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Maximum Efficiency (maximum + efficiency)
Selected AbstractsIs the efficiency of mammalian (mouse) skeletal muscle temperature dependent?THE JOURNAL OF PHYSIOLOGY, Issue 19 2010C. J. Barclay Myosin crossbridges in muscle convert chemical energy into mechanical energy. Reported values for crossbridge efficiency in human muscles are high compared to values measured in vitro using muscles of other mammalian species. Most in vitro muscle experiments have been performed at temperatures lower than mammalian physiological temperature, raising the possibility that human efficiency values are higher than those of isolated preparations because efficiency is temperature dependent. The aim of this study was to determine the effect of temperature on the efficiency of isolated mammalian (mouse) muscle. Measurements were made of the power output and heat production of bundles of muscle fibres from the fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus muscles during isovelocity shortening. Mechanical efficiency was defined as the ratio of power output to rate of enthalpy output, where rate of enthalpy output was the sum of the power output and rate of heat output. Experiments were performed at 20, 25 and 30°C. Maximum efficiency of EDL muscles was independent of temperature; the highest value was 0.31 ± 0.01 (n= 5) at 30°C. Maximum efficiency of soleus preparations was slightly but significantly higher at 25 and 30°C than at 20°C; the maximum mean value was 0.48 ± 0.02 (n= 7) at 25°C. It was concluded that maximum mechanical efficiency of isolated mouse muscle was little affected by temperature between 20 and 30°C and that it is unlikely that differences in temperature account for the relatively high efficiency of human muscle in vivo compared to isolated mammalian muscles. [source] An Alternative Approach to Constructing Solution Processable Multifunctional Materials: Their Structure, Properties, and Application in High-Performance Organic Light-Emitting DiodesADVANCED FUNCTIONAL MATERIALS, Issue 18 2010Shanghui Ye Abstract A new series of full hydrocarbons, namely 4,4,-(9,9,-(1,3-phenylene)bis(9H -fluorene-9,9-diyl))bis(N,N -diphenylaniline) (DTPAFB), N,N,-(4,4,-(9,9,-(1,3-phenylene)bis(9H -fluorene-9,9-diyl))bis(4,1-phenylene))bis(N -phenylnaphthalen-1-amine) (DNPAFB), 1,3-bis(9-(4-(9H -carbazol-9-yl)phenyl)-9H -fluoren-9-yl)benzene, and 1,3-bis(9-(4-(3,6-di- tert -butyl-9H -carbazol-9-yl)phenyl)-9H -fluoren-9-yl)benzene, featuring a highly twisted tetrahedral conformation, are designed and synthesized. Organic light-emitting diodes (OLEDs) comprising DNPAFB and DTPAFB as hole transporting layers and tris(quinolin-8-yloxy)aluminum as an emitter are made either by vacuum deposition or by solution processing, and show much higher maximum efficiencies than the commonly used N,N,-di(naphthalen-1-yl)- N,N,-diphenylbiphenyl-4,4,-diamine device (3.6 cd A,1) of 7.0 cd A,1 and 6.9 cd A,1, respectively. In addition, the solution processed blue phosphorescent OLEDs employing the synthesized materials as hosts and iridium (III) bis[(4,6-di-fluorophenyl)-pyridinato-N, C2] picolinate (FIrpic) phosphor as an emitter present exciting results. For example, the DTPAFB device exhibits a brightness of 47 902 cd m,2, a maximum luminescent efficiency of 24.3 cd A,1, and a power efficiency of 13.0 lm W,1. These results show that the devices are among the best solution processable blue phosphorescent OLEDs based on small molecules. Moreover, a new approach to constructing solution processable small molecules is proposed based on rigid and bulky fluorene and carbazole moieties combined in a highly twisted configuration, resulting in excellent solubility as well as chemical miscibility, without the need to introduce any solubilizing group such as an alkyl or alkoxy chain. [source] The application of spreadsheets to the analysis and optimization of systems and processes in the teaching of hydraulic and thermal engineeringCOMPUTER APPLICATIONS IN ENGINEERING EDUCATION, Issue 4 2006A. Rivas Abstract This article shows the capability of current spreadsheets to define, analyze and optimize models of systems and processes. Specifically, the Microsoft spreadsheet Excel is used, with its built-in solver, to analyze and to optimize systems and processes of medium complexity, whose mathematical models are expressed by means of nonlinear systems of equations. Two hydraulic and thermal engineering-based application examples are presented, respectively: the analysis and optimization of vapor power cycles, and the analysis and design of piping networks. The mathematical models of these examples have been implemented in Excel and have been solved with the solver. For the power cycles, the thermodynamic properties of water have been calculated by means of the add-in TPX (Thermodynamic Properties for Excel). Performance and optimum designs are presented in cases studies, according to the optimization criteria of maximum efficiency for the power cycle and minimum cost for the piping networks. © 2006 Wiley Periodicals, Inc. Comput Appl Eng Educ 14: 256,268, 2006; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20085 [source] Spatial Autocorrelation Analysis and the Identification of Operational Units for Conservation in Continuous PopulationsCONSERVATION BIOLOGY, Issue 4 2002José Alexandre Felizola Diniz-Filho We show that spatial autocorrelation analysis, applied to phenotypic or molecular data, can be used to describe the geographic structure and therefore can help define optimum strategies for conserving genetic variability within species. We propose that the intercept of a spatial correlogram can be an indication of the minimum distance between samples that can conserve and assess genetic diversity with maximum efficiency at lower costs. This parameter can be used both to define units and to establish sampling strategies for conservation programs. We illustrate the utility of this approach by autocorrelation analyses applied to three data sets: isozyme variability among Eugenia dysenterica populations in Brazilian Cerrado and within populations of Adenophora glandiflora in Korea, and microsatellite variation among Ursus arctos populations in North America. Our results suggest that the intercept of spatial correlograms is a useful parameter for establishing operational units for intraspecific conservation in continuous populations, based on overall genetic or phenotypic variability, by defining the minimum geographic distance at which samples are independent. Resumen: A pesar de los avances recientes en la identificación de la estructura genética poblacional mediante la tecnología de marcadores moleculares, la definición de las unidades intraespecíficas para la conservación es aún problemática. Esto sucede particularmente cuando la variación genética y fenotípica se encuentra distribuida de manera continua en un espacio geográfico. Demostramos que el análisis de autocorrelación espacial, aplicado a los datos fenotípicos o moleculares puede ser usado para describir la estructura geográfica y, por lo tanto, puede ayudar a definir estrategias óptimas para la conservación de la variabilidad genética en las especies. Proponemos que el intercepto de un correlograma espacial puede ser un indicador de la distancia mínima entre muestras que pueden conservar y evaluar la diversidad genética con mayor eficiencia a un costo más bajo. Este parámetro puede ser usado tanto para definir unidades como para establecer estrategias de muestreo para los programas de conservación. Ejemplificamos la utilidad de este método mediante la aplicación de análisis de autocorrelación a tres grupos de datos: variabilidad de isozomas entre poblaciones de Adenophora dysenterica en el cerrado brasileño, dentro de poblaciones de Adenophora glandiflora en Korea y variación microsatélite entre poblaciones de Ursus arctos en América del Norte. Nuestros resultados sugieren que el intercepto de los correlogramas espaciales son un parámetro útil que puede establecer unidades operacionales para conservación intraespecífica en poblaciones continuas, en base a la variabilidad general genética o fenótipica, al definir la distancia geográfica mínima a la cual las muestras son independientes. [source] Numerical modeling of frequency influence on the electromagnetic stirring of semiconductor meltsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 7 2006C. Stelian Abstract Alternating magnetic fields can be used in order to increase the level of convection and to mix the doped semiconductor alloys. A numerical analysis of the electromagnetic induced convection in GaInSb semiconductor melts is performed by using the software package CrysVUn. The magnetic field parameters are varied in order to obtain a maximum efficiency of the induced convection with a minimum quantity of the heat released in the melt. The influence of the electrical current frequency on the convection intensity is analyzed for samples with various radii (R = 0.5 , 3cm). Numerical procedure is validated by comparing the numerical results obtained in mercury samples with the experimental data given from the literature, which show a maximum stirring for a magnetic skin depth , = 0.2R , in the case of a mercury sample with the radius R = 10 cm. This maximum corresponds to a shielding parameter R, = 40. Our numerical results show that the value of the shielding parameter for which the convection intensity reaches the maximum depends on the sample radius and increases when the sample radius increases. The results of this analysis are important in the case of samples with small radius, when a good mixing of the melt can be obtained for frequencies much lower than those corresponding to a shielding parameter R, = 40. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Analysis of effect of electrolyte types on electrokinetic energy conversion in nanoscale capillariesELECTROPHORESIS, Issue 3 2010Reiyu Chein Abstract An analytical study on the effect of electrolyte types on the electrokinetic energy conversion is presented using nanoscale cylindrical capillary, which is either positively or negatively charged. The sign of surface charge determines the role and concentration magnitude of ions in the capillary and the energy conversion performance. Our study shows that the electrokinetic energy conversion performance (maximum efficiency, pressure rise and streaming potential) are approximately identical for 1:1 (KCl), 2:1 (CaCl2) and 3:1 (LaCl3) electrolytes when capillary is positively charged. For negatively charged capillary, energy conversion performance degrades significantly with the increase of counter-ion valence. For both positively and negatively charged capillaries, higher maximum efficiency can be resulted in low bulk concentration and surface charge density regimes. However, high maximum pressure rise generation for the pumping is found in the low bulk concentration and high surface charge density regimes. For the electric power generation, higher maximum streaming potential is found when both bulk concentration and surface charge density are low. [source] Layer-by-Layer All-Inorganic Quantum-Dot-Based LEDs: A Simple Procedure with Robust PerformanceADVANCED FUNCTIONAL MATERIALS, Issue 19 2010James S. Bendall Abstract A novel all-inorganic electroluminescent device is demonstrated based on highly luminescent CdTe nanocrystals intercalated within a laminar hydrotalcite-like structure. The laminar scaffold acts to both support and distribute the CdTe nanocrystals. The device is synthesized using simple wet chemical processes at room temperature in ambient conditions. It has high thermal stability, operating continuously up to 90 °C, and a maximum efficiency at J = 0.12 A cm,2. The device is targeted at the automotive industry. [source] Sensitive Explosive Vapor Detection with Polyfluorene LasersADVANCED FUNCTIONAL MATERIALS, Issue 13 2010Ying Yang Abstract Distributed feedback organic semiconductor lasers based on polyfluorene are shown to be suitable for use as chemical sensors for the detection of nitroaromatic-based explosive vapors. The laser threshold is increased by a factor of 1.8 and the slope efficiency is reduced by a factor of 3 after exposure to the vapor. The sensing efficiency depends strongly on the excitation energy with a maximum efficiency of 85%. The temporal dynamics of the laser response to the analyte have been investigated. The laser emission falls to 60% of its initial value in 46,s. A model is developed to offer some insight into the diffusion of the vapor molecules inside the polymer layer. [source] Conformal Nano-Sized Inorganic Coatings on Mesoporous TiO2 Films for Low-Temperature Dye-Sensitized Solar Cell FabricationADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Larissa Grinis Abstract Here, a new method based on sol,gel electrophoretic deposition to produce uniform high-quality inorganic conformal coatings on mesoporous nano-particulate films is presented. This novel sol preparation method allows for very fine control of the coating properties, thus inducing new adjustable functionalities to these electrodes. It is shown that the deposition of an amorphous TiO2 and/or MgO shell onto photoanodes used in dye-sensitized solar cells (DSSCs) improves their light-to-electric-power conversion efficiency without the need for sintering. It is proposed that the amorphous TiO2 coating improves the electronic inter-particle connection and passivates the surface states. The insulating MgO coating further reduces the electron transfer from the conduction band into the electrolyte while the electron injection from the excited dye state remains unperturbed for thin coatings. Using a low-temperature method for DSSC production on plastic substrates, a maximum efficiency of 6.2% applying pressure together with an optimized TiO2 coating is achieved. For systems that cannot be pressed a conversion efficiency of 5.1% is achieved using a double shell TiO2/MgO coating. [source] Estimating the Maximum Attainable Efficiency in Dye-Sensitized Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 1 2010Henry J. Snaith Abstract For an ideal solar cell, a maximum solar-to-electrical power conversion efficiency of just over 30% is achievable by harvesting UV to near IR photons up to 1.1,eV. Dye-sensitized solar cells (DSCs) are, however, not ideal. Here, the electrical and optical losses in the dye-sensitized system are reviewed, and the main losses in potential from the conversion of an absorbed photon at the optical bandgap of the sensitizer to the open-circuit voltage generated by the solar cell are specifically highlighted. In the first instance, the maximum power conversion efficiency attainable as a function of optical bandgap of the sensitizer and the "loss-in-potential" from the optical bandgap to the open-circuit voltage is estimated. For the best performing DSCs with current technology, the loss-in-potential is ,0.75,eV, which leads to a maximum power-conversion efficiency of 13.4% with an optical bandgap of 1.48,eV (840,nm absorption onset). Means by which the loss-in-potential could be reduced to 0.4,eV are discussed; a maximum efficiency of 20.25% with an optical bandgap of 1.31,eV (940,nm) is possible if this is achieved. [source] Disentangling effects of an experimentally imposed extreme temperature event and naturally associated desiccation on Arctic tundraFUNCTIONAL ECOLOGY, Issue 6 2006F. L. MARCHAND Summary 1Climate projections suggest that extreme events will increase in frequency during this century. As tundra is recognized to be among the most vulnerable biomes, we exposed patches of arctic tundra vegetation to an experimental heatwave (by infrared irradiation), followed by a recovery period. The heating increased the surface temperature with an average of 7·6 °C during 13 days, which slightly exceeded the longest climatic episode with such a temperature deviation since 1961. 2The heatwave decreased stomatal conductance (gs) and PSII maximum efficiency (Fv/Fm), although there were differences in response among the four target species. Salix arctica Pall. (shrub) was affected during the heatwave and could not recover. In Carex bigelowii Tor. ex Schwein (sedge) and Pyrola grandiflora Radius (forb), on the other hand, the effects on gs and Fv/Fm became clear, particularly in the aftermath of the heatwave, whereas Polygonum viviparum L. (forb) was never stressed. 3Effects of the heat on gs were mainly indirect, through increased desiccation, whereas effects on Fv/Fm were more related to leaf temperature (although not in all species). The observed changes can therefore probably be ascribed to a combination of heat and drought causing dysfunctions that ultimately led to senescence. 4Two conclusions of this study, species-specific responses and increased leaf mortality, indicate that more frequent extreme temperature events accompanied by desiccation might alter/endanger tundra communities in a future climate. Predictions of global change effects on arctic ecosystems should therefore take into account the impact of extremes. [source] Energy model based loss-minimized speed control of induction motor with a full-order observerIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 1 2006Mohammad Abdul Mannan Student Member Abstract In this paper, a loss-minimization algorithm is developed to achieve maximum efficiency in terms of slip frequency. The optimal value of slip frequency can be obtained by minimizing all controllable losses of the induction motor (IM). The ratio of magnetic energy converted to torque (WT) to magnetic energy stored in the rotating field (Wq) is defined in terms of slip frequency to obtain an error function that is used to design a controller to achieve the desired speed. Since the energy model of the IM can be expressed by the multi-input and multi-output (MIMO) system, an MIMO optimal regulator is proposed to achieve the desired speed with maximum efficiency. To design an optimal regulator, it is necessary to measure all state quantities. But WT and Wq cannot be measured directly. Therefore, a full-order observer is proposed to estimate these state quantities. The gains of the observer system are calculated by using the pole placement technique. Consequently, the observer system becomes stable. The performance of the proposed controller and observer system are verified by using simulation. With regard to the simulation results, it can be concluded that the desired speed can be achieved by using the proposed controller and the unknown state quantities can be estimated properly by using the proposed observer system. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Friction effect on the characteristic performance of Diesel enginesINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 11 2002Lingen Chen Abstract An irreversible model for an air standard Diesel engine is presented in this paper. This model takes into account the finite-time evolution of the cycle's compression and power strokes and it considers global losses lumped in a friction-like term. The relations between the power output and the compression ratio, as well as between the thermal efficiency and the compression ratio are derived. The maximum power output with the corresponding efficiency, and the maximum efficiency with the corresponding power output are calculated versus compression ratio. Copyright © 2002 John Wiley & Sons, Ltd. [source] Identification of denitrifying rhizobacteria from bentgrass and bermudagrass golf greensJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2004G. Wang Abstract Aims:, As high rates of nitrogen fertilization are used in turfgrass management, there is a great potential for nitrogen loss. Research on identification of denitrifiers in turfgrass has been limited. Therefore, the aim was to identify denitrifier species and genes from turfgrass roots. Methods and Results:, Rhizobacteria were isolated from roots of bentgrass and bermudagrass in sand-based United States Golf Association (USGA) golf greens and used for denitrification biochemical analysis. Seventeen per cent (34 isolates) were identified as denitrifiers, 47% were classified as nitrate-reducers and 36% were nondenitrifiers. Identification of species of the denitrifiers was performed by chromatography fatty acid methyl ester (GC-FAME) and16S rDNA analyses. Bacillus and Pseudomonas were the major turfgrass denitrifiers. The two methods showed a 60% agreement at the genus level. Nitrite reductase genes nirK and nirS were detected in 74 and 15% of the denitrifiers, respectively, but not in nondenitrifiers. The nosZ gene encoding nitrous oxide reductase was detected in all the denitrifiers, but also in some nondenitrifiers. Conclusions:, To our knowledge, this is the first report for identification of denitrifiers and denitrification-related genes associated with turfgrass roots. Significance and Impact of the Study:, These results provide valuable data for future denitrification studies that seek to improve turfgrass nitrogen management for maximum efficiency. [source] Synthesis and characterization of novel poly(arylenevinylene) derivativeJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Song Se-Yong Abstract The new poly(arylenevinylene) derivative composed naphthalene phenylene vinylene backbone was developed. The theoretical calculation showed that the model compound of the obtained polymer was highly distorted between the stryl and naphthalene units as well as between the backbone and fluorene side units. The polymer was synthesized by the palladium catalyzed Suzuki coupling reaction with 2,6-(1,,2,-ethylborate)-1,5-dihexyloxynaphtalene and 1,2-bis(4,-bromophenyl)-1-(9,,9,-dihexyl-3-fluorenyl)ethene. The structure of the polymer was confirmed by 1H NMR, IR, and elemental analysis. The weight,average molecular weight of the polymer is 29,800 with the polydispersity index of 1.87. The new polymer showed good thermal stability with high Tg of 195°C. The bright blue fluorescence (,max = 475 nm) was observed both in solution and film of new polymer with naphthalene phenylene vinylene backbone. Double layer LED devices with the configuration of ITO/PEDOT/polymer/LiF/Ca/Al showed a turn-on voltage at around 4.5 V, the maximum luminance of 150 cd/m2, and the maximum efficiency of 0.1 cd/A. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Compressive response and energy absorption of foam EPDMJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Biqin Wang Abstract Ethylene,propylene,diene terpolymer foam was prepared by two different processing routes. The microstructure and mechanical properties of the foams with wide relative density ranging from 0.11 to 0.62 have been studied via scanning electron microscopy and mechanical testing, respectively. Scanning electron microscopy shows that the foam with lower relative density has a unique bimodal cell size structure, which the larger cells inlay among the smaller cells, while the foam articles with higher relative density have thicker cell walls with few small cells. The compressive stress,strain curves show that the foam articles with lower relative density have three regimes: linear elastic, a wide slightly rising plateau, and densification, while the foam articles with higher relative density have only two regimes: the longer linear elastic and densification. The relative modulus increases with the increase in the relative density. The contribution of the gas trapped in the cell to the modulus could be neglected. The energy absorbed per unit volume is relationship with the permitted stress and the relative density. The efficiency and the ideality parameter were evaluated from the compressive stress,strain plots. The parameters were plotted against stress to obtain maximum efficiency and the maximum ideality region, which can be used for optimizing the choice for practical applications in cushioning and packaging. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Effect of adsorption characteristics of a modified cellulase on indigo backstainingJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2004Diomi Mamma Abstract The effect of limited proteolysis (digestion) of a commercial cellulase preparation (Ecostone® L350) on backstaining with indigo was investigated. The influence of protease (papain) concentration on limited proteolysis of cellulase preparation was studied, applying different ratios of papain/cellulase (w/w). Changes in adsorption on Avicel cellulose of the non-digested compared with the papain-digested Ecostone® L350 were examined using the Langmuir adsorption isotherm. The non-digested Ecostone® L350 exhibited stronger interaction to Avicel cellulose compared with the digested form, while the maximum efficiency of cellulase adsorption to Avicel cellulose decreased after digestion. When papain-digested Ecostone® L350 was applied on cotton fabrics during the dyeing procedure with indigo, a reduction of indigo backstaining was obtained compared with the non-digested Ecostone® L350. Copyright © 2004 Society of Chemical Industry [source] Operating and scale-up factors for the electrolytic removal of algae from eutrophied lakewaterJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2002Catalino G Alfafara Abstract Electrolytic removal of algae was conducted in batch and continuous reactors to investigate operating factors affecting removal efficiency and to explore engineering relationships which could be useful for operation and scale-up. The system integrated both electro-flocculation and electro-flotation mechanisms by using polyvalent metal anodes and inert metal cathodes. Batch reactor studies confirmed that high electrical input power or higher electrical current achieved higher and faster removal efficiencies. Natural liquid circulation was observed during electrolytic operation and increased with higher electrical power. However, a small degree of external mixing may be useful at lower electrical power input. Electro-flotation alone could not achieve complete algae removal (maximum efficiency 40,50%), and showed the importance of algal floc formation for the complete removal of algae. In continuous electrolysis experiments, the ratio of the volumetric current intensity (amperes,dm,3) and the chlorophyll a loading (mg,dm,3,h,1) was found to be a useful operating and scale-up factor to balance high algal removal efficiency with minimum release of excess aluminum. This ratio was eventually found to be just the charge dose or the amount of coulombs required to remove a unit mass of chlorophyll a. The optimum charge dose was determined and used to relate the operating current and electrolysis time of a continuous process. © 2002 Society of Chemical Industry [source] Preparation of polylactide-co-glycolide and chitosan hybrid microcapsules of amifostine using coaxial ultrasonic atomizer with solvent evaporationJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 3 2008Sarala Pamujula The objective of this study was to evaluate the effect of various processing and formulation factors on the characteristics of amifostine hybrid microcapsules. Amifostine-loaded hybrid microcapsules were prepared using PLGA and chitosan. In short, amifostine powder was dissolved in de-aerated water with or without chitosan. The amifostine solution was later emulsified into PLGA solution in dichloromethane containing phosphatidylcholine. The resultant emulsion was fed through the inner capillary of a coaxial ultrasonic atomizer. The liquid fed through the coaxial outer capillary was either water or chitosan solution. The atomized droplets were collected into PVA solution and the droplets formed microcapsules immediately. The hybrid microcapsules prepared with chitosan solution only as an outer layer liquid showed the maximum efficiency of encapsulation (30%). The median sizes of all three formulations were 33,44 ,m. These formulations with chitosan showed positive zeta-potential and sustained drug release with 13,45% amifostine released in 24 h. When chitosan was incorporated into inner as well as outer liquid layers, the drug release increased significantly, 45% (compared with other formulations) released in 24 h and almost 100% released in 11 days. Hybrid microcapsules of amifostine showed moderately high efficiency of encapsulation. The cationic charge (due to the presence of chitosan) of these particles is expected to favour oral absorption and thus overall bioavailability of orally administered amifostine. [source] The design and performance analysis of integrated amplifier patch antennaMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2008Adnan Kaya Abstract This work presents the design of an active amplifier antenna. Active integrated antennas can be obtained with active components directly connected to the antenna structure. In this article, a novel active integrated single microstrip antenna analysis and its radiation pattern and gain performance is proposed. A high-efficiency, low noise, and high linear compact amplifier integrated with a microstrip antenna at 1.6 GHz is presented for RF front-end circuit applications. The design in this study consists of a rectangular microstrip antenna with a pair of parallel slots loaded close to the radiating edge of the patch and three meandering narrow slots embedded in the antenna surface. With the proposed design a size reduction of 34% for the 1.6- and 2.6-GHz resonant frequencies is obtained and the two frequencies have an operation frequency ratio of 1.30. In this design approach, the measured antenna impedance is transformed with matching to the load impedance for maximum efficiency. With the proposed amplifier antenna design, the antenna radiation pattern can be better than an antenna radiation pattern without matching. In addition, it has been shown that compensation significantly improves the return loss matching level. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2732,2736, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23765 [source] A novel internal antenna with high gain for wireless phoneMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2007Ying Liu Abstract A novel internal antenna for synchronous code division multiple access band wireless phone is presented. Traditional internal antenna is monopole or Planar Inverted-F Antenna, which have no gain high enough in the limited space in phone. The proposed antenna is composed of two antenna elements with equal magnitude and 180° phase difference, to assure voice quality with high gain. The measured maximum gain is 2.69 dBi and maximum efficiency is 70.1% in the frequency band 450,470 MHz. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2112,2114, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22708 [source] Creative Destruction, Economic Insecurity, Stress, and Epidemic ObesityAMERICAN JOURNAL OF ECONOMICS AND SOCIOLOGY, Issue 3 2010Jon D. Wisman The percentage of Americans who are obese has doubled since 1980. Most attempts to explain this "obesity epidemic" have been found inadequate, including the "Big Two" (the increased availability of inexpensive food and the decline of physical exertion). This article explores the possibility that the obesity epidemic is substantially due to growing insecurity, stress, and a sense of powerlessness in modern society where high-sugar and high-fat foods are increasingly omnipresent. Those suffering these conditions may suffer less control over other domains of their lives. Insecurity and stress have been found to increase the desire for high-fat and high-sugar foods. After exploring the evidence of a link between stress and obesity, the increasing pace of capitalism's creative destruction and its generation of greater insecurity and stress are addressed. The article ends with reflections on how epidemic obesity is symptomatic of a social mistake,the seeking of maximum efficiency and economic growth even in societies where the fundamental problem of material security has been solved. I confess I am not charmed with the ideal of life held out by those who think that the normal state of human beings is that of struggling to get on; that the trampling, crushing, elbowing, and treading on each other's heels, which form the existing type of social life, are the most desirable lot of humankind, or anything but the disagreeable symptoms of one of the phases of industrial progress. (Mill 1848: 748) Thus we have been expressly evolved by nature,with all our impulses and deepest instincts,for the purpose of solving the economic problem ["the struggle for subsistence"]. If the economic problem is solved, mankind will be deprived of its traditional purpose . . . Will this be a benefit? If one believes at all in the real values of life, the prospect at least opens up the possibility of benefit. Yet I think with dread of the readjustment of the habits and instincts of the ordinary man, bred into him for countless generations, which he may be asked to discard within a few decades. (Keynes 1932: 366) [source] Influence of charge carrier mobility on the performance of organic solar cellsPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 4 2008Carsten Deibel Abstract The power conversion efficiency of organic solar cells based on donor,acceptor blends is governed by an interplay of polaron pair dissociation and bimolecular polaron recombination. Both processes are strongly dependent on the charge carrier mobility, the dissociation increasing with faster charge transport, with raised recombination losses at the same time. Using a macroscopic effective medium simulation, we calculate the optimum charge carrier mobility for the highest power conversion efficiency, for the first time accounting for injection barriers and a reduced Langevin-type recombination. An enhancement of the charge carrier mobility from 10,8 m2/V s for state of the art polymer,fullerene solar cells to about 10,6 m2/V s, which yields the maximum efficiency, corresponds to an improvement of only about 20% for the given parameter set. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Oxygen evolution and respiration of the cyanobacterium Synechocystis sp.PHYSIOLOGIA PLANTARUM, Issue 3 2005PCC 6803 under two different light regimes applying light/dark intervals in the time scale of minutes The photosynthetic performance of the cyanobacterium Synechocystis sp. PCC 6803 exposed to intermittent light was studied by measuring oxygen evolution, respiration and the fluorescence parameters for maximum efficiency of excitation energy capture by photosystem II (PSII) reaction centres (Fv/Fm), PSII quantum yield (,F/Fm1) and non-photochemical quenching (NPQ). Cultures were pre-acclimated to constant light conditions. Block and sinusoidal light regimes were tested using four photon-flux densities (PFDs) applied in light/dark intervals of 1:1, 5:5 and 10:10 min. Light use was higher under the sinusoidal light regime compared with the block regime. The accumulated gross photosynthesis of the cyanobacterium was lower under intermittent light conditions compared with predictions from the photosynthesis-irradiance curve (PI curve). The respiration rates were similar for all light/dark intervals tested. However, the respiration slightly increased with increasing oxygen production for both block and sinusoidal light regime. NPQ, ,F/Fm, and Fv/Fm depended on the PFD rather than on the duration of the light/dark intervals tested, and there was no detected influence of the two applied light regimes. [source] Is a short, sharp shock equivalent to long-term punishment?PLANT CELL & ENVIRONMENT, Issue 4 2009Contrasting the spatial pattern of acute, chronic ozone damage to soybean leaves via chlorophyll fluorescence imaging ABSTRACT Experimental investigations of ozone (O3) effects on plants have commonly used short, acute [O3] exposure (>100 ppb, on the order of hours), while in field crops damage is more likely caused by chronic exposure (<100 ppb, on the order of weeks). How different are the O3 effects induced by these two fumigation regimes? The leaf-level photosynthetic response of soybean to acute [O3] (400 ppb, 6 h) and chronic [O3] (90 ppb, 8 h d,1, 28 d) was contrasted via simultaneous in vivo measurements of chlorophyll a fluorescence imaging (CFI) and gas exchange. Both exposure regimes lowered leaf photosynthetic CO2 uptake about 40% and photosystem II (PSII) efficiency (Fq,/Fm,) by 20% compared with controls, but this decrease was far more spatially heterogeneous in the acute treatment. Decline in Fq,/Fm, in the acute treatment resulted equally from decreases in the maximum efficiency of PSII (Fv,/Fm,) and the proportion of open PSII centres (Fq,/Fv,), but in the chronic treatment decline in Fq,/Fm, resulted only from decrease in Fq,/Fv,. Findings suggest that acute and chronic [O3] exposures do not induce identical mechanisms of O3 damage within the leaf, and using one fumigation method alone is not sufficient for understanding the full range of mechanisms of O3 damage to photosynthetic production in the field. [source] Limiting efficiency of crystalline silicon solar cells due to Coulomb-enhanced Auger recombinationPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 2 2003Mark J. Kerr Excitonic effects are known to enhance the rate of intrinsic recombination processes in crystalline silicon. New calculations for the limiting efficiency of silicon solar cells are presented here, based on a recent parameterization for the Coulomb-enhanced Auger recombination rate, which accounts for its dopant type and dopant density dependence at an arbitrary injection level. Radiative recombination has been included along with photon recycling effects modeled by three-dimensional ray tracing. A maximum cell efficiency of 29.05% has been calculated for a 90-,m-thick cell made from high resistivity silicon at 25°C. For 1,,,cm p -type silicon, the maximum efficiency reduces from 28.6% for a 55-,m-thick cell in the absence of surface recombination, down to 27.0% for a thickness in the range 300,500,,m when surface recombination limits the open-circuit voltage to 720,mV. Copyright © 2002 John Wiley & Sons, Ltd. [source] Protein dynamics control proton transfer from bulk solvent to protein interior: A case study with a green fluorescent proteinPROTEIN SCIENCE, Issue 7 2005Anoop M. Saxena Abstract The kinetics of proton transfer in Green Fluorescent Protein (GFP) have been studied as a model system for characterizing the correlation between dynamics and function of proteins in general. The kinetics in EGFP (a variant of GFP) were monitored by using a laser-induced pH jump method. The pH was jumped from 8 to 5 by nanosecond flash photolysis of the "caged proton," o -nitrobenzaldehyde, and subsequent proton transfer was monitored by following the decrease in fluorescence intensity. The modulation of proton transfer kinetics by external perturbants such as viscosity, pH, and subdenaturing concentrations of GdnHCl as well as of salts was studied. The rate of proton transfer was inversely proportional to solvent viscosity, suggesting that the rate-limiting step is the transfer of protons through the protein matrix. The rate is accelerated at lower pH values, and measurements of the fluorescence properties of tryptophan 57 suggest that the enhancement in rate is associated with an enhancement in protein dynamics. The rate of proton transfer is nearly independent of temperature, unlike the rate of the reverse process. When the stability of the protein was either decreased or increased by the addition of co-solutes, including the salts KCl, KNO3, and K2SO4, a significant decrease in the rate of proton transfer was observed in all cases. The lack of correlation between the rate of proton transfer and the stability of the protein suggests that the structure is tuned to ensure maximum efficiency of the dynamics that control the proton transfer function of the protein. [source] Development of a simultaneous liquid,liquid extraction and chiral derivatization method for stereospecific GC-MS analysis of amphetamine-type stimulants in human urine using fractional factorial designBIOMEDICAL CHROMATOGRAPHY, Issue 9 2008W. R. Wan Aasim Abstract A stereospecific gas chromatography,mass spectrometry analysis method for amphetamine-type stimulants in human urine was recently developed. For maximum efficiency, liquid,liquid extraction and chiral derivatization of the analytes using (R)-(,)- , -methoxy- , -(trifluoromethyl)phenylacetyl chloride were performed simultaneously. The effects of (1) use of saturated sodium chloride in 2.0 m sodium hydroxide, (2) extraction solvent volume, (3) percentage of triethylamine, (4) derivatization reagent volume, (5) sample mixing time, (6) incubation temperature and (7) incubation time on method sensitivity and variability were assessed using a two-level, eight-run Plackett,Burman design followed by a fold-over design. The use of saturated sodium chloride solution and the derivatization reagent volume were significant factors (ANOVA, p < 0.01). The saturated sodium chloride solution decreased sensitivity whereas an increased volume of derivatization reagent increased sensitivity. Calibration curves for all analytes were linear between 5 and 500 µg/L, with correlation coefficients of >0.99. Detection limits were ,2.3 µg/L and quantitation limits ,7.7 µg/L. Reproducibility was good, with relative standard deviation values at <20%. Recovery exceeded 100% for most analytes. The experimental design enabled easy and rapid identification of significant factors using a minimal number of samples. This method has good potential for studies requiring rapid and sensitive stereospecific quantification of amphetamine-type stimulants. Copyright © 2008 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||