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Low Resistance (low + resistance)
Kinds of Low Resistance Selected AbstractsA prospective retrieval study to determine how speaking valve failure is effected by colonizationCLINICAL OTOLARYNGOLOGY, Issue 6 2000S.R. Ell Introduction. It has been suggested that Groningen Low Resistance (GLR) valve failure is associated with biofouling of the valve's oesophageal surface and hinge areas. However, the valve edges are responsible for efficient valve function. 1 Therefore, valve edge colonization should be the most important factor determining valve failure. The null hypothesis that valve edge colonization was not associated with failure was tested using 106 GLR valves retrieved, after failure, from 41 patients. Methods. The opening pressures, reverse opening pressures and forward resistances of the new valves were determined using apparatus validated previously. 2 The pressure/flow parameters were measured again after removal and the changes calculated. The degree of colonization of each valve edge, oesophageal surface, hinge area, tracheal surface and valve lumen was scored using 100-mm linear analogue scales. The changes, in pressure/flow parameters were examined for associated with colonization of the five areas described above. Results. The increase in the opening pressure and resistance, and decrease in reverse opening pressure, of the retrieved valves was significant compred with new valves. The increase in opening pressure was associated with colonization of the valve edge (rs = 0.262, P = 0.007). The decrease in reverse opening pressure was associated with colonization of the valve edge, hinge areas and oesophageal surface (rs = 0.266, P = 0.006; rs = 0.271, P = 0.005; rs = 0.271, P = 0.004, respectively). The increase in resistance was associated with colonization in all areas (rs , 0.367, P = 0.0005). Conclusion. This study demonstrated that colonization of the valve edge is associated significantly with the changes, in pressure/flow parameters of failed valves. [source] Assessing the Potential Impact of Cane Toads on Australian SnakesCONSERVATION BIOLOGY, Issue 6 2003BEN L. PHILLIPS Anecdotal reports suggest that the invasion of toads into an area is followed by dramatic declines in the abundance of terrestrial native frog-eating predators, but quantitative studies have been restricted to nonpredator taxa or aquatic predators and have generally reported minimal impacts. Will toads substantially affect Australian snakes? Based on geographic distributions and dietary composition, we identified 49 snake taxa as potentially at risk from toads. The impact of these feral prey also depends on the snakes' ability to survive after ingesting toad toxins. Based on decrements in locomotor (swimming) performance after ingesting toxin, we estimate the LD50 of toad toxins for 10 of the at-risk snake species. Most species exhibited a similar low ability to tolerate toad toxins. Based on head widths relative to sizes of toads, we calculate that 7 of the 10 taxa could easily ingest a fatal dose of toxin in a single meal. The exceptions were two colubrid taxa (keelbacks [ Tropidonophis mairii] and slatey-grey snakes [ Stegonotus cucullatus]) with much higher resistance to toad toxins (up to 85-fold) and one elapid (swamp snakes [ Hemiaspis signata]) with low resistance but a small relative head size and thus low maximum prey size. Overall, our analysis suggests that cane toads threaten populations of approximately 30% of terrestrial Australian snake species. Resumen: Los sapos (Bufo marinus) son anuros grandes muy tóxicos que fueron introducidos a Australia en 1937. Reportes anecdóticos sugieren que la invasión de sapos a un área es seguida de declinaciones dramáticas en la abundancia de depredadores terrestres nativos que se alimentan de ranas, pero los estudios cuantitativos se han restringido a taxones no depredadores o a depredadores acuáticos y generalmente han indicado impactos mínimos. ¿Los sapos afectarán sustancialmente a las serpientes australianas? Basado en la distribución geográfica y la composición de la dieta, identificamos 49 taxones de serpientes como potencialmente en riesgo por los sapos. El impacto de estas presas también depende de la habilidad de las serpientes para sobrevivir después de ingerir toxinas, estimamos la LD50 de toxinas de sapo para 10 de las especies de serpientes "en riesgo." La mayoría de las especies presentaron la misma poca habilidad para tolerar toxinas de sapo. Tomando en cuenta la anchura del cráneo en relación al tamaño de los sapos, calculamos que 7 de las 10 especies podrían fácilmente ingerir una dosis letal en una sola comida. Las excepciones fueron dos taxones de colúbridos (Tropidonophis mairii y Stegonotus cucullatus) con mucha más resistencia (hasta 85 veces más) a toxinas de sapos y un elápido (Hemiaspis signata) con resistencia baja pero de tamaño cefálico relativamente pequeño (y por lo tanto, tamaño máximo de presa pequeño). En general, nuestro análisis sugiere que los sapos amenazan a 30% de las poblaciones de especies de serpientes terrestres de Australia aproximadamente. [source] Mixed Aza-Thioether Crowns Containing a 1,10-Phenanthroline Sub-Unit as Neutral Ionophores for Silver IonELECTROANALYSIS, Issue 24 2002Mojtaba Shamsipur Abstract Three different recently synthesized aza-thioether crowns containing a 1,10-phenanthroline sub-unit (L1,L3) and a corresponding acyclic ligand (L4) were studied to characterize their abilities as silver ion ionophores in PVC-membrane electrodes. Novel conventional silver-selective electrodes with internal reference solution (CONISE) and coated graphite-solid contact electrodes (SCISE) were prepared based on one of the 15-membered crowns containing two donating S atoms and two phenanthroline-N atoms (L1). The electrodes reveal a Nernstian behavior over wide Ag+ ion concentration ranges (1.0×10,5,1.0×10,1,M for CONISE and 5.0×10,8,4.0×10,2,M for SCISE) and very low limits of detection (8.0×10,6,M for CONISE and 3.0×10,8,M for SCISE). The potentiometric response is independent from pH of the solution in the pH range 3.0,8.0. The electrodes manifest advantages of low resistance, very fast response and, most importantly, good selectivities relative to a wide variety of other cations. The electrodes can be used for at least 2 months (for CONISE) and 4 months for (SCISE) without any appreciable divergence in potentials. The electrodes were used as an indicator electrode in the potentiometric titration of Ag+ ion and in the determination of silver in photographic emulsions and in radiographic and photographic films. [source] Monitoring pyrethroid resistance in field collected Blattella germanica Linn. (Dictyoptera: Blattellidae) in IndonesiaENTOMOLOGICAL RESEARCH, Issue 2 2009Intan AHMAD Abstract The German cockroach, Blattella germanica, is a major and the most common pest in public areas in Indonesia. Although intensive control measures have been carried out to control the populations of this pest, results have been far from successful, which is believed to be because of its resistance to insecticides. A standard World Health Organization (WHO) glass jar test was carried out to determine the resistance level of this insect to pyrethroid insecticides, the most commonly used insecticides for cockroach control in Indonesia. A susceptible S1 strain collected from Tembagapura Papua was compared with four strains collected from Bandung, West Java: strain S2, from a local restaurant; strain S3, from the Bandung train station; and strains S4 and S5, from two different hotels. All strains showed low resistance to the pyrethroid, except the S5 strain, which had a Resistance Ratio (RR)50 of 95 for permethrin. The addition of piperonyl butoxide (PBO) suggests that the detoxifying enzyme mixed function oxidases (MFO) played an important role in the development of resistance to permethrin in the S5 strain, suggested by the high Synergist Ratio (SR) of 70.4. However, the low level of resistance to cypermethrin was not affected by PBO, suggesting that other mechanisms of pyrethroid resistance are involved. Our study is the first report of German cockroach resistance to permethrin in Indonesia, and the findings can be used in formulating potential strategies for cockroach resistance management. [source] Managing Environmental Impacts of Recreation and Tourism in Rainforests of the Wet Tropics of Queensland World Heritage AreaGEOGRAPHICAL RESEARCH, Issue 2 2005Stephen M. Turton Abstract This paper describes environmental impacts of tourism and recreation activities in the world heritage listed rainforests of northeast Australia and presents management strategies for sustainable visitor use of the protected area. Tropical rainforests are characterised by their low resistance and moderate to high resilience to impacts associated with human visitation. Visitor use in the World Heritage Area is mostly associated with walking tracks, camping areas, day use areas and off-road vehicle use of old forestry roads and tracks. Adverse environmental impacts range from vegetation trampling, soil compaction, water contamination and soil erosion at the local scale through to spread of weeds, feral animals and soil pathogens along extensive networks of old forestry roads and tracks at the regional scale. Concentration of visitor use is the most desirable management strategy for controlling adverse impacts at most World Heritage Area visitor nodes and sites, and includes methods such as site hardening and shielding to contain impacts. For dispersed visitor activities, such as off-road vehicle driving and long-distance walking, application of best practice methods by the tourist industry and recreational users such as removal of mud and soils from vehicle tyres and hiking boots before entering pathogen-free catchments, together with seasonal closure of roads and tracks, are the preferred management strategies. Retention of canopy cover at camping areas and day use areas, as well as along walking tracks and forestry roads is a simple, yet effective, management strategy for reduction of a range of adverse impacts, including dispersal of weeds and feral animals, edge effects, soil erosion and nutrient loss, road kill and linear barrier effects on rainforest fauna. [source] Orders-of-Magnitude Reduction of the Contact Resistance in Short-Channel Hot Embossed Organic Thin Film Transistors by Oxidative Treatment of Au-Electrodes,ADVANCED FUNCTIONAL MATERIALS, Issue 15 2007B. Stadlober Abstract In this study we report on the optimization of the contact resistance by surface treatment in short-channel bottom-contact OTFTs based on pentacene as semiconductor and SiO2 as gate dielectric. The devices have been fabricated by means of nanoimprint lithography with channel lengths in the range of 0.3,,m,<,L,<,3.0,,m. In order to reduce the contact resistance the Au source- and drain-contacts were subjected to a special UV/ozone treatment, which induced the formation of a thin AuOx layer. It turned out, that the treatment is very effective (i),in decreasing the hole-injection barrier between Au and pentacene and (ii),in improving the morphology of pentacene on top of the Au contacts and thus reducing the access resistance of carriers to the channel. Contact resistance values as low as 80,,,cm were achieved for gate voltages well above the threshold. In devices with untreated contacts, the charge carrier mobility shows a power-law dependence on the channel length, which is closely related to the contact resistance and to the grain-size of the pentacene crystallites. Devices with UV/ozone treated contacts of very low resistance, however, exhibit a charge carrier mobility in the range of 0.3,cm2,V,1,s,1,<,,,<,0.4,cm2,V,1,s,1 independent of the channel length. [source] Spatial foundation structures over no tension soilINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 14 2005A. Baratta Abstract The problem of the stress distribution induced in the soil by a single circular foundation structure is approached in a three-dimensional analysis. Since the soil is typically made by not-cohesive materials, its behaviour is modelled by means of the not resisting tension (NRT) hypothesis, thus assuming that its very low resistance to tensile stresses can be completely neglected and that it keeps linearly elastic under pure compression. After developing the problem from a theoretical point of view on the basis of an energetic approach, a numerical application,which is able to reproduce the stress distribution induced by a circular foundation on the soil,is performed. Copyright © 2005 John Wiley & Sons, Ltd. [source] Single-Crystal Polythiophene Microwires Grown by Self-Assembly,ADVANCED MATERIALS, Issue 6 2006H. Kim Single-crystal polythiophene microwires with unprecedented electrical characteristics such as low resistance (0.5,M,), a channel current as high as 25,,A, and well-resolved gate modulation (see figure) have been obtained by specific control over the supramolecular organization of individual polymer chains, which show preferential well-ordered interchain stacking along the wire axis. This approach offers a promising protocol for new flexible electronics. [source] Influence of wick characteristics on heat pipe performanceINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 7 2006Misheck G. Mwaba Abstract The performance of a heat pipe depends on several factors, one of which is the nature of the wick structure. Optimization of heat pipe performance requires wick structures that can provide high capillary pressure, and yet still offer low resistance to fluid flow. The current level of technology being developed in our laboratory makes it possible to engineer desired wick structures both micro- and macroscopically, especially tailored to optimize heat pipe performance. In order to assist the fabrication of unique wick structure, the influence of wick structure characteristics on heat pipe performance is numerically investigated in this work. Numerical methods are an effective tool to significantly reduce the number of experimental trials. Comparisons are made between performances of heat pipe with different wick structures; coarse pore sizes, fine pore sizes and a composite comprised of coarse and fine pore sizes. Results indicate superior performance, with a factor of up to 2, for heat pipe with composite structure combining coarse/fine wick. Validation of the simulation result presented using experimental data is being carried out. Copyright © 2005 John Wiley & Sons, Ltd. [source] Corrosion behavior of Ti-xNb-13Zr alloys in Ringer's solutionMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2008A. Robin Abstract Ti-6Al-4V alloy has been widely used in restorative surgery due to its high corrosion resistance and biocompatibility. Nevertheless, some studies showed that V and Al release in the organism might induce cytotoxic effects and neurological disorders, which led to the development of V-free alloys and both V- and Al-free alloys containing Nb, Zr, Ta, or Mo. Among these alloys, Ti-13Nb-13Zr alloy is promising due to its better biomechanical compatibility than Ti-6Al-4V. In this work, the corrosion behavior of Ti, Ti-6Al-4V, and Ti-xNb-13Zr alloys (x,=,5, 13, and 20) was evaluated in Ringer's solution (pH 7.5) at 37,°C through open-circuit potential measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy. Spontaneous passivity was observed for all materials in this medium. Low corrosion current densities (in the order of 10,7 A/cm2) and high impedance values (in the order of 105 ,cm2 at low frequencies) indicated their high corrosion resistance. EIS results showed that the passivating films were constituted of an outer porous layer (very low resistance) and an inner compact layer (high resistance), the latter providing the corrosion resistance of the materials. There was evidence that the Ti-xNb-13Zr alloys were more corrosion resistant than both Ti and Ti-6Al-4V in Ringer's solution. [source] Resistance of Pakistani field populations of spotted bollworm Earias vittella (Lepidoptera: Noctuidae) to pyrethroid, organophosphorus and new chemical insecticidesPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 4 2009Mushtaq Ahmad Abstract BACKGROUND: The spotted bollworm Earias vittella (Fab.) is a serious pest of cotton and okra in Pakistan. Owing to persistent use of insecticides, this pest has developed resistance, especially to pyrethroids. The present studies aimed at determining the extent of resistance to pyrethroid, organophosphorus and new chemical insecticides in Pakistani populations of E. vittella. RESULTS: Field populations of E. vittella were monitored at Multan, Pakistan, from 1999 to 2007 for their resistance against six pyrethroid, four organophosphorus and six new chemical insecticides using a leaf-dip bioassay. Of the pyrethroids, resistance was generally low to zeta-cypermethrin and moderate to high or very high to cypermethrin, deltamethrin, esfenvalerate, bifenthrin and lambda-cyhalothrin. Resistance to organophosphates chlorpyrifos, profenofos, triazophos and phoxim was recorded at very low to low levels. Among new chemicals, E. vittella had no or a very low resistance to spinosad, emamectin benzoate and methoxyfenozide, a very low to low resistance to abamectin, a very low to moderate resistance to indoxacarb and a moderate resistance to chlorfenapyr. CONCLUSION: The results indicate a lack of cross-resistance between pyrethroid and organophosphorus insecticides in E. vittella. Rotation of insecticides showing no, very low or low resistance, but belonging to different insecticide classes with unrelated modes of action, may prevent or mitigate insecticide resistance in E. vittella. Copyright © 2009 Society of Chemical Industry [source] Acetamiprid resistance and cross-resistance in the diamondback moth, Plutella xylostellaPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 9 2004Kodwo D Ninsin Abstract A 110-fold acetamiprid-resistant Plutella xylostella (L) strain was established after four selection experiments (in five generations) on a 9.5-fold resistant colony in the laboratory. The resistant strain did not show cross-resistance to chlorfluazuron or Bacillus thuringiensis subsp kurstaki Berliner, but displayed low resistance to cartap and phenthoate. Copyright © 2004 Society of Chemical Industry [source] Innovative process flow to achieve carbon nanotube based interconnectsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2008J. C. Coiffic Abstract We have achieved down to 140 nm diameter carbon nanotube via interconnects with both new single and dual damascene processes on 200 mm silicon wafers. High density 5 × 1010 nanotube/cm2 is obtained. The validity of these two new processes has been checked by performing electrical measurements. At high bias, a low resistance of 20 , has been reached for a 300 nm diameter via interconnect. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The use of Ti meshes with self-organized TiO2 nanotubes as photoanodes of all-Ti dye-sensitized solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 4 2010Yuanhao Wang Abstract This paper reports a simple and facile method for directly growing self-organized TiO2 nanotubular arrays around the whole Ti mesh by electrochemical anodization in organic electrolytes and their application in all-Ti dye-sensitized solar cells (DSSCs). Compared with the traditional fluorine-doped tin oxide (FTO)-based DSSC and the backside illuminated DSSC, this type of DSSC showed advantages such as low resistance, cheap fabrication cost and enhanced sunlight utilization. Different thicknesses of nanotubular array layers were investigated to find their influence on the photovoltaic parameters of the cell. We also considered three types of meshes as the substrates of anodes and found that the cell with 6,openings/mm2 exhibited the highest conversion efficiency of 5.3%. The area of the cell had only a little impact on the photovoltaic performances. Copyright © 2010 John Wiley & Sons, Ltd. [source] A Landscape Approach for Ecologically Based Management of Great Basin ShrublandsRESTORATION ECOLOGY, Issue 5 2009Michael J. Wisdom Abstract Native shrublands dominate the Great Basin of western of North America, and most of these communities are at moderate or high risk of loss from non-native grass invasion and woodland expansion. Landscape-scale management based on differences in ecological resistance and resilience of shrublands can reduce these risks. We demonstrate this approach with an example that focuses on maintenance of sagebrush (Artemisia spp.) habitats for Greater Sage-grouse (Centrocercus urophasianus), a bird species threatened by habitat loss. The approach involves five steps: (1) identify the undesired disturbance processes affecting each shrubland community type; (2) characterize the resistance and resilience of each shrubland type in relation to the undesired processes; (3) assess potential losses of shrublands based on their resistance, resilience, and associated risk; (4) use knowledge from these steps to design a landscape strategy to mitigate the risk of shrubland loss; and (5) implement the strategy with a comprehensive set of active and passive management prescriptions. Results indicate that large areas of the Great Basin currently provide Sage-grouse habitats, but many areas of sagebrush with low resistance and resilience may be lost to continued woodland expansion or invasion by non-native annual grasses. Preventing these losses will require landscape strategies that prioritize management areas based on efficient use of limited resources to maintain the largest shrubland areas over time. Landscape-scale approaches, based on concepts of resistance and resilience, provide an essential framework for successful management of arid and semiarid shrublands and their native species. [source] Thinnest Two-Dimensional Nanomaterial,Graphene for Solar EnergyCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 7 2010Yun Hang Hu Prof. Abstract Graphene is a rapidly rising star in materials science. This two-dimensional material exhibits unique properties, such as low resistance, excellent optical transmittance, and high mechanical and chemical stabilities. These exceptional advantages possess great promise for its potential applications in photovoltaic devices. In this Review, we present the status of graphene research for solar energy with emphasis on solar cells. Firstly, the preparation and properties of graphene are described. Secondly, applications of graphene as transparent conductive electrodes and counter electrodes are presented. Thirdly, graphene-based electron- (or hole) accepting materials for solar energy conversion are evaluated. Fourthly, the promoting effect of graphene on photovoltaic devices and the photocatalytic property of graphene,semiconductor composites are discussed. Finally, the challenges to increase the power conversion efficiency of graphene-based solar cells are explored. [source] | |||||||||||||||||||