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Sample records for aquaglyceroporin channels correlates

  1. Channel-mediated lactic acid transport: a novel function for aquaglyceroporins in bacteria.

    Science.gov (United States)

    Bienert, Gerd P; Desguin, Benoît; Chaumont, François; Hols, Pascal

    2013-09-15

    MIPs (major intrinsic proteins), also known as aquaporins, are membrane proteins that channel water and/or uncharged solutes across membranes in all kingdoms of life. Considering the enormous number of different bacteria on earth, functional information on bacterial MIPs is scarce. In the present study, six MIPs [glpF1 (glycerol facilitator 1)-glpF6] were identified in the genome of the Gram-positive lactic acid bacterium Lactobacillus plantarum. Heterologous expression in Xenopus laevis oocytes revealed that GlpF2, GlpF3 and GlpF4 each facilitated the transmembrane diffusion of water, dihydroxyacetone and glycerol. As several lactic acid bacteria have GlpFs in their lactate racemization operon (GlpF1/F4 phylogenetic group), their ability to transport this organic acid was tested. Both GlpF1 and GlpF4 facilitated the diffusion of D/L-lactic acid. Deletion of glpF1 and/or glpF4 in Lb. plantarum showed that both genes were involved in the racemization of lactic acid and, in addition, the double glpF1 glpF4 mutant showed a growth delay under conditions of mild lactic acid stress. This provides further evidence that GlpFs contribute to lactic acid metabolism in this species. This lactic acid transport capacity was shown to be conserved in the GlpF1/F4 group of Lactobacillales. In conclusion, we have functionally analysed the largest set of bacterial MIPs and demonstrated that the lactic acid membrane permeability of bacteria can be regulated by aquaglyceroporins.

  2. Arsenic transport by zebrafish aquaglyceroporins

    Directory of Open Access Journals (Sweden)

    Landfear Scott M

    2009-11-01

    Full Text Available Abstract Background Arsenic is one of the most ubiquitous toxins and endangers the health of tens of millions of humans worldwide. It is a mainly a water-borne contaminant. Inorganic trivalent arsenic (AsIII is one of the major species that exists environmentally. The transport of AsIII has been studied in microbes, plants and mammals. Members of the aquaglyceroporin family have been shown to actively conduct AsIII and its organic metabolite, monomethylarsenite (MAsIII. However, the transport of AsIII and MAsIII in in any fish species has not been characterized. Results In this study, five members of the aquaglyceroporin family from zebrafish (Danio rerio were cloned, and their ability to transport water, glycerol, and trivalent arsenicals (AsIII and MAsIII and antimonite (SbIII was investigated. Genes for at least seven aquaglyceroporins have been annotated in the zebrafish genome project. Here, five genes which are close homologues to human AQP3, AQP9 and AQP10 were cloned from a zebrafish cDNA preparation. These genes were named aqp3, aqp3l, aqp9a, aqp9b and aqp10 according to their similarities to the corresponding human AQPs. Expression of aqp9a, aqp9b, aqp3, aqp3l and aqp10 in multiple zebrafish organs were examined by RT-PCR. Our results demonstrated that these aquaglyceroporins exhibited different tissue expression. They are all detected in more than one tissue. The ability of these five aquaglyceroporins to transport water, glycerol and the metalloids arsenic and antimony was examined following expression in oocytes from Xenopus leavis. Each of these channels showed substantial glycerol transport at equivalent rates. These aquaglyceroporins also facilitate uptake of inorganic AsIII, MAsIII and SbIII. Arsenic accumulation in fish larvae and in different tissues from adult zebrafish was studied following short-term arsenic exposure. The results showed that liver is the major organ of arsenic accumulation; other tissues such as gill, eye

  3. Glycerol inhibits water permeation through Plasmodium falciparum aquaglyceroporin.

    Science.gov (United States)

    Chen, Liao Y

    2013-01-01

    Plasmodium falciparum aquaglyceroporin (PfAQP) is a multifunctional membrane protein in the plasma membrane of P. falciparum, the parasite that causes the most severe form of malaria. The current literature has established the science of PfAQP's structure, functions, and hydrogen-bonding interactions but left unanswered the following fundamental question: does glycerol modulate water permeation through aquaglyceroporin that conducts both glycerol and water? This paper provides an affirmative answer to this question of essential importance to the protein's functions. On the basis of the chemical-potential profile of glycerol from the extracellular bulk region, throughout PfAQP's conducting channel, to the cytoplasmic bulk region, this study shows the existence of a bound state of glycerol inside aquaglyceroporin's permeation pore, from which the dissociation constant is approximately 14μM. A glycerol molecule occupying the bound state occludes the conducting pore through which permeating molecules line up in single file by hydrogen-bonding with one another and with the luminal residues of aquaglyceroporin. In this way, glycerol inhibits permeation of water and other permeants through aquaglyceroporin. The biological implications of this theory are discussed and shown to agree with the existent in vitro data. It turns out that the structure of aquaglyceroporin is perfect for the van der Waals interactions between the protein and glycerol to cause the existence of the bound state deep inside the conducting pore and, thus to play an unexpected but significant role in aquaglyceroporin's functions.

  4. Expression and localization of aqua-glyceroporins AQP3 and AQP9 in rat oral epithelia.

    Science.gov (United States)

    Poveda, Marlene; Hashimoto, Sadamitsu; Enokiya, Yasunobu; Matsuki-Fukushima, Miwako; Sasaki, Hodaka; Sakurai, Kaoru; Shimono, Masaki

    2014-01-01

    Aquaporins (AQPs) are a family of small integral membrane proteins made up of 6 hydrophobic, a-helical, membrane-spanning domains surrounding a highly selective aqueous pore. AQP3, AQP7, and AQP9, termed aqua-glyceroporins, are known to be involved in the transport of water, glycerol, and other small molecules. In this study, we investigated the expression and localization of aqua-glyceroporins in rat oral stratified squamous epithelia of the palate, the buccal mucosa, the inferior aspect of the tongue, and the oral floor by using RT-PCR, immunofluorescence, and immunogold electron microscopy. AQP3 and AQP9 mRNAs were expressed in whole oral epithelium. Immunostaining for AQP3 was recognized in each type of epithelium. The results suggest that AQP3 synthesis begins predominantly in the cytoplasm of the basal cells. During the process of epithelial cell differentiation, AQP3 protein appears to accumulate and be transported to the plasma membrane, from where it is incorporated into the cornified or surface layers. The intracellular localization of AQP3 appears to correlate with the differentiation of keratinocytes, suggesting that it acts as an enhancer of the physiological permeability barrier together with membrane coating granules. The distribution pattern of AQP9 was limited to the marginal areas of the basal and suprabasal layers, which was different from that of AQP3. This difference in distribution between AQP3 and AQP9 suggests that AQP9 in rat oral epithelia acts as a channel by facilitating glycerol uptake from the blood through the endothelial cells of the capillary vessels to the oral stratified squamous epithelium. AQP3 and AQP9 facilitate both transcellular osmotic water flow and glycerol transport as pore-like passive transporters in the keratinocytes of oral epithelia, and may play a key role in not only hydration and the permeability barrier, but also cell proliferation, differentiation, migration, development, and wound healing by generating ATP.

  5. Aquaglyceroporins and metalloid transport: implications in human diseases.

    Science.gov (United States)

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

    2009-01-01

    Aquaglyceroporin (AQP) channels facilitate the diffusion of a wide range of neutral solutes, including water, glycerol, and other small uncharged solutes. More recently, AQPs have been shown to allow the passage of trivalent arsenic and antimony compounds. Arsenic and antimony are metalloid elements. At physiological pH, the trivalent metalloids behave as molecular mimics of glycerol, and are conducted through AQP channels. Arsenicals and antimonials are extremely toxic to cells. Despite their toxicity, both metalloids are used as chemotherapeutic agents for the treatment of cancer and protozoan parasitic diseases. The metalloid homeostasis property of AQPs can be a mixed blessing. In some cases, AQPs form part of the detoxification pathway, and extrude metalloids from cells. In other instances, AQPs allow the transport of metalloids into cells, thereby conferring sensitivity. Understanding the factors that modulate AQP expression will aid in a better understanding of metalloid toxicity and also provide newer approaches to metalloid based chemotherapy.

  6. Leptin administration restores the altered adipose and hepatic expression of aquaglyceroporins improving the non-alcoholic fatty liver of ob/ob mice.

    Science.gov (United States)

    Rodríguez, Amaia; Moreno, Natalia R; Balaguer, Inmaculada; Méndez-Giménez, Leire; Becerril, Sara; Catalán, Victoria; Gómez-Ambrosi, Javier; Portincasa, Piero; Calamita, Giuseppe; Soveral, Graça; Malagón, María M; Frühbeck, Gema

    2015-07-10

    Glycerol is an important metabolite for the control of lipid accumulation in white adipose tissue (WAT) and liver. We aimed to investigate whether exogenous administration of leptin improves features of non-alcoholic fatty liver disease (NAFLD) in leptin-deficient ob/ob mice via the regulation of AQP3 and AQP7 (glycerol channels mediating glycerol efflux in adipocytes) and AQP9 (aquaglyceroporin facilitating glycerol influx in hepatocytes). Twelve-week-old male wild type and ob/ob mice were divided in three groups as follows: control, leptin-treated (1 mg/kg/d) and pair-fed. Leptin deficiency was associated with obesity and NAFLD exhibiting an AQP3 and AQP7 increase in WAT, without changes in hepatic AQP9. Adipose Aqp3 and hepatic Aqp9 transcripts positively correlated with markers of adiposity and hepatic steatosis. Chronic leptin administration (4-weeks) was associated with improved body weight, whole-body adiposity, and hepatosteatosis of ob/ob mice and to a down-regulation of AQP3, AQP7 in WAT and an up-regulation of hepatic AQP9. Acute leptin stimulation in vitro (4-h) induced the mobilization of aquaglyceroporins towards lipid droplets (AQP3) and the plasma membrane (AQP7) in murine adipocytes. Our results show that leptin restores the coordinated regulation of fat-specific AQP7 and liver-specific AQP9, a step which might prevent lipid overaccumulation in WAT and liver in obesity.

  7. Roles of vertebrate aquaglyceroporins in arsenic transport and detoxification.

    Science.gov (United States)

    Liu, Zijuan

    2010-01-01

    Aquaporins are important channel proteins that are responsible for the balance of cellular osmolarity and nutrient transport in vertebrates. Recently, new functions of these ancient channels have been found in the conduction of metalloid arsenic (As). Chronic As exposure through contaminated water and food sources is associated with multiple human diseases and endangers millions of people's health worldwide. Therefore, identification of the As transport pathways is necessary to elucidate the mechanisms of As carcinogenesis. Arsenic detoxification systems have been studied in multiple vertebrates such as mammalian mouse, rat, humans and nonmammalian vertebrates. Multiple transporters and enzymes have been shown to be involved in As translocation and cellular transformation. In these vertebrates, members ofaquaglyceroporins, which include AQP7 in kidney and AQP9 in liver, catalyze uptake of inorganic trivalent arsenite [As(III)]. AQP9, the major liver aquaglyceroporin, conducts both inorganic As(III) and organic monomethylarsonous acid [MMA(III)], an intermediate that is generated during the cellular methylation. As a channel that facilitates a downhill movement of substances dependent on the concentration gradient, AQP9 may play an important role in the simultaneous influx of inorganic As(III) from blood to liver and efflux of As metabolite MMA(III) from liver to blood. In this chapter, we will discuss the function ofaquaglyceroporins ofvertebrates in uptake and detoxification of the metalloid As.

  8. The role of alanine 163 in solute permeability of Leishmania major aquaglyceroporin LmAQP1.

    Science.gov (United States)

    Mukhopadhyay, Rita; Mandal, Goutam; Atluri, Venkata Subba Rao; Figarella, Katherine; Uzcategui, Nestor L; Zhou, Yao; Beitz, Eric; Ajees, A Abdul; Bhattacharjee, Hiranmoy

    2011-01-01

    Leishmania major aquaglyceroporin LmAQP1 allows adventitious passage of antimonite, an activated form of the drug Pentostam, which is used as the first line treatment for leishmaniasis. The extracellular C-loop of an aquaglyceroporin confers substrate specificity. Alteration of Glu125 to serine in the Plasmodium falciparum aquaglyceroporin PfAQP has been shown to selectively affect water but not glycerol permeability. The C-loop of LmAQP1 is twelve residues longer than PfAQP, and Ala163 is at an equivalent position as Glu125 of PfAQP. The role of Ala163 in LmAQP1 solute permeability was investigated. Alteration of Ala163 to serine or threonine did not significantly affect conduction of solutes. However, alteration to aspartate, glutamate, and glutamine blocked passage of water, glycerol, and other organic solutes. While LmAQP1 is a mercurial insensitive water channel, mutation of the adjacent threonine (Thr164) to cysteine led to inhibition of water passage by Hg(2+). This inhibition could be reversed upon addition of β-mercaptoethanol. These data suggest that, unlike Glu125 (PfAQP), Ala163 is not involved in stabilization of the C-loop and selective solute permeability. Ala163 is located near the pore mouth of the channel, and replacement of Ala163 by bulkier residue sterically hinders the passage of solutes. Alteration of Ala163 to serine or threonine affected metalloid uptake in the order, wild-type>A163S>A163T. Metalloid conduction was near completely blocked when Ala163 was mutagenized to aspartate, glutamate, or glutamine. Mutations such as A163S and A163T that reduced the permeability to antimonite, without a significant loss in water or solute conductivity raises the possibility that, subtle changes in the side chain of the amino acid residue in position 163 of LmAQP1 may play a role in drug resistance.

  9. Ergodic channel capacity of the spatial correlated rayleigh MIMO channel

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hui-ping; WU Ping; LIU Ai-jun

    2007-01-01

    The theoretical capacity of the spatial correlated Rayleigh multiple input multiple output (MIMO) channel is an important issue in MIMO technology. In this article, an ergodic channel capacity formula of the spatial correlated rayleigh MIMO channel is provided, which is deduced when two antennas exist at either the transmitter or the receiver. The multi-dimensional least-squares fit algorithm is employed to narrow the difference between the theoretical formula capacity and the practical capacity. Simulation results show that the theoretical capacity approaches the practical one closely.

  10. 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...

  11. COOPERATIVE ARQ PROTOCOL FOR CORRELATED WIRELESS CHANNELS

    Institute of Scientific and Technical Information of China (English)

    Yu Guanding; Zhang Zhaoyang; Qiu Peiliang

    2006-01-01

    A novel Automatic repeat ReQuest (ARQ) protocol called cooperative ARQ is presented in this letter, where a relay terminal is requested to retransmit an erroneously received packet, instead of the source terminal. The data link layer Packet Error Rate (PER) performance of cooperative ARQ is derived in correlated wireless channel. The results show that even though the relay-destination channel is worse than the sourcedestination channel, the new protocol outperforms the traditional one as long as the average SNR of the relaydestination channel is better than a certain threshold. It is also demonstrated that a second order diversity gain can be achieved with the cooperative ARQ protocol.

  12. Dynamical memory effects in correlated quantum channels

    Science.gov (United States)

    Addis, Carole; Karpat, Göktuǧ; Macchiavello, Chiara; Maniscalco, Sabrina

    2016-09-01

    Memory effects play a fundamental role in the study of the dynamics of open quantum systems. There exist two conceptually distinct notions of memory discussed for quantum channels in the literature. In quantum information theory quantum channels with memory are characterized by the existence of correlations between successive applications of the channel on a sequence of quantum systems. In open quantum systems theory memory effects arise dynamically during the time evolution of quantum systems and define non-Markovian dynamics. Here we relate and combine these two different concepts of memory. In particular, we study the interplay between correlations between multiple uses of quantum channels and non-Markovianity as nondivisibility of the t -parametrized family of channels defining the dynamical map.

  13. Pentamidine Is Not a Permeant but a Nanomolar Inhibitor of the Trypanosoma brucei Aquaglyceroporin-2.

    Science.gov (United States)

    Song, Jie; Baker, Nicola; Rothert, Monja; Henke, Björn; Jeacock, Laura; Horn, David; Beitz, Eric

    2016-02-01

    The chemotherapeutic arsenal against human African trypanosomiasis, sleeping sickness, is limited and can cause severe, often fatal, side effects. One of the classic and most widely used drugs is pentamidine, an aromatic diamidine compound introduced in the 1940s. Recently, a genome-wide loss-of-function screen and a subsequently generated trypanosome knockout strain revealed a specific aquaglyceroporin, TbAQP2, to be required for high-affinity uptake of pentamidine. Yet, the underlying mechanism remained unclear. Here, we show that TbAQP2 is not a direct transporter for the di-basic, positively charged pentamidine. Even though one of the two common cation filters of aquaglyceroporins, i.e. the aromatic/arginine selectivity filter, is unconventional in TbAQP2, positively charged compounds are still excluded from passing the channel. We found, instead, that the unique selectivity filter layout renders pentamidine a nanomolar inhibitor of TbAQP2 glycerol permeability. Full, non-covalent inhibition of an aqua(glycero)porin in the nanomolar range has not been achieved before. The remarkable affinity derives from an electrostatic interaction with Asp265 and shielding from water as shown by structure-function evaluation and point mutation of Asp265. Exchange of the preceding Leu264 to arginine abolished pentamidine-binding and parasites expressing this mutant were pentamidine-resistant. Our results indicate that TbAQP2 is a high-affinity receptor for pentamidine. Taken together with localization of TbAQP2 in the flagellar pocket of bloodstream trypanosomes, we propose that pentamidine uptake is by endocytosis.

  14. Pentamidine Is Not a Permeant but a Nanomolar Inhibitor of the Trypanosoma brucei Aquaglyceroporin-2.

    Directory of Open Access Journals (Sweden)

    Jie Song

    2016-02-01

    Full Text Available The chemotherapeutic arsenal against human African trypanosomiasis, sleeping sickness, is limited and can cause severe, often fatal, side effects. One of the classic and most widely used drugs is pentamidine, an aromatic diamidine compound introduced in the 1940s. Recently, a genome-wide loss-of-function screen and a subsequently generated trypanosome knockout strain revealed a specific aquaglyceroporin, TbAQP2, to be required for high-affinity uptake of pentamidine. Yet, the underlying mechanism remained unclear. Here, we show that TbAQP2 is not a direct transporter for the di-basic, positively charged pentamidine. Even though one of the two common cation filters of aquaglyceroporins, i.e. the aromatic/arginine selectivity filter, is unconventional in TbAQP2, positively charged compounds are still excluded from passing the channel. We found, instead, that the unique selectivity filter layout renders pentamidine a nanomolar inhibitor of TbAQP2 glycerol permeability. Full, non-covalent inhibition of an aqua(glyceroporin in the nanomolar range has not been achieved before. The remarkable affinity derives from an electrostatic interaction with Asp265 and shielding from water as shown by structure-function evaluation and point mutation of Asp265. Exchange of the preceding Leu264 to arginine abolished pentamidine-binding and parasites expressing this mutant were pentamidine-resistant. Our results indicate that TbAQP2 is a high-affinity receptor for pentamidine. Taken together with localization of TbAQP2 in the flagellar pocket of bloodstream trypanosomes, we propose that pentamidine uptake is by endocytosis.

  15. 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.

  16. Quantum Correlations Evolution Asymmetry in Quantum Channels

    Science.gov (United States)

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

    2017-03-01

    It was demonstrated that the entanglement evolution of a specially designed quantum state in the bistochastic channel is asymmetric. In this work, we generalize the study of the quantum correlations, including entanglement and quantum discord, evolution asymmetry to various quantum channels. We found that the asymmetry of entanglement and quantum discord only occurs in some special quantum channels, and the behavior of the entanglement evolution may be quite different from the behavior of the quantum discord evolution. To quantum entanglement, in some channels it decreases monotonously with the increase of the quantum channel intensity. In some other channels, when we increase the intensity of the quantum channel, it decreases at first, then keeps zero for some time, and then rises up. To quantum discord, the evolution becomes more complex and you may find that it evolutes unsmoothly at some points. These results illustrate the strong dependence of the quantum correlations evolution on the property of the quantum channels. Supported by the National Natural Science Foundation of China under Grant Nos. 61327901, 61490711, 61225025, 11474268, and the Fundamental Research Funds for the Central Universities under Grant No. WK2470000018

  17. 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.

  18. Charm mass effects in bulk channel correlations

    CERN Document Server

    Burnier, Y

    2013-01-01

    The bulk viscosity of thermalized QCD matter at temperatures above a few hundred MeV could be significantly influenced by charm quarks because their contribution arises four perturbative orders before purely gluonic effects. In an attempt to clarify the challenges of a lattice study, we determine the relevant imaginary-time correlator (of massive scalar densities) up to NLO in perturbation theory, and compare with existing data. We find discrepancies much larger than in the vector channel; this may hint, apart from the importance of taking a continuum limit, to larger non-perturbative effects in the scalar channel. We also recall how a transport peak related to the scalar density spectral function encodes non-perturbative information concerning the charm quark chemical equilibration rate close to equilibrium.

  19. Crystal structure of the aquaglyceroporin PfAQP from the malarial parasite Plasmodium falciparum

    Science.gov (United States)

    Newby, Zachary E R; O’Connell, Joseph; Robles-Colmenares, Yaneth; Khademi, Shahram; Miercke, Larry J; Stroud, Robert M

    2008-01-01

    The 2.05-Å resolution structure of the aquaglyceroporin from the malarial parasite Plasmodium falciparum (PfAQP), a protein important in the parasite’s life cycle, has been solved. The structure provides key evidence for the basis of water versus glycerol selectivity in aquaporin family members. Unlike its closest homolog of known structure, GlpF, the channel conducts both glycerol and water at high rates, framing the question of what determines high water conductance in aquaporin channels. The universally conserved arginine in the selectivity filter is constrained by only two hydrogen bonds in GlpF, whereas there are three in all water-selective aquaporins and in PfAQP. The decreased cost of dehydrating the triply-satisfied arginine cation may provide the basis for high water conductance. The two Asn-Pro-Ala (NPA) regions of PfAQP, which bear rare substitutions to Asn-Leu-Ala (NLA) and Asn-Pro-Ser (NPS), participate in preserving the orientation of the selectivity filter asparagines in the center of the channel. PMID:18500352

  20. MIMO Interference Alignment Over Correlated Channels with Imperfect CSI

    CERN Document Server

    Nosrat-Makouei, Behrang; Heath, Robert W

    2010-01-01

    Interference alignment (IA), given uncorrelated channel components and perfect channel state information, obtains the maximum degrees of freedom in an interference channel. Little is known, however, about how the sum rate of IA behaves at finite transmit power, with imperfect channel state information, or antenna correlation. This paper provides an approximate closed-form signal-to-interference-plus-noise-ratio (SINR) expression for IA over multiple-input-multiple-output (MIMO) channels with imperfect channel state information and transmit antenna correlation. Assuming linear processing at the transmitters and zero-forcing receivers, random matrix theory tools are utilized to derive an approximation for the post-processing SINR distribution of each stream for each user. Perfect channel knowledge and i.i.d. channel coefficients constitute special cases. This SINR distribution not only allows easy calculation of useful performance metrics like sum rate and symbol error rate, but also permits a realistic compari...

  1. 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.

  2. Transmission of Correlated Messages over Interference Channels with Strong Interference

    Science.gov (United States)

    Choi, Suhan; Yoon, Eunchul; Moon, Hichan

    Transmission of correlated messages over interference channels with strong interference is considered. As a result, an achievable rate region is presented. It is shown that if the messages are correlated, the achievable rate region can be larger than the capacity region given by Costa and El Gamal. As an example, the Gaussian interference channel is considered.

  3. Mutual Information of Pauli Channels with Correlated Noise

    Institute of Scientific and Technical Information of China (English)

    HOU Li-zhen; FANG Mao-Fa

    2007-01-01

    A general formula for the mutual information of the Pauli channels with memory modelled by correlated noise is derived.It is shown that the mutual information depends on the channel shrinking factor,the input state parameter and the channel memory coefficient.The analyses based on the general formula reveal that the entanglement is always a useful resource to enhance the mutual information of some.Pauli channels,such as the bit flip channel and the bit-phase flip channel.Our analyses also show that the entanglement is not advantageous to the reliable transmission of classical information for Borne Pauli channels at any time,such as the phase flip channel and the phase damping channel.

  4. Aquaglyceroporins are involved in uptake of arsenite into murine gastrointestinal tissues.

    Science.gov (United States)

    Wang, Chun; Chen, Gang; Jiang, Junkang; Qiu, Lianglin; Hosoi, Kazuo; Yao, Chenjuan

    2009-01-01

    Aquaglyceroporins (AQGPs) are members of aquaporin (AQP) family and belong to a subgroup of this water channel family; they are transmembrane proteins that transport water as well as glycerol and other solutes of small molecules. Recent studies have also identified that AQGPs are important transporters of trivalent metalloid in some mammalian cells. However, the uptake routes of arsenite in mammals are still less defined. In this study, to understand the routes of arsenite intake in mammals, mice were treated with Hg(II), glycerol, and As(III) and uptake of As(III) into the gastrointestinal tissues was measured. The level of inorganic arsenic (iAs) in gastrointestinal tissues after As(III) stimulation was much higher than Hg(II) +As(III) or glycerol+As(III) group. RT-PCR results showed that AQGPs were extensively expressed in gastrointestinal tissues of mice. We also treated Caco-2 cells with Hg(II) and As(III); the level of iAs in a group treated with Hg(II)+As(III) decreased compared with As(III)-treated group. Our results suggested that AQGPs could be important transporters in arsenite uptake into gastrointestinal tissues of mice, but more data are need to prove if AQGPs is the only pathway involved in As transport in mammals or just one of them.

  5. Removing correlations in signals transmitted over a quantum memory channel

    Science.gov (United States)

    Lupo, Cosmo; Memarzadeh, Laleh; Mancini, Stefano

    2012-01-01

    We consider a model of a bosonic memory channel, which induces correlations among the transmitted signals. The application of suitable unitary transformations at the encoding and decoding stages allows the complete removal of correlations, thereby mapping the memory channel into a memoryless one. However, such transformations, being global over an arbitrarily large number of bosonic modes, are not realistically implementable. We then introduce a family of efficiently realizable transformations, which can be used to partially remove correlations among errors, and we quantify the reduction of the gap with memoryless channels.

  6. Removing correlations in signals transmitted over a quantum memory channel

    CERN Document Server

    Lupo, Cosmo; Mancini, Stefano

    2011-01-01

    We consider a model of bosonic memory channel, which induces correlations among the transmitted signals. The application of suitable unitary transformations at encoding and decoding stages allows the complete removal of correlations, mapping the memory channel into a memoryless one. However, such transformations, being global over an arbitrary large number of bosonic modes, are not realistically implementable. We then introduce a family of efficiently realizable transformations which can be used to partially remove correlations among errors, and we quantify the reduction of the gap with memoryless channels.

  7. Identification of key residues involved in Si transport by the aquaglyceroporins.

    Science.gov (United States)

    Carpentier, Gabriel A; Garneau, Alexandre P; Marcoux, Andrée-Anne; Noël, Micheline; Frenette-Cotton, Rachelle; Isenring, Paul

    2016-09-01

    We recently demonstrated that the aquaglyceroporins (AQGPs) could act as potent transporters for orthosilicic acid (H4SiO4). Although interesting, this finding raised the question of whether water and H4SiO4, the transportable form of Si, permeate AQGPs by interacting with the same region of the pore, especially in view of the difference in molecular radius between the two substrates. Here, our goal was to identify residues that endow the AQGPs with the ability to facilitate Si diffusion by examining the transport characteristics of mutants in which residues were interchanged between a water-permeable but Si-impermeable channel (aquaporin 1 [AQP1]) and a Si-permeable but water-impermeable channel (AQP10). Our results indicate that the composition of the arginine filter (XX/R), known to include three residues that play an important role in water transport, may also be involved in Si selectivity. Interchanging the identities of the nonarginine residues within this filter causes Si transport to increase by approximately sevenfold in AQP1 and to decrease by approximately threefold in AQP10, whereas water transport and channel expression remain unaffected. Our results further indicate that two additional residues in the AQP arginine filter may be involved in substrate selectivity: replacing one of the residues has a profound effect on water permeability, and replacing the other has a profound effect on Si permeability. This study has thus led to the identification of residues that could play a key role in Si transport by the AQGPs and shown that substrate selectivity is likely ensured by more than one checkpoint within or near the pore.

  8. Ion channel noise can explain firing correlation in auditory nerves.

    Science.gov (United States)

    Moezzi, Bahar; Iannella, Nicolangelo; McDonnell, Mark D

    2016-10-01

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

  9. The dynamic behaviors of complementary correlations under decoherence channels

    Science.gov (United States)

    Du, Ming-Ming; Wang, Dong; Ye, Liu

    2017-01-01

    Complementary correlations can reveal the genuine quantum correlations present in a composite quantum system. Here, we explore an effective method to identify the entangled Bell diagonal states by means of Pearson correlation, one of the complementary correlations. Then, we extend this method to expose the dynamic behavior of complementary correlations under various kinds of decoherence channels. The sudden death and revival of entanglement can be explained by the idea of Pearson correlation. The threshold that is used to identify entanglement is proposed. Furthermore, we put forward a new method to expound the underlying physical mechanisms for which classical and quantum correlations suffer a sudden change in the decoherence process.

  10. Channel cross correlations in transport through complex media

    Science.gov (United States)

    Gehler, Stefan; Köber, Bernd; Celardo, Giuseppe Luca; Kuhl, Ulrich

    2016-10-01

    Measuring transmission between four antennas in microwave cavities, we investigate directly the channel cross correlations C of the cross sections σa b from antenna at r⃗a to antenna r⃗b. Specifically we look for the CΣ and CΛ, where the only difference is that CΛ has none of the four channels in common, whereas CΣ has exactly one channel in common. We find experimentally that these two channel cross correlations are antiphased as a function of the channel coupling strength, as predicted by theory. This anticorrelation is essential to obtain the correct values for the universal conductance fluctuations. To obtain good agreement between experiment and predictions from random matrix theory the effect of absorption has to be included.

  11. Capacities of lossy bosonic channel with correlated noise

    Science.gov (United States)

    Lupo, Cosmo; Pilyavets, Oleg V.; Mancini, Stefano

    2009-06-01

    We evaluate the information capacities of a lossy bosonic channel with correlated noise. The model generalizes the one recently discussed by Pilyavets et al (2008 Phys. Rev. A 77 052324), where memory effects come from the interaction with correlated environments. Environmental correlations are quantified by a multimode squeezing parameter, which vanishes in the memoryless limit. We show that a global encoding/decoding scheme, which involves input-entangled states among different channel uses, is always preferable with respect to a local one in the presence of memory. Moreover, in a certain range of the parameters, we provide an analytical expression for the classical capacity of the channel showing that a global encoding/decoding scheme allows it to be attained. All the results can be applied to a broad class of bosonic Gaussian channels.

  12. Capacities of lossy bosonic channel with correlated noise

    Energy Technology Data Exchange (ETDEWEB)

    Lupo, Cosmo; Pilyavets, Oleg V; Mancini, Stefano [Dipartimento di Fisica, Universita di Camerino, I-62032 Camerino (Italy)], E-mail: cosmo.lupo@unicam.it, E-mail: pilyavets@gmail.com, E-mail: stefano.mancini@unicam.it

    2009-06-15

    We evaluate the information capacities of a lossy bosonic channel with correlated noise. The model generalizes the one recently discussed by Pilyavets et al (2008 Phys. Rev. A 77 052324), where memory effects come from the interaction with correlated environments. Environmental correlations are quantified by a multimode squeezing parameter, which vanishes in the memoryless limit. We show that a global encoding/decoding scheme, which involves input-entangled states among different channel uses, is always preferable with respect to a local one in the presence of memory. Moreover, in a certain range of the parameters, we provide an analytical expression for the classical capacity of the channel showing that a global encoding/decoding scheme allows it to be attained. All the results can be applied to a broad class of bosonic Gaussian channels.

  13. Effective capacity of multiple antenna channels: Correlation and keyhole

    KAUST Repository

    Zhong, Caijun

    2012-01-01

    In this study, the authors derive the effective capacity limits for multiple antenna channels which quantify the maximum achievable rate with consideration of link-layer delay-bound violation probability. Both correlated multiple-input single-output and multiple-input multiple-output keyhole channels are studied. Based on the closed-form exact expressions for the effective capacity of both channels, the authors look into the asymptotic high and low signal-to-noise ratio regimes, and derive simple expressions to gain more insights. The impact of spatial correlation on effective capacity is also characterised with the aid of a majorisation theory result. It is revealed that antenna correlation reduces the effective capacity of the channels and a stringent quality-of-service requirement causes a severe reduction in the effective capacity but can be alleviated by increasing the number of antennas. © 2012 The Institution of Engineering and Technology.

  14. A Simple Capacity Formula for Correlated Diversity Rayleigh Fading Channels

    Institute of Scientific and Technical Information of China (English)

    CHENG Xing-qing; SU Shu-chun; LI Dao-ben

    2004-01-01

    Abstract: The system capacity can be considerably increased if we appropriately exploit the randomness of multipath propagation. A simple average capacity formula is derived for correlated diversity Rayleigh fading channels through linear transformation method.Numerical results that illustrate the effect of correlation parameter and diversity order on the diversitycapacity are also presented.

  15. Metalloid transport by aquaglyceroporins: consequences in the treatment of human diseases.

    Science.gov (United States)

    Mukhopadhyay, Rita; Beitz, Eric

    2010-01-01

    Metalloids can severely harm human physiology in a toxicological sense if taken up from the environment in acute high doses or chronically. However, arsenic or antimony containing drugs are still being used as treatment and are often the sole regime for certain forms of cancer, mainly types of leukemia and diseases caused by parasites, such as sleeping sickness or leishmaniasis. In this chapter, we give an outline of the positive effects of arsenicals and antimonials against such diseases, we summarize data on uptake pathways through human and parasite aquaglyceroporins and we discuss the progress and options in the development of therapeutic aquaporin and aquaglyceroporin inhibitor compounds.

  16. Adaptive codebook selection schemes for image classification in correlated channels

    Science.gov (United States)

    Hu, Chia Chang; Liu, Xiang Lian; Liu, Kuan-Fu

    2015-09-01

    The multiple-input multiple-output (MIMO) system with the use of transmit and receive antenna arrays achieves diversity and array gains via transmit beamforming. Due to the absence of full channel state information (CSI) at the transmitter, the transmit beamforming vector can be quantized at the receiver and sent back to the transmitter by a low-rate feedback channel, called limited feedback beamforming. One of the key roles of Vector Quantization (VQ) is how to generate a good codebook such that the distortion between the original image and the reconstructed image is the minimized. In this paper, a novel adaptive codebook selection scheme for image classification is proposed with taking both spatial and temporal correlation inherent in the channel into consideration. The new codebook selection algorithm is developed to select two codebooks from the discrete Fourier transform (DFT) codebook, the generalized Lloyd algorithm (GLA) codebook and the Grassmannian codebook to be combined and used as candidates of the original image and the reconstructed image for image transmission. The channel is estimated and divided into four regions based on the spatial and temporal correlation of the channel and an appropriate codebook is assigned to each region. The proposed method can efficiently reduce the required information of feedback under the spatially and temporally correlated channels, where each region is adaptively. Simulation results show that in the case of temporally and spatially correlated channels, the bit-error-rate (BER) performance can be improved substantially by the proposed algorithm compared to the one with only single codebook.

  17. Spatial Variation of the Correlated Color Temperature of Lightning Channel

    CERN Document Server

    Shimoji, Nobuaki; Sakihama, Singo

    2014-01-01

    In this paper, we studied the spatial variation of the correlated color temperature (CCT) of lightning channel. We also discussed the energy of lightning channels relating to the CCT . First we applied digital image processing techniques to lightning images. In order to reduce the chromatic aberration, we created the reduction technique algorithm of the chromatic aberration on digital still images. We applied the reduction technique of the chromatic aberration to digital still images, and then the obtained results was mapped to the xy-chromaticity diagram. The CCT of the lightning channel was decided on the xy-chromaticity diagram. From results, the spatial variation of the CCT of the lightning channel was confirmed. Then the energy associated with the the CCT was discussed.

  18. Performance of VBLAST Systems Based on Spatial Correlated MIMO Channels

    Institute of Scientific and Technical Information of China (English)

    WANG Zhong-peng; QIU Zhong-yuan; WU Wei-ling

    2004-01-01

    Vertically-layered Bell Laboratories Layered Space-Time (VBLAST) is one of the most promising techniques for realizing high spectral efficiencies over wireless link. In previously published work, the performance of VBLAST has been primarily investigated in uncorrelated Rayleigh fading channels. However in real environments some correlation between antenna elements can be presented. In this paper, we study the impact of transmit correlation on the performance of VBLAST systems. Finally we provide simulation results demonstrating the impact of spatial fading correlation on the symbol error rate of VBLAST.

  19. A Demosaicking Algorithm with Adaptive Inter-Channel Correlation

    Directory of Open Access Journals (Sweden)

    Joan Duran

    2015-12-01

    Full Text Available Most common cameras use a CCD sensor device measuring a single color per pixel. Demosaicking is the interpolation process by which one can infer a full color image from such a matrix of values, thus interpolating the two missing components per pixel. Most demosaicking methods take advantage of inter-channel correlation locally selecting the best interpolation direction. The obtained results look convincing except when local geometry cannot be inferred from neighboring pixels or channel correlation is low. In these cases, these algorithms create interpolation artifacts such as zipper effect or color aliasing. This paper discusses the implementation details of the algorithm proposed in [J. Duran, A. Buades, ``Self-Similarity and Spectral Correlation Adaptive Algorithm for Color Demosaicking'', IEEE Transactions on Image Processing, 23(9, pp. 4031--4040, 2014]. The proposed method involves nonlocal image self-similarity in order to reduce interpolation artifacts when local geometry is ambiguous. It further introduces a clear and intuitive manner of balancing how much channel-correlation must be taken advantage of.

  20. 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.

  1. Channel capacity and digital modulation schemes in correlated Weibull fading channels with nonidentical statistics

    Institute of Scientific and Technical Information of China (English)

    Xiao Hailin; Nie Zaiping; Yang Shiwen

    2007-01-01

    The novel closed-form expressions for the average channel capacity of dual selection diversity is presented, as well as, the bit-error rate (BER) of several coherent and noncoherent digital modulation schemes in the correlated Weibull fading channels with nonidentical statistics.The results are expressed in terms of Meijer's Gfunction, which can be easily evaluated numerically.The simulation results are presented to validate the proposed theoretical analysis and to examine the effects of the fading severity on the concerned quantities.

  2. Robust MSE precoder for imperfectly known MIMO wireless correlated channel

    Institute of Scientific and Technical Information of China (English)

    MA Peng-fei; ZHAO Hui; WANG Wen-bo

    2009-01-01

    Aimed at that only one form of channel statistic information is utilized in traditional robust precoder schemes: either the channel mean or the transmit antenna correlation in multiple-input multiple-output (MIMO) wireless system, this paper proposes robust precoder designs which exploit both of statistic information to minimize the equalization mean-square error (MSE) with power constraint. Two different power constraints are studied. Besides the usual sum power constraint over all antennas, the per-antenna power constraint is imposed at transmitter in this paper. Since each antenna has its own amplifier, individual power constraint on each antenna is more realistic. Especially in MIMO-OFDM systems, the Peak-to-Average Ratio (PAR) is one of main practical problems. Simulations show that the proposed schemes have better performance than traditional normalized zero forcing schemes for imperfectly known correlated channel. Moreover, per-antenna power constraint can efficiently decrease the demand of dynamic range of power amplifier on each transmit antenna, especially in MIMO-OFDM systems.

  3. Cross Correlation Analysis of Multi-Channel Near Infrared Spectroscopy

    Directory of Open Access Journals (Sweden)

    Raul Fernandez Rojas

    2016-02-01

    Full Text Available In this paper we present the use of a signal proces sing technique to find dominant channels in near infrared spectroscopy (NIRS. Cross correlatio n is computed to compare measuring channels and identify delays among the channels. In addition, visual inspection was used to detect potential dominant channels. The results sho wed that the visual analysis exposed pain- related activations in the primary somatosensory co rtex (S1 after stimulation which is consistent with similar studies and the cross corre lation analysis found dominant channels on both cerebral hemispheres. The analysis also showed a relationship between dominant channels and neighbouring channels. Therefore, our results p resent a new method to detect dominant regions in the cerebral cortex using near-infrared spectroscopy. These results have also implications in the reduction of number of channels by eliminating irrelevant channels for the experiment

  4. Blind Cartography for Side Channel Attacks: Cross-Correlation Cartography

    Directory of Open Access Journals (Sweden)

    Laurent Sauvage

    2012-01-01

    Full Text Available Side channel and fault injection attacks are major threats to cryptographic applications of embedded systems. Best performances for these attacks are achieved by focusing sensors or injectors on the sensible parts of the application, by means of dedicated methods to localise them. Few methods have been proposed in the past, and all of them aim at pinpointing the cryptoprocessor. However it could be interesting to exploit the activity of other parts of the application, in order to increase the attack's efficiency or to bypass its countermeasures. In this paper, we present a localisation method based on cross-correlation, which issues a list of areas of interest within the attacked device. It realizes an exhaustive analysis, since it may localise any module of the device, and not only those which perform cryptographic operations. Moreover, it also does not require a preliminary knowledge about the implementation, whereas some previous cartography methods require that the attacker could choose the cryptoprocessor inputs, which is not always possible. The method is experimentally validated using observations of the electromagnetic near field distribution over a Xilinx Virtex 5 FPGA. The matching between areas of interest and the application layout in the FPGA floorplan is confirmed by correlation analysis.

  5. Aquaglyceroporin 2 controls susceptibility to melarsoprol and pentamidine in African trypanosomes.

    Science.gov (United States)

    Baker, Nicola; Glover, Lucy; Munday, Jane C; Aguinaga Andrés, David; Barrett, Michael P; de Koning, Harry P; Horn, David

    2012-07-03

    African trypanosomes cause sleeping sickness in humans, a disease that is typically fatal without chemotherapy. Unfortunately, drug resistance is common and melarsoprol-resistant trypanosomes often display cross-resistance to pentamidine. Although melarsoprol/pentamidine cross-resistance (MPXR) has been an area of intense interest for several decades, our understanding of the underlying mechanisms remains incomplete. Recently, a locus encoding two closely related aquaglyceroporins, AQP2 and AQP3, was linked to MPXR in a high-throughput loss-of-function screen. Here, we show that AQP2 has an unconventional "selectivity filter." AQP2-specific gene knockout generated MPXR trypanosomes but did not affect resistance to a lipophilic arsenical, whereas recombinant AQP2 reversed MPXR in cells lacking native AQP2 and AQP3. AQP2 was also shown to be disrupted in a laboratory-selected MPXR strain. Both AQP2 and AQP3 gained access to the surface plasma membrane in insect life-cycle-stage trypanosomes but, remarkably, AQP2 was specifically restricted to the flagellar pocket in the bloodstream stage. We conclude that the unconventional aquaglyceroporin, AQP2, renders cells sensitive to both melarsoprol and pentamidine and that loss of AQP2 function could explain cases of innate and acquired MPXR.

  6. Characteristic analysis on UAV-MIMO channel based on normalized correlation matrix.

    Science.gov (United States)

    Gao, Xi jun; Chen, Zi li; Hu, Yong Jiang

    2014-01-01

    Based on the three-dimensional GBSBCM (geometrically based double bounce cylinder model) channel model of MIMO for unmanned aerial vehicle (UAV), the simple form of UAV space-time-frequency channel correlation function which includes the LOS, SPE, and DIF components is presented. By the methods of channel matrix decomposition and coefficient normalization, the analytic formula of UAV-MIMO normalized correlation matrix is deduced. This formula can be used directly to analyze the condition number of UAV-MIMO channel matrix, the channel capacity, and other characteristic parameters. The simulation results show that this channel correlation matrix can be applied to describe the changes of UAV-MIMO channel characteristics under different parameter settings comprehensively. This analysis method provides a theoretical basis for improving the transmission performance of UAV-MIMO channel. The development of MIMO technology shows practical application value in the field of UAV communication.

  7. Diversity Gain and Coding Performance of OST-CPM System in Spatially Correlated Channels

    Directory of Open Access Journals (Sweden)

    Wen-Li Shen

    2013-03-01

    Full Text Available The Chernoff bound on Pair-Wise Error Probability (PWEP performance of orthogonal space-time coded CPM (OST-CPM systems is investigated, for two transmit antennas, over spatially correlated channels. Approximate Chernoff bound for high Signal-to-Noise Ratio (SNR is derived to evaluate the diversity gain and coding performance in correlated channels. The achievable diversity gain of this system decreases due to the signal correlation between the antennas. Simulation results show that the error performance over a correlated channel is degraded when the correlation coefficient increases. And the penalty on the code performance increases a lot in fully correlated channels. It can also be seen that the diversity gain decreases when the channel is fully correlated, which matches well with the theoretical analysis. The upper bounds can be looser when diversity order decreases.

  8. Trypanosoma Brucei Aquaglyceroporins Facilitate the Uptake of Arsenite and Antimonite in a pH Dependent Way

    Directory of Open Access Journals (Sweden)

    Néstor L. Uzcátegui

    2013-09-01

    Full Text Available Background: Trypanosoma brucei is a primitive parasitic protozoan that thrives in diverse environments such as the midgut of the tsetse fly and the blood of a mammalian host. For an adequate adaptation to these environments, the parasite´s aquaglyceroporins play an important role. Methods and Results: In order to test their ability to transport trivalent arsenic and antimony, we expressed the three known Trypanosoma brucei aquaglyceroporins (TbAQPs in the heterologous systems of yeast null aquaporin mutant and Xenopus laevis oocytes. For both expression systems, we found a pH dependent intracellular accumulation of As(III or Sb(III mediated by all of the three TbAQPs, with the exception of TbAQP1-As(III uptake. Additionally, we observed that Trypanosoma brucei aquaglyceroporins allow the passage of As(III in both directions. Conclusion: Taken together, these results demonstrated that T. brucei aquaglyceroporins can serve as entry routes for As(III and Sb(III into the parasitic cell, and that this uptake is pH sensitive. Therefore, aquaporins of protozoan parasites may be considered useful as a vehicle for drug delivery.

  9. Physical-Layer Security over Correlated Erasure Channels

    OpenAIRE

    Harrison, W. K.; Almeida, J; McLaughlin, S. W.; Barros, J.

    2011-01-01

    We explore the additional security obtained by noise at the physical layer in a wiretap channel model setting. Security enhancements at the physical layer have been proposed recently using a secrecy metric based on the degrees of freedom that an attacker has with respect to the sent ciphertext. Prior work focused on cases in which the wiretap channel could be modeled as statistically independent packet erasure channels for the legitimate receiver and an eavesdropper. In this paper, we go beyo...

  10. Zero-error channel capacity and simulation assisted by non-local correlations

    CERN Document Server

    Cubitt, Toby S; Matthews, William; Winter, Andreas

    2010-01-01

    Shannon's theory of zero-error communication is re-examined in the broader setting of using one classical channel to simulate another exactly, and in the presence of various resources that are all classes of non-signalling correlations: Shared randomness, shared entanglement and arbitrary non-signalling correlations. Specifically, when the channel being simulated is noiseless, this reduces to the zero-error capacity of the channel, assisted by the various classes of non-signalling correlations. When the resource channel is noiseless, it results in the "reverse" problem of simulating a noisy channel exactly by a noiseless one, assisted by correlations. In both cases, 'one-shot' separations between the power of the different assisting correlations are exhibited. The most striking result of this kind is that entanglement can assist in zero-error communication, in stark contrast to the standard setting of communicaton with asymptotically vanishing error in which entanglement does not help at all. In the asymptoti...

  11. A 32-channel photon counting module with embedded auto/cross-correlators for real-time parallel fluorescence correlation spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gong, S.; Labanca, I.; Rech, I.; Ghioni, M. [Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy)

    2014-10-15

    Fluorescence correlation spectroscopy (FCS) is a well-established technique to study binding interactions or the diffusion of fluorescently labeled biomolecules in vitro and in vivo. Fast FCS experiments require parallel data acquisition and analysis which can be achieved by exploiting a multi-channel Single Photon Avalanche Diode (SPAD) array and a corresponding multi-input correlator. This paper reports a 32-channel FPGA based correlator able to perform 32 auto/cross-correlations simultaneously over a lag-time ranging from 10 ns up to 150 ms. The correlator is included in a 32 × 1 SPAD array module, providing a compact and flexible instrument for high throughput FCS experiments. However, some inherent features of SPAD arrays, namely afterpulsing and optical crosstalk effects, may introduce distortions in the measurement of auto- and cross-correlation functions. We investigated these limitations to assess their impact on the module and evaluate possible workarounds.

  12. A cross-layer adaptive transmission scheme over correlated fading channels

    Institute of Scientific and Technical Information of China (English)

    XIAO Junfeng; QIU Jing; CHENG Shiduan

    2007-01-01

    Conventional adaptive transmission schemes perform poorly in wireless correlated slow-fading channels.A cross-layer adaptive transmission scheme combined with selective repeat automatic repeat request(SR-ARQ)is proposed.We apply a multi-state Markov system model for analyzing the performance of systems and optimizing the selection of modulation levels and packet sizes in correlated fading channels,which is also described by a finite-state Markov chain.A general closed-form expression of the average throughput for our suggested scheme is presented.Numerical results show that our adaptive scheme combined with SR-ARQ can obtain good performance in correlated fading channels.

  13. Spatial Correlation of PAN UWB-MIMO Channel Including User Dynamics

    DEFF Research Database (Denmark)

    Wang, Yu; Kovacs, Istvan Zsolt; Pedersen, Gert Frølund;

    In this paper we present and analyze spatial correlation properties of indoor 4x2 MIMO UWB channels in personal area network (PAN) scenarios. The presented results are based on measurement of radio links between an access point like device and a hand held or belt mounted device with dynamic user....... achieves an ergodic capacity close to i.i.d. Rayleigh channel capacity. However the outage capacity degrades due to the wideband power fluctuation / shadowing introduced by user’s body........ It is found the channel shows spatial correlated wideband power, and spatial uncorrelated complex channel coefficients at different frequencies and delays with respect to a correlation coefficient threshold of 0.7. The Kronecker model is proved not suitable for the investigated scenarios. The MIMO UWB channel...

  14. A deterministic equivalent for the capacity analysis of correlated multi-user MIMO channels

    CERN Document Server

    Couillet, Romain; Silverstein, Jack W

    2009-01-01

    This paper provides the analysis of capacity expressions in multi-user and multi-cell systems when the transmitters and receivers have a large number of correlated antennas. Our main contribution mathematically translates into a deterministic equivalent of the Shannon transform of a class of large dimensional random matrices. This class of large matrices is used in this contribution to model (i) multi-antenna multiple access (MAC) and broadcast channels (BC) with transmit and receive channel correlation, (ii) multiple-input multiple-output (MIMO) communications with inter-cell interference and channel correlation both at the base stations and at the receiver. These models extend the classical results on multi-user MIMO capacities in independent and identically distributed (i.i.d.) Gaussian channels to the more realistic Gaussian channels with separable variance profile. On an information theoretical viewpoint, this article provides: in scenario (i), an asymptotic description of the MAC and BC rate regions as ...

  15. Spatial-Temporal Correlation Properties of the 3GPP Spatial Channel Model and the Kronecker MIMO Channel Model

    Directory of Open Access Journals (Sweden)

    Wu Hanguang

    2007-01-01

    Full Text Available The performance of multiple-input multiple-output (MIMO systems is greatly influenced by the spatial-temporal correlation properties of the underlying MIMO channels. This paper investigates the spatial-temporal correlation characteristics of the spatial channel model (SCM in the Third Generation Partnership Project (3GPP and the Kronecker-based stochastic model (KBSM at three levels, namely, the cluster level, link level, and system level. The KBSM has both the spatial separability and spatial-temporal separability at all the three levels. The spatial-temporal separability is observed for the SCM only at the system level, but not at the cluster and link levels. The SCM shows the spatial separability at the link and system levels, but not at the cluster level since its spatial correlation is related to the joint distribution of the angle of arrival (AoA and angle of departure (AoD. The KBSM with the Gaussian-shaped power azimuth spectrum (PAS is found to fit best the 3GPP SCM in terms of the spatial correlations. Despite its simplicity and analytical tractability, the KBSM is restricted to model only the average spatial-temporal behavior of MIMO channels. The SCM provides more insights of the variations of different MIMO channel realizations, but the implementation complexity is relatively high.

  16. Spatial-Temporal Correlation Properties of the 3GPP Spatial Channel Model and the Kronecker MIMO Channel Model

    Directory of Open Access Journals (Sweden)

    Cheng-Xiang Wang

    2007-02-01

    Full Text Available The performance of multiple-input multiple-output (MIMO systems is greatly influenced by the spatial-temporal correlation properties of the underlying MIMO channels. This paper investigates the spatial-temporal correlation characteristics of the spatial channel model (SCM in the Third Generation Partnership Project (3GPP and the Kronecker-based stochastic model (KBSM at three levels, namely, the cluster level, link level, and system level. The KBSM has both the spatial separability and spatial-temporal separability at all the three levels. The spatial-temporal separability is observed for the SCM only at the system level, but not at the cluster and link levels. The SCM shows the spatial separability at the link and system levels, but not at the cluster level since its spatial correlation is related to the joint distribution of the angle of arrival (AoA and angle of departure (AoD. The KBSM with the Gaussian-shaped power azimuth spectrum (PAS is found to fit best the 3GPP SCM in terms of the spatial correlations. Despite its simplicity and analytical tractability, the KBSM is restricted to model only the average spatial-temporal behavior of MIMO channels. The SCM provides more insights of the variations of different MIMO channel realizations, but the implementation complexity is relatively high.

  17. Performance Analysis of Beamforming in Fixed-gain AF Relay Networks with Asymmetric Correlated Fading Channels

    Science.gov (United States)

    Li, Min

    2014-07-01

    In this paper, the performance of beamforming (BF) for a dual-hop amplify-and-forward (AF) relay network, where the source and destination are each equipped with multiple antennas, is investigated. It is assumed that the source-relay and relay-destination channels experience mixed fading distributions, namely, correlated Nakagami-m/Rician and correlated Rician/Nakagami-m, respectively. By considering fixed-gain relaying, analytical expressions for outage probability (OP) and average symbol error rate (ASER) are derived in closed-form. Numerical results are presented to demonstrate the efficacy of our performance analysis, also illustrate the impact of channel correlation, fading severity, Rician factor and antenna configuration on the performance of the system. It is shown that the correlated Nakagami-m/Rician fading channel can achieve better performance than the correlated Rician/Nakagami-m fading channel with the increase of fading severity parameter, and the correlated Rician/Nakagami-m fading channel may outperform the correlated Nakagami-m/Rician fading channel by enlarging the Rician factor.

  18. Generation and protection of steady-state quantum correlations due to quantum channels with memory

    Science.gov (United States)

    Guo, You-neng; Fang, Mao-fa; Wang, Guo-you; Zeng, Ke

    2016-09-01

    We have proposed a scheme of the generation and preservation of two-qubit steady-state quantum correlations through quantum channels where successive uses of the channels are correlated. Different types of noisy channels with memory, such as amplitude damping, phase damping, and depolarizing channels, have been taken into account. Some analytical or numerical results are presented. The effect of channels with memory on dynamics of quantum correlations has been discussed in detail. The results show that steady-state entanglement between two initial qubits whose initial states are prepared in a specific family states without entanglement subject to amplitude damping channel with memory can be generated. The entanglement creation is related to the memory coefficient of channel μ . The stronger the memory coefficient of channel μ is, the more the entanglement creation is, and the earlier the separable state becomes the entangled state. Besides, we compare the dynamics of entanglement with that of quantum discord when a two-qubit system is initially prepared in an entangled state. We show that entanglement dynamics suddenly disappears, while quantum discord dynamics displays only in the asymptotic limit. Furthermore, two-qubit quantum correlations can be preserved at a long time in the limit of μ → 1.

  19. Generation and protection of steady-state quantum correlations due to quantum channels with memory

    Science.gov (United States)

    Guo, You-neng; Fang, Mao-fa; Wang, Guo-you; Zeng, Ke

    2016-12-01

    We have proposed a scheme of the generation and preservation of two-qubit steady-state quantum correlations through quantum channels where successive uses of the channels are correlated. Different types of noisy channels with memory, such as amplitude damping, phase damping, and depolarizing channels, have been taken into account. Some analytical or numerical results are presented. The effect of channels with memory on dynamics of quantum correlations has been discussed in detail. The results show that steady-state entanglement between two initial qubits whose initial states are prepared in a specific family states without entanglement subject to amplitude damping channel with memory can be generated. The entanglement creation is related to the memory coefficient of channel μ . The stronger the memory coefficient of channel μ is, the more the entanglement creation is, and the earlier the separable state becomes the entangled state. Besides, we compare the dynamics of entanglement with that of quantum discord when a two-qubit system is initially prepared in an entangled state. We show that entanglement dynamics suddenly disappears, while quantum discord dynamics displays only in the asymptotic limit. Furthermore, two-qubit quantum correlations can be preserved at a long time in the limit of μ → 1.

  20. Evaluation of correlations of flow boiling heat transfer of R22 in horizontal channels.

    Science.gov (United States)

    Zhou, Zhanru; Fang, Xiande; Li, Dingkun

    2013-01-01

    The calculation of two-phase flow boiling heat transfer of R22 in channels is required in a variety of applications, such as chemical process cooling systems, refrigeration, and air conditioning. A number of correlations for flow boiling heat transfer in channels have been proposed. This work evaluates the existing correlations for flow boiling heat transfer coefficient with 1669 experimental data points of flow boiling heat transfer of R22 collected from 18 published papers. The top two correlations for R22 are those of Liu and Winterton (1991) and Fang (2013), with the mean absolute deviation of 32.7% and 32.8%, respectively. More studies should be carried out to develop better ones. Effects of channel dimension and vapor quality on heat transfer are analyzed, and the results provide valuable information for further research in the correlation of two-phase flow boiling heat transfer of R22 in channels.

  1. High dynamic range multi-channel cross-correlator for single-shot temporal contrast measurement

    Science.gov (United States)

    Kon, A.; Nishiuchi, M.; Kiriyama, H.; Ogura, K.; Mori, M.; Sakaki, H.; Kando, M.; Kondo, K.

    2016-05-01

    We have developed a multi-channel cross-correlator for high dynamic range (>1010), single-shot temporal contrast measurements. The correlator utilizes a third-order crosscorrelation technique and has a reference channel, to be normalized by the measured peak intensity, and four independent optical delay lines. The measurement results of the shot-to-shot temporal contrast clearly show the intensity fluctuations of short pre-pulses at -4.5 ps and -26 ps before main pulse.

  2. Optimal transmission strategy for spatially correlated MIMO systems with channel statistical information

    Institute of Scientific and Technical Information of China (English)

    ZHAO Zhen-shan; XU Guo-zhi

    2007-01-01

    In real multiple-input multiple-output (MIMO) systems, the perfect channel state information (CSI) may be costly or impossible to acquire. But the channel statistical information can be considered relatively stationary during long-term transmission.The statistical information can be obtained at the receiver and fed back to the transmitter and do not require frequent update. By exploiting channel mean and covariance information at the transmitter simultaneously, this paper investigates the optimal transmission strategy for spatially correlated MIMO channels. An upper bound of ergodic capacity is derived and taken as the performance criterion. Simulation results are also given to show the performance improvement of the optimal transmission strategy.

  3. The Finite Field Multi-Way Relay Channel with Correlated Sources: The Three-User Case

    CERN Document Server

    Ong, Lawrence; Lechner, Gottfried; Johnson, Sarah J; Kellett, Christopher M

    2011-01-01

    The three-user finite field multi-way relay channel with correlated sources is considered. The three users generate possibly correlated messages, and each user is to transmit its message to the two other users reliably in the Shannon sense. As there is no direct link among the users, communication is carried out via a relay, and the link from the users to the relay and those from the relay to the users are finite field adder channels with additive noise of arbitrary distribution. The problem is to determine the set of all possible achievable rates, defined as channel uses per source symbol for reliable communication. For two classes of source/channel combinations, the solution is obtained using Slepian-Wolf source coding combined with functional-decode-forward channel coding.

  4. A Deterministic Equivalent for the Analysis of Non-Gaussian Correlated MIMO Multiple Access Channels

    CERN Document Server

    Wen, Chao-Kai; Wong, Kai-Kit; Guo, Mei-Hui; Chen, Jung-Chieh

    2011-01-01

    Large dimensional random matrix theory (RMT) has provided an efficient analytical tool to understand multiple-input multiple-output (MIMO) channels and to aid the design of MIMO wireless communication systems. However, previous studies based on large dimensional RMT rely on the assumption that the transmit correlation matrix is diagonal or the propagation channel matrix is Gaussian. There is an increasing interest in the channels where the transmit correlation matrices are generally nonnegative definite and the channel entries are non-Gaussian. This class of channel models appears in several applications in MIMO multiple access systems, such as small cell networks (SCNs). To address these problems, we use the generalized Lindeberg principle to show that the Stieltjes transforms of this class of random matrices with Gaussian or non-Gaussian independent entries coincide in the large dimensional regime. This result permits to derive the deterministic equivalents (e.g., the Stieltjes transform and the ergodic mut...

  5. Eigenstructures of MIMO Fading Channel Correlation Matrices and Optimum Linear Precoding Designs for Maximum Ergodic Capacity

    Directory of Open Access Journals (Sweden)

    Bahrami Hamid Reza

    2007-01-01

    Full Text Available The ergodic capacity of MIMO frequency-flat and -selective channels depends greatly on the eigenvalue distribution of spatial correlation matrices. Knowing the eigenstructure of correlation matrices at the transmitter is very important to enhance the capacity of the system. This fact becomes of great importance in MIMO wireless systems where because of the fast changing nature of the underlying channel, full channel knowledge is difficult to obtain at the transmitter. In this paper, we first investigate the effect of eigenvalues distribution of spatial correlation matrices on the capacity of frequency-flat and -selective channels. Next, we introduce a practical scheme known as linear precoding that can enhance the ergodic capacity of the channel by changing the eigenstructure of the channel by applying a linear transformation. We derive the structures of precoders using eigenvalue decomposition and linear algebra techniques in both cases and show their similarities from an algebraic point of view. Simulations show the ability of this technique to change the eigenstructure of the channel, and hence enhance the ergodic capacity considerably.

  6. Correlation of apical fluid-regulating channel proteins with lung function in human COPD lungs.

    Directory of Open Access Journals (Sweden)

    Runzhen Zhao

    Full Text Available Links between epithelial ion channels and chronic obstructive pulmonary diseases (COPD are emerging through animal model and in vitro studies. However, clinical correlations between fluid-regulating channel proteins and lung function in COPD remain to be elucidated. To quantitatively measure epithelial sodium channels (ENaC, cystic fibrosis transmembrane conductance regulator (CFTR, and aquaporin 5 (AQP5 proteins in human COPD lungs and to analyze the correlation with declining lung function, quantitative western blots were used. Spearman tests were performed to identify correlations between channel proteins and lung function. The expression of α and β ENaC subunits was augmented and inversely associated with lung function. In contrast, both total and alveolar type I (ATI and II (ATII-specific CFTR proteins were reduced. The expression level of CFTR proteins was associated with FEV1 positively. Abundance of AQP5 proteins and extracellular superoxide dismutase (SOD3 was decreased and correlated with spirometry test results and gas exchange positively. Furthermore, these channel proteins were significantly associated with severity of disease. Our study demonstrates that expression of ENaC, AQP5, and CFTR proteins in human COPD lungs is quantitatively associated with lung function and severity of COPD. These apically located fluid-regulating channels may thereby serve as biomarkers and potent druggable targets of COPD.

  7. Experimental demonstration of entanglement-enhanced classical communication over a quantum channel with correlated noise

    CERN Document Server

    Banaszek, K; Wasilewski, W; Radzewicz, C

    2004-01-01

    We present an experiment demonstrating entanglement-enhanced classical communication capacity of a quantum channel with correlated noise. The channel is modelled by a fiber optic link exhibiting random birefringence that fluctuates on a time scale much longer than the temporal separation between consecutive uses of the channel. In this setting, introducing entanglement between two photons travelling down the fiber allows one to encode reliably up to one bit of information into their joint polarization degree of freedom. When no quantum correlations between two separate uses of the channel are allowed, this capacity is reduced by a factor of more than three. We demonstrated this effect using a fiber-coupled source of entagled photon pairs based on spontaneous parametric down-conversion, and a linear-optics Bell state measurement.

  8. WATER-FILLING SPACE-TIME CODE IN CORRELATED FLAT RAYLEIGH FADING MISO CHANNELS

    Institute of Scientific and Technical Information of China (English)

    Cheng Jian; Chen Ming; Cheng Shixin

    2003-01-01

    In this paper, STC with water-filling transmit power distribution in MISO systemis proposed when the partial channel information feedback is possible, for example, at slow fadingscenario. The performances of the water-filling STC including water-filling STTC and water-filling STBC are analyzed. Performance comparison of the Ungerboeck's 2/3 trellis coded 8PSKmodulated 2-STBC and 2-STTCs with QPSK is given out in different channel correlation.

  9. The Three-User Finite Field Multi-Way Relay Channel with Correlated Sources

    CERN Document Server

    Ong, Lawrence; Lechner, Gottfried; Johnson, Sarah J; Kellett, Christopher M

    2012-01-01

    This paper studies the three-user finite field multi-way relay channel with correlated sources, where three users exchange possibly correlated messages via a relay. Full data exchange is considered where each user is to decode the messages from the other two users. There is no direct link among the users; the uplink from the users to the relay and the downlinks from the relay to the users are finite field adder channels with independent additive noise of arbitrary distributions. The problem is to determine the set of all achievable rates, defined as channel uses per source symbol for reliable communication. Using the Slepian-Wolf source coding and a functional-decode-forward channel coding scheme, the solution is obtained for two classes of source and channel combinations. Furthermore, for correlated sources with common cores, two new functional-decode-forward coding schemes are constructed and are shown to obtain the set of all achievable rates for any source and channel combination.

  10. Outage Performance Analysis of Cooperative Diversity with MRC and SC in Correlated Lognormal Channels

    Directory of Open Access Journals (Sweden)

    Skraparlis D

    2009-01-01

    Full Text Available Abstract The study of relaying systems has found renewed interest in the context of cooperative diversity for communication channels suffering from fading. This paper provides analytical expressions for the end-to-end SNR and outage probability of cooperative diversity in correlated lognormal channels, typically found in indoor and specific outdoor environments. The system under consideration utilizes decode-and-forward relaying and Selection Combining or Maximum Ratio Combining at the destination node. The provided expressions are used to evaluate the gains of cooperative diversity compared to noncooperation in correlated lognormal channels, taking into account the spectral and energy efficiency of the protocols and the half-duplex or full-duplex capability of the relay. Our analysis demonstrates that correlation and lognormal variances play a significant role on the performance gain of cooperative diversity against noncooperation.

  11. Channel capacity of multiple-input multiple-output systems with transmit and receive correlation

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In order to investigate the impact of channel model parameters on the channel capacity of a multipleinput multiple-output (MIMO) system,a novel method is proposed to explore the channel capacity under Rayleigh flat fading with correlated transmit and receive antennas.The optimal transmitting direction which can achieve maximum channel capacity is derived using random matrices theory.In addition,the closed-form expression for the channel capacity of MIMO systems is given by utilizing the properties of Wishart distribution when SNR is high.Computer simulation results show that the channel capacity is maximized when the antenna spacing increases to a certain point,and furthermore,the larger the scattering angle is,the more quickly the channel capacity converges to its maximum.At high SNR (>12 dB),the estimation of capacity is close to its true value.And,when the same array configuration is adopted both at the transmitter and the receiver,the UCA yields higher channel capacity than ULA.

  12. Protecting entanglement from correlated amplitude damping channel using weak measurement and quantum measurement reversal

    Science.gov (United States)

    Xiao, Xing; Yao, Yao; Xie, Ying-Mao; Wang, Xing-Hua; Li, Yan-Ling

    2016-09-01

    Based on the quantum technique of weak measurement, we propose a scheme to protect the entanglement from correlated amplitude damping decoherence. In contrast to the results of memoryless amplitude damping channel, we show that the memory effects play a significant role in the suppression of entanglement sudden death and protection of entanglement under severe decoherence. Moreover, we find that the initial entanglement could be drastically amplified by the combination of weak measurement and quantum measurement reversal even under the correlated amplitude damping channel. The underlying mechanism can be attributed to the probabilistic nature of weak measurements.

  13. Capacity of MIMO LAS-CDMA System Under Correlating Multi-Path Fading Channels

    Institute of Scientific and Technical Information of China (English)

    WANG Jun-xuan; RAO Wen-yuan; LI Dao-ben

    2005-01-01

    Capacity of MIMO LAS-CDMA systems under multi-path fading channels with two different correlating models were studied in the paper. Influences of the two models parameters on capacity were analyzed. The numerical results present that: according to the Various Scattering Environments correlating model, when the inner-elements distance of antennas array is large than 0.5λ, correlation almost does not take from the system capacity; for the Salz-Winter correlating model, the spread angle at receiver is the other key factor, it also influence the system capacity greatly.

  14. A New Generation Method for Spatial-Temporal Correlated MIMO Nakagami Fading Channel

    Directory of Open Access Journals (Sweden)

    Qiu-Ming Zhu

    2012-01-01

    Full Text Available A new generation method for spatial and temporal correlated multiple-input multiple-output (MIMO Nakagami fading channel is proposed, which has low complexity and is applicable for arbitrary fading parameters and prespecified correlation coefficients of different subchannel. The new scheme can be divided into two steps: (1 generate independent Nakagami fading sequences for each subchannel based on a novel rejection method; (2 introduce the temporal and spatial correlation based on the relationships between Rayleigh, Gamma, and Nakagami random processes. The analysis and simulation results show that the proposed simulator has a good agreement with the theoretical model on fading envelope distribution, spatial-temporal correlation characteristic.

  15. Asymmetric Joint Source-Channel Coding for Correlated Sources with Blind HMM Estimation at the Receiver

    Directory of Open Access Journals (Sweden)

    Ser Javier Del

    2005-01-01

    Full Text Available We consider the case of two correlated sources, and . The correlation between them has memory, and it is modelled by a hidden Markov chain. The paper studies the problem of reliable communication of the information sent by the source over an additive white Gaussian noise (AWGN channel when the output of the other source is available as side information at the receiver. We assume that the receiver has no a priori knowledge of the correlation statistics between the sources. In particular, we propose the use of a turbo code for joint source-channel coding of the source . The joint decoder uses an iterative scheme where the unknown parameters of the correlation model are estimated jointly within the decoding process. It is shown that reliable communication is possible at signal-to-noise ratios close to the theoretical limits set by the combination of Shannon and Slepian-Wolf theorems.

  16. Asymmetric Joint Source-Channel Coding for Correlated Sources with Blind HMM Estimation at the Receiver

    Directory of Open Access Journals (Sweden)

    Ser Javier Del

    2005-01-01

    Full Text Available We consider the case of two correlated sources, S 1 and S 2 . The correlation between them has memory, and it is modelled by a hidden Markov chain. The paper studies the problem of reliable communication of the information sent by the source S 1 over an additive white Gaussian noise (AWGN channel when the output of the other source S 2 is available as side information at the receiver. We assume that the receiver has no a priori knowledge of the correlation statistics between the sources. In particular, we propose the use of a turbo code for joint source-channel coding of the source S 1 . The joint decoder uses an iterative scheme where the unknown parameters of the correlation model are estimated jointly within the decoding process. It is shown that reliable communication is possible at signal-to-noise ratios close to the theoretical limits set by the combination of Shannon and Slepian-Wolf theorems.

  17. An empirical correlation for isothermal parallel plate channel completely filled with porous media

    Directory of Open Access Journals (Sweden)

    Hamdan Mohammad O.

    2013-01-01

    Full Text Available This study reports a simple empirical correlation for friction factor and Nusselt number for laminar, steady state, hydraulically and thermally fully developed flow in isothermal parallel plate channel completely filled with porous media. The study is carried out using a finite difference numerical analysis. The Darcy-Brinkman-Forchheimer model is used to model the flow inside the porous media. The empirical correlations are developed to relate friction factor and Nusselt number to Darcy and Forchheimer coefficient.

  18. Avoiding disentanglement of multipartite entangled optical beams with a correlated noisy channel

    Science.gov (United States)

    Deng, Xiaowei; Tian, Caixing; Su, Xiaolong; Xie, Changde

    2017-01-01

    A quantum communication network can be constructed by distributing a multipartite entangled state to space-separated nodes. Entangled optical beams with highest flying speed and measurable brightness can be used as carriers to convey information in quantum communication networks. Losses and noises existing in real communication channels will reduce or even totally destroy entanglement. The phenomenon of disentanglement will result in the complete failure of quantum communication. Here, we present the experimental demonstrations on the disentanglement and the entanglement revival of tripartite entangled optical beams used in a quantum network. We experimentally demonstrate that symmetric tripartite entangled optical beams are robust in pure lossy but noiseless channels. In a noisy channel, the excess noise will lead to the disentanglement and the destroyed entanglement can be revived by the use of a correlated noisy channel (non-Markovian environment). The presented results provide useful technical references for establishing quantum networks. PMID:28295024

  19. Avoiding disentanglement of multipartite entangled optical beams with a correlated noisy channel

    Science.gov (United States)

    Deng, Xiaowei; Tian, Caixing; Su, Xiaolong; Xie, Changde

    2017-03-01

    A quantum communication network can be constructed by distributing a multipartite entangled state to space-separated nodes. Entangled optical beams with highest flying speed and measurable brightness can be used as carriers to convey information in quantum communication networks. Losses and noises existing in real communication channels will reduce or even totally destroy entanglement. The phenomenon of disentanglement will result in the complete failure of quantum communication. Here, we present the experimental demonstrations on the disentanglement and the entanglement revival of tripartite entangled optical beams used in a quantum network. We experimentally demonstrate that symmetric tripartite entangled optical beams are robust in pure lossy but noiseless channels. In a noisy channel, the excess noise will lead to the disentanglement and the destroyed entanglement can be revived by the use of a correlated noisy channel (non-Markovian environment). The presented results provide useful technical references for establishing quantum networks.

  20. Time-domain channel estimator based on cyclic correlation for OFDM systems with guard interval

    Institute of Scientific and Technical Information of China (English)

    JIA Min; GU Xue-mai; IM Se-bin; CHOI Hyung-jin

    2008-01-01

    Channel impulse response (CIR) can be estimated on the basis of cyclic correlation in time-domain for orthogonal frequency division multiplexing (OFDM) systems. This article proposes a generalized channel estimation method to reduce the estimation error by taking the average of different CIRs. Channel impulse responses are derived according to the different starting points of cyclic correlation. In addition, an effective CIR length estimation algorithm is also presented. The whole proposed methods are more effective to OFDM systems, especially to those with longer cyclic prefix. The analysis and the simulation results verify that the mean square error performance is 4-5 dB better than the conventional schemes under the same conditions.

  1. HIRS channel 12 brightness temperature dataset and its correlations with major climate indices

    Directory of Open Access Journals (Sweden)

    L. Shi

    2013-07-01

    Full Text Available A new version of the High-Resolution Infrared Radiation Sounder (HIRS upper tropospheric water vapor channel (channel 12 brightness temperature dataset is developed using intersatellite calibrated data. In this dataset, only those pixels affected by upper tropospheric clouds are discarded. Compared to the previous version that was based on column-clear-sky data, the new version has much better daily spatial coverage. The HIRS observation patterns are compared to microwave sounder measurements. The differences between the two types of sounders vary with respect to brightness temperature with larger differences for higher (dry values. Correlations between the HIRS upper tropospheric water vapor channel brightness temperatures and several major climate indices show strong signals during cold seasons. The selected climate indices track climate variation signals covering regions from the tropics to the poles. Qualitatively, moist signals are correlated with troughs and ascending branches of the circulation, while dry signals occur with ridges and descent. These correlations show the potential of using the upper tropospheric water vapor channel brightness temperature dataset together with a suite of many atmospheric variables to monitor regional climate changes and locate global teleconnection patterns.

  2. Broadband transceiver design of distributed amplify-and-forward MIMO relays in correlated channels

    Science.gov (United States)

    Hu, Chia-Chang; Tang, Kang-Tsao

    2013-12-01

    Combined optimization of the source precoder, relay weighting matrices, and destination decoder is proposed in dual-hop amplify-and-forward (AF) multiple-input multiple-output (MIMO) multiple-relay networks with the source-to-destination link in correlated channels. This broadband cooperative transceiver design is studied based on the minimum mean-squared error (MMSE) criterion under correlated fading channels. The optimization problem belongs neither concave nor convex so that an iterative nonlinear matrix conjugate gradient (MCG) search algorithm is applied to explore local optimal solutions. Simulation results show that the broadband cooperative transceiver joint architecture performs better the non-cooperative transceiver design in terms of the bit-error-rate (BER).

  3. Limited Feedback Over Temporally Correlated Channels for the Downlink of a Femtocell Network

    CERN Document Server

    Akoum, Salam; Heath, Robert W

    2011-01-01

    Heterogeneous networks are a {\\ss}exible deployment model that rely on low power nodes to improve the user broadband experience in a cost effective manner. Femtocells are an integral part of heterogeneous networks, whose main purpose is to improve the indoor capacity. When restricting access to home users, femtocells cause a substantial interference problem that cannot be mitigated through coordination with the macrocell base station. In this paper, we analyze multiple antenna communication on the downlink of a macrocell network, with femtocell overlay. We evaluate the feasibility of limited feedback beamforming given delay on the feedback channel, quantization error and uncoordinated interference from the femtocells. We model the femtocell spatial distribution as a Poisson point process and the temporal correlation of the channel according to a Gauss-Markov model. We derive the probability of outage at the macrocell users as a function of the temporal correlation, the femtocell density, and the feedback rate...

  4. Exploiting Channel Correlation and PU Traffic Memory for Opportunistic Spectrum Scheduling

    CERN Document Server

    Wang, Shanshan; Zhang, Junshan

    2012-01-01

    We consider a cognitive radio network with multiple primary users (PUs) and one secondary user (SU), where a spectrum server is utilized for spectrum sensing and scheduling the SU to transmit over one of the PU channels opportunistically. One practical yet challenging scenario is when \\textit{both} the PU occupancy and the channel fading vary over time and exhibit temporal correlations. Little work has been done for exploiting such temporal memory in the channel fading and the PU occupancy simultaneously for opportunistic spectrum scheduling. A main goal of this work is to understand the intricate tradeoffs resulting from the interactions of the two sets of system states - the channel fading and the PU occupancy, by casting the problem as a partially observable Markov decision process. We first show that a simple greedy policy is optimal in some special cases. To build a clear understanding of the tradeoffs, we then introduce a full-observation genie-aided system, where the spectrum server collects channel fa...

  5. Resource allocation algorithm for multi-user MIMO-OFDM downlink with correlated channels

    Institute of Scientific and Technical Information of China (English)

    Chengwen ZHANG; Zhongzhao ZHANG; Weixiao MENG

    2008-01-01

    To minimize transmitting power,an adaptive resource allocation algorithm is proposed for multi-user multiple input multiple output-orthogonal frequency divi sion multiplexing(MIMO-OFDM)downlink with correlated channels,which,based on the user's grouping according to their spatial correlations,combines the shared manner and the exclusive manner to allocate sub-carriers.Between different groups the shared manner with a null steering method based on group marginal users is applied,whereas within a group the exclusive manner is applied.The simulations show that the power efficiency and spectral efficiency are improved;the base station transmitting antenna number and the computational complexity is decreased.

  6. An Investigation of Self-Interference Reduction Strategy in a Spatially Correlated MIMO Channel

    Directory of Open Access Journals (Sweden)

    Rosdiadee Nordin

    2012-01-01

    Full Text Available One of the efficient ways to transmit high data rate is by employing a multiple-input multiple-output (MIMO transmission. One of the MIMO schemes, known as spatial multiplexing (SM, relies on the linear independence data streams from different transmit antennas to exploit the capacity from the fading channels. Consequently, SM suffers from the effect of spatial correlation which is the limiting factor in achieving the capacity benefit that SM can offer. In an attempt to increase the robustness of the SM transmission in a wide range of correlated channels, the use of dynamic subcarrier allocation (DSA is investigated. The effective signal-to-interference-and-noise ratio (SINR metric is used as the performance metric to determine the subcarrier quality which can then be utilised in the allocation. Two novel variants of the subcarrier allocation scheme are proposed. It is shown that the DSA-SINR approach improves the BER performance of SM transmission in highly correlated channels environment.

  7. Correlated ions in a calcium channel model: a Poisson-Fermi theory.

    Science.gov (United States)

    Liu, Jinn-Liang; Eisenberg, Bob

    2013-10-10

    We derive a continuum model, called the Poisson-Fermi equation, of biological calcium channels (of cardiac muscle, for example) designed to deal with crowded systems in which ionic species and side chains nearly fill space. The model is evaluated in three dimensions. It includes steric and correlation effects and is derived from classical hard-sphere lattice models of configurational entropy of finite size ions and solvent molecules. The maximum allowable close packing (saturation) condition is satisfied by all ionic species with different sizes and valences in a channel system, as shown theoretically and numerically. Unphysical overcrowding ("divergence") predicted by the Gouy-Chapman diffuse model (produced by a Boltzmann distribution of point charges with large potentials) does not occur with the Fermi-like distribution. Using probability theory, we also provide an analytical description of the implicit dielectric model of ionic solutions that gives rise to a global and a local formula for the chemical potential. In this primitive model, ions are treated as hard spheres and solvent molecules are described as a dielectric medium. The Poisson-Fermi equation is a local formula dealing with different correlations at different places. The correlation effects are apparent in our numerical results. Our results show variations of dielectric permittivity from bath to channel pore described by a new dielectric function derived as an output from the Poisson-Fermi analysis. The results are consistent with existing theoretical and experimental results. The binding curve of Poisson-Fermi is shown to match Monte Carlo data and illustrates the anomalous mole fraction effect of calcium channels, an effective blockage of permeation of sodium ions by a tiny concentration (or number) of calcium ions.

  8. Ultra-compact 32-channel system for time-correlated single-photon counting measurements

    Science.gov (United States)

    Antonioli, S.; Cuccato, A.; Miari, L.; Labanca, I.; Rech, I.; Ghioni, M.

    2013-05-01

    Modern Time-Correlated Single-Photon Counting applications require to detect spectral and temporal fluorescence data simultaneously and from different areas of the analyzed sample. These rising quests have led the development of multichannel systems able to perform high count rate and high performance analysis. In this work we describe a new 32-channel TCSPC system designed to be used in modern setups. The presented module consists of four independent 8-channel TCSPC boards, each of them including two 4-channel Time-Amplitude Converter arrays. These TAC arrays are built-in 0.35 μm Si-Ge BiCMOS technology and are characterized by low crosstalk, high resolution, high conversion rate and variable full-scale range. The 8-channel TCSPC board implements an 8-channel ADC to sample the TAC outputs, an FPGA to record and organize the measurement results and a USB 2.0 interface to enable real-time data transmission to and from an external PC. Experimental results demonstrate that the acquisition system ensures high performance TCSPC measurements, in particular: high conversion rate (5 MHz), good time resolution (down to 30 psFWHM with the full scale range set to 11 ns) and low differential non-linearity (rms value lower than 0.15% of the time bin width). We design the module to be very compact and, thanks to the reduced dimensions of the 8-channel TCSPC board (95×40 mm), the whole system can be enclosed in a small aluminum case (160×125×30 mm).

  9. The Modulus of the Complex Correlation Coefficient Between Co-Polarized Channels for Oil Spill Observation

    Science.gov (United States)

    Khenouchi, H.; Smara, Y.; Migliaccio, M.; Nunziata, F.; Buono, A.

    2016-08-01

    Sea oil pollution is a matter of great concern since it affects both the environment and human health. Recent studies demonstrated that synthetic aperture radar (SAR) polarimetry is able to provide additional information useful for environmental applications, i. e., oil spill observation. In this context, different approaches based on polarimetric SARs were developed. In this study, a dual-polarimetric feature, namely the modulus of the complex correlation coefficient between the co-polarized channels, is used to discriminate between sea oil spill and weak-damping look-alikes.The proposed approach relies on the fact that high correlation between co-polarized channels is expected over sea surface and weak-damping look- alikes due to the dominant Bragg scattering, while significantly lower correlation is expected over strong-damping oil spills since they are characterized by a no-Bragg scattering behaviour. Experimental results show that the modulus of the complex correlation between the co-polarized chan- nels can be successfully exploited for both the observation of sea oil slicks and their discrimination from weak-damping look-alikes.

  10. Inherent dynamics of the acid-sensing ion channel 1 correlates with the gating mechanism.

    Directory of Open Access Journals (Sweden)

    Huaiyu Yang

    2009-07-01

    Full Text Available The acid-sensing ion channel 1 (ASIC1 is a key receptor for extracellular protons. Although numerous structural and functional studies have been performed on this channel, the structural dynamics underlying the gating mechanism remains unknown. We used normal mode analysis, mutagenesis, and electrophysiological methods to explore the relationship between the inherent dynamics of ASIC1 and its gating mechanism. Here we show that a series of collective motions among the domains and subdomains of ASIC1 correlate with its acid-sensing function. The normal mode analysis result reveals that the intrinsic rotation of the extracellular domain and the collective motions between the thumb and finger induced by proton binding drive the receptor to experience a deformation from the extracellular domain to the transmembrane domain, triggering the channel pore to undergo "twist-to-open" motions. The movements in the transmembrane domain indicate that the likely position of the channel gate is around Leu440. These motion modes are compatible with a wide body of our complementary mutations and electrophysiological data. This study provides the dynamic fundamentals of ASIC1 gating.

  11. On the Ergodic Capacity of Dual-Branch Correlated Log-Normal Fading Channels with Applications

    KAUST Repository

    Al-Quwaiee, Hessa

    2015-05-01

    Closed-form expressions of the ergodic capacity of independent or correlated diversity branches over Log-Normal fading channels are not available in the literature. Thus, it is become of an interest to investigate the behavior of such metric at high signal-to-noise (SNR). In this work, we propose simple closed-form asymptotic expressions of the ergodic capacity of dual-branch correlated Log- Normal corresponding to selection combining, and switch-and-stay combining. Furthermore, we capitalize on these new results to find new asymptotic ergodic capacity of correlated dual- branch free-space optical communication system under the impact of pointing error with both heterodyne and intensity modulation/direct detection. © 2015 IEEE.

  12. Grassmannian Beamforming for MIMO-OFDM Systems with Frequency and Spatially Correlated Channels Using Huffman Coding

    CERN Document Server

    Gutman, Igor; Wulich, Dov

    2009-01-01

    Multiple input multiple output (MIMO) precoding is an efficient scheme that may significantly enhance the communication link. However, this enhancement comes with a cost. Many precoding schemes require channel knowledge at the transmitter that is obtained through feedback from the receiver. Focusing on the natural common fusion of orthogonal frequency division multiplexing (OFDM) and MIMO, we exploit the channel correlation in the frequency and spatial domain to reduce the required feedback rate in a frequency division duplex (FDD) system. The proposed feedback method is based on Huffman coding and is employed here for the single stream case. The method leads to a significant reduction in the required feedback rate, without any loss in performance. The proposed method may be extended to the multi-stream case.

  13. Resource allocation with CCI suppression for multiuser MIMO-OFDM downlink in correlated channels

    Institute of Scientific and Technical Information of China (English)

    Zhang Chengwen; Zhang Zhongzhao; Ma Yongkui

    2008-01-01

    To minimize the overall transmit power while maintaining a constant data rate and target BER,a downlink adaptive resource allocation algorithm with jointing the exclusive manner and the shared manner is proposed for multiuser MIMO-OFDM system in correlated channels. The algorithm allocates all the subcarriers to different users according to their spatial correlations. The users with high spatial correlation are allocated in the same group and the exclusive manner is applied. The shared manner with an improved null broadening method,which improves the performance of co-channel interference (CCI) suppression and decreases the number of transmit antennas required, is applied between the different group users. As the user's direction of departure (DOD) changes very slowly, a looking up table method is used to reduce the computational complexity. The simulation results show that despite the angle spread of DOD, when compared with the exclusive manner, the proposed algorithm improves the spectral efficiency, and when compared with the TDMA-ZF (zero forcing) shared manner, the proposed algorithm decreases the total transmit power by at least 1 dB.

  14. Spatial correlation in 3D MIMO channels using fourier coefficients of power spectrums

    KAUST Repository

    Nadeem, Qurrat-Ul-Ain

    2015-03-01

    In this paper, an exact closed-form expression for the Spatial Correlation Function (SCF) is derived for the standardized three-dimensional (3D) multiple-input multiple-output (MIMO) channel. This novel SCF is developed for a uniform linear array of antennas with non-isotropic antenna patterns. The proposed method resorts to the spherical harmonic expansion (SHE) of plane waves and the trigonometric expansion of Legendre and associated Legendre polynomials to obtain a closed-form expression for the SCF for arbitrary angular distributions and antenna patterns. The resulting expression depends on the underlying angular distributions and antenna patterns through the Fourier Series (FS) coefficients of power azimuth and elevation spectrums. The novelty of the proposed method lies in the SCF being valid for any 3D propagation environment. Numerical results validate the proposed analytical expression and study the impact of angular spreads on the correlation. The derived SCF will help evaluate the performance of correlated 3D MIMO channels in the future. © 2015 IEEE.

  15. Performance analysis of EGC combining over correlated Nakagami-m fading channels

    Directory of Open Access Journals (Sweden)

    Milić Dejan

    2012-01-01

    Full Text Available In this paper, performance analysis of diversity technique with equal gain combining method (EGC with two branches for the detection of signals in wireless communication systems is presented. In the following analysis, it is assumed that the fading via channels is Nakagami-m correlated. The first order statistical characteristics of the system are analysed. Useful formulae for the probability density function (pdf and cumulative distribution function (CDF of EGC output SIR are derived, and the effects of the fading severity on the output signal are observed.

  16. Outage probability analysis of wireless sensor networks in the presence of channel fading and spatial correlation

    KAUST Repository

    Al-Murad, Tamim M.

    2011-07-01

    Evaluating the reliability of wireless sensor networks is becoming more important as theses networks are being used in crucial applications. The outage probability defined as the probability that the error in the system exceeds a maximum acceptable threshold has recently been used as a measure of the reliability of such systems. In this work we find the outage probability of wireless sensor network in different scenarios of distributed sensing where sensors\\' readings are affected by spatial correlation and in the presence of channel fading. © 2011 IEEE.

  17. Scalable time-correlated photon counting system with multiple independent input channels.

    Science.gov (United States)

    Wahl, Michael; Rahn, Hans-Jürgen; Röhlicke, Tino; Kell, Gerald; Nettels, Daniel; Hillger, Frank; Schuler, Ben; Erdmann, Rainer

    2008-12-01

    Time-correlated single photon counting continues to gain importance in a wide range of applications. Most prominently, it is used for time-resolved fluorescence measurements with sensitivity down to the single molecule level. While the primary goal of the method used to be the determination of fluorescence lifetimes upon optical excitation by short light pulses, recent modifications and refinements of instrumentation and methodology allow for the recovery of much more information from the detected photons, and enable entirely new applications. This is achieved most successfully by continuously recording individually detected photons with their arrival time and detection channel information (time tagging), thus avoiding premature data reduction and concomitant loss of information. An important property of the instrumentation used is the number of detection channels and the way they interrelate. Here we present a new instrument architecture that allows scalability in terms of the number of input channels while all channels are synchronized to picoseconds of relative timing and yet operate independent of each other. This is achieved by means of a modular design with independent crystal-locked time digitizers and a central processing unit for sorting and processing of the timing data. The modules communicate through high speed serial links supporting the full throughput rate of the time digitizers. Event processing is implemented in programmable logic, permitting classical histogramming, as well as time tagging of individual photons and their temporally ordered streaming to the host computer. Based on the time-ordered event data, any algorithms and methods for the analysis of fluorescence dynamics can be implemented not only in postprocessing but also in real time. Results from recently emerging single molecule applications are presented to demonstrate the capabilities of the instrument.

  18. Multi-channel analysis of passive surface waves based on cross-correlations

    Science.gov (United States)

    Cheng, F.; Xia, J.; Xu, Z.; Hu, Y.

    2015-12-01

    Traditional active seismic survey can no longer be properly applied in highly populated urban areas due to restrictions in modern civilian life styles. Passive seismic methods, however, have gained much more attention from the engineering geophysics community because of their environmental friendly and deeper investigation depth. Due to extracting signal from noise has never been as comfortable as that in active seismic survey, how to make it more efficiently and accurately has been emphasized. We propose a multi-channel analysis of passive surface waves (MAPW) based on long noise sequences cross-correlations to meet the demand for increasing investigation depth by acquiring surface-wave data at a relative low-frequency range (1 Hz ≤ f ≤ 10 Hz) in urban areas. We utilize seismic interferometry to produce common virtual source gathers from one-hour-long noise records and do dispersion measurements by using the classic passive multi-channel analysis of surface waves (PMASW). We used synthetic tests to demonstrate the advantages of MAPW for various noise distributions. Results show that our method has the superiority of maximizing the analysis accuracy. Finally, we used two field data applications to demonstrate the advantages of our MAPW over the classic PMASW on isolating azimuth of the predominant noise sources and the effectivity of combined survey of active multi-channel analysis of surface waves (MASW) and MAPW. We suggest, for the field operation using MAPW, that a parallel receiver line which is close to a main road or river, if any, with one or two hours noise observation will be an effective means for an unbiased dispersion image. Keywords: passive seismic method, MAPW, MASW, cross-correlation, directional noise source, spatial-aliasing effects, inversion

  19. A Robust Pre-Filter and Power Loading Design for Time Reversal UWB Systems over Time-Correlated MIMO Channels

    Directory of Open Access Journals (Sweden)

    Sajjad Alizadeh

    2014-04-01

    Full Text Available Conventional Time Reversal (TR technique suffers from performance degradation in time varying Multiple-Input Multiple-Output Ultra-Wideband (MIMO-UWB systems due to outdating Channel State Information (CSI over time progressions. That is, the outdated CSI degrades the TR performance significantly in time varying channels. The correlation property of time correlated channels can improve the TR performance against other traditional TR designs. Based on this property, at first, we propose a robust TR-MIMO-UWB system design for a time-varying channel in which the CSI is updated only at the beginning of each block of data where the CSI is assumed to be known. As the channel varies over time, pre-processor blindly pre-equalizes the channel during the next symbol time by using the correlation property. Then, a novel recursive power allocation strategy is derived over time-correlated time-varying TR-MIMO-UWB channels. We show that the proposed power loading technique, considerably improves the BER performance of TR-MIMO-UWB system in imperfect CSI with robust pre-filter. The proposed algorithms lead to a cost-efficient CSI updating procedure for the TR optimization. Simulation results are provided to confirm the new design performance against traditional method.

  20. Performance Analysis of Selection Combining Over Correlated Nakagami-m Fading Channels with Constant Correlation Model for Desired Signal and Cochannel Interference

    Directory of Open Access Journals (Sweden)

    C. Stefanovic

    2013-12-01

    Full Text Available A very efficient technique that reduces fading and channel interference influence is selection diversity based on the signal to interference ratio (SIR. In this pa¬per, system performances of selection combiner (SC over correlated Nakagami-m channels with constant correlation model are analyzed. Closed-form expressions are obtained for the output SIR probability density function (PDF and cumulative distribution function (CDF which is main contribution of this paper. Outage probability and the average error probability for coherent, noncoherent modulation are derived. Numerical results presented in this paper point out the effects of fading severity and cor¬relation on the system performances. The main contribu¬tion of this analysis for multibranch signal combiner is that it has been done for general case of correlated co-channel interference (CCI.

  1. Correlation functions with fusion-channel multiplicity in W3 Toda field theory

    CERN Document Server

    Belavin, Vladimir; Foda, Omar; Santachiara, Raoul

    2016-01-01

    Current studies of WN Toda field theory focus on correlation functions such that the WN highest-weight representations in the fusion channels are multiplicity-free. In this work, we study W3 Toda 4-point functions with multiplicity in the fusion channel. The conformal blocks of these 4-point functions involve matrix elements of a fully-degenerate primary field with a highest-weight in the adjoint representation of sl3, and a semi-degenerate primary field with a highest-weight in the fundamental representation of sl3. We show that, when the fusion rules are obeyed, the matrix elements of the fully-degenerate adjoint field, between two arbitrary descendant states, can be computed explicitly, on equal footing with the matrix elements of the semi-degenerate fundamental field. Using null-state conditions, we obtain a fourth-order Fuchsian differential equation for the conformal blocks. Using Okubo theory, we show that, due to the presence of multiplicities, this differential equation belongs to a class of Fuchsian...

  2. How Equalization Techniques Affect the TCP Performance of MC-CDMA Systems in Correlated Fading Channels

    Directory of Open Access Journals (Sweden)

    Giacomo Leonardi

    2007-12-01

    Full Text Available This paper investigates the impact of several equalization techniques for multicarrier code division multiple access systems on the performance at both lower and upper layers (i.e., physical and TCP layers. Classical techniques such as maximal ratio combining, equal gain combining, orthogonality restoring combining, minimum mean square error, as well as a partial equalization (PE are investigated in time- and frequency-correlated fading channels with various numbers of interferers. Their impact on the performance at upper level is then studied. The results are obtained through an integrated simulation platform carefully reproducing all main aspects affecting the quality of service perceived by the final user, allowing an investigation of the real gain produced by signal processing techniques at TCP level.

  3. On the Ergodic Secret-Key Agreement over Spatially Correlated Multiple-Antenna Channels with Public Discussion

    KAUST Repository

    Zorgui, Marwen

    2015-09-28

    We consider secret-key agreement with public discussion over multiple-input multiple-output (MIMO) Rayleigh fast-fading channels under correlated environment. We assume that transmit, legitimate receiver and eavesdropper antennas are correlated. The legitimate receiver and the eavesdropper are assumed to have perfect channel knowledge while the transmitter has only knowledge of the correlation matrices. First, we derive the expression of the secret-key capacity under the considered setup. We prove that the optimal transmit strategy achieving the secret-key capacity consists in transmitting independent Gaussian signals along the eingenvectors of the transmit correlation matrix. The powers allocated to each channel mode are determined as the solution to a numerical optimization problem. A necessary and sufficient condition for beamforming (i.e., transmitting along the strongest channel mode) to be capacity-achieving is derived. Moreover, we analyze the impact of correlation matrices on the system performance. Finally, we study the system’s performance in the two extreme power regimes. In the high-power regime, we provide closed-form expressions of the gain/loss due to correlation. In the low signal-to-noise ratio (SNR) regime, we investigate the energy efficiency of the system by determining the minimum energy required for sharing a secret-key bit and the wideband slope while highlighting the impact of correlation matrices.

  4. Improvement of acetic acid tolerance and fermentation performance of Saccharomyces cerevisiae by disruption of the FPS1 aquaglyceroporin gene.

    Science.gov (United States)

    Zhang, Jun-Guo; Liu, Xiu-Ying; He, Xiu-Ping; Guo, Xue-Na; Lu, Ying; Zhang, Bo-Run

    2011-02-01

    The FPS1 gene coding for the Fps1p aquaglyceroporin protein of an industrial strain of Saccharomyces cerevisiae was disrupted by inserting CUP1 gene. Wild-type strain, CE25, could only grow on YPD medium containing less than 0.45% (v/v) acetic acid, while recombinant strain T12 with FPS1 disruption could grow on YPD medium with 0.6% (v/v) acetic acid. Under 0.4% (v/v) acetic acid stress (pH 4.26), ethanol production and cell growth rates of T12 were 1.7 ± 0.1 and 0.061 ± 0.003 g/l h, while those of CE25 were 1.2 ± 0.1 and 0.048 ± 0.003 g/l h, respectively. FPS1 gene disruption in an industrial ethanologenic yeast thus increases cell growth and ethanol yield under acetic acid stress, which suggests the potential utility of FPS1 gene disruption for bioethanol production from renewable resources such as lignocelluloses.

  5. MIMO-OFDM channel estimation method utilizing correlation in time domain for B3G-TDD uplink

    Institute of Scientific and Technical Information of China (English)

    ZHOU Ming-yu; LI Li-hua; JIANG Jun; ZHONG Ming-hua; TAG Xiao-feng

    2007-01-01

    This article proposes a simple pilot-aided channel estimation method based on correlation in time domain for multiple-input and multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. Pilot symbols in all transmit antennas are generated from different circular shifting of a certain sequence. Through once correlation, the receiver can obtain time-domain pulse responses for channel fading from all transmit antennas to a certain receive antenna, from which channel estimation in frequency domain can be obtained. Beyond 3G time-division duplex (B3G-TDD) uplink is introduced, and the channel estimation method is used in it. Theoretical analysis and simulation are both carried out. Mean square error (MSB) performance shows that the method can exhibit precise estimation. Complexity analysis proves it requires very low complexity. System simulation result shows that it guarantees the performance of B3G-TDD uplink very well.

  6. Double Space Time Transmit Diversity OFDM System with Antenna Shuffling in Spatial Correlated Frequency Selective MIMO Channels

    Science.gov (United States)

    Zhou, Liang; Shimizu, Masahiko

    In this paper, we study low complexity transceiver for double space time transmit diversity (DSTTD) and orthogonal frequency division multiplexing (OFDM) system with antenna shuffling. Firstly, we propose a novel antenna shuffling method based on the criterion of minimizing the condition number of channel correlation matrix. The condition number is an indicator about the quality of the channel. By selecting the minimum of condition number which has better channel quality, consequently, a linear detector with respect to this new channel may achieve better performance results. A low complexity variant of the condition number calculation is also proposed, and it is shown that this criterion can be reduced to the minimum mean square error (MMSE) based criterion. Furthermore, the weighted soft decision Viterbi decoding is applied to mitigate noise enhancement inherent to zero forcing (ZF) and MMSE linear receivers and improve error rate performance. Next, we propose an algorithm to reduce the amount of feedback by exploiting the fact that the channel frequency responses across OFDM subcarriers are correlated. In the proposed algorithm, subcarriers are clustered in blocks, which are allocated the same shuffling pattern with the largest number of the shuffling patterns in the cluster. This way, the signaling overhead can be reduced in comparison with each subcarrier based feedback. Extensive simulations show that the proposed techniques for DSTTD-OFDM system outperform other existing techniques under both uncorrelated and highly spatial correlated frequency selective MIMO fading channels.

  7. Secret-key agreement over spatially correlated fast-fading multiple-antenna channels with public discussion

    KAUST Repository

    Zorgui, Marwen

    2015-06-14

    We consider secret-key agreement with public discussion over multiple-input multiple-output (MIMO) Rayleigh fast-fading channels under correlated environment. We assume that transmit, legitimate receiver and eavesdropper antennas are correlated. The legitimate receiver and the eavesdropper are assumed to have perfect channel knowledge while the transmitter has only knowledge of the correlation matrices. First, we derive the expression of the secret-key capacity under the considered setup. Then, we prove that the optimal transmit strategy achieving the secret-key capacity consists in transmitting independent Gaussian signals along the eingenvectors of the transmit correlation matrix. The powers allocated to each channel mode are determined as the solution to a numerical optimization problem that we derive. A necessary and sufficient condition for beamforming (i.e., transmitting along the strongest channel mode) to be capacity-achieving is derived. Finally, we analyze the impact of correlation matrices on the system performance and provide closed-form expressions of the gain/loss due to correlation in the high power regime.

  8. Temporal evolution of helix hydration in a light-gated ion channel correlates with ion conductance.

    Science.gov (United States)

    Lórenz-Fonfría, Víctor A; Bamann, Christian; Resler, Tom; Schlesinger, Ramona; Bamberg, Ernst; Heberle, Joachim

    2015-10-27

    The discovery of channelrhodopsins introduced a new class of light-gated ion channels, which when genetically encoded in host cells resulted in the development of optogenetics. Channelrhodopsin-2 from Chlamydomonas reinhardtii, CrChR2, is the most widely used optogenetic tool in neuroscience. To explore the connection between the gating mechanism and the influx and efflux of water molecules in CrChR2, we have integrated light-induced time-resolved infrared spectroscopy and electrophysiology. Cross-correlation analysis revealed that ion conductance tallies with peptide backbone amide I vibrational changes at 1,665(-) and 1,648(+) cm(-1). These two bands report on the hydration of transmembrane α-helices as concluded from vibrational coupling experiments. Lifetime distribution analysis shows that water influx proceeded in two temporally separated steps with time constants of 10 μs (30%) and 200 μs (70%), the latter phase concurrent with the start of ion conductance. Water efflux and the cessation of the ion conductance are synchronized as well, with a time constant of 10 ms. The temporal correlation between ion conductance and hydration of helices holds for fast (E123T) and slow (D156E) variants of CrChR2, strengthening its functional significance.

  9. BER and Outage Probability Approximations for LMMSE Detectors on Correlated MIMO Channels

    CERN Document Server

    Kammoun, Abla; Hachem, Walid; Najim, Jamal

    2008-01-01

    This paper is devoted to the study of the performance of the Linear Minimum Mean-Square Error receiver for (receive) correlated Multiple-Input Multiple-Output systems. By the random matrix theory, it is well-known that the Signal-to-Noise Ratio (SNR) at the output of this receiver behaves asymptotically like a Gaussian random variable as the number of receive and transmit antennas converge to +$\\infty$ at the same rate. However, this approximation being inaccurate for the estimation of some performance metrics such as the Bit Error Rate and the outage probability, especially for small system dimensions, Li et al. proposed convincingly to assume that the SNR follows a generalized Gamma distribution which parameters are tuned by computing the first three asymptotic moments of the SNR. In this article, this technique is generalized to (receive) correlated channels, and closed-form expressions for the first three asymptotic moments of the SNR are provided. To obtain these results, a random matrix theory technique...

  10. The Time Division Multi-Channel Communication Model and the Correlative Protocol Based on Quantum Time Division Multi-Channel Communication

    Institute of Scientific and Technical Information of China (English)

    LIU Xiao-Hui; PEI Chang-Xing; NIE Min

    2010-01-01

    @@ Based on the classical time division multi-channel communication theory,we present a scheme of quantum time-division multi-channel communication(QTDMC).Moreover,the model of quantum time division switch(QTDS)and correlative protocol of QTDMC are proposed.The quantum bit error rate(QBER)is analyzed and the QBER simulation test is performed.The scheme shows that the QTDS can carry out multi-user communication through quantum channel,the QBER can also reach the reliability requirement of communication,and the protocol of QTDMC has high practicability and transplantable.The scheme of QTDS may play an important role in the establishment of quantum communication in a large scale in the future.

  11. Distributed Joint Source-Channel Coding for arbitrary memoryless correlated sources and Source coding for Markov correlated sources using LDPC codes

    CERN Document Server

    Aggarwal, Vaneet

    2008-01-01

    In this paper, we give a distributed joint source channel coding scheme for arbitrary correlated sources for arbitrary point in the Slepian-Wolf rate region, and arbitrary link capacities using LDPC codes. We consider the Slepian-Wolf setting of two sources and one destination, with one of the sources derived from the other source by some correlation model known at the decoder. Distributed encoding and separate decoding is used for the two sources. We also give a distributed source coding scheme when the source correlation has memory to achieve any point in the Slepian-Wolf rate achievable region. In this setting, we perform separate encoding but joint decoding.

  12. Multi-channel poloidal correlation reflectometry on experimental advanced superconducting tokamak

    Science.gov (United States)

    Qu, H.; Zhang, T.; Han, X.; Xiang, H. M.; Wen, F.; Geng, K. N.; Wang, Y. M.; Kong, D. F.; Cai, J. Q.; Huang, C. B.; Gao, Y.; Gao, X.; Zhang, S.

    2016-11-01

    A new multi-channel poloidal correlation reflectometry is developed at Experimental Advanced Superconducting Tokamak. Eight dielectric resonator oscillators with frequencies of 12.5 GHz, 13.5 GHz, 14.5 GHz, 15 GHz, 15.5 GHz, 16 GHz, 17 GHz, and 18 GHz are used as sources. Signals from the sources are up-converted to V band using active quadruplers and then coupled together. The output waves are launched by one single antenna after passing through a 20 dB directional coupler which can provide the reference signal. Two poloidally separated antennae are installed to receive the reflected waves from plasma. The reference and reflected signals are down-converted by mixing with a quadrupled signal from a phase-locked source with a frequency of 14.2 GHz and the IF signals pass through the filter bank. The resulting signals from the mixers are detected by I/Q demodulators. The setup enables the measurement of density fluctuation at 8 (radial) × 2 (poloidal) spatial points. A coherent mode with an increasing velocity from 50 kHz to 100 kHz is observed by using the system. The mode is located in the steep gradient region of the pedestal.

  13. Crystallized Rates Region of the Interference Channel via Correlated Equilibrium with Interference as Noise

    CERN Document Server

    Charafeddine, Mohamad; Paulraj, Arogyaswami; Cioffi, John

    2010-01-01

    Treating the interference as noise in the n-user interference channel, the paper describes a novel approach to the rates region, composed by the time-sharing convex hull of 2^n-1 corner points achieved through On/Off binary power control. The resulting rates region is denoted crystallized rates region. By treating the interference as noise, the n-user rates region frontiers has been found in the literature to be the convex hull of n hyper-surfaces. The rates region bounded by these hyper-surfaces is not necessarily convex, and thereby a convex hull operation is imposed through the strategy of time-sharing. This paper simplifies this rates region in the n-dimensional space by having only an On/Off binary power control. This consequently leads to 2^n-1 corner points situated within the rates region. A time-sharing convex hull is imposed onto those corner points, forming the crystallized rates region. The paper focuses on game theoretic concepts to achieve that crystallized convex hull via correlated equilibrium...

  14. BER analysis of MPSK space-time code with differential detection over correlated block-fading Rayleigh channel

    Institute of Scientific and Technical Information of China (English)

    ZOU Yu-long; ZHENG Bao-yu

    2008-01-01

    MIMO technology proposed in recent years can effectively combat the multipath fading of wireless channel and can considerably enlarge the channel capacity, which has been investigated widely by researchers. However, its performance analysis over correlated block-fading Rayleigh channel is still an open and challenging objective. In this article, an analytic expression of bit error rate (BER) is presented for multiple phase shift keying (MPSK) space-time code, with differential detection over correlated block-fading Rayleigh channel. Through theoretical analysis of BER, it can be found that the differential space-time scheme without the need for channel state information (CSI) at receiver achieves distinct performance gain compared with the traditional nonspace-time system. And then, the system simulation is complimented to verify the above result, showing that the diversity system based on the differential space-time block coding (DSTBC) outperforms the traditional nonspace- time system with diversity gain in terms of BER. Furthermore, the numerical results also demonstrate that the error floor of the differential space-time system is much lower than that of the differential nonspace-time system.

  15. Probability of Error of Linearly Modulated Signals with Gaussian Cochannel Interference in Maximally Correlated Rayleigh Fading Channels

    Directory of Open Access Journals (Sweden)

    Rugini Luca

    2010-01-01

    Full Text Available We evaluate the probability of error of linearly modulated signals, such as phase-shift keying (PSK and quadrature amplitude modulation (QAM, in the presence of Gaussian cochannel interference (CCI and Rayleigh fading channels. Specifically, we assume that the fading channel of the CCI is maximally correlated with the fading channel of the signal of interest (SOI. In practical applications, the maximal correlation of the CCI channel with the SOI channel occurs when the CCI is generated at the transmitter, such as the multiuser interference in downlink systems, or when a transparent repeater relays some thermal noise together with the SOI. We analytically evaluate the error probability by using a series expansion of generalized hypergeometric functions. A convenient truncation criterion is also discussed. The proposed theoretical approach favorably compares with alternative approaches, such as numerical integration and Monte Carlo estimation. Among the various applications of the proposed analysis, we illustrate the effect of nonlinear amplifiers in orthogonal frequency-division multiplexing (OFDM systems, the downlink reception of code-division multiple-access (CDMA signals, and the outdoor-to-indoor relaying of Global Positioning System (GPS signals.

  16. Sodium ion channel mutations in glioblastoma patients correlate with shorter survival

    Directory of Open Access Journals (Sweden)

    Velculescu Victor E

    2011-02-01

    Full Text Available Abstract Background Glioblastoma Multiforme (GBM is the most common and invasive astrocytic tumor associated with dismal prognosis. Treatment for GBM patients has advanced, but the median survival remains a meager 15 months. In a recent study, 20,000 genes from 21 GBM patients were sequenced that identified frequent mutations in ion channel genes. The goal of this study was to determine whether ion channel mutations have a role in disease progression and whether molecular targeting of ion channels is a promising therapeutic strategy for GBM patients. Therefore, we compared GBM patient survival on the basis of presence or absence of mutations in calcium, potassium and sodium ion transport genes. Cardiac glycosides, known sodium channel inhibitors, were then tested for their ability to inhibit GBM cell proliferation. Results Nearly 90% of patients showed at least one mutation in ion transport genes. GBM patients with mutations in sodium channels showed a significantly shorter survival compared to patients with no sodium channel mutations, whereas a similar comparison based on mutational status of calcium or potassium ion channel mutations showed no survival differences. Experimentally, targeting GBM cells with cardiac glycosides such as digoxin and ouabain demonstrated preferential cytotoxicity against U-87 and D54 GBM cells compared to non-tumor astrocytes (NTAs. Conclusions These pilot studies of GBM patients with sodium channel mutations indicate an association with a more aggressive disease and significantly shorter survival. Moreover, inhibition of GBM cells by ion channel inhibitors such as cardiac glycosides suggest a therapeutic strategy with relatively safe drugs for targeting GBM ion channel mutations. Key Words: glioblastoma multiforme, ion channels, mutations, small molecule inhibitors, cardiac glycosides.

  17. A Generalized Spatial Correlation Model for 3D MIMO Channels based on the Fourier Coefficients of Power Spectrums

    KAUST Repository

    Nadeem, Qurrat-Ul-Ain

    2015-05-07

    Previous studies have confirmed the adverse impact of fading correlation on the mutual information (MI) of two-dimensional (2D) multiple-input multiple-output (MIMO) systems. More recently, the trend is to enhance the system performance by exploiting the channel’s degrees of freedom in the elevation, which necessitates the derivation and characterization of three-dimensional (3D) channels in the presence of spatial correlation. In this paper, an exact closed-form expression for the Spatial Correlation Function (SCF) is derived for 3D MIMO channels. This novel SCF is developed for a uniform linear array of antennas with nonisotropic antenna patterns. The proposed method resorts to the spherical harmonic expansion (SHE) of plane waves and the trigonometric expansion of Legendre and associated Legendre polynomials. The resulting expression depends on the underlying arbitrary angular distributions and antenna patterns through the Fourier Series (FS) coefficients of power azimuth and elevation spectrums. The novelty of the proposed method lies in the SCF being valid for any 3D propagation environment. The developed SCF determines the covariance matrices at the transmitter and the receiver that form the Kronecker channel model. In order to quantify the effects of correlation on the system performance, the information-theoretic deterministic equivalents of the MI for the Kronecker model are utilized in both mono-user and multi-user cases. Numerical results validate the proposed analytical expressions and elucidate the dependence of the system performance on azimuth and elevation angular spreads and antenna patterns. Some useful insights into the behaviour of MI as a function of downtilt angles are provided. The derived model will help evaluate the performance of correlated 3D MIMO channels in the future.

  18. Code-Aided Estimation and Detection on Time-Varying Correlated Mimo Channels: A Factor Graph Approach

    Directory of Open Access Journals (Sweden)

    Simoens Frederik

    2006-01-01

    Full Text Available This paper concerns channel tracking in a multiantenna context for correlated flat-fading channels obeying a Gauss-Markov model. It is known that data-aided tracking of fast-fading channels requires a lot of pilot symbols in order to achieve sufficient accuracy, and hence decreases the spectral efficiency. To overcome this problem, we design a code-aided estimation scheme which exploits information from both the pilot symbols and the unknown coded data symbols. The algorithm is derived based on a factor graph representation of the system and application of the sum-product algorithm. The sum-product algorithm reveals how soft information from the decoder should be exploited for the purpose of estimation and how the information bits can be detected. Simulation results illustrate the effectiveness of our approach.

  19. From Multi-Keyholes to Measure of Correlation and Power Imbalance in MIMO Channels: Outage Capacity Analysis

    CERN Document Server

    Levin, George

    2008-01-01

    An information-theoretic analysis of a multi-keyhole channel, which includes a number of statistically independent keyholes with possibly different correlation matrices, is given. When the number of keyholes or/and the number of Tx/Rx antennas is large, there is an equivalent Rayleigh-fading channel such that the outage capacities of both channels are asymptotically equal. In the case of a large number of antennas and for a broad class of fading distributions, the outage capacity is shown to be asymptotically Gaussian in distribution, and compact, closed-form expressions for the mean and variance are given. Motivated by the asymptotic analysis, a simple, full-ordering scalar measure of spatial correlation and power imbalance in MIMO channels is introduced, which quantifies the negative impact of these two factors on the outage capacity in a simple and well-tractable way. It does not require the eigenvalue decomposition, and has the full-ordering property. The size-asymptotic results are used to prove Telatar'...

  20. Robust Frame Synchronization for Low Signal-to-Noise Ratio Channels Using Energy-Corrected Differential Correlation

    Directory of Open Access Journals (Sweden)

    Kim Pansoo

    2009-01-01

    Full Text Available Recent standards for wireless transmission require reliable synchronization for channels with low signal-to-noise ratio (SNR as well as with a large amount of frequency offset, which necessitates a robust correlator structure for the initial frame synchronization process. In this paper, a new correlation strategy especially targeted for low SNR regions is proposed and its performance is analyzed. By utilizing a modified energy correction term, the proposed method effectively reduces the variance of the decision variable to enhance the detection performance. Most importantly, the method is demonstrated to outperform all previously reported schemes by a significant margin, for SNRs below 5 dB regardless of the existence of the frequency offsets. A variation of the proposed method is also presented for further enhancement over the channels with small frequency errors. The particular application considered for the performance verification is the second generation digital video broadcasting system for satellites (DVB-S2.

  1. Evoked potential correlates of selective attention with multi-channel auditory inputs

    Science.gov (United States)

    Schwent, V. L.; Hillyard, S. A.

    1975-01-01

    Ten subjects were presented with random, rapid sequences of four auditory tones which were separated in pitch and apparent spatial position. The N1 component of the auditory vertex evoked potential (EP) measured relative to a baseline was observed to increase with attention. It was concluded that the N1 enhancement reflects a finely tuned selective attention to one stimulus channel among several concurrent, competing channels. This EP enhancement probably increases with increased information load on the subject.

  2. The study and development of the empirical correlations equation of natural convection heat transfer on vertical rectangular sub-channels

    Science.gov (United States)

    Kamajaya, Ketut; Umar, Efrizon; Sudjatmi, K. S.

    2012-06-01

    This study focused on natural convection heat transfer using a vertical rectangular sub-channel and water as the coolant fluid. To conduct this study has been made pipe heaters are equipped with thermocouples. Each heater is equipped with five thermocouples along the heating pipes. The diameter of each heater is 2.54 cm and 45 cm in length. The distance between the central heating and the pitch is 29.5 cm. Test equipment is equipped with a primary cooling system, a secondary cooling system and a heat exchanger. The purpose of this study is to obtain new empirical correlations equations of the vertical rectangular sub-channel, especially for the natural convection heat transfer within a bundle of vertical cylinders rectangular arrangement sub-channels. The empirical correlation equation can support the thermo-hydraulic analysis of research nuclear reactors that utilize cylindrical fuel rods, and also can be used in designing of baffle-free vertical shell and tube heat exchangers. The results of this study that the empirical correlation equations of natural convection heat transfer coefficients with rectangular arrangement is Nu = 6.3357 (Ra.Dh/x)0.0740.

  3. Secret-key agreement over spatially correlated multiple-antenna channels in the low-SNR regime

    KAUST Repository

    Zorgui, Marwen

    2015-09-28

    We consider secret-key agreement with public discussion over Rayleigh fast-fading channels with transmit, receive and eavesdropper correlation. The legitimate receiver along with the eavesdropper are assumed to have perfect channel knowledge while the transmitter has only knowledge of the correlation matrices. We analyze the secret-key capacity in the low signal-to-noise ratio (SNR) regime. We derive closed-form expressions for the first and the second derivatives of the secret-key capacity with respect to SNR at SNR= 0, for arbitrary correlation matrices and number of transmit, receive and eavesdropper antennas. Moreover, we identify optimal transmission strategies achieving these derivatives. For instance, we prove that achieving the first and the second derivatives requires a uniform power distribution between the eigenvectors spanning the maximal-eigenvalue eigenspace of the transmit correlation matrix. We also compare the optimal transmission scheme to a simple uniform power allocation. Finally, we express the minimum energy required for sharing a secret-key bit as well as the wideband slope in terms of the system parameters.

  4. Biocompatible channels for field-flow fractionation of biological samples: correlation between surface composition and operating performance.

    Science.gov (United States)

    Roda, Barbara; Cioffi, Nicola; Ditaranto, Nicoletta; Zattoni, Andrea; Casolari, Sonia; Melucci, Dora; Reschiglian, Pierluigi; Sabbatini, Luigia; Valentini, Antonio; Zambonin, Pier Giorgio

    2005-02-01

    Biocompatible methods capable of rapid purification and fractionation of analytes from complex natural matrices are increasingly in demand, particularly at the forefront of biotechnological applications. Field-flow fractionation is a separation technique suitable for nano-sized and micro-sized analytes among which bioanalytes are an important family. The objective of this preliminary study is to start a more general approach to field-flow fractionation for bio-samples by investigation of the correlation between channel surface composition and biosample adhesion. For the first time we report on the use of X-ray photoelectron spectroscopy (XPS) to study the surface properties of channels of known performance. By XPS, a polar hydrophobic environment was found on PVC material commonly used as accumulation wall in gravitational field-flow fractionation (GrFFF), which explains the low recovery obtained when GrFFF was used to fractionate a biological sample such as Staphylococcus aureus. An increase in separation performance was obtained first by conditioning the accumulation wall with bovine serum albumin and then by using the ion-beam sputtering technique to cover the GrFFF channel surface with a controlled inert film. XPS analysis was also employed to determine the composition of membranes used in hollow-fiber flow field-flow fractionation (HF FlFFF). The results obtained revealed homogeneous composition along the HF FlFFF channel both before and after its use for fractionation of an intact protein such as ferritin.

  5. Cx36 makes channels coupling human pancreatic beta-cells, and correlates with insulin expression

    NARCIS (Netherlands)

    Serre-Beinier, Veronique; Bosco, Domenico; Zulianello, Laurence; Charollais, Anne; Caille, Dorothee; Charpantier, Eric; Gauthier, Benoit R.; Diaferia, Giuseppe R.; Giepmans, Ben N.; Lupi, Roberto; Marchetti, Piero; Deng, Shaoping; Buhler, Leo; Berney, Thierry; Cirulli, Vincenzo; Meda, Paolo

    2009-01-01

    Previous studies have documented that the insulin-producing beta-cells of laboratory rodents are coupled by gap junction channels made solely of the connexin36 (Cx36) protein, and have shown that loss of this protein desynchronizes beta-cells, leading to secretory defects reminiscent of those observ

  6. Performance Analysis of Non Coherent M-ary FSK with Square Law Combiner on L Diversity Correlated Channels

    Directory of Open Access Journals (Sweden)

    Shailendra Jain,

    2010-10-01

    Full Text Available The probability of error for NMFSK with square law combining for diversity correlated Rician and Nakagami channels is analysed. The closed form expression using characteristics function is derived. The average SNR per branch is considered to be distinct. The effect of different noise powers for various diversity orders and fading parameters on probability of error and unequal SNR distribution is being studied. All the studies have been made for total SNR. The average SNR for each diversity branch is achieved from total SNR.

  7. New Exact and Asymptotic Results of Dual-Branch MRC over Correlated Nakagami-m Fading Channels

    KAUST Repository

    Al-Quwaiee, Hessa

    2015-05-01

    We present in this paper a new performance analysis results of dual-branch maximal-ratio combining over correlated Nakagami-m fading channels with arbitrary fading parameter. In particular, we derive exact closed-form expressions of the outage probability, the average bit error rate, and the ergodic capacity in terms of the extended generalized bivariate Meijer G- function. Moreover, we also provide simple closed- form asymptotic expressions in the high signal-to- noise ratio regime of these three fundamental performance measures. © 2015 IEEE.

  8. Angular correlations in t-channel single top production at the LHC

    CERN Document Server

    Motylinski, Patrick

    2009-01-01

    When a top quark decays there is a large amount of angular correlation, in its rest frame, between its spin orientation and the direction of flight of the charged lepton from its decay. In this letter we investigate the prospects of measuring this angular correlation using the MC@NLO framework. The strength of the correlation is investigated for different spin bases. The robustness against variations of PDF sets and uncertainties, factorization scale dependence, center-of-mass energy, and the jet R-parameter, is also examined.

  9. Removal of Muscle Artifacts from Single-Channel EEG Based on Ensemble Empirical Mode Decomposition and Multiset Canonical Correlation Analysis

    Directory of Open Access Journals (Sweden)

    Xun Chen

    2014-01-01

    Full Text Available Electroencephalogram (EEG recordings are often contaminated with muscle artifacts. This disturbing muscular activity strongly affects the visual analysis of EEG and impairs the results of EEG signal processing such as brain connectivity analysis. If multichannel EEG recordings are available, then there exist a considerable range of methods which can remove or to some extent suppress the distorting effect of such artifacts. Yet to our knowledge, there is no existing means to remove muscle artifacts from single-channel EEG recordings. Moreover, considering the recently increasing need for biomedical signal processing in ambulatory situations, it is crucially important to develop single-channel techniques. In this work, we propose a simple, yet effective method to achieve the muscle artifact removal from single-channel EEG, by combining ensemble empirical mode decomposition (EEMD with multiset canonical correlation analysis (MCCA. We demonstrate the performance of the proposed method through numerical simulations and application to real EEG recordings contaminated with muscle artifacts. The proposed method can successfully remove muscle artifacts without altering the recorded underlying EEG activity. It is a promising tool for real-world biomedical signal processing applications.

  10. Heat transfer in plate heat exchanger channels: Experimental validation of selected correlation equations

    Directory of Open Access Journals (Sweden)

    Cieśliński Janusz T.

    2016-09-01

    Full Text Available This study is focused on experimental investigation of selected type of brazed plate heat exchanger (PHEx. The Wilson plot approach was applied in order to estimate heat transfer coefficients for the PHEx passages. The main aim of the paper was to experimentally check ability of several correlations published in the literature to predict heat transfer coefficients by comparison experimentally obtained data with appropriate predictions. The results obtained revealed that Hausen and Dittus-Boelter correlations underestimated heat transfer coefficient for the tested PHEx by an order of magnitude. The Aspen Plate code overestimated heat transfer coefficient by about 50%, while Muley-Manglik correlation overestimated it from 1% to 25%, dependent on the value of Reynolds number and hot or cold liquid side.

  11. Gaussian Error Correction of Quantum States in a Correlated Noisy Channel

    DEFF Research Database (Denmark)

    Lassen, Mikael Østergaard; Berni, Adriano; Madsen, Lars Skovgaard;

    2013-01-01

    Noise is the main obstacle for the realization of fault-tolerant quantum information processing and secure communication over long distances. In this work, we propose a communication protocol relying on simple linear optics that optimally protects quantum states from non-Markovian or correlated n...

  12. On Small Terminal Antenna Correlation and Impact on MIMO Channel Capacity

    DEFF Research Database (Denmark)

    Yanakiev, Boyan Radkov; Nielsen, Jesper Ødum; Christensen, Morten;

    2012-01-01

    Analysis of the antenna correlation at the design stage is made, and then compared to real life performance in a typical propagation environment and in typical use cases. A traditional design flow is followed and conclusions are made on the performance of several handsets. These conclusions are t...

  13. Compressive Sensing With Prior Support Quality Information and Application to Massive MIMO Channel Estimation With Temporal Correlation

    Science.gov (United States)

    Rao, Xiongbin; Lau, Vincent K. N.

    2015-09-01

    In this paper, we consider the problem of compressive sensing (CS) recovery with a prior support and the prior support quality information available. Different from classical works which exploit prior support blindly, we shall propose novel CS recovery algorithms to exploit the prior support adaptively based on the quality information. We analyze the distortion bound of the recovered signal from the proposed algorithm and we show that a better quality prior support can lead to better CS recovery performance. We also show that the proposed algorithm would converge in $\\mathcal{O}\\left(\\log\\mbox{SNR}\\right)$ steps. To tolerate possible model mismatch, we further propose some robustness designs to combat incorrect prior support quality information. Finally, we apply the proposed framework to sparse channel estimation in massive MIMO systems with temporal correlation to further reduce the required pilot training overhead.

  14. On the performance of dual-hop systems with multiple antennas: Effects of spatial correlation, keyhole, and co-channel interference

    KAUST Repository

    Yang, Liang

    2012-12-01

    In this paper, taking into account realistic propagation conditions, namely, spatial correlation, keyhole channels, and unequal-power co-channel interference, we investigate the performance of a wireless relay network where all the nodes are equipped with multiple antennas. Considering channel state information assisted amplify-and-forward protocol, we present analytical expressions for the symbol error rate (SER) and outage probability. More specifically, we first derive the SER expressions of a relay system with orthogonal space-time block coding (OSTBC) over correlated/keyhole fading channels. We also analyze the outage probability of interference corrupted relay systems with maximal ratio combing (MRC) at the receiver as well as multiple-input multiple-output MRC (MIMO MRC). Numerical results are given to illustrate and verify the analytical results. © 2012 IEEE.

  15. The membrane lateral pressure-perturbing capacity of parabens and their effects on the mechanosensitive channel directly correlate with hydrophobicity.

    Science.gov (United States)

    Kamaraju, Kishore; Sukharev, Sergei

    2008-10-07

    Lipid bilayers provide a natural anisotropic environment for membrane proteins and can serve as apolar reservoirs for lipid-derived second messengers or lipophilic drugs. Partitioning of lipophilic agents changes the lateral pressure distribution in the bilayer, affecting integral proteins. p-Hydroxybenzoic acid esters (parabens) are amphipathic compounds widely used as food and cosmetics preservatives, but the mechanisms of their broad antibacterial action are unknown. Here we describe effects of ethyl, propyl, and butyl parabens on the gating of the bacterial mechanosensitive channel of small conductance (MscS) and compare them with the surface activity and lateral pressure changes measured in lipid monolayers in the presence of these substances. Near the bilayer-monolayer equivalence pressure of 35 mN/m, ethyl, propyl, or butyl paraben present in the subphase at 1 mM increased the surface pressure of the monolayer by 5, 12.5, or 20%, respectively. No spontaneous activation of MscS channels was observed in patch-clamp experiments with parabens added from either the cytoplasmic or periplasmic side. Increasing concentrations of parabens on the cytoplasmic side of excised patches shifted activation curves of MscS toward higher tensions. A good correlation between the pressure increases in monolayers and shifts in activation midpoints in patch-clamp experiments suggested that the more hydrophobic parabens partition more strongly into the lipid and exert larger effects on channel gating through changes in lateral pressure. We show that cytoplasmically presented ethyl or butyl parabens both hasten the process of desensitization of MscS and influence inactivation differently. The higher rate of desensitization is likely due to increased lateral pressure in the cytoplasmic leaflet surrounding the gate. Neither of the parabens strongly affects the rate of recovery and does not seem to penetrate the TM2-TM3 interhelical clefts in MscS. We conclude that the bacterial

  16. Direct numerical simulation of the turbulent MHD channel flow at low magnetic Reynolds number for electric correlation characteristics

    Institute of Scientific and Technical Information of China (English)

    LEE; ChunHian

    2010-01-01

    Direct numerical simulation (DNS) of incompressible magnetohydrodynamic (MHD) turbulent channel flow has been performed under the low magnetic Reynolds number assumption.The velocity-electric field and electric-electric field correlations were studied in the present work for different magnetic field orientations.The Kenjeres-Hanjalic (K-H) model was validated with the DNS data in a term by term manner.The numerical results showed that the K-H model makes good predictions for most components of the velocity-electric field correlations.The mechanisms of turbulence suppression were also analyzed for different magnetic field orientations utilizing the DNS data and the K-H model.The results revealed that the dissipative MHD source term is responsible for the turbulence suppression for the case of streamwise and spanwise magnetic orientation,while the Lorentz force which speeds up the near-wall fluid and decreases the production term is responsible for the turbulence suppression for the case of the wall normal magnetic orientation.

  17. Inter-channel effects in monosolvated atomic iodide cluster anion detachment: correlation of the anisotropy parameter with solvent dipole moment.

    Science.gov (United States)

    Mbaiwa, Foster; Dao, Diep; Holtgrewe, Nicholas; Lasinski, Joshua; Mabbs, Richard

    2012-03-21

    Photoelectron imaging results are presented for I(-)[middle dot]X cluster anions (X = CO(2), C(4)H(5)N [pyrrole], (CH(3))(2)CO, CH(3)NO(2)). The available detachment channels are labeled according to the neutral iodine atom states produced (channel I ≡ (2)P(3/2) and channel II ≡ (2)P(1/2)). At photon energies in the vicinity of the channel II threshold these data are compared to previously reported results for I(-)[middle dot]X (X = CH(3)CN, CH(3)Cl, CH(3)Br, and H(2)O). In particular, these results show a strong connection between the dipole moment of the solvent molecule and the behavior of the channel I photoelectron angular distributions in this region, which is consistent with an electronic autodetachment process. The evolution of the channel II:channel I branching ratios in this excitation regime supports this contention.

  18. Inter-channel effects in monosolvated atomic iodide cluster anion detachment: Correlation of the anisotropy parameter with solvent dipole moment

    Science.gov (United States)

    Mbaiwa, Foster; Dao, Diep; Holtgrewe, Nicholas; Lasinski, Joshua; Mabbs, Richard

    2012-03-01

    Photoelectron imaging results are presented for I-.X cluster anions (X = CO2, C4H5N [pyrrole], (CH3)2CO, CH3NO2). The available detachment channels are labeled according to the neutral iodine atom states produced (channel I ≡ 2P3/2 and channel II ≡ 2P1/2). At photon energies in the vicinity of the channel II threshold these data are compared to previously reported results for I-.X (X = CH3CN, CH3Cl, CH3Br, and H2O). In particular, these results show a strong connection between the dipole moment of the solvent molecule and the behavior of the channel I photoelectron angular distributions in this region, which is consistent with an electronic autodetachment process. The evolution of the channel II:channel I branching ratios in this excitation regime supports this contention.

  19. Study of electron beams within ISTTOK tokamak by means of a multi-channel Cherenkov detector; their correlation with hard X-rays

    Energy Technology Data Exchange (ETDEWEB)

    Jakubowski, L., E-mail: Lech.Jakubowski@ipj.gov.p [Andrzej Soltan Institute for Nuclear Studies, 05-400 Otwock-Swierk (Poland); Malinowski, K.; Sadowski, M.J.; Zebrowski, J. [Andrzej Soltan Institute for Nuclear Studies, 05-400 Otwock-Swierk (Poland); Plyusnin, V.V. [Association Euratom/IST, Instituto de Plasmas e Fusao Nuclear, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Rabinski, M. [Andrzej Soltan Institute for Nuclear Studies, 05-400 Otwock-Swierk (Poland); Fernandes, H.; Silva, C.; Duarte, P. [Association Euratom/IST, Instituto de Plasmas e Fusao Nuclear, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Jakubowski, M.J. [Andrzej Soltan Institute for Nuclear Studies, 05-400 Otwock-Swierk (Poland)

    2010-11-11

    The paper describes experimental studies of electron beams emitted from a plasma torus within the ISTTOK tokamak, which were performed by means of a new four-channel detector of the Cherenkov type. A range of electron energy was estimated. There were also measured hard X-rays, and their correlation with the fast run-away electron beams was investigated experimentally.

  20. Modeling correlated nakagami-MIMO channel based on 2D rank matching%相关Nakagami-MIMO信道二维秩匹配模型

    Institute of Scientific and Technical Information of China (English)

    陈学强; 王成华; 朱秋明; 陈超

    2013-01-01

    针对现有Nakagami-MIMO信道仿真方法非常复杂的问题,提出了一种基于二维秩匹配的Nakagami-MIMO空时相关衰落仿真模型.该模型首先利用高效舍弃法产生多支路独立Nakagami随机过程,然后基于二维秩匹配技术引入各子信道空时相关性且保持子信道原有统计特性不变.仿真结果表明,该模型输出各子信道的衰落包络分布和空时相关系数等统计特性均与理论结果吻合,可应用于任意衰落参数和空时相关特性的Nakagami-MIMO信道仿真场合.%The traditional Nakagami-MIMO(multiple-input & multiple-output) channel simulation methods are very complex,and a novel simulator for spatial and temporal correlated Nakagami-MIMO fading channel based on 2D rank matching technique was proposed.Firstly,a high efficient rejection method was used to generate several Nakagami random processes as sub-branches of the MIMO channel.Then,the spatial and temporal correlation between each sub-channels were introduced by a new two-dimensional rank matching technique,which keeps the statistical properties of Nakagami fading unchanged.Simulation results show that the new simulator agrees well with the theoretical results on envelope distribution and spatialtemporal correlation,which can be applied to simulating the Nakagami-MIMO channel with arbitrary fading parameters and correlation features.

  1. Space-time coded eigenbeamforming for downlink frequency-selective correlated fading channels%下行频率选择性相关衰落信道下的空时特征波束编码

    Institute of Scientific and Technical Information of China (English)

    李勇朝; 廖桂生; 仝文宁

    2006-01-01

    To improve the performance of space-time coding over downlink frequency-selective correlated fading channels, a novel transmission scheme combining eigenbeamforming and OFDM is proposed. Provided that the channel correlated statistics are available at the transmitter, the wideband correlated fading channels can be converted into an independent FIR channel with 2 transmitting antennas and N receiving antennas by eigenbeamforming and dimension reduction. OFDM is utilized to convert the FIR channel into a group of independent parallel subchannels to carry space-time codes. With the new structure, the performance of space-time coding over downlink wideband correlated fading channels is greatly improved and the system complexity is reduced. Validity of the proposed system is verified by simulations under different conditions. Comparison between the new structure and an available structure is made both theoretically and computationally.

  2. Multi-scaled normal mode analysis method for dynamics simulation of protein-membrane complexes: A case study of potassium channel gating motion correlations

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Xiaokun; Han, Min; Ming, Dengming, E-mail: dming@fudan.edu.cn [Department of Physiology and Biophysics, School of Life Sciences, Fudan University, Shanghai (China)

    2015-10-07

    Membrane proteins play critically important roles in many cellular activities such as ions and small molecule transportation, signal recognition, and transduction. In order to fulfill their functions, these proteins must be placed in different membrane environments and a variety of protein-lipid interactions may affect the behavior of these proteins. One of the key effects of protein-lipid interactions is their ability to change the dynamics status of membrane proteins, thus adjusting their functions. Here, we present a multi-scaled normal mode analysis (mNMA) method to study the dynamics perturbation to the membrane proteins imposed by lipid bi-layer membrane fluctuations. In mNMA, channel proteins are simulated at all-atom level while the membrane is described with a coarse-grained model. mNMA calculations clearly show that channel gating motion can tightly couple with a variety of membrane deformations, including bending and twisting. We then examined bi-channel systems where two channels were separated with different distances. From mNMA calculations, we observed both positive and negative gating correlations between two neighboring channels, and the correlation has a maximum as the channel center-to-center distance is close to 2.5 times of their diameter. This distance is larger than recently found maximum attraction distance between two proteins embedded in membrane which is 1.5 times of the protein size, indicating that membrane fluctuation might impose collective motions among proteins within a larger area. The hybrid resolution feature in mNMA provides atomic dynamics information for key components in the system without costing much computer resource. We expect it to be a conventional simulation tool for ordinary laboratories to study the dynamics of very complicated biological assemblies. The source code is available upon request to the authors.

  3. Multi-scaled normal mode analysis method for dynamics simulation of protein-membrane complexes: A case study of potassium channel gating motion correlations.

    Science.gov (United States)

    Wu, Xiaokun; Han, Min; Ming, Dengming

    2015-10-01

    Membrane proteins play critically important roles in many cellular activities such as ions and small molecule transportation, signal recognition, and transduction. In order to fulfill their functions, these proteins must be placed in different membrane environments and a variety of protein-lipid interactions may affect the behavior of these proteins. One of the key effects of protein-lipid interactions is their ability to change the dynamics status of membrane proteins, thus adjusting their functions. Here, we present a multi-scaled normal mode analysis (mNMA) method to study the dynamics perturbation to the membrane proteins imposed by lipid bi-layer membrane fluctuations. In mNMA, channel proteins are simulated at all-atom level while the membrane is described with a coarse-grained model. mNMA calculations clearly show that channel gating motion can tightly couple with a variety of membrane deformations, including bending and twisting. We then examined bi-channel systems where two channels were separated with different distances. From mNMA calculations, we observed both positive and negative gating correlations between two neighboring channels, and the correlation has a maximum as the channel center-to-center distance is close to 2.5 times of their diameter. This distance is larger than recently found maximum attraction distance between two proteins embedded in membrane which is 1.5 times of the protein size, indicating that membrane fluctuation might impose collective motions among proteins within a larger area. The hybrid resolution feature in mNMA provides atomic dynamics information for key components in the system without costing much computer resource. We expect it to be a conventional simulation tool for ordinary laboratories to study the dynamics of very complicated biological assemblies. The source code is available upon request to the authors.

  4. Correlation between long-term marine temperature time series from the eastern and western English Channel: Scaling analysis using empirical mode decomposition

    Science.gov (United States)

    Derot, Jonathan; Schmitt, François Guillaume; Gentilhomme, Valérie; Morin, Pascal

    2016-05-01

    High-frequency temperature fluctuations recorded in the English Channel are compared using two long-term autonomous underwater monitoring stations at less than 20-min time resolution. Measurements were taken from 2005 to 2011 from two systems 460 km apart in the western and eastern parts of the English Channel. Spectral analysis reveals similar statistical behaviors, with approximate 5/3 spectra and several forcing frequencies in relation to tidal and daily cycles. A co-spectra study reveals a transition scale of 11 days. The influence of this scale is also visible though Time-Dependent Intrinsic Correlation analysis (TDIC)-a recently introduced cross-correlation analysis based on Empirical mode decomposition. This helps to spatialize high-frequency temporal records at a fixed location.

  5. Lack of correlation between the amplitudes of TRP channel-mediated responses to weak and strong stimuli in intracellular Ca(2+) imaging experiments.

    Science.gov (United States)

    Alpizar, Yeranddy A; Sanchez, Alicia; Radwan, Ahmed; Radwan, Islam; Voets, Thomas; Talavera, Karel

    2013-11-01

    It is often observed in intracellular Ca(2+) imaging experiments that the amplitudes of the Ca(2+) signals elicited by newly characterized TRP agonists do not correlate with the amplitudes of the responses evoked subsequently by a specific potent agonist. We investigated this rather controversial phenomenon by first testing whether it is inherent to the comparison of the effects of weak and strong stimuli. Using five well-characterized TRP channel agonists in commonly used heterologous expression systems we found that the correlation between the amplitudes of the Ca(2+) signals triggered by two sequentially applied stimuli is only high when both stimuli are strong. Using mathematical simulations of intracellular Ca(2+) dynamics we illustrate that the innate heterogeneity in expression and functional properties of Ca(2+) extrusion (e.g. plasma membrane Ca(2+) ATPase) and influx (TRP channels) pathways across a cellular population is a sufficient condition for low correlation between the amplitude of Ca(2+) signals elicited by weak and strong stimuli. Taken together, our data demonstrate that this phenomenon is an expected outcome of intracellular Ca(2+) imaging experiments that cannot be taken as evidence for lack of specificity of low-efficacy stimuli, or as an indicator of the need of other cellular components for channel stimulation.

  6. Shannon information capacity of time reversal wideband multiple-input multiple-output system based on correlated statistical channels

    Science.gov (United States)

    Yu, Yang; Bing-Zhong, Wang; Shuai, Ding

    2016-05-01

    Utilizing channel reciprocity, time reversal (TR) technique increases the signal-to-noise ratio (SNR) at the receiver with very low transmitter complexity in complex multipath environment. Present research works about TR multiple-input multiple-output (MIMO) communication all focus on the system implementation and network building. The aim of this work is to analyze the influence of antenna coupling on the capacity of wideband TR MIMO system, which is a realistic question in designing a practical communication system. It turns out that antenna coupling stabilizes the capacity in a small variation range with statistical wideband channel response. Meanwhile, antenna coupling only causes a slight detriment to the channel capacity in a wideband TR MIMO system. Comparatively, uncorrelated stochastic channels without coupling exhibit a wider range of random capacity distribution which greatly depends on the statistical channel. The conclusions drawn from information difference entropy theory provide a guideline for designing better high-performance wideband TR MIMO communication systems. Project supported by the National Natural Science Foundation of China (Grant Nos. 61331007, 61361166008, and 61401065) and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120185130001).

  7. Correlated shadowing and fading characterization of MIMO off-body channels by means of multiple autonomous on-body nodes

    OpenAIRE

    Van Torre, Patrick; Vanveerdeghem, Peter; Rogier, Hendrik

    2014-01-01

    In off-body communication systems low-cost and compact transceivers are important for realistic applications. An autonomous off-body wireless node was designed and integrated onto a textile antenna. Channel measurements were performed for an indoor non line-off-sight 4x2 MIMO (Multiple-Input Multiple-Output) link using four off-body transmitting nodes and two similar fixed receiving nodes. The channel behavior is characterized as Rayleigh fading with lognormal shadowing and is fitted to a mod...

  8. Anatomo-Functional Correlation between Head Zones and Acupuncture Channels and Points: A Comparative Analysis from the Perspective of Neural Therapy

    Directory of Open Access Journals (Sweden)

    Martha Liliana Beltrán Molano

    2014-01-01

    Full Text Available Background. Neural therapy and traditional Chinese medicine (TCM are part of complementary and alternative medicine in western world. Both of them share characteristics in diagnosis and therapeutics in search of changes in tenderness, pain, and skin stiffness related to visceral disease, as well as therapeutic procedures with specific stimuli on the skin that generate local, segmental, or remote reactions. Head zones explain segmental viscerocutaneous relations in neural therapy; however, interference fields and remote reactions after infiltration of local anesthetic go beyond this segmental distribution. Methods. This descriptive research required review and analysis of texts of Henry Head and traditional Chinese medicine. Results. Anatomical and functional relationships were found between Head zones in body, and head and neck with 14 acupuncture channels and their points. Anatomical areas of strong correlations were found: Head zones of heart and lung with heart and pericardium channels; Head zones of genitals with bladder and kidney channels. Strong functional relations between all Head zones, channels, and acupoints were found when following the pattern of segmental dermatomes; 235 acupuncture points were found in concordance.

  9. Correlation Equations of Heat Transfer in Nanofluid Al2O3-Water as Cooling Fluid in a Rectangular Sub Channel Based CFD Code

    Directory of Open Access Journals (Sweden)

    Anwar Ilmar Ramadhan

    2015-03-01

    Full Text Available Safety is a major concern in the design, operation and development of a nuclear reactor. One aspect of nuclear reactor safety factor is thermal-hydraulics aspect. In a PWR-type nuclear power plant has been used lighter fluid coolant is water or H2O. In this research, using nanofluid Al2O3-Water with volume fraction of (1%, (2% and also (3%, used as a cooling fluid in a nuclear reactor core with sub channel PWR fuel element rectangular arrangement. This research was carried out modeling of fuel elements are arranged rectangular, then performed numerical simulations using Computational Fluid Dynamics (CFD code. In order to obtain the characteristic pattern of flow velocity of each fluid, the fluid temperature distribution along the cylinder wall temperature distribution of the fuel element. Then analyzed the heat transfer in a nuclear reactor core with sub channel PWR fuel element rectangular arrangement, including heat transfer coefficient, Nusselt number (Nu, as well as heat transfer correlations. Heat transfer correlation for nanofluid Al2O3-Water (1%, (2% and also (3% proved to core of PWR nuclear reactor fuel element sub channel rectangular arrangement with the Reynolds number (Re is stretched, namely: 404 096

  10. Models of Stochastic Differential Equations for Correlated Fading Channels%相关衰落信道的随机微分方程模型

    Institute of Scientific and Technical Information of China (English)

    扈罗全; 施亚申; 陆全荣; 朱洪波

    2009-01-01

    研究使用随机微分方程产生相关衰落信道中接收机的抽头统计量.使用Iangevin方程对发生Doppler频移的随机相位进行建模,在对多径分量的幅度增益进行合理建模以后,从理论上证明表征抽头带通信号的统计特性仍然服从Rayleigh分布.使用仿真方法研究了相关衰落信道统计量的一些统计特性,发现随机相位是具有一定相关关系的高斯变量,所得抽头为独立的Rayleigh变量.%Stochastic differential equations (SDE) are applied to generate correlated random variables as receiver taper of fading channels. It is assumed that the random phases can be modeled through a Langevin equation and the amplitude gains follow a reasonable distribution, which are characterized by SDE. We further prove that the band-passed signals of tap in multipath channel still follow Rayleigh distribution. Simulation results of statistical character-istics of correlated fading channel, such as correlation function and Doppler power spectrum, agree well with the theo-retic values. The random phase is correlated Ganssian variables and the taper is the independent Rayleigh variables, which demonstrate the applicability of the proposed methodology.

  11. Performance Analysis of Post-Detection Combining for NFSK and DPSK Systems over Arbitrarily Correlated Nakagami Channels with Distinct Fading Parameters

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    For differential phase shift keying (DPSK) and noncoherent frequency shift keying (NFSK) systems over fading channels, the post-detection combining method is a popular means for improving the bit error performance. However, the bit error performance of such systems over Nakagami channels with an arbitrary covariance matrix and real distinct fading parameters has been seldom described in the literature. This paper studies the problem using a generic correlated Nakagami fading model and presents a closed form solution which is used to study the influence of the fading parameters and the signal-to-noise ratio (SNR) distribution ratios among all the branches on the bit error performance. Moreover, the average SNRs of each branch are not restricted to one value in the analysis. The closed form solution developed for the problem can be used to study the influence of the fading parameters and the SNR distribution ratios on the error performance.

  12. Mechanisms of atrial fibrillation termination by rapidly unbinding Na+ channel blockers: insights from mathematical models and experimental correlates.

    Science.gov (United States)

    Comtois, Philippe; Sakabe, Masao; Vigmond, Edward J; Munoz, Mauricio; Texier, Anne; Shiroshita-Takeshita, Akiko; Nattel, Stanley

    2008-10-01

    Atrial fibrillation (AF) is the most common sustained clinical arrhythmia and is a problem of growing proportions. Recent studies have increased interest in fast-unbinding Na(+) channel blockers like vernakalant (RSD1235) and ranolazine for AF therapy, but the mechanism of efficacy is poorly understood. To study how fast-unbinding I(Na) blockers affect AF, we developed realistic mathematical models of state-dependent Na(+) channel block, using a lidocaine model as a prototype, and studied the effects on simulated cholinergic AF in two- and three-dimensional atrial substrates. We then compared the results with in vivo effects of lidocaine on vagotonic AF in dogs. Lidocaine action was modeled with the Hondeghem-Katzung modulated-receptor theory and maximum affinity for activated Na(+) channels. Lidocaine produced frequency-dependent Na(+) channel blocking and conduction slowing effects and terminated AF in both two- and three-dimensional models with concentration-dependent efficacy (maximum approximately 89% at 60 microM). AF termination was not related to increases in wavelength, which tended to decrease with the drug, but rather to decreased source Na(+) current in the face of large ACh-sensitive K(+) current-related sinks, leading to the destabilization of primary generator rotors and a great reduction in wavebreak, which caused primary rotor annihilations in the absence of secondary rotors to resume generator activity. Lidocaine also reduced the variability and maximum values of the dominant frequency distribution during AF. Qualitatively similar results were obtained in vivo for lidocaine effects on vagal AF in dogs, with an efficacy of 86% at 2 mg/kg iv, as well as with simulations using the guarded-receptor model of lidocaine action. These results provide new insights into the mechanisms by which rapidly unbinding class I antiarrhythmic agents, a class including several novel compounds of considerable promise, terminate AF.

  13. Thermal Performance Analysis and Empirical Correlations for Laminar Forced Convection over 30° V-Baffled Square Channel

    Directory of Open Access Journals (Sweden)

    Amnart Boonloi

    2014-09-01

    Full Text Available Thermal performance analysis for laminar forced convection in an isothermal wall square channel with 30° V-baffle is presented numerically. The parameters of the V-baffle, blockage ratio (b/H, BR, pitch ratio (P/H, PR, flow direction (V-Downstream and V-Upstream, and arrangement (in-line and staggered, are studied and compared with the previous works, 20° and 45° V-baffle. The Reynolds number based on the hydraulic diameter of the channel (Dh, Re = 100–2000, is used in range study. The results show that the flow configurations of 30° V-baffle are found similar as 20° and 45° V-baffle. The fully developed periodic flow and heat transfer are created around 7th-8th module, while the periodic flow and heat transfer profiles are found at 2nd module in all cases. Except for the periodic concept, the 30° V-baffle can help to reduce the pressure loss around 2.3 times in comparison with the 45° V-baffle at the maximum f/f0 value (BR = 0.3, PR = 1, V-Downstream. The optimum thermal enhancement factor for the 30° V-baffle is found around 4.25 at BR = 0.15, PR = 1, and Re = 2000 for V-Downstream case with in-line arrangement.

  14. On the Impact of Channel Cross-Correlations in High-Sensitivity Receivers for Galileo E1 OS and GPS L1C Signals

    Directory of Open Access Journals (Sweden)

    Davide Margaria

    2012-01-01

    Full Text Available One of the most promising features of the modernized global navigation satellite systems signals is the presence of pilot channels that, being data-transition free, allow for increasing the coherent integration time of the receivers. Generally speaking, the increased integration time allows to better average the thermal noise component, thus improving the postcorrelation SNR of the receiver in the acquisition phase. On the other hand, for a standalone receiver which is not aided or assisted, the acquisition architecture requires that only the pilot channel is processed, at least during the first steps of the procedure. The aim of this paper is to present a detailed investigation on the impact of the code cross-correlation properties in the reception of Galileo E1 Open Service and GPS L1C civil signals. Analytical and simulation results demonstrate that the S-curve of the code synchronization loop can be affected by a bias around the lock point. This effect depends on the code cross-correlation properties and on the receiver setup. Furthermore, in these cases, the sensitivity of the receiver to other error sources might increase, and the paper shows how in presence of an interfering signal the pseudorange bias can be magnified and lead to relevant performance degradation.

  15. 1,3-propanediol binds deep inside the channel to inhibit water permeation through aquaporins.

    Science.gov (United States)

    Yu, Lili; Rodriguez, Roberto A; Chen, L Laurie; Chen, Liao Y; Perry, George; McHardy, Stanton F; Yeh, Chih-Ko

    2016-02-01

    Aquaporins and aquaglyceroporins (AQPs) are membrane channel proteins responsible for transport of water and for transport of glycerol in addition to water across the cell membrane, respectively. They are expressed throughout the human body and also in other forms of life. Inhibitors of human AQPs have been sought for therapeutic treatment for various medical conditions including hypertension, refractory edema, neurotoxic brain edema, and so forth. Conducting all-atom molecular dynamics simulations, we computed the binding affinity of acetazolamide to human AQP4 that agrees closely with in vitro experiments. Using this validated computational method, we found that 1,3-propanediol (PDO) binds deep inside the AQP4 channel to inhibit that particular aquaporin efficaciously. Furthermore, we used the same method to compute the affinities of PDO binding to four other AQPs and one aquaglyceroporin whose atomic coordinates are available from the protein data bank (PDB). For bovine AQP1, human AQP2, AQP4, AQP5, and Plasmodium falciparum PfAQP whose structures were resolved with high resolution, we obtained definitive predictions on the PDO dissociation constant. For human AQP1 whose PDB coordinates are less accurate, we estimated the dissociation constant with a rather large error bar. Taking into account the fact that PDO is generally recognized as safe by the US FDA, we predict that PDO can be an effective diuretic which directly modulates water flow through the protein channels. It should be free from the serious side effects associated with other diuretics that change the hydro-homeostasis indirectly by altering the osmotic gradients.

  16. Onshore-Offshore Correlation of Geologic Evidence for Great Cascadia Earthquakes--Permissive Agreement Between Washington Estuaries and Cascadia Deep-Sea Channel

    Science.gov (United States)

    Atwater, B. F.; Goldfinger, C.; Nelson, C.

    2004-12-01

    Geologic dating permits one-for-one correlation between coseismic subsidence in coastal Washington and turbidity currents in Cascadia deep-sea channel in the past 4000 years. The correlations make sense if plate-boundary rupture off the Washington coast accounts for the coastal subsidence. Such rupture would radiate seismic shaking directly beneath the submarine canyonheads that feed turbidity currents to Cascadia channel. The correlation strengthens the basis for using the turbidites as proxy records of great Cascadia earthquakes in the early Holocene, beyond the typical reach of the region's coastal subsidence records. For the past 4000 years in southwest Washington, the estuarine record of coseismic subsidence contains eight events at irregular intervals. The record can be seen at low tide as buried marsh and forest soils each capped with tidal-flat mud and some also coated with sand from tsunamis or sand blows. Successive soils differ consistently in stratigraphic patterns that provide field criteria for correlating among outcrops and for estimating relative lengths of recurrence intervals. The field correlations have survived chronological tests that include 32 sample ages with one-sigma counting errors less than 20 radiocarbon years. Most of these were measured on inner rings of the roots of earthquake-killed trees, from which the difference between sample age and event age can be counted with annual growth rings. Other materials set limiting ages that constrain event ages less exactly. Event age ranges at >95-percent confidence, in calendric years before AD 1950: 3550-4150 [8 events ago]; 3310-3390 [7]; 2845-2925 [6]; 2420-2620 [5]; 1540-1610 [4]; 1229-1264 [3]; 760-1190 [2]. The most recent event [1] dates from AD 1680-1720 (radiocarbon), 1699-1700 (ring-width patterns), and January 27, 1700 (Japanese documents). Well-defined intervals between successive events range from a few centuries [4 to 3] to a millennium [5 to 4]. One interval [7 to 6] approximates

  17. Adaptation of ASTC in a Correlated Rayleigh Frequency-Selective Fading Channels in OFDM systems with PAPR Reduction

    Directory of Open Access Journals (Sweden)

    Ahmed BANNOUR

    2010-05-01

    Full Text Available In this paper we suggest to use the ASTC (Algebraic Space Time Codes as powerful coding technique for IEEE802.11x OFDM standard combined with PAPR reduction scheme. ASTC with their very Algebraic- constructionbased on Quaternionic algebra, have a full rate, full diversity, non-vanishing constant minimum determinant forincreasing spectral efficiency, uniform average transmitted energy per antenna and good shaping, readily lendthemselves to high data rate situations. However, by their construction they require a nonselective flat fadingchannels belonging to narrow-band systems. In fact, such systems are not readily found in airs interfaces. Inopen air we have what are commonly called frequency-selective fading channels. As a matter of fact, it becomesextremely necessary to harness their power for wide-band systems.

  18. Correlations for predicting single phase and two-phase flow pressure drop in pebble bed flow channels

    Energy Technology Data Exchange (ETDEWEB)

    Bai Bofeng, E-mail: bfbai@mail.xjtu.edu.cn [State Key Laboratory of Multiphase Flow in Power Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Liu Maolong; Lv Xiaofei; Yan Junjie [State Key Laboratory of Multiphase Flow in Power Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Yan Xiao; Xiao Zejun [Lab of Bubble Physics and Natural Circulation, Nuclear Power Institute of China, Chengdu 610041 (China)

    2011-12-15

    An experimental study was conducted on the pressure drop of the single phase and the air-water two-phase flow in the bed of rectangular cross sections densely filled with uniform spheres. Three kinds of glass spheres with different equivalent diameters (3 mm, 6 mm, and 8 mm) were used for the establishment of the test sections. The Reynolds number in the experiment ranged from a dozen to thousands for the single-phase flow and from hundreds to tens of thousands for the two-phase flow. In the present flow-regime model, the bed was subdivided into a near-wall region and a central region in order to take the wall effect into account to improve the prediction at low tube-to-particle diameter ratios. Improved correlations are obtained based on the previous study to consider the single-phase flow pressure drops for finite pebble beds with spherical particles and nonspherical particles by fitting the coefficients of that equation to both the database and the present experiment. The correlation is consistent with the observed physical behavior which explains its comparatively good agreement with the experimental data. A new empirical correlation for the prediction of two-phase flow pressure drops was proposed based on the gas phase relative permeability as a function of the gas phase saturation and the void fraction. The correlation fit well for both experimental data of spherical particles and nonspherical particles.

  19. 相关Nakagami衰落分集信道仿真与分析%Simulation and Analysis of Diversity Channels under Correlated Nakagami Fading

    Institute of Scientific and Technical Information of China (English)

    朱秋明; 徐大专; 王成华; 陈小敏; 孙翔

    2012-01-01

    针对传统Nakagami衰落仿真方法难以提供精确互相关性的问题,提出一种适用于不同支路功率和衰落系数的相关Nakagami衰落信道仿真模型.证明了Nakagami和Gamma随机变量相关系数的内在联系,利用相关Gamma变量的均方根获得相关Nakagami衰落,推导了该模型输出幅值分布的误差表达式.仿真结果表明:该模型实现简单,仿真输出衰落幅值、相位分布与理论值吻合,互相关性能优于传统模型;其中第1支路通常由单个Gamma变量直接产生,仿真输出衰落的分布误差为0.%Aiming at the problem of the traditional Nakagami fading simulation method that can not provide accurate cross-correlation, a simulation model for correlated Nakagami fading channels suitable for unequal branch powers and fading parameters is proposed. The relationships between the correlation coefficients of Gamma and Nakagami random variables are proved. The correlated Nakagami fadings are generated by using the square roots of correlated Gamma variables. The error expression of the model's output envelope distribution is derived. Simulation results show that: the model is easier to achieve, the simulation fading envelope and phase distributions are close to the theoretical results,and the cross-correlation is more accurate than other models;the distribution error of the first simulation branch is zero, because it is always generated by one Gamma variable.

  20. Electrophysiological correlates of object-repetition effects: sLORETA imaging with 64-channel EEG and individual MRI

    Directory of Open Access Journals (Sweden)

    Kim Myung-Sun

    2012-10-01

    Full Text Available Abstract Background We investigated the electrophysiological correlates of object-repetition effects using an object categorization task, standardized low-resolution electromagnetic tomography (sLORETA, and individual magnetic resonance imaging. Sixteen healthy adults participated, and a total of 396 line drawings of living and non-living objects were used as stimuli. Of these stimuli, 274 were presented only once, and 122 were repeated after one to five intervening pictures. Participants were asked to categorize the objects as living or non-living things by pressing one of two buttons. Results The old/new effect (i.e., a faster response time and more positive potentials in response to repeated stimuli than to stimuli initially presented was observed at 350-550 ms post-stimulus. The distributions of cortical sources for the old and new stimuli were very similar at 250-650 ms after stimulus-onset. Activation in the right middle occipital gyrus/cuneus, right fusiform gyrus, left superior temporal gyrus, and right inferior frontal gyrus was significantly reduced in response to old compared with new stimuli at 250-350, 350-450, 450-550, and 550-650 ms after stimulus-onset, respectively. Priming in response time was correlated with the electrophysiological priming at left parietal area and repetition suppression at left superior temporal gyrus in 450-550 ms. Conclusions These results suggest processing of repeated objects is facilitated by sharpening perceptual representation and by efficient detection or attentional control of repeated objects.

  1. Transient Receptor Potential Ankyrin 1 Channel Expression on Peripheral Blood Leukocytes from Rheumatoid Arthritic Patients and Correlation with Pain and Disability

    Science.gov (United States)

    Pereira, Ione; Mendes, Saulo J. F.; Pereira, Domingos M. S.; Muniz, Thayanne F.; Colares, Valderlane L. P.; Monteiro, Cinara R. A. V.; Martins, Mahiba M. R. de S.; Grisotto, Marcos A. G.; Monteiro-Neto, Valério; Monteiro, Sílvio G.; Calixto, João B.; Brain, Susan D.; Fernandes, Elizabeth S.

    2017-01-01

    Patients with rheumatoid arthritis (RA) suffer from pain and joint disability. The transient receptor potential ankyrin 1 (TRPA1) channel expressed on sensory neurones and non-neuronal cells mediates pain transduction and inflammation and it has been implicated in RA. However, there is little information on the contribution of TRPA1 for human disease. Here, we investigated the expression of TRPA1 on peripheral blood leukocytes and the circulating levels of its endogenous activators 4-hydroxynonenal (4-HNE) and hydrogen peroxide (H2O2) in RA patients treated or not with the anti-rheumatic leflunomide (LFN) or the anti-TNFα adalimumab (ADA). We also assessed whether TRPA1 expression correlates with joint pain and disability, in addition to the immune changes in RA. TRPA1 expression on peripheral blood leukocytes correlated with pain severity and disability. TRPA1 levels on these cells were associated with the numbers of polymorphonuclear and the activation of CD14+ cells. No correlations were found between the lymphocyte population and TRPA1 expression, pain or disability. Patients recently diagnosed with RA expressed increased levels of TRPA1 on their leukocytes whilst treatment with either LFN or ADA down-regulated this receptor probably by reducing the numbers of polymorphonuclears and the activation of CD14+ cells. We suggest that the activation levels of CD14+ cells, the numbers of PMNs in the peripheral blood and the expression of TRPA1 on peripheral blood leukocytes correlate with RA progression, affecting joint pain sensitivity and loss of function. PMID:28239353

  2. Irresponsiveness of two retinoblastoma cases to conservative therapy correlates with up- regulation of hERG1 channels and of the VEGF-A pathway

    Directory of Open Access Journals (Sweden)

    La Torre Agostino

    2010-09-01

    Full Text Available Abstract Background Treatment strategies for Retinoblastoma (RB, the most common primary intraocular tumor in children, have evolved over the past few decades and chemoreduction is currently the most popular treatment strategy. Despite success, systemic chemotherapeutic treatment has relevant toxicity, especially in the pediatric population. Antiangiogenic therapy has thus been proposed as a valuable alternative for pediatric malignancies, in particolar RB. Indeed, it has been shown that vessel density correlates with both local invasive growth and presence of metastases in RB, suggesting that angiogenesis could play a pivotal role for both local and systemic invasive growth in RB. We present here two cases of sporadic, bilateral RB that did not benefit from the conservative treatment and we provide evidence that the VEGF-A pathway is significantly up-regulated in both RB cases along with an over expression of hERG1 K+ channels. Case presentation Two patients showed a sporadic, bilateral RB, classified at Stage II of the Reese-Elsworth Classification. Neither of them got benefits from conservative treatment, and the two eyes were enucleated. In samples from both RB cases we studied the VEGF-A pathway: VEGF-A showed high levels in the vitreous, the vegf-a, flt-1, kdr, and hif1-α transcripts were over-expressed. Moreover, both the transcripts and proteins of the hERG1 K+ channels turned out to be up-regulated in the two RB cases compared to the non cancerous retinal tissue. Conclusions We provide evidence that the VEGF-A pathway is up-regulated in two particular aggressive cases of bilateral RB, which did not experience any benefit from conservative treatment, showing the overexpression of the vegf-a, flt-1, kdr and hif1-α transcripts and the high secretion of VEGF-A. Moreover we also show for the first time that the herg1 gene transcripts and protein are over expressed in RB, as occurs in several aggressive tumors. These results further stress

  3. Inflammatory cytokine signaling in insulin producing beta-cells enhances the colocalization correlation coefficient between L-type voltage-dependent calcium channel and calcium-sensing receptor.

    Science.gov (United States)

    Parkash, Jai

    2008-08-01

    The immunological processes in type 1 diabetes and metabolic/inflammatory disorder in type 2 diabetes converge on common signaling pathway(s) leading to beta-cell death in these two diseases. The cytokine-mediated beta-cell death seems to be dependent on voltage-dependent calcium channel (VDCC)-mediated Ca2+ entry. The Ca2+ handling molecular networks control the homeostasis of [Ca2+]i in the beta-cell. The activity and membrane density of VDCC are regulated by several mechanisms including G protein-coupled receptors (GPCRs). CaR is a 123-kDa seven transmembrane extracellular Ca2+ sensing protein that belongs to GPCR family C. Tumor necrosis factor-alpha (TNF-alpha), is a cytokine widely known to activate nuclear factor-kappaB (NF-kappaB) transcription in beta-cells. To obtain a better understanding of TNF-alpha-induced molecular interactions between CaR and VDCC, confocal fluorescence measurements were performed on insulin-producing beta-cells exposed to varying concentrations of TNF-alpha and the results are discussed in the light of increased colocalization correlation coefficient. The insulin producing beta-cells were exposed to 5, 10, 20, 30, and 50 ng/ml TNF-alpha for 24 h at 37 degrees . The cells were then immunolabelled with antibodies directed against CaR, VDCC, and NF-kappaB. The confocal fluorescence imaging data showed enhancement in the colocalization correlation coefficient between CaR and VDCC in beta-cells exposed to TNF-alpha thereby indicating increased membrane delimited spatial interactions between these two membrane proteins. TNF-alpha-induced colocalization of VDCC with CaR was inhibited by nimodipine, an inhibitor of L-type VDCC thereby suggesting that VDCC activity is required for spatial interactions with CaR. The 3-D confocal fluorescence imaging data also demonstrated that addition of TNF-alpha to RIN cells led to the translocation of NF-kappaB from the cytoplasm to the nucleus. Such molecular interactions between CaR and VDCC in tissues

  4. Expression of T-cell KV 1.3 potassium channel correlates with pro-inflammatory cytokines and disease activity in ulcerative colitis✩

    Science.gov (United States)

    Hansen, Lars Koch; Sevelsted-Møller, Linda; Rabjerg, Maj; Larsen, Dorte; Hansen, Tine Plato; Klinge, Lone; Wulff, Heike; Knudsen, Torben; Kjeldsen, Jens; Köhler, Ralf

    2014-01-01

    Background and aims Potassium channels, KV1.3 and KCa3.1, have been suggested to control T-cell activation, proliferation, and cytokine production and may thus constitute targets for anti-inflammatory therapy. Ulcerative colitis (UC) is a chronic inflammatory bowel disease characterized by excessive T-cell infiltration and cytokine production. It is unknown if KV1.3 and KCa3.1 in the inflamed mucosa are markers of active UC. We hypothesized that KV1.3 and KCa3.1 correlate with disease activity and cytokine production in patients with UC. Methods Mucosal biopsies were collected from patients with active UC (n = 33) and controls (n = 15). Protein and mRNA expression of KV1.3 and KCa3.1, immune cell markers, and pro-inflammatory cytokines were determined by quantitative-real-time-polymerase-chain-reaction (qPCR) and immunofluorescence, and correlated with clinical parameters of inflammation. In-vitro cytokine production was measured in human CD3+ T-cells after pharmacological blockade of KV1.3 and KCa3.1. Results Active UC KV1.3 mRNA expression was increased 5-fold compared to controls. Immunofluorescence analyses revealed that KV1.3 protein was present in inflamed mucosa in 57% of CD4+ and 23% of CD8+ T-cells. KV1.3 was virtually absent on infiltrating macrophages. KV1.3 mRNA expression correlated significantly with mRNA expression of pro-inflammatory cytokines TNF-α (R2 = 0.61) and IL-17A (R2 = 0.51), the mayo endoscopic subscore (R2 = 0.13), and histological inflammation (R2 = 0.23). In-vitro blockade of T-cell KV1.3 and KCa3.1 decreased production of IFN-γ, TNF-α, and IL-17A. Conclusions High levels of KV1.3 in CD4 and CD8 positive T-cells infiltrates are associated with production of pro-inflammatory IL-17A and TNF-α in active UC. KV1.3 may serve as a marker of disease activity and pharmacological blockade might constitute a novel immunosuppressive strategy. PMID:24793818

  5. Physical layer security scenario using artificial noise in correlation MISO channel%一种基于人工噪声的MISO相关信道物理层安全方法

    Institute of Scientific and Technical Information of China (English)

    申少君; 黄开枝; 李印海

    2013-01-01

    现有基于人工噪声的物理层安全方法都假设信道是相互独立的,但是多天线通信系统中存在的信道空间相关性会降低系统安全容量.针对这一问题,设计了一种基于人工噪声的多入单出(MISO)相关信道物理层安全方法.通过合法用户信道参数的协方差矩阵得到发送端的信道相关矩阵,利用该矩阵与合法用户信道参数乘积的零空间作为人工噪声的生成空间,随机生成人工噪声对窃听方实现干扰.仿真结果表明,在存在信道空间相关性的情况下,本方法比现有方法的平均系统安全容量提高了约0.5 bit/s/Hz.%Prior work on artificial noise approach of physical layer security has assumed the independency of different channels. However, in a practical multiple antenna system, the spatial correlation among channel taps would decline the security capacity. This paper explored a robust alternative for secure transmission on correlated multiple-input single-output ( MISO) channel based on artificial noise. The channel state information between transmitter and the legitimate user could provide the correlated matrix of the spatial correlation. With the null space of the product of the correlated matrix and channel state information, the transmitter produced random artificial interference to prevent from eavesdropping. The simulation result indicates that the robust method improves the average secure capacity about 0. 5 bit/s/Hz with the proposed method when channel correlation exists.

  6. 空时相关MIMO信道下的空时联合Huffman有限反馈预编码%Joint space-time Huffman limited feedback precoding for spatially and temporally correlated MIMO channels

    Institute of Scientific and Technical Information of China (English)

    居美艳; 葛欣; 李岳衡; 谭国平

    2013-01-01

    For the MIMO channels with space correlation and time correlation, a novel joint space-time Huffman limited feedback precoding scheme was proposed which improves the system performance and reduces the amount of feedback. Based on space correlation, the precoding structure under zero-forcing (ZF) criterion was derived and the rotating quan-tization codebook was designed which reduces the effect of space correlation on system performance. In addition, in view of time correlation of channels, the scheme reduces the feedback data of channel state information (CSI) in the slow fad-ing channel by using neighborhood-based limited feedback. Due to different probabilities of codewords in the neighbor-hood, Huffman coding was adopted to further reduce the amount of feedback.%针对空时相关的 MIMO 信道,提出了一种新颖的 Huffman 空时联合有限反馈预编码方法,提高了系统性能,并减少了反馈量。从信道的空间相关性出发,推导了迫零准则下预编码的构成,从而设计了一种旋转量化码本,减小了空间相关性对系统性能的影响。另外,针对信道的时间相关性,利用基于邻域的有限反馈来降低慢衰落信道的反馈量。同时,由于领域内各码字被选中的概率不同,可以利用Huffman编码进一步减少反馈量。

  7. A Digital Correlation Spectrometer Chip with 1 GHz Bandwidth, 4096 Spectral Channels, and 4 W Power Consumption for Passive Microwave Remote Sensing Instruments Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The scope of this project is to provide a digital auto-correlation spectrometer fabricated on a single integrated circuit for NASA's future Earth-Sun System missions...

  8. Average Fade Duration of Dual Selection Diversity over Correlated Unbalanced Nakagami-m Fading Channels in the Presence of Cochannel Interference

    Science.gov (United States)

    Panajotović, Aleksandra; Sekulović, Nikola; Drača, Dragan; Stefanović, Mihajlo; Stefanović, Časlav

    2013-12-01

    A dual selection combining (SC) receiver with correlated and unbalanced diversity branches operating in interference-limited Nakagami-m fading environment is considered in this paper. Actually, average fade duration (AFD) of SC system applying desired signal decision algorithm is obtained. Numerical results can be used to examine the effects of fading severity, input signal-to-interference ratio (SIR) unbalance and level of branch correlation on the AFD, as well as the correctness of proposed analytical formulation.

  9. 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.

  10. 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.

  11. LOFDM Time Domain Correlation Channel Estimation Based on the Time-Frequency Subspace Projection%基于时频子空间投影的LOFDM系统时域相关信道估计算法

    Institute of Scientific and Technical Information of China (English)

    高猛; 沈越泓; 许魁

    2011-01-01

    LOFDM ( Lattice Orthogonal Frequency Division Multiplexing) , which is proposed by Strohmer T and Beaver S in 2003 , has higher spectral efficiency and better bit error rate ( BER) performance compared with OFDM systems in the time-frequency dispersive channel. LOFDM systems need to adapt the parameters of signals' time-frequency lattice (TFL) and shaping-pulse scale to the channel dispersion characteristics in the transmitters , while the exact channel estimation is required for coherence demodulation in the receivers. The time-frequency interleaving characteristics of LOFDM signals induce that the time domain channel estimation can't be achieved via the received signals directly. In this work, we separate the odd and even carriers through the equivalent time-frequency subspace projection, and a low complexity time domain correlation channel estimation algonthm for LOFDM systems is proposed based on pilot design and frequency domain pilot time domain correlation method. The interference pmblem is analyzed and the Cramér-Rao bound ( CRB) of the time domain channel estimation for LOFDM systems is also deduced. Simulation results demonstrate that the proposed algorithm has good mean square error performance between the estimated CIR ( Channel Impulse Response) and the true one,while symbol error rate perfurmance of demodulation through the estimated CIR is near with the ideal channel.%Strohmer T与Beaver S于2003年提出了适用于时频散射信道的网格正交频分复用(LOFDM,Lattice Orthogonal Frequency Division Multiplexing)系统,与传统OFDM系统相比该系统具有更高的频带利用率和更好的误码性能.LOFDM系统发送端需要自适应地调整信号的原形脉冲和其时频分布的参数,使之与信道保持匹配;而接收端则需要准确的信道估计以实现相干解调.本文针对LOFDM系统由于其信号的时频交错特性接收端无法直接利用接收信号进行时域信道估计的问题,采用一种低复杂度

  12. 基于空频相关性的大规模MIMO-OFDM信道压缩反馈算法%Compressed Channel Feedback Based on Spatial-frequency Correlation for Massive MIMO-OFDM Systems

    Institute of Scientific and Technical Information of China (English)

    李晓辉; 王维猛; 黑永强

    2014-01-01

    In Massive MIMO-OFDM systems, the channel shows strong correlations in both spatial and frequency domain. Aiming at the problem that only spatial or frequency domain correlation is considered in most of the existing compressed feedback algorithms, a joint spatial-frequency compression algorithm is proposed. First, a two dimensional sparsity of channel in spatial-frequency domain is analyzed according to the compressed sensing theory. Then, a joint sparse matrix of channel is derived. Based on the joint sparse matrix, the joint spatial-frequency compression algorithm is presented. Simulation results and analysis show that, the proposed algorithm can significantly reduce the feedback load with acceptable accuracy.%大规模MIMO-OFDM系统中,信道常常存在较强的空间和频域相关性。针对多数信道压缩反馈算法仅考虑空间或频域相关性的问题,该文提出一种空频联合压缩反馈算法。首先,根据压缩感知理论进行了信道空频2维稀疏度分析;然后,推导了信道矩阵在空间和频域2维相关性下的联合稀疏基;最后,利用该联合稀疏基给出了空频联合压缩算法。仿真结果与分析表明,该算法在保证信道反馈精度的同时,可显著降低反馈量。

  13. Multi-user MIMO Transceiver Design in LOS Correlated Channels with Imperfect CSI%视距相关信道下考虑非理想CSI的多用户MIMO收发联合设计

    Institute of Scientific and Technical Information of China (English)

    陈磊; 祝锴; 王大鸣; 崔维嘉

    2011-01-01

    在FDD模式多用户MIMO(Multi-input Multi-output)系统下行链路中,由于信道估计、反馈信道等存在误差,使得发送端获取理想信道状态信息(CSI,channel state information)十分困难.针对获得非理想csI的多用户MIMO系统,考虑在基站和各用户的天线分别具有相关性并引入视距分量的信道条件下,提出了一种新的基于块对角化的MMSE准则收发联合设计算法.该算法首先通过块对角化消除用户间的共信道干扰,然后针对存在信道估计误差的用户信道依据MMSE准则分别迭代求解每个用户预编码和解码矩阵.论文设计出一种基于训练序列的信道估计误差算法,并获得等效信道模型,使得收发端获得的信道状态信息更有实际意义.本文假设反馈信道理想,发射端可以完整得到信道估计矩阵.在MMSE准则下,推导获得了Lagrange乘子的解析解,避免了求解非线性方程的复杂过程,显著降低了计算复杂度.和已有算法相比,该算法不仅可以获得良好的误码性能还可以对各用户进行独立优化,处理更加灵活.仿真分析了视距分量、信道相关性以及信道估计误差对算法性能的影响.仿真结果表明,该算法误码性能良好,算法收敛快,并且对信道估计误差带来的影响有较好的抑制作用.%Multi-user MIMO ( multi-input multi-output) system has been studied in number of papers in recent years. In this paper,a novel multi-user transceiver algorithm is proposed for the system. In the multi-user MIMO system under FDD mode for the downlink, because of the channel estimation error and feedback channel errer, it is difficult to obtain the perfect channel state information ( CSI) at transmitter. With the consideration of both the line-of-sight( LOS) component and the correlation at both the transmitter and users , a minimum sum MSE criterion MIMO transceiver design algorithm based on block diagonalization is proposed. It is supposed that

  14. Expression of T-cell KV1.3 potassium channel correlates with pro-inflammatory cytokines and disease activity in ulcerative colitis

    DEFF Research Database (Denmark)

    Koch Hansen, Lars; Møller, Linda Maria Sevelsted; Rabjerg, Maj;

    2014-01-01

    by excessive T-cell infiltration and cytokine production. It is unknown if KV1.3 and KCa3.1 in the inflamed mucosa are markers of active UC. We hypothesized that KV1.3 and KCa3.1 correlate with disease activity and cytokine production in patients with UC. METHODS: Mucosal biopsies were collected from patients...

  15. Positive correlation between the cyclotron line energy and luminosity in sub-critical X-ray pulsars: Doppler effect in the accretion channel

    Science.gov (United States)

    Mushtukov, Alexander A.; Tsygankov, Sergey S.; Serber, Alexander V.; Suleimanov, Valery F.; Poutanen, Juri

    2015-12-01

    Cyclotron resonance scattering features observed in the spectra of some X-ray pulsars show significant changes of the line centroid energy with the pulsar luminosity. Whereas for bright sources above the so-called critical luminosity, these variations are established to be connected with the appearance of the high-accretion column above the neutron star surface, at low, sub-critical luminosities the nature of the variations (but with the opposite sign) has not been discussed widely. We argue here that the cyclotron line is formed when the radiation from a hotspot propagates through the plasma falling with a mildly relativistic velocity on to the neutron star surface. The position of the cyclotron resonance is determined by the Doppler effect. The change of the cyclotron line position in the spectrum with luminosity is caused by variations of the velocity profile in the line-forming region affected by the radiation pressure force. The presented model has several characteristic features: (i) the line centroid energy is positively correlated with the luminosity; (ii) the line width is positively correlated with the luminosity as well; (iii) the position and the width of the cyclotron absorption line are variable over the pulse phase; (iv) the line has a more complicated shape than widely used Lorentzian or Gaussian profiles; (v) the phase-resolved cyclotron line centroid energy and the width are negatively and positively correlated with the pulse intensity, respectively. The predictions of the proposed theory are compared with the variations of the cyclotron line parameters in the X-ray pulsar GX 304-1 over a wide range of sub-critical luminosities as seen by the INTEGRAL observatory.

  16. Intermittency and exotic channels

    CERN Document Server

    Bialas, A

    1994-01-01

    It is pointed out that accurate measurements of short-range two-particle correlations in like-charge K\\pi and in \\pi^ 0\\pi^ 0 channels should be very helpful in determining the origin of the \\lq\\lq intermittency\\rq\\rq\\ phenomenon observed recently for the like-charge pion pairs.

  17. HCN Channels and Heart Rate

    Directory of Open Access Journals (Sweden)

    Ilaria Dentamaro

    2012-04-01

    Full Text Available Hyperpolarization and Cyclic Nucleotide (HCN -gated channels represent the molecular correlates of the “funny” pacemaker current (If, a current activated by hyperpolarization and considered able to influence the sinus node function in generating cardiac impulses. HCN channels are a family of six transmembrane domain, single pore-loop, hyperpolarization activated, non-selective cation channels. This channel family comprises four members: HCN1-4, but there is a general agreement to consider HCN4 as the main isoform able to control heart rate. This review aims to summarize advanced insights into the structure, function and cellular regulation of HCN channels in order to better understand the role of such channels in regulating heart rate and heart function in normal and pathological conditions. Therefore, we evaluated the possible therapeutic application of the selective HCN channels blockers in heart rate control.

  18. Iterative Detection of MIMO System over Frequency Selective and Spatial Correlative Channel%频率选择性信道下空间相关MIMO的迭代检测技术

    Institute of Scientific and Technical Information of China (English)

    燕兵; 史治平; 于清苹; 张忠培

    2009-01-01

    A model of MIMO system over spatial correlative and frequency selective channel is constructed. The non - binary RA codes are adapted as channel codes at the transmitter,and a correlative and uncorre-latod channel adaptive iterative detection method using soft interference cancellation is adapted at the re-ceiver. In this method, the sliding window based on MMSE method is used to cancel inter - symbol interfer-ence(ISI), then joint antenn as maximum likelihood detection is performed, finally soft information is pas-sod from detector to decoder,thus one iteration process(called JAD SC/MMSE) is completed. This model brings very low bit error rate (BER), and its advanced scheme, where diversity in modulation field is added at the transmitter,can achieve better performance. For contrast, BER of the common scheme, based on an-tenna by antenna detection which uses MMSE only (ABA SC/MMSE) is very poor. The simulation result also proves the opinion above.%给出了一种频率选择性信道下空间相关MIMO的系统模型,其发送端采用准循环系统RA码,接收端采用一种对空间相关和非相关信道均适用的软干扰消除迭代检测算法.该算法首先采用基于最小均方误差检测(MMSE)的滑动窗口模型进行干扰消除,然后采用多天线联合最大似然检测(ML)以得到软信息,再将得到的软信息传递到译码器译码并输出发送比特的软信息作为下一次迭代的先验信息,即完成一次迭代.此模型能够取得比较好的误码率性能(BER),其改进方案既增加了发送端的调制域分集,性能又有提升.作为比较,基于软干扰消除的逐天线MMSE迭代检测的方案(ABA SC/MMSE)性能很差.仿真结果也证明了以上观点.

  19. Mechanosensitive Channels

    Science.gov (United States)

    Martinac, Boris

    Living cells are exposed to a variety of mechanical stimuli acting throughout the biosphere. The range of the stimuli extends from thermal molecular agitation to potentially destructive cell swelling caused by osmotic pressure gradients. Cellular membranes present a major target for these stimuli. To detect mechanical forces acting upon them cell membranes are equipped with mechanosensitive (MS) ion channels. Functioning as molecular mechanoelectrical transducers of mechanical forces into electrical and/or chemical intracellular signals these channels play a critical role in the physiology of mechanotransduction. Studies of prokaryotic MS channels and recent work on MS channels of eukaryotes have significantly increased our understanding of their gating mechanism, physiological functions, and evolutionary origins as well as their role in the pathology of disease.

  20. 存在信道相关及估计误差时V-BLAST系统的功率分配算法%Power Allocation Algorithm for Correlated V-BLAST System with Channel Estimation Error

    Institute of Scientific and Technical Information of China (English)

    谭伟; 陈小敏; 朱益民; 朱秋明; 党小宇

    2015-01-01

    An adaptive transmit power allocation (TPA) scheme to minimize bit error rate (BER) is in‐vestigated in a vertical bell labs layered space‐time (V‐BLAST ) system with channel correlation and esti‐mation error .The closed expression for average BER can be derived according to the instantaneous sig‐nal‐to‐interference‐plus‐noise ratio (SINR) of each sub‐stream by system modeling and performance anal‐ysis .At the transmitter ,with the total TPA constraint condition ,TPA matrix is calculated through the Lagrange multiplier method .Numerical results demonstrate that the correlation structure and channel estimation error have a profound effect on the performance of V‐BLAST system .The proposed TPA scheme can improve the BER performance effectively and be practical for the actual communication sys‐tem .%针对信道相关及存在信道估计误差的垂直分层空时(Vertical bell lab layered space‐time ,V‐BLAST )系统,提出以最小化误比特率(Bit error rate ,BER)为优化目标的自适应功率分配算法。通过系统建模和性能分析,由接收信号子流的瞬时信干噪比(Signal‐to‐interference‐plus‐noise ratio ,SINR),推导出系统子流的平均BER闭式表达式。发送端在总功率约束条件下,以瞬时BER为优化目标,利用拉格朗日极值法得到自适应功率分配矩阵。仿真结果表明,信道相关及估计误差对V‐BLAST 系统的BER性能有极大影响,采用所提算法可显著改善系统的BER性能并更具实用性。

  1. Optimal superdense coding over memory channels

    Energy Technology Data Exchange (ETDEWEB)

    Shadman, Z.; Kampermann, H.; Bruss, D.; Macchiavello, C. [Institute fuer Theoretische Physik III, Heinrich-Heine-Universitaet Duesseldorf, DE-40225 Duesseldorf (Germany); Dipartimento di Fisica ' ' A. Volta' ' and INFM-Unita di Pavia, Via Bassi 6, IT-27100 Pavia (Italy)

    2011-10-15

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

  2. 基于EEMD子带提取相关机械振动信号单通道盲源分离%Blind source separation of single-channel statistically correlated mechanical vibration signals based on subband extraction of EEMD

    Institute of Scientific and Technical Information of China (English)

    孟宗; 蔡龙

    2014-01-01

    针对传统独立分量分析难以解决机械故障诊断中存在的相关源信号盲分离、欠定盲分离等问题,在相关振源信号部分子带满足统计独立的假设前提下,提出基于总体经验模态分解子带提取相关机械源单通道盲源分离方法。该方法将单通道观测信号进行总体经验模态分解获得到子带观测信号,将单通道信号及子带观测信号组成新的多维信号,利用奇异值分解及贝叶斯准则估计源信号数目;据互信息标准与源信号数目选若干独立性较强的子带观测信号重构,实现信号升维;对重构的观测信号进行白化预处理及联合近似对角化,获得源信号估计。并仿真、实验验证该方法在机械故障诊断中的有效性。%The traditional independent component analysis is too difficult to solve the problems of underdetermined blind source separation(BSS)and statistically correlated sources separation in mechanical fault diagnosis.Under the assumption of statistical indpendence between some sub-components of correlated machine vibration sources,a novel blind source separation method based on subband extraction of ensemble empirical mode decomposition (EEMD)was proposed to solve the problem of single-channel statistically correlated mechanical signals separation.In the method,the single-channel signal was decomposed into a series of subband observed signals by ensemble empirical mode decomposition,then the number of source signals was estimated by singular value decomposition and Bayesian information criterion.New observed signals were reconstructed by using some selected subband observed signals with high independence according to the mutual information criterion and the number of sources,and the dimension of the new observed signal was increased. The source signals were estimated through the reconstructed observed signals by using whitening preprocessing and joint approximate diagonalization

  3. 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.

  4. Positron Channeling

    CERN Document Server

    Badikyan, Karen

    2016-01-01

    The possibility of channeling the low-energy relativistic positrons around separate crystallographic axes with coaxial symmetry of negative ions in some types of crystals is shown. The process of annihilation of positrons with electrons of medium was studied in detail.

  5. 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.

  6. 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

  7. Single-channel kinetics of BK (Slo1 channels

    Directory of Open Access Journals (Sweden)

    Yanyan eGeng

    2015-01-01

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

  8. Spin chains and channels with memory

    OpenAIRE

    Plenio, M. B.; Virmani, S.

    2007-01-01

    In most studies of the channel capacity of quantum channels, it is assumed that the errors in each use of the channel are independent. However, recent work has begun to investigate the effects of memory or correlations in the error. This work has led to speculation that interesting non-analytic behaviour may occur in the capacity. Motivated by these observations, we connect the study of channel capacities under correlated error to the study of critical behaviour in many-body physics. This con...

  9. Nonlinear channelizer

    Science.gov (United States)

    In, Visarath; Longhini, Patrick; Kho, Andy; Neff, Joseph D.; Leung, Daniel; Liu, Norman; Meadows, Brian K.; Gordon, Frank; Bulsara, Adi R.; Palacios, Antonio

    2012-12-01

    The nonlinear channelizer is an integrated circuit made up of large parallel arrays of analog nonlinear oscillators, which, collectively, serve as a broad-spectrum analyzer with the ability to receive complex signals containing multiple frequencies and instantaneously lock-on or respond to a received signal in a few oscillation cycles. The concept is based on the generation of internal oscillations in coupled nonlinear systems that do not normally oscillate in the absence of coupling. In particular, the system consists of unidirectionally coupled bistable nonlinear elements, where the frequency and other dynamical characteristics of the emergent oscillations depend on the system's internal parameters and the received signal. These properties and characteristics are being employed to develop a system capable of locking onto any arbitrary input radio frequency signal. The system is efficient by eliminating the need for high-speed, high-accuracy analog-to-digital converters, and compact by making use of nonlinear coupled systems to act as a channelizer (frequency binning and channeling), a low noise amplifier, and a frequency down-converter in a single step which, in turn, will reduce the size, weight, power, and cost of the entire communication system. This paper covers the theory, numerical simulations, and some engineering details that validate the concept at the frequency band of 1-4 GHz.

  10. 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.

  11. Ion channel stability and hydrogen bonding. Molecular modelling of channels formed by synthetic alamethicin analogues.

    Science.gov (United States)

    Breed, J; Kerr, I D; Molle, G; Duclohier, H; Sansom, M S

    1997-12-04

    Several analogues of the channel-forming peptaibol alamethicin have been demonstrated to exhibit faster switching between channel substates than does unmodified alamethicin. Molecular modelling studies are used to explore the possible molecular basis of these differences. Models of channels formed by alamethicin analogues were generated by restrained molecular dynamics in vacuo and refined by short molecular dynamics simulations with water molecules within and at either mouth of the channel. A decrease in backbone solvation was found to correlate with a decrease in open channel stability between alamethicin and an analogue in which all alpha-amino-isobutyric acid residues of alamethicin were replaced by leucine. A decrease in the extent of hydrogen-bonding at residue 7 correlates with lower open channel stabilities of analogues in which the glutamine at position 7 was replaced by smaller polar sidechains. These two observations indicate the importance of alamethicin/water H-bonds in stabilizing the open channel.

  12. Influence of space between atmospheric channels and beams' number on scintillation

    Institute of Scientific and Technical Information of China (English)

    Weihui Liu (刘维慧); Jian Wu (吴健)

    2003-01-01

    On the basis of Kolmogorov's theorem, the physical meanings of beams' correlation function on received plane are extended. Approximate formula of channels' across correlation coefficient is deduced from multiple beams through atmosphere. And the scintillation variance of multiple beams is also induced. The result shows along with the channels close to one another, the correlation coefficient increases, and so does the scintillation variance. When the channels completely combine, the scintillation variance of multiple channels is with no difference from that of one channel.

  13. Control of the selectivity of the aquaporin water channel family by global orientational tuning

    DEFF Research Database (Denmark)

    Jensen, Morten Østergaard; Tajkhorshid, E.; Nollert, P.

    2002-01-01

    membrane. We have determined the structure of the Escherichia coli aquaglyceroporin GlpF with bound water, in native (2.7 angstroms) and in W48F/F200T mutant (2.1 angstroms) forms, and carried out 12-nanosecond molecular dynamics simulations that define the spatial and temporal probability distribution...

  14. 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.

  15. Zero-error source-channel coding with entanglement.

    NARCIS (Netherlands)

    Briët, J.; Buhrman, H.; Laurent, M.; Piovesan, T.; Scarpa, G.

    2013-01-01

    We study the use of quantum entanglement in the zero-error source-channel coding problem. Here, Alice and Bob are connected by a noisy classical one-way channel, and are given correlated inputs from a random source. Their goal is for Bob to learn Alice's input while using the channel as little as po

  16. Zero-error source-channel coding with entanglement.

    NARCIS (Netherlands)

    Briët, J.; Buhrman, H.; Laurent, M.; Piovesan, T.; Scarpa, G.

    2014-01-01

    We study the use of quantum entanglement in the zero-error source-channel coding problem. Here, Alice and Bob are connected by a noisy classical one-way channel, and are given correlated inputs from a random source. Their goal is for Bob to learn Alice's input while using the channel as little as po

  17. 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

  18. 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.

  19. Impact of channel estimation error on channel capacity of multiple input multiple output system

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In order to investigate the impact of channel estimation error on channel capacity of multiple input multiple output (MIMO) system, a novel method is proposed to explore the channel capacity in correlated Rayleigh fading environment. A system model is constructed based on the channel estimation error at receiver side. Using the properties of Wishart distribution, the lower bound of the channel capacity is derived when the MIMO channel is of full rank. Then a method is proposed to select the optimum set of transmit antennas based on the lower bound of the mean channel capacity. The novel method can be easily implemented with low computational complexity. The simulation results show that the channel capacity of MIMO system is sensitive to channel estimation error, and is maximized when the signal-to-noise ratio increases to a certain point. Proper selection of transmit antennas can increase the channel capacity of MIMO system by about 1 bit/s in a flat fading environment with deficient rank of channel matrix.

  20. Analysis and Realization on MIMO Channel Model

    Directory of Open Access Journals (Sweden)

    Liu Hui

    2014-04-01

    Full Text Available In order to build the MIMO (Multiple Input Multiple Output channel model based on IEEE 802.16, the way and analysis on how to build good MIMO channel model are described in this study. By exploiting the spatial freedom of wireless channels, MIMO systems have the potential to achieve high bandwidth efficiency, promoting MIMO to be a key technique in the next generation communication systems. As a basic researching field of MIMO technologies, MIMO channel modeling significantly serve to the performance evaluation of space-time encoding algorithms as well as system level calibration and simulation. Having the superiorities of low inner-antenna correlation and small array size, multi-polarization tends to be a promising technique in future MIMO systems. However, polarization characteristics have not yet been modeled well in current MIMO channel models, so establishing meaningful multi-polarized MIMO channel models has become a hot spot in recent channel modeling investigation. In this study, I have mainly made further research on the related theories in the channel models and channel estimation and implementation algorithms on the others’ research work.

  1. 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.

  2. Joint source-channel coding for a quantum multiple access channel

    Science.gov (United States)

    Wilde, Mark M.; Savov, Ivan

    2012-11-01

    Suppose that two senders each obtain one share of the output of a classical, bivariate, correlated information source. They would like to transmit the correlated source to a receiver using a quantum multiple access channel. In prior work, Cover, El Gamal and Salehi provided a combined source-channel coding strategy for a classical multiple access channel which outperforms the simpler ‘separation’ strategy where separate codebooks are used for the source coding and the channel coding tasks. In this paper, we prove that a coding strategy similar to the Cover-El Gamal-Salehi strategy and a corresponding quantum simultaneous decoder allow for the reliable transmission of a source over a quantum multiple access channel, as long as a set of information inequalities involving the Holevo quantity hold.

  3. Joint source-channel coding for a quantum multiple access channel

    CERN Document Server

    Wilde, Mark M

    2012-01-01

    Suppose that two senders each obtain one share of the output of a classical, bivariate, correlated information source. They would like to transmit the correlated source to a receiver using a quantum multiple access channel. In prior work, Cover, El Gamal, and Salehi provided a combined source-channel coding strategy for a classical multiple access channel which outperforms the simpler "separation" strategy where separate codebooks are used for the source coding and the channel coding tasks. In the present paper, we prove that a coding strategy similar to the Cover-El Gamal-Salehi strategy and a corresponding quantum simultaneous decoder allow for the reliable transmission of a source over a quantum multiple access channel, as long as a set of information inequalities involving the Holevo quantity hold.

  4. Quantum channels and memory effects

    Science.gov (United States)

    Caruso, Filippo; Giovannetti, Vittorio; Lupo, Cosmo; Mancini, Stefano

    2014-10-01

    Any physical process can be represented as a quantum channel mapping an initial state to a final state. Hence it can be characterized from the point of view of communication theory, i.e., in terms of its ability to transfer information. Quantum information provides a theoretical framework and the proper mathematical tools to accomplish this. In this context the notion of codes and communication capacities have been introduced by generalizing them from the classical Shannon theory of information transmission and error correction. The underlying assumption of this approach is to consider the channel not as acting on a single system, but on sequences of systems, which, when properly initialized allow one to overcome the noisy effects induced by the physical process under consideration. While most of the work produced so far has been focused on the case in which a given channel transformation acts identically and independently on the various elements of the sequence (memoryless configuration in jargon), correlated error models appear to be a more realistic way to approach the problem. A slightly different, yet conceptually related, notion of correlated errors applies to a single quantum system which evolves continuously in time under the influence of an external disturbance which acts on it in a non-Markovian fashion. This leads to the study of memory effects in quantum channels: a fertile ground where interesting novel phenomena emerge at the intersection of quantum information theory and other branches of physics. A survey is taken of the field of quantum channels theory while also embracing these specific and complex settings.

  5. 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.

  6. On superdense coding with noisy channels

    Energy Technology Data Exchange (ETDEWEB)

    Shadman, Zahra; Kampermann, Hermann; Bruss, Dagmar [Heinrich-Heine-Universitaet, Institut fuer Theoretische Physik III, Duesseldorf (Germany)

    2009-07-01

    We study the capacity of a superdense coding protocol in the case of a noisy channel. We consider the case where the channel acts on Alice's side, and the one where it acts both on Alice's and Bob's side. In the latter case, the noise can be correlated or uncorrelated. We study various noise models and various bipartite input states, and derive the optimal capacity.

  7. 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 Ecological engineering of stream corridors must focus at least as much energy on mediating hydrologic

  8. Upper Capacity Bounds of MIMO Wireless Systems Through Fading Channels

    Directory of Open Access Journals (Sweden)

    Rachna Mahey

    2015-01-01

    Full Text Available This paper investigates the upper capacity bounds of MIMO systems with correlation and antenna selection techniques in general fading environments. With Antenna Selection techniques, the increased hardware complexity due to multiple antennas and large number of RF chains can be reduced to a substantial amount, retaining the diversity benefits of MIMO systems. The channel Correlation also affects the capacity of MIMO fading channels. Hence, to evaluate the upper bounds of capacity through fading channels, performance of MIMO systems is exemplified under Nakagami-m and Rayleigh fading channels while considering that the channel characteristics are known at a transmitter. The obtained results give an assessment to the better understanding to the effect of antenna selection and correlation on the capacity of MIMO channels, and how they can be used in different fading environments.

  9. USACE Navigation Channels 2012

    Data.gov (United States)

    California Department of Resources — This dataset represents both San Francisco and Los Angeles District navigation channel lines. All San Francisco District channel lines were digitized from CAD files...

  10. 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...

  11. 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.

  12. Cardiac potassium channel subtypes

    DEFF Research Database (Denmark)

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

    2014-01-01

    About 10 distinct potassium channels in the heart are involved in shaping the action potential. Some of the K(+) channels are primarily responsible for early repolarization, whereas others drive late repolarization and still others are open throughout the cardiac cycle. Three main K(+) channels...

  13. Multi-Channel Autonomous Information System Performance with Positional Signal State Analyzers at the Channel Outputs

    Directory of Open Access Journals (Sweden)

    V. K. Hohlov

    2016-01-01

    Full Text Available The article presents a statement of technique to research performances of multi-channel combo standalone information systems with positional analyzers of the signal states at the channel outputs. In most cases, in considered multi-channel systems there has been impossible to coincide in time the random moments of signals coming from the objects through various channels in all ways of encounter environment and conditions of practical application. The analyzer makes decision on the signal using the discrete operations on the quantized signals of the certain duration from the channel outputs. The analyzer performance is described by a set of Boolean algebra functions defined for all possible states of the signals at the outputs of the channels, and in the general case is specified in a perfect disjunctive normal form. To determine the validity or falsity of functions of the algebra of logics, which are calculated statements concerning the available or unavailable useful signal at the system input, on the authority of the Poretsky’s theorem and the theory of coincidence in time of the random pulse flow of the channels response because of uncorrelated and correlated noise, are obtained dependences to calculate the probabilities of false alarms and omissions of the signals in discrete combined systems. It is shown that the flows of false alarms because of noise at the channel outputs in the system are Poisson streams. On the basis of the ordinary Poisson flows the paper justifies the relationships for calculating the false alarms of the system with uncorrelated and correlated noise in the channels. The paper also justifies the relationships for performance of multichannel combined systems with positional analyzers of the channels states. Based on the obtained relationships was calculated the average coincidence frequency of the extended pulses of the channel response in a dualchannel system, depending on the noise cross-correlation coefficient with

  14. Analysis of Correlation between Brand Value and Logistics Channel Development of Wuliangye%五粮液品牌价值与物流渠道发展关联性分析

    Institute of Scientific and Technical Information of China (English)

    陆霞

    2012-01-01

    采用经典的计量经济学模型-向量自回归模型(VAR模型),对五粮液晶牌价值与物流渠道发展进行深入分析与研究.研究所用数据分别来自CCER数据库和权威部门发布的品牌价值年报,透过图形化的分析方法,对五粮液品牌价值变化有了宏观的掌握.并对图形化分析存在的不足,采用VAR模型对其进行了深入计量分析,从物流渠道建设角度出发,找到了五粮液品牌价值迅速、持续提升的内在原因.从而以计量模型分析的结果为指导,从宏观层面为中国酒类企业深化发展提出了指导性意见和建议.%In this paper, we employed the VAR model, a classic econometric model, to analyzed in depth the value of the brand Wuliangye and the development of its logistics channels. The data used in this paper were collected from CCER database and the annual report of brand value released by relevant authorities and the graphic analytic method was used to obtain a macroscopic understanding of the changes in the brand value of Wuliangye. We supplemented the shortcomings of the graphic analysis with the VAR model and from the perspective of logistics channel construction, identified the internal causes for the swift and continuous improvement of the value of the brand Wuliangye. Then guided by the result of the analysis, we proposed opinions and suggestions for deepening the development of the liquor enterprises of China on the macroscopic level.

  15. Turbo Detection in Rayleigh flat fading channel with unknown statistics

    Directory of Open Access Journals (Sweden)

    Paul Fortier

    2010-11-01

    Full Text Available The turbo detection of turbo coded symbols over correlated Rayleigh flat fading channels generatedaccording to Jakes’ model is considered in this paper. We propose a method to estimate the channelsignal-to-noise ratio (SNR and the maximum Doppler frequency. These statistics are required bythe linear minimum mean squared error (LMMSE channel estimator. To improve the system convergence,we redefine the channel reliability factor by taking into account the channel estimationerror statistics. Simulation results for rate 1=3 turbo code and two different normalized fading ratesshow that the use of the new reliability factor greatly improves the performance. The improvementis more substantial when channel statistics are unknown.

  16. Simplified transmitter design for MIMO systems with channel uncertainty

    Institute of Scientific and Technical Information of China (English)

    DU Juan; KANG Gui-xia; ZHANG Ping

    2009-01-01

    This article investigates transmitter design in Rayleigh fading multiple input multiple output (MIMO) channels with spatial correlation when there are channel uncertainties caused by a combined effect of channel estimation error and limited feedback. To overcome the high computational complexity of the optimal transmit power allocation, a simple and suboptimal allocation is proposed by exploiting the transmission constraint and differentiating a bound based on Jensen inequality on the channel capacity. The simulation results show that the mutual information corresponding to the proposed power allocation closely approaches the channel capacity corresponding to the optimal one and meanwhile the computational complexity is greatly reduced.

  17. Capacity of orthogonal space-time block codes in MISO fading channels with co-channel interference and noise

    Institute of Scientific and Technical Information of China (English)

    YUE DianWu; WANG Qian

    2009-01-01

    Orthogonal space-time block codes (OSTBCs) are an efficient mean In order to exploit the diversity offered by the wireless multiple-input multiple-output (MIMO) channel.This paper considers capacity problems of OSTBCs over spatially correlated multiple-input single-out (MISO) Rayleigh fading channels in the presence of spatially correlated Rayleigh co-channel interference and additive Gaussian noise,and derives exact expressions of the ergodic capacity and outage probability (capacity distribution) for such OSTBCs.Some numerical examples are given to illustrate the effect of co-channel interference on the ergodic and outage capacity of OSTBCs.

  18. 基于空间相关性的大规模MIMO信道压缩反馈算法%Compressed channel feedback for spatial correlated massive MIMO systems

    Institute of Scientific and Technical Information of China (English)

    陈慧慧; 凌荣桢; 景小荣

    2015-01-01

    针对传统的信道状态信息(channel state information,CSI)反馈方法并不适用于大规模MIMO频分双工(frequency-division duplexing,FDD)系统的问题,提出一种基于导频设计的压缩反馈算法.基站通过对发送相关矩阵的平方根进行特征值分解(eigenvalue decomposition,EVD)得到稀疏基;根据最小二乘法(least squares,LS)设计出导频矩阵;根据该导频矩阵提出了一种基于导频设计的压缩反馈算法.理论分析与仿真结果表明,该算法能够以较低的反馈量获取较高的CSI反馈精度.

  19. Protocol channels as a new design alternative of covert channels

    CERN Document Server

    Wendzel, Steffen

    2008-01-01

    Covert channel techniques are used by attackers to transfer hidden data. There are two main categories of covert channels: timing channels and storage channels. This paper introduces a third category called protocol channels. A protocol channel switches one of at least two protocols to send a bit combination to a destination while sent packets include no hidden information themselves.

  20. Surface vacancy channels through ion channeling

    Energy Technology Data Exchange (ETDEWEB)

    Redinger, Alex; Standop, Sebastian; Michely, Thomas [II. Physikalisches Institut, Universitaet Koeln, Zuelpicher Strasse 77, 50937 Koeln (Germany); Rosandi, Yudi; Urbassek, Herbert M. [Fachbereich Physik, Technische Universitaet Kaiserslautern, Erwin-Schroedinger-Strasse, D-67663 Kaiserslautern (Germany)

    2009-07-01

    Damage patterns of single ion impacts on Pt(111) have been studied by scanning tunneling microscopy (STM) and molecular dynamics simulations (MD). Low temperature experiments, where surface diffusion is absent, have been performed for argon and xenon ions with energies between 1 keV and 15 keV at an angle of incidence of 86 {sup circle} measured with respect to the surface normal. Ions hitting preexisting illuminated step edges penetrate into the crystal and are guided in open crystallographic directions, one or more layers underneath the surface (subsurface channeling). In the case of argon channeling the resulting surface damage consists of adatom and vacancy pairs aligned in ion beam direction. After xenon channeling thin surface vacancy trenches along the ion trajectories - surface vacancy channels - are observed. They result from very efficient sputtering and adatom production along the ion trajectory. This phenomena is well reproduced in molecular dynamics simulations of single ion impacts at 0 K. The damage patterns of Argon and Xenon impacts can be traced back to the different energy losses of the particles in the channel. Channeling distances exceeding 1000 A for 15 keV xenon impacts are observed.

  1. Charged and Neutral Particles Channeling Phenomena Channeling 2008

    Science.gov (United States)

    Dabagov, Sultan B.; Palumbo, Luigi

    2010-04-01

    regime by a buried oxide layer / V. Guidi, A. Mazzolari and V. V. Tikhomirov -- A positron source using channeling in crystals for linear colliders / X. Artru ... [et al.] -- Parametric channeling and collapse of charged particles beams in crystals / M. Vysotskyy and V. Vysotskii.The formation and usage of coherent correlated charged particles states in the physics of channeling in crystals / S. V. Adamenko, V. I. Vysotskii and M. V. Vysotskyy -- Surface channeling of magnetic-charged particles on multilayer surface / S. V. Adamenko and V. I. Vysotskii -- Coherent creation of anti-hydrogen atoms in a crystal by relativistic antiproton / Yu. P. Kunashenko -- Thermal equilibrium of light ions in heavy crystals / E. Tsyganov -- Photon emission of electrons in a crystalline undulator / H. Backe ... [et al.] -- Channeling radiation from relativistic electrons in a crystal target as complementary x-ray and gamma ray source at synchrotron light facilities / K. B. Korotchenko, Yu. L. Pivovarov and T. A. Tukhfatullin -- Diffracted channeling radiation and other compound radiation processes / H. Nitta -- Collective scattering on the atom planes under the condition of full transition / A. R. Mkrtchyan ... [et al.] -- The proposal of the experiment on the research of the diffracted channeling radiation / D. A. Baklanov ... [et al.] -- Positron channeling at the DaOne BTF Facility: the cup experiment / L. Quintieri ... [et al.] -- Radiation spectra of 200 MeV electrons in diamond and silicon crystals at axial and planar orientations / K. Fissum ... [et al.] -- Channeling experiments with electrons at the Mainz Microtron Mami / W. Lauth ... [et al.] -- Dechanneling of positrons by dislocations: effects of anharmonic interactions / J. George and A. P. Pathak -- Diffracted channeling radiation from axially channeled relativistic electrons / K. B. Korotchenko ... [et al.] -- Intensive quasi-monochromatic, directed x-ray radiation of planar channeled positron bunch / L. Gevorgian

  2. A scalable correlator for multichannel diffuse correlation spectroscopy

    Science.gov (United States)

    Stapels, Christopher J.; Kolodziejski, Noah J.; McAdams, Daniel; Podolsky, Matthew J.; Fernandez, Daniel E.; Farkas, Dana; Christian, James F.

    2016-03-01

    Diffuse correlation spectroscopy (DCS) is a technique which enables powerful and robust non-invasive optical studies of tissue micro-circulation and vascular blood flow. The technique amounts to autocorrelation analysis of coherent photons after their migration through moving scatterers and subsequent collection by single-mode optical fibers. A primary cost driver of DCS instruments are the commercial hardware-based correlators, limiting the proliferation of multi-channel instruments for validation of perfusion analysis as a clinical diagnostic metric. We present the development of a low-cost scalable correlator enabled by microchip-based time-tagging, and a software-based multi-tau data analysis method. We will discuss the capabilities of the instrument as well as the implementation and validation of 2- and 8-channel systems built for live animal and pre-clinical settings.

  3. Channel Statistics for MIMO Handsets in Data Mode

    DEFF Research Database (Denmark)

    Nielsen, Jesper Ødum; Yanakiev, Boyan; Barrio, Samantha Caporal Del;

    2014-01-01

    The presented work is based on a large dual- band, dual-base outdoor-to-indoor multiple-input multiple- output (MIMO) channel measurement campaign, involving ten different realistic MIMO handsets, held in data mode by eight test users. Various different use cases (UCs) are measured. Statistics on...... on the channel capacity, mean effective gain (MEG), branch power ratio (BPR), and correlation coefficients between Rx, Tx, and cross-link channels are presented....

  4. 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...

  5. Score Correlation

    OpenAIRE

    Fabián, Z. (Zdeněk)

    2010-01-01

    In this paper, we study a distribution-dependent correlation coefficient based on the concept of scalar score. This new measure of association of continuous random variables is compared by means of simulation experiments with the Pearson, Kendall and Spearman correlation coefficients.

  6. Model validation of channel zapping quality

    NARCIS (Netherlands)

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

    2009-01-01

    In an earlier paper we showed, that perceived quality of channel zapping is related to the perceived quality of download time of web browsing, as suggested by ITU-T Rec.G.1030. We showed this by performing subjective tests resulting in an excellent fit with a 0.99 correlation. This was what we call

  7. NIRS-BASED CORTICAL ACTIVATION ANALYSIS BY TEMPORAL CROSS CORRELATION

    Directory of Open Access Journals (Sweden)

    Raul Fernandez-Rojas

    2016-02-01

    Full Text Available In this study we present a method of signal processing to determine dominant channels in near infrared spectroscopy (NIRS. To compare measuring channels and identify delays between them, cross correlation is computed. Furthermore, to find out possible dominant channels, a visual inspection was performed. The outcomes demonstrated that the visual inspection exhibited evoked-related activations in the primary somatosensory cortex (S1 after stimulation which is consistent with comparable studies and the cross correlation study discovered dominant channels on both cerebral hemispheres. The analysis also showed a relationship between dominant channels and adjacent channels. For that reason, our results present a new method to identify dominant regions in the cerebral cortex using near-infrared spectroscopy. These findings have also implications in the decrease of channels by eliminating irrelevant channels for the experiment.

  8. Quantum feedback channels

    CERN Document Server

    Bowen, G

    2002-01-01

    In classical information theory the capacity of a noisy 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 noisy quantum channel, in direct analogy to the classical case. It is also shown that in various cases of non-assisted capacities, feedback can increase the capacity of many quantum channels.

  9. Ion channels in asthma.

    Science.gov (United States)

    Valverde, Miguel A; Cantero-Recasens, Gerard; Garcia-Elias, Anna; Jung, Carole; Carreras-Sureda, Amado; Vicente, Rubén

    2011-09-23

    Ion channels are specialized transmembrane proteins that permit the passive flow of ions following their electrochemical gradients. In the airways, ion channels participate in the production of epithelium-based hydroelectrolytic secretions and in the control of intracellular Ca(2+) levels that will ultimately activate almost all lung cells, either resident or circulating. Thus, ion channels have been the center of many studies aiming to understand asthma pathophysiological mechanisms or to identify therapeutic targets for better control of the disease. In this minireview, we focus on molecular, genetic, and animal model studies associating ion channels with asthma.

  10. TRP channels in schistosomes

    Directory of Open Access Journals (Sweden)

    Swarna Bais

    2016-12-01

    Full Text Available Praziquantel (PZQ is effectively the only drug currently available for treatment and control of schistosomiasis, a disease affecting hundreds of millions of people worldwide. Many anthelmintics, likely including PZQ, target ion channels, membrane protein complexes essential for normal functioning of the neuromusculature and other tissues. Despite this fact, only a few classes of parasitic helminth ion channels have been assessed for their pharmacological properties or for their roles in parasite physiology. One such overlooked group of ion channels is the transient receptor potential (TRP channel superfamily. TRP channels share a common core structure, but are widely diverse in their activation mechanisms and ion selectivity. They are critical to transducing sensory signals, responding to a wide range of external stimuli. They are also involved in other functions, such as regulating intracellular calcium and organellar ion homeostasis and trafficking. Here, we review current literature on parasitic helminth TRP channels, focusing on those in schistosomes. We discuss the likely roles of these channels in sensory and locomotor activity, including the possible significance of a class of TRP channels (TRPV that is absent in schistosomes. We also focus on evidence indicating that at least one schistosome TRP channel (SmTRPA has atypical, TRPV1-like pharmacological sensitivities that could potentially be exploited for future therapeutic targeting.

  11. Secret Sharing over Fast-Fading MIMO Wiretap Channels

    Directory of Open Access Journals (Sweden)

    Bloch Matthieu

    2009-01-01

    Full Text Available Secret sharing over the fast-fading MIMO wiretap channel is considered. A source and a destination try to share secret information over a fast-fading MIMO channel in the presence of an eavesdropper who also makes channel observations that are different from but correlated to those made by the destination. An interactive, authenticated public channel with unlimited capacity is available to the source and destination for the secret sharing process. This situation is a special case of the "channel model with wiretapper" considered by Ahlswede and Csiszár. An extension of their result to continuous channel alphabets is employed to evaluate the key capacity of the fast-fading MIMO wiretap channel. The effects of spatial dimensionality provided by the use of multiple antennas at the source, destination, and eavesdropper are then investigated.

  12. Distributed Joint Source-Channel Coding in Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Lin Zhang

    2009-06-01

    Full Text Available Considering the fact that sensors are energy-limited and the wireless channel conditions in wireless sensor networks, there is an urgent need for a low-complexity coding method with high compression ratio and noise-resisted features. This paper reviews the progress made in distributed joint source-channel coding which can address this issue. The main existing deployments, from the theory to practice, of distributed joint source-channel coding over the independent channels, the multiple access channels and the broadcast channels are introduced, respectively. To this end, we also present a practical scheme for compressing multiple correlated sources over the independent channels. The simulation results demonstrate the desired efficiency.

  13. Asymptotically Optimal Downlink Scheduling over Markovian Fading Channels

    CERN Document Server

    Ouyang, Wenzhuo; Shroff, Ness B

    2011-01-01

    We consider the scheduling problem in downlink wireless networks with heterogeneous, Markov-modulated, ON/OFF channels. It is well-known that the performance of scheduling over fading channels heavily depends on the accuracy of the available Channel State Information (CSI), which is costly to acquire. Thus, we consider the CSI acquisition via a practical ARQ-based feedback mechanism whereby channel states are revealed at the end of only scheduled users' transmissions. In the assumed presence of temporally-correlated channel evolutions, the desired scheduler must optimally balance the exploitation-exploration trade-off, whereby it schedules transmissions both to exploit those channels with up-to-date CSI and to explore the current state of those with outdated CSI. In earlier works, Whittle's Index Policy had been suggested as a low-complexity and high-performance solution to this problem. However, analyzing its performance in the typical scenario of statistically heterogeneous channel state processes has remai...

  14. KΛ and KΣ photoproduction in a coupled-channels framework

    NARCIS (Netherlands)

    Usov, A.; Scholten, O.

    2005-01-01

    A coupled-channels analysis, based on the K-matrix approach, is presented for photo-induced kaon production. It is shown that channel coupling effects are large and should not be ignored. The importance of contact terms in the analysis, associated with short-range correlations, is pointed out. The e

  15. Fungal colonization with Pneumocystis correlates to increasing chloride channel accessory 1 (hCLCA1 suggesting a pathway for up-regulation of airway mucus responses, in infant lungs

    Directory of Open Access Journals (Sweden)

    Francisco J. Pérez

    2014-01-01

    Full Text Available Fungal colonization with Pneumocystis is associated with increased airway mucus in infants during their primary Pneumocystis infection, and to severity of COPD in adults. The pathogenic mechanisms are under investigation. Interestingly, increased levels of hCLCA1 – a member of the calcium-sensitive chloride conductance family of proteins that drives mucus hypersecretion – have been associated with increased mucus production in patients diagnosed with COPD and in immunocompetent rodents with Pneumocystis infection. Pneumocystis is highly prevalent in infants; therefore, the contribution of Pneumocystis to hCLCA1 expression was examined in autopsied infant lungs. Respiratory viruses that may potentially increase mucus, were also examined. hCLCA1 expression was measured using actin-normalized Western-blot, and the burden of Pneumocystis organisms was quantified by qPCR in 55 autopsied lungs from apparently healthy infants who died in the community. Respiratory viruses were diagnosed using RT-PCR for RSV, metapneumovirus, influenza, and parainfluenza viruses; and by PCR for adenovirus. hCLCA1 levels in virus positive samples were comparable to those in virus-negative samples. An association between Pneumocystis and increased hCLCA1 expression was documented (P=0.028. Additionally, increasing Pneumocystis burden correlated with increasing hCLCA1 protein expression levels (P=0.017. Results strengthen the evidence of Pneumocystis-associated up-regulation of mucus-related airway responses in infant lungs. Further characterization of this immunocompetent host-Pneumocystis-interaction, including assessment of potential clinical significance, is warranted.

  16. 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.

  17. Ion channels in toxicology.

    Science.gov (United States)

    Restrepo-Angulo, Iván; De Vizcaya-Ruiz, Andrea; Camacho, Javier

    2010-08-01

    Ion channels play essential roles in human physiology and toxicology. Cardiac contraction, neural transmission, temperature sensing, insulin release, regulation of apoptosis, cellular pH and oxidative stress, as well as detection of active compounds from chilli, are some of the processes in which ion channels have an important role. Regulation of ion channels by several chemicals including those found in air, water and soil represents an interesting potential link between environmental pollution and human diseases; for instance, de novo expression of ion channels in response to exposure to carcinogens is being considered as a potential tool for cancer diagnosis and therapy. Non-specific binding of several drugs to ion channels is responsible for a huge number of undesirable side-effects, and testing guidelines for several drugs now require ion channel screening for pharmaceutical safety. Animal toxins targeting human ion channels have serious effects on the population and have also provided a remarkable tool to study the molecular structure and function of ion channels. In this review, we will summarize the participation of ion channels in biological processes extensively used in toxicological studies, including cardiac function, apoptosis and cell proliferation. Major findings on the adverse effects of drugs on ion channels as well as the regulation of these proteins by different chemicals, including some pesticides, are also reviewed. Association of ion channels and toxicology in several biological processes strongly suggests these proteins to be excellent candidates to follow the toxic effects of xenobiotics, and as potential early indicators of life-threatening situations including chronic degenerative diseases.

  18. 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.

  19. Noise reduction algorithm for glueball correlators

    Energy Technology Data Exchange (ETDEWEB)

    Majumdar, Pushan, E-mail: tppm@iacs.res.in [Department of Theoretical Physics, Indian Association for the Cultivation of Science, Kolkata (India); Mathur, Nilmani, E-mail: nilmani@theory.tifr.res.in [Department of Theoretical Physics, Tata Institute of Fundamental Research, Mumbai (India); Mondal, Sourav, E-mail: tpsm5@iacs.res.in [Department of Theoretical Physics, Indian Association for the Cultivation of Science, Kolkata (India)

    2014-09-07

    We present an error reduction method for obtaining glueball correlators from Monte Carlo simulations of SU(3) lattice gauge theory. We explore the scalar and tensor channels at three different lattice spacings. Using this method we can follow glueball correlators to temporal separations even up to 1 fermi. We estimate the improvement over the naive method and compare our results with existing computations.

  20. Optimal training sequences for MIMO systems under correlated fading

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The optimal design of training sequences for channel estimation in multiple-input multiple-output (MIMO) systems under spatially correlated fading is considered.The channel is assumed to be a block-fading model with spatial correlation known at both the transmitter and the receiver.To minimize the channel estimation error,optimal training sequences are designed to exploit full information of the spatial correlation under the criterion of minimum mean square error (MMSE).It is investigated that the spatial correlation is helpful to decrease the estimation error and the proposed training sequences have good performance via simulations.

  1. 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.

  2. Gaussian matrix product states for coding in bosonic communication channels

    CERN Document Server

    Schäfer, Joachim; Cerf, Nicolas J

    2012-01-01

    The communication capacity of Gaussian bosonic channels with memory has recently attracted much interest. Here, we investigate a method to prepare the multimode entangled input symbol states for encoding classical information into these channels. In particular, we study the usefulness of a Gaussian matrix product state (GMPS) [G. Adesso and M. Ericsson, Phys. Rev. A 74, 030305 (2006)] as an input symbol state, which can be sequentially generated although it remains heavily entangled for an arbitrary number of modes. We show that the GMPS can achieve more than 99.9% of the Gaussian capacity for Gaussian bosonic memory channels with a Markovian or non-Markovian correlated noise model in a large range of noise correlation strengths. Furthermore, we present a noise class for which the GMPS is the exact optimal input symbol state of the corresponding channel. Since GMPS are ground states of particular quadratic Hamiltonians, our results suggest a possible link between the theory of quantum communication channels a...

  3. Paraunitary Oversampled Filter Bank Design for Channel Coding

    Directory of Open Access Journals (Sweden)

    Cooper Tom

    2006-01-01

    Full Text Available Oversampled filter banks (OSFBs have been considered for channel coding, since their redundancy can be utilised to permit the detection and correction of channel errors. In this paper, we propose an OSFB-based channel coder for a correlated additive Gaussian noise channel, of which the noise covariance matrix is assumed to be known. Based on a suitable factorisation of this matrix, we develop a design for the decoder's synthesis filter bank in order to minimise the noise power in the decoded signal, subject to admitting perfect reconstruction through paraunitarity of the filter bank. We demonstrate that this approach can lead to a significant reduction of the noise interference by exploiting both the correlation of the channel and the redundancy of the filter banks. Simulation results providing some insight into these mechanisms are provided.

  4. Channel Access in Erlang

    Energy Technology Data Exchange (ETDEWEB)

    Nicklaus, Dennis J. [Fermilab

    2013-10-13

    We have developed an Erlang language implementation of the Channel Access protocol. Included are low-level functions for encoding and decoding Channel Access protocol network packets as well as higher level functions for monitoring or setting EPICS process variables. This provides access to EPICS process variables for the Fermilab Acnet control system via our Erlang-based front-end architecture without having to interface to C/C++ programs and libraries. Erlang is a functional programming language originally developed for real-time telecommunications applications. Its network programming features and list management functions make it particularly well-suited for the task of managing multiple Channel Access circuits and PV monitors.

  5. An Insight to Covert Channels

    OpenAIRE

    Salwan, Nitish; Singh, Sandeep; Arora, Suket; Singh, Amarpreet

    2013-01-01

    This paper presents an overview of different concepts regarding covert channels. It discusses the various classifications and the detailing of various fields used to manipulate for the covert channel execution.Different evaluation criterias are presented for measuring the strength of covert channels. The defenses and prevention schemes for this covert channel will also be discussed. This paper also discuss about an advanced timing channel i.e.Temperature Based Covert Channel.

  6. 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....

  7. Correlator technology

    NARCIS (Netherlands)

    Schooneveld, C. van

    1968-01-01

    The paper reviews a number of designs of cross-correlation receivers for the detection of active underwater transmissions. Particular attention is given to the various structures of phase insensitive receivers, and to the problems concerned with clipping of the input signal and the reference functio

  8. Cooperative gating between ion channels.

    Science.gov (United States)

    Choi, Kee-Hyun

    2014-01-01

    Cooperative gating between ion channels, i.e. the gating of one channel directly coupled to the gating of neighboring channels, has been observed in diverse channel types at the single-channel level. Positively coupled gating could enhance channel-mediated signaling while negative coupling may effectively reduce channel gating noise. Indeed, the physiological significance of cooperative channel gating in signal transduction has been recognized in several in vivo studies. Moreover, coupled gating of ion channels was reported to be associated with some human disease states. In this review, physiological roles for channel cooperativity and channel clustering observed in vitro and in vivo are introduced, and stimulation-induced channel clustering and direct channel cross linking are suggested as the physical mechanisms of channel assembly. Along with physical clustering, several molecular mechanisms proposed as the molecular basis for functional coupling of neighboring channels are covered: permeant ions as a channel coupling mediator, concerted channel activation through the membrane, and allosteric mechanisms. Also, single-channel analysis methods for cooperative gating such as the binomial analysis, the variance analysis, the conditional dwell time density analysis, and the maximum likelihood fitting analysis are reviewed and discussed.

  9. A New Adaptive Channel Estimation for Frequency Selective Time Varying Fading OFDM Channels

    CERN Document Server

    Afifi, Wessam M

    2010-01-01

    In this paper a new algorithm for adaptive dynamic channel estimation for frequency selective time varying fading OFDM channels is proposed. The new algorithm adopts a new strategy that successfully increases OFDM symbol rate. Instead of using a fixed training pilot sequence, the proposed algorithm uses a logic controller to choose among several available training patterns. The controller choice is based on the cross-correlation between pilot symbols over two consecutive time instants (which is considered to be a suitable measure of channel stationarity) as well as the deviation from the desired BER. Simulation results of the system performance confirm the effectiveness of this new channel estimation technique over traditional non-adaptive estimation methods in increasing the data rate of OFDM symbols while maintaining the same probability of error.

  10. Regulation of sodium channel function by bilayer elasticity

    DEFF Research Database (Denmark)

    Lundbaek, Jens A; Birn, Pia; Hansen, Anker J

    2004-01-01

    be a general mechanism regulating membrane protein function, we examined whether voltage-dependent skeletal-muscle sodium channels, expressed in HEK293 cells, are regulated by bilayer elasticity, as monitored using gramicidin A (gA) channels. Nonphysiological amphiphiles (beta-octyl-glucoside, Genapol X-100......, Triton X-100, and reduced Triton X-100) that make lipid bilayers less "stiff", as measured using gA channels, shift the voltage dependence of sodium channel inactivation toward more hyperpolarized potentials. At low amphiphile concentration, the magnitude of the shift is linearly correlated to the change...... in gA channel lifetime. Cholesterol-depletion, which also reduces bilayer stiffness, causes a similar shift in sodium channel inactivation. These results provide strong support for the notion that bilayer-protein hydrophobic coupling allows the bilayer elastic properties to regulate membrane protein...

  11. 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.

  12. Covert Channels within IRC

    Science.gov (United States)

    2011-03-24

    Communications ....................................... 2 1.3 Steganography and Covert Channels .......................................................... 3...Internet Relay Chat ..................................................................................... 7 2.2 Steganography ...13 2.2.2 Encrypted Steganographic Systems .............................................. 15 2.2.3 Text-Based Steganography

  13. 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...

  14. Authentication over Noisy Channels

    CERN Document Server

    Lai, Lifeng; Poor, H Vincent

    2008-01-01

    In this work, message authentication over noisy channels is studied. The model developed in this paper is the authentication theory counterpart of Wyner's wiretap channel model. Two types of opponent attacks, namely impersonation attacks and substitution attacks, are investigated for both single message and multiple message authentication scenarios. For each scenario, information theoretic lower and upper bounds on the opponent's success probability are derived. Remarkably, in both scenarios, lower and upper bounds are shown to match, and hence the fundamental limit of message authentication over noisy channels is fully characterized. The opponent's success probability is further shown to be smaller than that derived in the classic authentication model in which the channel is assumed to be noiseless. These results rely on a proposed novel authentication scheme in which key information is used to provide simultaneous protection again both types of attacks.

  15. Cl- channels in apoptosis

    DEFF Research Database (Denmark)

    Wanitchakool, Podchanart; Ousingsawat, Jiraporn; Sirianant, Lalida

    2016-01-01

    , and cystic fibrosis transmembrane conductance regulator (CFTR) in cellular apoptosis. LRRC8A-E has been identified as a volume-regulated anion channel expressed in many cell types. It was shown to be required for regulatory and apoptotic volume decrease (RVD, AVD) in cultured cell lines. Its presence also......(-) channels or as regulators of other apoptotic Cl(-) channels, such as LRRC8. CFTR has been known for its proapoptotic effects for some time, and this effect may be based on glutathione release from the cell and increase in cytosolic reactive oxygen species (ROS). Although we find that CFTR is activated...... by cell swelling, it is possible that CFTR serves RVD/AVD through accumulation of ROS and activation of independent membrane channels such as ANO6. Thus activation of ANO6 will support cell shrinkage and induce additional apoptotic events, such as membrane phospholipid scrambling....

  16. Volume Regulated Channels

    DEFF Research Database (Denmark)

    Klausen, Thomas Kjær

    - serves a multitude of functions in the mammalian cell, regulating the membrane potential (Em), cell volume, protein activity and the driving force for facilitated transporters giving Cl- and Cl- channels a major potential of regulating cellular function. These functions include control of the cell cycle...... of volume perturbations evolution have developed system of channels and transporters to tightly control volume homeostasis. In the past decades evidence has been mounting, that the importance of these volume regulated channels and transporters are not restricted to the defense of cellular volume......, controlled cell death and cellular migration. Volume regulatory mechanisms has long been in focus for regulating cellular proliferation and my thesis work have been focusing on the role of Cl- channels in proliferation with specific emphasis on ICl, swell. Pharmacological blockage of the ubiquitously...

  17. 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.

  18. 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.

  19. 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.

  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. Fracture channel waves

    Science.gov (United States)

    Nihei, Kurt T.; Yi, Weidong; Myer, Larry R.; Cook, Neville G. W.; Schoenberg, Michael

    1999-03-01

    The properties of guided waves which propagate between two parallel fractures are examined. Plane wave analysis is used to obtain a dispersion equation for the velocities of fracture channel waves. Analysis of this equation demonstrates that parallel fractures form an elastic waveguide that supports two symmetric and two antisymmetric dispersive Rayleigh channel waves, each with particle motions and velocities that are sensitive to the normal and tangential stiffnesses of the fractures. These fracture channel waves degenerate to shear waves when the fracture stiffnesses are large, to Rayleigh waves and Rayleigh-Lamb plate waves when the fracture stiffnesses are low, and to fracture interface waves when the fractures are either very closely spaced or widely separated. For intermediate fracture stiffnesses typical of fractured rock masses, fracture channel waves are dispersive and exhibit moderate to strong localization of guided wave energy between the fractures. The existence of these waves is examined using laboratory acoustic measurements on a fractured marble plate. This experiment confirms the distinct particle motion of the fundamental antisymmetric fracture channel wave (A0 mode) and demonstrates the ease with which a fracture channel wave can be generated and detected.

  2. 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...

  3. Phenotype variation and newcomers in ion channel disorders.

    Science.gov (United States)

    Bulman, D E

    1997-01-01

    Ion channels are part of a large family of macromolecules whose functions include the control and maintenance of electrical potential across cell membranes, secretion and signal transduction. Close inspection of the physiological processes involved in channel function and the secondary structure of various ion channels has served as a basis for subdividing ion channels into a number of superfamilies. The voltage-gated ion channels are one of these superfamilies. Recent work has shown that mutations in various ion channel genes are responsible for a number of neuromuscular and neurological disorders. Correlation of the various mutations with the clinical phenotype is providing us with insight into the pathophysiology of these channel proteins. Interestingly, different mutations within the same gene may cause quite distinct clinical disorders, while mutations in different channel genes may result in very similar phenotypes (genetic heterogeneity). Examples of phenotypic variation and genetic heterogeneity are presented in the context of the periodic paralytic disorders of skeletal muscle, episodic ataxia, migraine, long QT syndrome and paroxysmal dyskinesia. Some of these disorders are known to be caused by mutations in ion channel genes, while in the episodic movement disorders, ion channel genes are considered excellent candidate genes.

  4. Markov modeling of ion channels: implications for understanding disease.

    Science.gov (United States)

    Lampert, Angelika; Korngreen, Alon

    2014-01-01

    Ion channels are the bridge between the biochemical and electrical domains of our life. These membrane crossing proteins use the electric energy stored in transmembrane ion gradients, which are produced by biochemical activity to generate ionic currents. Each ion channel can be imagined as a small power plant similar to a hydroelectric power station, in which potential energy is converted into electric current. This current drives basically all physiological mechanisms of our body. It is clear that a functional blueprint of these amazing cellular power plants is essential for understanding the principle of all aspects of physiology, particularly neurophysiology. The golden path toward this blueprint starts with the biophysical investigation of ion channel activity and continues through detailed numerical modeling of these channels that will eventually lead to a full system-level description of cellular and organ physiology. Here, we discuss the first two stages of this process focusing on voltage-gated channels, particularly the voltage-gated sodium channel which is neurologically and pathologically important. We first detail the correlations between the known structure of the channel and its activity and describe some pathologies. We then provide a hands-on description of Markov modeling for voltage-gated channels. These two sections of the chapter highlight the dichotomy between the vast amounts of electrophysiological data available on voltage-gated channels and the relatively meager number of physiologically relevant models for these channels.

  5. Broadcasting Correlated Gaussians

    CERN Document Server

    Bross, Shraga; Tinguely, Stephan

    2007-01-01

    We consider the transmission of a bi-variate Gaussian source over a one-to-two power-limited Gaussian broadcast channel. Receiver 1 observes the transmitted signal corrupted by Gaussian noise and wishes to estimate the first component of the source. Receiver 2 observes the transmitted signal in larger Gaussian noise and wishes to estimate the second component. We seek to characterize the pairs of mean squared-error distortions that are simultaneously achievable at the two receivers. Our result is that below a certain SNR-threshold an "uncoded scheme" that sends a linear combination of the source components is optimal. The SNR-theshold can be expressed as a function of the source correlation and the distortion at Receiver 1.

  6. Correlation between intra- and extracranial background EEG

    DEFF Research Database (Denmark)

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

    2012-01-01

    Scalp EEG is the most widely used modality to record the electrical signals of the brain. It is well known that the volume conduction of these brain waves through the brain, cerebrospinal fluid, skull and scalp reduces the spatial resolution and the signal amplitude. So far the volume conduction...... has primarily been investigated by realistic head models or interictal spike analysis. We have set up a novel and more realistic experiment that made it possible to compare the information in the intra- and extracranial EEG. We found that intracranial EEG channels contained correlated patterns when...... placed less than 30 mm apart, that intra- and extracranial channels were partly correlated when placed less than 40 mm apart, and that extracranial channels probably were correlated over larger distances. The underlying cortical area that influences the extracranial EEG is found to be up to 45 cm2...

  7. Estimation of MIMO channel capacity from phase-noise impaired measurements

    DEFF Research Database (Denmark)

    Pedersen, Troels; Yin, Xuefeng; Fleury, Bernard Henri

    2008-01-01

    phase noise samples affecting measurement samples collected with real TDMMIMO channel sounders are correlated. In this contribution a capacity estimator that accounts for the phase noise correlation is proposed. The estimator is based on a linear minimum mean square error estimate of the MIMO channel...

  8. σ Channel Chiral Loops in NN Interaction and Two-Pion Production

    Science.gov (United States)

    Clement, H. A.; Kaskulov, M. M.; Doroshkevich, E. A.

    After examination of the correlated two-pion exchange in the NN interaction in terms of chiral pion loops in the t-channel, we consider loops in the s-channel, which get lifted on mass shell in the two-pion production process. We show that the thus obtained dynamical correlations in the σ channel lead to a quantitative description of recent exclusive measuerements near threshold.

  9. 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.

  10. Correlation spectrometer

    Science.gov (United States)

    Sinclair, Michael B.; Pfeifer, Kent B.; Flemming, Jeb H.; Jones, Gary D.; Tigges, Chris P.

    2010-04-13

    A correlation spectrometer can detect a large number of gaseous compounds, or chemical species, with a species-specific mask wheel. In this mode, the spectrometer is optimized for the direct measurement of individual target compounds. Additionally, the spectrometer can measure the transmission spectrum from a given sample of gas. In this mode, infrared light is passed through a gas sample and the infrared transmission signature of the gasses present is recorded and measured using Hadamard encoding techniques. The spectrometer can detect the transmission or emission spectra in any system where multiple species are present in a generally known volume.

  11. Expression of α1D subunit of L-type calcium channels in mice Cochlea and its correlation with presbycusis%L型钙离子通道蛋白α1 D亚基与老年性耳聋关系的研究

    Institute of Scientific and Technical Information of China (English)

    陈金; 褚汉启; 周良强; 余洋; 陈请国; 冰丹; 刘云; 王少立; 张平

    2014-01-01

    Objective To investigate the expression of α1D subunit of L-type calcium channels (Cav1.3) in C57BL/6 mice cochlea and its correlation with presbycusis.Methods Auditory function was measured with auditory brainstem response(ABR) in C57BL/6 mice at 4,14,24 and 48 weeks.Morphological changes of the inner ear were studied by using hematoxylin and eosin staining.The expression of Cav1.3 channels was detected by immunofluorescence and the expression of CACNA1D mRNA was determined by reverse transcription-polymerase chain reaction (RT-PCR).Results Immunofluorescence photographs revealed that Cav1.3 channels were mainly localized in the hair cell,spiral ganglion cell,spiral ligment,stria vascularis,spiral limbus.The ABR threshold at click(27.08±9.19) dB SPL,4 KHz(23.79± 13.31)dB SPL,8 KHz(18.83± 12.18)dB SPL,was higher in 14-,24-,and 48-week group than in 4-week group (all P<0.05).The ABR threshold at click(87.81±8.36)dB SPL,4KHz(85.63±9.88)dB SPL,8KHz(79.50±9.83) dB SPL,was significantly higher in 48-week group than in 4-,14-,24-week groups (all P<0.01).Along with aging,the missing hair cells and spiral ganglion cells were increased,stria vascularis and spiral ligament were atrophied in a certain degree,and the expression of Cav1.3 channels was gradually decreased (4 weeks 218.94 ± 11.29 ; 14 weeks 184.67 ± 11.92 ; 24 weeks 148.18 ± 8.35 ; 48 weeks 98.04±4.52; all P<0.01).Conclusions The expression of Cav1.3 channels is decreased along with age.Dysfunction or missing of Cav1.3 calcium channels may be related to presbycusis.%目的 研究L型钙离子通道蛋白α1D亚基(Cav1.3)在老年性耳聋小鼠耳蜗组织中的表达和意义. 方法 应用听性脑干反应(ABR)分别检测4、14、24、48周龄的C57BL/6小鼠的听力,苏木素-伊红(HE)染色观察内耳形态的变化.免疫荧光方法观察Cav1.3在内耳组织中的分布,同时采用反转录聚合酶链反应(RT PCR)检测其基因CACNA1D在内耳组织的mRNA表达. 结果 Cav1.3

  12. Communication: Direct measurements of nascent O({sup 3}P{sub 0,1,2}) fine-structure distributions and branching ratios of correlated spin-orbit resolved product channels CO(ã{sup 3}Π; v) + O({sup 3}P{sub 0,1,2}) and CO(Χ{sup ~1}Σ{sup +}; v) + O({sup 3}P{sub 0,1,2}) in VUV photodissociation of CO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Zhou; Chang, Yih Chung; Gao, Hong; Benitez, Yanice; Song, Yu; Ng, C. Y., E-mail: cyng@chem.ucdavis.edu, E-mail: wmjackson@ucdavis.edu; Jackson, W. M., E-mail: cyng@chem.ucdavis.edu, E-mail: wmjackson@ucdavis.edu [Department of Chemistry, University of California, Davis, Davis, California 95616 (United States)

    2014-06-21

    We present a generally applicable experimental method for the direct measurement of nascent spin-orbit state distributions of atomic photofragments based on the detection of vacuum ultraviolet (VUV)-excited autoionizing-Rydberg (VUV-EAR) states. The incorporation of this VUV-EAR method in the application of the newly established VUV-VUV laser velocity-map-imaging-photoion (VMI-PI) apparatus has made possible the branching ratio measurement for correlated spin-orbit state resolved product channels, CO(ã{sup 3}Π; v) + O({sup 3}P{sub 0,1,2}) and CO(Χ{sup ~1}Σ{sup +}; v) + O({sup 3}P{sub 0,1,2}), formed by VUV photoexcitation of CO{sub 2} to the 4s(1{sub 0}{sup 1}) Rydberg state at 97,955.7 cm{sup −1}. The total kinetic energy release (TKER) spectra obtained from the O{sup +} VMI-PI images of O({sup 3}P{sub 0,1,2}) reveal the formation of correlated CO(ã{sup 3}Π; v = 0–2) with well-resolved v = 0–2 vibrational bands. This observation shows that the dissociation of CO{sub 2} to form the spin-allowed CO(ã{sup 3}Π; v = 0–2) + O({sup 3}P{sub 0,1,2}) channel has no potential energy barrier. The TKER spectra for the spin-forbidden CO(Χ{sup ~1}Σ{sup +}; v) + O({sup 3}P{sub 0,1,2}) channel were found to exhibit broad profiles, indicative of the formation of a broad range of rovibrational states of CO(Χ{sup ~1}Σ{sup +})  with significant vibrational populations for v = 18–26. While the VMI-PI images for the CO(ã{sup 3}Π; v = 0–2) + O({sup 3}P{sub 0,1,2}) channel are anisotropic, indicating that the predissociation of CO{sub 2} 4s(1{sub 0}{sup 1}) occurs via a near linear configuration in a time scale shorter than the rotational period, the angular distributions for the CO(Χ{sup ~1}Σ{sup +}; v) + O({sup 3}P{sub 0,1,2}) channel are close to isotropic, revealing a slower predissociation process, which possibly occurs on a triplet surface via an intersystem crossing mechanism.

  13. TRP channels and pain.

    Science.gov (United States)

    Julius, David

    2013-01-01

    Nociception is the process whereby primary afferent nerve fibers of the somatosensory system detect noxious stimuli. Pungent irritants from pepper, mint, and mustard plants have served as powerful pharmacological tools for identifying molecules and mechanisms underlying this initial step of pain sensation. These natural products have revealed three members of the transient receptor potential (TRP) ion channel family--TRPV1, TRPM8, and TRPA1--as molecular detectors of thermal and chemical stimuli that activate sensory neurons to produce acute or persistent pain. Analysis of TRP channel function and expression has validated the existence of nociceptors as a specialized group of somatosensory neurons devoted to the detection of noxious stimuli. These studies are also providing insight into the coding logic of nociception and how specification of nociceptor subtypes underlies behavioral discrimination of noxious thermal, chemical, and mechanical stimuli. Biophysical and pharmacological characterization of these channels has provided the intellectual and technical foundation for developing new classes of analgesic drugs.

  14. 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.

  15. 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.

  16. 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.

  17. Ionic Channels in Thunderclouds

    Science.gov (United States)

    Losseva, T. V.; Fomenko, A. S.; Nemtchinov, I. V.

    2007-12-01

    We proceed to study the formation and propagation of ionic channels in thunderclouds in the framework of the model of the corona discharge wave propagation (Fomenko A.S., Losseva T.V., Nemtchinov I.V. The corona discharge waves in thunderclouds and formation of ionic channels // 2004 Fall Meeting. EOS Trans. AGU. 2004. V. 85. ¹ 47. Suppl. Abstract AE23A-0835.). In this model we proposed a hypothesis that the structure of a thundercloud becomes nonuniform due to corona discharge on the drops and ice particles and formation of ionic channels with higher conductivity than the surrounding air. When the onset strength of corona discharge becomes smaller than the electric field strength the corona discharge increases concentrations of ions in a small part of the cloud (a hot spot). An additional charge at opposite ends of the hot spot forms due to polarization process. The increased electric field initiates corona discharge in other parts of the cloud on ice particles and water drops with smaller sizes. The corona discharge front moves as a wave with the velocity of the order of ion drift and formes a highly conductive channel. We model this non-stationary problem with Poisson equation which is solved simultaneously with a simplified set of kinetic equations for ions, small charged particles and electrons (at high electric fields), including ionization due to electronic impact, attachment and formation of positive ions. By applying 3D numerical simulations we obtain the parameters of formed ionic channels with respect to onset electric fields both from large particles (in hot spot) and from small particles (surrounding hot spot), microscopic currents from particles with different sizes and the external electric field in the cloud. The interaction of ionic channels is also investigated. This work was supported by Russian Foundation of Basic Research (Project No 07-05-00998-à).

  18. Communicating Under Channel Uncertainty

    CERN Document Server

    Warsi, Naqueeb; Shah, Tapan

    2010-01-01

    For a single transmit and receive antenna system, a new constellation design is proposed to combat errors in the phase estimate of the channel coefficient. The proposed constellation is a combination of PSK and PAM constellations, where PSK is used to provide protection against phase errors, while PAM is used to increase the transmission rate using the knowledge of the magnitude of the channel coefficient. The performance of the proposed constellation is shown to be significantly better than the widely used QAM in terms of probability of error. The proposed strategy can also be extended to systems using multiple transmit and receive antennas.

  19. On the ergodic secrecy capacity of the wiretap channel under imperfect main channel estimation

    KAUST Repository

    Rezki, Zouheir

    2011-11-01

    The ergodic secrecy capacity of the wiretap channel is known when the main channel (between the transmitter and the legitimate receiver) state information (CSI) is perfect at the transmitter and the coherence period is sufficiently large to enable random coding arguments in each block. In a fast fading scenario, when the codeword length spans many coherence periods, the secrecy capacity is still not known. In this paper, we present a framework that characterizes this secrecy capacity under imperfect main channel estimation at the transmitter. Inner and outer bounds on the ergodic secrecy capacity are derived for a class of independent identically distributed (i.i.d.) fading channels. The achievable rate is a simple on-off scheme using a Gaussian input. The upper bound is obtained using an appropriate correlation scheme of the main and the eavesdropper channels. The upper and the lower bounds coincide with recently derived ones in the perfect main CSI extreme. Furthermore, the lower bound matches the upper bound in no main CSI extreme, where the secrecy capacity is equal to zero. Numerical results are provided for independent identically distributed (i.i.d.) Rayleigh fading channels. © 2011 IEEE.

  20. Tensor correlations in nuclei and exlusive electron scattering

    CERN Document Server

    Ryckebusch, J; Van Nespen, W; Debruyne, D

    2000-01-01

    The effect of tensor nucleon-nucleon correlations upon exclusive and semi-exclusive electronuclear reactions is studied. Differential cross sections for the semi-exclusive ^{16}O(e,e'p) and exclusive ^{16}O(e,e'pn) processes are computed by explicitly evaluating the dynamical electromagnetic coupling to a tensor correlated nucleon pair. In both reaction channels the tensor correlations contribute in a very substantial way. Tensor correlations are found to generate more electronuclear strength than central Jastrow correlations do.

  1. Strategies for sustainable channel relations in mobile telecom sector

    Directory of Open Access Journals (Sweden)

    Githa Heggde

    2011-01-01

    Full Text Available The telecom sector in India largely comprises of wireless connections for phones. As of today, there are approximately 21 network providers in the country with about 7 per each circle, each offering competitive pricing to the consumers. The main objective of the study is to provide an accurate role for the company executive in developing channel relations. Further to this, the study explores the strategies which can sustain a good working relationship between the company and its channel members in the mobile telecom sector. The constructs identified for developing sustainable relationships were Setting distribution objectives, Channel design, Logistics, Image Building, Inventory management, Channel management, Payment & credit, Promotional assistance, Setting targets, Coverage frequency , Motivating channel members to perform. The sample selected contained distributors from the Mobile telecom sector and company executives/channel managers of leading telecom companies. Factor analysis and Friedman’s test was applied. The findings revealed a correlation in attitude between distributors and the executives. Motivating distributors was rated as the most important strategy by the company. The distributors felt that all channel partners needed to have positive attitude towards the channel while company executives felt that aggression made channel members perform effectively. Such findings will be of use to mobile telecom companies who are new entrants to the Indian market and to existing companies who plan to expand their coverage.

  2. Hexagonalization of Correlation Functions

    CERN Document Server

    Fleury, Thiago

    2016-01-01

    We propose a nonperturbative framework to study general correlation functions of single-trace operators in $\\mathcal{N}=4$ supersymmetric Yang-Mills theory at large $N$. The basic strategy is to decompose them into fundamental building blocks called the hexagon form factors, which were introduced earlier to study structure constants using integrability. The decomposition is akin to a triangulation of a Riemann surface, and we thus call it hexagonalization. We propose a set of rules to glue the hexagons together based on symmetry, which naturally incorporate the dependence on the conformal and the R-symmetry cross ratios. Our method is conceptually different from the conventional operator product expansion and automatically takes into account multi-trace operators exchanged in OPE channels. To illustrate the idea in simple set-ups, we compute four-point functions of BPS operators of arbitrary lengths and correlation functions of one Konishi operator and three short BPS operators, all at one loop. In all cases,...

  3. Energy calibration via correlation

    CERN Document Server

    Maier, Daniel

    2015-01-01

    The main task of an energy calibration is to find a relation between pulse-height values and the corresponding energies. Doing this for each pulse-height channel individually requires an elaborated input spectrum with an excellent counting statistics and a sophisticated data analysis. This work presents an easy to handle energy calibration process which can operate reliably on calibration measurements with low counting statistics. The method uses a parameter based model for the energy calibration and concludes on the optimal parameters of the model by finding the best correlation between the measured pulse-height spectrum and multiple synthetic pulse-height spectra which are constructed with different sets of calibration parameters. A CdTe-based semiconductor detector and the line emissions of an 241 Am source were used to test the performance of the correlation method in terms of systematic calibration errors for different counting statistics. Up to energies of 60 keV systematic errors were measured to be le...

  4. 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

  5. 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…

  6. MITOCHONDRIAL BKCa CHANNEL

    Directory of Open Access Journals (Sweden)

    Enrique eBalderas

    2015-03-01

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

  7. Ion Channels in Leukocytes

    Science.gov (United States)

    1991-07-01

    muscle k142), heart muscle (80), bo- are released. In recent years much has been learned vine pulmonar arter endothelial cells (251), and rat about the...channel analysbib of Lt. Potassium permeability in HeLa cancer BioL Chem. 265: 142416-141263, 1990. cells. evidence for a calcium-a’tivated potassium

  8. Ion channels in inflammation.

    Science.gov (United States)

    Eisenhut, Michael; Wallace, Helen

    2011-04-01

    Most physical illness in vertebrates involves inflammation. Inflammation causes disease by fluid shifts across cell membranes and cell layers, changes in muscle function and generation of pain. These disease processes can be explained by changes in numbers or function of ion channels. Changes in ion channels have been detected in diarrhoeal illnesses, pyelonephritis, allergy, acute lung injury and systemic inflammatory response syndromes involving septic shock. The key role played by changes in ion transport is directly evident in inflammation-induced pain. Expression or function of all major categories of ion channels like sodium, chloride, calcium, potassium, transient receptor potential, purinergic receptor and acid-sensing ion channels can be influenced by cyto- and chemokines, prostaglandins, leukotrienes, histamine, ATP, reactive oxygen species and protons released in inflammation. Key pathways in this interaction are cyclic nucleotide, phosphoinositide and mitogen-activated protein kinase-mediated signalling, direct modification by reactive oxygen species like nitric oxide, ATP or protons and disruption of the cytoskeleton. Therapeutic interventions to modulate the adverse and overlapping effects of the numerous different inflammatory mediators on each ion transport system need to target adversely affected ion transport systems directly and locally.

  9. 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....

  10. Robust Design of Pilot-symbol-aided MIMO Channel Estimation

    Institute of Scientific and Technical Information of China (English)

    LUO Zhen-dong; LIU Yuan-an; GAO Jin-chun

    2004-01-01

    This paper investigates pilot-symbol-aided channel estimation/prediction for Multiple-Input Multiple-Output (MIMO) systems in fast fading environments. We first derive the design criteria of the optimal pilot blocks for energy, power and bandwidth-limited systems, respectively. Then two low-complexity channel estimation schemes are provided. Finally, we present a robust Minimum Mean Square Error (MMSE) channel estimator based on channel time correlation. Simulation shows the proposed MMSE estimator is considerably insensitive to channel statistics and significantly outperforms the traditional estimators with a low additional complexity in fast fading environments. By simply adjusting some parameters, the MMSE estimator can work as an estimator and a predictor simultaneously.

  11. The Aquaporin Channel Repertoire of the Tardigrade Milnesium tardigradum.

    Science.gov (United States)

    Grohme, Markus A; Mali, Brahim; Wełnicz, Weronika; Michel, Stephanie; Schill, Ralph O; Frohme, Marcus

    2013-01-01

    Limno-terrestrial tardigrades are small invertebrates that are subjected to periodic drought of their micro-environment. They have evolved to cope with these unfavorable conditions by anhydrobiosis, an ametabolic state of low cellular water. During drying and rehydration, tardigrades go through drastic changes in cellular water content. By our transcriptome sequencing effort of the limno-terrestrial tardigrade Milnesium tardigradum and by a combination of cloning and targeted sequence assembly, we identified transcripts encoding eleven putative aquaporins. Analysis of these sequences proposed 2 classical aquaporins, 8 aquaglyceroporins and a single potentially intracellular unorthodox aquaporin. Using quantitative real-time PCR we analyzed aquaporin transcript expression in the anhydrobiotic context. We have identified additional unorthodox aquaporins in various insect genomes and have identified a novel common conserved structural feature in these proteins. Analysis of the genomic organization of insect aquaporin genes revealed several conserved gene clusters.

  12. A New Covert Channel over Cellular Voice Channel in Smartphones

    OpenAIRE

    Aloraini, Bushra; Johnson, Daryl; Stackpole, Bill; Mishra, Sumita

    2015-01-01

    Investigating network covert channels in smartphones has become increasingly important as smartphones have recently replaced the role of traditional computers. Smartphones are subject to traditional computer network covert channel techniques. Smartphones also introduce new sets of covert channel techniques as they add more capabilities and multiple network connections. This work presents a new network covert channel in smartphones. The research studies the ability to leak information from the...

  13. A channel differential EZW coding scheme for EEG data compression.

    Science.gov (United States)

    Dehkordi, Vahid R; Daou, Hoda; Labeau, Fabrice

    2011-11-01

    In this paper, a method is proposed to compress multichannel electroencephalographic (EEG) signals in a scalable fashion. Correlation between EEG channels is exploited through clustering using a k-means method. Representative channels for each of the clusters are encoded individually while other channels are encoded differentially, i.e., with respect to their respective cluster representatives. The compression is performed using the embedded zero-tree wavelet encoding adapted to 1-D signals. Simulations show that the scalable features of the scheme lead to a flexible quality/rate tradeoff, without requiring detailed EEG signal modeling.

  14. Noise reduction algorithm for glueball correlators

    Directory of Open Access Journals (Sweden)

    Pushan Majumdar

    2014-09-01

    Full Text Available We present an error reduction method for obtaining glueball correlators from Monte Carlo simulations of SU(3 lattice gauge theory. We explore the scalar and tensor channels at three different lattice spacings. Using this method we can follow glueball correlators to temporal separations even up to 1 fermi. We estimate the improvement over the naive method and compare our results with existing computations.

  15. Quantum transport with two interacting conduction channels.

    Science.gov (United States)

    White, Alexander J; Migliore, Agostino; Galperin, Michael; Nitzan, Abraham

    2013-05-07

    The transport properties of a conduction junction model characterized by two mutually coupled channels that strongly differ in their couplings to the leads are investigated. Models of this type describe molecular redox junctions (where a level that is weakly coupled to the leads controls the molecular charge, while a strongly coupled one dominates the molecular conduction), and electron counting devices in which the current in a point contact is sensitive to the charging state of a nearby quantum dot. Here we consider the case where transport in the strongly coupled channel has to be described quantum mechanically (covering the full range between sequential tunneling and co-tunneling), while conduction through the weakly coupled channel is a sequential process that could by itself be described by a simple master equation. We compare the result of a full quantum calculation based on the pseudoparticle non-equilibrium Green function method to that obtained from an approximate mixed quantum-classical calculation, where correlations between the channels are taken into account through either the averaged rates or the averaged energy. We find, for the steady state current, that the approximation based on the averaged rates works well in most of the voltage regime, with marked deviations from the full quantum results only at the threshold for charging the weekly coupled level. These deviations are important for accurate description of the negative differential conduction behavior that often characterizes redox molecular junctions in the neighborhood of this threshold.

  16. 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.

  17. Meson correlators in QCD vacuum is saturation the right approach?

    CERN Document Server

    Sheel, V; Parikh, J C; Sheel, Varun; Mishra, Hiranmaya; Parikh, Jitendra C

    1994-01-01

    Equal time, point to point correlation functions for spatially separated meson currents are calculated with respect to a variational construct for the ground state of QCD. With exact calculations, vector, axial vector and scalar channels show qualitative agreement with the phenomenological predictions, where as pseudoscalar channel does not. However, the pseudoscalar correlator, when approximated by saturating with intermediate one pion states agrees with results obtained from spectral density functions parametrised by pion decay constant and value obtained from chiral perturbation theory.

  18. 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.

  19. 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...

  20. ``Just Another Distribution Channel?''

    Science.gov (United States)

    Lemstra, Wolter; de Leeuw, Gerd-Jan; van de Kar, Els; Brand, Paul

    The telecommunications-centric business model of mobile operators is under attack due to technological convergence in the communication and content industries. This has resulted in a plethora of academic contributions on the design of new business models and service platform architectures. However, a discussion of the challenges that operators are facing in adopting these models is lacking. We assess these challenges by considering the mobile network as part of the value system of the content industry. We will argue that from the perspective of a content provider the mobile network is ‘just another’ distribution channel. Strategic options available for the mobile communication operators are to deliver an excellent distribution channel for content delivery or to move upwards in the value chain by becoming a content aggregator. To become a mobile content aggregator operators will have to develop or acquire complementary resources and capabilities. Whether this strategic option is sustainable remains open.

  1. 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.

  2. On partially entanglement breaking channels

    CERN Document Server

    Chruscinski, D; Chruscinski, Dariusz; Kossakowski, Andrzej

    2005-01-01

    Using well known duality between quantum maps and states of composite systems we introduce the notion of Schmidt number of a quantum channel. It enables one to define classes of quantum channels which partially break quantum entanglement. These classes generalize the well known class of entanglement breaking channels.

  3. 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).

  4. The Diversity Potential of Relay Selection with Practical Channel Estimation

    CERN Document Server

    Michalopoulos, Diomidis S; Schober, Robert; Karagiannidis, George K

    2011-01-01

    We investigate the diversity order of decode-and-forward relay selection in Nakagami-m fading, in cases where practical channel estimation techniques are applied. In this respect, we introduce a unified model for the imperfect channel estimates, where the effects of noise, time-varying channels, and feedback delays are jointly considered. Based on this model, the correlation between the actual and the estimated channel values, \\rho, is expressed as a function of the signal-to-noise ratio (SNR), yielding closed-form expressions for the overall outage probability as a function of \\rho. The resulting diversity order and power gain reveal a high dependence of the performance of relay selection on the high SNR behavior of \\rho, thus shedding light onto the effect of channel estimation on the overall performance. It is shown that when the channel estimates are not frequently updated in applications involving time-varying channels, or when the amount of power allocated for channel estimation is not sufficiently high...

  5. Automatic cross-talk removal from multi-channel data

    CERN Document Server

    Allen, B; Ottewill, A; Allen, Bruce; Hua, Wensheng; Ottewill, Adrian

    1999-01-01

    A technique is described for removing interference from a signal of interest ("channel 1") which is one of a set of N time-domain instrumental signals ("channels 1 to N"). We assume that channel 1 is a linear combination of "true" signal plus noise, and that the "true" signal is not correlated with the noise. We also assume that part of this noise is produced, in a poorly-understood way, by the environment, and that the environment is monitored by channels 2 to N. Finally, we assume that the contribution of channel n to channel 1 is described by an (unknown!) linear transfer function R_n(t-t'). Our technique estimates the R_i and provides a way to subtract the environmental contamination from channel 1, giving an estimate of the "true" signal which minimizes its variance. It also provides some insights into how the environment is contaminating the signal of interest. The method is illustrated with data from a prototype interferometric gravitational-wave detector, in which the channel of interest (differential...

  6. Modeling channel interference in an orbital angular momentum-multiplexed laser link

    Science.gov (United States)

    Anguita, Jaime A.; Neifeld, Mark A.; Vasic, Bane V.

    2009-08-01

    We study the effects of optical turbulence on the energy crosstalk among constituent orbital angular momentum (OAM) states in a vortex-based multi-channel laser communication link and determine channel interference in terms of turbulence strength and OAM state separation. We characterize the channel interference as a function of C2n and transmit OAM state, and propose probability models to predict the random fluctuations in the received signals for such architecture. Simulations indicate that turbulence-induced channel interference is mutually correlated across receive channels.

  7. Optimization of Training Signal Transmission for Estimating MIMO Channel under Antenna Mutual Coupling Conditions

    Directory of Open Access Journals (Sweden)

    Xia Liu

    2010-01-01

    Full Text Available This paper reports investigations on the effect of antenna mutual coupling on performance of training-based Multiple-Input Multiple-Output (MIMO channel estimation. The influence of mutual coupling is assessed for two training-based channel estimation methods, Scaled Least Square (SLS and Minimum Mean Square Error (MMSE. It is shown that the accuracy of MIMO channel estimation is governed by the sum of eigenvalues of channel correlation matrix which in turn is influenced by the mutual coupling in transmitting and receiving array antennas. A water-filling-based procedure is proposed to optimize the training signal transmission to minimize the MIMO channel estimation errors.

  8. The antiallodynic action target of intrathecal gabapentin: Ca2+ channels, KATP channels or N-methyl-d-aspartic acid receptors?

    Science.gov (United States)

    Cheng, Jen-Kun; Chen, Chien-Chuan; Yang, Jia-Rung; Chiou, Lih-Chu

    2006-01-01

    Gabapentin is a novel analgesic whose mechanism of action is not known. We investigated in a postoperative pain model whether adenosine triphosphate (ATP)-sensitive K+ (K(ATP)) channels, N-methyl-d-aspartic acid (NMDA) receptors, and Ca2+ channels are involved in the antiallodynic effect of intrathecal gabapentin. Mechanical allodynia was induced by a paw incision in isoflurane-anesthetized rats. Withdrawal thresholds to von Frey filament stimulation near the incision site were measured before and after incision and after intrathecal drug administration. The antiallodynic effect of gabapentin (100 mug) was not affected by intrathecal pretreatment with antagonists of K(ATP) channels, NMDA receptors or gamma-aminobutyric acid (GABA)(A) receptors. K(ATP) channel openers and GABA(A) receptor agonist, per se, had little effect on the postincision allodynic response. The Ca2+ channel blocker of N-type (omega-conotoxin GVIA, 0.1-3 microg), but not of P/Q-type (omega-agatoxin IVA), L-type (verapamil, diltiazem or nimodipine), or T-type (mibefradil), attenuated the incision-induced allodynia, as did gabapentin. Both the antiallodynic effects of gabapentin and omega-conotoxin GVIA were attenuated by Bay K 8644, an L-type Ca2+ channel activator. These results provide correlative evidence to support the contention that N-type Ca2+ channels, but not K(ATP) channels or NMDA or GABA(A) receptors, might be involved in the antiallodynic effect of intrathecal gabapentin.

  9. Ion Channels in Neurological Disorders.

    Science.gov (United States)

    Kumar, Pravir; Kumar, Dhiraj; Jha, Saurabh Kumar; Jha, Niraj Kumar; Ambasta, Rashmi K

    2016-01-01

    The convergent endeavors of the neuroscientist to establish a link between clinical neurology, genetics, loss of function of an important protein, and channelopathies behind neurological disorders are quite intriguing. Growing evidence reveals the impact of ion channels dysfunctioning in neurodegenerative disorders (NDDs). Many neurological/neuromuscular disorders, viz, Alzheimer's disease, Parkinson's disease, Huntington's disease, multiple sclerosis, amyotrophic lateral sclerosis, and age-related disorders are caused due to altered function or mutation in ion channels. To maintain cell homeostasis, ion channels are playing a crucial role which is a large transmembrane protein. Further, these channels are important as it determines the membrane potential and playing critically in the secretion of neurotransmitter. Behind NDDs, losses of pathological proteins and defective ion channels have been reported and are found to aggravate the disease symptoms. Moreover, ion channel dysfunctions are eliciting a range of symptoms, including memory loss, movement disabilities, neuromuscular sprains, and strokes. Since the possible mechanistic role played by aberrant ion channels, their receptor and associated factors in neurodegeneration remained elusive; therefore, it is a challenging task for the neuroscientist to implement the therapeutics for targeting NDDs. This chapter reviews the potential role of the ion channels in membrane physiology and brain homeostasis, where ion channels and their associated factors have been characterized with their functional consequences in neurological diseases. Moreover, mechanistic role of perturbed ion channels has been identified in various NDDs, and finally, ion channel modulators have been investigated for their therapeutic intervention in treating common NDDs.

  10. Why Waveform Correlation Sometimes Fails

    Science.gov (United States)

    Carmichael, J.

    2015-12-01

    Waveform correlation detectors used in explosion monitoring scan noisy geophysical data to test two competing hypotheses: either (1) an amplitude-scaled version of a template waveform is present, or, (2) no signal is present at all. In reality, geophysical wavefields that are monitored for explosion signatures include waveforms produced by non-target sources that are partially correlated with the waveform template. Such signals can falsely trigger correlation detectors, particularly at low thresholds required to monitor for smaller target explosions. This challenge is particularly formidable when monitoring known test sites for seismic disturbances, since uncatalogued natural seismicity is (generally) more prevalent at lower magnitudes, and could be mistaken for small explosions. To address these challenges, we identify real examples in which correlation detectors targeting explosions falsely trigger on both site-proximal earthquakes (Figure 1, below) and microseismic "noise". Motivated by these examples, we quantify performance loss when applying these detectors, and re-evaluate the correlation-detector's hypothesis test. We thereby derive new detectors from more general hypotheses that admit unknown background seismicity, and apply these to real data. From our treatment, we derive "rules of thumb'' for proper template and threshold selection in heavily cluttered signal environments. Last, we answer the question "what is the probability of falsely detecting an earthquake collocated at a test site?", using correlation detectors that include explosion-triggered templates. Figure Top: An eight-channel data stream (black) recorded from an earthquake near a mine. Red markers indicate a detection. Middle: The correlation statistic computed by scanning the template against the data stream at top. The red line indicates the threshold for event declaration, determined by a false-alarm on noise probability constraint, as computed from the signal-absent distribution using

  11. CORRELATED INTERFERENCE CANCELLATION FOR IR-UWB

    Institute of Scientific and Technical Information of China (English)

    Zhang Zaichen; Yu Xutao; Bi Guangguo

    2008-01-01

    In this letter,we propose a hybrid analog/digital detection algorithm,the Correlated Interference Cancellation (CIC) algorithm,for Impulse Radio Ultra-WideBand (IR-UWB) system. The CIC algorithm correlates received signal with its delayed versions in the analog domain and samples the correlation output at the symbol rate. The symbol rate samples are processed in the digital domain to perform interference cancellation. Therefore,CIC works for high data rate systems with heavy InterSymbol Interference (ISI). Simulation results show that CIC achieves good performance in typical UWB channels.

  12. Cholesterol binding to ion channels

    Directory of Open Access Journals (Sweden)

    Irena eLevitan

    2014-02-01

    Full Text Available Numerous studies demonstrated that membrane cholesterol is a major regulator of ion channel function. The goal of this review is to discuss significant advances that have been recently achieved in elucidating the mechanisms responsible for cholesterol regulation of ion channels. The first major insight that comes from growing number of studies that based on the sterol specificity of cholesterol effects, show that several types of ion channels (nAChR, Kir, BK, TRPV are regulated by specific sterol-protein interactions. This conclusion is supported by demonstrating direct saturable binding of cholesterol to a bacterial Kir channel. The second major advance in the field is the identification of putative cholesterol binding sites in several types of ion channels. These include sites at locations associated with the well-known cholesterol binding motif CRAC and its reversed form CARC in nAChR, BK, and TRPV, as well as novel cholesterol binding regions in Kir channels. Notably, in the majority of these channels, cholesterol is suggested to interact mainly with hydrophobic residues in non-annular regions of the channels being embedded in between transmembrane protein helices. We also discuss how identification of putative cholesterol binding sites is an essential step to understand the mechanistic basis of cholesterol-induced channel regulation. Clearly, however, these are only the first few steps in obtaining a general understanding of cholesterol-ion channels interactions and their roles in cellular and organ functions.

  13. On Ergodic Secrecy Capacity of Multiple Input Wiretap Channel with Statistical CSIT

    CERN Document Server

    Lin, Shih-Chun

    2012-01-01

    We consider the secure transmission in ergodic fast-Rayleigh fading multiple-input single-output single-antennaeavesdropper (MISOSE) wiretap channels. We assume that the statistics of both the legitimate and eavesdropper channels is the only available channel state information at the transmitter (CSIT). By introducing a new secrecy capacity upper bound, we prove that the secrecy capacity is achieved by Gaussian input without prefixing. To attain this, we form another MISOSE channel for upper-bounding, and tighten the bound by finding the worst correlations between the legitimate and eavesdropper channel coefficients. The resulting upper bound is tighter than the others in the literature which are based on modifying the correlation between the noises at the legitimate receiver and eavesdropper. Next, we fully characterize the ergodic secrecy capacity by showing that the optimal channel input covariance matrix is a scaled identity matrix, with the transmit power allocated uniformly among the antennas. The key t...

  14. TIME-FREQUENCY 2-D LMS BASED LONG-RANGE CHANNEL PREDICTION FOR WIRELESS OFDM SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Adaptive modulation can optimize the spectrum efficiency and system performance with the channel state information achieved by the long-range channel prediction. To avoid re-estimating channel correlation function as the channel stationarity varies and to track the channel adaptively,LMS (Least-Mean-Square) based long-range channel prediction is discussed in the existing literature,but it needs long observation interval to reach the convergence. Given that all OFDM (Orthogonal Frequency Division Multiplexing) subcarriers have the identical time-domain correlation and stationarity during the same time interval, this paper proposed a 2-D LMS based predictor which updates the filter weights in both time and frequency domain. The proposed scheme can effectively decrease the observation intervals and significantly speed up the convergence than the conventional LMS and Parallel LMS (PLMS). Complexity analysis and simulation results prove that the proposed scheme can improve the BER (Bit Error Rate) performance and spectrum efficiency with negligible complexity increase.

  15. Hybrid Codes Needed for Coordination over the Point-to-Point Channel

    CERN Document Server

    Cuff, Paul

    2011-01-01

    We consider a new fundamental question regarding the point-to-point memoryless channel. The source-channel separation theorem indicates that random codebook construction for lossy source compression and channel coding can be independently constructed and paired to achieve optimal performance for coordinating a source sequence with a reconstruction sequence. But what if we want the channel input to also be coordinated with the source and reconstruction? Such situations arise in network communication problems, where the correlation inherent in the information sources can be used to correlate channel inputs. Hybrid codes have been shown to be useful in a number of network communication problems. In this work we highlight their advantages over purely digital codebook construction by applying them to the point-to-point setting, coordinating both the channel input and the reconstruction with the source.

  16. A novel approach to correlation reflectometry

    Energy Technology Data Exchange (ETDEWEB)

    Meneses, Luis, E-mail: meneses@ipfn.ist.utl.pt [Associacao EURATOM/IST, Instituto de Plasmas e Fusao Nuclear - Laboratorio Associado, Instituto Superior Tecnico, P-1049-001 Lisboa (Portugal); Cupido, Luis; Manso, Maria Emilia [Associacao EURATOM/IST, Instituto de Plasmas e Fusao Nuclear - Laboratorio Associado, Instituto Superior Tecnico, P-1049-001 Lisboa (Portugal)

    2011-10-15

    The use of microwave synthesized sources improved significantly the performance of correlation reflectometry diagnostics for fusion plasmas providing broadband operation with high quality signals and fast frequency switching times. Recent new developments of those sources made at IPFN opened an all-new way to build correlation reflectometry diagnostics with improved performance and measuring capability. Some of the key features now attainable are independent probing and local oscillator signals generated by separated frequency synthesizers; very good frequency control and synchronization of both the local and the radio-frequency oscillators providing very high stability. The technological advances make it possible to further reduce the switching time between adjacent probing frequencies while keeping the ability to operate in a broad frequency range. Here we present a multichannel correlation system based on those novel technologies using several independent and self-contained fully synthesized broadband channels. With this type of system various type of measurements are possible: (i) fast stepwise radial scans to extract the radial profile of turbulence parameters (spectra, RMS, rotation from Doppler shift, etc.); (ii) radial scans of the plasma using two identical systems in parallel where one system operates in frequency steps and the other makes multiple small steps around each selected frequency of the first system. The proposed diagnostic is very powerful and versatile. With a system having n identical channels, all transmitting and receiving simultaneously, the number of simultaneous correlations measurements that can be performed is given by n x (n - 1)/2. The minimal configuration uses two channels thus providing one (time domain) correlation signal channels can be easily added at any time increasing the measuring capability of the diagnostic. Several examples are given that illustrate the wide range of measurements that can be made using the novel

  17. Channel Wall Landslides

    Science.gov (United States)

    2005-01-01

    [figure removed for brevity, see original site] The multiple landslides in this VIS image occur along a steep channel wall. Note the large impact crater in the context image. The formation of the crater may have initially weakened that area of the surface prior to channel formation. Image information: VIS instrument. Latitude -2.7, Longitude 324.8 East (35.2 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  18. 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.

  19. EARLINET Correlative Measurements For CALIPSO

    Science.gov (United States)

    Pappalardo, G.

    2006-12-01

    EARLINET, the European Aerosol Research Lidar Network, is the first aerosol lidar network, established in 2000, with the main goal to provide a comprehensive, quantitative, and statistically significant data base for the aerosol distribution on a continental scale. At present, 24 stations distributed over Europe are part of the network: 10 single backscatter lidar stations, 7 Raman lidar stations with the Raman channel in the UV for independent measurements of aerosol extinction and backscatter, and 7 multi-wavelength Raman lidar stations (elastic channel at 1064 nm, 532 nm, 355 nm, Raman channels at 532 nm and 355 nm, plus depolarization channel at 532 nm) for the retrieval of aerosol microphysical properties. The network activity is based on scheduled measurements, a rigorous quality assurance program addressing both instruments and evaluation algorithms, and a standardized data exchange format. In order to collect unbiased data, all the network stations perform measurements simultaneously at three fixed dates a week. Lidar observations are performed on a regular schedule of one daytime measurement on Monday around noon, when the boundary layer is usually well developed, and two night time measurements per week (Monday and Thursday), with low background light, in order to perform Raman extinction measurements. Additional network measurements are performed to address specifically important processes that are localized either in space or time, like Saharan dust outbreaks, forest fires, volcanic eruptions, photochemical smog. EARLINET represents an optimal tool to validate CALIPSO lidar data and to provide the necessary information to fully exploit the information from that mission. In particular, aerosol extinction measurements, provided by the network, will be important for the aerosol retrievals from the CALIPSO backscatter lidar. EARLINET started correlative measurements for CALIPSO since 14 June 2006. These EARLINET correlative measurements are performed at

  20. 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

  1. EVALUATION OF MIMO SYSTEM CAPACITY OVER RAYLEIGH FADING CHANNEL

    Directory of Open Access Journals (Sweden)

    Emad. Mohamed

    2015-06-01

    Full Text Available High transmission data rate, spectral efficiency and reliability are essential for future wireless communications systems. MIMO (multi-input multi-output diversity technique is a band width efficient system achieving high data transmission which eventually establishing a high capacity communication system. Without needing to increase the transmitted power or the channel bandwidth, gain in capacity can be considerably improved by varying the number of antennas on both sides. Correlated and uncorrelated channels MIMO system was considered in this paper for different number of antennas and different SNR over Rayleigh fading channel. At the transmitter both CSI(channel state information technique and Water filling power allocation principle was also considered in this paper

  2. The role of transient receptor potential channels in metabolic syndrome

    DEFF Research Database (Denmark)

    Liu, Daoyan; Zhu, Zhiming; Tepel, Martin

    2008-01-01

    Metabolic syndrome is correlated with increased cardiovascular risk and characterized by several factors, including visceral obesity, hypertension, insulin resistance, and dyslipidemia. Several members of a large family of nonselective cation entry channels, e.g., transient receptor potential (TRP......) canonical (TRPC), vanilloid (TRPV), and melastatin (TRPM) channels, have been associated with the development of cardiovascular diseases. Thus, disruption of TRP channel expression or function may account for the observed increased cardiovascular risk in metabolic syndrome patients. TRPV1 regulates...... there is no evidence that a single TRP channelopathy may be the cause of all metabolic syndrome characteristics, further studies will help to clarify the role of specific TRP channels involved in the metabolic syndrome. (Hypertens Res 2008; 31: 1989-1995)....

  3. Channel Estimation And Multiuser Detection In Asynchronous Satellite Communications

    CERN Document Server

    Chaouech, Helmi; 10.5121/ijwmn.2010.2411

    2010-01-01

    In this paper, we propose a new method of channel estimation for asynchronous additive white Gaussian noise channels in satellite communications. This method is based on signals correlation and multiuser interference cancellation which adopts a successive structure. Propagation delays and signals amplitudes are jointly estimated in order to be used for data detection at the receiver. As, a multiuser detector, a single stage successive interference cancellation (SIC) architecture is analyzed and integrated to the channel estimation technique and the whole system is evaluated. The satellite access method adopted is the direct sequence code division multiple access (DS CDMA) one. To evaluate the channel estimation and the detection technique, we have simulated a satellite uplink with an asynchronous multiuser access.

  4. Turbulent natural convection in vertical parallel-plate channels

    Energy Technology Data Exchange (ETDEWEB)

    Badr, H.M.; Habib, M.A.; Anwar, S.; Ben-Mansour, R.; Said, S.A.M. [King Fahd University of Petroleum and Minerals, Mechanical Engineering Department, Dhahran (Saudi Arabia)

    2006-11-15

    The problem of buoyancy driven turbulent flow in parallel-plate channels is investigated. The investigation is limited to vertical channels of uniform cross-section with different modes of heating. The details of the flow and thermal fields are obtained from the solution of the conservation equations of mass, momentum, and energy in addition to equations of the low Reynolds number turbulence model. The study covers Rayleigh number ranging from 10{sup 5} to 10{sup 7} and focuses on the effect of channel geometry on the characteristic of the flow and thermal fields as well as the local and average Nusselt number variation. A Nusselt number correlation has been developed in terms of a modified Rayleigh number and channel aspect ratio for the cases of symmetrically heated isothermal and isoflux conditions. (orig.)

  5. Frequency Dependence of Measured Massive MIMO Channel Properties

    DEFF Research Database (Denmark)

    Oliveras Martínez, Àlex; Carvalho, Elisabeth De; Nielsen, Jesper Ødum;

    2016-01-01

    A multi-user massive MIMO measurement campaign is conducted to study the channel propagation characteristics (e.g. user correlation, sum of eigenvalues and condition number), focusing on the stability over frequencies and the impact of the array aperture. We use 3 arrays with 64 antennas (6m linear...... array, 2m linear array and 25cm by 28cm squared 2D array) serving 8 users holding a handset with 2 antennas. The study of the measurements shows that the propagation characteristics of the channel are stable for all the measured frequencies. We also observe that user proximity and user handgrip...... stabilize the studied properties of the channel across the frequencies, and in such case the larger the aperture of the array the more stable the properties. The number of base station antennas improves the propagation characteristics of the channel and stabilizes the properties in the frequency domain....

  6. Selective transmission and channel estimation in massive MIMO systems

    Institute of Scientific and Technical Information of China (English)

    杨睿哲

    2016-01-01

    Massive MIMO systems have got extraordinary spectral efficiency using a large number of base station antennas, but it is in the challenge of pilot contamination using the aligned pilots.To address this issue, a selective transmission is proposed using time-shifted pilots with cell grouping, where the strong interfering users in downlink transmission cells are temporally stopped during the pilots transmission in uplink cells.Based on the spatial characteristics of physical channel models, the strong interfering users are selected to minimize the inter-cell interference and the cell grouping is designed to have less temporally stopped users within a smaller area.Furthermore, a Kalman estima-tor is proposed to reduce the unexpected effect of residual interferences in channel estimation, which exploits both the spatial-time correlation of channels and the share of the interference information. The numerical results show that our scheme significantly improves the channel estimation accuracy and the data rates.

  7. Pathlengths of open channels in multiple scattering media

    CERN Document Server

    Bosch, Jeroen; Mosk, Allard P

    2016-01-01

    We report optical measurements of the spectral width of open transmission channels in a three-dimensional diffusive medium. The light transmission through a sample is enhanced by efficiently coupling to open transmission channels using repeated digital optical phase conjugation. The spectral properties are investigated by enhancing the transmission, fixing the incident wavefront and scanning the wavelength of the laser. We measure the transmitted field to extract the field correlation function and the enhancement of the total transmission. We find that optimizing the total transmission leads to a significant increase in the frequency width of the field correlation function. Additionally we find that the enhanced transmission persists over an even larger frequency bandwidth. This result shows open channels in the diffusive regime are spectrally much wider than previous measurements in the localized regime suggest.

  8. Boiling heat transfer in horizontal and inclined rectangular channels

    Energy Technology Data Exchange (ETDEWEB)

    Morcos, S.M.; Mobarak, A.; Hilal, M.; Mohareb, M.R. (Cairo Univ. (Egypt))

    1987-05-01

    The present experimental investigation is concerned with boiling heat transfer of water inside both horizontal and inclined rectangular channels under a relatively low heat flux. These configurations simulate the absorber channel of line-focus solar concentrations under boiling conditions. The experimental facility includes electrically heated aluminum rectangular channels with aspect ratios of 2.67 and 0.37. The experimental results of the two-phase Nusselt number for the two aspect ratios and for the inclination angles 0, 15, 30, and 45 deg were correlated in terms of a ratio of the two-phase to the liquid-phase Reynolds number for the forced-convection vaporization region. The proposed correlations agree well with previous investigations. In the present work, classifications of the various flow patterns were made by direct observation through a glass window at the end of the test section.

  9. Ion channels-related diseases.

    Science.gov (United States)

    Dworakowska, B; Dołowy, K

    2000-01-01

    There are many diseases related to ion channels. Mutations in muscle voltage-gated sodium, potassium, calcium and chloride channels, and acetylcholine-gated channel may lead to such physiological disorders as hyper- and hypokalemic periodic paralysis, myotonias, long QT syndrome, Brugada syndrome, malignant hyperthermia and myasthenia. Neuronal disorders, e.g., epilepsy, episodic ataxia, familial hemiplegic migraine, Lambert-Eaton myasthenic syndrome, Alzheimer's disease, Parkinson's disease, schizophrenia, hyperekplexia may result from dysfunction of voltage-gated sodium, potassium and calcium channels, or acetylcholine- and glycine-gated channels. Some kidney disorders, e.g., Bartter's syndrome, policystic kidney disease and Dent's disease, secretion disorders, e.g., hyperinsulinemic hypoglycemia of infancy and cystic fibrosis, vision disorders, e.g., congenital stationary night blindness and total colour-blindness may also be linked to mutations in ion channels.

  10. Unifying Theories of Mobile Channels

    Directory of Open Access Journals (Sweden)

    Gerard Ekembe Ngondi

    2016-06-01

    Full Text Available In this paper we present the denotational semantics for channel mobility in the Unifying Theories of Programming (UTP semantics framework. The basis for the model is the UTP theory of reactive processes (precisely, the UTP semantics for Communicating Sequential Processes (CSP, which is slightly extended to allow the mobility of channels: the set of actions in which a process is authorised to participate, originally static or constant (set during the process's definition, is now made dynamic or variable: it can change during the process's execution. A channel is thus moved around by communicating it via other channels and then allowing the receiving process to extend its alphabet with the received channel. New healthiness conditions are stated to ensure an appropriate use of mobile channels.

  11. 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

  12. Robust Source Localization in a Random Shallow Water Channel

    CERN Document Server

    Sazontov, Alexander; Matveyev, Alexander

    2014-01-01

    This paper addresses source localization problem in a random shallow water channel. We present an extension of the generalized MUSIC method to the case, %in which when the signal correlation matrix is imprecisely known. The algorithm is validated by %simulations and its application to the experimental data observed in the Barents Sea. It has been found that the approach proposed demonstrates its excellent performance.

  13. Heavy Quark Coupled Channel Dynamics from Thermal Shifts

    CERN Document Server

    Arriola, Enrique Ruiz; Megias, Eugenio

    2016-01-01

    QCD at finite temperature below the phase transition should be determined in terms of colour singlet states such as hadrons and strings. We show how quark-hadron duality allows extracting sensible information concerning heavy quark and string breaking coupled channel dynamics from Polyakov loop correlators.

  14. Compressive sensing based Bayesian sparse channel estimation for OFDM communication systems: high performance and low complexity.

    Science.gov (United States)

    Gui, Guan; Xu, Li; Shan, Lin; Adachi, Fumiyuki

    2014-01-01

    In orthogonal frequency division modulation (OFDM) communication systems, channel state information (CSI) is required at receiver due to the fact that frequency-selective fading channel leads to disgusting intersymbol interference (ISI) over data transmission. Broadband channel model is often described by very few dominant channel taps and they can be probed by compressive sensing based sparse channel estimation (SCE) methods, for example, orthogonal matching pursuit algorithm, which can take the advantage of sparse structure effectively in the channel as for prior information. However, these developed methods are vulnerable to both noise interference and column coherence of training signal matrix. In other words, the primary objective of these conventional methods is to catch the dominant channel taps without a report of posterior channel uncertainty. To improve the estimation performance, we proposed a compressive sensing based Bayesian sparse channel estimation (BSCE) method which cannot only exploit the channel sparsity but also mitigate the unexpected channel uncertainty without scarifying any computational complexity. The proposed method can reveal potential ambiguity among multiple channel estimators that are ambiguous due to observation noise or correlation interference among columns in the training matrix. Computer simulations show that proposed method can improve the estimation performance when comparing with conventional SCE methods.

  15. Channel Acquisition for Massive MIMO-OFDM With Adjustable Phase Shift Pilots

    Science.gov (United States)

    You, Li; Gao, Xiqi; Swindlehurst, A. Lee; Zhong, Wen

    2016-03-01

    We propose adjustable phase shift pilots (APSPs) for channel acquisition in wideband massive multiple-input multiple-output (MIMO) systems employing orthogonal frequency division multiplexing (OFDM) to reduce the pilot overhead. Based on a physically motivated channel model, we first establish a relationship between channel space-frequency correlations and the channel power angle-delay spectrum in the massive antenna array regime, which reveals the channel sparsity in massive MIMO-OFDM. With this channel model, we then investigate channel acquisition, including channel estimation and channel prediction, for massive MIMO-OFDM with APSPs. We show that channel acquisition performance in terms of sum mean square error can be minimized if the user terminals' channel power distributions in the angle-delay domain can be made non-overlapping with proper phase shift scheduling. A simplified pilot phase shift scheduling algorithm is developed based on this optimal channel acquisition condition. The performance of APSPs is investigated for both one symbol and multiple symbol data models. Simulations demonstrate that the proposed APSP approach can provide substantial performance gains in terms of achievable spectral efficiency over the conventional phase shift orthogonal pilot approach in typical mobility scenarios.

  16. 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.

  17. Genetic Control of Potassium Channels.

    Science.gov (United States)

    Amin, Ahmad S; Wilde, Arthur A M

    2016-06-01

    Approximately 80 genes in the human genome code for pore-forming subunits of potassium (K(+)) channels. Rare variants (mutations) in K(+) channel-encoding genes may cause heritable arrhythmia syndromes. Not all rare variants in K(+) channel-encoding genes are necessarily disease-causing mutations. Common variants in K(+) channel-encoding genes are increasingly recognized as modifiers of phenotype in heritable arrhythmia syndromes and in the general population. Although difficult, distinguishing pathogenic variants from benign variants is of utmost importance to avoid false designations of genetic variants as disease-causing mutations.

  18. TRP channels and psychiatric disorders.

    Science.gov (United States)

    Chahl, Loris A

    2011-01-01

    Depression and schizophrenia are major psychiatric disorders that cause much human suffering. Current treatments have major limitations and new drug targets are eagerly sought. Study of transient receptor potential (TRP) channels in these disorders is at an early stage and the potential of agents that activate or inhibit these channels remains speculative. The findings that TRPC6 channels promote dendritic growth and are selectively activated by hyperforin, the key constitutent of St John's wort, suggest that TRPC6 channels might prove to be a new target for antidepressant drug development. There is now considerable evidence that TRPV1 antagonists have anxiolytic activity but there is no direct evidence that they have antidepressant activity. There is also no direct evidence that TRP channels play a role in schizophrenia. However, the findings that TRPC channels are involved in neuronal development and fundamental synaptic mechanisms, and that TRPV1 channels play a role in central dopaminergic and cannabinoid mechanisms is suggestive of potential roles of these channels in schizophrenia. Investigation of TRP channels in psychiatric disorders holds the promise of yielding further understanding of the aetiology of psychiatric disorders and the development of new drug treatments.

  19. Capacities of quantum amplifier channels

    Science.gov (United States)

    Qi, Haoyu; Wilde, Mark M.

    2017-01-01

    Quantum amplifier channels are at the core of several physical processes. Not only do they model the optical process of spontaneous parametric down-conversion, but the transformation corresponding to an amplifier channel also describes the physics of the dynamical Casimir effect in superconducting circuits, the Unruh effect, and Hawking radiation. Here we study the communication capabilities of quantum amplifier channels. Invoking a recently established minimum output-entropy theorem for single-mode phase-insensitive Gaussian channels, we determine capacities of quantum-limited amplifier channels in three different scenarios. First, we establish the capacities of quantum-limited amplifier channels for one of the most general communication tasks, characterized by the trade-off between classical communication, quantum communication, and entanglement generation or consumption. Second, we establish capacities of quantum-limited amplifier channels for the trade-off between public classical communication, private classical communication, and secret key generation. Third, we determine the capacity region for a broadcast channel induced by the quantum-limited amplifier channel, and we also show that a fully quantum strategy outperforms those achieved by classical coherent-detection strategies. In all three scenarios, we find that the capacities significantly outperform communication rates achieved with a naive time-sharing strategy.

  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.

  1. An Adaptive Channel Estimation Algorithm Using Time-Frequency Polynomial Model for OFDM with Fading Multipath Channels

    Directory of Open Access Journals (Sweden)

    Liu KJ Ray

    2002-01-01

    Full Text Available Orthogonal frequency division multiplexing (OFDM is an effective technique for the future 3G communications because of its great immunity to impulse noise and intersymbol interference. The channel estimation is a crucial aspect in the design of OFDM systems. In this work, we propose a channel estimation algorithm based on a time-frequency polynomial model of the fading multipath channels. The algorithm exploits the correlation of the channel responses in both time and frequency domains and hence reduce more noise than the methods using only time or frequency polynomial model. The estimator is also more robust compared to the existing methods based on Fourier transform. The simulation shows that it has more than improvement in terms of mean-squared estimation error under some practical channel conditions. The algorithm needs little prior knowledge about the delay and fading properties of the channel. The algorithm can be implemented recursively and can adjust itself to follow the variation of the channel statistics.

  2. Information-guided communications in MIMO systems with channel state impairments

    KAUST Repository

    Yang, Yuli

    2013-06-20

    Information-guided channel hopping (IGCH) is a promising technique for high-data-rate communications using multiple antennas for information mapping at the transmitter and optional antenna diversity at the receiver. Compared with some popular multi-antenna techniques, the advantage of this scheme is proven in ideal channel conditions, where the channel is spatially white and the perfect channel state information is assumed available at the receiver. The main objective of this paper is to present an information theoretical study on IGCH in realistic propagation environments with channel degeneracy due to spatial correlation and keyhole phenomena as well as imperfect channel estimation. It is proven that good performance promised by IGCH can be achieved in a variety of non-ideal channel conditions. Moreover, the analysis in this paper provides a convenient tool for the corresponding system design in practical operating environments. © 2013 John Wiley & Sons, Ltd.

  3. Mucolipins: Intracellular TRPML1-3 channels.

    Science.gov (United States)

    Cheng, Xiping; Shen, Dongbiao; Samie, Mohammad; Xu, Haoxing

    2010-05-17

    The mucolipin family of Transient Receptor Potential (TRPML) proteins is predicted to encode ion channels expressed in intracellular endosomes and lysosomes. Loss-of-function mutations of human TRPML1 cause type IV mucolipidosis (ML4), a childhood neurodegenerative disease. Meanwhile, gain-of-function mutations in the mouse TRPML3 result in the varitint-waddler (Va) phenotype with hearing and pigmentation defects. The broad spectrum phenotypes of ML4 and Va appear to result from certain aspects of endosomal/lysosomal dysfunction. Lysosomes, traditionally believed to be the terminal "recycling center" for biological "garbage", are now known to play indispensable roles in intracellular signal transduction and membrane trafficking. Studies employing animal models and cell lines in which TRPML genes have been genetically disrupted or depleted have uncovered roles of TRPMLs in multiple cellular functions including membrane trafficking, signal transduction, and organellar ion homeostasis. Physiological assays of mammalian cell lines in which TRPMLs are heterologously overexpressed have revealed the channel properties of TRPMLs in mediating cation (Ca(2+)/Fe(2+)) efflux from endosomes and lysosomes in response to unidentified cellular cues. This review aims to summarize these recent advances in the TRPML field and to correlate the channel properties of endolysosomal TRPMLs with their biological functions. We will also discuss the potential cellular mechanisms by which TRPML deficiency leads to neurodegeneration.

  4. Beyond the Manual Channel

    DEFF Research Database (Denmark)

    , the main focus there is on spoken languages in their written and spoken forms. This series of workshops, however, offers a forum for researchers focussing on sign languages. For the fourth time, the workshop had sign language corpora as its main topic. This time, the focus was on any aspect beyond......This collection of papers stems from the Sixth Workshop on the Representation and Processing of Sign Languages, held in May 2014 as a satellite to the Language Resources and Evaluation Conference in Reykjavik. While there has been occasional attention for sign languages at the main LREC conference...... 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...

  5. On Antenna Design Objectives and the Channel Capacity of MIMO Handsets

    DEFF Research Database (Denmark)

    Nielsen, Jesper Ødum; Yanakiev, Boyan; Barrio, Samantha Caporal Del;

    2014-01-01

    The branch correlation coefficient (BCC), the branch power ratio (BPR), and the total mean power (TMP) are often used to characterize the mobile multiple-input multiple- output (MIMO) channel. This work investigates to which degree these parameters are useful for maximizing the channel capacity o...

  6. Channel Floor Yardangs

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] Released 19 July 2004 The atmosphere of Mars is a dynamic system. Water-ice clouds, fog, and hazes can make imaging the surface from space difficult. Dust storms can grow from local disturbances to global sizes, through which imaging is impossible. Seasonal temperature changes are the usual drivers in cloud and dust storm development and growth. Eons of atmospheric dust storm activity has left its mark on the surface of Mars. Dust carried aloft by the wind has settled out on every available surface; sand dunes have been created and moved by centuries of wind; and the effect of continual sand-blasting has modified many regions of Mars, creating yardangs and other unusual surface forms. The yardangs in this image are forming in channel floor deposits. The channel itself is funneling the wind to cause the erosion. Image information: VIS instrument. Latitude 4.5, Longitude 229.7 East (133.3 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from

  7. Negative particle planar and axial channeling and channeling collimation

    Energy Technology Data Exchange (ETDEWEB)

    Carrigan, Richard A., Jr.; /Fermilab

    2009-12-01

    While information exists on high energy negative particle channeling there has been little study of the challenges of negative particle bending and channeling collimation. Partly this is because negative dechanneling lengths are relatively much shorter. Electrons are not particularly useful for investigating negative particle channeling effects because their material interactions are dominated by channeling radiation. Another important factor is that the current central challenge in channeling collimation is the proton-proton Large Hadron Collider (LHC) where both beams are positive. On the other hand in the future the collimation question might reemerge for electon-positron or muon colliders. Dechanneling lengths increase at higher energies so that part of the negative particle experimental challenge diminishes. In the article different approaches to determining negative dechanneling lengths are reviewed. The more complicated case for axial channeling is also discussed. Muon channeling as a tool to investigate dechanneling is also discussed. While it is now possible to study muon channeling it will probably not illuminate the study of negative dechanneling.

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

    NARCIS (Netherlands)

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

    2016-01-01

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

  9. Multiplexing efficiency for MIMO antenna-channel impairment characterisation in realistic multipath environments

    DEFF Research Database (Denmark)

    Chen, Xiaoming; Zhang, Shuai

    2016-01-01

    Multiple-input multiple-output (MIMO) systems in multipath environments suffer from high correlations (in the presence of small angular spreads of propagation waves and similar antenna patterns) and power imbalances [(due to cross-polarisation discrimination (XPD) of the propagation channel...... and possibly different antenna efficiencies)]. A simple performance metric that takes into account of the antenna-channel impairments on the MIMO system will be of great value for MIMO antenna characterizations. In this work, a generalized multiplexing efficiency (ME) is derived, which takesing into account...... efficiencyME, we use both the correlation-based channel model (where correlations and power imbalances can be readily specified) and the more realistic WINNER+ channel model (where correlations and power imbalances have to be indirectly controlled by changing the antenna setup)....

  10. 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.

  11. Mirrored serpentine flow channels for fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Rock, Jeffrey Allan (Rochester, NY)

    2000-08-08

    A PEM fuel cell having serpentine flow field channels wherein the input/inlet legs of each channel border the input/inlet legs of the next adjacent channels in the same flow field, and the output/exit legs of each channel border the output/exit legs of the next adjacent channels in the same flow field. The serpentine fuel flow channels may be longer, and may contain more medial legs, than the serpentine oxidant flow channels.

  12. Littoral steering of deltaic channels

    Science.gov (United States)

    Nienhuis, Jaap H.; Ashton, Andrew D.; Giosan, Liviu

    2016-11-01

    The typically single-threaded channels on wave-influenced deltas show striking differences in their orientations, with some channels oriented into the incoming waves (e.g., Ombrone, Krishna), and others oriented away from the waves (e.g., Godavari, Sao Francisco). Understanding the controls on channel orientation is important as the channel location greatly influences deltaic morphology and sedimentology, both subaerially and subaqueously. Here, we explore channel orientation and consequent feedbacks with local shoreline dynamics using a plan-form numerical model of delta evolution. The model treats fluvial sediment delivery to a wave-dominated coast in two ways: 1) channels are assumed to prograde in a direction perpendicular to the local shoreline orientation and 2) a controlled fraction of littoral sediment transport can bypass the river mouth. Model results suggest that channels migrate downdrift when there is a significant net littoral transport and alongshore transport bypassing of the river mouth is limited. In contrast, river channels tend to orient themselves into the waves when fluvial sediment flux is relatively large, causing the shoreline of the downdrift delta flank to attain the orientation of maximum potential sediment transport for the incoming wave climate. Using model results, we develop a framework to estimate channel orientations for wave-influenced deltas that shows good agreement with natural examples. An increase in fluvial sediment input can cause a channel to reorient itself into incoming waves, behavior observed, for example, in the Ombrone delta in Italy. Our results can inform paleoclimate studies by linking channel orientation to fluvial sediment flux and wave energy. In particular, our approach provides a means to quantify past wave directions, which are notoriously difficult to constrain.

  13. 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...

  14. 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.

  15. 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.

  16. 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...

  17. Channelling, a new immunization strategy.

    Science.gov (United States)

    Gacharna Romero, M G; Silva Pizano, E; Avendano Lamo, J

    1985-01-01

    In 1981, with PAHO/WHO technical assistance, the Ministry of Health, Colombia, designed what is known as the channelling strategy, aimed at improving immunization coverage. This name was given because the strategy is designed to establish communication channels through direct action aimed at promoting health. Health workers and community leaders or guides conduct household visits to identify unvaccinated children or those with incomplete vaccination schedules and "channel" them to health centers or health posts. The channelling strategy developed in Colombia was briefly mentioned in the case study on the Colombian Vaccination Crusade of 1984. It is now being employed for ORT and other PHC components in the Colombian Child Survival and Development Plan, 1985-1987. In the meantime, other countries have adopted the channelling strategy, which is described in this article.

  18. Flow dynamics and concentration polarisation in spacer-filled channels

    DEFF Research Database (Denmark)

    Lipnizki, Jens; Jonsson, Gunnar Eigil

    2002-01-01

    been shown that the mass transport along the membrane is not fully described by the Sherwood correlation, which describes a decreasing mass transfer with an increasing distance from the inlet. It was observed that in open channel without spacers, the slope of the Sherwood correlation is decreasing...... by increasing pressure. This effect is combined with regular stripes on the membrane depending on the crossflow velocity and pressure when using coloured particles. An explanation could be a mass transfer perpendicular to the flow direction due to vortices, which is not covered by the Sherwood correlation....... This phenomenon was also observed in spacer-filled channels. In this case the stripes on the surface depended on the spacer geometry. Furthermore, the experiments were used to calculate the energy consumption vs. the mass transfer coefficient for different spacers. This research can be used as a foundation...

  19. Comparison of Channel Emulation Techniques in Multiprobe Anechoic Chamber Setups

    DEFF Research Database (Denmark)

    Llorente, Ines Carton; Fan, Wei; Nielsen, Jesper Ødum;

    2015-01-01

    This paper compares two different techniques for channel emulation in multiprobe anechoic chamber based setups, which is a candidate solution for the standardization of MIMO OTA performance testing of mobile devices. The comparison is performed via simulations of the field distribution, temporal...... correlation, and spatial correlation emulated by these methods for different number of probes. Results show that the emulation accuracy of the field distribution and temporal correlation are degraded when the emulation technique uses a single sinusoid per probe antenna, while the emulation accuracy...

  20. The Wiretap Channel with Feedback: Encryption over the Channel

    CERN Document Server

    Lai, Lifeng; Poor, H Vincent

    2007-01-01

    In this work, the critical role of noisy feedback in enhancing the secrecy capacity of the wiretap channel is established. Unlike previous works, where a noiseless public discussion channel is used for feedback, the feed-forward and feedback signals share the same noisy channel in the present model. Quite interestingly, this noisy feedback model is shown to be more advantageous in the current setting. More specifically, the discrete memoryless modulo-additive channel with a full-duplex destination node is considered first, and it is shown that the judicious use of feedback increases the perfect secrecy capacity to the capacity of the source-destination channel in the absence of the wiretapper. In the achievability scheme, the feedback signal corresponds to a private key, known only to the destination. In the half-duplex scheme, a novel feedback technique that always achieves a positive perfect secrecy rate (even when the source-wiretapper channel is less noisy than the source-destination channel) is proposed....

  1. Color pattern recognition based on the joint fractional Fourier transform correlator

    Institute of Scientific and Technical Information of China (English)

    Weimin Jin; Yupei Zhang

    2007-01-01

    A new system of multi-channel single-output joint fractional Fourier transform correlator (JFRTC) for color pattern recognition is proposed based on the conventional system of multi-channel single-output joint transform correlator (JTC). The theoretical analysis and optical experiments are performed. With this method, one can obtain three correlation peaks at the output plane which show a pair of desired cross-correlation peaks and one auto-correlation peak. In comparison, the conventional system leads to more correlation peaks playing a noise role in color pattern recognition.

  2. Based on Channel Characteristics

    Directory of Open Access Journals (Sweden)

    Zhuo Hao

    2013-01-01

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

  3. 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.

  4. Phase-Type Models of Channel-Holding Times in Cellular Communication Systems

    DEFF Research Database (Denmark)

    Christensen, Thomas Kaare; Nielsen, Bo Friis; Iversen, Villy Bæk

    2004-01-01

    In this paper, we derive the distribution of the channel-holding time when both cell-residence and call-holding times are phase-type distributed. Furthermore, the distribution of the number of handovers, the conditional channel-holding time distributions, and the channel-holding time when cell re...... residence times are correlated are derived. All distributions are of phase type, making them very general and flexible. The channel-holding times are of importance in performance evaluation and simulation of cellular mobile communication systems....

  5. Quaternary geology of the Channeled Scabland and adjacent areas

    Science.gov (United States)

    Baker, V. R.

    1978-01-01

    The quaternary history of the channeled scabland is characterized by discrete episodes of catastrophic flooding and prolonged periods of loess accumulation and soil formation. The loess sequence was correlated with Richmond's Rocky Mountain glacial chronology. At least five major catastrophic flood events occurred in the general vicinity of the channeled scabland. The earliest episode occurred prior to the extensive deposition of the Palouse formation. The last major episode of flooding occurred between about 18,000 and 13,000 years ago. It probably consisted of two outbursts from glacial Lake Missoula.

  6. Aquaporin 2 mutations in Trypanosoma brucei gambiense field isolates correlate with decreased susceptibility to pentamidine and melarsoprol.

    Directory of Open Access Journals (Sweden)

    Fabrice E Graf

    Full Text Available The predominant mechanism of drug resistance in African trypanosomes is decreased drug uptake due to loss-of-function mutations in the genes for the transporters that mediate drug import. The role of transporters as determinants of drug susceptibility is well documented from laboratory-selected Trypanosoma brucei mutants. But clinical isolates, especially of T. b. gambiense, are less amenable to experimental investigation since they do not readily grow in culture without prior adaptation. Here we analyze a selected panel of 16 T. brucei ssp. field isolates that (i have been adapted to axenic in vitro cultivation and (ii mostly stem from treatment-refractory cases. For each isolate, we quantify the sensitivity to melarsoprol, pentamidine, and diminazene, and sequence the genomic loci of the transporter genes TbAT1 and TbAQP2. The former encodes the well-characterized aminopurine permease P2 which transports several trypanocides including melarsoprol, pentamidine, and diminazene. We find that diminazene-resistant field isolates of T. b. brucei and T. b. rhodesiense carry the same set of point mutations in TbAT1 that was previously described from lab mutants. Aquaglyceroporin 2 has only recently been identified as a second transporter involved in melarsoprol/pentamidine cross-resistance. Here we describe two different kinds of TbAQP2 mutations found in T. b. gambiense field isolates: simple loss of TbAQP2, or loss of wild-type TbAQP2 allele combined with the formation of a novel type of TbAQP2/3 chimera. The identified mutant T. b. gambiense are 40- to 50-fold less sensitive to pentamidine and 3- to 5-times less sensitive to melarsoprol than the reference isolates. We thus demonstrate for the first time that rearrangements of the TbAQP2/TbAQP3 locus accompanied by TbAQP2 gene loss also occur in the field, and that the T. b. gambiense carrying such mutations correlate with a significantly reduced susceptibility to pentamidine and melarsoprol.

  7. Aquaporin 2 mutations in Trypanosoma brucei gambiense field isolates correlate with decreased susceptibility to pentamidine and melarsoprol.

    Science.gov (United States)

    Graf, Fabrice E; Ludin, Philipp; Wenzler, Tanja; Kaiser, Marcel; Brun, Reto; Pyana, Patient Pati; Büscher, Philippe; de Koning, Harry P; Horn, David; Mäser, Pascal

    2013-01-01

    The predominant mechanism of drug resistance in African trypanosomes is decreased drug uptake due to loss-of-function mutations in the genes for the transporters that mediate drug import. The role of transporters as determinants of drug susceptibility is well documented from laboratory-selected Trypanosoma brucei mutants. But clinical isolates, especially of T. b. gambiense, are less amenable to experimental investigation since they do not readily grow in culture without prior adaptation. Here we analyze a selected panel of 16 T. brucei ssp. field isolates that (i) have been adapted to axenic in vitro cultivation and (ii) mostly stem from treatment-refractory cases. For each isolate, we quantify the sensitivity to melarsoprol, pentamidine, and diminazene, and sequence the genomic loci of the transporter genes TbAT1 and TbAQP2. The former encodes the well-characterized aminopurine permease P2 which transports several trypanocides including melarsoprol, pentamidine, and diminazene. We find that diminazene-resistant field isolates of T. b. brucei and T. b. rhodesiense carry the same set of point mutations in TbAT1 that was previously described from lab mutants. Aquaglyceroporin 2 has only recently been identified as a second transporter involved in melarsoprol/pentamidine cross-resistance. Here we describe two different kinds of TbAQP2 mutations found in T. b. gambiense field isolates: simple loss of TbAQP2, or loss of wild-type TbAQP2 allele combined with the formation of a novel type of TbAQP2/3 chimera. The identified mutant T. b. gambiense are 40- to 50-fold less sensitive to pentamidine and 3- to 5-times less sensitive to melarsoprol than the reference isolates. We thus demonstrate for the first time that rearrangements of the TbAQP2/TbAQP3 locus accompanied by TbAQP2 gene loss also occur in the field, and that the T. b. gambiense carrying such mutations correlate with a significantly reduced susceptibility to pentamidine and melarsoprol.

  8. 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.

  9. Near-threshold correlations of neutrons

    CERN Document Server

    Okołowicz, J; Nazarewicz, W

    2013-01-01

    The appearance of charged-particle clustering in near-threshold configuration is a phenomenon that can be explained in the Open Quantum System description of the atomic nucleus. In this work we apply the realistic Shell Model Embedded in the Continuum to elucidate the emergence of neutron correlations in near-threshold many-body states coupled to l=1,2 neutron decay channels. Spectral consequences of such continuum coupling are briefly discussed together with the emergence of complex multi-neutron correlations.

  10. Gaussian matrix-product states for coding in bosonic communication channels

    Science.gov (United States)

    Schäfer, Joachim; Karpov, Evgueni; Cerf, Nicolas J.

    2012-01-01

    The communication capacity of Gaussian bosonic channels with memory has recently attracted much interest. Here, we investigate a method to prepare the multimode entangled input symbol states for encoding classical information into these channels. In particular, we study the usefulness of a Gaussian matrix-product state (GMPS) as an input symbol state, which can be sequentially generated although it remains heavily entangled for an arbitrary number of modes. We show that the GMPS can achieve more than 99.9% of the Gaussian capacity for Gaussian bosonic memory channels with a Markovian or non-Markovian correlated noise model in a large range of noise correlation strengths. Furthermore, we present a noise class for which the GMPS is the exact optimal input symbol state of the corresponding channel. Since GMPS are ground states of particular quadratic Hamiltonians, our results suggest a possible link between the theory of quantum communication channels and quantum many-body physics.

  11. Backscattering/transmission of 2 MeV He{sup ++} ions quantitative correlation study

    Energy Technology Data Exchange (ETDEWEB)

    Berec, V., E-mail: bervesn@gmail.com [Institute of Nuclear Sciences Vinca, University of Belgrade, P.O. Box 522, 11001 Belgrade (Serbia); Germogli, G.; Mazzolari, A.; Guidi, V. [INFN Sezione di Ferrara and Dipartimento di Fisica e Scienze della Terra, Via Saragat 1, 44100 Ferrara (Italy); De Salvador, D. [Dipartimento di Fisica, Università di Padova, Via Marzolo n.8, 35131 Padova (Italy); INFN Laboratori Nazionali di Legnaro, Viale Università 2, 35020 Legnaro, PD (Italy); Bacci, L. [INFN Laboratori Nazionali di Legnaro, Viale Università 2, 35020 Legnaro, PD (Italy)

    2015-07-15

    In this work we report on detailed findings of planar channeling oscillations of 2 MeV He{sup ++} particles in (1 1 0) silicon crystal. The exact correlation and coherence mechanism between confined particles oscillating trajectories are analyzed theoretically and experimentally in backscattering/transmission geometry. Regular patterns of channeled He{sup ++} ion planar oscillations are shown to be dominated by the crystal harmonic-oscillator potential and multiple scattering effect. For the first time it was shown that under the planar channeling conditions trajectories of positively charged particles exhibit observable correlation dynamics, including the interference effect. Quantitative estimation of channeling efficiency is performed using path integral method.

  12. 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.

  13. Ion channels in neuronal survival

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The study of ion channels represents one of the most active fields in neuroscience research in China.In the last 10 years,active research in various Chinese neuroscience institutions has sought to understand the mechanisms responsible for sensory processing,neural development and neurogenesis,neural plasticity,as well as pathogenesis.In addition,extensive studies have been directed to measure ion channel activity,structure-function relationships,as well as many other biophysical and biochemical properties.This review focuses on the progress achieved in the investigation of ion channels in neuronal survival during the past 10 years in China.

  14. 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

  15. Skeletal Muscle Na+ Channel Disorders

    Directory of Open Access Journals (Sweden)

    Dina eSimkin

    2011-10-01

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

  16. Correlations in neutrino-nucleus scattering

    CERN Document Server

    Van Cuyck, Tom; Jachowicz, Natalie; González-Jiménez, Raul; Martini, Marco; Ryckebusch, Jan; Van Dessel, Nils

    2016-01-01

    We present a detailed study of charged-current quasielastic neutrino-nucleus scattering and of the influence of correlations on one- and two-nucleon knockout processes. The quasielastic neutrino-nucleus scattering cross sections, including the influence of long-range correlations, are evaluated within a continuum random phase approximation approach. The short-range correlation formalism is implemented in the impulse approximation by shifting the complexity induced by the correlations from the wave functions to the operators. The model is validated by confronting $(e,e^\\prime)$ cross-section predictions with electron scattering data in the kinematic region where the quasielastic channel is expected to dominate. Further, the $^{12}$C$(\

  17. Infinitely many kinds of quantum channels

    Energy Technology Data Exchange (ETDEWEB)

    Hastings, Matthew B [Los Alamos National Laboratory

    2008-01-01

    We define the ability of a quantum channel to simulate another by means of suitable encoding and decoding operations. While classical channels have only two equivalence classes under simulation (channels with non-vanishing capacity and those with vanishing capacity), we show that there are an uncountable infinity of different equivalence classes of quantum channels using the example of the quantum erasure channel. Our results also imply a kind of 'Matthew principle' for error correction on certain channels.

  18. 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.

  19. 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.

  20. 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...

  1. Quark Propagator and Meson Correlators in the QCD Vacuum

    CERN Document Server

    Sheel, V; Parikh, J C; Sheel, Varun; Mishra, Hiranmaya; Parikh, Jitendra C.

    1997-01-01

    Equal time, point to point correlation functions for spatially separated meson currents are calculated with respect to a variational construct for the ground state of QCD. Given such an ansatz we make no further approximations in the evaluation of the correlators. Our calculations for the vector, axial vector and scalar channels show qualitative agreement with the phenomenological predictions, whereas the pseudoscalar channel does not. However, the pseudoscalar correlator, when approximated by saturating with intermediate one pion states agrees with results obtained from spectral density functions parameterised by pion decay constant and $$ value obtained from chiral perturbation theory. We discuss this departure in the pseudoscalar channel, in context of the quark propagation in the vacuum.

  2. Cell swelling activates K+ and Cl- channels as well as nonselective, stretch-activated cation channels in ehrlich ascites tumor cells

    DEFF Research Database (Denmark)

    Christensen, Ove; Hoffmann, Else Kay

    1992-01-01

    not occur instantaneously but within a time delay of 1/2 to 1 min. The channel is permeable to Ba2+ and hence presumably to Ca2+. It seems likely that the function of the nonselective, stretch-activated channels is correlated with their inferred Ca2+ permeability, as part of the volume-activated signal...... external K+ is estimated at about 7 pS. A K+ channel with similar properties can be activated in the cellattached mode by addition of Ca2+ plus ionophore A23187. The channel is also activated by cell swelling, within 1 min following hypotonic exposure. No evidence was found of channel activation...... types of Cl– channels were regularly recorded in excised inside-out patches: a voltage-activated 400-pS channel and a 34-pS Cl– channel which show properties similar to the Cl– channel in the apical membrane in human airway epithelial cells. There is no evidence for a role in RVD for either of these two...

  3. Isospin considerations in correlations of pions and B mesons

    CERN Document Server

    Dunietz, Isard

    1995-01-01

    The correlations between a B meson and a pion produced nearby in phase space should respect isospin reflection symmetry I_3 \\to -I_3. Thus, one generally expects similar \\pi^+ B^0 and \\pi^- B^+ correlations (non-exotic channels), and similar \\pi^- B^0 and \\pi^+ B^+ correlations (exotic channels). Exceptions include (a) fragmentation processes involving exchange of quarks with the producing system, (b) misidentification of charged kaons as charged pions, and (c) effects of decay products of the associated \\overline{B}. All of these can affect the apparent signal for correlations of charged B mesons with charged hadrons. The identification of the flavor of neutral B mesons through the decay B^0 \\to K^{*0} J/\\psi requires good particle identification in order that the decay K^{*0} \\to K^+ \\pi^- not be mistaken for \\overline{K}^{*0} \\to K^- \\pi^+, in which case the correlations of neutral B mesons with hadrons can be underestimated.

  4. Covert Channel Synthesis for Transducers

    OpenAIRE

    Benattar, Gilles; Bérard, Béatrice; Lime, Didier; Mullins, John; Roux, Olivier Henri; Sassolas, Mathieu

    2010-01-01

    Research report; Covert channels are a security threat for information systems, since they permit illegal flows, and sometimes leaks, of classified data. Although numerous descriptions have been given at a concrete level, relatively little work has been carried out at a more abstract level, outside probabilistic models. In this paper, we propose a definition of covert channels based on encoding and decoding binary messages with transducers, in a finite transition system. We first compare this...

  5. The Degraded Poisson Wiretap Channel

    OpenAIRE

    Laourine, Amine; Wagner, Aaron B.

    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 ...

  6. TRP Channels in Human Prostate

    Directory of Open Access Journals (Sweden)

    Carl Van Haute

    2010-01-01

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

  7. Eight channel telephone telemetry system

    Science.gov (United States)

    Smith, R. E.

    1973-01-01

    A portable, indirectly coupled telephone system is reported which transmits/to a central receiving site eight channels of EEG data of sufficient fidelity for screening and/or limited diagnostic use. The system requires no electrical connection to the telephone at the transmitter or at the receiver and is compatible with common EEG recording practice for real-time recording. It accepts 8 input channels simultaneously with one telephone transmitter and one telephone receiver operates from standard power sources.

  8. On Cellular MIMO Channel Capacity

    Science.gov (United States)

    Adachi, Koichi; Adachi, Fumiyuki; Nakagawa, Masao

    To increase the transmission rate without bandwidth expansion, the multiple-input multiple-output (MIMO) technique has recently been attracting much attention. The MIMO channel capacity in a cellular system is affected by the interference from neighboring co-channel cells. In this paper, we introduce the cellular channel capacity and evaluate its outage capacity, taking into account the frequency-reuse factor, path loss exponent, standard deviation of shadowing loss, and transmission power of a base station (BS). Furthermore, we compare the cellular MIMO downlink channel capacity with those of other multi-antenna transmission techniques such as single-input multiple-output (SIMO) and space-time block coded multiple-input single-output (STBC-MISO). We show that the optimum frequency-reuse factor F that maximizes 10%-outage capacity is 3 and both 50%- and 90%-outage capacities is 1 irrespective of the type of multi-antenna transmission technique, where q%-outage capacity is defined as the channel capacity that gives an outage probability of q%. We also show that the cellular MIMO channel capacity is always higher than those of SIMO and STBC-MISO.

  9. Multi-Channel Noise Reduced Visual Evoked Potential Analysis

    Science.gov (United States)

    Palaniappan, Ramaswamy; Raveendran, Paramesran; Nishida, Shogo

    In this paper, Principal Component Analysis (PCA) is used to reduce noise from multi-channel Visual Evoked Potential (VEP) signals. PCA is applied to reduce noise from multi-channel VEP signals because VEP signals are more correlated from one channel to another as compared to noise during visual perception. Emulated VEP signals contaminated with noise are used to show the noise reduction ability of PCA. These noise reduced VEP signals are analysed in the gamma spectral band to classify alcoholics and non-alcoholics with a Fuzzy ARTMAP (FA) neural network. A zero phase Butterworth digital filter is used to extract gamma band power in spectral range of 30 to 50 Hz from these noise reduced VEP signals. The results using 800 VEP signals give an average FA classification of 92.50 % with the application of PCA and 83.33 % without the application of PCA.

  10. Modified Spatial Channel Model for MIMO Wireless Systems

    Directory of Open Access Journals (Sweden)

    Pekka Kyösti

    2007-12-01

    Full Text Available The third generation partnership Project's (3GPP spatial channel model (SCM is a stochastic channel model for MIMO systems. Due to fixed subpath power levels and angular directions, the SCM model does not show the degree of variation which is encountered in real channels. In this paper, we propose a modified SCM model which has random subpath powers and directions and still produces Laplace shape angular power spectrum. Simulation results on outage MIMO capacity with basic and modified SCM models show that the modified SCM model gives constantly smaller capacity values. Accordingly, it seems that the basic SCM gives too small correlation between MIMO antennas. Moreover, the variance in capacity values is larger using the proposed SCM model. Simulation results were supported by the outage capacity results from a measurement campaign conducted in the city centre of Oulu, Finland.

  11. Correlation and Entanglement

    Institute of Scientific and Technical Information of China (English)

    Shun-long Luo; You-feng Luo

    2003-01-01

    In quantum mechanics, it is long recognized that there exist correlations between observables which are much stronger than the classical ones. These correlations are usually called entanglement, and cannot be accounted for by classical theory. In this paper, we will study correlations between observables in terms of covariance and the Wigner-Yanase correlation, and compare their merits in characterizing entanglement. We will show that the Wigner-Yanase correlation has some advantages over the conventional covariance.

  12. Low-Complexity Interference-Free Downlink Channel Assignment with Improved Performance in Coordinated Small Cells

    KAUST Repository

    Radaydeh, Redha M.

    2015-05-01

    This paper proposes a low-complexity interference-free channel assignment scheme with improved desired downlink performance in coordinated multi-antenna small-coverage access points (APs) that employ the open-access control strategy. The adopted system treats the case when each user can be granted an access to one of the available channels at a time. Moreover, each receive terminal can suppress a limited number of resolvable interfering sources via its highly-correlated receive array. On the other hand, the operation of the deployed APs can be coordinated to serve active users, and the availability of multiple physical channels and the use of uncorrelated transmit antennas at each AP are exploited to improve the performance of supported users. The analysis provides new approaches to use the transmit antenna array at each AP, the multiple physical channels, the receive antenna array at each user in order to identify interference-free channels per each user, and then to select a downlink channel that provides the best possible improved performance. The event of concurrent interference-free channel identification by different users is also treated to further improve the desired link associated with the scheduled user. The analysis considers the practical scenario of imperfect identification of interference-free channel by an active user and/or the imperfectness in scheduling concurrent users requests on the same channel. The developed formulations can be used to study any performance metric and they are applicable for any statistical and geometric channel models. © 2015 IEEE.

  13. NALCN ion channels have alternative selectivity filters resembling calcium channels or sodium channels.

    Directory of Open Access Journals (Sweden)

    Adriano Senatore

    Full Text Available NALCN is a member of the family of ion channels with four homologous, repeat domains that include voltage-gated calcium and sodium channels. NALCN is a highly conserved gene from simple, extant multicellular organisms without nervous systems such as sponges and placozoans and mostly remains a single gene compared to the calcium and sodium channels which diversified into twenty genes in humans. The single NALCN gene has alternatively-spliced exons at exons 15 or exon 31 that splices in novel selectivity filter residues that resemble calcium channels (EEEE or sodium channels (EKEE or EEKE. NALCN channels with alternative calcium, (EEEE and sodium, (EKEE or EEKE -selective pores are conserved in simple bilaterally symmetrical animals like flatworms to non-chordate deuterostomes. The single NALCN gene is limited as a sodium channel with a lysine (K-containing pore in vertebrates, but originally NALCN was a calcium-like channel, and evolved to operate as both a calcium channel and sodium channel for different roles in many invertebrates. Expression patterns of NALCN-EKEE in pond snail, Lymnaea stagnalis suggest roles for NALCN in secretion, with an abundant expression in brain, and an up-regulation in secretory organs of sexually-mature adults such as albumen gland and prostate. NALCN-EEEE is equally abundant as NALCN-EKEE in snails, but is greater expressed in heart and other muscle tissue, and 50% less expressed in the brain than NALCN-EKEE. Transfected snail NALCN-EEEE and NALCN-EKEE channel isoforms express in HEK-293T cells. We were not able to distinguish potential NALCN currents from background, non-selective leak conductances in HEK293T cells. Native leak currents without expressing NALCN genes in HEK-293T cells are NMDG(+ impermeant and blockable with 10 µM Gd(3+ ions and are indistinguishable from the hallmark currents ascribed to mammalian NALCN currents expressed in vitro by Lu et al. in Cell. 2007 Apr 20;129(2:371-83.

  14. 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.

  15. Portable fluorescence meter with reference backscattering channel

    Science.gov (United States)

    Kornilin, Dmitriy V.; Grishanov, Vladimir N.; Zakharov, Valery P.; Burkov, Dmitriy S.

    2016-09-01

    Methods based on fluorescence and backscattering are intensively used for determination of the advanced glycation end products (AGE) concentration in the biological tissues. There are strong correlation between the AGE concentration and the severity of such diseases like diabetes, coronary heart disease and renal failure. This fact can be used for diagnostic purposes in medical applications. Only few investigations in this area can be useful for development of portable and affordable in vivo AGE meter because the most of them are oriented on using spectrometers. In this study we describe the design and the results of tests on volunteers of portable fluorescence meter based on two photodiodes. One channel of such fluorimeter is used for measurement of the autofluorescence (AF) intensity, another one - for the intensity of elastically scattered radiation, which can be used as a reference. This reference channel is proposed for normalization of the skin autofluorescence signal to the human skin photo type. The fluorimeter, that was developed is relatively compact and does not contain any expensive optical and electronic components. The experimental results prove that proposed tool can be used for the AGE estimation in human skin.

  16. Superhydrophobic surfaces in turbulent channel flow

    Science.gov (United States)

    Li, Yixuan; Alame, Karim; Mahesh, Krishnan

    2016-11-01

    The drag reduction effect of superhydrophobic surfaces in turbulent channel flow is studied using direct numerical simulation. The volume of fluid (VOF) methodology is used to resolve the dynamics of the interface. Laminar flow simulations show good agreement with experiment, and illustrate the relative importance of geometry and interface boundary condition. An analytical solution for the multi-phase problem is obtained that shows good agreement with simulation. Turbulent simulations over a longitudinally grooved surface show drag reduction even in the fully wetted regime. The statistics show that geometry alone can cause an apparent slip to the external flow. Instantaneous plots indicate that the grooves prevent the penetration of near wall vorticity, yielding overall drag reduction. Results for spectra, wall pressure fluctuations and correlations will be presented. Unsteady effects on the air-vapor interface will be discussed. Results for random roughness surfaces will be presented. Supported by Office of Naval Research.

  17. On the simple random-walk models of ion-channel gate dynamics reflecting long-term memory.

    Science.gov (United States)

    Wawrzkiewicz, Agata; Pawelek, Krzysztof; Borys, Przemyslaw; Dworakowska, Beata; Grzywna, Zbigniew J

    2012-06-01

    Several approaches to ion-channel gating modelling have been proposed. Although many models describe the dwell-time distributions correctly, they are incapable of predicting and explaining the long-term correlations between the lengths of adjacent openings and closings of a channel. In this paper we propose two simple random-walk models of the gating dynamics of voltage and Ca(2+)-activated potassium channels which qualitatively reproduce the dwell-time distributions, and describe the experimentally observed long-term memory quite well. Biological interpretation of both models is presented. In particular, the origin of the correlations is associated with fluctuations of channel mass density. The long-term memory effect, as measured by Hurst R/S analysis of experimental single-channel patch-clamp recordings, is close to the behaviour predicted by our models. The flexibility of the models enables their use as templates for other types of ion channel.

  18. Distribution, persistence, and hydrologic characteristics of salmon spawning habitats in clearwater side channels of the Matanuska River, southcentral Alaska

    Science.gov (United States)

    Curran, Janet H.; McTeague, Monica L.; Burril, Sean E.; Zimmerman, Christian E.

    2011-01-01

    Turbid, glacially influenced rivers are often considered to be poor salmon spawning and rearing habitats and, consequently, little is known about salmon habitats that do occur within rivers of this type. To better understand salmon spawning habitats in the Matanuska River of southcentral Alaska, the distribution and characteristics of clearwater side-channel spawning habitats were determined and compared to spawning habitats in tributaries. More than 100 kilometers of clearwater side channels within the braided mainstem of the Matanuska River were mapped for 2006 from aerial images and ground-based surveys. In reaches selected for historical analysis, side channel locations shifted appreciably between 1949 and 2006, but the relative abundance of clearwater side channels was fairly stable during the same period. Geospatial analysis of side channel distribution shows side channels typically positioned along abandoned bars at the braid plain margin rather than on bars between mainstem channels, and shows a strong correlation of channel abundance with braid plain width. Physical and geomorphic characteristics of the channel and chemical character of the water measured at 19 side channel sites, 6 tributary sites, 4 spring sites, and 5 mainstem channel sites showed conditions suitable for salmon spawning in side channels and tributaries, and a correlation of side channel characteristics with the respective tributary or groundwater source water. Autumn-through-spring monitoring of intergravel water temperatures adjacent to salmon redds (nests) in three side channels and two tributaries indicate adequate accumulated thermal units for incubation and emergence of salmon in side channels and relatively low accumulated thermal units in tributaries.

  19. Transient receptor potential channels in essential hypertension

    DEFF Research Database (Denmark)

    Liu, Daoyan; Scholze, Alexandra; Zhu, Zhiming;

    2006-01-01

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

  20. Minimum output entropy of Gaussian channels

    CERN Document Server

    Lloyd, S; Maccone, L; Pirandola, S; Garcia-Patron, R

    2009-01-01

    We show that the minimum output entropy for all single-mode Gaussian channels is additive and is attained for Gaussian inputs. This allows the derivation of the channel capacity for a number of Gaussian channels, including that of the channel with linear loss, thermal noise, and linear amplification.

  1. Asymptotic analysis of downlink MISO systems over Rician fading channels

    KAUST Repository

    Falconet, Hugo

    2016-06-24

    In this work, we focus on the ergodic sum rate in the downlink of a single-cell large-scale multi-user MIMO system in which the base station employs N antennas to communicate with K single-antenna user equipments. A regularized zero-forcing (RZF) scheme is used for precoding under the assumption that each link forms a spatially correlated MIMO Rician fading channel. The analysis is conducted assuming N and K grow large with a non trivial ratio and perfect channel state information is available at the base station. Recent results from random matrix theory and large system analysis are used to compute an asymptotic expression of the signal-to-interference-plus-noise ratio as a function of the system parameters, the spatial correlation matrix and the Rician factor. Numerical results are used to evaluate the performance gap in the finite system regime under different operating conditions. © 2016 IEEE.

  2. A Comparative Evaluation of Humphrey Perimetry and the Multi-channel Pattern Visual Evoked Potentials

    Institute of Scientific and Technical Information of China (English)

    Caiping Hu; Lezheng Wu; De-Zheng Wu; Shixian Long

    2000-01-01

    Purposes: To compare the multi-channel pattern visual evoked potentials to Humphrey perimetry in the assessment of central visual function in primary open angle glaucoma.Methods: The multi-channel checkerboard reversal PVEPs waves to full-field and half-field stimulus of 25 normal persons and 74 patients with primary open angle glaucoma were recorded and analyzed, All patients were examined using Humphrey Field Analyzer. The area of visual field corresponding to the area of retina stimulated during multi-channel PVEPs testing were analysed, straight-line correlation and regression analyses of the various multi-channel PVEPs parameters and the total dB losses were performed.Results: The multi-channel PVEPs demonstrated a low detection rate compared with Humprey perimetry in the early glaucoma, absolute latency and field loss were correlated in the late stage of glaucoma, and absolute amplitude and field loss were not correlated.Conclusions: In relation to signalling “early” loss the multi-channel PVEPs was inferior to Humphrey perimetry, in late loss of primary open angle glaucoma, multi-channel PVEPs can provide a valuable, objective complement to Humphrey perimetry.

  3. Correlated Sources in Distributed Networks--Data Transmission, Common Information Characterization and Inferencing

    Science.gov (United States)

    Liu, Wei

    2011-01-01

    Correlation is often present among observations in a distributed system. This thesis deals with various design issues when correlated data are observed at distributed terminals, including: communicating correlated sources over interference channels, characterizing the common information among dependent random variables, and testing the presence of…

  4. Single top quark production in t-channel at the LHC in noncommutative space-time

    Energy Technology Data Exchange (ETDEWEB)

    Yaser Ayazi, Seyed, E-mail: yaserayazi@ipm.ir [School of Particles and Accelerators, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Esmaeili, Sina [Science and Research Branch, Islamic Azad University (Iran, Islamic Republic of); Mohammadi Najafabadi, Mojtaba [School of Particles and Accelerators, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of)

    2012-05-30

    We study the production cross section of the t-channel single top quark at the LHC in the noncommutative space-time. It is shown that the deviation of the t-channel single top cross section from the Standard Model value because of noncommutativity is significant when |{theta}{sup {yields}}|{>=}0{sup -4} GeV{sup -2}. Using the present experimental precision in measurement of the t-channel cross section, we apply upper limit on the noncommutative parameter. When a single top quark decays, there is a significant amount of angular correlation, in the top quark rest frame between the top spin direction and the direction of the charged lepton momentum from its decay. We study the effect of noncommutativity on the spin correlation and we find that depending on the noncommutative scale, the angular correlation can enhance considerably. Then, we provide limits on the noncommutative scale for various possible relative uncertainties on the spin correlation measurement.

  5. 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

  6. 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.

  7. Update on the implication of potassium channels in autism: K+ channelautism spectrum disorder

    Directory of Open Access Journals (Sweden)

    Luca eGuglielmi

    2015-03-01

    Full Text Available Autism spectrum disorders (ASDs are characterized by impaired ability to properly implement environmental stimuli that are essential to achieve a state of social and cultural exchange. Indeed, the main features of ASD are impairments of interpersonal relationships, verbal and non-verbal communication and restricted and repetitive behaviors. These aspects are often accompanied by several comorbidities such as motor delay, praxis impairment, gait abnormalities, insomnia and above all epilepsy. Genetic analyses of autistic individuals uncovered deleterious mutations in several K+ channel types strengthening the notion that their intrinsic dysfunction may play a central etiologic role in ASD. However, indirect implication of K+ channels in ASD has been also reported. For instance, loss of fragile X mental retardation protein (FMRP results in K+ channels deregulation, network dysfunction and ASD-like cognitive and behavioral symptoms. Therefore, this review provides an update on direct and indirect implications of K+ channels in ASDs. Owing to a mounting body of evidence associating a channelopathy pathogenesis to autism and that nearly 500 ion channel proteins are encoded by the human genome, we also propose to classify ASDs − whose susceptibility is significantly enhanced by ion channels defects, either in a monogenic or multigenic condition − in a new category named channelAutism Spectrum Disorder (channelASD; cASD and introduce a new taxonomy (e.g.: Kvx.y-channelASD and likewise Navx.y-channelASD, Cavx.y-channelASD; etc.. This review also highlights some degree of clinical and genetic overlap between K+ channelASDs and K+ channelepsies, whereby such correlation suggests that a subcategory characterized by a channelASD-channelepsy phenotype may be distinguished. Ultimately, this overview aims to further understand the different clinical subgroups and help parse out the distinct biological basis of autism that are essential to establish patient

  8. The hitchhiker's guide to the voltage-gated sodium channel galaxy.

    Science.gov (United States)

    Ahern, Christopher A; Payandeh, Jian; Bosmans, Frank; Chanda, Baron

    2016-01-01

    Eukaryotic voltage-gated sodium (Nav) channels contribute to the rising phase of action potentials and served as an early muse for biophysicists laying the foundation for our current understanding of electrical signaling. Given their central role in electrical excitability, it is not surprising that (a) inherited mutations in genes encoding for Nav channels and their accessory subunits have been linked to excitability disorders in brain, muscle, and heart; and (b) Nav channels are targeted by various drugs and naturally occurring toxins. Although the overall architecture and behavior of these channels are likely to be similar to the more well-studied voltage-gated potassium channels, eukaryotic Nav channels lack structural and functional symmetry, a notable difference that has implications for gating and selectivity. Activation of voltage-sensing modules of the first three domains in Nav channels is sufficient to open the channel pore, whereas movement of the domain IV voltage sensor is correlated with inactivation. Also, structure-function studies of eukaryotic Nav channels show that a set of amino acids in the selectivity filter, referred to as DEKA locus, is essential for Na(+) selectivity. Structures of prokaryotic Nav channels have also shed new light on mechanisms of drug block. These structures exhibit lateral fenestrations that are large enough to allow drugs or lipophilic molecules to gain access into the inner vestibule, suggesting that this might be the passage for drug entry into a closed channel. In this Review, we will synthesize our current understanding of Nav channel gating mechanisms, ion selectivity and permeation, and modulation by therapeutics and toxins in light of the new structures of the prokaryotic Nav channels that, for the time being, serve as structural models of their eukaryotic counterparts.

  9. Processor operated correlator with applications to laser Doppler signals

    DEFF Research Database (Denmark)

    Bisgaard, C.; Johnsen, B.; Hassager, Ole

    1984-01-01

    A 64-channel correlator is designed with application to the processing of laser Doppler anemometry signals in the range 200 Hz to 250 kHz. The correlator is processor operated to enable the consecutive sampling of 448 correlation functions at a rate up to 500 Hz. Software is described to identify...... a Doppler frequency from each correlation and the system is especially designed for transient flow signals. Doppler frequencies are determined with an accuracy of about 0.1%. Review of Scientific Instruments is copyrighted by The American Institute of Physics....

  10. Bubbles, Gating, and Anesthetics in Ion Channels

    OpenAIRE

    Roth, Roland, imp.; Gillespie, Dirk; Nonner, Wolfgang; Eisenberg, Robert E.

    2008-01-01

    We suggest that bubbles are the bistable hydrophobic gates responsible for the on-off transitions of single channel currents. In this view, many types of channels gate by the same physical mechanism—dewetting by capillary evaporation—but different types of channels use different sensors to modulate hydrophobic properties of the channel wall and thereby trigger and control bubbles and gating. Spontaneous emptying of channels has been seen in many simulations. Because of the physics involved, s...

  11. Comparing dependent robust correlations.

    Science.gov (United States)

    Wilcox, Rand R

    2016-11-01

    Let r1 and r2 be two dependent estimates of Pearson's correlation. There is a substantial literature on testing H0  : ρ1  = ρ2 , the hypothesis that the population correlation coefficients are equal. However, it is well known that Pearson's correlation is not robust. Even a single outlier can have a substantial impact on Pearson's correlation, resulting in a misleading understanding about the strength of the association among the bulk of the points. A way of mitigating this concern is to use a correlation coefficient that guards against outliers, many of which have been proposed. But apparently there are no results on how to compare dependent robust correlation coefficients when there is heteroscedasicity. Extant results suggest that a basic percentile bootstrap will perform reasonably well. This paper reports simulation results indicating the extent to which this is true when using Spearman's rho, a Winsorized correlation or a skipped correlation.

  12. Multi-channel probes to understand fission dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Mosby, Shea Morgan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-04-15

    Explaining the origin of the elements is a major outstanding question in nuclear astrophysics. Observed elemental abundance distribution shows strong nuclear physics effects. In conclusion, neutron-induced reactions are important for nuclear astrophysics and applied fields in nuclear energy and security. LANSCE has a program to address many of these questions directly with neutron beams on (near-)stable nuclei. Increasing demand for correlated data to test details of fission models poses additional challenges. Possibilities exist to extend existing experimental efforts to radioactive beam facilities. Kinematic focusing from using inverse kinematics has potential to circumvent some challenges associated with measuring correlations between fission output channels.

  13. Joint Linear Processing for an Amplify-and-Forward MIMO Relay Channel with Imperfect Channel State Information

    Directory of Open Access Journals (Sweden)

    Vandendorpe Luc

    2010-01-01

    Full Text Available The problem of jointly optimizing the source precoder, relay transceiver, and destination equalizer has been considered in this paper for a multiple-input-multiple-output (MIMO amplify-and-forward (AF relay channel, where the channel estimates of all links are assumed to be imperfect. The considered joint optimization problem is nonconvex and does not offer closed-form solutions. However, it has been shown that the optimization of one variable when others are fixed is a convex optimization problem which can be efficiently solved using interior-point algorithms. In this context, an iterative technique with the guaranteed convergence has been proposed for the AF MIMO relay channel that includes the direct link. It has been also shown that, for the double-hop relay case without the receive-side antenna correlations in each hop, the global optimality can be confirmed since the structures of the source precoder, relay transceiver, and destination equalizer have closed forms and the remaining joint power allocation can be solved using Geometric Programming (GP technique under high signal-to-noise ratio (SNR approximation. In the latter case, the performance of the iterative technique and the GP method has been compared with simulations to ensure that the iterative approach gives reasonably good solutions with an acceptable complexity. Moreover, simulation results verify the robustness of the proposed design when compared to the nonrobust design that assumes estimated channels as actual channels.

  14. Joint Linear Processing for an Amplify-and-Forward MIMO Relay Channel with Imperfect Channel State Information

    Science.gov (United States)

    Chalise, Batu K.; Vandendorpe, Luc

    2010-12-01

    The problem of jointly optimizing the source precoder, relay transceiver, and destination equalizer has been considered in this paper for a multiple-input-multiple-output (MIMO) amplify-and-forward (AF) relay channel, where the channel estimates of all links are assumed to be imperfect. The considered joint optimization problem is nonconvex and does not offer closed-form solutions. However, it has been shown that the optimization of one variable when others are fixed is a convex optimization problem which can be efficiently solved using interior-point algorithms. In this context, an iterative technique with the guaranteed convergence has been proposed for the AF MIMO relay channel that includes the direct link. It has been also shown that, for the double-hop relay case without the receive-side antenna correlations in each hop, the global optimality can be confirmed since the structures of the source precoder, relay transceiver, and destination equalizer have closed forms and the remaining joint power allocation can be solved using Geometric Programming (GP) technique under high signal-to-noise ratio (SNR) approximation. In the latter case, the performance of the iterative technique and the GP method has been compared with simulations to ensure that the iterative approach gives reasonably good solutions with an acceptable complexity. Moreover, simulation results verify the robustness of the proposed design when compared to the nonrobust design that assumes estimated channels as actual channels.

  15. Teager Correlation Function

    DEFF Research Database (Denmark)

    Bysted, Tommy Kristensen; Hamila, R.; Gabbouj, M.;

    1998-01-01

    A new correlation function called the Teager correlation function is introduced in this paper. The connection between this function, the Teager energy operator and the conventional correlation function is established. Two applications are presented. The first is the minimization of the Teager err...... norm and the second one is the use of the instantaneous Teager correlation function for simultaneous estimation of TDOA and FDOA (Time and Frequency Difference of Arrivals)....

  16. 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...

  17. Experimental study of two phase flow in inclined channel

    Energy Technology Data Exchange (ETDEWEB)

    Park, Goon Cherl; Lee, Tae Ho; Lee, Sang Won [Seoul National University, Seoul (Korea, Republic of)

    1997-07-01

    Local two-phase flow parameters were measured to investigate the internal flow structures of steam-water boiling flow in an inclined channel. The vapor phase local flow parameters, such as void fraction, bubble frequency, vapor velocity, interfacial area concentration and chord length, were measured, using two conductivity probe method, and local liquid phase velocity was measured by pitot tube. In order to investigate the effects of channel inclination on two phase flow structure, the experiments were conducted for three angles of inclination; 0 degree(vertical), 30 degree and 60 degree. The experimental flow conditions were confined to the liquid superficial velocities less than 1.4 m/sec and nearly atmospheric pressure, and the flow regime was limited to the subcooled boiling. Using the measured distributions of the local phasic parameters, correlations for the drift-flux parameters such as distribution parameter and drift velocity were proposed. Those correlations were compared with the available correlation applicable to the inclined channel by the calculation of average void fraction using the present data. 44 refs., 4 tabs., 88 figs. (author)

  18. Modified Biserial Correlation Coefficients.

    Science.gov (United States)

    Kraemer, Helena Chmura

    1981-01-01

    Asymptotic distribution theory of Brogden's form of biserial correlation coefficient is derived and large sample estimates of its standard error obtained. Its relative efficiency to the biserial correlation coefficient is examined. Recommendations for choice of estimator of biserial correlation are presented. (Author/JKS)

  19. Universal correlators from geometry

    Energy Technology Data Exchange (ETDEWEB)

    Dijkgraaf, Robbert [Institute for Theoretical Physics, University of Amsterdam, Valckenierstraat 65, 1018 XE Amsterdam (Netherlands); Korteweg-de Vries Institute for Mathematics, University of Amsterdam, Valckenierstraat 65, 1018 XE Amsterdam (Netherlands); Temuerhan, Mine; Sinkovics, Annamaria [Institute for Theoretical Physics, University of Amsterdam, Valckenierstraat 65, 1018 XE Amsterdam (Netherlands)]. E-mail: sinkovic@science.uva.nl

    2004-11-01

    Matrix model correlators show universal behaviour at short distances. We provide a derivation for these universal correlators by inserting probe branes in the underlying effective geometry. We generalize these results to study correlators of branes and their universal behaviour in the Calabi-Yau crystals, where we find a role for a generalized brane insertion. (author)

  20. Universal Correlators from Geometry

    Science.gov (United States)

    Dijkgraaf, Robbert; Sinkovics, Annamaria; Temurhan, Mine

    2004-11-01

    Matrix model correlators show universal behaviour at short distances. We provide a derivation for these universal correlators by inserting probe branes in the underlying effective geometry. We generalize these results to study correlators of branes and their universal behaviour in the Calabi-Yau crystals, where we find a role for a generalized brane insertion.

  1. Universal Correlators from Geometry

    CERN Document Server

    Dijkgraaf, R; Temurhan, M; Dijkgraaf, Robbert; Sinkovics, Annamaria; Temurhan, Mine

    2004-01-01

    Matrix model correlators show universal behaviour at short distances. We provide a derivation for these universal correlators by inserting probe branes in the underlying effective geometry. We generalize these results to study correlators of branes and their universal behaviour in the Calabi-Yau crystals, where we find a role for a generalized brane insertion.

  2. Lubiprostone: a chloride channel activator.

    Science.gov (United States)

    Lacy, Brian E; Levy, L Campbell

    2007-04-01

    In January 2006 the Food and Drug Administration approved lubiprostone for the treatment of chronic constipation in men and women aged 18 and over. Lubiprostone is categorized as a prostone, a bicyclic fatty acid metabolite of prostaglandin E1. Lubiprostone activates a specific chloride channel (ClC-2) in the gastrointestinal (GI) tract to enhance intestinal fluid secretion, which increases GI transit and improves symptoms of constipation. This article reviews the role of chloride channels in the GI tract, describes the structure, function, and pharmacokinetics of lubiprostone, and discusses clinically important data on this new medication.

  3. Quantum Markov Channels for Qubits

    CERN Document Server

    Daffer, S; McIver, J K; Daffer, Sonja; Wodkiewicz, Krzysztof; Iver, John K. Mc

    2003-01-01

    We examine stochastic maps in the context of quantum optics. Making use of the master equation, the damping basis, and the Bloch picture we calculate a non-unital, completely positive, trace-preserving map with unequal damping eigenvalues. This results in what we call the squeezed vacuum channel. A geometrical picture of the effect of stochastic noise on the set of pure state qubit density operators is provided. Finally, we study the capacity of the squeezed vacuum channel to transmit quantum information and to distribute EPR states.

  4. Interference Decoding for Deterministic Channels

    CERN Document Server

    Bandemer, Bernd

    2010-01-01

    An inner bound to the capacity region of a class of three user pair deterministic interference channels is presented. The key idea is to simultaneously decode the combined interference signal and the intended message at each receiver. It is shown that this interference decoding inner bound is strictly larger than the inner bound obtained by treating interference as noise, which includes interference alignment for deterministic channels. The gain comes from judicious analysis of the number of combined interference sequences in different regimes of input distributions and message rates.

  5. Quantum teleportation without classical channel

    Science.gov (United States)

    Al Amri, M.; Li, Zheng-Hong; Zubairy, M. Suhail

    2016-11-01

    For the first time, we show how quantum teleportation can be achieved without the assistance of classical channels. Our protocol does not need any pre-established entangled photon pairs beforehand. Just by utilizing quantum Zeno effect and couterfactual communication idea, we can achieve two goals; entangling a photon and an atom and also disentangling them by non-local interaction. Information is completely transferred from atom to photon with controllable disentanglement processes. More importantly, there is no need to confirm teleportation results via classical channels.

  6. Joint shadowing process in urban peer-to-peer radio channels

    OpenAIRE

    Wang, Zhenyu; Tameh, Eustace K.; Nix, Andrew R.

    2008-01-01

    For multihop and ad hoc networks, a conventional 1-D channel model cannot capture the spatial correlation of the shadowing processes. This paper investigates the joint spatial correlation property of the shadowing process for peer-to-peer (P2P) radio links in urban environments. When a fixed base station is assumed, statistical analysis reveals that the shadowing process is mainly a result of spatial displacement at the mobile station (MS). Furthermore, the joint correlation property of the M...

  7. Correlations in Werner States

    Institute of Scientific and Technical Information of China (English)

    DONG Li; LUO Shun-Long; XIU Xiao-Ming; LI Nan; GAO Ya-Jun; CHI Feng

    2008-01-01

    Werner states are paradigmatic examples of quantum states and play an innovative role in quantum information theory. In investigating the correlating capability of Werner states, we find the curious phenomenon that quantum correlations, as quantified by the entanglement of formation, may exceed the total correlations, as measured by the quantum mutual information. Consequently, though the entanglement of formation is so widely used in quantifying entanglement, it cannot be interpreted as a consistent measure of quantum correlations per se if we accept the folklore that total correlations are measured (or rather upper bounded) by the quantum mutual information.

  8. Experimental fully contextual correlations

    CERN Document Server

    Amselem, Elias; Lopez-Tarrida, Antonio J; Portillo, Jose R; Bourennane, Mohamed; Cabello, Adan

    2011-01-01

    Quantum correlations are contextual yet, in general, nothing prevents the existence of even more contextual correlations. We identify and test a simple noncontextual inequality in which the quantum violation cannot be improved by any hypothetical post-quantum resource, and use it to experimentally obtain correlations in which the maximum noncontextual content, defined as the maximum fraction of noncontextual correlations, is less than 0.06. Our correlations are experimentally generated from the outcomes of sequential compatible measurements on a four-state quantum system encoded in the polarization and path of a single photon.

  9. Ion channel expression patterns in glioblastoma stem cells with functional and therapeutic implications for malignancy

    Science.gov (United States)

    Pollak, Julia; Rai, Karan G.; Funk, Cory C.; Arora, Sonali; Lee, Eunjee; Zhu, Jun; Price, Nathan D.; Paddison, Patrick J.; Ramirez, Jan-Marino; Rostomily, Robert C.

    2017-01-01

    Ion channels and transporters have increasingly recognized roles in cancer progression through the regulation of cell proliferation, migration, and death. Glioblastoma stem-like cells (GSCs) are a source of tumor formation and recurrence in glioblastoma multiforme, a highly aggressive brain cancer, suggesting that ion channel expression may be perturbed in this population. However, little is known about the expression and functional relevance of ion channels that may contribute to GSC malignancy. Using RNA sequencing, we assessed the enrichment of ion channels in GSC isolates and non-tumor neural cell types. We identified a unique set of GSC-enriched ion channels using differential expression analysis that is also associated with distinct gene mutation signatures. In support of potential clinical relevance, expression of selected GSC-enriched ion channels evaluated in human glioblastoma databases of The Cancer Genome Atlas and Ivy Glioblastoma Atlas Project correlated with patient survival times. Finally, genetic knockdown as well as pharmacological inhibition of individual or classes of GSC-enriched ion channels constrained growth of GSCs compared to normal neural stem cells. This first-in-kind global examination characterizes ion channels enriched in GSCs and explores their potential clinical relevance to glioblastoma molecular subtypes, gene mutations, survival outcomes, regional tumor expression, and experimental responses to loss-of-function. Together, the data support the potential biological and therapeutic impact of ion channels on GSC malignancy and provide strong rationale for further examination of their mechanistic and therapeutic importance. PMID:28264064

  10. Improving MIMO-OFDM decision-directed channel estimation by utilizing error-correcting codes

    Directory of Open Access Journals (Sweden)

    P. Beinschob

    2009-05-01

    Full Text Available In this paper a decision-directed Multiple-Input Multiple-Output (MIMO channel tracking algorithm is enhanced to raise the channel estimate accuracy. While DDCE is prone to error propagation the enhancement employs channel decoding in the tracking process. Therefore, a quantized block of symbols is checked on consistency via the channel decoder, possibly corrected and then used. This yields a more robust tracking of the channel in terms of bit error rate and improves the channel estimate under certain conditions.

    Equalization is performed to prove the feasibility of the obtained channel estimate. Therefore a combined signal consisting of data and pilot symbols is sent. Adaptive filters are applied to exploit correlations in time, frequency and spatial domain. By using good error-correcting coding schemes like Turbo Codes or Low Density Parity Check (LDPC codes, adequate channel estimates can be acquired even at low signal to noise ratios (SNR. The proposed algorithm among two others is applied for channel estimation and equalization and results are compared.

  11. Dynamic Analysis of Coolant Channel and Its Internals of Indian 540 MWe PHWR Reactor

    Directory of Open Access Journals (Sweden)

    N. Dharmaraju

    2008-01-01

    Full Text Available The horizontal coolant channel is one of the important parts of primary heat transport system in PHWR type of reactors. There are in all 392 channels in the core of Indian 540 MWe reactor. Each channel houses 13 natural uranium fuel bundles and shielding and sealing plugs one each on either side of the channel. The heavy water coolant flows through the coolant channel and carries the nuclear heat to outside the core for steam generation and power production in the turbo-generator. India has commissioned one 540 MWe PHWR reactor in September 2005 and another similar unit will be going into operation very shortly. For a complete dynamic study of the channel and its internals under the influence of high coolant flow, experimental and modeling studies have been carried out. A good correlation has been achieved between the results of experimental and analytical models. The operating life of a typical coolant channel typically ranges from 10 to 15 full-power years. Towards the end of its operating life, its health monitoring becomes an important activity. Vibration diagnosis plays an important role as a tool for life management of coolant. Through the study of dynamic characteristics of the coolant channel under simulated loading condition, an attempt has been made to develop a diagnostics to monitor the health of the coolant channel over its operating life. A study has been also carried out to characterize the fuel vibration under different flow condition.

  12. Alternative splicing modulates Kv channel clustering through a molecular ball and chain mechanism

    Science.gov (United States)

    Zandany, Nitzan; Marciano, Shir; Magidovich, Elhanan; Frimerman, Teddy; Yehezkel, Rinat; Shem-Ad, Tzilhav; Lewin, Limor; Abdu, Uri; Orr, Irit; Yifrach, Ofer

    2015-03-01

    Ion channel clustering at the post-synaptic density serves a fundamental role in action potential generation and transmission. Here, we show that interaction between the Shaker Kv channel and the PSD-95 scaffold protein underlying channel clustering is modulated by the length of the intrinsically disordered C terminal channel tail. We further show that this tail functions as an entropic clock that times PSD-95 binding. We thus propose a ‘ball and chain’ mechanism to explain Kv channel binding to scaffold proteins, analogous to the mechanism describing channel fast inactivation. The physiological relevance of this mechanism is demonstrated in that alternative splicing of the Shaker channel gene to produce variants of distinct tail lengths resulted in differential channel cell surface expression levels and clustering metrics that correlate with differences in affinity of the variants for PSD-95. We suggest that modulating channel clustering by specific spatial-temporal spliced variant targeting serves a fundamental role in nervous system development and tuning.

  13. Experimental investigation on the CHF in the narrow rectangular channel under the downward flow condition

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Huiyung; Yun, Byongjo; Bak, Jinyeong [Pusan national university, Pusan (Korea, Republic of); Park, Jonghark; Chae, Heetaek; Park, Cheol [KAERI, Daejeon (Korea, Republic of)

    2015-05-15

    The new research reactor under constructing in Kijang adopts a plate-type-fuel with downward flow cooling to prevent release of radioactive substance at pool surface. The thermal hydraulic design for the narrow rectangular channel differs from that for rod bundle channel. The licensing for construction of research reactor requires thermal hydraulic safety analysis of narrow rectangular channel. In the thermal hydraulic safety analysis, critical heat flux (CHF) on the fuel surface is considerably important to determine power and safety margin. The objectives of present study are, therefore, to carry out the experiment of CHF for downward flow in narrow rectangular channel, to obtain the correlation of CHF prediction applicable to a subchannel of plate-type-fuel. CHF experiments were carried out in the narrow rectangular channel simulating plate-type-fuel for research reactors under the downward flow condition. With the investigation of CHF data of the present experiment and previous studies, a new CHF correlation was proposed for the downward flow in the subchannel of plate-type-fuel. The predicted CHF by the new CHF correlation shows good agreement with experimental data in the present study. However, the correlation was based on the limited number of experimental data under low-flow conditions. Therefore, further studies for more data are needed to generalize the CHF correlation.

  14. Correlated dewetting patterns in thin polystyrene films

    Energy Technology Data Exchange (ETDEWEB)

    Neto, Chiara [Department of Applied Physics, University of Ulm, Albert Einstein Allee 11, D-89069 Ulm (Germany); Jacobs, Karin [Department of Applied Physics, University of Ulm, Albert Einstein Allee 11, D-89069 Ulm (Germany); Seemann, Ralf [Department of Applied Physics, University of Ulm, Albert Einstein Allee 11, D-89069 Ulm (Germany); Blossey, Ralf [Centre for Bioinformatics, Saarland University, PO Box 151150, D-66041 Saarbruecken (Germany); Becker, Juergen [Institute of Applied Mathematics, University of Bonn, Beringstr. 6, D-53115 Bonn (Germany); Gruen, Guenther [Institute of Applied Mathematics, University of Bonn, Beringstr. 6, D-53115 Bonn (Germany)

    2003-01-15

    We describe preliminary results of experiments and simulations concerned with the dewetting of thin polystyrene films (thickness < 7 nm) on top of silicon oxide wafers. In the experiments we scratched an initially flat film with an atomic force microscopy (AFM) tip, producing dry channels in the film. Dewetting of the films was imaged in situ using AFM and a correlated pattern of holes ('satellite holes') was observed along the rims bordering the channels. The development of this complex film rupture process was simulated and the results of experiments and simulations are in good agreement. On the basis of these results, we attempt to explain the appearance of satellite holes and their positions relative to pre-existing holes.

  15. Correlated dewetting patterns in thin polystyrene films

    CERN Document Server

    Neto, C; Seemann, R; Blossey, R; Becker, J; Grün, G

    2003-01-01

    We describe preliminary results of experiments and simulations concerned with the dewetting of thin polystyrene films (thickness < 7 nm) on top of silicon oxide wafers. In the experiments we scratched an initially flat film with an atomic force microscopy (AFM) tip, producing dry channels in the film. Dewetting of the films was imaged in situ using AFM and a correlated pattern of holes ('satellite holes') was observed along the rims bordering the channels. The development of this complex film rupture process was simulated and the results of experiments and simulations are in good agreement. On the basis of these results, we attempt to explain the appearance of satellite holes and their positions relative to pre-existing holes.

  16. ERP Energy and Cognitive Activity Correlates

    Science.gov (United States)

    Schillaci, Michael Jay; Vendemia, Jennifer M. C.

    2014-03-01

    We propose a novel analysis approach for high-density event related scalp potential (ERP) data where the integrated channel-power is used to attain an energy density functional state for channel-clusters of neurophysiological significance. The method is applied to data recorded during a two-stimulus, directed lie paradigm and shows that deceptive responses emit between 8% and 10% less power. A time course analysis of these cognitive activity measures over posterior and anterior regions of the cortex suggests that neocortical interactions, reflecting the differing workload demands during executive and semantic processes, take about 50% longer for the case of deception. These results suggest that the proposed method may provide a useful tool for the analysis of ERP correlates of high-order cognitive functioning. We also report on a possible equivalence between the energy functional distribution and near-infrared signatures that have been measured with other modalities.

  17. Color correlation for the recognition of Vibrio cholerae O1 in seawater

    Science.gov (United States)

    Mourino-Perez, Rosa R.; Alvarez-Borrego, Josue

    1999-07-01

    Application of color correlation optical systems for the recognition of Vibrio cholerae 01 in seawater samples with matched filters and phase only filters recorded in holographic plates in three channels (RGB).

  18. Design of Transmitter for CDM Based 2×2 Multiple Input Multiple Output Channel Sounder for Multipath Delay Measurement

    Directory of Open Access Journals (Sweden)

    M. H. Ullah

    2012-01-01

    Full Text Available Problem statement: Multiple Input Multiple Output (MIMO wireless communication system is an innovative solution to improve the bandwidth efficiency by exploiting multipath-richness of the propagation environment. The degree of multipath-richness of the channel will determine the capacity gain attainable by MIMO deployment. Approach: Therefore, it is very important to have accurate knowledge of the propagation environment/radio channel before MIMO implement. The radio channel behavior can be anticipated by channel measurement or channel sounding. Code Division Multiplexing (CDM is one of the channel sounding techniques that allow accurate measurement at the cost of hardware complexity. CDM based channel sounder, requires code with excellent auto-correlation and cross-correlation properties which generally difficult to be achieved simultaneously. Results: In this study, an efficient transmitter for CDM-based 2×2 MIMO channel sounding technique with Loosely Synchronous (LS codes is designed. Simulation results shows that the channel sounding scheme using LS codes gives very good performance for measuring 2×2 MIMO channel behavior. The BPSK transmitter is designed using MATLAB, Verilog and Xilinx system generator blocks. Conclusion: The whole design is simulated as a single ISE project by using ModelSim simulation tool and compiled using ISE 9.2. However the proposed design of transmitter using LS code of length 8190 bits can measure multipath delay of minimum 0.13 μs and maximum 520 μs.

  19. On the correlation analysis of electric field inside jet engine

    OpenAIRE

    A Krishna; Khattab, T.; Abdelaziz, A.F.; Guizani, M.

    2014-01-01

    A Simple channel modeling method based on correlation analysis of the electric field inside jet engine is presented. The analysis of the statistical propagation characteristics of electromagnetic field inside harsh jet engine environment is presented by using `Ansys® HFSS'. In this paper, we propose a method to locate the best position for receiving probes inside jet engine with minimum correlation between the receiver points which have strong average electric field. Moreover, a MIMO system c...

  20. Ion channels in development and cancer.

    Science.gov (United States)

    Bates, Emily

    2015-01-01

    Ion channels have emerged as regulators of developmental processes. In model organisms and in people with mutations in ion channels, disruption of ion channel function can affect cell proliferation, cell migration, and craniofacial and limb patterning. Alterations of ion channel function affect morphogenesis in fish, frogs, mammals, and flies, demonstrating that ion channels have conserved roles in developmental processes. One model suggests that ion channels affect proliferation and migration through changes in cell volume. However, ion channels have not explicitly been placed in canonical developmental signaling cascades until recently. This review gives examples of ion channels that influence developmental processes, offers a potential underlying molecular mechanism involving bone morphogenetic protein (BMP) signaling, and finally explores exciting possibilities for manipulating ion channels to influence cell fate for regenerative medicine and to impact disease.

  1. Statistical Hot Channel Analysis for the NBSR

    Energy Technology Data Exchange (ETDEWEB)

    Cuadra A.; Baek J.

    2014-05-27

    A statistical analysis of thermal limits has been carried out for the research reactor (NBSR) at the National Institute of Standards and Technology (NIST). The objective of this analysis was to update the uncertainties of the hot channel factors with respect to previous analysis for both high-enriched uranium (HEU) and low-enriched uranium (LEU) fuels. Although uncertainties in key parameters which enter into the analysis are not yet known for the LEU core, the current analysis uses reasonable approximations instead of conservative estimates based on HEU values. Cumulative distribution functions (CDFs) were obtained for critical heat flux ratio (CHFR), and onset of flow instability ratio (OFIR). As was done previously, the Sudo-Kaminaga correlation was used for CHF and the Saha-Zuber correlation was used for OFI. Results were obtained for probability levels of 90%, 95%, and 99.9%. As an example of the analysis, the results for both the existing reactor with HEU fuel and the LEU core show that CHFR would have to be above 1.39 to assure with 95% probability that there is no CHF. For the OFIR, the results show that the ratio should be above 1.40 to assure with a 95% probability that OFI is not reached.

  2. Fading Characteristics and Capacity of Deterministic Downlink MIMO Fading Channel with Non-Isotropic Scattering

    Institute of Scientific and Technical Information of China (English)

    WUGang; TANGYouxi; LIShaoqian

    2004-01-01

    A novel deterministic model for downlink Multiple-input multiple-output (MIMO) channel with nonisotropic scattering around Mobile station (MS) is presented. For both Space-time codes (STC) scenario and Downlink beam-forming (DBF) scenario, statistical fading characteristics, including level-crossing rate, average duration of fades, and envelope cross-correlation are investigated in frequency-selective fast fading channels. The impact of non-isotropic scattering on capacity of MIMO channel is also studied. Numerical results show that loss of ergodic capacity caused by non-isotropic scattering almost reach 1bit/Hz/s for a 2×2 MIMO channel and maximum achievable capacity will be degraded mainly by transmit correlation rather than non-isotropic scattering.

  3. Correlations between resonances in a statistical scattering model

    CERN Document Server

    Gorin, T; Müller, M; Rotter, I; Seligman, T H

    1997-01-01

    The distortion of the regular motion in a quantum system by its coupling to the continuum of decay channels is investigated. The regular motion is described by means of a Poissonian ensemble. We focus on the case of only few channels K<10. The coupling to the continuum induces two main effects, due to which the distorted system differs from a chaotic system (described by a Gaussian ensemble): 1. The width distribution for large coupling becomes broader than the corresponding $\\chi^2_K$ distribution in the GOE case. 2. Due to the coupling to the continuum, correlations are induced not only between the positions of the resonances but also between positions and widths. These correlations remain even in the strong coupling limit. In order to explain these results, an asymptotic expression for the width distribution is derived for the one channel case. It relates the width of a trapped resonance state to the distance between its two neighboring levels.

  4. Correlations between resonances in a statistical scattering model

    Energy Technology Data Exchange (ETDEWEB)

    Gorin, T. [Technische Univ. Dresden (Germany). Inst. fuer Theoretische Physik]|[Forschungszentrum Rossendorf e.V. (FZR), Dresden (Germany). Inst. fuer Kern- und Hadronenphysik; Dittes, F.M. [Forschungszentrum Rossendorf e.V. (FZR), Dresden (Germany). Inst. fuer Kern- und Hadronenphysik; Mueller, M. [Centro Internacional de Ciencias, Cuernavaca (Mexico); Rotter, I. [Technische Univ. Dresden (Germany). Inst. fuer Theoretische Physik]|[Forschungszentrum Rossendorf e.V. (FZR), Dresden (Germany). Inst. fuer Kern- und Hadronenphysik; Seligman, T.H. [Centro Internacional de Ciencias, Cuernavaca (Mexico)

    1997-01-01

    The distortion of the regular motion in a quantum system by its coupling to the continuum of decay channels is investigated. The regular motion is described by means of a Poissonian ensemble. We focus on the case of only few channels K < 10. The coupling to the continuum induces two main effects, due to which the distorted system differs from a chaotic system (described by a Gaussian ensemble): 1. The width distribution for large coupling becomes broader than the corresponding {chi}{sup 2}{sub K} distribution in the GOE case. 2. Due to the coupling to the continuum, correlations are induced not only between the positions of the resonances but also between positions and widths. These correlations remain even in the strong coupling limit. In order to explain these results, an asymptotic expression for the width distribution is derived for the one channel case. It relates the width of a trapped resonance state to the distance between its two neighboring levels. (orig.)

  5. Improved Ion-Channel Biosensors

    Science.gov (United States)

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

    2004-01-01

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

  6. Visualizing multi-channel networks

    DEFF Research Database (Denmark)

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

    2014-01-01

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

  7. 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

  8. Driven tracers in narrow channels

    Science.gov (United States)

    Cividini, J.; Mukamel, D.; Posch, H. A.

    2017-01-01

    Steady-state properties of a driven tracer moving in a narrow two-dimensional (2D) channel of quiescent medium are studied. The tracer drives the system out of equilibrium, perturbs the density and pressure fields, and gives the bath particles a nonzero average velocity, creating a current in the channel. Three models in which the confining effect of the channel is probed are analyzed and compared in this study: the first is the simple symmetric exclusion process (SSEP), for which the stationary density profile and the pressure on the walls in the frame of the tracer are computed. We show that the tracer acts like a dipolar source in an average velocity field. The spatial structure of this 2D strip is then simplified to a one-dimensional (1D) SSEP, in which exchanges of position between the tracer and the bath particles are allowed. Using a combination of mean-field theory and exact solution in the limit where no exchange is allowed gives good predictions of the velocity of the tracer and the density field. Finally, we show that results obtained for the 1D SSEP with exchanges also apply to a gas of overdamped hard disks in a narrow channel. The correspondence between the parameters of the SSEP and of the gas of hard disks is systematic and follows from simple intuitive arguments. Our analytical results are checked numerically.

  9. Higgs in Bosonic channel (CMS)

    CERN Document Server

    Gori, Valentina

    2015-01-01

    All the investigated properties result to be fully consistent with the SM predictions: the signal strength and the signal strength modifiers are consistent with unity in all the bosonic channels considered; the hypothesis of a scalar particle is strongly favored, ag...

  10. Store-Operated Calcium Channels.

    Science.gov (United States)

    Prakriya, Murali; Lewis, Richard S

    2015-10-01

    Store-operated calcium channels (SOCs) are a major pathway for calcium signaling in virtually all metozoan cells and serve a wide variety of functions ranging from gene expression, motility, and secretion to tissue and organ development and the immune response. SOCs are activated by the depletion of Ca(2+) from the endoplasmic reticulum (ER), triggered physiologically through stimulation of a diverse set of surface receptors. Over 15 years after the first characterization of SOCs through electrophysiology, the identification of the STIM proteins as ER Ca(2+) sensors and the Orai proteins as store-operated channels has enabled rapid progress in understanding the unique mechanism of store-operate calcium entry (SOCE). Depletion of Ca(2+) from the ER causes STIM to accumulate at ER-plasma membrane (PM) junctions where it traps and activates Orai channels diffusing in the closely apposed PM. Mutagenesis studies combined with recent structural insights about STIM and Orai proteins are now beginning to reveal the molecular underpinnings of these choreographic events. This review describes the major experimental advances underlying our current understanding of how ER Ca(2+) depletion is coupled to the activation of SOCs. Particular emphasis is placed on the molecular mechanisms of STIM and Orai activation, Orai channel properties, modulation of STIM and Orai function, pharmacological inhibitors of SOCE, and the functions of STIM and Orai in physiology and disease.

  11. EPICS: Channel Access security design

    Energy Technology Data Exchange (ETDEWEB)

    Kraimer, M.; Hill, J.

    1994-05-01

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

  12. 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

  13. 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.

  14. 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

  15. Explore Interregional EEG Correlations Changed by Sport Training Using Feature Selection

    OpenAIRE

    2016-01-01

    This paper investigated the interregional correlation changed by sport training through electroencephalography (EEG) signals using the techniques of classification and feature selection. The EEG data are obtained from students with long-time professional sport training and normal students without sport training as baseline. Every channel of the 19-channel EEG signals is considered as a node in the brain network and Pearson Correlation Coefficients are calculated between every two nodes as the...

  16. 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.

  17. 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

  18. Transceiver Design for Dual-Hop Nonregenerative MIMO-OFDM Relay Systems Under Channel Uncertainties

    Science.gov (United States)

    Xing, Chengwen; Ma, Shaodan; Wu, Yik-Chung; Ng, Tung-Sang

    2010-12-01

    In this paper, linear transceiver design for dual-hop non-regenerative (amplify-and-forward (AF)) MIMO-OFDM systems under channel estimation errors is investigated. Second order moments of channel estimation errors in the two hops are first deduced. Then based on the Bayesian framework, joint design of linear forwarding matrix at the relay and equalizer at the destination under channel estimation errors is proposed to minimize the total mean-square-error (MSE) of the output signal at the destination. The optimal designs for both correlated and uncorrelated channel estimation errors are considered. The relationship with existing algorithms is also disclosed. Moreover, this design is extended to the joint design involving source precoder design. Simulation results show that the proposed design outperforms the design based on estimated channel state information only.

  19. General Framework and Advanced Information Theoretical Results on Eigenmode MIMO Channel Inversion

    Directory of Open Access Journals (Sweden)

    J. Sykora

    2005-09-01

    Full Text Available This paper provides general and deep investigation of adaptationstrategies based on the channel inversion policy regarding wide varietyof channel modes. Our novel approach to the eigenmode space MIMOchannel inversion policy relies on the eigenmode space reductionproviding zero transmission outage probability regardless of theinstantaneous channel fading realization. Very detailed survey of thefeatures of channel capacity is provided in analytical closed formexpressions supported by many particular numerical results (Alamoutischeme is included. The correlated MIMO channel is involved into ourtreatment as well. We also address the trade-off between the capacityand transmission outage probability. The novel results are developed inthe general framework with exhaustive summary of well known SISO andSIMO results.

  20. Extract from Buthus martensii Karsch is associated with potassium channels on glioma cells

    Institute of Scientific and Technical Information of China (English)

    Mingxian Li; Hongmei Meng; Shao Wang; Min Huang; Li Cui; Weihong Lin

    2011-01-01

    Catilan extracted from Leiurus quinquestriatus is a specific ion channel blocker.It can specifically bind chloride channels of glioma cells and kill these tumor cells.The questions remain as to whether antigliomatin,the extract from scorpion venom of Buthus martensii Karsch in China,can inhibit glioma growth,and whether this inhibition is correlated with ion channels of tumor cells.The present study treated rat C6 glioma cells with 0.8,1.2,and 1.6 μg/mL antigliomatin for 20 hours.Whole-cell patch clamp technique showed that antigliomatin delayed rectifier potassium channels of C6 glioma cells.Antigliomatin inhibited tumor growth,which could potentially involve potassium channels of tumor cells.

  1. Pilot Beam Pattern Design for Channel Estimation in Massive MIMO Systems

    Science.gov (United States)

    Noh, Song; Zoltowski, Michael D.; Sung, Youngchul; Love, David J.

    2014-10-01

    In this paper, the problem of pilot beam pattern design for channel estimation in massive multiple-input multiple-output systems with a large number of transmit antennas at the base station is considered, and a new algorithm for pilot beam pattern design for optimal channel estimation is proposed under the assumption that the channel is a stationary Gauss-Markov random process. The proposed algorithm designs the pilot beam pattern sequentially by exploiting the properties of Kalman filtering and the associated prediction error covariance matrices and also the channel statistics such as spatial and temporal channel correlation. The resulting design generates a sequentially-optimal sequence of pilot beam patterns with low complexity for a given set of system parameters. Numerical results show the effectiveness of the proposed algorithm.

  2. Vectorized data acquisition and fast triple-correlation integrals for Fluorescence Triple Correlation Spectroscopy.

    Science.gov (United States)

    Ridgeway, William K; Millar, David P; Williamson, James R

    2013-04-01

    Fluorescence Correlation Spectroscopy (FCS) is widely used to quantitate reaction rates and concentrations of molecules in vitro and in vivo. We recently reported Fluorescence Triple Correlation Spectroscopy (F3CS), which correlates three signals together instead of two. F3CS can analyze the stoichiometries of complex mixtures and detect irreversible processes by identifying time-reversal asymmetries. Here we report the computational developments that were required for the realization of F3CS and present the results as the Triple Correlation Toolbox suite of programs. Triple Correlation Toolbox is a complete data analysis pipeline capable of acquiring, correlating and fitting large data sets. Each segment of the pipeline handles error estimates for accurate error-weighted global fitting. Data acquisition was accelerated with a combination of off-the-shelf counter-timer chips and vectorized operations on 128-bit registers. This allows desktop computers with inexpensive data acquisition cards to acquire hours of multiple-channel data with sub-microsecond time resolution. Off-line correlation integrals were implemented as a two delay time multiple-tau scheme that scales efficiently with multiple processors and provides an unprecedented view of linked dynamics. Global fitting routines are provided to fit FCS and F3CS data to models containing up to ten species. Triple Correlation Toolbox is a complete package that enables F3CS to be performed on existing microscopes.

  3. Channel Incision and Suspended Sediment Delivery at Caspar Creek, Mendocino County, California.

    Science.gov (United States)

    Dewey, N. J.; Lisle, T. E.; Reid, L. M.

    2003-12-01

    Tributary and headwater valleys in the Caspar Creek watershed, in coastal Mendocino County, California, show signs of incision along much of their lengths. An episode of incision followed initial-entry logging which took place between 1860 and 1906. Another episode of incision cut into skid-trails created for second-entry logging in the 1970's. Gullies resulting from both of these episodes of incision are sensitive to hydrologic fluctuations and feature active headcuts, deepening plungepools, and unstable banks, which continue to contribute sediment to the Caspar Creek channel network. Headcuts are numerous in each channel. In some cases headcuts define the upstream extent of an incised reach; in many cases headcuts migrate up previously incised reaches, increasing the depth of incision. Surveys indicate that bank retreat, plunge pool deepening, and headcut retreat all contributed sediment to the channels between 2000 and 2003. Since bank walls have considerably more surface area than headwalls per given length of channel, and headcuts have largely migrated into positions temporarily constrained by resistant lips, bankwall retreat appears to be a more significant chronic source of sediment than headwall retreat. Stream gage records show that some channels consistently deliver higher levels of suspended sediment than others. In comparing channels, ongoing levels of suspended sediment delivery correlate well with total amount of exposed channel bank (depth of incision integrated over length of channel) in the reaches upstream of stream gages. On an annual to decadal time-scale, rates of suspended sediment delivery per unit area of catchment correlate better with the amount of exposed bank area in reaches upstream of stream gages, than with the volume of sediment delivered by landslide events, with total catchment area, or with peak storm flow per unit area. The correlation between amount of exposed bank area and ongoing levels of suspended sediment delivery is

  4. Secrecy in Cooperative Relay Broadcast Channels

    CERN Document Server

    Ekrem, E

    2008-01-01

    We investigate the effects of user cooperation on the secrecy of broadcast channels by considering a cooperative relay broadcast channel. We show that user cooperation can increase the achievable secrecy region. We propose an achievable scheme that combines Marton's coding scheme for broadcast channels and Cover and El Gamal's compress-and-forward scheme for relay channels. We derive outer bounds for the rate-equivocation region using auxiliary random variables for single-letterization. Finally, we consider a Gaussian channel and show that both users can have positive secrecy rates, which is not possible for scalar Gaussian broadcast channels without cooperation.

  5. 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.

  6. The effect of correlated observations on the performance of distributed estimation

    KAUST Repository

    Ahmed, Mohammed

    2013-12-01

    Estimating unknown signal in Wireless Sensor Networks (WSNs) requires sensor nodes to transmit their observations of the signal over a multiple access channel to a Fusion Center (FC). The FC uses the received observations, which is corrupted by observation noise and both channel fading and noise, to find the minimum Mean Square Error (MSE) estimate of the signal. In this paper, we investigate the effect of the source-node correlation (the correlation between sensor node observations and the source signal) and the inter-node correlation (the correlation between sensor node observations) on the performance of the Linear Minimum Mean Square Error (LMMSE) estimator for three correlation models in the presence of channel fading. First, we investigate the asymptotic behavior of the achieved distortion (i.e., MSE) resulting from both the observation and channel noise in a non-fading channel. Then, the effect of channel fading is considered and the corresponding distortion outage probability, the probability that the distortion exceeds a certain value, is found. By representing the distortion as a ratio of indefinite quadratic forms, a closed-form expression is derived for the outage probability that shows its dependency on the correlation. Finally, the new representation of the outage probability allows us to propose an iterative solution for the power allocation problem to minimize the outage probability under total and individual power constraints. Numerical simulations are provided to verify our analytic results. © 2013 IEEE.

  7. Investigation of Heat Transfer in Mini Channels using Planar Laser Induced Fluorescence

    DEFF Research Database (Denmark)

    Bøgild, Morten Ryge; Poulsen, Jonas Lundsted; Rath, Emil Zacho

    2012-01-01

    In this paper an experimental investigation of the heat transfer in mini channels with a hydraulic diameter of 889 m is conducted. The method used is planar laser induceduorescence (PLIF), which uses the principle of laser excitation of rhodamine B in water. The goal of this study is to validate...... the applicability of PLIF to determine the convective heat transfer coecient in mini channels against conventional correlations of the convective heat transfer coecient. The applicability of the conventional theory in micro and mini channels has been discussed by several researchers, but to the authors knowledge...

  8. Design and implementation of photon correlator based on C8051F

    Science.gov (United States)

    Shen, Jin; Li, Yuming; Liu, Wei; Yang, Yan; Cheng, Yanting

    2008-02-01

    Correlation techniques are widely used to extract spectral information from light scattering and other stochastic processes. Within the photon correlation system, the correlating operation must work at a high speed. In this paper, a photon correlator based on microcontroller C8051F was developed. In the photon correlator, the work of counting and scratch is completed by the two 4-bits binary adder 74F161, which is connected to form an 8-bits adder., and the correlation operation of every channel is carried out by the software of C8051F. By probably choosing high speed devices counting of 10ns in width pulses can be counted. The correlation operations including multiplying and addition operation of 56 channels with the circulation program within 3μs were made in interrupt service routine of the C8051F. The work in this paper can be applied in the ultra-fine particle sizing with photon correlation spectroscopy.

  9. Receiver-channel based adaptive blind equalization approach for GPS dynamic multipath mitigation

    Institute of Scientific and Technical Information of China (English)

    Zhao Yun; Xue Xiaonan; Zhang Tingfei

    2013-01-01

    Aiming at mitigating multipath effect in dynamic global positioning system (GPS) satellite navigation applications,an approach based on channel blind equalization and real-time recursive least square (RLS) algorithm is proposed,which is an application of the wireless communication channel equalization theory to GPS receiver tracking loops.The blind equalization mechanism builds upon the detection of the correlation distortion due to multipath channels; there-fore an increase in the number of correlator channels is required compared with conventional GPS receivers.An adaptive estimator based on the real-time RLS algorithm is designed for dynamic estimation of multipath channel response.Then,the code and carrier phase receiver tracking errors are compensated by removing the estimated multipath components from the correlators' outputs.To demonstrate the capabilities of the proposed approach,this technique is integrated into a GPS software receiver connected to a navigation satellite signal simulator,thus simulations under controlled dynamic multipath scenarios can be carried out.Simulation results show that in a dynamic and fairly severe multipath environment,the proposed approach achieves simultaneously instantaneous accurate multipath channel estimation and significant multipath tracking errors reduction in both code delay and carrier phase.

  10. Hydraulic resistance of plane channels and annulus with different roughness on opposite walls

    Science.gov (United States)

    Korsun, A. S.; Kutsenko, K. V.; Pisarevsky, M. I.; Fedoseev, V. N.; Balberkina, Y. N.

    2017-03-01

    A new method for prediction of hydraulic resistance for a turbulent flow in plane channels and annulus is proposed. In spite of the importance of this issue, only very few publications devoted to the investigation into hydrodynamics in these channels are available, and there are no methods for predicting hydraulic resistance of a flow in these channels at all. The flow in channels with different roughness on the walls is described using the Prandtl semiempirical theory of a turbulent boundary layer. The flow in a channel cross-section is divided into two noninteracting layers of different thickness flowing along the walls with different roughness. The basic balance correlations are derived for a plane channel. To match the velocity profiles of both layers at the interface point, a logarithmic velocity profile is used. This yields a closed system of equations for predicting hydraulic resistance in plane channels with a given different roughness on opposite walls. It is demonstrated that the obtained correlation may be used for predicting hydraulic resistance in annulus as well. Experiments were carried out with a water flow in an annulus. Each annuli consisted of a pipe having a smooth wall into which a rod with artificial roughness on the surface was inserted coaxially. Two types of roughness were investigated: trapezoid and threadlike ones. Comparison of the predictions with the experimental data confirmed the validity of the proposed method. It can be used in designing flowpaths of various power installations.

  11. Heat transfer in a compact heat exchanger containing rectangular channels and using helium gas

    Science.gov (United States)

    Olson, D. A.

    1991-01-01

    Development of a National Aerospace Plane (NASP), which will fly at hypersonic speeds, require novel cooling techniques to manage the anticipated high heat fluxes on various components. A compact heat exchanger was constructed consisting of 12 parallel, rectangular channels in a flat piece of commercially pure nickel. The channel specimen was radiatively heated on the top side at heat fluxes of up to 77 W/sq cm, insulated on the back side, and cooled with helium gas flowing in the channels at 3.5 to 7.0 MPa and Reynolds numbers of 1400 to 28,000. The measured friction factor was lower than that of the accepted correlation for fully developed turbulent flow, although the uncertainty was high due to uncertainty in the channel height and a high ratio of dynamic pressure to pressure drop. The measured Nusselt number, when modified to account for differences in fluid properties between the wall and the cooling fluid, agreed with past correlations for fully developed turbulent flow in channels. Flow nonuniformity from channel-to-channel was as high as 12 pct above and 19 pct below the mean flow.

  12. Learning efficient correlated equilibria

    KAUST Repository

    Borowski, Holly P.

    2014-12-15

    The majority of distributed learning literature focuses on convergence to Nash equilibria. Correlated equilibria, on the other hand, can often characterize more efficient collective behavior than even the best Nash equilibrium. However, there are no existing distributed learning algorithms that converge to specific correlated equilibria. In this paper, we provide one such algorithm which guarantees that the agents\\' collective joint strategy will constitute an efficient correlated equilibrium with high probability. The key to attaining efficient correlated behavior through distributed learning involves incorporating a common random signal into the learning environment.

  13. Correlation Functions and Spin

    CERN Document Server

    Tyc, T

    2000-01-01

    The k-electron correlation function of a free chaotic electron beam is derived with the spin degree of freedom taken into account. It is shown that it can be expressed with the help of correlation functions for a polarized electron beam of all orders up to k and the degree of spin polarization. The form of the correlation function suggests that if the electron beam is not highly polarized, observing multi-particle correlations should be difficult. The result can be applied also to chaotic photon beams, the degree of spin polarization being replaced by the degree of polarization.

  14. On the sensitivity of Tropical Rainfall Measuring Mission (TRMM) Microwave Imager channels to overland rainfall

    Science.gov (United States)

    You, Yalei; Liu, Guosheng; Wang, Yu; Cao, Jie

    2011-06-01

    The response of brightness temperatures at different microwave frequencies to overland precipitation is investigated by using the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) and Microwave Imager (TMI) data. The Spearman correlation coefficients between observations at TMI channels or channel combinations and PR-measured near-surface rain are computed using 3 years of TRMM data. The results showed that the brightness temperature combinations from 19 and 37 GHz, that is, V19-V37 (the letter V denotes vertical polarization, and the numbers denote frequency in GHz) or V21-V37, can explain ˜10% more variance of near-surface rainfall rate than can the V85 brightness temperature. Also, the global distribution of the above correlation revealed that over almost all of the tropical land area covered by TRMM satellite, the V19-V37 channel has a closer response to the overland rainfall than does the V85 channel. This result is somewhat counterintuitive, because it has been long believed that the dominant signature of overland rainfall is the brightness temperature depression caused by ice scattering at high microwave frequencies (e.g., 85 GHz). To understand the underlying physics of this better low-frequency response, data analysis and radiative transfer modeling have been conducted to assess the influence on brightness temperatures from clouds with different ice and liquid water partitions. The results showed that under the condition of low frozen water and medium liquid water in the atmospheric column, the signal from the V19-V37 channel responded better to rainfall rate than did the one from the V85 channel. A plausible explanation to this result is that in addition to ice scattering signature, the V19-V37 channel contains liquid water information as well, which is more directly related to surface rain than to ice water aloft. At heavy rainfall conditions, the V19-V37, V37, and V85 channels all are correlated with near-surface rain reasonably well

  15. A novel aquaporin 3 in killifish (Fundulus heteroclitus) is not an arsenic channel.

    Science.gov (United States)

    Jung, Dawoon; MacIver, Bryce; Jackson, Brian P; Barnaby, Roxanna; Sato, J Denry; Zeidel, Mark L; Shaw, Joseph R; Stanton, Bruce A

    2012-05-01

    The Atlantic killifish (Fundulus heteroclitus) is a model environmental organism that has an extremely low assimilation rate of environmental arsenic. As a first step in elucidating the mechanism behind this phenomenon, we used quantitative real-time PCR to identify aquaglyceroporins (AQPs), which are arsenite transporters, in the killifish gill. A novel homolog killifish AQP3 (kfAQP3a) was cloned from the killifish gill, and a second homolog was identified as the consensus from a transcriptome database (kfAQP3b). The two were 99% homologous to each other, 98% homologous to a previously identified killifish AQP3 from embryos (kfAQP3ts), and 78% homologous to hAQP3. Expression of kfAQP3a in Xenopus oocytes significantly enhanced water, glycerol, and urea transport. However, kfAQP3a expressed in HEK293T cells did not transport significant amounts of arsenic. All sequence motifs thought to confer the ability of AQP3 to transport solutes were conserved in kfAQP3a, kfAQP3b, and kfAQP3ts; however, the C-terminal amino acids were different in kfAQP3a versus the other two homologs. Replacement of the three C-terminal amino acids of kfAQP3 (GKS) with the three C-terminal amino acids of kfAQP3b and kfAQP3ts (ANC) was sufficient to enable kfAQP3a to robustly transport arsenic. Thus, the C-terminus of kfAQP3b and kfAQP3ts confers arsenic selectivity in kfAQP3. Moreover, kfAQP3a, the only AQP expressed in killifish gill, is the first aquaglyceroporin identified that does not transport arsenic, which may explain, in part, why killifish poorly assimilate arsenic and are highly tolerant to environmental arsenic.

  16. Current correlations in quantum spin Hall insulators.

    Science.gov (United States)

    Schmidt, Thomas L

    2011-08-26

    We consider a four-terminal setup of a two-dimensional topological insulator (quantum spin Hall insulator) with local tunneling between the upper and lower edges. The edge modes are modeled as helical Luttinger liquids and the electron-electron interactions are taken into account exactly. Using perturbation theory in the tunneling, we derive the cumulant generating function for the interedge current. We show that different possible transport channels give rise to different signatures in the current noise and current cross correlations, which could be exploited in experiments to elucidate the interplay between electron-electron interactions and the helical nature of the edge states.

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

    CERN Document Server

    Rajesh, R

    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 provide several good joint source-channel coding schemes for a discrete/continuous source and discrete/continuous alphabet channel. Channels with feedback and fading are also considered. Keywords: Multiple access channel, side information, lossy joint source-channel coding, channels with feedback, fading channels.

  18. 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.

  19. 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...

  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. Enhancing robustness of multiparty quantum correlations using weak measurement

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Uttam, E-mail: uttamsingh@hri.res.in [Quantum Information and Computation Group, Harish-Chandra Research Institute, Chhatnag Road, Jhunsi, Allahabad 211 019 (India); Mishra, Utkarsh, E-mail: utkarsh@hri.res.in [Quantum Information and Computation Group, Harish-Chandra Research Institute, Chhatnag Road, Jhunsi, Allahabad 211 019 (India); Dhar, Himadri Shekhar, E-mail: dhar.himadri@gmail.com [School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067 (India)

    2014-11-15

    Multipartite quantum correlations are important resources for the development of quantum information and computation protocols. However, the resourcefulness of multipartite quantum correlations in practical settings is limited by its fragility under decoherence due to environmental interactions. Though there exist protocols to protect bipartite entanglement under decoherence, the implementation of such protocols for multipartite quantum correlations has not been sufficiently explored. Here, we study the effect of local amplitude damping channel on the generalized Greenberger–Horne–Zeilinger state, and use a protocol of optimal reversal quantum weak measurement to protect the multipartite quantum correlations. We observe that the weak measurement reversal protocol enhances the robustness of multipartite quantum correlations. Further it increases the critical damping value that corresponds to entanglement sudden death. To emphasize the efficacy of the technique in protection of multipartite quantum correlation, we investigate two proximately related quantum communication tasks, namely, quantum teleportation in a one sender, many receivers setting and multiparty quantum information splitting, through a local amplitude damping channel. We observe an increase in the average fidelity of both the quantum communication tasks under the weak measurement reversal protocol. The method may prove beneficial, for combating external interactions, in other quantum information tasks using multipartite resources. - Highlights: • Extension of weak measurement reversal scheme to protect multiparty quantum correlations. • Protection of multiparty quantum correlation under local amplitude damping noise. • Enhanced fidelity of quantum teleportation in one sender and many receivers setting. • Enhanced fidelity of quantum information splitting protocol.

  2. Effects of fading and spatial correlation on node selection for estimation in Wireless Sensor Networks

    KAUST Repository

    Al-Murad, Tamim M.

    2010-06-01

    In densely deployed sensor networks, correlation among measurements may be high. Spatial sampling through node selection is usually used to minimize this correlation and to save energy consumption. However because of the fading nature of the wireless channels, extra care should be taken when performing this sampling. In this paper, we develop expressions for the distortion which include the channel effects. The asymptotic behavior of the distortion as the number of sensors or total transmit power increase without bound is also investigated. Further, based on the channel and position information we propose and test several node selection schemes.

  3. 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.

  4. Covert channel detection using Information Theory

    CERN Document Server

    Hélouët, Loïc; 10.4204/EPTCS.51.3

    2011-01-01

    This paper presents an information theory based detection framework for covert channels. We first show that the usual notion of interference does not characterize the notion of deliberate information flow of covert channels. We then show that even an enhanced notion of "iterated multivalued interference" can not capture flows with capacity lower than one bit of information per channel use. We then characterize and compute the capacity of covert channels that use control flows for a class of systems.

  5. Covert channel detection using Information Theory

    Directory of Open Access Journals (Sweden)

    Loïc Hélouët

    2011-02-01

    Full Text Available This paper presents an information theory based detection framework for covert channels. We first show that the usual notion of interference does not characterize the notion of deliberate information flow of covert channels. We then show that even an enhanced notion of "iterated multivalued interference" can not capture flows with capacity lower than one bit of information per channel use. We then characterize and compute the capacity of covert channels that use control flows for a class of systems.

  6. 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

  7. Walking droplets in linear channels

    Science.gov (United States)

    Filoux, Boris; Hubert, Maxime; Schlagheck, Peter; Vandewalle, Nicolas

    2017-01-01

    When a droplet is placed onto a vertically vibrated bath, it can bounce without coalescing. Upon an increase of the forcing acceleration, the droplet is propelled by the wave it generates and becomes a walker with a well-defined speed. We investigate the confinement of a walker in different rectangular cavities, used as waveguides for the Faraday waves emitted by successive droplet bounces. By studying the walker velocities, we discover that one-dimensional confinement is optimal for narrow channels of width of D ≃1.5 λF . Thereby, the walker follows a quasilinear path. We also propose an analogy with waveguide models based on the observation of the Faraday instability within the channels.

  8. Identity Authentication over Noisy Channels

    Directory of Open Access Journals (Sweden)

    Fanfan Zheng

    2015-07-01

    Full Text Available Identity authentication is the process of verifying users’ validity. Unlike classical key-based authentications, which are built on noiseless channels, this paper introduces a general analysis and design framework for identity authentication over noisy channels. Specifically, the authentication scenarios of single time and multiple times are investigated. For each scenario, the lower bound on the opponent’s success probability is derived, and it is smaller than the classical identity authentication’s. In addition, it can remain the same, even if the secret key is reused. Remarkably, the Cartesian authentication code proves to be helpful for hiding the secret key to maximize the secrecy performance. Finally, we show a potential application of this authentication technique.

  9. ALMA correlator computer systems

    Science.gov (United States)

    Pisano, Jim; Amestica, Rodrigo; Perez, Jesus

    2004-09-01

    We present a design for the computer systems which control, configure, and monitor the Atacama Large Millimeter Array (ALMA) correlator and process its output. Two distinct computer systems implement this functionality: a rack- mounted PC controls and monitors the correlator, and a cluster of 17 PCs process the correlator output into raw spectral results. The correlator computer systems interface to other ALMA computers via gigabit Ethernet networks utilizing CORBA and raw socket connections. ALMA Common Software provides the software infrastructure for this distributed computer environment. The control computer interfaces to the correlator via multiple CAN busses and the data processing computer cluster interfaces to the correlator via sixteen dedicated high speed data ports. An independent array-wide hardware timing bus connects to the computer systems and the correlator hardware ensuring synchronous behavior and imposing hard deadlines on the control and data processor computers. An aggregate correlator output of 1 gigabyte per second with 16 millisecond periods and computational data rates of approximately 1 billion floating point operations per second define other hard deadlines for the data processing computer cluster.

  10. Correlations in multiparticle production

    CERN Document Server

    Troshin, S M

    2011-01-01

    We discuss correlations in the hadron production in the $pp$-collision with emphasize on the ridge-like structure origin in the two-particle correlation function. We suggest that this structure can appear due to a rotating nature of the transient state of matter generated in the intermidiate stage of proton collison.

  11. Vehicular Channel Characterization and Modeling

    OpenAIRE

    Oestges, Claude; 10th European Conference on Antennas and Propagation (EuCAP)

    2016-01-01

    Vehicle-to-vehicle transmissions have emerged as a key component of future communication standards, whose design and testing critically depends upon the understanding of propagation mechanisms. An important and specific aspect of vehicular communication channels lies in the fact that these are essentially non-stationary. Hence, this communication addresses two recent contributions in the field of non-stationary vehicular propagation, based on extensive measurements conducted at 5.3 GHz in sub...

  12. RECAT - Redundant Channel Alignment Technique

    Science.gov (United States)

    2016-06-07

    distribution unlimited 13. SUPPLEMENTARY NOTES NUWC2015 14. ABSTRACT A problem in the analog-to- digital , (A/D), conversion of broadband tape recorded...Alignment Technique, is used to align data taken on one pass with data from any other pass. The accuracy of this alignment is a function of the digital ...Redundant Channel Alignment Technique; analog-to- digital ; A/D; Broadband Bearing Time Processing 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF

  13. Channeled and microactiviation of materials

    Energy Technology Data Exchange (ETDEWEB)

    Maggiore, C.J.; Blacic, J.D.; Blondiaux, G.; Debrun, J.L.; Ali, M.H.; Mathez, E.; Misdaq, M.A.; Valladon, M.

    1988-01-01

    Charged particle activation analysis can be combined with channeling to determine lattice location of impurities at the trace level in single crystal samples. It can also be used with a nuclear microprobe to measure impurities at trace levels in small or spatially inhomogeneous samples. Examples of these extensions of activation analysis to realistic samples are carbon determination in organometallic vapor phase epitaxial layers of GaAlAs on GaAs and oxygen determination in diamonds. 5 refs., 2 figs.

  14. Higgs in bosonic channels (CMS

    Directory of Open Access Journals (Sweden)

    Gori Valentina

    2015-01-01

    The Higgs boson mass measurement from the combination of H → ZZ → 4ℓ and H → γγ channels gives a value mH = 125.03+0.26−0.27 (stat. +0.13−0.15 (syst.. An upper limit ΓH < 22 MeV can be put on the Higgs boson width thanks to the new indirect method.

  15. Channel selection for automatic seizure detection

    DEFF Research Database (Denmark)

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

    2012-01-01

    of an automatic channel selection method. The characteristics of the seizures are extracted by the use of a wavelet analysis and classified by a support vector machine. The best channel selection method is based upon maximum variance during the seizure. Results: Using only three channels, a seizure detection...

  16. Comments on Ionization Cooling Channel Characteristics

    OpenAIRE

    Neuffer, David

    2013-01-01

    Ionization cooling channels with a wide variety of characteristics and cooling properties are being developed. These channels can produce cooling performances that are largely consistent with the ionization cooling theory developed previously. In this paper we review ionization cooling theory, discuss its application to presently developing cooling channels, and discuss criteria for optimizing cooling.

  17. Electronic Commerce and Retail Channel Substitution

    NARCIS (Netherlands)

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

    2002-01-01

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

  18. 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.

  19. 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,...

  20. Transitional behavior of quantum Gaussian memory channels

    Science.gov (United States)

    Lupo, C.; Mancini, S.

    2010-05-01

    We address the question of optimality of entangled input states in quantum Gaussian memory channels. For a class of such channels, which can be traced back to the memoryless setting, we state a criterion which relates the optimality of entangled inputs to the symmetry properties of the channels’ action. Several examples of channel models belonging to this class are discussed.