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Power Levels (power + level)
Selected AbstractsSimulation of Direct-Current Microdischarges for Application in Electro-Thermal Class of Small Satellite Propulsion DevicesCONTRIBUTIONS TO PLASMA PHYSICS, Issue 1-2 2007P. S. Kothnur Abstract Microdischarges are miniature non-equilibrium plasma discharges with characteristic dimensions of ,10's,100's ,m and relatively high operating pressures of ,10's,100's Torr. Microdischarges possess several unique properties that have been exploited in a number of new applications. We have recently proposed amicrodischargebased electro-thermal class of microthrusters for small satellite propulsion. These devices utilize intense gas heating in microdischarges to preheat a propellant gas stream before it is expanded in a micronozzle to produce thrust; thereby improving specific impulse of the device over a conventional cold gas microthruster. This paper addresses direct-current microdischarge phenomena in a flowing gas stream. A two-dimensional, selfconsistent, fluid model of a helium microdischarge in a bulk gas flow is developed. For relatively high current/power levels considered in this study, the microdischarge operates in an abnormal glow mode with positive differential resistivity. Increasing discharge pressures for fixed power and bulk flow rates results in a decrease in charged species densities and the electron and gas temperatures. Also the discharge becomes increasingly constricted with increasing pressures, resulting in a more normal glow mode-like operation. Increasing bulk flow rates results in exactly the same trends as increasing pressures. For given input power and pressure, there exists an optimum flow rate for which the average outlet gas temperature from the discharge is a maximum. An increase in input electrical power results in an almost linear increase in the gas temperatures; this property of microdischarges is the key feature that is exploited in our microdischarge-based thruster concept. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Microwave-Induced Stereocontrol of , -Lactam Formation with an N -Benzylidene-9,10-dihydrophenanthren-3-amine via Staudinger CycloadditionHELVETICA CHIMICA ACTA, Issue 2 2010Debasish Bandyopadhyay Abstract The synthesis of 3-substituted 4-phenyl-1-(9,10-dihydrophenanthren-3-yl)azetidin-2-ones was achieved following Staudinger cycloaddition under microwave-induced conditions. The stereoselectivity of , -lactam formation depended on the power level of the microwave irradiation used in the experiments. [source] Selective partial PIC for wireless CDMA communicationsINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 6 2003Filippo Belloni Abstract This paper deals with a cancellation multiuser detector for CDMA communication systems. The proposed receiver, defined as selective partial parallel interference cancellation (SP-PIC), is supposed to be used at the end of an up-link channel characterized by multipath fading phenomena. The SP-PIC main feature is to perform a weighted selective cancellation of the co-channel interfering signals according to the received power level. With respect to other approaches, the proposed detector exhibits an improved bit error rate (BER) and a low computational complexity, linear with the number of users. Copyright © 2003 John Wiley & Sons, Ltd. [source] Antioxidant activities of red pepper (Capsicum annuum) pericarp and seed extractsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 10 2008Ki Hyeon Sim Summary In this study, we examined the antioxidant activities of red pepper (Capsicum annuum, L.) pericarp and red pepper seed extracts. The extracts were evaluated by various antioxidant assays, including 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, superoxide anion radical scavenging, hydroxyl radical scavenging, [2,2,-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid)] (ABTS) radical scavenging, ferrous chelating activity, superoxide dismutase (SOD) activity and reducing power, along with the determination of total phenolic and flavonoid contents. All the extracts showed strong antioxidant activity by the testing methods. The red pepper pericarp extract exhibited strong ferrous chelating activity and high scavenging activity against free radicals, including both the hydroxyl and DPPH radicals, but it exhibited weaker scavenging activity for the superoxide anion radical and for SOD. In contrast, the red pepper seed extract exhibited strong SOD activity and high scavenging activity against the superoxide anion radical, but showed weaker ferrous chelating activity, hydroxyl radical scavenging, and DPPH radical scavenging. We observed that the reducing power level and ABTS radical scavenging activity of the red pepper seed were higher than those of the red pepper pericarp at the highest tested concentration. Most of the test results for the red pepper seed and red pepper pericarp extracts increased markedly with increasing concentration; however, the metal chelating, SOD and ABTS radical scavenging activities did not increase with the concentration. Highest total phenolic and flavonoid contents were obtained from the red pepper pericarp extracts. Overall, the red pepper seed and red pepper pericarp extracts were highly effective for the antioxidant properties assayed, with the exceptions of ferrous chelating activity, hydroxyl radical scavenging and SOD activity. [source] Generalized nonlinear FET/HEMT modelingINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 2 2004J. Johnson Abstract A modeling procedure which provides an accurate large-signal response for variation in bias, input power level, and fundamental frequency for FET/HEMT transistors is designed. A procedure for measuring the large-signal input response on an easily implemented system is presented. The technique is illustrated by designing a nonlinear PHEMT model, which includes an accurate large-signal input response and works with variations in the aforementioned input conditions. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 122,133, 2004. [source] Effects of ultrasound on culture of Aspergillus terreusJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2008Nuria Sainz Herrán Abstract BACKGROUND: Fermentations of Aspergillus terreus are commercially used to produce lovastatin. How ultrasound might influence this fermentation is unknown. While high-intensity ultrasound is effective in disrupting microbial cells, ultrasound of low intensity is known to improve productivity of some fermentation processes without damaging cells. Mechanisms behind productivity improvements have not been clearly identified in earlier studies. This work reports on the effects of ultrasound on A. terreus fermentation for low (957 W m,3), medium (2870 W m,3) and high (4783 W m,3) values of sonication power input in a slurry bubble column sonobioreactor. RESULTS: Sonication at any power level did not affect biomass growth profiles in comparison with negative controls. In contrast, medium- and high-intensity sonication greatly reduced production of lovastatin and substantially altered the growth morphology. At medium and high intensity, ultrasound disrupted fungal pellets and caused the biomass to grow mainly as dispersed hyphae. Sonication affected broth rheology because rheology depends on the morphology of the suspended biomass. CONCLUSION: Sonication can be used to modify growth morphology and broth rheology without affecting growth of filamentous fungi. Sonication appears to influence the primary growth metabolism and secondary metabolism differently in different situations. Copyright © 2008 Society of Chemical Industry [source] A MODEL FOR TEMPERATURE AND MOISTURE DISTRIBUTION DURING CONTINUOUS MICROWAVE DRYING,JOURNAL OF FOOD PROCESS ENGINEERING, Issue 1 2005D. BOLDOR ABSTRACT A heat and mass transfer model of continuous drying of farmer stock (in-shell, uncured) peanuts (Arachis hypogaea L.) in a planar microwave applicator was developed and investigated. Transport phenomena equations previously developed for batch-type microwave drying were successfully adapted to account for the spatial variation of the electric field inside the applicator. The theoretical equations developed, together with experimental methods, were used to determine the effect of microwave power level and dielectric properties on the temperature profiles and reduction in peanuts' moisture content (mc). The temperature profiles from the solution of these equations matched the experimental ones determined using fiber optic temperature probes inserted into drying peanut pods. An exact theoretical determination of mc reduction during microwave drying was not possible due to the dependence of dielectric properties on mc. The surface temperature distribution of the peanut bed measured using infrared pyrometry was well correlated with internal temperature profiles. [source] RADIO FREQUENCY (RF) HEATING OF STARCH SOLUTIONS UNDER CONTINUOUS FLOW CONDITIONS: EFFECT OF SYSTEM AND PRODUCT PARAMETERS ON TEMPERATURE CHANGE ACROSS THE APPLICATOR TUBEJOURNAL OF FOOD PROCESS ENGINEERING, Issue 3 2002G.B. AWUAH ABSTRACT Studies were conducted to evaluate the effect of system and product parameters on the temperature change (,T) across a 1.5 kW radio frequency heater operating at 27.12 MHz. Starch solutions (1 to 4% w/w) were used at three different flow rates (0.35, 0.5 and 1 L/min) and four power levels (672, 912, 1152 and 1392 W). The average heating rate of starch solutions varied from 6 to 19C/min depending on flow rate, concentration and power level. The corresponding residence time varied from 1.5 to 4.3 min. Central composite designs involving power (830 to 1234 W) and starch concentration (1 to 4% w/w) at 0.5 L/min were used to study the effects of salt, pH and sugar. As expected fluid flow rate, power level and salt concentration had significant impact (P ± 0.05) on temperature change (,T) across the applicator tube. Although the interaction effect of salt and concentration influenced ,T (P < 0.05), observed trends were not clear cut. Sugar and pH had no significant (P >0.05) influence on ,T due probably to their relatively lower conductivities. However, the interaction effect of sugar and starch concentration affected ,T. Correlations were developed for estimating ,T across the tube as a function of power level, concentration, pH, added salt and sugar. Finally, dimensionless correlations involving the generalized Reynolds, Prandtl, Grashof numbers, dimensionless power and loss-factor ratios were developed for estimating the temperature ratio (U) across the RF applicator. [source] Magnetic Resonance Temperature Mapping of Microwave-Fried Chicken FingersJOURNAL OF FOOD SCIENCE, Issue 5 2009Isil Barutcu ABSTRACT:, The main objective of this study was to compare the heating patterns of chicken fingers deep-fried conventionally and using a microwave. Two dimensional internal temperature maps of fried chicken fingers with rectangular geometry were measured post frying using magnetic resonance imaging (MRI). Frying was performed in a microwave oven at 365 W power level for 0.5 and 1.5 min after bringing the oil temperature to 180 ± 1 °C. Samples were also fried in a conventional fryer at 180 °C for 2 and 5 min for comparison. Variations in internal temperature distribution increased proportionally to frying time in both microwave and conventional frying. Internal thermal equilibrium is reached in all samples after 13 min of holding time. Internal structural changes, void formation, were also visualized in the images. Void formation did not significantly impact cooling rates. [source] MRI monitoring of heating produced by ultrasound absorption in the skull: In vivo study in pigsMAGNETIC RESONANCE IN MEDICINE, Issue 5 2004Nathan McDannold The purpose of this study was to test the utility of MR thermometry for monitoring the temperature rise on the brain surface and in the scalp induced by skull heating during ultrasound exposures. Eleven locations in three pigs were targeted with unfocused ultrasound exposures (frequency = 690 kHz; acoustic power = 8.2,16.5 W; duration = 20 s). MR thermometry (a chemical shift technique) showed an average temperature rise in vivo of 2.8°C ± 0.6°C and 4.4°C ± 1.4°C on the brain surface and scalp, respectively, at an acoustic power level of 10 W. The temperature rise on the scalp agreed with that measured with a thermocouple probe inserted adjacent to the skull (average temperature rise = 4.6°C ± 1.0°C). Characterization of the transducer showed that the average acoustic intensity was 1.3 W/cm2 at an acoustic power of 10 W. The ability to monitor the temperature rise next to the skull with MRI-based thermometry, as shown here, will allow for safety monitoring during clinical trials of transcranial focused ultrasound. Magn Reson Med 51:1061,1065, 2004. © 2004 Wiley-Liss, Inc. [source] A high-power Cartesian feedback transmitter including a compact inverted Doherty amplifierMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2008Hanjin Cho Abstract A high-power Cartesian feedback transmitter including a compact inverted Doherty amplifier is presented. The system efficiency was further improved using a bias line adjustment method for the compact inverted Doherty amplifier. After the bias line adjustment from a ,/4 line for the Doherty amplifier, a power-added efficiency (PAE) of 6.9% points was improved from 41.3 to 48.2% at an output power level of 45 dBm. The whole Cartesian feedback transmitter system exhibited an efficiency of 40% and an adjacent channel leakage ratio of-51 dBc at an output power of 45 dBm for 859 MHz band ,/4-DQPSK applications. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 944,946, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23265 [source] A high-efficiency class-E power amplifier using SiC MESFETMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2007Yong-Sub Lee Abstract This article reports a high efficiency class-E power amplifier using a SiC MESFET, which is designed and tested at 2.14 GHz. To improve output power and efficiency by suppressing harmonic powers, an output matching circuit using the transmission lines is used. From measured results for a single tone, the harmonic power levels are maintained below ,58 dBc at a whole output power level. The peak power-added efficiency of 72.3% with a power gain of 10.27 dB is achieved at an output power of 40.27 dBm. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1447,1449, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22455 [source] High Frequency AC Power SystemNAVAL ENGINEERS JOURNAL, Issue 4 2008RAYMOND M. CALFO The Navy's Next Generation Integrated Power System (NGIPS) master plan calls for the evolution of the IPS system from its current medium voltage, 60 Hz state to a high-frequency, medium-voltage AC (HFAC) system in the next 10 years. Beyond that, and pending development of key protection components, a medium-voltage DC system will be considered for implementation. The master plan calls for power generation modules at three power levels across these systems: ,A low power level (2,5 MW) driven by a fuel-efficient diesel prime mover, ,A medium power level (10,15 MW) driven by a gas turbine, and ,A main propulsion power level (20,40 MW) driven by a gas turbine. EMD is currently developing a high-speed, high-frequency, liquid-cooled generator under contract with NAVSEA that will effectively demonstrate the mid-level generator for the HFAC system. It will be coupled directly to the output of a GE LM1600 Gas Turbine to provide a TG set with power density four times more favorable than conventional ATG sets. The generator development is proceeding favorably, with testing at the Navy's land-based test site (LBTS) expected to begin in July 2008. The technology embodied in the high-speed generator can be easily extrapolated to main turbine generator power levels. Given the availability of prime movers at appropriate speeds, the power generation modules for the HFAC system, at all three power levels, could be provided in a much shorter time frame than noted in the NGIPS master plan. This paper will explore the combinations of prime movers and advanced generators that would suit the three power generation modules of the HFAC system. A description of the prime mover and the generator used for each module will be provided to demonstrate the modest level of development needed. The performance parameters for each generation module will be provided, along with key characteristics and dimensions for the set. In the end, the paper will make the case that demonstration of a HFAC power generation system can be made in the short term, allowing the shipbuilding community to take advantage of the benefits of state-of-the-art power dense electrical generation. [source] Signal-to-interference-plus-noise ratio estimation for wireless communication systems: Methods and analysisNAVAL RESEARCH LOGISTICS: AN INTERNATIONAL JOURNAL, Issue 5 2004Daniel R. Jeske Abstract The Signal-to-Interference-plus-Noise Ratio (SINR) is an important metric of wireless communication link quality. SINR estimates have several important applications. These include optimizing the transmit power level for a target quality of service, assisting with handoff decisions and dynamically adapting the data rate for wireless Internet applications. Accurate SINR estimation provides for both a more efficient system and a higher user-perceived quality of service. In this paper, we develop new SINR estimators and compare their mean squared error (MSE) performance. We show that our new estimators dominate estimators that have previously appeared in the literature with respect to MSE. The sequence of transmitted bits in wireless communication systems consists of both pilot bits (which are known both to the transmitter and receiver) and user bits (which are known only by the transmitter). The SINR estimators we consider alternatively depend exclusively on pilot bits, exclusively on user bits, or simultaneously use both pilot and user bits. In addition, we consider estimators that utilize smoothing and feedback mechanisms. Smoothed estimators are motivated by the fact that the interference component of the SINR changes relatively slowly with time, typically with the addition or departure of a user to the system. Feedback estimators are motivated by the fact that receivers typically decode bits correctly with a very high probability, and therefore user bits can be thought of as quasipilot bits. For each estimator discussed, we derive an exact or approximate formula for its MSE. Satterthwaite approximations, noncentral F distributions (singly and doubly) and distribution theory of quadratic forms are the key statistical tools used in developing the MSE formulas. In the case of approximate MSE formulas, we validate their accuracy using simulation techniques. The approximate MSE formulas, of interest in their own right for comparing the quality of the estimators, are also used for optimally combining estimators. In particular, we derive optimal weights for linearly combining an estimator based on pilot bits with an estimator based on user bits. The optimal weights depend on the MSE of the two estimators being combined, and thus the accurate approximate MSE formulas can conveniently be used. The optimal weights also depend on the unknown SINR, and therefore need to be estimated in order to construct a useable combined estimator. The impact on the MSE of the combined estimator due to estimating the weights is examined. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004 [source] SWNT probed by multi-frequency EPR and nonresonant microwave absorptionPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2008B. Corzilius Abstract In addition to g = 2.00 signals seen frequently in EPR spectra of SWNT, signals at g = 2.07 of SWNT prepared by CVD were detected, exhibiting a Pauli susceptibility temperature dependence. This Pauli magnetism in combination with the large g shift is taken as evidence that these signals originate from itinerant electrons of metallic nanotubes. At temperatures below 150 K, a dominant narrow signal develops at g = 2.00. By applying multifrequency EPR up to 319 GHz, its inhomogeneous nature was confirmed. This signal is assigned to defects of the carbon network of the tubes. Comparing room temperature EPR spectra of CVD and arc-grown SWNT, we found a much lower concentration of metallic tubes in arc material. No g = 2.07 signals of itinerant spins could be observed, which might be also caused by the high amount of residing catalyst. A drastic increase in nonresonant microwave absorption is observed below 10 K for both types of samples, if a threshold microwave power level is passed. In the same temperature range a drop in EPR intensity is also detected. These observations are taken as evidence for a transition into a superconducting phase of part of the sample. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Three-dimensional ultrasound image-guided robotic system for accurate microwave coagulation of malignant liver tumoursTHE INTERNATIONAL JOURNAL OF MEDICAL ROBOTICS AND COMPUTER ASSISTED SURGERY, Issue 3 2010Jing Xu Abstract Background The further application of conventional ultrasound (US) image-guided microwave (MW) ablation of liver cancer is often limited by two-dimensional (2D) imaging, inaccurate needle placement and the resulting skill requirement. The three-dimensional (3D) image-guided robotic-assisted system provides an appealing alternative option, enabling the physician to perform consistent, accurate therapy with improved treatment effectiveness. Methods Our robotic system is constructed by integrating an imaging module, a needle-driven robot, a MW thermal field simulation module, and surgical navigation software in a practical and user-friendly manner. The robot executes precise needle placement based on the 3D model reconstructed from freehand-tracked 2D B-scans. A qualitative slice guidance method for fine registration is introduced to reduce the placement error caused by target motion. By incorporating the 3D MW specific absorption rate (SAR) model into the heat transfer equation, the MW thermal field simulation module determines the MW power level and the coagulation time for improved ablation therapy. Two types of wrists are developed for the robot: a ,remote centre of motion' (RCM) wrist and a non-RCM wrist, which is preferred in real applications. Results The needle placement accuracies were < 3 mm for both wrists in the mechanical phantom experiment. The target accuracy for the robot with the RCM wrist was improved to 1.6 ± 1.0 mm when real-time 2D US feedback was used in the artificial-tissue phantom experiment. By using the slice guidance method, the robot with the non-RCM wrist achieved accuracy of 1.8 ± 0.9 mm in the ex vivo experiment; even target motion was introduced. In the thermal field experiment, a 5.6% relative mean error was observed between the experimental coagulated neurosis volume and the simulation result. Conclusion The proposed robotic system holds promise to enhance the clinical performance of percutaneous MW ablation of malignant liver tumours. Copyright © 2010 John Wiley & Sons, Ltd. [source] Internal electrolyte temperatures for polymer and fused-silica capillaries used in capillary electrophoresisELECTROPHORESIS, Issue 22 2005Christopher J. Evenhuis Abstract Polymers are important as materials for manufacturing microfluidic devices for electrodriven separations, in which Joule heating is an unavoidable phenomenon. Heating effects were investigated in polymer capillaries using a CE setup. This study is the first step toward the longer-term objective of the study of heating effects occurring in polymeric microfluidic devices. The thermal conductivity of polymers is much smaller than that of fused silica (FS), resulting in less efficient dissipation of heat in polymeric capillaries. This study used conductance measurements as a temperature probe to determine the mean electrolyte temperatures in CE capillaries of different materials. Values for mean electrolyte temperatures in capillaries made of New Generation FluoroPolymer (NGFP), poly-(methylmethacrylate) (PMMA), and poly(ether ether ketone) (PEEK) capillaries were compared with those obtained for FS capillaries. Extrapolation of plots of conductance versus power per unit length (P/L) to zero power was used to obtain conductance values free of Joule heating effects. The ratio of the measured conductance values at different power levels to the conductance at zero power was used to determine the mean temperature of the electrolyte. For each type of capillary material, it was found that the average increase in the mean temperature of the electrolyte (,TMean) was directly proportional to P/L and inversely proportional to the thermal conductivity (,) of the capillary material. At 7.5,W/m, values for ,TMean for NGFP, PMMA, and PEEK were determined to be 36.6, 33.8, and 30.7°C, respectively. Under identical conditions, ,TMean for FS capillaries was 20.4°C. [source] Capillary zone electrophoresis with a dynamic double coating for analysis of carbohydrate-deficient transferrin in human serum: Impact of resolution between disialo- and trisialotransferrin on reference limitsELECTROPHORESIS, Issue 24 2003Christian Lanz Abstract Capillary electrophoresis with a dynamic double coating formed by charged polymeric reagents represents a very effective tool for the separation of iron-saturated transferrin (Tf) isoforms and thus the determination of carbohydrate-deficient transferrin (CDT) in human serum. The resolution between di- and trisialo-Tf is dependent on the applied voltage and capillary temperature. With a 50 ,m inside diameter (ID) capillary of about 60 cm total length mounted into the P/ACE MDQ, 28 kV and 40°C, the resolution of the two Tf isoforms is shown to be between 1.0 and 1.4, whereas with reduced voltage and/or temperature, increased resolution at the expense of elongated run times is observed. Best data with complete resolution (Rs , 1.4) are obtained at 20 kV and 30°C. For the determination of CDT in serum, incomplete separation of di- and trisialo-Tf is demonstrated to have an impact on the reference limits. Analysis of the sera of 54 healthy individuals with no or moderate alcohol consumption and using valley-to-valley peak integration, the upper (lower) reference limits for CDT in relation to total Tf at the two power levels are 1.33 (0.52) and 1.57 (0.81)%, respectively, representing intervals that are significantly different (P < 0.001). Furthermore, the reference intervals are shown to be strongly dependent on the peak integration approach used. Valley-to-valley peak integration should only be employed for conditions with complete resolution between disialo- and trisialo-Tf. [source] Analysis of electrocardiographic changes in partial epileptic patients by combining eigenvector methods and support vector machinesEXPERT SYSTEMS, Issue 3 2009Elif Derya Übeyli Abstract: In the present study, the diagnostic accuracy of support vector machines (SVMs) on electrocardiogram (ECG) signals is evaluated. Two types of ECG beats (normal and partial epilepsy) were obtained from the Physiobank database. Decision making was performed in two stages: feature extraction by eigenvector methods and classification using the SVM trained on the extracted features. The present research demonstrates that the power levels of the power spectral densities obtained by eigenvector methods are features which represent the ECG signals well and SVMs trained on these features achieve high classification accuracies. [source] On dichotomizing phenotypes in family-based association tests: quantitative phenotypes are not always the optimal choiceGENETIC EPIDEMIOLOGY, Issue 5 2007David Fardo Abstract In family-based association studies, quantitative traits are thought to provide higher statistical power than dichotomous traits. Consequently, it is standard practice to collect quantitative traits and to analyze them as such. However, in many situations, continuous measurements are more difficult to obtain and/or need to be adjusted for other factors/confounding variables which also have to be measured. In such scenarios, it can be advantageous to record and analyze a "simplified/dichotomized" version of the original trait. Under fairly general circumstances, we derive here rules for the dichotomization of quantitative traits that maintain power levels that are comparable to the analysis of the original quantitative trait. Using simulation studies, we show that the proposed rules are robust against phenotypic misclassification, making them an ideal tool for inexpensive phenotyping in large-scale studies. The guidelines are illustrated by an application to an asthma study. Genet. Epidemiol. 2007. © 2007 Wiley-Liss, Inc. [source] Microwave finish drying of (tapioca) starch pearlsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 2 2005Yi-Chung Fu Summary Starch pearls are extremely sensitive to the rate of drying. Fast drying leads to poor quality of final cooked (rehydrated) products. The objectives of this study were to reduce the lengthy drying time by incorporating low-power microwave finish drying and to evaluate the rehydrated quality of starch pearls. The effects of temperature and relative humidity on the drying rates of starch pearls in the constant-rate period were determined. When evaluating the saving of time, microwave energy efficiency and rehydration quality, the best results were obtained when combined natural convection and microwave finish drying were carried out at low power levels (119,143 W). Microwave finish drying reduced the natural convective drying time by about 50,75%, with an improvement in quality, as indicated by higher unbroken ratio, less cooking loss and shorter cooking time. [source] Automatic annular laser trapping: a system for high-throughput sperm analysis and sortingJOURNAL OF BIOPHOTONICS, Issue 3 2009Linda Shi Abstract An automatic microscope system is designed to study the response of sperm motility to an annular laser trap. A continuous annular laser trap provides a parallel way to analyze and sort sperm based on their motility and to study the effects of laser radiation, optical force and external obstacles. In the described automatic microscope system, the phase contrast images of swimming sperm are digitized to the computer at video rates. The microscope stage is controlled in real-time to relocate the sperm of interest to the annular trap with a normal or tangential entering angle. The sperm is continuously tracked and the swimming behavior is identified. Using this system, parallel sorting on human and gorilla sperm are achieved and threshold power levels separating the "fast" group and the "slow" group are compared for those two species. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Substance loss caused by scaling with different sonic scaler inserts , an in vitro studyJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 1 2001Thomas Kocher Abstract Background, aims: Depending on the phase of periodontal treatment, power-driven inserts with different power levels are necessary: during initial treatment and flap operations, it must be possible to remove calculus which firmly adheres to the root surface with great efficiency; in contrast, gentle root-surface instrumentation has a high priority during maintenance treatment. Recently, modified sonic scaler inserts have been introduced: diamond-coated inserts for open flap operations and slim probe-shaped sonic scaler inserts for deplaqueing during maintenance. Method: We compared the substance removal by these inserts to that of a conventional insert. In a bench system which allows application force, stroke height, and width and frequency of instrumentation to be monitored and also permits assessment of the topography before and after instrumentation (yielding depth removal and removed volume), we instrumented aluminum rods in triplicate and bovine roots in a 5-fold repetition. Results: With high application forces (1.0 N), the diamond-coated inserts removed 30 to 50% more substance than the conventional one. Except for the slim inserts, there was a significant linear relationship between increasing force and removed volume. Probe-shaped inserts do not remove considerable substance even with increasing pressures. Conclusions: Diamond-coated inserts remove tooth substance very effectively and must thus be handled with care: more pressure effects more removal. Probe-shaped inserts can be used without risk during maintenance visits. [source] RADIO FREQUENCY (RF) HEATING OF STARCH SOLUTIONS UNDER CONTINUOUS FLOW CONDITIONS: EFFECT OF SYSTEM AND PRODUCT PARAMETERS ON TEMPERATURE CHANGE ACROSS THE APPLICATOR TUBEJOURNAL OF FOOD PROCESS ENGINEERING, Issue 3 2002G.B. AWUAH ABSTRACT Studies were conducted to evaluate the effect of system and product parameters on the temperature change (,T) across a 1.5 kW radio frequency heater operating at 27.12 MHz. Starch solutions (1 to 4% w/w) were used at three different flow rates (0.35, 0.5 and 1 L/min) and four power levels (672, 912, 1152 and 1392 W). The average heating rate of starch solutions varied from 6 to 19C/min depending on flow rate, concentration and power level. The corresponding residence time varied from 1.5 to 4.3 min. Central composite designs involving power (830 to 1234 W) and starch concentration (1 to 4% w/w) at 0.5 L/min were used to study the effects of salt, pH and sugar. As expected fluid flow rate, power level and salt concentration had significant impact (P ± 0.05) on temperature change (,T) across the applicator tube. Although the interaction effect of salt and concentration influenced ,T (P < 0.05), observed trends were not clear cut. Sugar and pH had no significant (P >0.05) influence on ,T due probably to their relatively lower conductivities. However, the interaction effect of sugar and starch concentration affected ,T. Correlations were developed for estimating ,T across the tube as a function of power level, concentration, pH, added salt and sugar. Finally, dimensionless correlations involving the generalized Reynolds, Prandtl, Grashof numbers, dimensionless power and loss-factor ratios were developed for estimating the temperature ratio (U) across the RF applicator. [source] The effect of low-power microwaves on the growth of bacterial populations in a plug flow reactorAICHE JOURNAL, Issue 5 2010Renzo Carta Abstract A plug flow reactor (PFR) which permits the growth of bacteria in a microwave environment is described. The apparatus is used to analyse the effect of microwave radiation at the frequency of 2.45 GHz and at 37°C on the growth rate of three bacterial species: Bacillus clausii, Pseudomonas aeruginosa, and Staphylococcus aureus. The growth constant is determined for reacting mixtures irradiated with microwaves of different powers ranging from 0 to 400 mW. Analyses show that (a) the apparatus is able to perform the experimental runs maintaining an aseptic environment; (b) under the microwave power levels examined in the present study, no effects are detected for the Bacillus clausii and Pseudomonas aeruginosa species, while for the Staphylococcus aureus species, a few small effects are found (a minimum value of the growth constant at 200 mW and an increase of the constant between 200 and 400 mW). © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Characterization of ultrasound extrudated and cut citric acid/paracetamol blendsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2009P. Hoppu Abstract The purpose of the present work was to study the effect of ultrasound extrusion and cutting on the physical stability of a viscous and sticky supercooled melt containing (50/50, w/w, %) citric acid anhydrate and paracetamol. Samples were extrudated at temperatures of 50, 60, and 70°C using power levels of 0, 50, 100, and 150 W. Similarly, extrudates prepared at 60°C were cut at temperatures ranging from 25,60°C with an ultrasound knife in the range 0, 50, and 100 W. The characterization methods used were: high performance liquid chromatography, differential scanning calorimetry, Karl Fischer titration, X-ray powder diffraction, Fourier transform infrared microscopy, optical- and stereomicroscopy. There was no physical difference in extrudates or cut surfaces whether processed with or without ultrasound. During 1-year aging time in dry conditions, all the samples were observed to crystallize slowly and ultrasound processing did not enhance the crystallization. Ultrasound thus holds some promise for processing of viscous and sticky pharmaceuticals, provided the material is physically stable enough to withstand mechanical and thermal stress. Processing of sticky and viscous material would be difficult without ultrasound with the methods currently used in pharmaceutical industry. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:2140,2148, 2009 [source] The historical development of cryogenically cooled monochromators for third-generation synchrotron radiation sourcesJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2000Donald H. Bilderback In the period of the late-1980s, before the construction of multi-GeV third-generation storage rings with their intense insertion-device sources, the perceived number one problem for X-ray instrumentation was proper cooling of the first optical element in the beamline. This article, first given as an acceptance speech for the Compton Award ceremony at the Advanced Photon Source, presents a somewhat historical and anecdotal overview of how cryogenically cooled monochromator optics have been developed to provide a monochromator cooling solution adequate for today's power levels. A series of workshops and international collaborations were the key components for the progress and final success of this development. [source] Absorption of diode 810 nm used for transpupillary thermotherapy by blood.LASERS IN SURGERY AND MEDICINE, Issue 6 2006An in vitro study Abstract Background and Objectives To evaluate the in vitro energy attenuation by transpupillary thermotherapy (TTT) using an 810-nm diode laser after the treatment of exudative age-related macular degeneration. Study Design/Materials and Methods In this experiment, an 810-nm diode laser was coupled to a slit lamp to deliver laser energy to a laser-power sensor adjusted in the track of the laser light. The spotlight was 0.5 mm in diameter; duration of exposure, 3 seconds. Citrated Pasteur pipettes were filled with blood diluted in saline in several concentrations and placed in the path of the laser light. The absorption of the light measured by the power sensor was tested for various delivered irradiances between 50.92 and 509.29 W/cm2. The differences were analyzed statistically. Results There were significant differences in laser blockage comparing various conditions for all power levels (P<0.05). Increasing the proportion of blood resulted in more laser blockage with all irradiances (P<0.05). Conclusions Blood significantly blocks the transmission of the 810-nm diode TTT laser. Lasers Surg. Med. 38:643,646, 2006. © 2006 Wiley-Liss, Inc. [source] Complementary predistorter in CMOS differential power amplifierMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2010Inn-Yeah Oh Abstract For adaptive improvement of linearity above a 12 dB PAPR for 64QAM WiMAX, a complementary feedback loop in a differential amplifier is adopted as a pre-distorter that is realized using an NMOS cell operating in the triode region in order to compensate the gm3, the third order transconductance, of the differential amplifier. The power amplifier has been implemented in 0.18 ,m CMOS technology, and the chip size is 870 ,m × 1050 ,m. The proposed PA obtains the 42% efficiency at P1dB while improving the IMD by more than 10 dB above 15 dBm output power levels. It shows a gain of as much as 14.5 dB, and a return loss below ,12 dB for 2.3,2.4 GHz operation. Finally, the fabricated PA complies with the spurious emission of WiMAX standards up to 22 dBm. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:833,836, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25062 [source] Environmentally stable nonlinear optical polarization switching by using a nonreciprocal all-optical circuitMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2009Naoto Kishi Abstract We proposed and demonstrated a stable nonlinear optical polarization self-switching based on nonreciprocal nonlinear phase shift induced by self-phase modulation in optical fiber. The polarization self-switching was achieved at input power levels of around 10 mW in a nonreciprocal circuit using Faraday rotator mirrors. This nonlinear polarization switching is quite stable against polarization fluctuation caused by environmental perturbation. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2056,2059, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24548 [source] | |||||||||||||||||||||||||||||||||||||