channel Zapping

    OpenAIRE

    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, it could be interesting for the TV viewer, if the operator displays a screen with information instead of just a black screen. This information may be an advertisement, information about the target c...

  19. Reconstructive techniques for creation of catheterizable channels: tunneled and nipple valve channels.

    Science.gov (United States)

    Levy, Mya E; Elliott, Sean P

    2016-02-01

    Cutaneous catheterizable channels allow for continent bladder emptying when an alternate route is desired. The goals of channel creation in the neurogenic bladder population are successful urine elimination, renal preservation, continence and lastly cosmesis. In addition to a particular surgeon's comfort and experience with a given procedure, individual patient factors such as medical comorbidities, anatomic factors, and occupational function should be central to the selection of a surgical approach. An ideal channel is one that is short, straight, and well supported by associated blood supply and surrounding adventitia, so as to minimize difficulty with catheterization. Two types of channel continence mechanisms are discussed at length in this review-the tunneled channel, and the nipple valve. The appendicovesicostomy (Mitrofanoff), and reconfigured ileum (Yang-Monti) are both tunneled channels. The ileocecal valve is a commonly used nipple valve and provides continence when reinforced. The continent catheterizable ileal cecocystoplasty (CCIC) is an example of this channel technique. This method couples a tapered ileal limb as a catheterizable channel, the ileocecal valve as the continence mechanism, and the cecum and ascending colon as a bladder augmentation. While this procedure has higher perioperative complications relative to a simple tunneled channel, it has increased channel length flexibility and is also coupled with a bladder augment, which is completely performed using one bowel segment. Continent channel creation in adults can improve quality of life and minimize morbidity associated with neurogenic bladder. However, the decision to proceed with creation of a catheterizable channel should be made only after careful consideration of the patient's medical comorbidities, physical abilities social support, and surgeon experience. PMID:26904419

  20. On the secrecy capacity of the MISO wiretap channel under imperfect channel estimation

    KAUST Repository

    Rezki, Zouheir

    2014-12-01

    We consider a wiretap channel consisting of a source with multiple antennas, a legitimate receiver and an eavesdropper with a single antenna each. The channels between the source and the receivers undergo fast fading. We assume that the transmitter, in addition to the statistics of both channels, is only aware of a noisy version of the CSI to the legitimate receiver referred to as main channel. The legitimate receiver is aware of both its instantaneous channel gain and the transmitter\\'s estimate of the main channel. On the other hand, the eavesdropper\\'s receiver, in addition to its instantaneous channel realization, is aware of the actual main CSI and the transmitter\\'s estimate as well. While the capacity of this channel is still open even with perfect CSI at the transmitter, we provide in this paper upper and lower bounds on the secrecy capacity. The upper bound is tighter than the one corresponding to perfect main CSI and the gap between the two upper bounds is characterized in function of the channel estimation error variance, at high-SNR. Furthermore, we show that our upper and lower bounds coincide in the case of no main CSI providing a trivial secrecy capacity.

  1. Activation of TRPV1 channels inhibits mechanosensitive Piezo channel activity by depleting membrane phosphoinositides.

    Science.gov (United States)

    Borbiro, Istvan; Badheka, Doreen; Rohacs, Tibor

    2015-02-10

    Capsaicin is an activator of the heat-sensitive TRPV1 (transient receptor potential vanilloid 1) ion channels and has been used as a local analgesic. We found that activation of TRPV1 channels with capsaicin either in dorsal root ganglion neurons or in a heterologous expression system inhibited the mechanosensitive Piezo1 and Piezo2 channels by depleting phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] and its precursor phosphatidylinositol 4-phosphate [PI(4)P] from the plasma membrane through Ca(2+)-induced phospholipase Cδ (PLCδ) activation. Experiments with chemically inducible phosphoinositide phosphatases and receptor-induced activation of PLCβ indicated that inhibition of Piezo channels required depletion of both PI(4)P and PI(4,5)P2. The mechanically activated current amplitudes decreased substantially in the excised inside-out configuration, where the membrane patch containing Piezo1 channels is removed from the cell. PI(4,5)P2 and PI(4)P applied to these excised patches inhibited this decrease. Thus, we concluded that Piezo channel activity requires the presence of phosphoinositides, and the combined depletion of PI(4,5)P2 and PI(4)P reduces channel activity. In addition to revealing a role for distinct membrane lipids in mechanosensitive ion channel regulation, these data suggest that inhibition of Piezo2 channels may contribute to the analgesic effect of capsaicin.

  2. Low-Complexity Adaptive Channel Estimation over Multipath Rayleigh Fading Non-Stationary Channels Under CFO

    CERN Document Server

    Hadei, Sayed A

    2011-01-01

    In this paper, we propose novel low-complexity adaptive channel estimation techniques for mob ile wireless chan- n els in presence of Rayleigh fading, carrier frequency offsets (CFO) and random channel variations. We show that the selective p artial update of the estimated channel tap-weight vector offers a better trade-off between the performance and computational complexity, compared to the full update of the estimated channel tap-weight vector. We evaluate the mean-square weight error of th e proposed methods and demonstrate the usefulness of its via simulation studies.

  3. Design of Transport Layer Based Hybrid Covert Channel Detection Engine

    CERN Document Server

    K, Anjan; Jadhav, Mamatha; 10.5121/ijasuc.2010.1409

    2011-01-01

    Computer network is unpredictable due to information warfare and is prone to various attacks. Such attacks on network compromise the most important attribute, the privacy. Most of such attacks are devised using special communication channel called "Covert Channel". The word "Covert" stands for hidden or non-transparent. Network Covert Channel is a concealed communication path within legitimate network communication that clearly violates security policies laid down. The non-transparency in covert channel is also referred to as trapdoor. A trapdoor is unintended design within legitimate communication whose motto is to leak information. Subliminal channel, a variant of covert channel works similarly except that the trapdoor is set in a cryptographic algorithm. A composition of covert channel with subliminal channel is the "Hybrid Covert Channel". Hybrid covert channel is homogenous or heterogeneous mixture of two or more variants of covert channels either active at same instance or at different instances of time...

  4. Morphological dynamics of an englacial channel

    Science.gov (United States)

    Vatne, Geir; Irvine-Fynn, Tristram D. L.

    2016-07-01

    Despite an interest in the hydraulic functioning of supraglacial and englacial channels over the last 4 decades, the processes and forms of such ice-bounded streams have remained poorly documented. Recent glaciological research has demonstrated the potential significance of so-called "cut-and-closure" streams, where englacial or subglacial flow paths are created from the long-term incision of supraglacial channels. These flow paths are reported to exhibit step-pool morphology, comprising knickpoints and/or knickzones, exaggerated in dimensions in comparison to supraglacial channels. However, little is known of the development of such channels' morphology. Here, we examine the spatial organisation of step pools and the upstream migration of steps, many of which form knickzones, with repeated surveys over a 10-year period in an englacial conduit in cold-based Austre Brøggerbreen, Svalbard. The observations show upstream step recession to be the dominant process for channel evolution. This is paralleled by an increase in average step height and conduit gradient over time. Characteristic channel-reach types and step-riser forms are consistently observed in each of the morphological surveys reported. We suggest that the formation of steps has a hydrodynamic origin, where step-pool geometry is more efficient for energy dissipation than meanders. The englacial channel system is one in rapid transition towards a quasi-equilibrium form within a decadal timescale. The evolution and recession of knickzones reported here result in the formation of a 37 m deep moulin shaft, suggesting that over time an incising supraglacial channel may evolve towards an englacial channel form exhibiting a stable end-point characterised by a singular vertical descent, which potentially can reach the glacier bed. This challenges the prevailing notions that crevasses or hydrofractures are needed to form deep moulins. Our observations highlight the need to further examine the adjustment processes

  5. Fabrication of super-hydrophobic channels

    International Nuclear Information System (INIS)

    A new approach was developed in this work to create channels which had not only super-hydrophobic bottom surfaces but also super-hydrophobic sidewalls. Researchers have demonstrated that a flow experienced less drag forces and thus required smaller driving pressure in a channel of micro/nanostructure-formed top and bottom surfaces. The drag forces should be further reduced in a channel which has not only patterned top and bottom surfaces but also patterned sidewall surfaces. However, due to the limitation of the existing lithographic approaches, sidewalls could not be properly patterned. Therefore, a new approach was developed in this work to overcome this obstacle. Polydimethylsiloxane (PDMS) micropillars of aspect ratios 1.4, 2.0 and 2.7 were first generated on PDMS films using a molding method, and then transferred to the sidewalls and bottom surfaces of three 1 mm wide and 1 mm deep channels, respectively, applying a hot-embossing process. The corresponding deformation mechanism was considered. The widths of the PDMS films had a critical effect on the cross-section profiles of the generated channels. The radii of the channel corners and inclined degrees of the sidewalls increased with the film widths. Contact angles on the PDMS films before and after the deformations were measured and compared. The contact angles in the middle portions of the sidewalls, as well as at the bottoms of the generated channels, were little difference from those on the original PDMS films due to the small changes in the distances between the micropillars. However, the contact angles were increased and decreased, respectively, at the bottom and top corners of the generated channels since the PDMS films were compressed and stretched at these corners during the fabrication. The variation of the contact angle in each channel was further analyzed according to two existing theoretical formulas. These variations increased with the increasing aspect ratios of the PDMS micropillars. The super

  6. The human role in changing river channels

    Science.gov (United States)

    Gregory, K. J.

    2006-09-01

    Direct consequences of the human role, where human activity affects river channels through engineering works including channelization, dam construction, diversion and culverting, have been long recognised [Marsh, G.P., 1864. Man and Nature or Physical Geography as Modified by Human Action. Charles Scribner, New York; Thomas Jr., W.L., (ed.) 1956. Man's Role in Changing the Face of the Earth. Chicago, University of Chicago Press, Chicago.]. The less obvious indirect effects of point and reach changes occurring downstream and throughout the basin, however, are much more recently appreciated, dating from key contributions by Strahler [Strahler, A.N., 1956. The nature of induced erosion and aggradation. In W. L. Thomas (Ed.), Man's Role in Changing the Face of the Earth. University of Chicago Press, Chicago, 621-638.], Wolman [Wolman, M.G., 1967. A cycle of sedimentation and erosion in urban river channels. Geografiska Annaler 49A, 385-95.], Schumm [Schumm, S.A., 1969. River metamorphosis. Proceedings American Society of Civil Engineers, Journal Hydraulics Division 95, 255-73.], and Graf [Graf, W.L., 1977. The rate law in fluvial geomorphology. American Journal of Science, 277, 178-191.]. These are complemented by effects of alterations of land use, such as deforestation, intensive agriculture and incidence of fire, with the most extreme effects produced by building activity and urbanisation. Changing river channels are most evident in the channel cross-section where changes of size, shape and composition are now well-established, with up to tenfold increases or decreases illustrated by results from more than 200 world studies. In addition the overall channel planform, the network and the ecology have changed. Specific terms have become associated with changing river channels including enlargement, shrinkage and metamorphosis. Although the scope of adjustment has been established, it has not always been possible to predict what will happen in a particular location

  7. Ion channels to inactivate neurons in Drosophila

    Directory of Open Access Journals (Sweden)

    James J L Hodge

    2009-08-01

    Full Text Available Ion channels are the determinants of excitability; therefore, manipulation of their levels and properties provides an opportunity for the investigator to modulate neuronal and circuit function. There are a number of ways to suppress electrical activity in Drosophila neurons, for instance, over-expression of potassium channels (i.e. Shaker Kv1, Shaw Kv3, Kir2.1 and DORK that are open at resting membrane potential. This will result in increased potassium efflux and membrane hyperpolarisation setting resting membrane potential below the threshold required to fire action potentials. Alternatively over-expression of other channels, pumps or co-transporters that result in a hyperpolarised membrane potential will also prevent firing. Lastly, neurons can be inactivated by, disrupting or reducing the level of functional voltage-gated sodium (Nav1 paralytic or calcium (Cav2 cacophony channels that mediate the depolarisation phase of action potentials. Similarly, strategies involving the opposite channel manipulation should allow net depolarisation and hyperexcitation in a given neuron. These changes in ion channel expression can be brought about by the versatile transgenic (i.e. Gal4/UAS based systems available in Drosophila allowing fine temporal and spatial control of (channel transgene expression. These systems are making it possible to electrically inactivate (or hyperexcite any neuron or neural circuit in the fly brain, and much like an exquisite lesion experiment, potentially elucidate whatever interesting behaviour or phenotype each network mediates. These techniques are now being used in Drosophila to reprogram electrical activity of well-defined circuits and bring about robust and easily quantifiable changes in behaviour, allowing different models and hypotheses to be rapidly tested.

  8. Effective ATI channels in high harmonic generation

    Science.gov (United States)

    Kuchiev, M. Yu; Ostrovsky, V. N.

    2001-02-01

    Harmonic generation by an atom in a laser field is described by the three-step mechanism as proceeding via above-threshold ionization (ATI) followed by electron propagation in the laser-dressed continuum and subsequent laser-assisted recombination (LAR). The amplitude of the harmonic production is given by the coherent sum of contributions from different intermediate ATI channels labelled by the number, m, of absorbed laser photons. The range of m-values that give a substantial contribution is explored and found to be rather broad for high harmonic generation. The coherence effects are of crucial importance as they are responsible for the characteristic pattern of harmonic intensities with a plateau domain followed by a cut-off region. Due to the multiphoton nature of the process, an efficient summation of m-contributions can be carried out within the framework of the saddle-point method. The saddle points correspond to some complex-valued labels m = mc associated with the intermediate effective ATI channels in the three-step harmonic generation process. The advantage of this approach stems from the fact that summation over a large number of conventional ATI m-channels is replaced by summation over a small number of effective mc-channels. The equation governing mc has a transparent physical meaning: the electron ejected from the atom on the first (ATI) stage should return to the core to make LAR possible. The effective channel labels m move along characteristic trajectories in the complex plane as the system parameters vary. In the cut-off region of the harmonic spectrum a single effective channel contributes. For lower harmonics, in the plateau domain, two effective ATI channels become essential. The interference of their contributions leads to an oscillatory pattern in the harmonic generation rates. The calculated rates are in good agreement with the results obtained by other approaches.

  9. Channel morphology and flow structure of an abandoned channel under varying stages

    Science.gov (United States)

    Costigan, Katie H.; Gerken, Joseph E.

    2016-07-01

    Abandoned channels are those channels left behind as meandering rivers migrate over their floodplains and remain among the most enigmatic features of the riverscape, especially related to their hydraulics and geomorphology. Abandoned channels are being considered and implemented as restoration and rehabilitation strategies for large rivers but we do not yet have a sound understanding of their hydromorphodynamics. The overall objectives of this work were to assess the bed morphology and flow structure of a large, dynamically connected abandoned channel (e.g., the channel is inundated during annual or decadal floods through bank overflow) under varying stages. Here we document the hydromorphodynamics of an abandoned channel during 3.4, 9.2, and 37.9 return interval discharges using an acoustic Doppler current profiler. Flow separation was observed along the channel entrance during the lowest flow surveying campaign but was not seen during the higher flow campaign. Width to depth ratio and channel width at the exit both progressively decreased from the first surveying campaign, despite the final campaign having the highest measured discharge. Large zones of flow stagnation and recirculation were observed, with depth-averaged velocity vectors not aligning in one direction, in the abandoned channel where water from the entrance was meeting water coming up from the exit during moderate discharges. The abandoned channel has been maintained for at least 25 years due to its low diversion angle and it being perched above the Kansas River. Results of this study provide insights of how flow hydraulics and physical characteristics of abandoned channel change under varying stages.

  10. Optimization of bandwidth of communication channels of corporate networks

    Directory of Open Access Journals (Sweden)

    G. I. Bondarenko

    2014-09-01

    Full Text Available Introduction. This article contains overview of the organization of communication between applications on the corporate network. It is stated that the main digital channel (channel B - 64 kbit/s and the primary digital channel (channel E1 the digital stream - 2048 kbit/s are used as the main channels in corporate networks. Problem areas of the functioning of the corporate network are identified. There are the rent of communication channels, which is growing rapidly with increasing the quality and speed of data transmission, and optimal use of bandwidth of communication channels. Setting of task. Optimal use of transmission channels bandwidth and minimizing the rent cost of channels is possible in two ways - the use of compression techniques of voice and video information and the application of variable structure of channels by using various-speed transmission channels. Differential pulse code modulation, adaptive differential pulse code modulation are the modern methods of speech signals processing. Organization of various-speed channels is performed in the structure of the BCC (for speech signals or PCR (for video. Suggestions for optimizing the structure of the channel signals. Proposed method of various-speed channels formation by using the channel intervals appropriate BCC (octets in the structure of signals E1 as envelopes containing various-speed channels. Channels can be selected for synchronization procedure CRC to simplify recognition of channels in the structure of E1. In this case, the minimal speed in the channel is 4 kbit/s. Conclusions. The proposed structure of envelopes is based on octet channel intervals of standard group signal of the primary group plesiochronous hierarchy E1 when transferring various-speed digital signals maximum allows to use the bandwidth at a fixed structure of channel interval, it makes possible to agree on the structure of the various-speed signals with the existing in communication networks.

  11. Polyunsaturated fatty acids modify the gating of Kv channels

    Directory of Open Access Journals (Sweden)

    Cristina eMoreno

    2012-09-01

    Full Text Available Polyunsaturated fatty acids (PUFAs have been reported to exhibit antiarrhythmic properties, which are attributed to their capability to modulate ion channels. This PUFAs ability has been reported to be due to their effects on the gating properties of ion channels. In the present review, we will focus on the role of PUFAs on the gating of two Kv channels, Kv1.5 and Kv11.1. Kv1.5 channels are blocked by n-3 PUFAs of marine (docosahexaenoic and eicosapentaenoic acid, DHA and EPA and plant origin (alpha-linolenic acid, ALA at physiological concentrations. The blockade of Kv1.5 channels by PUFAs steeply increased in the range of membrane potentials coinciding with those of Kv1.5 channel activation, suggesting that PUFAs-channel binding may derive a significant fraction of its voltage sensitivity through the coupling to channel gating. A similar shift in the activation voltage was noted for the effects of arachidonic acid (AA and DHA on Kv1.1, Kv1.2, and Kv11.1 channels. PUFAs-Kv1.5 channel interaction is time-dependent, producing a fast decay of the current upon depolarization. Thus, Kv1.5 channel opening is a prerequisite for the PUFA-channel interaction. Similar to the Kv1.5 channels, the blockade of Kv11.1 channels by AA and DHA steeply increased in the range of membrane potentials that coincided with the range of Kv11.1 channel activation, suggesting that the PUFAs-Kv channel interactions are also coupled to channel gating. Furthermore, AA regulates the inactivation process in other Kv channels, introducing a fast voltage-dependent inactivation in non-inactivating Kv channels. These results have been explained within the framework that AA closes voltage-dependent potassium channels by inducing conformational changes in the selectivity filter, suggesting that Kv channel gating is lipid dependent.

  12. Conductance of Ion Channels - Theory vs. Experiment

    Science.gov (United States)

    Pohorille, Andrew; Wilson, Michael; Mijajlovic, Milan

    2013-01-01

    Transmembrane ion channels mediate a number of essential physiological processes in a cell ranging from regulating osmotic pressure to transmission of neural signals. Kinetics and selectivity of ion transport is of critical importance to a cell and, not surprisingly, it is a subject of numerous experimental and theoretical studies. In this presentation we will analyze in detail computer simulations of two simple channels from fungi - antiamoebin and trichotoxin. Each of these channels is made of an alpha-helical bundle of small, nongenomically synthesized peptides containing a number of rare amino acids and exhibits strong antimicrobial activity. We will focus on calculating ionic conductance defined as the ratio of ionic current through the channel to applied voltage. From molecular dynamics simulations, conductance can be calculated in at least two ways, each involving different approximations. Specifically, the current, given as the number of charges transferred through the channel per unit of time, can be obtained from the number of events in which ions cross the channel during the simulation. This method works well for large currents (high conductance values and/or applied voltages). If the number of crossing events is small, reliable estimates of current are difficult to achieve. Alternatively, conductance can be estimated assuming that ion transport can be well approximated as diffusion in the external potential given by the free energy profile. Then, the current can be calculated by solving the one-dimensional diffusion equation in this external potential and applied voltage (the generalized Nernst-Planck equation). To do so three ingredients are needed: the free energy profile, the position-dependent diffusion coefficient and the diffusive flux of ions into the channel. All these quantities can be obtained from molecular dynamics simulations. An important advantage of this method is that it can be used equally well to estimating large and small currents

  13. The branching channel network in the Yangtze Estuary

    NARCIS (Netherlands)

    Wang, Z.B.; Ding, P.X.

    2012-01-01

    The channels in the Yangtze Estuary have an ordered-branching structure: The estuary is first divided by the Chongming Island into the North Branch and the South Branch. Then the South Branch is divided into the North Channel and South Channel by the Islands Changxing and Hengsha. The South Channel

  14. INFORMATION CHARACTERIZATION OF COMMUNICATION CHANNELS FOR SYSTEM IDENTIFICATION

    Institute of Scientific and Technical Information of China (English)

    Le Yi WANG; G. George YIN

    2007-01-01

    This paper studies identification of systems in which the system output is quantized,transmitted through a digital communication channel, and observed afterwards. The concept of the CR Ratio is introduced to characterize impact of communication channels on identification. The relationship between the CR Ratio and Shannon channel capacity is discussed. Identification algorithms are further developed when the channel error probability is unknown.

  15. Rainwater Channelization and Infiltration in Granular Media

    Science.gov (United States)

    Cejas, Cesare; Wei, Yuli; Barrois, Remi; Durian, Douglas; Dreyfus, Remi; Compass Team

    2013-03-01

    We investigate the formation of fingered flow in dry granular media under simulated rainfall using a quasi-2D experimental set-up composed of a random close packing of mono-disperse glass beads. We determine effects of grain diameter and surface wetting properties on the formation and infiltration of water channels. For hydrophilic granular media, rainwater initially infiltrates a shallow top layer of soil creating a uniform horizontal wetting front before instabilities occur and grow to form water channels. For hydrophobic media, rainwater ponds on the soil surface rather than infiltrates and water channels may still occur at a later time when the hydraulic pressure of the ponding water exceeds the capillary repellency of the soil. We probe the kinetics of the fingering instabilities that serve as precursors for the growth and drainage of water channels. We also examine the effects of several different methods on improving rainwater channelization such as varying the level of pre-saturation, modifying the soil surface flatness, and adding superabsorbent hydrogel particles.

  16. The effect of search channel elimination on purchase incidence, order size and channel choice

    NARCIS (Netherlands)

    Konus, U.; Neslin, S.A.; Verhoef, P.C.

    2014-01-01

    This study investigates the impact of eliminating a search channel on purchase incidence, order size, channel choice and, ultimately, sales and profits. We analyze customer panel data from a large retailer over a five-year period. The retailer conducted a randomized field test in which the firm elim

  17. Channel Characteristics and Transmission Performance for Various Channel Configurations at 60 GHz

    Directory of Open Access Journals (Sweden)

    Haibing Yang

    2007-05-01

    Full Text Available Extensive measurements are conducted in room environments at 60 GHz to analyze the channel characteristics for various channel configurations. Channel parameters retrieved from measurements are presented and analyzed based on generic channel models. Particularly, a simple single-cluster model is applied for the parameter retrieval and performance evaluation. By this model, power delay profiles are simply described by a K-factor, a root-mean-squared delay spread, and a shape parameter. The considered channels are configured with the combination of omnidirectional, fan-beam, and pencil-beam antennas at transmitter and receiver sides. Both line-of-sight (LOS and non-LOS (NLOS channels are considered. Further, to evaluate the transmission performance, we analyze the link budget in the considered environments, then design and simulate an OFDM system with a data rate of 2 Gbps to compare the bit-error-rate (BER performance by using the measured and modeled channels. Both coded and uncoded OFDM systems are simulated. It is observed that the BER performance agrees well for the measured and modeled channels. In addition, directive configurations can provide sufficient link margins and BER performance for high data rate communications. To increase the coverage and performance in the NLOS area, it is preferable to apply directive antennas.

  18. Channel erosion in a rapidly urbanizing region of Tijuana, Mexico: Enlargement downstream of channel hardpoints

    Science.gov (United States)

    Taniguchi, Kristine; Biggs, Trent; Langendoen, Eddy; Castillo, Carlos; Gudiño, Napoleon; Yuan, Yongping; Liden, Douglas

    2016-04-01

    Urban-induced erosion in Tijuana, Mexico, has led to excessive sediment deposition in the Tijuana Estuary in the United States. Urban areas in developing countries, in contrast to developed countries, are characterized by much lower proportions of vegetation and impervious surfaces due to limited access to urban services such as road paving and landscaping, and larger proportions of exposed soils. In developing countries, traditional watershed scale variables such as impervious surfaces may not be good predictors of channel enlargement. In this research, we surveyed the stream channel network of an erodible tributary of the Tijuana River Watershed, Los Laureles Canyon, at 125 locations, including repeat surveys from 2008. Structure from Motion (SfM) and 3D photo-reconstruction techniques were used to create digital terrain models of stream reaches upstream and downstream of channel hardpoints. Channels are unstable downstream of hardpoints, with incision up to 2 meters and widening up to 12 meters. Coordinated channelization is essential to avoid piece-meal approaches that lead to channel degradation. Watershed impervious area is not a good predictor of channel erosion due to the overriding importance of hardpoints and likely to the high sediment supply from the unpaved roads which prevents channel erosion throughout the stream network.

  19. Channel Norm-Based User Scheduling Exploiting Channel Asymmetry in Base Station Cooperative Transmission Systems

    CERN Document Server

    Han, Shengqian; Bengtsson, Mats

    2010-01-01

    Base station cooperative transmission, which is also known as coordinated multi-point (CoMP) transmission, is a promising technique to improve spectrum efficiency in future cellular systems. However, they need large signalling overhead to gather the channel information. In this paper, we consider low feedback user scheduling in downlink coherent CoMP systems exploiting their inherent channel asymmetry. Through the analysis of the statistics of the angle between channel vectors and the tightness of a lower bound of the orthogonally projected norm, we show that channel norm provides sufficient information to judge the orthogonality among users in asymmetric channels. Based on this observation, we propose a channel norm-based user scheduler (NUS), a local channel aided NUS (LocalNUS) and a large-scale fading-based user scheduler (LUS). Simulation results show that the LocalNUS performs very close to the existing greedy user scheduler (GUS) and semi-orthogonal user scheduler (SUS) with full channel state informat...

  20. Customer Responses to Channel Migration Strategies Toward the E-channel

    NARCIS (Netherlands)

    Trampe, Debra; Konus, Umut; Verhoef, Peter C.

    2014-01-01

    Many firms stimulate customers to use the E-channel for services, which provokes various consumer responses to such limits on their freedom of choice. In a study on bank customers, we examine the extent of customer reactance in response to various E-channel migration strategies, the potential of inc

  1. Movements of native C505 during channel gating in CNGA1 channels.

    NARCIS (Netherlands)

    Nair, A.V.; Anselmi, C.; Mazzolini, M.

    2009-01-01

    We investigated conformational changes occurring in the C-linker and cyclic nucleotide-binding (CNB) domain of CNGA1 channels by analyzing the inhibition induced by thiol-specific reagents in mutant channels Q409C and A414C in the open and closed state. Cd(2+) (200 microM) inhibited irreversibly mut

  2. Channel Characteristics and Transmission Performance for Various Channel Configurations at 60 GHz

    Directory of Open Access Journals (Sweden)

    Yang Haibing

    2007-01-01

    Full Text Available Extensive measurements are conducted in room environments at 60 GHz to analyze the channel characteristics for various channel configurations. Channel parameters retrieved from measurements are presented and analyzed based on generic channel models. Particularly, a simple single-cluster model is applied for the parameter retrieval and performance evaluation. By this model, power delay profiles are simply described by a -factor, a root-mean-squared delay spread, and a shape parameter. The considered channels are configured with the combination of omnidirectional, fan-beam, and pencil-beam antennas at transmitter and receiver sides. Both line-of-sight (LOS and non-LOS (NLOS channels are considered. Further, to evaluate the transmission performance, we analyze the link budget in the considered environments, then design and simulate an OFDM system with a data rate of 2 Gbps to compare the bit-error-rate (BER performance by using the measured and modeled channels. Both coded and uncoded OFDM systems are simulated. It is observed that the BER performance agrees well for the measured and modeled channels. In addition, directive configurations can provide sufficient link margins and BER performance for high data rate communications. To increase the coverage and performance in the NLOS area, it is preferable to apply directive antennas.

  3. Performance Evaluation of channel estimation in TD-SCDMA system

    Directory of Open Access Journals (Sweden)

    Rashmi Mishra

    2012-09-01

    Full Text Available In previous B. Steiner channel estimation algorithm adopted in TD-SCDMA system, but there are some errors in estimated channel due to noise. In this paper, we evaluate the performance of Time Division-Synchronous Code Division Multiple Access (TD-SCDMA systems with channel estimation. In channel estimation we implement the channel estimation algorithm to equalize the channel and reduce the BER in the received signal. The Channel estimation is carried out at the receiver. In TDSCDMA, the uplink and downlink transmissions use the same frequency band for duplex transmission by using synchronized time intervals. The simulation result shows that the system performance is effectively increased.

  4. Channel estimation for MIMO-OFDM systems in wireless mobile channels

    Institute of Scientific and Technical Information of China (English)

    Lu Zhen; Ge Jianhua

    2008-01-01

    New training sequences and frame structure are proposed to estimate time-varying channel for multiple-input multiple-output and orthogonal frequency division multiplexing (MIMO-OFDM) systems. The training sequences are modulatable orthogonal polyphase sequences, which have both good autocorrelations and cross-correlations. The channel impulse response (CIR) can be obtained by measuring the correlation between the received training sequence and the locally generated training sequence. The training sequences are used as guard interval instead of cyclic prefix, which not only improve the transmission efficiency but also enable the channel estimator to track time-varying channel. The simulation results show that the proposed method has about 2dB SNR gain over conventional methods in fast time-varying channel.

  5. On the capacity of Rician fading channels with full channel state information at low SNR

    KAUST Repository

    Rezki, Zouheir

    2012-06-01

    The capacity of flat Rayleigh fading channels with full channel state information (CSI) at the transmitter and at the receiver at asymptotically low SNR has been recently shown to scale essentially as SNR log (1/SNR). In this paper, we investigate the Rician fading channel capacity with full CSI, and show that the capacity of this channel scales essentially as 1/1+K SNR log (1 /SNR), where K is the Rician factor. This characterization includes perfect CSI at both the transmitter and the receiver or noisy CSI at the transmitter and perfect CSI at the receiver. We also show that one-bit CSI at the transmitter is enough to achieve this asymptotic capacity using an On-Off power control scheme. Our framework may be seen as a generalization of previous works as it captures the Rayleigh fading channel as a special case by letting K goes to zero. © 2012 IEEE.

  6. Comparison of proton irradiated P-channel and N-channel CCDs

    Energy Technology Data Exchange (ETDEWEB)

    Gow, Jason P.D., E-mail: j.p.d.gow@open.ac.uk [e2v Centre for Electronic Imaging, Planetary and Space Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Murray, Neil J.; Holland, Andrew D. [e2v Centre for Electronic Imaging, Planetary and Space Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Burt, David; Pool, Peter J. [e2v Technologies plc, 106 Waterhouse Lance, Chelmsford, Essex CM1 2QU (United Kingdom)

    2012-09-11

    Charge transfer inefficiency and dark current effects are compared for e2v Technologies plc p-channel and n-channel CCDs, both irradiated with protons. The p-channel devices, prior to their irradiation, exhibited twice the dark current and considerable worse charge transfer inefficiency (CTI) than a typical n-channel. The radiation induced increase in dark current was found to be comparable with n-channel CCDs, and its temperature dependence suggest that the divacancy is the dominant source of thermally generated dark current pre- and post-irradiation. The factor of improvement in tolerance to radiation induced CTI varied by between 15 and 25 for serial CTI and 8 and 3 for parallel CTI, between -70 Degree-Sign C and -110 Degree-Sign C, respectively.

  7. Long Channel Carbon Nanotube as an Alternative to Nanoscale Silicon Channels in Scaled MOSFETs

    Directory of Open Access Journals (Sweden)

    Michael Loong Peng Tan

    2013-01-01

    Full Text Available Long channel carbon nanotube transistor (CNT can be used to overcome the high electric field effects in nanoscale length silicon channel. When maximum electric field is reduced, the gate of a field-effect transistor (FET is able to gain control of the channel at varying drain bias. The device performance of a zigzag CNTFET with the same unit area as a nanoscale silicon metal-oxide semiconductor field-effect transistor (MOSFET channel is assessed qualitatively. The drain characteristic of CNTFET and MOSFET device models as well as fabricated CNTFET device are explored over a wide range of drain and gate biases. The results obtained show that long channel nanotubes can significantly reduce the drain-induced barrier lowering (DIBL effects in silicon MOSFET while sustaining the same unit area at higher current density.

  8. Insight toward epithelial Na+ channel mechanism revealed by the acid-sensing ion channel 1 structure.

    Science.gov (United States)

    Stockand, James D; Staruschenko, Alexander; Pochynyuk, Oleh; Booth, Rachell E; Silverthorn, Dee U

    2008-09-01

    The epithelial Na(+) channel/degenerin (ENaC/DEG) protein family includes a diverse group of ion channels, including nonvoltage-gated Na(+) channels of epithelia and neurons, and the acid-sensing ion channel 1 (ASIC1). In mammalian epithelia, ENaC helps regulate Na(+) and associated water transport, making it a critical determinant of systemic blood pressure and pulmonary mucosal fluidity. In the nervous system, ENaC/DEG proteins are related to sensory transduction. While the importance and physiological function of these ion channels are established, less is known about their structure. One hallmark of the ENaC/DEG channel family is that each channel subunit has only two transmembrane domains connected by an exceedingly large extracellular loop. This subunit structure was recently confirmed when Jasti and colleagues determined the crystal structure of chicken ASIC1, a neuronal acid-sensing ENaC/DEG channel. By mapping ENaC to the structural coordinates of cASIC1, as we do here, we hope to provide insight toward ENaC structure. ENaC, like ASIC1, appears to be a trimeric channel containing 1alpha, 1beta, and 1gamma subunit. Heterotrimeric ENaC and monomeric ENaC subunits within the trimer possibly contain many of the major secondary, tertiary, and quaternary features identified in cASIC1 with a few subtle but critical differences. These differences are expected to have profound effects on channel behavior. In particular, they may contribute to ENaC insensitivity to acid and to its constitutive activity in the absence of time- and ligand-dependent inactivation. Experiments resulting from this comparison of cASIC1 and ENaC may help clarify unresolved issues related to ENaC architecture, and may help identify secondary structures and residues critical to ENaC function.

  9. Understanding Sodium Channel Function and Modulation Using Atomistic Simulations of Bacterial Channel Structures.

    Science.gov (United States)

    Boiteux, C; Allen, T W

    2016-01-01

    Sodium channels are chief proteins involved in electrical signaling in the nervous system, enabling critical functions like heartbeat and brain activity. New high-resolution X-ray structures for bacterial sodium channels have created an opportunity to see how these proteins operate at the molecular level. An important challenge to overcome is establishing relationships between the structures and functions of mammalian and bacterial channels. Bacterial sodium channels are known to exhibit the main structural features of their mammalian counterparts, as well as several key functional characteristics, including selective ion conduction, voltage-dependent gating, pore-based inactivation and modulation by local anesthetic, antiarrhythmic and antiepileptic drugs. Simulations have begun to shed light on each of these features in the past few years. Despite deviations in selectivity signatures for bacterial and mammalian channels, simulations have uncovered the nature of the multiion conduction mechanism associated with Na(+) binding to a high-field strength site established by charged glutamate side chains. Simulations demonstrated a surprising level of flexibility of the protein, showing that these side chains are active participants in the permeation process. They have also uncovered changes in protein structure, leading to asymmetrical collapses of the activation gate that have been proposed to correspond to inactivated structures. These observations offer the potential to examine the mechanisms of state-dependent drug activity, focusing on pore-blocking and pore-based slow inactivation in bacterial channels, without the complexities of inactivation on multiple timescales seen in eukaryotic channels. Simulations have provided molecular views of the interactions of drugs, consistent with sites predicted in mammalian channels, as well as a wealth of other sites as potential new drug targets. In this chapter, we survey the new insights into sodium channel function that

  10. Channel changes downstream from a dam

    Science.gov (United States)

    Hadley, R.F.; Emmett, W.W.

    1998-01-01

    A flood-control dam was completed during 1979 on Bear Creek, a small tributary stream to the South Platte River in the Denver, Colorado, area. Before and after dam closure, repetitive surveys between 1977 and 1992 at five cross sections downstream of the dam documented changes in channel morphology. During this 15-year period, channel width increased slightly, but channel depth increased by more than 40 percent. Within the study reach, stream gradient decreased and median bed material sizes coarsened from sand in the pools and fine gravel on the riffle to a median coarse gravel throughout the reach. The most striking visual change was from a sparse growth of streamside grasses to a dense growth of riparian woody vegetation.

  11. Interannual variability in the Yucatan Channel flow

    Science.gov (United States)

    Athié, Gabriela; Sheinbaum, Julio; Leben, Robert; Ochoa, José; Shannon, Michael R.; Candela, Julio

    2015-03-01

    Mooring measurements in the Yucatan Channel, from May 2010 to May 2011 and from July 2012 to June 2013 yield a mean transport of 27 and 25 Sv, respectively, with a subinertial standard deviation of 3.5 Sv. These mean transport values are higher than the 23 Sv reported from 21 months of similar measurements (1999-2001). Analysis of low-frequency variations of a transport proxy based on 20 years of altimetry data indicates that during 1999-2001, the flow through Yucatan Channel was anomalously low. This suggests that a sizable compensation through other channels off the Gulf of Mexico is required to match the transport cable measurements of the Florida Current at 27°N.

  12. Capacity Bounds for Parallel Optical Wireless Channels

    KAUST Repository

    Chaaban, Anas

    2016-01-01

    A system consisting of parallel optical wireless channels with a total average intensity constraint is studied. Capacity upper and lower bounds for this system are derived. Under perfect channel-state information at the transmitter (CSIT), the bounds have to be optimized with respect to the power allocation over the parallel channels. The optimization of the lower bound is non-convex, however, the KKT conditions can be used to find a list of possible solutions one of which is optimal. The optimal solution can then be found by an exhaustive search algorithm, which is computationally expensive. To overcome this, we propose low-complexity power allocation algorithms which are nearly optimal. The optimized capacity lower bound nearly coincides with the capacity at high SNR. Without CSIT, our capacity bounds lead to upper and lower bounds on the outage probability. The outage probability bounds meet at high SNR. The system with average and peak intensity constraints is also discussed.

  13. 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...... to be a versatile but yet very simple module producing high-speed and high-efficiency plasma separation. The resulting lab-on-a-chip is manufactured using biocompatible materials. Purity efficiency is measured for mussel and human blood suspensions as different parameters, such as flow rate and geometries...... of the parent and daughter channels are varied. The issues of blood plasma separation at the microscale are discussed in relation to the different regimes of flow. Results are compared with those obtained by other researchers in the field of micro-separation of blood....

  14. The earliest ion channels in protocellular membranes

    Science.gov (United States)

    Mijajlovic, Milan; Pohorille, Andrew; Wilson, Michael; Wei, Chenyu

    Cellular membranes with their hydrophobic interior are virtually impermeable to ions. Bulk of ion transport through them is enabled through ion channels. Ion channels of contemporary cells are complex protein molecules which span the membrane creating a cylindrical pore filled with water. Protocells, which are widely regarded as precursors to modern cells, had similarly impermeable membranes, but the set of proteins in their disposal was much simpler and more limited. We have been, therefore, exploring an idea that the first ion channels in protocellular membranes were formed by much smaller peptide molecules that could spontaneously self-assemble into short-lived cylindrical bundles in a membrane. Earlier studies have shown that a group of peptides known as peptaibols is capable of forming ion channels in lipid bilayers when they are exposed to an electric field. Peptaibols are small, non-genetically encoded peptides produced by some fungi as a part of their system of defense against bacteria. They are usually only 14-20 residues long, which is just enough to span the membrane. Their sequence is characterized by the presence of non-standard amino acids which, interestingly, are also expected to have existed on the early earth. In particular, the presence of 2-aminoisobutyric acid (AIB) gives peptaibols strong helix forming propensities. Association of the helices inside membranes leads to the formation of cylindrical bundles, typically containing 4 to 10 monomers. Although peptaibols are excellent candidates for models of the earliest ion channels their struc-tures, which are stabilized only by van der Waals forces and occasional hydrogen bonds between neighboring helices, are not very stable. Although it might properly reflect protobiological real-ity, it is also a major obstacle in studying channel behavior. For this reason we focused on two members of the peptaibol family, trichotoxin and antiamoebin, which are characterized by a single conductance level. This

  15. Cohering and decohering power of quantum channels

    Science.gov (United States)

    Mani, Azam; Karimipour, Vahid

    2015-09-01

    We introduce the concepts of cohering and decohering power of quantum channels. Using the axiomatic definition of the coherence measure, we show that the optimization required for calculations of these measures can be restricted to pure input states and hence greatly simplified. We then use two examples of this measure, one based on the skew information and the other based on the l1 norm; we find the cohering and decohering measures of a number of one-, two-, and n -qubit channels. Contrary to the view at first glance, it is seen that quantum channels can have cohering power. It is also shown that a specific property of a qubit unitary map is that it has equal cohering and decohering power in any basis. Finally, we derive simple relations between cohering and decohering powers of unitary qubit gates and their tensor products, results which have physically interesting implications.

  16. Mixed convection in a baffled grooved channel

    Indian Academy of Sciences (India)

    Aayush K Sharma; Pallab S Mahapatra; Nirmal K Manna; Koushik Ghosh

    2015-05-01

    In the present numerical work, flow structure and heat transfer characteristics are investigated in a baffled grooved channel, differentially heated from the sides. The baffle is placed vertically downward from the top wall of grooved channel geometry, with the motive of diverting outside forced flow towards the inside of the square cavity. In-house CFD code based on finite volume method has been used to solve the 2D equations of continuity, momentum and energy. The effect of change in baffle position and height is investigated in the range of Richardson numbers 0.1 to 10. For the present study, external flow from both left and right of the grooved channel are considered. A remarkable enhancement of heat transfer is observed in presence of baffle. The study has also pointed out that for optimal performance, the position and height of the baffle need to be adjusted depending on the direction of external flow.

  17. Blind estimation of shallow water acoustic channel

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    This paper proposed a method for blind estimation of underwater channels in shallow water environment by using received data at a single hydrophone or from single beam.First, the received signal is used for source signal reconstruction by means of signal-dependent TF (Time-Frequency) distribution, in association with instantaneous frequency estimation and TF inversion. Then the shallow-water channel estimation is achieved via WRELAX technique by use of the received signal and the estimated source signal. Finally, the results of numerical simulation and experimental test from real data taken in South China Sea trial have proved satisfactory. It is shown that the proposed method is useful for underwater channel estimation.

  18. Potassium channels in pulmonary arterial hypertension.

    Science.gov (United States)

    Boucherat, Olivier; Chabot, Sophie; Antigny, Fabrice; Perros, Frédéric; Provencher, Steeve; Bonnet, Sébastien

    2015-10-01

    Pulmonary arterial hypertension (PAH) is a devastating cardiopulmonary disorder with various origins. All forms of PAH share a common pulmonary arteriopathy characterised by vasoconstriction, remodelling of the pre-capillary pulmonary vessel wall, and in situ thrombosis. Although the pathogenesis of PAH is recognised as a complex and multifactorial process, there is growing evidence that potassium channels dysfunction in pulmonary artery smooth muscle cells is a hallmark of PAH. Besides regulating many physiological functions, reduced potassium channels expression and/or activity have significant effects on PAH establishment and progression. This review describes the molecular mechanisms and physiological consequences of potassium channel modulation. Special emphasis is placed on KCNA5 (Kv1.5) and KCNK3 (TASK1), which are considered to play a central role in determining pulmonary vascular tone and may represent attractive therapeutic targets in the treatment of PAH. PMID:26341985

  19. Secure quantum communication using classical correlated channel

    Science.gov (United States)

    Costa, D.; de Almeida, N. G.; Villas-Boas, C. J.

    2016-10-01

    We propose a secure protocol to send quantum information from one part to another without a quantum channel. In our protocol, which resembles quantum teleportation, a sender (Alice) and a receiver (Bob) share classical correlated states instead of EPR ones, with Alice performing measurements in two different bases and then communicating her results to Bob through a classical channel. Our secure quantum communication protocol requires the same amount of classical bits as the standard quantum teleportation protocol. In our scheme, as in the usual quantum teleportation protocol, once the classical channel is established in a secure way, a spy (Eve) will never be able to recover the information of the unknown quantum state, even if she is aware of Alice's measurement results. Security, advantages, and limitations of our protocol are discussed and compared with the standard quantum teleportation protocol.

  20. Effective capacity of correlated MISO channels

    KAUST Repository

    Zhong, Caijun

    2011-06-01

    This paper presents an analytical performance investigation of the capacity limits of correlated multiple-input single-output (MISO) channels in the presence of quality-of-service (QoS) requirements. Exact closed-form expression for the effective capacity of correlated MISO channels is derived. In addition, simple expressions are obtained at the asymptotic high and low signal-to-noise ratio (SNR) regimes, which provide insights into the impact of various system parameters on the effective capacity of the system. Also, a complete characterization of the impact of spatial correlation on the effective capacity is provided with the aid of a majorization theory result. The findings suggest that antenna correlation reduce the effective capacity of the channels. Moreover, a stringent QoS requirement causes a significant reduction in the effective capacity but this can be effectively alleviated by increasing the number of antennas. © 2011 IEEE.

  1. Mechanosensor Channels in Mammalian Somatosensory Neurons

    Directory of Open Access Journals (Sweden)

    Patrick Delmas

    2007-09-01

    Full Text Available Mechanoreceptive sensory neurons innervating the skin, skeletal muscles andviscera signal both innocuous and noxious information necessary for proprioception, touchand pain. These neurons are responsible for the transduction of mechanical stimuli intoaction potentials that propagate to the central nervous system. The ability of these cells todetect mechanical stimuli impinging on them relies on the presence of mechanosensitivechannels that transduce the external mechanical forces into electrical and chemical signals.Although a great deal of information regarding the molecular and biophysical properties ofmechanosensitive channels in prokaryotes has been accumulated over the past two decades,less is known about the mechanosensitive channels necessary for proprioception and thesenses of touch and pain. This review summarizes the most pertinent data onmechanosensitive channels of mammalian somatosensory neurons, focusing on theirproperties, pharmacology and putative identity.

  2. Secure quantum communication using classical correlated channel

    Science.gov (United States)

    Costa, D.; de Almeida, N. G.; Villas-Boas, C. J.

    2016-07-01

    We propose a secure protocol to send quantum information from one part to another without a quantum channel. In our protocol, which resembles quantum teleportation, a sender (Alice) and a receiver (Bob) share classical correlated states instead of EPR ones, with Alice performing measurements in two different bases and then communicating her results to Bob through a classical channel. Our secure quantum communication protocol requires the same amount of classical bits as the standard quantum teleportation protocol. In our scheme, as in the usual quantum teleportation protocol, once the classical channel is established in a secure way, a spy (Eve) will never be able to recover the information of the unknown quantum state, even if she is aware of Alice's measurement results. Security, advantages, and limitations of our protocol are discussed and compared with the standard quantum teleportation protocol.

  3. Roles and Regulation of Renal K Channels.

    Science.gov (United States)

    Welling, Paul A

    2016-01-01

    More than two dozen types of potassium channels, with different biophysical and regulatory properties, are expressed in the kidney, influencing renal function in many important ways. Recently, a confluence of discoveries in areas from human genetics to physiology, cell biology, and biophysics has cast light on the special function of five different potassium channels in the distal nephron, encoded by the genes KCNJ1, KCNJ10, KCNJ16, KCNMA1, and KCNN3. Research aimed at understanding how these channels work in health and go awry in disease has transformed our understanding of potassium balance and provided new insights into mechanisms of renal sodium handling and the maintenance of blood pressure. This review focuses on recent advances in this rapidly evolving field. PMID:26654186

  4. Enzyme clustering can induce metabolic channeling

    Science.gov (United States)

    Castellana, Michele

    2015-03-01

    Direct channeling of intermediates via a physical tunnel between enzyme active sites is an established mechanism to improve metabolic efficiency. In this talk, I will present a theoretical model that demonstrates that coclustering multiple enzymes into proximity can yield the full efficiency benefits of direct channeling. The model predicts the separation and size of coclusters that maximize metabolic efficiency, and this prediction is in agreement with the spacing between coclusters in yeast and mammalian cells. The model also predicts that enzyme agglomerates can regulate steady-state flux division at metabolic branch points: we experimentally test this prediction for a fundamental branch point in Escherichia coli, and the results confirm that enzyme colocalization within an agglomerate can accelerate the processing of a shared intermediate by one branch. Our studies establish a quantitative framework to understand coclustering-mediated metabolic channeling and its application to both efficiency improvement and metabolic regulation.

  5. Majorization preservation of Gaussian bosonic channels

    Science.gov (United States)

    Jabbour, Michael G.; García-Patrón, Raúl; Cerf, Nicolas J.

    2016-07-01

    It is shown that phase-insensitive Gaussian bosonic channels are majorization-preserving over the set of passive states of the harmonic oscillator. This means that comparable passive states under majorization are transformed into equally comparable passive states by any phase-insensitive Gaussian bosonic channel. Our proof relies on a new preorder relation called Fock-majorization, which coincides with regular majorization for passive states but also induces another order relation in terms of mean boson number, thereby connecting the concepts of energy and disorder of a quantum state. The consequences of majorization preservation are discussed in the context of the broadcast communication capacity of Gaussian bosonic channels. Because most of our results are independent of the specific nature of the system under investigation, they could be generalized to other quantum systems and Hamiltonians, providing a new tool that may prove useful in quantum information theory and especially quantum thermodynamics.

  6. Ion fluxes through nanopores and transmembrane channels

    Science.gov (United States)

    Bordin, J. R.; Diehl, A.; Barbosa, M. C.; Levin, Y.

    2012-03-01

    We introduce an implicit solvent Molecular Dynamics approach for calculating ionic fluxes through narrow nanopores and transmembrane channels. The method relies on a dual-control-volume grand-canonical molecular dynamics (DCV-GCMD) simulation and the analytical solution for the electrostatic potential inside a cylindrical nanopore recently obtained by Levin [Europhys. Lett.EULEEJ0295-507510.1209/epl/i2006-10240-4 76, 163 (2006)]. The theory is used to calculate the ionic fluxes through an artificial transmembrane channel which mimics the antibacterial gramicidin A channel. Both current-voltage and current-concentration relations are calculated under various experimental conditions. We show that our results are comparable to the characteristics associated to the gramicidin A pore, especially the existence of two binding sites inside the pore and the observed saturation in the current-concentration profiles.

  7. The Earliest Ion Channels in Protocellular Membranes

    Science.gov (United States)

    Mijajlovic, Milan; Pohorille, Andrew; Wilson, Michael; Wei, Chenyu

    2010-01-01

    Cellular membranes with their hydrophobic interior are virtually impermeable to ions. Bulk of ion transport through them is enabled through ion channels. Ion channels of contemporary cells are complex protein molecules which span the membrane creating a cylindrical pore filled with water. Protocells, which are widely regarded as precursors to modern cells, had similarly impermeable membranes, but the set of proteins in their disposal was much simpler and more limited. We have been, therefore, exploring an idea that the first ion channels in protocellular membranes were formed by much smaller peptide molecules that could spontaneously selfassemble into short-lived cylindrical bundles in a membrane. Earlier studies have shown that a group of peptides known as peptaibols is capable of forming ion channels in lipid bilayers when they are exposed to an electric field. Peptaibols are small, non-genetically encoded peptides produced by some fungi as a part of their system of defense against bacteria. They are usually only 14-20 residues long, which is just enough to span the membrane. Their sequence is characterized by the presence of non-standard amino acids which, interestingly, are also expected to have existed on the early earth. In particular, the presence of 2-aminoisobutyric acid (AIB) gives peptaibols strong helix forming propensities. Association of the helices inside membranes leads to the formation of cylindrical bundles, typically containing 4 to 10 monomers. Although peptaibols are excellent candidates for models of the earliest ion channels their structures, which are stabilized only by van der Waals forces and occasional hydrogen bonds between neighboring helices, are not very stable. Although it might properly reflect protobiological reality, it is also a major obstacle in studying channel behavior. For this reason we focused on two members of the peptaibol family, trichotoxin and antiamoebin, which are characterized by a single conductance level. This

  8. Bayesian Inference Methods for Sparse Channel Estimation

    DEFF Research Database (Denmark)

    Pedersen, Niels Lovmand

    2013-01-01

    This thesis deals with sparse Bayesian learning (SBL) with application to radio channel estimation. As opposed to the classical approach for sparse signal representation, we focus on the problem of inferring complex signals. Our investigations within SBL constitute the basis for the development...... complex prior representation achieve improved sparsity representations in low signalto- noise ratio as opposed to state-of-the-art sparse estimators. This result is of particular importance for the applicability of the algorithms in the field of channel estimation. We then derive various iterative...... and computational complexity. We also analyze the impact of transceiver filters on the sparseness of the channel response, and propose a dictionary design that permits the deployment of sparse inference methods in conditions of low bandwidth....

  9. Role of Tryptophan Residues in Gramicidin Channel Organization and Function

    OpenAIRE

    Chattopadhyay, Amitabha; RAWAT, SATINDER S.; Greathouse, Denise V.; Kelkar, Devaki A.; Koeppe, Roger E.

    2008-01-01

    The linear peptide gramicidin forms prototypical ion channels specific for monovalent cations and has been used extensively to study the organization, dynamics, and function of membrane-spanning channels. The tryptophan residues in gramicidin channels are crucial for maintaining the structure and function of the channel. We explored the structural basis for the reduction in channel conductance in the case of single-tryptophan analogs of gramicidin with three Trp → hydrophobic substitutions us...

  10. Protein kinase CK2 is coassembled with small conductance Ca(2+)-activated K+ channels and regulates channel gating

    DEFF Research Database (Denmark)

    Bildl, Wolfgang; Strassmaier, Tim; Thurm, Henrike;

    2004-01-01

    Small conductance Ca(2+)-activated K+ channels (SK channels) couple the membrane potential to fluctuations in intracellular Ca2+ concentration in many types of cells. SK channels are gated by Ca2+ ions via calmodulin that is constitutively bound to the intracellular C terminus of the channels and...

  11. Channel properties of Nax expressed in neurons.

    Directory of Open Access Journals (Sweden)

    Masahito Matsumoto

    Full Text Available Nax is a sodium-concentration ([Na+]-sensitive Na channel with a gating threshold of ~150 mM for extracellular [Na+] ([Na+]o in vitro. We previously reported that Nax was preferentially expressed in the glial cells of sensory circumventricular organs including the subfornical organ, and was involved in [Na+] sensing for the control of salt-intake behavior. Although Nax was also suggested to be expressed in the neurons of some brain regions including the amygdala and cerebral cortex, the channel properties of Nax have not yet been adequately characterized in neurons. We herein verified that Nax was expressed in neurons in the lateral amygdala of mice using an antibody that was newly generated against mouse Nax. To investigate the channel properties of Nax expressed in neurons, we established an inducible cell line of Nax using the mouse neuroblastoma cell line, Neuro-2a, which is endogenously devoid of the expression of Nax. Functional analyses of this cell line revealed that the [Na+]-sensitivity of Nax in neuronal cells was similar to that expressed in glial cells. The cation selectivity sequence of the Nax channel in cations was revealed to be Na+ ≈ Li+ > Rb+ > Cs+ for the first time. Furthermore, we demonstrated that Nax bound to postsynaptic density protein 95 (PSD95 through its PSD95/Disc-large/ZO-1 (PDZ-binding motif at the C-terminus in neurons. The interaction between Nax and PSD95 may be involved in promoting the surface expression of Nax channels because the depletion of endogenous PSD95 resulted in a decrease in Nax at the plasma membrane. These results indicated, for the first time, that Nax functions as a [Na+]-sensitive Na channel in neurons as well as in glial cells.

  12. Advanced Concepts for Underwater Acoustic Channel Modeling

    Science.gov (United States)

    Etter, P. C.; Haas, C. H.; Ramani, D. V.

    2014-12-01

    This paper examines nearshore underwater-acoustic channel modeling concepts and compares channel-state information requirements against existing modeling capabilities. This process defines a subset of candidate acoustic models suitable for simulating signal propagation in underwater communications. Underwater-acoustic communications find many practical applications in coastal oceanography, and networking is the enabling technology for these applications. Such networks can be formed by establishing two-way acoustic links between autonomous underwater vehicles and moored oceanographic sensors. These networks can be connected to a surface unit for further data transfer to ships, satellites, or shore stations via a radio-frequency link. This configuration establishes an interactive environment in which researchers can extract real-time data from multiple, but distant, underwater instruments. After evaluating the obtained data, control messages can be sent back to individual instruments to adapt the networks to changing situations. Underwater networks can also be used to increase the operating ranges of autonomous underwater vehicles by hopping the control and data messages through networks that cover large areas. A model of the ocean medium between acoustic sources and receivers is called a channel model. In an oceanic channel, characteristics of the acoustic signals change as they travel from transmitters to receivers. These characteristics depend upon the acoustic frequency, the distances between sources and receivers, the paths followed by the signals, and the prevailing ocean environment in the vicinity of the paths. Properties of the received signals can be derived from those of the transmitted signals using these channel models. This study concludes that ray-theory models are best suited to the simulation of acoustic signal propagation in oceanic channels and identifies 33 such models that are eligible candidates.

  13. Inhibiting bacterial toxins by channel blockage.

    Science.gov (United States)

    Bezrukov, Sergey M; Nestorovich, Ekaterina M

    2016-03-01

    Emergent rational drug design techniques explore individual properties of target biomolecules, small and macromolecule drug candidates, and the physical forces governing their interactions. In this minireview, we focus on the single-molecule biophysical studies of channel-forming bacterial toxins that suggest new approaches for their inhibition. We discuss several examples of blockage of bacterial pore-forming and AB-type toxins by the tailor-made compounds. In the concluding remarks, the most effective rationally designed pore-blocking antitoxins are compared with the small-molecule inhibitors of ion-selective channels of neurophysiology.

  14. Market and Marketing Peculiarities of Vending Channels

    OpenAIRE

    Dobromir Stoyanov

    2014-01-01

    In recent years there has been an ever-increasing rise in the importance of non-store distribution formats as a cost-effective, as well as providing considerable consumer convenience alternative to the traditional store forms. The subject of the present article are the high-tech vending channels as a typical representative of this fast developing type of distribution. The main aim of the present article is to analyse the market and marketing specifics of vending channels. In this connection t...

  15. REVIEW OF REGIME THEORY OF ALLUVIAL CHANNELS

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    One of the most important problems in river engineering is to determine a stable cross section geomenry and slope for an alluvial channel. This has been the subject of considerable research for about a century and continues to be of great practical interest. Lgnoring plan geometry, an alluvi-al channel can adjust its slope, depth and width, to develop a dynamic stable condition in which it can transport a certain a-mount of water and sediment. The brief history of regime the-ory and its new development are reviewed in this paper.

  16. Fading channel issues in system engineering

    Science.gov (United States)

    Stein, Seymour

    1987-02-01

    The character of multipath-induced propagational fading is reviewed, along with the interpretations underlying use of the Rayleigh fading model to describe the process statistics. The relationship between this model and contemporary laboratory fading simulators is also outlined. The effects of the fading upon data communications are described, along with the techniques of modulation, diversity, coding, and adaptive equalization used in modern modem designs for operation over such channels. Finally, the system engineering problems are discussed of attempting to provide quantitative estimates of long-term link or network performance that takes into account the longer term channel variabilities.

  17. Experimental testbed for seawater channel characterization

    CERN Document Server

    Mena, Pablo; Quintana, Gara; Pérez-Álvarez, Iván; Jiménez, Eugenio; Zazo, Santiago; Pérez, Marina; Cardona, Laura; Hernández, J Joaquin

    2016-01-01

    Shallow seawaters are problematic for acoustic and optical communications. Sensor networks based on electromagnetic (EM) communications are evaluated in this environment. In order to characterize the subaquatic channel, several measurement systems have been designed, built and tested in the sea obtaining very reliable results. Experiments carried out with dipoles and loop antennas showed serious disagreement with the state of the art, especially when dipole antennas are used. Dipoles performance was poor while magnetic loops showed relevant results. Measurement system is described in detail and real attenuation of the subaquatic channel is obtained for several distances and antennas. Finally, measured and simulated results are compared with good agreement.

  18. Vapor fraction distribution within pipelines and channels

    International Nuclear Information System (INIS)

    Three-dimensional distribution of vapor volumetric fractions in subcooled boiling is analyzed for circular tubes and rectangular channels. The model is based on three major assumptions: 1) vapor bubble mation is controlled by diffusion due to flow turbulence; 2) the diffusion coefficient and bubble velocity are constant within the channel cross-section as well as the coolant temperature; 3) the vapor bubble generation and condensation rates are calculated according to one-dimensional models. The vapor void distribution is obtained from an analytical solution of the vapor bubble diffusion equation with a simplified approximation of subcooling profile. A method of boundary conditions formulation for the diffusin equation is also presented

  19. NUMERICAL MODELING OF COMPOUND CHANNEL FLOWS

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A numerical model capable of predicting flow characteristics in a compound channel was established with the 3-D steady continuity and momentum equations along with the transport equations for turbulence kinetic energy and dissipation rate. Closure was achieved with the aid of algebraic relations for turbulent shear stresses. The above equations were discretized with implicit difference approach and solved with a step method along the flow direction. The computational results showing the lateral distribution of vertical average velocities and the latio of total flow in the compound channel agree well with the available experimental data.

  20. Imperfect Secrecy in Wiretap Channel II

    OpenAIRE

    Cheng, Fan; Yeung, Raymond W.; Shum, Kenneth W.

    2012-01-01

    In a point-to-point communication system which consists of a sender, a receiver and a set of noiseless channels, the sender wishes to transmit a private message to the receiver through the channels which may be eavesdropped by a wiretapper. The set of wiretap sets is arbitrary. The wiretapper can access any one but not more than one wiretap set. From each wiretap set, the wiretapper can obtain some partial information about the private message which is measured by the equivocation of the mess...

  1. OCCIMA: Optical Channel Characterization in Maritime Atmospheres

    Science.gov (United States)

    Hammel, Steve; Tsintikidis, Dimitri; deGrassie, John; Reinhardt, Colin; McBryde, Kevin; Hallenborg, Eric; Wayne, David; Gibson, Kristofor; Cauble, Galen; Ascencio, Ana; Rudiger, Joshua

    2015-05-01

    The Navy is actively developing diverse optical application areas, including high-energy laser weapons and free- space optical communications, which depend on an accurate and timely knowledge of the state of the atmospheric channel. The Optical Channel Characterization in Maritime Atmospheres (OCCIMA) project is a comprehensive program to coalesce and extend the current capability to characterize the maritime atmosphere for all optical and infrared wavelengths. The program goal is the development of a unified and validated analysis toolbox. The foundational design for this program coordinates the development of sensors, measurement protocols, analytical models, and basic physics necessary to fulfill this goal.

  2. Capacities of Lossy Bosonic Memory Channels

    Science.gov (United States)

    Lupo, Cosmo; Giovannetti, Vittorio; Mancini, Stefano

    2010-01-01

    We introduce a general model describing correlated noise effects in quantum optical communication via attenuating media. The memory effects account for the environment finite relaxation times, which are unavoidable in any realistic model. The use of a proper set of collective field variables allows us to unravel the memory, showing that the n-fold concatenation of the memory channel is unitarily equivalent to the direct product of n single-mode lossy bosonic channels. We then compute the ultimate (classical and quantum) transmission rates, showing their enhancement with respect to the memoryless case and proving that coherent state encoding is optimal.

  3. Mobile radio channel as a complex medium

    DEFF Research Database (Denmark)

    Matic, Dusan; Prasad, Ramjee; Kalluri, Dikshitulu K.

    2001-01-01

    physical phenomena, their implications on the transmitted signal, and how the radio channels are modelled. Special attention is given to the small-scale effects, such as multipath, and Rayleigh and Rice distributions of received signal, as these dominate in the case of indoor communication systems.......Optical fibres have almost unlimited capacity, but can not the address the users desire for mobility and ubiquitous access. The synergy of these two worlds can be seen in the direction of the Radio-over-Fibre. This paper presents to the reader an introduction for the mobile radio channel - basic...

  4. Joint source-channel video transmission

    CERN Document Server

    Zhai, Fan

    2007-01-01

    This book deals with the problem of joint source-channel video transmission, i.e., the joint optimal allocation of resources at the application layer and the other network layers, such as data rate adaptation, channel coding, power adaptation in wireless networks, quality of service (QoS) support from the network, and packet scheduling, for efficient video transmission. Real-time video communication applications, such as videoconferencing, video telephony, and on-demand video streaming, have gained increased popularity. However, a key problem in video transmission over the existing Internet an

  5. Multi-channel coherent perfect absorbers

    KAUST Repository

    Bai, Ping

    2016-05-18

    The absorption efficiency of a coherent perfect absorber usually depends on the phase coherence of the incident waves on the surfaces. Here, we present a scheme to create a multi-channel coherent perfect absorber in which the constraint of phase coherence is loosened. The scheme has a multi-layer structure such that incident waves in different channels with different angular momenta can be simultaneously and perfectly absorbed. This absorber is robust in achieving high absorption efficiency even if the incident waves become "incoherent" and possess "random" wave fronts. Our work demonstrates a unique approach to designing highly efficient metamaterial absorbers. © CopyrightEPLA, 2016.

  6. Covering a Crucible with Metal Containing Channels

    Science.gov (United States)

    Grugel, Richard N.

    2006-01-01

    In a procedure that partly resembles the lost-wax casting process, a crucible made of a brittle material (ceramic, quartz, or glass) is covered with a layer of metal containing channels. The metal cover and the channels can serve any or all of several purposes, depending upon the application: Typically, the metal would serve at least partly to reinforce the crucible. The channels could be used as passages for narrow objects that could include thermocouples and heat-transfer strips. Alternatively or in addition, channels could be used as flow paths for liquid or gaseous coolants and could be positioned and oriented for position- or direction-selective cooling. In some cases, the channels could be filled with known gases and sealed so that failure of the crucibles could be indicated by instruments that detect the gases. The process consists of three main steps. In the first step, a pattern defining the channels is formed by wrapping or depositing a material in the desired channel pattern on the outer surface of the crucible. The pattern material can be a plastic, wax, low-ash fibrous material, a soluble material, or other suitable material that can subsequently be removed easily. In a proof-of-concept demonstration (see figure), the crucible was an alumina cylinder and the mold material was plastic tie-down tape. In the second step, the patterned crucible is coated with metal. In one variation of the second step, a very thin layer containing or consisting of an electrically conductive material (e.g., gold, silver, or carbon) is painted or otherwise deposited on the mold-covered crucible, then the covering metal required for the specific application is electrodeposited on the very thin conducting layer. In another variation of the second step, the metal coat is formed by chemical vapor deposition. In the proof-of-concept demonstration, a layer of nickel 0.003 in. ( 0.08 mm) thick was electrodeposited. In the third step, the patterned material is removed. This is

  7. Computer Simulation Studies of Gramicidin Channel

    Science.gov (United States)

    Song, Hyundeok; Beck, Thomas

    2009-04-01

    Ion channels are large membrane proteins, and their function is to facilitate the passage of ions across biological membranes. Recently, Dr. John Cuppoletti's group at UC showed that the gramicidin channel could function at high temperatures (360 -- 390K) with significant currents. This finding may have large implications for fuel cell technology. In this project, we will examine the experimental system by computer simulation. We will investigate how the temperature affects the current and differences in magnitude of the currents between two forms of Gramicidin, A and D. This research will help to elucidate the underlying molecular mechanism in this promising new technology.

  8. Joint Channel Estimation and Data Detection for Multihop OFDM Relaying System under Unknown Channel Orders and Doppler Frequencies

    CERN Document Server

    Min, Rui

    2012-01-01

    In this paper, channel estimation and data detection for multihop relaying orthogonal frequency division multiplexing (OFDM) system is investigated under time-varying channel. Different from previous works, which highly depend on the statistical information of the doubly-selective channel (DSC) and noise to deliver accurate channel estimation and data detection results, we focus on more practical scenarios with unknown channel orders and Doppler frequencies. Firstly, we integrate the multilink, multihop channel matrices into one composite channel matrix. Then, we formulate the unknown channel using generalized complex exponential basis expansion model (GCE-BEM) with a large oversampling factor to introduce channel sparsity on delay-Doppler domain. To enable the identification of nonzero entries, sparsity enhancing Gaussian distributions with Gamma hyperpriors are adopted. An iterative algorithm is developed under variational inference (VI) framework. The proposed algorithm iteratively estimate the channel, re...

  9. Impact of the internet as a direct sales channel on established distribution channels and the management of channel conflict; an exploratory study in the Taiwanese IT industry

    OpenAIRE

    Chang, Jen-Yun

    2009-01-01

    The internet has had a profound effect on communication, entertainment, buying, and selling (Webb 2002) and, in particular, as a distribution channel (Van den Poel and Leunis 1999). Increasingly companies in a variety of industries have established their own online direct sales channels instead of merely relying on conventional intermediaries (Coughlan et al 2006). Hence, multi-channel distribution strategies, combining both off- and online channels are being adopted. Frazier (...

  10. Multi-Channel Retail Supply Chain Management: Fulfillment systems in Multi-Channel Retailing - Customer Expectations and Economic Performance

    OpenAIRE

    Lang, Gerald

    2010-01-01

    International audience Increasingly, store-based retailers are opening an additional online sales channel and becoming multi-channel retailers. The integration of these different channels raises the question how to redefine the strategic marketing elements and the operations, as the two channels have different constraints and require different competences. This multi-channel retailing has major impacts on the operations and the supply-chain management. Order fulfillment for the customers u...

  11. Functional Expression of an Arachnid Sodium Channel Reveals Residues Responsible for Tetrodotoxin Resistance in Invertebrate Sodium Channels*

    OpenAIRE

    Du, Yuzhe; Nomura, Yoshiko; Liu, Zhiqi; Huang, Zachary Y.; Dong, Ke

    2009-01-01

    Tetrodotoxin (TTX) is a potent blocker of voltage-gated sodium channels, but not all sodium channels are equally sensitive to inhibition by TTX. The molecular basis of differential TTX sensitivity of mammalian sodium channels has been largely elucidated. In contrast, our knowledge about the sensitivity of invertebrate sodium channels to TTX remains poor, in part because of limited success in functional expression of these channels. In this study, we report the functional characterization in X...

  12. On the secrecy capacity of the wiretap channel with imperfect main channel estimation

    KAUST Repository

    Rezki, Zouheir

    2014-10-01

    We study the secrecy capacity of fast fading channels under imperfect main channel (between the transmitter and the legitimate receiver) estimation at the transmitter. Lower and upper bounds on the ergodic secrecy capacity are derived for a class of independent identically distributed (i.i.d.) fading channels. The achievable rate follows from a standard wiretap code in which a simple on-off power control is employed along with a Gaussian input. The upper bound is obtained using an appropriate correlation scheme of the main and eavesdropper channels and is the best known upper bound so far. The upper and lower bounds coincide with recently derived ones in case of perfect main CSI. Furthermore, the upper bound is tight in case of no main CSI, where the secrecy capacity is equal to zero. Asymptotic analysis at high and low signal-to-noise ratio (SNR) is also given. At high SNR, we show that the capacity is bounded by providing upper and lower bounds that depend on the channel estimation error. At low SNR, however, we prove that the secrecy capacity is asymptotically equal to the capacity of the main channel as if there were no secrecy constraint. Numerical results are provided for i.i.d. Rayleigh fading channels.

  13. On the low SNR capacity of MIMO fading channels with imperfect channel state information

    KAUST Repository

    Benkhelifa, Fatma

    2014-06-01

    The capacity of multiple-input multiple-output (MIMO) Rayleigh fading channels with full knowledge of channel state information (CSI) at both the transmitter and the receiver (CSI-TR) has been shown recently to scale at low signal-to-noise ratio (SNR) essentially as SNR log(1/SNR), independently of the number of transmit and receive antennas. In this paper, we investigate the ergodic capacity of MIMO Rayleigh fading channel with estimated channel state information at the transmitter (CSI-T) and possibly imperfect channel state information at the receiver (CSI-R). Our framework can be seen as a generalization of previous works as it can capture the perfect CSI-TR as a special case when the estimation error variance goes to zero. In this paper, we mainly focus on the low SNR regime, and we show that the capacity scales as (1-α) SNR log(1/SNR), where α is the estimation error variance. This characterization shows the loss of performance due to error estimation over the perfect channel state information at both the transmitter and the receiver. As a by-product of our new analysis, we show that our framework can be also extended to characterize the capacity of MIMO Rician fading channels at low SNR with possibly imperfect CSI-T and CSI-R. © 1972-2012 IEEE.

  14. On the low SNR capacity of MIMO fading channels with imperfect channel state information

    KAUST Repository

    Benkhelifa, Fatma

    2014-05-01

    The capacity of Multiple Input Multiple Output (MIMO) Rayleigh fading channels with full knowledge of channel state information (CSI) at both the transmitter and the receiver (CSI-TR) has been shown recently to scale at low Signal-to-Noise Ratio (SNR) essentially as SNR log(1=SNR), independently of the number of transmit and receive antennas. In this paper, we investigate the ergodic capacity of MIMO Rayleigh fading channel with estimated channel state information at the transmitter (CSI-T) and possibly imperfect channel state information at the receiver (CSI-R). Our framework can be seen as a generalization of previous works as it can capture the perfect CSI-TR as a special case when the estimation error variance goes to zero. In our work, we mainly focus on the low SNR regime and we show that the capacity scales as (1-α) SNR log(1=SNR), where α is the estimation error variance. This characterization shows the loss of performance due to error estimation over the perfect channel state information at both the transmitter and the receiver. As a by-product of our new analysis, we show that our framework can also be extended to characterize the capacity of MIMO Rician fading channels at low SNR with possibly imperfect CSI-T and CSI-R. © 2014 IFIP.

  15. Channel Estimation Based in Comb-Type Pilots Arrangement for OFDM System over Time Varying Channel

    Directory of Open Access Journals (Sweden)

    Hala M. Mahmoud

    2010-07-01

    Full Text Available Orthogonal Frequency Division Multiplexing (OFDM has been recently applied widely in wireless communication systems, due to its high data rate, transmission capability with high bandwidth, efficiency and its robustness to multipath delay .Channel estimation is an essential problem in OFDM system. Pilot-aided channel estimation has been used; a good choice of the pilot pattern should match the channel behavior both in time and frequency domains. We explored comb pilot arrangements. The advantage for comb type pilots arrangement in channel estimation is the ability to track the variation of the channel caused by doppler frequency, it is observed that the doppler effect can be reduced, and so this will increase the system mobility. Kalman and Least Square (LS estimators have been proposed to estimate the Channel Frequency Response (CFR at the pilots location, then CFR at data sub channels are obtained by mean of interpolation between estimates at pilot locations. Different types of interpolations have been used such as; low pass interpolation; spline cubic interpolation and linear interpolation. Kalman estimation has better performance than LS estimation. The estimators perform about the same for SNR lower than 10 dB. The performances of all schemes have been compared by finding Bit Error Rate (BER, where BPSK modulation scheme was used.

  16. Channel allocation and rate adaptation for relayed transmission over correlated fading channels

    KAUST Repository

    Hwang, Kyusung

    2009-09-01

    We consider, in this paper, channel allocation and rate adaptation scheme for relayed transmission over correlated fading channels via cross-layer design. Specifically, jointly considering the data link layer buffer occupancy and channel quality at both the source and relay nodes, we develop an optimal channel allocation and rate adaptation policy for a dual-hop relayed transmission. As such the overall transmit power for the relayed system is minimized while a target packet dropping rate (PDR) due to buffer over flows is guaranteed. In order to find such an optimal policy, the channel allocation and rate adaptation transmission framework is formulated as a constraint Markov decision process (CMDP). The PDR performance of the optimal policy is compared with that of two conventional suboptimal schemes, namely the channel quality based and the buffer occupancy based channel allocation schemes. Numerical results show that for a given power budget, the optimal scheme requires significantly less power than the conventional schemes in order to maintain a target PDR. ©2009 IEEE.

  17. Secure Bidirectional Communication Protocol without Quantum Channel

    OpenAIRE

    Zhang, Z. J.; Man, Z. X.

    2004-01-01

    In this letter we propose a theoretical deterministic secure direct bidirectional quantum communication protocol by using swapping quantum entanglement and local unitary operations, in which the quantum channel for photon transmission can be discarded, hence any attack with or without eavesdropping or even the destructive attack without scruple is impossible.

  18. Study on multiple channel radiation dosimeter

    International Nuclear Information System (INIS)

    An intelligent radiation dosimeter, with multiple channel signal collection and data processing, storing, printing and display, has been developed. It can measure doses at six different positions at one time. The device consists of six micro-semiconductors. This dosimeter can be used in irradiation experiments by 60Co source, radiotherapeutic facilities and radiation processing

  19. Recent improvements in channel catfish reproduction

    Science.gov (United States)

    Control of reproduction in fish is a primary requisite for reliable, predictable and quality seed stock for aquaculture production or a stock enhancement program. Channel catfish is the leading aquaculture species in USA, accounting for 335 million pounds with a farm gate value of over $ 400 millio...

  20. Channelization of plumes beneath ice shelves

    KAUST Repository

    Dallaston, M. C.

    2015-11-11

    © 2015 Cambridge University Press. We study a simplified model of ice-ocean interaction beneath a floating ice shelf, and investigate the possibility for channels to form in the ice shelf base due to spatial variations in conditions at the grounding line. The model combines an extensional thin-film description of viscous ice flow in the shelf, with melting at its base driven by a turbulent ocean plume. Small transverse perturbations to the one-dimensional steady state are considered, driven either by ice thickness or subglacial discharge variations across the grounding line. Either forcing leads to the growth of channels downstream, with melting driven by locally enhanced ocean velocities, and thus heat transfer. Narrow channels are smoothed out due to turbulent mixing in the ocean plume, leading to a preferred wavelength for channel growth. In the absence of perturbations at the grounding line, linear stability analysis suggests that the one-dimensional state is stable to initial perturbations, chiefly due to the background ice advection.

  1. Radio frequency channel coding made easy

    CERN Document Server

    Faruque, Saleh

    2016-01-01

    This book introduces Radio Frequency Channel Coding to a broad audience. The author blends theory and practice to bring readers up-to-date in key concepts, underlying principles and practical applications of wireless communications. The presentation is designed to be easily accessible, minimizing mathematics and maximizing visuals.

  2. Multi-channel electric aerosol spectrometer

    Science.gov (United States)

    Mirme, A.; Noppel, M.; Peil, I.; Salm, J.; Tamm, E.; Tammet, H.

    Multi-channel electric mobility spectrometry is a most efficient technique for the rapid measurement of an unstable aerosol particle size spectrum. The measuring range of the spectrometer from 10 microns to 10 microns is achieved by applying diffusional and field charging mechanisms simultaneously. On-line data processing is carried out with a microcomputer. Experimental calibration ensures correctness of measurement.

  3. Channel coding for digital HDTV terrestrial broadcasting

    Science.gov (United States)

    Beakley, Guy W.

    1991-01-01

    The Federal Communications Commission of the United States has ruled that high-definition television (HDTV) will occupy no more than 6 MHz of the VHF and UHF bands now used for conventional TV. In order to transmit the HDTV signal in 6 MHz, the four United States digital HDTV proponents, the DigiCipher, DSC-HDTV, ADTV, and ATVA-P systems, are reducing the video data rate of HDTV to 15-17 Mb/s, a compression ratio of approximately 60-70 times. The high compression dictates that channel coding be used to avoid block errors and multiframe error propagation. High efficiency in channel utilization required by the 6-MHz limitation means that the channel must be properly equalized and that the multipath and interfering signals must be severely limited. The channel coding techniques used for error reduction include data interleaving, error detection and replacement, and error correction at different levels of protection for bits and blocks of unequal importance.

  4. P-channel silicone gate FET

    Science.gov (United States)

    Ostis, S.; Woo, D. S.

    1973-01-01

    Modified fabrication technique for P-channel MOSFET devices eliminates problems involving gate placement and gate overlap. Technique provides self-aligned gate, eliminating complexity of mask aligning. Devices produced by this process are considerably faster than conventional MOSFET's and process increases yield.

  5. Vibrational Spectra of a Mechanosensitive Channel

    NARCIS (Netherlands)

    Liang, Chungwen; Louhivuori, Martti; Marrink, Siewert J.; Jansen, Thomas L.C.; Knoester, Jasper

    2013-01-01

    We report the simulated vibrational spectra of a mechanosensitive membrane channel in different gating states. Our results show that while linear absorption is insensitive to structural differences, linear dichroism and sum-frequency generation spectroscopies are sensitive to the orientation of the

  6. Water transport in graphene nano-channels

    DEFF Research Database (Denmark)

    Wagemann, Enrique; Oyarzua, Elton; Walther, J. H.

    enhancement, defined as the ratio of the computed flow rate to that predicted from the classical Poiseuille model. Moreover, these studies point to the fact that the flow enhancement is a function of channel height and the fluid-wall physical-chemistry. In spite of the intensive research, an explicit relation...

  7. Fermi Liquid Instabilities in the Spin Channel

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Congjun; /Santa Barbara, KITP; Sun, Kai; Fradkin, Eduardo; /Illinois U., Urbana; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-03-16

    We study the Fermi surface instabilities of the Pomeranchuk type in the spin triplet channel with high orbital partial waves (F{sub l}{sup a} (l > 0)). The ordered phases are classified into two classes, dubbed the {alpha} and {beta}-phases by analogy to the superfluid {sup 3}He-A and B-phases. The Fermi surfaces in the {alpha}-phases exhibit spontaneous anisotropic distortions, while those in the {beta}-phases remain circular or spherical with topologically non-trivial spin configurations in momentum space. In the {alpha}-phase, the Goldstone modes in the density channel exhibit anisotropic overdamping. The Goldstone modes in the spin channel have nearly isotropic underdamped dispersion relation at small propagating wavevectors. Due to the coupling to the Goldstone modes, the spin wave spectrum develops resonance peaks in both the {alpha} and {beta}-phases, which can be detected in inelastic neutron scattering experiments. In the p-wave channel {beta}-phase, a chiral ground state inhomogeneity is spontaneously generated due to a Lifshitz-like instability in the originally nonchiral systems. Possible experiments to detect these phases are discussed.

  8. The Growth Opportunity Channel of Debt Structure

    NARCIS (Netherlands)

    E. Giambona; J. Golec

    2013-01-01

    This paper studies the importance of growth opportunities for debt structure decisions. High growth firms use more unsecured debt to preserve financial flexibility (in the form of untapped secured debt capacity) in connection with future growth opportunities: the growth opportunity channel of debt s

  9. The Growth Opportunity Channel of Debt Structure

    NARCIS (Netherlands)

    E. Giambona; J. Golec

    2012-01-01

    This paper studies the importance of growth opportunities for debt structure decisions. High growth firms use more unsecured debt to preserve financial flexibility (in the form of untapped secured debt capacity) in connection with future growth opportunities: the growth opportunity channel of debt s

  10. Calcium channel as a potential anticancer agent.

    Science.gov (United States)

    Kriazhev, L

    2009-11-01

    Anticancer treatment in modern clinical practices includes chemotherapy and radiation therapy with or without surgical interventions. Efficiency of both methods varies greatly depending on cancer types and stages. Besides, chemo- and radiotherapy are toxic and damaging that causes serious side effects. This fact prompts the search for alternative methods of antitumor therapy. It is well known that prolonged or high increase of intracellular calcium concentration inevitably leads to the cell death via apoptosis or necrosis. However, stimulation of cell calcium level by chemical agents is hardly achievable because cells have very sophisticated machinery for maintaining intracellular calcium in physiological ranges. This obstacle can be overridden, nevertheless. It was found that calcium channels in so called calcium cells in land snails are directly regulated by extracellular calcium concentration. The higher the concentration the higher the calcium intake is through the channels. Bearing in mind that extracellular/intracellular calcium concentration ratio in human beings is 10,000-12,000 fold the insertion of the channel into cancer cells would lead to fast and uncontrollable by the cells calcium intake and cell death. Proteins composing the channel may be extracted from plasma membrane of calcium cells and sequenced by mass-spectrometry or N-terminal sequencing. Either proteins or corresponding genes could be used for targeted delivery into cancer cells.

  11. TRESK potassium channel in human T lymphoblasts

    Energy Technology Data Exchange (ETDEWEB)

    Sánchez-Miguel, Dénison Selene, E-mail: amurusk@hotmail.com [Center for Biomedical Research, University of Colima, Av. 25 de Julio 965, Villa San Sebastian, C.P. 28045 Colima (Mexico); García-Dolores, Fernando, E-mail: garciaddf@yahoo.com [Department of Pathology, Institute of Forensic Sciences, Av. Niños Héroes 130, Col. Doctores, C.P. 06720 Mexico, DF (Mexico); Rosa Flores-Márquez, María, E-mail: mariafo31@yahoo.com.mx [National Medical Center of Occident (CMNO) IMSS, Belisario Dominguez 735, Col. Independencia Oriente, C.P. 44340 Guadalajara, Jalisco (Mexico); Delgado-Enciso, Iván [University of Colima, School of Medicine, Av. Universidad 333, Col. Las Viboras, C.P. 28040 Colima (Mexico); Pottosin, Igor, E-mail: pottosin@ucol.mx [Center for Biomedical Research, University of Colima, Av. 25 de Julio 965, Villa San Sebastian, C.P. 28045 Colima (Mexico); Dobrovinskaya, Oxana, E-mail: oxana@ucol.mx [Center for Biomedical Research, University of Colima, Av. 25 de Julio 965, Villa San Sebastian, C.P. 28045 Colima (Mexico)

    2013-05-03

    Highlights: • TRESK (KCNK18) mRNA is present in different T lymphoblastic cell lines. • KCNK18 mRNA was not found in resting peripheral blood lymphocytes. • Clinical samples of T lymphoblastic leukemias and lymphomas were positive for TRESK. • TRESK in T lymphoblasts has dual localization, in plasma membrane and intracellular. -- Abstract: TRESK (TWIK-related spinal cord K{sup +}) channel, encoded by KCNK18 gene, belongs to the double-pore domain K{sup +} channel family and in normal conditions is expressed predominantly in the central nervous system. In our previous patch-clamp study on Jurkat T lymphoblasts we have characterized highly selective K{sup +} channel with pharmacological profile identical to TRESK. In the present work, the presence of KCNK18 mRNA was confirmed in T lymphoblastic cell lines (Jurkat, JCaM, H9) but not in resting peripheral blood lymphocytes of healthy donors. Positive immunostaining for TRESK was demonstrated in lymphoblastic cell lines, in germinal centers of non-tumoral lymph nodes, and in clinical samples of T acute lymphoblastic leukemias/lymphomas. Besides detection in the plasma membrane, intracellular TRESK localization was also revealed. Possible involvement of TRESK channel in lymphocyte proliferation and tumorigenesis is discussed.

  12. Optimization of Spatiotemporal Apertures in Channel Sounding

    DEFF Research Database (Denmark)

    Pedersen, Troels; Pedersen, Claus; Yin, Xuefeng;

    2008-01-01

    In this paper we investigate the impact of the spatio-temporal aperture of a channel sounding system equipped with antenna arrays at the transmitter and receiver on the accuracy of joint estimation of Doppler frequency and bi-direction. The contribution of this work is three-fold. Firstly, we sta...

  13. Control microprocessor system for charge particle channeling

    International Nuclear Information System (INIS)

    Control microprocessor systems are widely applied not only in designing industrial robots but in providing functioning of different experimental plants. The experiment control system for charge particle channeling has been considered in the paper. Flexibility, relatively low cost and high reliability are advantages of these systems

  14. Detonation diffraction from an annular channel

    Science.gov (United States)

    Meredith, James; Ng, Hoi Dick; Lee, John H. S.

    2010-12-01

    In this study, gaseous detonation diffraction from an annular channel was investigated with a streak camera and the critical pressure for transmission of the detonation wave was obtained. The annular channel was used to approximate an infinite slot resulting in cylindrically expanding detonation waves. Two mixtures, stoichiometric acetylene-oxygen and stoichiometric acetylene-oxygen with 70% Ar dilution, were tested in a 4.3 and 14.3 mm channel width ( W). The undiluted and diluted mixtures were found to have values of the critical channel width over the cell size around 3 and 12 respectively. Comparing these results to values of the critical diameter ( d c ), in which a spherical detonation occurs, a value of critical d c / W c near 2 is observed for the highly diluted mixture. This value corresponds to the geometrical factor of the curvature term between a spherical and cylindrical diverging wave. Hence, the result is in support of Lee's proposed mechanism [Lee in Dynamics of Exothermicity, pp. 321, Gordon and Breach, Amsterdam, 1996] for failure due to diffraction based on curvature in stable mixtures such as those highly argon diluted with very regular detonation cellular patterns.

  15. Acceptable Channel Switching Delays for Mobile TV

    DEFF Research Database (Denmark)

    Fleury, Alexandre; Pedersen, Jakob Schou; Larsen, Lars Bo

    2011-01-01

    This paper presents a user study investigating the acceptability of channel switching delays on mobile television systems. The authors first review the previous work in the area, then propose a study design and present results from its implementation, focusing on the overall acceptability threshold...

  16. Channel adaptive rate control for energy optimization

    Institute of Scientific and Technical Information of China (English)

    BLANCH Carolina; POLLIN Sofie; LAFRUIT Gauthier; EBERLE Wolfgang

    2006-01-01

    Low energy consumption is one of the main challenges for wireless video transmission on battery limited devices. The energy invested at the lower layers of the protocol stack involved in data communication, such as link and physical layer, represent an important part of the total energy consumption. This communication energy highly depends on the channel conditions and on the transmission data rate. Traditionally, video coding is unaware of varying channel conditions. In this paper, we propose a cross-layer approach in which the rate control mechanism of the video codec becomes channel-aware and steers the instantaneous output rate according to the channel conditions to reduce the communication energy. Our results show that energy savings of up to30% can be obtained with a reduction of barely 0.1 dB on the average video quality. The impact of feedback delays is shown to be small. In addition, this adaptive mechanism has low complexity, which makes it suitable for real-time applications.

  17. The interrelationships between brand and channel choice

    NARCIS (Netherlands)

    Neslin, Scott A.; Jerath, Kinshuk; Bodapati, Anand; Bradlow, Eric T.; Deighton, John; Gensler, Sonja; Lee, Leonard; Montaguti, Elisa; Telang, Rahul; Venkatesan, Raj; Verhoef, Pieter; Zhang, Z. John

    2014-01-01

    We propose a framework for the joint study of the consumer's decision of where to buy and what to buy. The framework is rooted in utility theory where the utility is for a particular channel/brand combination. The framework contains firm actions, the consumer search process, the choice process, and

  18. Four channel analog router for spectroscopy applications

    International Nuclear Information System (INIS)

    A four input analog multiplexer/router has been developed in order to acquire spectral data from four different detector systems on first-come-first-sort basis. The circuit is incorporated in a single width NIM module and is fully compatible with the HPD 4K MCA developed in the Health Physics Division. The analog router accepts output from upto 4 detectors after these are passed through individual preamplifiers and linear amplifiers. The router generates signal for the channel whose input crosses set LLD limits first and simultaneously disables other inputs. The selected input is then passed to the ADC for further processing. The processed signal generates a channel dependent two bit address along with normal digital outputs of the ADC. The channel dependent two bit address is directly used to store the event in one of the four 1k segment of the HPD 4K MCA. The multiplexer is re-enabled to accept next input on priority basis. One such unit has already been commissioned to acquire data from four solid state detectors used for spectrometry. The paper discusses hardware of the router, its linearity resolution cross-talk between the channels and other performance characteristics. (author). 3 figs

  19. How Cannibalistic is the Internet Channel?

    NARCIS (Netherlands)

    B. Deleersnyder (Barbara); I. Geyskens; K. Gielens (Katrijn); M.G. Dekimpe (Marnik)

    2002-01-01

    textabstractDuring the past decade, irrational exuberance has turned into a possibly equally irrational pessimism about what the Internet can accomplish. The fear of getting ruined through cannibalization losses has recently deterred many firms from deploying the Internet as a distribution channel.

  20. Weighted OFDM for wireless multipath channels

    DEFF Research Database (Denmark)

    Prasad, Ramjee; Nikookar, H.

    2000-01-01

    simulation and is compared for the above mentioned weighting factors. Results show that by weighting of the OFDM signal the PAPR reduces. Bit error performance of weighted multicarrier transmission over a multipath channel is also investigated. Results indicate that there is a trade off between PAPR...