Distribution by Scientific Domains
Distribution within Life Sciences

Kinds of Channels

  • activated k+ channel
  • active channel
  • alluvial channel
  • alternative channel
  • anion channel
  • annular channel
  • artificial channel
  • atp-sensitive k+ channel
  • atp-sensitive potassium channel
  • bkca channel
  • broadcast channel
  • bypass channel
  • ca2+ channel
  • calcium channel
  • calcium-activated potassium channel
  • cardiac ion channel
  • cardiac l-type ca2+ channel
  • cation channel
  • cationic channel
  • cav2.1 channel
  • central channel
  • chloride channel
  • clear channel
  • communication channel
  • conducting channel
  • continuous channel
  • crac channel
  • curved channel
  • cyclic nucleotide-gated channel
  • cylindrical channel
  • decay channel
  • different channel
  • dissociation channel
  • distributary channel
  • distribution channel
  • drainage channel
  • english channel
  • epithelial na+ channel
  • epithelial sodium channel
  • fading channel
  • flow channel
  • fluvial channel
  • form channel
  • fragmentation channel
  • functional channel
  • gap junction channel
  • guard channel
  • hcn channel
  • herg channel
  • herg potassium channel
  • heteromeric channel
  • hexagonal channel
  • individual channel
  • information channel
  • intercellular channel
  • ion channel
  • ionic channel
  • irrigation channel
  • junction channel
  • k+ channel
  • katp channel
  • kca channel
  • kcnq channel
  • kcnq1 potassium channel
  • kir channel
  • kv channel
  • kv4 channel
  • l-type ca2+ channel
  • l-type calcium channel
  • l-type channel
  • large channel
  • ligand-gated ion channel
  • lymphatic channel
  • m channel
  • main channel
  • major channel
  • marketing channel
  • meltwater channel
  • membrane ca2+ channel
  • membrane channel
  • microfluidic channel
  • mimo channel
  • mitokatp channel
  • mobile satellite channel
  • multipath channel
  • multipath fading channel
  • mutant channel
  • n-type calcium channel
  • na channel
  • na+ channel
  • narrow channel
  • natural channel
  • non-selective cation channel
  • nonselective cation channel
  • nucleotide-gated channel
  • one-dimensional channel
  • open channel
  • other channel
  • p ca2+ channel
  • p channel
  • parallel channel
  • pentacene channel
  • permeable cation channel
  • permeable channel
  • permeable ion channel
  • plasma membrane ca2+ channel
  • pore channel
  • porous channel
  • potassium channel
  • potential channel
  • private channel
  • product channel
  • propagation channel
  • proton channel
  • rayleigh fading channel
  • reaction channel
  • receptor channel
  • receptor potential channel
  • rectangular channel
  • release channel
  • rf channel
  • rician fading channel
  • ring channel
  • river channel
  • sarcolemmal katp channel
  • satellite channel
  • selective channel
  • separation channel
  • service channel
  • several channel
  • single channel
  • sk channel
  • sk3 channel
  • sodium channel
  • square channel
  • straight channel
  • stream channel
  • stretch-activated channel
  • television channel
  • tidal channel
  • transfer channel
  • transient receptor potential channel
  • transistor channel
  • transmission channel
  • transport channel
  • trp channel
  • two-dimensional channel
  • various channel
  • vascular channel
  • voltage-dependent ca2+ channel
  • voltage-dependent calcium channel
  • voltage-dependent k+ channel
  • voltage-dependent na+ channel
  • voltage-dependent sodium channel
  • voltage-gated ca2+ channel
  • voltage-gated calcium channel
  • voltage-gated ion channel
  • voltage-gated k+ channel
  • voltage-gated na+ channel
  • voltage-gated potassium channel
  • voltage-gated sodium channel
  • water channel
  • wild-type channel
  • wireless channel

  • Terms modified by Channels

  • channel activation
  • channel activator
  • channel activity
  • channel agonist
  • channel allocation scheme
  • channel angular pressing
  • channel antagonist
  • channel assignment
  • channel bank
  • channel blocker
  • channel blocker tetrodotoxin
  • channel blocker verapamil
  • channel capacity
  • channel catfish
  • channel catfish ictalurus punctatu
  • channel characteristic
  • channel closure
  • channel complex
  • channel condition
  • channel conductance
  • channel current
  • channel dimension
  • channel downregulation
  • channel estimation
  • channel expression
  • channel family
  • channel feature
  • channel flow
  • channel form
  • channel formation
  • channel function
  • channel gating
  • channel gene
  • channel geometry
  • channel gradient
  • channel habitat
  • channel height
  • channel inactivation
  • channel inhibition
  • channel inhibitor
  • channel instability
  • channel interaction
  • channel island
  • channel isoform
  • channel layer
  • channel lead
  • channel length
  • channel margin
  • channel member
  • channel migration
  • channel model
  • channel modulator
  • channel morphology
  • channel mutation
  • channel opening
  • channel parameter
  • channel pattern
  • channel pore
  • channel property
  • channel protein
  • channel reach
  • channel response
  • channel slope
  • channel structure
  • channel subtype
  • channel subunit
  • channel surface
  • channel system
  • channel toxin
  • channel type
  • channel used
  • channel wall
  • channel widening
  • channel width

  • Selected Abstracts

    Effects of stimulation rates on Cantonese lexical tone perception by cochlear implant users in Hong Kong

    D.K.K. Au
    Effects of stimulation rates on Cantonese lexical tone perception by cochlear implant users in Hong Kong High, moderate and low stimulation rates of 1800, 800 and 400 pulse per second (pps)/channel, respectively, were used to test the effects of stimulation rates on the discrimination and identification of Cantonese lexical tones in 11 Chinese post-lingually deafened adults with cochlear implants (CIs). The subjects were implanted with the MED-EL Combi 40+ CI system. They were randomly assigned to each of the stimulation rate conditions according to an ABC design. In both the Cantonese lexical tone perception tests, the subjects reached the highest scores in the high-stimulation-rate condition, and the lowest scores in the low-stimulation-rate condition (P < 0.01). Post hoc comparisons between different stimulation rates did not yield consistent results. This study demonstrated that the maximum stimulation rate of 1800 pps/channel could be an ,optimal' stimulation rate and an informed choice of parameter for the benefit of Cantonese-speaking CI users in lexical tone perception. [source]

    Efficient multiwavelength linear cavity erbium-doped fiber laser over 1570,1600 nm

    Chun-Liu Zhao
    Abstract A simple and efficient L-band multiwavelength linear cavity fiber laser was obtained at room temperature by recycling detrimental 1550-nm band amplified spontaneous emission as a secondary pump source for the unpumped EDF section of fiber laser. The cavity was formed by two linear fiber loops. By changing the states of PCs inserted to fiber loops, stable dual- and tri-wavelength lasers with about 1-mW/channel were generated at room temperature. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 296,299, 2002; Published online in Wiley InterScience ( DOI 10.1002/mop.10441 [source]

    Unified Medical Language System Coverage of Emergency-medicine Chief Complaints

    Debbie A. Travers PhD
    Abstract Background Emergency department (ED) chief-complaint (CC) data increasingly are important for clinical-care and secondary uses such as syndromic surveillance. There is no widely used ED CC vocabulary, but experts have suggested evaluation of existing health-care vocabularies for ED CC. Objectives To evaluate the ED CC coverage in existing biomedical vocabularies from the Unified Medical Language System (UMLS). Methods The study sample included all CC entries for all visits to three EDs over one year. The authors used a special-purpose text processor to clean CC entries, which then were mapped to UMLS concepts. The UMLS match rates then were calculated and analyzed for matching concepts and nonmatching entries. Results A total of 203,509 ED visits was included. After cleaning with the text processor, 82% of the CCs matched a UMLS concept. The authors identified 5,617 unique UMLS concepts in the ED CC data, but many were used for only one or two visits. One thousand one hundred thirty-six CC concepts were used more than ten times and covered 99% of all the ED visits. The largest biomedical vocabulary in the UMLS is the Systematized Nomenclature of Medicine Clinical Terms (SNOMED CT), which included concepts for 79% of all ED CC entries. However, some common CCs were not found in SNOMED CT. Conclusions The authors found that ED CC concepts are well covered by the UMLS and that the best source of vocabulary coverage is from SNOMED CT. There are some gaps in UMLS and SNOMED CT coverage of ED CCs. Future work on vocabulary control for ED CCs should build upon existing vocabularies. [source]

    Cross-sectional analysis of the association between age and corpus callosum size in chimpanzees (Pan troglodytes)

    William D. Hopkins
    Abstract The CC is the major white matter tract connecting the cerebral hemispheres and provides for interhemispheric integration of sensory, motor and higher-order cognitive information. The midsagittal area of the CC has been frequently used as a marker of brain development in humans. We report the first investigation into the development of the corpus callosum and its regional subdivisions in chimpanzees (Pan troglodytes). Magnetic resonance images were collected from 104 chimpanzees (female n,=,63, male n,=,41) ranging in age from 6 years (pre-pubescent period) to 54 years (old age). Sustained linear growth was observed in the area of the CC subdivision of the genu; areas of the posterior midbody and anterior midbody displayed nonlinear growth during development. After adjusting for total brain size, we observed linear growth trajectories of the total CC and CC subdivisions of the genu, posterior midbody, isthmus and splenium, and nonlinear growth trajectories of the rostral body and anterior midbody. These developmental patterns are similar to the development of the CC in humans. As the growth curves of the CC mirrors growth seen in the percentage of white matter in humans, our results suggest chimpanzees show continued white matter development in regions related to cognitive development. © 2010 Wiley Periodicals, Inc. Dev Psychobiol 52:133,141, 2010 [source]

    Application of supercritical fluid extraction to regenerate spent Pd-active carbon catalyst

    Lidia D
    Abstract Pd-active carbon-type catalysts are used in a wide variety of processes, typical examples of which are liquid-phase hydrogenation reactions. In the case of these catalysts, a loss of their catalytic activity is observed. The aim of the present work was to assess the possibility of regenerating spent Pd/AC catalysts using supercritical fluid extraction. The following Pd/AC catalyst samples were investigated and compared: a commercial 10 wt % Pd catalyst (Aldrich) (denoted by CC), a spent catalyst (SC), SC subjected to supercritical fluid,CO2 extraction (SC/SFE/C), SC subjected to supercritical fluid,CO2,ethanol extraction (SC/SFE/C-Et), and SC subjected to supercritical fluid,ethane,propane extraction (SC/SFE/E-P). The last three catalysts were additionally subjected to heating in a hydrogen atmosphere at 410 K for 3 h. These were denoted by SC/SFE/C/H, SC/SFE/C-Et/H, and SC/SFE/E-P/H, respectively. The spent Pd/AC catalyst (SC) consists of mixed CC samples used in the reduction with hydrogen of various organic compounds. The catalysts CC, SC/SFE/C, SC/SFE/C/H, SC/SFE/C-Et/H, and SC/SFE/E-P/H were tested in the reduction of octanoylbenzene with hydrogen. The activity of the catalysts was estimated by measuring the reaction time and also the amount of hydrogen used in relation to the theoretical quantity required for the reaction. XPS and XRD methods were used to evaluate the changes occurring in the form of the palladium present on the Pd/AC catalyst surface during the regeneration processes. It was found that supercritical fluid-CO2 extraction followed by heating in a hydrogen atmosphere is the most effective method for regenerating that catalyst. The results of our investigations indicate that regeneration of a spent Pd/AC catalyst, irrespective of the reaction in which it has been used, should be based on the complete removal of byproducts, the purification of the catalyst surface, and the restoration of the original form of the palladium. The procedure proposed in this paper, i.e. SFE (CO2) and heating in H2, fulfils both the conditions mentioned above. © 2007 American Institute of Chemical Engineers Environ Prog, 2007 [source]

    The carrying capacity of ecosystems

    GLOBAL ECOLOGY, Issue 6 2004
    Pablo Del Monte-Luna
    ABSTRACT We analyse the concept of carrying capacity (CC), from populations to the biosphere, and offer a definition suitable for any level. For communities and ecosystems, the CC evokes density-dependence assumptions analogous to those of population dynamics. At the biosphere level, human CC is uncertain and dynamic, leading to apprehensive rather than practical conclusions. The term CC is widely used among ecological disciplines but remains vague and elusive. We propose the following definition: the CC is ,the limit of growth or development of each and all hierarchical levels of biological integration, beginning with the population, and shaped by processes and interdependent relationships between finite resources and the consumers of those resources'. The restrictions of the concept relate to the hierarchical approach. Emergent properties arise at each level, and environmental heterogeneity restrains the measurement and application of the CC. Because the CC entails a myriad of interrelated, ever-changing biotic and abiotic factors, it must not be assumed constant, if we are to derive more effective and realistic management schemes. At the ecosystem level, stability and resilience are dynamic components of the CC. Historical processes that help shape global biodiversity (e.g. continental drift, glaciations) are likely drivers of large-scale changes in the earth's CC. Finally, world population growth and consumption of resources by humanity will necessitate modifications to the paradigm of sustainable development, and demand a clear and fundamental understanding of how CC operates across all biological levels. [source]

    Pathology of peripheral intrahepatic cholangiocarcinoma with reference to tumorigenesis

    Yasuni Nakanuma
    Cholangiocarcinomas (CCs) are neoplasms with cholangiocyte differentiation, and may arise from cholangiocytes of the biliary tree and possibly cholangiocyte progenitor cells. Intrahepatic CCs can be divided into the perihilar and peripheral types. Peripheral CCs present grossly as a mass forming tumor, and histologically as an adenocarcinoma of varying shapes and phenotypes. Some peripheral CCs (ductular type) are characterized by: (i) a histological resemblance to reactive bile ductules; (ii) the expression of neural cell adhesion molecule (NCAM) and vimentin. This type shows: (i) grossly, a blurred border; and (ii) histologically, carcinoma cells replacing the adjoining hepatocytes at the border of the tumor. It is frequently associated with neutrophilic infiltration and also with granulocyte and granulocyte macrophage colony-stimulating factors. We propose to call this type "ductular CC." The other peripheral CC (duct type) includes ordinary adenocarcinoma with well to moderately differentiated tubular and micropapillary patterns and is negative for NCAM but positive for mucin. This type can be called "duct CC," and shows a rather compressive growth. Interestingly, CC components of combined hepatocellular CC share the features of ductular CC, suggesting that hepatic progenitor cells may be involved in the tumorigenesis of ductular CC. The biological behavior of ductular CC and duct CC remains obscure, and follow-up and molecular studies on these tumors are required in order for these two CCs to be recognized as disease entities, and so as to evaluate their carcinogenesis. [source]

    Anandamide improves the impaired nitric oxide-mediated neurogenic relaxation of the corpus cavernosum in diabetic rats: involvement of cannabinoid CB1 and vanilloid VR1 receptors

    BJU INTERNATIONAL, Issue 6 2007
    Mehdi Ghasemi
    OBJECTIVE To investigate the ability of acute administration of the endogenous cannabinoid, anandamide, in vitro to alter the nonadrenegic noncholinergic (NANC)-mediated relaxation of corpus cavernosum (CC) in diabetic rats and the possible role of nitric oxide (NO), as it is well known that erectile dysfunction (ED) affects 35,75% of men with diabetes mellitus and several studies have been conducted to find appropriate strategies for treating diabetes-induced ED. MATERIALS AND METHODS Diabetes was induced in rats by streptozotocin administration and was maintained for 8 weeks. The CC were removed and isolated in organ baths for pharmacological studies. Agonist-evoked or electrical-field stimulation (EFS)-evoked smooth muscle tensions in CC strips from control and diabetic rats were measured. RESULTS The neurogenic relaxation of phenylephrine (7.5 µm)-precontracted isolated CC strips was impaired in diabetic rats. Anandamide (0.3, 1 and 3 µm) enhanced the relaxant responses to EFS in diabetic CC strips in a dose-dependent manner. This effect was antagonized by the selective cannabinoid CB1 receptor antagonist AM251 (1 µm) and the selective vanilloid receptor antagonist capsazepine (3 µm). Concurrent administration of partially effective doses of l -arginine (10 µm) and anandamide (0.3 µm) exerted a synergistic improvement in EFS-induced relaxation of diabetic CC strips (P < 0.001). The relaxant responses to the NO donor, sodium nitroprusside, were similar between diabetic and control groups. CONCLUSION For the first time, we show that acute administration of anandamide, an endogenous cannabinoid, alone or combined with l -arginine can improve nitrergic nerve-mediated relaxation of the CC in diabetic rats. This effect was mediated by cannabinoid CB1 and vanilloid VR1 receptors within the CC. [source]

    Toward Vocabulary Control for Chief Complaint

    Stephanie W. Haas PhD
    Abstract The chief complaint (CC) is the data element that documents the patient's reason for visiting the emergency department (ED). The need for a CC vocabulary has been acknowledged at national meetings and in multiple publications, but to our knowledge no groups have specifically focused on the requirements and development plans for a CC vocabulary. The national consensus meeting "Towards Vocabulary Control for Chief Complaint" was convened to identify the potential uses for ED CC and to develop the framework for CC vocabulary control. The 10-point consensus recommendations for action were 1) begin to develop a controlled vocabulary for CC, 2) obtain funding, 3) establish an infrastructure, 4) work with standards organizations, 5) address CC vocabulary characteristics for all user communities, 6) create a collection of CC for research, 7) identify the best candidate vocabulary for ED CCs, 8) conduct vocabulary validation studies, 9) establish beta test sites, and 10) plan publicity and marketing for the vocabulary. [source]


    Victor Dorofeenko
    E4; E5; E2 ABSTRACT We extend the Carlstrom and Fuerst (American Economic Review, 1997, 87, pp. 893,910) agency cost model of business cycles by including time-varying uncertainty in the technology shocks that affect capital production. We first demonstrate that standard linearization methods can be used to solve the model yet second moments enter the economy's equilibrium policy functions. We then demonstrate that an increase in uncertainty causes, ceteris paribus, a fall in investment supply. We also show that persistence of uncertainty affects both quantitatively and qualitatively the behaviour of the economy. [source]


    Patricia C. Henshaw
    ABSTRACT: Stream channels are known to change their form as a result of watershed urbanization, but do they restabilize under subsequent conditions of constant urban land use? Streams in seven developed and developing watersheds (drainage areas 5,35 km2) in the Puget Sound lowlands were evaluated for their channel stability and degree of urbanization, using field and historical data. Protocols for determining channel stability by visual assessment, calculated bed mobility at bankfull flows, and resurveyed cross-sections were compared and yielded nearly identical results. We found that channel restabilization generally does occur within one or two decades of constant watershed land use, but it is not universal. When (or if) an individual stream will restabilize depends on specific hydrologic and geomorphic characteristics of the channel and its watershed; observed stability is not well predicted by simply the magnitude of urban development or the rate of ongoing land-use change. The tendency for channel restabilization suggests that management efforts focused primarily on maintaining stability, particularly in a still-urbanizing watershed, may not always be necessary. Yet physical stability alone is not a sufficient condition for a biologically healthy stream, and additional rehabilitation measures will almost certainly be required to restore biological conditions in urban systems. [source]


    NEPHROLOGY, Issue 1 2002
    Rahgozar M


    Ping-Ying Lee
    SUMMARY 1We have shown previously that lignocaine inhibits the upregulation of inducible nitric oxide synthase (iNOS), a crucial factor that initiates the systemic inflammatory response during sepsis, possibly through voltage-sensitive sodium channels (VSSC). Toll-like receptor-4 (TLR-4), nuclear factor (NF)-,B and mitogen activated protein kinases (MAPKs) participate in the upstream regulation of iNOS expression induced by endotoxin. In the present study, we investigated the effects of lignocaine in the regulation of the expression of these enzymes. The role of VSSC in the effects of lignocaine was also investigated. 2Confluent murine macrophages (RAW264.7 cells) were randomized to receive lipopolysaccharide (LPS; 100 ng/mL), LPS + lignocaine (50 µmol/L), LPS + tetrodotoxin (TTX; 1 µmol/L; a VSSC inhibitor), LPS + lignocaine + veratridine (Ver; 50 µmol/L; a VSSC activator) or LPS + TTX + Ver. After reacting with LPS for 0, 15, 30, 45 and 60 min, cell cultures were harvested and enzyme expression was evaluated. 3We found that LPS significantly increased the concentrations of TLR-4, NF-,B and MAPKs, including extracellular regulated kinase (ERK), c-jun N-terminal kinase (JNK) and p38 MAPK, in activated macrophages. Lignocaine and TTX significantly attenuated the effects of LPS on TLR-4, NF-,B, ERK and p38 MAPK expression, but not on JNK. Veratridine mitigated the effects of lignocaine and TTX. 4These data demonstrate that lignocaine has significant inhibitory effects on the activation of TLR-4, NF-,B and MAPKs in activated macrophages. Moreover, these effects involve VSSC. [source]


    Il-Ha Lee
    SUMMARY 1The epithelial sodium channel (ENaC) is tightly regulated by hormonal and humoral factors, including cytosolic ion concentration and glucocorticoid and mineralocorticoid hormones. Many of these regulators of ENaC control its activity by regulating its surface expression via neural precursor cell-expressed developmentally downregulated (gene 4) protein (Nedd4-2). 2During the early phase of aldosterone action, Nedd4-2-dependent downregulation of ENaC is inhibited by the serum- and glucocorticoid-induced kinase 1 (Sgk1). 3Sgk1 phosphorylates Nedd4-2. Subsequently, phosphorylated Nedd4-2 binds to the 14-3-3 protein and, hence, reduces binding of Nedd4-2 to ENaC. 4Nedd4-2 is also phosphorylated by protein kinase B (Akt1). Both Sgk1 and Akt1 are part of the insulin signalling pathway that increases transepithelial Na+ absorption by inhibiting Nedd4-2 and activating ENaC. [source]


    ES Louise Faber
    SUMMARY 1SK channels are small-conductance calcium-activated potassium channels that are widely expressed in neurons. The traditional view of the functional role of SK channels is in mediating one component of the after-hyperpolarization that follows action potentials. Calcium influx via voltage-gated calcium channels active during action potentials opens SK channels and the resultant hyperpolarization lowers the firing frequency of action potentials in many neurons. 2Recent advances have shown that, in addition to controlling action potential firing frequency, SK channels are also important in regulating dendritic excitability, synaptic transmission and synaptic plasticity. 3In accordance with their role in modulating synaptic plasticity, SK channels are also important in regulating several learning and memory tasks and may also play a role in a number of neurological disorders. 4The present review discusses recent findings on the role of SK channels in central neurons. [source]


    M Chebib
    SUMMARY 1.,The present review gives an overview of studies conducted on GABAC receptors over the past 10 years since the author started at the University of Sydney. It concentrates on the structure,activity relationship profiles of the receptor and how these studies were used to: (i) develop selective GABAC receptor ligands; and (ii) understand the impact of amino acid changes on GABAC receptor pharmacology and function. 2.,Structure,activity relationship studies involving variations of both ligands and their receptor targets are vital to the discovery of drugs that interact selectively with particular native and mutant receptor subtypes. Such agents may be useful for treating anxiety, depression, epilepsyand memory related disorders, such as Alzheimer's disease. [source]

    Cross-validation Criteria for Setar Model Selection

    Jan G. De Gooijer
    Three cross-validation criteria, denoted by respectively C, Cc, and Cu, are proposed for selecting the orders of a self-exciting threshold autoregressive (SETAR) model when both the delay and the threshold value are unknown. The derivation of C is within a natural cross-validation framework. The criterion Cc is similar in spirit as AICc, a bias-corrected version of AIC for SETAR model selection introduced by Wong and Li (1998). The criterion Cu is a variant of Cc having a similar poperty as AICu, a model selection proposed by McQuarrie et al. (1997) for linear models. In a Monte Carlo study, the performance of each of the criteria C, Cc, Cu, AIC, AICc, AICu, and BIC is investigated in detail for various models and various sample sizes. It will be shown that Cu consistently outperforms all other criteria when the sample size is moderate to large. [source]

    Adaptive Units for Conservation: Population Distinction and Historic Extinctions in the Island Scrub-Jay

    Aphelocoma; diversidad genética especie; endémica; genética de conservación; Islas Channel Abstract:,The Island Scrub-Jay (Aphelocoma insularis) is found on Santa Cruz Island, California, and is the only insular bird species in the continental United States. We typed seven microsatellite loci and sequenced a portion of the mitochondrial DNA control region of Island Scrub-Jays and their closest mainland relative, the Western Scrub-Jay (Aphelocoma californica), to assess levels of variability and effective population size and to examine the evolutionary relationship between the two species. The estimated female effective population size, Nef, of the Island Scrub-Jay was 1603 (90% confidence interval: 1481,1738) and was about 7.5% of the size of the mainland species. Island and Western Scrub-Jays have highly divergent control-region sequences, and the value of 3.14 ± 0.09% sequence divergence between the two species suggests a divergence time of approximately 151,000 years ago. Because the four northern Channel Islands were joined as one large island as recently as 11,000 years ago, extinctions must have occurred on the three other northern Channel islands, Santa Rosa, San Miguel, and Anacapa, highlighting the vulnerability of the remaining population. We assessed the evolutionary significance of four island endemics, including the Island Scrub-Jay, based on both genetic and adaptive divergence. Our results show that the Island Scrub-Jay is a distinct species of high conservation value whose history and adaptive potential is not well predicted by study of other island vertebrates. Resumen:, Aphelocoma insularis se encuentra en la Isla Santa Cruz, California, y es la única especie de ave insular en Estados Unidos continental. Clasificamos siete locus microsatelitales y secuenciamos una porción de la región control del ADN mitocondrial de A. insularis y su pariente continental más cercano A. californica para evaluar niveles de variabilidad y tamańo poblacional efectivo y examinar las relaciones evolutivas entre las dos especies. El tamańo poblacional efectivo de hembras, Neh, de A. insularis fue estimado en 1603 (90% CI: 1481-1738) y fue aproximadamente 7.5% del tamańo de la especie continental. Aphelocoma insularis y A. californica tienen secuencias muy divergentes en la región control, y el valor de divergencia secuencial de 3.14 ± 0.09% entre las dos especies sugiere un tiempo de divergencia de aproximadamente 151,000 ańos. Debido a que las cuatro Islas Channel estuvieron unidas en una sola isla tan recientemente como hace 11,000 ańos, deben haber ocurrido extinciones en las otras tres islas Channel, Santa Rosa, San Miguel y Anacapa, acentuando la vulnerabilidad de la población remanente. Evaluamos el significado evolutivo de cuatro especies insulares endémicas incluyendo A. insularis con base en la divergencia genética y adaptativa. Nuestros resultados muestran que A. insularis es una especie distinta de alto valor de conservación, cuya historia y potencial adaptativo no es pronosticado correctamente por el estudio de otros vertebrados insulares. [source]

    Optimal Design of the Online Auction Channel: Analytical, Empirical, and Computational Insights,

    DECISION SCIENCES, Issue 4 2002
    Ravi Bapna
    ABSTRACT The focus of this study is on business-to-consumer (B2C) online auctions made possible by the advent of electronic commerce over an open-source, ubiquitous Internet Protocol (IP) computer network. This work presents an analytical model that characterizes the revenue generation process for a popular B2C online auction, namely, Yankee auctions. Such auctions sell multiple identical units of a good to multiple buyers using an ascending and open auction mechanism. The methodologies used to validate the analytical model range from empirical analysis to simulation. A key contribution of this study is the design of a partitioning scheme of the discrete valuation space of the bidders such that equilibrium points with higher revenue structures become identifiable and feasible. Our analysis indicates that the auctioneers are, most of the time, far away from the optimal choice of key control factors such as the bid increment, resulting in substantial losses in a market with already tight margins. With this in mind, we put forward a portfolio of tools, varying in their level of abstraction and information intensity requirements, which help auctioneers maximize their revenues. [source]

    Channel head location and characteristics using digital elevation models

    G. R. Hancock
    Abstract The drainage network is the conduit through which much surface water and sediment are routed within a catchment. In a catchment, the position of where hillslopes begin and channels end has long been considered the position of transition between diffusive processes upslope and the more incisive fluvial processes downslope. Consequently, understanding channel head location is an important issue in understanding catchment hydrology and geomorphology. This study examines channel head position and characteristics in a catchment in Arnhem Land, Northern Territory, Australia. In this study the position of channel heads was mapped within the catchment and plotted on a reliable digital elevation model of the catchment. It was found that the majority of channel heads have relatively small source areas and that graphical catchment descriptors, such as the area,slope relationship and cumulative area distribution, can provide reliable measures of the field position of the heads of first-order streams and the transition from hillslope to channel. The area,slope relationship and cumulative area distribution are also shown to be good tools for determining digital elevation model grid size which can capture hillslope detail and the transition from hillslope to channel. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    Competing with the Public Sector in Broadcasting

    ECONOMIC AFFAIRS, Issue 4 2000
    David Elstein
    There are two public sector broadcasters in the UK: the BBC and Channel 4. In their different ways, their behaviour attracts criticism from the private sector. However, this critique is unfocused and potentially counter-productive. A more efficient , or privatised , public sector would create greater, not lesser, problems for the private sector. The allegations of abuse of privilege and unfair competition may be justified, but the private sector needs a coherent alternative rationale for public funding of broadcasting before it can expect to win a public and political debate. [source]

    Detection of glycolate oxidase gene glcD diversity among cultured and environmental marine bacteria

    W. W. Y. Lau
    Summary Of eight laboratory cultures of marine ,- and ,- Proteobacteria tested, growth on glycolate as a sole carbon source was detected for only three species: Pseudomonas stutzeri, Oceanimonas doudoroffii and Roseobacter sp. isolate Y3F. Degenerate polymerase chain reaction (PCR) primers were designed to amplify glcD, which encodes the D-subunit of the enzyme glycolate oxidase; glcD could be amplified only from those cultures that grew on glycolate. The PCR primers were used to explore glcD diversity in four field samples collected from different ocean environments: an Atlantic Gulf Stream Ring, sampled above and below the thermocline and two Pacific coastal sites, Parks Bay and San Juan Channel, WA. Environmental glcD sequences belonged to six major bacterial phylogenetic groups, with most sequences forming novel clades with no close relatives. Different patterns of glcD diversity were observed within and between the two nutrient regimes. Comparison of glcD and 16S rDNA diversity and analyses of available bacterial genomes and a metgenomic library from the Sargasso Sea show that glycolate-utilizing potential exists in only a subset of bacteria. Glycolate is produced in marine environments mainly by phytoplankton. Examination of glcD diversity will aid in understanding the influence of phytoplankton on bacterial community structure. [source]

    Relationship between lysosomal membrane destabilization and chemical body burden in eastern oysters (Crassostrea virginica) from Galveston Bay, Texas, USA

    Hyun-Min Hwang
    Abstract Lysosomal destabilization was measured by using hemocytes of eastern oysters (Crassostrea virginica) collected along a chemical concentration gradient in Galveston Bay, Texas, USA. Results of the lysosomal response were compared to concentrations of organic compounds and trace elements in oyster tissue. Concentrations (on a dry-wt basis) ranged from 288 to 2,390 ng/g for polycyclic aromatic hydrocarbons (PAHs), 38 to 877 ng Sn/g for tri- n -butyltin (TBT), 60 to 562 ng/g for polyclorinated biphenyls (PCBs), and 7 to 71 ng/g for total DDT. Trace element concentrations (on a dry-wt basis) ranged from 1.1 to 4.0 ,g/g for Cd, 105 to 229 ,g/g for Cu, 212 to 868 ,g/g for Al, and 1,200 to 8,180 ,g/g for Zn. The percentage of destabilized lysosomes ranged from 34 to 81%. A significant positive correlation (p < 0.05) was observed between lysosomal destabilization and body burden of organic compounds (PAHs, PCBs, TBT, and chlorinated pesticides). No significant correlation was found between metal concentrations and lysosomal destabilization. Based on lysosomal destabilization, the study sites in Galveston Bay can be placed in one of three groups: healthy (Hanna Reef and Confederate Bay), moderately damaged (Offats Bayou and Todd's Dump), and highly damaged (Yacht Club and Ship Channel). Lysosomal destabilization that is consistent with toxic chemical body burdens supports previous observations that lysosomal membranes are damaged by toxic chemicals and indicates that this method can serve as an early screening tool to assess overall ecosystem health by using oysters. [source]

    Loss of the Potassium Channel ,-Subunit Gene, KCNAB2, Is Associated with Epilepsy in Patients with 1p36 Deletion Syndrome

    EPILEPSIA, Issue 9 2001
    Heidi A. Heilstedt
    Summary: ,Purpose: Clinical features associated with chromosome 1p36 deletion include characteristic craniofacial abnormalities, mental retardation, and epilepsy. The presence and severity of specific phenotypic features are likely to be correlated with loss of a distinct complement of genes in each patient. We hypothesize that hemizygous deletion of one, or a few, critical gene(s) controlling neuronal excitability is associated with the epilepsy phenotype. Because ion channels are important determinants of seizure susceptibility and the voltage-gated K+ channel ,-subunit gene, KCNAB2, has been localized to 1p36, we propose that deletion of this gene may be associated with the epilepsy phenotype. Methods: Twenty-four patients were evaluated by fluorescence in situ hybridization with a probe containing KCNAB2. Clinical details were obtained by neurologic examination and EEG. Results: Nine patients are deleted for the KCNAB2 locus, and eight (89%) of these have epilepsy or epileptiform activity on EEG. The majority of patients have a severe seizure phenotype, including infantile spasms. In contrast, of those not deleted for KCNAB2, only 27% have chronic seizures, and none had infantile spasms. Conclusions: Lack of the , subunit would be predicted to reduce K+ channel,mediated membrane repolarization and increase neuronal excitability, suggesting a possible relation between loss of this gene and the development of seizures. Because some patients with seizures were not deleted for KCNAB2, there may be additional genes within 1p36 that contribute to epilepsy in this syndrome. Hemizygosity of this gene in a majority of monosomy 1p36 syndrome patients with epilepsy suggests that haploinsufficiency for KCNAB2 is a significant risk factor for epilepsy. [source]

    On extrinsic information of good binary codes operating over Gaussian channels

    M. Peleg
    We show that the extrinsic information about the coded bits of any good (capacity achieving) binary code operating over a Gaussian channel is zero when the channel capacity is lower than the code rate and unity when capacity exceeds the code rate, that is, the extrinsic information transfer (EXIT) chart is a step function of the signal to noise ratio and independent of the code. It follows that, for a common class of iterative receivers where the error correcting decoder must operate at first iteration at rate above capacity (such as in turbo equalization, iterative channel estimation, parallel and serial concatenated coding and the like), classical good codes which achieve capacity over the Additive White Gaussian Noise Channel are not effective and should be replaced by different new ones. Copyright © 2006 AEIT. [source]

    Involvement of Calmodulin in Glucagon-Like Peptide 1(7-36) Amide-Induced Inhibition of the ATP-Sensitive K+ Channel in Mouse Pancreatic ,-Cells

    W. G. Ding
    The present investigation was designed to examine whether calmodulin is involved in the inhibition of the ATP-sensitive K+ (KATP) channel by glucagon-like peptide 1(7-36) amide (GLP-1) in mouse pancreatic ,-cells. Membrane potential, single channel and whole-cell currents through the KATP channels, and intracellular free Ca2+ concentration ([Ca2+]i) were measured in single mouse pancreatic ,-cells. Whole-cell patch-clamp experiments with amphotericin-perforated patches revealed that membrane conductance at around the resting potential is predominantly supplied by the KATP channels in mouse pancreatic ,-cells. The addition of 20 nM GLP-1 in the presence of 5 mM glucose significantly reduced the membrane KATP conductance, accompanied by membrane depolarization and the generation of electrical activity. A calmodulin inhibitor N -(6-aminohexyl)-5-chloro-1-naphthalenesulphonamide (W-7, 20 ,M) completely reversed the inhibitory actions of GLP-1 on the membrane KATP conductance and resultant membrane depolarization. Cell-attached patch recordings confirmed the inhibition of the KATP channel activity by 20 nM GLP-1 and its restoration by 20 ,M W-7 or 10 ,M calmidazolium at the single channel level. Bath application of 20 ,M W-7 also consistently abolished the GLP-1-evoked increase in [Ca2+]i in the presence of 5 mM glucose. These results strongly suggest that the mechanisms by which GLP-1 inhibits the KATP channel activity accompanied by the initiation of electrical activity in mouse pancreatic ,-cells include a calmodulin-dependent mechanism in addition to the well-documented activation of the cyclic AMP-protein kinase A system. [source]

    Functional Characterisation of the Volume-Sensitive Anion Channel in Rat Pancreatic ,-Cells

    L. Best
    The whole-cell and perforated patch configurations of the patch-clamp technique were used to characterise the volume-sensitive anion channel in rat pancreatic ,-cells. The channel showed high permeability (P) relative to Cl, to extracellular monovalent organic anions (PSCN/PCll= 1.73, Pacetate/PCll= 0.39, Plactate/PCll= 0.38, Pacetoacetate/PCll= 0.32, Pglutamate/PCll= 0.28) but was less permeable to the divalent anion malate (Pmalate/PCll= 0.14). Channel activity was inhibited by a number of putative anion channel inhibitors, including extracellular ATP (10 mM), 1,9-dideoxyforskolin (100 ,M) and 4-OH tamoxifen (10 ,M). Inclusion of the catalytic subunit of protein kinase A in the pipette solution did not activate the volume-sensitive anion channel in non-swollen cells. Furthermore, addition of 8-bromoadenosine 3,,5,-cyclic monophosphate (8-BrcAMP) or forskolin failed to activate the channel in intact cells under perforated patch conditions. Addition of phorbol 12,13-dibutyrate (200 nM), either before or after cell swelling, also failed to affect channel activation. Our findings do not support the suggestion that the volume-sensitive anion channel in pancreatic ,-cells can be activated by protein kinase A. Furthermore, the ,-cell channel does not appear to be subject to regulation via protein kinase C. [source]

    A Novel Background Potassium Channel in Rat Atrial Cells

    Z. Shui
    A K+ channel activated by intracellular ATP has been observed in inside-out patches from rat atrial cells. The channel has a slope conductance of 130 ± 5 pS in symmetrical 140 mM K+ solution, and is almost independent of voltage over the range from -80 to +80 mV. There is no detectable inactivation during application of ATP over a few minutes. In the presence of 3 mM intracellular ATP, channel openings occur as bursts with a mean open time of 1.7 ms, a mean closed time of 0.4 ms, a mean burst duration of 18 ms and a mean burst interval of 41 ms. Kinetic analysis suggests that ATP mainly affects the burst duration and the burst interval of the channel. Based on the properties above, the channel differs from other known K+ channels in cardiac cells and may contribute to background K+ current. [source]

    Linking spatial pattern of bottom fish assemblages with water masses in the North Sea

    Abstract Understanding the links between large scale spatial structuring of fish assemblages and shaping factors is essential to develop comprehensive ecosystem-based fisheries management. In this study, we investigated spatial patterns of bottom fish assemblages in the North Sea in relation to prevailing water masses in the region. We based our analysis on catch data from the German Small-Scale Bottom Trawl Survey conducted between 1987 and 2005 and used both ordination techniques and Mantel tests. Spatial variability of bottom fish assemblages was larger than inter-annual variability. Five significantly different bottom fish assemblages were associated with the following prevailing hydrographical regimes: i) the English Channel, ii) Continental Coastal, iii) central North Sea, iv) northern North Sea, and v) northern Atlantic water masses. Associations were generated by gradients in relative proportions of abundant species such as grey gurnard (Eutrigla gurnardus), dab (Limanda limanda), whiting (Merlangius merlangus), haddock (Melanogrammus aeglefinus) and Norway pout (Trisopterus esmarki). Taking into account large scale spatial structuring of catch data Mantel tests confirmed significant correlation between the fish assemblages and hydrographical variables. In summary, our results strongly support the hypotheses that hydrographical features such as water masses, fronts, and residual currents could shape bottom fish associations in the North Sea. Spatial demarcations of bottom fish assemblages indicated by this study can be used to support ecosystem-based fisheries management strategies. [source]

    Geolocation of Atlantic cod (Gadus morhua) movements in the Gulf of Maine using tidal information

    J. P. GRÖGER
    Abstract Information derived from archival tags (digital storage tags, DSTs) were used to backtrack the migration of 11 tagged Atlantic cod (Gadus morhua) during 2001 in Massachusetts Bay, the Gulf of Maine, and Georges Bank. The DST tags continuously recorded time, temperature and depth. To geolocate fish positions during its time at large, we first extracted the tidal signal from the pressure recordings on the DST tags, and then compared the resulting data to data predicted with a Massachusetts Bay tidal model that provided us with geographical coordinates at a given date and time. Using least-squares criteria within an estimated geographical region of confidence that was constrained by biological and statistical information (e.g. swimming speed, known release and recapture location, and bottom depth) we were able to geolocate the fish. The resultant geolocated migration tracks indicate a large degree of movement of Atlantic cod in the region and an elevated importance of the Great South Channel (GSC) migration corridor between Massachusetts Bay and the western Georges Bank and Nantucket Shoals region. This observation contrasts strongly with inferences of limited movements by Atlantic cod based on conventional tag recapture methods (mean of 1200 km traveled versus 44 km traveled as measured by conventional tagging and geolocation, respectively). This study demonstrates that geolocation methodologies applied to archival tag studies hold great promise of becoming an important new tool for fisheries managers to quantify the movements of fishes. It also points out the need for greater collaboration between fisheries scientists and oceanographers, and particularly for the development of improved tidal models to cover stock regions more accurately and with higher precision. [source]